bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metabolic fate of sphingomyelin of high‐density lipoprotein in rat plasma
Authors: Bentejac Marc , Bugaut Maurice , Delachambre Marie Claire , Lecerf Jean 
Published: November 2006

AbstractThe metabolic fate of high density lipoprotein (HDL) sphingomyelin in plasma was studied in rats over a 24‐hr period after injection of HDL containing sphingomyelin which was14C‐labeled in the stearic (18∶0) or lignoceric acid (24∶0) moiety and3H‐labeled in the choline methyl groups. Decay of label in plasma followed three phases. The first two phases were similar for both isotopes and both types of sphingomyelin (t1/2≃10 and 110 min). However, during the third phase (from 10 hr after injection),3H label disappeared more slowly than14C label from 18∶0 sphingomyelin, whereas the3H/14C ratio remained relatively constant when 24∶0 sphingomyelin was used. Intact, doubly‐labeled 18∶0 sphingomyelin disappeared from HDL rapidly (t1/2=38 min) by tissue uptake and by transfer to very low density lipoprotein (VLDL). VLDL contained up to 12% of the sphingomyelin 1 hr after injection. This is the first demonstration of a transferin vivo of sphingomyelin from HDL to VLDL. A similarly rapid transfer was also observedin vitro. Some nontritated, [14C]18∶0 or [14C]24∶0 sphingomyelin was redistributed more slowly into HDL. Doubly‐labeled phosphatidylcholine appeared in VLDL and HDL within 1 hr after injection and reached 1.8 and 2.1% of the injected14C and3H in VLDL at 1 hr, and 4.8 and 6.9% in HDL at 3 hr, respectively.
A fluorimetric method for measuring lipase activity based on umbelliferyl esters
Authors: de Monpezat Thierry de Laborde , de Jeso Bernard , Butour Jean‐Luc , Chavant Louis , Sancholle Michel 
Published: November 2006

AbstractA new fluorimetric method for measuring lipase activity is described. The fluorescent compound umbelliferone (UMB) was esterified with various unsaturated and saturated fatty acids of different carbon chain lengths, and the non‐fluorescent esters were used as substrates for measuring the activity of two lipases purified fromRhizopus delemar andCandida cylindracea. The fluorescence intensity of UMB liberated by hydrolysis of the substrates gives an indication of the lipase activity towards the respective esters. UMB was found to be somewhat more sensitive and stable than 4‐methylumbelliferone (4‐MU), which has been used previously. The highly sensitive method (nmoles UMB/mL/hr) described here was tested on five different esters. The method has the advantage of not requiring extraction of the lipolysis products. It also can be carried out quickly, in two to three minutes, and thus lends itself to the screening of lipase‐producing micro‐organisms. The method offers an interesting alternative or can be complementary to assays based on the use of 4‐methylumbelliferone esters as substrates.
Studies on the transfer of tocopherol between lipoproteins
Authors: Traber Maret G. , Lane Jerome C. , Lagmay Nora R. , Kayden Herbert J. 
Published: November 2006

AbstractThe net transfer of labeled α‐tocopherol from donor to acceptor lipoproteins at physiological concentrations was investigated. Labeled lipoproteins were isolated i) followingin vitro addition of [3,4‐3H]all rac‐α‐tocopherol to plasma, or ii) from plasma obtained 12–16 h after ingestion by normal subjects of an oral dose (100 mg each) of 2R,4′R,8′R‐α‐[5,7‐(C2H3)2]tocopheryl acetate and 2S,4′R′,R‐α‐[5‐C2H3]tocopheryl acetate. A constant amount (on a protein basis) of labeled lipoprotein was incubated with an increasing amount of unlabeled acceptor lipoprotein for 2 h at 37°C. No discrimination between stereoisomers of α‐tocopherol was detected. Labeled VLDL and labeled LDL (very low and low density lipoproteins, respectively) tended to retain their labeled tocopherol. Labeled high density lipoproteins (HDL) readily transferred the labeled tocopherol to VLDL (>60% transferred), while the transfer to LDL was dependent upon the ratio of labeled HDL/LDL with a lower net transfer at higher ratios. This dependency of the distribution of tocopherol upon the ratio of HDL/LDL was also observedin vivo. The tocopherol/mg HDL protein was measured in 11 subjects with varying HDL levels. As the %HDL in the plasma increased from 14 to 50%, the tocopherol/HDL protein also increased (r2=0.37,P<0.05).
Lipoprotein receptor mediated metabolism of [14C]arachidonic acid labeled chylomicron remnants by Hep G2 cells
Authors: Chen Qi , Florén Claes‐Henrik , Nilsson Åke 
Published: November 2006

AbstractDuring lipolysis of chylomicron triacylglycerol by lipoprotein lipase, arachidonic acid (AA) esters are hydrolyzed at a slower rate than the predominant 16–18 carbon fatty acid esters. The further metabolism of the AA that is hereby enriched in the chylomicron remnant acylglycerols has not been investigated. In the present study, we examined the low density lipoprotein (LDL) dependent and independent metabolism of [14C]AA present in chylomicron remnants in the human hepatoma cell line Hep G2. Mesenteric duct cannulated rats were fed [14C]AA and [3H]cholesterol in corn oil, and the chyle obtained was injected intravenously into hepatectomized rats to form chylomicron remnants labeled with [14C]AA in the triacylglycerol (TG) and with3H in the cholesteryl ester portion. The remnants were then incubated with Hep G2 cells. The uptake of [14C]AA within 2–4 h was similar to that of [3H]cholesteryl ester. After uptake into the cells, [14C]AA was preferentially incorporated into phospholipids, a high proportion being found in phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol. [14C]AA and [3H]cholesteryl ester uptake were influenced to similar extents by factors unknown to regulate the LDL receptor and by an anti‐LDL receptor antibody. Addition of compactin thus increased the uptake of [14C]AA by 50% in 4 h and mevalonolactone decreased the uptake by 86%. Using an anti‐LDL receptor antibody, 25.0% of [3H]cholesterol/cholesteryl ester and 37.7% of [14C]AA binding to the cells at 4°C were blocked. There was no lipolysis of [14C]TG or [14C]diacylglycerol by lipase secreted into the medium during incubations. The study shows that after the uptake of chylomicron remnants by Hep G2 cells, which in part occursvia the LDL receptor, AA is liberated from the acylglycerols and is preferentially incorporated into phospholipids.
Myogenic differentiation of the muscle clonal cell line BC3H‐1 is accompanied by changes in its lipid composition
Authors: Pediconi M. F. , Politi L. E. , Bouzat C. B. , De Los Santos E. B. , Barrantes F. J. 
Published: November 2006

AbstractPhospholipid and neutral lipid composition was studied in the course of myogenic differentiation of the clonal cell line BC3H‐1. Total phospholipid content increased during differentiation, predominantly in the major classes of choline and ethanolamine glycerophospholipids. The contents of other lipids, such as triacylglycerols, diminished more than 50% during this period. The content and distribution of fatty acids also underwent marked differentiation‐dependent changes. The polyunsaturated (tetrapenta‐ and hexaenoic) fatty acid species of several phospholipid classes diminished during differentiation, especially those in choline, serine and inositol glycerophospholipids. Most noticeable were the changes in phosphatidylserine; long‐chain fatty acids having 20 to 22 carbon atoms and 4 to 6 double bonds decreased from about 30 to about 10 mol%. Although increased levels of saturation in other phospholipid fatty acyl chains appear to accompany the myogenic changes of BC3H‐1 cells, some unsaturated fatty acids, such as oleic acid (18∶1), increased by as much as 80% during the same period, suggesting the activation of a Δ9 desaturase. Sphingomyelin contained only saturated and monoenoic fatty acids and exhibited a four‐ to five‐fold decrease in its content of monoenoic acyl groups. Diacylglycerols became enriched in arachidonate and docosahexaenoate. The amount of cholesterol and its esters increased slightly during differentiation of BC3H‐1 cells. The data show that several metabolic pathways change during myogenic differentiation of the BC3H‐1 clonal cell line, particularlyde novo biosynthetic pathways, elongation/desaturation reactions, and acyl chain turnover. As a consequence of this, the lipid composition of the myoblast form of the BC3H‐1 cell, in which the nicotinic acetylcholine receptor and other cell surface receptors are expressed, is thus different from that of the nondifferentiated cell.
Specificity of soybean lipoxygenase‐1 in hydrated reverse micelles of sodiumbis(2‐ethylhexyl)sulfosuccinate (aerosol OT)
Authors: Shkarina Tatyana N. , Kühn Hartmut , Schewe Tankred 
Published: November 2006

AbstractSoybean lipoxygenase‐1 (EC 1.13.11.33) was purified by fast protein liquid chromatography on a MONO Q column and studied with respect to the conversion of linoleic and arachidonic acids in reverse micelles of sodiumbis(2‐ethylhexyl)sulfosuccinate inn‐octane. In this system the specific activities were lower by one order of magnitude than those in the corresponding aqueous system. High‐performance liquid chromatography analyses indicated the predominant formation of 13S‐hydroperoxy‐9Z,11E‐octadecadienoic acid (13‐HpODE) from linoleic acid and of 15S‐hydroperoxy‐5Z,8Z,11Z,13E‐eicosatetraenoic acid (15) from arachidonic acid both in the aqueous system and in the reverse micelles. After sedimentation of the hydrated reverse micelles by ultracentrifugation, both linoleic acid and 13‐HpODE were found to be enriched in the micelles with only small amounts of these compounds present inn‐octane. It is proposed that substrates and products of the lipoxygenase reaction are located mainly in the surfactant shell of the hydrated reverse micelles and reach the micelle‐entrapped enzyme by diffusion into the aqueous interior space.
Cell membranes and multilamellar vesicles: Influence of pH on solvent induced damage
Authors: Jacobsohn Myra K. , Lehman Melanie M. , Jacobsohn Gert M. 
Published: November 2006

AbstractPigment leakage from sheep and horse erythrocytes and from red beet tissue induced by non‐polar solvents was determined as a function of pH. The results were compared to disruption of multilamellar vesicles (MLV) composed of phospholipids with equimolar cholesterol under identical conditions of solvent exposure and pH. Solvent access to cholesterol was used to measure vesicle disruption. MLV were made from 1,2‐dioleoyl phosphatidylethanolamine sphingomyelin (SP) and various phosphatidylcholines to simulate the major lipid components of membranes. Pigment leakage from erythrocytes caused by petroleum hydrocarbon (b.p. 60–80°C) was maximal at pH 2–4 and at pH 10, but minimal at pH 6.8; alcohols caused less pigment leakage than petroleum hydrocarbon. Betacyanin leakage from beet tissue induced by petroleum hydrocarbon was maximal at pH 2, with very little leakage at pH 4, 6.6 and pH 10. Alcohols caused minimal damage to beet tissue above pH 2. Cholesterol removal by petroleum hydrocarbon from MLV of mixed lipid composition was maximal at pH 2–4, reduced at pH 6.8 and minimal at pH 10. Lipid mixtures in which fatty acyl side chains of one phospholipid were of a different length than the other lost more sterol than mixtures in which the acyl side chains were of identical chain length. MLV with more than 25% SP lost more sterol than those with less or no SP. Results show that in mixtures of phospholipids, SP exposes the hydrocarbon phase of a bilayer to solvent extraction, a property that was also observed in native membranes. Erythrocyte membranes, which contain SP, were more severely damaged by petroleum hydrocarbon than beet cells, which have none. Membranes from erythrocytes were more prone to solvent disruption at pH 10 than MLV, but they were more resistant at physiological pH. It is suggested that conformational changes in membrane proteins due to shifts in pH cause exposure of hydrophobic portions of surrounding lipids to the environment. At neutral pH, the native conformation of proteins is expected to stabilize the bilayer of membranes.
Evaluation of an oleic acid water‐in‐oil‐in‐water‐type multiple emulsion as potential drug carrierviathe enteral route
Authors: Oba Noriyuki , Sugimura Hisao , Umehara Yasuhiko , Yoshida Masayuki , Kimura Talzo , Yamaguchi Takaji 
Published: November 2006

AbstractA water‐in‐oil‐in‐water (W/O/W) emulsion composed of oleic acid was used as a carrier of carboxyfluorescein (CF)viathe enteral route, as a model for future drug transport. The absorption of CF in the small intestine of rats given the emulsion (W/O/W group) was compared with the absorption in a group administered CF alone (CF group), and a surface‐active agent in CF solution (MM group). Higher amounts of CF were absorbed in the W/O/W and MM groups than in the CF group. At 120 min, the amount of CF remaining in the intestinal tract was smaller in the MM group than in the W/O/W group. In the early period, CF excretion into bile was higher in the MM group than in the W/O/W group was higher than in the MM group (non‐specific). The blood CF level was significantly higher at 240 and 360 min in the W/O/W group than in the other two groups. The highest concentration in lymph was found in the W/O/W group. The W/O/W emulsion was considered superior to the micelles because it maintained a higher blood level of CF over long periods and transferred it to the lymph. This suggests that the W/O/W emulsion is applicable as a drug carrierviathe enteral route.
Effect of dietary linoleic acid content on the distribution of triacylglycerol molecular species in rat adipose tissue
Authors: Huang Yung‐Sheng , Lin X. , Smith R. S. , Redden P. R. , Jenkins D. K. , Horrobin D. F. 
Published: November 2006

AbstractThe present study examined the effect of varying dietary linoleate intake (0.01, 0.24, 2.4, 24, 80 or 160 g/kg diet) for 24 weeks on the distribution of triacylglycerol (TG) molecular species in rat epididymal adipose tissue. Adipose TG fractions were purified by thin‐layer chromatography and separated into different molecular species by reversephase high‐performance liquid chromatography. The identification of TG species was based on fatty acid composition, retention time and the theoretical carbon number. When the dietary 18∶2n−6 content was equal to or less than 24 g/kg, no significant amounts of n−6 fatty acids (mainly 18∶2n−6) were observed in adipose tissue TG despite the fact that the levels of 20∶4n−6 in liver phospholipids increased significantly. There were 12 major molecular species in adipose tissue when the dietary 18∶2n−6 content was less than 2.4 g/kg. When the diteary 18∶2n−6 content reached 24 g/kg, an additional six TG species containing one, two or three molecules of 18∶2n−6 were observed. The levels of TG molecules containign two or three 18∶2n−6 residues were further increased when the diet contained very large amounts of linoleic acid (160 g/kg). Conversely, those TG species containing only one 18∶2n−6 residue became less abundant. It is suggested that the accumulation of these linoleate‐rich TG molecular species in adipose tissue, particularly di‐ and trilinoleoyl containing TG, is the result of an adequate or an excessive intake of linoleic acid.
Site‐specific differences in the fatty acid composition of human adipose tissue
Authors: Calder P. C. , Harvey D. J. , Pond C. M. , Newsholme E. A. 
Published: November 2006

AbstractThe fatty acid composition of triacylglycerols from fifteen distinct adipose depots taken from each of seven adult male human subjects was compared. Oleic, palmitic, linoleic, stearic, myristic, palmitoleic and vaccenic acids accounted for more than 90% of the triacylglycerol fatty acids in all sites from all subjects; a number of other fatty acids were also identified and quantified. There were large differences in theaverage fatty acid composition between individual subjects. There were no site‐specific differences in the proportions of myristic (3.8–4.7% of triacylglycerol fatty acids), palmitic (23–29%), linoleic (6.7–9.8%) or vaccenic (4.1–4.7%) acids or in the proportions of any of the less abundant fatty acids. There were some significant site‐specific differences in the proportions of palmitoleic, oleic and stearic acids. The calf depot contained more palmitoleic acid (6.41±1.09%) than the trapezius (3.12±0.55%), perirenal (3.59±0.50%) and mesenteric (3.70±0.43%) depots, more oleic acid (42.13±1.27%) than the trapezius (36.03±2.18%), perirenal (36.50±1.56%) and breast (37.13±1.55%) depots and less stearic acid (5.18±0.89%) than the trapezius (8.57±0.97%), perirenal (8.49±0.75%), mesenteric (7.87±0.42%), breast (8.02±0.75%) and clavicular (8.34±0.78%) depots. The buttock depot contained less stearic acid (6.06±0.65%) than the perirenal, mesenteric and clavicular depots, while the anterior thigh depot contained less stearic acid (6.07±0.70%) than the perirenal depot. These findings indicate that, while most human adipose depots differ little in fatty acid composition, some sites, in particular the calf, perirenal, trapezius and mesenteric depots, have site‐specific properties.
Mechanisms of free radical oxidation of unsaturated lipids
Authors: Porter Ned A. , Caldwell Sarah E. , Mills Karen A. 
Published: November 2006

AbstractThe primary producs formed from the autoxidation of lipids can be understood based upon a mechanism that involves five different reaction types. These reactions are: reaction of a carbon radical and molecular oxygen, atom transfer of a hydrogen from substrate to the chain carrying peroxyl, fragmentation of the chain carrying peroxyl to give oxygen and a carbon radical, rearrangement of the peroxyl, and cyclization of the peroxyl. The mechanisms of these primary reaction steps has been the focus of extensive research over the past fifty years, and the current level of understanding of these transformations is the subject of this review.
Cholesteryl ester transfer protein inhibition in hypercholesterolemic hamsters: Kinetics of apoprotein changes
Authors: Zuckerman Steven H. , Evans Glenn F. 
Published: November 2006

AbstractInhibition of cholesteryl ester transfer protein (CETP) activity in hypercholesterolemic hamsters results in elevated high‐density lipoprotein (HDL) cholesterol, an increase in HDL size, and the appearance of apolipoprotein E (apo E)‐rich, apo A‐I‐poor particles. The present study has focused on the kinetics of apoprotein redistribution among the HDL particles and the relative increase in HDL‐associated apo E and CETP in hypercholesterolemic hamsters, following inhibition of transfer activity using the monoclonal antibody, TP2. A 60% inhibition in CETP activity was observed 24 h after antibody injection and was associated with an increase in HDL cholesterol and HDL size. Increased amounts of apo E were associated with these HDL particles and remained in this fraction throughout the duration of the study. In contrast, while CETP was also detected on large HDL particles, this distribution shifted back toward the pretreatment pattern by 14 d. The dynamic changes in apoprotein distribution may represent a compensatory physiologic response following disruption of reverse cholesterol transport.
Uptake by macrophages of low‐density lipoprotein damaged by nitrogen dioxide in air
Authors: Kikugawa Kiyomi , Beppu Masatoshi , Okamoto Yutaka 
Published: November 2006

AbstractIn order to know whether nitrogen dioxide, an environmental and endogenous free radical toxin, can participate in the formation of atherosclerotic lesions, damage to low‐density lipoprotein (LDL) by nitrogen dioxide and uptake of the damaged LDL by macrophages were investigated. A solution of LDL at pH 7.5 was exposed to an atmosphere of nitrogen dioxide (70 ppm) in air at 37°C for 5 or 10 h. Lipid oxidation was induced by the exposure as assessed by the formation of thiobarbituric acid reactive substances. Apolipoprotein B was covalently cross‐linked via nondisulfide bonds. Fluorescence analysis showed that tryptophan residues were extensively decreased, and amino acid analysis indicated that the contents of histidine, lysine, and tyrosine residues were decreased by 30–40, 10–20, and 20–30%, respectively. Binding of LDL to thioglycolate‐induced mouse peritoneal macrophages was markedly increased by the exposure as observed by the binding of mouse erythrocytes coated with LDL. The activity of LDL to convert macrophages into lipid‐laden foam cells was also increased by the exposure. Modification of lysine residues of apo B with lipid oxidation products formed by the exposure may be responsible for the uptake by macrophages. The results suggest the possibility that exposure of LDLin vivo to nitrogen dioxide participates in the formation of atherosclerotic lesions.
Antioxidant activity of thiocholesterol on copper‐induced oxidation of low‐density lipoprotein
Authors: Tanaka Mitsuo , Nakagawa Mitsuo 
Published: November 2006

AbstractThe effect of thiocholesterol (SH‐Chol) on the copper‐inducedin vitro oxidation of low‐density lipoprotein (LDL; 1.019<d<1.063) was investigated. Among the antioxidants tested, including cysteine, glutathione, 2‐mercaptoethanol, dithiothreitol, probucol, thiopalmitic acid,. and SH‐Chol, SH‐Chol was the most effective antioxidant in copper‐induced LDL oxidation. Also, SH‐Chol completely inhibited the formation oxysterols i.e., 7‐hydroxycholesterol and 7‐ketocholesterol, in LDL particles and reduced 1,1‐diphenyl‐2‐picrylhydrazyl used as stable free‐radical model. Moreover, SH‐Chol suppressed the degradation of endogenous α‐tocopherol in LDL particles. These findings indicate that SH‐Chol acts as antioxidant in the oxidative damage of LDLin vitro and as a free‐radical scavenger in lipid peroxidation.
Thermotropic behavior of stratum corneum lipids containing a pseudo‐ceramide
Authors: Mizushima Hiromoto , Fukasawa Jun‐ichi , Suzuki Toshiyuki 
Published: November 2006

AbstractThe mechanism of the self‐assembly of the lamellar structure of natural stratum corneum lipids (SCL) has been a subject of considerable interest. We have examined this question by using a synthetic pseudo‐ceramide (sphingolipid E, SLE) which was analogous to the naturally occurring ceramide type 2. The thermotropic properties and the structural characteristics of SLE, together with other main components of SCL, fatty acids, and cholesterol, were investigated by differential scanning calorimetry and X‐ray analysis. A mixture of SLE and stearic acid was in a stable α‐form having a lamellar structure, which is very similar to that of natural SCL. However, lipid mixtures in which stearic acid were replaced by oleic acid did not form lamellar structures, and existed in the crystalline states. This indicates that the stable bilayer formation of the natural SCL is strongly dependent on the molecular fatty acid structure. Moreover, incorporation of cholesterol (0–50%) into equimolar mixtures of SLE/stearic acid and of SLE/oleic acid caused a marked decrease of melting entropies, while the aggregation states of both systems were not changed. This effect of cholesterol can be attributed to the disorder of the molecular packing. These results suggest that the hydrophobic interactions between the SCL are important for bilayer formation as are the hydrophilic interactions between the polar groups.