Exploration of plant growth and development using the European Modular Cultivation System facility on the International Space Station

Space experiments provide a unique opportunity to advance our knowledge of how plants respond to the space environment, and specifically to the absence of gravity. The European Modular Cultivation System (EMCS) has been designed as a dedicated facility to improve and standardise plant growth in the International Space Station (ISS). The EMCS is equipped with two centrifuges to perform experiments in microgravity and with variable gravity levels up to 2.0 g. Seven experiments have been performed since the EMCS was operational on the ISS. The objectives of these experiments aimed to elucidate phototropic responses (experiments TROPI‐1 and ‐2), root gravitropic sensing (GRAVI‐1), circumnutation (MULTIGEN‐1), cell wall dynamics and gravity resistance (Cell wall/Resist wall), proteomic identification of signalling players (GENARA‐A) and mechanism of InsP₃ signalling (Plant signalling). The role of light in cell proliferation and plant development in the absence of gravity is being analysed in an on‐going experiment (Seedling growth). Based on the lessons learned from the acquired experience, three preselected ISS experiments have been merged and implemented as a single project (Plant development) to study early phases of seedling development. A Topical Team initiated by European Space Agency (ESA), involving experienced scientists on Arabidopsis space research experiments, aims at establishing a coordinated, long‐term scientific strategy to understand the role of gravity in Arabidopsis growth and development using already existing or planned new hardware.     

Development of a plant growth support system for experiments on the ISS

The European Modular Cultivation System (EMCS) is one of a wide range of laboratory modules under construction by ESA that will be placed on the International Space Station (ISS). In the present study the development and construction of an important component in the EMCS, the Plant Cultivation Container (PCC), is described. The PCC as a "flower pot" will automatically provide the plants with water and liquid nutrients as needed. The PCC is located inside the plant growth unit, the Experiment Container (EC), on the EMCS and interfaces with the EMCS. The essential parts of the PCC are a Peltier element, a micro valve, a monitoring RH sensor with an integrated platinum RTD temperature sensor, a RH sensor that detects air leaving the PCC and controls the peristaltic pump, a DC-DC board that provides correct current to the Peltier element, and a switch/connector board. The PCC is presently being tested out at ESTEC/ESA.     

BIOLAB, EPU and EMCS for cell culture experiments on the ISS

Two ESA facilities are under development for biological research on the International Space Station: BIOLAB as part of the European "Columbus" Laboratory and the European Modular Cultivation System (EMCS), foreseen for accommodation in the US Lab "Destiny". Both facilities have an incubator (18-40 degrees C) and use standard Experiment Containers, mounted on two centrifuge rotors providing either microgravity or variable g-levels from 0.001 x g to 2.0 x g. Standard interface plates supply each container with power and data lines, with gas (controlled CO2, O2 and water vapour concentration; trace gas removal), and--for EMCS only--with water. The degree of automation is higher in BIOLAB: it contains a robotic Handling Mechanism for automatic sampling and handling of liquids, which can be stored at cool or cold temperatures or injected for automatic on-board analysis into a microscope or a spectrophotometer. For analyses on the running centrifuge, small automatic microscopes can be installed in the Experiment Containers. Several designs for supporting cell culture experiments have been studied for BIOLAB and EMCS. BIOLAB has in addition a Bio-Glovebox, which can be sterilised and where new cell cultures may be prepared under 1 x g conditions from deep-frozen samples in the Experiment Preparation Unit (EPU): the cryo-protectant will be removed by automatic washing cycles. Both facilities, EMCS and BIOLAB (with EPU), have also provisions for telescience operations through video, data and command lines, either operated by the crew or by the experimenter on ground.     

On-line estimation of the specific growth rate based on viable biomass measurements: experimental validation

The application of model based control techniques to biotechnological processes is often hampered due to the lack of reliable on-line sensors. This problem can be tackled by the application of software sensors, in which the available hardware measurements are combined with the model equations. The resulting estimates serve as additional measurements useful for process monitoring and control. In this paper, an observer based estimator for the specific growth rate based on on-line viable biomass measurements is studied. Several fed-batch experiments with baker's yeast in a stirred tank bioreactor illustrate the design, tuning, and implementation from a practical point of view. The main contributions of this paper are to illustrate (i) the implementation and validation of the presented algorithm in real-time, (ii) the use of an advanced on-line biomass measurement, and (iii) the design and tuning of the algorithm from a practical point of view. Real-time knowledge of the specific growth rate is important because it yields information on the viability of the cells and it can be used in real-time feedback control algorithms.     

Plant growth using EMCS hardware on the ISS

Under separate contracts with ESA (FUMO and ERM Study) and as a link in the development of the European Modular Cultivation System's (EMCS) functionality and biocompatibility, plant studies have been performed at The Plant Biocentre in Trondheim, Norway. The main goal was to test whether the breadboards containing the major components planned for use in the EMCS would be optimal for space experiments with plant material. The test plans and the experimental set-up for the verification of biocompatibility and biological functionality included the use of a few model plant species including cress (Lepidium sativum L.) and Arabidopsis thaliana. The plants were tested at different developmental levels of morphological and physiological complexity (illumination, life support, humidity control, water supply, observation, short- and long-term plant growth experiments and contamination prevention). Results from the tests show that the EMCS concept is useful for long duration plant growth on the ISS.     

A Simple Geometrical Pattern for the Branching Distribution of the Bronchial Tree, Useful to Estimate Optimality Departures

The design of the bronchial tree has largely been proposed as a model of optimal design from a physical-functional perspective. However, the distributive function of the airway may be more related to a geometrical than a physical problem. The bronchial tree must distribute a three dimensional volume of inspired air on a two dimensional alveolar surface, included in a limited volume. It is thus valid to ask whether an optimal bronchial tree from a physical perspective is also optimum from a geometrical point of view. In this paper we generate a simple geometric model for the branching pattern of the bronchial tree, deducing relationships that permit estimation of the departures from the geometrical optimum of each bifurcation. We also, for comparative purposes, estimate the departures from the physical optimum. From the geometrical assumptions: i) a symmetrical dichotomic fractal design, ii) with minimum volume and iii) maximum dispersion of the terminal points; and several simulations we suggest that the optimality is characterized by a bifurcation angle theta approximately 60 degrees and a length reduction scale gamma = (1/2)(1/3) = 0.7937. We propose distances from the physical and geometrical optimality defined as Euclidean distances from the expected optima. We show how the advanced relationships and the distances can be used to estimate departures from the optimality in bronchographs of four species. We found lower physical and geometrical departures in the distal zone than those of the proximal zones, as well as lower physical than geometrical departures from optimality.     

NMR radiofrequency microcoil design: usefulness of electromagnetic simulation

The extraction of the Nuclear Magnetic Resonance (NMR) spectra of samples having smaller and smaller volumes is a real challenge. Either these reductions of volume are dictated by the difficulties of production of sufficiently large samples or by necessities of miniaturisation of the analysing system, in both cases a careful design of the radiofrequency coil, ensuring an optimum reception of the NMR signal, is required. We have also evaluated the usefulness of electromagnetic simulation software for the design and optimisation of these radio-frequency coils, which are more and more used in biology and health research projects.     

Polymer networks as actuator and sensor systems to be used for automation of biomedical devices]

Polymer networks are based on molecules which are covalently or physically connected in a three-dimensional network. In presence of an appropriate solvent these networks swell by solvent absorption to form gels. These gels, which are called hydrogels in case of water absorption, are able to change their volume by more than a hundred-fold. During the swelling or shrinking process the hydrogels perform a mechanical work. Their volume standardized working capacity can be ten-times larger than that of an electromagnet. Due to their simple design, miniaturisation properties, and their ability to realize many automatic sensor and actuator functions, smart hydrogels offer new solutions in biomedical technology.     

A magnetoelastic resonance biosensor immobilized with polyclonal antibody for the detection of Salmonella typhimurium

Mass-sensitive, magnetoelastic resonance sensors have a characteristic resonant frequency that can be determined by monitoring the magnetic flux emitted by the sensor in response to an applied, time varying, magnetic field. This magnetostrictive platform has a unique advantage over conventional sensor platforms in that measurement is wireless and remote. A biosensor for the detection of Salmonella typhimurium was constructed by immobilizing a polyclonal antibody (the bio-molecular recognition element) onto the surface of a magnetostrictive platform. The biosensor was then exposed to solutions containing S. typhimurium bacteria. Binding between the antibody and antigen (bacteria) occurred and the additional mass of the bound bacteria caused a shift in the sensor's resonant frequency. Sensors with different physical dimensions were exposed to different concentrations of S. typhimurium ranging from 10(2) to 10(9)CFU/ml. Detection limits of 5x10(3) CFU/ml, 10(5) CFU/ml and 10(7) CFU/ml were obtained for sensors with the size of 2 mmx0.4 mmx15 microm, 5 mmx1 mmx15 microm and 25 mmx5 mmx15 microm, respectively. Good agreement between the measured number of bound bacterial cells (as measured by scanning electron microscopy (SEM)) and frequency shifts was obtained.     

A Three-Dimensional Finite Element Scheme to Investigate the Apparent Mechanical Properties of Trabecular Bone

A computational technique is described for investigating the apparent mechanical properties of trabecular bone based on tissue geometry obtained from the marching cubes volume rendering scheme. Using this scheme, a 3D representation of the trabecular bone was extracted from two-dimensional cross-sections of the tissue originating from a quantitative serial sectioning procedure. Surface information consists of node coordinates and polygon connectivity in a 3D space. A custom, adaptive mesh generation technique using a normal offset was used to prepare 3D finite element volume meshes (4-node tetrahedral elements) of variable mesh density from the extracted surface geometry. Nine target mesh resolutions (32 μm to 107 μm) were examined for a (1.5 mmx 1.5 mmx 2 mm) volume of trabecular bone. A mesh density of 50,000 elements/mm(3) of bone tissue was found to be adequate for convergence of apparent (bulk) modulus for 1% uniaxial compression. For this convergent case, the maximum local normal compressive tissue stress was 400 MPa which was six hundred-fold greater than the computed apparent stress. Variation in the apparent modulus was less than 5% when Poisson's ratio values were varied between 0.1 and 0.4. Poisson's ratio values greater than 0.4 had a more marked effect on the apparent modulus. Based upon these results, approximately 1 million, 4-node tetrahedral elements are required to analyze a continuum scale model of trabecular bone (5 mm cube).     

Sensitivity of the cell cycle to TGFβ1 does not correlate with transformation of a rat liver epithelial cell line

The effects of TGF1 on cell cycle events in a rat liver derived epithelial cell line (BL9) and in two in vitro transformants of this line were studied by flow cytometry. Using either ethidium bromide staining or the incorporation of bromodeoxyuridine to evaluate DNA synthesis it was shown that TGF1 prevented the entry of G0/G1 phase BL9 cells into S phase. TGF1 did not exert its inhibitory effect(s) on DNA synthesis by the modulation of early events in the cell cycle. The tumorigenic transformed BL9 cell lines gave contrasting responses to the effects of TGF1. DNA synthesis in a BL9 cell line derived by transfection with an active N-ras oncogene was unaffected by TFG1 and thus appeared refractory to its growth controlling effects. On the other hand cells from a BL9 cell line derived by in vitro transformation with activated aflatoxin B₁ retained their sensitivity to the effects of TGF1. Thus the loss of the inhibitory effect of TGF1 on DNA synthesis is not obligatory for the malignant transformation of rat liver epithelial cells.Abbreviations TGF1 transforming growth factor 1 - BSA bovine serum albumin - FBS foetal bovine serum - BrdUrd bromodeoxyuridine - PI propidium iodide - PBS phosphate buffered saline     

The chemical-biological interface: developments in automated and miniaturised screening technology

The rapidly changing developments in genomics and combinatorial chemistry, generating new drug targets and large numbers of compounds, have caused a revolution in high-throughput screening technologies. Key to this revolution has been the introduction of robotics and automation, together with new biological assay technologies (e.g., homogeneous time resolved fluorescence). With ever increasing workloads, together with economic and logistical constraints, miniaturisation is rapidly becoming essential for the future of high-throughput screening and combinatorial chemistry. This is evident from the introduction of high-density microtitre plates, small volume liquid handling robots and associated detection technology.     

Organic contamination problems in the Viking molecular analysis experiment

The combination of analytical instrumentation selected for the molecular analysis experiment can carry out a survey of the organic compounds present on Mars regardless of their origin. The high sensitivity of this analysis, the limited number of samples which can be analyzed, the close proximity to the landed spacecraft on the surface of Mars which is accessible to the sampling device, the implications of the positive detection of indigenous organic matter in the Martian soil, and our previous experience with meteorites and lunar samples point to the need for a carefully designed program to maintain the inteprity of the analyzed Martian surface samples. A principal problem in interpreting the results of an organic analysis of an extraterrestrial sample is that of distinguishing contaminating material from indigenous material when unknown types and amounts of contaminants make their way into the sample being analyzed. An approach for control of sample integrity in the Viking molecular analysis experiment has been devised which we believe will eliminate such problems. Basically this involves (1) placing an upper limit on the amount of terrestrial contamination that can be tolerated and still allow scientifically meaningful analyses, (2) identifying the potential sources of contamination and analyzing their relative significance, (3) establishing methods to control these sources, and (4) obtaining complete information on the chemical composition of potential contaminants. Our previous experience in the Apollo mission has been of great value in developing the Viking program, perhaps the most important carryover being the recognition of the importance of establishing a comprehensive contamination control program in the early stages of mission planning and hardware design. The upper limit of total allowable organic contamination has been established as 1 μg g^?1. The principal source types, or modes, which contribute to the contamination load have been identified, each requiring a different approach to control. Spacecraft outgassing is controlled by materials selection to minimize outgassing and hermetic sealing whenever possible. Particulate fallout is controlled by selection of materials, particulate seals, cleaning of the spacecraft exterior, and clean room handling. The cleanliness of the direct sample path is controlled by severe materials limitations, ultracleaning, and pressurized sealing of the assembled hardware. Analysis of the relative probabilities of the sources contributing to the allowable contamination and consideration of the practical aspects of achieving a desired level of control for a particular source has resulted in an allocation ‘tree’ whereby fractions of the total allowable contamination are distributed to the various individual sources. These efforts have pointed out the need for more information concerning some of these sources and have actually dictated certain design changes in the spacecraft. Additional information was obtained experimentally on descent engine exhaust characteristics which led to the use of an organically cleaner fuel. In summary, the early recognition in the Viking mission of the importance of organic contamination control has allowed the evolution of a complete contamination control program encompassing spacecraft design, mission operations, flight operations, and the design of the science instrumentation for the molecular analysis experiment.     

Gene expression and nuclear architecture during development and differentiation

Development requires a precise program of gene expression to be carried out. Much work has focussed on the regulatory networks that control gene expression, for example in response to external cues. However, it is important to recognize that these regulatory events take place within the physical context of the nucleus, and that the physical position of a gene within the nuclear volume can have strong influences on its regulation and interactions. The first part of this review will summarize what is currently known about nuclear architecture, that is, the large-scale three-dimensional arrangement of chromosome loci within the nucleus. The remainder of the review will examine developmental processes from the point of view of the nucleus.     

Estimation of aortic distensibility and instantaneous left ventricular volume in living man

A method is presented in this paper for the estimation of aortic distensibility and instantaneous systolic left ventricular volume in living man in the absence of valvular regurgitation. The method is based on a simple, elastic-reservoir-theory, model of the circulatory system and requires no assumption concerning the geometry of the left ventricle. The input data required for this mathematical model consists of stroke volume, an aortic pressure record over an entire cardiac cycle and end diastolic ventricular volume. The procedure developed here for the estimation of aortic distensibility and instantaneous left ventricular volume is very practical from a computational point of view. It is believed that it will yield useful information concerning two clinically important quantities which cannot be measured directly in living man and will facilitate the study of correlations between these quantities and various physiological and pathological states. Results are presented in the paper for six cardiac patients. The requisite data in each case was obtained in the Cardiac Research Laboratory at the Peter Bent Brigham Hospital.     

Electroviscous effect of lysozyme in aqueous solutions

Reduced viscosity of a dilute aqueous solution of hen egg white lysozyme is measured in the pH range from 1.4 to 12.7 for various NaCI concentrations. The viscosity decreases with increasing pH below the isoelectric point (pH 11) on account of diminution in the electroviscous effect, reaches a minimum at pH 11, and then increases at high pH's because of coagulation. The electroviscous effect is depressed by the increase in the small ion concentration. The dependence of reduced viscosity on small ion concentration and pH is discussed on the basis of Booth's theory and a partial agreement between theory and experiment is obtained. The discrepancy between theory and experiment is attributed to non-spherical distribution of charges in the protein. The volume of lysozyme obtained through Einstein's equation by extrapolating the reduced viscosity to a sufficiently high ion concentration compares well with the molecular volume in the crystal.     

Material Flow Indicators in the Czech Republic in Light of the Accession to the European Union

This article deals with the economy‐wide material flows in the Czech Republic in 1990–2006. It presents in brief the overall trends of the material flow indicators in 1990–2002. The major part of the article is focused on the years 2002–2006, which immediately preceded and followed the accession of the Czech Republic to the European Union in 2004. It is shown that this accession had quite a significant impact on the volume and character of the material flows of the Czech Republic. The accession was beneficial from an economic point of view, as it allowed for an increased supply of materials needed for economic growth. Furthermore, it was accompanied by an improvement in the efficiency of material transformation into economic output. From an environmental and broader sustainability point of view, however, this accession brought about some controversial outcomes. There was a significant increase in the net export of environmental pressure, on one hand, and an increase in net additions to the physical stock of the economy, on the other. Although the former is controversial from the viewpoint of equity in sharing area and resources, the latter places an additional burden on future generations because all physical stocks will turn into waste and emissions at some point, when their life span expires.     

Parametric analysis of volume distributions of Schizosaccharomyces pombe and other cells

Time-lapse photomicrographic data have been obtained on mating strains of the yeast Schizosaccharomyces pombe to evaluate the effect of the variability of the patterns of cell cycle behavior on population structure. These have been used to design a computer model which accepts volume distribution data from exponential cultures of a cell and yields estimates of the mean and standard deviation of daughter cell volume and telophase cell volume, as well as a stop-grow point, and the degree of cell volume doubling. Given a cell population's volume distribution and a volume distribution from a subpopulation, the program will estimate the mean age and display how the age is distributed in the subpopulation. Several cell types have been examined.     

Plasma volume expansion increases lysophosphatidylcholine and digitalis-like activity in rat plasma

A circulating factor with digitalis-like activity has been proposed to play a role in the regulation of plasma volume. Lysophosphatidylcholine has been found to be active in many assays for digitalis-like activity. To examine the relationship between plasma digitalis-like activity and plasma lysophosphatidylcholine, the effect of plasma volume expansion with saline on the plasma levels of phospholipids and on the ability of delipidated extracts of plasma to displace tritiated ouabain from the digitalis receptor was determined. Lysophosphatidylcholine was elevated after 15, 30, and 120 minutes of volume expansion but was decreased at 60 minutes. Phosphatidylcholine was decreased at 15, 60, and 120 minutes. Plasma sphingomyelin was not altered at any time point. The ability of plasma to displace tritiated ouabain was increased only at the 60 minute time point. These results indicate that the increase in digitalis-like activity in volume expanded states is mediated by a combination of at least two factors, lysophosphatidylcholine and another factor whose digitalis-like activity is not related to the surfactant actions of a lipid.