KINETICS OF PRIMARY REACTIONS AND CHEMICAL PROTECTION 325 



not have a two-peak curve, as is tlu> casc^ in. your experiments, whereas the 

 niaxiniuni in the green region is identical to that found in the case of visible hio- 

 luminescence. In other words our data differ from the phenomenon you have 

 described. 



TOBIAS : When chain reactions are being studied it often happens that the initia- 

 tion of the reactions depends on the radiation intensity. Did you find any de- 

 pendence on intensity? 



TARUSOV : In our experiments the main parameter was the time. Radiation was 

 ahnost always the same, i.e. in most cases we did not vary either the dose or the 

 radiation intensity. We tried to work in the region of low radiation density. Under 

 these conditions protective effects manifest themselves more readily. 



BACQ : I also studied peroxides following irradiation and found that the appear- 

 ance of peroxides is not an early, but an immediate, reaction. Another important 

 point is that in animals there is a natural anti-oxidant, a-tocopherol. When you 

 take a fasting animal, the fat disappears, bvit a-tocopherol does not disappear. 

 Thus tissue is living under conditions of increased a-tocopherol content, and this 

 should be borne in mind. 



TARUSOV : We have also found that peroxides appear immediately. In the work 

 of Romanzev (who is present here), it was established that peroxides and lipoper- 

 oxides make their appearance during the irradiation. But I guarantee that there 

 are no analytical methods which would enable us to discover them at the levels 

 of the irradiation present. And it is a proof that at once, already at the first stage, 

 the chain reactions occur. By the way, Romanzev has shown that this initial 

 accumulation of the peroxides is inhibited by sulphydryl protective compounds. 



passynsky: Did you study whether the oxidation chain-reactions occur in two- 

 layer films of the lipids? 



TARUSOV: Of course there are in the body two-layer films of lipids, but there are 

 also films in which these two layers are lacking; not all is distributed in two layers. 



PASSYNSKY: Whatever the chain reaction is it may occur only when a certain 

 critical mass is present. What is the critical mass for the oxidation of lipids? 



TARUSOV : We did not determine the critical mass. 



PASSYNSKY : I think that determination of the critical mass is quite indispensable 

 if the existence of chain reactions for lipid oxidation is to be accepted. 



TARUSOV : I do not believe that these concepts can yet be applied to the cell. 



