Scanning Electron Microscopic Observations on the Intracellular Structures of the Ciliated Tracheal Epithelium-Especially on the Morphological Differences between Conventional Rats and Specific Pathogen-Free Rats

The three-dimensional architecture of the intracellular structures of the tracheal ciliated epithelium was studied by scanning electron microscopy, paying particular attention to the morphological difference between conventional rats and specific pathogen-free (SPF) rats. The surface of the trachea was densely covered with cilia in conventional rats, but less in SPF rats. The smooth endoplasmic reticulum (ER) formed a three-dimensional tubular meshwork under the basal bodies in both rats. In conventional rats, the Golgi apparatus was highly developed and many Golgi vesicles were attached to the lateral margin of the Golgi cisternae. In addition, the rough ER spread around the nucleus. In the SPF rats, however, the Golgi appatatus was not so highly developed and the rough ER was scarcely visible. The development of the Golgi apparatus and rough ER observed in the conventional rats indicate the active protein synthesis for the formation of the cilia which plays an important role in antimicrobial defense mechanisms.