Hair Cell Micromechanics, Biophysics and Pathophysiology 
    Individual hair cells or epithelial sheets containing many hair cells can be harvested from the chick cochlea and kept alive in culture medium for hours.  These hair cells are viewed at high magnification with specially designed and equipped microscopes.  An underwater loudspeaker with a 10 micron diameter has been engineered to stimulate the sensory hairs on the isolated hair cells.  This speaker produces a water micro jet that can blow the hairs back and forth as fast as 5.0 – 6.0 kHz.  The hair motion can be rendered in slow motion by illuminating the microscope with stroboscopic light.  An animated GIF image is available as a demonstration (~63kb GIF). 
    Patch clamp electrodes attached to the plasma membrane of the hair cell allow us to measure receptor currents in response to the hair bundle stimulation. 
    There are currently two hair cell projects in progress.  One of these over-stimulates the hair bundle to examine the consequences of acoustic injury on the hair cell response.  These studies examine the consequences of damage to the hair bundle, and its tip links on the physiology of the cell itself.  The second area is concerned with the relationship between hair bundle stimulation and neurotransmitter release.  Capacitance measures are used to determine the degree of vesicle fusion with the plasma membrane during the injection of depolarizing current into the hair cell.  The quantitative relationship between hair cell stimulation and neurotransmitter release remains one of the most poorly understood processes of the hair cells, and these studies address this issue. 
    In addition, we are examining quantitatively the damage and repair of chick hair cell tip links following exposure to intense sound.  The morphologic shapes of the hair bundles when viewed in profile is also being mapped across the sensory epithelium of the chick basilar papilla.  These studies use the scanning electron microscope to examine the hair bundles. 
    Finally, studies are under way to examine the mRNA of in vitro damaged hair cells to ascertain the response to injury at the molecular level.