208 ALEXANDER HOLLAENDER 



believe that this latter effect may be seen only when irradiation is given in small 

 doses and at a particular time. In this direction studies were made by Dr. Shirin 

 who applied comparatively small irradiation doses between phases. As a result 

 a delay of the next phase was observed. 



hercik: Please explain whether you consider the effect of the fasting in your 

 interesting observations as specific, or whether the fasting is acting in the same 

 way as other agents in lowering the cell division rate? If it is so, then agents in- 

 creasing mitotic activity should increase cell sensitivity. Is it possible to explain 

 by these relationshijas the differences, sometimes very considerable, in the sensi- 

 tivity of mitosis not only in different species, but within the tissues of the same 

 species? 



STKELiN : According to your data is the effect of fasting specific or is it only a 

 factor which lowers the intensity of cell division? If it is so then is it possible, 

 beside the activity of cell division, to establish also in an adequate manner cell 

 sensitivity changes using those criteria which have been studied? And if these ai'e 

 general regularities, then could they account for differences in the radiosensi- 

 tivity, including those regarding mitotic activity, not only in different animal 

 and plant species but within the same species? Sometimes this sensitivity differs 

 a thousand-fold. 



hollaender: If I undei'stood the questions correctly, you ask whether it is 

 possible to explain the difference in sensitivity not only between different 

 species but within the same species with regard to radiation effects on mitosis. I 

 have no explanation for different radiosensitivity. I can only emphasise the fact 

 that we have no bacteria that could be studied when irradiated with a dose of a 

 million roentgens. They do not survive. There are hardly any bacteria that would 

 survive it. 



ERRERA : I would like to give some details pertinent to the question of metabolism 

 in sperm . In sperm there is no protein synthesis whatsoever and metabolic activity 

 of the respiratory systems present is directed towards ensuring the movements 

 of the sperm. In the nucleus no metabolic processes occur. 



MARKOViCH: Did you study the influence of the dose rate while studying the 

 effect of light? 



HOLLAENDER: This effect was discovered several months ago: we did not study 

 the effect of the dose rate. To our dissatisfaction, when we collected the pollen 

 on a misty dark daj^ we observed effects, different froni those observed when 

 collection was made on a sunny day. Very careful controls had to be made before 

 consistent results were obtained. In one case we got 18 per cent, in another 12 

 per cent. The effect exists, but I am unable to give any details with regard to it. 



POWERS : What mutations in Aspergillus did you record and do you know any- 

 thing about their stability? 



HOLLAENDER: The mutations which we recorded were morphological mutations 

 connected with pigment formation and so forth. They are stable. During the last 

 15 to 20 years we have studied them very carefully and you will find a description 

 of these phenomena in our work. But sexual process here is lacking and crossing 

 could not be realized. 



POWERS : I remember your first work and because of it I joossibly got a wrong 

 conception. Maybe the changes obtained are non-nuck^ai'? Since sexuality is 

 lacking, we have no test to check on it. 



