Tritiated thymidine in the chick embryo inner ear

1989 ◽  
Vol 47 ◽  
pp. 846-847
Author(s):  
Cesar D. Fermin
Keyword(s):  
Inner Ear ◽  
Hair Cells ◽  
Tritiated Thymidine ◽  
Nerve Fibers ◽  
Basilar Papilla ◽  
Short Exposure ◽  
Short Hair ◽  
Efferent Nerve ◽  
Sensory Epithelia ◽  
Dividing Cells

Development of the chick (Gallus domesticus) inner ear has been studied, and the maturation of cells that detect sound has been analyzed at the E.M. level [1,2,3]. Other workers showed correspondence between ultrastructural maturation and behavioral responses [4,5]. In mammals [6] hair cells mature after ceasation of mitosis {Fig.l}, in a pattern so that older cells are in the base of the cochlea while younger cells are in the apex [7]. But, electrophysiology indicates that cells at the base do not function first. Chicks are precocious with well developed sensory organs at birth, and their embryonic development follows, on a very short time span, a sequence that resembles that of the human ear. This study was undertaken to standarize tritiated thymidine (TT) because resolution of TT in avian embryos differs significantly from mammals [6]. Embryos were injected with 100 μl of TT, and sacrificed 1 or 2 hours later in order to label only those cells that were actively dividing cells at the time of the injection. Specimens were fixed and processed for autoradiography [6].Actively dividing cells incorporate TT after short exposure, with minimal background. It seems that vestibular sensory epithelia {Fig.2} have more dividing cells than the auditory sensory epithelia {Fig.3}, even though the vestibule develop before the cochlea. The ratio between the number of labeled cells over the length of the sensory epithelia is lower in the auditory basilar papilla (0.098 cell/(μm) than in the vestibular utricle (0.77 cell/μm) and saccule (1.66 cell/ μm). When dividing cells were analyzed in the basilar papilla alone, and their distribution displayed along the length of the cochlea over time, older cells were opposite to the VIIIth nerve fibers that innervate those hair cells. A lateral and a longitudinal gradient has been established and hair cells closer to the nerve in the mid-basal area mature earlier than hair cells at both ends of the cochlea [2]. This finding, if occuring in mammals, may explain why mid-frequency are the first to appear [5]. The first 1/3 of the chick cochlea contains mainly short hair cells and are innervated primarily by efferent nerve fibers, which arrive in the cochlea almost a week after the afferent do. Moreover, tall hair cells extend 2/3 of the cochlear length from apex to mid-base and show mature innervation patterns before the short hair cells do. In the short embryonic cochlea, frequencies may be produced first in the what will later be the mid-region because, early in development, that area contains more mature receptors [1,2,3].

scholarly journals Molecular Identity and Functional Properties of a Novel T-Type Ca2+ Channel Cloned From the Sensory Epithelia of the Mouse Inner Ear

2008 ◽  
Vol 100 (4) ◽  
pp. 2287-2299 ◽  
Author(s):  
Liping Nie ◽  
Jun Zhu ◽  
Michael Anne Gratton ◽  
Amy Liao ◽  
Karen J. Mu ◽  
...  
Keyword(s):  
Inner Ear ◽  
Hair Cells ◽  
Synapse Formation ◽  
Divalent Cations ◽  
Functional Expression ◽  
Basilar Papilla ◽  
Vestibular Hair Cells ◽  
Molecular Identity ◽  
Sensory Epithelia ◽  
Permeation Properties

The molecular identity of non-Cav1.3 channels in auditory and vestibular hair cells has remained obscure, yet the evidence in support of their roles to promote diverse Ca2+-dependent functions is indisputable. Recently, a transient Cav3.1 current that serves as a functional signature for the development and regeneration of hair cells has been identified in the chicken basilar papilla. The Cav3.1 current promotes spontaneous activity of the developing hair cell, which may be essential for synapse formation. Here, we have isolated and sequenced the full-length complementary DNA of a distinct isoform of Cav3.1 in the mouse inner ear. The channel is derived from alternative splicing of exon14, exon25A, exon34, and exon35. Functional expression of the channel in Xenopus oocytes yielded Ca2+ currents, which have a permeation phenotype consistent with T-type channels. However, unlike most multiion channels, the T-type channel does not exhibit the anomalous mole fraction effect, possibly reflecting comparable permeation properties of divalent cations. The Cav3.1 channel was expressed in sensory and nonsensory epithelia of the inner ear. Moreover, there are profound changes in the expression levels during development. The differential expression of the channel during development and the pharmacology of the inner ear Cav3.1 channel may have contributed to the difficulties associated with identification of the non-Cav1.3 currents.

scholarly journals Electrical tuning and transduction in short hair cells of the chicken auditory papilla

2013 ◽  
Vol 109 (8) ◽  
pp. 2007-2020 ◽  
Author(s):  
Xiaodong Tan ◽  
Maryline Beurg ◽  
Carole Hackney ◽  
Shanthini Mahendrasingam ◽  
Robert Fettiplace
Keyword(s):  
Hair Cells ◽  
Calcium Binding ◽  
Outer Hair Cells ◽  
Basilar Papilla ◽  
Resting Potential ◽  
Auditory Nerve Fiber ◽  
Buffer Concentration ◽  
Short Hair ◽  
Open Probability ◽  
Calbindin D

The avian auditory papilla contains two classes of sensory receptor, tall hair cells (THCs) and short hair cells (SHCs), the latter analogous to mammalian outer hair cells with large efferent but sparse afferent innervation. Little is known about the tuning, transduction, or electrical properties of SHCs. To address this problem, we made patch-clamp recordings from hair cells in an isolated chicken basilar papilla preparation at 33°C. We found that SHCs are electrically tuned by a Ca2+-activated K+ current, their resonant frequency varying along the papilla in tandem with that of the THCs, which also exhibit electrical tuning. The tonotopic map for THCs was similar to maps previously described from auditory nerve fiber measurements. SHCs also possess an A-type K+ current, but electrical tuning was observed only at resting potentials positive to −45 mV, where the A current is inactivated. We predict that the resting potential in vivo is approximately −40 mV, depolarized by a standing inward current through mechanotransducer (MT) channels having a resting open probability of ∼0.26. The resting open probability stems from a low endolymphatic Ca2+ concentration (0.24 mM) and a high intracellular mobile Ca2+ buffer concentration, estimated from perforated-patch recordings as equivalent to 0.5 mM BAPTA. The high buffer concentration was confirmed by quantifying parvalbumin-3 and calbindin D-28K with calibrated postembedding immunogold labeling, demonstrating >1 mM calcium-binding sites. Both proteins displayed an apex-to-base gradient matching that in the MT current amplitude, which increased exponentially along the papilla. Stereociliary bundles also labeled heavily with antibodies against the Ca2+ pump isoform PMCA2a.

scholarly journals Connectomics of the zebrafish's lateral-line neuromast reveals wiring and miswiring in a simple microcircuit

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Eliot Dow ◽  
Adrian Jacobo ◽  
Sajjad Hossain ◽  
Kimberly Siletti ◽  
A J Hudspeth
Keyword(s):  
Hair Cell ◽  
Lateral Line ◽  
Hair Cells ◽  
Planar Cell Polarity ◽  
Developmental Stages ◽  
Notch Signaling Pathway ◽  
Nerve Fibers ◽  
Directional Sensitivity ◽  
Efferent Nerve ◽  
Polarity Gene

The lateral-line neuromast of the zebrafish displays a restricted, consistent pattern of innervation that facilitates the comparison of microcircuits across individuals, developmental stages, and genotypes. We used serial blockface scanning electron microscopy to determine from multiple specimens the neuromast connectome, a comprehensive set of connections between hair cells and afferent and efferent nerve fibers. This analysis delineated a complex but consistent wiring pattern with three striking characteristics: each nerve terminal is highly specific in receiving innervation from hair cells of a single directional sensitivity; the innervation is redundant; and the terminals manifest a hierarchy of dominance. Mutation of the canonical planar-cell-polarity gene vangl2, which decouples the asymmetric phenotypes of sibling hair-cell pairs, results in randomly positioned, randomly oriented sibling cells that nonetheless retain specific wiring. Because larvae that overexpress Notch exhibit uniformly oriented, uniformly innervating hair-cell siblings, wiring specificity is mediated by the Notch signaling pathway.

Delta1 expression during avian hair cell regeneration

Development ◽  
1999 ◽  
Vol 126 (5) ◽  
pp. 961-973 ◽  
Author(s):  
J.S. Stone ◽  
E.W. Rubel
Keyword(s):  
Hair Cell ◽  
Inner Ear ◽  
Hair Cells ◽  
Cell Injury ◽  
Basilar Papilla ◽  
Cell Regeneration ◽  
Mrna Levels ◽  
Hair Cell Regeneration ◽  
Drug Induced ◽  
In Cells

Postembryonic production of hair cells, the highly specialized receptors for hearing, balance and motion detection, occurs in a precisely controlled manner in select species, including avians. Notch1, Delta1 and Serrate1 mediate cell specification in several tissues and species. We examined expression of the chicken homologs of these genes in the normal and drug-damaged chick inner ear to determine if signaling through this pathway changes during hair cell regeneration. In untreated post-hatch chicks, Delta1 mRNA is abundant in a subpopulation of cells in the utricle, which undergoes continual postembryonic hair cell production, but it is absent from all cells in the basilar papilla, which is mitotically quiescent. By 3 days after drug-induced hair cell injury, Delta1 expression is highly upregulated in areas of cell proliferation in both the utricle and basilar papilla. Delta1 mRNA levels are elevated in progenitor cells during DNA synthesis and/or gap 2 phases of the cell cycle and expression is maintained in both daughter cells immediately after mitosis. Delta1 expression remains upregulated in cells that differentiate into hair cells and is downregulated in cells that do not acquire the hair cell fate. Delta1 mRNA levels return to normal by 10 days after hair cell injury. Serrate1 is expressed in both hair cells and support cells in the utricle and basilar papilla, and its expression does not change during the course of drug-induced hair cell regeneration. In contrast, Notch1 expression, which is limited to support cells in the quiescent epithelium, is increased in post-M-phase cell pairs during hair cell regeneration. This study provides initial evidence that Delta-Notch signaling may be involved in maintaining the correct cell types and patterns during postembryonic replacement of sensory epithelial cells in the chick inner ear.

scholarly journals Low-frequency sound affects active micromechanics in the human inner ear

2014 ◽  
Vol 1 (2) ◽  
pp. 140166 ◽  
Author(s):  
Kathrin Kugler ◽  
Lutz Wiegrebe ◽  
Benedikt Grothe ◽  
Manfred Kössl ◽  
Robert Gürkov ◽  
...  
Keyword(s):  
Inner Ear ◽  
Hair Cells ◽  
Otoacoustic Emissions ◽  
Low Frequency ◽  
Short Exposure ◽  
Low Frequencies ◽  
Spontaneous Otoacoustic Emissions ◽  
Human Cochlea ◽  
Human Hearing ◽  
The Impact

Noise-induced hearing loss is one of the most common auditory pathologies, resulting from overstimulation of the human cochlea, an exquisitely sensitive micromechanical device. At very low frequencies (less than 250 Hz), however, the sensitivity of human hearing, and therefore the perceived loudness is poor. The perceived loudness is mediated by the inner hair cells of the cochlea which are driven very inadequately at low frequencies. To assess the impact of low-frequency (LF) sound, we exploited a by-product of the active amplification of sound outer hair cells (OHCs) perform, so-called spontaneous otoacoustic emissions. These are faint sounds produced by the inner ear that can be used to detect changes of cochlear physiology. We show that a short exposure to perceptually unobtrusive, LF sounds significantly affects OHCs: a 90 s, 80 dB(A) LF sound induced slow, concordant and positively correlated frequency and level oscillations of spontaneous otoacoustic emissions that lasted for about 2 min after LF sound offset. LF sounds, contrary to their unobtrusive perception, strongly stimulate the human cochlea and affect amplification processes in the most sensitive and important frequency range of human hearing.

scholarly journals Aquaporin-6 Expression in the Cochlear Sensory Epithelium Is Downregulated by Salicylates

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
Paola Perin ◽  
Simona Tritto ◽  
Laura Botta ◽  
Jacopo Maria Fontana ◽  
Giulia Gastaldi ◽  
...  
Keyword(s):  
Inner Ear ◽  
Expression Pattern ◽  
Hair Cells ◽  
Organ Of Corti ◽  
Sensory Epithelium ◽  
Outer Hair Cells ◽  
Rt Pcr ◽  
Supporting Cells ◽  
Sensory Epithelia ◽  
Mechanical Compliance

We characterize the expression pattern of aquaporin-6 in the mouse inner ear by RT-PCR and immunohistochemistry. Our data show that in the inner ear aquaporin-6 is expressed, in both vestibular and acoustic sensory epithelia, by the supporting cells directly contacting hair cells. In particular, in the Organ of Corti, expression was strongest in Deiters' cells, which provide both a mechanical link between outer hair cells (OHCs) and the Organ of Corti, and an entry point for ion recycle pathways. Since aquaporin-6 is permeable to both water and anions, these results suggest its possible involvement in regulating OHC motility, directly through modulation of water and chloride flow or by changing mechanical compliance in Deiters' cells. In further support of this role, treating mice with salicylates, which impair OHC electromotility, dramatically reduced aquaporin-6 expression in the inner ear epithelia but not in control tissues, suggesting a role for this protein in modulating OHCs' responses.

scholarly journals NTPDase1 and NTPDase2 Immunolocalization in Mouse Cochlea: Implications for Regulation of P2 Receptor Signaling

2002 ◽  
Vol 50 (11) ◽  
pp. 1435-1441 ◽  
Author(s):  
Srdjan M. Vlajkovic ◽  
Peter R. Thorne ◽  
Jean Sévigny ◽  
Simon C. Robson ◽  
Gary D. Housley
Keyword(s):  
Hair Cells ◽  
Spiral Ganglion ◽  
Organ Of Corti ◽  
Nerve Fibers ◽  
Outer Hair Cells ◽  
Spiral Ligament ◽  
Receptor Signaling ◽  
P2 Receptor ◽  
Efferent Nerve ◽  
Root Region

Cellular, molecular, and physiological studies have demonstrated an important signaling role for ATP and related nucleotides acting via P2 receptors in the cochlea of the inner ear. Signal modulation is facilitated by ectonucleotidases, a heterologous family of surface-located enzymes involved in extracellular nucleotide hydrolysis. Our previous studies have implicated CD39/NTPDase1 and CD39L1/NTPDase2, members of the ectonucleoside triphosphate diphosphohydrolase (E-NTPDase) family, as major ATP-hydrolyzing enzymes in the tissues lining the cochlear endolymphatic and perilymphatic compartments. NTPDase1 hydrolyzes both nucleoside triphosphates and diphosphates. In contrast, NTPDase2 is a preferential nucleoside triphosphatase. This study characterizes expression of these E-NTPDases in the mouse cochlea by immunohistochemistry. NTPDase1 can be immunolocalized to the cochlear vasculature and neural tissues (primary auditory neurons in the spiral ganglion). In contrast, NTPDase2 immunolabeling was principally localized to synaptic regions of the sensory inner and outer hair cells, stereocilia and cuticular plates of the outer hair cells, supporting cells of the organ of Corti (Deiters’ cells and inner border cells), efferent nerve fibers located in the intraganglionic spiral bundle, and in the outer sulcus and root region of the spiral ligament. This differential expression of NTPDase1 and 2 in the cochlea suggests spatial regulation of P2 receptor signaling, potentially involving different nucleotide species and hydrolysis kinetics.

scholarly journals Conserved and Divergent Principles of Planar Polarity Revealed by Hair Cell Development and Function

2021 ◽  
Vol 15 ◽  
Author(s):  
Michael R. Deans
Keyword(s):  
Hair Cell ◽  
Inner Ear ◽  
Hair Cells ◽  
Model Organism ◽  
Vestibular Function ◽  
Sensory Receptor ◽  
Apical Surface ◽  
Planar Polarity ◽  
Vestibular Hair Cells ◽  
Sensory Epithelia

Planar polarity describes the organization and orientation of polarized cells or cellular structures within the plane of an epithelium. The sensory receptor hair cells of the vertebrate inner ear have been recognized as a preeminent vertebrate model system for studying planar polarity and its development. This is principally because planar polarity in the inner ear is structurally and molecularly apparent and therefore easy to visualize. Inner ear planar polarity is also functionally significant because hair cells are mechanosensors stimulated by sound or motion and planar polarity underlies the mechanosensory mechanism, thereby facilitating the auditory and vestibular functions of the ear. Structurally, hair cell planar polarity is evident in the organization of a polarized bundle of actin-based protrusions from the apical surface called stereocilia that is necessary for mechanosensation and when stereociliary bundle is disrupted auditory and vestibular behavioral deficits emerge. Hair cells are distributed between six sensory epithelia within the inner ear that have evolved unique patterns of planar polarity that facilitate auditory or vestibular function. Thus, specialized adaptations of planar polarity have occurred that distinguish auditory and vestibular hair cells and will be described throughout this review. There are also three levels of planar polarity organization that can be visualized within the vertebrate inner ear. These are the intrinsic polarity of individual hair cells, the planar cell polarity or coordinated orientation of cells within the epithelia, and planar bipolarity; an organization unique to a subset of vestibular hair cells in which the stereociliary bundles are oriented in opposite directions but remain aligned along a common polarity axis. The inner ear with its complement of auditory and vestibular sensory epithelia allows these levels, and the inter-relationships between them, to be studied using a single model organism. The purpose of this review is to introduce the functional significance of planar polarity in the auditory and vestibular systems and our contemporary understanding of the developmental mechanisms associated with organizing planar polarity at these three cellular levels.

scholarly journals Release and Elementary Mechanisms of Nitric Oxide in Hair Cells

2010 ◽  
Vol 103 (5) ◽  
pp. 2494-2505 ◽  
Author(s):  
Ping Lv ◽  
Adrian Rodriguez-Contreras ◽  
Hyo Jeong Kim ◽  
Jun Zhu ◽  
Dongguang Wei ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Inner Ear ◽  
Hair Cells ◽  
Single Channel ◽  
Cell Types ◽  
Cellular Mechanism ◽  
Open Probability ◽  
Potential Oscillations ◽  
Efferent Nerve ◽  
Membrane Oscillations

The enzyme nitric oxide (NO) synthase, that produces the signaling molecule NO, has been identified in several cell types in the inner ear. However, it is unclear whether a measurable quantity of NO is released in the inner ear to confer specific functions. Indeed, the functional significance of NO and the elementary cellular mechanism thereof are most uncertain. Here, we demonstrate that the sensory epithelia of the frog saccule release NO and explore its release mechanisms by using self-referencing NO-selective electrodes. Additionally, we investigated the functional effects of NO on electrical properties of hair cells and determined their underlying cellular mechanism. We show detectable amounts of NO are released by hair cells (>50 nM). Furthermore, a hair-cell efferent modulator acetylcholine produces at least a threefold increase in NO release. NO not only attenuated the baseline membrane oscillations but it also increased the magnitude of current required to generate the characteristic membrane potential oscillations. This resulted in a rightward shift in the frequency–current relationship and altered the excitability of hair cells. Our data suggest that these effects ensue because NO reduces whole cell Ca2+ current and drastically decreases the open probability of single-channel events of the L-type and non L-type Ca2+ channels in hair cells, an effect that is mediated through direct nitrosylation of the channel and activation of protein kinase G. Finally, NO increases the magnitude of Ca2+-activated K+ currents via direct NO nitrosylation. We conclude that NO-mediated inhibition serves as a component of efferent nerve modulation of hair cells.

scholarly journals Identification of a 275-kD protein associated with the apical surfaces of sensory hair cells in the avian inner ear.

1990 ◽  
Vol 110 (4) ◽  
pp. 1055-1066 ◽  
Author(s):  
G P Richardson ◽  
S Bartolami ◽  
I J Russell
Keyword(s):  
Hair Cell ◽  
Inner Ear ◽  
Hair Cells ◽  
Proximal Region ◽  
Basilar Papilla ◽  
Relative Molecular Mass ◽  
Apical Surface ◽  
Sensory Hair ◽  
Sensory Hair Cells ◽  
Avian Inner Ear

Immunological techniques have been used to generate both polyclonal and monoclonal antibodies specific for the apical ends of sensory hair cells in the avian inner ear. The hair cell antigen recognized by these antibodies is soluble in nonionic detergent, behaves on sucrose gradients primarily as a 16S particle, and, after immunoprecipitation, migrates as a polypeptide with a relative molecular mass of 275 kD on 5% SDS gels under reducing conditions. The antigen can be detected with scanning immunoelectron microscopy on the apical surface of the cell and on the stereocilia bundle but not on the kinocilium. Double label studies indicate that the entire stereocilia bundle is stained in the lagena macula (a vestibular organ), whereas in the basilar papilla (an auditory organ) only the proximal region of the stereocilia bundle nearest to the apical surface is stained. The monoclonal anti-hair cell antibodies do not stain brain, tongue, lung, liver, heart, crop, gizzard, small intestine, skeletal muscle, feather, skin, or eye tissues but do specifically stain renal corpuscles in the kidney. Experiments using organotypic cultures of the embryonic lagena macula indicate that the antibodies cause a significant increase in the steady-state stiffness of the stereocilia bundle but do not inhibit mechanotransduction. The antibodies should provide a suitable marker and/or tool for the purification of the apical sensory membrane of the hair cell.

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