bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cholesteryl ester hydrolysis in rat liver cytosol. Modulation by female sex hormones
Authors: Gandarias J. M. , Lacort M. , Ochoa B. 
Published: November 2006

AbstractThe regulation of cholesterol ester hydrolase activity by female sex hormones was studied in cytosolic preparations from female rat liver. The investigation was undertaken in order to determine whether a reduction in the enzyme activity might be responsible for the increased content of esterified cholesterol found in rat liver after estradiol or progesterone treatments. The single injection of estradiol (0.75 mg/100 g) or progesterone (1.50mg/100g) produced respectively significant decreases and increases in sterol hydrolase activity. Both opposite effects were noted after a similar lag period of 3–4 hr and were of short duration. No alterations were observed in rats receiving short‐term treatments. When hormones were added to the incubation medium, the activity of cholesterol ester hydrolase decreased progressively with increasing concentrations of hormones. Kinetic studies demonstrate that both estradiol and progesterone compete with the substrate (cholesteryl oleate) for the active center. The findings of the present paper exclude a direct relationship between hepatic hydrolytic activity and lipid deposition. However, they provide evidences that female sex hormones act as modulatory agents of the hydrolysis of cholesteryl esters in rat liver cytosol and suggest that other factors besides competitive inhibition are involved in such regulatory effects.
Characterization of γ‐linolenic acid inRibes seed
Authors: Traitler Helmut , Winter Heike , Richli Urs , Ingenbleek Yves 
Published: November 2006

AbstractThe total lipid content of fruit seeds of theRibes family ranges by weight from 18.3% in gooseberries (Ribes uva Crispa) to 30.5% in black currants (Ribes nigrum). Isolation procedures and analytical methods (gas chromatography, mass spectrometry, high performance thin layer chromatography and stereospecific analysis) demonstrate that the oils fromRibes seeds contain up to 19% by weight of γ‐linolenic acid (γ‐LA, C18∶3, n−6) in black currant oil. This lastRibes species thus constitutes one of the richest natural sources in γ‐LA yet described. These oils appear promising for critically ill patients who seem unable to convert linoleic acid into subsequent EFA fractions.
Cholesterol blocks the disordering effects of ethanol in biomembranes
Authors: Chin Jane H. , Goldstein Dora B. 
Published: November 2006

AbstractTo assess the relation between the physical order of a membrane and its sensitivity to ethanol, we enriched biomembranes with cholesterol, both in vivo and in vitro. Japanese quail of the SEA line (selectively bred for susceptibility to experimental atherosclerosis) were treated for 9 to 16 weeks with a diet that contained 2% cholesterol. This regimen increased the cholesterol content of serum and erythrocytes. The cholesterol content of brain synaptosomal plasma membranes (SPM) was unaffected by the high cholesterol diet. In other experiments, isolated mouse synaptosomal plasma membranes were incubated with cholesterol/phospholipid (C/P) vesicles; different amounts of cholesterol were transferred according to the sterol content of the donor vesicles. Membrane order was determined in both types of membranes by a sensitive electron paramagnetic resonance (EPR) technique. The order parameter with 5‐ and 12‐doxylstearic acid increased along with the cholesterol content. As expected, ethanol disordered membranes (decreased the order parameter) in a concentration‐related manner. The slope of the concentration response curve was less steep in high cholesterol than low cholesterol membranes, indicating that cholesterol enrichment partially blocks the membrane action of ethanol in both types of membranes.
Homeostatic control of membrane fatty acid composition in the rat after dietary lipid treatment
Authors: Gibson R. A. , McMurchie E. J. , Charnock J. S. , Kneebone G. M. 
Published: November 2006

AbstractDiets in which both the lipid content and composition (polyunsaturated to saturated fatty acid ratio) were varied were fed to rats for 20 weeks, and the effects on the tissue lipid profiles were determined. The fatty acid profile of the plasma lipids, and the phospholipid fatty acids of the mitochondrial and microsomal fractions of liver, heart, kidney and brain, as well as erythrocyte membranes were determined. Despite large differences in the level and type of lipid present in the experimental diets and in the proportion of saturated fatty acids in the plasma lipids in response to the various diets, there was little effect on the proportion of saturated to unsaturated fatty acids in the phospholipids of the various membranes examined. The major effect of altering the dietary level of polyunsaturated to saturated fatty acids was on the ratio of the ω6/ω3 series of unsaturated fatty acids in the membrane lipids. This change occurred in all tissues except the brain, in which only a small response to altered dietary lipid intake was observed. The ω6/ω3 ratio was elevated upon feeding a diet rich in ω6 polyunsaturated fatty acids, but decreased when a diet rich in saturated fatty acids was fed. The failure to significantly alter membrane lipid saturation/unsaturation in the tissues examined would suggest that a homeostatic mechanism is operative in biological membranes and may act to buffer membranes from the effects of changes in the nature of the dietary lipid intake.
Lipid composition of millet (Pennisetum americanum) seeds
Authors: Osagie A. U. , Kates M. 
Published: November 2006

AbstractThe composition of lipids extracted from a sample of millet seeds by each of 8 solvent systems is reported. Lipid components were separated by silicic acid column and thin layer chromatography (TLC) and quantitated by analysis of fatty acid methyl esters by gas liquid chromatography (GLC), with heptadecanoic acid as internal standard. Best results were obtained by extraction with hot water‐saturated butanol. Lipids extracted amounted to 7.2% of the seed dry weight and consisted of 85% neutral lipids, 12% phospholipids and 3% glycolipids. Neutral lipids contained mostly (85%) triacylglycerols and small amounts of mono‐ and diacylglycerols, sterols and free fatty acids. Sterols consisted of campesterol, stigmasterol and 2 unidentified sterols, occurring in the same proportions in free and esterified forms. Ten glycolipid and 10 phospholipid components were separated and characterized. Contrary to previously published observations, lysophosphatidylcholine was the major phospholipid (42%) in millet seeds; smaller amounts of phosphatidylcholine (24%), lysophosphatidylethanolamine (21%) and trace amounts of phosphatidylglycerol, phosphatidic acid, phosphatidylserine and phosphatidylinositol also were present. The major glycolipids were esterified sterol glycoside, sterol glycoside, monogalactosyldiacylglycerol, digalactosyldiacylglycerol and cerebrosides (ceramide monohexosides).
A modified radiometric assay for 3‐hydroxy‐3‐methylglutaryl coenzyme a reductase
Authors: Georgopapadakou Nafsika H. , Dix Barbara A. 
Published: November 2006

AbstractA radiometric assay for measuring the activity of 3‐hydroxy‐3‐methylglutaryl‐coenzyme A (HMG‐CoA) reductase is described. The assay is based on the separation of the mevalonate product from HMG‐CoA by high‐voltage electrophoresis. This method is more sensitive and more specific than the NADPH‐based spectrophotometric assay, and less tedious than available radiometric assays. It has been used to measure HMG‐CoA reductase activity in crude extracts ofSaccharomyces cerevisiae and in human skin fibroblasts.
Effects of organic solvents on lipase for fat splitting
Authors: Kim Kee H. , Kwon Dae Y. , Rhee Joon S. 
Published: November 2006

AbstractThe effect of organic solvents on the stability and catalytic activity of the microbial lipase fromCandida rugosa for hydrolysis of triglyceride (fat splitting) has been examined. The solvents examined were 5 hydrocarbons (n‐hexane, n‐heptane, n‐octane, iso‐octane and cyclohexane) and 3 ethers (diethyl‐ether, diisopropylether and di‐n‐butylether). The results revealed that iso‐octane and cyclohexane are superior to the other solvents examined for enzymatic fat splitting in organic solvent systems.
The occurrence of long chain α,ω‐diols in the lipids of steer and human meibomian glands
Authors: Nicolaides N. , Santos Evelyn C. , Papadakis Konstantine , Ruth Edward C. , Müller Luciano 
Published: November 2006

AbstractA group of long chain α,ω‐diols (C29 to C34) has been identified in the lipids of steer and human meibomian gland excreta (meibum). These new lipids were isolated from the steer meibum unsaponifiables. Proof of structure was provided by 1) the column chromatographic behavior and TLC of the diols and their diacetates; 2) GLC on glass capillary columns; 3) fragmentation patterns in GC‐MS; 4) NMR data, and 5) ozonolysis studies of the unsaturates. Chain types for the steer sample were 51% straight monoenes, 8.5% straight saturates, 39% iso and anteiso saturates and 1.5% iso and anteiso unsaturates. GC for the human sample gave straight monoenes 83%, straight saturates 8%, and iso plus anteiso saturates 9%. Close correspondence of the α,ω‐diol chain lengths and types with meibum ω‐hydroxy fatty acids suggests a biochemical precursor relationship.
Metabolism of sterols of varying ring unsaturation and methylation byCaenorhabditis elegans
Authors: Lozano Ruben , Salt Thomas A. , Chitwood David J. , Lusby William R. , Thompson Malcolm J. 
Published: November 2006

AbstractThe metabolism of three dietary 4,4‐desmethylsterols and two 4α‐methylsterols was investigated in the free‐living nematodeCaenorhabditis elegans. Dietary cholestanol was converted mostly to lathosterol. Dietary lathosterol, 7‐dehydrocholesterol, 4α‐methylcholest‐7‐enol and 4α‐methylcholest‐8(14)‐enol each remained largely unchanged. An absolute requirement for a substantial quantity of 7‐dehydrocholesterol inC. elegans did not exist.C. elegans was unable to remove a 4α‐methyl group or introduce a double bond at C‐5 and also demonstrated the lack of a Δ7‐reductase. Its nutritional sterol requirement was satisfied by cholestanol, lathosterol or 7‐dehydrocholesterol; growth was comparable to that obtained previously in media containing Δ5‐sterols. However, the two 4α‐methylsterols appeared to be unsatisfactory sterol nutrients. The possible physiological importance of 4α‐methylsterols is discussed briefly.
Measurement of free and bound malondialdehyde in vitamin E‐deficient and‐supplemented rat liver tissues
Authors: Lee Hye‐Sung , Saari Csallany A. 
Published: November 2006

AbstractThe quantity of free malondialdehyde (MDA) in liver tissues of rats fed vitamin E‐deficient or‐supplemented diets for 43 wk was measured by a newly developed high performance liquid chromatographic (HPLC) method. Bound MDA was quantified by the same HPLC method after alkaline hydrolysis of tissue homogenates. Tissues from vitamin E‐deficient animals showed levels of free MDA about 15 times higher but levels of bound MDA less than 2 times higher than the vitamin E‐supplemented animals. Free MDA is the major form in vitamin E‐deficient tissues, but bound MDA is predominant in vitamin E‐supplemented tissues. Conventional thiobarbituric acid (TBA) test results revealed that the content of TBA‐reactive substances expressed in MDA equivalents was much higher than the actual free MDA levels in all groups. Results indicate that free MDA level measured by HPLC is a more sensitive index than the TBA value for lipid peroxidation. Some other TBA‐reactive substances seem to exist in liver tissue regardless of the dietary treatment.
Cholesteryl esterase activities in ventricles, isolated heart cells and aorta of the rat
Authors: Stam Hans , Broekhoven‐Schokker Sietske , Schoonderwoerd Kees , Hülsmann Willem C. 
Published: November 2006

AbstractCholesteryl esterase activities were determined in homogenates of rat heart (ventricles), isolated, calcium‐tolerant, cardiac myocytes and aortic tissue and were compared with acid and neutral triglyceride lipase activities in these fractions.Using cholesteryl oleate/phosphatidylcholine/taurocholate emulsions and digitonin pretreatment of the enzyme fractions, acid and neutral cholesteryl esterase activities were measured in all tissue preparations. In contrast to the acid and neutral triglyceridase and acid cholesteryl esterase activity, the neutral cholesteryl esterase activity was subject to substrate inhibition. Upon isolation of cardiac myocytes, and in contrast with the recovery of neutral triglyceride lipase activity, only a small portion of the neutral cholesteryl esterase (6%) was recovered, suggesting that nonmyocyte neutral cholesteryl esterase activity markedly contributes to the relatively high activity detectable in whole ventricular homogenates. The recovery of large amounts of neutral cholesteryl esterase activity in the supernatant of collagenase‐digested heart tissue, obtained during the isolation of myocytes, which is also markedly enriched in activities of two endothelial marker enzymes (5′‐nucleotidase and angiotesine‐converting enzyme) may indicate the predominant contribution of neutral cholesteryl esterase activity from coronary endothelial cells to this activity detectable in ventricular homogenates. Relative to the activity in ventricular and myocyte homogenates, aorta homogenates possessed the highest specific neutral cholesteryl esterase activity. We propose that in addition to coronary endothelium, smooth muscle cells also contribute to the neutral cholesteryl esterase activity in ventricular homogenates. Pretreatment of rats with carrageenan an agent toxic to macrophages, lymphocytes and fibroblasts, induced a significant drop in myocardial neutral cholesteryl esterase and triglyceride lipase activity, suggesting that interstitially trapped macrophages may also contribute to lipolytic activities present in whole ventricular homogenates. Our data indicate that caution has to be taken upon extrapolation of experimental findings in heart homogenates to myocardial muscle cells.
Resolution of radiolabeled molecular species of phospholipid in human platelets: Effect of thrombin
Authors: Purdon A. David , Patelunas D. , Smith J. Bryan 
Published: November 2006

AbstractResolution of individual molecular species of human platelet 1,2‐diradyl‐sn‐glycero‐3‐phosphocholines and 1,2‐diradyl‐sn‐glycero‐3‐phosphoethanolamines by reverse phase high pressure liquid chromatography (HPLC) allowed a thorough analysis of those phospholipids labeled with [3H]arachidonic acid. Approximately 54% and 16% of the total incorporated radiolabel was found in choline glycerophospholipids and ethanolamine glycerophospholipids, respectively, with ca. 90% of this being found in the 1,2‐diacyl molecular species. Eighty percent of [3H]‐arachidonic acid incorporated into 1‐acyl‐2‐arachidonoyl‐sn‐glycero‐3‐phosphocholine in resting platelets was equally distributed between 1‐palmitoyl‐2‐arachidonoyl and 2‐stearoyl‐2‐arachidonoyl‐sn‐glycero‐3‐phosphocholine, while 70% of the radiolabel in 1‐acyl‐2‐arachidonoyl‐sn‐glycero‐3‐phosphoethanolamine was found in 1‐stearoyl‐2‐arachidonoyl‐sn‐glycero‐3‐phosphoethanolamine. Thrombin stimulation (5 U/ml for 5 min) resulted in deacylation of all 1‐acyl‐2‐[3H]arachidonoyl molecular species of 1‐acyl‐2‐arachidonoyl‐sn‐glycero‐3‐phosphocholine and 1‐acyl‐2‐arachidonoyl‐sn‐glycero‐3‐ethanolamine. There was also a slight increase in 1‐O‐alkyl‐2‐[3H]arachidonoyl‐sn‐glycero‐3‐phosphocholine and a significant increase in 1‐O‐alk‐1′‐enyl‐2‐[3H]arachidonoyl‐sn‐glycero‐3‐phosphoethanolamine molecular species of over 300%. Thus, HPLC methodology indicates that arachidonoyl‐containing molecular species of phosphatidylcholine and phosphatidylethanolamine are the major source of arachidonic acid in thrombin‐stimulated human platelets, while certain ether phospholipid molecular species become enriched in arachidonate.
Electrochemical detection of phospholipid hydroperoxides in reverse‐phase high performance liquid chromatography
Authors: Yamada K. , Terao J. , Matsushita S. 
Published: November 2006

AbstractHydroperoxy derivatives of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) can be separated from their respective phospholipids by reverse‐phase high performance liquid chromatography (HPLC). However, ultraviolet absorption due to conjugated diene cannot detect the hydroperoxy group. In this work, an electrochemical (EC) detector was first applied to the analysis of hydroperoxy phospholipids. Both the PC and PE hydroperoxides from rat liver were reduced quantitatively by the glassy carbon electrode at −300 mV vs Ag/AgCl. Since neither the hydroxy derivatives nor unoxidized phospholipids showed any response, it would seem this technique can be used to distinguish phospholipid hydroperoxides from their hydroxy derivatives. Thus, the reverse phase HPLC‐EC detection method is proposed for the specific analysis of hydroperoxy phospholipids in biological tissues.
The major gangliosides of the bovine pineal body
Authors: Whalen Margaret M. , Wild Gaynor C. 
Published: November 2006

AbstractAcetone powders of fresh‐frozen pineals were extracted with chloroform/methanol mixtures. By column chromatography on silicic acid, mild alkaline methanolysis, ion‐exchange high performance liquid chromatography and a final thin layer chromatography on silicic acid, the major glycosphingolipids were purified from the extracts of a total of 300 bovine pineal bodies. Chromatographically purified fractions were characterized by gas chromatographic analysis. The most prominent glycosphingolipid appeared to be cerebroside. In addition, five different gangliosides were found in detectable levels. The two major gangliosides have the chromatographic and component characteristics of GD3 and GM3, with disialoganglioside predominating. Gangliosides indistinguishable from purchased standards of GM1 and GD1a were third and fourth, respectively, in amount. The fatty acid profiles of the two lactosyl gangliosides are similar and significantly different from those of the two gangliotetraose gangliosides. The fifth most prominent ganglioside, present at a level of 1.09% of total recovered ganglioside sialic acid, appears to be a novel trisialoganglioside, called GTx. This new molecule has a component ratio of gal:glc:sialic acid:amino sugar of approximately 1∶2∶3∶1. Similarities between bovine pineal and rod outer segments are discussed.
Onset and persistence of changes in intestinal transport following dietary fat manipulation
Authors: Thomson A. B. R. , Keelan M. , Clandinin M. T. 
Published: November 2006

AbstractIn this study we determined the time‐course for the onset and the loss of the effect of short‐term feeding rats isocaloric semisynthetic diets containing a high content of saturated (HS) or polyunsaturated (HP) fatty acids on the jejunal and ileal uptake of medium‐ and long chain fatty acids, cholesterol and glucose. Animals were fed HP or HS for 3, 7 or 14 days; then the diet was switched to standard Purina® rat chow for a further 3, 7 or 14 days. The uptake of medium chain fatty acids was unchanged. The differences between HP and HS in glucose uptake occurred within 3 days, but persisted for 14 days, whereas there were qualitative as well as quantitative changes in the pattern of lipid uptake: differences in uptake of stearic, oleic, linoleic and linolenic acids and cholesterol occurred after 7 days of feeding HP or HS. Jejunal uptake of linoleic acid was greater in HP than HS on day 7, but HS was greater than HP on day 14. The effect of diet on lipid uptake was similar in the jejunum and ileum. The altered uptake of stearic and oleic acids persisted after the rats were switched back to chow, whereas the uptake of the other nutrients became similar. Thus, (i) changes in dietary content of saturated and polyunsaturated fatty acids have early effects on intestinal transport function; (ii) some of these changes persist even when animals are returned to feeding on chow; and (iii) glucose transport is rapidly altered by dietary changes, whereas lipid uptake changes only after 7 days. We conclude that the transport function of the intestine is responsive to changes in dietary fatty acids.
Intestinal cholesterol and oleic acid uptake from solutions supersaturated with lipids
Authors: Reynier M. O. , Crotte C. , Montet J. C. , Sauve P. , Gerolami A. 
Published: November 2006

AbstractTo test the role of nonmicellar phases in lipid absorption, intestinal uptake of fatty acids and cholesterol has been studied in vitro from supersaturated and micellar solutions. The micellar solubility limit at equilibrium was established for cholesterol and oleate/monoolein (2∶1) at pH 6.7 with 10 mM taurocholate. Uptake by rat intestinal everted sacs was measured during incubation of 5 min. Cholesterol uptake increased linearly with the cholesterol content of micellar or supersaturated solutions up to a supersaturation of 150%. Oleate uptake, by contrast, remained essentially the same from either saturated or supersaturated (130–280%) mixtures. The difference between cholesterol and oleate uptake rates is explained by their distinct effects on micellar size, which is unchanged by cholesterol supersaturation but is increased by oleate. Solutions largely supersaturated (280%) with oleatemonoolein are polydisperse and contain viscous isotropic and paracrystalline phases similar to those observed during lipid absorption. These results suggest that, in the presence of such solutions, uptake occurs from both the micellar saturated and nonmicellar supersaturated phases.
Intestinal absorption of ester and ether glycerophospholipids in guinea pig. Role of a phospholipase A2from brush border membrane
Authors: Diagne A. , Mitjavila S. , Fauvel J. , Chap H. , Douste‐Blazy L. 
Published: November 2006

AbstractIn vivo intestinal perfusion was used to follow the absorption of three different choline glycerophospholipids (CGP) in guinea pig. These included 1‐[3H]palmitoyl‐2‐acyl‐sn‐glycero‐3‐phosphocholine (diacyl‐GPC), 1‐[3H]‐O‐hexadecyl‐2‐acyl‐sn‐glycero‐3‐phosphocholine (alkylacyl‐GPC) and 1,2‐di‐O‐hexadecyl‐sn‐glycero‐3‐phospho‐[3H]‐choline (dialkyl‐GPC). About 80% of diacyl‐GPC was absorbed within 4 hr, compared to 60% of alkylacyl‐GPC and 30% of dialkyl‐GPC. The radioactivity disappearing from the perfusion fluid was recovered in intestinal lipids, mostly triacylglycerol, free fatty acid and CGP from diacyl‐GPC, CGP from alkylacyl‐GPC and dialkyl‐GPC. These results indicated that the nonhydrolyzable substrate dialkyl‐GPC was much less absorbed, whereas diacyl‐GPC, which released over 80% of [3H]palmitic acid in the perfusion fluid, displayed the highest absorption rate. The intermediate picture observed for alkylacyl‐GPC suggested the possible involvement of a phospholipase A2, which was detected in the entire intestinal tract. This enzyme was further found to concentrate in villus cells, where it is localized in the brush border membrane, as shown using two different subcellular fractionation procedures. These data suggest a possible role of this new enzyme in the digestion of alimentary phospholipids.