942 
GENETIC AND BIOLOGICAL EFFECTS OF RADIATION 
problem of knowing precisely what the dose to 
the susceptible cell population is. Local body 
radiation, either from internally deposited radi- 
onuclides or from partial body external radia- 
tion, causes life shortening which can be ex- 
plained exclusively on the basis of induction of 
neoplasms. 
Farouk a. S. Molokhia, Harvard Medical 
School: What biological endpoints should be 
used to monitor the effects of radiation emitted 
by the implanted devices? 
Dr. Walburg: I think that unless one is 
prepared to mount a very large program with 
sufficient numbers of animals to detect the effect 
of low doses by measuring the induction of 
neoplasms, one can't really do much. What I 
am saying is that the cell doesn't know, and 
doesn't care, where the radiation comes from, 
whether outside the body or from within. It's 
the effect of the radiation on the cell and on the 
tissue that matters. I think that the endpoints 
that were described in the preceding paper are 
very important but they require higher doses 
of radiation for effect than are required to 
induce neoplasms. I would predict on the basis 
of the available data, that radiation which 
causes cell death or tissue necrosis will also 
induce neoplasms. 
