Some Observations on Radiation Effects on 



the Blood-Brain Barrier and Cerebral 



Blood Vessels* 



Carmine D. Clemexte 



University of California at Los Angeles Medical Center, and 



the V. A. Hospitals, Los Angeles and Sepulveda, California 



AND 



Harold E. Richardson, Tr. 



Donner Laboratory. Uni; ersity of California, Berkeley, California'^ 



For many years it has been supposed that the adult nerxous system is rela- 

 tively resistant to radiation dosaces capable of injuring or destroyino cells 

 of other tissues and ora;ans. The primary reason usually forwarded to ex- 

 plain this phenomenon has been that the primitive cells in the body are 

 more radiosensitive than cells differentiated to a hisih order of specializa- 

 tion. In this regard obser\ations seem to su^cest the thesis that cellular 

 radiosensiti\ity depends somewhat on the rate of nucleic acid synthesis. It is 

 usually stated that lymphocytes, developing germ cells, and maturing neuro- 

 blasts are among the most radiosensitive of cells, whereas the adult neuron 

 is among those most resistant. 



When assessing the effects of radiations on the brain, it seems difficult to 

 speak in generalizations as to the radiosensiti\"ity or radioresistance of the 

 entire organ. For in the central ner\ous system, as in other organs, the 

 pathology which develops with ionizing radiations can be considered to 

 result from several sources or a combination of them. We describe paren- 

 chymal, stromal, and intercelkdar effects of radiation in most other organs 

 in the body. Therefore, it seems wise not to ha\e our opinions of the radio- 

 sensitivity of the brain as an organ unduly influenced, just because the adult 

 neuron has been described as being relati\ely radioresistant. As a matter 

 of fact, even this latter generality has been questioned recently (Grigoriev 

 and Tsypin, 1957; Lebedinsky ct al., 1959; Livanov and Biryukov, 1959: 



* These in\estigations were supported in pait by the U.S. Pubhc Health Service and 

 in part by work under contract with the U.S. Atomic Energy Commission. 



t The authors wish to thank Dr. C. Tobias for his ad\ice and enthusiasm in the 

 experiments dealing with high energy radiations. Mr. A. Huish for his photographic 

 assistance, and Miss B. Kulgren and Mrs. J. Luce for their technical assistance. 



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