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Biomedical subjects

David C Mountain

Publications and source records attributed to David C Mountain.

3 recordsLinked to original sources
PubMed2006

A hydromechanical biomimetic cochlea: experiments and models.

The construction, measurement, and modeling of an artificial cochlea (ACochlea) are presented in this paper. An artificial basilar membrane (ABM) was made by depositing discrete Cu beams on a piezomembrane substrate. Rather than two fluid channels, as in the mammalian cochlea, a single fluid channel was implemented on one side of the ABM, facilitating the use of a laser to detect the ABM vibration on the other side. Measurements were performed on both the ABM and the ACochlea. The measurement results on the ABM show that the longitudinal coupling on the ABM is very strong. Reduced longitudinal coupling was achieved by cutting the membrane between adjacent beams using a laser. The measured results from the ACochlea with a laser-cut ABM demonstrate cochlear-like features, including traveling waves, sharp high-frequency rolloffs, and place-specific frequency selectivity. Companion computational models of the mechanical devices were formulated and implemented using a circuit simulator. Experimental data were compared with simulation results. The simulation results from the computational models of the ABM and the ACochlea are similar to their experimental counterparts.

Acoustic Stimulation↗
PubMed2004

Progression of hair cell ejection and molecular markers of apoptosis in the avian cochlea following gentamicin treatment.

Aminoglycoside treatment induces caspase-dependent apoptotic death in inner ear sensory hair cells. The timing of apoptotic signaling in sensory hair cells following systemic aminoglycoside treatment has not been characterized in vivo. We administered a single subcutaneous injection of the aminoglycoside gentamicin (300 mg/kg) to 12-16-day-old chicks and used immunocytochemical techniques to document the following responses in affected hair cells: T-cell restricted intracellular antigen-related protein (TIAR) translocation from the nucleus to the cytoplasm, cytochrome c release from the mitochondria, caspase-3 activation, nuclear condensation, and an orderly progression of hair cell ejection from the proximal end of the basilar papilla. Hair cells in the proximal tip exhibited TIAR translocation from the nucleus and aggregation into punctate granules in the cytoplasm 12 hours after injection and the response progressed distally. Cytochrome c release from the mitochondria into the cytoplasm and caspase-3 activation were observed in affected hair cells immediately prior to and during ejection. Hair cell ejection occurred between 30 and 54 hours after injection, beginning in the proximal tip and progressing distally. Nuclear condensation accompanied ejection while the loss of: 1) membrane integrity; 2) phalloidin labeling of F-actin; and 3) TO-PRO-1 labeling of nuclear contents occurred within 48 hours following ejection. Our results present a timeline of aminoglycoside-induced inner ear sensory hair cell apoptotic death that includes an 18-hour window between the initial apoptotic response and the later stages of programmed death signaling that accompany ejection and a gradual breakdown of hair cells following ejection.

Animals↗