[Changes in the utricular otoconia of the chick embryo developed under 2G-gravity]

Whether or not vestibular adaptation occurs upon exposure to altered gravity is an important human problem. Studies have been performed to ascertain whether morphological changes in vestibular organs occur in animal models upon exposure to microgravity. On the other hand, the morphological changes which occur in vestibular organs under hypergravity have not yet been fully elucidated and morphological changes in the otoconia of the chick embryo exposed to hypergravity during the embryonic period remain to be thoroughly examined. The purpose of this paper is to clarify the effects of hypergravity on vestibular organs, especially its effects on otoconial formation in the developing chick embryo. Thus, we designed an apparatus which creates artificial gravity, creating approximately 2G gravity by means of centrifugation. The utricular macula was chosen for study because it can be prepared for examination with a minimum of dissection artifacts. The data presented show that morphological changes were confined to otoconial size alterations according to scanning electron microscopic observations. Giant otoconia were observed along the marginal zones of utricle .