| 1. |
- Felder, E, et al.
(författare)
-
Quantitative evaluation of cochlear neurons and computer-aided three-dimensional reconstruction of spiral ganglion cells in humans with a peripheral loss of nerve fibres
- 1997
-
Ingår i: Hearing Research. - 0378-5955 .- 1878-5891. ; 105:1-2, s. 183-190
-
Tidskriftsartikel (refereegranskat)abstract
- Quantitative data on human cochlear neuronal elements were collected from various regions in five patients with high-tone hearing loss due to presbycusis and in two patients with normal hearing. The number of nerve fibers was assessed in the spiral lamina and in the inner acoustic meatus together with counts of spiral ganglion cells. The results show that the number of neurons decreased peripherally, i.e., with increasing distance from the central nervous system in patients with high-tone hearing loss due to presbycusis. In two patients with normal hearing no significant difference in the number of neurons was found in the lamina spiralis as compared to the inner acoustic canal. Computer-aided 3-dimensional reconstruction of the human spiral ganglion displayed large bipolar neurons (type I cells), but also large ganglion cells with one missing axon. The results may indicate that a slow retrograde degeneration occurs from the periphery towards the spiral ganglion in presbycusis. Transmission electron microscopy analysis of freshly fixed human spiral ganglions displayed interneural connections. It is speculated whether a trophic supply from other neurons at the level of the spiral ganglion can prevent or delay further degeneration of the central axon.
|
|
| 2. |
- Flock, Å., et al.
(författare)
-
Methods for integrating fluorimetry in the study of hearing organ structure and function
- 1997
-
Ingår i: Hearing Research. - : Elsevier. - 0378-5955 .- 1878-5891. ; 106:1-2, s. 29-38
-
Tidskriftsartikel (refereegranskat)abstract
- The measurement of function in the intact organ of Corti has up to now been achieved by three methods: electrophysiology, mechanical measurement and biochemical analysis. The two former methods have supplied information at the level of single identified cells. We have used a fourth method, optical fluorimetry, to measure hair cell function at the cellular level in the intact organ of Corti. Here we describe the methods involved in fluorescence labelling and video-enhanced microscopy in combination with electrophysiological recording of cochlear microphonic (CM) and summating potentials (SP). The guinea pig temporal bone containing an intact ear drum, ossicular chain and cochlea can be maintained in the isolated state by perfusion of the scala tympani with oxygenated tissue culture medium. Substances added to the perfusate readily diffuse through the basilar membrane into the organ of Corti. In this way cells in the organ can be stained by a number of fluorescent probes which label different structures and functions. Here we have used two dyes which label mitochondria and fluoresce with an intensity proportional to metabolic activity. By simultaneous measurement of CM and SP the functional state of the organ can be monitored.
|
|
| 3. |
- Fridberger, Anders, 1966-, et al.
(författare)
-
Alterations of basilar membrane response phase and velocity after acoustic overstimulation
- 2002
-
Ingår i: Hearing Research. - : Elsevier. - 0378-5955 .- 1878-5891. ; 167:1-2, s. 214-222
-
Tidskriftsartikel (refereegranskat)abstract
- To investigate the physiology of noise-induced hearing loss, the sound-induced vibrations of the basilar membrane (BM) of the inner ear were measured in living anesthetized guinea pigs before and after intense sound exposure. The vibrations were measured using a laser Doppler velocimeter after placing reflective glass beads on the BM. Pseudo-random noise waveforms containing frequencies between 4 and 24 kHz were used to generate velocity tuning curves. Before overstimulation, sharp response peaks were seen at stimulus frequencies between 15 and 17 kHz, consistent with the expected best frequency of the recording location. The response to low level stimuli lagged the high level ones by up to 90 degrees at the characteristic frequency. Following exposure to loud sound, the BM vibrations showed a pronounced reduction in amplitude, primarily at low stimulus levels, and the best frequency moved to approximately 12 kHz. At higher levels, the reduction was either absent or much smaller. In addition to the amplitude changes, increased phase lags were seen at frequencies near the characteristic frequency. In animals with more severe exposures, response phases were altered also at frequencies showing no change of the amplitude. The phase was independent of stimulus level after severe exposures.
|
|
| 4. |
|
|
| 5. |
- Takumida, Masaya, et al.
(författare)
-
Lipopolysaccharide-induced expression of inducible nitric oxide synthase in the guinea pig organ of Corti
- 2000
-
Ingår i: Hearing Research. - 0378-5955 .- 1878-5891. ; 140:1-2, s. 91-8
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of the investigation was to ascertain whether inoculation of bacterial lipopolysaccharide (LPS) into the cochlea of the guinea pig could elicit formation of inducible nitric oxide synthase (iNOS). Immunohistochemical study revealed that immunoreactivity to iNOS was seen below outer hair cells representing nerve fibers and synaptic nerve endings. iNOS-staining could also be observed in phalangeal dendrites of Deiter's cells pointing to the cuticular membrane, Hensen's cells and on stria vascularis 48 h after inoculation with LPS. Immunohistochemical investigation with a specific anti-nitrotyrosine antibody also revealed intense immunoreactivity identical to that of iNOS, suggesting formation of peroxynitrite in the organ of Corti by the reaction of NO with O(2)(-). On the basis of these findings, it can be concluded that NO together with O(2)(-), which form the more reactive peroxynitrite, are the most important pathogenic agents in LPS-induced damage of cochlea in the guinea pig.
|
|
| 6. |
- Anderson, Malin, et al.
(författare)
-
Structure and locomotion of adult in vitro regenerated spiral ganglion growth cones : a study using video microscopy and SEM
- 2006
-
Ingår i: Hearing Research. - : Elsevier BV. - 0378-5955 .- 1878-5891. ; 215:1-2, s. 97-107
-
Tidskriftsartikel (refereegranskat)abstract
- Neuronal development and neurite regeneration depends on the locomotion and navigation of nerve growth cones (GCs). There are few detailed descriptions of the GC function and structure in the adult auditory system. In this study, GCs of adult dissociated and cultured spiral ganglion (SG) neurons were analyzed in vitro utilizing combined high resolution scanning electron microscopy (SEM) and time lapse video microscopy (TLVM). Axon kinesis was assessed on planar substratum with growth factors BDNF, NT-3 and GDNF. At the nano-scale level, lamellipodial abdomen of the expanding GC was found to be decorated with short surface specializations, which at TLVM were considered to be related to their crawling capacity. Filopodia were devoid of these surface structures, supporting its generally described sensory role. Microspikes appearing on lamellipodia and axons, showed circular adhesions, which at TLVM were found to provide anchorage of the navigating and turning axon. Neurons and GCs expressed the DCC-receptor for the guidance molecule netrin-1. Asymmetric ligand-based stimulation initiated turning responses suggest that this attractant cue influences steering of GC in adult regenerating auditory neurites. Hopefully, these findings may be used for ensuing tentative navigation of spiral ganglion neurons to induce regenerative processes in the human ear.
|
|
| 7. |
- Ashmore, J, et al.
(författare)
-
The remarkable cochlear amplifier
- 2010
-
Ingår i: Hearing research. - : Elsevier BV. - 1878-5891 .- 0378-5955. ; 266:1-2, s. 1-17
-
Tidskriftsartikel (refereegranskat)
|
|
| 8. |
- Asp, Filip, et al.
(författare)
-
The effect of simulated unilateral hearing loss on horizontal sound localization accuracy and recognition of speech in spatially separate competing speech
- 2018
-
Ingår i: Hearing Research. - : Elsevier BV. - 1878-5891 .- 0378-5955. ; 357, s. 54-63
-
Tidskriftsartikel (refereegranskat)abstract
- Unilateral hearing loss (UHL) occurs in 25% of cases of congenital sensorineural hearing loss. Due to the unilaterally reduced audibility associated with UHL, everyday demanding listening situations may be disrupted despite normal hearing in one ear. The aim of this study was to quantify acute changes in recognition of speech in spatially separate competing speech and sound localization accuracy, and relate those changes to two levels of temporary induced UHL (UHL 30 and UHL 43 ; suffixes denote the average hearing threshold across 0.5, 1, 2, and 4 kHz) for 8 normal-hearing adults. A within-subject repeated-measures design was used (normal binaural conditions, UHL 30 and UHL 43 ). The main outcome measures were the threshold for 40% correct speech recognition and the overall variance in sound localization accuracy quantified by an Error Index (0 = perfect performance, 1.0 = random performance). Distinct and statistically significant deterioration in speech recognition (2.0 dB increase in threshold, p < 0.01) and sound localization (Error Index increase of 0.16, p < 0.001) occurred in the UHL 30 condition. Speech recognition did not significantly deteriorate further in the UHL 43 condition (1.0 dB increase in speech recognition threshold, p > 0.05), while sound localization was additionally impaired (Error Index increase of 0.33, p < 0.01) with an associated large increase in individual variability. Qualitative analyses on a subject-by-subject basis showed that high-frequency audibility was important for speech recognition, while low-frequency audibility was important for horizontal sound localization accuracy. While the data might not be entirely applicable to individuals with long-standing UHL, the results suggest a need for intervention for mild-to-moderate UHL.
|
|
| 9. |
|
|
| 10. |
- Berggren, Diana, et al.
(författare)
-
Spontaneous hair-cell renewal following gentamicin exposure in postnatal rat utricular explants
- 2003
-
Ingår i: Hearing Research. - 0378-5955 .- 1878-5891. ; 180:1-2, s. 114-125
-
Tidskriftsartikel (refereegranskat)abstract
- We have established an in vitro model of long-time culture of 4-day-old rat utricular maculae to study aminoglycoside-induced vestibular hair-cell renewal in the mammalian inner ear. The explanted maculae were cultured for up to 28 days on the surface of a membrane insert system. In an initial series of experiments utricles were exposed to 1 mM of gentamicin for 48 h and then allowed to recover in unsupplemented medium or in medium supplemented with the anti-mitotic drug aphidicolin. In a parallel control series, explants were not exposed to gentamicin. Utricles were harvested at specified time points from the second through the 28th day in vitro. Whole-mount utricles were stained with phalloidin-fluorescein isothiocyanate and their stereociliary bundles visualized and counted. In a second experimental series 2'-bromo-5'deoxyuridine labeling was used to confirm the antimitotic efficacy of aphidicolin. Loss of hair-cell stereociliary bundles was nearly complete 3 days after exposure to gentamicin, with the density of stereociliary bundles only 3-4% of their original density. Renewal of hair-cell bundles was abundant (i.e. 15x increase) in cultures in unsupplemented medium, with a peak of stereociliary bundle renewal reached after 21 days in vitro. A limited amount of hair-cell renewal also occurred in the presence of the anti-mitotic drug, aphidicolin. These results suggest that spontaneous renewal of hair-cell stereociliary bundles following gentamicin damage in utricular explants predominantly follows a pathway that includes mitotic events, but that a small portion of the hair-cell stereociliary bundle renewal does not require mitotic activity.
|
|
| 11. |
|
|
| 12. |
- Burwood, G., et al.
(författare)
-
Outer hair cell driven reticular lamina mechanical distortion in living cochleae
- 2022
-
Ingår i: Hearing Research. - : ELSEVIER. - 0378-5955 .- 1878-5891. ; 423
-
Tidskriftsartikel (refereegranskat)abstract
- Cochlear distortions afford researchers and clinicians a glimpse into the conditions and properties of inner ear signal processing mechanisms. Until recently, our examination of these distortions has been limited to measuring the vibration of the basilar membrane or recording acoustic distortion output in the ear canal. Despite its importance, the generation mechanism of cochlear distortion remains a substantial task to understand. The ability to measure the vibration of the reticular lamina in rodent models is a recent experimental advance. Surprising mechanical properties have been revealed. These properties merit both discussion in context with our current understanding of distortion, and appraisal of the significance of new interpretations of cochlear mechanics. This review focusses on some of the recent data from our research groups and discusses the implications of these data on our understanding of vocalization processing in the periphery, and their influence upon future experimental directions. (C) 2021 Elsevier B.V. All rights reserved.
|
|
| 13. |
- Canlon, Barbara, et al.
(författare)
-
Associations between stress and hearing problems in humans
- 2013
-
Ingår i: Hearing Research. - : Elsevier BV. - 0378-5955 .- 1878-5891. ; 295:1-2, s. 9-15
-
Tidskriftsartikel (refereegranskat)abstract
- Hearing problems are a public health issue with prevalence figures far more common than previously estimated. There are well-established risk factors of hearing problems such as age, sex and noise exposure history. Here, we demonstrate additional risk factors, i.e. socioeconomic status and long-term stress exposure that are found to increase the risk of hearing problems. In order to proactively intervene and prevent hearing problems, these newly recognized risk factors need to be taken into consideration. When taking these new risk factors into account, sex differences become even more apparent than previously found. The aim of this review is to summarize our recent findings about the associations between stress and hearing problems.
|
|
| 14. |
- Canlon, B, et al.
(författare)
-
Introduction: Pathology of the inner ear
- 2011
-
Ingår i: Hearing research. - : Elsevier BV. - 1878-5891 .- 0378-5955. ; 281:1-2, s. 1-2
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 15. |
- Canlon, B
(författare)
-
Introduction to Annual Reviews 2011
- 2011
-
Ingår i: Hearing research. - : Elsevier BV. - 1878-5891 .- 0378-5955. ; 276:1-2, s. 1-1
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 16. |
|
|
| 17. |
- Canlon, B
(författare)
-
Progress in hearing research 2014
- 2014
-
Ingår i: Hearing research. - : Elsevier BV. - 1878-5891 .- 0378-5955. ; 311, s. 1-2
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 18. |
|
|
| 19. |
|
|
| 20. |
- Carlsson, Per-Inge, et al.
(författare)
-
The influence of genetic variation in oxidative stress genes on human noise susceptibility
- 2005
-
Ingår i: Hearing Research. - 0378-5955 .- 1878-5891. ; 202:1-2, s. 87-96
-
Tidskriftsartikel (refereegranskat)abstract
- Noise induced hearing loss (NIHL) is a complex disease caused by an interaction between genetic and environmental factors. Damage in the cochlea as a result of noise exposure appears to be mediated by reactive oxygen species (ROS). To investigate whether genetic variation in the human protective antioxidant system is associated with high or low susceptibility to NIHL, genetic polymorphisms derived from genes involved in the oxidative stress response were analysed in the 10% most susceptible and 10% most resistant extremes of 1200 Swedish noise-exposed workers. The genetic polymorphisms included 2 deletion polymorphisms for the GSTM1 and GSTT1 gene, and 14 SNPs derived from the CAT, SOD, GPX, GSR and GSTP1 genes. No significant differences were found between susceptible and resistant groups, providing no support for a major role of genetic variation of antioxidant enzymes in the susceptibility to NIHL.
|
|
| 21. |
|
|
| 22. |
- Couchman, Kiri, et al.
(författare)
-
Lateral superior olive function in congenital deafness
- 2011
-
Ingår i: Hearing Research. - : Elsevier BV. - 0378-5955 .- 1878-5891. ; 277:1-2, s. 163-175
-
Tidskriftsartikel (refereegranskat)abstract
- The development of cochlear implants for the treatment of patients with profound hearing loss has advanced considerably in the last few decades, particularly in the field of speech comprehension. However, attempts to provide not only sound decoding but also spatial hearing are limited by our understanding of circuit adaptations in the absence of auditory input. Here we investigate the lateral superior olive (LSO), a nucleus involved in interaural level difference (ILD) processing in the auditory brainstem using a mouse model of congenital deafness (the dn/dn mouse). An electrophysiological investigation of principal neurons of the LSO from the dn/dn mouse reveals a higher than normal proportion of single spiking (SS) neurons, and an increase in the hyperpolarisation-activated I(h) current. However, inhibitory glycinergic input to the LSO appears to develop normally both pre and postsynaptically in dn/dn mice despite the absence of auditory nerve activity. In combination with previous electrophysiological findings from the dn/dn mouse, we also compile a simple Hodgkin and Huxley circuit model in order to investigate possible computational deficits in ILD processing resulting from congenital hearing loss. We find that the predominance of SS neurons in the dn/dn LSO may compensate for upstream modifications and help to maintain a functioning ILD circuit in the dn/dn mouse. This could have clinical repercussions on the development of stimulation paradigms for spatial hearing with cochlear implants.
|
|
| 23. |
- Cros, Olivier, et al.
(författare)
-
Determination of the mastoid surface area and volume based on micro-CT scanning of human temporal bone : Geometrical parameters dependence on scanning resolutions
- 2016
-
Ingår i: Hearing Research. - : Elsevier BV. - 0378-5955 .- 1878-5891. ; 340, s. 127-134
-
Tidskriftsartikel (refereegranskat)abstract
- The mastoid air cell system (MACS) with its large complex of interconnected air cells reflects an enhanced surface area (SA) relative to its volume (V), which may indicate that the MACS is adapted to gas exchange and has a potential role in middle ear pressure regulation. Thus, these geometric parameters of the MACS have been studied by high resolution clinical CT scanning. However, the resolution of these scans is limited to a voxel size of around 0.6 mm in all dimensions, and so, the geometrical parameters are also limited. Small air cells may appear below the resolution and cannot be detected. Such air cells may contribute to a much higher SA than the V, and thus, also the SA/V ratio. More accurate parameters are important for analysis of the function of the MACS including physiological modeling.Our aim was to determine the SA, V, and SA/V ratio in MACS in human temporal bones at highest resolution by using micro-CT-scanning. Further, the influence of the resolution on these parameters was investigated by downsampling the data. Eight normally aerated temporal bones were scanned at the highest possible resolution (30-60 μm). The SA was determined using a triangular mesh fitted onto the segmented MACS. The V was determined by summing all the voxels containing air. Downsampling of the original data was applied four times by a factor of 2.The mean SA was 194 cm2, the mean V was 9 cm3, and the mean SA/V amounted to 22 cm-1. Decreasing the resolution resulted in a non-linear decrement of SA and SA/V, whereas V was mainly independent of the resolution.The current study found significantly higher SA and SA/V compared with previous studies using clinical CT scanning at lower resolutions. These findings indicate a separate role of the MACS compared with the tympanum, and the results are important for a more accurate modeling of the middle ear physiology.
|
|
| 24. |
- Cros, Olivier, et al.
(författare)
-
Mastoid structural properties determined by imaging analysis of high resolution CT-scanning
- 2010
-
Ingår i: Hearing Research. - : Elsevier. - 0378-5955 .- 1878-5891. ; 263:1-2, s. 242-243
-
Tidskriftsartikel (refereegranskat)abstract
- Hypothesis: The structure of the mastoid air cells can be described by quantitative imaging analysis of high-resolution CT-scans, which may contribute to understand its function in normal and pathological ears. Background: Negative middle ear pressure is a common factor in middle ear diseases resulting from an imbalance between mastoid gas exchange and Eustachian tube function. While the Eustachian tube function has been the main focus of research, more recent studies indicate that the mastoid may play an active role in pressure regulation. The mastoid structure with numerous air cells reflects a large area to volume ratio (AV-ratio) adapted to efficient gas exchange. Imaging analysis applied to high resolution CT-scanning can describe quantitative measures, which may reveal important information about mastoid function and its role in healthy and diseased ears. Materials and methods: Quantitative analysis was performed on a series of unselected high resolution CT-scans (voxel size: 0.29 _ 0.29 _ 0.625 mm) from 36 ears in 24 patients. Area and volume were determined using Cavalieri’s method, i.e. by summing cross-sectional areas. The AV-ratio was computed for each scan. Results: Mean area was 69 cm2 (range: 23–134cm2), mean volume was 4 cm3 (range: 1.3–10.8 cm3), and mean AV-ratio was 16 cm-1 (range: 11.2–21.0 cm-1). The area correlated linearly to the volume by A = 17.2*V-0.2. Conclusion: The area and volume values corresponded with previous studies, and the additional AV-ratio reflected the functional properties of the mastoid in terms of capability for gas exchange. Due to a series of similarities between structure and function of the lungs and mastoid, it seems likely to propose a tree-structure of dividing mastoid cells. In respiratory research, analysis describing the dimensions of series of bronchi generations has been applied, and based on current results; our aim of future research is to establish similar details of mastoid tree-structure. Funding source: Various private Danish funds.
|
|
| 25. |
- Cros, Olivier, et al.
(författare)
-
Micro-channels in the mastoid anatomy. Indications of a separate blood supply of the air cell system mucosa by micro-CT scanning
- 2013
-
Ingår i: Hearing Research. - : Elsevier. - 0378-5955 .- 1878-5891. ; 301, s. 60-65
-
Tidskriftsartikel (refereegranskat)abstract
- The mastoid air cell system has traditionally been considered to have a passive role in gas exchange and pressure regulation of the middle ear possibly with some acoustic function. However, more evidence has focused on the mucosa of the mastoid, which may play a more active role in regulation of middle ear pressure.In this study we have applied micro-CT scanning on a series of three human temporal bones. This approach greatly enhances the resolution (40–60 μm), so that we have discovered anatomical details, which has not been reported earlier. Thus, qualitative analysis using volume rendering has demonstrated notable micro-channels connecting the surface of the compact bone directly to the mastoid air cells as well as forming a network of connections between the air cells. Quantitative analysis on 2D slices was employed to determine the average diameter of these micro-channels (158 μm; range = 40–440 μm) as well as their density at a localized area (average = 75 cm−2; range = 64–97 cm−2).These channels are hypothesized to contain a separate vascular supply for the mastoid mucosa. However, future studies of the histological structure of the micro-channels are warranted to confirm the hypothesis. Studies on the mastoid mucosa and its blood supply may improve our knowledge of its physiological properties, which may have important implications for our understanding of the pressure regulation of the middle ear.
|
|
| 26. |
|
|
| 27. |
- Dobrev, Ivo, et al.
(författare)
-
Sound wave propagation on the human skull surface with bone conduction stimulation
- 2017
-
Ingår i: Hearing Research. - : ELSEVIER SCIENCE BV. - 0378-5955 .- 1878-5891. ; 355
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Bone conduction (BC) is an alternative to air conduction to stimulate the inner ear. In general, the stimulation for BC occurs on a specific location directly on the skull bone or through the skin covering the skull bone. The stimulation propagates to the ipsilateral and contralateral cochlea, mainly via the skull bone and possibly via other skull contents. This study aims to investigate the wave propagation on the surface of the skull bone during BC stimulation at the forehead and at ipsilateral mastoid. Methods: Measurements were performed in five human cadaveric whole heads. The electro-magnetic transducer from a BCHA (bone conducting hearing aid), a Baha (R) Cordelle II transducer in particular, was attached to a percutaneously implanted screw or positioned with a 5-Newton steel headband at the mastoid and forehead. The Baha transducer was driven directly with single tone signals in the frequency range of 0.25-8 kHz, while skull bone vibrations were measured at multiple points on the skull using a scanning laser Doppler vibrometer (SLDV) system and a 3D LDV system. The 3D velocity components, defined by the 3D LDV measurement coordinate system, have been transformed into tangent (in-plane) and normal (out-of-plane) components in a local intrinsic coordinate system at each measurement point, which is based on the cadaver heads shape, estimated by the spatial locations of all measurement points. Results: Rigid-body-like motion was dominant at low frequencies below 1 kHz, and clear transverse traveling waves were observed at high frequencies above 2 kHz for both measurement systems. The surface waves propagation speeds were approximately 450 m/s at 8 kHz, corresponding trans-cranial time interval of 0.4 ms. The 3D velocity measurements confirmed the complex space and frequency dependent response of the cadaver heads indicated by the ID data from the SLDV system. Comparison between the tangent and normal motion components, extracted by transforming the 3D velocity components into a local coordinate system, indicates that the normal component, with spatially varying phase, is dominant above 2 kHz, consistent with local bending vibration modes and traveling surface waves. Conclusion: Both SLDV and 3D LDV data indicate that sound transmission in the skull bone causes rigid body-like motion at low frequencies whereas transverse deformations and travelling waves were observed above 2 kHz, with propagation speeds of approximately of 450 m/s at 8 kHz. (C) 2017 Elsevier B.V. All rights reserved.
|
|
| 28. |
- Eeg-Olofsson, Måns, 1967, et al.
(författare)
-
Transmission of bone conducted sound – Correlation between hearing perception and cochlear vibration
- 2013
-
Ingår i: Hearing Research. - : Elsevier. - 0378-5955 .- 1878-5891. ; 306, s. 11-20
-
Tidskriftsartikel (refereegranskat)abstract
- The vibration velocity of the lateral semicircular canal and the cochlear promontory was measured on 16 subjects with a unilateral middle ear common cavity, using a laser Doppler vibrometer, when the stimulation was by bone conduction (BC). Four stimulation positions were used: three ipsilateral positions and one contralateral position. Masked BC pure tone thresholds were measured with the stimulation at the same four positions. Valid vibration data were obtained at frequencies between 0.3 and 5.0 kHz. Large intersubject variation of the results was found with both methods. The difference in cochlear velocity with BC stimulation at the four positions varied as a function of frequency while the tone thresholds showed a tendency of lower thresholds with stimulation at positions close to the cochlea. The correlation between the vibration velocities of the two measuring sites of the otic capsule was high. Also, relative median data showed similar trends for both vibration and threshold measurements. However, due to the high variability for both vibration and perceptual data, low correlation between the two methods was found at the individual level. The results from this study indicated that human hearing perception from BC sound can be estimated from the measure of cochlear vibrations of the otic capsule. It also showed that vibration measurements of the cochlea in cadaver heads are similar to that measured in live humans.
|
|
| 29. |
|
|
| 30. |
|
|
| 31. |
- Ghoncheh, Mohammad, et al.
(författare)
-
Output performance of the novel active transcutaneous bone conduction implant Sentio at different stimulation sites
- 2022
-
Ingår i: Hearing Research. - : ELSEVIER. - 0378-5955 .- 1878-5891. ; 421
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: The output performance of a novel semi-implantable transcutaneous bone conduction device was compared to an established percutaneous bone-anchored hearing system device using cadaver heads. The influence of actuator position, tissue growth below the actuator and mounting it on the surface or in a flattened bone bed on the performance of the implanted actuator was investigated.Materials and Methods: The percutaneous and the new transcutaneous device were sequentially implanted at two sites in five human cadaver heads: 55 mm superior-posterior to the ear canal opening (position A) and, closer to the cochlea, about 20 mm inferior-posterior to the ear canal opening behind the pinna on the mastoid (position B). The ipsi-and contralateral cochlear promontory (CP) velocity magnitude responses to percutaneous and transcutaneous stimulation were measured using laser Doppler vibrometry. In addition, the CP vibration of the transcutaneous device placed directly on the skull bone surface was compared with the placement in a flattened bone bed at a depth of about 3 mm. Finally, the influence of placing a thin silicone interposition layer under the implanted transducer was also explored.Results: The percutaneous device provided about an 11 dB higher average CP vibration level than the transcutaneous device at frequencies between 0.5 and 10 kHz. The ipsilateral CP vibration responses with stimulations at position B were on average 13 dB higher compared to stimulation at position A. The placement of the transcutaneous transducer at position B provided similar or higher average vibration magnitudes than the percutaneous transducer at position A. The 3 mm deep flattened bone bed had no significant effects on the output performance. Placing a thin silicone layer under the transcutaneous transducer had no significant influence on the output of the transcutaneous device.Conclusions: Our results using the CP vibration responses show that at frequencies above 500 Hz the new transcutaneous device at position B provides similar output levels as the percutaneous device at position A. The results also indicated that neither a bone bed for the placement of the transcutaneous transducer nor a simulated tissue growth between the actuator and the bone affect the output performance of the device.
|
|
| 32. |
- Glueckert, R., et al.
(författare)
-
Anatomical basis of drug delivery to the inner ear
- 2018
-
Ingår i: Hearing Research. - : Elsevier. - 0378-5955 .- 1878-5891. ; 368, s. 10-27
-
Forskningsöversikt (refereegranskat)abstract
- The isolated anatomical position and blood-labyrinth barrier hampers systemic drug delivery to the mammalian inner ear. Intratympanic placement of drugs and permeation via the round-and oval window are established methods for local pharmaceutical treatment. Mechanisms of drug uptake and pathways for distribution within the inner ear are hard to predict. The complex microanatomy with fluid filled spaces separated by tight-and leaky barriers compose various compartments that connect via active and passive transport mechanisms. Here we provide a review on the inner ear architecture at light-and electron microscopy level, relevant for drug delivery. Focus is laid on the human inner ear architecture. Some new data add information on the human inner ear fluid spaces generated with high resolution microcomputed tomography at 15 urn resolution. Perilymphatic spaces are connected with the central modiolus by active transport mechanisms of mesothelial cells that provide access to spiral ganglion neurons. Reports on leaky barriers between scala tympani and the so-called cortilymph compartment likely open the best path for hair cell targeting. The complex barrier system of tight junction proteins such as occludins, claudins and tricellulin isolates the endolymphatic space for most drugs. Comparison of relevant differences of barriers, target cells and cell types involved in drug spread between main animal models and humans shall provide some translational aspects for inner ear drug applications. (C) 2018 The Authors. Published by Elsevier B.V.
|
|
| 33. |
- Grondin, Yohann, et al.
(författare)
-
Pulmonary delivery of d-methionine is associated with an increase in ALCAR and glutathione in cochlear fluids.
- 2013
-
Ingår i: Hearing Research. - : Elsevier BV. - 0378-5955 .- 1878-5891. ; 298, s. 93-103
-
Tidskriftsartikel (refereegranskat)abstract
- In animals, hearing loss resulting from cochlear mechanosensory cell damage can be mitigated by antioxidants such as d-methionine (d-met) and acetyl-l-carnitine (ALCAR). The systemic routes of administration of these compounds, that must of necessity transit trough the cochlear fluids, may affect the antioxidant levels in the cochlea and the resulting oto-protective effect. In this study, we analyzed the pharmacokinetics of [C]d-met in the cochlea and four other tissues after intratracheal (IT), intranasal (IN), and oral by gavage (OG) administration and compared it to intravenous administration (IV). We then analyzed the effect of these four routes on the antioxidant content of the cochlear fluids after d-met or ALCAR administration, by liquid chromatography/mass spectrometry. Our results showed that the concentration of methionine and ALCAR in cochlear fluids significantly increased after their respective systemic administration. Interestingly, d-met administration also contributed to an increase of ALCAR. Our results also showed that the delivery routes differently affected the bioavailability of administered [C]d-met as well as the concentrations of methionine, ALCAR and the ratio of oxidized to reduced glutathione. Overall, pulmonary delivery via IT administration achieved high concentrations of methionine, ALCAR, and oxidative-related metabolites in cochlear fluids, in some cases surpassing IV administration, while IN route appeared to be the least efficacious. To our knowledge, this is the first report of the direct measurements of antioxidant levels in cochlear fluids after their systemic administration. This report also demonstrates the validity of the pulmonary administration of antioxidants and highlights the different contributions of d-met and ALCAR allowing to further investigate their impact on oxidative stress in the cochlear microenvironment.
|
|
| 34. |
- Göthberg, Hanna, 1973, et al.
(författare)
-
Cross-sectional assessment of hearing acuity of an unscreened 85-year-old cohort - Including a 10-year longitudinal study of a sub-sample.
- 2019
-
Ingår i: Hearing research. - : Elsevier BV. - 1878-5891 .- 0378-5955. ; 382
-
Tidskriftsartikel (refereegranskat)abstract
- As the proportion of older people increases, it is important to investigate hearing acuity in older individuals and to calculate hearing decline for older ages, using standardised test protocols. The main aim of this study was to determine pure-tone hearing thresholds in an unscreened birth cohort of 85-year-olds born in 1930, living in an industrial Swedish city. A further aim was to describe hearing decline in men and women from 75 to 85 years of age with the aid of longitudinal data. The study was part of the Gothenburg H70 Birth Cohort Studies in Sweden. Hearing thresholds (0.25-8kHz) were measured using automated pure-tone audiometry for 286 85-year-old participants. A subsample (n=182) was hearing examined at 75 years of age and studied longitudinally from 75 to 85 years. At age 85 years, men had better hearing at low frequencies but poorer hearing at high frequencies than women. The longitudinal study showed a considerable decline between 75 and 85yearsat mid-high frequencies (>1kHz) and the amount of decline was similar between sexes. The results contribute to the estimation of the future need for hearing health services.
|
|
| 35. |
- Hartel, Bas P., et al.
(författare)
-
A combination of two truncating mutations in USH2A causes more severe and progressive hearing impairment in Usher syndrome type IIa
- 2016
-
Ingår i: Hearing Research. - Amsterdam, Netherlands : Elsevier. - 0378-5955 .- 1878-5891. ; 339, s. 60-68
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: Usher syndrome is an inherited disorder that is characterized by hearing impairment (HI), retinitis pigmentosa, and in some cases vestibular dysfunction. Usher syndrome type IIa is caused by mutations in USH2A. HI in these patients is highly heterogeneous and the present study evaluates the effects of different types of USH2A mutations on the audiometric phenotype. Data from two large centres of expertise on Usher Syndrome in the Netherlands and Sweden were combined in order to create a large combined sample of patients to identify possible genotype-phenotype correlations.Design: A retrospective study on HI in 110 patients (65 Dutch and 45 Swedish) genetically diagnosed with Usher syndrome type IIa. We used methods especially designed for characterizing and testing differences in audiological phenotype between patient subgroups. These methods included Age Related Typical Audiograms (ARTA) and a method to evaluate the difference in the degree of HI developed throughout life between subgroups.Results: Cross-sectional linear regression analysis of last-visit audiograms for the best hearing ear demonstrated a gradual decline of hearing over decades. The congenital level of HI was in the range of 16-33 dB at 0.25-0.5 kHz, and in the range of 51-60 dB at 1-8 kHz. The annual threshold deterioration was in the range of 0.4-0.5 dB/year at 0.25-2 kHz and in the range of 0.7-0.8 dB/year at 4-8 kHz. Patients with two truncating mutations, including homozygotes for the common c.2299delG mutation, developed significantly more severe HI throughout life than patients with one truncating mutation combined with one nontruncating mutation, and patients with two nontruncating mutations.Conclusions: The results have direct implications for patient counselling in terms of prognosis of hearing and may serve as baseline measures for future (genetic) therapeutic interventions.
|
|
| 36. |
- He, Wenxuan, et al.
(författare)
-
An outer hair cell-powered global hydromechanical mechanism for cochlear amplification
- 2022
-
Ingår i: Hearing Research. - : ELSEVIER. - 0378-5955 .- 1878-5891. ; 423
-
Forskningsöversikt (refereegranskat)abstract
- It is a common belief that the mammalian cochlea achieves its exquisite sensitivity, frequency selectiv-ity, and dynamic range through an outer hair cell-based active process, or cochlear amplification. As a sound-induced traveling wave propagates from the cochlear base toward the apex, outer hair cells at a narrow region amplify the low level sound-induced vibration through a local feedback mechanism. This widely accepted theory has been tested by measuring sound-induced sub-nanometer vibrations within the organ of Corti in the sensitive living cochleae using heterodyne low-coherence interferometry and optical coherence tomography. The aim of this short review is to summarize experimental findings on the cochlear active process by the authors group. Our data show that outer hair cells are able to gener-ate substantial forces for driving the cochlear partition at all audible frequencies in vivo. The acoustically induced reticular lamina vibration is larger and more broadly tuned than the basilar membrane vibration. The reticular lamina and basilar membrane vibrate approximately in opposite directions at low frequen-cies and in the same direction at the best frequency. The group delay of the reticular lamina is larger than that of the basilar membrane. The magnitude and phase differences between the reticular lamina and basilar membrane vibration are physiologically vulnerable. These results contradict predictions based on the local feedback mechanism but suggest a global hydromechanical mechanism for cochlear amplifi-cation. This article is part of the Special Issue Outer hair cell Edited by Joseph Santos-Sacchi and Kumar Navaratnam. (c) 2021 Elsevier B.V. All rights reserved.
|
|
| 37. |
|
|
| 38. |
|
|
| 39. |
- Henson, M.M., et al.
(författare)
-
Smooth muscle in the annulus fibrosus of the tympanic membrane in bats, rodents, insectivores and humans
- 2005
-
Ingår i: Hearing Research. - : Elsevier BV. - 0378-5955 .- 1878-5891. ; 200:1-2, s. 29-37
-
Tidskriftsartikel (refereegranskat)abstract
- The annulus fibrosus and its attachment to the bony tympanic ring were studied in a series of mammals. In the pallid bat, Antrozous pallidus, there is an extensive plexus of large interconnected blood sinuses in the part of the annulus that borders the tympanic bone. The spaces between the sinuses are packed with smooth muscle cells. Most of the cells have a predominately radial orientation; they extend from the bony tympanic sulcus to a dense collagenous matrix (apical zone) where radially oriented fibers of the pars tensa are confluent with the annulus. The muscles and vessels constitute a myovascular zone. A structurally similar myovascular zone is also present in the European hedgehog. In rodents, the annulus lacks the large interconnected blood sinuses but many small vessels are present. Smooth muscle is concentrated in the broad area of attachment of the annulus to the tympanic bone. In the gerbil, smooth muscle seems to be concentrated in the central part of the width of the annulus where it is attached to bone and radiates toward the tympanic membrane. In humans collections of radially oriented smooth muscle cells were found in several locations. The smooth muscle in all species studied appears to form a rim of contractile elements for the pars tensa. This arrangement suggests a role in controlling blood flow and/or creating and maintaining tension on the tympanic membrane.
|
|
| 40. |
|
|
| 41. |
|
|
| 42. |
- Koelewijn, Thomas, et al.
(författare)
-
The effect of monetary reward on listening effort and sentence recognition
- 2021
-
Ingår i: Hearing Research. - : Elsevier. - 0378-5955 .- 1878-5891. ; 406
-
Tidskriftsartikel (refereegranskat)abstract
- Recently we showed that higher reward results in increased pupil dilation during listening (listening effort). Remarkably, this effect was not accompanied with improved speech reception. Still, increased listening effort may reflect more in-depth processing, potentially resulting in a better memory representation of speech. Here, we investigated this hypothesis by also testing the effect of monetary reward on recognition memory performance. Twenty-four young adults performed speech reception threshold (SRT) tests, either hard or easy, in which they repeated sentences uttered by a female talker masked by a male talker. We recorded the pupil dilation response during listening. Participants could earn a high or low reward and the four conditions were presented in a blocked fashion. After each SRT block, participants performed a visual sentence recognition task. In this task, the sentences that were presented in the preceding SRT task were visually presented in random order and intermixed with unfamiliar sentences. Participants had to indicate whether they had previously heard the sentence or not. The SRT and sentence recognition were affected by task difficulty but not by reward. Contrary to our previous results, peak pupil dilation did not reflect effects of reward. However, post-hoc time course analysis (GAMMs) revealed that in the hard SRT task, the pupil response was larger for high than low reward. We did not observe an effect of reward on visual sentence recognition. Hence, the current results provide no conclusive evidence that the effect of monetary reward on the pupil response relates to the memory encoding of speech. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )
|
|
| 43. |
- Koelewijn, Thomas, et al.
(författare)
-
The effect of reward on listening effort as reflected by the pupil dilation response
- 2018
-
Ingår i: Hearing Research. - : ELSEVIER SCIENCE BV. - 0378-5955 .- 1878-5891. ; 367, s. 106-112
-
Tidskriftsartikel (refereegranskat)abstract
- Listening to speech in noise can be effortful but when motivated people seem to be more persevering. Previous research showed effects of monetary reward on autonomic responses like cardiovascular reactivity and pupil dilation while participants processed auditory information. The current study examined the effects of monetary reward on the processing of speech in noise and related listening effort as reflected by the pupil dilation response. Twenty-four participants (median age 21 yrs) performed two speech reception threshold (SRT) tasks, one tracking 50% correct (hard) and one tracking 85% correct (easy), both of which they listened to and repeated sentences uttered by a female talker. The sentences were presented with a single male talker or, in a control condition, in quiet. Participants were told that they could earn a high (5 euros) or low (0.20 euro) reward when repeating 70% or more of the sentences correctly. Conditions were presented in a blocked fashion and during each trial, pupil diameter was recorded. At the end of each block, participants rated the effort they had experienced, their performance, and their tendency to quit listening. Additionally, participants performed a working memory capacity task and filled in a need-for-recovery questionnaire as these tap into factors that influence the pupil dilation response. The results showed no effect of reward on speech perception performance as reflected by the SRT. The peak pupil dilation showed a significantly larger response for high than for low reward, for the easy and hard conditions, but not the control condition. Higher need for recovery was associated with a higher subjective tendency to quit listening. Consistent with the Framework for Understanding Effortful Listening, we conclude that listening effort as reflected by the peak pupil dilation is sensitive to the amount of monetary reward. (C) 2018 The Authors. Published by Elsevier B.V.
|
|
| 44. |
- Koelewijn, Thomas, et al.
(författare)
-
The pupil response is sensitive to divided attention during speech processing
- 2014
-
Ingår i: Hearing Research. - : Elsevier. - 0378-5955 .- 1878-5891. ; 312, s. 114-120
-
Tidskriftsartikel (refereegranskat)abstract
- Dividing attention over two streams of speech strongly decreases performance compared to focusing on only one. How divided attention affects cognitive processing load as indexed with pupillometry during speech recognition has so far not been investigated. In 12 young adults the pupil response was recorded while they focused on either one or both of two sentences that were presented dichotically and masked by fluctuating noise across a range of signal-to-noise ratios. In line with previous studies, the performance decreases when processing two target sentences instead of one. Additionally, dividing attention to process two sentences caused larger pupil dilation and later peak pupil latency than processing only one. This suggests an effect of attention on cognitive processing load (pupil dilation) during speech processing in noise.
|
|
| 45. |
- Koelewijn, Thomas, et al.
(författare)
-
The pupil response reveals increased listening effort when it is difficult to focus attention
- 2015
-
Ingår i: Hearing Research. - : Elsevier. - 0378-5955 .- 1878-5891. ; 323, s. 81-90
-
Tidskriftsartikel (refereegranskat)abstract
- Recent studies have shown that prior knowledge about where, when, and who is going to talk improves speech intelligibility. How related attentional processes affect cognitive processing load has not been investigated yet. In the current study, three experiments investigated how the pupil dilation response is affected by prior knowledge of target speech location, target speech onset, and who is going to talk. A total of 56 young adults with normal hearing participated. They had to reproduce a target sentence presented to one ear while ignoring a distracting sentence simultaneously presented to the other ear. The two sentences were independently masked by fluctuating noise. Target location (left or right ear), speech onset, and talker variability were manipulated in separate experiments by keeping these features either fixed during an entire block or randomized over trials. Pupil responses were recorded during listening and performance was scored after recall. The results showed an improvement in performance when the location of the target speech was fixed instead of randomized. Additionally, location uncertainty increased the pupil dilation response, which suggests that prior knowledge of location reduces cognitive load. Interestingly, the observed pupil responses for each condition were consistent with subjective reports of listening effort. We conclude that communicating in a dynamic environment like a cocktail party (where participants in competing conversations move unpredictably) requires substantial listening effort because of the demands placed on attentional processes. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
|
|
| 46. |
|
|
| 47. |
- Kundu, Soumi, et al.
(författare)
-
Folic acid improves inner ear vascularization in hyperhomocysteinemic mice
- 2012
-
Ingår i: Hearing Research. - : Elsevier BV. - 0378-5955 .- 1878-5891. ; 284:1-2, s. 42-51
-
Tidskriftsartikel (refereegranskat)abstract
- More than 29 million adults in the United States have been diagnosed with hearing loss. Interestingly, elevated homocysteine (Hcy) levels, known as hyperhomocysteinemia (HHcy), are also associated with impaired hearing. However, the associated mechanism remains obscure. The collagen receptor such as discoidin domain receptor 1 and matrix metalloproteinase (MMP) play a significant role in inner ear structure and function. We hypothesize that HHcy increases hearing thresholds by compromise in inner ear vasculature resulted from impaired Hcy metabolism, increased oxidative stress, collagen IVa and collagen Ia turnover. The treatment with folic acid (FA) protects elevated hearing thresholds and prevents reduction in vessel density by lowering abundant collagen deposition and oxidative stress in inner ear. To test this hypothesis we employed 8 weeks old male wild type (WT), cystathionine-beta-synthase heterozygote knockout (CBS+/-) mice, WT + FA (0.0057 mu g/g/day, equivalent to a 400 mu g/70 kg/day human dose in drinking water); and CBS(+/-) +FA. The mice were treated for four weeks. The hearing thresholds were determined by recording the auditory brainstem responses. Integrity of vessels was analyzed by perfusion of horseradish peroxidase (HRP) tracer. Endothelial permeability was assessed, which indicated restoration of HRP leakage by FA treatment. A total Hcy level was increased in stria vascularis (SV) and spiral ligament (SL) of CBS+/- mice which was lowered by FA. Interestingly, FA treatment lowered Col IVa Immunostaining by affecting its turnover. The levels of MMP-2, -9, methylenetetrahydrofolate reductase (MTHFR) and cystathione gamma lyase (CSE) were measured by Western blot analysis. The oxidative stress was high in SV and SL of CBS+/- compared to WT however the treatment with FA lowered oxidative stress in CBS+/- mice. These data suggested that hearing loss in CBS+/- mice was primarily due to leakage in inner ear circulation, also partly by induced collagen imbalance, increase in Hcy and oxidative stress in inner ear.
|
|
| 48. |
- Kytövuori, Laura, et al.
(författare)
-
A nonsynonymous mutation in the WFS1 gene in a Finnish family with age-related hearing impairment
- 2017
-
Ingår i: Hearing Research. - Amsterdam, Netherlands : Elsevier. - 0378-5955 .- 1878-5891. ; 355, s. 97-101
-
Tidskriftsartikel (refereegranskat)abstract
- Wolfram syndrome (WS) is caused by recessive mutations in the Wolfram syndrome 1 (WFS1) gene. Sensorineural hearing impairment (HI) is a frequent feature in WS and, furthermore, certain mutations in WFS1 cause nonsyndromic dominantly inherited low-frequency sensorineural HI. These two phenotypes are clinically distinct indicating that WFS1 is a reasonable candidate for genetic studies in patients with other phenotypes of HI. Here we have investigated, whether the variation in WFS1 has a pathogenic role in age-related hearing impairment (ARHI). WFS1 gene was investigated in a population sample of 518 Finnish adults born in 1938-1949 and representing variable hearing phenotypes. Identified variants were evaluated with respect to pathogenic potential. A rare mutation predicted to be pathogenic was found in a family with many members with impaired hearing. Twenty members were recruited to a segregation study and a detailed clinical examination. Heterozygous p.Tyr528His variant segregated completely with late-onset HI in which hearing deteriorated first at high frequencies and progressed to mid and low frequencies later in life. We report the first mutation in the WFS1 gene causing late-onset HI with audiogram configurations typical for ARHI. Monogenic forms of ARHI are rare and our results add WFS1 to the short list of such genes.
|
|
| 49. |
- Lim, Jongwoo, et al.
(författare)
-
Development of a finite element model of a human head including auditory periphery for understanding of bone-conducted hearing
- 2022
-
Ingår i: Hearing Research. - : ELSEVIER. - 0378-5955 .- 1878-5891. ; 421
-
Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional finite-element (FE) model of a human head including the auditory periphery was developed to obtain a better understanding of bone-conducted (BC) hearing. The model was validated by comparison of cochlear and head responses in both air-conducted (AC) and BC hearing with experimental data. Specifically, the FE model provided the cochlear responses such as basilar membrane velocity and intracochlear pressure corresponding to BC stimulations applied to the mastoid or the conventional bone-anchored-hearing-aid (BAHA) positions. This is a strength of the model because it is difficult to obtain the cochlear responses from experiments corresponding to the BC stimulation applied at a specific position on the head surface. In addition, there have been few studies based on an FE model that can calculate the head and cochlear responses simultaneously from a BC stimulation. Moreover, in this study, the intracochlear sound pressure at multi-positions along the BM length was calculated and used to clarify the effect of stimulating force direction on the cochlear and promontory velocities in BC hearing. Also, the relationship between BC and AC stimulation and the basilar membrane velocity in the FE model was used to calculate the stimulation level at hearing thresholds which has been investigated only by psychoacoustical methods.
|
|
| 50. |
- Liu, Wei, et al.
(författare)
-
Unique expression of connexins in the human cochlea
- 2009
-
Ingår i: Hearing Research. - : Elsevier BV. - 0378-5955 .- 1878-5891. ; 250:1-2, s. 55-62
-
Tidskriftsartikel (refereegranskat)abstract
- Mutations in the genes GJB2 and GJB6, which encode the proteins Connexin 26 (Cx26) and Connexin 30 (Cx30), have been linked to nonsyndromic prelingual deafness in humans. These proteins may form so-called gap junctions (GJ) or transcellular pathways between cells. The pathogenesis of deafness due to GJ Connexin mutations remains unclear partly because examinations performed in the human ear are infrequent. Here we analysed the expression and distribution of Cx26 and Cx30 in five fresh normal human cochleae taken out at occasional surgery. Immunohistochemistry including confocal microscopy in decalcified specimen showed that these proteins are widely expressed in the human cochlea. In the lateral wall there was strong antibody co-labeling for Cx26 and Cx30 that support the existence of channels comprising heteromeric Cx26/Cx30 connexons. In the organ of Corti there were some co-labeling in the supporting cell area including mainly the Claudius cells and Deiter cells of these two Cxs, apart from isolated Cx26 and Cx30 labeling in the same area, suggestive of both homomeric/homotypic pattern and hybrid pattern (heteromeric or heterotypic). Cx30, Cx26 and Connexin 36 (Cx36) immunoreactivity was also associated with spiral ganglion type I neurons, the latter being a gap junction protein specific to neurons. Gap-junction-based electrical synapses are not known to occur in mammalian auditory system other than in bats where they may play a role for fast electrical nerve transmission useful for echolocation. Their potential role in the processing of human auditory nerve signaling as well as non-GJ roles of the connexins in human cochlea is discussed.
|
|
