Intranuclear inclusions in neurons of the cat primary olfactory system.

Abstract The ultrastructure of two diverse types of intranuclear inclusions are described for neurons of the cat olfactory system. One is a rod or spindle-shaped structure of densely packed parallel filaments and the other has a crystalline lattice appearance. Apparently, both inclusions are more widespread in the olfactory brain than many other brain regions. Three-dimensional analysis was carried out using serial section methods to assess the solid geometry of the rodlet and lattice and the relationship of these intranuclear structures to the nucleolus and nuclear membrane. By this technique it is demonstrated that the rodlet crosses the nucleoplasm from pole to pole but does not penetrate the nuclear membrane. The lattice is also extensive in its intranuclear arrangement. From analytical measurements obtained from micrographs through different orientation planes of the lattice, an interpretative model is proposed that accords with all the various structural features of this extraordinary intranuclear body. The prevalence of both of these intranuclear inclusions in the cat anterior olfactory nucleus affords an opportunity for conducting cytochemical experiments attempting to understand the fundamental nature of these structures.