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At least 649 records · Page 36Linked to original sources
PubMed2004

Otx2, Gbx2, and Fgf8 expression patterns in the chick developing inner ear and their possible roles in otic specification and early innervation.

The chick inner ear is a complex structure containing auditory and vestibular sensory organs innervated by neurons of the acoustic-vestibular ganglion. The molecular signals involved in the specification and initial innervation of the otic epithelium are poorly understood. Here, we present a detailed description of the Otx2, Gbx2, and Fgf8 gene expression patterns in the chick developing inner ear, comparing them with the Bmp4 expression, a putative sensory-organ marker. The Otx2 expression was detected in the ventro-lateral wall of the otic anlage and could play a role in the segregation of the saccule and utricle maculae. The relationship between Gbx2 and Fgf8 expression changed during inner ear development but was always related to the macula sacculi innervation and endolymphatic duct formation. Our results also suggest that the maculae of the saccule and lagena, and the medial portion of the macula utriculi could arise within a broad Fgf8-positive domain previously observed at the otocyst stage. The spatial and temporal relationships between these gene expression domains and the initial innervation of the epithelium by some subpopulations of otic axons suggest that expression domain boundaries could be involved in the specification and early innervation of presumptive sensory patches.

Animals↗
PubMed1993

[Scanning electron microscopic study on inner ear barotrauma: in the guinea pig with one eustachian tube occluded].

In order to investigate the mechanism of inner ear barotrauma, guinea pigs, with one eustachian tube occluded, were subjected to compression and decompression between 1 absolute pressure and 2 absolute pressures in a high pressure chamber. The authors divided the animals into three groups according to the speed of compression and decompression. Each group contained 10 guinea pigs. Morphological changes in the cochlear sensory hairs were examined by means of scanning electron microscope. On the occluded side, hair cells were damaged more frequently and more severely by rapid compression than by rapid decompression. There was no difference in the degree of damage produced by slow decompression and rapid decompression. On the control side, slight or moderate damage to hair cells was observed mainly as a result of rapid decompression. These findings led us to hypothesize that, in the setting of normal eustachian tube function, inner ear barotrauma would generally be caused by the relative positive pressure in the middle ear cavity that occurs during decompression. Furthermore, animals deprived of eustachian tube function would not have sufficient endurance for rapid compression and would sustain inner ear barotrauma far more readily, and of far greater severity, with rapid compression than would animals with normal eustachian tube function. The difference may be due to the presence of another pressure transmission pathway to the inner ear. The mechanism of cochlear sensory hair damage due to atmospheric pressure changes is presumed to be distortion of the reticular lamina and cuticular plate caused by the difference in pressure between cortilymph (perilymph) and the subtectorial space (endolymph) resulting in injury to stereocilia.

Animals↗
PubMed1993

High affinity aldosterone binding sites (type I receptors) in the mammalian inner ear.

The presence of aldosterone (Type 1) binding sites in the mammalian inner ear has been previously suggested by an increase in inner ear Na, K-ATPase ouabain binding sites in response to the administration of aldosterone in vivo (Pitovski et al., 1993). Type I binding sites have now been identified and characterized in the lateral wall of the basal turn of the cochlea and in the ampullae of the semicircular canals of the guinea pig. In the presence of RU 28362, which blocks low-affinity binding of the labeled hormone to Type II sites, [3H]-aldosterone binds to a single class of high-affinity (Type I) sites with Kd values of 34.7 nM in lateral wall of the basal turn of the cochlea and 31.3 nM in the ampullae of the semicircular canals. Bmax is 17.1 fmol/mg dry tissue for the cochlear sample and 17.4 fmol/mg dry tissue for the ampullae, comparable to reported values in renal tissue (17-31 fmol/mg protein). Thus, the results of receptor-binding experimental protocols with [3H]-aldosterone clearly suggest that these inner ear tissues are a target site of mineralocorticoid action.

Aldosterone↗
PubMed1976

[Causal therapy for diseases of the inner ear? (author's transl)].

The examples of sudden deafness and Meniere's Disease are used to discuss the possibilities of causal therapy for inner ear dysfunctions. In sudden deafness, etiological and therapeutic considerations are focused on the problem of disorders of the arterial and venous microcirculation, contributing to oxygen deprivation of the organ of Corti. Disruption of the arterial microcirculation leads to irreversible damage of the sensory organ within minutes and non-responsiveness to therapy, whereas even serious venous circulation disturbances can be treated successfully within days after onset of the acute disease. While knowledge of pathological changes in sudden deafness is still limited, temporal bone studies in Meniere's disease provides important information on its pathogenesis. Many authors have described enlargement of the cochlear duct as evidence for endolymphatic hydrops. Maximum enlargement of the endolymphatic system disrupts the membrane system which separates endo- from perolymph, and can be confirmed by histologic examination. This indicates that a change of the ionic concentration in the inner ear fluids is responsible for inner ear dysfunction. Thus, the acute Meniere attack can be explained as a consequence of the "burst hydrops." Because of the still unknown etiology of hydrops, only its consequences can be treated at the present time: i.c., immediate removal of the toxic potassium concentration from the perilymph by increasing the microcirculation of the inner ear before irreversible damage occurs.

Deafness↗
PubMed2005

The retinoblastoma gene pathway regulates the postmitotic state of hair cells of the mouse inner ear.

Precursors of cochlear and vestibular hair cells of the inner ear exit the cell cycle at midgestation. Hair cells are mitotically quiescent during late-embryonic differentiation stages and postnatally. We show here that the retinoblastoma gene Rb and the encoded protein pRb are expressed in differentiating and mature hair cells. In addition to Rb, the cyclin dependent kinase inhibitor (CKI) p21 is expressed in developing hair cells, suggesting that p21 is an upstream effector of pRb activity. p21 apparently cooperates with other CKIs, as p21-null mice exhibited an unaltered inner ear phenotype. By contrast, Rb inactivation led to aberrant hair cell proliferation, as analysed at birth in a loss-of-function/transgenic mouse model. Supernumerary hair cells expressed various cell type-specific differentiation markers, including components of stereocilia. The extent of alterations in stereociliary bundle morphology ranged from near-normal to severe disorganization. Apoptosis contributed to the mutant phenotype, but did not compensate for the production of supernumerary hair cells, resulting in hyperplastic sensory epithelia. The Rb-null-mediated proliferation led to a distinct pathological phenotype, including multinucleated and enlarged hair cells, and infiltration of hair cells into the mesenchyme. Our findings demonstrate that the pRb pathway is required for hair cell quiescence and that manipulation of the cell cycle machinery disrupts the coordinated development within the inner ear sensory epithelia.

Animals↗
PubMed1997

Survival of inner ear sensory neurons in trk mutant mice.

Analysis of trkB-/-; trkC-/- double mutant mice revealed that peripheral and central inner ear sensory neurons are affected in these mice. However, a substantial amount of cochlear and vestibular neurons survive, possibly due to maintenance or upregulation of TrkA expression. To clarify the function of the TrkA receptor during development of the cochlear and vestibular ganglion we analysed trkA-/- mice and the expression of this receptor in inner ear sensory neurons of trkB-/-; trkC-/- animals. TrkA homozygous mutant mice showed normal numbers of neurons and no TrkA expression was detected in neurons of trkB-/-; trkC-/- double mutant mice. We conclude that TrkA is not essential for inner ear development and that in the absence of any of the known catalytic Trk receptors peripheral inner ear sensory neurons are prone to undergo cell death or must use a different signaling mechanism to survive.

Animals↗
PubMed2001

A post-processing protocol for three-dimensional visualization of the inner ear using the volume-rendering technique based on a standard magnetic resonance imaging protocol.

A superior diagnostic quality compared to other post-processing (PP) techniques for three-dimensional (3D) inner ear imaging has been attributed to volume rendering (VR). We defined and assessed a VR protocol for 3D visualization of the inner ear in a routine imaging setting. Following definition of a VR protocol by using lower threshold values, surface shading, perspective views and related parameters, standardized 3D views of the inner ear were generated and evaluated in 32 patients suffering from sensorineural or combined hearing loss. Comprehensive inner ear visualization was achieved in 28 patients by means of two 3D shaded-surface views. Incomplete data acquisition (1/32), motion and pulsation artefacts (2/32) and interposed fluid-retaining mastoid cells (1/32) were responsible for non-diagnostic image quality in 4/32 patients. In 5/32 patients modifications of the PP protocol involving the threshold value and depth-cueing parameters helped to establish diagnostic image quality. Mean post-processing time amounted to 5.8 min per site. 3D imaging with the VR technique is suitable for routine inner ear assessment if direct VR, predefined PP protocols and standardized labyrinthine views are used.

Artifacts↗
PubMed1997

Expression of the cytoskeletal protein MAP5 and its regulation by neurotrophin 3 (NT3) in the inner ear sensory neurons.

Microtubule-associated proteins (MAPs) are essential cytoskeletal components during development for neurogenesis and neuronal plasticity. Inner ear innervation is accomplished by cochleovestibular ganglion (CVG) neurons in a highly specific, well-defined pattern, which is regulated by neurotrophic factors belonging to the neurotrophin family. The inner ear offers a suitable model for studying the expression of MAPs and assessing their role in neurotrophin-induced effects that are required for neuron-target innervation. The present study was undertaken to analyze the expression and localization of MAP5 isoforms during development of CVG neurons in vivo an in vitro; as well as the regulation of MAP5 by neurotrophin-3 (NT3) in cell culture. MAP5 expression in the inner ear of chick embryos and postnatal specimens was monitored using immunoblots and immunohistochemistry on frozen sections. MAP5 was highly expressed during the early stages of CVG development, at embryonic day (E)4, being located in both neuronal perikarya and neurites. Expression was maintained during the neurite outgrowth phase (E6-E12), when strong MAP5 immunostaining was observed at the same cellular locations. MAP5 expression decreased suddenly at E14, after the establishment of specific connections between the CVG neurons and their targets, the sensory epithelium of the inner ear. In cultured CVG neurons addition of NT3 led to increased MAP5 expression and produced neurite outgrowth. Both effects are differentially regulated in parallel by low (0.5 ng/ml) and high (5 ng/ml) NT3 concentrations. Present results suggest that MAP5 may be involved in neurotrophin-induced microtubule bundling during neurite outgrowth of auditory neurons.

Age Factors↗
PubMed1995

Expression of S100 beta in sensory and secretory cells of the vertebrate inner ear.

We evaluated anti-S100 beta expression in the chick (Gallus domesticus) inner ear and determined that: 1) the monomer anti-S100 beta is expressed differentially in the vestibular and auditory perikarya; 2) expression of S100 beta in the afferent nerve terminals is time-related to synapse and myelin formation; 3) the expression of the dimer anti-S100 alpha alpha beta beta and monomer anti-S100 beta overlaps in most inner ear cell types. Most S100 alpha alpha beta beta positive cells express S100 beta, but S100 beta positive cells do not always express S100 alpha alpha beta beta. 4) the expression of S100 beta is diffused over the perikaryal cytoplasm and nuclei of the acoustic ganglia but is concentrated over the nuclei of the vestibular perikarya. 6) S100 beta is expressed in secretory cells, and it is co-localized with GABA in sensory cells. 7) Color thresholding objective quantitation indicates that the amount of S100 beta was higher (mean 22, SD +/- 4) at E19 than at E9 (mean 34, SD +/- 3) in afferent axons. 8) Moreover, S100 beta was unchanged between E11-E19 in the perikaryal cytoplasm, but did change over the nuclei. At E9, 74%, and at E21, 5% of vestibular perikarya were positive. The data suggest that S100 beta may be physically associated with neuronal and ionic controlling cells of the vertebrate inner ear, where it could provide a dual ionic and neurotrophic modulatory function.

Animals↗
PubMed2004

Survival of neuronal tissue following xenograft implantation into the adult rat inner ear.

The poor regenerative capacity of the spiral ganglion neurons of the mammalian inner ear has initiated research on how to assist the functional recovery of the injured auditory system. A possible treatment is to use a biological implant with a potential to establish central or peripheral synaptic contacts to develop into a functional auditory unit. The feasibility of this approach was tested by xenograft implantation of dorsal root ganglion (DRG) neurons from embryonic days 13 to 14, mouse expressing either LacZ or enhanced green fluorescent protein (EGFP) into the scala tympani of the adult rat inner ear. Transplanted DRG neurons survived in the scala tympani for a postoperative period ranging from 3 to 10 weeks, as verified by histochemical detection of LacZ, EGFP fluorescence and immunohistochemical labeling of the neuronal markers neurofilament and Thy 1.2. DRG neurons were found close to structures near the sensory epithelium (the organ of Corti) as well as adjacent to the spiral ganglion neurons with their peripheral dendrites. These results illustrate not only the survival of xenografted DRG neurons in the adult inner ear but also the feasibility of a neuronal transplantation strategy in the degenerated auditory system, thereby creating possibilities to replace spiral ganglion neurons.

Animals↗
PubMed1997

Effects of retinoid and thyroid receptors during development of the inner ear.

The sensory epithelia of the vertebrate inner ear are comprised of a complex pattern of hair cells and supporting cells. Several different families of signaling molecules have been shown to play a role in the development and maintenance of this structure. In particular, the steroid/thyroid receptor superfamily, and specifically retinoid and thyroid receptors appear to influence the determination, differentiation, maintenance, and possibly regeneration, of the sensory epithelia of the vertebrate inner ear. Clinical and experimental evidence demonstrates that changes in the relative availability of retinoic acid and thyroid hormone, the ligands for retinoid and thyroid receptors, result in perturbations in the development of hair cell sensory epithelia. Retinoic acid and retinoid receptors appear to play a role in early developmental events including cellular proliferation and determination whereas thyroid hormone and thyroid receptors appear to play a role in later events including differentiation and maintenance.

Journal Article↗
PubMedDate not supplied

Human leukocyte antigens in patients with inner ear diseases of unknown etiology.

The immune response genes that control the immune response and recognition of 'self' from 'nonself' are closely linked with the human leukocyte antigen (HLA) complex. Sixty-six HLA antigens were typed in 42 Caucasian patients with inner ear diseases of unknown etiology. All of these patients had positive serum antibodies against the inner ear structures as detected by an indirect immunofluorescence assay. Results revealed that none of the 66 HLA antigens was associated with the inner ear diseases. Reviewing results from other studies on HLA association in inner ear diseases shows that the findings are inconsistent with each other. The conclusion that HLA associations occur with inner ear diseases cannot be reached.

Adult↗
PubMed1999

Topographic analysis of inner ear lesions in profoundly deafened patients with tympanogenic and meningogenic labyrinthitis using three-dimensional magnetic resonance imaging.

OBJECTIVE: High-resolution magnetic resonance imaging (MRI) provided clear images of three-dimensional (3D) reconstruction of the inner ear in candidates for cochlear implantation. In this study. semiquantitative analysis of the 3D MRI findings was performed to investigate topographic lesions of the inner ear caused by tympanogenic and meningogenic labyrinthitis. STUDY DESIGN: This was an observational study. SETTING: The study was performed in an academic, comprehensive, multispecialty group practice. PATIENTS: Postlingual deafened patients with cochlear implantation. The cause of deafness was tympanogenic or meningogenic labyrinthitis. INTERVENTION: High-resolution 3D MRI and postoperative speech recognition tests were used. RESULTS: Abnormal findings in the inner ear detected with MRI were found before surgery in 58.3% of the patients with meningogenic labyrinthitis, although the incidence was lower in patients with tympanogenic labyrinthitis. Abnormal MRI findings were frequently observed in the cochlear basal turn and semicircular canals more than in the middle and apical turn in cases with meningogenic etiology. Patients with tympanogenic labyrinthitis suffered less with a vestibular apparatus than did those patients with meningogenic labyrinthitis. Regarding the analysis of the inner ear lesions at the implanted side, the postoperative speech recognition ability did not correlate to the extent of abnormal MRI findings of the implanted ear. CONCLUSION: Improvement in 3D MRI technology provided an accurate preoperative picture of the inner ear apparatus. In cochlear implant patients with infectious labyrinthitis, the extent of the inner ear lesion detected with 3D MRI was different among etiologies of deafness.

Adult↗
PubMed2003

[Cochlear implantation in patients with inner ear malformations, clinical analysis of 25 cases].

OBJECTIVE: To explore the clinical experience of multi-channel cochlear implantation in patients with bilateral inner ear malformations. METHOD: Multi-channel cochlear implantation was conducted among 180 patients from 1997 to 2001. Twenty-five of them, being with inner ear malformations, were given hearing and speech rehabilitation including sound detection, word discrimination, auditory comprehension and spoken language skill development. A follow-up lasting 4 - 24 months was conducted after the operation. A retrospective analysis was performed among these 25 patients to observe the surgical outcomes and mapping characteristics after surgery. RESULTS: (1) All patients restored their auditory sensations after the operation. (2) Stapedial gusher was found in 13 cases with inner ear malformations, especially those with Mondini malformation, much more frequently than among the patients with other malformations. (3) Most of the action electrodes were inserted in the "cochleostomy" in full length, only 2 pairs of them remained outside of the "cochleostomy". (4) No serious complications occurred after implantation. (5) The impedance of the electrodes, T level and C level were higher in the 25 cases than in the normal cochlear implantation, however, with the hearing similar hearing threshold. (6) After training, the abilities of speech discrimination and spoken language were improved in comparison with those before operation. CONCLUSION: The cochlear implantation can be performed safely in patients with bilateral inner ear malformations. The primary outcome of cochlear implantation in hearing rehabilitation is similar for both the patients with inner ear malformations and those with normal cochlear structure.

Adolescent↗
PubMed1990

Physiologic status of regenerated hair cells in the avian inner ear following aminoglycoside ototoxicity.

Regeneration of avian inner ear hair cells has been demonstrated after administration of aminoglycoside and after acoustic trauma. However, no published study to date has documented functional recovery of these regenerated sensory receptor cells. Newborn chicks were treated with gentamicin sulfate (50 mg/kg/day) for a total of either 5 (n = 10) or 10 (n = 76) days. Evoked potential thresholds were obtained one day after the 5-day treatment, or at intervals between one day and 20 weeks after the 10-day treatment course, and compared to thresholds of age-matched control animals. A significant hearing loss, predominantly in the high frequencies, was present after as few as 5 days of drug administration. The magnitude of hearing loss continued to increase, especially at lower frequencies, as survival increased from 1 day to 5 weeks after gentamicin treatment. Sixteen-to-20 weeks after treatment, partial recovery of thresholds was evident. These findings demonstrate that functional recovery does occur in the avian inner ear following aminoglycoside administration. Recovery occurs at all frequencies, but predominantly at low and middle frequencies, leaving significant residual high-frequency threshold elevation. Recovery lags 14 to 18 weeks behind anatomic evidence of hair cell regeneration, which was demonstrated in one study by 2 weeks after comparable administration of gentamicin.

Animals↗
PubMed2006

Studying inner ear protein-protein interactions using FRET and FLIM.

Molecular genetic studies of the inner ear have recently revealed a large number of previously undescribed proteins, but their functions remain unclear. Optical methods such as FRET and FLIM are just beginning to be applied to the study of functional interactions between novel inner ear proteins. This review discusses the various methods for employing FRET and FLIM in protein-protein interaction studies, their advantages and pitfalls, with examples drawn from inner ear studies.

Animals↗
PubMedDate not supplied

Serum antibody to inner ear proteins in patients with progressive hearing loss. Correlation with disease activity and response to corticosteroid treatment.

OBJECTIVE: To test whether detection of serum antibody to a 68-kd inner ear protein distinguishes among different causes of sensorineural hearing loss, and identifies patients with active disease and those likely to respond to corticosteroid therapy. DESIGN: Serum samples were tested by Western blot using bovine inner ear extract as antigen, and results were correlated with patient information obtained by chart review. SETTING: Referral center. SUBJECTS OF STUDY: Serum samples were obtained from patients with idiopathic, progressive, bilateral sensorineural hearing loss (IPBSNHL) (n = 72) otosclerosis (n = 11), Cogan's syndrome (n = 8), patients with positive tests for antinuclear antibodies (n = 10), and normal controls (n = 53). MAIN OUTCOME MEASURE: Detection of serum antibody to a 68-kd inner ear protein. RESULTS: Serum from 42 to 72 patients with IPBSNHL reacted with a 68-kd protein constituent of inner ear extract. This reactivity was not detected in serum from 11 of 11 patients with otosclerosis, or in eight of eight with Cogan's syndrome. It was found in serum from one of 10 patients with a positive test for antinuclear antibody and in one of 53 normal controls. Antibody to the 68-kd protein was detected in serum from 89% of patients with actively progressing IPBSNHL and none of the 25 patients with inactive disease (P < .001). Patients who were antibody-positive responded to steroid treatment more frequently than did those who were antibody-negative (P < .001). CONCLUSIONS: These results indicate that the presence of circulating antibody to a 68-kd constituent of bovine inner ear extract serves as a marker for IPBSNHL and that its presence correlates with disease activity and responsiveness to corticosteroid treatment.

Adolescent↗
PubMed1996

Inner ear defects induced by null mutation of the isk gene.

The isk gene is expressed in many tissues. Pharmacological evidence from the inner ear suggests that isk mediates potassium secretion into the endolymph. To examine the consequences of IsK null mutation on inner ear function, and to produce a system useful for examining the role(s) IsK plays elsewhere, we have produced a mouse strain that carries a disrupted isk locus. Knockout mice exhibit classic shaker/waltzer behavior. Hair cells degenerate, but those of different inner ear organs degenerate at different times. Functionally, we show that in mice lacking isk, the strial marginal cells and the vestibular dark cells of the inner ear are unable to generate an equivalent short circuit current in vitro, indicating a lack of transepithelial potassium secretion.

Animals↗