Nitric oxide (NO) has been implicated as a mediator of vasodilation and neurotransmission in the mammalian cochlea. This is demonstrated by the presence of nitric oxide synthase (NOS) and nitric oxide (NO) in the blood vessels and the organ of Corti in the cochlea. It is not certain if the neurons in the spiral ganglion produce NO since no fluorescent signal could be detected by 4,5-diaminofluorescein diacetate (DAF-2DA), a fluorescent indicator of NO. To determine if NO/peroxynitrite plays any role in neurodestruction observed in ischemic cochlea of the guinea pig, the effects of NO donors, such as S-nitrosocysteine (S-NC) and nitroglycerine (NTG); peroxynitrite generators, such as 3-morpholinosydnonimine (SIN-1); peroxynitrite inhibitors, such as superoxide dismutase plus catalase (SOD/Cat); and NOS inhibitors, such as NG-nitro-L-arginine methyl ether (L-NAME) were tested on normal and ischemic cochleae. The level of NO in the cochlea after 20 to 120 minutes of ischemia was indicated by ...
TY - JOUR. T1 - Intra-tympanic delivery of short interfering RNA into the adult mouse cochlea. AU - Oishi, Naoki. AU - Chen, Fu Quan. AU - Zheng, Hong Wei. AU - Sha, Su Hua. PY - 2013/2/1. Y1 - 2013/2/1. N2 - Trans-tympanic injection into the middle ear has long been the standard for local delivery of compounds in experimental studies. Here we demonstrate the advantages of the novel method of intra-tympanic injection through the otic bone for the delivery of compounds or siRNA into the adult mouse cochlea. First, a fluorescently-conjugated scrambled siRNA probe was applied via intra-tympanic injection into the middle ear cavity and was detected in sensory hair cells and nerve fibers as early as 6 h after the injection. The fluorescent probe was also detected in other cells of the organ of Corti, the lateral wall, and in spiral ganglion cells 48 h after the injection. Furthermore, intra-tympanic delivery of Nox3 siRNA successfully reduced immunofluorescence associated with Nox3 in outer hair ...
In the chicken basilar papilla it has been reported that overexpression of activated β-catenin induces ectopic HC formation (Stevens et al., 2003) and, more recently, it has been shown that canonical Wnt activation can induce proliferation within dissociated epithelial cells of the avian utricle (Alvarado et al., 2011). The role for this pathway during mammalian cochlear development, however, was unknown. Although multiple transgenic canonical Wnt reporter mice have been generated (listed on the Wnt homepage http://www.stanford.edu/group/nusselab/cgi-bin/wnt/), inconsistencies existed as to the exact spatiotemporal pattern of endogenous Wnt/β-catenin activity (Barolo, 2006). In the inner ear, Qian et al. (Qian et al., 2007) reported no Wnt/β-catenin activity in the otocyst and developing cochlea using the BAT-gal mouse (Maretto et al., 2003), whereas Laine et al. (Laine et al., 2010) identified low-level activity in cochleae of the same BAT-gal strain as well as in the TOP-gal reporter ...
Authors: Suh, Myung Whan , Shin, Dong Hoon , Lee, Ho Sun , Park, Ji Yeong , Kim, Chong Sun , Oh, Seung Ha Article Type: Research Article Abstract: Unlike mammals, avian cochlear hair cells can regenerate after acoustic overstimulation. The WDR1 gene is one of the genes suspected to play an important role in this difference. In an earlier study, we found that the WDR1 gene is over-expressed in the chick cochlea after acoustic overstimulation. The aim of this study was to compare the expression of WDR1 before and after acoustic overstimulation in the chick vestibule. Seven-day-old chicks were divided into three groups: normal …group, damage group, and regeneration group. The damage and regeneration group was exposed to 120 dB SPL white noise for 5-6 hours. The damage group was euthanized shortly after the impulse, but the regeneration group was allowed to recover for 2 days. The utricle, saccule, and the three ampullae of each semicircular canal were dissected and immunohistochemically stained ...
By using a device that provides high-resolution images of the inner ear, researchers are learning about the mechanics of hearing. In order to develop therapies for hearing loss, its important to understand the functions of different areas of the cochlea, and until now, that hasnt been very easy.. Because the cochlea is so small and difficult to access, researchers havent been able to study it very easily without causing damage to the ear. But by using this technology (OCT, or optical coherence tomography), researchers at Texas A&M and Stanford have been able to gather information about the way the cochlea converts vibrations into nerve impulses to create sound without having to open the bone around it.. The concept has been proven in mice, and researchers have been able to gather measurements without causing any damage to the mouse cochlea or surrounding tissues. A prototype device has been developed for human use. If researchers can map the human cochlea and determine what happens to the ...
Maturation of neurotransmission in the developing rat cochlea: immunohistochemical evidence from differential expression of synaptophysin and synaptobrevin 2
Cochlea: The cochlea contains the sensory organ of hearing. It bears a striking resemblance to the shell of a snail and in fact takes its name from the Greek word for this object. The cochlea is a spiral tube that is…
By using a device that provides high-resolution images of the inner ear, researchers are learning about the mechanics of hearing. In order to develop therapies for hearing loss, its important to understand the functions of different areas of the cochlea, and until now, that hasnt been very easy.. Because the cochlea is so small and difficult to access, researchers havent been able to study it very easily without causing damage to the ear. But by using this technology (OCT, or optical coherence tomography), researchers at Texas A&M and Stanford have been able to gather information about the way the cochlea converts vibrations into nerve impulses to create sound without having to open the bone around it.. The concept has been proven in mice, and researchers have been able to gather measurements without causing any damage to the mouse cochlea or surrounding tissues. A prototype device has been developed for human use. If researchers can map the human cochlea and determine what happens to the ...
The risks and efficacy of transplanting two varieties of stem cells into mouse cochlea have been evaluated by Japanese researchers.
The cochlea is a fluid-filled structure in the middle ear. The sound waves are translated to fluid waves in the cochlea that are then sensed by nerves connected to fine hairs that float in the fluid and is then sent on to the brain for interpretation. This is the area that a human "cochlear implant" stimulates to help correct hearing loss. The feline cochlea has 3 complete turns while the human cochlea only has 2.75 turns. They have 10,000 more auditory nerves than humans. Near the cochlea is another fluid- and carbonate crystal-filled structure called the vestibular apparatus that is in charge of balance.. Cats are exquisitely adept at locating prey. They can distinguish between two different sound sources 8 cm apart (shorter than the length of an iPhone) at 2 yards and 40cm apart (about 1 foot, or a little longer than 3 iPhones) at 20 yards. They can hear a rustling mouse 20-30 yards away. They can hear 10 distinct octaves of notes vs. humans 8.5 octaves. They even hear one octave above their ...
You may find this publication the answer to your problems. Brain Research Protocols Volume 6, Issue 3, February 2001, Pages 159-166 Cryoembedding and sectioning of cochleas for immunocytochemistry and in situ hybridization Donna S. Whitlon, Renee Szakaly, Mary A. Greiner Abstract Current emphasis on biochemical and molecular aspects of cochlear anatomy underscores the necessity for high quality cryostat sections of the inner ear. The large volume of fluid space within the cochlea makes cryoembedding and sectioning of the organ more problematic than that of other, more homogeneous tissues. Our method for cryoembedding of cochleas for immunocytochemistry and in situ hybridization uses slow infiltration with increasing concentrations of sucrose followed by degassed embedding medium before final orientation and freezing. This method permits high quality cryosections to be cut which preserve overall structure and cellular resolution. Author Keywords: Cryosections; Cochlea; Immunocytochemistry; In ...
The cochlea receives its main blood supply from the basilar artery, via the anterior inferior cerebellar artery and the spiral modiolar artery. It is of clinica...
The observed disorganization and expansion of the organ of Corti, in addition to the proliferation following ectopic β-catenin activation, suggested changes in the adhesion complexes within the epithelium. In addition to roles in proliferation and differentiation, β-catenin plays a role in cell adhesion by binding to the cytoplasmic tail of cadherins at the plasma membrane (Ozawa et al., 1989). Similar to β-catenin, E-cadherin is expressed within the cell membranes of the cochlear sensory epithelium (Whitlon, 1993; Leonova and Raphael, 1997; Simonneau et al., 2003). When we overexpressed β-catenin in the cochlea after initiation of tamoxifen at E13.5 in the Sox2-CreER;β-cateninflox(exon3) mouse, elongation of the sensory epithelium proceeded into the apical region (Fig. 8A) as expected, and staining for EdU as well as Ki67, a cell proliferation marker, were observed (Fig. 8B), but E-cadherin expression within the cell membranes was decreased (Fig. 8C,E). The cochlea contained multiple rows ...
Our aims are to identify the molecular mechanisms that regulate the expression of Fgf20 during the embryonic development of the cochlea; to determine how FGF20 regulates sensory progenitor cell growth and the differentiation of cochlear outer hair and supporting cells in the organ of Corti; and to identify the specific genes and pathways that act downstream of FGF20 during cochlear development using Next Gen mRNA sequencing. We are testing the hypothesis that FGF signaling can enhance sensory cell regeneration following ototoxic damage.. 2. Regulation of neuronal excitability by intracellular FGFs.. We are studying a unique subfamily of FGFs that act intracellularly (iFGFs) in neurons and cardiomyocytes and that are important for regulating cell excitability through interactions with voltage gated sodium channels. Disruption of FGF14, one of four iFGFs, results in an anatomically normal mouse with severe neurobehavioral phenotypes including ataxia, seizure, paroxysmal dystonia and cognitive ...
Sounds pass from the outer ear through to the inner ear, which contains the cochlea and auditory nerve. The cochlea is a coiled, spiral tube containing a large number of sensitive hair cells. The auditory nerve transmits sound signals to the brain.. If part of the cochlea is damaged, it will stop sending information to your brain. The brain may then actively "seek out" signals from parts of the cochlea that still work. These signals might then become over-represented in the brain, which may cause the sounds of tinnitus.. In older people, damage to the cochlea often occurs naturally with age. In younger people, it can be caused by repeated exposure to excessive noise.. ...
Sounds pass from the outer ear through to the inner ear, which contains the cochlea and auditory nerve. The cochlea is a coiled, spiral tube containing a large number of sensitive hair cells. The auditory nerve transmits sound signals to the brain.. If part of the cochlea is damaged, it will stop sending information to your brain. The brain may then actively "seek out" signals from parts of the cochlea that still work. These signals might then become over-represented in the brain, which may cause the sounds of tinnitus.. In older people, damage to the cochlea often occurs naturally with age. In younger people, it can be caused by repeated exposure to excessive noise.. ...
Figure 1. Vangl2 is asymmetrical localized in the organ of Corti. A, Schematic diagram illustrating a surface view of the OC in the mammalian cochlea. Proximal-to-distal and basal-to-apical axes are indicated. The OC comprises a single row of IHCs and three rows of OHCs (O1-O3) that extend along the basal-to-apical axis. Individual hair cells are separated by specific types of supporting cells including IPh cells located between IHCs, Deiters cells (D1-D3), located between OHCs and OPs, located between OHCs in OHC1 and IPs, which create a space between the row of IHC and OHC1. Finally, the proximal edge of IHCs is contacted by a row of border cells (BC). Each HC has a stereociliary bundle (red) located on its lumenal surface. Each bundle is oriented such that its central vertex is located closest to the distal edge of the epithelium. B, Affinity-purified Vangl2 antibody recognizes a band ∼65 kDa in lysates from HEK293 transfected with an untagged Vangl2 construct (lane 1), cochlea (lane2), and ...
Eight patients implanted with multiple-channel cochlear prostheses have displayed good discrimination of sound sensations elicited at different sites within the cochlea. All patients rank the sensations from "sharp" to "dull" in an order which corresponds with basal to apical position in the cochlea. Detailed psychophysical studies have been carried out on two patients. These showed that discrimination of rate of (pulsatile) stimulation is good for frequencies up to 300 Hz and falls off sharply for frequencies above this. Electrode transitions (changes in position along the cochlea) are well discriminated for fast changes (25 msec), whereas rate transitions are not well discriminated for changes faster than 100 msec. From these results a speech processing strategy was formulated where second formant information is mapped to position in the cochlea and fundamental frequency mapped to rate of stimulation. Vowel and consonant confusion studies show consistent results for all patients using this ...
The avian cochlea has a remarkable ability to regenerate sensory hair cells after injury, and a major goal of our research is to understand the molecular basis of this regenerative process. An ongoing study, conducted in collaboration with the Lovett lab (Dept. of Genetics), is using Next-Gen sequencing to profile the transcriptome of the chick cochlea throughout the time course of regeneration. Additional data suggest that the lack of FGF signaling in the mature mammalian ear may be one factor that limits regenerative ability in mammals. We are presently collaborating with the Orntiz lab (Dept. of Developmental Biology) to determine whether reactivating FGF signaling in the injured mouse cochlea can evoke some degree of sensory repair ...
Department of Physiology, Medical School, University Walk, Bristol. 1. Outer hair cells from the cochlea of the guinea-pig were isolated and their motile properties studied in short-term culture by the whole-cell variant of the patch recording technique. 2. Cells elongated and shortened when subjected to voltage steps. Cells from both high- and low-frequency regions of the cochlea responded with an elongation when hyperpolarized and a shortening when depolarized. The longitudinal motion of the cell was measured by a differential photosensor capable of responding to motion frequencies 0-40 kHz. 3. Under voltage clamp the length change of the cell was graded with command voltage over a range +/- 2 microns (approximately 4% of the length) for cells from the apical turns of the cochlea. The mean sensitivity of the movement was 2.11 nm/pA injected current, or 19.8 nm/mV membrane polarization. 4. The kinetics of the cell length change during a voltage step were measured. Stimulated at their basal end, ...
Chris - We all take our ears for granted, I think. How do they actually work?Bob - Basically, sound is vibration in the air and it is picked up by the floppy bit on the side of your head. This is called the pinna. Sound is then transmitted to the inner ear, inside of which theres a membrane which is thin and stiff at one end and wobbly at the other end. The thin, stiff bit
J:173382 Basch ML, Ohyama T, Segil N, Groves AK, Canonical Notch Signaling Is Not Necessary for Prosensory Induction in the Mouse Cochlea: Insights from a Conditional Mutant of RBPj{kappa}. J Neurosci. 2011 Jun 1;31(22):8046-58 ...
In chapter 3, "The Sense of Sensibility," author Wendy Jones uses scenes from one of Jane Austens most celebrated novels to illustrate the functioning of the bodys stress response system.. 0 Comments. ...
In chapter 3, "The Sense of Sensibility," author Wendy Jones uses scenes from one of Jane Austens most celebrated novels to illustrate the functioning of the bodys stress response system.. 0 Comments. ...
Subject: Re: physiological or ecological basis of auditory sharpness From: Eckard Blumschein ,Eckard.Blumschein(at)E-TECHNIK.UNI-MAGDEBURG.DE, Date: Tue, 17 Sep 2002 08:15:58 +0200 Yes, undoubtedly, high CFs are required for localization. I would like to mention a nice tutorial by Duda: http://www-engr.sjsu.edu/~knapp/HCIROD3D/3D_psych/reverb.htm He includes an explanation of IED (interaural envelope delay) and Franssen effect, and he summarizes: With some risk of oversimplification, we can generalize and say that in reverberant environments it is the high-frequency energy, not the low-frequency energy, that is important for localization. The question was: What might be the basis of (the extremely unpleasant) auditory sharpness evoked by spectral components... As we understand from the tutorial, the basal turn of cochlea is designed for localization of single events like clicks or bat calls rather than for recognition of any continuous tone. Maybe, Duda intentionally wrote high-frequency ...
Theres much more to our ears than meets the eye! The human ear contains a chain of important links that work together to help us hear the world around us. From the ears tiny bones to its fluid-filled cochlea, each part is important. In this title, young readers will learn about the small wonders inside the human ear.
TY - JOUR. T1 - Do "optimal" conditions improve distortion product otoacoustic emission test performance?. AU - Kirby, Benjamin J.. AU - Kopun, Judy G.. AU - Tan, Hongyang. AU - Neely, Stephen T.. AU - Gorga, Michael P.. PY - 2011/3. Y1 - 2011/3. N2 - OBJECTIVES: To determine whether an "optimal" distortion product otoacoustic emission (DPOAE) protocol that (1) used optimal stimulus levels and primary-frequency ratios for each f2, (2) simultaneously measured 2f2 - f1 and 2f1 - f2 distortion products, (3) controlled source contribution, (4) implemented improved calibration techniques, (5) accounted for the influence of middle ear reflectance, and (6) applied multivariate analyses to DPOAE data results in improved accuracy in differentiating between normal-hearing and hearing-impaired ears, compared with a standard clinical protocol. DESIGN: Data were collected for f2 frequencies ranging from 0.75 to 8 kHz in 28 normal-hearing and 78 hearing-impaired subjects. The protocol included a control ...
TY - JOUR. T1 - Regeneration of Stereocilia of Hair Cells by Forced Atoh1 Expression in the Adult Mammalian Cochlea. AU - Yang, Shi Ming. AU - Chen, Wei. AU - Guo, Wei Wei. AU - Jia, Shuping. AU - Sun, Jian He. AU - Liu, Hui Zhan. AU - Young, Wie Yen. AU - He, David Z.Z.. PY - 2012/9/27. Y1 - 2012/9/27. N2 - The hallmark of mechanosensory hair cells is the stereocilia, where mechanical stimuli are converted into electrical signals. These delicate stereocilia are susceptible to acoustic trauma and ototoxic drugs. While hair cells in lower vertebrates and the mammalian vestibular system can spontaneously regenerate lost stereocilia, mammalian cochlear hair cells no longer retain this capability. We explored the possibility of regenerating stereocilia in the noise-deafened guinea pig cochlea by cochlear inoculation of a viral vector carrying Atoh1, a gene critical for hair cell differentiation. Exposure to simulated gunfire resulted in a 60-70 dB hearing loss and extensive damage and loss of ...
TY - JOUR. T1 - Electrically stimulated increases in cochlear blood flow. T2 - I. frequency and intensity effects. AU - Sillman, Jonathon S.. AU - LaRouere, Michael J.. AU - Masta, Robert I.. AU - Miller, Josef M.. AU - Nuttall, Alfred L.. PY - 1989/4. Y1 - 1989/4. N2 - Charge-balanced, sinusoidal current was passed differentially between the apex and round window of the guinea pig cochlea. Cochlear blood flow was measured using a laser Doppler flow monitor. Systemic blood pressure was monitored from a cannula within the common carotid artery. Electrical stimulation increased cochlear blood flow, while systemic blood pressure was unaffected. A cochlear blood flow response parameter, normalized for transient changes in systemic blood pressure, was defined. The magnitude of the response parameter was found to be frequency selective and was also found to be an increasing function of current intensity, with maximum responses obtained with 500 Hz sinusoids. This cochlear blood flow response was not ...
Auditory hair cells are the sensory cells that transduce sound waves into electric signals, and are located in the cochlea, the organ responsible for hearing, in the inner ear. The loss of the hair cells is the leading cause of hearing impairment. The mammalian cochlea cannot regenerate its complement of mature hair cells and therefore hearing impairment caused by hair cell loss is difficult to cure. The developmental process of cochlea, including hair cells, is complex and has not been sufficiently elucidated yet. A better understanding of it would provide clues that could lead to new strategies for hair cell regeneration. The mammalian cochlea is highly developed and hair cells are regularly arranged in rows. Research on cochlear development has shown that the cochlea is highly sensitive to disorders caused by abnormal cellular differentiation and tissue organization. This seminar will present our research on mammalian cochlear development and to discuss the approach to hair cell ...
TY - JOUR. T1 - Targeted PCR Array Analysis of Genes in Innate Immunity and Glucocorticoid Signaling Pathways in Mice Cochleae Following Acoustic Trauma. AU - Maeda, Yukihide. AU - Kariya, Shin. AU - Omichi, Ryotaro. AU - Noda, Yohei. AU - Sugaya, Akiko. AU - Fujimoto, Shohei. AU - Nishizaki, Kazunori. PY - 2018/8/1. Y1 - 2018/8/1. N2 - Aim: To comprehensively analyze cochlear gene expressions related to innate immunity and glucocorticoid signaling at onset of acute noise-induced hearing loss (NIHL). Background: Recent studies suggested innate immunity is involved in the cochlear pathology of NIHL. Glucocorticoids may modulate immune actions in cochleae. Methods: Mice were exposed to 120 dB-octave band noise for 2 hours. Twelve hours later, a targeted PCR array analyzed cochlear expressions of 84 key genes in inflammation and immune pathways and 84 genes in the glucocorticoid signaling pathway. Real-time RT-PCR was used to analyze expression of two immune-related genes, Ccl12 and Glycam1, in ...
Afferent synapses between inner hair cells (IHCs) and spiral ganglion neurons in the cochlea translate sound information into a discrete spike code, providing us the opportunity to directly observe the output of the cochlea. The availability of mutant strains with genetic hearing impairment makes the mouse a valuable species to investigate the molecular mechanisms of cochlear function. In this thesis, mouse was used as a model species to study cochlear sound encoding by recording single unit activities from auditory nerve fibers (ANFs) in vivo. First, developmental changes of ANF responses before and after hearing onset were characterized as an introduction on how normal ANF responses mature during the early postnatal age. Spontaneous bursting activity from ANFs/cochlear nucleus neurons was observed before hearing onset. After hearing onset, the average spontaneous and evoked spike rates of single ANFs increased, while tuning threshold and frequency selectivity improved between p14-15 to p20-21. ...
Our knowledge of the fine structure of the Human Spiral Ganglion (HSG) is still inadequate and new treatment techniques for deafness using electric stimulation, call for further information and studies on the neuronal elements of the human cochlea. This thesis presents results of analyses of human cochlear tissue and specimens obtained during neurosurgical transpetrosal removal of life-threatening meningeomas. The use of surgical biopsies produced a well-preserved material suitable for ultrastructural and immunohistochemical studies on the human inner ear. The SG was studied with respect to fine structure, using TEM technique and the immunostaining pattern of synaptophysin, which is an integral membrane protein of neuronal synaptic vesicles. The immunostaining patterns of the tight junctional protein ZO-1 and the gap junctional proteins Cx26 and Cx43 in the human cochlea were also studied. The ultrastructural morphology revealed an absence of myelination pattern in the HSG, thus differing from ...
The mechanism of hearing loss arises from trauma to stereocilia of the cochlea, the principal fluid filled structure of the inner ear. The pinna combined with the middle ear amplifies sound pressure levels by a factor of twenty, so that extremely high sound pressure levels arrive in the cochlea, even from moderate atmospheric sound stimuli. Underlying pathology to the cochlea are reactive oxygen species, which play a significant role in noise-induced necrosis and apoptosis of the stereocilia. Exposure to high levels of noise have differing effects within a given population, and the involvement of reactive oxygen species suggests possible avenues to treat or prevent damage to hearing and related cellular structures.. The elevated sound levels cause trauma to the cochlear structure in the inner ear, which gives rise to irreversible hearing loss. A very loud sound in a particular frequency range can damage the cochleas hair cells that respond to that range thereby reducing the ears ability to ...
Ben Creisler [email protected] A new paper (in open access) that may be of interest: Eric G. Ekdale (2015) Form and function of the mammalian inner ear. Journal of Anatomy (advance online publication) DOI: 10.1111/joa.12308 http://onlinelibrary.wiley.com/doi/10.1111/joa.12308/abstract http://onlinelibrary.wiley.com/doi/10.1111/joa.12308/epdf The inner ear of mammals consists of the cochlea, which is involved with the sense of hearing, and the vestibule and three semicircular canals, which are involved with the sense of balance. Although different regions of the inner ear contribute to different functions, the bony chambers and membranous ducts are morphologically continuous. The gross anatomy of the cochlea that has been related to auditory physiologies includes overall size of the structure, including volume and total spiral length, development of internal cochlear structures, including the primary and secondary bony laminae, morphology of the spiral nerve ganglion, and the nature of cochlear ...
The K+ circulation in the cochlea is thought to be tightly regulated in the inner compartment of the cochlea by a transport network in the stria vascularis of the cochlea (Wangemann 2006). In the OHC case, K+ passes through the transduction channels and is released into the intercellular space of organ of Corti through several types of K+ channel at the base of the hair cell. These channels include KCNQ4 channels (Kharkovets et al. 2006) and calcium-activated SK and BK channels (Marcotti et al. 2004). From there, K+ is taken up by the supporting cells via the K-Cl cotransporters (Boettger et al. 2002). The supporting cells of the organ of Corti form an extensive epithelial tissue gap-junction system that is essential for buffering extracellular K+ ions in the organ of Corti into the perilymph (Kikuchi et al. 2000). From perilymph, K+ is actively pumped by the K+/Na+ ATPase and K+/Na+/2Cl− cotransporter back into the type II fibrocytes of the spiral ligament and from there back via the stria ...
This study was designed to determine whether the sympathetic nervous system exerts a protective or enhancing effect in acoustic overstimulation. The compound action potential of the cochlea (CAP) was recorded in guinea pigs while the cervical sympathetic nervous system (SNS) was electrically stimulated or after it was surgically eliminated. The stimulation or the elimination of the cervical SNS has no effect on the threshold of CAP. The threshold shift in CAP after acoustic overstimulation (110, 115, or 130 dB SPL for 10 min) was measured in the cervical SNS stimulation group, in the cervical SNS elimination group, and in the control group. When the animal was under insufficient sedation, there was no difference among these three groups. However, the CAP threshold shift was significantly smaller in the cervical SNS stimulation group than in the other two groups when the animals were sufficiently sedated. The cervical SNS stimulation had some protective effect on the susceptibility to acoustic trauma
On the basis of recent advances in auditory physiology, new tests of cochlear function have been developed using measures of otoacoustic emissions. In the present report, the clinical potential for each of the four basic emission types is examined. In addition, the practical advantages of examining the ear with two specific types of evoked emissions, transiently evoked and distortion-product otoacoustic emissions, are reviewed in detail. Finally, the future role of tests of otoacoustic emissions in the diagnosis of hearing impairment is discussed. The current view is that evoked emissions hold promise as an essential part of the clinical examination of the auditory system.. ...
PubMed comprises more than 30 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full-text content from PubMed Central and publisher web sites.
Kiluchi, T. (1995) Gap junction in the rat cochlea immunohisto-chemical and ultrastructural analysis. Anatomy and Embryology, 2, 101-118.
Prevention of auditory hair cell death offers therapeutic potential to rescue hearing. Pharmacological blockade of JNK/c-Jun signaling attenuates injury-induced hair cell loss, but with unsolved mechanisms. We have characterized the c-Jun stress response in the mouse cochlea challenged with acoustic overstimulation and ototoxins, by studying the dynamics of c-Jun N-terminal phosphorylation. It occurred acutely in glial-like supporting cells, inner hair cells and in the cells of the cochlear ion trafficking route, and was rapidly downregulated after exposures. Notably, death-prone outer hair cells lacked c-Jun phosphorylation. As phosphorylation was triggered also by non-traumatic noise levels and as none of the cells showing this activation were lost, c-Jun phosphorylation is a biomarker for cochlear stress rather than an indicator of a death-prone fate of hair cells. Preconditioning with a mild noise exposure before a stronger traumatizing noise exposure attenuated the cochlear c-Jun stress ...
TY - JOUR. T1 - Short-term plasticity and modulation of synaptic transmission at mammalian inhibitory cholinergic olivocochlear synapses. AU - Katz, Eleonora. AU - Elgoyhen, Ana Belén. PY - 2014/12/2. Y1 - 2014/12/2. N2 - The organ of Corti, the mammalian sensory epithelium of the inner ear, has two types of mechanoreceptor cells, inner hair cells (IHCs) and outer hair cells (OHCs). In this sensory epithelium, vibrations produced by sound waves are transformed into electrical signals. When depolarized by incoming sounds, IHCs release glutamate and activate auditory nerve fibers innervating them and OHCs, by virtue of their electromotile property, increase the amplification and fine tuning of sound signals. The medial olivocochlear (MOC) system, an efferent feedback system, inhibits OHC activity and thereby reduces the sensitivity and sharp tuning of cochlear afferent fibers. During neonatal development, IHCs fire Ca2+ action potentials which evoke glutamate release promoting activity in the ...
Sensorineural hearing loss (sometimes called "nerve deafness") occurs when the cilia (hair cells) of the inner ear (the cochlea) do not function properly. In an undamaged ear, the pressure from sound waves goes into your pinna (the outer ear, the part you can see), makes the eardrum move back and forth, is passed along the small bones of the middle ear (the smallest bones in your body!), and then transfers to the middle ear, where those sound waves cause actual waves in the fluid-filled cochlea. The waves of fluid cause the hair cells to move. This sets off a beautiful chemical chain reaction, which ultimately causes stimulation of the auditory nerve (cranial nerve VIII), which sends the sensation of "sound" to the brain. The hair cells in the cochlea are tonotopically arranged, meaning that each region corresponds to different tones, going from high frequency sounds at the basal end to low frequency sounds at the apex of the cochlea, which looks like a snail shell. Think of a piano keyboard ...
Intracellular recordings were made from the low frequency region (third turn) of the guinea pig cochlea. Response characteristics are compared to gross potentials obtained from the organ of Corti fluid space. Inner hair cells (IHCs) possess relatively low (median, -32 mV) initial membrane potentials, whereas that of outer hair cells (OHCs) is higher (median, -53.5 mV). In response to tone burst stimuli, both cell types produce a combination of AC and DC responses. The latter are depolarizing for IHCs but may be of either polarity for OHCs. In terms of their AC responses, IHCs are about 12 dB more sensitive than OHCs. At low sound levels these cells are more linear than high frequency hair cells (Russell, I. J., and P. M. Sellick (1978) J. Physiol. (Lond.) 284: 261-290), judging from the relation between AC and DC response components. At high sound levels pronounced response saturation is seen. The overall tuning properties of the two hair cell types are rather similar, even though IHCs exhibit ...
Neurons in the developing auditory system fire bursts of action potentials before the onset of hearing. This spontaneousactivity promotes the survival and maturation of auditory neurons and the refinement of synaptic connections in auditory nuclei; however, the mechanisms responsible for initiating this activity remain uncertain. Previous studies indicate that inner supporting cells (ISCs) in the developing cochlea periodically release ATP, which depolarizes inner hair cells (IHCs), leading to bursts of action potentials in postsynaptic spiral ganglion neurons (SGNs). To determine when purinergic signaling appears in the developing cochlea and whether it is responsible for initiating auditory neuron activity throughout the prehearing period, we examined spontaneousactivity from ISCs, IHCs, and SGNs in cochleae acutely isolated from rats during the first three postnatal weeks. We found that ATP was released from ISCs within the cochlea from birth until the onset of hearing, which led to periodic ...
Mechanical responses in the basal turn of the guinea-pig cochlea are measured with low-level broad-band noise as the acoustical stimulus [for details see de Boer and Nuttall, J. Acoust. Soc. Am. 101, 3583-3592 (1997)]. Results are interpreted within the framework of a classical three-dimensional model of the cochlea that belongs to a very wide class of nonlinear models. The use of linear-systems analysis for this class of nonlinear models has been justified earlier [de Boer, Audit. Neurosci. 3, 377-388 (1997)]. The data are subjected to inverse analysis with the aim to recover the effective basilar-membrane impedance. This is a parameter function that, when inserted into the model, produces a model response, the resynthesized response, that is similar to the measured response. With present-day solution methods, resynthesis leads back to an almost perfect replica of the original response in the spatial domain. It is demonstrated in this paper that this also applies to the response in the frequency
Photograph of a receptor cell, known as an outer hair cell (OHC), in the mammalian cochlea with its large nucleus (N) located at the base of the cell. Receptor cells in the cochlea have structures known as stereocilia (S) at their apex. These structures convert the mechanical energy of sound to an electrochemical signal that can be processed by the peripheral and central auditory nerves. Outer hair cells have an additional feature; they can contract and extend in response to hyper- and depolarization of the cell. Their motility is regulated by signals from the brain, thereby allowing for the fine-tuning of mechanical signals that impinge on the cochlea. The photo was taken at a magnification of 7100 X using an electron microscope by Margaret Harvey, Senior Biological Scientist. Check out the link to see an outer hair cells response to music: https://www.youtube.com/watch?v=c91ubWbScs4 ...
About 95 percent of sound input to the brain comes from the ears inner hair cells.. "These inner hair cells are like spark plugs in an 8-cylinder engine," says Salvi. "A car wont run well if you remove half of those spark plugs, but people can still present with normal hearing thresholds if theyve lost half or even three-quarters of their inner hair cells.". Ear damage reduces the signal that goes the brain. That results in trouble hearing, but thats not whats happening here, because the brain "has a central gain control, like a radio, the listener can turn up the volume control to better hear a distant station." Salvi says.. Sound is converted to neural activity by the inner hair cells in the auditory part of the ear, called the cochlea.. Sound-evoked neural activity then travels from the cochlea to the auditory nerve and into the central auditory pathway of the brain. Halfway up the auditory pathway the information is relayed into a structure known as the inferior colliculus, before ...
The researchers show that this is due to a molecular signalling pathway in the cochlea, mediated by a chemical compound called ATP, released by the cochlear tissue with noise and activating specific ATP receptors in the cochlear cells.. "Interestingly, if the pathway is removed, such as by genetic manipulations, this adaptive mechanism doesnt occur and the ear becomes very vulnerable to longer term noise exposure and the effects of age, eventually resulting in permanent hearing loss.". "In other words the adaptive mechanism also protects the ear," says Professor Thorne.. The second paper, done in collaboration with United States colleagues, reveals a new genetic cause of deafness in humans which involves exactly the same mechanism.. People (two families in China) who had a mutation in the ATP receptor showed a rapidly progressing hearing loss which was accelerated if they worked in noisy environments.. "This work is important because it shows that our ears naturally adapt to their environment, ...
INTRODUCTION: the aim of this study was to investigate cochlear functions in patients with hyperemesis gravidarum (HG). METHODES: twenty-nine HG patients (58 ears) and 31 healthy control subjects (62 ears) were included. Audiometry testings at 250 and 500 Hz and 1, 2, 4, 8, 10, 12, 14, 16 kHz were performed to the patients and controls. RESULTS: mean age of patients with HG was 26,5 4,4 years and the mean age of control group was 28,0 4,2 years. At the time of the tests mean gestational age of the HG group and controls were 9 and 11 weeks respectively. No differences were observed between the groups in tympanic membrane status, orother otolaringological evaluations. No significant differences were observed in audiometric tests at any frequencies between the groups (p values for all>0.05). CONCLUSION: there was not a difference between pregnant cases with HG and cases with normal pregnancy in terms of audimetric tests. Cochlear functions are not affectedremarkably in women with HG.