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G K Martin

Publications and source records attributed to G K Martin.

76 records · Page 5Linked to original sources
PubMedDate not supplied

Otoacoustic emissions in ears with hearing loss.

Fifty ears of 37 patients demonstrating several common types of hearing impairment were examined for the presence of spontaneous and evoked otoacoustic emissions to investigate the relationship of acoustic emissions to hearing pathology. Of the 50 ears, 44 exhibited various degrees of sensorineural hearing loss. Evoked otoacoustic emissions to clicks were detected in 34 of 35 sensorineural hearing loss ears with a subjective click threshold less than 55 dB SPL (25 dB nHL). None of nine ears with sensorineural hearing impairment and a subjective click threshold greater than 55 dB SPL demonstrated click-evoked emissions. Spectral analyses revealed that the constituent frequency components of evoked emissions were always within the frequency range where audiometric thresholds were less than 35 dB HL, and in the majority (94%) of cases, thresholds were less than 25 dB HL. In ears with relatively well-preserved hearing within the frequency range of click or 1.5-kHz toneburst stimuli, the basic features of evoked emissions were similar to those described for normal ears. Similarly, for ears demonstrating spontaneous otoacoustic emissions, estimated audiometric thresholds at the emitted frequencies were always less than 20 dB HL. The influence of the type of otologic pathology on acoustic emissions was studied in a subset of ears exhibiting typical high-frequency hearing losses. Ears with a noise-induced impairment showed a significant reduction in the incidence of both spontaneous emissions and spectral peaks in evoked emissions that was not evident in ears with similar patterns of hearing loss caused by other factors.

Acoustic Stimulation↗
PubMedDate not supplied

Frozen-section autoradiography of the cochlea: evidence for differential distribution of amino acids.

A histological method is described for embedding the whole cochlea in an egg yolk medium that permits frozen sectioning in the mid-modiolar plane. Resulting tissues can be processed using standard autoradiographic techniques and stained with Nissl or silver impregnation methods. Following identical intracochlear injections of tritiated proline or leucine and frozen sectioning of embedded cochleae, differential uptake patterns within the cochlea were revealed for these amino acids. Frozen sectioning of the cochlea promises to provide an efficient means to examine specific labeling patterns within the cochlear duct for compounds suspected of contributing to cochlear function by permitting the application of multiple histological techniques including routine stains and anterograde and retrograde tracers.

Animals↗