Experimental Approaches to the Preimplantation Ova with Emphasis on Cytoplasmic Factors, Cell Cycle and Intercellular Connections

Abstract

Eight years have already passed since the first success of a test tube baby by Edwards and Steptoe in 1978. During this period a lot of laboratories have been involved in in vitro fertilization and embryo transfer (IVF-ET). Through their efforts to improve this procedure the present success rate of IVF-ET is about 20% per treatment cycle, which is considered similar to the pregnancy rate of healthy couples per cycle (Jones et al. 1983). However, the actual success rate of IVF-ET per recovered oocytes remains low, because usually two to four oocytes are recovered and used for one cycle of IVF-ET. In order to increase the pregnancy rate of the IVF-ET program, it is important to assess the basic problems of preimplantation ova. In 1959 Chang reported the first success of IVF-ET in the rabbit at the Worcester Foundation. Therefore it took almost 20 years before an animal experiment was applied to the clinical practice in human infertility, although the technical procedure for the manipulation of the rabbit ova was basically the same as for human ova. Recently detailed findings on oocyte maturation, fertilization, and early development have been reported on the basis of new techniques in the manipulation and microanalysis of ova at the cellular level (Suzuki et al. 1983. 1984; Palmiter et al. 1982). Basic physiology of ova during the preimplantation stage, as well as the procedure for artificial manipulation of ova, is now understood better than before.