Changes in the plasma membrane phospholipid composition may alter the structure and/or fluidity and lead to a variety of changes in membrane functions. Dietary fats are known to influence the composition of lipids in the plasma membrane. The purpose of this investigation was to compare effects of dietary linoleic and stearic acid on the composition of the phospholipids in the plasma membranes of mammary tumors in A/St mice.Plasma membranes were isolated and lipids were extracted. Phospholipids were separated by thin-layer chromatography and identified by detection with molybdenum blue reagent. The Rf values and integration of optical densities were used to compare phospholipid composition in membranes of tumors from mice fed experimental diets. It appears that the amount of dietary fat, but not the type, affects the phospholipid distributions. The phosphatidylinositol was the phospholipid most affected, representing the smallest amount in membranes from tumors in mice fed the low fat diets. / Department of Biology

It has been suggested that plasma membranes play a role in tumor production. Changes in plasma membrane lipid composition may change membrane fluidity and disrupt cellular communication. These changes in membrane lipid composition appear to be related to the fatty acid content of the animal's diet. The purpose of this investigation was to compare the effect of dietary linoleic and stearic acids and tumor size on cholesterol/phospholipid ratios and fatty acids in membranes of mammary adenocarcinomas.Plasma membranes of mammary tumors from Strain A/St mice were isolated by centrifugation and the lipids extracted. Phospholipid content was assayed by the method of Bartlett (102); cholesterol and fatty acids by gas liquid chromatography.Plasma membranes of tumors from mice fed the high linoleic diet (SAFF) were found to have the highest cholesterol/phospholipid ratios (Mean=0.396); mice fed high stearic acid diets produced tumors with the lowest ratios (0.280). Membranes of tumors from mice fed SA-4 and Stock diets had intermediate ratios (0.0.341 and 0.0.346, respectively). / Department of Biology

The possibility that changes in membrane transport systems may contribute to the pathophysiology of the uraeraic syndrome has not been extensively studied. This thesis presents a study of eight erythrocyte membrane transport systems, namely the Na/K pump, the amino acid systems y⁺, ASC, gly, L and T, the nucleoside and choline transporters. The results indicate that, compared to normal controls, K⁺ flux through the Na/K pump was reduced in chronic renal failure patients (CRF), on haemodialysis (HD), and on continuous ambulatory peritoneal dialysis (CAPD), but was normal in functional transplant (FT) patients' erythrocytes. The number of Na/K pumps per erythrocyte was decreased in CRF and CAPD but showed no differences between HD, FT and Normal controls. The mean turnover rate per pump site was reduced in patients on HD, whereas other groups were not significantly different from controls. Cross-incubation experiments suggest that the lowered pump flux seen in the HD group was due to plasma factors since reversibility of the defect was achieved when those cells were incubated in normal plasma. The defect was completely reversed with a successful transplant. Erythrocytes from haemodialysis patients exhibited an increased uptake of L-lysine through the y⁺ system. The uptake of L-serine was decreased and the affinity of the ASC system for L-serine was increased in these patients compared with controls. The glycine transporter showed a significant increase in affinity for glycine. The flux of L-leucine and L-tryptophan showed no differences from control cells. Erythrocyte membrane transport of uridine was similar in normal control cells and in those obtained from uraemic patients. Choline influx rates were significantly increased and affinity of the transporter for choline reduced in dialysis patients' erythrocytes. Renal transplant and CRF patients showed variable influx rates which gave a significant negative correlation with creatinine clearance. These results show that there are selective abnormalities in some membrane transport system of the erythrocyte in patients with renal failure. The mechanism and possible significance of these changes are discussed.