The distribution in the cell cycle of normal cells and of irradiated tumour cells in mice.

Abstract Flow microfluorometry (FMF) instrumentation was used to make a rapid, quantitative measurement of the DNA content of individual cells from normal tissues and from KHT tumour cells of mice. These normal tissues are some of the limiting normal tissues in radiation therapy. The DNA content of tumour cells was also measured at different times after X-ray exposure. Preliminary results indicated that the cellular DNA content of all normal tissues was about the same and that a large fraction of cells were in the G0 or G1 stage. In the KHT tumour, nearly 75 per cent of the cells were in the G0 or G1 stage, 20 per cent in the S stage, and the remaining 5 per cent in the G2 + M stage. Ten hours after 300 rads of X rays, the number of tumour cells in the G1 stage decreased to about 40 per cent, cells in the G2 + M stage increased to about 30 per cent, and about 30 per cent of the cells were in the S stage. The cellular DNA content was very nearly the same as unirradiated controls at 24 hours after exposure....