470 WALTER R. STAHL 



Radiation Damage which is Histologically Apparent 



As is well known, beyond a certain dose nerve tissue shows major damage 

 with cytolysis, fiber degeneration and eventually scarring. In the Soviet 

 literature, such pathology has been reported to occur after 1,500 r in some 

 cases, though doses of 5,000 r are often mentioned also as the threshold for 

 really major damage (Livshits, 1956; I. A. Brodskaya and Merkulova, 1956). 

 A demyelinization syndrome following several thousand r was cited recently 

 by Bibikova (1959). 



However, many Soviets have found injury at levels far below these. For 

 instance, Lebedinsky (1959a, b; Lebedinsky and Moskalev, 1959) describes 

 rather selective injury to the cortex, hypothalamus, certain autonomic struc- 

 tures, and elsewhere following near-lethal mammalian doses. Selective 

 damage to afTerent neurons of the spinal cord has been reported by several 

 workers, such as Shabadash et al. (1959) who used a special RNA isoelectric- 

 point staining technique. Others have found autonomic, and especially sym- 

 pathetic peripheral structures, to be most sensitive (Smirnov, 1960). Spinal 

 synapses were found partially damaged following exposures to 450-600 r 

 (Lev, 1957). 



In these studies, injury was fairly general in the structures cited. Scattered, 

 random injury with quite low doses has been reported by Soviet workers. For 

 instance, Aleksandrovskaya (1958) found an increase in numbers of patho- 

 logic cells after only 50-150 r, with 150 r also damaging a few glial cells. 

 Spotty damage to peripheral nerve has been cited after a few hundred r 

 by Garvey (1960), Anisimova- Aleksandrovskaya (1959), and others. 



Many Russian papers have dealt with postirradiation injury to nerve 

 structures within specific organs. For instance, Zarat'yants (1960) states that 

 only 60-90 r of chronic exposure induces alterations in the nervous structures 

 of the gastrointestinal tract; this pathology is said to be the first seen under 

 the cited exposure conditions. The extent of injury was small. Levinson et al., 

 (1957) could find only slight injury in nerve structures of the gut following 

 3,000 r. In skin structures of rats exposed to 700 r (Garvey, 1960), changes 

 were slight during the latent period of the radiation syndrome, marked at 

 about 5-20 days, and still evident as late as 60 days after exposure. Damage 

 to cutaneous nerve structures only 30 minutes after irradiation is noted by 

 Oleynikova (1959). Gromada and Polachek (1959) found significant injury 

 to receptor endings in heart muscle, fascia, and elsewhere after many hun- 

 dreds of r. Major injury of nerve endings in the spleen and lymphatic organs 

 following near-lethal doses have been reported by various Soviet workers 

 such as Alekseyeva (1958). 



Scattered, low level pathology is not easy to demonstrate. It is evident that 

 the researcher must use extensive controls and analyze his results statistically. 



