112 HOLLAENDER, StAPLETON AND BuRNETT 



Lamerton: Recently, when I was visiting the United States of 

 America, I discussed with Huff at Berkeley some of the work he has 

 been doing with *^Fe. It was suggested to me, in \'iew of the interest 

 of these studies, that I should say something about them. Some of the 

 work is unpublished, but I am sure that Huff would not mind my 

 mentioning it at this meeting. 



A few months ago Hennessy and Huff published a paper {Proc. Soc. 

 exp. Biol., N.Y., 1950, 73, 436) in which they showed that the uptake 

 of radioactive iron, ^^Fe, by red blood cells was determined critically 

 by a previous exposure of the animal to whole body irradiation. The 

 technique was to expose the animal to whole body irradiation and then 

 at a given time later to inject radioactive iron, afterwards taking a 

 specimen of blood and determining the activity in the red blood cells. 

 It has been found that if the injection is made 24 hours after the whole 

 body irradiation, then quite small doses of radiation will affect the 

 uptake. A dose of 5 roentgens is sufficient to cause an appreciable 

 decrease in the uptake of iron by the red blood cells, and doses of 50 

 or 100 roentgens make a very great difference indeed. \Vliat is 

 apparently being measured is an effect of the radiation on the erythro- 

 poietic tissue, and the fact that the maximum effect is obtained when 

 the injection is made 24 hours after irradiation is consistent with his- 

 tological evidence of the damage to the marrow. 



I think these studies have a considerable interest since we are very 

 much in need of criteria of whole body irradiation. By far the greater 

 part of the radiation work being done with animals uses as a criterion 

 of effect median lethal dose or some variant of it. This has for certain 

 investigations considerable disadvantages, as I think many workers 

 agree. In the first place, if you give a dose of the order of mean lethal 

 dose you create widespread intense tissue destruction and the secondary 

 effects of that may very well hide important effects that you would 

 otherwise observe. Secondly, death from acute exposure is a very 

 complex phenomenon indeed, and there may be several more or less 

 independent mechanisms at work here, as has been shown by work 

 with rabbits and also with rats. 



A very promising line seems to be to use tracers to provide quantita- 

 tive criteria of metabolic processes that could afterwards be used to 

 measure the effect of radiation. Obviously there is no one metabolic 

 process that one should aim to measure; many will be needed. Radio- 

 active iron does, however, offer one possibility there, and one which is 

 very sensitive. Another possibility involves the use of ^*C. 



The use of radioactive iron has been extremely valuable in other types 

 of investigation. In patients with various blood disorders Huff has 

 been giving radioactive iron in the form of ferric chloride and after these 

 injections making measurements of the counting rate over the surface 

 of the body ,using a highly coUimated scintillation counter, the normal 

 sites chosen being over the sacrum, the liver, the spleen and the heart. 

 It is found that tlie pattern of the rise or fall in counting rate over the 

 first few hours gives a fairly characteristic picture of the particular 

 blood condition. For instance, in the normal male one finds that the 



