The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Gerald T. Ankley - One of the best experts on this subject based on the ideXlab platform.
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a method for the determination of genetic sex in the fathead minnow pimephales promelas to support testing of endocrine active chemicals
Environmental Science & Technology, 2011Co-Authors: Allen W Olmstead, Daniel L Villeneuve, Gerald T. Ankley, Jenna E Cavallin, Annelie Lindberglivingston, Leah C Wehmas, Sigmund J DegitzAbstract:Certain endocrine-active toxicants have been reported to completely sex reverse both male and female individuals in amphibian, avian, fish, invertebrate, and reptile species, resulting in a phenotype indistinguishable from unaffected individuals. Detection of low-level sex reversal often requires large numbers of organisms to achieve the necessary statistical power, especially in those species with predominantly genetic sex determination and cryptic/homomorphic sex chromosomes. Here we describe a method for determining the genetic sex in the commonly used ecotoxicological model, the fathead minnow (Pimephales promelas). Analysis of amplified fragment length polymorphisms (AFLP) in a spawn of Minnows resulted in detection of 10 sex-linked AFLPs, which were isolated and sequenced. No recombination events were observed with any sex-linked AFLP in the animals examined (n = 112). A polymerase chain reaction (PCR) method was then developed that determined the presence of one of these sex-linked polymorphisms fo...
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expression signatures for a model androgen and antiandrogen in the fathead minnow pimephales promelas ovary
Environmental Science & Technology, 2009Co-Authors: Natalia Garciareyero, Daniel L Villeneuve, Gerald T. Ankley, Kevin J Kroll, Li Liu, Edward F Orlando, Karen H Watanabe, Maria S Sepulveda, Nancy D DenslowAbstract:Trenbolone, an anabolic androgen, and flutamide, an antiandrogen, are prototypical model compounds for agonism and antagonism of the androgen receptor. We hypothesized that 48 h exposures of female fathead Minnows (Pimephales promelas) to environmentally relevant concentrations of these chemicals would alter genes regulated by the androgen receptor and that a mixture of the two compounds would block the effects. Gene expression in the ovaries was analyzed using a fathead minnow-specific 22 000-gene microarray. Flutamide altered about twice the number of genes as trenbolone, most of which appeared to be through pathways not associated with the androgen receptor. A group of 70 genes, of which we could identify 37, were reciprocally regulated by trenbolone and flutamide. These are candidates for specific biomarkers for androgen receptor mediated gene expression. Four genes stand out as specifically related to reproduction: sperm associated antigen 8 (SPAG8), CASP8 and FADD-like apoptosis regulator (CFLAR), c...
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comparison of fathead minnow ovary explant and h295r cell based steroidogenesis assays for identifying endocrine active chemicals
Ecotoxicology and Environmental Safety, 2007Co-Authors: Daniel L Villeneuve, Lindsey S Blake, Katie J Greene, Eric Higley, Elizabeth A Makynen, Gerald T. Ankley, John L. Newsted, John P GiesyAbstract:An in vitro steroidogenesis assay using H295R human adenocarcinoma cells has been suggested as a possible alternative to gonad explant assays for use as a Tier I screening assay to detect endocrine active chemicals capable of modulating steroid hormone synthesis. This study is one of the first to investigate the utility of the H295R assay for predicting effects and/or understanding mechanisms of action across species and tissues. Six chemicals, including one selective aromatase inhibitor (fadrozole), four fungicides (fenarimol, ketoconazole, prochloraz, and vinclozolin), and one herbicide (prometon), were tested in both the H295R steroidogenesis assay, and an in vitro steroidogenesis assay using fathead minnow ovary explants. All six chemicals caused significant alterations in 17β-estradiol (E2) and/or testosterone (T) production in vitro. Effects of ketoconazole, prochloraz, and prometon were similar in both assays. However, there were differences in the profile of responses for T for fadrozole and fenarimol, and for T and E2 for vinclozolin. In terms of sensitivity, steroid production in the H295R assay was most sensitive for detecting the effects of fadrozole, fenarimol, and prochloraz, but was less sensitive than the fathead minnow ovary explant assay to the effects of ketoconazole and vinclozolin. The H295R assay was consistently less variable (among replicates) than the fathead minnow ovary explant assay. However, the ovary explant assay was more predictive of in vivo effects of the six chemicals on fathead Minnows than the H295R system. Further characterization of autoregulatory capacities, interaction of steroid-hormone receptor pathways with steroidogenesis, and metabolic capabilities of each system are needed for either system to provide clear and informative insights regarding a chemical's mechanism of action. Overall, however, results of this study suggest that both the H295R and fathead minnow ovary explant assays have utility for identifying endocrine-active chemicals in screening-type applications.
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linkage of biochemical responses to population level effects a case study with vitellogenin in the fathead minnow pimephales promelas
Environmental Toxicology and Chemistry, 2007Co-Authors: David H Miller, Daniel L Villeneuve, Elizabeth J Durhan, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Gerald T. AnkleyAbstract:A challenge in the field of ecotoxicology is the linkage of alterations at molecular and biochemical levels of organization to adverse outcomes in individuals and populations. In the present study, a predictive relationship between plasma vitellogenin (VTG) concentration and fecundity in female fathead Minnows (Pimephales promelas) was derived from 21-d laboratory toxicity tests with five chemicals (17β-trenbolone, 17α-trenbolone, prochloraz, fenarimol, and fadrozole) that inhibit VTG production through different mechanisms. Because VTG is key to egg production in female oviparous animals, changes in the lipoprotein could, theoretically, serve as an indicator of reproductive success. Regression of fecundity versus VTG concentration from the various studies yielded a highly significant linear model (fecundity = −0.042 + 0.95-VTG, p < 0.01, r2 = 0.88). This relationship was integrated into a population model to translate changes in VTG concentrations of female fathead Minnows to alterations in population growth. The model predicted relatively profound effects on population size offish experiencing moderate decreases in vitellogenesis. For example, a fathead minnow population at a carrying capacity exposed to a chemical stressor that causes a 25% decrease in VTG concentration in females from baseline values would exhibit a 34.6% projected decrease in size after two years of exposure and reach an equilibrium population size that was only 30.2% of the preexposed population. Overall, the current study provides an example of how changes in a biomarker (VTG concentration) can be quantitatively translated into adverse effects at the individual and population levels.
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characterization of responses to the antiandrogen flutamide in a short term reproduction assay with the fathead minnow
Aquatic Toxicology, 2004Co-Authors: Kathleen M Jensen, Brian C Butterworth, Michael D Kahl, Joseph J Korte, Elizabeth A Makynen, Richard L. Leino, Gerald T. AnkleyAbstract:Abstract A short-term reproduction assay with the fathead minnow (Pimephales promelas) has been developed to detect chemicals with the potential to disrupt reproductive endocrine function controlled by estrogen- and androgen-mediated pathways. The objective of this study was to use the assay to characterize responses of fathead minnow reproductive endocrinology and physiology to the mammalian antiandrogen, flutamide. Male and female fish were exposed to nominal (target) concentrations of 50 and 500 μg flutamide/l for 21-days, following which plasma steroid and vitellogenin concentrations were determined and gonadal morphology assessed. Fecundity of the fish was significantly reduced by exposure to a measured test concentration of 651 μg flutamide/l. In addition, embryo hatch was significantly reduced at this concentration. Qualitative histological assessment of ovaries from females exposed to flutamide indicated a decrease in mature oocytes and an increase in atretic follicles. Testes of males exposed to flutamide exhibited spermatocyte degeneration and necrosis. Concentration-dependent increases in plasma testosterone and vitellogenin concentrations were observed in the females. Flutamide also altered reproductive endocrinology of male fathead Minnows. Males exposed to 651 μg flutamide/l exhibited elevated concentrations of β-estradiol and vitellogenin. In summary, the results of this study with the fathead minnow demonstrate that flutamide affects reproductive endocrine function in fish and that the type of hormonal pattern and histopathology effects observed are consistent with an antiandrogenic mode-of-action. Consequently, our findings suggest that the 21-day reproduction assay utilizing fathead Minnows is a sensitive short-term screening method for the detection of endocrine-disrupting chemicals, including antiandrogens.
Brian D. Wisenden - One of the best experts on this subject based on the ideXlab platform.
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Field verification of chondroitin sulfate as a putative component of chemical alarm cue in wild populations of fathead Minnows (Pimephales promelas)
Chemoecology, 2017Co-Authors: Alexai E. Faulkner, Ingrid E. Holstrom, Samantha A. Molitor, Mikaela E. Hanson, Whitney R. Shegrud, Joshua C. Gillen, Samuel J. Willard, Brian D. WisendenAbstract:Chemical characterization of damage-released alarm cues in ostariophysan fishes has lagged far behind the study of the ecological role that these cues play in behavioral decision-making of prey fishes. Chondroitin sulfate has been identified as a putative component of alarm cue based on two laboratory studies of zebrafish, Danio rerio , and the northern studfish, Fundulus catenatus . The fathead minnow, Pimephales promelas , is a model organism in the study of chemically mediated predator–prey interactions, in part because they can be studied in the laboratory and under field conditions. Here, we conducted a field experiment on wild populations of fathead Minnows, to test for area avoidance of chondroitin sulfate relative to conspecific skin extract (containing alarm cues = positive control) or water (negative control). We repeated the experiment in two small lakes in central Minnesota using minnow traps containing blocks of sponge with one of the three test cues. We found that fathead Minnows avoided traps chemically labeled with conspecific alarm cue more than control traps labeled with water, and that the number of Minnows caught in traps labeled with chondroitin sulfate was intermediate between alarm cue traps and water traps. These data are consistent with laboratory findings that chondroitin sulfate is a component of alarm cue, but that other species-specific compounds are needed for a full behavioral response.
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Bold, Sedentary Fathead Minnows Have More Parasites.
Zebrafish, 2016Co-Authors: Kelsey Gladen, Elizabeth C. Duncan, Sehoya Cotner, Daniel C. Mcewen, James B. Cotner, Brian D. WisendenAbstract:Abstract Parasites that rely on trophic transmission can manipulate the behavior of an intermediate host to compromise the host's antipredator competence and increase the probability of reaching the next host. Selection for parasite manipulation is diminished when there is significant risk of host death to causes other than consumption by a suitable definitive host for the parasite. Consequently, behavioral manipulation by parasites can be expected to be subtle. Ornithodiplostomum ptychocheilus (Op) is a trematode parasite that has a bird–snail–fish host life cycle. Fathead Minnows are a common intermediate host of Op, where metacercariae encyst in the minnow brain. In this study, we report a link between metacercarial intensity and behavior in fathead Minnows. In the field, we found that roaming distance by free-living Minnows over 24 h was negatively correlated with parasite intensity. In the laboratory, we found that boldness in an open field test was positively correlated with parasite intensity. Thes...
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Shoaling as an antiparasite defence in Minnows (Pimephales promelas) exposed to trematode cercariae
Journal of Animal Ecology, 2012Co-Authors: Anthony D. Stumbo, Clayton T. James, Cameron P. Goater, Brian D. WisendenAbstract:Summary 1. Individuals that live in groups benefit from increased foraging success and decreased predation. Protection from some types of parasites may provide an additional benefit of groupliving. For fish, the extent to which shoaling can reduce an individual’s risk of exposure to the infective stages of parasites is unknown. 2. We tested for antiparasite benefits of shoaling in fathead Minnows exposed to larvae (cercariae) of two of their most common species of trematode, Ornithodiplostomum ptychocheilus and Posthodiplostomum minimum. As developing stages (metacercariae) of these trematodes cause reductions in minnow activity, growth and survival, natural selection should favour the evolution of cercariae-avoidance behaviours. 3. We evaluated shoal dimensions in groups of Minnows exposed to O. ptychocheilus and to other chemical/physical stimuli within aquaria. To compare risk of exposure in shoaling vs. non-shoaling fish, we confined groups of Minnows into mesh cages in outdoor mesocosms, exposed them to cercariae, then compared mean worm numbers in grouped vs. solitary fish. Lastly, we tested whether fish located within the centre of an artificial shoal reduced their risk of cercariae exposure compared with those along peripheral edges. 4. Minnows distinguished infective cercariae from other potential aquatic threats and responded with activity that reduced the 2-dimensional area of their shoals 15-fold compared with water-only controls. Fish confined within artificial shoals had 3-fold fewer worms than single fish and Minnows located within the centre of artificial shoals had significantly fewer worms than those without peripheral Minnows. 5. These results show that shoaling reduces a Minnows’ risk of exposure to cercariae, either directly via detection of cercariae in the water column followed by behavioural avoidance or indirectly via behaviour-mediated differences in exposure between shoaling vs. non-shoaling fish.
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active space of chemical alarm cue in natural fish populations
Behaviour, 2008Co-Authors: Brian D. WisendenAbstract:Summary Chemical cues released from injured fish skin during a predator attack provide reliable information about the presence of predation risk. Here, I report estimates of the area avoided by littoral fishes after experimental release of chemical alarm cues in two small lakes in northern Minnesota. Minnow traps were labeled chemically with either water (control) or skin extract (chemical alarm cue) made from 2 cm2 of cyprinid skin (redbelly dace in experiment 1, fathead Minnows in experiment 2). Traps labeled with water were placed 1, 2, or 8 m from traps labeled with alarm cue. After 2 h, water-traps that were either 1 or 2 m distant from an alarm-trap caught significantly fewer fish than water-traps 8 m distant from alarm-traps. Conspecific and heterospecific skin extract produced similar area avoidance by fathead Minnows. Redbelly dace showed a larger active space in response to conspecific than heterospecific alarm cues. Brook stickleback showed reduced catches within 2 m of skin extract of fathead Minnows. Overall, the radius of active space was between 2 and 8 m under lake conditions with average subsurface currents of 0.82 cm/s. These data are the first field estimates of active space of ostariophysan chemical alarm cues.
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Field verification of predator attraction to minnow alarm substance.
Journal of Chemical Ecology, 2002Co-Authors: Brian D. Wisenden, Travis A. ThielAbstract:Fishes such as Minnows in the superorder Ostariophysi possess specialized alarm substance cells (ASC) that contain an alarm cue. Alarm substance can only be released by damage to the epidermis; thus, the release of alarm substance is a reliable indicator of predation risk. When nearby Minnows detect the cue, they adopt a range of antipredator behaviors that reduce their probability of predation. Predator–predator interactions afford prey an opportunity to escape and, thus, a fitness benefit that maintains alarm substance calls over evolutionary time. Here, we present data from a simple field experiment verifying that nearby predators are attracted to minnow alarm substance because it signals an opportunity to pirate a meal. Fishing lures were baited with sponge blocks scented with either (1) water (control for sponge odor and appearance), (2) skin extract from non-ostariophysan convict cichlids (superorder Acanthopterygii, Archocentrus “Cichlasoma” nigrofasciatus) to control for general injury-released cues from fish, or (3) skin extract from fathead Minnows (superorder Ostariophysi, Pimephales promelas). Predator strike frequency on each sponge type was 1,1, and 7 for water, cichlid, and minnow cues, respectively. These data provide the first field test using fish predators of the predator-attraction hypothesis for the evolution of Ostariophysan alarm substance cells.
Kathleen M Jensen - One of the best experts on this subject based on the ideXlab platform.
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reproductive effects in fathead Minnows pimphales promelas following a 21 d exposure to 17α ethinylestradiol
Chemosphere, 2016Co-Authors: Brandon M Armstrong, Kathleen M Jensen, James M Lazorchak, Herman J Haring, Mark E Smith, Robert W Flick, David C Bencic, Adam D BialesAbstract:17α-ethinylestradiol (EE2) is a synthetic estrogen that is an active ingredient in oral contraception and hormone replacement therapy. Surveys of wastewater treatment plant effluents and surface waters throughout the world have reported EE2 concentrations in the ng/L range, and these low levels can cause significant reproductive effects in fish. This study tested the effects of three environmentally relevant EE2 concentrations: 0.47, 1.54 and 3.92 ng/L using a 21 d short-term reproductive assay to investigate the effects of EE2 on fathead minnow (Pimephales promelas) reproduction. The two highest EE2 concentrations tested in this study caused significant liver gene expression and induction of vitellogenin plasma protein in male fathead Minnows. Exposure to 3.92 ng EE2/L increased the production of plasma vitellogenin in the females. Plasma estradiol concentrations were significantly reduced in females exposed to 1.54 and 3.92 ng EE2/L. All three tested concentrations significantly reduced fathead minnow egg production after a 21 d exposure to EE2. The results of this study indicate that the previously reported no observed adverse effect concentration (NOAEC) for EE2 on fathead minnow egg production (1.0 ng/L) may be too high. Because all three treatments resulted in significantly reduced egg production, the lowest observed adverse effect concentration (LOAEC) for EE2 on fathead minnow egg production is 0.47 ng EE2/L. This research estimates a NOAEC for fathead minnow reproduction at 0.24 ng EE2/L following a 21 d exposure. Additionally, induction of vitellogenin is a sensitive indicator of estrogen exposure but does not appear to be predictive of fathead minnow egg production.
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linkage of biochemical responses to population level effects a case study with vitellogenin in the fathead minnow pimephales promelas
Environmental Toxicology and Chemistry, 2007Co-Authors: David H Miller, Daniel L Villeneuve, Elizabeth J Durhan, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Gerald T. AnkleyAbstract:A challenge in the field of ecotoxicology is the linkage of alterations at molecular and biochemical levels of organization to adverse outcomes in individuals and populations. In the present study, a predictive relationship between plasma vitellogenin (VTG) concentration and fecundity in female fathead Minnows (Pimephales promelas) was derived from 21-d laboratory toxicity tests with five chemicals (17β-trenbolone, 17α-trenbolone, prochloraz, fenarimol, and fadrozole) that inhibit VTG production through different mechanisms. Because VTG is key to egg production in female oviparous animals, changes in the lipoprotein could, theoretically, serve as an indicator of reproductive success. Regression of fecundity versus VTG concentration from the various studies yielded a highly significant linear model (fecundity = −0.042 + 0.95-VTG, p < 0.01, r2 = 0.88). This relationship was integrated into a population model to translate changes in VTG concentrations of female fathead Minnows to alterations in population growth. The model predicted relatively profound effects on population size offish experiencing moderate decreases in vitellogenesis. For example, a fathead minnow population at a carrying capacity exposed to a chemical stressor that causes a 25% decrease in VTG concentration in females from baseline values would exhibit a 34.6% projected decrease in size after two years of exposure and reach an equilibrium population size that was only 30.2% of the preexposed population. Overall, the current study provides an example of how changes in a biomarker (VTG concentration) can be quantitatively translated into adverse effects at the individual and population levels.
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a graphical systems model to facilitate hypothesis driven ecotoxicogenomics research on the teleost brain pituitary gonadal axis
Environmental Science & Technology, 2007Co-Authors: Daniel L Villeneuve, Elizabeth J Durhan, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Patrick Larkin, Iris Knoebl, Ann L Miracle, Barbara J Carter, Nancy D DenslowAbstract:Graphical systems models are powerful tools that can help facilitate hypothesis-driven ecotoxicogenomic research and aid in mechanistic interpretation of results. This paper describes a novel graphical model of the teleost brain−pituitary−gonadal (BPG) axis designed for ecotoxicogenomics research on endocrine-disrupting chemicals using small fish models. The model incorporates six compartments representing the major organs involved in the fish reproductive axis and depicts the interactions of over 105 proteins and 40 simple molecules, transcriptional regulation of 25 genes, and over 300 different reactions/processes. Application of the model is illustrated in the context of a study examining effects of the competitive aromatase inhibitor, fadrozole, on gene expression in gonad, brain, and liver tissue of fathead Minnows. Changes in mRNA transcript abundance were measured using a fathead minnow oligonucleotide microarray and quantitative real-time polymerase chain reaction. Gene expression changes observed...
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characterization of responses to the antiandrogen flutamide in a short term reproduction assay with the fathead minnow
Aquatic Toxicology, 2004Co-Authors: Kathleen M Jensen, Brian C Butterworth, Michael D Kahl, Joseph J Korte, Elizabeth A Makynen, Richard L. Leino, Gerald T. AnkleyAbstract:Abstract A short-term reproduction assay with the fathead minnow (Pimephales promelas) has been developed to detect chemicals with the potential to disrupt reproductive endocrine function controlled by estrogen- and androgen-mediated pathways. The objective of this study was to use the assay to characterize responses of fathead minnow reproductive endocrinology and physiology to the mammalian antiandrogen, flutamide. Male and female fish were exposed to nominal (target) concentrations of 50 and 500 μg flutamide/l for 21-days, following which plasma steroid and vitellogenin concentrations were determined and gonadal morphology assessed. Fecundity of the fish was significantly reduced by exposure to a measured test concentration of 651 μg flutamide/l. In addition, embryo hatch was significantly reduced at this concentration. Qualitative histological assessment of ovaries from females exposed to flutamide indicated a decrease in mature oocytes and an increase in atretic follicles. Testes of males exposed to flutamide exhibited spermatocyte degeneration and necrosis. Concentration-dependent increases in plasma testosterone and vitellogenin concentrations were observed in the females. Flutamide also altered reproductive endocrinology of male fathead Minnows. Males exposed to 651 μg flutamide/l exhibited elevated concentrations of β-estradiol and vitellogenin. In summary, the results of this study with the fathead minnow demonstrate that flutamide affects reproductive endocrine function in fish and that the type of hormonal pattern and histopathology effects observed are consistent with an antiandrogenic mode-of-action. Consequently, our findings suggest that the 21-day reproduction assay utilizing fathead Minnows is a sensitive short-term screening method for the detection of endocrine-disrupting chemicals, including antiandrogens.
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mechanistic basis for estrogenic effects in fathead minnow pimephales promelas following exposure to the androgen 17α methyltestosterone conversion of 17α methyltestosterone to 17α methylestradiol
Aquatic Toxicology, 2003Co-Authors: Michael W. Hornung, Elizabeth J Durhan, Kathleen M Jensen, Michael D Kahl, Joseph J Korte, Jeffrey S Denny, Tala R Henry, Gerald T. AnkleyAbstract:Abstract Exposure of adult fathead Minnows (Pimephales promelas) to the androgen 17α-methyltestosterone (MT) produces both androgenic and estrogenic effects, manifested as nuptial tubercle formation in females, and vitellogenin production in males and females, respectively. The present study was conducted to determine if the unanticipated estrogenic effects are produced by conversion of MT via aromatase activity to 17α-methylestradiol (ME2). Aromatase activity at the end of a 7-day waterborne MT exposure (20, 200 μg/l) was significantly decreased in ovarian microsomes and brain homogenates from exposed fish, to about 30–50% of control activity. Although aromatase activity was decreased by 7 days, it is possible that the conversion of MT to ME2 occurred soon after initial exposure. In support of this, ME2 was detected in plasma samples of the fish following the 7-day exposure, confirming their ability convert the androgen MT to the estrogen ME2. The concentration of ME2 in plasma was within the range of plasma 17s-estradiol (E2) found in control female fathead Minnows (4–5 ng/ml). These results, in conjunction with competitive binding assays that indicate ME2 binds to the fathead minnow estrogen receptor with a relative binding affinity of 68.3% of E2, support the hypothesis that aromatization of MT to ME2 contributes to the estrogenic effects in fathead Minnows following exposure to this androgen.
John P Giesy - One of the best experts on this subject based on the ideXlab platform.
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effects of chemical fractions from an oil sands end pit lake on reproduction of fathead Minnows
Chemosphere, 2020Co-Authors: Garrett Morandi, Steve Wiseman, Chenxing Sun, Jonathan W Martin, John P GiesyAbstract:Oil sands process-affected water (OSPW) is a byproduct of bitumen extraction in the surface-mining oil sands industry in Alberta, Canada. Organic compounds in OSPW can be acutely or chronically toxic to aquatic organisms, so part of a long-term strategy for remediation of OSPW is ageing of water in artificial lakes, termed end-pit lakes. BaseMine Lake (BML) is the first oil sands end-pit lake, commissioned in 2012. At the time of its establishment, an effects-directed analysis of BML-OSPW showed that naphthenic acids and polar organic chemical species containing sulfur or nitrogen contributed to its acute lethality. However, the chronic toxicity of these same chemical fractions has not yet been investigated. In this work, the short-term fathead minnow reproductive bioassay was used to assess endocrine-system effects of two fractions of BML-OSPW collected in 2015. One of the fractions (F1) contained predominantly naphthenic acids, while the other (F2) contained non-acidic polar organic chemical species. Exposure of Minnows to F1 or F2 at concentrations equivalent to 25% (v/v) of the 2015 BML-OSPW sample (5-15% of the 2012 BML-OSPW sample) did not alter reproductive performance, fertilization success, or concentrations of sex steroids in female or male Minnows. Additionally, there were no significant differences in fertility, hatching success, or incidence of morphological indices of embryos collected on day 7 or 14 from exposed breeding trios. However, exposure of male fathead minnow to 25% (v/v) intact 2015 BML-OSPW resulted in a significantly greater hepatosomatic index. Exposure of fathead minnow to refined fractions of dissolved organic chemicals in 2015 BML-OSPW, or a 25% (v/v) of the intact mixture did not affect fertility or fecundity as measured by use of the 21-day reproductive bioassay. These data will be useful in setting future threshold criteria for OSPW reclamation and treatment.
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comparison of fathead minnow ovary explant and h295r cell based steroidogenesis assays for identifying endocrine active chemicals
Ecotoxicology and Environmental Safety, 2007Co-Authors: Daniel L Villeneuve, Lindsey S Blake, Katie J Greene, Eric Higley, Elizabeth A Makynen, Gerald T. Ankley, John L. Newsted, John P GiesyAbstract:An in vitro steroidogenesis assay using H295R human adenocarcinoma cells has been suggested as a possible alternative to gonad explant assays for use as a Tier I screening assay to detect endocrine active chemicals capable of modulating steroid hormone synthesis. This study is one of the first to investigate the utility of the H295R assay for predicting effects and/or understanding mechanisms of action across species and tissues. Six chemicals, including one selective aromatase inhibitor (fadrozole), four fungicides (fenarimol, ketoconazole, prochloraz, and vinclozolin), and one herbicide (prometon), were tested in both the H295R steroidogenesis assay, and an in vitro steroidogenesis assay using fathead minnow ovary explants. All six chemicals caused significant alterations in 17β-estradiol (E2) and/or testosterone (T) production in vitro. Effects of ketoconazole, prochloraz, and prometon were similar in both assays. However, there were differences in the profile of responses for T for fadrozole and fenarimol, and for T and E2 for vinclozolin. In terms of sensitivity, steroid production in the H295R assay was most sensitive for detecting the effects of fadrozole, fenarimol, and prochloraz, but was less sensitive than the fathead minnow ovary explant assay to the effects of ketoconazole and vinclozolin. The H295R assay was consistently less variable (among replicates) than the fathead minnow ovary explant assay. However, the ovary explant assay was more predictive of in vivo effects of the six chemicals on fathead Minnows than the H295R system. Further characterization of autoregulatory capacities, interaction of steroid-hormone receptor pathways with steroidogenesis, and metabolic capabilities of each system are needed for either system to provide clear and informative insights regarding a chemical's mechanism of action. Overall, however, results of this study suggest that both the H295R and fathead minnow ovary explant assays have utility for identifying endocrine-active chemicals in screening-type applications.
Michael D Kahl - One of the best experts on this subject based on the ideXlab platform.
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linkage of biochemical responses to population level effects a case study with vitellogenin in the fathead minnow pimephales promelas
Environmental Toxicology and Chemistry, 2007Co-Authors: David H Miller, Daniel L Villeneuve, Elizabeth J Durhan, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Gerald T. AnkleyAbstract:A challenge in the field of ecotoxicology is the linkage of alterations at molecular and biochemical levels of organization to adverse outcomes in individuals and populations. In the present study, a predictive relationship between plasma vitellogenin (VTG) concentration and fecundity in female fathead Minnows (Pimephales promelas) was derived from 21-d laboratory toxicity tests with five chemicals (17β-trenbolone, 17α-trenbolone, prochloraz, fenarimol, and fadrozole) that inhibit VTG production through different mechanisms. Because VTG is key to egg production in female oviparous animals, changes in the lipoprotein could, theoretically, serve as an indicator of reproductive success. Regression of fecundity versus VTG concentration from the various studies yielded a highly significant linear model (fecundity = −0.042 + 0.95-VTG, p < 0.01, r2 = 0.88). This relationship was integrated into a population model to translate changes in VTG concentrations of female fathead Minnows to alterations in population growth. The model predicted relatively profound effects on population size offish experiencing moderate decreases in vitellogenesis. For example, a fathead minnow population at a carrying capacity exposed to a chemical stressor that causes a 25% decrease in VTG concentration in females from baseline values would exhibit a 34.6% projected decrease in size after two years of exposure and reach an equilibrium population size that was only 30.2% of the preexposed population. Overall, the current study provides an example of how changes in a biomarker (VTG concentration) can be quantitatively translated into adverse effects at the individual and population levels.
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a graphical systems model to facilitate hypothesis driven ecotoxicogenomics research on the teleost brain pituitary gonadal axis
Environmental Science & Technology, 2007Co-Authors: Daniel L Villeneuve, Elizabeth J Durhan, Kathleen M Jensen, Michael D Kahl, Elizabeth A Makynen, Patrick Larkin, Iris Knoebl, Ann L Miracle, Barbara J Carter, Nancy D DenslowAbstract:Graphical systems models are powerful tools that can help facilitate hypothesis-driven ecotoxicogenomic research and aid in mechanistic interpretation of results. This paper describes a novel graphical model of the teleost brain−pituitary−gonadal (BPG) axis designed for ecotoxicogenomics research on endocrine-disrupting chemicals using small fish models. The model incorporates six compartments representing the major organs involved in the fish reproductive axis and depicts the interactions of over 105 proteins and 40 simple molecules, transcriptional regulation of 25 genes, and over 300 different reactions/processes. Application of the model is illustrated in the context of a study examining effects of the competitive aromatase inhibitor, fadrozole, on gene expression in gonad, brain, and liver tissue of fathead Minnows. Changes in mRNA transcript abundance were measured using a fathead minnow oligonucleotide microarray and quantitative real-time polymerase chain reaction. Gene expression changes observed...
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characterization of responses to the antiandrogen flutamide in a short term reproduction assay with the fathead minnow
Aquatic Toxicology, 2004Co-Authors: Kathleen M Jensen, Brian C Butterworth, Michael D Kahl, Joseph J Korte, Elizabeth A Makynen, Richard L. Leino, Gerald T. AnkleyAbstract:Abstract A short-term reproduction assay with the fathead minnow (Pimephales promelas) has been developed to detect chemicals with the potential to disrupt reproductive endocrine function controlled by estrogen- and androgen-mediated pathways. The objective of this study was to use the assay to characterize responses of fathead minnow reproductive endocrinology and physiology to the mammalian antiandrogen, flutamide. Male and female fish were exposed to nominal (target) concentrations of 50 and 500 μg flutamide/l for 21-days, following which plasma steroid and vitellogenin concentrations were determined and gonadal morphology assessed. Fecundity of the fish was significantly reduced by exposure to a measured test concentration of 651 μg flutamide/l. In addition, embryo hatch was significantly reduced at this concentration. Qualitative histological assessment of ovaries from females exposed to flutamide indicated a decrease in mature oocytes and an increase in atretic follicles. Testes of males exposed to flutamide exhibited spermatocyte degeneration and necrosis. Concentration-dependent increases in plasma testosterone and vitellogenin concentrations were observed in the females. Flutamide also altered reproductive endocrinology of male fathead Minnows. Males exposed to 651 μg flutamide/l exhibited elevated concentrations of β-estradiol and vitellogenin. In summary, the results of this study with the fathead minnow demonstrate that flutamide affects reproductive endocrine function in fish and that the type of hormonal pattern and histopathology effects observed are consistent with an antiandrogenic mode-of-action. Consequently, our findings suggest that the 21-day reproduction assay utilizing fathead Minnows is a sensitive short-term screening method for the detection of endocrine-disrupting chemicals, including antiandrogens.
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mechanistic basis for estrogenic effects in fathead minnow pimephales promelas following exposure to the androgen 17α methyltestosterone conversion of 17α methyltestosterone to 17α methylestradiol
Aquatic Toxicology, 2003Co-Authors: Michael W. Hornung, Elizabeth J Durhan, Kathleen M Jensen, Michael D Kahl, Joseph J Korte, Jeffrey S Denny, Tala R Henry, Gerald T. AnkleyAbstract:Abstract Exposure of adult fathead Minnows (Pimephales promelas) to the androgen 17α-methyltestosterone (MT) produces both androgenic and estrogenic effects, manifested as nuptial tubercle formation in females, and vitellogenin production in males and females, respectively. The present study was conducted to determine if the unanticipated estrogenic effects are produced by conversion of MT via aromatase activity to 17α-methylestradiol (ME2). Aromatase activity at the end of a 7-day waterborne MT exposure (20, 200 μg/l) was significantly decreased in ovarian microsomes and brain homogenates from exposed fish, to about 30–50% of control activity. Although aromatase activity was decreased by 7 days, it is possible that the conversion of MT to ME2 occurred soon after initial exposure. In support of this, ME2 was detected in plasma samples of the fish following the 7-day exposure, confirming their ability convert the androgen MT to the estrogen ME2. The concentration of ME2 in plasma was within the range of plasma 17s-estradiol (E2) found in control female fathead Minnows (4–5 ng/ml). These results, in conjunction with competitive binding assays that indicate ME2 binds to the fathead minnow estrogen receptor with a relative binding affinity of 68.3% of E2, support the hypothesis that aromatization of MT to ME2 contributes to the estrogenic effects in fathead Minnows following exposure to this androgen.
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evaluation of the aromatase inhibitor fadrozole in a short term reproduction assay with the fathead minnow pimephales promelas
Toxicological Sciences, 2002Co-Authors: Gerald T. Ankley, Michael W. Hornung, Kathleen M Jensen, Michael D Kahl, Joseph J Korte, Elizabeth A Makynen, Richard L. LeinoAbstract:Cytochrome P450 aromatase (CYP19) is a key enzyme in vertebrate steroidogenesis, catalyzing the conversion of C19 androgens to C18 estrogens such as b-estradiol (E2). The objective of this study was to assess effects of the CYP19 inhibitor fadrozole on fathead minnow (Pimephales promelas) reproductive endocrinology and physiology in a short-term reproduction assay proposed for identifying specific classes of endocrine-disrupting chemicals. A concentration-dependent reduction in fecundity was observed in fish exposed for 21 days to water concentrations of fadrozole ranging from 2 to 50 mg/l. Consistent with the expected mechanism of action, there was a significant inhibition of brain aromatase activity in both male and female fathead Minnows exposed to fadrozole. In females, this inhibition was accompanied by a concentration-dependent decrease in plasma E2 and vitellogenin concentrations; the latter observation is consistent with the fact that activation of the estrogen receptor by E2 initiates hepatic vitellogenin production in oviparous vertebrates. Histological assessment of ovaries from females exposed to fadrozole indicated a decrease in mature oocytes and an increase in preovulatory atretic follicles. Exposure of male fathead Minnows to fadrozole significantly increased plasma concentrations of the androgens testosterone (T) and 11-ketotestosterone (KT) and resulted in a marked accumulation of sperm in the testes. Results of this study indicate that the proposed fathead minnow assay should effectively identify test chemicals as potential aromatase inhibitors, both in the context of their reproductive toxicity and the specific mechanism of action. These results also should be of utility in assessing the potential ecological risk of CYP19 inhibitors, in particular in the context of relating alterations in subcellular indicators of endocrine function (changes in steroids, proteins) to adverse consequences in the whole organism.