Distribution of aspartate and glutamate in cochlear nucleus (CN) following destruction of organ of Corti (OC)

Noise-induced hearing loss (NIHL) can lead to secondary changes that induce neural plasticity in the central auditory pathway. These changes include decreases in the number of synapses, the degeneration of auditory nerve fibers, and reorganization of the cochlear nucleus (CN) and inferior colliculus (IC) in the brain. This study investigated the role of microRNAs (miRNAs) in the neural plasticity of the central auditory pathway after acute NIHL. Male Sprague–Dawley rats were exposed to white band noise at 115 dB for 2 h, and the auditory brainstem response (ABR) and morphology of the organ of Corti were evaluated on days 1 and 3. Following noise exposure, the ABR threshold shift was significantly smaller in the day 3 group, while wave II amplitudes were significantly larger in the day 3 group compared to the day 1 group. The organ of Corti on the basal turn showed evidence of damage and the number of surviving outer hair cells was significantly lower in the basal and middle turn areas of the hearing loss groups relative to controls. Five and three candidate miRNAs for each CN and IC were selected based on microarray analysis and quantitative reverse transcription PCR (RT-qPCR). The data confirmed that even short-term acoustic stimulation can lead to changes in neuroplasticity. Further studies are needed to validate the role of these candidate miRNAs. Such miRNAs may be used in the early diagnosis and treatment of neural plasticity of the central auditory pathway after acute NIHL.

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Carcinomatous Encephalomyelitis with Auditory and Vestibular Manifestations

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348947608500121 ◽

1976 ◽

Vol 85 (1) ◽

pp. 120-126 ◽

Cited By ~ 4

Author(s):

Trevor McGill

Keyword(s):

Cochlear Nucleus ◽

Stria Vascularis ◽

Neuronal Loss ◽

Organ Of Corti ◽

Sensory Neuropathy ◽

Pathological Study ◽

Striking Change ◽

Oat Cell Carcinoma ◽

Cochlear Neurons ◽

Microglial Response

A clinical and pathological study of carcinomatous encephalomyelitis is presented. Attention is drawn to the various types of nonmetastatic paraneoplastic syndromes and their particular association with oat cell carcinoma of the lung. The feature of special interest in this study is the onset with otologic symptoms, sudden deafness in the left ear and vertigo, at a time when the neoplastic basis for the disease was not clinically evident. The most striking change in the left temporal bone is the almost total loss of cochlear neurons in Rosenthal's canal and degeneration of both divisions of the vestibular nerve. The organ of Corti and stria vascularis are normal throughout the cochlear duct. The vestibular sense organs are normal. The left cochlear nucleus is devoid of neurons, this neuronal loss is accompanied by a well developed astrocytic and microglial response similar to that in the medulla and spinal cord. This represents a carcinomatous sensory neuropathy involving the left VIII nerve with simultaneous involvement of the left cochlear nucleus. The pathogenesis of this condition still defies explanation, but there are some insights in the autoimmune sector.

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A technique for protecting delicate specimens during processing

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100156894 ◽

1989 ◽

Vol 47 ◽

pp. 982-983

Author(s):

R.J. Mount ◽

R.V. Harrison

Keyword(s):

Basilar Membrane ◽

Low Cost ◽

Organ Of Corti ◽

Region Of Interest ◽

Sensory Epithelium ◽

Physical Damage ◽

Air Drying ◽

Specimen Handling ◽

Two Component

The sensory end organ of the ear, the organ of Corti, rests on a thin basilar membrane which lies between the bone of the central modiolus and the bony wall of the cochlea. In vivo, the organ of Corti is protected by the bony wall which totally surrounds it. In order to examine the sensory epithelium by scanning electron microscopy it is necessary to dissect away the protective bone and expose the region of interest (Fig. 1). This leaves the fragile organ of Corti susceptible to physical damage during subsequent handling. In our laboratory cochlear specimens, after dissection, are routinely prepared by the O-T- O-T-O technique, critical point dried and then lightly sputter coated with gold. This processing involves considerable specimen handling including several hours on a rotator during which the organ of Corti is at risk of being physically damaged. The following procedure uses low cost, readily available materials to hold the specimen during processing ,preventing physical damage while allowing an unhindered exchange of fluids.Following fixation, the cochlea is dehydrated to 70% ethanol then dissected under ethanol to prevent air drying. The holder is prepared by punching a hole in the flexible snap cap of a Wheaton vial with a paper hole punch. A small amount of two component epoxy putty is well mixed then pushed through the hole in the cap. The putty on the inner cap is formed into a “cup” to hold the specimen (Fig. 2), the putty on the outside is smoothed into a “button” to give good attachment even when the cap is flexed during handling (Fig. 3). The cap is submerged in the 70% ethanol, the bone at the base of the cochlea is seated into the cup and the sides of the cup squeezed with forceps to grip it (Fig.4). Several types of epoxy putty have been tried, most are either soluble in ethanol to some degree or do not set in ethanol. The only putty we find successful is “DUROtm MASTERMENDtm Epoxy Extra Strength Ribbon” (Loctite Corp., Cleveland, Ohio), this is a blue and yellow ribbon which is kneaded to form a green putty, it is available at many hardware stores.

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Hair cell changes after cationic stimulation of corti's organ

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100155967 ◽

1989 ◽

Vol 47 ◽

pp. 798-799

Author(s):

Cesar D. Fermin ◽

Hans-Peter Zenner

Keyword(s):

Organ Of Corti ◽

Cross Sectional ◽

Surface Areas ◽

High K ◽

Anatomical Arrangement ◽

Cell Cytosol ◽

High Concentrations ◽

K Concentration ◽

Cell Changes

Contraction of outer and inner hair cells (OHC&IHC) in the Organ of Corti (OC) of the inner ear is necessary for sound transduction. Getting at HC in vivo preparations is difficult. Thus, isolated HCs have been used to study OHC properties. Even though viability has been shown in isolated (iOHC) preparations by good responses to current and cationic stimulation, the contribution of adjoining cells can not be explained with iOHC preparations. This study was undertaken to examine changes in the OHC after expossure of the OHC to high concentrations of potassium (K) and sodium (Na), by carefully immersing the OC in either artifical endolymph or perilymph. After K and Na exposure, OCs were fixed with 3% glutaraldehyde, post-fixed in osmium, separated into base, middle and apex and embedded in Araldite™. One μm thick sections were prepared for analysis with the light and E.M. Cross sectional areas were measured with Bioquant™ software.Potassium and sodium both cause isolated guinea pig OHC to contract. In vivo high K concentration may cause uncontrolled and sustained contractions that could contribute to Meniere's disease. The behavior of OHC in the vivo setting might be very different from that of iOHC. We show here changes of the cell cytosol and cisterns caused by K and Na to OHC in situs. The table below shows results from cross sectional area measurements of OHC from OC that were exposed to either K or Na. As one would expect, from the anatomical arrangement of the OC, OHC#l that are supported by rigid tissue would probably be displaced (move) less than those OHC located away from the pillar. Surprisingly, cells in the middle turn of the cochlea changed their surface areas more than those at either end of the cochlea. Moreover, changes in surface area do not seem to differ between K and Na treated OCs.

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