Intracytoplasmic hyaline inclusions in the hippocampal neurons of two cattle

This report deals with the large intracytoplasmic hyaline inclusions observ ed in hippocampal large pyramidal cells of two Holstein-Friesian cattle. Th ese inclusions were round to elongated polyhedral in shape with consistentl y homogeneous glassy appearance; they varied in size and were positive for the periodic acid-Schiff reaction and silver impregnation. Electron microsc opic examination revealed that the inclusions consisted of granular materia ls showing moderate electron density and were bounded by a unit membrane. O n the external surface of the unit membrane, there were direct connections to cellular organelles, including ribosome, rough endoplasmic reticulum, an d mitochondria. These findings suggest that the inclusions might be derived from neuronal endoplasmic reticulum.