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PubMed1995

Comparative observations on lingual papillae and their connective tissue cores in three primates. A scanning electron microscopic study.

The 3-D structure of the connective tissue cores (CTCs) of the lingual papillae in three primates (treeshrew, crab-eating monkey and man) was observed by scanning electron microscopy. Each filiform papilla has some slender protrusions on the top in the three kinds of primates. After removal of the epithelium, the CTC of the filiform papillae has a columnar primary core with some rod shaped secondary protrusions whose number and size vary among the three species. The number of secondary protrusions on the filiform CTC is generally small in the treeshrew and is the greatest in man. The stereo structure of the filiform CTC is fundamentally similar in all these three species and is different from those of other animal orders (i.e. Insectivora, Rodentia etc.). The fungiform CTC in man as well as in the crab-eating monkey is coralliform in shape and branched several times with small depressions for taste buds on the top of each one, though there were some differences between the two species in stereo structure. On the other hand, the fungiform CTC in the treeshrew was columnar in shape and was rather similar to that of Insectivora and Rodentia. In the treeshrew there are several finger-like processes in the region where foliate papillae are located in man as well as in the crab-eating monkey.

Animals↗
PubMed1980

New contribution on the oesophageal mucous innervation in certain monkeys (Cercopithecidae).

Spindle-shaped, barrel-like, or bush-like corpuscular neural structures situated in the mucous epithelium of the upper third of the oesophagus are described. These structures are not homogeneously distributed in this area. Some are very close to the pharyngooesophageal sphincter, spanning the thickness of the epithelium and communicating with the basal membrane by means of a thin pedicle and with the lumen by a small hilus or pore, their morphology being that of a taste bud. The others are situated deeper in the mucous epithelium of the upper third, communicating with the basal membrane only by means of either a thin pedicle or a thicker one, and separated from the lumen by a thick layer of epithelial cells. The bush-like apparatuses lie closely adjacent to the basal membrane of the epithelium.

Animals↗
PubMed1999

alpha-Gustducin expression in the vomeronasal organ of the mouse.

The expression of alpha-gustducin, a G protein alpha subunit involved in bitter and sweet taste transduction, was investigated in chemosensory tissues of adult mice. By immunohistochemistry, alpha gustducin was absent in the olfactory neuroepithelium. Instead, alpha gustducin was expressed in a subset of bipolar cells in the proliferative zone of the vomeronasal neuroepithelium as well as in taste buds. Northern blot analysis confirmed the presence of alpha gustducin in isolated vomeronasal organs. Moreover, immunohisto- chemistry revealed the expression of alpha gustducin in scattered cells of the nasal respiratory epithelium. These results show for the first time that alpha gustducin is expressed in chemosensory tissue outside the alimentary tract, suggesting that common transduction mechanisms could be shared by apparently unrelated chemosensory tissues.

Animals↗
PubMed1986

Taste responses from the chorda tympani nerve in young and old Fischer rats.

To determine whether neurophysiological taste responses are different in young and old rats, recordings were made from the whole chorda tympani nerve which innervates taste buds on the anterior tongue. Fischer 344 male and female rats in three age groups were studied: 5 to 7 months, 23 to 25 months, and 29 to 32 months. Chemical stimuli included single concentrations of five salts, two acids, sucrose and quinine hydrochloride, and concentration series of the five salts. Neural response magnitudes were expressed as ratios relative to the NaCl(0.1M) response. Substantial neural responses were obtained to all chemicals at all ages. Response ratios for NH4Cl and sucrose, however, increased significantly with age; ratios for MgCl2 and citric acid decreased. Ratios for HCl decreased when data from either sex were analyzed separately. Shapes of response/concentration functions for NaCl, but not other salts, also differed with age. In general, though, the magnitudes of all age-related differences were small and neural recordings demonstrate that the peripheral taste system functions well in old age.

Acids↗
PubMed1976

Histochemical studies on the mucins of the vertebrate tongues. VII. Histochemical analysis of mucosubstances in the tongues of some fishes.

The tongues of three fishes were investigated histochemically to determine the distribution and nature of mucosubstances by employing recent techniques and the results were considered comparatively with the lingual mucosubstances of other vertebrates. A heterogenous distribution of neutral mucosubstances, sulfomucins and sialomucins in various lingual sites was noted. The taste buds and/or free nerve endings were found to be restricted in the areas containing abundance of goblet cells. In non-gustatory areas of tongue, the goblet cells were very few or absent. Importance of lingual histology in establishing phylogenetic relationships and the possible functional significance of the mucosubstances in the physiology of gustation is discussed in detail.

Alcian Blue↗
PubMed1995

Effect of denervation on morphogenesis of the rat fungiform papilla.

In an attempt to elucidate the effects of denervation on development and maintenance of the structure of the fungiform papilla, unilateral neurectomy of the chorda tympani-lingual nerve of rats was performed at day 1 and at weeks 1, 2, 3, 4, 7, and 10 after birth. Specimens were obtained at days 3, 7 and 10, weeks 2, 3, 4, 6, and 8, and months 3 and 4 after neurectomy for examination by light and scanning electron microscopy. At first, the fungiform papillae were atrophic, then progressed to forms resembling filiform papillae. When an immature fungiform papilla was denervated, it eventually changed to papilla identical to normal filiform papillae. The elicited changes differed according to the time of neurectomy; it was found that early neurectomy resulted in a more rapid and marked morphological change of the fungiform papillae. The filiform-like papillae derived from the fungiform ones showed various shapes, sizes, and orientations and were rarely present on the unoperated control side of the lingual dorsum. Sections of the filiform-like papillae revealed that they had no taste buds. These findings suggest: (1) Morphogenesis and structural maintenance of the fungiform papillae require the presence of the chorda tympani and/or lingual nerve. (2) Completion of differentiation and maturation differ in time among fungiform papillae. (3) Fungiform papillae may be transformed filiform papillae induced and maintained by a neurotrophic factor of factors coming from the chorda tympani and/or lingual nerve. (4) Fungiform papillae are rarely innervated contralaterally.

Animals↗
PubMed1990

Identification of electrophysiologically distinct subpopulations of rat taste cells.

The gustatory sensory system provides animals with a rapid chemical analysis of a potential food substance providing information necessary to facilitate ingestion or rejection of the food. The process of gustatory transduction is initiated in the taste cells in the lingual epithelium. However, due to the small size, scarcity of the cells and their location, embedded in a keratinized squamous epithelium, it has been difficult to study the primary events in the transduction process. Recently, we have developed a preparation of dissociated rat taste cells that permits studies of the taste transduction process in single isolated cells. We have now investigated the electrophysiological properties of the rat taste cells using the patch-clamp technique. We have identified two populations of cells within the taste bud: one expressing a voltage-dependent potassium current and the second containing both voltage-dependent sodium and potassium currents. The potassium current in both cell groups is blocked by external TEA, Ba2+, and quinine. Two types of K+ channels have been identified: a 90-pS delayed rectifier K+ channel and a "maxi" calcium-activated K+ channel. The sodium current is blocked by TTX, but not by amiloride.

Animals↗
PubMed1993

Distribution of calcium binding proteins in sensory organs of the ear, nose and throat.

Distributions of spot-35 protein (S-35), calbindin (CaB), and parvalbumin (PaV), three types of calcium-binding protein, were examined immunohistochemically in sensory organs of the ear, nose and throat in guinea pigs and rats. Immunoreactivity of S-35 and CaB was found in the outer hair cells and in vestibular sensory cells situated at the top of the ampulla, and in some cells in the macula. Microvillar cells in the olfactory epithelium, periglomerular cells, and small numbers of cells in the mitral cell layer in the olfactory bulb reacted to anti-S-35 and anti-CaB antisera. In taste buds, most gustatory receptor cells reacted to anti-CaB, although a few reacted to anti-S-35 antiserum. Neuron-like cells in the upper respiratory tract reacted similarly to these antisera. No PaV-immunoreactivity was found in any region. These results indicate that S-35 and CaB play important roles in the special kinds of mechanoreceptor and chemoreceptor cells found in the otolaryngeal area.

Animals↗
PubMedDate not supplied

Radiation therapy of the oral cavity: sequelae and management, part 1.

This is the first article in a two-part series dealing with the effects and manifestations in the oral cavity of radiation therapy of head and neck tumors. In this section, oral mucous membranes, taste buds, edema and trismus, diet, salivary glands, bone, periodontium, teeth, and composition of oral flora are discussed. Dental management of the dentulous patient is then approached; criteria for preradiation extraction are delineated. In the next issue of Head & Neck Surgery, the final article in this series will discuss preradiation and postradiation extractions and will elaborate on the dental management (fluoride treatments, follow-up, and restorative care) of the dentulous patient. Dental management of the edentulous patient will also be presented.

Bacteria↗
PubMedDate not supplied

Modularity and sense organs in the blind cavefish, Astyanax mexicanus.

Mexican tetra (Astyanax mexicanus) exist as two morphs: a sighted (surface) form and a blind (cavefish) form. In the cavefish, some modules are lost, such as the eye and pigment modules, whereas others are expanded, such as the taste bud and cranial neuromast modules. We suggest that modularity can be viewed as being nested in a manner similar to Baupläne so that modules express unique sets of genes, cells, and processes. In terms of evolution, we conclude that natural selection can act on any of these hierarchical levels within modules or on all the sensory modules as a whole. We discuss interactions within and between modules with reference to the blind cavefish from both genetic and developmental perspectives. The cavefish represents an illuminating example of module interaction, uncoupling of modules, and module expansion.

Animals↗
PubMed1991

Peptide-containing nerve fibers in the fungiform papillae of pigs and rats.

The occurrence and distribution of an array of neuropeptides and dopamine-beta-hydroxylase in the fungiform papillae of pigs and rats were studied by immunocytochemistry. Structural differences between the fungiform papillae of the two species were correlated to differences in the occurrence and distribution of neuropeptides. Calcitonin gene-related peptide-, substance P- and neurokinin A-containing fibers were numerous in the fungiform papillae of both species, although their distribution within the papilla differed. In the pig, the majority of these fibers ended within the taste buds, while in the rat numerous fibers also penetrated the adjacent epithelium. Galanin- and bombesin-immunoreactive nerve fibers could not be detected in the rat fungiform papillae, while in the pig many, but not all, of the fungiform papillae contained bombesin- and galanin-positive nerve fibers. Vasoactive intestinal peptide- and peptide histidine isoleucine-immunoreactive fibers occurred in the fungiform papillae of both species. A few neuropeptide Y-containing fibers and dopamine-beta-hydroxylase-positive (presumably adrenergic) fibers could be observed in the porcine papillae only.

Animals↗
PubMed1996

Late-onset hereditary ataxia with global thermoanalgesia and absence of fungiform papillae on the tongue in a Japanese family.

Two Japanese male siblings, aged 68 and 59 years, affected by late-onset progressive ataxia distinguished by extensive sensory and mild autonomic disturbances are described. They had global thermoanalgesia, positive Romberg signs, sensorineural deafness, canal paresis and ageusia. Their autonomic disturbances consisted of absence of overflow tears with usual stimuli, dysphagia, blood pressure and vasomotor instability, diarrhoea/constipation, and urinary frequency. Sensory nerve action potentials were completely absent, whereas motor conduction velocity was slightly reduced only in the lower extremities. Sural nerve biopsy on the younger brother demonstrated a marked loss of myelinated fibres and a reduction in the number of unmyelinated axons. Tongue histology revealed absence of fungiform papillae and taste buds. Autonomic function tests showed widespread but mild sympathetic and parasympathetic failures. Neuro-imaging studies revealed atrophy of the spinal cord, cerebellum, brainstem and corpus callosum, and enlargement of the lateral, third and fourth ventricles. These siblings represent a previously unrecognized variant of late-onset hereditary spinocerebellar degeneration with global thermoanalgesia and absence of fungiform papillae on the tongue.

Biopsy↗
PubMed2002

Hypoosmotic stimuli activate a chloride conductance in rat taste cells.

The oral cavity is subjected to a wide range of osmotic conditions, yet little is known about how solution osmolarity affects performance of the gustatory system. In order to elucidate the mechanism by which hypoosmotic stimuli affect the peripheral taste system, I have attempted to characterize the effects of hypoosmotic stimuli on individual rat taste receptor cells (TRCs) using whole-cell patch clamp recording. Currents elicited in response to voltage ramps (-90 to +60 mV) were recorded in control saline and in solutions varying only in osmolarity (-30, -60 and -90 mOsm). In roughly two-thirds of cells, hypoosmotic solutions (230 mOsm) caused a 15% increase in cell capacitance and activated a reversible conductance that exhibited marked adaptation in the continued presence of the stimulus. Similar responses could be elicited in taste cells from taste buds in the foliate and vallate papillae, the soft palate, the nasopharynx and the epiglottis. Ion substitution experiments were consistent with the interpretation that the predominant ion carried through these apparent volume- or stretch-activated channels was Cl(-) under normal conditions. Reversal potentials for the hypoosmotic-induced current closely matched those predicted by the Goldman-Hodgkin-Katz constant field equation for a Cl(-) conductance. The relative permeability sequence of the hypoosmotic-activated current in TRCs was thiocyanate(-) > or = l(-) > or = Br(-) > Cl(-) > or = F(-) > or = isethionate(-) > gluconate(-). Pharmacological experiments revealed that this Cl(-) conductance was inhibited by 4,4'-diisothiocyanatostilbene-2, 2'-disulfonic acid and 5-nitro-3-(3-phenyl-propylamino)benzoic acid (EC(50) = 1.3 and 4.6 microM, respectively), but not by CdCl(2) (300 microM) nor GdCl(3) (200 microM). I hypothesize that this hypoosmotic-activated Cl(-) conductance, which is similar to the well-characterized swelling-activated Cl(-) current, may contribute to volume regulation and could represent the transduction mechanism by which the presence of hypoosmotic stimuli, including water, may be signaled in taste receptor cells.

Algorithms↗
PubMed2005

TRPM8 protein localization in trigeminal ganglion and taste papillae.

TRPM8 is a TRP family cation channel which can be activated by cold stimuli or l-menthol. However, TRPM8 protein localization of nerve terminals in sensory organs remains unknown. Here we generated an antibody against TRPM8 and analyzed TRPM8 protein localization in trigeminal ganglia (TG) and in sensory nerve fibers in the tongue. TRPM8 immunoreactivity was detected in a subset of neurons with a small diameter in TG and in nerve fibers in the tongue. TRPM8-immunoreactive nerve fibers were rich in fungiform papillae, but sparse in foliate and circumvallate papillae. The TRPM8-immunoreactive nerve fibers reached the outer epithelial layer in each papilla, while no TRPM8-immunoreactive nerve fibers penetrated into taste buds. Double labeling analysis revealed that TRPM8 immunoreactivity was co-expressed with a part of TRPV1 or CGRP-immunoreactive neurons in TG. However, TRPM8 immunoreactivity was not observed in TRPV1- or CGRP-positive nerve fibers in fungiform, foliate, and circumvallate papillae. These results suggest that TRPM8 protein is present in sensory lingual nerve fibers mainly projected from TG and might work as cold and l-menthol receptors on tongue.

Animals↗
PubMed2005

CD36 involvement in orosensory detection of dietary lipids, spontaneous fat preference, and digestive secretions.

Rats and mice exhibit a spontaneous attraction for lipids. Such a behavior raises the possibility that an orosensory system is responsible for the detection of dietary lipids. The fatty acid transporter CD36 appears to be a plausible candidate for this function since it has a high affinity for long-chain fatty acids (LCFAs) and is found in lingual papillae in the rat. To explore this hypothesis further, experiments were conducted in rats and in wild-type and CD36-null mice. In mice, RT-PCR experiments with primers specific for candidate lipid-binding proteins revealed that only CD36 expression was restricted to lingual papillae although absent from the palatal papillae. Immunostaining studies showed a distribution of CD36 along the apical side of circumvallate taste bud cells. CD36 gene inactivation fully abolished the preference for LCFA-enriched solutions and solid diet observed in wild-type mice. Furthermore, in rats and wild-type mice with an esophageal ligation, deposition of unsaturated LCFAs onto the tongue led to a rapid and sustained rise in flux and protein content of pancreatobiliary secretions. These findings demonstrate that CD36 is involved in oral LCFA detection and raise the possibility that an alteration in the lingual fat perception may be linked to feeding dysregulation.

Animals↗
PubMed2003

Age related decreases in neural sensitivity to NaCl in SHR-SP.

To determine whether neurophysiological taste responses of young and old rats are different, recordings were made from the whole chorda tympani nerve which innervates taste buds on the anterior tongue. SHR-SP (Stroke-Prone Spontaneously Hypertensive Rats) in two age groups were studied. Chemical stimuli included single concentrations of 250 mM NH(4)Cl, 100 mM NaCl, 100 mM KCl, 500 mM sucrose, 20 mM quinine-hydrochloride, 10 mM HCl, 10 mM monosodium glutamate (MSG), 10 mM L- glutamic acid (L-Glu) and an NaCl concentration series. The magnitude of the neural response (response ratio) was calculated by dividing the amplitude of the integrated response by the amplitude of the spontaneous activity that preceded it. Substantial neural responses to all chemicals were obtained at both ages. The responses to KCl, sucrose, quinine-hydrochloride, HCl, monosodium glutamate (MSG) and glutamic acid (Glu) did not change with age, but the response to NaCl did decrease significantly. The profile of the response/concentration function for NaCl differed with age. In particular, the responses to solutions more concentrated than 100 mM NaCl were significantly weaker in aged than in young SHR-SPs. We also observed that recovery from amiloride treatment on the tongue of SHR-SPs was faster in aged rats than in young ones, suggesting that there is some functional difference in the sodium-specific channels on the taste cell. These results suggest that aged SHR-SP may be less able than young SHR-SPs to discriminate among higher concentrations of NaCl solutions.

Aging↗
PubMed2002

General pseudoreceptor model for sweet compounds: a semiquantitative prediction of binding affinity for sweet-tasting molecules.

The chemical structures of sweet compounds are very different, ranging from sugars to amino acids and peptides or other compounds such as saccharin. The biological mechanism underlying the generation of sweet taste is still unknown, although in the past few years much research has provided evidence for the existence of a true chemoreception process, mediated by receptor proteins on the taste buds. In particular, the initial step of the process involves the reversible binding of the sweet compounds to their receptor(s). In this work, we have investigated this binding via a pseudoreceptor model, which has been developed using a training set of 24 compounds belonging to different families including sugars, peptides, and other intensive sweeteners. This model provided a correlation coefficient (r(2)) of 0.985 between the calculated and the experimental free energies of binding, which are related to the molar relative sweetness, for the training set and is able to predict semiquantitatively free energies of ligand binding for an independent set of five test ligand molecules within 0.3-2.1 kcal mol(-1) of the experimental values.

Binding Sites↗
PubMed1998

Morphology of the brain and sense organs in the snailfish Paraliparis devriesi: neural convergence and sensory compensation on the Antarctic shelf.

The Antarctic snailfish Paraliparis devriesi (Liparidae) is an epibenthic species, inhabiting depths of 500-650 m in McMurdo Sound. Liparids are the most speciose fish family in the Antarctic Region. We examine the gross morphology and histology of the sense organs and brain of P. devriesi and provide a phyletic perspective by comparing this morphology to that of four scorpaeniforms and of sympatric perciform notothenioids. The brain has numerous derived features, including well-developed olfactory lamellae with thick epithelia, large olfactory nerves and bulbs, and large telencephalic lobes. The retina contains only rods and exhibits a high convergence ratio (82:1). Optic nerves are small and nonpleated. The tectum is small. The corpus of the cerebellum is large, whereas the valvula is vestigial. The rhombencephalon and bulbospinal junction are extended and feature expanded vagal and spinal sensory lobes as well as hypertrophied dorsal horns and funiculi in the rostral spinal cord. The lower lobes of the pectoral fins have taste buds and expanded somatosensory innervation. Although the cephalic lateral line and anterior lateral line nerve are well developed, the trunk lateral line and posterior lateral line nerve are reduced. Near-field mechanoreception by trunk neuromasts may have been compromised by the watery, gelatinous subdermal extracellular matrix employed as a buoyancy mechanism. The expanded somatosensory input to the pectoral fin may compensate for the reduction in the trunk lateral line. The brains of P. devriesi and sympatric notothenioids share well-developed olfactory systems, an enlarged preoptic-hypophyseal axis, and subependymal expansions. Although the functional significance is unknown, the latter two features are correlated with habitation of the deep subzero waters of the Antarctic shelf.

Animals↗