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Biomedical subjects

R R Brenner

Publications and source records attributed to R R Brenner.

At least 109 records · Page 6Linked to original sources
PubMed1980

Effect of epinephrine and dibutyryl cyclic AMP on delta 5-desaturation activity of rat liver microsomes.

The effect of epinephrine and dibutyryl cyclic AMP on the oxidative desaturation of [1-14C]-eicosatrienoic acid to arachidonic acid of rat liver microsomes has been studied. Epinephrine, at a dose of 1 mg/kg/body weight, produced a significant decrease on delta 5-desaturation activity 3 hr after the injection. This effect was maintained up to 12 hr and reached the control values 48 hr after the hormone administration. Dibutyryl cyclic AMP treatment for 24 hr (5 mg/8 hr/100 g body weight) also produced a significant decrease of the conversion of eicosatrienoic acid to arachidonic acid in rat liver microsomes. The effect of epinephrine on delta 5-desaturation activity was postulated to be evoked through an increase of the intracellular concentration of cyclic AMP.

8,11,14-Eicosatrienoic Acid↗
PubMed1980

Effect of ethanol administration on fatty acid desaturation.

The effect of ethanol on the fatty acid desaturation by rat liver has been studied using liquid diets of different composition. Acute ethanol administration increased triacylglycerols of total liver lipids, but did not modify significantly the lipidic composition of microsomes. The delta 6 and delta 5 desaturases were inhibited by ethanol whereas the delta 9 desaturase and fatty acid synthetase were apparently modified only by diet composition. NADH-cytochrome (cyt.) c reductase was partially inhibited, whereas NADH-cyt. b5 reductase remained practically unaltered and NADPH-cyt. c reductase activity was enhanced. Decreased electrons supplied by the microsomal cyt. b5 electron transport chain would not be the reason for the inhibition of delta 6 and delta 5 desaturases by ethanol.

Animals↗
PubMed1980

Effect of temperature on the structure of rat liver microsomes studied by electron spin resonance, fluorescence and activity of enzymes involved in fatty acid biosynthesis.

The structural properties of rat liver microsomes were studied by physical and kinetic methods. The microsomes and the lipids extracted from the microsomes were labeled with 16-doxyl-stearic acid- and N-phenyl-1-naphthylamine. The electron spin resonance spectra and the fluorescence intensities were respectively determined at different temperatures from approximately 10 to 40 C. Both methods suggested the absence of a transition temperature indicative of a phase change in the bulk of the lipids of the microsomes in the temperature range studied. The fluidity of the lipid bilayer increased smoothly with the temperature. The Arrhenius plots of the NADH-ferricyanide reductase, NADH-cyt.c reductase, delta 9 desaturase, delta 6 desaturase and palmitic elongation to stearic acid also indicated the absence of a detectable change of phase from crystalline to liquid crystalline in the boundary lipids of these enzymes from 10 C to 40 C. The transference of electrons from the NADH-cyt.b5 reductase to the cyt.b5 is the rate limiting step in the first parts of the electron transport chain. However, the delta 9 desaturase is the rate limiting step of all the series of reactions involved in the delta 9 fatty acid desaturation. Similar conclusions may be extended to the delta 6 desaturation of fatty acids. The physical state of the lipids surrounding the desaturating system would be different from boundary lipids of the cyt.P450 system.

Animals↗
PubMed1980

Effect of polyunsaturated fatty acids of the alpha-linolenic series in the lipid composition of rat testicles during development.

The effect of 22:6 omega 3 acid provided by dietary fish oil on the lipids composition of rat testes and liver during the development of the germinal tissue, was investigated. Results were compared to those obtained in animals fed on sunflower seed oil (linoleate) and methyl palmitate. At 7 and 9 weeks of age, both fish oil and methyl palmitate evoked a decrease of phosphatidyl-choline and ethanolamine and an increase of triacylglycerols. However, only in the group of rats administered with omega 6 or omega 3 acids and not in the palmitate group, the maturation of germinal epithelium was normal. It is suggested, as in a previous work, that 22:6 omega 3 may functionally replace 22:5 omega 6 in rat germinal tissue.

Age Factors↗
PubMed1980

[Biochemistry of the cyclic evolution of Triatoma infestans (Vinchuca). III. Dynamics of the incorporation of fatty acids in lipids].

More than 80% of total lipids of Triatoma infestans are triacylglycerols and only 3.7% and 4.0% are phosphatidyl-ethanolamine and phosphatidylcholine, whereas the diacylglycerols are 0.2%. However in hemolymph that contains 6.8 mg of lipids per ml predominate the phospholipids and there are approximately 22% of diacylglycerols with very little triacylglycerols. Therefore these diacylglycerols may play an important function in fatty acid transport since they incorporate in a few minutes injected 1 14C oleate. The radioactivity is later on transferred to the choline and ethanolamine phospholipids and then to the energy stores represented by the triacylglycerols.

Animals↗
PubMed1980

[Biochemistry of the cyclic evolution of Triatoma infestans (Vinchuca). IV. De novo biosynthesis of lipids in fat body and testicles].

The de novo biosynthesis of lipids by isolated fat bodies and testicles of Triatoma infestans was demonstrated by incubation with 1 14C sodium acetate. The fat body synthetized preferentially triacylglycerols but the label was also found in phospholipids. When hemolymph was added to the medium the label found in diacylglycerols was largely increased. In the testicles the label was preferentially incorporated to the phospholipids and little was found in diacylglycerols and triacylglycerols.

Acetates↗
PubMed1979

Fatty acid metabolism in the calanoid copepod Paracalanus parvus: 1. Polyunsaturated fatty acids.

The metabolic fate of radioactive linoleate and alpha-linolenate administered to the South Atlantic copepod Paracalanus parvus was studied. The wild copepod was able to incorporate the labeled acids dissolved in seawater. The radioactive linoleate was elongated to 20:2omega6 and 22:2omega6 and desaturated by a delta6 desaturase to 18:3omega6. alpha-Linolenate was also desaturated by a delta6 desaturase to 18:4omega3 and elongated to 20:3omega3. The copepod was able to convert alpha-18:3 to 20:5omega3 and 22:6omega3.

Animals↗
PubMed1979

Fatty acid metabolism of the calanoid copepod Paracalanus parvus: 2. Palmitate, stearate, oleate and acetate.

The de novo biosynthesis of fatty acids in the wild, calanoid copepod Paracalanus parvus was studied. The incubation of labeled acetate proved the de novo biosynthesis of saturated and monounsaturated even fatty acids from 14 to 20 carbons and the 22:1 acid. Saturated and monounsaturated uneven fatty acids from 15 to 21 carbons were also synthesized. The copepod could not synthesize linoleic and alpha-linolenic acids. By administration of [1-14C]palmitate, [1-14C]stearate and [1-14C]oleate, it was possible to elucidate the general pattern of the de novo biosynthesis of fatty acids in the wild P. parvus.

Acetates↗
PubMed1979

Lipid binding properties of a factor necessary for linoleic acid desaturation.

Suspension and centrifugation of crude microsomes of rat liver in low ionic strength solution separated a soluble protein fraction that is necessary for the full activity of the linoleic acid desaturase. The fraction partially purified through Sephadex G-150 still retains lipids which are mainly constituted by phosphatidycholine. Linoleic acid predominates in the fatty acid composition. By NaCl gradient centrifugation and electrophoresis in gelatinized cellulose acetate, the factor behaves like a lipoprotein. The factor binds linoleic acid and linoleyl-CoA that are desaturated to gamma-linolenic acid when incubated with washed microsomes. Albumin does not replace the factor.

Animals↗
PubMed1979

[Biochemistry of the developmental cycle of Triatoma infestans (Vinchuca). 2. Biosynthesis of fatty acids].

The biosynthesis of fatty acids in Triatoma infestans was studied in all the nymph stages and adult insects by feeding experiments with 1-14C acetate. In other experiments labeled acetate, 1-14C palmitate or 1-14C stearate were injected in the abdomen. In another group of experiments the abdominal non intestinal tissue of adult insects was homogenized and the supernatants of 10 000 X g and 105 000 X g were incubated with 1-14C acetyl-CoA. The incorporation of the labeling in the fatty acids was studiel by gas liquid radiochromatography. It was proved that the supernatant of 105 000 X g possessed a fatty acid synthetase able to synthesize de novo the saturated fatty acids of 10 to 18 carbons with a maximal yield in the myristic and palmitic acids. The fatty acid synthetase was active from Nymph L stage. The supernatant of 10 000 X g was able to synthesize fatty acids tentatively identified as eicosenoic and eicosadienoic acids. The T. infestans has also an enzyme that elongated palmitate to stearate. In the fraction precipitable between 10 000 X g and 105 000 X g was apparently present a desaturating enzyme that converts saturated to monoethylenic acids. The enzyme was apparently only active from Nymph II stage.

Acetates↗
PubMed1979

Effect of glucocorticoids on the oxidative desaturation of fatty acids by rat liver microsomes.

The effect of glucocorticoids on the oxidative desaturation of fatty acids by liver microsomal preparations of rats has been studied. Hydrocortisone produced a significant decrease in the conversion of [1-14C]linoleic acid to gamma-linolenic acid and [1-14C]eicosa-8, 11, 14-trienoic acid to arachidonic acid. Triamcinolone and dexamethasaone were more active than hydrocortisone in depressing delta 6 and delta 5 fatty acid desaturating activity in liver microsomes. The glucocorticoids evoked a maximal response approximately 24 hr after admission. Palmitic acid conversion to palmitoleic acid showed no statistically significant changes by any of the glucocorticoids. The mechanism of action of glucocorticoids is apparently different from other hyperglycemic hormones that produce similar effects.

Animals↗
PubMed1978

Effect of catecholamines and beta-blockers on linoleic acid desaturation activity.

The effect of catecholamines and adrenergic blocking agents on the oxidative desaturation of linoleic acid in rat liver microsomes was studied. Epinephrine (1 mg/kg/body weight) produced a significant decrease on the conversion of [1-14C]linoleic acid to gamma-linolenic acid. The effect of epinephrine was blocked by single injections of the beta blockers propranolol (10 mg/kg body weight) or dichloroisoproterenol 30 min before the hormone treatment. Isoproterenol (100 microgram/kg body weight) produced a significant decrease on the activity of the linoleyl-CoA desaturase. The effect of the catecholamines was postulated to be mediated through beta receptors by an enhancement of the intracellular levels of cyclic AMP.

Adrenergic beta-Antagonists↗
PubMed1978

[Biochemistry of the life cycle of Triatoma infestans (vinchuca). 1. Lipids and fatty acids composition].

The lipid composition of Triatoma infestans (Vinchuca) was studied by thin layer chromatography and gas lipid chromatography. The main fatty acids found were oleic and palmitic followed by stearic, palmitoleic and linoleic. Only very small amounts of arachidonic and docosahexenoic acids were present. The composition depended on the incorporation of the fatty acids of the blood ingested, but it was modified in a small extent by the insect. The fatty acid composition changed during the development of the eggs to the following stages. The main lipids found were triacylglycerol, phósphatidyl ethanolamine, phosphatidyl choline, cholesterol esters and cholesterol. The analysis of the fatty acid composition of phosphatidyl ethanolamine and phosphatidyl choline spots showed the presence of little amounts of palmityl and stearyl aldehydes, suggesting the existence of the corresponding plasmalogens.

Animals↗
PubMed1977

Incorporation and metabolism of stearic, oleic, linoleic and alpha-linolenic acids in minimal deviation hepatoma 7288 C cells.

Minimal Deviation Hepatoma 7288 C cells were cultured in confluent layer with labeled stearic, oleic, linoleic and alpha-linolenic acids. The kinetics of incorporation and conversion to higher homologs was studied. The maximum amounts incorporated in nmoles per mg of cellular protein for stearic, oleic, linoleic and alpha-linolenic acids were 39, 115.6, 90 and 230 respectively. alpha-linolenic acid was converted to octadeca-6,9,12,15-tetraenoic acid (18:1), eicosa-11,14,17-trienoic acid (20:3), eicosa-8,11,14,17 and 5,11,14,17-tetraenoic acids (20:4) and eicosa-5,8,11,14,17-pentaenoic acid (20:5), and also to myristic, palmitic, palmitoleic, stearic and oleic acids. By a mathematical approach, the endogenous pool size of alpha-linolenic acid available for conversion to eicosa-5,8,11,14,17-pentaenoic acid, were calculated. Both values decreased when the cells were preincubated with unlabeled alpha-linolenic acid.

Carcinoma, Hepatocellular↗
PubMed1977

Specificity of delta 6 desaturase--effect of chain length and number of double bonds.

Rat liver microsomes contain a delta 6 desaturase that is active not only with the unsaturated acids of 18 carbons: oleic, linoleic and alpha-linolenic but also with similar acids of 20 carbons with the double bonds in delta 9, 12 and delta 12, 15. The rate of the reaction increases with the number of double bonds of the substrate but the acids of 20 carbons are less desaturated than the corresponding homologs of 18 carbons proving that the enzyme recognizes the number and position of double bonds as well as the chain length. The investigation of the inhibitory effect of different poly-unsaturated acids suggests that the acids would not only bind to the enzyme by means of the -CoA but also by other parts of the molecule different of the active center. The geometry of the molecule would be a substantial factor.

Animals↗