Colony formation of bone marrow cultures.

HPCs were obtained from ED14 quail embryonic bone marrow by separation on Ficoll-Paque density gradients and subsequent removal of cells adherent to tissue-culture plastic. The enrichment of progenitor cells by these procedures was confirmed by staining of bone marrow cellular isolates with May-Grünwald-Giemsa (MGG) solution either before (A) or following (B) Ficoll-Paque separation. Note that prior to separation, fully differentiated RBCs were the predominant cell type obtained from the bone marrow (A), whereas the Ficoll-Paque gradients allowed for the isolation of cellular populations that were primarily nondifferentiated blasts (arrows) (B). (C-F) HPC-enriched bone marrow cells were incubated in MeC cultures as described in “Materials and methods.” Cultures were incubated for 6 days prior to microscopic imaging. Representative examples of the types of colonies that formed in these cultures are erythroid (C), granulocyte/macrophage (D), granulocyte/erythroid/macrophage (E), and macrophage (F). Scale bar: A, 15 μm; B, 17 μm; C, 40 μm; D, F, 36 μm; E, 48 μm.