Effects Of Simulated Microgravity Research Articles

Simulated microgravity modulates the mesenchymal stromal cell response to inflammatory stimulation

The duration and distance of manned space flights emphasizes the importance of advanced elucidation of space flight factors and their effects on human beings. The exposure to inflammatory mediators under microgravity may contribute to the activity of different cells, perivascular stromal cells (MSCs) in particular. Inflammatory activation is now considered as a principal cue of MSC engagement in reparative remodeling. In the present paper, the effect of simulated microgravity (sµg) on TNFα-mediated priming of adipose tissue-derived MSC (ASCs) was examined. Sµg per se did not induce inflammatory-related changes, such as elevation of ICAM-1 and HLA-ABC expression, soluble mediator production, or shifting of the transcription profile in ASCs. Moreover, the attenuated ASC response to TNFα priming under sµg was manifested in decreased production of TNFα-dependent pleiotropic cytokines (IL-8 and MCP-1), matrix remodeling proteases, and downregulation of some genes encoding growth factors and cytokines. Time-dependent analysis detected the first signs of priming attenuation after 48 hours of 3D-clinorotation. A reduced response of MSCs to priming under sµg can be a negative factor in terms of MSC involvement in tissue remodeling processes.

Effects of Spaceflight and Simulated Microgravity on YAP1 Expression in Cardiovascular Progenitors: Implications for Cell-Based Repair.

Spaceflight alters many processes of the human body including cardiac function and cardiac progenitor cell behavior. The mechanism behind these changes remains largely unknown; however, simulated microgravity devices are making it easier for researchers to study the effects of microgravity. To study the changes that take place in cardiac progenitor cells in microgravity environments, adult cardiac progenitor cells were cultured aboard the International Space Station (ISS) as well as on a clinostat and examined for changes in Hippo signaling, a pathway known to regulate cardiac development. Cells cultured under microgravity conditions, spaceflight-induced or simulated, displayed upregulation of downstream genes involved in the Hippo pathway such as YAP1 and SOD2. YAP1 is known to play a role in cardiac regeneration which led us to investigate YAP1 expression in a sheep model of cardiovascular repair. Additionally, to mimic the effects of microgravity, drug treatment was used to induce Hippo related genes as well as a regulator of the Hippo pathway, miRNA-302a. These studies provide insight into the changes that occur in space and how the effects of these changes relate to cardiac regeneration studies.

Simulated microgravity induces nuclear translocation of Bax and BCL-2 in glial cultured C6 cells

Alterations in the control of apoptotic processes were observed in cells during space flight or under simulated microgravity, the latter obtained with the 3D-Random Positioning Machine (3D-RPM).Usually the proteins Bax and Bcl-2, act as pro- or anti-apoptotic regulators. Here we investigated the effects of simulated microgravity obtained by the 3D-RPM on cell viability, localization and expression of Bax and Bcl-2 in cultures of glial cancerous cells. We observed for the first time a transient cytoplasmic/nuclear translocation of Bax and Bcl-2 triggered by changing gravity vector. Bax translocates into the nucleus after 1 h, is present simultaneously in the cytoplasm after 6 h and comes back to the cytoplasm after 24 h. Bcl-2 translocate into the nucleus only after 6 h and comes back to the cytoplasm after 24 h. Physiological meaning, on the regulation of apoptotic event and possible applicative outcomes of such finding are discussed.

The comparison of the apoptosis effects of titanium dioxide nanoparticles into MDA-MB-231 cell line in microgravity and gravity conditions

Objective (s): Gravity could affect some system features and perform directly as an organizing field factor. Recent investigations have examined the titanium dioxide nanoparticles (TiO2 NPs) in biomedical applications, mostly in the cancer treatment field. This study aimed to evaluate the effects of simulated microgravity combined with TiO2 NPs in MDA-MB-231 cells proliferation for the first time. In other words, this study examined the utility of the microgravity environment in nano-therapy. Materials and Methods: The MDA-MB-231 human breast cancer cell line and TiO2 NPs were purchased. The 2D clinostat was applied for the simulation of the microgravity. The morphological studies, MTT cytotoxicity assay, Acridine orange/Ethidium bromide double staining studies and flow cytometry analysis were utilized.Results: The MTT assay, the morphological studies, Acridine orange/Ethidium bromide double staining studies and flow cytometry analysis confirmed the apoptosis-inducing effect of microgravity in combination with TiO2 NPs. The IC50 of simulated microgravity in the presence of TiO2 NPs was determined to be 130 µM. Furthermore, MDA-MB-231 cells exposed to microgravity adopted a different phenotype. Conclusion: Based on our observation, although the relative mechanisms need to be explored further, microgravity can strictly affect the TiO2 NPs effects on MDA-MB-231 cells. The significance of this study lied in the fact that simulating microgravity can be a powerful physical cure for cancer therapy and open new horizons for the studies in the field of biology, biophysics, and medicine.

Overexpression of Catalase in Mitochondria Mitigates the Inflammatory Effects of Simulated Microgravity and Social Isolation in Mouse Hippocampus

Space flight missions are becoming longer and more common and evidence points to the physiological toll the missions have on the human body. Aging, sedentary lifestyle, and spaceflight have similar degenerative effects on almost every part of our body; both exposure to the space environment and aging result in cardiovascular deconditioning, bone loss, muscle atrophy, brain changes, and immune response impairment. We hypothesize that exposure to the space environment generates excessive Reactive Oxygen Species (ROS), which results in neuroinflammation and aging‐like degenerative symptoms in the brain. We used the hindlimb unloading (HU) model to mimic microgravity with either paired or single housed animals (social isolation). Responses to 30d of HU were compared in wildtype or transgenic MCAT mice, in which mitochondrial ROS is quenched by over‐expression of human catalase. Expression of 4‐Hydroxynonenal (4HNE) and Park7 (redox‐sensitive chaperone and sensor of oxidative stress) were measured by ELISA, a protein array quantified from the hippocampal cytokines and 8‐hydroxy‐2’‐deoxyguanosine in serum was measured by ELISA to assess oxidative DNA damage. Preliminary analysis of cage behavior patterns from video collected at the end of the study showed that MCAT HU mice (socially housed) were more active and conducted more exploratory activities compared to NL. Our biochemical results showed simulated microgravity and/or social isolation caused changes in levels of cytokines related to immune responses. Two‐way ANOVA revealed significant interaction effects of HU and genotype in expression levels of five cytokines (out of 35) in socially‐housed animals. Elevation of these generally pro‐inflammatory cytokines by HU in WT mice was mitigated in MCAT mice, suggesting a role for mitochondrial ROS signaling in inflammatory CNS responses to microgravity. Interestingly, some of these cytokines in the hippocampus displayed strong correlations to the 4HNE levels. We also found substantive cytokine responses to social isolation in the hippocampus; housing and genotype interaction effects were significant (by 2‐Factor ANOVA) for 15 cytokines, most of which were mitigated in MCAT mice.Taken together, our results showed that both simulated microgravity and social isolation influenced cytokine levels in the hippocampus and MCAT mice were at least partially protected from these changes. These findings implicate a potentially important role for mitochondrial ROS in CNS responses to the challenges posed by long duration spaceflight.Support or Funding InformationThis work is supported by a NASA Space Biology Grant to RKG (NNH14ZTT001N). LG was supported by a Space Biology NASA Postdoctoral Fellowship AwardThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of simulated microgravity induced PI3K-nos2b signalling on zebrafish cardiovascular plexus network formation

Local abnormal angiogenesis and cardiovascular system reorganization have been observed in embryos exposed to a simulated microgravity (SM) environment. In this study, changes in key molecular signals and pathways in cardiovascular development have been investigated under microgravity conditions. In particular, the caudal vein plexus (CVP) network, formed by sprouting angiogenesis has been chosen. Zebrafish embryos were exposed to SM using a ground-based microgravity bioreactor for 24 and 36 h. The SM was observed to have no effect on the zebrafish length, tail width and incubation time whereas it was observed to significantly reduce the heart rate frequency and to promote abnormal development of the CVP network in the embryos. Nitric oxide (NO) content demonstrated that the total proteins in zebrafish embryos were significantly higher in SM than in the control group grown under normal conditions. It was then preliminarily determined how NO signals were involved in SM regulated zebrafish CVP network formation. nos2b MO was injected and CVP network evolution was observed in 36 h post fertilization (hpf) under SM condition. The results showed that the CVP network formation was considerably decreased in the nos2b MO treated group. However, this inhibition of the CVP network development was not observed in control MO group, indicating that nos2b is involved in the SM-regulated vascular development process in zebrafish. Moreover, specific phosphoinositide 3-kinase (PI3K) inhibitors such as LY294002 were also tested on zebrafish embryos under SM condition. This treatment significantly inhibited the formation of zebrafish CVP network. Furthermore, overexpression of nos2b partly rescued the LY294002-caused CVP network failure. Therefore, it can be concluded that SM affects zebrafish CVP network remodeling by enhancing angiogenesis. Additionally, the PI3K-nos2b signaling pathway is involved in this process.

3D-clinorotation induces specific alterations in metabolite profiles of germinating Brassica napus L. seeds

During the whole history of their life on Earth, higher plants evolved under the constant gravity stimulus. Therefore, plants developed efficient mechanisms of gravity perception, underlying their ability to adjust the direction of growth to the gravity vector, i.e. the phenomenon of gravitropism. In this context, alterations in the magnitude and vector of the gravity field might compromise plant growth and development. This aspect was successfully addressed in gravity fields of low intensity (microgravity). On the other hand, microgravity can be simulated on the Earth by clinorotation, i.e. rotation of the experimental plant along one or several axes. This approach is routinely used for studies of gravity-related responses of crop plants, although the effect of simulated microgravity on the most sensitive ontogenetic stages — germination and seedling development — is still not sufficiently characterized. Recently, we addressed the effects of clinorotation on the proteome of germinating oilseed rape (Brassica napus) seeds. Here we extend this study to the seedling primary metabolome and address its changes in the presence of 3D-clinorotation. GC-MS analysis revealed essential alterations in patterns of sugars and sugar phosphates (specifically glucose-6-phosphate), methionine and glycerol. Thereby, abundances of individual metabolites showed high dispersion, indicating high lability and plasticity of the seedling metabolome.

The Effect of Short-and Long-Term Simulated Microgravity on Immune Cells

Long-term space flight will be a major mission for International Space Administration. However, it has been shown that exposure to space flight result in immune system dysfunction. Therefore, understand the mechanism of immun... | Find, read and cite all the research you need on Tech Science Press

Combined Effects of Low-Dose Proton Radiation and Simulated Microgravity on the Mouse Retina and the Hematopoietic System.

The purpose of the current study was to characterize the effects of simulated microgravity and radiation-induced changes in retina and retinal vasculature, and to assess the accompanying early changes in immune cells and hematological parameters. To better understand the effects of spaceflight, we used a combination of treatments designed to simulate both the radiation and low-gravity aspects of space conditions. To simulate the broad energy spectrum of a large solar particle event (SPE) and galactic cosmic ray (GCR) radiation, male C57BL/6J mice were exposed to whole-body irradiation using fully modulated beams of 150-MeV protons containing particles of energy from 0 to 150 MeV and a uniform dose-vs.-depth profile. The mice were also hindlimb-unloaded (HLU) by tail suspension. Mice were unloaded for 7 days, exposed to 50 cGy, unloaded for an additional 7 days and then sacrificed for tissue isolation at days 4 and 30 after the combined treatments. Increases in the number of apoptotic cells were observed in the endothelial cells of mice that received radiation alone or with HLU compared to controls at both days 4 and 30 (P < 0.05). Endothelial nitric oxide synthase (eNOS) levels were significantly elevated in the retina after irradiation only or combined with HLU compared to controls at the 30-day time point (P < 0.05). The most robust changes were observed in the combination group, suggesting a synergistic response to radiation and unloading. For hematopoietic parameters, our analysis indicated the main effects for time and radiation at day 4 after treatments (day 11 postirradiation) (P < 0.05), but a smaller influence of HLU for both white blood cell and lymphocyte counts. The group treated with both radiation and HLU showed greater than 50% reduction in lymphocyte counts compared to controls. Radiation-dependent differences were also noted in specific lymphocyte subpopulations (T, B, natural killer cells). This study shows indications of an early effect of low-dose radiation and spaceflight conditions on retina and immune populations.

Investigation on rat intestinal homeostasis alterations induced by 7-day simulated microgravity effect based on a proteomic approach

The present study aims at investigating alterations of rat intestinal homeostasis induced by 7-day simulated microgravity (SMG) effect through a proteomic approach. Tail-suspension model was used to simulate microgravity effect and a label-free quantitative proteomic strategy was employed to determine proteins in rat intestine. As a result, 717 differently expressed proteins were identified and 29 proteins were down-regulated while 688 proteins were up-regulated. 283 out of 717 proteins were categorized into 7 clusters with DAVID (version 6.8). The three highest enrichment scores were annotation cluster I about cell-cell adhesion (46 proteins with enrichment score of 16.67), annotation cluster II about carbohydrate metabolism (32 proteins with enrichment score of 6.17) and annotation cluster III about activity of pepdtidase (17 proteins with enrichment score of 4.74). Results of rat intestine proteomics indicate that SMG might disrupt intestinal homeostasis, which possibly resulted in opening of intestinal epithelial barrier (IEB), potentially leading to risk of systemic inflammatory response (SIR) and inflammatory bowel diseases (IBD). The present results also provide some useful information for mechanism and countermeasures of intestine injuries induced by microgravity.

Effects of simulated microgravity on the expression profiles of RNA during osteogenic differentiation of human bone marrow mesenchymal stem cells.

ObjectivesExposure to microgravity induces many adaptive and pathological changes in human bone marrow mesenchymal stem cells (hBMSCs). However, the underlying mechanisms of these changes are poorly understood. We revealed the gene expression patterns of hBMSCs under normal ground (NG) and simulated microgravity (SMG), which showed an interpretation for these changes by gene regulation and signal pathways analysis.Materials and methodsIn this study, hBMSCs were osteogenically induced for 0, 2, 7 and 14 days under normal ground gravity and simulated microgravity, followed by analysis of the differences in transcriptome expression during osteogenic differentiation by RNA sequencing and some experimental verification for these results.ResultsThe results indicated that 837, 399 and 894 differentially expressed genes (DEGs) were identified in 2, 7 and 14 days samples, respectively, out of which 13 genes were selected for qRT‐PCR analysis to confirm the RNA‐sequencing results. After analysis, we found that proliferation was inhibited in the early stage of induction. In the middle stage, osteogenic differentiation was inhibited, whereas adipogenic differentiation benefited from SMG. Moreover, SMG resulted in the up‐regulation of genes specific for tumorigenesis in the later stage.ConclusionOur data revealed that SMG inhibits the proliferation and inhibits the differentiation towards osteoblasts but promotes adipogenesis. SMG also selects highly tumorigenic cells for survival under prolonged SMG.

Effects of RCCS simulated microgravity on proliferation and cell cytoskeleton of human HaCaT keratinocyte

Objective To investigate the effects of simulated microgravity by RCCS on proliferation and cell cytoskeleton of human HaCaT keratinocyte. Methods The rotary cell culture system (RCCS) was used to simulate the microgravity environment, and human HaCaT keratinocytes were divided randomly(random number) into the simulated microgravity group (SMG) and normal gravity group (NG). HaCaT cells in the two groups were harvested respectively after 32, 36 and 42 h culture. The HaCaT cells proliferation and cycles were detected by flow cytometry, the concentration of hb-EGF in supernatant was detected by ELISA, and the cell cytoskeleton was observed after 42 hours’ culture under laser confocal microscope with FITC-labeled technique. SPSS 23.0 statistical software was used for statistical analysis, and P <0.05 was considered statistically significant. Results The flow cytometry showed that the proportions of human HaCaT keratinocytes in G1 and G2/M phases were increased while the proportion of HaCaT cells in S stage was decreased significantly after 32, 36 and 42 h RCCS culture compared with those in the normal gravity group. The HaCaT cells in G1 stage were declined along with incubation time. ELISA results showed that the hb-EGF concentration in HaCaT supernatant under simulated microgravity culture for 24 and 36 h was lower than that in the normal control group (P<0.01). The laser confocal microscope revealed that the HaCaT fluorescence intensity was decreased, and there were disordered microfilaments, structural ambiguity, pseudopodia reduction and irregular shape among FITC-labeled HaCaT cells cultured 42 h in RSSC compared with the normal gravity group. Conclusions RCCS simulated microgravity environment could inhibit the cell cycle transformation and proliferation of human HaCaT keratinocyte, affect the keratinocyte-secreting function, and induce alterations of the cell cytoskeleton. Key words: Simulated microgravity; RCCS; Keratinocyte; HaCaT cell line; Proliferation; Cell cycle; hb-EGF; Cytoskeleton

Effect of simulated microgravity on the circadian rhythm of Drosophila melanogaster

Biological interactions and environmental constraints alter life-history traits, modifying organismal performances. Trematode parasites often impact their hosts by inducing parasitic castration, frequently correlated with increased body size in the host (i.e., gigantism hypothesis), which is postulated to reflect the re-allocation of energy released by the reduction in the reproductive process. In this study, we compared the effect of a trematode species on shell size and morphology in adult individuals of the intertidal mussels Perumytilus purpuratus (>20 mm) collected from two local populations of contrasting environmental regimes experienced in central-southern Chile. Our field data indicates that in both study locations, parasitized mussels evidenced higher body sizes (shell length, total weight and volume) as compared with non-parasitized. In addition, parasitized mussels from the southern location evidenced thinner shells than non-parasitized ones and those collected from central Chile, suggesting geographical variation in shell carbonate precipitation across intertidal habitats of the Chilean coast. In laboratory conditions, mussels collected from a local population in central Chile were exposed to two temperature treatments (12 and 18 °C). Parasitized mussels showed higher growth rates than non-parasitized, regardless of the seawater temperature treatments. However, the metabolic rate was not influenced by the parasite condition or the temperature treatments. Our field and laboratory results support the parasite-induced gigantism hypothesis, and suggest that both the thermal environment and geographic location explain only a portion of the increased body size, while the parasitic condition is the most plausible factor modulating the outcome of this host-parasite interaction.

Effects of miR-503-5p on apoptosis of human pulmonary microvascular endothelial cells in simulated microgravity.

Recent studies have shown that microRNA (miRNAs) can play important roles in the regulation of endothelial cell (EC) function. However, the expression profile of miRNAs and their effects on the apoptosis of ECs under microgravity conditions remains unclear. In this study, the apoptosis of human pulmonary microvascular endothelial cells (HPMECs) under simulated microgravity was identified by Annexin V and propidium iodide double staining and transmission electron microscopy. miRNA microarray assay was used to screen the differentially expressed miRNAs in HPMECs under simulated microgravity, and eight differentially expressed miRNAs were identified. Specifically, miR-503-5p, which was found to be most significantly upregulated in both microarray and quantitative reverse-transcription polymerase chain reaction assays, was selected for further functional investigation. Overexpression of miR-503-5p induced apoptosis of HPMECs under normal gravity and aggravated the negative effects of simulated microgravity on HPMECs. Furthermore, silencing of miR-503-5p expression effectively attenuated the negative effects of simulated microgravity on HPMECs. Further experiments showed that the mRNA and protein expression of anti-apoptotic factor B-cell lymphoma-2 (Bcl-2), which has been confirmed as a direct target of miR-503-5p, was inhibited by the upregulation of miR-503-5p and increased by the downregulation of miR-503-5p. Taken together, our findings demonstrate, for the first time, that miR-503-5p can induce apoptosis of HPMECs under simulated microgravity through, at least in part, inhibiting the expression of Bcl-2.

Microgravity-Induced Alterations of Inflammation-Related Mechanotransduction in Endothelial Cells on Board SJ-10 Satellite.

Endothelial cells (ECs) are mechanosensitive cells undergoing morphological and functional changes in space. Ground-based study has provided a body of evidences about how ECs can respond to the effect of simulated microgravity, however, these results need to be confirmed by spaceflight experiments in real microgravity. In this work, we cultured EA.hy926 ECs on board the SJ-10 Recoverable Scientific Satellite for 3 and 10 days, and analyzed the effects of space microgravity on the ECs. Space microgravity suppressed the glucose metabolism, modulated the expression of cellular adhesive molecules such as ICAM-1, VCAM-1, and CD44, and depressed the pro-angiogenesis and pro-inflammation cytokine secretion. Meanwhile, it also induced the depolymerization of actin filaments and microtubules, promoted the vimentin accumulation, restrained the collagen I and fibronectin deposition, regulated the mechanotransduction through focal adhesion kinase and Rho GTPases, and enhanced the exosome-mediated mRNA transfer. Unlike the effect of simulated microgravity, neither three-dimensional growth nor enhanced nitric oxide production was observed in our experimental settings. This work furthers the understandings in the effects and mechanisms of space microgravity on ECs, and provides useful information for future spaceflight experimental design.

Long-Term Effects of Simulated Microgravity and Vibration Exposure on Skeletal Development in Zebrafish.

Most studies utilizing fish to study the effects of simulated microgravity (SMG) only observe the effects during the first week of development. They also do not take into account the potential impact on development of vibrations caused by the equipment. In this study we analyze the effects of both SMG and vibration on development of the skeleton. We analyze three different exposure durations and starting points that coincide with cranial neural crest cell migration. We use a combination of bone staining and morphometrics to analyze the effects. Our data show that both vibration and SMG affect vertebra number and body size; however, not all vertebrae are equally affected by each treatment. We also show that delayed ossification manifests during development, particularly after SMG exposure, and this translates into buckled and bent bones in adults. This study highlights the large impact of even very short exposure periods when they coincide with critical time points of development.

The subsequent biological effects of simulated microgravity on endothelial cell growth in HUVECs

PurposeMicrogravity is known to cause endothelium dysfunction in astronauts returning from spaceflight. We aimed to reveal the regulatory mechanism in alterations of human endothelial cells after simulated microgravity (SMG). MethodsWe utilized the rotary cell culture system (RCCS-1) to explore the subsequent effects of SMG on human umbilical vein endothelial cells (HUVECs). ResultsSMG-treated HUVECs appeared obvious growth inhibition after return to normal gravity, which might be attributed to a set of responses including alteration of cytoskeleton, decreased cell adhesion capacity and increased apoptosis. Expression levels of mTOR and its downstream Apaf-1 were increased during subsequent culturing after SMG. miR-22 was up-regulated and its target genes SRF and LAMC1 were down-regulated at mRNA levels. LAMC1 siRNAs reduced cell adhesion rate and inhibited stress fiber formation while SRF siRNAs caused apoptosis. ConclusionSMG has the subsequent biological effects on HUVECs, resulting in growth inhibition through mTOR signaling and miR-22-mediated mechanism.

Hindlimb Unloading Effects on β-Endorphin Receptor in Rats

Background: Space is a harsh environment that affects the body in many ways. Humans venturing into the environment of space can have negative effects on the body. Objectives: This study focused on the effects of simulated microgravity on β-endorphin receptor concentration. Methods: Rats (n = 16) were divided in two groups (n = 8/group), freely moving (control group) and hindlimb unloading. A rat-tail suspension model was used in experiment groups for 14 days to explore the effect of simulated microgravity on the β-endorphin receptor concentration in the hippocampus, brain stem, and prefrontal cortex. Results: The results showed that the concentration of β-endorphin receptor in the brain stem and prefrontal cortex, but not in hippocampus, was significantly higher in hindlimb unloading rats than controls. Conclusions: It is possible that simulated microgravity may increase the β-endorphin receptor expression in the prefrontal cortex and brain stem in the rat.

The combined effects of real or simulated microgravity and red-light photoactivation on plant root meristematic cells.

Red light is able to compensate for deleterious effects of microgravity on root cell growth and proliferation. Partial gravity combined with red light produces differential signals during the early plant development. Light and gravity are environmental cues used by plants throughout evolution to guide their development. We have investigated the cross-talk between phototropism and gravitropism under altered gravity in space. The focus was on the effects on the meristematic balance between cell growth and proliferation, which is disrupted under microgravity in the dark. In our spaceflight experiments, seedlings of three Arabidopsis thaliana genotypes, namely the wild type and mutants of phytochrome A and B, were grown for 6days, including red-light photoactivation for the last 2days. Apart from the microgravity and the 1g on-board control conditions, fractional gravity (nominally 0.1g, 0.3g, and 0.5g) was created with on-board centrifuges. In addition, a simulated microgravity (random positioning machine, RPM) experiment was performed on ground, including both dark-grown and photostimulated samples. Photoactivated samples in spaceflight and RPM experiments showed an increase in the root length consistent with phototropic response to red light, but, as gravity increased, a gradual decrease in this response was observed. Uncoupling of cell growth and proliferation was detected under microgravity in darkness by transcriptomic and microscopic methods, but red-light photoactivation produced a significant reversion. In contrast, the combination of red light and partial gravity produced small but consistent variations in the molecular markers of cell growth and proliferation, suggesting an antagonistic effect between light and gravity signals at the early plant development. Understanding these parameters of plant growth and development in microgravity will be important as bioregenerative life support systems for the colonization of the Moon and Mars.

Effects of simulated microgravity on rice (MR219) growth and yield

Rice (Oryza sativa L.) is a staple food in many Asian countries with an ever increasing demand. However, the production of high quality rice seeds is insufficient to meet this demand. Research on plant growth in space related to the exposure of a microgravity environment are rare, costly and time-limited. Similar experiments can be conducted on the ground to simulate the microgravity condition using a 2-D clinostat which compensates for the unilateral influence of gravity. This study was conducted to establish a simple and cost effective technique to enhance the quality of the Malaysian rice seed variety MR 219 by using a 2-D clinostat and to determine the effects of simulated microgravity on the growth and yield of the rice seeds. The experiments were performed at different rotation speeds (2 rpm and 10 rpm) for 10 days at room temperature. The rice growth and yield parameters were measured every 2 weeks and at harvest time (day 110), respectively. The data were analysed using the MINITAB statistical software package. The mean value estimates of the parameters obtained under different conditions were compared using analysis of variance (ANOVA) with the Tukey test for multiple comparisons using a 0.05 significance level. Significant differences in the number of tiller, stem width , chlorophyll content , weight of grains and panicles and total grain weight per plant were identified at rotation speed 10 rpm when compared to rotation speed 2 rpm and control. The highest means were mainly obtained under 10 rpm clinorotated rice seeds. In general, plants grown from 10 rpm clinorotated seeds are also more resistant to rice diseases (rice blast disease, rice tungro disease and hopper burn). These results suggest that simulated microgravity using a 2-D clinostat affected several rice (MR219) growth and yield parameters significantly.