Intravenously administered isoproterenol sulfate dose-response curves in man.
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Biomedical subjects
Publications and source records attributed to T Fenyvesi.
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1. The effects of three beta-adrenoceptor blocking agents on isoprenaline induced changes in systemic and regional blood flow have been investigated in rats anaesthetized with pentobarbitone. The blood flow to the principal vascular beds was measured by the (86)Rb fractionation method.2. Isoprenaline infusion at a rate of 0.3 (mug/kg)/min intravenously caused an increase in cardiac output and a decrease in peripheral resistance which affected different vascular fields unevenly. The coronary and carcass fractions of cardiac output increased while the cutaneous, renal and splenic fractions decreased.3. Pretreatment with propranolol (2 mg/kg intravenously) blocked all isoprenaline effects. Practolol (8 mg/kg intravenously) lessened the effect on cardiac output but did not prevent the vascular effects except those on the coronary circulation. LB 46 (0.2 mg/kg) had less marked beta-adrenoceptor blocking activity than propranolol (2.0 mg/kg).
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Prothrombinase-induced clotting time (PiCT) is a clotting-time test for heparins and direct thrombin inhibitors to reduce drawbacks of aPTT. Effects of the direct thrombin inhibitors lepirudin, argatroban, melagatran and of unfractionated heparin (UFH) were investigated in normal and oral anticoagulant plasma samples. Lepirudin showed potentiating interferences with phenprocoumon effects. Melagatran, argatroban and UFH delivered distinct linear additive effects in both plasma sample groups. PiCT ratio reduces differences between both groups with UFH, and argatroban inhibitor-receptor-binding mode plays a role in interaction patterns.
Heparin induced thrombocytopenia (HIT) is a severe complication of heparin therapy. It is generally accompanied by a paradoxical decrease in platelets leading to activation of platelets and of the coagulation system. HIT type I is a mild, transient, non-immune disorder. HIT type II is an immune-mediated reaction towards neo-antigen on PF4, which is platelet factor 4 (PF4) that is exposed upon binding to heparins. A low sulfated octasaccharide is required for binding to PF4. The generated immunoglobulines bridge platelets by binding to the FcgRIIa-receptor. In patients with HIT type II heparin/LMW-heparin has to be discontinued immediately upon clinical suspicion. Diagnosis can be confirmed by laboratory tests. As patients are at high risk for or because they have developed thromboembolism, anticoagulation is mandatory, despite thrombocytopenia. Treatment options are danaparoid, r-hirudin, bivalirudin, argatroban, dextransulfate, and dermatansulfate. In future, fondaparinux and ximelagatran may be considered for treatment.