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PubMedDate not supplied

[Update on the presence of taste buds on the laryngeal surface of the epiglottis].

Previous investigations have ascertained, according to the results obtained by Bradley et al. (1980) in the sheep, that the laryngeal surface of the epiglottis of goat and bovine is always provided with numerous taste buds. These observations have verified in other ruminant species, as the moufflon and the buffalo, the validity of the above-named datum and have ascertained that it is always inconstant in the other animal species considered (wild boar, coypu). These taste buds show a typical structure (diameter of the outer taste pore varying from 2.7 to 4.2 micron, width of the chemoreceptors varying from 30 to 60 micron and length from 27.5 to 57.5 micron). Moreover, the normal structure of the above-named taste buds is also testified by the arrangement of their innervation and particularly by the integrity of the synaptic contacts. The results of the present research have permitted a critical and more severe examination of the probable functional role of those laryngeal receptors. In fact, in the ruminants they may protect the deep airways precluding to food particles the larynx in the phase of food regurgitation.

Animals↗

PubMed1985

Ontogeny of substance P-like immunoreactive fibers in the taste buds and their surrounding epithelium of the circumvallate papillae of the rat. II. Electron microscopic analysis.

We studied the ontogeny of the fine structure of substance P-like immunoreactive (SPI) fibers in the extragemmal epithelium and taste buds of the circumvallate papillae in the rat tongue by electron microscopy and by the unlabeled antibody-enzyme method. SPI fibers in the lamina propria first appeared at gestational day 19, and those in the extragemmal epithelium and in the taste buds at day 21. These fibers did not form synaptic contact with underlying cells. In addition, the occurrence of nonimmunoreactive fibers in these areas preceded that of SPI fibers. Our findings suggest that SPI fibers are not primarilly involved in the differentiation of the extragemmal epithelium and taste bud cells.

Animals↗

PubMed2001

"Type III" cells of rat taste buds: immunohistochemical and ultrastructural studies of neuron-specific enolase, protein gene product 9.5, and serotonin.

Taste buds contain a variety of morphological and histochemical types of elongate cells. Serotonin, neuron-specific enolase (NSE), ubiquitin carboxyl terminal hydrolase (PGP 9.5), and neural cell adhesion molecule (N-CAM) all have been described as being present in the morphologically defined Type III taste cells in rats. In order to determine whether these substances coexist in a single cell, we undertook immunohistochemical and ultrastructural analysis of taste buds in rats. Double-label studies show that PGP 9.5 and NSE always colocalize. In contrast, PGP 9.5 and serotonin seldom colocalize. Further, whereas the serotonin-immunoreactive cells are always slender and elongate, the PGP 9.5/NSE population comprise two morphological types--one slender, the other broader and pyriform. Although gustducin-immunoreactive taste cells appear similar in overall shape to the pyriform PGP 9.5/NSE population, gustducin never colocalizes with PGP 9.5 or NSE. The serotonin-immunoreactive taste cells have an invaginated nucleus, synaptic contacts with nerve fibers, and taper apically to a single, large microvillus. These are all characteristics of Type III taste cells described previously in rabbits (Murray [1973] Ultrastructure of Sensory Organs I. Amsterdam: North Holland. p 1-81). PGP 9.5-immunoreactive taste cells exhibit two morphological varieties. One type is similar to the serotonin-immunoreactive population, containing an invaginated nucleus, synapses with nerve fibers, and a single large microvillus. The other type of PGP 9.5-immunoreactive taste cell has a large round nucleus and the apical end of the cell tapers to a tuft of short microvilli, which are characteristics of Type II taste cells. Thus, in rats, some Type III cells accumulate serotonin but do not express PGP 9.5, whereas others express PGP 9.5 but do not accumulate amines. Similarly, Type II taste cells come in at least two varieties: those immunoreactive for gustducin and those immunoreactive for PGP 9.5.

Animals↗

PubMedDate not supplied

Localization, morphology and ultrastructure of taste buds in the domestic duck (Cairina moschata domestica L.) oral cavity.

The Authors report on localization of the taste buds in epithelium of the palate (70%), the floor of the oral cavity (28%) and the tongue (2%) in Domestic Duck. Each taste bud is oval-shaped, measuring roughly 130 x 60 microm, and communicates with the oral cavity by a short duct. There is topographical correspondence between the buds and the parietal salivary glands. Ultrastructural examination showed the following 4 cell types: 1) light cells--characterized by cytoplasm containing sparse perinuclear filaments, numerous light vesicles, a uniformly granular nucleus. 2) dark cells--with electron-dense cytoplasm, numerous perinuclear filaments, occasional light vesicles, an irregular and densely granular nucleus. 3) intermediate cells--with characteristics common to the two previous cell types. 4) basal cells--located at the ventral part of the button.

Animals↗

PubMed1996

Immunohistochemical studies on protein gene product 9.5, serotonin and neuropeptides in vallate taste buds and related nerves of the guinea pig.

The occurrence, distribution and innervation of guinea pig vallate papillae were investigated by means of indirect immunofluorescence and immunoperoxidase methods using antibodies against: a neuron-specific protein, protein gene product 9.5 (PGP 9.5); various neuropeptides including calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP) and galanin; a monoamine, serotonin (5-hydroxytryptamine; 5HT). Numerous PGP 9.5-immunoreactive nerve fibers were found to form plexuses in the lingual epithelium both intragemmally and extragemmally and to comprise dense bundles in the lamina propria just beneath the epithelium. Moderate numbers of PGP 9.5-immunoreactive cells were observed in the taste buds. These cells, typically spindle in shape, extended through the entire thickness of the taste bud. CGRP-immunoreactive nerve fibers were numerous in the subgemmal connective tissue and entered the epithelium to form intragemmal and extragemmal networks. A dense subgemmal SP-immunoreactive network in the vallate papilla can be linked to the presence of taste buds, even though SP-immunoreactive nerve fibers rarely occurred intragemmally. No taste cells immunoreactive for CGRP and for SP were observed. Immunoreactivity for VIP or galanin was not detected in nerve fibers and taste cells. In contrast, some taste cells and a few, fine networks of nerve fibers in the connective tissue were immunoreactive for 5HT; none of the intraepithelial fibers were 5HT-immunoreactive. We suggest that: 1) functionally, 5HT-containing cells and the CGRP-containing nerve fibers may be primarily involved in the neural transmission or its modulation of the taste sensation; and 2) VIP and galanin can be excluded from that group of substances which plays important roles in taste sensation.

Animals↗

PubMed2000

Sucrose-stimulated subsecond transient increase in cGMP level in rat intact circumvallate taste bud cells.

Initial sweet taste transduction is expected to occur in the subsecond time range. We demonstrate a rapid and transient (75-250 ms) increase of cGMP (but not cAMP) level in rat intact circumvallate taste cells after stimulation by sucrose. This rapid increase does not occur in nonsensory epithelial cells. Pretreatment with a nonspecific phosphodiesterase (PDE) inhibitor (IBMX), a specific cAMP-PDE4 inhibitor (denbufylline), or an adenylyl cyclase activator (forskolin) all increased basal cAMP and abolished the sucrose-stimulated cGMP increase at 150 ms. Pretreatment with a soluble guanylyl cyclase inhibitor (1H-[1,2,4]oxadiazolo[4, 3-a]quinoxalin-1-one) reduced, whereas a specific cGMP-PDE inhibitor (zaprinast) abolished, the sucrose-stimulated cGMP increase. It is proposed that cGMP is involved in the initial stage of sugar taste transduction and that cGMP is more significant than cAMP at this stage. Activation of soluble guanylyl cyclase and inhibition of cGMP-PDE may be involved in the transient elevation of cGMP in response to sucrose stimulation. Moreover, it appears that cAMP level must remain low for sucrose to stimulate an increase in cGMP.

Adenylyl Cyclase Inhibitors↗

PubMed1988

Exocytotic release of neurotransmitter substances from nerve endings in the taste buds of rat circumvallate papillae.

Exocytotic release of neurotransmitters from nerve endings was demonstrated ultrastructurally in the taste buds of rat circumvallate papillae by stimulation of high K+ and Ca2+ Ringer perfusion and application of tannic acid-Ringer incubation (TARI) method. Omega-shaped images of large cored vesicles and small clear vesicles, indicating exocytotic release of their contents, were found only in the non-synaptic sites. Occasionally exocytosis occurred at sites facing other nerve fibers. Many coated pits were also seen, which presumably represent membrane retrieval at a later stage of exocytosis. It is likely that the taste buds receive more than one type of innervation.

Animals↗

PubMed1977

The fine structural localization of adenosine triphosphatase activity on the taste bud in the fungiform papillae of the rat.

The localization of Mg++ activated adenosine triphosphatase (ATPase) activity in rat fungiform taste buds was demonstrated by electron microscopic histochemistry. Reaction product was found on the cell membrane of the taste cells, but not within their cytoplasm. Especially strong reaction occurred in the taste pore. Besides, enzymes were observed in axon-Schwann cell and axon-type I cell interspace, but not in the contacts of the nerve fiber and type II cell. The taste bud could well be distinguished from the surrounding epithelium by the existence of the reaction product. ATPase activity was absent at the synaptic portion where type III cells faced nerve fibers. No reaction product was seen along the basal lamina. In fungiform buds, the nerve fibers were frequently shown to make contact with each other, and these sites were devoid of deposits for ATPase.

Adenosine Triphosphatases↗

PubMed1990

Quantitative study of fungiform papillae and taste buds on the cat's tongue.

The number of fungiform papillae has been counted on the tongues of six adult cats and of kittens both at birth and aged 2 and 4 months. Papillae were sampled from different regions of the tongue, and their size and the number of taste buds they contained were determined using histological sections taken parallel to the tongue surface. There were approximately 250 fungiform papillae on the tongues of the adult cats, the papillae were most numerous at the tip of the tongue, and there was no significant difference between the number of papillae on each side. The size of the papillae increased from a mean maximum diameter of 0.28 mm at the tip of the tongue to 0.48 mm at the back; the mean number of taste buds increased correspondingly from 6.9 to 16.6. The kitten tongues had a number and distribution of fungiform papillae similar to that found in the adults. In the neonate, papillae were smaller and contained fewer taste buds; these parameters increased with the corresponding increase in tongue size in the 2- and 4-month-old kittens.

Animals↗

PubMed1998

Occurrence of ENaC subunit mRNA and immunocytochemistry of the channel subunits in taste buds of the rat vallate papilla.

Epithelial Na+ channels (ENaCs) are thought to mediate the amiloride-blockable salt taste. The rat vallate papilla does not contribute to amiloride-blockable salt taste, yet the presence of ENaC-mRNA in this tissue has been reported. Is ENaC actually contained in the taste cells, or is it merely present in the supporting lingual epithelium? To avoid contamination by ENaC contained in the lingual epithelium, we physically isolated taste buds from the vallate papilla and used mRNA purification followed by reverse transcriptase polymerase chain reaction (RT-PCR) to investigate the presence of ENaC-type message in the isolated buds. mRNA of alpha-, beta- and gamma-subunits was detected, the alpha-signal being the strongest. These results provide first molecular evidence for the presence of ENaC subunits in taste buds that were isolated from the posterior tongue and were free of epithelial contamination. In addition, we used immunohistochemistry to show ENaC-like reactivity in posterior tongue taste cells. Interestingly, the immunoreactivity was not predominantly apical but was intracellular and close to or at the basolateral membrane. The function of basolateral ENaC-type channels is unknown. Possibly, the channels are normally closed or of very low open probability in the resting state.

Animals↗

PubMed1978

The reversible effect of colchicine on the taste bud cells of the central circumvallate papilla in the rat.

It is believed that differentiation and maintenance of taste buds in vertebrates is dependent on the trophic function of their sensory nerve supply. In the present work, colchicine was injected into the circumvallate papilla of the rat. This produced a reversible blockade of neuroplasmic transport and disappearance of taste buds. Colchicine inhibited the further differentiation of bud cells, but apparently did not change the life cycle of the cells present already at the time of injection. It is speculated that the neurotrophic factors in this particular cell system are effective to induce cell differentiation only.

Acetylcholinesterase↗

PubMed2003

Peptides that regulate food intake: somatostatin alters intake of amino acid-imbalanced diets and taste buds of tongue in rats.

The present studies were designed to evaluate a potential dose-dependent effect of somatostatin (SRIF) administered peripherally on intake of either a low-protein basal diet or threonine-imbalanced diet (THR-IMB), on body weight gain (DeltaBW), gut motility, and on the histology of taste buds in rats. SRIF administration had a dual effect related to its concentration, increasing the intake of THR-IMB diet at low concentration and decreasing THR-IMB diet at high concentration. During the light phase, SRIF treatment increased the intake of THR-IMB diet, suggesting that the usual anorectic effect induced by intake of THR-IMB diet was attenuated. High-dosage SRIF decreases gastrointestinal motility, which, in turn, can decrease food intake and DeltaBW. The combination of THR-IMB diet regimen and SRIF treatment also induced significant modifications on the taste buds of the tongue. The feeding response to an amino acid-imbalanced diet includes a learned aversion to the diet, and animals may use taste in establishing that aversion. Modifications of taste buds of SRIF-treated rats eating THR-IMB diet might explain the increase of imbalanced diet intake if treated rats perceive this food as less aversive.

Amino Acids↗

PubMed1987

Morphological evidence of innervation of taste buds of rat fungiform papillae after acute X-ray irradiation.

An acute dose of 2000 Roentgens (R) of x-ray was delivered to the head and neck area of Sprague-Dawley rats. Groups of rats were sacrificed at 0, 3, 7, 14, 21 and 30 days after x-ray irradiation. Both general nerve staining and localization of cholinergic nerves by special staining of fungiform papillae were performed. No apparent change in number and distribution of nerve fibres were observed light microscopically within the fungiform papillae containing normal, degenerating and regenerating taste buds. Similarly, cholinesterase activity was present in all control and experimental groups. These preliminary findings do not support the theory that taste bud degeneration is due to x-ray irradiation causing damage to related nerve fibres. A theoretical model of taste bud degeneration after acute x-ray irradiation is proposed.

Animals↗

PubMed1990

Morphological changes of taste buds and fungiform papillae following long-term neurectomy.

Long-term neurectomy of chorda tympani-lingual nerves results in a complete disappearance of taste buds from rabbit fungiform papillae. This supports the view that taste buds of mammalian fungiform papillae are neurally dependent. Furthermore, the covering epithelium of denervated fungiform papillae develops a characteristic keratinization pattern corresponding to that of filiform papillae.

Animals↗

PubMed2002

Time course of morphological alterations of fungiform papillae and taste buds following chorda tympani transection in neonatal rats.

The time course of structural changes in fungiform papillae was analyzed in rats that received unilateral chorda tympani nerve transection at 10 days of age. Morphological differences between intact and denervated sides of the tongue were first observed at 8 days postsection, with an increase in the number of fungiform papillae that did not have a pore. In addition, the first papilla with a filiform-like appearance was noted on the denervated side at 8 days postsectioning. By 11 days after surgery, the total number of papillae and the number of papillae with a pore were significantly lower on the transected side of the tongue as compared to the intact side. At 50 days postsection, there was an average of 70.5 fungiform papillae on the intact side and a mean of only 20.8 fungiform papillae the denervated side. Of those few remaining papillae on the cut side, an average of 13.5 papillae were categorized as filiform-like, while no filiform-like papillae occurred on the intact side. Significant reduction in taste bud volume was noted at 4 days posttransection and further decrements in taste bud volume were noted at 8 and 30 days postsection. Electron microscopy of the lingual branch of the trigeminal nerve from adult rats that received neonatal chorda tympani transection showed normal numbers of both myelinated and unmyelinated fibers. Thus, in addition to the well-characterized dependence of taste bud maintenance on the chorda tympani nerve, the present study shows an additional role of the chorda tympani nerve in papilla maintenance during early postnatal development.

Animals↗

PubMed1999

Subepithelial nerve plexus (with ganglion cells) associated with taste buds.

OBJECTIVE: The purpose of this investigation was to confirm the presence of subepithelial nerve plexuses associated with taste buds in the human tongue and to study the histomorphologic features of each plexus. STUDY DESIGN: Through use of a light microscope, several hundred microslides representing biopsies of the human tongue were reviewed so that the histomorphologic character of subepithelial nerve plexuses could be detected and studied. Tissue sections were stained with hematoxylin-erythrosin, Bodian, and Masson's trichrome, as well as with immunohistochemical stains for neuron-specific enolase and S-100 protein. RESULTS: Twelve examples of the subepithelial nerve plexus, many with mature ganglion cells, were selected for microscopic evaluation. The plexuses were quite small, ranging from 1 to 3 millimeters in diameter. With one exception, each plexus was an incidental finding in a biopsy of a definitive soft tissue lesion, such as fibroma, papilloma, granular cell tumor, lymphoepithelial cyst, lingual tonsil, or foliate papilla. Ganglion cells, 1 to 5 in number and confirmed by neuron-specific enolase and S-100 protein, were observed in 9 of the cases. CONCLUSIONS: The subepithelial (subgemmal) nerve plexus is a tortuous neural proliferation associated with the taste buds of the human tongue, with ganglion cells and intergemmal/intragemmal branches. When hyperplastic, it should be recognized as such and not diagnosed as a neoplastic process--eg, a ganglioneuroma, neurofibroma, syndrome-associated neuroma, or traumatic neuroma.

Adult↗

PubMed1986

Dividing type II cell in rabbit taste bud.

Examination of rabbit foliate papillae by electron microscopy revealed for the first time the existence of a dividing cell within a taste bud. The ultrastructure of this cell was in keeping with that of type II cells of the sort located in the center of taste buds. Whether this cell is capable of differentiating into other cell types is still unclear.

Animals↗

PubMed1999

Expression of the neural cell adhesion molecule in mouse taste buds after denervation.

Expression of the neural cell adhesion molecule (NCAM) was studied by use of an immunocytochemical technique in the taste buds of mouse circumvallate papillae after bilateral transection of the glossopharyngeal nerves. In untreated mice, innervated type-III cells reacted with anti-NCAM antibody. After denervation the taste buds gradually decreased in number and size, and were practically absent within 11 days. In parallel, NCAM-reactive cells decreased at 3 and 8 days after surgery and at 11 days they were no longer found. Three days after denervation, synaptic contacts between type-III cells and nerve fibres were not found because of the disappearance of nerve fibres. However, remaining type-III cells, characterized with dense-cored vesicles, still maintained NCAM expression on their plasma membrane until day 8.

Animals↗