Reproduction Abstracts

Growth hormone (GH) is necessary to grow to normal adult size. While GH plasma concentrations are highest during early development, there is no evidence that GH influences somatic growth until after birth when GH-receptors are upregulated in peripheral tissues. The gradual decline in plasma GH during fetal life in a range of mammals suggests that negative feedback to the developing pituitary occurs progressively to decrease pituitary GH output. We have tested this hypothesis u...

In photoperiodic species, the pattern of pineal melatonin secretion translates the effects of day length on the annual reproductive cycle. Continuous delivery of exogenous melatonin to sheep during the non-breeding season is known to activate the gonadotrophic axis, and to suppress prolactin secretion through a mechanism involving the pars tuberalis (PT) of the pituitary gland. Recent studies have revealed that vascular endothelial growth factor (VEGF), a major regulator of an...

Recent studies have shown that microvasculature remodelling of the ovine pituitary gland is seasonally regulated through mechanisms involving the differential expression of pro-angiogenic (VEGF165) and anti-angiogenic (VEGF165b) isoforms of vascular endothelial growth factor (VEGF). As for other photoperiodic species, the pattern of pineal melatonin secretion mediates the effects of day length on the sheep seasonal reproductive cycle. In this study, we in...