Abstract
In a previous paper it has been shown that DPNH-diaphorase activity presumably appeared around prophase in mitotic cycle of Ehrlich's ascites tumor cells. The present study was undertaken to determine the exact period of appearance of the DPNH-diaphorase activity by means of the combined technique of histochemistry and autoradiography. Samples of ascitic fluid from mouse were obtained at various intervals after a single injection of tritiated thymidine, and the percentage of labeled ones among the cells showing DPNH-diaphorase activity was scored on autoradiographs of smears. The result showed that the percentage was 36% at 2 hours, 78% at 5 hours, 90% at 8 hours, 92% at 11 hours, 87% at 14 hours, 64% at 17 hours, and 35% at 20 hours. From the result the author deduced that the DPNH-diaphorase activity might begin to appear at antephase in mitotic cycle of Ehrlich's ascites tumor cells.
