Plasma Plasmalogen

The most logical material for the analysis of PUFA and plasmalogens are the erythrocytes. Fatty acids can also be quantitated in plasma. The plasmalogens are also easily detectable in homogenates of cultured fibroblasts and may add to the definitive diagnosis of patients with a generalised or isolated peroxisomal dysfunction. 

Patients with Refsum disease may have extremely high phytanic acid levels, up to 1500 pmol/1, whereas pristanic acid is low (< 1 pmol/1) as a consequence of the phytanoyl-CoA hydroxylase deficiency. Less pronounced phytanic acid elevations will be observed in RCDP type 1 patients, which applies to both the classical form as well as the variant forms. Values may range from 200 to 900 pmol/1, somewhat depending on age. There is some discussion on the time of onset of phytanic acid accumulation in the classical neonatal RCDP-patients. Normal plasma phytanic acid levels (0.7-5.8 pmol/1) were recorded in the authors laboratory in patients aged less than 1 week. Two- to three-week-old RCDP patients had increased phytanic acid levels of 9.1 -13.2 pmol/1. Classical patients invariably had undetectable plasmalogen levels of the erythrocytes at any age. 

Plasma amine oxidase 886 Plasma antithrombin III 177 Plasma membrane 12, 379 Plasmalemma. See Plasma membrane Plasmalogens 383s, 384 Plasmids 5, 248249 ColEl 248 drug resistance 248 Plasmin 634 Plasminogen 634 Plasmodesmata 10... 

Myelin is modified plasma membrane. Myelin of the PNS resembles that of the CNS with respect to lipid composition. There is an enrichment in such specialized lipids as cerebroside and ethanolamine plasmalogen, and the high content of cholesterol plays an important role in control of membrane fluidity. The protein composition of PNS myelin is, however, distinct from that of CNS myelin. A single protein, P0, accounts for half of all protein of PNS myelin. Of the other proteins present, most are expressed in the CNS as well as the PNS but in quantitatively different amounts. Prominent among these proteins are myelin basic proteins and myelin-associated glycoprotein. 

As already noted, the final steps In the synthesis of cholesterol and phospholipids take place primarily In the ER, although some of these membrane lipids are produced In mitochondria and peroxisomes (plasmalogens). Thus the plasma membrane and the membranes bounding other organelles (e.g., Golgi, lysosomes) must obtain these lipids by means of one or more Intracellular transport processes. For example. In one Important pathway, phosphatidylserine made In the ER Is transported to the Inner mitochondrial membrane where It Is decarboxylated to phosphatidylethanolamlne, some of which either returns to the ER for conversion Into phosphatidylcholine or moves to other organelles. 

The choline- and ethanolamine-containing phospholipids of human platelets can be subdivided, based on the nature of the linkage to the fatty acid residue at the sn-1 position of the glycerol backbone, into 1,2-diacyl, l-O-alkyl-2-acyl and l-0-alk-l -enyl-2-acyl species (Table 1.2). The majority of arachidonic acid in the phosphatidylcholines is present in the diacyl species while 1-0-alk-l enyl-2-acyl-PE (plasmalogen) contains most of the arachidonic acid in the phosphatidylethanolamines. The amount of arachidonic acid present in the diacyl species of phosphatidylethanolamine is similar to that in diacyl phosphatidylcholine. Ferret et al have shown that the distribution of arachidonate in the phospholipids of the platelet plasma membrane is asymmetric, the majority of it being present in the inner leaflet. 

Phospholipids and similar substances are fractionated into compound classes more according to partition than adsorption effects, in contrast to the separation of non-polar lipids. Alkenyl ether-esters ( plasma-logens ) are usually not entirely separated from the corresponding ether-ester and diester-phosphatides. Phosphatide plasmalogens concentrate in thin-layer chromatograms on the forward edge of the phosphatide spots. 

Very-long-chain fatty acids (VLCFA), trihydroxycholestanoic acid (THCA), phytanic acid and pristanic acid can all be measured in plasma/serum (> 1 ml). From the same blood sample erythrocytes, platelets and/or leukocytes can be prepared for determination of plasmalogens and dihydroxyacetone-phosphate acyltransferase (DHAPAT), respectively. 

Reaction 12), to plasmalogenic diglyceride with the formation of chohne plasma-logen (Reaction 17), or to ceramide with the formation of sphingomyelin (Reaction 18). 

Hanahan et al. 1960 DeGier and van Deenen 1961 Farquhar 1962) was found in three cases studied by Mabry et al. (1960), Mier et al. (1960) and Ways et al. (1963), respectively. Lipid phosphorus was slightly low in one of the cases. As in plasma, red cell lecithin was absolutely and relatively decreased, while the sphingomyelin concentration was increased. Plasmalogens were low. The concentrations of cephalin and of cholesterol were normal (Ways et al. 1963 Fredrickson 1966). 

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