Subpixel tracking for the analysis of outer hair cell movements.
CONCLUSIONS
Videomicroscopy with subpixel analysis is an excellent system for quantification of outer hair cell (OHC) movements. The resolution of a few nanometers is accurate enough to show induced differences of electromotility.


OBJECTIVE
Electromotility of OHCs is a voltage-dependent process resulting from a membrane protein named prestin. Voltage sensitivity is conferred to prestin by intracellular anions. Reduction of these anions reduces electromotility. Videomicroscopy and subpixel tracking combine video-based analysis with a resolution of few nanometers. The aim of this study was to show the feasibility of a system for quantification of OHC movements.


METHODS
Electromotility was investigated under normal and reduced intracellular chloride conditions. Cells were stimulated by the patch-clamp technique. Voltage steps were 500 ms long, ranging from -170 to +30 mV in 10 mV steps.


RESULTS
As in previous studies our results show the following. The direction of OHC movement depends on the polarity of voltage steps, length changes are not equal for symmetrical voltage steps of opposite polarity, average shortening for a depolarizing step (-70 mV to +30 mV) is about 13 nm/mV. Hyperpolarization (-70 mV to -170 mV) on average evokes elongations of about 3 nm/mV. Half maximal chloride concentration reduces motility by 14%; half maximal electromotility is reached by a 94% reduction of chloride.
Canis
M
M
Department of Otorhinolaryngology, Head and Neck Surgery, University of Munich, Germany. martin.canis@med.uni-muenchen.de
Ortner
M
M
Olzowy
B
B
Jahn
K
K
Strupp
M
M
Hemmert
W
W
Berghaus
A
A
Suckfuell
M
M
D000818:Animals; D002465:Cell Movement / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D018715:Microscopy, Video; D036103:Nanotechnology; D018408:Patch-Clamp Techniques; D011506:Proteins / Q000502:physiology; D050994:Voltage-Dependent Anion Channels / Q000502:physiology
D002712:Chlorides; C498722:Pres protein, Cavia porcellus; D011506:Proteins; D050994:Voltage-Dependent Anion Channels