ON THE NATURE OF THE SPLEEN -BONE 

 MARROW RADIATION RECOVERY FACTOR* 



Leonard J. Cole and Marie E. Ellis 



Biological and Medical Sciences Division U.S. Naval Radiological Defense Laboratory, 



San Francisco 24, California 



For the past few years our research efforts have been directed towards the 

 problem of the nature of the radiation recovery factor(s) present in the 

 spleen and/or bone marrow of certain animal species, as first shown by 

 means of spleen shielding and spleen implant studies by Jacobson et al^, 

 and by Lorenz et al- with bone marrow injection. In the present paper, 

 we will discuss briefly the properties of the recovery factor in mouse spleen ; 

 take up the question of the presence of viable cells in protective spleen 

 preparations ; compare some properties of bone marrow and splenic 

 homogenates with respect to protective activity, and discuss some implica- 

 tions thereof. 



In following up the initial work of Jacobson et al we were able to demon- 

 strate the post-protective efficacy of Potter-Elvejhm homogenates of spleens 

 from immature LAfj mice, when administered in a single intraperitoneal 

 injection to otherwise lethally X-irradiated adult LAf^ mice^. Under these 

 conditions, the LD50 of spleen homogenate-treated mice was increased by 

 approximately 200 r. What can we now say about the properties of this 

 recovery factor ? 



(7) The factor appears to be particulate in nature ; and is insoluble in 

 aqueous saline or phosphate buffer media. Thus far, it has been impossible 

 to obtain the active principle in solution*. 



{2) It is localized in the nuclear fraction, obtained by differential centri- 

 fugation of sucrose-salt homogenates of spleen, and is not present in the 

 microsome or mitochondria particulate fractions^. 



{3) It is thermally labile — being inactivated when kept at 60° C for 20 

 minutes*'. 



{4) It is inactivated by relatively low doses of X-irradiation in vitro (725r) ; 

 and is also inactivated by exposure to ultrasonic vibrations. 

 (5) It is inactivated by treatment with the enzyme deoxyribonuclease 

 (DNA-ase), or with trypsin, but not by ribonuclease''. 



{6) Thus far, we have been unable to obtain active preparations by lyophil- 

 ization of saline or phosphate buffer spleen homogenates. 

 (7) It does not dialyse through cellophane membranes. After 3 hours of 

 dialysis at 5°C, the protective activity of spleen homogenates is retained 

 in the non-dialysable fraction. 

 {8) The factor exhibits properties of species and strain specificity. 



* These studies have been supported in part by funds from The Bureau of Medicine and 

 Surgery, U.S. Navy Department. The opinions and assertions contained herein are the 

 private ones of the authors and are not to be construed as official, or reflecting the views 

 of the Navy Department. 



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