Thermal-noise-limited transduction observed in mechanosensory receptors of the inner ear

Hair cells, the mechanosensory receptors of the inner ear, underlie the senses of hearing and balance. Adult mammals cannot adequately replenish lost hair cells, whose loss often results in deafness or balance disorders. To determine the molecular basis of this deficiency, we investigated the development of a murine vestibular organ, the utricle. Here we show that two members of the SoxC family of transcription factors, Sox4 and Sox11, are down-regulated after the epoch of hair cell development. Conditional ablation of SoxC genes in vivo results in stunted sensory organs of the inner ear and loss of hair cells. Enhanced expression of SoxC genes in vitro conversely restores supporting cell proliferation and the production of new hair cells in adult sensory epithelia. These results imply that SoxC genes govern hair cell production and thus advance these genes as targets for the restoration of hearing and balance.

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Thermal Noise and Active Processes in the Inner Ear: Relating Theory to Experiment

HEARING — Physiological Bases and Psychophysics ◽

10.1007/978-3-642-69257-4_8 ◽

1938 ◽

pp. 51-57

Author(s):

William Bialek

Keyword(s):

Inner Ear ◽

Thermal Noise ◽

Active Processes

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Otoconia formation in the chick embryo

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100076494 ◽

1983 ◽

Vol 41 ◽

pp. 572-573

Author(s):

C.D. Fermin ◽

M. Igarashi

Keyword(s):

Chick Embryo ◽

Inner Ear ◽

Gallus Domesticus ◽

The Body ◽

Abnormal Behavior ◽

Intensive Study ◽

Basic Fuchsin ◽

Gestational Period ◽

Sensory Epithelia ◽

Transmission Electron

Otoconia are microscopic geometric structures that cover the sensory epithelia of the utricle and saccule (gravitational receptors) of mammals, and the lagena macula of birds. The importance of otoconia for maintanance of the body balance is evidenced by the abnormal behavior of species with genetic defects of otolith. Although a few reports have dealt with otoconia formation, some basic questions remain unanswered. The chick embryo is desirable for studying otoconial formation because its inner ear structures are easily accessible, and its gestational period is short (21 days of incubation).The results described here are part of an intensive study intended to examine the morphogenesis of the otoconia in the chick embryo (Gallus- domesticus) inner ear. We used chick embryos from the 4th day of incubation until hatching, and examined the specimens with light (LM) and transmission electron microscopy (TEM). The embryos were decapitated, and fixed by immersion with 3% cold glutaraldehyde. The ears and their parts were dissected out under the microscope; no decalcification was used. For LM, the ears were embedded in JB-4 plastic, cut serially at 5 micra and stained with 0.2% toluidine blue and 0.1% basic fuchsin in 25% alcohol.

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Ultra-spatially resolved synchrotron powered FT-IR microspectroscopy of individual cells of biological material

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100140798 ◽

1995 ◽

Vol 53 ◽

pp. 884-885

Author(s):

David L. Wetzel ◽

John A. Reffner ◽

Gwyn P. Williams

Keyword(s):

Thermal Noise ◽

Spot Size ◽

Acquisition Time ◽

Thermal Source ◽

Signal To Noise ◽

Spatially Resolved ◽

Good Spatial Resolution ◽

Small Spot ◽

Ft Ir ◽

Ir Microspectroscopy

Synchrotron radiation is 100 to 1000 times brighter than a thermal source such as a globar. It is not accompanied with thermal noise and it is highly directional and nondivergent. For these reasons, it is well suited for ultra-spatially resolved FT-IR microspectroscopy. In efforts to attain good spatial resolution in FT-IR microspectroscopy with a thermal source, a considerable fraction of the infrared beam focused onto the specimen is lost when projected remote apertures are used to achieve a small spot size. This is the case because of divergence in the beam from that source. Also the brightness is limited and it is necessary to compromise on the signal-to-noise or to expect a long acquisition time from coadding many scans. A synchrotron powered FT-IR Microspectrometer does not suffer from this effect. Since most of the unaperatured beam’s energy makes it through even a 12 × 12 μm aperture, that is a starting place for aperture dimension reduction.

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