scholarly journals Electron Microscopic Observations on the Taste Buds of the Rabbit

1958 ◽  
Vol 4 (2) ◽  
pp. 143-150 ◽  
Author(s):  
A. J. de Lorenzo
Keyword(s):  
Plasma Membranes ◽  
Supporting Cell ◽  
Nerve Fibers ◽  
Taste Buds ◽  
Taste Bud ◽  
Electron Microscopic ◽  
Gustatory Receptors ◽  
Sustentacular Cells ◽  
Granular Cytoplasm ◽  
Dense Substance

An examination of the fine structure of the taste buds in the rabbit was undertaken. Gustatory epithelium was fixed in OsO4 or 1 per cent KMnO4 solution, containing polyvinylpyrrolidone (PVP). Thick sections were examined in the phase microscope and contiguous sections prepared for the electron microscope. The bud contains two types of cells, gustatory receptors and sustentacular cells. The receptors are characterized by a dark nucleus and densely granular cytoplasm. The apical processes bear numerous microvilli which extend into the taste pore. Imbedded between the microvilli there is a dense substance, which is also present in the apical cytoplasm of the receptors. The sustentacular cells contain a large pale nucleus and less dense cytoplasm. Their basal surfaces rest upon a basement membrane. The subepithelial nerve plexuses comprise the fibers which innervate the gustatory receptors. The nerve fibers vary in diameter from 500 A to 0.3 µ, and are ensheathed by Schwann cells. The intragemmal fibers enter the taste bud between adjacent cells, and are ensheathed by the plasma membranes of the supporting cell until they synapse upon the gustatory cell. The synaptic terminals contain synaptic vesicles, which at this junction reside in the postsynaptic element. This observation is discussed with reference to synapses described elsewhere in the nervous system.

Embryonic taste buds develop in the absence of innervation

Development ◽  
1996 ◽  
Vol 122 (4) ◽  
pp. 1103-1111 ◽  
Author(s):  
L.A. Barlow ◽  
C.B. Chien ◽  
R.G. Northcutt
Keyword(s):  
Embryonic Development ◽  
Taste Receptor ◽  
Nerve Fibers ◽  
Taste Buds ◽  
Taste Bud ◽  
Taste Cells ◽  
Experimental Approaches ◽  
Well Differentiated ◽  
Serotonin Immunoreactivity

It has been hypothesized that taste buds are induced by contact with developing cranial nerve fibers late in embryonic development, since descriptive studies indicate that during embryonic development taste cell differentiation occurs concomitantly with or slightly following the advent of innervation. However, experimental evidence delineating the role of innervation in taste bud development is sparse and equivocal. Using two complementary experimental approaches, we demonstrate that taste cells differentiate fully in the complete absence of innervation. When the presumptive oropharyngeal region was taken from a donor axolotl embryo, prior to its innervation and development of taste buds, and grafted ectopically on to the trunk of a host embryo, the graft developed well-differentiated taste buds. Although grafts were invaded by branches of local spinal nerves, these neurites were rarely found near ectopic taste cells. When the oropharyngeal region was raised in culture, numerous taste buds were generated in the complete absence of neural elements. Taste buds in grafts and in explants were identical to those found in situ both in terms of their morphology and their expression of calretinin and serotonin immunoreactivity. Our findings indicate that innervation is not necessary for complete differentiation of taste receptor cells. We propose that taste buds are either induced in response to signals from other tissues, such as the neural crest, or arise independently through intrinsic patterning of the local epithelium.

scholarly journals OLFACTORY NERVE FIBERS

1956 ◽  
Vol 39 (4) ◽  
pp. 473-496 ◽  
Author(s):  
Herbert S. Gasser ◽  
Keyword(s):  
Action Potential ◽  
Cross Sections ◽  
Plasma Membranes ◽  
Size Variation ◽  
Olfactory Nerve ◽  
Nerve Fibers ◽  
Bipolar Cells ◽  
Basal Cells ◽  
Sustentacular Cells ◽  
Physiological Properties

Cross sections of olfactory nerves present a unique appearance. They indicate the presence of large numbers of very small nerve fibers, with a modal diameter of about 0.2 µ and a narrow range for their size variation. From one side of the nasal septum of a pig the yield of fibers was estimated at 6,000,000; the number arising from the turbinates would be considerably larger. The fibers are attached to the membranes of the Schwann sheaths in large bundles through mesaxons longer and more branched than those that have been seen in other nerves. Continuity of the axons between the nerves and the bipolar cells was traced in an examination of the olfactory mucous membrane; and the indication of a one-to-one relationship between cells and axons was reinforced by a comparative count. After the axons leave the bipolar cells they become incased in the central projections of the sustentacular cells. Where the latter come into contact with the basal cells the axons emerge to push back the plasma membranes of the basal cells in the first step in acquiring their nerve sheaths. Later steps are described. When the axons are delivered by the basal cells to the collecting Schwann tubes, they are already aggregated into small bundles with sheaths fundamentally the same as those they will possess until they are delivered to the glia in the olfactory bulb. Some of the aspects of the cytology of the bipolar cells and adjoining sustentacular cells are described. A survey of the physiological properties of olfactory nerve fibers was made in some experiments on the olfactory nerve of the pike. Almost all of the action potential is encompassed within a single elevation, manifesting at its front a conduction velocity of 0.2 m./sec. For a comparison, the last elevation in the C action potential in the sciatic nerve of the frog is cited as an example of conduction at the same velocity. Though expressed through long time constants, the properties of the pike olfactory fibers conform to the generalized schema for properties of vertebrate nerve fibers. This conformity signalizes that they differ from the exceptional properties of the unmedullated fibers of dorsal root origin. An afferent function for unmedullated nerve fibers does not imply that the fibers concerned are alike in their physiological properties.

scholarly journals Ecto-calcium-dependent ATPase activity of mammalian taste bud cells.

1992 ◽  
Vol 40 (12) ◽  
pp. 1919-1928 ◽  
Author(s):  
M A Barry
Keyword(s):  
Plasma Membranes ◽  
Taste Buds ◽  
Taste Bud ◽  
Basal Cells ◽  
Calcium Dependent ◽  
The Core ◽  
Dependent Atpase ◽  
Peripheral Cells ◽  
External Face ◽  
Taste Bud Cells

Histochemistry was utilized to characterize Ca-ATPases associated with lingual taste buds in the golden hamster. Taste buds showed elevated staining for magnesium- or calcium-dependent ATPase (Ca-ATPase) relative to the surrounding epithelium. At low calcium concentrations (0.1-0.5 mM), intracellular staining predominated. Most of the studies were conducted at calcium concentrations of > or = 10 mM, in which most of the staining was localized to the external face of plasma membranes of taste bud cells (including receptor and basal cells) located in the core of fungiform taste buds, or the entire vallate or foliate taste buds. The peripheral fungiform taste bud cells stained much less intensely, but the peripheral cells adjacent to the core showed intermediate levels. GTP and ITP were just as effective substrates as ATP. Millimolar concentrations of magnesium were as effective as calcium. Inhibitors of intracellular ATPases, including quercetin, sodium azide, and 2,4-dinitrophenol, had no effect on the staining. Therefore, the Ca-ATPase staining of plasma membranes at mM concentrations of calcium is thought to correspond to one or more ecto-Ca-ATPase activities with unknown functions. Roles related to increased energy requirements or to the possible function of ATP as a neurotransmitter or -modulator are proposed.

scholarly journals Electron Microscopic Observations of the Carotid Body of the Cat

1959 ◽  
Vol 6 (2) ◽  
pp. 253-262 ◽  
Author(s):  
Leonard L. Ross
Keyword(s):  
Golgi Complex ◽  
Carotid Body ◽  
Nerve Fibers ◽  
Osmic Acid ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Sustentacular Cells ◽  
Carotid Bodies ◽  
Unmyelinated Nerve ◽  
Chemoreceptor Cells

Carotid bodies were removed from cats, fixed in buffered 1 per cent osmic acid, embedded in deaerated, nitrogenated methacrylate, and cut into thin sections for electron microscopic study. The carotid body is seen to be composed of islands of chemoreceptor and sustentacular cells surrounded by wide irregular sinusoids. These cells are separated from the sinusoids by relatively broad interstitial spaces which are filled with collagen, fibroblasts, and many unmyelinated nerve fibers with their Schwann cell sheaths. The chemoreceptor cells are surrounded by the flattened, multiprocessed sustentacular cells which serve to convey the axons from an interstitial to a pericellular location. These sustentacular cells are assumed to be lemmoblastic in origin. Relatively few axons are seen to abut on the chemoreceptor cells. The cytoplasm of the chemoreceptor cell is characterized by numerous small mitochondria, units of granular endoplasmic reticulum, a small Golgi complex, and a variety of vesicles. There are many small vesicles diffusely scattered throughout the cytoplasm. In addition, there is a small number of dark-cored vesicles of the type which has been previously described in the adrenal medulla. These are usually associated with the Golgi complex. These findings are discussed in relation to the concepts of the origin of the chemoreceptor cell and the nature of the synapse.

A paracrine signaling role for serotonin in rat taste buds: expression and localization of serotonin receptor subtypes

2004 ◽  
Vol 286 (4) ◽  
pp. R649-R658 ◽  
Author(s):  
Namik Kaya ◽  
Tiansheng Shen ◽  
Shao-gang Lu ◽  
Fang-li Zhao ◽  
Scott Herness
Keyword(s):  
Serotonin Receptor ◽  
Taste Receptor ◽  
Nerve Fibers ◽  
Taste Buds ◽  
Taste Bud ◽  
Receptor Subtype ◽  
Receptor Subtypes ◽  
Double Labeling ◽  
Receptor Cells ◽  
Taste Receptor Cells

Recent advances in peripheral taste physiology now suggest that the classic linear view of information processing within the taste bud is inadequate and that paracrine processing, although undemonstrated, may be an essential feature of peripheral gustatory transduction. Taste receptor cells (TRCs) express multiple neurotransmitters of unknown function that could potentially participate in a paracrine role. Serotonin is expressed in a subset of TRCs with afferent synapses; additionally, TRCs respond physiologically to serotonin. This study explored the expression and cellular localization of serotonin receptor subtypes in TRCs as a possible route of paracrine communication. RT-PCR was performed on RNA extracted from rat posterior taste buds with 14 primer sets representing 5-HT1 through 5-HT7 receptor subtype families. Data suggest that 5-HT1A and 5-HT3 receptors are expressed in taste buds. Immunocytochemistry with a 5-HT1A-specific antibody demonstrated that subsets of TRCs were immunopositive for 5-HT1A. With the use of double-labeling, serotonin- and 5-HT1A-immunopositive cells were observed exclusively in nonoverlapping populations. On the other hand, 5-HT3-immunopositive taste receptor cells were not observed. This observation, combined with other data, suggests 5-HT3 is expressed in postsynaptic neural elements within the bud. We hypothesize that 5-HT release from TRCs activates postsynaptic 5-HT3 receptors on afferent nerve fibers and, via a paracrine route, inhibits neighboring TRCs via 5-HT1A receptors. The role of the 5-HT1A-expressing TRC within the taste bud remains to be explored.

Sensory Nerve Endings in the Mucosa of the Epiglottis—Morphologic Investigations with Silver Impregnation, Immunohistochemistry, and Electron Microscopy

1987 ◽  
Vol 96 (1) ◽  
pp. 55-62 ◽  
Author(s):  
Takemoto Shin ◽  
Shun Watanabe ◽  
Shigeru Wada ◽  
Tadatsugu Maeyama
Keyword(s):  
Electron Microscopy ◽  
Substance P ◽  
Sensory Nerve ◽  
Nerve Fibers ◽  
Silver Impregnation ◽  
Taste Bud ◽  
Nerve Endings ◽  
Electron Microscopic ◽  
Sensory Nerve Endings ◽  
Microscopic Studies

This study was conducted in order to investigate the structure of sensory nerve endings of the human epiglottis and substance P immunoreactive nerve fibers of the canine epiglottis in relationship to physiologic functions of the larynx. The human epiglottis was observed by light microscopy (silver impregnation) and electron microscopy, and the canine epiglottis was studied by peroxidase-anti-peroxidase (PAP) immunohistochemistry. The results are summarized as follows: (1) In the membranes of the epiglottis, we observed free endings of simple or complex tree shape, corpuscle endings with glomerular patterns, and taste-bud-like structures, and (2) electron microscopic studies revealed varicosity of the terminal axon with processes that contained small, clear and large, dense cored vesicles. Substance P was observed in these structures, and it was suggested that substance P was related to perception in the larynx.

scholarly journals Taste Bud Connectome: Implications for Taste Information Processes

2021 ◽  
Author(s):  
Courtney E Wilson ◽  
Ruibaio Yang ◽  
Robert S Lasher ◽  
Yannick Dzowo ◽  
John C Kinnamon ◽  
...  
Keyword(s):  
Information Transfer ◽  
Cell Types ◽  
Nerve Fibers ◽  
Taste Buds ◽  
Taste Bud ◽  
Type Ii Cells ◽  
Type Ii ◽  
Fiber System ◽  
Line System ◽  
Type Iii

Taste buds, the sensory end organs for the sense of taste, consist of 3 types of morphologically identifiable mature cells, 2 of which mediate transduction of specific taste qualities: Type III cells for sour and Type II cells for either sweet, bitter or umami. A long-standing controversy in the field is whether the nerve fibers innervating these cells are wired specifically, in a labeled-line fashion, or non-specifically, leading to broad responsiveness across taste qualities, the so-called cross-fiber system of encoding. Using serial blockface scanning electron microscopy through 5 circumvallate mouse taste buds, we reconstructed the pattern of connectivity of nerve fibers as well as the degree of potential interaction between the two types of transducing taste cells. Type II and Type III cells show few points of contact, which constrains the opportunity for direct information transfer between these cell types. Of the 133 nerve fibers traced in the 5 taste buds, 87 fibers synapsed with Type II cells (n=43), 46 fibers with Type III cells (n=33) with 4 of these fibers (3%) synapsing with both Type II and Type III cells. Since Type II and Type III cells transduce different taste qualities, these few mixed fibers do not follow a labeled line system of transmission of taste quality information although the large majority of fiber connectivity is consistent with the labeled line model.

Combining HVEM and computer-assisted reconstructions to elucidate the three-dimensional structure of taste buds

1987 ◽  
Vol 45 ◽  
pp. 584-587
Author(s):  
John C. Kinnamon
Keyword(s):  
Developmental Process ◽  
Sensory Nerve ◽  
Nerve Fibers ◽  
Taste Buds ◽  
Taste Bud ◽  
Dimensional Structure ◽  
Computer Assisted ◽  
Oral Epithelium ◽  
Synaptic Connections ◽  
Taste Cells

The vertebrate taste bud contains 50 to 150 spindle-shaped cells assembled in an onion-shaped structure approximately 60 μm wide and 80-100 μm tall. Located on the tongue and other portions of the oral epithelium, taste buds are always in a state of flux, with new cells continually entering the bud and moving from the periphery to the core as they mature. During the developmental process, young taste cells form afferent synaptic connections with sensory nerve fibers which enter the taste bud at the base and course tortuously throughout the bud. As taste cells age and become senescent, they lose their synaptic connections with the nerve fibers, degenerate, and eventually disappear. All of the processes described above result in the complete turnover of the cells within a taste bud in a period of from 10 days to two weeks in the rat.

scholarly journals New description of vagal nerve commanted intrapancreatic taste buds and blood glucose level: An experimental analysis

Bioimpacts ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 181-185
Author(s):  
Mehmet Dumlu Aydin ◽  
Aybike Aydin ◽  
Ozgur Caglar ◽  
Muhammed Enes Aydin ◽  
Erdem Karadeniz ◽  
...  
Keyword(s):  
Blood Glucose ◽  
Blood Glucose Level ◽  
Glucose Level ◽  
Nerve Fibers ◽  
Taste Buds ◽  
Taste Bud ◽  
Glucose Levels ◽  
Blood Glucose Levels ◽  
The Mean ◽  
Mean Glucose

Introduction: There have been thousands of neurochemical mechanism about blood glucose level regulation, but intrapancreatic taste buds and their roles in blood glucose level has not been described. We aimed to investigate if there are taste buds cored neural networks in the pancreas, and there is any relationship between blood glucose levels. Methods: This examination was done on 32 chosen rats with their glucose levels. Animals are divided into owned blood glucose levels. If mean glucose levels were equal to 105 ± 10 mg/dL accepted as euglycemic (G-I; n = 14), 142 ± 18 mg/dL values accepted as hyperglycemic (G-II; n = 9) and 89 ± 9 mg/dL accepted as hypoglycemic (G-III; n = 9). After the experiment, animals were sacrificed under general anesthesia. Their pancreatic tissues were examined histological methods and numbers of newly described taste bud networks analyzed by Stereological methods. Results compared with Mann-Whitney U test P < 0.005 considered as significant. Results: The mean normal blood glucose level (mg/dL) and taste bud network densities of per cm3 were: 105 ± 10 mg/dL; 156±21 in G-I; 142 ± 18 mg/dL and 95 ± 14 in G-II and 89 ± 9 mg/dL and 232 ± 34 in G-III. P values as follows: P < 0.001 of G-II/G-I; P < 0.005 of G-III/G-I and P < 0.0001 of G-III/G-II. We detected periarterial located taste buds like cell clusters and peripherally located ganglia connected with Langerhans cells via thin nerve fibers. There was an inverse relationship between the number of taste buds networks and blood glucose level. Conclusion: Newly described intrapancreatic taste buds may have an important role in the regulation of blood glucose level.

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