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Biomedical subjects

A Nilsson

Publications and source records attributed to A Nilsson.

At least 289 records · Page 16Linked to original sources
PubMed1994

Interconversion of alpha-linolenic acid in rat intestinal mucosa: studies in vivo and in isolated villus and crypt cells.

The desaturation-elongation of [14C]linolenic acid (n-3) in the rat small intestine was examined in homogenates of villus and crypt cells in vitro and in mesenteric lymph duct cannulated rats in vivo, using high performance liquid chromatography of fatty acid methyl esters with continuous flow measurement of 14C. Desaturation-elongation of [14C]18:3 to [14C]18:4, [14C]20:4, and [14C]20:5 (n-3) could be demonstrated in both villus and crypt cell homogenates, the rate of interconversion generally being highest in the villus cell fraction. For example, during incubation with 20 nmol [14C]linolenic acid (n-3), the average rates of delta 6 desaturation were 1.35 pmol/min per mg protein in villus and 0.93 pmol/min per mg protein in crypt cell homogenates. The acylation of [14C]linolenic acid (n-3) into phospholipids in crypt cells was twofold higher than in villus cells. Addition of 1-palmitoyl-sn-glycero-3-phosphocholine (20-240 microM) increased the incorporation of [14C]linolenic acid (n-3) into phosphatidylcholine, and decreased the interconversion of [14C]linolenic acid (n-3) to delta 6 and delta 5 desaturation products in both villus and crypt cells. 1-Palmitoyl-sn-glycero-3-phosphocholine also decreased the incorporation of 14C into triacylglycerols and phosphatidic acid, the decrease being more pronounced in the crypt cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Acylation↗
PubMed1993

The effect of retinoids and clofibric acid on the peroxisomal oxidation of palmitic acid and of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid in rat and rabbit hepatocytes.

The effects of retinoids and the peroxisome proliferator clofibric acid on peroxisomal enzyme pathways were studied in hepatocytes from both rat and rabbit. Retinoic acid and retinol increased the activity of acyl-CoA oxidase in rabbit hepatocytes around 60% and around 30% in rat hepatocytes. Exposure to clofibric acid caused an increase in acyl-CoA oxidase activity of 115% in rat hepatocytes and of 40% in rabbit hepatocytes, indicating that rabbit is less sensitive to peroxisome proliferator than rat. Simultaneous exposure to clofibric acid and retinoids did not act additatively or synergistically. Both rabbit and rat hepatocytes expressed mRNA for the peroxisome proliferator activated receptor, (PPAR), although the transcript in rabbit was slightly smaller compared to that expressed in rat hepatocytes. The effect of retinoic acid in 7800 C1 Morris rat hepatoma cells, a cell line known to have an inducible peroxisomal beta-oxidation of fatty acids, was only slight with an increase of the acyl-CoA oxidase activity of 25% compared with control cells. As for clofibric acid, which gave a 2-fold induction of the acyl-CoA oxidase activity, the effect of retinoic acid was potentiated by dexamethasone. These cells also expressed mRNA for PPAR, with the same size as that found in rat hepatocytes. The oxidation of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestanoic acid (THCA), an intermediate in bile acid formation, in rat hepatocytes increased 110% by clofibric acid and around 80% by retinoic acid. In rabbit hepatocytes, clofibric acid increased the oxidation rate 75% and retinoic acid 100%. The results presented here show similarities in the effects of retinoids and clofibric acid on the acyl-CoA oxidase activity and the oxidation rate of THCA, since they increase these two peroxisomal activities in hepatocytes in vitro. A decrease in both these enzyme activities occurs during cultivation time in untreated primary hepatocyte cultures. The present data may therefore either be explained by an increased expression or an induced stability of the enzymes involved.

Animals↗
PubMed1993

Elongation factor 2-specific calcium and calmodulin dependent protein kinase III activity in rat livers varies with age and calorie restriction.

Elongation factors involved in polypeptide chain elongation are considered to be rate limiting for the slowing down of total protein synthesis during ageing. The activities of elongation factors are themselves regulated by various means, including phosphorylation. Here we have compared the activity of a protein kinase, called calcium- and calmodulin-dependent protein kinase III (CaM PK III), specific for the phosphorylation of elongation factor eEF-2, in cell-free extracts prepared from livers isolated from young and old male Fischer 344 rats maintained under freely fed or calorie-restricted dietary regimes. There was a significant increase of more than 70% in the activity of CaM PK III in 24 month old freely fed rat livers as compared with young animals. This age-related increase was found but to a lower extent (46%) in calorie-restricted rats of the same age. Therefore, slowing down of ageing in calorie-restricted animals is also reflected at the level of the regulation of the activity of protein elongation factor eEF-2 by CaM PK III.

Aging↗
PubMed1993

Desaturation and chain elongation of n - 3 and n - 6 polyunsaturated fatty acids in the human CaCo-2 cell line.

Human CaCo-2 cells were incubated with [14C]linoleic (18:2(n - 6)), [14C]linolenic (18:3(n - 3)) and [3H]eicosapentaenoic acid (20:5(n - 3)), and the interconversion of the radioactive fatty acids to higher homologues and their acylation into triacylglycerols (TG) and phospholipids were examined. An active conversion of [14C]18:3 to [14C]20:5 and [14C]docosapentaenoic acid (22:5(n - 3)) and of [3H]20:5 to [3H]22:5, but not to [3H]docosahexaenoic acid (22:6(n - 3)) was observed. In relation to the amounts that had been incorporated into cellular phospholipids and TG, the interconversion of [14C]18:3 clearly exceeded that of [14C]18:2. Addition of 10-100 microM 18:2 or 10-50 microM arachidonic acid (20:4(n - 6)) increased the percent interconversion of [14C]18:2 to [14C]20:4. E.g., addition of 50 microM 20:4 increased the formation of [14C]20:4 from 4.4 +/- 0.1% to 5.9 +/- 0.8%, decreased the incorporation into phospholipids from 64.8 +/- 6.3% to 31.4 +/- 1.2% and increased the incorporation into TG from 8.8 +/- 0.4% to 28.8 +/- 1.1%. In contrast, addition of 10-100 microM 18:3 or 20:5 significantly decreased the interconversion of both [14C]18:2 and [14C]18:3. E.g., addition of 50 microM 20:5 decreased the formation of [14C]20:4 from [14C]18:2 from 4.4 +/- 0.1% to 0.9 +/- 0.1%, whereas the effects on the acylation reactions were very similar to those of 20:4. 20:5 also decreased the formation of interconversion products from [14C]18:3. 18:2 and 20:4 caused a smaller decrease in the formation of [14C]20:5 and actually increased percent conversion to [14C]22:5. The percent conversion of [3H]20:5 to [3H]22:5 was also increased by the addition of 50-100 microM unlabeled 20:5. [14C]18:2 and [14C]18:3 were predominantly incorporated into phosphatidylcholine (PC) whereas more of the radioactive 20:4, 20:5 and 22:5 was incorporated into phosphatidylethanolamine (PE). An active fatty acid interconversion catalyzed by delta 6 and delta 5 desaturases thus occurs in the human CaCo-2 cell line, whereas conversion of 20:5(n - 3) to 22:6(n - 3) could not be demonstrated. The desaturation-elongation pathway has a preference for 18:3(n - 3) and is subjected to an efficient feedback regulation by 20:5(n - 3). Formation of 22:5 increases with available 20:5 mass and by the presence of other polyunsaturated fatty acids competing with 20:5 for acylation into phospholipids.

Carbon Radioisotopes↗
PubMed1993

Cellular aspects on treatment of cartilage injuries.

Cellular aspects on articular cartilage growth and development are discussed. Cells with chondrogenic potential are described and current treatment models for cartilage injuries are considered. A rabbit model for treatment of articular cartilage defects with autologous cultured and transplanted chondrocytes for treatment of knee cartilage defects in humans are discussed.

Animals↗
PubMed1993

Growth hormone-receptor messenger RNA in the rat ovary: regulation and localization.

The results of several reports indicate that GH can modulate ovarian function. In the present study, the expression of the growth hormone-receptor (GH-R) mRNA was studied in the rat ovary using an RNA probe corresponding to a part of the extracellular domain of the GH-R. The probe hybridized to two major transcripts with estimated sizes of 4.0 kb and 1.2 kb in RNA extracted from liver and ovary. Recently, these transcripts have been shown to encode the GH-R and the GH-binding protein (GH-BP). The ontogeny of the GH-R/GH-BP mRNA expression was studied using Northern blot analysis and a solution hybridization RNase protection assay. In the liver GH-R/GH-BP mRNA levels increased with age, while in the ovary, the levels decreased between 1 and 5 weeks of age. Hypophysectomy caused a decrease in GH-R/GH-BP gene expression in the ovary, an effect which could be partly reversed with a single injection of GH (2 mg/kg). No significant changes in the ovarian concentration of GH-R/GH-BP transcripts were seen during the estrus cycle. Using in situ hybridization GH-R/GH-BP transcripts were found to be most abundant in follicles. Northern blot analysis of RNA extracted from isolated granulosa cells and corpora lutea showed that both these compartments contained GH-R and GH-BP mRNA, although more abundant in granulosa cells. Immunoreactive GH-R was detected in granulosa cells of healthy follicles, corpus luteum, and in the germinal epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗