DISCUSSION 



Additional evidence indicating that the recovery factor in rat bone marrow 

 possesses properties similar to that in mouse spleen, has been obtained. 

 Thus, protective activity of rat bone marrow homogenates injected into 

 homologous X-irradiated rats, is associated with the nuclei fraction, obtained 

 by differential centrifugation in sucrose-salt medium and not with the 

 mitochondria, microsome or supernatant subcellular fractions. Rat bone 

 marrow homogenates lose their protective activity following iti vitro X- 

 irradiations with 725 r ; and marrow removed from irradiated rats f725r) 

 two days after exposure is no longer protective. 



The implications of these experimental data have been discussed. 



REFERENCES 



^ Jacobson, L. O., Simmons, E. J., Marks, E. K. and Eldredge, J. H. Science, 



1951,113 510. 

 - Lorenz, E., Uphoff, D., Reed, T. R. and Shelton, E. J. Nat. Cancer Inst. 1951, 



12 197. 

 ^ Cole, L. J., Fishler, M. C, Ellis, M. E. and Bond. V. P. Proc. Soc. exper. Biol. 



Med. 1952, 80 112. 

 * Cole, L. J., Ellis, M. E., Fishler, M. C. and Bond, V. P. Federation Proc. 1952, 



11 26. 

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39 759. 

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8 Northrup, J. H. J. Gen. Physiol. 1926, 9 497. 



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1954, 177 236. 

 1* Lorenz, E., Congdon, D. and Uphoff, D. Radiology. 1952, 58 863. 

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DISCUSSION 



R. F. Mouton : If I have correctly understood, the activity of the spleen-bone 

 marrow recovery factor is destroyed by the process of lyophilization. 



L. Cole : Yes. 



R. F. Mouton : It is known that some proteins can be denatured by lyophilization, 

 lipoproteins, for instance. This adverse effect can be in some cases avoided by ad- 

 dition of sucrose in the medium before lyophilization. Did you lyophilize in presence 

 of sucrose ? 



L. Cole : No. 



147 



