Biomedical subjects

S Clejan

Publications and source records attributed to S Clejan.

At least 55 records · Page 3Linked to original sources

PubMed1987

Incorporation of specific exogenous fatty acids into membrane lipids modulates protonophore resistance in Bacillus subtilis.

Attempts to manipulate the level of C16:1 fatty acids in membrane phospholipids were made by using Bacillus subtilis and its protonophore-resistant mutants to test the hypothesis that C16:1 fatty acid levels relate to the bioenergetic properties of the mutant strains. Growth of the three mutants in the presence of palmitoleic acid restored the level of C16:1 fatty acids in the membrane lipids to somewhat above those found in the wild type. The palmitoleic acid was preferentially incorporated into diphosphatidylglycerol (cardiolipin) and phosphatidylethanolamine and was associated with increased levels of these phospholipids. These membrane preparations showed no increase in the levels of free fatty acids. The increase in C16:1 fatty acids achieved by growth in the presence of palmitoleic acid was accompanied by secondary changes in membrane lipids as well as a pronounced diminution in the protonophore resistance of growth and ATP synthesis. Other membrane-associated properties that had been observed in these mutants, e.g., elevated ATPase levels, were not altered coordinately with protonophore resistance and C16:1 fatty acid levels. Growth of the wild type in the presence of palmitic acid caused a modest elevation of the C16:0 of the membrane lipids and a modest increase in the protonophore resistance of growth and ATP synthesis. Growth of the wild type at elevated temperatures, in the absence of fatty acid supplementation, also enhanced its resistance to protonophores. The results support the hypothesis that specific changes in membrane lipid composition underlie the bioenergetic changes associated with protonophore resistance.

Adenosine Triphosphatases↗

PubMed1987

Kinetics of cholesterol and phospholipid exchange between mycoplasma membranes and lipid vesicles.

The following modifications in the lipid composition of Mycoplasma gallisepticum or M. capricolum membranes led to changes in the rates of [14C]cholesterol and [14C]phospholipid exchange between cell membranes and an excess of small unilamellar vesicles: 1) increase in the cholesterol/phospholipid molar ratio from 0.25 to 0.92; 2) incorporation of synthetic, cross-linked phosphatidylethanolamine (PE) derivatives, 3) incorporation of sphingomyelin (SPM); and 4) increase in the phosphatidylglycerol/cardiolipin ratio of M. capricolum cell membranes by supplementing the growth medium with 0.5 mM CaCl2 CaCl2, and decrease in this ratio by supplementing the growth medium with 0.5 mM CaCl2 and 20 micrograms/ml egg phosphatidylcholine or with isopalmitic acid. The rates of radiolabeled lipid exchange decreased when the content of cholesterol, cross-linked PE, or SPM increased, indicating an inverse correlation between exchange rate and membrane lipid order. This is consistent with an exchange mechanism that involves the slow dissolution of the lipid from the surface of the donor particle. Lipidic particles appeared in trypsin-treated M. capricolum membranes obtained from cells grown with both Ca2+ and PC, whereas the hexagonal-II phase appeared in membranes from cells grown with Ca2+. Cholesterol and phospholipid exchange rates were enhanced under the conditions in which the bilayer structure was destabilized by transitional states between the lamellar and hexagonal-II phases. Thus, mycoplasmas are well suited for examination of the influence of membrane lipid composition on rates of lipid exchange between membranes.

Calcium Chloride↗

PubMed1986

Effect of growth hormone on fatty acid oxidation: growth hormone increases the activity of 2,4-dienoyl-CoA reductase in mitochondria.

The effect of growth hormone on the beta-oxidation of saturated and unsaturated fatty acids was studied with mitochondria isolated from control rats, hypophysectomized rats, and hypophysectomized rats treated with growth hormone. Rates of respiration supported by polyunsaturated fatty acylcarnitines, in contrast to rates observed with palmitoylcarnitine or oleoylcarnitine, were slightly lower in hypophysectomized rats than in normal rats, but were higher in hypophysectomized rats treated with growth hormone. The effects were most pronounced with docosahexaenoylcarnitine, the substrate with the highest degree of unsaturation. Since uncoupling of mitochondria with 2,4-dinitrophenol resulted in lower rates of docosahexaenoylcarnitine-supported respiration, while substitution of ATP for ADP yielded higher rates, it appears that energy is required for the effective oxidation of polyunsaturated fatty acids. Growth hormone treatment of hypophysectomized rats caused a threefold increase in the activity of 2,4-dienoyl-CoA reductase or 4-enoyl-CoA reductase (EC 1.3.1.34) in mitochondria, but not in peroxisomes. The activities of other beta-oxidation enzymes remained virtually unchanged. Rates of acetoacetate formation from linolenoylcarnitine, but not from palmitoylcarnitine, were stimulated by glutamate in mitochondria from hypophysectomized rats and hypophysectomized rats treated with growth hormone. All data together lead to the conclusion that the mitochondrial oxidation of highly polyunsaturated fatty acids is limited by the availability of NADPH and the activity of 2,4-dienoyl-CoA reductase which is induced by growth hormone treatment.

Acetoacetates↗

PubMed1986

The effect of cholesterol on glycerophosphono- and glycerophosphinocholines. Permeability measurements in lipid vesicles.

The kinetics of spontaneous chloride ion efflux and valinomycin-mediated rubidium-86 efflux from vesicles prepared from synthetic phospholipids with carbon-phosphorus linkages were investigated at temperatures above the gel-to-liquid-crystalline phase transition. The rate constants for the movement of chloride and rubidium ions were reduced by incorporation of cholesterol into bilayers of phosphono- and phosphinocholines. Nonisosteric phosphonolipids in which the oxygen was removed from the glycerol side of phosphorus without substitution by a methylene group interacted less with cholesterol than the analogous isosteric derivatives, as judged from the magnitude of the decrease in the rate constants for chloride and rubidium ion efflux. The experiments reported in this study suggest that steric factors in the glycerol side of the phosphorus function are important in phosphatidylcholine-cholesterol interaction. However, the oxygen atom on the choline side of the phosphorus in the phosphatidylcholine molecule is not required for strong phosphatidylcholine-cholesterol interaction, since isosteric glycerophosphinocholines interacted as well as the corresponding isosteric glycerophosphonocholines. Furthermore, steric requirements on the choline side of phosphorus are not important in this interaction since phosphinates whose head-group structures are -P(O-)CH2CH2N+(CH3)3 and -P(O-)CH2CH2CH2N+(CH3)3 interacted equally well with cholesterol, as estimated by these permeability studies.

Chlorides↗

PubMed1986

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.

Animals↗

PubMed1986

Long-term study of gammopathies. Clinically benign cases showing transition to malignant plasmacytomas after long periods of observation.

Since 1968, our Clinical Chemistry laboratory has been performing protein electrophoresis on sera of patients with total protein levels of over 85.0 g/L and under 55.0 g/L. Monoclonal gammopathies were found in 534 cases. Immunoelectrophoresis was carried out using antisera to the heavy chains gamma, alpha, mu, delta, and epsilon, and to the light chains kappa and lambda. Urine from these patients was tested for Bence-Jones protein. Records and smears, when available, were examined for clinical or hematologic evidence of multiple myeloma and other lymphoid malignancies. Sixty-five percent of these 534 cases were referred to the laboratory with a provisional diagnosis of plasmacytoma but 35% were not clinically suspected. Twenty-two cases with gammopathy, but no clinical or hematologic symptoms of plasma cell dyscrasia, were selected and followed up. Eight of these patients (36%) had converted to malignancy by the end of ten years. These results show the value of screening for abnormal proteins and the need for a long-term follow-up in such patients, prior to diagnosis of plasma cell dyscrasia.

Adult↗

PubMed1986

Membrane lipid composition of obligately and facultatively alkalophilic strains of Bacillus spp.

The membrane lipids from two obligately and two facultatively alkalophilic strains of Bacillus spp. were characterized in a comparative study that included B. subtilis. Preparations of membrane lipids were made from pH 10.5-grown cells of all of the alkalophiles and from pH 7.5- or 7.0-grown cells of the two facultative strains and B. subtilis. The two obligate alkalophiles contained high ratios of membrane lipid to membrane protein, and the lipid fraction contained a high proportion of neutral lipid. These characteristics are probably not prerequisites for growth at very high pH since one or another of the facultative strains failed to show these properties at high pH. All of the alkalophiles contained appreciable amounts of squalene and C40 isoprenoids. Among the polar lipids, the alkalophiles all contained high concentrations of anionic phospholipids, including phosphatidylglycerol and especially large amounts of cardiolipin; phosphatidylethanolamine was the other major phospholipid. Small amounts of bis(monoacylglycero)phosphate were found in most, but not all, of the alkalophile preparations. Glycolipids and phosphoglycolipids were absent. The fatty acid composition of the total phospholipid and individual fractions revealed two features that distinguished between the obligate and facultative strains. Membranes from the obligately alkalophilic species contained a high concentration of branched-chain fatty acids, comparable to that in membranes from B. subtilis, as well as a relatively high content of unsaturated fatty acids. By contrast, the facultatively alkalophilic strains contained almost no unsaturated fatty acids and a lower concentration of branched-chain fatty acids than either the obligate alkalophiles or B. subtilis.

Bacillus↗

PubMed1986

Growth hormone and liver mitochondria: time course of effects on respiration and fatty acid composition in hypophysectomized rats.

The time course of the effects of GH on state 3 respiration and fatty acid composition of liver mitochondria was investigated up to 48 h after an injection of bovine GH to hypophysectomized rats. The respiratory rate increased significantly by 12 h, whereas the docosahexaenoic acid level, the total unsaturation index, and the ratio of arachidonic acid to linoleic acid of total phospholipids increased as early as 4 h after the hormone injection. A linear association was found between the respiratory rate and the three measures of fatty acid composition. It is concluded that the hormonal effects on respiration may be partly mediated through changes in fatty acid composition, which have an additive effect on increased synthesis of proteins and respiratory chain components.

Animals↗

PubMed1985

Movement of cholesterol between vesicles prepared with different phospholipids or sizes.

The rates of exchange of [4-14C]cholesterol between lipid vesicles prepared with different phospholipids and with different sizes have been measured. The first-order rate constants were higher using vesicles prepared from phosphatidylcholines with highly branched or polyunsaturated fatty acyl chains than with saturated diacyl or di-O-alkyl chains. The rate measurements indicate that the affinity of cholesterol for phospholipid does not vary significantly on change of the type of linkage (ether or ester) in phosphatidylcholine (PC) or of the positions of the fatty acyl chains in 1,2-diacyl-PC bearing one saturated and one unsaturated chain; furthermore, egg phosphatidylglycerol and egg phosphatidylethanolamine appear to have comparable affinities for cholesterol. However, the molecular packing in the bilayer and nearest-neighbor interactions involving cholesterol appear tightened more by N-palmitoylsphingomyelin than by dipalmitoyl-PC; on incorporation of 44 mol % of these phospholipids (which have the same fatty acyl chain composition) into either small or large unilamellar vesicles prepared with egg phosphatidylglycerol, the exchange rates were strikingly slower when the donor species contained sphingomyelin compared with PC. The rate of cholesterol exchange was 100% faster with small unilamellar vesicles than with large unilamellar vesicles as donors, suggesting that the looser packing in the highly curved small vesicles facilitates cholesterol desorption. The cholesterol exchange rate did not vary with the size of the acceptor vesicles, which indicates that desorption is the rate-limiting step in the exchange process in the presence of excess acceptors.

Calcium↗

PubMed1985

Kinetics of cholesterol and phospholipid exchange from membranes containing cross-linked proteins or cross-linked phosphatidylethanolamines.

Mono- and dipalmitoylphosphatidylethanolamine derivatives have been synthesized and used to evaluate the role of cross-links between the amino groups of two phospholipid molecules in the rate of cholesterol movement between membranes. Incorporation of the cross-linked phospholipids into small unilamellar vesicles (the donor species) decreased the rate of spontaneous cholesterol exchange with acceptor membranes (small unilamellar vesicles or Mycoplasma gallisepticum cells). These results suggest that the cross-linking of aminophospholipids by reactive intermediates, which may be one of the degenerative transformations associated with peroxidation of unsaturated lipids and cellular aging, can inhibit cholesterol exchangeability in biological membranes. The rates of spontaneous [14C]cholesterol and protein-mediated 14C-labeled phospholipid exchange from diamide-treated mycoplasma and erythrocyte membranes have also been measured. The formation of extensive disulfide bonds in the membrane proteins of M. gallisepticum enhanced the 14C-labeled phospholipid exchange rate but did not affect the rate of [14C]cholesterol exchange. The rates of radiolabeled cholesterol and phospholipid exchange between erythrocyte ghosts and vesicles were both enhanced (but to different extents) when ghosts were treated with diamide. These observations suggest that diamide-induced oxidative cross-linking of sulfhydryl groups in membrane proteins does not lead to random defects in the lipid domain.

Cholesterol↗

PubMed1985

Rates of amphotericin B and filipin association with sterols. A study of changes in sterol structure and phospholipid composition of vesicles.

The influence of structural modifications in sterols and phospholipids on the rate of polyene antibiotic-sterol interaction was studied. For filipin and amphotericin B association with sterols in vesicles, a preferential interaction was found with sterols whose side chain length is close to that of cholesterol. Introduction of trans double bonds into the sterol side chain did not alter the rate of interaction in vesicles. The delta 7-bond of the sterol appears to be of critical importance in amphotericin B-sterol interaction, whereas the delta 5-bond is not essential. These observations are relevant to the well-known effects of amphotericin B on cell membranes containing ergosterol compared with those containing cholesterol. The dependence of the rates of sterol-polyene antibiotic interaction on the phospholipid composition of the vesicles indicates that phospholipid vesicles may be an inadequate model for reaching a comprehensive understanding of the effects exerted on biological membranes by these agents.

Amphotericin B↗

PubMed1984

Decreases in rates of lipid exchange between Mycoplasma gallisepticum cells and unilamellar vesicles by incorporation of sphingomyelin.

The kinetics of exchange of radiolabeled cholesterol and phospholipids between Mycoplasma gallisepticum cells and an excess of small unilamellar phospholipid/cholesterol vesicles were studied using cells enriched with different phospholipid classes but the same fatty acyl content. The rates of the rapidly exchanging cholesterol and phospholipid pools were markedly slower in sphingomyelin-containing cells than in phosphatidylcholine-containing cells. The decreased rates of spontaneous cholesterol and protein-mediated phospholipid exchange from the outer leaflet of the mycoplasma membrane are attributed to stronger interactions between sphingomyelin and cholesterol than between phosphatidylcholine and cholesterol. On the other hand, an increase in cholesterol exchange rate was found on incorporation of a cyclopentano-1,3-diacyl-2-phosphatidylglycerol, which interacts less with cholesterol than does the analogous glycero-1,2-diacyl-sn-3-phosphatidylglycerol.

Cell Membrane↗

PubMed1984

Influence of cholesterol on bilayers of ester- and ether-linked phospholipids. Permeability and 13C-nuclear magnetic resonance measurements.

13C-NMR and permeability studies are described for sonicated vesicles of phosphatidylcholines bearing two 16-carbon saturated hydrocarbon chains with (a) one ether linkage at carbon 1 (3) or 2 of glycerol and one ester linkage at carbon 2 or 1 (3) of glycerol; (b) two ether linkages and (c) two ester linkages at carbons 1 (3) and 2 of glycerol. The results of 13C-NMR relaxation enhancement measurements using cholesterol enriched with 13C at the 4 position indicate that no significant relocation of the cholesterol molecules takes place in the bilayer when a methylene group is substituted for a carbonyl group in phosphatidylcholine. The 4-13C atom of cholesterol undergoes similar fast anisotropic motions in diester- and diether -phosphatidylcholine bilayers, as judged by spin-lattice relaxation time measurements in the liquid-crystalline phase; although the fast motions are unaltered, linewidth and spin-spin relaxation time measurements suggested some restriction of the slow motions of cholesterol molecules in bilayers from phosphatidylcholines containing an O-alkyl linkage at the sn-2 position instead of an acyl linkage. At temperatures above the gel to liquid-crystal phase transition, the kinetics of ionophore A23187-mediated 45Ca2+ efflux from vesicles prepared from each type of phosphatidylcholine molecule were the same; the kinetics of spontaneous carboxyfluorescein diffusion from diester- and diether -phosphatidylcholine vesicles were the same, whereas mixed ether/ester phosphatidylcholine molecules gave bilayers which are less permeable. The rate constants were reduced on cholesterol incorporation into the bilayers of each type of phosphatidylcholine molecule. The reductions were not statistically significant for 45Ca2+ release. The rate constants for carboxyfluorescein release were also reduced by cholesterol to the same extent in vesicles from diester-, diether -, and 1-ether, and 1-ether-2-ester-phosphatidylcholines; however, a smaller reduction was noted in bilayers from the 1-ester-2-ether analog. The results provide further evidence that there are no highly specific requirements for ester or ether linkages in phosphatidylcholine for cholesterol to reduce bilayer permeability. This is a reflection of the fact that in both diester- and diether -phosphatidylcholine bilayers, the 4-13C atom of cholesterol is located in the region of the acyl carboxyl group or the glyceryl ether oxygen atom.

Cholesterol↗

PubMed1984

Kinetics of cholesterol and phospholipid exchange between Mycoplasma gallisepticum cells and lipid vesicles. Alterations in membrane cholesterol and protein content.

The kinetics of exchange of radiolabeled cholesterol and phospholipids between intact Mycoplasma gallisepticum cells and unilamellar lipid vesicles were investigated over a wide range of cholesterol/phospholipid molar ratio. The change in cholesterol/phospholipid molar ratio was achieved by adapting the sterol-requiring M. gallisepticum to grow in cholesterol-poor media, providing cells with decreased unesterified cholesterol content. At least 90% of the cholesterol molecules in unsealed M. gallisepticum membranes underwent exchange at 37 degrees C as a single kinetic pool in the presence of albumin (2%, w/v). However, we observed biphasic exchange kinetics with intact cells, indicating that cholesterol translocation from the inner to outer monolayers was rate-limiting in the exchange process. Approximately 50% of the cholesterol molecules were localized in each kinetic pool, independent of the cholesterol/phospholipid molar ratio in the cells and vesicles. A striking change in the kinetic parameters for cholesterol exchange occurred between 20 and 26 mol % cholesterol; for example, when the cholesterol/phospholipid molar ratio was decreased from 0.36 to 0.25, the half-time for equilibration of the two cholesterol pools at 37 degrees C decreased from 4.6 +/- 0.5 to 2.5 +/- 0.1 h. Phospholipid exchange rates were also enhanced on decreasing the membrane cholesterol content. The ability of cholesterol to modulate its own exchange rate, as well as that of phospholipids, is suggested to arise from the sterol's ability to regulate membrane lipid order. Extensive chemical modification of the membrane surface by cross-linking of some of the protein constituents with 1,4-phenylenedimaleimide decreased the cholesterol exchange rate. Depletion of membrane proteins by treatment of growing cultures with chloramphenicol increased the cholesterol exchange rate, possibly because of removal of some of the protein mass that may impede lipid translocation. The observations that phospholipid exchange was one order of magnitude slower than cholesterol exchange and that dimethyl sulfoxide, potassium thiocyanate, and potassium salicylate enhanced the cholesterol exchange rate are consistent with a mechanism involving lipid exchange by diffusion through the aqueous phase.

Cholesterol↗

PubMed1984

Distribution and movement of sterols with different side chain structures between the two leaflets of the membrane bilayer of mycoplasma cells.

Mycoplasma gallisepticum was adapted to grow with delta 5-sterols modified in the aliphatic side chain, and stopped-flow kinetic measurements of filipin association were made to estimate the sterol distribution between the two leaflets of the membrane. Cholesterol derivatives with unsaturated side chains (desmosterol, cis- and trans-22-dehydrocholesterol, and cholesta-5,22E,24-trien-3 beta-ol) or an alkyl substituent (beta-sitosterol) were predominantly (86-94%) localized in the outer leaflet of the bilayer. However, cholesterol, 20-isocholesterol, and sterols with side chains of varying lengths (in the 20(R)-n-alkylpregn-5-en-3 beta-ol series where the alkyl group ranged from ethyl to undecyl) were distributed nearly symmetrically between the two halves of the bilayer. Kinetic measurements of beta-[14C]sitosterol and [14C]desmosterol exchange between M. gallisepticum cells and an excess of sonicated sterol/phosphatidylcholine vesicles confirmed the filipin-binding studies. More than 90% of these radiolabeled sterols underwent exchange at 37 degrees C with unlabeled sterols in vesicles over a period of 12-14 h in the presence of 2% (w/v) albumin. beta-[14C]Sitosterol exchange was characterized by biphasic exchange kinetics, indicative of two pools of sitosterol molecules in the cell membrane. Only a single kinetic pool was detected for [14C]desmosterol exchange. Stopped flow measurements of filipin binding to beta-sitosterol and stigmasterol also revealed an asymmetrical localization of these sterols in membranes of growing Mycoplasma. capricolum cells. When an early exponential culture of beta-sitosterol- or stigmasterol-adapted M. capricolum was transferred to a sterol-rich medium at 37 degrees C, approximately three-quarters of the beta-sitosterol or stigmasterol was localized in the outer leaflet after growth was continued for 6 h; in contrast, cholesterol was distributed symmetrically after about 1 h. The asymmetric localization of sterols with alkylated or unsaturated side chains suggests that growth-supporting sterols need not be translocated extensively into the inner leaflet of the bilayers of M. gallisepticum and M. capricolum.

Desmosterol↗

PubMed1983

Growth hormone receptors in lymphocytes of growth hormone-deficient children.

Human growth hormone was injected intravenously into 18 growth hormone-deficient children and growth hormone binding sites in lymphocytes were investigated. Fresh circulating lymphocytes had a low initial value for the binding of growth hormone to solubilized receptors (3.45 +/- 1.46%) but after growth hormone injection, the binding rapidly increased to 14.8 +/- 4.2% at 2 1/2 h and 8.7 +/- 1.8% at 5 h. The sharp increase in binding is due to increase in the number of binding sites. Two control children who received chorionic gonadotropin had no change in lymphocyte growth hormone receptors. The methodological differences between the present study and previous attempts to identify human growth receptors in lymphocytes were (1) lymphocytes were separated and disrupted with Triton X-100 as quickly as possible (to avoid error from receptor leaking out of the cell) and (2) the receptors were assayed at 2 1/2 h after growth hormone administration (previous studies were 12-24 h later). One possible explanation for the data is that growth hormone receptor from liver is taken up by lymphocytes and rapidly released again, thus, contributing to the hormonal receptor economy in humans.

Adolescent↗

PubMed1982

Effects of zinc deficiency and castration on fatty acid composition and desaturation in rats.

The effects of zinc deficiency and testosterone on fatty acid composition of plasma lipids and microsomes of liver, intestine and testes were studied. The activities of fatty acid desaturase (delta 6 and delta 5) in rat liver and testes were also measured. A significant decrease in the level of arachidonic acid was observed in plasma of normal rats fed the zinc-deficient diet. Castration significantly decreased arachidonic acid but increased 20:3 fatty acid, which is negligible in normal rats. Testosterone and zinc administration restored arachidonic acid to normal values. Zinc deficiency does not significantly change the fatty acid profile in liver, but castration decreased both arachidonic and 22:6 fatty acid. Intestinal mucosal microsomes showed that the predominant fatty acid in this tissue, palmitic acid, is independent of zinc status, whereas polyunsaturated fatty acids 18:2 and 20:4 were decreased by zinc-deficient diet or castration. Zinc deficiency sharply decreased 22:5 fatty acid and to some extent, other polyunsaturated fatty acids in testis microsomes. These changes in fatty acids are in agreement with increased delta 9 desaturation and decreased delta 5 desaturase activity. In testes, both delta 6 and delta 5 desaturase activities are decreased in zinc deficiency. It appears that zinc influences the conversion of linoleic to arachidonic acid, whereas testosterone influences delta 6 desaturase activity. The data suggest that zinc deficiency may be one of the important factors in the causation of polyunsaturated fatty acid deficiency, which, in turn, may induce serum hypertriglyceridemia.

Animals↗

PubMed1981

Influence of growth hormone and thyroxine on thermotropic effects of respiration and 1-anilino-8-naphthalene sulfonate fluorescence and on lipid composition of cardiac membranes.

The effects of hypophysectomy and subsequent administration of growth hormone and/or L-thyroxine on thermotropic properties of State 3 respiration (ADP-induced), cholesterol, phospholipid and fatty acid composition of phospholipid fraction were examined in myocardial mitochondria of rats. Temperature-dependence of 1-anilino-8-naphthalene sulfonate fluorescence was determined in vesicles prepared from lipids of heart mitochondria. Transition temperature obtained from the Arrhenius plots of respiration occurred at 21 and 24 degrees C for heart mitochondria of normal and hypophysectomized rats, respectively. Most notably, after hypophysectomy the rate of respiration was lower below 24 degrees C, but was progressively higher above that temperature when compared to normal rats. The energy of activation was 148 and 36% larger below and above the transition temperature, respectively. Growth hormone restored almost completely the energy of activation and respiratory rates to normal levels. Administration of L-thyroxine, with or without growth hormone, did not significantly change the rate of respiration but decreased the transition temperature to 17.7-17.9 degrees C. Lipid and phospholipid content, as well as percent distribution of phospholipids and their fatty acid composition were not statistically different among the different groups of rats. Only cholesterol content was increased after hypophysectomy. Administration of growth hormone and thyroxine did not significantly change the total unsaturation index of fatty acids, but growth hormone increased the content of arachidonic acid (20 : 4) by 70% but decreased the docosahexaenoic acid (22 : 6) three times which may have a beneficial effect on mitochondrial membranes. These and other results suggest that hormones exert different effects on subcellular organelles in different tissues, like heart and liver.

Anilino Naphthalenesulfonates↗