A platelet factor stimulating human normal glial cells.

Multiplication stimulating activities of human serum and fractions thereof have been determined as stimulation of [³H]thymidine incorporation of serum-deprived human glial cells. Serum prepared from cell-free plasma had a considerably lower activity than serum prepared from whole blood. The major part of the growth-promoting activity of serum could be ascribed to a platelet factor, released during the coagulation process. The factor was trypsin-labile and heat-stable. A partial purification of the factor was achieved by ion exchange chromatography on CM-Sephadex at neutral pH. The purified material was 600–700 times as active as normal human serum on a protein basis.