Discussion 87 



organism by just looking at curves. But if you experimentally 

 interfere with the conditions and find that those curves move, then 

 you do know something, and that seems to me very exciting. People 

 working on mice have mentioned cases where specific diseases have 

 been shifted to a younger or older age by specific environmental 

 causes. What they have not discussed is whether either dietary 

 restrictions or irradiation, or any other environmental treatment, 

 have a common effect on a number of apparently unrelated diseases. 

 If you delay one disease in the mouse by restricting diet, do you 

 expect to delay the others or not ? This is of enormous theoretical 

 importance and it may one day be of great practical importance. 



Rothlat: It has been dealt with to a certain extent by Curtis, who 

 has tried six different environmental effects (2nd International Con- 

 ference on the Peaceful Uses of Atomic Energy, September 19.58). 



Sacher: Curtis reported only on the after-expectations, and not on 

 the kinds of pathology present. 



Maynard Smith: I want to know whether the ages of the onset of 

 tumours, of kidney diseases, etc., are shifted in the same direction 

 by the same environmental causes. 



Berg: Yes. The delay in onset of all lesions including tumours 

 produced by dietary restriction points to a single factor that controls 

 the time of onset of disease. 



Before the discovery of the tubercle bacillus the various forms of 

 tuberculosis involving different organs were considered to be 

 different diseases. With the discovery of the tubercle bacillus these 

 conditions were found to be various consequences of a single cause. 

 Although this analogy is not exact it is possible that a single mechan- 

 ism may be involved in the onset of many widely different diseases. 



Wigglesworth : An even better analogy is that of malaria. If you 

 reduce malaria in a region the mortality from many other diseases is 

 reduced. 



Have you had the opportunity yet to switch over the diet at some 

 stage of life in your experiments ? In other words, is it indulgence in 

 youth or indulgence in age which is significant in these effects ? 



Berg: We are planning such experiments. 



Comfort: I can think of two factors which could produce exactly 

 such a non-specific effect on many diseases. One is the so-called 

 stress response. I do not know whether you measured the adrenal 

 weight in these creatures. The other is immunological ; I am thinking 

 of auto-immunization processes taking place in the body, and 

 depending on the escape of cell antigens with the passage of time. 

 Either of those could quite readily produce marked changes in many 

 apparently unrelated diseases. 



