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Biomedical subjects

B Akesson

Publications and source records attributed to B Akesson.

At least 127 records · Page 7Linked to original sources
PubMed1984

Effects of pectin and wheat bran on intraluminal pancreatic enzyme activities and on fat absorption as examined with the triolein breath test in patients with pancreatic insufficiency.

In totally pancreatectomized patients breath 14CO2 excretion after ingestion of 14C-labeled triolein was significantly increased by a granulated pancreatic enzyme preparation and was reduced when pectin was added to the enzyme supplement. In the same patients pectin reduced trypsin, lipase, and amylase activities of jejunal aspirates after a test meal supplemented with pancreatic enzyme substitution, which was shown to give good enzyme activities in the intestine. In patients with chronic pancreatitis, breath 14CO2 excretion was reduced by wheat bran, which also caused a reduction in lipase and amylase activities of duodenal aspirates after a test meal. The findings demonstrate the efficiency of treatment with a granulated pancreatic enzyme preparation in restoring intraluminal enzyme activities and fat absorption in patients with pancreatic insufficiency. They also show that pectin and wheat bran may induce fat malabsorption and inhibit digestive enzyme activities in vivo.

Adult↗
PubMed1984

Use of the triolein breath test for the demonstration of fat malabsorption in coeliac disease.

Different screening tests for fat malabsorption were evaluated in patients with coeliac disease. The triolein breath test correlated well with results of faecal fat determination. Urinary excretion of oxalate with or without dietary oxalate loading was not correlated with faecal fat measurements. It is concluded that the triolein breath test is a useful procedure for the detection of fat malabsorption in patients with coeliac disease.

Adult↗
PubMed1983

Structural requirements of the phospholipid substrate for phospholipid N-methylation in rat liver.

The role of endogenous phospholipid substrates for phospholipid methylation was investigated in rat liver microsomes. The amount of phosphatidylethanolamine could be drastically reduced by treatment of microsomes with an amino group-blocking compound, methylacetimidate. Simultaneously, the formation of labelled phospholipids from S-adenosyl[Me-3H]methionine decreased, indicating that the amount of endogenous substrate influenced the reaction rate. Phosphatidylmonomethylethanolamine, phosphatidyldimethylethanolamine and phosphatidylmonoethylethanolamine added as dispersions to untreated or treated microsomes stimulated phospholipid methylation, whereas several other phospholipids were inactive. In other experiments the role of phospholipid substrates in intact cells was studied. Cultured rat hepatocytes were enriched in different phospholipids by preincubation with different amino alcohols, and the effects of phospholipid methylation was measured by incubation with [Me-14C]methionine. Phospholipid methylation was significantly stimulated after preincubation with ethanolamine, monomethylethanolamine, monoethylethanolamine and 2-aminobutanol. The results show that both the number and chain length of N-alkyl substituents on phosphatidylethanolamine, as well as other changes in the ethanolamine moiety, will affect the ability of different phospholipids to act as methyl acceptors.

Animals↗
PubMed1983

Uptake of beta-hexosaminidase by nonparenchymal liver cells and peritoneal macrophages.

The uptake of beta-hexosaminidase (EC 3.2.1.30) in nonparenchymal liver cells (i.e. endothelial and Kupffer's cells) and peritoneal macrophages has been determined by an enzymatic assay. A considerable uptake was noted in nonparenchymal liver cells, whereas no measurable uptake was seen in peritoneal macrophages. The endothelial cells were more active in the uptake of beta-hexosaminidase than were the Kupffer's cells. The uptake of beta-hexosaminidase by nonparenchymal liver cells showed saturation kinetics and was competitively inhibited by mannan. These findings support the concept that a cell surface receptor on nonparenchymal liver cells mediates uptake of beta-hexosaminidase and suggests a difference in the receptor mechanisms on liver and peritoneal macrophages.

Animals↗
PubMed1983

Increased frequency of lymphocyte micronuclei in workers producing reinforced polyester resin with low exposure to styrene.

A new micronucleus method based on the analysis of lymphocytes with preserved cytoplasm revealed an increased frequency of micronuclei in 38 workers employed in a plant producing styrene-modified polyester resin as compared to the frequency in 20 referents (5.9 vs 3.6%). The time-weighted average of the styrene concentration in the workroom air varied between 1 and 36 ppm (mean 13 ppm) during the last year and correlated well to low urinary levels of mandelic acid, which ranged from 9 to 316 mg/g of creatinine (mean 65 mg/g of creatinine).

Adult↗
PubMed1982

Content of phospholipids in human diets studied by the duplicate-portion technique.

1. The phospholipid intake by eight healthy women was studied by the duplicate-portion technique, i.e. chemical analyses of duplicates of the food consumed. Their intake of phospholipids was 1.5-2.5 mmol lipid-phosphorus/d, which corresponds to 0.023-0.059 mmol lipid-P/g dietary fat and 0.24-0.45 mmol lipid-P/MJ respectively. 2. Choline phosphoglyceride constituted 480-700 mmol/mol and ethanolamine phosphoglyceride 170-240 mmol/mol total lipid-P. Most of the choline in nature occurs as choline phospholipids, the intake of which ranged between 0.91-1.85 mmol/d or 0.15-0.33 mmol/MJ. 3. Palmitate, stearate, oleate, and linoleate ere the four major fatty acids both in choline phosphoglyceride and ethanolamine phosphoglyceride. Significant amounts of highly unsaturated, C20 and C22 fatty acids were also observed. It was calculated that 13-33 mg/g total dietary fatty acids was consumed as phospholipids. Together with bile phospholipids, dietary phospholipids and their degradation products may be important in the digestion and absorption processes.

Adult↗
PubMed1982

Effect of experimental folate deficiency on lipid metabolism in liver and brain.

1. Rats were given a purified folate-deficient diet containing 5 g succinylsulphathiazole/kg for 4-5 months in two experiments. Control rats were supplemented with folic acid in the drinking-water. 2. Weight gain was much below normal in the folate-deprived rats after the first month. Very low folate levels were recorded in blood, liver and peripheral nerve (12-33% of control). In the central nervous system, including the cerebrospinal fluid, the folate depletion was less conspicuous (50-80% of control). Only marginal signs of anaemia were found and no signs of neurological dysfunction were detected, using nerve conduction velocity measurement and co-ordination tests. 3. Light and electron microscopy of the folate deficient liver revealed fatty infiltration, and enlargement of liver parenchymal cells, nuclei and nucleoli. There was often a considerable amount of bile ductular cells in the lobuli but no cirrhosis. The morphological changes resembled those observed in choline deficiency. 4. Phospholipid N-methylation in liver was depressed in folate-deficiency. This was probably due to a decreased availability of S-adenosylmethionine caused by the low concentrations of methylated folate in liver. Intraperitoneal administration of methionine did not normalize phospholipid methylation. 5. In folate deficiency the proportion of ethanolamine phosphoglyceride in liver was increased at the expense of choline phosphoglyceride, which is consistent with a decreased phospholipid methylation. Also an increase in liver triacylglycerol was noted, in accordance with the morphological observations. Brain lipid composition was unchanged. 6. After the injection of labelled ethanolamine, isotope accumulated in liver phosphoethanolamine in folate deficiency, probably due to an impairment of the CTP:ethanolaminephosphate cytidylyltransferase (EC 2.7.7.14) reaction. The mechanism of this impairment is discussed. 7. Although the low concentrations of folate was the main nutritional change in the deprived animals, changes with respect to vitamin B12 and maybe also choline cannot be excluded. We conclude that some of the changes in folate deficiency, i.e. fatty liver and decreased biosynthesis of liver phospholipids may be due to a precipitated deficiency of lipotropic agents, whereas other differences may be specific for deficiency of folate per se, such as changes in liver phospholipid fatty acids and some of the morphological aberrations.

Animals↗
PubMed1982

Postprandial effects of dietary phosphatidylcholine on plasma lipoproteins in man.

To evaluate the effects of dietary phospholipids on plasma lipoproteins in the postprandial phase six normolipidemic men were fed alternatively a test meal rich in phosphatidylcholine and a control meal low in phosphatidylcholine. Plasma very low-density lipoproteins, low-density lipoproteins, and high-density lipoproteins were isolated at 2, 4 and 6 h after the meals. The changes in lipoprotein cholesterol, triacylglycerol, and phospholipid after feeding the phospholipid-rich meal were indistinguishable from those after the low-phospholipid meal. The phospholipid composition in high-density lipoproteins was also unchanged. The amount of phosphatidylcholine used in this trial was approximately 10-fold higher than that found in the normal Swedish diet. It is therefore concluded that the normal dietary intake of phosphatidylcholine has little influence on the plasma lipoprotein parameters measured in the present study.

Adult↗
PubMed1982

Occupational and in vitro exposure to styrene assessed by unscheduled DNA synthesis in resting human lymphocytes.

Lymphocytes from 38 individuals occupationally exposed to styrene concentrations in workroom air of 1 p.p.m. t0 40 p.p.m. were examined for any genotoxic effects using unscheduled DNA synthesis (UDS) as the indicator of DNA damage. The mean level of N-acetoxy-2-acetylaminofluorene (NA-AAF) induced UDS was significantly increases (p less than 0.001) for the styrene exposed group when compared to the mean level for the unexposed controls. There was no significant effect on u.v.-induced UDS from the in vivo styrene exposure. Lymphocyte cultures exposed in in vitro to styrene concentrations up to 100 micro M have confirmed the UDS data collected on individuals occupationally exposed to styrene. In addition, the in vitro study has also shown that the increased NA-AAF induced UDS resulting from styrene exposure was paralleled by a similar increase in NA-AAF binding to DNA. Taken together these results indicate that styrene exposure does not inhibit DNA repair synthesis, but rather it predisposes lymphocytes to an increased risk for DNA damage induction from subsequent genotoxic exposures.

Acetoxyacetylaminofluorene↗
PubMed1981

Digestion and absorption of a sulphoxide analogue of triacylglycerol in the rat.

The stereochemistry of fat digestion and absorption was studied by feeding a triacylglycerol analogue to rats with a thoracic duct cannula. The analogue, rac-1,2-dioleoyl-3-S-tetradecyl-3-thioglycerol-S-oxide was chosen since its enantiomers exhibited high rotation in optical rotary dispersion (ORD) and circular dichroism (CD). In the chyle, triacylglycerol was the major lipid but X-1,2-diacyl-3-S-tetradecyl-3-thioglycerol-S-oxide constituted 8% of lipid weight. It was resolved by thin-layer chromatography (TLC) into two diastereomers. Each of the diastereomers were analyzed for the proportions of 1-thio-sn-glycerol/3-thio-sn-glycerol isomers by ORD and CD. The 1-thio-sn-glycerol isomers dominated for both compounds indicating that they were enriched during the absorption processes, since a racemic compound was fed. The stereospecificities are probably exerted by acyltransferase(s) during chyle lipid synthesis. The methods used will be valuable tools in studies on the metabolism of enantiomeric glycerides and also for characterization of naturally occurring sulphur-containing lipids.

Animals↗
PubMed1981

Vitamin E and fatty acid composition of human milk.

The vitamin E and fatty acid composition of human milk was determined in 40 milk samples (six colostral, 10 transitional, and 24 mature) obtained at different stages of lactation. Vitamin E was determined by high performance liquid chromatography with fluorescence detection of the various tocopherols. The total tocopherol level was significantly higher in early milk than in mature milk. The difference was due to a high content of alpha-tocopherol, as the content of beta- and gamma-tocopherol was similar in the three milk types. The total tocopherol content in mature milk correlated significantly with both the total lipid and the linoleic acid content. Significantly higher tocopherol/linoleic acid ratios were found in both colostrum and transitional milk than in mature milk. The colostral milk differed from the other milk types in fatty acid composition, as it had a lower content of lauric acid and a higher content of arachidonic acid and docosahexaenoic acid. The linoleic acid levels reported here are considerably higher than those reported previously in Sweden. Still, the ratio of alpha-tocopherol equivalent/linoleic acid exceeded 0.5 mg/g in all but three milk samples.

Colostrum↗
PubMed1981

Nutrient intake and health status of vegans. Chemical analyses of diets using the duplicate portion sampling technique.

A strict vegetarian diet [vegan diet (VD)] was investigated. Six middle-aged vegans (three men and three women) collected copies of 24-h diets using the duplicate portion sampling technique. By chemical analyses, the nutrient composition was determined in detail and compared with corresponding figures of a normal mixed Swedish diet. In the VD 30% of the energy originated from fat compared with 40% in normal Swedish mixed diet (MD). Linoleic acid was the dominant fatty acid (60% of total fat in VD versus 8% in MD). The VD contained 24 g protein/1000 kcal compared to 30 g/1000 kcal in MD, but the intake of essential amino acids by the vegans exceeded the recommendations. Dietary fiber was about 5 times higher in the vegan diet (29 versus 6 g/1000 kcal) and sucrose similar to MD (18 versus 21 g/1000 kcal). Among the inorganic nutrients the concentration of calcium (351 versus 391 mg/1000 kcal) and sodium (53 versus 49 mmol/1000 kcal) were similar in both types of diets but the amount of potassium (56 versus 30 mmol/1000 kcal, magnesium (300 versus 110 mg/1000 kcal), iron (9 versus 6.5 mg/1000 kcal), zinc (6.5 versus 4.7 mg/1000 kcal), and copper (2 versus 0.7 mg/1000 kcal) were nearly doubled. Iodine (39 versus 156 micrograms/1000 kcal and selenium (5 versus 17 micrograms/1000 kcal) were much lower in the VD, selenium even being undetectable in several 24-h diets. The VD was rich in folic acid (301 versus 90 micrograms/1000 kcal in MD) but the intake of vitamin B12 was only 0.3 to 0.4 microgram/day (MD: 3 to 4 micrograms/day). No clinical signs of nutritional deficiency were observed in the vegans. Serum protein levels of the vegans as well as their serum lipoproteins were near the lower range of the reference group. In addition, none of the vegans was overweight and their blood pressures were low for their age.

Blood Pressure↗
PubMed1981

Content of trans-octadecenoic acid in vegetarian and normal diets in Sweden, analyzed by the duplicate portion technique.

The intake of trans fatty acids by subjects adhering to the normal Swedish diet or to different vegetarian regimes was studied, using chemical analysis of duplicate portions. Trans-octadecenoic acid was 5.0, 3.9, and 1.8% of dietary fatty acid in the normal, lactovegetarian, and vegan diets, respectively, corresponding to 2.0, 1.3, and 0.5% of energy intake. The results are related to the content of trans-octadecenoic acid in some edible fats.

Butter↗
PubMed1980

Aberrations of the classic codon reading scheme during protein synthesis in vitro.

Using a protein synthesizing in vitro system programmed with MS2-RNA, the ability of alanine tRNAs with the anticodons U*GC (U* represents 5-oxyacetic acid uridine monophosphate) and IGC to read the alanine codons in the coat protein cistron of MS2 has been determined both under conditions of no competition, where the alanyl-tRNA used was the only aminoacylated tRNAAla present in the system, and in experiments where the two alanyl-tRNAs were competing against each other. Under conditions of no competition, each of the anticodons can read all four alanine codons. However, when the anticodons compete for the codon GCC, the anticodon IGC, which can read all three positions of the codon according to the rules of Watson-Crick base pairing, is considerably more efficient than U*GC, which misreads the codon by reading only the first two positions and presumably disregards the third nucleotide of the codon. The outcome of the competition experiments also reveals two apparent violations of the wobble restrictions: the anticodon U*GC reads the codon GUU almost as effectively as does the anticodon IGC, and IGC is almost as effective as U*GC in reading the codon GCG.

Alanine-tRNA Ligase↗
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↗