Thesis (Ph.D.)--Ohio University, November, 2006. / Includes bibliographical references (leaves 155-168).

No / Summary. Background: Endothelial nitric oxide synthase (eNOS) activity in endothelial cells is regulated by post-translational phosphorylation of critical serine, threonine and tyrosine residues in response to a variety of stimuli. However, the post-translational regulation of eNOS in platelets is poorly defined. Objectives: We investigated the role of tyrosine phosphorylation in the regulation of platelet eNOS activity. Methods: Tyrosine phosphorylation of eNOS and interaction with the tyrosine phosphatase SHP-1 were investigated by coimmunoprecipitation and immunoblotting. An in vitro immunoassay was used to determine eNOS activity together with the contribution of protein tyrosine phosphorylation. Results: We found platelet eNOS was tyrosine phosphorylated under basal conditions. Thrombin induced a dose- and time-dependent increase in eNOS activity without altering overall level of tyrosine phosphorylation, although we did observe evidence of minor tyrosine dephosphorylation. In vitro tyrosine dephosphorylation of platelet eNOS using a recombinant protein tyrosine phosphatase enhanced thrombin-induced activity compared to thrombin alone, but had no effect on endothelial eNOS activity either at basal or after stimulation with bradykinin. Having shown that dephosphorylation could modulate platelet eNOS activity we examined the role of potential protein phosphatases important for platelet eNOS activity. We found SHP-1 protein tyrosine phosphatase, co-associated with platelet eNOS in resting platelets, but does not associate with eNOS in endothelial cells. Stimulation of platelets with thrombin increased SHP-1 association with eNOS, while inhibition of SHP-1 abolished the ability of thrombin to induce elevated eNOS activity. Conclusions: Our data suggest a novel role for tyrosine dephosphorylation in platelet eNOS activation, which may be mediated by SHP-1.

Malaria parasite (Plasmodium spp.) infection in the mosquito Anopheles stephensi induces significant expression of A. stephensi nitric oxide synthase (AsNOS) in the midgut epithelium as early as 6 h post-infection and intermittently thereafter. This induction results in the synthesis of inflammatory levels of nitric oxide (NO) in the blood-filled midgut that limit parasite development. However, the Plasmodium-derived factors that can induce AsNOS expression and the signaling pathways responsible for transduction in A. stephensi have not been identified until completion of the work described herein. In my studies, I have determined that P. falciparum glycosylphosphatidylinositol (PfGPIs) can induce AsNOS expression in A. stephensi cells in vitro and in the midgut epithelium in vivo. Based on related work in mammals, I hypothesized that parasite-derived AsNOS-inducing factors signal through the insulin signaling pathway and the NF-kappaB-dependent Toll and Immune deficiency (Imd) signaling pathways. In support of this hypothesis, I have determined that signaling by P. falciparum merozoites and PfGPIs is mediated through A. stephensi protein kinase B (Akt/PKB) and DSOR1 (mitogen activated protein kinase kinase, MEK)/Extracellular signal-regulated protein kinase (ERK), kinases which are associated with the insulin signaling pathway. However, signaling by P. falciparum and PfGPIs is distinctively different from signaling by insulin and these parasite signals are not insulin-mimetic to A. stephensi cells. In other studies, treatment with pyrrolidine dithiocarbamate (PDTC), an inhibitor of NF-kappaB, reduced AsNOS expression by P. falciparum merozoites in A. stephensi cells. This result suggested the involvement of Toll and Imd pathways in parasite signaling of mosquito cells. Knockout of Pelle, a proximal signaling protein in the Toll pathway, increased AsNOS expression following parasite stimulation, suggesting that the Toll pathway may negatively regulate signaling by Plasmodium-derived AsNOS-inducing factors. In contrast, knockout of TGF-beta-activated kinase 1 (Tak1), a proximal signaling protein in the Imd pathway, reduced AsNOS expression by 20% relative to the control, suggesting that the Imd pathway is required for signaling by Plasmodium-derived AsNOS-inducing factors. Despite the NO-rich environment of the midgut, Plasmodium development is not completely inhibited. This observation suggests that Plasmodium may have efficient detoxification systems during sexual development in A. stephensi. To identify Plasmodium defense genes that may defend parasites against nitrosative stress caused by AsNOS induction, expression of several antioxidant defense genes known to function in nitrosative stress defense in a variety of organisms were examined during sporogonic development. Notably, increased expression levels of P. falciparum peroxiredoxins containing 1 or 2 cysteines (1-cys or 2-cys PfPrx) were associated with periods of parasite development just prior to and during parasite penetration of midgut epithelium, an event associated with significant AsNOS induction in the midgut. The provision of N omega-L-arginine (L-NAME), a known inhibitor of NOS enzyme activity, to A. stephensi with Plasmodium culture by artificial bloodmeal significantly reduced expression of 1-cys and 2-cys PfPrx indicating that these gene products may function to protect parasites against nitrosative stress induced by AsNOS. / Ph. D.

Xue, Hongmei. / "December 2010." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 165-206). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

by Wong Ho Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 107-129). / Abstract --- p.i / List of Abbreviations --- p.ii / Contents --- p.iii / Chapter Chapter 1. --- Introduction / Chapter 1.1 --- Introduction of aging in central nervous system --- p.1 / Chapter 1.2 --- Introduction of hippocampus / Structure of the hippocampus --- p.4 / Function of hippocampus --- p.6 / Chapter 1.3 --- A literature review of aging in hippocampus / Cell loss in aging --- p.8 / Ultrastructural changes in aging --- p.9 / Changes in neurotransmitter system --- p.10 / Neuroglial change --- p.11 / Change in potentiation --- p.13 / Chapter 1.4 --- A literature survey of Nitric Oxide Synthase (NOS) / General introduction of Nitric Oxide Synthase --- p.15 / Introduction of nNOS --- p.15 / Introduction of iNOS --- p.16 / Introduction of eNOS --- p.17 / Similarities and differences among isoforms --- p.18 / Role of NO/NOS in neurotransmission --- p.19 / Role of NO in neurotoxicity --- p.23 / Chapter 1.5 --- Aim of study --- p.25 / Chapter Chapter 2. --- Change of nNOS in aging / Chapter 2.1 --- Purpose and approach --- p.27 / Chapter 2.2 --- Basic principle of the techniques / Basic principle of immunohistochemistry --- p.28 / Basic principle of RT-PCR --- p.28 / Chapter 2.3 --- Experimental procedure / nNOS immunohistochemistry --- p.32 / RT-PCR of nNOS --- p.34 / Chapter 2.4 --- Result / nNOS immunohistochemistry --- p.38 / RT-PCR of nNOS --- p.44 / Chapter Chapter 3. --- Expression of iNOS in aging / Chapter 3.1 --- Purpose and approach --- p.50 / Chapter 3.2 --- Experimental procedure / iNOS immunohistochemistry --- p.50 / RT-PCR analysis of iNOS --- p.51 / Chapter 3.3 --- Result / iNOS immunohistochemistry --- p.52 / RT-PCR analysis of iNOS --- p.56 / Chapter Chapter 4. --- Verification of the RT-PCR product of iNOS / Chapter 4.1 --- Purpose and approach --- p.58 / Chapter 4.2 --- Basic principle --- p.58 / Chapter 4.3 --- Experimental procedure / Elution of PCR product from PAGE gel --- p.60 / Restriction digestion of the eluted PCR product --- p.61 / Chapter 4.4 --- Result --- p.62 / Chapter Chapter 5. --- Identification of the iNOS-positive cells / Chapter 5.1 --- Purpose and approach --- p.64 / Chapter 5.2 --- Experimental procedure --- p.64 / Chapter 5.3 --- Result --- p.65 / Chapter Chapter 6. --- Quantitation of astrocyte in aging hippocampus / Chapter 6.1 --- Purpose and approach --- p.67 / Chapter 6.2 --- Experimental procedure --- p.68 / Chapter 6.3 --- Result --- p.69 / Chapter Chapter 7. --- Detection of apoptosis in aging / Chapter 7.1 --- Introduction of apoptosis --- p.74 / Chapter 7.2 --- Purpose and approach --- p.75 / Chapter 7.3 --- Basic principle --- p.76 / Chapter 7.4 --- Experimental procedure / TUNEL method --- p.77 / DNA gel electrophoresis --- p.78 / Chapter 7.5 --- Result / TUNEL method --- p.80 / DNA gel electrophoresis --- p.82 / Chapter Chapter 8. --- Discussion / Chapter 8.1 --- Pattern of neuronal NOS in aging / Localization of nNOS --- p.84 / Decrease in staining of nNOS in the hippocampus during aging --- p.87 / No change in nNOS mRNA level --- p.88 / nNOS in aging - past and present works --- p.89 / Implication of the result --- p.91 / Chapter 8.2 --- Increased iNOS expression in aging / Neurotoxicity of iNOS --- p.93 / Circumstances of iNOS expression --- p.95 / Discussion of the present study --- p.96 / Chapter 8.3 --- Detection of apoptosis in aging --- p.103 / Chapter Chapter 9. --- Conclusion --- p.106 / Biblography --- p.107 / Appendix --- p.130 / Acknowledgements --- p.134

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Thesis (Ph. D.)--University of Missouri--Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 132-150). Also available on the Internet.