THE INFLUENCE OF CHEMICAL PRE- AND 



POSTTREATMENTS ON RADIOSENSITIVITY 



OF BACTERIA, AND THEIR SIGNIFICANCE 



FOR HIGHER ORGANISMS* 



Alexander Hollaender and George E. Stapleton 



Biology Division, Oak Ridge National Laboratory, Tennessee 



Protection against ionizing radiation by chemicals can be 

 discussed on the basis of model experiments with polymers or 

 on experience with living materials. In some ways, experi- 

 ments conducted with chemicals and living cells fit into a 

 pattern related to model tests; however, for the purpose of 

 this discussion, model experiments are not sufficient since 

 they do not give information on metabolizing systems. The 

 most extensive work in the field of model experiments has 

 been done by Alexander, Charlesby, and Ross (1954). A 

 large number of compounds that protect readily against 

 radiation in the polymers are not necessarily effective on 

 biological materials, but they could serve as a guide to practi- 

 cal applications. Alexander and co-workers (1955) have 

 shown a close parallelism between the protective ability of 

 many compounds for polymers and the survival of irradiated 

 mice. The number of compounds that actually protect 

 mice to a highly significant degree, and with a minimum 

 of detrimental effects, is relatively small. Our interpre- 

 tation was that these compounds compete for the oxygen 

 present in the suspension and/or for radiation-produced 

 radicals and peroxides. Alexander and co-workers (1955) 

 beheve that these compounds act chiefly by competing for 

 HO2 radicals. On the basis of present knowledge, it is very 

 difficult to distinguish between these two mechanisms since 



* Work performed under contract W-7405-eng-26 for the Atomic Energy 

 Commission in the Biology Division, Oak Ridge National Laboratory. 



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