Biochemical Effects of Irradiation in the 

 Brain of the Neonatal Rat* 



O. A. ScHjEiDE. J. N. Yamazaki, C. D. Clemente. Nancy Ragan, and 



Sue Simons 



University of California School of Medicine, Los Angeles; 

 and V.A. Hospitals, Los Angeles and Sepidveda. California. 



Introduction 



From several perspccti\es the brain of the neonatal rat may be regarded 

 as embryonic. The cortex and the cerebellum are relatively small compared 

 to the brain stem (the more basic and primitive structure), and even in the 

 brain stem the nerve tracts are incompletely myelinated ( Folch-Pi, 1955). 

 The cell nuclei are lartjer and more hydrated than adult nuclei, and the 

 neurons have not yet assumed their characteristic elongate and dendrite 

 configurations. During the first 2 weeks, extensive cell division takes place in 

 the cerebellum and cortex. In the brain stem cells increase greatly in total 

 volume, but there is less cell division. 



Hicks I 1952 I has shown that neuroblasts in the brains of newborn rats 

 may be exposed to more than an hour of total anoxia without breakdown, 

 a finding that indicates a well developed glycolytic mechanism and relates 

 these structures metabolically to other embnonic tissues (Gal rt al., 1952). 



Aside from purely practical applications of studies on irradiation damage 

 to brain tissue in young animals, these embryonic properties of the brains 

 of neonatal rats make them useful tools in the assay of radiation effects on 

 cell mechanisms in general (and on ner\ous tissue in particular). The neo- 

 natal brain presents a continuously changing aspect over a period of weeks. 

 During this time radiation-produced lesions may manifest themselves in 

 various ways. C'.onversely. certain mechanisms of difTerentiation may be 

 further elucidated by the changes induced by radiations given soon after 

 birth. 



The present work is a preliminary sur\ey of the effects of sublethal doses 

 of x-irradiation to the heads of newborn rats. Several aspects of brain mor- 

 phology, biochemistry, and metabolism have been followed up to 40 days 

 after birth. 



* These studies were partially supported l)y the .\tomic Energy Commission. 



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