Intercellular contacts between chick stereocilia after acoustic overstimulation.

The goal of this study was to analyze the distribution of actin and the shape of stereocilia of chick hair cells that survive acoustic trauma. Chicks were exposed to intense octave band noise for 4 h. They were killed either immediately after the exposure, after 6 or after 72 h. The basilar papillae were examined using scanning electron microscopy and fluorescence microscopy, with phalloidin as an actin-specific probe. Injured hair cells which survived the trauma displayed disorganized stereocilia bundles, elongated stereocilia, and supernumerary stereocilia bundles. Tips of stereocilia in the damaged region of the basilar papilla appeared to be in contact with tips of stereocilia of neighboring hair cells. These contacts may represent 'stress links' which appear in traumatized hair cells. These results show that substantial changes in stereocilia occur within hours of exposure to intense noise. We speculate that surviving hair cells may play a role in the process of repair of the basilar papilla after noise trauma and that the changes in stereocilia structure described here are related to this role.