SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Taste bud surface cells suffer from a desquamation process that modifies the pores' shape and size and the amount of amorphous substance in the pits region. We have studied this phenomenon-which probably plays an important functional role-by light, electron and scanning microscopy.
Taste buds were found to stain strongly and selectively in intact papillae with highly acidic dyes such as ponceau S. In intact tongues the taste buds in the fungiform, circumvallate and foliate papillae of the cynomolgus monkey and in the fungiform papillae of the rat as well as the taste discs in the fungiform papillae of the frog could be visualized. This method enables a rapid location and counting of taste buds in taste papillae without preparing histological sections. In cynomolgus tongue material fixed in formalin, the dyes penetrate into the buds. In fresh tongues only the taste pore region of the buds stains, which suggests that in vivo taste buds are impenetrable underneath the pore.
Taste buds in the rat and other mammals share a secretory activity with their transduction function as taste receptor. The present work shows the effect of bilateral removal of the main salivary glands on taste bud cells' components related to secretion in the vallate papilla of the rat. In the sialectomized rats remarkable changes were evidence in the dark and intermediate types of taste bud cells, which are known to be the secretory components. Such changes involve hypertrophy of either the protein synthetizing machinery, the smooth endoplasmic reticulum or the Golgi complex. Lucent and coated vesicles associated to Golgi cisternae increased in number but the amount of dense-core vesicles (secretory vesicles) at the apical cytoplasm of cells decreased. Images of exocytosis of secretory products were observed. The hypertrophy of Golgi complex components was clearly detected with the OsO4 impregnation method for light and electron microscopy. Alteration in the acid phosphatase activity of taste bud cells was not observed in the sialectomized rats. These findings suggest that sialectomy stimulates the entire secretory cycle of dark and intermediate taste bud cells. The light taste bud cells, which are not engaged in secretion, are hardly affected by the treatment. Although taste buds in mammals are neuro-dependent structures, present evidence indicates that they are also sensitive to non-neural influences.
External taste buds abound on barbels of the adult catfish Corydoras arcuatus. When examined by scanning electron microscopy, they are visualized as a series of punctate, conical elevations projecting from the general surface epithelium. All taste buds were found to be of one type. Both their external and internal surface features could be clearly elucidated on intact barbels and in barbels fractured transversely at various positions along their length. An extensive nerve terminal network penetrates the base of each taste bud. Two populations of elongated cells bearing prominent microvilli project through the central pore at the tip of each bud. One set of microvilli is thicker, longer and more club-shaped than its counterpart. While both are randomly distributed within each central pore, the small, short microvilli appear to outnumber the larger ones. A third population of cells, devoid of any apical microvilli, was also seen in some of the taste buds examined internally. These cells do not project to the external surface and are interpreted as "basal" cells described in previous light and transmission electron microscope studies of taste buds in other vertebrate species. The functional significance of some of these morphological findings is discussed.
Renewal of taste bud cells on the barbels of channel catfish was studied. Groups of catfish, held in and acclimitized to 14 degrees C, 18 degrees C, 22 degrees C and 30 degrees C dechlorinated tap water were injected with [3H]thymidine (3.0 muCi/g body weight intraperitoneally). Barbels were sampled at various times after injection and prepared for light microscope autoradiography. Results show that epithelial cells surrounding the taste buds divide and some of their daughter cells migrate into the taste buds. The time at which 50% of the labelled cells have degenerated is taken as the average turnover time or average life span of the taste bud cells. The average life span as well as the time spent inside the taste buds is highly temperature-dependent. At 14 degrees C, 18 degrees C, 22 degrees C and 30 degrees C the average life span is on the order of 40, 30, 15 and 12 days respectively. Further studies indicate that both light and dark staining cells of the taste bud were labelled.
Monoamines in the taste bud cells of the mouse circumvallate papilla were studied by fluorescence histochemistry and electron microscopy. With administration of 5-HTP (5-hydroxytryptophan) after a pretreatment with nialamide, yellow fluorescence appeared in some of the taste bud cells, while no fluorescence was observed in untreated, L-DOPA treated on serotonin treated mice. Electron microscopic study after treatment with both nialamide and 5-HTP showed small dense-cored vesicles intermingled with small clear vesicles (30-60 nm in diameter accumulated at the membranes of the gustatory cells in typical afferent synaptic contacts with nerve terminals. Definite ultrastructural change in large dense-cored vesicles (70-100 nm in diameter) could not be observed. It is suggested that the gustatory cells of the mouse take up 5-HTP and convert it to serotonin. The synaptic vesicles in the gustatory cells are believed capable of storing and releasing serotonin which presumably acts as the neurotransmitter involved in the impulse transmission from the gustatory cells to the sensory nerve fibers.
Serial sections of 182 fungiform papillae, obtained at autopsy from 22 individuals aged 2 days to 90 years, were examined by light microscopy with regard to location and number of taste buds. The taste buds were always found on the convex, dorsal surface of the papillae but otherwise failed to display any preferential location pattern. A total of 262 taste buds, an average of 1.4 per papilla, were found. However, there was considerable variation in the occurrence of taste buds, both from papilla to papilla and from case to case. While the number of taste buds in a single papilla varied from 0 to 27, 63% of the papillae had no taste buds at all, 26% had 1-3 buds and the remainder 4 or more buds. The mean number of taste buds per papilla varied from 0 to 9 between individuals; no dependence upon sex or age could be demonstrated for this variation. The significance of these anatomical findings with regard to physiological studies on taste involving the fungiform papillae is discussed.
Autografts of tongue onto the liver contained taste buds without nerves for up to 30 days. However, these denervated taste buds were generally smaller than normal and distorted in structure. Nerve fibers invaded the graft from the liver and after 30 days normal appearing taste buds were found only in implants of tongue which contained extensive nerve fibers. Thus it appears that certain visceral nerves can maintain and possibly induce taste bud formation in implants of tongue. This is interpreted as additional evidence for the trophic influence of nerves upon taste buds. Moreover, this ability to maintain taste buds is not restricted to gustatory nerves in the newt.
The distribution of taste buds on the fungiform and circumvallate papillae of the cow tongue has been determined. The two tongues studied were from Holstein-Friesian cows four to six years of age; they contained 14,765 and 21,691 taste buds, respectively. The tip of the tongue is well supplied with fungiform papillae, and the posterior portion contains the circumvallate papillae. The midportion of the tongue contains relatively few taste papillae. The fungiform papillae contained 1,580 and 1,838 taste buds on the two tongues, respectively, and the circumvallate papillae were estimated to contain 13,185 and 19,853 taste buds. The highest concentration of taste buds therefore occurs in the circumvallate papillae; these relatively few papillae contain approximately 90% of the taste buds. On a circumvallate papilla, taste buds are found only on the papillary sidewall, with none either on the apical surface of the papilla or on the outer wall of the moat.
Taste buds were generally found on the posterior side of the tongue. Neural elements (nerve fibres, mainly thick myelinated, and ganglia arranged in a chain-like fashion) participated in the innervation of the taste buds. Cholinesterase activity was much marked in the bottom of the taste buds, while the marginal surface showed no such activity.
The gross morphology of the tongue of the Mongolian gerbil Meriones unguiculatus), the location of papillae and taste buds, and the normal innervation pattern of the tongue and taste buds were determined. The chorda tympani nerve was interrupted to produce degeneration of fungiform taste buds. Regenerating chorda tympani axons followed the original nerve pathways in the tongue en route to the fungiform papillae in the epithelium where they initiated the regeneration of taste buds. The spatial distribution of reinnervated fungiform papillae and reformed taste buds was examined 7 to 19 days following surgery. Beginning at eight days following chorda tympani interruption there was a progressive increase, first, in the proportion of fungiform papillae that were reinnervated, and later in the number of reformed taste buds. On the basis of these measures it was concluded that a taste bud is reformed one to two days after reinnervation of its papilla. From the time course of reinnervation of the fungiform papillae it was calculated that some fibers regenerated at rates in excess of 2 mm/day. Regeneration was precise and systematic. The regenerating chorda tympani fibers accurately returned to the fungiform papillae; they did not follow the pathways of lingual nerve axons. In the initial stages of recovery both reinnervated papillae and reformed taste buds were preferentially located toward the front of the tongue; the reinnervation of posterior fungiform papillae was delayed.
A method to prepare suspensions of taste bud cells is described. Bovine circumvallate papillae, which contain most of the taste buds in this animal, are incubated in collagenase-containing medium and the epidermal sidewall tissue is then dissected from the inner gelatinous dermis. The sidewall tissue, which contains the taste buds, is gently homogenized by manual operation of an all-glass homogenizer with a loose-fitting pestle. The suspended material is separated on a discontinous Ficoll gradient (2%, 8%, 10%, 12% w/w). The material banding at the 8-2% interface is greatly enriched in spindle-shaped cells that are morphologically similar to taste bud cells as they appear in situ. These cells are not seen when the procedure is done with tissues devoid of taste buds, namely the upper surface of the circumvallate papilla or epithelium from the intermolar eminence. Fluorescence analysis indicates that the hydrophobic probe, 8-anilino-1-naphthalenesulfonate (ANS), binds to relatively nonpolar sites in the suspension. It is postulated that the probe is adsorbing onto the surface membrane of the cell. These preparations may be useful in studying specificity and transduction in taste sensation.
The epithelial cells in the taste buds of C. jacchus and C. penicillata show a moderate amount of ribonucleic acid an a concentration of a PAS-positive diastase-resistant material at their apical part. These cells are devoid of UDPG-GT, phosphorylases, G-6-PA, alanyl aminopeptidase, leucine aminopeptidase, cholinesterase and MAO; they present a weak reaction of F-1, 6-P Ald, LDH, SDH, MDH, cytochrome oxidase, beta-OHBDH, nonspecific esterase and acid phosphatase and a stronger reaction to ADH, NADPH2-TR, ATPases, alpha-GPDH, alkaline phosphatase, 5-nucleotidase and GDH. Although some enzymes (alkaline phosphatase, 5-nucleotidase and ATPases) have an almost uniform reactivity by the several taste buds, the other ones react with a lesser intensity in the smaller uniform reactivity by the several taste buds, the other ones react with a lesser intensity in the smaller taste buds of the fungiform papillae. As a rule the apical part of the cells shows a stronger enzymatic reactivity. The taste buds of the marmosets are penetrated by acetylcholinesterase positive nerve fibers whereas the autonomic ganglia in the connective tissue contain both-acetyl and butyrylcholinesterase.
Binding of various sugars was compared in purified subfractions of taste buds isolated from bovine circumvallate papillae and of non-taste bud-bearing epithelium isolated from tissue surrounding these papillae. Binding of 14C-labeled sugars was greater in purified subfractions obtained from taste bud than from non-taste bud-bearing tissue and was, in general, greater in those taste bud subfractions in which a greater membrane purification was achieved. Binding specificity of the 14C-labeled sugars sucrose, fructose, glucose and of 14C-labeled cyclamate and saccharine was measured by competition of each 14C-labeled sugar or synthetic sweetener with its unlabeled homologous sugar in P4(B) taste bud subfractions; this binding, as shown for sucrose, was reversible and temperature dependent. Essentially no competition of the 14C-lageled sugars sucrose, fructose, glucose or 14C-labeled cyclamate and saccharine by their respective unlabeled homologues occurred in epithelial tissue P4(B) subfractions; this binding was not reversible. Binding specificity was further observed by the competition of 14C-labeled sucrose, fructose and glucose with each unlabeled sugar for binding sites on P4(B) taste bud subfractions; unlabeled sucrose was more effective in competing with each 14C-labeled surgar than was unlabeled fructose or glucose. The relatively non-sweet sugar lactose did not compete with 14C-labeled lactose in P4(B) subfractions from either taste bud or non-taste bud-bearing epithelial tissue. Binding of 14C-labeled sucrose in purified P4(B) bud subfractions was inhibited by increased concentrations of unlabeled sucrose, phospholipase C, neuraminidase, EDTA, NaCl and urea. Dissociation constants for sugar or synthetic sweetener binding were low (approx. 10(-3) M) but in a rank order (sucrose greater than fructose greater than glucose greater than saccharine) consistent with preference and electrophysiological responses in cow. The cow is behaviorally indifferent to saccharine and lactose consistent with the data obtained in the present study.
There is some uncertainty in the literature as to the existence of taste buds in the palate of the human adult. In those histologic studies in which the ages of the individuals have been reported, taste buds have not been found in the palates of adults, but have been found in fetuses or newborn. However, clinical studies have demonstrated taste perception in the palate of the human adult. Thus, the aim of the present study was to attempt to find taste buds in the human palate in subjects of different ages. In serial sections of selected areas of the palatal mucosa from autopsy material from individuals 0--80 years of age no taste buds could be demonstrated. However, in four of seven subjects aged 25--44 years, one or two taste buds were found in biopsies from areas of the soft palate where taste perception had been demonstrated clinically just prior to excision. Thus the present study indicates that scattered taste buds exist also in the soft palate of human adults.
The work is devoted to the study of the structure of the innervation apparatus of taste buds in the epiglottis of monkeys (Macacus rhesus). The Campos inpregnation method was used. It is established that several afferent myelinated fibers participate in the innervation of each taste bud of the epiglottis. The peculiarity of structure of their preterminal and terminal parts having the appearance of complex windings and spirals is noted. The polyaxonic principle of the innervation of taste buds of the epiglottis in monkeys is considered as a possible mechanism of generalization of the afferent impulses. It is suggested that the innervation apparatus of the taste buds of the epiglottis constitutes part of unique afferent system of this organ, ensuring its defensive function. The incongruity (from the histophysiological standpoint) of the term 'taste bud' in relation to the epiglottis is noted. It is proposed to call these formations special structures of the chemo-receptors.
The taste buds of rat circumvallate papillae contain three distinct types of cells. The type I (dark) cell is characterized by the presence of dense round granules, which are precursor to the dense substance of the taste pore. The granules are discharged into the pore by exocytosis. The type II (light) cell is filled with numerous vesicles and smooth-surfaced endoplasmic reticulum. The type III cell contains in its basal cytoplasm characteristic dark-cored vesicles and masses of clear vesicles, and makes synapse-like contacts with nerve fibers. The fine structure of foliate buds corresponds to that of circumvallate papillae, while fungiform buds differ in their apical regions. In the latter the pore is filled with vesicles alone, and the type I cell contains rod-shaped granules of moderate density. When polysaccharides were examined by means of the periodic acid-silver methenamine and the periodic acid-thiocarbohydrazide methods, slightly positive reactions were found on the dense granules of the type I cell and the dense substance in the pore, whereas the membranes of the pore vesicles, apical cytoplasmic processes and cytoplasmic vesicles in type II cells showed intense reactions.
The taste bud of the vallate papillae of the rat has been examined in the electron microscope by using the freeze-fracture technique. Tight junctions as a junctional complex are located at the taste pore, and form a seal between the oral environment and the taste buds. Tight junctions are not only within the taste buds, but also are demonstrated in the granular cell layers of the surrounding lingual epithelium. The present finding suggests that tight junctions of the taste pore link with those of the lingual epithelium. Desmosomes are observed in the buds, but they are smaller in size than in the surrounding lingual epithelium. Besides these junctions, within the buds, gap junctions containing particle-free zones are demonstrated which are called a subcompartment type.