Composition lipids

l Extraction and Measurement of Total Lipids Basic Protocol 1 Solvent Extraction of Oilseeds, Nutmeg, and Other Foods Dl.1.1 

2 Analysis of Fatty Acids in Food Lipids Basic Protocol 1 Preparation of Fatty Acid Methyl Esters from Lipid Dl.2.1 

6 Quantitation of Lipid Classes by Thin-Layer Chromatography with  

7 Infrared Spectroscopic Determination of Total Trans Fatty Acids Dl.7.1 

Approximately 95% of total lipids of LD from bovine heart are constituted by TAG. The amount of protein present in these LD is about 5% of total mass, and the amount of phospholipids varies from 3 to 7% of total lipid. The major phospholipids forming the monolayer of these LD are phosphatidylcholine (ca. 50%) and phosphatidylethanolamine (30-40%). The NEFA content is very low. The chemical composition of LD in beef heart with their high TAG content and the rather small amount of phospholipids resembles the composition of chylomicrons. A striking difference, however, is the lack of cholesterol and cholesteryles-ters in LD from beef heart whereas these lipid species occur at approximately 1-2% of total lipid in chylomicrons. Furthermore, the protein content of LD is two to three times higher than of chylomicrons. In contrast to bovine heart LD, those of stellate cells from the rat liver consist of retinylesters, TAG, free cholesterol and a small amount of phospholipids [142]. A general characteristic of LD regardless of the cell type appears to be the content of approximately 5% phospholipids of the total mass (reviewed in Ref. [143]). 

However, electron microscopy of conventional resin-embedded ultrathin sections cannot visualize any membranous structure around the LD. In the ultrathin section 

A phospholipid monolayer in the surface is consistent with the current model that LD are formed by TAG deposition between the two leaflets of the ER membrane and may remain connected to it [144, 145 see below]. Distribution of acyl-CoA cholesterol acyltransferase-1, a major enzyme that synthesizes cholesterylester, in the entire ER [148] seems to indicate that LD may bud anywhere along the membrane. However, Cap-LC/ESI mass spectrometry showed that FA moieties of phosphatidylcholine and lyso-phosphatidylchohne in LD are distinct from those in the rough ER [149]. The results do rule out the generation of the LD surface generated from the ER membrane but indicate that the former is a highly differentiated domain. Mature LD might be independent of the ER. Alternatively, the LD may be connected to the ER, but some molecular mechanism may demarcate the LD surface from the bulk ER membrane as postulated for other ER domains [150]. Whatever is true, TAG synthesized in wide areas of the ER do not deposit indiscriminately but are concentrated to loci specialized to make LD. ADRP or other LD-associated proteins may be involved (see below). 

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Mitochondria Mitochondria are organelles surrounded by two membranes that differ markedly in their protein and lipid composition. The inner membrane and its interior volume, the matrix, contain many important enzymes of energy metabolism. Mitochondria are about the size of bacteria, 1 fim. Cells contain hundreds of mitochondria, which collectively occupy about one-fifth of the cell volume. Mitochondria are the power plants of eukaryotic cells where carbohydrates, fats, and amino acids are oxidized to CO9 and H9O. The energy released is trapped as high-energy phosphate bonds in ATR... 

Cells adjust the lipid composition of their membranes to maintain proper fluidity as environmental conditions change. 

Sodium dodecyl sulfate has been used to induce a dry, scaly skin condition in human subjects by daily treatment with a 4% aqueous solution on one leg over a period of 2 weeks. Measurements were made of stratum comeum hydration, scaliness, and lipid composition which were used to assess in vivo surfactant perturbations on desquamation [381]. 

The mitochondrion has an outer and an inner membrane (Figure 1). The outer membrane contains pores formed from a protein, porin, which allow exchange of molecules with molecular weights up to about 2,000 between the cytosol and the intermembrane space. The inner membrane is extensively invaginated to increase its surface area. It has a different lipid composition from the outer membrane and is rich in the acidic phospholipid cardiolipin (diphosphatidyl-glycerol) which is only found in animal cells in mitochondria. Cardiolipin confers good electrical insulating properties on the inner membrane which is impermeable... 

The earliest morphological change in the sebaceous follicle is an abnormal follicular epithelial differentiation, which results in ductal hypercornification. Cornified cells in the upper section of the follicular canal become abnormally adherent. Comedones represent the retention of hyperproliferating ductal keratinoc-ytes in the duct. Several factors have been implicated in the induction of hyperproliferation sebaceous lipid composition, androgens, local cytokine production (IL-i, EGF) and bacteria (P. acnes). 

Several studies have been performed in order to investigate the effect of liposomal size (Hirano and Hunt, 1985), lipid composition (Senior and Gregoriadis, 1982 Hirano et al., 1985), and lipid dose (Ellens et al., 1983, Kim et al., 1987) on the fate of liposomes after intraperitoneal administration. In the size range studied (0.048-0.72 Min), no size-dependent absorption could be expected (Hirano and Hunt, 1985). Particles larger than 22.5 pm are not expected to enter the lymphatic capillaries (Allen, 1956). After intraperitoneal administration of multivesicular liposomes (19 + 7 ym), Kim and Howell (1987a) and Kim et al. (1987) showed that liposomal entrapment of Ara-C prolongs the half-Ufe of the drug in the peritoneal... 

Barza, M., Stuart, M., and Szoka, F. (1987). Effect of size and lipid composition on the pharmacokinetics of intravitreal liposomes, Invest. Ophthalmol. Visual Sci., 28, 893-900. 

Crommelin, D. J. A. (1984). Influence of lipid composition and ionic strength on the physical stability of liposomes, J. Pharm. Sci.. 73, 1559-1563. 

A. (1990b). Effect of lipid composition on the in vivo integrity of doxorubicin-containing liposomes. Two pathways for sustained release of doxorubicin. Submitted. 

In multiple sclerosis, which is a demyelinating disease, there is loss of both phospholipids (particularly ethanolamine plasmalogen) and of sphingolipids from white matter. Thus, the lipid composition of white matter resembles that of gray matter. The cerebrospinal fluid shows raised phospholipid levels. 

The lipid content of the membranes can be varied, allowing systematic examination of the effects of varying lipid composition on certain functions. For instance, vesicles can be made that are composed solely of phosphatidylchohne or, alternatively, of known mixtures of different phospholipids, glycohpids, and cholesterol. The fatty acid moieties of the lipids used can also be varied by employing synthetic lipids of known... 

Majd, S. and Mayer, M. (2005) Hydrogel stamping of arrays of supported lipid bilayers with various lipid compositions for the screening of drug-membrane and protein-membrane interactions. Angew. Chem. Int. Ed., 44, 6697-6700. 

The fate of injected liposomes is drastically altered by administration route, dose and size, lipid composition, surface modification, and encapsulated drugs. Liposomes encapsulating drugs are often administered iv, therefore, the stability of liposomes in plasma is important. When liposomes composed of PC with unsaturated fatty acyl chains are incubated in the presence of serum, an efflux of internal solute from the liposomes is observed. This increase in permeability is caused by the transfer of phospholipids to high density lipoprotein (HDL) in serum (55). To reduce the efflux of liposomal contents, cholesterol is added as a liposomal component... 

The half-life of liposomes administered in the blood stream is affected by the composition, size, charge, and fluidity. Liposomes with a small size or with a rigid lipid bilayer have a longer half-life (38 9). Large liposomes administered iv tend to accumulate at a lymph node near the injected site. This tendency can be useful for preventing metastases. Liposomes which pass through the lymph node have a tendency to accumulate in the RES, such as the liver and spleen (40,41). The disposition of liposomes is altered by the dose of liposomes as well as size or lipid composition of liposomes. Cholesterol rich liposomes are cleared slower due to... 

Sugano et al. [561,562] explored the lipid model containing several different phospholipids, closely resembling the mixture found in reconstituted brush border lipids [433,566] and demonstrated dramatically improved property predictions. The best-performing lipid composition consisted of a 3% wt/vol lipid solution in 1,7-octadiene (lipid consisting of 33% wt/wt cholesterol, 27% PC, 27% PE, 7% PS, 7% PI). The donor and acceptor compartments were adjusted in the pH interval between 5.0 and 7.4 [562]. With such a mixture, membrane retention is expected to be extensive when lipophilic drugs are assayed. The use of 1,7-octadiene in the assay was noted to require special safety precautions. 

Different tissues have different lipid compositions. The most common lipid components of membranes are PC and PE. Lipid extracts from brain and lung are also rich in PS heart tissue is rich in PG, and liver is rich in PI [567]. Human blood cells, as ghost erythrocytes (with cytoplasm contents removed), are often used as membrane models. These have different compositions between the inner and outer leaflets of the bilayer membrane. Phospholipids account for 46% of the outer leaflet membrane constituents, with PC and Sph about equal in amount. The inner leaflet is richer in phospholipids (55%), with the mix 19% PE, 12% PS, 7% PC and 5% Sph [567],... 

The increase of negative charge from 0.6% to 1.1% wt/vol in dodecane (modeling the expected increase between BBM and BBB lipid compositions see Table 7.1) shows further increases to the permeabilities of the dramatically affected molecules, especially amiloride, which becomes effectively more permeable than piroxicam. 

Cells Binding, adsorption, partitioning Physical dimensions Metabolism Monolayer integrity Membrane domain characteristics (polarity) surface area transporters, receptors lipid composition charge Cell phenotype and culture conditions... 

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