Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thrombotic thrombocytopenic purpura (TTP) is a rare syndrome of unknown etiology. It is characterized by platelet microthrombi in small vessels, which results in tissue dysfunction and a microangiopathic hemolytic anemia. Activation of coagulation is not a prominent feature of TTP. It is not known whether the process which results in platelet aggregate formation might also activate platelets. Using GMP-140 as a marker of activation, we examined the activation state of circulating platelets in seven TTP patients and three normal controls, as well as the ability of purified platelets from three TTP patients and three controls to be activated in vitro. There was no statistically significant difference in the percentage of activated platelets circulating in patients and controls (4% vs. 2%). Both TTP and control platelets increased GMP-140 expression and procoagulant activity after stimulation with thrombin or the calcium ionophore A23187. Thus, we conclude that TTP patients do not have a significantly increased proportion of circulating activated platelets, and their platelets can be activated normally by thrombin or a calcium ionophore.
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PMID:Platelet activation in patients with thrombotic thrombocytopenic purpura. 767 78

Cytotoxic drugs may potentiate the thrombotic complications in patients with malignancies and platelet function abnormalities have been reported after initiation of cisplatin therapy. This report describes a prolonged activation of platelets over 6-24 h co-culture with peripheral blood mononuclear cells (PBM) by pharmacological doses of cisplatin. Cisplatin had no direct effect on platelets and depended on PBM to produce aggregation which was apparently not mediated by products of the cyclooxygenase or lipoxygenase pathways, by platelet activation factor (PAF) or by thrombin. Although platelet aggregation normally involves the binding of fibrinogen to the beta 3 integrin, GP IIb-IIIa, on activated platelets, the cisplatin-dependent platelet aggregation observed in the co-culture experiments was not inhibited by an anti-GP IIb-IIIa monoclonal antibody which blocks fibrinogen-dependent aggregation nor by an adhesive peptide containing the RGDS integrin recognition sequence. Rather, aggregation appeared to involve a novel 140 kD granule membrane protein (GMP-140) mediated mechanism since aggregation was almost completely blocked by Fab fragments of an antibody to GMP-140 and was inhibited by fluid-phase GMP-140. At concentrations of cisplatin, adriamycin, and LPS that induced equivalent levels of tissue factor of blood monocytes, prothrombinase activity was significantly greater in cultures containing cisplatin. Prothrombinase activity was dependent on the presence of platelets and the rate of thrombin formation was enhanced by factor Xa generated by the tissue factor-factor VIIa complex. These studies suggest that the vascular and thrombotic complications associated with cisplatin therapy are mediated, at least in part, by platelet activation and aggregation and monocyte procoagulant activity.
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PMID:Cisplatin-induced platelet activation requires mononuclear cells: role of GMP-140 and modulation of procoagulant activity. 768 17

Rapid upregulation of the adhesion molecule GMP-140 (P-selectin) on endothelial cells is believed to play an important role in the initial binding of leukocytes to endothelium, a very early step in the inflammatory response. Activated platelets that are involved in the coagulation system and in inflammatory processes also express GMP-140 on their surfaces. The objectives of the present study were to develop a monoclonal antibody against this adhesion molecule in the dog and to use this antibody to study platelet-neutrophil interactions in whole blood and to characterize the in vivo localization of GMP-140 in canine tissues. Five Balb/c mice were immunized with thrombin-stimulated dog platelets, and clones were screened using an enzyme-linked immunosorbent assay. The clone MD3 (IgG1) showed preferential binding to activated as compared with resting platelets. Flow cytometric analysis using MD3 revealed that 27% of circulating neutrophils in unstimulated blood had platelets bound to their surfaces; stimulation with platelet activating factor increased this percentage to 85%. Immunoblot analysis of solubilized dog platelets resolved by sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated that the antibody MD3 recognized an approximately 140-kd protein. Immunohistochemical study of normal dog tissues with MD3 revealed that the antigen was present in endothelial cells of arteries, capillaries, and veins, depending on the specific tissue examined. Blood vessels staining positively with MD3 were most abundant in the digestive system (liver, stomach, small and large intestines), moderate in the lungs, kidneys, spleen, lymph nodes, and endocrine glands, and minimal in the brain, myocardium, skeletal system, and skin. Based on its presence on stimulated but not resting platelets, its molecular weight, and its vascular distribution, the antigen recognized by MD3 appears to be the selectin GMP-140 of the dog. This study documents that the cellular and tissue distribution of GMP-140 in dogs is very similar to that in human beings.
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PMID:Production of a monoclonal antibody against canine GMP-140 (P-selectin) and studies of its vascular distribution in canine tissues. 768 99

1. P-selectin (PADGEM, GMP140, or CD62) a member of lectin-like adhesive proteins is expressed on the surface of activated degranulated canine platelets and is the calcium-dependent receptor for leukocyte adhesion. 2. The electrophoretic mobility of P-selectin, by Western blot analysis and immunoprecipitation from radiolabeled membranes of canine and human platelets, was similar or identical and immunocytochemical studies localized P-selectin in internal vesicles similar to the alpha granule localization in human platelets. 3. Two antibodies to human P-selectin KC4.1 and AC1.2 crossreacted with canine platelets whose surface binding, in response to agonists thrombin, calcium ionophore (A23187), phorbol esters and ADP, was similar. 4. Anti-P-selectin antibodies in conjunction with crossreacting anti-GPIIb/IIIa antibodies (A2A9, 7E3, RUU-PL7F12) enables the analysis of activated platelets, platelet-derived microparticles and platelet-leukocyte interactions in canine models by flow cytometry.
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PMID:Characterization of canine platelet P-selectin (CD 62) and its utility in flow cytometry platelet studies. 768 39

The stimulated release of von Willebrand factor (vWF) from endothelial cells by secretagogues such as thrombin is associated with the translocation of Weibel-Palade bodies to the cell membrane and the surface expression of P-selectin (also known as GMP 140, PADGEM and CD 62). P-selectin, which is stored in Weibel-Palade bodies, is a neutrophil and monocyte adhesion molecule important in the initiation of inflammation. We have developed a simple assay for the detection of P-selectin on endothelial cells using indirect immunofluorescence and flow cytometry and have confirmed that this is temporally related to vWF release. The assay has been used to demonstrate that IL-1 does not cause Weibel-Palade body degranulation but that trypsin does. This has implications for the use of passaged endothelial cells in the study of vWF release and the assay has numerous possible applications in study of mechanisms of stimulated vWF release.
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PMID:von Willebrand factor release and P-selectin expression is stimulated by thrombin and trypsin but not IL-1 in cultured human endothelial cells. 769 90

This study characterizes a new congenital thrombocytopenia with mild hemorrhagic tendency occurring in a woman and her child with the following features. We found a deletion of the distal part of one chromosome 11 [del(11)q23.3-->qter] that was detected by cytogenetic analysis and confirmed by chromosome painting in the two patients and also an increased number of bone marrow megakaryocytes (MKs), including numerous micromegakaryocytes (mMKs) associated with a normal platelet life span. A normal number of MK colonies in culture was observed with one third of them containing a few large MKs; however, these were always associated with mMKs identified by immunologic staining. A massive cell lysis was observed at the end of the maturation. Fifteen percent of the platelets in the peripheral blood showed giant alpha-granules resulting from the fusion of alpha-granules. These giant granules, which appeared in red on giemsa stain, had a mean diameter of 1.5 microns and showed all markers (detected at electron microscopy by immunogold method) of matrix and alpha-granule membrane, ie, von Willebrand factor, fibrinogen, CD41, CD62P (P-selectin); however, they differed from lysosomes because acid phosphatases were not present. These giant alpha-granules were unable to release their contents after stimulation by thrombin, in contrast to platelets with normal morphology. Abnormalities in bone marrow MK maturation that were detected at the electron microscopic level and that led to lysis of numerous MKs were responsible for thrombocytopenia and were similar in both patients. MK abnormalities are probably the consequence of the chromosome aberration. ETS 1 and FLI, two proto-oncogenes that appear to be essential with GATA1 for the normal expression of MK-specific genes, map to 11q23-q24 and are, thus, deleted in this thrombocytopenia. In conclusion, the association of all these abnormalities constitutes a new familial platelet disorder and may present a valuable model for exploring the role of some genes involved in the regulation of thrombopoiesis.
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PMID:A new congenital dysmegakaryopoietic thrombocytopenia (Paris-Trousseau) associated with giant platelet alpha-granules and chromosome 11 deletion at 11q23. 863 71

Magnesium deficiency and its association with platelet hyperreactivity has been well recognised in a variety of diseases including myocardial infarction, preeclampsia, and diabetes. In order to investigate potential effects of intravenous Mg2+ supplementation, platelet function was studied by measurements of in vitro bleeding time (BT) and of fibrinogen (Fg)-mediated aggregation of washed platelets. In addition, the effect of Mg2+ on platelet adhesion onto immobilised Fg, on Fg binding to activated platelets, and on surface expression of GMP-140 or GP53 was evaluated. Mg2+ (4 mM) prolonged in vitro BT by 30% and inhibited Fg-mediated aggregation significantly, independent of the agonist used to initiate platelet aggregation (ADP, collagen, epinephrine, thrombin, phorbol ester). Adhesion of resting platelets to immobilised Fg was reduced by 50% in the presence of 2 mM Mg2+. Moreover, Mg2+ reduced Fg binding to ADP- or collagen-stimulated platelets as well as surface expression of GMP-140 with an IC50 of approximately 3 mM. Intravenous administration of Mg2+ to healthy volunteers inhibited both ADP-induced platelet aggregation (p < 0.05) by 40% and binding of Fg or surface expression of GMP-140 by 30% (p < 0.05). Thus, pharmacological concentrations of Mg2+ effectively inhibit platelet function in vitro and ex vivo.
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PMID:Effects of magnesium on platelet aggregation and adhesion. Magnesium modulates surface expression of glycoproteins on platelets in vitro and ex vivo. 774 Apr 63

Patients with antiphospholipid syndrome, whether primary or secondary to systemic lupus erythematosus, may have thrombocytopenia. Their antibodies to anionic phospholipids might bind to phospholipids on the platelet wall but anionic phospholipids are asymmetrically located in the inner leaflet. In addition, antibodies to anionic phospholipids may require beta 2 glycoprotein I (beta 2GPI) as a cofactor in order to bind to phospholipids. In turn, beta 2GPI has high affinity for anionic phospholipids. Loss of this asymmetry occurs upon platelet activation and could thus permit such antibody-beta 2GPI-platelet interaction. We studied this by flow cytometry using purified beta 2GPI-FITC labelled and similarly labelled affinity-purified polyclonal antibodies to cardiolipin or phosphatidylserine (aPL) obtained from sera of patients with primary antiphospholipid syndrome. Five percent of resting platelets were bound by aPL in the presence of beta 2GPI. Such binding increased when we activated platelets with various agonists, reaching 31% with the concurrent use of thrombin and the calcium ionophore A23187. Platelet activation resulted in the expression of GMP140 but this did not correlate with aPL binding. This probably reflects that the expression of GMP140, which depends on their secretion of alpha granules, has different agonist responses and occurs at different times than do microvesicle formation and expression of prothrombinase activity which coincide with the loss of phospholipid asymmetry on the platelet wall. When we studied the binding of purified beta 2GPI we also found that it binds preferentially to activated platelets and that it seems to be a prerequisite for the binding of aPL onto them. Our findings indicate that aPL from patients with antiphospholipid syndrome may bind to activated platelets through beta 2GPI.
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PMID:Exposure of anionic phospholipids upon platelet activation permits binding of beta 2 glycoprotein I and through it that of IgG antiphospholipid antibodies. Studies in platelets from patients with antiphospholipid syndrome and normal subjects. 791 7

Vascular diseases and related complications still represent the main cause of death in diabetic patients. Neuropathy, nephropathy, retinopathy, and disturbed nutritive tissue perfusion may result from reduced capillary microcirculation. These disturbances are diabetes specific. Macroangiopathy does not differ structurally from atherosclerotic lesions of nondiabetic subjects, but leads to accelerated cerebral, coronary, and peripheral artery disease. Occurrence of life-terminating thrombotic events, which are superimposed on those vascular lesions, are increased. Thus, morbidity and mortality of diabetics depend mainly on vascular complications. Normal blood flow is a prerequisite of adequate organ perfusion and results from vasomotion, plasma components, corpuscular blood elements, vascular architecture, and the undisturbed interaction of these components at the endothelial interface. Functional thromboresistance of the endothelial layer is reduced in the diabetic state. Increased intravascular thrombin generation, reduced fibrinolytic potential, and hyperactive platelets lead to a prethrombotic state. This thrombotic diathesis increases the permanent danger of acute flow interruption. Activated platelets operate by three mechanisms: (1) Microembolization of the capillaries; (2) local progression of preexisting vascular lesions by secretion of constrictive, mitogenic, and oxidative substances; (3) trigger of the prognosis-limiting arterial thrombotic event. We were able to show that the increased functional properties of diabetic platelets result from the primary release of larger platelets with enhanced thromboxane formation capacity and increased numbers of functional glycoprotein receptors GPIb and GPIIb/IIIa, which are synthesized in the megakaryocytes. The megakaryocyte-platelet system is turned on in diabetes mellitus. It could be demonstrated with the Duesseldorf III method of flow cytometric activation marker testing (CD62, CD63, thrombospondin) that predominantly large platelets circulate in an activated state in diabetes mellitus.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Platelets in diabetes: the role in the hemostatic regulation in atherosclerosis. 835 57

Changes in the platelet plasma membrane during activation were investigated by flow cytometry in a comparative study of in vitro platelet activation during platelet storage and cardiopulmonary bypass surgery. We studied changes in the expression of the plasma membrane glycoproteins lb and llla and CD31 antigen (PECAM-1), the alpha-granule membrane proteins GMP-140 (PADGEM, CD62 antigen) and GMP-33, and lysosomal integral membrane protein-CD63. A simultaneous change in the expression of the various glycoproteins induced by platelet activation was seen after thrombin stimulation in vitro and during platelet storage. Platelet activation in vivo in patients showed a more complex change in the expression of membrane glycoproteins. During cardiopulmonary bypass the mean fluorescence values for glycoprotein llla, GMP-33, and the percentage of GMP-140 and lysosome integral membrane protein-CD63 expressing platelets increased significantly. CD31 antigen expression was significantly decreased, whereas glycoprotein lb expression did not change. We conclude that flow cytometry is useful for the detection of changes in the expression of membrane glycoproteins induced by platelet activation in vitro and during platelet storage. Application of flow cytometry as clinical tool for screening platelet activation in patients or for identification of a prethrombotic state requires evaluation of a panel of platelet membrane glycoproteins because the changes in membrane expression may be different in various clinical situations.
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PMID:Comparison of platelet membrane markers for the detection of platelet activation in vitro and during platelet storage and cardiopulmonary bypass surgery. 845 40


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