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At least 865 records · Page 48Linked to original sources
PubMed1992

Electrical potential dissipation induced by free fatty acids in pea stem mitochondria.

Linolenic, linoleic, oleic, palmitic and stearic acids (FFA) collapse the electrical potential of pea stem mitochondria in the absence or in the presence of 0.5 mM Mg2+. Higher concentrations of this cation (5 mM) lower the rate of dissipation caused by linoleic, oleic and palmitic acids, while abolishing that induced by stearic acid. Carboxyatractyloside and ADP do not reverse the FFA-induced collapse both in the presence or absence of Mg2+. EDTA, EGTA or BHT do not influence the dissipation caused by FFA that, in addition, is not linked to lipid peroxidation evaluated as malondialdehyde or conjugated diene formation. Only linolenic acid sustains a peroxidation which, however, appears to be caused by its own oxidation catalysed by lipoxygenases rather than by membrane lipoperoxidation induced by this free fatty acid. These results suggest that neither the ATP/ADP exchanger nor lipid peroxidation appear to be involved in FFA-induced uncoupling in pea stem mitochondria.

Cations, Divalent↗
PubMed1988

Differential utilization of long chain fatty acids during triacylglycerol depletion. I. Rat heart after ischemic perfusion.

Rat hearts were perfused with Krebs-Henseleit buffer for 90 min according to the Langendorff procedure. Normoxic perfusion for 90 min resulted in minor changes in fatty acid composition and a decrease in residual heart triacylglycerol to 60% of preperfusion values. When the protocol included 30 min of slow perfusion-induced ischemia, the hearts were observed to be depleted of 89% of their initial triacylglycerol content. The triacylglycerol fatty acid composition (mg %) remained similar after compared to before perfusion except for a 121 mg % increase in stearic acid and a 225 mg % increase in arachidonic acid. The percentage composition of both fatty acids was significantly inversely correlated with the amount of triacylglycerol remaining in the heart after perfusion. Postperfusion, arachidonic acid and stearic acids were present at nearly 1:1 in the residual heart triacylglycerol, suggesting that a common mechanism may be involved in the selective retention of these fatty acids by the heart.

Animals↗
PubMed1985

The partition of charged liposomes in aqueous two-phase systems.

Surface charge has been conveyed upon phosphatidylcholine liposomes by incorporation of varying amounts of stearic acid and stearylamine. The partition behaviour of these charged liposomes in several aqueous two-phase polymer systems containing a range of potential differences across the interface was investigated. Changes in partition were observed that were dependent on the stearylamine concentration of the liposomes. Incorporation of stearic acid produced no major changes in partition. Identical changes in partition were detected for stearic acid and stearylamine containing liposomes in a phase system with little or no potential difference. These changes in partition therefore represent the effect of the 'non-charged' portion of the lipid molecule. The use of aqueous two-phase partition as a method for detecting liposome surface charge is discussed.

Amines↗
PubMed2002

[In vitro and in vivo study of two kinds of long-circulating solid lipid nanoparticles containing paclitaxel].

AIM: To prepare long-circulating solid lipid nanoparticles containing paclitaxel with stearic acid, and investigate the in vitro and in vivo characterization of nanoparticles. METHODS: The method of "emulsion evaporation-solidification at low temperature" was used to prepare the stearic acid solid lipid nanoparticles containing paclitaxel. Its morphology was examined by transmission electron microscope. The HPLC method for determination of paclitaxel in nanoparticles or serum samples was established. The release of paclitaxel in vitro and the pharmacokinetics after i.v. bolus injection to mice were studied. RESULTS: The mean diameter of Brij78-SLN and F68-SLN is (103.5 +/- 29.2) nm and (220 +/- 98) nm, respectively. The nanoparticles release paclitaxel slowly and linearly, within 24 h, Brij78-SLN and F68-SLN release 8% and 20% of total drug, respectively. Long-circulation nanoparticles was found to stay in the blood circulation, with T 1/2 beta 10.1 h of F68-SLN, and T 1/2 beta 4.88 h of Brij78-SLN more than one commercialized paclitaxel injection, T 1/2 beta 1.3 h. CONCLUSION: Stearic acid might be a new drug carrier material in the future.

Animals↗
PubMed1975

Electron spin resonance studies on the lipid-protein interaction between cardiolipin and anti-cardiolipin antibodies.

Electron spin resonance measurements were performed in order to investigate the influence of anti-cardiolipin antibodies on cardiolipin-containing liposomes. The physical state of the lipid structures and the alterations caused by the interaction with specific antibody were determined by measuring the freedom of motion of spin-labeled stearic acid derivatives incorporated into the lipid structures. The interaction of the cardiolipin-containing liposomes with the anti-cardiolipin antibodies reduced the mobility of the spin-labeled stearic acid probe I (12, 3), whose nitroxide group is assumed to be located near the polar region of the lipid bilayer. The restricted mobility, which qualitatively resembles the interaction of cardiolipin liposomes with calcium ions, is probably the result of a tighter packing of the polar groups in their crystalline array. The binding sites of the cardiolipin structures for anti-cardiolipin antibodies and Ca2 ions seem to be identical. As indicated by the spin-labeled stearic acid probe I (1, 14), the apolar region of the lipid bilayer is not affected by the interaction of the cardiolipin-containing liposomes with the anti-cardiolipin antibodies.

Antigen-Antibody Reactions↗
PubMed1997

Characterization of polar and nonpolar seed lipid classes from highly saturated fatty acid sunflower mutants.

The seed lipids from five sunflower mutants, two with high palmitic acid contents, one of them in high oleic background, and three with high stearic acid contents, have been characterized. All lipid classes of these mutant seeds have increased saturated fatty acid content although triacylglycerols had the highest levels. The increase in saturated fatty acids was mainly at the expense of oleic acid while linoleic acid levels remained unchanged. No difference between mutants and standard sunflower lines used as controls was found in minor fatty acids: linolenic, arachidic, and behenic. In the high-palmitic mutants palmitoleic acid (16:1n-7) and some palmitolinoleic acid (16:2n-7, 16:2n-4) also appeared. Phosphatidylinositol, the lipid with the highest palmitic acid content in controls, also had the highest content of palmitic or stearic acids, depending on the mutant type, suggesting that saturated fatty acids are needed for its physiological function. Positional analysis showed that mutant oils have very low content of saturated fatty acids in the sn-2 position of triacylglycerols, between the content of olive oil and cocoa butter.

Fatty Acids↗
PubMed2003

The effect of supplementing layer diets with shark cartilage or chitosan on egg components and yolk lipids.

1. An experiment was designed to evaluate the effects of the addition of shark cartilage (SC) or chitosan (CH) to layer diets on egg component weights, yolk lipids and hen plasma lipids. 2. Hy-Line laying hens (80) were used during a 56 d feeding trial. Treatments were: basal diet (BD), BD + 20 g/kg SC, BD + 30 g/kg SC, BD + 20 g/kg CH and BD + 30 g/kg CH. Eggs were analysed on d 14, 28, 42 and 56. 3. Egg weight and egg component weights were not affected by these treatments throughout the experimental period. 4. After 14d of experimental feeding, cholesterol levels were higher in eggs from birds given BD + 20 g/kg CH and BD + 30 g/kg CH than in those from birds given BD. 5. Furthermore, eggs from hens given BD + 20 g/kg SC or BD + 20 g/kg CH were higher in palmitic and stearic acids and lower in oleic acid than those from birds fed on BD. After 56 d feeding, however, palmitic and stearic acid contents in eggs from hens given any of the supplemented diets were lower than in those from hens given BD, and oleic acid in eggs from hens given BD + 20 g/kg SC, BD + 30 g/kg SC and BD + 30 g/kg CH was higher than in those from birds fed on BD. 6. Plasma cholesterol and triacylglycerol levels were not significantly affected by dietary treatment. 7. Shark cartilage or chitosan at up to 30 g/kg in layer diets did not affect egg component weights (yolk, white and shell) and total lipid contents. During the period from 42 to 56d of experimental feeding, diets containing up to 30 g/kg chitosan reduced egg yolk contents of cholesterol, palmitic and stearic acids and increased the content of oleic acid.

Animal Feed↗
PubMed1988

Distinct long chain and very long chain fatty acyl CoA synthetases in rat liver peroxisomes and microsomes.

Mitochondria, peroxisomes, and microsomes were isolated from rat liver homogenates, and stearic acid and lignoceric acid beta-oxidation, as well as stearoyl CoA synthetase and lignoceroyl CoA synthetase activities in the three organelles, were compared. Stearic acid beta-oxidation in peroxisomes was sixfold greater compared to the oxidation in mitochondria. Lignoceric acid beta-oxidation, observed only in peroxisomes, was fivefold lower compared to stearic acid beta-oxidation. Stearoyl CoA synthetase was present whereas lignoceroyl CoA synthetase was absent in mitochondria. Stearoyl CoA synthetase and lignoceroyl CoA synthetase activities were present in microsomes and peroxisomes, but the activity of stearoyl CoA synthetase was several-fold greater compared to lignoceroyl CoA synthetase in both organelles. The differing responses to detergents and phospholipids of stearoyl CoA and lignoceroyl CoA synthetase activities in microsomes as well as peroxisomes indicated that each activity was catalyzed by a separate enzyme. Differences in detergent and phospholipid response were also noted when either stearoyl CoA or lignoceroyl CoA synthetase activity in one organelle was compared with the corresponding activity in the other organelle, suggesting that the same activity in different organelles may be catalyzed by separate enzyme proteins.

Animals↗
PubMed1990

Relationship between lipid saturation and lipid-protein interaction in liver mitochondria modified by catalytic hydrogenation with reference to cardiolipin molecular species.

Lipid acyl double bonds in isolated mitochondrial membranes were gradually reduced by palladium-complex-catalysed hydrogenation, and the resulting saturation was monitored by fatty acid analysis of phosphatidylcholine, phosphatidylethanolamine and cardiolipin. The courses of hydrogenation of these phospholipids suggested that cardiolipin is in a membrane compartment which is less accessible to the applied catalyst. Native cardiolipin and its hydrogenation products were further characterized by analysis of their molecular diacylglycerol species. A decrease in the double bond content was accompanied by an increased amount of motionally restricted lipids at the hydrophobic interface of proteins as measured by two different spin-labelled lipids (C-14 positional isomers of spin-labelled stearic acid and phosphatidylcholine analogues). The protein-immobilized fraction of spin-labelled stearic acid increased in parallel with the hydrogenation of cardiolipin rather than of phosphatidylcholine or phosphatidylethanolamine. These data are interpreted in terms of a tight association of cardiolipin with membrane proteins, which becomes looser upon double bond reduction leading to the replacement of cardiolipin by spin-labelled stearic acid in the solvation shell. Thus the hydrophobic moiety of cardiolipin, characterized by double-unsaturated C18-C18 diacylglycerol species, seems to be an important structural requirement for the high protein affinity of this compound.

Animals↗
PubMed1982

Inhibition of ovine gastric acid secretion by intraduodenal long-chain fatty acids.

Effects on ovine gastric function of procedures that increase intestinal unsaturated fatty acid content are unknown, and the present aim was to compare the effects of duodenal unsaturated and saturated fatty acids on gastric secretion in conscious sheep. During the maximal gastric secretory response to a meal, 10 ml gallbladder bile alone or with myristic, palmitic, and stearic acids and oleic, linoleic, and linolenic acids were infused into the duodenum at a rate of 5 g fatty acid . h-1 for 1 h. Compared with control 154 mM NaCl (100%), acid output was reduced to 4-7% of control with infusion of oleic, linoleic, and linolenic acids and myristic acids plus bile. Reductions in acid secretion persisted for up to 5 h from the end of infusion. In contrast, the infusion of palmitic and stearic acids with bile caused mean maximal reductions in acid output, respectively, to only 64 and 55% of control, and levels returned to control within 1 h of the end of infusion. Bile infusion alone caused no reduction in acid secretion. Under the conditions used, C18 unsaturated fatty acids and myristic acid were potent inhibitors of ovine gastric acid secretion. The lesser effects of palmitic and stearic acids were probably related to their reduced solubility and absorption.

Animals↗
PubMed1967

The incorporation of long-chain fatty acids into phospholipids of respiring slices of rat cerebrum.

1. Respiring slices of adult rat cerebrum have been shown to incorporate long-chain (14)C-labelled fatty acids into phospholipid. 2. Labelling was almost entirely confined to lecithin and ethanolamine phospholipid, only traces being present in serine phospholipid. 3. Palmitic acid, oleic acid and linoleic acid were incorporated more actively into lecithin than into ethanolamine phospholipid, but the converse was found with stearic acid. 4. All four acids labelled the 1- and 2-positions of both lipids; palmitic acid, oleic acid and linoleic acid were approximately evenly distributed, but stearic acid was incorporated predominantly at the 1-position. 5. It is considered that incorporation is most likely brought about through acylation of endogenously derived lysophosphatides. 6. The possible implications of this pathway of lipid metabolism in nervous tissue are discussed.

Animals↗
PubMed1992

Differential effects of saturated fatty acids on low density lipoprotein metabolism in the guinea pig.

Studies have shown that dietary fat saturation affects guinea pig plasma low density lipoprotein (LDL) levels by altering both LDL receptor-mediated catabolism and flux rates of LDL (Fernandez et al. 1992. J. Lipid Res. 33: 97-109). The present studies investigated whether saturated fatty acids of varying chain lengths have differential effects on LDL metabolism. Guinea pigs were fed 15% (w/w, 35% calories) fat diets containing either palm kernel oil (PK), 52% lauric acid/18% myristic acid; palm oil (PO), 43% palmitic acid/4% stearic acid; or beef tallow (BT), 23% palmitic acid/14% stearic acid. Plasma LDL cholesterol levels were significantly higher for animals fed the PK diet (P < 0.001) with values of 83 +/- 19 (n = 12), 53 +/- 8 (n = 12) and 44 +/- 16 (n = 10) mg/dl for PK, PO, and BT diets, respectively. The relative percentage composition of LDL was modified by fat type; however, LDL diameters and peak densities were not different between diets, indicating no effect of saturated fatty acid composition on LDL size. ApoB/E receptor-mediated LDL fractional catabolic rates (FCR) were significantly lower in animals fed the PK diet (P < 0.01) and LDL apoB flux rates were reduced (P < 0.01) in animals fed the BT diet. A correlation was found between plasma LDL levels and receptor-mediated LDL catabolism (r = -0.66, P < 0.01). A higher apoB/E receptor number (Bmax), determined by in vitro LDL binding to guinea pig hepatic membranes, was observed for animals fed BT versus PK or PO diets and Bmax values were significantly correlated with plasma LDL levels (r = -0.776, P < 0.001). These results indicate that saturated fatty acids of varying chain length have differential effects on hepatic apoB/E receptor expression and on LDL apoB flux rates which in part account for differences in plasma LDL cholesterol levels of guinea pigs fed these saturated fats.

Animals↗
PubMed1988

The protonophore resistance of Bacillus megaterium is correlated with elevated ratios of saturated to unsaturated fatty acids in membrane phospholipids.

Growth of the protonophore-resistant strain of Bacillus megaterium, strain C8, in the presence of oleic acid markedly reduced its resistance to low concentrations of carbonylcyanide m-chlorophenylhydrazone (CCCP). Growth of the CCCP-sensitive wild-type strain in the presence of stearic acid increased the resistance of that strain to growth inhibition by protonophore. Studies of the membrane lipids indicated that in the absence of additions to the medium, membranes from C8 contained greatly reduced levels of monounsaturated fatty acids relative to the wild type; wild-type levels were restored by growth of C8 in the presence of oleic acid, concomitant with the loss of resistance. Conversely, growth of the wild type on stearic acid increased the ratio of saturated/unsaturated fatty acids in the membrane, concomitant with a modest increase in the resistance of the wild-type strain to CCCP. The exogenous oleic acid was preferentially incorporated into phosphatidylethanolamine, diphosphatidylglycerol, and 1,2-diacylglycerol, whereas stearic acid was incorporated preferentially into phosphatidylglycerol, and into the small component of free fatty acids. Depending upon the growth conditions, changes in membrane lipid-to-membrane protein ratio and in the ratios of polar lipid components were observed, but none of those changes correlated as did the changes in saturated fatty-acid-to-unsaturated fatty-acid ratio with protonophore resistance. This latter correlation was further suggested by experiments in which the protonophore resistance of wild type B. megaterium was shown to increase with increasing growth temperature without any temperature-dependent loss of protonophore efficacy. The experiments here support the hypothesis developed from work with Bacillus subtilis that changes in the fatty acid composition of the membrane phospholipids affect energy coupling, and make it clear that simple increases or decreases in the hydrolytic activity of ATPase in the uncoupler-resistant mutants of bacilli are not correlated with resistance in some direct way.

Bacillus megaterium↗
PubMed1981

Increased synthesis of hexacosanoic acid (C23:0) by cultured skin fibroblasts from patients with adrenoleukodystrophy (ALD) and adrenomyeloneuropathy (AMN).

We studied the metabolism of radioactive stearic acid by cultured skin fibroblasts from patients wtih adrenoleukodystrophy (ALD) and its variant, adrenomyeloneuropathy (AMN), to clarify the mechanism of the increased content of very long chain saturated fatty acids in cholesterol esters and sphingolipids, which are known to be the characteristic biochemical changes in ALD and AMN. A substantial amount of hexacosanoic acid (C26 : 0) wa synthesized from stearic acid by ALD and AMN fibroblasts, whereas only a trace amount of hexacosanoic acid was synthesized by control fibroblasts. This indicates that the primary biochemical defect in ALD and AMN may involved the elongation system of very long chain fatty acids.

Adrenal Gland Diseases↗
PubMed1987

Lipid asymmetry induced by transmembrane pH gradients in large unilamellar vesicles.

We have investigated the influence of transmembrane pH gradients across large unilamellar vesicle membranes on the transbilayer distributions of simple lipids with weak base and weak acid characteristics. Trinitrobenzenesulfonic acid labeling results consistent with a rapid and complete migration of stearylamine and sphingosine to the inner monolayer of the large unilamellar vesicles are observed when the large unilamellar vesicles' interior is acidic. Alternatively, when the vesicle interior is basic, oleic and stearic acid cannot be removed by external bovine serum albumin, indicating a localization in the inner monolayer. Moreover, effects corresponding to the decrease in external surface charge predicted upon the migration of stearylamine or stearic acid to the inner monolayer are readily detected employing ion exchange chromatography. These results are consistent with transbilayer distributions of these agents dictated by a Henderson-Hasselbach equilibrium. The possible implications for metabolic regulation by pH gradients, as well as factors giving rise to phospholipid transbilayer asymmetry, are discussed.

Affinity Labels↗
PubMed2004

Antimicrobial and physicochemical properties of chitosan-HPMC-based films.

To prepare composite films from biopolymers with anti-listerial activity and moisture barrier properties, the antimicrobial efficiency of chitosan-hydroxy propyl methyl cellulose (HPMC) films, chitosan-HPMC films associated with lipid, and chitosan-HPMC films chemically modified by cross-linking were evaluated. In addition, the physicochemical properties of composite films were evaluated to determine their potential for food applications. The incorporation of stearic acid into the composite chitosan-HPMC film formulation decreased water sensitivity such as initial solubility in water and water drop angle. Thus, cross-linking of composite chitosan-HPMC, using citric acid as the cross-linking agent, led to a 40% reduction in solubility in water. The water vapor transfer rate of HPMC film, approximately 270 g x m(-2) x day(-1) x atm(-1), was improved by incorporating chitosan and was further reduced 40% by the addition of stearic acid and/or cross-linking. Anti-listerial activity of films was determined on solid medium by a numeration technique. Chitosan-HPMC-based films, with and without stearic acid, inhibited the growth of Listeria monocytogenes completely. On the other hand, a loss of antimicrobial activity after chemical cross-linking modification was observed. FTIR and 13C NMR analyses were then conducted in order to study a potential chemical modification of biopolymers such as a chemical reaction with the amino group of chitosan. To complete the study, the mechanical properties of composite films were determined from tensile strength assays.

Anti-Infective Agents↗
PubMed2003

Accumulation of a cocoa-butter-like lipid by Yarrowia lipolytica cultivated on agro-industrial residues.

Yarrowia lipolytica was cultivated on mixtures of saturated free fatty acids (an industrial derivative of animal fat called stearin), technical glycerol (the main by-product of bio-diesel production facilities), and glucose. The utilization of technical glycerol and stearin as co-substrates resulted in higher lipid synthesis and increased citric acid production than the combination of glucose and stearin. The lipids produced contained significant amounts of stearic acid (50-70%, wt/wt) and lower ones of palmitic (15-20%, wt/wt), oleic (7-20%, wt/wt), and linoleic (2-7%, wt/wt) acid. Single-cell oil having a composition similar to cocoa-butter up to 3.4 g/L was produced, whereas in some cases relatively increased citric acid quantities (up to 14 g/L) were excreted into the growth medium. The microorganism presented a high specificity for lauric, myristic, and palmitic acid, while a discrimination for the stearic acid was observed. As a conclusion, microbial metabolism could be directed by using mixtures of inexpensive saturated fats, glycerol, and glucose as co-substrates, in order to accumulate lipids with predetermined composition, e.g., cocoa-butter equivalents.

Citric Acid↗
PubMed1982

Fatty acid effects on calcium influx and efflux in sarcoplasmic reticulum vesicles from rabbit skeletal muscle.

Low concentrations of fatty acids inhibited initial Ca uptake by sarcoplasmic reticulum vesicles, the extent of inhibition varying with chain length and unsaturation in a series of C14-C20 fatty acids. Oleic acid was a more potent inhibitor of initial Ca uptake than stearic acid at 25 degrees C, whereas at 5 degrees C there was less difference between the inhibitory effects of low concentrations of these fatty acids. When the fatty acids were added later, during the phase of spontaneous Ca release that follow Ca uptake in reactions carried out at 25 degrees C 1-4 microM oleic and stearic acids caused Ca content to increase. This effect was due to marked inhibition of Ca efflux and slight stimulation of Ca influx. At concentrations of greater than 4 microM, both fatty acids inhibited the Ca influx that occurs during spontaneous Ca release; in the case of oleic acid, this inhibition resembled that of initial Ca uptake at 5 degrees C. The different effects of fatty acids at various times during Ca uptake reactions may be explained in part if alterations in the physical state of the membranes occur during the transition from the phase of initial Ca uptake to that of spontaneous Ca release.

Animals↗