Bioscientifica Proceedings

The corpus luteum is a transient gland, which is only functional for 17–18 days in the cyclic cow or for up to 200 days in the pregnant cow. Regression of the corpus luteum is essential for normal cyclicity as it allows the development of a new ovulatory follicle, whereas prevention of luteolysis is necessary for the maintenance of pregnancy. Evidence acquired over the past three decades indicated that PGF2α is the luteolytic hormone in ruminants. Neverthe...

Abstract unavailableKeywords: progesterone; protein kinase C; intracellular calcium; prostaglandins; arachidonic acid; luteal cells; cattle© 1991 Journals of Reproduction & Fertility Ltd...

Summary. Primary cultures of ovine epithelial and stromal cells have been used to examine paracrine interactions between the endometrium and the preimplantation sheep blastocyst, and in particular the actions of the blastocyst α-interferon, ovine trophoblast protein-1 (oTP-1), on endometrial cell metabolism. The synthesis and secretion of several ‘pregnancy-related’ acidic proteins with molecular weights in the range 70 000–120 000 can be i...

Placental growth during early and mid-pregnancy has a powerful, constraining influence on fetal growth during late pregnancy. Studies involving surgical and environmental reduction of placental size in sheep have shown an associated reduction in capacity to transport oxygen, glucose and amino acids. Oxygen transport is limited by placental blood flow but transport of glucose and amino acids is determined by the abundance and activity of specific transport proteins. Glucose tra...

Exposure of Ihe sheep fetus to testosterone from day 30 to day 90 of a 147 day gestation causes the neurones that control GnRH secretion, the GnRH neuronal network, to become organized in a sex-specific manner. After androgen exposure in utero, GnRH neurones are activated in a sexually differentiated pattern by gonadal steroid hormones. Specifically, follicular phase concentrations of oestrogen trigger a GnRH 'surge' in ewes, but not in rams or females treated...