A scanning electron microscopic study of vestibular organ malformation following prenatal gamma irradiation.

Pregnant CBA/CBA mice were exposed to 1 and 2 Gy whole-body gamma irradiation on the 13th and 16th gestational days, respectively. The litters were born on the 21st day of gestation and were tested for vestibular function at the age of 1 month. The animals were then sacrificed and their inner ears were analyzed by scanning electron microscopy. No disturbances of vestibular function were noted in the animals studied. However, the cristae ampullares showed severe malformations as regards their gross shape, with irregularities of their outer contours. Type I hair cells seemed to be more severely changed than Type II hair cells, with fusion of sensory hairs, giant hair formation and bulging of the cuticular plate. In certain sites the hair cells were totally missing. These derangements were usually located in the central areas of the cristae ampullares and in the striolar portion of the maculae utriculi. The morphological damage found showed a dose-dependent, time-related pattern.