Biochemical constraints for survival under Martian conditions.

A wide variety of terrestrial organisms, the so-called "anhydrobiotes," has learned to survive in a state of extreme dehydration in dry environments. Strategies for survival include the accumulation of certain polyols and nonreducing saccharides, which help to prevent damage to membranes and proteins, but at low water partial pressure DNA is also progressively damaged by various lesions, including strand breaks and cross-linking to proteins. These lesions, if they are not too numerous, can be repaired before the first replication step after rehydration, but long-term exposure to dry conditions finally diminishes the chances of survival as these lesions accumulate. If an organism has no chance to repair the accumulated DNA damage during intermittent periods of active life, survival will not exceed a few decades. The restriction of survival by dryness-induced DNA lesions is corroborated by new data on conidia of Aspergillus and the free plasmid pBR 322. Our results will be discussed with respect to the chance of finding dormant life or biochemical fossils on the surface of Mars.     

Survival in extreme dryness and DNA-single-strand breaks.

A wide variety of organisms (the so-called "anhydrobiotes') is able to survive long periods of time in a state of utmost dehydration and can thus survive in extremely dry environments including artificially imposed or space vacuum. Known strategies of survival include the accumulation of certain polyols, especially disaccharides, which help prevent damage to membranes and proteins. Here we report that DNA in vacuum-dried spores is damaged to a very substantial degree by processes leading to DNA strand breaks. Most of these lesions are obviously repaired during germination, but extensive damage to DNA and enzymes after long exposure times (months to years) finally diminish the chances of survival.     

Mortality and morphological anomalies related to the passage of cosmic heavy ions through the smallest flowering aquatic plant Wolffia arrhiza

Radiobiological effects of single cosmic heavy ions on individual, actively metabolizing test organisms, plants of Wolffia arrhiza, have been explored in an experiment flown aboard the Russian Biosatellite 10. Mortality induced during space flight, population dynamics during subsequent cultivation, and morphological anomalies occurring in the plants of these cultures were investigated. Correlation of these effects with the passage of a heavy ion was achieved by inserting monolayers of plants in a stack of surrounding plastic nuclear track detectors (BIO-STACK). Enhanced initial mortality and delayed decline of induced anomalies have been significantly associated with the passage of single heavy ions, in particular if ions penetrated the budding region of the plants. The prolonged persistence of anomalies in filial generations as an indication of delayed genetic damage has been detected for the first time as the consequence of the hit by a single heavy ion. Regarding radiation protection of space crew during prolonged missions, especially outside the magnetosphere, this appears to be a significant finding.     

A review and comparative analysis of the biological damage induced during space flight by HZE particles and space hadrons

We have studied the somatic and genetic effects of heavy ions (HZE particles) and the very high energy hadrons of space radiation on various organisms ranging in complexity from bacteriophage to man. Experimental data were obtained in space, on high mountains and in a proton accelerator at energies of 76 GeV. In all these experiments local micro- and macroradiational damage was observed. This damage was characterized by severity over large local regions and for the most part was due to cascades of secondary particle bundles resulting from the collosion of very high energy space hadrons with atomic nuclei rather than from cellular hits from relatively low energy single HZE particles. At present there does not appear to be any effective way to provide shielding against these cosmic hadrons.     

The role of gravity in the evolutionary emergence of multicellular complexity: Microgravity effects on arthropod development and aging

While experiments carried out in Space with isolated cells have shown that eucaryotic cells are able to sense and respond to the absence of gravity by modifying their reactions, experiments in which more complex processes have been investigated, such as Biological Systems undergoing development under Microgravity, have been surprisingly unaffected by the space environment. This can be considered a curious result since all organisms are evolutionarily adapted to the current level of the gravity force in our planet and should eventually change if this parameter will vary in a permanent manner. In fact, the small effects of the modifications in gravity on development in short term experiments may be equivalent to the difficulties in detecting the involvement of other basic physical processes such as diffusion-controled auto-organizative reactions in currently developing biological systems. An apparent exception to this lack of effect is experiments where brine shrimp dormant gastrulae directly exposed to the space environment accumulate developmental defects as a consequence of cosmic irradiation. In this article we discuss the idea that at a certain stage during the evolutionary emergence of multicellular organisms the cues laid by generic forces such as gravity were involved in the evolutionary organization of these primitive organisms. As evolution proceed, these early mechanisms may have been obscured and/or made redundant by the appearance of new internal, environment-independent biological regulatory mechanisms. On the other hand, behavioral responses that may be important, for example, in setting the life-spans of organisms may still be more readily susceptible to manipulation by external cues as experiments carried out by our group in Space and on the ground with Drosophila melanogaster indicate.     

复合材料层压板低速冲击行为及剩余拉伸强度

通过实验研究了复合材料层压板的低速冲击行为和剩余拉伸强度。首先,通过冲击实验研究了冲头类型和铺层形式对层压板冲击响应的影响,并通过凹坑深度、损伤投影面积、冲击力和冲击能量转化等对冲击损伤特性进行评估。其次,通过准静态拉伸实验调查了层压板的冲击后拉伸响应和剩余拉伸强度。最后,分析了冲头类型和铺层形式对层压板冲击行为和剩余拉伸强度的影响机理。结果表明:冲头类型对层压板冲击损伤的影响与冲击接触面投影面积和凹坑深度的函数关系密切相关;在较高的冲击能量下,条刃形冲头是造成损伤的关键冲击威胁,而立方角形冲头造成的损伤相对不严重;铺层形式对层压板的冲击损伤阻抗性能和拉伸断裂形貌有明显的影响。      

DNA fragmentation in mammalian cells exposed to various light ions.

Elucidation of how effects of densely ionizing radiation at cellular level are linked to DNA damage is fundamental for a better understanding of the mechanisms leading to genomic damage (especially chromosome aberrations) and developing biophysical models to predict space radiation effects. We have investigated the DNA fragmentation patterns induced in Chinese hamster V79 cells by 31 keV/micrometer protons, 123 keV/micrometer helium-4 ions and gamma rays in the size range 0.023-5.7 Mbp, using calibrated Pulsed Field Gel Electrophoresis (PFGE). The frequency distributions of fragments induced by the charged particles were shifted towards smaller sizes with respect to that induced by comparable doses of gamma rays. The DSB yields, evaluated from the fragments induced in the size range studied, were higher for protons and helium ions than for gamma rays by a factor of about 1.9 and 1.2, respectively. However, these ratios do not adequately reflect the RBE observed on the same cells for inactivation and mutation induced by these beams. This is a further indication for the lack of correlation between the effects exerted at cellular level and the initial yield of DSB. The dependence on radiation quality of the fragmentation pattern suggests that it may have a role in damage repairability. We have analyzed these patterns with a "random breakage" model generalized in order to consider the initial non-random distribution of the DNA molecules. Our results suggest that a random breakage mechanism can describe with a reasonable approximation the DNA fragmentation induced by gamma rays, while the approximation is not so good for light ions, likely due to the interplay between ion tracks and chromatin organization at the loop level.     

The effect of alpha particles on bacteriophage T4Br+.

It is generally accepted that heavy charged particles play an important part in generating the secondary flux of nuclear particles formed by the interaction of space hadrons with nuclei. It is assumed that these particles are responsible for the high biological efficiency of space hadrons in causing cellular damage by their strong interactions. To examine this assumption we investigated the effects of 5.3 MeV alpha particles on bacteriophage T4. This energy provides a LET value of 88.6 KeV/micrometer lying in the range of the highest biological efficiency.     

Life on Mars: how it disappeared (if it was ever there).

The cryptoendolithic microbial community in the Ross Desert (McMurdo Dry Valleys) of Antarctica exists at temperatures significantly below the temperature optima of the primary producers. Surviving near the limit of their physiological adaptability, the organisms are under severe environmental stress, so further deterioration in the environment results in cell damage and death. The sequence of events leading to extinction is considered to be a terrestrial analog for disappearance of possible life on early Mars. Progressive stages of cell damage and death in the Ross Desert material are documented with transmission electron microscopy.     

Classification of gravity effects on “free” cells

When cell physiologists detect gravity related reactions of their objects it is often difficult to decide where the receptors for the observed effects are located. Answering this question is necessary for any further analysis of a detected gravity effect on cells. In previous papers we have discussed direct and indirect gravity effects in relation to the smallest functional units where the primary receptor, which interacts with gravity, is positioned inside and outside of such a unit, respectively. So, in a first approximation we can conclude that in a multicellular aquatic organism, which changes its metabolism in weightlessness, the primary receptors of gravity are located inside the cells of that organism. A special approach is necessary when free living cells, the density of which may be higher than the one of the (liquid) medium, or even cells living on a free surface are observed. In these two cases also indirect effects have to be taken into account, which will be demonstrated with the aid of the slime mold . Additionally the environment of the organisms can be changed directly and indirectly by gravity.     

钛合金表面抗激光涂层损伤特性及热效应影响研究

实验研究了钛合金和高反射型陶瓷涂层材料抗连续型激光烧蚀的损伤及温度分布特性，并从热效应影响角度对比分析了二者在抗激光损伤效果方面的差异性。研究结果表明：相比于钛合金，高反射型陶瓷涂层材料能有效增强钛合金基底抗激光损伤的能力；在同等激光功率密度辐照下，陶瓷涂层材料能有效提升钛合金基底耐受激光辐照的时间长度。实验结果表明该陶瓷涂层材料的激光损伤阈值比钛合金高约5.8倍。实验发现陶瓷涂层温升速率高于钛合金，但由于陶瓷材料具有较高的反射特性，以及良好的热吸收和热传导特性，因此能使由激光辐照产生的热量在其表面较快地扩散，而降低向基底方向传导的程度，最终提升陶瓷涂层的抗激光损伤阈值。     

Influence of different natural physical fields on biological processes.

In space flight conditions gravity, magnetic, and electrical fields as well as ionizing radiation change both in size, and in direction. This causes disruptions in the conduct of some physical processes, chemical reactions, and metabolism in living organisms. In these conditions organisms of different phylogenetic level change their metabolic reactions undergo changes such as disturbances in ionic exchange both in lower and in higher plants, changes in cell morphology for example, gyrosity in Proteus (Proteus vulgaris), spatial disorientation in coleoptiles of Wheat (Triticum aestivum) and Pea (Pisum sativum) seedlings, mutational changes in Crepis (Crepis capillaris) and Arabidopsis (Arabidopsis thaliana) seedling. It has been found that even in the absence of gravity, gravireceptors determining spatial orientation in higher plants under terrestrial conditions are formed in the course of ontogenesis. Under weightlessness this system does not function and spatial orientation is determined by the light flux gradient or by the action of some other factors. Peculiarities of the formation of the gravireceptor apparatus in higher plants, amphibians, fish, and birds under space flight conditions have been observed. It has been found that the system in which responses were accompanied by phase transition have proven to be gravity-sensitive under microgravity conditions. Such reactions include also the process of photosynthesis which is the main energy production process in plants. In view of the established effects of microgravity and different natural physical fields on biological processes, it has been shown that these processes change due to the absence of initially rigid determination. The established biological effect of physical fields influence on biological processes in organisms is the starting point for elucidating the role of gravity and evolutionary development of various organisms on Earth.     

The mechanics of air-breathing in anuran larvae: implications to the development of amphibians in microgravity.

Because of their rapid development, amphibians have been important model organisms in studies of how microgravity affects vertebrate growth and differentiation. Both urodele (salamanders) and anuran (frogs and toads) embryos have been raised in orbital flight, the latter several times. The most commonly reported and striking effects of microgravity on tadpoles are not in the vestibular system, as one might suppose, but in their lungs and tails. Pathological changes in these organs disrupt behavior and retard larval growth. What causes malformed (typically lordotic) tadpoles in microgravity is not known, nor have axial pathologies been reported in every flight experiment. Lung pathology, however, has been consistently observed and is understood to result from the failure of the animals to inflate their lungs in a timely and adequate fashion. We suggest that malformities in the axial skeleton of tadpoles raised in microgravity are secondary to problems in respiratory function. We have used high speed videography to investigate how tadpoles breathe air in the 1G environment. The video images reveal alternative species-specific mechanisms, that allow tadpoles to separate air from water in less that 150 ms. We observed nothing in the biomechanics of air-breathing in 1G that would preclude these same mechanisms from working in microgravity. Thus our kinematic results suggest that the failure of tadpoles to inflate their lungs properly in microgravity is due to the tadpoles' inability to locate the air-water interface and not a problem with the inhalation mechanism per se.     

一个控制超强电离辐射抗性开关基因的研究进展

电离辐射广泛存在于地球和空间,会引起生物体内的DNA损伤,导致机体突变甚至死亡.生物体的DNA损伤响应对于稳定基因组的完整性至关重要.耐辐射奇球菌因其超强的DNA修复能力成为研究DNA损伤修复的模式生物之一.PprI-DdrO系统是近年来发现的一种新型且高效的损伤响应途径,PprI作为响应损伤的重要开关蛋白,通过酶切D...     

Femme: A precursor ecosystem on the Moon

An efficient regenerative life Support system for manned base cannot be conceived without biological processes. Therefore since the 1960's, numerous projects have been initiated to close, as far as possible, the biological loop. Based on the selected concepts (i.e. carbon and/or nitrogen cycles, microbial organisms and/or higher plants) mathermatical models have been studied and built. Unfortunately, to our knowledge these robust models do not take into account the effects of the space environment (i.e. reduced gravity, radiation,…). In the past, a large number of scientific studies has been performed to understand these effects but only a few of them have tried to quantify them. In this paper we present a very simplified concept of an ecosystem. Its objectives, which are compatible with a non-pressurised mission, are on one hand to quantify microbial kinetics and on the other hand to demonstrate the validity of several technologies and technical concepts.     

Do heavy ions cause microlesions in cell membranes?

Heavy ions are a hazard in manned deep space missions. It has been theoretically postulated that when they interact with cells, localized damage in the forms of "microlesions" may occur. Purported morphological evidence of these lesions, however, has not been confirmed in the most extensively studied tissue so far, the cornea. Recent morphological evidence from rat corneas demonstrated that holes in membranes do not form as consequence of heavy ion irradiation. This does not mean, however, that some other form of damage is excluded. For example such damage may be physiological in nature, impairing the ability of cells or tissues to function properly. In order to uncover any physiological effects, we investigated the microlesion question by monitoring the electrical potential difference across the endothelium of rat corneas in vitro before, during, and after irradiation. When the corneas were exposed to 1 Gy of 56Fe ions (450 and 600 MeV/a.m.u.), we detected no effect on this parameter. These results suggest that direct physical damage to cell membranes, as predicted by the microlesion theory, does not take place.     

氮化硼纳米片作为抗原子氧腐蚀填料的应用

对氮化硼纳米片(BNNS)作为填料提高聚合物的抗原子氧腐蚀性能进行了实验研究.利用液相剥离在聚乙烯醇(PVA)水溶液中制备了稳定分散的BNNS,采用基于离心技术的尺寸筛选方法,获得了具有3种不同横向尺寸的BNNS,其平均面积分别约为21.4,4.1, 1.0 μm2.采用浇注法,将PVA/BNNS分散液原位复合成复合薄膜.原子氧腐蚀实验表明:3种 BNNS均能提高PVA的抗原子氧腐蚀性能,添加约1.0 wt%的BNNS(平均面积为21.4 μm2) 可使质量损失降低87%.BNNS对原子氧的成键和壁垒效应,是其提高抗原子氧腐蚀性能的主要原因.      

Dictyostelium discoideum, a lower eukaryote model for the study of DNA repair: implications for the role of DNA-damaging chemicals in the evolution of repair proficient cells.

The evolution of the ability of living cells to cope with stress is crucial for the maintenance of their genetic integrity. Yet low levels of mutation must remain to allow adaptation to environmental changes. The cellular slime mold D. discoideum is a good system for studying molecular aspects of the repair of lethal and mutagenic damage to DNA by radiation and chemicals. The wild-type strains of this soil microorganism are extremely resistant to DNA damaging agents. In nature the amoeboid cells in their replicative stage feed on soil bacteria and are exposed to numerous DNA-damaging chemicals produced by various soil microorganisms. It is probable that the evolution of repair systems in this organism and perhaps in others is a consequence of the necessity to cope with chemical damage which also confers resistance to radiation.     

Inactivation, mutation induction and repair in Bacillus subtilis spores irradiated with heavy ions.

Studies on the response of bacterial spores to accelerated heavy ions (HZE particles) help in understanding problems of space radiobiology and exobiology. Layers of spores of Bacillus subtilis strains, differing in repair capabilities, were irradiated with accelerated boron, carbon and neon ions of linear energy transfer (LET) values up to 14000 MeV cm2/g. Inactivation as measured by loss of colony forming ability and induction of mutations as measured by reversion to histidine prototrophy and resistance to 150 micrograms/ml sodium azide were tested, as well as the influence of repair processes on these effects. For inactivation, the cross-sectional values sigma plotted as a function of LET follow a saturation curve. The plateau, which is reached around a LET of 2000 MeV cm2/g, occurs at 2.5 x 10(-9) cm2, a value in good agreement with the dimensions of the spore protoplast. Lethal damage produced at LET values < 2000 MeV cm2/g is reparable. Recombination repair is more effective than excision repair. At higher LET values, lethal damage could not be reconstituted by the repair mechanisms studied. In addition, at these high LET values, the frequency of induced mutations was drastically decreased. The data support the assumption of at least two qualitatively different types of lesion, depending on the LET of the affecting heavy ion.     

Single ion actions: the induction of micronuclei in V79 cells exposed to individual protons.

Understanding the effects of single-particles from conventional radiation biology experiments is problematic due to the stochastics of particle tracks. This complicates the determinations of risk associated with low doses. We have developed a charged particle microbeam, which allows individually counted particles to be delivered to precise cellular locations. The system is capable of delivering a single charged particle with > 99% efficiency. Of these particles 90% are delivered with a resolution of +/- 2 micrometers and 96% with a resolution of +/- 5 micrometers. We have carried out preliminary studies in Chinese hamster V79 cells to monitor the effectiveness of low energy protons at inducing cytological damage. We have used the micronucleus assay as a measure of predominantly lethal chromosome damage. The effects of a single 3.2 MeV proton delivered individually to cells could be measured, with less than 2% of the exposed cells producing micronuclei 24 hours later. The yield of micronuclei formation was essentially linear up to the highest dose (30 particles per cell nucleus) delivered. Ultimately, the ability to target particles to different parts of the cell nucleus may start to impact on models available for chromosome aberration formation and chromosomal Organisation and mechanisms underlying genomic instability.