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PubMed1988

Light and electron microscopic appearance of the inner ear in juvenile ceroid lipofuscinosis (CL).

Inner ear cells were studied by histology, histochemistry and electron microscopy in one case of juvenile form of ceroid lipofuscinosis (Batten's disease). It was found that despite the clinically normal range of auditory acuity (nonaudiometric evaluation) there was a storage process of moderate degree with intralysosomal deposition of a lipopigment of variable ultrastructure with two patterns predominating, curvilinear and fingerprint. Storage was demonstrable in slightly variable degree in every cell type including the receptor cells of the organ of Corti and sensory cells of crista ampullaris. The cochlear neurons displayed a so far unique storage with enormous monovacuolar distension of perikarya comparable only to the lymphocytic vacuolization also present in the juvenile form of the disease. The distension of vacuoles was only partly caused by accumulation of the lipopigment mass and actually led to neuronal deterioration. The results shown here offer a new modell for functional-structural relationship and point to the urgent need of further studies of the inner ear in CL and lysosomal storage generally.

Child↗
PubMed1997

Can sensitized lymphocytes retain reactivity to inner ear antigens after retrieval from frozen storage?

Immune inner ear disease results in rapidly progressive, bilateral sensorineural hearing loss and is one of the few forms of sensorineural hearing loss that can be treated medically. The purpose of this study is to identify and preserve several populations of sensitized lymphocytes from patients with immune inner ear disease as a first step toward cloning autoreactive T cells, in order to study the pathogenesis of disease. Lymphocytes from four patients with high reactivity (stimulation index of 2.5 or greater) were placed in frozen storage. At 8 to 14 months they were thawed and restimulated. All four samples were viable. Two reacted again to inner ear homogenate, but with different intensities. Some lymphocytes sensitized to inner ear antigens can retain reactivity after frozen storage. This methodology may be useful to clone highly reactive T cells.

Adolescent↗
PubMed2002

[Preliminary study on inner ear ischemic model induced by ferromagnetic embolism].

OBJECTIVE: To set up an inner ear ischemic model in guinea pig with ferromagnetic embolism. METHODS: A magnet was fitted in the external auditory canal and carbonyl iron filings (1%, 1 ml/kg) was injected into jugular, then the inner ear vessels were obstructed by ferromagnetic spheres. Cochlear blood flow (CBF) and number of red blood cells in the stria vessels were used to detect the model's ischemia of cochleae. The slice of temple bone and basal membrane stained by silver nitrate were used for inner ear's histopathological observations. RESULTS: The iron spheres were amassed in the one and two-day-later's model of inner ear vessels, which resulted in embolism. The number of red blood cells in the stria vessels decreased and then recovered to normal level after 4 days, but the CBF decreased to 50% +/- 10% of basic level immediately and recovered to 99% +/- 41% 4 days later. Scattered lesion of out hair cell cilium could be seen in cochleae in eight-day-later's model, and degenerations in different degree were found in vascular stria. CONCLUSION: The methods of inner ear ischemic model with ferromagnetic embolism could be practical and the decrease of CBF was reversible, so it may be an ideal model for studying some ischemic inner ear diseases and evaluating the effects of therapeutic drugs.

Animals↗
PubMed1993

Do magnesium infusions protect the inner ear during middle ear surgery? A randomized double blind study.

Joachims et al. recently demonstrated that magnesium was able to protect the inner ear during exposure to noise and fire arms. During middle ear surgery, the inner ear is subjected to noise from fraising and drilling. We saw fit, therefore, to conduct a random double blind study to establish whether magnesium infusions would protect the inner ear during middle ear surgery. We examined 80 patients (38 verum, 42 placebo). The verum patients received 10 mg/kg body weight magnesium 12 hours and 1 hour prior to operation. Plasma and red cell magnesium levels were measured pre-operatively and intra-operatively; they rose as expected. Post-operative auditory tests showed that magnesium had no tendency to prevent inner ear damage. Advocates of magnesium criticize the limited number of patients in our study as well as the administration of the magnesium substitute. In our opinion, however, it should be borne in mind when evaluating these findings that noise from drilling and fraising is only one factor among many which can induce inner ear injury during middle ear surgery.

Adult↗
PubMedDate not supplied

Functional recovery of hearing following ampa-induced reversible disruption of hair cell afferent synapses in the avian inner ear.

Hair cells in the avian inner ear can regenerate after acoustic trauma or ototoxic insult, and significant functional recovery from hearing loss occurs. However, small residual deficits remain, possibly as a result of incomplete reestablishment of the hair cell neural synaptic contacts. The aim of the present study was to determine if intracochlear application of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA), an excitotoxic glutamate agonist, causes reversible disruption of hair cell neural contacts in the bird, and to what extent functional recovery occurs if synaptic contacts are reestablished. Compound action potential (CAP) responses to tone bursts were recorded to determine hearing thresholds during a recovery period of up to 4 months. Subsequently, the response properties of single auditory nerve fibers were analyzed in the same animals. Instillation of AMPA into the perilymph of the scala tympani led to immediate abolition of CAP thresholds. Partial recovery occurred over a period of 2-3 weeks, without further improvement of thresholds thereafter. High-frequency thresholds did not reach control values even after 3-4 months of recovery. Single-ganglion cell response properties, obtained 3-4 months after AMPA treatment, showed elevated thresholds at the fiber's characteristic frequency (CF) for units with CF above 0.3 kHz. Sharpness of tuning (Q(10 dB)) was reduced in units with CF above 0.4 kHz. The spontaneous firing rate was higher in units with CF above 0.18 kHz. The maximum sound-evoked discharge rate was also increased. Transmission electron micrographs of the basilar papilla showed that, following AMPA treatment, the nerve endings went through a sequence of swelling, degeneration and recovery over a period of 3-7 days. The process of neosynaptogenesis was completed 14 days after exposure. The present findings are strong evidence for a role of glutamate or a related excitatory amino acid as the afferent transmitter in the avian inner ear. In addition they show that functional recovery after disruption and regeneration of hair cell neural synapses, without apparent damage to the hair cells, is incomplete.

Animals↗
PubMed1992

Inner ear malformations induced by isotretinoin in hamster fetuses.

Inner ear malformations induced in anotic hamster fetuses following maternal treatment with 50 mg/kg isotretinoin (13-cis-retinoic acid) on gestational day 8 are described. Computer-assisted three dimensional reconstruction was used. Two general types of defective vestibulocochlear development were seen. Defects were bilateral and correlated with extent of middle ear deficiency and severity of mandibular defects. In the more severely affected fetuses the inner ear was limited to an epithelial sac with occasional small projections, no apparent innervation and a correspondingly reduced otic capsule. In most of the fetuses examined the inner ear was less severely affected and was characterized by a reduction in the number of semicircular ducts and alterations in the size and shape of the cochlear duct. These defects are similar to those seen in a child with the isotretinoin embryopathy. Pathogenesis may result from a direct effect on otic epithelium or from faulty inductive interactions with the rhombencephalon or with periotic neural crest cells.

Abnormalities, Drug-Induced↗
PubMed2000

Stereocilia defects in the sensory hair cells of the inner ear in mice deficient in integrin alpha8beta1.

The mammalian inner ear contains organs for the detection of sound and acceleration, the cochlea and the vestibule, respectively. Mechanosensory hair cells within the neuroepithelia of these organs transduce mechanical force generated by sound waves or head movements into neuronal signals. Defects in hair cells lead to deafness and balance defects. Hair cells have stereocilia that are indispensable for mechanosensation, but the molecular mechanisms regulating stereocilia formation are poorly understood. We show here that integrin alpha8beta1, its ligand fibronectin and the integrin-regulated focal adhesion kinase (FAK) co-localize to the apical hair-cell surface where stereocilia are forming. In mice homozygous for a targeted mutation of Itga8 (encoding the alphabeta8 subunit), this co-localization is perturbed and hair cells in the utricle, a vestibular subcompartment, lack stereocilia or contain malformed stereocilia. Most integrin alpha-8beta1-deficient mice die soon after birth due to kidney defects. Many of the survivors have difficulty balancing, consistent with the structural defects of the inner ear. Our data suggest that integrin alpha8beta1, and potentially other integrins, regulates hair-cell differentiation and stereocilia maturation. Mutations affecting matrix molecules cause inherited forms of inner ear disease and integrins may mediate some effects of matrix molecules in the ear; thus, mutations in integrin genes may lead to inner-ear diseases as well.

Actins↗
PubMed1991

Identification and localization of a kainate binding protein in the frog inner ear by electron microscopy immunocytochemistry.

A kainate binding protein (KBP) was studied in Rana pipiens inner ear using monoclonal and polyclonal antibodies against affinity purified KBP from frog brain. The KBP identified and analyzed in inner ear tissue homogenates, with one- and two-dimensional immunoblots, was similar to the affinity purified KBP and to the antibody-identified frog brain KBP. As brain KBP, inner ear KBP had 5 main components in the molecular weight dimension, centered at Mr = 48,000; however, inner ear KBP had a greater abundance of the higher molecular weight components. Light and electron microscopy observations showed KBP immunostaining at two locations: (1) in the dendrites of the eight nerve afferent fibers contacting sensory hair cells, with the postsynaptic density being more intensely stained; and (2) on the cytoplasmic membrane of fibroblasts present in the inner ear connective tissue which displayed intense immunostaining. The presence of kainate (KA) binding sites in the inner ear was assessed using in vitro receptor autoradiography. [3H]KA binding sites were found in connective tissue areas confirming the immunocytochemistry results. The postsynaptic localization of the KBP in afferent endings, strongly supports it as being a component of the KA receptor complex. However, its presence on fibroblasts situated in the inner ear connective tissue makes its function hypothetical. The dual presence of the KBP on non-neuronal cells as well as at postsynaptic membrane sites suggests the existence of a family of proteins involved in KA binding and KA receptors with a complex organization.

Afferent Pathways↗
PubMedDate not supplied

Inner ear immunology.

Previously the authors proposed that the perilymphatic inner ear immune system is independent of that of the cerebrospinal fluid. In the present study, the effect of dilatation of blood vessels surrounding the cochlea of chinchillas on the transfer of serum antibodies to the perilymph was tested. The possibility of local production of antibodies in the perilymphatic space was also investigated by antigen introduction into the inner ear through the facial nerve canal. The dilatation of blood vessels accelerated the transfer of serum antibodies to the perilymph, even though this transfer activity was limited. Results of the study, showing the effect of antibody production in the perilymphatic space upon introduction of antigen into the inner ear through the facial nerve canal, would deny local antibody production in the inner ear, particularly in the perilymphatic space.

Animals↗
PubMed1998

Intercellular adhesion molecule-1 expression in the inner ear of rats following secondary immune reaction in the endolymphatic sac.

An immunological aetiology for inner ear diseases has long been proposed. The endolymphatic sac (ES) is the only immunoprivileged site in the inner ear with a resident population of immunocompetent cells. By keyhole limpet hemocyanin (KLH) challenge into the ES of systemically pre-immunized guinea pigs, we previously demonstrated an infiltration of inflammatory cells into the perilymphatic space of the cochlea. In order to understand the mechanisms involved in the recruitment of immunocompetent cells into the inner ear, and their relation to the development of endolymphatic hydrops (EH), we investigated the expression and time-kinetics of intercellular adhesion molecule 1 (ICAM-1) in the inner ear of systemically pre-immunized rats after antigen (KLH) challenge into the ES, its relation to cell infiltration in the cochlea and subsequent development of EH. By immunohistochemistry, strong ICAM-1 expression was detected in the spiral ligament, suprastrial region, spiral prominence, spiral modiolar veins, spiral collecting venules, surface membrane of the perilymphatic compartment, perilymphatic space and ES of immunized rats, but not of control rats. ICAM-1 expression was detected at 5-6 h, peaked at 10-15 h, and gradually reduced by 2 weeks. Cell infiltration into the cochlea started at 6-12 h and peaked at day one. By 6 h, 50% of challenged rats developed EH. This figure rose to 70% at 12 h, and then gradually reduced. However, immunoreactivity for KLH (antigen) was only detected in the ES. These results emphasize that the sac is the central immunological organ of the inner ear, and suggest that ICAM-1 may play a pivotal role in the aetiology of immune-mediated inner ear diseases through the recruitment of immunocompetent cells into the inner ear and subsequent development of EH.

Animals↗
PubMed1997

Human autoantibodies and monoclonal antibody KHRI-3 bind to a phylogenetically conserved inner-ear-supporting cell antigen.

Autoimmunity is thought to be one cause of sensorineural hearing loss (SNHL). Sera from patients with rapidly progressive hearing loss have been shown to contain antibodies to a 68-kD protein in heterologous inner-ear tissue. Using guinea pig inner-ear tissue as the antigenic substrate and either Western blot or immunofluorescence (IF) or both, we tested sera from 74 patients suspected to have autoimmune hearing loss for inner-ear antibodies. Sera from 73 patients were tested by Western blot, and sera from 36 were tested by IF. Thirty-seven of 73 (51%) had antibody to a 68-70-kD protein by Western blot. Sera positive by IF stained supporting cells with a staining pattern like that previously observed with the KHRI-3 monoclonal antibody. There was concordance between Western blot and IF assays. Of 36 patients tested by both assays, 29/31 (94%) that were positive in Western blot were also positive by IF, three were negative by both tests, and two each were positive by one assay but negative by the other. Absorption of patient sera with human inner-ear tissue removed antibody reactivity to the guinea pig supporting cells, indicating that the antigen detected by the autoantibody is also present in the human inner ear. Absorption with an equal volume of white or red blood cells from the tissue donor did not remove the antibody reactivity to inner ear, showing that the absorption by inner-ear tissue is specific. Sera from three patients positive in both assays also stained a 68-70-kD inner-ear protein immunoprecipitated by the KHRI-3 monoclonal antibody, indicating that the monoclonal and human antibodies recognize the same antigen. The results support the hypothesis that patients with autoimmune sensorineural hearing loss produce autoantibodies to an inner-ear supporting cell antigen that is phylogenetically conserved and defined by the murine monoclonal antibody KHRI-3. Since KHRI-3 can induce hearing loss after infusion into the inner ear, it is likely that autoantibodies with the same antigenic target are also pathogenic in humans.

Animals↗
PubMed1994

Histochemical detection of glycogen and glycoconjugates in the inner ear with modified concanavalin A-horseradish peroxidase procedures.

Inner ears from neonatal and adult Mongolian gerbils were examined to determine developmental changes in the content of glycogen and glycoconjugates as shown by histochemical application of the jack bean lectin, concanavalin A (con A). Sections of fixed paraffin-embedded inner ears were stained using the con A-horseradish peroxidase sequence in conjunction with prior treatments including periodate oxidation with or without subsequent reduction and diastase digestion. In adult inner ear, brief periodate oxidation followed by reduction and con A-horseradish peroxidase staining demonstrated abundant glycogen in Deiters' cells and in fibrocytes of the spiral ligament and submacular plaque. This procedure also detected diastase-resistant glycoprotein, probably containing N-linked complex-type saccharides, in the basal and marginal regions of the tectorial membrane and in the otolithic membrane. During morphogenesis and maturation, various cochlear cells showed changes in their glycogen content possibly related to stage-specific energy requirements. Cellular glycogen storage reached adult levels by postnatal day 14. The tectorial membrane gradually acquired con A reactivity during the first postnatal week. Thus, application of modified con A staining procedures has provided further knowledge for comparison with data from previous biochemical and histochemical studies of carbohydrate-rich components in the inner ear.

Animals↗
PubMed2006

Intratympanic injection of dexamethasone: time course of inner ear distribution and conversion to its active form.

HYPOTHESIS: Intratympanically injected dexamethasone 21-phosphate is converted to its active form dexamethasone in the inner ear and follows the distribution of the glucocorticoid receptor. BACKGROUND: Although dexamethasone is routinely delivered intratympanically for hearing loss, we know little of its inner ear pharmacokinetics. Dexamethasone 21-phosphate is the pharmaceutical compound available for injection, but it must be converted to its biologically active form (dexamethasone) to bind to the glucocorticoid receptor. Therefore, the current study was conducted to determine the time course of dexamethasone 21-phosphate movement from the middle ear into the inner ear, its conversion to dexamethasone, and the distribution of both forms relative to the glucocorticoid receptor. METHODS: BALB/c mice were injected intratympanically with the prodrug dexamethasone 21-phosphate and inner ears collected at postinjection times ranging from 5 minutes to 7 days. Ears were immunohistochemically stained for dexamethasone 21-phosphate, dexamethasone, and the glucocorticoid receptor. RESULTS: Both forms of dexamethasone were seen in the inner ear within 15 minutes, reaching their highest staining intensity at 1 hour. Neither drug was seen after 24 hours. The strongest staining occurred in the spiral ligament, organ of Corti, spiral ganglion, and vestibular sensory epithelia. Distribution of the drug paralleled locations of the glucocorticoid receptor except in the stria vascularis marginal cells, which stained heavily for the receptor but not the drug. CONCLUSION: Dexamethasone rapidly travels from the middle ear into the inner ear and converts to its active form. The drug distribution follows that of the glucocorticoid receptor. However, it probably has little impact on ear tissues after 24 hours.

Animals↗
PubMed1992

Expression of glycoconjugates in the mouse inner ear after prenatal irradiation.

Irradiation of the murine fetal inner ear is known to produce damage both to the vestibular and cochlear parts in the adult mouse. Fluorescein-labelled lectins were used to reveal possible differences in the glycoconjugate content between normal and irradiated inner ears. In the vestibular part, the otoconia showed the highest uptake of labelled sugars. This uptake was weaker after irradiation when compared to non-irradiated specimens. The type I hair cells in the ampulla and in the utricle showed a weaker uptake, but no labelling was demonstrated in the type II hair cells compared to the non-irradiated controls. In the cochlear part of the inner ear almost no uptake of fluorescent-binding lectins could be demonstrated in the irradiated groups except for in the tectorial membrane. In the endolymphatic sac no uptake was shown after prenatal irradiation. These findings are discussed and correlated to the already known damage of the inner ear following prenatal irradiation.

Animals↗
PubMedDate not supplied

Vascular inner ear partition: a concept for some forms of sensorineural hearing loss and vertigo.

The results of a series of scanning electron microscopical studies were used to construct a model for the vascular pathways in the inner ear. Corrosion cast preparations of the vessels of the inner ear of the adult rat were used in this study. The inner ear is, like a hand, an end organ containing four sense organs (cochlea, saccule, utricle and the cristae ampullaris). All these specific inner ear structures have their own vascular supply. We have developed a blood flow diagram of the inner ear. This model was used for a classification of different types of ischemia in the inner ear and forms a concept for some forms of sensorineural hearing loss and vertigo. Four types of inner ear ischemia are proposed. In type I (a or b) of inner ear ischemia only the vessels of the cochlea are involved resulting in two types of hearing loss without vertigo. Type II is characterized by ischemia of a part of the cochlea and a part of the vestibular system. In type III (a or b) only the vestibular system is involved, while in type IV no blood circulation will be present in the inner ear resulting in total deafness and severe vertigo. Inner ear partition at ultramicroscopical level of these structures may be possible in the future and new imaging techniques will probably support the vascular schematic model presented in this study.

Animals↗
PubMed2000

Hes1 is a negative regulator of inner ear hair cell differentiation.

Hair cell fate determination in the inner ear has been shown to be controlled by specific genes. Recent loss-of-function and gain-of-function experiments have demonstrated that Math1, a mouse homolog of the Drosophila gene atonal, is essential for the production of hair cells. To identify genes that may interact with Math1 and inhibit hair cell differentiation, we have focused on Hes1, a mammalian hairy and enhancer of split homolog, which is a negative regulator of neurogenesis. We report here that targeted deletion of Hes1 leads to formation of supernumerary hair cells in the cochlea and utricle of the inner ear. RT-PCR analysis shows that Hes1 is expressed in inner ear during hair cell differentiation and its expression is maintained in adulthood. In situ hybridization with late embryonic inner ear tissue reveals that Hes1 is expressed in supporting cells, but not hair cells, of the vestibular sensory epithelium. In the cochlea, Hes1 is selectively expressed in the greater epithelial ridge and lesser epithelial ridge regions which are adjacent to inner and outer hair cells. Co-transfection experiments in postnatal rat explant cultures show that overexpression of Hes1 prevents hair cell differentiation induced by Math1. Therefore Hes1 can negatively regulate hair cell differentiation by antagonizing Math1. These results suggest that a balance between Math1 and negative regulators such as Hes1 is crucial for the production of an appropriate number of inner ear hair cells.

Animals↗
PubMed2004

[Combined middle and inner ear abnormality: report of a case].

Congenital anomalies of the middle ear associated to anomalies of the inner ear are rarely described. Our case displays a malformation due to an association of congenital absence of the round window and aplasia of the semi-circular canals, causing conductive hearing loss. First diagnosis was a congenital atresia isolated of the round window, related to a previous surgical exploration. We tried a novel technique designed to restore the function of the round window. Labyrinthine anomalies prevented a good outcome. This kind of malformative association could be due to the complexity of early genetic control of ear development. Attentive analysis of imaging should be performed before middle ear surgery to determine the presence of inner ear anomalies which are quite frequent and which would limit its usefulness.

Abnormalities, Multiple↗
PubMed2006

Generation of inner ear cell types from embryonic stem cells.

The senses of hearing and balance are mediated by hair cells located in the cochlea and in the vestibular organs of the vertebrate inner ear. Loss of hair cells and other cell types of the inner ear results in hearing and balance disorders that substantially diminish the quality of life. The irreversibility of hearing loss in mammals is caused by the inability of the cochlea to replace lost hair cells. No drugs are available that stimulate inner ear cell regeneration. We describe here protocols to generate inner ear progenitor cells from murine ES cells and to differentiate these progenitors into hair cells and potentially into other inner ear cell types. In addition, we provide a modification of the protocol describing culture conditions in which human ES cells express a similar set of inner ear markers. Inner ear progenitor cells, generated from ES cells, may be used for the development of cell replacement therapy for the diseased inner ear, for high-throughput drug screening, and for the study of inner ear development.

Animals↗