Membrane cholesterol content

Chin, J.H., and D.B. Goldstein. 1997. Membrane disordering action of ethanol Variation with membrane cholesterol content and depth of the spin label probe. Mol Pharmacol 13 435. 

The fluidization and increase in permeability of tumor cell membranes has been reported [43, 44], as well as changes in cellular lipid synthesis during ether phospholipid-induced cytolysis [45]. Direct evidence was found by Diomede et al. [46] and Principe et al. [47] for the importance of the lipid composition of membranes for the sensitivity to antineoplastic ether phospholipids. These authors studied the influence of tumor cell membrane cholesterol content on the sensitivity of leukemic cells [46] and cells derived from three human carcinomas [47] with different rates of cell... 

Cholesterol and phospholipids. Most lipids found in myelin are common to other cellular membranes. Cholesterol content is high and cholesterol esters are not present in normal myelin. Phospholipids are also common to other cellular membranes, except for the great quantity of ethanolamine phosphoglycerides in the plasmalogen form. The synthesis of plasmalogens is modified in Zellweger syndrome which is a peroxisomal syndrome that also increases VLCFA. This syndrome and other peroxisomal diseases may cause demyelination (Powers, 2005). 

While an increase in the membrane cholesterol content may be linked with an increase in the number of thrombin receptors, flie changes in platelet My acid composition, which also affects mettibrane fluidity, do not affect binding of thrombin or yohimbin to platelets (79). It has been suggested that changes in My acid composition in SHR platelet rttembranes leading to changes in microenvironment fluidity may be a possible cause of... 

Abramov AY, Ionov M, Pavlov E, Duchen MR. Membrane cholesterol content plays a key role in the neurotoxicity of P-amyloid impUcations for Alzheimer s disease. Aging Cell. 2011 10(4) 595-603. 

Michal P, Rudajev V, El-Fakahany EE, Dolezal V. Membrane cholesterol content influences binding properties of muscarinic M2 receptors and differentially impacts activation of second messenger pathways. EurJ Pharmacol. 2009 606(l-3) 50-60. 

Ray et al. studied the different cytotoxic effects for a number compormds, including various tributyltin halobenzoates on human leukemic K562 cells. They also studied the role of extraceUrrlar calcium ion influx and ROS formation in inducing apotosis in this cell line. Human breast cancer MCF-7 cells were also employed in the studies. The R562 has a low membrane cholesterol content, while the MCF-7... 

Proulx [30] summarized the published lipid compositions of BBM isolated from epithelial cells from pig, rabbit, mouse and rat small intestines. Table 3.1 shows the lipid make-up for the rat, averaged from five reported studies [30], On a molar basis, cholesterol accounts for about 50% of the total lipid content (37% on a weight basis). Thus, the cholesterol content in BBM is higher than that found in kidney epithelial (MDCK) and brain endothelial cells (Table 3.1). Slightly different BBM lipid distribution was reported by Alcorn et al. [31] here, the outer (luminal) leaflet of the BBM was seen to be rich in sphingomyelin content, while the inner leaflet (cytosol) was rich in PE and PC. Apical (brush border) and basolateral lipids are different in epithelia. The basolateral membrane content (not reported by... 

An important question arises about the effects of phospholipid composition and the function of membrane-bound enzymes. The phospholipid composition and cholesterol content in cell membranes of cultured cells can be modified, either by supplementing the medium with specific lipids or by incubation with different types of liposomes. Direct effects of phospholipid structure have been observed on the activity of the Ca2+-ATPase (due to changes in the phosphorylation and nucleotide binding domains) [37]. Evidence of a relationship between lipid structure and membrane functions also comes from studies with the insulin receptor [38]. Lipid alteration had no influence on insulin binding, but modified the kinetics of receptor autophosphorylation. 

Bolard J, Seigneuret M, Boudet G. Interaction between phospholipid bilayer membranes and the polyene antibiotic amphotericin B lipid state and cholesterol content dependence. Biochim Biophys Acta 1980 599 280. 

The fluidity of membranes primarily depends on their lipid composition and on temperature. At a specific transition temperature, membranes pass from a semicrystalline state to a more fluid state. The double bonds in the alkyl chains of unsaturated acyl residues in the membrane lipids disturb the semicrystalline state. The higher the proportion of unsaturated lipids present, therefore, the lower the transition temperature. The cholesterol content also influences membrane fluidity. While cholesterol increases the fluidity of semicrystalline, closely-packed membranes, it stabilizes fluid membranes that contain a high proportion of unsaturated lipids. 

The solubility of cholesterol in bile is determined by the relative proportions of bile acids, lecithin, and cholesterol. Although prolonged ursodiol therapy expands the bile acid pool, this does not appear to be the principal mechanism of action for dissolution of gallstones. Ursodiol decreases the cholesterol content of bile by reducing hepatic cholesterol secretion. Ursodiol also appears to stabilize hepatocyte canalicular membranes, possibly through a reduction in the concentration of other endogenous bile acids or through inhibition of immune-mediated hepatocyte destruction. 

Brown, M.S., Goldstein, J.L. (1999) A proteolytic pathway that controls the cholesterol content of membranes, cells, and blood. Proc. Natl. Acad. Sci. USA 96, 11,041-11,048. 

Many of the proteins of membranes are enzymes. For example, the entire electron transport system of mitochondria (Chapter 18) is embedded in membranes and a number of highly lipid-soluble enzymes have been isolated. Examples are phosphatidylseiine decarboxylase, which converts phosphatidylserine to phosphatidylethanolamine in biosynthesis of the latter, and isoprenoid alcohol phosphokinase, which participates in bacterial cell wall synthesis (Chapter 20). A number of ectoenzymes are present predominantly on the outsides of cell membranes.329 Enzymes such as phospholipases (Chapter 12), which are present on membrane surfaces, often are relatively inactive when removed from the lipid environment but are active in the presence of phospholipid bilay-ers.330 33 The distribution of lipid chain lengths as well as the cholesterol content of the membrane can affect enzymatic activities.332... 

As expected, due to the small headgroup area of cholesterol (Achol = 40 A2, while ADOpc = 72 A2) [40, 41], the membrane charge density of DOTAP/DOPC/ Chol-DNA complexes increases with cholesterol content. Exchanging DOPC for cholesterol reduces the total membrane area while the membrane charge, given by dotap = 0-3, remains constant thus cM increases. A particularly strong increase in cM occurs for Choi > 0.4, where part of the cholesterol is not incorporated in the complex. This results in an increased <2>DOTap and thus aM. 

TE of the DOTAP/DOPC/Chol-DNA complexes strongly deviates from the universal bell-shaped curve observed for binary systems. The TE of cholesterol-containing complexes increases more rapidly with increasing cholesterol content than the increase in membrane charge density predicts for 0 < 4>chol < 0.4. No further TE increase is seen for 4>chol > 0.4 (where the membrane is saturated with cholesterol [Pg.201]

Wodtke, E. (1978). Lipid adaptation in liver mitochondrial membranes of carp acclimated to different environmental temperatures. Phospholipid composition, fatty acid pattern and cholesterol content. Biochimica etBiophysicaActa 529,280-291. 

FIGURE 6.4. (a) An epifluorescence image of a 4 x 4 membrane array, (b) A quantitative plot of fluorescence intensity vs. cholesterol content at each DNP ligand concentration. 

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