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PubMed1997

Effects of varying the type of saturated fatty acid in the rat diet upon serum lipid levels and spleen lymphocyte functions.

To obtain further information about the effects of specific dietary saturated fatty acids, weanling male rats were fed for 6 weeks on low fat (7.7% by weight) or high fat (17.8% by weight) diets which differed according to the principal fatty acids present. The diets were rich in caprylic and capric acids (medium chain triacylglycerols; MCT), lauric acid, palmitic acid at the sn-1(3) position, palmitic acid at the sn-2 position or stearic acid. The total proportions of saturated (42-46%), monounsaturated (36%), n-6 polyunsaturated (15%) and n-3 polyunsaturated (2.2%) fatty acids were the same in all diets. Serum cholesterol concentrations were not different among rats fed the different diets, except that the concentration in the serum of rats fed the high fat diet with palmitic acid in the sn-2 position was high. This was reflected in higher HDL and LDL cholesterol concentrations in the serum of animals fed this diet. Triacylglycerol (TAG) concentrations tended to be higher in the serum of rats fed the low fat diets compared with those fed the high fat diets. They were lowest in the serum of MCT-fed rats irrespective of the level of fat in the diet and were highest in the serum of rats fed the low fat diet rich in stearic acid. These differences were due to lower chylomicron and VLDL TAG concentrations in the serum of MCT-fed rats and higher chylomicron and VLDL TAG concentrations in the serum of low fat, stearic acid-fed animals. The fatty acid compositions of the serum and of spleen lymphocytes were influenced by that of the diet fed. The ex vivo proliferation of lymphocytes from the spleens of rats fed the high fat diet rich in palmitic acid at the sn-2 position was greater than that of lymphocytes from animals fed the other diets. Natural killer (NK) cell activity tended to be lower for spleen lymphocytes from rats fed high fat diets than for those fed low fat diets irrespective of the principal saturated fatty acid present. NK cell activity was highest for spleen lymphocytes from animals fed the diets rich in palmitic acid and was lowest for those from animals fed the high fat diet rich in stearic acid. Spleen lymphocytes from the latter animals had the lowest proportion of CD16+ cells, a marker for NK cells. Thus, this study shows that the type of saturated fatty acid present in the diet not only has subtle effects upon blood lipid and lipoprotein levels but can significantly affect lymphocyte functions. Spleen lymphocyte NK cell activity is decreased as the fat content of the diet increases. NK cell number and activity are reduced by a high fat diet rich in stearic acid. Spleen lymphocyte proliferation is enhanced by palmitic acid-rich diets, particularly if palmitic acid is in the sn-2 position of dietary TAG.

Animals↗
PubMed1992

Albumin and fatty acid effects on the stimulated production of 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (PAF) by human polymorphonuclear leukocytes.

Production of platelet-activating factor (PAF) during opsonized zymosan stimulation of human polymorphonuclear leukocytes is dependent on the concentration of extracellular albumin and on the presence of exogenous fatty acids. Fatty acid-free albumin caused a concentration-dependent increase in PAF synthesis up to 5% albumin concentrations (w/v) where the amount of PAF produced was three- to four-fold higher than in controls containing no albumin. The addition of free fatty acids, particularly arachidonic acid and palmitic acid, to 5% fatty acid-free albumin media caused a concentration-dependent decrease in PAF synthesis. A 50% inhibition of PAF synthesis was observed at an arachidonic acid concentration of 120 microM and at a palmitic acid concentration of 100 microM. The inhibition of PAF production by palmitic acid was also dependent on the concentration of extracellular albumin. In 0.5% fatty acid-free albumin media, a palmitic acid concentration of 40 microM produced a 50% inhibition in PAF synthesis. The addition of palmitic acid did not affect the release of endogenous arachidonic acid during stimulation. In contrast, the addition of stearic acid up to 120 microM in 5% fatty acid-free albumin media had no effect on PAF production. The different inhibitory effects of palmitic acid and stearic acid on PAF production may be related to differences in intracellular utilization of these two fatty acids during cell stimulation.

Fatty Acids, Nonesterified↗
PubMed1976

On the mechanism of regulation of omega oxidation of fatty acids.

The stimulatory effect of starvation on omega oxidation of stearate by the 20,000 X g supernatant fluid of rat liver homogenates was studied. The effect was obtained after starvation for 24 hours. Starvation for longer times did not further increase omega oxidation. The stimulatory effect of starvation on omega oxidation of stearic acid was accompanied by a reduced incorporation of stearic acid into phosphatidic acid, diglycerides, and triglycerides. Substitution of the 100,000 X g supernatant fluid from liver homogenate of starved rats with 100,000 X g supernatant fluid from liver homogenates of control rats reduced the microsomal omega oxidation of stearic acid with a simultaneous increase in incorporation of stearic acid into the different glycerides. Under the latter conditions almost no free stearic acid could be isolated from the incubation mixture after the incubation. Of three different soluble factors necessary for glyceride formation, ATP appeared to be the most important from a regulatory point of view. Thus the soluble fraction of liver homogenate from a starved rat was shown to contain suboptimal concentrations of ATP. Addition of physiological amounts of ATP to the 20,000 X g supernatant fluid of homogenate of liver of starved rats had the same effect as addition of 100, 000 X g supernatant fluid from liver homogenate of control rats, i.e. decrease in omega oxidation and increase in formation of glycerides. Addition of sn-glycerol 3-phosphate and CoA-SH in amounts optimal for glyceride formation to the 20,000 X g supernatant fluid of liver homogenate of starved rats had only small effects on omega oxidation and glyceride formation. The results are consistent with a competition for free fatty acids between the acyl-CoA synthetases involved in biosynthesis of glycerides and the microsomal hydroxylase(s) involved in omega oxidation of fatty acids. The concentration of ATP in the soluble fraction is of importance in this competition. The possibility is discussed that this competition is of importance also under in vivo conditions and that a decreased rate of esterification in the starved state is responsible for the higher excretion of omega-oxidized fatty acids in urine in the ketotic state.

Animals↗
PubMed2002

Pheromone biosynthetic pathways in the moths Helicoverpa zea and Helicoverpa assulta.

Sex pheromones of many Lepidopteran species have relatively simple structures consisting of a hydrocarbon chain with a functional group and usually one to several double bonds. The sex pheromones are usually derived from fatty acids through a specific biosynthetic pathway. We investigated the incorporation of deuterium-labeled palmitic and stearic acid precursors into pheromone components of Helicoverpa zea and Helicoverpa assulta. The major pheromone component for H. zea is (Z)11-hexadecenal (Z11-16:Ald) while H. assulta utilizes (Z)9-hexadecenal (Z9-16:Ald). We found that H. zea uses palmitic acid to form Z11-16:Ald via delta 11 desaturation and reduction, but also requires stearic acid to biosynthesize the minor pheromone components Z9-16:Ald and Z7-16:Ald. The Z9-16:Ald is produced by delta 11 desaturation of stearic acid followed by one round of chain-shortening and reduction to the aldehyde. The Z7-16:Ald is produced by delta 9 desaturation of stearic acid followed by one round of chain-shortening and reduction to the aldehyde. H. assulta uses palmitic acid as a substrate to form Z9-16:Ald, Z11-16:Ald and 16:Ald. The amount of labeling indicated that the delta 9 desaturase is the major desaturase present in the pheromone gland cells of H. assulta; whereas, the delta 11 desaturase is the major desaturase in pheromone glands of H. zea. It also appears that H. assulta lacks chain-shortening enzymes since stearic acid did not label any of the 16-carbon aldehydes.

Animals↗
PubMed1986

A new chemical procedure for the preparation of gangliosides carrying fluorescent or paramagnetic probes on the lipid moiety.

A new chemical procedure is described for preparing labelled GM1 molecular species, carrying as acyl moiety pyrene-decanoic acid, 5-doxyl-stearic acid and 16-doxyl-stearic acid. It makes use of a mixed anhydride formed by ethylchloroformate and the labelled acyl chain, as the reagent for N-acylation of a deacetylated, deacylated GM1 ganglioside, which is prepared by alkaline hydrolysis of natural GM1. The reaction performed with a unitary GM1 derivative/mixed anhydride molar ratio, occurs with a yield of above 40%. The labelled deacetylated GM1 molecular species are then N-acetylated by means of acetic anhydride with quantitative yield. The chemical process of insertion of labelled fatty acid and reconstitution of GM1 ganglioside has been confirmed by GLC-MS and NMR analyses. Fluorescence and electron spin resonance experiments indicate that the labelled gangliosides behave similarly to natural GM1, in both the aggregation properties and the capability to be transferred from micelles to vesicular dispersions of phospholipids.

Animals↗
PubMed2007

Stearic acid-rich interesterified fat and trans-rich fat raise the LDL/HDL ratio and plasma glucose relative to palm olein in humans.

BACKGROUND: Dietary trans-rich and interesterified fats were compared to an unmodified saturated fat for their relative impact on blood lipids and plasma glucose. Each fat had melting characteristics, plasticity and solids fat content suitable for use as hardstock in margarine and other solid fat formulations. METHODS: Thirty human volunteers were fed complete, whole food diets during 4 wk periods, where total fat (approximately 31% daily energy, >70% from the test fats) and fatty acid composition were tightly controlled. A crossover design was used with 3 randomly-assigned diet rotations and repeated-measures analysis. One test fat rotation was based on palm olein (POL) and provided 12.0 percent of energy (%en) as palmitic acid (16:0); a second contained trans-rich partially hydrogenated soybean oil (PHSO) and provided 3.2 %en as trans fatty acids plus 6.5 %en as 16:0, while the third used an interesterified fat (IE) and provided 12.5 %en as stearic acid (18:0). After 4 wk the plasma lipoproteins, fatty acid profile, as well as fasting glucose and insulin were assessed. In addition, after 2 wk into each period an 8 h postprandial challenge was initiated in a subset of 19 subjects who consumed a meal containing 53 g of test fat. RESULTS: After 4 wk, both PHSO and IE fats significantly elevated both the LDL/HDL ratio and fasting blood glucose, the latter almost 20% in the IE group relative to POL. Fasting 4 wk insulin was 10% lower after PHSO (p > 0.05) and 22% lower after IE (p < 0.001) compared to POL. For the postprandial study the glucose incremental area under the curve (IAUC) following the IE meal was 40% greater than after either other meal (p < 0.001), and was linked to relatively depressed insulin and C-peptide (p < 0.05). CONCLUSION: Both PHSO and IE fats altered the metabolism of lipoproteins and glucose relative to an unmodified saturated fat when fed to humans under identical circumstances.

Journal Article↗
PubMed1975

Lipids of cultured hepatoma cells. VI. Glycerolipid and monoenoic fatty acid biosynthesis in minimal deviation hepatoma 7288C-1.

1-14C-Acetic, 1-14C-palmitic, or 1-14C-stearic acid was incubated with minimal deviation hepatoma 7288C cells grown in culture to assess: de novo fatty acid synthesis, oxidation, desaturation, and elongation of saturated fatty acids, as well as the ability of media fatty acids to serve as precursors of cellular glycerolipids. Distribution of radioactivity in the individual lipid classes and the various fatty acids of triglyceride, phosphatidyl choline, and phosphatidyl ethanolamine was determined. The radioactivity among the monoenoic acid isomers derived from triglyceride, phosphatidyl choline, and phosphatidyl ethanolamine was analyzed by reductive ozonolysis. Only small amounts of the labeled substrates were oxidized to carbon dioxide. Except for labeled stearic acid, which also was incorporated heavily into phosphatidyl inositol and phosphatidyl serine, most radioactivity was recovered in triglyceride, phosphatidyl choline, and phosphatidyl ethanolamine. Synthesis of cholesterol and long chain fatty acids from labeled acetic acid demonstrated that these cells can perform de novo synthesis of fatty acids and cholesterol. Both labeled palmitic and stearic acids were desaturated to the corresponding delta9 monoenes, and palmitic and palmitoleic acids were elongated. The nexadecenoic acid fraction isolated from triglyceride, phosphatidyl choline, and phosphatidyl ethanolamine, when acetic or palmitic acid was the labeled substrate, showed that greater than 70 percent of the labeled acids were the delta9 isomer. Radioactivity of the octadecenoic acid fraction derived from labeled acetic or palmitic acids was nearly equally divided between the delta9 isomer, oleic acid, and the delta11 isomer, vaccenic acid. Desaturation of labeled stearic acid produced only oleic acid. These data demonstrate that the biosynthesis of vaccenic acid in these cultured neoplastic cells proceeds via the elongation of palmitoleic acid. The relatively high level of vaccenic acid synthesis in these cells suggests that the reported elevation of "oleic acid" in many neoplasms may result from increased concentration of vaccenic acid.

Acetates↗
PubMed1983

Effects of dietary fatty acids and calcium levels on performance and mineral metabolism of broiler chickens.

The influence of inclusion of 8% linoleic/oleic, oleic, palmitic, and stearic acids as the major source of fat in the presence of low (.8%) and high (1.2%) calcium in broiler diets was investigated using broiler chicks from day-old to 3 weeks of age. Palmitic and stearic acid caused an increase (P less than .01) in daily feed intake and weight gain with a decrease in feed efficiency compared to oleic and linoleic acid. There was variation (P less than .01) in energy utilization with palmitic and stearic acid being essentially unavailable. An interaction (P less than .05) between type of fatty acid and dietary calcium level was observed with fat retention. Increasing dietary calcium increased fecal soap concentration (P less than .01). Palmitic and stearic acid caused a significant increase in fecal soap formation and decrease in calcium retention. A significant interaction between type of fatty acid and dietary calcium level was observed with magnesium retention. Bone ash and bone calcium level were reduced (P less than .01) in the presence of palmitic and stearic acid while oleic acid had no significant effect on these parameters. A significant interaction of fatty acid type and level of calcium was observed for bone magnesium content, while bone phosphorus was not affected. Plasma calcium level was significantly reduced (P less than .01) by the addition of fatty acids relative to the control diets. Increasing dietary calcium level did not alleviate the decrease in calcium retention and bone calcium content associated with addition of fat.

Animals↗
PubMed1998

Selectivity of lipid-protein interactions with trypsinized Na, K-ATPase studied by spin-label EPR.

The selectivity of the lipid-protein interactions in trypsinised Na, K-ATPase membranes from Squalus acanthias has been determined by using EPR spectroscopy with different lipid probes spin-labelled on the 14-C atom of the fatty acid chain. From measurements at low ionic strength and different pH values, the pattern of selectivity is: (stearic acid)->(phosphatidylserine)->(stearic acid)0>(phosphatidylcholine)+/-, where superscripts indicate the formal electrostatic charge on the lipid headgroup. This is in the same order as that determined with native Na,K-ATPase membranes [M. Esmann, D. Marsh, Biochemistry 24 (1985) 3572-3578]. The selectivity for phosphatidylserine is independent of pH, over the range pH 6.0-9. 0, as found also for native membranes. For membranes trypsinised in the presence of Rb+ ions, and in the presence of Na+ (which allows more extensive proteolysis), the relative association constants, Kr, of all lipids are the same as for control membranes, with the exception of ionised (stearic acid)- that shows the highest specificity. Therefore, both the stoichiometry and the principal determinants of the specificity of lipid-protein interaction are preserved on extensive trypsinisation of Na,K-ATPase membranes. This has implications for the location and arrangement of those amino acid side chains that determine the lipid selectivity of the native Na,K-ATPase.

Animals↗
PubMed1990

A comparative study of straight chain and branched chain fatty acid oxidation in skin fibroblasts from patients with peroxisomal disorders.

The beta-oxidation of stearic acid and of alpha- and gamma-methyl isoprenoid-derived fatty acids (pristanic and tetramethylheptadecanoic acids, respectively) was investigated in normal skin fibroblasts and in fibroblasts from patients with inherited defects in peroxisomal biogenesis. Stearic acid beta-oxidation by normal fibroblast homogenates was several-fold greater compared to the oxidation of the two branched chain fatty acids. The effect of phosphatidylcholine, alpha-cyclodextrin, and bovine serum albumin on the three activities suggests that different enzymes are involved in the beta-oxidation of straight chain and branched chain fatty acids. Homogenates of fibroblasts from patients with a deficiency in peroxisomes (Zellweger syndrome and infantile Refsum's disease) showed a normal ability to beta-oxidize stearic acid, but the oxidation of pristanic and tetramethylheptadecanoic acid was decreased. Concomitantly, 14CO2 production from the branched chain fatty acids by Zellweger fibroblasts in culture (but not from stearic acid) was greatly diminished. The Zellweger fibroblasts also showed a marked reduction in the amount of water-soluble metabolites from the radiolabeled branched chain fatty acids that are released into the culture medium. The data presented indicate that the oxidation of alpha- and gamma-methyl isoprenoid-derived fatty acids takes place largely in peroxisomes in human skin fibroblasts.

Adrenoleukodystrophy↗
PubMed2004

Lymphatic absorption of structured triacylglycerols, 1(3)-stearoyl-2,3 (1)-dilinoleoylglycerol and 2-linoleoyl-1,3-distearoylglycerol in rats.

Lymphatic recovery of 1(3)-stearoyl-2,3(1)-dilinoleoylglycerol (SLL) and 2-linoleoyl-1,3-distearoylglycerol (SLS) which had been enzymatically synthesized were compared with those of trilinoleoylglycerol (LLL) and the randomly esterified triacylglycerol which contained stearic acid and linoleic acid at 1:2. Recoveries of linoleic acid in all of the triacylglycerols were more than 94.0%. Lymphatic 24 h-recoveries of stearic acid given as SLL and SLS were significantly lower than that of stearic acid given as the randomly esterified triacylglycerol. Recoveries of stearic acid from SLL, SLS and the randomly esterified triacylglycerol were 88.49%, 68.3% and 101%. respectively.

Absorption↗
PubMed2003

Individual saturated fatty acids and nonfatal acute myocardial infarction in Costa Rica.

BACKGROUND: Epidemiological studies on the effect of individual saturated fatty acids (SFAs) on cardiovascular disease, especially in developing countries with different dietary patterns, are scarce. OBJECTIVE: To determine the risk of nonfatal acute myocardial infarction (MI) associated with consumption of individual SFAs and their food sources in Costa Rica. DESIGN: The cases (n=485) were survivors of a first acute MI and were matched by age, sex and area of residence to population controls (n=508). Data on anthropometrical measurements, lifestyle and diet were collected using interviewer-administered questionnaires. RESULTS: In analyses adjusted for confounders, consumption of total and individual SFAs was associated with an increased risk of MI. The odds ratio (OR) (95% confidence intervals) for 1% increase in energy from total saturated fat was 1.12 (1.03-1.21) while it was 1.51 (1.03-2.22) for lauric acid+myristic acid, 1.14 (1.01-1.30) for palmitic acid and 2.00 (1.34-3.00) for stearic acid. Although lauric and myristic acids were associated with increased risk of MI, they were consumed in small amounts and most of the saturated fat (87%) came from palmitic and stearic acids, which derived mainly from red meat and fried foods. Consumption of cheese (1-2 vs 0 servings/day) was associated with increased risk of MI (OR=3.07; 95% confidence interval: 1.74-5.39; P for trend <0.0001), while consumption of low-fat milk was not. CONCLUSION: Increased consumption of total and individual SFAs is associated with increased risk of MI. Lauric, myristic and stearic acids were more potent than palmitic acid.

Acute Disease↗
PubMed2005

Comparative study of sex pheromone composition and biosynthesis in Helicoverpa armigera, H. assulta and their hybrid.

Two Helicoverpa species, H. armigera and H. assulta use (Z)-11-hexadecenal and (Z)-9-hexadecenal as their sex attractant pheromone components but in opposite ratios. Since both female and male interspecific hybrids produced by female H. assulta and male H. armigera have been obtained in our laboratory, we can make a comparative study of sex pheromone composition and biosynthesis in the two species and their hybrid. With GC and GC-MS analyses using single gland extracts, the ratio of (Z)-9-hexadecenal to (Z)-11-hexadecenal was determined as 2.1:100 in H. armigera, and 1739:100 in H. assulta. The hybrid has a ratio of 4.0: 100, which is closer to that of H. armigera, but significantly different from H. armigera. We investigated pheromone biosynthesis with labeling experiments, using various fatty acid precursors in H. armigera, H. assulta and the hybrid. In H. armigera, (Z)-11-hexadecenal is produced by delta11 desaturation of palmitic acid, followed by reduction and terminal oxidation; (Z)-9-hexadecenal results from delta11 desaturation of stearic acid, followed by one cycle of chain shortening, reduction and terminal oxidation. delta11 desaturase is the unique desaturase for the production of the two pheromone components. In our Chinese strain of H. assulta, palmitic acid is used as the substrate to form both the major pheromone component, (Z)-9-hexadecenal and the minor one, (Z)-11-hexadecenal. Our data suggest that delta9 desaturase is the major desaturase, and delta11 desaturase is responsible for the minor component in H. assulta, which is consistent with previous work. However, the weak chain shortening acting on (Z)-9 and (Z)-11-octadecenoic acid, which is present in the pheromone glands, does occur in this species to produce (Z)-7 and (Z)-9-hexadecenoic acid. In the hybrid, the major pheromone component, (Z)-11-hexadecenal is produced by delta11 desaturation of palmitic acid, followed by reduction and terminal oxidation. The direct fatty acid precursor of the minor component, (Z)-9-hexadecenoic acid is mainly produced by delta9 desaturation of palmitic acid, but also by delta11 desaturation of stearic acid and one cycle of chain shortening. The greater relative amounts of (Z)-9-hexadecenal in the hybrid are due to the fact that both palmitic and stearic acids are used as substrates, whereas only stearic acid is used as substrate in H. armigera. The evolutionary relationships between the desaturases in several Helicoverpa species are also discussed in this paper.

Aldehydes↗
PubMed1991

Chorea-acanthocytosis: abnormal composition of covalently bound fatty acids of erythrocyte membrane proteins.

Phospholipid class, peak profile of each phospholipid class, loosely bound fatty acids, covalently (tightly) bound fatty acids of the erythrocyte membranes, and plasma fatty acids were investigated using high-performance liquid chromatography in six patients with chorea-acanthocytosis and 14 age- and sex-matched normal control subjects. Additionally, six patients with Huntington's disease were included as disease control subjects in the study of covalently bound fatty acids. Study of covalently (tightly) bound fatty acids in erythrocyte membrane proteins after alkaline hydrolysis, hitherto undescribed in chorea-acanthocytosis, revealed that palmitic acid (C16:0) was significantly increased and stearic acid (C18:0) was decreased in the patients with chorea-acanthocytosis. Analyses for total covalently bound fatty acids disclosed that palmitic and docosahexaenoic (C22:6) acids were increased and stearic acid was decreased in chorea-acanthocytosis. Phospholipid class (phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, and phosphatidylserine) and peak profile of each phospholipid class from the erythrocyte membranes did not differ between the patients with chorea-acanthocytosis and the control subjects. Of the loosely bound fatty acids, linoleic acid (C18:2) was significantly decreased in those with chorea-acanthocytosis, which seemed to be nonspecific.

Acanthocytes↗
PubMed1991

Influence of rapeseed meal, whole rapeseed, and soybean meal on fatty acid composition and cholesterol content of muscle and adipose tissue from ram lambs.

Twenty-four Suffolk x Hampshire ram lambs (average 46 kg) were assigned to one of three diets containing rapeseed meal (RM), soybean meal (SBM), or whole rapeseed-soybean meal (RSSBM) as the protein source. Diets contained 75% roughage, 14% CP and 2.0 Mcal of ME/kg and lambs were allowed ad libitum access to diets for 35 d. Lipid composition of the longissimus, semimembranosus, and triceps brachii muscles and their corresponding s.c. adipose tissue was determined by gas-liquid chromatography (GLC). The total lipid content in either muscle or subcutaneous fat was not different (P greater than .01) by diet. In lean tissue, palmitic and palmitoleic acids were higher and stearic acid was lower (P less than .01) in rams fed RM than in rams fed RSSBM or SBM, regardless of anatomical location. In the s.c. adipose tissue, the amounts of myristoleic, pentadecylic, and palmitoleic acids were lower and the amount of stearic acid was higher (P less than .01) in rams fed RSSM than in those fed RM or SBM, regardless of anatomical location. The semimembranosus and triceps brachii muscles from all treatments contained 12 to 19% more polyunsaturated fatty acids (PUFA) than the longissimus muscle. The cholesterol content of the three muscles was highest in SBM-fed lambs, lowest in RM-fed lambs, and intermediate in RSSBM-fed lambs. These results demonstrate that dietary treatments of the types used in the present study elicit changes in fatty acid composition of both adipose and muscle tissue without affecting the quantity of total lipid.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1979

Effect of some saturated and unsaturated fatty acids on in vitro platelet utilization of arachidonic acid.

The effect of some saturated and unsaturated fatty acids pre-incubated with human washed platelets was examined on the platelet utilization of (1-14C) arachidonic acid. The platelets were incubated with the radioactive arachidonic acid for periods of either 10 min or 30 sec. The following results were obtained. Conversion of arachidonic acid to thromboxane B2 was increased during 10 min in the presence of oleic, alpha-linolenic and lauric acids. Increased conversion of 14C-arachidonic acid to hydroxy fatty acids (HHT and HETE) was observed in the presence of stearic acid (10 min incubation) and lauric acid (30 sec incubation). Their synthesis, however, was decreased in presence of gamma-linolenic acid (10 min incubation). Endoperoxide generation from arachidonate was reduced by alpha-linolenic acid but increased by stearic acid. The conversion to PGE2 was not altered by these acids during 10 min incubation with arachidonic acid. However, in presence of gamma-linolenic, lauric and stearic acids conversion of arachidonic acid into PGE2 during 30 sec incubation was increased. Under these conditions, production of PGF2 alpha and PGD2 remained unchanged.

Arachidonic Acids↗
PubMed2006

Interfacial tension of the lipid membrane formed from lipid-fatty acid and lipid-amine systems.

Interfacial tension has been determined for phosphatidylcholine-stearic acid and phosphatidylcholine-stearylamine membranes. Phosphatidylcholine, stearic acid and stearylamine were used in the experimental. The interfacial tension values of the pure components are 1.62x10(-3) N/m, - 1.54x10(-2) N/m and 4.40x10(-3) N/m (hypothetical values), respectively. The 1:1 complexes were formed during formation of phosphatidylcholine-stearic acid and phosphatidylcholine-stearylamine membranes. The following parameters describing the complexes were determined: the surface concentrations of the lipid membranes formed from these complexes, A(3)(-1), the interfacial tensions of such membranes, gamma(3) and the stability constants of these complexes, K.

Amines↗
PubMed2005

Protein-lipid interactions at the air/water interface.

Surface pressure measurements and external reflection FTIR spectroscopy have been used to probe protein-lipid interactions at the air/water interface. Spread monomolecular layers of stearic acid and phosphocholine were prepared and held at different compressed phase states prior to the introduction of protein to the buffered subphase. Contrasting interfacial behaviour of the proteins, albumin and lysozyme, was observed and revealed the role of both electrostatic and hydrophobic interactions in protein adsorption. The rate of adsorption of lysozyme to the air/water interface increased dramatically in the presence of stearic acid, due to strong electrostatic interactions between the negatively charged stearic acid head group and lysozyme, whose net charge at pH 7 is positive. Introduction of albumin to the subphase resulted in solubilisation of the stearic acid via the formation of an albumin-stearic acid complex and subsequent adsorption of albumin. This observation held for both human and bovine serum albumin. Protein adsorption to a PC layer held at low surface pressure revealed adsorption rates similar to adsorption to the bare air/water interface and suggested very little interaction between the protein and the lipid. For PC layers in their compressed phase state some adsorption of protein occurred after long adsorption times. Structural changes of both lysozyme and albumin were observed during adsorption, but these were dramatically reduced in the presence of a lipid layer compared to that of adsorption to the pure air/water interface.

Adsorption↗