CKR05I0SOME ABERRATIONS IN LIVER CELLS 



253 



animals, kept in the same room but sliielded from the radiation are also 

 shown. It is apparent that radiation given at this rate increases the aberration 

 frequency relatively little above that of the control (Fig. 1). 



O 



60 



100 140 180 



220 260 300 340 380 420 

 Age (doys) 



Fig. 1. Increase in percentage of chromosome aberrations with age for control and chronic- 

 ally irradiated mice. The accumulated dose is shown for various times. 



c 

 o 



a> 



X) 



o 



Q) 



E 

 o 

 ui 

 o 



E 

 o 



100 h 

 90 

 80 

 70 

 60 

 50 

 40 

 30 

 20 

 10 



"1 I I 1 



— • 300 r fast neutrons, single dose 10 mice 

 —^ 300 r fast neutrons, single dose 5 mice 

 -• • Control 10 mice 

 — * Control 5 mice 



L 



I I I 



60 



100 140 ISO 



220 260 300 

 Age (days) 



I I I ' 1 ! ! ! L 



340 380 420 460 



Fig. 2. Percentage of chromosome aberrations following a dose of 300 rads of fission neutrons. 



The next experiment, shown m Fig. 2, followed the chromosome aberra- 

 tions as a function of tune following a single dose of 300 rads of fast neutrons 

 (an LDio dose). The curve shown is actually the average of two experiments 

 both of which showed a very significant increase of aberrations with time. In 

 the neutron-treated mice the aberrations were very severe, with many of the 

 cells scored having several chromosomal injuries. 



