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It has been suggested that membrane characteristics associated with carcinomas could be related to an altered molecular structure of lipids in the plasma membrane. The microsomal fraction, mitochondria and soluble fractions of the cell are major sites of de novo synthesis and elongation of fatty acids. It was the purpose of this study to compare the utilization of AcSCoA in the biosynthetic pathway for saturated fatty acids in tumor and normal tissue, and discern if any deviations in the initial steps of the pathway were responsible forr the observed differences in the plasma membrane of tumors. Labeled 14C-AcSCoA was incorporated into saturated fatty acids in both adenocarcinomas and normal mammary tissue. The distribution and degree of incorporation of labeled 14C-AcSCoA was hoped to demonstrate any deviations in the pathway.Crude supernate, microsomal fraction, mitochondria and soluble fractions were isolated from mammary adenocarcinomas and from normal mammary tissue of Strain A female mice by differential centrifugation. The activity of fatty acid synthetase in the soluble fraction was determined. The crude supernate, the soluble fraction, the mitochondria + soluble fraction and the microsomal fraction + soluble fraction of both the adenocarcinoma and normal mammary tissue were incubated with labeled 14C-AcSCoA, Ma1SCoA and all necessary cofactors. The now labeled fatty acids were extracted from these incubation mixtures. The total percent of incorporated labeled 14C-AcSCoA in each fraction was determined. The percent of incorporation of label into individual saturated fatty acids in each fraction was determined by gas liquid chromatography and liquid scintillation counting. Carrier mixtures of known fatty acids were added to the samples used for GLC analysis to confirm the identity of the labeled fatty acids.Results of this study show that the percent of labeled i4C-AcSCoA incorporated into the various saturated fatty acids was similar in tumor and normal tissue. However, the total uptake of AcSCoA was nearly twice as great in normal tissue. The activity of fatty acid synthetase appearsto be characteristic of each individual mouse. In tumored mice fatty acid synthetase activity appears to be related to tumor weight, that is the larger the tumor the greater the activity. These results do not demonstrate support for a shift in the biosynthesis of saturated fatty acids in carcinomas. It may be that the altered lipid composition of the plasma membrane of tumor cells arises from the carcinoma's ability to utilize exogenous fatty acids.

Thesis (M.Phil.)--Chinese University of Hong Kong. / Bibliography: leaves 73-84.

The class B scavenger receptor CD36, or fatty acid translocase (FAT), is an 88 kDa plasma membrane glycoprotein that is the founding member of the class B scavenger receptor family. It has a number of natural ligands and has different functions at various locations in the body. It contributes to adhesion of platelets via its binding to thrombospondin-1. In monocytes and macrophages, it contributes to recognition and phagocytosis of apoptotic cells and it mediates the binding and uptake of oxidatively damaged low-density lipoproteins (oxLDL). In adipose and muscle tissues, FAT/CD36 mediates high-affinity binding and uptake of long-chain fatty acids (LCFAs) and is therefore a key regulator of lipid storage (particularly in adipocytes) and mitochondrial beta oxidation (particularly in muscle). Interestingly FAT/CD36 also binds native lipoproteins (including high-density lipoproteins [HDL]) with high affinity in vitro, although the physiological significance of this is unclear at present. Expression of FAT/CD36 by hepatocytes has not been recognised until recently, mainly because it is gender-regulated in both humans, and rats. However, the primary function of FAT/CD36 in the liver is unknown. The work described in this thesis has used various transfected cell lines to examine the possibility that FAT/CD36 contributes to hepatic LCFA uptake and/or the uptake of cholesteryl esters (and other lipids) from HDL. The subcellular localization of FAT/CD36 has been explored in rat liver and in cell lines of hepatic and non-hepatic origin, especially with respect to its association with specialized plasma membrane lipid raft microdomains known as caveolae. Furthermore, the importance of the cytoplasmic carboxyl-terminus of FAT/CD36 in both subcellular localization of the molecule and its activity as a LCFA transporter has been examined using truncated mutants and chimeric variants of FAT/CD36. The results indicate that FAT/CD36 contributes to LCFA uptake by hepatocyte-derived cell lines. In these cells it resides in both non-raft and lipid raft domains of the plasma membrane that may not always include caveolae. The studies also indicate that the cytoplasmic C-terminus of FAT/CD36 contributes to the attachment of FAT/CD36 to membranes, including raft-derived detergent-resistant membranes. This domain is necessary also for correct targeting of the receptor to the plasma membrane and for its activity as a LCFA transporter. Finally, DNA constructs have been prepared and tested, with the objective of producing transgenic mice in which expression of FAT/CD36 can be induced and over-expressed specifically in the liver. This model could be used to confirm whether FAT/CD36 has a role as a LCFA transporter in the liver and to explore whether it has additional significance as a hepatic transporter of HDL-derived cholesteryl esters or as a scavenger of oxidised LDL. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1294862 / Thesis (Ph.D.) -- School of Molecular and Biomedical Science, 2007

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 101-107). Also available on the World Wide Web.