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At least 271 records · Page 15Linked to original sources
PubMed1998

The role of the chinchilla pinna and ear canal in electrophysiological measures of hearing thresholds.

Measurements of the acoustic transfer function (ATF) of the pinnae of 8 chinchillas were compared with the auditory-evoked potential (AEP) thresholds of 16 chinchillas measured in free field and with insert earphones. The ATF was measured in anesthetized chinchillas in a far-field condition in a semi-anechoic room using a logarithmic frequency sweep from 100 Hz to 20 kHz. Probe microphone measurements were collected with the probe opening at the tympanic membrane and in the same approximate position with the chinchilla removed from the sound field. For each animal's acoustic transfer function, the average of five in-the-ear and three free-field measurements were determined. The ATF exhibited a 5-dB passive gain at about 1 kHz and a broad resonance between 2.5 and 6 kHz of about a 10-dB gain. AEP thresholds were obtained from monaural chronically implanted chinchillas at 0.5, 1, 2, 4, and 8 kHz using first free-field and then insert earphone stimuli. The free-field sound pressure was measured with a microphone in the approximate position of the chinchilla's head. The earphone sound pressures were measured with a probe microphone positioned near the tympanic membrane. The free-field AEP hearing thresholds exhibited +10-dB gain at 4 kHz compared to the insert earphone AEP thresholds. The agreement between the ATF and AEP derived transfer function suggested that the threshold differences at 4 kHz between the two testing configurations can be accounted for by the pinna and ear canal gain.

Acoustic Stimulation↗
PubMed1994

Mycoplasma auris sp. nov., Mycoplasma cottewii sp. nov., and Mycoplasma yeatsii sp. nov., new sterol-requiring mollicutes from the external ear canals of goats.

Three mycoplasma strains, designated GIHT (T = type strain), UIAT, and VIST, were isolated from the external ear canals of goats and were shown to be serologically distinct from each other and from previously described Acholeplasma, Entomoplasma, Mesoplasma, and Mycoplasma species. Using light and transmission electron microscopy, we showed that the cells of these organisms were small, pleomorphic, coccoid, nonmotile, and nonhelical and that each cell was surrounded by a single cytoplasmic membrane. There was no evidence of a cell wall, and the organisms grew freely in media containing penicillin at concentrations of 1,000 U/ml or more and thallous acetate (final concentration, 1:4,000) and produced the "fried-egg" morphology typical of most mollicutes. Growth occurred both aerobically and anaerobically (as determined by the GasPak method). The ability to catabolize glucose and mannose and the ability to hydrolyze arginine varied among the three strains. All three strains required sterol for growth, and none of the strains hydrolyzed urea. The guanine-plus-cytosine contents of the DNAs of strains UIAT, VIST, and GIHT were determined to be 26.9, 27.0, and 26.6 mol%, respectively. Our data indicate that the three strains represent new Mycoplasma species, for which we propose the names Mycoplasma auris, Mycoplasma cottewii, and Mycoplasma yeatsii. The type strain of M. auris is UIA (= ATCC 51348 = NCTC 11731), the type strain of M. cottewii is VIS (= ATCC 51347 = NCTC 11732), and the type strain of M. yeatsii is GIH (= ATCC 51346 = NCTC 11730).

Animals↗
PubMed2000

An animal model for external ear canal inflammation.

OBJECTIVE: To develop an animal model for testing efficacy of anti-inflammatory drugs designed to treat external ear canal (EAC) disease. METHODS: Histological and morphometric methods were used to characterize EAC inflammation produced by topical application of tetradecanoylphorbol acetate (TPA) in mice. The effects of both single and repeated TPA applications were studied. A treatment trial was performed to evaluate the effects of a ciprofloxacin/hydrocortisone suspension on TPA-induced EAC inflammation. In 10 animals, two bilateral applications of TPA were made, spaced 24 hours apart. Immediately after the second TPA application, otic suspension was applied unilaterally four times over a 48-hour period. The contralateral EACs were left untreated to provide TPA-only controls. RESULTS: Twenty-four hours after a single TPA application, EAC skin showed polymorphonuclear (PMN) leukocyte infiltration, vascular dilation, and thickening of the dermis and epidermis. Dermal and epidermal thickening were more pronounced after two TPA applications and PMN leukocyte infiltration remained high 48 hours after a second TPA placement. After treatment with the otic suspension, PMN leukocyte counts were reduced by an average of 76% relative to EACs that received TPA only. There was also statistically significant reduction of dermal swelling and a trend toward reduced epidermal thickness. Vascular dilation was clearly reduced as well EACs that received four applications of the suspension alone showed no adverse effects compared with those that received saline. CONCLUSION: TPA-induced inflammation of the mouse EAC provides a suitable model for testing the therapeutic efficacy of anti-inflammatory agents being considered for clinical use.

Administration, Topical↗
PubMed1994

Diseases of the ear canal.

Otitis externa can be a complicated and difficult disease to diagnose and treat. Because of the unique physiology of the ear canal and common pathophysiology of otitis externa regardless of the underlying cause, the clinician must rely on history, dermatologic examination, and ancillary tests to determine the cause and appropriate therapy for a particular case.

Animals↗
PubMed1997

Comparison of air- and bone-conducted brain stem auditory evoked responses in young dogs and dogs with bilateral ear canal obstruction.

Brain stem responses to air- and bone-conducted stimuli were analyzed in 11 young dogs, using an in-the-ear transducer and a vibrator designed for human hearing tests, respectively. The mean thresholds were 0 to 10 dB for air-conducted stimuli and 50 to 60 dB for bone-conducted stimuli. The wave forms and inter-peak latencies of the waves of the auditory evoked responses elicited by air-conducted and bone-conducted stimuli were similar. This indicated that the signals had the same origin and thus both the air-conducted and the bone-conducted responses could be considered to be auditory responses. Measurement of air-conducted and bone-conducted brain stem-evoked responses in five dogs with bilateral chronic obstructive ear disease revealed thresholds of 50 to 60 dB for air-conducted stimuli and 60 to 70 dB for bone-conducted stimuli. By comparison of these results with those in the 11 young dogs, it could be concluded that there was hearing loss other than that caused by obstruction of the ear canals.

Aging↗
PubMed1984

Spontaneous otoacoustic emissions in chinchilla ear canals: correlation with histopathology and suppression by external tones.

Two cases of spontaneous otoacoustic emissions (SOAEs) have been found among a sample of 28 chinchilla ears after noise exposure, and no cases of SOAEs have been found among 28 unexposed ears. Further observations of the characteristics of SOAEs recorded in the ear canals of two chinchillas after noise exposure are described. These signals were tonal, robust, and could be suppressed by presenting external tones to the ear. Histopathological evaluation of the cochlea of emitting ears revealed discrete basal-turn lesions near the positions corresponding to the frequencies of the emissions. Behavioral threshold shifts measured in one animal after noise exposure and acoustic intermodulation distortion product behavior in the other both suggest a region of increased vibratory response of the cochlear partition near the location of the SOAE. Results from these emitting ears support a hypothesis that a punctate loss of the organ of Corti (OC) may facilitate the occurrence of an SOAE. We further hypothesize that the following conditions are both necessary and sufficient for an SOAE to occur: (1) functional disruption of a normally present biomechanical control mechanism in a region of the OC; (2) presence of functionally active OC (especially outer hair cells) adjacent to the region. The observations from ears possessing SOAEs provide strong, though indirect support for active and nonlinear models in interpreting cochlear biomechanical phenomena.

Acoustic Stimulation↗
PubMed1990

Effects of electrode placement on the auditory brainstem response using ear canal electrodes.

The effects of electrode placement on the latency and amplitude of the auditory brainstem response (ABR) were investigated in normal-hearing subjects. Ear canal (EC) electrodes were used in conjunction with surface electrodes to obtain ABRs. Three electrode combinations were evaluated: (1) vertex-EC-EC; (2) vertex-EC-neck; and (3) forehead-EC-neck. Absolute and interwave latencies and absolute and relative amplitudes were computed for Waves I, III, and V at 75 dB SL. Standard errors of measurement (SEmeas) revealed excellent test-retest reliability for latency (SEmeas = 0.06 ms) but only fair reliability for amplitude (SEmeas = 55 nv). No reliability differences were observed among the three electrode combinations. No significant latency or interwave latency differences were found among the three montages. No amplitude differences were found for Waves I and III among the montages. However, the Wave V amplitude was larger for the vertex-EC-EC and vertex-EC-neck montages than for the forehead-EC-neck montage. Because the vertex-EC-EC montage does not require additional electrodes on the contralateral neck, this montage is recommended.

Acoustic Stimulation↗
PubMed1999

Correction of low-set ear: superoposterior mobilization of the ear as a transposition flap pivoted on the ear canal with burring of the superoposterior canal wall.

In a number of congenital, developmental, and postoperative conditions, many patients have a difference in the vertical and anteroposterior position of the ears. On correction of this deformity, the most difficult problem is the low and anterior location of the external auditory canal. To overcome this unyielding limitation, the authors perform superoposterior transposition of the low-set ear pivoted on the ear canal after making a new path for the canal by burring of the thick superoposterior canal wall. A mastoid hairline incision is followed by three-quarters circumferential subpericranial dissection around the bony ear canal posteriorly. A preauricular incision is followed by subcutaneous dissection anteriorly. By using the natural deformability of the cartilaginous ear canal, the S-shaped canal can be straightened through a new path made by burring of the thick superoposterior wall. Then the low-set ear can be mobilized superoposteriorly as a transposition flap pivoted on the ear canal with minimal tension by straightening of the canal. The corrected auricular position can be maintained by (1) several permanent sutures between the cavum conchae and the mastoid and deep temporal fascia, (2) a suspensory temporoparietal fascial loop, and (3) a skin support provided by the repair in an elevated position and V-Y-plasty or Z-plasty on the lower pole of the ear. From December of 1997 to October of 1998, three cases with a maximum follow-up of 15 months were examined. Symmetric ear position was achieved and maintained on both frontal and lateral views after the operation in all cases. This new technique for correction of low-set ear produces symmetric ear position in both vertical and anteroposterior dimensions for a long time. In addition, it can be performed with various other surgical procedures safely and simultaneously in a variety of pathologic conditions.

Adolescent↗
PubMed1986

Acoustic distortion in the ear canal. I. Cubic difference tones: effects of acute noise injury.

Acoustic emissions in the form of cubic difference tones (CDT's), 2f1-f2, were measured in the ear canals of gerbils and cats. The state of the cochlea was manipulated by means of acute exposure to noise and was monitored with the aid of the whole-nerve response to tone pips. The resulting shifts in the levels of emissions generated by pairs of primary tones of equal intensity were then compared to the corresponding threshold shifts of the whole-nerve response across frequency. Data obtained from normal ears before injury indicate that the absolute thresholds of the whole-nerve responses across frequency are not necessarily good predictors of the absolute levels of CDT emissions generated by 70- and 80-dB SPL primaries. While high emission levels were often linked to low whole-nerve thresholds in pre-exposed ears, instances of animals with sensitive whole-nerve thresholds coupled with very weak emissions were also found. Conversely, animals with poor whole-nerve thresholds (shifted by up to 30 dB) could occasionally have high levels of emissions. After acute noise injury, however, the shifts of emission levels as a function of the center frequency of the primary-tone pair largely corresponded to the threshold shifts seen in the whole-nerve response. In other words, the temporary level shift of an acoustic emission largely reflected the acute change to a specific cochlear region associated with the primary frequencies.

Acoustic Stimulation↗
PubMedDate not supplied

Comparison of microbial isolates and susceptibility patterns from the external ear canal of dogs with otitis externa.

Otic exudate was obtained from 33 dogs with otitis externa for cytopathology and culture. Two samples were taken from the same location in the external ear canal, for a total of 100 samples. Thirty-six (36%) samples isolated only a single organism, of which 21 (21%) were Malassezia spp. Two organisms were present in 23 (23%) of the samples. Cultures of the two samples agreed in 40 (80%) of the 50 pairs. Cytopathology agreed with culture results only 68% of the time. Cytopathology and culture may not be as definitive as previously assumed because of apparent variability of the microbial population within the external canal.

Animals↗
PubMed2006

Benign vascular lesions involving the external ear canal.

Benign vascular lesions include various forms whose classification has created some controversies in the literature. The observation of two rare cases of vascular bulge of the external ear canal prompted us to analyze the essential features of these lesions. One case was observed during an episode of otitis media, the other one was an incidental finding, and both are still on follow-up without treatment. The lesions are unmodified after 4 and 10 years, respectively. Vascular malformations can be differentiated from vascular tumors since they are present at birth, are generally stable, and do not involute. An attending strategy is justified unless symptoms occur.

Aged↗
PubMed1992

[Bacterial flora of the external ear canal. 2. Effect of irradiation].

A group of 34 patients with nasopharyngeal cancer was studied to observe the influence of the radiation effect on the bacterial flora of the external ear canal. The effects were observed before and after radiation therapy. The Gram-positive aerobes, especially the Staphylococcus epidermidis, were found to have decreased (57.1% to 37.7%). Though there was a slight increase of the Gram-negative aerobes (44.6% to 50.8%), it was not statistically significant. We concluded that the higher incidence of otitis externa induced by irradiation is due to the local radiation reaction, but not the shifted colonization of the potentially pathologic flora.

Adolescent↗