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The role of myosin molecules in the transduction process adaptation in hair cells is discussed. Hair cells were isolated from the bullfrog's sacculus and their transduction currents were recorded in whole-cell, tight-seal electrodes. An amplifier operating without series-resistance compensation was used to measure these currents. Results indicate that adenine nucleotides are part of hair cell adaptation and that this process is myosin motor-powered.

A hair bundle is a cluster of stereocilia which forms a direct mechanical connection with transduction channels through gating springs. A simplified approach to quantify force and time variables in the gating springs was developed. This approach makes use of a displacement-clamp system which permits a bundle to be deflected or held at a particular position while the requisite force is monitored. Using this system, it was shown that each gating spring exerts a tension of about 8 pN in the resting bundle and can sustain at least 4-13 pN of additional tension.

An individual may hear not only the primary tones but also a different tone of frequencies when listening to two tones, one of frequency f1 and the second of a higher frequency f2. In the early 18th century, Tartini discovered that these illusory sounds were employed to carry melodies in classical compositions. Distortion originates in the cochlea, where they manifest themselves in the basilar membrane's vibration. Hair bundles constitute mechanical impedance to basilar membrane motion and that distortion product forces produced by hair bundles should reciprocally produce propagating distortion products in basilar membrane motion. Hair bundles can thus enhance basilar membrane motion, as they contain myosin.

Bacteriophage display of antibodies provides a method for the generation of immunological reagents against rare and uncharacterized antigens. To ascertain the usefulness of this approach for the characterization of inner-ear proteins, we produced a bacteriophage-displayed antibody-fragment library directed against proteins from the bullfrog's sacculus. This library was probed for bacteriophage that bound to proteins present in a lysate of hair cells, the sensory receptors of the inner ear. The predominant bacteriophage clone after selection expressed an antibody fragment that recognized a single protein in the inner ear. This antigen occurred in both the nonsensory and sensory epithelia of the sacculus. The specificity of the antibody fragment indicates that our bacteriophage-displayed library provides a useful source of immunological tools that should facilitate the identification and biochemical characterization of novel proteins in the inner ear.

We suggest that the vertebrate myosin-I field adopt a common nomenclature system based on the names adopted by the Human Genome Organization (HUGO). At present, the myosin-I nomenclature is very confusing; not only are several systems in use, but several different genes have been given the same name. Despite their faults, we believe that the names adopted by the HUGO nomenclature group for genome annotation are the best compromise, and we recommend universal adoption.

The internal ear works constantly to provide use with the senses of hearing and balance. Evolution has created this efficient, even elegant, structure no larger than a marble, which guides our movement and transmits sounds from the environment. We are usually oblivious to the internal ear's functions because it is so reliable. Our abilities to stand still, move on foot or travel in vehicles at high speeds all depend on the physiology of the internal ear. This organ also provides hearing by translating frequency waves into sounds we can interpret, and amplifying them. The smaller units of the internal ear are the hair cells, which are capable of responding to the minuscule movements of atoms in the environment. Hair cells react over 100,000 times per second. The hair cells are not all alike, but are specialized to pick up certain frequencies. Hair cells respond to mechanical forces, translating them into electrical energy. The electrical messages are carried by the nervous system to the brain where the intensity, duration and frequency of a stimulus is decoded. Internal ears with hair cells have proven to be a successful evolutionary adaptation since they exist in all vertebrates (animals with a spinal column). The number of hair cells is surprisingly small in relation to cells in other sensory organs such as the eye. Our sense of hearing is quite vulnerable to injury from loud noises. Destruction of only 166,000 hair cells would cause severe deafness and loss of balance, whereas a similar loss of cells in the retina of the eye would have a minimal effect on vision.

The Cellular Basis of Hearing: The Biophysics of Hair Cells With over a million essential moving parts, the auditory receptor organ, or cochlea, is the most complex mechanical apparatus in [...]

Abstract. The response properties of hair cells and nerve fibers in the alligator lizard cochlea are frequency selective and tonotopically organized with longitudinal position in the organ. The lengths of [...]

The β subunits of voltage-gated Ca[sup 2+] channels are known to be regulators of the channels' gating properties. Here we report a striking additional function of a β subunit. Screening of chicken cochlear and brain cDNA libraries identified β[sub 4c], a short splice variant of the β[sub 4] subunit. Although β[sub 4c] occurs together with the longer isoforms β[sub 4a] or β[sub 4b] in the brain, eye, heart, and lung, the cochlea expresses exclusively β[sub 4c]. The association of β[sub 4c] with the Ca[sup 2+]-channel α[sub 1] subunit has slight but significant effects on the kinetics of channel activation and inactivation. Yeast two-hybrid and biochemical assays revealed that β[sub 4c] interacts directly with the chromo shadow domain of chromobox protein 2/heterochromatin protein 1γ, (CHCB2/HP1γ), a nuclear protein involved in gene silencing and transcriptional regulation. Coexpression of this protein specifically recruits β[sub 4c] to the nuclei of mammalian cells. Furthermore, β[sub 4c] but not β[sub 4a] dramatically attenuates the genesilencing activity of chromobox protein 2/heterochromatin protein 1γ. The β[sub 4c] subunit is therefore a multifunctional protein that not only constitutes a portion of the Ca[sup 2+] channel but also regulates gene transcription. [ABSTRACT FROM AUTHOR]

Examines the role of claudin protein in vertebrate primordia. Use of protein for mediating cellular adhesion and migration; Elimination of tight junction in myelin and testis; Abolishment of magnesium resorption in the kidney.

Focuses on the role of hair cells in putting ion channels of sensory receptors to work. Functions of ion channels; Comparison between electrically and mechanically sensitive channels; Purpose of active hair bundles' production of forces.