Reversal by Light of the Action of N-methyl N-desacetyl Colchicine on Mitosis

Colchicine, in low concentrations, inhibits cell division in a wide variety of cell types through an effect which results in dissolution of the spindle (1, p . 62 et seq .) This is especially clearly shown in the work of Inoué (2) . When exposed to sunlight, colchicine undergoes a photochemical rearrangement to give a, ß, and y lumicolchicines (3, 4) (Fig . 1) . There is also evidence that exposure to sunlight and air reduces the biological activity of colchicine (1, p. 374) . This suggests the possibility of photochemically reversing colchicine effects in living cells . The N-methyl derivative of N-desacetyl colchicine (Ciba's trade name is Colcemid) was used in this study in preference to colchicine because of its effectiveness at lower external concentrations and because of fewer irreversible effects .