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At least 649 records · Page 36Linked to original sources
PubMed1970

Lipids in alfalfa leaves in relation to cold hardiness.

The lipid composition of the leaves of hardy Vernal and cold-sensitive Caliverde alfalfa plants, grown at different temperatures, was determined. Phosphatidyl glycerol, phosphatidyl inositol, and the sulfolipid content were directly related to growth temperature. Mono- and digalactose diglyceride and phosphatidyl choline and ethanolamine were inversely related to temperature. At corresponding growth temperatures Vernal plants showed higher percentages of mono- and digalactose diglyceride and phosphatidyl choline and ethanolamine than Caliverde plants, while the opposite was true for phosphatidyl glycerol and inositol and sulfolipid. Differences in fatty acid composition of corresponding leaf lipid fractions of plants grown at different temperatures or differences in fatty acid composition between lipid fractions of plants of different varieties in general were negligible.

Journal Article↗
PubMed1970

The structure and biosynthesis of phosphatidyl inositol in cauliflower inflorescence.

Phosphatidyl inositol has been isolated from cauliflower inflorescence and soybean. Analysis of the fatty acid distribution showed that unsaturated fatty acids were preferred at position 2, and that saturated fatty acids were preferred at position 1.Mitochondrial preparations from cauliflower inflorescence were capable of synthesizing phosphatidyl inositol from myo-inositol and cytidine diphosphate diglyceride. The optimal pH for the reaction was 9.0. Metal ions were required for the reaction: Mn(2+) ions were optimally effective at 1.5 mm, and Mg(2+) ions were maximally effective at 30 mm. The maximal rate in the presence of Mn(2+) was 9 times as great as that in the presence of Mg(2+). Phosphatidyl inositol could also be synthesized when cytidine diphosphate diglyceride was replaced by cytidine triphosphate, but the pH optimum then shifted to 8.1.

Journal Article↗
PubMed1970

Effect of Growth Temperature on the Lipid Composition of Cyanidium caldarium: II. Glycolipid and Phospholipid Components.

Cyanidium caldarium was grown at 20 and 55 C and harvested during exponential growth phase. Lipids were extracted and separated by silicic acid column and thin layer chromatography. The major glycolipids were identified as mono- and digalactosyl diglyceride and sulfolipid. Major phospholipids were identified as phosphatidyl choline and phosphatidyl ethanolamine. The cells grown at 20 C contained significantly larger quantities of these glycolipids and phospholipids than cells grown at 55 C.Fatty acid analysis showed that in all cases the cells grown at 20 C contained more unsaturated fatty acids than the cells grown at 55 C. Cells grown at 55 C were shown to lack linolenic acid, in contrast to cells grown at 20 C, which contained appreciable quantities in certain lipid components. For example, monogalactosyl diglyceride had 57% of its fatty acids in the form of linolenic acid. Cells grown at 55 C were 10 to 15 C more stable to disruption by heating than cells grown at 20 C. The greater thermostability of the latter was attributed to a higher degree of saturation of their membrane fatty acids.

Journal Article↗
PubMed1971

Lipid biosynthesis by isolated barley chloroplasts in relation to plastid development.

The effect of seedling age and of the time of greening on the incorporation of 1-(14)C-acetate into lipids by isolated barley (Hordeum vulgare cultivar Svalöf's Bonus) plastids was examined. The fatty acid synthesizing capacity of plastids isolated from 5-day-old seedlings did not increase markedly from zero to 36 hours of greening nor was a light stimulation of fatty acid synthesis observed. However, an increasing capacity for fatty acid synthesis and an increasing light stimulation of this process with greening were attained by the plastids isolated from 7-, 9-, and 11-day-old seedlings.Plastids of 7-day-old dark-grown plants, which were illuminated at 2 foot-candles showed increasing capacity of (14)C-acetate incorporation with significant flow into phospholipids and sulfolipid, low flow into digalactosyl diglyceride, and considerable flow into 6-methyl salicylic acid. Exposure of these plants to high light intensity for an hour resulted in chloroplasts that after isolation had a 10-fold increased capacity to incorporate (14)C label into digalactosyl diglyceride, while the flow of (14)C label into phospho- and sulfolipids was unaltered, and that into 6-methyl salicylic acid was drastically curtailed.With plastids from 7-day-old dark-grown plants in early stages of greening, essentially all the (14)C label in the stroma fraction could be accounted for by 6-methyl salicylic acid, while the membrane lipids only contained small amounts of (14)C label. As greening proceeded, the flow of (14)C label into 6-methyl salicylic acid diminished sharply, and the lipids of the lamellar systems became increasingly labeled.Only palmitic and oleic acids were main sites of (14)C label in the membrane lipids.The activity of acetyl CoA carboxylase present in plastids of 5- and 7-day-old dark-grown plants fell sharply as the etioplasts differentiated into chloroplasts.

Journal Article↗
PubMed1973

Compartmental utilization of carboxyl-C-tripalmitin by tissue homogenate of pine seeds.

A tissue homogenate of megagemetophyte of germinating seeds of Jeffrey pine (Pinus Jefferii Grev. and Balf.) was incubated with sonication-dispersed and albumin-carried (14)C-tripalmitin in order to elucidate the sequential and quantitative role of cellular organelles in utilizing lipid reserve in seeds. After 5 minutes at 30 C, 25% of the tracer was localized in the fat body fraction, 9% in the pellet containing mitochondria and glyoxysomes, 14% in the supernatant, and 2% was found as CO(2). Radioactivity increased with time of incubation in the latter three fractions indicating the forward direction of utilization. Fat bodies contained mainly lipases and hydrolyzed the tracer to palmitate with diglyceride and monoglyceride as intermediates. About two-thirds of the palmitate had left the fat bodies in 5 minutes and entered the pellet fraction within which the tracer was distributed 1:2 in mitochondria and glyoxysomes, respectively. Longer incubation reduced the ratio to 1:3 while both organelles acquired more radioactive intermediates. Labeled acetyl-CoA and intermediate of beta-oxidation were found in both organelle-containing fractions. The supernatant fraction contained radioactive diglycerides, monoglycerides, palmitate, sterol esters, and phospholipids, indicating lipase activity and direct utilization of fatty acid for the synthesis of sterol esters and polar lipids.

Journal Article↗
PubMed1973

Differences in Lipid Composition between Undifferentiated and Mature Maize Chloroplasts.

Lipid compositions of undifferentiated maize (Zea mays) chloroplasts, capable of fixing CO(2), were compared with the lipid compositions of mature chloroplasts, which do not fix CO(2), located in both the mesophyll and bundle sheath cells. The major lipids found in all three chloroplast types were the glycolipids, monogalactosyl diglyceride and digalactosyl diglyceride, followed by decreasing amounts of sulfolipid, phosphatidyl glycerol, phosphatidyl choline, phosphatidyl inositol, and diphosphatidyl glycerol. Quantitative differences in lipid components were observed among the chloroplast types. The mesophyll and bundle sheath maize chloroplasts differed in their chlorophyll a/chlorophyll b ratios (2.27 and 4.13 respectively) and their content of glycolipid relative to chlorophyll (51.8% glycolipid to 20.9% chlorophyll and 84.5% glycolipid to 10.1% chlorophyll respectively). A comparison between the lipid compositions of maize mesophyll chloroplasts and mesophyll chloroplasts obtained from spinach, sugar beet, and tobacco showed many similarities.

Journal Article↗
PubMed1975

Studies on Phospholipid-synthesizing Enzyme Activities during the Growth of Etiolated Cucumber Cotyledons.

The enzymatic incorporation of sn-glycerol 3-phosphate into lipid by extracts of cucumber (Cucumis sativus) cotyledons showed an absolute requirement for ATP (saturation 2 mM). The incorporation was stimulated 4-fold by 0.2 mM oleate. Ethyldiaminetetraacetate stimulated the incorporation at concentrations below 1 mM and inhibited at higher concentrations. Mg(2+) did not affect the reaction. Triton X-100 and Cutscum inhibited the reaction, while a third detergent, Span 80, was stimulatory. p-Mercuribenzoate was inhibitory. The enzymatic reaction has a pH optimum in the range of 8.8 to 9.6. The Michaelis constant was 112 muM for sn-glycerol 3-phosphate. The major amount of product was phosphatidic acid, the remainder was diacylglycerol, monoacylglycerol, and an unknown phospholipid.The activity profiles for two glyoxysmal enzymes, malate synthetase and catalase, were compared to the activities of four enzymes involved in phospholipid synthesis. Phosphatidylcholine and phosphatidylethanolamine synthesis paralleled the activity profiles of catalase and malate synthetase, as well as the levels of endogenous diglycerides. sn-Glycerol 3-phosphate incorporation peaked at a later stage of cucumber cotyledon growth than the glyoxysomal enzymes and seemed to be the major pathway of phosphatidic acid synthesis. Diglyceride phosphokinase activity did not reach appreciable levels during the first 11 days of cucumber cotyledon growth.

Journal Article↗
PubMed1976

Studies on lipid synthesis and degradation in developing soybean cotyledons.

The metabolic activity of individual lipid classes found in developing soybean cotyledons (Glycine max.) is estimated by determining the degradation rate of the compound under given conditions. Pulse-labeling and dual substrate labeling are used to evaluate this parameter. These studies indicate first order decay kinetics for phosphatidic acid, phosphatidylinositol, phosphatidylcholine, phosphatidylethanolamine, N-acyl-phosphatidylethanolamine, diglyceride, and zero order kinetics for triglyceride in cotyledons var. "Harosoy 63" at 30 days after flowering. Decay coefficients for acyl groups and lipid-glycerol moieties within specific lipid classes from either method are comparable. Half-life (t((1/2))) calculations from the decay coefficients indicate extremely rapid turn-over rates (0.08 to 3.4 hours at 25 C) and suggest similar turnover rates of acyl groups and lipid-glycerol in diglyceride and all phospholipids except N-acylphosphatidylethanolamine where acyl groups are replaced independent of the glycerol moiety. These experiments reveal not only different metabolic activity between lipid components of soybean cotyledons, but also describe a new method for measuring lipid turnover in plants.

Journal Article↗
PubMed1977

Phospholipid-synthesizing Enzymes Associated with Golgi Dictyosomes from Pea Tissue.

Golgi dictyosomal membranes isolated from pea (Pisum sativum) stem tissue, using a combination of rate zonal and isopycnic sucrose density centrifugation, were shown to bear cytidine diphosphate-choline:diglyceride phosphorylcholinetransferase, CDP-ethanolamine:diglyceride phosphorylethanolaminetransferase, and CTP:phosphorylcholine cytidyltransferase activities. Although the majority of the activity of the phospholipid-synthesizing enzymes was associated with the endoplasmic reticulum, the activity found in the Golgi system was about 25% of the total activity. These results suggest that Golgi dictyosomes probably synthesize at least part of the membrane phospholipids that they may need for their secretory function and for dictyosomal proliferation during cell growth, rather than importing this material entirely from the endoplasmic reticulum.

Journal Article↗
PubMed1979

Effect of Growth Temperature on the Lipid and Fatty Acid Composition, and the Dependence on Temperature of Light-induced Redox Reactions of Cytochrome f and of Light Energy Redistribution in the Thermophilic Blue-Green Alga Synechococcus lividus.

The thermophilic blue-green alga Synechococcus lividus was grown at 55 and 38 C. Arrhenius plots of the transient reduction of cytochrome during actinic illumination with light that excited both pigment systems revealed breaks near 43 and 26 C for cells grown at 55 C. In cells grown at 38 C these breaks occurred near 37 and 28 C, respectively. The shift from pigment state 1 to state 2 measured by fluorescence transients also showed characteristic breaks in the Arrhenius plots at 44 C for cells grown at 55 C and at 37 to 38 C and possibly at 25 C for cells grown at 38 C. The break points in the Arrhenius plots for the state shift as well as for the cytochrome f reduction are discussed in relation to phase transitions of thylakoid membrane lipids as studied by the temperature dependence of chlorophyll a fluorescence.The variations of fatty acid composition with growth temperature was also studied. When the growth temperature was lowered from 55 to 38 C, the amount of the saturated fatty acid 18:0 in the negatively charged lipids sulfoquinovosyl diglyceride and phosphatidyl glycerol decreased while the unsaturated fatty acids 18:1 and 16:1 increased. In mono- and digalactosyl diglycerides the saturated fatty acids 18:0 and 16:0 decreased and the unsaturated fatty acid 16:1 increased. In general there was an increase in the more fluid lipids in all of the lipid classes when the cells were grown at the lower temperature.

Journal Article↗
PubMed1979

Phospholipid metabolism in plant mitochondria: submitochondrial sites of synthesis.

Intact mitochondria from the endosperm of castor bean were isolated on linear sucrose gradients. These mitochondria were ruptured and the membranes separated on discontinuous sucrose gradients into outer membrane, intact inner membrane, and ruptured inner membrane fractions. Each membrane fraction was examined for its capacity to synthesize phosphatidylglycerol, CDP-diglyceride, phosphatidylcholine via methylation, and phosphatidic acid. The syntheses of phosphatidylglycerol, CDP-diglyceride, and phosphatidylcholine were localized exclusively in the inner mitochondrial membrane fractions while phosphatidic acid synthesis occurred in both the inner and outer mitochondrial membranes.

Journal Article↗
PubMed1980

Lipid Composition and Metabolism of Volvox carteri.

The membrane structural lipids of somatic cells and gonidia isolated from Volvox carteri f. nagariensis spheroids have been characterized. The principal polar lipid components of both cell types are sulfoquinovosyl diglyceride, mono- and digalactosyl diglyceride, phosphatidylglycerol, phosphatidylethanolamine, and 1(3), 2-diacylglyceryl-(3)-O-4'-(N,N,N,-trimethyl)homoserine. Light-synchronized cultures of spheroids were shown to incorporate [(14)C]bicarbonate, [(35)S]sulfate, [(14)C]palmitic acid, and [(14)C]lauric acid into complex lipids. [(14)C]Palmitic acid was incorporated mainly into diacylglyceryltrimethylhomoserine and was not significantly modified by elongation or desaturation. In contrast, [(14)C]lauric acid was incorporated into a wider variety of complex lipids and was also converted into longer chain saturated and unsaturated fatty acids. Volvox is a promising system for studying the role of membranes in algal cellular differentiation.

Journal Article↗
PubMed1982

Low Temperature-Induced Alterations in the Chloroplast and Microsomal Membranes of Dunaliella salina.

The metabolic regulation of membrane lipid composition has been examined using the cell wall-less, unicellular green alga Dunaliella salina (UTEX 1644) as a model system. Low temperature stress was employed to initiate and study the regulatory response.When cultures growing logarithmically at 30 degrees C were chilled to 12 degrees C, cell division ceased for approximately 100 hours, and then the cells resumed logarithmic growth at a slower rate. The phospholipid, glycolipid and protein content, on a per cell basis, was, in each case, approximately 20% higher in cells grown at 12 degrees C. The volume of the 12 degrees C-acclimated cells was 2.8 times that of 30 degrees C-grown cells. The quantity of chloroplast membrane, as determined by morphometric analysis, was 20% greater, whereas the content of microsomal membrane material was more elevated, being approximately 2.8 times that of 30 degrees C-grown cells.Lipid compositional analyses were carried out on purified chloroplasts and microsomes isolated from Dunaliella grown at 30 and 12 degrees C and also from cells 12 and 60 hours following a shift from 30 to 12 degrees C. In both chloroplast and microsomal phospholipids fatty acid unsaturation increased during acclimation to low temperature. Generally, microsomal phospholipids responded more quickly and to a greater extent than did chloroplast phospholipids. Despite these alterations, little change in the relative proportions of phospholipid classes was observed in either cell fraction.In sharp contrast to the pattern of phospholipid change, chloroplast glycolipids responded to low temperature by significantly increasing the proportion of one specific class, digalactosyl diglycerides, relative to monogalactosyl diglycerides, while showing minimal change in fatty acid distribution within any given glycolipid class.The ease and rapidity with which Dunaliella cells can be manipulated with respect to environmental stress and isolation of intact cell organelles makes it particularly well suited for research on intermembrane lipid dynamics within the plant cell.

Journal Article↗
PubMed1985

Effect of frost hardening on lipid and Fatty Acid composition of chloroplast thylakoid membranes in two wheat varieties of contrasting hardiness.

Lipid and fatty acid composition of chloroplast thylakoid membranes was determined in two varieties of wheat (Triticum aestivum L.), the hardy Miranovskaja and the sensitive Penjamo. Plants were grown at room temperature or under frost hardening conditions (1.5 degrees C). Changes in lipid and fatty acid composition of the isolated thylakoids could be related to the temperature dependence of light-stimulated proton uptake. Changes in the thylakoid phospholipids upon hardening of the two varieties did not show any direct relation with low temperature tolerance of light-dependent H(+) uptake; neither did changes in phospholipid fatty acid chain lengthening to 20 and 22 C-atoms in combination with increased desaturation up to 6 double bonds. Increased low temperature tolerance of light-induced H(+) uptake by hardening was correlated with the following glycolipid changes: maintained glycolipid level, a proportionally increased digalactosyl diglyceride fraction, a decrease in thylakoid monogalactosyl diglyceride, increased sulfolipid fatty acid chain lengthening (20 and 22 C-atoms), and increased sulfolipid desaturation (4-6 double bonds). We suggest that the above mentioned changes in glycolipids have adaptive value for low temperature tolerance of light-dependent proton uptake.

Journal Article↗
PubMed1977

Skin surface lipid composition, acne, pubertal development, and urinary excretion of testosterone and 17-ketosteroids in children.

Fifty-two children, age 5-10, from acne-prone families, were studied for a period of 1 year to examine the interrelationship between sebum, acne, pubertal development, and urinary steroid excretion. In each of the subjects, 30 boys and 22 girls, the composition of forehead skin lipid was determined 4 times yearly by thin-layer chromatography, with measurement of triglycerides, diglycerides, free fatty acids, wax esters, squalene, cholesterol, and cholesterol esters. Twice yearly, examination was made of the presence or absence of acne, pubertal maturation and the 24-hour urinary excretion of testosterone as determined by radioimmunnoassay, and of total 17-ketosteroids, dehydroepiandrosterone, androsterone, and etiocholanolone, as determined by paper chromatography. The relative amount of sebaceous lipids was positively correlated with age of the subjects (wax esters p less than .001, squalene p less than .05), as was the triglyceride-diglyceride component (p less than .05). No significant correlation was seen with the fatty acids. Acne, primarily comedonal, occurred in 27/52 subjects (15 girls, 12 boys) and was associated with higher sebum values. One-half of the children with acne had no signs of pubertal development. A significantly positive correlation was observed between the relative amount of sebaceous lipid and the urinary excretion of 17-ketosteroids, androsterone, and etiocholanolone in both sexes, and of testosterone and dehydroepiandrosterone in boys. The development of acne in children is an early pubertal event, often evident before other signs of pubertal maturation, and it is associated with an increase in sebum and in the urinary excretion of androgenic steroids.

17-Ketosteroids↗
PubMed1985

Effect of light on the metabolism of lipids in the rat retina.

The effect of light on the in vitro incorporation of a variety of radioactive precursors into glycerolipids was tested in isolated retinas of albino rats. There was an increase in the incorporation of [2-3H]myo-inositol, 32Pi, [2-3H]glycerol, and [methyl-3H]choline into retinal phospholipids in light compared to that in darkness. [2-3H]myo-Inositol was incorporated primarily into phosphatidylinositol. 32Pi was incorporated primarily into the phosphoinositides, although there were significant increases in the specific activities of all retinal phospholipids in light compared to those in darkness. Likewise, [2-3H]glycerol incorporation into all retinal phospholipids and diglycerides was greater in light than in the dark. There was no effect of light on the incorporation of [2-3H]ethanolamine into phosphatidylethanolamine or of [3-3H]serine into phosphatidylserine, although these phospholipids were labeled to a greater extent in light with [2-3H]glycerol. There was no effect of light on the incorporation of [3H]palmitic acid into diglycerides and phospholipids, with the exception of phosphatidylinositol. Light also had no effect on the uptake of [2-3H]glycerol, [2-3H]inositol, or [methyl-3H]choline into the retina. We conclude from these studies that light stimulates the phosphoinositide effect in the rat retina. Although some of the results are consistent with a stimulation of de novo synthesis of all lipid classes, our studies with [3H]palmitate, [2-3H]ethanolamine, and [3-3H]serine do not support this conclusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

The mechanism and regulation of fat mobilization from adipose tissue: desnutrin, a newly discovered lipolytic enzyme.

A new member of a family of proteins functioning in the regulation of lipolysis in adipose tissue has been discovered and named "desnutrin." Desnutrin is transiently induced by fasting and decreased by re-feeding. A close homolog, termed adiponutrin, has the opposite expression pattern, being induced by feeding and disappearing upon fasting. Desnutrin functions by acting as the first enzyme in lipolysis, hydrolyzing triglycerides to diglycerides, whereas the well-known hormone-sensitive lipase takes the diglycerides to monoglycerides and on to free fatty acids.

Adipose Tissue↗
PubMed1994

Changes in Ester-Linked Phospholipid Fatty Acid Profiles of Subsurface Bacteria during Starvation and Desiccation in a Porous Medium.

Ester-linked phospholipid fatty acid (PLFA) profiles of a Pseudomonas aureofaciens strain and an Arthrobacter protophormiae strain, each isolated from a subsurface sediment, were quantified in a starvation experiment in a silica sand porous medium under moist and dry conditions. Washed cells were added to sand microcosms and maintained under saturated conditions or subjected to desiccation by slow drying over a period of 16 days to final water potentials of approximately - 7.5 MPa for the P. aureofaciens and - 15 MPa for the A. protophormiae. In a third treatment, cells were added to saturated microcosms along with organic nutrients and maintained under saturated conditions. The numbers of culturable cells of both bacterial strains declined to below detection level within 16 days in both the moist and dried nutrient-deprived conditions, while direct counts and total PLFAs remained relatively constant. Both strains of bacteria maintained culturability in the nutrient-amended microcosms. The dried P. aureofaciens cells showed changes in PLFA profiles that are typically associated with stressed gram-negative cells, i.e., increased ratios of saturated to unsaturated fatty acids, increased ratios of trans- to cis-monoenoic fatty acids, and increased ratios of cyclopropyl fatty acids to their monoenoic precursors. P. aureofaciens starved under moist conditions showed few changes in PLFA profiles during the 16-day incubation, whereas cells incubated in the presence of nutrients showed decreases in the ratios of both saturated fatty acids to unsaturated fatty acids and cyclopropyl fatty acids to their monoenoic precursors. The PLFA profiles of A. protophormiae changed very little in response to either nutrient deprivation or desiccation. Diglyceride fatty acids, which have been proposed to be indicators of dead or lysed cells, remained relatively constant throughout the experiment. Only the A. protophormiae desiccated for 16 days showed an increase in the ratio of diglyceride fatty acids to PLFAs. The results of this laboratory experiment can be useful for interpreting PLFA profiles of subsurface communities of microorganisms for the purpose of determining their physiological status.

Journal Article↗