Showing papers on "Phosphatidylethanolamine published in 1980"
01 Jan 1980
TL;DR: This research attacked the mode of action of phosphatidylcholine-like deposits in response to the presence of ribonucleic acid by exploiting its role as a “spatially aggregating substance” in the response to EMT.
Abstract: IAbbreviations used in this article are as follows: AraC= l -,B-d arabinofuranosyl cytosine, Chol=cholesterol, DNA=deoxyribonucleic acid, DMPA=dimyristoyl phos phatidic acid, DMPC = dimyristoyl phosphatidylcholine, DMPE = dimyristoyl phos phatidylethanolamine, DOPC = dioleoyl phosphatidylcholine, DOPE = dioleoyl phos phatidylethanolamine, DPPA=dipaJmitoyl phosphatidic acid, DPPC=dipaJmitoyl phos phatidylcholine, DPPG = dipaJmitoyl phosphatidylglycerol, DPPS;= dipalmitoyl phos phatidylserine, DSPC = distearoyl phosphatidylcholine, EPC = egg phosphatidylcholine, EDTA=ethylene diamine tetracetic acid, HDL=high density lipoprotein, HPLC=high performance liquid chromatography, LUV = large unilamellar vesicle, MLV = multilamellar vesicle, NT A = nitrilotriacetic acid, NMR = nuclear magnetic resonance, PA phosphatidic acid, PC = phosphatidylcholine, PE = phosphatidylethanolamine, PO = phosphatidylglycerol, PS = phosphatidylserine, REV = reverse-phase evaporation vesicle, RNA = ribonucleic acid, SUV=small unilameUar vesicle, Tc=transition temperature. 2Present address: Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111.
1,666 citations
TL;DR: Biosynthesis of Phosphatidylglycerol and Cardiolipin 474 Biosynthetic pathways for bis-Monoacylglyc erol-P 474 PHOSPHOGLYCERIDE MODIFICATION REACfIONS 475 Base Exchange Re reactions 475 Reacyiation Reactions 475
Abstract: INTRODUCfION AND PERSPECfIVES ... ... 460 FATTY ACID ACTIVATION . . . . ..... . .. . . . . . . . . . . .. . .. . . . . . . . .. . .. .. . .. . 463 BIOSYNTHESIS OF PHOSPHATIDIC ACID .... ......... 464 Acylation of Glycerol-P • 464 Acylation of Lysophosphatidic Acid 465 Dihydroxyacetone-P Pathway 466 Diacylglycerol Kinase 467 BIOSYNTHESIS OF DIACYLGLYCEROL 468 BIOSYNTHESIS OF TRIACYLGL YCEROL ......... 469 BIOSYNTHESIS OF PHOSPHATIDYLCHOLINE AND . PHOSPHATIDYLETHANOLAMINE.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 Choline and Ethanolamine Kinases 470 Choline-P and Ethanolamine-P Cytidyltransferases 470 Cholineand Ethanoiaminephosphotransferases 471 Phosphatidylethanolamine N-methyltransferases 472 BIOSYNTHESIS OF CDP-DIACYLGL YCEROL AND THE ANIONIC PHOSPHOGLYCERIDES .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. . .. ... . . . . . . 473 Biosynthesis of Phosphatidylglycerol and Cardiolipin 474 Biosynthesis of Phosphatidylinositol 474 Biosynthesis of bis-Monoacylglyc erol-P 474 PHOSPHOGLYCERIDE MODIFICATION REACfIONS 475 Base Exchange Reactions 475 Reacyiation Reactions 475
602 citations
TL;DR: The concept that platelets, rather than phospholipid micelles, are the primary locus of prothrombin and Factor X activation in normal hemostasis is supported.
Abstract: Prolongation of all phospholipid-dependent coagulation tests was found in a patient with macroglobulinemia, despite absence of bleeding manifestations. The purified monoclonal IgM lambda protein and its Fabmu tryptic fragment induced similar changes in normal plasma. Patient IgM and Fabmu completely inhibited Ca++-dependent binding of radiolabeled prothrombin and Factor X to mixed phospholipid micelles. The patient's IgM lambda paraprotein reacted with phosphatidylserine and, to a lesser extent, with phosphatidylinositol and phosphatidic acid, but not with phosphatidylcholine or phosphatidylethanolamine. Prior incubation of phospholipid with patient Fabmu blocked the positive reactions. Substitution of washed platelets for phospholipid led to normalization of patient coagulation tests and corrected all abnormalities produced in normal plasma by patient IgM. Furthermore, binding of 125I-Factor Xa to thrombin-treated platelets was entirely normal in the presence of patient IgM. These studies support the concept that platelets, rather than phospholipid micelles, are the primary locus of prothrombin and Factor X activation in normal hemostasis.
359 citations
TL;DR: It is suggested that severe cerebral ischemia disintegrates membrane phospholipids, probably through activation of hydrolytic enzymes, and that overt peroxidative processes take place during reflow by means of restoration of oxygen supply and may indeed, cause additional damage during the postischemic phase.
Abstract: ✓ The effect of transient bilateral carotid occlusion on levels of free fatty acids, phospholipids, and lipid peroxides in the brain was studied in gerbils. During occlusion, both saturated and polyunsaturated free fatty acids increased strikingly to approximately 11-fold in total by 30 minutes. During recirculation, however, a selectively rapid decrement occurred in arachidonic acid, while saturated fatty acids gradually decreased to their basal levels in 180 minutes. The peroxide level, estimated by a thiobarbituric acid test, did not change during occlusion, but was elevated on reperfusion. Phosphatidylethanolamine content decreased throughout the periods examined. These results do not support a hypothesis that lipid peroxidation is initiated during ischemia by the lack of oxygen at the terminus of the mitochondrial respiratory chain. Instead, it is suggested that severe cerebral ischemia disintegrates membrane phospholipids, probably through activation of hydrolytic enzymes, and that overt peroxidativ...
336 citations
TL;DR: Rabbit intestinal brush border membrane vesicles were prepared either from frozen or fresh tissue and the lipid composition was analysed, finding individual phospholipids are characterised by distinct fatty acid compositions and differ markedly in the ratio of unsaturated-to-saturated fatty acid.
271 citations
TL;DR: Platelet phospholipase A2 activity is enhanced by increasing the pH (7.5 to 9.5), a condition which severely suppresses the phospholIPase C activity, which seems to be degraded nearly exclusively by phosphatidylinositol.
268 citations
TL;DR: The results of cytochrome c addition are compared with the effect of Ca2+ on cardiolipin and are discussed in relation to the structure and function of the inner mitochondrial membrane.
216 citations
TL;DR: The cho1 mutant appears to use almost exclusively the alternative pathway described by Kennedy and Weiss (1956) J. Biol.
205 citations
TL;DR: Rat brain was found to enzymatically methylate phospholipids to form phosphatidylcholine with S‐adenosyl‐l‐methionine serving as the methyl donor and methyltransferase activity was localized in the microsomes and synaptosomes.
Abstract: Rat brain was found to enzymatically methylate phospholipids to form phosphatidylcholine with S-adenosyl-l-methionine serving as the methyl donor Methyltransferase activity was localized in the microsomes and synaptosomes In synaptosomes, at least two enzymes were found to be involved in the formation of phosphatidylcholine The first methyltransferase which catalyzes the methylation of phosphatidylethanolamine to form phosphatidyl-N-monomethylethanolamine was found to have a pH optimum of 75, a low Km for 5-adenosyl-l-methionine and a partial requirement for Mg2 Methyltransferase I is tightly bound to membranes The second methyltransferase (II) catalyzes the successive methylations of phosphatidyl-N-monomethylethanolamine to phosphatidyl-N, N-dimethylethanolamine and then to phosphatidylcholine In contrast to methyltransferase I, methyltransferase II has a pH optimum of 105, a high apparent Km for S-adenosyl-l-methionine and no requirement for Mg2 Methyltransferase II is easily solubilized by sonication The highest specific activity for both enzymes was found in the synaptosomal plasma membrane
202 citations
TL;DR: Three mutants of the yeast Saccharomyces cerevisiae which require exogenous ethanolamine or choline were isolated and the lipid composition suggests that cho1 mutants do not synthesize phosphatidylserine under any growth conditions.
Abstract: Three mutants of the yeast Saccharomyces cerevisiae which require exogenous ethanolamine or choline were isolated. The mutants map to a single locus (cho1) on chromosome V. The lipid composition suggests that cho1 mutants do not synthesize phosphatidylserine under any growth conditions. If phosphatidylethanolamine or phosphatidylcholine, which are usually derived from phosphatidylserine, were synthesized from exogenous ethanolamine or choline, the mutants grew and divided relatively normally. However, mitochondrial abnormalities were evident even when ethanolamine and choline were supplied. Diploids homozygous for the cho1 mutation were defective in sporulation. Growth on nonfermentable carbon sources was slow, and a high proportion of respiratory-deficient (petite) cells were generated in cho1 cultures.
185 citations
TL;DR: One product, phosphocholine, has been identified by its behavior during Dowex 1-formate anion exchange chromatography, which appears to be the first demonstration in mammalian systems of a phospholipase C which is active against all phosphoglycerides.
TL;DR: An aminophospholipid asymmetry in synaptosomal plasma membranes was demonstrated which was independent of serum‐lipoprotein exchange processes and also of phosphatidylethanolamine‐methylatingenzymes.
Abstract:
The asymmetric distribution of aminophospholipids in isolated murine synaptosomal plasma membranes was determined by a chemical labeling procedure. Under nonpenetrating conditions, mouse brain synaptosomes were reacted with trinitrobenzenesulfonic acid (TNBS) to label outermonolayer aminophospholipids covalently. About 10-15% of the phosphatidylethanolamine and 20% of the phosphatidylserine were found to be in the outer monolayer of the synaptosomal plasma membrane. Furthermore, the fatty acyl group composition of the labeled phosphatidylethanolamine (outer monolayer) consisted of more saturated fatty acid than did the unlabeled phosphatidylethanolamine (inner monolayer). These results demonstrated an aminophospholipid asymmetry in synaptosomal plasma membranes which was independent of serum-lipoprotein exchange processes and also of phosphatidylethanolamine-methylatingenzymes.
TL;DR: Neutral and polar spore lipids of the vesicular-arbuscular (VA) endophyte Glomus caledonius, were identified and quantitatively determined during spore germination, germ tube growth, and germ tube senescence.
Book•
03 Apr 1980
TL;DR: The Intracellular Movement of Lipids Via "Membrane Flow" and the Maintenance of Membrane Lipid Asymmetry are studied.
Abstract: A RATIONALE GOVERNING THE REGULATION OF LIPID METABOLISM. Tissue-Specific Distribution of Lipids. The Physiological Significance of Lipid Tissue Specificity. Response of Membrane Lipid Composition to Environmental Perturbation. The Role of Membrane Lipids in Abnormal and Disease States. Recapitulation. FATTY ACID BIOSYNTHESIS. The Pathway. Cellular Location. The Regulatory Enzymes. FATTY ACID MODIFICATION. Fatty Acid Activation. Fatty Acid Elongation. Fatty Acid Desaturation. Metabolism of Cyclopropane Fatty Acids. Conversion of Straight-Chain to Branched-Chain Fatty Acids. Biohydrogenation of Unsaturated Fatty Acids. Fatty Acid Oxidation. Reduction of Fatty Acids to Fatty Alcohols. PHOSPHOLIPIDS. Regulation of the Phosphatidic Acid Pool. Regulation of the Diacylglycerol Pool. De Novo Synthesis of Phosphatidylcholine. De Novo Synthesis of Phosphatidylethanolamine. Phospholipid Interconversion by Exchange of Polar Head Groups. Formation of Phosphatidylethanolamine and Phosphatidylcholine by Enzymatic Modification of Phosphatidylserine. Formation of CDP-Diacylglycerols From Phosphatidic Acid. De Novo Synthesis of Phosphatidylserine, Phosphatidylinositol, Phosphatidylglycerol and Cardiolipin. Metabolism of Polyphosphoinositides. Phosphonolipids. Phospholipids Containing Ether Bonds. Metabolism of Sphingomyelin. Regulatory Function of Lipid-Degrading Enzymes. Turnover of Phospholipid Acyl Groups. Overview of Phospholipid Metabolism in Bacteria. Overview of Phospholipid Metabolism in Animals. Overview of Phospholipid Metabolism in Plants. STEROL METABOLISM. The Mechanisms of Sterol Biosynthesis. Regulation of Cholesterol Biosynthesis. Regulation of Sterol Analog Metabolism. Regulation of Sterol Catabolism. THE REGULATION OF NON-STEROID ISOPRENOID METABOLISM. Chlorophyll. Carotenoids. Lipids of Archaebacteria. THE REGULATION OF GLYCOLIPID METABOLISM. Glycolipid Metabolism in Animals. Glycolipid Metabolism in Plants. LIPIDS COVALENTLY BOUND TO PROTEINS. Fatty Acylated Proteins. Isoprenylated Proteins. Proteins Anchored to the Membranes by a Phosphatidylinositol Glycan. THE SPECIFICITY AND RATES OF INTRACELLULAR LIPID MOVEMENT. The Intracellular Movement of Lipids Via "Membrane Flow". Unimolecular Transport of Lipids. The Maintenance of Membrane Lipid Asymmetry. THE EFFECTS OF EXOGENOUS LIPIDS UPON LIPID METABOLISM. Effects of Exogenous Fatty Acids. Effects of Exogenous Ether Lipids. Effects of Exogenous Sterols. Effects of Exogenous Precursors of Phospholipid Head Groups. THE EFFECTS OF ENVIRONMENTAL FACTORS ON LIPID METABOLISM. Adaptive Responses to Environmental Stress. Conclusions.
TL;DR: Calculations reported here show that this enzymatic activity in reticulocytes, erythrocytes and mammary gland membranes is 0.1% of that observed in liver microsomes, and there is considerable doubt that methylation of phosphatidylethanolamine could account for the many physiological responses attributed to this activity.
Abstract: The conversion of phosphatidylethanolamine to phosphatidylcholine was first reported in rat liver microsomes by Bremer and Greenberg1. The reaction requires three successive methylations of the ethanolamine moiety by S-adenosyl-methionine. The highest activity for this enzyme has been found in liver microsomes and the enzyme from rat liver was recently solubilized and partially purified2. Although the activity is highest in liver, it is the minor pathway in this tissue for the synthesis of phosphatidylcholine3. The enzyme has recently been identified in bovine adrenal medulla4 and reports exist on the activity of phosphatidylethanolamine methyltransferase in erythrocyte ghosts5, reticulocyte ghosts6,7 and mammary gland membranes8. In view of the relatively minor importance of the methylation pathway in phosphatidylcholine biosynthesis in liver, we were intrigued by the reports of significant physiological changes attributed to phospholipid methylation6–9. Calculations reported here show that this enzymatic activity in reticulocytes, erythrocytes and mammary gland membranes is 0.1% of that observed in liver microsomes. Furthermore, in conditions where marked changes in microviscosity of the erythrocyte membrane were observed, only extremely small amounts of phosphatidylethanolamine were methylated9. For these and other reasons, there is considerable doubt that methylation of phosphatidylethanolamine could account for the many physiological responses attributed to this activity.
TL;DR: The polymorphic phase behaviour of bovine brain sphingomyelin alone and in the presence of soya phosphatidylethanolamine has been investigated employing 31 P NMR techniques and indicates that the local motion and conformation in the phosphate group region is similar to that of glycerol-based phospholipids.
TL;DR: The results confirm in an independent way the asymmetric distribution of phosphatidylcholine over the membrane of human and rat erythrocytes as well as the occurrence of a slow transbilayer movement of this lipid in rat eriesomes.
Abstract: 1. The exchange of phosphatidylcholine between intact human or rat erythrocytes and rat liver microsomes was greatly stimulated by phosphatidylcholine-specific exchange proteins from rat liver and beef liver. It was found, however, that compared to the exchange reaction between phospholipid vesicles and rat liver microsomes, much higher concentrations of exchange protein were required in the case of intact red blood cells and microsomes. 2. In human erythrocytes, 75 % of the phosphatidylcholine was available for exchange within 2 h at 37 "C. No additional exchange was observed during the next 2 h, indicating slow, if any, transbilayer movement of the residual phosphatidylcholine. 3. In rat erythrocytes 50 - 60 % of the phosphatidylcholine was readily available for the exchange proteins. The residual phosphatidylcholine was exchanged at a much lower rate with a half time for equilibration of 7 h. 4. These results confirm in an independent way the asymmetric distribution of phosphatidylcholine over the membrane of human and rat erythrocytes as well as the occurrence of a slow transbilayer movement of this lipid in rat erythrocytes. The human erythrocyte was the first cell in which an asymmetric distribution of phospholipids over both sides of the bilayer membrane was established. The outer monolayer mainly consists of the cholinecontaining phospholipids, phosphatidylcholine and sphingomyelin, whereas phosphatidylethanolamine and phosphatidylserine are preferentially located in the inner monolayer. Chemical labelling studies showed that the aminophospholipids were labelled much faster and, to a larger extent, in open ghosts than in intact cells [l-41. Treatment of intact cells with phospholipases resulted in the hydrolysis of 50 % of the total phospholipids among which 76% of the phosphatidylcholine 82 % of the sphingomyelin and 20 % of the phosphatidylethanolamine whereas all
TL;DR: It is shown that decrease of cardiolipin in mitochondrial membrane occurs early during ischemic injury, and only during the irreversible phase of ischemia are phosphatidylethanolamine and phosph atidylcholine broken down.
TL;DR: Scanning calorimetry of equimolar mixtures of phosphatidylethanolamines with phosph atidylcholines, which show either ideal or nonideal mixing properties, reveals that when cholesterol is added to these mixtures it shows no preferential affinity for either of the phospholipids.
Abstract: The thermotropic behavior of aqueous dispersions of phosphatidylethanolamine-cholesterol and phosphatidyl-ethanolamine-phosphatidylcholine-cholesterol mixtures has been studied by high-sensitivity differential scanning calorimetry. The gel to liquid-crystalline phase transition of phosphatidylethanolamines is broadened and shifted to lower temperature when cholesterol is incorporated into the bilayer. When the cholesterol content is below 25 mol %, the calorimetric endotherms seem to consist of two components, a broad one at considerably lower temperature than the original transition and another component at only slightly lower temperature. This thermotropic behavior can be explained by the assumption of a homogenous distribution of cholesterol in phosphatidylethanolamine bilayers. Scanning calorimetry of equimolar mixtures of phosphatidylethanolamines with phosphatidylcholines, which show either ideal or nonideal mixing properties, reveals that when cholesterol is added to these mixtures it shows no preferential affinity for either of the phospholipids.
TL;DR: 31P-NMR shows that poly(L-lysine) binding to cardiolipin, phosphatidylserine or phosph atidylglycerol does not affect the macroscopic structure or local order (in the phosphate region) of the phospholipids.
TL;DR: It is concluded that a protonated nitrogen is necessary for competition with Ca for binding sites at lipid monolayers; the potency for replacing Ca is, however, determined by the hydrophobicity of the molecule.
TL;DR: It is suggested that the uncoupling action of high Ca2+ concentrations on intact mitochondria may be related to a Ca2-induced disruption of the integrity of the inner mitochondrial phospholipid bilayer, and the possibility that non-bilayer lipid structures such as inverted micelles occur in the inner mitochondria cannot be excluded.
TL;DR: The experiments demonstrate that special compositions of the phospholipid membrane are required for a high activity of the reconstituted carrier.
TL;DR: Results show that the viruses bud from localized lipid regions that do not reflect the average properties of the plasma membrane.
TL;DR: Electron microscopy revealed that vegetative cells of M. xanthus possessed an envelope similar to that of other gram-negative bacteria; however, the vesicular appearance of the isolated membranes was somewhat different from those reported for Escherichia coli and Salmonella typhimurium.
Abstract: We have developed methods for separating the cytoplasmic and outer membranes of vegetative cells of Myxococcus xanthus. The total membrane fraction from ethylenediaminetetraacetic acid-lysozyme-treated cells was resolved into three major fractions by isopycnic density centrifugation. Between 85 and 90% of the succinate dehydrogenase and cyanide-sensitive reduced nicotinamide adenine dinucleotide oxidase activity was found in the first (I) fraction (rho = 1.221 g/ml) and 80% of the membrane-associated 2-keto-3-deoxyoctonate was found in the third (III) fraction (rho = 1.166 g/ml). The middle (II) fraction (rho = 1.185 g/ml) appeared to be a hybrid membrane fraction and contained roughly 10 to 20% of the activity of the enzyme markers and 2-keto-3-deoxyoctonate. No significant amounts of deoxyribonucleic acid or ribonucleic acid were present in the three isolated fractions, although 26% of the total cellular deoxyribonucleic acid and 3% of the total ribonucleic acid were recovered with the total membrane fraction. Phosphatidylethanolamine made up the bulk (60 to 70%) of the phospholipids in the membrane fractions. However, virtually all of the phosphatidylserine and cardiolipin were found in fraction I. Fraction III appeared to contain elevated amounts of lysophospholipids and contained almost three times the amount of total phospholipid as compared with fraction I. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis resolved approximately 40 polypeptides in the total membrane fraction. Two-thirds of these polypeptides were enriched in fraction I, and the remainder was enriched in fraction III. Fraction II contained a banding pattern similar to the total membrane fraction. Electron microscopy revealed that vegetative cells of M. xanthus possessed an envelope similar to that of other gram-negative bacteria; however, the vesicular appearance of the isolated membranes was somewhat different from those reported for Escherichia coli and Salmonella typhimurium. The atypically low bouyant density of the outer membrane of M. xanthus is discussed with regard to the high phospholipid content of the outer membrane.
TL;DR: These spectra bear on two interrelated topics involving mixtures of phosphatidylcholine and cholesterol: lipid phase equilibria and the lateral ordering and diffusion of lipid molecules and model membrane immunochemistry using spin-label lipid haptens.
Abstract: We have observed the paramagnetic resonance spectra of a head group spin-labeled phosphatidylethanolamine (L-alpha-dipalmitoylphosphatidyl-N-ethanolamine) as a function of temperature and cholesterol concentration in binary mixtures of cholesterol and dimyristoylphosphatidylcholine. These spectra bear on two interrelated topics involving mixtures of phosphatidylcholine and cholesterol: (1) lipid phase equilibria and the lateral ordering and diffusion of lipid molecules and (2) model membrane immunochemistry using spin-label lipid haptens.
TL;DR: Results are discussed which suggest that the resultant membrane in the Sprague-Dawley male rat is more fragile, leading to greater cellular breakdown and focal necrosis, and the effect of such changes in cardiac phospholipids on membrane structure and function is impossible to estimate.
Abstract: Male Sprague-Dawley rats were fed diets for 1 or 16 weeks, containing 20% by weight vegetable oils differing widely in their oleic, linoleic and linolenic acid content. No significant changes were observed in the level of the cardiac lipid classes. The fatty acid composition of the 2 major phospholipids, phosphatidylcholine and phosphatidylethanolamine, showed a remarkable similarity between diets in the concentration of total saturated, C22 polyunsaturated and arachidonic acids. Monounsaturated acids were incorporated depending on their dietary concentration, but the increases were moderate. Dietary linolenic acid rapidly substituted C22 polyunsaturated fatty acids of the linoleic acid family (n-6) with those from the linolenic acid family (n-3). The results suggest that dietary linolenic acid of less than 15% does not inhibit the conversion of linoleic to arachidonic acid but the subsequent conversion of arachidonic acid to the C22 polyunsaturates was greatly reduced. Significant amounts of dietary monounsaturated fatty acids were incorporated into cardiac cardiolipin accompanied by increases in polyunsaturated fatty acids, apparently to maintain an average of 2 double bonds/molecule. The cardiac sphingomyelins also accumulated monounsaturated fatty acids depending on the dietary concentration. It is quite evident from the results of this study that the incorporation of oleic acid and the substitution of linolenic for linoleic acid-derived C22 polyunsaturated fatty acids into cardiac phospholipids was related to the dietary concentration of these fatty acids and was not peculiar to any specific oil. Even though it is impossible to estimate the effect of such changes in cardiac phospholipids on membrane structure and function, results are discussed which suggest that the resultant membrane in the Spragu-Dawley male rat is more fragile, leading to greater cellular breakdown and focal necrosis.
TL;DR: Plasma membranes of Drosophila larval cells, containing or lacking cholesterol, were also disrupted by polymyxin, and the cell membranes of guinea pig sperm were likewise disrupted but in specific functional areas.
Abstract: Polymyxin B was used to explore distribution of anionic phospholipids in sperm plasma membranes by electron microscopy of freeze-fracture replicas. After exposure to Hepes/Tris-buffered polymyxin at 4 mM, phosphatidylcholine liposomes showed no perturbations nor did they fluoresce with dansylated incubation. When phosphatidylethanolamine was included in the liposomes, they became perturbed and fluoresced. Plasma membranes of Drosophila larval cells, containing or lacking cholesterol, were also disrupted by polymyxin. The cell membranes of guinea pig sperm were likewise disrupted but in specific functional areas. Fusional membrane domains showed protrusions; the stable membrane of the flagellum revealed diffuse bubbling. Regions of well-defined particle arrays and the postacrosomal segment maintained smooth contours. By fluorescence microscopy, we detected the same heterogeneous binding of the polymyxin dansyl derivative.
TL;DR: It is demonstrated that significant biochemical and structural disorganization occurs during 3 h of ischemia in the myocardium and raised the possibility that one of the initiating events is the activation of sarcolemmal and mitochondrial phospholipases.
Abstract: Sarcolemmal and mitochondrial phospholipids were extracted from normally perfused and ischemic regions of the dog heart and the composition of these extracts was analyzed. Relatively pure sarcolemmal fraction obtained from myocardium subjected to 3 h of ischemia exhibited a significantly lower concentration of phospholipids than that obtained from normal myocardium. In particular, phosphatidylcholine and phosphatidylethanolamine were reduced by approximately 33%. The fatty acid content in the sarcolemmal phospholipid fraction was also reduced by approximately 30% without any change in the relative composition. In the mitochondrial fraction, the relative phospholipid composition was also altered by ischemia; the major components (phosphatidylcholine, phosphatidylethanolamine, and cardiolipin) being reduced by approximately 15-20%. An attempt was made to correlate these biochemical changes with ultrastructural lesions observed electron microscopically. These observations revealed extensive regional variability and a wide heterogeneity in the extent of ultrastructural damage evident in the different organelles even in a single cell. This may suggest that ischemic damage, in the early stages, may advance at widely varying rates in different regions. Our findings demonstrate that significant biochemical and structural disorganization occurs during 3 h of ischemia in the myocardium and raise the possibility that one of the initiating events is the activation of sarcolemmal and mitochondrial phospholipases.