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PubMed2000

Gastric proton pump is expressed in the inner ear and choroid plexus of the rat.

Inner ear fluids and cerebrospinal fluid show remarkably stable ionic concentrations, particularly that of K(+) and H(+), but the mechanisms which control the homeostasis of these media are not well understood. We investigated a possible role of the gastric H, K-ATPase (gH,K-ATPase) pump in this control since this pump is known to be expressed in other tissues than gastric parietal cells. Here, we show by reverse transcription-polymerase chain reaction that the rat gH,K-ATPase alpha- and beta-subunits are expressed in the inner ear (lateral wall, organ of Corti and spiral ganglion cells), while only the alpha-subunit is expressed in the choroid plexus (CP). The presence of the alpha-subunit in the inner ear and CP was confirmed by immunoblotting. Immunohistochemistry localized this protein in the intermediate cells of the stria vascularis, in the spiral ligament and the spiral ganglion. gH,K-ATPase could be involved in the maintenance of H(+) and K(+) equilibria in cerebrospinal and labyrinthine fluids.

Animals↗
PubMed2003

Establishment of normative cochlear and vestibular measurements to aid in the diagnosis of inner ear malformations.

OBJECTIVE: We sought to establish normative measurements of the inner ear using computed tomography (CT) of the temporal bone to aid in the diagnosis of inner ear malformations. STUDY DESIGN AND SETTING: Prospective measurements of the inner ear structures were made on axial and coronal temporal bone CT scans on 15 patients with normal hearing and 15 patients with sensorineural hearing loss. RESULTS: The vertical height of the cochlea on coronal scan and the size of the central bony island within the lateral semicircular canal on axial scan along with visual inspection identified 7 inner ear abnormalities in 6 patients: 5 cases of lateral semicircular canal dysplasia and 2 cases of cochlear hypoplasia. In contrast, visual inspection alone identified only 4 of the 7 abnormalities. CONCLUSIONS AND SIGNIFICANCE: Routine measurement of the cochlear height and bony island of the lateral semicircular canal, in conjunction with visual inspection of CT images, will increase recognition of common inner ear malformations.

Adult↗
PubMed1993

[Correlation between inner ear disorders and temporomandibular joint diseases].

Acute and chronic inner ear diseases involve many etiological factors, some as yet unknown. ENT-specific, orthopedic, hemorrheological, immunological and neurological disorders can affect the cochleovestibular system and induce hearing loss, vertigo and/ortinnitus. We performed a prospective study to analyze factors of the dentognathological system and of the temporomandibular joint that can influence acute and chronic inner ear dysfunctions. A total of 138 patients (49.3% female, 50.9% male) receiving clinical treatment for inner ear dysfunctions (12.3% chronic sensorineural hearing loss, 15.2% Ménière's disease, 52.2% sudden hearing loss, 13.8% isolated tinnitus, 6.5% recurrent hearing loss) underwent a prospective dental and gnathological examination. In particular, the patient's dental status and a functional investigation of the masticatory muscles and the temporomandibular joint were analyzed. In 20.3% patients the examination showed no pathology of the dentognathological system. In contrast, there were pathological findings in 110 patients (79.7%): in 43.5% a temporomandibular joint syndrome was diagnosed, in 29% parafunction of the occlusion, and in 35% a myopathy of the masticatory muscles. Additionally 32.6% patients showed dental disorders that required treatment; 11.65% had problems with dentures and 20.3% malpositioned wisdom teeth. In 16 patients the recommended dental treatment was followed up and improvement of otological symptoms was found in 56.6%. The present investigation shows that many patients with inner ear dysfunction suffer from dentognathological disorders. For a subgroup of patients there exists the possibility of improving otological symptoms by dental treatment. Therefore we recommend a dentognathological examination in patients with inner ear dysfunctions of unknown etiology.

Adult↗
PubMed2004

Transplantation of neural stem cells into explants of rat inner ear.

Damage and loss of hair cells in the inner ear is the most frequent cause of hearing loss and balance disorders. Mammalian hair cells do not regenerate in the conventional ways. To regenerate the hair cell in the mammalian inner ear we transplanted neural stem cells into explants of rat inner ear. The stem cells integrated successfully into the sensory epithelium of the vestibular organs, but not into the organ of Corti. This method is useful to investigate efficient ways to transplant stem cells into the inner ear.

Animals↗
PubMed1993

Immunohistochemical localization of brain type glucose transporter in mammalian inner ears: comparison of developmental and adult stages.

Inner ears from five mammalian genera were examined immunohistochemically with a rabbit polyclonal antiserum against the brain type glucose transporter (GLUT1). Vascular endothelial cells distributed widely in soft tissues of the cochlea and vestibular system in all five genera showed uniform immunostaining. The basal cell layer of the stria vascularis also contained GLUT1 in all genera, and in the guinea pig, the strial marginal cells reacted as well. GLUT1 was expressed in satellite cells surrounding spiral ganglion neurons but only in the gerbil and cat. In the developing inner ear of the gerbil, endothelial cells expressed GLUT1 at 2 days after birth, the earliest stage examined. Immunoreactive transporter also was detected at this time in cells lying under strial marginal cells and interpreted as immature basal cells. Satellite cells acquired affinity for GLUT1 antibody between days 12 and 16 after birth. The expression of GLUT1 by the various cell types correlates well with their structural and functional maturation. GLUT1 apparently plays a role in glucose transport in the inner ear where it mediates efflux from blood vessels into perilymph. It also appears to facilitate uptake of glucose by the stria vascularis from interstitial fluid via the basal cell layer and, in some species, by spiral ganglion neurons through satellite cells.

Animals↗
PubMedDate not supplied

Experimental alteration of physiological state of inner ear fluids.

Mechanisms of endolymphatic hydrops formation in the inner ear are not yet fully understood. The available knowledge of the composition and the function of inner ear fluids, of mechanisms for maintenance of microhomeostasis, and the possible factors responsible for hydrops formation were reviewed. The nature of the functional barrier systems of the inner ear was investigated by measuring the amount of intravenously or intracisternally injected test substances which entered the perilymph. Based on studies of the osmotic relationship between the blood and the perilymph, an hypothesis of hydrops formation is proposed. The hypothesis predicts an osmotic imbalance, resulting from an upset of the homeostasis between the fluid compartments and the tissues of the inner ear, as a factor responsible for endolymphatic hydrops formation. An osmotic imbalance can be induced by various experimental conditions including metabolic disorders. The results of animal experiments strongly suggest the necessity of further survey of metabolic imbalance in Ménière's patients.

Adenosine Triphosphatases↗
PubMed1993

Effect of a Ca2+ entry blocker, nilvadipine, on hearing disturbances and equilibrium dysfunction caused by microcirculatory disorders of the rat inner ear.

We evaluated the effects of Ca2+ entry blockers, nilvadipine and flunarizine, on microcirculatory disorders of the inner ear and on blood flow in the inner ear of rats. Under sodium pentobarbital anesthesia, the middle ear was opened by a ventrolateral approach. A green light (wave length 540 nm) was applied to the cochlea or the vestibule to induce a hearing disturbance or equilibrium dysfunction as a result of inner ear microcirculatory disorders, while rose bengal solution was infused intravenously. In a hearing disturbance model, a compound cochlear nerve action potential was recorded by electrocochleography every minute after the beginning of illumination. The sound stimulus was an 8 kHz sine wave 100 dB normal hearing level. The action potential was calculated 128 times. The action potential disappeared about 12 min after the beginning of illumination. In another model of equilibrium dysfunction, the photoillumination was applied for 40 min under the infusion of rose bengal. The behavior of rats was observed in the swimming test and nystagmus was recorded 24 h after the completion of photoillumination. In a separate experiment, blood flow in the inner ear was measured with a laser Doppler flowmeter under sodium pentobarbital anesthesia. In this study, both nilvadipine and flunarizine prolonged the time required for complete suppression of the action potential, prevented equilibrium dysfunction in the swimming test and reduced the occurrence of nystagmus. Flunarizine significantly increased inner ear blood flow and nilvadipine failed to decrease blood flow in the inner ear, despite a reduced systemic blood pressure. In conclusion, Ca2+ entry blockers may prevent microcirculatory disorders of the inner ear in rats.

Acoustic Stimulation↗
PubMed2006

Inner ear anomalies in cochlear implantees: importance of radiologic measurements in the classification.

OBJECTIVE: To classify the inner ear anomalies of cochlear implantees with profound sensorineural hearing loss. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: For the normative data of the inner ear structures, the temporal bone computed tomography of 60 patients (120 ears) with normal bone-conduction threshold (< 15 dB) were used, and the data were applied to 570 ears of 285 cochlear implantees. INTERVENTIONS: Predesignated inner ear structures were measured in temporal bone computed tomography images from the normal and cochlear implantation groups using a computer-based caliper that formed part of a picture archiving and communication system. MAIN OUTCOME MEASURES: The inner ear anomalies were defined when the structures presented visually obvious malformations or the measurements deviated 2 standard deviations from the means in the normative data. RESULTS: The application of normative data to 570 profound SNHL ears resulted in the identification of 293 individual anomalies in 127 anomalous ears. An enlarged vestibular aqueduct was the most common individual anomaly (49 cases), followed by vestibular enlargement (38 cases) and other semicircular canal dysplasia (37 cases). When the individual anomalies were reaccounted according to the more prominent anomaly where multiple anomalies were present in each ear, incomplete partition type II was the most common (34 ears), followed by cochlear hypoplasia (22 ears) and incomplete partition type I (20 ears). CONCLUSION: We suggested a measurement technique for the inner ear structures using computed tomography and derived normative measurements helpful for diagnosing inner ear anomalies. Using these normative data, we classified the inner ear anomalies of profound SNHL ears in cochlear implantees.

Adolescent↗
PubMed2006

Molecular and functional characterization of gap junctions in the avian inner ear.

To analyze the fundamental role of gap junctions in the vertebrate inner ear, we examined molecular and functional characteristics of gap junctional communication (GJC) in the auditory and vestibular system of the chicken. By screening inner ear tissues for connexin isoforms using degenerate reverse transcription-PCR, we identified, in addition to chicken Cx43 (cCx43) and the inner-ear-specific cCx30, an as yet uncharacterized connexin predicted to be the ortholog of the mammalian Cx26. In situ hybridization indicated that cCx30 and cCx26 transcripts were both widely expressed in the cochlear duct and utricle in an overlapping pattern, suggesting coexpression of these isoforms similar to that in the mammalian inner ear. Immunohistochemistry demonstrated that cCx43 was present in gap junctions connecting supporting cells of the basilar papilla, in which its immunofluorescence colocalized with that of cCx30. However, cCx43 was absent from supporting cell gap junctions of the utricular macula. This variation in the molecular composition of gap junction plaques coincided with differences in the functional properties of GJC between the auditory and vestibular sensory epithelia. Fluorescence recovery after photobleaching, adapted to examine the diffusion of calcein in inner ear explants, revealed asymmetric communication pathways among supporting cells in the basilar papilla but not in the utricular macula. This study supports the hypothesis that the coexpression of Cx26/Cx30 is unique to gap junctions in the vertebrate inner ear. Furthermore, it demonstrates asymmetric GJC within the supporting cell population of the auditory sensory epithelium, which might mediate potassium cycling and/or intercellular signaling.

Animals↗
PubMed2026

A single-nucleus transcriptomic atlas of human inner ear development.

Hearing and balance rely on coordinated activity of multiple inner ear cell types, yet the mechanisms governing their development and specification in humans remain unclear. Consequently, this limits our understanding of how disease genes affect cell type formation and function, limiting the development of targeted treatments, including gene therapies. Here we present the Human Inner Ear Development snRNA-seq Atlas (HIEDRA), a single-nucleus transcriptomic atlas of the human inner ear spanning the first and second trimesters. HIEDRA maps sensory and nonsensory epithelia, neurons and mesenchyme-associated populations, including undercharacterized secretory cells required for ion homeostasis. We identify selective vulnerability in sensory and secretory lineages to disease-associated genes, infer regulatory networks and show that Hedgehog signaling suppression is required for secretory cell specification. We validate this mechanism in human inner ear organoids, expanding the model to include all major cell types. Altogether, these findings provide insights into human inner ear cell type specification, improve in vitro models and establish HIEDRA as a resource for investigating human inner ear development.

Journal Article↗
PubMed1992

[Localization of Na/K ATP-ase in the inner ear].

The perilymphatic compartment of the inner ear resembles plasma ultrafiltrate, whereas the endolymphatic compartment is characterized by a high potassium and low sodium concentration. Perilymph is considered to be the precursor of endolymph. The chemical composition of endolymph and the generation of the transepithelial potential is regulated by Na-K-activated adenosine triphosphatase. The cytochemical localization of Na/K ATP-ase is demonstrated in the guinea pig inner ear. The mechanism for cation regulation in the endolymphatic compartment is discussed.

Animals↗
PubMed1986

The endolymphatic sac: its importance in inner ear immune responses.

The present study investigated the role of the endolymphatic sac in the generation of inner ear immune responses. The inner ear immune response to KLH antigen challenge was examined in animals whose endolymphatic sac was surgically obliterated and in a sham operated control group. In primary inner ear immune responses, endolymphatic sac obliteration resulted in reduced serum anti-KLH levels, compared to controls, while no difference was observed for perilymph anti-KLH levels. In secondary inner ear immune responses, endolymphatic sac obliteration resulted in significantly suppressed perilymph anti-KLH levels and greatly reduced cellular infiltration within the cochlea. In contrast, the sham operated animals showed a greatly increased number of plasma cells and lymphocytes in the perisaccular space and the endolymphatic sac lumen. These findings suggested that the endolymphatic sac must play an integral role in the generation of both systemic and local antibody responses following inner ear antigen challenge. The endolymphatic sac, like the gut, appears to have an immunological as well as a resorptive role in the host.

Animals↗
PubMed2003

Inner ear perfusion: indications and applications.

PURPOSE OF REVIEW: To examine the indications and applications of inner ear perfusion in the treatment of common otologic diseases, including Meniere disease, sudden sensorineural hearing loss, and autoimmune inner ear disease. RECENT FINDINGS: The number of surgical procedures, including vestibular neurectomy, labyrinthectomy, and endolymphatic sac surgery, decreased during the 1990s. Intratympanic gentamicin therapy has become the most frequently performed invasive procedure for treatment of Meniere disease. Reports on successful control of vertigo in patients with Meniere disease have ranged from 71.4 to 100%. There is a correlation between the degree of vestibular ablation in transtympanic gentamicin, the control of vertigo, and the risk of hearing loss. Patients with less than 75% ice-reduced vestibular response had a statistically lower risk of hearing loss, but they had a higher rate of persistent vertigo than patients with 100% reduced vestibular response. One hundred percent reduced vestibular response may not be indicative of complete vestibular ablation and may not be necessary for control of vertigo symptoms. In preliminary studies, inner ear perfusion of methylprednisolone in patients with severe, profound sudden sensorineural hearing loss who fail to respond to standard treatment is beneficial, with improvement in hearing thresholds of 16 to 25 dB and dramatic improvement in speech discrimination scores. No immunosuppressive medication has been found effective in suppressing inner ear inflammatory infiltrates or reducing hearing loss in an animal model. SUMMARY: Transtympanic chemical perfusion of the inner ear is safe, inexpensive, and easily performed by an otologic surgeon. With inner ear perfusion, high inner ear concentrations of medication can be achieved, and systemic side effects are minimized.

Autoimmune Diseases↗
PubMed1995

Inner ear barotrauma: computed tomographic evaluation.

Eight patients with inner ear barotrauma were evaluated by computed tomography. The causes of the inner ear barotrauma were diving in four, flying in an airplane in three, and climbing in one. Regarding the width of the cochlear aqueduct, no significant difference was observed between the affected side (3.28 +/- 0.49 mm) and non-affected side (3.63 +/- 0.79 mm) at the base of the infundibulum. The jugular fossa could not be identified on the affected side in three patients. Some relationship may exist between inner ear barotrauma and poor development of the jugular fossa.

Adult↗
PubMed2004

[An improved animal model of autoimmune inner ear disease].

OBJECTIVE: To establish an experimental autoimmune inner ear disease model, which could exhibit high reproducibility and be adopted for detailed immunological analysis. METHODS: Extraction of guinea pig inner ear antigens (IEAg). The inbred mice were given a single subcutaneous injection of diluted solution of pertussis and an emulsion containing equal parts of CFA and IEAg. The ABR threshold shifts were evaluated. The antibody level to IEAg in serum was detected by ELISA. Inner ear specimen were examined by light microscopy with hematoxylin and eosin staining. The infiltrated cells within cochlea were clarified with immunohistochemical techniques. RESULTS: The ABR thresholds of IEAg-sensitized animals were elevated significantly. Histological changes in cochlea were significant. Inflammatory cell infiltration was clearly observed in the cochlea of the animals following sensitization with IEAg. Degeneration of the spiral ganglion cells, which characterizes a decrease in cell numbers, and formation of endolymphatic hydrops were often seen too. Serum anti-IEAg levels after inoculation were significantly increased in the IEAg sensitised groups. Most of the infiltrated lymphocytes in scala tympani were CD4+ T cells. CONCLUSIONS: The experimental autoimmune inner ear disease can be induced by a single inoculation of IEAg-CFA emulsion and pertussis in inbred C57BL/6 mice.

Animals↗
PubMed1986

Somatostatin (somatostatinlike) immunoreactive cells in the human inner ear.

Certain epithelia of the human inner ear and human endolymphatic sac display somatostatin and/or somatostatin-like immunoreactivity. Histologic sections from 13 human temporal bones and from 15 endolymphatic sacs were studied using the unlabeled antibody peroxidase-antiperoxidase technique. The somatostatin and/or somatostatin-like immunoreactive cells were located exclusively in the covering epithelium of the spiral prominence and in the epithelium of the intermediate and rugosal part of the endolymphatic sac. In the epithelium of the spiral prominence and endolymphatic sac, secretory granules of the same size and appearance as those of intestinal or pancreatic somatostatin-producing cells were demonstrated ultrastructurally. The findings are consistent with a local exocrine, paracrine, and/or endocrine system of the inner ear.

Cytoplasmic Granules↗
PubMed2001

The Notch ligand Jagged1 is required for inner ear sensory development.

Within the mammalian inner ear there are six separate sensory regions that subserve the functions of hearing and balance, although how these sensory regions become specified remains unknown. Each sensory region is populated by two cell types, the mechanosensory hair cell and the supporting cell, which are arranged in a mosaic in which each hair cell is surrounded by supporting cells. The proposed mechanism for creating the sensory mosaic is lateral inhibition mediated by the Notch signaling pathway. However, one of the Notch ligands, Jagged1 (Jag1), does not show an expression pattern wholly consistent with a role in lateral inhibition, as it marks the sensory patches from very early in their development--presumably long before cells make their final fate decisions. It has been proposed that Jag1 has a role in specifying sensory versus nonsensory epithelium within the ear [Adam, J., Myat, A., Roux, I. L., Eddison, M., Henrique, D., Ish-Horowicz, D. & Lewis, J. (1998) Development (Cambridge, U.K.) 125, 4645--4654]. Here we provide experimental evidence that Notch signaling may be involved in specifying sensory regions by showing that a dominant mouse mutant headturner (Htu) contains a missense mutation in the Jag1 gene and displays missing posterior and sometimes anterior ampullae, structures that house the sensory cristae. Htu/+ mutants also demonstrate a significant reduction in the numbers of outer hair cells in the organ of Corti. Because lateral inhibition mediated by Notch predicts that disruptions in this pathway would lead to an increase in hair cells, we believe these data indicate an earlier role for Notch within the inner ear.

Amino Acid Sequence↗
PubMed2006

Inner ear dysplasia is common in children with Down syndrome (trisomy 21).

OBJECTIVES/HYPOTHESIS: Middle and external ear anomalies are well recognized in Down syndrome (DS, trisomy 21). Inner ear anomalies are much less frequently described. This study reviews inner ear morphology on imaging to determine the prevalence of cochlear and vestibular anomalies in children with DS. STUDY DESIGN: The authors conducted a retrospective review of imaging features of (DS) inner ear structures. METHODS: Fifty-nine sequential patients with DS with imaging of the inner ear were identified by a radiology report text search program. Quantitative biometric assessment of the inner ear was performed on patients with high-resolution computed tomography or magnetic resonance images of the petrous bone. Petrous imaging was performed for evaluation of inflammatory disease or hearing loss. Spinal imaging, which included petrous views, was performed in most cases to exclude C1 to 2 dislocation, a potential complication of DS. Measurements were compared with normative data. RESULTS: Inner ear dysplasia is much more common in DS than previously reported. Inner ear structures are universally hypoplastic. Vestibular malformations are particularly common and a small bony island of the lateral semicircular canal (<3 mm in diameter) appears highly typical. Additional findings in some patients were persistent lateral semicircular anlage with fusion of the lateral semicircular canal and vestibule into a single cavity, vestibular aqueduct and endolymphatic sac fossa enlargement, cochlear nerve canal hypoplasia, and stenosis or duplication of the internal auditory canal. Stenosis of the external meatus, poor mastoid pneumatization, middle ear and mastoid opacification, and cholesteatoma were common, as expected.

Adolescent↗