PATHOLOGIC CHANGES IN BRAIN CAUSED BY ALPHA PARTICLES 395 



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Fig. 9. Proton radiation. 6.(HJ0 rad surface dose; sacrifice at 30 days. Cajal impreg- 

 nation of the cerebral corte.x. showing a wide ner\e-cell-free band through which apical 

 dendrites are coursing. In the region of their passage through the band, some of the 

 dendrites have decreased affinity for gold chloride and some appear somewhat swollen. 

 Scattered reactive astrocytes are to be seen. X220. 



''skeletonization" type of ner\e cell necrosis pre\ailecl. Nerve cells abo\e the 

 band had a strikinoly decreased affinity for tiold chloride, as did some den- 

 dritic processes traversino- the band 1 Fia,. 9). 



From these data, a time-dose relationship in the development of lesions 

 emerged (Table III). At the 1,500 rad surface close the feature that stood 

 out was the presence of a nerve-cell-poor band in the cerebrum, but not 

 in the cerebellum. At a smface dose of 3 /)00 rad both the cerebelhnn and cere- 

 brum contained a distinct zone of nerve cell damage at 20 days. Precise time of 

 initial damage at this dose level could not be ascertained because of lack of ma- 

 terial between the 4 day and 20 day stages. At a surface dose of 6,000 rad, 

 necrotic nerve cells were observed in the cerebellimi and cerebral cortex 

 beginning at 6 hours after irradiation. In the cerebellum at the 6 hour stage 

 a zone of granule cell pyknosis had been established, but it was not until 

 the 42 hoiu- stage that a zone of nerve cell damage was encountered in the 

 cerebrum. At the 12,000 rad surface dosage, nerve cell necrosis was evident 



