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At least 199 records · Page 11Linked to original sources
PubMed1992

Vasopressin elevation of Na+/H+ exchange is inhibited by genistein in human blood platelets.

The regulation of intracellular Na+ and pHi in human blood platelets is known to be controlled by the function of the Na+/H+ exchanger. The phosphorylation state of the Na+/H+ exchanger which determines the exchanger activity in human blood platelets is regulated by the activities of protein kinases and protein phosphatases. Observations in this study indicate that arginine vasopressin (AVP) that interacts with a V1 receptor, activates the Na+/H+ exchange in human blood platelets through a genistein-inhibited mechanism. The AVP-activated Na+/H+ exchange is probably not regulated by protein kinase C (PKC), since this activation is not inhibited by staurosporine. The multiple ways in which platelet Na+/H+ exchange can be modulated may indicate the critical role played by this exchanger in the homeostasis control of pHi in human blood platelets.

Adult↗
PubMed2006

Antioxidant and antiaggregatory effects of an extract from Conyza canadensis on blood platelets in vitro.

The antioxidative activity of the polysaccharide extract from Conyza canadensis in blood platelets treated with peroxynitrite (ONOO-) was studied. Peroxynitrite as a strong biological oxidant has toxic effects on blood platelets and induces the oxidation of thiols, carbonylation and nitration of platelet proteins and lipid peroxidation. Therefore, the aim of our study was to assess if the natural extract from herbal plant, Conyza Canadensis, may protect platelet proteins against nitrative and oxidative damage induced by ONOO-. In our study we measured oxidative damage of platelet proteins induced by peroxynitrite and protectory effects of this extract by estimation of the level of carbonyl groups and nitrotyrosine (a marker of platelet protein nitration). We also used cytochrome c reduction method to test the ability of this extract to change O2-* generation in platelets. Moreover, we determined the effects of the extract on blood platelet aggregation induced by ADP. We observed that the extract from Conyza canadensis distinctly reduced oxidation and nitration of proteins in blood platelets treated with ONOO-(0.1mM) and O2-* production in these cells. The extract from Conyza canadensis also inhibited platelet aggregation. The ability of the extract to decrease O2-* generation in blood platelets supports the importance of free radicals in platelet functions, including aggregation process. The present study suggests that the natural polysaccharide extract from Conyza canadensis has antiaggregatory and antioxidative activities, and therefore may be beneficial in the prevention of peroxynitrite-related diseases, such as cardiovascular or inflammatory diseases.

Analysis of Variance↗
PubMed1997

The bactericidal activity of blood platelets in patients infested with Entamoeba histolytica/Entamoeba dispar.

Blood platelets participate actively in organism defensive reactions and particularity in antiparasitic immunity. Platelets stimulation can be the result of contact with a parasite, the presence of immunoglobulins, complement and lymphokines. The aim of the study was to evaluate the blood platelets bactericidal activity in the course of amoebiasis. The examination was carried out in the group of 22 patients with E. histolytica/E. dispar, diagnosed on the basis of cyst forms presence in faeces. The results show that blood platelets bactericidal activity is significantly impaired in the course of amoebiasis.

Adolescent↗
PubMed2002

Resveratrol and vitamin C as antioxidants in blood platelets.

We investigated the effects of two different compounds with potential antioxidative action (found in many fruits, which can be used in therapy of cardiovascular disorders): trans-resveratrol (3,4',5-trihydroxystilbene) and vitamin C on oxidative stress in blood platelets. Oxidative stress in blood platelets was estimated by the measurement of: (1) the generation of superoxide radicals (O(2)(-*)) (reduction of cytochrome c) and other reactive oxygen species--ROS: H(2)O(2), singlet oxygen and organic radicals (chemiluminescence), (2) the production of thiobarbituric acid reactive substances (TBARS) and the level of conjugate dienes as markers of lipid peroxidation. We have shown that vitamin C at the concentrations of 750-3000 microM, but not at the concentration of 100 microM (prooxidative action) significantly inhibited peroxidation of lipids (measured by TBARS and conjugate dienes) and the production of ROS in blood platelets. After the incubation of blood platelets for 30 min at 37 degrees C with vitamin C at the concentration of 3000 microM, inhibition of ROS generation (above 90%) was achieved. The inhibition of ROS production caused by resveratrol at physiological plasma concentrations 0.05-2 microM was lower than by vitamin C. At the highest concentration of vitamin C used (3000 microM), the inhibition of O(2)(-*) generation was about 40%. Moreover, we did not observe any synergistic action of resveratrol and vitamin C at antioxidative dose (3000 microM) on the inhibition of lipid peroxidation and the production of O(2)(-*) or ROS in blood platelets. Resveratrol as an antioxidant reduced oxidative stress in blood platelets caused by vitamin C at prooxidative dose (100 microM).

Animals↗
PubMed1985

Effect of protein concentration on kinetic constants (Kd and Bmax) of 3H-imipramine binding in blood platelets.

3H-imipramine binding was studied in the blood platelets of 80 normal controls and 50 depressed (psychotic and nonpsychotic) patients. Protein concentration in the incubation mixture, and Kd and Bmax values were correlated in normal controls and depressed patients. A small but significant correlation between protein in the incubation mixture and Bmax was observed in normal controls and depressed patients. There was also a significant correlation between protein and Kd of imipramine binding in the blood platelets of unipolar psychotic depressed patients. However, analysis of covariance to remove the effect of protein on Kd and Bmax did not change the basic finding of decreased Bmax in the blood platelets of psychotic depressed patients.

Adult↗
PubMed2000

Vitamin C suppresses the cisplatin toxicity on blood platelets.

The effects of vitamin C on the oxidative stress in blood platelets induced by cisplatin were studied. In the presence of vitamin C we measured in blood platelets the production of thiobarbituric acid reactive substances (TBARS), the generation of superoxide radicals (O2*-), other reactive oxygen species (H2O2, singlet oxygen and organic radicals) and catalase activity. Vitamin C at a low concentration (0.1 mM), like cisplatin (20 microM), induced blood platelet oxidative stress: an increase of TBARS, chemiluminescence and generation of superoxide radicals. After treatment of blood platelets with vitamin C at a high concentration (3 mM), chemiluminescence (p>0.05), the levels of O2*- (p<0.01) and TBARS (p<0.002) were reduced. We have shown that vitamin C at a high concentration (3 mM) had a protective effect against oxidative stress in platelets caused by cisplatin (20 microM). It diminished platelet lipid peroxidation and reactive oxygen species generation induced by cisplatin. In the presence of vitamin C, the catalase activity was suppressed.

Animals↗
PubMed1991

Human blood platelet as research tool in neuropsychopharmacology.

The use of blood platelets as a nerve terminal model for serotonin is well documented. However, it is clear that the use of platelets as a model can be justified only for those parameters where it may be shown that blood platelets and neural cells share almost identical features. The excellent similarity between the serotonin transport mechanisms in platelets and in nerve terminals, and the existence of various receptors for biogenic amines, peptides and substances with neuronal activity on platelet membrane offer a really unique opportunity to utilize blood platelets as a system for drug evaluation. In our work platelet benzodiazepine binding sites and their modulation by different benzodiazepines in normals and in demented patients are examined.

Adult↗
PubMed1986

Inhibition of whole blood platelet aggregation by nicardipine, and synergism with prostacyclin in-vitro.

Platelets are involved in the pathogenesis of vascular disease, and calcium channel blocking agents (CCB) such as nicardipine, are being used in the treatment of such disorders. CCB's are known to have minor anti-platelet actions from studies performed in platelet rich plasma (PRP). Recently it has become possible to study platelet aggregation in whole blood. The effects of nicardipine on whole blood platelet aggregation were studied in-vitro using the Clay-Adams Ultra Flo 100 whole blood platelet counter. Nicardipine inhibited aggregation to 0.5 micrograms/ml collagen, and 0.5 mM arachidonic acid in a dose dependent manner, but had minimal effects on aggregation to 10 microM ADP. Nicardipine also acted synergistically with prostacyclin to inhibit aggregation. The effect of nicardipine on generation of PGI2 and TxA2 from whole blood was studied. Nicardipine did not affect TxA2 production, but significantly increased PGI2 production at high concentration. The effect of nicardipine on vascular PGI2 production was also assessed using umbilical artery rings, but nicardipine had no effect on PGI2 production. This study confirms that CCBs have inhibitory actions on platelet aggregation, and this may be of value in the treatment of vascular disease.

Adenosine Diphosphate↗
PubMed1993

Changes in antioxidant enzymes activities, aggregability and malonyldialdehyde concentration in blood platelets from patients with coronary heart disease.

In 41 patients with coronary heart disease (CHD) the concentrations of total blood platelet malonyldialdehyde (MDA: 2.11 +/- 0.25 nmol/10(9) platelets) and MDA corresponding to thromboxane A2 (TXA2 0.84 +/- 0.13 nmol/10(9) platelets) were increased in comparison with values in blood platelets of healthy subjects (1.19 +/- 0.09 and 0.71 +/- 0.05 nmol/10(9) platelets), respectively. The increased aggregability with ADP and thrombin of patient platelets was also observed. In relation to the blood platelets of healthy subjects, the antioxidant enzymes activities of patient blood platelets were significantly (P < 0.001) decreased. Platelet glutathione peroxidase (GSH-Px) activity of the patients (11.3 +/- 0.85 U/g protein) was significantly lower than controls (18.3 +/- 1.12 U/g protein). In patients with CHD the activities of the other antioxidative platelet enzymes: catalase (Cat, 7.37 +/- 1.38 U/g protein) and superoxide dismutase (SOD, 1529.4 +/- 167 U/g protein) were also significantly decreased in comparison with values for healthy subjects (Cat: 9.06 +/- 1.30 U/g protein and SOD: 1987 +/- 230 U/g protein, respectively). It is suggested that antioxidative defense in blood platelets may affect the haemostatic processes and lipid peroxidation in patients with CHD.

Adenosine Diphosphate↗
PubMedDate not supplied

[The number and affinity of fibrinogen receptors in blood platelets of patients with ischemic stroke].

Parameters of fibrinogen binding with blood platelets (number of receptors and their affinity) have been studied in patients with ischemic stroke. Due to the increased platelet ability to aggregate in the ischemic diseases such studies seem helpful. The studies involved 13 patients with ischemic stroke. Blood platelets collected from younger patients (under 50 years) possessed significantly higher number of receptors binding fibrinogen than blood platelets of healthy individuals (p less than 0.02). These receptors significantly more strongly bound ligand than those in the control group (p less than 0.05), and in the group of older patients with stroke (less than 0.05). Fibrinogen binding to blood platelets in patients over 50 years of age did not differ significantly from that in the control group. These results may indicate, that the increased platelet aggregation might be a significant pathogenic factor of the stroke in younger patients.

Adult↗
PubMed1986

Does the blood platelet phagocytic capacity depend on the sex and plasma thrombopoietic activity?

In 16 men and 25 women we tested the phagocytic activity of blood platelets. In women a higher phagocytosis index, increased blood platelet count and lower percentage of phagocytizing cells could be noted in comparison to men. Blood platelet count was significantly higher in women than in men. From this group we chose 10 men and 10 women and determined the plasma thrombopoietic activity. The results obtained were divided into two subgroups A with high and B low plasma thrombopoietic activity. In subgroup A a higher blood platelet count and phagocytosis index and a decreased percentage of phagocytizing platelets in relation to subgroup B could be found. The phagocytic activity of blood platelets in relation to sex and plasma thrombopoietic activity is briefly discussed. The role of blood platelets in antibacterial mechanisms is emphasized.

Adult↗
PubMed1981

[Fluid storage of thrombocytes. Reaction of stored blood platelets from ACD-AG blood to hypotonic shock].

During liquid storage of platelet concentrates (PC) at 277 K (4 degrees C) and 295 K (22 degrees C) prepared from ACD-AG-blood the cells lost their ability to hypotonic shock response (HSR) within 3 days. The HSR maintained on the initial level during 3 days in platelets as platelet rich plasma (PRP) at 295 K, but fell significantly at 277 K. The number of platelets decreased more rapidly at room temperature than at 277 degrees K, but a statistical difference did not exist. At room temperature the pH-fall was accelerated and came to 6.5 even after 1 day storage of PC but only after roughly 5 days in PRP.

Acids↗
PubMed1977

Cyclic 3',5'-adenosine monophosphate level and adenylate cyclase activity in human blood platelets during storage in ACD solution.

The level of cyclic 3',5'-adenosine monophosphate (cAMP) in human platelets and the activity of platelet adenylate cyclase in response to prostaglandin E1 stimulation do not change during two days storage at room temperature in ACD solution. However, the level of cyclic AMP is lower in platelets stored in ACD solution than in platelets from blood anticoagulated by ethylenediamine tetra-acetic acid.

Adenylyl Cyclases↗