PATHOLOGIC CHANGES IN BRAIN CAUSED BY ALPHA PARTICLES 405 



Fig. 14. Alpha particle radiation. 6,000 rad surface dose: sacrifice at 48 hours. The 

 animal was injected with 2 cc of 8''f fluorescent albumin 24 hours before sacrifice. 

 A capillary in the irradiated corte.x, showing droplets of extravasated fluorescent al- 

 bimiin. .Approximately x400. 



days, the outer surface of a few small blood vessels in the cortex was still 

 studded with FLSP droplets. The superficial leptomeninses contained nu- 

 merous FLSP-laden macrophages. In animals sacrificed at 4 and 5 months, 

 no abnormal permeation of FLSP was noted. 



The first appearance of FLSP fluorescence in the f^ross brain was ob- 

 ser\ed at 72 hours. At this stage the irradiated region of both cerebellum 

 and cerebrum fluoresced. In coronally cut blocks of the cerebellum, the 

 fluorescence was confined to the irradiated region of the folia. In the cere- 

 brum a faint green fluorescence was noted in the irradiated part of the cor- 

 tex and a brighter green fluorescence in the underlying white matter, in- 

 cluding the corpus callosum. In the next jeie days the white matter below 

 the irradiated medial cerebral cortex exhibited intense green fluorescence, 

 particularly in the region close to the interhemispheric fissme. The cortex 

 showed much less intense green fluorescence. In both cerebellum and cere- 

 brum grossly visible fluorescence persisted for approximately a week and 

 then diminished. Faint fluorescence was last seen at 13 days after irradiation. 



