A new system of hemopoietic colony formation for permanent slides and medium changes: use of glass-fiber filters.

A new method for hemopoietic colony formation that allows the preparation of permanent slides and medium changes during the incubation period was developed in vitro. Bone marrow cells from mice were spread over glass-fiber filters, which were placed on agar medium and cultivated for 7 days. Hemopoietic colonies appeared on the glass-fibers filters. The glass-fiber filters with colonies were stained by a peroxidase and nonspecific esterase double-staining method and mounted as permanent slides. Each colony could be clearly identified and easily counted after the staining. The dose-response relationship between the number of seeded cells and the colony counts was a linear one, with the line very nearly passing through the origin on extrapolation. The colonies were classified into three types by the staining results: granuloid type, monocyte-macrophage type, and mixed type, the last containing both granuloid and monocyte-macrophage cells. Medium change during the incubation period was attempted in the experiment for phagocytic activity of the cultured cells and proved to be useful. This system appears to be useful and convenient in the study of hemopoietic colony formation.