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At least 235 records · Page 13Linked to original sources
PubMed1997

R-phenylisopropyladenosine attenuates noise-induced hearing loss in the chinchilla.

Reactive oxygen species, which are cytotoxic to living tissues, are thought to be partly responsible for noise-induced hearing loss. In this study R-phenylisopropyladenosine (R-PIA), a stable non-hydrolyzable adenosine analogue which has been found effective in upregulating antioxidant enzyme activity levels, was topologically applied to the round window of the right ears of chinchillas. Physiological saline was applied to the round window of the left ears (control). The animals were then exposed to a 4 kHz octave band noise at 105 dB SPL for 4 h. Inferior colliculus evoked potential thresholds and distortion product otoacoustic emissions (DPOAE) were measured and hair cell damage was documented. The mean threshold shifts immediately after the noise exposure were 70-90 dB at frequencies between 2 and 16 kHz. There were no significant differences in threshold shifts at this point between the R-PIA-treated and control ears. By 4 days after noise exposure, however, the R-PIA-treated ears showed 20-30 dB more recovery than saline-treated ears at frequencies between 4 and 16 kHz. More importantly, threshold measurements made 20 days after noise exposure showed 10-15 dB less permanent threshold shifts in R-PIA-treated ears. The amplitudes of DPOAE also recovered to a greater extent and outer hair cell losses were less severe in the R-PIA-treated ears. The results suggest that administration of R-PIA facilitates the recovery process of the outer hair cell after noise exposure.

Adenosine↗
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↗
PubMed1979

Cochlear and fast electrical responses to frequency modulated tones: a frequency specific stimulus.

Some characteristics of "the fast response" to frequency modulation were explored here by examining (1) CM and AP in animal experiment and (2) BER in human study. CM to frequency modulated tone showed frequency change and amplitude change, the latter of which is probably due to frequency characteristics of the sound conductive system of the ear. Compared with AP to tone burst, latency and amplitude of AP to FM tone depends less on stimulus intensity. AP to FM tone is suspected to be a result of new excitement of the restricted area stimulated by shifted frequency. The result of analysis on human BER is well consistent with the result of AP study in animal experiment, and latency curves of BER were to some extent linear to a log scale of shifted frequencies. Thus, FM tone is possibly a frequency specific stimulus.

Acoustic Stimulation↗
PubMed1998

Forty years of stapes surgery.

OBJECTIVE: This study reports the results of 14,449 stapedectomy operations performed during the past 40 years. STUDY DESIGN: The study design was a retrospective case review. Approximately 100 operations were selected from each of the past 40 years, for a total of 5,444 operations, from which the results with the whole group were extrapolated. SETTING: All operations were performed in a hospital during the first 30 years and in an ambulatory surgery center in the past 10 years. PATIENTS: All patients in the study were the private patients of the author and were operated on by him personally. These patients had otosclerosis only. INTERVENTIONS: Stapedectomy was performed on all patients. MAIN OUTCOME MEASURES: The change in hearing after the operation was reported. Using the hearing of the average for 500, 1,000, and 2,000 Hz, the criteria for success were defined as closure of the air-bone gap to 10 dB or less and no decline in speech discrimination of >10%. RESULTS: In the primary stapedectomy group, success was achieved in 95.1% of ears after 1 year, 94.7% of ears after 2-5 years, and 62.5% after >30 years. In the revision stapedectomy group, success was achieved in 71.1% after 1 year, 62.4% after 2-5 years, and 59.4% after 6-36 years. CONCLUSIONS: The immediate success rate after primary and revision stapedectomy declines slowly over time, because of delayed conductive hearing loss and further sensorineural hearing loss, more than one would expect in matched control subjects without otosclerosis. Stapedectomy has stood the test of time as the first successful microsurgical operation.

Adolescent↗
PubMed1994

[Relationship between summating potentials and perilymphatic fistula].

Serial electrocochleogram (ECochG) recordings were obtained within 24 hours from 40 guinea pigs with experimentally induced PLF, and the cochlears of 30 guinea pigs (60 ears) were histopathologically observed under light microscope. -SP occurred in 100% experimented ears within 1-3 hours after PLF, but distention of Ressner's membrane was found only in 30% ones. CAP thresholds and N1 latencies of 10 animals were improved, accompanying disappearance of -SP in 6 of the 10 animals in 24 hours after PLF. It is presumed that -SP is not a specifically electrophysiologic indicator of ELH, and that the generation of -SP may chiefly result from reversible damage of cochlear hair cells. The mechanical factor of basilar membrane displacement can hardly be considered as a main cause of SP abnormality. The mechanism of the ELH following PLF was also discussed.

Animals↗
PubMed1981

On the overload effect of sound impulses to the inner ear.

Test series with both continuous and intermittent sound exposure to guinea pig ears yielded an area within the coordinates load frequency and load level in which a dose principle is valid more or less exactly. Exceeding the upper (level) borderline of this area provokes a damage of the organ of Corti nearly independent of the load dose. Sound levels of such order of magnitude mainly occur at sound impulses. However, to estimate the hair-cell damaging effect of a given sound impulse one needs its time or frequency function in addition to the peak level. A first order approximation seems to be possible by means of a 1/3-octave band level analysis.

Acoustic Stimulation↗
PubMed1992

Morphologic and electrophysiologic effects of cochlear implantation and electrical stimulation.

The nondeafened guinea pig model was utilized in this study to assess the functional and morphologic effects of cochlear implantation and electrical stimulation. Auditory brainstem responses (ABRs) were recorded prior to and following intrascalar implantation of a 3M-House cochlear electrode (n = 41 ears), as well as after electrical stimulation (n = 23 ears). The experimental population was divided into the following groups according to implantation and stimulation parameters: 200 microA for 3 hours (group I); 200 microA for 24 hours (group II); 400 microA for 3 hours (group III); implanted, but not stimulated (group IV); and nonimplanted, not stimulated ears (group V). Of those cochleae that sustained the trauma of implantation, 32 percent had no detectable ABR to 110 dB SPL clicks, while only 7 percent additionally failed to respond to 130 dB SPL clicks. No significant difference (one-way ANOVA with repeated measures at the 95 percent confidence limit) could be detected when comparing those ears that retained ABRs according to experimental grouping. Morphologic analysis was performed on 29 cochleae. Spiral ganglion "packing densities" were not found to be significantly different among the groups (ANOVA). The status of the organ of Corti was significantly better in groups II and V in comparison to the other groups (Kruskal-Wallis test with pairwise comparisons, p less than 0.05); there was no discernible dose-response relationship. Morphologic and electrophysiologic changes correlated with insertion trauma and infection rather than with electrical stimulation at the levels tested in this study.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1991

Effects of persistent perilymph fistula on the inner ear.

To study the effects of a persistent perilymph fistula on the cochlea, a small cannula was inserted into the scala tympani of the basal turn of cochlea in guinea pigs. A month later, cochlear morphology and blood flow were studied using either histological evaluation or the microsphere surface preparation technique. Some animals showed no cochlear morphologic changes or no cochlear blood-flow reduction, even if tubal patency was maintained and perilymph leakage lasted for 1 month. This suggests that a prolonged perilymph fistula, per se, causes no permanent cochlear damage. However, in some animals, hair cell damage and cochlear blood-flow disorders were observed. These observations and the causes of hearing loss in clinical cases of perilymph fistula were studied.

Animals↗
PubMed1985

Ontogenic changes in cochlear characteristic frequency at a basal turn location as reflected in the summating potential.

In these experiments the development of summating potential (SP) responses in gerbils from neonates to adults was followed. Special recording techniques were used to eliminate maturational effects associated with the middle ear so that developmental changes in cochlear physiology were isolated for study. Results indicate that as development proceeds the frequency that maximally excites the basilar membrane (BM) of the gerbil at a specific mid-basal turn electrode location progresses from low to high, demonstrating a 1.5 octave shift from the onset of the generation of electrical activity until adult-like response are obtained. These findings support the theory proposed by E.W. Rubel (in: Handbook of Sensory Physiology, Vol. IX: Development of Sensory Systems, pp. 135-237. Editor: M. Jacobsen. Springer-Verlag, New York) which explains the observed development of physiological responses measured in the cochlea and higher centers in terms of changing micromechanical transduction properties of the BM.

Aging↗
PubMedDate not supplied

Inner ear pathology in the deafness mutant mouse.

A distinctive cochlear pathology was found in deafness mutant mice. There was a delay in the formation of the fluid-filled Nuel and tunnel spaces in the organ of Corti, the hair cells were distorted and degenerate, and there was poor maintenance of synapses. No hair cells appeared normal by TEM, but SEM revealed some areas where stereocilia appeared relatively normal, suggesting that SEM of the surface of the organ of Corti is not necessarily a good indicator of hair cell pathology in hereditary hearing impairment. Mutant mice show normal development of endocochlear potential, but have no measurable cochlear microphonics or compound action potential. The data suggest that the deafness gene affects the organ of Corti and that cochlear hair cells in deafness mice are never functional.

Action Potentials↗
PubMed2001

Origin of cubic difference tones generated by high-intensity stimuli: effect of ischemia and auditory fatigue on the gerbil cochlea.

Cubic difference tone (CDT) otoacoustic emissions are thought to arise from the feedback loop allowing outer hair cells to enhance the sensitivity and tuning of the organ of Corti. The existence of residual CDTs during complete cochlear ischemia is therefore disturbing. That stimulus intensities must exceed 50-60 dB SPL for residual CDTs to be recorded and for level notches to be present in CDT growth functions is often cited as evidence for a two-component, "active/passive" model: one component, the residual one, would originate from a passive, hardly vulnerable mechanism and thus be unsuitable for hearing screening purposes. This model was probed in gerbil ears after complete interruption of the cochlear blood flow. Cochlear potentials and CDTs were controlled simultaneously through continuous monitoring of CDT level and phase for 50 and 60 dB SPL stimuli and group-delay measurements. After a clear initial decay, CDT levels elicited at 60 dB SPL plateaued for several minutes at about 20 dB below initial level, and when early level notches were observed, CDT phase changes remained minor. The CDT group delays decreased by less than 30%. Later CDT level notches were associated with sharp phase reversals but the similarity between CDT characteristics before and after a notch was hardly consistent with a two-component interpretation. When mild sound overexposure (pure tone, 90-95 dB SPL, 15-30 min) had been performed prior to ischemia, little or no ischemic CDT came from the frequency bands where auditory fatigue had been detected (within 1 kHz), irrespective of the stimulus intensity. It suggests that instead of being passive, residual ischemic CDTs were vulnerable and produced according to a near-normal tonotopy by the same mechanisms that were sensitive to auditory fatigue. All the results lined up with a simple feedback model of cochlear function assuming a single CDT source related to mechano-electrical transduction in outer hair cells. More parsimonious than a two-component model, it posits that although early stages of ischemia dramatically impair the overall performance of the cochlea, the nonlinear mechanical stages responsible for the existence of CDTs keep working albeit at higher intensities.

Acoustic Stimulation↗
PubMed1978

Deafness in Osteodysplasty of Melnick and Needles.

A 12-year-old boy had osteodysplasty of Melnick and Needles and a mixed conductive and perceptive deafness of both ears. Deafness in this rare, inherited skeletal disorder is exceptional. Structurally, the pinnae and external auditory canals were small; thin, serous fluid was found in both middle ears, and on surgical exploration of the right ear, no round window could be found.

Bone and Bones↗
PubMed1982

Dynamics of the flow of perilymph in the cochlea of the guinea pig.

The dynamics of perilymph flow in the cochlea was studied in guinea pigs. After placement of sodium chloride crystals on the round window membrane, the potassium ion concentration in the scala vestibuli in the basal turn does not change. The potassium ion concentrations in the scala tympani in the basal turn increases rapidly, while the potassium ion concentration in the scala tympani in the third turn increases slowly and to a lesser extent. The cochlear microphonic potential decreases in the basal turn and to a lesser extent in the third turn. After placement of sodium chloride on the fenestra in the scala tympani of the third turn, the chochlear microphonic potential in the basal turn does not change. These data lend support to the theory of longitudinal flow of perilymph in the scala tympani.

Animals↗
PubMed1983

Compound action potential input-output decruitment. Effect of topically applied antiseptics.

The ototoxic effect of povidone-iodine antiseptics topically applied to the chinchilla round window was examined with particular emphasis on the action potential (AP) input-output function at 2 and 4 kHz. A group of chinchillas exhibited a marked elevation of AP threshold at 8 and 12 kHz, with only a slight threshold elevation at 2 and 4 kHz. A distinct decruitment (less than normal growth of response with increasing sound intensity) of the AP input-output function was, however, found at the lower frequencies. There are implications of an ototoxically induced high-frequency hearing loss on speech frequencies.

Action Potentials↗
PubMed1984

The human round window membrane. An electron microscopic study.

The normal adult human round window membrane was examined by transmission electron microscopy. The membrane consists of the following three layers: (1) an outer squamous epithelial layer with an underlying basement membrane; (2) a middle fibrous layer containing collagen, elastin, fibrocytes, vessels, and nerves; and (3) an inner layer of mesothelial cells. Mucosal membrane veils that cover the round window membrane, forming "false" round window membranes, are also described. These membranes are also three layered, including (1) an outer epithelial layer with an underlying basement membrane, (2) a middle fibrous layer containing collagen, elastin, fibrocytes, vessels, and nerves, and (3) an inner epithelial layer with an underlying basement membrane. Ultrastructural differences between these two structures are discussed.

Aged↗
PubMed1987

Thickness of the human round window membrane in different forms of otitis media.

The thickness and morphologic characteristics of the round window membrane were evaluated in temporal bones from normal subjects as well as those with serous otitis media, purulent otitis media, and chronic otitis media. Temporal bones were studied in chronological order in six age ranges to determine the possibility of age-related differences. No significant difference in the mean thickness of the round window membrane was observed in terms of age groups in normal temporal bones or temporal bones from patients with otitis media; however, a significant difference in the mean thickness was observed in the various forms of otitis media compared with the normal round window membrane in all age groups. The membrane was thickest in patients with chronic otitis media when compared with that in normal subjects or those with serous or purulent otitis media. The epithelial layer (including the subepithelial space) and the fibrous layer were measured individually to determine in which layer the change in mean thickness occurred. These measurements showed an involvement of all layers of the round window membrane in those groups with otitis media, with maximal involvement of the combined epithelial layer and subepithelial space.

Adolescent↗