Dual effect of tannic acid on the preservation and ultrastructure of phosphatidyl choline vesicles

Summary The use of tannic acid has been proposed to improve the preservation of phospholipids in tissues. We investigated the effects of tannic acid on the preservation of small unilamellar vesicles, prepared from sonicated aqueous suspensions of phospholipids.With cryo-electron microscopy it is demonstrated that small unilamellar vesicles are formed after sonication of the phospholipid suspensions. Fixation of vesicles without tannic acid results in extraction of the phospholipids during dehydration and embedding. Fixation of vesicles containing phosphatidyl choline with tannic acid, with or without glutaraldehyde, results in a fast (within a second) aggregation of the vesicles and the resulting sediment can be dehydrated and embedded when a postfixation in osmium tetroxide is carried out. Small unilamellar vesicles fixed in this way are retrieved in thin sections as multilamellar vesicles with a periodicity of about 5 nm for dimyristoylphosphatidyl choline and about 6 nm for dioleoylphosphatidyl choline.By using ¹³C-phosphatidyl choline it was also demonstrated that tannic acid prevents to a large extend the extraction of phosphatidyl choline during fixation, dehydration and embedding. This dual effect of tannic acid on phosphatidyl choline, aggregation and fixation, should be considered when using tannic acid in tissue preparation.     

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.     

Phospholipids of wheat chloroplast and its membranes under water stress

Phospholipids showed a differential change in the chloroplast membranes in two cultivars under water stress. Amongst the individual phospholipids, phosphatidyl choline (PC) increased under stress in the low water requiring cultivar C-306 but it decreased in high water requiring cultivar S-308. PC of chloroplast envelope and chloroplast thylakoids showed similar response. Increase in PC content in chloroplasts and its membranes of resistant cultivar may suggest a basis for stress resistance.     

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.     

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.     

IGF-1、IGFBP-3在大鼠非酒精性脂肪性肝病进展中的变化

目的：观察非酒精性脂肪性肝病（NAFLD）大鼠血清胰岛素样生长因子1（IGF-1）、胰岛素样生长因子结合蛋白3（ IGFBP-3）的表达及多烯磷脂酰胆碱对其的影响。方法采用高脂饲料喂养建立大鼠NAFLD模型,以多烯磷脂酰胆碱进行干预。 HE染色动态观察大鼠4、8、12周时肝组织病理学变化,IRMA法动态监测血清IGF-1、IGFBP-3含量。结果正常组大鼠各时间点肝组织病理均无明显异常;模型组随高脂饮食时间延长,在4、8、12周3个时相点肝组织脂肪变、炎症程度、气球样变及NAFLD活动度积分逐渐增强,血清IGF-1、IGFBP-3逐渐明显下降,且模型组各时相点IGF-1、IGFBP-3的水平较正常组同一时相点明显降低;应用多烯磷脂酰胆碱干预后,大鼠肝组织炎症程度、NAFLD活动度积分较模型组显著降低,IGF-1、IGFBP-3的水平则较模型组明显增高。结论血清IGF-1、IGFBP-3水平随大鼠NAFLD进展而降低。     

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.     

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.     

Identification of a second synexin-like adrenal medullary and liver protein that enhances calcium-induced membrane aggregation

Synexin, an approximately 47,000 Mr soluble protein isolated from adrenal medulla or liver, shows Ca2+-specific enhancement of the aggregation of chromaffin granule or other negatively charged biological or artificial membranes. We report the identification of second synexin-like protein (Mr approximately 56,000) from the same sources with similar Ca2+-specific membrane aggregation activities. However, the molecular weight, aggregation kinetics, susceptibility to protease inactivation and peptide maps of the two synexins are quite different, suggesting that they are entirely different proteins, and that the aggregation assay is only a convenient method for identifying a large number of Ca2+-specific proteins with diverse, yet to be defined activities.     

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.     

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.     

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.     

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.     

Isolation,purification and characterization of Cardiolipin synthase from Mycobacterium phlei {PRIVATE}

It has been observed that mycobacterial species has high content of cardiolipin (CL) in their cell membranes more so pathogenic mycobacteria and in bacteria CL activates polymerases, gyrases by removing the bound ADP. Therefore, in the present study cardiolipin synthase (cls) which catalyses the formation of CL was isolated purified and characterized from the cell membrane of Mycobacterium phlei. The purified cls obtained from C-18 RP-HPLC column had a molecular weight of 58 kDa with an isoelectric point of 4.5. The enzyme activity (11.5+0.15 µM of CL phosphorous. ml-1 minute-1 for PG as substrate and 14+0.35µM of CL phosphorous. ml-1 minute-1 for CDP-DG as substrate) was optimal at pH 4.8 and showed K_M values of 55+0.05µM and 2.56+0.04µM for phosphatidyl glycerol and CDP-diacylglycerol, respectively, with an absolute requirement of Mg²⁺ and Mn²⁺ ions for its activity however, Ca²⁺ ions inhibited the activity of the cls. The partial amino acid sequence of cls showed significant homology with pgsA3 gene of M. tuberculosis and in this organism the CL biosynthesis is very high having three genes coding for PLs biosynthesis therefore, enzymes involved in CL biosynthesis may be an attractive drug target in the development of new antimycobacterial drugs.     

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.     

Lysophosphatidic acid and bradykinin have opposite effects on phenotypic transformation of normal rat kidney cells

The bioactive lipid lysohosphatidic acid is besides a strong mitogen for quiescent fibroblasts, a potent inducer of phenotypic transformation on normal rat kidney cells. The lysophosphatidic acid induced loss of densityarrest is strongly inhibited by bradykinin. Although their effects on normal rat kidney cell proliferation are opposite, bradykinin mimics many of the intracellular effects induced upon lysophosphatidic acid receptor activation, including phosphoinositide turnover, Ca²⁺-mobilization and arachidonic acid release. Bradykinin does not counteract the lysophosphatidic acid induced reduction of cAMP levels in normal rat kidney cells. However, bradykinin inhibits the lysophosphatidic acid and other growth factor induced phenotypic transformation through the induction of a so far uncharacterized prostaglandin G/H synthase product. The growth inhibitory effect of bradykinin is limited to density-arrested cells, while upon prolonged treatment bradykinin itself is capable to induce the loss of densitydependent growth control. It is concluded that bradykinin is a bifunctional regulator of normal rat kindney cell proliferation and that its inhibitory effects are midiated via induction of a prostaglandin dervative.     

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.     

Lipid composition of adult Foleyella agamae

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& Obiamiwe B. A. 1986. Lipid composition of adult Foleyella agamae. International Journal for Parasitology 16: 655–657. The lipid and fatty acid composition of the filarial parasite Foleyella agamae were investigated. Total lipids accounted for 7.05% of the parasite fresh weight. Neutral lipids comprised 56.34% of the total and polar lipids 43.66%. The major lipid classes detected include sterol esters, cholesterol, phosphatidyl choline and phosphatidyl ethanolamine. Fatty acids varying in chain length from 10 carbon atoms through 20 carbon atoms were identified in the total lipid extract. The 18 carbon fatty acids formed the predominant components. The 20 carbon fatty acids were confined to the polar lipds.