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PubMed1976

[Effect of sensory and sympathetic denervation of the frog tongue on the catecholamine containing cells of the taste buds].

The structure of catecholamine-containing dumb-bell shaped cells of the taste buds was studied by luminescent microscopy in the epithelial layer of the frog's tongue (Rana temporaria). On the unilateral section of the lingual nerve, a maintained adrenergic innervation of vessels and of the epithelium was observed, a decreased number of dumb-bell shaped cells in the taste bud, and their significant enlargement, and increased cathecholamine luminescence. With desympathization, no adrenergic nerves were observed on the vessels and the epithelium of the tongue. The size of the taste buds in desympathized cells of the tongue is sharply decreased and their number is increased. There is a tendency to grouping of the dumbbell shaped cells into 3--4 taste buds in one fungiform papillina. The experiments with sensory and sympathetic denervation of the frog tongue distinctly showed the trophic action of sensory and sympathetic nerves on the taste organ of the frog.

Animals↗
PubMed2000

Distribution and innervation of taste buds in the axolotl.

Adult axolotls have approximately 1,400 taste buds in the epithelium of the pharyngeal roof and floor and the medial surfaces of the visceral bars. These receptors are most dense on the lingual surfaces of the upper and lower jaws, slightly less dense throughout lateral portions of the pharyngeal roof and floor, and more sparse within medial portions of the pharyngeal roof and floor, except for a median oval patch of receptors located rostrally between the vomerine tooth fields. Each taste bud is a pear-shaped organ, situated at the center of a raised hillock and averaging 80 and 87 microm in height and width, respectively. Each comprises 50 to 80 cells, which can be classified as basal, dark fusiform, or light fusiform, based on differences in their morphology. The distal ends of the apical processes of the fusiform cells reach the surface of each hillock, forming a single taste pore with an average diameter of 15 microm. Each apical process terminates in one of three ways: as short, evenly spaced microvilli; as long clustered microvilli; or as large, stereocilia-like microvilli. The pharyngeal epithelium and associated taste buds in axolotls are innervated solely by rami of the facial, glossopharyngeal and vagal nerves. Approximately, the rostral one half of the pharyngeal roof is innervated by the palatine rami of the facial nerve, whereas the caudal one half of the pharyngeal roof is innervated by the pharyngeal rami of the glossopharyngeal and vagal nerves. The lingual surface of the lower jaw is innervated by the pretrematic (mandibular) ramus of the facial nerve. The dorsal two-thirds of the visceral arches, and the ventral one-third of the visceral arches and the pharyngeal floor, are innervated by both the pretrematic and post-trematic rami of the glossopharyngeal and vagal nerves, respectively.

Ambystoma↗
PubMed2005

Chorda tympani nerve transection at different developmental ages produces differential effects on taste bud volume and papillae morphology in the rat.

Chorda tympani nerve transection (CTX) results in morphological changes to fungiform papillae and associated taste buds. When transection occurs during neonatal development in the rat, the effects on fungiform taste bud and papillae structure are markedly more severe than observed following a comparable surgery in the adult rat. The present study examined the potential "sensitive period" for morphological modifications to tongue epithelium following CTX. Rats received unilateral transection at 65, 30, 25, 20, 15, 10, or 5 days of age. With each descending age at the time of transection, the effects on the structural integrity of fungiform papillae were more severe. Significant losses in total number of taste buds and filiform-like papillae were observed when transection occurred 5-30 days of age. Significant reduction in the number of taste pores was indicated at every age of transection. Another group of rats received chorda tympani transection at 10, 25, or 65 days of age to determine if the time course of taste bud degeneration differed depending on the age of the rat at the time of transection. Taste bud volumes differed significantly from intact sides of the tongue at 2, 8, and 50 days post-transection after CTX at 65 days of age. Volume measurements did not differ 2 days post-transection after CTX at 10 or 25 days of age, but were significantly reduced at the other time points. Findings demonstrate a transitional period throughout development wherein fungiform papillae are highly dependent upon the chorda tympani for maintenance of morphological integrity.

Age Factors↗
PubMed2005

Calretinin immunoreactivity in taste buds and afferent fibers of the grey mullet Chelon labrosus.

The presence of the calcium-binding protein calretinin in taste buds of a teleost, the thick-lipped grey mullet, was investigated using immunohistochemical techniques. Taste bud sensory cells had calretinin immunoreactivity. The nerve fiber plexus innervating taste buds, the ganglia and the viscerosensory roots projecting to the vagal lobe, also showed calretinin immunoreactivity. These results demonstrate for the first time the occurrence of calretinin in the taste buds and the taste afferent system of a teleost.

Animals↗
PubMed1989

Cytoskeleton in the apical region of mouse taste bud cells.

The cytoskeletal structures in the apical region of mouse taste bud cells were examined by immunocytochemistry and electron microscopy. Immunostaining for actin showed positive reactions in the apical portions of the taste buds. These regions contained bundles of longitudinally oriented filaments (5-7 nm in diameter) extending from the tip of microvilli to the apical cytoplasm of type I, II, and III cells. After incubation with heavy meromyosin, arrowhead formation was observed along these filaments, thus indicating these filaments to be composed of actin. The plasmalemmal undercoat, which was composed of vertical and horizontal layers, was observed on the zonula occludens. It is supposed that this undercoat gives the structural support for the lateral membrane of the apical region in the taste bud cells.

Animals↗
PubMed1984

Taste bud morphology in the fetal and neonatal dog.

Light microscopy and scanning electron microscopy were used to examine tongues of beagle puppies at 38, 47, and 54 days of gestation (term = 63 days) and at postnatal ages ranging from birth to adulthood, to follow the time course of morphological maturation of the papillae and taste buds. Fungiform and circumvallate papillae were present on the 38th fetal day, although taste buds were not observed until the 47th fetal day. Large multipored buds and increasing taste bud numbers were noted from 47 days of gestation until birth. Keratinization of tongue epithelium, development of submucosal glands, deepening of the circumvallate trenches, and further increase in taste bud numbers occurred after birth. Anatomical findings indicate that the puppy's peripheral gustatory system is functional at birth but has not yet reached adult form. The presence of mature taste buds in the fetal dog suggests that it may be responsive to chemical stimuli at, or before birth.

Animals↗
PubMed1985

Regeneration of taste buds by nongustatory nerve fibers.

Previous cross-reinnervation studies in situ by other investigators have demonstrated that cutaneous sensory and motor axons are incapable of trophically supporting mammalian taste buds. The present experiments examined the gustatory trophic potency of chemosensory and barosensory axons of the carotid sinus nerve. We report here that morphologically normal taste buds appeared on cat circumvallate papillae at 2 to 19 months after cross-anastomosis of the carotid sinus and lingual nerves, branches of the IXth cranial (glossopharyngeal) nerve. However, neurophysiologic and histologic data also indicated that, despite microsurgical procedures designed to direct regenerating lingual nerve fibers toward the carotid body and carotid sinus, some lingual axons escaped the anastomosis and subsequently grew within their native distal stump. The principal objective of this study was thus to determine whether foreign innervation of taste buds did indeed occur, or regenerated lingual nerve fibers were instead responsible for the newly formed buds. Our results showed that stray lingual fibers were not responsible for the reappearance of taste buds because transection of the original proximal lingual nerve stump (cross-anastomosed to the distal carotid sinus nerve stump) did not reduce the incidence of taste buds or the accumulation of radiolabeled material axoplasmically transported from the petrosal (sensory) ganglion. Autoradiography of labeled tissue samples showed that more than 90% of the taste buds were labeled at 8 and 9 days after lingual nerve transection. These data support the hypothesis that sensory axons in the carotid sinus nerve share an important trophic chemistry with gustatory neurons.

Animals↗
PubMed1976

Particular features of the innervation of taste buds of the epiglottis in monkeys.

The work is devoted to the study of the structure of the innervation apparatus of taste buds in the epiglottis of monkeys (Macacus rhesus). The Campos inpregnation method was used. It is established that several afferent myelinated fibers participate in the innervation of each taste bud of the epiglottis. The peculiarity of structure of their preterminal and terminal parts having the appearance of complex windings and spirals is noted. The polyaxonic principle of the innervation of taste buds of the epiglottis in monkeys is considered as a possible mechanism of generalization of the afferent impulses. It is suggested that the innervation apparatus of the taste buds of the epiglottis constitutes part of unique afferent system of this organ, ensuring its defensive function. The incongruity (from the histophysiological standpoint) of the term 'taste bud' in relation to the epiglottis is noted. It is proposed to call these formations special structures of the chemo-receptors.

Animals↗
PubMed1997

Isolation, partial purification, and ultrastructure of taste bud cells from rabbit foliate papillae.

A method is described for obtaining large numbers of isolated taste bud cells from lingual epithelium of rabbit foliate papillae. The isolation method is based on isopyenic sedimentation in a Percoll gradient. The purification of taste bud cells was evaluated by electron microscopy and by immunohistochemistry using CK 20 antibody. The cytology of the isolated taste bud cells remained very similar to in situ cells. The type III cells, which are regarded as gustatory cells, retained their characteristic dense-cored granules in the cytoplasm. This method will permit study of various parameters of taste bud cell biology.

Animals↗
PubMed2004

Expression of GDNF and GFR alpha 1 in mouse taste bud cells.

GDNF (glial cell line-derived neurotrophic factor) affects the survival and maintenance of central and peripheral neurons. Using an immunocytochemical method, we examined whether the taste bud cells in the circumvallate papillae of normal mice expressed GDNF and its GFR alpha 1 receptor. Using double immunostaining for either of them and NCAM, PGP 9.5, or alpha-gustducin, we additionally sought to determine what type of taste bud cells expressed GDNF or GFR alpha 1, because NCAM is reported to be expressed in type-III cells, PGP 9.5, in type-III and some type-II cells, and alpha-gustducin, in some type-II cells. Normal taste bud cells expressed both GDNF and GFR alpha 1. The percentage of GDNF-immunoreactive cells among all taste bud cells was 31.63%, and that of GFR alpha 1-immunoreactive cells, 83.21%. Confocal laser scanning microscopic observations after double immunostaining showed that almost none of the GDNF-immunoreactive cells in the taste buds were reactive with anti-NCAM or anti-PGP 9.5 antibody, but could be stained with anti-alpha-gustducin antibody. On the other hand, almost all anti-PGP 9.5- or anti-alpha-gustducin-immunoreactive cells were positive for GFR alpha 1. Thus, GDNF-immunoreactive cells did not include type-III cells, but type-II cells, which are alpha-gustducin-immunoreactive; on the other hand, GFR alpha 1-immunoreactive cells included type-II and -III cells, and perhaps type-I cells. We conclude that GDNF in the type-II cells may exert trophic actions on type-I, -II, and -III taste bud cells by binding to their GFR alpha 1 receptors.

Animals↗
PubMed1996

The taste bud and its innervation in the rat as studied by immunohistochemistry for PGP 9.5.

The taste bud in the rat vallate papillae was observed by immunohistochemistry for PGP 9.5 at the light and electron microscope levels; routine transmission electron microscopy was also performed. Immunoreactivity for PGP 9.5, a marker protein of paraneurons, was localized in the cytoplasm of the Type III or gustatory cells. More intensive immunoreactivity occurred in the nerve fibers, though a part of the nerve fibers remained unstained. The nerve fibers as detected by the immunostaining and by routine electron microscopy formed a coarse subepithelial plexus which issued branches upwards through the basal lamina. In the basal portion of the taste bud, these fibers formed a hitherto unknown intragemmal plexus of dense and delicate meshwork. This plexus, in turn, extended beaded fibers between the taste bud cells, forming synaptic contacts with Type III cells. Some of the immunoreactive nerve fibers were confirmed to reach the taste pore by light microscopy; electron-microscopic examination could not demonstrate their directly being exposed to the space of the taste pore. This study also deals with the fine structure of the rat taste bud with special reference to the Type III cells and their synapses with nerve fibers, as the rat has recently been rather seldom used in this field of study.

Animals↗
PubMed1990

Ultracytochemical localization of Ca(2+)-ATPase in the mouse taste bud during the early postnatal period.

Calcium-ATPase (Ca(2+)-ATPase) in the cells of the taste bud in the mouse vallate papilla was detected by the electron microscopic cytochemical procedure. In the mature taste bud, the enzyme was intensively located on the plasma membrane of various cell types and at the periphery of nerve fibers, but not in the subcellular organelles such as mitochondria, rough endoplasmic reticulum (rER) and the Golgi apparatus. Probably, plasma membrane Ca(2+)-ATPase plays primary role in determining the cytosolic Ca2+ concentration of the taste bud cell and nerve at a very low range about 10(-7) M. In the developing taste bud during the early postnatal period, on the other hand, CA(2+)-ATPase was apparently located in the lumen and cisternae of the rER. Golgi apparatus and small vesicles in the gustatory epithelial cells. These results suggest that Ca(2+)-ATPase synthesized in the rER passes through the Golgi apparatus to the plasma membrane, mediated by transport vesicles.

Animals↗
PubMed2005

Distinct expression pattern of insulin-like growth factor family in rodent taste buds.

The insulin-like growth factor (IGF) system is an important regulator of growth and differentiation in a variety of tissues. In the present study, the expression of IGF family members in the taste buds of mice and rats was examined. By reverse transcriptase polymerase chain reaction (RT-PCR) analysis, mRNA of IGF-I and -II, IGF-I receptor (IGF-IR), insulin receptor (insulin R), and IGF-binding protein (IGFBP)-2, -3, -4, -5, and -6 was detected in the taste bud-containing epithelium of the circumvallate papillae of mice. As suggested by the study using degenerate PCR (McLaughlin [2000] J. Neurosci. 20:5679-5688), IGF-IR was expressed in most of the taste bud cells of adult mice, as found by immunohistochemistry, and in those of postnatal day (P) 6 mice by in situ hybridization. Insulin R, which has strong homology to IGF-IR, was also detected in most of the taste bud cells of mice by immunohistochemistry and in situ hybridization. IGF-I immunoreactivity was detected in a few taste bud cells and in the epithelium surrounding taste buds. Northern blot analysis revealed that the amount of IGF-I mRNA in taste bud-containing epithelium was very low compared with that in liver. IGF-II immunoreactivity was weakly detected in mouse taste buds and the surrounding epithelium. In the rat tissue, a subset of the taste bud cells was positive for IGF-II. Among the six IGFBPs, IGFBP-2, -5, and -6 were detected in the mouse taste buds: IGFBP-2 and -5 immunoreactivity was seen in the majority of the taste bud cells, whereas IGFBP-6 immunoreactivity was found in the nerve fibers innervating the taste buds. In situ hybridization study also revealed that IGFBP-2 and -5 mRNA was synthesized in the taste buds of P6 mice and that the expression of these mRNAs overlapped in von Ebner's glands. These data reveal that IGF-I and -II might be produced in taste bud cells and (or) surrounding lingual epithelium and act through IGF-IR and insulin R locally in a paracrine and autocrine manner. The activity of these IGFs may be modulated through their interaction with IGFBP-2, -5, and 6.

Age Factors↗
PubMed1984

Quantitative study of taste buds in fungiform and circumvallate papillae of young and aged rats.

To ascertain whether an age-related decrease in number of taste buds occurs in the tongue of aged rats, taste buds were counted in fungiform and circumvallate papillae of Wistar-derived rats aged 5-7 months and 23-24 months. There was no difference in number or size of taste buds in papillae in anterior and posterior areas of the tongue from the two age groups. However, both fungiform and circumvallate papillae were larger in old rats. These results complement a recent study demonstrating no difference in numbers of taste buds in human fungiform papillae from birth to old age (Arvidson, 1979). Both anatomical investigations and human taste threshold studies indicate that age-related differences in the gustatory system are not as substantial as investigators have suggested in the past.

Aging↗
PubMed1981

[Lingual taste buds following application of colchicine to the glossopharyngeal nerve in the rat].

Dissection of the glossopharyngeal nerve and application to it of colchicine that blocks axoplasmic drug transport were performed to study the effect of the nerves on the taste buds of foliate lingual papillae. It was observed that colchicine application to the nerve gave rise to destruction of the taste buds. The process of destruction proceeded more slowly as compared to that induced by nerve dissection. Colchicine application led to changes in the protein spectrum of the epithelium of foliate papillae. The absence of changes in the protein spectrum of the epithelium of foliate papillae and the presence of nerve fibers in the epithelium of the taste buds on exposure to colchicine provide evidence against its direct toxic effect on the taste buds, giving rise to their destruction. The changes seen in the taste buds result from the blocked transport of factors that participate in neurotropic control of the taste buds.

Animals↗
PubMed1985

Number and distribution of taste buds in the oral cavity of hatchling chicks.

The location and number of taste buds were mapped in palatal epithelia of one-day old chicks and bud widths measured. Bud counts additionally were recorded for the tongue, and floor of the lower beak. An average of 316 taste buds was observed in the oral cavity of which 69%, 29% and 2% were distributed across oral epithelium in the upper beak (palate), lower beak and posteroventrolateral region of the anterior tongue, respectively. In each oral region, salivary gland ducts lying adjacent as well as gland ductules penetrating through the buds were prevalent. This relation may provide the bio-fluid milieu for receptor stimulation during feeding. Widths of palatal buds were bimodally distributed, peaking at diameters between 40-49 and 60-69 microns. The taste bud-rich oral epithelium in these one-day old chicks is consonant with their precocial nature. The topographic distribution of taste buds appears to be in register with those regions of epithelium contacted by food which is transported anteroposteriorly through the oral cavity by the chicken's prehensile tongue.

Age Factors↗
PubMed1989

Mercury and cadmium induced structural alterations in the taste buds of the fish Alburnus alburnus.

The ultrastructural damages of the taste buds of the fish, Alburnus alburnus were studied after applying 0.05 microM and 0.5 microM mercury chloride as well as 0.1 microM and 1 microM cadmium chloride. The most conspicuous alterations were induced during the first week of heavy metal exposition. The main structural alterations are: 1) the swelling of sensory microvilli and cilia; 2) the extreme dilation of the rER tubules and nuclear membranes, which is most expressed after cadmium exposition; 3) the increase in the number of lysosomes and dens bodies, which is more expressed after mercury exposition; 4) the swelling of the innervating nerve fibres at the synaptic areas of the taste buds, especially after mercury exposition. The damaging processes induced by the applied dose of heavy metals did not increase after the first week of exposition. The taste buds showed regenerated structural appearance after two weeks of exposition to 1 microM CdCl2, while the evoked structural alterations could be detected even after two weeks of exposition to 0.5 microM HgCl2.

Animals↗
PubMed1998

Identified taste bud cell proliferation in the perihatching chick.

Developing taste buds in the anterior mandibular floor of perihatching chicks were studied by high voltage electron microscopic autoradiography in order to identify proliferating gemmal cell types. Montaged profiles of 29 taste buds in five cases euthanized between embryonic day 21 and posthatching day 2 were analyzed after a single [3H]thymidine injection administered on embryonic day 16, 17 or 18. Results showed that dark cells comprised 55% of identified (n = 900 cells) and 62% of labeled (n = 568 cells) gemmal cells as compared with light, intermediate, basal or perigemmal bud cells. Dark cells had both a greater (P < 0.05) number of labeled cells and a greater amount of label (grains/nucleus) than the other four bud cell types, irrespective of injection day. The nuclear area (micron 2) of dark cells was not significantly larger (P > 0.05) than that of the other gemmal cell types and therefore cannot account for the greater amount for label in the dark cells. Interestingly, only dark cells showed a positive correlation (P < 0.003) between amount of label and nuclear area. Results suggest that, during the perihatching period of robust cell proliferation, dividing dark cells may give rise primarily, but not exclusively, to dark cell progeny.

Animals↗