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PubMed1995

Anionic sites on Reissner's membrane, stria vascularis, and spiral prominence.

We demonstrated anionic sites on the lateral wall of cochlear duct and Reissner's membrane (RM) of ICR mice by Lowicryl K4M resin post-embedding and poly-L-lysine-colloidal gold conjugate (PL-CG) as a polycationic probe. The basement membrane and endolymphatic cell surface of RM were labeled with PL-CG pH 2.5 and pH 1.0. However, the perilymphatic cell surface was not labeled. PL-CG pH 2.5 and pH 1.0 strongly labeled the endolymphatic surface of the spiral prominence epithelium (SP), whereas the endolymphatic surface of the marginal cell (MC) in the stria vascularis was not labeled. Pre-digestion with several glycosidases eliminated PL-CG labeling. Our result suggests that an anionic charge located on the basement membrane of RM is largely due to the presence of heparan sulfate, chondroitin sulfate, and hyaluronic acid. An anionic charge on the endolymphatic cell surface of RM was mainly dependent on the presence of heparan sulfate. An anionic charge on the SP epithelium was caused to a substantial degree by chondroitin sulfate. We obtained histochemical evidence that the glycoconjugate content of the MC surface was quite different from that of the endolymphatic cell surface of RM and SP. We also identified RM-MC and SP-MC junctions at the ends of the stria vascularis between the marginal cells and the other endolymphatic epithelial cells of the cochlear duct.

Acrylic Resins↗
PubMed2002

Ultrastructure and blood supply of the tegmentum vasculosum in the cochlea of the duckling.

The tegmentum vasculosum of the duckling consists of a highly folded epithelium which extends over the dorsal and lateral walls of the cochlear duct, separating the scala media from the scala vestibuli. This epithelium consists of two distinct cell types, dark cells and light cells, and is well vascularized. The surface of the epithelium is formed by a mosaic of alternating dark and light cells. The goblet-shaped dark cells have an electron-dense, organelle-rich cytoplasm, and are expanded basally by extensive basolateral plasma membrane infoldings, within which are numerous mitochondria. Dark cells are isolated from each other and from the capillaries within the epithelium by intervening light cells. In contrast, columnar light cells exhibit an electron-lucent, organelle-poor cytoplasm and may extend from the underlying capillaries to the endolymphatic surface. Light cells contain abundant, coated endocytic vesicles on their apical surfaces and are bound, apically, to other light cells or to dark cells by tight junctions and desmosomes. Laterally, light cells are linked to each other either by complex, fluid-filled membrane interdigitations or by extensive gap junctions. Plasma membrane interdigitations and obvious, fluid-filled intercellular spaces characterize the lateral borders between light and dark cells. Vascular corrosion casting reveals the three-dimensional anatomy of the cochlear vasculature. A continuous arteriolar loop fed by anterior and posterior cochlear arterioles encircles the cochlear duct. The rich capillary beds of the tegmentum vasculosum are supplied by arching arterioles arising from this loop. These capillaries are the continuous type and are situated primarily within the core of the epithelium or along its border with the scala vestibuli. The structure and blood supply of the tegmentum vasculosum are characteristic of an epithelium involved in active transport.

Animals↗
PubMed2001

[The early postnatal development of the hamster cochlea].

The Early Postnatal Development of the Hamster Cochlea. Inborn deafness can be diagnosed very early. Deafness in early childhood can be caused by: genetic defects (30 % - 40 %), embryopathies, embryonic noxae (60 %) and pre-, peri- and postnatal noxae. Which structures of the cochlea are disturbed, is unknown in most cases. Systematic studies are necessary with directed experimental impairments of the cochlea in the early development to elucidate these mechanisms. An animal model has to be established in which directed impairments can be carried out in single individuals. The cochlea of the hamster is at birth in a very early state of development. In the apical turn the epithelial layer of the cochlear duct is undifferentiated, whereas in the basal turn the papilla basilaris (Kölliker's organ), the lateral wall and Reissner's membrane are visible. Between the base of the cochlea (1st coil lateral) and the apical part (3rd coil lateral) the difference in the development of the hamster cochlea is exactly four days. This is evident for the 1st and the 5th day after birth. The cochlea development of the hamster is very rapid. The development during one day represents one week of development in the human cochlea. The difference in development in one hamster cochlea from the apex to the base at a certain day representing four days of development is comparable with the development time of four weeks in human. The different developmental stages which are present in the hamster cochlea of a certain day represent the development of the human cochlea of a whole month. The hamster cochlea at the 1st day after birth covers the 2nd embryonic month of the human (4th to 8th week) and at the 5th day the 3rd embryonic month (8th to 12th week). The hamster cochlea at the 1st and the 5th day after birth is especially suitable to study experimental disturbances in the early stages of the development of the cochlear duct when the tectorial membrane, the spiral limbus, the stria vascularis, Reissners membrane and the external spiral Sulcus with the root cells are differentiating. The biggest advantage is that the noxae (hypoxia, teratogenic substances, ototoxic antibiotics and intense noise) can be applied to single individuals which offers better control than the treatment of the mother.

Animals↗
PubMedDate not supplied

Distribution of glycoconjugates during cochlea development. A histochemical study.

Specific occurrence and distribution of glycoconjugates in the developing mouse cochlea was investigated using Alcian blue/PAS staining. The AB/PAS positive staining occurred intracellularly, extracellularly, pericellularly, and as glycocalyx. Pericellular staining occurred between certain epithelial cells in early stages of development, and extracellular deposit occurred mostly in mesenchymal tissue surrounding the cochlear duct and later in developing spiral ligament. During early stages of development, mesenchymal tissue and pericellular space of different epithelial cells of the cochlear duct were intensely stained, suggesting that these glycoconjugates may play an important role in the differentiation of the cochlear structures. Different supporting cells (e.g. Deiters' cells, pillar cells) were intensely stained at different development stages coinciding with the time when the subcomponents of the tectorial membrane (TM) were being formed. This finding suggests that glycoconjugates in the TM are produced by these cells.

Alcian Blue↗
PubMed1999

Retinoic acid signaling is necessary for the development of the organ of Corti.

The cellular mosaic of the mammalian organ of Corti represents one of the most highly ordered structures in any vertebrate system. A single row of inner hair cells and three or four rows of outer hair cells extend along the basal-to-apical axis of the cochlea. The factors that play a role in the development of specific cell types within the cochlea are largely unknown; however, the results of previous studies have strongly suggested that retinoic acid plays a role in the development of cells as hair cells. To determine whether cochlear progenitor cells can respond directly to retinoic acid, the expression patterns for each of the RAR and RXR receptors within the embryonic cochlear duct were determined by in situ hybridization. Results indicate that RARalpha, RXRalpha, and RXRgamma are initially expressed throughout the cochlear duct. As development continues, the expression of each receptor becomes more intense in cells that will develop as hair cells. At the same time, receptor expression is down-regulated in cells that will develop as nonsensory cell types. To determine the effects of retinoic acid signaling during the development of the organ of Corti, activation of retinoid receptors was blocked in cultures of the embryonic cochlea through receptor-specific antagonism or inhibition of retinoic acid synthesis. Results indicate that inhibition of retinoic acid signaling induces a significant decrease in the number of cells that develop as hair cells and a disruption in the development of the organ of Corti. These results demonstrate that cells within the developing cochlea can respond to retinoic acid and that signaling by retinoic acid is necessary for the normal development of the organ of Corti.

Animals↗
PubMedDate not supplied

Bilateral deafness in a maltese terrier and a great pyrenean puppy: inner ear morphology.

Two puppies, a 4-month-old female Maltese terrier and a 6-week-old male Great Pyrenean, were presented for confirmation of bilateral deafness by electrophysiological testing. In both puppies, brainstem auditory potentials were not evoked by 90 dB NHL click stimulation of each ear. Examination of the inner ear revealed a bilateral cochleo-saccular degeneration in both animals. The lesions were characterized by generalized atrophy of the stria vascularis, collapse of the cochlear duct, degeneration of the organ of Corti, an abnormal tectorial membrane, and saccular collapse, with a normal spiral ganglion. The cochlear duct was entirely obliterated throughout the cochleae in the Maltese terrier puppy, but was locally and asymmetrically affected in the Great Pyrenean. The abnormalities observed in the Maltese terrier puppy were identical with those previously described in deaf Dalmatian puppies; the lesions observed in the Great Pyrenean, however, were less typical. This is the first histopathological description of cochleo-saccular degeneration in the Maltese terrier and Great Pyrenean breeds. In both puppies the defect was probably congenital.

Animals↗
PubMed2002

Temporal bone histopathology related to cochlear implantation in congenital malformation of the bony cochlea.

HYPOTHESIS: Histopathologic findings in temporal bones with congenital malformations of the bony cochlea may provide insight into cochlear implantation planning, surgical approach, and complications. BACKGROUND: Patients with congenitally malformed cochleae account for an increasing percentage of candidates for cochlear implantation. Few studies on the relationship between histopathologic findings of temporal bones with malformation of the bony cochlea and cochlear implantation have been reported. METHODS: We studied 21 temporal bones from 12 cases with congenital malformations of the bony cochlea. Ages ranged from stillborn to 50 years. Length of the cochleae and dimensions of facial recesses were measured with light microscopy. Other malformations associated with a shortened cochlea were determined, emphasizing how they affect cochlear implantation. RESULTS: The average length of the malformed cochlear duct was 22.84 +/- 0.69 mm. Average dimensions of facial recesses were not significantly different between malformed cochleae and the controls. Other malformations included enlarged cochlear aqueduct (43%), abnormal facial nerve course (57%), enlarged vestibular aqueduct (52%), aplasia of the middle ear (19%), malformed ossicles (67%), abnormal oval window (57%), and abnormal round window (29%). CONCLUSION: A shortened cochlear duct may cause an incomplete insertion of the implant electrode. Because dimensions of the facial recesses are similar to normal cases, a facial recess surgical approach is recommended. An enlarged cochlear aqueduct may cause perilymphatic oozing or gushing on fenestration of the cochlea. An anomalous course of the facial nerve is a common finding. Tympanic malformations such as round and oval window deformities and small middle ear cleft should be noted preoperatively to better guide surgery.

Adolescent↗
PubMed1975

Experimental endolymphatic hydrops and its relief by interrupting the lateral semicircular duct in guinea pigs.

It has been demonstrated that endolymphatic hydrops can be produced in guinea pigs by obliteration of the endolymphatic sac and this phenomenon was reproduced in our own laboratory. Interruption of the lateral semicircular duct of animals with labyrinthine hydrops produced a diminution of the hydrops in 4 out of 8 cases, and these did not show any collapse in the cochlear duct. It was considered that the hydrops was diminished by drainage of the surplus endolymph into the perilymphatic space, and that the cochlear duct was kept secure from collapse because of its distance from the operated lateral semicircular duct and of the utriculo-endolymphatic valve. Persistence of hydrops in the other four cases was thought to be due to closure of the operated lateral semicircular duct or to labyrinthitis. Although this series is not comprehensive enough, it seems to indicate that interruption of the lateral semicircular duct has a possibility of diminishing labyrinthine hydrops, as in cases of Ménière's disease, without hearing disturbance, provided that complications do not develop. Further investigation with many more animals, for a longer period of time after the operation, is required to gain more precisely detailed information.

Animals↗
PubMed2003

Postnatal maturation of the dog stria vascularis-- an immunohistochemical study.

The lateral wall of the dog cochlear duct was investigated by classical staining and immunohistochemistry for NaK/ATPase beta2 isoform, cytokeratins (Cks), vimentin, nestin, and S100A6 during the postnatal cochlear maturation, i.e., from birth to postnatal day 110. The dog stria vascularis was immature at birth. Fine melanin granules were evident in the stria from the second week of life, and melanin concentration increased drastically beyond the first month. The marginal cells were NaK/ATPase- and Ck-positive; intermediate cells were either nestin- and S100A6-positive or vimentin-positive; the basal cells were vimentin-positive; the capillary endothelium showed vimentin and nestin labeling; the cell layer underlying the stria was nestin-positive. The fibrocytes of the spiral ligament and spiral prominence expressed nestin and vimentin. The epithelial cells overlaying the spiral prominence and the external sulcus were Ck-positive, and transiently nestin- and vimentin-positive. Double immunolabeling, for S100A6 and either nestin, vimentin, or NaK/ATPase, and for nestin and vimentin suggested the presence of two distinct intermediate cell types. The results enabled us to differentiate the cell types forming the lateral wall of the dog cochlear duct, and to follow their postnatal maturation. This study may form a basis for future investigations about spontaneous cochleosaccular degeneration in dogs. This species is an important companion animal, and a possible model for the study of comparable diseases in humans.

Animals↗
PubMed1992

[Effects of furosemide on endocochlear potentials, auditory action potentials and summating potentials and the changes of inner ear pathology].

Guinea pigs were injected with furosemide 50 mg/kg (group A) and 25mg/kg (group B). Two minutes after injection, EP of group A decreased to -13.9mv while that of group B decreased to +65 mv. Also, AP of group A disappeared, and recovered at 8.5 mins. while AP amplitude of group B decreased to 78%. The SP value of group A changed from -14.5mv to +23.4mv 1 min after injection and returned to negative polarity in 12 min. Edema of stria vascularis was observed under light microscope. Transmission electron microscope showed edema between marginal cells and intermedia cells, cytoplasm of the marginal cell protruded to the cochlear duct, and cell membrane of outer hair cell folded. The finding of this study illustrates that furosemide inhibits the transportation of the active ions of cochlear duct tissue resulting in decrease of EP and alters the function of hair cells causing the change of AP amplitude. -SP depends on the ion transportation, the polarity can be inversed while large dosage of furosemide was used.

Action Potentials↗
PubMed2005

Gbx2 is required for the morphogenesis of the mouse inner ear: a downstream candidate of hindbrain signaling.

Gbx2 is a homeobox-containing transcription factor that is related to unplugged in Drosophila. In mice, Gbx2 and Otx2 negatively regulate each other to establish the mid-hindbrain boundary in the neural tube. Here, we show that Gbx2 is required for the development of the mouse inner ear. Absence of the endolymphatic duct and swelling of the membranous labyrinth are common features in Gbx2-/- inner ears. More severe mutant phenotypes include absence of the anterior and posterior semicircular canals, and a malformed saccule and cochlear duct. However, formation of the lateral semicircular canal and its ampulla is usually unaffected. These inner ear phenotypes are remarkably similar to those reported in kreisler mice, which have inner ear defects attributed to defects in the hindbrain. Based on gene expression analyses, we propose that activation of Gbx2 expression within the inner ear is an important pathway whereby signals from the hindbrain regulate inner ear development. In addition, our results suggest that Gbx2 normally promotes dorsal fates such as the endolymphatic duct and semicircular canals by positively regulating genes such as Wnt2b and Dlx5. However, Gbx2 promotes ventral fates such as the saccule and cochlear duct, possibly by restricting Otx2 expression.

Animals↗
PubMed1998

[Cochlear and retrocochlear deafness induced by immunity with different inner ear tissue antigens].

OBJECTIVES: To inquire into whether the different inner ear tissue antigens could cause different kind of hearing loss, and to find out the disorder positions of auditory system. METHODS: The basilar membrane (BM), spiral ligament (SL), and spiral ganglion (SG) of guinea pigs were removed for making antigens, respectively. Then, we used these antigens to immune guinea pigs. The special humour and cellular immune reaction, hearing function, and inner ear histopathological changes were observed. RESULTS: In BM-antigen and SL-antigen immune group, the various degrees of cochlear microphonic potential disturbance, recruitment, and immune pathological inflammation in cochlear duct and stria vascularis were found. In SG-antigen immune group, auditory nerve compound action potential changes were prominent, and the inner ear pathological damage mainly existed in cochlear axis vessels or surround areas, and SG. CONCLUSIONS: It was confirmed that the inner ear antigens come from different part of auditory system, which could cause cochlear or retrocochlear autoimmune disease.

Animals↗
PubMed1992

Postnatal development of the rat organ of Corti. II. Hair cell receptors and their supporting elements.

The development of cochlear receptor cells and their supporting elements was studied by means of semi-thin and ultra-thin sections during the first postnatal weeks in the rat. The temporal and spatial patterns of the receptor cell development were investigated between the 4th and 24th days after birth. At approx. ten equidistant positions along the entire cochlear duct length of inner and outer hair cells, width of outer hair cell triad and stereocilia-length of the outer hair cells were quantitatively analyzed. Striking maturational changes take place before the 12th day after birth, that is, when the onset of hearing occurs. These changes are the formation of the tunnel of Corti, of the Nuel spaces, the appearance of filaments within the supporting elements and the change in cell shape of the hair cells. Between 4 days and 20 days after birth the maturation of outer hair cells is characterized by a decrease of organelles in the cytoplasm and establishment of the subsurface cistern. The quantitative analysis revealed a unique developmental pattern of the length of the outer hair cells, the width of the outer hair cell triad and the stereocilia length of the outer hair cells. Shortly after birth these structures have an almost constant size along the whole cochlear duct, but with increasing age the structures shorten at the cochlear base and enlarge at the apex. This pattern results in the establishment of a baso-apical gradient of the above mentioned structures. We assume that this baso-apical gradient is of central importance for the frequency representation.

Animals↗
PubMed1982

Studies on fibrous tissues of the basilar membrane in inner ear.

Of a number of electron microscope studies on the basilar membrane of the inner ear cochlear duct so far reported, none seems to have been conducted using PAM of R.R. staining, excellent stainings especially suited for the observation of connective tissue. In this study the basilar membrane of the cochlear duct in young and mature guinea pigs and human fetuses was examined with an electron microscope using these stainings, and obtained the interesting results described below. Fibrils of the basilar membrane, although strongly PAM-positive, all lacked periodic stripes, indicating that they were collagenous fibrils in an immature state. Young guinea pigs clearly differed from mature ones in that numerous fibroblasts were present. In human fetuses, the basilar membrane exhibited no clear fibrillar structure in the 13th week, but had PAM-positive fibrils in the 20th week. By the 23rd week, it had assumed roughly the same structure as in adults, although numerous fibroblasts were still present, and resembled the basilar membrane in young guinea pigs. The basilar membrane is a part of a unique organ, a sensory organ. Though comparison is difficult because of the extremely complicated anatomy of the organ, it is concluded that the fibrils of basilar membrane are collagenous fibrils in a peculiarly immature state, and similar to those in the cartilage and tympanic membrane.

Aged↗
PubMedDate not supplied

Development of the cochlea and its coiling mechanism.

The growth and shape of the membraneous labyrinth appears to be organized and restricted by the formation of the cartilaginous capsule. Coiling of the cochlear duct appears to be the result of the physical barrier and support provided by the cartilage cells differentiating from mesenchyme surrounding the otocyst. In addition, tissue interactions between this mesenchyme and the developing cochlear duct may be the source of a genetic message for the coiling mechanism.

Animals↗
PubMed1995

Traumatic endolymphatic hydrops.

Traumatic endolymphatic hydrops is an accumulation of endolymph in the cochlear duct caused by traumatic insult. The causative mechanisms are: (1) fistulization of the bony labyrinth, which causes a disturbance in the normal perilymph-endolymph pressure relationship; (2) direct injury to the membranous labyrinth, which may be just a collection of fluid in the cochlear duct from irritation, resulting in endolymphatic hydrops that may not be progressive and may subside in a short period of time after injury and hearing loss may occur; and (3) injury to the endolymphatic fluid drainage system, including a temporal bone fracture in which the fissure happens to extend through the vestibular aqueduct, causing fibro-osseous blockage of the endolymphatic duct and surgical injury to the saccule with obstruction of the longitudinal flow of endolymph, resulting in endolymphatic hydrops that may be delayed in onset and is usually persistent. The diagnosis of traumatic endolymphatic hydrops is made by a history of trauma, such as barotrauma, a blow to the head, or perhaps a previous ear operation, such as stapedectomy; the presence of typical symptoms of endolymphatic hydrops, including fullness, tinnitus, fluctuant hearing loss, and episodic vertigo; and an elevated negative summating potential and an increased summating potential:action potential ratio by electrocochleography. Three patients are presented to demonstrate this clinical entity.

Adult↗
PubMedDate not supplied

Delineation of cochlear glycogen by electron microscopy.

Two techniques for the demonstration and identification of glycogen by electron microscopy were applied to the cochlear duct tissues of normal guinea pigs and chinchillas. A modified osmium tetroxide fixative (with potassium ferricyanide) has been described by De Bruijn to selectively stain the glycogen particle. Identification of the stained particle was effected by its selective removal from the tissue with amyloglucosidase, an enzyme specific in its degradation of the glycogen molecule. Glycogen particles were noted in several cell types within the cochlear duct, but concentrations were greater in outer hair cells of both species and in the stria vascularis of the chinchilla. The fact that amyloglucosidase completely eliminated these particles from the liver of both species as well as cochlear tissue, led to the conclusion that these particles are indeed glycogen.

Amylases↗
PubMed2006

Expression of TGFbeta family in the developing internal ear of rat embryos.

In order to investigate the expression patterns of the transforming growth factor (TGF)beta isoforms in the internal ear, an immunohistochemical study of rat embryos was performed. Rat embryos were taken on the 13th, 15th, 17th, and 19th day after conception and their internal ears were immunohistochemically stained against TGF beta1, beta2, and beta3. As a result, the 13-day-old embryo showed a very weak positivity to TGF beta1. After the 15th day of pregnancy, no reactivity to TGF beta1 was defected. Immunoreactivity to TGF beta2 was observed from the 15th day of pregnancy throughout the rest of the period. The ampulla of the semicircular canal and the cochlear duct showed a notably strong immunohistochemical reaction. A strong reaction to TGF beta3 was observed on the 15th day of pregnancy. However, no positive reactions were observed thereafter. A strong immunoreactivity was observed especially on the apical cytoplasms, the surfaces of the epithelial cells, and basement membranes of the cochlear duct, as well as the semicircular canals of the developing internal ear of rat embryo.

Animals↗