13 



Some Factors Influencing Cell Radiosensitivity 



by Acting at the Level 



of the Primary Biochemical Action 



RAYMOND LATARJET 



L'Institut Pasteur 

 Paris, France 



The primary biochemical processes that result from the interaction 

 of radiation and living tissues are not accessible to direct observation. 

 Various indirect pathways provide some indication concerning these 

 processes. Chemical actions in vitro will be considered in later papers; 

 action on isolated cell constituents, such as enzymes, viruses, and chro- 

 mosomes, and on cellular metabolism, will be presented by other con- 

 tributors. 



Another indirect approach involves the study of factors capable of 

 influencing cellular radiosensitivity. If such a factor alters the sensi- 

 tivity, this means that it intervenes in some step of the process, and its 

 nature may provide some hint as to the process itself. This report will 

 deal with this indirect pathway by examining several factors which un- 

 doubtedly influence sensitivity by acting at the level of the primary 

 biochemical process.* This approach, at the same time, will bear on 

 the problem of cell sensitivity, which greatly depends on the course of 

 this primary process. In that which follows, the terms "lesion," "sensi- 

 tivity," and "resistance" will be used for "radiolesion," "radiosensi- 

 tivity," and "radioresistance." They will always concern a well-defined 

 effect in a given type of cell rather than the totality of possibly observ- 

 able lesions which correspond to unrelated sensitivities. 



In this paper I shall develop mainly general considerations, and it 

 will be only in order to substantiate them by experimental facts that I 

 will sometimes cite particular experiments. French works are discussed 

 preferentially, because it seems to me that one of the aims of this sym- 

 posium is to exchange information about the work going on around us. 



* Other such factons will be discussed by Hollaender. 



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