No abstract

No abstract

1 3 5 tioned that this greater yield would also be expected on the hypothesis that SF is required solely for "extrinsic thromboplastin." The work of Flynn and Coon( 1) suggests that this hypothesis is correct. These workers sedimented "extrinsic thromboplastin" by centrifugation and then washed it by suspension in saline and recentrifugation ; they showed that this washed material was active in converting purified prothrombin to thrombin in presence of calcium. The method of preparation of prothrombin was such that it is unlikely to have contained SF. However, this evidence is not entirely conclusive for some free SF not utilized in the initial formation of "extrinsic thromboplastin" might have been adsorbed onto this complex.When factor VII is excluded from both incubation mixture and substrate clotting tubes in thromboplastin generation test, normal yield is obtained, and there is also normal rate of evolution. Therefore, the finding that absence of factor VII from incubation mixture and substrate tubes affects rate of "extrinsic thromboplastin" formation although having little or no effect on yield is interesting. SF is essential for "intrinsic thromboplastin" generation, primarily affecting yield, so that finding that this factor also primarily affects yield of "extrinsic thromboplastin" was not surprising.Summary. Previous work showing that factor V, serum, brain and calcium react together to form an active prothrombin conversion factor ("extrinsic thromboplastin") is confirmed. The active components in serum in respect of this reaction include both factor VII and SF but not PTC. SF appears to influence yield while factor VII primarily determines rate.Although SF appears to affect yield rather than rate of formation of both "extrinsic" and "intrinsic" thromboplastin formation, work of Fisch and Duckert (Thromb. Diath. Haem., 1959, v3, 98) appearing since this paper was submitted indicates that SF acts as an enzyme in "intrinsic thromboplastin" formation.The author is extremely grateful to Drs. of the U. of N. Carolina for use of their laboratories and generous supplies of rare sera.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.