SEARCH · Search PubMed
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.
The biohydrogenation products from methyl linolenate varied according to its concentration in the rumen. At low concentrations, over 60% of the biohydrogenated products was stearic acid, but when the concentration was raised above 100 mg/100 ml of rumen liquor, monoenoic acids, including cis-octadec-15-enoic acid, were the major products.
Consumption of plant sterol esters reduces plasma LDL cholesterol concentration by inhibiting intestinal cholesterol absorption. Commercially available plant sterol esters are prepared by esterifying free sterols to fatty acids from edible plant oils such as canola, soybean, and sunflower. To determine the influence of the fatty acid moiety on cholesterol metabolism, plant sterol esters were made with fatty acids from soybean oil (SO), beef tallow (BT), or purified stearic acid (SA) and fed to male hamsters for 4 wk. A control group fed no plant sterol esters was also included. Hamsters fed BT and SA had significantly lower cholesterol absorption and decreased concentrations of plasma non-HDL cholesterol and liver esterified cholesterol, and significantly greater fecal sterol excretion than SO and control hamsters. Cholesterol absorption was lowest in hamsters fed SA (7.5%), whereas it was 72.9% in control hamsters. Cholesterol absorption was correlated with fecal sterol excretion (r = -0.72, P < 0.001), liver cholesterol concentration (r = 0.88, P < 0.001), and plasma non-HDL cholesterol concentration (r = 0.85, P < 0.001). A multiple regression model that included each sterol ester type vs. cholesterol absorption indicated that intake of steryl stearate was the only dietary component that contributed significantly to the model (R2 = -0.75, P < 0.001). Therefore, our results demonstrate that BT and SA are more effective than SO in reducing cholesterol absorption, liver cholesterol, and plasma non-HDL cholesterol concentration, suggesting that cardioprotective benefits can be achieved by consuming stearate-enriched plant sterol esters.
The streptococcal group A and group E cell wall polysaccharide antigens were extracted with trichloroacetic acid from the cell or cell wall and esterified with stearic acid. The stearoyl derivatives contained 5 to 8% (by weight) of the ester. Sheep or human red blood cells were sensitized with the esterified antigens and were shown to agglutinate in the presence of specific rabbit antisera. Sera from (i) children hospitalized with group A streptococcal respiratory disease and (ii) swine possessing group E streptococcal lymphadenitis were shown to possess antibody titers significantly higher than the controls. The use of the two esterified antigens as controls for each other established the specificity of the reaction in each case. The general shape of the antigen-antibody precipitin curves was not changed when the stearoyl antigens were used; however, the quantitative aspects differed markedly. Oligosaccharides which inhibit the normal antigen-antibody precipitin reaction did not inhibit the hemagglutination reaction. The adsorption of antisera with whole streptococcal cells reduced the hemagglutination titer in relation to the quantity of cells employed. Data are given on the (i) optimal concentration of stearoyl antigen for sensitization, (ii) time of adsorption of antigen to red cells, (iii) use of albumin as diluting fluid, and (iv) condition of red cells. Properties of the esterified antigens and the mechanism of the agglutination reaction are discussed. The results indicate that polysaccharide antigens of other bacteria may be esterified and employed in a similar manner.
Resonance energy transfer between a local anaesthetic, dibucaine (donor) and a set of functionalized probes [n-(9-anthroyloxy)stearic acids, n = 2, 3, 6, 7, 9 and 12 and 16-(9-anthroyloxy)palmitic acid] (acceptors) was found to be an efficient process with a critical radius of transfer Ro = 2.1 nm, this interaction being used to locate the drug in a model membrane system, small unilamellar vesicles of dipalmitoylglycerophosphocholine, both above and below the temperature of the gel-to-the-liquid-crystal transition of the phospholipid. From the sequence of relative quenching efficiencies of dibucaine fluorescence upon incorporation of the probes, it was concluded that the drug intercalates in the membrane near the glycerol backbone of the lipid. In addition, it was found that dibucaine location is not significantly affected upon crossing the phase-transition temperature of the phospholipid. Dibucaine photophysics was also studied and the short lifetime of the neutral form of the anaesthetic with respect to that of the monoprotonated species was attributed to an intramolecular charge-transfer interaction. From the study of its partition coefficient between the membrane and the aqueous phase, it was concluded that the only significant species present in the membrane is the charged one.
L-Carnitine induces reversibility upon the lipid-graph of a rabbit with a surgically denerved heart after 90 days since it reduces the percentage of stearic acid but also increases thoroughly linoleic acid that notoriously has a plastic and regulatory effect on the heart.
This study was designed to determine whether the exchange of specific fatty acids (palmitic (16:0) for stearic (18:0)), would exert differential effects on plasma and lipoprotein lipids, when diets contained approximately 30%en from fat with adequate levels of linoleic acid (18:2). Thirty-two male Golden Syrian hamsters were fed isocaloric purified diets with comparable amounts of 18:2 (approximately 10.5%en). The 18:0-rich diet (50% cocoa butter, 41% safflower oil, 9% sunflower oil) provided 4.8%en 16:0 and 5.3%en from 18:0, while the 16:0-rich diet (59% palm oil, 36% safflower oil, 5% olive oil) provided 8.7%en from 16:0 and 1.2%en from 18:0, resulting in a 16:0/18:0 exchange of approximately 4%en. Both diets contained negligible amounts of lauric and myristic acid (< 0.2%en), approximately 9.5%en from oleic acid and 77 mg cholesterol/1000 kcal. Animals were fed their respective diets for 4 weeks at which point various lipid and lipoprotein parameters were measured. There were no significant difference between dietary groups for any of the measured parameters, which included body weights, food consumption, plasma lipids, lipoprotein lipid and apoprotein concentrations, as well as lipoprotein compositions. Additionally, estimated diameters of various lipoprotein particles were not affected by the fatty acid exchanges employed. Thus these data suggest that when total fat is restricted to 30%en and 18:2 levels are approximately 10%en, a 4%en exchange between 16:0 and 18:0 (representing intakes of approximately 9 g/d/2000 kcal diet) produces comparable plasma lipids.
Four ionophores differing in cation selectivity were compared for their effect on microbial fermentation and biohydrogenation by ruminal bacteria in continuous culture. Monensin and nigericin are monovalent antiporters with selective binding affinities for Na+ and K+, respectively. Tetronasin is a divalent antiporter that binds preferentially with Ca2+ or Mg2+. Valinomycin is a monovalent uniporter and does not exchange K+ for H+. Steady-state concentrations of 2 micrograms/ml of monensin, nigericin, tetronasin, or valinomycin were maintained by constant infusion into fermenters. Molar percentages of acetate were lower, and those of propionate were higher, in the presence of monensin, nigericin, and tetronasin; all three ionophores also decreased CH4 production. Concentrations of valinomycin as high as 8 micrograms/ml had no effect on volatile fatty acids or CH4 production. Monensin, nigericin, and tetronasin inhibited the rate of biohydrogenation of linoleic acid. Continuous infusion of C18:2n-6 at a steady-state concentration of 314 micrograms/ml into fermenters receiving monensin, nigericin, or tetronasin resulted in lower amounts of stearic acid and higher amounts of oleic acid. Ionophores increased total C18:2 conjugated acids mainly because of an increase in the cis-9, trans-11-C18:2 isomer. If reflected in milk fat, ionophore-induced changes in ruminal lipids could enhance the nutritional qualities of milk.
The effect of high levels of dietary fat on the promotion phase of rat mammary tumorigenesis and the effect of unsaturated and saturated fatty acids on metabolic cooperation in hamster cells were examined. Female Sprague-Dawley rats were given iv injections of 5 mg 7,12-dimethylbenz[a]anthracene (DMBA) and subsequently placed on 20% high-fat (HF) and 4.5% corn oil control (CF) diets. Rats treated with DMBA and fed HF diet for the entire duration of the experiment developed more tumors with shorter latency than rats fed CF diet for the entire experiment. Rats fed HF diet for 3 weeks at different times after DMBA treatment showed similar, enhanced mammary tumor development. Lengthening the duration of HF diet treatment (0, 3, 6, 16 wk) increased mammary tumor development, suggesting a time dose-response relationship. Removal of the HF diet treatment partially reversed its stimulatory effects on tumor development. These results indicate that dietary fat acts as a classical tumor promoter to enhance mammary tumorigenesis. The influence of unsaturated and saturated fatty acids on metabolic cooperation between 6-thioguanine-sensitive (6-TGS) and 6-thioguanine-resistant (6-TGr) Chinese hamster V79 cells was examined. Linoleic acid, palmitoleic acid, and arachidonic acid significantly increased the recovery of 6-TGr cells at noncytotoxic concentrations. Stearic acid, palmitic acid, and arachadic acid had no effect on the recovery of 6-TGr cells at either cytotoxic or noncytotoxic concentrations. These results demonstrate that unsaturated fatty acids but not saturated fatty acids can inhibit metabolic cooperation between Chinese hamster V79 cells, and suggest, mechanistically, that high dietary levels of polyunsaturated fat could promote tumorigenesis by inhibition of intercellular communication.
The hydrolysis of chylomicrons enriched in long-chain n-3 fatty acids by cardiac lipoprotein lipase was studied. In 60 min, 24.8% of the triacylglycerol fatty acids were released as free fatty acids. The fatty acids were hydrolyzed at different rates. DHA (docosahexaenoic acid, 22:6n-3) and EPA (eicosapentaenoic acid, 20:5n-3) were released at rates significantly less than average. Stearic acid (18:0), 20:1n-9, and alpha-linolenic acid (18:3n-3) were released significantly faster than average. There was no relationship between the rate of release of a fatty acid and the number of carbons or the number of double bonds. Lipoprotein lipase selectively hydrolyzes the fatty acids of chylomicron triacylglycerols. This selectively will result in remnants that are relatively depleted in 18:0, 20:1, and 18:3 and relatively enriched in 20:5 and 22:6.
The present study was undertaken to determine the effects of two classes of calcium channel blockers (CCB), nisoldipine (N) and verapamil (V), on the jejunal uptake of lipids in rabbits. The uptake of cholesterol and long-chain fatty acids into rabbit jejunum was examined after 6 and 36 min of exposure to N or V in vitro ("acute" studies), and after 3-wk feeding of N or V ("chronic" studies). Animals were fed either a low (0.08%) cholesterol diet (LCD) or a high (2.8%) cholesterol diet (HCD), with or without N or V added. Acute in vitro exposure of the jejunum to N or V did not affect the uptake of cholesterol or palmitic acid in rabbits fed LCD or HCD. The effect of N or V feeding depended upon the cholesterol content of the diet; adding N or V to LCD increased cholesterol uptake while adding N or V to HCD enhanced or lowered cholesterol uptake, respectively. Both N and V increased the uptake of stearic acid in LCD. N in HCD had no effect on fatty acid uptake, whereas V lowered the uptake of stearic and linoleic acids and increased the uptake of oleic acid. These changes in lipid uptake were not due to variation in the animals' food intake, body weight gain, or intestinal mucosal surface area. The chronic administration of N or V results in an intestinal adaptative process that alters the jejunal uptake of lipids, the direction of which is influenced by the class of CCB, and by the cholesterol content of the diet. (ABSTRACT TRUNCATED AT 250 WORDS)
alpha-Fetoprotein (AFP) binds a series of endogenous fatty acids. To identify the fatty acid binding site, this protein, purified from umbilical cord blood by immunoaffinity chromatography, was covalently labeled using 12-(9-anthroyloxy) stearic acid conjugated with Woodward's reagent K. After digestion with lysyl endopeptidase, the fatty acid-labeled peptide was isolated. Amino acid sequence analysis showed that this peptide consisted of the amino acid residue 210-227. The fact that no appreciable PTH-amino acid was detected at 14th cycle on the degradation suggested that Lys223 was modified with the fatty acid. The finding that lysyl endopeptidase did not cleave off at the Lys223 supported this suggestion. These results indicate that the carboxyl group of the bound fatty acid is located close to Lys223 in human AFP.
The decomposition of a human cadaver was stopped after solidification of putrefactive liquid during a GIS Burial experiment. Knowledge of this phenomenon is necessary to optimize burial conditions and to decrease cemetery congestion. In this preliminary study, we devised a method using thin-layer chromatography and gas chromatography to compare different putrefactive liquids. A comparison of lipid composition among two cadavers revealed a decrease in the decomposition rate of the cadaver that had the gelled putrefactive liquid. Essentially, fatty acids were observed in two types of extracts. The difference was quantitative: there was a higher amount of fatty acids in the gelled sample than in the standard liquid, suggesting a decrease of decomposition rate in the gelled extract. A large quantity of oleate salts may be favourable for solidification. In addition, an isomer of oleic acid (elaidic acid) could be present which may have a determining factor in the phenomenon of gelled putrefaction. A large amount of stearic acid was present in the gelled extract and may be involved in solidification. This method was efficient for comparing the lipid composition of different putrefactive liquids and may be used for a large-scale study. This is the first report concerning methods to determine the lipid composition of human decomposition liquids after 4 years postmortem.
The total lipid content of a dermatophyte, Epidermophyton floccosum, grown under controlled environmental conditions, varies with growth stage and represents 7.0 to 19.8% of the dry weight. The main lipid classes, determined by quantitative thin-layer chromatography, were: triglycerides, free fatty acids, sterols and phospholipids. The fatty acid composition was established with the aid of combined gas chromatography-mass spectrometry. The major components, linoleic, palmitic and stearic acids represent 42.8, 18.9 and 9.6 per cent respectively. The fatty acid biosynthesis, their taxonomic value and their role in the disease mechanism are discussed.
Glutathione S-transferase P (GST-P) bound a series of endogenous fatty acids (C12-C18). To clarify the function and the binding site of the fatty acids, interaction between fatty acids and GST-P was investigated by using 12-(9-anthroyloxy) stearic acid conjugated with Woodward's reagent K. The fluorescence-conjugated fatty acid noncompetitively inhibited GST activity. After GST-P was covalently labeled with the fatty acid, the enzyme was digested with Lysyl Endopeptidase. From the peptide mapping, a single fluorescence-labeled peptide was obtained. By the sequence analysis, the peptide binding fatty acid was determined as the residues of 141-188 from the amino terminus.
Cultured chick fibroblasts supplemented with stearic acid in the absence of serum at 37 degrees C degenerate and die in contrast to cells grown at 41 degrees C which appear normal in comparison with controls. These degenerative effects at 37 degrees C are alleviated by addition to stearate-containing media of fatty acids known to fluidize bilayers. These observations suggest that cell degeneration at 37 degrees C may involve alterations in the physical state of the membrane. Fatty acid analysis of plasma membrane obtained from stearate-supplemented cells clearly demonstrates the enrichment of this fatty acid species into bilayer phospholipids. Moreover, the extent of enrichment is similar in cells grown at both 37 and 41 degrees C. Stearate enrichment at either temperature does not appear to alter significantly membrane cholesterol or polar lipid content. Fluorescence anisotropy measurements for perylene and diphenylhexatriene incorporated into stearate-enriched membranes reveals changes suggestive of decreased bilayer fluidity. Moreover, analysis of temperature dependence of probe anisotropy indicates that a similarity in bilayer fluidity exists between stearate-enriched membranes at 41 degrees C and control membranes at 37 degrees C. Calorimetric data from liposomes prepared from polar lipids isolated from these membranes show similar melting profiles, consistent with the above lipid and fluorescence analyses. Arrhenius plot of stearate-enriched membrane glucose transporter function reveals breaks which coincide with the main endotherm of the pure phospholipid phase transition, indicating the sensitivity of the transporter to this transition which is undetectable in these native bilayers. These data suggest the existence of regions of bilayer lipid microheterogeneity which affect integral enzyme function, cell homeostasis and viability.
Studies with teleost larvae have reported poor performance associated with quantitative lipid imbalances in the diet. The present study examined the effect of dietary protein:neutral lipid ratio on fatty acid (FA) absorption efficiency and metabolism in larval Senegalese sole. In addition, the effect of lipid class (triolein (TRI) and l-3-phosphatidylcholine-1,2-di-oleoyl (PC)), carbon number and degree of saturation of the labelled NEFA, stearic acid (SA), oleic acid (OA) and DHA) was tested. FA absorption was determined by tube feeding [1-14C]-labelled lipids and NEFA after a single meal of either non-enriched Artemia (NEA) or Artemia enriched on a soyabean oil emulsion (EA), or after feeding these diets over an extended period of time (18 d). The tested dietary protein:lipid ratios had no short-term influence but long-term feeding of a diet higher in neutral lipid (EA) increased lipid accumulation within the gut epithelium and resulted in lower FA absorption (higher label evacuation and lower retention of dietary FA), which may partially explain the trend for lower growth observed with this diet. The lipids and NEFA, showed different digestive and metabolic properties, independent of feeding regime. FA absorption increased with unsaturation, being lowest for SA, followed by OA, and highest for DHA. In addition, sole larvae had a lower capacity to digest and absorb FA esterified to TRI, compared with PC, with the order of decreasing absorption being NEFA>PC>>TRI. Moreover, larvae appeared to discriminate between the source of OA, as this FA in the free form or esterified to PC was catabolised less than TRI.
Thiastearic acid positional isomers (8, 9, 10, 11) were examined for their ability to inhibit population growth and the biosynthesis of a phosphatidylethanolamine cyclopropane fatty acyl group, cis-9,10-methyleneoctadecanoic acid (dihydrosterculic acid), by promastigotes of Leishmania species. Thiastearic acids are candidate chemotherapeutic agents, since cyclopropane fatty acids are not formed by vertebrate cells. 8- and 10-thiastearic acids strongly inhibited the growth of strains containing the most dihydrosterculic acid (Leishmania tropica and Leishmania donovani; 25-35% phosphatidylethanolamine fatty acyl groups) and less strongly inhibited strains containing no dihydrosterculic acid (Leishmania major). The 11-thiastearic acid was less effective and 9-thiastearic acid ineffective. Strains containing 1-15% dihydrosterculic acid (L. donovani, Leishmania braziliensis, Leishmania aethiopica and Leishmania mexicana mexicana) were with few exceptions not inhibited by any of the isomers. All the thiastearic acid isomers caused a dose-dependent loss of dihydrosterculic acid. This was accompanied by a loss of phosphatidylethanolamine in the case of dihydrosterculic acid-rich leishmanial strains exposed to the 8- and 10-isomers. The 8- and 10-thiastearic acids also caused a loss of C18 unsaturated fatty acyl groups and increases in palmitic and stearic acids in the phosphatidylethanolamine and phosphatidylcholine of the dihydrosterculic acid-rich and dihydrosterculic acid-free leishmanial strains. 11-Thiastearic acid was much less effective and 9-thiastearic acid ineffective. These changes were not evident in those strins which contained 1-15% dihydrosterculic acid and whose growth was not inhibited by the thiastearic acid isomers. It is concluded that thiastearic acid isomers may inhibit both dihydrosterculic acid biosynthesis and fatty acid desaturation, with the 9-isomer having the highest specificity for dihydrosterculic acid biosynthesis. Population growth of promastigotes of Leishmania species in culture is not dependent upon dihydrosterculic acid biosynthesis but is dependent upon fatty acid desaturation.
Prior studies have suggested that the lipid composition and lipid fluidity of cellular membranes of various organs are altered in the hypothyroid rat. To date, the effects of hypothyroidism on these parameters have not been examined in rat colonic apical plasma membranes. In the present experiments, male Sprague-Dawley rats were fed a pelleted diet (control group) or the same diet containing 0.1% propylthiouracil (hypothyroid group) for 3 weeks. The lipid composition and lipid fluidity of apical plasma membranes prepared from colonocytes of these two groups of animals were then examined and compared. Membranes prepared from the hypothyroid animals were found to possess a higher level of linoleic acid (18:2) and a lower level of arachidonic acid (20:4) than membranes from control animals. The molar ratio of cholesterol/phospholipid was also lower in hypothyroid membranes secondary to a decreased cholesterol content compared to their control counterparts. Moreover, the lipid fluidity of colonic apical plasma membranes, as assessed by (1) the ratio of excimer to monomer fluorescence intensities of the lipid-soluble fluorophore pyrenedecanoic acid and (2) the anisotropy values of the fluorophore DL-12-(9-anthroyloxy)stearic acid using steady-state fluorescence polarization techniques, was greater in hypothyroid animals. These data, therefore, indicate that alterations in the lipid composition and fluidity of colonic apical plasma membranes can be detected in hypothyroid rats.