The Role of Glycogen Synthase Kinase-3 in the Regulation of Ribosome Biogenesis in Rat Soleus Muscle under Disuse Conditions

It is well-established that prolonged exposure to real or simulated microgravity/disuse conditions results in a significant reduction in the rate of muscle protein synthesis (PS) and loss of muscle mass. Muscle protein synthesis is largely dependent upon translational capacity (ribosome content), the regulation of which is poorly explored under conditions of mechanical unloading. Glycogen synthase kinase-3 (GSK-3) (a negative regulator of PS) is known to be activated in rat soleus muscle under unloading conditions. We hypothesized that inhibition of GSK-3 activity under disuse conditions (hindlimb suspension, HS) would reduce disuse-induced downregulation of ribosome biogenesis in rat soleus muscle. Wistar rats were randomly divided into four groups: (1) vivarium control (C), (2) vivarium control + daily injections (4 mg/kg) of AR-A014418 (GSK-3 inhibitor) for 7 days, (3) 7-day HS, (4) 7-day HS + daily injections (4 mg/kg) of AR-A014418. GSK-3beta and glycogen synthase 1 (GS-1) phosphorylation levels were measured by Western-blotting. The key markers of ribosome biogenesis were assessed via agarose gel-electrophoresis and RT-PCR. The rate of muscle PS was assessed by puromycin-based SUnSET method. As expected, 7-day HS resulted in a significant decrease in the inhibitory Ser9 GSK-3beta phosphorylation and an increase in GS-1 (Ser641) phosphorylation compared to the C group. Treatment of rats with GSK-3 inhibitor prevented HS-induced increase in GS1 (Ser641) phosphorylation, which was indicative of GSK-3 inhibition. Administration of GSK-3 inhibitor partly attenuated disuse-induced downregulation of c-Myc expression as well as decreases in the levels of 45S pre-rRNA and 18S + 28S rRNAs. These AR-A014418-induced alterations in the markers of ribosome biogenesis were paralleled with partial prevention of a decrease in the rate of muscle PS. Thus, inhibition of GSK-3 during 7-day HS is able to partially attenuate the reductions in translational capacity and the rate of PS in rat soleus muscle.     

High Resolution Synchrotron X-Radiation Diffraction Imaging of Crystals Grown in Microgravity and Closely Related Terrestrial Crystals

Irregularities in three crystals grown in space and in four terrestrial crystals grown under otherwise comparable conditions have been observed in high resolution diffraction imaging. The images provide important new clues to the nature and origins of irregularities in each crystal. For two of the materials, mercuric iodide and lead tin telluride, more than one phase (an array of non diffracting inclusions) was observed in terrestrial samples; but the formation of these multiple phases appears to have been suppressed in directly comparable crystals grown in microgravity. The terrestrial seed crystal of triglycine sulfate displayed an unexpected layered structure, which propagated during directly comparable space growth. Terrestrial Bridgman regrowth of gallium arsenide revealed a mesoscopic structure substantially different from that of the original Czochralski material. A directly comparable crystal is to be grown shortly in space.     

Reanalysis of Microgravity Heat Capacity Measurements Near the SF<Subscript>6</Subscript> Liquid–Gas Critical Point

The earlier microgravity heat capacity measurements in SF₆ by Haupt and Straub have been reanalyzed in this study. A simple power law as well as the minimal-subtraction renormalization (MSR) scheme were used to fit the measurements. In this paper the unexpected result that the SF₆ heat capacity measurements appear to be within the asymptotic critical region all the way out to a reduced temperature |t| 10^–2 is presented. This conclusion is in contradiction with the smaller asymptotic region |t| < 1.6× 10^–4 found in the original investigation. These heat capacity measurements were found to be inconsistent with renormalization group predictions using SF₆ compressibility measurements.     

溶质表面张力对流模型及其对空间实验的解析

空间高温实时观察装置（SHITISOI）被用于观察和记录在Li₂B₄O₇溶体中KNbO₃胞状结晶的整个生长过程,并对胞状结晶生长过程中浮力对流和表面张力对流的影响进行了研究．首次观察到空间条件下,Li₂B₄O₇溶体中稳态表面张力对流图像,它呈镜面对称的抛物线状．由于表面张力对流的作用,KNbO₃胞晶生长且充满了整个的溶体．而在地面上,由于浮力抑制表面张力,降低了胞晶在流体中的生长速度,使溶质KNbO₃胞晶在Li₂B₄O₇溶体中分布不均匀,本文还提出了胞状结晶生长理论的模型．这个模型的主要特点是表面张力对流起始于KNbO₃胞晶的界面上;这是由于KNbO₃溶质扩散速率减少而引起的KNbO₃溶质表面张力梯度．本模型的预言和实验所观察的现象吻合得比较好,这说明该理论模型是合理、可靠的．     

微重力条件下偏晶合金的研究进展

介绍了重力对偏晶合金凝固过程的影响,综述了微重力环境下偏晶合金凝固研究中的新进展,总结了不同磁场模拟微重力环境下的实验研究成果,探讨了不同微重力条件制备偏晶合金的特点,指出了利用磁场制备偏晶合金的发展前景,最后提出了微重力条件下偏晶合金今后研究的方向和途径。     

空间微重力环境下蛋白质晶体生长的研究进展

空间微重力环境可消除或减弱常重力场下溶液中存在的对流和沉降,为蛋白质晶体生长提供一个相对均一和稳定的环境,有利于得到尺寸更大、衍射分辨率更高的蛋白质晶体。通过对这些高质量空间晶体进行X射线衍射分析,可获得多种蛋白质的精细三维结构。从空间蛋白质晶体生长的发展历史、研究成果、生长机理、存在的问题与对策等方面总结了空间微重力环境下蛋白质晶体生长的研究进展,展望了空间蛋白质结晶的未来。     

Metabolic Dynamics in Short- and Long-Term Microgravity in Human Primary Macrophages

Microgravity acts on cellular systems on several levels. Cells of the immune system especially react rapidly to changes in gravity. In this study, we performed a correlative metabolomics analysis on short-term and long-term microgravity effects on primary human macrophages. We could detect an increased amino acid concentration after five minutes of altered gravity, that was inverted after 11 days of microgravity. The amino acids that reacted the most to changes in gravity were tightly clustered. The observed effects indicated protein degradation processes in microgravity. Further, glucogenic and ketogenic amino acids were further degraded to Glucose and Ketoleucine. The latter is robustly accumulated in short-term and long-term microgravity but not in hypergravity. We detected highly dynamic and also robust adaptative metabolic changes in altered gravity. Metabolomic studies could contribute significantly to the understanding of gravity-induced integrative effects in human cells.     

空间烟幕的扩散机理及衰减性能研究

烟幕干扰是针对红外探测器的一种无源干扰手段,在战场环境中,可以在目标与探测器之间释放烟幕形成屏障,降低探测器对目标的能见度,达到对目标的有效遮蔽。首先研究了在微重力高真空环境中,采用气固两相流喷射方法形成烟幕云的机理,并进行了数值模拟。然后,基于烟幕的扩散规律、材料特性及其吸收、散射和反射能力,建立了空间烟幕对红外信号的衰减性能模型。最后,基于实例仿真验证了利用空间烟幕衰减目标红外信号的可行性。     

Effect of baffles on orbital accelerations - Induced bubble oscillations in microgravity

The behavior of sloshing dynamics modulated fluid systems driven by the orbital accelerations including gravity gradient and jitter accelerations with partially-filled rotating fluids has been studied. Present study is applicable to a full-scale Gravity Probe-B Spacecraft dewar tank with and without baffle. Results of slosh wave excitation along the liquid—vapor interface induced by jitter acceleration-dominated orbital accelerations provide a torsional moment with an up-and-down movement of bubble oscillations in the rotating dewar. The results show rightward and leftward movement of bubble oscillations transverse to the rotating axis, and up-and-down movement of bubble oscillations longitudinal to the rotating axis of dewar container. The orbital accelerations also induce an eccentric contour of bubble oscillations in a horizontal r—θ plane. As viscous force between liquid—solid interface, and surface tension force between liquid—vapor—solid interface can greatly contribute to the damping effect of slosh wave excitation, the rotating dewar with baffle provides more areas of liquid—solid and liquid—vapor—solid interfaces than that of a rotating dewar without baffle. Results show that the damping effect provide by a baffle reduce the amplitude of slosh wave excitation and reduce the degree of asymmetry in liquid—vapor distribution. Computation of bubble (helium vapor) mass center fluctuations also verifies that a rotating dewar with baffle produces less fluctuations than that of a rotating dewar without baffle.     

Noncontact temperature measurement of a falling drop

The 105-m drop tube at the Marshall Space Flight Center has been used in a number of experiments to determine the effects of containerless, microgravity processing on the undercooling and solidification behavior of metals and alloys. These experiments have been limited, however, because direct temperature measurement of the falling drops has not been available. Undercooling and nucleation temperatures are calculated from thermophysical properties based on droplet cooling models. In most cases these properties are not well known, particularly in the undercooled state. This results in a large amount of uncertainty in the determination of nucleation temperatures. If temperature measurement can be accomplished, then the thermal history of the drops could be well documented. This would lead to a better understanding of the thermophysical and thermal radiative properties of undercooled melts. An effort to measure the temperature of a falling drop is under way at Vanderbilt and Marshall Space Flight Center. The technique uses two-color pyrometry and high-speed data acquisition. The approach is presented along with some preliminary data from drop tube experiments. The results from droplet cooling models will be compared with noncontact temperature measurements.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.