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British Medical Journal (Clinical... Jul 1986
Topics: Ear, Inner; Fistula; Humans; Labyrinthine Fluids; Perilymph
PubMed: 3089460
DOI: 10.1136/bmj.293.6541.220 -
Journal of the Association For Research... Feb 2017Comparative auditory studies make it possible both to understand the origins of modern ears and the factors underlying the similarities and differences in their... (Comparative Study)
Comparative Study Review
Comparative auditory studies make it possible both to understand the origins of modern ears and the factors underlying the similarities and differences in their performance. After all lineages of land vertebrates had independently evolved tympanic middle ears in the early Mesozoic era, the subsequent tens of millions of years led to the hearing organ of lizards, birds, and mammals becoming larger and their upper frequency limits higher. In extant species, lizard papillae remained relatively small (<2 mm), but avian papillae attained a maximum length of 11 mm, with the highest frequencies in both groups near 12 kHz. Hearing-organ sizes in modern mammals vary more than tenfold, up to >70 mm (made possible by coiling), as do their upper frequency limits (from 12 to >200 kHz). The auditory organs of the three amniote groups differ characteristically in their cellular structure, but their hearing sensitivity and frequency selectivity within their respective hearing ranges hardly differ. In the immediate primate ancestors of humans, the cochlea became larger and lowered its upper frequency limit. Modern humans show an unusual trend in frequency selectivity as a function of frequency. It is conceivable that the frequency selectivity patterns in humans were influenced in their evolution by the development of speech.
Topics: Animals; Biological Evolution; Ear; Ear, Inner; Ear, Middle; Hearing; Humans; Lizards
PubMed: 27539715
DOI: 10.1007/s10162-016-0579-3 -
BMC Genetics Jul 2010The inner ear is one of the most complex and detailed organs in the vertebrate body and provides us with the priceless ability to hear and perceive linear and angular... (Review)
Review
The inner ear is one of the most complex and detailed organs in the vertebrate body and provides us with the priceless ability to hear and perceive linear and angular acceleration (hence maintain balance). The development and morphogenesis of the inner ear from an ectodermal thickening into distinct auditory and vestibular components depends upon precise temporally and spatially coordinated gene expression patterns and well orchestrated signaling cascades within the otic vesicle and upon cellular movements and interactions with surrounding tissues. Gene loss of function analysis in mice has identified homeobox genes along with other transcription and secreted factors as crucial regulators of inner ear morphogenesis and development. While otic induction seems dependent upon fibroblast growth factors, morphogenesis of the otic vesicle into the distinct vestibular and auditory components appears to be clearly dependent upon the activities of a number of homeobox transcription factors. The Pax2 paired-homeobox gene is crucial for the specification of the ventral otic vesicle derived auditory structures and the Dlx5 and Dlx6 homeobox genes play a major role in specification of the dorsally derived vestibular structures. Some Micro RNAs have also been recently identified which play a crucial role in the inner ear formation.
Topics: Animals; Ear, Inner; Gene Expression Regulation, Developmental; Genes, Developmental; Humans; Mice; Morphogenesis; PAX2 Transcription Factor; Proteomics; Vestibule, Labyrinth
PubMed: 20637105
DOI: 10.1186/1471-2156-11-68 -
Cold Spring Harbor Perspectives in... Jun 2019Macrophages are present in most somatic tissues, where they detect and attack invading pathogens. Macrophages also participate in many nonimmune functions, particularly... (Review)
Review
Macrophages are present in most somatic tissues, where they detect and attack invading pathogens. Macrophages also participate in many nonimmune functions, particularly those related to tissue maintenance and injury response. The sensory organs of the inner ear contain resident populations of macrophages, and additional macrophages enter the ear after acoustic trauma or ototoxicity. As expected, such macrophages participate in the clearance of cellular debris. However, otic macrophages can also influence the long-term survival of both hair cells and afferent neurons after injury. The signals that recruit macrophages into the injured ear, as well as the precise contributions of macrophages to inner ear pathology, remain to be determined.
Topics: Animals; Apoptosis; Ear, Inner; Hair Cells, Auditory; Humans; Labyrinth Supporting Cells; Macrophages; Mammals; Models, Animal; Phagocytosis
PubMed: 30181352
DOI: 10.1101/cshperspect.a033555 -
Development (Cambridge, England) Oct 2023Inner ear development requires the coordination of cell types from distinct epithelial, mesenchymal and neuronal lineages. Although we have learned much from animal...
Inner ear development requires the coordination of cell types from distinct epithelial, mesenchymal and neuronal lineages. Although we have learned much from animal models, many details about human inner ear development remain elusive. We recently developed an in vitro model of human inner ear organogenesis using pluripotent stem cells in a 3D culture, fostering the growth of a sensorineural circuit, including hair cells and neurons. Despite previously characterizing some cell types, many remain undefined. This study aimed to chart the in vitro development timeline of the inner ear organoid to understand the mechanisms at play. Using single-cell RNA sequencing at ten stages during the first 36 days of differentiation, we tracked the evolution from pluripotency to various ear cell types after exposure to specific signaling modulators. Our findings showcase gene expression that influences differentiation, identifying a plethora of ectodermal and mesenchymal cell types. We also discern aspects of the organoid model consistent with in vivo development, while highlighting potential discrepancies. Our study establishes the Inner Ear Organoid Developmental Atlas (IODA), offering deeper insights into human biology and improving inner ear tissue differentiation.
Topics: Animals; Humans; Ear, Inner; Hair Cells, Auditory; Organoids; Cells, Cultured; Cell Differentiation
PubMed: 37796037
DOI: 10.1242/dev.201871 -
Developmental Dynamics : An Official... Oct 2014Damage or destruction of sensory hair cells in the inner ear leads to hearing or balance deficits that can be debilitating, especially in older adults. Unfortunately,... (Review)
Review
BACKGROUND
Damage or destruction of sensory hair cells in the inner ear leads to hearing or balance deficits that can be debilitating, especially in older adults. Unfortunately, the damage is permanent, as regeneration of the inner ear sensory epithelia does not occur in mammals.
RESULTS
Zebrafish and other non-mammalian vertebrates have the remarkable ability to regenerate sensory hair cells and understanding the molecular and cellular basis for this regenerative ability will hopefully aid us in designing therapies to induce regeneration in mammals. Zebrafish not only possess hair cells in the ear but also in the sensory lateral line system. Hair cells in both organs are functionally analogous to hair cells in the inner ear of mammals. The lateral line is a mechanosensory system found in most aquatic vertebrates that detects water motion and aids in predator avoidance, prey capture, schooling, and mating. Although hair cell regeneration occurs in both the ear and lateral line, most research to date has focused on the lateral line due to its relatively simple structure and accessibility.
CONCLUSIONS
Here we review the recent discoveries made during the characterization of hair cell regeneration in zebrafish.
Topics: Animals; Animals, Genetically Modified; Cell Death; Ear, Inner; Gene Expression; Hair Cells, Auditory; Lateral Line System; Regeneration; Zebrafish
PubMed: 25045019
DOI: 10.1002/dvdy.24167 -
Hearing Research Oct 2011Na(+) concentrations in endolymph must be controlled to maintain hair cell function since the transduction channels of hair cells are cation-permeable, but not... (Review)
Review
Na(+) concentrations in endolymph must be controlled to maintain hair cell function since the transduction channels of hair cells are cation-permeable, but not K(+)-selective. Flooding or fluctuations of the hair cell cytosol with Na(+) would be expected to lead to cellular dysfunction, hearing loss and vertigo. This review briefly describes cellular mechanisms known to be responsible for Na(+) homeostasis in each compartment of the inner ear, including the cochlea, saccule, semicircular canals and endolymphatic sac. The influx of Na(+) into endolymph of each of the organs is likely via passive diffusion, but these pathways have not yet been identified or characterized. Na(+) absorption is controlled by gate-keeper channels in the apical (endolymphatic) membrane of the transporting cells. Highly Na(+)-selective epithelial sodium channels (ENaCs) control absorption by Reissner's membrane, saccular extramacular epithelium, semicircular canal duct epithelium and endolymphatic sac. ENaC activity is controlled by a number of signal pathways, but most notably by genomic regulation of channel numbers in the membrane via glucocorticoid signaling. Non-selective cation channels in the apical membrane of outer sulcus epithelial cells and vestibular transitional cells mediate Na(+) and parasensory K(+) absorption. The K(+)-mediated transduction current in hair cells is also accompanied by a Na(+) flux since the transduction channels are non-selective cation channels. Cation absorption by all of these cells is regulated by extracellular ATP via apical non-selective cation channels (P2X receptors). The heterogeneous population of epithelial cells in the endolymphatic sac is thought to have multiple absorptive pathways for Na(+) with regulatory pathways that include glucocorticoids and purinergic agonists.
Topics: Animals; Cochlea; Ear, Inner; Endolymphatic Sac; Homeostasis; Humans; Ion Transport; Saccule and Utricle; Semicircular Canals; Sodium
PubMed: 21620939
DOI: 10.1016/j.heares.2011.05.003 -
Hearing Research Sep 2021Wideband tympanometry performs a more thorough analysis of middle-ear mechanics than the conventional single-frequency method with a 226-Hz probe tone. The present work...
Wideband tympanometry performs a more thorough analysis of middle-ear mechanics than the conventional single-frequency method with a 226-Hz probe tone. The present work examines the sensitivity of wideband tympanometry to the stiffness of the stapes-annular ligament system in relation to intracranial pressure (ICP) and labyrinthine fluid pressure. Here, body tilt allowed ICP to be set at different values. Sixty-eight ears of volunteers were tested sequentially in upright, supine, head-down (-30°) and upright postures. Energy absorbance of the ear was measured in these postures with a commercially available wideband-tympanometry device between 0.25 and 3 kHz, at ear-canal pressures between -600 and 300 daPa. In each posture, it was possible to find a single (posture-dependent) pressure in the ear canal at which a tympanometric peak occurred at all frequencies below about 1.1 kHz. The average across ears of tympanometric-peak pressure (TPP), close to 0 in upright posture, got increasingly positive, +19 daPa in supine and +27 daPa in head-down positions. The three-dimensional plot of energy absorbance against frequency and pressure displayed an invariant shape, merely shifting with TPP along the pressure axis. Thus, a properly adjusted ear-canal pressure neutralized the effects of ICP on the ear's energy absorbance. Comparisons to published invasive assessments of ICP in the different tested body positions led to the proposed relationship ICP ≈ 15 TPP, likely describing the transformer effect between tympanic membrane and stapes-annular ligament system at quasi-static pressures. With wideband tympanometry, the middle ear may serve as a precision scales for noninvasive ICP measurements.
Topics: Acoustic Impedance Tests; Ear, Inner; Ear, Middle; Humans; Intracranial Pressure; Tympanic Membrane
PubMed: 34298416
DOI: 10.1016/j.heares.2021.108312 -
The Journal of International Advanced... Mar 2021It has been revealed that the pure-tone audiometry demonstrates large air-bone gaps at low pitches due to the presence of inner ear fistulae. When a third mobile window... (Review)
Review
It has been revealed that the pure-tone audiometry demonstrates large air-bone gaps at low pitches due to the presence of inner ear fistulae. When a third mobile window resulting from an inner ear fistula is present, in addition to the 2 normally present windows consisting of the oval window and the round window, a portion of the air-conducted waves escape from the scala vestibuli through the inner ear fistula. On the other hand, bone-conducted waves traveling to the scala vestibuli are reduced by an inner ear fistula; however, bone-conducted waves traveling to the scala tympani are not affected by an inner ear fistula. This results in a larger gap than usual in compliance between both perilymphatic spaces and leads to a decrease in the bone conduction threshold. This phenomenon, so-called the third mobile window effects, sometimes may lead otology/neuro-otology surgeons to misunderstand the reason why large air-bone gaps still exist after ossicular reconstruction in tympanoplasty. This review article gives good examples regarding the third mobile window effects in otology/neuro-otology diseases and surgeries.
Topics: Bone Conduction; Cochlea; Neurotology; Round Window, Ear; Scala Tympani
PubMed: 33893786
DOI: 10.5152/JIAO.2021.8632 -
The International Journal of... 2009The inner ear is a complex structure responsible for the senses of audition and balance in vertebrates. The ear is organised into different sense organs that are... (Review)
Review
The inner ear is a complex structure responsible for the senses of audition and balance in vertebrates. The ear is organised into different sense organs that are specialised to detect specific stimuli such as sound and linear or angular accelerations. The elementary sensory unit of the ear consists of hair cells, supporting cells, neurons and Schwann cells. Hair cells are the mechano-electrical transducing elements, and otic neurons convey information coded in electrical impulses to the brain. With the exception of the Schwann cells, all cellular elements of the inner ear derive from the otic placode. This is an ectodermal thickening that is specified in the head ectoderm adjacent to the caudal hindbrain. The complex organisation of the ear requires precise coupling of regional specification and cell fate decisions during development, i.e. specificity in defining particular spatial domains containing particular cell types. Those decisions are taken early in development and are the subject of this article. We review here recent work on: i) early patterning of the otic placode, ii) the role of neural tube signals in the patterning of the otic vesicle, and iii) the genes underlying cell fate determination of neurons and sensory hair cells.
Topics: Animals; Body Patterning; Cell Differentiation; Chickens; Ear, Inner; Gene Expression Regulation, Developmental; Hair Cells, Auditory; Mice; Models, Biological; Rhombencephalon
PubMed: 19247974
DOI: 10.1387/ijdb.072422ba