The influence of colcemid concentration on mitotic index and length of bone marrow chromosomes

Bone marrow cells from 25 patients with different hematological disorders were cultured overnight and then exposed to colcemid, varying both concentration and time of exposure, in order to obtain optimal results. PHA stimulated lymphocytes were treated in a similar manner for comparison. Results showed that with concentrations at or below 0.4 microgram/ml, the mitotic index of PHA stimulated lymphocytes was reduced and the metaphase spreads were of poor quality, but spreads of bone marrow chromosomes were not adversely affected at even much lower concentrations. Furthermore, both chromosome length and mitotic index were found to increase with lower concentrations. These observations, together with results obtained by comparing mitotic indices after varying exposure times, suggest that bone marrow cells may be inhibited from passing through G2 by high concentrations of colcemid. Thus by lowering the concentration of the colcemid for bone marrow cultures, we have been able to increase greatly the yield of bandable metaphases.