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Endolymphatic Duct (endolymphatic + duct)
Selected AbstractsDevelopmental Expression of Aquaporin 2 in the Mouse Inner Ear ,THE LARYNGOSCOPE, Issue 11 2000Michele Merves Abstract Objectives The maintenance of endolymph homeostasis is critical for the inner ear to perform its functions of hearing and maintaining balance. The identification and cloning of aquaporins (a family of water channel proteins) has allowed the study of a novel cellular mechanism potentially involved in endolymph homeostasis. The objective of the present study was to define the developmental temporal and spatial e-pression pattern of aquaporin 2 (Aqp2) in the developing mouse inner ear. Study Design A systematic immunohistochemical study of Aqp2 protein e-pression was performed on embryonic mouse inner ears ranging from embryonic day 10 (otocyst stage) to embryonic day 18 (just before birth). Methods Serial cryosections of embryonic mouse inner ears were used for immunohistochemical e-periments. A rabbit polyclonal antisera raised against a synthetic Aqp2 peptide was used with a standard nickel intensified 3,3-diaminobenzidine reaction protocol for immunolocalization of Aqp2 in tissue sections. Results Aquaporin 2 is e-pressed diffusely in the early otocyst, then becomes progressively restricted as the inner ear matures. During early cochlear duct formation (embryonic days 12 and 13), e-pression of Aqp2 is homogeneous; later, it becomes restricted to specific regions of the endolymphatic compartment (embryonic days 15 and 18). Similar restriction of e-pression patterns could be noted for the vestibular structures. Endolymphatic duct and sac and stria vascularis e-pression of Aqp2 was noted to occur fairly late during development but demonstrated a distinct pattern of immunolabeling. Conclusions Aquaporin 2 shows an early and specific pattern of e-pression in the developing mouse inner ear, suggesting a significant role for this water channel protein in the development of endolymph homeostasis and meriting further functional studies of Aqp2 in the inner ear. [source] Dan is required for normal morphogenesis and patterning in the developing chick inner earDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 1 2007Takahiro Yamanishi During vertebrate inner ear development, compartmentalization of the auditory and vestibular apparatuses along two axes depends on the patterning of transcription factors expressed in a region-specific manner. Although most of the patterning is regulated by extrinsic signals, it is not known how Nkx5.1 and Msx1 are patterned. We focus on Dan, the founding member of the Cerberus/Dan gene family that encodes BMP antagonists, and describe its function in morphogenesis and patterning. First, we confirmed that Dan is expressed in the dorso-medial region of the otic vesicle that corresponds to the presumptive endolymphatic duct and sac (ed/es). Second, we used siRNA knockdown to demonstrate that depletion of Dan induced both a severe reduction in the size of the ed/es and moderate deformities of the semicircular canals and cochlear duct. Depletion of Dan also caused suppression of Nkx5.1 in the dorso-lateral region, suppression of Msx1 in the dorso-medial region, and ectopic induction of Nkx5.1 and Msx1 in the ventro-medial region. Most of these phenotypes also appeared following misexpression of the constitutively active form of BMP receptor type Ib. Thus, Dan is required for the normal morphogenesis of the inner ear and, by inhibiting BMP signaling, for the patterning of the transcription factors Nkx5.1 and Msx1. [source] Atlas of the developing inner ear in zebrafishDEVELOPMENTAL DYNAMICS, Issue 4 2002Michele Miller Bever Abstract This report provides a description of the normal developing inner ear of the zebrafish, Danio rerio, with special focus on the pars inferior. Zebrafish specimens, ranging in age from 3 to 30 days postfertilization (dpf), were processed for standard histologic sections or with a paint-fill method to show three-dimensional morphogenesis of the membranous labyrinth. Adult zebrafish (age 2 years) were also processed for inner ear paint-fills. Although development of the semicircular canals occurs rapidly (by 3 dpf), the pars inferior develops more gradually during days 5,20 postfertilization. A rudimentary endolymphatic duct emerges by 8 dpf. Differentiated hair cells of the lagenar macula are evident by 15 dpf, in a chamber located lateral and posterior to the saccule. By 20 dpf, the saccule itself is separated from the utricle, but remains connected by means of the utriculosaccular foramen. The maculae neglectae, each with differentiated hair cells, lie on the floor of the utricle near this foramen. A medial connection between the sacculi of right and left ears, the transverse canal, is also complete by 20 dpf. A ridge of mesenchyme, previously undescribed, bisects the saccule in zebrafish fry at 20,30 dpf. The images in the paint-fill atlas should provide a baseline for future studies of mutant zebrafish ears. © 2002 Wiley-Liss, Inc. [source] Enlarged vestibular aqueduct in two male siblingsDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 10 2002C M Varghese MSc MRCP FRCPCH This report describes the case history of two male siblings with sensorineural hearing loss and an enlarged vestibular aqueduct (EVA). Sibling 1 presented with a history of intermittent self-limiting ataxia and hearing loss at the age of 25 months and sibling 2 presented with a similar history at the age of 18 months. MRI showed an enlarged endolymphatic duct and sac bilaterally in both children. Perchlorate discharge tests were positive in both infants leading to a diagnosis of Pendred syndrome. A number of conditions associated with EVA are discussed with a view to devising management strategies. [source] | |||||||||||||