X-RAY INDUCED C\S CHANGES 47 



changes, characterized by beading and swelling, were noted in all groups 

 I Fig. 4). Occasional areas of cell necrosis were observed in the 5.000 r level. 



Hypothalamic neurons demonstrated occasional evidence of swelling, 

 chromatolysis, pyknosis, and hyperchromatic staining qualities, but these 

 changes were largely inconsistent. The presence of PAS-positi\e globules 

 within the extraneuronal tissue was clearly evident over the entire dosage 

 range of radiation, demonstrating no specific alteration. 



Brain stem neurons were not observed to ha\e undergone major changes 

 at any level of radiation. Those changes that were obser\ed were mild to 

 moderate chromatolysis. pyknosis. and hyperchromatism. In the 5.000 r 

 level maintained 228 days, hyperchromatic neurons were in excess with no 

 chromatolysis observed. 



The neuroglial cells underwent slight but consistent degrees of scattered 

 hyperplasia in the subpial cortex ( Fig. 5 1 . These changes were somewhat 

 localized and similar at the 1,820, 2,000, and 3,000 r levels. Astrocytes seem 

 to have been the most regularly reactive cells and in inany instances could 

 be termed gemestocytic. Glial cell hyperplasia and hypertrophy became quite 

 noticeable in the cortex at the 4,000 and 5,000 r level, especially in the 

 group surviving 228 days. Small areas of infarction (Fig. 6) were in 

 the cortex and subcoitical white matter in all groups of animals. There 

 seems to have been a more intensive cellular and fibrillary gliosis about 

 these areas in the 4,000 and 5,000 r animals. 



The ependymal and subependymal cells were significantly reactive at all 

 levels of radiation. There appeared to ha\e been a thinning of cells in all 

 groups. The pyknosis and hyperchromatic cells were scattered throughout 

 the varied exposuie le\els in different \entricular areas as well as within 

 the same areas. It was not uncommon to find nests of hyperchromatic 

 subependymal cell foci i Fig. 7). P.\S-positive accumulations of globules 

 both within the basal position of the ependymal cell and subependymal 

 areas were increasingly evident as the le\ el ot radiation was increased. Heavy 

 deposits of such materials were noted in the 4.000 and 5,000 r groups. 



Meninges, specifically the leptomeninges. and the pial-glial membranes 

 underwent changes Fig. 5i. \arying from mild thickening at 1,820 and 

 2.000 r to moderately severe in the 5.000 r range. Such changes were 

 noted to have been scattered o\er the brain in local areas. Throughout 

 all of the \aried dosage levels occasional cellular and fibrillary infiltrations 

 were present in these foci. .Astrocytes were gemestocytic in such areas along 

 the piaglial membrane. 



Blood vessels underwent \arious alterations at the different dosage le\els. 

 Vessels most often in\ol\ ed were capillaries and small arteries. Mild to mod- 

 erate hypertrophy and hyperplasia of endothelium and increase in adventitia 

 were noted in animals receiving 1.820, 2,000 and 3.000 r (Fig. 8) and were 



