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At least 19 recordsLinked to original sources
PubMed1992

Postnatal development of the rat organ of Corti. I. General morphology, basilar membrane, tectorial membrane and border cells.

The development of the rat organ of Corti was studied during the first postnatal weeks. The temporal and the spatial patterns of cochlear development were investigated between 4 and 24 days after birth by means of semi-thin sections at approx. ten equidistant positions along the entire cochlear duct. At all examined positions width, thickness and cross sectional area of basilar membrane, cross-sectional area of tectorial membrane, of cells of Hensen, Claudius and Boettcher and of the organ of Corti were quantitatively analyzed. The most conspicuous maturational changes occur between 8 and 12 days after birth. These are the detachment of the tectorial membrane, the first appearance of filaments within the basilar membrane, the formation of the tunnel of Corti and the opening of the inner spiral sulcus. Quantitative analysis revealed that structures of a given position along the cochlear duct do not develop synchronously. Width of the basilar membrane and cross-sectional area of the tectorial membrane are already mature at the onset of hearing (10-12 days after birth). Length, thickness and cross-sectional area of the basilar membrane as well as cross-sectional area of the organ of Corti and of the cells of Hensen, Claudius and Boettcher still develop after the onset of hearing (up to 20-24 days after birth). We suggest that basic cochlear function is established by structures which are mature before the onset of hearing. Cochlear structures which develop after the onset of hearing might be involved in this improvement during this period.

Animals↗
PubMed1994

A radial gradient of fibril density in the gerbil tectorial membrane.

The tectorial membrane plays a key role in the transduction of mechanical to neural energy in the inner ear. To better understand the transduction process the composition of the tectorial membrane needs to be elucidated. This study was done to determine if Type A collagen fibrils are distributed homogeneously in the tectorial membrane or if there are longitudinal or radial gradients of fibril concentrations. Our results suggest that while there is no longitudinal gradient, there is a radial gradient of fibril concentration. The concentration of fibrils in the limbal (inner) zone of the tectorial membrane exceeds that in the marginal (outer) zone in all cochlear locations examined. This gradient is most marked in the basal, high frequency coding region of the cochlea. While fibril gradients in the tectorial membrane have not been the focus of previous investigations, several findings by other authors support the proposition that the marginal zone of the tectorial membrane is more compliant than the limbal zone. This radial gradient of tectorial membrane stiffness is likely to contribute to the characteristics of movement of the cochlear partition.

Analysis of Variance↗
PubMed1993

[Biochemical profile of proteoglycans and glucosaminoglycans of the mammalian tectorial membrane].

The tectorial membrane is an acellular connective tissue which plays an essential role in cochlear function. While a comparatively large amount of information is available on the collagen network of the tectorial membrane, studies on the biochemical nature of this highly hydrated matrix, which is composed of proteoglycans (PGs) and glycosaminoglycans (GAGs), have been quite limited. Previous reports on the biochemical analysis of the tectorial membrane have failed to detect uronic acid, which is present in large amounts in all mammalian GAGs except keratan sulfate. Applying a colorimetric assay based on the binding of GAGs to cationic dye Safranin-0 in combination with enzymatic techniques, we were able to measure GAGs in the murine tectorial membrane. Approximately 0.3% uronic acid-containing GAGs (mainly in the form of chondroitin/dermatan sulfate) and 0.17% keratan sulfate were detected in the tectorial membrane (both on a wet weight basis). In addition, various types of electrophoresis revealed one large PG with a molecular mass similar to that of the large type cartilage PGs and three small PGs, containing chondroitin sulfate and keratan sulfate side chains, respectively. Judging by coelution of standards, one of the small PGs seemed to correspond to fibromodulin, which has at least one keratan sulfate side chain, and binds to type I and type II collagen to regulate collagen organization in tissues. Our results suggest: (1) Donnan equilibrium is established in the tectorial membrane because sulfated GAGs are highly negatively charged and consequently bring about an influx of large amounts of water and cations into the matrix.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Ultrastructural localization and semiquantitative analysis of glycoconjugates in the tectorial membrane.

The tectorial membrane of the gerbil cochlea was analyzed with lectin-gold cytochemical methods for demonstrating and characterizing glycoconjugates (GCs) in situ. Binding of lectins from Limax flavus (LFA), Lens culinaris (LCA), Datura stramonium (DSA), Ricinus communis (RCA I), Ulex europeus (UEA I) and Phaseolus vulgaris (PHA L) was assayed semiquantitatively on ultrathin sections. Binding occurred throughout the tectorial membrane with all lectins except UEA I but the labelling density with a given lectin differed among substructures. The cover net disclosed the highest level of GC with four lectins whereas the fibrous layer revealed the lowest level. DSA, LCA and PHA L demonstrated considerable similarity between the cover net and the marginal band in content of GC with N-linked oligosaccharide. The cover net differed from the marginal band, however, in containing more RCA I reactive GC with terminal lactosamine. Hensen's stripe, with which inner hair cell stereocilia are thought to interact, differed from other substructures in containing the highest level of PHA L-reactive traintennate N-linked chains and except for the basal layer the lowest concentration of GC with terminal lactosamine. Fucosylated GC detectable with UEA I-gold was present at low levels in all substructures except the cover net and marginal band. Distribution of GCs in the fibrous layer and less consistently in the cover net differed between limbal and middle zones. The differences observed here in the carbohydrate composition among substructures in the tectorial membrane support and extend previous cytochemical observations and imply a role for different classes of GCs in determining the biophysical and physiological properties of the tectorial membrane.

Animals↗
PubMed1980

Hereditary deafness in the cat: an electron-microscopic study of the tectorial membrane.

The tectorial membrane is affected at an early stage of the cochlear degeneration in the hereditarily deaf white cat. The membrane first descends towards the organ of Corti with obliteration of the intervening sub-tectorial space in the basal coil during the second post-natal week. Both the microvilli of supporting and Hensen's cells, and the hair cell stereocilia make deep indentations on the under-surface of the membrane. Cells are found insinuated between the tectorial membrane and Corti's organ, and numerous cellular processes occur within the former. A phagocytic function would appear probable for these cells, which seem to originate from the internal sulcus region. The membrane is retracted into the latter around the 2-month stage. At all ages, small spherical structures, which may represent altered interdental cell secretions, are found within the membrane, these becoming calcified in older animals.

Animals↗
PubMed1978

Ultrastructure of the different zones of the tectorial membrane.

The tectorial membrane (t.m.) of mammals, which lies over the organ of Corti, is made up of an agglomerate of protofibrils of varying degrees of hydration. Two types of protofibrils are clearly distinguishable in the mouse t.m. While type-A protofibrils are straight and unbranched (thickness: 110A) demonstrating a periodic structure (period = 70 A), type-B protofibrils are branched and coiled (thickness: 150-200 A). These protofibrils could be systematically ordered according to the different t.m. zones. Type-A protofibrils predominate in the basal layer and in the entire middle zone, where they are interlaced with strongly hydrated type-B protofibrils. Weakly hydrated type-B protofibrils essentially make up the marginal zone (with the marginal net), the covering net, Hensen's stripe and the immediate contact layer with the limbus.

Animals↗
PubMed1993

Glycerol effect on the guinea pig tectorial membrane.

The tectorial membrane (Tm) of guinea pigs has been found to have an altered organization of its matrix fibers in response to intravenously administered glycerol. Following treatment, the Tm middle zone shows an increase in waviness and clumping of fibers in non-hydropic and several hydropic ears in contrast to non-treated control ears. Residue of the internal sulcus cells occasionally fills the subtectorial space. In the present study, additional investigations were performed with scanning electron microscopy in order to study the relationship between the Tm and the organ of Corti, as well as the relationship between Hensen's stripe and the inner hair cell. Present findings provide evidence for a connection between the inner hair cell stereocilia and Hensen's stripe which may be the molecular basis for the modulation of hearing during the glycerol test in a patient with Meniere's disease.

Animals↗
PubMed1996

Crystalline arrays of proteoglycan and collagen in the tectorial membrane.

Ultrastucture of the tectorial membrane in the chinchilla cochlea was studied by transmission electron microscopy using different fixatives and staining procedures. It was shown that the tectorial membrane is a highly structured matrix composed of collagen type A fibrils, noncollagenous type B fibrils and proteoglycan. The localization of type B fibrils surrounding bundles of parallel type A fibrils was observed. Staining of the tectorial membranes with the cationic dye Cuprolinic blue in a "critical electrolyte concentration" method revealed proteoglycan, D-periodically associated with collagen type A fibrils and orthogonal to them. The appearance and size of the proteoglycan, and its binding to collagen, were similar to small proteoglycans observed in cartilage and other tissues. In many regions of the tectorial membrane the collagen-bound proteoglycan forms crystalline-like arrays. The images of these arrays processed by Fourier analysis show long linear aggregates of proteoglycan arranged parallel each other.

Alcian Blue↗
PubMed1995

Postnatal development of the mammalian tectorial membrane.

The various stages of tectorial membrane development were observed postnatally, using the scanning electron microscope. Hamster cochleas were obtained at 2-day intervals beginning with the day of birth and ending at 22 days after birth. Changes in the tectorial membrane structure were quantified by studying the transformation from a pattern of widely spaced fiber bundles to the continuous sheet-like membrane of the adult. Specifically, this transformation was quantified by summing the widths of the fiber bundles along a 25-micron traverse drawn parallel to the outer edge of the minor tectorial membrane, overlying the middle hair cell row. Such measures were performed at different locations along the cochlear spiral. The results indicate a base-to-apex progression of tectorial membrane development with attainment of mature characteristics between 18 and 22 days after birth. Comparison with previous studies indicate that the maturation of the tectorial membrane coincides with a period of major improvement in evoked potential thresholds in the central auditory system.

Adult↗
PubMed1985

Development of the embryonic chick's tectorial membrane.

The nascent tectorial membrane (TM) is identifiable as early as stage 33 (7th day) as thin, wispy material. By stage 37 (11th day), the dense mesh of the immature TM and fibrous webs (subtectorial threads) that attach the TM to the basilar papilla are distinct but scanty. The TM condenses slightly in its upper face. The growth of the columnar cells and basilar papilla during the following days pulls the TM, lifting it upward, and resembling the cables on a suspension bridge in cross-section. As a result, a large hollow wedge forms. During stages 40-44 (14th-18th days), the columnar cells secrete large amounts of fibrous material, which fills the hollow wedge and condenses into the dense meshes. The honeycombed patterns appear at this time. The supporting cells secrete the fibrous webs. Their secretory activity closely corresponds to that of the columnar cells. The secretory material from both cell types remains attached to the apical ends of their respective cells after secretory activity ends. By hatching (stage 46-21 days), the columnar cells have filled with fibrous material and their cytoplasmic organelles are restricted to the apices. The cytoplasm of supporting cells is relatively clear, with few cytoplasmic remnants of their intense secretory activity earlier.

Animals↗
PubMed1989

The surface morphology of the avian tectorial membrane.

The structure of the tectorial membrane of the chick was evaluated by scanning electron microscopy (SEM), using standard techniques, and, for the first time, by studying unfixed tectorial membranes with video-enhanced light microscopy techniques (AVEC-DIC). The SEM pictures show a widely varying morphology, ranging from a fully perforated tectorial membrane to a completely closed upper boundary, with a smooth surface. Based on several indicators, it is concluded that the latter presents the more natural state. This was confirmed by the results of the AVEC-DIC technique, which show a highly homogeneous structure. In contrast to the bulk of the tectorial membrane, its lower surface shows discrete structures, especially regularly oriented fibril bundles.

Animals↗
PubMed1989

Tectorial membrane. II: Stiffness measurements in vivo.

The tectorial membrane is assumed to play a crucial role in the stimulation of the cochlear hair cells and was thought for decades to serve as a stiff anchor for the tips of the hair-cell stereocilia, particularly those belonging to the OHCs. Yet, its stiffness has never been measured under conditions approximating its normal environment in live animals. We have developed a method for doing this. The tectorial membrane is approached through the lateral wall of scala media. The bony cochlear capsule is removed along scala media over somewhat less than 1/4 turn, and the underlying spiral ligament and stria vascularis are carefully reflected. With the help of a three axial hydraulic manipulator, a flexible micropipette filled with isotonic KCl is inserted into the tectorial membrane at one of two different angles and moved either transversally, away from the basilar membrane, or radially, toward or away from the modiolus. This causes the tectorial membrane to be deformed and the micropipette to bend. The micropipette stiffness is calibrated on an instrument of a new kind, so as to convert the bend into force. The calibration allows us to determine the point stiffness of the tectorial membrane from the amount of micropipette bend. The stiffness of the tectorial membrane per unit length has been calculated from the point stiffness with the help of the deformation pattern. Transversal and radial stiffness magnitudes have been determined in the second cochlear turn in Mongolian gerbils. Both are smaller by almost an order of magnitude than the corresponding aggregate stiffness of the OHC stereocilia. As a consequence, the tectorial membrane cannot act as a stiff anchor for the stereocilia but only as a mass load, except at relatively low sound frequencies where mass effects are negligible. This means that the classical model of shear motion between the tectorial membrane and the reticular lamina must be replaced.

Animals↗
PubMed1992

The protein composition of the avian tectorial membrane.

Gel electrophoretic analysis of the avian tectorial membrane under non-reducing conditions reveals the presence of 2 major proteins with apparent molecular masses of 195 and 41 kDa on 8.25% gels. Under reducing conditions, 6 polypeptides with apparent molecular masses of 146, 60, 56, 43, 35 and 31 kDa are consistently observed. None of these six polypeptides observed under reducing conditions are sensitive to digestion with collagenase, and all, except for the 43 kDa component, are degraded by treatment with cold acidic pepsin. The 60, 56 and 43 kDa polypeptides bind the peroxidase conjugated lectins from Canavalia ensiformis and Triticum vulgaris, indicating the presence of mannose, N-acetyl glucosamine and/or sialic acid. The 146, 60 and 56 kDa bands undergo a shift in electrophoretic mobility after treatment of native tectorial membranes with the enzyme neuroaminidase. Fibronectin and Type II collagen cannot be detected in the avian tectorial membrane by either immunoblotting or immunofluorescence techniques. Polyclonal antisera raised against the different polypeptides after partial purification by one dimensional gel electrophoresis confirm that these proteins are all components of the tectorial membrane, and show that they are restricted to the otolithic and tectorial membranes within the inner ear. Analysis of a wide variety of other tissue types indicates that the 60, 43 and 35 kDa components can only be detected within the inner ear, and that the antisera recognising the 146 and 31 kDa components only show cross-reactivity within the head, with the anti-146 kDa antibodies staining the mucus ducts supplying the olfactory epithelium and the anti-31 kDa antibodies staining granular elements in the cells of the respiratory epithelium. The results suggest that certain of the tectorial membrane components may be novel matrix molecules unique to the inner ear, and that some of the other proteins may be antigenically related to mucins.

Animals↗
PubMedDate not supplied

Structure of the avian tectorial membrane.

The avian tectorial membrane is a thick massive-appearing structure permeated by cavities, which probably facilitate the diffusion of endolymph. As revealed by scanning and transmission electron microscopy, the cavities are arranged in a characteristic honeycomb-like pattern and each hair bundle is enclosed in an alveolus. The open ends of the alveoli show the impressions of sensory hairs on one side. The rims about the cavities are attached to the microvilli of the supporting cells by means of fibrous material. These morphological aspects are compared with those reptiles and mammals, and the functional significance of the fibrillar anchors is discussed.

Animals↗
PubMed1996

Resonant tectorial membrane motion in the inner ear: its crucial role in frequency tuning.

The tectorial membrane has long been postulated as playing a role in the exquisite sensitivity of the cochlea. In particular, it has been proposed that the tectorial membrane provides a second resonant system, in addition to that of the basilar membrane, which contributes to the amplification of the motion of the cochlear partition. Until now, technical difficulties had prevented vibration measurements of the tectorial membrane and, therefore, precluded direct evidence of a mechanical resonance. In the study reported here, the vibration of the tectorial membrane was measured in two orthogonal directions by using a novel method of combining laser interferometry with a photodiode technique. It is shown experimentally that the motion of the tectorial membrane is resonant at a frequency of 0.5 octave (oct) below the resonant frequency of the basilar membrane and polarized parallel to the reticular lamina. It is concluded that the resonant motion of the tectorial membrane is due to a parallel resonance between the mass of the tectorial membrane and the compliance of the stereocilia of the outer hair cells. Moreover, in combination with the contractile force of outer hair cells, it is proposed that inertial motion of the tectorial membrane provides the necessary conditions to allow positive feedback of mechanical energy into the cochlear partition, thereby amplifying and tuning the cochlear response.

Animals↗
PubMed1987

Regeneration of the tectorial membrane in the chick cochlea following severe acoustic trauma.

Damage to the tectorial membrane caused by acoustic trauma was examined with scanning and transmission electron microscopy immediately after exposure and at selected time points over a 10 day recovery period. At 0 h of recovery the structure of the tectorial membrane overlying the region of hair cell damage was severely disrupted and connections between the membrane and the basilar papilla were lost. By 24 h of recovery, regeneration of the tectorial membrane was evident in the secretion of new matrix materials by the supporting cells of the basilar papilla. By 10 days of recovery a new honeycomb-like matrix had replaced the segment of damaged tectorial membrane, re-established connections with hair cell stereocilia and become fused with adjacent regions of undamaged tectorial membrane. However, the regenerated segment included only the honeycomb-like structure of the lower layer of the normal tectorial membrane. The laterally-oriented fibers which form the upper layer of the membrane were not regenerated over the damaged region. These findings indicate that the tectorial membrane is regenerated in parallel with the hair cells during recovery from acoustic trauma but the full extent of this recovery and its effect on cochlear function are not yet clear.

Animals↗
PubMed1993

Uronic acid-containing glycosaminoglycans and keratan sulfate are present in the tectorial membrane of the inner ear: functional implications.

The tectorial membrane is a gel-like, acellular connective tissue overlying the microscopic organ of Corti--the auditory sensory structure. It is instrumental in the sound-synchronous deflection of the stereocilia of the hair cells, a central event in auditory transduction. It is well established that collagen, primarily type II, constitutes the major protein of the tectorial membrane, with smaller amounts of types IX and XI also present. However, conclusive information on the proteoglycans in this structure is lacking. Tectorial membranes were extracted with a 4 M guanidine--HCl solvent, and proteoglycans isolated after ethanol precipitation and collagenase treatment. A colorimetric assay based on the binding of the cationic dye safranin O to glycosaminoglycans, in combination with enzymatic techniques, detected significant amounts of chondroitin sulfate and keratan sulfate (0.29 and 0.17% on a wet weight basis, respectively). Agarose-polyacrylamide electrophoresis of chondroitinase-digested samples revealed a core protein with a similar molecular mass to that of the large cartilage proteoglycan aggrecan. This proteoglycan reacted with the antibody 3-B-3 (recognizing modified chondroitin 6-sulfate linkage region oligosaccharides). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed several low molecular mass proteins which reacted with 5-D-4, specific for keratan sulfate, one of which showed characteristics of fibromodulin. Comparison of the quantitative aspects of various connective tissue components of tectorial membrane with other type II collagen-containing structures revealed that this tissue resembles highly hydrated cartilage.

Animals↗