A comparative study of surface preparations of the organ of Corti of the harp seal (Pagophilus groenlandicus Erxleben 1777) and the ringed seal (Pusa hispida). 1. Sensory cell population and density

1976 ◽  
Vol 54 (1) ◽  
pp. 1-9 ◽  
Author(s):  
F. Ramprashad ◽  
K. Ronald ◽  
J. Geraci ◽  
T. G. Smith
Keyword(s):  
Cell Population ◽  
Hair Cells ◽  
Sensory Cell ◽  
Organ Of Corti ◽  
Ringed Seal ◽  
Outer Hair Cells ◽  
Harp Seal ◽  
Sensory Cells ◽  
Unit Surface Area ◽  
Inner Hair Cells

The surface preparation technique was used to estimate the sensory cell population and density in the organ of Corti of seven harp seals and four ringed seals. The average total of inner hair cells for the harp seal was 3654 (3078–263) as compared with an average total of 3232 (3120–3354) in the ringed seal. The average total number of outer hair cells in the harp seal was 14 318 (12 173 – 15 709) as compared with an average total of 13 497 (12 903 – 14 894).The distribution of outer and inner hair cells showed an increase in density from base to apex. An increase in density of about 21% and 29% was observed in the inner hair cells of the ringed and harp seal. The increase in density for each row of outer hair cells was 21% in the harp seal and 17% in the ringed seal. The density of outer hair cells per unit surface area decreased from a maximum value at the base to about half its value at the apex.The average total sensory cells of seals exceeded the average total sensory cells of both man and dolphin but were within the range of variation of the human.

Ultrastructural Cochlear Changes following Acoustic Hyperstimulation and Ototoxicity

1976 ◽  
Vol 85 (6) ◽  
pp. 740-751 ◽  
Author(s):  
David J. Lim
Keyword(s):  
Hair Cells ◽  
Sensory Cell ◽  
Ganglion Cells ◽  
Organ Of Corti ◽  
Acoustic Trauma ◽  
Nerve Fibers ◽  
Outer Hair Cells ◽  
Type I ◽  
Cell Degeneration ◽  
Inner Hair Cells

Using guinea pigs and chinchillas as experimental animals, modes and patterns of sensory cell damage by acoustic hyperstimulation and kanamycin intoxication were compared. In general, outer hair cells were more vulnerable to both acoustic trauma and ototoxicity (particularly in the basal turn) than inner hair cells. However, in kanamycin ototoxicity, the inner hair cells were more vulnerable in the apical coil. Nerve endings and nerve fibers generally were resistant to both acoustic trauma and kanamycin intoxication, and their degeneration appears to be secondary to the sensory cell degeneration. A large number of unmyelinated nerve fibers were seen in both the organ of Corti and the osseous spiral lamina even three months after the organ of Corti had been completely degenerated by ototoxicity. The total number of unmyelinated and myelinated nerve fibers in the osseous spiral lamina far exceeded the scanty surviving ganglion cells in Rosenthal's canal, indicating the possibility of regeneration of these fibers following kanamycin intoxication. The remaining few ganglion cells were mainly type II or type III cells, and a majority of the type I ganglion cells appeared to be degenerated. Signs of strial damage were observed in both acoustic trauma and ototoxicity, but their pattern did not correlate well with that of sensory cell degeneration.

Organ of Corti in the Human Fetus

1979 ◽  
Vol 88 (6) ◽  
pp. 749-758 ◽  
Author(s):  
Katsuhiko Tanaka ◽  
Noboru Sakai ◽  
Yoshihiko Terayama
Keyword(s):  
Hair Cells ◽  
Human Fetus ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Sensory Cells ◽  
Single Row ◽  
Inner Hair Cells ◽  
Morphological Aspects ◽  
Scanning Electronmicroscopy ◽  
Hair Bundles

The organ of Corti in the five-month human fetus was studied by transmission and scanning electronmicroscopy. Differentiation of the surface organization of the organ of Corti into a single row of inner and three to four rows of outer hair cells was complete at this stage except at the apical end. The morphological aspects of the hair bundles changed with maturation of the sensory cells; the inner hair cells preceded the outer hair cells in cytodifferentiation at a given location.

scholarly journals Static length changes of cochlear outer hair cells can tune low-frequency hearing

2017 ◽  
Author(s):  
Nikola Ciganović ◽  
Rebecca L. Warren ◽  
Batu Keçeli ◽  
Stefan Jacob ◽  
Anders Fridberger ◽  
...  
Keyword(s):  
Inner Ear ◽  
Hair Cells ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Frequency Selectivity ◽  
Apical Region ◽  
Low Frequencies ◽  
Inner Hair Cells ◽  
Length Changes ◽  
The Brain

AbstractThe cochlea not only transduces sound-induced vibration into neural spikes, it also amplifies weak sound to boost its detection. Actuators of this active process are sensory outer hair cells in the organ of Corti, whereas the inner hair cells transduce the resulting motion into electric signals that propagate via the auditory nerve to the brain. However, how the outer hair cells modulate the stimulus to the inner hair cells remains unclear. Here, we combine theoretical modeling and experimental measurements near the cochlear apex to study the way in which length changes of the outer hair cells deform the organ of Corti. We develop a geometry-based kinematic model of the apical organ of Corti that reproduces salient, yet counter-intuitive features of the organ’s motion. Our analysis further uncovers a mechanism by which a static length change of the outer hair cells can sensitively tune the signal transmitted to the sensory inner hair cells. When the outer hair cells are in an elongated state, stimulation of inner hair cells is largely inhibited, whereas outer hair cell contraction leads to a substantial enhancement of sound-evoked motion near the hair bundles. This novel mechanism for regulating the sensitivity of the hearing organ applies to the low frequencies that are most important for the perception of speech and music. We suggest that the proposed mechanism might underlie frequency discrimination at low auditory frequencies, as well as our ability to selectively attend auditory signals in noisy surroundings.Author summaryOuter hair cells are highly specialized force producers inside the inner ear: they can change length when stimulated electrically. However, how exactly this electromotile effect contributes to the astonishing sensitivity and frequency selectivity of the inner ear has remained unclear. Here we show for the first time that static length changes of outer hair cells can sensitively regulate how much of a sound signal is passed on to the inner hair cells that forward the signal to the brain. Our analysis holds for the apical region of the inner ear that is responsible for detecting the low frequencies that matter most in speech and music. This shows a mechanisms for how frequency-selectivity can be achieved at low frequencies. It also opens a path for the efferent neural system to regulate hearing sensitivity.

Outer Hair Cells Provide Active Tuning in the Organ of Corti

Physiology ◽  
1998 ◽  
Vol 13 (3) ◽  
pp. 107-111 ◽  
Author(s):  
Mats Ulfendahl ◽  
Åke Flock
Keyword(s):  
Mechanical Behavior ◽  
Hair Cells ◽  
Organ Of Corti ◽  
High Sensitivity ◽  
Outer Hair Cells ◽  
Sensory Cells ◽  
Effector Cells ◽  
Hearing Organ

The detection of sound by the mammalian hearing organ, the organ of Corti, is far from a passive process with the sensory cells acting as mere receptors. The high sensitivity and sharp tuning of the auditory apparatus are very much dependant on the active mechanical behavior of the outer hair cells, acting as effector cells.

scholarly journals Sensory Transduction and Adaptation in Inner and Outer Hair Cells of the Mouse Auditory System

2007 ◽  
Vol 98 (6) ◽  
pp. 3360-3369 ◽  
Author(s):  
Eric A. Stauffer ◽  
Jeffrey R. Holt
Keyword(s):  
Hair Cells ◽  
Slow Component ◽  
Outer Hair Cells ◽  
Fast Component ◽  
Sensory Transduction ◽  
Hair Bundle ◽  
Sensory Cells ◽  
Auditory Hair Cells ◽  
Inner Hair Cells ◽  
The Difference

Auditory function in the mammalian inner ear is optimized by collaboration of two classes of sensory cells known as inner and outer hair cells. Outer hair cells amplify and tune sound stimuli that are transduced and transmitted by inner hair cells. Although they subserve distinct functions, they share a number of common properties. Here we compare the properties of mechanotransduction and adaptation recorded from inner and outer hair cells of the postnatal mouse cochlea. Rapid outer hair bundle deflections of about 0.5 micron evoked average maximal transduction currents of about 325 pA, whereas inner hair bundle deflections of about 0.9 micron were required to evoke average maximal currents of about 310 pA. The similar amplitude was surprising given the difference in the number of stereocilia, 81 for outer hair cells and 48 for inner hair cells, but may be reconciled by the difference in single-channel conductance. Step deflections of inner and outer hair bundles evoked adaptation that had two components: a fast component that consisted of about 60% of the response occurred over the first few milliseconds and a slow component that consisted of about 40% of the response followed over the subsequent 20–50 ms. The rate of the slow component in both inner and outer hair cells was similar to the rate of slow adaptation in vestibular hair cells. The rate of the fast component was similar to that of auditory hair cells in other organisms and several properties were consistent with a model that proposes calcium-dependent release of tension allows transduction channel closure.

scholarly journals Scanning Electron Microscopy of the Human Organ of Corti

1983 ◽  
Vol 76 (4) ◽  
pp. 269-278 ◽  
Author(s):  
A Wright
Keyword(s):  
Hair Cells ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Sensory Cells ◽  
Surface Appearance ◽  
Human Organ ◽  
Human Cochlea ◽  
Temporal Bones ◽  
Subsequent Staining ◽  
Scanning Electron

The human cochlea has been preserved from post-mortem autolysis by perfusion with a fixative shortly after death. Subsequent staining with osmium permits dissection of this structure from the temporal bone. (Temporal bones were obtained from eight patients). When prepared for examination in the scanning electron microscope, the auditory sensory cells are found to be located in the band-like organ of Corti which extends the length of the cochlea. The sensory cells have a cluster of stereocilia projecting from their free upper surface and because of this are called hair cells. The hair cells are divided into two separate groups: a single row of inner hair cells, which show little variation in their surface appearance along the length of the cochlea, and three or four rows of outer hair cells whose cilia change in conformation and increase in length along the cochlea.

The developing organ of Corti contains retinoic acid and forms supernumerary hair cells in response to exogenous retinoic acid in culture

Development ◽  
1993 ◽  
Vol 119 (4) ◽  
pp. 1041-1053 ◽  
Author(s):  
M.W. Kelley ◽  
X.M. Xu ◽  
M.A. Wagner ◽  
M.E. Warchol ◽  
J.T. Corwin
Keyword(s):  
Retinoic Acid ◽  
Hair Cells ◽  
Organ Of Corti ◽  
Sensory Epithelium ◽  
Outer Hair Cells ◽  
Supporting Cells ◽  
Embryonic Mouse ◽  
Inner Hair Cells ◽  
Sensory Epithelia

The mammalian organ of Corti has one of the most highly ordered patterns of cells in any vertebrate sensory epithelium. A single row of inner hair cells and three or four rows of outer hair cells extend along its length. The factors that regulate the formation of this strict pattern are unknown. In order to determine whether retinoic acid plays a role during the development of the organ of Corti, exogenous retinoic acid was added to embryonic mouse cochleae in vitro. Exogenous retinoic acid significantly increased the number of cells that developed as hair cells and resulted in large regions of supernumerary hair cells and supporting cells containing two rows of inner hair cells and up to 11 rows of outer hair cells. The effects of retinoic acid were dependent on concentration and on the timing of its addition. Western blot analysis indicated that cellular retinoic acid binding protein (CRABP) was present in the sensory epithelium of the embryonic cochlea. The amount of CRABP apparently increased between embryonic day 14 and postnatal day 1, but CRABP was not detectable in sensory epithelia from adults. A retinoic acid reporter cell line was used to demonstrate that retinoic acid was also present in the developing organ of Corti between embryonic day 14 and postnatal day 1, and was also present in adult cochleae at least in the vicinity of the modiolus. These results suggest that retinoic acid is involved in the normal development of the organ of Corti and that the effect of retinoic acid may be to induce a population of prosensory cells to become competent to differentiate as hair cells and supporting cells.

Blebs in inner and outer hair cells: a pathophysiological hypothesis

2008 ◽  
Vol 122 (11) ◽  
pp. 1151-1155 ◽  
Author(s):  
R Ramírez-Camacho ◽  
J R García-Berrocal ◽  
A Trinidad ◽  
J M Verdaguer ◽  
J Nevado
Keyword(s):  
Hair Cells ◽  
Outer Hair Cell ◽  
Ganglion Cells ◽  
Stria Vascularis ◽  
Spiral Ganglion ◽  
Organ Of Corti ◽  
Outer Hair Cells ◽  
Inner Hair Cells ◽  
Hearing Thresholds

AbstractIntroduction:The ototoxic effects of cisplatin include loss of outer hair cells, degeneration of the stria vascularis and a decrease in the number of spiral ganglion cells. Scanning microscopy has shown balloon-like protrusions (blebs) of the plasma membrane of inner hair cells following cisplatin administration. The present study was undertaken to identify the possible role of inner and outer hair cell blebs in the pathogenesis of cisplatin-induced ototoxicity.Materials and methods:Twenty-five guinea pigs were injected with cisplatin and their hearing tested at different time-points, before sacrifice and examination with scanning electron microscopy.Results and analysis:Seven animals showed blebs in the inner hair cells at different stages. Hearing thresholds were lower in animals showing blebs.Discussion:Cisplatin seems to be able to induce changes in inner hair cells as well as in other structures in the organ of Corti. Blebbing observed in animals following cisplatin administration could play a specific role in the regulation of intracellular pressure.

scholarly journals Fine-tuning of Notch signaling sets the boundary of the organ of Corti and establishes sensory cell fates

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Martin L Basch ◽  
Rogers M Brown ◽  
Hsin-I Jen ◽  
Fatih Semerci ◽  
Frederic Depreux ◽  
...  
Keyword(s):  
Hair Cell ◽  
Notch Signaling ◽  
Hair Cells ◽  
Sensory Cell ◽  
Organ Of Corti ◽  
Fine Tuning ◽  
Pharmacological Treatments ◽  
Cell Fates ◽  
Inner Hair Cells ◽  
Mouse Mutants

The signals that induce the organ of Corti and define its boundaries in the cochlea are poorly understood. We show that two Notch modifiers, Lfng and Mfng, are transiently expressed precisely at the neural boundary of the organ of Corti. Cre-Lox fate mapping shows this region gives rise to inner hair cells and their associated inner phalangeal cells. Mutation of Lfng and Mfng disrupts this boundary, producing unexpected duplications of inner hair cells and inner phalangeal cells. This phenotype is mimicked by other mouse mutants or pharmacological treatments that lower but not abolish Notch signaling. However, strong disruption of Notch signaling causes a very different result, generating many ectopic hair cells at the expense of inner phalangeal cells. Our results show that Notch signaling is finely calibrated in the cochlea to produce precisely tuned levels of signaling that first set the boundary of the organ of Corti and later regulate hair cell development.

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