Tatiana B. Gasic

Effects of trypsin on the platelet-aggregating activity of mouse tumor cells

Abstract A platelet-aggregating factor is found in cells of two mouse tumors and in cell-free supernatants released spontaneously by tumor cells. The factor disappears from cells after trypsin treatment and its recovery in the cell-free supernatant depends on the degree of cell trypsinization. Activity of cells regenerates during subsequent incubation by a process requiring protein synthesis. The latter, and the fact that the non-dialyzable cell-free material is sensitive to heat and trypsin, suggest that it is a protein or a protein complex.

REMOVAL OF PAS POSITIVE SURFACE SUGARS IN TUMOR CELLS BY GLYCOSIDASES.

Summary Structural components of the coat of fixed TA3 tumor cells are stained both by the Hale and the PAS procedures. The Hale positive material can be removed by active neuramidase, indicating the presence of neuraminic acid. The PAS positive component is not influenced by lipid extraction or by diastase digestion and is only slightly affected by neuramidase. However, it is strongly affected by an enzyme preparation from Clostridium perfringens, containing a mixture of glycosidases. By specific blocking of individual glycosidases in the incubation medium, it was determined that galactose and acetyl-galactosamine are important components for the PAS positivity of the cell coat. Fucose is of less significance and perhaps less abundant than other PAS positive sugar units. N-acetyl-hexosaminidase from fungi of Genus Chalaropsis was also active against the PAS positive cell coat but differed from the glycosidases of CI. perfringens in that it did not require the previous removal of the Hale positive component and was not blocked by N-acetyl-galactosamine, galactose, and fucose.

Mechanisms of Platelet Aggregation by Murine Tumor Cell Sheddings

Cells from a variety of animal and human neoplasms can induce the aggregation of platelets in plasma (1–3). While the mechanism of this effect has not been fully elucidated preliminary evidence suggests that several mechanisms may exist. With human tumor cells platelet aggregation may be induced via mechanisms involving the leakage of tumor cell ADP (2, 4, 5; see also Chapters 11 and 12). In rodents aggregation may occur with both whole cells and cell sheddings. This suggests that the aggregating activity of intact cells is mediated by the spontaneous release of some subcellular component. We found that a mixture of membrane vesicles and cytoplasmic dense granules were shed (6). Normal cells are also capable of shedding a small amount of material which is much less active in platelet aggregation (6,7).