Bovine seminal plasma (BSP) contains a family of phospholipid-binding proteins (BSP-A1/-A2, BSP-A3 and BSP-30-kDa, collectively called BSP proteins) that potentiate sperm capacitation induced by high-density lipoproteins. We showed recently that BSP proteins stimulate cholesterol efflux from epididymal spermatozoa and play a role in capacitation. Here, we investigated whether or not BSP proteins could stimulate cholesterol and phospholipid efflux from fibroblasts. Cells were radiolabeled ([3H]cholesterol or [3H]choline) and the appearance of radioactivity in the medium was determined in the presence of BSP proteins. Alcohol precipitates of bovine seminal plasma (designated crude BSP, cBSP), purified BSP-A1/-A2, BSP-A3 and BSP-30-kDa proteins stimulated cellular cholesterol and choline phospholipid efflux from fibroblasts. Efflux mechanistic differences were observed between BSP proteins and other cholesterol acceptors. Preincubation of BSP-A1/-A2 proteins with choline prevented cholesterol efflux, an effect not observed with apolipoprotein A-I. Also, the rate of BSP-induced efflux was rapid during the first 20 min, but leveled off thereafter in contrast to a relatively slow, but constant, rate of cholesterol efflux mediated by apolipoprotein A-I, apolipoprotein A-I-containing reconstituted lipoproteins (LpA-I) and high-density lipoproteins. These results indicate that fibroblasts are a good cell model to study the mechanism of lipid efflux mediated by BSP proteins. (+info)
A comparison of the metabolism of [3-14C]-labeled 22- and 24-carbon (n-3) and (n-6) unsaturated fatty acids by rat testes and liver.
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The unsaturated fatty acid composition of phospholipids from different tissues frequently varies. Rat liver phospholipids contain esterified 22:6(n-3) while 22:5(n-6) is the major esterified 22-carbon acid in testes phospholipids. Both testes and liver synthesize polyunsaturated fatty acids. Microsomes, particularly from liver, have been used extensively to measure reaction rates as they relate to polyunsaturated fatty acid and phospholipid biosynthesis. None of these rate studies explain why specific acids are synthesized and subsequently esterified. In this study we compared the metabolism of [3-14C]-labeled (n-3) and (n-6) acids when injected via the tail vein, as a measure of hepatic metabolism, versus when they were injected directly into the testes. Liver preferentially metabolizes [3-14C]-labeled 24:5(n-3) and 24:6(n-3) to yield esterified 22:6(n-3), when compared with the conversion of [3-14C]-labeled 24:4(n-6) and 24:5(n-6) to yield 22:5(n-6). Both 24-carbon (n-3) acids were also converted to 22:5(n-3) but no labeled 22:4(n-6) was detected after injecting the two 24-carbon (n-6) acids. Differences in the hepatic metabolism of 24-carbon (n-3) and (n-6) acids to 22:6(n-3) and 22:5(n-6), versus their partial beta-oxidation to 22:5(n-3) and 22:4(n-6), are important in vivo controls. Surprisingly, in testes a higher percentage of radioactivity was found in esterified 22:6(n-3) versus 22:5(n-6) following injections, respectively, of [3-14C]-labeled 22:5(n-3) versus 22:4(n-6), which is the corresponding metabolic analog. Corresponding pairs of 24-carbon (n-3) and (n-6) acids, as they relate to metabolism, were processed in similar ways by testes. The relative absence of esterified 22-carbon (n-3) fatty acids, versus the abundance of 22- and 24-carbon (n-6) acids in testes phospholipids, does not appear per se to be due to differences in the ability of testes to metabolize (n-3) and (n-6) fatty acids. It remains to be determined if there is selective uptake of specific fatty acids by testes for use as precursors to synthesize polyunsaturated fatty acids. (+info)
Beneficial effects of thyme oil on age-related changes in the phospholipid C20 and C22 polyunsaturated fatty acid composition of various rat tissues.
(67/11419)
The aim of this study was to determine any age-related changes in phospholipid polyunsaturated fatty acid composition, in particular C20 and C22 fatty acids in rat liver, brain, kidney and heart, and to assess and compare the effects of dietary supplementation (42.5 mg/kg body weight/day) of the natural antioxidant thyme oil and its major component thymol throughout the rat life span. The fatty acid composition in the various tissues from young (7 months) and aged (28 months) rats was determined and compared. Livers from aged control, thyme oil and thymol treated rats exhibited an increase in 22:6(n-3). In contrast, 22:6(n-3) content of brain, kidney and heart declined in aged rats in all three dietary groups. However, aged rats treated with thyme oil and thymol displayed significantly higher levels of 22:6(n-3) than the respective age-matched controls. Tissue compositions of 20:4(n-6) were found to be significantly lower in the liver and kidney from aged control rats but not those fed either thyme oil or thymol. In aged rats, the composition of 20:4(n-6) in all tissues was highest in rats fed either thyme oil or thymol. These results show that dietary supplementation with thyme oil tended to maintain higher PUFA levels in all tissues studied. The majority of protection provided by thyme oil was by virtue of its thymol component, which comprises 49% of the whole oil. Thymol administered alone did not provide significantly higher protection than the whole oil, suggesting that other components within thyme oil are also contributing antioxidant activity. (+info)
Inhibition of lecithin cholesterol acyltransferase by phosphatidylcholine hydroperoxides.
(68/11419)
To gain insight into the nature of the lecithin-cholesterol acyltransferase inhibitory factor(s), we separated and collected the oxidation products from oxidized lipoproteins after lipoxygenase treatment. Isolated fractions identified by chemiluminescence, as hydroperoxides of phosphatidylcholine, were found to produce a significant reduction of lecithin-cholesterol acyltransferase activity. The reaction kinetics of lecithin-cholesterol acyltransferase with reconstitued high density lipoproteins were studied in the presence of 0.6 and 1.2 microM hydroperoxides of phosphatidylcholine. No significant changes in the apparent Vmax were observed but a concentration-dependent increase in slope of the reciprocal plots and in the apparent Km values was observed with increasing hydroperoxide concentrations. These results show that the active site of lecithin-cholesterol acyltransferase is not affected by the presence of phosphatidylcholine hydroperoxides. Nevertheless, hydroperoxides of phosphatidylcholine altered the reactivity of lecithin-cholesterol acyltransferase for reconstitued high density lipoproteins suggesting either an alteration of the binding of lecithin-cholesterol acyltransferase to the reconstitued high density lipoproteins or a competitive inhibition mechanism. (+info)
DSC and NMR spectroscopic studies of the interaction between camphorated phenol and phospholipid liposomes.
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To clarify the interaction mechanism of biological activities induced by camphorated phenol (CP), the interactions between CP and phospholipid liposomes [dipalmitoyl phosphatidylcholine (DPPC) liposomes, dimyristoyl phosphatidylcholine (DMPC) liposomes and DMPC/dilauloyl phosphatidylethanolamine (DLEA) liposomes] were studies by DSC and NMR spectroscopy. CP exhibited a larger DSC phase transition properties [shift of phase transition temperature to a lower temperature and decrease in Height/Half-Height Width (H/HHW) of DSC peak)] than phenol in the various liposome systems. It was concluded from the NMR studies that CP is highly incorporated into the DPPC bilayer, the 1H and 13C signals of phenol in a complex between phenol and camphor being markedly broadened but shielded in the presence of DPPC liposomes. It was clear that CP is incorporated as a complex into the lipid bilayers. (+info)
Water maze performance is unaffected in artificially reared rats fed diets supplemented with arachidonic acid and docosahexaenoic acid.
(70/11419)
Four groups of male Long-Evans rats were reared artificially from postnatal d 5 to 18 by being fed through a gastrostomy tube with rat milk substitutes containing oils providing 10% linoleic acid and 1% alpha-linolenic acid (g/100 g fat); with the use of a 2 x 2 design, they were fed one of two levels of arachidonic acid (AA) and docosahexaenoic acid (DHA) (0.0 and 2.5 g/100 g of fatty acids). A fifth artificially reared group was fed a diet high in saturated fat, and a sixth group was reared by dams fed a standard AIN-93M diet. The pups were weaned onto modified AIN-93G diets, with a fat composition similar to that fed during the artificial rearing period. Behavioral testing was conducted between 6 and 9 wk of age; brain lipid composition was then assessed. Relative to the unsupplemented group (0.0 g/100 g AA and DHA), dietary supplementation resulted in a wide range of AA (84-103%) and particularly DHA (86-119%) levels in forebrain membrane phospholipids. AA supplementation increased AA levels and decreased DHA levels, and DHA supplementation increased DHA levels and decreased AA levels, with the magnitude of these effects dependent on the level of the other fatty acid. DHA levels were very low in the saturated fat group. The groups did not differ on the place or cued version of the Morris water-maze, but on a test of working memory, the saturated fat group was impaired relative to the suckled control group. Further correlational analyses in the artificially reared animals did not support a relationship between the wide range of DHA and AA levels in the forebrain and working-memory performance. (+info)
Clinical and veterinary isolates of Salmonella enterica serovar enteritidis defective in lipopolysaccharide O-chain polymerization.
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Twelve human and chicken isolates of Salmonella enterica serovar Enteritidis belonging to phage types 4, 8, 13a, and 23 were characterized for variability in lipopolysaccharide (LPS) composition. Isolates were differentiated into two groups, i.e., those that lacked immunoreactive O-chain, termed rough isolates, and those that had immunoreactive O-chain, termed smooth isolates. Isolates within these groups could be further differentiated by LPS compositional differences as detected by gel electrophoresis and gas liquid chromatography of samples extracted with water, which yielded significantly more LPS in comparison to phenol-chloroform extraction. The rough isolates were of two types, the O-antigen synthesis mutants and the O-antigen polymerization (wzy) mutants. Smooth isolates were also of two types, one producing low-molecular-weight (LMW) LPS and the other producing high-molecular-weight (HMW) LPS. To determine the genetic basis for the O-chain variability of the smooth isolates, we analyzed the effects of a null mutation in the O-chain length determinant gene, wzz (cld) of serovar Typhimurium. This mutation results in a loss of HMW LPS; however, the LMW LPS of this mutant was longer and more glucosylated than that from clinical isolates of serovar Enteritidis. Cluster analysis of these data and of those from two previously characterized isogenic strains of serovar Enteritidis that had different virulence attributes indicated that glucosylation of HMW LPS (via oafR function) is variable and results in two types of HMW structures, one that is highly glucosylated and one that is minimally glucosylated. These results strongly indicate that naturally occurring variability in wzy, wzz, and oafR function can be used to subtype isolates of serovar Enteritidis during epidemiological investigations. (+info)
Cell cholesterol efflux: integration of old and new observations provides new insights.
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Numerous studies using a variety of cell/acceptor combinations have demonstrated differences in cholesterol efflux among cells. These studies also show that different acceptors, ranging from simple molecules like cyclodextrins to serum, stimulate efflux through a variety of mechanisms. By combining early observations with data derived from recent studies, it is now possible to formulate a model for cell cholesterol efflux which proposes that an array of different mechanisms, including aqueous diffusion, lipid-free apolipoprotein membrane microsolubilization, and SR-BI-mediated cholesterol exchange contribute to cholesterol flux. In this model the relative importance of each mechanism would be determined both by the cell type and the nature of the extracellular cholesterol acceptor. (+info)