202 NORBERT SCHUMMELFEDER 



Single Cell Necrosis Within the Cerebellum After Exposure to 

 X-RAv Doses Below 4,000 r 



X-ray doses below 4,000 r resulted in loss only of single cells or small cell 

 groups, not in necrosis of larger areas of the irradiated cerebellar tissue. 

 The latent period between irradiation and the appearance of damage was 

 increased. Following an x-ray dose of 3,000 r, morphologic changes within 

 the irradiated cerebellar tissue were not observed in less than 45 days. At 

 this time, focal loss of granule cells and destruction of some Purkinje cells 

 were noted in the most superficial cerebellar folia, i.e., those nearest the 

 radiation source. The better preserved Purkinje cells often showed regressive 

 changes, which were of differing types. Cell shadows were occasionally 

 observed. Together with fresh hemorrhages within the damaged brain tissue 

 were residues of older ones in the form of hemosiderin in scavenger cells. 

 The blood vessels were dilated, and their walls often showed hyalinosis. 

 Perivascular infiltrates of mononuclear cells were found over the entire 

 irradiated field. 



At 4 months after irradiation with 3,000 r the various components of the 

 irradiated cerebellar folia were relatively well preserved. The granular layer 

 showed patchy looseness due to disseminated loss of granule cells. This layer 

 contained proliferated glial elements and was traversed by capillaries. 

 Hyaline thickening was found in the wall of blood vessels in the lepto- 

 meninges and brain tissue. The lumens of many vessels were dilated. Some 

 Purkinje cells were destroyed and replaced by glial nodules from which 

 glial shrubberies extended into the molecular layer. The preserved Purkinje 

 cells seemed imaltered. 



Early Changes in Cellular Nucleoproteins of Irradiated 

 Cerebellum 



All these observations indicate that local irradiation of the cerebellum of 

 mice with sufficiently high doses of x-rays results in marked alterations of 

 cerebellar tissue which are limited to the irradiated field. One of the most 

 remarkable changes is the pyknosis of nuclei of granule cells. Another im- 

 portant observation is that during the course of the radiation damage dif- 

 ferent types of regressive changes are observed in the Piukinje cells. 



We have applied the fluorescence technique, using the basic fluorochrome 

 acridine orange, to study alterations in nerve cells. This histochemical 

 method is especially suitable for investigation of cytoplasmic and nuclear 

 nucleic acids (Schiimmelfeder et al., 1958). Using buffered acridine orange 

 solutions, pH 4.0 to 7.0, all ribonucleic acid (RNA ) -containing material, 

 e.g., the cytoplasm of Purkinje cells, fluoresces bright orange or red. In 



