Bioscientifica Proceedings

Collagen breakdown and apoptotic cell death within the apex of the preovulatory ovine follicle are hallmarks of impending ovarian rupture. An integrative mechanism is proposed whereby gonadotrophic stimulation of urokinase-type plasminogen activator secretion by the follicular-contiguous ovarian surface epithelium elicits a localized increase in tissue plasmin, which activates collagenolysis and tumour necrosis factor α-induced cell death within the formative ovulatory st...

The ovulatory process is extraordinary in that it constitutes a hormone- induced injury. Gonadotropin delivered via the follicular vascular wreath stimulates secretion of plasminogen activator by contiguous ovarian surface epithelial cells. A consequent elevation in interstitial plasmin activates collagenases and cleaves tumor necrosis factor α from its anchors on endothelium. Collagen fibril degradation and cellular death at the apex of the preovulatory follicle are hall...

The pituitary response in cattle to treatment with GnRH agonist has two phases. In the acute phase secretion of LH is increased, while the chronic phase is characterized by a downregulation of GnRH receptors and insensitivity of gonadotrophs to natural sequence GnRH. After long-term treatment with GnRH agonist, cattle do not have pulsatile secretion of LH but maintain basal LH. This is associated with reduced pituitary contents of LH, LH mRNA, FSH and FSH mRNA. Long-term treat...

Abstract unavailable© 2009 Society for Reproduction and Fertility...

Summary. In Exp. 1, sheep fetuses (2 male and 3 female) were gonadectomized between Days 70 and 120 of gestation and their blood LH and FSH levels were compared to those of control animals (4 male, 6 female) at regular times during the first year after birth. In Exp. 2. fetuses (3 male and 5 female) were gonadectomized between Days 50 and 60 of gestation and gonadotrophin levels at Day 90 of gestation were compared to those of control fetuses of the same age. ...

Summary. The relationship between the pituitary gland and testis in rams was studied from birth to sexual maturity. The concentrations of LH, FSH and testosterone increased between 5 and 7 weeks of age; the rise was not correlated with any specific cytological change in the testis. An augmented pituitary response to LH-RH was demonstrated as levels of gonadotrophin increased. It is unclear whether this change in sensitivity plays a role in initiation of the pu...