344 GENERAL DISCUSSION 



that of organic macromolecules with diverse i^roiDerties. One can obtain 

 variations in the permeability by diverse means: by an alteration in 

 the solution, an alteration in the Donnan equilibrium, and on the other 

 hand as a result of a variation in the biochemical proi^erties of the mem- 

 branes themselves. 



The question of the permeability of a cell cannot stand in isolation, 

 because the cellular membrane with its highly organized structure has 

 a direct relation to this problem. The external cellular membrane 

 consists for the most XDart of lipoproteins and if irradiation acts on this 

 cellular membrane, then identical variations under the influence of 

 radiation must also arise in many other intracellular structures identi- 

 cal in res^^ect of their ultramicroscopic structure. 



bacq: I agree with Hug. I have not used the term "jjermeability". 

 I know many cases where negative results in regard to the variations 

 of permeability in irradiation conditions have been discovered. For 

 example, the gills of the freshwater crab absorb potassium and sodium 

 from the surrounding medium. My colleague, Ghosh, of Louvain Uni- 

 versity, could not find any variations of the permeability after irra- 

 diation, Init the conditions of the experiment were such that one would 

 be able to carry out observations during irradiation. 



meissel: I would like to draw your attention to two facts. The first 

 is this: in the structure of mitochondria there are portions that are 

 more sensitive and portions that are less sensitive to radiation effects. 

 Those enzymes which are connected with mitochondrial membranes 

 and with the cristae of the mitochondria are as a rule extremely radio- 

 resistant. The enzyme systems which are located inside the mitocho- 

 dria are much more radiosensitive and the most radiosensitive systems 

 are those which are connected with the structural integrity of the 

 mitochondria as such. Consequently, the radiation damage to the 

 membrane and the membraneless mechanisms of the mitochondria has 

 considerable significance for an understanding of the initial radiation 

 effects. 



A second comment: Shabadash, in his contribution, rightly dii'ected 

 attention to the value of the destruction of the mutual relationships 

 between mitochondria and the nucleus of the cell which occurs as a result 

 of irradiation. 



I would like to direct attention to the destruction of the inter- 

 connections between the mitochondria and the endoplasmic reticulum 

 which unquestionably arises under irradiation conditions and which is 

 expressed by the fact that, even for comparatively small irradiation 



