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At least 433 records · Page 24Linked to original sources
PubMed1982

Nature of the endocochlear dc potential in kanamycin-poisoned guinea pigs.

The endocochlear dc potential (EP) was measured in normal guinea pigs and in a group poisoned with kanamycin sulfate for 60 minutes after the administration of furosemide intravenously (IV) or by perfusion into the scala tympani. The EP decreased rapidly and developed a large negative potential after IV administration of furosemide, but the EP decreased more slowly and did not develop a negative potential in kanamycin-poisoned animals. With perfusion of the scala media, the EP declined slowly and did not develop a large negative potential in either group. With perfusion of the scala tympani, the EP declined slowly in the kanamycin-poisoned animals and did not develop a large negative potential, while in the normal animals the EP declined rapidly and developed a large negative potential.

Animals↗
PubMed1982

Perilymphatic and endolymphatic PO2. Variations during anoxia, hyperoxia, and hypercapnia.

Cochlear microcirculation was studied with oxygen-sensitive microelectrodes simultaneously in all three scalas during anoxia, hyperoxia, and hypercapnia. The anoxia caused a sharp decline of Po2 in the scala media (SM), scala vestibuli (SV), and scala tympani (ST). Hyperoxia and hypercapnia resulted in an elevation of Po2 in all three scalas. During anoxia, the SM showed the earliest and largest decline in Po2, with the shortest recovery and reoxygenation time. When Po2 slopes (during anoxia) were compared, the SM to ST and the SM to SV were substantially different and remained different even when the partial pressures of oxygen quantified as oxygen in nanomoles. Our experiments also showed that changes in Po2 within the SM closely correlate with changes of endocochlear potential and BP.

Animals↗
PubMed1985

Endolymphatic hydrops in guinea pigs after cauterizing the sac with silver nitrate.

There have been several reports of perisaccular fibrosis of the endolymphatic sac in some autopsied cases of Meniere's disease. We attempted to initiate perisaccular fibrosis of the sac in guinea pigs by injecting a small amount of 10% silver nitrate solution that cauterizes the tissue readily to produce scar, ie, fibrosis. Ninety-nine guinea pigs out of 108 (92%) that were treated with silver nitrate showed the endolymphatic hydrops in varied extent, from slight to profound. The extent of hydrops might depend on the extent of destruction of the sac following the cauterization. The lumen of the sac was sometimes occupied with dense fibrous connective tissue with deposition of black-silver particles in it. The silver nitrate injection method is an easy way to produce endolymphatic hydrops in guinea pigs.

Animals↗
PubMed1991

Cochleosacculotomy revisited. Long-term results poorer than expected.

Cochleosacculotomy has been described as a simple, efficacious treatment for relief of vertigo in patients with Meniere's disease in whom medical therapy has failed. We reviewed records of 11 elderly patients with good vestibular function who were thought to be ideal candidates for this procedure. Average follow-up was 17 months. Contrary to previous reports, long-term control of vertigo was poor, and more than 80% of the patients suffered a significant hearing loss from this procedure. Four of 11 patients required a second surgical procedure to control their vertigo. Audiometric measures revealed statistically significant postoperative increases in puretone thresholds at all frequencies and speech reception threshold, and a decrease in discrimination scores. Based on the results of this study, we no longer plan to use cochleosacculotomy for the treatment of elderly patients with Meniere's disease.

Adult↗
PubMed1997

Apical tubules in marginal cells of the differentiating stria vascularis.

BACKGROUND: Apical tubules (ATs) in marginal cells (MCs) of the stria vascularis appear in limited stages of differentiation of the MCs, but their origin and roles remain uncertain. The present study was designed to solve the problem of whether the ATs are intracellular compartments derived from the Golgi apparatus (GA). METHODS: The cochleae of Wistar rats at ages of postnatal days 1, 3, and 5 were prepared for electron microscopy and cytochemistry using thiamine pyrophosphatase (TPPase) and coenzyme A phosphatase (CoA-Pase) as marker enzymes of trans Golgi cisterns and fluorescent labelled lectin, griffonia simplicifolia agglutinin-I (GS-1). RESULTS: The ATs appeared in the apical cytoplasm of the MCs between postnatal days 1 and 5. Reaction products of TPPase and CoA-Pase activities were localized in the trans-Golgi cisterns and the ATs, which were occasionally in a close apposition to the GA. The reaction was found along the apical plasma membrane of the MCs only in case of TPPase. Heavy reactions to GS-1 were seen in the supranuclear region as well as along the apical plasma membrane of the MCs. CONCLUSIONS: The present ultrastructural and cytochemical studies indicate that the ATs, which appear in the MCs at limited perinatal stages, originate from the trans-Golgi cisterns. These ATs may be involved in the apical plasma membrane supply for the differentiation of the MCs prior to the generation of EP.

Animals↗
PubMed1978

Scanning electron microscope studies of the papilla basilaris of some turtles and snakes.

The papillae basilares of three species of turtles and four species of snakes were studied by SEM. The papillae of turtle are relatively large among reptiles and are characterized by a long, horizontal middle section resting on wide basilar membrane. Both terminal ends of the papilla extend onto the surrounding limbus in the form of a forked or "T" -shaped end or as a curved, "hook"- like processes. Details vary with the species. In the three species of turtles studied, there were between 1,100 and 1,400 hair cells on a papilla. The tectorial membrane covering the horizontal portion of the papilla is heavy in appearance and tightly attached to the kinocilial bulbs. The terminal ends of the papilla are covered by a thin gelatinous material. In addition, mat-like tectorial network covers the supporting cells and extends from the microvilli of the supporting cells to the overlying tectorial membrane. All hair cells are unidirectionally and abneurally oriented. The supporting cell surfaces form a large part of the papilla and, thus, hair cell density is low. The papillae of the two boid snake species studied are moderately long among snakes and contain a moderate number of hair cells (574 in Epicrates and 710-780 in Constrictor). Papillar form is elongate, avoid, or canoe-shaped. The tectorial membrane may be either highly fenestrated or moderately dense and covers all but a few of the terminal hair cells. A tectorial-like mat covers all but a few of the terminal hair cells. Most hair cells are unidirectionally and abneurally oriented. A few terminal cells in boids may show reverse orientation. Hair cell density is similar to that of turtles.

Animals↗
PubMed1978

A light and scanning electron microscopic study of the basial papilla in the salamander, Ambystoma tigrinum.

The basilar papilla and basilar recess of Ambystoma tigrinum have been investigated by light and scanning electron microscopy. The recess is an evagination of the lagena, and is invested externally by dense periotic connective tissue, except over a thin area of one wall abutting against a periotic diverticulum communicating with the periotic sac. The surface and histological features of the non-sensory lining epithelium are described. The basilar papilla occupies both slopes of an elevation adjacent to the thin wall of the recess, and consists of 40 to 80 sensory cells interposed between sustentacular cells. The sensory cells are innervated by 30 to 40 nerve fibers exhibiting two ranges of diameter, and they are capped by typical ciliary bundles that are taller at the center of the receptor than at its periphery. Bundles in the proximal and distal halves of the papilla are polarized, respectively, toward the saccule and toward the thin wall in contact with the periotic diverticulum; this divergent pattern of polarization has not been reported previously in the basilar papilla of other vertebrates. A tectorial body overlies only the bundles in the distal half of the receptor, and is attached to both the neuroepithelium and the opposite wall of the recess. Functional considerations are discussed, and comparisons are made with conditions reported in frogs and toads. The findings suggest that the basilar papilla and recess in caudate and anuran amphibians arose from common precursors and probably function in a similar manner.

Ambystoma↗
PubMed1978

Structure of the chicken's inner ear: SEM and TEM study.

The inner ears of 35 adult chickens were studied by TEM, SEM and light microscopy. Two well differentiated hair cell/nerve ending units were present: tall hair cells with small vesiculated nerve endings were located on the attached part of the basilar membrane; short hair cells with large vesiculated nerve endings were located on the free basilar membrane except for the distal tip. In this respect the chicken ear is similar to that of the pigeon. The chickens examined did have some unique features. Sensory cells of lenticular and hemispheric shape were also present at the proximal end. Bundles of long dense tubules were seen frequently within the sensory cell cytoplasm. Kinocilia were absent from the hair bundles of many of the sensory cells. The internal structure of the kinocilia which were present was atypical and consisted of a variable number of doublets. Eight peripheral plus one central doublet were found most frequently.

Animals↗
PubMed2004

Circling behavior in the Ecl mouse is caused by lateral semicircular canal defects.

The epistatic circler mouse (Ecl mouse) is a preexisting mutant, which displays a circling phenotype and hyperactivity. It has been shown that the circling phenotype in this mutant results from a complex inheritance pattern, but the vestibular pathology has not been analyzed. The present study deals with the morphological and functional basis responsible for the circling behavior in the Ecl mouse. Morphological examination of the inner ears revealed a bilateral malformation of the horizontal (lateral) semicircular canal and duct. No cochlear abnormalities were detected, and auditory brainstem response (ABR) measurements indicated that the auditory system is not affected. Investigation of the vestibuloocular reflex (VOR) in Ecl mice showed that their horizontal VOR on stimulation is virtually absent, which correlates with the morphological findings.

Animals↗
PubMed2001

The cell adhesion molecule BEN defines a prosensory patch in the developing avian otocyst.

The distribution of the cell adhesion molecule BEN in the developing chick inner ear is described. BEN is first detected in the otic placode at stage 11. As the placode begins to invaginate, BEN becomes concentrated in a ventromedial region extending from the anterior to the posterior end of the otic pit. BEN expression levels increase in this region as the pit closes to form the otocyst, and distinct boundaries become defined along the dorsal and ventral edges of the ventromedial band of BEN expression. BEN expression also becomes concentrated dorsally within the otic epithelium as the pit closes and is observed in the condensing otic ganglion. By stage 22, the ventromedial band of BEN expression splits into two distinct regions, a small caudal patch within which the posterior crista will develop, and a larger anterior patch. By stage 26, this larger anterior patch of cells expressing BEN becomes subdivided into five separate areas corresponding to the regions within which the anterior crista, the lateral crista, the utricle, the saccule, and both the basilar papilla and lagenar macula form. Hair cells only develop within these regions defined by BEN distribution. The data suggest that the ventromedial patch of BEN expression observed from stage 11 onwards defines a single sensory competent zone from which all sensory organs of the inner ear develop. BEN immunoreactivity in the inner ear declines after stage 38. In response to noise exposure, upregulation of BEN expression is mainly detected in regions of the posthatch papilla where the damage is severe and regenerating hair cells are not observed. The regenerating hair and supporting cells do not express BEN, highlighting a molecular difference between the processes of development and regeneration.

Activated-Leukocyte Cell Adhesion Molecule↗
PubMed1985

The very distal part of the basilar papilla in the chicken: a morphological approach.

The very distal part of the chicken basilar papilla was investigated by light and electron (scanning and transmission) microscopy. The rostral tip of the basilar papilla has a lenticular area with atypical sensory hair cells which are more similar to vestibular than to auditory cells. The structure of the lenticular area appears to be suitable for vestibular function or, more likely, for auditory perception at very low frequencies. Several hypotheses can be proposed to explain this very peculiar portion of the avian cochlea. It is difficult to consider it a continuously growing area since it remains stable in adulthood. A better explanation would be that there is an incomplete ontogenetic or phylogenetic process.

Animals↗
PubMed2004

TRAF6-dependent NF-kB transcriptional activity during mouse development.

Nuclear factor-kappa B (NF-kB) transcriptional activity is induced by numerous stimuli. To identify tissues exhibiting NF-kB transcriptional activity during development, we analyzed transgenic reporter mice that express beta-galactosidase from an NF-kB-responsive element. We report that NF-kB activation is widespread and present in numerous epithelial structures and within vasculature. Several regions of the developing central nervous system, including the roof plate and floor plate of the midbrain, show prominent NF-kB activation. To assess the role of the TRAF6 adaptor protein in developmental NF-kB activity, we analyzed NF-kB activation in reporter mice rendered null for TRAF6. Deletion of TRAF6 resulted in the loss of NF-kB activity in epithelia, in vasculature, and in roof and floor plate but had no effect on NF-kB activity developing telencephalon, choroid plexus, cochlear canal, and thymus. These data indicate that NF-kB transcriptional activity is present in a broad range of structures during development and that TRAF6 plays a critical role mediating developmental NF-kB activation in many but not all tissues.

Animals↗
PubMed2007

Comparative analysis of Gata3 and Gata2 expression during chicken inner ear development.

The inner ear is a complex sensory organ with hearing and balance functions. Gata3 and Gata2 are expressed in the inner ear, and to gain more insight into their roles in otic development, we made a detailed expression analysis in chicken embryos. At early stages, their expression was highly overlapping. At later stages, Gata2 expression became prominent in vestibular and cochlear nonsensory epithelia. In contrast to Gata2, Gata3 was mainly expressed in the developing sensory epithelia, reflecting the importance of this factor in the sensory-neural development of the inner ear. While the later expression patterns of both Gata3 and Gata2 were highly conserved between chicken and mouse, important differences were observed especially with Gata3 during early otic development, providing indications of divergent molecular control during placode invagination in mice and chickens. We also found indications that the regulatory hierarchy observed in mouse, where Gata3 is upstream of Gata2 and Fgf10, could be conserved in chicken.

Animals↗
PubMed1979

A morphometric study of the cochlea of the little brown bat (Myotis lucifugus).

A detailed morphometric study of the basilar membrane was made from serial sections and graphic reconstructions of the cochlea of three little brown bats. Four distinct morphometric changes were observed within the basilar membrane. First, between 0-1.4 mm from the basal end of the cochlea, there is a rapid increase in width and cross-sectional area of the basilar membrane. Secondly, between 1.4-2.5 mm, there is little change in width of the basilar membrane (its cross-sectional area is at its greatest in this region). Thirdly, between 2.7-3.1 mm, there is a sudden decrease in cross-sectional area concomitant with an increase in the width of the basilar membrane. Finally, between 3.1 mm and the apex, there is a gradual decrease in cross-sectional area concomitant with an increase in the width of the basilar membrane. The magnitudes of the cross-sectional areas of the scalae media and vestibuli decrease from base to apex, but this is not true for the scala tympani. The cross-sectional area of the scala tympani appears to decrease from the base to 0.7 mm, then it increases up to 1.4 mm, and then it decreases to the apex. These morphometric changes in the basilar membrane of the little brown bat are compared to those in other echolocating and non-echolocating mammals. The significance of these changes is discussed in relation to the range of hearing in the little brown bat.

Animals↗
PubMed1983

Spatial organization in the saccule and lagena of a teleost: hair cell pattern and innervation.

The relationship between the hair cell orientation pattern and innervation in the saccule and lagena of the teleost Helostoma temmincki (the kissing gourami) was investigated with scanning electron microscopy and the Winkelmann-Schmitt silver impregnation technique. The hair cell pattern in the saccule consists of four orthogonally oriented groups. The anterior two groups are oriented along the animal's rostrocaudal axis, and the posterior two are oriented along its dorsoventral axis. The pattern of hair cell orientations in the lagena is a typical bidirectional one. Two divisions of the eighth nerve innervate the saccule. The anterior division innervates the horizontally oriented hair cell groups, and the posterior division innervates the dorsoventrally oriented groups. A single nerve innervates the lagena, with the majority of fibers innervating one or the other of the two lagenar hair cell groups. The segregated pattern of innervation according to hair cell orientation groups in the saccule was confirmed in other species. Individual types of axonal terminations appear to innervate hair cells of specific ciliary bundle types.

Animals↗
PubMed1991

Hearing loss and pneumococcal meningitis: an animal model.

Clinical studies of predisposing factors in the development of hearing loss secondary to bacterial meningitis have produced conflicting results. An animal model of meningogenic labyrinthitis was developed for more precise study of these parameters. Rabbits were inoculated intrathecally with 10(5) pneumococci to induce meningitis. Hearing thresholds were measured using auditory-evoked responses to 1 kHz, 10 kHz, and click stimuli before infection and every 12 hours thereafter. Profound deafness occurred in all subjects at an average of 48 hours following infection. The incidence and severity of hearing loss was strongly correlated with the duration of meningitis. Temporal bone histology revealed acute inflammation of all perilymphatic spaces including the cochlear aqueduct. This model demonstrated that the risk and severity of hearing loss increase with the duration of meningitis and suggested that the cochlear aqueduct is an anatomic pathway for the extension of infection from the cerebrospinal fluid to the cochlea. The implications for therapy in humans is discussed.

Acoustic Stimulation↗
PubMed1999

Identification of aquaporin 5 (AQP5) within the cochlea: cDNA cloning and in situ localization.

Dysfunction of fluid and electrolyte homeostasis is considered to cause variety of inner ear disorders. One group of candidate proteins that may play a critical role in the inner ear fluid homeostasis is the aquaporins, a family of proteins whose members have well defined roles in fluid transport in variety of organs. This study reports the identification of AQP5, a member of the aquaporin family, within the rat inner ear and its in situ localization. AQP5 was initially identified within rat cochlear RNA via RT-PCR and sequence analysis of the amplified fragments. Immunoblot of cochlear homogenate yielded a predominant AQP5-immunoreactive band of M(r) 35 kDa. The anti-AQP5 immunoreactivity, indicating expression of the AQP5 polypeptide, was localized within the cochlea in situ to the cell types that form the lateral wall of the cochlear duct-the external sulcus (ES) cells and the cells of the spiral prominence. Expression of AQP5 was observed in the apical turn but not the basal turn of the cochlea; nor was it observed in the vestibular neuroepithelia or its supporting cells. The restricted expression of AQP5 to the apical turns of the cochlea suggests its potential role in low frequency hearing.

Animals↗
PubMed1997

Mapping and characterization of a novel cochlear gene in human and in mouse: a positional candidate gene for a deafness disorder, DFNA9.

Previously we identified a partial human cDNA for a novel cochlear transcript, hCoch-5B2 (HGMW-approved symbol D14S564E), using subtractive hybridization techniques. Herein we report isolation and characterization of both human and mouse (D12H14S564E) cDNAs for Coch-5B2. Full-length Coch5B2 deduced amino acid sequences reveal a very high degree of conservation in the coding region (89% nucleotide and 94% amino acid identity and a potential signal peptide and two regions of extensive homology to the collagen-binding type A domains of von Willebrand factor, also present in other secreted proteins, including extracellular matrix components. High levels of hCoch-5B2 expression are seen only in human fetal inner ear structures, cochlea, and vestibule, among a large panel of human fetal and adult tissues. Coch-5B2 expression in the mouse is more widespread than in the human, with message detected in mouse adult spleen, cerebrum, cerebellum/medulla, and thymus. In both species very low level expression is detected in total eye. More specifically, mouse retina shows a higher level of mCoch-5B2 message than sclera and choroid. We have mapped hCoch-5B2 to human 14q11.2-q13 by somatic cell hybrid analysis and FISH and, more precisely, using radiation hybrids to a region of markers linked to DFNA9, a nonsyndromic autosomal dominant sensorineural hearing loss with vestibular defects. Furthermore, we detect hCoch-5B2 on three overlapping YACs, two of which also contain one of the markers linked to DFNA9. mCoch-5B2 was genetically mapped in the mouse to chromosome 12, in a region of homologous synteny with human 14q11.2-q13, which contains the asp1 (audiogenic seizure prone) locus in the mouse.

Amino Acid Sequence↗