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.     

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.     

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.     

An apolipoprotein preferentially enriched in cholesteryl ester-rich very low density lipoproteins

Phosphatidyl glycerol is present in lamellar bodies and in the material obtained by alveolar wash representing 12.3 and 11.5%, respectively, of the total phospholipid phosphorus. Lung microsomes catalyze the formation of phosphatidyl glycerol from the known precursors, L-glycerol 3-phosphate and CDP-diglyceride. The rate of [¹⁴C]L-glycerol 3-phosphate incorporation into phosphatidyl glycerol was 30% higher in microsomes as compared to mitochondria. The addition of mercuric chloride inhibited the synthesis of phosphatidyl glycerol, and stimulated the incorporation into another as yet incompletely identified lipid. After pulse labeling of microsomal phosphatidyl glycerol $\text{in vitro}$, further incubation of microsomes with lamellar bodies or alveolar wash resulted in nearly quantitative appearance of label in surfactant.     

Stimulation of phospholipid methylation by glucose in pancreatic islets

A two fold stimulation in the incorporation of [3H-methyl] groups from [3H-methyl] methionine into phospholipids was seen in intact pancreatic islets within six minutes of exposure to a glucose concentration that stimulates insulin release. Nonstimulatory sugars, L-glucose and D-galactose, as well as dibutyryl cAMP, did not affect phospholipid methylation in islet cells. A calcium channel blocker, verapamil, inhibited methylation. These studies suggest that the signal for glucose-induced insulin release could involve phospholipid methylation.     

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.     

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.     

A Glycosphingolipid spin label: Ca2+ effects on sphingolipid distribution in bilayers containing phosphatidyl serine.

A glycosphingolipid (galactosyl ceramide) has been synthesized which has a spin label covalently attached near the methyl end of the fatty acid chain. This is to our knowledge the first glycolipid spin label to be reported. It is being used to study glycosphingolipid behaviour in lipid bilayers — especially with a view to potential differences from phospholipids. Like phospholipids it assumes a random distribution in fluid lipid bilayers but tends to be excluded from regions rich in phosphatidyl serine in the face of a Ca²⁺-induced lateral phase separation.     

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.     

Focused lipidomics by tandem mass spectrometry

In this paper we performed focused analyses of phospholipids by using the data of precursor ion scanning and neutral loss scanning of their polar head groups and fatty acyl moieties for the specific search of categorical phospholipids. By using precursor ion scanning or neutral loss scanning of polar head groups in the positive ion mode, more sensitive identification were obtained than that in the negative ion mode. Precursor ion scanning of carbonic anions in the negative ion mode was also effective to identify molecular species of phospholipids having specified fatty acyl moieties. By using these analytical methods, the detection limits of individual metabolites are going up to 5-20-fold of former conventional methods. The important factor is that by focusing in some limited categories of molecules, detection limit is greatly enhanced, thus minor but important molecules can be detected. Moreover, combination of LC-MS/MS and focused scanning for head group was revealed to be useful to identify very minor molecular species in the focused class of phospholipids.