SEQIENCE OF X-RAY DAMAGE IN MOUSE CEREBELLUM 



195 



change in the blood vessels was observed. Occasionally a slight dilatation 

 of the capillaries was seen as an expression of hyperemia. 



In 5 to 6 hovns after x-irradiation of a 3 X 3 mm field with 60,000 r 

 the mice died. Further evolution of radiation damage could be followed 

 only after use of a dose of 60,000 r through a smaller aperture 0.5 X 2 mm) 

 or by using lower x-ray doses (40,000 to 20,000 ri. 



At 12 to 14 hours after 60.000 r. using a 0.5 X 2 mm field, the pyknotic 

 nuclei of the granular layer underwent disintegration, mostly as karyorrhexis. 

 The damaged area was still limited to the irradiated field, as a section cut 

 transversely to the direction of the x-ray beam illustrates ( Fig. 4 ) . The 

 Purkinje cells also exhibited signs of disintegration. Some of these cells had 

 greatly swollen cytoplasm and nuclei and showed lytic changes ( Fig. 5 ) . 

 Within other Purkinje cells, the nuclear chromatin was initially condensed, 

 simulating pyknosis, and then the cytoplasm and nucleus underwent lysis. 



At 20 to 30 hours after irradiation with 60.000 to 40.000 r. necrosis was 

 completely established in the superficial part of the cerebellar folia, i.e.. 

 nearest the radiation soiuce ( Fis.. 6 ) . The necrosis was strictly limited to 





'J:rM - 





Fig. 4. Radiation damage 12 hours after exposure to 60.000 r (0.5 X 2 mm field). 

 Plane of section is trans\erse to direction of the x-ray beam. Pyknosis and disinte- 

 gration of nuclei in the granular layer. X 4(1. Hematoxylin-eosin. 



