Correlated histochemical and electron microscopic studies of the esophageal epithelium in the salamander, Hynobius nebulosus.

The esophageal epithelium of the adult salamander, Hynobius nebulosus, was studied by histochemistry, including periodic acid-Shiff (PAS), alcian blue both at pH 2.5 and pH 1.0, and alcian blue (pH 2.5)-PAS with or without neuraminidase-digestion, and scanning and transmission electron microscopy. The epithelium was columnar in type, comprising partly pseudostratified and partly two-layered architecture; it consisted mainly of ciliated cells, goblet cells, and basal cells. The ciliated cells consisted of two types, light and dark: both types, especially the latter, frequently contained numerous small mucous granules in their apical portion. Ciliated-mucous cells were also occasionally present. Immature ciliated cells were frequently found. Goblet cells were divided into two types: Type I cells possessed electron lucent mucous granules, which frequently contained dense specific inclusions, and frequently bulged into the lumen; Type II cells had moderately electron-dense mucous granules with no inclusions and a conical apex which did not exceed the level of the lumen. The Type I cells were closely distributed throughout the esophagus, while the Type II were mainly dispersed in the cranial portion, remarkably decreasing in the caudal portion. Correlated histochemical and electron microscopic observations suggested that, in the Type I cell, mucous granules contain acid mucosubstances, while in the Type II, they possess neutral mucosubstances, and that in the Type I cell mucous granules consist of sialic acid-containing glycoproteins and their swollen portions are more highly sulfated than the non-swollen ones.