The effect of gamma irradiation on cell division in tissue culture in vitro .—Part II

Abstract

In a previous paper (1) the effects of the gamma rays of radium upon the number of cells in mitosis in tissue cultures has been described, the cultures being examined 80 minutes after irradiation. Under the conditions of the experiment it was shown that there was a threshold of intensity below which no diminution in the number of cells in mitosis was apparent, and also a threshold of time for each intensity which must be exceeded before diminution could be observed. Gilman and Baetjer (2) showed that there was an acceleration in the development of the eggs of Amblystoma after irradiation by X-rays. Hastings, Beckton and Wedd (4) showed an increase in the rate of hatching out of silk-worm eggs which had been irradiated by X-rays; and Lazarus-Barlow and Beckton (3) showed that small intensities of beta-rays acting for a long period were followed by a greater rate of cell division in the eggs of Ascaris Megalocephala. In the case of tissue cultures Canti and Donaldson (5) described an experiment in which cessation of mitosis having been caused by exposure to the gamma rays of radium a return of mitosis was observed after removal of the radium. Since the completion of the present experiments it has been shown by Spear (6) that by lowering the temperature of tissue cultures to 0° C. for 4 hours and subsequently incubating for various periods there is a fall in the number of cells in mitosis followed by a return in increased numbers which is compensatory.