EFFECTS OF PROLONGED BED REST ON PHYSIOLOGICAL FUNCTIONS AND COUNTER-MEASUREMENT AGAINST THE EFFECTS IN HUMAN SUBJECTS

为探讨长时间卧床对人体生理状态的影响，自1992年以来，对29名年轻受试者（男18名，女11名）进行了为期3年的水平卧床前后20天的研究。与BR前相比，BR后的测量变量结果如下：(1)在体重不变的情况下，体脂量增加，下体肌肉量特别是反重力肌肉量减少，肌肉力量下降。(2)轻、中等强度仰卧和直立运动时最大摄氧量、心输出量（CO）和脑卒中量（SV）均降低，最大心率（HR）不变，机械效率提高。(3)平卧时左室舒张末期内径（LVDd）降低，SV降低，HR升高，摄氧量略有降低，CO和动脉血压不变。(4)低血压-40 mmHg时LVDd、LBNP和直立性不耐受降低，HR升高。然而，尽管心率降低，但静脉注射心得安对LBNP直立耐受时间的减少并没有改善。BR后LBNP加重的心动过速不能用颈动脉、主动脉和心肺反射或自主反应性的改变来解释。(5) BR未改变手臂和静脉顺应性。(6) BR后木材骨的骨密度（BMD）降低，尿中脱氧三吡啶的日排泄量在第10天升高，第20天下降。然而，碱性磷酸酶和抗酒石酸盐酸性磷酸酶都没有改变。骨基质吸收因子与外周单核细胞互锁1 α和肿瘤坏死因子α的相互关系不变。(7) BR后空腹血中总胆固醇、高密度脂蛋白胆固醇、甘油三酯、游离脂肪酸、载脂蛋白B的血浆浓度无变化，而载脂蛋白AI从第3天开始下降，一直保持到第20天。在极低密度脂蛋白部分，甘油三酯和胆固醇增加。在脂肪酶活性方面，凝集素胆固醇酰基转移酶活性升高，脂蛋白脂肪酶活性降低，而肝甘油三酯脂肪酶活性不变。(8) 75 g口服糖耐量试验总葡萄糖浓度不变，BR后总胰岛素浓度升高，血糖/胰岛素比值下降。(9) BR后一般健康问卷评分增加，Zung抑郁自评量表升高，第9天尿17-羟基皮质类固醇排泄量增加。（10） BR后身体重力作用中心波动增大，维持站立位置的功能减弱。（11）深度感觉对膝关节角度的调节可以通过re Less来降低

To investigate the effects of prolonged bed rest on human physiological conditioning, total 29 young subjects (18 males, 11 females) had been studied before and after 20 days of horizontal bed rest (BR) for 3 years period since 1992. The results of measured variables after BR as compared before BR were as following : (1) Despite unchanged body weight body fat mass increased, and muscle mass of lower body, specially antigravity muscle mass, was decreased as well as the muscle strength. (2) Maximal oxygen uptake, and cardiac output (CO) and stroke volume (SV) during both supine exercise and upright exercise with mild-moderate intensities were decreased, but maximal heart rate (HR) was unchanged and mechanical efficiency was increased. (3) supine resting left ventricular end diastolic diameter (LVDd) was decreased as well as the SV in order to the increased HR,while the oxygen uptake was slightly decrease and CO and arterial blood pressure were unchanged. (4) LVDd during -40 mmHg lower bo … More dy negative pressure (LBNP) and orthostatic intolerance were decreased and the HR increased. However, despite the decreased HR the orthostatic tolerance time reduced against LBNP was not improved by intravenous propranolol. The tachycardia exaggerated during LBNP after the BR could not be explained by changes in carotid, aortic, and cardiopulmonary reflexes or autonomous reactivity. (5) Neither arm nor venous compliance was changed by the BR.(6) Bone mineral density (BMD) of the lumber bone decreased after BR, and also urinary daily excretion of deoxtptridinoline increased at day 10 and declined at day 20. However, neither alkaline phosphataes nor tartarated-resistant acid phosphatase changed. The interrelation between resorption makers for bone matrix and peripheral monocyte of the cytokines interlocking 1 alpha and tumor necrosis factor alpha was unchanged. (7) plasma concentrations of total cholesterol, high density lipoprotein cholesterol, triglyceride, free fatty acid and apolipoprotein B were unchanged in fasting blood after BR,while apolipoprotain AI decreased from day 3 and remained the decrease until day 20. In the very low density lipoprotein fraction, triglyceride and cholesterol increased. In the lipolytic enzyme activity, lectin cholesterol acyltrasferase activity increased, lipoprotein lipase activity decreased, but hepatic triglyceride lipase activity was unchanged. (8) total glucose concentration summed during 75 g oral glucose tolerance test was unchanged, but the total insulin concentration increased after BR,and thus blood glucose/insulin ratio decreased. (9) The General Health Questionnaire increased, Zung' self-rating depression scale elevated after BR, and urinary excretion of 17-hydroxycorticosteroid increased at day 9. (10) Fluctuation of body action center of gravitational weight was increased and thus functions of maintaining standing position was reduced after BR.(11) An adjustment of deep sensation to knee angle might be lowered by the re Less