Evidence suggests that thyroid hormone acts by binding to nuclear receptors which regulate expression of a discrete number of proteins, including cardiac ventricular myosin isoenzymes. Administration of thyroid hormone is known to stimulate synthesis of ventricular α-myosin heavy chain and inhibit production of a (beta)-myosin heavy chain. The first part of this study examines the effects of naturally occurring and synthetic thyroid analogs, catecholamines and high carbohydrate diets on ventricular myosin isoenzyme expression in thyroidectomized and hypophysectomized rats. Also, the effects on myosin isoenzyme expression of adrenalectomy and hydrocortisone replacement have been studied in euthyroid animals. Myocardial CO₂ production and hepatic α-glycerol phosphate dehydrogenase activity were measured to monitor the effects of these interventions on tissue respiration. The results indicate that thyroid hormone analogs do not selectively stimulate myosin isoenzyme expression as compared with their effects on energy production. No significant separation between the actions of these analogs on metabolic parameters and myosin isoenzyme patterns was found. However, high carbohydrate feeding in thyroidectomized and hypophysectomized rats increased the content of the α-myosin heavy chain. β-Adrenergic stimulation with isoproterenol and blockade with propranalol did not affect myosin isoenzyme expression. Adrenalectomy in euthyroid rats decreased the α-myosin heavy chain with a corresponding increase in the β-myosin heavy chain. This could be reversed by treatment with hydrocortisone. The results suggest that the mechanism for regulation of cardiac myosin isoenzymes may involve a primary signal related to dietary carbohydrate, which is modulated by thyroid hormone, and possibly glucocorticoids. The method for purification of the T₃-receptor-DNA complex is described. This complex is thought to mediate the action of T₃ on gene expression. The results indicate that a relatively pure form of an intact receptor-DNA complex (M.W. 111,000) can be isolated from a T₃-affinity gel. Only a single protein component (M.W. 58,000) was identified by electrophoresis and coomasie blue staining of the purified complex. The associated double stranded DNA fragment (M.W. 52,000) was estimated to contain about 88 basepairs. This complex could be dissociated by treatment with 0.4 M KCl or DNase I, but did not undergo spontaneous exchange with exogenous labeled DNA fragments. Equilibrium binding studies demonstrated a single class of high affinity T₃-binding site with a dissociation constant (50 pM) which was significantly lower than that of the micrococcal digest (1.1 nM).

No description available.

Walleye are an important recreational and commercial fish species that are distributed over an expansive geographic range across North America. However, its palatable white flesh and appeal to anglers have lead to declines in natural populations throughout Canada and the United States. These declines have prompted the idea that aquaculture may serve as a means of satisfying consumer demands and decreasing pressure on wild stocks. While culture programs exist for walleye, little is known about the growth physiology of walleye in a culture system. The goals of this thesis, therefore, were to develop a molecular marker that could be used to rapidly assess growth in juvenile walleye, and to make improvements to culture practices that will optimize growth. To begin, we examined the relationship between growth and the expression of the myosin heavy chain gene (MyHC) in the white muscle of juvenile walleye. The coding region of MyHC from the fast skeletal muscle of walleye was amplified using a full length cDNA. Growth was then characterized using traditional measurements of growth (length, weight and condition factor), as well as MyHC protein concentration and MyHC mRNA levels. Both MyHC mRNA and protein expression were highly correlated with faster growth in juvenile walleye. Over shorter time scales, the MyHC mRNA marker was sensitive enough to detect impacts of fasting that could not be detected using traditional measurements of growth. Next, MyHC mRNA quantification was applied to an aquaculture setting. Feed training is an important bottleneck during juvenile walleye culture that often leads to mortalities and cannibalism. These experiments showed that the brief fasting period during the diet switch from plankton to commercial pellet feed caused a significant decrease in MyHC mRNA levels. Furthermore, the success of feed training in terms of survivorship and growth potential increased significantly for larger fish. The final section of this thesis examined how acute and chronic temperature exposure impacted MyHC mRNA and protein expression. Results showed that the nature of the heat stress can significantly affect the MyHC response. These findings are important as the temperature stresses induced in these studies are common during the summer months in southern Ontario. / Thesis (Ph.D, Biology) -- Queen's University, 2009-02-19 12:30:51.406

Thesis (Ph. D.)--University of North Texas, Aug., 2007. / Title from title page display. Includes bibliographical references.

Thesis (Ph. D.)--University of Oregon, 2008. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 164-171). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.

Thesis (M.S.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains viii, 97 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 87-88).

Typescript. Includes vita and abstract. Includes bibliographical references (leaves 88-107). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.

Universiẗat, Diss., 2002--Heidelberg.

Universiẗat, Diss., 2003--Heidelberg.

Thesis (Ph.D.)--Baylor University, 2006. / Includes bibliographical references (p. 121-127).