Changes in the lipid and fatty acid composition of hemolymph and ovaries during the reproductive cycle of Labidura riparia

Lipid metabolism was investigated during the reproductive cycle of Labidura riparia (Pallas). The lipid classes and their constitutive fatty acids present in hemolymph and ovaries were measured using thin‐layer chromatography and gas‐liquid chromatography. In the hemolymph, total lipids increase steadily from the previtellogenic period to vitellogenic arrest. These lipids are predominantly diacylglycerols and phospholipids. In the ovaries, total lipids increase during vitellogenesis then decrease during the vitellogenesis arrest period. The major lipids are triacylglycerols, followed by phospholipids. In both hemolymph and ovaries, all lipid classes contained variable proportions of seven main fatty acids: the saturated fatty acids myristic acid (14:0), palmetic acid (16:0), and stearic acid (18:0); the monounsaturated fatty acids palmitoleic acid (16:1) and oleic acid (18:1); and the polyunsaturated fatty acids linoleic acid (18:2) and linolenic acid (18:3). Unsaturated fatty acids predominate throughout the reproductive cycle. The percentage compositions of total and triacylglycerol fatty acids do not change markedly during the reproductive cycle in hemolymph nor in ovaries, with 18:2, 18:1 and 16:0 fatty acids being the major components. However, for diacylglycerols and phospholipids, the proportions of fatty acids vary systematically. For phospholipids during the vitellogenesis period, 18:2 increases considerably whereas other fatty acids decrease; for diacylglycerols, these fatty acids vary in the reverse way.     

Changes in fatty acid composition of lipid classes in developing mustard seed

Maturation of mustard (Sinapis alba) seed proceeds with a sharp decrease in the amounts of palmitic and linoleic acids in the total lipids up to 6 weeks after flowering (WAF). Concomitantly, the concentration of oleic acid increases, reaching a plateau at 4 WAF, which is followed by chain elongation of oleic acid to gadoleic and erucic acids. Compositional changes in constituent fatty acids of individual lipid classes indicate that the very long-chain monounsaturated fatty acids (C₂₀ and C₂₂), as opposed to common long-chain fatty acids (C₁₆ and C₁₈), are metabolized to triacylglycerols mainly by esterification to preformed diacylglycerols and monoacylglycerols, rather than via esterification to glycerol-3-phosphate or lysophosphatidic acids.     

Food reserves of scots pine (Pinus sylvestris L.)

Summary Starch, soluble sugars, triacylglycerols, diacylglycerols and free fatty acids were measured in 30-year-old Scots pine (Pinus sylvestris L.) trees during an annual cycle in the sapwood (youngest ten xylem rings). The radial distribution of carbohydrates and lipids was studied in the trunkwood of 90 -to 150-year-old Scots pine trees collected at the end of the growing season. Determination of the compounds was performed using specific enzymatic assays, capillary gas chromatography and thin layer chromatography. The amounts of glucose, fructose, sucrose, and galactose/arabinose in the sapwood were slightly higher in winter than in summer. Raffinose/stachyose increased up to 5-fold during the cold period. At the beginning of the growing season starch amounts rose, and then decreased in summer and autumn. No concentration changes were observed in the total amounts of diacylglycerols and fatty acids throughout the year. Triacylglycerol levels were slightly higher in February than in summer and autumn. Relative frequencies of individual fatty acids were similar in all lipid fractions. Glucose, fructose, sucrose, starch and triacylglycerols disappeared almost entirely at the transition zone from sapwood to heartwood. In contrast, free fatty acids and galactose/arabinose rose in centripetal direction, and diacylglycerols remained constant across trunk cross-sections. The relative amounts of individual fatty acids changed markedly in the free fatty acid fraction and in the triacylglycerols when crossing the sapwood-heartwood boundary. Concentration changes of reserve materials are discussed in relation to season, mobilization and translocation processes, dormancy, frost resistance, and heartwood formation. The results are compared to those found in needles.     

Characterization of the total lipid and fatty acid composition of rat olfactory mucosa

Phospholipid accounted for 81% (by weight) of the total lipid of rat olfactory mucosa. Phosphatidylcholine (46% of total phospholipids) and phosphatidylethanolamine (26%) were the predominant phospholipids. Phosphatidylinositol (8%), sphingomyelin (6%), and phosphatidylserine (7%) were the next most abundant phospholipids, with cardiolipin (4%) and phosphatidic acid (1%) present in lesser amounts. Only trace amounts of the polyphosphoinositides, phosphatidylinositol monophosphate, and phosphatidylinositol bisphosphate were detected. Sterol was the major neutral lipid present (83% of the total neutral lipid mass) with lesser amounts of triacylglycerols (7%), steryl esters (6%), free fatty acids (4%), and diacylglycerols (1%). Monoacylglycerols were detected only in trace amounts. The sterol to phospholipid ratio was 0.39:1. Most of the phospholipids of the olfactory mucosa showed a high polyunsaturated fatty acid content, with the arachidonic acid (20:4) and docosahexaenoic acid (22:6) residues predominating. The fatty acids in sphingomyelin, however, were almost totally saturated and included the 24:0 and 24:1 residues, which were not detected in other phospholipids. Polyunsaturated fatty acids accounted for less than 25% of the total fatty acid of any individual neutral lipid and comprised largely linoleic and arachidonic acids. The results are discussed in relation to the putative role of lipids in olfactory signal transduction.     

Formation of intracytoplasmic lipid inclusions by Rhodococcus opacus strain PD630

An oleaginous hydrocarbon-degrading Rhodococcus opacus strain (PD630) was isolated from a soil sample. The cells were able to grow on a variety of substrates and to produce large amounts of three different types of intracellular inclusions during growth on alkanes, phenylalkanes, or non-hydrocarbon substrates. Electron microscopy revealed large numbers of electron-transparent inclusions with a sphere-like structure. In addition, electron-dense inclusions representing polyphosphate and electron-transparent inclusions with an elongated disc-shaped morphology occurred in small amounts. The electron-transparent inclusions of alkane- or gluconate-grown cells were composed of neutral lipids (98%, w/w), phospholipids (1.2%, w/w), and protein (0.8%, w/w). The major component of the cellular inclusions was triacylglycerols; minor amounts of diacylglycerols and probably also some free fatty acids were also present. Free fatty acids and/or fatty acids in acylglycerols in cells of R. opacus amounted up to 76 or 87% of the cellular dry weight in gluconate- or olive-oil-grown cells, respectively. The fatty acid composition of the inclusions depended on the substrate used for cultivation. In cells cultivated on n-alkanes, the composition of the fatty acids was related to the substrate, and intermediates of the β-oxidation pathway, such as hexadecanoic or pentadecanoic acid, were among the acylglycerols. Hexadecanoic acid was also the major fatty acid (up 36% of total fatty acids) occurring in the lipid inclusions of gluconate-grown cells. This indicated that strain PD630 utilized β-oxidation and de novo fatty acid biosynthesis for the synthesis of storage lipids. Inclusions isolated from phenyldecane-grown cells contained mainly the non-modified substrate and phenylalkanoic acids derived from the hydrocarbon oxidation, such as phenyldecanoic acid, phenyloctanoic acid, and phenylhexanoic acid, and approximately 5% (w/w) of diacylglycerols. The lipid inclusions seemed to have definite structures, probably with membranes at their surfaces, which allow them to maintain their shape, and with some associated proteins, probably involved in the inclusion formation. Received: 22 December 1995 / Accepted: 12 March 1996     

Distribution of dietary trans-octadecenoate among acyl-CoA and other lipid fractions of rat liver and heart

Groups of rats were fed diets containing 10% of either corn oil, partially hydrogenated soybean oil, or a mixture of the two. The partially hydrogenated oil contained a high level of trans-octadecenoate and a low level of linoleate, and all diets were adjusted to contain similar levels of cis-octadecenoate. The fatty acid compositions of five tissue lipid fractions from liver and heart (non-esterified fatty acids, acyl-CoA, diacylglycerols, triacylglycerols and phospholipids) were analyzed to measure the effect of the dietary supply on the accumulation of trans-octadecenoates and other fatty acids at different steps of glycerolipid synthesis. Although trans-octadecenoate was increased in all of the lipid fractions when the dietary supply was increased, the accumulation did not exceed 15% of the acyl chains in any of the lipid pools even when the dietary trans acid accounted for 46% of the fatty acids supplied in the diet. The trans-octadecenoate accumulated in a similar manner in the lipids of both liver and heart, and the amounts found in the acyl-CoA esters of both tissues were relatively low compared to the diet. A high dietary supply of trans-octadecenoate appeared to diminish the relative content of stearate in the acyl-CoA and phospholipid fractions. The level of cis-octadecenoate maintained in tissue phospholipids was similar to that in the acyl-CoA fractions, whereas the trans-octadecenoate content in phospholipids more closely resembled that in the diacylglycerols. Normal proportions of arachidonate were maintained in the tissue phospholipids during high intake of trans acids, even though lower levels were observed in the acyl-CoA and diacylglycerols of liver.     

Influence of nitrogen deficiency on biochemical composition of the green alga <Emphasis Type="Italic">Botryococcus</Emphasis>

A study has been carried out to investigate the influence of nitrogen deficiency on intracellular lipid composition, including total fatty acid composition of lipids, polar lipids, and triacylglycerols, of the alga Botryococcus braunii Kütz IPPAS H-252 in batch culture. Under nitrogen limitation, the alga accumulates lipids as triacylglycerols and the total fatty acid (FA) composition changes: trienoic acids decrease (from 52.8–57.2 to 19.5–24.7% of the total FAs) and the oleic acid increases (from 1.1–1.2 to 17.1–24.4%) as does the saturated acids (from 23.7–26 to 32.9–46.1%). A similar rearrangement in the FA spectrum occurs at later times in the control culture, but it is less pronounced. Under nitrogen limitation, considerable changes in the polar lipid FAs are registered at day 13: saturated acids increase (from 28.6–35.5 to 76.8%) and all polyenoic acids markedly decrease (from 56.9–64.1 to 6.8%). Changes in the triacylglycerol fatty acid spectrum are seen on day 7: the oleic acid increases (from 14.7 to 34.2%) and remains at a high level till the end of the culture. In the control, triacylglycerols with large contents of oleic acid are detected at day 13, the total lipids and triacylglycerols still remaining unchanged.     

Lipid biosynthesis in developing mustard seed: formation of triacylglycerols from endogenous and exogenous Fatty acids

Cotyledons of developing mustard (Sinapis alba L.) seed have been found to synthesize lipids containing the common plant fatty acids and very long-chain monounsaturated (icosenoic, erucic, and tetracosenic) and saturated (icosanoic, docosanoic, and tetracosanoic) fatty acids from various radioactive precursors. The in vivo pattern of labeling of acyl lipids, either from fatty acids synthesized `endogenously' from radioactive acetate or malonate, or from radioactive fatty acids added `exogenously', indicates the involvement of the following pathways in the biosynthesis of triacylglycerols. Palmitic, stearic, and oleic acid, synthesized in the acyl carrier protein-track, are channeled to the Coenzyme A (CoA)-track and converted to triacylglycerols via the glycerol-3-phosphate pathway. Pools of stearoyl-CoA and oleoyl-CoA are elongated to very long-chain saturated and monounsaturated acyl-CoA, respectively. Most of the very long-chain saturated acyl-CoAs acylate preformed diacylglycerols. Very long-chain monounsaturated acyl-CoAs are converted to triacylglycerols, partly via phosphatidic acids and diacylglycerols, and partly by acylation of preformed diacylglycerols.     

Fatty acid composition and lipid synthesis in developing safflower seeds

Linoleic acid predominated in every lipid class during the whole period of seed development of safflower, while linolenic acid decreased with increasing maturation and it was not detected in mature seeds. Just before the initiation of triacylglycerol accumulation, the fatty acid composition of triacylglycerols changed more rapidly than those of phospholipids and glycolipids. Saturated fatty acids tended to accumulate at the 1- and 3-positions of the glycerol molecule and the more highly unsaturated acids at the 2-position. The fatty acid compositions at the 1- and 3-positions were similar in all cases investigated, but in none of the triacylglycerols was the distribution completely symmetrical. The positional distribution of linolenic acid in triacylglycerols prepared from the immature seeds 2 days after flowering and from the leaves was unusual; in spite of its highest degree of unsaturation, it was preferentially esterified at the 1- and 3-positions. When triacylglycerol was most rapidly accumulated (14–18 days after flowering), the incorporation of acetate-[U- ¹⁴C] into total lipids was also maximum and dienoic fatty acids were the principal acids labelled. Diacylglycerols and compound lipids reached the highest rate of synthesis 15 days after flowering, and then a maximum incorporation into triacylglycerol occurred 18 days after flowering. Incubation temperature affected the synthesis of individual lipid classes. Triacylglycerol was more rapidly synthesized at 32° than at 10°, while diacylglycerols and compound lipids were accumulated under the low-temperature condition. A rise of incubation temperature caused a depression in dienoic acid synthesis.     

Biochemistry of the cyclic evolution of Triatoma infestans (Vinchuca). III. Dynamics of the incorporation of fatty acids in lipids

More than 80% of total lipids of Triatoma infestans are triacylglycerols and only 3.7% and 4.0% are phosphatidyl-ethanolamine and phosphatidylcholine, whereas the diacylglycerols are 0.2%. However in hemolymph that contains 6.8 mg of lipids per ml predominate the phospholipids and there are approximately 22% of diacylglycerols with very little triacylglycerols. Therefore these diacylglycerols may play an important function in fatty acid transport since they incorporate in a few minutes injected 1 14C oleate. The radioactivity is later on transferred to the choline and ethanolamine phospholipids and then to the energy stores represented by the triacylglycerols.     

Isolation and composition of the carotenoid-containing oil droplets from cone photoreceptors.

A procedure for isolating the carotenoid-containing oil droplets of cone retinal photoreceptors of Gallus domesticus is described. The oil droplets, composed almost entirely of neutral lipids and carotenoids, have been separated into ten chromatographic components. Similar separations have been carried out on the total retinal neutral lipids for comparison. The neutral lipids represented 26.1% of the total retinal lipid. Cholesterol, cholesterol ester, mono-, di- and triacylglycerols represented 92.6% of the total neutral lipid. Each of these and other minor neutral lipid components were also present in the lipids extracted from the isolated oil droplets in correspondingly similar concentrations. However, the concentrations of carotenoids were greatly enriched in the neutral lipids of the oil droplets. Each of the major fatty acyl-containing neutral lipids from the chromatography of oil droplet lipids is greatly enriched in polyunsaturated fatty acids when compared with the corresponding component from the total neutral lipid chromatography. In the acylglycerols and free fatty acid fraction from the oil droplets, linoleic and arachidonic acid together represented 52-83% of the total polyunsaturated fatty acids present. The remainder was generally distributed about equally among six other acids. Except for the diacylglycerol fraction, linoleic acid was usually the most enriched acid in a specific oil droplet fraction when compared with any other polyunsaturated fatty acids. A similar pattern of polyunsaturated fatty acid enrichment observed in the fatty acids of the outer segment phospholipids relative to the corresponding total phospholipid fractions of this cone rich retina (Johnston, D. and Hudson, R.A. (1974) Biochim. Biophys. Acta 369, 269) suggest possible metabolic relationships between the oil droplet neutral lipids and the outer segment membrane phospholipids of the cone photoreceptors. A mechanism for the accumulation of the carotenoids in the oil droplets is also discussed.     

The transfer of fatty acids across the sheep placenta

Maternal and fetal plasma concentrations of free fatty acids, triacylglycerols and phospholipids and the profile of their fatty acids were measured in three catheterized and unanaesthetized sheep. Fetal concentrations of all three lipid fractions were low and did not correlate with maternal concentrations. There were no measurable umbilical venous-arterial differences. Linoleic acid concentrations were low in both mother and fetus. The fatty acid composition of fetal adipose tissue, liver, lung and cerebellum of five animals was analysed. Again linoleic acid levels were very low, but phospholipids contained 2-8% arachidonic acid. [14C] linoleic acid and [3H] palmitic acid were infused intravenously into three ewes. Only trace amounts of labelled fatty acids were found in fetal plasma and these were confined to the free fatty acids. 14C-label was incorporated into fetal tissue lipids, but most of this probably was due to fetal lipid synthesis from [14C] acetate or other water-soluble products of maternal [14C] linoleic acid catabolism. It is concluded that only trace amounts of fatty acids cross the sheep placenta. They are derived mainly from the maternal plasma free fatty acids and might just be sufficient to be the source of the small amounts of essential fatty acids found in the lamb fetus, but are insignificant in terms of energy supply or lipid storage.     

Changes of lipid composition in non-cultured and cultured porcine embryos

The objective of the present study was to evaluate the lipid composition of cultured and non-cultured pig embryos during cleavage using histochemical methods. The authors studied pig zygotes as well as 2-to 4-cell embryos, morulae, and blastocysts that were either non-cultured or cultured in NCSU-23 medium. To detect different types of lipids, the authors used the Churukian method with Oil red O, the Sudan black B method, the Cain method with Nile blue sulfate, and the modified osmium tetroxide-ethanol treatment. In the zygotic lipid droplets, diverse classes of unsaturated and saturated lipids were found, with particularly high levels of unsaturated hydrophobic lipids, mainly triglycerides and other esters, free fatty acids, and phospholipids. In the zygotic cytoplasm, the authors observed high levels of fatty acids and phospholipids. The total lipid content remained constant up to the morula stage, decreasing later at the blastocyst stage, but the overall amount of unsaturated lipids declined earlier, at the 2-to 4-cell stage. The amount of free fatty acids and phospholipids decreased during cleavage in both non-cultured and cultured porcine embryos. The main differences between the non-cultured and cultured embryos were the more pronounced reduction in the amount of unsaturated hydrophobic lipids in droplets and the cytoplasmic free fatty acids observed in the cultured morula and the lower content of phospholipids in the cytoplasm of the cultured 2-to 4-cell embryos relative to the non-cultured embryos. The decrease in the unsaturated lipid, free fatty acid, and phospholipid content during in vivo development and the differences in the amount of these types of lipids between developmentally matched cultured and non-cultured pig embryos correlate well with modifications of lipid and carbohydrate metabolism.     

Lipid composition of plasma membranes isolated from sunflower seedlings grown under water-stress

Plasma membranes were isolated by aqueous two-phase-partitioning from sunflower ( Helianthus annuus cv. Isabel) seedlings grown both under field irrigation and dryland conditions. Water-stressed plants showed a decrease in the leaf water potential and in the osmotic potential at full turgor, with the turgor pressure remaining at positive values. Dryland conditions also induced a reduction in the bulk modulus of elasticity. Plasma membranes of irrigated plants were characterized by high contents of phospholipids (68% of total lipids), free sterols (15. 7%) and glycolipids (9. 1%), mainly glycosphingolipids and steryl glycosides. Diacylglycerols, triacylglycerols and free fatty acids were also present. The major phospholipids were phosphatidylcholine and phosphatidylethanolamine with smaller amounts of phosphatidylinositol and phosphatidylglycerol. Following water stress, the plasma membranes showed a reduction of about 24 and 31% in total lipids and phospholipids, respectively. Also the amounts of glycolipids and diacylglycerols decreased significantly upon water stress. There was no change in free fatty acids, however, and triacylglycerols and free sterols increased. As a consequence, the free sterol to phospholipid molar ratio increased from 0. 4 to 0. 7 under water deficit conditions. The ratio of phosphatidylcholine to phosphatidylethanolamine increased from 1. 1 (control plants) to 1. 6 (water-stressed plants), while phosphatidic acid rose to 4% of total phospholipids. Dehydration did not result in any substantial change in the unsaturation level of the individual lipid classes, however. The results show that dryland conditions resulted in a marked alteration in the lipid composition of the sunflower leaf plasma membrane     

Essential fatty acid uptake and esterification in primary culture of rat hepatocytes

Primary cultures of adult rat hepatocytes were used to compare the uptake and esterification of essential polyunsaturated fatty acids (18:2, 20:3 and 20:4 of the n-6 series) with those of palmitic and oleic acids. The uptake of unesterified fatty acids was linearly related to the free fatty acid/albumin molar ratio for 14 h and did not depend on the unbound free fatty acid level. Whatever the initial free fatty acid/albumin molar ratio, it dropped to 0.5 +/- 0.1 mM after 14 h, thus showing that hepatocytes have a high capacity for clearing free fatty acids from the medium at high free fatty acid/albumin molar ratios. The free fatty acid uptake become saturable when the free fatty acid and albumin concentrations were raised and the free fatty acid/albumin ratio remained constant. This strongly suggests that albumin-hepatocyte interaction mediates free fatty acid uptake. This uptake was identical whatever the fatty acid tested and did not depend on the relative amounts of fatty acids when they were added simultaneously. Triacylglycerol accumulation and synthesis, monitored by labelled fatty acids, were related to the free fatty acid/albumin molar ratio and exhibited no specificity for the series of fatty acids tested. Triacylglycerols were enriched in all the fatty acids tested by up to 60%, and fatty acid incorporation into diacylglycerols and triacylglycerols reflected the free fatty acid composition of the medium. By contrast, neither the level nor the synthesis of phospholipids varied with free fatty acid/albumin, but the rate of phospholipid turnover depended on the fatty acids tested. Accumulation of these acids was smaller in phospholipids than in triacylglycerols. When linoleic and arachidonic acids were added together, phospholipids (especially phosphatidylethanolamine and phosphatidylinositol) were more enriched in arachidonic acid than triacylglycerols. This might be due to the specificity for fatty acid of the enzymes involved in phospholipid metabolism.     

Lipidomics reveals that adiposomes store ether lipids and mediate phospholipid traffic

Lipid droplets are accumulations of neutral lipids surrounded by a monolayer of phospholipids and associated proteins. Recent proteomic analysis of isolated droplets suggests that they are part of a dynamic organelle system that is involved in membrane traffic as well as packaging and distributing lipids in the cell. To gain a better insight into the function of droplets, we used a combination of mass spectrometry and NMR spectroscopy to characterize the lipid composition of this compartment. In addition to cholesteryl esters and triacylglycerols with mixed fatty acid composition, we found that approximately 10-20% of the neutral lipids were the ether lipid monoalk(en)yl diacylglycerol. Although lipid droplets contain only 1-2% phospholipids by weight, >160 molecular species were identified and quantified. Phosphatidylcholine (PC) was the most abundant class, followed by phosphatidylethanolamine (PE), phosphatidylinositol, and ether-linked phosphatidylcholine (ePC). Relative to total membrane, droplet phospholipids were enriched in lysoPE, lysoPC, and PC but deficient in sphingomyelin, phosphatidylserine, and phosphatidic acid. These results suggest that droplets play a central role in ether lipid metabolism and intracellular lipid traffic.     

Lipids of the zygomycete Absidia corymbifera F-965

The cell lipids of the zygomycete Absidia corymbifera F-965 extracted with isopropanol and CHCl3-MeOH mixtures at the exponential growth phase comprise 20+/-2% of mycelium dry wt. The lipids consist of: triacylglycerols (51% of the total lipids extracted), diacylglycerols (9%), monoacylglycerols (3%), ergosterol (5%), ergosterol peroxide (5alpha,8alpha-epidioxyergosta-6,22-diene-3beta-ol) (3%), fatty-acid esters of ergosterol (less than 0.5%), free fatty acids (4%), glucocerebroside (3%), and glycerophospholipids (22%). The main phospholipids are phosphatidylethanolamine (39% of the total phospholipids), phosphatidyl-myo-inositol (17%), diphosphatidylglycerol (12%), phosphatidic acid (7%), phosphatidylcholine (6%), phosphatidylglycerol (3%), and two unusual phospholipids reported earlier, N-acetylphosphatidylethanolamine (7%) and N-ethoxycarbonyl phosphatidylethanolamine (9%). In addition, two unknown acidic phospholipids are present in traces. Saturated fatty acids of the lipids are dominated by n-hexadecanoic acid and unsaturated ones by octadecenoic acid; octadecadienoic and octadecatrienoic acids are present in lesser amounts. Ergosterol peroxide as well as the above glucocerebroside which contains 9-methylsphinga-4(E),9(E)-dienine have first been revealed in zygomycetes.     

Lipids in plant tissue cultures. VI. Effect of temperature on the lipids of Brassica napus and Tropaeolum majus cultures

The lipid contents of callus cultures of rape (Brassica napus) and nasturtium (Tropaeolum majus) increase in response to decreasing the temperature, though to different degree. Irrespective of the incubation temperature the lipids in cultures of both plants contain as predominant classes steryl glycosides, esterified steryl glycosides, sterols, steryl esters and fatty acids and, as minor constituents, various proportions of triacylglycerols, phospholipids and several unidentified fractions.The ratio of phospholipids to triacylglycerols as well as the ratio of diacylglycerophosphorylethanolamines to dicylglycerophosphorylcholines increase with time both in rape cultures incubated at 30°C and in those kept at 5°C.The lipids in rape and nasturtium cultures grown at 30°C contain smaller proportions of polyunsaturated fatty acids than the lipids in cultures incubated at 5°C. Erucic acid, the major constituent fatty acid of the seed lipids, in both plants, occurs only in trace amounts in the lipids of callus cultures. In contrast, linoleic and linolenic acids, which occur only in traces in the seed lipids of nasturtium, are major constituent fatty acids in the lipids of callus cultures derived from seedlings of this plant.The levels of constituent polyunsaturated fatty acids in the diacylglycerophosphorylethanolamines and the diacylglycerophosphorylcholines increase with time whereas in the triacylglycerols only linolenic acid is slightly increased.     

Functional role of lipid metabolism in activated T-lymphocytes

Exogenous long-chain fatty acids are readily taken up by unstimulated lymphocytes derived from the thymus of calves or rabbits and esterified to complex lipids, primarily phospholipids and triacylglycerols. Compared to saturated fatty acids, unsaturated fatty acids are incorporated preferentially. Furthermore, unsaturated fatty acids are transferred from triacylglycerols to phospholipids. The transfer cannot be observed with palmitic acid. With regard to individual phospholipid species, oleic acid and linoleic acid are found primarily in phosphatidylcholine. Arachidonic acid, however, is transferred to phosphatidylethanolamine and phosphatidylinositol as well. This suggests an arachidonic-specific transfer between individual phospholipids. Stimulation of the cells with the mitogen concanavalin A results in an enhanced incorporation of the fatty acids and an enhanced transfer from triacylglycerols to phospholipids. Triacylglycerols may thus be regarded as a labile intracellular storage pool that may be activated upon mitogenic stimulation.     

Analysis of lipids by gas-liquid chromatography and complementary methods in four strains of Aedes aegypti mosquitoes

Fatty acid composition of total lipids, neutral lipids and phospholipids of strains of Aedes aegypti were determined. The fatty acid composition of the strains differed quantitatively with regard to the relative percentage of commonly occurring fatty acids. Gas-liquid chromatography of fatty acid methyl esters showed 18:1 (oleic or elaidic) to be the predominant fatty acid. The fatty acid was identified as oleic by argentation thin-layer chromatography. A modified colorimetric method was used to determine tissue-free fatty acids. The lipids were predominantly triacylglycerol with lesser amounts of free fatty acids and decreasing amount of sterol ester, sterol, monoacylglycerol, diacylglycerol and hydrocarbons. The data show considerable lipid differences between the Caribbean strains (Les Cayes, Haiti, and San Juan, Puerto Rico) and the Jakarta (Indonesia) strain. The Shimba Hills (Kenya) strain was more similar to Jakarta than to the Caribbean strains. The results obtained with the different strains are discussed in relation to the established oral susceptibility to Dengue 1 and Dengue 2, yellow fever, and genetic analysis by isoenzyme studies.