Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 96-112). Also available in print.

Thesis (Ph.D.)--Ohio University, August, 2009. / Release of full electronic text on OhioLINK has been delayed until September 1, 2012. Includes bibliographical references (p. 253-288)

Thesis (Ph.D.)--Ohio University, August, 2009. / Title from PDF t.p. Release of full electronic text on OhioLINK has been delayed until September 1, 2012. Includes bibliographical references (p. 253-288)

Not available / text

(Uncorrected OCR) Abstract of thesis entitled NOVEL ASPECTS OF AUTOCRINEIP ARACRINE REGULATION OF GROWTH HORMONE SECRETION AND SYNTHESIS IN GRASS CARP PITUITARY CELLS Submitted by ZHOUHONG for the degree of Doctor of Philosophy at The University of Hong Kong in March 2003 In this study, autocrine/paracrine regulation of growth hormone (GH) synthesis and secretion by local interactions of gonadotrophs and somatotrophs was examined in vitro in pituitary cells prepared from Chinese grass carp (Ctenopharyngodon idellus). Treatment with exogenous OH and gonadotropin (OTH) resulted in a dose-dependent increase in basal GH release, GH production, and GH mRNA levels. However, the opposite effects were observed by removing endogenous OR and OTH using immunoneutralization. Furthermore, GR and OTH immunoneutralizations at the pituitary level were effective in blocking the stimulatory influence on GH mRNA expression induced by GH-releasing factors in fish, including GnRH, dopamine, and PACAP38�Apparently" GH-induced GH gene expression was mediated by increasing the T1/2 ofGH mRNA in the cytoplasm and enhancing the production of GH primary transcripts in the nucleus. Since GH-induced OR mRNA gene expression could be blocked by inhibiting JAK2, P42144MAPK, P38MAPK, and PI3K, it is likely that the JAK/MAPK and JAK/PI3K pathways are involved in the GH receptor signaling. Similarly, exogenous GTH increased the production ofGH primary transcripts. However, it did not improve OR mRNA stability but rather enhanced the turnover of GH transcripts. GTR also increased cAMP production in carp pituitary cells. GTH-induced GH mRNA expression Was mimicked by activating cAMP synthesis and blocked by inhibiting adenylate cyclase (AC) and PKA.. GTH-induced OR mRNA expression was also sensitive to inhibition of JAKz, P42/44MAPK, P3SM.AP1C and PI3K. Similar inhibitions, except for PI3K, were all effective in blocking OR mRNA expression induced by activation of cAMP synthesis. These results indicate that GTH may induce GR gene expression through the AC/ cAMP/PKA pathway secondary coupled to JAK.2 andlor MAPK. Apparently, a cAMP-independent PI3K component is also involved in the post-receptor signaling. Using a colunm perifusion approach, the dynamic interactions between somaotrophs and gonadotrophs were examined. In this case, exogenous OTR induced a rapid rise in basal GH secretion, whereas exogenous GR was found to inhibit basal GTR release. In parallel studies, GTHinduced OR mRNA expression was abolished by OR immunoneutralization. Similarly, GTR immunoneutralization blocked GR-induced OR mRNA expression in carp pituitary cells. These results, as a whole, indicate that endogenously secreted OH and GTR, besides their functions as endocrine hormones, serve as novel autocrine/paracrine factors at the pituitary level to modulate GH secretion, OH production, OH gene expression, and somatotroph sensitivity to stimulation by hypothalamic regulators. These stimulatory influences of GH and GTR on OR gene expression axe exerted at the level of GR rnRNA stability and OH gene transcription, presumably via a direct coupling to the JAK/MAPK and JAKiPI3K cascades or an indirect coupling via the AC/cAMP/PKA pathway. Apparently, a local il1trapituitary feedback loop is present. In this case, GTH released from gonadotrophs stimulates GH secretion in neighboring somatotrophs. GR release from somatotrophs is essential to maintain basal GH synthesis and secretion and also exerts a negative feedback on basal GTB release. This intrapituitary feedback loop formed by local interactions between gonadotrophs and somatotrophs may represent a novel mechanism to control OR gene expression in lower vertebrates. / abstract / toc / Zoology / Doctoral / Doctor of Philosophy

published_or_final_version / Zoology / Master / Master of Philosophy

published_or_final_version / Zoology / Master / Master of Philosophy

Efficacy of a sustained-release formulation of bST was evaluated for two consecutive lactations. Response in milk and milk component yield was positive and very consistent for multiparous cows between lactations. Average responses in milk production for the first lactation and for the 320-, 640-, and 960-mg$ cdot$28d$ sp{-1}$ doses of bST were 4.3, 5.2 and 5.9 kg$ cdot$d$ sp{-1}$, respectively. Response was 4.9 kg$ cdot$d$ sp{-1}$ for the average of the second lactation with 640 mg bST$ cdot$28d$ sp{-1}$. Primiparous cows responded with the same numerical magnitude as multiparous cows but with higher variability. BST caused a response in milk yield irrespective of the stage of lactation when injections commenced, but the magnitude of response was greater at latter stages of lactation. No adverse effect of treatment on final body condition score and achievement of proper condition for a subsequent lactation was found. No effect of treatment was observed on health parameters in either lactation. Trends towards longer days open and more breedings per conception were apparent for both lactations. Total milk protein, caseins and whey proteins were not changed at any stage of lactation and for the average of the full lactation. BST did not significantly change proportions of $ alpha sb{s}$-, $ beta$- and K-caseins. Milk fat percentage and milk fatty acid profiles were not different between control and any dose level of bST for a complete lactation. Maximum response in milk yield for the different doses of bST was from d8 to 12 of the 28d cycle and was almost eliminated by d22 to 24. A 3.1 and 3.6 kg$ cdot$d$ sp{-1}$ milk augmentation with bST was estimated in cows infused for 6d with glucose and saline, respectively during peak lactation. There was no apparent milk yield response when cows were infused with insulin + glucose but cows exhibited positive energy balance, weight gain and only 5% less milk. Insulin + glucose infusion increased milk protein 11% and 14% compa

The ability of human growth hormone (hGH) to alleviate the effects of zinc deficiency on growth was investigated in the rat. Human GH treatment had no significant effect on food consumption, growth parameters or plasma IGF-I. Food consumption, tail length, liver weight, and tibia weight were significantly lower in the zinc deficient group. Body weight was significantly reduced in the zinc deficient and pair fed groups compared to the control. A significant interaction between zinc and hGH was found for tibial epiphyseal cartilage width but there were no significant differences between the groups receiving hGH and the respective shams. Tissue zinc content and plasma alkaline phosphatase were significantly decreased by the dietary zinc deficiency. Plasma zinc was higher in the groups receiving hGH. Significant interactions between zinc and hGH was found for liver iron, tibial zinc, and tibial copper. Copper and iron showed a competitive interaction with zinc and were lower in the rats receiving the control diet. Both lowered zinc and food intake contributed to the effects of the zinc deficiency; however, these effects were not equally distributed. Food intake had the greater effect on growth and plasma IGF-I while tissue mineral content showed a greater effect for zinc intake.