To study the relationships among the frequency of chromosomal aberration induced by radiation, mouse age at the time of exposure and elapsed time after the irradiation, the 40,150 and 300 day old mice were irradiated by gamma rays to 200 rad of acute whole body doses. The bone marrow chromosomes were observed in 8 experimental groups such as 1,2,3,4,8,16, 30,60 and 90 days after irradiation.
In the 40 day old mice the frequencies of cell with chromosomal aberration were 53.0%, 21.5%, 8.4%, 8.4%, 12.0%, 8.0%, 7.0% and 5.0% in 8 experimental groups, in the 150 day old mice 32.5%, 12.1%, 10.5%, 12.8%, 0.03%, 9.7%, 7.0% and 4.2%. The 300 day old mice showed that the frequencies of cells with chromosomal aberration were 27.7%, 13.6%, 9.0%, 9.3%, 13.3%, 14.4%, 7.5% and 9.5% in each experimental group.
There were tendencies that the frequencies of cell with chromosomal aberration were higher in the .young mice than the old ones within 2 days after the irradiation but in the old mice than the young ones after 4 days.
|