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At least 667 records · Page 37Linked to original sources
PubMed1975

Effect of hyperbilirubinemia on the inner ear in Gunn rats.

The effect of hyperbilirubinemia on the inner ear was studied in fifteen jaundiced homozygous Gunn rats. Seven non-jaundiced heterozygous littermates served as controls. Histopathological examination of the temporal bone in these animals showed normal sensory and neuronal structures of the inner ear. This cannot be taken as conclusive evidence that a central, rather than a peripheral, lesion is the cause of hearing loss in hyperbilirubinemia.

Animals↗
PubMed2001

Specific expression of the retinoic acid-synthesizing enzyme RALDH2 during mouse inner ear development.

Retinoid binding proteins and nuclear receptors are expressed in the developing mouse inner ear. Here, we report that the retinaldehyde dehydrogenase 2 (Raldh2) gene, whose product is involved in the enzymatic generation of retinoic acid (RA), exhibits a restricted expression pattern during mouse inner ear ontogenesis. The Raldh2 gene is first expressed at embryonic day (E) 10.5 in a V-shaped medio-dorsal region of the otocyst outer epithelium, which evolves as two separate domains upon otocyst morphogenesis. At E14.5, Raldh2 is expressed in two areas of the utricle epithelium and specific regions of the saccule and cochlear mesenchyme. Later, Raldh2 transcripts are restricted to two cochlear areas, the stria vascularis and Reissner membrane. Raldh2 mesenchymal expression did not correlate with migrating neural crest-derived melanoblasts. These restricted expression domains may correspond to specific sites of RA synthesis during inner ear morphogenesis.

Aldehyde Oxidoreductases↗
PubMed1997

Surgical techniques for cochlear implantation of the malformed inner ear.

OBJECTIVE: The objective was to describe surgical techniques helpful in implanting children with inner ear malformations. STUDY DESIGN: This was a retrospective chart review and description of surgical techniques in the setting of a tertiary referral center. PATIENTS: The study population was composed of 10 children with inner ear deformities who received 22-channel implants. RESULTS: The primary surgical challenges encountered in these procedures include complete electrode insertion, cerebrospinal fluid gusher, identification of cochleostomy site in the absence of the round window and aberrant facial nerve, and fixation and stabilization of the electrode. CONCLUSIONS: The techniques described allow safe and effective insertion of multichannel electrodes in patients with inner ear malformations.

Child↗
PubMed1975

Alkaline phosphatase activity in the inner ear of fetuses, newborn and adult guinea pigs.

The distribution pattern of alkaline phosphatase in the inner ear of fetuses, newborn and adult guinea pigs is described. In the inner ear of fetuses, remarkable alkaline phosphatase was noted throughout the entire tissue of spiral ligament, statoacoustic nerve fibers and the wall of small blood vessels. In newborns, however, less enzyme activity was seen in the spiral ligament and statoacoustic nerve. In adult guinea pigs, no enzyme activity was detectable in the spiral ligament and statoacoustic nerve fibers except for the wall of small blood vessels and efferent nerve fibers. It is evident that the distribution pattern of alkaline phosphatase is altered during the development of the inner ear of the guinea pig.

Alkaline Phosphatase↗
PubMed2000

Genetic patterning of embryonic inner ear development.

The commitment of the otocyst to form balance (pars superior) and hearing (pars inferior) receptors is under the control of patterning genes. Intersecting patterns of gene expression has been proposed to explain the regionalization of inner ear sensory receptor development. Insights into the roles of patterning genes is being acquired from the analysis of inner ear development of null mutation mice. An example of the consequences of the loss of expression of a single patterning gene is the effect of a null mutation of paired-box gene 2 (Pax2) on formation of the cochlea. Pax2 transcripts are expressed in the pars inferior of the otocyst and null mutant inner ears show agenesis of the cochlea. This is an example of the profound effect that loss of a single patterning gene can have on inner ear development. However, more typically there is redundancy of gene action during inner ear development as exemplified by the overlapping pattern of expression of two closely related homeobox-containing genes (i.e. Hmx2 and Hmx3) in the pars superior of the otocyst. Hmx2 and Hmx3 genes are both expressed early in otic development with Hmx3 transcripts present in the placode. However, null mutation of the Hmx3 patterning gene produced only a limited vestibular defect, and did not result in the agenesis of the vestibule. This result suggests that there is redundancy in genes that have similar patterns of regional expression in the otic anlagen.

Animals↗
PubMed2000

Identification with a recombinant antibody of an inner-ear cytokeratin, a marker for hair-cell differentiation.

Extensive biochemical characterization of cells in the inner ear has been hampered by a lack of tools with which to identify inner-ear proteins. By using a single-chain antibody fragment isolated from a bacteriophage-displayed library, we have identified a cytokeratin that is abundant in nonsensory cells of the frog inner ear. Although the progenitors of hair cells exhibit strong immunoreactivity to this cytokeratin, the signal declines in immature hair cells and vanishes as the cells mature. The correlation between diminished immunoreactivity and hair-cell differentiation indicates that the cytokeratin is down-regulated during the transition from a nonsensory to a sensory cell and suggests that the marker is an early index of hair-cell differentiation.

Amino Acid Sequence↗
PubMed1997

Immortalized cell lines from embryonic avian and murine otocysts: tools for molecular studies of the developing inner ear.

Recently, our studies have focused on genes expressed at the earliest stages of inner ear development. Our aim is to identify and characterize genes that are involved in determining the axes of the semicircular canals, in otic crest delamination and in early innervation of the inner ear. Many elegant studies of auditory development have been done in animal models. However, the need for large amounts of well-characterized embryonic material for molecular studies makes the development of otocyst cell lines with different genetic repertoires attractive. We have therefore derived immortalized otocyst cells from two of the most widely used animal models of ear development: avians and mice. Avian cell isolates were produced from quail otocysts (embryonic stage 19) that were transformed with temperature-sensitive variants of the Rous sarcoma virus (RSV). Among the individual transformed cells are those that produce neuron-like derivatives in response to treatment with 10(-9) M retinoic acid. Mammalian cell isolates were derived from otocysts, of 9 day (post coitus) embryos of the H2kbtsA58 transgenic mouse (Immortomouse), which carries a temperature-sensitive variant of the Simian Virus 40 Tumor antigen. The vast majority of cells of the Immortomouse are capable of being immortalized at 33 degrees C, the permissive temperature for transgene expression, in the presence of gamma-interferon. Several putative clones et these cells differentiated into neuron-like cells after temperature shift and withdrawal of gamma-interferon; another isolate of cells assumed a neuron-like morphology on exposure to brain-derived neurotrophic factor even at the permissive temperature. We describe also a cell isolate that expresses the Pax-2 protein product and two putative cell lines that express the protein product of the chicken equivalent of the Drosophila segmentation gene engrailed. These genes and their protein products are expressed in specific subpopulation of otocyst cells at early stages. Both mouse and quail immortalized cell lines will be used to study inner ear development at the molecular level.

Animals↗
PubMedDate not supplied

Middle and inner ear: improved depiction with multiplanar reconstruction of volumetric CT data.

Many anatomic structures of the middle and inner ear are not optimally depicted at computed tomography (CT) with image reconstruction in the standard axial and coronal planes. Recent advances in multidetector CT, including the development of scanners with 32 detector rows, allow the acquisition of isotropic voxels that can be reconstructed in any plane of section. This technique gives radiologists the opportunity to visualize the anatomic structures of the middle and inner ear (the ossicular chain, stapedial footplate-oval window complex, round window, cochlea, vestibular aqueduct, and bones of the superior semicircular canal and facial nerve canal) in greater detail and may help increase the accuracy of CT for the diagnosis of diseases of the middle and inner ear.

Ear Diseases↗
PubMed2003

Technical report: modification of a cochlear implant electrode for drug delivery to the inner ear.

OBJECTIVE: To investigate the possibility of modifying a cochlear implant electrode for the purpose of drug delivery to the cochlea. BACKGROUND: Animal experiments suggest that local therapy of the inner ear could be a promising new approach to the interventional treatment of inner ear disease, and that pharmacologic intervention could possibly enhance cochlear implant performance. One of the key aspects is the deployment of a means of drug delivery to the human inner ear. METHODS: The tip of the Contour electrode array was cut to open the lumen of the array, and a connecting piece was developed to connect the electrode to a pump. The feasibility of using the array for drug delivery was tested using both an Alzet mini-osmotic pump and a mechanical pump. The connection was tested for its stability in terms of leakage and resistance to tractive forces. The system was also applied to temporal bones to evaluate its applicability to the human cochlea. RESULTS: The modified Contour electrode is easy to handle in temporal bones and can be used to simulate drug delivery to the inner ear. The connection to the pump was sealed for all tested pump rates and resisted tractive forces up to 50 N. CONCLUSIONS: The described modified electrode could provide a safe and easy-to-handle means of combining electrical stimulation with the beneficial effects of a local drug therapy applied to the inner ear.

Cochlear Implantation↗
PubMed2005

Cerebrospinal fluid otorhinorrhoea due to inner-ear malformations: clinical presentation and new perspectives in management.

OBJECTIVE: In children cerebrospinal fluid (CSF) otorhinorrhoea can be due to congenital inner-ear malformations. Cochlear dysplasia associated with a defect in the stapes footplate is usually the cause of the CSF leak. Repair of the CSF leak in these cases is usually done by packing the vestibule with muscle or fascia. This traditional method of repair has a 30 to 60 per cent failure rate. MATERIAL AND METHODS: CSF otorhinorrhoea due to congenital inner-ear anomalies in four patients was repaired using multiple-layer packing of the vestibule with glue, muscle and fascia, reinforced by a pedicle temporalis muscle graft. Intra-operatively, continous lumbar drainage was performed. RESULTS: Repair of the CSF leak was successful in four cases and no recurrence was noticed. Inner-ear magnetic resonance imaging (MRI) using three-dimensional fast-spin echo (3D FSE) T2-weighted imaging (T2WI) and 3D steady-state free precession (FIESTA) sequences was found to be a very helpful, noninvasive investigation to localize the site and route of the CSF leak. CONCLUSIONS: Children presenting with recurrent meningitis and CSF rhinorrhoea should be investigated for congenital inner-ear anomalies. In these cases CSF fistulae should be repaired using fibrin or cyanoacrylate glue and intra-operative continuous lumbar drainage; 3D FSE T2WI and 3D FIESTA MRI sequences of the inner ear are helpful.

Cerebrospinal Fluid Otorrhea↗
PubMed2003

Optical recordings of Ca2+ signaling activities from identified inner ear cells in cochlear slices and hemicochleae.

One of the major obstacles hindering the progress of studies on mammalian cochlear physiology is the inaccessibility of inner ear cells located in a complex structure of the bony labyrinth. We describe here a technique to record cellular fluorescent signals from any identified inner ear cells in cochlear slices and hemicochleae. Cochlear slices were obtained from postnatal rats (P0-P7) before the cochlea completely ossify, and hemicochleae were cut from older animals (P7-adult). Individual inner ear cells were visually identified using infrared differential interference contrast or oblique illumination optics. Techniques were developed for either bulk-loading cells or loading selected single cells with Ca(2+) indicator dyes, and for maintaining functional viability of cochlear slices/hemicochleae for recordings. Robust and reliable responses of ligand-gated receptors were recorded from individual inner ear cells (e.g. hair cells, spiral ganglion neurons etc.) for at least 24 h after slices/hemicochleae were cut by an oscillating tissue slicer. The technique described here allowed direct observations of [Ca(2+)](i) activities from multiple cells simultaneously in situ, thus providing a feasible way to study the intercellular communication or networking activities from identified cells in the inner ear.

Action Potentials↗
PubMed2006

Embryonic inner ear cells use migratory mechanisms to establish cell patterns in vitro.

The hair cells of the sensory epithelium in the inner ear are among the most precisely organized cells in vertebrates. The mechanisms that lead to this orderly arrangement are only beginning to be understood. It has been suggested that hair cells use migratory mechanisms to help achieve their final position in the organ of Corti. The small size and complex organization of the intact inner ear have made it difficult to monitor changes in hair cell location over time in vivo. In the present study, an established in vitro assay of dissociated, embryonic inner ear cells was used to monitor how hair cells reorganize over time. The hair cell specific marker myosin-VI demonstrated that hair cell precursors from both cochlear and vestibular regions reorganized into specific patterns between 3-24 hr in vitro. In contrast to the unlabeled cells, the myosin-VI-positive cells extended processes while establishing the hair cell patterning within an aggregate. These studies support the hypothesis that hair cell precursors actively migrate to help achieve final patterning within the inner ear sensory epithelium.

Animals↗
PubMed1996

Cell fate specification in the inner ear.

From its origin as a single ectodermal patch, the inner ear becomes a labyrinth of chambers housing six to eight sensory organs. Along the way, specific cell fates are realized. The secrets underlying these cell fate specifications are beginning to be revealed through the application of several molecular-genetic approaches. Recent papers describing such approaches have included gene expression studies in the early otic epithelium and inner ear sensory epithelia. large-scale screens of zebrafish mutants to identify ear defects, and targeted gene perturbations of neurotrophins. of their receptors or of the Brn-3.1 transcription factor in mice.

Animals↗
PubMed2004

From placode to polarization: new tunes in inner ear development.

The highly orchestrated processes that generate the vertebrate inner ear from the otic placode provide an excellent and circumscribed testing ground for fundamental cellular and molecular mechanisms of development. The recent pace of discovery in developmental auditory biology has been unusually rapid, with hundreds of papers published in the past 4 years. This review summarizes studies addressing several key issues that shape our current thinking about inner ear development, with particular emphasis on early patterning events, sensory hair cell specification and planar cell polarity.

Animals↗
PubMed1995

[High resolution MR imaging of the inner ear apparatus using 3D-Fast spin echo sequence].

To evaluate the efficacy of high resolution MR imaging of the inner ear with 3D-Fast spin echo sequence, one volunteer and 12 patients were imaged with a 1.5 T MR scanner. High resolution T2-weighted images were obtained with a head coil in 13 minutes, and the voxel size was 0.39mm x 0.45mm x 1.2mm in most subjects. Original images and maximum intensity projection (MIP) images of the inner ear were evaluated. On original images, the endolymphatic duct was visualized in 72% of subjects, the cochlear aqueduct in 96%, three branches of the cranial nerves in the internal auditory canal in 100%, and flow void of the vessel in the cerebellopontine angle in 100%. On MIP images, more than two cochlear turns were visualized in 92% of subjects, three semicircular canals in 100%, and the anterior and posterior ampulla in 100%. MR imaging of the inner ear with 3D-Fast Spin Echo sequence provides a variety of useful information regarding the anatomy around the inner ear.

Ear, Inner↗
PubMedDate not supplied

Optimization of submillimeter-resolution MR imaging methods for the inner ear.

Submillimeter-resolution magnetic resonance (MR) imaging of the inner ear is valuable for diagnosis and treatment planning. Its main advantage for investigations of underlying disease is that it can directly depict the fluid spaces of the membranous labyrinth rather than define only the bony canal, as does computed tomography. A systematic evaluation of factors influencing high-resolution three-dimensional (3D) gradient-echo imaging of the inner ear with a standard clinical MR system is presented. This includes the evaluation of various radio-frequency coils, the design of steady-state pulse sequences, and the optimization of acquisition parameters. A quantitative analysis was facilitated by computer simulations and image processing. The highest signal-to-noise ratio for the membranous labyrinth was obtained with a single 3-inch (7.6-cm) receiver coil and a 3D GRASS (gradient-recalled acquisition in the steady state) sequence with the minimal achievable TR msec/TE msec of 25/7 and a 40 degrees--60 degrees flip angle, which yielded acceptable images with minimal voxel volumes of 0.1 mm3 in 14 minutes.

Ear, Inner↗
PubMed2000

Virtual endoscopy of the inner ear and the auditory canal.

To assess the role of virtual endoscopy (VE) in the examination of intracisternal structures and of the inner ear, we studied the anatomy of the labyrinth and internal auditory canal using the original CT slices and VE on the unaffected side in three female and three male patients, age range 3-46 years, with contralateral retrocochlear hearing loss. We also examined seven patients with different pathological findings. VE was performed using an advanced postprocessing program with high-resolution 3D data sets of CT (1-1.5 mm thickness, pitch 1.25) and MRI-CISS-3D (constructive interference in steady state) images of the basal cisterns (1.5 T, slice thickness 0.7-1 mm). VE provides an endoscopic-like view from a given point within the basal cisterns of vessels and nerves (on MRI) or of the structures of the inner ear (on CT). The complex anatomy and pathological changes in the inner ear can be faithfully shown. The main advantage is not basic diagnostic information but demonstration of topographically complex situations, such as the canalicular system of the inner ear, for discussion, preoperative planning and teaching.

Adolescent↗
PubMed1976

Histopathologic features of the inner ear associated with Kearns-Sayre syndrome.

We describe the histopathologic features of the inner ear in a 19-year-old girl with bilateral total deafness associated with Kearns-Sayre syndrome. The inner ear shows advanced degree of cochleo-saccular degeneration, with almost complete absence of the organ of Corti in all turns. The spiral ganglion shows a reduction of about 60% to 70% of cells, with almost complete degeneration of nerve fibers in the bony spiral lamina. PAS-positive material was found accumulated in globules between the collapsed Reissner membrane and remains of marginal cells of the stria and in the degenerated sensory cell area of the saccular macula.

Adult↗