Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Taste Buds”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,135 records · Page 63Linked to original sources
PubMed1988

Response properties of fibers in the hamster superior laryngeal nerve.

The purpose of the present investigation was to record electrophysiological responses from single fibers in the hamster superior laryngeal nerve (SLN) that were responsive to chemical stimulation of the larynx. Twenty chemical solutions, commonly used in studies of mammalian gustatory physiology, were applied to taste buds on and around the epiglottis. These stimuli were dissolved in physiological saline. Responses were the number of impulses elicited over a 15-s period following stimulus onset, above or below the background activity elicited by a previous rinse with saline. Unlike fibers in the hamster chorda tympani or glossopharyngeal nerves, SLN units were not easily classifiable into response types. Excitatory stimuli were primarily acids and bitter-tasting stimuli, with the order of their effectiveness being urea much greater than tartaric acid greater than HCl greater than KCl greater than citric acid greater than caffeine greater than quinine hydrochloride greater than acetic acid. The sweet-tasting stimuli and most salts other than KCl were primarily inhibitory, with the order of inhibitory effectiveness being CaCl2 greater than sucrose greater than fructose greater than LiCl greater than NaNO3 greater than Li2SO4 greater than NaCl. A hierarchical cluster analysis of fibers yielded no distinct clusters, yet differing sensitivities across the fibers were suggested. SLN fibers are highly responsive to sour and bitter stimuli, although they are not sensitive to fine differences in taste quality, as are fibers in other gustatory nerves.

Action Potentials↗
PubMed2000

Reduction in carbonic anhydrase activity in the tongue epithelium and submandibular gland in zinc-deficient rats.

We investigated the effects of zinc deficiency on carbonic anhydrase (CA) activity in the tongue epithelium and submandibular gland in rats. Male 4-week-old SD rats were given free access to a diet containing 2.2 (zinc-deficient), 4.1 (low-zinc), or 33.7 (zinc-sufficient) mg zinc/kg diet for 6 weeks. Rats in the fourth group (receiving 33.7 mg zinc/kg) were pair-fed against the zinc-deficient rats. Biochemical analysis at the end of the experimental period indicated that zinc deficiency significantly reduced CA activity in the tongue epithelium and submandibular gland, and the CA activity levels in these tissues seemed to parallel the dietary zinc levels. By enzyme histochemistry, an intensely positive reaction for CA was observed in the middle and basal regions of the taste buds in the circumvallate papilla in the zinc-sufficient and pair-fed (control) rats. The cells in von Ebner's glands also showed a strong positive reaction in control rats, although only a weak reaction product was found in zinc-deficient rats. These results suggest that CA activity is affected by the dietary content of zinc, which is considered to be an indispensable factor for the maintenance of normal taste sensation.

Animal Feed↗
PubMed1976

Conformational transitions of monellin, an intensely sweet protein.

Conformational transitions of monellin, an intensely sweet protein from the berries of Dioscoreophyllum cumminsii, were studied by the circular dichroism (CD) probe. According to the CD spectra, monellin has a low content of the helical structure and a significant amount of the pleated sheet (beta) conformation. The native conformation was found to be sensitive to alkali, sodium dodecyl sulfate, and guanidine-HC1, but it was stable in acid (e.g. pH 2.4) as shown by CD and persistence or the disappearance of sweet taste. The main chain conformation of the alkali-denatured monellin (pH 10.9) was restored upon acidification (pH 3.3) of the alkaline solutions. The tertiary structure, however, was not completely restroed, as indicated by CD in the 230-300 nm spectral zone, although the sweet taste reappeared. If the pH of a neutral solution was raised to 9.6, the CD in the near ultraviolet was significantly altered, though the sweet taste persisted. This indicates that a slight conformational change did not interfere with the effects on the taste buds. While sodium dodecyl sulfate readily disorganized the tertiary structure, the main chain was reconstructed by this reagent into a new form of higher helix content than in the native macromolecule. Reconstruction into a modified conformation of higher helix content was achieved also with 50% ethanol. The main chain conformation was not affected by 25% ethanol which produced slight changes in the CD at 230-260 nm zone and did not abolish the sweet taste.

Circular Dichroism↗
PubMed1982

Environmental factors affecting chemoreceptors: an overview.

Vertebrate olfactory and gustatory receptors are necessarily exposed to the fluid which contains their relevant chemosensory environment. In terrestrial mammals, the nasal airways serve as protective accessory tissues for the olfactory receptors, but tastes receptors in all vertebrates and olfactory receptors in fish are directly exposed to the liquids which bring chemosensory stimuli to them. The differentiated epithelial cells which form taste buds and the specialized neurons which are the vertebrate olfactory receptors are constantly replaced in normal adult animals, suggesting that chemosensory function per se is damaging to the receptors. Organic and sulfur-containing air pollutants may be among those which adversely affect olfactory receptors, but adequate data are not available. Surfactants and heavy metals can produce physiological and/or morphological damage in gustatory receptors. Some heavy metals are concentrated in saliva, a liquid which interacts closely with taste receptors. A failure to evaluate human chemosensory function in relation to potential chemosensory toxicants accounts for the present inability to specify the incidence of the problem.

Animals↗
PubMed1995

Glossopharyngeal nerve transection does not compromise the specificity of taste-guided sodium appetite in rats.

The chorda tympani nerve (CT) has been shown to be critical in the sodium-specific drinking behavior of sodium-depleted rats, but the role of other gustatory nerves and the contribution of the major salivary glands remain to be elucidated. In this study, rats received either bilateral section of the CT (CTX) or the glossopharyngeal nerve (GLX), extirpation of the sublingual and submaxillary salivary glands (DSAL), or sham surgery. After recovery, rats were sodium depleted with furosemide and tested for their licking responses to 0.05 and 0.3 M NaCl, KCl, CaCl2, and NH4Cl, as well as distilled water in an automated gustometer. Rats that received GLX maintained a specific sodium appetite comparable to controls despite denervation of approximately 64% of the taste buds. In contrast, compared with control rats, CTX and DSAL rats had altered response profiles, showing much smaller differences in licking to NaCl relative to the other stimuli. This was accompanied by a substantially lower lick rate in DSAL rats, raising the possibility that general licking impairments contributed to the decreased NaCl responsiveness in these rats. These findings imply that the CT, but not the glossopharyngeal nerve, is necessary for the maintenance of normal sodium-specific, taste-guided behavior under sodium deplete conditions.

Animals↗
PubMed1986

Comparison of fatty acid patterns of polar and neutral lipid classes and cyclo-oxygenase activity in taste and non-taste epithelium of steer tongues.

Epithelial tissues and papilla from several regions of the steer tongue were isolated and the fatty acids from each lipid class in the polar and neutral fractions were assayed. The observed profiles indicated regional differences. Arachidonic acid and other fatty acids containing long carbon chains (greater than 22) were found in all tissues sampled, particularly in the phosphatidyls of the inositols, ethanolamines, cholines, and in the cholesterylesters. Production of prostaglandin E2 was measured through cyclo-oxygenase activity and the presence of plasmalogens was observed in the phosphatidylethanolamine and choline fractions. Higher rates of PGE2 synthesis and greater amounts of plasmologens were found in taste-related epithelial samples compared to lingual epithelial control samples not containing taste buds. The heterogeneity of patterns of lipids and fatty acids found in the epithelium of the tongue suggests possible zonal specialization to satisfy regional physiological needs.

Animals↗
PubMed2006

In-mouth amylase activity can reduce perception of saltiness in starch-thickened foods.

Sensory scores for saltiness and thickness obtained for savory liquids thickened with starches or the nonstarch hydrocolloid hydroxypropylmethyl cellulose (HPMC) were correlated with the panelists' amylase activity. Although higher enzyme activities were linked to lower thickness scores for systems thickened by starch, they were also associated with a decreased taste perception, particularly for starches retaining a granular structure after gelatinization (wheat and modified waxy maize). Microscopic evidence showed that the enzyme can disrupt such structures, and this is associated with a decreased mixing efficiency with water and consequently a reduced transport of tastant (sodium) to the saliva (aqueous) phase and to the taste buds. This explains the lower saltiness scores for subjects with higher amylase activity, even if they are associated with a lower perceived thickness.

Adult↗
PubMed1986

Autonomic mechanisms underlying capsaicin induced oral sensations and salivation in man.

The effects of capsaicin, citric acid and nicotine applied to the apex or radix of the tongue on taste sensations and salivation were studied in relation to the presence of substance P immunoreactive neurones in man. Application of capsaicin (30 micron) to the apex of the tongue or to the palatinal mucosa, but not to the radix of the tongue, caused a reproducible burning sensation and salivation from the submandibular-sublingual and parotid glands. The salivation response to capsaicin was reduced by methylscopolamine pretreatment. Similar levels of substance P immunoreactivity were present in the lingual apex and radix area (including vallate papillae) of man, while in the cat about 4 times higher levels of substance P immunoreactivity were present in the vallate papillae than in the lingual apex. Immunohistochemistry showed that in the cat many substance P immunoreactive nerves were associated with the taste buds of the vallate papillae, while in man substance P immunoreactive fibres were only seen penetrating into the epithelium of the lingual apex. In addition some subepithelial blood vessels in all regions were surrounded by substance P immunoreactive nerves in both cat and man. Citric acid application to the tongue apex caused both submandibular-sublingual and parotid salivary secretion concomitant with a burning sensation. Salivary secretion was also seen after citric acid application to the radix of the tongue. This response was associated with a sour taste. The salivation response to citric acid was not significantly reduced by methylscopolamine pretreatment. Lingual apex application of nicotine was associated with a sweet taste and a small rise in salivary secretion rate. This response was not significantly reduced by methylscopolamine. In conclusion, the sensitivity to capsaicin of the human tongue is restricted to the apex portion. This is in parallel with the occurrence of intraepithelial substance P immunoreactive nerve fibres. Capsaicin induced salivary secretion seems mainly to be mediated via parasympathetic, cholinergic reflex mechanisms. Citric acid and nicotine induced salivation responses are comparatively more resistant to methylscopolamine pretreatment.

Adolescent↗
PubMed2006

Arachidonic acid can function as a signaling modulator by activating the TRPM5 cation channel in taste receptor cells.

Vertebrate sensory cells such as vomeronasal neurons and Drosophila photoreceptor cells use TRP channels to respond to exogenous stimuli. In mammalian taste cells, bitter and sweet substances as well as some amino acids are received by G protein-coupled receptors (T2Rs or T1Rs). As a result of activation of G protein and phospholipase Cbeta2, the TRPM5 channel is activated. Intracellular Ca(2+) is known to be a TRPM5 activator, but the participation of lipid activators remains unreported. To clarify the effect of arachidonic acid on TRPM5 in taste cells, we investigated the expression profile of a series of enzymes involved in controlling the intracellular free arachidonic acid level, with the result that in a subset of taste bud cells, monoglyceride lipase (MGL) and cyclooxygenase-2 (COX-2) are expressed as well as the previously reported group IIA phospholipase A(2) (PLA(2)-IIA). Double-labeling analysis revealed that MGL, COX-2 and PLA(2)-IIA are co-expressed in some cells that express TRPM5. We then investigated whether arachidonic acid activates TRPM5 via a heterologous expression system in HEK293 cells, and found that its activation occurred at 10 microM arachidonic acid. These results strongly suggest the possibility that arachidonic acid acts as a modulator of TRPM5 in taste signaling pathways.

Animals↗
PubMed2005

Pseudogenization of a sweet-receptor gene accounts for cats' indifference toward sugar.

Although domestic cats (Felis silvestris catus) possess an otherwise functional sense of taste, they, unlike most mammals, do not prefer and may be unable to detect the sweetness of sugars. One possible explanation for this behavior is that cats lack the sensory system to taste sugars and therefore are indifferent to them. Drawing on work in mice, demonstrating that alleles of sweet-receptor genes predict low sugar intake, we examined the possibility that genes involved in the initial transduction of sweet perception might account for the indifference to sweet-tasting foods by cats. We characterized the sweet-receptor genes of domestic cats as well as those of other members of the Felidae family of obligate carnivores, tiger and cheetah. Because the mammalian sweet-taste receptor is formed by the dimerization of two proteins (T1R2 and T1R3; gene symbols Tas1r2 and Tas1r3), we identified and sequenced both genes in the cat by screening a feline genomic BAC library and by performing PCR with degenerate primers on cat genomic DNA. Gene expression was assessed by RT-PCR of taste tissue, in situ hybridization, and immunohistochemistry. The cat Tas1r3 gene shows high sequence similarity with functional Tas1r3 genes of other species. Message from Tas1r3 was detected by RT-PCR of taste tissue. In situ hybridization and immunohistochemical studies demonstrate that Tas1r3 is expressed, as expected, in taste buds. However, the cat Tas1r2 gene shows a 247-base pair microdeletion in exon 3 and stop codons in exons 4 and 6. There was no evidence of detectable mRNA from cat Tas1r2 by RT-PCR or in situ hybridization, and no evidence of protein expression by immunohistochemistry. Tas1r2 in tiger and cheetah and in six healthy adult domestic cats all show the similar deletion and stop codons. We conclude that cat Tas1r3 is an apparently functional and expressed receptor but that cat Tas1r2 is an unexpressed pseudogene. A functional sweet-taste receptor heteromer cannot form, and thus the cat lacks the receptor likely necessary for detection of sweet stimuli. This molecular change was very likely an important event in the evolution of the cat's carnivorous behavior.

Journal Article↗
PubMed1985

Vitamin A deficiency and sensory function.

Morphological investigation of tongue, olfactory epithelia, trachea and inner ear in vitamin A deficiency are reported. The results support assumptions concerning the loss of sensory function as been at least a secondary effect of alterations of the neighbourhood of the sensory cells caused by vitamin A deficiency. Taste buds are hindered in function by a dense layer of squamous cells and olfaction is decreased by atrophy of the surrounding respiratory epithelium. Inner ear functionality seems to be affected by vitamin A status via a stabilizing effect on the endolymph-perilymph barrier.

Animals↗
PubMed1992

Maltose: the primary signal of hunger and satiation in human beings.

In rats, blood glucose concentration serves as the primary signal responsible for the induction of the sensation of hunger. In human beings, however, blood glucose concentration has been shown not to be the primary signal for the production of hunger sensation. Disaccharide, in the form of lactose in milk, sucrose in nature, and maltose from the breakdown of starch in the mouth, is part and parcel of human diet. The present study tested the hypothesis that maltose could be the primary signal responsible for the induction of the sensation of hunger and satiation in human beings. The hunger-moderating effect of maltose was compared with that of glucose by applying the test materials to the sweet-sensing taste buds on the tongue. Even at lower dosages, the effect of maltose was significant. At higher dosages, both glucose and maltose caused significant moderation of hunger. Maltose, a disaccharide, can be the agent responsible for the primary signals to induce the sensations of hunger and satiation in human beings.

Adult↗
PubMed1998

The arginine taste receptor. Physiology, biochemistry, and immunohistochemistry.

The amino acid, L-arginine (L-Arg), is a potent taste stimulus for the channel catfish, Ictalurus punctatus. Receptor binding studies demonstrated a high-affinity binding of L-Arg to putative taste receptor sites. This binding could be inhibited by preincubation of the tissue in the lectins Phaseolus vulgaris agglutinin (PHA) and Ricinus communis agglutinin I (RCA I). Neurophysiological studies demonstrated that the L-Arg receptor is a stimulus-gated ion channel type receptor whose conductance was stimulated by L-Arg and inhibited by D-arginine (D-Arg). To purify the receptor we subjected CHAPS solubilized partial membrane preparation from barbel epithelium to RCA I lectin affinity chromatography. The bound proteins were eluted with D-galactose. When these proteins were reconstituted into lipid bilayers, L-Arg activated single channel currents with conductances between 45 and 85 pS. Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the eluted protein showed a distinct band at approximately 83 kDa. Polyclonal antibodies raised against this 83-kDa band in guinea pigs reacted with numerous small (approximately 1 micron) sites within the taste pore of every taste bud when applied to fixed nonpermeabilized barbels. This observation suggests that the antibodies recognize an externally-facing epitope of the putative Arg receptor. The antibodies also inhibited L-Arg-stimulated currents in reconstitution studies. Sephacryl S-300 HR chromatography of the eluant from the affinity column showed a high molecular weight peak (> 700 kDa) which was recognized by the antibodies. Reconstitution of the protein from this peak into a lipid bilayer resulted in L-Arg-stimulated channels that could be inhibited by D-Arg. This high molecular weight component may be aggregates of the arginine taste receptor.

Animals↗
PubMed2006

Neurological causes of taste disorders.

In caring for patients with taste disorders, the clinical assessment should include complete examination of the cranial nerves and, in particular, gustatory testing. Neurophysiological methods such as blink reflex and masseter reflex allow the testing of trigeminofacial and trigeminotrigeminal pathways. Modern imaging methods (MRI and computed tomography) enable the delineation of the neuroanatomical structures which are involved in taste and their relation to the bony skull base. From a neurological point of view, gustatory disorders can result from damage at any location of the neural gustatory pathway from the taste buds via the peripheral (facial, glossopharyngeal and vagal nerve) and central nervous system (brainstem, thalamus) to its representation within the cerebral cortex. Etiopathogenetically, a large number of causes has to be considered, e.g. drugs and physical agents, cerebrovascular disorders including dissection of the carotid artery and pontine/thalamic lesions, space-occupying processes - in particular tumors compressing the cerebellopontine angle and the jugular foramen of the skull base - head trauma and skull base fractures, isolated cranial mononeuropathy (e.g. Bell's palsy) or polyneuropathy, epilepsy, dementia, multiple sclerosis and major depression. In addition to this, aging can also lead to diminished taste perception. Due to the broad differential diagnostic considerations, it is essential to look for additional, even mild, neurological signs and symptoms. Treatment must relate to the underlying cause. Zinc may be tried in idiopathic dysgeusia.

Aging↗
PubMed1995

Functional expression of the taste specific G-protein, alpha-gustducin.

The taste-specific G-protein alpha-subunit, alpha-gustducin, was expressed using a baculovirus based system. alpha-Gustducin was demonstrated to be myristoylated and was also palmitoylated in insect larval cells. Recombinant alpha-gustducin was purified to homogeneity. Neither receptors nor effectors that interact with gustducin in taste are known. However, alpha-gustducin has a close structural similarity to the visual G-protein, alpha-transducin. Therefore alpha-gustducin was reconstituted with components of the visual system to determine the degree of its functional similarity with alpha-transducin. Despite the fact that the sequences of alpha-gustducin and alpha-transducin share only 80% identity with each other, the interactions and functions of these two proteins were quantitatively identical. These included the interaction with receptor, bovine rhodopsin, with effector, bovine retinal cyclic GMP-phosphodiesterase, and with bovine brain and retinal G-protein beta gamma-heterodimers; receptor-catalysed GDP-GTP exchange and the intrinsic GTPase activity of alpha-gustducin and alpha-transducin were also identical. Gi alpha which is 70% identical with alpha-transducin interacts with different receptor and effector proteins and has very different guanine-nucleotide binding properties. Therefore, the functional equivalence of alpha-gustducin and alpha-transducin suggest that taste buds are likely to contain receptor and effector proteins that share many properties with their retinal equivalents.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1995

Regulation of nutrient intake in humans: a theory based on taste and smell.

Oral and pharyngeal recognition of the chemical structure of physiologically relevant nutrients is proposed as a mechanism for regulating nutrient intake. Taste buds and olfactory receptors are proposed as the primary sites of recognition. Oral and pharyngeal sensory signals may be sufficient for producing satiation and termination of a meal provided the initiation of the meal is triggered by the body's need to replenish a deficient nutrient. A discussion of the impact of disturbances of normal regulation and some questions this model generates are also incorporated.

Eating↗
PubMed1999

Distribution of trigeminal fibers in the primary facial gustatory center of channel catfish, Ictalurus punctatus.

Previous studies in several fishes including catfish, have shown that primary trigeminal nerve (NV) axons terminate not only in the principal and spinal trigeminal nuclei, but in the facial (gustatory) lobes. The present study was undertaken to determine the extent and distribution of trigeminal terminations within the facial lobe (FL) and principal trigeminal nucleus (nVpr) in the channel catfish, Ictalurus punctatus. In order to reveal the distribution of trigeminal fibers, the carbocyanine dye, diI, was applied to the central cut stump of the trigeminal root in isolated, paraformaldehyde-fixed brains. After a diffusion period of 10-90 days, the brains were serially sectioned on a vibratome and examined with epifluorescence. The trigeminal motor nucleus (nVm) and principal sensory nucleus lie near the level of entrance of NV. The majority of primary trigeminal fibers, however, sweep caudally after entering into the brain to form the descending root. At the level of the caudal third of the FL, collaterals emitted by the descending root fibers turn medially and dorsally to terminate in the FL. The trigeminal fibers are coarser than the facial nerve (NVII) fibers which terminate within the same structure. The trigeminal fibers terminate throughout the FL except for the lateral-most lobule which contains the representation of taste buds innervated by the recurrent branch of NVII, i.e., those over the trunk and tail of the animal. These results show that in catfish, the trigeminal input to the primary gustatory complex is restricted to those portions of the nucleus receiving chemosensory inputs from the face and barbels, i.e., the trigeminally innervated sensory fields.

Animals↗
PubMed1996

Food selection by the domestic cat, an obligate carnivore.

The domestic cat Felis silvestris catus is the most accessible member of the family Felidae for the study of the relationship between food selection and nutrition. In contrast to pack-living animals such as the dog, and opportunistic omnivores such as the rat, the cat is generally able to maintain its normal body weight even when allowed ad libitum access to palatable food by taking small meals and adjusting intake according to the energy density of the food(s) available. The most extreme adaptations to carnivory discovered to date lie in the taste buds of the facial nerve, which are highly responsive to amino acids and unresponsive to many mono- and disaccharides. Preferences for particular foods can be modified by their relative abundance, their novelty, and by aversive consequences such as emesis: the mechanisms whereby these are brought about appear to be similar to those used by omnivorous mammals.

Animal Nutritional Physiological Phenomena↗