| 研究概要 |
The ability to maintain normal body orientation in relation to the external environment is important for the adaptation to altered gravity. However, the physiological limits for adaptation or disruption of body orientation are not known. In this study, we analyzed postural changes in animals exposed to various rates of deceleration into partial-gravity. This Kakenhi project allowed us to build a device for the study of jaw and limb movements in the mouse through a high-definition x-ray movie system. The use of cineradiographic technology enabled us to study detailed jaw and limb movements in the mouse in a detailed and minimally invasive fashion. Male C57BL6/J mice (n = 6) were exposed to partial-gravity deceleration by customized parabolic flight-maneuvers targeting the levels of 0.60, 0.30, 0.15, and 0.01 G. Detailed video recordings of postural responses were obtained by high-definition cineradiography. Landmarks were identified on the mouse skeleton from which measurements were made. As a result, the initial phase of gravity deceleration produced coordinated and generalized extension of the head, spine, and hindlimbs. Joint angles in partial gravity widened about 30% or more in relation to the average 1 g posture. Reflex jaw-opening was observed during gravity deceleration. The magnitude of postural responses was associated positively with gravity deceleration. These results suggest that adaptability to partial gravity may be not only dependent on the partial-gravity level, but also on the rate of gravity change from normal gravity into any given partial-gravity level.
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