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The role of Calcium ions (Ca2+) in the phytochrome-controlled unrolling of 6-d-old etiolated barley leaf sections was evaluated through the manipulation of light treatments, Ca2+ levels and antagonists and agonists of Ca2+ metabolism. The Ca2+-chelator ethyleneglycol-bis-(Baminoethylether) - N, N, N', N', - tetraacetic acid (EGTA) inhibited the response. Ca2+ restored responsivity when supplied within 1h of light treatment. Subsequent escape from responsivity to Ca2+ involved uncoupling of measurable phytochrome from response level. A second Red- light treatment (R) given, with Ca2+, to EGTA-treated sections following Ca2+ escape from the initial R effect induced full unrolling. Similar results were obtained with the relatively independent phytochrome- controlled nitrate reductase activity induction in the sections. It is proposed that Ca2+ escape arises from phytochrome signal attenuation. Measurable Pfr and response recoupled following Ca2+-escape for the second R, given with Ca2+. This relationship was identical to that observed with a single light treatment without EGTA, despite a 50% reduction in phytochrome levels at the time of the second R. This indicated that either the ratio of Pfr/Ptot governs response induction, or that the majority of detectable phytochrome is functionally irrelevant. It is suggested that phytochrome deactivation is reversible via phytochrome cycling. A23187-induced movement of Ca2+ also induced unrolling. This, and the R effect appeared to be separate, thus Ca2+ does not mediate the phytochrome signal via simple amplitude modulation. Treatment with 1.2-Diacylglycerol (1,2,-DG) induced unrolling. The interaction of 1,2-DG and A23187 demonstrated Ca2+ sensitivity modulation, indicating involvement of Protein Kinase C. The interaction of A23187 and phytochrome did not show this. It is suggested that the induction of unrolling centres around protein phosphorylation via separate 1,2,-DG, Ca2+-sensitive and phytochrome regulated kinases.

Versican, a chondroitin sulfate proteoglycan, is one of the main components of the extracellular matrix and hence plays a central role in tissue morphogenesis and a number of pathologic processes. My main goal has been to investigate the mechanisms of versican gene regulation, focusing on the signal transduction pathways, promoter regions, cis-acting elements, and trans- factors. This thesis puts forth new knowledge regarding transcriptional regulation of the human versican gene. In chapter III, I present the cloning of a 752-bp fragment of the human versican promoter (- 634/+118 bp) and nine stepwise 5' deletion fragments in the PGL3-luciferase reporter plasmid. Furthermore, I identify three potential enhancer and two repressor regions in this promoter. I also demonstrate that both cAMP and C/EBPβ enhanced and repressed versican transcription in HeLa cells and rat aortic smooth muscle cells (SMC), respectively, suggesting that versican transcription is differentially regulated by the respective mediator and transcription factor in epithelial cells and SMC. In chapter IV, I reveal the role of PI3K/PKB/GSK-3β signaling pathway in regulating versican promoter activity and transcription. Furthermore, I identify that the β-catenin/TCF-4 transcription factor complex, one of the downstream targets of GSK-3β, mediates versican promoter activity and transcription. In chapter V, I identify that variations in C-terminal regions of TCF family members determine their repressor or enhancer properties on Wnt target genes. Furthermore, I show that curcumin is a strong inhibitor of the β-catenin/TCF-p300 mediated gene expression. In chapter VI, I demonstrate that the androgen receptor trans-activates versican transcription in prostate cancer cells. Furthermore, I show cross-talk between the androgen receptor and β-catenin in regulating versican transcription in prostate stromal fibroblasts. Overall, this study charts previously uncharacterized promoter elements, transcription factors, and signal transduction pathways involved in regulation of the versican gene. / Medicine, Faculty of / Pathology and Laboratory Medicine, Department of / Graduate

The process of encystation in the soil amoeba, Hartmannella rhysodes is a morphogenetic event. During morphogenesis the subcellular structure of the amoeba undergoes striking changes. The endoplasmic reticulum increases in amount, the mitochondria degenerate, lipid droplets accumulate and cytolysomes form. Two cyst walls are produced. These structural changes are correlated with physiological changes known to occur during encystation. / Science, Faculty of / Zoology, Department of / Graduate

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Thesis (M.S.)--University of Michigan, 1976.

Thesis (M.S.)--University of Michigan, 1976.

No description available.