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PubMed2001

A new mouse model with cochleo-saccular type inner ear defects.

We found a new inner ear mutant exhibiting abnormal behavior, such as circling and head shaking, in a breeding stock of SJL/J mice. The traits are inherited in a simple autosomal-recessive fashion. Animals homozygous for the responsible gene, designated cosa, show no startle response to sounds and an inability to swim. In the inner ears of cosa/cosa homozygous, but not +/cosa heterozygous adults, histopathological features of severe damage that are typical for 'cochleo-saccular' or 'spotting' mutants have been demonstrated. We suggest here that the abnormal mice carry a mutation of a gene that is developmentally switched on in the early stages of development and is involved in endolymph homeostasis.

Animals↗
PubMed2006

Recurrent diving-related inner ear barotrauma.

OBJECTIVE: To present two cases of recurrent diving-related inner ear barotrauma (IEB) and to discuss the possible cause and pathogenesis of the increased inner ear vulnerability. STUDY DESIGN: Case series. SETTING: Tertiary referral center. PATIENTS: Two scuba divers suffering from repeated cochleovestibular barotrauma. INTERVENTIONS: Neurotological evaluation, perilymphatic fistulae repair, and conservative treatment. MAIN OUTCOME MEASURE: The increasing popularity of scuba diving expose the individuals involved in this sport to unique pathologies that are not common under terrestrial conditions. The otolaryngologist who is involved in the care of these patients is required to diagnose and treat diving-related ear injuries and to consider the risk for recurrent inner ear injury when diving is resumed. CONCLUSION: IEB carries a risk for permanent hearing loss and chronic vestibulopathy. We recommend complete neurotological evaluation including high-resolution CT of the temporal bones as a routine workup for IEB. The presence of a significant residual sensorineural hearing loss, evidence for noncompensated vestibular damage, and CT findings of possible enhanced cerebrospinal fluid-perilymph connection should be considered when a return to diving activity is considered.

Adult↗
PubMed1989

The endolymphatic sac and inner ear homeostasis. II: Effect of glycerol on the sensory end organs with or without colchicine pretreatment.

The effects of glycerol and colchicine on the sensory end organs of the inner ear were investigated in mice. Glycerol alone induced a widening of the intercellular spaces lining vestibular dark and transitional cells as well as the marginal cells of the stria vascularis. This was noted within 30 min after the injection of glycerol and was normalized again within 4 h after the injection. Colchicine induced some morphological changes in the inner ear sensory cells, such as dissociation of Golgi complexes etc. These isolated glycerol or colchicine injections did not cause any signs of inner ear functional impairment. Treatment with glycerol following pretreatment with colchicine, however, induced marked inner ear dysfunction with impaired sense of balance and audition. The inner ear morphology revealed a combination of changes as compared with what was observed after isolated treatment with glycerol or colchicine i.e. edema of the stria vascularis, and vestibular dark and transitional cells as well as dissociation of Golgi complexes in the sensory cells. The cochlea showed moderate endolymphatic hydrops. These findings indicate that colchicine affects the inner ear fluid regulating mechanisms which may lead to severe functional derangement after additional glycerol treatment. It is conceivable that the present experiment may serve as a useful model for further studies on inner ear changes related to endolymphatic hydrops and Ménière's disease.

Animals↗
PubMed2004

Effect of acute inner ear pressure changes on low-level distortion product otoacoustic emissions in the guinea pig.

OBJECTIVE: To determine a relation between acute inner ear pressure changes and cochlear function as measured by low-level 2f(1)-f(2) distortion product otoacoustic emissions (DPOAEs). MATERIAL AND METHODS: During and after a change in inner ear pressure induced by injection or aspiration of perilymph, the 2f(1)-f(2) DPOAE at 4.5 kHz generated by low-level primaries was recorded in the guinea pig. RESULTS: Large changes in overall inner ear pressure produced only small changes in the 2f(1)-f(2) amplitude and phase. During injection of 0.5 microl of artificial perilymph into the scala tympani over a 10-s period, the mean inner ear pressure increased by approximately 500 Pa, with an accompanying mean increase in the 2f(1)-f(2) amplitude of 0.7 dB. During aspiration of 0.5 microl of perilymph over a 10-s period, the mean inner ear pressure decreased by approximately 700 Pa, with an accompanying mean decrease in the 2f(1)-f(2) amplitude of 0.9 dB. Changes in DPOAE amplitude followed inner ear pressure changes with a delay of 1-2 s. The magnitude and sign of the amplitude changes can (partly) be explained by a change in oval window stiffness. No explanation was found for the measured delay. CONCLUSION: Clinically, these experiments can be of value in gaining insight into the pathophysiological mechanisms of pathological pressure changes as seen in Meniere's disease and perilymphatic fistulae.

Animals↗
PubMed2005

In vitro isolation and cell culture of vestibular inner ear melanocytes.

INTRODUCTION: Melanocytes of the membranous labyrinth of the inner ear have been described morphologically in various contexts. Nature and functions of these cells are as yet not completely clear, even though several hypotheses exist regarding the same. The limited knowledge is due in part to a lack of methods regarding in vitro cell culture. The aim of this study was to describe conditions for the successful cell culture of vestibular inner ear melanocytes (VIEM), to compare their growth properties with those of epidermal melanocytes, and to characterize them immunohistochemically. MATERIALS AND METHODS: Membranous labyrinth cells from freshly slaughtered sheep were isolated, and melanocytes and fibroblasts subsequently cultured. In addition, melanocytes from the skin of the same sheep were cultured. Antibodies specific to tyrosinase, tyrosinase-related protein 1 (TRP-1/Mel-5), and melanoma-specific antigen A (Melan A) were used to analyze the cultured cells. RESULTS: The proliferation of VIEM was retarded in comparison to epidermal melanocytes. After 14 days, VIEM began to proliferate for the first time, whereas epidermal melanocytes proliferated already after 7 days. In contrast to epidermal melanocytes, the culturing process of VIEM seemed to be dependent on the presence of fibroblasts, and VIEM often accumulated in the vicinity of fibroblasts forming three-dimensional clusters. Moreover, VIEM showed a higher ratio of highly pigmented cells with a round cell shape and small dendrites in comparison to epidermal melanocytes. Immunohistochemical techniques proved the VIEM to be positive for Melan A, TRP-1 and, in the majority of cases, also for tyrosinase. CONCLUSION: We successfully cultured melanocytes of the inner ear vestibular labyrinth for the first time and demonstrated melanocytic characteristics of these cells. This accomplishment will provide the opportunity to investigate VIEM in more detail in future experiments.

Animals↗
PubMed1992

[Immuno-injury to the inner ear auditory system following secondary endolymphatic sac immune response].

This study investigated immuno-injury to the inner ear auditory system following inner ear immune response in the guinea pig. The endolymphatic sac (ES) was directly challenged with keyhole limpet hemocyanin (KLH). Auditory brainstem response with click sound stimulation was assessed pre and post KLH challenge of the ES. In systematically presensitized animals, secondary KLH challenge to the ES produced significant elevation of the mean threshold level on day 3 and 17 as compared to that of pre challenge levels. However, no significant prolongation of the latency (N1-N3) was observed. On the other hand, neither phosphate buffered saline injection into the ES nor primary KLH challenges of the ES were capable of elevating the threshold level and changing the latency. These results indicate that elevation of threshold was apparently induced by a secondary immune response of the ES, not by nonspecific mechanical damage to the ES, the central auditory system or KLH toxicity to the inner ear, suggesting that local immune response of the ES is a possible pathogenesis of sensorineural hearing loss.

Animals↗
PubMed2004

The role of Pax2 in mouse inner ear development.

The paired box transcription factor, Pax2, is important for cochlear development in the mouse inner ear. Two mutant alleles of Pax2, a knockout and a frameshift mutation (Pax21Neu), show either agenesis or severe malformation of the cochlea, respectively. In humans, mutations in the PAX2 gene cause renal coloboma syndrome that is characterized by kidney abnormalities, optic nerve colobomas and mild sensorineural deafness. To better understand the role of Pax2 in inner ear development, we examined the inner ear phenotype in the Pax2 knockout mice using paint-fill and gene expression analyses. We show that Pax2-/- ears often lack a distinct saccule, and the endolymphatic duct and common crus are invariably fused. However, a rudimentary cochlea is always present in all Pax2 knockout inner ears. Cochlear outgrowth in the mutants is arrested at an early stage due to apoptosis of cells that normally express Pax2 in the cochlear anlage. Lack of Pax2 affects tissue specification within the cochlear duct, particularly regions between the sensory tissue and the stria vascularis. Because the cochlear phenotypes observed in Pax2 mutants are more severe than those observed in mice lacking Otx1 and Otx2, we postulate that Pax2 plays a key role in regulating the differential growth within the cochlear duct and thus, its proper outgrowth and coiling.

Animals↗
PubMed2002

Sonic hedgehog regulates otic capsule chondrogenesis and inner ear development in the mouse embryo.

Development of the cartilaginous capsule of the inner ear is dependent on interactions between otic epithelium and its surrounding periotic mesenchyme. During these tissue interactions, factors endogenous to the otic epithelium influence the differentiation of the underlying periotic mesenchyme to form a chondrified otic capsule. We report the localization of Sonic hedgehog (Shh) protein and expression of the Shh gene in the tissues of the developing mouse inner ear. We demonstrate in cultures of periotic mesenchyme that Shh alone cannot initiate otic capsule chondrogenesis. However, when Shh is added to cultured periotic mesenchyme either in combination with otic epithelium or otic epithelial-derived fibroblast growth factor (FGF2), a significant enhancement of chondrogenesis occurs. Addition of Shh antisense oligonucleotide (AS) to cultured periotic mesenchyme with added otic epithelium decreases levels of endogenous Shh and suppresses the chondrogenic response of the mesenchyme cells, while supplementation of Shh AS-treated cultures with Shh rescues cultures from chondrogenic inhibition. We demonstrate that inactivation of Shh by targeted mutation produces anomalies in the developing inner ear and its surrounding capsule. Our results support a role for Shh as a regulator of otic capsule formation and inner ear development during mammalian embryogenesis.

Animals↗
PubMed2005

Eya1 acts upstream of Tbx1, Neurogenin 1, NeuroD and the neurotrophins BDNF and NT-3 during inner ear development.

Cell fate specification during inner ear development is dependent upon regional gene expression within the otic vesicle. One of the earliest cell fate determination steps in this system is the specification of neural precursors, and regulators of this process include the Atonal-related basic helix-loop-helix genes, Ngn1 and NeuroD and the T-box gene, Tbx1. In this study we demonstrate that Eya1 signaling is critical to the normal expression patterns of Tbx1, Ngn1, and NeuroD in the developing mouse otocyst. We discuss a potential mechanism for the absence of neural precursors in the Eya1-/- inner ears and the primary and secondary mechanisms for the loss of cochleovestibular ganglion cells in the Eya1bor/bor hypomorphic mutant.

Animals↗
PubMed1993

Inner ear damage due to lipoid nephrosis.

Inner ear pathology was studied in adult rats with lipoid nephrosis induced by puromycin aminonucleoside. Although no abnormality was observed in auditory brain-stem responses, significant changes were noted in the stria vascularis. The most striking observation was that intermediate cells were markedly swelled, there-by pressing adjacent marginal cells. Severely affected marginal cells have vacuoles and increased lysosomes and protruded toward the endolymphatic space. The organ of Corti remained virtually intact. Although the vestibular maculae were relatively normal, type I hair cells in the semicircular canal underwent a conspicuous vaculolization. These findings support a postulate that the inner ear is liable to damage in lipoid nephrosis.

Animals↗
PubMed1975

Tomographic findings of the inner ears of 24 patients with Waardenburg's syndrome.

The tomographic findings in the Stenvers' projection of inner ears of 24 patients with Waardenburg's syndrome are described. In 12 of these 48 inner ears deafness was found. The roentgenographic examination did not show any malformation of the inner ears of these patients. In the literature on this subject, the tomographic findings of the inner ears of 12 deaf patients with Waardenburg's syndrome have been described. In 8 of them malformations were reported, especially of the semicircular canals. These findings in the literature could not be confirmed by our study.

Abnormalities, Multiple↗
PubMedDate not supplied

Determinants of ganglion-receptor cell interaction during development of the inner ear. A heterochronic ganglia study.

It has been suggested that inner ear sensory receptors produce attractant fields that guide neurite outgrowth from statoacoustic ganglion (SAG) neurons to appropriate target sites within the developing labyrinth. This experiment tested the temporal limitations of SAG neurons in their ability to respond to these attractant fields. Statoacoustic ganglia were excised from 12, 13, 14 and 15 gestation day (GD) mouse embryos. This temporal series of SAG was implanted into aganglionic 12 GD otocysts. All cultures were grown for 7 days in vitro, then fixed and processed for nerve fiber staining. Specimens were evaluated for the presence of neurites associated with the inner ear sensory receptors that developed within the otic explants. All of the implanted heterochronic ganglia (i.e. 13, 14 or 15 GD) as well as the homochronic (i.e. 12 GD) ganglion controls extended neurites to sensory epithelium of both vestibular and auditory character. Neurites made contact with the base of hair cells in all of the sensory structures. These findings demonstrate that SAG neurons are capable of extending processes in response to otic attractant fields for an extended period during the embryonic development of this ganglion. This observation supports the hypothesis that the onset and duration of receptor generated attractant fields may act as a controlling factor in establishing patterns of innervation within the developing inner ear.

Animals↗
PubMed1999

TUNEL staining of inner ear structures may reflect autolysis, not apoptosis.

A recent study (Usami et al., 1997) using the TUNEL method has suggested that age-related cell death in the senescence-accelerated mouse inner ear is due to apoptosis. TUNEL staining detects not only apoptosis but also late necrosis or autolysis because it detects DNA breaks. Autolysis may occur in inner ear structures during fixation. To determine whether or not age-related cell death is due to apoptosis, TUNEL staining of the inner ear of normal mice should be understood. However, studies of TUNEL staining of the normal inner ear have not yet been reported. We investigated whether the fixation method or the interval between the death of normal mice and the initiation of fixation influences the results of TUNEL staining of the inner ear. Marginal cells of the stria vascularis and hair cells of the saccule were TUNEL-positive, irrespective of the fixation method or the interval between death and fixation. Interdental cells, Reissner membrane cells, fibrocytes in the suprastrial region, and inner and outer hair cells were also occasionally stained. Transmission electron microscopy showed no morphological characteristics of apoptosis in the hair cells of the saccule. Moreover, patterns of TUNEL staining in the normal and senescence-accelerated mouse inner ear were similar. These stained tissues may require a high level of oxygen, making them more susceptible to autolysis. We concluded that the results of TUNEL staining in the inner ear require confirmation by morphological studies.

Animals↗
PubMedDate not supplied

TUNEL-positive labeling in mouse inner ear caused by tubulin immunization is not apoptosis.

Apoptosis is involved in all fundamental processes of the immune system. To study whether apoptosis plays any role in the pathogenesis of autoimmune inner ear disease, we immunized Balb/c mice with tubulin. The inner ears were examined with TUNEL (in situ terminal dUTP nick-end labeling) and immunocytochemistry of the apoptosis regulatory proteins Bcl-2 and Bax. TUNEL-positive cells are found in the tubulin-immunized inner ears but not in the control inner ears. The positive cells are the marginal cells in the stria vascularis, and the hair cells in Corti's organ and the saccule. However, under morphological analysis by light microscope, these cells lack the features characteristic of apoptosis. Moreover, no cells staining positive for Bcl-2 and Bax are found in any structures of the inner ears. These results suggest that positive TUNEL staining in this model does not indicate apoptosis and apoptosis may be not involved in autoimmune inner ear disease.

Animals↗
PubMed1985

Developmental morphology of the mouse inner ear. A scanning electron microscopic observation.

The developing inner ears of mice (CBA/CBA), ages ranging from gestational day 12 through postnatal day 21, were examined using scanning electron microscopy following the epoxy-embedding/freeze-fracture technique. This technique provides unique three-dimensional views of surface and fractured structures of the developing inner ear, thus allowing excellent preservation of the relationships between the developing sensory epithelium and the overlying membranes (i.e. the tectorial membrane and cupula) during their development. The tectorial membrane is formed of two distinct parts: the major (medial) and the minor (distal). The major portion is produced by the cells of the greater epithelial ridge prior to the formation of the minor part, which is produced largely by the primordial supporting cells of the lesser epithelial ridge. The developing tectorial membrane has two types of fibers: radial (found mainly in the major part) and slanted (found mainly in the minor part). The slanted fibers become the cover net, which fuses with the marginal band. The marginal zone of the developing tectorial membrane is completely sealed during development by the third row of Deiters' cells. The surfaces of cells that produce the tectorial membrane are characterized by numerous long microvilli which are largely lost when the tectorial membrane completely forms and separates from the supporting cells. The surface of developing auditory sensory cells is initially covered with numerous microvilli, some of which become future stereocilia. Stereocilia form stepped rows in the shape of a "W", with the tallest row located at the periphery of the cell. As the sensory cell matures, the short transitional stereocilia gradually disappear. Kinocilia on hair cells are still seen in the 14-day-old mouse (even though the organ of Corti is morphologically mature) but not in the 21-day-old mouse, indicating that complete maturation of the sensory cells in all turns is attained by 21 days of age. The mouse has upper radial tunnel fibers and basal tunnel fibers. Neural contacts of the upper radial tunnel fibers with the outer hair cells at the apical portions are frequent in the developing organ of Corti. The external sulcus cells undergo drastic changes during development, forming numerous pits that are often covered with mucus-like droplets or grape-like spherical structures of varying sizes. This phenomenon was observed only during postnatal days 6 and 14. The developing cupula starts as a thin amorphous membrane, which later becomes compact and fibrotic-like as the mass increases. By the 6th postnatal day well-developed cupular canals occur.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1997

[Ossicular vibration changes associated with pressure changes in inner ear and cerebrospinal fluid in guinea pigs].

The effects of increase in the inner ear and cerebrospinal fluid (CSF) pressures on the vibration of the ossicular chain were studied in guinea pigs by using a laser doppler vibrometer. Velocity of the malleus umbo and that of the incus long crus in response to a constant sound stimulus of 90dB SPL at the tympanic membrane were measured at 13 frequencies between 0.125 kHz and 10 kHz. Loading pressures to the inner ear and the CSF were adjusted by changing the height of a saline bottle hooked up to the respective site by a 24G Teflon catheter. The pressure was monitored with a pressure transducer placed in the catheter. Positive and negative pressure loads to the inner ear decreased the velocity of the umbo at low and high frequencies. The maximum change was 4.7 dB at 0.125 kHz with a positive pressure load of 400 mmH2O. Similar results were obtained for the umbo and the long crus by a positive pressure load to the CSF, with the exception that the umbo velocity showed no change at higher frequencies. These results suggest that the inner ear and CSF pressure changes affect not only the function of the organ of Corti but also the vibration of the ossicular chain. These changes occurred mainly at lower frequencies.

Animals↗
PubMed2001

The functional and structural outcome of inner ear gene transfer via the vestibular and cochlear fluids in mice.

Mice present an ideal model for inner ear gene therapy because their genome is being rapidly sequenced, their generation time is relatively short, and they serve as a valuable model for human hereditary inner ear disease. However, the small size of the mouse inner ear poses a particular challenge for surgical procedures. We have developed a new approach for viral inoculation into the mature mouse inner ear, using a replication-deficient adenovirus expressing the bacterial gene lacZ. We administered the virus through the posterior semicircular canal (canalostomy) and into the cochlea (cochleostomy). Both approaches caused lacZ to be expressed in cells lining the perilymphatic space. One canalostomy case showed gene expression in sensory cells of the crista ampullaris, whereas the cochleostomy group showed gene expression in the sensory cells in the organ of Corti and saccule. Functional tests after the surgery showed that the canalostomy preserved hearing, whereas the cochleostomy did not. Any vestibular function transiently lost after the canalostomy was recovered. Our findings indicate that inoculation of adenovirus vectors into the mouse inner ear through the semicircular canal has the potential to efficiently introduce transgenes to the vestibular system and the cochlea without compromising hearing.

Adenoviridae↗
PubMedDate not supplied

Functional significance of nitric oxide in the inner ear.

Significant advances have been made in our understanding of the functional significance of nitric oxide (NO) in the inner ear. The localization of NO synthase and the nitric oxide production site has now been established by immunohistochemistry and the fluorescent indicator of NO. The functional significance of NO in the inner ear, especially as a neurotransmitter, is becoming increasingly clear. Mounting evidence suggests that excessive NO production may play an essential role in inner ear disorders as well. The production of an inducible type of NO synthase may be closely related to this phenomenon. Based on the mechanisms of inner ear disorders, new pharmacological strategies for preventing and/or treating inner ear disorders have also been suggested.

Animals↗