Molecular cloning related to skeletal or muscle atrophy under microgravity

研究了飞行14天对快速生长大鼠椎体的影响。在机械硬度和骨密度方面，飞行大鼠与地面对照组无显著差异（p>0.05）。然而，组织学检查显示飞行大鼠皮质骨内表面不规则增厚，而地面对照组则均匀增厚。飞行大鼠板层骨相对面积显著减小（p<0.001）。这些结果表明，结构紊乱是由于内膜模型和重塑的延迟。接下来，研究了14天的太空飞行对跖肌β -肾上腺素能受体（β - ar）、线粒体酶活性和纤维类型组成的影响。飞行后β - ar的最大结合能力（bmax）显著降低（>29%），在1-G环境下9天后恢复不完全。在飞行后5小时内测量肌肉样本的琥珀酸脱氢酶（SDH）活性，并在恢复后9天内恢复正常。结果表明，太空飞行诱导的植物β - ar的bmax降低伴随着线粒体内膜酶SDH活性的降低。最后，采用mRNA差异显示法比较航天大鼠和地面对照组棘旁肌mRNA的表达，以确定微重力下肌肉萎缩的相关分子。研究发现，在14天的太空飞行中，70 kDa热休克蛋白（HSP70）及其相关基因TCP-1显著升高，而参与线粒体代谢的基因（线粒体腺苷核酸酶易位子、线粒体细胞色素氧化酶亚基）、醛缩酶A和肌细胞特异性增强子结合因子（MEF）显著降低。我们还发现了一些与肌肉萎缩有关的新基因，并对这些分子的生物学功能进行了研究。

The effect of 14 days of flight on the vertebrae of rapidly growing rats was studied. No significant difference (p>0.05) was observed between flight rats and ground controls with regard to mechanical hardness or bone mineral density. however, histological examination revealed irregular thickening of the endosteal surface of cortical bones in flight rats, whereas it was uniform in the ground controls. The relative area of lamellar bone showed a significant reduction (p<0.001) in the flight rats. These findings suggest that structural disturbances were due to retardation of endosteal modeling and remodeling. Next, the effects of 14 days of space-flight on beta-adrenoceptor (beta-AR), mitochondrial enzyme activities, and fiber type composition were studied in plantaris muscles. The maximum binding capacity of beta-AR (B max) was significantly lower (>29%) after flight, and the recovery was not complete after 9 days in a 1-G environment. The activity of succinate dehydrogenase (SDH) was measured in muscle samples <5 hr after flight and were found to normalize during 9 days of recovery. It is suggested that the space-flight-induced decrease of B max of beta-AR in plantaris was accompanied by a decreased activity of a mitochondrial inner-membrane enzyme, SDH.Finally, the expression of mRNA in paraspinal muscles between space-flight rats and ground controls was compared using mRNA differential display method in order to identify molecules related to muscle atrophy under microgravity. We found that 70 kDa heat-shock protein (HSP70) and its retated gene, TCP-1, were makedly elevated during 14 days of space-flight, while genes involved in mitochondrial metabolism (mitochondrial adenosine nuclease translocator, mitochondrial cytochrome oxidase subunits), aldolase A and myocyte-specific enhancer binding factor (MEF) were significantly decreased. Some new genes related to muscle atrophy were also detected and we studied the biological functions of these molecules.