Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.68 (tissue plasminogen activator)
 11,311 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thrombin promotes the formation of arterial thrombi by converting fibrinogen to fibrin and by causing platelets to aggregate. We have examined the combined effects of plasminogen activators and inhibitors of platelet aggregation on the lysis of platelet-rich fibrin clots formed by alpha-thrombin in citrated platelet-rich plasma. The extent of platelet aggregation and clot formation were measured by recording light transmission in an aggregometer. Immediately after the formation of platelet-rich fibrin clots, addition of 2,000 U/ml streptokinase or 50 micrograms/ml recombinant tissue-type plasminogen activator alone resulted in the degradation of polymerized fibrin and the release of trapped platelet aggregates without causing significant platelet deaggregation. Preincubation of the platelet-rich plasma with 20 microM indomethacin for 1 min before thrombin stimulation or simultaneous addition of prostaglandin E1 (10 microM) with the plasminogen activators after thrombin stimulation resulted in spontaneous platelet deaggregation. Because platelet aggregation is, in part, mediated by the binding of Arg-Gly-Asp-containing adhesive proteins to activated platelets, the effect of Arg-Gly-Asp peptides on platelet deaggregation was examined. By itself, Gly-Arg-Gly-Asp-Ser-Pro specifically caused dose- and time-dependent deaggregation of platelet aggregates formed by ADP or by thrombin in the presence of 1 mM Gly-Pro-Arg-Pro, but had no effect on the dissociation of thrombin-induced platelet-rich fibrin clots. In combination with streptokinase or recombinant tissue-type plasminogen activator, Gly-Arg-Gly-Asp-Ser-Pro enhanced the rate of lysis of platelet-rich fibrin clots. The control Gly-Arg-Gly-Glu-Ser-Pro peptide was completely ineffective.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Rapid dissociation of platelet-rich fibrin clots in vitro by a combination of plasminogen activators and antiplatelet agents. 176 85

Thrombus removal using percutaneous rotational thrombectomy (PRT), followed by tissue plasminogen activator (t-PA), was studied by contrast angiography and fiberoptic angioscopy in a canine femoral artery model of thrombosis. After thrombus induction and following each treatment, comparisons were made between angioscopy and angiography for the detection of thrombus and subintimal dissection. Angioscopic images were scored in a blinded fashion for lining, protruding, or occlusive thrombus (class 1,2, or 3) as well as estimated wall coverage by thrombus. Angiograms were studied for percent diameter stenosis and the presence of flaps. Following external forceps crush injury of 18 arteries, two hour occlusion, and injection of thrombin, mean angiographic stenosis was 66%, thrombus coverage by angioscopy was 81%, and mean angioscopy class was 2.5. Following PRT, stenosis decreased to 27% (p less than 0.008), thrombus coverage was reduced to 49% (p less than 0.02), and angioscopy class dropped to 2.0 (p less than 0.07). After t-PA treatment, these values were further reduced to 25% (p = NS), 26% (p less than 0.02), and 1.3 (p less than 0.008), respectively. In comparison to angiography, subintimal dissection (seen as flaps) and thrombus (lining, protruding, or occlusive) were present significantly more often by angioscopy (p less than 0.001). It is concluded that PRT results in significant thrombolysis, apparent by angiography and angioscopy. Follow-up t-PA can produce additional, incremental thrombolysis, apparent only by angioscopy. A beneficial role for t-PA following mechanical thrombolysis is suggested by this model. The superior sensitivity of angioscopy for detection of flaps and thrombus is underscored by this study.
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PMID:Thrombolysis by rotational thrombectomy followed by tissue plasminogen activator: evaluation by angioscopy. 176 46

PAI-1 antigen, tPA antigen and thrombin - antithrombin III complexes (TAT) levels were measured in 10 males with stable angina and type-II diabetes mellitus and in 16 males with stable angina without diabetes or other risk factors (hyperfibrinogenaemia, hyperlipidaemia, diabetes, hypertension, smoking and obesity) known to increase PAI levels. Ten healthy men of equivalent age served as controls. Because only diabetics with coronary artery disease (CAD) showed a decreased fibrinolytic capacity, a second study was performed on the 16 non-diabetic CAD patients to determine whether submaximal workload induces significant changes of tPA and PAI levels. TAT levels were increased in CAD, and significantly so in the diabetic group. tPA levels were increased only in the CAD patients without diabetes. PAI levels were significantly increased in diabetic CAD patients (5.26 +/- 1.96 ng/ml) but not in the stable angina patients without diabetes (2.97 +/- 1.44 ng/ml). Immunologically-reactive tPA released after exercise was higher in the 16 CAD patients without diabetes than in controls. Our data could indicate that in stable angina without diabetes there is no chronic latent activation of the clotting system, with no impairment of fibrinolytic activity. On the other hand, the presence of diabetes mellitus seems to influence the fibrinolytic capacity in CAD, particularly increasing PAI levels.
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PMID:Increased plasminogen activator inhibitor antigen levels in diabetic patients with stable angina. 177 97

Plasma levels of fibrinopeptide A (FPA), D-dimer and tissue-plasminogen activator antigen (t-PA-Ag) were measured serially in 38 patients with acute myocardial infarction undergone emergency coronary angiography and/or PTCR (percutaneous transluminal coronary recanalization). A special attention has been focussed in the possible correlation of the variables of coagulation and fibrinolysis with the degree of patency of infarct-related coronary arteries (IRAs). Before PTCR, 26 patients with completely occluded IRAs had significantly higher plasma levels of FPA when compared with those of 12 patients with incompletely occluded IRAs (33.8 +/- 2.4 vs 11.0 +/- 1.3 ng/ml, mean +/- SD, p less than 0.05, respectively). Successful recanalization were resulted in 19 of 26 patients with completely occluded IRAs. Though plasma D-dimer levels significantly increased after PTCR both in patients with or without successful reperfusion, there were neither differences in the two groups before nor after PTCR (154.8 +/- 1.9 to 257.0 +/- 3.0 vs 131.6 +/- 4.8 to 254.9 +/- 4.1 ng/ml, mean +/- SD, respectively). Coronary angiography in 30 patients, performed about a month after the onset of acute myocardial infarction, revealed good patency (the stenosis was less than 90% evaluated according to the American Heart Association Committee Report in 1975) of IRAs in 17 patients and poor patency (the stenosis was 99% or 100%) of IRAs in 13 patients. The former patients had significantly higher plasma levels of t-PA-Ag after 24 hours from the onset than those of the latter patients (26.6 +/- 10.7 vs 17.4 +/- 4.2 ng/ml, mean +/- SD, p less than 0.05, respectively). These findings suggest that the increase in thrombin activity affects unfavorably the patency of IRAs in the evolving of myocardial infarction, and that the responsiveness of endothelial cells to acute phase stimuli such as thrombin and heparin affects favorably the patency of IRAs in the chronic phase; Elevated plasma levels of D-dimer do not necessarily indicate coronary thrombolysis.
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PMID:[Contributory changes in variables of coagulation and fibrinolysis to the patency of coronary arteries in patients with acute myocardial infarction]. 177 11

The development of hemodialysis treatment has remarkably improved the prognosis of chronic hemodialysis (HD) patients. However, as the patient's survival time is prolonged, vascular damages due to the abnormalities of calcium and lipid metabolism and hypertension has become the important complications in HD patients. In addition to coagulation and fibrinolysis, vascular endothelial function has been pursued to clarify the pathogenesis for occurrence of thrombosis in HD patients with more than ten years' duration. Twenty-two HD patients including twelve of less than ten years' duration and ten of more than ten years' were subjected to this study. Twelve healthy controls were also involved in this study. Fibrinopeptide A (FPA) and thrombin-antithrombin III complex (TAT) as indexes of coagulation, antithrombin III (AT III) as an index of coagulation inhibitor and D-dimer as an index of fibrinolysis were measured. A special attention has been focused in changes in the levels of tissue plasminogen activator (t-PA) activity and antigen and plasminogen activator inhibitor-1 (PAI-1) as indexes of fibrinolysis capacity, representing parameters of vascular endothelial functions. Levels of FPA, TAT and D-dimer were significantly higher in HD patients when compared with those in healthy controls. In particular, levels of FPA were significantly higher in HD patients with more than ten years' duration as compared to those in HD patients with less than ten years'. AT III values were significantly lower in HD patients with more than ten years' duration than those in healthy controls. T-PA activity and antigen levels were significantly lower in HD patients than those in healthy controls. T-PA activity levels were lower in HD patients with more than ten years' duration than those in HD patients with less than ten years'. Among HD patients, a significant negative correlation was found between t-PA activity and hemodialysis duration. PAI-1 values in HD patients were not significantly differ from those in healthy controls. These results suggest that in spite of increased coagulability, fibrinolytic capacity of vascular endothelium decreased in HD patients, and that the incidence is accelerated as hemodialysis duration is prolonged. Therefore, it is concluded that long-term HD patients are in the state of a higher risk of thrombosis.
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PMID:[Long-term hemodialysis and changes in variables of coagulation and fibrinolysis]. 177 13

In order to evaluate precisely the fibrinolytic states in clinical disorders, plasma levels of D dimer (cross-linked fibrin degradation products) were measured by a newly developed, rapid quantitative method based on the latex photometric immunoassay in patients with hematological malignancies, diabetes mellitus, collagen disease, liver disease, thrombotic disease and disseminated intravascular coagulation (DIC). Plasma levels of D dimer were elevated in a variety of diseases, especially in DIC. Patients with hematological malignancies, liver disease and thrombotic disease also had relatively high levels of D dimer. On the whole, D dimer values were positively correlated with plasmin-alpha 2-plasmin inhibitor complex and thrombin-antithrombin III complex. In addition, plasma D dimer was measured during fibrinolytic therapy with urokinase or tissue-type plasminogen activator; its elevation was detected in some patients. These findings indicate that accelerated fibrinolysis is frequently observed in a variety of diseases, and that a rapid quantitative measurement of D dimer would be valuable for the precise assessment of fibrinolysis in these disease states.
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PMID:[Evaluation of clinical usefulness of a rapid quantitative measurement of D dimer (cross-linked fibrin degradation products)]. 177 52

After a bite by the aglyphous red-necked keelback snake Rhabdophis subminiatus a complete defibrinogenation syndrome with severe hemorrhagic diathesis developed in a 25-year-old man. In vitro studies showed that the venom gland extract of the snake contains a very active prothrombin (Factor II) activator. The thrombin generated is inhibited neither by antithrombin III nor the antithrombin-III-heparin complex. The venom gland extract stimulated also the tissue plasminogen activator; however, it did not cause direct activation of plasminogen, protein C, Factor X or direct degradation of fibrinogen.
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PMID:Hemostatic changes due to the venom gland extract of the red-necked keelback snake (Rhabdophis subminiatus). 180 26

Prothrombin fragment 1 + 2 (F1 + 2) and thrombin-antithrombin complexes (TAT), as well as other coagulation and fibrinolysis parameters, were studied in a series of 13 patients affected by thrombotic thrombocytopenic purpura (TTP) or hemolytic-uremic syndrome (HUS). Fragment F1 + 2 was found to be increased in all patients at diagnosis (patients' range, 1.21-19.03 nmol/l; normal limits, 0.28-1.08 nmol/l), and remained also higher than normal after treatment with plasma exchange (patients' range, 1.5-4.01 nmol/l). Even though the analysis of fibrinolysis markers did not show a definite state of hypo or hyperfibrinolysis in the systemic circulation, enhanced circulating D-dimer levels (0.53-12.6 micrograms/ml, normal levels of 0.03-0.29 micrograms/ml) indicated that a certain grade of fibrin lysis was present at previously formed thrombi. Plasma PAI-1 activities either on admission (9.2-38.2 U/ml) and after plasma exchange therapy (2.6-38.6 U/ml) showed a behavior irrespective of t-PA:Ag changes, and post-plasmapheresis values remained high only in patients with fatal neurological outcome. Nevertheless, no correlations between clinical and laboratory data could be established useful for the TTP/HUS prognosis. We conclude that increased thrombin generation occurring in damaged areas is appropriately inhibited by antithrombin III in the systemic circulation, avoiding consumption coagulopathy to develop in uncomplicated patients. In addition, fibrinolysis data suggest that elevated PAI-1 may decisively favor the development of microvascular thrombi.
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PMID:Thrombin generation and fibrinolysis in the thrombotic thrombocytopenic purpura and the hemolytic-uremic syndrome. 151 82

Poloxamer 188, N.F. (RheothRx), a nonionic block copolymer composed of 2 hydrophilic polyoxyethylene chains connected by a hydrophobic polyoxypropylene chain, normalizes the viscosity of whole blood high in soluble fibrin(ogen) complexes. Normalization may be via a poloxamer 188-induced decrease in fibrin(ogen)-red cell interaction. Our study examined the influences of poloxamer 188 on fibrin assembly and structure. Studies were performed in both purified and plasma systems with a poloxamer 188 concentration range of 0.1-20 mg/ml and specific clotting conditions (fibrinogen 1 mg/ml, thrombin 1 NIH u/ml, pH 7.4 [Tris 0.05 M], ionic strength 0.15 and calcium 5 mM). Fibrin assembly was accelerated in the presence of poloxamer 188. As poloxamer 188 concentration was increased from 0 to 8 mg/ml in plasma: a) the lag phase prior to initial turbidity rise decreased from 25 to less than 5 s; b) the final gel optical density (OD) increased from 0.65 to 1.28 and c) fiber size (mass/length ratio [mu]) increased from 4.3 to 12.6 x 10(13) daltons/cm. Similar results were seen in the purified system with a poloxamer 188 concentration range of 0-8 mg/ml. OD increased from 0.26 to 0.51, and mu increased from 2.3 to 5.3 x 10(13) daltons/cm. Above 8 mg/ml, precipitation of fibrinogen was noted in this system. Since large fibrin fibers tend to be degraded more rapidly, possible poloxamer mediated enhancement of r-tPA-mediated clot lysis was investigated. With r-tPA (70 lu/ml) present at the time of clotting, clot lysis in the presence of ploxamer 188 (8 mg/ml) was 50% complete at 1,600 s compared to 2,540 s for the control. Thus, poloxamer 188-induced alterations in fibrin structure and fibrin-cell interactions may explain some of this agent's interesting hemorrheologic and antithrombotic properties.
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PMID:Effects of poloxamer 188 on the assembly, structure and dissolution of fibrin clots. 180 21

Coronary thrombolysis is the treatment of choice for patients with acute Q wave myocardial infarcts who have no contraindication to such therapy. However, the time required for thrombolysis to occur and the possibility of reocclusion of the infarct-related artery following thrombolytic therapy are problems. The time required for thrombolysis to occur with currently available agents ranges from 40 to 60 minutes and the frequency of reocclusion of the infarct-related artery after tissue-type plasminogen activator is 10 to 20%. We review experimental studies and clinical evaluations in which attempts have been made to develop adjunctive therapies that when coupled with available thrombolytic interventions might shorten the time to thrombolysis and delay or prevent reocclusion. From the studies done to date, it appears that a combination of thromboxane synthesis inhibitor and receptor antagonist with a serotonin receptor antagonist and heparin shortens the time to thrombolysis and delays or prevents coronary artery reocclusion in experimental canine models with copper coil-induced coronary artery thrombi. A monoclonal antibody to the platelet glycoprotein IIb/IIIa receptor given with tissue plasminogen activator and heparin also shortens the time to thrombolysis and delays or prevents reocclusion in experimental canine models. A mutant tissue plasminogen activator with a glycosylation defect and prolonged systemic clearance delays coronary artery reocclusion following lysis of three-hours coronary thrombi, induced by a copper coil. Thrombin inhibitors, including heparin, and synthetic inhibitors, given with tissue plasminogen activator and aspirin, appear to shorten the time to thrombolysis and delay or prevent coronary artery reocclusion in experimental canine models.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Thrombolytic therapy: enhancement by platelet and platelet-derived mediator antagonists. 180 65


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