During the development of the nervous system, neurons migrate to their final location and extend neurites that navigate long distances in the extracellular environment to reach their synaptic targets. The proper functioning of the nervous system depends on correct connectivity, and mistakes in the wiring of the nervous system lead to brain abnormalities and mental illness. Growth cones are motile structures located at the tip of extending neurites that sense and respond to guidance cues encountered along the path toward their targets. Binding of these cues to receptors located on growth cone filopodia and lamellipodia triggers intracellular signaling pathways that regulate growth cone cytoskeletal dynamics. Although studies on extracellular cues and their effects on neuronal guidance are well documented, less is known about the intracellular signaling mechanisms that regulate growth cone motility. This dissertation focuses on two signaling pathways and describes how they might be involved in determining growth cone morphology during neuronal development. The specific aims of this work address: (1) the role of phosphatidylinositol-3-kinase (PI-3K) and its downstream signaling pathway in regulating growth cone motility, and (2) the effect of nitric oxide (NO) release from a single cell on growth cone morphology of neighboring neurons. This study employs defined neurons from the pond snail, Helisoma trivolvis, to demonstrate that inhibition of PI-3K induces a concomitant increase in filopodial length and a decrease in the rate at which neurites advance. These effects are mediated through the lipid and protein kinase activities of PI-3K, and filopodial elongation is due to an increase in the rate at which filopodia elongate and the time that individual filopodia spend extending. Additionally, this study demonstrates that NO release from a single cell can affect growth cone dynamics on neighboring neurons via soluble guanylyl cyclase (sGC), and that NO has a physiological effect up to a distance of 100 ìm. Overall this study provides new information on cellular mechanisms regulating growth cone motility, and suggests a potential role of PI-3K and NO in neuronal pathfinding in vivo.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 102-114).

Thesis (Ph. D.)--University of Oklahoma. / Bibliography: leaves 120-130.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 77-87).

Univ., Diss., 2006--Frankfurt (Main)

Thesis (Ph.D.)--Medical College of Ohio, 2005. / "In partial fulfillment of the requirements for the degree of Doctor of Philosophy in Medical Sciences." Major advisor: William Maltese. Includes abstract. Document formatted into pages: iv, 134 p. Title from title page of PDF document. Bibliography: pages 107-132.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 94-116).

Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains ix, 224 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Phosphatidylinositol 3-kinase δ (PIK3δ) is a tyrosine kinase essential for B cell survival, making it an important target in the treatment of chronic lymphocytic leukemia. Idelalisib is an inhibitor of PIK3δ demonstrating initial success in disease response, but is now shown to have a decreased overall survival and life-threatening serious adverse events. The following is an unfortunate case of a grade III adverse skin reaction secondary to idelalisib with the likely complication of methicillin-resistant Staphylococcus aureus bacteremia.

Aim: To explore the protective effects and involved mechanisms of two angiogenic growth factors, vascular endothelial growth factor (VEGF165) and angiopoietin-1 in cardiac myoblasts. Methods: Replication-deficient adenovirus encoding for human VEGF165 (Ad-VEGF165) or angiopoietin-1 (Ad-Ang1) were transfected into H9C2 cardiac myoblasts. Recombinant adenovirus encoding for green fluorescent protein (Ad-GFP) was used as vehicle control. Twenty-four hours later, cell apoptosis was induced by 300 μmmol of H2O2. Genomic DNA was extracted and DNA fragmentation was analyzed in 1.6% agarose gels. Phosphatidylinositol-3 kinase(PI-3 K) activity and bcl-2 expression level were investigated in H9C2 after gene transfection 24 hours later by an immol/Lunoprecipitated kinase assay and Western blot assay respectively. The effect of wartmannin, a specific inhibitor of PI-3 K, on DNA fragmentation, PI-3 K activity and bcl-2 expression was also analyzed by a pre-treatment of 30 minutes before transfection. Results: Apoptotic DNA fragmentation induced by H2O2 was significantly inhibited by the transfaction of Ad-VEGF165 and/or Ad-Ang1 but then aborted by the pretreatment of wartmannin. PI-3 K activity was significantly elevated after Ad-VEGF165 + Ad-Ang1 transfection as compared to Ad-GFP transfection group(2.60 vs 1.32, P < 0.01). Anti-apoptotic factor bcl-2 expression was upregulated in Ad-VEGF165 (2.1-fold), Ad-Ang1 (1.7-fold) and Ad-VEGF165 + Ad-Ang1 (1.7-fold) treated groups as compared to Ad-GFP transfection group. Wortmannin suppressed PI-3 K activiation induced by Ad-VEGF165 (from 1.83 to 0.69, P < 0.05). Ad-Ang1 (from 1.80 to 0.97, P = 0.07) or Ad-VEGF165a + Ad-Ang1 (from 2.60 to 0.42, P < 0.01). However, upregulation of bcl-2 induced by Ad-VEGF165 and/or Ad-Ang1 was not aborted by wortmannin pretreatment. Conclusions: VEGF165 and/or Ang1 can protect cardiac myoblasts from apoptosis induced by H2O2 throught PI-3 K and bcl-2 pathway. The anti-apoptotic function of either VEGF165 or Ang1 could be served as a now therapeutic target including their angiogenic benefits.