Frank D. Mann

Observations on the Conversion of Prothrombin to Thrombin

Summary Fresh plasma, serum and platelet extracts contain a material which potentiates the action of tissue thromboplastin on stored plasma. Platelet extract apparently contains a greater degree of this activity than plasma or serum and potentiates the action of tissue thromboplastin on fresh plasma. This factor favoring prothrombin conversion apparently is present in the circulating blood.

Species Specificity of Thromboplastin Role of the Cothromboplastin Reaction

Summary Species specificity of thromboplastin is largely eliminated by brief treatment of the thromboplastin with dilute homologous serum. This appears to be an example of the cothromboplastin reaction.

Clinical Experiences with 4-Hydroxycoumarin Anticoagulant No. 63 and the Antagonistic Effect of Menadione and Vitamin K1

The successful use of dicumarol in the prevention of intravascular thrombosis and subsequent embolism has led to the investigation of other coumarin compounds as therapeutic anticoagulants. 4-Hydroxycoumain anticoagulant No. 63 is such a compound. Like dicumarol, it induces hypoprothrombinemia and daily tests of prothrombin time are necessary as a guide to dosage. Our experience indicates that a less fluctuating and somewhat more consistent therapeutic hypoprothrombinemia can be established and maintained with anticoagulant No. 63 than with dicumarol. The potential disadvantage of the prolonged hypoprothrombinemia after administration is stopped is counter balanced by the strong and relatively rapid antagonistic effect of vitamin K1.

Relation of Complement to Blood Coagulation

Summary Inactivation of the complement of plasma by aging or by treatment with zymin or with ammonia blocks conversion of prothrombin to thrombin while leaving ample reactive prothrombin.