Lipid-rich particles

Plasma lipoproteins are usually classified according to their density (Chapter 17). Since the buoyant density of lipids is lower than that of proteins, lipoproteins with a high ratio of lipid to protein have a lower density than lipoproteins with a low ratio of lipid to protein. Electron micrographs of the major classes of plasma lipoproteins are shown in Fig. 2. CM the largest and most lipid-rich particles, whose major lipid component is TG, are secreted by the intestine and are abundant in plasma only after a meal. VLDLs are also rich in TG and are secreted mainly by the liver, although some are of intestinal origin. 

Pheromone (sex attractant). Ether extract of the stem, produced equivocal effect on Aspiculuris tetraptera, female and male Dacus dorsalis, male Mediterranean fruit flies, and male and female melon flies " k Pheromone (signaling). Ether extract of the stem, produced equivocal effect on Aspiculuris tetraptera, female and male Dacus dorsalis, male Mediterranean fruit flies, and male and female melon flies " k Phospholipidemic effect. Oil, administered to phospholipids transfer protein knockout (PLTPO)-deficient mice, produced an increase of phospholipids and free cholesterol in the VLDL-LDL region of PLTPO mice. Accumulation of phospholipids and free cholesterol was dramatically increased in PLTPO/HLO mice compared to PLTPO mice. Turnover studies indicated that coconut oil was associated with delayed catabolism of phospholipids and phospho-lipids/free cholesterol-rich particles. Incubation of these particles with hepatocytes of coconut-fed mice produced a reduced removal of phospholipids and free cholesterol by SRBI, even though SRBI protein expression levels were unchanged . 

Chylomicrons transport dietary triacylglycerol and cholesteryl ester from the intestine to other tissues in the body. Very-low-density lipoprotein functions in a manner similar to the transport of endogenously made lipid from the liver to other tissues. These two types of triacylglycerol-rich particles are initially degraded by the action of lipoprotein lipase, an extracellular enzyme that is most active within the capillaries of adipose tissue, cardiac and skeletal muscle, and the lactating mammary gland. Lipoprotein lipase catalyzes the hydrolysis of triacylglycerols (see fig. 18.3). The enzyme is specifically activated by apoprotein C-II, which... 

PAHs have been found all over the globe in all compartments of the environment. They are ubiquitous because the are persistent. Recalcitrance in PAHs may stem, in part, from the delocalized electrons in the planar pi orbitals of the aromatic structure. Their relatively high octanol-water partition coefficients, Kows, make them rather lipophilic. The lipophilicity of PAHs forces them from the dissolved phase to particles and also into lipid rich organisms, but they can be metabolized in higher organisms. However, these metabolites are often more toxic than their parent PAHs. When combined with other stressors, particularly ultraviolet radiation, PAHs can exert enhanced toxicity. 

Wakeham, S.G., Cowen, J.P., Burd, B.J. and Thomson, R.E. (2001) Lipid-rich ascending particles from die hydrothermal plume at Endeavour Segment, Juan de Fuca Ridge. Geochimica et Cosmochimica... 

Each newly synthesized intestinal apo B-containing lipoprotein particle (chylomicron) consists of a core lipid droplet rich in TG, surrounded by a monolayer made up mainly of protein, phospholipids, and cholesterol. The chylomicron lipid core contains a small amount of CE. The lipids of TG-rich particles are in a dynamic equilibrium where each lipid can exchange rapidly between the surface and core. As a result, while the great majority of TG is in the core, the surface contains a small but rapidly replenished pool ofTG which is the direct substrate of the plasma lipases responsible for chylomicron metabolism in the circulation. 

Apo A1 recycles extracellularly between lipid-poor (pre-beta-migrating) and lipid-rich (spheroidal) species (Fig. 7). Each spheroidal apo A1 particle transports multiple lipid loads from peripheral tissues to the liver. In contrast other lipid-binding proteins (e.g., apo B and apo E) are cleared by hepatocytes as part of whole lipoprotein particles. 

One of the lipid abnormalities that has been associated with T2DM is an increased plasma TG levels [60,61], Most fasting plasma TG is carried in the form of very low-density lipoprotein (VLDL) [62,63], Increased secretion of VLDL by the liver, and decreased clearance of VLDL and intestinally derived chylomicrons result in prolonged plasma retention of TG-rich particles in the plasma that lead to the accumulation of TG-rich lipoproteins. Studies by Chisolm and cowoikers [64] as well by Henriksen et al. [65] over 4 decades showed that diabetic serum was toxic to cells and such toxicity could be inhibited by antioxidants. They also showed most of the toxicity resided in the TG-rich lipoproteins. 

Weinberg RB, Spector MS (1985) Human apolipoprotein A-IV displacement from the surface of triglyceride-rich particles by HDl -assodated C-apoproteins. J Lipid Res 26 26-37... 

Cholesterol-rich lipoprotein particles that carry dietary lipids absorbed in the intestine and deliver them to the liver for uptake. 

An attractive way to overcome this problem is to use microheterogeneous photocatalytic systems based on lipid vesicles, i.e. microscopic spherical particles formed by closed lipid or surfactant bilayer membranes (Fig. 1) across which it is possible to perform vectorial photocatalytic electron transfer (PET). This leads to generation of energy-rich one-electron reductant A" and oxidant D, separated by the membrane and, thus, unable to recombine. As a result of such PET reactions, the energy of photons is converted to the chemical energy of spatially separated one electron reductant tmd oxidant. 

A higher PL TG ratio in the 10% lipid emulsion has been proposed to cause the appearance of the abnormal lipoprotein X particles [rich in phospholipids (-60%) and cholesterol (-25%), small amounts of triglycerides] in the blood.9,35 Lipoprotein X... 

The typical cream, a soft, emulsified mass of solidified particles in an aqueous, micelle-rich medium, does not form a water-impermeable (occlusive) film on the skin. Nevertheless, creams contain lipids and other moisturizers that replace substances lost from the skin in the course of everyday living. Creams thus make good emollients because, by replenishing lipids and in some instances also polar, hygroscopic substances,... 

The best-known effect of APOE is the regulation of lipid metabolism (see Fig. 10.13). APOE is a constituent of TG-rich chylomicrons, VLDL particles and their remnants, and a subclass of HDL. In addition to its role in the transport of cholesterol and the metabolism of lipoprotein particles, APOE can be involved in many other physiological and pathological processes, including immunoregu-lation, nerve regeneration, activation of lipolytic enzymes (hepatic lipase, lipoprotein lipase, lecithin cholesterol acyltransferase), ligand for several cell receptors, neuronal homeostasis, and tissue repair (488,490). APOE is essential... 

Lipoprotein metabolism. Entero-cytes release absorbed lipids in the form of triglyceride-rich chylomicrons. Bypassing the liver, these enter the circulation mainly via the lymph and are hydrolyzed by extrahepatic endothelial lipoprotein lipases to liberate fatty acids. The remnant particles move on into liver cells and supply these with cholesterol of dietary origin. 

Solidification of the particles may not be the final step in the formation process of solid lipid particles. Lipidic materials exhibit rich polymorphism [69,70], which may also occur in the dispersed state. In nanoparticles, the polymorphic behavior of the matrix lipids may, however, differ distinctly from that in the bulk material. Polymorphic transitions are usually accelerated in the nanoparticles compared with the bulk lipids [2,62]. In some cases, polymorphic forms not observable in the corresponding bulk materials were detected in lipid nanoparticles [1,65]. Because polymorphism can affect pharmaceutically relevant properties of the particles, such as the drug incorporation capacity [65], corresponding investigations should also be included in the characterization process. As long as polymorphic or other crystalaging phenomena have not terminated, the particle matrix cannot be regarded as static, and alterations of the particle properties may still occur. 

Cardiovascular heart diseases (CHD) are considered as the clinical expression of advanced atherosclerosis. One of the initial steps in atherogenesis is the oxidative modification of LDL and the uptake of the modified lipoprotein particles by macrophages, which in turn become lipid laden cholesterol-rich cells, so-called foam cells [159]. An accumulation of foam cells in the arterial wall is the first visible sign of atherosclerosis and is termed fatty streak, the precursor to the development of the occlusive plaque [160]. It is well known that oxidation of LDL can be initiated in vitro by incubating isolated LDL particles with cells (macrophages, lymphocytes, smooth muscle cells, or endothelial cells), metal ions (copper or iron), enzymes, oxygen radicals, or UV-light. However less is known about the mechanisms by which... 

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