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A test is described for the estimation of antithrombin in the blood. The chief advantage of the test is that it is simple, and does not require the preparation of fibrinogen and of thrombin, which are difficult to prepare and to maintain in a pure state. The principle consists in titrating the antithrombin against normal human plasma; in this way we obtain an estimation of its power to delay co...

Factor VII clotting activity increases about five-fold when blood is clotted in glass. Prior studies suggested that this results from activation induced by activated factor IX (IXa). However, in purified systems containing phospholipid and calcium, activated factor X (Xa) is known to activate factor VII rapidly. Therefore, we studied activation of factor VII by IXa and X, in systems using purif...

By HENRY II. IIENSTELL AN!) MIRIAM KLICERMAN T COMMUNICATION is concerned with a systematic study of pr gressive antithrombic activity. The results imidicate that amititlirombic activity is not due to a single entity but consists of a three-phase system: a plasma antithrombin which appears to be identical with Antithrombin III, a plasma inhibitor which neutralizes the plasma antithrombin, and a...

I NVESTIGATIONS on the possible mechanism of the anticoagulant action of heparin have centered largely on the problem of its cofactor. In 1918, Howell and Holt (I) showed that heparin requires a blood factor to prevent the coagulation of fibrinogen by thrombin. Subsequently Quick (2) suggested that an albumin fraction contains normal antithrombin, which together with heparin, exerts a powerful ...