ULTRASTRUCTURAL COMPARISON OF BOVINE BLASTOCYSTS DEVELOPED IN VIVO AND IN VITRO

The ultrastructures of in vitro-derived bovine blastocysts have been compared with those of blastocysts obtained from a superovulated cow. In vivo blastocysts obtained from the uterus showed well-differentiated features, while in vitro-derived embryos, which were developed from in vitro fertilized ovum, showed insufficient cellular organizations. In vitro-derived embryos contained many undefined cellular organizations in the perivitelline spaces compared with in vivo-derived blastocysts. Other features of in vivo and in vitro blastocysts were characterized by differential development of microvilli projection into blastocoele from the surface of the trophoblast cells. The conceivable reason for the difference between in vivo and in vitro developments of bovine embryos is that it is likely that in vitro culture system adopted in the present experiment may not be sufficient for better embryonic development.