OBSERVATIONS ON THE EFFECT OF SPLEEN-SHIELDING 



as effective as higher concentrations. This is probably not, however, a true 

 comparison since the bone marrow represents the effect of adult (10- to 

 12-week) tissue, whereas the liver and spleen were obtained from embryos 

 or 2-day-old mice. 



The effect of cells from Ihe liver on the survival of irradiated mice — In previous 

 experiments, it was found that cells obtained from embryonic mouse liver 

 effectively enhanced the survival of mice exposed to 900 r. Therefore, 

 studies were made on cells obtained from the livers of 2-day-old mice to 

 determine whether such cells are equally effective when the liver is no longer 

 an embryonic organ. 



The mice were killed by cervical fracture, and the liver was removed and 

 mashed by pushing it several times through a syringe, using Locke's solution 

 as the diluent. The cells were removed with a 26-gauge needle and cell 

 counts were made. The suspension was then injected intravenously into the 

 irradiated mice. 



Table VI. A comparison of the effect of intravenous injections of bone marrow, spleen, embryo and liver 

 cell suspensions on the survival of mice exposed to 900 r 



In a preliminary experiment, the cells were obtained from 2-day-old CF 

 No. 1 mice and were given intravenously to LAFj females exposed pre- 

 viously to 900 r. No deaths occurred during the first 21 days after irradia- 

 tion ; however, 3 of 8 died before the 28-day period of observation was 

 completed. In subsequent experiments, the CF No. 1 mice were used as 

 both recipients and donors. Of the 97 mice that have been injected with 

 cells from the livers of 2-day mice, 44 (43 per cent) survived. Mice that 

 received 2 to 3 x 10® nucleated cells appeared to survive equally as well as 

 those that were given 4-3 to 5-1 cells {Table VII). With total nucleated cells 

 of the order of 0-75 x 10®, there was 20 per cent survival. A suspension of 

 cells obtained from the liver has been photomicrographed {Figure 1, page 

 129) to show the various cell types that are present in the injection solution. 



The effect of injections of irradiated bone marrow cell suspensions on the survival of 

 mice — In some experiments, mice were exposed to 600 r total-body X- 

 radiation. In others, exposures ranging from 100 to 500 r were given. At 

 intervals following exposure, marrow from the irradiated mice was removed 

 and given intravenously to mice exposed previously to 900 r. An attempt 

 was made to prepare a suspension that contained the same number of cells 

 that would produce the maximum protection provided by normal non- 

 irradiated marrow. 



128 



