308 



Hubert P. Yockey 



agree with the normal aging curves as well as these curves agree with each other. 

 There are several interesting details which should be pointed out. The 

 gamma-ray data show a remarkable coUinearity with aging data below the 

 10 to 20 per cent survivorship value but rise above the aging curve to a much 

 sharper 'knee'. This effect is probably due to recovery, a phenomenon which 

 is associated with radiation damage but not with aging. Cronkite et al. noted 



« (woeks) 24 

 100 



• r DOSE (r ) 100 



300 



500 



700 



900 



13 



15 



17 



1100 



21 23(months) o 



o (months) I 



17 



Fig. 5. Normalized survivorship of certain strains of mice for normal aging and 



acute radiation killing for LAF^ (51, 52, 53). LAFj normal aging curve is due 



to A. C. Upton and A. W. Kimball, personal communication (see also (48)). 



Radiation dose and age are plotted linearly. 



a small mortality below about 600 r and took pains to establish its reality 

 as a radiation effect. This feature is also present in the aging curves — a bit 

 more pronounced, to be sure, since there is no recovery. This feature of these 

 curves, incidentally, fits very well with the present theory, or any theory which 

 relates aging and radiation damage, but is otherwise quite a puzzle. These 

 mice were presumed to be as nearly identical as possible and so should have been 

 killed by nearly the same dose. (A discussion of a possible molecular basis 

 for recovery has been given (10). This effect is left out of this article for simplicity.) 

 Cole, Nowell, and Ellis (54) have reported the late survivorship of 

 LAFj mice protected from 800 r of 250 kVP x-rays by spleen homogenate. 

 The survivorship curve has the same shape but is shifted so that the mean 

 age at death is eight months earher than the unirradiated control. This shows 

 that even if a certain organ system, in this case the hematopoietic system, 

 is so aided in repair that its role as a cause of death is greatly modified, neverthe- 

 less, the survivorship curve has the same shape. 



