Colony quantitation.

(A) Quantitation of myeloid colonies (CFU-G and CFU-GM) derived from the bone marrow cells of either wild type or β^6I/β^6I mice using growth conditions that permitted myeloid differentiation after 8 days of culture. (B) Quantitation of erythroid colonies (BFU-E) using conditions that permitted only erythroid growth after 8 days of culture. There was no significant difference in the numbers of myeloid or erythroid colonies derived from either the β^6I/β^6I or the β^wt/β^wt mice in the absence of G418. The addition of 900 μg/mL active G418 caused near-complete suppression of colony formation from wild-type bone marrow cells. In contrast, G418 did not suppress myeloid or the erythroid colony numbers (or the sizes of colonies) derived from the bone marrow cells of β^6I/β^6I mice. Graphs represent means and standard deviations from 3 separate experiments.