@misc{leblanc_2023, title={Everyday Chemicals}, ISBN={9780231556255}, url={http://dx.doi.org/10.7312/lebl20596}, DOI={10.7312/lebl20596}, abstractNote={This book is a layperson’s guide to understanding chemical risk. The toxicologist Gerald A. LeBlanc offers a nontechnical overview of the key factors in evaluating whether exposure to chemicals in our daily lives could be harmful.}, publisher={Columbia University Press}, author={LeBlanc, Gerald A.}, year={2023}, month={Feb} }
 @article{guo_xia_ruan_wang_zhang_leblanc_an_2022, title={Ignored microplastic sources from plastic bottle recycling}, volume={838}, ISSN={["1879-1026"]}, DOI={10.1016/j.scitotenv.2022.156038}, abstractNote={The recovery and recycling of plastic products has increased dramatically in recent years as a strategy to achieve sustainable production and minimization of plastic pollution. However, the release of microplastics during plastic recycling has received little attention. We evaluated the generation and fate of microplastics in three typical facilities which make polyethylene terephthalate (PET) flakes using post-consumer PET bottles as raw material. Microplastics, 0.1- 5.0 mm in size, were detected in production wastewater at concentrations ranging from 23.43 ± 1.04 mg/L to 1836.37 ± 31.73 mg/L, while decreased to (8.13 ± 0.42-83.83 ± 0.93) mg/L in discharge effluent and (52,166 ± 2858-68,866 ± 2500) μg/g in sludge. Interestingly, the profiles of microplastics in samples from production wastewater, effluents, and sludge showed significant differences. Although, in all three compartments, the mass of microplastics increased, and the particle number decreased with increasing particle size. Overall, the removal ratio of total microplastics from the production wastewater was 53.47 ± 4.48% to 99.56 ± 0.02% in mass, and from 90.08 ± 0.82% to 99.56 ± 0.05% in quantity. The loss of microplastics from wastewater resulted in their concentration in sludge. Factors that influence the transfer of microplastics from wastewater to sludge should be identified and utilized to maintain a high level of removal and prevent leakage of these particles into the environment.}, journal={SCIENCE OF THE TOTAL ENVIRONMENT}, author={Guo, Yuwen and Xia, Xinyue and Ruan, Jiuli and Wang, Yibo and Zhang, Jinyu and LeBlanc, Gerald A. and An, Lihui}, year={2022}, month={Sep} }
 @article{you_gao_fu_leblanc_guo_zhang_li_2022, title={Organotins in a food web from the Three Gorges Reservoir, China: Trophic enrichment and potential health risk}, volume={845}, ISSN={["1879-1026"]}, DOI={10.1016/j.scitotenv.2022.157276}, abstractNote={Triphenyltin (TPhT) and tributyltin (TBT) remain widely present in various aquatic environments despite restrictions on their use in many countries for many years. The biomagnification of these compounds in the aquatic food web remains controversial. This study reports the bioaccumulation of TPhT and TBT in aquatic animals in the Three Gorges Reservoir (TGR), a deep-water river channel-type reservoir and the largest reservoir in China. We measured TPhT, TBT and their metabolites in 2 invertebrates, 27 fish and the aquatic environment. The logarithmic bioaccumulation factors of TPhT and TBT were 4.37 and 3.77, respectively, indicating that TPhT and TBT were enriched in organisms of the TGR. Both TPhT and TBT concentrations were significantly and positively correlated with trophic level, with trophic magnification factors of 3.71 and 3.63, respectively, indicating that TPhT and TBT exhibited similar trophic enrichment in the freshwater food web of the TGR. The results of health risk assessment showed that although all hazard index (HI) values were <1, more attention should be paid to the health risk to children associated with consumption of aquatic products (HI = 0.67). This study provides powerful evidence of trophic enrichment of TPhT and TBT in a freshwater food web in a deep-water river channel-type reservoir and provides valuable data regarding organotins in aquatic animals in the TGR.}, journal={SCIENCE OF THE TOTAL ENVIRONMENT}, author={You, Jia and Gao, Jun-min and Fu, Ping-ting and LeBlanc, Gerald A. and Guo, Jin-song and Zhang, Li-xia and Li, Mao-qiu}, year={2022}, month={Nov} }
 @misc{knigge_leblanc_ford_2021, title={A Crab Is Not a Fish: Unique Aspects of the Crustacean Endocrine System and Considerations for Endocrine Toxicology}, volume={12}, ISSN={["1664-2392"]}, DOI={10.3389/fendo.2021.587608}, abstractNote={Crustaceans-and arthropods in general-exhibit many unique aspects to their physiology. These include the requirement to moult (ecdysis) in order to grow and reproduce, the ability to change color, and multiple strategies for sexual differentiation. Accordingly, the endocrine regulation of these processes involves hormones, receptors, and enzymes that differ from those utilized by vertebrates and other non-arthropod invertebrates. As a result, environmental chemicals known to disrupt endocrine processes in vertebrates are often not endocrine disruptors in crustaceans; while, chemicals that disrupt endocrine processes in crustaceans are often not endocrine disruptors in vertebrates. In this review, we present an overview of the evolution of the endocrine system of crustaceans, highlight endocrine endpoints known to be a target of disruption by chemicals, and identify other components of endocrine signaling that may prove to be targets of disruption. This review highlights that crustaceans need to be evaluated for endocrine disruption with consideration of their unique endocrine system and not with consideration of the endocrine system of vertebrates.}, journal={FRONTIERS IN ENDOCRINOLOGY}, author={Knigge, Thomas and LeBlanc, Gerald A. and Ford, Alex T.}, year={2021}, month={Mar} }
 @article{shi_cui_wu_leblanc_wang_an_2021, title={A proposed nomenclature for microplastic contaminants}, volume={172}, ISSN={["1879-3363"]}, DOI={10.1016/j.marpolbul.2021.112960}, abstractNote={Microplastics are emerging contaminants with a wide environmental distribution and potential to elicit adverse impacts on organisms. Despite this lack of consistency among reports, data obtained from different investigations are often compared, resulting in the potential for misrepresentation of global microplastic contamination. Major interlaboratory variability in quantification of microplastic levels stem from size-related differences in sampling and analysis with different density solutions to separate microplastics. Herein, we propose a nomenclature that provides key information relating to the microplastics abundance in samples. That is, the proposed nomenclature, MPsca, b, informs on mesh or filter size used in sampling, the density of flotation solution used to separate the microplastics, and the detection limit during the analysis progress of microplastics. This proposed nomenclature would facilitate comparisons among studies to avoid over- or under-estimation of global microplastic levels. Moreover, it would also facilitate the interpretation of meta-data in future assessments.}, journal={MARINE POLLUTION BULLETIN}, author={Shi, Wenzhuo and Cui, Tiefeng and Wu, Haiwen and LeBlanc, Gerald A. and Wang, Feifei and An, Lihui}, year={2021}, month={Nov} }
 @article{xu_deng_leblanc_an_2020, title={An effective method for evaluation of microplastic contaminant in gastropod from Taihu Lake, China}, volume={27}, ISSN={["1614-7499"]}, DOI={10.1007/s11356-020-08747-8}, number={18}, journal={ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH}, author={Xu, Qiujin and Deng, Ting and LeBlanc, Gerald A. and An, Lihui}, year={2020}, month={Jun}, pages={22878–22887} }
 @article{ford_leblanc_2020, title={Endocrine Disruption in Invertebrates: A Survey of Research Progress}, volume={54}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.0c04226}, abstractNote={Manmade chemicals can interfere with endocrine processes and have permeated many ecosystems. Arguably, the most devastating example of endocrine disruption occurred in gastropod molluscs which led to the banning of tributyltin. The invertebrates consist of ∼95% of all known animals and possess endocrine systems that can significantly differ from that of vertebrates. An expert group in the late 1990s highlighted considerable paucity in our knowledge of these endocrine systems and the limited ability to ascertain risks of endocrine-disrupting chemicals (EDCs) to invertebrates. Twenty years later, we surveyed experts in this field on the current state of the science. Respondents agreed that endocrine disruption is still a significant issue and noted that there was key evidence that EDCs were impacting invertebrates groups. Respondents noted a variety of impediments to advancing the science, including inadequate funding, insufficient knowledge to develop appropriate assays, and generally low support for invertebrate studies. Several scientists highlighted that resources were being misdirected with studies that address impacts of vertebrate EDCs or using biomarkers specific to vertebrate endocrine disruption. Sadly, many of the recommendations proposed by respondents matched those made over two decades ago. Accordingly, the field has not advanced as much as one might have expected.}, number={21}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Ford, Alex T. and LeBlanc, Gerald A.}, year={2020}, month={Nov}, pages={13365–13369} }
 @article{xu_gao_xu_shi_wang_leblanc_cui_an_lei_2020, title={Investigation of the microplastics profile in sludge from China's largest Water reclamation plant using a feasible isolation device}, volume={388}, ISSN={["1873-3336"]}, DOI={10.1016/j.jhazmat.2020.122067}, abstractNote={Sewage sludge, which is widely applied to land as a fertilizer, is a key source of microplastics in the environment. We sought to develop a feasible device for isolation of microplastic from sewage sludge for further understanding their fates in the environment. In the present study, an effective isolation device, consisting of a fritted glass funnel and a glass filtration apparatus, was constructed to extract microplastics from sludge with nearly 100% recovery efficiency. Then, a high abundance of microplastics was detected in sludge sampled from China's largest sewage treatment plant. Among the 25 types of microplastic polymers confirmed by Fourier transform infrared spectroscopy, poly(11-bromoundecyl acrylate) (PBA) and poly(11-bromoundecyl methacrylate) (PBMA) accounted for 23.63% of total microplastics detected. Rayon, polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and copolymers, such as PP/PE and poly(styrene:acrylonitrile:butadiene) (ABS), were also detected. The shapes of these microplastics consisted of pellets, fragments, films, and microfibers. Characterization of the isolated microplastics revealed that domestic applications and vehicle products were the major sources of microplastic in sewage treatment sludge. Some priority recommendations were issued based on these results. In conclusion, the present study demonstrate that the device is effective for the isolation of microplastics from sludge.}, journal={JOURNAL OF HAZARDOUS MATERIALS}, author={Xu, Qiujin and Gao, Yiyao and Xu, Li and Shi, Wenzhuo and Wang, Feifei and LeBlanc, Gerald A. and Cui, Song and An, Lihui and Lei, Kun}, year={2020}, month={Apr} }
 @article{camp_yun_chambers_haeba_leblanc_2020, title={Involvement of glutamate and serotonin transmitter systems in male sex determination in Daphnia pulex}, volume={121}, ISSN={["1879-1611"]}, DOI={10.1016/j.jinsphys.2020.104015}, abstractNote={Environmental sex determination occurs in many organisms, however the means by which environmental stimuli are translated into endocrine messages remains poorly understood. The N-methyl-ᴅ-aspartate receptor (NMDAR) was evaluated as a candidate neural sensor of environmental signals linking environmental cues to endocrine responses using the crustacean Daphnia pulex. NMDAR agonists, modulators, and antagonists were evaluated for their ability to impact D. pulex male sex determination during early stages of reproductive maturity under conditions that simulated seasonal change. The antagonists MK-801 and desipramine significantly increased male sex determination. Both chemicals are also modulators of serotonergic and noradrenergic systems, thus, we evaluated several modulators of monoamine neurotransmission in an effort to discern which signaling pathways might contribute to male sex determination. Compounds that altered serotonergic signaling also stimulated male sex determination. The involvement of the glutamate and monoamine signaling in male sex determination was supported by the increase in mRNA levels of related receptors and transporters under conditions that stimulate male sex determination. Further, mRNA levels of components of the terminal endocrine pathway responsible for male sex determination were also elevated under stimulatory conditions. Overall, we provide evidence that glutamatergic and serotonergic systems function upstream of the endocrine regulation of male sex determination in early life stage daphnids.}, journal={JOURNAL OF INSECT PHYSIOLOGY}, author={Camp, Allison A. and Yun, Jeonga and Chambers, Samantha A. and Haeba, Maher H. and LeBlanc, Gerald A.}, year={2020} }
 @article{xu_zhou_lei_leblanc_an_2020, title={Phthalate Esters and Their Potential Risk in PET Bottled Water Stored under Common Conditions}, volume={17}, ISSN={["1660-4601"]}, DOI={10.3390/ijerph17010141}, abstractNote={A great deal of attention has been paid lately to release of phthalate esters (PAEs) from polyethylene terephthalate (PET) bottles into PET bottled drinking water due to their potential endocrine-disrupting effects. Three kinds of PAEs, including diethyl phthalate (DEP), dimethyl phthalate (DMP) and dibutyl phthalate (DBP), were detected in 10 popular brands of PET bottles in Beijing, ranging from 101.97 μg/kg to 709.87 μg/kg. Meanwhile, six kinds of PAEs, including DEP, DMP, DBP, n-butyl benzyl phthalate (BBP), di-n-octyl phthalate (DOP) and di(2-ethylhexyl) phthalate (DEHP), were detected in PET bottled water, ranging from 0.19 μg/L to 0.98 μg/L, under an outdoor storage condition, while their concentrations ranged from 0.18 μg/L to 0.71 μg/L under an indoor storage condition. Furthermore, the concentrations of PAEs in brand D and E bottles were slightly increased when the storage time was prolonged. In addition, the concentrations of PAEs in commercial water contained in brand B and H bottles and pure water contained in brand E and G bottles were also slightly increased with the increase of storage temperature. Interestingly, DBP mainly contributed to the increased PAEs levels in simulation water. These results suggest that a part of the PAEs in PET bottled water originated from plastic bottles, which was related to the storage time and temperature. However, the PAEs in PET bottled water only pose a negligible risk to consumers if they follow the recommendations, such as storage at a common place (24 °C), away from sun and in a short period of time.}, number={1}, journal={INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH}, author={Xu, Xiangqin and Zhou, Gang and Lei, Kun and LeBlanc, Gerald A. and An, Lihui}, year={2020}, month={Jan} }
 @misc{le blanc_2019, place={Raleigh, NC}, title={Being certain about uncertainty}, url={https://news.ncsu.edu/2019/07/being-certain-about-uncertainty/}, journal={The Abstract,}, publisher={North Carolina State University}, author={Le Blanc, G.A}, year={2019}, month={Jul} }
 @article{camp_haeba_leblanc_2019, title={Complementary roles of photoperiod and temperature in environmental sex determination in Daphnia spp.}, volume={222}, ISSN={0022-0949 1477-9145}, url={http://dx.doi.org/10.1242/jeb.195289}, DOI={10.1242/jeb.195289}, abstractNote={Daphnia spp., a keystone genus in freshwater lentic habitats, are subject to environmental sex determination wherein environmental conditions dictate offspring sex and whether they reproduce asexually or sexually. The introduction of males into a population denotes the first step in the switch from asexual parthenogenetic reproduction to sexual reproduction. We tested the hypothesis that photoperiod and temperature co-regulate male sex determination and that these environmental stimuli would activate elements of the male sex determination signaling cascade. The results revealed that photoperiod was a critical cue in creating permissive conditions for male production. Further, under photoperiod-induced permissive conditions, male sex determination was temperature dependent. The two daphnid species evaluated, Daphnia pulex and Daphnia magna, exhibited different temperature dependencies. Daphnia pulex produced fewer males with increasing temperatures between 16 and 22°C, and D. magna exhibited the opposite trend. We found consistent expression patterns of key genes along the male sex-determining signaling pathway in D. pulex independent of environmental stimuli. mRNA levels for the enzyme responsible for synthesis of the male sex-determining hormone, methyl farnesoate, were elevated early in the reproductive cycle, followed by increased mRNA levels of the methyl farnesoate receptor subunits Met and SRC Environmental conditions that stimulated male offspring production significantly increased Met mRNA levels. The results indicate that male sex determination in daphnids is under the permissive control of photoperiod and the regulatory control of temperature. Further, these environmental cues may stimulate male sex determination by increasing levels of the Met subunit of the methyl farnesoate receptor.}, number={4}, journal={The Journal of Experimental Biology}, publisher={The Company of Biologists}, author={Camp, Allison A. and Haeba, Maher H. and LeBlanc, Gerald A.}, year={2019}, month={Jan}, pages={jeb195289} }
 @article{ma_han_an_lei_qi_leblanc_2019, title={Freshwater snail Parafossarulus striatulus estrogen receptor: Characteristics and expression profiles under lab and field exposure}, volume={220}, ISSN={["1879-1298"]}, DOI={10.1016/j.chemosphere.2018.12.176}, abstractNote={The modes of action by which putative endocrine disrupting chemicals (EDCs) elicit toxicity in mollusks remains unclear due to our limited understanding of the molluscan endocrine system. We identified and partially characterised the estrogen receptor (ER) of the mollusk Parafossarulus striatulus. The full-length cDNA of the ER of P. striatulus (psER) was isolated and found to have an ORF of 1386 bp which corresponded to 461 amino acids. Phylogenetic analysis revealed that psER is an orthologue of ER of other mollusks. Moreover, the DNA-binding domain, ligand-binding domain, P-box, D-box, and AF2 domain were also identified in psER. Exposure of females and males to 17β-estradiol (E2, 100 ng/L) for 24 h and 72 h did not alter psER transcription, but exposure to 17α-methyltestosterone (MT, 100 μg/L) for 72 h significantly decreased ER transcription in females only (p < 0.05). psER transcription was surveyed in males and females seeded in different regions in Taihu Lake, China. psER transcription were elevated among females and males maintained at site ML. This elevation was statistically significant (p < 0.05) among male snails as compared to snails held at the more pristine site of SZ. This was different to the results from lab, implying that some unknown chemicals or other environmental factors in field could affect psER transcription level in snails. Furthermore, females and males held at site ML also exhibited a significant elevation in vitellogenin transcription as compared to snails held at site SZ, suggesting that vitellogenin production may be directly regulated by psER or co-regulated with psER in this species.}, journal={CHEMOSPHERE}, author={Ma, Fujun and Han, Xuemei and An, Lihui and Lei, Kun and Qi, Hongli and LeBlanc, Gerald A.}, year={2019}, month={Apr}, pages={611–619} }
 @article{street_eytcheson_leblanc_2019, title={The role of nuclear receptor E75 in regulating the molt cycle of Daphnia magna and consequences of its disruption}, volume={14}, ISSN={1932-6203}, url={http://dx.doi.org/10.1371/journal.pone.0221642}, DOI={10.1371/journal.pone.0221642}, abstractNote={Biological rhythms regulate innumerable physiological processes, yet little is known of factors that regulate many of these rhythms. Disruption in the timing of these rhythms can have devastating impacts on population sustainability. We hypothesized that the timing of the molt infradian rhythm in the crustacean Daphnia magna is regulated by the joint action of the protein E75 and nitric oxide. Further, we hypothesized that disruption of the function of E75 would adversely impact several physiological processes related to growth and reproduction. Analysis of mRNA levels of several genes, involved in regulating the molt cycle in insects, revealed the sequential accumulation of E75, its dimer partner HR3, FTZ-F1, and CYP18a1 during the molt cycle. Exposure to the nitric oxide donor sodium nitroprusside early in the molt cycle had no effect on E75 or HR3 mRNA levels, but delayed the peak accumulation of FTZ-F1 and CYP18a1 mRNA. The subsequent exuviation was also delayed consistent with the delay in peak accumulation of FTZ-F1 and CYP18a1. These results supported our assertion that nitric oxide binds E75 rendering it incapable of binding HR3. Excess HR3 protein then enhanced the accumulation of the downstream products FTZ-F1 and CYP18a1. Similarly, suppression of E75 mRNA levels, using siRNA, had no effect on mRNA levels of HR3 but elevated mRNA levels of FTZ-F1. Consistent with these molecular responses, the suppression of E75 using siRNA increased the duration of the molt cycle and reduced the number of offspring produced. We conclude that the molt cycle of daphnids is regulated in a manner similar to insects and disruption of E75 results in a lengthening of the molt cycle and a reduction the release of viable offspring.}, number={8}, journal={PLOS ONE}, publisher={Public Library of Science (PLoS)}, author={Street, Stephanie M. and Eytcheson, Stephanie A. and LeBlanc, Gerald A.}, editor={Englert, ChristophEditor}, year={2019}, month={Aug}, pages={e0221642} }
 @article{eytcheson_leblanc_2018, title={Hemoglobin Levels Modulate Nitrite Toxicity to Daphnia magna}, volume={8}, ISSN={2045-2322}, url={http://dx.doi.org/10.1038/s41598-018-24087-7}, DOI={10.1038/s41598-018-24087-7}, abstractNote={Nitrogenous compounds enter the environment through various anthropogenic sources. Among these are nitrate (NO3-) and nitrite (NO2-) which can oxidize the heme moiety of hemoglobin and reduce the oxygen-carrying capacity of the molecule resulting in toxicity. Of the two anions, nitrite is more toxic. Hemoglobin levels are influenced by environmental conditions; thus, we hypothesized that hemoglobin levels would influence the toxicity of nitrite with low hemoglobin levels resulting in enhanced toxicity and high hemoglobin levels resulting in reduced toxicity. We tested this hypothesis by elevating hemoglobin levels with pyriproxyfen treatment and lowering hemoglobin levels using siRNA in Daphnia magna. Exposure to pyriproxyfen significantly elevated hemoglobin mRNA levels and induced copper coloration of the organisms, indicative of increased hemoglobin protein accumulation. siRNA treatment significantly reduced hemoglobin mRNA levels in both untreated and pyriproxyfen-treated organisms and attenuated copper coloration. Pyriproxyfen treatment increased the tolerance of daphnids to the acute toxicity of nitrite approximately 2-fold while siRNA treatment significantly decreased the tolerance of daphnids to nitrite toxicity. Results indicate that increased hemoglobin levels increase the tolerance of daphnids to nitrite toxicity which may serve to protect daphnids in environments subject to hemoglobin-elevating hypoxia or elevated temperatures.}, number={1}, journal={Scientific Reports}, publisher={Springer Science and Business Media LLC}, author={Eytcheson, Stephanie A. and LeBlanc, Gerald A.}, year={2018}, month={May} }
 @article{le blanc_2018, title={New method lights the way for future toxicity testing}, number={26}, journal={Euro Cosmetics}, author={Le Blanc, G.A}, year={2018}, month={Jan} }
 @article{qiao_lei_han_wei_zhao_an_leblanc_2018, title={No impacts of microcystins on wild freshwater snail Bellamya Aeruginosa fecundity from a eutrophic lake}, volume={60}, ISSN={1382-6689}, url={http://dx.doi.org/10.1016/j.etap.2018.04.024}, DOI={10.1016/j.etap.2018.04.024}, abstractNote={The preliminary investigation at shoreline along Taihu lake with different degrees of eutrophication status found no significant relationship between the microcystin-LR concentrations and the freshwater snail Bellamya aeruginosa fecundity or the abundance of wild freshwater snails. To further confirm the impact of eutrophication on the reproductive ability of snails, ecological mesocosm experiments were employed at four sites in Taihu lake during the algal blooming period, and no significant relationship was also found between MC-LR concentrations and snail fecundity. These results implied that eutrophication does not negatively or positive affect snail fecundity in Taihu Lake, a typical eutrophication lake in China.}, journal={Environmental Toxicology and Pharmacology}, publisher={Elsevier BV}, author={Qiao, Fei and Lei, Kun and Han, Xuemei and Wei, Zhanliang and Zhao, Xingru and An, Lihui and LeBlanc, Gerald A.}, year={2018}, month={Jun}, pages={165–168} }
 @article{kakaley_wang_leblanc_2017, title={Agonist-mediated assembly of the crustacean methyl farnesoate receptor}, volume={7}, ISSN={2045-2322}, url={http://dx.doi.org/10.1038/srep45071}, DOI={10.1038/srep45071}, abstractNote={The methyl farnesoate receptor (MfR) orchestrates aspects of reproduction and development such as male sex determination in branchiopod crustaceans. Phenotypic endpoints regulated by the receptor have been well-documented, but molecular interactions involved in receptor activation remain elusive. We hypothesized that the MfR subunits, methoprene-tolerant transcription factor (Met) and steroid receptor coactivator (SRC), would be expressed coincident with the timing of sex programming of developing oocytes by methyl farnesoate in daphnids. We also hypothesized that methyl farnesoate activates MfR assembly. Met mRNA was expressed rhythmically during the reproductive cycle, with peak mRNA accumulation just prior period of oocytes programming of sex. Further, we revealed evidence that Met proteins self-associate in the absence of methyl farnesoate, and that the presence of methyl farnesoate stimulates dissociation of Met multimers with subsequent association with SRC. Results demonstrated that the Met subunit is highly dynamic in controlling the action of methyl farnesoate through temporal variation in its expression and availability for receptor assembly.}, number={1}, journal={Scientific Reports}, publisher={Springer Science and Business Media LLC}, author={Kakaley, Elizabeth K. Medlock and Wang, Helen Y. and LeBlanc, Gerald A.}, year={2017}, month={Mar} }
 @article{medlock kakaley_eytcheson_leblanc_2017, title={Ligand-Mediated Receptor Assembly as an End Point for High-Throughput Chemical Toxicity Screening}, volume={51}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/acs.est.7b02882}, DOI={10.1021/acs.est.7b02882}, abstractNote={The high throughput screening of chemicals for interaction with intracellular targets is gaining prominence in the toxicity evaluation of environmental chemicals. We describe ligand-mediated receptor assembly as an early event in receptor signaling and its application to the screening of chemicals for interaction with targeted receptors. We utilized bioluminescence resonance energy transfer (BRET) to detect and quantify assembly of the methyl farnesoate receptor (MfR) in response to various high-production volume and other chemicals. The hormone methyl farnesoate binds to the MfR to regulate various aspects of reproduction and development in crustaceans. The MfR protein subunits Met and SRC, cloned from Daphnia pulex, were fused to the fluorophore, mAmetrine and the photon generator, Rluc2, respectively. Ligand-mediated receptor assembly was measured by photon transfer from the photon donor to the fluorophore resulting in fluorescence emission. Overall, the BRET assay had comparable or greater sensitivity as compared to a traditional reporter gene assay. Further, chemicals that screened positive in the BRET assay also stimulated phenotypic outcomes in daphnids that result from MfR signaling. We concluded the BRET assay is an accurate, sensitive, and cost/time efficient alternative to traditional screening assays.}, number={16}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Medlock Kakaley, Elizabeth K. and Eytcheson, Stephanie A. and LeBlanc, Gerald A.}, year={2017}, month={Jul}, pages={9327–9333} }
 @article{lei_qiao_liu_wei_an_qi_cui_leblanc_2017, title={Preliminary evidence for snail deformation from a Eutrophic lake}, volume={53}, ISSN={["1872-7077"]}, DOI={10.1016/j.etap.2017.06.019}, abstractNote={The incidence of deformities in snails Bellamya aeruginosa was investigated in a typical eutrophicated lake – Taihu Lake. A total of 15 105 specimens were collected, and 0.18–0.93% of the snails exhibited abnormal tentacle bifurcations. Abnormally developed snails were all female and were found in regions with relatively high Chlorophyll a levels (12.40 ± 7.23 μg/L). As tentacles are sexually dimorphic in B. aeruginosa, we postulated that factors associated with eutrophication might be responsible for the partial masculinization of tentacles in females. Differential gene expression analyses revealed that a number of unigenes were significantly up-regulated or down-regulated in snails sampled from three locations having high Chlorophyll a levels compared with snails sampled from the region with lower Chlorophyll a level (2.95 μg/L). Thus, transcriptomic profiling revealed potential molecular signal of eutrophication that can lead to developmental abnormalities in this species.}, journal={ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY}, author={Lei, Kun and Qiao, Fei and Liu, Qing and Wei, Zhanliang and An, Lihui and Qi, Hongli and Cui, Song and LeBlanc, Gerald A.}, year={2017}, month={Jul}, pages={219–226} }
 @misc{le blanc_2017, place={Raleigh, NC}, title={The value of science is reflected in your everyday decisions}, url={https://news.ncsu.edu/2017/03/the-value-of-science-leblanc-2017/}, journal={The Abstract}, publisher={North Carolina State University}, author={Le Blanc, G.A}, year={2017}, month={Mar} }
 @article{barata_campos_rivetti_leblanc_eytcheson_mcknight_tobor-kaplon_de vries buitenweg_choi_choi_et al._2017, title={Validation of a two-generational reproduction test in Daphnia magna: An interlaboratory exercise}, volume={579}, ISSN={0048-9697}, url={http://dx.doi.org/10.1016/J.SCITOTENV.2016.11.066}, DOI={10.1016/J.SCITOTENV.2016.11.066}, abstractNote={Effects observed within one generation disregard potential detrimental effects that may appear across generations. Previously we have developed a two generation Daphnia magna reproduction test using the OECD TG 211 protocol with a few amendments, including initiating the second generation with third brood neonates produced from first generation individuals. Here we showed the results of an inter-laboratory calibration exercise among 12 partners that aimed to test the robustness and consistency of a two generation Daphnia magna reproduction test. Pyperonyl butoxide (PBO) was used as a test compound. Following experiments, PBO residues were determined by TQD-LC/MS/MS. Chemical analysis denoted minor deviations of measured PBO concentrations in freshly prepared and old test solutions and between real and nominal concentrations in all labs. Other test conditions (water, food, D. magna clone, type of test vessel) varied across partners as allowed in the OECD test guidelines. Cumulative fecundity and intrinsic population growth rates (r) were used to estimate "No observed effect concentrations "NOEC using the solvent control as the control treatment. EC10 and EC-50 values were obtained regression analyses. Eleven of the twelve labs succeeded in meeting the OECD criteria of producing >60 offspring per female in control treatments during 21days in each of the two consecutive generations. Analysis of variance partitioning of cumulative fecundity indicated a relatively good performance of most labs with most of the variance accounted for by PBO (56.4%) and PBO by interlaboratory interactions (20.2%), with multigenerational effects within and across PBO concentrations explaining about 6% of the variance. EC50 values for reproduction and population growth rates were on average 16.6 and 20.8% lower among second generation individuals, respectively. In summary these results suggest that the proposed assay is reproducible but cumulative toxicity in the second generation cannot reliably be detected with this assay.}, journal={Science of The Total Environment}, publisher={Elsevier BV}, author={Barata, Carlos and Campos, Bruno and Rivetti, Claudia and LeBlanc, Gerald A. and Eytcheson, Stephanie and McKnight, Stephanie and Tobor-Kaplon, Marysia and de Vries Buitenweg, Selinda and Choi, Suhyon and Choi, Jinhee and et al.}, year={2017}, month={Feb}, pages={1073–1083} }
 @article{barata_campos_rivetti_leblanc_eytcheson_mcknight_tobor-kaplon_buitenweg_choi_choi_et al._2017, title={Validation of a two-generational reproduction test in Daphnia magna: an interlaboratory exercise}, volume={579}, journal={Science of the Total Environment}, author={Barata, C. and Campos, B. and Rivetti, C. and LeBlanc, G.A. and Eytcheson, S. and McKnight, S. and Tobor-Kaplon, M. and Buitenweg, S.D. and Choi, S. and Choi, J. and et al.}, year={2017}, pages={1073–1083} }
 @article{le blanc_2016, title={Differential Interactions of the Flame Retardant Triphenyl Phosphate within the PPAR Signaling Network}, volume={2}, ISSN={2379-6294}, url={http://dx.doi.org/10.15406/mojt.2016.02.00039}, DOI={10.15406/mojt.2016.02.00039}, number={3}, journal={MOJ Toxicology}, publisher={MedCrave Group, LLC}, author={Le Blanc, Gerald A}, year={2016}, month={Dec} }
 @article{leblanc_2016, title={Retrospective: Acute Toxicity of Priority Pollutants}, volume={97}, ISSN={0007-4861 1432-0800}, url={http://dx.doi.org/10.1007/s00128-016-1859-7}, DOI={10.1007/s00128-016-1859-7}, number={3}, journal={Bulletin of Environmental Contamination and Toxicology}, publisher={Springer Nature}, author={LeBlanc, Gerald A.}, year={2016}, month={Jun}, pages={301–302} }
 @misc{wilson_leblanc_kullman_crofton_schmieder_jacobs_2016, title={Where do we go from here: Challenges and the future of endocrine disrupting compound screening and testing}, url={http://dx.doi.org/10.7287/peerj.preprints.2605v1}, DOI={10.7287/peerj.preprints.2605v1}, abstractNote={Worldwide concern about the impacts of endocrine disrupting compounds on both human and environmental health has led to implementation of multiple screening and testing programs. In most cases these programs have focused on impacts to the estrogen, androgen and thyroid hormone (EAT) signaling pathways. The goal of the presentations in session five of the Society of Environmental Toxicology and Chemistry (SETAC) North America Focused Topic Meeting: Endocrine Disruption (February 4 – 6, 2014) was to discuss moving beyond EAT pathways to address current challenges and identify future approaches for the expansion of screening and testing programs. The session was chaired by Drs. Gerald A. LeBlanc and Vickie S. Wilson and included five presentations. Dr. Gerald A. LeBlanc provided insight on non-EAT endocrine targets that are known to be susceptible to endocrine disrupting compounds. Dr. Seth Kullman gave an overview of emerging technologies that hold promise for the screening of chemicals for interaction with EAT and other endocrine pathways. These were followed by two presentations on the current status and future promise of computational (Dr. Kevin Crofton) and in silico (Dr. Patricia Schmieder) approaches for screening and ranking chemicals for endocrine activity. Dr. Miriam Jacobs culminated the session with an overview of the current understanding of the role of epigenetics in endocrine regulation and approaches for evaluating chemicals for their ability to disrupt the epigenetic regulation of endocrine processes.}, publisher={PeerJ}, author={Wilson, Vickie S and LeBlanc, Gerald A and Kullman, Seth and Crofton, Kevin and Schmieder, Patricia and Jacobs, Miriam N}, year={2016}, month={Nov} }
 @article{adoteye_banks_flores_leblanc_2015, title={Estimation of time-varying mortality rates using continuous models for Daphnia magna}, volume={44}, ISSN={["1873-5452"]}, DOI={10.1016/j.aml.2014.12.014}, abstractNote={Structured population models that make the assumption of constant demographic rates do not accurately describe the complex life histories seen in many species. We investigated the accuracy of using constant versus time-varying mortality rates within discrete and continuously structured models for Daphnia magna. We tested the accuracy of the models we considered using density-independent survival data for 90 daphnids. We found that a continuous differential equation model with a time-varying mortality rate was the most accurate model for describing our experimental D. magna survival data. Our results suggest that differential equation models with variable parameters are an accurate tool for estimating mortality rates in biological scenarios in which mortality might vary significantly with age.}, journal={APPLIED MATHEMATICS LETTERS}, author={Adoteye, Kaska and Banks, H. T. and Flores, Kevin B. and LeBlanc, Gerald A.}, year={2015}, month={Jun}, pages={12–16} }
 @misc{leblanc_medlock_2015, title={Males on demand: the environmental-neuro-endocrine control of male sex determination in daphnids}, volume={282}, ISSN={["1742-4658"]}, DOI={10.1111/febs.13393}, abstractNote={Branchiopod crustaceans (e.g., Daphnia sp.) and some other taxa utilize both asexual and sexual reproduction to maximize population sustainability. The decision to switch from asexual to sexual reproduction is triggered by environmental cues that foretell a potentially detrimental change in environmental conditions. This review describes the cascade of events beginning with environmental cues and ending with changes in gene expression that dictate male sex determination in daphnids, the initial event in the switch to sexual reproduction. Several environmental cues have been identified which, either in isolation or in combination, stimulate male sex determination. These cues are typically associated with change of season, exhaustion of resources or loss of habitat. Maternal daphnids receive and respond to these cues, we propose, through the secretion of neuropeptides, which suppress (hyperglycemic hormone-like neuropeptides, allatostatin) or stimulate (allatotropin) the male sex differentiation program. In response, maternal daphnids produce the male sex-determining hormone, methyl farnesoate. Methyl farnesoate binds to a protein MET that dimerizes with the protein SRC forming an active transcription factor. This complex then regulates the expression of genes, primarily doublesex (dsx), involved in programming the single-celled embryo to develop into a male. In the absence of methyl farnesoate programming, the embryo develops into a female. Epigenetic modifications of the genome as a possible mode of methyl farnesoate action and the utility of this model to decipher the role of epigenetics in sex differentiation in other species are discussed.}, number={21}, journal={FEBS JOURNAL}, author={LeBlanc, Gerald A. and Medlock, Elizabeth K.}, year={2015}, month={Nov}, pages={4080–4093} }
 @article{mihaich_erler_le blanc_gallagher_2015, title={Short-term fish reproduction assays with methyl tertiary butyl ether with zebrafish and fathead minnow: Implications for evaluation of potential for endocrine activity}, volume={34}, ISSN={0730-7268}, url={http://dx.doi.org/10.1002/etc.3017}, DOI={10.1002/etc.3017}, abstractNote={Abstract The authors report on short‐term fish reproduction assays in zebrafish and fathead minnow conducted to examine the potential for methyl tertiary butyl ether (MTBE) to cause effects on the endocrine system. Both studies were performed under good laboratory practice and in accordance with Organisation for Economic Co‐operation and Development and US Environmental Protection Agency test guidelines. The results of the first study demonstrated that exposure to a high test concentration (147 mg/L) of MTBE impaired reproductive output of female zebrafish, evident by a reduction in fecundity. Based on the endpoints evaluated in the present study however, there was no supporting evidence to indicate that this effect was caused by disruption of or interaction with the endocrine system. In the second study, fathead minnows exposed to a wider but lower range of test concentrations showed no effects on any reproductive parameter of male or female fish, at the maximum recommended testing concentration of 100 mg/L (62 mg/L measured). The results of these 2 guideline studies indicate that MTBE does not interact with the hypothalamic–pituitary–gonadal axis of zebrafish or fathead minnow. Environ Toxicol Chem 2015;34:2013–2022. © 2015 The Authors. Published by Wiley Periodicals, Inc. on behalf of SETAC.}, number={9}, journal={Environmental Toxicology and Chemistry}, publisher={Wiley}, author={Mihaich, Ellen and Erler, Steffen and Le Blanc, Gerald and Gallagher, Sean}, year={2015}, month={Aug}, pages={2013–2022} }
 @article{adoteye_banks_cross_eytcheson_flores_leblanc_nguyen_ross_smith_stemkovski_et al._2015, title={Statistical validation of structured population models for Daphnia magna}, volume={266}, ISSN={0025-5564}, url={http://dx.doi.org/10.1016/j.mbs.2015.06.003}, DOI={10.1016/j.mbs.2015.06.003}, abstractNote={In this study we use statistical validation techniques to verify density-dependent mechanisms hypothesized for populations of Daphnia magna. We develop structured population models that exemplify specific mechanisms and use multi-scale experimental data in order to test their importance. We show that fecundity and survival rates are affected by both time-varying density-independent factors, such as age, and density-dependent factors, such as competition. We perform uncertainty analysis and show that our parameters are estimated with a high degree of confidence. Furthermore, we perform a sensitivity analysis to understand how changes in fecundity and survival rates affect population size and age-structure.}, journal={Mathematical Biosciences}, publisher={Elsevier BV}, author={Adoteye, Kaska and Banks, H.T. and Cross, Karissa and Eytcheson, Stephanie and Flores, Kevin B. and LeBlanc, Gerald A. and Nguyen, Timothy and Ross, Chelsea and Smith, Emmaline and Stemkovski, Michael and et al.}, year={2015}, month={Aug}, pages={73–84} }
 @article{dennis_leblanc_beckerman_2014, title={Endocrine regulation of predator-induced phenotypic plasticity}, volume={176}, ISSN={0029-8549 1432-1939}, url={http://dx.doi.org/10.1007/s00442-014-3102-8}, DOI={10.1007/s00442-014-3102-8}, abstractNote={Elucidating the developmental and genetic control of phenotypic plasticity remains a central agenda in evolutionary ecology. Here, we investigate the physiological regulation of phenotypic plasticity induced by another organism, specifically predator-induced phenotypic plasticity in the model ecological and evolutionary organism Daphnia pulex. Our research centres on using molecular tools to test among alternative mechanisms of developmental control tied to hormone titres, receptors and their timing in the life cycle. First, we synthesize detail about predator-induced defenses and the physiological regulation of arthropod somatic growth and morphology, leading to a clear prediction that morphological defences are regulated by juvenile hormone and life-history plasticity by ecdysone and juvenile hormone. We then show how a small network of genes can differentiate phenotype expression between the two primary developmental control pathways in arthropods: juvenoid and ecdysteroid hormone signalling. Then, by applying an experimental gradient of predation risk, we show dose-dependent gene expression linking predator-induced plasticity to the juvenoid hormone pathway. Our data support three conclusions: (1) the juvenoid signalling pathway regulates predator-induced phenotypic plasticity; (2) the hormone titre (ligand), rather than receptor, regulates predator-induced developmental plasticity; (3) evolution has favoured the harnessing of a major, highly conserved endocrine pathway in arthropod development to regulate the response to cues about changing environments (risk) from another organism (predator).}, number={3}, journal={Oecologia}, publisher={Springer Science and Business Media LLC}, author={Dennis, Stuart R. and LeBlanc, Gerald A. and Beckerman, Andrew P.}, year={2014}, month={Oct}, pages={625–635} }
 @article{lei_liu_an_luo_leblanc_2014, title={Estrogen alters the profile of the transcriptome in river snail Bellamya aeruginosa}, volume={24}, ISSN={0963-9292 1573-3017}, url={http://dx.doi.org/10.1007/s10646-014-1381-9}, DOI={10.1007/s10646-014-1381-9}, number={2}, journal={Ecotoxicology}, publisher={Springer Science and Business Media LLC}, author={Lei, Kun and Liu, Ruizhi and An, Li-hui and Luo, Ying-feng and LeBlanc, Gerald A.}, year={2014}, month={Nov}, pages={330–338} }
 @article{leblanc_wang_holmes_kwon_medlock_2013, title={A Transgenerational Endocrine Signaling Pathway in Crustacea}, volume={8}, ISSN={1932-6203}, url={http://dx.doi.org/10.1371/journal.pone.0061715}, DOI={10.1371/journal.pone.0061715}, abstractNote={Environmental signals to maternal organisms can result in developmental alterations in progeny. One such example is environmental sex determination in Branchiopod crustaceans. We previously demonstrated that the hormone methyl farnesoate could orchestrate environmental sex determination in the early embryo to the male phenotype. Presently, we identify a transcription factor that is activated by methyl farnesoate and explore the extent and significance of this transgenerational signaling pathway.Several candidate transcription factors were cloned from the water flea Daphnia pulex and evaluated for activation by methyl farnesoate. One of the factors evaluated, the complex of two bHLH-PAS proteins, dappuMet and SRC, activated a reporter gene in response to methyl farnesoate. Several juvenoid compounds were definitively evaluated for their ability to activate this receptor complex (methyl farnesoate receptor, MfR) in vitro and stimulate male sex determination in vivo. Potency to activate the MfR correlated to potency to stimulate male sex determination of offspring (pyriproxyfen>methyl farnesoate>methoprene, kinoprene). Daphnids were exposed to concentrations of pyriproxyfen and physiologic responses determined over multiple generations. Survivial, growth, and sex of maternal organisms were not affected by pyriproxyfen exposure. Sex ratio among offspring (generation 2) were increasingly skewed in favor of males with increasing pyriproxyfen concentration; while, the number of offspring per brood was progressively reduced. Female generation 2 daphnids were reared to reproductive maturity in the absence of pyriproxyfen. Sex ratios of offspring (generation 3) were not affected in this pyriproxyfen lineage, however, the number of offspring per brood, again, was significantly reduced.Results reveal likely components to a hormone/receptor signaling pathway in a crustacean that orchestrates transgenerational modifications to important population metrics (sex ratios, fecundity of females). A model is provided that describes how these signaling processes can facilitate population sustainability under normal conditions or threaten sustainability when perturbed by environmental chemicals.}, number={4}, journal={PLoS ONE}, publisher={Public Library of Science (PLoS)}, author={LeBlanc, Gerald A. and Wang, Ying H. and Holmes, Charisse N. and Kwon, Gwijun and Medlock, Elizabeth K.}, editor={He, BinEditor}, year={2013}, month={Apr}, pages={e61715} }
 @book{le blanc_kullman_norris_baldwin_w._greally_2012, series={OECD Environment, Health and Safety Publications Series on Testing & Assessment}, title={Detailed review paper on the state of the science on novel in vitro and in vivo screening and testing methods and endpoints for evaluating endocrine disruptors}, number={178}, institution={Organization for Economic Co-operation and Development}, author={Le Blanc, G.A. and Kullman, S.W. and Norris, D.O. and Baldwin, W.S. and W., Kloas and Greally, J.M}, year={2012}, month={Aug}, collection={OECD Environment, Health and Safety Publications Series on Testing & Assessment} }
 @article{hannas_wang_thomson_kwon_li_leblanc_2011, title={Regulation and dysregulation of vitellogenin mRNA accumulation in daphnids (Daphnia magna)}, volume={101}, ISSN={["1879-1514"]}, DOI={10.1016/j.aquatox.2010.11.006}, abstractNote={The induction of vitellogenin in oviparous vertebrates has become the gold standard biomarker of exposure to estrogenic chemicals in the environment. This biomarker of estrogen exposure also has been used in arthropods, however, little is known of the factors that regulate the expression of vitellogenin in these organisms. We investigated changes in accumulation of mRNA products of the vitellogenin gene Vtg2 in daphnids (Daphnia magna) exposed to a diverse array of chemicals. We further evaluated the involvement of hormonal factors in the regulation of vitellogenin expression that may be targets of xenobiotic chemicals. Expression of the Vtg2 gene was highly responsive to exposure to various chemicals with an expression range spanning approximately four orders of magnitude. Chemicals causing the greatest induction were piperonyl butoxide, chlordane, 4-nonylphenol, cadmium, and chloroform. Among these, only 4-nonylphenol is recognized to be estrogenic. Exposure to several chemicals also suppressed Vtg2 mRNA levels, as much as 100-fold. Suppressive chemicals included cyproterone acetate, acetone, triclosan, and atrazine. Exposure to the estrogens diethylstilbestrol and bisphenol A had little effect on vitellogenin mRNA levels further substantiating that these genes are not induced by estrogen exposure. Exposure to the potent ecdysteroids 20-hydroxyecdysone and ponasterone A revealed that Vtg2 was subject to strong suppressive control by these hormones. Vtg2 mRNA levels were not significantly affected from exposure to several juvenoid hormones. Results indicate that ecdysteroids are suppressors of vitellogenin gene expression and that vitellogenin mRNA levels can be elevated or suppressed in daphnids by xenobiotics that elicit antiecdysteroidal or ecdysteroidal activity, respectively. Importantly, daphnid Vtg2 is not elevated in response to estrogenic activity.}, number={2}, journal={AQUATIC TOXICOLOGY}, author={Hannas, Bethany R. and Wang, Ying H. and Thomson, Susanne and Kwon, Gwijun and Li, Hong and LeBlanc, Gerald A.}, year={2011}, month={Jan}, pages={351–357} }
 @article{wang_kwon_li_leblanc_2011, title={Tributyltin Synergizes with 20-Hydroxyecdysone to Produce Endocrine Toxicity}, volume={123}, ISSN={["1096-0929"]}, DOI={10.1093/toxsci/kfr154}, abstractNote={One of the great challenges facing modern toxicology is in predicting the hazard associated with chemical mixtures. The development of effective means of predicting the toxicity of chemical mixtures requires an understanding of how chemicals interact to produce nonadditive outcomes (e.g., synergy). We hypothesized that tributyltin would elicit toxicity in daphnids (Daphnia magna) by exaggerating physiological responses to 20-hydroxyecdysone signaling via synergistic activation of the retinoid X receptor (RXR):ecdysteroid receptor (EcR) complex. Using reporter gene assays, we demonstrated that RXR, alone, is activated by a variety of ligands including tributyltin, whereas RXR:EcR heterodimers were not activated by tributyltin. However, tributyltin, in combination with the daphnid EcR ligand 20-hydroxyecdysone, caused concentration-dependent, synergistic activation of the RXR:EcR reporter. Electrophoretic mobility shift assays revealed that tributyltin did not enhance the activity of 20-hydroxyecdysone by increasing binding of the receptor complex to a DR-4 DNA-binding site. Exposure of daphnids to elevated concentrations of 20-hydroxyecdysone caused premature and incomplete ecdysis resulting in death. Tributyltin exaggerated this effect of exogenous 20-hydroxyecdysone. Further, exposure of daphnids to tributyltin enhanced the inductive effects of 20-hydroxyecdysone on expression of the 20-hydroxyecdysone-inducible gene HR3. Continuous, prolonged exposure of maternal daphnids to concentrations of tributyltin resulted in mortality concurrent with molting. Taken together, these results demonstrate that xenobiotics, such as tributyltin, can interact with RXR to influence gene expression regulated by the heterodimeric partner to RXR. The result of such interactions can be toxicity due to inappropriate or exaggerated hormonal signaling. The application of the in vitro/in vivo approach used in this study is discussed in relation to modeling of nonadditive interactions among constituents of chemical mixtures.}, number={1}, journal={TOXICOLOGICAL SCIENCES}, author={Wang, Ying H. and Kwon, Gwijun and Li, Hong and LeBlanc, Gerald A.}, year={2011}, month={Sep}, pages={71–79} }
 @inbook{leblanc_2010, place={Hoboken, NJ}, edition={4}, title={Acute Toxicity}, booktitle={A Textbook of Modern Toxicology}, publisher={Wiley}, author={LeBlanc, G.A}, editor={Hodgson, EEditor}, year={2010}, pages={225–236} }
 @inbook{le blanc_2010, place={Hoboken, NJ}, edition={4}, title={Elimination of Toxicants}, booktitle={A Textbook of Modern Toxicology}, publisher={Wiley}, author={Le Blanc, G.A}, editor={Hodgson, E.Editor}, year={2010}, pages={213–222} }
 @inbook{leblanc_2010, place={Hoboken, NJ}, edition={4}, title={Endocrine Toxicology}, booktitle={A Textbook of Modern Toxicology}, publisher={Wiley}, author={LeBlanc, G.A}, editor={Hodgson, EEditor}, year={2010}, pages={345–362} }
 @misc{sternberg_gooding_hotchkiss_leblanc_2010, title={Environmental-endocrine control of reproductive maturation in gastropods: implications for the mechanism of tributyltin-induced imposex in prosobranchs}, volume={19}, ISSN={["1573-3017"]}, DOI={10.1007/s10646-009-0397-z}, number={1}, journal={ECOTOXICOLOGY}, author={Sternberg, Robin M. and Gooding, Meredith P. and Hotchkiss, Andrew K. and LeBlanc, Gerald A.}, year={2010}, month={Jan}, pages={4–23} }
 @article{hannas_leblanc_2010, title={Expression and ecdysteroid responsiveness of the nuclear receptors HR3 and E75 in the crustacean Daphnia magna}, volume={315}, ISSN={["0303-7207"]}, DOI={10.1016/j.mce.2009.07.013}, abstractNote={Ecdysteroids initiate signaling along multiple pathways that regulate various aspects of development, maturation, and reproduction in arthropods. Signaling often involves the induction of downstream transcription factors that either positively or negatively regulate aspects of the pathway. We tested the hypothesis that crustaceans express the nuclear receptors HR3 (ortholog to vertebrate ROR) and E75 (ortholog to vertebrate rev-erb) in response to ecdysteroid signaling. HR3 and E75 cDNAs were cloned from the crustacean Daphnia magna. The DNA-binding domain and ligand-binding domain of the daphnid HR3 were 95% and 61% identical to those of Drosophila melanogaster. The DNA-binding domain and ligand-binding domain of the daphnid E75 were 100% and 71% identical to those of D. melanogaster. Both receptors exhibited structural characteristics of binding to DNA as a monomer. The expression of these receptor mRNAs was evaluated through the adult molt cycle and during embryo development. E75 levels were relatively constant throughout the adult molt cycle and through embryo development. HR3 levels were comparable to those of E75 during the initial phases of the adult molt cycle but were elevated approximately 30-fold at a time in the cycle co-incident with the pre-molt surge in ecdysteroid levels. HR3 mRNA levels in embryos also varied co-incident with ecdysteroid levels. To substantiate a role of ecdysteroids in the expression of HR3, daphnids were continuously exposed to 20-hydroxyecdysone and changes in gene expression were measured. HR3 levels were significantly induced by 20-hydroxyecdysone; while E75 levels were minimally affected. These results are consistent with the premise that transcription of HR3 is regulated by ecdysteroids in the crustacean D. magna and that HR3 likely serves as a mediator of ecdysteroid regulatory action in crustaceans. The marginal induction of E75 by 20-hydroxyecdysone may represent limited, tissue or cell-type-specific induction of this transcription factor.}, number={1-2}, journal={MOLECULAR AND CELLULAR ENDOCRINOLOGY}, author={Hannas, Bethany R. and LeBlanc, Gerald A.}, year={2010}, month={Feb}, pages={208–218} }
 @article{hannas_wang_baldwin_li_wallace_leblanc_2010, title={Interactions of the crustacean nuclear receptors HR3 and E75 in the regulation of gene transcription}, volume={167}, ISSN={["1095-6840"]}, DOI={10.1016/j.ygcen.2010.03.025}, abstractNote={Endocrine signal transduction occurs through cascades that involve the action of both ligand-dependent and ligand-independent nuclear receptors. In insects, two such nuclear receptors are HR3 and E75 that interact to transduce signals initiated by ecdysteroids. We have cloned these nuclear receptors from the crustacean Daphnia pulex to assess their function as regulators of gene transcription in this ecologically and economically important group of organisms. Both nuclear receptors from D. pulex (DappuHR3 (group NR1F) and DappuE75 (group NR1D)) exhibit a high degree of sequence similarity to other NR1F and NR1D group members that is indicative of monomeric binding to the RORE (retinoid orphan receptor element). DappuE75 possesses key amino acid residues required for heme binding to the ligand-binding domain. Next, we developed a gene transcription reporter assay containing a luciferase reporter gene driven by the RORE. DappuHR3, but not DappuE75, activated transcription of the luciferase gene in this system. Co-transfection experiments revealed that DappuE75 suppressed DappuHR3-dependent luciferase transcription in a dose-dependent manner. Electrophoretic mobility shift assays confirmed that DappuHR3 bound to the RORE. However, we found no evidence that DappuE75 similarly bound to the response element. These experiments further demonstrated that DappuE75 prevented DappuHR3 from binding to the response element. In conclusion, DappuHR3 functions as a transcriptional activator of genes regulated by the RORE and DappuE75 is a negative regulator of this activity. DappuE75 does not suppress the action of DappuHR3 by occupying the response element but presumably interacts directly with the DappuHR3 protein. Taken together with the previous demonstration that daphnid HR3 is highly induced by 20-hydroxyecdysone, these results support the premise that HR3 is a major component of ecdysteroid signaling in some crustaceans and is under the negative regulatory control of E75.}, number={2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Hannas, Bethany R. and Wang, Ying H. and Baldwin, William S. and Li, Yangchun and Wallace, Andrew D. and LeBlanc, Gerald A.}, year={2010}, month={Jun}, pages={268–278} }
 @article{hannas_das_li_leblanc_2010, title={Intracellular Conversion of Environmental Nitrate and Nitrite to Nitric Oxide with Resulting Developmental Toxicity to the Crustacean Daphnia magna}, volume={5}, ISSN={1932-6203}, url={http://dx.doi.org/10.1371/journal.pone.0012453}, DOI={10.1371/journal.pone.0012453}, abstractNote={Nitrate and nitrite (jointly referred to herein as NO(x)) are ubiquitous environmental contaminants to which aquatic organisms are at particularly high risk of exposure. We tested the hypothesis that NO(x) undergo intracellular conversion to the potent signaling molecule nitric oxide resulting in the disruption of endocrine-regulated processes.These experiments were performed with insect cells (Drosophila S2) and whole organisms Daphnia magna. We first evaluated the ability of cells to convert nitrate (NO(3)(-)) and nitrite (NO(2)(-)) to nitric oxide using amperometric real-time nitric oxide detection. Both NO(3)(-) and NO(2)(-) were converted to nitric oxide in a substrate concentration-dependent manner. Further, nitric oxide trapping and fluorescent visualization studies revealed that perinatal daphnids readily convert NO(2)(-) to nitric oxide. Next, daphnids were continuously exposed to concentrations of the nitric oxide-donor sodium nitroprusside (positive control) and to concentrations of NO(3)(-) and NO(2)(-). All three compounds interfered with normal embryo development and reduced daphnid fecundity. Developmental abnormalities were characteristic of those elicited by compounds that interfere with ecdysteroid signaling. However, no compelling evidence was generated to indicate that nitric oxide reduced ecdysteroid titers.Results demonstrate that nitrite elicits developmental and reproductive toxicity at environmentally relevant concentrations due likely to its intracellular conversion to nitric oxide.}, number={8}, journal={PLoS ONE}, publisher={Public Library of Science (PLoS)}, author={Hannas, Bethany R. and Das, Parikshit C. and Li, Hong and LeBlanc, Gerald A.}, editor={Pan, XiaopingEditor}, year={2010}, month={Aug}, pages={e12453} }
 @inbook{hodgson_le blanc_meyer_smart_2010, place={Hoboken, NJ}, edition={4}, title={Introduction to Biochemical and Molecular Methods in Toxicology}, ISBN={9780470462065}, booktitle={A Textbook of Modern Toxicology}, publisher={Wiley}, author={Hodgson, E. and Le Blanc, G.A. and Meyer, S.A. and Smart, R.C}, editor={Hodgson, E.Editor}, year={2010}, pages={15–28} }
 @article{thomson_baldwin_wang_kwon_leblanc_2009, title={Annotation, phylogenetics, and expression of the nuclear receptors in Daphnia pulex}, volume={10}, ISSN={1471-2164}, url={http://dx.doi.org/10.1186/1471-2164-10-500}, DOI={10.1186/1471-2164-10-500}, abstractNote={Abstract Background The nuclear receptor superfamily currently consists of seven gene subfamilies that encompass over 80 distinct receptor proteins. These transcription factors typically share a common five-domain structure with a highly conserved DNA-binding domain. Some nuclear receptors are ubiquitous among the metazoans, while others are unique to specific phylogenetic groups. Crustaceans represent the second largest group of arthropods with insects being the largest. However, relative to insects, little is known about the nuclear receptors of crustaceans. The aim of this study was to identify putative nuclear receptors from the first assembled genome of a crustacean Daphnia pulex http://wFleaBase.org . Nuclear receptor expression was evaluated and receptors were subjected to phylogenetic analyses to gain insight into evolution and function. Results Twenty-five putative nuclear receptors were identified in D. pulex based on the presence of a conserved DNA-binding domain. All of the nuclear receptor protein sequences contain a highly homologous DNA-binding domain and a less conserved ligand-binding domain with the exception of the NR0A group. These receptors lack a ligand-binding domain. Phylogenetic analysis revealed the presence of all seven receptor subfamilies. The D. pulex genome contains several nuclear receptors that have vertebrate orthologs. However, several nuclear receptor members that are represented in vertebrates are absent from D. pulex . Notable absences include receptors of the 1C group (peroxisome proliferators-activated receptors), the 3A group (estrogen receptor), and the 3C group (androgen, progestogen, mineralcorticoid, and glucocorticoid receptors). The D. pulex genome also contains nuclear receptor orthologs that are present in insects and nematodes but not vertebrates, including putative nuclear receptors within the NR0A group. A novel group of receptors, designated HR97, was identified in D. pulex that groups with the HR96/CeNHR8/48/DAF12 clade, but forms its own sub-clade. Gene products were detected in adult female D. pulex for 21 of the 25 receptors. Conclusion Nuclear receptors are ancient proteins with highly conserved DNA-binding domains. The DNA-binding domains of the nuclear receptors of D. pulex contain the same degree of conservation that is typically found within nuclear receptors of other species. Most of the receptors identified in D. pulex have orthologs within the vertebrate and invertebrate lineages examined with the exception of the novel HR97 group and the Dappu-HR10 and potentially the Dappu-HR11 receptors found in D. pulex . These groups of receptors may harbour functions that are intrinsic to crustacean physiology.}, number={1}, journal={BMC Genomics}, publisher={Springer Nature}, author={Thomson, Susanne A and Baldwin, William S and Wang, Ying H and Kwon, Gwijun and LeBlanc, Gerald A}, year={2009}, pages={500} }
 @article{wang_leblanc_2009, title={Interactions of methyl farnesoate and related compounds with a crustacean retinoid X receptor}, volume={309}, ISSN={0303-7207}, url={http://dx.doi.org/10.1016/j.mce.2009.05.016}, DOI={10.1016/j.mce.2009.05.016}, abstractNote={While a functional role for the sesquiterpenoid hormone methyl farnesoate in arthropods has been recognized for decades, the identification of a receptor that mediates the action of this hormone remains equivocal. Luciferase reporter assays were used in the present study to evaluate the ability of methyl farnesoate and other putative ligands to activate gene transcription associated with the retinoid X receptor (RXR) and RXR:EcR heterodimeric complexes from the crustacean (Daphnia magna). The daphnid RXR constructs, transfected into HepG2 cells along with the reporter construct, significantly activated luciferase gene expression in response to tributyltin indicating that the crustacean RXR is indeed ligand activated. However, RXR was not activated by methyl farnesoate or other putative RXR ligands. Cells co-transfected with the daphnid RXR and EcR produced luciferase in response to ecdysteroids and this activation was significantly enhanced when cells were also provided either methyl farnesoate or other putative RXR ligands. This synergy among RXR and EcR ligands was not dependent upon the co-activator SRC-1 and did not correlate to a physiological response of daphnids to juvenoid hormones (male sex determination). Results indicate that methyl farnesoate, along with compounds that are functionally similar to methyl farnesoate synergize with ecdysteroids to activate the RXR:EcR receptor complex. However, this effect appears to be unrelated to the ability of these compounds to stimulate male sex determination.}, number={1-2}, journal={Molecular and Cellular Endocrinology}, publisher={Elsevier BV}, author={Wang, Ying H. and LeBlanc, Gerald A.}, year={2009}, month={Oct}, pages={109–116} }
 @inbook{leblanc_2009, place={London}, edition={3}, series={Target Organ Toxicology Series}, title={Overview of Endocrine Disruptor Ecotoxicity in Wildlife}, booktitle={Endocrine Toxicology}, publisher={Informa Healthcare}, author={LeBlanc, G.A}, editor={Ethridge, C. and Stevens, J.Editors}, year={2009}, pages={280–312}, collection={Target Organ Toxicology Series} }
 @article{flippin_hedge_devito_leblanc_crofton_2009, title={Predictive Modeling of a Mixture of Thyroid Hormone Disrupting Chemicals That Affect Production and Clearance of Thyroxine}, volume={28}, ISSN={["1092-874X"]}, DOI={10.1177/1091581809341883}, abstractNote={Thyroid hormone (TH) disrupting compounds interfere with both thyroidal and extrathyroidal mechanisms to decrease circulating thyroxine (T 4 ). This research tested the hypothesis that serum T 4 concentrations of rodents exposed to a mixture of both TH synthesis inhibitors (pesticides) and stimulators of T 4 clearance in the liver (polyhalogenated aromatic hydrocarbons, PHAHs) could be best predicted by an integrated addition model. Female Long-Evans rats, 23 days of age, were dosed with dilutions of a mixture of 18 PHAHs (2 dioxins, 4 dibenzofurans, and 12 PCBs, including dioxin-like and non-dioxin like PCBs) and a mixture of 3 pesticides (thiram, pronamide, and mancozeb) for four consecutive days. Serum was collected 24 hours after the last exposure and T 4 concentrations were measured by radioimmunoassay. Animals exposed to the highest dose of the mixture experienced a 45% decrease in serum T 4 . Three additivity model predictions (dose addition, effect addition, and integrated addition) were generated based on single chemical data, and the results were compared. Effect addition overestimated the effect produced by the combination of all 21 chemicals. The results of the dose- and integrated-addition models were similar, and both provided better predictions than the effect-addition model. These results support the use of dose- and integrated additivity models in predicting the effects of complex mixtures.}, number={5}, journal={INTERNATIONAL JOURNAL OF TOXICOLOGY}, author={Flippin, J. L. and Hedge, J. M. and DeVito, M. J. and LeBlanc, G. A. and Crofton, K. M.}, year={2009}, month={Sep}, pages={368–381} }
 @article{hotchkiss_sternberg_leblanc_2008, title={Environmental cues trigger seasonal regression of primary and accessory sex organs of the mud snail, Ilyanassa obsoleta}, volume={74}, ISSN={["0260-1230"]}, DOI={10.1093/mollus/eyn009}, journal={JOURNAL OF MOLLUSCAN STUDIES}, author={Hotchkiss, Andrew K. and Sternberg, Robin M. and LeBlanc, Gerald A.}, year={2008}, month={Aug}, pages={301–303} }
 @inbook{leblanc_2008, place={Hoboken, New Jersey}, edition={4}, title={Immunochemical Techniques in Toxicology}, booktitle={Molecular and Biochemical Toxicology}, publisher={John Wiley & Sons}, author={LeBlanc, G.A}, editor={Hodgson, E. and Smart, R.CEditors}, year={2008}, pages={109–128} }
 @article{sternberg_hotchkiss_leblanc_2008, title={Synchronized expression of retinoid X receptor mRNA with reproductive tract recrudescence in an imposex-susceptible mollusc}, volume={42}, ISSN={["1520-5851"]}, DOI={10.1021/es702381g}, abstractNote={The biocide tributyltin (TBT) causes the development of male sex characteristics in females of some molluscan species, a phenomenon known as imposex. Recent evidence suggests that the retinoid X receptor (RXR) participates in TBT-induced imposex. Accordingly, we hypothesized that RXR may contribute to the seasonal development of the male reproductive tract in molluscs and would be expressed in concert with this phenomenon. RXR was cloned and sequenced from an imposex-susceptble species, the eastern mud snail Ilyanassa obsoleta. The DNA-binding domain of the receptor protein was 100 and 97% identical to those of the rock shell Thais clavigera and the freshwater snail Biomphalaria glabrata. The ligand-binding domain was 93 and 92% identicalto the LBD of these two molluscan species, respectively. Phylogenetic analyses revealed that RXR is an ancient nuclear receptor whose origin predates the emergence of the Bilateria. Interestingly, though inexplicably, the molluscan RXRs were more similar to sequences of vertebrate RXRs than to the RXRs of other lophotrochozoan invertebrates. Next, the expression of RXR mRNA levels in the reproductive tract was determined through the reproductive cycle. RXR mRNA levels increased commensurate with reproductive tract recrudescence in both sexes. However, the timing of coordinate recrudescence-RXR expression differed between sexes. Results demonstrate that RXR expression is associated with reproductive tract recrudescence in both sexes; although, the timing of recrudescence may dictate sex-specific development. Retinoid signaling initiated by TBT during an inappropriate time in females may result in imposex.}, number={4}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Sternberg, Robin M. and Hotchkiss, Andrew K. and Leblanc, Gerald A.}, year={2008}, month={Feb}, pages={1345–1351} }
 @article{sternberg_hotchkiss_leblanc_2008, title={The contribution of steroidal androgens and estrogens to reproductive maturation of the eastern mud snail Ilyanassa obsoleta}, volume={156}, ISSN={["1095-6840"]}, DOI={10.1016/j.ygcen.2007.12.002}, abstractNote={Molluscs exposed to endocrine-disrupting chemicals (EDCs) have exhibited changes in reproductive tract development that are typically associated with androgen or estrogen signaling in vertebrates. However, a role for androgens and estrogens in molluscan reproductive endocrinology has yet to be established. In this study, we investigated putative roles for steroidal androgens and estrogens in recrudescence of the eastern mud snail Ilyanassa obsoleta. Our objectives were to: (1) identify associations among concentrations of testosterone and 17beta-estradiol, sex, and reproductive status in mud snails that suggest these hormones are involved in recrudescence; and (2) determine whether mud snails express NR3C4-like (androgen receptor) and NR3A-like (estrogen receptor) mRNAs in a manner indicative of a role in recrudescence. Temporal changes in testosterone levels in males were consistent with a positive role in recrudescence. Such a trend was not evident in females or for 17beta-estradiol in either sex. Efforts to identify an androgen receptor from the mud snail using targeted, degenerate RT-PCR were unsuccessful. However, an estrogen receptor (ER) cDNA was identified that is highly similar to known ERs of other molluscs. Studies with the ER of other molluscs have shown that this protein does not actually bind estrogens. We therefore considered the possibility that the mud snail ER may regulate reproductive maturation as a ligand-independent transcription factor based upon its tissue abundance. Males expressed greater levels of ER mRNA than did females over the entire reproductive cycle, and this difference was most evident during recrudescence. ER mRNA levels were significantly elevated during recrudescence in males but not females. In conclusion, testosterone may have a role in male reproductive tract recrudescence; however, this putative activity is independent of a NR3C4-type androgen receptor. The ER also may function in male recrudescence, though apparently independent of 17beta-estradiol. The retinoid signaling pathway is discussed as a possible alternative hormone/receptor-mediated signaling pathway that regulates male recrudescence.}, number={1}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Sternberg, Robin M. and Hotchkiss, Andrew K. and LeBlanc, Gerald A.}, year={2008}, month={Mar}, pages={15–26} }
 @misc{crain_eriksen_iguchi_jobling_laufer_leblanc_guillette_2007, title={An ecological assessment of bisphenol-A: Evidence from comparative biology}, volume={24}, ISSN={["1873-1708"]}, DOI={10.1016/j.reprotox.2007.05.008}, abstractNote={This review assesses the effects of environmental concentrations of bisphenol-A (BPA) on wildlife. Water concentrations of BPA vary tremendously due to proximity to point and non-point sources, but reported concentrations in stream/river water samples are less than 21 microg/L, and concentrations in landfill leacheate are less than 17.2mg/L. Extensive evidence indicates that BPA induces feminization during gonadal ontogeny of fishes, reptiles, and birds, but in all cases the amount of BPA necessary to cause such ontogenetic disruption exceeds concentrations in the environment. Extensive evidence also exists that adult exposure to environmental concentrations of BPA is detrimental to spermatogenetic endpoints and stimulates vitellogenin synthesis in model species of fish. Most of the reported effects of BPA on vertebrate wildlife species can be attributed to BPA acting as an estrogen receptor agonist, but mechanisms of disruption in invertebrates are less certain. A comparison of measured BPA environmental concentrations with chronic values suggests that no significant margin of safety exists for the protection of aquatic communities against the toxicity of BPA. Further studies should examine the most vulnerable vertebrate and invertebrate species.}, number={2}, journal={REPRODUCTIVE TOXICOLOGY}, author={Crain, D. Andrew and Eriksen, Marcus and Iguchi, Taisen and Jobling, Susan and Laufer, Hans and LeBlanc, Gerald A. and Guillette, Louis J., Jr.}, year={2007}, pages={225–239} }
 @article{vom saal_akingbemi_belcher_birnbaum_crain_eriksen_farabollini_guillette_hauser_heindel_et al._2007, title={Chapel Hill bisphenol A expert panel consensus statement: Integration of mechanisms, effects in animals and potential to impact human health at current levels of exposure}, volume={24}, ISSN={0890-6238}, url={http://dx.doi.org/10.1016/j.reprotox.2007.07.005}, DOI={10.1016/j.reprotox.2007.07.005}, abstractNote={Existing cross-sectional studies indicated a positive association of bisphenol A (BPA) with overweight and obesity. However, the relationship and potential mechanisms underlying this association remain to be elucidated in prospective studies.This study was designed to investigate whether serum BPA is associated with incident overweight and obesity risk, and to further explore whether adiponectin plays a mediating role in the association.We measured blood BPA and adiponectin in Chinese populations. The association of serum BPA with overweight and obesity risk was evaluated using multivariable logistic regression models. We further examined the mediating effect of adiponectin by causal mediation analysis.Among 796 participants free of overweight and obesity at baseline, 133 individuals developed overweight and obesity during the follow-up period. Compared with those in the lowest quartile of serum BPA, those in the second and third quartiles were positively associated with incident overweight and obesity risk adjusting for covariates (all P-values < 0.05), whereas this association was not observed in the fourth quartile. Further spline analysis showed an inverted U-shaped dose-response relationship (Pnon-linear = 0.04). Furthermore, each unit of serum log10-transformed BPA levels was associated with higher changes in waist-to-height ratio and body roundness index (all P-values < 0.05). Mediation analysis indicated significant indirect effects of adiponectin on the associations of BPA with overweight and obesity prevalence (mediation proportion: 46.08%; P = 0.02), and BMI levels (mediation proportion: 30.32%; P = 0.03).Serum BPA displayed a positive association with incident overweight and obesity risk in a non-monotonic pattern, and adiponectin might mediate the association. Further mechanistic studies are warranted.}, number={2}, journal={Reproductive Toxicology}, publisher={Elsevier BV}, author={vom Saal, Frederick S. and Akingbemi, Benson T. and Belcher, Scott M. and Birnbaum, Linda S. and Crain, D. Andrew and Eriksen, Marcus and Farabollini, Francesca and Guillette, Louis J., Jr. and Hauser, Russ and Heindel, Jerrold J. and et al.}, year={2007}, month={Aug}, pages={131–138} }
 @misc{chapel hill bisphenol a expert panel consensus statement: integration of mechanisms, effects in animals and potential to impact human health at current levels of exposure_2007, volume={24}, number={2}, journal={Reproductive Toxicology (Elmsford, N.Y.)}, year={2007}, pages={131–138} }
 @article{wang_wang_leblanc_2007, title={Cloning and characterization of the retinoid X receptor from a primitive crustacean Daphnia magna}, volume={150}, ISSN={["0016-6480"]}, DOI={10.1016/j.ygcen.2006.08.002}, abstractNote={Terpenoid hormones function as morphogens throughout the animal kingdom and many of these activities are mediated through members of the retinoid X group of nuclear receptors (RXR; NR2B). In the present study, RXR was cloned from the water flea Daphnia magna, a primitive crustacean of the class Branchiopoda, and characterized with respect to phylogeny, developmental expression, and hormonal regulation. The full length daphnid RXR cDNA was cloned by initial PCR amplification of a cDNA fragment from the highly conserved DNA-binding domain followed by extension of the fragment using RACE PCR. The full length cDNA was 1888 base pairs in length and coded for a 400 amino acid protein that exhibited the five-domain structure of a nuclear receptor superfamily member. The RXR protein shared significant identity with other NR2B group members. Phylogenetic analyses of the ligand-binding domain of the receptor revealed that daphnid RXR clustered with RXR from decapod crustaceans on a branch of the phylogenetic tree that was distinct from RXRs known to bind retinoic acids and juvenile hormones. Daphnid RXR mRNA levels were greatest in embryos that were early in development and progressively declined through the initial five stages of embryo development. Adult females expressed higher levels of RXR mRNA than did males and exposure of females to the terpenoid mimic pyriproxyfen reduced RXR mRNA to levels approaching levels in males. RXR mRNA levels in males were refractory to pyriproxyfen. These results show that branchiopod crustaceans dynamically express RXR which should be evaluated as a candidate receptor for the terpenoid hormone methyl farnesoate which functions as a sex determinant in these organisms.}, number={2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Wang, Ying H. and Wang, Guirong and LeBlanc, Gerald A.}, year={2007}, month={Jan}, pages={309–318} }
 @misc{leblanc_2007, title={Crustacean endocrine toxicology: a review}, volume={16}, ISSN={["1573-3017"]}, DOI={10.1007/s10646-006-0115-z}, number={1}, journal={ECOTOXICOLOGY}, author={LeBlanc, Gerald A.}, year={2007}, month={Feb}, pages={61–81} }
 @article{blystone_furr_lambright_howdeshell_ryan_wilson_leblanc_gray_2007, title={Prochloraz inhibits testosterone production at dosages below those that affect androgen-dependent organ weights or the onset of puberty in the male Sprague Dawley rat}, volume={97}, ISSN={["1096-0929"]}, DOI={10.1093/toxsci/kfm004}, abstractNote={Prochloraz (PCZ) is an imidazole fungicide that inhibits gonadal steroidogenesis and antagonizes the androgen receptor (AR). We hypothesized that pubertal exposure to PCZ would reduce testosterone production and delay male rat reproductive development. Sprague Dawley rats were dosed by gavage with 0, 31.3, 62.5, or 125 mg/kg/day of PCZ from postnatal day (PND) 23 to 42 or 51. There was a significant delay in preputial separation (PPS) at 125 mg/kg/day PCZ and several of the androgen-dependent organ weights were decreased significantly, but the significant organ weight effects were not consistent between the 2 necropsies (PND 42 vs. 51). At both ages, serum testosterone levels and ex vivo testosterone release from the testis were significantly decreased whereas serum progesterone and 17α-hydroxyprogesterone levels were significantly increased at dose levels below those that affected PPS or reproductive organ weights. The hormone results suggested that PCZ was inhibiting CYP17 activity. In a second pubertal study (0, 3.9, 7.8, 15.6, 31.3, or 62.5 mg/kg/day PCZ), serum testosterone levels and ex vivo testosterone production were significantly reduced at 15.6 mg/kg/day PCZ. In order to examine the AR antagonism effects of PCZ, independent of its effects on testosterone synthesis, castrated immature male rats were dosed with androgen and 0, 15.6, 31.3, 62.5, or 125 mg/kg/day PCZ for 10–11 days (Hershberger assay). In this assay, androgen-sensitive organ weights were only significantly decreased at 125 mg/kg/day PCZ. These data from the pubertal assays demonstrate that PCZ decreases testosterone levels and delays rat pubertal development, as hypothesized. However, the fact that hormone levels were affected at dosage eightfold below that which delayed the onset of puberty suggests that rather large reductions in serum testosterone may be required to delay puberty and consistently reduce androgen-dependent tissue weights.}, number={1}, journal={TOXICOLOGICAL SCIENCES}, author={Blystone, Chad R. and Furr, Johnathan and Lambright, Christy S. and Howdeshell, Kembra L. and Ryan, Bryce C. and Wilson, Vickie S. and LeBlanc, Gerald A. and Gray, Leon Earl, Jr.}, year={2007}, month={May}, pages={65–74} }
 @article{blystone_lambright_howdeshell_furr_sternberg_butterworth_durhan_makynen_ankley_wilson_et al._2007, title={Sensitivity of fetal rat testicular steroidogenesis to maternal prochloraz exposure and the underlying mechanism of inhibition}, volume={97}, ISSN={["1096-6080"]}, DOI={10.1093/toxsci/kfm055}, abstractNote={The fungicide prochloraz (PCZ) induces malformations in androgen-dependent tissues in male rats when administered during sex differentiation. The sensitivity of fetal testicular steroidogenesis to PCZ was investigated to test the hypothesis that the reported morphological effects from maternal exposure were associated with reduced testosterone synthesis. Pregnant Sprague-Dawley rats were dosed by gavage with 0, 7.8, 15.6, 31.3, 62.5, and 125 mg PCZ/kg/day (n = 8) from gestational day (GD) 14 to 18. On GD 18, the effects of PCZ on fetal steroidogenesis were assessed by measuring hormone production from ex vivo fetal testes after a 3-h incubation. Lastly, PCZ levels in amniotic fluid and maternal serum were measured using liquid chromatography/mass spectroscopy and correlated to the inhibition of steroidogenesis. Fetal progesterone and 17alpha-hydroxyprogesterone production levels were increased significantly at every PCZ dose, whereas testosterone levels were significantly decreased only at the two high doses. These results suggest that PCZ inhibits the conversion of progesterone to testosterone through the inhibition of CYP17. To test this hypothesis, PCZ effects on CYP17 gene expression and in vitro CYP17 hydroxylase activity were evaluated. PCZ had no effect on testicular CYP17 mRNA levels as measured by quantitative real-time polymersase chain reaction. However, microsomal CYP17 hydroxylase activity was significantly inhibited by the fungicide (K(i) = 865nM). Amniotic fluid PCZ concentrations ranged from 78 to 1512 ppb (207-4014nM) and testosterone production was reduced when PCZ reached approximately 500 ppb, which compares favorably with the determined CYP17 hydroxylase K(i) (326 ppb). These results demonstrate that PCZ lowers testicular testosterone synthesis by inhibiting CYP17 activity which likely contributes to the induced malformations in androgen-dependent tissues of male offspring.}, number={2}, journal={TOXICOLOGICAL SCIENCES}, author={Blystone, Chad R. and Lambright, Christy S. and Howdeshell, Kembra L. and Furr, Johnathan and Sternberg, Robin M. and Butterworth, Brian C. and Durhan, Elizabeth J. and Makynen, Elizabeth A. and Ankley, Gerald T. and Wilson, Vickie S. and et al.}, year={2007}, month={Jun}, pages={512–519} }
 @misc{leblanc_2007, title={Testosterone and male fertility in red deer}, volume={316}, number={5827}, journal={Science}, author={LeBlanc, G. A.}, year={2007}, pages={980} }
 @article{olmstead_leblanc_2007, title={The environmental-endocrine basis of gynandromorphism (intersex) in a crustacean}, volume={3}, DOI={10.7150/ijbs.3.77}, abstractNote={Commensurate with the decline in many crustacean populations has been an accumulation in reports of sexually ambiguous individuals within these populations. The cause of gynandromorphism or intersex among crustaceans is unknown. We show that gynandromorphism in the branchiopod crustacean Daphnia magna is initiated by the sex-determining hormone methyl farnesoate when levels of the hormone are intermediate between low levels that stimulate the production of broods containing all female offspring and high levels that stimulate the production of broods of all male offspring. The incidence of hormonally-induced gynandromorphism was low (0.14% at the maximum stimulatory hormone concentrations) but was significantly increased (46-fold) when the animals were hormone-treated at 30 degrees C. Some environmental chemicals also can stimulate the gynandromorphic phenotype as we demonstrated with the insecticide pyriproxyfen. Gynandromorphism occurs due to inadequate signaling of male-sex determination since: a) gynandromorphs did not occur in a population that was producing only female offspring; and, b) conditions that stimulated gynandromorphism also reduced the incidence of male offspring. We suggest that male sex determination normally occurs prior to the first embryonic cleavage. Elevated temperature may alter the timing of sex determination such that methyl farnesoate signaling occurs after the first embryonic cleavage and bilateral gynandromorphism occurs as a consequence of signaling to only one of the daughter cells. These results demonstrate that environmental factors can cause aberrant sex determination via perturbations in methyl farnesoate signaling.}, number={2}, journal={International Journal of Biological Sciences}, author={Olmstead, A. W. and LeBlanc, Gerald}, year={2007}, pages={77–84} }
 @article{gorr_rider_wang_olmstead_leblanc_2006, title={A candidate juvenoid hormone receptor cis-element in the Daphnia magna hb2 hemoglobin gene promoter}, volume={247}, ISSN={["0303-7207"]}, DOI={10.1016/j.mce.2005.11.022}, abstractNote={Hemoglobin levels are significantly elevated in the crustacean Daphnia magna by juvenoid hormones. The present study was undertaken to identify the specific globin (hb) genes that are induced by juvenoids and to identify putative juvenoid response elements (JREs) that may mediate this induction. Gene product of globin 2 (hb2), but not globin 1 and globin 3, was robustly elevated following juvenoid treatment of daphnids. A candidate JRE, located in the promoter of hb2, bound activated factor(s) in response to juvenoid treatment of daphnids. This hormone-induced protein:JRE interaction was robust when daphnids were reared at high oxygen tension but was inhibited when daphnids were reared under low pO2, implying that hypoxia might act to disrupt juvenoid-mediated endocrine signaling. The candidate JRE consists of a steroid/retinoid-response element-like core adjacent to a 5' AT-rich extension and thus bears resemblance to response elements that bind monomeric nuclear receptors. The induction of hb2 mRNA levels by juvenoid treatment occurred rapidly (within 4 h of exposure) and was not attenuated by treatment of daphnids with cycloheximide. In contrast, cycloheximide treatment did block hormone-mediated elevations in hemoglobin protein levels. Thus, induction of hb2 by juvenoids was not dependent upon the synthesis of secondary transcription factors that bound the JRE but was likely due to activation of the gene directly by the juvenoid-receptor complex. Affinity pull-down experiments with nuclear proteins extracted from juvenoid-treated daphnids using the JRE as bait yielded a 52kDa candidate for a monomeric nuclear receptor in D. magna that may mediate the regulatory activity of juvenoids.}, number={1-2}, journal={MOLECULAR AND CELLULAR ENDOCRINOLOGY}, author={Gorr, TA and Rider, CV and Wang, HY and Olmstead, AW and LeBlanc, GA}, year={2006}, month={Mar}, pages={91–102} }
 @article{rider_leblanc_2006, title={Atrazine stimulates hemoglobin accumulation in Daphnia magna: Is it hormonal or hypoxic?}, volume={93}, ISSN={["1096-6080"]}, DOI={10.1093/toxsci/kfl067}, abstractNote={Hemoglobin accumulation in daphnids is an important adaptive response that is regulated by at least two distinct molecular pathways: an endocrine pathway stimulated by terpenoid hormones and an oxygen-sensing pathway involving the hypoxia-inducible factor. We found that the herbicide atrazine elevated hemoglobin levels in Daphnia magna and hypothesized that atrazine induced hemoglobin in daphnids through the hormonal regulatory pathway. This hypothesis was tested by modeling the combined effects of atrazine and the terpenoid hormone mimic pyriproxyfen on hemoglobin mRNA levels assuming the same mechanism of action (concentration addition model) and alternatively, assuming different mechanisms of action (response addition model). Model predictions were then compared to experimental assessments of the combined action of these two chemicals on hemoglobin mRNA levels. Changes in hemoglobin expression were evaluated using real-time RT PCR with primers specific to each of three D magna hemoglobin genes (dhb1, dhb2, and dhb3). Both atrazine and pyriproxyfen significantly elevated levels of the hb2 gene product, while having little effect on hb1 and hb3 gene products. Induction of dhb2 by combinations of atrazine and pyriproxyfen did not conform to the concentration addition predictions. Rather, dhb2 induction by these binary combinations was highly consistent with response addition model predictions. These results indicate that atrazine does not induce hemoglobin through the terpenoid hormone–signaling pathway. Results from this study demonstrate that mixtures modeling can be used to assess a chemical's mechanism of action and that atrazine likely stimulates hemoglobin accumulation through the oxygen-sensing pathway.}, number={2}, journal={TOXICOLOGICAL SCIENCES}, author={Rider, Cynthia V. and LeBlanc, Gerald A.}, year={2006}, month={Oct}, pages={443–449} }
 @misc{leblanc_wang_2006, title={Chemical mixtures: Greater-than-additive effects?}, volume={114}, number={9}, journal={Environmental Health Perspectives}, author={LeBlanc, G. A. and Wang, G. R.}, year={2006}, pages={A517–518} }
 @article{sternberg_leblanc_2006, title={Kinetic characterization of the inhibition of acyl coenzyme A: Steroid acyltransferases by tributyltin in the eastern mud snail (Ilyanassa obsoleta)}, volume={78}, ISSN={["1879-1514"]}, DOI={10.1016/j.aquatox.2006.03.004}, abstractNote={Exposure to tributyltin (TBT) has been causally associated with the global occurrence of a pseudohermaphroditic condition called imposex in neogastropod species. TBT elevates free testosterone levels in these organisms, and this upsurge in testosterone may be involved in the development of imposex. We investigated the ability of TBT to inhibit acyl coenzyme A:testosterone acyltransferase (ATAT) activity as well as microsomal acyl-coenzyme A:17β-estradiol acyltransferase (AEAT) in a neogastropod, the eastern mud snail Ilyanassa obsoleta as a mechanism by which TBT elevates free testosterone. TBT significantly inhibited both ATAT and AEAT activities in vitro at toxicologically relevant in vivo concentrations. Kinetic analyses revealed that TBT is a competitive inhibitor of ATAT (Ki = ∼9 μM) and is a weaker, noncompetitive inhibitor of AEAT (Ki = ∼31 μM). ATAT and AEAT activities associated with different microsome preparations were significantly correlated, and 17β-estradiol competitively inhibited the fatty acid esterification of testosterone suggesting that one enzyme is responsible for biotransforming both testosterone and 17β-estradiol to their corresponding fatty acid esters. Overall, the results of this study supply the much-needed mechanistic support for the hypothesis that TBT elevates free testosterone in neogastropods by inhibiting their major regulatory process for maintaining free testosterone homeostasis—the fatty acid esterification of testosterone.}, number={3}, journal={AQUATIC TOXICOLOGY}, author={Sternberg, Robin M. and LeBlanc, Gerald A.}, year={2006}, month={Jun}, pages={233–242} }
 @article{janer_leblanc_porte_2005, title={A  comparative study on androgen metabolism in three invertebrate species}, volume={143}, DOI={10.1016/j.ygen.2005.03.016}, number={3}, journal={General and Comparative Endocrinology}, author={Janer, G. and LeBlanc, Gerald and Porte, C.}, year={2005}, pages={211–221} }
 @article{janer_leblanc_porte_2005, title={A comparative study on androgen metabolism in three invertebrate species}, volume={143}, ISSN={0016-6480}, url={http://dx.doi.org/10.1016/j.ygcen.2005.03.016}, DOI={10.1016/j.ygcen.2005.03.016}, abstractNote={A comparative approach was taken in this study to evaluate androgen (androstenedione and testosterone) metabolism in three invertebrate species: the gastropod Marisa cornuarietis, the amphipod Hyalella azteca, and the echinoderm Paracentrotus lividus. The existence of 17beta/3beta-hydroxysteroid dehydrogenase (HSD) and 5alpha-reductase catalyzed reactions was demonstrated in all three species. Androstenedione was primarily converted to 5alpha-androstanedione in M. cornuarietis, while it was primarily metabolized to testosterone in P. lividus and H. azteca. In addition, and consistent with vertebrate findings, tissue specific pathways and sexual dimorphism in androgen metabolism were observed. Namely, testosterone was metabolized to dihydrotestosterone in P. lividus gonads (via 5alpha-reductase), and metabolized to 4-androstene-3beta,17beta-diol in the digestive tube (via 3beta-hydroxysteroid dehydrogenase). Furthermore, the synthesis of 17beta-reduced metabolites of androstenedione (testosterone and dihydrotestosterone) was 3- to 4-fold higher in males of M. cornuarietis than in females. Organotin compounds, which have been shown to interfere with some aspects of androgen metabolism, had no major effect on testosterone metabolism in any of the three species. Fenarimol enhanced 5alpha-reductase-mediated catalysis in gonads of P. lividus. Overall, results demonstrate the ubiquity of some androgen biotransformation processes in invertebrates and reveals interphyla differences in androgen metabolic pathways, and different sensitivity of these pathways to some xenobiotics.}, number={3}, journal={General and Comparative Endocrinology}, publisher={Elsevier BV}, author={Janer, G. and LeBlanc, G.A. and Porte, C.}, year={2005}, month={Sep}, pages={211–221} }
 @article{rider_leblanc_2005, title={An integrated addition and interaction model for assessing toxicity of chemical mixtures}, volume={87}, ISSN={["1096-0929"]}, DOI={10.1093/toxsci/kfi247}, abstractNote={The high propensity for simultaneous exposure to multiple environmental chemicals necessitates the development and use of models that provide insight into the toxicity of chemical mixtures. In this study, we developed a mathematical model that combines concepts of concentration addition, response addition, and toxicokinetic chemical interaction to assess toxicity of chemical mixtures. A ternary mixture of acetylcholinesterase inhibiting organophosphates (malathion and parathion) and the P450 inhibitor piperonyl butoxide was used to model toxicity. Concentration-response curves were generated for individual chemicals as well as for mixtures of the chemicals using acute toxicity tests with Daphnia magna. The toxicity of binary combinations of malathion and parathion adhered to the principles of concentration addition. The contribution of piperonyl butoxide to mixture toxicity was integrated using a model for response addition. Piperonyl butoxide also modified the toxicity of the organophosphates by inhibiting their metabolic activation. The antagonistic effects of piperonyl butoxide towards the organophosphates were quantified as coefficients of interactions (K-functions) and incorporated into the mixture model. Finally, toxicity of the ternary mixture was modeled at 30 different mixture formulations using three additive models that assumed no interaction (concentration addition, response addition, and integrated addition) and using the integrated addition and interaction (IAI) model. Toxicity of the 30 mixtures was then experimentally determined and compared to model results. Only the IAI model accurately predicted the toxicity of the mixtures. The IAI model holds promise as a means for assessing hazard of complex chemical mixtures.}, number={2}, journal={TOXICOLOGICAL SCIENCES}, author={Rider, CV and LeBlanc, GA}, year={2005}, month={Oct}, pages={520–528} }
 @article{janer_leblanc_porte_2005, title={Androgen metabolism in invertebrates and its modulation by xenoandrogens - A comparative study}, volume={1040}, ISBN={["1-57331-569-9"]}, ISSN={["0077-8923"]}, DOI={10.1196/annals.1327.060}, abstractNote={Marisa cornuarietis (Mollusc), Hyalella azteca (Crustacean), and Paracentrotus lividus (Echinoderm) demonstrated the ability to metabolize androgens through different pathways catalyzed by 5alpha-reductases (5alpha-R), hydroxysteroid dehydrogenases (HSD), hydroxylases, sulfotransferases (SULT), and fatty-acid acyl-CoA acyltransferases (ATAT). Interspecies differences and tissue-specific distribution of those enzymatic activities were observed. Xenobiotics, such as triphenyltin, tributyltin, and fenarimol, interfered with some of the pathways studied, namely, testosterone sulfation, testosterone esterification, and 5alpha-R activity. The work evidenced different sensitivity of those pathways to androgenic compounds, together with interphyla differences in androgen metabolism.}, journal={TRENDS IN COMPARATIVE ENDOCRINOLOGY AND NEUROBIOLOGY}, publisher={New York, NY: New York Academy of Sciences}, author={Janer, G and LeBlanc, GA and Porte, C}, year={2005}, pages={354–356} }
 @article{mu_rider_hwang_hoy_leblanc_2005, title={Covert signal disruption: Anti-ecdysteroidal activity of bisphenol a involves cross talk between signaling pathways}, volume={24}, ISSN={["1552-8618"]}, DOI={10.1897/04-063r.1}, abstractNote={Bisphenol A is a key industrial chemical used in the manufacture of polycarbonate plastics and other products. Several recent reports ascribe toxicological properties to this compound that have been attributed to the disruption of endocrine-related processes. In the present study, the toxicity of bisphenol A was definitively characterized in the water flea (Daphnia magna) in an effort to discern whether this compound may elicit endocrine toxicity in an invertebrate species and to establish the mechanism by which this toxicity is elicited. The ability of bisphenol A to interfere with two ecdysteroid-dependent physiological processes--molting and embryonic development--was evaluated. Bisphenol A elicited antiecdysteroidal activity as indicated by its prolongation of the intermolt period and interference with embryonic development. This apparent antiecdysteroidal activity was not due to reduced availability of endogenous ecdysteroid nor due to ecdysteroid-receptor antagonism. The ability of bisphenol A to elicit antiecdysteroidal activity by functioning as a juvenoid hormone was next evaluated. Bisphenol A, alone, did not elicit juvenoid activity. However, bisphenol A did enhance the activity of the crustacean juvenoid hormone methyl farnesoate. A definitive assessment of the effects of bisphenol A on the reproductive capacity of daphnids revealed a concentration-response relationship that extended at least one order of magnitude below exposure levels that were overtly toxic to the maternal organisms. These results demonstrate that bisphenol A is chronically toxic to daphnids, probably through its ability to interfere with ecdysteroid/juvenoid regulated processes. However, effects are elicited at levels that are not likely to pose environmental concern.}, number={1}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Mu, XY and Rider, CV and Hwang, GS and Hoy, H and LeBlanc, GA}, year={2005}, month={Jan}, pages={146–152} }
 @article{olmstead_leblanc_2005, title={Joint action of polycyclic aromatic hydrocarbons: Predictive modeling of sublethal toxicity}, volume={75}, ISSN={["1879-1514"]}, DOI={10.1016/j.aquatox.2005.08.007}, abstractNote={Polycyclic aromatic hydrocarbons (PAHs) typically contaminate the environment as complex assemblages of different chemical compounds. Modeling approaches provide a means of estimating the toxicity of these PAH mixtures. In the present study, we tested the hypothesis that the joint effects of four PAHs: pyrene, phenanthrene, fluoranthene and naphthalene, on the growth rate of the crustacean Daphnia magna during sub-chronic exposure could be accurately predicted using a mathematical algorithm for concentration addition based upon the assumption that these PAHs impact growth by a common mode of action. Assessment of the individual toxicity of the four PAHs confirmed that these compounds elicited the common effect of retarding growth of daphnids at concentrations below those that were lethal to the organisms. Using the experimentally derived toxicity parameters for the individual chemicals, the toxicity of multiple mixtures of these four PAHs was modeled. These mixtures were based on concentrations reported in the environment and on equi-toxic concentrations. The effects of over 140 combinations of four mixture formulations on the growth rate of daphnids were experimentally determined and compared to model predictions. The concentration addition models tended to over predict the joint toxicity of these PAH mixtures and experimental data was better represented by an alternative model based upon the concept of independent joint action. Mixtures at environmentally relevant concentrations were predicted and experimentally demonstrated to have no effect on daphnid growth rates. Results indicate that PAHs elicit toxicity to daphnids by multiple mechanisms and demonstrate an appropriate modeling approach to assess the toxicity of these mixtures.}, number={3}, journal={AQUATIC TOXICOLOGY}, author={Olmstead, AW and LeBlanc, GA}, year={2005}, month={Nov}, pages={253–262} }
 @article{rider_gorr_olmstead_wasilak_leblanc_2005, title={Stress signaling: coregulation of hemoglobin and male sex determination through a terpenoid signaling pathway in a crustacean}, volume={208}, ISSN={["1477-9145"]}, DOI={10.1242/jeb.01343}, abstractNote={Environmental signals can activate neuro-endocrine cascades that regulate various physiological processes. In the present study, we demonstrate that two responses to environmental stress signaling in the crustacean Daphnia magna--hemoglobin accumulation and male offspring production--are co-elevated by the crustacean terpenoid hormone methyl farnesoate and several synthetic analogs. Potency of the hormones with respect to the induction of both hemoglobin and male offspring was highly correlated, suggesting that both processes are regulated by the same terpenoid signaling pathway. Six clones of the D. pulex/pulicaria species complex that were previously characterized as unable to produce male offspring and five clones that were capable of producing males were evaluated for both hemoglobin induction and male offspring production in response to methyl farnesoate. Four of the five male-producing clones produced both hemoglobin and male offspring in response to the hormone. Five of the six non-male-producing clones produced neither hemoglobin nor males in response to the hormone. These results provide additional evidence that both physiological processes are regulated by the same signaling pathway. Furthermore, the results indicate that the non-male-producing clones are largely defective in some methyl farnesoate signaling component, downstream from methyl farnesoate synthesis but upstream from the genes regulated by the hormone. A likely candidate for the site of the defect is the methyl farnesoate receptor. As a consequence of this defect, non-male-producing clones have lost their responsiveness to environmental signals that are transduced by this endocrine pathway. This defect in signaling would be likely to enhance population growth in stable environments due to the elimination of males from the population, assuming that other processes critical to population growth are not also compromised by this defect.}, number={1}, journal={JOURNAL OF EXPERIMENTAL BIOLOGY}, author={Rider, CV and Gorr, TA and Olmstead, AW and Wasilak, BA and Leblanc, GA}, year={2005}, month={Jan}, pages={15–23} }
 @article{janer_sternberg_leblanc_porte_2005, title={Testosterone conjugating activities in invertebrates: are they targets for endocrine disruptors?}, volume={71}, ISSN={["1879-1514"]}, DOI={10.1016/j.aquatox.2004.11.024}, abstractNote={Testosterone conjugation activities, microsomal acyltransferases and cytosolic sulfotransferases, were investigated in three invertebrate species, the gastropod Marisa cornuarietis, the amphipod Hyalella azteca, and the echinoderm Paracentrotus lividus. The goals of the study were to characterize steroid conjugation pathways in different invertebrate phyla and to assess the susceptibility of those processes to disruption by environmental chemicals. All three species exhibited palmitoyl-CoA: testosterone acyltransferase activity (ATAT) in the range of 100-510 pmol/min/mg protein. Despite similarities in specific activities, kinetic studies indicated that ATAT had a higher affinity for testosterone but a lower V(max) in M. cornuarietis than in P. lividus, and intermediate values were found for H. azteca. In contrast, the activity of testosterone sulfotransferase (SULT) was rather low (0.05-0.18 pmol/min/mg protein) in M. cornuarietis and H. azteca. The low activity precluded kinetic analyses and inhibition studies with these species. P. lividus digestive tube displayed high SULT activity (50-170 pmol/min/mg protein) at moderate testosterone concentrations, but was inhibited at high testosterone concentrations. The interference of model pollutants (triphenyltin (TPT), tributyltin (TBT), and fenarimol) with these conjugation pathways was investigated in vitro. Both TPT and TBT (100 microM) inhibited ATAT in P. lividus (68 and 42% inhibition, respectively), and appeared to act as non-competitive inhibitors. ATAT activity in M. cornuarietis was less affected by organotins, and a significant inhibition (20% inhibition) was detected only with TBT. Fenarimol (100 microM) did not affect ATAT in any of the species tested. Sulfation of testosterone was suppressed by the organotins as well as fenarimol when using cytosolic preparations from P. lividus. These results demonstrated the existence of interphyla differences in testosterone conjugation, and revealed that these processes can serve as targets for endocrine disrupting chemicals.}, number={3}, journal={AQUATIC TOXICOLOGY}, author={Janer, G and Sternberg, RM and LeBlanc, GA and Porte, C}, year={2005}, month={Feb}, pages={273–282} }
 @article{leblanc_gooding_sternberg_2005, title={Testosterone-fatty acid esterification: A unique target for the endocrine toxicity of tributyltin to gastropods}, volume={45}, ISSN={["1557-7023"]}, DOI={10.1093/icb/45.1.81}, abstractNote={Over the past thirty years, a global occurrence of sexual aberration has occurred whereby females among populations of prosobranch snails exhibit male sex characteristics. This condition, called imposex, has been causally associated with exposure to the biocide tributyltin. Tributyltin-exposed, imposex snails typically have elevated levels of testosterone which have led to the postulate that this endocrine dysfunction is responsible for imposex. This overview describes recent evidence that supports this postulate. Gastropods maintain circulating testosterone levels and administration of testosterone to females or castrates stimulates male sex differentiation in several snail species. Studies in the mud snail (Ilyanassa obsoleta) have shown that gastropods utilize a unique strategy for regulating free testosterone levels. Excess testosterone is converted to fatty acid esters by the action of a testosterone-inducible, high capacity/low affinity enzyme, acyl-CoA:testosterone acyl transferase, and stored within the organisms. Free testosterone levels are regulated during the reproductive cycle apparently due to changes in esterification/desterification suggesting that testosterone functions in the reproductive cycle of the organisms. Testosterone esterification provides a unique target in the testosterone regulatory machinery of snails that is altered by tributyltin. Indeed, imposex and free testosterone levels were elevated in field collected snails containing high tin levels, while testosterone-fatty acid ester pools were reduced in these organisms. These observations indicate that tributyltin elevates free testosterone by reducing the retention of testosterone as fatty acid-esters. This endocrine effect of tributyltin may be responsible for imposex.}, number={1}, journal={INTEGRATIVE AND COMPARATIVE BIOLOGY}, author={LeBlanc, GA and Gooding, MP and Sternberg, RM}, year={2005}, month={Feb}, pages={81–87} }
 @article{wang_olmstead_li_leblanc_2005, title={The screening of chemicals for juvenoid-related endocrine activity using the water flea Daphnia magna}, volume={74}, ISSN={["1879-1514"]}, DOI={10.1016/j.aquatox.2005.05.010}, abstractNote={U.S. Environmental Protection Agency is charged with developing a screening and testing paradigm for detecting endocrine toxicity of chemicals that are subject to regulation under the Food Quality Protection and the Safe Drinking Water Acts. In this study, we developed and evaluated a screening assay that could be employed to detect juvenoid-related endocrine-modulating activity in an invertebrate species. Juvenoid activity, anti-juvenoid activity, and juvenoid potentiator activity of chemicals was assessed using the water flea Daphnia magna. Male sex determination is under the regulatory control of juvenoid hormone, presumably methyl farnesoate, and this endpoint was used to detect juvenoid modulating activity of chemicals. Eighteen chemicals were evaluated for juvenoid agonist activity. Positive responses were detected with the juvenoid hormones methyl farnesoate and juvenile hormone III along with the insect growth regulating insecticides pyriproxyfen, fenoxycarb, and methoprene. Weak juvenoid activity also was detected with the cyclodiene insecticide dieldrin. Assays performed repetitively with compounds that gave either strong positive, weak positive, or negative response were 100% consistent indicating that the assay is not prone to false positive or negative responses. Five candidate chemicals were evaluated for anti-juvenoid activity and none registered positive. Four chemicals (all trans-retinoic acid, methoprene, kinoprene, bisphenol A) also were evaluated for their ability to potentiate the activity of methyl farnesoate. All registered positive. Results demonstrate that an in vivo assay with a crustacean species customarily employed in toxicity testing can be used to effectively screen chemicals for juvenoid-modulating activity.}, number={3}, journal={AQUATIC TOXICOLOGY}, author={Wang, HY and Olmstead, AW and Li, H and LeBlanc, GA}, year={2005}, month={Sep}, pages={193–204} }
 @article{olmstead_leblanc_2005, title={Toxicity Assessment of Environmentally Relevant Pollutant Mixtures Using a Heuristic Model}, volume={1}, ISSN={["1551-3793"]}, DOI={10.1897/ieam_2004-005r.1}, abstractNote={Abstract In this study, 9 chemicals were chosen from a recent report on surface water concentrations of a variety of xenobiotics to test the hypothesis that the toxicity of chemical mixtures could be estimated using a model based on the toxicity of the individual chemicals. Concentration‐response curves for the endpoints of lifespan, growth rate, and fecundity were generated for each chemical experimentally using the crustacean, Daphnia magna. From this data, a mathematical model for the combined toxicity of these chemicals was generated that merged the concepts of concentration addition and independent joint action. Toxicity of a mixture was modeled at various levels at which the ratio of the chemicals within the mixture was maintained at that reported for median detected environmental levels. Toxicity of the mixture was then determined experimentally and compared to model predictions. The model accurately predicted the most sensitive endpoint, as well as the lowest toxic effect level of the mixture. Results demonstrated that, for this mixture of chemicals, toxicity was not influenced significantly by interactions among the chemicals and a single constituent dominated toxicity. According to model predictions and experimental results, the median detected environmental concentrations of chemicals constituting this mixture provided no margin of safety.}, number={2}, journal={INTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT}, author={Olmstead, Allen W. and LeBlanc, Gerald A.}, year={2005}, month={Apr}, pages={114–122} }
 @inbook{leblanc_2004, title={Acute Toxicity}, ISBN={9780471646778 9780471265085}, url={http://dx.doi.org/10.1002/0471646776.ch11}, DOI={10.1002/0471646776.ch11}, abstractNote={The concepts of acute exposure and effect, as contributors to acute toxicity, are discussed. These concepts are contrasted to those relating to chronic toxicity. Dose-response relationships are described in detail with special attention given to non-monotonic relationships. Various common mechanisms of acute toxicity are described with example chemicals provided for each mechanism.}, booktitle={A Textbook of Modern Toxicology}, publisher={John Wiley & Sons, Inc.}, author={Leblanc, Gerald A.}, year={2004}, month={Mar}, pages={213–224} }
 @inbook{leblanc_2004, title={Basics of Environmental Toxicology}, ISBN={9780471646778 9780471265085}, url={http://dx.doi.org/10.1002/0471646776.ch26}, DOI={10.1002/0471646776.ch26}, abstractNote={This chapter begins with a discussion of the development of environmental toxicology as a subdisclipline of toxicology. Major factors that contribute to the fate and effects of chemicals in the environment are described (eg. persistence, bioaccumulation, acute toxicity, etc.). Toxicity of chemicals in the environment resulting from interactions with biotic or abiotic components of the environment is discussed as major sources of toxicity in the modern world.}, booktitle={A Textbook of Modern Toxicology}, publisher={John Wiley & Sons, Inc.}, author={Leblanc, Gerald A.}, year={2004}, month={Mar}, pages={463–478} }
 @article{mu_leblanc_2004, title={Cross communication between signaling pathways: Juvenoid hormones modulate ecdysteroid activity in a crustacean}, volume={301A}, ISSN={["2471-5646"]}, DOI={10.1002/jez.a.104}, abstractNote={Methyl farnesoate is a juvenoid hormone that regulates a variety of processes in crustaceans including male sex determination among daphnids (Branchiopoda, Cladocera). The synthetic juvenoids pyriproxyfen and fenoxycarb mimic the action of methyl farnesoate in daphnids. In the present study we tested the hypothesis that juvenoids also can regulate ecdysteroid activity in a crustacean (Daphnia magna). Methyl farnesoate, pyriproxyfen, and fenoxycarb all disrupted ecdysteroid-regulated aspects of embryo development in daphnids. Exposure of ecdysteroid-responsive cells to 20-hydroxyecdysone reduced cell proliferation and increased mRNA levels of the ecdysone receptor and its partner protein ultraspiracle. Co-treatment of cells with the juvenoid pyriproxyfen attenuated all of these ecdysteroid mediated responses. While juvenoids functioned as anti-ecdysteroids in both intact embryos and in cultured cells, 20-hydroxyecdysone showed no evidence of acting as an anti-juvenoid. The combined effects of pyroproxyfen with the ecdysteroid synthesis inhibitor fenarimol and the ecdysteroid receptor antagonist testosterone were evaluated in an effort to discern whether the action of the juvenoids were additive with those of know anti-ecdysteroids. The anti-ecdysteroid effects of pyriproxyfen were non-additive with those of either anti-ecdysteroid. Rather, joint effects conformed to a model of synergy. These results demonstrated that juvenoids elicit anti-ecdysteroidal activity in a crustacean through a unique mechanism of action. A model involving receptor partner deprivation is proposed that explains the synergistic interactions observed.}, number={10}, journal={JOURNAL OF EXPERIMENTAL ZOOLOGY PART A-ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY}, author={Mu, XY and Leblanc, GA}, year={2004}, month={Oct}, pages={793–801} }
 @inbook{leblanc_2004, title={Elimination of Toxicants}, ISBN={9780471646778 9780471265085}, url={http://dx.doi.org/10.1002/0471646776.ch10}, DOI={10.1002/0471646776.ch10}, abstractNote={This chapter describes general attributes of organisms that have necessitated the evolution of complex pathways for the elimination of toxic materials from the body. Specialized function of the liver and kidney in toxicant elimination are discussed at organ, cellular, and molecular levels. This chapter emphasizes the coordinated activity of various contributors (eg. blood binding proteins, active transporters, biotransformation enzymes) in the vectorial elimination of chemicals.}, booktitle={A Textbook of Modern Toxicology}, publisher={John Wiley & Sons, Inc.}, author={Leblanc, Gerald A.}, year={2004}, month={Mar}, pages={203–211} }
 @inbook{leblanc_2004, title={Endocrine System}, ISBN={9780471646778 9780471265085}, url={http://dx.doi.org/10.1002/0471646776.ch17}, DOI={10.1002/0471646776.ch17}, abstractNote={This chapter provides a basic overview of hormone signal transduction pathways particularly as related to steroid hormones. Major mechanisms by which chemicals can disrupt steroid hormone-regulated activities are reviewed. Types of toxicity resulting from these actions of chemicals on key regulatory processes are discussed along with examples of chemicals that elicit specific effects.}, booktitle={A Textbook of Modern Toxicology}, publisher={John Wiley & Sons, Inc.}, author={Leblanc, Gerald A.}, year={2004}, month={Mar}, pages={299–315} }
 @misc{leblanc_olmstead_2004, title={Evaluating the toxicity of chemical mixtures}, volume={112}, ISSN={["0091-6765"]}, DOI={10.1289/ehp.112-a729}, abstractNote={Vol. 112, No. 13 PerspectivesOpen AccessEvaluating the Toxicity of Chemical Mixtures Gerald A. LeBlanc and Allen W. Olmstead Gerald A. LeBlanc Search for more papers by this author and Allen W. Olmstead Search for more papers by this author Published:1 September 2004https://doi.org/10.1289/ehp.112-a729Cited by:8AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit Tinwell and Ashby (2004) provided a detailed evaluation of the joint action of a mixture of estrogenic chemicals using the immature rat uterotrophic assay. The researchers demonstrated that a mixture of estrogenic chemicals in which each individual chemical was present in the mixture at levels approximating the no observed effect level (NOEL) elicited a measurable response. This work advances our understanding of the toxicity of endocrine-active substances, and Tinwell and Ashby are to be commended for providing detailed results of their experiments suitable for evaluation by others.The analysis of the data, however, stopped short of providing insights into the joint action of mixtures of endocrine disruptors. Tinwell and Ashby (2004) proposed three avenues for the analysis of the joint action of chemicals. The first, a simple addition-of-effects approach, is overly simplistic and unrealistic, as demonstrated by the authors. The second, graphic isobole analysis, was rejected by the authors for any mixture in excess of three chemicals. We concur that isobole analysis poses limitations for more complex mixtures of chemicals. The third, concentration addition, was deemed impractical by Tinwell and Ashby due to the requirement of detailed characterization of the concentration–response relationship of each chemical within the mixture. We agree that analysis of mixtures toxicity using concentration addition requires an understanding of the toxicity of the individual constituents within a mixture. However, we disagree that such a data requirement should discourage efforts to model and predict toxicity of chemical mixtures using this approach. Results reported by Tinwell and Ashby (2004), along with published data cited by the authors, provided sufficient information on the toxicity of the individual chemicals for us to accurately model the joint action of the mixture based upon concentration addition.The authors’ recommendation that toxicity of chemical mixtures be directly assessed on a case-by-case basis (Tinwell and Ashby 2004) would provide a Band-Aid but not a cure to the dilemma of characterizing the hazards of chemical mixtures. Chemical mixtures are ever varying with respect to constituents and to concentrations of those constituents. Granted, the individual toxicity of many, if not most, chemicals has not been adequately evaluated to provide the concentration–response information required for the joint evaluation of toxicity. Rather than avoid such endeavors, the scientific community should mobilize to generate such data; the data should be made available in the public domain; and, alternative approaches (i.e., in vitro analyses of ligand–receptor interactions) should be explored as means to rapidly generate surrogate data for use in mixtures toxicity assessments. Thanks to the efforts of investigators such as Tinwell and Ashby, who are generous with the data they have generated, a growing database exists for estrogenic chemicals. Hopefully, key agencies (i.e., the National Institute of Environmental Health Sciences, the U.S. Environmental Protection Agency) will take the initiative to generate public-domain databases on chemicals harboring other mechanisms of toxicity. With such data resources, we may someday have the ability to routinely model the toxicity of chemical mixtures.ReferencesTinwell H, Ashby J. 2004. Sensitivity of the immature rat uterotrophic assay to mixtures of estrogens. Environ Health Perspect 112:575-58215064164. Link, Google ScholarFiguresReferencesRelatedDetailsCited By Shaw J, Moore M, Readman J, Mou Z, Langston W, Lowe D, Frickers P, Al-Moosawi L, Pascoe C and Beesley A (2019) Oxidative stress, lysosomal damage and dysfunctional autophagy in molluscan hepatopancreas (digestive gland) induced by chemical contaminants, Marine Environmental Research, 10.1016/j.marenvres.2019.104825, (104825), Online publication date: 1-Oct-2019. Moore M, Wedderburn R, Clarke K, McFadzen I, Lowe D and Readman J (2018) Emergent synergistic lysosomal toxicity of chemical mixtures in molluscan blood cells (hemocytes), Environmental Pollution, 10.1016/j.envpol.2018.01.019, 235, (1006-1014), Online publication date: 1-Apr-2018. Dawson D, Genco N, Bensinger H, Guinn D, Il’Giovine Z, Wayne Schultz T and Pöch G (2012) Evaluation of an asymmetry parameter for curve-fitting in single-chemical and mixture toxicity assessment, Toxicology, 10.1016/j.tox.2011.12.006, 292:2-3, (156-161), Online publication date: 1-Feb-2012. Cao Z, Shafer T, Crofton K, Gennings C and Murray T (2011) Additivity of Pyrethroid Actions on Sodium Influx in Cerebrocortical Neurons in Primary Culture, Environmental Health Perspectives, 119:9, (1239-1246), Online publication date: 1-Sep-2011.Miller M, Crofton K, Rice D and Zoeller R (2009) Thyroid-Disrupting Chemicals: Interpreting Upstream Biomarkers of Adverse Outcomes, Environmental Health Perspectives, 117:7, (1033-1041), Online publication date: 1-Jul-2009.Wolansky M, Gennings C, DeVito M and Crofton K (2009) Evidence for Dose-Additive Effects of Pyrethroids on Motor Activity in Rats, Environmental Health Perspectives, 117:10, (1563-1570), Online publication date: 1-Oct-2009. Crofton K (2008) Thyroid disrupting chemicals: mechanisms and mixtures, International Journal of Andrology, 10.1111/j.1365-2605.2007.00857.x, 31:2, (209-223), Online publication date: 1-Apr-2008. Crofton K, Craft E, Hedge J, Gennings C, Simmons J, Carchman R, Carter W and DeVito M (2005) Thyroid-Hormone–Disrupting Chemicals: Evidence for Dose-Dependent Additivity or Synergism, Environmental Health Perspectives, 113:11, (1549-1554), Online publication date: 1-Nov-2005. Vol. 112, No. 13 September 2004Metrics About Article Metrics Publication History Originally published1 September 2004Published in print1 September 2004 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.}, number={13}, journal={ENVIRONMENTAL HEALTH PERSPECTIVES}, author={LeBlanc, GA and Olmstead, AW}, year={2004}, month={Sep}, pages={A729–A730} }
 @article{wolf_leblanc_gray_2004, title={Interactive effects of vinclozolin and testosterone propionate on pregnancy and sexual differentiation of the male and female SD Rat}, volume={78}, ISSN={["1096-0929"]}, DOI={10.1093/toxsci/kfh018}, abstractNote={In mammals, androgens are essential in directing mammalian sexual differentiation of the male phenotype. Administration of testosterone during this period alters female development in a male-like direction, whereas exposure to an androgen receptor antagonist like vinclozolin (V) demasculinizes and feminizes the male offspring. In the current study, we administered V (gavage at 200 mg/kg/day) and/or testosterone propionate (TP, sc, at 1 mg/rat/day), alone and in combination to Sprague-Dawley (SD) rats on days 14 through 19 of pregnancy, to determine if V would antagonize the effects of TP in the female and, conversely, if TP would antagonize the effects of V in the male offspring. These doses of TP and V were selected because they significantly alter sexual differentiation in the majority of female and male rat offspring, respectively, without producing severe toxicity in the dam or offspring. The study design is a 2 × 2 factorial (7 dams per group) including vehicle control, V, TP, and V + TP groups. As expected, individually, both V and TP reduced maternal weight gain and the V + TP group was affected in a cumulative fashion. Litter size on postnatal day (PND) 2 was reduced only by V + TP, whereas pup body weight was reduced in all three treated groups, the effect of V + TP again being cumulative. In female offspring, TP-induced alterations (i.e., increased anogenital distance [AGD] and fewer nipples, vaginal agenesis, hydrometrocolpos, induced prostate and bulbourethral glands, and levator ani muscle tissues) were all reversed by coadministration of V. In male offspring, V-induced alterations were only modestly antagonized by TP. At the dosage levels used herein, V + TP-treated male offspring had less well-developed nipples as infants and adults and a lower incidence of ectopic testis than did the V group. However, V-induced changes in reproductive organ weights, AGD, atrophic testes, vaginal pouch, and agenesis of the sex accessory tissues were not antagonized by concurrent TP treatment in male offspring. We observed that the combination of V and TP, two chemicals with opposing endocrine action, antagonized one another during sexual differentiation, especially in the female offspring and induced cumulative effects on maternal and neonatal toxicity. We suspect that antagonism of V by TP would be enhanced in the male if lower dose levels of V were used, but then the antagonism of TP by V in the female would likely be attenuated.}, number={1}, journal={TOXICOLOGICAL SCIENCES}, author={Wolf, CJ and LeBlanc, GA and Gray, LE}, year={2004}, month={Mar}, pages={135–143} }
 @inbook{hodgson_leblanc_meyer_smart_2004, place={New York}, title={Introduction to Biochemical and Molecular Methods in Toxicology}, ISBN={9780471646778 9780471265085}, url={http://dx.doi.org/10.1002/0471646776.ch2}, DOI={10.1002/0471646776.ch2}, abstractNote={A brief introduction to recently developed molecular and cellular methods currently in use in toxicology, including cell culture techniques (suspension cell culture, monolayer cell culture, indicators of toxicity in cultured cells), molecular cloning techniques (molecular cloning, cDNA and genomic libraries, Northern and Southern blot analysis, PCR, evaluation of gene expression, regulation and function) as well as immunochemical methods.}, booktitle={A Textbook of Modern Toxicology}, publisher={John Wiley & Sons, Inc.}, author={Hodgson, Ernest and Leblanc, Gerald A. and Meyer, Sharon A. and Smart, Robert C.}, editor={Hodgson, E.Editor}, year={2004}, month={Mar}, pages={13–22} }
 @article{thompson_young_edens_olmstead_leblanc_hodgson_roe_2004, title={Non-target toxicology of a new mosquito larvicide, trypsin modulating oostatic factor}, volume={80}, ISSN={["1095-9939"]}, DOI={10.1016/j.pestbp.2004.06.009}, abstractNote={Trypsin modulating oostatic factor (TMOF), a peptide hormone originally isolated from the ovaries of adult Aedes aegypti, is currently under commercial development as a new pesticide chemistry with a novel mode of action for the control of larval mosquitoes. The objective of the current research is to evaluate potential risks of the use of TMOF as an insecticide on non-target organisms. TMOF (YDPAP6) was degraded in vitro (as determined by HPLC and LC/MS) to DPAP6, PAP6, and then AP6 by leucine aminopeptidase, a pancreatic enzyme found in the digestive system of vertebrates. The rate of degradation of TMOF and PAP6 was significantly greater than that of DPAP6, while no metabolism of AP6 was found. TMOF technical insecticide was produced on a commercial scale by recombinant yeast (heat-killed before application). The technical TMOF when administered in a single dose by gavage to male and female mice at 2000 mg dry weight/kg body weight produced no negative effects as compared to controls up to 12 days after treatment. When male and female mallard ducks were treated by gavage with 1250 mg dry weight of technical TMOF/kg body weight each day for 5 days, again no toxic effects were noted through 35 days after the last treatment. TMOF technical insecticide was also applied to the shaved skin of male and female rabbits at the rate of 2000 mg/kg for 1–2 days, with no effect. The end point observations in these in vivo experiments were mortality; changes in growth rate, behavior, body structure, and color; and possible lesions observed during necropsy. Finally, Daphnia incubated with technical TMOF in rearing water at the level of 1.0 × 106 yeast cells/ml (10 mg/ml) also demonstrated no negative effects on mortality, growth, molting, time to first brood, and production of viable neonates. It appears from these studies that TMOF can be degraded by vertebrate digestive proteases and technical TMOF is not toxic to the non-target organisms examined.}, number={3}, journal={PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY}, author={Thompson, DM and Young, HP and Edens, FW and Olmstead, AW and LeBlanc, GA and Hodgson, E and Roe, RM}, year={2004}, month={Nov}, pages={131–142} }
 @article{gooding_leblanc_2004, title={Seasonal variation in the regulation of testosterone levels in the eastern mud snail (Ilyanassa obsoleta)}, volume={123}, DOI={10.1111/j.1744-7410.2004.tb00158.x}, abstractNote={Abstract. Some gastropods appear to utilize a strategy for regulating testosterone levels that is atypical of such processes thus far identified in other metazoans. While most animals convert testosterone largely to polar derivatives that are readily eliminated from the organism, the mud snail Ilyanassa obsoleta converts testosterone to apolar testosterone-fatty acid esters that are retained by the organism. In the present study, we tested the hypothesis that fatty acid esteri-fication serves to store testosterone and that stored testosterone-fatty acid ester pools vary through the reproductive cycle of the snail. This hypothesis was tested by 1) modulating total testosterone levels in individual snails and measuring the amount of the hormone stored as the fatty acid ester relative to the amount retained as free steroid and 2) measuring changes in esterified testosterone in a field population of snails during their reproductive cycle. Adult snails were experimentally manipulated to contain from ∼36–300% the level of total testosterone measured in unmanipulated individuals. The amount of testosterone-fatty acid ester present in these organisms increased in direct proportion to the level of total testosterone, while, free testosterone levels remained relatively constant. These observations suggest that free testosterone levels are regulated in the snail by fatty acid esterification/de-esterification processes. Among field sampled snails, testosterone existed predominantly in the free, non-esterified form at the onset and end of the egg laying period. At other times, the majority of testosterone was sequestered as fatty acid esters. This study provides compelling evidence that free testosterone levels in the mud snail are regulated through fatty acid esterification/de-esterification processes and this regulatory function contributes to seasonal fluctuations in free testosterone levels.}, number={3}, journal={Invertebrate Biology}, author={Gooding, M. P. and LeBlanc, Gerald}, year={2004}, pages={237–243} }
 @article{mu_leblanc_2004, title={Synergistic interaction of endocrine-disrupting chemicals: Model development using an ecdysone receptor antagonist and a hormone synthesis inhibitor}, volume={23}, ISSN={["1552-8618"]}, DOI={10.1897/03-273}, abstractNote={Abstract Endocrine toxicants can interfere with hormone signaling through various mechanisms. Some of these mechanisms are interrelated in a manner that might result in synergistic interactions. Here we tested the hypothesis that combined exposure to chemicals that inhibit hormone synthesis and that function as hormone receptor antagonists would result in greater‐than‐additive toxicity. This hypothesis was tested by assessing the effects of the ecdysteroid‐synthesis inhibitor fenarimol and the ecdysteroid receptor antagonist testosterone on ecdysteroid‐regulated development in the crustacean Daphnia magna . Both compounds were individually characterized for effects on the development of isolated embryos. Fenarimol caused late developmental abnormalities, consistent with its effect on offspring‐derived ecdysone in the maturing embryo. Testosterone interfered with both early and late development of embryos, consistent with its ability to inhibit ecdysone provided by maternal transfer (responsible for early developmental events) or de novo ecdysone synthesis (responsible for late developmental events). We predicted that, by decreasing endogenous levels of hormone, fenarimol would enhance the likelihood of testosterone binding to and inhibiting the ecdysone receptor. Indeed, fenarimol enhanced the toxicity of testosterone, while testosterone had no effect on the toxicity of fenarimol. Algorithms were developed to predict the toxicity of combinations of these two compounds based on independent joint action (IJA) alone as well as IJA with fenarimol‐on‐testosterone synergy (IJA+SYN). The IJA+SYN model was highly predictive of the experimentally determined combined effects of the two compounds. These results demonstrate that some endocrine toxicants can synergize, and this synergy can be accurately predicted.}, number={4}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Mu, XY and LeBlanc, GA}, year={2004}, month={Apr}, pages={1085–1091} }
 @article{olmstead_leblanc_2003, title={Insecticidal juvenile hormone analogs stimulate the production of male offspring in the crustacean Daphnia magna}, volume={111}, ISSN={["0091-6765"]}, DOI={10.1289/ehp.5982}, abstractNote={Juvenile hormone analogs (JHAs) represent a class of insecticides that were designed specifically to disrupt endocrine-regulated processes relatively unique to insects. Recently we demonstrated that the crustacean juvenoid hormone methyl farnesoate programs oocytes of the crustacean Daphnia magna to develop into males. We hypothesized that insecticidal JHAs might mimic the action of methyl farnesoate, producing altered sex ratios of offspring. Daphnids were exposed chronically (3 weeks) to sublethal concentrations of methyl farnesoate, the JHA pyriproxyfen, and several nonjuvenoid chemicals to discern whether excess male offspring production is a generic response to stress or a specific response to juvenoid hormones. Only methyl farnesoate and pyriproxyfen increased the percentage of males produced by exposed maternal organisms. As previously reported with methyl farnesoate, acute exposure (24 hr) to either pyriproxyfen or the JHA methoprene caused oocytes maturing in the ovary to develop into males. We performed experiments to determine whether combined effects of a JHA and methyl farnesoate conformed better to a model of concentration addition (indicative of same mechanism of action) or independent joint action (indicative of different mechanisms of action). Combined effects conformed better to the concentration-addition model, although some synergy, of unknown etiology, was evident between the insecticides and the hormone. These experiments demonstrate that insecticidal JHAs mimic the action of the crustacean juvenoid hormone methyl farnesoate, resulting in the inappropriate production of male offspring. The occurrence of such an effect in the environment could have dire consequences on susceptible crustacean populations.}, number={7}, journal={ENVIRONMENTAL HEALTH PERSPECTIVES}, author={Olmstead, AW and LeBlanc, GA}, year={2003}, month={Jun}, pages={919–924} }
 @article{gooding_wilson_folmar_marcovich_leblanc_2003, title={The biocide tributyltin reduces the accumulation of testosterone as fatty acid esters in the mud snail (Ilyanassa obsoleta)}, volume={111}, ISSN={["0091-6765"]}, DOI={10.1289/ehp.5779}, abstractNote={Imposex, the development of male sex characteristics by female gonochoristic snails, has been documented globally and is causally associated with exposure to the ubiquitous environmental contaminant tributyltin (TBT). Elevated testosterone levels in snails also are associated with TBT, and direct exposure to testosterone has been shown to cause imposex. We discovered previously that the mud snail (Ilyanassa obsoleta)biotransforms and retains excess testosterone primarily as fatty acid esters. The purpose of this study was to determine whether TBT interferes with the esterification of testosterone, resulting in the elevated free (unesterified) testosterone levels associated with imposex. Exposure of snails to environmentally relevant concentrations of TBT (> or = 1.0 ng/L as tin) significantly increased the incidence of imposex. Total (free + esterified) testosterone levels in snails were not altered by TBT; however, free testosterone levels increased with increasing exposure concentration of TBT. TBT-exposed snails were given [14C]]testosterone to measure the production of [14C]testosterone-fatty acid esters. The production of testosterone-fatty acid esters decreased with increasing exposure concentration of TBT. These results indicate that TBT elevates free testosterone levels in snails by decreasing the production or retention of testosterone-fatty acid esters. These findings were confirmed among field-sampled snails where individuals collected from a high-tin-affected site exhibited a greater incidence of imposex, higher free testosterone levels, and lower testosterone-fatty acid ester levels when compared with individuals sampled from a low-tin-affected site. Decreased testosterone-fatty acid esterification among TBT-treated snails was not caused by direct inhibition of the acyl coenzyme A:testosterone acyltransferase (ATAT) enzyme responsible for testosterone esterification, nor by suppressed ATAT protein expression. The target of TBT may be a co-contributor to the testosterone fatty esterification process or a factor in the enhanced hydrolysis of the testosterone-fatty acid pool.}, number={4}, journal={ENVIRONMENTAL HEALTH PERSPECTIVES}, author={Gooding, MP and Wilson, VS and Folmar, LC and Marcovich, DT and LeBlanc, GA}, year={2003}, month={Apr}, pages={426–430} }
 @inbook{leblanc_mastone_paradice_wilson_lockhart_robillard_2003, place={Pensacola, FL}, title={The influence of speciation on the toxicity of silver to fathead minnows (Pimephales promelas)}, booktitle={Silver : environmental transport, fate, effects, and models : papers from Environmental toxicology and chemistry, 1983 to 200}, publisher={SETAC}, author={LeBlanc, G.A. and Mastone, J.D. and Paradice, A.P. and Wilson, B.F. and Lockhart, H.B. and Robillard, K.A}, editor={Gorsuch, J.W. and Kramer, J.R. and LaPoint, T.W.Editors}, year={2003}, pages={313–322} }
 @article{mu_rider_leblanc_2002, title={Abstracts from the Eleventh International Symposium on Pollutant Responses in Marine Organisms (PRIMO 11) - Endocrine disrupters}, volume={54}, number={3-5}, journal={Marine Environmental Research}, author={Mu, X. Y. and Rider, C. V. and Leblanc, G. A.}, year={2002}, pages={741–754} }
 @inbook{luoma_hogstrand_bell_bielmyer_galvez_leblanc_lee_purcell_santore_santschi_et al._2002, place={Pensacola, FL}, title={Biological Processes}, booktitle={Silver in the Environment: Transport, Fate and Effects}, publisher={SETAC Press}, author={Luoma, S.N. and Hogstrand, C. and Bell, R.A. and Bielmyer, G.K. and Galvez, F. and LeBlanc, G.A. and Lee, Byeong-Gweon and Purcell, T.W. and Santore, R.C. and Santschi, P.H. and et al.}, editor={Andren, AW and Bober, TWEditors}, year={2002}, pages={65–96} }
 @article{mu_leblanc_2002, title={Developmental toxicity of testosterone in the crustacean Daphnia magna involves anti-ecdysteroidal activity}, volume={129}, ISSN={["0016-6480"]}, DOI={10.1016/S0016-6480(02)00518-X}, abstractNote={Testosterone has been shown to cause developmental arrest of embryonic daphnids (Daphnia magna). The present study was undertaken to determine whether this toxicity might be due to anti-ecdysteroidal activity associated with testosterone. The effect of testosterone on molt frequency of early instar daphnids was first evaluated to determine whether testosterone interfered with this ecdysteroid-regulated process. Molt frequency was delayed by exposure to testosterone and this effect was mitigated by co-exposure to the ecdysteroid 20-hydroxyecdysone. Testosterone exposure concentrations that interfered with molting also elicited developmental abnormalities among neonatal organisms produced by maternal organisms that were continuously exposed to testosterone or among embryos that were removed from unexposed mothers and exposed directly to the hormone. Embryos were significantly protected against the developmental toxicity of testosterone by co-exposure to 20-hydroxyecdysone. Taken together, these results demonstrated that the embryo toxicity of testosterone to daphnids is due largely to its ability to interfere with ecdysteroid control of development. Experiments next were conducted to determine whether testosterone interfered with ecdysteroidal activity by acting as an ecdysone receptor antagonist or by reducing endogenous ecdysone levels. Testosterone significantly antagonized the action of 20-hydroxyecdysone in an ecdysone-responsive cell line. Testosterone had no discernable effect on endogenous ecdysone levels in daphnids. These results demonstrated that (1). ecdysteroids regulate critical processes in daphnid embryo development, (2). testosterone elicits embryo toxicity to daphnids by interfering with ecdysteroid activity, and (3). ecdysteroid receptor antagonism could be one mechanism by which testosterone elicits these effects.}, number={2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Mu, XY and LeBlanc, GA}, year={2002}, month={Nov}, pages={127–133} }
 @article{wolf_hotchkiss_ostby_leblanc_gray_2002, title={Effects of prenatal testosterone propionate on the sexual development of male and female rats: A dose-response study}, volume={65}, ISSN={["1096-6080"]}, DOI={10.1093/toxsci/65.1.71}, abstractNote={Testosterone plays a major role in male sexual development. Exposure of females to testosterone in utero can induce masculine characteristics such as anovulation, increased anogenital distance (AGD), absence of nipples, retention of male-like tissues, and agenesis of the lower vagina. In addition, high levels of androgens during fetal development can lead to toxic effects such as reduced litter size and viability. The study of the effects of testosterone administration during sexual differentiation provides a foundation for understanding the effects of environmental androgens on fetuses, a sensitive subpopulation. In the current study, we investigated the ability of a range of concentrations of testosterone propionate (TP) administered prenatally to masculinize female and alter male offspring, and measured maternal and fetal T levels. Pregnant Sprague-Dawley rats were dosed by sc injection on gestational day (GD) 14–19 (GD 1= day of plug) with either corn oil (vehicle; 0.1 ml/rat) or with 0.1 ml of TP solution at 0.1, 0.5, 1, 2, 5, or 10 mg/0.1 ml. Parturition was delayed at 2, 5, and 10 mg TP, litter size was reduced at 5 and 10 mg TP, and pup weight was significantly reduced in both sexes at 0.5 mg TP and higher doses. Viability of offspring was unaffected at any dosage level. Androgenic effects seen at 0.5 mg TP in females included increased AGD at weaning and adulthood, reduced number of areolas and nipples, cleft phallus, small vaginal orifice, and presence of prostate tissue. This dose of TP elevated maternal T levels 10× but had no effect on fetal T levels. At 1 mg TP and above, female AGD on postnatal day (PND) 2 (or postcoital day 24 [gestation length = 22½]) was increased; areolas and nipples were virtually eliminated; levator ani muscle, bulbourethral glands, and seminal vesicles (2 mg TP and above) were present; none of the females developed a vaginal orifice and many females in the 1 and 2 mg TP dose groups developed a greatly distended, fluid-filled uterus after puberty. Maternal T levels at 1 mg TP were elevated 30×, and female fetal T levels showed an 80% increase. Male offspring displayed a reduced AGD and body weight on PND 2 at 0.5 mg TP and higher doses. These effects were not evident by weaning and male offspring displayed no malformations. We conclude that gestational administration of 0.5 and 1 mg TP masculinizes female offspring without greatly affecting pup viability or pregnancy of the dam. This study provides a useful model for in utero testing of environmental androgens for their potential to induce developmental abnormalities.}, number={1}, journal={TOXICOLOGICAL SCIENCES}, author={Wolf, CJ and Hotchkiss, A and Ostby, JS and LeBlanc, GA and Gray, LE}, year={2002}, month={Jan}, pages={71–86} }
 @article{mu_leblanc_2002, title={Environmental antiecdysteroids alter embryo development in the crustacean Daphnia magna}, volume={292}, ISSN={["0022-104X"]}, DOI={10.1002/jez.10020}, abstractNote={The role of ecdysteroids in crustacean embryo development and the susceptibility of the developing embryo to the antiecdysteroidal properties of an environmental chemical were evaluated. The agricultural fungicide fenarimol was shown to exhibit antiecdysteroidal activity to the crustacean Daphnia magna by lowering endogenous ecdysone levels and delaying molting in a concentration-dependent fashion that was mitigated by co-exposure to exogenous 20-hydroxyecdysone. Exposure of either gravid maternal organisms or isolated embryos to fenarimol resulted in embryo abnormalities ranging from early partial developmental arrest to incomplete development of antennae and shell spines. Developmental abnormalities were associated with suppressed ecdysone levels in the embryos and the abnormalities could be prevented by co-exposure to 20-hydroxyecdysone. Developmental abnormalities caused by the antiecdysteroid were associated with reduced fecundity of the parental organisms. These results demonstrate that ecdysteroids are critical to normal crustacean embryo development and environmental antiecdysteroids can disrupt normal embryo development and compromise the production of viable offspring. Antiecdysteroidal activity may provide a means by which environmental chemicals impact crustacean species while not affecting vertebrates. J. Exp. Zool. 292:287–292, 2002. © 2002 Wiley-Liss, Inc.}, number={3}, journal={JOURNAL OF EXPERIMENTAL ZOOLOGY}, author={Mu, XY and LeBlanc, GA}, year={2002}, month={Feb}, pages={287–292} }
 @article{olmstead_leblanc_2002, title={Juvenoid hormone methyl farnesoate is a sex determinant in the crustacean Daphnia magna}, volume={293}, ISSN={["0022-104X"]}, DOI={10.1002/jez.10162}, abstractNote={Daphnids (Daphnia magna) utilize cyclic parthenogenesis as a reproductive strategy. During periods of abundant resources, these organisms reproduce asexually. In response to environmental cues that signal the onset of environmental adversity, daphnids produce males and reproduce sexually. The environmental cues that stimulate the sexual reproductive phase are well known; however, the endocrine signals that transduce these environmental cues remain unknown. The present study was undertaken to test the hypothesis that the crustacean juvenoid hormone, methyl farnesoate, is a male sex determinant in this species. Continuous exposure to aqueous concentrations of methyl farnesoate greater than approximately 30 nM stimulated a concentration-dependent production of male-containing broods of organisms. Short-term exposures to methyl farnesoate during periods of egg and embryo maturation revealed that male sex determination occurred during a specific 12-hour period of ovarian egg development. Exposure of eggs to 400 nM methyl farnesoate during this sensitive developmental period resulted in the production of all-male broods of offspring, while exposure to concentrations as low as 52 nM produced mixed broods of males and females. This active concentration range of methyl farnesoate is consistent with levels measured in the hemolymph of some decapod crustaceans. These results demonstrate that methyl farnesoate is capable of programming daphnid embryos to develop into males and is likely the endocrine factor responsible for initiating the sexual reproductive phase in these organisms.}, number={7}, journal={JOURNAL OF EXPERIMENTAL ZOOLOGY}, author={Olmstead, AW and Leblanc, GA}, year={2002}, month={Dec}, pages={736–739} }
 @article{gunderson_leblanc_guillette_2001, title={Alterations in sexually dimorphic biotransformation of testosterone in juvenile American alligators (Alligator mississippiensis) from contaminated lakes}, volume={109}, ISSN={["0091-6765"]}, DOI={10.2307/3454748}, abstractNote={The goal of this study was to determine whether hepatic biotransformation of testosterone is normally sexually dimorphic in juvenile alligators and whether living in a contaminated environment affects hepatic dimorphism. Lake Woodruff served as our reference site. Moonshine Bay, located on the west side of Lake Okeechobee, served as an intermediate site. Lake Apopka, the Belle Glade area located at the south end of Lake Okeechobee, and Water Conservation Area 3A, in the northern Everglades, served as our contaminated sites (all lakes are in Florida). Normal testosterone hydroxylase activity exhibited sexually dimorphic patterns of expression, with reference animals from Lake Woodruff exhibiting a female:male ratio of 1.44. This pattern was perturbed in all of the intermediate and contaminated sites investigated. Normal testosterone oxido-reductase activity exhibited sexually dimorphic expression (Lake Woodruff female:male ratio of 1.45). This pattern was altered in all contaminated sites investigated. UDP-Glucuronosyltransferase activity exhibited no sexually dimorphic pattern in animals collected from our reference site, with Lake Woodruff animals exhibiting a female:male ratio of 1.06. This pattern was perturbed in animals from Water Conservation Area 3A, which exhibited a female:male ratio of 0.65. Sulfotransferase activity demonstrated no sexual dimorphism at any of the sites investigated, although elevated activity was observed in males from the Lake Okeechobee watershed compared to those from Lake Woodruff. These data demonstrate different patterns of hepatic androgen biotransformation in animals living in contaminated environments.}, number={12}, journal={ENVIRONMENTAL HEALTH PERSPECTIVES}, author={Gunderson, MP and LeBlanc, GA and Guillette, LJ}, year={2001}, month={Dec}, pages={1257–1264} }
 @article{gooding_leblanc_2001, title={Biotransformation and disposition of testosterone in the eastern mud snail Ilyanassa obsoleta}, volume={122}, ISSN={["0016-6480"]}, DOI={10.1006/gcen.2001.7630}, abstractNote={Elevated testosterone levels have been reported to be associated with imposex (pseudohermaphroditism), the superimposition of male characteristics such as a penis and vas deferens on female gonachoristic snails. Tributyltin (TBT), a marine biocide in anti-fouling paints, is a known causal agent of imposex. Evidence suggests that imposex is elicited by TBT-mediated changes in the biotransformation and disposition of testosterone. To identify potential targets of TBT in gastropod species susceptible to imposex, biotransformation and disposition of testosterone in normal individuals must first be characterized. Nonimposex mud snail, Ilyanassa obsoleta, readily extracted [(14)C]testosterone, added to aqueous media, and converted the testosterone to at least five apolar conjugates designated AP1 through AP5. All were retained by the organisms. No significant amount of [(14)C]testosterone was retained or eliminated as polar metabolites. Following enzymatic hydrolysis of the most abundant metabolite (AP1), free fatty acids and [(14)C]testosterone were liberated. Furthermore, AP1 was produced when homogenized snail tissue was incubated with [(14)C]testosterone and oleoyl coenzyme A or palmitoyl coenzyme A. These results indicate that AP1, which represents over 70% of the testosterone biotransformation products, is a fatty acid ester of testosterone. Apolar metabolites AP2-AP5 might represent testosterone derivatives that are multiply conjugated to fatty acid molecules. Fatty acid conjugates of testosterone have not been previously described in the gastropods. The esterification of testosterone to fatty acids might be a mechanism where by steroid titers are regulated and could represent a target of TBT toxicity.}, number={2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Gooding, MP and LeBlanc, GA}, year={2001}, month={May}, pages={172–180} }
 @inbook{leblanc_2001, place={New York}, edition={3rd}, title={Conjugation and Elimination of Toxicants}, ISBN={9780471333340 9780471267300}, booktitle={Introduction to Biochemical Toxicology}, publisher={Wiley}, author={LeBlanc, G.A}, editor={Hodgson, E and Smart, RCEditors}, year={2001}, pages={115–136} }
 @inbook{leblanc_2001, place={New York}, edition={3rd}, title={Immunochemical Techniques in Toxicology}, ISBN={9780471333340 9780471267300}, booktitle={Introduction to Biochemical Toxicology}, publisher={Wiley}, author={LeBlanc, G.A}, editor={Hodgson, E. and Smart, RCEditors}, year={2001}, pages={33–50} }
 @article{olmstead_le blanc_2001, title={Low Exposure Concentration Effects of Methoprene on Endocrine-Regulated Processes in the Crustacean Daphnia magna}, volume={62}, ISSN={1096-0929}, url={http://dx.doi.org/10.1093/toxsci/62.2.268}, DOI={10.1093/toxsci/62.2.268}, abstractNote={Methoprene is a growth-regulating insecticide that manifests its toxicity to target organisms by acting as a juvenile hormone agonist. Methoprene similarly may exert toxicity to crustaceans by mimicking or interfering with methyl farnesoate, a crustacean juvenoid. We hypothesized that methoprene interferes with endocrine-regulated processes in crustaceans by several mechanisms involving agonism or antagonism of juvenoid receptor complexes. In the present study, we evaluated this hypothesis, in part, by characterizing and comparing the concentration-response curves for methoprene and several endpoints related to development and reproduction of the crustacean Daphnia magna. Our results demonstrate that methoprene has multiple mechanisms of toxicity and low-exposure concentration effects. Methoprene reduced the growth rate of daphnids with evidence of only a single concentration-response line, having a threshold of 12.6 nM. Molt frequency was reduced by methoprene in a concentration-dependent manner, with a response curve corresponding to a 2-segmented line and thresholds at 4.2 and 0.21 nM. An endpoint related to reproductive maturation, the time of first brood deposition, was also affected by methoprene, with a clear concentration-dependent response and a NOEC of 32 nM. Methoprene reduced fecundity according to a 2-segmented line, with thresholds of 24 and < or =0.18 nM. These results demonstrate that methoprene elicits significant toxicity to endocrine-related processes in the 5-50 nM concentration range. Furthermore, molting and reproduction were impacted at significantly lower methoprene concentrations, with a distinct concentration response and a threshold of < or =0.2 nM. The different concentration-dependent response from that of methoprene could involve agonism or antagonism of various juvenoid receptor configurations.}, number={2}, journal={Toxicological Sciences}, publisher={Oxford University Press (OUP)}, author={Olmstead, A.W. and Le Blanc, G.A}, year={2001}, month={Aug}, pages={268–273} }
 @article{putz_schwartz_kim_leblanc_cooper_prins_2001, title={Neonatal low- and high-dose exposure to estradiol benzoate in the male rat: I. Effects on the prostate gland}, volume={65}, ISSN={["0006-3363"]}, DOI={10.1095/biolreprod65.5.1496}, abstractNote={Brief exposure of rats to high doses of natural estrogens early in life results in permanent alterations of the prostate gland, which include differentiation defects, altered gene expression, and dysplasia with aging. Whether low-dose treatments can cause similar effects in the developing prostate remains controversial. The current project was designed to determine the dose-response relationship of the prostate gland to estradiol exposure during the developmentally critical neonatal period in the rat. Male Sprague-Dawley (SD) rats were treated on Days 1, 3, and 5 of life by s.c. injections of a 7-log range of doses (0.015 μg/kg to 15.0 mg/kg) of β-estradiol-3-benzoate (EB) in 25 μl of peanut oil (Arachis) as vehicle. In a separate block, neonatal Fisher 344 (F344) rats received 0.15, 15.0, or 1500.0 μg EB/kg. Rats were killed on Postnatal Day (PND) 35 or 90, and the prostates were microdissected, weighed, and frozen for immunohistochemistry. Preputial separation and hepatic testosterone hydroxlase activities were monitored and measured to determine the onset of puberty. On PND 35, there was an increase in prostate weights of SD rats treated with low doses of EB and a decrease in prostate weights of SD rats treated with high doses. The low-dose effect was entirely abolished by PND 90, and only high-dose suppression of organ sizes was found. The transient nature of the effect in low-dose animals suggests an advancement of puberty as the cause for increased reproductive organ weights on PND 35. F344 rats were more sensitive than SD rats to the suppressive effects of high doses of neonatal EB on PND 90. Despite this heightened responsiveness in the F344 rats, a low-dose estrogenic effect on adult prostate weights was not observed. Thus, in the rat model a sustained effect at low doses of natural estrogens is not present in the prostate glands.}, number={5}, journal={BIOLOGY OF REPRODUCTION}, author={Putz, O and Schwartz, CB and Kim, S and LeBlanc, GA and Cooper, RL and Prins, GS}, year={2001}, month={Nov}, pages={1496–1505} }
 @article{putz_schwartz_leblanc_cooper_prins_2001, title={Neonatal low- and high-dose exposure to estradiol benzoate in the male rat: II. Effects on male puberty and the reproductive tract}, volume={65}, ISSN={["0006-3363"]}, DOI={10.1095/biolreprod65.5.1506}, abstractNote={Environmental contaminants with estrogenic properties have been cause for heightened concern about their possible role in inducing adverse health effects. Brief exposure of rodents to high doses of natural estrogens early in life results in permanent alterations of the male reproductive tissues, but the question of whether environmentally relevant doses can cause the same effects remains controversial. The current project was designed to determine the dose-response relationship between neonatal estradiol exposure and the development of the male reproductive tract in the rat. Neonatal male Sprague-Dawley (SD) and Fisher 344 (F344) rats were exposed to β-estradiol-3-benzoate (EB) at concentrations ranging from 0.015 μg/kg body weight (BW) to 15.0 mg/kg BW and 0.15 μg/kg BW to 1.5 mg/kg BW, respectively. Results showed an inverted U-shaped dose-response profile for testis and epididymis weights in 35-day-old SD rats, with increased organ sizes at the low-dose end of the treatment. This effect was transient and was not sustained into adulthood. Increased hepatic testosterone hydroxylase activities in low-dose animals suggest an advancement of puberty as the cause for increased reproductive organ weights. On postnatal day (PND) 90, a stimulatory low-dose response to EB was present in SD rat testicular and epididymal weights, however at one order of magnitude lower dose than that seen on PND 35, suggesting a separate effect. All SD male reproductive tract organs and serum hormones showed a permanent inhibitory response to high doses of neonatal EB. F344 rats exhibited greater estrogen sensitivity on PND 90. Despite this heightened responsiveness, F344 rats did not exhibit a low-dose effect for any endpoint. These low-dose responses to estradiol are organ and strain specific.}, number={5}, journal={BIOLOGY OF REPRODUCTION}, author={Putz, O and Schwartz, CB and LeBlanc, GA and Cooper, RL and Prins, GS}, year={2001}, month={Nov}, pages={1506–1517} }
 @article{olmstead_leblanc_2001, title={Temporal and quantitative changes in sexual reproductive cycling of the cladoceran Daphnia magna by a juvenile hormone analog}, volume={290}, ISSN={["0022-104X"]}, DOI={10.1002/jez.1044}, abstractNote={Cyclic parthenogens, such as the cladoceran, Daphnia magna, utilize both asexual (parthenogenetic) and sexual reproduction in order to maximize population fitness in variable environments. Parthenogenetic reproduction is the default strategy among D. magna, while various environmental cues trigger cycles of sexual reproduction. Experiments were conducted with the juvenile hormone analog methoprene to test the hypothesis that members of the insect juvenile hormone/vertebrate retinoic acid family of transcription factors are involved in the regulation of sexual reproduction in daphnids. Neither methoprene, food reduction, or crowding independently stimulated entry into the sexual reproductive phase of the daphnids. However, the combination of food deprivation and crowding stimulated entry into the sexual reproductive phase characterized by an initial high production of males and the subsequent intermittent production of haploid egg-containing ephippia. Exposure to 160 nM methoprene along with food deprivation and crowding caused a significant reduction in the percentage of males produced during the early phase of the sexual cycle and significantly increased the percentage of males produced during the later stages of the cycle. Methoprene concentrations as low as 6.4 nM significantly reduced the number of resting eggs produced and proportionately increased the production of parthenogenetically-produced neonates. These experiments demonstrate that methoprene uncouples the coordinate production of males and resting eggs during the sexual reproductive period of D. magna. Methoprene stimulates male offspring production and defers their production to latter stages of the sexual reproductive period, while inhibiting the production of resting eggs and promoting the continuance of parthenogenetic reproduction. J. Exp. Zool. 290:148–155, 2001. © 2001 Wiley-Liss, Inc.}, number={2}, journal={JOURNAL OF EXPERIMENTAL ZOOLOGY}, author={Olmstead, AW and LeBlanc, GA}, year={2001}, month={Jul}, pages={148–155} }
 @article{kast-hutcheson_rider_leblanc_2001, title={The fungicide propiconazole interferes with embryonic development of the crustacean Daphnia magna}, volume={20}, ISSN={["1552-8618"]}, DOI={10.1897/1551-5028(2001)020<0502:TFPIWE>2.0.CO;2}, abstractNote={Propiconazole is a fungicide used in a variety of agricultural applications. Preliminary studies had suggested that embryos of the crustacean Daphnia magna are particularly susceptible to the toxicity of this chemical. The goals of the present study were to define endpoints of daphnid embryonic development that could be routinely used to assess the embryo toxicity of chemicals and to characterize definitively the embryo toxicity of propiconazole to daphnids. Daphnid embryonic development was characterized into six readily distinguishable stages based on the degree of tissue differentiation. Embryonic development could be monitored either in the brood chamber of the maternal organism or using embryos removed from the brood chamber and incubated ex vivo. Standard toxicity assessment revealed that propiconazole elicited no significant adverse effects on daphnid survival or fecundity during a 21-d exposure to concentrations as high as 0.25 mg/L. Exposure to 0.25 mg/L propiconazole, however, caused a significant incidence of developmental abnormalities and embryonic death. Abnormalities were consistent with developmental arrest at later stages of embryonic maturation. Propiconazole elicited a steep concentration-response curve with respect to embryo toxicity, with a 10% and a 90% incidence of embryo toxicity measured at 0.50 and 0.82 mg/L, respectively. Direct exposure of embryos to propiconazole resulted in toxicity, though the incidence and characteristics of developmental abnormalities were not consistent with that observed during chronic exposures. However, maternal exposure to propiconazole followed by transfer of early embryos to propiconazole-free media resulted in embryo toxicity consistent with that observed during chronic exposure. These results indicate that propiconazole interferes with the later stages of daphnid embryonic development, and that this toxicity is manifested largely via maternal exposure to the fungicide.}, number={3}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Kast-Hutcheson, K and Rider, CV and LeBlanc, GA}, year={2001}, month={Mar}, pages={502–509} }
 @article{leblanc_mclachlan_2000, title={Changes in the metabolic elimination profile of testosterone following exposure of the crustacean Daphnia magna to tributyltin}, volume={45}, ISSN={["1090-2414"]}, DOI={10.1006/eesa.1999.1859}, abstractNote={The biocide tributyltin has been found to cause the development of pseudohermaphroditic conditions in some neogastropod species. These abnormalities of the reproductive system have adversely affected the fecundity of some field populations of gastropods, resulting in local population declines. Current evidence suggests that tributyltin elicits these effects by interfering with the biotransformation of testosterone to other steroid derivatives, resulting in an elevation in endogenous testosterone or some of its bioactive derivatives. The purpose of the present study was to determine whether tributyltin altered testosterone metabolism in daphnids (Daphnia magna), a species commonly used in ecotoxicology testing. Exposure of daphnids to 1.2 microg (tin)/L caused a general increase in the rate of elimination of oxido-reduced, hydroxylated, and glucose-conjugated derivatives of testosterone. However, tributyltin exposure had no significant effect on the rate of elimination of the glucose-conjugated forms of the various oxido-reduced and hydroxylated derivatives of testosterone. As a result, the percentage of the oxido-reduced and hydroxylated metabolites of testosterone eliminated as glucose conjugates decreased with increasing tributyltin exposure levels. These results demonstrate that tributyltin causes alterations in testosterone metabolism in daphnids that would result in an increase in the production of oxido-reduced derivatives. These products are preferentially retained in the tissues of daphnids and are variously androgenic in vertebrates. The increased production of oxido-reduced derivatives of testosterone may be mechanically responsible for the masculinizing effects of tributyltin in some species and suggests that daphnids may be a suitable surrogate for evaluating the potential of chemicals to elicit this form of toxicity.}, number={3}, journal={ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY}, author={LeBlanc, GA and McLachlan, JB}, year={2000}, month={Mar}, pages={296–303} }
 @article{wolf_leblanc_ostby_gray_2000, title={Characterization of the period of sensitivity of fetal male sexual development to vinclozolin}, volume={55}, ISSN={["1096-0929"]}, DOI={10.1093/toxsci/55.1.152}, abstractNote={Vinclozolin is a fungicide whose metabolites are androgen receptor (AR) antagonists. Previous work in our laboratory showed that perinatal administration of vinclozolin to rats results in malformations of the external genitalia, permanent nipples, reduced anogenital distance (AGD), and reduced seminal vesicle, ventral prostate, and epididymal weights. The objectives of this study were to determine the most sensitive period of fetal development to antiandrogenic effects of vinclozolin and to identify a dosing regime that would induce malformations in all of the male offspring. Pregnant rats were dosed with 400 mg vinclozolin/kg/day on either GD 12-13, GD 14-15, GD 16-17, GD 18-19, or GD 20-21, or with corn oil (2.5 ml/kg) from GD 12 through GD 21 (Experiment 1). All 2-day periods in which significant effects were produced were included in an extended dosing period, GD 14 through GD 19, in which pregnant rats were dosed with 200 or 400 mg vinclozolin/kg (Experiment 2). In Experiment 1, significant effects of vinclozolin were observed in rats dosed on gestation days (GD) 14-15, GD 16-17, and GD 18-19, while the most significant effects were observed in rats treated on GD 16-17. These effects include reduced AGD; presence of areolas, nipples, and malformations of the phallus; and reduced levator ani/bulbocavernosus weight. In contrast, ventral prostate weight was reduced only in the GD 18-19 group. The expanded dosing regime (Experiment 2) increased the percentage of male offspring with genital malformations (> 92%), and retained nipples (100%), further reduced the weight of the ventral prostate, and reduced the weight of the seminal vesicles. In addition, malformations were more severe and included vaginal pouch and ectopic/undescended testes. The latter was induced only in the 400 mg/kg group. These data indicate that the reproductive system of the fetal male rat is most sensitive to antiandrogenic effects of vinclozolin on GD 16 and 17, although effects are more severe and 100 % of male offspring are affected with administration of vinclozolin from GD 14 through GD 19.}, number={1}, journal={TOXICOLOGICAL SCIENCES}, author={Wolf, CJ and LeBlanc, GA and Ostby, JS and Gray, LE}, year={2000}, month={May}, pages={152–161} }
 @article{olmstead_leblanc_2000, title={Effects of endocrine-active chemicals on the development of sex characteristics of Daphnia magna}, volume={19}, ISSN={["1552-8618"]}, DOI={10.1897/1551-5028(2000)019<2107:EOEACO>2.3.CO;2}, number={8}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Olmstead, AW and LeBlanc, GA}, year={2000}, month={Aug}, pages={2107–2113} }
 @article{leblanc_mu_rider_2000, title={Embryotoxicity of the alkylphenol degradation product 4-nonylphenol to the crustacean Daphnia magna}, volume={108}, ISSN={["0091-6765"]}, DOI={10.2307/3434824}, abstractNote={Laboratory studies have suggested that some alkylphenols and pesticides elicit developmental toxicity to crustaceans. The purpose of the present study was to evaluate the possibility that the alkylphenol degradation product 4-nonylphenol is embryotoxic to the crustacean Daphnia magna through its known ability to interfere with the metabolic elimination of testosterone. Direct exposure of maternal daphnids to testosterone caused developmental abnormalities in neonates that consisted of partial arrest of early embryonic development and abnormalities in shell spine and first antennae development. Exposure of maternal daphnids to concentrations of 4-nonylphenol also produced developmental abnormalities though the profile of abnormalities was distinct from that observed throughout the testosterone concentration-response curve. Thus, 4-nonylphenol is a developmental toxicant in daphnids, but its toxicity is not consistent with that elicited by elevated testosterone accumulation. Further experiments demonstrated that testosterone was directly toxic to developing embryos, and the maternal organism can serve as the vector for this toxicity. In contrast, neither direct embryo exposure nor early maternal exposure to 4-nonylphenol elicited embryotoxicity consistent with that observed during continuous maternal and gestational exposure. Thus, 4-nonylphenol is not directly embryotoxic at these exposure levels, but rather toxicity is mediated by maternal influences during gestation. The threshold concentration for the occurrence of developmental abnormalities ( approximately 44 microg/L) indicates that typical environmental concentrations of 4-nonylphenol pose no imminent hazard with respect to developmental toxicity. However, these effects do occur at sufficiently low levels to warrant evaluation of the relative susceptibility of other crustacean species to this previously uncharacterized mode of toxicity.}, number={12}, journal={ENVIRONMENTAL HEALTH PERSPECTIVES}, author={LeBlanc, GA and Mu, XY and Rider, CV}, year={2000}, month={Dec}, pages={1133–1138} }
 @article{korte_kahl_jensen_pasha_parks_leblanc_ankley_2000, title={Fathead minnow vitellogenin: Complementary DNA sequence and messenger RNA and protein expression after 17 beta-estradiol treatment}, volume={19}, ISSN={["1552-8618"]}, DOI={10.1897/1551-5028(2000)019<0972:FMVCDS>2.3.CO;2}, number={4}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Korte, JJ and Kahl, MD and Jensen, KM and Pasha, MS and Parks, LG and LeBlanc, GA and Ankley, GT}, year={2000}, month={Apr}, pages={972–981} }
 @article{weisbrod_shea_leblanc_moore_stegeman_2000, title={Organochlorine bioaccumulation and risk for whales in a northwest Atlantic food web}, volume={50}, ISSN={0141-1136}, url={http://dx.doi.org/10.1016/s0141-1136(00)00216-6}, DOI={10.1016/s0141-1136(00)00216-6}, abstractNote={Abstract The poor recovery of multiple whale populations raises concern for the integrity of the US marine environment. Fifty organochlorines were measured in samples of pilot whales, white-sided dolphins, endangered right whales and their prey. As expected from their high trophic position and proximity to land-based sources, the bioaccumulation of 4,4′-DDE, several chlordanes and polychlorinated biphenyl (PCB) congeners was substantial (ppm) in squid and the stranded odontocetes. Concentrations in fish and right whale biopsies were one to two orders of magnitude less than in odontocetes. Although the prevalent pesticides were different between odontocetes and balaenopterids, the magnitude of pesticide concentrations was similar across species. PCB concentrations were higher in the Gulf of Maine dolphins than pilot and right whales. Gender and tissue type were the important characteristics contributing to the bioaccumulation patterns observed in dolphins. Season of sample collection and exposure to different prey seemed critical for the bioaccumulation observed in right and pilot whales. Dolphin and pilot whale organs contained ample concentrations of specific compounds, notably 4,4′-DDE, that have been shown to alter endocrine function.}, number={1-5}, journal={Marine Environmental Research}, publisher={Elsevier BV}, author={Weisbrod, A. and Shea, D. and Leblanc, G. and Moore, M. and Stegeman, J.J.}, year={2000}, month={Jul}, pages={440–441} }
 @article{wilson_leblanc_2000, title={Petroleum pollution}, volume={3}, ISSN={1382-6980}, journal={Reviews in Toxicology}, author={Wilson, V.S. and LeBlanc, G.A}, year={2000}, pages={77–112} }
 @inbook{le blanc_2000, place={London}, title={Steroid hormone-regulated processes in invertebrates and their susceptibility to environmental endocrine disruption}, ISBN={9780203379608 9780203362808}, url={http://dx.doi.org/10.4324/9780203362808_chapter_5}, DOI={10.4324/9780203362808_chapter_5}, booktitle={Environmental Endocrine Disrupters: An Evolutionary Perspective}, publisher={Taylor & Francis}, author={Le Blanc, G.A}, editor={Guillette, L., Jr. and Crain, DA.Editors}, year={2000}, pages={126–154} }
 @article{wilson_leblanc_2000, title={The contribution of hepatic inactivation of testosterone to the lowering of serum testosterone levels by ketoconazole}, volume={54}, number={1}, journal={Toxicological Sciences}, author={Wilson, V. S. and LeBlanc, G. A.}, year={2000}, pages={128–137} }
 @article{wilson_mclachlan_falls_leblanc_1999, title={Alteration in sexually dimorphic testosterone biotransformation profiles as a biomarker of chemically induced androgen disruption in mice}, volume={107}, ISSN={["1552-9924"]}, DOI={10.2307/3434541}, abstractNote={Assessment of the impact of environmental chemicals on androgen homeostasis in rodent models is confounded by high intraindividual and interindividual variability in circulating testosterone levels. Our goal was to evaluate changes in testosterone biotransformation processes as a measure of androgen homeostasis and as a biomarker of exposure to androgen-disrupting chemicals. Sex-specific differences in hepatic testosterone biotransformation enzyme activities were identified in CD-1 mice. Gonadectomy followed by replacement of individual steroid hormones identified specific sex differences in biotransformation profiles that were due to the inductive or suppressive effects of testosterone. Notably, significant androgen-dependent differences in testosterone 6[alpha]- and 15[alpha]-hydroxylase activities were demonstrated, and the ratio of 6[alpha]- and 15[alpha]-hydroxylase activities proved to be an excellent indicator of the androgen status within the animal. The male or "masculinized" testosterone 6[alpha]/15[alpha]-hydroxylase ratio was significantly less than the female or "feminized" ratio. Male mice were exposed to both an antiandrogen, vinclozolin, and to a compound that modulates serum androgen levels, indole-3-carbinol, to test the utility of this ratio as a biomarker of androgen disruption. Treatment with the antiandrogen vinclozolin significantly increased the 6[alpha]/15[alpha]-hydroxylase ratio. Indole-3-carbinol treatment resulted in a dose-dependent, but highly variable, decrease in serum testosterone levels. The 6[alpha]/15[alpha]-hydroxylase ratio increased as serum testosterone levels decreased in these animals. However, the increase in the ratio was much less variable and more sensitive than serum testosterone levels. These investigations demonstrate that the 6[alpha]/15[alpha]-hydroxylase ratio is a powerful measure of androgen modulation and a sensitive indicator of exposure to androgen-disrupting chemicals in CD-1 mice.}, number={5}, journal={ENVIRONMENTAL HEALTH PERSPECTIVES}, author={Wilson, VS and McLachlan, JB and Falls, JG and LeBlanc, GA}, year={1999}, month={May}, pages={377–384} }
 @article{parks_cheek_denslow_heppell_mclachlan_leblanc_sullivan_1999, title={Fathead minnow (Pimephales promelas) vitellogenin: purification, characterization and quantitative immunoassay for the detection of estrogenic compounds}, volume={123}, ISSN={["1878-1659"]}, DOI={10.1016/s0742-8413(99)00010-9}, abstractNote={The egg yolk precursor protein, vitellogenin (VTG), was purified from blood plasma of 17beta-estradiol (E2)-treated male fathead minnows (Pimephales promnelas) by anion-exchange chromatography on DEAE-agarose. A rabbit antiserum was raised against their blood plasma and then adsorbed with plasma from untreated (control) males to render the antiserum specific to VTG. The adsorbed antiserum was used to detect fathead minnow VTG (fVTG) in Western and dot blotting experiments and in an enzyme-linked immunosorbent assay (ELISA). The antiserum recognised fVTG as a approximately 156 kDa protein in plasma from vitellogenic females and E2-injected males but not untreated males. Its identity was confirmed by analysis of: (1) amino acid composition; (2) an internal amino acid sequence; (3) reactivity to the homologous antiserum; and (4) recognition by monoclonal antibodies prepared against the VTG from common carp (Cyprinus carpio) and brown bullhead (Ameiurus nebulosus). Specificity of the homologous antiserum to fVTG was confirmed by Western blotting of serially diluted plasma from vitellogenic females. Utility of the antiserum and purified fVTG for detecting exposure of male fathead minnows to estrogenic compounds was verified using a dot blotting immunoassay of fVTG and detected by chemiluminescence. Adult male fish were exposed to various concentrations of E2 (10(-8), 10(-9) and 10(-10) M) in their rearing water and plasma assayed for the presence of VTG at different time points (2, 7, 14 and 21 days). A competitive, antibody-capture, quantitative ELISA was then developed based on the purified fVTG and its respective antiserum. The ELISA was validated by demonstrating parallel binding slopes of dilution curves prepared with plasma from E2-injected males, vitellogenic females, and aqueous egg extracts as compared with purified fVTG standard. Plasma concentrations of VTG as low as 3 ng ml(-1) were detected in the ELISA, for which inter- and intra-assay coefficients of variation were both less than 5%. Furthermore, plasma from control males was unreactive with the fVTG antiserum. The VTG ELISA could be useful for the detection of estrogenic properties associated with certain compounds and could be easily incorporated into standard laboratory toxicity assays using this species.}, number={2}, journal={COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY C-TOXICOLOGY & PHARMACOLOGY}, author={Parks, LG and Cheek, AO and Denslow, ND and Heppell, SA and McLachlan, JA and LeBlanc, GA and Sullivan, CV}, year={1999}, month={Jun}, pages={113–125} }
 @article{gooding_gallardo_leblanc_1999, title={Imposex in three marine gastropod species in Chile and potential impact on muriciculture}, volume={38}, ISSN={["1879-3363"]}, DOI={10.1016/S0025-326X(99)00167-8}, abstractNote={A survey of imposex was conducted between the Bay of San Vicente, Concepción, Chile (36° 50′) and the Bay of Renocavi, Puerto Montt, Chile (41° 35′), to determine if imposex is occurring in an area of collection and cultivation of the gastropod, Chorus giganteus. Imposex was recorded in three chilean muricids C. giganteus, Xanthochorus cassidiformis and Nucella crassilabrum complex. Percentage of imposex in females sampled ranged from 0% to 100%. The degree of expression of imposex was not so severe as to elicit sterility in the individuals surveyed. Incidence of imposex was as high as 47% in areas of harvest of C. giganteus for reproductive and cultivation studies for commercial production of this species. A six percent incidence of imposex was observed in Nucella proximal to the facility for cultivation of C. giganteus. Gastropods of the genus Nucella are used in other countries to monitor incidence of imposex and have demonstrated sensitivity toward tributyltin (TBT), the associated causal agent. Since sex of individuals in muriciculture is determined by the presence or absence of a penis, imposex may lead to erroneous classification of males and females. The incidence and severity of imposex in C. giganteus and related species may have a negative impact on sustainable cultivation and harvest of gastropods in Chile.}, number={12}, journal={MARINE POLLUTION BULLETIN}, author={Gooding, M and Gallardo, C and Leblanc, G}, year={1999}, month={Dec}, pages={1227–1231} }
 @article{leblanc_mclachlan_1999, title={Molt-independent growth inhibition of Daphnia magna by a vertebrate antiandrogen}, volume={18}, ISSN={["1552-8618"]}, DOI={10.1897/1551-5028(1999)018<1450:MIGIOD>2.3.CO;2}, number={7}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={LeBlanc, GA and McLachlan, JB}, year={1999}, month={Jul}, pages={1450–1455} }
 @inbook{leblanc_1999, place={West Conshohocken, PA}, title={Screening approaches for the evaluation of endocrine disruption in invertebrates}, volume={8}, DOI={10.1520/STP15795S}, booktitle={Environmental Toxicology and Risk Assessment: Standardization of Biomarkers for Endocrine Disruption and Environmental Assessment}, publisher={American Society of Testing and Materials International}, author={LeBlanc, G.A}, editor={Henshel, D. and Harrass, M. and Black, M.Editors}, year={1999}, pages={3–23} }
 @inbook{leblanc_cambell_den besten_brown_chang_coats_defur_dhaldialla_edwards_riddiford_et al._1999, place={Pensacola, FL}, title={The endocrinology of invertebrates}, booktitle={Endocrine Disruption in Invertebrates: Endocrinology, Testing, and Assessment}, publisher={SETAC Press}, author={LeBlanc, G.A. and Cambell, P.M. and den Besten, P. and Brown, R.P. and Chang, E. and Coats, J. and deFur, PL and Dhaldialla, T. and Edwards, J. and Riddiford, L.M. and et al.}, editor={Crane, M. and deFur, PL and Ingersoll, C. and Tattersfield, LEditors}, year={1999}, pages={23–106} }
 @inbook{defur_crane_tattersfield_ingersoll_stahl_matthiessen_leblanc_1999, place={Pensacola, FL}, title={Workshop on Endocrine Disruption in Invertebrates: Endocrinology, Testing, and Assessment (EDIETA): Executive Summary}, ISBN={9781880611272}, booktitle={Endocrine Disruption in Invertebrates: Endocrinology, Testing, and Assessment}, publisher={SETAC Press}, author={DeFur, PL and Crane, M. and Tattersfield, LJ and Ingersoll, CG and Stahl, RG, Jr. and Matthiessen, P and LeBlanc, GA}, editor={Crane, M. and DeFur, PL and Ingersoll, C. and Tattersfield, LEditors}, year={1999} }
 @article{oberdorster_rittschof_leblanc_1998, title={Alteration of [C-14]-testosterone metabolism after chronic exposure of Daphnia magna to tributyltin}, volume={34}, ISSN={["0090-4341"]}, DOI={10.1007/s002449900281}, number={1}, journal={ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY}, author={Oberdorster, E and Rittschof, D and LeBlanc, GA}, year={1998}, month={Jan}, pages={21–25} }
 @article{baldwin_graham_shea_leblanc_1998, title={Altered metabolic elimination of testosterone and associated toxicity following exposure of Daphnia magna to nonylphenol polyethoxylate}, volume={39}, ISSN={["0147-6513"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032005539&partnerID=MN8TOARS}, DOI={10.1006/eesa.1997.1614}, abstractNote={The ability of nonylphenol polyethoxylate (nonylphenyl polyethylene glycol, NPPG) to alter the metabolic elimination of testosterone and elicit reproductive toxicity to Daphnia magna was assessed. NPPG (5.0 mg/liter) inhibited the elimination of testosterone as glucose and sulfate conjugates, but had minimal effect on the rate of elimination of oxido-reduced and hydroxylated derivatives of the steroid hormone. This exposure concentration of NPPG also approximated the acute threshold-effect concentration and the chronic value for daphnids. Results demonstrated that NPPG qualitatively elicits similar effects on the metabolic elimination of testosterone by daphnids as previously characterized with its degradation product 4-nonylphenol. Unlike 4-nonylphenol, significant chronic toxicity of NPPG, due to effects on steroid elimination processes, was not evident. Results from the present study provide no indication that concentrations of nonylphenol polyethoxylates typically measured in the environment pose a risk of chronic toxicity to invertebrates.}, number={2}, journal={ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY}, author={Baldwin, WS and Graham, SE and Shea, D and LeBlanc, GA}, year={1998}, month={Feb}, pages={104–111} }
 @inbook{hamelink_le blanc_1998, place={New York}, title={Bioaccumulation}, volume={1}, ISBN={9780122272202}, booktitle={Encyclopedia of Toxicology}, publisher={Academic Press Inc}, author={Hamelink, J. and Le Blanc, G.A}, editor={Wexler, P.Editor}, year={1998}, pages={148} }
 @article{wilson_leblanc_1998, title={Endosulfan elevates testosterone biotransformation and clearance in CD-1 mice}, volume={148}, ISSN={["1096-0333"]}, DOI={10.1006/taap.1997.8319}, abstractNote={Toxicant-mediated induction of hepatic biotransformation enzymes is a mechanism by which endogenous steroid hormone metabolism and elimination may be altered. Endosulfan, an organochlorine insecticide that has been demonstrated to induce hepatic P450 biotransformation enzymes, was examined for its ability to alter the rate of steroid hormone metabolism in CD-1 mice. Our objective was to evaluate whether endosulfan-induced changes in the rate of testosterone metabolism were reflected in the rate of testosterone clearance and if those alterations were sufficient to disrupt steroid hormone homeostasis within the animal. Major pathways for testosterone metabolism in the liver, including hydroxylation, conjugation to glucuronic acid or sulfate, and reduction/dehydrogenation, were examined for changes due to endosulfan exposure. In female mice, endosulfan treatment elicited a dose-dependent increase in the rate of total testosterone hydroxyl metabolite formation by selectively increasing the rate of production of 16β-, 6α-, and 16α-hydroxytestosterone metabolites. The hydroxylation of testosterone in the 16β position was most sensitive to endosulfan with a 3.3-fold increase in the rate of production of this metabolite observed following exposure to 7.5 mg/kg/day for 7 days. The rate of testosterone dehydrogenation to androstenedione was increased by 7.5 mg/kg/day of endosulfan, but the rate of direct glucuronic acid or sulfate conjugation to testosterone was not affected by any of the dosages investigated. Endosulfan was generally more toxic to male mice and did not significantly alter the rate of total hydroxytestosterone metabolite formation or glucuronic acid or sulfate conjugation. The ability of endosulfan to enhance the elimination of testosterone was, therefore, investigated in female mice. Exposure of mice to 7.5 mg/kg/day of endosulfan resulted in an ∼3.6-fold increase in the rate of urinary elimination of [14C]androgen, but had no significant effect on the fecal elimination of [14C]androgen. The increase in androgen clearance was associated only with a small, nonsignificant decrease in serum testosterone levels. Results indicate that increases in testosterone biotransformation from endosulfan exposure can result in increases in the elimination of the steroid. However, homeostatic processes apparently compensate for the effect and minimize any consequences on serum hormone levels.}, number={1}, journal={TOXICOLOGY AND APPLIED PHARMACOLOGY}, author={Wilson, VS and LeBlanc, GA}, year={1998}, month={Jan}, pages={158–168} }
 @article{pontius_rushing_foegeding_1998, title={Heat resistance of Alicyclobacillus acidoterrestris spores as affected by various pH values and organic acids}, volume={61}, ISSN={["0362-028X"]}, DOI={10.4315/0362-028X-61.1.41}, abstractNote={Alicyclobacillus acidoterrestris, a thermoacidophilic sporeformer, has caused spoilage of fruit juices which had been treated with thermal processes intended to commercially sterilize the juice. The objective of this research was to document the effect of pH, acid, and temperature on the heat resistance of spores of three fruit-juice isolates of A. acidoterrestris. The thermal resistance of spores of A. acidoterrestris strains VF, WAC, and IP were studied in a model fruit-juice system composed of 12% glucose and 30 mM of either citric, malic, or tartaric acid, adjusted to selected pH values ranging from 2.8 to 4.0. Decimal reduction times (D values) and inactivation rates were determined. Spores of strains VF and WAC were similarly resistant to heat under acidic conditions, while strain IP spores were less resistant. In the range of pH 2.8 to 4.0, a statistically effect of hydrogen ion concentration on heat resistance was observed at lower temperatures, but not at the higher temperatures, but not at the higher temperatures. For examples, at 91 degrees C and pH 3.1 and 3.7, D values were 31.3 and 54.3 min, respectively, while at 97 degrees C D values at pH 3.1 and 3.7 were 7.9 and 8.8 min, respectively. The type of acid did not significantly affect the heat resistance. The zd values ranged from 5.9 to 10 degrees C, depending on the acid, pH, and the strain. The models generated from this research can be used to determine adequate thermal processes, accounting for the acid type, pH, and temperature, to destroy A. acidoterrestris spores in beverages, since this organism is able to survive the typical hot-fill and hold process (2 min at 88 to 96 degrees C) currently used to process fruit juice.}, number={1}, journal={JOURNAL OF FOOD PROTECTION}, author={Pontius, AJ and Rushing, JE and Foegeding, PM}, year={1998}, month={Jan}, pages={41–46} }
 @article{parks_leblanc_1998, title={Involvement of multiple biotransformation processes in the metabolic elimination of testosterone by juvenile and adult fathead minnows (Pimephales promelas)}, volume={112}, ISSN={["0016-6480"]}, DOI={10.1006/gcen.1998.7131}, abstractNote={Steroid hormone metabolic clearance pathways are susceptible to induction and suppression resulting from exposure to many xenobiotics. These biochemical effects have the potential to alter steroid hormone homeostasis and, ultimately, steroid hormone-dependent processes such as growth, development, and reproduction. In this study, the metabolic clearance of 17β-hydroxy-4-androsten-3-one (testosterone) by adult male, adult female, and juvenile fathead minnows (Pimephales promelas) was evaluated. Individual elimination metabolites were identified and rates of metabolite elimination were quantified. Fathead minnows produced a variety of testosterone metabolites including oxido-reduced, hydroxylated, and conjugated derivatives. Metabolites identified by TLC/GC/MS included 4-androstene-3,17-dione (androstenedione), 17β-hydroxy-5α-androstan-3-one (5α-dihydrotestosterone), 5α-androstane-3α,17β-diol (3α-androstanediol), 5α-androstane-3β,17β-diol (3β-androstanediol), 17β-hydroxy-4-androstene-3,11-dione (11-ketotestosterone), 16β-hydroxy-4-androsten-3-one (16β-hydroxytestosterone), and 6β-hydroxy-4-androsten-3-one (6β-hydroxytestosterone). Testosterone and its metabolites were eliminated in both free and conjugated form. Adult male, adult female, and juvenile fathead minnows eliminated the same profile of testosterone metabolites. However, adult females eliminated androstanediols at a significantly greater rate than did males, and juvenile fish eliminated nearly all testosterone metabolites at greater weight-normalized rates than did adults. These results demonstrate that fathead minnows extensively metabolize testosterone leading to its elimination and provide the foundation upon which the effects of xenobiotics on testosterone metabolism can be assessed.}, number={1}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Parks, LG and LeBlanc, GA}, year={1998}, month={Oct}, pages={69–79} }
 @misc{ankley_mihaich_stahl_tillitt_colborn_mcmaster_miller_bantle_campbell_denslow_et al._1998, title={Overview of a workshop on screening methods for detecting potential (anti-) estrogenic/androgenic chemicals in wildlife}, volume={17}, ISSN={["1552-8618"]}, DOI={10.1897/1551-5028(1998)017<0068:OOAWOS>2.3.CO;2}, abstractNote={The U.S. Congress has passed legislation requiring the U.S. Environmental Protection Agency (U.S. EPA) to develop, validate, and implement screening tests for identifying potential endocrine-disrupting chemicals within 3 years. To aid in the identification of methods suitable for this purpose, the U.S. EPA, the Chemical Manufacturers Association, and the World Wildlife Fund sponsored several workshops, including the present one, which dealt with wildlife species. This workshop was convened with 30 international scientists representing multiple disciplines in March 1997 in Kansas City, Missouri, USA. Participants at the meeting identified methods in terms of their ability to indicate (anti-) estrogenic/androgenic effects, particularly in the context of developmental and reproductive processes. Data derived from structure-activity relationship models and in vitro test systems, although useful in certain contexts, cannot at present replace in vivo tests as the sole basis for screening. A consensus was reached that existing mammalian test methods (e.g., with rats or mice) generally are suitable as screens for assessing potential (anti-) estrogenic/ androgenic effects in mammalian wildlife. However, due to factors such as among-class variation in receptor structure and endocrine function, it is uncertain if these mammalian assays would be of broad utility as screens for other classes of vertebrate wildlife. Existing full and partial life-cycle tests with some avian and fish species could successfully identify chemicals causing endocrine disruption; however, these long-term tests are not suitable for routine screening. However, a number of short-term tests with species from these two classes exist that could serve as effective screening tools for chemicals inducing (anti-) estrogenic/androgenic effects. Existing methods suitable for identifying chemicals with these mechanisms of action in reptiles and amphibians are limited, but in the future, tests with species from these classes may prove highly effective as screens. In the case of invertebrate species, too little is known at present about the biological role of estrogens and androgens in reproduction and development to recommend specific assays.}, number={1}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Ankley, G and Mihaich, E and Stahl, R and Tillitt, D and Colborn, T and McMaster, S and Miller, R and Bantle, J and Campbell, P and Denslow, N and et al.}, year={1998}, month={Jan}, pages={68–87} }
 @article{le blanc_1998, title={The state of the debate}, volume={13}, number={3}, journal={Forum for Applied Research and Public Policy}, author={Le Blanc, G.A}, year={1998}, pages={6–10} }
 @article{ma_wang_yin_pan_guo_leblanc_reinecke_watson_krawiec_1998, title={Two pimarane diterpenoids from Ephemerantha lonchophylla and their evaluation as modulators of the multidrug resistance phenotype}, volume={61}, ISSN={["1520-6025"]}, DOI={10.1021/np970065o}, abstractNote={Two new pimarane diterpenoids, lonchophylloids A (1) and B (2), were isolated from the stems of Ephemerantha lonchophylla. The structures of 1 and 2 were established predominantly through the application of extensive 1H-and 13C-NMR, 1D- and 2D-homonuclear and heteronuclear correlation NMR experiments, and X-ray diffraction methods. Consistent with structure--activity predictions, both compounds were capable of sensitizing cells that expressed the multidrug resistance phenotype to the toxicity of the anticancer drug doxorubicin.}, number={1}, journal={JOURNAL OF NATURAL PRODUCTS}, author={Ma, GX and Wang, TS and Yin, L and Pan, Y and Guo, YL and LeBlanc, GA and Reinecke, MG and Watson, WH and Krawiec, M}, year={1998}, month={Jan}, pages={112–115} }
 @article{leblanc_bain_wilson_1997, title={At the cutting edge - Pesticides: Multiple mechanisms of demasculinization}, volume={126}, ISSN={["0303-7207"]}, DOI={10.1016/S0303-7207(96)03968-8}, abstractNote={Many pesticides are known to produce reproductive and developmental effects in chronically exposed non-target organisms, including humans. Recent evidence suggests that demasculinization may be an important mechanism responsible for some of these effects. Some pesticides have been shown to interact with the androgen receptor and to act as antagonists, while others have been shown to interact with the estrogen receptor and function as estrogens in both in vitro and in vivo. Many pesticides can also lower serum androgen levels by altering rates of synthesis or metabolism. Given the ubiquity of pesticides in the environment and the multiple mechanisms whereby they can elicit demasculinizing effects, synergy between such compounds may produce clinical endocrine dysfunction at current human exposure levels.}, number={1}, journal={MOLECULAR AND CELLULAR ENDOCRINOLOGY}, author={LeBlanc, GA and Bain, LJ and Wilson, VS}, year={1997}, month={Jan}, pages={1–5} }
 @inbook{le blanc_1997, place={Stamford, CT}, edition={2nd}, title={Basics of Environmental Toxicology}, booktitle={A Textbook of Modern Toxicology}, publisher={Appleton & Lange}, author={Le Blanc, G.A}, editor={Hodgson, E. and Levi, P.E.Editors}, year={1997}, pages={389–406} }
 @inbook{le blanc_1997, place={San Diego, California}, series={Current Controversies}, title={Chemical contamination affects wildlife}, booktitle={Garbage & Waste}, publisher={Greenhaven Press, Inc.}, author={Le Blanc, G.A}, editor={Cozic, Charles P.Editor}, year={1997}, pages={92–95}, collection={Current Controversies} }
 @article{leblanc_bain_1997, title={Chronic toxicity of environmental contaminants: Sentinels and biomarkers}, volume={105}, DOI={10.2307/3433398}, number={Suppl. 1}, journal={Environmental Health Perspectives}, author={LeBlanc, Gerald and Bain, L. J.}, year={1997}, pages={65–80} }
 @inbook{levi_hodgson_le blanc_1997, place={Stamford, CT}, edition={2nd}, title={Elimination of Toxicants}, booktitle={A Textbook of Modern Toxicology}, publisher={Appleton & Lange}, author={Levi, P.E. and Hodgson, E. and Le Blanc, G.A}, editor={Hodgson, E. and Levi, P.E.Editors}, year={1997}, pages={107–118} }
 @inbook{le blanc_1997, place={Southborough, MA}, series={IBC Library Series}, title={Invertebrates as sentinels of xenobiotic-induced endocrine disruption}, volume={2}, booktitle={Endocrine Disruptors: Advances in Measuring and Analyzing Their Effects}, publisher={International Business Communications}, author={Le Blanc, G.A.}, editor={Guttry, P.Editor}, year={1997}, pages={1–24}, collection={IBC Library Series} }
 @article{baldwin_graham_shea_leblanc_1997, title={Metabolic androgenization of female Daphnia magna by the xenoestrogen 4-nonylphenol}, volume={16}, ISSN={["1552-8618"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0030807616&partnerID=MN8TOARS}, DOI={10.1897/1551-5028(1997)016<1905:MAOFDM>2.3.CO;2}, number={9}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Baldwin, WS and Graham, SE and Shea, D and LeBlanc, GA}, year={1997}, month={Sep}, pages={1905–1911} }
 @article{christensen_parks_mcnutt_leblanc_1997, title={Reversal of multidrug resistance by derivatives of acrivastine: a study of structure activity relationships of P glycoprotein inhibitors in vitro and in vivo}, volume={4}, number={6}, journal={Oncology Reports}, author={Christensen, J. G. and Parks, L. G. and McNutt, R. W. and Leblanc, G. A.}, year={1997}, pages={1353–1360} }
 @article{bain_mclachlan_leblanc_1997, title={Structure-activity relationships for xenobiotic transport substrates and inhibitory ligands of P-glycoprotein}, volume={105}, ISSN={["0091-6765"]}, DOI={10.2307/3433698}, abstractNote={The multixenobiotic resistance phenotype is characterized by the reduced accumulation of xenobiotics by cells or organisms due to increased efflux of the compounds by P-glycoprotein (P-gp) or related transporters. An extensive xenobiotic database, consisting primarily of pesticides, was utilized in this study to identify molecular characteristics that render a xenobiotic susceptible to transport by or inhibition of P-gp. Transport substrates were differentiated by several molecular size/shape parameters, lipophilicity, and hydrogen bonding potential. Electrostatic features differentiated inhibitory ligands from compounds not catagorized as transport substrates and that did no interact with P-gp. A two-tiered system was developed using the derived structure-activity relationships to identify P-gp transport substrates and inhibitory ligands. Prediction accuracy of the approach was 82%. We then validated the system using six additional pesticides of which tow were predicted to be P-gp inhibitors and four were predicted to be noninteractors, based upon the structure-activity analyses. Experimental determinations using cells transfected with the human MDR1 gene demonstrated that five of the six pesticides were properly catagorized by the structure-activity analyses (83% accuracy). Finally, structure-activity analyses revealed that among P-gp inhibitors, relative inhibitory potency can be predicted based upon the surface area or volume of the compound. These results demonstrate that P-gp transport substrates and inhibitory ligands can be distinguished using molecular characteristics. Molecular characteristics of transport substrates suggest that P-gp may function in the elimination of hydroxylated metabolites of xenobiotics.}, number={8}, journal={ENVIRONMENTAL HEALTH PERSPECTIVES}, author={Bain, LJ and McLachlan, JB and LeBlanc, GA}, year={1997}, month={Aug}, pages={812–818} }
 @article{baldwin_leblanc_1996, title={Expression and induction of an immunochemically related class of glutathione S-transferases in Daphnia magna}, volume={113}, ISSN={1096-4959}, url={http://dx.doi.org/10.1016/0305-0491(95)02021-7}, DOI={10.1016/0305-0491(95)02021-7}, abstractNote={The cytosolic glutathione S-transferases (GSTs) are dimeric enzymes that are responsible for the conjugation of glutathione to an electrophilic center of a variety of lipophilic compounds. The purpose of the present study was to characterize the GSTs of Daphnia magna with respect to enzyme multiplicity, molecular weight, isoelectric points, and immunochemical distinction and to determine the inducibility of these enzymes by the prototypical mammalian GST inducer, phenobarbital. GSTs were purified from crude cystosols prepared from daphnids by glutathione-sepharose affinity chromatography. SDS-polyacrylamide gel electrophoresis of the affinity purified GSTs revealed the presence of multiple subunits with molecular weights ranging from 26.9 to 30.2 kDa. Preparative electrofocusing separated GST activity into three major fractions having approximate isoelectric points of 4.5, 4.8 and 5.6. All of the catalytically active fractions contained a single protein band of the same molecular weight (30.2 kDa) during SDS-PAGE. A monoclonal antibody, prepared against the affinity-purified GST proteins, recognized three distinct proteins separated during analytical-scale isoelectric focusing (pI 4.6, 4.7 and 4.8). These proteins may represent a class of GSTs distinct from the GST having a pI of 5.6. Treatment of daphnids with phenobarbital elevated both GST catalytic activity and immunodetectable protein. These results demonstrate that multiple immunochemically related proteins of the same molecular weight but varying isoelectric points are responsible for most of the GST catalytic activity with the substrate 1-chloro-2,4-dinitrobenzene.}, number={2}, journal={Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology}, publisher={Elsevier BV}, author={Baldwin, W.S. and Leblanc, G.A.}, year={1996}, month={Feb}, pages={261–267} }
 @article{bain_leblanc_1996, title={Interaction of structurally diverse pesticides with the human MDR1 gene product P-glycoprotein}, volume={141}, ISSN={0041-008X}, url={http://dx.doi.org/10.1016/s0041-008x(96)80035-4}, DOI={10.1016/s0041-008x(96)80035-4}, abstractNote={P-glycoprotein (P-gp) is a 170-kDa membrane-bound glycoprotein shown to efflux a wide variety of chemicals, such as chemotherapeutic agents and carcinogens. Experiments were conducted using B16/F10 murine melanoma cells transfected with the human MDR1 gene (B16/hMDR1 cells), which codes for P-gp, to determine whether this transporter may contribute to the cellular efflux of some pesticides. Thirty-eight pesticides representing several classes of compounds were evaluated for their potential to bind to P-gp, as measured by the inhibition of efflux of the P-gp substrate doxorubicin. Carbamate and pyrethroid insecticides exhibited little interaction with P-gp, while many of the organophosphorus and organochlorine pesticides significantly inhibited the efflux of doxorubicin. Pesticides that significantly inhibited the efflux of doxorubicin were then assessed for P-gp-mediated efflux. One pesticide, endosulfan, exhibited slight though significant transport mediated by P-gp. Competition experiments performed with the P-glycoprotein ligand [3H]azidopine demonstrated that the P-gp inhibitory pesticides bound to P-gp. Both lipophilicity and molecular mass were major physical/chemical determinants in dictating pesticide binding to P-gp, with optimum binding occurring with compounds having a log Kow value of 3.6-4.5 and a molecular weight of 391-490 Da. The transport substrate endosulfan possessed optimal binding characteristics. These results demonstrated that many pesticides are capable of binding to P-gp; however, binding does not infer transport.}, number={1}, journal={Toxicology and Applied Pharmacology}, publisher={Elsevier BV}, author={Bain, Lisa J. and LeBlanc, Gerald A.}, year={1996}, month={Nov}, pages={288–298} }
 @article{bain_leblanc_1996, title={Mobilization of Pentachlorophenol by GlutathioneS-Transferase μ Increases Cellular Toxicity}, volume={54}, ISSN={0048-3575}, url={http://dx.doi.org/10.1006/pest.1996.0010}, DOI={10.1006/pest.1996.0010}, abstractNote={Abstract Glutathione S -transferases (GSTs) are a class of proteins that have intracellular binding and sequestration, as well as catalytic, capabilities. This study investigated the role of GSTs in the intracellular mobilization of pentachlorophenol (PCP). A single mouse GST isoform, GST μ , specifically and competitively bound PCP with a k i = 7 μ M with respect to the substrate 1-chloro-2,4-dinitrobenzene (CDNB), yet did not metabolize PCP. Instead, the binding of GST μ to PCP resulted in the partitioning of PCP from lipid to aqueous compartments. The physiological significance of the mobilization was then investigated using two mouse hepatocyte cell lines that differ significantly in their expression of GST μ . These cells were treated with butylated hydroxyanisole (BHA) to induce GST μ and provided several levels of GST μ expression. The toxicity of PCP to these cells based on trypan blue dye exclusion was assessed, which demonstrated a significant correlation between GST μ levels within the cell and PCP toxicity. The BHA-treated, high GST μ expressor cells were approximately 40% more sensitive to PCP toxicity than were the untreated low GST μ expressors, suggesting that GST μ was acting to make PCP more bioavailable to elicit toxicity. Furthermore, the increase in toxicity was not due to a difference in PCP accumulation or in GST metabolism by the cells. These results suggest that GST μ may increase the cellular toxicity of PCP by mobilizing this lipophilic compound within the cell.}, number={1}, journal={Pesticide Biochemistry and Physiology}, publisher={Elsevier BV}, author={Bain, Lisa J. and LeBlanc, Gerald A.}, year={1996}, month={Jan}, pages={65–72} }
 @article{dunn_hughes_leblanc_cullen_1996, title={Overexpression of ap-glycoprotein in hepatocellular carcinomas from woodchuck hepatitis virus-infected woodchucks (Marmota monax)}, volume={23}, ISSN={0270-9139 1527-3350}, url={http://dx.doi.org/10.1002/hep.510230402}, DOI={10.1002/hep.510230402}, abstractNote={The leading cause of human hepatocellular carcinomas (HCCs) is hepatitis B virus (HBV) infection. Woodchucks infected with a closely related hepadnavirus, woodchuck hepatitis virus (WHV), serve as a model for HBV because woodchucks chronically infected with WHV also develop hepatocellular carcinomas. Increased expression of p-glycoprotein (pgp) in human HCCs is a common obstacle in successful cancer chemotherapy. Pgps are encoded by a family of multidrug-resistance (MDR) genes. Livers from uninfected and WHV-infected woodchucks were examined to determine if pgp was expressed in HCCs and if there was a difference in expression between HCCs and nonneoplastic liver. A 170-kd protein was identified by Western blot in HCCs, whereas, constitutive pgp was not detected in normal liver taken from the same animals in 3 of 3 cases. Immunolocalization of the pgp with a panel of monoclonal antibodies revealed intensification of staining in 7 of 20 foci and 12 of 22 HCCs from six animals. Using primers for the human MDR1 gene, a single product was detected by reverse-transcribed polymerase chain reaction (RT-PCR) from HCCs. We have shown an increase in pgp in HCCs compared with normal liver from WHV-infected woodchucks. This is the first example of the induction of a pgp in a naturally hepadnavirus infected rodent system. It suggests the woodchuck can be a useful model for the study of the acquisition of resistance to chemotherapeutic agents in virally induced HCCs.}, number={4}, journal={Hepatology}, publisher={Wiley}, author={Dunn, S E and Hughes, C S and LeBlanc, G A and Cullen, J M}, year={1996}, month={Apr}, pages={662–668} }
 @article{parks_leblanc_1996, title={Reductions in steroid hormone biotransformation/elimination as a biomarker of pentachlorophenol chronic toxicity}, volume={34}, ISSN={0166-445X}, url={http://dx.doi.org/10.1016/0166-445x(95)00045-6}, DOI={10.1016/0166-445x(95)00045-6}, abstractNote={Alterations in steroid hormone metabolism by environmental endocrine disrupters can significantly affect steroid hormone-dependent processes such as growth and reproduction. The identification of biomarkers of endocrine-disrupting effects would facilitate targeting chemicals that would warrant reproductive toxicity assessment. The present study was undertaken to determine whether perturbations in steroid hormone biotransformation capabilities following short-term exposure to the endocrine-disrupting biocide pentachlorophenol (PCP) would serve as a biomarker of concentrations of this chemical that would adversely affect the reproductive capacity of Daphnia magna. Reproduction of daphnids was significantly compromised from continuous exposure to PCP concentrations as low as 0.25 mg/l. Following chronic exposure to PCP, daphnids were incubated with [14C]testosterone and the elimination rate of several testosterone metabolites was quantified. The rate of testosterone hydroxylmetabolite elimination was not significantly altered by PCP exposure. However, elimination of several of the glucose-conjugated metabolites of testosterone decreased in a PCP concentration-dependent manner. Adult daphnids were then exposed to these concentrations of PCP for 48 h and effects on steroid metabolism assessed. As observed following chronic exposure, PCP had no effect on the elimination of hydroxyl-metabolites of testosterone. However, PCP concentrations as low as 0.062 mg/l significantly inhibited the elimination of glucose conjugates of testosterone; and, sulfate conjugated metabolites decreased in a PCP concentration-dependent manner. These results demonstrate that: (1) PCP alters steroid hormone biotransformation/elimination capacities at concentrations that adversely affect reproduction and (2) effects on steroid hormone biotransformation can be detected following short-term exposure to PCP. Thus, this biochemical parameter may serve as a biomarker of chronic toxicity associated with PCP and perhaps other endocrine-disrupting chemicals.}, number={4}, journal={Aquatic Toxicology}, publisher={Elsevier BV}, author={Parks, Louise G. and LeBlanc, Gerald A.}, year={1996}, month={Apr}, pages={291–303} }
 @article{christensen_le blanc_1996, title={Reversal of multi-drug resistance in vivo by dietary administration of the phytochemical indole-3-carbinol}, volume={56}, number={3}, journal={Cancer Research}, author={Christensen, J.G. and Le Blanc, G.A}, year={1996}, month={Feb}, pages={574–581} }
 @article{leblanc_1995, title={Are environmental sentinels signaling?}, volume={103}, ISSN={0091-6765 1552-9924}, url={http://dx.doi.org/10.1289/ehp.95103888}, DOI={10.1289/ehp.95103888}, abstractNote={There is an increasing perception that environmental contamination by chemicals no longer poses a significant health threat and that relaxation of environmental regulations is warranted. However, many wildlife populations are showing signs of developmental, behavioral, and reproductive dysfunction due to environmental contamination by endocrine-disrupting chemicals. Scientists, regulators, and legislators must mobilize to identify current health threats posed by environmental pollutants, develop testing protocols that will detect such properties of new chemicals, and strengthen legislation designed to protect environmental health.}, number={10}, journal={Environmental Health Perspectives}, publisher={Environmental Health Perspectives}, author={LeBlanc, G A}, year={1995}, month={Oct}, pages={888–890} }
 @article{baldwin_milam_leblanc_1995, title={PHYSIOLOGICAL AND BIOCHEMICAL PERTURBATIONS IN DAPHNIA MAGNA FOLLOWING EXPOSURE TO THE MODEL ENVIRONMENTAL ESTROGEN DIETHYLSTILBESTROL}, volume={14}, ISSN={0730-7268 1552-8618}, url={http://dx.doi.org/10.1897/1552-8618(1995)14[945:pabpid]2.0.co;2}, DOI={10.1897/1552-8618(1995)14[945:pabpid]2.0.co;2}, number={6}, journal={Environmental Toxicology and Chemistry}, publisher={Wiley}, author={Baldwin, William S. and Milam, David L. and LeBlanc, Gerald A.}, year={1995}, pages={945} }
 @article{le blanc_1995, title={Subtle effects: devastating consequences}, volume={15}, number={3}, journal={SETAC News}, author={Le Blanc, G.A}, year={1995}, pages={30–31} }
 @article{leblanc_1995, title={Trophic-Level Differences in the Bioconcentration of Chemicals: Implications in Assessing Environmental Biomagnification}, volume={29}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es00001a020}, DOI={10.1021/es00001a020}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTrophic-Level Differences in the Bioconcentration of Chemicals: Implications in Assessing Environmental BiomagnificationGerald A. LeBlancCite this: Environ. Sci. Technol. 1995, 29, 1, 154–160Publication Date (Print):January 1, 1995Publication History Published online1 May 2002Published inissue 1 January 1995https://doi.org/10.1021/es00001a020RIGHTS & PERMISSIONSArticle Views855Altmetric-Citations99LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts}, number={1}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={LeBlanc, Gerald A.}, year={1995}, month={Jan}, pages={154–160} }
 @article{leblanc_1994, title={Assessing deleterious ecosystem-level effects of environmental pollutants as a means of avoiding evolutionary consequences.}, volume={102}, ISSN={0091-6765 1552-9924}, url={http://dx.doi.org/10.1289/ehp.94102266}, DOI={10.1289/ehp.94102266}, abstractNote={Recent interest has been expressed in the possible need to develop ways to detect and quantify pollutants that affect evolution. Although environmental pollutants clearly can affect evolutionary processes, the evolutionary changes are a response to ecosystem-level toxicity elicited by the pollutant, rather than a direct effect of the pollutant on evolution. Accordingly, emphasis needs to be placed on assessing the adverse effects of environmental pollutants on ecosystem structure and function in order to avoid subsequent evolutionary consequences.}, number={3}, journal={Environmental Health Perspectives}, publisher={Environmental Health Perspectives}, author={LeBlanc, G A}, year={1994}, month={Mar}, pages={266–267} }
 @article{le blanc_stuart_dunn_baldwin_1994, title={Effect of the plant compound indole-3-carbinol on hepatic cholesterol homoeostasis}, volume={32}, ISSN={["1873-6351"]}, DOI={10.1016/0278-6915(94)90007-8}, abstractNote={The aim of this study was to elucidate the effects of the compound indole-3-carbinol (I3C), which is found in cruciferous vegetables, on hepatic cholesterol homoeostasis and metabolism in male CD-1 mice. Oral administration of 500 and 750 mg I3C/kg/day to mice for 1 wk resulted in increased liver mass and microsomal protein content. Hepatic microsomal cholesterol levels were not significantly altered following treatment with 100 and 250 mg I3C/kg/day, but were significantly decreased following treatment with 500 and 750 mg/kg/day. Conversely, the lower doses of I3C administered decreased serum cholesterol levels whereas the higher doses of I3C had no effect on this parameter. Alterations in cholesterol homoeostasis by I3C were not related to liver hypertrophy, since administration of phenobarbital to mice increased liver size, but had no significant effect on hepatic microsomal or serum cholesterol levels. Activities of the hepatic enzymes cholesterol ester hydrolase and cholesterol 7 alpha-hydroxylase were not altered by I3C. However, 500 and 750 mg I3C/kg/day elevated the activity of hepatic acyl-CoA:cholesterol acyltransferase (ACAT), the enzyme responsible for the formation of hepatic cholesteryl esters. These results demonstrate that (a) I3C lowers serum cholesterol levels at concentrations that have no discernible effect on hepatic cholesterol homoeostasis, and (b) at higher doses of I3C, hepatic microsomal cholesterol levels are significantly lowered and ACAT activity is significantly elevated. These latter effects are not accompanied by changes in serum cholesterol levels and may represent compensatory mechanisms to restore cholesterol homoeostasis in the body. Mechanisms responsible for the effects of I3C on cholesterol homoeostasis are proposed.}, number={7}, journal={Food and Chemical Toxicology}, author={Le Blanc, G.A. and Stuart, J.D. and Dunn, S.E. and Baldwin, W.S}, year={1994}, month={Jul}, pages={633–639} }
 @article{leblanc_1994, title={Hepatic vectorial transport of xenobiotics}, volume={90}, ISSN={0009-2797}, url={http://dx.doi.org/10.1016/0009-2797(94)90097-3}, DOI={10.1016/0009-2797(94)90097-3}, abstractNote={The vectorial transport of xenobiotics across the hepatocyte is mediated by various transport and transfer proteins that differ in ligand specificity and function. The influx of xenobiotics from the blood across the sinusoidal membrane of the hepatocyte can occur through passive or active transport processes. Once in the cell, xenobiotics can be sequestered by intracellular transfer proteins that prevent refluxing of the chemical back through the sinusoidal membrane. Transfer proteins may also facilitate the localization of the xenobiotics within the cell to sites of metabolism (i.e., the endoplasmic reticulum) or elimination (i.e., the canalicular membrane). Intracellular transfer proteins include glutathione S-transferases, fatty acid-binding proteins, and 3 alpha-hydroxysteroid dehydrogenase. Intracellular nuclear transfer proteins have also been identified that facilitate the transfer of chemical carcinogens from the cytoplasm into the cell nucleus. Several active transport proteins exist on the canalicular membrane of the hepatocyte that mediate the efflux of chemicals from the cell into the biliary canaliculus. Xenobiotic efflux proteins include the multispecific organic anion transporter, that eliminates xenobiotics that have undergone conjugation with glutathione, glucuronic acid, and possibly sulfate; and, P-glycoprotein, an active transporter that actively effluxes a variety of structurally diverse xenobiotics. Induction of P-glycoprotein by the amplification of its gene has been identified as a major cause of resistance of tumor cells to the toxicity of a variety of anti-cancer drugs. The hepatic induction of P-glycoprotein may also contribute to acquired resistance of organisms to environmental toxicants. Continued elucidation of xenobiotic transport and transfer processes at the cellular levels will significantly advance our understanding of processes involved in xenobiotic toxicity and acquired resistance to chemical toxicity.}, number={2}, journal={Chemico-Biological Interactions}, publisher={Elsevier BV}, author={LeBlanc, Gerald A.}, year={1994}, month={Feb}, pages={101–120} }
 @article{dunn_leblanc_1994, title={Hypocholesterolemic properties of plant indoles}, volume={47}, ISSN={0006-2952}, url={http://dx.doi.org/10.1016/0006-2952(94)90027-2}, DOI={10.1016/0006-2952(94)90027-2}, abstractNote={Studies were undertaken to investigate the effects of the plant compound indole-3-carbinol (I3C) and its acid condensation products, which are generated in the stomach following ingestion of I3C, on cholesterol homeostasis in mice. Individual acid condensation products were synthesized and purified by HPLC. In vitro experiments revealed that several of the acid condensation products effectively inhibited the enzyme acyl-CoA:cholesterol acyltransferase (ACAT), which is responsible for the conversion of free cholesterol to the cholesteryl ester, at micromolar concentrations. Since the inhibition of ACAT in vivo should reduce serum cholesterol levels, I3C was administered to mice, and the effects on serum cholesterol levels were evaluated. Total serum cholesterol levels were elevated by 29% in mice provided a 3% cholesterol-supplemented diet, but this elevation was attenuated significantly (P < or = 0.05) by approximately 50% when I3C (100 mg/kg/day) was added to this diet. This effect of I3C was entirely on low density lipoprotein (LDL)/very low density lipoprotein (VLDL) cholesterol, which was lowered significantly (P < or = 0.05) by approximately 30%. In summary, I3C lowered serum LDL/VLDL cholesterol levels in mice, and this effect was likely mediated by the inhibition of ACAT by some of the acid condensation products of I3C. These results provide a possible mechanism by which I3C-rich vegetables lower serum cholesterol levels.}, number={2}, journal={Biochemical Pharmacology}, publisher={Elsevier BV}, author={Dunn, Sandra E. and LeBlanc, Gerald A.}, year={1994}, month={Jan}, pages={359–364} }
 @article{baldwin_leblanc_1994, title={IDENTIFICATION OF MULTIPLE STEROID HYDROXYLASES IN DAPHNIA MAGNA AND THEIR MODULATION BY XENOBIOTICS}, volume={13}, ISSN={0730-7268 1552-8618}, url={http://dx.doi.org/10.1897/1552-8618(1994)13[1013:iomshi]2.0.co;2}, DOI={10.1897/1552-8618(1994)13[1013:iomshi]2.0.co;2}, number={7}, journal={Environmental Toxicology and Chemistry}, publisher={Wiley}, author={Baldwin, William S. and LeBlanc, Gerald A.}, year={1994}, pages={1013} }
 @article{baldwin_leblanc_1994, title={In vivo biotransformation of testosterone by phase I and II detoxication enzymes and their modulation by 20-hydroxyecdysone in Daphnia magna}, volume={29}, ISSN={0166-445X}, url={http://dx.doi.org/10.1016/0166-445x(94)90051-5}, DOI={10.1016/0166-445x(94)90051-5}, abstractNote={Phase I and phase II chemical detoxication processes were elucidated in Daphnia magna using in vivo techniques and [14C]testosterone as a substrate. Testosterone was used because this compound undergoes multiple biotransformations and its metabolites are well characterized in other species. In addition, regulation of these processes by the endogenous steroid hormone, 20-hydroxyecdysone, was investigated. Daphnids produced at least ten polar phase I metabolites and four nonpolar phase I metabolites of testosterone. Six of the ten polar metabolites have been identified as monohydroxy-products of testosterone. The polar metabolites were preferentially excreted while the nonpolar metabolites were preferentially retained by the daphnids. In addition, testosterone and all phase I metabolites were also excreted as glucose conjugates. A polar metabolite designated ‘C’ was preferentially conjugated with glucose over the other metabolites. Testosterone and its polar phase I metabolites were also excreted as sulfate conjugates with 2α-hydroxytestosterone being the predominant sulfate-conjugated metabolite. In contrast to glucose conjugation, no nonpolar phase I metabolites of testosterone were sulfate conjugated. Twenty-four hour pre-exposure of daphnids to 4.2 μM 20-hydroxyecdysone did not affect phase I metabolism of testosterone, but differentially modulated phase II conjugation in a manner suggesting the presence of at least two glucosyltransferases and two sulfotransferases. Treatment with 20-hydroxyecdysone significantly increased the elimination of sulfate conjugates due largely to increased sulfate conjugation of unmetabolized testosterone. These results demonstrate that daphnids can convert polycyclic compounds to multiple polar and nonpolar metabolites resulting from both phase I and phase II biotransformations, and that some phase II activities are under the regulatory control of 20-hydroxyecdysone.}, number={1-2}, journal={Aquatic Toxicology}, publisher={Elsevier BV}, author={Baldwin, William S. and LeBlanc, Gerald A.}, year={1994}, month={Jun}, pages={103–117} }
 @article{le blanc_gillette_1993, title={Elevation of serum cholesterol levels in mice by the antioxidant butylated hydroxyanisole}, volume={45}, DOI={10.1016/0006-2952(93)90090-J}, abstractNote={The food antioxidants butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are structurally related to the hypocholesterolemic drug probucol. The purpose of this study was to determine if BHA can lower serum cholesterol levels as is observed with probucol. Treatment of mice with 0.75% BHA in their feed for 10 days resulted in a significant (P < or = 0.01) elevation of serum cholesterol levels. This effect contrasts with the cholesterol-lowering effect of probucol. Further, the degree of cholesterol elevation was comparable to that observed in mice administered 3% cholesterol in their feed for 7 days. The enzyme acyl CoA:cholesterol acyltransferase (ACAT) was decreased significantly (P < or = 0.01) in liver microsomes from BHA-treated mice. In contrast, hepatic microsomal ACAT activity was increased significantly (P < or = 0.01) in cholesterol-fed mice. These results suggested that the increased serum cholesterol observed in BHA-treated mice was not accompanied by an increase in hepatic cholesterol levels. Indeed, hepatic microsomal cholesterol levels were reduced in BHA-treated mice, but were increased significantly (P < or = 0.01) in cholesterol-fed mice. These results demonstrate that the common food additive BHA elevates serum cholesterol levels by a mechanism that apparently involves the decreased uptake of cholesterol by the liver.}, number={2}, journal={Biochemical Pharmacology}, author={Le Blanc, G.A. and Gillette, J.S}, year={1993}, month={Jan}, pages={513–515} }
 @article{leblanc_kantoff_ng_frei_waxman_1992, title={Hormonal perturbations in patients with testicular cancer treated with cisplatin}, volume={69}, ISSN={0008-543X 1097-0142}, url={http://dx.doi.org/10.1002/1097-0142(19920501)69:9<2306::aid-cncr2820690917>3.0.co;2-f}, DOI={10.1002/1097-0142(19920501)69:9<2306::aid-cncr2820690917>3.0.co;2-f}, abstractNote={Patients with testicular cancer treated with cisplatin can undergo feminization that is understood poorly. Rat model studies recently showed that cisplatin can feminize in part the profile of hepatic steroid-metabolizing enzymes and circulating hormone levels. This study was undertaken to determine whether cisplatin similarly might contribute to the perturbations in gonadotropin or steroid hormone levels that can occur in patients undergoing cisplatin-based treatment for testicular cancer. Analysis of serum free testosterone, total testosterone, and androstenedione levels revealed that these hormones were not altered significantly in patients during a 38-week period of cisplatin-based treatment and follow-up. Estradiol levels were elevated before chemotherapy and were reduced to normal levels during treatment. This reduction was attributed to the cytotoxic effect of chemotherapy on the tumors and the resultant reduction in serum chorionic gonadotropin levels. Serum dihydrotestosterone (DHT) levels were normal before chemotherapy but progressively became elevated during treatment with cisplatin in five of ten patients examined. The rise in DHT may relate to the previously described increase in hepatic androgen 5α-reductase activity in cisplatin-treated rats. Levels of the gonadotropins, luteinizing hormone, and follicle-stimulating hormone (FSH) were normal before cisplatin-based treatment was administered; however, FSH was elevated selectively during chemotherapy, This selective induction of FSH may reflect an effect of cisplatin on the hypothalamic secretion of gonadotro-pin-releasing hormone. Taken together, these findings suggest that cisplatin contributes to the perturbation of steroid and peptide hormone levels in patients with testicular cancer and perhaps in others undergoing cisplatin-based chemotherapy.}, number={9}, journal={Cancer}, publisher={Wiley}, author={Leblanc, Gerald A. and Kantoff, Philip W. and Ng, Sze-Fong and Frei, Emil and Waxman, David J.}, year={1992}, month={May}, pages={2306–2310} }
 @article{danger_baldwin_leblanc_1992, title={Photoaffinity labelling of steroid-hormone-binding glutathione S-transferases with [3H]methyltrienolone. Inhibition of steroid-binding activity by the anticarcinogen indole-3-carbinol}, volume={288}, DOI={10.1042/bj2880361}, abstractNote={The identification and characterization of steroid-hormone-binding glutathione S-transferases (GST) were undertaken using photoaffinity-labelling techniques. Irradiation of mouse liver cytosol, in the presence of 50 nM-[3H]methyltrienolone, resulted in the specific affinity labelling of five proteins. One of these proteins, designated MBP27, had an approximate molecular mass of 27 kDa under denaturing conditions and was induced by treatment of mice with either 2(3)-t-butyl-4-hydroxyanisole (BHA) or phenobarbital (PB). An additional affinity-labelled protein, MBP25, which was not detected in untreated mouse cytosol, was induced in the liver cytosols from BHA- and PB-treated mice. The molecular masses of these proteins and their induction by BHA and PB suggested that they may be steroid-hormone-binding GST subunits. Irradiation of mouse liver cytosol in the presence of [3H]methyltrienolone, followed by immunoprecipitation using GST-specific antibodies established that both GST mu and GST alpha bind [3H]methyltrienolone and both contribute to the affinity-labelled protein designated MBP27. GST Ya1 Ya1, an alpha class GST that is not expressed in untreated mouse liver but is induced by BHA and PB, was also found to bind [3H]methyltrienolone and is identical with the affinity-labelled protein designated MBP25. Experiments were undertaken next to assess the effects of the anticarcinogenic plant compound indole-3-carbinol (I3C) on GST-mediated steroid hormone-binding using the photoaffinity labelling techniques. Treatment of mice with I3C resulted in the induction of immunoreactive GST mu and GST Ya1 Ya1. However, the steroid-binding activity of these proteins in vitro was severely inhibited by the acid-condensation products of I3C that are generated in the stomach after ingestion. These results suggest that I3C may inhibit GST-mediated steroid-binding activity which could contribute to the anticarcinogenic activity of this compound.}, number={2}, journal={Biochemical Journal}, author={Danger, D.P. and Baldwin, W.S. and LeBlanc, G.A}, year={1992}, month={Dec}, pages={361–367} }
 @article{le blanc_sundseth_weber_waxman_1992, title={Platinum Anticancer Drugs Modulate P-450 mRNA Levels and Differentially Alter Hepatic Drug and Steroid Hormone Metabolism in Male and Female Rats}, volume={52}, number={3}, journal={Cancer Research}, author={Le Blanc, G.A. and Sundseth, S.S. and Weber, G.F. and Waxman, D.J}, year={1992}, month={Feb}, pages={540–547} }
 @article{baldwin_leblanc_1992, title={The anti-carcinogenic plant compound indole-3-carbinol differentially modulates P450-mediated steroid hydroxylase activities in mice}, volume={83}, ISSN={0009-2797}, url={http://dx.doi.org/10.1016/0009-2797(92)90043-k}, DOI={10.1016/0009-2797(92)90043-k}, abstractNote={Indole-3-carbinol (I3C), a component of cruciferous vegetables, exhibits anti-carcinogenic activity in a variety of model systems. This activity has been attributed in part to the induction of cytochrome P450 CYP1A subfamily members and the resulting increased metabolic inactivation of chemical carcinogens. The present study was undertaken to assess the effects of I3C on several constitutive P450 activities that contribute to both carcinogen and steroid hormone metabolism. Mice were administered I3C in their diet at estimated daily doses of 250, 500 and 750 mg/kg for 1 week. Liver microsomes from treated and untreated mice were subsequently assayed for CYP1A-mediated ethoxy-resorufin O-deethylase (EROD) activity, estradiol 2-hydroxylase activity and seven different testosterone hydroxylase activities. I3C elevated EROD, estradiol 2-hydroxylase and testosterone 6 alpha-hydroxylase activities in a dose-dependent manner. The other six testosterone hydroxylase activities were not significantly affected by in vivo treatment with I3C. In addition to its effects on steroid hydroxylase activities, I3C also elevated NADPH-cytochrome P450 reductase activity, a necessary component to the P450 monooxygenase system. We next examined the direct in vitro effects of I3C and its acid condensation products, as are generated in the stomach following ingestion, on the P450 catalytic activities. Testosterone 6 beta-hydroxylase, the major testosterone hydroxylase activity in untreated mice, was significantly inhibited (IC50 approximately 12 micrograms/ml) by the acid condensation products of I3C. In contrast, all other P450 activities were not appreciably affected by I3C or its acid condensation products. These results indicate that I3C can elicit both inductive and suppressive effects on the constitutive P450s that participate in carcinogen and steroid hormone metabolism. This pleiotropic effect on hepatic catalytic enzymes may contribute to the anti-carcinogenic properties of this compound.}, number={2}, journal={Chemico-Biological Interactions}, publisher={Elsevier BV}, author={Baldwin, William S. and Leblanc, Gerald A.}, year={1992}, month={Aug}, pages={155–169} }
 @article{janeczko_waxman_le blanc_morville_adesnik_1990, title={Hormonal Regulation of Levels of the Messenger RNA Encoding Hepatic P450 2c (IIC11), a Constitutive Male-Specific Form of Cytochrome P450}, volume={4}, DOI={10.1210/mend-4-2-295}, abstractNote={A cDNA clone for rat hepatic cytochrome P450 2c (gene product IIC11) was isolated and used to study the sex specificity, expression during development, and hormonal regulation of the mRNA encoding this protein in rat liver. P450 2c mRNA levels were about 16-fold higher in males than in females and were only slightly increased in male rats after administration of phenobarbital, a drug that dramatically raises the levels of mRNAs encoding several other members of the P450 II family. In contrast to the mRNA encoding P450 f (gene product IIC7), which increases gradually over the first 6 weeks of life, P450 2c mRNA showed a dramatic increase at puberty, between 4.5-5.5 weeks of life. The roles of sex steroids and GH in controlling this male-specific, developmentally regulated mRNA were then examined. A dependence on adult androgen was demonstrated by the 2- to 4-fold decrease in P-450 2c mRNA levels after castration of adult male rats and their restoration to normal by administration of the synthetic androgen methyltrienolone. Prolonged treatment (15 days) of ovariectomized female rats with this androgen also increased the levels of P450 2c mRNA and its encoded testosterone 16 alpha-hydroxylase to those of intact males. In male rats treated with estradiol valerate, mRNAs for P450 2c and alpha 2u-globulin, a major male-specific hepatic secretory protein that is under complex hormonal control, fell to negligible levels. None of these hormonal perturbations had a detectable effect on the levels of PB-1 (gene product IIC6) mRNA, which is not expressed in a sex-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)}, number={2}, journal={Molecular Endocrinology}, author={Janeczko, R. and Waxman, D.J. and Le Blanc, G.A. and Morville, A. and Adesnik, M}, year={1990}, month={Feb}, pages={295–303} }
 @article{le blanc_waxman_1990, title={Mechanisms of cyclophosphamide action on hepatic P-450 expression}, volume={50}, number={18}, journal={Cancer Research}, author={Le Blanc, G.A. and Waxman, D.J}, year={1990}, month={Sep}, pages={5720–5726} }
 @article{waxman_ram_notani gur_le blanc_alberta_morrissey_sundseth_1990, title={Pituitary Regulation of the Male-Specific Steroid 6β-Hydroxylase P-450 2a (gene product IIIA2) in Adult Rat Liver. Suppressive Influence of Growth Hormone and Thyroxine Acting at a Pretranslational Level}, volume={4}, DOI={10.1210/mend-4-3-447}, abstractNote={Oligonucleotide probes that distinguish between two closely related mRNAs encoding steroid 6β-hydroxylases of rat P-450 gene family CYP3A were used to individually assess their responsiveness to pituitary hormone regulation. Northern blot analysis revealed that the elevation of immunoreactive P-450 IIIA2 in livers of hypophysectomized rats reflects an elevation of the constitutive, male-specific P-450 IIIA2 (P-450 2a) and not an induction of the drug-inducible P-450 IIIA1 (P-450p). P-450 IIIA2 mRNA levels in intact adult male rats were found to be markedly reduced by GH administered as a continuous infusion at levels as low as 1 mU/h, indicating that GH acts at a pretranslational step to suppress expression of this P-450 enzyme. In hypophysectomized male rats, however, this same hormone treatment was only partially effective at suppressing P-450 IIIA2 mRNA and protein, suggesting that other pituitary-dependent factors contribute to the suppression observed in the intact rats. Further analysis revealed that T4, but not ACTH or human CG, can act in concert with GH to effect a more complete suppression of hepatic P-450 IIIA2 mRNA and protein in hypophysectomized rats. T4 also suppressed the expression of another GH-regulated, male-specific hepatic enzyme, designated P-450 IIA2 (P-450 RLM2), particularly in hypophysectomized female rats. In contrast, the GH-responsive P-450 IIA1 (P-450 3) was much less affected by T4 treatment. Thus, while T4 can modulate P-450 IIIA2 expression, it does not serve as a universal regulator for hepatic expression of GH-responsive P-450s.}, number={3}, journal={Molecular Endocrinology}, author={Waxman, D.J. and Ram, P.A. and Notani Gur, G. and Le Blanc, G.A. and Alberta, J.A. and Morrissey, J.J. and Sundseth, S.S}, year={1990}, month={Mar}, pages={447–454} }
 @article{leblanc_waxman_1990, title={Regulation and ligand-binding specificities of two sex-specific bile acid-binding proteins of rat liver cytosol.}, volume={265}, DOI={10.1016/S0021-9258(19)39412-8}, abstractNote={Rat liver cytosolic proteins were photoaffinity labeled with the synthetic steroid [3H]methyltrienolone in order to identify and characterize hepatic proteins that may participate in the intracellular binding and transport of steroid hormones and other sterols. A male-specific and a female-specific sterol-binding protein (SBP) that migrated to the 4 S region of a sucrose gradient and had similar molecular weights (male-specific 34-kDa protein (SBP34), female-specific 31-kDa protein (SBP31] were thus identified. Experiments were undertaken to determine the biochemical basis for the sex-specific expression of these two proteins. In vivo hormonal manipulations established that the female-specific expression of SBP31 could, in part, be accounted for by the suppressive effects of androgen on SBP31 levels in male rats. In contrast, androgen stimulated expression of the male-specific SBP34, while estrogen and the estrogen-regulated continuous plasma growth hormone profile that is characteristic of adult female rats were suppressive toward this protein. Unlike several other androgen-dependent hepatic proteins, however, SBP34 did not require an intact pituitary for androgen-stimulated expression, nor was its expression stimulated by the intermittent pulses of plasma growth hormone that are characteristic of adult male rats. SBP34 and SBP31 were not induced but were suppressed to various extents by dexamethasone, phenobarbital, and clofibrate, drugs that are known to induce other hepatic proteins involved in steroid binding and metabolism. Competition experiments revealed that SBP31 has a relatively broad ligand specificity, with significant competition for [3H]methyltrienolone binding exhibited by bile acids (chenodeoxycholic acid and lithocholic acid) and a range of steroid hormones (progesterone, estradiol, testosterone, and 5 alpha-dihydrotestosterone) when present in the low micromolar range. No binding was detected with this protein toward cholesterol, triamcinolone acetonide, 5 alpha-androstan-3 alpha,17 beta-diol, cholic acid, and deoxycholic acid. In contrast, SBP34 exhibited greater binding specificity, with competition for [3H]methyltrienolone binding observed only with primary bile acids (cholic acid and chenodeoxycholic acid) and their metabolites (deoxycholic acid and lithocholic acid). On the basis of these binding specificities and the relatively high concentration of bile acids found in the liver, it is proposed that SBP31 and SBP34 function in the intracellular binding and/or transport of bile acids.}, number={10}, journal={Journal of Biological Chemistry}, author={LeBlanc, G.A. and Waxman, D.J}, year={1990}, month={Apr}, pages={5654–5661} }
 @article{waxman_morrissey_leblanc_1989, title={Female-Predominant Rat Hepatic P-450 Forms j (IIE1) and 3 (IIA1) Are under Hormonal Regulatory Controls Distinct from Those of the Sex-Specific P-450 Forms}, volume={124}, ISSN={0013-7227 1945-7170}, url={http://dx.doi.org/10.1210/endo-124-6-2954}, DOI={10.1210/endo-124-6-2954}, abstractNote={Hepatic expression of cytochrome P-450j (alcohol- inducible nitrosamine demethylase; P-450 gene IIE1) and P- 450 3 (testosterone 7α-hydroxylase; P-450 gene IIAl) is female predominant in adult rats [female/male = 1.5-2 (P-450j) or 3-4 (P-450 3)]. This sex difference emerges during the postsuckling period, when P-450 3 declines significantly (60-70% decrease) in male, but not female, rats, and P-450j declines in both sexes, but to a lower constitutive level in males than in females. The biochemical factors and regulatory events that control these developmental changes were investigated and found to be distinct from those that regulate expression of the female-specific hepatic enzymes P-450 2d (P-450 gene IIC12) and steroid 5α-reductase. Immunoquantitation of the changes in P-450j and P- 450 3 levels in hormonally altered rats established that both P- 450s are under gonadal control. However, while androgen and estrogen both suppress P-450j expression, estrogen stimulates and androgen suppresses the expression of P-450 3. Since many of the effects of gonadal hormones on hepatic enzyme levels are mediated by the pituitary, the contribution of pituitary hormones to P-450j and P-450 3 expression was evaluated. Hypophysectomy of adult rats of either sex elevated P-450j to the levels found in immature rats (3- to 5-fold increase). This elevation was largely reversed in both sexes by GH administered either intermittently or continuously, demonstrating that P-450j is under the suppressive control of this pituitary hormone. The regulation of P-450 3 was more complex. Hypophysectomy elevated P-450 3 to prepubertal levels in adult male rats, but had no effect on P-450 3 levels in adult females. In both sexes GH suppressed P-450 3 expression when administered to hypophysectomized rats intermittently, but stimulated P-450 3 expression when infused continuously. Corresponding changes in hepatic microsomal P-450 3-dependent testosterone 7α-hydroxylase and P-450j-dependent aniline hydroxylase activities were observed in response to hypophysectomy and GH replacement, but only after supplementation of microsomal NADPH P-450 reductase [which was 63-77% suppressed by hypophysectomy] with exogenous purified NADPH P-450 reductase. These studies demonstrate that these female-predominant hepatic P-450 enzymes are regulated by different mechanisms, and that both are under hormonal regulatory controls distinct from those that govern expression of the female-specific hepatic enzymes. The developmental suppression of P-450j in female rats and of P- 450 3 and P-450j in male rats is proposed to result from the onset of elevated serum GH levels in the postsuckling period. P- 450 3 in female rats is, however, positively regulated by the more continuous serum GH profile characteristic of adult rats of this sex and is, therefore, not subject to the developmental suppression that occurs in maturing male rats. (Endocrinology124: 2954-2966,1989)}, number={6}, journal={Endocrinology}, publisher={The Endocrine Society}, author={Waxman, David J. and Morrissey, Joseph J. and Leblanc, Gerald A.}, year={1989}, month={Jun}, pages={2954–2966} }
 @article{waxman_morrissey_le blanc_1989, title={Hypophysectomy differentially alters P-450 protein levels and enzyme activities in rat liver. Pituitary control of hepatic NADPH cytochrome P-450 reductase}, volume={35}, number={4}, journal={Molecular Pharmacology}, author={Waxman, D.J. and Morrissey, J.J. and Le Blanc, G.A}, year={1989}, month={Apr}, pages={519–525} }
 @article{leblanc_waxman_1989, title={Interaction of Anticancer Drugs with Hepatic Monooxygenase Enzymes}, volume={20}, ISSN={0360-2532 1097-9883}, url={http://dx.doi.org/10.3109/03602538909103550}, DOI={10.3109/03602538909103550}, abstractNote={(1989). Interaction of Anticancer Drugs with Hepatic Monooxygenase Enzymes. Drug Metabolism Reviews: Vol. 20, No. 2-4, pp. 395-439.}, number={2-4}, journal={Drug Metabolism Reviews}, publisher={Informa UK Limited}, author={LeBlanc, Gerald A. and Waxman, David J.}, year={1989}, month={Jan}, pages={395–439} }
 @article{yeowell_waxman_leblanc_linko_goldstein_1989, title={Suppression of male-specific cytochrome P450 2c and its mRNA by 3,4,5,3′,4′,5′-hexachlorobiphenyl in rat liver is not causally related to changes in serum testosterone}, volume={271}, ISSN={0003-9861}, url={http://dx.doi.org/10.1016/0003-9861(89)90302-0}, DOI={10.1016/0003-9861(89)90302-0}, abstractNote={Rat cytochrome P450 2c (P450 gene IIC11) is a constitutive, male-specific hepatic enzyme which is suppressed greater than 90% by treatment with 3,4,5,3',4',5'-hexachlorobiphenyl (HCB) [H. N. Yeowell et al. (1987) Mol. Pharmacol. 32, 340-347]. HCB also decreases serum testosterone levels in adult male rats (greater than 98% loss). The present study assesses whether the suppression of P450 2c by HCB is a direct result of its effects on serum testosterone levels. Further, the site along the hypothalamic-pituitary-testicular axis at which HCB acts to depress testosterone secretion was examined. Administration of the synthetic androgen methyltrienolone to HCB-treated rats failed to prevent the suppression of P450 2c mRNA and its associated microsomal steroid 16 alpha-hydroxylase activity under conditions where it effectively reversed the large decrease in P450 2c mRNA and steroid 16 alpha-hydroxylase activity produced by castration. Hepatic steroid 6 beta-hydroxylase activity, which is catalyzed primarily by P450 2a (P450 gene IIIA2), was also suppressed by HCB and was not protected by methyltrienolone. Administration of either human chorionic gonadotropin, an analog of pituitary-derived luteinizing hormone, or the hypothalamic luteinizing hormone releasing hormone elevated serum testosterone levels to a much smaller extent in HCB-treated rats than in control rats. These results indicate that the effects of HCB on serum testosterone levels reflect its effects on testicular function rather than the pituitary or hypothalamus. However, the present study demonstrates that the consequential reduction in serum testosterone levels in HCB-treated rats is not causally related to the reduction in hepatic P450 2c levels. Thus, HCB must also act on some other regulatory mechanism involved in the expression of this protein.}, number={2}, journal={Archives of Biochemistry and Biophysics}, publisher={Elsevier BV}, author={Yeowell, Heather N. and Waxman, David J. and LeBlanc, Gerald A. and Linko, Patricia and Goldstein, Joyce A.}, year={1989}, month={Jun}, pages={508–514} }
 @article{waxman_le blanc_morrissey_staunton_lapenson_1988, title={Adult male-specific and neonatally programmed rat hepatic P-450 forms RLM2 and 2a are not dependent on pulsatile plasma growth hormone for expression}, volume={263}, DOI={10.1016/S0021-9258(18)37970-5}, abstractNote={Rat hepatic cytochrome P-450 form RLM2 is a testosterone 15 alpha-hydroxylase reported to be male-specific on the basis of purification studies (Jansson, I., Mole, J., and Schenkman, J. B. (1985) J. Biol. Chem. 260, 7084-7093). The sex dependence, developmental regulation, xenobiotic induction, and hormonal control of P-450 RLM2 expression were studied using P-450 form-specific immunochemical and catalytic assays. Polyclonal antibodies raised to rat hepatic P-450 3 (P-450 gene IIA1) were found to cross-react strongly with P-450 RLM2, but not with 10 other rat P-450 forms, suggesting that P-450 3 and P-450 RLM2 are highly conserved in primary structure. Western blotting of liver microsomes under conditions where P-450s 3 and RLM2 are resolved electrophoretically revealed that P-450 RLM2 is markedly induced at puberty in male rats, with no protein detected (less than or equal to 5% of adult male levels) in adult females or immature animals of either sex. A similar developmental dependence was observed for hepatic microsomal testosterone 15 alpha-hydroxylase activity, which was found to be catalyzed primarily by P-450 RLM2. P-450 RLM2 was resistant to induction by several xenobiotics and in the case of phenobarbital and beta-naphthoflavone, was suppressed by 50-60%. Studies on the steroid hormonal regulation of P-450 RLM2 revealed that its adult male-specific expression is imprinted (programmed) in response to neonatal testosterone exposure. Ovariectomy studies demonstrated that suppression by estrogen does not contribute significantly to the absence of P-450 RLM2 in adult female rats. Although the male-specific developmental induction of P-450 RLM2 in response to neonatal testosterone is strikingly similar to that of P-450 2c (testosterone 2 alpha/16 alpha-hydroxylase; gene IIC11), P-450 RLM2 expression is not dependent on the pulsatile pituitary growth hormone secretion required for P-450 2c synthesis. Rather, hypophysectomy of adult male rats increased P-450 RLM2 and its associated testosterone 15 alpha-hydroxylase activity by 50-100%.(ABSTRACT TRUNCATED AT 400 WORDS)}, number={23}, journal={The Journal of Biological Chemistry}, author={Waxman, D.J. and Le Blanc, G.A. and Morrissey, J.J. and Staunton, J. and Lapenson, D.P}, year={1988}, month={Aug}, pages={11396–11406} }
 @article{le blanc_waxman_1988, title={Feminization of rat hepatic P-450 expression by cisplatin. Evidence for perturbations in the hormonal regulation of steroid-metabolizing enzymes}, volume={263}, DOI={10.1016/S0021-9258(19)37649-5}, abstractNote={The biochemical basis for the complex effects of the anti-cancer drug cisplatin on hepatic cytochrome P-450 activity was studied in adult male rat liver using P-450 form-specific steroid hydroxylase assays and antibody probes. Cisplatin treatment of adult male rats resulted in a marked and prolonged feminization of the pattern of P-450 enzymes expressed in hepatic tissue. The adult male-specific cytochrome P-450 forms designated P-450 2c (P-450 gene IIC11), P-450 2a (gene IIIA2), and P-450 RLM2 were decreased by 70-90% after 7-14 days, with parallel decreases in their respectively associated microsomal steroid hydroxylase activities. Concomitantly, hepatic levels of the female-predominant enzymes P-450 3 (gene IIA1) and P-450j (gene IIE1) were elevated approximately 2-4-fold. The female-specific microsomal enzyme androstenedione 5 alpha-reductase was induced approximately 20-fold by cisplatin; however, no elevation of the female-specific P-450 2d was detected. The underlying hormonal basis for these effects of cisplatin was then examined. Serum testosterone levels were found to be depleted by cisplatin in a time- and dose-dependent manner which correlated with the observed changes in these hepatic enzymes. Furthermore, castration of adult rats altered the profile of these enzymes in a manner which resembled that observed with cisplatin treatment, suggesting that androgen depletion was the primary cause for the observed feminization of hepatic enzyme expression. Consistent with this possibility, the synthetic androgen methyltrienolone effectively blocked the changes in hepatic enzyme expression induced by cisplatin. Moreover, hepatic enzyme feminization was significantly reversed by chorionic gonadotropin, which fully restored serum testosterone levels in the cisplatin-treated rat. Luteinizing hormone-releasing hormone challenge experiments demonstrated that the responsiveness of the pituitary to this hypothalamic regulator of testicular androgen production was unimpaired by cisplatin treatment, indicating that hypothalamic production or secretion of luteinizing hormone-releasing hormone may be deficient in the cisplatin-treated animals. These studies establish that the effects of cisplatin on hepatic P-450 enzyme expression result from its interruption of the hypothalamic-pituitary stimulation of testicular androgen production and that this, in turn, leads to a depletion of circulating androgens required for maintenance of normal P-450 enzyme expression in adult male rats.}, number={30}, journal={The Journal of Biological Chemistry}, author={Le Blanc, G.A. and Waxman, D.J}, year={1988}, month={Oct}, pages={15732–15739} }
 @article{yeowell_waxman_le blanc_linko_goldstein_1988, title={Induction of cytochrome P-450 3 and its mRNA by 3,4,5,3',4',5'-hexachlorobiphenyl}, volume={33}, number={3}, journal={Molecular Pharmacology}, author={Yeowell, H.N. and Waxman, D.J. and Le Blanc, G.A. and Linko, P. and Goldstein, J.A}, year={1988}, month={Mar}, pages={272–278} }
 @article{leblanc_hilgenberg_cochrane_1988, title={Relationships between the structures of chlorinated phenols, their toxicity, and their ability to induce glutathione S-transferase activity in Daphnia magna}, volume={12}, ISSN={0166-445X}, url={http://dx.doi.org/10.1016/0166-445x(88)90032-x}, DOI={10.1016/0166-445x(88)90032-x}, abstractNote={The effects of six chlorinated phenols on Daphnia magna were assessed with respect to acute toxicity, as well as their abilities to induce activity of the chemical detoxification enzyme glutathione S-transferase. Toxicities were demonstrated to be directly related to lipophilicity, with those compounds having higher numbers of chlorine substitutions being more toxic. All of these compounds induced enzyme activity; however, there was no evident relationship between compound structure and potency as an inducer. It is suggested that in fact all of these compounds act in a similar manner internally to modulate enzyme activity, and that apparent differences in activity are a reflection of differences in bioconcentration of the different compounds.}, number={2}, journal={Aquatic Toxicology}, publisher={Elsevier BV}, author={LeBlanc, Gerald A. and Hilgenberg, Barbara and Cochrane, Bruce J.}, year={1988}, month={Feb}, pages={147–155} }
 @article{leblanc_cochrane_1987, title={A rapid method for staining proteins in acrylamide gels}, volume={161}, ISSN={0003-2697}, url={http://dx.doi.org/10.1016/0003-2697(87)90668-3}, DOI={10.1016/0003-2697(87)90668-3}, abstractNote={A negative staining procedure for the rapid visualization of proteins in acrylamide gels is described. In the absence of proteins, staining of the gel occurs through the reduction of nitroblue tetrazolium by reduced glutathione. No staining occurs in the presence of proteins. The procedure can be completed in 20 min and is at least as sensitive as Coomassie brilliant blue staining.}, number={1}, journal={Analytical Biochemistry}, publisher={Elsevier BV}, author={LeBlanc, Gerald A. and Cochrane, Bruce J.}, year={1987}, month={Feb}, pages={172–175} }
 @article{le blanc_cochrane_1987, title={Identification of multiple glutathione S-tansferases from Daphnia magna}, volume={88}, DOI={10.1016/0305-0491(87)90076-9}, abstractNote={1. Six anionic glutathione S-transferases (GST) were purified from the crustacean, Daphnia magna, by means of affinity chromatography, that are responsible for ca. 40% of cytosolic GST activity. 2. Electrophoresis in the presence of sodium dodecyl sulfate (SDS) revealed the presence of three proteins, with molecular weights of 27,500, 28,000, and 30,200. 3. Separation under nondenaturing conditions revealed six proteins, all of which exhibited GST activity, with molecular weights ranging from 55,000 to 61,700. 4. Ethacrynic acid is a competitive inhibitor of activity towards CDNB of all six GSTs, binding each with similar affinities. 5. Chlorinated phenols are also competitive inhibitors of the enzyme, with the degree of inhibition being directly correlated with the lipophilicity of the compounds. 6. Analysis of inhibition of separated isoforms reveals that form 4 is most strongly inhibited by these chlorinated phenols, with forms 5 and 6 being inhibited to a lesser degree.}, number={1}, journal={Comparative Biochemistry and physiology. B, Comparative Biochemistry}, author={Le Blanc, G.A. and Cochrane, B.J}, year={1987}, month={Jan}, pages={39–45} }
 @article{cochrane_morrissey_leblanc_1987, title={The genetics of xenobiotic metabolism in Drosophila—IV: Purification and characterization of the major glutathione S-transferase}, volume={17}, ISSN={0020-1790}, url={http://dx.doi.org/10.1016/0020-1790(87)90043-6}, DOI={10.1016/0020-1790(87)90043-6}, abstractNote={Abstract Glutathione S- transferase from Drosophila melanogaster was purified to apparent homogeneity by means of affinity chromatography on a glutathione-agarose column. This single step resulted in a ca 300-fold purification. The enzyme is a dimer, with subunits of 35,000 and 28,500 daltons, and comprises ca 0.3% of the total soluble protein in adults. Monoclonal antibodies to this protein were obtained, and Western blot analysis revealed the existence of one antigenic domain shared by the two subunits. The enzyme was found to possess many of the multiple functions reported for mammalian ones, including heme and bilirubin binding capacities and glutathione peroxidase activity. These results suggest that, in this species, a single enzyme has evolved that possesses many of the properties of the multiple isozymes of higher organisms.}, number={5}, journal={Insect Biochemistry}, publisher={Elsevier BV}, author={Cochrane, Bruce J. and Morrissey, Joseph J. and LeBlanc, Gerald A.}, year={1987}, month={Jan}, pages={731–738} }
 @article{cochrane_leblanc_1986, title={The genetics of xenobiotic metabolism in Drosophila. I. Genetics and environmental factors affecting glutathione S-transferase in larvae}, volume={35}, ISSN={0006-2952}, url={http://dx.doi.org/10.1016/0006-2952(86)90323-0}, DOI={10.1016/0006-2952(86)90323-0}, abstractNote={The enzyme glutathione-S-transferase, which plays a crucial role in xenobiotic detoxification, was investigated in Drosophila melanogaster. Based upon examination of substrate specificities and pH optima, it was observed that the enzyme in Drosophila is considerably more restricted in its activities than in mammals. The effects of various xenobiotics on activities in third instar larvae were examined. While β-naphthoflavone and phenobarbital had no effect, pentamethyl benzene (PMB) administration resulted in a 50% increase in enzyme activity. Comparison of lines of known genetic composition indicates that the degree of response to PMB is modulated by genes on chromosome II, and that differences exist with respect to the patterns of response of activities towards the substrates 1-chloro-2,4-dinitrobenzene and ethacrynic acid. Results obtained suggest the existence of at least two loci on chromosome II that code for glutathione 5-transferase isozymes.}, number={10}, journal={Biochemical Pharmacology}, publisher={Elsevier BV}, author={Cochrane, Bruce J. and LeBlanc, Gerald A.}, year={1986}, month={May}, pages={1679–1684} }
 @inbook{leblanc_surprenant_1985, place={West Conshohocken, PA}, title={A Method of Assessing the Toxicity of Contaminated Freshwater Sediments}, ISBN={9780803104105}, url={http://dx.doi.org/10.1520/stp36272s}, DOI={10.1520/stp36272s}, booktitle={Aquatic Toxicology and Hazard Assessment: Seventh Symposium}, publisher={ASTM International}, author={LeBlanc, GA and Surprenant, DC}, editor={Cardwell, R.D. and Purdy, R. and Comotto, R.B.Editors}, year={1985}, month={Dec}, pages={269–283} }
 @article{leblanc_1985, title={Effects of copper on the competitive interactions of two species of cladocera}, volume={37}, ISSN={0143-1471}, url={http://dx.doi.org/10.1016/0143-1471(85)90021-2}, DOI={10.1016/0143-1471(85)90021-2}, abstractNote={The purpose of this study was to assess the influence of copper on the competitive interactions between Daphnia magna and Daphnia pulex. Prior studies indicated that D. magna could develop tolerance to the toxic effects of copper whereas D. pulex could not. Although D. pulex is generally a superior competitor over D. magna, it was hypothesised that the presence of copper may lend competitive superiority to D. magna, thus ensuring its survival under this environmental condition. D. magna and D. pulex were cocultured during this study: (1) in the absence of exogenous copper; (2) after temporary exposure to a sublethal copper concentration (10 μg litre−1); (3) after temporary exposure to a copper concentration lethal to a portion of the exposed population (30 μg litre−1); and (4) after temporary exposure to successive treatments of 10 and 30 μg litre−1 copper. D. pulex populations consistently exceeded D. magna populations when cocultured in the absence of copper or after temporary exposure to 10 μg litre−1 copper. Exposure to 30 μg litre−1 or sequential treatments of 10 and 30 μg litre−1 copper severely reduced the initial population growth of D. pulex whereas D. magna were unaffected. Although the D. magna populations were dominant by day 14 under these conditions, they did not suppress growth of the D. pulex populations. D. pulex subsequently gained population dominance and inhibited further growth of the D. magna populations. The reduced size of the D. magna suggested that D. pulex was outcompeting D. magna for available food. This study, in conjunction with others, suggests that D. magna population growth is augmented by the presence of low levels of copper. In addition, the inhibiting effect of copper on D. pulex population growth relieves D. magna of the competitive inhibition experienced when these species are together.}, number={1}, journal={Environmental Pollution Series A, Ecological and Biological}, publisher={Elsevier BV}, author={LeBlanc, Gerald A.}, year={1985}, month={Jan}, pages={13–25} }
 @article{leblanc_cochrane_1985, title={Modulation of substrate-specific glutathione S-transferase activity in daphnia magna with concomitant effects on toxicity tolerance}, volume={82}, ISSN={0306-4492}, url={http://dx.doi.org/10.1016/0742-8413(85)90206-3}, DOI={10.1016/0742-8413(85)90206-3}, abstractNote={Glutathione S-transferase (GST) activity was measured in Daphnia magna and Ceriodaphnia reticulata using 1-chloro-2,4-dinitrobenzene (CDNB) and ethacrynic acid (EA) as conjugation substrates. Levels of GST activity were comparable between species with CDNB; however, D. magna had nearly twice the GST activity with EA as compared to C. reticulata. GST activity with CDNB was elevated from exposure of daphnids to either CDNB or sodium pentachlorophenate (PCP), but not from exposure to EA. GST activity with EA could not be modulated from exposure to CDNB or EA. GST activity towards CDNB and EA was biochemically separated into different protein fractions suggesting the existence of two distinct isozymes. Preexposure of daphnids to CDNB or PCP increased the organisms' tolerance to the toxic effects of PCP, but not CDNB.}, number={1}, journal={Comparative Biochemistry and Physiology Part C: Comparative Pharmacology}, publisher={Elsevier BV}, author={Leblanc, Gerald A. and Cochrane, Bruce J.}, year={1985}, month={Jan}, pages={37–42} }
 @article{leblanc_dean_1984, title={Antimony and thallium toxicity to embryos and larvae of fathead minnows (Pimephales promelas)}, volume={32}, ISSN={0007-4861 1432-0800}, url={http://dx.doi.org/10.1007/bf01607538}, DOI={10.1007/bf01607538}, number={1}, journal={Bulletin of Environmental Contamination and Toxicology}, publisher={Springer Science and Business Media LLC}, author={LeBlanc, Gerald A. and Dean, Jerry W.}, year={1984}, month={Dec}, pages={565–569} }
 @inbook{le blanc_1984, place={Dordrecht, Holland}, title={Comparative structure-toxicity relationships between acute and chronic effects to aquatic organisms}, booktitle={QSAR in Environmental Toxicology}, publisher={Reidel Publishing Company}, author={Le Blanc, G.A}, editor={Kaiser, K.L.E.Editor}, year={1984}, pages={245–260} }
 @article{leblanc_1984, title={Interspecies relationships in acute toxicity of chemicals to aquatic organisms}, volume={3}, ISSN={0730-7268 1552-8618}, url={http://dx.doi.org/10.1002/etc.5620030107}, DOI={10.1002/etc.5620030107}, abstractNote={The acute sensitivities of several species of aquatic organisms to chemicals categorized as nonpesticide organics, pesticides and metals were correlated using polynomial regression analyses. All species analyzed—fresh- and saltwater fish, invertebrates and algae—responded similarly to the toxicity of nonpesticide organics. Different groups of organisms responded differently to the pesticides. Different species of fish of the same family responded almost identically to the toxicity of pesticides, whereas fishes of different families responded similarly, but to a lesser degree. No relationship existed between the acute sensitivities of a fish and an invertebrate. A significant correlation was determined in acute sensitivities to metals between bluegill and fathead minnows, and between bluegill and Daphnia magna. The mode of toxicity of metals seems to be the same among species, although the degree of toxicity may differ.}, number={1}, journal={Environmental Toxicology and Chemistry}, publisher={Wiley}, author={Leblanc, Gerald A.}, year={1984}, month={Jan}, pages={47–60} }
 @article{le blanc_surprenant_1984, title={The influence of mineral salts on the fecundity of the water flea (Daphnia magna) and the implications on toxicity testing of industrial wastewater}, volume={108}, DOI={10.1007/BF00028179}, journal={Hydrobiologia}, author={Le Blanc, G.A. and Surprenant, D.C}, year={1984}, pages={25–31} }
 @article{leblanc_mastone_paradice_wilson_jr_robillard_1984, title={The influence of speciation on the toxicity of silver to fathead minnow (Pimephales promelas)}, volume={3}, ISSN={0730-7268 1552-8618}, url={http://dx.doi.org/10.1002/etc.5620030106}, DOI={10.1002/etc.5620030106}, abstractNote={Silver sulfide, silver thiosulfate complex and silver chloride complexes were tested and compared with free silver ion for their toxic effects in 96 h flow through acute toxicity tests using fathead minnows (Pimephales promelas). Thirty day fathead minnow embryo larval tests were conducted with silver sulfide and silver thiosulfate complex. Extensive chemical analyses were performed to quantify actual exposures. Compared with free silver ion, silver chloride complexes were about 300 times less toxic acutely silver sulfide was at least 15,000 times less toxic acutely and silver thiosulfate complex was more than 17,500 times less toxic acutely. The estimated maximum acceptable toxicant concentrations (MATCs) determined from the embryo larval tests with silver sulfide and silver thiosulfate complex were greater than 11 mg/L (as total silver) and greater than 16 but less than 35 mg/L (as total silver), respectively. The MATC previously reported for free silver ion from tests with rainbow trout (Salmo gairdneri) was greater than 0 00009 but less than 0 00017 mg/L. These differences in acute toxicities and the differences of five orders of magnitude in the MATC values are attributed to the influence of chemical speciation on the effects of silver in the aquatic environment. Thus, the speciation of silver is an essential factor in its potential to affect fish and, presumably, other aquatic life, and therefore should be considered in environmental risk assessment.}, number={1}, journal={Environmental Toxicology and Chemistry}, publisher={Wiley}, author={Leblanc, Gerald A and Mastone, Joseph D and Paradice, Arthur P and Wilson, Brenda F and Jr, Haines B Lockhart and Robillard, Kenneth A}, year={1984}, month={Jan}, pages={37–46} }
 @article{leblanc_surprenant_1983, title={The acute and chronic toxicity of acetone, dimethyl formamide, and triethylene glycol to Daphnia magna (Straus)}, volume={12}, ISSN={0090-4341 1432-0703}, url={http://dx.doi.org/10.1007/bf01059407}, DOI={10.1007/bf01059407}, number={3}, journal={Archives of Environmental Contamination and Toxicology}, publisher={Springer Science and Business Media LLC}, author={LeBlanc, Gerald A. and Surprenant, Donald C.}, year={1983}, month={May}, pages={305–310} }
 @inbook{le blanc_schoenfeld_surprenant_1983, place={Philadelphia}, title={The effects of food concentration, animal interactions and water volume on survival, growth, and reproduction of Daphnia magna under flow-through conditions}, booktitle={Aquatic Toxicology and Hazard Assessment}, publisher={American Society for Testing and Materials}, author={Le Blanc, G.A. and Schoenfeld, D.A. and Surprenant, D.C}, editor={Bishop, W.E. and Cardwell, R.D. and Heidolph, B.B.Editors}, year={1983}, pages={494–508} }
 @article{leblanc_1982, title={Laboratory investigation into the development of resistance of Daphnia magna (strauus) to environmental pollutants}, volume={27}, ISSN={0143-1471}, url={http://dx.doi.org/10.1016/0143-1471(82)90159-3}, DOI={10.1016/0143-1471(82)90159-3}, abstractNote={The purpose of this study was to determine the ability of Daphnia magna (Straus) to develop resistance to selected environmental pollutants through physiological adaptation or the selection of genetically fit organisms. The results of the study demonstrated that daphnids pre-exposed to copper, lead or zinc for 20 h had become significantly resistant to the toxic effects of these metals. Similar tests performed with sodium lauryl sulphate, however, resulted in no increased resistance. Exposure of successive generations of daphnids to copper resulted in the development of significant resistance to copper. However, this resistance was determined to be the result of physiological adaptation and was not due to the selection of genetically fit organisms. Multigeneration exposures to sodium lauryl sulphate failed to produce any increased resistance to the toxic effects of this compound. Exposure of successive generations to sodium lauryl sulphate increased each generation's sensitivity to the toxicity of this compound. To determine if resistance to one pollutant might confer resistance to others, the resistance, to zinc and lead, of daphnids pre-exposed to copper was assessed. Copper-resistant daphnids demonstrated no increased resistance to the toxic effects of zinc or lead.}, number={4}, journal={Environmental Pollution Series A, Ecological and Biological}, publisher={Elsevier BV}, author={LeBlanc, Gerald A.}, year={1982}, month={Apr}, pages={309–322} }
 @article{buccafusco_ells_leblanc_1981, title={Acute toxicity of priority pollutants to bluegill (Lepomis macrochirus)}, volume={26}, ISSN={0007-4861 1432-0800}, url={http://dx.doi.org/10.1007/bf01622118}, DOI={10.1007/bf01622118}, number={1}, journal={Bulletin of Environmental Contamination and Toxicology}, publisher={Springer Science and Business Media LLC}, author={Buccafusco, R. J. and Ells, S. J. and LeBlanc, G. A.}, year={1981}, month={Jan}, pages={446–452} }
 @article{leblanc_1980, title={Acute toxicity of priority pollutants to water flea (Daphnia magna)}, volume={24}, ISSN={0007-4861 1432-0800}, url={http://dx.doi.org/10.1007/bf01608174}, DOI={10.1007/bf01608174}, number={1}, journal={Bulletin of Environmental Contamination and Toxicology}, publisher={Springer Science and Business Media LLC}, author={LeBlanc, Gerald A.}, year={1980}, month={Dec}, pages={684–691} }
 @article{gledhill_kaley_adams_hicks_michael_saeger_leblanc_1980, title={An environmental safety assessment of butyl benzyl phthalate}, volume={14}, ISSN={0013-936X 1520-5851}, url={http://dx.doi.org/10.1021/es60163a001}, DOI={10.1021/es60163a001}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn environmental safety assessment of butyl benzyl phthalateWilliam E. Gledhill, Robert G. Kaley, William J. Adams, Orville. Hicks, Paul R. Michael, Victor W. Saeger, and Gerald A. LeBlancCite this: Environ. Sci. Technol. 1980, 14, 3, 301–305Publication Date (Print):March 1, 1980Publication History Published online1 May 2002Published inissue 1 March 1980https://doi.org/10.1021/es60163a001RIGHTS & PERMISSIONSArticle Views585Altmetric-Citations111LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (711 KB) Get e-Alerts Get e-Alerts}, number={3}, journal={Environmental Science & Technology}, publisher={American Chemical Society (ACS)}, author={Gledhill, William E. and Kaley, Robert G. and Adams, William J. and Hicks, Orville. and Michael, Paul R. and Saeger, Victor W. and LeBlanc, Gerald A.}, year={1980}, month={Mar}, pages={301–305} }
 @article{leblanc_1979, title={Utilization of bacterial colony counters to count early instar water fleas (Daphnia magna)}, volume={23}, ISSN={0007-4861 1432-0800}, url={http://dx.doi.org/10.1007/bf01770051}, DOI={10.1007/bf01770051}, number={1}, journal={Bulletin of Environmental Contamination and Toxicology}, publisher={Springer Science and Business Media LLC}, author={LeBlanc, Gerald A.}, year={1979}, month={Dec}, pages={837–839} }
 @book{sauter_le blanc_ells_buxton_1978, place={Duluth, Minnesota}, title={The chronic toxicity of methomyl, propachlor, baygon, and baytex to aquatic organisms}, institution={U.S. Environmental Protection Agency}, author={Sauter, S. and Le Blanc, G.A. and Ells, S.J. and Buxton, K}, year={1978} }
 @book{bentley_dean_ells_hollister_le blanc_sauter_sleight_1977, place={Fort Detrick, Maryland}, title={Acute toxicity of HMX to aquatic organisms}, number={DAMD-17-74-C-4101}, institution={U.S. Army Medical Research and Development Command}, author={Bentley, R.E. and Dean, J.W. and Ells, S.J. and Hollister, T.A. and Le Blanc, G.A. and Sauter, S. and Sleight, B.H., III}, year={1977} }
 @book{bentley_dean_ells_hollister_le blanc_sauter_sleight iii_1977, place={Fort Detrick, Maryland}, title={Laboratory Evaluation of the Toxicity of Cyclotrimethylene Trinitramine (RDX) to Aquatic Organisms}, url={http://dx.doi.org/10.21236/ada061730}, DOI={10.21236/ada061730}, abstractNote={Abstract : The toxicity of nitroglycerine to a wide variety of aquatic organisms representing several different trophic levels in aquatic ecosystems was studied. Results of static acute toxicity tests indicate that the acute LC50 values are greater than 3 mg/1 RDX. There was an apparent lack of bioaccumulation in edible or nonedible tissues or organs in all species tested. Effects were observed on growth at 5.8 mg/1 RDX during egg and fry studies, on survival at 4.9-6.3 mg/1 during chronic exposure of fathead minnows, and on number of young produced per parthenogenetic female at concentrations equal to or greater than 4.8 mg/1. Applying an application factor of 0.1 to the lower limit of observed acute toxicity values (3.6 mg/1, 96-hour LC50 for bluegill at pH 6.0) a water quality criterion of 0.35 mg/1 RDX is proposed. (Author)}, number={DAMD-17-74-C-4101DAMD-17-74-C-4101}, institution={U.S. Army Medical Research and Development Command}, author={Bentley, R.E. and Dean, J.W. and Ells, S.J. and Hollister, T.A. and Le Blanc, G.A. and Sauter, S. and Sleight III, B.H.}, year={1977}, month={Dec} }
 @book{bentley_le blanc_hollister_sleight_1976, place={Fort Detrick, Maryland}, title={Acute toxicity of diisopropylmethyl phosphate and dichloropentadiene to aquatic organisms}, number={DAMD-17-75-C-5073}, institution={U.S. Army Medical Research and Development Command}, author={Bentley, R.E. and Le Blanc, G.A. and Hollister, T.A. and Sleight, B.H., III}, year={1976} }
 @book{bentley_le blanc_hollister_sleight_1976, place={Fort Derrick, Maryland}, title={Laboratory evaluation of the toxicity of nitrocellulose to aquatic organisms}, number={DAMD-17-74-C-401}, institution={U.S. Army Medical Research and Development Command}, author={Bentley, R.E. and Le Blanc, G.A. and Hollister, T.A. and Sleight, B.H.}, year={1976} }