RESUMO
A new mutation of the inner ear was discovered in golden hamsters raised in our laboratories. Although scanning electron microscopy showed a normal arrangement of individual stereocilia on the first row of outer hair cells, the entire bundle of stereocilia were irregular in orientation and scattered in several directions. Seventy per cent to 85% of the stereociliary bundles were found to be abnormal throughout the cochlea, with no apparent difference between the right and left sides. Transmission electron microscopy showed that the cuticles of the first row of the outer hair cells were dislocated, but no dislocation due to this mutation was apparent in the lower portions. This mutation of the inner ear was already present in the basal turn four days after birth. The kinocilium was located outside of the stereocilia in the first row of outer hair cells, but sensory hairs were scattered in every direction, as in the adult animals. A comparison of auditory brainstem response tests revealed no difference between the abnormal and normal hamsters.
