title: Mechanical amplification exhibited by quiescent saccular hair bundles.
abstract: Spontaneous oscillations exhibited by free-standing hair bundles from the Bullfrog sacculus suggest the existence of an active process that might underlie the exquisite sensitivity of the sacculus to mechanical stimulation. However, this spontaneous activity is suppressed by coupling to an overlying membrane, which applies a large mechanical load on the bundle. How a quiescent hair bundle utilizes its active process is still unknown. We studied the dynamics of motion of individual hair bundles under different offsets in the bundle position, and observed the occurrence of spikes in hair-bundle motion, associated with the generation of active work. These mechanical spikes can be evoked by a sinusoidal stimulus, leading to an amplified movement of the bundle with respect to the passive response. Amplitude gain reached as high as 100-fold at small stimulus amplitudes. Amplification of motion decreased with increasing amplitude of stimulation, ceasing at ∼6-12 pN stimuli. Results from numerical simulations suggest that the adaptation process, mediated by myosin 1c, is not required for the production of mechanical spikes.
authors.affiliation: Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California.
authors.forename: Yuttana
authors.initials: Y
authors.lastname: Roongthumskul
authors.affiliation: Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California. Electronic address: bozovic@physics.ucla.edu.
authors.forename: Dolores
authors.initials: D
authors.lastname: Bozovic
mesh_terms: D000818:Animals; D003198:Computer Simulation; D006198:Hair Cells, Auditory / Q000502:physiology*; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D008959:Models, Neurological; D009038:Motion; D061848:Optical Imaging; D010507:Periodicity; D010812:Physical Stimulation / Q000379:methods; D011892:Rana catesbeiana; D012444:Saccule and Utricle / Q000502:physiology*; D046509:Tissue Culture Techniques