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At least 37 records · Page 2Linked to original sources
PubMed1987

Kinetics of the beta-thromboglobulin release from alpha-granules of blood platelets activated by ADP.

Mathematical model of the beta-thromboglobulin (BTG) release from alpha-granules stimulated with ADP is compared with experimental data. Secretion of BTG was analysed using platelets washed by different procedures in the presence or absence of inhibitors of platelet activation. The release of BTG was monitored in response to 5-100 microM ADP. The rate constant of the release of BTG (K = 1.83 X 10(3) M-1 min-1) and efficient amount of ADP molecules secreted by a single platelet (W = 5.2 X 10(-18) mole) were estimated. The model precisely describes the release of BTG associated with the isolation of platelets (blood collection, washing procedure) and allows to estimate the extent of activation of blood platelets in the suspension.

Adenosine Diphosphate↗
PubMed1976

Evaluation of Mannich bases and related compounds as inhibitors of mitochondrial function in yeast and inhibition of blood platelet aggregation, blood clotting, and in vitro metabolism of 5-dimethylamino-1-phenyl-1-penten-3-one hydrochloride.

Dimethylamino-1-phenyl-1-penten-3-one hydrochloride (Ia) and 32 analogs were tested for inhibition of respiratory-dependent growth in Saccharomyces cerevisiae. Thirteen of the 33 compounds tested appeared to affect mitochondrial function, since the inhibition of respiratory-dependent growth was statistically greater than the inhibition of growth on fermentable energy sources. Inhibition of mitochondrial function in yeast and growth inhibition of an in vitro culture of human epidermoid carcinoma (KB) were positively correlated since 83% of the compounds tested either had mitochondrial-inhibiting properties and significant activity in the KB test or were inactive in both tests. Similarly, 78% of compounds tested showed murine toxicity and mitochondrial inhibition or had no effect on murine toxicity and yeast mitochondrial function. Injection of Ia into rats resulted in the appearance of blood in the urine and feces. Compound Ia inhibited adenosine diphosphate and collagen-induced aggregation of rat platelets but had no effect on blood clotting. TLC, following incubation of Ia with a rat liver extract, showed that the structure of Ia was not enzymatically modified and indicated activity per se on platelet aggregation and mitochondrial function.

Adenosine Diphosphate↗
PubMed1975

Insignificance of gluconeogenesis in human blood platelets.

Human blood platelets contain no detectable activity of the enzymes fructose diphosphatase (EC 3.1.3.11), phospho-enolpyruvate carboxykinase (EC 4.1.1.32) and pyruvate carboxylase (EC 6.4.1.1.). Glucose-6-phosphatase (EC 3.1.3.9) activity is very low. Phosphofructokinase present in human blood platelets, catalyzes a reaction which can be stimulated by AMP in a platelet homogenate, due to the presence of endogenous ADP and myokinase. These enzymes are responsible for the formation of fructose-6-phosphate from fructose-1, 6-diphosphate. Pyruvate kinase (EC 2.7.1.40) in human blood platelets belongs to the M-type, which is not inhibited by ATP, at least not under the conditions applied. The results obtained indicate that gluconeogenesis in human blood platelets is not present in the way which has been established for liver and kidney.

Adult↗
PubMed1983

Maprotiline in the treatment of endogenous depression: comparison of therapeutic effect with serotonin level in blood platelets.

In blood platelets of untreated patients with endogenous depression a significantly lower concentration of serotonin (5-HT) was found than in healthy persons (P less than 0.05). The patients were afterwards divided into two groups: group I with mild symptoms of depression (total scores by Hamilton Depression Rating Scale below 40) and group II with severe depression (total scores above 40). The gradual diminishing of symptoms in both groups was accompanied by no change in 5-HT level in the first group and by progressive and well marked increases in platelet 5-HT content in the second one, attaining average normal values at the end of week 3 of treatment with maprotiline. In in vitro experiments maprotiline inhibited the uptake of 5-HT into blood platelets of healthy persons less than doxepin. After injection of maprotiline in rats (50 mg/kg IP) the turnover rate of 5-HT in the brain was only marginally affected if measured by 5-HT rise and 5-hydroxyindoleacetic acid (5-HIAA) decline after administration of the MAO inhibitor pargyline, or by estimation of 5-HIAA increase after blocking active transport with probenecid. However, after treatment with maprotiline alone, the 5-HIAA level in the rat brain was significantly increased, although the concentration of 5-HT was not altered. These results suggest: a) the possibility of an action of maprotiline on serotoninergic neurons and b) the suitability of blood platelets as a model for such an investigation.

Adult↗
PubMed1986

Velocity profiles of blood platelets and red blood cells flowing in arterioles of the rabbit mesentery.

Velocity profiles were determined in rabbit mesenteric arterioles (diameter 17-32 micron). A good spatial resolution was obtained by using the blood platelets as small and natural markers of flow, providing for the first time in vivo detailed, quantitative information about the shape of the velocity profiles in microvessels. In some experiments red blood cell velocity profiles were recorded as well. Easy detection of the cells of interest could be achieved by labelling them selectively with a fluorescent dye and visualizing them by intravital fluorescence video microscopy, using flashed illumination. Pairs of flashes were given with a short, preset time interval between both flashes, yielding in one TV picture two images of the same cell displaced over a certain distance for the given time interval. Velocity and mean radial position of cells, flowing within an optical section around the median plane of the vessel, were determined. The shape of the velocity profiles of platelets and red blood cells was similar. The profiles were flattened as compared to a parabola, both in systole and diastole. Vessel diameter did not change measurably during the cardiac cycle. As an index of the degree of blunting of the profiles, the ratio of the maximal and mean velocity of the profile was used, which is 2 for a parabola and 1 for complete plug flow. The index ranged from 1.39 to 1.54 (median 1.50), and increased with vessel diameter. Calculations showed that the blunting of the profiles cannot be explained by an influence of the finite depth of the optical section.

Animals↗
PubMedDate not supplied

[Adenyl cyclase activity of human blood platelets in various blood diseases].

Adenyl cyclase activity was estimated in blood platelets of healthy persons and of patients with myeloleukosis, osteomyelofibrosis and with Glanzmann's thrombasthenia. Six-fold decrease in the adenyl cyclase activity from the platelets was observed in chronic myeloleukosis. The enzymatic activity in platelets was similar to normal level in osteomyelofibrosis and Glanzmann's thrombasthenia.

Adenylyl Cyclases↗