GENERAL DISCUSSION 



Paul Henshaw (U. S. Atomic Energy Commission, IVashingtoti, D. C): I am 

 indeed interested in the information Dr. Rugh presented with his spectacular slides 

 of early embryos. Seeing evidence of deteriorating embryos at an early stage is to 

 be expected in view of what is known about the quality of germ cells and the 

 uterine bed in some situations. Certainly, degeneration is inevitable as a consequence 

 of some of these conditions. Dr. Rugh has called attention to the kinds of ab- 

 normalities that occur following different levels of exposure to germ cells and to 

 early embryos, and it was particularly interesting that abnormalities show in 

 organisms exposed to doses of 5-15 r. This is an extremely low level of irradiation, 

 and I am sure it will be quoted repeatedly. I feel, therefore, that we should ask 

 questions about the confidence he has in the findings. Dr. Rugh has shown abnor- 

 malizes which indeed do show in samples of organisms that have been exposed 

 to low doses of radiation, but such abnormalities will show as a consequence of 

 other agents as well. I would be pleased if Dr. Rugh would cite the specific 

 evidence he has that permits him to say the low level changes are due to radiation. 

 The second point pertains to the abnormality that showed in the third generation. 

 Were these actually due to radiation change involved in a germ cell? We know 

 something about how cerebral hernias will result from damage to neural fold 

 primordia, the failure to close the neural crest, which permits the brain to turn 

 inside out. This is a developmental abnormality not connected with germ cell 

 damage. If the same can come from irradiation of germplasm, this is exceedingly 

 interesting. I would like Dr. Rugh to indicate whether he feels there is evidence 

 that cerebral hernias may result from mutations in germ cells. Third, Dr. Rugh 

 has emphasized that low levels of radiation produce developmental abnormalities 

 and went so far as to call attention to the possibility that a large portion of the 

 naturally occurring developmental abnormalities may be due to background radia- 

 tion. If I were a physician, I think I would go along with Dr. Rugh's warning and 

 be cautious about any exposure of embryos or germ cells, but I am a laboratory 

 man. I would like Dr. Rugh to give his strongest evidence that environmental 

 radiation is having a significant effect. Does he feel that background radiation 

 can or does account for a substantial proportion of the abnormalities, having 

 knowledge as we do that many things can produce the kind of abnormalities des- 

 cribed? 



Roberts Rugh (Columbia University): In regard to your first question con- 

 cerning whether we are dealing with low level effects of radiation or possibly 

 other traumatic effects: We are currently studying the embryos found in 98 pairs 

 of uteri of mice exposed to 15 r at 1/2 days, because we felt this sort of statement 

 had to be quantitative and proven. We will have statistical data from over 1,000 

 embryos which received 15 r at 1/2 days with an appropriate number of controls. 

 It is true that we get anomalies without irradiation, that is, without superimposed 



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