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PubMedDate not supplied

Glycogen in the cochlea during development.

A recently developed technique for demonstrating glycogen by electron microscopy was used to study its location at various stages of cochlear development. It appears first in dispersed form in most of the cells of the otocyst at the stage of the 14-day rat embryo. Glycogen clums were found in Reissner's membrane at 17 days and in the future pillar cells shortly afterwards. Near the time of birth, glycogen appeared in the stria vascularis. By a few days after birth, heavy deposits were evident in the stria but glycogen had faded from the pillar cells and Reissner's membrane. Ten days after birth glycogen is no longer apparent in any of the cells of the cochlear duct except the outer hair cells.

Amylases↗
PubMedDate not supplied

A note on development of Corti's organ.

The structure and postnatal transformation of Kölliker's organ in the cat were studied by means of both light and electron microscopes. Kölliker's organ, which is located in the inner sulcus area of the cochlear duct during embryonic development of the kitten, appeared to undergo a major transformation during the first 30 days after birth. On the level of the organ as a whole the possible nature of this transformation is briefly discussed. On the cellular level, the transformation of this organ was found to involve a process of cellular autophagocytosis. Kölliker's organ consists of numerous tightly packed, tall columnar cells filling the inner sulcus. Autophagic vacuoles containing cell organelles were observed in these cells in all stages of transformation of the organ. Cellular autophagocytosis reduced the number of cells present in each section from approximately 50 in the newborn, to approximately 12 in the 30-day-old kitten. The apparent transformation of Kölliker's organ was observed as progressing from base to apex and from the limbus to the inner hair cell. The relationship of the tectorial membrane to Kölliker's organ and that of the tectorial membrane to the area in and around the inner hair cells are discussed.

Animals↗
PubMedDate not supplied

Effects of exposure to noise on permeability to potassium of the endolymph-perilymph barrier in guinea pigs.

Healthy guinea pigs were exposed to broadband noise at 115 dBA for 7 days. When perfusion of the scala vestibuli was carried with artificial perilymph containing 43K, the 43K concentrations in the perilymph of the scala tympani were very low in both control and noise-exposed guinea pigs. The transport rate constant for K+ was computed by utilizing compartmental analysis. The results indicate that exposure to noise at 115 dBA for 7 days does not alter the permeability to K+ of Reissner's membrane or the lateral wall of the cochlear duct but does decrease K+ conductance of the organ of Corti.

Action Potentials↗
PubMed1984

Pathogenesis of Meniere's disease and Meniere's syndrome.

Meniere's disease can only be studied in patients, since it does not occur spontaneously in animals nor can it be induced in them. However, aspects of the disease such as endolymphatic hydrops can be usefully studied in animals. A study of the natural history (epidemiology) of Meniere's disease demonstrated the three major symptoms (triad) to be vestibular symptoms, auditory symptoms, and aural pressure. Bilaterality occurs in at least one out of 3 patients, and may approach 50% over full lifespans. Aural pressure (74.1%) was common, as was positional vertigo (85.9%) during and/or between attacks. Clinical variants such as vestibular Meniere's disease could persist for 25 years or more. Understanding the pathogenesis of Meniere's requires a study of known and unknown causes. In this study, Meniere's disease (cause unknown) was differentiated from Meniere's syndrome (cause known). Meniere's disease or syndrome can occur years after some inciting cause; thus all forms of Meniere's can be considered to have a delayed onset. Meniere's syndrome can occur as a sequel to syphilis, otosclerosis, infection (for example otitis media), or trauma. Endolymphatic hydrops explained on the basis of quantity and quality of endolymph is found in all forms of Meniere's disease and syndrome. Representative cases and pathological examples are discussed. Hydrops of the pars inferior (cochlear duct and saccule) is the most important finding in Meniere's disease. In some (but not most) cases, ruptures of the membranes are seen. The saccule can distend into the lateral semicircular canal. Symptomatic attacks are explained on the basis of both physical and biochemical phenomena. This study discusses concepts of pathogenesis of the disease, finding both theories of longitudinal (slow) and radial (fast) flow to be operational. Longitudinal flow, however, appears to be more important than radial flow, especially in advanced Meniere's where perilymph in the scala vestibuli and vestibule disappears and is replaced by membranous labyrinth. Meniere's disease (idiopathic) and Meniere's syndrome (cause known) probably occur as a result of endolymphatic absorptive dysfunction (the site being endolymphatic duct and sac). Hypocellularity of the mastoid and periaqueductal air cells, hypodevelopment of Trautmann's triangle, and anterior displacement of the lateral sinus are likely to be important findings associated with developmentally dysfunctional absorption of endolymph.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1989

An electron microscopic study of the function of the root cells in the external spiral sulcus of the cochlea.

The ultrastructure of the area of the external spiral sulcus of the cochlea was studied in 15 hamsters. Intravital fixation with glutaraldehyde was followed by osmium citrate fixation and embedding in araldite. The endolymphatic surface of the external spiral sulcus is nearly completely covered by Claudius cells under which the root cells are situated. These epithelial cells are composed of bundles (roots), which protrude into the connective tissue of the spiral ligament in a tree-like fashion, forming primary, secondary, and tertiary branches. The basement membrane is a reliable landmark in this complex region, serving as a differentiating zone between the root cells and the mesenchymal tissue. Two different types of root cells are found. There are organelle rich "dark" cells and "light" cells which contain only a few cell organelles. All types of transitional forms between these two cell types are found, which can be interpreted as an expression of different metabolic activity of the same cell type. Between the root cells are seen extracellular clefts into which the "dark" cells, with their high synthetic and secretory activity, expel their secretions. These clefts lead to the endolymphatic space. A continuous production and secretion of part of the endolymph by the root cells is very likely. The anchoring of fibrils at the basement membrane of the root cell bundles, and their continuity with the basilar membrane leads to the assumption that this whole system may act as a mechanical pump. At high sound pressure levels, the strong vibration of the basilar membrane may lead to a locally and temporarily enhanced secretion of substances from the root cells into the cochlear duct.

Animals↗
PubMedDate not supplied

Hensen's cell cyst of the organ of Corti.

The temporal bone collection at the Massachusetts Eye and Ear Infirmary contains the bones of two subjects with bilaterally symmetrical cyst formations in the Hensen's cell areas of the organs of Corti. In both subjects the cysts are located in the 8-14-mm regions of the cochlear ducts. Both cochleas of one subject show pressure atrophy of the outer hair cells, demonstrating that the cysts may have the potential for producing high-tone hearing loss. While the genesis and contents of the cysts are unknown, it is postulated that they may represent the coalescence of lipid droplets extruded from Hensen's cells.

Aged↗
PubMedDate not supplied

Electrocochleography in an experimental animal model of acute endolymphatic hydrops.

A reliable animal model of acute type of endolymphatic hydrops was made with injection of artificial endolymph into the cochlear duct. In 12 animals without Reissner's membrane rupture, the endolymphatic potentials (EP) were kept normal after injection of artificial endolymph, but their electrocochleography (ECoG) showed as: a rise of summating potentials (SP) amplitude, a decrease of action potentials (AP) amplitude, an increase of SP/AP ratio, as well as a delay of N1 latency. In 7 animals with membrane rupture, the EP significantly decreased. ECoG showed as: a decrease of hearing function in all test frequencies, a distortion of SP-AP wave and even a loss of AP. Based on the results of our experiment it can be assumed that the dominant -SP may be seen in the acute stage of endolymphatic hydrops without a rupture of Reissner's membrane. Therefore, the dominant -SP may only be of value in the clinical diagnosis during episodic vertigo and fluctuating hearing loss of Meniere's disease.

Action Potentials↗
PubMedDate not supplied

Modulation of the rat stria vascularis in the absence of circulating adrenocorticosteroids.

Structural changes in the cellular morphology of the rat stria vascularis from a standardized region of the basal region and from a standardized region in the apical region of the rat cochlear duct were measured using stereological methods after removal of endogenous levels of adrenal steroids by bilateral adrenalectomy. Although there were some inconsistent and insignificant alterations in the volume density of intermediate and basal cells, a decreased volume density of marginal cells in both the basal region and in the apical region in adrenalectomized (ADX) animals as compared to sham animals was consistent with a concomitant significant increased (p less than or equal to 0.05) volume density of intercellular space as observed in both the basal and apical regions of the stria vascularis of ADX animals. Findings of this study indicate that the strial cells of the stria vascularis react differently and independently in response to the removal of adrenal steroids, and such strial responses occur uniform in both the base and apex.

Adrenal Cortex Hormones↗
PubMed1993

Differential physiologic effects of perfusion of scala tympani versus scala vestibuli in the ischemic cochlea.

The effectiveness of perilymphatic perfusion with oxygenated artificial media upon the endocochlear potential (EP) was measured during systemic ischemia in the guinea pig. Differences in the effects of perfusion of the two perilymphatic scalae were determined. Perfusion of scala vestibuli with oxygenated artificial perilymph at a high flow rate resulted in complete recovery of the EP to the pre-ischemic level, whereas perfusion of scala tympani with the same medium was unable to effect complete recovery. The recovery obtained by perfusion of scala tympani was about half that obtained of scala vestibuli. The pO2 in scala media was measured during perfusion by means of oxygen-sensitive microelectrodes. perfusion of scala vestibuli led to an approximately two-fold higher pO2 in scala media than perfusion of scala tympani. During perfusion, the pO2 in scala media varied dependent upon depth of electrode insertion, with a gradient decreasing toward the stria vascularis, a direction opposite to that seen under normal metabolic conditions. These findings suggest that, in the ischemic cochlea, oxygen enters scala media more easily from scala vestibuli across Reissner's membrane than from scala tympani via the basilar membrane/organ of Corti complex.

Animals↗
PubMed1994

Strial dysfunction in a melanocyte deficient mutant rat (Ws/Ws rat).

A homozygous mutant rat at the white spotting (Ws) locus showing a deficiency of melanocytes has recently been found (4, 5). The function and morphology of the inner ear of the Ws/Ws rat were examined by auditory brainstem response (ABR), endocochlear DC potential (EP), and electron microscopy. The mean ABR threshold of the Ws/Ws rat was significantly higher than that of the control +/+ rat. Most Ws/Ws rats showed no or very little EP. In electron microscopy, the stria vascularis of the Ws/Ws rat proved to be very thin and flat with poor interdigitation of marginal cells, and absence of intermediate cells. The organ of Corti appeared to be intact in both the +/+ rat and the Ws/Ws rat. These electrophysiological and morphological findings suggest that the Ws/Ws rat suffered from severe hearing loss caused by strial dysfunction.

Acoustic Stimulation↗
PubMed1994

Effects of combined rupture of Reissner's membrane and the round window on hearing in the guinea pig.

Hearing impairment caused by sequential rupture of Reissner's membrane and the round window was investigated in guinea pigs to determine if the double-membrane break can cause acute profound sensorineural hearing loss. Reissner's membrane was lacerated through the stria vascularis at one of the turns of the cochlea, followed by rupture of the round window to create leakage of the perilymph. Action potentials (APs) to tone pip stimuli were recorded from the Fallopian canal electrode before and 90 min after these procedures. The results showed that the ears with the double-membrane break at the second turn showed a larger increase in AP threshold than did the control ears with only round window rupture. However, this was not seen when Reissner's membrane had been ruptured at the other turns.

Acoustic Stimulation↗
PubMed1996

Appearance of glucocorticoid receptors in the inner ear of the mouse during development.

CBA mice were sacrificed at different ages of developments at embryonic day 13 (E13), E14, E16, E19, E20 and postnatal day 1 (P1), P2, P3, P4, P6, P8, P10, P14, P16, P18, P20 and P30. The temporal bones were quickly removed and deep frozen in order to prepare cryosections for immunohistochemical staining with polyclonal antibodies against glucocorticoid receptors. The avidin-biotin, ABC-method was used to visualize binding. Both the vestibular and the cochlear regions of the inner ear were analysed. A faint staining of the crista ampullaris, the utricle and the cochlear duct was seen at E19; and staining became clearly visible at P1. A decrease in labelling was found at day 2-5 post partum whereafter an increased staining was again noticed until postnatal day 14 when an adult pattern was observed. The appearance of glucocorticoid receptors in the inner ear during development does not follow a linear curve. Further, the labelling pattern may indicate an impact of glucocorticoid receptors on the embryologic maturation itself as well as a functional role in the adult ear.

Animals↗
PubMed1989

Diode pump cochlear audition theory three dimensional model.

A three dimensional model of the cochlea is developed that pumps activated fluid through the tectorial gap of the organ of Corti. The activated fluid generates neural pulses at specific locations along the cochlear duct which are related to specific simple tonal inputs. A computer program, based on an electrical analog of the model, calculates matrices of the transfer factors for section elements in the model and for a range of sound input frequencies. Using these matrices, the program calculates the neural output for a variety of complex sound inputs into the model and compares the calculated output to experimental measurements on actual cochlea. Differences and similarities between the audition model and a proposed vision model are discussed.

Auditory Pathways↗
PubMed1993

Sudden onset deafness as a presenting manifestation of chronic lymphocytic leukemia.

An unusual patient with typical Rai Stage 2 (Binet Stage A) chronic lymphocytic leukaemia (CLL), who presented with sudden onset deafness as the initial manifestation of disease is reported. This sensorineural hearing loss improved dramatically after the administration of chemotherapy. This unique observation was also associated with reduction of the circulating B-CLL cells and with the achievement of a partial response, lasting for almost three years. Recently there was another episode of sudden deafness, associated with a rising leukocyte count, and disease activity followed once again by recovery after chemotherapy. Audiograms were recorded showing positive findings on presentation and recovery after therapy. This very rare manifestation of CLL was presumed to be due to infiltration of the cochlear duct or the 8th cranial nerve although all imaging techniques were negative, because of the rapid relief and recovery achieved after specific chemotherapy. The importance of early diagnosis and therapy is stressed in the light of the rapid clinical recovery observed here.

Adult↗
PubMed2001

Inherited connexin mutations associated with hearing loss.

One of the most dramatic discoveries in the field of hereditary hearing loss is the association of this sensory defect with connexin mutations. Most significant is the large proportion, 30-50%, of inherited hearing loss that is due to mutations in connexin 26. The proteins these genes encode are expressed in the cochlear duct, in regions containing gap junctions. Together, these findings suggest a crucial role for gap junction proteins in the mammalian inner ear. Mouse models with specific connexin mutations leading to deafness will help resolve the many questions regarding the role of these gap junction proteins in the inner ear.

Animals↗
PubMed1976

[Causal therapy for diseases of the inner ear? (author's transl)].

The examples of sudden deafness and Meniere's Disease are used to discuss the possibilities of causal therapy for inner ear dysfunctions. In sudden deafness, etiological and therapeutic considerations are focused on the problem of disorders of the arterial and venous microcirculation, contributing to oxygen deprivation of the organ of Corti. Disruption of the arterial microcirculation leads to irreversible damage of the sensory organ within minutes and non-responsiveness to therapy, whereas even serious venous circulation disturbances can be treated successfully within days after onset of the acute disease. While knowledge of pathological changes in sudden deafness is still limited, temporal bone studies in Meniere's disease provides important information on its pathogenesis. Many authors have described enlargement of the cochlear duct as evidence for endolymphatic hydrops. Maximum enlargement of the endolymphatic system disrupts the membrane system which separates endo- from perolymph, and can be confirmed by histologic examination. This indicates that a change of the ionic concentration in the inner ear fluids is responsible for inner ear dysfunction. Thus, the acute Meniere attack can be explained as a consequence of the "burst hydrops." Because of the still unknown etiology of hydrops, only its consequences can be treated at the present time: i.c., immediate removal of the toxic potassium concentration from the perilymph by increasing the microcirculation of the inner ear before irreversible damage occurs.

Deafness↗
PubMed1999

Case report and discussion of hearing preservation after translabyrinthine excision of small acoustic tumors.

OBJECTIVE: Since 1991, three separate reports have shown how hearing may be salvaged after translabyrinthine excision of small acoustic tumors. The authors submit yet another report of a complete translabyrinthine excision of a 1.4-cm intracanalicular acoustic tumor with modest hearing preservation. An attempt is made to retrace the steps of the operation and recognize and discuss what particular events may have safeguarded the viability of the cochlea. With the availability of cochlear implantation, there should be added incentive to preserve the cochlear neurones if hair cells cannot be saved. STUDY DESIGN: The study design was a retrospective case review. SETTING: The study was conducted at a primary care hospital. INTERVENTION: Therapeutic and rehabilitative measures were performed. MAIN OUTCOME MEASURES: Hearing preservation was measured. CASE REPORT: A 55-year-old woman presented with a left-sided hearing loss and a 1.4-cm left acoustic tumor completely filling the internal auditory canal (speech reception threshold [SRT] 30 dB, discrimination [Pb] 28%). A successful translabyrinthine excision of the tumor was performed in November 1995. A 1-year postoperative audiogram showed a mixed hearing loss in the left ear with SRT 85 dB and Pb 0%. Average pure-tone threshold for 500 Hz, 1 kHz, and 3 kHz was 50 dB and aided SRT 40 dB with Pb 64%. Postoperative magnetic resonance imaging confirmed complete excision of the tumor. CONCLUSION: An exceptional case of hearing preservation after translabyrinthine excision of a small acoustic tumor illustrates how it may be possible to preserve cochlear hair cells and neurones simultaneously in certain selected cases. A review of the surgical events shows the value of sealing the cochlear duct with bone wax, selectively removing the vestibular nerves with the tumor by sharp dissection, and safeguarding the meatal segment of the anterior inferior cerebellar artery by a limited dural incision.

Cranial Nerve Neoplasms↗