Morphologic Changes in Vestibular Hair Cells in a Strain of the Waltzing Guinea Pig

Abstract

Genetically deaf animals have been known for many years. Some of these animals combine deafness with a waltzing behaviour. In the present work some characteristics of the morphology of the vestibular hair cells from labyrinths of waltzing guinea pigs of various ages were studied with electron microscopical methods. In survey studies with low magnification clear pathological changes were found in labyrinths from adult animals; severely degenerated sensory cells and cellular debris pushed out into the endolymphatic space. With high resolution even the sensory cells of the newborn animals were found to be pathologically changed with variation in sensory hair diameter and balloonshaped protrusions of the sensory cell apical cytoplasm. In the sensory cells of type I a specific rod shaped cytoplasinic inclusion was regularly present. This inclusion body was composed of an electron dense substance seemingly consisting of fine tubules or fibrils. The synaptic region was normal in the sensory cells as long as the degeneration of the cell was not very advanced. Both afferent and efferent nerve endings were normally present. The morphological changes demonstrable in the vestibular sensory cells already from the birth lead us to believe the waltzing behaviour to be closely related to this peripheral sensory cell damage. The failure of earlier investigators to demonstrate pathological changes in the sensory epithelia is considered due to the limitations of the light microscopical methods used.