Body-weight distribution on forelimbs in rat tail-suspension model. Aviakosm Ekolog Med
ABSTRACT To understand the tail-suspension model to simulate weightlessness better, this study was to investigate the relationship of the amount of body weight supported by forelimbs between the tilt angles of rat in the model. Normal rat had at least two basic postures. One was standing or walking, in which the forelimbs bear 44.6% of the body weight; the other one was resting, in which 23.9% of body weight was placed on the forelimbs. As for tail-suspended rat, body-weight distribution on forelimbs was linearly related to tilt angle. The linear relationship was y = -0.7423x + 70.849, R2 = 0.9269. The tilt angle should be approximately 35 degrees if normal standing load of 44.6% body weight was placed on the forelimbs. On the other hand, it should be approximately 63 degrees if normal resting load of 23.9% of body weight was placed on forelimbs. Furthermore, the body load on forelimbs in tail-suspension model became much larger if the period of different postures was considered. Therefore, it should be careful if forelimbs are used to be as convenient internal control in tail-suspended rats.
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ABSTRACT: Life on Earth has developed under the influence of gravity and remains adapted to unit gravity. As different organisms evolved to survive optimally in water, ground, and air habitats, special adaptive mechanisms developed to deal with gravity. In humans and most land mammals, maintaining postural equilibrium requires constant integration of visual, vestibular, and somatosensory systems to compensate for gravity. The gravity sensors located in the inner ear make connections to the eyes, vestibulocerebellum, and postural muscles. The vestibulocerebellum, due to direct connections with the vestibular gravity receptors, is the primary gravity response center. It is involved in spatial orientation and regulation of gait and, together with the spinocerebellum and pontocerebellum, plays an important role in motor control. Several cerebellar pathologies, including ataxias and dystonia in humans and animals, are characterized by altered gravity perception and affect posture, gait, and small motor coordination and timing. In space, where the gravitational sense of up and down diminishes, the vestibulocerebellar system must adapt and establish a new way to interpret the altered gravitational environment. This chapter explores cerebellar disorders in the context of altered interactions with Earth’s gravity in humans and animal models and the reaction of astronauts to altered gravity in space (microgravity). This chapter also considers the effects of microgravity and hypergravity on the development of cerebellar structure and function in experimental animals. Understanding how the cerebellum responds to altered gravity should provide insight into the nature of altered gravity perception in various neurological disorders and accelerate the development of therapeutic tools.Handbook of the Cerebellum and Cerebellar Disorders, 01/2013: pages 1241-1255; , ISBN: 978-94-007-1332-1