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PubMed2000

Predominant role of the chorda tympani nerve in the maintenance of the taste pores: the influence of gustatory denervation in ear surgery.

The effect on the taste pores of denervation of the chorda tympani nerve in the middle-ear cavity was studied comparing confocal laser microscopy with lingual nerve resection. Taste pore cells were stained for actin with rhodamine-phalloidin and positive fluorescence was observed as a ring shape at the transverse cross sections. Within three days after chorda tympani nerve resection the ring reaction disappeared, although the pore morphology remained intact as seen by scanning electron microscopy. On the other hand, lingual nerve resection did not induce such rapid disappearance of the ring reaction. These results suggest that the chorda tympani nerve plays a predominant role in the maintenance of actin filaments in taste pore cells.

Actins↗
PubMed1989

Merkel cells in lower vertebrates.

In lower vertebrates, Merkel cells are widely distributed in the epidermis. Dense-cored specific granules similar to those in mammalian Merkel cells are found in amphibians, dipnoans and lampreys, but only in some species of teleosts, others having few and small-cored vesicles. The characteristic microvilli are found in all these groups, but their number and disposition vary. In amphibians a Merkel cell is associated with a single nerve fibre, known to be mechanoreceptive, which forms reciprocal synapses at a varicosity against the cell and continues on in the epidermis. In lampreys most of the specific granules are grouped around spur-like processes of a nerve fibre which has other branches in the epidermis. In teleosts, one or more nerve fibres wind around a Merkel cell; synaptic modifications are variable. Fluorescence histochemistry shows the presence of quinacrine, neuron-specific enolase, met-enkephalin and serotonin in Merkel cells of some species that have been investigated, but experimental results from amphibians suggest that the receptive element may be the nerve fibre. The Merkel cell can act as a target for growing nerve fibres, but other functions, especially connected with the synapses, most of which are morphologically afferent, remain unknown. Merkel cells do not require trophic maintenance from the nerve. The basal cells of taste buds in teleosts and amphibians have been compared to Merkel cells, but are not identical, although in frogs the basal cells have dense-cored vesicles. In teleosts, both cell types qualify as paraneurons, but there are considerable differences in their cytology especially in the form of the synaptic specializations.

Amphibians↗
PubMed1999

The existence of Merkel cells in the lingual connective tissue of the Surinam caiman, Caiman crocodilus crocodilus (order Crocodilia).

The tongue of the Surinam caiman (a reptilian species) was studied by light microscopy including immunohistochemistry for protein gene product 9.5 (PGP 9.5), and transmission electron microscopy. The connective tissue immediately under taste buds housed a cluster of cells immunoreactive for PGP 9.5. These cells synapsed on nerves, and their cytoplasm contained characteristic granules of 90 nm in the mean diameter, glycogen particles, and bundles of intermediate filaments. In light of these ultrastructural features, they were identified as Merkel cells. The Merkel cells were also surrounded by Schwann cells. These findings indicate that the present Merkel cell-neurite-Schwann cell complex is comparable to the avian Merkel corpuscle. On the basis of the granule localization in the cytoplasm, the caiman Merkel cell was presumed to be involved in not only mechanoreception but also endocrine or paracrine functions.

Alligators and Crocodiles↗
PubMed1978

Taste profiles from single human taste papillae.

Earlier psychophysical research on single human fungiform taste papillae employed a procedure which limited subjects to selecting only one taste to describe the sensations they experienced. That procedure precludes the possibility of determining whether single papillae can mediate complex tastes, i.e., tastes consisting of more than one sensation experienced simultaneously. By using highly trained subjects and allowing them freedom to describe all sensations simultaneously elicited by a given taste stimulus, single papilla taste profiles were obtained. It is suggested that obtaining taste profiles may increase the utility of single papillae as models for study of the taste system.

Adult↗
PubMedDate not supplied

Severe chemotherapy-induced parosmia.

BACKGROUND: Smell and taste disorders are among the side effects of chemo- and radiotherapy. Although direct radionecrosis of the salivary glands and the taste buds might explain the chemosensory problems after radiotherapy, the olfactory and gustatory complaints seen after chemotherapy remain unexplained. The patients reporting olfactory symptoms rarely complain about qualitative olfactory disorders such as parosmia or phantosmia. Quantitative olfactory loss such as anosmia and hyposmia seem to be more frequent. METHODS: We present the case of a 63-year-old woman with chemotherapy-induced parosmia leading to severe nutrition and appetite problems resulting in a life-threatening weight loss. RESULTS: With the aid of a simple nose clip the parosmia could be abolished and oral food intake became possible again. Parosmia resolved gradually over an observation period of 9 months, in parallel to an increase of olfactory sensitivity. The patient progressively gained appetite and weight. CONCLUSION: Parosmia can occur as a severe and potentially life-threatening complication of chemotherapy. This rare presentation of parosmia illustrates the importance of olfactory testing with an adequate recognition of the underlying problem and a consecutive treatment.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2005

Morphometric evaluation of the human tractus solitarius.

We measured the cross-sectional area (CSA) of the human tractus solitarius (HTS) with the help of an image-analyzer system on a cross section of the upper part of the medulla oblongata in 44 Japanese cadavers (22 males and 22 females) and examined the relationship between age, sex and whether the subjects were dentulous or edentulous. The results showed no significant differences between the left and right sides of the HTS in either male or female subjects. However, the size of HTS decreased slightly with age in males but not at all in females, whereas tooth loss had a definite incidence on the size of HTS in females but not in male, as the CSA was smaller in edentulous females but not in edentulous males. This would tend to indicate that a decreases in taste function is connected with the aging process in male, and with tooth loss in females.

Age Factors↗
PubMed1991

Tridimensional architecture of the lamina propria in the mouse soft palate, with special reference to the connective tissue papilla of the palatal papilla.

The NaOH cell-maceration method was applied to the oral surface of the mouse soft palate to demonstrate the tridimensional architecture of the connective tissue papillae (CTP) of the "palatal papillae", and of the openings of the glandular ducts. The CTP of the palatal papillae extremely differed from those of any types of the lingual papillae, and appeared as elliptical wall. Within the elliptical wall, there existed the semicircular or circular internal ridge which surrounded the round depression corresponding to the taste bud. The openings of the glandular ducts were rimmed by the collagen fibers running concentrically. Many fibrils derived from the concentrical fibers, turned to the sagittal direction and then concentrated into the sagittal fibers in the vicinity of the openings.

Animals↗
PubMed1993

The occurrence and fine structure of Merkel cells in the lingual epithelium of the turtle, Clemmys japonica.

Electron microscopic examination of the lingual mucosa of the turtle, Clemmys japonica, revealed the occurrence of Merkel cells that shared many morphological features with Merkel cells in other vertebrates. Merkel cells were located exclusively in the basal portion of the epithelium near the taste buds. We also found occasional Merkel cells devoid of nerve contact. Nerve terminals approaching these non-innervated Merkel cells were occasionally found in the connective tissue just beneath these cells.

Animals↗
PubMed1979

Taste acuity of the human palate. II. Studies with electrogustometry on subjects in different age groups.

The electrical taste acuity on the hard and soft palate and the tip of the tongue was determined in 140 subjects aged 13-81 years using an electrogustometer constructed for the study. The possible influence of several variables including age, sex, wearing of a full upper denture, smoking as well as medical and social factors on the threshold values was also studied. Taste perception was demonstrated on the soft palate and on an area of the hard palate close to the junction of the hard and soft palate in most subjects. No perception of the electrical taste was found in eleven subjects (8%) on either the hard or the soft palate and in an additional 33 subjects (24%) on the hard palate alone and 2 subjects (1%) on the soft palate alone. The taste thresholds on the hard palate were very high compared to those on the soft palate and those on the tongue. Older subjects generally had higher thresholds than did younger subjects and the differences were greater for the thresholds on the hard and soft palate than for those on the tongue. No statistically significant differences in threshold values were found between women and men, denture wearers and non-denture wearers or smokers and non-smokers.

Adolescent↗
PubMed1979

Taste acuity of the human palate. III. Studies with taste solutions on subjects in different age groups.

The taste acuity at the midline of the hard and soft palate near their junction and, for comparison, on representative areas of the tongue was determined in 80 subjects aged 11-79 years by applying test solutions of the four basic tastes. Twenty-one subjects (26%) could identify at least one taste on the hard palate but none could recognize all four tastes. Seventy subjects (87%) could identify at least one taste on the soft palate and 37 subjects (46%) could recognize all four tastes. Taste thresholds were much higher on the hard palate than on the tongue and were in most cases higher on the soft palate than on the tongue. The ability to recognize all four tastes was less frequent in older than in younger subjects and the difference was greatest on the soft palate and least at the foliate papillae. The differences were greatest for citric acid and least for sucrose. There was a tendency to lower thresholds for women compared to men for all four tastes on all areas examined which was most pronounced on the soft palate. No differences in taste thresholds were found between denture wearers and subjects with natural dentition. Smokers had higher thresholds than non-smokers only for salt on the soft palate and the base of the tongue.

Adolescent↗
PubMedDate not supplied

The relationship between electrode area and sensory qualities in electrical human tongue stimulation.

The relationship between the size of the stimulated human tongue area, the stimulating electric current intensity and the provoked sensory qualities was examined. Five different electrode areas and four anodal current intensities were used. The observed sensations were of three kinds: sour taste, somatosensory, and undefined ones. At a given current intensity level the proportion of taste increases with the increase in the stimulation area, while somatosensory sensations decrease. These results imply that at the suprathreshold level there is a certain interdependence between the area, current intensity and sensory effects. In order to achieve optimal activation of the taste system alone, it is more effective to use a larger electrode and stronger current, than to use smaller areas and weaker stimuli: in this case the electrical sour taste is satisfactorily clear, since the somatosensory system is still not activated. These findings may have implications in clinical electrogustometry.

Adult↗
PubMed1988

Electrogustometry of the soft palate as a topographic diagnostic method for facial paralysis.

Electrogustometry (EGM) of the soft palate, innervated by the gustatory fibers running via the greater petrosal nerve, was performed in 10 cases with facial paralysis due to suprageniculate lesions to evaluate its clinical validity as a topographic diagnostic method. Lacrimal function was also examined for comparison. The results obtained from EGM showed a significantly increased threshold on the affected side in 90% of the cases. However, the lacrimal secretion decreased only in 40% using Schirmer No. 2 test. The results of the present study strongly suggest that EGM of the soft palate reflects the function of this nerve better than Schirmer test, and EGM is clinically useful for the topographic diagnosis of peripheral facial nerve lesions.

Adult↗
PubMed1993

Distributions of the calcitonin gene-related peptide and substance P in the monkey larynx.

The distribution of calcitonin gene-related peptide (CGRP)- and substance P (SP)-like immunoreactivity in the monkey larynx was studied with light microscopy using the immunofluorescence method. We divided the larynx into the following six regions: epiglottis, arytenoid region, false cords, ventricle, vocal cords and subglottis. The distribution of immunoreactivity in the epithelium and subepithelial layer was determined. CGRP- and SP-like immunoreactive nerve fibers were observed in all regions of the laryngeal epithelium except in the vocal cords. In the epithelium of the epiglottis and arytenoid region, numerous taste buds containing several CGRP- and SP-like immunoreactive nerve fibers were observed. In the subepithelial layer, CRGP- and SP-like immunoreactive nerve fibers were observed in all regions of the larynx. In order of decreasing density, these fibers were found in the arytenoid region (especially the corniculate tubercle), the epiglottis, the false cords, the subglottis, the ventricle, and the vocal cords. In the corniculate tubercle, CGRP- and SP-like immunoreactive nerve fibers formed a network, whereas around the cuneiform tubercle, dense CRPG- and SP-like immunoreactive nerve fibers were noted parallel to the basement membrane. SP-like immunoreactive nerve fibers showed a very similar distribution to the CRPG fibers in the epithelium and the subepithelial layer, but SP-like fibers were sparser in all regions of the larynx. These results, together with previous findings indicate that the arytenoid region and the epiglottis of the monkey larynx play very important roles in airway protection, swallowing, and respiration.

Animals↗
PubMed1993

Distribution of the 75-kD low-affinity nerve growth factor receptor in the primate peripheral nervous system.

Disruption of the 75-kD low-affinity nerve growth factor (NGF) receptor (p75) has been shown to result in sensory and sympathetic nervous system deficits (Lee et al., 1992a,b). In order to establish precisely which subsets of neurons are capable of responding to neurotrophins (NTs) through the low-affinity NGF receptor, p75 was localized in the primate autonomic and somatic sensory nervous systems. In the autonomic system, cell bodies of some parasympathetic and enteric neurons expressed detectable levels of p75, whereas all sympathetic neurons expressed the protein. In the sensory system, some, but not all, cell bodies were labeled in cranial and spinal sensory ganglia and in the mesencephalic nucleus. Some peripheral and central projections of the sensory neurons were also labeled. Centrally, most of the labeled processes were found in regions containing primarily small unmyelinated fibers, including lamina II of Rexed and areas of the solitary tract and nucleus. Peripherally, labeled processes were associated with unmyelinated nerves and specialized structures such as taste buds and Meissner corpuscles, but not with myelinated processes. This study indicates that the subset of neurons in the autonomic nervous system likely to be capable of responding to neurotrophins is broader than generally thought, and that p75-expressing neurons tend to be clustered. Moreover, in the sensory nervous system p75 is expressed by most cell bodies, but expression in their projections is restricted both peripherally and centrally to unmyelinated processes and nerve terminals.

Animals↗