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At least 937 records · Page 52Linked to original sources
PubMed1994

Lipid selection in the assembly of the phospholipid bilayer membrane of the lipid-containing bacteriophage PR4.

Phage PR4 contains a lipid bilayer within the phage protein capsid. The phospholipids of the bilayer are derived from those of the host. We report that phage morphogenesis selects against the unusually bulky phospholipids synthesized by Escherichia coli grown in the presence of various sugar alcohols. These data indicate that assembly of the PR4 lipid bilayer is a selective process rather than the bulk appropriation of host membrane lipids. We also demonstrates that phage PR4 morphogenesis is compatible with the incorporation of several abnormal lipids, monoacylglycerol, diacylglycerol, and phosphatidylinositol into the phage particle.

Coliphages↗
PubMed1992

The relationship between serum lipids, nucleation time, and biliary lipids in patients with gallstones.

The relationship between biliary lipids, cholesterol saturation index, nucleation time, and serum lipids was studied in a group of 45 gallstone patients (10 male, 35 female; age 50.1 +/- 14.5 years). Bile was obtained by direct fine-needle puncture of the gallbladder under local anesthesia and sonographic monitoring. No significant correlation between the serum lipids and either the cholesterol saturation index or total biliary cholesterol levels was observed. We found a positive correlation between the nucleation time and serum triglycerides content (r = 0.45, p = 0.0018) and a negative correlation between nucleation time and biliary cholesterol level (r = -0.38, p = 0.009). The fatty acids derived from the triglycerides are primarily resynthesized to phospholipids in the liver. When the supply of free fatty acids exhausts the metabolic capacity of the liver as, for example, in fat-rich diets, triglycerides accumulate in the liver cells and may possibly by excreted in the bile. Free fatty acids stimulate mucin hypersecretion in the gallbladder. This mucosal hypersecretion has been assigned a significant role in the formation of gallbladder stones. We also found a positive correlation between the total biliary bile acids and serum high density lipoprotein (HDL)-cholesterol in patients with a rapid nucleation time (r = 0.50, p = 0.0128). This supports the findings of other researchers, which suggests that HDL-cholesterol is devoted primarily to bile acid synthesis. In patients with a short nucleation time, the cholesterol saturation index, total lipid concentration, biliary cholesterol, mean age, and biliary bile acids were statistically different in comparison with patients with a prolonged nucleation time.

Aged↗
PubMed1979

Elevation of serum lipid peroxide level associated with doxorubicin toxicity and its amelioration by [dl]-alpha-tocopheryl acetate or coenzyme Q10 in mouse (doxorubicin, toxicity, lipid peroxide, tocopherol, coenzyme Q10).

Elevations of serum lipid peroxide levels were demonstrated in mice after an equitoxic dose of doxorubicin. When BDF1 mice were injected with doxorubicin (20 mg/kg body weight, IP), lipid peroxide levels in sera were elevated 1 day after the injection and the levels declined on subsequent days. 5-Fluorouracil (400 mg/kg body weight, IP) never changed the peroxide levels in serum. Furthermore, it was found that the co-administration of [dl]-alpha-tocopheryl acetate or coenzyme Q10 IM strongly inhibited the doxorubicin-induced elevation of lipid peroxides in serum. The effectiveness of [dl]-alpha-tocopheryl acetate or coenzyme Q10 in reducing the lethality of doxorubicin in mice was also confirmed. These results indicate that the measurement of serum 2-thiobarbituric acid-reacting substances provided a useful measurement of lipid peroxide levels, which may be involved in some way with doxorubicin toxicity, and that the administration of antioxidants provide protection against some of the side effects of doxorubicin.

Animals↗
PubMed1975

Studies in lipid histochemistry. XIII. The OPA (osmiumtetroxide-periodic acid-alpha-naphthylamine) method for the detection of apolar lipids.

A new procedure for the detection of apolar lipids is described. It is a modification of the OTAN method (Adams, 1959) using periodic acid which oxidatively removes lower osmium derivatives from polar sites only, leaving those in apolar lipids intact and demonstrable with alpha-naphthylamine. Control steps for the exclusion of the possible interference of some less polar complex lipids and of lipopigments are described. The described technic is superior to the conventionally used sudan dyes due partly to the fact that only aqueous solutions are employed thus excluding any extraction of lipids, partly to the more distinct coloration.

1-Naphthylamine↗
PubMed1987

Effect of succinate on mitochondrial lipid peroxidation. 2. The protective effect of succinate against functional and structural changes induced by lipid peroxidation.

The damaging effects of ADP/Fe/NADPH-induced lipid peroxidation were studied on the enzymes and membranes of rat liver mitochondria. Succinate, an inhibitor of mitochondrial lipid peroxidation, prevented or delayed most of the damage caused by the peroxidation on different mitochondrial structures and functions. There were marked abnormalities on the electrophoretic pattern of mitochondrial proteins during the course of lipid peroxidation. The disappearance of particular polypeptide bands and the accumulation of high-molecular-weight aggregates could be observed. Succinate was found to delay these effects. As a consequence of lipid peroxidation the succinate oxidase activity of mitochondria was decreased. The succinate dehydrogenase enzyme and the component(s) of the respiratory chain were inactivated. Succinate prevented the inactivation of succinate dehydrogenase but did not protect the other components of terminal oxidation chain. From the matrix enzymes the glutamate dehydrogenase retained its full activity but the NADP-linked isocitrate dehydrogenase was inactivated. The mitochondrial membranes became permeable to large protein molecules. Succinate prevented the inactivation of isocitrate dehydrogenase and delayed the release of protein molecules from mitochondria.

Animals↗
PubMed1996

Changes in high density lipoprotein subfraction lipids during neutral lipid transfer in healthy subjects and in patients with insulin-dependent diabetes mellitus.

While it is known that the transfer of cholesteryl ester (CE) from high density lipoprotein (HDL) to the apo B-containing lipoproteins is increased in patients with diabetes, the extent to which the various lipoprotein fractions engage in neutral lipid exchange and the magnitude to which triglyceride (TG) is translocated is not known. To examine in greater detail neutral lipid net mass transfer in diabetes, the HDL subfractions and the apo B-containing lipoproteins were separated, and the net mass transfer of CE and TG was compared to that of control subjects. In both groups, bidirectional transfer of CE from HDL3 to very low density lipoprotein (VLDL) + low density lipoprotein (LDL) and of TG from VLDL + LDL to HDL3, took place, but this process was significantly greater (P < .01) in insulin-dependent diabetes mellitus (IDDM). In contrast, CE and TG accumulated in HDL2 to a similar degree in normal and IDDM subjects. In recombination experiments with each of the apo B-containing lipoproteins, IDDM VLDL had a greater capacity to facilitate the exchange of core lipids from both IDDM and control HDL3: on the other hand, LDL from IDDM and control subjects both donated TG and CE to HDL2 and affected little change in HDL3. These findings indicate that all the major plasma fractions normally participate in the trafficking of CE and TG among the lipoproteins during neutral lipid transfer and show that the principal perturbation in cholesteryl ester transfer in IDDM involves altered interaction between VLDL and the HDL3 subfraction.

Cholesterol Esters↗
PubMed1975

Lipids of freshwater Dolphin Sotalia fluviatilis: comparison of odontocete bioacoustic lipids and habitat.

The melon and jaw lipids of the freshwater dolphin Sotalia fluviatilis are composed mainly of isovaleroyl wax esters and diisovaleroyl triglycerides. The blubber fat contains only a trace of wax ester and is mostly tri-(long chain) and monoisovaleroyl triglycerides. Detailed gas liquid chromatographic analyses of the intact wax esters and triglycerides and of the derived fatty acids and fatty alcohols indicate common compositional patterns in the wax esters and triglycerides of the respective head lipids. Both odd and even long chain (C12-C16) isostructures are prominent in the melon and jaw lipids, but only higher odd chain length iso-acids are major components in the blubber. Sotalia fluviatilis (family Delphinidae) and Inia geoffrensis (family Platanistidae) share the same freshwater habitat in the upper Amazon River, and both utilize echolocation to navigate and to find food. Comparison of their respective bioacoustical lipid compositions show distinctive types of head fats, Sotalia being rich in iso-5:0 and Inia lacking iso-5:0. This indicates that iso-valeric acid per se has no obligatory role in dolphin echolocation.

Acoustics↗
PubMed1988

Rapid separation of neutral lipids, free fatty acids and polar lipids using prepacked silica Sep-Pak columns.

A method is described for the separation of neutral lipid, free fatty acid and polar lipid classes using small (600 mg), prepacked silica Sep-Pak columns. Combinations of hexane and methyltertiarybutylether were used to progressively elute cholesteryl ester first then triglyceride from the column. After column acidification, fatty acids were eluted followed by cholesterol. Recoveries of these lipids were 96% or greater. Polar lipids were eluted from the column using combinations of methyltertiarybutylether, methanol and ammonium acetate. Phospholipid classes could not be separated completely from each other. Phosphatidylethanolamine and phosphatidylinositol eluted together, whereas the more polar phosphatidylcholine, sphingomyelin and lysophosphatidylcholine were eluted as a second fraction. Recoveries of each phospholipid was greater than 98%.

Chromatography↗
PubMed1976

Lipid metabolism of the yellow clam, Mesodesma mactroides: I. Composition of the lipids.

The lipid composition of the yellow clam, Mesodesma mactroides, that lives in the northern beaches of the Buenos Aires province of Argentina was studied. The main nonpolar lipids are triglycerides and alkoxyglycerides. Phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl serine are the main phospholipids. The predominant fatty acids are 16:0, 16:1omega7, 18:0, 18:1omega9, 20:5omega3, and 22:6omega3. They are mainly provided by the clam's food and stored in the hepatopancreas. The content of polyunsaturated acids increases in summer together with an increase in nonpolar lipids and is correlative with an increase in phytoplankton in the sea water. Sexual maturity modifies the lipid composition of gametes.

Animals↗
PubMed2004

Effects of tonicity on the release of neutral lipids in Echinostoma caproni adults and observations on lipids in excysted metacercariae.

High performance thin layer chromatography was used to analyze neutral lipids in worm incubates isotonic, hypotonic, and hypertonic to the intestinal habitat of adult Echinostoma caproni. Qualitative analysis revealed the presence of free sterols, free fatty acids, triacylglycerols, and a steryl ester/hydrocarbon fraction in all incubate samples. The most abundant neutral lipid fraction released into the incubation medium was the triacylglycerol fraction. This fraction was quantified after worms were maintained for 2 h at 37.5 degrees C in hypertonic (Locke's 2x solution), isotonic (Locke's 0.5x solution) and hypotonic (deionized water) media. Percentages of triacylglycerols on a wet-weight basis found in Locke's 2x, 0.5x, and deionized water were 0.369, 3.23, and 0.242, respectively, suggesting that the optimal medium to obtain maximal excretory-secretory products is the Locke's 0.5x solution. Histochemical staining of whole excysted metacercariae with oil red O did not detect neutral lipids. Analysis of 500 excysted metacercariae incubated for 2 h at 37.5 degrees C revealed that free sterols, free fatty acids, and triacylglycerols were released in amounts of 16.2, 1.59, and 5.34 ng/organism, respectively. Our results were compared with previous studies on neutral lipids in excysted metacercariae and adults of E. trivolvis. Variations in the results of our study compared with others reflect intrinsic differences in the species of echinostome used.

Animals↗
PubMed1992

Biosynthesis of lipid-linked oligosaccharides. I. Preparation of lipid-linked oligosaccharide substrates.

In order to purify the glycosyltransferases involved in the assembly of lipid-linked oligosaccharides and to be able to study the acceptor substrate specificity of these enzymes, methods were developed to prepare and purify a variety of lipid-linked oligosaccharides, differing in the structure of the oligosaccharide moiety. Thus, Man9 (GlcNAc)2-pyrophosphoryl-dolichol was prepared by isolation and enzymatic synthesis using porcine pancreatic microsomes, while Glc3Man9(GlcNAc)2-PP-dolichol was isolated from Madin-Darby canine kidney cells. Treatment of these oligosaccharide lipids with a series of selected glycosidases led to the preparation of Man alpha 1,2Man alpha 1,2Man alpha 1,3[Man alpha 1,6(Man alpha 1,3)Man alpha 1,6]Man beta 1,4GlcNAc beta 1,4GlcNAc-PP-dolichol; Man alpha 1,2Man alpha 1,2Man alpha 1,3[Man alpha 1,6]Man beta 1,4GlcNAc beta 1, 4GlcNac-PP-dolichol; and Man alpha 1,6(Man alpha 1,3)Man alpha 1, 6[Man alpha 1,3]Man beta 1,4GlcNAc-beta 1,4GlcNAc-PP-dolichol. The preparation, isolation, and characterization of each of these lipid-linked oligosaccharide substrates are described.

Animals↗
PubMed1992

Thermodynamic elucidation of solute-induced lipid interdigitation phase: lipid interactions with hydrophobic versus amphipathic species.

Comparative thermodynamic studies on the interactions of aqueous dispersions of dipalmitoyl phosphatidylcholine (DPPC) bilayer vesicles with hydrophobic and amphipathic species were conducted to elucidate the nature of the solute-induced interdigitated lipid phase. Cyclohexanol, a strong hydrophobic species, lowers the temperature (tm) of the lipid main phase transition from the gel to the liquid-crystalline phase. Unlike ethanol (an amphipathic species), as reported previously, cyclohexanol does not exert a biphasic effect on tm (lowering tm at lower concentrations and raising tm at higher concentrations). At cyclohexanol greater than or equal to 15.4 mg/ml or 0.154 M, the thermogram of DPPC vesicles exhibits a small transition adjacent to the main phase transition but at a lower temperature. In contrast, ethanol does not promote such a small transition. Furthermore, the enthalpy (delta H) of the transition is increased in the presence of cyclohexanol. The sign of the enthalpy change (delta H-delta Ho) is positive and that of the free energy change (delta G-delta Go) is negative, a characteristic of solute-solute hydrophobic interaction. In contrast, DPPC bilayer vesicles exhibit both (delta H-delta Ho) and (delta G-delta Go) greater than 0 in the presence of ethanol in a concentration range where lipid vesicles exist in an interdigitated phase. To support the above distinct thermodynamic observations, fluorescence steady-state polarization (P) measurements were also performed. At the temperature below tm, the value of P decreases as cyclohexanol concentration increases, while a biphasic effect on P was found in the presence of ethanol. These findings support the postulation that the solute-induced interdigitated lipid phase requires the solute molecule to be amphipathic in nature.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1975

Variations of lipid-protein interactions in erythrocyte ghosts as a function of temperature and pH in physiological and non-physiological ranges. A study using a paramagnetic quenching of protein fluorescence by nitroxide lipid analogues.

1. Incorporation of stearic acid nitroxides into erythrocyte ghosts markedly depresses the fluorescence of membrane protein tryptophan residues. 5-Nitroxide stearate quenches fluorescence more efficiently than 16-nitroxide stearate. Both compounds exhibit dynamic (diffusion-limited) quenching above 0.28 mumol/mg protein and static quenching at lower nitroxide protein ratios. Static quenching can be attributed to high affinity binding of nitroxide stearates by membrane protein. The dynamic phase represents distribution of the stearate analogues into a fluid lipid system. 2. Protein fluorophores accessible to quenching by a cholesterol analogue, androstane nitroxide, are saturated at low nitroxide/protein ratios (less than 0.14 mumol/mg protein), without resolution of a static quenching phase. This suggests that sterols are segregated away from protein, probably in CLusters". 3. Paramagnetic quenching by stearate nitroxides increases abruptly between 35 and 50 degrees C. This discontinuous enhancement of quenching by temperature is reversible up to 41 degrees C but irreversible at higher temperatures. The discontinuity is also diminished by lowering pH from 7.3 through 6.5 to 6.0. Quenching by androstane nitroxide increases linearly with temperature up to approx. 41 degrees C and then rises exponentially. We attribute the reversible quenching thermotropism detected by stearate derivatives to reversible, thermotropic unfolding and/or depolymerisation of membrane proteins. The irreversible phase, detected also by the sterol derivative can be attributed to non-reversible protein denaturation. 4. Paramagnetic quenching of membrane tryptophan fluorescence by stearate derivatives is minimal at approx. pH 7.1 (35 degrees C) and increases sharply at lower and higher pH values, suggesting that two categories of protein residues, titrating between pH 6 and 8, profoundly influence the association of fatty acyl chains and penetrating protein segments. Quenching by androstane nitroxide exhibits no significant variation between pH 6 and 8, consistent with other data indicating that erythrocyte membrane sterols are segregated from membrane proteins, probably in clusters. 5. Our new approach confirms previous suggestions of a boundary layer of lipid in close association with some proteins in erythrocyte membranes, as well as experiments indicating that the lipid status in this boundary layer depends on that state of membrane proteins. However, sterols appear to be largely excluded from this boundary domain. Our data further show that lipid-protein interactions in erythrocyte membranes can vary significantly with fluctuations of temperature and pH in the physiological range.

Binding Sites↗
PubMed1977

The molecular organization of asymmetric lipid bilayers and lipid-peptide complexes.

Oriented fatty acid bilayers with asymmetric distributions of lipid head group types, hydrocarbon chain lengths, and associated polypeptides have been analyzed by a combined use of high resolution electron microscopy and X-ray diffraction techniques. The exclusion of fixatives, stains, and embedding materials has made it possible to relate unequivocally microscopic images to molecular composition. The ultrastructure of asymmetric bilayers has been determined by a novel analysis in which one half of the bilayer serves as a structural reference for the entire bilayer. Absolute electron density profiles at 7 A resolution have been computed for bilayers formed from long and short chain length lipids either segregated to opposite sides or mixed together in both sides of the bilayer. The data indicate that the two lipids self organize in a specific paired configuration. Detailed analysis of bilayers associated with poly-L-lysine shows that although this hydrophilic peptide resides near the lipid head group region, its presence alters the arrangement of the bilayer hydrocarbon chains.

Barium↗
PubMed1982

Interaction of a human plasma lipid transfer protein complex with lipid monolayers.

The interaction of a purified human plasma lipid transfer complex with cholesteryl ester, triacylglycerol and phosphatidylcholine in binary and ternary lipid monolayers was investigated. The lipid transfer complex, designated LTC, catalyzes the removal of cholesteryl oleate and triacylglycerol from phosphatidylcholine monolayers. Preincubation of LTC with p-chloromercuriphenyl sulfonate inhibits LTC-catalyzed removal of triacylglycerol; cholesteryl ester removal is not affected. The rate of LTC-facilitated removal of cholesteryl oleate from a phosphatidylcholine monolayer depends on the amount of LTC added to the subphase up to 100 micrograms protein. In addition, the rate of the LTC-catalyzed transfer of cholesteryl oleate to the subphase increases linearly as the amount of cholesteryl oleate in the monolayer increases to 6 mol%. LTC also removes cholesterol from phosphatidylcholine-cholesterol monolayers, albeit at a rate which is 15% of that for removal of cholesteryl oleate. The ability of LTC to facilitate triacylglycerol and cholesteryl ester removal depends on the composition of the monolayer. Phosphatidylcholine supports cholesteryl ester transfer whereas sphingomyelin-cholesteryl ester monolayers are almost refractory to LTC. In contrast, LTC removes triacylglycerol from either a phosphatidylcholine or a sphingomyelin monolayer. The results suggest the existence of at least two lipid transfer proteins, one of which catalyzes the removal of cholesteryl ester and the other triacylglycerol. The role of these proteins as they relate to lipoprotein metabolism is discussed.

Carrier Proteins↗
PubMed1984

Self-adaptive modification of red-cell membrane lipids in lecithin: cholesterol acyltransferase deficiency. Lipid analysis and spin labeling.

In a patient with lecithin: cholesterol acyltransferase deficiency, free cholesterol was markedly increased, and esterified cholesterol was diminished. In the patient's plasma, an increase in phosphatidylcholine (PC) and a decrease in sphingomyelin were observed. Concomitantly, an increase in a shorter acyl chain 16:0 was noted in PC, sphingomyelin and phosphatidylethanolamine (PE). In contrast to these results, longer chains such as 22:0 and 24:0 were decreased, especially in sphingomyelin. Unsaturated double bonds such as 18:1 was also increased in PC and PE. In the red-cell membrane lipids, the increase in free cholesterol was counteracted by an increase in PC and by a decrease in sphingomyelin and PE, reflecting changes in the patient's plasma lipids. Increased 16:0 (in PC) and decreased 18:0 and 24:0 were observed. The increased plasma free cholesterol due to metabolic defect (lecithin: cholesterol acyltransferase deficiency) led to decreased red-cell membrane fluidity. This effect appeared to be counteracted by changing phospholipid composition (increased PC and decreased sphingomyelin and PE), by increasing shorter chains (16:0), by decreasing longer chains (18:0 and 24:0) and by increasing unsaturated double bonds (18:2). These results can be interpreted as a self-adaptive modification of lecithin: cholesterol acyltransferase deficiency-induced red-cell membrane abnormalities, to maintain normal membrane fluidity. This speculation was supported by the ESR spin-label studies on the patient's membrane lipids. The normal order parameters in intact red cells and in total lipid liposomes were decreased if cholesterol-depleted membrane liposomes were prepared. Thus, the hardening effect of cholesterol appeared to be counteracted by the softening effects described above. Overall membrane fluidity in intact red cells of the lecithin: cholesterol acyltransferase-deficient patient was maintained normally, judged by order parameters in ESR spin-label studies.

Cholesterol↗
PubMed1987

Dehydration of the lipid-protein microinterface on binding of phospholipase A2 to lipid bilayers.

A novel method is described to demonstrate inaccessibility to the bulk aqueous phase of the microinterface between pig pancreatic phospholipase A2 and lipid bilayers to which this protein is bound. The method is based on the fact that the fluorescence emission quantum yields of the tryptophan residue of the protein and of a 5-dimethylaminonaphthalene-1-sulfonyl (dansyl) chromophore attached to a lipid are lower in water as compared to that in deuterated water. The fluorescence emission quantum yield of these chromophores is measured in water and in deuterated water under conditions where the protein is either bound or not bound to the surface of a lipid bilayer containing the dansyl chromophore. Under conditions where the protein is tightly bound to the surface of the bilayer, desolvation of both fluorophores abolishes the observed effect of deuterated water. The tryptophan residue in the bound phospholipase A2 also becomes inaccessible to fluorescence quenching by acrylamide or succinimide. Desolvation of the microinterface is observed only under conditions that are significant for the catalytic action of phospholipase A2 in the scooting mode and not in the hopping mode. Also, under similar conditions, binding of pro-phospholipase A2 to anionic vesicles does not cause dehydration of the microinterface. The mechanistic significance of these observations for lipid-protein interactions, in general, and for interfacial catalysis and interfacial activation, in particular, is discussed.

Animals↗
PubMed1980

Rat hepatic cytosolic glutathione-dependent enzyme protection against lipid peroxidation in the NADPH-microsomal lipid peroxidation system.

Dialyzed rat liver cytosol (105 000 X g supernatant), when added along with 2.5 mM glutathione, blocked malonaldehyde formation in the NADPH-microsomal lipid peroxidation system, thus protecting against lipid peroxidation. Preheating the cytosol for 10 min at 60 degrees C destroyed its protective ability. Ammonium sulfate fractionation and Sephadex G-100 gel filtration of cytosol indicated that more than one glutathione-dependent protective enzyme was present. Fractions from the G-100 column containing the selenoenzyme glutathione peroxidase failed to protect, but fractions containing the glutathione S-transferases, which have non selenium-dependent glutathione peroxidase activity, did protect. The glutathione S-transferases were purified further with ion exchange chromatography and shown to have protective activity. Thus the rat hepatic cytosolic glutathione-dependent enzyme protection against lipid peroxidation in the NADPH-microsomal lipid peroxidation system is in part due to some of the glutathione S-transferases. The selenium-dependent glutathione peroxidase appears to have no protective effect in this system.

Animals↗