In vitro platelet stain preventing (degranulating) effect of various substances, Study of mechanism of action.

A few years ago a patients, T.L., with metastatic leiomyosarcoma found to have a serum and tumor factor which caused the granulomere of normal platelets to disappear as seen using light microscopy. The present report describes the effect on platelet granules of several different substances using various anticoagulants. Ultramicroscopy showed in all instances that the platelet stain preventing effect as seen in May-Grünwald & Giemsa stained films reflected a degranulation. Ultramicroscopy was little better than light microscopy in the differentiation between the mechanisms of the various degranulating substances. Different conditions such as variation in anticoagulant or combination of anticoagulants, storage at room temperature for 24h, heating to 56 degrees C for 1 h on the other hand were very useful methods for differentiating between the various degranulating substances. These methods failed, however, to differentiate between patient T.L.-serum and patient T.L.-tumour fraction SSS, probably because the active factor was the same in both.