122 Alexander Hollaender and George E. Stapleton 



2. Cells grown in inorganic salts and glucose do not require 

 a complete medium for highest protection. 



3. Significant protection is still obtained if cysteamine is 

 washed off the cells immediately before irradiation, probably 

 a large part of the MEA is absorbed by the cell. 



t.O-i 



10--^ 



o 

 o 

 o 



o 



10^ 



o 

 < 

 cr 



o 



> 



cr 



to 



«o--5 



10 



.-4 



— I ' 1 I I I 



0.002 0006 001 0.02 



MOLAR CONCN. OF CYSTEAMINE 



-JJ- 



04 



Fig. 1. Effect of cysteamine on the survival 



of Esch. coli IB/r during exposure to 60 kr of 



250-kv X-rays. 



4. Limiting concentrations of cysteamine do not change 

 the shape of the survival curves ; however, reduced survival is. 

 obtained at each dose level. 



5. The protection is somewhat strain-dependent; a careful 

 technique must be used for the highest expression of protective 

 ability. Some points can easily be obscured by changing 

 some conditions of experimentation. 



