Mitotic Rate of Malignant C1300 Mouse Neuroblastoma

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Abstract
The generation time or the doubling time of tumor cell populations was defined as the period during which 100 per cent of cells of a tumor passed through a mitotic cycle. A series of mice of the A/J strain was injected subcutaneously with 0.1 cc of a sus pension of C1300 neuroblastoma. The animals were sacrificed after having received 6 hours earlier an injection of colchicine 0.20 mg/100 g body weight. Under chloroform anesthesia the tumor was removed and thin sections were prepared and stained with hematoxylin and eosin. Colchicine metaphases were counted in microscopic fields. In the group of the 13th to 14th day series the daily mitotic rate was 37.7% of cells; in the 21 -22 day of transplant group the mitotic rate was 35.2 per cent. Diurnal fluctuation of mitotic rate was not significant in the first group of tumor bearing mice. In this group division of 100% of cells (genera tion time) occurred every 66 hours. In the second group with a trans plantation time of three weeks cell necrosis accounted for a significant reduction in the proliferating cell fraction of the tumor.