The Action of Colchicine in Arresting Epidermal Mitosis

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Abstract
Three-mo. - old male mice of the Kreyberg white label strain were injected with 0.1 mg. of colchicine dissolved in 0.25 cc. of water. Controls received water only. Ear clips were removed at the time of injn. and at 2-hr. intervals up to 12 hrs. and mitoses counted in unit sections 1 cm. long. In one series injected at 8 A.M., controls showed the typical peak of mitoses at 2 P.M. but colchicine-injected ones did not. The data indicated that an arrest of mitoses in the metaphase had occurred and also that cells had been inhibited from entering the prophase within 5 hrs. after injn. of colchicine. A 2d expt. confirmed this time interval and demonstrated that the hr. in the diurnal cycle when treatment is begun is important, since animals injected at 10 A.M. had twice as many mitoses because the 5-hr. interval included the normal peak of mitotic activity. Blood sugar detns. after colchicine admn. did not indicate that changes in blood sugar concn. are involved in the depression in mitotic activity. On the basis of the data, it is suggested that in studies of mitotic activity, colchicine ought not to act for more than about 5 hrs. rather than for the 9.5 hrs. usually employed.

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