Biomedical subjects

T Morizono

Publications and source records attributed to T Morizono.

88 records · Page 5Linked to original sources

PubMedDate not supplied

Round window membrane permeability to human serum albumin in antigen-induced otitis media.

The round window membrane (RWM) permeability to human serum albumin (HSA) was investigated in both normal chinchillas and chinchillas sensitized with HSA. The effect of a corticosteroid agent (triamcinolone) on the RWM permeability was also analyzed. It was found that HSA could not be detected in either the perilymph or the cerebrospinal fluid of normal chinchillas within 1 hour after instillation into the middle ear bulla. Perilymph levels of HSA peaked 24 hours after instillation. In antigen-induced otitis media, the HSA level in the perilymph at 12 hours after challenge was significantly higher than that in normal chinchillas (P less than .01), but it did not increase with the development of otitis media. A significant difference of HSA level in the perilymph of animals with and without steroid treatment was noted (P less than .025 at 24 hours and P less than .05 at 48 hours). It is concluded that little HSA passes through the normal RWM in a short time and that the RWM permeability to HSA increases in the early stage (about 12 hours) of antigen-induced otitis media. Corticosteroids can affect the RWM permeability to HSA by reducing the level of antigen-induced otitis media.

Adjuvants, Immunologic↗

PubMedDate not supplied

A 'neural' response with 3-ms latency evoked by loud sound in profoundly deaf patients.

A large negative deflection with a latency of 3 ms was observed in the auditory brainstem response (ABR) waveforms of some patients with peripheral profound deafness. This deflection was termed the N3 potential. In this paper, we review patients with the N3 potential and discuss the characteristics of abnormal ABR waveforms. The origin of the N3 potential was also discussed, especially with respect to vestibular evoked potentials. In most of the patients, audiograms showed no response to the maximum output of an audiometer in the high-frequency range and a residual response in the low-frequency range. The N3 potentials were noted at intensities of 80 dB nHL or greater. As the stimulus intensity increased, the amplitude of the potential increased and the latency decreased. A high repetition rate (83.3/s) of the click stimulus influenced the latency and amplitude of the N3 potential. The potential was replicated on retest within less than a month, and had a consistent latency and amplitude over the scalp. The results indicate that the N3 potential is not an electrical artifact but a physiological neural response evoked by a loud sound. The N3 potential is most likely not an auditory evoked response from cochlear or a response from a semicircular canal, because it has a 3-ms latency, a sharp waveform, and is unassociated with vertigo. The results suggest that the N3 potential may be a saccular acoustic response.

Acoustic Stimulation↗

PubMedDate not supplied

Hypercholesterolemia and auditory dysfunction. Experimental studies.

Rabbits were used for the long-term study of auditory function associated with experimental hypertension and hypercholesterolemia. Auditory dysfunction (threshold changes of sound evoked responses) was monitored with an electrode, chronically implanted into the contralateral inferior colliculus. Hypertension was created using the renal encapsulation technique. Auditory function in the hypertension trial demonstrated a dip at higher frequencies as well as improvement at lower frequencies. One gram of cholesterol fed daily for three months was capable of making rabbits atherosclerotic. Cholesterol-fed rabbits showed increasing auditory dysfunction over time at all frequencies. When experimental hypertension was combined with hypercholesterolemia, the auditory changes appeared additive. This work, although in preliminary stages, seems to provide experimental evidence that auditory dysfunction is associated with cholesterol diet.

Animals↗

PubMedDate not supplied

Neurophysiologic assessment of endolymphatic hydrops.

An electrophysiological method for assessing endolymphatic hydrops of the cochlea in an animal model of Meniere's disease is described. Eighth nerve gross action potentials (AP) were evoked by tone bursts presented at discrete phases of a simultaneously delivered 50-Hz pure tone. Hydropic cochleas showed significantly less modulation of AP amplitude and latency than normal cochleas. This method may be useful in objectively evaluating Meniere's disease with electrocochleography.

Animals↗

PubMedDate not supplied

Sensorineural hearing loss in otitis media.

Additional evidence is presented to support the hypothesis that both acute purulent otitis media (POM) and chronic suppurative otitis media (COM) can cause high frequency sensorineural hearing loss. In selected patients and in animals (chinchillas) in a pilot study using electrophysiological methods, both temporary threshold shifts and permanent threshold shifts of basal cochlear turn involvement were demonstrated in POM. Data of cochlear involvement in 475 ears with bilateral COM, 607 ears with unilateral COM, and 607 ears serving as controls were obtained from six centers in five countries. In group 1 (15 dB or greater), 43% of ears with unilateral COM and 42% of ears with bilateral COM showed losses, for a combined odds ratio eight times that in controls. In group 2 (30 dB or greater), 16% of ears with unilateral COM and 17% of ears with bilateral COM demonstrated, respectively, seven and ten times that in controls. These statistically significant findings influence clinical considerations.

Acoustic Impedance Tests↗

PubMedDate not supplied

Measurement of action potential thresholds in experimental endolymphatic hydrops.

Unilateral experimental endolymphatic hydrops was created by endolymphatic sac and duct obstruction in guinea pigs. Studies of action potential (AP) threshold were then performed and compared with histologic findings. Action potential thresholds were significantly increased in the hydrops ears. The close relationship between AP changes and hydrops was sufficient to allow the detection of hydrops by AP threshold measurements alone. The AP threshold changes were positively related to the degree of hydrops and postoperative interval in a manner consistent with hearing changes seen in Meniere's disease. Based upon the foregoing, experimental endolymphatic hydrops appears to be a valid and usable model for the study of the cochlear aspects of Meniere's disease.

Action Potentials↗

PubMedDate not supplied

Hearing loss following potassium bromate: two case reports.

Bromate has not been regarded as an ototoxic drug. Potassium bromate, marketed as a neutralizer in home permanent cold wave hair kits, has caused several cases of accidental poisoning in children, resulting from the ingestion of this solution. Two cases of hearing loss following ingestion of this solution for the purpose of suicide have been reported here and in the literature review.

Adolescent↗

PubMedDate not supplied

Effects of topical sodium potassium ATPase inhibitors upon endocochlear potential in chinchilla.

Sodium orthovanadate (vanadate) is a recently discovered inhibitor of the enzyme sodium potassium adenosine triphosphatase, which has properties similar to ouabain in peripheral tissues. The effects of topical application of vanadate and ouabain to the round window membrane of the chinchilla were studied using endocochlear potential (EP) and action potential as measures of cochlear function. The EP demonstrated an initial elevation followed by a secondary decline after topical application of 2 mmol vanadate to the round window membrane. During the EP elevation, the resistance was unchanged, but the action potential response declined, with a greater effect on responses to 8-kHz tone bursts than to 2-kHz tone bursts. Thus, it does not appear that the initial increase of endocochlear potential that was observed was due to a change in the resistance of the cochlear duct; rather, some other mechanism must be involved. The round window topical application of potentially ototoxic drugs accompanied by cochlear function monitoring appears to be a useful method for testing drugs with marked systemic effects such as ouabain or vanadate and is simpler to perform than perilymphatic or vascular perfusion.

Administration, Topical↗

PubMedDate not supplied

Experimental hypercholesterolemia and auditory function in the chinchilla.

Possible harmful effects of a high-cholesterol diet on auditory function were suggested by our previous work in rabbits, in which evoked potentials were measured from a chronic electrode inserted into the inferior colliculus. However, serum cholesterol levels in those rabbits tended to be extraordinarily high, i.e., more than 1,500 mg/dL. Chinchillas were used in the present work as an animal model to study the relationship between hypercholesterolemia and auditory dysfunction. One percent cholesterol in standard Chinchow was fed to chinchillas for three months. The experimental groups showed a high mean cholesterol level of 437 +/- 394 mg/dL (N = 9). Isopotential curve of the cochlear microphonics, threshold of action potentials (AP), and endocochlear DC potential did not differ from those in the control group. When moderately intense sound (12 kHz, 95 dB SPL) was given for ten minutes, however, the reduction in AP threshold was significantly greater (P = .036) in the cholesterol group. It is postulated that hypercholesterolemia may be one of the factors involved in differential susceptibility to noise.

Animals↗

PubMedDate not supplied

Ototoxicity of topically applied gentamicin using a statistical analysis of electrophysiological measurement.

Ototoxicity of topically applied gentamicin was studied in guinea pigs. 0.3% gentamicin was instilled in one side of the middle ear cavity and Ringer's solution was instilled in the other side, and the difference in the cochlear microphonics measured with the round window electrode was analysed statistically. Instillation of Ringer's solution in the middle ear cavity for 1 day did not cause any significant sensorineural hearing loss, but on the 3rd day of instillation significantly reduced responses were observed, compared with the responses from non-treated ears, followed by a partial recovery starting on the 4th day. When gentamicin 0.3% was instilled into the middle ear cavity, significant deafness occurred 24 hours later, and highly significant deafness on the 2nd and 3rd day. The usage of gentamicin ear drops of the current formula should be discouraged until a better formula is provided.

Acoustic Stimulation↗

PubMedDate not supplied

Ototoxicity of ethanol in the tympanic cleft in animals.

This work was undertaken to study the ototoxicity of topically applied ethanol in quantitative terms. Using guinea pigs, ethanol was administered (1) on the round window for 10 min, (2) instilled in the middle ear cavity for 24 hours, and (3) perfused into the cochlear canal (into the scala tympani) at the rat of 10 microliter/min for 10 min. Cochlear microphonics from the electrode on the round window were recorded. The critical concentration (the maximum dilution ratio) of the ethanol that appears to be ototoxic in the experimental condition mentioned above was determined to be (1) 50%, (2) 10%, (3) 0.1% respectively. Using chinchillas, the effect of ethanol with round window application on the Endocochlear Potential (EP) was studied. Simultaneous recording of EP from the 1st and 3rd turn of the cochlea showed a more marked decline in EP in the 1st turn. 70% ethanol caused an irreversible, plateauing decline in EPO, while 35% ethanol caused a reversible decline in EP.

Action Potentials↗

PubMedDate not supplied

Changes in EP and inner ear ionic concentrations in experimental endolymphatic hydrops.

Unilateral endolymphatic hydrops was created in guinea pigs by endolymphatic duct obstruction. Using microelectrodes, studies of endocochlear potential (EP) and inner ear ionic concentrations were performed. EP was significantly decreased whereas Na+, K+, and Cl- concentrations in both scala media and scala tympani were not significantly altered. The presence of a decreased EP after endolymphatic duct obstruction appears to be a reliable indicator for the presence of hydrops. This decrease in EP without ionic concentration changes suggests that it is the electrogenic portion of EP which is altered in hydrops.

Animals↗

PubMedDate not supplied

Hyperlipidemia and noise in the chinchilla.

Chinchillas were maintained on a 1% cholesterol diet for 6 months. Auditory Brainstem Response (ABR) measurements were obtained before and at 1, 3, 5, and 6 months after initiation of diet. Compound Action Potential (AP) measurements were obtained at sacrifice at 6 months. A significant reduction in ABR was seen at 5 months-on-diet. At 5 months, the animals were exposed to a 2 octave bandpass noise centered at 1 kHz at 105 dB for 220 min. One month following noise exposure, the cholesterol-fed animals exhibited a greater ABR latency shift at low intensities, and an elevated AP threshold at higher frequencies, vis-à-vis a control group.

Animals↗

PubMedDate not supplied

Diet-induced hyperlipidemia and auditory dysfunction.

Chinchillas rendered hyperlipidemic by a 1% cholesterol diet or maintained on a normal diet were either exposed to a 2-octave bandpass noise (700-2,800 Hz for 220 min at 105 or 114 dB) or else not exposed to noise. The animals were assessed with tone-burst (2-16 kHz) elicited compound action potentials (CAP). Compared with normal diet animals, the hyperlipidemic animals: not exposed to noise exhibited elevated thresholds at 8 kHz and higher frequencies; exposed to 105-dB noise exhibited elevated thresholds at 16 kHz; and exposed to 114-dB noise exhibited elevated thresholds at 2-16 kH. Surface preparations were made of the left cochleae of all noise-exposed animals. There was essentially no difference in hair cell counts between hyperlipidemic animals exposed to the 105-dB noise and normal animals similarly exposed. The hyperlipidemic animals exposed to the 114-dB noise exhibited a greater hair cell loss in the first turn of the cochlea than did similarly exposed normal animals. We conclude that maintenance on a high-cholesterol diet can cause a high-frequency hearing loss, probably due to vascular pathology resulting from a hyperlipidemic state. Furthermore, maintenance on a high-cholesterol diet can increase susceptibility to noise-induced hearing losses.

Animals↗

PubMedDate not supplied

Effects of carbon dioxide in the middle ear cavity upon the cochlear potentials and cochlear pH.

To elucidate the effects of CO2 in the middle ear upon the cochlea, measurements were made of the cochlear potentials (compound action potential and endocochlear potential) and of the pH of the inner ear fluids and the organ of Corti. Gas containing CO2 did not affect the AP threshold, except for a slight decrease in AP threshold elicited by an 8 kHz tone burst with 10% CO2 flow. The EP did not vary with CO2 gas. The CO2 gas mixture reduced the pH in perilymph significantly, by 0.11 +/- 0.05 with 5% CO2 and by 0.17 +/- 0.04 with 10% CO2, in comparison with 100% N2. The CO2 gas slightly but significantly decreased the endolymph pH, by 0.05 +/- 0.04 with 5% CO2 and by 0.09 +/- 0.06 with 10% CO2. The removal of perilymph led to a greater acidification of endolymph with CO2 gas. Acidification of the organ of Corti was also noted with the CO2 gas flush. These findings indicate that CO2 in the middle ear influences the acid-base regulation of inner ear fluids and the cochlear function.

Animals↗

PubMedDate not supplied

Low-frequency biasing of round window responses in guinea pigs and chinchillas.

The acoustic biasing technique using low-frequency sound is of increasing interest to investigators, not only as a means of studying cochlear transduction but also as a promising tool for assessing cochlear pathology such as endolymphatic hydrops. We compared normal modulation patterns of round window responses in guinea pigs and chinchillas, whose low-frequency auditory characteristics are known to be different. A 50-Hz sine wave (90 dB SPL for guinea pigs and 80 dB SPL for chinchillas), which evoked an equivalent magnitude of cochlear microphonics (CM) in both species, was used to modulate the compound action potential (CAP) and the summating potential (SP) elicited by 8-kHz tone bursts. Overall patterns of CAP and SP modulation were almost identical between the two species except for a difference in the phase of 50 Hz CM. The phase of maximum SP enlargement was in accord with that of maximum CAP suppression, which led to inferred basilar membrane (BM) position at maximum scala tympani displacement by between 45 and 90 degrees. More complex or hysteresis effects seemed to be involved in the modulation of CAP and SP magnitude, in addition to the biasing effect owing solely to BM displacement.

Acoustic Stimulation↗