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| 2. |
- Kawaguchi, S, et al.
(author)
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Vestibular morphology in the German Waltzing guinea pig
- 2010
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In: Journal of otolaryngology - head & neck surgery = Le Journal d'oto-rhino-laryngologie et de chirurgie cervico-faciale. - 1916-0216. ; 39:2, s. 115-121
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Journal article (peer-reviewed)
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- Hu, Zhengqing, et al.
(author)
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Functional Evaluation of a Cell Replacement Therapy in the Inner Ear
- 2009
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In: Otology and Neurotology. - : Lippincott Williams & Wilkins. - 1531-7129 .- 1537-4505. ; 30:4, s. 551-558
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Journal article (peer-reviewed)abstract
- HYPOTHESIS:Cell replacement therapy in the inner ear will contribute to the functional recovery of hearing loss.BACKGROUND:Cell replacement therapy is a potentially powerful approach to replace degenerated or severely damaged spiral ganglion neurons. This study aimed at stimulating the neurite outgrowth of the implanted neurons and enhancing the potential therapeutic of inner ear cell implants.METHODS:Chronic electrical stimulation (CES) and exogenous neurotrophic growth factor (NGF) were applied to 46 guinea pigs transplanted with embryonic dorsal root ganglion (DRG) neurons 4 days postdeafening. The animals were evaluated with the electrically evoked auditory brainstem responses (EABRs) at experimental Days 7, 11, 17, 24, and 31. The animals were euthanized at Day 31, and the inner ears were dissected for immunohistochemistry investigation.RESULTS:Implanted DRG cells, identified by enhanced green fluorescent protein fluorescence and a neuronal marker, were found close to Rosenthal canal in the adult inner ear for up to 4 weeks after transplantation. Extensive neurite projections clearly, greater than in nontreated animals, were observed to penetrate the bony modiolus and reach the spiral ganglion region in animals supplied with CES and/or NGF. There was, however, no significant difference in the thresholds of EABRs between DRG-transplanted animals supplied with CES and/or NGF and DRG-transplanted animals without CES or NGF supplement.CONCLUSION:The results suggest that CES and/or NGF can stimulate neurite outgrowth from implanted neurons, although based on EABR measurement, these interventions did not induce functional connections to the central auditory pathway. Additional time or novel approaches may enhance functional responsiveness of implanted cells in the adult cochlea
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| 10. |
- Johansson, Göran A., et al.
(author)
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Exploring the use of soft X-ray microscopy for imaging subcellular structures of the inner ear
- 2004
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In: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 215, s. 203-212
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Journal article (peer-reviewed)abstract
- The soft X-ray microscope at the Lawrence Berkeley National Laboratory was developed for visualization of biological tissue. Soft X-ray microscopy provides high-resolution visualization of hydrated, non-embedded and non-sectioned cells and is thus potentially an alternative to transmission electron microscopy. Here we show for the first time soft X-ray micrographs of structures isolated from the guinea-pig inner ear. Sensory outer hair cells and supporting pillar cells are readily visualized. In the hair cells, individual stereocilia can easily be identified within the apical hair bundle. The underlying cuticular plate is, however, too densely composed or too thick to be clearly visualized, and thus appears very dark. The cytoplasmic structures protruding from the cuticular plates as well as the fibrillar material surrounding and projecting from the cell nuclei can be seen. In the pillar cells the images reveal individual microtubule bundles. Soft X-ray images of the acellular tectorial membrane and thin two-layered Reissner's membrane display a level of resolution comparable to low-power electron microscopy.
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| 15. |
- Ulfendahl, M., et al.
(author)
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Mechanical response characteristics of the hearing organ in the low-frequency regions of the cochlea
- 1996
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In: Journal of Neurophysiology. - : American Physiological Society. - 0022-3077 .- 1522-1598. ; 76:6, s. 3850-3862
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Journal article (peer-reviewed)abstract
- 1. With the use of an in vitro preparation of the guinea pig temporal bone, in which the apical turns of the cochlea are exposed, the mechanical and electrical responses of the cochlea in the low-frequency regions were studied during sound stimulation. 2. The mechanical characteristics were investigated in the fourth and third turns of the cochlea with the use of laser heterodyne interferometry, which allows the vibratory responses of both sensory and supporting cells to be recorded. The electrical responses, which can be maintained for several hours, were recorded only in the most apical turn. 3. In the most apical turn, the frequency locations and shapes of the mechanical and electrical responses were very similar. 4. The shapes of the tuning curves and the spatial locations of the frequency maxima in the temporal bone preparation compared very favorably with published results from in vivo recordings of hair cell receptor potentials and sound-induced vibrations of the Reissner's membrane. 5. Compressive nonlinearities were present in both the mechanical and the electrical responses at moderate sound pressure levels. 6. The mechanical tuning changed along the length of the cochlea, the center frequencies in the fourth and third turns being approximately 280 and 570 Hz, respectively. 7. The mechanical responses of sensory and supporting cells were almost identical in shape but differed significantly in amplitude radially across the reticular lamina.
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| 17. |
- Von Tiedemann, M., et al.
(author)
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Image adaptive point-spread function estimation and deconvolution for in vivo confocal microscopy
- 2006
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In: Microscopy research and technique (Print). - : Wiley. - 1059-910X .- 1097-0029. ; 69:1, s. 10-20
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Journal article (peer-reviewed)abstract
- Visualizing deep inside the tissue of a thick biological sample often poses severe constraints on image conditions. Standard restoration techniques (denoising and deconvolution) can then be very useful, allowing one to increase the signal-to-noise ratio and the resolution of the images. In this paper, we consider the problem of obtaining a good determination of the point-spread function (PSF) of a confocal microscope, a prerequisite for applying deconvolution to three-dimensional image stacks acquired with this system. Because of scattering and optical distortion induced by the sample, the PSF has to be acquired anew for each experiment. To tackle this problem, we used a screening approach to estimate the PSF adaptively and automatically from the images. Small PSF-like structures were detected in the images, and a theoretical PSF model reshaped to match the geometric characteristics of these structures. We used numerical experiments to quantify the sensitivity of our detection method, and we demonstrated its usefulness by deconvolving images of the hearing organ acquired in vitro and in vivo.
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| 24. |
- Anvari, B, et al.
(author)
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Photonics in the auditory system
- 2007
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In: JOURNAL OF BIOMEDICAL OPTICS. - : SPIE-Intl Soc Optical Eng. - 1083-3668. ; 12:2
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Journal article (other academic/artistic)
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| 30. |
- Chen, ZQ, et al.
(author)
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Pharmacokinetics of caroverine in the inner ear and its effects on cochlear function after systemic and local administrations in Guinea pigs
- 2003
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In: Audiology & neuro-otology. - : S. Karger AG. - 1420-3030. ; 8:1, s. 49-56
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Journal article (peer-reviewed)abstract
- Caroverine, an N-methyl-<i>D</i>-aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist, has been shown to protect the inner ear from excitotoxicity and to be effective in the treatment of cochlear synaptic tinnitus. Local administration of caroverine on the round window membrane (RWM) could be a more effective means of administration to avoid systemic side/adverse effects. The present study investigates the pharmacokinetics of caroverine in the perilymph, cerebrospinal fluid (CSF) and plasma following intravenous and local applications at different dosages. High-performance liquid chromatography was used to determine the drug concentrations. Our results show much higher caroverine concentrations in the perilymph with lower concentrations in CSF and plasma following local applications compared with systemic administration. Auditory brainstem responses were measured to evaluate the changes in auditory function. The effects on hearing were transient and fully reversible 24 h after local caroverine applications. The findings suggest that local application of caroverine on the RWM for the treatment of excitotoxicity-related inner ear diseases, such as tinnitus and noise-induced hearing loss, might be both safe and more efficacious while avoiding high blood and CSF caroverine levels seen with systemic administration.
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| 31. |
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| 32. |
- Conradi, P, et al.
(author)
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Outer hair cells isolated from the organ of corti exposed to increased hydrostatic pressure
- 1999
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In: ORL. - : S. Karger AG. - 0301-1569 .- 1423-0275. ; 61:2, s. 57-62
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Journal article (peer-reviewed)abstract
- A model using outer hair cells isolated from the guinea pig organ of Corti was used to study the effects of changes in hydrostatic pressure. Outer hair cells were placed in a closed chamber and the pressure was raised to levels corresponding to pressures measured inside the cochlea or higher. No changes in cell shape could be detected using either videomicroscopy or confocal microscopy. No clear changes were observed using a potentiometric vital dye.
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| 42. |
- Flock, Å., et al.
(author)
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Supporting cells contribute to control of hearing sensitivity
- 1999
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In: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 19:11, s. 4498-4507
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Journal article (peer-reviewed)abstract
- The mammalian hearing organ, the organ of Corti, was studied in an in vitro preparation of the guinea pig temporal bone. As in vivo, the hearing organ responded with an electrical potential, the cochlear microphonic potential, when stimulated with a test tone. After exposure to intense sound, the response to the test tone was reduced. The electrical response either recovered within 10-20 min or remained permanently reduced, thus corresponding to a temporary or sustained loss of sensitivity. Using laser scanning confocal microscopy, stimulus-induced changes of the cellular structure of the hearing organ were simultaneously studied. The cells in the organ were labeled with two fluorescent probes, a membrane dye and a cytoplasm dye, showing enzymatic activity in living cells. Confocal microscopy images were collected and compared before and after intense sound exposure. The results were as follows. (1) The organ of Corti could be divided into two different structural entities in terms of their susceptibility to damage: an inner, structurally stable region comprised of the inner hair cell with its supporting cells and the inner and outer pillar cells; and an outer region that exhibited dynamic structural changes and consisted of the outer hair cells and the third Deiters' cell with its attached Hensen's cells. (2) Exposure to intense sound caused the Deiters' cells and Hensen's cells to move in toward the center of the cochlear turn. (3) This event coincided with a reduced sensitivity to the test tone (i.e., reduced cochlear microphonic potential). (4) The displacement and sensitivity loss could be reversible. It is concluded that these observations have relevance for understanding the mechanisms behind hearing loss after noise exposure and that the supporting cells take an active part in protection against trauma during high-intensity sound exposure.
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| 47. |
- Fridberger, Anders, 1966-, et al.
(author)
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Acoustic overstimulation increases outer hair cell Ca2+ concentrations and causes dynamic contractions of the hearing organ
- 1998
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In: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 95:12, s. 7127-7132
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Journal article (peer-reviewed)abstract
- The dynamic responses of the hearing organ to acoustic overstimulation were investigated using the guinea pig isolated temporal bone preparation. The organ was loaded with the fluorescent Ca2+ indicator Fluo-3, and the cochlear electric responses to low-level tones were recorded through a microelectrode in the scala media. After overstimulation, the amplitude of the cochlear potentials decreased significantly. In some cases, rapid recovery was seen with the potentials returning to their initial amplitude. In 12 of 14 cases in which overstimulation gave a decrease in the cochlear responses, significant elevations of the cytoplasmic [Ca2+] in the outer hair cells were seen. [Ca2+] increases appeared immediately after terminating the overstimulation, with partial recovery taking place in the ensuing 30 min in some preparations. Such [Ca2+] changes were not seen in preparations that were stimulated at levels that did not cause an amplitude change in the cochlear potentials. The overstimulation also gave rise to a contraction, evident as a decrease of the width of the organ of Corti. The average contraction in 10 preparations was 9 microm (SE 2 microm). Partial or complete recovery was seen within 30-45 min after the overstimulation. The [Ca2+] changes and the contraction are likely to produce major functional alterations and consequently are suggested to be a factor contributing strongly to the loss of function seen after exposure to loud sounds.
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| 48. |
- Fridberger, Anders, 1966-, et al.
(author)
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Acute mechanical overstimulation of isolated outer hair cells causes changes in intracellular calcium levels without shape changes
- 1996
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In: Acta Oto-Laryngologica. - : Informa Healthcare. - 0001-6489 .- 1651-2251. ; 116:1, s. 17-24
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Journal article (peer-reviewed)abstract
- Impaired auditory function following acoustic overstimulation, or noise, is mainly reported to be accompanied by cellular changes such as damage to the sensory hair bundles, but changes in the cell bodies of the outer hair cells have also been described. To investigate more closely the immediate cellular responses to overstimulation, isolated guinea pig outer hair cells were subjected to a 200 Hz oscillating water jet producing intense mechanical stimulation. The water jet was aimed at the cell body of the isolated outer hair cell. Cell shape changes were studied using video microscopy, and intracellular calcium concentration changes were monitored by means of the fluorescent calcium indicator Fluo-3. Cells exposed to a high-intensity stimulus showed surprisingly small light-microscopical alterations. The cytoplasmic calcium concentration increased in most cells, although some cells appeared very resistant to the mechanical stress. No correlation could be found be tween the calcium concentration changes and the cell length. The changes in calcium concentration reported here are suggested to be involved in the long-term pathogenesis of noise-induced hair cell damage.
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| 49. |
- Fridberger, Anders, 1966-, et al.
(author)
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An in vitro model for acoustic overstimulation
- 1998
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In: Acta Oto-Laryngologica. - : Informa Healthcare. - 0001-6489 .- 1651-2251. ; 118:3, s. 352-361
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Journal article (peer-reviewed)abstract
- Although many studies have been performed on the effects of acoustic overstimulation on the inner ear, our knowledge about the cellular processes underlying reduced hearing sensitivity and auditory cell death is still limited. In order to further our understanding of cellular processes occurring in conjunction with acoustic trauma, we designed an in vitro model to study the effects of overstimulation directly on sensory hair cells isolated from the low-frequency part of the guinea pig cochlea. The isolated outer hair cells were subjected to pressure jets delivered by a glass micropipette positioned close to the cell, in order to mimic the pressure changes occurring in the intact inner ear during sound stimulation. A second micropipette coupled to a piezoresistive pressure transducer was used as a probe measuring the pressure at precise locations at and around the cell. In a previous study, we found that such stimulation gave rise to increases in the intracellular calcium concentration. The present study characterizes the stimulus, describes the computer-controlled setup used for calibration, and gives examples of different modes of overstimulation at the cellular level. The peak pressure that could be generated using the pressure jet was around 325 Pa, or 144 dB (re 20 microPa) at 140 Hz. The pressure jet elicited large mechanical vibrations of the cell bodies of isolated cells. The vibration mode of the cells often changed over time, implying that the stimulation caused changes of the cellular stiffness. However, most cells appeared quite resistant to the high intensity mechanical stimulation.
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| 50. |
- Fridberger, Anders, 1966-, et al.
(author)
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Pressure-induced basilar membrane position shifts and the stimulus-evoked potentials in the low-frequency region of the guinea pig cochlea
- 1997
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In: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 161:2, s. 239-252
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Journal article (peer-reviewed)abstract
- We have used the guinea pig isolated temporal bone preparation to investigate changes in the non-linear properties of the tone-evoked cochlear potentials during reversible step displacements of the basilar membrane towards either the scala tympani or the scala vestibuli. The position shifts were produced by changing the hydrostatic pressure in the scala tympani. The pressures involved were calculated from measurements of the fluid flow through the system, and the cochlear DC impedance calculated (1.5 x 10(11) kg m-4 s-1, n = 10). Confocal microscopic visualization of the organ of Corti showed that pressure increases in the scala tympani caused alterations of the position of the reticular lamina and stereocilia bundles. For low pressures, there was a sigmoidal relation between the DC pressure applied to the scala tympani (and thus the position shift of the organ of Corti) and the amplitude of the summating potential. The cochlear microphonic potential also showed a pronounced dependence on the applied pressure: pressure changes altered the amplitude of the fundamental as well as its harmonics. In addition, the sound pressure level at which the responses began to saturate was increased, implying a transition towards a linear behaviour. An increase of the phase lag of the cochlear microphonic potential was seen when the basilar membrane was shifted towards the scala vestibuli. We have also measured the intracochlear DC pressure using piezoresistive pressure transducers. The results are discussed in terms of changes in the non-linear properties of cochlear transduction. In addition, the implications of these results for the pathophysiology and diagnosis of Meniérè's disease are discussed.
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