A Quantitative Description of Latent Injury from Ionizing Radiation 339 



Irreversible radiation injury has the special property that it is closely related 

 to premature aging abruptly laid down and probably persisting thereafter 

 at a level constant or nearly so. This suggests the possibility that premature 

 aging may be studied in young animals without waiting for them to die naturally. 

 Of special interest is the possibility that irreversible injury may be prevented, 

 at least in part, or altered once it has been laid down. This possibility should 

 be studied in relation to exposure problems in man and also with respect to 

 its bearing on natural aging. If, however, irreversible injury is wholly in the 

 form of somatic mutations, as is often suggested, the possibility of altering it 

 or its consequences would presumably be remote. 



The acute injury described here in terms of radiation dose has antecedents 

 in the form of disturbances of cellular structure and function from absorbed 

 radiation and consequences in the form of the clinical syndrome of radiation 

 sickness. Only the last stage has been at all well described in physiological 

 terms, and the connections between the stages has not been elucidated at all. 

 The ability to measure latent injury in terms of radiation dose should assist 

 in deriving its description in biochemical or physiological terms. This is also 

 true of irreversible injury. 



Nearly all aspects of the long-term effects of radiation injury are markedly 

 deficient in data, especially of those based on sufficient numbers of animals 

 to be reasonably exact. 



For this reason no formulation of the kinetics of the injury process can 

 be adequately tested at present for its quantitative exactness. The virtue of 

 a particular scheme is measurable rather in its ability to designate the phenomena 

 involved, to make useful predictions and to serve as a basis for designing 

 critical experiments. 



REFERENCES 



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