Time-lapse and ultrastructure studies on the reversal of mitotic arrest induced by vinblastine sulfate in earle's l cells

L cells exposed to vinblastine sulfate (Velban, Lilly) for 4–24 hours did not show any spindle microtubules in association with centrioles or centromeres. More than one pair of centrioles were seen in many of these cells. Velban-induced mitotic inhibition could be readily removed when cells were washed and reincubated in fresh medium. A large number of these metaphase-blocked and multimicronucleated cells would divide within the first 4 hours after removal of the inhibition. Multipolar chromosome formations, multipolar divisions, and aberrant cytokinesis were seen in many cells released from the mitotic arrest. Aggregates of fine, amorphous, or fibrillar material and large numbers of spindle microtubules were associated with centromeres, chromosomes, and centrioles of cells recovering from the mitotic arrest.