Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0034065 (pulmonary embolism)
 14,979 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tissue-type plasminogen activator (t-PA) is a serine protease that converts a zymogen plasminogen into an active serine protease, namely, plasmin. Plasmin is the proteolytic enzyme that degrades fibrin. In the absence of fibrin, e.g., in circulating plasma, t-PA activates plasminogen at a very slow rate. However, when fibrin is present, this activity is enhanced two to three orders of magnitude. As a consequence of these kinetic characteristics, plasmin is predominantly generated on the fibrin surface. This in turn results in a relative sparing of circulating fibrinogen and other plasma proteins to plasmin--mediated degradation. Following the demonstration of the potential of natural t-PA as a thrombolytic agent, an intensive effort was launched to enhance its production by recombinant DNA technology. The pharmacological action and the clinical efficacy of t-PA has been tested by several Authors in the treatment of acute myocardial infarction (AMI), and more recently, of pulmonary embolism, a condition for which this drug seems to be very promising: from this point of view this short article provides evidence that the various thrombolytic agents are of equal ability in mediating the rapid lysis of a coronary thrombus after i.v. administration when given appropriately and at the proper time; clinical experience provides little support for the contention of the superiority of t-PA over other thrombolytic agents, particularly for coronary thrombolysis. We are waiting for the results that will come from the GISSI-2 study, that is comparing streptokinase (SK) vs. t-PA in AMI's patients.
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PMID:[Tissue-type plasminogen activator]. 211 66

A new abnormal plasminogen, Frankfurt I, has been identified in the plasma of a 42 year-old male patients who had recurring thromboses, thrombophlebitis and pulmonary embolism since his age of 29. Reduced functional and also slightly reduced antigen plasminogen concentrations were found in both the proposituts and his mother. Plasmin generation rates carried out by Streptokinase and Urokinase were also abnormal. The plasmin generated was very unstable in the absence of stabilizing ligands and/or substrates. Crossed immunoelectrophoresis of the purified Frankfurt I revealed a peak with normal size and shape, but displaced with respect to normal Glu-plasminogen toward the anode. Isoelectric focusing followed by zymography on an agarose-fibrin plate proved this observation but did not indicate a separation of the normal from the abnormal plasminogen molecular species, also, fewer bands were found in the abnormal plasminogen isozyme pattern. Kinetic studies of Frankfurt I Glu-plasminogen and plasmin showed that most of the functional abnormality is related to absence of active sites in half of the molecules.
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PMID:Congenital abnormal plasminogen, Frankfurt I, a cause for recurrent venous thrombosis. 296 86

In 1933 Streptokinase (SK) was isolated from bacterial strains of haemolytic Streptococci. Since then it has become the widest spread drug for fibrinolysis. SK, a protein, consists of 415 aminoacids and has a molecular weight of 47,000u. Together with the plasminogen (PLG) of the blood it forms activator complexes, which then convert other PLG molecules of the blood to plasmin. Plasmin attacks and dissolves fibrin deposits. As a substance produced by bacteria SK stimulates antibody formation in the body, the titer will increase during therapy, and SK lysis should be terminated after 6 days of treatment. Usually SK is administered intravascularly to treat a wide range of diseases, associated with pathological activation of hemostasis, like deep vein thrombosis, pulmonary embolism, myocardial infarction etc.. Contraindications can be traced back to the effects of SK on coagulation and the immune system. Bleeding is the most common side effect, but also a few anaphylactic reactions, caused by massive antigen-antibody precipitation have been observed. The rate of lethality of the treatment was established at 0.7% of the cases. To reduce the incidence of side effects modifications of the drug have been proposed, such as activator complex, light B chain SK, and acylated activator therapy. Compared with Urokinase, SK shows a higher rate of side effects, especially in the field of the immune system. Therapy with Urokinase can be controlled more easily. Nevertheless because of considerable price differences and logistics, SK is preferred in Europe and the USA. If strict guidelines in therapeutic use are followed, the rate of side effects of the drug can be curtailed and will be comparable to those of Urokinase.
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PMID:Review and current status of thrombolytic therapy with streptokinase. 354 44

The fibrinolytic system comprises a proenzyme, plasminogen, which can be converted to the active enzyme, plasmin, which degrades fibrin. Plasminogen activation is mediated by plasminogen activators, which are classified as either tissue-type plasminogen activators (t-PA) or urokinase-type plasminogen activators (u-PA). Inhibition of the fibrinolytic system may occur at the level of the activators or at the level of generated plasmin. Plasmin has a low substrate specificity, and when circulating freely in the blood it degrades several proteins including fibrinogen, factor V, and factor VIII. Plasma does, however, contain a fast-acting plasmin inhibitor, alpha 2-antiplasmin, which inhibits free plasmin extremely rapidly but which reacts much slower with plasmin bound to fibrin. A "systemic fibrinolytic state" may, however, occur by extensive activation of plasminogen and depletion of alpha 2-antiplasmin. Clot-specific thrombolysis therefore requires plasminogen activation restricted to the vicinity of the fibrin. Two physiological plasminogen activators, t-PA and single-chain u-PA (scu-PA) induce clot-specific thrombolysis, via entirely different mechanisms, however. t-PA is relatively inactive in the absence of fibrin, but fibrin strikingly enhances the activation rate of plasminogen by t-PA. This is explained by an increased affinity of fibrin-bound t-PA for plasminogen and not by alteration of the catalytic rate constant of the enzyme. The high affinity of t-PA for plasminogen in the presence of fibrin thus allows efficient activation on the fibrin clot, while no significant plasminogen activation by t-PA occurs in plasma. scu-PA has a high affinity for plasminogen (Km = 0.3 microM) but a low catalytic rate constant (kcat = 0.02 sec-1). However, scu-PA does not activate plasminogen in plasma in the absence of a fibrin clot, owing to the presence of (a) competitive inhibitor(s). Fibrin-specific thrombolysis appears to be due to the fact that fibrin reverses the competitive inhibition. The thrombolytic efficacy and fibrin specificity of natural and recombinant t-PA has been demonstrated in animal models of pulmonary embolism, venous thrombosis, and coronary artery thrombosis. In all these studies intravenous infusion of t-PA at sufficiently high rates caused efficient thrombolysis in the absence of systemic fibrinolytic activation. The efficacy and relative fibrinogen-sparing effect of t-PA was recently confirmed in three multicenter clinical trials in patients with acute myocardial infarction.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Molecular mechanisms of fibrinolysis and their application to fibrin-specific thrombolytic therapy. 355 13

Thrombophlebitis and pulmonary embolism are major causes of disability and death in both medical and surgical patients. Etiological factors are still poorly understood. Preventive measures as currently practised are non-specific and based on questionable premises. Diagnostic measures to predict the silent fatal embolus are inadequate. Currently accepted treatment measures are designed to prevent extension of the thrombus but have no effect on the existing clot. Theoretically, thrombolytic preparations now being marketed offer some hope for dissolution of preformed thrombi. An experimental study was carried out on artificially induced thrombi in jugular and femoral veins of mongrel dogs. Human fibrinolysin (Actase, Ortho) was infused locally and systemically in varying doses. No thrombi were successfully lyzed by either method. Thirty-six cases of acute deep thrombophlebitis in the leg, one of axillary thrombosis, three of chronic postphlebitis of a lower limb with massive edema and eight of pulmonary emboli were observed and carefully documented clinically. All these patients received anticoagulants unless there was a contraindication. Fibrinolysin infusions in varying dosages were administered to 27 patients; 10 served as controls. The observers were unaware of the identity of those receiving the actual drug or of those given the placebo until completion of the study. Progress of the disease was judged by the rate of dis-appearance of symptoms and signs. No significant benefit could be noted in the treated as compared to the control group, in terms of rate of recovery or incidence of embolus.
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PMID:Fibrinolysin therapy of thrombophlebitis and pulmonary embolism--a double-blind study. 1397 84

Deep vein thrombosis (DVT) is a major health problem affectinga significant portion of population. Primary complications are Pulmonary Embolism (PE) in the short term and Post-Thrombotic Syndrome (PTS) in the long term. Thrombolytic drugs act by activating plasminogen which in turn forms the enzyme plasmin. Plasmin consequently degrades blood clots by breaking down the fibrin molecules which make up the clots help to degrade the already formed clot. They can be used using different route of administration, doses and durations. The purpose of this systematic review was to assess the outcome of thrombolytic therapy in terms of the efficacy, safety and effectiveness of the medicines. Electronic searches of databases (MEDLINE and Google Scholar) were queried for articles written in English since 2000 GC. A total of 760 results were obtained using the search keys, and after excluding duplicates, 275 articles were selected. Finally, 9 randomized controlled trials (RCTs) which met the language of publication, study design and exclusion criteria were included in this systematic review. The data were obtained from nine trials (6 countries), providing a study-level data of 1309 participants. Almost all studies revealed that thrombolytic treatment was effective in the management of acute DVT. In most of the studies, the rate of rethrombosis was lower in case of thrombolytic than standard management. Hence, addition of thrombolytic results in persistence and increases the clinical benefits. Thrombolytic therapy was very effective in reversing closed veins, in boosting the patency rate,whilereflux was higher in patients treated with anticoagulants. Thrombolytic offers potential advantages over the standard treatment of DVT by reducing the proportion of patients with chronic disabling leg symptoms (such as PTS) by triple in the longer term. However, the incident of major bleeding was higher in patients receiving thrombolytics than anticoagulants.
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PMID:Outcome of Acute Deep Venous Thrombosis Using Standard Treatment versus Thrombolytics: A Literature Review. 3187 95