Fine structure of guinea pig vestibular kinocilium.

The fine structure of the utricular kinocilium of the guinea pig was examined with transmission electron microscopy after treatment with tannic acid to enhance resolution of internal morphology. The utricular kinocilium was devoid of inner dynein arms and a central pair of microtubules, while a set of outer dynein arms and radial spokes was found. This supports the hypothesis that the vestibular kinocilium is non-motile. Internal electron-dense particles at the attachment sites of the stereo-kinociliar bonds were situated in the immediate periphery of the outer dynein arms, although no visible connection existed between these structures. Findings obtained in the present study seem to give insight on the mechanism of mechanosensory transduction in the vestibular sensory cells.