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At least 253 records · Page 14Linked to original sources
PubMed1989

Experimental autoimmune inner ear disease.

A guinea pig animal model of autoimmune inner ear disease is presented. The functional, anatomical, and immunological inner ear changes were tested electrophysiologically, histologically and by the immunofluorescence test. Using a homologous crude inner ear antigen (CIEAg) we were able to induce endolymphatic hydrops, vasculitis, mild cellular infiltration of the endolymphatic sac, and occasional spiral ganglion degeneration. Threshold shift was seen in 20% of the tested ears. Specific fluorescence was revealed around the modiolar vessels and in the basilar membrane. The endolymphatic sac and duct showed occasional fluorescence in the epithelial and/or subepithelial layers. The findings were discussed in light of the other models immunized with various forms of inner ear antigens. Similarities between the detected specific fluorescence and the fluorescence revealed by sera of patients with cochleovestibular disorders were discussed.

Action Potentials↗
PubMed1995

[Experimental research of autoimmune inner ear disease].

16 guinea pigs were immunized with homologous crude inner ear antigen. Their hearing thresholds were recorded, morphological changes in inner ear were observed, autoantibodies against inner ear were tested. We found that these animals uniformly developed antibodies to inner ear antigen in their sera; 12 of 32 ears showed significant increases in Ap (N1) thresholds (P < 0.01); endolymphatic hydrops, vasculitis of modiolus, degeneration and loss of the cochlear neural elements were the main histopathological lesions; and especially IgG deposition was noted in the modiolar vessels and stria vascularis in most of the examined cochlears. These indicated that an experimental model of AIED can be established in partial immunized guinea pigs.

Animals↗
PubMed1996

Receptors for glucocorticoids in the human inner ear.

Glucocorticoid receptors were detected in the human inner ear. The highest concentration of glucocorticoid receptor protein was measured by enzyme-linked immunosorbent assay in the spiral ligament tissues; the lowest concentration of glucocorticoid receptors was measured in the macula of the saccule. The demonstration of the presence of glucocorticoid receptors in human Inner ear tissues provides a basis to consider the direct effects of glucocorticoid action on select inner ear cells, rather than assuming a systemic antiinflammatory or immunosuppressive effect during the therapeutic treatment of patients with given inner ear disorders.

Acoustic Maculae↗
PubMed1992

[Inner ear decompression sickness following a scuba dive].

Inner ear decompression sickness (IEDCS) is one form of Type II decompression sickness. Most cases of IEDCS have been associated with saturation dives, so there are very few reports of occurrence following shallow scuba dives. We present here the case of a diver who suffered from IEDCS following a shallow scuba dive (30m), and was successfully treated by the protocol outlined in U.S. Navy treatment table 6. This case suggests that there is the possibility of occurrence of IEDCS, even following a shallow scuba dive, if proper decompression procedures are not adhered to. In addition, detailed analysis of diving profiles should be used to distinguish the inner ear dysfunction seen in some divers from inner ear barotrauma which may be attributable to IEDCS.

Adult↗
PubMed2004

Fgf9 signaling regulates inner ear morphogenesis through epithelial-mesenchymal interactions.

The mammalian inner ear comprises the cochleovestibular labyrinth, derived from the ectodermal otic placode, and the encasing bony labyrinth of the temporal bone. Epithelial-mesenchymal interactions are thought to control inner ear development, but the modes and the molecules involved are largely unresolved. We show here that, during the precartilage and cartilage stages, Fgf9 is expressed in specific nonsensory domains of the otic epithelium and its receptors, Fgfr1(IIIc) and Fgfr2(IIIc), widely in the surrounding mesenchyme. To address the role of Fgf9 signaling, we analyzed the inner ears of mice homozygous for Fgf9 null alleles. Fgf9 inactivation leads to a hypoplastic vestibular component of the otic capsule and to the absence of the epithelial semicircular ducts. Reduced proliferation of the prechondrogenic mesenchyme was found to underlie capsular hypoplasticity. Semicircular duct development is blocked at the initial stages, since fusion plates do not form. Our results show that the mesenchyme directs fusion plate formation and they give direct evidence for the existence of reciprocal epithelial-mesenchymal interactions in the developing inner ear. In addition to the vestibule, in the cochlea, Fgf9 mutation caused defects in the interactions between the Reissner's membrane and the mesenchymal cells, leading to a malformed scala vestibuli. Together, these data show that Fgf9 signaling is required for inner ear morphogenesis.

Animals↗
PubMed2003

Applications of genomics in the inner ear.

Understanding the development and function of the inner ear requires knowledge of the genes expressed and the pathways involved. Such knowledge is also essential for the development of therapeutic approaches for a wide range of inner ear diseases affecting millions of people. The completion of the Human Genome Project and emergence of genomics-based technologies have made it possible to analyze the expression patterns of the inner ear genes at the whole genome level, generating an unprecedented amount of information on gene expression patterns. This review will discuss the current status of work using genomics, in particular the functional genomics approach, to study different aspects of inner ear genes. It will also illustrate how the approach can help to identify and characterize deafness genes, as well as contributing to work related to hair cell regeneration.

Animals↗
PubMedDate not supplied

Involvement of insulin-like growth factor-I in inner ear organogenesis and regeneration.

The verterbrate inner ear is an excellent model system to study signalling mechanisms in embryonic development. During the last years, insulin-like growth factor-I (IGF-I) has attracted attention in relation to the regulation of inner ear ontogenesis. IGF-I and its high-affinity tyrosine-kinase receptor are expressed during early stages of inner ear development. IGF-I is a powerful mitogen for the otic vesicle, where it stimulates cell-division and mitogenic signalling cascades. Later in development, IGF-I also promotes survival and neurogenesis of the otic neurones in the cochleovestibular ganglion (CVG). The actions of IGF-I are associated with the generation of lipidic messengers and the activation of Raf kinase, which results in the rapid induction of the expression of the proliferative cell nuclear antigen (PCNA) and the nuclear proto-oncogenes c-fos and c-jun. Regulation of organogenesis involves a dynamic balance of the mechanisms regulating cell division, differentiation and death. A model is proposed where this balance is the consequence of the action of IGF-I and NGF, which converge in Raf activation or suppression. The combinatorial expression of jun and Fos family members in particular domains of the otic vesicle would be the final result of such cascade. Some of these mechanisms may be also implicated in otic regeneration.

Animals↗
PubMed1988

Physiology and pathophysiology of inner ear melanin.

The presence of melanin in the inner ear was established more than a century ago, but the exact biological function of the pigment in the labyrinth has yet to be determined. In this brief review, the correlation of pigmentation and inner ear function, as well as the presumed role of melanocytes in hereditary diseases are discussed. Special attention was drawn to the composition of melanin and its presumed function as a biological reservoir for divalent ions and as an ion exchanger, as well as an intracellular buffering system for calcium. It is pointed out that melanin is capable of binding ototoxic drugs. Finally, morphological responses of melanocytes to local disturbance of Ca++ homeostasis in the inner ear are described as 1) intracellular movement and intraepithelial deposition of melanosomes; 2) cell motility; 3) neomelanogenesis; and 4) enhanced exocytotoxic/endocytotic activity. The possible consequences of this malfunction of the melanocytes on the inner ear function are discussed.

Animals↗
PubMed1984

The freeze fracture technique in inner ear research.

Freeze-fracture studies on the inner ear have been focused mainly on the normal structure of junctions sealing the endolymphatic compartment, the compartmentalization of the stria vascularis and the junctional stability of the hair cells towards adjacent supporting cells. The hair cells have a very tight type of zonulae occludenetes as compared with other non-sensory epithelia in the inner ear. In contrast to other epithelial cells, the mature hair cells are in most species lacking gap junctions. During embryonic development a loss of gap junctions is an early and significant feature of cells differentiating into future hair cells. The tight junctions in the secretory epithelia (stria vascularis in the cochlea and dark cells around vestibular organs) are morphologically mature before the onset of the ionic maturation of endolymph. Freeze-fracture studies on inner ear pathology are few. The structural alterations of tight junctions in the diseased inner ear are minimal. The functional significance of such small morphological derangements is not known.

Animals↗
PubMed2006

Leupeptin, a calpain inhibitor, protects inner ear hair cells from aminoglycoside ototoxicity.

Inner ear hair cells play a major role in the auditory pathway that converts sound stimulation into electrical signals, and then into a neural code. However this function is often lost by aminoglycoside ototoxicity. The injury of inner ear hair cells from aminoglycoside treatment is considered apoptosis, and caspase is an important participant in the apoptosis pathway in many organs. It has been reported that calpain, a calcium-dependent protease, is essential for mediation and promotion of cell death. The purpose of the present study was to investigate effects of caspase and calpain inhibitors on the inner ear hair cells after aminoglycoside treatment, and to explore the cell death pathway. Cochlea explant cultures were prepared from mice of postnatal 6 days, cultured with neomycin and/or protease inhibitors, and then stained with phalloidin-fluorescein isothiocyanate (phalloidin-FITC), which was used as a marker to identify surviving hair cells. We demonstrated that neomycin (0.1-1 mM) reduced the number of outer hair cells in a dose-dependent manner. Furthermore, we showed that leupeptin, a calpain inhibitor, significantly protects against the neomycin-induced loss of outer hair cells, whereas a caspase inhibitor was effective only against a lower concentration of neomycin (0.2 mM). Using the TdT-mediated dUTP-biotin nick and labeling method, we also found that a calpain inhibitor, but not a caspase inhibitor, prevents apoptotic DNA fragmentation after treatment with 1 mM neomycin. These results suggest that calpain, rather than caspase, may be responsible for apoptosis induced by aminoglycoside. Thus, leupeptin may prevent hearing loss from aminoglycoside ototoxity.

Animals↗
PubMed2005

Local inner-ear drug delivery and pharmacokinetics.

Several drugs that are applied directly to the inner ear are in widespread clinical use for the treatment of inner-ear disorders. Many new substances and drug delivery systems specific to the inner ear are under development and in some cases are being evaluated in animal experiments and in clinical studies. However, the pharmacokinetics of drugs in the inner ear is not well defined and the field is plagued by technical problems in obtaining pure samples of the inner-ear fluids for analysis. Nevertheless, a basic understanding of the mechanisms of drug dispersal in the inner ear has emerged, which facilitates the design and interpretation of future pharmacokinetic studies.

Animals↗
PubMed1989

[Electric stimulation of the inner ear].

Electrical stimulation of the inner ear is a valuable tool for the diagnosis and treatment of inner ear disorders. Its most known application is the cochlear implant, but it is also useful in the assessment of high frequency hearing and for the management of tinnitus. Patients receiving ototoxic drugs can be audiometrically followed with high-frequency electrostimulation audiometry. Results obtained with this technique are discussed. Tests for tinnitus suppression by means of transcutaneous electrostimulation are also presented.

Audiometry, Evoked Response↗
PubMed2005

Advances in inner ear gene therapy: exploring cochlear protection and regeneration.

PURPOSE OF REVIEW: To review the application of gene therapy in the inner ear. Gene delivery to the inner ear was first reported in 1996. Since then the field has progressed on multiple fronts. RECENT DEVELOPMENTS: More diverse and sophisticated vectors are improving the efficiency of delivery to the inner ear. Research is transitioning from the delivery of marker genes to the delivery of therapeutic genes in animal models of inner ear disease. Three distinct areas of research are developing: (1) delivery of genes for protection of spiral ganglion neurons with potential application in cochlear implantation, (2) delivery of genes for protection of hair cells and hearing preservation in degenerative diseases and cochlear insults and (3) the use of gene therapy to transform cells from one phenotype to another and replace lost cells, potentially restoring lost function. SUMMARY: Currently, no specific drugs are targeted at inner ear disease. The use of gene therapy in the inner ear is being applied in animal models of ototoxicity and ischemia reperfusion injury. Gene therapy can protect the inner ear from damage and even restore function through the regeneration of hair cells.

Animals↗
PubMed2006

Magnetic resonance appearance of the inner ear after hearing-preservation surgery.

OBJECTIVE: To determine whether the appearance of the inner ear on T2-weighted follow-up magnetic resonance imaging correlates with hearing status after hearing-preservation surgery for vestibular schwannoma. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary referral medical center. PATIENTS: The study includes patients undergoing hearing-preservation surgery for vestibular schwannoma from 1998 to 2003. INTERVENTION: Diagnostic evaluation with magnetic resonance imaging and audiometric evaluation. MAIN OUTCOME MEASURES: Hearing results as reported in charts was correlated with appearance of membranous labyrinth on T2-weighted magnetic resonance images obtained at least 1 year after surgery. RESULTS: Twenty-nine patients were identified, 16 of whom satisfied the inclusion criteria. All 16 of the patients underwent middle fossa removal of vestibular schwannoma. Serviceable hearing according to American Academy of Otolaryngology-Head and Neck Surgery criteria was preserved in eight patients (50%). Of the eight patients without serviceable hearing, six had the cochlear nerve sacrificed at the time of surgery. All patients with serviceable hearing had normal appearing cochleovestibular signal on T2-weighted images, whereas six of eight patients (75%) with no hearing or poor hearing had abnormal low signal in the inner ear, suggesting inner ear ossification. The positive predictive value of a normal labyrinth for preserved hearing was 90%, whereas the negative predictive value of an abnormal labyrinth for no hearing was 100%. All but one patient who had the cochlear nerve sacrificed showed abnormal morphology of the labyrinth on T2-weighted magnetic resonance imaging. CONCLUSION: We describe the T2-weighted magnetic resonance findings after hearing-preservation surgery for acoustic tumor removal. Loss of inner ear signal on T2-weighted images correlates with loss of hearing postoperatively, whereas preserved inner ear signal correlates with hearing preservation after middle fossa surgery for vestibular schwannoma removal.

Auditory Threshold↗
PubMed1991

Cochlear blood flow under increased inner ear pressure.

The effect of elevation of inner ear pressure on cochlear blood flow in guinea pigs was studied with use of nonradioactive microspheres and a laser-Doppler flowmeter. Hydrostatic pressure was applied to the perilymph through a glass capillary tube inserted into the scala tympani of the basal turn. Because of the elevation of the inner ear pressure, the cochlear blood flow, except to the modiolus, decreased significantly. Above all, the blood flow in the capillaries or microcirculation in the cochlea was most easily impaired by the elevation of inner ear pressure.

Animals↗
PubMed2006

Mutation of the atrophin2 gene in the zebrafish disrupts signaling by fibroblast growth factor during development of the inner ear.

The development of the vertebrate inner ear depends on the precise expression of fibroblast growth factors. In a mutagenesis screen for zebrafish with abnormalities of inner-ear development and behavior, we isolated a mutant line, ru622, whose phenotypic characteristics resembled those of null mutants for the gene encoding fibroblast growth factor 8 (Fgf8): an inconsistent startle response, circular swimming, fused otoliths, and abnormal semicircular canals. Positional cloning disclosed that the mutant gene encodes the transcriptional corepressor Atrophin2. Both the Fgf8 protein and zebrafish "similar expression to fgf genes" protein (Sef), an antagonist of fibroblast growth factors induced by Fgf8 itself, were found to be overexpressed in ru622 mutants. We therefore hypothesized that an excess of Sef eliminates Fgf8 signals and produces an fgf8 null phenotype in ru622 mutants. In support of this idea, we could rescue larvae whose atrophin2 expression had been diminished with morpholinos by reducing the expression of Sef as well. We propose that Atrophin2 plays a role in the feedback regulation of Fgf8 signaling. When mutation of the atrophin2 gene results in the overexpression of both Fgf8 and Sef, the excessive Sef inhibits Fgf8 signaling. The resultant imbalance of Fgf8 and Sef signals then underlies the abnormal aural development observed in ru622.

Animals↗
PubMed2003

Fate of neural stem cells grafted into injured inner ears of mice.

Loss of sensory hair cells in the inner ear is a major cause of permanent hearing loss, since regeneration of hair cells rarely occurs in mammals. The aim of this study was to examine the potential of neural stem cell transplantation to restore inner ear hair cells in mice. Fetal neural stem cells were transplanted into the mouse inner ear after drug-induced injury. Histological analysis demonstrates that the majority of grafted cells differentiated into glial or neural cells in the inner ear. Strikingly, however, we show that grafted cells integrate in vestibular sensory epithelia and express specific markers for hair cells. This finding suggests that transplanted neural stem cells have the potential to differentiate and restore inner ear hair cells.

Animals↗
PubMed2005

[MRI evidence of exogenous vascular endothelial growth factor-enhanced transport across inner ear barriers in guinea pigs].

OBJECTIVE: Increased vascular endothelial growth factor (VEGF) and VEGF receptor expression is the important biological response under shear stress, ischemia and hypoxia conditions. Mechanical vibration induced cochlea shear stress and trauma obviously upregulate VEGF and VEGF receptor 2 (VEGFR2) expression in the cochlea. To evaluate the possibility of VEGF varying the transport in blood-labyrinth barrier and blood-perilymphatic barrier. METHODS: Eleven guinea pigs, male and female, weighing from 300 g to 900 g were kept under general anaesthesia with xylazine (16 mg/kg) and ketamine (60 mg/kg) for both drug delivery and MRI measurement. VEGF (6 ears) and phosphate-buffered saline (PBS, 5 ears) were delivered to the inner ear via the round window membrane (soaked in gelfoam). The T1 contrast agent gadodiamide (Gd-DTPA-BMA) chelated bound paramagnetic gadolinium was used as the inner ear barrier transportation tracer. A Bruker Biospec Avance 47/40 experimental MRI system with a magnetic field strength of 4. 7 Tesla and a 40 cm bore was used for the 2-dimensional cochlea MRI evaluation. The Paravision software was used for image intensity measurement and the Adobe Photoshop 6.0 software was used for image presentation. RESULTS: VEGF induced significant Gd uptake in the scala tympani and scala vestibuli, but had little effect on the uptake of Gd in the scala media. CONCLUSIONS: VEGF significantly increased the transportation of blood-perilymphatic barrier and adapted the inner ear for compensation and repair.

Animals↗