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Plasma retinol transport system and taste acuity in patients with obstructive jaundice.

A study was conducted to elucidate the correlation between the plasma retinol transport system and taste acuity in patients with obstructive jaundice (OJ). Plasma levels of retinol, retinol-binding protein (RBP), transthyretin (TTR) and holo-RBP (retinol-RBP complex unbound to TTR), as well as the threshold of taste acuity, were determined in 8 cases with OJ (6 cases with common bile duct cancer and 2 cases with pancreas head cancer) and in 20 apparently healthy volunteers. These parameters were also measured serially in patients with OJ before and after percutaneous transhepatic biliary drainage (PTBD). Plasma levels of retinol, RBP and TTR were significantly decreased in every patients with OJ as compared with healthy controls, whereas changes in holo-RBP levels were not consistent. Taste acuity was found to be reduced in patients with decreased holo-RBP levels, while the acuity was preserved well in patients whose holo-RBP levels remained normal. Impaired taste acuity was rapidly improved in every patients after treatment with PTBD, significantly correlating with the recovery of plasma RBP and holo-RBP levels, and with the reduction of plasma total bilirubin levels. These results suggest that taste acuity is affected by the plasma retinol transport system, including serum levels of holo-RBP, from which retinol is delivered, presumably through a receptor-mediated manner, to the taste buds.

Adult↗

Effects of reversible block of callosal afferent inputs on the response characteristics of single neurons in the cortical taste area in rats.

We examined the change in magnitude of the taste responses of single neurons in the cortical taste area (CTA) in one side by reversibly blocking the CTA in the other side with a local anesthetic, procaine-HCl, in urethane-anesthetized rats. Taste responses of 68 taste neurons were continuously recorded for up to 2 h until recovery from the treatment, and those in 50 of them were found to be affected significantly. No remarkable difference was noted in the spatial distribution of the affected and non-affected neurons in the CTA. Many of the affected neurons were located in layers IV and V of area GI and in layer V of area DI. In most cases, changes in the taste responses of single neurons were in one direction, i.e., either a decrease or an increase, but in a few cases they decreased or increased depending on the stimulus. The taste profile of callosal inputs was estimated by subtracting responses after treatment from the control responses before treatment. The results suggest that the CTAs on both sides are functionally connected by way of callosal fibers as anatomical studies indicate, and that the CTA in one side receives excitatory or inhibitory inputs from the other side.

Anesthetics, Local↗

Innervation of developing human taste buds. An immunohistochemical study.

Morphological changes in developing human gustatory papillae during the 6th to the 23rd postovulatory week have been studied. The general innervation pattern of taste papillae and taste bud primordia was revealed immunohistochemically using antibodies against protein gene product 9.5 (PGP9.5), neurofilament H (NFH), neurofilament L (NFL), neurone-specific enolase (NSE), and tubulin. The autonomic and somatosensory nerve supply has been investigated using antibodies against substance P (SP), calcitonin gene-related peptide (CGRP), tyrosine hydroxylase (TH), neuropeptide Y (NPY), the neuronal form of nitric oxide synthase (n-NOS), and, enzyme histochemically, NADPH-diaphorase. Nerve fibers approach the basal membrane of the lingual epithelium around the 7th postovulatory week and invade the epithelium of papilla-like structures at the 8th week, but some also penetrate the basal membrane of the non-papillary epithelium. They are in close contact with slender epithelial cells that are considered to be the taste bud's progenitor cells. Early human taste buds situated at the anterior part of the tongue do not necessarily require a dermal (later fungiform) papilla. The NADPH-diaphorase reaction revealed positive results in dermal nerve fibers, but the immunohistochemical reaction against n-NOS was negative. Immunohistochemical detection of neuropeptides and vasoactive substances rendered negative results for developmental stages of 7-18 postovulatory weeks. By the 18th week, only SP was detected in dermal papillae, but not in the vicinity of taste buds' primordia. Thus, autonomic and somatosensory nerves seem not to play a key role in formation and maintenance of early human taste buds.

Biomarkers↗

Expression of NeuroD in the mouse taste buds.

NeuroD, a basic helix-loop-helix transcription factor, has been shown to play a role in the differentiation of neurons, olfactory cells, and neuroendocrine tissues. Since the taste buds have characteristics of typical paraneurons, we examined the expression of NeuroD in the taste buds of mice. By RT-PCR analysis, NeuroD mRNA was found to be expressed in the epithelium of circumvallate papillae-containing taste buds, but not in the lingual epithelium lacking them. NeuroD immunoreactivity was detected in a subset of taste bud cells in the circumvallate, foliate, and fungiform papillae and in the soft palate. NeuroD-expressing cells had a spindle-like shape, first appeared at postnatal day 3, and increased in number during postnatal development. After bisection of the glossopharyngeal nerves, NeuroD-expressing cells decreased in number at day 4 and disappeared from the trench wall of the circumvallate papillae by day 14. A few NeuroD-expressing taste buds reappeared at postoperative day 28. Denervation and regeneration experiments showed that expression of NeuroD in the taste buds was dependent upon gustatory innervation. Double immunolabeling with gustducin or with neural cell adhesion molecule (NCAM) showed that NeuroD-expressing cells did not express NCAM, but did express gustducin. These results suggest that NeuroD is expressed in a mature cell type, type-II cells, but not in type-III cells.

Animals↗

P2Y isoforms operative in mouse taste cells.

Recent functional evidence indicates that mouse taste cells express P2Y receptors coupled to IP(3) production and Ca(2+) mobilization. Our studies of the expression profile of particular P2Y isoforms in the taste tissue of the mouse have revealed that ATP and UTP equipotently mobilize intracellular Ca(2+) at saturating concentrations, suggesting that common receptors for both nucleotides, i.e., P2Y(2) and P2Y(4) subtypes, might be involved. Reverse transcription/polymerase chain reaction and immunohistochemistry have confirmed the presence of P2Y(2) and P2Y(4) receptors in a population of taste bud cells from the circumvallate and foliate papillae. Transcripts for the P2Y(1) and P2Y(6) isoforms have also been detected in taste tissue preparations, this observation being consistent with the ADP and UDP responsiveness of taste cells. Together, our data suggest that P2Y(2) and P2Y(4) receptors play a predominant role in mediating taste cell responses to ATP and UTP.

Adenosine Triphosphate↗

Induction of apoptosis by colchicine in taste bud and epithelial cells of the mouse circumvallate papillae.

Apoptotic cells in the taste buds and epithelia of mouse circumvallate papillae after colchicine treatment were examined by the methods of in situ DNA nick-end labeling, immunocytochemistry, and electron microscopy. After colchicine treatment, numerous positive cells appeared in the taste buds by DNA nick-end labeling, and some epithelial cells in the basal and suprabasal layers in and around the circumvallate papillae also revealed positive staining. Condensed and fragmented nuclei with a high density were occasionally found in the taste bud cells and in the basal and suprabasal layer epithelial cells by electron-microscopic observation. An immunocytochemical reaction for tubulin revealed weak staining in taste bud cells, because of the depolymerization of microtubules, and a decrease of the microtubules in the taste bud cells was observed by electron microscopy. These results indicate that colchicine treatment of mice induces the apoptosis of taste bud and epithelial cells in the circumvallate papillae and dorsal epithelial cells around the circumvallate papillae.

Animals↗

Altered food intake and taste perception in children with cancer after start of chemotherapy: perspectives of children, parents and nurses.

GOALS OF WORK: The purpose of this study was to better understand various variables related to food intake and eating problems in children with cancer during their chemotherapy. PATIENTS AND METHODS: Twenty-two consecutively admitted children, diagnosed with cancer and undergoing chemotherapy, participated in this study. Twenty-one of them, their parents and attending nurses participated in semi-structured interviews. Ten of the children underwent a taste acuity test, and recognition thresholds for the four basic tastes were determined. MAIN RESULTS: The shared view of both children and parents was that altered taste was the predominant cause of the eating problems. In contrast, the nurses perceived that nausea was the most important cause of the children's eating problems. In addition, psychological aspects such as learned food aversions and negative attitudes towards hospital food were regarded as important by children, parents and nurses. The taste test showed that the patients had higher thresholds for bitter taste and made more taste recognition errors compared to controls. CONCLUSIONS: Changes seem to exist both in the primary gustatory sense as well as in food perception in paediatric cancer patients undergoing chemotherapy. Single solutions, such as efforts to serve "tasty food", do not suffice alone. A more effective solution may be to combine different strategies and combinations of oral, enteral and parenteral nutrition should be considered to prevent malnutrition.

Adolescent↗

The distribution of fungiform papillae and taste buds on the human tongue.

Investigations on monkeys have shown that the application of the acidic dye Ponceau S red or the basic dye Alcian blue to the tongue surface facilitates identification of fungiform papillae and taste buds. Both of these dyes were now used in varying degrees of acidity on fixed and unfixed human cadaveric tongues in an attempt to determine the regional distribution of papillae and buds. Satisfactory staining was obtained with acidic Ponceau S red in 10% formalin and 10% trichloracetic acid (pH 2.5). For six tongues, the number of fungiform papillae ranged from 171 to 253 (mean 195) and these were located predominantly at the tip. Of the fungiform papillae, 67% had no staining of taste bud pores. The average number of visible taste pores on the other fungiform papillae was 3 (range 1-21). The correlation between the number of stained taste pores and underlying taste buds was confirmed using serial histological sections of 90 fungiform papillae. This work has shown that a mean of 193 taste buds are carried on fungiform papillae of the human tongue and that 87% of these are located in the anterior 2 cm.

Adolescent↗

Axonal transport maintains taste responses.

Transection of the gerbil's IXth nerve causes gustatory action potentials to decline in 1-6 h; the rate of decline is a linear function of the length of the nerve stump remaining attached to the tongue. To test the implication that taste discharge mechanisms depend upon axonal transport in the IXth nerve, we injected 40 nl of [3H]leucine into the petrosal ganglion of one IXth nerve of the gerbil, Meriones unguiculatus. Subsequent liquid scintillation counting of the petrosal ganglion, IXth nerve segments, and representative areas of the tongue indicated that labeled materials were transported down the IXth nerve primarily to the vallate and ipsilateral foliate taste papillae of the tongue. A significant impairment of axonal transport and a substantial decline in summated IXth nerve taste responses occurred within 2-3 h after colchicine was applied to the IXth nerve trunk between the tongue and the petrosal ganglion. Similarly, cooling the IXth nerve with a 3-10 degrees C thermocouple junction or metal probe impaired axonal transport and caused a taste response decline. Since impulse mechanisms of the nerve trunk continued to function distal to these sites of treatment, we concluded that the maintenance of taste discharges at the level of the taste bud depends upon unimpeded axonal transport.

Action Potentials↗

Ion dependence of the eel taste response to amino acids.

The effects of changed ionic environments on the taste responses to amino acids were examined by recording the activity of the palatine nerve. The responses to glycine, L-proline and L-arginine dissolved in deionized water were greatly reduced after ions were removed from the surface of the palatine epithelium by treatment with 5 mM EDTA. The addition of various species of salts to amino acid solutions caused reversible recovery of the responses. The response to 0.1 mM glycine increased with an increase in salt concentration in amino acid solutions and reached saturation level. The effects of salts of divalent cations (CaCl2 and MgCl2) appeared at much lower concentration (10(-7) M) than those of salts of monovalent cations (NaCl and KCl) (10(-4) M), suggesting that cations support the taste response. All the organic cations examined, including those of large molecular weights (choline, Tris, bis-Tris, bis-Tris propane, tetraethylammonium, triethanolamine and D-glucosamine), also supported the taste responses. The results obtained led to a conclusion that not a specific cation but various species of cations can support the eel taste responses. It is suggested that the cations do not act as current carrying ions to depolarize the taste cells but that the binding of the cations to the receptor membrane plays an essential role in taste reception.

Amino Acids↗

Neuropeptides are present in projection neurones at all levels in visceral and taste pathways: from periphery to sensory cortex.

Using combined immuno-staining and retrograde tracing techniques many of the ascending visceral and taste pathways within the rat central nervous system have been shown to be composed of a variety of neuropeptide and catecholamine synthesizing enzyme containing neurones. The pathway we examined extended from the periphery to sensory cortex and included: the nodose ganglion (periphery)----solitary nucleus (medulla)----parabrachial nucleus (pons)----ventral posterior medial nucleus (thalamus)----visceral and taste sensory areas (cortex). In the solitary nucleus of the medulla many neuronal cell bodies could be shown to be both immuno-positive for one of 6 neuropeptides including avian pancreatic peptide (APP), cholecystokinin (CCK), enkephalin (ENK), neurotensin (NT), somatostatin (SOM) and substance P (SP) or the catecholamine synthesizing enzyme tyrosine hydroxylase (TOH) and to have a projection to the parabrachial nucleus of the pons. In the parabrachial nucleus of the pons many neuronal cell bodies could be shown to be immuno-positive for one of 5 neuropeptides (CCK, ENK, NT, SOM, SP) and have a projection to the ventral posterior medial nucleus of the thalamus. In the ventral posterior medial nucleus of the thalamus several neuronal cell bodies were shown to be immuno-positive for one of 3 neuropeptides (CCK, ENK, SOM) and project to the visceral and taste sensory cortex. This is the first report of neuropeptides being present in the projection neurones of any sensory system in the central nervous system and for the first time describes an entire set of putative neurotransmitters which extends from the periphery to the sensory cortex. From previous studies it also appears that in all cases examined the relevant receptors are present in these visceral and taste relay nuclei in order for the neuropeptide or catecholamine to produce an effect upon release. Comparisons between rat and other animals suggest that a similar organization of these visceral and taste pathways may also be present in other mammals including man. Functionally these neuropeptides containing projection neurones appear to be primarily involved in relaying visceral information rather than taste information. In this capacity activation of these neurones may produce such visceral sensations as malaise, well being, hunger, satiety or thirst.

Afferent Pathways↗

Responses of the hamster chorda tympani nerve to binary component taste stimuli: evidence for peripheral gustatory mixture interactions.

Studies of taste mixtures suggest that stimuli which elicit different perceptual taste qualities physiologically interact in the gustatory system and thus, are not independently processed. The present study addressed the role of the peripheral gustatory system in these physiological interactions by measuring the effects of three heterogeneous taste mixtures on responses of the chorda tympani (CT) nerve in the hamster (Mesocricetus auratus). Binary taste stimuli were presented to the anterior tongue and multi-fiber neural responses were recorded from the whole CT. Stimuli consisted of a concentration series of quinine.HCl (QHCl: 1-30 mM), sodium chloride (NaCl: 10-250 mM), sucrose (50-500 mM) and binary combinations of the three different chemicals. Each mixture produced a unique pattern of results on CT response magnitudes measured 10 s into the response. Sucrose responses were inhibited by quinine in QHCl-sucrose mixtures. Neural activity did not increase when quinine was added to 50-250 mM NaCl in QHCl-NaCl mixtures. However, the neural activity elicited by sucrose-NaCl mixtures was greater than the activity elicited by either component stimulus presented alone. The results demonstrate that gustatory mixture interactions are initiated at the level of the taste bud or peripheral nerve. Mechanisms for these interactions are unknown. The results are consistent with one component stimulus modifying the interaction of the other component stimulus with its respective transduction mechanism. Alternatively, peripheral inhibitory mechanisms may come into play when appetitive and aversive stimuli are simultaneously presented to the taste receptors.

Analysis of Variance↗

Regeneration of taste buds by nongustatory nerve fibers.

Previous cross-reinnervation studies in situ by other investigators have demonstrated that cutaneous sensory and motor axons are incapable of trophically supporting mammalian taste buds. The present experiments examined the gustatory trophic potency of chemosensory and barosensory axons of the carotid sinus nerve. We report here that morphologically normal taste buds appeared on cat circumvallate papillae at 2 to 19 months after cross-anastomosis of the carotid sinus and lingual nerves, branches of the IXth cranial (glossopharyngeal) nerve. However, neurophysiologic and histologic data also indicated that, despite microsurgical procedures designed to direct regenerating lingual nerve fibers toward the carotid body and carotid sinus, some lingual axons escaped the anastomosis and subsequently grew within their native distal stump. The principal objective of this study was thus to determine whether foreign innervation of taste buds did indeed occur, or regenerated lingual nerve fibers were instead responsible for the newly formed buds. Our results showed that stray lingual fibers were not responsible for the reappearance of taste buds because transection of the original proximal lingual nerve stump (cross-anastomosed to the distal carotid sinus nerve stump) did not reduce the incidence of taste buds or the accumulation of radiolabeled material axoplasmically transported from the petrosal (sensory) ganglion. Autoradiography of labeled tissue samples showed that more than 90% of the taste buds were labeled at 8 and 9 days after lingual nerve transection. These data support the hypothesis that sensory axons in the carotid sinus nerve share an important trophic chemistry with gustatory neurons.

Animals↗

Role of thought, sight, smell, and taste of food in the cephalic phase of gastric acid secretion in humans.

The relative importance of thought, sight, smell, and taste of food in the cephalic phase of gastric acid secretion has not been studied systematically. We found that discussing appetizing food for 30 min (without sight, smell, or taste) increased acid secretion from 4 to 13 mmol/h in healthy human subjects (p less than 0.001) and also increased serum gastrin concentrations significantly (p less than 0.02). Discussing food resulted in an acid secretory response that averaged 66% +/- 10% of the response to modified sham feeding, which activates thought, sight, smell, and taste. Discussing topics other than food (e.g., current events, sports) did not increase acid secretion significantly. The sight of appetizing food (without smell or taste), the smell of appetizing food (without sight or taste), or the combination of sight and smell (without taste) also increased acid secretion and serum gastrin concentrations significantly. However, sight and smell were significantly less potent stimulants of acid secretion than sham feeding, with responses averaging only 23%-46% of the response to sham feeding. These studies indicate that thinking about food is a potent stimulant of gastric secretion in healthy humans. Moreover, the sight and smell of food increase gastric acid secretion and serum gastrin concentrations, probably by provoking thoughts related to food.

Adult↗

Veterans Administration Cooperative Studies Project No. 147: association of metallic taste with metal ceramic alloys.

We examined patients to find out whether they noticed the prevalence of metallic taste and set out to determine the association of metallic taste with demographic, medical, and dental factors. Data were collected as part of a Veterans Administration Cooperative Study investigating the suitability of alternative metal ceramic alloys as substitutes for alloys that contain gold. Crowns and fixed partial dentures were made from control and alternative alloys for accepted volunteer patients. A month after placement of the restorations and at regularly scheduled recall appointments, the patients were asked if they tasted a metallic flavor. Of the 2023 times the question was asked, 101 positive responses were given by 68 patients (46 reported metallic flavor once, and 22 reported it more than once). Results indicated that youth, sensitivity to heat and cold, bruxism, grinding, and an increasing number of restorative units were significantly related to metallic taste. For any given visit, about 5% of the patients reported tasting a metallic flavor regardless of the type of alloy that was used in the restoration. Metallic taste does not appear to be a problem with alternative alloys.

Adult↗

Distribution of taste buds on the lips and inside the mouth in a minnow, Pseudorasbora parva.

The distribution and abundance of taste buds were quantitatively examined by observing silver impregnated serial sections. The taste buds were widely dispersed on the skin, the lips, the mucosa in the oro-pharyngeal cavity, the esophagus, and the branchial apparatus. The great majority of them was found on the lips and inside the mouth. The external buds were concentrated especially on the outer lips and the adjacent skin, while their number diminished in a caudal direction. Very few were found on the scaled skin. The total number of external buds in a specimen of 6 cm in length was 1,486. The number of taste buds inside the mouth was 6,600. On the inner lips and the palatal organ densities were found to reach over 140 per mm2. High concentrations of taste buds were also found on the gill arches and rakers. These taste buds varied to some extent in size and shape, depending on the thickness of the epithelial layer. It is suggested that the minnow may use the lips, gills and palatal organ as its main taste organs.

Animals↗

Conditioned aversion to a taste perceived while grooming.

Four experiments were conducted to determine how the characteristics of conditioned taste aversion (CTA), as described from studies conducted in the drinking and feeding contexts, applied in the grooming context. In Experiment 1, sodium saccharin was mixed with a "neutral-tasting" jelly and applied to the fur of male Sprague-Dawley rats. Rats injected with LiCl after the applications strongly avoided saccharin solutions in subsequent 1-hr, 2-choice (Saccharin solution vs water) drinking tests, whereas rats injected with NaCl or given plain jelly on the fur showed only an initial neophobic response to the saccharin solution. Thus, the taste of saccharin was perceived while grooming and the CTA formed in the grooming context generalized to drinking. In experiments 2-4, we obtained evidence that: (a) rats discriminated between one intensity of saccharin applied to the fur and another used in the test solution; and (b) rats differentiated between qualities of the two tastants applied to the fur in that saccharin overshadowed NaCl; and (c) taste qualities were more important than toxic properties when two stimuli (Saccharin, LiCl) were used (saccharin overshadowed NaCl in subsequent drinking tests). We speculate that taste, while grooming might play a role in social communication in some vertebrates. Further, CTA and grooming might have uses in rodent control (e.g., in agricultural situations) not previously considered such as in delivering a non-attractive, low-salience toxin so that the taste of the crop overshadows that of the bait, and induces crop aversion.

Animals↗

The effect of amygdala-kindled seizures on the acquisition of taste and odor aversions.

Two experiments were conducted to investigate the effect of amygdala-kindled seizures on the acquisition of fluid aversions using taste, odor, and compound taste-odor cues. In Experiment 1 all subjects were poisoned with lithium chloride 30 minutes after ingesting a novel taste. Experimental subjects were either kindled 15 minutes following ingestion or 15 minutes following LiCl injection. The strength of the taste aversion in the kindled animals was significantly attenuated compared to nonkindled controls. There was a tendency for kindling within the CS-US interval to be more disruptive than kindling that occurred after LiCl injection. The second study explored the effect of kindling after the CS on the development of aversions to an odor cue or a compound taste-odor cue. This study found that kindling after drinking effectively blocked the acquisition of both odor and taste aversions and compounding did not affect the strength of the odor aversion.

Amygdala↗