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Biomedical subjects

B Akesson

Publications and source records attributed to B Akesson.

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

Effect of different fatty acids on triacylglycerol secretion in isolated rat hepatocytes.

Lipoprotein triacylglycerol secretion was studied in isolated rat hepatocytes incubated with different albumin-bound fatty acids and labeled glycerol. The release of labeled triacylglycerol was stimulated more by unsaturated fatty acids than by saturated ones. When lipoprotein secretion was related to cell triacylglycerol synthesis, an effect of unsaturation was no longer observed. Instead the secretion rate, expressed in this manner, increased with increasing fatty acid chain length. For the first time, the secretion of molecular species of triacylglycerol has been studied. The distribution of labeled glycerol among different species was the same in the cells and in th secreted product, indicating that different triacylglycerols were secreted without selectivity. It is concluded that the fatty acid structure influences lipoprotein triacylglycerol secretion and it is emphasized that the effects observed depend on the method of quantitation of the secretion rate.

Animals↗
PubMed1980

Comparison of energy and nutrient intakes in women with high and low blood pressure levels.

The present study found no link between the intake of energy and various nutrients, on the one hand, and high or low blood pressure (BP) in women, on the other. Sixty women not on treatment for hypertension were selected from a defined population and examined, applying the duplicate portion technique, with respect to the relationships between BP and the intake of energy and nutrients. They were selected from above the 95th percentile for BP (group A) and from below the 30th (group B). The two groups were age-matched. The food sampling comprised six days, divided into three periods of two consecutive days within a period of four weeks. Twenty-four hour urine specimens were collected in each period and on two other occasions. The mean values for intake of energy, fat, protein, carbohydrates, minerals and electrolytes did not differ between the two groups despite the large differences in BP and obesity. The mean values for urinary excretion of minerals, electrolytes and nitrogen (calculated as crude protein) did not differ between groups. The present findings for the effect of salt on BP do not justify restriction of the salt intake as a means for decreasing BP in the population.

Adult↗
PubMed1980

Fever induced by fluorine-containing lubricant on stainless steel tubes.

Three subjects, all smokers, handling stainless steel tubes suffered repeated attacks of general malaise, chills, and fever lasting for several hours, mainly after gas soldering. Provocations by rubbing smoking tobacco against a tube produced similar attacks, and leucocytosis, after a few hours. The presence of fluorine on the tubes and in the febrifacient tobacco was shown. A fluorocarbon polymer lubricant was suspected of causing the attacks. Heating (1000 degrees C) of the tubes eliminated the effect.

Adult↗
PubMed1979

Relative efficiency of anticodons in reading the valine codons during protein synthesis in vitro.

Using a protein synthesizing in vitro system programmed with MS 2-RNA, the relative efficiency (in the presence of each other) of valine tRNAs with the anticodons U*AC (U* represents 5-oxyacetic acid uridine monophosphate), GAC, and IAC to read the valine codons was investigated. An anticodon which can read all three positions of the codon according to the rules of Watson-Crick base-pairing and the wobble hypothesis is an order of magnitude more efficient than an anticodon which misreads the codon by reading only the first two positions and presumably disregards the third nucleotide of the codon. There are two seeming exceptions to this behavior: the anticodon U*AC reads the codon GUU quite efficiently and IAC is as effective as U*AC in reading the codon GUG. The significance of these exceptions is evaluated with respect to the organization and evolution of the genetic code.

Anticodon↗
PubMed1979

Effect of sphingosine and other amphiphilic amines on the biosynthesis of phosphatidylethanolamine and other glycerolipids in isolated rat hepatocytes.

The importance of ethanolamine and sphingosine as precursors of phosphoethanolamine was investigated by incubating them with [3H]glycerol and isolated rat hepatocytes. Sphingosine (0.1--0.5 mM) stimulated the synthesis of phosphatidylethanolamine from [3H]glycerol, but the stimulation by ethanolamine was more pronounced. Furthermore, more phosphoethanolamine accumulated in the heptatocytes after incubation with ethanolamine than after incubation with sphingosine. It is concluded that ethanolamine is the most important phosphoethanolamine precursor in rat liver. Higher concentrations of sphingosine caused accumulation of [3H]phosphatidate and inhibition of total glycerolipid synthesis in isolated hepatocytes, when incubated in the presence of [3H]glycerol. These effects were very similar to those of fenfluramine and norfenfluramine described previously. Simpler cationic amphiphilic amines, like oleoylamine and octadecyltrimethylammonium bromide, also caused these effects. Variation of alkyl chain length and amphiphile charge showed that both a positive charge and a certain alkyl chain length were necessary for interference with phosphatidate metabolism. A much wider range of compounds inhibited total glycerolipid synthesis from [3H]glycerol.

Amines↗
PubMed1979

Lipid composition and metabolism in liver and brain of vitamin B12-deficient rat sucklings.

1. Rat sucklings (18-d-old) bred from vitamin B12-deprived dams were compared with vitamin B12-supplemented dams' offspring, which were considered normal rat sucklings. 2. The vitamin B12-deficient rat sucklings had lower body-weight, liver weight and brain weight. 3. Vitamin B12 deficiency was also evident from the tenfold lower concentrations of vitamin B12 in liver and cerebellum. 4. The concentration of liver lipid was markedly increased in vitamin B12-deficient rats; triacylglycerol accounted for most of the increase. In brain the lipid concentration was slightly decreased (less than 0.05). 5. The methylation of ethanolamine phosphoglyceride to choline phosphoglyceride was reduced in both liver and brain in vitamin B12-deficient rats, as measured after the administration of [14C]ethanolamine. A slight decrease in choline phosphoglyceride concentration could be a consequence of this finding. The composition of phospholipids was otherwise normal. 6. Odd-chain fatty acids (pentadecanoate and heptadecanoate) accumulated in both liver and brain of the vitamin B12-deficient rat sucklings and constituted approximately 1% of total fatty acid. 7. The biosynthesis of fatty acid and cholesterol from intraperitoneally-injected 3H2O and [14C]propionate was unchanged in vitamin B12 deficiency.

Animals↗
PubMed1979

Micromethods for analysis of lipids in endomyocardial biopsy specimens.

Triglycerides and phospholipids extracted from endomyocardial biopsy specimens were quantitated with sensitive photometric methods and the fatty acid composition of phospholipids was determined after separation of the methyl esters by gas chromatography. The degree of triglyceride accumulation was expressed as the molar ratio triglyceride/phospholipid since in most cases the phospholipid concentration is relatively constant. The representativity of the analysis of endomyocardial biopsy was investigated by comparing lipid analyses of large and small myocardial specimens obtained at necropsy. The methods described may be valuable tools in studies on metabolic disturbances in different cardiomyophaties.

Biopsy↗
PubMed1978

Simultaneous purification and some properties of aspartate: tRNA ligase and seven other amino-acid:tRNA ligases from Escherichia coli.

A procedure is described for the purification of the aspartate:tRNA ligase from Escherichia coli to a stage where it was homogeneous by polyacrylamide gel electrophoresis. From the same batch of E. coli the lysine, phenylalanine and serine ligases were obtained in an apparently homogeneous form while the alanine, glutamine, leucine and valine enzymes had a purity varying from 20% to 80%. Aspartate: tRNA ligase, which has not been obtained in a highly purified form before, has been characterized in terms of its molecular parameters.

Aspartic Acid↗
PubMed1978

Absorption of synthetic, stereochemically defined acylglycerols in the rat.

The stereochemistry of fat digestion and absorption was investigated in rats with thoracic duct fistulas, after feeding synthetic triacylglycerol or alkyldiacylglycerol. After feeding 1,2-dilauroyl-3-oleoyl-sn-glycerol, dilauroyloleoylglycerol and lauroyldioleoylglycerol were the most abundant chyle triacylglycerols. Positional analysis of the fatty acid distribution and the absence of optical activity indicated that the following structures dominated: rac-1,2-dilauroyl-3-oleoylglycerol and rac-1,3-dioleoyl-2-lauroylglycerol. Therefore, the triacylglycerol resynthesized from 2-lauroylglycerol (pre-cursor to 60% of chyle triacylglycerol) and other precursors was essentially racemic. Chyle phospholipids contained largely endogenous fatty acids, and the proportion of lauric acid was very low. A racemic mixture of 1,2-di[3H] oleoyl-3-tetradecyl-sn-glycerol and 1-tetradecyl-2,3-di[12C] oleoyl-sn-glycerol was absorbed to a lower degree than triacylglycerol. The appearace of oleic acid with different labels in chyle and intestinal lipids did not differ, indicating the absence of stereospecificity in fat digestion. Possible explanations for the low absorption are discussed.

Animals↗
PubMed1978

Effects of vitamin B12 deficiency on lipid metabolism of the rat liver and nervous system.

1. Rats bred from vitamin B12-depleted dams were fed on a vitamin B12-deficient diet for 12-15 months and developed a severe vitamin B12 deficiency, as judged from methylmalonic acid excretion and tissue vitamin B12 levels at slaughter. Control rats were supplemented with vitamin B12 in the drinking-water. 2. Neurological signs were recorded after 7 months but the motor nerve conduction velocities remained normal. Neuropathological examination revealed mild changes in the peripheral nerves but no changes in the central nervous system. 3. The amounts of total lipids and phospholipids were normal, but in all examined tissues the proportions of pentadecanoate (C15 fatty acid) and heptadecanoate (C17 fatty acid) were considerably increased in vitamin B12 deficiency. 4. 3H2O was incorporated to the same extent into the fatty acids of nervous tissue from vitamin B12-deficient and control rats after 48 h. Less 3H was found in the liver fatty acids of the vitamin B12-deficient rats. 5. Neurological dysfunction can be demonstrated in the vitamin B12-deficient rat; the relation of the biochemical and neuropathological changes to the neurological signs needs further study.

Animals↗
PubMed1978

Effect of vitamin B12 deficiency on phosphatidylethanolamine methylation in rat liver.

1. In vitamin B12 deficiency the activity of tetrahydropteroylglutamate methyltransferase (EC 2.1.1.13) is depressed and the synthesis of methionine is reduced. Because the methyl group of methionine is largely utilized for the methylation of phosphatidylethanolamine, we investigated the effects of vitamin B12 deficiency on phosphatidylcholine synthesis. 2. The incorporation of injected [14C]formaldehyde into liver phosphatidylcholine was reduced by approximately 50% in vitamin B12-deficient rats. Also the corresponding incorporation of 5-[14C]methyltetrahydrofolic acid tended to decrease. The findings are consistent with a lower conversion of these precursors to methionine. 3. The effect of the deficient methyl-group supply on phosphatidylcholine synthesis was also investigated by the injection of [14C]ethanolamine. The amount (%) of lipid-14C recovered in phosphatidylcholine was significantly reduced in vitamin B12 deficiency. 4. Chemical analysis of liver phospholipids showed that the vitamin B12-deficient rats had a higher proportion of phosphatidylethanolamine and a lower proportion of phosphatidylcholine, indicating that the impaired synthesis of phosphatidylcholine by methylation leads to changes in membrane phospholipid composition.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗