@article{weber_moore_sullivan_2007, title={In vitro actions of insulin-like growth factor-I on ovarian follicle maturation in white perch (Morone americana)}, volume={151}, ISSN={["1095-6840"]}, DOI={10.1016/j.ygcen.2007.01.007}, abstractNote={Previous studies of follicle maturation in temperate basses showed that insulin-like growth factor (IGF)-I and -II can induce meiotic resumption, indicated by germinal vesicle breakdown (GVBD), and oocyte maturational competence (OMC), the ability to respond to the maturation-inducing hormone (MIH, 17,20beta-21-trihydroxy-4-pregnen-3-one, 20beta-S). The IGFs-induced GVBD but not OMC in striped bass follicles in vitro, but OMC and not GVBD in white bass follicles. Striped bass are group-synchronous single-clutch spawners whereas white bass and white perch are group-synchronous multiple-clutch spawners. In the present study, we found that IGFs-induced OMC in white perch. Although IGF-I weakly stimulated GVBD in follicles from some late stage fish, it is likely that IGF-I did not directly induce GVBD but instead induced OMC, enabling endogenous MIH to act. Bovine insulin was less potent than IGFs at inducing OMC, suggesting that the IGFs were acting through an IGF-I receptor. IGF-I increased testosterone and estradiol-17beta production by ovarian fragments but decreased production of 17,20beta-dihydroxy-4-pregnen-3-one, a precursor to the MIH, which was below detection levels. As with the other Morone species, phosphatidylinositiol 3-kinase inhibitors, wortmannin and LY 294002, and the translation inhibitor cyclohexamide, attenuated GVBD induced by human chorionic gonadotropin (hCG), 20beta-S, and a combination of IGF-I and 20beta-S. Only hCG-induced GVBD was attenuated by the transcription inhibitor actinomycin D. The IGFs have shared and disparate actions on ovarian follicle maturation among Morone species that appear to be linked to reproductive strategy and exhibit similarities in mechanisms of action.}, number={2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Weber, Gregory M. and Moore, Alicia B. and Sullivan, Craig V.}, year={2007}, month={Apr}, pages={180–187} }
 @article{weber_sullivan_2005, title={Insulin-like growth factor-1 induces oocyte maturational competence but not meiotic resumption in white bass (Morone chrysops) follicles in vitro: Evidence for rapid evolution of insulin-like growth factor action}, volume={72}, ISSN={["1529-7268"]}, DOI={10.1095/biolreprod.104.036251}, abstractNote={Abstract A combination of recombinant human (rh) insulin-like growth factor-I (IGF-I) (25 nM) and the maturation-inducing hormone (MIH), 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S; 72.5 nM), induced germinal vesicle breakdown (GVBD) in ovarian follicles of white bass incubated in vitro, whereas a four times greater concentration of each hormone was ineffective alone. These results indicate that IGF-I induces oocyte maturational competence (OMC) but not meiotic resumption in white bass. Culture medium concentrations of 20β-S remained below detection limits for ovarian fragments incubated with rhIGF-I. Actinomycin D blocked GVBD in response to hCG but not to rhIGF-I plus 20β-S, suggesting that IGF-I requires de novo translation but not transcription to induce OMC. Gap junction uncouplers, 1-octanol and 1-heptanol, and the phosphatidylinositiol 3-kinase (PI 3-K) inhibitors, wortmannin and LY 294002, attenuated hCG-, 20β-S-, and rhIGF-I plus 20β-S-induced GVBD. Although these inhibitors reduced hCG-induced progestin release, PI 3-K inhibitors did not alter MIH synthesis in some incubations and addition of 20β-S to the incubations did not fully overcome the effects of either class of inhibitors, suggesting that decreasing MIH production is not their only inhibitory effect on gonadotropin (GtH) action. Our data suggest that gap junctions and PI 3-K activity are necessary for GtH and IGF-I to induce and maintain OMC in white bass. The induction of OMC but not meiotic resumption by IGF-I in white bass, compared with the induction of meiotic resumption but not OMC by IGF-I discovered in the congeneric striped bass suggests rapid evolution of the reproductive actions of IGF-I among temperate basses (genus Morone).}, number={5}, journal={BIOLOGY OF REPRODUCTION}, author={Weber, GM and Sullivan, CV}, year={2005}, month={May}, pages={1177–1186} }
 @article{tipsmark_weber_strom_grau_hirano_borski_2005, title={Involvement of phospholipase C and intracellular calcium signaling in the gonadotropin-releasing hormone regulation of prolactin release from lactotrophs of tilapia (Oreochromis mossambicus)}, volume={142}, ISSN={["1095-6840"]}, DOI={10.1016/j.ygcen.2004.11.009}, abstractNote={Gonadotropin-releasing hormone (GnRH) is a potent stimulator of prolactin (PRL) secretion in various vertebrates including the tilapia, Oreochromis mossambicus. The mechanism by which GnRH regulates lactotroph cell function is poorly understood. Using the advantageous characteristics of the teleost pituitary gland from which a nearly pure population of PRL cells can be isolated, we examined whether GnRH might stimulate PRL release through an increase in phospholipase C (PLC), inositol triphosphate (IP3), and intracellular calcium (Ca(i)2+) signaling. Using Ca(i)2+ imaging and the calcium-sensitive dye fura-2, we found that chicken GnRH-II (cGnRH-II) induced a rapid dose-dependent increase in Ca(i)2+ in dispersed tilapia lactotrophs. The Ca(i)2+ signal was abolished by U-73122, an inhibitor of PLC-dependent phosphoinositide hydrolysis. Correspondingly, cGnRH-II-induced tPRL188 secretion was inhibited by U-73122, suggesting that activation of PLC mediates cGnRH-II's stimulatory effect on PRL secretion. Pretreatment with 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8), an inhibitor of Ca2+ release from intracellular stores, impeded the effect of cGnRH-II on Ca(i)2+. To further address the possible involvement of intracellular Ca2+ stores, IP3 concentrations in the tilapia rostral pars distalis (RPD containing 95-99% PRL cells) was determined by a radioreceptor assay. We found that GnRH-II induces a rapid (<5min) and sustained increase in IP3 concentration in the RPD. Secretion of tPRL(188) in response to cGnRH-II was suppressed by Ca2+ antagonists (TMB-8 and nifedipine). These data, along with our previous findings that show PRL release increases with a rise in Ca(i)2+, suggest that GnRH may elicit its PRL releasing effect by increasing Ca(i)2+. Furthermore, the rise in Ca(i)2+ may be derived from PLC/IP3-induced mobilization of Ca2+ from intracellular stores along with influx through L-type voltage-gated Ca2+ channels.}, number={1-2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Tipsmark, CK and Weber, GM and Strom, CN and Grau, EG and Hirano, T and Borski, RJ}, year={2005}, month={May}, pages={227–233} }
 @article{sullivan_hiramatsu_kennedy_clark_weber_matsubara_hara_2003, title={Induced maturation and spawning: opportunities and applications for research on oogenesis}, volume={28}, ISSN={["1573-5168"]}, DOI={10.1023/B:FISH.0000030635.92568.0a}, number={1-4}, journal={FISH PHYSIOLOGY AND BIOCHEMISTRY}, author={Sullivan, CV and Hiramatsu, N and Kennedy, AM and Clark, RW and Weber, GM and Matsubara, T and Hara, A}, year={2003}, pages={481–486} }
 @article{hiramatsu_hara_hiramatsu_fukada_weber_denslow_sullivan_2002, title={Vitellogenin-derived yolk proteins of white perch, Morone americana: Purification, characterization, and vitellogenin-receptor binding}, volume={67}, ISSN={["1529-7268"]}, DOI={10.1095/biolreprod67.2.655}, abstractNote={Abstract The objectives of this study were to 1) purify and characterize vitellogenin-derived yolk proteins of white perch (Morone americana), 2) develop a nonisotopic receptor binding assay for vitellogenin, and 3) identify the yolk protein domains of vitellogenin recognized by the ovarian vitellogenin receptor. Four yolk proteins derived from vitellogenin (YP1, YP2 monomer [YP2m] and dimer [YP2d], and YP3) were isolated from ovaries of vitellogenic perch by selective precipitation, ion exchange chromatography, and gel filtration. The apparent molecular masses of purified YP1, YP2m, and YP2d after gel filtration were 310 kDa, 17 kDa, and 27 kDa, respectively. YP3 appeared in SDS-PAGE as a ∼20-kDa band plus some diffuse smaller bands that could be visualized by staining for phosphoprotein with Coomassie Brilliant Blue complexed with aluminum nitrate. Immunological and biochemical characteristics of YP1, YP2s, and YP3 identified them as white perch lipovitellin, β′-components, and phosvitin, respectively. A novel receptor-binding assay for vitellogenin was developed based on digoxigenin (DIG)-labeled vitellogenin tracer binding to ovarian membrane proteins immobilized in 96-well plates. Lipovitellin from white perch and vitellogenin from perch and other teleosts effectively displaced specifically bound DIG-vitellogenin in the assay, but phosvitin and the β′-component could not, demonstrating for the first time that the lipovitellin domain of teleost vitellogenin mediates its binding to the oocyte receptor. Lipovitellin was less effective than vitellogenin in this regard, suggesting that the remaining yolk protein domains of vitellogenin may interact with its lipovitellin domain to facilitate binding of vitellogenin to its receptor.}, number={2}, journal={BIOLOGY OF REPRODUCTION}, author={Hiramatsu, N and Hara, A and Hiramatsu, K and Fukada, H and Weber, GM and Denslow, ND and Sullivan, CV}, year={2002}, month={Aug}, pages={655–667} }
 @article{weber_sullivan_2001, title={In vitro hormone induction of final oocyte maturation in striped bass (Morone saxatilis) follicles is inhibited by blockers of phosphatidylinositol 3-kinase activity}, volume={129}, ISSN={["1096-4959"]}, DOI={10.1016/S1096-4959(01)00349-9}, abstractNote={Oocyte germinal vesicle breakdown (GVBD) was induced in striped bass ovarian fragments when tissues were incubated with 100-nM recombinant human insulin-like growth factor-I (rhIGF-I), 25-IU human chorionic gonadotropin (hCG) ml−1, or 290 nM of the maturation-inducing steroid (MIS), 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S). Inhibitors of phosphatidylinositol 3-kinase (PI 3-K), wortmannin (100 nM) and LY 294002 (50 μM), inhibited GVBD induced by these hormones. Furthermore, the inhibitors attenuated hCG-induced steroid hormone synthesis. Previous studies report that gap junction uncouplers inhibit GVBD induced by hCG, but not by rhIGF-I, in striped bass. We show that 20β-S-induced GVBD is also attenuated by 1 mM 1-heptanol or 1-octanol without being affected by incubation with 3 mM ethanol. Thus, the effects of inhibiting PI 3-K activity on GtH and MIS actions are similar to effects of uncoupling gap junctions. These data suggest that PI 3-K activity is required for GtH- MIS- and IGF-I induction of GVBD in striped bass. Our data are also consistent with the notion that a ligand that regulates PI 3-K activity, possibly an IGF, participates in maintenance of gap junctional communication required for maximal GtH and MIS action.}, number={2-3}, journal={COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY}, author={Weber, GM and Sullivan, CV}, year={2001}, month={Jun}, pages={467–473} }
 @article{rodgers_weber_sullivan_levine_2001, title={Isolation and characterization of myostatin complementary deoxyribonucleic acid clones from two commercially important fish: Oreochromis mossambicus and Morone chrysops}, volume={142}, ISSN={["0013-7227"]}, DOI={10.1210/en.142.4.1412}, abstractNote={In mammals, skeletal muscle mass is negatively regulated by a muscle-derived growth/differentiating factor named myostatin (MSTN) that belongs to the transforming growth factor-beta superfamily. Although putative MSTN homologs have been identified from several vertebrates, nonmammalian orthologs remained poorly defined. Thus, we isolated and characterized MSTN complementary DNA clones from the skeletal muscle of the tilapia Oreochromis mossambicus and the white bass Morone chrysops. The nucleic and amino acid sequences from both fish species are highly homologous to the previously identified mammalian and avian orthologs, and both possess conserved cysteine residues and putative RXXR proteolytic processing sites that are common to all transforming growth factor-beta family members. Western blotting of conditioned medium from human embryonal kidney (HEK293) cells overexpressing a His-tagged tilapia MSTN indicates that the secreted fish protein is processed in a manner similar to mouse MSTN. However, in contrast to mice, MSTN expression in tilapia is not limited to skeletal muscle as it occurs in many tissues. Furthermore, the timing of MSTN expression in developing tilapia larvae coincides with myogenesis. These results suggest that the biological actions of MSTN in the tilapia and possibly in other fishes may not be limited to myocyte growth repression, but may additionally influence different cell types and organ systems.}, number={4}, journal={ENDOCRINOLOGY}, author={Rodgers, BD and Weber, GM and Sullivan, CV and Levine, MA}, year={2001}, month={Apr}, pages={1412–1418} }
 @article{rodgers_weber_2001, title={Sequence conservation among fish myostatin orthologues and the characterization of two additional cDNA clones from Morone saxatilis and Morone americana}, volume={129}, ISSN={["1879-1107"]}, DOI={10.1016/S1096-4959(01)00350-5}, abstractNote={Myostatin (MSTN) negatively regulates mammalian skeletal muscle growth and development by inhibiting myoblast proliferation. Mice and cattle possessing mutant MSTN alleles display a 'double muscling' phenotype characterized by extreme skeletal muscle hypertrophy and/or hyperplasia. MSTN orthologues have been previously characterized in 12 vertebrate species, including the white bass Morone chrysops. Presented herein is the identification and characterization of novel cDNA clones from two additional Morone species: saxatilis (striped bass) and americana (white perch), which were obtained by PCR amplification and subsequent TA-cloning. The predicted amino acid sequence of each cDNA clone contains a putative signal sequence, conserved cysteine residues and a RXXR proteolytic processing site. The different Morone proteins were 97-99% identical to each other and approximately 91, 81, 68 and 67% identical to the tilapia, zebrafish, mammalian and avian proteins, respectively. However, the bioactive domains, which lie downstream of each processing site, were considerably more conserved. They were 99-100% identical within the genus and were approximately 99, 95, 88 and 88% identical to the tilapia, zebrafish, mammalian and avian domains, respectively. This high level of sequence conservation among all known MSTN orthologues suggests that the structure/function relationship of each is equally well conserved among vertebrates.}, number={2-3}, journal={COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY}, author={Rodgers, BD and Weber, GM}, year={2001}, month={Jun}, pages={597–603} }
 @article{weber_sullivan_2000, title={Effects of insulin-like growth factor-I on in vitro final oocyte maturation and ovarian steroidogenesis in striped bass, Morone saxatilis}, volume={63}, ISSN={["1529-7268"]}, DOI={10.1095/biolreprod63.4.1049}, abstractNote={Abstract Recombinant human (rh) insulin-like growth factor-I (IGF-I) was more potent than rhIGF-II at inducing in vitro germinal vesicle breakdown (GVBD), a marker for resumption of meiosis, in oocytes of striped bass. Treatment of ovarian fragments containing oocytes in intact follicles with rhIGF-I increased concentrations of estradiol-17β and maturation-inducing steroid (MIS) 17,20β,21-trihydoxy-4-pregnen-3-one (20β-S) in the culture medium and decreased testosterone levels. The follicles were too immature for oocytes to complete GVBD in response to 20β-S (MIS incompetent) or hCG. Addition of 20β-S to cultures did not increase the percentage of oocytes completing GVBD in response to rhIGF-I or rhIGF-II. Bovine insulin was without effect on GVBD or steroid production. Incubation of MIS-competent follicles with actinomycin D, cyanoketone, trilostane, 1-heptanol, or 1-octanol had no effect on rhIGF-I-induced GVBD, but attenuated hCG-induced GVBD and 20β-S production. Cycloheximide inhibited rhIGF-I-induced GVBD. Collectively, these observations indicate that IGF-I can induce GVBD via MIS- and transcription-independent pathways without coupled gap junctions between oocytes and granulosa cells or among granulosa cells, but requires protein synthesis to do so. An rhIGF-I analogue that does not bind IGF-binding proteins, des(1,3)IGF-I, was more potent than rhIGF-I in inducing GVBD, suggesting ovarian IGF-binding proteins may inhibit IGF-I action.}, number={4}, journal={BIOLOGY OF REPRODUCTION}, author={Weber, GM and Sullivan, CV}, year={2000}, month={Oct}, pages={1049–1057} }
 @article{weber_king_clark_hodson_sullivan_2000, title={Morpho-physiological predictors of ovulatory success in captive striped bass (Morone saxatilis)}, volume={188}, ISSN={["1873-5622"]}, DOI={10.1016/S0044-8486(00)00328-8}, abstractNote={This study evaluates morpho-physiological characters as predictors of ovulatory success in cultured striped bass, Morone saxatilis, that could be used by farmers to select females for induced spawning. Diameter, size homogeneity and growth of ovarian follicles; blood plasma levels of testosterone (T), oestradiol-17β (E2) and vitellogenin (VTG); and in vitro maturation of oocytes, in response to a combination of insulin-like growth factor-I (IGF-I, 100 nM) and 17,20β,21-trihydroxy-4-pregnen-3-one (20β-S, 290 nM) were examined for females prior to spawning induction and compared with their subsequent ovulatory response. Fish spawning within 8 days of implantation with pelleted analogue of mammalian gonadotropin-releasing hormone analogue (GnRHa; [d-Ala6-des-Gly10-NEt]-LHRH) were considered to have given a satisfactory maturational response. The in vitro assay was the most reliable predictor for ovulatory success. All fish whose oocytes completed final oocyte maturation (FOM) in vitro in response to the combination of IGF-I and 20β-S spawned, whereas, 12 out of 13 fish, whose oocytes did not complete FOM in vitro, failed to spawn within 8 days of GnRHa treatment. The in vitro assay was field-tested on commercial farms, and correctly identified all four females that spawned out of the eight females that were given hormone treatment. Among the other measurements, follicle diameter best differentiated between fish that later spawned and those that did not spawn. Plasma T concentrations were greater on average in fish that spawned, but the technical complexity of the assay and overlap in T concentrations between fish that spawned and those that did not limits the value of this measurement to farmers. There was no significant difference in follicle size homogeneity, follicle growth over the 2-week period prior to hormone treatment, or plasma levels of E2 and VTG between fish that spawned and those that did not.}, number={1-2}, journal={AQUACULTURE}, author={Weber, GM and King, W and Clark, RW and Hodson, RG and Sullivan, CV}, year={2000}, month={Aug}, pages={133–146} }
 @article{weber_grau_1999, title={Changes in serum concentrations and pituitary content of the two prolactins and growth hormone during the reproductive cycle in female tilapia, Oreochromis mossambicus, compared with changes during fasting}, volume={124}, ISSN={["0742-8413"]}, DOI={10.1016/s0742-8413(99)00081-x}, abstractNote={Patterns of change in serum concentrations and pituitary content of GH and two tilapia prolactins (PRL177 and PRL188) were examined during the reproductive cycle of female tilapia, Oreochromis mossambicus, adapted to fresh water and to seawater. Changes in these hormones during fasting were examined to elucidate whether changes observed during brooding could be attributed to a reduction in feeding during brooding. Serum concentrations of GH increased prior to pituitary content during the brooding phase of the reproductive cycle. In contrast, pituitary content of GH increased prior to serum concentrations during fasting. There was no consistent pattern of change in serum or pituitary PRL levels during the reproductive cycle, among experiments. Serum concentrations of PRL177 were elevated in all fasted fish, whereas PRL188 was elevated during fasting in males but not females. The increases in the serum concentration of PRLs and GH, and in the pituitary content of GH in response to fasting support the notion that these hormones are involved in the regulation of the use of metabolic substrates in tilapia. We conclude that reduced food intake during brooding may contribute to changes in serum and pituitary levels of the PRLs and GH observed during the reproductive cycle. Nevertheless, differences between changes in serum and pituitary GH during brooding and fasting suggest GH has actions in reproduction, and changes in GH during brooding are not only in response to fasting.}, number={3}, journal={COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY C-PHARMACOLOGY TOXICOLOGY & ENDOCRINOLOGY}, author={Weber, GM and Grau, EG}, year={1999}, month={Nov}, pages={323–335} }
 @article{heppell_jackson_weber_sullivan_1999, title={Enzyme-linked immunosorbent assay (ELISA) of vitellogenin in temperate basses (Genus Morone): Plasma and in vitro analyses}, volume={128}, ISSN={["1548-8659"]}, DOI={10.1577/1548-8659(1999)128<0532:ELIAEO>2.0.CO;2}, abstractNote={Abstract Blood levels of the egg yolk precursor vitellogenin (VTG) can be used as a definitive marker for the onset and progress of maturation in female teleosts. In the present study, an enzyme-linked immunosorbent assay (ELISA) was developed to measure VTG in blood plasma from three species of temperate basses. The antigen capture, competitive ELISA is based on a rabbit antiserum raised against striped bass Morone saxatilis VTG and uses purified striped bass VTG as standard and in the final antigen capture step. The assay was validated for detecting VTG in the plasma of maturing female striped bass, white perch M. americana and white bass M. chrysops. Serial dilutions of blood plasma from vitellogenic females of all three species yielded VTG curves that paralleled the standard curve in the ELISA, whereas no cross reactivity was observed for plasma obtained from males of any Morone species. The working range of the ELISA was 33–1,118 ng/mL (90–10% of binding), and the intra- and interassay coefficients o...}, number={3}, journal={TRANSACTIONS OF THE AMERICAN FISHERIES SOCIETY}, author={Heppell, SA and Jackson, LF and Weber, GM and Sullivan, CV}, year={1999}, month={May}, pages={532–541} }
 @article{weber_powell_park_fischer_craig_rivier_nanakorn_parhar_ngamvongchon_grau_et al._1997, title={Evidence that gonadotropin-releasing hormone (GnRH) functions as a prolactin-releasing factor in a teleost fish (Oreochromis mossambicus) and primary structures for three native GnRH molecules}, volume={155}, ISSN={["0022-0795"]}, DOI={10.1677/joe.0.1550121}, abstractNote={Three forms of gonadotropin-releasing hormone (GnRH) are isolated and identified here by chemical sequence analysis for one species of tilapia, Oreochromis niloticus, and by HPLC elution position for a second species of tilapia, O. mossambicus. Of the three GnRH forms in O. mossambicus, chicken GnRH-II (cGnRH-II) and sea bream GnRH (sbGnRH) are present in greater abundance in the brain and pituitary than salmon GnRH (sGnRH). These three native forms of GnRH are shown to stimulate the release of prolactin (PRL) from the rostral pars distalis (RPD) of the pituitary of O. mossambicus in vitro with the following order of potency: cGnRH-II > sGnRH > sbGnRH. In addition, a mammalian GnRH analog stimulated the release of PRL from the pituitary RPD incubated in either iso-osmotic (320 mosmol/l) or hyperosmotic (355 mosmol/l) medium, the latter normally inhibiting PRL release. The response of the pituitary RPD to GnRH was augmented by co-incubation with testosterone or 17 beta-estradiol. The effects of GnRH on PRL release appear to be direct effects on PRL cells because the RPD of tilapia contains a nearly homogeneous mass of PRL cells without intermixing of gonadotrophs. Our data suggest that GnRH plays a broad role in fish, depending on the species, by affecting not only gonadotropins and growth hormone, but also PRL.}, number={1}, journal={JOURNAL OF ENDOCRINOLOGY}, author={Weber, GM and Powell, JFF and Park, M and Fischer, WH and Craig, AG and Rivier, JE and Nanakorn, U and Parhar, IS and Ngamvongchon, S and Grau, EG and et al.}, year={1997}, month={Oct}, pages={121–132} }