Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: HUMANGGP:001400 (PRP)
 1,320 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The potential in vitro (heparinized or citrated PRP) and in vivo effects of urethane and thiopental sodium on arachidonic acid, collagen, or ADP-induced rat platelet aggregation has been investigated. Both anesthetics antagonized platelet aggregation in vitro at concentrations higher than those found in plasma during anesthesia. Neither anesthetic altered the piastrinopenia induced by intravenous administration of these aggregating agents. These findings suggest that both anesthetics are suitable for in vivo platelet aggregation studies.
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PMID:The effect of urethane and thiopental sodium on platelet aggregation in vitro and in vivo. 644 35

During acute malaria infection, platelets in human platelet-rich plasma re hypersensitive to the addition of ADP between 1.0 micro M and 5.0 micro M, or adrenaline 0.11 micro M as aggregating agents. The mean maximum aggregation amplitude (as % of light transmission) obtained from 8 subjects in response to added ADP (1.0 micro M) , 39.8 +/- 27 (1SD), was significantly greater than the value in 6 controls (5.2 +/- 6.7 (1SD); t = 3,51 P less than 0.005). A similar pattern of response was obtained with higher ADP concentrations (2,4, 4.5 or 5.0 micro M) in 22 patients and 20 control subjects (89.9 +/- 14.9 % vs 77.8 +/- 16.5% (1SD) t = 2,45, P less than 0.02). Addition to 4.5 microM ADP to patient PRP usually evoked only a single aggregation wave (fused primary and secondary waves) while the typical primary and secondary wave pattern was usually obtained from controls. Mean plasma B-thromboglobulin (BTG) concentration in 7 patients (208.3 +/0 15.6 ng/ml) was significantly higher than the value in 6 control subjects (59.2 +/- 15.7 ng/ml; t=13.44, P less than 0.002).
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PMID:Platelet hypersensitivity in acute malaria (Plasmodium falciparum) infection in man. 645 13

The ultrastructure, cytochemistry, biochemistry, and functions of platelets from two patients with the familial gray platelet syndrome are described. Ultrastructural studies showed a lack of alpha-granules in the megakaryocytes in the vicinity of a marrow myelofibrosis and/or in platelets. A normal number of mitochondria and a slight increase of dense bodies was confirmed by labeling the whole patient with mepacrine. Platelet peroxidase (in the dense tubular system) and catalase-positive granules (revealed by the cytochemistry) were present. Platelets from both patients had severe deficiency of beta TG either after tritonization (less than 4% of normal) or thrombin treatment (less than 15% of normal), and the plasma beta TG levels were slightly increased. Functional studies of these platelets showed an uptake of [14C]5HT inhibited by reserpine similar to that in the control platelets. Thromboxane formation was within normal limits in the presence of arachidonic acid, ADP, collagen, or ionophore A23187, indicating that (1) the cyclooxygenase/thromboxane synthetase systems were not altered and (2) the phospholipase activities were not impaired. Although the platelet adhesion to prepolymerized fibrillar type III collagen and the ADP-, arachidonic acid-, and ionophore A23187-mediated aggregations were apparently normal, in every case the release of [14C]5HT was either at the low side of the normal range or decreased. This abnormality was increased when collagen or thrombin was added to either PRP or washed platelets from both patients, where at the same time, the aggregation and the release were markedly reduced. The results suggest that alpha-granules or their content has an influence on not only the platelet aggregation but also the dense bodies involved in the [14C]5HT release reaction.
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PMID:Gray platelet syndrome: alpha-granule deficiency. Its influence on platelet function. 645 43

The effect of heparin on platelet aggregation was systematically examined on platelets in plasma (PRP), as well as on gel-filtered, washed, and formaldehyde-fixed platelets. Results indicate that, although heparin causes a mild potentiation of platelet aggregation in the PRP systems, a significant inhibitory activity is observed when heparin is added to isolated platelets. This inhibitory activity appears to be specific and not related to the impurities in the heparin preparations, as heparinase, as well as protamine, effectively neutralizes the heparin-mediated inhibitory activity on platelet aggregation. Although heparin-mediated inhibitory activity can be demonstrated in the presence of a number of different agonists (ADP, arachidonic acid, thrombin, Ionophore A23187, epinephrine, and ristocetin), the most pronounced inhibition is seen in the presence of ristocetin. Further studies show that heparin enhances thromboxane generation in isolated platelets. Platelets pretreated with heparin, however, fail to respond to preformed thromboxane. These findings suggest that, in addition to the potentiation of thromboxane production in platelets, heparin may also attribute some change(s) to the platelet(s)/platelet membrane, which interferes with their ability to respond to the agonists of platelet aggregation. This antiaggregatory activity of heparin was found to be inhibited by a factor(s) present in plasma but not in serum.
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PMID:Effect of heparin on platelet aggregation. 647 40

Evidence has been reported to indicate that red blood cells (RBCs) may potentiate platelet adherence and platelet aggregation (PAG) in different flow systems in vitro as well as hemostatic platelet plug formation in response to vascular injury. In this study, we demonstrate that RBCs enhance PAG induced by well-defined, low-intensity, uniform, laminar shear stress. Potentiation by RBCs of shear-induced PAG was associated with appreciable loss of adenine nucleotides from 14C-adenine-labeled RBCs, the extent of which increased with increasing RBC concentration. The concentrations of RBC-derived ADP measured in the medium after shear, as determined by both high pressure liquid chromatography and the luciferin/luciferase system, were within the range of concentrations of ADP which may trigger PAG or potentiate PAG induced by low concentrations of other platelet agonists in the aggregometer. To assess the relative contribution of chemical (ADP) and physical (platelet surface transport) mechanisms in the RBC-mediated potentiation of shear-induced PAG, aliquots of citrated platelet-rich plasma (C-PRP) were exposed to shear stress in the presence of untreated RBCs or RBCs exposed to an antihemolytic concentration (5 mumol/L) of the membrane stabilizing agent, chlorpromazine (CPZ). Potentiation of shear-induced PAG in the RBC-CPZ system was significantly less than that in the untreated RBC system. However, CPZ-induced reduction of PAG potentiation was associated with an increase rather than a decrease in loss of adenine nucleotides from RBC. Furthermore, shear-induced PAG in C-PRP as well as ADP- and collagen-induced PAG in C-PRP in the aggregometer was significantly inhibited by 5 mumol/L CPZ, indicating that the observed reduced potentiation of shear-induced PAG by RBCs in the presence of CPZ was due to a direct inhibitory effect of the drug on platelets rather than a reduction of shear-induced liberation of ADP from RBCs. When aliquots of C-PRP were exposed to shear stress in the presence of RBCs completely depleted of ADP by fixation in 1% glutaraldehyde, potentiation of PAG was approximately half of that observed with intact RBCs. These findings indicate that both RBC-derived ADP and RBC-mediated platelet surface transport are involved in the potentiation by RBCs of PAG induced by laminar shear stress.
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PMID:Potentiation by red blood cells of shear-induced platelet aggregation: relative importance of chemical and physical mechanisms. 649 35

Piribedil at high concentrations inhibits in vitro ADP and thrombin aggregation effect on the rabbit PRP.
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PMID:Piribedil and platelet aggregation. 659 6

Thirty-five patients affected by acute vestibular dysfunction (A.V.D.) and/or sudden deafness (S.D.) were studied. Twenty-seven of them presented, as major component of the clinical disorder, a vestibular dysfunction, eight a sudden deafness. The control group was matched for sex, age, smoking habit and family history of diabetes and myocardial infarction. In all the subjects the following tests were carried out: platelet aggregation (Born's method), PF3 (Spaet and Cintron), PF4 and BTg (RIA), aPTT, AT III, cholesterol and triglycerides. The results indicate in the patients group increase of P.A.: SAV = 27 vs 43% (p = 0.03) at 1.2 X 10(-6) M ADP, a larger availability of PF3 in PPP and PRP, increase of PF4: 7.2 vs 17.2 (p = 0.01) and BTg: 32.4 vs 49.1 (p = 0.009). The data indicate in A.V.D. and S.D. a platelet hyperactivity; if so, an antiplatelet therapy may be reasonable.
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PMID:[Evaluation of platelet function and coagulation in deafness and sudden vestibular disorders]. 660 6

The inhibitory effect of etafenone hydrochloride (etafenone) on platelet aggregation in rabbit platelet rich plasma and the involvement of the arachidonic acid (AA) cascade in the inhibitory mechanism for etafenone on platelet aggregation were studied. 1) Etafenone exhibited a dose-dependent inhibitory effect on collagen (15--20 micrograms/ml)-induced platelet aggregation, and its median inhibitory concentration (IC50) was 1.7 X 10(-5)M. 2) In ADP (20 microM)-induced aggregation, etafenone also exhibited a dose-dependent inhibitory effect, but its IC50 was 2.7 X 10(-4)M and was significantly higher than that in the case of collagen. 3) Etafenone inhibited AA (0.3--0.5mM)-induced platelet aggregation dose-dependently. Its IC50 was 2.8 X 10(-5)M. 4) In thromboxane (TX) A2-induced aggregation, etafenone exhibited a dose-dependent inhibition, and the IC50 was 3.2 X 10(-4)M. 5) Trapidil which was reported to inhibit platelet aggregation via phosphodiesterase (PDE) inhibition had a similar IC50 on ADP- and TXA2-induced platelet aggregation to that of etafenone, but in collagen- and AA-induced aggregation, its IC50 was higher than that of etafenone. 6) Etafenone (3 X 10(-6)--3 X 10(-4)M) dose-dependently inhibited the production of TXB2 in PRP induced by collagen. 7) Etafenone scarcely affected TXA2 synthetase activity in rabbit platelet homogenate. 8) The correlation between the inhibitory effect of etafenone on platelet aggregation and inhibition of AA metabolism activation and PDE inhibition was discussed.
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PMID:[Studies on the inhibitory effect of etafenone hydrochloride on platelet aggregation]. 661 41

We studied the ultrastructural morphology and function of platelets collected by apheresis procedure with discontinuous flow using the Surge Pump Technique. The platelet concentrates obtained by this technique are free of erythrocyte and lymphocyte contamination. The platelet morphology as well as the platelet aggregation induced by ADP, adrenaline and collagen of platelet concentrates were similar to those observed in PRP before the apheresis. The response to the hypotonic shock of platelet concentrates was also normal, indicating membrane integrity and good platelet metabolism. These results show that platelet concentrates obtained by the Surge Pump Technique maintain their haemostatic effects and may be infused in thrombocitopenic patients, reducing the risk of alloimmunization related to the presence of erythrocytes and lymphocytes.
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PMID:[Platelet aggregation and resistance to osmotic shock of platelet concentrates obtained by discontinuous-flow cell separation with the surge pump technic]. 671 34

A method is described for characterizing disaggregatory and proaggregatory prostanoids in a single assay. This "post-addition assay" consists of adding the test agent to PRP containing PGI2 (4-6 nM) 90 sec after an ADP challenge. The relative potencies of known inhibitors of ADP-induced aggregation were identical to the relative disaggregatory potencies determined by post-addition. The proaggregatory relative potencies for 16, 16-Me2-PGE2,PGE2,PGH2 and 11 alpha,9 alpha-epoxymethano-15 alpha-hydroxy-prostadienoic acid were 5.8 :2 : 1.8 : 1, respectively, revealing the significant thrombosis promoting activity of PGE2 and its analogs.
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PMID:A single platelet aggregometric assay for pro-and antiaggregatory prostanoids. 675 67


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