Project description:Metformin, along with its biotransformation product guanylurea, are commonly observed in municipal wastewaters and subsequent surface waters. Previous studies in fish have identified metformin as a potential endocrine active compound but there are inconsistencies in the literature with regard to effects. To further investigate the potential reproductive toxicity of metformin and guanylurea to fish, a series of experiments were performed with reproductively mature fathead minnows (Pimephales promelas). First, explants of mature fathead minnow ovary tissue were exposed to 0.001-100 µM metformin or guanylurea to investigate whether they can directly perturb steroidogenesis. Second, spawning pairs of fathead minnows were exposed to metformin (0.41, 4.1, 41 µg/L) or guanylurea (1.0, 10, 100 µg/L) for 23 d to assess impacts on reproduction. Lastly, male fathead minnows were exposed to 41 µg/L metformin, 100 µg/L guanylurea, or a mixture of both compounds, with samples collected over a 96 h time course to investigate potential impacts to the hepatic transcriptome or metabolome. Neither metformin or guanylurea effected estradiol or testosterone by ovary tissue exposed in vitro. In the 23 d exposure, neither compound significantly impacted transcription of endocrine-related genes in male liver or gonad, circulating steroid concentrations in male or female fish, or fecundity of spawning pairs. In the 96 h time course, 100 µg guanylurea/L elicited more differential gene expression than 41 µg metformin/L , and showed the greatest impacts after 96 h. A number of DEGs up-regulated after 24 h were subsequently down-regulated after 96 h, demonstrating time-dependent impacts of guanylurea on the liver. Overall, metformin and guanylurea did not elicit effects consistent with reproductive toxicity in adult fathead minnows at environmentally relevant concentrations. Where effects were identified using ‘omics approaches, guanylurea induced greater impacts than metformin.
Project description:We investigated the impacts of wastewater effluent exposure on gene expression in adult fathead minnows, a freshwater fish commonly used as an ecotoxicological model.
Project description:Global hepatic gene expression patterns associated with reproductive success of fathead minnows and environmental variables in streams across varying landscapes
Project description:We evaluated the possible mechanisms by which exposure to a sequentially treated pulp and paper mill effluent affects gene expression in the liver of male and female fathead minnows. Sexually mature fathead minnows were exposed to either river water, which served as our control (C), 10% untreated kraft effluent (UTK), 25% treated kraft effluent (TK) or 100% final effluent (CMO) from a multiprocess pulp and paper mill for 6 days. A total of 4 treatments. Each exposure aquarium consisted of a 42.1 L column that contained individual 5.3 L chambers. Each chamber contained a FHM breeding pair. A total of 3 biological replicates for male and female FHM per treatment were sent for microarray analysis resulting in a total of 24 arrays run as a reference design with a pooled sample of the 6 river water exposed fish serving as the reference sample..
Project description:Propranolol is a beta-adrenergic receptor antagonist (β-blocker) that has been detected in United States wastewater effluents at concentrations ranging from 0.026 to 1.90 µg/l. In mammals, there is evidence that β-blockers can cause sexual dysfunction, and alter serotonergic pathways which may impact reproductive behavior but little is known about the effects on fish behavior. The present study tested the effects of propranolol on fecundity and on reproductive behavior of the fathead minnow, Pimephales promelas, a fish that exhibits male parental care. Sexually mature fathead minnows were housed at a ratio of one male and two females per tank and exposed to nominal concentrations of 0, 0.1, 1, 10 µg/l for 21 days. Measured concentrations (±SD) of propranolol were 0.05±0.02, 0.88±0.34 and 4.11±1.19 µg/l. There were no statistically significant differences in fecundity, fertilization rate, hatchability and time to hatch. Propranolol exposure was not associated with a change in nest rubbing behavior, time spent in the nest or approaching the females. There was a significant difference in the number of visits to the nest with males receiving low and medium propranolol treatments. The microarray analysis showed that there were 335 genes up-regulated and 400 genes down-regulated in the brain after exposure to the highest dose of propranolol. Among those genes, myoglobin and calsequestrin transcripts (fold change=10.84 and 5.49, respectively) were highly up-regulated. Ontological analyses indicated changes in genes involved in calcium ion transport, transcription, proteolysis and apoptosis/anti-apoptosis. The results showed that exposure to propranolol at concentrations as high as 4.11 µg/l did not significantly impact reproductive behavior or spawning abilities of fathead minnow but did alter the regulation of genes within the brain of fish. Effects of propanolol exposure were investigated in the brain of adult male fathead minnow exposed to 10 µg/L of propanolol or a solvent control solution (0.01% ethanol). For each treatment, the brain of four different fish were analyzed.
Project description:We evaluated the possible mechanisms by which exposure to a sequentially treated pulp and paper mill effluent affects gene expression in the liver of male and female fathead minnows.