Oncogenesis of human adenovirus type 12 in the brain
of rats was examined. Newborn rats of Sprague-Dawley and Donryu　strains were injected intracranially with human adenovirus type 12.　The incidence of intracranial tumors was 91% (30/33) in SpragueDawley　and 56% (14/25) in Donryu rats. Except for one tumor nodule　located in the parietal cortex of a Sprague.Dawley rat, all tumors　developed in the paraventricular areas or in the meninges. Tumors
were quite similar histologically to those induced in hamsters and　mice resembling the undifferentiated human brain tumors such as medulloblastoma,　ependymoblastoma and embryonic gliomas. From　the histological features and primary sites of tumor development, it is　suggested that the tumors in the brain of rats induced by adenovirus
type 12 originate from the embryonic cells in the　paraventricular area　and also from the undifferentiated supporting cells of the peripheral　nerves in the　leptomeninges.</p
