| 1. |
- Videhult Pierre, Pernilla, et al.
(författare)
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Self-reported hearing difficulties, main income sources, and socio-economic status; a cross-sectional population-based study in Sweden
- 2012
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Ingår i: BMC Public Health. - : Springer Science and Business Media LLC. - 1471-2458. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Hearing difficulties constitute the most common cause of disability globally. Yet, studies on people with hearing difficulties regarding socio-economic status (SES), work, long-term unemployment, sickness absence, and disability pension are scarce. The aim of the present study was to investigate the main income sources of men and women of working ages with and without self-reported hearing difficulties and associations with gender, age, SES, type of living area, and country of birth.METHODS: A cross-sectional population-based study, using information on self-reported hearing difficulties and SES of 19 045 subjects aged 20-64 years participating in Statistics Sweden's annual Living Conditions Surveys in any of the years 2004 through 2008. The information was linked to a nationwide database containing data on demographics and income sources. Odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated, using binary logistic regression analysis.RESULTS: Hearing difficulties increased with age and were more common in men (age-adjusted OR: 1.42 (95% CI: 1.30-1.56)) with an overall prevalence of 13.1% in men and 9.8% in women. Using working men as reference, the OR of having hearing difficulties was 1.23 (0.94-1.60) in men with unemployment benefits and 1.36 (1.13-1.65) in men with sickness benefits or disability pension, when adjusting for age and SES. The corresponding figures in women were 1.59 (1.17-2.16) and 1.73 (1.46-2.06). The OR of having sickness benefits or disability pension in subjects with hearing difficulties was 1.36 (1.12-1.64) in men and 1.70 (1.43-2.01) in women, when adjusting for age and SES and using men and women with no hearing difficulties as reference.CONCLUSIONS: Hearing difficulties were more prevalent in men. After adjustment with age and SES as well as with type of living area and country of birth, a significant association with unemployment benefits was found only in women, and the associations with long-term sickness absence and disability pension tended to be stronger in women.
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| 2. |
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| 3. |
- Brownell, William E, et al.
(författare)
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Membrane cholesterol modulates cochlear electromechanics
- 2011
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Ingår i: Pflügers Archiv. - : Springer Science and Business Media LLC. - 0031-6768 .- 1432-2013. ; 461:6, s. 677-686
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Tidskriftsartikel (refereegranskat)abstract
- Changing the concentration of cholesterol in the plasma membrane of isolated outer hair cells modulates electromotility and prestin-associated charge movement, suggesting that a similar manipulation would alter cochlear mechanics. We examined cochlear function before and after depletion of membrane cholesterol with methyl-β-cyclodextrin (MβCD) in an excised guinea pig temporal bone preparation. The mechanical response of the cochlear partition to acoustic and/or electrical stimulation was monitored using laser interferometry and time-resolved confocal microscopy. The electromechanical response in untreated preparations was asymmetric with greater displacements in response to positive currents. Exposure to MβCD increased the magnitude and asymmetry of the response, without changing the frequency tuning of sound-evoked mechanical responses or cochlear microphonic potentials. Sodium salicylate reversibly blocked the enhanced electromechanical response in cholesterol depleted preparations. The increase of sound-evoked vibrations during positive current injection was enhanced following MβCD in some preparations. Imaging was used to assess cellular integrity which remained unchanged after several hours of exposure to MβCD in several preparations. The enhanced electromechanical response reflects an increase in outer hair cell electromotility and may reveal features of cholesterol distribution and trafficking in outer hair cells.
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| 4. |
- Chen, Fangyi, et al.
(författare)
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A differentially amplified motion in the ear for near-threshold sound detection
- 2011
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Ingår i: Nature Neuroscience. - : Springer Science and Business Media LLC. - 1097-6256 .- 1546-1726. ; 14:6, s. 770-774
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Tidskriftsartikel (refereegranskat)abstract
- The ear is a remarkably sensitive pressure fluctuation detector. In guinea pigs, behavioral measurements indicate a minimum detectable sound pressure of ∼20 μPa at 16 kHz. Such faint sounds produce 0.1-nm basilar membrane displacements, a distance smaller than conformational transitions in ion channels. It seems that noise within the auditory system would swamp such tiny motions, making weak sounds imperceptible. Here we propose a new mechanism contributing to a resolution of this problem and validate it through direct measurement. We hypothesized that vibration at the apical side of hair cells is enhanced compared with that at the commonly measured basilar membrane side. Using in vivo optical coherence tomography, we demonstrated that apical-side vibrations peaked at a higher frequency, had different timing and were enhanced compared with those at the basilar membrane. These effects depend nonlinearly on the stimulus sound pressure level. The timing difference and enhancement of vibrations are important for explaining how the noise problem is circumvented.
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| 5. |
- Dash-Wagh, Suvarna, et al.
(författare)
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Intracellular Delivery of Short Interfering RNA in Rat Organ of Corti Using a Cell-penetrating Peptide PepFect6
- 2012
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Ingår i: Molecular Therapy Nucleic Acids. - : Elsevier BV. - 2162-2531. ; 1:e61
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Tidskriftsartikel (refereegranskat)abstract
- RNA interference (RNAi) using short interfering RNA (siRNA) is an attractive therapeutic approach for treatment of dominant-negative mutations. Some rare missense dominant-negative mutations lead to congenital-hearing impairments. A variety of viral vectors have been tested with variable efficacy for modulating gene expression in inner ear. However, there is concern regarding their safety for clinical use. Here, we report a novel cell-penetrating peptide (CPP)-based nonviral approach for delivering siRNA into inner ear tissue using organotypic cultures as model system. PepFect6 (PF6), a variant of stearyl-TP10, was specially designed for improved delivery of siRNA by facilitating endosomal release. We show that PF6 was internalized by all cells without inducing cytotoxicity in cochlear cultures. PF6/siRNA nanoparticles lead to knockdown of target genes, a housekeeping gene and supporting cell-specific connexin 26. Interestingly, application of PF6/connexin 26 siRNA exhibited knockdown of both connexin 26 and 30 mRNA and their absence led to impaired intercellular communication as demonstrated by reduced transfer of calcein among the PF6/connexin 26-siRNA-treated cells. Thus, we conclude that PF6 is an efficient nonviral vector for delivery of siRNA, which can be applied as a tool for the development of siRNA-based therapeutic applications for hearing impairments.
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| 6. |
- Felix, Richard A, et al.
(författare)
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Sound rhythms are encoded by postinhibitory rebound spiking in the superior paraolivary nucleus
- 2011
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Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 31:35, s. 12566-12578
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Tidskriftsartikel (refereegranskat)abstract
- The superior paraolivary nucleus (SPON) is a prominent structure in the auditory brainstem. In contrast to the principal superior olivary nuclei with identified roles in processing binaural sound localization cues, the role of the SPON in hearing is not well understood. A combined in vitro and in vivo approach was used to investigate the cellular properties of SPON neurons in the mouse. Patch-clamp recordings in brain slices revealed that brief and well timed postinhibitory rebound spiking, generated by the interaction of two subthreshold-activated ion currents, is a hallmark of SPON neurons. The I(h) current determines the timing of the rebound, whereas the T-type Ca(2+) current boosts the rebound to spike threshold. This precisely timed rebound spiking provides a physiological explanation for the sensitivity of SPON neurons to sinusoidally amplitude-modulated (SAM) tones in vivo, where peaks in the sound envelope drive inhibitory inputs and SPON neurons fire action potentials during the waveform troughs. Consistent with this notion, SPON neurons display intrinsic tuning to frequency-modulated sinusoidal currents (1-15Hz) in vitro and discharge with strong synchrony to SAMs with modulation frequencies between 1 and 20 Hz in vivo. The results of this study suggest that the SPON is particularly well suited to encode rhythmic sound patterns. Such temporal periodicity information is likely important for detection of communication cues, such as the acoustic envelopes of animal vocalizations and speech signals.
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| 7. |
- Hakizimana, Pierre, et al.
(författare)
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Sound-induced length changes in outer hair cell stereocilia
- 2012
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Hearing relies on mechanical stimulation of stereocilia bundles on the sensory cells of the inner ear. When sound hits the ear, each stereocilium pivots about a neck-like taper near their base. More than three decades of research have established that sideways deflection of stereocilia is essential for converting mechanical stimuli into electrical signals. Here we show that mammalian outer hair cell stereocilia not only move sideways but also change length during sound stimulation. Currents that enter stereocilia through mechanically sensitive ion channels control the magnitude of both length changes and bundle deflections in a reciprocal manner: the smaller the length change, the larger is the bundle deflection. Thus, the transduction current is important for maintaining the resting mechanical properties of stereocilia. Hair cell stimulation is most effective when bundles are in a state that ensures minimal length change.
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| 8. |
- Hakizimana, Pierre, et al.
(författare)
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Sound‐Evoked Length Changes of the Outer Hair Cell Stereocilia Bundle are Modulated by Endocochlear Currents
- 2011
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Ingår i: WHAT FIRE IS IN MINE EARS: PROGRESS IN AUDITORY BIOMECHANICS: Proceedings of the 11th International Mechanics of Hearing Workshop. - : American Institute of Physics (AIP).
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Konferensbidrag (refereegranskat)abstract
- The apical surface of vertebrate inner ear sensory cells is characterized by a bundle of giant microvilli commonly known as stereocilia. Stereocilia bend about a neck‐like thinning near their base and more than three decades of research has established that the direction and magnitude of sideways bundle deflection is the basis of the mechanoelectrical signalling that initiates sound perception. Aside from its ability to bend at the neck, the stereocilium is usually considered as a stiff inelastic rod. Here we show that the length of OHC stereocilia changes during sound transduction, demonstrating their axial compliance, and that the magnitude of the length change is modulated by currents that mimic in vivo endocochlear currents. A reciprocal relation between length change and bundle deflection is evident: the smaller the length changes, the larger the bundle deflection.
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| 9. |
- He, Wenxuan, et al.
(författare)
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Fast reverse propagation of sound in the living cochlea
- 2010
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 98:11, s. 2497-2505
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Tidskriftsartikel (refereegranskat)abstract
- The auditory sensory organ, the cochlea, not only detects but also generates sounds. Such sounds, otoacoustic emissions, are widely used for diagnosis of hearing disorders and to estimate cochlear nonlinearity. However, the fundamental question of how the otoacoustic emission exits the cochlea remains unanswered. In this study, emissions were provoked by two tones with a constant frequency ratio, and measured as vibrations at the basilar membrane and at the stapes, and as sound pressure in the ear canal. The propagation direction and delay of the emission were determined by measuring the phase difference between basilar membrane and stapes vibrations. These measurements show that cochlea-generated sound arrives at the stapes earlier than at the measured basilar membrane location. Data also show that basilar membrane vibration at the emission frequency is similar to that evoked by external tones. These results conflict with the backward-traveling-wave theory and suggest that at low and intermediate sound levels, the emission exits the cochlea predominantly through the cochlear fluids.
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| 10. |
- Jacob, Stefan, et al.
(författare)
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Noise-induced alterations in cochlear mechanics, electromotility, and cochlear amplification
- 2013
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Ingår i: Pflügers Archiv. - : Springer. - 0031-6768 .- 1432-2013. ; 465:6, s. 907-917
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Tidskriftsartikel (refereegranskat)abstract
- Loud sounds are a common cause of hearing loss. Very intense sounds may result in permanent hearing loss, but lower levels typically cause a transient decrease in auditory sensitivity. Studies have arrived at different conclusions as regards the physiological mechanisms underlying such temporary threshold shifts. Here, we investigated the effect of acoustic overstimulation on the mechanics of the low-frequency areas of the guinea pig cochlea. We demonstrate that brief loud sound exposure results in an increased phase lag and a paradoxical frequency-specific increase of sound-evoked displacement. Despite the increased displacement, electrically evoked motion is reduced. Because electromotility is important for amplifying low-level sounds, this change was associated with a decrease in measures of cochlear amplification. These changes recovered over the course of 30-40 min. Overstimulation also caused an increase in cytoplasmic calcium levels of both hair cells and supporting cells. These data suggest that reduced organ of Corti stiffness contributes to temporary threshold shifts.
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| 11. |
- Jacob, Stefan, et al.
(författare)
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The endocochlear potential alters cochlear micromechanics
- 2011
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 100:11, s. 2586-2594
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Tidskriftsartikel (refereegranskat)abstract
- Acoustic stimulation gates mechanically sensitive ion channels in cochlear sensory hair cells. Even in the absence of sound, a fraction of these channels remains open, forming a conductance between hair cells and the adjacent fluid space, scala media. Restoring the lost endogenous polarization of scala media in an in vitro preparation of the whole cochlea depolarizes the hair cell soma. Using both digital laser interferometry and time-resolved confocal imaging, we show that this causes a structural refinement within the organ of Corti that is dependent on the somatic electromotility of the outer hair cells (OHCs). Specifically, the inner part of the reticular lamina up to the second row of OHCs is pulled toward the basilar membrane, whereas the outer part (third row of OHCs and the Hensen's cells) unexpectedly moves in the opposite direction. A similar differentiated response pattern is observed for sound-evoked vibrations: restoration of the endogenous polarization decreases vibrations of the inner part of the reticular lamina and results in up to a 10-fold increase of vibrations of the outer part. We conclude that the endogenous polarization of scala media affects the function of the hearing organ by altering its geometry, mechanical and electrical properties.
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| 12. |
- Neng, Lingling, et al.
(författare)
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Isolation and culture of endothelial cells, pericytes and perivascular resident macrophage-like melanocytes from the young mouse ear
- 2013
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Ingår i: Nature Protocols. - : Nature Publishing Group. - 1754-2189 .- 1750-2799. ; 8:4, s. 709-720
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Tidskriftsartikel (refereegranskat)abstract
- This protocol describes a growth medium-based approach for obtaining cochlear endothelial cells (ECs), pericytes (PCs) and perivascular resident macrophage-like melanocytes (PVM/Ms) from the stria vascularis of mice aged between P10 and P15 (P, postnatal day). The procedure does not involve mechanical or enzymatic digestion of the sample tissue. Explants of stria vascularis, 'mini-chips', are selectively cultured in growth medium, and primary cell lines are obtained in 7-10 d. The method is simple and reliable, and it provides high-quality ECs, PVM/Ms and PCs with a purity >90% after two passages. This protocol is suitable for producing primary culture cells from organs and tissues of small volume and high anatomical complexity, such as the inner ear capillaries. The highly purified primary cell lines enable cell culture-based in vitro modeling of cell-cell interactions, barrier control function and drug action.
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| 13. |
- Nuttall, Alfred L, et al.
(författare)
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Instrumentation for studies of cochlear mechanics : from von Békésy forward
- 2012
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Ingår i: Hearing Research. - : Elsevier BV. - 0378-5955 .- 1878-5891. ; 293:1-2, s. 3-11
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Tidskriftsartikel (refereegranskat)abstract
- Georg von Békésy designed the instruments needed for his research. He also created physical models of the cochlea allowing him to manipulate the parameters (such as volume elasticity) that could be involved in controlling traveling waves. This review is about the specific devices that he used to study the motion of the basilar membrane thus allowing the analysis that lead to his Nobel Prize Award. The review moves forward in time mentioning the subsequent use of von Békésy's methods and later technologies important for motion studies of the organ of Corti. Some of the seminal findings and the controversies of cochlear mechanics are mentioned in relation to the technical developments.
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| 14. |
- Ramamoorthy, Sripriya, et al.
(författare)
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Filtering of Acoustic Signals within the Hearing Organ
- 2014
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Ingår i: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 34:27, s. 9051-9058
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Tidskriftsartikel (refereegranskat)abstract
- The detection of sound by the mammalian hearing organ involves a complex mechanical interplay among different cell types. The inner hair cells, which are the primary sensory receptors, are stimulated by the structural vibrations of the entire organ of Corti. The outer hair cells are thought to modulate these sound-evoked vibrations to enhance hearing sensitivity and frequency resolution, but it remains unclear whether other structures also contribute to frequency tuning. In the current study, sound-evoked vibrations were measured at the stereociliary side of inner and outer hair cells and their surrounding supporting cells, using optical coherence tomography interferometry in living anesthetized guinea pigs. Our measurements demonstrate the presence of multiple vibration modes as well as significant differences in frequency tuning and response phase among different cell types. In particular, the frequency tuning at the inner hair cells differs from other cell types, causing the locus of maximum inner hair cell activation to be shifted toward the apex of the cochlea compared with the outer hair cells. These observations show that additional processing and filtering of acoustic signals occur within the organ of Corti before inner hair cell excitation, representing a departure from established theories.
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| 15. |
- Ren, Tianying, et al.
(författare)
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Light-induced vibration in the hearing organ
- 2014
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Ingår i: Scientific Reports. - : Nature Publishing Group: Open Access Journals - Option B / Nature Publishing Group. - 2045-2322. ; 4, s. 5941-
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Tidskriftsartikel (refereegranskat)abstract
- The exceptional sensitivity of mammalian hearing organs is attributed to an active process, where force produced by sensory cells boost sound-induced vibrations, making soft sounds audible. This process is thought to be local, with each section of the hearing organ capable of amplifying sound-evoked movement, and nearly instantaneous, since amplification can work for sounds at frequencies up to 100 kHz in some species. To test these fundamental precepts, we developed a method for focally stimulating the living hearing organ with light. Light pulses caused intense and highly damped mechanical responses followed by traveling waves that developed with considerable delay. The delayed response was identical to movements evoked by click-like sounds. This shows that the active process is neither local nor instantaneous, but requires mechanical waves traveling from the cochlear base toward its apex. A physiologically-based mathematical model shows that such waves engage the active process, enhancing hearing sensitivity.
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| 16. |
- von Tiedemann, Miriam, et al.
(författare)
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Brightness-compensated 3-D optical flow algorithm for monitoring cochlear motion patterns
- 2010
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Ingår i: Journal of biomedical optics. - : SPIE-Intl Soc Optical Eng. - 1560-2281 .- 1083-3668. ; 15:5, s. 056012-
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Tidskriftsartikel (refereegranskat)abstract
- A method for three-dimensional motion analysis designed for live cell imaging by fluorescence confocal microscopy is described. The approach is based on optical flow computation and takes into account brightness variations in the image scene that are not due to motion, such as photobleaching or fluorescence variations that may reflect changes in cellular physiology. The 3-D optical flow algorithm allowed almost perfect motion estimation on noise-free artificial sequences, and performed with a relative error of <10% on noisy images typical of real experiments. The method was applied to a series of 3-D confocal image stacks from an in vitro preparation of the guinea pig cochlea. The complex motions caused by slow pressure changes in the cochlear compartments were quantified. At the surface of the hearing organ, the largest motion component was the transverse one (normal to the surface), but significant radial and longitudinal displacements were also present. The outer hair cell displayed larger radial motion at their basolateral membrane than at their apical surface. These movements reflect mechanical interactions between different cellular structures, which may be important for communicating sound-evoked vibrations to the sensory cells. A better understanding of these interactions is important for testing realistic models of cochlear mechanics.
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| 17. |
- Watanabe, Futoshi, et al.
(författare)
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Signaling through erbB receptors is a critical functional regulator in the mature cochlea
- 2010
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 32:5, s. 717-724
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Tidskriftsartikel (refereegranskat)abstract
- Noise, ototoxic substances and various genetic factors are common causes of profound hearing loss. Cochlear implants can often restore hearing in these cases, but only if a sufficient number of responsive auditory nerve fibers remain. Over time, these nerve fibers degenerate in the damaged ear, and it is therefore important to establish factors that control neuronal survival and maintain neural excitability. Recent studies show that neuregulins and their receptors are important for survival and proper targeting of neurons in the developing inner ear. A role for neuregulins as maintainers of the neuronal population in the mature inner ear was therefore hypothesized. Here, this hypothesis was directly tested by chronic local application of substances that block neuregulin receptors. Using auditory brainstem response measurements, we demonstrate that such receptor block leads to a progressive hearing impairment that develops over the course of weeks. This impairment occurs despite a normal number of auditory neurons and preserved outer hair cell function. Real-time quantitative reverse transcriptase-polymerase chain reaction shows alterations in neurotrophin-3 expression, suggesting that this growth factor participates in regulating cochlear sensitivity. The present work demonstrates the critical importance of neuregulin/erbB signaling in long-term functional regulation in the mature guinea pig hearing organ.
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| 18. |
- Zha, Dingjun, et al.
(författare)
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In vivo outer hair cell length changes expose the active process in the cochlea
- 2012
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 7:4, s. e32757-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Mammalian hearing is refined by amplification of the sound-evoked vibration of the cochlear partition. This amplification is at least partly due to forces produced by protein motors residing in the cylindrical body of the outer hair cell. To transmit power to the cochlear partition, it is required that the outer hair cells dynamically change their length, in addition to generating force. These length changes, which have not previously been measured in vivo, must be correctly timed with the acoustic stimulus to produce amplification.METHODOLOGY/PRINCIPAL FINDINGS: Using in vivo optical coherence tomography, we demonstrate that outer hair cells in living guinea pigs have length changes with unexpected timing and magnitudes that depend on the stimulus level in the sensitive cochlea.CONCLUSIONS/SIGNIFICANCE: The level-dependent length change is a necessary condition for directly validating that power is expended by the active process presumed to underlie normal hearing.
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| 19. |
- Zhang, Fei, et al.
(författare)
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Perivascular macrophage-like melanocyte responsiveness to acoustic trauma--a salient feature of strial barrier associated hearing loss
- 2013
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Ingår i: The FASEB Journal. - : Federation of American Societies for Experimental Biology. - 0892-6638 .- 1530-6860. ; 27:9, s. 3730-3740
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Tidskriftsartikel (refereegranskat)abstract
- Tissue perivascular resident macrophages (PVM/Ms), a hybrid cell type with characteristics of both macrophages and melanocytes, are critical for establishing and maintaining the endocochlear potential (EP) required for hearing. The PVM/Ms modulate expression of tight- and adherens-junction proteins in the endothelial barrier of the stria vascularis (intrastrial fluid-blood barrier) through secretion of a signaling molecule, pigment epithelium growth factor (PEDF). Here, we identify a significant link between abnormalities in PVM/Ms and endothelial barrier breakdown from acoustic trauma to the mouse ear. We find that acoustic trauma causes activation of PVM/Ms and physical detachment from capillary walls. Concurrent with the detachment, we find loosened tight junctions between endothelial cells and decreased production of tight- and adherens-junction protein, resulting in leakage of serum proteins from the damaged barrier. A key factor in the intrastrial fluid-blood barrier hyperpermeability exhibited in the mice is down-regulation of PVM/M modulated PEDF production. We demonstrate that delivery of PEDF to the damaged ear ameliorates hearing loss by restoring intrastrial fluid-blood barrier integrity. PEDF up-regulates expression of tight junction-associated proteins (ZO-1 and VE-cadherin) and PVM/M stabilizing neural cell adhesion molecule (NCAM-120). These studies point to the critical role PVM/Ms play in regulating intrastrial fluid-blood barrier integrity in healthy and noise-damaged ears.
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| 20. |
- Zhang, WJ, et al.
(författare)
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Perivascular-resident macrophage-like melanocytes in the inner ear are essential for the integrity of the intrastrial fluid-blood barrier
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 109:26, s. 10388-10393
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Tidskriftsartikel (refereegranskat)abstract
- The microenvironment of the cochlea is maintained by the barrier between the systemic circulation and the fluids inside the stria vascularis. However, the mechanisms that control the permeability of the intrastrial fluid–blood barrier remain largely unknown. The barrier comprises endothelial cells connected to each other by tight junctions and an underlying basement membrane. In a recent study, we found that the intrastrial fluid–blood barrier also includes a large number of perivascular cells with both macrophage and melanocyte characteristics. The perivascular-resident macrophage-like melanocytes (PVM/Ms) are in close contact with vessels through cytoplasmic processes. Here we demonstrate that PVM/Ms have an important role in maintaining the integrity of the intrastrial fluid–blood barrier and hearing function. Using a cell culture-based in vitro model and a genetically induced PVM/M-depleted animal model, we show that absence of PVM/Ms increases the permeability of the intrastrial fluid–blood barrier to both low- and high-molecular-weight tracers. The increased permeability is caused by decreased expression of pigment epithelial-derived factor, which regulates expression of several tight junction-associated proteins instrumental to barrier integrity. When tested for endocochlear potential and auditory brainstem response, PVM/M-depleted animals show substantial drop in endocochlear potential with accompanying hearing loss. Our results demonstrate a critical role for PVM/Ms in regulating the permeability of the intrastrial fluid–blood barrier for establishing a normal endocochlear potential hearing threshold.
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| 21. |
- Zheng, Jiefu, et al.
(författare)
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Persistence of past stimulations : storing sounds within the inner ear
- 2011
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 100:7, s. 1627-1634
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Tidskriftsartikel (refereegranskat)abstract
- Tones cause vibrations within the hearing organ. Conventionally, these vibrations are thought to reflect the input and therefore end with the stimulus. However, previous recordings of otoacoustic emissions and cochlear microphonic potentials suggest that the organ of Corti does continue to move after the end of a tone. These after-vibrations are characterized here through recordings of basilar membrane motion and hair cell extracellular receptor potentials in living anesthetized guinea pigs. We show that after-vibrations depend on the level and frequency of the stimulus, as well as on the sensitivity of the ear. Even a minor loss of hearing sensitivity caused a sharp reduction in after-vibration amplitude and duration. Mathematical models suggest that after-vibrations are driven by energy added into organ of Corti motion after the end of an acoustic stimulus. The possible importance of after-vibrations for psychophysical phenomena such as forward masking and gap detection are discussed.
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