[Ultrastructural changes in the receptor portion of the vestibular apparatus in response to noise]

The experiments have been performed on 24 guinea pigs (48 labyrinthes), 6 of them--control and 18 have been subjected to noise (one octava) with the average geometrical in diaposone of 2,000 Hz, at intensity level 100 dB. Six animals are subjected to a single effect for 6 h and 12--to repeated effect during 6 days running, 4-6 h daily. Isolation of both the vestibular and the cochlear parts of the membranous labyrinth is performed simultaneously. This gives a possibility to study all the receptors of the internal ear as a whole. Certain ultrastructural changes in all the vestibular receptors both at a single and repeated effects are revealed. Dilatation of the granular endoplasmic reticulum is observed, situating mainly in the basal part of the cell; swelling of mitochondria is accompanied with a sharp clearance of their matrix. In some mitochondria there is a local destruction of their external and internal membranes. Moreover, in cytoplasm of the receptory cells sharply osmiophilic fibrillar structures are revealed, they resemble crists and are arranged in bundles. In some cells they are not numerous and localize mainly in mitochondria, in others--their number is greater, and they localize not only in mitochondria, but in the surrounding cytoplasm, too. Similar structures are observed in some preganglionic myelin fibers. These phenomena can be considered as development of calcification processes. The changes described, evidently, form the basis of the vestibular disorders under the noise effect.