骨特异性转录因子Runx2对抗空间骨丢失效应的初步研究

为了构建稳定过表达Runx2 (骨特异性转录因子)的C2C12 (小鼠成肌细胞)和MG63 (前成骨细胞)细胞株, 并用于研究Runx2在对抗空间骨丢失效应中的作用. 利用实时定量聚合酶链式反应鉴定Runx2下游基因I型胶原、碱性磷酸酶表达情况, 在二维回转器中培养稳定细胞株, 通过定量聚合酶链式反应,观察在模拟失重效应下Runx2基因对其下游基因表达的影响. 结果表明, 通过筛选获得稳定转染的C2C12-Runx2和MG63-Runx2细胞株, 经鉴定都能过表达Runx2. 转染后的细胞 I 型胶原和碱性磷酸酶mRNA表达增高. 回转组与对照组相比, MG63, C2C12-Runx2, MG63-Runx2细胞的I型胶原和碱性磷酸酶mRNA表达降低, 但在模拟失重效应下, 转染细胞中I型胶原和碱性磷酸酶的mRNA表达下降程度明显低于未转染细胞株. 所构建的C2C12-Runx2和MG63-Runx2细胞株比较稳定, 并证实Runx2能部分对抗失重引起的成骨特异性分子的降低.      

-6°卧床模拟失重对T淋巴细胞的影响及内分泌调节机制的研究

本文研究了-6°卧床模拟失重对T淋巴细胞受到有丝分裂原刺激后增殖能力和外周血总T淋巴细胞亚群(CD3+T细胞)、辅助/炎性T细胞亚群(CD4+T细胞)、杀伤T细胞亚群(CD8+T细胞)、及表达CD25分子细胞数的影响,同时观察生长激素、促肾上腺皮质激素、皮质激素的改变,来探讨免疫功能的变化与内分泌系统改变的关系.结果表明,模拟失重造成的免疫功能下降与内分泌系统紊乱有关.      

重力对植物细胞生长的效应

从地基研究植物向重性和在神舟八号卫星微重力条件下培养植物细胞出发,探讨重力变化对植物细胞发生作用时产生的生物学效应.已有结果显示,在植物向重性反应和处于失重状态时,重力方向和大小变化对细胞壁代谢具有一定影响.推断细胞形状的维持是由细胞壁的刚性与细胞内膨压平衡所致,当细胞膨压大于细胞壁刚性导致上述平衡打破时就会引起细胞体积增大.因此,重力的变化可能会通过影响植物细胞壁刚性与细胞内膨压的平衡影响细胞生长.      

地球文明是惟一的吗?

茫茫宇宙，究竟是否存在地外文明？这个问题在今天不仅是一个哲学问题，而且在实验研究工作中也有十分实际的意义。不久前，一个由俄罗斯科学院地壳研究新古生物学研究所、微生物学研究所的专家们组成的研究小组进行了一项新的试验——运用电子显微镜对陨石结构里的浸渗生成物进行分析。结果在陨石碳结构的表面发现了一些球形细胞链和类似这种细胞团的空心球。同时还查明，类似球形细菌在4．5亿年前即在古波罗的海沿岸的浅水地带形成了气垫。专家们还在陨石的表面结构中发现了一些线状石化遗迹。这些线状石化遗迹分叉成类似细胞结构的节点，…     

用Hamilton方法研究地球自转的长期减慢

本文用Hamilton方法研究了弹性地球在日月引潮力势作用下产生形变后对地球自转速率的影响，考虑了潮汐形变的相位延迟，选择地球模型PREM参数进行了计算，理论上求得地球自转长期减慢值为-5．711×10(-22)rad／s2，与观测结果符合很好．结果表明，对地球自转长期减慢起主要影响是扇谐潮，由月亮引潮力势产生的影响远比太阳重要．     

赤霉素介导模拟失重诱导的胡萝卜细胞中淀粉粒降解

空间微重力环境会影响生命活动，本文利用回转器来模拟微重力(失重)的生物学效应．回转处理可以引起胡萝卜愈伤组织细胞中内源活性赤霉素(GAs)水平上升，总淀粉酶活力提高(其中主要是α-淀粉酶活力增加)，淀粉粒降解．且GAs和α-淀粉酶活力的升高趋势一致．GAs合成性抑制剂，ancymidol能显著抑制回转处理中α-淀粉酶活力的增加．由此推测：回转处理中GAs的升高诱导了α-淀粉酶基因表达增加，后者促使淀粉粒降解和能量物质动员，以响应模拟失重的刺激．     

模拟失重对心血管自主神经调节功能的影响

载人航天或模拟失重后，航天员会出现运动能力与立位耐力降低，其发生机理与多种因素的改变有关．为进一步验证这种变化与中枢神经系统调节功能障碍的可能相关，本文研究模拟失重过程中心脏与外周血管自主神经调节功能的动态变化及与卧床后立位耐力降低的关系．结果表明，6名被试者的HRV谱的总功率（TP）及低频（LF）、高频（HF）成份均减少，而LF：HF比值在卧床后期有增大趋势．卧床后HUT初始6min所有被试者心率明显快于卧床前的相应值．说明模拟失重后心脏迷走神经反应与外周血管交感神经活动水平降低，心脏交感神经活动水平逐渐升高．但卧床后HUT时心血管自主神经调节反应基本正常．     

科学家培育出“类囊胚”

正科学家距离在不使用精子和卵子的情况下制造出人工生命又迈出了一大步。研究人员将来自小鼠的两种胚胎干细胞在培养皿中结合之后,这些干细胞会长成类似囊胚——可植入子宫的早期胚胎形态——的结构,研究人员称其为"类囊胚"。囊胚是一团球形的细胞群结构,由滋养层、内细胞群和充满液体的囊胚腔组成。当植入子宫之后,这种"类囊胚"先是触发子宫发生改变,像3.5天的正常囊胚一     

近壁区流向涡生成的数值模拟

对于在湍流边界层近壁区,作为相干结构的主要特征的流向涡的产生及发展的全过程进行了研究.采用准二维的共振三波作为湍流边界层近壁区相干结构初值,用直接数值模拟方法模拟了准二维波发展到明显的三维扰动以及其中流向涡生成的整个过程,经分析发现,在该过程中,由于非线性作用,相干结构出现了明显的三维性,并产生了马蹄涡,与实验结果相一致,而且也研究了压力梯度对于流向涡生成以及发展的影响, 在逆压梯度下,流向涡的生成得更早、更快,相干结构幅值增长较快,结构变得更加复杂.这些都说明了逆压梯度对相干结构具有激励作用.     

航天器贮箱气液自由界面追踪数值模拟

主要讨论了航天器贮箱在轨道航行时的微重力状态下其液体推进剂在贮箱内的形态分布及控制.文中采用VOF方法,加入了表面张力的效应,追踪气液两相流的自由界面,对液面在微重力条件下的位形变化进行了数值模拟.通过比较不同重力加速度及接触角下的两相流的相图,分析了影响贮箱中液体推进剂位形变化的主要因素及对其有效的控制方法.      

Thin film bioreactors in space.

Studies from the Skylab, SL-3 and D-1 missions have demonstrated that biological organisms grown in microgravity have changes in basic cellular functions such as DNA, mRNA and protein synthesis, cytoskeleton synthesis, glucose utilization and cellular differentiation. Since microgravity could affect prokaryotic and eukaryotic cells at a subcellular and molecular level, space offers us an opportunity to learn more about basic biological systems with one important variable removed. The thin film bioreactor will facilitate the handling of fluids in microgravity, under constant temperature and will allow multiple samples of cells to be grown with variable conditions. Studies on cell cultures grown in microgravity would enable us to identify and quantify changes in basic biological function in microgravity which are needed to develop new applications of orbital research and future biotechnology.     

Function of the cytoskeleton in gravisensing during spaceflight.

Since astronauts and cosmonauts have significant bone loss in microgravity we hypothesized that there would be physiological changes in cellular bone growth and cytoskeleton in the absence of gravity. Investigators from around the world have studied a multitude of bone cells in microgravity including Ros 17/2.8, Mc3T3-E1, MG-63, hFOB and primary chicken calvaria. Changes in cytoskeleton and extracellular matrix (ECM) have been noted in many of these studies. Investigators have noted changes in shape of cells exposed to as little as 20 seconds of microgravity in parabolic flight. Our laboratory reported that quiescent osteoblasts activated by sera under microgravity conditions had a significant 60% reduction in growth (p<0.001) but a paradoxical 2-fold increase in release of the osteoblast autocrine factor PGE2 when compared to ground controls. In addition, a collapse of the osteoblast actin cytoskeleton and loss of focal adhesions has been noted after 4 days in microgravity. Later studies in Biorack on STS-76, 81 and 84 confirmed the increased release of PGE2 and collapse of the actin cytoskeleton in cells grown in microgravity conditions, however flown cells under 1 g conditions maintained normal actin cytoskeleton and fibronectin matrix. The changes seen in the cytoskeleton are probably not due to alterations in fibronectin message or protein synthesis since no differences have been noted in microgravity. Multiple investigators have observed actin and microtubule cytoskeletal modifications in microgravity, suggesting a common root cause for the change in cell architecture. The inability of the O g grown osteoblast to respond to sera activation suggests that there is a major alteration in anabolic signal transduction under microgravity conditions, most probably through the growth factor receptors and/or the associated kinase pathways that are connected to the cytoskeleton. Cell cycle is dependent on the cytoskeleton. Alterations in cytoskeletal structure can block cell growth either in G1 (F-actin microfilament collapse), or in G2/M (inhibition of microtubule polymerization during G2/M-phase). We therefore hypothesize that microgravity would inhibit growth in either G1, or G2/M.     

Gravitational force regulates elongation growth of Arabidopsis hypocotyls by modifying xyloglucan metabolism.

Growth of dark-grown Arabidopsis hypocotyls was suppressed under hypergravity conditions (300 g), or was stimulated under microgravity conditions in space (Space Shuttle STS-95). The mechanical extensibility of cell walls decreased and increased under hypergravity and microgravity conditions, respectively. The amounts of cell wall polysaccharides (pectin, hemicellulose-I, hemicellulose-II and cellulose) per unit length of hypocotyls increased under hypergravity conditions, and decreased under microgravity conditions. The amount and the molecular mass of xyloglucans also increased under the hypergravity conditions, while those decreased under microgravity conditions. The activity of xyloglucan-degrading enzymes extracted from hypocotyl cell walls decreased and increased under hypergravity and microgravity conditions, respectively. These results indicate that the amount and the molecular mass of xyloglucans are affected by the magnitude of gravity and that such changes are caused by changes in xyloglucan-degrading activity. Modifications of xyloglucan metabolism as well as the thickness of cell walls by gravity stimulus may be the primary event determining the cell wall extensibility, thereby regulating the growth rate of Arabidopsis hypocotyls.     

Inhibitory effect of simulated microgravity on differentiating preosteoblasts

The bone loss induced by microgravity is partly due to the decrease of mature osteoblasts. In the present study, we employed the random positioning machine (RPM) to simulate microgravity and investigated the acute effects of simulated microgravity on the differentiation of 2T3 preosteoblasts. Following 7 days’ culture under normal (1 g) condition, cells were exposed to simulated microgravity for 24 h. The results showed that 24 h treatment of simulated microgravity significantly decreased alkaline phosphatase (ALP) activity without changing the cell morphology. In addition, the mRNA expressions of osteogenic genes, including runt-related gene 2 (Runx2), osterix, osteocalcin (OC), type I collagen (Col I) and bone morphogenetic protein (BMP), were dramatically downregulated. Moreover, western blot analysis of total extracellular signal-regulated kinase (Erk) and phosphorylated Erk (p-Erk) indicated that p-Erk level, which represents the Erk activation status, was increased. Taken together, our results suggested that acute exposure to simulated microgravity inhibited osteoblast differentiation through modulating the expression of osteogenic genes and the Erk activity. These findings provide new insight for bone loss due to microgravity and unloading.     

Upregulation of erythropoietin receptor in UT-7/EPO cells inhibits simulated microgravity-induced cell apoptosis

Hematopoietic progenitor cell proliferation can be altered in either spaceflight or under simulated microgravity experiments on the ground, however, the underlying mechanism remains unknown. Our previous study showed that exposure of the human erythropoietin (EPO)-dependent leukemia cell line UT-7/EPO to conditions of simulated microgravity significantly inhibited the cellular proliferation rate and induced cell apoptosis. We postulated that the downregulation of the erythropoietin receptor (EPOR) expression in UT-7/EPO cells under simulated microgravity may be a possible reason for microgravity triggered apoptosis. In this paper, a human EPOR gene was transferred into UT-7/EPO cells and the resulting expression of EPOR on the surface of UT-7/EPO cells increased approximately 61% (p < 0.05) as selected by the antibiotic G418. It was also shown through cytometry assays and morphological observations that microgravity-induced apoptosis markedly decreased in these UT-7/EPO–EPOR cells. Thus, we concluded that upregulation of EPOR in UT-7/EPO cells could inhibit the simulated microgravity-induced cell apoptosis in this EPO dependent cell line.     

用国产装置进行的空间蛋白质结晶实验

使用国内研制的管式汽相扩散结晶装置,在我国返回式卫星上,成功地完成了两次空间蛋白质晶体生长实验,10种不同种类的蛋白质配制的48个样品在空间的出晶率分别达52%和80%,其中少数蛋白质生长出了较高质量的蛋白质晶体。结果表明,空间的微重力环境利于改善蛋白质晶体的生长,而且在结晶条件优化足够好的条件下,在空间里能生长出比地面晶体尺寸较大、形态较好和内部有序性较高的蛋白质晶体。本文还就微重力对蛋白质晶体生长的具体作用及其开发利用做了讨论。      

The declined phosphorylation of Heat shock protein 27 in rat cardiac muscle after hindlimb unloading

Hindlimb unloading can induce the cardiac atrophy and diminished cardiac function, however, the mechanisms responsible for which remain elusive. The chronic volume unloading of heart, which decreases the local mechanical stress, may lead to cardiac atrophy after hindlimb unloading. Many studies showed that integrin signaling, p38 MAPK, Heat shock protein 27 and cytoskeleton involved in the hypertrophic growth induced by mechanical stress. However, the mechanisms responsible for cardiac atrophy after hindlimb unloading are still unclear. In this study, we used the tail-suspended, hindlimb unloading rat model to simulate the effects of microgravity. Western blot analysis was used to detect the protein expression of Heat shock protein 27, focal adhesion kinase, p38 MAPK and their phosphorylation levels in rat cardiac muscle after 14d hindlimb unloading. The results showed that the phosphorylation levels of both Heat shock protein 27 and p38 MAPK were decreased significantly in rat cardiac muscle after hindlimb unloading. However, the phosphorylation level of focal adhesion kinase was not decreased significantly. The results suggested that Heat shock protein 27, the downstream of p38 MAPK, might play a critical role in the cardiac atrophy in response to simulated microgravity induced by hindlimb unloading.     

The effects of simulated microgravity on cultured chicken embryonic chondrocytes.

Using the cultured chicken embryonic chondrocytes as a model, the effects of simulated microgravity on the microtubular system of the cellular skeleton, extracellular matrix, alkaline phosphatase activity, intracellular free calcium concentration and mitochondrial ATP synthase activity with its oligomycin inhibition rate were studied with a clinostat. The microtubular content was measured by a flow cytometer. The decrease of microtubular content showed the impairment of the cellular skeleton system. Observation on the extracellular matrix by the scanning electron microscopy showed that it decreased significantly after rotating, and the fibers in the extracellular matrix were more tiny and disorderly than that of the control group. It can be concluded that the simulated microgravity can affect the secreting and assembly of the extracellular matrix. In contrast to the control, there was a time course decrease in alkaline phosphatase activity of chondrocytes, a marker of matrix mineralization. Meanwhile a significant drop in the intracellular calcium concentration happened at the beginning of rotation. These results indicate that simulated microgravity can suppress matrix calcification of cultured chondrocytes, and intracellular free calcium may be involved in the regulation of matrix calcification as the second signal transmitter. No significant changes happened in the mitochondrial ATP synthase activity and its oligomycin inhibition rate. Perhaps the energy metabolism wasn't affected by the simulated microgravity. The possible mechanisms about them were discussed.     

Free and membrane-bound calcium in microgravity and microgravity effects at the membrane level.

The changes of [Ca2+]i controlled is known to play a key regulatory role in numerous cellular processes especially associated with membranes. Previous studies from our laboratory have demonstrated an increase in calcium level in root cells of pea seedlings grown aboard orbital station "Salyut 6". These results: 1) indicate that observed Ca(2+)-binding sites of membranes also consist in proteins and phospholipids; 2) suggest that such effects of space flight in membrane Ca-binding might be due to the enhancement of Ca2+ influx through membranes. In model presented, I propose that Ca(2+)-activated channels in plasma membrane in response to microgravity allow the movement of Ca2+ into the root cells, causing a rise in cytoplasmic free Ca2+ levels. The latter, in its turn, may induce the inhibition of a Ca2+ efflux by Ca(2+)-activated ATPases and through a Ca2+/H+ antiport. It is possible that increased cytosolic levels of Ca2+ ions have stimulated hydrolysis and turnover of phosphatidylinositols, with a consequent elevation of cytosolic [Ca2+]i. Plant cell can response to such a Ca2+ rise by an enhancement of membranous Ca(2+)-binding activities to rescue thus a cell from an abundance of a cytotoxin. A Ca(2+)-induced phase separation of membranous lipids assists to appear the structure nonstable zones with high energy level at the boundary of microdomains which are rich by some phospholipid components; there is mixing of molecules of the membranes contacted in these zones, the first stage of membranous fusion, which was found in plants exposed to microgravity. These results support the hypothesis that a target for microgravity effect is the flux mechanism of Ca2+ to plant cell.     

微重力下胶原蛋白纤维化及羟基磷灰石结晶的初步研究

在长期空间飞行过程中, 骨质丢失是一个严重问题. 羟基磷灰石(HAP)晶体是骨骼的主要成分, 骨骼中的胶原蛋白纤维在HAP生长结晶过程中起到关键作用. 研究了胶原蛋白纤维化过程在模拟微重力和常重力条件下的变化, 对以胶原 蛋白纤维作为模板生长出的HAP晶体形貌进行了观察. 结果表明, 不同浓度胶原蛋白溶液中形成的胶原蛋白纤维, 其内部孔隙数量和尺寸在模拟微重力条件下要明显大于常重力条件下, 胶原蛋白纤维内部孔隙的分布也不同于常重力条 件下的结果. 以模拟微重力条件下形成的胶原蛋白纤维为模板生长出的HAP 晶体主要为立方体状, 而以常重力条件下形成的胶原蛋白纤维为模板生长出的 HAP晶体形貌主要为板状. 该结果有助于未来进一步阐明空间骨质丢失的机理.