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At least 595 records · Page 33Linked to original sources
PubMed1991

Transport of HRP through Reissner's membrane in experimental endolymphatic hydrops.

Unilateral endolymphatic hydrops was produced in guinea pigs by cauterization of the endolymphatic sac. Measurements of compound action potential (CAP), cochlear microphonics (CM) and negative summating potential (-SP) confirmed endolymphatic hydrops three months after surgery. In both control and hydropic ears, reaction product of HRP was observed only on the perilymphatic surface of the epithelial cells of Reissner's membrane after 10 min perfusion, while it was observed on both the endolymphatic and perilymphatic surfaces after 30 min perfusion. Epithelial tight junctions were not stained and labelled pinocytotic vesicles were observed in the epithelial cells. These findings suggest that the transport of HRP through Reissner's membrane is unchanged in endolymphatic hydrops and that the epithelial junctions are tight regardless of the distension of Reissner's membrane.

Animals↗
PubMed1993

The ultrastructure of the basilar papilla of the budgerigar's inner ear.

The basilar papilla in the inner ear of the adult budgerigar was studied by scanning and transmission electron microscopy. The sickle-shaped basilar papilla has short hair bundles on the proximal tip and long ones on the distal tip. The tectorial membrane shows a honeycomb-like pattern and enclosed a hair bundle in its alveolus. The papilla consists of two different types of hair cells; short and tall hair cells. The short hair cells with large efferent nerve endings are located on the free basilar membrane in the inferior part. The tall hair cells with large afferent nerve endings are located in the superior part. The similarity and difference of the structure are discussed between the budgerigar and other birds, and between birds and mammals.

Animals↗
PubMed1993

Effects of adenylate cyclase activation on electrical resistance of scala media.

Electrical resistance of scala media at the second turn of the guinea pig cochlea was measured while cochlear adenylate cyclase was activated by perilymphatic perfusion with 2 x 10(-4) M forskolin. The electrical resistance decreased from the pre-forskolin value (6.36 +/- 0.27 k omega to 5.22 +/- 0.33 k omega, n = 5), while the endocochlear potential (EP) increased from the pre-forskolin value (70.2 +/- 2.1 mV to 81.2 +/- 2.8 mV, n = 5). The time course of the electrical resistance change was more rapid than that of the EP change but almost identical to the time course of the change in the Cl- activity of the endolymph. The results suggest that the forskolin-induced decrease in the electrical resistance of the perilymph-endolymph barrier (presumably Reissner's membrane), and the consequent increase in Cl- flux into the endolymph may trigger EP elevation.

Adenylyl Cyclases↗
PubMed1994

The blood vessels in Reissner's membrane of the rat.

Blood vessels on Reissner's membrane were electron-microscopically found in 24 out of 30 rats of the Wistar strain. The vessels were noted in the upper turns, mainly in the third turn of the cochlea. They originated from radiating arterioles in the upper spiral ligament and took straight courses radially down to the spiral limbus, and further to the modiolus, running along the surface of the scala vestibuli side of the membrane. Their diameter was approximately 4 microns. Bifurcated blood vessels were occasionally detected in 3 out of the 24 rats that possessed the vessels in the membrane. From the morphological point of view the blood vessels in Reissner's membrane may possibly have some function in the inner ear of the rat.

Animals↗
PubMed1994

Immunolocalization of Na+, K(+)-ATPase, Ca(++)-ATPase, calcium-binding proteins, and carbonic anhydrase in the guinea pig inner ear.

The distribution of Na+, K(+)-ATPase, Ca(++)-ATPase, carbonic anhydrase, and calcium-binding proteins were investigated immunohistochemically in paraffin sections of guinea pig inner ears. Marginal cells of the stria vascularis, type II fibrocytes of the spiral ligament, and cells in supralimbal and suprastrial regions, were positive for Na+, K(+)-ATPase. Type I fibrocytes of the spiral ligament were positive for Ca(++)-ATPase, carbonic anhydrase, calmodulin and osteopontin. In the vestibular system, dark cells were positive for Na+, K(+)-ATPase. However, these cells and subepithelial fibrocytes were negative for Ca(++)-ATPase, carbonic anhydrase, and the calcium-binding proteins. In the endolymphatic sac, epithelial cells in intermediate and distal portions were positive for Na+, K(+)-ATPase, but the reaction was less than that in the stria. The same endolymphatic sac cells that were positive for Na+, K(+)-ATPase were also positive for Ca(++)-ATPase and calcium-binding proteins, but negative for carbonic anhydrase. The presence of Ca(++)-ATPase and calcium-binding proteins in the type I fibrocytes of the spiral ligament suggests that these cells are involved in mediating Ca++ regulation. Lower levels of Na+, K(+)-ATPase and the co-existence of Ca(++)-ATPase and calcium-binding proteins in the epithelial cells of the endolymphatic sac indicate that these cells have a distinctive role in ion transport that is different from that of the cells of the stria vascularis and vestibular dark cells.

Animals↗
PubMed1994

Swimming test for evaluating vestibular function in guinea pigs.

A swimming test was used to evaluate vestibular function in guinea pigs. We first observed tracings of the swimming patterns of 20 healthy guinea pigs to establish the normal range. Then the same test was used in a group of 49 guinea pigs with endolymphatic hydrops induced by immunologic techniques. They did not show spontaneous nystagmus or body deviation while walking, but a total of 20 out of 49 animals displayed abnormal swimming patterns, with 8 swimming clockwise and 4 counterclockwise. This swimming test is easily able to detect mild vestibular dysfunction in guinea pigs, and can be repeated, so that we consider it useful for examining vestibular function in these animals.

Animals↗
PubMed1994

Electrocochleography in experimental endolymphatic hydrops.

This study investigated whether dominant negative summating potential (DNSP) is absent at all stages of induced hydrops development, including the early stages of hydrops formations. Electrocochleography (ECoG) was done 3 days to 20 weeks after obliteration of the endolymphatic sac in guinea pigs, by electrodes attached to the cochlear bony wall on the scala vestibuli of the basal turn. DNSP was noticed only during the early stages of endolymphatic hydrops formation, before hydrops was fully developed. There was no DNSP when the distension of Reissner's membrane was marked. Increased endolymphatic pressure and/or changes in biochemical composition were thought to be the causes of DNSP.

Action Potentials↗
PubMed1994

Acute measles infection in the hamster cochlea.

Measles virus has been implicated in sudden sensorineural hearing loss (SNHL) in adults as well as in children. Furthermore, sensorineural hearing loss following live measles virus vaccination has been reported. As of yet, however, there has been only few reports on human temporal bone pathology due to measles, and on experimental animal models of measles infection. This study was undertaken to examine acute measles infection in adult hamster cochlea morphologically and immunohistochemically for precise understanding of this viral infection. Atrophy of the stria vascularis, loss of the organ of Corti, "rolled-up" tectorial membrane, and cell infiltration with a positive immunofluorescent reaction primarily within the scale media indicating endolymphatic labyrinthitis were the principal findings. These results were generally consistent with previous ones on human temporal bone pathology not only due to measles but also to SNHL. We consider measles virus to be one of the possible pathogens, even if low in frequency, causing profound and irreversible hearing loss, including SNHL. Completion of measles vaccination without complication and selective or mass revaccination may be necessary to prevent such hearing loss.

Acute Disease↗
PubMed1994

Effects of contrast media on the stria vascularis.

The effects of contrast media on the stria vascularis were electron microscopically studied in mice after intravenous injection of amidotrizoate, iopamidol or ioxaglic acid at 10 or 20 ml/kg body weight. In furosemide-load groups, contrast media were injected via the tail vein at 10 ml/kg with preadministration of furosemide at 20 mg/kg body weight. In both groups, the stria vascularis was prepared for study 10 min after the injection of contrast media. No morphological changes could be found after administration of 10 ml/kg injection of any of the three contrast media. However, administration of 20 ml/kg of amidotrizoate caused a high degree of intercellular dilatation between marginal and intermediate cells. Iopamidol caused a slight degree of dilatation, and ioxaglic acid caused no change. In the furosemide-load groups, amidotrizoate induced severer effects than iopamidol while ioxaglic acid induced no effect. From these results it was concluded that contrast media affect the stria vascularis parallel with osmolality, although some ionic effect of amidotrizoate should be considered when it is used in combination with furosemide.

Animals↗
PubMed1995

Mechanical properties of human round window, basilar and Reissner's membranes.

In order to measure the mechanical strength of small and delicate biological specimens, a microtesting system was developed. We measured the mechanical properties of the round window, basilar and Reissner's membranes taken from the autopsied cases. The testing method was a displacement of the specimen by a force sensor needle until rupture. A load-displacement curve was then drawn and the mechanical value of each specimen was calculated. Reissner's membrane was the weakest, though it showed a measurable strength. From the load-displacement curve of the basilar membrane, it could be displaced by a smaller force than the rupture strength of Reissner's membrane. Speculation about the concept of a negative summating potential in Meniere's disease is therefore theoretically possible from a mechanical point of view.

Aged↗
PubMed1995

Morphologic and morphometric study of human spiral ganglion development.

A light microscopic study of the spiral ganglion was done in human embryos and fetuses measuring 45, 50, 60, 74, 90, 134, 270 mm crown-rump length (crl), and in a one-day-old neonate. Morphometric evaluations of i) cell and nuclear area, ii) nuclear area/cell area ratio, iii) ganglion area, iv) cell concentration/surface unit, and v) distance between the first neuron and the receptor were made, and the results statistically evaluated. In earlier stages of development, spiral ganglion primordia appeared as a cluster of neuroblasts and some schwannoblasts immersed in the mesenchymal tissue, close to the ductus cochlearis. A honeycomb pattern in the spiral ganglion neurons was observed in the basal turn of a 74 mm crl fetus. In later stages, the basal turn of a 90 mm crl fetus showed a spatial organization. Peripheral and central fibers of the acoustic nerve appeared stratified in early periods of development (45 mm crl embryo). From this stage on, both phenomena progress apicalwards until the neonatal period. A significant decrease in the nuclear area/cell area ratio was observed from the 134 mm crl fetus (17 weeks) to the neonatal stage in all turns. This led to a significant increase in cellular area from the 270 mm crl fetus (32 weeks) to the neonate, with no significant variation in nuclear area. The distance from the primordium of the organ of Corti to the spiral ganglion in the interval between 45 and 74 mm crl showed a significant increase in all turns.(ABSTRACT TRUNCATED AT 250 WORDS)

Cochlear Duct↗
PubMed1996

Is perilymphatic pressure altered in tinnitus?

Tinnitus is characterized by the continuous or intermittent auditory perception of various sounds (buzzing, whistling, etc.) in the absence of any external stimulus. Perilymphatic hyperpressure is one of the numerous mechanisms which could hypothetically be involved in tinnitus generation. In the present experiment, perilymphatic pressure was measured indirectly using the tympanic membrane displacement technique. Twenty-five tinnitus patients were investigated at 10, 15 and 20 dB above the acoustic reflex threshold with ipsilateral stimulation. The variables Vi (inward tympanic displacement), Vm (mean tympanic displacement) and their variations according to stimulus level were compared between tinnitus sufferers and age-matched or hearing-matched controls. Tympanic displacement was measured in sitting and supine positions so as to evaluate cochlear aqueduct patency. No systemic changes in response occurred in tinnitus patients, except at a high stimulation level, perhaps due to hearing impairment.

Adult↗
PubMed1998

Bilateral otoacoustic emissions pass in a baby with Mondini deformity and subsequently confirmed profound bilateral hearing loss.

Evoked otoacoustic emissions are well established as a hearing screening technique and are used extensively in paediatric audiology. They are believed to originate from the outer hair cells and can be detected in almost 100% of normally hearing ears; even a mild hearing loss has been shown to abolish otoacoustic emissions. Results are presented of a baby boy born at 29 weeks' gestation requiring 77 days of neonatal care, but experiencing no complications following discharge from the neonatal unit. This child had clear bilateral evoked otoacoustic emissions at almost four months of age, but was subsequently found to have a profound bilateral hearing impairment and absent otoacoustic emissions. Radiological investigations revealed bilateral Mondini dysplasia, and this child has now been implanted with a multi-channel MXM Digisonic cochlear implant. He is progressing well and shows awareness of sound. Approximately 10 previous cases of otoacoustic emissions occurring in profoundly deaf ears have been reported in the literature. Although it is likely that this child's hearing loss was progressive in nature, the authors believe that this is the first reported case of otoacoustic emissions being recorded in the presence of Mondini dysplasia. This raises concerns about the use of neonatal screening in isolation without adequate mechanisms for later identification of hearing impairment, although it is acknowledged that it represents a rare situation.

Child, Preschool↗
PubMed1993

[Acute sensory deafness originating from experimental double-membrane rupture].

Combined rupture of Reissner's membrane and the round window membrane (double-membrane rupture) as a cause of acute profound sensorineural hearing loss was investigated in guinea pigs. Action potentials (APs) of the cochlear nerve in response to tone pip stimuli (1, 2, 4, 8kHz) were recorded before and after rupture of Reissner's membrane at each turn of the cochlea. Then the round window was perforated to create leakage of the perilymph. Ninety minutes later, AP was again recorded. After these procedures, the animal was sacrificed for histological study to confirm the rupture of Reissner's membrane. The ears with double-membrane rupture showed a larger decrease in AP amplitude at all test frequencies than did control ears with round window rupture alone. The ears in which Reissner's membrane was ruptured at the second turn showed more a pronounced decrease in AP amplitude than those ruptured at the third and apical turns. It was concluded that double-membrane rupture could be a cause of sudden deafness, but that the disturbance of cochlear function depends on where Reissner's membrane ruptures.

Action Potentials↗
PubMedDate not supplied

[Protein study on perilymph susbstitution during cerebrospinal fluid flow through cochlear aqueduct].

Total protein contents in the perilymphy of Scala vestibuli and Scala tympani as well as in the cerobrospinal fluid (CSF) of guinea-pigs were determined, by which specimens were taken under the following various conditions: With or without subarachnoidal puncture before perilymph collection, by varying the amount of perilymph taken from Scala tympani, by fractionating collection and under post mortem condition. The results suggest that under physiological conditions the CSF also flows through the cochleae aqueduct and the protein concentration in the Scala tympani decreases especially in the basal winding. Because the protein content in CSF is inaverage four times lower than in fluids of the inner ear it is of preference to consider the question of connection between the CSF and the fluids of the inner ear. In the specimens taken the blood contamination was estimated on the basisof erythrocytes in the connection capillaries under microscope. The protein content in the perilymph of Scala vestibuli was found significantly higher in relation to perilymph of Scala tympani.

Animals↗
PubMed2000

Experimental studies of vibratory trauma of Corti's organ. I: Electrophysiological measurements.

In the present-day environment, vibration concomitant with noise is most frequently observed, but even though it is regarded as only a weak, additional traumatic factor affecting the organ of hearing. This opinion is contrary to a number of reports on the damage of the hearing organ caused by vibration in workers of various branches of industry. As experiments on humans are rather difficult, the harmful effect of vibration is usually examined on laboratory animals. In the majority of studies dealing with this problem the presence of noise (purposely or casually) was found in most cases. The aim of this study was to determine the effect of isolated long-term whole-body vibration and vertical sinusoidal shaking (10 Hz frequency, 5 mm amplitude, and 2 g acceleration) on Corti's organ. The study was carried out on young guinea pigs of both sexes. Eighty four animals (30 control and 54 experimental) with Preyer's reflex and without otoscopically detectable changes were used. A group of 18 animals was subjected to vibration in noiseless shaking apparatus for 30, 90 and 180 days. After a one-month rest, cochlear microphonics were performed under urethane anaesthesia. Our modification of the phase-sensitive detection method was used. Cochlear microphonics at frequencies of 260 Hz, 500 Hz, 1 kHz and 2 kHz was recorded from the apex of the cochlea and for 4 kHz and 8 kHz from the region of the round window. As the cochlear microphonics values showed significant individual differences, all experimental samples were examined by means of non-parametric tests. The outcome of the study demonstrated a gradual but considerable cochlear microphonics voltage decrease in the range to 2 kHz. This result pointed to the generation of vibration-induced damage in outer hair cells of the fourth and third turnings of the cochlea in the guinea pigs under study.

Animals↗