CONCEPT AND CRITERIA OF RADIOLOGIC AGEING 203 



consequent generalized arteriosclerosis and its consequences following 

 irradiation is a good example (Casarett, 1952). 



Unfortunately there has been relatively little study of the long-term effects 

 of irradiation on body functions, especially functional reserve capacities, 

 directed toward the problem of ageing. However, some of the functional 

 studies which have been done suggest that functions which decline with 

 age tend to decline prematurely as a result of life-shortening irradiation, in 

 accordance with the deterioration of tissue as observed histopathologically. 



There is also a paucity of biochemical information on effects of irradiation 

 directly related to manifestations of ageing. However, some pertinent data 

 have been obtained which indicate premature ageing manifestations following 

 irradiation. One of the most notable examples is the work of Sobel (1960) 

 showing premature decrease of the hexosamine-coUagen ratio following 

 irradiation of skin, indicating a relative decrease of ground substance and a 

 relative increase in collagen. Whether this change is primary or secondary to 

 histopathological effects of irradiation in vasculature or parenchyma, or 

 represents only the increase in collagenous tissue in replacement fibrosis, is 

 not yet clear. 



CONCLUSION 



The foregoing general considerations of actuarial, pathological, histo- 

 pathological, and physiological changes following irradiation, in comparison 

 with the manifestations of "normal" ageing, indicate a strong resemblance 

 between the late effects of life-shortening total-body irradiation and the 

 manifestations of premature ageing, especially with respect to the histo- 

 pathological manifestations preceding age-dependent disease. The histo- 

 pathological changes preceding disease development at the site of localized 

 irradiation from external sources, or from internal radioisotopic sources, also 

 bears a strong resemblance to the histopathological manifestations of ageing 

 and therefore suggest the concept of premature localized ageing resulting 

 from localized irradiation. Although the processes and manifestations of 

 "normal ageing" and "radiologic ageing" at the histopathological level are 

 similar, their nonspecificity makes it impossible to predict whether or not the 

 more fundamental underlying processes, whatever they may be, will be 

 similar or quite different. 



REFERENCES 



Alexander, P. (1957). Gerontologia 1, 174. 

 Blair, H. A. (1956). USAEC Document UR-442. 



Brues, a. M., and Sacher, G. A. (1952). In "Symposium on Radiobiology" 

 (J. J. Nickson, ed.), p. 441. Wiley, New York. 



