References: Lecithin
Arterioscler Thromb. 1992 Nov;12(11):1274-83.
Hepatic ACAT activity in African green monkeys is highly correlated to plasma LDL cholesteryl ester enrichment and coronary artery atherosclerosis.
Carr TP, Parks JS, Rudel LL.
Department of Comparative Medicine, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, N.C. 27157-1040.
Previous studies and this study of African green monkeys show a strong positive correlation between plasma low density lipoprotein (LDL) size and the extent of coronary artery atherosclerosis (CAA). Increased LDL size was principally due to the accumulation of cholesteryl oleate molecules within the particle core, suggesting that many of these cholesteryl esters were of tissue origin, i.e., from the acyl-coenzyme A:cholesterol acyltransferase (ACAT) reaction instead of the lecithin:cholesterol acyl-transferase (LCAT) reaction. The current study was conducted to test the hypothesis that ACAT in the liver is the source of the increased numbers of cholesteryl oleate molecules in plasma LDL particles that appear to increase the atherogenic potential of LDL. Monkeys were fed diets rich in fat (lard, safflower oil, or fish oil) and cholesterol for 3-6 years before liver perfusion, ACAT assay, and evaluation of CAA. Hepatic ACAT activity was positively correlated with hepatic cholesteryl ester secretion (r = 0.61, p < 0.001), plasma LDL cholesteryl ester content (r = 0.60, p < 0.0001), and the extent of CAA (r = 0.62, p < 0.0001). The number of cholesteryl oleate molecules within LDL increased proportionally with LDL size in each of the diet groups. Hepatic cholesteryl oleate concentration was correlated with the accumulation of cholesteryl oleate in liver perfusate (r = 0.72, p < 0.01) and with plasma LDL cholesterol oleate content (r = 0.73, p < 0.0001). Our interpretation is that these data, obtained in a relevant primate model of CAA, suggest that hepatic ACAT increases the atherogenicity of LDL by augmenting both the secretion by the liver and
Exp Lung Res. 1995 Jan-Feb;21(1):17-39.
Marker proteins in the particulate fraction of third-trimester amniotic fluid.
Wiehle RD, Richardson M, Besch N, Besch P, Kirshon B, Reiter A, Hutchens TW.
Department of Obstetrics & Gynecology, Baylor College of Medicine, Houston, Texas 77030.
The present clinical evaluation of fetal lung maturity relies largely on the determination of the amniotic surfactant phospholipids phosphotidylglycerol, lecithin, and sphingomyelin, but there are many false negatives as well as false positives among diabetics. The use of other components of lung surfactant, namely, the hydrophobic surfactant proteins (SPs) has long been suggested as an alternative to the classical assay, but tests based on the detection of immunoreactive SP-A have not proved superior or supplanted phospholipid ratios as an index. This report investigates the proteins in a fraction of third-trimester human amniotic fluid (the particulate fraction) enriched in the SP complexes that form the surfactant monolayer. The proteins were analyzed by two-dimensional polyacrylamide gel electrophoresis and visualized by silver staining and immunoblotting. Eight proteins are of particular interest. Three novel proteins (termed AFPP-1, AFPP-4, and AFPP-8) and the alpha-fetoprotein/human serum albumin complex (AFPP-7) can be detected throughout the 28- to 38-week gestational window. The protein that is referred to as AFPP-2 could be identified as SP-A on the basis of immunologic cross-reactivity as well as size and charge characteristics. The time course of appearance of AFPP-2 was also followed in patients with Rh isoimmunization syndrome and was found to be the same as that seen for SP-A. The SP-A was detected as at least five major charged isoforms with multiple subisoforms of different molecular weight and can be distinguished from a related set of proteins (AFPP-5) that appear with a different time course but are possible precursors. Two other proteins (AFPP-3, AFPP-6), which are detectable inconsist
umich.edu
A series of inhibitors of glucosylceramide synthesis, the PDMP based family of compounds, has been developed as a tool for the study of sphingolipid biochemistry and biology. During the course of developing more active glucosylceramide synthase inhibitors, we identified a second site of inhibitory activity for PDMP and its structural homologues that accounted for the ability of the inhibitors to raise cell and tissue ceramide levels. This inhibitory activity was directed against a previously unknown pathway for ceramide metabolism, viz. the formation of 1- O -acylceramide. In this pathway the addition of a fatty acyl group to the primary hydroxyl of ceramide occurs through a transacylation with either phosphatidylethanolamine or phosphatidylcholine as a substrate. However, both in the absence and presence of ceramide, water serves as an acceptor for the fatty acid. Thus the enzyme may be considered to be a phospholipase A(2). The enzyme is unique in that it has an acidic pH optimum and is localized to lysosomes by cell fractionation. More recently, the 1- O -acylceramide synthase has been purified, sequenced, and cloned. This phospholipase A(2) was discovered to be structurally homologous to lecithin cholesterol acyltransferase (LCAT). However, this phospholipase A(2) does not recognize cholesterol and lacks the defined lipoprotein-binding domain present in LCAT. We now refer to this enzyme as lysosomal phospholipase A(2) (LPLA(2)). Although acidic phospholipase A(2) activities have been previously identified, LPLA(2) appears to be the first lysosomal PLA(2) to have been sequenced. This new phospho
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