CELL DAMAGE IN THE MAMMALIAN RADIATION SYNDROME 249 



amount of (X)HI) lurined and on the 02-tensi<)n in the tissues (Gray- 

 evsky and Konstantinova, 1958 and Fig. 8). 



3. The maximum protective action of adrenaline, morphine and 

 heroin corresponds to the period of maximal decrease of 02-tension in 

 the Uver and in the spleen (Fig. 9; Konstantinova and Grayevsky, 



1900). 



4. Dimercapto-compounds (BAL-intravenous, dimercaptopropionic 

 acid) have been found to protect during the period of maximum de- 

 crease of 02-tension in tissues (Fig. 9 ; Grayevsky and Konstantinova, 



1960a). 



5. Strong reducing agents, ascorbic acid (40 mg per mouse), pyro- 

 gallol (5 mg). hyposulphite (60 mg) fail to bring about hypoxia of tissues 

 and do not possess radioprotective action (Konstantinova and Gray- 

 evsky, 1960). 



6. KCN (0-15 mg per mouse) while causing cytotoxic hypoxia only 

 slightly decreased 02-tension in the tissues. We could not find a 

 protective effect of KCN either on mice or on micro-organisms (Kon- 

 stantinova and Grayevsky, 1960; Grayevsky and Konstantinova, 

 1957). 



7. Monothiols and thiourea derivatives (cysteine, SH-glutathione, 

 cystamine, cysteamine, 2-aminoethylisothiuronium BrHBr, 2-amino- 

 5-isothiuronium methyl-thiazoline Br HBr) exert distinct protection 

 without changing the level of 02-tension in tissues (Fig. 10; Grayevsky 

 and Konstantinova, 1960b). 



CONCLUSIONS 



Some questions concerning the processes of damage and recovery in 

 irradiated organism are discussed. Death of a significant proportion 

 of cells of haematopoietic organs and in intestinal crypts and inability 

 of the tissues to regenerate quickly enough undoubtedly play an im- 

 portant role in the mammalian radiation syndrome. 



Causes of the early mass destruction of cells in radiosensitive systems 

 which develops soon after exposure have been insufficiently studied 

 though this process is one of the most important consequences of irra- 

 diation. It has been shown that: (1) early mass destruction takes place 

 only in directly irradiated tissues; (2) radiosensitivity of bone-marrow 

 cells in vivo and in vitro does not differ significantly; (3) the early 

 destruction is unlikely to be related to the process of division or to 

 some radiation-induced chromosome damage; (4) early death occurs 

 only in those cases where an affected substrate is put into operation. 

 The specific function which makes radiation damage apparent may be 

 assumed to be the process of differentiation. 



