THE MODIFICATION OF THE RADIATION RESPONSE BY SHIELDING PROCEDURES 



shielding of a small portion of the femur will reduce very considerably the 

 severity of the anaemia, whereas shielding of a skin tube or skin flap will not. 

 It appears that these effects are due to shielding of a small part of active 

 bone-marrow. Platelet changes in the shielded animals have been studied 

 and it has been found that one effect of shielding is to reduce very consider- 

 ably the platelet fall, by virtue of megakaryocyte activity in the shielded 

 part. It is therefore possible that reduction in the platelet fall accounts 

 for the effectiveness of the shielding procedure, but it is also necessary 

 to determine to what extent the shielding procedure modifies the pattern of 







'W 

 5 

 



^ 5 



3 Days 



7 Days 



5 10 75 days 5 10 15 



J \ \ L. ^ I 1 



5 10 15 days 5 10 15 



_i I I 



10 Days 



15 Days 



21 Days 



5 10 15 



_i 1 I 



5 10 15 



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5 10 15 days 5 10 15 20 



I I I I 



5 70 15 days 5 10 15 20 



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 ^ 



Figure 2{a). Uptake of^^Fe, expressed as percentage of injected dose, in liver, spleen and hind 

 limbs of irradiated rats {albino strain) 4-5 hours after subcutaneous injection 



erythropoietic activity in the various tissues of the animal. This has been 

 studied by a radioactive iron technique as follows. 



hwestigation of radioactive iron turnover in shielded and unshielded rats 



In the experiment described here, two groups of rats were irradiated, one 

 group given 450 r whole body irradiation and the other group 450 r with 

 one hind leg shielded. The rats were sacrificed in pairs at various times 

 after irradiation (3, 7, 10, 15 and 21 days). At a time of 4-5 hours before 

 sacrifice the rats were injected subcutaneously with 1 [J.c '^^Fe as ferric 

 chloride in citrate buffer (carrier iron content <l[j.g). Immediately 

 before killing, the animals were exsanguinated under anaesthetic by with- 

 drawing blood by cardiac puncture at the same time as Ringer solution was 

 injected into a lateral tail vein. By this means 90 per cent or more of the 

 blood can be removed. Various tissues were then dissected out and their 



138 



