Phospholipids in plasma

The solvent chloroform-methanol-water (65 + 25 + 4), described by Wagner et al. [175] has foimd extensive apphcation in the thin-layer chromatographic separation of serum phospholipids on silica gel 6 layers. Habebmann and co-workers [67] have published in this connection a method for quantitative determination of the single phospholipid fractions. The methods so far known for separating phospholipids fractionate them only into groups of compounds this contrasts with the TLC of cholesteryl esters, where separation into individual substances is possible. The results hitherto obtained are summarised in Table 124. 

Serum from n mg- % Total Phospholipid % Cepha- lin 1 % Leci- thin % Sphin- gomye- lin % Lysolec ithin References 

Carbohydrate-induced hyper-lipaemia 1 390 7.4 75.0 9.7 7.9 Christian and co-workers [23] 

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In blood, phosphatidylcholine is quantitatively the most important phospholipid. Sphingomyelin is present in varying amounts in perhaps all of the animal organs, most of it in the soft organs, and to a lesser degree in skeletal muscles and eggs (4). Total blood contains about 0.2% to 0.3% phospholipids. In plasma and serum, phosphatidylcholine predominates, whereas in corpuscles, phosphatidylethanolamine and sphingomyelin constitute the bulk of phospholipids. Most workers have found... 

By comparison of the adsorption behavior of phospholipids on MPC copolymers with that of proteins, a mechanism of nonthrombogenicity observed on MPC copolymers is considered as shown in Fig. 7 (77). Since the molecular size of phospholipids is smaller than that of proteins and the molar concentration of phospholipids is larger than that of proteins, the diffusion of phospholipid molecules from plasma to the polymer surface occurs more easily than that of proteins. Moreover, the MPC copolymers have both a strong affinity for phospholipids (5,72-74) and protein adsorption-resistant properties in buffered aqueous protein solution (70,75,7(5). From these findings, it is concluded that the phospholipids in plasma are adsorbed immedi-... 

Kasamo K, Nouchi I. The role of phospholipids in plasma membrane ATPase activity in Viqna radiata L. (mung bean) roots and hypocotyls. Plant Physiol. 1987 83 323-328. 

New concepts for making blood compatible polymer materials have been proposed based on the characteristics of natural phospholipid molecules in plasma. It was considered that if a polymer surface possesses a phospholipid-like structure, a large amount of natural phospholipids in plasma can be adsorbed on the surface by their self-assembling character. Based on this idea, a methacrylate monomer with a phospholipid polar group, 2-methacryloyloxy ethyl phosphorylcholine (MFC), was designed and synthesized The polymers, composed of MFC and various alkyl methacrylates (as shown in Fig. 1) or styrene derivatives were prepared and their blood compatibility carefully evaluated ". Flatelet adhesion and activation were significantly suppressed on the surface of the MFC polymers when the MFC composition was above 30 mol%. These excellent... 

Phospholipids. Phospholipids, components of every cell membrane, are active determinants of membrane permeabiUty. They are sources of energy, components of certain enzyme systems, and involved in Hpid transport in plasma. Because of their polar nature, phosphoUpids can act as emulsifying agents (42). The stmcture of most phosphoUpids resembles that of triglycerides except that one fatty acid radical has been replaced by a radical derived from phosphoric acid and a nitrogen base, eg, choline or serine. 

There are three groups of eicosanoids that are synthesized from C20 eicosanoic acids derived from the essential fatty acids linoleate and a-linolenate, or directly from dietary arachidonate and eicosapentaenoate (Figure 23-5). Arachidonate, usually derived from the 2 position of phospholipids in the plasma membrane by the action of phospholipase Aj (Figure 24-6)—but also from the diet—is the substrate for the synthesis of the PG2, 1X2 series (prostanoids) by the cyclooxygenase pathway, or the LT4 and LX4 series by the lipoxygenase pathway, with the two pathways competing for the arachidonate substrate (Figure 23-5). 

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... 

Finally, an intriguing possible future therapy arises from a radical idea of Horrobin (2001) that schizophrenia is a nutritional disorder linked to a decreased intake of essential polyunsaturated fatty acids. Recent 31P-MRS studies have shown changes in plasma membrane phospholipids in the neocortex of unmedicated schizophrenics, which would have deleterious consequences on synaptic neurotransmission (Fukuzako, 2001). A clinical trial with the co6 fatty acid derivative ethyleicosa-pentaenoic acid (LAX-101) in patients who had been unresponsive to clozapine, reported that a daily dose of 2g LAX-101 gave a 26% improvement in symptoms over 12 weeks compared with 6% with placebo (Peet and Horrobin, 2001). Maybe in... 

A variety of methods have been developed to study exocytosis. Neurotransmitter and hormone release can be measured by the electrical effects of released neurotransmitter or hormone on postsynaptic membrane receptors, such as the neuromuscular junction (NMJ see below), and directly by biochemical assay. Another direct measure of exocytosis is the increase in membrane area due to the incorporation of the secretory granule or vesicle membrane into the plasma membrane. This can be measured by increases in membrane capacitance (Cm). Cm is directly proportional to membrane area and is defined as Cm = QAJV, where Cm is the membrane capacitance in farads (F), Q is the charge across the membrane in coulombs (C), V is voltage (V) and Am is the area of the plasma membrane (cm2). The specific capacitance, Q/V, is the amount of charge that must be deposited across 1 cm2 of membrane to change the potential by IV. The specific capacitance, mainly determined by the thickness and dielectric constant of the phospholipid bilayer membrane, is approximately 1 pF/cm2 for intracellular organelles and the plasma membrane. Therefore, the increase in plasma membrane area due to exocytosis is proportional to the increase in Cm. 

Bazan, N. G., Scott, B. L., Reddy, T. S. and Pelias, M. Z. Decreased content of docosahexaenoate and arachidonate in plasma phospholipids in Usher s syndrome. Biochem. Biophys. Res. Commun. 141 600-604,1986. 

Phospholipid ( 9% of fatty acid in plasma membrane is arachidonic acid Koletzko, 1996)... 

As host defense peptides are membrane-active molecules, safety mechanisms must be employed to avoid deleterious contacts with host cells. These mechanisms may involve the limitation of peptide activation to specific environments or niche-specific amplification. That most ct-helical peptides remain unstructured in aqueous solution and undergo conformational transitions to an activated state within hydrophobic environments supports this postulate. It has also been postulated that the order of anionic phospholipids in microbial plasma membranes likely induces optimal periodicity of polar residues within host defense peptides at the membrane surface. ... 

It is re-emphasised that the fatty acids that are precursors for many of these messengers are derived from the phospholipids that are components of the plasma membrane. This is possible since the amount of phospholipid in the... 

Trans fatty acids The phospholipids in the plasma and in membranes of all cells contain long-chain polynnsatnrated fatty acids (PUFA). During periods of growth and development of organs, PUFAs are reqnired for phospholipid synthesis. The PUFAs are, of conrse, obtained from dietary triacylglycerol and phospholipids. The donble bonds in most natural fatty acids are cis not trans Nonetheless trans fatty acids do occur in dietary fats. If the diet contains trans fatty acids, they might be incorporated into the phospholipids along with the cis fatty acids and hence into membranes. The presence of these abnormal fatty acids will modify the stmctnre of the phospholipids which conld impair the fnnction of the membrane. There are two main sonrces of trans fatty acids in the diet foods produced from ruminants contain trans fatty... 

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