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Reproduction in Domestic Ruminants III

Reproduction in Domestic Ruminants III

Regulation of Gonadal Function

bp0003rdr24 | Regulation of Gonadal Function | REDR1994

Investigating local regulation of the testes of ruminants

Maddocks S , Kern S , Setchell BP

In addition to endocrine regulation by the gonadotrophic hormones, the functions of the testes are regulated locally by paracrine and autocrine factors. Some attempts have been made to isolate cells from the testes of immature bulls and rams for investigation of cell function in vitro. However, most studies have used in vitro cultures of cells isolated from the testes of rats and a large variety of factors have been identified as potential local regulators. T...

bp0003rdr25 | Regulation of Gonadal Function | REDR1994

Growth factors and the control of folliculogenesis

Monget P , Monniaux D

There is increasing evidence that growth factors modulate folliculogenesis. However their precise role in the processes of follicular growth, differentiation and atresia is still unknown. Growth factors belong to complex systems, including all the factors structurally and functionally related, their receptor(s) and, in most cases, binding proteins or proteoglycans. In this review, the insulin-like growth factor (IGF) system is presented as a paradigm for the study of other gro...

bp0003rdr26 | Regulation of Gonadal Function | REDR1994

Control of antral follicle development and selection in sheep and cattle

Campbell BK , Scaramuzzi RJ , Webb R

The development of antral follicles in sheep and cattle is dependent on FSH, but large antral follicles can shift their gonadotrophic dependence from FSH to LH. The mechanisms that result in the selection of at least one ovulatory follicle from identical follicular cohorts, exposed to the same endocrine environment, still remain to be elucidated. The aim of this research was to extend in vitro results from the rodent to sheep and cattle and, using both in vivo</em...

bp0003rdr27 | Regulation of Gonadal Function | REDR1994

Immunological manipulation of ovulation rate for twinning in cattle

Hillard MA , Wilkins JF , Cummins LJ , Bindon BM , Tsonis CG , Findlay JK , O’Shea T

Unlike in sheep, in which immunization against androstenedione causes mild and reasonably controlled increased ovulation rate, in similar studies cattle showed highly variable responses ranging from increased ovulation rate and fertility through to anovulation/anoestrus or superovulation. As a consequence, interest in manipulation of ovulation rate through this approach has declined and is now focused on immunological manipulation of endogenous inhibin following successful stu...

bp0003rdr28 | Regulation of Gonadal Function | REDR1994

Involvement of immune cells in regulation of ovarian function

Pate JL

Primary cultures of luteal cells have been used to determine both acute and chronic effects of cytokines on luteal cell function and viability. Gonadotrophin-stimulated progesterone production is inhibited by interleukin 1β (IL-1β), tumour necrosis factor a (TNF-α), or gamma-interferon (IFN-γ), the last two cytokines being more effective than IL-I. In contrast, all three cytokines are potent stimulators of prostaglandin production by these cells. The mechan...

bp0003rdr29 | Regulation of Gonadal Function | REDR1994

Dynamics of molecular mechanisms underlying ovarian oxytocin secretion

Stormshak F , Orwig KE , Bertrand JE

In the ruminant ovary, synthesis and secretion of oxytocin begin in the granulosa cells of the preovulatory follicle and are markedly stimulated by the surge of LH and FSH. Luteinization of the granulosa cells results in a further increase in oxytocin gene expression, but translation ol mRNA appears to be retarded because the peak concentration of luteal oxytocin occurs later than the maximal accumulation of the message. Several hormones have been shown to stimulate oxytocin s...