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Biomedical subjects

A M Bakken

Publications and source records attributed to A M Bakken.

9 recordsLinked to original sources
PubMed1992

The activities of acyl-CoA:1-acyl-lysophospholipid acyltransferase(s) in human platelets.

The activities of acyl-CoA:1-acyl-lysophospholipid acyltransferases (EC 2.3.1.23) have been studied in human platelet lysates by using endogenously formed [14C]acyl-CoA from [14C]fatty acid, ATP and CoA in the presence of 1-acyl-lysophosphatidyl-choline (lysoPC), -ethanolamine (lysoPE), -serine (lysoPS) or -inositol (lysoPI). Linoleic acid as fatty acid substrate had the highest affinity to acyl-CoA:1-acyl-lysophospholipid acyltransferase with lysoPC as variable substrate, followed by eicosapentaenoic acid (EPA) and arachidonic acid (AA). The activity at optimal conditions was 7.4, 7.3 and 7.2 nmol/min per 10(9) platelets with lysoPC as substrate, with linoleic acid, AA and EPA respectively. EPA and AA were incorporated into all lyso-forms. Linoleic acid was also incorporated into lysoPE at a high rate, but less into lysoPS and lysoPI. DHA was incorporated into lysoPC and lysoPE, but only slightly into lysoPI and lysoPS. Whereas incorporation of all fatty acids tested was maximal for lysoPC and lysoPI at 200 and 80 microM respectively, maximal incorporation needed over 500 microM for lysoPE and lysoPS. The optimal concentration for [14C]fatty acid substrates was in the range 15-150 microM for all lysophospholipids. Competition experiments with equimolar concentrations of either lysoPC and lysoPI or lysoPE resulted in formation of [14C]PC almost as if lysoPI or lysoPE were not added to the assay medium.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1992

The activity and subcellular distribution of the peroxisomal enzyme acyl-CoA oxidase in human blood platelets.

The peroxisomal enzyme acyl-CoA oxidase is localized in the 'dense-tubular-system-enriched fraction', probably identical with the endoplasmic reticulum, in human blood platelets. This localization is strongly different from the localization of catalase which seems to be a cytosolic enzyme, in agreement with Marcus, Zucker-Franklin, Safir & Ullman [(1966) J. Clin. Invest. 45, 14-28]. A localization of acyl-CoA oxidase in the endoplasmic reticulum seems to be in good accordance with the important role of peroxisomes in the metabolism of prostaglandins, as recently demonstrated by Diczfalusy, Kase, Alexson & Bjørkhem [(1991) J. Clin. Invest. 88, 978-984].

Acyl-CoA Oxidase↗
PubMed1991

Identity between palmitoyl-CoA synthetase and arachidonoyl-CoA synthetase in human platelet?

Apparent Km values have been determined for the substrates ATP, CoA and fatty acids for the long-chain acyl-CoA synthetase (EC 6.2.1.3) reaction in lysates of human blood platelets. The apparent Km for ATP was higher for saturated fatty acids (C12:0 to C18:0) than for unsaturated acids (C18:1 to C22:6). Other apparent Km values were very similar for all long-chain fatty acids tested. Palmitic acid inhibited the formation of [14C]arachidonoyl-CoA, and arachidonic acid inhibited the formation of [14C]palmitoyl-CoA, with [14C]arachidonate or [14C]palmitate respectively as substrate. After chromatography of Triton X-100-extracted platelet protein in several systems (hydroxyapatite, DEAE-Sepharose, Sephacryl S-200 HR, CoA-Sepharose, Sephadex G-100 and AcA 34), both arachidonoyl-CoA synthetase and palmitoyl-CoA synthetase activities were eluted together in the various protein peaks, and with approximately the same ratio of activities in all peaks. After some purification steps (DEAE-Sepharose and Sephacryl S-200 HR), the acyl-CoA synthetase activity was up to 37 nmol/min per mg of protein with [14C]palmitate as substrate, and up to 116 nmol/min per mg of protein with [14C]arachidonate as substrate. The purification was respectively about 8- and 10-fold. The results indicate that palmitoyl-CoA (or unspecific) synthetase and arachidonoyl-CoA (or specific) synthetase are in fact the same enzyme, in agreement with previously reported results from this laboratory.

Blood Platelets↗
PubMed1991

Fatty acids in human platelets and plasma. Fish oils decrease sensitivity toward N2 microbubbles.

Platelet aggregation induced by N2 microbubbles (simulating microbubbles developed during deep diving) was measured in seven volunteers before and after intake of ethyl-eicosapentaenoate (-EPA, 3.5 g/day) and ethyl-docosahexaenoate (-DHA, 2.5 g/day) for 2 wk. The relative content of arachidonic acid (AA) decreased in platelets from all individuals, whereas the content of EPA and DHA increased. The decrease of AA was almost identical with the increase of EPA plus DHA. In plasma the AA content was unchanged, while EPA and DHA increased. The N2 microbubble-induced aggregation showed a significant negative correlation with the DHA content both in platelets and in plasma. Less aggregation was also observed with high EPA content in platelets or plasma. A significant correlation between AA content in platelets and aggregation was seen. Intake of marine oils may be beneficial to divers under deep diving and to patients during extracorporeal circulation, because this may reduce the microbubble-induced aggregation.

Adult↗
PubMed1990

Thrombin-induced serotonin release as an in vitro indicator of the functional integrity of stored platelets.

Measurements of endogenous serotonin and the thrombin-induced serotonin release reaction in platelet concentrates were compared with other methods of quality control: particle counting and pH and gas analyses. A discrepancy between the serotonin release reaction and the other data was observed after seven days of storage. The decline in the release reaction was not predictable from pH measurements or the number of platelets or leukocytes in the concentrate. There was a significant positive correlation between endogenous serotonin content and the thrombin-induced serotonin secretion after seven days of storage. We conclude that the current methods for routine control of platelet concentrates may not ensure the quality of the product after it has been stored for seven days. The thrombin-induced serotonin release may provide a valuable addition to the battery of tests available.

Blood Gas Analysis↗
PubMed1989

Identical subcellular distribution of palmitoyl-CoA and arachidonoyl-CoA synthetase activities in human blood platelets.

Fractionation of human blood platelets showed that palmitoyl-CoA synthetase and arachidonoyl-CoA synthetase activities had an identical distribution among subcellular fractions. The activity was highest with arachidonic acid as substrate in all fractions, with an enzyme activity of 50 nmol/min per mg of protein, in a 'dense-tubular-system'-enriched fraction. The ratio activities with arachidonate and palmitate as substrates was about 1.5 in all fractions. Heat inactivation did not distinguish between arachidonoyl-CoA synthetase and a palmitoyl-CoA synthetase. On the other hand, heat inactivation indicated two pools of long-chain acyl-CoA synthetases: one in a mitochondria- and one in the dense-tubular-system-enriched fraction.

Blood Platelets↗
PubMed1985

Effects of isoproterenol on adenine nucleotide catabolism in cat hearts with acute regional ischaemia.

Previous studies have demonstrated that beta-adrenergic agonists cause extension of ischaemic lesions in the myocardium. In the present study the effects of isoproterenol on adenine nucleotide metabolism were investigated in cat hearts with regional ischaemia following permanent coronary occlusion for 45 min. Adenine nucleotides and their metabolites were measured by high performance liquid chromatography and regional myocardial blood flow was measured by 15-microns radiolabelled microspheres in a total of 255 paired tissue samples. Compared with untreated control cats, ATP and the energy charge were more reduced in ischaemic myocardium of isoproterenol-treated cats. Increased amounts of the degradation products inosine and hypoxanthine/xanthine were also found in these regions. These results could be ascribed to increased cardiac performance caused by isoproterenol, which augments the imbalance between energy production and oxygen supply in ischaemic myocardium.

Adenosine Diphosphate↗