Cytoplasmic Inclusion Bodies in the Pancreas and Salivary Glands of Small Laboratory Animals

Summary Hitherto undescribed cytoplasmic inclusion bodies have been found in the pancreas of apparently healthy mice, rats, and rabbits and in the salivary glands of the rats. In both organs the inclusions were confined to the acinus cells. They were not encountered in guinea pigs. Their etiology is unknown. The possibility that the inclusions were caused by disturbance of secretory function was not supported by the results of experiments to test the effects of pilocarpine and atropine. Pilocarpine provoked no change in the incidence, abundance, or appearance of the inclusions and atropine, if it had any effect at all, was only mildly inhibitory. There is no evidence that dietary factors were responsible. Evidence for viral origin is only suggestive and consists of the following points: 1. The presence of inclusion bodies in the absence of non-viral factors known to produce them. 2. Strong resemblance of the inclusions to those described in infectious ectromelia of mice, a disease of proved virus etiology. 3. Absence of inclusions in animals under 30 days of age and an increasing incidence thereafter with increasing age. 4. A seasonal variation in the incidence and abundance of the inclusion bodies.