Proton Magnetic Resonance Imaging of Specimens in Simulated Microgravity

In situ proton stray-field (STRAFI) nuclear magnetic resonance (NMR) imaging of diamagnetic samples in simulated microgravity is described. The magnetic field gradient at the edge of the superconductive coil in the magnet of a NMR spectrometer is exploited to levitate diamagnetic samples and, at the same time, obtain their corresponding one-dimensional NMR images. Proton T ₂ (spin-spin relaxation time)/ diffusion-weighted profiles of samples under simulated microgravity conditions are acquired with a solid-echo radiofrequency pulse sequence. Since water is a diamagnetic main constituent substance of living systems, the methodology described could be useful to monitor non-destructively changes in the NMR properties of water protons induced by simulated microgravity and magnetic forces. Furthermore, this approach may be used to observe other NMR-sensitive nuclei of interest, e.g., fluor-19, phosphorous-31, carbon-13, etc.     

Germination of Arabidopsis Seed in Space and in Simulated Microgravity: Alterations in Root Cell Growth and Proliferation

Changes have been reported in the pattern of gene expression in Arabidopsis on exposure to microgravity. Plant cell growth and proliferation are functions that are potentially affected by such changes in gene expression. In the present investigation, the cell proliferation rate, the regulation of cell cycle progression and the rate of ribosome biogenesis (this latter taken to estimate cell growth) have been studied using morphometric markers or parameters evaluated by light and electron microscopy in real microgravity on the International Space Station (ISS) and in ground-based simulated microgravity, using the Random Positioning Machine and the Magnetic Levitation Instrument. Results showed enhanced cell proliferation but depleted cell growth in both real and simulated microgravity, indicating that the two processes are uncoupled, unlike the situation under normal gravity on Earth in which they are strictly co-ordinated events. It is concluded that microgravity is an important stress condition for plant cells compared to normal ground gravity conditions.     

Influence of Oxygen in the Cultivation of Human Mesenchymal Stem Cells in Simulated Microgravity: An Explorative Study

Previous studies indicated that human Adipose Tissue-derived Mesenchymal Stem Cells (AT-MSCs) cultured in simulated microgravity (sim-μg) in standard laboratory incubators alter their proliferation and differentiation. Recent studies on the stem cell (SC) niches and the influence of oxygen on SC proliferation, senescence, and differentiation point to oxygen level as one of the key regulators of SC fate. Here we present the results of a study that focussed at the evaluation of the influence of oxygen level in the cultivation of AT-MSCs in sim-μg. In detail, cells were cultured for 14 days in sim-μg using the Random Positioning Machine (RPM) and two different oxygen concentrations: 5 % and 20 %. The results were compared with those obtained at 1g in the same conditions. Affymetrix Human Gene 1.0 ST array and Gene Ontology (GO) analysis were performed. The results confirmed that in all of the sim-μg experiments oxygen concentration modulates cell signalling and adhesion, in line with the knowledge that sim-μg affects cell shape and cytoskeletal organization.     

Seed Germination and Seedling Growth under Simulated Microgravity Causes Alterations in Plant Cell Proliferation and Ribosome Biogenesis

The study of the modifications induced by altered gravity in functions of plant cells is a valuable tool for the objective of the survival of terrestrial organisms in conditions different from those of the Earth. We have used the system “cell proliferation–ribosome biogenesis”, two inter-related essential cellular processes, with the purpose of studying these modifications. Arabidopsis seedlings belonging to a transformed line containing the reporter gene GUS under the control of the promoter of the cyclin gene CYCB1, a cell cycle regulator, were grown in a Random Positioning Machine, a device known to accurately simulate microgravity. Samples were taken at 2, 4 and 8 days after germination and subjected to biometrical analysis and cellular morphometrical, ultrastructural and immunocytochemical studies in order to know the rates of cell proliferation and ribosome biogenesis, plus the estimation of the expression of the cyclin gene, as an indication of the state of cell cycle regulation. Our results show that cells divide more in simulated microgravity in a Random Positioning Machine than in control gravity, but the cell cycle appears significantly altered as early as 2 days after germination. Furthermore, higher proliferation is not accompanied by an increase in ribosome synthesis, as is the rule on Earth, but the functional markers of this process appear depleted in simulated microgravity-grown samples. Therefore, the alteration of the gravitational environmental conditions results in a considerable stress for plant cells, including those not specialized in gravity perception.     

甘氨酸辅助合成BiOI及其模拟太阳光光催化性能研究

以甘氨酸分子作为模板, 硝酸铋作为铋源, 采用水热合成的方法一步制备了尺寸均一的具有片层花状微球形貌的四方晶相BiOI光催化材料。通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、紫外-可见漫反射光谱(UV-Vis/DRS)、N₂吸附-脱附等手段考察了五水硝酸铋与甘氨酸的摩尔比、水热反应时间对BiOI材料形貌、晶相结构及光学吸收等物理化学性质的影响。进一步以罗丹明B和水杨酸为目标污染物对其模拟太阳光光催化性能进行了评价。实验结果显示, 当五水硝酸铋与甘氨酸的摩尔比为1: 2, 水热时间为12 h所合成的BiOI光催化降解活性最高。经40 min模拟太阳光照射后, 罗丹明B和水杨酸的反应速率常数分别达到0.0232和0.0223 min^-1, 与未添加甘氨酸同等条件下合成的BiOI的反应速率常数(0.0111和0.0143 min^-1)相比, 有显著提升。光催化活性提高的主要原因是甘氨酸辅助合成的BiOI材料具有更为规则的形貌和更大的比表面积。     

Effects of Simulated Microgravity on Otolith Growth of Larval Zebrafish using a Rotating-Wall Vessel: Appropriate Rotation Speed and Fish Developmental Stage

Stimulus dependence is a general feature of developing animal sensory systems. In this respect, it has extensively been shown earlier that fish inner ear otoliths can act as test masses as their growth is strongly affected by altered gravity such as hypergravity obtained using centrifuges, by (real) microgravity achieved during spaceflight or by simulated microgravity using a ground-based facility. Since flight opportunities are scarce, ground-based simulators of microgravity, using a wide variety of physical principles, have been developed to overcome this shortcoming. Not all of them, however, are equally well suited to provide functional weightlessness from the perspective of the biosystem under evaluation. Therefore, the range of applicability of a particular simulator has to be extensively tested. Earlier, we have shown that a Rotating-Wall Vessel (RWV) can be used to provide simulated microgravity for developing Zebrafish regarding the effect of rotation on otolith development. In the present study, we wanted to find the most effective speed of rotation and identify the appropriate developmental stage of Zebrafish, where effects are the largest, in order to provide a methodological basis for future in-depth analyses dedicated to the physiological processes underlying otolith growth at altered gravity. Last not least, we compared data on the effect of simulated microgravity on the size versus the weight of otoliths, since the size usually is measured in related studies due to convenience, but the weight more accurately approximates the physical capacity of an otolith. Maintaining embryos at 10 hours post fertilization for three days in the RWV, we found that 15 revolutions per minute (rpm) yielded the strongest effects on otolith growth. Maintenance of Zebrafish staged at 10 hpf, 1 day post fertilization (dpf), 4 dpf, 7 dpf and 14 dpf for three days at 15 rpm resulted in the most prominent effects in 7 dpf larvae. Weighing versus measuring the size of otoliths yielded basically similar results, but the data gained by weighing were more distinct. Overall, our results clearly support the concept that the environmental gravity vector regulates fish otolith growth in terms of the pendulum model of otolith test masses, and that wall vessel rotation is a valuable means to provide functional weightlessness from the perspective of developing Zebrafish. We recommend that Zebrafish embryos staged 7 dpf (or possibly slightly elder) are rotated at 15 rpm in a Rotating-Wall Vessel as used in the present study for further experiments designed to elucidate the mechanisms underlying (altered gravity affected) otolith growth.     

Differential Regulation of cGMP Signaling in Human Melanoma Cells at Altered Gravity: Simulated Microgravity Down-Regulates Cancer-Related Gene Expression and Motility

Altered gravity is known to affect cellular function by changes in gene expression and cellular signaling. The intracellular signaling molecule cyclic guanosine-3^′,5^′-monophosphate (cGMP), a product of guanylyl cyclases (GC), e.g., the nitric oxide (NO)-sensitive soluble GC (sGC) or natriuretic peptide-activated GC (GC-A/GC-B), is involved in melanocyte response to environmental stress. NO-sGC-cGMP signaling is operational in human melanocytes and non-metastatic melanoma cells, whereas up-regulated expression of GC-A/GC-B and inducible NO synthase (iNOS) are found in metastatic melanoma cells, the deadliest skin cancer. Here, we investigated the effects of altered gravity on the mRNA expression of NOS isoforms, sGC, GC-A/GC-B and multidrug resistance-associated proteins 4/5 (MRP4/MRP5) as selective cGMP exporters in human melanoma cells with different metastatic potential and pigmentation. A specific centrifuge (DLR, Cologne Germany) was used to generate hypergravity (5 g for 24 h) and a fast-rotating 2-D clinostat (60 rpm) to simulate microgravity values ≤?0.012 g for 24 h. The results demonstrate that hypergravity up-regulates the endothelial NOS-sGC-MRP4/MRP5 pathway in non-metastatic melanoma cells, but down-regulates it in simulated microgravity when compared to 1 g. Additionally, the suppression of sGC expression and activity has been suggested to correlate inversely to tumor aggressiveness. Finally, hypergravity is ineffective in highly metastatic melanoma cells, whereas simulated microgravity down-regulates predominantly the expression of the cancer-related genes iNOS and GC-A/GC-B (shown additionally on protein levels) as well as motility in comparison to 1 g. The results suggest that future studies in real microgravity can benefit from considering GC-cGMP signaling as possible factor for melanocyte transformation.     

微振动对空间实验室微重力环境的影响研究

针对大型刚柔组合体空间结构(空间实验室)的特点,建立系统的动力学方程,并对机柜内设备、太阳阵的转动、宇航员活动产生的激扰力进行了简化。利用计算机建立组合体的简化模型,对空间组合体在各种微振动激扰下的加速度响应进行了仿真研究,并将这些仿真结果用于空间实验室微重力环境的预测。     

Cyclophosphamide Loaded Albumin Microspheres: Liver Entrapment and Fate in Mice

Abstract

Microspheres offer the possibility of target selectivity through choice of appropriate size or surface charecteristics, slow release of drug and also minimize systemic toxicity. The active substance of this investigation, cyclophosphamide (CP), interferes with the growth of cancer cells which are eventually destroyed. Since side effects of CP are frequently dose related, by incorporating low dose of CP to human serum albumin (HSA) microspheres, the normal body cells are not affected while the tumour cells are destroyed.

Cyclophosphamide microspheres were prepared by the modification of the method of Scheffel et al and Gürkan et al. 2,3-butanedione was used as a cross-linking agent. The albumin microspheres containing CP were labelled by ^99mTc by incorporating SnC1₂.2H₂0 at a concentration of 5% of the matrix material. All the microspheres used in this study ranged between 1–5 μm.

A suspension of ^99mTc labelled cyclophosphamide microspheres was injected into swiss albino mice intravenously. At 15 min, 30 rain, 6 h and 24 h mice were killed and the organs assayed for radioactivity accumulated in each organ. 1 hour later the radioactivity in the liver increased to 4.73 percent. By 24 hours, 2.68 percent of the radioactivity was found in the liver. Whereas the percentage of free cyclophosphamide at 1 and 24 hours was 2.22 and 2.57 percent, respectively. Based on the evidence obtained from these results, the application of CP loaded HSA microspheres seems advantages in accumulation in liver.     

贮藏温度对葡萄果胶含量及相关酶活性的影响

为研究贮藏温度对葡萄果胶含量及相关酶活性的影响,本文对超冰温(-3℃及-2℃)、冰温(-1℃)及普通冷库(4℃)4种不同贮藏温度下葡萄的果胶物质含量和果胶酶活性进行测定并分析。研究发现:随着贮藏时间的增加,葡萄果实和果皮的原果胶含量均呈下降趋势,可溶性果胶呈上升趋势,-3℃超冰温条件下原果胶下降及可溶性果胶升高幅度最小,4℃时变化幅度最大。葡萄的硬度与原果胶间呈显著正相关,与可溶性果胶呈显著负相关。-3℃超冰温条件可以很好的抑制葡萄原果胶水解速率,防止果实变软;同时还能有效抑制葡萄中果胶酯酶的活性,最大限度的降低多聚半乳糖醛酸酶对葡萄原果胶水解的促进作用,防止葡萄贮藏期出现腐烂变质,有利于进一步延缓其贮藏时间。     

Effect of Oxygen Enrichment in Propane Laminar Diffusion Flames under Microgravity and Earth Gravity Conditions

Diffusion flames are the most common type of flame which we see in our daily life such as candle flame and match-stick flame. Also, they are the most used flames in practical combustion system such as industrial burner (coal fired, gas fired or oil fired), diesel engines, gas turbines, and solid fuel rockets. In the present study, steady-state global chemistry calculations for 24 different flames were performed using an axisymmetric computational fluid dynamics code (UNICORN). Computation involved simulations of inverse and normal diffusion flames of propane in earth and microgravity condition with varying oxidizer compositions (21, 30, 50, 100 % O₂, by mole, in N₂). 2 cases were compared with the experimental result for validating the computational model. These flames were stabilized on a 5.5 mm diameter burner with 10 mm of burner length. The effect of oxygen enrichment and variation in gravity (earth gravity and microgravity) on shape and size of diffusion flames, flame temperature, flame velocity have been studied from the computational result obtained. Oxygen enrichment resulted in significant increase in flame temperature for both types of diffusion flames. Also, oxygen enrichment and gravity variation have significant effect on the flame configuration of normal diffusion flames in comparison with inverse diffusion flames. Microgravity normal diffusion flames are spherical in shape and much wider in comparison to earth gravity normal diffusion flames. In inverse diffusion flames, microgravity flames were wider than earth gravity flames. However, microgravity inverse flames were not spherical in shape.     

Inhibition of Drug-Metabolizing Enzymes in Mouse Liver by a Water Soluble Fullerene C60

The microsomal cytochrome P450-dependent monooxygenase system is responsible for the metabolism a variety of xenobiotics including drugs and carcinogens. Fullerenol-1 is a water soluble polyhydroxylated C₆₀ derivative synthesized by a sequence of reactions involving the electrophilic attack of nitronium tetrafluoroborate on fullerenes in the presence of organocarboxylic acids. The present study has evaluated the acute toxicity of fullerenol-1 and determined the effects of the C₆₀ compound on the P450-dependent drug-metabolzing activities. Pretreatments with 0.5 and 1.0g/kg fullerenol-1 decreased P450 and cytochrome b₅ contents, and NADPH-cytochrome P450 reductase, as well as drug metabolizing activities toward test substrates benzo[a]pyrene, 7-ethoxycoumarin, aniline, and erythromycin in liver microsomes. Pretreatments with 0.01 and 0.1 g/kg fullerenol-1 had no effect on these monooxygenases. Immunoblotting anlysis of the microsomal proteins revealed that pretreatments with fullerenol-1 did not alter the protein levels of P450s 1A, 2E and 3A. Additions of fullerenol-1 to mouse liver microsomes suppressed monooxygenases activities toward benzo[a]pyrene, 7-ethoxycoumarin, aniline, and erythromycin with IC₅₀ values of 42, 94, 102 and 349 μM, respectively. These results demonstrate that fullerenol-1 can decrease the activities of microsomal drug-metabolizing enzymes in vivo and in vitro. Proper adjustment of the functionalized fullerene compound may facilitate the biomedical application of the new material.     

Effect of Coil Inclination on Thermomagnetic Convection of Air in a Porous Cubic Enclosure Under Microgravity Environment

The thermomagnetic convection of air in a porous cubic enclosure with an electric coil inclined in general orientations was numerically investigated under microgravity environment. Biot-Savart’s was used to calculate magnetic field. The governing equations in primitive variables were discretized by the finite-volume method and solved by the SIMPLE algorithm. The Darcy model was used to solve the momentum equations. The results show that both the magnetic force and the coil inclination have significant effect on the flow field and heat transfer in a porous cubic enclosure; the natural convection heat transfer of air can be enhanced or controlled by applying gradient magnetic field     

Determination of the Secondary Bjerknes Force in Acoustic Resonators on Ground and in Microgravity Conditions

We propose an experimental methodology to determine the secondary Bjerknes force between rigid particles. Measurements done for different particles sizes showed acoustical inter particles interactions. We use and extend the methodology presented in a previous work. The determination of this force will lead us a better understanding of the aggregation process in acoustic resonators. We report in this work, the results of two parabolic flights campaigns performed at the Airbus A300 ZERO-G (Novespace, France).     

碳化钨涂层模拟氧化及其对老化性能的影响

为了分析国产某大型装备关键部件表面喷涂的钴-碳化钨涂层在厂房放置后出现蓝紫色现象,并评估其对涂层服役性能的影响,采用同样的超音速火焰喷涂工艺制备一批钴-碳化钨涂层样品,利用环境试验箱调节湿度和温度,模拟现场环境进行加速氧化试验并实时观察。采用拉拔法、往复摩擦法和电化学试验对腐蚀后的样品进行结合力、摩擦以及抗腐蚀性能测试。发现采用同样参数制备的钴-碳化钨涂层在模拟条件下成功复现了现场腐蚀样貌。对比研究腐蚀前后钴-碳化钨涂层各项性能发现,腐蚀前后涂层的结合力均大于60 MPa;腐蚀前后涂层同条件下的磨损体积基本一致,无明显下降;腐蚀氧化仅发生在涂层表面,未深入涂层内部,涂层内部和基体并无损伤。分析认为,现场发生的涂层表面变色是由于当地夏季环境高温高湿,导致涂层表面发生Co的氧化。氧化后涂层的结合强度和耐磨性无明显下降,经过综合研究认定,现场涂层表面氧化不会影响其服役性能及寿命。