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PubMed1991

Developmental variation of glycosylphosphatidylinositol membrane anchors in Trypanosoma brucei. Identification of a candidate biosynthetic precursor of the glycosylphosphatidylinositol anchor of the major procyclic stage surface glycoprotein.

The major surface antigen of the mammalian bloodstream form of Trypanosoma brucei, the variant surface glycoprotein (VSG), is attached to the cell membrane by a glycosylphosphatidylinositol (GPI) anchor. The VSG anchor is susceptible to phosphatidylinositol-specific phospholipase C (PI-PLC). Candidate precursor glycolipids, P2 and P3, which are PI-PLC-sensitive and -resistant respectively, have been characterized in the bloodstream stage. In the insect midgut stage, the major surface glycoprotein, procyclic acidic repetitive glycoprotein, is also GPI-anchored but is resistant to PI-PLC. To determine how the structure of the GPI anchor is altered at different life stages, we characterized candidate GPI molecules in procyclic T. brucei. The structure of a major procyclic GPI, PP1, is ethanolamine-PO4-Man alpha 1-2Man alpha 1-6 Man alpha 1-GlcN-acylinositol, linked to lysophosphatidic acid. The inositol can be labeled with [3H]palmitic acid, and the glyceride with [3H]stearic acid. We have also found that all detectable ethanolamine-containing GPIs from procyclic cells contain acylinositol and are resistant to cleavage by PI-PLC. This suggests that the procyclic acidic repetitive glycoprotein GPI anchor structure differs from that of the VSG by virtue of the structures of the GPIs available for transfer.

Animals↗
PubMed1979

Human serum albumin. Spectroscopic studies of binding and proximity relationships for fatty acids and bilirubin.

Binding and proximity relationships of hydrophobic ligands on human serum albumin have been studied using absorption, fluorescence, circular dichroism, and electron paramagnetic resonance spectroscopy. The ligands studied were bilirubin, two conjugated linear polyene fatty acids, cis-parinaric acid and cis-eleostearic acid, and three nitroxide derivatives of stearic acid with doxyl groups at positions 5, 10, and 12, respectively. Binding of polyene fatty acids was monitored by absorption peak shifts, induced circular dichroism, enhancement of fluorescence, and energy transfer between albumin's single tryptophanyl residue and the polyene chromophore. Induced circular dichroism studies indicate excitonic ligand-ligand interaction between bound fatty acids. Fluorescence enhancement of cis-parinaric acid was analyzed using a stepwise multiple equilibrium model, and six binding constants in the range 10(8) to 10(6) M-1 were obtained, in agreement with previous measurements for other fatty acids. The temperature dependence of the equilibrium constants indicates that the binding enthalpy is nearly zero. Fluorescence energy transfer was similarly used to quantitate bilirubin binding to albumin. Energy transfer, nitroxide quenching of fluorescence, and electron paramagnetic resonance spectroscopy were used to elucidate binding geometries which support and extend proposed structural models for albumin. It is suggested that the first two fatty acids bind side-by-side in an antiparallel fashion in domain III of human serum albumin.

Bilirubin↗
PubMedDate not supplied

[Fatty acid makeup of the cestodes, Eubothrium crassum and Diphyllobothrium dendriticum].

The fat-acidic composition of E. crassum and D. dendriticum was investigated. Lipids of E. crassum differ in greater unsaturation as compared to these of D. dendriticum as well as in greater amount of acids of type omega 3, whereas acids of type omega 6 and stearic acid were found in extracts of E. crassum in less quantity than in D. dendriticum. This phenomenon is characteristic of organisms living under conditions of low temperatures.

Animals↗
PubMed1981

[Behavior of serum lipid parameters--results of a longitudinal gerontologic study].

Within the Leipzig longitudinal study from 1968 to 1978 in 158 test persons (46 males, 112 females) cholesterol and the total fatty acid spectre were gas-chromatographically determined in regular intervals. Serum cholesterol as well as proportions of linoleic acid increased significantly. By the significant decrease of the palmitic acid the percentages of the saturated fatty acids altogether decreased despite increase of stearic acid. In these cases the differences between males and females as well as between persons with normal weight and overweight more and more evened up. Ascertained correlations existed between reduction of the relative weight and decrease or more insignificant increase of cholesterol on the one hand and increase of linoleic acid on the other. The latter phenomenon is above all to be traced back to the fat-reduced diet and to the diet rich in polyene fatty acids which was more and more applied mainly by older test persons in the course of the longitudinal study, which thus may lead to antiatherogenic constellations of serum fatty acids.

Aged↗
PubMedDate not supplied

Tumor-promoting and tumor-protective effects of high-fat diets on chemically induced mammary cancer in rats.

We studied the effects of different dietary fats on experimental rat mammary lumorigenesis induced by 9,10-dimethyl-1, 2-benzanthracene (DMBA). Rats were randomly placed into four groups fed different diets: a chow diet, and high-fat (15%) diets derived from avocado, soybean or olive oils. The rats were killed 12 weeks after treatment with DMBA (a single dvse of 10 mg/rat) and maintenance on these diets. The olive diet was associated with a significant reduction in the tumorigenic effect of DMBA: tumor incidence decreased to 30%, as compared to 44%-55% in the other dietary groups studied (p < 0.05). The protective antitumor effect of the olive diet was found to be connected to its dietary content of monounsaturated fatty acids such as oleic and palmitic acids and with serum concentrations of stearic acid. The promotive tumorigenic effects of the other high-fat diets were associated with their high levels of some polyunsaturated fatty acids (linoleic and alinolenic). Malignant mammary tissue exhibited higher values than benign tissue for all the argyrophilic-nucleolar-organizer region parameters measured. The tumor-associated protein p53 was accumulated to high levels in the blood of tumor-bearing rats, but not in that of the non tumor-bearing rats.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

Chemical and pharmacological studies on fixed oil of Ocimum sanctum.

Gas liquid chromatographic analysis of fixed oil of O. sanctum revealed the presence of five fatty acids (stearic, palmitic, oleic, linoleic and linolenic acids). The triglyceride fraction of the oil showed higher protection compared to fixed oil against carrageenam-induced paw edema and acetic acid-induced writhings in rats and mice, respectively. The pharmacological activity of the fixed oil could be attributed to its triglyceride fraction or the fatty acids.

Analgesics↗
PubMed1992

Incorporation of free fatty acids can explain alterations in the molecular species composition of phosphatidylcholine and phosphatidylethanolamine in human erythrocytes as induced by Plasmodium falciparum.

Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) species composition of human erythrocytes changes upon intraerythrocytic development of Plasmodium falciparum. Though the activity of the phosphotransferases which catalyze the last step of the Kennedy pathway for the synthesis of PC and PE is dependent of the species on diacylglycerol, it appeared that this cannot, by itself, explain the alterations found in PC and PE molecular species composition. When the incorporation of radiolabeled palmitic and stearic acids in PC and PE was studied, it became clear that differences in the incorporation of fatty acids in those phospholipids might be responsible for the observed alterations in their molecular species composition.

Animals↗
PubMed1984

The lipids of the rumen fungus Piromonas communis.

The major phospholipids of the anaerobic rumen phycomycete Piromonas communis were phosphatidylethanolamine (38%), phosphatidylcholine (26%) and phosphatidylinositol (13%); no sphingolipids, glycolipids, plasmalogens or phosphonyl lipids were detected. Free fatty acids, triacylglycerols, 1:2 diacylglycerols and a variable amount of 1:3 diacylglycerol were identified, as were minor amounts of squalene and a triterpenol which is probably tetrahymanol. Approximately half the fatty acids were straight chain, even 12 to 24 carbon, saturated acids, the remainder being even 16 to 24 carbon, mono-unsaturated fatty acids. The double bonds in all except the 16 carbon acid were in the omega 9 position. The unsaturation is introduced by a delta 9 desaturase which uses stearic acid as substrate and which does not use oxygen as a terminal electron acceptor. 14C from acetate and glucose was incorporated into the fatty acids of all complex lipids, as were lauric, myristic, palmitic, stearic and oleic acids. [14C]Choline was incorporated into phosphatidylcholine and [14C]ethanolamine into phosphatidylethanolamine and phosphatidylcholine. Label from [14C]serine was recovered in phosphatidylserine and phosphatidylethanolamine, but was not detected in phosphatidylcholine.

Animals↗
PubMed2003

Rhodopsin exhibits a preference for solvation by polyunsaturated docosohexaenoic acid.

An all-atom molecular dynamics simulation of rhodopsin in a membrane environment has been carried out with lipid composition similar to that of the retinal membrane. The initial conformation of the protein was taken from the X-ray crystallographic structure (1F88), while those of the lipids came from a previous molecular dynamics simulation. During the course of the 12.5 ns simulation, the initially randomly placed lipids adopt an anisotropic solvation structure around the protein. The lipids, having one saturated stearic acid chain and one polyunsaturated docosohexaenoic acid chain with a zwitterionic phosphatidylcholine headgroup, arrange themselves to maximize contact between the polyunsaturated chain and the protein surface. This organization is driven by energetically favorable interactions between the transmembrance helices and the docosohexaenoyl chains that are largely of the van der Waals type. These observations are consistent with various experimental studies on rhodopsin and other G-protein coupled receptors and with the picture of extreme flexibility in polyunsaturated fatty acid chains that has arisen from recent NMR and computational work.

Computer Simulation↗
PubMedDate not supplied

Experimental modulation of the plasmalemmal microfluidity. Studies on endothelial and aortic smooth muscle cells.

The microfluidity of cell membranes has been modified experimentally in endothelial cells and smooth muscle cells of bovine or monkey aorta cultured in vitro. Microfluidity was estimated by fluorescence depolarization measurements of diphenyl-hexatriene (DPH)-labelled cells. In both types of cells investigated, the arachidonic acid at concentration of 90 microM induced an increase in the microfluidity by 26-53% whereas the cholesterol at the same concentration produced a decrease in the microfluidity by 16-25%. The oleic acid in the range of 30 to 90 microM increased the monkey smooth muscle cell membranes microfluidity by 21-33% but did not change the microfluidity of endothelial and bovine aortic smooth muscle cells. The stearic acid did not influence the microfluidity of either type of cells under investigation. Cortisol at 90 microM changed the microfluidity of the bovine aortic endothelial cells plasmalemma depending on the incubation time. Possible factors of error in the physical measurements due to the extracellular localization of DPH have been identified.

Animals↗
PubMed1996

The effect of unsaturated fatty acids on membrane composition and signal transduction in HT-29 human colon cancer cells.

The objective of the present study was to investigate the effect of membrane fatty acid (FA) composition on the activity of phospholipase C (PLC) in HT-29 human colon cancer cells. The membrane FA composition was altered by supplementing cultured cells with FAs of different composition. The FAs were stearic acid (18:0; SA), gamma linolenic acid (18:3 omega 6; gamma LnA); alpha linolenic acid (18:3 omega 3; alpha LnA;); eicosapentaenoic acid (20:5 omega 3; EPA) and docosahexaenoic acid (22:6 omega 3; DHA). The fatty acids were supplemented as a FA/BSA complex. Cells supplemented with SA served as the control. Tumor growth was followed by counting the number of cells in culture. The results indicate that polyunsaturated fatty acid (PUFA) supplementation had no consistent effect on tumor growth from 1 day to another throughout the 15 days of growth. The fatty acid composition of membranes indicates that cells incorporated and modified the supplemented fatty acids by desaturation, elongation and retroconversion. The unsaturation index (UI) of membranes of cells supplemented with EPA and DHA was higher than other groups. PLC activity; measured in the absence of GTP gamma(S) in the assay mixture; was not influenced by membrane FA modification. However, in the presence of GTP gamma(S) PLC of cells supplemented with 18:3(omega 6) was the lowest among the groups. It has been shown that 18:3(omega 6) accumulated the most in the phosphatidylethanolamine (PE) fraction. There was a negative correlation between the activity of PLC in the presence of G protein activation and PE 18:3 (omega 6) content without affecting UI. It was concluded that G protein may be sensitive to the level of 18:3(omega 6) content and not to the general fluidity of the membranes.

Animals↗
PubMed1990

A comment on the localization of cyanine dye binding to brush-border membranes by the fluorescence quenching of n-(9-anthroyloxy) fatty acid probes.

This work comments on the location and orientation of 3,3'-dipropylthiodicarbocyanine (diS-C3-(5)) in renal brush-border membrane vesicles (RBBMV) (Cabrini, G. and Verkman, A.S. (1986) Biochim. Biophys. Acta 862, 285-293) evaluated from collisional quenching of n-(9-anthroyloxy)stearic acid (n-AS) fluorescence. At variance with these authors, it is concluded that the quenching is due to resonance energy transfer. It is also shown that the fluorescence data are not clear evidence for the reported monomer and dimer locations.

Benzothiazoles↗
PubMed2000

Production of healthier goat milk. Use of a concentrate supplemented with a "protected" fat rich in PUFA.

In order to obtain healthier goat milk as far as its fat composition is concerned, milk production and composition trials were carried out with Granadina goats kept in semi-extensive breeding conditions. The animals were feeding indoors with a concentrate supplemented or not with 7% of fat conveniently protected against the action of rumen, which had 35% of polyunsaturated fatty acids (PUFA). The amount of milk produced was higher (p < 0.05) with consumption of the fat supplemented concentrate. At the same time, and although there was no difference in the milk concentration of fat and protein nitrogen (p > 0.05), the corresponding yields were higher for consumption of the fat supplemented concentrate. As for the composition of milk fat, the use of the supplemented concentrate resulted in fat with a higher (p < 0.05) concentration of PUFA and a lower (p < 0.05) concentration of stearic acid. At the same time, the concentration of medium chain triglycerides, which is the specific nutritional value particular to goats' milk, was the same whichever concentrate was consumed.

Animal Nutritional Physiological Phenomena↗
PubMed2005

Nanomolar protein sensing with embedded receptor molecules.

A new concept of protein sensing at the air-water interface is introduced, based on amphiphilic receptor molecules embedded in a lipid monolayer. The process begins with incorporation of a small amount (0.13 equiv) of one or two different calix[4]arenes, adorned with charged functional groups at their upper rims, into a stearic acid monolayer. These doped monolayers are subsequently shown to attract peptides and proteins from the aqueous subphase. Depending on the host structure, the monolayers can be made selective for basic or acidic proteins. A working model is proposed, which explains the large observed p/A shifts with reincorporation of excess receptor molecules into the lipid monolayer after complex formation with the oppositely charged protein. This requires a self-assembly of multiple calixarene units over the protein surface, which bind the protein in a cooperative fashion. Oppositely charged calixarene derivatives do not form molecular capsules inside the monolayer, but rather remain separate inside the lipid layer, adopting a perpendicular orientation. They combine their hydrogen bond donor and acceptor capacities, and thus markedly enhance the sensitivity of the sensor system toward proteins, pushing the detection limits to 10 pM concentrations. The response pattern obtained from various receptor units inside the monolayer toward the same protein creates a fingerprint for this protein, which can hence be selectively detected at nanomolar concentrations (pattern recognition).

Amino Acids↗
PubMed1995

Cholinergic activation of phospholipase D in lacrimal gland acini is independent of protein kinase C and calcium.

To determine if rat lacrimal gland acini contain phospholipase D (PLD) activity, we took advantage of PLD's unique ability, in the presence of ethanol, to catalyze a transphosphatidylation reaction to produce phosphatidylethanol (PEth). Lacrimal gland acini were labeled for 3 h with [14C]stearic acid, preincubated for 20 min in the presence of 2% ethanol, and incubated for 20 min with or without agonists. Total cellular lipids were then extracted and analyzed by thin-layer chromatography, and the radioactivity was determined by liquid scintillation counting. Carbachol (1 mM), a cholinergic agonist, stimulated the production of both [14C]PEth and [14C]phosphatidic acid ([14C]PA) twofold. This effect was completely blocked by the muscarinic antagonist atropine (10 microM). [14C]PEth accumulation was also stimulated twofold by the active phorbol esters, 4 beta-phorbol 12-myristate 13-acetate and 4 beta-phorbol 12,13-dibutyrate at 1 microM. Ionomycin (1 microM), a Ca2+ ionophore, also stimulated the production of [14C]PEth twofold. In contrast to carbachol, neither phorbol esters nor ionomycin stimulated [14C]PA production. Neither [14C]PEth nor [14C]PA production was altered by epinephrine (1 mM), a nonselective adrenergic agonist, or phenylephrine (0.1 and 1 mM), a specific alpha 1-adrenergic agonist. We concluded that PLD activity, modulated by muscarinic receptors, protein kinase C, and Ca2+, but not by adrenergic receptors, is present in rat lacrimal gland acini. We also concluded that cholinergic activation of PLD appears to be independent of PKC and Ca2+.

Animals↗
PubMed1989

Alpha-oxidation of alpha-hydroxyfatty acids in rat brain. Possible involvement of an alpha-peroxylactone.

Combined--but not individual--microsomal and supernatant fractions obtained from rat brains not only consume oxygen but also provoke emission from added chlorophyll. These results are consistent with literature data (Levis and Mead, J. Biol. Chem. 239, 77 [1964]) for trapping of radioactive 14CO2 following addition of alpha-hydroxy-[1-14C]stearic acid. The most plausible explanation for emission is the interaction of chlorophyll with an alpha-peroxylactone. An intermediary alpha-peroxylactone in alpha-oxidation is consistent with other available data (Salim-Hanna, Campa and Cilento, Photochem. Photobiol. 45, 849 [1987]; Campa, Salim-Hanna and Cilento, Photochem. Photobiol. 49, 349 [1989]) and, on chemical grounds, provides a feasible route to the final products.

Animals↗
PubMed1990

Fatty acid metabolism in human lymphocytes. II. Activation of fatty acid desaturase-elongase systems during blastic transformation.

The fatty acid desaturation-elongation ability of human T-lymphocytes during blastic transformation was determined both by gas-liquid chromatography and incubation with radiolabeled precursors. Human peripheral blood mononuclear cells (PBMC) were activated with phytohemagglutinin (PHA) and cultured in media supplemented with different fatty acids (18:0, 18:1(n - 9), 18:2(n - 6), 18:3(n - 3) and 20:4(n - 6)) at a final concentration of 30 microM. All the fatty acids added were elongated by activated PBMC and the maximal activity was observed on 20:4(n - 6) (a 25% of conversion to 22:4(n - 6)). Supplementation with stearic acid increased the proportion of oleic (from 21.4% to 23.7%) and eicosaenoic (from 3.1% to 5.7%) acids in cellular lipids, indicating the existence of a delta 9-desaturase activity. Supplementation with linoleic and linoleic acids increased slightly the cell content in their more unsaturated derivatives. Direct measurement of desaturase activities was performed by incubating quiescent and activated PBMC with [1-14C]stearic, [1-14C]linoleic and [1-14C]linolenic acids. Quiescent cells exhibited a very low delta 9-desaturase and no sign of delta 6-desaturase activity. A moderate and progressive activation of delta 9-, delta 6- and delta 5-desaturases was observed during blastic transformation of human PBMC. Up to 8% of 18:0 was converted to monoenes, 4% and 1.5% of 18:2(n - 6) was converted to trienes and tetraenes, respectively, and 14.5% of 18:3(n - 3) was converted to pentaenes. The maximal relative activities were found after 48 h of PHA-stimulation for delta 9-desaturase (around 90 pmol of 18:0 converted per 10(6) cells in the last 24 h) and at 72 h for delta 6- and delta 5-desaturases (around 75 and 140 pmol of 18:2 and 18:3, respectively, converted per 10(7) cells in the last 24 h). Although these activities are not enough to explain all the changes in fatty acid composition of human PBMC during blastic transformation, they may contribute to a more controlled cell phospholipid composition.

Acetyltransferases↗