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1.
2.
In the cochlea, cell damage triggers intercellular Ca2+ waves that propagate through the glial-like supporting cells that surround receptor hair cells. These Ca2+ waves are thought to convey information about sensory hair cell-damage to the surrounding supporting cells within the cochlear epithelium. Mitochondria are key regulators of cytoplasmic Ca2+ concentration ([Ca2+]cyt), and yet little is known about their role during the propagation of such intercellular Ca2+ signalling. Using neonatal rat cochlear explants and fluorescence imaging techniques, we explore how mitochondria modulate supporting cell [Ca2+]cyt signals that are triggered by ATP or by hair cell damage. ATP application (0.1–50 μM) caused a dose dependent increase in [Ca2+]cyt which was accompanied by an increase in mitochondrial calcium. Blocking mitochondrial Ca2+ uptake by dissipating the mitochondrial membrane potential using CCCP and oligomycin or using Ru360, an inhibitor of the mitochondrial Ca2+ uniporter, enhanced the peak amplitude and duration of ATP-induced [Ca2+]cyt transients. In the presence of Ru360, the mean propagation velocity, amplitude and extent of spread of damage-induced intercellular Ca2+ waves was significantly increased. Thus, mitochondria function as spatial Ca2+ buffers during agonist-evoked [Ca2+]cyt signalling in cochlear supporting cells and play a significant role in regulating the spatio-temporal properties of intercellular Ca2+ waves. 相似文献
3.
Feng Wang Li Zuo Bo Hong Dongyi Han Ethan M Range Lingyun Zhao Yanan Sui Weiwei Guo Liangfa Liu 《Journal of biomedical science》2013,20(1):91
Background
Noise induced injury of the cochlea causes shifts in activation thresholds and changes of frequency response in the inferior colliculus (IC). Noise overexposure also induces pathological changes in the cochlea, and is highly correlated to hearing loss. However, the underlying mechanism has not been fully elucidated. In this study, we hypothesized that overexposure to noise induces substantial electrophysiological changes in the IC of guinea pigs.Results
During the noise exposure experiment, the animals were undergoing a bilateral exposure to noise. Additionally, various techniques were employed including confocal microscopy for the detection of cochlea hair cells and single neuron recording for spontaneous firing activity measurement. There were alterations among three types of frequency response area (FRA) from sound pressure levels, including V-, M-, and N-types. Our results indicate that overexposure to noise generates different patterns in the FRAs. Following a short recovery (one day after the noise treatment), the percentage of V-type FRAs considerably decreased, whereas the percentage of M-types increased. This was often caused by a notch in the frequency response that occurred at 4 kHz (noise frequency). Following a long recovery from noise exposure (11–21 days), the percentage of V-types resumed to a normal level, but the portion of M-types remained high. Interestingly, the spontaneous firing in the IC was enhanced in both short and long recovery groups.Conclusion
Our data suggest that noise overexposure changes the pattern of the FRAs and stimulates spontaneous firing in the IC in a unique way, which may likely relate to the mechanism of tinnitus. 相似文献4.
We describe a method to use point-stiffness (PtSt) measurements, i.e., indentation measurements, to obtain elastic moduli of different organ of Corti (OC) tissues. A detailed finite element (FE) model of the OC is used to account for geometric effects in the indentation measurements. We also present a sensitivity analysis, performed within a Bayesian estimation framework, that can be used to improve experimental design. The sensitivity analysis shows that the basilar membrane (BM) PtSt is most sensitive to changes in the BM properties and to changes in the pillar cells (PC) properties. This result suggests that the BM and the PC dominate the macromechanics of the OC. The most likely values of the Young?s modulus predicted for the middle turn for the BM arcuate, BM pectinate, and the PC are found to be 935 KPa (range 640–1360 KPa), 300 KPa (range 190–460 KPa), and 3 GPa (range 1–9 GPa), respectively. 相似文献
5.
Dr. P. Gil-Loyzaga R. Pujol R. Mollicone A.-M. Dalix R. Oriol 《Cell and tissue research》1989,257(1):17-21
Summary The presence of human blood-group antigens was analyzed in the rat cochlea during its postnatal development, using anti-A, anti-B and anti-H antibodies. At no stage was reactivity with anti-A antibody observed. With the anti-H antibody, a strong reactivity was observed from 1 to 9 days after birth within hair cells and some other surface epithelial cells of the cochlear duct. After postnatal day 9, only a faint reactivity persisted in a few non-sensory cells. With the anti-B antibody, only hair cells were selectively labeled. At early stages (postnatal day 1 and 3), the reactivity was intense and observed both around the cell surface and within the supranuclear region of cytoplasm. Later on, the reactivity decreased; it was limited at postnatal day 9 to a reactive spot below the cuticular plate. Results are compared with a preliminary finding describing the first appearance of B and H antigens in the organ of Corti at a prenatal stage, and with data concerning other sensory and neural structures. The appearance and progressive disappearance of B and H antigens on sensory and non-sensory cells can be correlated with significant events in the development of the cochlea. The transient expression of B and H antigens in cochlear sensory cells may correspond to developmental changes in their surface glycoconjugates. 相似文献
6.
Christine Köppl Regina Nickel 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2007,193(6):613-624
Cochlear microphonics (CMs), which represent the electrical activity of hair cells, and compound action potentials (CAPs),
which represent the activity of the auditory nerve, were recorded from the round window of the inner ear, in owlets aged between
5 and 97 days posthatching, i.e., from soon after hatching to beyond fledgling. At the earliest ages examined, animals showed
very insensitive CM and virtually no CAP responses. Thus, hearing in barn owls develops entirely posthatching and the birds
appear to be profoundly deaf well into the second week. Thresholds improved gradually after that and CMs reached their adult
sensitivity at 5 weeks posthatching at all frequencies. Compound action potential responses appeared progressively later with
increasing frequency. Adult neural sensitivity was achieved about 1 week later than for the CM responses at most frequencies,
but took until 9–10 weeks posthatching at the highest frequencies (8–10 kHz). This indicates an apex-to-base maturation sequence
of neural sensitivity within the cochlea, with a disproportionately long period to maturity for the most basal regions. Compound
action potential amplitudes matured even later, at about 3 months posthatching, at all frequencies. This suggests a prolonged
immaturity in the temporal synchrony of spiking in the auditory nerve. 相似文献
7.
Auditory function and cochlear morphology have previously been described in the postnatal German waltzing guinea pig, a strain with recessive deafness. In the present study, cochlear histopathology was further investigated in the inner ear of the developing German waltzing guinea pig (gw/gw). The lumen of the cochlear duct diminished progressively from embryonic day (E) 35 to E45 and was absent at E50 because of the complete collapse of Reissner's membrane onto the hearing organ. The embryonic stria vascularis, consisting of a simple epithelium, failed to transform into the complex trilaminar tissue seen in normal animals and displayed signs of degeneration. Subsequent degeneration of the sensory epithelium was observed from E50 and onwards. Defective and insufficient numbers of melanocytes were observed in the developing gw/gw stria vascularis. A gene involved in cochlear melanocyte development, Pax3, was markedly reduced in lateral wall tissue of the cochlea of both E40 and adult gw/gw individuals, whereas its expression was normal in the skin and diaphragm muscle of adult gw/gw animals. The Pax3 gene may thus be involved in the pathological process but is unlikely to be the primary mutated gene in the German waltzing guinea pig. TUNEL assay showed no signs of apoptotic cell death in the developing stria vascularis of this type of guinea pig. Thus, malformation of the stria vascularis appears to be the primary defect in the inner ear of the German waltzing guinea pig. Defective and insufficient numbers of melanocytes might migrate to the developing stria vascularis but fail to provide the proper support for the subsequent development of marginal and basal cells, thereby leading to stria vascularis malformation and dysfunction in the inner ear of the German waltzing guinea pig. 相似文献
8.
Forli F Passetti S Mancuso M Seccia V Siciliano G Nesti C Berrettini S 《Bioscience reports》2007,27(1-3):113-123
Mitochondrial diseases (MD) are a clinically heterogeneous group of disorders that arise as a result of dysfunction of the
mitochondrial respiratory chain. Sensorineural hearing loss (SNHL) is often associated to mitochondrial dysfunctions both
in syndromic, nonsyndromic forms. SNHL has been described in association to different mitochondrial multisystemic syndromes,
often characterized by an important neuromuscular involvement. Because of the clinical relevance of the associated neurological
symptoms, the occurrence of SNHL is often underestimated and undiagnosed. In this study we evaluated the incidence of SNHL
in a group of 17 patients with MD. We detected some degree of hearing impairment in 8/17 patients (47%), thus confirming the
frequency of hearing impairment in MD. Furthermore, we want to highlight the role of the audiologist and otolaryngologist
in the diagnosis and characterization of a MD, which should be suspected in all the cases in which the hearing loss is associated
to signs and symptoms characteristic of mitochondrial dysfunction, especially if the family history is positive for hearing
loss or MD in the maternal line. 相似文献
9.
Takebayashi S Yamamoto N Yabe D Fukuda H Kojima K Ito J Honjo T 《Developmental biology》2007,307(1):165-178
Notch signaling inhibits hair cell differentiation, based on studies on mice deficient in Notch signaling-related genes and its downstream genes. However, the precise mechanisms of this inhibition are unknown because it is difficult to control the timing and duration of the suppression of Notch signaling. Here, we developed a novel in vitro culture and analysis method for mouse fetal cochleae and examined the roles of Notch signaling by its reversible inhibition through the use of Notch signaling inhibitors of gamma-secretase and TNF-alpha-converting enzyme. Notch inhibition with Notch signaling inhibitor treatment increases the number of cochlear hair cells, as observed in gene deletion experiments. We elucidated that this increase is regulated by the dichotomy between hair cells and supporting cells from common progenitors. We also propose other roles of Notch signaling in cochlear development. First, Notch signaling arrests the cell cycle of the cochlear epithelium containing putative hair cells and supporting cell progenitors because Notch inhibition with inhibitor treatment increases the number of 5-bromo-2'-deoxyuridine (BrdU)-positive cells that can differentiate into hair cells or supporting cells. Second, Notch signaling is required for the induction of Prox1-positive supporting cells. Third, Notch signaling is required for the maintenance of supporting cells. 相似文献
10.
Doleviczényi Z Vizi ES Gacsályi I Pallagi K Volk B Hársing LG Halmos G Lendvai B Zelles T 《Neurochemical research》2008,33(11):2364-2372
In humans, serotonin (5-HT) has been implicated in numerous physiological and pathological processes in the peripheral auditory
system. Dopamine (DA), another transmitter of the lateral olivocochlear (LOC) efferents making synapses on cochlear nerve
dendrites, controls auditory nerve activation and protects the sensory nerve against overactivation. Using in vitro microvolume
superfusion techniques we tested 5-HT6 and 5-HT7 receptor antagonists whether they can influence dopamine (DA) release from the guinea-pig cochlea in control and in ischemic
conditions using currently available and new 5-HT6 and 5-HT7 antagonists and mixed antagonists, which were synthesized and characterized for the current study. While the 5-HT7 antagonist SB-258719 was ineffective, SB-271046, which blocks the 5-HT6 receptor, caused a significant increase in cochlear DA release what is contradictory with the excitatory nature of this type
of receptor. Moreover, the mixed 5-HT6/7 antagonist EGIS-12233 induced an even more pronounced increase in the resting DA release. To understand why the block of
an excitatory receptor results in an increase instead of a decrease in function, we investigated the possible involvement
of an indirect neural mechanism through an inhibitory system. In the presence of the GABAA receptor blocker bicuculline, EGIS-12233 failed to increase the release of DA, suggesting that the serotonin receptor modulation
of DA release from the lateral olivocochlear efferents in the cochlea was produced indirectly by decreasing the GABAergic
inhibitory tone on dopaminergic nerve endings. The mixed 5-HT7/D4 receptor antagonist EGIS-11983 significantly increased both the stimulation-evoked and the resting DA release, while the
selective D4 blocker L-741,741 alone had no significant effect. Ischemia, simulated by oxygen and glucose deprivation from
the perfusion solution had no action on the effect of the drugs. Drugs that can increase the release of DA from LOC terminals
in the cochlea may have a role in the treatment of sensorineural hearing loss. 相似文献