TIlE ULTRASTRUCTURE OF TASTE BUDS IN THE NEWBORN PIG

Tichy, F.: The Ultrastructure of Taste Buds in the Newborn Pig. ACta 'vet. Brno, 61,1992: 171-177. . . Taste buds localized on circumvallate papillae of the porcine tongue were investigated for the occurrence of dark, light and receptor cells and the stage of their differentiation, the morphology of the taste pore area, the occurrence and distrioution of intragemmal nerve endings and the way in which these are connected with each cell type. It was observed that, as early as two days after birth, the porcine taste buds included all three cell types. These were elongated towards the taste pore. Their apical parts, however, did not come up to level with the epithelial surface nor were they shaped into microvilli typical of the bud ultrastructure described in adult animals of other mammalian species. The cytoplasm of the dark cells had only a low amount of dark secretory granules and the receptor cells showed only occasional occurrence of dark vesicles. The dark, light and receptor cells were connected with nerve fibres and the way of contact was different in each cell type. Taste bud, taste pore, gustatory nerve. ultrastructure ". The ultrastructure of taste bud has been studied and thoroughly described in a number of amphibian and avian species (Farbman and Yonkers 1971; and others), in laboratory mammals (Farbman 1965a; Murray et al. 1969, 1972; Fujimoto and Murray 1970; Takeda and Hoshino 1975; Takeda 1976; and others) and also in man (Takeda 1972; Paran et aI. 1975; etc.) The results of ultrsstructura1 studies of taste buds have revealed considerable differences which are species-specific and also related to the position of the bud in the lingual mucosa (B e i dler 1969; Murray 1971, 1973; Mattern and Paran 1974; Takeda and Hoshino 1975; and others). Farbman (1965a, b), Murray and Murray (1967) and others showed the existence of two basic cell types constituting the taste bud, which they called dark and light cells. Later it was (Murray at a1. 1969) that the taste bud contains one more cell type which was designated the receptor cell. Although the functions of these three cell types have not been clearly determined, the evidence so far obtained suggests that their respective roles are similar in all the taste buds (Mattern and Paran 1974; Paran and Mattern 1975; Takeda 1977; and others). The dark cells are implemented in secretory and supportive function, light cells mediate contact between the taste stimuli and receptor cells, the true receivers of the stimulus. Still incomplete is the information on the mechanism by which each cell type in the taste bud is replaced or regenerated. The view of some authors (Beidler and Smalman 1965; Farbman 1965b) that the cells are differentiated by a continual process from so-called perigemmal cells of the surrounding epithelium is likely to hold only for the dark cells (and possibly also for the light ones). Later investigations by Takeda (1977) and Farbman (1980) indicate that in the receptor cells the presence of some specific structures in the cytoplasm relates the cells to nervous tissue. It is not known whether the light cells develop from the dark or the receptor cells or are an independent cell type. In association with this some authors discUss the process of taste bud formation in the lingual epithelium (Beidler and Smallman 1965; Farbman 1965b, 1980; Fujimoto and Murray 1970; Takeda 1976). They suggest that the origin of a taste bud and its localization are both determined and initiated by contact of epithelial cells with a nerve fibre. Some observations on the development of taste buds in relation to age of the animal have been