LIPIDS OF SUBCELLULAR PARTICLES

Chloroplasts Isolation from Chlamydomonas reinhardtii under Nitrogen Stress

Triacylglycerols are produced in abundance through chloroplast and endoplasmic reticulum pathways in some microalgae exposed to stress, though the relative contribution of either pathway remains elusive. Characterization of these pathways requires isolation of the organelles. In this study, an efficient and reproducible approach, including homogenous batch cultures of nitrogen-deprived algal cells in photobioreactors, gentle cell disruption using a simple custom-made disruptor with mechanical shear force, optimized differential centrifugation and Percoll density gradient centrifugation, was developed to isolate chloroplasts from Chlamydomonas reinhardtii subjected to nitrogen stress. Using this approach, the maximum limited stress duration was 4 h and the stressed cells exhibited 19 and 32% decreases in intracellular chlorophyll and nitrogen content, respectively. Chloroplasts with 48 - 300 μg chlorophyll were successfully isolated from stressed cells containing 10 mg chlorophyll. These stressed chloroplasts appeared intact, as monitored by ultrastructure observation and a novel quality control method involving the fatty acid biomarkers. This approach can provide sufficient quantities of intact stressed chloroplasts for subcellular biochemical studies in microalgae.

An overview of the toxic effect of potential human carcinogen Microcystin-LR on testis

The worldwide occurrence of cyanobacterial blooms due to water eutrophication evokes extreme concerns. These blooms produce cyanotoxins which are hazardous to living organisms. So far among these toxins, Microcystin-LR (MC-LR) is the most toxic and the most frequently encountered toxin produced by the cyanobacteria in the contaminated aquatic environment. Microcystin-LR is a potential carcinogen for animals and humans, and the International Agency for Research on Cancer has classified Microcystin-LR as a possible human carcinogen. After liver, testis has been considered as one of the most important target organs of Microcystin-LR toxicity. Microcystin-LR crosses the blood–testis barrier and interferes with DNA damage repair pathway and also increases expression of the proto-oncogenes, genes involved in the response to DNA damage, cell cycle arrest, and apoptosis in testis. Toxicity of MC-LR disrupts the motility and morphology of sperm and also affects the hormone levels of male reproductive system. MC-LR treated mice exhibit oxidative stress in testis through the alteration of antioxidant enzyme activity and also affect the histopathology of male reproductive system. In the present review, an attempt has been made to comprehensively address the impact of MC-LR toxicity on testis.

Observations on lipid composition with particular reference to cardiolipin of rat heart after feeding rapeseed oil

The influence of dietary rapeseed oil on the lipid classes and fatty acid pattern of rat heart homogenate and mitochondria has been investigated after feeding a diet with 9.8 weight- % erucic acid for 10 days and 1.4 and 2.6% erucic acid for 28 days. The rats treated with 9.8% erucic acid showed a significant increase in the triglycerides of the heart mitochondria. This tendency was much less pronounced in rats treated with 1.4 resp. 2.6% erucic acid. These results confirm those of other investigators. A slight increase in the cholesterol esters of the mitochondria could be seen in all the treated rats. The total phospholipids were decreased in the experiment with 9.8% erucic acid and slightly increased in experiments with 1.4 and 2.6% erucic acid. The concentration of phosphatidylcholine showed a tendency to increase and the concentration of phosphatidylethanolamine to decrease in the experiment with 9.8% erucic acid in the diet. The concentration of cardiolipin was mainly unchanged. In all experiments the triglycerides of the heart mitochondria showed a high content of erucic acid. The fatty acids of the cholesterol esters of the heart mitochondria were also influenced of dietary rapeseed oil but to a less extent than the triglycerides. The fatty acids of phosphatidylcholine, phosphatidylethanolamine and cardiolipin were all influenced by the dietary rapeseed oil, but the erucic acid seemed to have a specific affinity to cardiolipin. Cardiolipin of rat heart mitochondria was isolated and identified with gas chromatography and mass spectrometry. The isolated cardiolipin was found to contain 12 per cent erucic acid after feeding 9.8% erucic acid as rapeseed oil for 10 days. Similar results were obtained after feeding glyceryl trierucate for 5 days to rats. The incorporation of erucic acid into cardiolipin was followed by a corresponding decrease of linoleic acid. This observation is of great interest because the molecular structure of fatty acids in lipid molecules has a profound influence of the packing of these molecules in a bilayer. Since cardiolipin is a component of the inner membrane of mitochondria its high affinity for erucic acid might influence the normal function of the inner membrane of heart mitochondria.

Maternal dietary supplementation with saturated, but not monounsaturated or polyunsaturated fatty acids, leads to tissue-specific inhibition of offspring Na+,K+-ATPase

In rats, a maternal diet rich in lard is associated with reduced Na(+),K(+)-ATPase activity in adult offspring kidney. We have addressed the role of different fatty acids by evaluating Na(+),K(+)-ATPase activity in offspring of dams fed diets rich in saturated (SFA), monounsaturated (MUFA) or polyunsaturated (PUFA) fatty acids. Female Sprague-Dawley rats were fed, during pregnancy and suckling, a control diet (4% w/w corn oil) or a fatty acid supplemented diet (24% w/w). Offspring were reared on chow (4% PUFA) and studied at 6 months. mRNA expression (real-time PCR) of Na(+),K(+)-ATPase alpha subunit and protein expression of Na(+),K(+)-ATPase subunits (Western blot) were assessed in kidney and brain. Na(+),K(+)-ATPase activity was reduced in kidney (P < 0.05 versus all groups) and brain (P < 0.05 versus control and MUFA offspring) of the SFA group. Neither Na(+),K(+)-ATPase alpha1 subunit mRNA expression, nor protein expression of total alpha, alpha1, alpha2, alpha3 or beta1 subunits were significantly altered in kidney in any dietary group. In brains of SFA offspring alpha1 mRNA expression (P < 0.05) was reduced compared with MUFA and PUFA offspring, but not controls. Also in brain, SFA offspring demonstrated reduced (P < 0.05) alpha1 subunit protein and increased phosphorylation (P < 0.05) of the Na(+),K(+)-ATPase modulating protein phospholemman at serine residue 63 (S63 PLM). Na(+),K(+)-ATPase activity was similar to controls in heart and liver. In utero and neonatal exposure to a maternal diet rich in saturated fatty acids is associated with altered activity and expression of Na(+),K(+)-ATPase in adulthood, but mechanisms appear tissue specific.

Mechanisms by which docosahexaenoic acid and related fatty acids reduce colon cancer risk and inflammatory disorders of the intestine

A growing body of epidemiological, clinical, and experimental evidence has underscored both the pharmacological potential and the nutritional value of dietary fish oil enriched in very long chain n-3 PUFAs such as docosahexaenoic acid (DHA, 22:6, n-3) and eicosapentaenoic acid (EPA, 20:5, n-3). The broad health benefits of very long chain n-3 PUFAs and the pleiotropic effects of dietary fish oil and DHA have been proposed to involve alterations in membrane structure and function, eicosanoid metabolism, gene expression and the formation of lipid peroxidation products, although a comprehensive understanding of the mechanisms of action has yet to be elucidated. In this review, we present data demonstrating that DHA selectively modulates the subcellular localization of lipidated signaling proteins depending on their transport pathway, which may be universally applied to other lipidated protein trafficking. An interesting possibility raised by the current observations is that lipidated proteins may exhibit different subcellular distribution profiles in various tissues, which contain a distinct membrane lipid composition. In addition, the current findings clearly indicate that subcellular localization of proteins with a certain trafficking pathway can be subjected to selective regulation by dietary manipulation. This form of regulated plasma membrane targeting of a select subset of upstream signaling proteins may provide cells with the flexibility to coordinate the arrangement of signaling translators on the cell surface. Ultimately, this may allow organ systems such as the colon to optimally decode, respond, and adapt to the vagaries of an ever-changing extracellular environment.

Distribution of polyunsaturated fatty acids including conjugated linoleic acids in total and subcellular fractions from healthy and cancerous parts of human kidneys

Differences in the FA composition of subcellular fractions from healthy and cancerous kidney tissues from the same patients were examined. Only minor differences in CLA content were found between the healthy and the cancerous tissue portions. Regarding the distribution pattern, CLA incorporation into nuclei and cytosol was significantly higher than incorporation into plasma membranes and mitochondria, which could be correlated to the neutral lipid content of these fractions. The subcellular distribution pattern of CLA was similar to that observed with monounsaturated FA but unlike that found with 18:2n-6, which underlines the different physiological properties of CLA and 18:2n-6. Because PUFA have been suggested to have an effect on cancer risk, the contents of n-3 and n-6 PUFA were determined in kidney and renal cell carcinoma (RCC). The 18:2n-6 content and delta5 desaturase activity were significantly lower, and the 18:3n-6, 20:3n-6, and 20:5n-3 contents and delta6 desaturase activity were significantly higher in RCC than in healthy renal tissue, indicating a changed PUFA metabolism in RCC. Previous research has suggested that CLA inhibits the elongation and desaturation of 18:2n-6 into 20:4n-6. In that case, one might speculate that a diet enriched in CLA would be a useful tool in preventing RCC. However, the involvement of CLA in preventing renal cancer could not be demonstrated definitively from the design of this experiment. Further understanding of the cause and/or consequence of the difference in FA metabolism may lead to a better understanding of RCC.

Review of the carcinogenic activity of diethanolamine and evidence of choline deficiency as a plausible mode of action

Diethanolamine (DEA) is a chemical used widely in a number of industries and is present in many consumer products. Studies by the National Toxicology Program (NTP) have indicated that lifetime dermal exposure to DEA increased the incidence and multiplicity of liver tumors in mice, but not in rats. In addition, DEA was not carcinogenic when tested in the Tg.Ac transgenic mouse model. Short-term genotoxicity tests have yielded negative results. In view of these apparent inconsistencies, we have critically evaluated the NTP studies and other data relevant to assessing the carcinogenic potential of DEA. The available data indicate that DEA induces mouse liver tumors by a non-genotoxic mode of action that involves its ability to cause choline deficiency. The following experimental evidence supports this hypothesis. DEA decreased the hepatic choline metabolites and S-adenosylmethionine levels in mice, similar to those observed in choline-deficient mice. In contrast, DEA had no effect in the rat, a species in which it was not carcinogenic at a maximum tolerated dose level. In addition, a consistent dose-effect relationship had been established between choline deficiency and carcinogenic activity since all DEA dosages that induced tumors in the NTP studies were also shown to cause choline deficiency. DEA decreased phosphatidylcholine synthesis by blocking the cellular uptake of choline in vitro, but these events did not occur in the presence of excess choline. Finally, DEA induced transformation in the Syrian hamster embryo cells, increased S-phase DNA synthesis in mouse hepatocytes, and decreased gap junctional intracellular communication in primary cultured mouse and rat hepatocytes, but all these events were prevented with choline supplementation. Since choline is an essential nutrient in mammals, this mode of action is qualitatively applicable to humans. However, there are marked species differences in susceptibility to choline deficiency, with rats and mice being far more susceptible than other mammalian species including humans. These differences are attributed to quantitative differences in the enzyme kinetics controlling choline metabolism. The fact that DEA was carcinogenic in mice but not in rats also has important implications for human risk assessment. DEA has been shown to be less readily absorbed across rat and human skin than mouse skin. Since a no observed effect level for DEA-induced choline deficiency in mice has been established to be 10 mg/kg/d, this indicates that there is a critical level of DEA that must be attained in order to affect choline homeostasis. The lack of a carcinogenic response in rats suggests that exposure to DEA did not reach this critical level. Since rodents are far more sensitive to choline deficiency than humans, it can be concluded that the hepatocarcinogenic effect of DEA in mice is not predictive of similar susceptibility in humans.

Influence of a dietary n-3 fatty acid deficiency on the cerebral catecholamine contents, EEG and learning ability in rat

Female rats were fed on a diet deficient in (n-3) fatty acid or enriched in docosahexaenoic acid (DHA) diet from mating and throughout pregnancy and lactation. Pups fed on the same diet as their dams were used for experiments. The effects of dietary (n-3) fatty acid deficiency on cerebral catecholamine contents and electroencephalogram (EEG) in rat pups during the postnatal development were investigated. The (n-3) deficient rat pups showed significantly lower levels of noradrenaline (NA) in cerebral cortex, hippocampus and striatum, compared with those in the DHA adequate rats. Dopamine (DA) contents were significantly lower in the (n-3) deficient rats until the 7th day of age. These results were consistent with observations in the EEG analysis, relative powers of fast activities in the EEG recorded from the (n-3) deficient rats were significantly lower than those in the DHA adequate rats. The effect of supplementation with DHA in (n-3) deficient rats on learning ability was also studied in a model of learning, active avoidance test and three-panel run way test, after weaning. Although the percentages of avoidance in the (n-3) deficient rats (saline group) were constantly 20% or less until the 3rd session, the percentage of avoidance in the DHA supplemented rats rapidly increased to 53% following the first administration. While in the three-panel runway test, there were no significant differences between two groups. These results suggest that chronic consumption of a (n-3) fatty acid deficient diet could modify the biosynthesis of catecholamine in the brain, and might induce the behavioral disturbances. Furthermore, the decreased learning ability induced by (n-3) deficiency in the active avoidance test is a reversible following a supplementing DHA after the weaning.

Maternal dietary fish oil enriches docosahexaenoate levels in brain subcellular fractions of offspring

Prompted by the speculated essentiality of docosahexaenoic acid (DHA) for neural development, this study was undertaken to investigate the incorporation of (n-3) fatty acids in the maternal diet into various phospholipids of infant rat brain subcellular fractions: microsomes (Ms), synaptosomes (Sy), myelin (My), and mitochondria (Mt). Two groups of infant rats were nourished by dams fed diets containing 20% of either corn oil (CO) or menhaden oil (MO) from 2 until 12 days of age. DHA but not eicosapentaenoic acid (EPA) was distributed to all subcellular fractions of infant rats in the CO group. The levels of DHA were higher in Ms and Mt than Sy and My, and higher in phosphatidylethanolamine (PE) and phosphatidylserine (PS) than phosphatidylcholine (PC) and phosphatidylinositol (PI). The MO feeding enriched DHA in PE of all subcellular fractions, PS of all subcellular fractions, except My, PC of Sy, My and Mt, and PI of My. EPA was enriched in phospholipids in all subcellular fractions, except mitochondrial PS of the MO group. In the MO group, the ratios of EPA/DHA, ranging from 0.01 to 0.85, in all subcellular phospholipids were markedly lower than that found in the mother's milk (i.e., 1.5), suggesting an ability to elongate and desaturate EPA to DHA and/or disproportional uptake of the fatty acids by the brain. In PE of all subcellular fractions, the increased levels of DHA and EPA, with a concomitant reduction of arachidonic and/or linoleic acid, yielded higher ratios of total (n-3)/(n-6) fatty acids in the MO than the CO group. The inclusion of preformed DHA and EPA in the maternal diet provides an effective means to enrich these fatty acids in developing brains.

Cytophotometric assay of cytochrome oxidase, lactate dehydrogenase and glucose-6-phosphate dehydrogenase activities in human peroxidized spermatozoa

Human spermatozoa contain appreciable amounts of intracellular glutathione, which has a protective function against peroxidative degradation of spermatozoal polyunsaturated fatty acids by the NADPH-dependent glutathione peroxidase/reductase enzymatic system. The glutathione system provides a basic defense against peroxidative damage, without which the superoxide dismutase system would dominate. Since oxidative damage is said to include enzyme leakage and changes in metabolism, cytochrome oxidase and lactate dehydrogenase activities were used as indicators of the energy metabolism in unwashed and washed human spermatozoa during lipid peroxidation. Lipid peroxidation was induced by aerobic incubation of sperms in the presence of sodium ascorbate and ferrous sulphate. In addition, since NADPH concentrations influence the concentration of reduced glutathione, we studied glucose-6-phosphate dehydrogenase activity as an indicator of pentose phosphate shunt activity, the main source of NADPH. Microdensitometric measurements of the three enzymes were made by a Vickers M85a scanning microdensitometer. We found that the lipid peroxidation process greatly affects the 3 enzymatic activities examined and that seminal plasma protects against the extensive deleterious effects of lipid peroxidation.

Cardiolipins and biomembrane function

Evidence is discussed for roles of cardiolipins in oxidative phosphorylation mechanisms that regulate State 4 respiration by returning ejected protons across and over bacterial and mitochondrial membrane phospholipids, and that regulate State 3 respiration through the relative contributions of proteins that transport protons, electrons and/or metabolites. The barrier properties of phospholipid bilayers support and regulate the slow proton leak that is the basis for State 4 respiration. Proton permeability is in the range 10(-3)-10(-4) cm s-1 in mitochondria and in protein-free membranes formed from extracted mitochondrial phospholipids or from stable synthetic phosphatidylcholines or phosphatidylethanolamines. The roles of cardiolipins in proton conductance in model phospholipid membrane systems need to be assessed in view of new findings by Hübner et al. [313]: saturated cardiolipins form bilayers whilst natural highly unsaturated cardiolipins form nonlamellar phases. Mitochondrial cardiolipins apparently participate in bilayers formed by phosphatidylcholines and phosphatidylethanolamines. It is not yet clear if cardiolipins themselves conduct protons back across the membrane according to their degree of fatty acyl saturation, and/or modulate proton conductance by phosphatidylcholines and phosphatidylethanolamines. Mitochondrial cardiolipins, especially those with high 18:2 acyl contents, strongly bind many carrier and enzyme proteins that are involved in oxidative phosphorylation, some of which contribute to regulation of State 3 respiration. The role of cardiolipins in biomembrane protein function has been examined by measuring retained phospholipids and phospholipid binding in purified proteins, and by reconstituting delipidated proteins. The reconstitution criterion for the significance of cardiolipin-protein interactions has been catalytical activity; proton-pumping and multiprotein interactions have yet to be correlated. Some proteins, e.g., cytochrome c oxidase are catalytically active when dimyristoylphosphatidylcholine replaces retained cardiolipins. Cardiolipin-protein interactions orient membrane proteins, matrix proteins, and on the outerface receptors, enzymes, and some leader peptides for import; activate enzymes or keep them inactive unless the inner membrane is disrupted; and modulate formation of nonbilayer HII-phases. The capacity of the proton-exchanging uncoupling protein to accelerate thermogenic respiration in brown adipose tissue mitochondria of cold-adapted animals is not apparently affected by the increased cardiolipin unsaturation; this protein seems to take over the protonophoric role of cardiolipins in other mitochondria. Many in vivo influences that affect proton leakage and carrier rates selectively alter cardiolipins in amount per mitochondrial phospholipids, in fatty acyl composition and perhaps in sidedness; other mitochondrial membrane phospholipids respond less or not at all.(ABSTRACT TRUNCATED AT 400 WORDS)

Tissue distribution of an endogenous ligand to the Na, K ATPase molecule

A variety of evidence indicates the presence of a circulating ligand to the Na, K ATPase molecule that is involved in the regulation of extracellular sodium metabolism. To examine the potential role of endogenous ligands to the Na, K ATPase molecule in the regulation of intracellular sodium metabolism, the tissue distribution of digitalis-like activity was quantitated in several brain regions and peripheral organs. The digitalis-like activity of desalted and delipidated extracts of tissue was widely distributed and produced a displacement of tritiated ouabain that was parallel to the displacement produced by cold ouabain. These results suggest that tissue contains an endogenous ligand to the Na, K ATPase molecule and that this ligand may regulate intracellular sodium metabolism in an autocoid-like manner.

Effects of flavonoids on nonenzymatic lipid peroxidation: structure-activity relationship

The in vitro effects of several flavonoids on nonenzymatic lipid peroxidation in the rat brain mitochondria was studied. The lipid peroxidation was indexed by measuring the MDA production using the 2-thiobarbituric acid TBA test. The flavonoids, apigenin, flavone, flavanone, hesperidin, naringin, and tangeretin promoted the ascorbic acid-induced lipid peroxidation, the extent of which depended upon the concentration of the flavonoid and ascorbic acid. The other flavonoids studied, viz., quercetin, quercetrin, rutin, taxifolin, myricetin, myricetrin, phloretin, phloridzin, diosmetin, diosmin, apiin, hesperetin, naringenin, (+)-catechin, morin, fisetin, chrysin, and 3-hydroxyflavone, all showed varying extents of inhibition of the nonenzymatic lipid peroxidation, induced by either ascorbic acid or ferrous sulfate. The flavonoid aglycones were more potent in their antiperoxidative action than their corresponding glycosides. Structure-activity analysis revealed that the flavonoid molecule with polyhydroxylated substitutions on rings A and B, a 2,3-double bond, a free 3-hydroxyl substitution and a 4-keto moiety, would confer upon the compound potent antiperoxidative properties.

Growth hormone and liver mitochondria: effects on phospholipid composition and fatty acyl distribution

Effects of growth hormone on phospholipid composition and fatty acyl distribution were studied in liver mitochondria of hypophysectomized rats. After hypophysectomy, only cardiolipin showed a 25% decrease. Its fatty acyl distribution, which consisted mainly of linoleic acid (55-60%) and oleic acid (20%), was unchanged. In phosphatidylcholine and phosphatidylethanolamine fractions the contents of docosahexaenoic and arachidonic acids were decreased with a concomitant increase in linoleic acid content. These changes could be accounted for by small but significant decreases in the activities of delta 9-desaturase (sucrose-induced), delta 5-desaturase and mitochondrial elongation enzymes. The activities of delta 6-desaturase, NADH cytochrome b5 ferri-reductase, cytochrome b5, NADH cytochrome c reductase and microsomal elongation enzymes remained virtually unchanged. Injection of bovine growth hormone daily for seven days restored cardiolipin and fatty acyl distribution and the enzyme activities. From these and other results, we conclude that growth hormone-dependent increase of respiratory activity of liver mitochondria may be partly mediated by the hormonal effects on membrane lipid distribution.

Evaluation of microsomes isolated from fresh and frozen myotomal tissue of Atlantic cod (Gadus morhua)

Microsomes were isolated from fresh and frozen myotomal tissue of Atlantic cod by two procedures. Electron microscopy revealed one method to yield microsomes containing greater quantities of myofibrillar debris than the other and this was reflected as reduced 5'-nucleotidase, acid phosphatase and succinate dehydrogenase marker enzyme activity. Overnight freezing of myotomal tissue did not affect the marker enzyme activity of microsomes isolated by either procedure. Morphological changes were observed among microsomes prepared from myotomal tissue retained for 8 weeks at -30 degrees C. Accordingly, 5'-nucleotidase was marginally elevated and acid phosphatase and succinate dehydrogenase activity reduced in comparison to fresh microsome preparations.

Interaction of PGBx and peroxides with cytochrome c and inhibition of lipid peroxidation

PGBx, a derivative of prostaglandin B1, stimulated the oxidation of cytochrome c in the presence of H2O2. Although the reaction was nonenzymatic, the apparent activation energies of 12 and 4.9 kcal above and below the transition at 21.5 degrees C were similar to those for oxidation by cytochrome oxidase. Depletion of H2O2 and oxidation of cytochrome c followed similar time courses, suggesting that H2O2 was consumed in the reaction. PGBx was a specific requirement, but organic hydroperoxides (ethyl and T-butyl) could replace H2O2. Low concentrations of ethyl or t-butyl hydroperoxide initially stimulated the oxidation of cytochrome c; this stimulation disappeared before completion of the oxidation, but was restored when the hydroperoxide concentration was renewed, suggesting that these hydroperoxides were probably also consumed in the reaction. The concentration of PGBx (8.9 microM) required for half-maximum stimulation of the oxidation was similar to the apparent Kd for its dissociation from oxidized cytochrome c (6.8 microM). Binding data and CD spectra suggested that a 1:1 complex between cytochrome c and PGBx was formed, altering the conformation of the heme region. This conformational change caused a shift of the Soret absorption peak from 410 to 406 nm and may be responsible for the enhanced oxidizability of the cytochrome c by H2O2. Cytochrome c inhibited lipid peroxidation in microsomes, an effect enhanced by the addition of PGBx. In the absence of lipid peroxidation, cytochrome c and PGBx stimulated NADPH oxidation via NADPH-cytochrome c reductase. Thus the inhibition of lipid peroxidation by cytochrome c and PGBx may involve either the removal of hydroperoxides or deviation of electron transfer away from the pathway for lipid peroxidation.

Modification of alkenyl chain profile in plasmalogens of rat heart mitochondria by dietary trielaidin

Effects of dietary trielaidin upon the alkenyl chain profile of plasmalogens were studied using heart mitochondria of rats fed a semi-purified diet containing 10% of fat supplement in which elaidic acid accounted for 69% of total fatty acids. Alkyl substituted dioxane (ASD) derivatives of the alkenyl groups of plasmalogens were prepared and analyzed by silver nitrate TLC and by GLC on different phases (BDS and OV-275). After two months of feeding the experimental diet, 40% of the ASD contained a trans-octadecenyl chain, suggesting that dietary elaidic acid was reduced in vivo to the corresponding alcohol and incorporated into plasmalogens. There was a simultaneous decrease in the percentage of ASD containing saturated chains, but the percentage of ASD substituted with cis-octadecenyl chains was not significantly affected. These observations suggested that elaidic acid may compete with saturated fatty acids, but not with cis-octadecenoic acids during the plasmalogen biosynthesis. Feeding trielaidin did not seem to have any significant influence on the relative proportions of plasmalogens, which accounted for 11-12%, on a phosphorus basis, of total heart mitochondria phospholipids.

The phospholipids associated with cytochrome c oxidase isolated from beef, dogfish and cod heart

Beef (Bos taurus), dogfish (Squalus acanthias) and cod (Gadus morhua) heart submitochondrial particles and cytochrome c oxidase (EC 1.9.3.1) were prepared. The head groups and side chains of the phospholipids associated with these samples were analysed quantitatively. The fish phospholipids contained a higher proportion of long chain poly-unsaturated fatty acids than was found in the beef samples. The enzyme fraction showed no head group or fatty acyl chain preference when compared with the composition of the whole tissue, implying no special lipid requirement for enzyme activity other than membrane fluidity. No cardiolipin was associated with the dogfish oxidase. The cod oxidase was inseparable from a CO-binding "b-type" cytochrome.

Phospholipids of Golgi subfractions determined with an enzymatic method

Golgi apparatus subfractions are still under consideration both for morphological, biochemical and functional characterization. In this note, we determined glycerophospholipids and Golgi subfractions from rat liver by a method that requires the complete enzymatic hydrolysis of phospholipids with phospholipase C from CL perfringens. The main advantages of this procedure are that small amounts of protein membranes are required, the precision and the rapidity.

Time course of changes in porcine myocardial phospholipid levels during ischemia. A reassessment of the lysolipid hypothesis

This study was performed to determine the early and delayed metabolic effects of myocardial ischemia on the major membrane phospholipids and to reassess the potential role of lysophospholipids in the genesis of malignant dysrhythmias induced by ischemia. Samples taken from in situ hearts before ant at various intervals up to 40 minutes after abrupt ligation of LAD were extracted by the classical Folch technique with modifications to avoid artifactual lysophospholipid production and losses. Following thin layer chromatography of lipid extracts, phospholipid fractions were quantified by phosphorus estimation and lysophospholipids by a more sensitive method employing gas liquid chromatography. The total phospholipid content with the exception of lysophospholipids remained essentially constant throughout the early phases of acute ischemia, but fell by 6 and 14% after 8 and 24 ours, respectively. At 8 minutes, lysophospholipid levels n ischemic myocardium were significantly increased by 60% compared to pre-occlusion controls in the ischemic zone and by 25% in post-occlusion controls. They changed little thereafter. The molecular species of lysophospholipids remained unchanged throughout the period of ischemia studied. The mole fraction of other phospholipids as well as their fatty acyl and aldehyde profiles also were unchanged. Despite significant elevations in lysophospholipids levels, their absolute quantities were very small (0.6% of total phospholipid P) and 15-fold smaller than that reported in vitro to simulate electrophysiological manifestation of ischemia. However, such small amounts in vivo, if produced in the microenvironment of certain membrane-bound enzymes along with acidosis, hypoxia, and fatty acids, could be potentially deleterious to cell functions.

Phospholipid requirements for the reconstitution of complex-III vesicles exhibiting controlled electron transport

Phospholipid requirements for the reconstitution of Complex-III vesicles exhibiting respiratory control (electron-transport control) were studied. Vesicles prepared from pure phosphatidylethanolamine gave maximal control ratios. Phosphatidylcholine alone did not support respiratory control, although these vesicles were capable of maintaining stable K+-diffusion gradients. Apparently Complex III cannot insert into a bilayer of phosphatidylcholine. Formation of mixed phosphatidylcholine/phosphatidylethanolamine (6:1, w/w) vesicles was sufficient, however, to allow Complex-III insertion and to restore respiratory control. Mixtures of acidic phospholipids with either phosphatidylethanolamine or phosphatidylcholine did not improve respiratory control over that obtained with pure phosphatidylethanolamine. Phosphatidylethanolamine from bovine heart mitochondria, soya beans or Escherichia coli was equally effective in reconstituting respiratory control, suggesting that the specificity is referable to the head group and not to the fatty-acid moiety.

Thyroid control over biomembranes. Liver-microsomal cytochrome b5 in hypothyroidism

Hypothyroid rats were prepared by thyroidectomy and maintenance on a low-iodine diet (group A); Group B was additionally pretreated with 0.5 mCi of 131I as NaI, given intraperitoneally. Liver microsomes obtained from hypothyroid and normal rats were compared. After fasting and refeeding on 20% sucrose solution, high levels of microsomal fatty-acyl-CoA delta 9-desaturase (as measured spectrophotometrically by the rate constants for cytochrome b5 reoxidation) were induced in all the normal animals, half of the group A hypothyroid rats, and none of the group B hypothyroid rats. Hypothyroidism did not change desaturase Arrhenius profiles or V and Km for NADH-cytochrome c reductase, but increased content of cytochrome b5. The inability of adequately hypothyroid rats to induce the delta 9-desaturase seems to be specific, in that injection of methylcholanthrene successfully induced microsomal benzpyrene monooxygenase activity and increased cytochrome b5 contents in hypothyroid animals. The defects in overall fatty acyl desaturation reported in hypothyroid animals [Landriscina, C., Gnoni, G. V. & Quagliariello, E. (1976) Eur. J. Biochem. 71, 135-143] are suggested to be due to deficiencies in the specific desaturase(s).

Surface properties of membrane systems: interaction of electrolyte and lipid with Ca2+ ionophores

When spread from organic solvents onto electrolyte solutions, the Ca2+ ionophores A23187 (I) and X537A (II) formed films with relatively high surface pressures potentials. Ionophores I had collapse pressures between 16 and 19 dynes/cm and nearly equal surface activity on distilled water and on 1000 mEq of either sodium chloride or calcium chloride. Film pressure did not reveal appreciable ion selectivity. However, the surface potential of I on calcium chloride solution was higher than that on sodium chloride, and the potential difference, delta(deltaV), of 40 mv was independent of the electrolyte concentration. In contrast, the ion selectivity of II was dependent on the electrolyte concentrations since the delta(deltaV) value between calcium chloride and sodium chloride was maximal (130 mv) on 1000 mEq and negligible on 500- and 2000-mEq salt solutions. The isotherms of phospholipid-ionophore films were markedly different from those of the individual components, although they revealed ionophore characteristics at low film pressures and phospholipid behavior at high film pressures. The magnitude of the surface potential indicated that dipalmitoyl phosphatidylcholine enhanced, whereas mitochondrial lipid and cardiolipin reduced, the preference of the two ionophores for Ca2+ over Na+. Since the ion selectivity was manifested most at both high electrolyte and high lecithin concentrations, the ionophore probably prefers the low dielectric constant of neutral lipid membranes to complex with the selected cation.

A precise localization of cardiolipin in plant cells

Cardiolipin and cytochrome aa3 contents of isolated plant cells (sycamore cells) and their purified mitochondria were measured. Since the cardiolipin/cytochrome aa3 ratio was the same in the intact cells and in the isolated mitochondria it was strongly suggested that cardiolipin is present only in the mitochondria. Furthermore, outer and inner mitochondria membranes of purified sycamore cells and mung bean hypocotyl mitochondria were separated and it was shown that cardiolipin is localized in the inner mitochondrial membrane.

Surface properties of membrane systems: interaction of ketamine with monomolecular films of ganliosides and mitochondrial lipids

Ketamine solutions did not form a film (pi=0) but had an appreciable surface potential (delta V=500 mv), indicating a significant array of +/- oriented charge dipoles at the air-water interface, as opposed to calcium chloride solutions whose delta V was zero. The delta V values of ganglioside films spread on the aqueous phase varied in the order water less than sodium chloride less than calcium chloride less than ketamine hydrochloride. At equivalent concentrations, calcium chloride was 500 times as effective as sodium chloride, and ketamine at the clinical concentrations of 10-20 microgram/ml (36-72 micrometer) was 6000 times as effective as calcium chloride in raising the surface potential of gangliosides; the delta V effect with mitochondrial lipid was in the reverse order; water less than sodium chloride = ketamine hydrochloride less than calcium chloride. This calcium-ketamine inversion indicates a unique specificity of ketamine for gangliosides. Since ketamine acts on the brain and did not affect mitochondrial respiration, the surface potential data suggest that part of the mechanism of action of ketamine could be its interaction with synaptic surfaces and, specifically, with the sialic acid of gangliosides and/or glycoproteins present on the synaptic membrane surface.

Fatty acid pattern and cholesterol in skeletal muscle of men aged 22 to 73

In order to examine the relationship between fatty acid distribution of skeletal muscle membranes and age, a needle biopsy was performed on the vastus lateralis muscle of 20 healthy, non-obese males, ranging in age from 22 to 73 years. The muscle sample was homogenized, centrifuged at 100,000 x g, and the resulting pellet was saponified and acidified. The fatty acids and cholesterol were removed by a single hexane extraction and analyzed by gas--liquid chromatography with flame ionization detection. All subjects regardless of age had no consistent differences in the fatty acid profiles and cholesterol composition in the tissue. Correlation coefficients indicated no significant relationship between the age of the individual and any of the analyzed lipids. The results of this study indicated that aging may not be reflected by gross changes in the composition of structural lipids in the cell.

Calcium-dependent lipolytic acyl-hydrolase activity in purified plant mitochondria

Ageing of isolated potato mitochondria induced by CaCl2 resulted in rapid enzymatic hydrolysis of the membrane phospholipids with the liberation of free fatty acids. The enzyme responsible for this effect was identified as a membrane bound lipolytic acyl-hydrolase which was unmasked by CaCl2. The presence of this lipolytic acyl-hydrolase induced severe functional impairments in the mitochondrial oxidative and phosphorylative properties.

Electrogenesis from an ATPase-ATP-sodium pseudo pump

The short circuit current and the open circuit voltage responses of membranes to ATP, which have been attributed to membrane ATPase acting as a sodium pump, have been reproduced not only in a lipid membrane containing solubilized ATPase but also in membranes formed of the phospholipids contained in ATPase. The response is greatest with cardiolipin, but occurs with other acidic phospholipids. This observation of electrogenesis without hydrolysis is a surface phenomenon probably due to the alignment of ATP on the phospholipid by ion association at its interface with the water phase. The finding constitutes a precaution for interpreting studies of membrane Na-K-ATPase or for its incorporation into an artificial membrane. The substances necessary for electrogenesis are present at the mitochondrial membrane, and the particular orientation of the ATP on the phospholipids in vitro suggests a role for this ion association in the function of Na-K-ATPase.