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)

We compared the thrombolytic activity of a novel modified tissue-type plasminogen activator (t-PA; del 92-173, 275Arg-->Glu), YM866, with that of t-PA in a platelet-rich thrombosis model. Thrombus was induced in guinea pig mesenteric artery by irradiation with filtered light in combination with intravenous (i.v.) administration of fluorescent dye. When occlusion by the thrombus extended to 99% of the luminal area of the vessel, test drug (YM866, t-PA, or saline) was administered by i.v. bolus injection under heparinization. Both YM866 and t-PA exhibited dose-dependent thrombolytic activity; however, the improvement in occlusion rate and the incidence of successful thrombolysis induced by YM866 were three times higher than those induced by t-PA. With YM866 1 mg/kg, alpha 2-plasmin inhibitor levels decreased significantly to 58% of saline group values, but no change was noted in fibrinogen levels. YM866 antigen levels at this dose were seven times higher than those of t-PA. These results suggest that YM866 in single bolus injection is a thrombolytic agent superior to t-PA in platelet-rich thrombi without systemic fibrinolytic activation and that this efficacy is due to the prolonged half-life (t1/2) of the drug.
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PMID:Thrombolytic activity of YM866, a novel modified tissue-type plasminogen activator, in a photochemically induced platelet-rich thrombosis model. 752 79

1. We studied DMP728, a non-peptide glycoprotein (GP) IIb/IIIa receptor antagonist, for prevention of coronary artery thrombosis or rethrombosis in a chronic canine model subjected to arterial injury. 2. In protocol I, DMP728 (1.0 mg kg-1, i.v., n = 8) or saline (n = 8) was administered and a 150 microA anodal current was applied to the intimal surface of the left circumflex coronary artery (LCX). Dogs were monitored for 6 h and again on each of 5 subsequent days. 3. Ex vivo platelet aggregation was inhibited but returned to baseline 1 day after drug administration. Thrombus weight was reduced (saline, 20.7 +/- 5.0 mg; DMP728 1.7 +/- 0.4 mg; P < 0.05), as was infarct size [saline, 27.5 +/- 4.3; DMP728, 1.6 +/- 0.7 (per cent left ventricle); P < 0.05]. All control animals died by day 3, while all but one of the treated dogs survived the entire protocol (P < 0.05). 4. In protocol II, an LCX thrombus was induced and thrombolytic therapy was initiated 30 min later. DMP728 (1.0 mg kg-1, i.v., n = 8) or saline (n = 8) was administered 5 min after recombinant tissue-type plasminogen activator infusion had begun. The incidence of reocclusion was reduced by DMP728 (saline, 4/8; DMP728, 1/8). One day after thrombolysis, 7/8 DMP728-treated animals were alive compared with 1/8 in the control group (P = 0.01). 5. DMP728 inhibited ex vivo platelet aggregation, prevented primary and secondary occlusive thrombus formation, reduced thrombus weight and infarct size and increased survival in a chronic canine model of coronary artery thrombus formation. DMP728 is an effective anti-platelet intervention when used as the singular adjunctive agent in association with thrombolytic therapy.
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PMID:Prevention of thrombosis and rethrombosis and enhancement of the thrombolytic actions of recombinant tissue-type plasminogen activator in the canine heart by DMP728, a glycoprotein IIb/IIIa antagonist. 788 89

Thrombotic obstruction of glomerular capillaries causes acute renal failure in patients with hemolytic-uremic syndrome (HUS). Recanalization of occluded vessels normally occurs by activation of the endogenous fibrinolytic system, mediated by plasminogen activators, which are stored and synthesized in the endothelial cells. However, endothelial injury is considered the primary event in the pathogenesis of HUS, and this may result in impaired fibrinolysis. In five children with HUS we performed a prospective study of plasminogen activator activity and two plasminogen activator antigens: tissue-type plasminogen activator and urokinase-type plasminogen activator before and after intravenous desmopressin. Plasminogen activator inhibitor type-1 antigen was also studied. In the acute stage of HUS plasminogen activating activity was low, in spite of elevated levels of total plasminogen activator antigens. This decrease of plasminogen activating activity was due to high levels of the plasminogen activator inhibitor. Improvement of fibrinolysis paralleled recovery from HUS. We conclude that decreased fibrinolysis is an important pathophysiologic feature of HUS.
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PMID:Impaired fibrinolysis in the hemolytic-uremic syndrome of childhood. 811 Aug 78

Thrombotic vascular occlusion may complicate the clinical course of many neonatal and pediatric pathologic processes. Systemic thrombolytic therapy with heparin, urokinase, or streptokinase may not be appropriate in the critically ill neonate because these agents generate a diffuse coagulopathic state. Direct surgical intervention for repair may be precluded by the small size of the vessels involved. Recombinant tissue plasminogen activator (rTPA) induces only a minimal proteolytic state while inducing thrombolysis within the local environment of the clot. We report our experience with regional rTPA infusion in four critically ill patients with venous and arterial thrombotic disorders. there were two brachial artery occlusive lesions--a neonate with iatrogenic occlusion due to a misplaced intravenous catheter and a 2-year-old child with inadvertent arterial ligation during an attempted venous cutdown. Two venous lesions consisted of a full-term neonate with renal vein/inferior vena caval thrombosis and a 32-week infant with partial superior vena caval thrombosis due to a Broviac catheter. Systemic thrombolytic therapy was contraindicated in these patients because of underlying illnesses. Pretherapy vascular evaluation included Doppler examination and angiography. The rTPA infusion was continued until there was evidence of clot lysis by ultrasound, angiogram, or venogram. Infusion rate of rTPA was adjusted according to fibrinogen levels. All three neonates responded successfully to rTPA therapy. Two neonates required only bolus administration and one responded to combined bolus and continuous infusion therapy after 58 hours. rTPA failed to reverse brachial artery occlusion in the 2-year-old child with purpura fulminans.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Recombinant tissue plasminogen activator for neonatal and pediatric vascular thrombolytic therapy. 826 84

The antiaggregatory and antithrombotic actions of MK-0852, a cyclic heptapeptide antagonist of the platelet GP IIb/IIIa, were evaluated in a variety of canine models. In vitro, MK-0852 inhibited the aggregation of canine platelet-rich plasma induced by 10 microM ADP in the presence of 1 microM epinephrine with an IC50 value of 0.10 microM. The i.v. infusion of 1.0 and 3.0 micrograms/kg/min MK-0852 to anesthetized dogs significantly inhibited ex vivo platelet aggregation responses to ADP and collagen, with the 3.0 micrograms/kg/min infusion completely inhibiting ex vivo aggregation responses to both agonists. The i.v. administrations of 100 and 300 micrograms/kg MK-0852 suppressed platelet-dependent cyclic flow reductions in stenosed canine left circumflex (LCX) coronary artery for periods of 24 +/- 3 and 64 +/- 4 min, respectively. In a canine model of copper coil-induced femoral arterial thrombosis, i.v. MK-0852 (100 micrograms/kg + 1 microgram/kg/min), initiated 15 min before coil placement, reduced the incidence of occlusive thrombosis during the 45-min post-coil time period of continued therapy (1/5 MK-0852 vs. 7/7 saline; P < .01). MK-0852 was administered as an adjunctive therapy with tPA to evaluate its effects on thrombolysis after copper coil-induced femoral arterial thrombus formation. MK-0852 (i.v.; 100 micrograms/kg + 1 microgram/kg/min), initiated 15 min before tPA, reduced the incidence of post-thrombolysis reocclusion. During the 60-min period of continued drug infusion after the termination of tPA, 0 of 5 animals receiving MK-0852 reoccluded vs. 7/8 saline (P < .01). In a canine model of electrically induced LCX coronary artery thrombosis, i.v. MK-0852 (100 micrograms/kg + 3 micrograms/kg/min), initiated 15 min before the initiation of electrical injury, prevented occlusive thrombosis in 4 of 6 preparations despite the continued electrical stimulation of the vessel for 180 min. Thrombotic occlusion was delayed in the remaining two preparations (99 and 100 min), compared with occlusion in 4 of 4 saline-treated preparations (69.3 +/- 6.3 min). When administered as an adjunct to thrombolytic agents for lysis of electrically induced LCX coronary artery thrombi, i.v. MK-0852 (300 micrograms/kg + 3 micrograms/kg/min), initiated 15 min before tPA or streptokinase, both increased the incidence of reperfusion (tPA: 8/8 MK-0852 vs. 3/8 saline; streptokinase: 5/8 MK-0852 vs. 2/8 saline) and accelerated reperfusion. The incidence of reocclusion during continued adjunctive therapy was reduced.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Antithrombotic effects of MK-0852, a platelet fibrinogen receptor antagonist, in canine models of thrombosis. 837 Nov 53

The effects of intrathrombic and intravenous injection of prostaglandin E1 (PGE1) during pulse-spray thrombolysis were studied in a rabbit model. Thrombi were produced in the inferior vena cava of 46 rabbits by means of vessel wall injury and placement of steel coils. At 2 days, pulse-spray thrombolysis was performed by using a catheter with multiple side holes spanning the clot. A control group received injections of saline. In all other rabbits, 3 mg of tissue-type plasminogen activator (tPA) was injected into the thrombus over 1 hour, and 500 U of heparin was intravenously administered. PGE1 was administered either intravenously (50 micrograms) or directly into the thrombus (10, 25, or 50 micrograms) in four groups. After treatment, the rabbits were killed and the residual clot was weighed. The relationship between clot length and volume measured on angiograms and clot weight was assessed in 13 additional untreated rabbits. Linear regression analysis was used to estimate the initial clot weight on the basis of measured clot length in treated animals. The extent of clot lysis was significantly greater with injection of tPA and 10-, 25-, or 50-micrograms PGE1 directly into the thrombous than with administration of tPA alone.
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PMID:Effects of intrathrombic administration of prostaglandin E1 during pulse-spray thrombolysis with tissue-type plasminogen activator in experimental thrombosis. 843 Feb 1

Thrombotic and hemorrhagic complications are frequent in patients with essential thrombocythemia (ET), a myeloproliferative syndrome with an increased number of circulating platelets. Since platelets are a physiological reservoir for the plasminogen activator inhibitor (PAI-1) contained in plasma, we evaluated plasma and platelet tissue plasminogen activator (tPA) and PAI-1 in 20 ET patients with and without thrombotic complications and in 13 control subjects. In ET patients with thrombotic complications there was a significantly greater platelet PAI-1 functional activity than in ET patients without thrombotic complications and in the control group (p < 0.05 and p < 0.025, respectively). Moreover, platelet tPA activity was significantly low in all ET patients (p < 0.001). This fibrinolytic imbalance (increased plasminogen inhibitor and lowered activator) might be a critical cofactor in the thrombotic complications in ET patients.
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PMID:Fibrinolytic imbalance in essential thrombocythemia: role of platelets. 847 7

1. We compared the direct thrombin inhibitor, desulfatohirudin (REVASC) and the indirect thrombin inhibitor, heparin, as adjuncts to thrombolytic therapy with reteplase in a canine model of coronary artery thrombosis. 2. Reteplase (BM 06.022) is a recombinant unglycosylated variant of human tissue-type plasminogen activator. Thrombus formation in anaesthetized open chest dogs was induced by electrical injury. Left circumflex coronary artery blood flow was monitored for 210 min with an electromagnetic flow probe. Twenty eight dogs were randomized to receive i.v. heparin (120 iu kg-1 bolus plus 80 iu kg-1 per h) or i.v. hirudin (2.0 mg kg-1 bolus plus 2.0 mg kg-1 per h) 10 min before thrombolysis preceded by i.v. acetylsalicyclic acid (20 mg kg-1) 5 min prior to anticoagulation. Every dog received an i.v. double bolus injection of 0.14 + 0.14 u kg-1 ( = 0.24 + 0.24 mg kg-1) reteplase, 30 min apart, 1 h after thrombus formation. 3. At comparable reperfusion rates (12 out of 12 vs. 15 out of 16 dogs), hirudin enhanced time to reperfusion (14.3 +/- 1.4 vs. 23.2 +/- 3.4 min; P < 0.05) and completely prevented reocclusion after reperfusion in contrast to heparin (0 out of 11 vs. 7 out of 11 dogs; P < 0.05). Coronary blood flow quality was improved by hirudin as shown by a higher maximum blood flow after reperfusion (130 +/- 14.3 vs. 83 +/- 9.3% of baseline; P < 0.05), a higher blood flow level at 20, 30, 40, and 50 min after onset of thrombolysis (P < 0.05) and a longer cumulative patency time (195 +/- 1.7 vs. 166 +/- 12 min; P < 0.05). Activated partial thromboplastin time and buccal mucosa bleeding time were prolonged (P < 0.05) by either anticoagulant, but did not differ significantly between groups. 4. The direct thrombin inhibitor, desulfatohirudin, enhanced thrombolysis, prevented reocclusion and increased blood flow as compared with the indirect thrombin inhibitor, heparin, when investigated at one dose level each and used in conjunction with reteplase.
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PMID:Comparison of desulfatohirudin (REVASC) and heparin as adjuncts to thrombolytic therapy with reteplase in a canine model of coronary thrombosis. 873 26

The efficacy of the local delivery of an antithrombotic drug in preventing thrombosis and enabling thrombolysis was investigated in 29 dogs. An antithrombotic drug (heparin, 25 U/kg), or an antithrombin (argatroban, 0.05 mg/kg) was infused into injured canine iliac arteries, using a double-occlusion balloon catheter, and the preventive effect of the drug was evaluated. Local delivery of low-dose tissue-type plasminogen activator (t-PA; Tisokinase, 50,000 U; Kowa, Nagoya and Asahi Chemical Industries, Fuji, Japan) into thrombosed canine iliac arteries, using the same catheter, or intravenous infusion of low-dose or high-dose t-PA (30,000 U/kg) was also performed. Angiographically, stenotic thrombosis was 2% by local delivery of argatroban and 7% by local delivery of heparin (P < 0.01 vs each control; 47% and 51% respectively). Thrombotic stenosis, as observed by angiography, decreased from 91% to 9% after local delivery of t-PA, and from 94% to 52% in controls. Local delivery of t-PA effectively reduced the thrombus size (P < 0.01 vs control). After systemic intravenous delivery of low-dose t-PA, no reduction of residual thrombotic stenosis, was observed. Reduction of residual thrombotic stenosis after intravenous delivery of high-dose t-PA, was similar to that achieved by local delivery of the drug. Angioscopy demonstrated a similar trend. High-dose drug delivery reduced systemic coagulability. Local delivery of an antithrombotic drug, using a double-occlusion balloon catheter, effectively prevented thrombus formation, and local delivery of t-PA induced thrombolysis without exerting a significant influence on coagulability.
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PMID:Induction of thrombolysis and prevention of thrombus formation by local drug delivery with a double-occlusion balloon catheter. 889 61

The case is described of a potentially life threatening complication relating to the use of a totally implantable venous access device (Port-a-Cath) in a 28 year old patient with cystic fibrosis. The device was inserted in 1990 and used repeatedly for antibiotic therapy without any complications. In 1995, during assessment for double lung transplantation, a 3 cm thrombus was found at the tip of the catheter in the right atrium. Embolisation of the thrombus to the pulmonary arteries occurred after the infusion of recombinant tissue plasminogen activator (rt-PA). Thrombus formation may be associated with totally implantable venous access devices and thromboembolism may occur following the use of thrombolytic agents in the treatment of such thrombosis.
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PMID:Thromboembolism related to a Port-a-Cath device in a patient with cystic fibrosis. 903 50


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