Endocrinology Commons^™

Neuroendocrine Regulation Of The Luteinizing Hormone Surge And Puberty Onset In Sheep, Max J. Griesgraber

Graduate Theses, Dissertations, and Problem Reports (ETD)

Gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), and follicle stimulating hormone (FSH) are essential for the reproduction of all mammalian species, including both sheep and humans. GnRH is secreted by hypothalamic neurons into the hypophyseal portal vasculature in a pulsatile manner, which then acts within the anterior pituitary to elicit the release of LH and FSH into wider systemic circulation. In females LH and FSH act on the ovaries to promote estradiol (E2) production, follicular development, and under certain conditions in regard to LH, ovulation. Furthermore, while E2 inhibits GnRH and subsequent LH secretion under most conditions, at high concentrations E2 …

Estradiol’S Role In Timely Puberty Onset In The Ewe, Eliana Gerardine Aerts

Graduate Theses, Dissertations, and Problem Reports (ETD)

In female sheep, the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus triggers luteinizing hormone (LH) to be released from the pituitary. Luteinizing hormone, in turn, acts on the ovaries to elicit estradiol (E₂) release. E₂ acts in a negative feedback manner to control the amount of LH released. The increase in LH release that drives puberty onset results from a decrease in sensitivity to E₂ as the animal ages. However, the neural mechanisms mediating this change in sensitivity are not known, as is where in the hypothalamus E₂-negative feedback occurs. In the arcuate …

Morphological And Functional Evidence Of Sexual Dimorphism In The Retrochiasmatic Area Population Of Nk3r-Containing Neurons In Sheep, Justin A. Lopez

Graduate Theses, Dissertations, and Problem Reports (ETD)

Neurokinin B (NKB) and kisspeptin are critical for fertility and potent stimulators of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) secretion in sheep. We previously demonstrated that administration of NKB receptor (NK3R) agonist, senktide, within the retrochiasmatic area (RCh) resulted in surge-like release of LH and increased expression of kisspeptin neurons in the arcuate nucleus (ARC) of female lambs. We concluded that NKB-responsive neurons in the RCh stimulate GnRH secretion by inducing kisspeptin release from neurons in the ARC.

We have demonstrated morphological and functional evidence of sexual dimorphism in NKB-NK3R signaling in ovine RCh. RCh senktide administration resulted in …

Control Of Clover Infertility In Sheep, H G. Neil, H. E. Fels, C. M. Francis

Journal of the Department of Agriculture, Western Australia, Series 4

A summary of practices recommended for the control of infertility caused by subterranean clover in West Australian sheep.

PROLONGED grazing of green subterranean clover pastures often reduces ewe fertility. In more extreme cases, obvious signs of clover disease occur.

Clover Disease Of Sheep In Western Australia, A B. Beck, M. R. Gardiner

Journal of the Department of Agriculture, Western Australia, Series 4

DURING the past five years there has been a marked increase in the incidence of breeding abnormalities of sheep associated with the grazing of subterranean clover pastures.

This complex of diseases first became a major problem in Western Australia in the years following 1940 and eventually became known as "clover disease".