408 JANSSEN ET AL. 



clearly shown in Fi^. 8C. From their study of the brains of mice exposed to 

 a 25-/i,-wide beam of deuterons with an energy of 22.5 Mev per nucleon, 

 in which the width of the track corresponded to the width of our bands, 

 Zeman et al. (1959) reached the conclusion that damage to nerve cells and 

 glia represented a direct irradiation efTect. 



Further evidence pointing to primary cellular damage in our animals, 

 which would not be expected if circulatory disturbance and an edematous 

 process were the sole factors, was the close correlation of the granule cell 

 pyknosis with the magnitude of the energy given off" along the slopes and at 

 the peak of the Bragg curve (Figs. 5 and 6) and the straightness of the lower 

 border of the irradiated zone. In later stages following exposure to particle 

 radiation (i.e., from 5 or 6 days onward), it would be difficult to judge 

 to what extent circulatory disturbances contributed to the extent of the 

 damage. There were two pieces of evidence that circulatory disturbances 

 did contribute to further advance of lesions. In sections stained by the 

 Pickworth-Lepehne method (6,000 rad surface dose), collapse of occa- 

 sional small vessels in the band of cellular damage was noted at 4 days, 

 and numerous filling defects were found in the vascular tree from the 9th 

 day to about the 24th day. Secondly, lesions in the cerebral cortex were 

 particvdarly striking in the region of the interhemispheric fissure (Figs. 4, 

 7C, and IIC), and cortical nerve cells below the band in this general region 

 were sometimes damaged in association with astrogliosis and microgliosis, 

 which extended down into the subcortical white matter and corpus callosum. 

 Such effects were considered to be related to greater circulatory disturbances 

 in this region than elsewhere, perhaps because in this "angle" the vascular 

 tree is more prone to be constricted by a generalized edematous process 

 than elsewhere. 



With regard to the blood-brain-barrier permeability studies, the FLSP 

 technique had the advantage over the sodium fluorescein indicator in that the 

 labeled proteins could be demonstrated microscopically both before and 

 after the gross fluorescence was perceptible (Table III). Extension of the 

 fluorescence to regions far beyond the irradiated area was considered to 

 have been due to disturbance of vascular permeability initiated in the irra- 

 diated area. Even ependymal epithelial cells lining the upper wall of the 

 ventricle contained large quantities of fluorescent protein. 



Summary and Conclusions 



This article deals with the effects on the cerebellum and cerebrum of 

 alpha particles with an energy of about 12 Mev per nucleon at surface doses 

 of 50 to 6,000 rad, and of protons of the same energy at a surface dose of 

 6,000 rad. The dorsal surface of much of the cerebellum and cerebrum was 



