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)

We studied in vitro the antiplatelet activity of a new nitroderivative chemically related to acetylsalicylic acid: 2 acetoxybenzoate 2-[1-nitroxy-methyl]-phenyl ester (NCX 4016), in order to identify any effects due to the release of nitric oxide and the blockade of cyclo-oxygenase. The effects of scalar doses of NCX 4016 on the early phase of platelet activation, platelet aggregation and thromboxane A2 production were investigated. We observed inhibitory effects of NCX 4016 on platelet adhesion (IC50 = 7.3 x 10(-5) M), platelet cytosolic calcium concentration, assayed by fluorescent probe Fura 2, and the expression of glycoprotein IIb/IIIa (CD41/alpha IIb beta 3) (IC50 = 3.4 x 10(-5) M) and P-selectin (CD62/GMP-140) (IC50 = 4.9 x 10(-5) M) measured by flow cytometry. NCX 4016 also prevented thrombin-induced platelet aggregation (IC50 = 3.9 x 10(-5) M). None of these parameters were affected by acetylsalicylic acid. These inhibitory activities of NCX 4016 were abolished by oxyhaemoglobin and methylene blue. Intracellular cyclic GMP observed during thrombin-induced aggregation was increased by incubation with NCX 4016. These results appear to be attributable to the release of nitric oxide, which activates soluble platelet guanylylcyclase and promotes intracellular cyclic GMP increase. NCX 4016 almost completely inhibited platelet thromboxane A2 production and arachidonic acid-induced platelet aggregation. This also occurred in the presence of oxyhaemoglobin and methylene blue, indicating that its antiplatelet activity can be attributed not only to nitric oxide release but also to cyclo-oxygenase inhibition.
 ...
PMID:The antiplatelet effects of a new nitroderivative of acetylsalicylic acid--an in vitro study of inhibition on the early phase of platelet activation and on TXA2 production. 895 Jul 92

The initial reactions of two TiO2 surfaces with blood were investigated by short-time exposure to capillary blood and analysis of surface-adsorbed plasma proteins and surface-adhering cells by using immunofluorescence techniques. Antibodies directed against platelet membrane antigen and P-selectin were used to visualize platelet adhesion and activation. Acridine orange and anti-CD11b were used to detect adhesion and activation of polymorphonuclear granulocytes (PMNs). Antibodies against thrombospondin were used as markers for platelet alpha-granules. The fluorescence intensity was quantitated by computer-aided image analysis. Commercially pure, polished sheet titanium was oxidized in two different ways: (1) the natural oxide was dissolved with hydrofluoric acid and a new oxide layer was grown by oxidation in nitric acid, or (2) annealing was performed at 700 degrees C in air. Auger electron spectroscopy and x-ray photoelectron spectroscopy showed that both surfaces had similar composition consisting of TiO2 covered by a carbonaceous surface contamination layer. The thickness of the oxide layer was 4 nm on the acid-oxidized surface and 39 nm on the annealed surface. Optical profilometry and scanning electron microscopy showed that the acid-oxidized surface was rough and the annealed surface was smooth. The fibrinogen/prothrombin-thrombin ratio in the initial protein film differed between the surfaces. The number of adhering platelets was larger at the surface with a high surface concentration of adsorbed fibrinogen. Platelet activation (CD62) and priming of PMNs (CD 11b) were also significantly higher on the acid-oxidized surface. The results indicate that non-self recognition of biomaterials is an array of transient reactions comprising protein-material, protein-cell, and cell-cell interactions.
 ...
PMID:Adhesion and activation of platelets and polymorphonuclear granulocyte cells at TiO2 surfaces. 901 89

This study compares granule membrane protein (GMP)-140 expression measured by flow cytometry, release of beta-thromboglobulin (beta-TG), and platelet aggregometry as markers of platelet activation in vitro. Whole blood was activated with different concentrations of thrombin. There was a significant increase in beta-TG plasma levels after stimulation with 0.01 and 0.04 U thrombin/ml. There was also an increase in GMP-140 expression, but interindividual variability was high. Aggregometry of platelet-rich plasma did not detect platelet activation and formation of platelet aggregates with 0.05 and 0.1 U thrombin/ml, while flow cytometry showed an early and significant increase of GMP-140 expression with these doses. Beta-TG release is a more sensitive marker of platelet activation than GMP-140 while flow cytometry is easier to perform and less susceptible to artifacts.
 ...
PMID:Comparison of beta-thromboglobulin, flow cytometry, and platelet aggregometry to study platelet activation. 911 89

In the absence of appropriate stimuli, polymorphonuclear neutrophils rapidly undergo characteristic changes indicative of programmed cell death or apoptosis. We report here that neutrophils cultured in the presence of platelets (neutrophil:platelet ratios of 1:50, 1:25, and 1:10) show a dramatic inhibition of apoptosis compared with neutrophils cultured alone. Similar degrees of apoptosis delay were induced by viable unstimulated platelets, fixed unstimulated platelets, or fixed activated (1 U/ml thrombin) platelets. Inhibition of apoptosis was associated with prolongation of the functional lifespan of the neutrophil, as indicated by the higher capacity of platelet-treated neutrophils to display chemiluminescence responses triggered by FMLP, immune complexes, and zymosan. The mechanism responsible for the inhibition of neutrophil apoptosis by platelets has not yet been defined. However, it seems that classical recognition systems such as those mediated by the interaction between platelet P-selectin (CD62) or glycoprotein IIb/IIIa complex and their counter-receptors expressed by neutrophils are not involved.
 ...
PMID:Inhibition of human neutrophil apoptosis by platelets. 912 Feb 96

P-selectin (GMP-140, PADGEM, CD62P) is a cell adhesion receptor which is believed to play an important role in inflammatory diseases by supporting leucocyte rolling. P-selectin is located on the granule membrane of Weibel-Palade bodies in resting endothelial cells and is expressed on the cell surface during cellular activation with various stimulators such as thrombin. Thereafter, P-selectin is internalized and sorted to the Golgi region and Weibel-Palade bodies again. However, whether P-selectin is re-expressed upon subsequent cellular stimulation has, to date, been unclear. To address this question, we measured the cellular content and surface expression of P-selectin, using indirect immunofluorescence and confocal laser cytometry. Surface expression of P-selectin reached a maximum < 2 min after thrombin stimulation and declined to basal levels after 180 min. Rechallenge with thrombin induced rapid surface re-expression of P-selectin, which was independent of de novo protein synthesis, since cycloheximide did not inhibit re-expression. Moreover, re-expressed P-selectin supported the adherence of HL60 promyelocytic cells. These results clearly demonstrated that functional P-selectin molecule was recycled after repeated stimulation with thrombin, raising the possibility that P-selectin is involved in chronic inflammation.
 ...
PMID:Re-expression of functional P-selectin molecules on the endothelial cell surface by repeated stimulation with thrombin. 916 1

Hemodialysis only partially corrects the defects in platelet function associated with uremia. Platelet contact with the artificial surfaces of the dialysis filter during hemodialysis can itself cause platelet activation, degranulation, and loss of platelet membrane glycoproteins. Although the transient platelet dysfunction that occurs after platelet contact with foreign surfaces during cardiopulmonary bypass has been well characterized, there has been no such investigation of hemodialysis. In this study of hemodialysis patients, bleeding times (BT) and the response of their platelets to thrombin, ristocetin, and collagen were measured before, immediately after, and in some patients, the day after hemodialysis. In addition, membrane glycoproteins in platelets obtained at these time intervals were studied using fluorescein isothiocyanate (FITC) conjugated monoclonal antibodies (mAb) CD42b (anti-GPIb), CD41a (anti-GPIIb/IIIa), and CD62 (anti-P-selectin), with flow cytometry. BT was significantly prolonged, and response to thrombin and ristocetin was significantly decreased immediately after hemodialysis (P < 0.01). Binding of CD42b mAb to the platelet membrane was decreased in platelets obtained immediately after hemodialysis. Most patients had shortened BT and demonstrated increased response of their platelets to thrombin and increased CD42b binding to their platelets the day after hemodialysis. These findings suggest that in uremic patients, hemodialysis is associated with transient platelet dysfunction and decreased membrane expression of GPIb.
 ...
PMID:Studies on platelet membrane glycoproteins and platelet function during hemodialysis. 917 50

The pathophysiology of platelet dysfunction in the Wiskott-Aldrich immune deficiency syndrome (WAS) remains unclear. Using flow cytometry, we have characterized the functional properties of platelets from 10 children with WAS. Patients with WAS had thrombocytopenia, small platelets, increased platelet-associated IgG and reduced platelet-dense granule content. Levels of reticulated 'young' platelets were normal in the WAS patients. Although the mean numbers of platelet glycoprotein (GP) Ib, GPIIbIIIa and GPIV molecules per platelet appeared lower in WAS patients than in healthy controls, analysis of similar-sized platelets revealed the mean number of GPIb molecules per platelet to be comparable in patients and normal controls. Surface GPIIbIIIa and GPIV expression was, however, significantly lower on the WAS platelets than on normal platelets. Compared with normal platelets, WAS platelets showed a reduced ability to modulate GPIIbIIIa expression following thrombin stimulation. In addition, thrombin- and ADP-induced expression of CD62P and CD63 was defective in WAS platelets. Phallacidin staining of the WAS platelets revealed less F-actin content than in normal platelets. Together, these data suggest that the reduced platelet number and function in WAS reflects, at least in part, a defect in bone marrow production as well as an intrinsic platelet abnormality.
 ...
PMID:Flow cytometric analysis of platelets from children with the Wiskott-Aldrich syndrome reveals defects in platelet development, activation and structure. 921 72

Three different separation methods, all using centrifugation, are routinely used to prepare therapeutic platelet concentrates from human donor blood. Platelet concentrates derived from platelet-rich plasma (PRP-PC), buffy coat (BC-PC) and apheresis (AP-PC) were investigated at the end of production, and over an 8 d storage period. Change in platelet surface markers were measured by flow cytometry, using fluorescein-conjugated antibodies to fibrinogen, P-selectin (CD62P), GPIIb-IIIa (CD41), GPIb alpha (CD42b) and GPV (CD42d), and fluorescein-conjugated Annexin V was used to measure expression of anionic phospholipid. All concentrates showed some changes during preparation but PRP-PC underwent the greatest changes with significantly higher levels of P-selectin (P<0.001) and bound Annexin V (P=0.001) than AP-PC or BC-PC, and lower levels of GPIb alpha (P=0.002) and GPV (P<0.001). These changes were attributable to component separation rather than venesection. These markers all continued to change on storage with a strong positive correlation between the changes seen during production and those after 5 d storage. PRP-PC continued to show the greatest changes whereas BC-PC showed the least. Fibrinogen was bound to 40-50% of platelets in all preparations and this did not alter significantly on storage whereas total expression of GPIIb-IIIa remained unchanged throughout. There was no evidence that the platelet surface changes were thrombin-mediated and leucocyte depletion of BP-PC by filtration had no effect on the changes. It is proposed that the deterioration of platelet concentrates during storage may be related to activation occurring during preparation. 'Whole blood' flow cytometry using a panel of fluorescein-labelled reagents provides an informative method for evaluating platelet concentrates.
 ...
PMID:Activation during preparation of therapeutic platelets affects deterioration during storage: a comparative flow cytometric study of different production methods. 923 69

Danazol, a synthetic attenuated anabolic steroid, has been administered for 36 months to a 32 year old male with hereditary Protein S (PS) deficiency who had become non-compliant for warfarin therapy. The patient has an eleven year history of venous thrombosis. Since danazol therapy was initiated, the patient has not experienced a thrombotic event or adverse side-effects. Levels of PS, other inhibitors, fibrinolytic components, and markers for thrombin and platelet activation were measured prior and subsequent to therapy. Following danazol administration, marked and sustained increases were noted in Free Protein S, Antithrombin, and Protein C. Platelet CD62 (P-selectin) positivity which was elevated before therapy, decreased to assay threshold limits within five weeks. Both Prothrombin Fragment 1.2 and thrombin-antithrombin complexes were elevated post danazol therapy indicating continued clearance of generated thrombin. These data suggest that the protective effect provided by danazol in this patient with hereditary PS deficiency, may in large part be due to suppression of platelet activation by thrombin inhibition than simply through elevation of PS.
 ...
PMID:Efficacy of danazol in a patient with congenital protein-S deficiency: paradoxical evidence for decreased platelet activation with increased thrombin generation. 930 21

The initial reactions of graphite and gold with blood were investigated by short-time exposure to capillary blood and detection of surface-adsorbed plasma proteins and cells with an immunofluorescence technique. Antibodies specific to fibrinogen, complement factors C1q and C3c, prothrombin/thrombin, von Willebrand factor, and platelet- and leukocyte-membrane antigens were used. The fluorescence intensity was quantitated by computer-aided image analysis. Fibrinogen was the most abundant plasma protein immobilized on either surface, and dense populations of platelets adhered to the protein layer. Complement factors and prothrombin/thrombin were found on the graphite surface, localized in fibrin clots or related to platelets. Platelets were activated (expression of selectin CD62) on both surfaces but more extensively so on the gold surface. Activation of polymorphonuclear granulocytes (PMNGs), measured as expression of integrin CD11b, was seen on both surfaces but with different kinetics. On the graphite surface, the CD11b expression was only transient whereas on gold it increased with time. Our data indicate that graphite is more thrombogenic than gold but less inflammatory.
 ...
PMID:The initial reactions of graphite and gold with blood. 933 58


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>