Effects of spaceflight and simulated microgravity on microbial growth and secondary metabolism

Spaceflight and ground-based microgravity analog experiments have suggested that microgravity can affect microbial growth and metabolism. Although the effects of microgravity and its analogs on microorganisms have been studied for more than 50 years, plausible conflicting and diverse results have frequently been reported in different experiments, especially regarding microbial growth and secondary metabolism. Until now, only the responses of a few typical microbes to microgravity have been investigated; systematic studies of the genetic and phenotypic responses of these microorganisms to microgravity in space are still insufficient due to technological and logistical hurdles. The use of different test strains and secondary metabolites in these studies appears to have caused diverse and conflicting results. Moreover, subtle changes in the extracellular microenvironments around microbial cells play a key role in the diverse responses of microbial growth and secondary metabolisms. Therefore, "indirect" effects represent a reasonable pathway to explain the occurrence of these phenomena in microorganisms. This review summarizes current knowledge on the changes in microbial growth and secondary metabolism in response to spaceflight and its analogs and discusses the diverse and conflicting results. In addition, recommendations are given for future studies on the effects of microgravity in space on microbial growth and secondary metabolism.

论Manned Spaceflight的文体特征及其翻译策略——以被动句为研究案例

Manned Spaceflight一文陈述客观准确,逻辑结构严密,专业术语性强,语气正式。其文体特征包括被动语态、名词化、非谓语、专业词汇、割裂、并列、无灵主语、介词、长句、省略等。以被动句为例,通过Manned Spaceflight中翻译实践发现,被动句翻译为主动句、被动句和无主句时,翻译策略各不相同。

Analyses on schedule-cost coefficient correlation of spaceflight project based on historical statistics and its application

When analyze the uncertainty of the cost and the schedule of the spaceflight project, it is needed to know the value of the schedule-cost correlation coefficient. This paper deduces the schedule distribution, considering the effect of the cost, and proposes the estimation formula of the correlation coefficient between the in（schedule） and the cost. On the basis of the fact and Taylor expansion, the relation expression between the schedule-cost correlation coefficient and the in-schedule-cost correlation coefficient is put forward. By analyzing the value features of the estimation formula of the in-schedule-cost correlation coefficient, the general rules are proposed to ascertain the value of the schedule-cost correlation coefficient. An example is given to demonstrate how to approximately amend the schedule-cost correlation coefficient based on the historical statistics, which reveals the traditional assigned value is inaccurate. The universality of this estimation method is analyzed.

Mutagenic Effects of Spaceflight Treatment on the Second-Generation Seeds of Alfalfa

[ Objective] To explore the effects of spaceflight on the second-generation seeds of alfalfa and provide a theoretical basis for mutation breeding. [Method] The seeds of Medicago stavia L. lines no. 1, no. 2 and no. 4 were carried into space by the Shijian-8 seed breeding satellite for a 15-d spaceflight treatment. After returning to the ground, seedlings were transplanted to field. Traits of the second-generation seeds of alfalfa were evaluated. [Result] The 1 000-grain weight of the second-generation seeds were 5% -9% significantly higher than that the control （P 〈 0.05）. The germination rate, seedling weight, shoot length and root length were significantly increased （P 〈 0.05）. The hard seed rate and the rate of moldy seeds were significantly decreased （ P 〈 0.05）. However, the rate of dead seeds was increased. [ Conclusion] Spaceflight treatment has positive mutagenic effects on the second-generation seeds of alfalfa.

Speed kills: Highly relativistic spaceflight would be fatal for passengers and instruments

Highly relativistic speeds are desirable for interstellar travel. Relativistic time dilation would reduce the subjective duration of the trip for the travelers, so that they can cover galaxy-scale distances in a reasonable amount of personal time. Unfortunately, as spaceship velocities approach the speed of light, interstellar hydrogen H, although only present at a density of approximately 1.8 atoms/cm3, turns into intense radiation that would quickly kill passengers and destroy electronic instrumentation. In addition, the energy loss of ionizing radiation passing through the ship’s hull represents an increasing heat load that necessitates large expenditures of energy to cool the ship. Stopping or diverting this flux, either with material or electromagnetic shields, is a daunting problem. Going slow to avoid severe H irradiation sets an upper speed limit of v ~ 0.5 c. This velocity only gives a time dilation factor of about 15%, which would not substantially assist galaxy-scale voyages. Diffuse interstellar H atoms are the ultimate cosmic space mines and represent a formidable obstacle to interstellar travel.

Estimation Method of Schedule-cost Correlation Coefficient of Spaceflight Project

To evaluate the cost risk and the schedule risk of the spaceflight project,the schedule-cost(S-C) correlation coefficient is directly appointed according to the experts' experience usually.This paper deduces SDMCU(the schedule distribution model considering the effect of the cost uncertainty),and then proposes the approximate formula to estimate the ln(S)-C correlation coefficient based on the models of SDMCU and CDMSU(the cost distribution model considering the effect of the schedule uncertainty).Furthermore,an approximate relationship expression of the S-C and the ln(S)-C correlation coefficients is put forward according to general facts and the Taylor expansion,and advanced by means of mass numerical validation is the general rule of obtaining the estimation value of the schedule-cost correlation coefficient based on the historical data.

Remarkable Achievements of China’s Manned Spaceflight Project

On September 21,1992, the feasibility report on implementing China's Manned Spaceflight Project was approved and a three-step development strategy was also determined. From then on, China's Manned Spaceflight Project has developed rapidly.

LM-2F: A Great Launch Vehicle for China's Manned Spaceflight

The LM-2F launch vehicle is China's first launch carrier developed for China's Manned Space Program,which is one of the most important parts of the Program.It is developed from the LM-2E launch vehicle,with addition of two new systems,an escape system and a fault detection system.

关于“Some Theoretical Problems of the Spaceflight Mechanics”(Ⅲ)

改善了文献［２］的前言

关于“Some Theoretical Problems of the Spaceflight Mechanics” (Ⅳ)

本文完善了文献［１］的一些结果。

Variation of photosynthesis,secondary metabolites and antioxidant activities in third generation of spaceflight-induced Salvia miltiorrhiza

Objective: Spaceflight has long been perceived as an effective way to improve the quantity and quality of plants with wide applications. In order to obtain stable and inheritable descendants of spaceflightinduced Salvia miltiorrhiza lines, we investigated and analyzed four lines m16, m50, m51, m57(three individuals of each line) and the ground control(three individuals) of the third generation of spaceflight-induced S. miltiorrhiza from primary/secondary metabolism and antioxidative abilities.Methods: A portable photosynthesis system(Li-6400) with red/blue LED light source was used to perform the photosynthetic characteristics to evaluate their primary productivity. The secondary metabolites(phenolic acids, tanshinones, total phenolics and flavonoids) and antioxidant activity of roots were analyzed to assess their quality.Results: Compared with control, line m16 presented weak photosynthetic ability, but high apparent quantum yield(AQY), higher contents of secondary metabolites, and stronger antioxidative abilities.Line m57 had a strong gas exchange ability, relatively higher secondary metabolites contents, and ascending antioxidative abilities. Lines m50 and m51 were in the middle level of lines m16 and m57.The principal component analysis for all the original data revealed three components including a rootrelated index, a leaf-related index, and a CO_(2) response parameter could be used to distinguish spaceflight-induced S. miltiorrhiza lines.Conclusion: Line m57 could be an appropriate material for the investigation of targeted breeding towards high production, and line m16 could be used to identify essential genes and unravel sophisticated pathways underlying the secondary metabolisms.

Genome and clonal hematopoiesis stability contrasts with immune,cfDNA,mitochondrial,and telomere length changes during short duration spaceflight

Background The Inspiration4(I4)mission,the first all-civilian orbital flight mission,investigated the physiological effects of short-duration spaceflight through a multi-omic approach.Despite advances,there remains much to learn about human adaptation to spaceflight's unique challenges,including microgravity,immune system perturbations,and radiation exposure.Methods To provide a detailed genetics analysis of the mission,we collected dried blood spots pre-,during,and post-flight for DNA extraction.Telomere length was measured by quantitative PCR,while whole genome and cfDNA sequencing provided insight into genomic stability and immune adaptations.A robust bioinformatic pipeline was used for data analysis,including variant calling to assess mutational burden.Result Telomere elongation occurred during spaceflight and shortened after return to Earth.Cell-free DNA analysis revealed increased immune cell signatures post-flight.No significant clonal hematopoiesis of indeterminate potential(CHIP)or whole-genome instability was observed.The long-term gene expression changes across immune cells suggested cellular adaptations to the space environment persisting months post-flight.Conclusion Our findings provide valuable insights into the physiological consequences of short-duration spaceflight,with telomere dynamics and immune cell gene expression adapting to spaceflight and persisting after return to Earth.CHIP sequencing data will serve as a reference point for studying the early development of CHIP in astronauts,an understudied phenomenon as previous studies have focused on career astronauts.This study will serve as a reference point for future commercial and non-commercial spaceflight,low Earth orbit(LEO)missions,and deep-space exploration.

Physiological effects of weightlessness: countermeasure system development for a long-term Chinese manned spaceflight

The Chinese space station will be built around 2020. As a national space laboratory, it will offer unique opportunities for studying the physiological effects of weightlessness and the efficacy of the countermeasures against such effects. In this paper, we described the development of countermeasure systems in the Chinese space program. To emphasize the need of the Chinese space program to implement its own program for developing countermeasures, we reviewed the literature on the negative physiological effects of weightlessness, the challenges of completing missions, the development of countermeasure devices, the establishment of countermeasure programs, and the efficacy of the countermeasure techniques in American and Russian manned spaceflights. In addition, a brief overview was provided on the Chinese research and development on countermeasures to discuss the current status and goals of the development of countermeasures against physiological problems associated with weightlessness.

Long-term spaceflight and the cardiovascular system

While early investigations into the physiological effects of spaceflight suggest the body’s ability to reversibly adapt,the corresponding effects of long-term spaceflight(>6months)aremuch less conclusive.Prolonged exposure to microgravity and radiation yields profound effects on the cardiovascular system,including a massive cephalad fluid translocation and altered arterial pressure,which attenuate blood pressure regulatory mechanisms and increase cardiac output.Also,central venous pressure decreases as a result of the loss of venous compression.The stimulation of baroreceptors by the cephalad shift results in an approximately 10%–15%reduction in plasma volume,with fluid translocating from the vascular lumen to the interstitium.Despite possible increases in cardiac workload,myocyte atrophy and notable,yet unexplained,alterations in hematocrit have been observed.Atrophy is postulated to result from shunting of protein synthesis from the endoplasmic reticulum to the mitochondria via mortalin-mediated action.While data are scarce regarding their causative agents,arrhythmias have been frequently reported,albeit sublethal,during both Russian and American expeditions,with QT interval prolongation observed in long,but not short duration,spaceflight.Exposure of the heart to the proton and heavy ion radiation of deep space has also been shown to result in coronary artery degeneration,aortic stiffness,carotid intima thickening via collagen-mediated action,accelerated atherosclerosis,and induction of a pro-inflammatory state.Upon return,long-term spaceflight frequently results in orthostatic intolerance and altered sympathetic responses,which can prove hazardous should any rapidmobilization or evacuation be required,and indicates that these cardiac risks should be especially monitored for future missions.

Effects of spaceflight and simulated microgravity on cell sub-microstructure and antioxidant enzyme activity in tomato

Controlled ecological life support systems provide food, air, water, and other basic living resources for crew members on long-duration spaceflight missions. Plants are an important basic requirement of these systems and their biological characteristics in space have very high research value. Based on experiments of spaceflight in Shenzhou 8 spacecraft and simulating microgravity effects on three-dimensional （3-D） clinostat, the biological characteristics of tomato＇s leaf cell sub-microstructure and antioxidant enzyme activities were studied and compared in this work. Results showed that leaf cell sub-microstructure of the tomato samples experiencing spaceflight had more changes than effects, and both peroxidase （POD） and superoxide dismutase （SOD） that of the samples processed by simulated microgravity activities increase obviously in both the environments.

An online error calibration method for spaceflight TT&C systems based on LEO-ground DDGPS

To overcome the shortcomings of the traditional measurement error calibration methods for spaceflight telemetry, tracking and command(TT&C) systems, an online error calibration method based on low Earth orbit satellite-to-ground doubledifferential GPS(LEO-ground DDGPS) is proposed in this study. A fixed-interval smoother combined with a pair of forward and backward adaptive robust Kalman filters(ARKFs) is adopted to solve the LEO-ground baseline, and the ant colony optimization(ACO) algorithm is used to deal with the ambiguity resolution problem. The precise baseline solution of DDGPS is then used as a comparative reference to calibrate the systematic errors in the TT&C measurements, in which the parameters of the range error model are solved by a batch least squares algorithm. To validate the performance of the new online error calibration method, a hardware-in-the-loop simulation platform is constructed with independently developed spaceborne dual-frequency GPS receivers and a Spirent GPS signal generator. The simulation results show that with the fixed-interval smoother, a baseline estimation accuracy(RMS, single axis) of better than 10 cm is achieved. Using this DDGPS solution as the reference, the systematic error of the TT&C ranging system is effectively calibrated, and the residual systematic error is less than 5 cm.

Spaceflight decelerates the epigenetic clock orchestrated with a global alteration in DNA methylome and transcriptome in the mouse retina

Astronauts exhibit an assortment of clinical abnormalities in their eyes during long-duration spaceflight.The purpose of this studywas to determinewhether spaceflight induces epigenomic and transcriptomic reprogramming in the retina or alters the epigenetic clock.The mice were flown for 37 days in animal enclosure modules on the International Space Station;ground-based control animals weremaintained under similar housing conditions.Mouse retinas were isolated and both DNA methylome and transcriptome were determined by deep sequencing.We found that a large number of genes were differentially methylated with spaceflight,whereas there were fewer differentially expressed genes at the transcriptome level.Several biological pathways involved in retinal diseases such as macular degeneration were significantly altered.Our results indicated that spaceflight decelerated the retinal epigenetic clock.This study demonstrates that spaceflight impacts the retina at the epigenomic and transcriptomic levels,and such changes could be involved in the etiology of eye-related disorders among astronauts.

Reduced function and disassembled microtubules of cultured cardiomyocytes in spaceflight

Lack of gravity during spaceflight has profound effects on cardiovascular system, but little is known about how the cardiomyocytes respond to microgravity. In the present study, the effects of spaceflight on the structure and function of cultured cardiomyocytes were reported. The primary cultures of neo- natal rat cardiomyocytes were carried on Shenzhou-6 spacecraft and activated at 4 h in orbit. 8 samples were fixed respectively at 4, 48 and 96 h after launching for immunofluorescence of cytoskeleton, and 2 samples remained unfixed to analyze contractile and secretory functions of the cultures. Ground sam- ples were treated in our laboratory in parallel. After 115 h spaceflight, video recordings displayed that the number of spontaneous beating sites in flown samples decreased significantly, and the cells in the beating aggregate contracted in fast frequency without synchrony. Radioimmunoassay of the medium showed that the atrial natriuretic peptide secreted from flown cells reduced by 59.6%. Confocal images demonstrated the time-dependant disassembly of mirotubules versus unchanged distribution and or- ganization of microfilaments. In conclusion, above results indicate reduced function and disorganized cytoskeleton of cardiomyocytes in spaceflight, which might provide some cellular basis for further investigations to probe into the mechanisms underlying space cardiovascular dysfunction.

失重环境下航天员平衡控制专项防护策略分析

航天飞行面临的失重会引起航天员运动感觉减弱,进而影响姿势维持和平衡控制,从而限制了出舱活动或着陆等紧急突发状况时航天员快速脱离险境的能力,严重影响航天任务的完成并危及航天员的安全。当前基于运动锻炼的失重对抗措施可在一定程度上有效缓解失重所致的骨骼、肌肉及心血管问题,但并不能有效防止航天飞行后的运动感觉功能紊乱。因此,需要新的失重对抗专项体能训练措施以预防长期空间飞行后人体平衡控制能力的下降。通过对以往航天飞行及模拟失重研究结果的回顾,笔者系统分析了人体平衡控制的影响因素,并对比体育领域平衡控制提升专项体能训练方案提出基于体医融合的失重环境防护策略。肌肉张力、触觉和本体感觉反馈调节在人体姿势平衡和动作控制中起重要作用,而航天失重环境下人体重力负荷的卸载会大大减少上述感觉的输入输出反馈调节,导致平衡功能障碍。在航天飞行中通过纵轴轴向负荷加载、触觉反馈增强和基于不稳定机械应力刺激的本体感觉响应等航天失重环境下航天员专项体能训练,或许可以改善飞行后的平衡控制功能障碍。

自修复弹性体材料的研究进展及应用

综述了基于外援型和本征型2种体系的弹性体材料自修复机理和自修复技术在弹性体材料中的应用,并展望了自修复弹性体材料在载人航天领域的应用前景。