X-RAY INDUCED CNS CHANGES 55 



structural alterations amon<j cortical neurons has been pointed out re- 

 peatedly by many in\estioators ( Gerstner it al., 1956: Haymaker et al., 

 1954, 1958: Russell vt al., 1949i for a wide ranse of experimental variables. 



Gliosis was evident in increasino quantity in direct relationship to the in- 

 creasing) level of cumulated dosage or the postirradiation time or both. The 

 sjliosis was characterized by increased cellularity and, for the most part, ap- 

 peared within the molecular layer of the cortex, specifically the subpial 

 area. The cell hyperplasia occurred predominantly in astrocytes, many of 

 which appeared gemestocytic. 



Oligodendroglia and microglia remained relatixelv nonresponsi\e or 

 negative. Increased fibrillary responses were noted only as thickenings or 

 encapsulating responses about small areas of infarct. Arnold and Bailey 

 I 1954) ha\e placed particular emphasis on glial response in the monkey 

 brain to high and low energy x-rays. They reported that glial responses 

 were related to dose intensity and time. High energy, low doses, e.g., 

 3.000-5,000 r. initiated astrocytic responses as hypertrophy and hyperplasia 

 months after exposure. Globus and others i 1952) implanted radon seeds in 

 the brain stem of dogs and after 106 days reported the appearance of astro- 

 cytosis. In an earlier study of glial response to 1.500 r x-irradiation in the 

 guinea pig. Brownson ( 1960) found no significant alteration of either quali- 

 tative or quantitati\e relationships of perineuronal satellite glial cells in 

 various ages of animals 33 days after exposure. Glia have been reported (o 

 demonstrate responses related to duiation of time after irradiation, that is, 

 initially inhibition, then reco\ery. and eventually intense gliosis (Arnold 

 and Bailey, 1954). 



Ependymal and subependymal cells lining the ventricular system appeared 

 to demonstrate selectixe sensiti\ity. Rats. 7 days after exposure to cumulated 

 doses between 1,000-5,000 r ot total head x-ray. frec]uently demonstrated 

 ependymal and subependymal cell swelling and pyknosis (Brownson. 1961). 

 Hicks and Montgomery i 1952) ha\e noted subependymal necrosis in rats 

 6-12 hours following head exposure to 1,200 r. There were occasional scat- 

 tered nuclear pyknosis of ependymal cells and nests of hyperchromatic 

 subependymal cells in all le\els of .x-irradiation doses. Heavy accumulations 

 of PAS-positive globules were present in all radiation groups. These dark 

 globules were located within the basal portion of ependymal cells and sub- 

 jacent extracellular areas and were not affected by previous treatment with 

 salivary enzymes i diastase ) . 



C:hanges in the walls of blood \essels were regular throughout the tissues 

 studied. These alterations predominantly appeared as hypertrophy and hy- 

 perplasia of the ad\entitia, often with extra nuclei. Less obvious were 

 changes in endothelium demonstrated as hypertrophy and hyperplasia. The 

 total picture suggested that the dosage accumulated up to and including 



