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SCHJEIDE, YAMAZAKI, CLEMENTE, RAGAN AND SIMONS 



16 17 20 

 Days of Age 



Fig. 8. Ratios of palmitic acid to combinL-d total of stearic and oleic acids in nuclei 

 of control and x-irradiated neonatal rat cortices and brain stems. 



in the brain stem. Because of the important relationship that has been (in- 

 directly) established between the neural cells and closely adjacent oligoden- 

 droglia cells with respect to the production of myelin (lipid), it would 

 appear to be important to determine histologically the ratio of oligodendrog- 

 lia to neural cells in irradiated brain stem, for in this organ complex, not 

 only does the inhibition of lipid synthesis correlate closely with the retarda- 

 tion of dehydration, but the inhibition is first noted (ca 16 days) at a point 

 in development when a large increase in myelination processes takes place. 

 These results point up the fact that the various sections of the brain are by 

 no means homogeneous tissues and offer the possibility that in brain stems 

 the oligodendroglia are vulnerable to radiations at a time when the strictly 

 neural elements may be relatively less so. (Such vulnerability could be ex- 

 pressed either as outright destruction of the cells or alteration of their syn- 

 thetic abilities.) Histological studies currently being carried out by one of 

 the authors of this paper (C D. Clemente) should help in the elucidation of 

 this issue. 



A second point of interest concerns the radiation-induced decreases in 

 mitochondrial populations as obserxed in the cortices of some younger and 



