Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains vii, 64 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 48-63).

These studies were undertaken to characterize the adenylate cyclase system of the primate (rhesus monkey) corpus luteum, and to correlate gonadotropin-sensitive adenylate cyclase activity with the functional activity of the corpus luteum at specific stages of the luteal phase of the menstrual cycle, particularly near the time of luteolysis. The conversion of [α-³²P] ATP to [³²P] cAMP was assayed in preparations of luteal tissue obtained from rhesus monkeys at midluteal phase of the menstrual cycle. Cyclic AMP production was influenced by the pH, osmolality, and ionic strength of the assay buffer, and was acutely sensitive to Mg⁺². Michaelis-Menten kinetics were seen when the ATP:Mg ratio was constant. The gonadotropins, hLH and hCG but not hFSH, stimulated cAMP production in a similar dose-dependent manner. Deglycosylated hCG blocked the stimulation of adenylate cyclase by hLH and hCG. The addition of GTP increased maximal activation of adenylate cyclase by hLH or hCG but did not alter sensitivity to the hormones. The adenylate cyclase of macaque luteal tissue did not respond to the addition of isoproterenol or epinephrine; furthermore, these catecholamines did not affect hCG-stimulation of adenylate cyclase. Forskolin and fluoride stimulated cAMP production in a dose-dependent manner. The activity of adenylate cyclase was examined in corpora lutea obtained from rhesus monkeys at specific stages in the luteal phase of the menstrual cycle (days 3-5, 6-8, 9-12, 13-15, 16-menses after the midcycle LH surge). Basal adenylate cyclase activity, activity stimulated by GMP-P(NH)P, GTP, GTP + hLH, and GTP + hCG, sensitivity of the enzyme to hLH (measured by K(act)), and peripheral progesterone levels were low in the early luteal phase (days 3-5), increased by midluteal phase (days 6-8 and 9-12), and then decreased by the late luteal phase days 13-15 and 16-menses). In contrast, there were no significant differences among the age groups tested for forskolin-stimulated activity. Thus the adenylate cyclase system of the rhesus monkey undergoes significant changes during the luteal phase which are associated with the development and regression of the corpus luteum of the menstrual cycle. Mechanisms which modulate gonadotropin and nucleotide activation of adenylate cyclase without interfering directly with the catalytic unit are implicated in the changes which accompany luteolysis.

published_or_final_version / Physiology / Master / Master of Philosophy

These studies were conducted to determine the mechanisms by which prolactin (PRL) exerts its luteotropic effects on the mink corpus luteum (CL). Three experimental models were developed and utilized in these studies. In the first model, the ovaries from pregnant mink were collected at regular intervals throughout gestation, half the animals were treated with the dopamine agonist 2-bromo-$ alpha$-ergocryptine (bromocryptine), to suppress their endogenous PRL levels, and half were exposed to their endogenous PRL levels. The second model consisted of treating anestrous animals with exogenous gonadotropins to induce follicular development and ovulation, half the animals were then treated with PRL while the other half were left as untreated controls. In the third model, CL were collected from mink at several stages of mink gestation. The cells were enzymatically dispersed, placed in culture and incubated with different concentrations of PRL, luteinizing hormone (LH), follicle stimulating hormone (FSH) and (Bu)$ sb2$cAMP. Using these 3 models, the effects of PRL on P450 side chain cleavage (P450scc), 3$ beta$-hydroxysteroid dehydrogenase (3$ beta$-HSD), steroidogenic acute regulatory protein (StAR), luteinizing hormone receptor (LHr) and prolactin receptor (PRLr) mRNA were determined. Messenger RNA levels for P450scc did not vary significantly over the course of mink gestation and treatment of animals with bromocryptine did not alter the abundance. In the anestrous model, treatment of mink with PRL reduced P450scc mRNA levels below that of the untreated control, while treatment of cultured mink luteal cells with increasing concentrations of PRL had no effect on the abundance of P450scc mRNA. The abundance of 3$ beta$-HSD mRNA varied over the course of mink gestation. Levels were low during embryonic diapause, increased during CL reactivation and peaked during post-implantation gestation. Treatment of mink with bromocryptine prevented the pre-implantation rise in 3$ bet

It has been reported world wide that over the past fifty years production has dramatically increased in dairy cattle but at the same time fertility rates have steadily declined, particularly in mature cows. Fertility of heifers that were bred for the first time has not been affected. One of the major reasons for such fertility decline in mature cows could be impaired progesterone production. Therefore relationships of parity with reproductive performance, its effect on progesterone concentrations and genes associated with progesterone synthesis were examined in this thesis. In the first experiment, breeding records of 163 Holstein heifers and cows in 1st, 2nd, and 3rd/4th parities were used to compare pregnancy rates among heifers and parity cows and between parity cows. Progesterone levels of heifers, 1st, 2nd, and 3rd/4th parity (10 animals each group) were measured from milk and blood samples. First and second inseminations pregnancy rates were higher in heifers compared to other parity cows. Furthermore 1st parity cows showed higher pregnancy rates than 2nd and 3rd/4th parity cows. However, P₄ levels were not significantly different among animals of different parity. In the second experiment, expression levels of steroidogenic genes – StAR, P450scc, 3-β HSD; apoptotic genes Bax and Bcl-2; and HSP70 in corpus luteum obtained from six heifers and three 2nd/3rd parity lactating cows were compared using RT-PCR. Relative optical density with house keeping gene was obtained for each gene. Analysis of variance revealed that expression levels of steroidogenic and Bax genes are higher (p<0.05) in cows than heifers. HSP70 gene and Bcl-2 gene expressions were not different (P>0.05) between the two groups. This study confirmed a clear relationship between parity and reproductive performance. There was no significance relationship between parity and circulating progesterone levels. Steroidogenic genes expression was higher in lactating cows than heifers and no differences were seen in mRNA levels of Bcl2, and HSP70 genes between heifers and mature cows. Bax mRNA expression was higher in mature cows suggesting that the lifespan of corpus luteum may be compromised in 2nd and 3rd parity cows, resulting in early embryonic mortality and reduced pregnancy rates.

It has been reported world wide that over the past fifty years production has dramatically increased in dairy cattle but at the same time fertility rates have steadily declined, particularly in mature cows. Fertility of heifers that were bred for the first time has not been affected. One of the major reasons for such fertility decline in mature cows could be impaired progesterone production. Therefore relationships of parity with reproductive performance, its effect on progesterone concentrations and genes associated with progesterone synthesis were examined in this thesis. In the first experiment, breeding records of 163 Holstein heifers and cows in 1st, 2nd, and 3rd/4th parities were used to compare pregnancy rates among heifers and parity cows and between parity cows. Progesterone levels of heifers, 1st, 2nd, and 3rd/4th parity (10 animals each group) were measured from milk and blood samples. First and second inseminations pregnancy rates were higher in heifers compared to other parity cows. Furthermore 1st parity cows showed higher pregnancy rates than 2nd and 3rd/4th parity cows. However, P₄ levels were not significantly different among animals of different parity. In the second experiment, expression levels of steroidogenic genes – StAR, P450scc, 3-β HSD; apoptotic genes Bax and Bcl-2; and HSP70 in corpus luteum obtained from six heifers and three 2nd/3rd parity lactating cows were compared using RT-PCR. Relative optical density with house keeping gene was obtained for each gene. Analysis of variance revealed that expression levels of steroidogenic and Bax genes are higher (p<0.05) in cows than heifers. HSP70 gene and Bcl-2 gene expressions were not different (P>0.05) between the two groups. This study confirmed a clear relationship between parity and reproductive performance. There was no significance relationship between parity and circulating progesterone levels. Steroidogenic genes expression was higher in lactating cows than heifers and no differences were seen in mRNA levels of Bcl2, and HSP70 genes between heifers and mature cows. Bax mRNA expression was higher in mature cows suggesting that the lifespan of corpus luteum may be compromised in 2nd and 3rd parity cows, resulting in early embryonic mortality and reduced pregnancy rates.

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xvi, 218 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 92-114).

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 126-145). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 126-145). Also available on the Internet.

Thesis (Ph. D.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains xvi, 155 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 103-152).