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PubMed1980

Apical lesions of the cochlea in idiopathic endolymphatic hydrops and other disorders: pathophysiological implications.

Apical lesions of the cochlea may be caused by direct trauma, impairment of blood supply, contamination of perilymphatic fluid and endolymphatic hydrops. It is proposed that endolymphatic hydrops causes apical lesions when endolymph or its components leak into the perilymphatic fluid and pass through the helicotrema to degrade the tissue fluid environment of the sensory and neural structures in this area.

Aged↗
PubMed1986

Alfonso Corti (1822-1876)--discoverer of the sensory end organ of hearing in Würzburg.

Alfonso Corti was born at Gambarana in Lombardy. As a medical student he enrolled first at the University of Pavia, later at the University of Vienna. There he received his degree in medicine. In the years 1850/51, in the laboratory of Albert von Kölliker at the University of Würzburg, he described for the first time the sensory epithelium, the spiral ganglion, the tectorial membrane, and the stria vascularis of the inner ear.

Cochlea↗
PubMedDate not supplied

Movement of monovalent ions across the membranes of marginal cells of the stria vascularis in the guinea pig cochlea.

The resting potential and monovalent ions in the marginal cells and scala media were measured before and 20 min after the onset of anoxia using ion-sensitive microelectrodes. The resting potential of the marginal cells decreased from 62.7 to -2.4 mV. The K+ activity decreased from 77.7 to 53.2 mEq/l, while the Na+ activity increased from 2.6 to 24.7 mEq/l. The Cl- activity did not change significantly. In the scala media, the endocochlear potential decreased rapidly from 80.9 to -28.0 mV after the onset of anoxia. The K+ activity decreased from 119.0 to 96.5 mEq/l, the Na+ activity increased from 1.3 to 9.5 mEq/l and that of Cl- decreased from 127.0 to 115.1 mEq/l. The electrochemical gradients determined for each ion based on the ionic changes in the scala media and marginal cells, suggested the existence of an Na/K pump and Na-K-2Cl cotransport at the basolateral membrane of the marginal cells, and a rheogenic K pump and Na-K-2Cl transport at the luminal membrane of the marginal cells. The Na+ and K+ must be recycled at the basolateral membrane and luminal membrane of marginal cells, respectively.

Animals↗
PubMedDate not supplied

Human Reissner's membrane in patients with age-related normal hearing and with sensorineural hearing loss.

Morphological features of Reissner's membrane were investigated in 6 patients with age-related normal hearing (ARNH) and in 4 with sensorineural hearing loss (SNHL) stemming from various causes. The membrane consisted of an epithelium, a basement membrane and a mesothelium with melanocytes. There were two major forms of epithelial cells: flat and rounded. In all specimens, the rounded cells formed whorls, clusters, strands and bands. The bands were wider and the whorls larger in the basal turn and decreased gradually in size toward the apex. The number of melanocytes was 2-4 times higher in both the upper half of the basal turn and the lower half of the middle turn than in the rest of the turns. In specimens from patients with SNHL, whorls and clusters were both more numerous and larger, and the number of melanocytes was higher in the upper half of the middle turn and in the apical turn than that in the ARNH group. Ultrastructural examination of epithelial and mesothelial cells as well as of melanocytes showed more pronounced cellular degeneration in patients with SNHL than in those with ARNH. A possible correlation between structural alterations of Reissner's membrane and sensorineural degeneration is discussed.

Aged↗
PubMedDate not supplied

Distribution of hyaluronan in the middle and inner ear. A light microscopical study in the rat using a hyaluronan-binding protein as a specific probe.

The histochemical distribution of hyaluronan (hyaluronic acid, HYA) was analyzed in middle and inner ear tissues from rats by use of microwave-aided fixation, a hyaluronan-binding protein and the avidin-biotin/peroxidase staining procedure. In the middle ear HYA was mainly localized in the pars flaccida, the ossicles, the round window membrane and in the endomysium of the middle ear muscles. The subepithelial stroma of the Eustachian tube was strongly HYA-positive. In the inner ear, the spiral ligament of the cochlea and the connective tissue surrounding the nerve fibers emerging from the crista ampullaris stained intensely for HYA. Except for a weak staining of the basilar membrane, the Corti organ was devoid of HYA. The heterogenous distribution of HYA may indicate its specific involvement in middle and inner ear physiology and pathology.

Animals↗
PubMedDate not supplied

Microtubule-associated proteins in adult human sensory organs.

The distribution of microtubule-associated proteins MAP-1 and MAP-2 was analysed with immunomorphological techniques in the serially sectioned adult human membranous labyrinth. In the organ of Corti, monoclonal antibodies to MAP-1 did not stain. Positivity for MAP-2 occurred in the entire outer hair cell cytoplasm, in the inner hair cells (?), in the nerve fibres and in the cytoplasm of epithelial cells of the spiral prominence. In addition, staining for MAP-2 was identified in many (but not all) cells or Reissner's membrane. Immunofluorescence for MAP-1 occurred in the supporting cells of the cristae and maculae interpreted to be localized in the apical region adjacent to the sensory cells. Thus, the distribution of MAP-1 and MAP-2 in the adult human membranous labyrinth was the same as described for several animal species with regard to the cochlea. In contrast to such a pattern, both MAP-1 and MAP-2 were identified in the human vestibular organs, thus identifying a subpopulation of centrally located nerve calyces and possibly also the apical portion of vestibular hair cells.

Acoustic Maculae↗
PubMedDate not supplied

Hyaluronic acid as a molecular filter and friction-reducing lubricant in the human inner ear.

Immunofluorescence for hyaluronic acid occurred intracellularly in morphologically highly specialized areas in the adult human inner ear, for instance in the cuticular plates of all types of hair cells, at the apposition between outer hair cells and Deiter's cell bodies and in the near-surface area of Hensen's cells. The cytoskeletal organization in these regions is characterized by tightly packed filamentous proteins. Under physiological stimulus these regions undergo micromechanical change, either actively moving (force generation) or passively vibrating with changes in elasticity. Hyaluronic acid might therefore act as a friction-reducing molecular lubricant. In the lateral wall of the cochlea an accumulation of hyaluronic acid occurred in the loose connective tissue of the spiral ligament, in particular close to the stria vascularis. Due to its complex molecular network, hyaluronic acid offers considerable resistance to bulk flow of water and may exclude molecules. The basal cell region of the stria vascularis is thus given additional support to minimize (seal?) the stria vascularis towards all other areas except the endolymphatic space. Here, hyaluronic acid could act as a molecular filter.

Adolescent↗
PubMedDate not supplied

Calbindin-D28K localization in the primate inner ear.

The distribution of one of the calcium-binding proteins, calbindin-D28K (CB-D28K), was studied in the adult human and squirrel monkey inner ear by means of immunocytochemical methods. Inner and outer hair cells in the organ of Corti and vestibular hair cells showed CB-D28K immunoreactivity, though some vestibular hair cells were devoid of immunoreactivity. In the spiral and vestibular ganglion, immunoreactive cells were found in both the squirrel monkey and human. The present results indicate that CB-D28K is localized within afferent neuronal components in these sensory organs and may regulate Ca++ levels for optimal neurotransmission in the primate auditory and vestibular systems. This study also provides evidence of two nonneuronal localizations of CB-D28K in the squirrel monkey. Subpopulations of fibrocytes in the spiral ligament and vestibular end organs were enriched with CB-D28K, suggesting that these cells are possibly equipped with the function to regulate Ca++ concentration in the perilymphatic fluid. In the maculae, many CB-D28K-immunoreactive particles were found in the otoconial membrane, indicating that CB-D28K may participate in the formation of otoconia.

Adolescent↗
PubMedDate not supplied

Effects of hypercapnia on cochlear and cerebral blood flow in rabbits.

Cochlear blood flow (CoBF) and cerebral blood flow (CBF) were measured using laser Doppler flowmetry and the microsphere method during CO2 and O2 gas mixture inhalation in rabbits. Both methods revealed that CBF was increased by CO2 inhalation. CoBF measured by laser Doppler measurement decreased during CO2 inhalation while that measured by the microsphere method showed a slight increase, but lateral wall blood flow in the cochlea measured by the microsphere method showed no significant change. Our results obtained with laser Doppler flowmetry were not inconsistent with those reported in humans. It is considered that the rabbit, in which thick bone surrounds the cochlea, is a good model for the experimental evaluation of the laser Doppler technique used in the clinical measurement of CoBF.

Administration, Inhalation↗
PubMed2001

Changes in permeability of strial vessels following vibration given to auditory ossicle by drill.

We produced drill-induced damage of the auditory ossicles of guinea pigs to study changes over time in the permeability of the blood vessels of the stria vascularis to horseradish peroxidase (HRP). In group A, the stimulus was applied for 10 seconds after intravenous injection of HRP. In group B, it was applied for 30 seconds, and in group C, for 60 seconds. The cochlea was fixed with 2% glutaraldehyde perfused through the round window, and the guinea pigs were then decapitated. The stria vascularis of the basal and third turns was examined. The leakage of HRP from the blood vessels of the stria vascularis significantly increased in relation to the duration of the stimulus in both the basal and third turns. The damage to intermediate cells also tended to be in relation to the duration of the stimulus. Extravascular permeation of HRP took place through the tubules in the endothelial cytoplasm. The vibratory stimulation presumably opened channels that are not normally open.

Animals↗
PubMedDate not supplied

Total energy and critical intensity concepts in noise damage.

Groups of chinchillas were given a series of noise exposures of approximately equal energy ranging from 22 minutes at 120 dB SPL to 150 days at 82 dB. For all exposures involving levels of 112 dB or less, the same average permanent hearing losses (15-20 dB) and degree of outer hair cell destruction (8-10%) resulted, thus confirming the validity of the total energy principle for assessing the hazard associated with single continuous exposures at moderate levels. The 22-minute, 120-dB exposure, however, produced a 60-dB hearing loss and massive hair cell destruction (70-80%), indicating that some critical level had been exceeded, thus producing acoustic trauma. Further histological study suggests that the massive destruction is a result of breaks in the organ of Corti, produced by severe mechanical stress, that permit the mixture of endolymph with perilymph, thus creating a hostile environment for the hair cells.

Animals↗
PubMed1990

Lermoyez's syndrome: histopathologic report of a case.

This paper reports findings in a pair of temporal bones from a patient with clinical evidence of Lermoyez's syndrome, a rare variant of Meniere's disease. Endolymphatic hydrops is limited to the basal turn of the cochlea and saccule in Lermoyez's syndrome, but more generalized in Meniere's disease.

Cochlear Duct↗
PubMed1990

Delayed endolymphatic hydrops and its relationship to Meniére's disease.

Delayed endolymphatic hydrops (EH) can be characterized as having ipsilateral and contralateral types. They are similar in that both have early and late phases of otologic symptoms and that the early phase is a profound hearing loss in one ear. The late phases differ, however, in that the ipsilateral type develops the symptoms of EH (episodic vertigo) in the deaf ear and the contralateral type develops the symptoms of EH (fluctuating hearing loss and/or episodic vertigo) in the hearing ear. In more than half the cases of both types of delayed EH, the profound hearing losses in the early phase are simply discovered to be present in early childhood without a known time of onset. The temporal bones of two patients with contralateral delayed EH show pathologic changes in the deaf ears that are similar to those known to occur in mumps and measles labyrinthitis, whereas the pathologic changes in the hearing ears are similar to those known to occur in Meniere's disease. These observations support the proposition that Meniere's disease may occur as a delayed sequela of inner ear damage sustained during an attack of subclinical viral labyrinthitis occurring in childhood.

Adolescent↗
PubMed1995

Comparison of endolymph cross-sectional area measured histologically with that measured in vivo with an ionic volume marker.

In order to establish how endolymph volume is regulated, it is essential to be able to measure endolymph volume or cross-sectional area in vivo. We have developed methods to accomplish this by injecting the volume marker ion hexafluoroarsenate (AsF6) into endolymph by iontophoresis. For an injection at a constant rate, the endolymph concentration is inversely dependent on the cross-sectional area of the scala into which injection occurred. Marker concentrations were monitored by inserting ion-selective microelectrodes into endolymph near the injection site. In a previous study we quantified the degree of hydrops in animals following ablation of the endolymphatic sac. In the present study we validated the technique by comparing the endolymphatic cross-sectional area measured in vivo with AsF6 with that measured by established histologic procedures. The correlation between the two measures was good, with a coefficient of .903, although the area measured histologically was a little lower than that measured in vivo.

Animals↗
PubMedDate not supplied

Experimental study on Meniere's disease.

Experimental hydrops caused by underabsorption of endolymphatic fluid is a model of remissional stage of Meniere's disease. In this study, another type of model, ie, hydrops caused by overproduction of endolymphatic fluid, was accomplished by applying various pressures into scala media through a micropipette via stria vascularis. This type of hydrops could be a model of attacks of Meniere's disease. By using two types of the model, effects of glycerol administration and of opening the endolymphatic sac were discussed.

Animals↗
PubMed1998

Axial specification for sensory organs versus non-sensory structures of the chicken inner ear.

A mature inner ear is a complex labyrinth containing multiple sensory organs and nonsensory structures in a fixed configuration. Any perturbation in the structure of the labyrinth will undoubtedly lead to functional deficits. Therefore, it is important to understand molecularly how and when the position of each inner ear component is determined during development. To address this issue, each axis of the otocyst (embryonic day 2.5, E2.5, stage 16-17) was changed systematically at an age when axial information of the inner ear is predicted to be fixed based on gene expression patterns. Transplanted inner ears were analyzed at E4.5 for gene expression of BMP4 (bone morphogenetic protein), SOHo-1 (sensory organ homeobox-1), Otx1 (cognate of Drosophila orthodenticle gene), p75NGFR (nerve growth factor receptor) and Msx1 (muscle segment homeobox), or at E9 for their gross anatomy and sensory organ formation. Our results showed that axial specification in the chick inner ear occurs later than expected and patterning of sensory organs in the inner ear was first specified along the anterior/posterior (A/P) axis, followed by the dorsal/ventral (D/V) axis. Whereas the A/P axis of the sensory organs was fixed at the time of transplantation, the A/P axis for most non-sensory structures was not and was able to be re-specified according to the new axial information from the host. The D/V axis for the inner ear was not fixed at the time of transplantation. The asynchronous specification of the A/P and D/V axes of the chick inner ear suggests that sensory organ formation is a multi-step phenomenon, rather than a single inductive event.

Animals↗