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DISCUSSION 



UPTON: I should like to enquire about the electron microscope changes in radiation 

 nephrosclerosis. Do you know how soon one might visualize such changes? Do you think 

 they would become detectable first m the basement membrane or perhaps fii'st in the 

 foot processes? 



BRINKMAN: Well, the mtercapiUary hypertrophy of tissues can be shoAvn in pigs about 4 

 months after hradiation, then it starts and goes on rapidly, especially in young pigs, and 

 it is until now not further analysed as far as I know, but if you look at the beautiful 

 pictures of Palade and his collaborators, there is no choice at all. The basement mem- 

 brane is the only barrier — there is no barrier in the epithelium, there is no primary 

 barrier in the endothelium at all, so it has to be there. I don't think there are any other 

 references, but if you look at those beautiful pictures — well, I, at least, was convinced. 

 UPTON: The question is, do you visualize that the changes occur as a result of cellular 

 injury, or as a result of injury to the intracellular material? Does the basement membrane 

 find its origin in the foot processes of the cells? Is it, if you will, an excretion, or is it a 

 deposition from the vascular system? What do you think to be the chain of events or 

 what would you speculate about the chain of events that would ultimately manifest 

 itself as a defect in basement membrane? 



BRINKMAN: I tliink that this basement membrane is a formation of the amorphous ground 

 substance in the space between the endothelium and the epithelium. You can see its 

 formation there and it has to be a formation of the ground substance. It is not formed by 



