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W Luxford

Publications and source records attributed to W Luxford.

4 recordsLinked to original sources
PubMed2000

Human nonsyndromic hereditary deafness DFNA17 is due to a mutation in nonmuscle myosin MYH9.

The authors had previously mapped a new locus-DFNA17, for nonsyndromic hereditary hearing impairment-to chromosome 22q12.2-q13. 3. DFNA17 spans a 17- to 23-cM region, and MYH9, a nonmuscle-myosin heavy-chain gene, is located within the linked region. Because of the importance of myosins in hearing, MYH9 was tested as a candidate gene for DFNA17. Expression of MYH9 in the rat cochlea was confirmed using reverse transcriptase-PCR and immunohistochemistry. MYH9 was immunolocalized in the organ of Corti, the subcentral region of the spiral ligament, and the Reissner membrane. Sequence analysis of MYH9 in a family with DFNA17 identified, at nucleotide 2114, a G-->A transposition that cosegregated with the inherited autosomal dominant hearing impairment. This missense mutation changes codon 705 from an invariant arginine (R) to histidine (H), R705H, within a highly conserved SH1 linker region. Previous studies have shown that modification of amino acid residues within the SH1 helix causes dysfunction of the ATPase activity of the motor domain in myosin II. Both the precise role of MYH9 in the cochlea and the mechanism by which the R705H mutation leads to the DFNA17 phenotype (progressive hearing impairment and cochleosaccular degeneration) remain to be elucidated.

Amino Acid Sequence↗
PubMed2000

The Clarion electrode positioner: temporal bone studies.

OBJECTIVE: To study the relationship of the Clarion electrode to the modiolus when using an intracochlear positioner. BACKGROUND: There are theoretical advantages to positioning a cochlear implant electrode in close proximity to the modiolus. This may allow more focused, discrete fields of electrical current, reducing both requirements to achieve threshold and the channel interactions associated with the simultaneous and nonsimultaneous stimulation of closely spaced electrodes. METHODS: Ten fresh temporal bones were used to assess the position of the electrode in the scala tympani with the positioner in place. The bones were X-rayed after implantation. The relationship of the electrode to the modiolus was studied by calculating a ratio between the curve assumed by the electrode in relationship to the outer wall of the cochlea. The depth of insertion was evaluated in degrees or number of turns around the modiolus. RESULTS: The electrode was brought closer to the modiolus and a greater depth of insertion was achieved in all cases with the positioner. CONCLUSION: The intracochlear positioner is capable of bringing the electrode consistently closer to the neural elements within the modiolus.

Cochlear Implantation↗
PubMed1991

Absence of both auditory evoked potentials and auditory percepts dependent on timing cues.

An 11-yr-old girl had an absence of sensory components of auditory evoked potentials (brainstem, middle and long-latency) to click and tone burst stimuli that she could clearly hear. Psychoacoustic tests revealed a marked impairment of those auditory perceptions dependent on temporal cues, that is, lateralization of binaural clicks, change of binaural masked threshold with changes in signal phase, binaural beats, detection of paired monaural clicks, monaural detection of a silent gap in a sound, and monaural threshold elevation for short duration tones. In contrast, auditory functions reflecting intensity or frequency discriminations (difference limens) were only minimally impaired. Pure tone audiometry showed a moderate (50 dB) bilateral hearing loss with a disproportionate severe loss of word intelligibility. Those auditory evoked potentials that were preserved included (1) cochlear microphonics reflecting hair cell activity; (2) cortical sustained potentials reflecting processing of slowly changing signals; and (3) long-latency cognitive components (P300, processing negativity) reflecting endogenous auditory cognitive processes. Both the evoked potential and perceptual deficits are attributed to changes in temporal encoding of acoustic signals perhaps occurring at the synapse between hair cell and eighth nerve dendrites. The results from this patient are discussed in relation to previously published cases with absent auditory evoked potentials and preserved hearing.

Acoustic Stimulation↗