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PubMed2004

Observation of tongue papillae by video microscopy and contact endoscopy to investigate their correlation with taste function.

OBJECTIVES: Contact endoscopy is a technique used to obtain detailed images of living epithelium in the fields of gynecology, rhinology and laryngology. Video microscopy is useful for observation of the surface of tongue papillae. In the present study, we attempted to apply the contact endoscopy technique together with video microscopy to observe tongue papillae, and to study the correlation between the condition of fungiform papillae and taste function. METHODS: Ten subjects (3 men, 7 women) were divided into two groups based on the results of a taste examination by electrogustometry. We compared the shape and blood vessels of the papillae between normal taste and taste disorder groups. RESULTS: In the normal taste group, round shaped papillae and clear blood vessels were observed with both microscopy and contact endoscopy. In the taste disorder group, flat and irregular papillae were observed with microscopy. Blood vessel flow of the papillae was observed to be poor with contact endoscopy. CONCLUSION: These findings suggested that the images of microscopy and contact endoscopy were related to taste function, and both techniques were useful for evaluating taste function.

Adult↗
PubMed2005

Clinical and biological features associated with taste loss in internal medicine patients. A cross-sectional study of 100 cases.

Which are the main features associated with taste loss in patients exposed to a wide range of drugs and diseases? In 100 consecutive patients admitted to a ward of internal medicine, we assessed taste complaints, performance status, alcohol and tobacco consumptions, diseases, drugs and laboratory data, measuring the electrical taste threshold as primary outcome. After adjusting for age, taste thresholds were not associated with sex, body mass index, tobacco, thrush, drugs, aliageusia and phantogeusia. Features associated with threshold increase included alcohol intake>or=10 gd-1, impaired performance status, complaint of taste loss, atrophic glossitis, cerebral disease, and an erythrocyte mean corpuscular volume. A multivariate analysis identified age, alcohol intake, complaint of loss or altered taste, mean corpuscular volume, and performance status as independent factors associated with taste loss. Inpatients may be screened for taste loss by a few features, to identify those for whom a nutritional intervention should be focused.

Adult↗
PubMed2004

Facial responses to four basic tastes in newborn rhesus macaques (Macaca mulatta) and chimpanzees (Pan troglodytes).

Newborn humans are known to show specific facial expressions in response to various kinds of taste stimuli and are presumed to be able to discriminate those kinds of tastes from just after birth. As the closest relatives to humans, the taste reactivity (threshold, preference and taste-elicited facial expression) of non-human primates has long been of great interest. To date, however, there have been few investigations in newborn non-human primates. In the present study, we investigated the facial expressions elicited in response to four basic taste stimuli, sweet, salty, sour and bitter, in the newborns of two non-human primate species, rhesus macaques and chimpanzees. The taste-elicited facial expressions were compared among the kinds of taste stimuli and between the two species. Rhesus macaques of less than 7 days old showed different patterns of facial expressions for water/sweet than for bitter, and chimpanzees less than 30 days old did so for sweet and bitter. The differences between these two species were evident in the presence and absence of certain facial expressions and the emerging patterns of certain components for each stimulus. In particular, chimpanzee response patterns to the bitter stimulus resembled to those of humans rather than rhesus macaques. Overall, rhesus macaques and chimpanzees responded differently to the same kinds of tastes, presumably reflecting differences in their evolutionary backgrounds.

Animals↗
PubMed2005

Chemesthesis and taste: evidence of independent processing of sensation intensity.

The ability to perceive taste from temperature alone ("thermal taste") was recently shown to predict higher perceptual responsiveness to gustatory and olfactory stimuli. This relationship was hypothesized to be due in part to individual differences in CNS processes involved in flavor perception. Here we report three experiments that tested whether subjects who differ in responsiveness to thermal taste and/or chemical taste also differ in responsiveness to oral chemesthesis. In experiment 1, subjects identified as 'thermal tasters' (TTs) or 'thermal non-tasters' (TnTs) used the general Labeled Magnitude Scale to rate the intensity of sensations produced on the tongue tip by capsaicin, menthol, sucrose, NaCl, citric acid, and QSO4. TTs rated all four taste stimuli higher than did TnTs, whereas sensations of burning/stinging/pricking and temperature from capsaicin and menthol did not differ significantly between groups. In experiment 2, testing with capsaicin on both the front and back of the tongue confirmed there was no difference in ratings of burning/stinging/pricking when subjects were grouped according to the ability to perceive thermal taste. In experiment 3, subjects were classified as high- or low-tasters according to their ratings of sucrose sweetness rather than thermal taste. No group difference was found for perception of capsaicin even when presented in mixture with sucrose or NaCl. The results are discussed in the context of previous evidence of an association between chemesthesis and sensitivity to the bitter tastant PROP, and in terms of the various peripheral and central neural processes that may underlie intensity perception in taste and chemesthesis.

Adolescent↗
PubMed2006

Chorda tympani nerve transection alters linoleic acid taste discrimination by male and female rats.

Taste is intimately associated with food choice, yet little is known about the role of taste in preferences for dietary fat, a major component of many foods. We measured the taste threshold for linoleic acid (LA), an essential free fatty acid found in dietary fat, before and after bilateral transections of the chorda tympani nerve (CTX) in adult male and female rats. We conditioned a taste aversion to 88 microM LA and assessed the generalization of the aversion to lower LA concentrations to determine LA discrimination thresholds. We discovered that female rats had a lower LA discrimination threshold (approximately 2.75 microM LA) than did male rats (approximately 11 microM LA). In another set of animals, we performed CTX and found that CTX elevated LA threshold to the same level (approximately 22 microM LA) in male and female rats. Finally, we evaluated licking responses to 11, 22, 44 and 88 microM LA mixed in sucrose by male rats and ovariectomized (OVX) female rats treated with estradiol benzoate or oil vehicle. All rats increased licking to increasing LA concentrations, but OVX rats responded to a lower LA concentration (22 microM) than did males (44 microM) in 10-s trials. However, estradiol did not affect this outcome. Collectively, these experiments show that male and female rats use taste to discriminate LA and that the chorda tympani nerve, which innervates taste buds on the anterior tongue, plays a role in this discrimination. Furthermore, sex differences in fat preferences may depend on differences in fatty acid taste thresholds as well as on the taste stimuli with which fat is combined.

Analysis of Variance↗
PubMedDate not supplied

Effect of antimicrobial and anti-inflammatory medications on the sense of taste.

Elderly individuals and HIV-infected patients have a disproportionate number of taste complaints relative to the general population, and these taste alterations are correlated with the use of medications. Clinical reports of taste disorders have been associated with many drugs, including antimicrobial and anti-inflammatory medications. The purpose of this study was to quantify the taste effects of 6 nonsteroidal anti-inflammatory drugs (NSAIDS) and 13 antimicrobial drugs. The six NSAIDS were: diclofenac sodium salt, fenoprofen calcium salt, ibuprofen, ketoprofen, nabumetone, and sulindac. The 13 antimicrobials were: acyclovir, ampicillin, atovaquone, dapsone, enoxacin, ethambutol, lomefloxacin HCl, ofloxacin, pentamidine isethionate, pyrimethamine, sulfamethoxazole, tetracycline HCl, and trimethoprim. These 19 medications were applied topically to the tongues of unmedicated young and elderly volunteers as well as unmedicated HIV-infected patients to measure the direct effect of the drug on taste receptors. Topical application of drugs to the apical tongue surface was used to mimic the situation in which the drug is secreted into the saliva. The main finding was that the taste qualities of these drugs were perceived as predominantly bitter, metallic, and/or sour, although several did not have a taste. Elderly subjects had higher thresholds than young subjects for one-third of the drugs that were tested. Thresholds for HIV-infected patients were statistically equivalent to young controls; however, HIV-infected patients rated the drugs as more intense at four times above the detection threshold than young subjects. Most of these drugs when applied directly to the tongue also modified the taste intensity of other tastants (e.g., NaCl, citric acid).

Administration, Oral↗
PubMed2006

Transient receptor potential family members PKD1L3 and PKD2L1 form a candidate sour taste receptor.

Animals use their gustatory systems to evaluate the nutritious value, toxicity, sodium content, and acidity of food. Although characterization of molecular identities that receive taste chemicals is essential, molecular receptors underlying sour taste sensation remain unclear. Here, we show that two transient receptor potential (TRP) channel members, PKD1L3 and PKD2L1, are coexpressed in a subset of taste receptor cells in specific taste areas. Cells expressing these molecules are distinct from taste cells having receptors for bitter, sweet, or umami tastants. The PKD2L1 proteins are accumulated at the taste pore region, where taste chemicals are detected. PKD1L3 and PKD2L1 proteins can interact with each other, and coexpression of the PKD1L3 and PKD2L1 is necessary for their functional cell surface expression. Finally, PKD1L3 and PKD2L1 are activated by various acids when coexpressed in heterologous cells but not by other classes of tastants. These results suggest that PKD1L3 and PKD2L1 heteromers may function as sour taste receptors.

Calcium↗
PubMed2001

Neural networks distinguish between taste qualities based on receptor cell population responses.

Response features of taste receptor cell action potentials were examined using an artificial neural network to determine whether they contain information about taste quality. Using the loose patch technique to record from hamster taste buds in vivo we recorded population responses of single fungiform papillae to NaCl (100 mM), sucrose (200 mM) and the synthetic sweetener NC-00274-01 (NC-01) (200 microM). Features of each response describing both burst and inter-burst characteristics were then presented to an artificial neural network for pairwise classification of taste stimuli. Responses to NaCl could be distinguished from those to both NC-01 and sucrose with accuracies of up to 86%. In contrast, pairwise comparisons between sucrose and NC-01 were not successful, scoring at chance (50%). Also, comparisons between two different concentrations of NaCl, 0.01 and 0.005 M, scored at chance. Pairwise comparisons using only those features that relate to the inter-burst behavior of the response (i.e. bursting rate) did not hinder the performance of the neural network as both sweeteners versus NaCl received scores of 75--85%. Comparisons using features corresponding to each individual burst scored poorly, receiving scores only slightly above chance. We then compared the sweeteners with varying concentrations of NaCl (0.1, 0.01, 0.005 and 0.001 M) using only those features corresponding to bursting rate within a 1 s time window. The neural network was capable of distinguishing between NaCl and NC-01 at all concentrations tested; while comparisons between NaCl and sucrose received high scores at all concentrations except 0.001 M. These results show that two different taste qualities can be distinguished from each other based solely on the bursting rates of action potentials in single taste buds and that this distinction is independent of stimulation intensity down to 0.001 M NaCl. These data suggest that action potentials in taste receptor cells may play a role in taste quality coding.

Action Potentials↗
PubMed2003

The time course of taste bud regeneration after glossopharyngeal or greater superficial petrosal nerve transection in rats.

We previously have published data detailing the time course of taste bud regeneration in the anterior tongue following transection of the chorda tympani (CT) nerve in the rat. This study extends the prior work by determining the time course of taste bud regeneration in the vallate papilla, soft palate and nasoincisor ducts (NID) following transection of either the glossopharyngeal (GL) or greater superficial petrosal (GSP) nerve. Following GL transection in rats (n = 6 per time point), taste buds reappeared in the vallate papilla between 15 and 28 days after surgery, and returned to 80.3% of control levels (n = 12) of taste buds by 70 days postsurgery. The first appearance and the final percentage of the normal complement of regenerated vallate taste buds after GL transection resembled that seen previously in the anterior tongue after CT transection. However, in the latter case, regenerated taste buds reached asymptotic levels by 42 days after surgery, whereas within the time frame of the present study, a clear asymptotic return of vallate taste buds was not observed. In contrast to the posterior (and anterior) tongue, only 25% of the normal complement of palatal taste buds regenerated by 112 days and 224 days after GSP transection (n = 9). The difference in regenerative capacity might relate to the surgical approach used to transect the GSP. These experiments provide useful parametric data for investigators studying the functional consequences of gustatory nerve transection and regeneration.

Animals↗
PubMed1988

Human taste bud density across adult age groups.

Some of the subjective variability attributed to taste experience could be related to wide variations of taste bud density. Studies of taste perception show a direct relationship between sensation and the number of receptors. Taste bud densities are quantified in this study using light microscopy to reconstruct two regions of 18 human cadaver tongues. Specimens came from male and female cadavers representing three age groups: young adults, middle-aged adults, and older adults. The results show a range of more than 100-fold in taste bud density that is evenly distributed among age groups and sexes. The disparity is not attributable to the state of health of the adults prior to death, and it is corroborated in the literature. Differences in taste bud density that extend across age groups probably confound some inferences about the effects of aging on taste sensitivity that are derived from cross-sectional studies of human populations. It is not clear from the data whether or not human taste bud density in individuals and in populations is stable or changing with time.

Adult↗
PubMed2005

Expression of glial cell line-derived neurotrophic factor (GDNF) and GDNF family receptor alpha1 in mouse taste bud cells after denervation.

Glial cell line-derived neurotrophic' factor (GDNF) has been isolated as a neurotrophic factor that affects the survival and maintenance of central and peripheral neurons. Using immunocytochemical methods, we examined whether the taste bud cells in mouse circumvallate papillae after transection of the glossopharyngeal nerves expressed GDNF and its receptor, GDNF family receptor alpha1 (GFRalpha1). By 5 and 10 days after denervation, the number of taste buds had decreased markedly; however, the remaining taste bud cells still expressed GDNF and GFRalpha1. By 14 days after denervation, most of the taste buds had disappeared and GDNF- and GFRalpha1-immunoreactive cells were not seen. By 4 weeks after denervation, numerous TrkB-immunoreactive nerve fibers had invaded the papilla and a few taste buds expressing GDNF and GFRalpha1 had regenerated. Thus, GDNF- and GFRalpha1-immunoreactive taste bud cells after denervation vanished following the disappearance of the taste buds and reappeared at the same time as the taste buds reappeared.

Animals↗
PubMed1998

The role of innervation in induction and differentiation of taste organs: introduction and background.

To establish lingual receptive fields that are the basic unit of taste function, ganglion cells must extend neurites of peripheral and central targets and form connections. This symposium concerns developmental interactions between the geniculate, trigeminal and petrosal ganglia and peripheral taste organs, the gustatory papillae and resident taste buds. Investigators present data from organ and tissue culture, from mice with targeted gene deletions and from grafting experiments, in pursuit of principles that direct early innervation of the taste system. The lingual ganglia and the taste papillae initially develop independently, but then become reciprocally dependent as ganglia drive neurotrophin support from gustatory papillae and the papillae require sensory innervation for growth and morphogenesis. The issue of subsequent taste bud induction is discussed with results from amphibian and mammalian models, yielding conclusions that are not yet totally convergent. However, an essential role for sensory innervation in mammalian taste bud differentiation and acquisition of appropriate quantitative relations between ganglion cells and target organs is clearly demonstrated. A working outline is presented for periods of ganglion cell/target organ independence and interdependence during early innervation of the peripheral taste system.

Animals↗
PubMed1998

Temporal process from receptors to higher brain in taste detection studied by gustatory-evoked magnetic fields and reaction times.

Using magnetoencephalography (MEG) and a taste stimulator with rapid-rise time, we previously located the primary gustatory area in the human cerebral cortex and also investigated the relation between the onset latency of the gustatory-evoked magnetic fields (GEM) and reaction times (RT) in different taste qualities. In the present study, we investigated the temporal process from receptors to the higher brain in taste detection based on the results of the GEM and RT of different tastes. We used 100 mM, 300 mM and 1 M NaCl and 3 mM saccharine. The duration of each stimulus was 400 ms. The interstimulus interval was approximately 30 s. The temperature of both taste solution and deionized water was maintained the same as that of the tongue. Four subjects participated in this experiment. The 64-channel whole-head SQUID system (CTF Systems Inc., Canada) was used to measure GEM. The sampling rate was 250 Hz, and the low-pass filter was 40 Hz. In each subject, GEM and RT to a given taste were measured separately by applying 40 trials of stimulation. After each trial of both measurements, subjects showed a perceived intensity by using their fingers. In the GEM study, the trials contaminated with eye movements were rejected and the remaining trials were averaged. Averaged GEM were super-imposed on the same sheet with all 64 channels to measure the onset latency of GEM from the stimulus onset. RT and onset latencies of GEM were longer for saccharine than NaCl, and the value of RT minus the onset latency of GEM from RT, presumably indicating the time for higher brain process plus motor process, did not differ between 3 mM saccharine and 1 M NaCl. With increased concentrations of NaCl, RT became shorter, but onset latencies of GEM remained constant. Sweet taste took a longer time than salty taste at receptor process including the time for diffusion to receptors.

Cerebral Cortex↗
PubMed1967

Altered temperature and taste responses from cross-regenerated sensory nerves in the rat's tongue.

1. The chorda tympani nerve, which innervates the front of the rat tongue, was found to be much less responsive to tongue cooling than the IXth nerve, which innervates the back of the tongue. The two nerves also differed in their relative responsiveness to various taste chemicals.2. Through cross-union the IXth nerve was made to innervate the front of the tongue, and in other rats the chorda tympani nerve the back of the tongue.3. After an average of 15 post-operative weeks, electrophysiological recordings of whole nerve action potential discharges were made from normal, control regenerated, and cross-regenerated nerves. Cooling, and chemical and mechanical stimulation of the tongue demonstrated that the control regenerated and cross-regenerated nerves had established functional connexions.4. Neither the response to cooling nor the relative taste responses were altered by either of two types of control chorda tympani nerve regeneration.5. In contrast, the cross-regenerated chorda increased its responsiveness to tongue cooling and the cross-regenerated IXthe nerve lost much of its responsiveness to cooling.6. Cross-regeneration also caused the relative taste responses to change and appear quite similar to the responses obtained from the nerve which normally innervated that tongue region (e.g. the cross-regenerated IXth nerve responded like a chorda tympani nerve).7. It is suggested that the sensory response evoked in the chorda tympani and IXth nerves by tongue cooling or taste stimulation is at least partially dependent upon the character of the tongue tissue in which the nerve terminates-the epithelium at the front differs from that at the back of the rat tongue.8. These results rule out the following two hypotheses: (a) that the nerve ending itself functions as a taste receptor in direct contact with applied chemicals and yet is uninfluenced by the character of the tissue in which it terminates, (b) that assuming the taste bud cells are an integral part of the receptive process, the taste nerve ending determines the chemical specificity of the taste cell which it induces, without any previous modification of the nerve by the tissue in which it terminates.

Action Potentials↗
PubMed1989

The cell biology of vertebrate taste receptors.

New technologies in neurophysiology and ultrastructural research are bringing about rapid advances in our understanding of taste, particularly at the cellular level. The model of chemosensory processing in the taste bud presented here can now be explored in great detail. The synaptic organization of the taste bud indicates a potential for intriguing peripheral integrative mechanisms, including cross-talk between taste cells, summation of chemoreceptor responses by interneurons (basal cells) in the taste bud, and centrifugal control of taste buds via efferent input from the CNS. Figure 2 summarizes these findings. The existence of voltage-gated ionic channels on taste cells and their unequal distribution in apical and basolateral membrane suggests mechanisms for chemosensory transduction: A primary event in the transduction process for many taste stimuli is likely to be the closure of apical potassium channels, thus leading to a depolarizing receptor potential. The closure of these apical potassium channels is probably mediated via cyclic nucleotides or intracellular Ca2+.

Animals↗
PubMed1997

Analysis and comparison of partial sequences of clones from a taste-bud-enriched cDNA library.

Differential patterns of cellular development and function are determined, at least in part, by the specific gene expression of particular cells. Thus, determination of differential patterns of gene expression between tissues is likely to help elucidate molecular details of tissue-specific processes. Our hypothesis was that cells of the circumvallate papilla involved in taste perception would express genes that are not expressed in the surrounding epithelium and that determination of the nature of these genes could be helpful in our understanding of the molecular details of taste. Using partial sequencing of clones derived from rat circumvallate papillae, we have begun to characterize genes that could be important in taste. We prepared a cDNA library of whole circumvallate papillae and, by means of a novel subtraction procedure, enriched taste-specific clones. Characterization of the libraries showed that subtraction resulted in good enrichment of taste-specific clones. Here we report the partial sequencing and analysis of 410 cDNA clones from the taste-bud-enriched cDNA library. Approximately 25% of the genes were identified on the basis of their high homology to known transcripts. These included the developmentally important molecules Pax-1, esp1, Notch 1, and Notch 3 that may play roles in the continuous turnover of taste receptor cells. A further 20% of the genes had no significant homology to known DNA sequences and were identified as taste-specific by Southern blot analysis.

Animals↗
PubMed2004

Acid-sensing ion channel-2 is not necessary for sour taste in mice.

The acid-sensitive cation channel acid-sensing ion channel-2 (ASIC2) is widely believed to be a receptor for acid (sour) taste in mammals on the basis of its physiological properties and expression in rat taste bud cells. Using reverse transcriptase-PCR, we detected expression of ASIC1 and ASIC3, but not ASIC4, in mouse and rat taste buds and nonsensory lingual epithelium. Surprisingly, we did not detect mRNA for ASIC2 in mouse taste buds, although we readily observed its expression in rat taste buds. Furthermore, in Ca2+ imaging experiments, ASIC2 knock-out mice exhibited normal physiological responses (increases in intracellular Ca2+ concentrations) to acid taste stimuli. Our results indicate that ASIC2 is not required for acid taste in mice, and that if a universal mammalian acid taste transduction mechanism exists, it likely uses other acid-sensitive receptors or ion channels.

Acid Sensing Ion Channels↗
PubMed2004

[Clinical experiences of the medication to taste disturbance by serum trace deficiency, especially serum iron deficiency].

Serum zinc deficiency is known to be a major cause of taste disturbances, but the effects of serum iron deficiency on taste disturbances are not widely known. In the present study, we clinically investigated the relationship between taste disturbances and serum iron deficiency as well as the results of pharmacological therapy. The clinical and serological test results of 25 patients with serum iron deficiency (3 men and 22 women; mean age +/- SD, 56.1 +/- 16.5 years) were reviewed at the Department of Otolaryngology, Hospital of Hyogo College of Medicine. All of the patients had been seen at the hospital between January 1999 and February 2003. Electrogustometry (EGM) and the filter paper disc method (FPD) were used to measure taste function. The patients were treated with iron and zinc supplements. The age distribution of the patients peaked at the ages of 40 and 70 years. The ratio of males to females was 1:7. Based on the EGM results, 70% of the patients exhibited taste disturbances. The FPD results showed that the recognition threshold of sour tastes was slightly higher than that of the other tastes. No significant difference in the results of treatment was seen, regardless of the duration of the deficiency. These results suggest that treatment with iron and zinc medicine is useful for correcting taste disturbances caused by serum deficiencies of trace elements.

Adult↗