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Biomedical subjects

R R Brenner

Publications and source records attributed to R R Brenner.

At least 145 records · Page 8Linked to original sources
PubMed1975

Uptake and metabolism of exogenous eicosa-8,11,14-trienoic acid in minimal deviation hepatoma 7288 C cells.

Minimal deviation hepatoma 7288 C cells were cultured in Swim's medium containing 10% serum for 48 hr. The growth medium was replaced with serum free media containing different concentrations of [1-14C] eicosa-8,11,14-trienoic acid and the cells were incubated for 24 hr. Incorporation into cell lipids, oxidation to CO2, and desaturation to arachidonic acid were studied. The oxidation of the acid was very low. It was preferentially incorporated into the polar lipids of the cell. The incorporation depended on the number of cells and fatty acid concentration. Saturation of the cells with the acid was reached when 144.7 nmoles per mg of cellular protein were incorporated. The acid was desaturated readily to arachidonic acid. The nmoles of eicosatrienoic acid converted to arachidonic acid per mg of cellular protein were hyperbolic function of the acid incorporated. Maximal desaturation, 23 nmoles per mg of cellular protein, was reached when the cells were saturated with the acid. The calculations of the desaturation capacity and of the endogenous pool of eicosatrienoic acid available for desaturation in the cell are discussed.

8,11,14-Eicosatrienoic Acid↗
PubMed1975

Oxidative desaturation of alpha-linoleic, linoleic, and stearic acids by human liver microsomes.

The desaturation of stearic, linoleic, and alpha-linolenic acids by human liver microsomes were studied. The microsomes were isolated from liver biopsies obtained during operation. It was shown that human liver microsomes are able to desaturate 1-14-C-alpha-linoleic acid to octadeca-6,9,12,15,-telraenoic acid: 1-15-C-linoleic acid to gammalinolenic acid; and 1-14-C-stearic acid to oleic acid in the same system described in the rat. However, the desaturation activity obtained was low compared to other mammals. This effect was attributed to fasting, pre-medication, or the anaesthesia.

Adult↗
PubMed1975

Dietary and hormonal effects upon activity of "soluble" protein and particulate fraction of fatty acid desaturation system of rat liver microsomes.

Rat liver microsomes were extracted with a buffered 0.15 M KCl and 0.25 M sucrose solution and fractionated by centrifugation into a particulate component and a supernatant containing a protein factor necessary for fatty acid desaturation. The delta 6 fatty acid desaturation activity of the extracted microsomes was reduced significantly, and the readdition of the supernatant restored the enzymatic activity to the original value of the whole microsomes. A protein diet or a fat-free diet increased the delta 6 desaturation activity of the whole microsomes. The activating effect was evoked upon the particulate components of the enzymatic desaturation system and not upon the protein factor present in the supernatant. Fasting, refeeding, and refeeding plus glucagon and theophylline treatments of rats also modified the delta 6 desaturation activity of whole liver microsomes. The effect also was evoked on the delta 6 desaturation system tightly bound to the microsomal membrane but not on the protein factor of the supernatant. Accordingly, the protein factor of the supernatant is considered to be different from the cyanide sensitive factor and the desaturase.

Animals↗
PubMed1975

[Effect of an essential fatty acids free diet on the lipidic composition of rat testicles (author's transl)].

The effect of a fat free diet on the fatty acid composition and histological changes of the testis of old rats was studied to investigate the possible function of docosa-4,7,10,13,16-pentaenoic acid in rat testicles. The lipidic composition, the fatty acid composition, the conversion of docosa-7,10,13,16-tetraenoic acid to arachidonic acid and the activity of the 6-desaturase were determined during the different periods in which the rats received a fat free diet. Comparatively, the changes in the fatty acid composition of the liver were also studied. Only the liver showed a change in the triglyceride content during the first month of treatment, and it regained its normal values afterwards. Both liver and testis changed the fatty acid composition. An increase of the acids of the oleic series and a decrease of the components of the linoleic series were shown. These changes were similar to the ones provoked by an essential fatty acid deficient diet on young animals. The amount of docosa-4,7,10,13,16-pentaenoic acid was very little changed. No significant change was shown either in the retroconversion of docosa-7,10,13,16-tetraenoic acid to arachidonic acid. However, the 6-desaturase activity of the testis was enhanced by the fat deficient diet. The possibility that arachidonic acid in the adult rat is mainly supplied by linoleic acid and not by the retroconversion of docosa-4,7,10,13,16-pentaenoic acid is discussed.

Animals↗
PubMed1975

[Inestability of fatty acid desaturation enzymes in liver slices (author's transl)].

A study was made on the microsomal oxidative desaturating activity of fatty acids in rat liver slices incubated in different media. [1-14C] linoleic acid desaturation activity decreased during the incubation in Krebs-Ringer-Bicarbonate. The addition of glucose or pyruvate in the incubation medium did not alter the decrease of the linoleic desaturation activity compared to the controls. Linoleic desaturation to gamma-linolenic acid descreased even when the slices were incubated in different media and at different temperatures. However, the inclusion of aminoacids in the media prevented the decrease of linoleic acid desaturation. Microsomal stearic acid desaturation to oleic acid in liver slices was less modified by incubation than linoleic acid desaturation. Glucose inclusion in the medium enhanced 9-desaturation. The stability of the desaturases in the liver slices is discussed. The results evidence once more that 9-desaturation and 6-desaturation are accomplished by different enzymes controlled by separate mechanisms.

Animals↗
PubMed1975

[Effect of alloxan diabetes on the biosynthesis of unsaturated fatty acids from linoleic and arachidonic acids in rat liver and testis (author's transl)].

The effect of alloxan diabetes on the desaturating, elongating, and elongating-desaturating activity of the microsomes of rat liver and testis was studied. Linoleic and arachidonic acids were tested. It was found that in both liver and testis linoleic acid was desaturated to gamma-linolenic acid (18:3) when the conditions were exclusively desaturating. Diabetes deceased the 6-desaturase activity of both tissues. In elongating and desaturating conditions linoleic acid was converted to 18:3, 20:2, 20:3, 20:4, 22:2, 22:5 and 24:2 in both tissues. Alloxan diabetes decreased the activity of the reactions controlled by the 6-desaturase reducing the conversion to 18:3 in both tissues and to 20:4 only in liver. The elongating reactions were not significantly modified. When only elongating conditions were tested, either liver or testis synthetized only 20:2, 22:2 and 24:2 from linoleic acid and 22:4 from arachidonic acid. The elongating activity for both fatty acids was not decreased by diabetes. Therefore, it was proved that alloxan diabetes interferes with the metabolism of linoleic acid in both tissues, decreasing only the desaturation reaction, whereas the elongation of the fatty acid is not reduced.

Animals↗
PubMed1975

Effects of glucagon and dibutyryl adenosine 3', 5'-cyclic monophosphate on oxidative desaturation of fatty acids in the rat.

The present work was undertaken to study the effect of anti-insulinic and glycogenolytic factors on the oxidative desaturation of fatty acids. The effects of glucagon and dibutyryl cyclic AMP on the desaturation of linoleic acid to gamma-linolenic acid, alpha-linolenic acid to octadeca-6,9,12,15-tetraenoic acid, stearic acid to oleic acid, and eicosa-8,11,14-trienoic acid to eicosa-5,8,11,14-tetraenoic acid by rat liver microsomal preparations were investigated. Fasted rats had low desaturating activity, but refeeding a fat-free diet enhanced the activity. Administration of glucagon or dibutyryl cyclic AMP abolished the increase of the 6-desaturase activity elicited by refeeding. However, a similar effect on the 9-desaturase and 5-desaturase activity was not observed. The relationship between these effects and glucose metabolism is discussed.

Animals↗
PubMed1975

Biosynthesis of unsaturated fatty acids in cultured minimal deviations hepatoma 7288 C cells.

Minimal Deviation Hepatoma 7288 C cells were cultured in confluent layer with labeled linoleic, alpha-linolenic, eicosa-8,11,14-trienoic and stearic acids. The cells in culture preserved their ability to convert stearic acid to oleic acid. They also synthesized arachidonic acid from linoleic acid or eicosa-8,11,14-trienoic acid. The conversion was very low with linoleic acid and high with eicosatrienoic acid. Eicosapentaenoic acid and other homologs of the alpha-linolenic acid family were synthesized from alpha-linolenic acid. The biosynthetic patterns were the cells was modified by the fatty acid composition of the media.

Carcinoma, Hepatocellular↗
PubMed1975

Comparative biosynthesis of polyethylenic fatty acids in Acanthamoeba castellanii and Ochromonas danica.

Acanthamoeba castellanii were incubated in vivo with 1(-14)C linoleic and 1(-14)C-alpha-linolenic acids. The incorporation of the acids into lipid fractions was studied. Labeling was found mainly in triglycerides and phospholipids. Homogenized cells and subcellular fractions separated by centrifugation were incubated with 1-14C-linoleic. 1-14C -alpha-linoleic and 1-14C eicosa-8,11-dienoic acids in the presence of NADH, ATP, and CoA. Different metabolic routes were demonstrated. omega3 and omega6 desaturases of the vegetal type, as well as a delta6 desaturation of alpha-linolenic acid of the animal type were present. The supernatant of 100000 x g contained both types of desaturating enzymes, whereas the corresponding particulated fraction was inactive. The ultrastructure of Acanthamoeba showed the endoplasmic reticulum with a poorly developed membrane component. The metabolic pathways found with Acanthamoeba were compared to Ochromonas danica incubated with linoleic acid in the light and in darkness. Desaturases typical of "vegetal" and "animal" pathways were found in both organisms. In both of them, alpha-linolenic and arachidonic acids could be synthetized. However, alpha-linolenic acid, typical of vegetal synthesis, was only stored in Ochromonas due to the presence of a photosynthetic machinery.

Adenosine Triphosphate↗
PubMed1973

Fate of linoleic, arachidonic, and docosa-7,10,13,16-tetraenoic acids in rat testicles.

A comparative study was made on the fate of linoleic, arachidonic, and docosa-7,10,13,16-tetraenoic acids in various subcellular fractions of liver and testis from rats of different ages. It was demonstrated that testicular microsomes can desaturate and elongate linoleic and arachidonic acids in a manner similar to liver microsomes, and that testicular mitochondria can convert docosa-7,10,13,16-tetraenoic acid to arachidonic acid. Testicular or liver microsomes actively desaturate linoleic acid to gamma-linolenic acid and eicosa-8,11,14-trienoic acid to arachidonic acid. However, it was impossible to measure in vitro any direct conversion of adrenic acid (22:4 [n - 6]) to docosapentaenoic acid (22:5 [n - 6]) by either liver or testicular microsomes. Docosa-7,10,13,16-tetraenoic acid is incorporated preferentially into the triglyceride fraction of total testis, mitochondria, and microsomes, while linoleic and arachidonic acids are incorporated more into phospholipids. The capacity of testicular microsomes, but not of liver microsomes, to synthesize polyunsaturated fatty acids declines with age. It is proposed that the synthesis of acids of the linoleic family proceeds in two stages, a rapid one in which arachidonic acid is made and a second, slower, one in which C(22) and C(24) acids are synthesized. In addition, there appears to be a cycle between microsomes and mitochondria that acts to conserve essential polyunsaturated C(20) and C(22) fatty acids by means of synthesis and partial degradation, respectively. This cycle would restrict the loss of essential fatty acids and might be of importance for the supply of arachidonic acid in testis under specific requirements and especially in older animals.

Aging↗