ホンドタヌキ (Nyctereutes procyonoides viverrinus) の舌乳頭ならびに味蕾の微細構造的研究

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Lingual papillae of four Japanese raccoon dogs (Nyctereutes procyonoides viverrinus) were invesigated by scanning electron microscopy. A well-developed Lyssa, running parallel to the long axis of the tongue, was observed in the middle portion of the anterior part of the tongue. Four types of distinct papillae could be distinguished on the dorsal lingual surface. These were filiform, fungiform, foliate and circumvallate papillae. Among them, circumvallate papillae, 5-7 in number, were located in the root of the tongue and were the largest among the papillae. Remak's ganglion cells and mechanosensory nerve corpuscles were frequently appeared in the lamina propria of the circumvallate papillae. Further, taste buds of circumvallate papillae were examined by transmission electron microscopy. Taste bud was composed of four distinct cell types, type I, type II, type III and type IV cells as well as nerve terminals. Most characteristic features of type III cells was the presence of numerous dense-cored granules, ranging from 80 to 120nm in diameter, and synaptic type vesicles in the cytoplasm. This type of cells made synaptic contacts with adjoining nerve terminals and was considered to be gustatory transducing cells. Type III cells of racoon dog taste buds occasionally contained well-developed smooth endoplasmic reticulum which arranged in the form of concentric circles. At the fringes of these structures, the smooth endoplasmic reticulum were sometimes in direct continuity with the rough endoplasmic reticulum. Type I cells were dark in appearance and contained numerous secretory granules in the apical portion of the cytoplasm, and were considered to be exocrine cells. Whereas, type II cells were light cells and characterized by the presence of smooth endoplasmic reticulum throughout the cytoplasm and special contacts with nerve terminals. Taste bud cells occasionally contained unusual nuclear inclusions. Further, they sometimes showed condensed and fragmentary nuclei suggesting the occurrence of cell death by apoptosis. It is tempting to speculate that there might exist multiple cell lines in cell lineage of taste bud cells.
九州歯科学会の論文
2000-02-25

ホンドタヌキ (Nyctereutes procyonoides viverrinus) の舌乳頭ならびに味蕾の微細構造的研究

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