Summary: Condition in which no acceleration, whether due to gravity or any other force, can be detected by an observer within a system. It also means the absence of weight or the absence of the force of gravity acting on a body. Microgravity, gravitational force between 0 and 10 -6 g, is included here. (From NASA Thesaurus, 1988)

Top Publications

  1. Schneider S, Brümmer V, Carnahan H, Dubrowski A, Askew C, Strüder H. What happens to the brain in weightlessness? A first approach by EEG tomography. Neuroimage. 2008;42:1316-23 pubmed publisher
    ..Several studies have reported impairment of central nervous processes during weightlessness. There is ongoing debate as to whether these impairments are attributable to primary physiological effects or ..
  2. Chang T, Walther I, Li C, Boonyaratanakornkit J, Galleri G, Meloni M, et al. The Rel/NF-?B pathway and transcription of immediate early genes in T cell activation are inhibited by microgravity. J Leukoc Biol. 2012;92:1133-45 pubmed publisher
    ..Results from these experiments indicate that ?g was the causative factor for impaired T cell activation during spaceflight by inhibiting transactivation of key immediate early genes. ..
  3. Liu Y, Wang E. Transcriptional analysis of normal human fibroblast responses to microgravity stress. Genomics Proteomics Bioinformatics. 2008;6:29-41 pubmed publisher
    ..Hence, our results suggest that microgravity travel may impact changes in gene expression mostly associated with cellular stress signaling, directing cells to either apoptotic death or premature senescence. ..
  4. Miller C, Peters B, Brady R, Richards J, Ploutz Snyder R, Mulavara A, et al. Changes in toe clearance during treadmill walking after long-duration spaceflight. Aviat Space Environ Med. 2010;81:919-28 pubmed
    ..The joint angle analysis suggested that the crewmembers tried to reestablish their normal walking pattern postflight, instead of developing a new motor control strategy. ..
  5. Petersen L, Damgaard M, Petersen J, Norsk P. Mechanisms of increase in cardiac output during acute weightlessness in humans. J Appl Physiol (1985). 2011;111:407-11 pubmed publisher
    ..A Bainbridge-like reflex could be the mechanism for the HR-induced increase in CO during 0 G in particular in supine subjects. ..
  6. Mognato M, Girardi C, Fabris S, Celotti L. DNA repair in modeled microgravity: double strand break rejoining activity in human lymphocytes irradiated with gamma-rays. Mutat Res. 2009;663:32-9 pubmed publisher
    ..Our results provide evidences that MMG incubation during DNA repair delayed the rate of radiation-induced DSB rejoining, and increased, as a consequence, the genotoxic effects of ionising radiation. ..
  7. Okada A, Ichikawa J, Tozawa K. [Kidney stone formation during space flight and long-term bed rest]. Clin Calcium. 2011;21:1505-10 pubmed publisher
    ..Bisphosphonate is useful for the prevention of renal stone formation during space flight and long-term bed-rest. ..
  8. Ortega M, Pecaut M, Gridley D, Stodieck L, Ferguson V, Chapes S. Shifts in bone marrow cell phenotypes caused by spaceflight. J Appl Physiol (1985). 2009;106:548-55 pubmed publisher
    ..However, the reduction in less differentiated cells may forebode future consequences for macrophage production and host defenses. This is of particular importance to considerations of future long-term spaceflights. ..
  9. Pan Z, Yang J, Guo C, Shi D, Shen D, Zheng Q, et al. Effects of hindlimb unloading on ex vivo growth and osteogenic/adipogenic potentials of bone marrow-derived mesenchymal stem cells in rats. Stem Cells Dev. 2008;17:795-804 pubmed publisher

More Information


  1. Zwart S, Crawford G, Gillman P, Kala G, Rodgers A, Rogers A, et al. Effects of 21 days of bed rest, with or without artificial gravity, on nutritional status of humans. J Appl Physiol (1985). 2009;107:54-62 pubmed publisher
    ..These data provide evidence that artificial gravity itself does not negatively affect nutritional status during bed rest. Likewise, artificial gravity has no protective effect on nutritional status during bed rest. ..
  2. Bock O, Weigelt C, Bloomberg J. Cognitive demand of human sensorimotor performance during an extended space mission: a dual-task study. Aviat Space Environ Med. 2010;81:819-24 pubmed
  3. Singh K, Kumari R, DuMond J. Simulated microgravity-induced epigenetic changes in human lymphocytes. J Cell Biochem. 2010;111:123-9 pubmed publisher
    ..The findings of this study suggest that epigenetic events could be one of the mechanistic bases for microgravity-induced gene expression changes and associated adverse health effects. ..
  4. Crabb A, Pycke B, Van Houdt R, Monsieurs P, NICKERSON C, Leys N, et al. Response of Pseudomonas aeruginosa PAO1 to low shear modelled microgravity involves AlgU regulation. Environ Microbiol. 2010;12:1545-64 pubmed publisher
    ..aeruginosa activated in response to spaceflight-analogue conditions, and could direct future research regarding the risk assessment and prevention of Pseudomonas infections during spaceflight and in immunocompromised patients...
  5. Simons D, Gardner E, Lelkes P. Intact T cell receptor signaling by CD4(+) T cells cultured in the rotating wall-vessel bioreactor. J Cell Biochem. 2010;109:1201-9 pubmed publisher
  6. Makihira S, Kawahara Y, Yuge L, Mine Y, Nikawa H. Impact of the microgravity environment in a 3-dimensional clinostat on osteoblast- and osteoclast-like cells. Cell Biol Int. 2008;32:1176-81 pubmed publisher
    ..7 cells, suggesting that long-term mechanical unloading suppresses bone formation and resorption. ..
  7. Schuenke M, Reed D, Kraemer W, Staron R, Volek J, Hymer W, et al. Effects of 14 days of microgravity on fast hindlimb and diaphragm muscles of the rat. Eur J Appl Physiol. 2009;106:885-92 pubmed publisher
    ..However, the longer period of gravitational unloading did result in additional loss in muscle fiber cross-sectional area with involvement of more major fiber types. ..
  8. Nabavi N, Khandani A, Camirand A, Harrison R. Effects of microgravity on osteoclast bone resorption and osteoblast cytoskeletal organization and adhesion. Bone. 2011;49:965-74 pubmed publisher
    ..The observed effects on both major bone cell types likely accelerate bone loss in microgravity environments, and additionally offer a potential explanation to the development of disuse osteoporosis on Earth...
  9. Qi F, Dai D, Liu Y, Kaleem I, Li C. Effects of low-shear modeled microgravity on the characterization of recombinant ?-D-glucuronidase expressed in Pichia pastoris. Appl Biochem Biotechnol. 2011;163:162-72 pubmed publisher
    ..61). The results initially reveal the significant alterations in catalytic properties of recombinant enzyme in response to LSMMG environment and have potential application in bioprocessing and biocatalysis. ..
  10. Kang C, Zou L, Yuan M, Wang Y, Li T, Zhang Y, et al. Impact of simulated microgravity on microvascular endothelial cell apoptosis. Eur J Appl Physiol. 2011;111:2131-8 pubmed publisher
    ..Endothelial dysfunction at microcirculatory sites might contribute to cardiovascular deconditioning induced by weightlessness. Recent studies have reported changes in the morphology and gene expression of endothelial cells exposed to ..
  11. Aubert A, Verheyden B, d Ydewalle C, Beckers F, Van den Bergh O. Effects of mental stress on autonomic cardiac modulation during weightlessness. Am J Physiol Heart Circ Physiol. 2010;298:H202-9 pubmed publisher
    Sustained weightlessness affects all body functions, among these also cardiac autonomic control mechanisms. How this may influence neural response to central stimulation by a mental arithmetic task remains an open question...
  12. Pietsch J, Bauer J, Egli M, Infanger M, Wise P, Ulbrich C, et al. The effects of weightlessness on the human organism and mammalian cells. Curr Mol Med. 2011;11:350-64 pubmed
    ..different aspects which make space medicine appealing: i) finding better strategies for adapting astronauts to weightlessness; ii) identification of microgravity-induced diseases (e.g...
  13. Rizzo A, Corsetto P, Montorfano G, Milani S, Zava S, Tavella S, et al. Effects of long-term space flight on erythrocytes and oxidative stress of rodents. PLoS ONE. 2012;7:e32361 pubmed publisher
    ..Future experiments should provide information helpful to reduce the effects of oxidative stress exposure and space anemia, possibly by integrating appropriate dietary elements and natural compounds that could act as antioxidants. ..
  14. Grimm D, Infanger M, Westphal K, Ulbrich C, Pietsch J, Kossmehl P, et al. A delayed type of three-dimensional growth of human endothelial cells under simulated weightlessness. Tissue Eng Part A. 2009;15:2267-75 pubmed publisher
    ..These results suggest that culturing ECs under conditions of modeled gravitational unloading represents a new technique for studying the formation of tubes that resemble vascular intimas. ..
  15. Liu M, Gao H, Shang P, Zhou X, Ashforth E, Zhuo Y, et al. Magnetic field is the dominant factor to induce the response of Streptomyces avermitilis in altered gravity simulated by diamagnetic levitation. PLoS ONE. 2011;6:e24697 pubmed publisher
    ..Hence, these results are significant, and timely to researchers considering the use of diamagnetic levitation to explore effects of weightlessness on living organisms and on physical phenomena.
  16. Crucian B, Stowe R, Quiriarte H, Pierson D, Sams C. Monocyte phenotype and cytokine production profiles are dysregulated by short-duration spaceflight. Aviat Space Environ Med. 2011;82:857-62 pubmed
    ..Also, monocyte/macrophage function may be highly sensitive to mission specific parameters. ..
  17. Dijkstra C, Larkin O, Anthony P, Davey M, Eaves L, Rees C, et al. Diamagnetic levitation enhances growth of liquid bacterial cultures by increasing oxygen availability. J R Soc Interface. 2011;8:334-44 pubmed publisher
    ..levitation is a technique that uses a strong, spatially varying magnetic field to reproduce aspects of weightlessness, on the Earth...
  18. Trappe S, Costill D, Gallagher P, Creer A, Peters J, Evans H, et al. Exercise in space: human skeletal muscle after 6 months aboard the International Space Station. J Appl Physiol (1985). 2009;106:1159-68 pubmed publisher
    ..Future long-duration space missions should modify the current ISS exercise prescription and/or hardware to better preserve human skeletal muscle mass and function, thereby reducing the risk imposed to crewmembers. ..
  19. Marcu O, Lera M, Sanchez M, Levic E, Higgins L, Shmygelska A, et al. Innate immune responses of Drosophila melanogaster are altered by spaceflight. PLoS ONE. 2011;6:e15361 pubmed publisher
    ..coli post-flight, remained robust. We show that spaceflight altered both cellular and humoral immune responses in Drosophila and that the disruption occurs at multiple interacting pathways. ..
  20. Millar K, Johnson C, Edelmann R, Kiss J. An endogenous growth pattern of roots is revealed in seedlings grown in microgravity. Astrobiology. 2011;11:787-97 pubmed publisher
    ..Our hypothesis is that an endogenous response in plants causes the roots to skew and that this default growth response is largely masked by the normal 1?g conditions on Earth. ..
  21. Stowe R, Kozlova E, Sams C, Pierson D, Walling D. Latent and lytic Epstein-Barr virus gene expression in the peripheral blood of astronauts. J Med Virol. 2011;83:1071-7 pubmed publisher
    ..These data also suggest the possibility of EBV-related complications in future long-duration missions, in particular interplanetary travel. ..
  22. Uddin S, Hadjiargyrou M, Cheng J, Zhang S, Hu M, Qin Y. Reversal of the detrimental effects of simulated microgravity on human osteoblasts by modified low intensity pulsed ultrasound. Ultrasound Med Biol. 2013;39:804-12 pubmed publisher
    ..001) along with restoring formation of actin stress fibers in the SMG-exposed osteoblasts. These data suggest that the acoustic wave can potentially be used as a countermeasure for disuse osteopenia. ..
  23. Gridley D, Slater J, Luo Owen X, Rizvi A, Chapes S, Stodieck L, et al. Spaceflight effects on T lymphocyte distribution, function and gene expression. J Appl Physiol (1985). 2009;106:194-202 pubmed publisher
    ..Collectively, the data show that T cell distribution, function, and gene expression are significantly modified shortly after return from the spaceflight environment. ..
  24. Spector E, Smith S, Sibonga J. Skeletal effects of long-duration head-down bed rest. Aviat Space Environ Med. 2009;80:A23-8 pubmed
    ..The FAP appears to be a valid test bed for skeletal disuse studies, and should provide a useful research platform for evaluating countermeasures to spaceflight-induced bone loss. ..
  25. Reschke M, Bloomberg J, Paloski W, Mulavara A, Feiveson A, Harm D. Postural reflexes, balance control, and functional mobility with long-duration head-down bed rest. Aviat Space Environ Med. 2009;80:A45-54 pubmed
    ..Furthermore, the data suggest that procedures designed to alleviate modifications to the sensory substrate serving the soles of the feet may provide a countermeasure to help maintain support afferentation of the postural muscles. ..
  26. Paul A, Manak M, Mayfield J, Reyes M, Gurley W, Ferl R. Parabolic flight induces changes in gene expression patterns in Arabidopsis thaliana. Astrobiology. 2011;11:743-58 pubmed publisher
  27. Ding Y, Zou J, Li Z, Tian J, Abdelalim S, Du F, et al. Study of histopathological and molecular changes of rat kidney under simulated weightlessness and resistance training protective effect. PLoS ONE. 2011;6:e20008 pubmed publisher
    To explore the effects of long-term weightlessness on the renal tissue, we used the two months tail suspension model to simulate microgravity and investigated the simulated microgravity on the renal morphological damages and related ..
  28. Crabb A, Schurr M, Monsieurs P, Morici L, Schurr J, Wilson J, et al. Transcriptional and proteomic responses of Pseudomonas aeruginosa PAO1 to spaceflight conditions involve Hfq regulation and reveal a role for oxygen. Appl Environ Microbiol. 2011;77:1221-30 pubmed publisher
    ..aeruginosa remains to be determined and will be important for infectious disease risk assessment and prevention, both during spaceflight missions and for the general public...
  29. Smith S, Heer M, Wang Z, Huntoon C, Zwart S. Long-duration space flight and bed rest effects on testosterone and other steroids. J Clin Endocrinol Metab. 2012;97:270-8 pubmed publisher
    ..Testosterone concentrations dropped before and soon after bed rest, but bed rest itself had no effect on testosterone. There was no evidence for decrements in testosterone during long-duration space flight or bed rest. ..
  30. Tavella S, Ruggiu A, Giuliani A, Brun F, Canciani B, Manescu A, et al. Bone turnover in wild type and pleiotrophin-transgenic mice housed for three months in the International Space Station (ISS). PLoS ONE. 2012;7:e33179 pubmed publisher
    ..Apparently, the PTN transgene protection was the result of a higher osteoblast activity in the flight mice...
  31. Kim W, Tengra F, Young Z, Shong J, Marchand N, Chan H, et al. Spaceflight promotes biofilm formation by Pseudomonas aeruginosa. PLoS ONE. 2013;8:e62437 pubmed publisher
  32. Lebsack T, Fa V, Woods C, Gruener R, Manziello A, Pecaut M, et al. Microarray analysis of spaceflown murine thymus tissue reveals changes in gene expression regulating stress and glucocorticoid receptors. J Cell Biochem. 2010;110:372-81 pubmed publisher
    ..These data explain, in part, the reported systemic compromise of the immune system after exposure to the microgravity of space. ..
  33. Boser S, Dournon C, Gualandris Parisot L, Horn E. Altered gravity affects ventral root activity during fictive swimming and the static vestibuloocular reflex in young tadpoles (Xenopus laevis). Arch Ital Biol. 2008;146:1-20 pubmed
  34. Ishihara A, Fujino H, Nagatomo F, Takeda I, Ohira Y. Gene expression levels of heat shock proteins in the soleus and plantaris muscles of rats after hindlimb suspension or spaceflight. J Physiol Sci. 2008;58:413-7 pubmed publisher
  35. Allen D, Bandstra E, Harrison B, Thorng S, Stodieck L, Kostenuik P, et al. Effects of spaceflight on murine skeletal muscle gene expression. J Appl Physiol (1985). 2009;106:582-95 pubmed publisher
    ..Together these data demonstrate that spaceflight induces significant changes in mRNA expression of genes associated with muscle growth and fiber type. ..
  36. Mulavara A, Feiveson A, Fiedler J, Cohen H, Peters B, Miller C, et al. Locomotor function after long-duration space flight: effects and motor learning during recovery. Exp Brain Res. 2010;202:649-59 pubmed publisher
    ..Further, this early motor learning appears to reinforce the adaptive realignment, facilitating re-adaptation to Earth's 1-g environment on return from space flight. ..
  37. Zwart S, Pierson D, Mehta S, Gonda S, Smith S. Capacity of omega-3 fatty acids or eicosapentaenoic acid to counteract weightlessness-induced bone loss by inhibiting NF-kappaB activation: from cells to bed rest to astronauts. J Bone Miner Res. 2010;25:1049-57 pubmed publisher
    ..is inhibited by eicosapentaenoic acid (EPA), but the influence of this omega-3 fatty acid on the effects of weightlessness are unknown. We report here cellular, ground analogue, and spaceflight findings...
  38. Crevecoeur F, Thonnard J, Lefevre P. Forward models of inertial loads in weightlessness. Neuroscience. 2009;161:589-98 pubmed publisher
    ..The prediction of self-induced variation of inertial loads permits fine modulation of grip force, which ensures a stable grip during manipulation of an object in a new environment. ..
  39. Gao H, Liu M, Zhuo Y, Zhou X, Liu J, Chen D, et al. Assessing the potential of an induced-mutation strategy for avermectin overproducers. Appl Environ Microbiol. 2010;76:4583-6 pubmed publisher
    ..The results showed for the first time that a microgravity environment could introduce larger phenotype distribution and diversity than UV and N-methyl-N-nitro-N-nitrosoguanidine (NTG) could. ..
  40. De Saedeleer C, Vidal M, Lipshits M, Bengoetxea A, Cebolla A, Berthoz A, et al. Weightlessness alters up/down asymmetries in the perception of self-motion. Exp Brain Res. 2013;226:95-106 pubmed publisher
    In the present study, we investigated the effect of weightlessness on the ability to perceive and remember self-motion when passing through virtual 3D tunnels that curve in different direction (up, down, left, right)...
  41. Guo F, Li Y, Liu Y, Huang J, Zhang Z, Wang J, et al. Identification of genes associated with tumor development in CaSki cells in the cosmic space. Mol Biol Rep. 2012;39:6923-31 pubmed publisher
  42. Tian J, Pecaut M, Slater J, Gridley D. Spaceflight modulates expression of extracellular matrix, adhesion, and profibrotic molecules in mouse lung. J Appl Physiol (1985). 2010;108:162-71 pubmed publisher
    ..Taken together, the data demonstrate that significant changes can be readily detected shortly after return from spaceflight in the expression of factors that can adversely influence lung function. ..
  43. Johnsson A, Solheim B, Iversen T. Gravity amplifies and microgravity decreases circumnutations in Arabidopsis thaliana stems: results from a space experiment. New Phytol. 2009;182:621-9 pubmed publisher
    ..The importance of these findings for the modelling of gravity effects on self-sustained oscillatory movements is discussed. ..
  44. Kumari R, Singh K, DuMond J. Simulated microgravity decreases DNA repair capacity and induces DNA damage in human lymphocytes. J Cell Biochem. 2009;107:723-31 pubmed publisher
    ..Any resistance to apoptosis seen in cells with damaged DNA may eventually lead to malignant transformation of those cells. ..
  45. Seaton K, Slack K, Sipes W, Bowie K. Cognitive functioning in long-duration head-down bed rest. Aviat Space Environ Med. 2009;80:A62-5 pubmed
    ..Cognitive functioning does not appear to be adversely affected by long-duration head-down bed rest. Individual differences in underlying cognitive ability and motivation level are likely explanations for the current findings. ..
  46. Kawahara Y, Manabe T, Matsumoto M, Kajiume T, Matsumoto M, Yuge L. LIF-free embryonic stem cell culture in simulated microgravity. PLoS ONE. 2009;4:e6343 pubmed publisher
    ..We used feeder-free and serum-free media without LIF. Here we show that simulated microgravity allows novel LIF-free and animal derived material-free culture methods for mouse ES cells. ..
  47. Alexandre C, Vico L. Pathophysiology of bone loss in disuse osteoporosis. Joint Bone Spine. 2011;78:572-6 pubmed publisher
    ..A better knowledge of these mechanisms should promote the development of preventive therapies for the often neglected osteoporotic fractures that occur in patients with spinal cord injury. ..
  48. Li J, Zhang S, Chen J, Du T, Wang Y, Wang Z. Modeled microgravity causes changes in the cytoskeleton and focal adhesions, and decreases in migration in malignant human MCF-7 cells. Protoplasma. 2009;238:23-33 pubmed publisher
    ..We suggest that reduced migration response in MCF-7 cells following MMG is linked to changes of cytoskeleton and FAs. ..
  49. Sieberer B, Kieft H, Franssen Verheijen T, Emons A, Vos J. Cell proliferation, cell shape, and microtubule and cellulose microfibril organization of tobacco BY-2 cells are not altered by exposure to near weightlessness in space. Planta. 2009;230:1129-40 pubmed publisher
    ..At near weightlessness, tubulin polymerizes into microtubules in vitro, but these microtubules do not self-organize in the ordered ..
  50. Tamma R, Colaianni G, Camerino C, Di Benedetto A, Greco G, Strippoli M, et al. Microgravity during spaceflight directly affects in vitro osteoclastogenesis and bone resorption. FASEB J. 2009;23:2549-54 pubmed publisher
    ..These results indicate for the first time osteoclasts and their precursors as direct targets for microgravity and mechanical forces. ..
  51. Kirkpatrick A, Keaney M, Hemmelgarn B, Zhang J, Ball C, Groleau M, et al. Intra-abdominal pressure effects on porcine thoracic compliance in weightlessness: implications for physiologic tolerance of laparoscopic surgery in space. Crit Care Med. 2009;37:591-7 pubmed publisher
    ..Prolonged weightlessness induces physiologic deconditioning that questions the ability of ill or injured astronauts to tolerate IAH...
  52. Smith S, Zwart S, Heer M, Baecker N, Evans H, Feiveson A, et al. Effects of artificial gravity during bed rest on bone metabolism in humans. J Appl Physiol (1985). 2009;107:47-53 pubmed publisher
    ..05) effect of time for whole body total BMC and total hip and trochanter BMD. These data failed to demonstrate efficacy of this AG prescription to prevent the changes in bone metabolism observed during 3 wk of bed rest. ..
  53. Crucian B, Stowe R, Pierson D, Sams C. Immune system dysregulation following short- vs long-duration spaceflight. Aviat Space Environ Med. 2008;79:835-43 pubmed
    ..In addition, a detectable Th2 cytokine shift appears to be associated with spaceflight. ..