Human prothrombin was acetylated to produce a modified prothrombin that upon activation by platelet-bound prothrombinase generates a form of thrombin that does not activate platelets but retains its amidolytic activity on a chromogenic peptide substrate. If normal prothrombin is used in such an assay, the thrombin that is generated activates the platelets in a feedback manner, accelerating the ...

DETERMINATION OF STREPTOKINASE ACTIVITY IS USUALLY ACCOMPLISHED THROUGH TWO ASSAY METHODS: a) Clot lysis, b) Chromogenic substrate assay. In this study the biological activity of two streptokinase products, namely Streptase®, which is a native product and Heberkinasa®, which is a recombinant product, was determined against the third international reference standard using the two forementioned a...

Proficiency testing surveys in the state of New York indicate that despite increased sophistication in instrumentation, there has been no real improvement in interlaboratory reproducibility in prothrombin-time determinations over the last 10 years. This lack of improvement most pronounced in the therapeutic range of 20 to 30 sec. One reason may be that between types produced by the same manufac...

A rapid and precise assay for neuraminidase using 2-(3'-methoxyphenyl)-N-acetyl-alpha-neuraminic acid (MPN) is described. It is proposed that this substrate be used for the standardization of activity of neuraminidases from viral, bacterial, and mammalian sources. MPN is also used as a chromogenic substrate to localize influenza and parainfluenza virus foci in tissue culture. This technique per...