Megakaryocytes in agar cultures of mouse bone marrow

Cytologic and immunofluorescent data demonstrate that cells morphologically resembling megakaryocytes appear in thin layer agar cultures of cellular fractions of mouse bone marrow and increase in number from zero to a maximum of approxiamately 60 per culture on day 6. It would appear that these "candidate" megakaryocytes are derived from a morphologically unidentified precursor(s) since they are not present in the original cell suspension cultured but begin to appear 24 hours later. Similarities between the ultrastructure of "candidate" megakaryocytes and that of femoral marrow megakaryocytes support morphological similarities at the light microscopic level. Pretreatment of mice with either vinblastine and nitrogen mustard or antiplatelet serum has no effect on the number of "candidate" megakaryocytes appearing in cultures of their marrow. Preliminary data suggest that the rate of appearance of these cells in culture is responsive to serum from thrombocytopenic donors.