MORPHOLOGIC AND PATHOPHYSIOLOGIC SIGNS 299 



It has been demonstrated that there is a relationship between the size of 

 the radiation dose and the character of the morphologic changes (Aleksan- 

 drovskaya, 1959) . With a dose of 650 r, cerebral anemia occurs macroscop- 

 ically, with hyperemia in some parts of the brain. Histologically, dystrophic 

 changes can be detected in the cortex, subcortical ganglia, and hypothala- 

 mus and vacuolation accompanies partial destruction of the nerve elements 

 in the corpora quadrigemina, nuclei of cranial nerves, and structures of the 

 reticular formation. Swelling or edema becomes established, and the nerve 

 fibers break up. Wrinkling of the astrocytes takes place. Aleksandrovskaya 

 (1959) characterizes the above picture as toxicohypoxic encephalopathy 

 with dystrophic changes of the nerve cells and productively dystrophic re- 

 actions on the part of the glia. 



All these changes were deeper and more diffuse after irradiation with a 

 dose of 1,300 r. Subarachnoid and perivascular hemorrhages were observed. 

 Portugalov (1957) found the most substantial changes in the diencephalon 

 and mesencephalon. Several authors have pointed to morphologic changes 

 (necrobiosis) of particular cell groups in the cortex, accompanied by chro- 

 matolytic and karyolytic phenomena [Kurkovsky, 1958 (see in this review 

 the following authors : Kyandaryan ; Papoyan ; Beglai7an, Zagotskaya, Aruty- 

 anyan, 1957)]. Bibikova (1959) obtained acute or chronic demyelination 

 after irradiating dogs with 5,000-30,000 r. 



Smirnov (1960) observed changes in the distribution and quantity of 

 tigroid substance (Nissl bodies) in the neurons of the reflex arc, an index to 

 the functional condition of a neuron. 



Manina (1959) demonstrated the destruction of neuroblasts and severe 

 disturbance of the architectonics in different parts of the cell as a result of 

 irradiation with radioactive phosphorus (P^-). 



Definite morphologic shifts occur under the effect not only of large doses 

 of radiation but also of single or repeated small doses (Aleksandrovskaya, 

 1957) . These shifts take the form of proliferation responses by microglia and 

 ectodermal glia. Profound morphologic changes are observed in the progeny 

 of rats irradiated with a dose of 150-200 r during the antenatal jDcriod. 



Shabadash (1957) has demonstrated that irradiation with a dose of 

 25-100 r causes a shift of — 0.3 to — 0.4 in the pH of the nucleoproteins. 

 The response is detected first in the mitochondria, then in the tigroid sub- 

 stance. These changes are caused by depolymerization processes and reduc- 

 tion in the quantity of nitrous bases. A typical feature is that the huge 

 number of mitochondria in the diencephalic region and the reticidar fornia- 

 tion suflfer from ribonucleoprotein deficiency as a result of irradiation; this 

 indicates local respiratory disorders. There is undoubtedly a good prospect 

 that this cytochemical change will be useful in revealing the mechanism by 

 which ionizing radiation afTects the organism. 



These findings are evidence that morphologic changes occur in the brain 



