2 MODES OF AUDITORY HEIR CELL LOSS FOLLOWING ACOUSTIC OVERSTIMULATIONIN THE AVIAN INNER-EAR

To determine the type of cell death occurring and how the removal of d amaged cells proceeds following overstimulation, we examined chick bas ilar papillae using an in situ DNA nick end labeling method and transm ission electron microscopy. Two distinct modes of hair cell loss were identified. First, hair cells which had not progressed into typical ce ll death processes, apoptosis or ncecrosis, were deleted by extrusion from the epithelium just after sound exposure. Second, hair cells mani fested degeneration through the process of apoptosis, then further det erioration within the epithelium after the beginning of the process of hair cell regeneration. The latter mode may contribute to the followi ng repair processes.