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PubMed1999

Tissue-specific levels and cellular distribution of epidermal growth factor receptors within control and neomycin-damaged neonatal rat Organ of Corti.

Epidermal growth factor receptor (EGFR) levels were assayed by an enzyme-linked immunosorbent assay (ELISA) in microdissected organ of Corti (OC) from neonatal rats directly after isolation and after 3 days in culture with and without neomycin treatment. In addition, the cellular distribution of the EGFR in the OC was determined by immunohistochemistry. The in vitro level of EGFR determined by ELISA assays doubled after neomycin damage to OC, suggesting that EGFR is subject to up-regulation following this treatment. Immunohistochemistry of both in vivo and in vitro controls indicates that EGFR is predominantly localized in the stereociliary bundles of the hair cells; supporting cells and the apical junctions between the remaining Kolliker organ cells were also immunolabeled. In neomycin-treated cultures, sensory cells were degenerated, so no labeling could be seen. However, supporting and Kolliker organ cells continued to show labeling. In addition, nerve fibers in the region of the future osseous spiral lamina and projecting out toward the damaged sensory epithelium were immunostained. The up-regulation of the EGFR and its redistribution within the OC following neomycin damage support the earlier observation that growth factors that act through EGFR, such as EGF and transforming growth factor-alpha can induce neonatal mammalian auditory hair cell replacement under culture conditions, after aminoglycoside treatment.

Animals↗
PubMed2006

The effect of organ of corti loss on ganglion cell survival in humans.

HYPOTHESIS: Severe spiral ganglion cell loss does not necessarily follow loss of hair cells or supporting cells in humans. BACKGROUND: Despite some publications to the contrary, statements that loss of hair cells and/or supporting cells of the organ of Corti results in a severe loss of spiral ganglion cells in humans still appear in the literature, especially in respect to cochlear implants. This assumption is apparently based on studies in animals or cell culture and not from studies of human temporal bones. METHODS: Morphological analysis of archival temporal bones with microscopic and statistical analysis of ganglion cell, hair cell, and supporting cell populations was performed in 33 ears with total hearing losses of varying causes and durations of deafness. None of the ears had remaining hair cells. Six ears had had cochlear implants. RESULTS: Ganglion cell counts ranging from 2,889 to 34,299 and the corresponding percentage of remaining ganglion cells based on age-normative data were not significantly related to the duration of hearing loss (r = -0.13 and 0.02, respectively, p > 0.05) or to remaining supporting cell populations (r's from 0.15 to 0.27, p > 0.05). More than half of ears (51.5%) had ganglion cell counts within two standard deviations of age-normative means. Mean ganglion cell counts and percentage of remaining ganglion cells of ears with surviving peripheral processes (dendrites) did not differ significantly from those of ears with no peripheral processes. CONCLUSION: The loss of hair and supporting cells in the organ of Corti in humans does not necessarily result in as significant a loss of spiral ganglion cells as has been reported animals. In fact, our results suggest that ganglion cell loss may be a primary concomitant loss due to the disease process.

Adult↗
PubMedDate not supplied

Acetylcholinesterase activity in the chinchilla organ of Corti in normal and acoustically overstimulated animals.

The distribution of acetylcholinesterase (AChE) positive nerve fibers and endings in the organ of Corti of normal and acoustically overstimulated chinchillas is described. The strongest activity was located in the inner spiral bundle, ane remained almost unchanged even after all the outer and the majority of the inner hair cells had degenerated as a result of intense exposure. In the chinchilla even the apical coil had three rows of AChE-positive nerve endings under the outer hair cells.

Acetylcholinesterase↗
PubMed1987

Wheat germ agglutinin binding sites in the organ of Corti as revealed by lectin-gold labeling.

The distribution of wheat germ agglutinin(WGA)-binding sites in the organ of Corti of the guinea pig and mongolian gerbil was studied. WGA was conjugated with gold particles and applied on thin sections of the cochlea embedded in Spurr's resin and in Lowicryl K4M. WGA-binding sites were found on the plasma membrane, lysosomes and cytoskeletons of hair and supporting cells as well as on the tectorial and basilar membranes. No distinct difference was discovered between hair cells and supporting cells in terms of WGA-binding activities.

Animals↗
PubMedDate not supplied

Reciprocal synapses at the base of outer hair cells in the organ of corti of man.

Reciprocal synapses have been found between nerve terminals and the outer hair cells in the human organ of Corti. A single nerve ending of the nonvesiculated type may possess two types of synaptic specialization of opposite polarity. The first is typical of the "afferent" synapse with a presynaptic body in the hair cell and pre- and postsynaptic membrane thickening.. The second consists of a small collection of presynaptic vesicles in the neural cytoplasm near the plasma membrane facing the hair cell and a subsynaptic cisterna within the hair cell cytoplasm. The second type of specialization is similar to the synapses seen in "efferent" endings. This suggests that both an afferent (hair cell to neuron) and efferent (neuron to hair cell) synaptic relationship may exist between an outer hair cell and a single nerve terminal.

Hair Cells, Auditory↗
PubMedDate not supplied

Cytoskeletal basis for contractility of outer hair cells in the normal adult human organ of Corti: comparisons with vestibular hair cells.

The present study is the first consecutive analysis of the adult normal human organ of Corti and vestibular hair cells with regard to the expression of F-actin, actin-associated proteins (alpha-actinin, alpha- and beta-spectrins, vinculin and tropomyosin), beta-tubulin and the calcium-binding protein synaptophysin. The expression of these cytoskeletal and their associated proteins in man is largely similar to, although not identical with, that previously described for several other mammalian species. However, a few very unusual staining patterns were found. In several long outer hair cells a rod of F-actin extended from the infracuticular area to the cell nucleus. Fluorescence for tropomyosin occurred both in the cuticular plates of the outer and inner hair cells, and in the area of close apposition between the base of the outer hair cell and the apical part of Deiter's cell. In contrast, the vestibular hair cells showed immunoreactivity for tropomyosin only in the cuticular plates.

Actinin↗
PubMed2003

Vanilloid receptors in hearing: altered cochlear sensitivity by vanilloids and expression of TRPV1 in the organ of corti.

Capsaicin, the vanilloid that selectively activates vanilloid receptors (VRs) on sensory neurons for noxious perception, has been reported to increase cochlear blood flow (CBF). VR-related receptors have also been found in the inner ear. This study aims to address the question as to whether VRs exist in the organ of Corti and play a role in cochlear physiology. Capsaicin or the more potent VR agonist, resiniferatoxin (RTX), was infused into the scala tympani of guinea pig cochlea, and their effects on cochlear sensitivity were investigated. Capsaicin (20 microM) elevated the threshold of auditory nerve compound action potential and reduced the magnitude of cochlear microphonic and electrically evoked otoacoustic emissions. These effects were reversible and could be blocked by a competitive antagonist, capsazepine. Application of 2 microM RTX resulted in cochlear sensitivity alterations similar to that by capsaicin, which could also be blocked by capsazepine. A desensitization phenomenon was observed in the case of prolonged perfusion with either capsaicin or RTX. Brief increase of CBF by capsaicin was confirmed, and the endocochlear potential was not decreased. Basilar membrane velocity (BM) growth functions near the best frequency and BM tuning were altered by capsaicin. Immunohistochemistry study revealed the presence of vanilloid receptor type 1 of the transient receptor potential channel family in the hair cells and supporting cells of the organ of Corti and the spiral ganglion cells of the cochlea. The results indicate that the main action of capsaicin is on outer hair cells and suggest that VRs in the cochlea play a role in cochlear homeostasis.

Acoustic Stimulation↗
PubMed2005

Localization of neurotensin immunoreactivity in neurons and organ of Corti of rat cochlea.

The distribution of neurotensin-containing cell bodies and fibers has been observed in the central and peripheral nervous system, including sensory ganglia, but no description has been found in the peripheral auditory system. Here, we investigated the presence of neurotensin immunoreactivity in the cochlea of the adult Wistar rat. Strong neurotensin immunoreactivity was detected in the cytoplasm of the inner hair cells (IHC) and Deiters' cells of the organ of Corti. Outer hair cells (OHC) show weak immunoreaction. Neurotensin immunoreactivity was also found in the neurons and fibers of the spiral ganglia. Quantitative microdensitometric image analysis of the neurotensin immunoreactivity showed a strong immunoreaction in the hair cells of organ of Corti and a moderate to strong labeling in the spiral ganglion neurons. A series of double immunolabeling experiments demonstrated a strong neurotensin immunoreactivity in the parvalbumin immunoreactive IHC and also in the calbindin immunoreactive Deiters' cells. Weak neurotensin immunoreactivity was seen in the calbindin positive OHC. Neurofilament and parvalbumin immunoreactive neurons and fibers in the spiral ganglia showed neurotensin immunoreactivity. Calbindin immunoreactivity was not detected in the spiral ganglion neurons, which are labeled by neurotensin immunoreactivity. The presence of neurotensin in the cochlea may be related to its modulation of neurotransmission in the peripheral auditory pathway.

Animals↗
PubMed1993

Morphologic damage and changes of intracellular calcium-binding sites after acute noise trauma in the organ of Corti of the guinea pig.

In guinea pigs, an acute acoustic trauma was created by 6 consecutive gunshots. The sound pressure at the ear drum was 156 +/- 4 dB, the frequency maximum was between 4 and 6 kHz. Sixty hours after the noise trauma, the animals were decapitated, and the cochleae were prepared for microscopic analysis of the resulting trauma to the organ of Corti. During the process of fixation, the potassium-pyroantimonate precipitation reaction was performed to localize calcium-binding sites. The pattern of cell morphology and the distribution of calcium-binding sites was compared to that of normal control animals. Morphologic changes of the cells in the organ of Corti correlated with changes of the cellular calcium distribution, indicating the crucial role of calcium in cell damage and necrosis after acute noise trauma.

Animals↗
PubMed1993

[Mechanism of hearing. I. Efferent system of innervation of the organ of Corti].

The authors present some morphological, physiological and pathophysiological aspects of efferent system of innervation (i.e. olivocochlear system) of the organ of Corti. The cochlea is innervated by two different systems: 1) the medial efferent system which originates in the medial nucleus of the trapezoid body and synapses on outer hair cells, 2) the lateral efferent system which originates in the superior olivary nucleus and synapses on the dendrites of the auditory nerve under inner hair cells. An electrical stimulation as well as an acoustic stimulation of efferent fibers results in: a) suppression of the auditory nerve response (N1 amplitude reduction), b) increase in amplitude of cochlear microphonics and c) reduction of the endolymphatic potential. Due to presence of the crossed olivocochlear bundle, an ipsilateral stimulation of efferent fibers results in both ipsi- and contralateral response. Efferent fibers response is a feedback response to afferent fibers stimulation. There are some evidence that efferent system of innervation protects the cochlea against the effects of intense sound exposure.

Auditory Pathways↗
PubMed2004

Gene expression profile of the mouse organ of Corti at the onset of hearing.

We describe the generation of an expressed sequence tag (EST) database of the mouse organ of Corti (OC). Over 20,000 independent clones were isolated, analyzed, and grouped into 8690 unique gene clusters. A large pool of novel genes unique to the OC was identified. Sequence alignments frequently revealed alternatively spliced forms of known genes potentially relevant in the OC function. We have also electronically mapped a subset of OC mouse ESTs to several syntenic regions associated with human autosomal and recessive deafness, which may prove useful for the identification of new positional candidates for these human diseases. The EST dataset is available as an interactive Web-based public database at. This resource provides both a view of the profile of gene expression in the OC at the onset of hearing and a tool to identify novel genes of importance in hearing.

Animals↗
PubMed1983

Sustentacular cells of the organ of Corti--the tectal cells of the outer tunnel.

The cells which form the roof of the outer tunnel of the organ of Corti were studied by light microscopy and scanning and transmission electron microscopy. In the mustache bat, Pteronotus p. parnellii, the cells are characterized by: (1) a unique position in the roof and along the lateral wall of the outer tunnel; (2) no contact with the basilar membrane; (3) isolation of adjacent cell bodies; (4) an extensive endolymphatic surface with a sparse population of short microvilli; (5) a loose association with the adjacent mat of polypous surface projections on the outer tunnel surface of the first row of Hensen's cells; and (6) a darkly staining cytoplasm. These cells occur in certain other mammals (cats and mice) and have been classified previously as Hensen's or Deiters' cells, but since they lack the distinct morphological characteristics of either of these types of cells, it is suggested that they be recognized as a distinct cell type, the tectal cells of the outer tunnel.

Animals↗
PubMed1990

Freeze-fracture organization of hair cell synapses in the sensory epithelium of guinea pig organ of Corti.

The fine structure of both the afferent and efferent hair cell synapses in the sensory epithelium of guinea pig organ of Corti was examined by freeze-fracture electron microscopy. In the afferent synapse, barlike aggregates of intramembrane particles (IMPs) of about 10 nm in diameter were seen on the P-face of the afferent presynaptic membrane directly beneath the presynaptic dense projection which is located in the active zone of the presynaptic membrane. Small and large depressions have been seen on the presynaptic membrane. The former were observed in the proximity of the barlike aggregates, while the latter were observed some distance from the aggregate. In outer hair cells, IMPs of about 10 nm in diameter were seen on the P-face of the afferent postsynaptic membrane at a density of 3,000/microns 2. In the efferent synapse, many aggregates composed of from several to tens of large IMPs of 13 nm in diameter were observed on the presynaptic membrane. These aggregates were localized to small membrane depressions, which tended to be deeper as particle number per aggregate increased. Dense populations of IMPs of about 9 nm in diameter were observed on the P-face of the efferent postsynaptic membrane at a density of 4,000/microns 2. A fenestrated subsynaptic cistern completely covers the efferent postsynaptic membrane. Moreover, the subsynaptic cistern spans several efferent postsynaptic membranes when efferent synapses are gathered in a group. In the afferent and efferent synapses of hair cells, specializations of the synaptic membranes were represented by marked aggregates characteristic of IMPs. In the efferent synapse, IMP movement inside the synaptic membrane was proposed in relationship to retrival of synaptic vesicle membrane. Structural relationship between the subsynaptic cistern and efferent postsynaptic membrane was revealed.

Animals↗
PubMed1992

Height changes in the organ of Corti after noise exposure.

To determine whether or not exposure to noise causes an alteration in the height of the organ of Corti (OC), 16 cochleas which had been exposed for one or two hours to an octave band of noise with a center frequency of 4 kHz and a sound pressure level of 108 dB were examined microscopically as whole mounts. These specimens were divided into four groups: early ears (N = 3) recovered less than 0.6 hours following the exposure; intermediate ears (N = 5) recovered 0.6-4.0 hours; 1-day ears (N = 3) recovered 24 hours; and late ears (N = 5) recovered 2-21 days. Height was measured at three positions across the OC and at multiple percentage locations from apex to base. The OC-height data from the noise-exposed cochleas were compared statistically to those from ten control cochleas. A significant reduction (P < or = 0.01) in OC height at the third outer hair cell (OHC) was first evident in the early ears in the region 65-95% distance from the apex. The height was reduced even further in the intermediate ears and included a region from 15-25% distance from the apex as well as the 65-95% region. In the late ears, heights had returned to control values, except within focal OC lesions. Height at the first row of OHCs was less affected than at the third row, and height at the inner hair cell (IHC) was least affected. These height changes were accompanied by distortion of the shape and position of OHCs, the shape of Deiters' cells and buckling of inner and outer pillar bodies. Sometimes IHCs had distorted shapes and were displaced from their usual positions. Although no functional measures were obtained from these ears, data from the literature indicate that the exposure described above would have produced a sizable threshold shift. Transient reduction in OC height likely accounts for some portion of noise-induced threshold shifts.

Acoustic Stimulation↗
PubMed2005

High resolution scanning electron microscopy of the human organ of Corti. A study using freshly fixed surgical specimens.

Scanning electron microscopy on immediately fixed human cochleae obtained during surgery for life-threatening petro-clival meningioma showed excellently preserved morphology. We compared the morphological findings with those from transmission electron microscopic sections of well preserved human and animal tissue. The characteristics of neural innervation, the pathways of the nerves through the organ of Corti and the intimate relation of nerves to supporting cells along their route could be studied in detail. The lateral membranes of Hensen and Claudius cells were folded creating a surface enlargement. Marginal pillars extended the distal end of the tectorial membrane and correspond to the marginal net or "randfasernetz" described earlier. Stereocilia imprints at the undersurface of the tectorial membrane go as far as to the distal end of the marginal pillars. The presence of an irregularly distributed fourth row of outer hair cell, attached to the marginal pillars, raises questions about differences in the excitation of the last row of outer hair cells. The complex nature of many supporting cells, stria vascularis and Reissner's membrane, intracellular complexities as well as surface features are described. Supernumerary inner hair cells were observed and the different arrangement of outer spiral fibres in contrast to findings in animals and variations of nerve fibres within the organ of Corti between apex and base are discussed.

Animals↗
PubMed1995

The arrangements of F-actin, tubulin and fodrin in the organ of Corti of the horseshoe bat (Rhinolophus rouxi) and the gerbil (Meriones unguiculatus).

The composition of cytoskeletal elements in hair cells and non-sensory cells was studied in paraformaldehyde fixed cochleae of the horseshoe bat and the gerbil using phallotoxins and antibodies directed against actin, alpha-tubulin and fodrin. In both species, cryostat sections of the organ of Corti were studied using confocal fluorescence microscopy; in the bat, ultrathin sections were investigated using actin-immunoelectron and classical electron microscopy. F-actin was found in stereocilia and cuticular plates of inner and outer hair cells (IHCs and OHCs) of both species. In fixed material from both species, no F-actin staining was detected in the cytoplasm or along the lateral cell membrane of OHCs, whereas in freshly isolated OHCs of the gerbil, a faint F-actin staining was detected along the lateral wall. In the bat, the patterns of F-actin staining were confirmed with actin-immunoelectron microscopy. The alpha-tubulin antibody strongly labeled IHCs of both species. They contained a complex network of microtubules especially in the neck portion. In the bat, OHCs showed no distinct alpha-tubulin reactivity, as would be expected given the scarcity of microtubules observed at the ultrastructural level. In the gerbil, alpha-tubulin reactivity was found throughout the OHC body with highest intensity in the cell apex. In Deiters cells, pillar cells and Boettcher cells of both species, F-actin and microtubules were colocalized at contact zones with the basilar membrane. In Deiters cups, F-actin staining was most pronounced in the basal turn of the bat cochlea. In the gerbil, a distinct baso-apical gradient was found in immunostaining properties and morphology of the Deiters cells. Intense fodrin reactivity was found in the cuticular plates and along the lateral cell membrane of both types of hair cells of the bat. Cytoplasmic fodrin staining was localized within the IHCs of the bat. In the gerbil, intense fodrin staining was only found in cuticular plates of hair cells and staining of the lateral cell membrane of hair cells was faint. A faint fodrin staining was also seen in Deiters cells of both species. The basic arrangement of the cytoskeletal elements in the batś organ of Corti is similar to that of other mammals, however, certain features suggest the presence of subtle differences in micromechanical properties: there is an increased concentration of microtubules in the neck portion of IHCs, an increase in the amount of F-actin within the Deiters cups and a reduced amount of microtubules in the OHCs.

Actins↗
PubMed1990

Electron microscopic demonstration of sialic acid residues in the organ of Corti with lectin from Limax flavus.

The localization of sialic acid (N-acetyl- and N-glyconylneuraminic acid) in the organ of Corti of the mongolian gerbil was examined with electron microscopy by postembedding labeling using Limax flavus agglutinin and feutin-gold. Gold labeling was observed on the fibrous structure of the tectorial membrane, the basilar membrane and the spiral limbus. The labeling was also observed on the cuticular plate of the hair cells, the head and cone of the pillar cells and the head plate of Deiters' cells and other supporting cells. Collagen or cytoskeletal glycoproteins are suggested to be the source of the sialic acid in these structures.

Animals↗