Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “STEARIC ACID”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44Linked to original sources
PubMed1986

Spin-label studies on phosphatidylcholine-cholesterol membranes: effects of alkyl chain length and unsaturation in the fluid phase.

Dynamic properties of phosphatidylcholine-cholesterol membranes in the fluid phase and water accessibility to the membranes have been studied as a function of phospholipid alkyl chain length, saturation, mole fraction of cholesterol, and temperature by using spin and fluorescence labelling methods. The results are the following: (1) The effect of cholesterol on motional freedom of 5-doxyl stearic acid spin label (5-SASL) and 16-doxyl stearic acid spin label (16-SASL) in saturated phosphatidylcholine membrane is significantly larger than the effects of alkyl chain length and introduction of unsaturation in the alkyl chain. (2) Variation of alkyl chain length of saturated phospholipids does not alter the effects of cholesterol except in the case of dilauroylphosphatidylcholine, which possesses the shortest alkyl chains (12 carbons) used in this work. (3) Unsaturation of the alkyl chains greatly reduces the ordering effect of cholesterol at C-5 and C-16 positions although unsaturation alone gives only minor fluidizing effects. (4) Introduction of 30 mol% cholesterol to dimyristoylphosphatidylcholine membranes decreases the lateral diffusion constants of lipids by a factor of four, while it causes only a slight decrease of lateral diffusion in dioleoylphosphatidylcholine membranes. (5) If compared at the same temperature, 5-SASL mobilities plotted as a function of mole fraction of cholesterol in the fluid phases of dimyristoylphosphatidylcholine-, dipalmitoylphosphatidylcholine- and distearoylphosphatidylcholine-cholesterol membranes are similar in wide ranges of temperature (45-82 degrees C) and cholesterol mole fraction (0-50%). (6) In isothermal experiments with saturated phosphatidylcholine membranes, 5-SASL is maximally immobilized at the phase boundary between Regions I and III reported by other workers (Recktenwald, D.J. and McConnell, H.M. (1981) Biochemistry 20, 4505-4510) and becomes more mobile away from the boundary in Regions I and III. (7) 5-SASL in unsaturated phosphatidylcholine membranes showed a gradual monotonic immobilization with increase of cholesterol mole fraction without showing any maximum in the range of cholesterol fractions studied. (8) By rigorously determining rigid-limit magnetic parameters of cholestane spin labels in membranes from Q-band second-derivative ESR spectra to monitor the dielectric environment around the nitroxide radical, it is concluded that cholesterol incorporation increases water accessibility in the hydrophilic loci of the membrane. In contrast, 12-(9-anthroyloxy)stearic acid fluorescence showed that water accessibility is decreased in the hydrophobic loci of the membrane.

Cholesterol↗
PubMed1988

Cardiovascular effects of leukotoxin (9, 10-epoxy-12-octadecenoate) and free fatty acids in dogs.

Leukotoxin (9,10-epoxy-12-octadecenoate) biosynthesised from linoleate by neutrophils is highly toxic to cellular function. Its cardiovascular effects were studied in dogs together with the effects of various fatty acids. Aortic flow, left ventricular peak dP.dt-1, and aortic pressure were measured in 60 anaesthetised dogs, which were divided into 10 groups of six animals each--namely, control group (10 ml of physiological saline), three leukotoxin groups (5, 10, and 50 mg.kg-1), two linoleic acid groups (10 and 50 mg.kg-1), two oleic acid groups (10 and 50 mg.kg-1), and two stearic acid groups (10 and 50 mg.kg-1). Leukotoxin injected intravenously depressed cardiac function in a dose dependent manner. Administration of leukotoxin 5 mg.kg-1 showed no significant cardiotoxic effect. However, 10 mg.kg-1 of leukotoxin significantly decreased aortic flow from 0.74(0.04) to 0.40(0.07) litre.min-1 (mean(SEM], left ventricular peak dP.dt-1 from 2040(205) to 1140(217) mmHg.s-1, and aortic pressure from 106(7.1)/67(6.3) to 75(9.2)/48(6.5) mmHg 5 min after injection. Dogs given leukotoxin 50 mg.kg-1 showed more pronounced cardiodepressive effects; aortic flow was decreased to 0.19(0.06), left ventricular dP.dt-1 to 560(134), and aortic pressure to 72(15.1)/41(10.6) 5 min after injection. All dogs in this group were dead within 45 min. Administration of 10 mg.kg-1 of linoleic acid, oleic acid, or stearic acid caused no significant haemodynamic changes. Administration of linoleic acid 50 mg.kg-1 had cardiotoxic effects, but the effect was less than that of leukotoxin. Since leukotoxin appears to be a potent cardiodepressive agent it may be an important factor in the development of heart failure observed in patients with severe burns.

Animals↗
PubMed1994

Influence of vesicle curvature on fluorescence relaxation kinetics of fluorophores.

The effect of membrane curvature on the fluorescence decay of 2-p-toluidinyl-naphthalene-6-sulfonic acid (TNS), 2-(9-anthroyloxy) stearic acid (2-AS) and 12-(9-anthroyloxy)-stearic acid (12-AS) was investigated for egg lecithin vesicles of average diameter dm = 22 nm and 250 nm. The biexponential fluorescence decay of TNS at the red edge of the emission spectrum was analysed according to the model of Gonzalo and Montoro [1]. Over the entire temperature range (1-40 degrees C) the small TNS labelled vesicles showed significantly shorter solvent relaxation times tau(r) than their larger counterparts (e.g. 1.3 ns compared with 2.1 ns at 5 degrees C), indicating a higher mobility of the hydrated headgroups in the highly curved, small vesicles. The fluorescence decay of both AS derivatives is also biexponential. While the shorter decay times (1-3 ns) are practically identical for small and large vesicles, the longer decay times (5-14 ns) are identical only for 12-AS but not for 2-AS. This indicates that the microenvironment is similar in small and large vesicles deep in the membrane in spite of the differences in curvature.

Journal Article↗
PubMed1989

Beta-oxidation of medium chain (C8-C14) fatty acids studied in isolated liver cells.

The beta-oxidation and esterification of medium-chain fatty acids were studied in hepatocytes from fasted, fed and fructose-refed rats. The beta-oxidation of lauric acid (12:0) was less inhibited by fructose refeeding and by (+)-decanoyl-carnitine than the oxidation of oleic acid was, suggesting a peroxisomal beta-oxidation of lauric acid. Little lauric acid was esterified in triacylglycerol fraction, except at high substrate concentrations or in the fructose-refed state. With [1-14C]myristic acid (14:0), [1-14C]lauric acid (12:0), [1-14C]octanoic acid (8:0) and [2-14C]adrenic acid (22:4(n - 6] as substrate for hepatocytes from carbohydrate-refed rats, a large fraction of the 14C-labelled esterified fatty acids consisted of newly synthesized palmitic acid (16:0), stearic acid (18:0) and oleic acid (18:1) while intact [1-14C]oleic acid substrate was esterified directly. With [9,10-3H]myristic acid as the substrate, small amounts of shortened 3H-labelled beta-oxidation intermediates were found. With [U-14C]palmitic acid, no shortened fatty acids were detected. It was concluded that when the mitochondrial fatty acid oxidation is down-regulated such as in the carbohydrate-refed state, medium-chain fatty acids can partly be retailored to long-chain fatty acids by peroxisomal beta-oxidation followed by synthesis of C16 and C16 fatty acids which can then stored as triacylglycerol.

Animals↗
PubMed1983

Relative fatty acid composition of serum lecithin in the normal puerperium.

21 women who had been followed regularly during their normal pregnancies were examined in the puerperium. The relative fatty acid composition of serum lecithin was analyzed by means of gas-liquid chromatography. Palmitic acid decreased and stearic acid increased, which indicates a shift to more pathway II-synthesized lecithin in the puerperal period. Linoleic acid increased and the longer polyunsaturated fatty acids decreased. These changes were slow as compared to the changes in the saturated fatty acids. No correlations were found between the saturated fatty acids and linoleic acid dominating the polyunsaturated fatty acids. The results indicate different incorporational ways into the lecithin molecule of these fatty acid groups. It is suggested that the deacylation-reacylation cycle is responsible for the high content of longer polyunsaturated fatty acids still 1 week after delivery. 6 weeks after delivery normal values were recorded. Breast-feeding did not seem to influence the fatty acid pattern of serum lecithin.

Adult↗
PubMed1979

Fatty acid composition of human adipose tissue from two anatomical sites in a biracial community.

This report describes the age-race specific distribution of fatty acids in samples of adipose tissue taken from both the perirenal and buttock areas of 406 men autopsied in a community pathology study. This analysis of fatty acid composition of adipose tissue is part of a comprehensive investigation of atherosclerosis and coronary heart disease in a community setting. The findings from analysis of fatty acids are expressed as mass percentage of all fatty acids in adipose tissue triglyceride. For each age-site subgroup, white men tended to have higher mean percentages of myristic acid and palmitoleic acid than did black men. The converse was found for stearic acid. In the younger age groups only, the whites showed a higher mean percentage of linoleic acid than the blacks in adipose tissue from both sites. Age was associated with a decrease in mean percentage of stearic acid and an increase in mean percentage of oleic acid and palmitoleic acid in both races. The older age group had a lower mean percentage of linoleic acid than the younger age groups. The mean percentages of myristic, palmitic, and stearic acids were higher in perirenal tissue, while the mean percentages of palmitoleic and oleic acids were higher in buttock adipose tissue in both races.

Adipose Tissue↗
PubMed2005

Stable dispersions of silver nanoparticles in carbon dioxide with fluorine-free ligands.

Iso-stearic acid, a short, stubby compound with branched, methylated tails has been shown to have high solubility in carbon dioxide. Tail solvation by carbon dioxide makes iso-stearic acid a good choice for use as a ligand to sterically stabilize metallic nanoparticles. Iso-stearic acid coated silver nanoparticles have been stably dispersed in carbon dioxide with hexane cosolvent. Neat carbon dioxide has successfully dispersed iso-stearic acid coated silver nanoparticles that had been deposited on either quartz or polystyrene surfaces. These results are the first reports of sterically stabilized nanoparticles in carbon dioxide without the use of any fluorinated compounds.

Journal Article↗
PubMedDate not supplied

The fate of ingested glyceran esters of condensed castor oil fatty acids [polyglycerol polyricinoleate (PGPR)] in the rat.

Samples of the emulsifier polyglycerol polyricinoleate (PGPR) were synthesized using the radiolabelled precursors [1-14C]glycerol ([14C]polyglycerol PGPR), [9,10-3H] or [12-3H]ricinoleic acid ([3H] PGPR) or [1-14C]stearic acid ([14C]stearyl PGPR). The absorption, tissue distribution, metabolism and excretion of these 14C- or tritium-labelled PGPR samples administered to rats was studied. The effects of intestinal and porcine pancreatic lipases on PGPR preparations were examined. Rats were dosed with [1-14C]glycerol, [14C]polyglycerol and ([14C]polyglycerol)PGPR by gavage and their urine. faeces and expired CO2 monitored for 14C. The results from the [1-14C]glycerol treated animals showed extensive metabolism of glycerol. For [14C]polyglycerols, the lower polyglycerols were preferentially absorbed from the intestine and were excreted unchanged in the urine while the higher polyglycerols were found in the faeces. After 4 days, 93% of the dose of polyglycerols was recovered, of which some 30% was found in the urine and 60% in the faeces. Traces of 14C activity were found in depot fat and liver. The excretory pattern and urinary metabolites from ([14C]polyglycerol) PGPR was very similar to that of [14C]polyglycerol. Analysis of urinary and faecal 14C material indicated that the PGPR polymer was digested to give free polyglycerol and polyricinoleic acid. PGPR was synthesised incorporating [1-14C]stearic into polyricinoleic acid which was then esterified with polyglycerol. The resulting [14C]PGPR or [1-14C] stearic acid in a dietary slurry was administered to groups of fed or starved rats by gavage. The results indicated complete digestion of PGPR and absorption of the fatty acids. The 14C-material absorbed was extensively laid down in depot fat and some metabolism to 14CO2 was demonstrated. The fate of the stearic acid was similar whether dosed alone or incorporated into the PGPR polymer. Samples of PGPR were synthesized containing 3H-labelled ricinoleic acid. The resulting [3H]PGPR was intubated into rats as a component of a dietary slurry. The results indicated that the polymer is extensively digested and 90% of the administered tritium is absorbed. The absorbed material was extensively metabolized within 24 hr so that large amounts of tritium were present in the aqueous phase of the tissues examined. After 24 hr, less than 5% of the administered material was present as lipid material, of which a large proportion was as non-hydroxy fatty acids. No traces of polymer material were found in the tissues examined. In vitro digestion of PGPR by porcine pancreatic lipase and rat intestinal fractions was demonstrated. The results indicate very extensive digestion of the PGPR polymer to polyglycerols and fatty acids. The fatty acids are metabolized extensively. The mono-, di- and triglycerols are extensively absorbed from the intestinal tract and rapidly excreted in the urine unchanged but the hexa-, penta- and higher polyglycerols are essentially not absorbed and excreted in the faeces unchanged.

Animals↗
PubMed1977

Fatty acid composition of adipose tissue in patients with coronary heart disease.

In order to study the relationship between the fatty acid composition of adipose tissue and coronary heart disease (CHD), 34 consecutive male patients with acute myocardial infarction and 33 hospitalized men free of CHD were compared. Patients with diabetes mellitus, endocrine disorders, liver and kidney diseases, recent changes in body weight and deviations from the "normal", customary diet were exlcuded. A statistically significant difference between the two groups was observed only in stearic acid, its proportion being lower in CHD patients (3.25% vs. 4.13%). Using multivariate discriminant analysis, age discriminated best between the groups, followed by stearic acid. The signs observed were positive for the former and negative for the latter. All other acids, relative body weight, and skinfold measurements did not significantly contribute to the discrimination. Age did not correlate with the proportion of stearic acid. Blood lipids from samples taken within 24 h of admission did not significantly differ between the groups. Three months later they had risen considerably in the infarct patients. The metabolic basis of the relationship between CHD and stearic acid is not clear at present. Additional studies are necessary to substantiate the importance of this acid as an indicator of CHD.

Acute Disease↗
PubMed1986

Inhibition of sperm motility and agglutination of sperm cells by free fatty acids in whole semen.

The effects of a serial dilution of linoleic acid on human spermatozoa in whole semen was tested on 21 semen samples obtained from 11 normal volunteers. The minimal concentration of linoleic acid required to stop the movement of at least 75% of the moving sperm ranged from 1 to greater than 100 mg/dl. Fifteen of 21 (71%) of the semen samples were inhibited by added free fatty acids (FFA) concentrations that were less than or close to the physiologic concentration ranges of FFA in blood plasma (1 to 30 mg/dl). The immobilized sperm often formed aggregates similar to those formed by the action of autoantibodies against sperm cells. Preliminary studies conducted on a variety of other FFA have indicated that oleic acid (18/1) was less toxic than linoleic acid (18/2) and that linolenic acid (18/3) was more toxic than linoleic acid. The saturated FFA palmitic acid (16/0) and stearic acid (18/0) at concentrations up to 100 mg/dl showed little or no toxicity to sperm cells. It is suggested that FFA toxicity be included among physiologic factors that affect the motility and spontaneous aggregation of sperm cells.

Ascorbic Acid↗
PubMed2006

Within and between breed differences in freezing tolerance and plasma membrane fatty acid composition of boar sperm.

The response of sperm to cryopreservation and the fertility of frozen-thawed semen varies between species. Besides species differences in sperm physiology, structure and biochemistry, factors such as sperm transport and female reproductive tract anatomy will affect fertility of frozen-thawed semen. Therefore, studying differences in sperm cryotolerance between breeds and individuals instead of between species may reveal sources of variability in sperm cryotolerance. In the present study, the effect of cooling, re-warming and freezing and thawing on plasma membrane and acrosome integrity of sperm within and between Norwegian Landrace and Duroc breeds was studied. Furthermore, the relation between post-thaw survival rate and fatty acid composition of the sperm plasma membranes was investigated. Flow cytometry assessments of plasma membrane and acrosome integrity revealed no significant differences between breeds; however there were significant male-to-male variations within breeds in post-thaw percentages of live sperm (plasma membrane intact). The most abundant fatty acids in the plasma membranes from both breeds were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1, n-9), docosapentaenoic acid (22:5, n-6) and docosahexaenoic acid (22:6, n-3). The ratio of sigma operator 22:5, n-6 and 22:6, n-3/ sigma operator all other membrane fatty acids was significantly related to survival rate (plasma membrane integrity) of sperm for both Norwegian Landrace (correlation coefficient (r(s)) = 0.64, P < 0.05) and Duroc (r(s) = 0.67, P < 0.05) boars. In conclusion, male-to-male differences in sperm survival rate after freezing and thawing may be partly related to the amount of long-chain polyunsaturated fatty acids in the sperm plasma membranes.

Acrosome Reaction↗
PubMed1993

Metabolism of exogenous ganglioside GM1 in cultured cerebellar granule cells. The fatty acid and sphingosine moieties formed during degradation are re-used for lipid biosynthesis.

Cerebellar granule cells, differentiated in vitro, were parallelly fed with [Sph-3H]GM1 and [stearoyl-14C]GM1, under identical conditions (10(-6) M ganglioside; pulse, from 1-4 h; chase, up to 24 h after 4 h pulse) and the salvage pathways of sphingosine and stearic acid were investigated. It was observed that both sphingosine and stearic acid, liberated during the intralysosomal degradation of ganglioside, are metabolically recycled, along distinct pathways. Sphingosine is used for the biosynthesis of a number of sphingolipids, particularly ceramide, glucosyl-ceramide, gangliosides and sphingomyelin; stearic acid is utilized for the biosynthesis of sphingolipids, and to a greater extent, glycero-phospholipids, especially those endogenously richer in stearic acid (phosphatidyl-ethanolamine and phosphatidyl-choline). No evidence was provided for a salvage pathway for ceramide.

Animals↗
PubMed2004

Investigating fatty acids inserted into magnetically aligned phospholipid bilayers using EPR and solid-state NMR spectroscopy.

This is the first time (2)H solid-state NMR spectroscopy and spin-labeled EPR spectroscopy have been utilized to probe the structural orientation and dynamics of a stearic acid incorporated into magnetically aligned phospholipid bilayers or bicelles. The data gleaned from the two different techniques provide a more complete description of the bilayer membrane system. Both methods provided similar qualitative information on the phospholipid bilayer, high order, and low motion for the hydrocarbon segment close to the carboxyl groups of the stearic acid and less order and more rapid motion at the end towards the terminal methyl groups. However, the segmental order parameters differed markedly due to the different orientations that the nitroxide and C-D bond axes transform with the various stearic acid acyl chain conformations, and because of the difference in dynamic sensitivity between NMR and EPR over the timescales examined. 5-, 7-, 12-, and 16-doxylstearic acids spin-labels were used in the EPR experiments and stearic acid-d(35) was used in the solid-state NMR experiments. The influence of the addition of cholesterol and the variation of temperature on the fatty acid hydrocarbon chain ordering in the DMPC/DHPC phospholipid bilayers was also studied. Cholesterol increased the degree of ordering of the hydrocarbon chains. Conversely, as the temperature of the magnetically aligned phospholipid bilayers increased, the order parameters decreased due to the higher random motion of the acyl chain of the stearic acid. The results indicate that magnetically aligned phospholipid bilayers are an excellent model membrane system and can be used for both NMR and EPR studies.

Dimyristoylphosphatidylcholine↗
PubMed2004

Compatibility of sennoside A and B with pharmaceutical excipients.

This study reports the incompatibility of sennoside A and B with the following commonly used pharmaceutical excipients: stearic acid, sodium carbonate, glucose, lactose, propyl paraben, sodium carbonate, stearic acid, citric acid, PEG, and sorbitol. Drug-excipient compatibility was tested using thermal (DSC) and analytical (HPLC) methods of analysis. Compatibility evaluation showed that dry powder mixtures could be used to formulate sennoside A and B products. However, when mixed with water--propyl paraben, sodium carbonate, stearic acid, citric acid, PEG, and sugar derivatives such as lactose, glucose and sorbitol--should not be used in sennoside containing products.

Anthraquinones↗
PubMed2004

Solid-liquid phase behavior of binary fatty acid mixtures. 1. Oleic acid/stearic acid and oleic acid/behenic acid mixtures.

Solid-liquid phase behavior of binary fatty acid mixtures was investigated by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) for the mixture composed of oleic acid (OA) and stearic acid (SA) and that composed of OA and behenic acid (BA). The DSC results provided a monotectic type T-X phase diagram for these mixtures, from which it was suggested that the two fatty acid species are completely immiscible in a solid phase regardless of the two polymorphs of OA, i.e., alpha-form or gamma-form. The solid phase immiscibility was confirmed by the FT-IR observation that the spectra obtained for the mixtures correspond to the superposition of the two spectra for respective components. Thermodynamic analysis of liquidus line demonstrated that OA and SA form an ideal mixture in a liquid phase, whereas the mixing of OA and BA in a liquid phase is slightly non-ideal.

Calorimetry, Differential Scanning↗
PubMed1979

Mechanism of the inhibitory action of linoleic acid on the growth of Staphylococcus aureus.

Linoleic acid, but not stearic acid, inhibited the growth of Staphylococcus aureus NCTC 8325. Growth inhibition was associated with an increase in the permeability of the bacterial membrane. The presence of a plasmid conferring resistance to penicillin (PC plasmid, e.g. pI258blaI-) increased the growth inhibitory and membrane permeability effects of linoleic acid. Under growth inhibitory conditions, linoleic acid was incorporated into the lipid of both PC plasmid-containing and PC plasmid-negative bacteria and there was little difference between these cultures in the uptake or fate of linoleic acid. Experiments using a glycerol auxotroph of S. aureus suggested that free linoleic acid, rather than lipid containing this acid, inhibits growth. Linoleic acid probably inhibits growth by increasing the permeability of the bacterial membrane as a result of its surfactant action, and the presence of the PC plasmid increases these effects.

Bacterial Proteins↗
PubMed1990

pH-sensitive liposomes composed of phosphatidylethanolamine and fatty acid.

pH-induced destabilization, aggregation and fusion of liposomes composed of phosphatidylethanolamine (PE) and various fatty acid were studied. Destabilization was examined as a fluorescent change caused by leakage of coencapsulated aminonaphthalene-3,6,8-trisulfonic acid (ANTS) and N,N-p-xylylenebispyridinium bromide (DPX). Fusion was monitored by two different methods, that is, intermixing assay of internal aqueous contents of liposomes, and lipid dilution assay of liposomes labeled with fluorescent phospholipids. Contents leakage from liposomes was observed by lowering the pH, and pH where the leakage began depended on fatty acid used. Fifty percent leakage of contents from PE liposomes containing alpha-hydroxypalmitic acid or alpha-hydroxy-stearic acid was observed at pH 5.5, that from liposomes containing stearic acid or palmitic acid was observed at pH 6.5-6.7, and that from ricinoleic acid at pH 7.2. Aggregation and fusion of the respective liposomes also occurred at a similar pH region. These results were interpreted by the notion that the protonation of the fatty acid triggers a series of pH-sensitive events. The liposomes developed in this study may be useful as a drug carrier which could release the contents in response to pH changes in their environment.

Chemical Phenomena↗