The Use of the Supravital Method in a Study of Cells Susceptible to Damage in Smears of Normal and Regenerating Bone Marrow

P AMAGED CELLS or “smudge cells” are a common feature of bone marrow smears, although in clinical reports only rarely is any attention payed to them. In smears of normal marrow at least 10-15 per cent of all cells are unidentifiable because of damage. This represents the greatest source of error in all quantitative estimations of cell populations which are based on counts in fixed smears. The number of damaged cells varies considerably under various experimental and pathologic conditions.1’2 During recovery from sublethal irradiation a threefold increase in damaged cells was reported in the guinea pig3 and comparable values have been obtained after sublethal doses of nitrogen mustard.4 Furthermore, a considerable proportion of damaged cells are in DNA synthesis.25 An evaluation of what types of cells are most susceptible to damage would be of considerable importance to workers in the clinical, as well as in the experimental field of hematology, particularly since during the process of marrow regeneration the rate of cell damage in smears seems to be increased. The present study was prompted by these considerations and it was intended to answer two questions : 1 ) What are the cells which are damaged in significant numbers in normal marrow? and 2 ) Is there any change in the proportion of damage in individual cellular compartments during marrow regeneration?