Polychlorinated biphenyls (PCBs) have been reported to adversely affect reproduction in laboratory and wild animals. The present study was undertaken to determine the toxic potential of Aroclor-1254 (A-1254) on in vitro fertilizing ability of oocytes and epididymal sperm and on preimplantation embryo development in the mouse. A-1254 was added to the IVF medium at concentrations of 0.01, 0.1, 1.0, and 10.0 micrograms/mL. Cumulus masses containing the oocytes were obtained from superovulated B6D2F1 mice and were placed in the culture medium containing A-1254 to which epididymal sperm, capacitated in a medium without A-1254, were added. The IVF rate was assessed 20 to 24 h after insemination. A-1254 significantly reduced the mean percent ova fertilized even at 0.1 microgram/mL. Incubation of the cumulus masses in various concentrations of A-1254 for 6 h, followed by insemination with sperm capacitated in the presence of A-1254, also significantly reduced the IVF rate. Capacitation of sperm in A-1254-containing medium, followed by coculture with untreated oocytes, failed to affect the IVF rate. No significant effect on sperm motility was observed following exposure to 1 and 10 micrograms/mL of A-1254. Estradiol-17 beta also reduced the IVF rate, however, the effect of A-1254 was more severe compared to the estradiol treatment. Furthermore, addition of A-1254 to the embryo culture medium was associated with a significant decrease in embryo growth at 48 h and 96 h. These results demonstrate adverse effects of A-1254 on oocytes, IVF, and embryonic development in the mouse.

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Effects of polychlorinated biphenyls (PCBs) on in vitro fertilization in the mouse.

Polychlorinated biphenyls (PCBs) are industrial chemicals that are long-lasting global environmental contaminants. PCBs have been reported to adversely affect reproduction in laboratory and wild animals by reducing the incidence of breeding and the survival rate of young. The present study was undertaken to determine the toxic potential of PCBs on in vitro fertilization (IVF) in the mouse. Aroclor 1221, 1254, and 1268, and 3, 3', 4, 4'-tetrachlorobiphenyl (TCB), a PCB congener, were added to IVF medium at various concentrations (0.01, 0.1, 1, and 10 micrograms/mL). Cumulus masses containing oocytes were obtained from superovulated B6D2F1 mice and cultured in medium containing PCB to which capacitated sperm were added. Oocytes were assessed for fertilization 20 to 24 h after insemination. A-1221, A-1268, and TCB reduced the fertilization rate at the 1 microgram/mL and 10 micrograms/mL doses, while inhibition of fertilization by A-1254 reached significance at 0.1 microgram/ml. Furthermore, all of these chemicals caused an increased incidence of degenerative ova and abnormal 2-cell embryos at the higher dose levels (1 microgram/mL and 10 micrograms/mL). The results suggest that higher dosages of PCB and TCB adversely affect fertilization and cause an increased incidence of degeneration of oocytes and abnormality in the early mouse embryos.

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Intrauterine device-induced embryonic mortality in rabbits.

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Effects of a DNA-specific fluorochrome, Hoechst 33258, on mouse sperm motility and fertilizing capacity.

DNA specific fluorochrome (Hoechst 33342 and 33258) as non-toxic stains, have been widely used to measure cell density and proliferation, detect sperm-egg fusion, and observe the development of pre-implantation embryos. It has been reported that Hoechst 33342 at a concentration of 10 micrograms ml-1 had significant inhibition on embryo cleavage. In this study, we incubated B6D2F1 mouse sperm and eggs with different concentrations of Hoechst 33258, 0, 1.0, 10.0, 20.0, 100 micrograms ml-1. We found that: (1) 100 micrograms ml-1 of H-33258 significantly decreased the sperm motility at 90 min and 4 h. (P less than 0.05), (2) 20 micrograms ml-1 and 100 micrograms ml-1 of Hoechst 33258 significantly inhibited mouse fertilization in vitro (P less than 0.05), and (3) 1.0 micrograms ml-1 and 10.0 micrograms ml-1 Hoechst 33258 had no effect on fertilization rate. But when we pre-incubated sperm at 10 micrograms ml-1 Hoechst 33258 for 90 min, and inseminated oocytes in the medium with same concentration of Hoechst 33258, the embryo cleavage was significantly inhibited.

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