published_or_final_version / abstract / Paediatrics and Adolescent Medicine / Master / Master of Philosophy

published_or_final_version / abstract / toc / Botany / Master / Master of Philosophy

published_or_final_version / abstract / toc / Biochemistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / toc / Pharmacology / Doctoral / Doctor of Philosophy

No description available.

No description available.

loki was identified in our lab in a screen for novel serine-threonine protein kinases that are specifically expressed in the ovary. loki transcripts are expressed in early embryos and adult ovaries. In the ovaries, loki transcripts accumulate in the oocyte during early oogenesis, and by stage 8, are found to localize anteriorly to the oocyte-nurse cell interface. In order to understand the role of loki in Drosophila development, I created a loki mutant through excision of a P-element that had inserted 700bp upstream of loki. loki mutants display no apparent phenotype. / I was also able to identify the transcription unit responsible for valois (vls) function since it is located downstream from loki in the 38B region. vls is a member of the posterior group gene family and vls mutant mother produce embryos that lack pole cells and show abdomen patterning defects. Further characterization of vls indicates that it is a fairly direct activator of Vasa protein: vls function is required between Oskar protein and Vasa in the posterior patterning pathway since Vasa fails to localize to the posterior pole of vls mutant eggchambers. I also find that Vasa is differentially modified in vls ovaries and embryos, even though it is not yet known whether this modification is required for localization, proper function or both processes.

This thesis describes three studies on mammalian 25-hydroxyvitamin D$ sb3$-24-hyroxylase (24-hydroxylase), the first enzyme in the C24-oxidation pathway, a major catabolic pathway for vitamin D metabolites in kidney and other target tissues for vitamin D hormone. The first study examines the involvement of protein kinase C in the regulation of 24-hydroxylase activity in mouse kidney. Evidence is presented supporting a stimulatory role for protein kinase C in the regulation of constitutive, but not inducible, renal 24-hydroxylase. The kinase is also implicated in the aberrant expression of renal vitamin D metabolism in the mutant X-linked hypophosphatemic (Hyp) mouse. The second study investigates the mechanism(s) by which forskolin, a classic activator of adenylate cyclase, inhibits 24-hydroxylase activity in mouse kidney. Both the traditional cAMP-dependent mechanism and a novel cAMP-independent mode of action are observed. A direct interaction between forskolin and the substrate binding site of 24-hydroxylase is suggested for the latter based on kinetic analyses and structural similarities between the diterpene and the steroid substrate for the hydroxylase. The third study addresses the structural relationship between renal 1-hydroxylase and renal and target cell 24-hydroxylase(s) by assessing 24-hydroxylase activity in patients with vitamin D dependency rickets type I (VDDR-I), a Mendelian disorder of 1-hydroxylase function. Both constitutive renal 24-hydroxylase, indirectly ascertained through measurement of circulating levels of relevant vitamin D metabolites, and inducible target cell 24-hydroxylase, directly measured in cultured skin fibroblasts, are shown to be intact in VDDR-I patients undergoing calcitriol therapy. These findings suggest that the 1- and 24-hydroxylase activities likely represent or contain distinct gene products.

There is no abstract available for this thesis. / School of Physical Education

Members of the Dlg/PSD-95 protein family have a modular organization with multiple protein interaction domains and are thought to be important in the organization of synapses. A degenerate primer PCR strategy was used to screen for members of this family in the central nervous system of Apteronotus leptorhynchus, which possesses an electrosensory system that is well-suited for the study of synaptic organization and the subcellular localization of proteins. A. leptorhynchus was found to express at least four Dlg/PSD-95 family genes as in mammals, and the full coding sequences of the homologues of mammalian PSD-95 and SAP102 were determined. In situ hybridization experiments performed for the A. leptorhynchus Dig/PSD-95 family members in brain showed that they have a differential pattern of expression.