314 Z. M. BACQ AND P. ALEXANDER 



migi'ation occurs in the solid conipoiuids and suggests that cysteamine at these 

 temperatiu'es also is acting as a hydrogen donator and reacts with the radicals. 



ALEXANDER: We rule out this possibility on the groimds not so much of dynamic, 

 as of kinetic, considerations. At such low temperatures cysteamine cannot reach 

 the place where it is protecting. 



SHABADASH : I would like to know Prof. Bacq's opinion regarding disagreements 

 between his and Prof. Arbuzov's (Leningi'ad) data on the quantity of sulfhydryl 

 protectors in animal organs. According to Arbuzov's data 1 to 4 hr following 

 administration of ^^g-labelled cysteamine the highest cysteamine concentration 

 is observed in the central nervous system. 



What are the quantitative data obtained in your laboratory on the cysteamine 

 content of the brain, especially of the subcortical structm-es and the hypothala- 

 mic region? 



BACQ: Wliat I was talking about was a veiy short review of three different in- 

 vestigations. Some of the experiments had been carried out by vis, some performed 

 by other authors. Recently in Sweden the topography of ^sg distribution has 

 been studied following administration of the 35S-labelled cysteamine to a mouse. 

 We analysed the brain as a whole, and not its particular areas. As to the Swedish 

 investigation, in that work no specific concentration of the substance in par- 

 ticular areas of the brain was found. 



The difficulty is that while assaying ^^ii we should be sure that it is still con- 

 nected with the cysteamine molecule; this molecule breaks down very rapidly 

 while in the body. 



I have no explanations for the discrepancies you referred to. 



GRAY : I fully share Prof. Bacq's view. It seems to me that the protection given 

 by the majority of the active agents may be connected with anoxia. Nevertheless 

 maximum protection due to anoxia is slightly less than that produced by pharma- 

 cological agents. We should adopt a highly critical attitude. It would be better 

 to experiment on cell suspensions at known oxygen pressure levels. Under these 

 conditions we could study more effectively the metabolic changes occurring when 

 protective agents are used. 



kalmanson: What is the absolute sensitivity of the equijiment? What is the 

 miniuuun quantity of the radicals you can still record? W'hat are the free radical 

 concentration values of the curves you have shown? What are the absolute 

 changes of free radical concentration in your experiments? 



ALEXANDER: At the sensitivity used 7 X lO^"* radicals could be detected in a 100 mg 

 sample. In most of the experiments the concentration of radicals was of radicals 

 of the order of IQi''. We detected no free radicals in imirradiated protein and 

 the effect of radiation was therefore to introduce about 10^^ radicals in 100 mg 

 tmd this requires doses of the order of several megarads. 



