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

为探讨长期卧床对人体生理调节的影响，自1992年以来，对29名（男18名，女11名）青年进行了为期3年的卧床前、后生理调节研究。结果表明：（1）在体重不变的情况下，体脂肪量增加，下半身肌肉量，特别是反重力肌量减少，肌力下降; (2)仰卧位运动和中等强度直立位运动时最大摄氧量、心输出量（CO）和每搏输出量（SV）均降低，但最大心率（HR）不变，机械效率增加。(3)卧位静息时左室舒张末期内径（LVDd）减小，SV减小，HR增加，而氧摄取量略有下降，CO和动脉血压无明显变化。(4)低压-40 mmHg期间的LVDd ...更多信息 结果显示，治疗后患者的下肢负压（LBNP）、立位耐力下降，心率增加。然而，尽管心率下降，立位耐受时间减少对LBNP没有改善静脉普萘洛尔。BR后LBNP期间的心动过速加重不能用颈动脉、主动脉和心肺反射或自主反应性的变化来解释。(5)BR未改变手臂和静脉顺应性。(6)腰椎的骨密度（BMD）下降后BR，尿中的每日排泄的deoxtridinoline增加，在第10天，并在第20天下降。然而，碱性磷酸酶和抗酒石酸酸性磷酸酶都没有变化。骨基质和外周血单核细胞的细胞因子互锁1 α和肿瘤坏死因子α的再吸收标记物之间的相互关系没有改变。(7)BR后空腹血中总胆固醇、高密度脂蛋白胆固醇、甘油三酯、游离脂肪酸和载脂蛋白B的血浆浓度无变化，而载脂蛋白AI从第3天开始下降，并保持该下降趋势直至第20天。在极低密度脂蛋白组分中，甘油三酯和胆固醇增加。在脂解酶活性方面，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)在75 g口服葡萄糖耐量试验期间的总葡萄糖浓度没有变化，但BR后总胰岛素浓度增加，因此血糖/胰岛素比降低。(9)BR后一般健康问卷增加，Zung抑郁自评量表升高，第9天尿17-羟皮质类固醇排泄增加。(10)BR后重心运动中心波动增大，维持站立位功能下降。(11)深度感觉对膝关节角度的调整可能会因重新调整而降低。

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