X-IRRADIATED CNS OF THE SYRIAN HAMSTER 271 







V 





Fig. 12. Cen-bral cortex, 168 hr after exposure to 7.500 r showing alterations in a 

 capillary in an area of total necrosis. Basement membrane (BM) is still preserved, 

 while endothelial cytoplasm is swollen and contains vacuoles (V), myelin figures 

 (MyF), and various other types of inclusions. Er, erythrocytes. X 10,800. 



Conclu-sions 



The early alterations consisting of astrocytic swelling, plasma exudation, 

 and erythrodiapedesis are all to be considered secondary to increased vascular 

 permeability. It would seem that an acute effect of ionizing radiation is to 

 interfere with basic cellular mechanisms of the cell and. while probably 

 affecting all elements of the central nervous system, to have its most dramatic 

 effect on the blood \essels which manifest this functional derangement by 

 increased permeability, thus allowing fluid and erythrocytes to pass. Changes 

 in the granular cells of the cerebellum similar to those lollowing x-irradia- 

 tion ha\e been described in a number of conditions where there was definite 

 or presimiptive e\idence of edema 1 Leigh and Meyer, 1949: Notzel, 1955: 

 Olsen, 1959a, b; Schmidt, 1958: Upners. I939'i. It is. therefore, entirely 

 possible that the striking change of granidar cells is not a direct radiation 

 effect, but is a nonspecific reaction of this type of cell to the presence of 

 edema. A study on ultrastructural alterations in the brain following extensive 

 cerebral trauma has been made in oiu" laboratory, parallel with investigations 

 on the effect of x-ray-induced damage Hager, 1960). These different, but 

 complementary, studies can profitably be compared when seeking cytologic 



