Cytoplasmic crystalline inclusions in hepatocytes of a steer with shipping fever.

Needle-shaped crystalline inclusion bodies were found in vacuolated liver cells of a steer affected with pneumonic pasteurellosis. The inclusions were eosinophilic and refractive, and ranged in size from 3 to 6 microns long and from 150 to 250 nm wide. Histochemical examination revealed that they contained lipid and protein. Electron microscopic examination showed finely fibrillar or granular material. Cross-striations with a periodicity of 45 nm were seen in longitudinal section of the inclusions. The possible origin and pathogenic significance of the inclusions are discussed.