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At least 19 recordsLinked to original sources
PubMed1979

Hair cell polarization in the gravity receptor systems of the statocysts of the cephalopods Sepia officinalis and Loligo vulgaris.

The complete patterns of polarization of the sensory epithelia of the various gravity receptor systems of the decapods Sepia and Loligo have been described (Fig. 6). Each individual receptor cell (hair cell) bears up to 150 kinocilia, but is polarized unidirectionally by 3 morphological features: (I) by the orientation of the internal 9X2+2 tubuli structure of each kinocilium, (II) by the location of their basal feet. Each hair cell is additionally polarized (III), in that its kinociliary group is inclined toward the plane of the macula surface, forming an angle of 40-60 degrees with it (Figs. 1-3); the direction of polarization, as given by the ultrastructural features (I and II), is always opposite to this acute angle (Fig. 4). The results are discussed with reference to their physiological consequences.

Acoustic Maculae↗
PubMedDate not supplied

Structure and development of vestibular hair cells in the larval bullfrog.

Structure and development of hair cells in vestibular sensory organs of the larval bullfrog were examined with scanning electron microscopy. The larval vestibular sensory epithelia resembled those of the adult frog. Based on morphology of the ciliary tufts, seven hair cell types were identified. One of them, the type A hair cell, appears to be the morphogenetic precursor of other hair cell types. The size of the stereocilia of type A hair cells is comparable to the surrounding microvilli. The distribution of immature type A hair cells suggests that the periphery of the sensory epithelia is the principal growth zone and the site of formation of new hair cells. However, a far greater number of type A hair cells were found in high frequency sensitive sensory organs (sacculus, amphibian and basilar papillae) than low frequency sensitive vestibular sensory structures (canal cristae, utriculus and lagena). This phenomenon may suggest that the time period required for the maturation of type A hair cells to their ultimate hair cell types in the low frequency sensitive vestibular organs is shorter than in the high frequency sensory structures. It is also possible that the low frequency sensitive vestibular organs may have completed their morphogenetic development in the early larval stages, while morphogenesis of hair cells in the high frequency sensory structures continues throughout the lifetime of a bullfrog.

Animals↗
PubMed1977

Sensitivity, polarity, and conductance change in the response of vertebrate hair cells to controlled mechanical stimuli.

Hair cells, the primary receptors of the auditory, vestibular, and lateral-line sensory systems, produce electrical signals in response to mechanical stimulation of their apical hair bundles. We employed an in vitro preparation and intracellular recording to investigate the transduction mechanism of hair cells in the sacculus from the inner ear of the bullfrog (Rana catesbeiana). When stimulated directly by mechanical deflection of their hair bundles, these cells gave graded responses up to 15 mV in amplitude; the peak sensitivity was about 20 mV/micron deflection. The depolarizing component of the receptor potential corresponding to stimuli directed towards the kinocilium. Depolarizing responses were associated with a membrane resistance decrease, and hyperpolarizing responses with a resistance increase. Action potentials, possibly calcium spikes, were occasionally evoked in hair cells by mechanical or electrical stimulation.

Animals↗
PubMed1979

Stereocilia mediate transduction in vertebrate hair cells (auditory system/cilium/vestibular system).

The vertebrate hair cell is a sensory receptor that responds to mechanical stimulation of its hair bundle, which usually consists of numerous large microvilli (stereocilia) and a single true cilium (the kinocilium). We have examined the roles of these two components of the hair bundle by recording intracellularly from bullfrog saccular hair cells. Detachment of the kinocilium from the hair bundle and deflection of this cilium produces no receptor potentials. Mechanical stimulation of stereocilia, however, elicits responses of normal amplitude and sensitivity. Scanning electron microscopy confirms the assessments of ciliary position made during physiological recording. Stereocilia mediate the transduction process of the vertebrate hair cell, while the kinocilium may serve primarily as a linkage conveying mechanical displacements to the stereocilia.

Animals↗
PubMed1979

A common origin of voltage noise and generator potentials in statocyst hair cells.

Voltage noise, generator potentials, and hair movements in the Hermissenda statocyst were analyzed. Motile hairs on the cyst's luminal surface moved as rods through +/- 10 degrees Hz when free and at 7 Hz when loaded with the weight of the statoconia (at 120 degrees C). For hair cells oriented opposite to a centrifugal force vector, rotation caused depolarization and increase of voltage noise variance. The depolarizing generator potential and the increase in voltage noise variance were similarly reduced by perfusion with zero external sodium or chloral hydrate. Cooling, perfusion with zero external sodium or chloral hydrate reduced the movement frequencies of the hairs but increased their range of motion. The same treatments reduced voltage noise variance and increased input resistance of the hair cell membrane. The results indicate that voltage noise and hair cell generator potential have a common origin: exertion of force on statocyst hairs by the weight of statoconia. The collision of statoconia with the motile hairs, not the hairs' bending, produces most of the voltage noise.

Action Potentials↗
PubMed1979

Response latency of vertebrate hair cells.

An in vitro preparation of hair cells from the bullfrog sacculus produces a transepithelial microphonic potential in response to well-defined mechanical stimuli. If corrected for the electrical time constant of the epithelium, the response follows a fast stimulus with a 40-microsecond delay at 22 degree C. The short latency and its modest temperature dependence limit possible models for transduction by hair cells.

Animals↗
PubMed1979

Freeze-fracture studies on the synapse between the type I hair cell and the calyceal terminal in the guinea-pig vestibular system.

The apposition between type I hair cells and the calyceal terminals of vestibular ganglion cell peripheral processes was studied in the vestibular epithelium of the guinea-pig, using thin-sectioned and freeze-fractured specimens. Chemical synaptic junctions were exceedingly rare in thin-sectioned specimens, and were not seen in freeze-fracture replicas. Furthermore, no gap junctions were present between the hair cell and the calyx. There were, however, regions along the apposition where the membranes were closely apposed. At these regions, the hair cell was invaginated by cytoplasmic protrusions of the calyx and the plasmalemmata of the two cells were separated by only 6-7 nm. The number and conformation of the close appositions varied between different cells. In freeze-fracture replicas, the closely-apposed plasmalemmata of the hair cell and the calyx had no special distribution of intramembrane particles on either membrane leaflet. However, on the external membrane leaflet of the hair cell, a large patch of widely-spaced, large particles surrounded the regions of close apposition. The corresponding region of the plasmalemma of the calyx had no special distribution of particles on either membrane leaflet. The scarcity of chemical synaptic junctions, the absence of gap junctions between the cells and the unique arrangement of particles in the hair cell plasmalemma surrounding regions of close membrane apposition may indicate an unusual mode of synaptic transmission between the type I hair cell and the calyx.

Animals↗
PubMed1975

Responses of hair cells to statocyst rotation.

A new technique is described for stimulating hair cells of the Hermissenda statocyst. The preparation and recording apparatus can be rotated at up to 78 rpm while recording intracellular potentials. Hair cells in front of the centrifugal force vector depolarize in response to rotation. Hair cells in back of the centrifugal force vector hypoerpolarize in response to rotation. Mechanisms by which the hair cell generator potential might arise are examined.

Animals↗
PubMed1979

Hearing thresholds with outer and inner hair cell loss.

Hearing impairment and related cochlear histopathologic changes were evaluated in experimental animals after treatment with aminoglycoside antibiotics or exposure to intense sound. In the course of treatment with kanamycin, neomycin, or dihydrostreptomycin, permanent hearing loss in monkeys and guinea pigs occurred first at the high frequencies and progressed toward the lows. Exposure to different octave bands of noise at 120 dB SPL in monkeys and chinchillas produced permanent hearing loss at frequencies related to the spectral characteristics of the octave band. In most instances loss of outer hair cells was substantially greater than that of inner hair cells. In fact, the pattern and location of missing outer hair cells on the basilar membrane were most often correlated with threshold shifts of 50 dB or less. Generally inner hair cell loss was observed when the threshold shift was greater than 50 dB. Our data support the place principle and the inference that the outer hair cells are essential for hearing from threshold to about 50 dB SL. The inner hair cells, if functioning normally, apparently take over above that level. Although there is little doubt that such a generalization will, in the long term, be found to have been greatly oversimplified, there is every reason to believe that a combination of behavioral and morphologic procedures, as used in this study, will play an important part in elucidating the differences in functional significance of the two types of hair cells.

Animals↗
PubMed1979

Genesis and maturation of vestibular hair cells.

The embryologic development in vivo and in vitro of mammalian hair cells in the crista ampullaris was continuously followed with regard to structural differentiation and maturation from the terminal mitosis to the morphological condition at partus or equivalent age in vitro. Otocysts were explanted both early and late during embryologic development: 13th and 16 gestation day, respectively. Both in fetal life and during in vitro conditions, the surface structures of the developing hair cell with regular arrangement of kinocilium/stereocilia were first differentiated, followed by a cytologic transformation intracellularly and subsequent development of nerve endings. Hair cells were able to develop without any morphologic contact with the nervous system. The afferent nerve system developed before the efferent nerve system (CBA/CBA mouse).

Animals↗
PubMed1978

The coding of sound pressure and frequency in cochlear hair cells of the terrapin.

Intracellular recordings have been made from single hair cells in the cochlea of the terrapin, and the site of recording has been verified by injection of a fluorescent dye through the recording electrode. A hair cell gives periodic voltage responses graded with the intensity and frequency of the sound stimulus, and produces the largest response at its characteristic frequency. When small current steps are injected through the recording electrode, the voltage response of the cell exhibits damped oscillations at its characteristic frequency. The results are consistent with the idea that the cochlear frequency selectivity arises in two stages and it is suggested that the second stage resides within the hair cell itself.

Action Potentials↗
PubMed1979

Psychophysical tuning curves and auditory thresholds after hair cell damage in the chinchilla.

Chinchillas were treated with kanamycin sulfate (150--200 mg/kg/day) to produce high-frequency hearing loss extending to about 4.0 kHz. Thresholds and psychophysical tuning curves (PTCs) were obtained before and after treatment, utilizing a shuttlebox avoidance procedure, and cochlear hair cells were evaluated under phase contrast microscopy. Hair cell loss resulting from kanamycin treatment varied from restricted lesions of the outer hair cells (OHCs) in the cochlear base, with no loss of inner hair cells (IHCs), to more extensive lesions involving both OHCs and IHCs. Threshold shift of at least 40 dB was always associated with OHC loss. PTCs obtained from frequency regions exhibiting 40--50 dB of threshold shift were normal in shape. With threshold shift in excess of 50 dB, PTCs were progressively distorted, with truncation of the tip segment and in some cases increased sensitivity of the tail segment. The results suggest that the threshold of optimally functional IHCs after kanamycin-induced OHC loss is about 40 dB higher than normal. Threshold shift in excess of 40 dB may represent IHC damage. IHCs are capable of transducing the fine-frequency information necessary for generating normally sharp PTCs in the absence of OHCs. However, with threshold shift in excess of approximately 50 dB, this frequency resolution is increasingly compromised.

Animals↗
PubMed1979

Synaptic structures in the type II hair cell in the vestibular system of the guinea pig. A freeze-fracture and TEM study.

The synaptic contacts of the type II hair cell in the vestibular system of the guinea pig was described in thin-sectioned and freeze-fractured specimens. Synaptic bodies were present at the apposition with both large and small afferent terminals. About 20% of the synaptic bodies observed consisted of complexes of two or more adjacent synaptic discs. In freeze-fracture replicas, the cytoplasmic leaflet of the hair cell plamalemma beneath the synaptic body had a bar-shaped aggregate of large particles. The size and shape of the particle aggregate was the same as that of the synaptic body. Small plasmalemmal deformations, interpreted as sites of synaptic vesicle exocytosis, were found immediately adjacent to the particle aggregate. On the postsynaptic membrane, an aggregate of intramembrane particles was present at the synaptic junction. The type II hair cell had no gap junctions or close membrane appositions between it an the apposed afferent fiber. Efferent boutons ending on the type II hair cell had no intramembrane particle specialization on the postsynaptic membrane; however those efferent boutons ending on large and small afferent fibers had an aggregate of medium-sized particles on the external leaflet of the postsynaptic bouton beneath the presynaptic active zone.

Animals↗
PubMedDate not supplied

Permanent threshold shift and cochlear hair cell loss in the kanamycin-treated guinea pig.

The differential contribution of the inner hair cells (IHC) and the outer hair cells (OHC) in the mammalian cochlea to hearing sensitivity was assessed in six behaviorally-trained guinea pigs by comparing audiograms preadministration and postadministration of kanamycin, an antibiotic that predominantly destroys guinea pig OHC while leaving the IHC structurally unchanged. The results support the hypothesis that only the IHC of the cochlea responds to tones approximately 50 to 60 dB above the threshold of the intact cochlea.

Animals↗
PubMed1979

Further studies on the Schroeder-Hall hair-cell model.

The Schroeder-Hall hair-cell model [M.R. Shroeder and J.L. Hall, "Model for mechanical to neural transduction in the auditory receptor," J. Acoust. Soc. Am. 55, 1055-1060 (1974] was further explored using additional stimulus waveforms and analysis techniques. The model is shown to have other interesting properties such as the ability to generate realistic two-tone interactions. Amended to limit the growth of transmitter release, the model also produces realistic adaptation and incremental response data. Other amendments improved high-intensity period histogram waveshapes. No one amendment, however, allowed the model to produce both realistic adaptation curves as well as period histogram waveforms that faithfully mimicked physiological data.

Hair Cells, Auditory↗
PubMed2026

CASZ1 regulates the maturation of outer hair cells and is required for hearing in mice.

The transcription factor ATOH1 is a master regulator of mechanosensory hair-cell (HC) development in the ear. Here, we report that its target gene Casz1 regulates the maturation of outer HCs (OHCs). Genetic deletion of Casz1 during (but not after) cochlear development in the mouse caused: hearing loss; disorganization of mechanosensory stereocilia bundles in OHCs; reduced F-actin density in OHC cuticular plates; progressive OHC loss; and mild morphological alterations in inner HCs. This deletion also altered gene expression, delaying downregulation of genes expressed in immature OHCs, including the actin regulator-encoding gene Coro2a, and accelerating upregulation of genes expressed in mature OHCs. Deleting Coro2a in Casz1 mutant mice restored F-actin density in cuticular plates but increased stereocilia bundle disorganization and hearing thresholds, revealing that CORO2A provides an overall beneficial effect. Our data indicate that CASZ1 regulates transcriptional and morphological maturation of OHCs, and that CASZ1 in maturing HCs is necessary for hearing.

CASZ1↗
PubMed1979

Pathological actin in vestibular hair cells of the waltzing guinea pig.

Vestibular type 1 hair cells in the waltzing guinea pig contain needle-shaped inclusion bodies which grow in an uncontrolled fashion associated with the destruction of the cell. The needles are shown to be composed by filaments of actin, a protein identified in the electron microscope by its ability to bind subfragment 1 of myosin. Whereas actin filaments in stereocilia are oriented down towards the cell body, filaments in the needles point up towards the cuticular plate. The hereditary lesion appears to be associated with a defective control of polymerization of actin into filaments.

Actins↗
PubMedDate not supplied

Element content of intracochlear fluids, outer hair cells, and stria vascularis as determined by energy-dispersive roentgen ray analysis.

Roentgen ray spectrometry was used to obtain element spectra from isolated samples of perilymph, endolymph, outer hair cells, and stria vascularis obtained by microdissection from the freeze-dried inner ears of chinchillas. The spectra of perilymph and endolymph residues indicated that no cross-contamination of the two cochlear fluids occurs during freeze-drying or sampling. The spectra of outer hair cells suggested that the extracellular fluid in the organ of Corti spaces is similar to perilymph in its ionic content. The spectra of stria vascularis samples indicated low sodium and high phosphorus contents. Energy-dispersive roentgen ray analysis of freeze-dried inner ears appears to be a promising method for low-contamination measurement of ion distribution in the cochlea.

Animals↗