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At least 361 records · Page 20Linked to original sources
PubMed1991

Subcellular distribution and phosphorylation of vinculin isoforms in human blood platelets.

In this study we investigated human blood platelet vinculin microheterogeneity, the subcellular localization and phosphorylation of the different isoforms before and after platelet stimulation. At least 5 vinculin isoforms could be detected, as well as meta-vinculin. These isoforms did not demonstrate a specific subcellular localization, i.e. their relative content was similar in cytoskeleton, membrane skeleton and cytosol. Upon platelet stimulation with thrombin a small increase in alpha-vinculin was noted in all platelet subfractions. The cytoskeleton of non-stimulated platelets contained a minor quantity of vinculin. Upon thrombin stimulation of the platelets the cytoskeletal vinculin content increased significantly; previously we already reported a maximal 10% incorporation of the total platelet vinculin content into the cytoskeleton upon stimulation. A phosphorylation of a minor vinculin-isoform, i.e. at the alpha'/alpha location was mainly detected in the cytoskeleton. This phosphorylation was observable in the non-stimulated platelet cytoskeletal vinculin. These findings argue against a regulatory role for vinculin phosphorylation in the uptake of the main isoforms of this protein in the platelet cytoskeleton upon thrombin stimulation. The function of the phosphorylated cytoskeletal vinculin remains to be established.

Blood Platelets↗
PubMed1985

Distribution of blood platelets flowing in arterioles.

The distribution of blood platelets flowing in arterioles (21-35 microns) of the mesentery of anesthetized rabbits was studied using intravital fluorescence microscopy. Sites were selected without upstream branch points within at least 10 vessel diameters. The distribution was determined by counting in flashed video frames the number of platelets present in each of six equal segments across the vessel. Only platelets were counted that could be localized objectively within a thin optical section around the median plane of the vessel. It could be shown that differences in counting volume between the six segments were negligible. Because of the use of flashed pictures (flash duration less than 0.1 ms; interval 180 ms), the method is independent of differences in velocity over the cross-sectional area of the vessel. In all measurements (15 sites in 13 vessels in 10 animals) the distribution was nonuniform, the wall segments containing the highest platelet numbers. The general distribution as calculated from all measurements (total platelet number 6,571) and expressed in percentages was found to be 23.0, 14.6, 12.5, 12.1, 13.6, and 24.2.

Animals↗
PubMed1990

Dialyzable factors from uremic serum increase 125I-fibrinogen binding by normal blood platelets.

The influence of uremic serum on 125I-fibrinogen binding by normal blood platelets after induction with adenosine diphosphate was evaluated. The study was performed on 12 hemodialyzed uremic patients. The control group included 12 healthy subjects. It has been demonstrated that the uremic serum from the patients before hemodialysis significantly augmented fibrinogen binding by normal blood platelets (33.8 +/- 11.8%) in comparison with control subjects (14.4 +/- 8.9%). After hemodialysis, fibrinogen binding was comparable with the control group (14.9 +/- 10.1%). Uremic toxins removable during hemodialysis are probably responsible for the potentiation of 125I-fibrinogen binding by platelets.

Adult↗
PubMed1993

Effect of the esters of gallic acid on model and human blood platelet membranes studied by Fourier transform infrared spectroscopy.

Gallic acid is one of the components of Chinese herbal drug Radix paeoniae used for promoting blood circulation to remove blood stasis. This paper studied the effects of gallic acid and its esters (e.g. ethyl, propyl, isobutyl and butyl gallate) on model and human blood platelet membranes by FTIR which was used for monitoring the physical state of the acyl chain, interfacial and head group region of the membrane lipid bilayer. From the experimental results it can be seen that the gallic acid and its esters have the modifying function on the pure and cholesterol-containing DPPC model membranes, and have the quantity-effective and structural-effective relationships. In addition, it is discovered that these esters have the modifying effect on the structure of human blood platelet membrane and can reverse the effect of ADP. That the effect of the esters of gallic acid counteracts the effect of cholesterol and ADP on human blood platelet perhaps provides a new explanation of the mechanism of Chinese herbal drugs used for promoting blood circulation to remove blood stasis.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1980

Modifications of biochemical parameters in blood platelets of schizophrenic and depressive patients.

The blood platelet may be considered as an interesting model of the serotoninergic neuron in biology and pharmacology. We studied some platelet parameters in neuropsychiatric patients (depressive and schizophrenic ones): serotonin (5-HT) uptake was abnormal for all schizophrenics and lowered for depressive patients; uptake of mepacrine, a marker of 5-HT passive diffusion, was diminished for manic patients; MAO and glutathione peroxidase activities were modified, essentially for paranoid schizophrenics and some alterations of the platelet hydroxyindole level were noticed; during treatment with neuroleptics of antidepressants biological parameters led to 'normality'. These results are discussed with clinical data and a hypothesis is proposed to join the biological modifications of paranoid schizophrenics.

Blood Platelets↗
PubMed1985

Blood platelet uptake of serotonin in men alcoholics.

Blood platelet uptake of 3H-serotonin (5HT uptake) was determined in a group of inpatient alcoholics who had just undergone detoxication (N = 19) and an age-matched group of nonalcoholic controls (N = 19). Mean 5HT uptake was 18% lower in the alcoholics (p less than .01). A 3-min 5HT uptake of less than 6 pmoles/10(7) platelets identified 58% of the alcoholics, but only 15% of the controls had a 5HT uptake lower than this value. These results support the hypothesis that serotonergic dysfunction may exist in alcoholics.

Adult↗
PubMed1998

Collagen-induced whole blood platelet aggregation in patients undergoing surgical procedures associated with minimal to moderate blood loss.

Intraoperative bleeding due to platelet disorders is a persistent problem. Therefore, a screening assay to identify patients who are likely to bleed as a result of platelet dysfunction would be useful in formulating decisions about patient care. A previous study indicated that preoperative collagen-induced whole blood platelet aggregation predicts bleeding in patients undergoing surgery with cardiopulmonary bypass, a procedure associated with substantial blood loss. In the current study, we assessed the ability of the same whole blood platelet aggregation test to predict blood loss in patients undergoing surgical procedures not associated with substantial blood loss. The study included 369 adult patients (165 men and 204 women). Patients were categorized in three groups depending on the invasiveness of the operation and the expected blood loss. The intraoperative estimated blood loss value, obtained from the operative report in the patient record, increased significantly with increasing surgical invasiveness. Patients with excessive blood loss (defined as blood loss at or above the 75th or 90th percentile of the estimated blood loss values of patients undergoing procedures of similar invasiveness) had similar platelet aggregation values as patients who did not experience excessive blood loss. Thus, for patients undergoing operations not associated with substantial blood loss, the results of preoperative collagen-induced whole blood platelet aggregation are not effective in identifying patients likely to experience excessive blood loss.

Blood Coagulation Tests↗
PubMed1986

Effect of solute concentration on intracellular water volume and hydraulic conductivity of human blood platelets.

The intracellular water volume of human blood platelets was determined using tritiated water. The cells responded as osmometers over an observed range of solute concentration from 0.292 to 2.180 osmol kg-1. Only 87% of intracellular water was apparently osmotically active (i.e. Ponder's R was 0.87). Changes in cell volume induced by small step changes in external osmolality were followed photometrically and the time constant for the exponential approach of cell volume to its new equilibrium value was determined. Hydraulic conductivity (LP) was calculated from the time constant and was 1.41 X 10(-6) cm atm-1 s-1 under isotonic conditions at 37 degrees C. LP was inversely dependent on extracellular solute concentration, but it was independent of the direction of movement of water across the plasma membrane.

Blood Platelets↗
PubMed1990

3H-imipramine binding in the blood platelets of normal twins.

3H-Imipramine binding (IB) was studied in the blood platelets of 13 pairs of monozygotic (MZ) and dizygotic (DZ) twins, and 15 pairs of unrelated normal volunteers, to determine if IB is under genetic control. The intrapair variance of Bmax (the maximum number of 3H-IB sites) was significantly smaller in MZ twins and unrelated control pairs than in DZ twins. The intraclass correlations (ICC) of Bmax were significant for all the pairs with no difference between these correlations. The ICC of the Kd (inversely related to the affinity for 3H-imipramine) of IB was significant only for the normal control pairs and the DZ twins. These results suggest that the kinetic constants of IB in blood platelets are not under genetic control and that interassay variance significantly affects the absolute values for Kd and Bmax of 3H-IB. The environmental and assay factors that influence 3H-IB may account for the numerous discrepancies in platelet 3H-IB between various research reports.

Adult↗
PubMed2000

Endotoxins stimulate generation of superoxide radicals and lipid peroxidation in blood platelets.

Lipopolysaccharide (LPS, endotoxin) is an important structural constituent of the membrane of gram-negative bacteria with a wide range of biological effects. It can activate blood platelets. The purpose of present study was to determine the direct effect of endotoxins from Proteus mirabilis, differing significantly in their composition, on the generation of superoxide radicals and thiobarbituric acid reactive substances (TBARS) in blood platelets. Superoxide radicals were measured by means of superoxide dismutase-inhibitable reduction of cytochrome C. The TBARS determination (malonyldialdehyde) was used as a marker of endogenous arachidonate metabolism and thromboxane A2 synthesis. Results demonstrate that three endotoxins (LPS S1959, LPS R110, LPS R45) after 2 min of action, even at the lowest concentration (0.03 microg/10(8) platelets) stimulated the generation of TBARS and release of superoxide radicals. All LPS contain lipid A as a component but differ in their chemical composition in the polysaccharide part. It is suggested that the observed effects of LPS on blood platelets are attributable to their lipid A portion.

Animals↗
PubMed2002

[Significens of blood platelet CD62p in treating sudden deafness].

OBJECTIVE: To compare different treatment methods for sudden deafness of different blood platelet CD62p levels. METHODS: Blood platelet was measured with flow cytometer. Patients with platelet CD62p over or less than 2% were treated with routine treatment (low molecular weight dextran, ATP, CoA and dexamethasone) or routine treatment plus batroxobin (thrombolysis) separately. RESULTS: In the group with platelet CD62p > or = 2%, the effective rates of routine treatment was 60.5%, and that of routine treatment plus thrombolysis was 84.6%. There was significant difference between them. In the group with platelet CD62p < 2%, the effective rates of two methods were 65.0% and 71.8% respectively(no significant difference between them). CONCLUSIONS: Detecting CD62p in sudden deafness patients makes sense for deciding treatment project.

Adolescent↗
PubMed1999

Effects of catechins on human blood platelet aggregation and lipid peroxidation.

The activity of catechins was studied for inhibitory activity in human blood platelets. Platelet aggregation and peroxidation were evaluated in platelet rich plasma (PRP) obtained from samples of healthy volunteers. Human blood platelets were submitted to stimulation with 300 microM arachidonic acid, 3 microM adenosine diphospate (ADP) and 6 microM epinephrine. Treatment with (200 microg/mL) catechin or epicatechin was sufficient to exhibit a potent inhibitory effect of the three agents. The inhibitory effect was dose dependent at concentrations of 20-200 microg/mL. Using malondialdehyde (MDA) as an index of total lipid peroxidation capacity, decreased production of MDA of the platelets treated with catechin or epicatechin after stimulation by arachidonic acid was observed. These findings suggest that catechins protect platelets from peroxidative stress and their aggregation.

Adenosine Diphosphate↗
PubMed1980

Changes of 32P-incorporation in vitro into phospholipids of blood platelets after whole-body irradiation of rabbits. I. Comparison of 32P-incorporation with some platelet functional tests during early development of postirradiation thrombocytopenia.

In the period of postirradiation bone-marrow activity depression, changes of the 32P incorporation into phospholipids of blood platelets in rabbits after whole-body exposure to 103.2 mC/kg were noted in vitro. Increased incorporation into phosphatidylcholine, phosphatidylethanolamine and sphingomyeline on the 11th day and into phosphatidylserine on the 8th and 11th day were recorded. On the 5th, 8th and 11th days the pattern of incorporation is changed. During this period a pronounced decrease of 32P incorporation into phosphatidylinositols of the blood platelets was noted, no changes in the representation of the phospholipids of interest (PC, PE, SM, PS, PI) were observed and no alterations of the blood platelet adhesiveness were found. The PF3-A and PF3-F test did not reveal any significant changes of the role of PF 3 in the blood clotting process.

Animals↗
PubMed1981

Catabolism of thymidine in human blood platelets: purification and properties of thymidine phosphorylase.

A pyrimidine nucleoside phosphorylase was partially purified from human blood platelets. The purified enzyme, as well as crude enzyme preparations, catalyses the phosphorolysis of thymidine and deoxyuridine, but not of uridine, and is able to catalyse direct pentosyl transfer from these deoxyribonucleosides to uracil or thymine; this enzyme has the properties of a thymidine phosphorylase. It has a molecular weight of about 110,000 and is composed of two identical subunits; it is phosphate dependent, has a maximal activity at a pH value of 5.7, and an isoelectric point of 4.4. This enzyme was mainly of cytoplasmic origin. Although platelet thymidine phosphorylase could promote the degradation or synthesis of thymidine, intact platelets degraded thymidine but were not able to synthesize thymidine from thymine. Blood platelets may play an important role in the degradation of plasma thymidine.

Blood Platelets↗
PubMed2001

[Evaluation of functional state of blood platelets in patients infected with Echinococcus granulosus].

Blood platelets actively participate in defense mechanisms of the organism. eg. in antiparasitic immunology. The study involved 17 patients infected with Echinococcus granulosus. Blood for analysis was collected twice, before treatment (E1) and after it (E2). Control group consisted of 30 healthy people. The concentrations of beta-thromboglobulin and platelet factor 4 were assayed using a set of ASSERACHROM (Boehringer Mannheim) according to the immunoenzymatic method with labelled antibodies. The level of platelet factor 4 (before and after the antiparasitic treatment) indicates platelet activation by parasite.

Adolescent↗
PubMed1993

Effect of electric charge on the adhesion of human blood platelets.

The paper presents the results of research into the effect of the size and depth of the implanted electric charge on the adhesion of human blood platelets. The experiments were carried out on polyethylene terephthalate PET foil of 36 microns thickness. The electret formation process was carried out in an electron-beam device. The electrization conditions were such that electrets with the excess electric charge accumulated at various depths were obtained. The selection of conditions was verified by investigating the space charge distribution with the use of the virtual electrode method. The microscopic observation of non-electrified foils and electrets as well as the quantitative examination of the adhesion of human blood platelets has explicitly confirmed the positive influence of the electret effect on the thrombogenesis of PET foil. This made it possible to define the optimum electrization conditions. The research has additionally indicated that the relationship between the amount of adherent blood platelets and the size of the electric charge is not a simple relation of the kind: the larger negative charge, the more thrombogenic material. The decisive and positive effect of the space charge has been confirmed by analysing the effectiveness of the surface and space charge.

Biocompatible Materials↗