Post-mortem changes in hair bundles of the guinea pig and human cochlea studied by high-resolution scanning microscopy.

High-resolution scanning electron microscopic studies have been made on the guinea pig cochlea on material fixed from 15 min to 4 h post-mortem. Changes in the surface texture and cross-links of stereocilia were detected after only 15 min. Such changes included an increase in granularity of the surface membrane, thickening, stretching and fracturing of all types of cross-links accompanied by splaying apart and loss of rigidity of stereocilia. These changes were more pronounced in the basal turns of the cochlea and in general increased in severity and spread more apically with increasing times post-mortem. By 4 h, many hair bundles consisted of a fused amorphous mass in which individual stereocilia were not discernible. Remarkably at this time, some hair bundles appeared to have suffered little damage. These results will facilitate better discrimination between effects solely due to post-mortem necrotic changes and those due to specific actions of ototoxic drugs and other insults.