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PubMed1998

Increase in inositol 1,4,5-triphosphate levels of the fungiform papilla in response to saccharin and bitter substances in mice.

Inositol 1,4,5-trisphosphate (IP3) levels of the mouse fungiform papilla and nonsensory epithelial tissue in response to various taste stimuli were measured by use of a competitive protein binding assay. Stimulation of the tongue with 20 mM saccharin induced a significant increase in IP3 levels of the fungiform papillae without affecting those of the nonsensory epithelial tissue, whereas stimulations with 20 mM quinine and denatonium raised IP3 levels in not only the fungiform papilla but slightly also nonsensory epithelial tissue. No such increases in IP3 levels were observed to lower concentrations of saccharin, denatonium and quinine, and other basic taste stimuli, such as 0.5 M sucrose, 0.1 M NaCl and 10 mM HCl. Pretreatment of the tongue with pronase, a proteolytic enzyme which inhibits sweet responses, completely eliminated the increase in IP3 levels induced by saccharin, but not those induced by quinine or denatonium. These results suggest that an IP3 pathway in taste cells of the mouse fungiform taste bud is involved in the transduction not only for denatonium and quinine, but also for 20 mM saccharin. The increase of IP3 induced by saccharin, but not by denatonium and quinine, may occur through pronase-sensitive membrane components.

Animals↗
PubMed1976

Gustatory pathways in the bullhead catfish. 1. Connections of the anterior ganglion.

The central projections of the external gustatory system in bullhead catfish were examined using orthograde degeneration and retrograde transport of horseradish peroxidase (HRP) techniques. Both large and small cells were observed in the anterior ganglion which contains a mixture of elements from the trigeminal, facial and anterior lateral line nerves. Some of the large cells on the lateral margin of the ganglion were found to belong to the lateral line system. No separation of trigeminal and facial nerve connections could be made. Using HRP, the relation between the barbels and specific ganglion regions was determined. The dorsalmost portion of the ganglion received recurrens nerve inputs (from taste buds on the trunk); the rostromedial portion of the ganglion, from the maxillary and mandibular barbel nerves. The facial lobe (similar to part of the n. solitarius) was found to be divided into lobules by fascicles of nerve fibers. The lateral lobule received input only from the dorsal-most part of the ganglion (recurrens nerve: trunk receptors); the intermediate lobule from the rostro-lateral part of the ganglion (nasal barbel); and the medial lobule from the ventral areas of the ganglion (maxillary and mandibular barbels). Thus a topographical relationship exists between the different taste receptor groups and their locus of representation in the facial lobe. The trunk receptors connect to the lateral lobule; the nasal barbel receptors to the intermediate lobule, and the maxillo-mandibular receptors to the medial lobule.

Afferent Pathways↗
PubMed2006

Association of Shh and Ptc with keratin localization in the initiation of the formation of circumvallate papilla and von Ebner's gland.

The development of gustatory papillae in mammalian embryos requires the coordination of a series of morphological events, such as proliferation, differentiation and innervation. In mice, the circumvallate papilla (CVP) is a specialized structure that develops in a characteristic spatial and temporal pattern in the posterior region of the tongue dorsal surface. The distinct expression patterns of Shh and Ptc, which play important roles in the development of other epithelial appendages, have been localized in the trench wall that gives rise to von Ebner's gland (VEG). To define the cellular mechanisms responsible for morphogenesis and differentiation during early development of CVP and VEG, the localization patterns of keratins (cytokeratins) K7, K8, K18, K19, K14 and connexin-43, which are dependent on Shh expression in other developmental systems, have been examined in detail. The distinct localization of keratins K7, K8, K18, K19, K14 and connexin-43 in the epithelium giving rise to the CVP and VEG suggests that cytodifferentiation is established prior to morphological changes. Interestingly, the localization of proliferating cell nuclear antigen, a marker for cell proliferation, is similar to that of Shh. An understanding of the regulatory roles of cell-cell interactions and signalling molecules in orchestrating a mutual network will bring us nearer to defining the molecular and cellular mechanisms underlying morphogenesis in mammalian taste bud development.

Animals↗
PubMed1980

Histochemical distribution and functional role of phosphatases, cholinesterase and succinic dehydrogenase in the gustatory epithelium and lingual glands of the rat.

The distribution pattern of cholinesterase, alkaline and acid phosphatases, adenosine triphosphatase and succinic dehydrogenase in the various cellular constituents of the gustatory epithelium, taste buds and lingual glands of the rat was subjected to a detailed histochemical study. An attempt was made to explain the structural and functional relationship on the basis of the distribution of the enzymes in these regions of the rat tongue.

Acetylcholinesterase↗
PubMed2001

Machado-Joseph disease associated with an absence of fungiform papillae on the tongue.

The authors report the case of a family with Machado-Joseph disease (MJD) associated with sensory and autonomic disturbances-particularly the absence of fungiform papillae on the tongue and taste buds. Sural nerve biopsy showed a loss of myelinated fibers. Autonomic function tests showed bladder-bowel dysfunction, hypohidrosis, and low coefficients of variation of R-R intervals on electrocardiogram. These findings may be another possible variant or previously unrecognized symptoms in MJD.

Adult↗
PubMed1998

Solitary chemosensory cells in the developing chemoreceptorial epithelium of the vallate papilla.

The solitary chemosensory cells are considered typical of aquatic vertebrates and have never been described in the oral cavity of terrestrial vertebrates. We describe elements with ultrastructural characteristics of the solitary chemosensory cell in the gustatory epithelium of rats in the first week of extrauterine life. These elements appeared isolated, located among keratinocytes, and wrapped by glial-like elements. They showed a bipolar shape with a round cell body, a thin apical process, and a thicker basal one. Nerve fibers contacted the cell body and the processes. The cells showed small dense granules mainly located near nerve contacts. Small bundles of tonofilaments were visible in the perinuclear cytoplasm. Similar elements were not found in rats after the first week of extrauterine life. The present study demonstrates in a mammal that the development of taste buds is preceded by the presence of epithelial elements with ultrastructural characteristics of the solitary chemosensory cells described in lower vertebrates. This finding suggests that the oral chemoreception in the suckling rats may be mediated by three different pathways (i.e., gustatory system, common chemical sense, and solitary chemosensory cell system).

Animals↗
PubMedDate not supplied

Preneural phase of taste.

The preneural phase of taste has been studied, describing first the pit region of taste buds and its dynamics. The biochemical regulation of the preneural phase is then analyzed, with emphasis on thiol and metal (certain metals) interactions: the first inhibit and the second facilitate. The equilibrium between thiol and metal ions regulates the flux of tastants, probably at the level of the microvilli membrane. The hypothetical role of the pore and dense substance is considered.

Animals↗
PubMed1996

Vallate, foliate and fungiform human papillae gustatory cells. An immunocytochemical and ultrastructural study.

We studied the classifications, topographic distribution and cellular lines of taste bud components in vallate, foliate and fungiform papillae of young, mature and old men with light microscopy, SEM, and TEM. By identifying ultrastructural and immunocytochemical characteristics, three distinct sensorial cells were identified, along with a few basal cells: dark type I cells, light type II cells and light type III cells. These cells extend from the epithelial basal lamina to the gustatory canal, where their apical cytoplasm sends long microvillous expansions. Excluding those of the fungiform papillae-which never go beyond the lower third of the gustatory canal, and are always void of dense substance-the microvillous expansions continue to the external border of the taste pore. Dark type I cells are rich in free ribosomes, tubular RER and large dense granules. Light type II cells with scarce ribosomes and RER, do not have enough peculiar ultrastructural characteristics to be considered effector or phagocyte elements. Light type III cells are characterizes by dense core vesicles whose peculiar ultrastructural characteristics in the foliate and vallate papillae, should be considered a consequence of different functional phases. After comparative evaluation the authors hypothesized on the functional value of some ultrastructural aspects and on the dense core vesicles which are immunoreactive to 5-HT. They observed that all gustatory cells are involved in taste transduction based on behaviours caused by microvilli in the gustatory canal and gustatory cell relationships with nerve endings. Moreover the authors noted that age does not seem to influence taste perception.

Adult↗
PubMed1979

Structure of the soft palate and composition of the oral mucous membrane in monkeys.

The soft palate of monkeys (M. irus, mulatta, fasciculata; 2.3 +/- 0.4 kg in weight) was studied morphologically and stereologically. After fixation by perfusion, the tissue was disected free, divided in halves and the halves into 5 segments each, and processed for light, transmission- and scanning electron microscopy. Morphometric techniques and a newly developed computer program for automatic data processing (Mumana) were employed in order to estimate, at the light microscopic level, the volumetric composition of the oral soft palate mucosa. The latter showed a different composition in anterior and uvular segments, without significant differences between male and female animals, but with slight changes possibly due to age. The main constituents of the oral soft palate mucosa were glandular and connective tissue, and lymph follicles, the latter being associated with the glandular duct system. The epithelial lining of the oral and nasal aspects were described, and taste buds embedded in island of orthokeratinizing stratified epithelium were demonstrated. The association between lymph follicles and the glandular duct system was discussed in relation to similar structures in man, and in relation to the hypothesis that they are concerned in local antigen recognition.

Age Factors↗
PubMed1978

Dental management of the irradiated patient.

There is an increasing number of patients receiving radiation therapy for oral malignancies. In many malignant tumors, radiation is often the treatment of choice, while in others it may be used in conjunction with surgery or chemotherapy. There are inherent dental and oral problems associated with radiation therapy. It is the purpose of this paper to deal briefly with the physical principles and the biological basis of radiation therapy. In addition, the specific radiation effects on oral mucous membranes, taste buds, salivary glands, bone, the periodontium and teeth will be discussed. Radiation complications in edentulous patients, and in particular the problems of wearing dentures in such patients will be evaluated. An approach to the problem of dental extractions and other dental treatments in the pre- and post-irradiated patient is suggested.

Bone and Bones↗
PubMed1987

Ultrastructure of apical specializations of taste cells in the mudpuppy, Necturus maculosus.

The first interaction of taste stimuli with lingual chemoreceptors occurs on the apical membrane of taste cells, since only that portion is exposed to the oral cavity. To gain better insight into this interaction, we examined the pore region of taste buds in Necturus maculosus with scanning electron microscopy (SEM), transmission electron microscopy, and high-voltage electron microscopy. SEM of the pore reveals a patchwork distribution of three morphologically distinct types of apical specializations: long and branched (LB) microvilli, short and unbranched (SU) microvilli, and bundles of stereocilia. As demonstrated in thin and thick sections, LB microvilli are specializations of dark cells, SU microvilli are the apical specializations of light cells, and stereocilia arise from a cell that has the cytoplasmic markers characteristic of light cells. When left in place, the pore mucus completely covers the SU microvilli and partially covers the LB microvilli. However, stereocilia project above the surface and thus are highly exposed to taste stimuli in the oral cavity. These three morphologically distinct types of apical specializations may reveal functional differences among taste cells. The initial interaction between chemical stimulus and taste cell, and possibly chemoreceptor specificity itself, may be influenced by the morphology of the apical ending.

Animals↗
PubMed1997

Ultrastructure and immunocytochemistry of gustatory cells in man.

Ultrastructural and immunocytochemical features of the taste buds of the vallate, foliate and fungiform papillae in young, adult and elderly men, revealed three types of sensorial cells: dark type I cells rich in free ribosomes and large dense granules, light type II cells with large amorphous areas of cytoplasmic matrix and light type III cells with a dense core immunoreactive for 5-HT. All sensorial cells send microvillous protrusions of the apical cytoplasm into the gustative canal and make contact with nerve endings. After comparative studies, we made several hypothetical propositions on the functional value of microvillous protrusions, as well as on the apical and basal dense core vesicles of the foliate and vallate papillae. Moreover, we think that sensorial cells are implicated in taste transduction and that subject age does not seem to play any role in taste perception.

Adult↗
PubMed2004

Neurochemistry of the gustatory subgemmal plexus.

Nerve fibers present in the basal plexus of the vallate papilla of the rat tongue were analyzed using cytochemical, immunocytochemical and ultrastructural methods to investigate whether the subgemmal plexus is subdivided into neurochemical compartments and to provide a clear definition of the reciprocal spatial relationships between nitrergic, peptidergic and acetylesterase positive structures. Several neuronal fibers were detected under the chemoreceptorial epithelium. Some of these fibers were in contact with the taste buds and in some cases neuronal projections were also present between the buds or inside them; some others fibers were present below this layer but in a more peripheral area. Antibodies against CGRP, SP and CCK stained fibers just below the chemoreceptorial epithelium, whereas fibers more distally located were immunolabeled by anti VIP, NOS-1 and NF-200 antibodies. Some double staining experiments were conducted using confocal microscopy. Other sections were processed cytochemically for AChE and subsequently for NADPH-d in colocalization experiments. All the data obtained using these techniques confirmed the results obtained with single immunostaining, as did the ultrastructural results. In conclusion, the present work demonstrates that the subgemmal plexus is a bilayered structure, suggesting that the complex relationship between the two layers plays a pivotal role in taste and in the control of processes ancillary to taste, such as control of vascular or secretory mechanisms.

Acetylcholine↗
PubMed1992

Calretinin-immunoreactivity in the oro-facial and pharyngeal regions of the rat.

Calretinin-immunoreactivity (CR-ir) was examined in the rat oro-facial and pharyngeal tissues using an immunofluorescence method. CR-ir was distributed in the entire size range of trigeminal ganglion neurons. CR-ir was also observed in nerve fibers surrounding neuronal cell bodies in autonomic ganglia, and in nerve endings in the lip, tongue, incisal papilla, soft palate, pharynx and epiglottis. CR-immunoreactive nerve endings were all in close proximity to the epithelium, and classified into 2 types; simple (free nerve ending) and taste-bud-related types. In the salivary gland, positive nerve fibers were seen around large excretory ducts. The present study indicates that viscerosensory (probably including gustatory) nerve fibers innervating the oral and pharyngeal tissues contain CR, while somotosensory nerve fibers innervating the facial skin are devoid of CR.

Animals↗
PubMedDate not supplied

Taste cell function. Structural and biochemical implications.

Maintenance of constant relations between receptor cell types and branching from a single gustatory nerve fiber during normal cell turnover and regeneration requires cell-cell recognition likely mediated by timed expression of molecules at surfaces of taste bud cells, nerve endings, and in extracellular matrix. These processes assure stability of gustatory quality representation during intragemmal remodeling. Coincidentally, features of gemmal cell lifespan, including elongation, differentiation, and migration prior to apoptosis, must also be orchestrated by molecular signals. This article reviews the potential roles played by a variety of molecular markers for some relevant classes of proteins, peptides, and enzymes, which were presumed to be important for carrying out these gustatory cellular functions.

Animals↗
PubMed1994

Scanning electron microscopy of the wild boar and pig lingual papillae.

Lingual papillae of wild boar and pig were studied by means of scanning electron microscopy (SEM). Vallate papillae appear with the typical circumvallate morphology. Their papillary bodies show conical or fungiform-like and spicule-like pseudopapillae in both animals. Taste pores were seen in the papillary grooves. Microplicae or pits are visible at high magnification. In pig and wild boar similar foliate papillae were observed. Pig has less but wider leaves than wild boar. Taste pores on papillary walls were viewed. At high magnification microplicae were seen. Morphologically, fungiform papillae correspond with their denomination. Taste pores open onto the upper surface and they are easily identifiable by SEM. The rostral and lateral regions contain the major number of fungiform papillae. The lateral papillae of wild boar and pig show a high number of pores per papilla. These regions must be considered important in taste sensitivity. Lateral papillae in both animals could provide a source of taste buds for study. In both animals the fungiform papillary epithelium showed a pitted appearance as a consequence of keratinization by food environmental stress. The filiform papillae can be both simple and compound (with body and hairs). Large conical papillae are located caudally and curved in the same direction. Filiform and conical papillae have a function in food mastication, handling and deglutition.

Animals↗
PubMed2005

Inhibition of voltage-gated potassium currents by gambierol in mouse taste cells.

Ciguatera is a food poisoning caused by toxins of Gambierdiscus toxicus, a marine dinoflagellate. The neurological features of this intoxication include sensory abnormalities, such as paraesthesia, heightened nociperception, and also taste alterations. Here, we have evaluated the effect of gambierol, one of the possible ciguatera toxins, on the voltage-gated ion currents in taste cells. Taste cells are excitable cells endowed with voltage-gated Na+, K+, and Cl- currents (I(Na), I(K), and I(Cl), respectively). By applying the patch-clamp technique to single cells in isolated taste buds obtained from the mouse vallate papilla, we have recorded such currents and determined the effect of bath-applied gambierol. We found that this toxin markedly inhibited I(K) in the nanomolar range (IC50 of 1.8 nM), whereas it showed no significant effect on I(Na) or I(Cl) even at high concentration (1 microM). The block of I(K) was irreversible even after a 50-min wash. In addition to affecting the current amplitude, we found that gambierol significantly altered both the activation and inactivation processes of I(K). In conclusion, unlike other toxins involved in ciguatera, such as ciguatoxins, which affect the functioning of voltage-gated sodium channels, the preferred molecular target of gambierol is the voltage-gated potassium channel, at least in taste cells. Voltage-gated potassium currents play an important role in the generation of the firing pattern during chemotransduction. Thus, gambierol may alter action potential discharge in taste cells and this could be associated with the taste alterations reported in the clinical literature.

Action Potentials↗
PubMedDate not supplied

Embryonic development of the head and neck: part 4, organs of special sense.

A synopsis of the embryonic development of the eye, the ear, and the olfactory organ and taste buds is presented. The eye is discussed in terms of the sensory and nonsensory protions of the eyeball and of such associated structures as the extrinsic eye muscles, eyelids, conjuctiva, and lacrimal apparatus. The embryology of the internal, middle, and external ear is reviewed, as well as positional changes of both the eye and ear relative to other sturctures of the head and neck. Various congenital defects affecting the eye and ear are also discussed.

Ear↗