Salivary sodium and potassium concentrations in adrenalectomized rats.
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Adrenalectomy↗
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CGRP and substance P in intraepithelial neuronal structures of the human upper respiratory system.
The distribution of intraepithelial nerve fibres and neuroendocrine cells within the surface and glandular epithelium of human nasal mucosa and larynx was examined using immunohistochemical techniques. Neuronal structures were immunostained for the general neuroendocrine marker protein gene-product (PGP) 9.5, and the two neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) using immunofluorescence and streptavidin-biotin-peroxidase complex (S-ABC) methods. Intraepithelial nerve fibres with free nerve endings contained PGP 9.5 and were found within the respiratory surface epithelium of the nasal mucosa and the squamous epithelium of the larynx. A subpopulation of these nerve fibres showed positive immunoreactivties with antibodies against SP and CGRP. Nerve fibres within the ductal epithelium of subepithelial excretory ducts passing the basal membrane and reaching the luminal part were detected. These nerve fibres showed CGRP-like immunoreactivity but not for SP. A dense network of nerve fibres within the squamous surface epithelium was detected in the subglottic and epiglottic region containing CGRP and SP in a small subpopulation of nerve fibres. Single intraepithelial taste buds in the epiglottic region and neuroendocrine cells within the subglottic epithelium expressed PGP 9.5.
Calcitonin Gene-Related Peptide↗
Cloning, characterization, and chromosomal localization of rec1.3, a member of the G-protein-coupled receptor family highly expressed in brain.
During a project to identify G-protein-coupled receptors (GPCR) expressed within taste buds, we have isolated a novel receptor-like sequence. The full length sequence of this receptor (rec1.3) has been obtained in both cow and mouse. Rec1.3 bears little sequence similarity to any GPCR whose ligand is known: the closest identity (33%) is to the orphan receptor edg-1. In cow, rec1.3 is expressed most prominently in the brain, with moderate expression in testis and tongue; in the mouse the expression is more widespread. No specific binding for a range of ligands was detected when the mouse coding sequence was expressed in eukaryotic cells. In situ hybridization showed that rec1.3 is widely expressed throughout the mouse brain and is highly expressed in localized regions of the hindbrain, midbrain and hypothalamus. The rec1.3 gene was localized to the centromeric region of chromosome 4 in mouse, a region associated with neonatal seizures.
Amino Acid Sequence↗
Clinical evaluation of taste.
Partial loss of taste function can take a variety of forms. Losses can be specific to one taste quality or to one tongue locus. In addition, the shapes of psychophysical functions can be altered so that taste intensity no longer grows normally with concentration. Magnitude matching, an efficient psychophysical scaling method (based on magnitude estimation of stimuli from two sensory continua), can provide a relatively quick assessment of a patient's ability to taste the four taste qualities--sweet, salty, sour, and bitter. When taste intensity and loudness are scaled in the same session, a person with normal hearing who has taste loss will match taste intensities to abnormally weak sounds. Spatial losses are detected by placing pieces of filter paper soaked in taste solutions on specific tongue loci. Dysgeusia, the presence of a chronic taste in the mouth, can result from abnormal substances in the mouth (e.g., via saliva or from poor oral hygiene) or can reflect disorders of the central nervous system.
Humans↗
Loss of fungiform papillae.
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Chorda Tympani Nerve↗
Serotonin transporter messenger RNA expression in neural crest-derived structures and sensory pathways of the developing rat embryo.
A growing body of evidence suggests that serotonin plays an important role in the early development of both neural and non-neural tissues from vertebrate and invertebrate species. Serotonin is removed from the extracellular space by the cocaine- and antidepressant-sensitive serotonin transporter, thereby limiting its action on receptors. In situ hybridization histochemistry was used to delineate serotonin transporter messenger RNA expression during rat embryonic development. Serotonin transporter messenger RNA was widely expressed beginning prior to organogenesis and throughout the second half of gestation. Strikingly, serotonin transporter messenger RNA was detected in neural crest cells, some of which respond to serotonin in vitro, and neural crest-derived tissues, such as autonomic ganglia, tooth primordia, adrenal medulla, chondrocytes and neuroepithelial cells, in the skin, heart, intestine and lung. Within the peripheral sensory pathways, two major cells types were serotonin transporter messenger RNA-positive: (i) sensory ganglionic neurons and (ii) neuroepithelial cells which serve as targets for the outgrowing sensory neurons. Several sensory organs (cochlear and retinal ganglionic cells, taste buds, whisker and hair follicles) contained serotonin transporter messenger RNA by late gestation. The expression of serotonin transporter messenger RNA throughout the sensory pathways from central nervous system relay stations [Hansson S. R. et al. (1997) Neuroscience 83, 1185-1201; Lebrand C. et al. (1996) Neuron 17, 823-835] to sensory nerves and target organs as shown in this study suggests that serotonin may regulate peripheral synaptogenesis, and thereby influence later processing of sensory stimuli. If the early detection of serotonin transporter messenger RNA in skin and gastrointestinal and airway epithelia correlates with protein activity, it may permit establishment of a serotonin concentration gradient across epithelia, either from serotonin in the amniotic fluid or from neuronal enteric serotonin, as a developmental cue. Our results demonstrating serotonin transporter messenger RNA in the craniofacial and cardiac areas identify this gene product as the transporter most likely responsible for the previously identified accumulation of serotonin in skin and tooth germ [Lauder J. M. and Zimmerman E. F. (1988) J. craniofac. Genet. devl Biol. 8, 265-276], and the fluoxetine-sensitive effects on craniofacial [Lauder J. M. et al. (1988) Development 102, 709-720; Shuey D. L. et al. (1992) Teratology 46, 367-378; Shuey D. L. et al. (1993) Anat. Embryol., Berlin 187, 75-85] and cardiac [Kirby M. L. and Waldo K. L. (1995) Circulation Res. 77, 211-215; Yavarone M. S. et al. (1993) Teratology 47, 573-584] malformations. Serotonin transporter messenger RNA was detected in several neural crest cell lineages and may be useful as an early marker for the sensory lineage in particular. The distribution of serotonin transporter messenger RNA in early development supports the hypothesis that serotonin may play a role in neural crest cell migration and differentiation [Lauder J. M. (1993) Trends Neurosci. 16, 233-240], and that the morphogenetic actions of serotonin may be regulated by transport. The striking pattern of serotonin transporter messenger RNA throughout developing sensory pathways suggests that serotonin may play a role in establishing patterns of connectivity critical to processing sensory stimuli. As a target for drugs, such as cocaine, amphetamine derivatives and antidepressants, expression of serotonin transporter during development may reflect critical periods of vulnerability for fetal drug exposure. The widespread distribution of serotonin transporter messenger RNA during ontogeny suggests a previously unappreciated role of serotonin in diverse physiological systems during embryonic development.
Animals↗
Clinical applications and mechanism of intravenous taste tests.
It is well known that there are two ways to measure human blood circulation time: the arm-to-lung and the arm-to-tongue method. The decholin (20% dehydrocholic acid) test is usually used to measure the arm-to-tongue circulation time. In this study, this procedure was used to examine taste function. Findings on the clinical application of this intravenous taste test using decholin and a study on the mechanism of venous taste perception are reported here. The following method was used: Five ml of 20% decholin were injected into the right cubital vein over a 10-sec period and the latent time, the duration, the quality of the taste sensation and the region of the tongue where the taste appeared were noted. The results were as follows: 1) In dysgeusic subjects, the latent period was longer, and the duration of the taste sensation was shorter than in normal subjects (p is less than 0.01, p is less than 0.05). 2) Some of the dysgeusic subjects perceived the taste as other than bitter; their prognosis of taste dysfunction tended to be worse than that of other subjects. 3) Some of the dysgeusic subjects perceived the taste in regions of the tongue other than the bilateral edges or over the entire tongue; their prognosis of taste dysfunction tended to be worse than that of other subjects. 3) Some of the dysgeusic subjects perceived the taste in regions of the tongue other than bilateral edges or over the entire tongue; their prognosis tended to be worse than that of other subjects. In addition, photofluorograms of the tongue were taken to clarify the mechanism of intravenous taste; the time needed for fluorescence to appear in the fungiform papillae and their diffusion form in the papillae were observed and investigated.
Adolescent↗
Characteristics of laryngeal receptors analyzed by presynaptic recording from the cat medulla oblongata.
In order to clarify the neural mechanisms for the protective laryngeal reflex, we conducted physiological analysis of laryngeal sensory receptors. In the present study, presynaptic unit activities, which might accurately reflect characteristics of the laryngeal receptor, were recorded with a glass microelectrode in the nucleus of the tractus solitarius of the medulla oblongata in ketamine-urethane anesthetized cats, and the responses to the mechanical and/or chemical stimuli were analyzed. From the results, it was demonstrated that highly sensitive mechanoreceptors and polymodal receptors exist in the laryngeal mucosa; they are particularly numerous in the laryngeal surface of the epiglottis and arytenoid region, and uncommon in the vocal fold. Mechanoreceptors on the laryngeal mucosa were classified into a rapidly adapting group and a slowly adapting group, while all polymodal receptors adapted rapidly to mechanical stimulation. These results suggest that these non-specific polymodal and rapidly adapting receptors may correspond to more superficial receptors such as free nerve endings and some taste buds, and also monomodal slowly adapting mechanoreceptors may correspond to deeper terminals in the subepithelium. It is also considered possible that the structures and the characteristics of these receptors are appropriate to elicit the protective laryngeal reflexes by non-specifically detecting various kinds of stimuli.
Animals↗
Immunohistochemical dystrophin reaction in synaptic regions.
To investigate the functional significance of dystrophin, we studied various tissues of control and mdx mice, and rats immunohistochemically, using anti-dystrophin antibodies. In control animals, we observed the immunohistochemical localization of dystrophin in synaptic regions such as neuromuscular junctions, the cornea and outer plexiform layer of the retina, the taste buds and neurons in the brain, as well as on the surface membrane of skeletal, cardiac and smooth muscle fibers. In mdx mice, dystrophin was absent from the surface membrane of muscle fibers and the outer plexiform layer of the retina. These results suggest that dystrophin plays an important physiological and/or structural role in the conduction system.
Animals↗
Effects of artificial sweeteners on insulin release and cationic fluxes in rat pancreatic islets.
Beta-L-glucose pentaacetate, but not alpha-D-galactose pentaacetate, was recently reported to taste bitter and to stimulate insulin release. This finding led, in the present study, to the investigation of the effects of both bitter and non-bitter artificial sweeteners on insulin release and cationic fluxes in isolated rat pancreatic islets. Sodium saccharin (1.0-10.0 mM), sodium cyclamate (5.0-10.0 mM), stevioside (1.0 mM) and acesulfame-K (1.0-15.0 mM), all of which display a bitter taste, augmented insulin release from islets incubated in the presence of 7.0 mM D-glucose. In contrast, aspartame (1.0-10.0 mM), which is devoid of bitter taste, failed to affect insulin secretion. A positive secretory response to acesulfame-K was still observed when the extracellular K+ concentration was adjusted to the same value as that in control media. No major changes in 86Rb and 45Ca outflow from pre-labelled perifused islets could be attributed to the saccharin, cyclamic or acesulfame anions. It is proposed that the insulinotropic action of some artificial sweeteners and, possibly, that of selected hexose pentaacetate esters may require G-protein-coupled receptors similar to those operative in the recognition of bitter compounds by taste buds.
Animals↗
Eating in space--from an astronaut's perspective.
Food systems and meal components are constantly under review and development at the National Aerospace and Space Administration. The goal of this work is to generate a diet that meets the nutrient requirements of astronauts and satiates them. The constraints involved in shorter- and longer-term missions are described. The insight provided by observations of astronauts from the Skylab and Shuttle eras will allow researchers to consider the fact that, for any nutritional regimen to work, it must consider the limitations and taste buds of the individuals involved. Otherwise, the best diet design generated by their work may never be consumed.
Astronauts↗
Morphological study on the gills of two species of fresh water fishes: Oreochromis niloticus and Clarias gariepinus.
The gross and microscopic morphology of the gills of both Nile tilabia (Oreochromis niloticus) and sharptooth catfish (Clarias gariepinus) were described including light and scanning electron microscopy. The anatomical differences between the gill system of the two species were basically related to the geometry of the head and opercular cavities. Each species had four pairs of gills which were connected in a median interbranchial septum. In addition, a fifth rudimentary gill without gill filaments was found in catfish. The lengths and gaps between the gill arches in both species decreased medialwards. The gill rakers of tilabia were generally short and widely spaced compared to the long and narrow spaced rakers of the catfish. The gill filaments and lamellae of tilabia were longer than those of the catfish indicating a greater gill surface area in the former species. The catfish was additionally supplied by modified gills in the form of branched bulbous dendritic structures originating from the second and fourth gill arches. Scanning electron microscopy revealed that the surface of both gill filaments and lamellae was covered by polyhedral cells in tilabia and oval or elongated cells in catfish. These cells carried numerous microplicae which were better developed in tilabia. All gill parts, as revealed by light microscope, were nearly covered by mucous epithelium, however, the mucous cells were present on the lamellae of the catfish only. The rakers of both species demonstrated many taste buds and infiltrating lymphocytes in the epithelial covering. In catfish, in particular, several alarm substance cells were also scattered in this epithelium.
Animals↗
Comparative morphological studies on the stereo structure of the lingual papillae of selected primates using scanning electron microscopy.
A scanning electron microscope was used to observe the lingual papillae and their connective tissue cores (CTCs) in five primates (tupai, tamarin, crab-eating monkey, mandrill, and human). There were some slender protrusions rising from the top of the filiform papilla in all five types of primate. After removing the epithelium the filiform CTC from the tupai, tamarin and crab-eating monkey displayed a U-shaped arrangement of rod-shaped protrusions. The filiform CTC from the crab-eating monkey also had a columnar base. The human filiform CTC consisted of a primary columnar base, numerous short rod-shaped secondary protrusions from its upper periphery, and a few central protrusions. The filiform CTC from the Mandrill was fundamentally similar to that of the human, however, its base was shorter. The fungiform CTC from the tupai was column shaped, with several depressions for taste buds on the top. There were three vallate papillae in the tupai, tamarin, and mandrill, approximately four in the monkey, and between five and twelve in the human. Moderately developed foliate papillae were found in the tamarin, monkey, mandrill and human. The tupai, however, possessed a finger-like lateral organ instead. The lingual root area of the tupai, tamarin, crab-eating monkey and mandrill was relatively small with a smooth surface. Only the human had a tonsil-structure, which was located on the surface of its larger lingual root.
Animals↗
Development of the chick tongue. A scanning electron microscopical investigation.
With the aim of clarifying certain morphological aspects of lingual development, chick tongues between the 8th day of incubation and hatching and also during the early postincubation period were investigated by means of the Scanning Electron Microscope. During this time, the tongue anlage underwent some remarkable morphogenetic changes, mostly involving the superficial epithelium but also including the appearance of the lingual glands at the level of the lingual root. With regards to the epithelium, it was possible to observe that in the first days of the incubation period examined, the superficial cells appeared dome-shaped, with microvilli on the apical surface; later they tended to become more flattened, and the microvilli were replaced by a thick net of microplicae. During the final days of incubation, and after hatching desquamative phenomena became evident. At no site of the tongue rudiment were taste buds ever observed, possibly because of the different functional role played by the avian tongue in comparison with that of the mammals.
Age Factors↗
Scanning electron microscopy of the lingual mucosa of the nine-banded armadillo, Dasypus novemcinctus.
The lingual mucosa of the nine-banded armadillo, Dasypus novemcinctus, was studied by scanning electron microscopy in order to analyse its morphology. The tongue of the armadillo is long and thin, and has filiform, fungiform and vallate papillae. In the anterior part of the tongue and near the vallate papillae, single or bifurcated filiform papillae are found. The vallate papillae are located on the dorsal surface of the middle third of the tongue, and have two or four slender extremities. The fungiform papillae are elliptical or rounded, and are concentrated mainly on the tip and lateral surface of the tongue, reaching as far as the middle third of the dorsal surface. Their surfaces are flat and smooth on the dorsal side, with some taste pores. Their taste buds are located near the vallum. In the material for which freeze-cracking was used, the epithelial layer showed a characteristic mucosal structure, with many epithelial papillae containing blood vessels and bundles of collagen fibers. The basal epithelial surface of the tongue mucosa showed irregular projections that are rounded or polygonal in shape, with a depression in the center. These depressions varied in diameter.
Animals↗
Morphological study of the vagal afferent nerve endings in the laryngeal mucosa of the dog.
The afferent nerve endings in the laryngeal mucosa of the dog were investigated by immunohistochemical staining specific for neurofilament protein of whole-mount preparation. In the laryngeal mucosa, two kinds of nerve endings, namely, laminar and glomerular endings, were observed. The laminar endings were distributed on the laryngeal side of the epiglottis, the mucosa overlying the arytenoid cartilage and the vocalis muscle. The laminar endings were 100-350 microns long and 60-200 microns wide. Some axons gave rise to a single ending while others continued to two endings. The terminal portions were round, oval or triangular in shape, and occasionally had an immunopositive rim with a negative center. Cryostat sections revealed that the laminar endings were located immediately beneath the laryngeal epithelium. The endings were flattened and extended in two dimensions. The glomerular endings could be divided into two subtypes, large ones and small ones. The large ones were 150-250 microns long and 90-200 microns wide, and they were distributed in the mucosa of the intercartilaginous part of the glottis and the laryngeal side of the epiglottis. Several nerve fibers were gathered in the subepithelial region and arranged in a glomerular pattern. In some large glomerular endings, the terminal portions formed laminar arborizations. The small glomerular endings were 100-200 microns long and 40-120 microns wide, and their distribution was restricted to the mucosa of the corniculate process of the arytenoid cartilage. They were simple in terms of shape and were also located in the subepithelial region. Some small endings were accompanied by mucosal protrusions and were located near taste buds. Dogs that had been subjected to surgical denervation of the internal branch of the cranial (superior) laryngeal nerve suggested that both the laminar and the glomerular endings were mainly derived from this branch of ipsilateral side.
Afferent Pathways↗
The lingual epithelium of Salamandra salamandra: metamorphotic changes during its ontogenesis.
The development of the epithelia of the secondary tongue of Salamandra salamandra is described on the basis of light microscopic and scanning electron microscopic studies of defined developmental stages. A glandular area with radial ridges and furrows is formed anterior to the primary tongue during the larval phase. Epithelial cones--each a compact anlage of a gland lying in the furrows--displace the lamina propria. The glandular area grows upward and latero-caudad during metamorphosis and forms the secondary tongue by fusing with the primary tongue. Lumina within the gland anlage appear at the beginning of metamorphosis. They open as glandular tubules towards the oral cavity at the climax of metamorphosis. The epithelial lining becomes single layered and differentiates into gland cells. The glands are increasingly surrounded by fibers of the musculus genioglossus. At the orifice of the gland, the gland cells mingle with the multilayered epithelium of the surface of the tongue. This contains two types of goblet cells in addition to the villus-shaped covering cells which leave gaps for the taste buds. The goblet cells are formed before (type I) and during (type II) metamorphosis and replace the typical larval goblet cells. The new mushroom-shaped part of the secondary tongue is characterized by aborally running septae of connective tissue, visible after digestion with pankreatin. The tip of the primary tongue which originally covers the glandular part becomes completely integrated. It is characterized by crypts which become shallower caudally.
Animals↗
Taste processing: whetting our appetites.
Two G-protein-coupled receptors have been identified that are present in the apical membranes of rat and mouse taste cells and differentially distributed across the tongue and palate. They are strong candidates for being taste receptors and their discovery has provided new tools for research into gustatory processing.
Animals↗