Stereo-kinociliar bonds in mammalian vestibular organs.

The ultrastructure of the apical end of the hair bundle of the vestibular hair cell in the guinea pig was studied by transmission electron microscopy using osmium and aldehyde-osmium fixed specimens. Stereo-kinociliar bonds were a regular finding in both cristae and maculae. The bond unit consisted of two parts: extracellular, interciliar filaments of macromolecular size and an intracellular structure, bound to the plasma membrane within the kinocilia. In the cristae, the stereo-kinociliar bonding was usually effected by only one bond unit between a single stereocilium and the kinocilium; in the maculae the units were generally paired and several stereocilia were coupled to each kinocilium.