This proposal is concerned with the micromechanical properties of the sensory hair bundles. The author believes that most of our knowledge about hair bundle behavior is derived from stimuli that produce a static, low frequency or pulse displacement of the hairs. Data from these sources have advanced our understanding of hair micromechanics a great deal. However, the cochlear hair cell is designed to respond at high frequencies, and a physiology based on these stimuli may bias the picture of hair bundle and hair cell behavior. A microwaterjet has been developed which is capable of delivering a non-contact stimulus over a relatively wide bandwidth. Similarly, imaging technology, using stroboscopic illumination or photodiode detection has been developed, and this permits either direct visual observation of high frequency hair bundle motion, or examination of an electrical analogue of that motion. In vitro studies of hair cells on the chick basilar papilla are proposed in which hair bundle behavior is examined in relation to the stimulus waveshape, hair bundle stiffness, differential hair movements, and hair bundle resonance. In addition, the pathophysiology of hair behavior is studied following overstimulation. Hair bundle micromechanics are correlated with the receptor potential of the hair cell, and with the structural morphology of the bundle. Finally, new technological developments will be explored to improve and expand the measurement system. These include the development of reflected light microscopy to image inaccessible hair cells, the implementation of vital dye methods to study Ca++ flux in hair cells during stimulation, and isolated cochlear preparation for the gerbil, and micromechanical studies on isolated hair cells. The investigations presented in this proposal offer a new way of looking at hair cell micromechanics and I am confident that important observations, which expand our appreciation of the transduction process, will emerge.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC000710-05
Application #
2125935
Study Section
Hearing Research Study Section (HAR)
Project Start
1990-07-01
Project End
1996-03-31
Budget Start
1994-07-01
Budget End
1996-03-31
Support Year
5
Fiscal Year
1994
Total Cost
Indirect Cost
Name
University of Pennsylvania
Department
Otolaryngology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Bergevin, Christopher; Freeman, Dennis M; Saunders, James C et al. (2008) Otoacoustic emissions in humans, birds, lizards, and frogs: evidence for multiple generation mechanisms. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 194:665-83
Lazaridis, Evelyn; Saunders, James C (2008) Can you hear me now? A genetic model of otitis media with effusion. J Clin Invest 118:471-4
Saunders, James C (2007) The role of central nervous system plasticity in tinnitus. J Commun Disord 40:313-34
Crumling, Mark A; Saunders, James C (2007) Tonotopic distribution of short-term adaptation properties in the cochlear nerve of normal and acoustically overexposed chicks. J Assoc Res Otolaryngol 8:54-68
Avissar, Michael; Furman, Adam C; Saunders, James C et al. (2007) Adaptation reduces spike-count reliability, but not spike-timing precision, of auditory nerve responses. J Neurosci 27:6461-72
Furman, Adam C; Avissar, Michael; Saunders, James C (2006) The effects of intense sound exposure on phase locking in the chick (Gallus domesticus) cochlear nerve. Eur J Neurosci 24:2003-10
Crumling, Mark A; Saunders, James C (2005) Temperature insensitivity of short-term adaptation in single-units of the chick cochlear nerve. Synapse 58:243-8
Lifshitz, J; Furman, A C; Altman, K W et al. (2004) Spatial tuning curves along the chick basilar papilla in normal and sound-exposed ears. J Assoc Res Otolaryngol 5:171-84
Spassova, Maria A; Avissar, Michael; Furman, Adam C et al. (2004) Evidence that rapid vesicle replenishment of the synaptic ribbon mediates recovery from short-term adaptation at the hair cell afferent synapse. J Assoc Res Otolaryngol 5:376-90
Samaranayake, Haresha; Saunders, James C; Greene, Mark I et al. (2004) Ca(2+) and K(+) (BK) channels in chick hair cells are clustered and colocalized with apical-basal and tonotopic gradients. J Physiol 560:13-20

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