Ultrastructural findings in medulloepitheliomatous neoplasms induced by human adenovirus 12 in rodents

Human-adenovirus-12-induced medulloepitheliomatous tumors from seven Sprague-Dawley rats, seven Syrian hamsters, and seven C3Hf/Bi mice were subjected to electron microscopic examination. A single intracerebral inoculation of 0.01 ml of human adenovirus fluid, 104.1 TCID50 HeLa cells/0.1 ml was made in the rats and hamsters within 24 hrs after birth, and a similar intraperitoneal inoculation was made in the C3Hf/Bi mice. Within 2 months, all rats and hamsters developed solid hemispherical neoplasms in close proximity to the cerebral ventricular system. The mice also developed multiple intraperitoneal neoplasms within almost the same latency period. Fixation was performed by whole-body perfusion. Examination revealed highly primitive tumor cells containing one cilium per cell, with a 9+0 pattern within the apical region. Intracytoplasmic myelin figures were prevalent in tumors in all three species. Intranuclear and intramitochondrial myelin figures were also common, while intramitochondrial rodlets were only occasionally seen. Virions of types A, B, and C were detected in both the Sprague-Dawley rats and C3H mice.