EFFECTS ON BLOOD-BRAIN BARRIER, CEREBRAL BLOOD VESSELS 415 



Fig. 2. A midsaggital \iew of the brain of a monkey which had recci\cd 4,500 r of 

 x-irradiation (250 kw 118 r per min) to the head and which sur\'ived for 21 hours. 

 Notice the trypan bhie discoloration in the medulla, hypothalamus, thalamus, and 

 septum brought about by the radiation effects on the permeability of the blood-brain 

 barrier. (Taken from Clemente and Hoist. 1954.) 



age (Figs. 3A-E ! was obser\able microscopically, and the areas of trypan 

 blue penetration into the brain were characteristically those regions in 

 which astrocytic damage was most intense. 



Monkeys subjected to a 1 .500 r head x-radiation dose and sacrificed 4 to 

 8 months after irradiation showed pinpoint areas of degeneration surround- 

 ing blood vessels in cortical and subcortical white matter (Fig. 4). The 

 lesions were characterized by a.xon swelling, myelin breakdown, phagocytosis, 

 and astrocytic scar gliosis. With higher doses of x-ray radiation to the brain 

 in adult rats (20,000 to 23.000 v), Brishtman (1959) likewise found vascu- 

 lar changes characterized by petechial hemorrhagic foci, and "the hem- 

 orrhagic areas were stained a dark blue in those rats gi\en trypan blue."" 



Although obvious early changes in the permeability of the blood-brain 

 barrier were difficult to obser\e with trypan blue in monkeys gi\en 1.500 r 

 ( Clemente and Hoist, 1953, 1954), it was felt that a more sensiti\e method 

 of evaluating increases in the permeability of the blood-brain barrier might 

 reveal such alterations. The study by R. G. Rose (1958) seems to have sub- 

 stantiated these suspicions. He utilized the rate of passage of intravenously 

 injected radioactixe sodium into the brain and cerebrospinal fluid of radi- 

 ated and nonradiated rabbits to determine the influence of lower x-ray doses 

 (^100 to 1.500 ri on cerebral capillary permeability. His data indicate an 



