No abstract

X concentrate of antithroinbin was made from bovine plasma. When examined with an analytical ultracentrifuge it was found to contain a main component and a sinall ail~ount of more rapidly sediinentating material. For the main component S j , , was 4.01 S. The antithroinbin concentrate destroyed the activity of purified autoprothrombin C, and most likely antithrombin and antiautoprothrombin C are one and the same substance. The antithrombin preparation was limited in its capacity to destroy autoprothrombin C activity, and equilibriunl conditions were reached in 3 to 4 hours. At equilibrium the quantity of autoprothrombin C destroyed \\;as proportional to the antithrombin added to an "excess" of autoprothroinbin C. 'The last traces of the latter activity could only be neutralized with difficulty. 1;nder optimum conditions 1 ml of plasma can neutralize the autoprothrombin C that inight generate froill 27 ml of plasma. About 0.83 ml of oxalated bovine plasma can neutralize the activity in 1 mg of purified autoprothrombin C.

Spicules from sickle red cells were examined for their effects on the clotting activity of blood. The spicules were obtained from the sickle red cells after deoxygenation and oxygenation and were tested for clotting activity with Russell's viper venom assay. A marked increase in clotting activity was observed when spicules were added to the system. The increase was distinctly greater than that observed after the addition of sickle red cells while normal red cells had little effect. Vesicles prepared from sickle or normal red cells by incubation with the ionophore A-23187+Ca2+ also markedly increased clotting activity. The effect of spicules or vesicles on the clotting system may be related to reorganization of phospholipid in the spectrin-poor membrane of the spicules or vesicles. Because of these effects, the spicules from the sickle red cells may contribute to the hypercoagulable state in these patients and possibly to their vaso-occlusive crises since free spicules are present in their plasma. Vesicles from red cells from other types of anaemia with hypercoagulability may have a similar effect on coagulation.