[The neuronal Torres bodies in experimental yellow fever encephalomyelitis. An additional example of the heterogeneous nature of Cowdry type A intranuclear inclusions].

In experimental yellow fever virus encephalomyelitis of adult albino mice, the occurrence of intranuclear inclusions within nerve cells, in particular, within spinal and bulbar motoneurons, is a constant finding. The light microscopic features of these so-called neuronal Torres bodies correspond entirely to the criteria laid down by Cowdry for the type A intranuclear inclusions. At the ultrastructural level, these karyoplasmic formations consist of haphazardly distributed patches of an essentially amorphous material of various density. Unlike the Cowdry type A intranuclear inclusions characteristic of several herpesvirus and paramyxovirus infections, neuronal Torr-s bodies do not contain any viral structures. The frequency with which neuronal Torres bodies, certain nucleolar alterations and severe tigrolytic changes occur together, possibly indicates that this sort of type A intranuclear inclusion developes as a consequence of a virus induced disturbance of the cell nucleic acid and/or protein anabolism.