Thesis (Ph. D.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 106-112).

Investigations were carried out on the role of glucagon and calcium in the regulation of hepatic phospholipid biosynthesis. It was found that glucagon inhibits de novo phosphatidylcholine biosynthesis in cultured rat hepatocytes. This inhibition was associated with an inhibition of CTP:phosphochocline cytidylyltransferase activity, which is the regulatory enzyme for phosphatidylcholine biosynthesis. Calcium was shown to inhibit the uptake of choline in hepatocytes by decreasing the Vmax of the saturatable uptake system. It also slightly inhibited the rate of phosphatidylcholine biosynthesis by the de novo pathway, but not by the N-methylation of phosphatidylethanolamine. However, these experiments were difficult to interpret due to the use of ionophore A23187 to vary cytosolic calcium concentrations. This ionophore has many other effects on hepatocytes which could indirectly alter the synthesis of phosphatidylcholine. In vitro studies were carried out to determine the effect of calmodulin on CTP:phosphocholine cytidylyltransferase activity. Although calmodulin did not effect the activity under the conditions of the assay, an impurity of some calmodulin preparations was found which inhibited the cytidylyltransferase in a calcium independent fashion. The inhibitor had some peptide like properties. The effect of calcium on the incorporation of[3- ³H] serine into phospholipids was also investigated. Calcium was found to increase the amount of label recovered in phospholipid. It was also found that,the label was rapidly transfered from phosphatidyserine to phosphatidylethanolamine. On the basis of these results, a model is presented for the relationships between calcium and phosphatidylserine metabolism. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

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Lipid systems containing charged species are examined by both experiment and theory. Experimental studies of the mixing of phosphatidylcholine or phosphatidylethanolamine with phosphatidic acid show that calcium induces fast ($ leq$1s) phase separation of these otherwise miscible systems, and that this can occur in an isolated bilayer. Ionogenic behaviour is theoretically investigated using a new electrolyte model which explicitly includes both the solvent and particle sizes, and a binding model which uses Guggenheim combinatorics to treat non 1-1 binding stoichiometries. This work predicts a reduced dielectric constant near charged surfaces and strong repulsive forces between closely spaced ($<$15A) surfaces. A reanalysis of data from charged monolayers experiments indicates (1) that the new electrolyte model describes double layer behaviour at high surface charge densities better than the traditional Derjaguin - Landau - Verwey - Overbeek (DLVO) theory, (2) that calcium and magnesium bind to phosphatidylserine monolayers with a 1-1 stoichiometry.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Also available in print.

Thesis (Ph. D.)--Oregon State University, 1965. / Typescript. Includes bibliographical references (leaves 121-125). Also available on the World Wide Web.

Thesis--Université de Liège. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. 316-334).

Thesis--Université de Liège. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. 316-334).