BACKGROUND AND OBJECTIVES: Cisplatin is frequently used in the treatment of various forms of malignancies. It's therapeutic efficacy, however, is limited due to the occurrence of sensorineural hearing loss. Little is known about the course of hearing loss after cessation of cisplatin administration. We observed the cochlear duct morphology with normal and cisplatin treated animals. MATERIALS AND METHODS: Healthy rats (strain Sprague-Dawly, weighting 80-100 mg) were used for all experiments. Total 15 rats were selected. They were divided into two groups, a treated group and a control. Four survival groups (n=3, respectively) were assigned as the treated group. After treatment with cisplatin, each survival group was sacrificed 1, 4, 10, 20 days. Except for the normal control (n=3), twelve animals were treated with cisplatin by daily I.P. injection of 1.5 mg/kg for 8 consecutive days. RESULTS: One day after cessation of cisplatin administration, outer hair cells (OHCs) loss and stria vascularis were degenerated especially in the basal turn. At 4, 10, 20 days, the OHCs and stria vascularis morphology of the survival group were similar to those of the survival group at one day. CONCLUSION: Our findings suggest cisplatin ototoxicity is predominantly involved in the basal turn of cochlear duct. This finding was significantly correlated with high frequency hearing loss of cisplatin ototoxicity.
Animals ; Cisplatin* ; Cochlear Duct ; Hair ; Hearing Loss ; Hearing Loss, Sensorineural ; Rats ; Stria Vascularis

BACKGROUND AND OBJECTIVES: Although the role of aquaporin-2 (AQP2) in the kidney has been well defined, its role in the inner ear remains to be determined. The present study was to investigate the effect of water deprivation on the expression of AQP2 in the inner ear. MATERIALS AND METHOD: Healthy male guinea pigs weighing 250 g were used. The experimental group underwent water restriction and the control underwent water loading with sucrose-containing water for 3 days. Concentrations of plasma arginine-vasopressin (AVP) were determined and electrocochleography (ECoG) recordings were made. An RT-PCR, real-time PCR and Westernblotting analysis were used for quantitative analysis of AQP2 mRNA and AQP2 protein expression. Immunohistochemistry was also used to evaluate the distribution of AQP2 water channel proteins in the inner ear. RESULTS: AQP2 was mainly expressed in the epithelium of endolymphatic sac, spiral limbus, spiral ligament and stria vascularis of scala media. The concentrations of plasma AVP were 9.2+/- 0.8 pg/mL in the experimental group and 0.78+/-0.3 pg/mL in the control. The summation potential/ action potential (SP/AP) ratio in ECoG was markedly increased in the experimental group (0.55 in the experimental and 0.29 in the control). RT-PCR and real time PCR as well as Western blot analysis showed that the level of AQP2 mRNA and protein in the cochlea and endolymphactic sac of the water-deprived group was significantly higher than those in the control group. CONCLUSION: These data suggest that AQP2 is one of the important water channels in fluid homeostasis in the inner ear. Moreover, the volume of endolymphatic space can be increased via AVP-AQP2 system in response to water deprivation.
Action Potentials ; Animals ; Aquaporin 2 ; Aquaporins ; Arginine Vasopressin ; Audiometry, Evoked Response ; Blotting, Western ; Cochlea ; Cochlear Duct ; Ear, Inner ; Endolymphatic Hydrops ; Endolymphatic Sac ; Epithelium ; Guinea ; Guinea Pigs ; Homeostasis ; Humans ; Immunohistochemistry ; Kidney ; Male ; Plasma ; Real-Time Polymerase Chain Reaction ; RNA, Messenger ; Spiral Ligament of Cochlea ; Stria Vascularis ; Water Deprivation

BACKGROUND AND OBJECTIVES: Nitric oxide (NO) is an inorganic, gaseous free radical that carries a variety of messages between cells. The histochemical demonstration of neuronal betaNADPH-d is the demonstration of the presence of NOS. The purpose of this study was to identify the existence of NOS and the difference of the expression of betaNADPH-d in mouse and gerbil cochleae. MATERIALS AND METHODS: Each of the eight cochleae of Mongolian gerbil (Meriones unguiculatus) and mice (CJU/A) were fixed by cardiac perfusion with 4% paraformaldehyde in 0.1M phosphate buffer solution. The en-bloc cochleae were incubated after decalcification, and stained with betaNADPH-d and counterstained with acid fuchsin. The relative intensity of staining was decided in the same location of cochlea. RESULTS: Most supporting cells were strongly stained except Claudius cells and Boettcher's cells in gerbil. However, Boettcher's cells were strongly stained in mice. Outer hair cells, inner hair cells, basial membrane and lining cells of spiral limbus were strongly stained. Interdental cells of spiral limbus, inner border cells and intermediate cells of stria vascularis were moderately stained. Tectorial membrane and amorphous layer of basial membrane were not stained. CONCLUSION: Using betaNADPH-d staining, this study documents the presence of nitric oxide synthase in mice and gerbil cochleae and the difference of staining between two species.
Animals ; Cochlea* ; Gerbillinae* ; Hair ; Membranes ; Mice* ; Neurons ; Nitric Oxide ; Nitric Oxide Synthase ; Perfusion ; Rosaniline Dyes ; Stria Vascularis ; Tectorial Membrane

No abstract available.
Stria Vascularis*

Cochlea ; Humans ; Macrophages ; Stria Vascularis

Mass and stiffness affect on the peculiar characteristics of transmission of the middle ear and the distinctive behavior of the cochlear mechanics. Applying the principle of the mass and stiffness, the band-pass characteristic transfer function of the middle ear has been explained. The greatest transfer function of the middle ear, approximately 24-29 dB, is observed at 1-2 kHz in both cat and human species. However, at lower frequencies, the transfer function was disturbed by the stiffness of the middle ear primarily due to middle ear cavity. At higher frequencies, the transfer function was disturbed by the stiffness of the middle ear primarily due to middle ear bones. Several examples, such as an acoustic reflex, otitis media, and otosclerosis are discussed. For understanding the traveling wave of the basilar membrane, different place tuning at certain stimulus frequencies, contrastingly shaped basilar membrane to the cochlear duct, and the structural and physical characteristics of the whole cochlear partition were reviewed in terms of changing width, mass, and stiffness from the base to apex. Being about ten times wider, more massive, and one hundredfold stiffer at the base than the apex, the nature of the cochlear partition to absorb high-frequency energy changes in fluid pressure declines toward the apex. Consequently, at the base of the cochlea, high frequencies stimuli are decoded while low frequencies stimuli are decoded at the apex of the cochlea. Due to these characteristics of the cochlear partition, the direction of the traveling wave was also proved to be in the fashion of base-to-apex always.
Animals ; Basilar Membrane ; Cats ; Cochlea ; Cochlear Duct ; Ear, Middle* ; Humans ; Mechanics ; Otitis Media ; Otosclerosis ; Reflex, Acoustic

The ability of to discern distinct sound frequencies is attributed to frequency specificity in various locations in the auditory pathway. The cochlear duct is tonotopically organized along its longitudinal axis so that the basal turn responds to high frequency and the apical turn to low frequency sounds. Since the cochlear duct is comprised of heterogeneous components including sensory hair cells, neurons and other cellular and acellular components, integration of their diverse features is essential for establishment of tonotopicity. Recent studies aim to investigate the molecular mechanisms responsible for the cochlear tonotopicity.
Auditory Pathways ; Axis, Cervical Vertebra ; Cochlear Duct ; Hair ; Neurons ; Sensitivity and Specificity

PURPOSE: To evaluate the CT and MRI findings of the large endolymphatic duct or sac syndrome (LEDS) and its associated anomalies, with clinical features. MATERIALS AND METHODS: We retrospectively reviewed the MR and CT images of 52 ears obtained from 26 patients with LEDS. We reviewed the clinical findings, audiology testing, and treatment results. The degree of hearing loss was classified from normal to profound, based on pure tone audiometry. The largest areas were measured at each endolymphatic duct and analyzed to determine whether a correlation exists with the degree of hearing loss. We also analyzed the differences in measurements between CT and MRI findings. RESULTS: All 26 patients had some degree of sensorineural hearing loss, which resulted in 18 ears to undergo a cochlear implantation. One patient was diagnosed with Cornelia de Lange syndrome. Five patients had a sudden hearing loss onset. Ten ears had incomplete cochlear partitions, whereas 28 ears had enlarged vestibules. All patients had severe to profound hearing loss. We found no statistical correlation between the size of the largest area of the endolymphatic duct and the degree of hearing loss. The mean area of the endolymphatic ducts, as per an MRI examination, revealed slightly greater areas than the CT findings, although the differences were not significant. CONCLUSION: Enlarged vestibules and incomplete partitions of the cochlea were common anomalies associated with LEDS. We found no statistical correlation between the largest area of the endolymphatic duct or sac with the degree of hearing loss.
Audiology ; Audiometry ; Cochlea ; Cochlear Implantation ; Cochlear Implants ; De Lange Syndrome ; Ear ; Ear, Inner ; Endolymphatic Duct ; Hearing Loss ; Hearing Loss, Sensorineural ; Hearing Loss, Sudden ; Humans ; Retrospective Studies

The inner ear is composed of a cochlear duct and five vestibular organs in which mechanosensory hair cells play critical roles in receiving and relaying sound and balance signals to the brain. To identify novel genes associated with hair cell differentiation or function, we analyzed an archived gene expression dataset from embryonic mouse inner ear tissues. Since atonal homolog 1a (Atoh1) is a well known factor required for hair cell differentiation, we searched for genes expressed in a similar pattern with Atoh1 during inner ear development. The list from our analysis includes many genes previously reported to be involved in hair cell differentiation such as Myo6, Tecta, Myo7a, Cdh23, Atp6v1b1, and Gfi1. In addition, we identified many other genes that have not been associated with hair cell differentiation, including Tekt2, Spag6, Smpx, Lmod1, Myh7b, Kif9, Ttyh1, Scn11a and Cnga2. We examined expression patterns of some of the newly identified genes using real-time polymerase chain reaction and in situ hybridization. For example, Smpx and Tekt2, which are regulators for cytoskeletal dynamics, were shown specifically expressed in the hair cells, suggesting a possible role in hair cell differentiation or function. Here, by reanalyzing archived genetic profiling data, we identified a list of novel genes possibly involved in hair cell differentiation.
Animals ; Brain ; Cell Differentiation ; Cochlear Duct ; Ear, Inner ; Gene Expression ; Hair ; In Situ Hybridization ; Mice ; Real-Time Polymerase Chain Reaction

Endolymphatic hydrops (EH) represents a histopathologic finding in which the structures bounding the endolymphatic space are distended by an enlargement of endolymphatic volume. EH primarily involves the cochlear duct and saccule but can involve the utricle and ampullae of the semicircular canals. EH is a consistent finding in patients with Meniere's disease, however, the reverse is not true. EH may occur as a consequence of a variety of disorders, including DFNA 9, Alport syndrome, serous labyrinthitis, suppurative labyrinthitis, otosyphilis, temporal bone fracture, surgical trauma, neoplasm, immune disorders, otosclerosis, or Paget's disease. The mechanism of development of hydrops is also unclear. This review provides information to understand the recent pathophysiologic mechanism and causal disoders in EH.
Cochlear Duct ; Ear, Inner ; Edema ; Endolymphatic Hydrops ; Humans ; Immune System Diseases ; Labyrinthitis ; Meniere Disease ; Nephritis, Hereditary ; Otosclerosis ; Saccule and Utricle ; Semicircular Canals ; Temporal Bone