Age dependent changes in phospholipids and galactolipids in primary bean leaves (Phaseolus vulgaris)

Primary leaves of Phaseolus vulgaris show concomitant changes in phospholipid, galactolipid, chlorophyll and fresh weight during leaf development from 3 to 32 days after planting. Phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl inositol show only small changes on a mole per cent lipid phosphate basis during leaf development. The chloroplast lipids, phosphatidyl glycerol, monogalactosyl diglyceride (MGDG) and digalactosyl diglyceride (DGDG) all show marked increases and decreases which are coincident with chloroplast development. The decline in the leaf content of chloroplast polar lipids and chlorophyll become evident upon reaching maximal leaf size. The molar ratio of galactolipids (MGDG/DGDG), reaches a maximum value of 2.3 in expanding leaves, but steadily declines during senescence to a minimum value of 1.5 at abscission. The declining ratio is caused by a preferential loss of MGDG in the senescing leaves.     

Alterations in lipid turnover in developing muscle

The incorporation and turnover of [³H] glycerol into skeletal muscle cell cultures derived from embryonic chickens was studied. Both rates of incorporation and turnover of specific lipids were dependent on culture age and lipid species. The pattern of glycerol incorporation showed that prefusion myoblasts primarily synthesized both phosphatidylcholine and triglycerides whereas postfusion myotubes primarily synthesized phosphatidyl choline. This pattern could be modified in postfusion but not prefusion cells by briefly incubating the cells with unilammelar phosphatidyl choline vesicles. Analysis of major lipid species revealed that muscle triglycerides and phospholipids turned over at a higher rate in prefusion cultures compared to the postfusion state. These findings are discussed in light of the marked shift in lipid metabolism which occurs during myogenesis.     

Lipid variation of the green alga Fritschiella tuberosa during growth in axenic batch culture

The lipid and pigment pattern of the chaetophoralean green alga Fritschiella tuberosa was studied during different growth periods. Four phases in axenic batch culture are observed. The first phase commences at the end of logarithmic growth and results in a decrease of phosphatidyl inositol and hexadecatetraenoic acid.The second phase coincides with the end of linear growth and is characterized by a decrease in glycolipids, phospholipids and α-linolenic acid, and an increase of linoleic and oleic acid. The third phase starts with the beginning of the stationary phase. During this time glycolipids, phospholipids, and α-linolenic acid decrease and oleic acid, linoleic acid and triacylglycerol increase. The fourth phase begins about one week after the onset of the stationary growth phase. A marked accumulation of triacylglycerol took place, secondary carotenoids were detectable and the long filamentous cells of Fritschiella changed into slightly rotund short cells.     

Formation of biomass,total protein,chlorophylls, lipids and fatty acids in green and blue-green algae during one growth phase.

Batch cultures (8–32 l.) of Chlorella vulgaris and Scenedesmus obliquus and of Anacystis nidulans and Microcystis aeruginosa were grown in media containing 0.001 % KNO₃ and at several stages in growth sampled for biomass, total protein, chlorophylls, lipids and fatty acids. With increasing time and decreasing nitrogen concentrations, the biomass of all of the algae increased, whereas the total protein and chlorophyll content dropped. Green and blue-green algae, however, behaved differently in their lipid metabolism. In the green algae the total lipid and fatty acid content as well as the composition of these compounds changed considerably during one growth phase and was dependent on the nitrogen concentration in the media at any given day of growth. More specifically, during the initial stages of growth the green algae produced larger amounts of polar lipids and polyunsaturated C₁₆ and C₁₈ fatty acids. Towards the end of growth, however, these patterns changed in that the main lipids of the green algae were neutral with mainly saturated fatty acids (mostly 18:1 and 16:0). Such changes did not occur in the blue-green algae. These differences between prokaryotic and eukaryotic algae can possibly be explained by the ‘endosymbiont theory’.     

In vivo covalent binding of 14CCl4 metabolites in liver microsomal lipids

Covalently bound ¹⁴C from ¹⁴CCl₄ is preferentially localized in the lipids of hepatic microsomes of rats within 15 min. Label was recovered in all classes of lipids isolated from the microsomal lipid extract by diethylaminoethyl column chromatography. Among phospholipids, specific activity was the highest in the fraction containing phosphatidyl serine and lowest in phosphatidyl choline. Cholesterol esters had more than ten times the specific activity of cholesterol.     

Microscopic studies of fatty acid vesicles

Microscopic vesicles enclosed by membranes formed entirely of oleic or linoleic acids (ufasomes) were studied by the freeze-etching and birefringence techniques. The results suggest the presence of one or more membranes around the particles, in which the fatty acid chains lie perpendicular to the surface. Comparison with results obtained with phospholipid liposomes shows that both types of particles are basically similar, although ufasomes have a less regular structure.     

Biomass production,total protein,chlorophylls, lipids and fatty acids of freshwater green and blue-green algae under different nitrogen regimes

Two green algae (Chlorella vulgaris and Scenedesmus obliquus) and four blue-green algae (Anacystis nidulans, Microcystis aeruginosa, Oscillatoria rubescens and Spirulina platensis) were grown in 81 batch cultures at different nitrogen levels. In all the algae increasing N levels led to an increase in the biomass (from 8 to 450 mg/l), in protein content (from 8 to 54 %) and in chlorophyll. At low N levels, the green algae contained a high percentage of total lipids (45 % of the biomass). More than 70 % of these were neutral lipids such as triacylglycerols (containing mainly 16:0 and 18:1 fatty acids) and trace amounts of hydrocarbons. At high N levels, the percentage of total lipids dropped to about 20 % of the dry weight. In the latter case the predominant lipids were polar lipids containing polyunsaturated C₁₆ and C₁₈ fatty acids. The blue-green algae, however, did not show any significant changes in their fatty acid and lipid compositions, when the nitrogen concentrations in the nutrient medium were varied. Thus the green but not the blue-green algae can be manipulated in mass cultures to yield a biomass with desired fatty acid and lipid compositions. The data may indicate a hitherto unrecognized distinction between prokaryotic and eukaryotic organisms.     

Activation of phosphorylating vesicles by net transfer of phosphatidyl choline by phospholipid transfer protein

Vesicles formed with phosphatidyl ethanolamine, phosphatidyl choline, cardiolipin, coupling factors and hydrophobic proteins from bovine heart mitochondria catalyzed a rapid³²P_i-ATP exchange. When phosphatidyl choline was deleted during the assembly of the vesicles, little³²P_i-ATP exchange was observed. Exchange activity was induced by incubating such deficient vesicles with phosphatidyl choline liposomes in the presence of a phosphatidyl choline transfer protein isolated from bovine heart. Transfer of [³²P] phosphatidyl choline was demonstrated by isolation of the activated vesicles by sucrose density centrifugation.     

Effects of Mojave toxin on rat skeletal muscle sarcoplasmic reticulum.

Effects of the lethal fraction (MD-9) from the venom of the Mojave rattlesnake, Crotalus scutulatus, on sarcoplasmic reticulum were investigated. The calcium sequestering activity of the vesicles was reduced by the lethal fraction and subsequent release of calcium was enhanced. These effects were observed to be dependent upon MD-9 concentration and the length of preincubation time with the vesicles. An enhanced ATPase activity that was affected by concentration and MD-9 preincubation time was also observed. Both calcium uptake and ATPase activity effects may be due to a phospholipase activity associated with the fraction.     

Lipids of Chlamydomonas reinhardi under different growth conditions

Photo-, mixo- and heterotrophically grown cultures of Chlamydomonas reinhardi (wild type ss and 2 streptomycin-resistant mutants sr₃ and sr₃₅) have been analyzed for lipids and fatty acids. Ether-soluble lipids, chlorophyll, monogalactosyl diglyceride, digalactosyl diglyceride, sulfolipid, phosphatidyl ethanolamine, phosphatidyl choline, phosphatidyl glycerol and the relative amounts of fatty acids in total and individual lipids have been determined. The lipid and fatty acid compositions are very similar in the 3 strains and are not affected by the mutations. Fatty acids belong exclusively to the C₁₆ and C₁₈ series, 16:0, 16:4, 18:1, 18:2, 18:3 (6,9,12) and 18:3 (9,12,15) comprising about 90% of the total. 18:3 (6,9,12) is concentrated in phosphatidyl ethanolamine. In streptomycin-bleached sr₃ cells, ether-soluble lipids increase from 7 to 11% of dry weight on greening, mostly due to synthesis of monogalactosyl diglyceride and chlorophyll. Monogalactosyl diglyceride of bleached cells exhibits the same fatty acid pattern before and after greening.     

The phospholipid fatty acids of Porphyridium purpureum cultured in the presence of triton x-100 and sodium desoxycholate

The phospholipid fatty acid composition of Porphyridium purpureum grown on a solid medium was studied in the presence of Triton X-100 (TX) and sodium desoxycholate (SDC). The most common fatty acids in PC and PE were palmitic (16:0), stearic (18:0), linoleic (18:2ω6), arachidonic (20:4ω6) and eicosapentaenoic (20:5ω3) acids, 20:4ω6 being very abundant. In PG the most common acids were 16:0, trans-hexaenoic acid (tr16:1ω3), oleic acid (18:1) and 20:4ω6. Both detergents caused an increase in the saturation of PC and, to a lesser extent, of PE. The relative amounts of short chain fatty acids increased. Both detergents increased the amounts of 16:0 and, correspondingly, decreased the amounts of 20:4ω6. In PG the amounts of both 16:0 and tr 16:1ω3 increased and the amounts of 18:0, 18:2ω6 and 20:4ω6 decreased in the presence of detergents. The changes were always greatest at the concentrations of 5–10 ppm TX or SDC. At 20 ppm the fatty acid compositions, especially with SDC, were very similar to the controls, which suggests a change in the detergent effect between 10–20 ppm. The normal PC/PE ratio was 5.6 and the (PC+ PE)/PG ratio 39.0. Both detergents caused a marked decrease in these ratios. Because the detergent effects are not linear, it seems that even very low detergent concentrations have an important influence on algae in polluted waters.     

Effects of frost hardening on the composition of galactolipids and phospholipids occurring during isolation of chloroplast thylakoids from needles of scots pine

Frost hardening of seedlings of Scots pine (Pinus sylvestris) at a non-freezing temperature of 4°C resulted in a 2-fold increase of the acyl lipids of the needles. This was because of increases in phospholipids and triglycerides. The galactolipid content of the needles was almost the same in unhardened and frost-hardened seedlings. In unhardened seedlings the mol ratio of monogalactosyl diacylglycerol (MGDG) to digalactosyl diacylglycerol (DGDG) was 1.7 ± 0.3 and 0.9 ± 0.2 in needles and isolated thylakoids, respectively. Corresponding ratios for frost-hardened seedlings were 1.5 ± 0.2 and 0.3 ± 0.03. The lower ratios found in isolated thylakoids, particularly in thylakoids from frost-hardened seedlings, are suggested to depend on the enzyme galactolipid: galactolipid galactosyltransferase being active during the isolation procedure. This is deduced from the result that the content of MGDG decreased and that of DGDG and 1.2 diglycerides increased. Needles of Scots pine also contain phospholipidase D. This enzyme was active during thylakoid preparation, particularly after frost hardening, as judged from the large amount of phosphatidic acid found the in thylakoid fraction isolated from frost-hardening needles. The fatty acid composition of the acyl lipids showed no major changes due to hardening at non-freezing temperature.     

Effect of lipid composition changes on carbocyanine dye fluorescent response

Egg yolk phosphatidyl choline liposomes containing variable amounts of phosphatidyl ethanolamine, phosphatidyl inositol or phosphatidyl serine demonstrated important variations in the fluorescence of 3.3' dipropylthiodicarbocyanine. When the membrane contained no cholesterol, fluorescence was not correlated with membrane fluidity as measured by diphenyl hexatriene polarization. Increasing cholesterol concentration in valinomycin containing liposome membranes decreased the potassium induced apparent membrane potential and prevented sorption of dye to the membrane. Discontinuity in the apparent potential occurred at 30 mol% cholesterol but could not be correlated with changes in microviscosity. These results indicate that great care should be taken when correlating rapid variations of fluorescence to changes in membrane potential. We propose that changes in phospholipid metabolism could well explain fluorescent changes when monitoring the fluorescence of cyanine dye molecules sorbed to biological membranes.     

Galactolipase, phospholipase and triacylglycerol lipase activities in the midgut of six species of lepidopteran larvae feeding on different lipid diets

Galactolipase, phospholipase and triacylglycerol lipase activities were measured from the midgut of six species of lepidopteran larvae, two folivores, Epiphyas postvittana (Tortricidae) and Helicoverpa armigera (Noctuidae); two granivores, Plodia interpunctella (Pyralidae) and Ephestia kuehniella (Pyrallidae); a presumptive carnivore, Galleria mellonella (Pyralidae); and a keratinophage, Tineola bisselliella (Tineidae). Galactolipase has not been previously reported in insects. Galactolipase and phospholipase activities were high in the folivores and triacylglycerol lipase activity was low, matching the high galactolipid content of leaves. Conversely, galactolipase and phospholipase activities were low, but not absent, and triacylglycerol lipase activity high in the four other non-folivorous species, matching the high acylglycerol content of their diets. These data suggest the utility of reclassification, for evolutionary studies, of phytophagous lepidoptera into two feeding classes; folivore and granivore, the latter having similarity to the fungivore line of feeders in terms of its lipase activities and ability to retrieve essential polyunsaturated long chain fatty acids from their diets. All the digestive lipases have alkaline pH optima for activity, matching the pH of the lepidopteran midgut and their amino acid content show modifications likely to stabilize the proteins in that environment.     

Phospholipid changes in wheat and barley leaves under water stress

Total phospholipid content of leaves of wheat and barley increased and phospholipid components changed under water stress. Notable among these were the absence of phosphatidyl serine in barley varieties, decrease in phosphatidyl glycerol content in a less drought-tolerant variety of wheat (S-308) and barley (BG-25), and appearance of phosphatidic acid in both crops. The phospholipid content and its components did not return to normal upon release of the stress by subsequent irrigations. Such observations are indicative of water stress effected alterations in membranes.     

Structural-functional state of thylakoid membranes of wheat genotypes under water stress

Plants were grown in field conditions in the wide area under normal water supply and severe water deficit. Two wheat (Triticum aestivum L.) genotypes contrasting by architectonics and differing in drought-resistance were used: Giymatli-2/17, short stature, with broad and drooping leaves, drought-sensitive, and Azamatli-95, short stature, with vertically oriented small leaves, drought-tolerant). It was found out that Giymatli-2/17 was characterized by relatively low content of Chl a-protein of PS I (CP I) and β-subunit of ATP-synthase complex, the high content of proteins in the 33-30.5 kDa region and LHC polypeptides (28-24.5 kDa), the intensive fluorescence at 740 nm and more high photochemical activity of PS II under normal irrigation compared with Azamatli-95. However, the content of CP I (M_r 115 kDa) and apoprotein of P700 with M_r 63 kDa insignificantly increases in the drought-resistant genotype Azamatli-95 under extreme water supply condition while their content decreases in drought-sensitive cv Giymatli-2/17. Intensity of synthesis α- and β-subunits of CF₁ (55 and 53.5 kDa) also decreases in Giymatli-2/17. The levels of the core antenna polypeptides of FS II with M_r 46 and 44.5 kDa (CP47 and CP43) remains stable both in normal, and stressful conditions. At the same time the significant reduction is observed in the content of polypeptides in the 33-30.5 kDa region in the more sensitive genotype Giymatli-2/17. There is an increase in the LHC II polypeptides level in tolerant genotype Azamatli-95 in contrast to Giymatli-2/17 (where the content of these subunits is observed decreasing). The intensity of short wavelength peaks at 687 and 695 nm sharply increases in the fluorescence spectra (77 K) of chloroplasts from sensitive genotype Giymatli-2/17 under water deficiency and there is a stimulation of the ratio of fluorescence band intensity F687/F740. After exposure to drought, cv Giymatli-2/17 shows a larger reduction in the actual PS II photochemical efficiency of chloroplasts than cv Azamatli-95.     

The superlattice model of lateral organization of membranes and its implications on membrane lipid homeostasis

Most biological membranes are extremely complex structures consisting of hundreds of different lipid and protein molecules. According to the famous fluid-mosaic model lipids and many proteins are free to diffuse very rapidly in the plane of the membrane. While such fast diffusion implies that different membrane lipids would be laterally randomly distributed, accumulating evidence indicates that in model and natural membranes the lipid components tend to adopt regular (superlattice-like) distributions. The superlattice model, put forward based on such evidence, is intriguing because it predicts that 1) there is a limited number of allowed compositions representing local minima in membrane free energy and 2) those energy minima could provide set-points for enzymes regulating membrane lipid compositions. Furthermore, the existence of a discrete number of allowed compositions could help to maintain organelle identity in the face of rapid inter-organelle membrane traffic.     

Effects of water stress on lipid metabolism in cotton leaves

After 2, 10 and 24 hr labelling with [1-¹⁴C] acetate, radioactivity incorporated into the lipids of cotton leaves is mainly found in phosphatidylcholine, phosphatidylglycerol and neutral lipids. Galactolipids are slowly synthesized and after 24 hr, account for only 10% of the total radioactivity. Under water stress, a marked decrease of precursor incorporation into leaf lipids occurs, particularly in phosphatidylcholine and galactolipids. Relative incorporation into neutral lipids, on the contrary, increases. Water deficits provoke an inhibition of the fatty acid desaturation, resulting in a sharp decrease of linoleic and linolenic acid biosynthesis. The decrease in unsaturated fatty acid biosynthesis occurs in all lipid classes, but is most pronounced in the galactolipid fractions. In the drought-resistant cotton variety (Mocosinho), the variations in lipid and fatty acid metabolism under water stress are less pronounced than in the drought-sensitive variety (Reba), and this attests a greater stability of the membrane system.