[Fine structure of the epithelial cells of the lingual dorsal mucosa in the guinea pig].

The fine structure of the lingual dorsal epithelium of the guinea pig was examined in detail by transmission electron microscopy. In the epithelium of the posterior side of filiform papillae, the surface layer was strongly stained by toluidine blue. This staining pattern is a characteristic feature of hard keratinization. By contrast, in the epithelium on the anterior side of filiform papillae, the surface layer was stained with moderate efficiency by toluidine blue, a characteristic feature of "soft keratinization." The surface area of the interpapillary epithelium was not stained as effectively as these other areas by toluidine blue (Fig. 1). When examined by transmission electron microscopy, cells in the germinal layer of the epithelium on the anterior and posterior sides off iliform papillae and those of the interpapillary epithelium appeared to have an almost identical oval shape. The nuclei of these cells were located in their central areas. In the cytoplasm of these cells, many mitochondria, many free ribosomes, and a few of tonofibrils were seen. Cellular processes were seen to be distributed almost all around each cell. A basal lamina was intercalated between the basal cells of the epithelium and the underlying connective tissue (Fig. 2). In the intermediate layers between the germinal layer and the surface layer of the epithelium, a large number of ketatohyaline granules was observed on the anterior side of filiform papillae. In the deep intermediate layer, mitochondria, kertohyaline granules and free ribosomes were abundant, although the keratohyaline granules were fewer in number and smaller than those in the shallow intermediate layer. Each cell had a rugged surface with spines. The spines of neighbouring cells were linked together by desmosomes (Figs. 3, 4). Both the number and size of the keratohyaline granules tended to increase in the cells of the shallow intermediate layer. Abundant free ribosomes were observed, as was the case in the deep intermediate layer, although the mitochondria were fewer in number than in the deep layers. Relatively flat nuclei were scattered in cells of both the deep and the shallow intermediate layers (Fig. 5). The cells of the surface layer showed a continuous gradation in their composition from that of the cells of the intermediate layer, the major part of their cytoplasm was filled with electron-dense, fibrous structures, and amorphous, moderately electron-dense materials were dispersed between these fibrous structures. A marginal band was located in the contact zone just beneath the cytoplasmic membrane.(ABSTRACT TRUNCATED AT 400 WORDS)