132 Alexander Hollaender and George E. Stapleton 



at 18° C in yeast extract show essentially normal synthesis of 

 all components (Fig. 9). To date, the results do not permit 

 one to decide whether these alterations in nucleic acid syn- 

 thesis are the cause or the result of the viability changes in the 

 irradiated population. Further control of growth conditions — 

 for example, the division cycle — might accentuate the re- 

 covery phenomenon. Synchronization of division might very 

 well produce an essentially homogeneous population for 



4.0 



o 

 d: 



UJ 



r-g 



UJ 



3.0 



> 



z2.0 



o 



z 



o 



o 



1.0 



0M 



All 



/ 



V 



A 



60 120 180 240 360 

 ACID-SOLUBLE 



60 120180 240 360 

 RNA 



60 120 180 240 360 

 ONA 



60 (20 ISO 240 360 

 PROTEIN-N 



INCUBATION TIME(min) 



Fig. 9. Relative rates of synthesis of nucleic acids and pro- 

 tein by irradiated (0) and non-irradiated (□) Esch. coli on 

 yeast extract at 18° C. 



The acid-soluble fraction represents that fraction of the 

 cells soluble in cold 10 per cent trichloroacetic acid; only ribose 

 was estimated in this fraction by orcinol test. 



recovery studies. Such studies are just beginning in the overall 

 programme of bacterial recovery. 



Mention should be made of the results of our studies on 

 mammals, i.e., chemical protection during irradiation and 

 posttreatment with bone marrow or spleen. AET will raise 

 the LD50 30 days for C3H X 101 mice from 692 to 1148 r. 

 Bone marrow will raise the LD50 to 1292. A combination of 

 both treatments will bring the LD50 to 1863 (Congdon, 

 Upton, and Doherty, 1956, in preparation). Survival after 

 very high exposures (2400 r of gamma-rays) can be obtained 

 if, in addition to the combination treatment, daily injections 



