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PubMed1979

Clearance by the mucociliary system in 'simple chronic otitis media'.

This is a study of the rate of middle ear clearance in chronic otitis media and atelectatic ears. The clearance rate was measured with the aid of non-soluble saccharin, introduced into the middle ear through an existing perforation in 'chronic ears', or through a ventilating tube in atelectatic ears. Cholesteatomatous ears were excluded. Altogether 122 ears were examined and about two-thirds of the subjects felt the sweet taste in their mouths thereafter. The average time it took for the saccharin to be transported from the middle ear to the taste buds was 33' 22" minutes in non-infected (i.e. dry) chronic ears (38 patients or 66 per cent). Wet or infected ears with chronic otitis media (30 patients, or 58 per cent) showed a slower transport rate, averaging 54' 22" minutes--the difference was significant at the 0.01 level. 8 (63 per cent) of the atelectatic ears transported the saccharin at an average rate of 50' 25". This study demonstrated that most ears with 'simple' chronic otitis media and atelectatic ears have a patent eustachian tube and that their mucociliary system can transport foreign particles through it. When the ear is infected, transport tends to be slowed down.

Chronic Disease↗
PubMed2005

Scanning electron microscopic structure of the lingual papillae of the common opossum (Didelphis marsupialis).

The mammalian tongue has evolved for specialized functions in different species. The structure of its papillae tells about the animal's diet, habit, and taxonomy. The opossum has four kinds of lingual papillae (filiform, conical, fungiform, vallate). Scanning electron microscopy of the external features, connective tissue cores, and corrosion casts of the microvasculature show the filiform papillae have a spearhead-like main process and spiny accessory processes around the apical part of the main process. The shape and number of both processes depend on their position on the tongue. On the apex, the main processes have shovel-like capillary networks and the accessory processes have small conical networks. On the lingual radix, the processes have small capillary loops. In the patch region, conical papillae have capillaries arranged as a full sail curving posteriorly. The fungiform papillae are scattered among the filiform papillae and have capillary baskets beneath each taste bud. Giant fungiform papillae on the tongue tip are three to four times larger than the ones on the lingual body. Capillaries of giant papillae form a fan-shaped network. The opossum has three vallate papillae arranged in a triangle. Their tops have secondary capillary loops but not their lateral surfaces. Mucosal folds on the posterolateral border have irregular, fingerlike projections with cylindrical capillary networks. These findings and the structure of the rest of the masticatory apparatus suggest the lingual papillae of opossum have kept their ancestral carnivorous features but also developed the herbivore characteristics of other marsupials.

Animals↗
PubMed1979

Cross-enhancement of the sour taste on single human taste papillae.

The subjective intensity of one taste quality can be increased by prior exposure of the tongue to a different taste quality stimulus. This phenomenon, called cross-enhancement, may be the result of interactions among the physiological mechanisms that code taste quality. Another possible explanation is that the water solvent of the second stimulus acquires a taste after exposure of the tongue to the first stimulus. This water taste could add to the taste of the solute in the second stimulus and result in an increase of its subjective intensity. A third possibility is that taste receptors on the tongue may be sensitized by exposure to a taste stimulus. Using a small number of highly trained subjects, we have demonstrated that sucrose can enhance the intensity of an acid taste on the single papilla. Neither water taste nor sweet taste system activation played any role in the mediation of this enhancement. Through a series of experimentally derived inferential steps, we conclude that this phenomenon depends on the removal of protons from the acid receptors. In addition, we have demonstrated in the single papilla, that suppression of the acid taste when in mixture with sucrose can occur without sweet system activity. We conclude that sugars, through their capacity to bind protons, act to reduce the availability of protons to the acid receptors.

Adult↗
PubMed1990

Alterations of salt taste perception in the developing rat.

Behavioral correlates of changing neurophysiological taste sensitivities during development were assessed with a conditioned taste aversion procedure. Young rats (age 25-30 days) avoided 0.1M monochloride salts and 1.0M sucrose reliably less than adults (age 90-105 days), but the two groups did not differ when the conditioned stimulus (CS) was 0.1M citric acid. Analyses of generalization gradients revealed that young rats were unable to discriminate among the tastes of NaCl, NH4Cl, and KCl, whereas adults readily made such discriminations. Both age groups had similar generalization gradients when the CS was 1.0M sucrose or 0.1M citric acid. These data indicate that quantitative and qualitative aspects of salt taste perception alter with age. Furthermore, the behavioral changes noted in the present study correspond closely with previous findings from developmental studies of neurophysiological taste responses.

Aging↗
PubMed1991

Sodium deficient rats are unmotivated by sodium chloride solutions mixed with the sodium channel blocker amiloride.

Rats were made sodium deficient by furosemide injection and then offered 20 min of access to 0.05 M NaCl mixed with the sodium channel blocker amiloride. Compared with a sodium deficient control group that was also offered 0.05 M NaCl, these rats drank very little. A subsequent test conducted in the same manner with 20 min of access to 0.3 M NaCl mixed with amiloride produced similar results. It is concluded that amiloride blocks the neural information required for generating the attractive taste of NaCl to the sodium deficient rat.

Amiloride↗
PubMed1993

Taste receptors on the anterior tongue and nasoincisor ducts of rats contribute synergistically to behavioral responses to sucrose.

In four groups of rats, behavioral responsiveness to sucrose was tested by allowing them to lick solutions in a computer-controlled gustometer (10-s trials; 0.01-1.0 M). Rats with cautery lesions of the nasoincisor ducts (NID) behaved no differently from controls. After bilateral chorda tympani nerve (CT) section, which removes taste input from the anterior tongue (AT), rats demonstrated a marginal attenuation in their responsiveness to sucrose. Combining the two lesions, however, had the greatest effect on the concentration-response curve. By shifting the curve to the right and lowering the asymptotic licking rate, the combined lesion reduced the area under the curve by one third. The effects of the combined treatments were larger than would be predicted from the sum of either one alone. This presumably reflects the central convergence of primary afferent axons from the NID and AT. Neurophysiological data have demonstrated such convergence within the nucleus of the solitary tract.

Afferent Pathways↗
PubMed1994

Combined, but not single, gustatory nerve transection substantially alters taste-guided licking behavior to quinine in rats.

On the basis of electrophysiological studies, the glossopharyngeal nerve (GL) is far more responsive to quinine than the chorda tympani (CT) or greater superficial petrosal (GSP) nerves. The licking behavior of water-deprived rats to quinine (0.03-3.0 mM) and distilled water (10-s trails) was tested before and after various nerve transections. GL+CT section caused a substantial reduction in responsiveness. GSP+CT section had a moderate effect, and GL section alone produced only marginal impairments. Control, partially desalivated, and CT-sectioned rats were unaffected. Thus, the GL is not necessary for normal unconditioned taste-guided appetitive responsiveness to quinine, but the collective input from the GSP and CT is necessary and most likely sufficient. These data suggest that the quinine-evoked input of the GL and CT converge centrally.

Animals↗
PubMed1997

Chorda tympani nerve transection disrupts taste aversion learning to potassium chloride, but not sodium chloride.

In Experiment 1, rats with chorda tympani nerve transection (CTX) acquired a LiCl-conditioned taste aversion to 0.1 M NaCl at the same rate as controls. After 3 conditioning trials, the aversion generalized to 0.03 and 0.3 M NaCl, but did not generalize to KCI (0.03, 0.1, and 0.3 M), in either the sham or CTX group. In Experiment 2, the sham group, but not the CTX group, formed an aversion to 0.1 M KCI after 1 trial. The CTX rats did form a moderate aversion after 2 conditioning trials. Following the 3rd trial, the CTX group did not suppress licking to 0.03 or 0.3 M KCI or any concentration of NaCl in relation to controls. Although there is strong evidence that CTX affects NaCl taste perception, these findings indicate that, under certain conditions, rats can nonetheless distinguish NaCl from KCI after such neurotomy. Moreover, CTX appears to have a substantial effect on the perceived intensity of KCl.

Animals↗
PubMed1985

Adrenalectomy reduces peripheral neural responses to gustatory stimuli in the rat.

In the rat, sodium need leads to an increase in sodium intake, which depends on salt taste sensitivity. The adrenalectomized rat, because of excessive body sodium loss, has been an important animal model for studying the physiological mechanisms underlying salt ingestion. In order to investigate the mediation by peripheral taste responsivity of changes in salt intake, multiunit responses of the chorda tympani nerve to various concentrations of sodium chloride, potassium chloride, lithium chloride, hydrochloric acid, and quinine hydrochloride were recorded from adrenalectomized and control rats. In order to control for a generalized decrease in sensory sensitivity, recordings from the auriculotemporal nerve to tactile stimulation of the pinna were also performed. There were no group differences in amplitude of the integrated neural responses to tactile stimulation. The largest decrease in gustatory responsivity occurred for suprathreshold concentrations of sodium chloride and lithium chloride. The data are discussed with reference to possible mechanisms underlying this neural alteration and to the role that reductions in salt taste responsivity play in mediating increases in salt intake.

Adrenal Glands↗
PubMed2004

Effects of selective lingual gustatory deafferentation on suprathreshold taste intensity discrimination of NaCl in rats.

In rats, chorda tympani nerve transection (CTX) greatly increases the detection threshold of sodium chloride (NaCl) and severely disrupts salt discriminability. Here it is shown that CTX has surprisingly little effect, if any, on suprathreshold intensity discrimination. Glossopharyngeal nerve transection (GLX), which has no reported effect on salt sensibility, also did not affect performance. Rats were tested in a 2-response, operant taste intensity discrimination task. Difference thresholds for CTX rats were only slightly higher (-0.15 log/10 unit) than those for GLX and sham-transected rats, when 0.05 M served as the standard, and did not significantly differ when 0.1 M NaCl was the standard. Although the perceived intensity of NaCl might be reduced by CTX, input from remaining taste nerves sufficiently maintains the relative discriminability of suprathreshold NaCl concentrations.

Analysis of Variance↗
PubMed1993

Oxygen sensing in airway chemoreceptors.

Pulmonary neuroepithelial bodies, composed of innervated clusters of amine- and peptide-containing cells, are widely distributed throughout the airway mucosa of human and animal lungs. Structurally, neuroepithelial bodies resemble chemoreceptors (such as carotid body, taste buds) and are thought to function as hypoxia sensitive airway sensors. Evidence for this is indirect, however, and the mechanism of oxygen sensing by these cells is unknown. Here we culture neuroepithelial bodies isolated from rabbit fetal lungs and identify voltage-activated potassium, calcium and sodium currents using the whole-cell patch clamp technique. Upon exposure to hypoxia there is a reversible reduction (25-30%) in the outward potassium current, with no change in inward currents. In addition, we demonstrate the expression of an oxygen-binding protein (b-cytochrome, NADPH oxidase) on the plasma membrane of these cells. The identification of an oxygen-sensing mechanism (namely the presence of an O2-sensitive potassium channel coupled to an O2 sensor protein) in the cells of pulmonary neuroepithelial bodies indicates that they are transducers of the hypoxia stimulus and hence may function as airway chemoreceptors in the regulation of respiration.

Animals↗
PubMed1961

Taste receptors.

Explore the source record for details and available documents.

Humans↗
PubMed2003

Electrogustometry: strengths, weaknesses, and clinical evidence of stimulus boundaries.

Electrogustometry is well established as a clinical tool for the estimation of taste detection thresholds. Nevertheless, the user is sometimes unaware of the impact of superficially minor procedural and psychophysical factors upon the reliability and comparability of threshold estimates. The inherent strengths and limitations of the procedure are outlined, and aspects of the control and specification of the stimulus that moderate threshold measures are discussed. In addition, threshold estimates from two individuals with severe unilateral taste loss are used to illustrate the level at which anodal dc current may elicit common, rather than taste, sensation. Where chorda tympani section is complete and historical (older than 7-14 days), very high stimulus levels, conservatively over 5 micro A/mm2 (100 micro A linear current with a 5-mm diameter electrode), are required to activate trigeminal responses.

Adult↗
PubMed2000

Neurotrophin 3 potentiates glutamatergic responses of IHC afferents in the cochlea in vivo.

Neurotrophins have traditionally been regarded as slow-acting signals essential for neuronal survival and differentiation. Recent studies with neuronal slices, cultures and nerve ending preparations have shown that neurotrophins generate acute changes in nerve activity. Among the secondary sensory cells are the inner hair cells (IHC) and taste buds, cells which express the neurotrophic factors necessary for the survival of their innervating neurons. If in these cells neurotrophins acutely affect the nerve activity of their afferent neurons, as in the central nervous system (CNS), this may have important functional implications for the corresponding sensory transduction processes. The neurotrophin NT-3 has been reported to be expressed in IHCs. We chose an in vivo application system for the microiontophoretic supply of NT-3 in the subsynaptic region of the IHC. The effect of NT-3 on spontaneous and evoked afferent cochlear nerve activities in adult guinea pig inner ear was studied. We observed that NT-3 rapidly increases the spontaneous and glutamate-evoked firing rate of IHC afferents. Moreover, firing induced by both N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) were specifically enhanced during the presence of NT-3, a process which was selectively blocked by the tyrosine kinase receptor inhibitor K252a. Because we localized NT-3 mRNA not only in IHCs but also in the spiral ganglion, we propose that similar to other sensory systems, afferent and autocrine neurotrophin activities may be responsible for survival of cochlear neurons. In addition, NT-3 in IHCs may operate as a signal-dependent, intrinsic neuromodulator and/or neuroprotector.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2003

[Contact endoscopic quantification of fungiform papillae--correlation to taste ability?].

BACKGROUND: Besides anamnestic data and taste test, the clarification of epithelial taste disorders makes macroscopic evaluation of the surface of the tongue necessary. METHODS: In this article the contact endoscopy is evaluated for examination of the tongue epithelium and for quantification of the fungiforme papillae. These results are related to the results of the spatial taste test (1. chemical taste test with sodium chloride in 2 different suprathreshold concentrations and sucrose in also 2 different suprathreshold concentrations; 2. electrogustometry with a bipolar electrode). PATIENTS: In a prospective study we performed contact endoscopy in 16 healthy volunteers from ages 7 to 68 years. The subjects were divided into 2 age groups (< or = 45 years and > 45 years) and 2 papillae density groups. In 34 patients with either taste disorders of unknown cause or in patients with macroscopic changes at the tongue surface, the spatial and whole mouth taste tests and contact endoscopy were used to clarify the cause of the complaints. RESULTS: Density and shape of the fungiform papillae as well as the shape of the subepithelial vessels of the papillae vary among the investigated human subjects in the different age groups. No correlation between intensity ratings, papillae density und age was found after stimulation with 40 % sucrose at the tongue tip in the younger age group. Stimulation of the tongue edge with 15 % sodium chloride, however, showed a relationship between the two different density groups and the different age groups. CONCLUSIONS: The contact endoscopy allows the evaluation of the epithelium in the oral cavity. It is a nondestructive method and is additionally easy to handle, but the evaluation of the observed epithelia needs interdisciplinary co-operation with pathologists. No relevant informations are supplied in diagnostics of taste disorders.

Adolescent↗
PubMed1979

Salt taste adaptation: the psychophysical effects of adapting solutions and residual stimuli from prior tastings on the taste of sodium chloride.

The paper reviews how adaptation to sodium chloride, changing in concentration as a result of various experimental procedures, affects measurements of the sensitivity, intensity, and quality of the salt taste. The development of and evidence for the current model that the salt taste depends on an adaptation level (taste zero) determined by the sodium cation concentration is examined and found to be generally supported, despite great methodological complications. It would seem that lower adaptation levels elicit lower thresholds, higher intensity estimates, and altered quality descriptions with predictable effects on psychophysical measures.

Adaptation, Physiological↗