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Oocyte Atresia (oocyte + atresia)
Selected AbstractsEffects of the estrogen agonist 17,-estradiol and antagonist tamoxifen in a partial life-cycle assay with zebrafish (Danio rerio)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2007Leo T. M. van der Ven Abstract A partial life-cycle assay (PLC) with zebrafish (Danio rerio) was conducted to identify endocrine-disrupting effects of 17,-estradiol (E2) and tamoxifen (TMX) as reference for estrogen agonist and antagonist activity. Adult zebrafish were exposed for 21 d and offspring for another 42 d, allowing differentiation of gonads in control animals. The assessed end points included reproductive variables (egg production, fertilization, and hatching), gonad differentiation of juveniles, histopathology, and vitellogenin (VTG) expression. With E2, the most sensitive end points were feminization of offspring (at 0.1 nM) and increased VTG production in males (at 0.32 nM). At 1 nM, decreased F1 survival, increased F1 body length and weight, VTG-related edema and kidney lesions, and inhibited spermatogenesis were observed. Oocyte atresia occurred at even higher concentrations. Exposure to TMX resulted in specific effects at an intermediate test concentration (87 nM), including oocyte atresia with granulosa cell transformation and disturbed spermatogenesis (asynchrony within cysts). In F1, decreased hatching, survival, and body weight and length as well as decreased feminization were observed. Decreased vitellogenesis and egg production in females and clustering of Leydig cells in males occurred at higher concentrations. Toxicological profiles of estrogen agonists and antagonists are complex and specific; a valid and refined characterization of endocrine activity of field samples therefore can be obtained only by using a varied set of end points, including histology, as applied in the presented PLC. Evaluation of only a single end point can easily produce under- or overestimation of the actual hazard. [source] The effects of thermal effluent exposure on the gametogenesis of female fishJOURNAL OF FISH BIOLOGY, Issue 1 2000D. Luk High temperature in Swedish and Lithuanian thermal effluent areas influenced gametogenesis of female perch Perca fluviatilis, roach Rutilus rutilus and pike Esox lucius negatively, indicating reduced reproductive capacity. Oocyte atresia started during vitellogenesis in autumn, and was often followed by asynchronous egg cell development. Among other anomalies, multi-nucleus oocytes and hermaphroditism were observed. No significant impact was seen in silver bream Blicca bjoerkna. Ruffe Gymnocephalus cernuus reacted by a tendency to produce an additional mature oocyte generation during the spawning period. Ovaries in roach from coastal areas were often infected by a microsporidian parasite Pleistophora mirandellae, causing severe damage to the gonad. Parasites were also detected in pike, but neither in perch nor in lake populations of roach. Fish living in open coastal environments did not avoid impact by moving out of the heated areas. There seems to be a conflict in some temperate fish between temperature preference behaviour and safeguarding normal reproduction. [source] Effects of the estrogen agonist 17,-estradiol and antagonist tamoxifen in a partial life-cycle assay with zebrafish (Danio rerio)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2007Leo T. M. van der Ven Abstract A partial life-cycle assay (PLC) with zebrafish (Danio rerio) was conducted to identify endocrine-disrupting effects of 17,-estradiol (E2) and tamoxifen (TMX) as reference for estrogen agonist and antagonist activity. Adult zebrafish were exposed for 21 d and offspring for another 42 d, allowing differentiation of gonads in control animals. The assessed end points included reproductive variables (egg production, fertilization, and hatching), gonad differentiation of juveniles, histopathology, and vitellogenin (VTG) expression. With E2, the most sensitive end points were feminization of offspring (at 0.1 nM) and increased VTG production in males (at 0.32 nM). At 1 nM, decreased F1 survival, increased F1 body length and weight, VTG-related edema and kidney lesions, and inhibited spermatogenesis were observed. Oocyte atresia occurred at even higher concentrations. Exposure to TMX resulted in specific effects at an intermediate test concentration (87 nM), including oocyte atresia with granulosa cell transformation and disturbed spermatogenesis (asynchrony within cysts). In F1, decreased hatching, survival, and body weight and length as well as decreased feminization were observed. Decreased vitellogenesis and egg production in females and clustering of Leydig cells in males occurred at higher concentrations. Toxicological profiles of estrogen agonists and antagonists are complex and specific; a valid and refined characterization of endocrine activity of field samples therefore can be obtained only by using a varied set of end points, including histology, as applied in the presented PLC. Evaluation of only a single end point can easily produce under- or overestimation of the actual hazard. [source] Gonadal differentiation in frogs exposed to estrogenic and antiestrogenic compoundsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2003Constanze A. Mackenzie Abstract Exposure of amphibians to endocrine disrupting compounds (EDCs) may alter differentiationof gonads, especially when exposures begin during early life stages. Gonadal differentiation was observed in leopard frogs (Rana pipiens) and wood frogs (Rana sylvatica) exposed as tadpoles to estrogenic (estradiol, ethinylestradiol, nonylphenol) and antiestrogenic compounds (an aromatase inhibitor, flavone, and an antiestrogen, ICI 182780). Exposure to all compounds at ,g/L concentrations altered gonadal differentiation in some animals by inducing either complete feminization or an intersex condition, and altered testicular tubule morphology, increased germ cell maturation (vitellogenesis), and oocyte atresia. Comparisons between the two species indicate that R. pipiens are more susceptible to sex reversal and development of intersex gonads. However, R. sylvatica also showed alterations to testicular morphology, germ cell maturation, and ooctye atresia. These laboratory results indicate that amphibians could be susceptible to altered gonadal differentiation and development when exposed to estrogenic and antiestrogenic compounds in aquatic environments, such as those impacted by agricultural, industrial, and municipal runoff. [source] Thyroglobulin type-1 domain protease inhibitors exhibit specific expression in the cortical ooplasm of vitellogenic rainbow trout oocytesMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 2 2004Antony W. Wood Abstract The synthesis, uptake, and processing of yolk proteins remain poorly described aspects of oviparous reproductive development. In this study, we report the identification and characterization of two protease inhibitors in rainbow trout ovary whose expression and distribution are directly associated with yolk protein uptake in vitellogenic oocytes. The first transcript, termed "oocyte protease inhibitor-1" (OPI-1), is predicted to encode a 9.1 kDa, 87 amino acid protein containing a single thyroglobulin type-1 (TY) domain, identifying it as a putative TY domain inhibitor. The second transcript, termed OPI-2, is predicted to encode an 18.3 kDa, 173 amino acid protein with two similar, but not identical, TY domains. Messenger RNA expression of both genes was first detected in ovarian tissues at the onset of vitellogenesis, and persisted throughout the vitellogenic growth phase. We did not detect expression of either gene in previtellogenic ovaries, nor in any somatic tissues examined. Expression of OPI-1 mRNA was significantly reduced in atretic follicles as compared to healthy vitellogenic follicles, suggesting a downregulation of inhibitor expression during oocyte atresia. Western immunoblot analyses of whole yolk from vitellogenic oocytes revealed the presence of two immunoreactive proteins that corresponded to the predicted sizes of OPI-1 and OPI-2. We detected strong crossreactivity of this antiserum with specific vesicles in the cortical ooplasm of vitellogenic oocytes, in regions directly associated with vitellogenin processing. The identification of OPI-1 and OPI-2 provides new evidence for the expression of multiple TY domain protease inhibitors likely involved in the regulation of yolk processing during oocyte growth in salmonids. Mol. Reprod. Dev. 69: 205,214, 2004. © 2004 Wiley-Liss, Inc. [source] | ||||||||||