GENERAL DISCUSSION 351 



BACQ: In this connection I might come back to the suggestions brought forward by Dr. 

 Martinovitch. One way of doing a maybe even cleaner experiment would be to irradiate 

 an autologous graft in vitro at certain doses and then piit it back in an organism. You 

 then know that not a single cell of that organism has been irradiated. Or you could graft 

 it back in the organism irradiated in a certain way, so the two factors, the origin of the 

 tumour and the influence of the organism can be worked out independently. 

 pochin: I want to come back to this single organ irradiation in looking for an organ in 

 which you can get clean irradiation without involving others; lung obviously might be a 

 possibilit}^ with inhaled j8-emitters, although one might run into trouble from generalized 

 lung fibrosis. Liver is obviously a possibility. Has anybody tried gut with absorbed short- 

 range soft j3-emitters? 



MAYNEORD: I think the answer again is that the dosimetry is extremely complex. 

 UPTON: The ovary may offer an mteresting system. It has been emphasized already in the 

 course of the meeting that tumorigenesis in the ovary depends on pituitary activity, but it 

 is quite possible experimentally by exteriorizing the ovary to irradiate it without irradiat- 

 ing the rest of the animal. One has to irradiate both ovaries admittedly, but very small 

 amounts of radiation will induce tumour formation. I don't think anyone has carefully 

 worked out the dose -response relationship in detail for the kinds of mechanism involved 

 here. 



mole: Some of the answers to these questions depend on whether we feel we want to get 

 results fairly quicldy or not. If we do, let us work on tumours that are hormone-dependent. 

 Perhaps we ought to stop using the laboratory mouse. We have learned a very great deal 

 about it and if you accept that there is the possibility that, underlying tumours, there are 

 cliromosomal charges then why not do comparisons between different kinds of species 

 with different kmds of clu-omosomes to see if there is any kind of correlation. In this 

 connection, perhaps I should mention that, in the last few years, we have been using 

 Chinese hamsters, partly with this idea in mind, and we have found it impossible (with 

 but relatively small numbers) to produce any appreciable amount of leukaemia by giving 

 single doses or multiple fractionated doses of the kind that are so effective in the labora- 

 tory mouse. 



BACQ: What about Syrian hamsters? 



mole: We have not tried these. All I am suggestmg is that concentrating on the labora- 

 tory mouse will only tell us perhaps something more about what we know aheady. If we 

 try usmg different species we might learn something quite different. 

 CURTIS: In the United States there are rather extensive studies along these lines with 

 dogs and with primates. These results are very very slow in coming — it will be years 

 before one gets anything there, but I think you are quite right, that this is sometliing 

 that has to be done. 



lamerton: I am not sure whether Dr. Curtis is referring to work with bone-seeking 

 isotopes. If he is, of course, you have this very great problem of what you mean by the 

 dose and where you are to measure it. I would doubt very much in fact what one is going 

 to learn from comparative studies on different species with the bone-seeking isotopes, 

 particularly with the a-emitters. On the other hand, whole-body uniform X-irradiation — 

 if you can get it — will probably tell you much more. 



BACQ: In order to get on with the discussion I want to ask Professor Berenblum if it is 

 possible for him to go a bit further than he so far has? He was very cautious in his 

 paper. Is it not possible to try at least to translate in other terms what he calls initiating 

 and promoting action? I know it is a way to understand, to express the results, but it 

 is a concept and a concept has to be translated into some kmd of biochemical or his- 

 tological terms. 



