Distribution and life history of rat brain tumors induced by human adenovirus type 12 in their early stages of the oncogenesis.
Newborn rats were intracranially inoculated with human adenovirus type 12 within 24 hours after birth and their brains were sequentially investigated by conventional histological techniques and autoradiography to clarify the early process of tumor growth. At the end of the 2nd week atypical cells having bizarre configuration first appeared singly in the tapetum. From the end of the 3rd week small clusters of slightly atypical subependymal cells ("abnormal clusters") appeared in the subependymal area. From the end of the 4th week a few "microtumors" showing compact nodular growth of atypical glial cells were observed among the "abnormal clusters". These early neoplastic changes in the rat brains had close relationship to subependymal cells. The perinatal subependymal cells showed most dense distribution in the subependymal area of lateral ventricle with open ventricular space ("open ventricular area") especially in the region of anterior horn. In contrast, the microtumors and the enlarged tumors were recognized much more in number in the subependymal area of bulbus olfactorius and tapetum where ventricular cavities closed in the young period of maturation ("closed ventricular area"). "Abnormal clusters" were located in both of the areas with more preponderence in the open ventricular area. The reasons for this discrepancy of occurrence were discussed from the viewpoint of environmental factors. Subsequent investigation revealed that the average number of microtumors, after reaching its peak at the end of the 5th week, diminished gradually and, finally, only one or two enlarged tumors were found per each tumor-bearing animal. The mechanisms for this phenomenon are open to further investigation.
Shinozaki
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Department of Pathology, Okayama University Medical School, Okayama, Japan.
D000258:Adenovirus Infections, Human / Q000473:pathology*; D000260:Adenoviruses, Human; D000818:Animals; D001932:Brain Neoplasms / Q000473:pathology* / Q000821:virology*; D051381:Rats; D017207:Rats, Sprague-Dawley