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PubMed1997

Effect of denervation on lymphocytes and dendritic cells in the rat circumvallate and foliate papillae.

The distribution of dendritic (Langerhans) cells and lymphocytes in rat circumvallate and foliate papillae was examined by immunohistochemistry and electron microscopy. Light microscopic immunohistochemistry using anti-OX62 antibody, which recognizes both gammadelta T lymphocytes and dendritic cells, showed that many OX62-immunoreactive cells had invaded into the trench wall epithelium from the connective tissue at 6 days after sectioning of the glossopharyngeal nerves. The presence of OX62-immunoreactive cells in the epithelium was observed up to 17 days after the denervation, by which time the taste buds had disappeared from the trench wall. The OX62-positive cells were again observed in the connective tissue at 24 and 40 days when taste buds regenerated. The local circulation of OX62-positive cells between the epithelium and connective tissue is suggested. Most of the OX62-positive-cells in the epithelium of circumvallate and foliate papillae were suggested to be gammadelta T cells, since they were round or spindle-shaped. Electron micrographs of OX62-positive cells also indicated that they were lymphocytes. Furthermore, they expressed CD3 but lacked CD4 and CD8 surface markers. A few dendritic cells, which reacted with anti-OX6 antibody, were observed in the circumvallate and foliate papillae in the control and denervated animals, and they were irregular in shape with long cytoplasmic processes. Electron micrographs taken at 6 days showed that the dendritic cells, which were characterized by the presence of Birbeck granules in the cytoplasm, were in contact with lymphocytes. The finding suggests that gammadelta T lymphocytes and dendritic cells in the rat circumvallate and foliate papillae interact with each other to respond to changes such as the presence or absence of taste buds in the epithelium.

Animals↗
PubMed1994

PTC/PROP tasting: anatomy, psychophysics, and sex effects.

Taste worlds of humans vary because of taste blindness to phenylthiocarbamide (PTC) and its chemical relative, 6-n-propylthiouracil (PROP). We review early PTC studies and apply modern statistical analyses to show that a higher frequency of women tasted PTC crystals, and were tasters (threshold classification). In our laboratory, scaling of PROP bitterness led to the identification of a subset of tasters (supertasters) who rate PROP as intensely bitter. Supertasters also perceive stronger tastes from a variety of bitter and sweet substances, and perceive more burn from oral irritants (alcohol and capsaicin). The density of taste receptors on the anterior tongue (fungiform papillae, taste buds) correlate significantly with perceived bitterness of PROP and support the supertaster concept. Psychophysical data from studies in our laboratory also show a sex effect; women are supertasters more frequently. The anatomical data also support the sex difference; women have more fungiform papillae and more taste buds. Future investigations of PTC/PROP tasting and food behaviors should include scaling to identify supertasters and separate sex effects.

Female↗
PubMed1997

Scanning electron microscopical studies of developing gustatory papillae in humans.

Development and morphological changes of human gustatory papillae during postovulatory weeks 6-15 have been studied using scanning and transmission electron microscopy. The first papilla of the tongue appears around postovulatory week 6 in its caudal midline near the foramen caecum. In contrast, the dorsal epithelium of the anterior part of the tongue shows only small hillock- or papilla-like elevations from week 6 on, which comprise an aggregation of 5-20 epithelial cells. From week 7 on, most prominent fungiform papillae develop near the median sulcus and at the margins of the anterior part of the tongue. At their tops, the first primitive taste pores are found around week 10; these are often covered with processes of adjacent epithelial cells. Most pores, however, develop around weeks 14-15. The maturation of taste buds does not coincide with the appearance of taste pores, since taste bud cells are not fully differentiated in the observed period of time. Fungiform papillae are developed before filiform papillae, which do not occur within the first 15 weeks of gestation. Fungiform papillae tend to grow between weeks 8 and 15 of gestation, whereas the size of vallate papillae seems to be constant during this period.

Humans↗
PubMed2006

Group IIA phospholipase A(2) is coexpressed with SNAP-25 in mature taste receptor cells of rat circumvallate papillae.

The taste buds are composed of heterogeneous cell populations with diverse properties and at different stages of maturity. It is important to define the relationships between cell properties and cell maturity to understand the molecular events involved in intracellular taste signaling. In the present study, in situ hybridization analysis indicated that group IIA phospholipase A(2) (PLA(2)-IIA) is expressed in a subset of taste bud cells. Immunohistochemical studies showed that PLA(2)-IIA was expressed in a subset of cells expressing phospholipase Cbeta2, a molecule essential for taste signaling in taste receptor cells, and also that some PLA(2)-IIA-positive cells expressed gustducin (Ggust), a bitter-taste-signaling molecule. Although PLA(2)-IIA and Ggust were expressed at similar frequencies in taste buds, bromodeoxyuridine (BrdU) chase experiments indicated that the expression of Ggust began 2 days after BrdU injection, whereas the expression of PLA(2)-IIA commenced after 4 days. In addition, PLA(2)-IIA was coexpressed with SNAP-25, a synaptosomal-associated protein. These results indicated that PLA(2)-IIA is expressed in mature taste receptor cells that possess exocytotic machinery.

Animals↗
PubMed1992

Calcium-binding proteins in chemoreceptors of Xenopus laevis.

Calcium-binding proteins were investigated immunohistochemically in chemo-receptors of the olfactory epithelium and taste buds of the clawed frog, Xenopus laevis. Calmodulin-, S-100- and calbindin-immunoreactive material were found in sensory cells of the olfactory epithelium; however, parvalbumin-like material was absent in these cells. Taste buds of the palate showed calmodulin-, S-100- and parvalbumin-immunoreactive material in sensory cells, while calbindin-immunoreactive material in supporting cells. Merkel cells, surrounding the base of the taste buds in a ring-like manner, exhibited calmodulin- and S-100-immunoreactive material.

Animals↗
PubMed2000

An in vitro model for the study of taste papillae morphogenesis using branchial arch explants.

It is generally accepted that innervation is required for the maintenance of taste papillae and taste buds, but it is not entirely clear what role, if any, innervation plays in papillae and taste bud formation. Events in taste papillae formation and differentiation take place almost entirely in utero and, therefore, the study of the role of innervation in these events requires a suitable in vitro model. In the past, investigators have made use of various culture techniques to study mammalian taste papillae development in vitro and the role of innervation in this process with varying success. All of these models examined papillae development in isolated tongue or tongue fragments and have lacked the ability to manipulate the innervation of developing taste papillae in these explants. We have established a protocol for an in vitro model of taste papillae morphogenesis using branchial arch explants and roller tube culture methodology. Our results demonstrate that this model supports the morphogenesis of the circumvallate papilla with an integrated nerve. In addition, the use of branchial arch explants allows the inclusion or exclusion of geniculate and petrosal ganglia to examine directly the effects of the presence or absence of innervation on papillae formation and maintenance.

Animals↗
PubMedDate not supplied

Comparative anatomical and ultrastructural features of the sensory papillae in the tongue of hibernating bats.

The papillae of the tongue dorsal surface of the insectivorous, hibernating bats (Vespertilionidae and Rhinolophidae), whose function is mainly sensorial, consist of two circumvallate papillae, two foliate papillae, located at the side edges at the glossopalatine arch, and numerous fungiform papillae. The circumvallate and foliate papillae are characterized not only by their position, but also by presence of several taste buds which open through the external orifice of the gustatory canal into the cavity of the vallum, or furrow, which divides the two folds of the lingual mucosa. The fungiform papillae (extremely numerous on the whole dorsal surface) are characterized by an unusual arrangement (along 3 oblique lines on the anterior two-thirds and predominantly on the middle line of the tongue body) and by the presence of only one to three taste buds which open on the heavily keratinized dorsal epithelial surface. The taste buds are made up of sensory cells with a light or dark matrix; their apical cytoplasmic expansions are not found beyond the middle part of the gustatory canal, in contrast with the circumvallate and foliate papillae which protrude from the orifice of the gustatory pore. Comparisons with the papillae of other types of bats and Insectivora and evaluations of the morphological characteristics and their functional values (unusual areas of distribution of the papillae, apical cytoplasmic expansions and behaviour of microfolds observed under SEM) have been made in different environmental conditions and nutritional habits, with attention to the mechanical events in the course of feeding.

Animals↗
PubMed1988

Gustatory responsiveness of fibers in the hamster glossopharyngeal nerve.

1. Mammalian taste receptors are distributed within separate subpopulations, innervated by branches of cranial nerves VII, IX, and X. Most gustatory electrophysiology has focused on input from the fungiform papillae on the anterior portion of the tongue, carried by the chorda tympani branch of the VIIth nerve. However, only a small percentage of the taste buds are located in the fungiform papillae (approximately 18% in the hamster). There have been no studies on the hamster's IXth nerve, which innervates greater than 50% of its taste buds, and most other studies of IXth nerve function have employed only whole-nerve recording. 2. Action potentials were recorded from 83 individual fibers in the IXth nerve of the hamster. Stimuli were five concentrations each of sucrose, NaCl, HCl, and quinine hydrochloride (QHCl), all presented to every fiber at 37 degrees C. Responses were quantified as the number of impulses in 10 s minus the preceding 10 s of spontaneous activity. 3. Across these concentration series, HCl and QHCl were by far the most excitatory stimuli, with mean responses across all cells three to four times greater than those evoked by sucrose or NaCl. The order of effectiveness of the stimuli was H greater than Q much greater than N greater than S. 4. Of the 83 fibers, 56 were stimulated via the foliate papillae and 27 via the single vallate papilla. No fibers responded to both of these fields. There were generally no differences in the sensitivity of these two subpopulations of taste buds, except that QHCl was more effective when applied to the foliates. 5. A "total" response measure was derived by summing the excitatory responses to each stimulus across the entire concentration series. The fibers were then classified according to the best total response, resulting in 52 HCl-, 19 QHCl-, 8 sucrose- and 4 NaCl-best cells. Considering the slope of the concentration-response functions as a criterion for classification produced very similar results. The fiber classification varied somewhat with concentration, with more fibers categorized as HCl- and QHCl-best at the higher concentration levels. 6. Breadth of responsiveness was measured using the equation developed by Smith and Travers. At the concentrations used to examine hamster chorda tympani fibers, IXth nerve fibers were not very responsive and were quite narrowly tuned to the four taste qualities. At higher concentrations the fibers became more broadly responsive across the four stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1996

Measurement of membrane potential and [Ca2+]i in cell ensembles: application to the study of glutamate taste in mice.

We have studied the spectral properties of the voltage-sensitive dye, 1-(3-sulfonatopropyl)-4-[beta [2-(di-n-octylamino)-6-naphtyl]vinyl] pyridinium betaine (di-8-ANEPPS), and the Ca(2+)-sensitive dye, fura-2, in azolectin liposomes and in isolated taste buds from mouse. We find that the fluorescence excitation spectra of di-8-ANEPPS and fura-2 are largely nonoverlapping, allowing alternate ratio measurements of membrane potential and intracellular calcium ([Ca2+]i). There is a small spillover of di-8-ANEPPS fluorescence at the excitation wavelengths used for fura-2 (340 and 360 nm). However, voltage-induced changes in the fluorescence of di-8-ANEPPS, excited at the fura-2 wavelengths, are small. In addition, di-8-ANEPPS fluorescence is localized to the membrane, whereas fura-2 fluorescence is distributed throughout the cytoplasm. Because of this, the effect of spillover of di-8-ANEPPS fluorescence in the [Ca2+]i estimate is < 1%, under the appropriate conditions. We have applied this method to study of the responses of multiple taste cells within isolated taste buds. We show that membrane potential and [Ca2+]i can be measured alternately in isolated taste buds from mouse. Stimulation with glutamate and glutamate analogs indicates that taste cells express both metabotropic and ionotropic receptors. The data suggest that the receptors responding to 2-amino-4-phosphonobutyrate (L-AP4), presumably metabotropic L-glutamate receptors, do not mediate excitatory glutamate taste responses.

Animals↗
PubMed2005

Liposome-mediated transfection of mature taste cells.

The introduction and expression of exogenous DNA in neurons is valuable for analyzing a range of cellular and molecular processes in the periphery, e.g., the roles of transduction-related proteins, the impact of growth factors on development and differentiation, and the function of promoters specific to cell type. However, sensory receptor cells, particularly chemosensory cells, have been difficult to transfect. We have successfully introduced plasmids expressing green and Discosoma Red fluorescent proteins (GFP and DsRed) into rat taste buds in primary culture. Transfection efficiency increased when delaminated taste epithelium was redigested with fresh protease, suggesting that a protective barrier of extracellular matrix surrounding taste cells may normally be present. Because taste buds are heterogeneous aggregates of cells, we used alpha-gustducin, neuronal cell adhesion molecule (NCAM), and neuronal ubiquitin carboxyl terminal hydrolase (PGP9.5), markers for defined subsets of mature taste cells, to demonstrate that liposome-mediated transfection targets multiple taste cell types. After testing eight commercially available lipids, we identified one, Transfast, that is most effective on taste cells. We also demonstrate the effectiveness of two common "promiscuous" promoters and one promoter that taste cells use endogenously. These studies should permit ex vivo strategies for studying development and cellular function in taste cells.

Animals↗
PubMed2002

Vanilloid receptor subtype-1 (VR1) is specifically localized to taste papillae.

Pungent sensation of hot peppers is thought to be mediated by vanilloid receptor subtype-1 (VR1), which can be activated by capsaicin, but there is little information regarding its histological localization in the tongue. We examined the immunohistochemical distribution of VR1 in the rat tongue. Intensely labeled VR1-immunoreactive (VR1-IR) fibers were concentrated in the circumvallate, foliate, and fungiform papillae, while sparse VR1-IR fibers were scattered throughout the tongue. VR1-positive taste-bud cells were not observed. Many VR1-positive nerve fibers surrounded the furrows of the circumvallate and foliate papillae, forming plexuses. Some of these VR1-positive fibers penetrated the apical epithelium and the trench wall epithelium, while a few of them entered taste buds. These VR1 distribution patterns resembled those of substance P (SP) and the calcitonin gene-related peptide (CGRP). Double-labeling experiments revealed that most of the VR1-immunoreactivity coexisted with SP- or CGRP-immunoreactivity in the nerve terminals in the circumvallate and foliate papillae. On the other hand, in the fungiform papillae, most of the VR1-IR fibers were positive for SP, but fewer were also positive for CGRP. Although VR1-immunoreactivity was not observed in taste-bud cells, our findings that a large number of VR1-IR fibers concentrated in the taste papillae suggest that capsaicin easily reaches the VR1 nerve terminals because of its lipophilic nature.

Animals↗
PubMed1999

The anatomy and functional role of the circumvallate papilla/von Ebner gland complex.

We suggest that the description of the reciprocal relationships between the circumvallate papilla (CP) and von Ebner glands (VEGs) reported in most textbooks of anatomy must be rewritten. In the past, the VEG was described as a gland ancillary to the taste buds, mainly involved in the washing of the vallum around the CP or in perireceptorial events. Recent data obtained in our laboratory or reported in the literature indicate that both these structures form a single functional unity which could be called circumvallata papilla/von Ebner gland (CP/VEG) complex. The CP/VEG complex seems to represent an important enzyme- and pheromone-producing system composed of a sensitive (taste buds) and an effectory (VEG) branch linked by feedback mechanisms of control. In our hypothesis, the taste buds located in the distal portion of the VEG ductal system can be considered similar to the chemoreceptory cells located in other portions of the digestive apparatus such as pancreatic and bile ducts. Therefore, the CP/VEG complex represents a rare example of chemoreceptor-secretory organ.

Humans↗
PubMed1999

Alpha-gustducin-immunoreactive solitary chemosensory cells in the developing chemoreceptorial epithelium of the rat vallate papilla.

The presence of solitary chemosensory cells was studied in rat vallate papillae during the first week of post-natal life by alpha-gustducin immunocytochemistry. In 1- to 3-day-old rats, isolated alpha-gustducin-immunoreactive cells were found within the epithelium of the vallate papilla. These cells, mainly located in the basal layer, were scattered among keratocytes and wrapped in alpha-gustducin-negative epithelial cells in a glia-like fashion. The alpha-gustducin-immunoreactive cells were usually round and some of them gave rise to short, large processes directed towards the lumen of the oral cavity or the basal lamina. Rarely, some cells showed an evident bipolar shape. Small taste buds containing either alpha-gustducin-immunoreactive or alpha-gustducin-negative cells appeared in the vallate papillae of 4-day-old rats in which isolated, bipolar-shaped alpha-gustducin-immunoreactive cells were also found. After the first week of post-natal life, the taste buds appeared basically similar to those of adult animals. In conclusion, the present study demonstrates that the presence of epithelial cells with characteristics of solitary chemosensory cells precedes the development of the taste buds.

Age Factors↗
PubMed1997

Lingual deficits in BDNF and NT3 mutant mice leading to gustatory and somatosensory disturbances, respectively.

A combination of anatomical, histological and physiological data from wild-type and null-mutated mice have established crucial roles for BDNF and NT3 in gustatory and somatosensory innervation of the tongue, and indeed for proper development of the papillary surface of the tongue. BDNF is expressed in taste buds, NT3 in many surrounding epithelial structures. Absence of BDNF in mice leads to severely malformed taste bud-bearing papillae and severe reduction of taste buds, a loss of proper innervation of remaining taste buds and a loss of taste discrimination although not of the suckling reflex per se. In contrast, absence of NT3 leads to a massive loss of somatosensory innervation of lingual structures. These findings demonstrate distinct roles for BDNF and NT3 in the establishment of the complex innervation apparatus of the tongue with non-overlapping roles for the lingual gustatory and somatosensory systems. The distinction between different sensory modalities, being dependent on either BDNF or NT3 may also have clinical implications.

Animals↗
PubMed2002

Individual mouse taste cells respond to multiple chemical stimuli.

Sensory organs are specialized to detect and decode stimuli in terms of intensity and quality. In the gustatory system, the process of identifying and distinguishing taste qualities (e.g. bitter versus sweet) begins in taste buds. A central question in gustatory research is how information about taste quality is extracted by taste receptor cells. For instance, whether and how individual taste cells respond to multiple chemical stimuli is still a matter for debate. A recent study showed that taste cells expressing bitter-responsive taste receptors do not also express sweet-responsive taste receptors and vice versa. These results suggest that the gustatory system may use separate cellular pathways to process bitter and sweet signals independently. Results from electrophysiological studies, however, reveal that individual taste receptor cells respond to stimuli representing multiple taste qualities. Here we used non-invasive Ca(2+) imaging in slices of lingual tissue containing taste buds to address the issue of quality detection in murine taste receptor cells. We recorded calcium transients elicited by chemical stimuli representing different taste qualities (sweet, salty, sour and bitter). Many receptor cells (38 %) responded to multiple taste qualities, with some taste cells responding to both appetitive ("sweet") and aversive ("bitter") stimuli. Thus, there appears to be no strict and separate detection of taste qualities by distinct subpopulations of taste cells in peripheral gustatory sensory organs in mice.

Animals↗
PubMed1995

Morphostructural characteristics of the vallate papillae in Bos taurus.

The Morpho-structural characteristics of the vallate papillae of the bovine tongue were studied utilizing LM, SEM and TEM techniques. In the bovine, the vallate papillae are numerous and different in size. They have a prominent vallum papillae which surrounds a deep sulcus papillae. The sulcus has many elongated taste buds on its inner wall. Nervous fibers enter the taste bud and sometimes have rosary shaped axons. The gustative sensitivity of these animals may be instrumental, in their choice of food and avoidance of noxious plants.

Animals↗
PubMed1975

[Where lies the boundary between common sensation and taste perception in electrogustometry (author's transl)].

The shift of the electrogustatory threshold following section of the corda tympani has been investigated in 14 patients. Postoperatively the anterior half of the tongue showed complete ageusia. Two thirds of the patients were able to recognize stimulations of 50-127 muA as a burning, and not a sour metallic, sensation for at least 1-2 weeks. Probably the trigeminal nerve endings perceive this burning sensation during the period of taste bud degeneration. A similar situation exists in cases where the gustatory fibres are interrupted proximal to the gustatory ganglion, because the tasts buds do not degenerate. It is therefore important to ask the patient to describe the sensation experienced. Only a sour metallic taste during electrogustometry should be regarded as a true gustatory sensation.

Adult↗
PubMed1975

Functional morpho-histology of the alimentary canal of an Indian frewhwater major carp, Labeo rohita (Hamilton) during it's different life-history stages.

1. The alimentary canal of the fry of L. rohita (Hamilton) is of the carnivorous type in nature and disposition with a low relative length of the gut (R. L. G.). 2. End-buds are present. The buccopharyngeal region has a simple epithelial surface. Mucous cells are small and few throughout the length of the alimentary canal. The presence of these structures in association with a zooplankton feeding habit indicate that the fries are primarily sightfeeders and carnivorous. 3. With increase in age and body-length, the food and feeding habits of the fish undergo changes and accordingly the fingerlings and adults become herbivorous. The value of the R. L. G. steadily increases and the alimentary canal gradually develops into the typically herbivorous type. 4. Tast buds by now become completely developed and have lamina propria, sustentacular cells, neuroepithelial cells, gustatory pores and gustatory canals. 5. Taste buds are abundant in the lip, buccopharynx and anterior oesophagus. The buccopharyngeal region is also provided with distinct villi. Mucous cells are abundant and large being present throughout the alimentary canal. 6. The frequency, length, breadth and distribution of the mucous cells and taste buds are significantly different in marked contrast with those of the fry thus indicating that the fingerlings and adults depend primarily on their gustatory organs for feeding. The fingerlings and adults therefore, are herbivorous and tast feeders.

Animals↗