No abstract

No abstract

Effects of two model imidazole-type fungicides, prochloraz (PCZ) and ketoconazole (KTC), on the hypothalamic-pituitary-gonadal (HPG) axis of the Japanese medaka (Oryzias latipe) [corrected] were examined by use of real time PCR (RT-PCR) array. Fourteen-week-old Japanese medaka were exposed for seven days to concentrations of PCZ or KTC from 3.0 to 300 microg/L Exposure [corrected] to KTC or PCZ caused significant reduction of fecundity of Japanese medaka and down-regulated expression of estrogen receptor (ER)-alpha and egg precursors in livers of males and females. However, PCZ was more potent than KTC both in modulating transcription and causing lesser fecundity. Exposure to nominal 30 microg PCZ/L resulted in 50% less fecundity and significant down-regulation of vitellogenin II expression, but KTC did not cause such effects at this concentration. Exposure to PCZ caused a compensatory upregulation in cytochrome P450 c17alphahydroxylase, 17,20-lyase (CYP17) and aromatase (CYP19) expression in the ovary, while KTC did not. Furthermore, the ecologically relevant end point, fecundity was log-log related to mRNA level of six genes in livers of females.

No abstract

Populations of sturgeon (Acipenseridae) are declining in many places in the world because of several potential factors, including overharvesting, habitat alteration, and pollution. In North America, populations of the white sturgeon (Acipenser transmontanus) have been experiencing poor annual recruitment in major river systems for more than three decades. Metal pollution has been hypothesized as a potential contributing factor to the poor recruitment in some of the water bodies. In general, little is known about the toxicity of metals such as Cu, Cd, and Zn to white sturgeon and their potential influence on survival of embryos and juveniles. The present study was conducted to establish baseline toxicity data for the subchronic exposure of early life stages of white sturgeon to Cu, Cd, and Zn that can be used in metal-related risk assessments. Embryos, larvae, and fry were exposed to increasing concentrations of dissolved Cu, Cd, or Zn for 66 d using laboratory-based flow-through exposure systems. Hatching success was greater than 79% for all controls, and no significant differences were observed among treatment groups or between treatments and controls. Chronic lethal concentrations at which 20% mortality occurred (LC20s) for Cd (1.5 µg/L), Cu (5.5 µg/L), and Zn (112 µg/L) obtained for white sturgeon in the present study were comparable to those of sensitive salmonid species. Based on LC20 values for 19 or 58 d posthatch white sturgeon, the United States national ambient water quality criteria and the Canadian water quality guidelines for the protection of aquatic life that have been established for Cd, Cu, and Zn protect white sturgeon early life stages.

Abstract-Both the anabolic androgen 17␤-trenbolone (TRB) and the aromatase inhibitor fadrozole (FAD) can cause decreased plasma concentrations of estrogen (E2) and reduce fecundity of fish. However, the underlying mechanisms and the molecular pathways involved are largely unknown. The present study was designed to assess time-dependent effects of FAD and TRB on the transcriptional responses of the hypothalamic-pituitary-gonadal (HPG) axis of Japanese medaka (Oryzias latipes). Fourteen-weekold Japanese medaka were exposed to 50 g FAD/L or 2 g TRB/L in a 7-d static renewal test, and the expression profiles of 36 HPG axis genes were measured by means of a medaka HPG real-time reverse-transcription polymerase chain reaction array after 8 h, 32 h, or 7 d of exposure. Exposure to TRB or FAD caused lesser fecundity of Japanese medaka and down-regulated transcription of vitellogenin and choriogenin (CHG) gene expression in the liver of females. Exposure to FAD for 8 h resulted in an 8-fold and 71-fold down-regulation of expression of estrogen receptor ␣ and choriogenin L (CHG L), respectively, in female liver. 17␤-Trenbolone caused similar down-regulation of these genes, but the effects were not observed until 32 h of exposure. These results support the hypothesis that FAD reduces plasma E2 more quickly by inhibiting aromatase enzyme activity than does TRB, which inhibits the production of the E2 precursor testosterone. Exposure to FAD and TRB resulted in rapid (after 8 h) down-regulation of luteinizing hormone receptor and low-density-lipoprotein receptor in the testis to compensate for excessive androgen levels. Overall, the molecular responses observed in the present study differentiate the mechanisms of the reduced fecundity by TRB and FAD.

No abstract

No abstract