Allergic delayed skin reactions from lipid fractions of trichophytin.

Crude trichophytin was fractionated to find out if its lipid fraction could cause inflammatory delayed allergic skin reactions in dermatophyte-sensitized guinea pigs. The following fractions were obtained: polysaccharide-peptide, total lipids, total lipids without free fatty acids and free fatty acids. The crude trichophytin and polysaccharide-peptide fraction gave rise to strong and equal allergic delayed skin reactions after 24 h. The total lipids gave statistically significant weaker, but clearly positive reactions, and of the same degree as the free fatty acid fraction. The total lipids without free fatty acids did not produce reactions in the sensitized animals, indicating that free fatty acids are responsible for the allergic skin reactions. In some cases the free fatty acids showed comparatively intense reactions. It can be concluded that free fatty acids are antigenic substances that are, sometimes, involved in the allergic delayed skin reactions in dermatophytosis.     

Interrelationships between fatty acid biosynthesis and acyl-lipid synthesis in Chlorella vulgaris

1. Fatty acid synthesis from [2-(14)C]acetate by Chlorella vulgaris cells grown and incubated in the dark is limited almost entirely to the production of saturated and monoenoic acids. 2. In light-incubated cells, both saturated and polyunsaturated fatty acids are rapidly synthesized. 3. Two groups of lipids can be distinguished in both dark- and light-incubated cells. The first group, consisting of phosphatidyl-glycerol, monogalactosyl diglyceride, lecithin and neutral glyceride, has a very high turnover rate for certain fatty acids. The second group, consisting of digalactosyl diglyceride, sulpholipid, phosphatidylethanolamine and phosphatidylinositol, has a slow turnover of fatty acids. 4. The lipids with rapid fatty acid turnover may be involved in the sequences of saturated and unsaturated fatty acid synthesis. A classification of lipids is made on the basis of their suggested functions.     

Free fatty acids associated with the high molecular weight aminoacyl-tRNA synthetase complex influence its structure and function

Aminoacyl-tRNA synthetases from higher eukaryotes often are isolated as high molecular weight complexes associated with other components such as lipids. Since hydrophobic interactions are involved in the organization of the complex, it has been suggested that interaction of synthetases with these lipids might be important for their structure and function. Delipidation is known to affect certain properties of synthetases within the complex including sensitivity to detergents plus salts, temperature inactivation, hydrophobicity, sensitivity to proteases, and, as shown here, sensitivity to p-mercuribenzoate and sites of papain cleavage. Of the lipids known to co-purify with the complex, cholesterol esters, phospholipids and free fatty acids, we show that the particular lipids responsible for many of these changes are the free fatty acids. Specific removal of fatty acids results in a complex with properties similar to one totally delipidated by detergent treatment, and readdition of the fatty acid fraction reverses the effects. The fatty acid fraction contains both saturated and unsaturated fatty acids, but unsaturated fatty acids are much more effective in reversing the properties of the delipidated complex that are saturated fatty acids. These results indicate that the free fatty acids co-purifying with the synthetase complex bind to the synthetases and affect their structure and function.     

Effect of phosphatidylcholine and free fatty acids on the activity of pancreatic lipase-colipase

Mixed micelles of bile salt and phospholipids inhibit the lipase-colipase-catalysed hydrolysis of triacylglycerols. Free fatty acids can reverse this inhibition and reactivate lipase-colipase. This reactivation is either due to the formation of a high-affinity complex between lipase and colipase induced by free fatty acids and/or to a change of the quality of the interface. Lauric acid, oleic acid and linoleic acid are the most potent reactivators, while short-chain free fatty acids have no effect and long-chain, saturated free fatty acids inhibit the lipase-colipase activity further. The physiological relevance of these results is evident as the glyceride emulsion reaching the duodenum already contains free fatty acids due to the activity of lingual lipase in the stomach.     

Membrane Lipids of Mycoplasma hominis

Essentially all of the lipids of Mycoplasma hominis (200 mug/mg of cell protein) were found to be located in the cell membrane. Over one-half were neutral lipids incorporated from the growth medium and consisting of 43% free cholesterol, 19% esterified cholesterol, 23% triglycerides, 10% free fatty acids, and small amounts of di- and monoglycerides. The polar lipids accounting for about 40% of the total were synthesized by the organisms. Phosphatidylglycerol was the predominant lipid of this fraction. The minor components, tentatively identified as lysophosphatidylglycerol and phosphatidic acid, seem to represent breakdown products of phosphatidylglycerol. No glycolipids were detected. Being unable to synthesize long-chain fatty acids, M. hominis utilized the fatty acids of the growth medium for polar lipid synthesis, preferentially the saturated ones, so that the polar lipids had highly saturated hydrocarbon chains. It is proposed that the large take up of unsaturated neutral lipids and cholesterol from the medium offsets the marked condensing effect of the saturated polar lipids, although electron paramagnetic resonance spectrometry of spin-labeled fatty acids incorporated into the M. hominis membrane indicated that the lipid region is still more rigid than that of the Acholeplasma laidlawii membrane.     

Molecular dynamics simulations of stratum corneum lipid models: fatty acids and cholesterol

We report the results of an investigation on stratum corneum lipids, which present the main barrier of the skin. Molecular dynamics simulations, thermal analysis and FTIR measurements were applied. The primary objective of this work was to study the effect of cholesterol on skin structure and dynamics. Two molecular models were constructed, a free fatty acid bilayer (stearic acid, palmitic acid) and a fatty acid/cholesterol mixture at a 1:1 molar ratio. Our simulations were performed at constant pressure and temperature on a nanosecond time scale. The resulting model structures were characterized by calculating surface areas per headgroup, conformational properties, atom densities and order parameters of the fatty acids. Analysis of the simulations indicates that the free fatty acid fraction of stratum corneum lipids stays in a highly ordered crystalline state at skin temperatures. The phase behavior is strongly influenced when cholesterol is added. Cholesterol smoothes the rigid phases of the fatty acids: the order of the hydrocarbon tails (mainly of the last eight bonds) is reduced, the area per molecule becomes larger, the fraction of trans dihedrals is lower and the hydrophobic thickness is reduced. The simulation results are in good agreement with our experimental data from FTIR analysis and NIR-FT Raman spectroscopy.     

Changes in Composition of Non-polar Lipids of the Axis and Root of Germinating Soybeans

Soybean seedlings were grown at 28°C under dark or light conditions for 12 days. Non-polar lipids (NPL) were separated by silicic acid column chromatography from total lipids in epicotyl containing young leaves, hypocotyl and root. The glyceride (TG, DG, and MG), free fatty acid (FFA) and sterol lipid (SE) components in NPL were analyzed mainly by thin-layer and gas-liquid chromatographies (TLC and GLC).

During germination, the amounts of polar lipids (PL) markedly increased in the tissues of soybean seedlings, especially in light-grown seedlings, whereas these of NPL increased slightly or maintained constant values. The features of the compositions and changing patterns of NPL in the tissues were more clarified in light-grown seedlings than in dark-grown ones. The pattern of change in fatty acid composition was similar in TG and 1,2-DG, which showed higher proportions of linoleic and linolenic acids, whereas FFA, 1,3-DG or MG had high proportions of saturated fatty acids. These results indicate that the compositions and changing patterns of NPL and their fatty acids in the tissues depend on the differences under two germinating conditions tested.     

Release of Neurotransmitter Amino Acids from Synaptosomes: Enhancement of Calcium-Independent Efflux by Oleic and Arachidonic Acids

Abstract: The release of preloaded [¹⁴C]neuroactive amino acids (glutamic acid, proline, γ-aminobutyric acid) from rat brain synaptosomes can occur via a time-dependent, Ca²⁺ -independent process. This Ca²⁺-independent efflux is increased by compounds that activate Na⁺ channels (veratridine, scorpion venoms), by the ionophore gramicidin D, and by low concentrations of unsaturated fatty acids (oleic acid and arachidonic acid). Saturated fatty acids have no effect on the efflux process. Neither saturated nor unsaturated fatty acids have an effect on the release of [¹⁴C]leucine, an amino acid not known to possess neurotransmitter properties. The increase in the efflux of neuroactive amino acids by oleic and arachidonic acids can also be demonstrated using synaptosomal membrane vesicles. Under conditions in which unsaturated free fatty acids enhance amino acid efflux, no effect on ²²Na⁺ permeability is observed. Since Na⁺ permeability is not altered by fatty acids, the synaptosomes are not depolarized in their presence and, thus, the Na⁺ gradient can be assumed to be undisturbed. We conclude that unsaturated fatty acids represent a potentially important class of endogenous modulators of neuroactive amino acid transport in nerve endings and further postulate that their action is the result of an uncoupling of amino acid transport from the synaptosomal Na⁺ gradient.     

Lipid biosynthesis by chloroplasts from olive tree leaves

In vitro incubation of isolated chloroplasts from young olive tree leaves ( Olea europaea L. cv. Marteño) in acetate-1-¹⁴C showed a high labelling of saturated fatty acids (palmitic + stearic) and, above all, of the monounsatured ones (oleic); the low biosynthetic rate of α-linolenic acid being noteworthy. These fatty acids are mainly found as free ones, or incorporated in mono-and diglyceride molecules. Phosphoand galactolipids, the most abundant acyl-lipid components of chloroplast lamellae, showed low incorporation rates. The fatty acid synthesis by isolated chloroplasts depends on exogenous CoA, ATP, NADPH and, especially, on added ACP (acyl carrier protein) preparation from Escherichia coli , whereas it was strongly inhibited by Triton X-100.
In vivo experiments with acetate-1-¹⁴C infiltration into young excised leaves showed a high labelling of chloroplast phospholipids, but a low ¹⁴C incorporation into galactolipids, a remarkable feature because these latter are main components of chloroplast lamellae. The high biosynthetic rate of α-linolenic acid is noteworthy and appears mainly linked to monogalactosyldiglycerides. Also the low incorporation of saturated fatty acids to neutral lipids is remarkable. The low in vitro synthesis of α-linolenic acid in comparison with that of the in vivo conditions, suggests the existence of a cooperation between chloroplasts and other parts of the cell to carry out the synthesis of this compound.     

Lipids of Pseudomonas aeruginosa Cells Grown on Hydrocarbons and on Trypticase Soy Broth

Lipids were extracted from cells of Pseudomonas aeruginosa grown on a pure hydrocarbon (tridecane), mixed hydrocarbons (JP-4 jet fuel), and on Trypticase Soy Broth. Total lipids produced from each substrate represented from 7.1 to 8.2% of cellular dry weight, of which 5.0 to 6.4% were obtained before cellular hydrolysis (free lipids) and 1.7 to 2.0% were extracted after cellular hydrolysis (bound lipids). Free lipids from cells grown on each medium were separated into four fractions by thin-layer chromatography. All fractions were present in cells from each type of medium, and the "neutral fraction" constituted the largest fraction. The fatty acid composition of free lipids was determined by gas-liquid chromatography. Cells grown on each medium contained saturated and unsaturated C(14) to C(20) fatty acids. Trace amounts of C(13) fatty acids were found in tridecane-grown cells. Saturated C(16) and C(18) were the major acids present in all cells. Quantitative differences were found in fatty acids produced on the three media, but specific correlations between substrate carbon sources and fatty acid content of cells were not evident. Tridecane-grown cells contained only traces of C(13) acid and small amounts of C(15) and C(17) acids, suggesting that the organism's fatty acids were derived from de novo synthesis rather than by direct incorporation of the hydrocarbon.     

Chemical and carbon isotopic composition of fatty acids in adipose tissue as indicators of dietary history in wild arctic foxes (A lopex lagopus) on Svalbard

The chemical and carbon isotope compositions of triacylglycerol fatty acids were analysed in samples from two or more adipose depots dissected from adult and subadult arctic foxes collected between November 1991 and March 1992 in four different areas of Spitsbergen in the Svalbard archipelago (latitude 78° 5' to 79° 50' N). Site-specific differences were minor but there were large and consistent differences in the fatty acid composition of the storage lipids of foxes caught in the same areas, suggesting that residents of contiguous territories may have had quite different diets. The adipose tissue of adult foxes caught in Austfjordneset, an area where reindeer are rare, contained a much greater proportion of unsaturated fatty acids, suggesting that these animals were feeding mainly in the marine ecosystem, probably on seabirds and/or fish in summer and the remains of polar bear kills in winter. Measurements of the relative abundance of the carbon isotopes ¹²C and ¹³C in individual fatty acids show that palmitoleic acid (C16:1) in storage triacylglycerols originates from the marine food chain, probably together with most other unsaturated lipids, but that the foxes obtain oleic acid (C18:1), and probably most saturated fatty acids, from either terrestrial or marine sources.     

INCORPORATION OF [1-14C]OLEIC ACID AND [1-14C]ARACHIDONIC ACID INTO LIPIDS IN THE SUBCELLULAR FRACTIONS OF MOUSE BRAIN

Abstract— The distribution of radioactivity among lipids of subcellular membrane fractions was examined after intracerebral injections of [1-¹⁴C]oleic and [1-¹⁴C]arachidonic acids. Labelled free fatty acids were distributed among the synaptosomal-rich, microsomal, myelin and cytosol fractions at 1 min after injection. However, incorporation of the fatty acids into phospholipids and trïacylglycerols after pulse labelling occurred mainly in the microsomal and synaptosomal-rich fractions. With both types of labelled precursors, there was a higher percentage of radioactivity of diacyl-glycerophosphoryl-inositols in the synaptosomal-rich fraction as compared to the microsomal fraction. Radioactivity of [1-¹⁴C]oleic acid was effectively incorporated into the triacylglycerols in the microsomal fraction whereas radioactivity of the [1-¹⁴C]arachidonic acid was preferentially incorporated into the diacyl-glycerophosphorylinositols in the synaptosomal-rich fraction. Result of the study indicates that synaptosomal-rich fraction in brain is able to metabolize long chain free fatty acids in vivo and to incorporate these precursors into the membrane phosphoglycerides.     

Lipids and fatty acids in cellulosomes of Clostridium thermocellum

A lipid component was found in cellulosomes (multienzymatic cellulase complexes) of the thermophilic bacterium Clostridium thermocellum. Two major fractions of the cellulosomes have been studied, one with a relative molecular mass (M_r) of 10–50 million (polycellulosomes, fraction A) and the other with an M_r 0.5–10 million (fraction B) It was found that the larger cellulosomes contained higher relative amounts of lipids (8.1%) as well as Ca²⁺ ions (0.6%), and showed higher cellulolytic activity Among the lipids was cardiolipin, 1,2- and 1,3-diglycerides, triglycerides, and up to 11 free fatty acids, including both saturated (palmitic, lauric, myristic, pentadecanoic, stearic, arachinic) and unsaturated (myristoleic, palmitoleic, and oleic) moieies Cardiolipin was a major phospholipid component in cellulosomes and was also found to be a major phospholipid component of the cell membrane, palmitic acid was a major fatty acid Fraction B contained less fatty acids (0.5% vs 1.27% in fraction A) with fewer acids detected than in fraction A Removal of the extractable lipids led to fragmentation of the cellulosomes with a concurrent sharp drop in their enzymatic activity Total removal of the lipids from cellulosomes was possible only when the proteins were completely denatured The qualitative composition of the extractable and non-extractable fatty acids was the same The lipid component of the cellulosomes, containing a high content of the unsaturated fatty acids, was located mainly in the part of cellulosomes that is in tight contact with the cellulose surface, and it apparently plays an important role in the tight adsorption of the cellulosomes on cellulose.     

Lipids of Aureobasidium (Pullularia) pullulans]

Fractional composition of free and bound lipids was studied in Aureobasidium (Pullularia) pullulans 8 by preparative TLC on Silufol. Bound lipids contained a fraction (27.76 +/- 0.5%) of dark brown colour, similar to melanin. The composition of fatty acids was studied by GLC. The following fatty acids were identified and determined quantitatively: C12:0, C14:0, C15:0, C16:0, C18:0, C18:1+C15:2. The following fatty acids predominated in free and bound lipids: C16:0, C18:1+C18:2. The ratio between unsaturated and saturated fatty acids in all fractions of free and bound lipids was more than unity. The following parameters were determined for lipids; ester number (173.89 and 178.53); iodine number (44.1 and 33.10), and saponification number (181.17 and 206.03) (the values are given for free and bound lipids, respectively).     

Isoprostane levels in lipids extracted from atherosclerotic arteries of nonhuman primates

Nonhuman primates used in these studies had been fed for 5 years diets enriched with cholesterol and one of three classes of fatty acids: saturated, monounsaturated, or polyunsaturated fatty acids. Atherosclerotic iliac artery lipid extracts were quantitatively analyzed for cholesterol, cholesteryl esters, fatty acid composition, and a marker of lipid oxidation, the F₂-isoprostanes. There was no significant difference in the mean accumulation of F₂-isoprostanes among the different diet groups. To account for the small, individual variation in the arachidonate concentration the F₂-isoprostane mass from each sample was normalized by dividing by arachidonate mass: F₂-isoprostane mass/(mass arachidonate). At lower levels of cholesterol accumulation, the F₂-isoprostane mass/(mass arachidonate) ratio was greater in lipids from POLY arteries compared to SAT arteries, but the reverse was true at high levels of cholesterol. F₂-isoprostane/(mass arachidonate) increased with mole fraction linoleate for the SAT group, but decreased for the POLY group. In summary, these studies demonstrated that there is no simple explanation of how F₂-isoprostane accumulation did not depend on the concentration of oxidizable lipids that promote free-radical lipid oxidation.     

Rearing system and oleic acid supplementation effect on carcass and lipid characteristics of two muscles from an obese pig breed

Quality of pork depends on genotype, rearing and pre- and post-slaughter conditions. However, no information is available on rearing system changes and oleic acid supplementation on carcass characteristics and fatty acid (FA) profile of pork from the Alentejano (AL) pig, an obese breed. This study evaluates the effects of feeding low (LO) or high oleic acid diets (HO) to AL pigs reared in individual pens (IND) or outdoor (OUT) with access to pasture. Carcass composition was obtained and longissimus dorsi and semimembranosus samples were collected to analyse chemical composition and neutral and polar intramuscular lipids FA profile by gas chromatography. Statistical analysis was performed by a two-way ANOVA for rearing system and diet effects. OUT-reared pigs presented leaner carcasses than IND-reared ones. Both muscles presented lower intramuscular lipid content in OUT-reared pigs. Treatments affected the FA profile of muscles. Overall, OUT-reared pigs presented lower n-6/n-3 FA ratios, whereas pigs fed the HO diet exhibited lower saturated fatty acids (SFA), higher monounsaturated fatty acids (MUFA) levels and lower thrombogenic indexes on neutral intramuscular lipids than LO-fed pigs. On the polar fraction, OUT-reared pigs presented lower SAT and n-6/n-3 FA ratio, and higher polyunsaturated fatty acids (PUFA) levels on both muscles. Pigs fed the HO diet exhibited higher MUFA and lower PUFA levels on both muscles, and lower SAT levels on semimembranosus. This study shows rearing system and oleic acid supplementation have complementary effects and influence carcass composition and the nutritional quality of meat.     

Nature and store of fatty acid lipids in the blood of newborn calves with dyspepsia

The content of fatty acids of lipids extracted from the whole blood as well as from erythrocytes, leucocytes, plasma and serum samples of newborn dyspeptic calves were investigated for the first time. Twenty three (23) saturated, mono-non-saturated and poly-non-saturated fatty acids were detected. Native, palmitoleic, stearic, oleic, linoleic and arachidonic fatty acids, are the main components of the whole blood lipid fraction and its components. The fatty acids found in lipids and other components of the whole blood in the samples of dyspeptic and healthy calves are the same, their ratios, however, are different. The decrease in the nonsaturated fatty acids content and its increase in saturated fatty acids are considerable. The saturation coefficient is different in native blood lipids, erythrocytes, leukocytes, serum and plasma.     

Metabolism of endogenous sterol ester by the superovulated rat ovary in vitro

Sterol, glyceride and phospholipid were found to account for more than 90% (w/w) of the lipid extracted from whole superovulated rat ovaries. These lipids, together with non-esterified fatty acids, were assayed in slices of the tissue after incubation for various times. Whereas the concentrations of triglyceride, diglyceride and phospholipid did not change significantly during incubation, that of sterol ester markedly decreased and those of free sterol, monoglyceride and non-esterified fatty acid increased. Evidence is presented that in this tissue (in contrast with other mammalian tissues) the main endogenous substrate for respiration is fatty acid derived from sterol ester.     

The influence of fatty acids on model cholesterol/phospholipid membranes

The aim of this work was to verify the influence of the saturated (SFA) (stearic acid) and the unsaturated (UFA) (oleic and alpha-linolenic) fatty acids on model cholesterol/phospholipid membranes. The experiments were based on the Langmuir monolayer technique. Cholesterol and phospholipid were mixed in the molar ratio that corresponds to the proportion of these lipids in the majority of natural human membranes. Into the binary cholesterol/phospholipid monolayers, various amounts of fatty acids were incorporated. Our investigations were based on the analysis of the interactions between molecules in ternary (cholesterol/phospholipids/fatty acid) mixtures, however, also binary (cholesterol/fatty acid and phospholipids/fatty acid) mixed system were examined. It was concluded that the influence of the fatty acids on model cholesterol/phospholipid membrane is closely connected with the shape of the fatty acid molecule, resulting from the saturation degree of the hydrocarbon chain. It was found that the saturated fatty acid makes the model membrane more rigid, while the presence of unsaturated fatty acid increases its fluidity. The increasing amount of stearic acid gradually destabilizes model membrane, however, this effect is the weakest at low content of SFA in the mixed monolayer. Unsaturated fatty acids in a small proportion make the membrane thermodynamically more stable, while higher content of UFA decreases membrane stability. This explains low proportion of the free fatty acids to other lipids in natural membrane.     

Oxidative degradation of model lipids representative for main paper pulp lipophilic extractives by the laccase–mediator system

Different model lipids-alkanes, fatty alcohols, fatty acids, resin acids, free sterols, sterol esters, and triglycerides-were treated with Pycnoporus cinnabarinus laccase in the presence of 1-hydroxybenzotriazole as mediator, and the products were analyzed by gas chromatography. The laccase alone decreased the concentration of some unsaturated lipids. However, the most extensive lipid modification was obtained with the laccase-mediator system. Unsaturated lipids were largely oxidized and the dominant products detected were epoxy and hydroxy fatty acids from fatty acids and free and esterified 7-ketosterols and steroid ketones from sterols and sterol esters. The former compounds suggested unsaturated lipid attack via the corresponding hydroperoxides. The enzymatic reaction on sterol esters largely depended on the nature of the fatty acyl moiety, i.e., oxidation of saturated fatty acid esters started at the sterol moiety, whereas the initial attack of unsaturated fatty acid esters was produced on the fatty acid double bonds. In contrast, saturated lipids were not modified, although some of them decreased when the laccase-mediator reactions were carried out in the presence of unsaturated lipids suggesting participation of lipid peroxidation radicals. These results are discussed in the context of enzymatic control of pitch to explain the removal of lipid mixtures during laccase-mediator treatment of different pulp types.