[Electron microscopic observations of the porcine middle ear--inflammatory changes]

In previous studies, the morphology of the mucoepithelial cells of the middle ear of normal pigs has been found to be similar to that of humans. In this study, otitis media was induced in 18 ears by transcanal injection of glycerin into the middle ear cleft and morphological changes were investigated by scanning and transmission electron microscopy. The mucoepithelial cells of the inflamed porcine middle ear consisted of ciliated cells, non-ciliated cells, secretory cells and basal cells, and the distribution of these cells was similar to that of normal cases. In the inflamed Eustachian tube and middle ear cleft, the epithelial cells were detached, the intracellular junctions ruptured and there was subepithelial thickening in some places. In addition, the cilia were detached or deformed irregularly. On the other hand, ciliated cells, bulging non-ciliated cells, secretory cells and columnar cells were increased in numbers. These features suggested that the muco-ciliary system of the inflamed ears had been stimulated. In the air cell system, however, there were signs of mucoepithelial cell injury, but no evidence suggesting that the muco-ciliary system had been stimulated as in the Eustachian tube or middle ear cleft. The inflammatory changes in the mucoepithelial cells in the Eustachian tube and middle ear cleft gradually returned to normal but in the air cell system, the changes were persistent. Moreover, the signs of mucoepithelial cell injury remained longer when inflammation occurred at a younger age.(ABSTRACT TRUNCATED AT 250 WORDS)