The Sheep Ovary: Regulation of Steroidogenic, Haemodynamic and Structural Changes in the Largest Follicle and Adjacent Tissue Before Ovulation

Effects of steroids on mouse oocyte maturation in vitro

“…The culture methods described were chosen to examine efficiently the effect of a single variable (one concentration of a specific steroid) on the process of nuclear maturation. No (Hay & Moor, 1973;Moor, Hay & Seamark, 1975;Hillensjö, Bauminger & Ahren, 1976;Eiler & Nalbandov, 1977) or fall to low or immeasurable levels after an initial increase (YoungLai, 1972;Mills & Savard, 1973;Patwardhan & Lanthier, 1976;Szohys, 1976;Bahr, 1978;Lau, Saksena & Chang, 1978). It is possible that in animals which show decreasing concentrations of follicular fluid steroids after mating or LH stimulation, oocytes might be stimulated to resume meiosis by exposure to follicular fluid depleted of these hormones.…”

“…In some species the secretion of progestagens increases late in the preovulatory period after the concentrations of other steroids have declined in follicles exposed to LH in vitro or in vivo (Hay & Moor, 1973;Moor et al, 1975;Hillensjö et al, 1976;McNatty, 1978). In contrast, progestagens in follicular fluid decrease as the concentrations of androgens and oestrogens decline in the pig (Eiler & Nalbandov, 1977) and rabbit (YoungLai, 1972;Patwardhan & Lanthier, 1976;Bahr, 1978), decrease during the preovulatory period in dissected intact rat (Szoftys, 1976) and rabbit (Mills & Savard, 1973) follicles, and decrease as androgens and oestrogens decline in whole hamster ovaries (Saidapur & Greenwald, 1978) on the day of pro-oestrus.…”

Distribution of 5-3 -Hydroxysteroid Dehydrogenase Activity in the Graafian Follicle of the Sheep

“…Acquisition of enzyme activity by the membrana granulosa, however, may well be dependent on the occurrence ofmarked structural changes within this layer of cells. These changes, which include dissociation of indi¬ vidual granulosa cells and breakdown of the basal lamina, occur both in the normal cycle about 12 hr after the preovulatory LH peak and in vitro within 24 hr of the addition of LH to the culture medium (Moor, Hay & Seamark, 1975).…”

Presence of follicular fluid in the porcine oviduct and its contribution to the acrosome reaction

“…Such an increase in progesterone may, however, not be characteristic of aIl species (eg. sheep) (Wheeler et al, 1975;Moor et al, 1975;McNatty, 1978).…”