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Taste buds are specialized epithelial cell clusters in the oral squamous cell epithelium. Although taste buds have been reported to renew rapidly, the mechanism of cell cycle control in these specialized structures remains unresolved. To clarify the cell cycle status and role of cyclin-dependent kinase inhibitors (CDKI) for cell cycle control in the taste buds, we analyzed cell proliferation activity using bromodeoxyuridine (BrdU) and Ki-67 immunostainings and the expression of the Cip/Kip family of CDKI (p21Cip1, p27Kip1, and p57Kip2) in the circumvallate papillae of mouse and hamster. BrdU-positive cells were detected in the basal layer of the oral epithelium. In the taste buds, Ki-67-positive cells were seen in the basal area, with only a very few positive cells in the taste buds. Both p21Cip1 and p27Kip1 positive cells were seen in the suprabasal layer of the non-gustatory oral epithelium. In the taste buds, stronger p27Kip1 staining was detected than in the non-gustatory epithelium. Western blotting analysis revealed that p27Kip1 was abundant in the mucosal tissues from circumvallate papillae. Thus, our study suggests that the taste bud cells except for basal cells are post-mitotic cells and that the cell cycle arrest associated with taste bud cell differentiation could be regulated predominantly by p27Kip1.  相似文献   

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Apoptotic cells in the taste buds of mouse circumvallate papillae after the sectioning of bilateral glossopharyngeal nerves were examined by the method of DNA nick-end labeling (TUNEL), together with standard electron microscopy. The taste buds decreased in number and size 3–11 days after denervation and disappeared at 11 days. The TUNEL method revealed only a few positively stained nuclei in normal taste buds but, in those of mice 1–5 days after denervation, the number of positive nuclei had increased to 3–5 times that of taste buds from normal mice. Electron-microscopic observation after denervation demonstrated taste bud cells containing condensed and fragmentary nuclei in a cytoplasm with increased density. The results show that taste bud cells under normal conditions die by apoptosis at the end of their life span, and that gustatory nerve sectioning causes apoptosis of taste bud cells with taste buds decreasing in number and ultimately disappearing. Received: 20 November 1995 / Accepted: 15 May 1996  相似文献   

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Summary Mouse taste buds were investigated following administration of monoamines and their precursors by fluorescence and electron microscopy. The appearance of fluorescent cells within the taste bud and the ultrastructural changes of vesicles in the gustatory cells were due to the treatment of 5-hydroxytryptophan. Small dense-cored vesicles (30–60 nm in diameter) appeared throughout the cytoplasm and accumulated especially at the presynaptic membranes of afferent synapses. Large dense-cored vesicles (80–100 nm) increased twice in number, and electron densities of their cores became more dense as compared with untreated mice. Fluorescent cells appeared in the taste bud of l-DOPA treated mice, whereas no ultrastructural changes were observed. These results suggest that the gustatory cells of the taste bud are capable of taking up and storing monoamines, which might act as neurotransmitters from the gustatory cells to the nerves.  相似文献   

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Summary Effect of colchicine on the ultrastructure of taste bud cells was studied in the mouse. In untreated mice microtubules were abundant throughout the entire cytoplasm of type-III cells, but only in the apical cytoplasm of type-I cells. After 2 h of colchicine treatment, no microtubules were observed in any taste bud cells; dense secretory granules in the apical cytoplasm of type-I cells mostly disappeared, and instead, numerous phagosomes appeared. It is suggested that colchicine causes an interruption of the transport of the secretory granules in type-I cells from the Golgi apparatus to the membrane of the apical surface, from which release occurs. In type-III cells, after 4 or 5 h of treatment, dense-cored vesicles scattered throughout the cytoplasm tended to increase in number; they were often observed to accumulate in the vicinity of the Golgi apparatus. Five hours after treatment with 5-hydroxy-l-tryptophan (5-HTP) following colchicine pretreatment, monoamine specific fluorescent cells and vesicles with highly electron-dense cores of type-III cells were still present. On the other hand, 5 h after 5-HTP treatment alone both fluorescent cells and vesicles with highly electron-dense cores had already disappeared. These observations suggest that the treatment with colchicine interrupts the transport of densecored vesicles of type-III cells to synaptic areas, in which those vesicles are presumed to discharge the neurotransmitter substance.  相似文献   

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Although it has been long accepted that innervation by a tastenerve is essential for maintenance of taste buds, it is notclear what role, if any, innervation plays in the morphogenesis oftaste papillae and taste bud development. The following studywas undertaken to determine what effects lack of sensory innervationhave on the development of taste papillae and the formationof taste buds in the mouse. Timed-pregnant female mice (n =3) at gestational day 12 (gd12) were anesthetized and a 1 µlsolution (1 µg/µl) of ß-bungarotoxin (ß-BTX),a neurotoxin that disrupts sensory and motor neuron development,was injected into the amniotic cavity of two embryos per dam.Two shams were injected with PBS. Fetuses were harvested atgd18, 1 day before birth, and four ß-BTX-injected embryos,two shams and two controls were fixed in buffered paraformaldehyde.Serial sections were examined for the presence and morphologyof taste papillae and taste buds. No nerve profiles were observedin ß-BTX-injected tongues. Although circumvallate papillaewere present on ß-BTX tongues, only five fungiform papillaecould be identified. Taste buds were present on a large percentageof fungiform papillae profiles (24% and on circumvallate papillaein sham and control fetuses; in contrast, no taste buds wereassociated with taste papillae in ß-BTX fetuses. Theseresults implicate a significant role for innervation in tastepapillae and taste bud morphogenesis.  相似文献   

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Taste buds endure extreme changes in temperature, pH, osmolarity, so on. Even though taste bud cells are replaced in a short span, they contribute to consistent taste reception. Each taste bud consists of about 50 cells whose networks are assumed to process taste information, at least preliminarily. In this article, we describe a neural network model inspired by the taste bud cells of mice. It consists of two layers. In the first layer, the chemical stimulus is transduced into an irregular spike train. The synchronization of the output impulses is induced by the irregular spike train at the second layer. These results show that the intensity of the chemical stimulus is encoded as the degree of the synchronization of output impulses. The present algorithms for signal processing result in a robust chemical-sensing system.  相似文献   

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Denervation of taste buds in the rabbit   总被引:1,自引:0,他引:1  
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Cutaneous taste buds in cod   总被引:1,自引:0,他引:1  
The distribution of cutaneous taste buds was determined quantitatively in larvae, juveniles and young adults of cod, using scanning electron microscopy. Changes in these distributions associated with development were followed in laboratory reared fish. Taste buds were first seen on the snout and lips of cod at a total length of 8 mm, and on the barbel at a length of 22 mm. The highest taste bud densities were seen at a length of around 90 mm, and subsequently declined on the barbel and pelvic fins with further growth. In these late 0-group fish, mean taste bud densities over much of the head, e.g. throat, dentary and sides of the snout were <100 mm−2. On the tip of the snout and the lips, mean densities were in the region of 350–400 mm−2, while on projecting parts of the fish, especially the barbel, anterior naris flap and extremities of the fins, spot densities occasionally exceeded 1000 mm−2 at some sites. Mean taste bud diameter increased rapidly from 2.23μ± 0.35 μm (S.D.) at a length of 22 mm to 7.19 ± 0.23 μm at 90 mm length, with a much slower increase to about 8 μm associated with a further doubling in body length. These changes indicate a phase of rapid proliferation and growth in size of cutaneous taste buds in the period preceding the adoption of a benthic habit in their first summer. The presence of high taste bud densities on the barbel and pelvic fins in particular appears to correlate with the known feeding behaviour of cod.  相似文献   

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Summary Empty spaces are seen under both light and electron microscopes inside the taste buds of the dog lingual circumvallate papillae. They average 10 in diameter and 20 in length. Lacking endothelial lining, they are bordered directly by cell membranes of neighboring bud cells, and thus represent enlarged intercellular spaces. Intergemmal blood capillaries encircle the buds in close proximity to these intragemmal spaces. It is suggested that these spaces act as reservoirs for tissue fluid which may flow from them to the exterior via the intercellular spaces and the gustatory pores. This provides an effective mechanism whereby taste buds may be flushed of stimulating agents.Supported by Emory University Research Funds; Publication No. 650 of Division of Basic Health Sciences.  相似文献   

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J S Law  K Watanabe  R I Henkin 《Life sciences》1985,36(12):1189-1195
Calmodulin is higher in particulate fractions from bovine taste buds containing taste bud membranes which specifically bind sweet tastants compared to corresponding fractions from control non-taste bud bearing lingual epithelial tissue. As biochemical purity (i.e., membrane enzyme marker activity) of these membrane enriched fractions increased (P4B greater than P3B greater than P2B) calmodulin correspondingly increased (P4B greater than P3B greater than P2B); these increases also correlated with increased membrane purity as demonstrated by electron microscopy. All PB subfractions from taste buds contained a greater membrane concentration than those from PD subfractions and calmodulin was significantly increased in each corresponding subfraction. The presence of calmodulin in taste bud membranes, its correlation with membrane purification and reports that numerous drugs which induce taste loss are potent inhibitors of calmodulin suggest a role for calmodulin in taste function.  相似文献   

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Summary Several precursor substances and biogenic amines were admistered intraperitoneally to mice and were examined by the histochemical formaldehyde induced fluorescence method. It was found that after treatment with l-Dopa a number of cells inside the taste buds showed fluorescence.  相似文献   

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The palatal region of the oral cavity in rodents houses 100-300 taste buds and is particularly sensitive to sweet and umami compounds; yet, few studies have examined the expression patterns of transduction-related molecules in this taste field. We investigated the interrelationships between members of the T1R family and between each T1R and gustducin in palatal taste buds. Similar to lingual taste buds, T1R1 and T1R2 are generally expressed in separate palatal taste cells. In contrast to lingual taste buds, however, T1R2 and T1R3-positive palatal taste cells almost always coexpress gustducin, suggesting that sweet taste transduction in the palate is almost entirely dependent on gustducin. T1R1-positive palate taste cells coexpress gustducin about half the time, suggesting that other G proteins may contribute to the transduction of umami stimuli in this taste field.  相似文献   

19.
Electron microscopic studies have been made on the developing taste buds in fungiform and vallate papillae of prenatal rats. Three stages of differentiation of these buds are described. The first stage is characterized by presence of the nervous fibers in the connective tissue of the papillae and dense granules of various size, as well as dense-cored vesicles (500-700 A in diameter) in the basal parts of some epithelial cells at the top of the papillae (16-17th days of gestation). The second stage is characterized by nerve processes entering the epithelium and by formation of afferent synaptic contacts between the differentiating epithelial cells and the nervous fibers (19th day of gestation). At the third stage, the cluster of differentiating epithelial cells attains a form which is similar to mature taste buds (21-22nd days of gestation). Thus, to the birthday of rats, differentiation of the basal parts of the taste buds takes place, whereas the apical parts of the taste buds remain undeveloped and do not communicate with the oral cavity. Peculiarities of fine structure of differentiating epithelial cells at the three stages are discussed.  相似文献   

20.
Huang YA  Grant J  Roper S 《PloS one》2012,7(1):e30662
Recent studies suggest that l-glutamate may be an efferent transmitter released from axons innervating taste buds. In this report, we determined the types of ionotropic synaptic glutamate receptors present on taste cells and that underlie this postulated efferent transmission. We also studied what effect glutamate exerts on taste bud function. We isolated mouse taste buds and taste cells, conducted functional imaging using Fura 2, and used cellular biosensors to monitor taste-evoked transmitter release. The findings show that a large fraction of Presynaptic (Type III) taste bud cells (~50%) respond to 100 μM glutamate, NMDA, or kainic acid (KA) with an increase in intracellular Ca(2+). In contrast, Receptor (Type II) taste cells rarely (4%) responded to 100 μM glutamate. At this concentration and with these compounds, these agonists activate glutamatergic synaptic receptors, not glutamate taste (umami) receptors. Moreover, applying glutamate, NMDA, or KA caused taste buds to secrete 5-HT, a Presynaptic taste cell transmitter, but not ATP, a Receptor cell transmitter. Indeed, glutamate-evoked 5-HT release inhibited taste-evoked ATP secretion. The findings are consistent with a role for glutamate in taste buds as an inhibitory efferent transmitter that acts via ionotropic synaptic glutamate receptors.  相似文献   

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