Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Pharmaceutical Science." Includes bibliographical references (p. 99-107).

Human ISG15 is a 17 kDa ubiquitin-like protein (Ubl) that is induced by type I interferons (interferons [alpha] and [beta]) and plays a role in antiviral responses. ISG15 is conjugated via its C-terminus to more than 150 cellular proteins, and like ubiquitin, an E1-E2-E3 enzymatic cascade is required for conjugation. Ube1L and UbcH8 were previously identified as the E1 and E2 enzymes for this pathway. My experiments identified Herc5, a HECT domain E3, as the major ligase for ISG15. Like ISG15, Ube1L, and UbcH8, expression of Herc5 is transcriptionally induced by type I interferons. siRNAs against Herc5 abrogated ISG15 conjugation to the vast majority of target proteins in interferon-treated cells. Wild type Herc5, but not the catalytically inactive C994A mutant, supported conjugation of ISG15 in non-interferon-treated cells co-transfected with Ube1L, UbcH8 and ISG15. IQGAP1, a scaffold protein, was identified as another essential component of the ISG15 system. IQGAP1 was discovered to interact with Herc5, and this interaction was mediated by the C-terminal domain of IQGAP1 and the N-terminal RCC1-like repeats of Herc5. IQGAP1 was required for auto-conjugation of ISG15 to Herc5, and I propose a model where IQGAP1 functions, at least in part, by relieving an auto-inhibitory conformation of Herc5. Thus, I have identified two factors that are critical for ISG15 conjugation and my discoveries have increased our understanding of the ISG15 pathway. Identification and characterization of the conjugation apparatus will aid in establishing an in vitro biochemical system for ISG15 conjugation, which in turn, will be important to decipher the biological function of ISG15 modification. / text

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 105-116). Also available on the World Wide Web.

Thesis (Ph.D.). / Written for the Dept. of Biochemistry. Title from title page of PDF (viewed 2009/06/08). Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri--Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 177-200). Also available on the Internet.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Plant Biology." Includes bibliographical references (p. 178-184).

Thesis (Ph. D.)--Cornell University, May, 2008. / Vita. Includes bibliographical references (leaves 159-179).

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

The effect of thyroid hormones on purine biosynthesis was studied in vitro. With 100,000 x g supernatant fraction of rat liver homogenate, the results suggested that thyroid hormones stimulated total purine synthesis from labeled glycine-1-¹⁴C. Further studies indicated that these hormones stimulated AMP synthesis but inhibited GMP synthesis. The stimulatory effect on AMP synthesis was found to be due to the stimulation of adenylosuccinate synthetase. Adenylosuccinate synthetase was isolated and purified from rat liver. The maximum stimulatory effect of these hormones occurred with 2.5 x 10⁻⁵ M thyroxine (T₄) and 2.5 x 10⁻⁹ M triiodo-L-thyronine (T₃). A slight increase or decrease in concentration of these hormones caused a drastic decrease in their stimulatory effect. Some analogues of T₄ were also studied and results of such experiments agreed qualitatively with their effects in vivo. Those which are physiologically active are capable of stimulating this enzyme and those which are physiologically inactive had little or no effect on this enzyme. Based on these results, a hypothesis, that thyroid hormones regulate the levels of AMP and GMP synthesis, was proposed. The significance of this preferential stimulatory effect on AMP synthesis was discussed. / Ph. D.

Scanning and transmission electron microscopy and platelet aggregometry were employed to study erythrocyte morphology and thrombocyte morphology and function during ovine pregnancy-induced hypertension (OPIH). Nine multiparous gravid ewes were observed during normal pregnancy, OPIH, and thromboxane synthetase inhibitor administration. Blood pressure, plasma thromboxane B2, serum chemistries and electrolytes, fibrin/fibrinogen degratory products, and total platelet count were monitored throughout the investigation to document the circulatory environment during this syndrome. Arterial blood pressure, plasma thromboxane B2 levels, and serum chemistries and electrolytes were significantly altered (p≤0.005) during hypertension. However, no change in total platelet count or fibrin/fibrinogen degratory product levels were detected. Collagen-induced platelet aggregation also became abnormal during this time, while ADP-induced aggregatory response remained essentially unchanged. Platelet aggregation changes seemed to correspond to degranulation and swelling of the canalicular tubule system of these cells. Echinocytosis was present during baseline measurement and persisted throughout hypertension. However, changes in shistocyte numbers were not detected. Administration of the thromboxane synthetase inhibitors CGSl3080 or CGS12970 lowered blood pressure (p≤0.005) and serum thromboxane B₂ (p≤0.005), and. normalized serum chemistries and electrolytes (p≤0.005). Echinocyte numbers decreased (p≤0.05) and discocyte numbers increased (p≤0.005) after treatment. Platelet counts decreased after drug therapy, but normal collagen-induced aggregation was restored. No ultrastructural abnormalities were observed in thrombocytes after treatment. There is good evidence that thromboxane synthetase inhibition is appropriate and effective treatment for pregnancy-induced hypertension. These data suggest that such therapy is especially indicated in cases complicated by hematologic disorders as evidenced in an ovine model of this syndrome. / Master of Science