RESPONSES OF OOCYTES AND EMBRYOS TO THE CULTURE ENVIRONMENT

Embryo development is strongly influenced by events occuring during oo cyte maturation. Although many immature oocytes are capable of complet ing meiosis in vitro, only a small percentage of the original pool of immature oocytes is competent to continue development to the blastocys t stage and subsequently result in a pregnancy. This indicates that ma turation of oocytes in vitro may not be occuring in an entirely normal manner. Cytoplasmic changes occuring during maturation, collectively termed cytoplasmic maturation, are essential for embryonic development . The cytoplasm of the oocyte may play a crucial role in assembling th e correct metabolic machinery for production of sufficient energy for cellular functions during maturation, cleavage and blastocyst formatio n. A better understanding of the structural, functional and metabolic characteristics of the oocyte during maturation, and the consequence o f changes in these parameters on developmental competence is needed. U nderstanding the role of cytoplasmic changes during oocyte maturation will help increase the efficiency of in vitro embryo production. Bette r embryo production strategies will facilitate basic research into the control of early development, improve implementation in endangered sp ecies, provide a source of high quality oocytes for nuclear transfer a nd transgenic technologies and benefit the commercial embryo transfer industry. (C) 1998 by Elsevier Science Inc.