Hormonal and follicular factors affecting maturation of sheep oocytes in vitro and their subsequent developmental capacity

Abstract

Oocytes removed from, or retained within, non-atretic and atretic follicles of different sizes were cultured for 24 h in the presence of a variety of hormones in an attempt to identify the factors affecting oocyte maturation in vitro. Resumption of meiosis was assessed morphologically; the developmental capacity of oocytes after culture was determined by transfer to the oviducts of inseminated ewes. About 70% of oocytes cultured after removal from follicles of different sizes resumed meiosis in vitro, but they did not undergo normal development after transplantation. Oocytes cultured within the follicle in hormone-free medium remained at the germinal vesicle stage. In the presence of FSH and LH some oocytes reached the second meiotic metaphase: 19% in small (2-3 mm diam.) and 73% in larger (3-5 mm diam.) non-atretic follicles, and 54% in small and 45% in larger atretic follicles. Less than 5% of oocytes cultured in follicles developed into normal blastocysts after transplantation when either no hormone or only FSH and LH were added to the culture medium. The addition of oestradiol-17beta to medium containing FSH (2 mug/ml) and LH (1 mug/ml) resulted in the development to blastocysts of 26% of oocytes from small non-atretic follicles, 46% from large non-atretic follicles and 50% from atretic follicles. Blastocyst formation was greatly depressed and fragmentation rate signinificantly increased with concentrations of 10 mugFSH/ml and 2 mug LH/ml. Developmental capacity after culture was further demonstrated by the birth of lambs from 63% of blastocysts derived from oocytes matured in vitro; 52% of control blastocysts developed to lambs after transfer.

Oxygen consumption by rat oocytes and cumulus cells during induced atresia

“…This would permit resumption of oocyte meiosis in a manner similar to normal maturation until the degenerative process affects the oocyte as well. That oocyte maturation during atresia is similar to normal maturation is suggested not only by the present findings on oocyte respiration, but also by the finding that maturing oocytes isolated from atretic follicles can be fertilized (sheep: Moor & Trounson, 1977;rat: R. H. Braw, unpublished).…”

Development of bovine embryos in vitro following oocyte maturation under defined conditions

“…Un total de 4 615 ovocytes a été utilisé dans une série d'expériences destinées à évaluer l'effet respectif des différents composants du milieu de maturation in vitro (MIV) sur l'acquisition par les ovocytes bovins de leur compétence à se développer in vitro après fécondation (compétence cytoplasmique). Les (Moor and Trounson, 1977;Zhang and Armstrong, 1989); 2) the presence of serum in the IVM medium (Downs etal, 1986); and 3) the association of follicular or cumulus cells (ie somatic factors) with the maturing oocyte (Vanderhyden and Armstrong, 1989 (Staigmiller and Moor, 1984;Critser et al, 1986;Lu and Gordon, 1987;Lutterbach et al, 1987;Faundez et al, 1988;Chikamatsu et al, 1989 It has been shown that cumulus expansion is not necessary to achieve normal nuclear configurations during IVM (Sirard et al, 1988 (Jinno et al, 1989;Downs et al, 1991 ), rat (Shalgi et al, 1979;Vanderhyden and Armstrong, 1990), rabbit (Yoshimura et al, 1989), goat (Younis et al, 1991 sheep (Moor and Trounson, 1977;Staigmiller and Moor, 1984), and cow (Fukushima and Fukui, 1985;Brackett et al, 1989;Zuelke and Brackett, 1990). However, other authors have reported no effect of exogenous hormones (Fukui and Ono, 1989;Keefer et al, 1993).…”

Mammalian oocyte maturation

“…ln vitro matured cumulus enclosed bovine oocytes behave similarly (Thibault, G6rard andMdn6zo, 1975, 1976). Even when a male pronucleus develops after fertilization, regular cleavage seldom occurs (ovine, Moor and Trounson, 1977 ;bovine, Trounson et aL, 1977 ;.…”