Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We recently described a monoclonal antibody, 10E5 , that completely blocks adenosine diphosphate (ADP) induced fibrinogen binding to platelets and aggregation induced by ADP, epinephrine, and thrombin. Multiple lines of evidence indicate that 10E5 binds to platelet membrane glycoproteins IIb and/or IIIa. Because it has been reported that platelets treated with chymotrypsin aggregate when fibrinogen is added, we tested the effect of 10E5 antibody on chymotrypsin-induced fibrinogen binding and platelet aggregation. Aspirin-treated human platelets were washed in modified Tyrode's buffer (pH 7.5), incubated for 5 minutes at 22 degrees C with 300 micrograms/mL chymotrypsin, and washed again. The amount of 10E5 antibody bound to these platelets (37,232 +/- 2,928 molecules/platelet; mean +/- SEM, N=9) was similar to that bound to unstimulated control platelets (36,910 +/- 2,669) and did not differ significantly from the amount of antibody bound to ADP-treated platelets (P less than .01, N = 5). The amount of 10E5 bound to chymotrypsin-treated platelets correlated directly with the amount of fibrinogen bound to separate aliquots of the same platelet samples (r = .876, P less than .001). The 10E5 antibody caused virtually complete inhibition of both the binding of fibrinogen to chymotrypsin-treated platelets and the aggregation induced by exogenous fibrinogen. Immunoprecipitation studies of 125I-labeled chymotrypsin-treated platelets revealed that the 10E5 antibody bound proteins with molecular weights characteristic of glycoproteins IIb and IIIa. These data suggest that the fibrinogen receptor on chymotrypsin-treated platelets is identical to that on ADP-treated platelets and that this receptor is either near to, or on, the glycoprotein IIb/IIIa complex.
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PMID:A murine monoclonal antibody that blocks fibrinogen binding to normal platelets also inhibits fibrinogen interactions with chymotrypsin-treated platelets. 673 83

Soluble fibrinogen binding to agonist-stimulated blood platelets is the essential physiologic function of the glycoprotein IIb-IIIa (GPIIb-IIIa) receptor. We describe a method of quantifying this receptor-ligand interaction by using flow cytometry to detect the binding of fluorescein-labeled fibrinogen to activated platelets. Fibrinogen conjugated with fluorescein isothiocyanate (FITC-FGN) was structurally and functionally indistinguishable from native fibrinogen when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, thrombin clottability, and receptor affinity studies. Platelet samples, at a concentration of 2 x 10(7) ml, were incubated with FITC-FGN and activated with adenosine diphosphate (ADP) before cytometric acquisition of fluorescence and scatter data. ADP-induced binding of soluble FITC-FGN to platelet GPIIb-IIIa was specific, time dependent, and saturable. Cytometric analysis of FITC calibration beads allowed generation of standard curves relating bead fluorescence intensity to the number of fluorescein equivalents per bead. With this information, platelet fluorescence intensity was converted into the number of FITC-FGN molecules bound per platelet. Such quantitative analysis of fibrinogen binding yielded a dissociation constant of 2.48 +/- 0.5 x 10(-7) mol/L and a maximum fibrinogen binding capacity of 42, 124 +/- 5, 628 molecules per platelet (mean +/- SEM), which are comparable to published results with radioligand assays. The simplicity, sensitivity, and quantifiability of this method may make it a useful technique for basic and clinical research involving GPIIb-IIIa function.
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PMID:Quantitation of soluble fibrinogen binding to platelets by fluorescence-activated flow cytometry. 751 93

F2-isoprostanes are prostaglandin (PG) isomers produced in vivo through free radical-catalyzed peroxidation of arachidonic acid, which may affect platelet function. The current study investigated the effects of 8-epiprostaglandin F2alpha (8-epi-PGF2alpha) on critical events of platelet activation. A dose-dependent increase in platelet adhesion to fibrinogen- and plasma-coated microwells by 8-epi-PGF2alpha (1 to 1000 nmol/L) was observed when resting platelets (plasma from 1.3+/-0.2% to 5.5+/-0.2%, EC50 of 48 nmol/L; fibrinogen from 3.3+/-0.3% to 6.4+/-0.2%, EC50 of 35 nmol/L; mean+/-SEM, n=8, P<0.001) and thrombin-stimulated human platelets were used. The expression of the adhesion molecule glycoprotein IIb/IIIa was increased by 10 to 1000 nmol/L 8-epi-PGF2alpha in resting platelets (from 64.8+/-2.1% to 83.9+/-1.3%; n=5, P<0.01) and in stimulated platelets. The secretion of the glycoprotein GMP-140 increased only in the presence of both thrombin and 10 to 1000 nmol/L 8-epi-PGF2alpha (from 48.5+/-3.1% to 63.1+/-2.0%, P<0.05). The antiaggregatory effects of both the NO donor NOR-3 (basal, 21.4+/-4.6%; with 8-epi-PGF2alpha, 30.8+/-6.9%; n=14, P<0.05) and endothelial cells that release NO (basal, 18.5+/-4.6%; with 8-epi-PGF2alpha, 30.7+/-5.3%; n=15, P<0.001) were also reduced. All of these effects were prevented by the thromboxane receptor antagonist GR32191 but not affected by acetylsalicylic acid. An increase in free intracellular calcium concentration, measured with the use of fura 2, was observed with 8-epi-PGF2alpha. In conclusion, F2-isoprostanes may participate in oxidative injury by inducing platelet activation and by reducing the antiplatelet activity of NO: increased platelet adhesiveness and expression of the fibrinogen receptor are induced by nanomolar amounts of 8-epi-PG-F2alpha. Platelet secretion and aggregation can also be induced in the presence of platelet agonists.
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PMID:The F2-isoprostane 8-epiprostaglandin F2alpha increases platelet adhesion and reduces the antiadhesive and antiaggregatory effects of NO. 971 31

Platelet function and levels of vascular adhesion molecule-1 (VCAM-1) were investigated in 24 patients with peripheral arterial disease at Fontaine stage II undergoing a 2 weeks treatment with iloprost (0.5-2 ng/kg/h i.v. infused, 6 h/day) or a 2 weeks supervised physical training, randomly assigned. Patients were studied before (T0) and after (T14) treatments and 10 days later (T24). The adhesion of washed platelets to fibrinogen coated microwells was reduced after treatment both with iloprost (1.9+/-0.4 vs 6.8+/-0.7%; T24 vs T0; M+/-SEM; p<0.05) and physical exercise (3.0+/-1.0 vs 6.7+/-0.7; p<0.05) while adhesion to human plasma coated microwells was reduced only after treatment with iloprost (1.9+/-0.8 vs 5.8+/-0.9; p<0.05). The expression of fibrinogen receptor (glycoprotein IIb/IIIa) on platelets, measured by flow-cytometry was also reduced after iloprost treatment (17.1+/-1.5 vs 31.8+/-4.8 AU; p<0.05) and physical exercise (14.6+/-1.5 vs 34.0+/-3.3; p<0.05). Theurinaryexcretion of platelet thromboxane A2 metabolite 2,3-dinor-thromboxane B2 decreased only in patients treated with iloprost (154.7+/-97.9 vs 256.2+/-106.4 pg mg creatinine(-1); p<0.05). Similarly plasma VCAM-1 was lower in patients who were treated with iloprost (827.7+/-77.4 vs 999.0+/-83.8 ng ml(-1); p<0.05). In conclusion, both iloprost and physical exercise seem to act on reversible phenomena such as the expression of adhesion molecules or ex vivo adhesion, whereas only iloprost reduces thromboxane A2 biosynthesis in vivo. This anti-platelet activity seems to be extended in time and to be associated with an improvement in vascular function.
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PMID:Vascular adhesion molecule-1 and markers of platelet function before and after a treatment with iloprost or a supervised physical exercise program in patients with peripheral arterial disease. 1145 33

Platelets, a major constituent of thrombus, play a crucial role in the pathogenesis of acute ischemic coronary syndromes. The effect of ultraviolet laser emission on platelets within thrombi is unknown. The effects of increasing levels of laser energy on platelets in whole blood were investigated. Blood samples were obtained by aseptic venipuncture and anticoagulated with 3.8% sodium citrate. Samples were exposed to increased levels (0, 30, 45, 60 mJ/mm2; 25 Hz) of ultraviolet excimer laser fluence (308 nm wave-length) and then tested for ADP and collagen induced platelet aggregation, platelet concentration, and for platelet contractile force (PCF) development. Scanning electron microscopy was used to detect laser induced morphologic changes of platelets and by flow cytometric analysis to detect changes in expression of platelet surface antigens p-selectin (CD 62) and glycoprotein IIb/IIIa (CD 43). Exposure to excimer laser energy produced dose dependent suppression of platelet aggregation and force development ("stunned platelets"). ADP aggregation decreased from 8.0+/-1.1 Ohms (mean+/-SEM) to 3.7+/-0.8 Ohms (p<0.001) to 2.7+/-0.6 Ohms (p <0.001) and to 1.8+/-0.5 Ohms (p <0.001) as the laser energy increased from 0 to 30 to 45 to 60 mJ/mm2, respectively. Collagen induced aggregation decreased from 21.4+/-1.4 Ohms to 15.7+/-1.2 Ohms (p <0.001) to 11.7+/-1.1 Ohms (p <0.001) and to 9.9+/-1.0 Ohms (p <0.001), in response to the same incremental range of laser energy. Platelet contractile forces declined from 34,500+/-3700 to 27.800+/-2700 dynes as laser energy increased from 0 to 60 mJ/mm2 (p <0.03). Platelet concentration did not change with increasing laser energy. The expression of platelet surface antigen p-selectin (CD 62) remained stable through increasing levels of laser energy exposures while the percentage of CD 43 positive platelets significantly increased with exposure to laser energy, yet the level of expression did not exceed 0.5% of cells. Thus, aggregation kinetics are altered in platelets exposed to ultraviolet laser energy as manifested by decreased platelet aggregation and reduction in platelet force development capability. The response is dose dependent and most pronounced at higher energy levels such as 60 mJ/mm2.
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PMID:Alterations of platelet aggregation kinetics with ultraviolet laser emission: the "stunned platelet" phenomenon. 1168 28

1. Ischaemia-reperfusion (IR) injury is an important contributor to tissue damage and has been shown to be attenuated by preconditioning (PC) in some animal models. A recent report has suggested that the forearm can be used for the study of this phenomenon in humans. We aimed to reproduce and further characterize this model. 2. Healthy young adult volunteers (mean (+/-SEM) age 32+/-6 years) were studied on two occasions. During one visit, IR alone was induced by 10 min of upper arm cuff occlusion, whereas on another occasion a PC stimulus (three 3 min cuff inflations) preceded IR. Endothelial function in the ischaemic arm was assessed by measuring arterial flow-mediated dilatation (FMD) and by calculation of forearm blood flow at baseline and 15 and 60 min after IR. Systemic venous blood was sampled from the non-ischaemic arm at baseline, after PC and at 2, 15 and 30 min after IR to assess neutrophil/leucocyte (CD11b) and platelet (bound glycoprotein IIb/IIIa and fibrinogen) activation, as well as numbers of platelet-leucocyte complexes, which were determined by flow cytometry. Because of a lack of measurable effects, the IR experiment was repeated with 20 min ischaemia in six subjects. 3. Five females and eight males completed the study. Flow-mediated dilatation was significantly impaired 30 min after IR (4.1 vs 6.2% at baseline; P<0.05);however, this was not significantly attenuated by ischaemic PC (FMD reduction at 30 min compared with baseline was 2.1+/-0.5% with IR alone and 2.6+/-1.4% with IR after PC; NS). No significant effect was seen on the number of platelet-leucocyte aggregates or on white cell or platelet activation after IR alone or after IR with PC (P>0.6 for all comparisons). Similar results were obtained in six subjects studied subjected to 20 min ischaemia. 4. In conclusion, in healthy young adults, brief periods of skeletal muscle ischaemia lead to arterial endothelial dysfunction, but no significant platelet or white cell activation. Preconditioning does not attenuate this effect on the endothelium. Further experiments with longer ischaemia times and varying PC stimuli may be necessary to produce measurable effects; however, this may prove difficult in conscious human subjects.
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PMID:Reperfusion injury in the human forearm is mild and not attenuated by short-term ischaemic preconditioning. 1573 Apr 40

The interaction of platelets with the polymeric surface of drug eluting stents has not been fully described in the literature. Our aim was to analyze the patterns of activation and deposition of platelets exposed to two different stent platforms; (a) the polymeric surface of the paclitaxel eluting stent (Taxus((R)) stent, PES,) and (b) the metallic surface of a stent with identical structural design (Express((R)) stent, BMS). Platelet activation was tested by deploying stents in an in vitro flow chamber model. Anticoagulated blood of 25 healthy volunteers was circulated (flow rate 10 ml/min for 60 min) into the flow chamber system. P-selectin expression, glycoprotein IIb/IIIa activation (PAC-1 binding) and platelet-monocyte complexes (PMC) formation were evaluated at 0, 10, 30 and 60 min. Surface platelet deposition was assessed by surface electron microscopy in stents implanted in the in vitro system for 60 min and in stents implanted in normal porcine coronary arteries for 24 h. Platelet activation evaluation showed a higher P-Selectin expression (92.9% of baseline in PES versus 68.3 % in BMS, P = 0.01) and higher PMC formation (125.7 % of baseline in PES versus 75.6% in BMS, P < 0.01) in the PES compared to the BMS control group. PAC-1 binding levels did not differ among groups. In the in vitro study, SEM analysis of the stent surface showed no statistical differences on platelet deposition between the groups. In addition, presence of proteinaceous material was more frequently seen on the BMS group (moderate to complete coverage = 80% in BMS versus 26% in PES, P < 0.01). In the in vivo study, complete platelet coverage was similar between groups (PES = 7% versus BMS = 8%, P = NS). However, there was an overall trend towards less platelet deposition on the BMS surface (mild and moderate coverage = 83%, 9% in BMS versus 49%, 44% in PES, P < 0.001 for both) but thrombus formation was not observed in either group. The polymeric surface of the PES appears to induce a higher degree of platelet activation and deposition compared to the BMS surface. The biological implications of these findings on the patterns of vascular healing need to be further studied in vivo. Condensed Abstract The interaction of human platelets with the surface of drug eluting stents has not been fully characterized. Patterns of platelet activation and adhesion were evaluated in vitro and in vivo after exposing platelets to the surface of the paclitaxel-eluting stent and identical bare metal stent. The degree of PMC formation and P-selectin expression was increased in PES compared to BMS. In the in vivo study, complete platelet coverage was similar between groups. There was an overall trend towards less platelet deposition on the BMS surface, however, thrombus formation was not observed on either surface. The polymeric surface of the PES appears to induce a higher degree of platelet activation and deposition compared to the BMS surface.
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PMID:Patterns of activation and deposition of platelets exposed to the polymeric surface of the paclitaxel eluting stent. 1946 81