Electron microscopical studies of the effect of time lapse on outer hair cells in acoustically exposed rabbits.

After acoustic exposure of a pure tone of 2 kHz, 100 dB for 2 hours, the outer hair cells of the rabbits were observed by electron microscope. The infranuclear region of the cells in the lower half of the second turn were observed in this experiment. In this region, small vesicles, free ribosomes and coated vesicles decreased or increased in number, and the cytoplasmic matrix became lower or higher in electron density after acoustic exposure. Immediately after exposure the percentage of normal cells was 25% and increased to 60% within a period of one month. The effect of time lapse on the damaged cells' recovery is discussed.