In this work, we hypothesize that a surface modified with both polyethylene glycol (PEG) and hirudin may provide a non-fouling, thrombin-neutralizing surface suitable for blood contacting applications. With gold as a model substrate we used two different approaches to the preparation of such a surface: (1) a "direct" method in which PEG was conjugated to hirudin and the conjugate was then immob...

Evidence for the potential use of direct thrombin inhibition in the treatment of acute stroke is reviewed. Reduction of secondary microthrombi and improved regional collateral cerebral blood flow is the proposed mechanism of action of thrombin inhibition for the treatment of cerebral ischemia. A clinical study in Japan found that argatroban administered within 48 h of stroke symptom onset is sa...

A new G-protein was detected in human platelets which was ADP-ribosylated in a pertussis-toxin-dependent manner, was located in the supernatant of saponized platelets and was of a slightly lower molecular mass (40 kDa) than platelet membrane Gi alpha. This soluble ADP-ribosylated protein was immunoprecipitated by an antiserum to Gi alpha, but not by one to Go alpha. Prior thrombin stimulation o...

The physiologically most important activator of intravascular fibrinolysis is tissue-type plasminogen activator (t-PA) released from endothelial cells. In man, sympathomimetic drugs increase the systemic concentration of t-PA. It is therefore of interest to investigate whether cardiac sympathetic activation can induce a local t-PA release, which could counteract intracoronary clot formation. Th...

A method is described by which the time-course of thrombin generation in plasma can be obtained from a continuous optical density recording of p-nitroaniline (pNA) production in a 2:3 diluted plasma. A chromogenic substrate, methylmalonyl-methylanalyl-arginyl-pNA (SQ 68), is used that is specifically split by thrombin but at a low rate. The thrombin that appears and disappears in the plasma doe...

The antifactor Xa activities of heparin fractions are widely used as an ex vivo index of their antithrombotic efficacy. Its clinical meaning, however, remains speculative. In the study reported, we measured the effects of standard heparin, a synthetic pentasaccharide heparin (antifactor Xa activity only), and a low molecular weight heparin (LMWH) on factor Xa, factor Va, and thrombin generation...

Great advances have been made in recent years in understanding the haemostatic system and the molecular and cellular basis of thrombus formation. Although directly targeting factor Xa or thrombin (factor IIa) for effective anticoagulation is now well established, evidence has emerged suggesting that factor Xa and thrombin are involved in other physiological and pathophysiological cellular proce...

The kinetics of inhibition of human thrombin and Factor Xa by antithrombin III or heparin cofactor II were examined under pseudo-first-order conditions as a function of the concentration of naturally occurring oversulphated chondroitin and dermatan sulphates. The sulphated glycosaminoglycans (GAGs) studied were chondroitin sulphate D (CSD) (GlcA-2-SO4-GalNAc-6-SO4), chondroitin sulphate K (CSK)...

Factor Xa and thrombin, two critical pro-coagulant enzymes of the clotting cascade, are the primary target of current anticoagulation research that aims to develop potent, orally bioavailable, synthetic small-molecule inhibitors. To determine structural features that might play important roles in factor Xa and thrombin recognition and oral bioavailability, quantitative structure-activity and st...