@article{heppell_sullivan_2000, title={Identification of gender and reproductive maturity in the absence of gonads: muscle tissue levels of sex steroids and vitellogenin in gag (Mycteroperca microlepis)}, volume={57}, DOI={10.1139/f99-188}, abstractNote={Gag (Mycteroperca microlepis) are often landed eviscerated, so their gonads are not available for histological verification of gender and stage of maturity. Information on gender is particularly important for the management of hermaphroditic grouper, where increased mortality through fishing can directly affect sex ratio and therefore the reproductive capacity of the population. Alternative techniques for evaluating fish gender and maturity therefore need to be developed for gag and other grouper. We utilized sensitive immunoassays to measure levels of the sex steroids estradiol-17beta (E 2 ), testosterone (T), and 11-ketotestosterone (11KT) and the egg-yolk precursor vitellogenin (VTG) in gag on a quarterly basis. Plasma and muscle levels of E 2 , T, and VTG in females were lowest during summer, rising in winter to reach peak values in spring. During winter and spring, plasma and muscle levels of 11KT were significantly higher in males than in adult females or immature fish. Combined measurement of VTG and 11KT in gag muscle proved useful for differentiating between males, adult females, and immature fish between December and April, the period of active gonadal recrudescence. This technique should prove useful in cases where fishery data are primarily collected through port sampling and gonads are not available for analysis.}, number={1}, journal={Canadian Journal of Fisheries and Aquatic Sciences}, author={Heppell, S. A. and Sullivan, C. V.}, year={2000}, pages={148–159} }
 @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={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 of variation (100 × SD/mean) at 50% binding were 3.8% (N = 20) and 5.94% (N = 4), respectively. Complete recovery (detection) in the ELISA was verified for a known quantity of VTG added to male striped bass plasma. Changes in plasma VTG concentrations during the annual reproductive cycle of female striped bass were measured both by ELISA and an established radial immunodiffusion assay (RIDA) based on the same antiserum and standard. Vitellogenin was detected in maturing females 7–8 months prior to spawning and the correlation between individual VTG values measured by ELISA and the RIDA was very high (r2 = 0.95). The highly sensitive and precise VTG ELISA should allow aquaculture and fisheries biologists to evaluate the gender and maturational status of individual fish of any Morone species during most of the year. Finally, VTG was detected by ELISA in incubation medium following culture of white perch liver fragments with 1 × 10−6 M estradiol-17β, providing the basis for an in vitro method to study the physiology and toxicology of vitellogenesis in temperate basses.}, 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{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{heppell_sullivan_1999, title={Gag (Mycteroperca microlepis) vitellogenin: purification, characterization and use for enzyme-linked immunosorbent assay (ELISA) of female maturity in three species of grouper}, volume={20}, ISSN={["1573-5168"]}, DOI={10.1023/A:1007730816797}, number={4}, journal={FISH PHYSIOLOGY AND BIOCHEMISTRY}, author={Heppell, SA and Sullivan, CV}, year={1999}, month={May}, pages={361–374} }
 @article{heppell_walters_crowder_1994, title={EVALUATING MANAGEMENT ALTERNATIVES FOR RED-COCKADED WOODPECKERS - A MODELING APPROACH}, volume={58}, ISSN={["0022-541X"]}, DOI={10.2307/3809319}, abstractNote={Managers often must evaluate an array of enhancement proposals for endangered species. We present a male-only, stage-based matrix model to assess potential effects of various management techniques used to enhance red-cockaded woodpecker (Picoides borealis) populations. We analyzed the elasticity of population growth to changes in each matrix parameter and predicted the population-level effects of 5 proposed management techniques that affect stage-specific survival, growth, and fecundity. Maintaining existing habitat and increasing the number of nesting cavities in unoccupied, but suitable, habitat are most likely to help restore declining populations}, number={3}, journal={JOURNAL OF WILDLIFE MANAGEMENT}, author={HEPPELL, SS and WALTERS, JR and CROWDER, LB}, year={1994}, month={Jul}, pages={479–487} }