Cholesterol phospholipids

Cholesterol-phospholipid-lipoprotein liquid crystal phase, 15 112 Cholestyramine, 14 420... 

MD simulations have provided a unique molecular description of cholesterol-phospholipid interactions [31]. Atomistic simulations have succeeded in reproducing the condensing effect of cholesterol on phospholipid bilayers [32-34], With atomistic detail, many properties can be determined, such as the effect of cholesterol on lipid chain ordering or on hydrogen bond formation. Other simulations have focused on the interaction of cholesterol and SM [35-37], Aittoniemi et al. [38] showed that hydrogen bonding alone cannot explain the preferential interaction between cholesterol and SM compared to cholesterol and POPC. 

McMullen, T.P.W., Lewis, R.N.A.H., McElhaney, R.N. Cholesterol-phospholipid interactions, the liquid-ordered phase and lipid rafts in model and biological membranes. Curr. Opin. Colloid Interface Sci. 2004, 8, 459-68. 

Lipoproteins have a spherical core of neutral lipids, such as cholesteryl esters and triacylglycerols, which is coated with unesterifed cholesterol, phospholipids, and apoUpoproteins. 

Lipoproteins have hydrophobic core regions containing cholesteryl esters and triglycerides surrounded by unesterified cholesterol, phospholipids, and apoproteins. Certain lipoproteins contain very high-molecular-weight proteins that exist in two forms B-48, formed in the intestine and found in chylomicrons and their remnants and B-lOO, synthesized in liver and found in VLDL, VLDL remnants(IDL),LDL (formed from VLDL), and Lp(a) lipoproteins. HDL consist of at least 15 discrete molecular species. All species contain apolipoprotein A-I (apoA-I). Fifty-three other proteins are known to be distributed variously among the HDL species. 

In adipose tissue, TAG is stored in the cytosol of the cells in a nearly anhydrous form. It serves as "depot fat," ready for mobilization when the body requires it for fuel. Little TAG is stored in the liver. Instead, most is exported, packaged with cholesteryl esters, cholesterol, phospholipid, and protein (apolipoprotein B-100, see p. 229) to form lipoprotein particles called very low density lipoproteins (VLDL). Nascent VLDL are secreted into the blood where they mature and function to deliver the endogenously-derived lipids to the peripheral tissues. [Note Recall that chylomicrons deliver primarily dietary (exogenously-derived) lipids.] Plasma lipoproteins are discussed in Chapter 18, p. 225. 

Along with the C.fcr-hydroxyl group, bile acids may contain a hydroxy] at C7a. at Cl 2a, and at other positions. Bile salts, cholesterol, phospholipids, and other minor components arc secreted by the liver. 

It is generally believed that the mechanism of bioavailability enhancement by CD complexation is through solubility and dissolution rate improvement. However, it should be also noted that CDs might also alter the lipid barrier of the absorption site, which may contribute to the enhanced drug absorption. This effect of CDs on the lipid barrier can be attributed to CDs ability to form complexes with membrane components such as cholesterol, phospholipids, and proteins (Nakanishi et al., 1992). Jambhekar et al. (2004) compared the solubilizing effeqte D, HP-ft-CD, and H -CD on IM. 

Full fat milk contains about 3% fat and triacylglycerols account for about 95% of the lipid fraction. Other components of the lipid fraction are diacylglycerols, cholesterol, phospholipids, and free fatty acids. The lipid structures contain many fatty acids from all major classes, that is, saturated, monounsaturated, and polyunsaturated fatty acids (Haug et al., 2007). More than 60% of the fatty acids in cow s milk and consequently in dairy products are saturated, including shorter and medium... 

Wistar) (GO) cholesterol, phospholipids, 31% increase in liver weight) Robinson 1964... 

PBS and gently blotted to remove blood and tissue fluids, then suspended over the lip of a small (250 pi) microcentrifuge tube and punctured with a needle to allow the bile to drain into the tube. Store frozen until assay. There is usually enough material to measure lipid composition (bile acids, cholesterol, phospholipids) with standard colorimetric kits (<1 pi needed for each assay). In addition to biliary cholesterol levels, it is important to take note of bile salt concentrations, since these are the detergents which suspend dietary lipids in micelles and deliver them to the intestinal epithelium for absorption by enterocytes. Differences in bile salt concentration alone could lead to differences in cholesterol absorption. 

We then examined the effect of phospholipid composition on the transfection activity. Liposomes containing various combinations of phospholipids were tested for transfection activity on BHK-21 and HeLa-S3 cells. As described in HVJ-AVE liposomes, the cationic liposomes containing all of ePC, DOPE, and eSph in equal molar amounts showed the highest transfection efficiency both with BHK-21 and HeLa-S3 cells. The same results were obtained with Ltk-, HEK 293, and NB-1 cells. We also examined other phospholipids, but none was observed to be more effective. We then examined the effect of the cholesterol/phospholipid ratio on the transfection efficiency. The phospholipid composition (ePC DOPE eSph = 1 1 1) and DC-Chol content (10% of total... 

Bile is a mixture of electrolytes, bile acids, cholesterol, phospholipids and bilirubin. Adults produce between 400 and 800 ml of bile daily. Hepatocytes secrete bile into canaliculi, then into bile ducts, where it is modified by addition of a bicarbonate-rich secretion from ductal epithelial cells. Further modification occurs in the gall bladder, where it is concentrated up to fivefold, through absorption of water and electrolytes. Gallstones, most of which are composed... 

Bile is produced by hepatocytes from several essential components, including water, bile acids, cholesterol, phospholipids and bilirubin. Most of these substances are absorbed in the distal ileum and delivered to the hepatocyte via the portal vein. The liver excretes approximately 500-600 mL of bile each day, most of which is stored in the gallbladder. Bile acids have an important function in emulsifying lipids in the digestive tract, which improves digestion by pancreatic lipases. 

The liver is central to both lipid and lipoprotein metabolism and homeostasis. There are three major plasma lipids cholesterol, phospholipids and triglycerides. All are highly insoluble in water. 

Bile is a complex fluid containing 95% water, electrolytes and organic molecules, including bile acids/salts, cholesterol, phospholipids and conjugated bilirubin that flows through the biliary tract into the small intestine (Table 2.6). 

Synthesis and metabolism of cholesterol, phospholipids, triglycerides and lipoproteins. 

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