The ratio of elastic moduli of cochlear outer hair cells derived from osmotic experiments

Ratnanather, J. Tilak; Zhi, Man; Brownell, William E.; Popel, Aleksander S.

doi:10.1121/1.414631

Cited by 24 publications

(16 citation statements)

References 17 publications

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“…Following Ratnanather et al (1996a), the strains for each treated cell, e z and e c , were calculated at the data points indicated by the error bars in Fig. 1c and then averaged.…”

Section: Results and Analysismentioning

confidence: 99%

“…Isotonicity was defined as a final osmolarity of 293-297 mOsm. Hypotonicity was defined as a solution which differed from the isotonic solution by DC = À17, À30 and À45 mOsm (Ratnanather et al, 1996a) and was made by diluting the isotonic solution with distilled water. Four types of solutions were made: phosphate buffered saline (PBS), salicylate, salt and ketoglutarate.…”

Section: Solutionsmentioning

confidence: 99%

“…In addition, we have used data from OHC shape changes in response to osmotic challenge of different magnitudes (À17, À30 and À45 mOsm) to assess the mechanical properties of the OHC (Ratnanather et al, 1996a). The ratio of the longitudinal strain to the circumferential strain was found to be À0.72 and independent of the magnitude of the osmotic challenge, and was used by Spector et al (1998) along with other data to estimate the in-plane and bending stiffnesses of the OHC wall.…”

Section: Introductionmentioning

confidence: 99%

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Hypotonic swelling of salicylate-treated cochlear outer hair cells

et al. 2007

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The outer hair cell (OHC) is a hydrostat with a low hydraulic conductivity of Pf=3x10(-4) cm/s across the plasma membrane (PM) and subsurface cisterna that make up the OHC's lateral wall. The SSC is structurally and functionally a transport barrier in normal cells that is known to be disrupted by salicylate. The effect of sodium salicylate on Pf is determined from osmotic experiments in which isolated, control and salicylate-treated OHCs were exposed to hypotonic solutions in a constant flow chamber. The value of Pf=3.5+/-0.5x10(-4) cm/s (mean+/-s.e.m., n=34) for salicylate-treated OHCs was not significantly different from Pf=2.4+/-0.3x10(-4) cm/s (mean+/-s.e.m., n=31) for untreated OHCs (p=.3302). Thus Pf is determined by the PM and is unaffected by salicylate treatment. The ratio of longitudinal strain to radial strain epsilonz/epsilonc=-0.76 for salicylate-treated OHCs was significantly smaller (p=.0143) from -0.72 for untreated OHCs, and is also independent of the magnitude of the applied osmotic challenge. Salicylate-treated OHCs took longer to attain a steady-state volume which is larger than that for untreated OHCs and increased in volume by 8-15% prior to hypotonic perfusion unlike sodium alpha-ketoglutarate-treated OHCs. It is suggested that depolymerization of cytoskeletal proteins and/or glycogen may be responsible for the large volume increase in salicylate-treated OHCs as well as the different responses to different modes of application of the hypotonic solution.

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“…Following Ratnanather et al (1996a), the strains for each treated cell, e z and e c , were calculated at the data points indicated by the error bars in Fig. 1c and then averaged.…”

Section: Results and Analysismentioning

confidence: 99%

Section: Solutionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hypotonic swelling of salicylate-treated cochlear outer hair cells

et al. 2007

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“…The elastic property of the membrane in treated cells is characterized by the area modulus. The value 0.13 Ϯ 0.02 for the area modulus K of trypsin-digested cells is larger by at least a factor two than those of undigested cells: 0.07 N͞m (21) and 0.054 N͞m (22). Standard values for the modulus of lipid bilayers range from 1.5 to 10 N͞m (23).…”

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confidence: 96%

Electrically driven motor in the outer hair cell: Effect of a mechanical constraint

Adachi

Iwasa

1999

Proc. Natl. Acad. Sci. U.S.A.

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The outer hair cell has a unique voltagedependent motility associated with charge transfer across the plasma membrane. To examine mechanical changes in the membrane that are coupled with such charge movements, we digested the undercoating of the membrane with trypsin. We inf lated the cell into a sphere and constrained the surface area by not allowing volume changes. We found that this constraint on the membrane area sharply reduced motor-associated charge movement across the membrane, demonstrating that charge transfer is directly coupled with membrane area change. This electromechanical coupling in the plasma membrane must be the key element for the motile mechanism of the outer hair cell.The outer hair cell changes the length of its cylindrical cell body in response to changes in the membrane potential (1-5), reaching a frequency of at least 20 kHz (6, 7). Because of its strategic location in the inner ear connecting the basilar membrane and the reticular lamina, this mechano-receptor cell presumably serves as an actuator in a feedback loop affecting vibrations of these tissues and thereby modulating the sensitivity of the mammalian ear (see refs. 8 and 9 for review). For this reason, the mechanism of this motility and its biological function have been a focus of intense research. For operating at high frequencies, a direct transduction mechanism would be advantageous. Indeed, the cell appears to be driven by a membrane-based motor that directly uses electrical energy available at the plasma membrane. The lateral membrane of the cell has charges that are transferable across the membrane (10-12), analogous to gating charges of voltage-gated ion transporters. These charges enable the cell to obtain electrical energy. If the electrical energy obtained by charge transfer across the membrane is directly converted into mechanical energy in a manner similar to piezoelectricity, the charge transfer must be reciprocally affected by an externally applied tension. That has indeed been experimentally verified (12-14), leading to estimates of the area change of a single motor unit (7,12,13).However, the simple characterization of the motor as described above is somewhat uncertain because of the structural complexity of the lateral membrane of the outer hair cell. The structural complexity obscures the molecular identity of the motor. In addition, the lateral membrane, where the motor resides, has an intricate structure of many elements (see ref. 15 for review) whose role in motility is uncertain. These factors leave uncertainties in the magnitude of tension that affects the motor.To characterize the elements of the motile mechanism in the plasma membrane, we examine a simplified system, in which the cortical cytoskeleton is digested with trypsin (13,16,17). The cells treated internally with trypsin can no longer maintain their ordinary cylindrical shape and become spherical when the internal pressure is elevated. The conspicuous length changes (up to 5%), which are elicited by changes in the membrane potential of ...

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“…The dead time for volume changes induced by hypotonic challenge was 210 sec in the data of Ratnanather et al (1996), and a time constant of 480 sec may be obtained from their plots. In contrast to these results, activation of purinergic receptors produced cell swelling within seconds (Housley et al, 1995).…”

Section: Time-dependent Volume Changesmentioning

confidence: 99%

Acetylcholine, Outer Hair Cell Electromotility, and the Cochlear Amplifier

et al. 1997

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The dominant efferent innervation of the cochlea terminates on outer hair cells (OHCs), with acetylcholine (ACh) being its principal neurotransmitter. OHCs respond with a somatic shape change to alterations in their membrane potential, and this electromotile response is believed to provide mechanical feedback to the basilar membrane. We examine the effects of ACh on electromotile responses in isolated OHCs and attempt to deduce the mechanism of ACh action. Axial electromotile amplitude and cell compliance increase in the presence of the ligand. This response occurs with a significantly greater latency than membrane current and potential changes attributable to ACh and is contemporaneous with Ca 2ϩ release from intracellular stores. It is likely that increased axial compliance largely accounts for the increase in motility. The mechanical responses are probably related to a recently demonstrated slow efferent effect. The implications of the present findings related to commonly assumed efferent behavior in vivo are considered.

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The ratio of elastic moduli of cochlear outer hair cells derived from osmotic experiments

Cited by 24 publications

References 17 publications

Hypotonic swelling of salicylate-treated cochlear outer hair cells

Hypotonic swelling of salicylate-treated cochlear outer hair cells

Electrically driven motor in the outer hair cell: Effect of a mechanical constraint

Acetylcholine, Outer Hair Cell Electromotility, and the Cochlear Amplifier

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