Zwart S.R.,Universities Space Research Association |
Gibson C.R.,Wyle |
Mader T.H.,Alaska Native Medical Center |
Ericson K.,Indiana University - Purdue University Fort Wayne |
And 4 more authors.
Journal of Nutrition | Year: 2012
Approximately 20% (7 of 38) of astronauts on International Space Station (ISS) missions have developed measurable ophthalmic changes after flight. This studywas conducted to determine if the folate- and vitamin B-122dependent 1-carbon metabolic pathway is altered in these individuals. Since 2006, we have conducted experiments on the ISS to evaluate nutritional status and related biochemical indices of astronauts before, during, and after flight. Dataweremodeled to evaluate differences between individuals with ophthalmic changes (n = 5) and those without them (n = 15), all of whom were on ISS missions of 48-215 d. We also determined whether mean preflight serum concentrations of the 1-carbon metabolites and changes in measured cycloplegic refraction after flight were associated. Serum homocysteine (Hcy), cystathionine, 2-methylcitric acid (2MCA), and methylmalonic acid concentrations were 25-45% higher (P < 0.001) in astronauts with ophthalmic changes than in those without them. These differences existed before, during, and after flight. Preflight serum concentrations of Hcy and cystathionine, and mean in-flight serum folate, were correlated with change (postflight relative to preflight) values in refraction (P < 0.05), and preflight serumconcentrations of 2MCA tended to be associated (P = 0.06)with ophthalmic changes. The biochemical differences observed in crewmembers with vision issues strongly suggest that their folate2 and vitamin B-122dependent 1-carbon transfer metabolism was affected before and during flight. The consistent differences in markers of 1-carbon metabolism between those who did and those who did not develop changes in vision suggest that polymorphisms in enzymes of this pathway may interact with microgravity to cause these pathophysiologic changes.
James J.T.,National Aeronautics and Space Administration Johnson Space Center |
Lam C.-W.,Wyle |
Santana P.A.,Universities Space Research Association |
Inhalation Toxicology | Year: 2013
Brief exposures of Apollo astronauts to lunar dust occasionally elicited upper respiratory irritation; however, no limits were ever set for prolonged exposure to lunar dust. The United States and other space faring nations intend to return to the moon for extensive exploration within a few decades. In the meantime, habitats for that exploration, whether mobile or fixed, must be designed to limit human exposure to lunar dust to safe levels. Herein we estimate safe exposure limits for lunar dust collected during the Apollo 14 mission. We instilled three respirable-sized (∼2 μ mass median diameter) lunar dusts (two ground and one unground) and two standard dusts of widely different toxicities (quartz and TiO2) into the respiratory system of rats. Rats in groups of six were given 0, 1, 2.5 or 7.5mg of the test dust in a saline-Survanta® vehicle, and biochemical and cellular biomarkers of toxicity in lung lavage fluid were assayed 1 week and one month after instillation. By comparing the dose-response curves of sensitive biomarkers, we estimated safe exposure levels for astronauts and concluded that unground lunar dust and dust ground by two different methods were not toxicologically distinguishable. The safe exposure estimates were 1.3±0.4mg/m (jet-milled dust), 1.0±0.5mg/m (ball-milled dust) and 0.9±0.3mg/m (unground, natural dust). We estimate that 0.5-1mg/m of lunar dust is safe for periodic human exposures during long stays in habitats on the lunar surface. © 2013 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.
Ray E.S.,BLVD Jets |
Machin R.A.,National Aeronautics and Space Administration Johnson Space Center
Aerodynamic Decelerator Systems Technology Conferences | Year: 2015
The coupled dynamics of a cluster of parachutes to a payload are notoriously difficult to predict. Often the payload is designed to be insensitive to the range of attitude and rates that might occur, but spacecraft generally do not have the mass and volume budgeted for this robust of a design. The National Aeronautics and Space Administration (NASA) Orion Capsule Parachute Assembly System (CPAS) implements a cluster of three mains for landing. During testing of the Engineering Development Unit (EDU) design, it was discovered that with a cluster of two Mains (a fault tolerance required for human rating) the capsule coupled to the parachute cluster could get into a limit cycle pendulum motion which would exceed the spacecraft landing capability. This pendulum phenomenon could not be predicted with the existing models and simulations. A three phased effort has been undertaken to understand the consequence of the pendulum motion observed, and explore potential design changes that would mitigate this phenomenon. This paper will review the early analysis that was performed of the pendulum motion observed during EDU testing, summarize the analysis ongoing to understand the root cause of the pendulum phenomenon, and discuss the modeling and testing that is being pursued to identify design changes that would mitigate the risk. © 2015, AIAA American Institute of Aeronautics and Astronautics. All rights reserved.
Spatz J.M.,Beth Israel Deaconess Medical Center |
Spatz J.M.,Harvard Massachusetts Institute of Technology Division of Health Sciences and Technology |
Spatz J.M.,Massachusetts General Hospital |
Fields E.E.,Enterprise Advisory Services |
And 7 more authors.
Journal of Clinical Endocrinology and Metabolism | Year: 2012
Context: Animal models and human studies suggest that osteocytes regulate the skeleton's response to mechanical unloading in part by an increase in sclerostin. However, few studies have reported changes in serum sclerostin in humans exposed to reduced mechanical loading. Objective: We determined changes in serum sclerostin and bone turnover markers in healthy adult men undergoing controlled bed rest. Design, Setting, and Participants: Seven healthy adult men (31 ± 3 yr old) underwent 90 d of 6° head down tilt bed rest at the University of Texas Medical Branch Institute for Translational Sciences-Clinical Research Center. Outcomes: Serum sclerostin, PTH, vitamin D, bone resorption and formation markers, urinary calcium and phosphorus excretion, and 24-h pooled urinary markers of bone resorption we reevaluated before bed rest [baseline (BL)] and at bed rest d 28 (BR-28), d60 (BR-60), and d 90 (BR-90). Bone mineral density was measured at BL, BR-60, and 5 d after the end of the study (BR+5). Data are reported as mean ± SD. Results: Consistent with prior reports, bone mineral density declined significantly (1-2% per month) at weight-bearing skeletal sites. Serum sclerostin was elevated above BL at BR-28 (+29 ±20%; P = 0.003) and BR-60 (+42 ± 31%; P < 0.001), with a lesser increase at BR-90 (+22 ± 21%; P = 0.07). Serum PTH levels were reduced at BR-28 (-17 ± 16%; P = 0.02) and BR-60 (-24 ± 14%; P = 0.03) and remained lower than BL at BR-90 (-21 ± 21%; P = 0.14), but did not reach statistical significance. Serum bone turnover markers were unchanged; however, urinary bone resorption markers and calcium were significantly elevated at all time points after bed rest (P < 0.01). Conclusions: In healthy men subjected to controlled bed rest for 90 d, serum sclerostin increased, with a peak at 60, whereas serum PTH declined, and urinary calcium and bone resorption markers increased. Copyright © 2012 by The Endocrine Society.
Lofgren G.E.,National Aeronautics and Space Administration Johnson Space Center |
Horz F.,LZ Technology Engineering Science Contract Group |
Eppler D.,National Aeronautics and Space Administration Johnson Space Center
Special Paper of the Geological Society of America | Year: 2011
This paper discusses the philosophy and major aspects of the geology training of the Apollo 15, 16, and 17 astronauts. This training concentrated on monthly fi eld trips that were intended to develop the crew's observational skills in recognizing basic geologic structures and rocks and translating observations into an interpretative framework for local geologic evolution. Individual fi eld trips became increasingly mission-like as their training matured. The crews worked with predetermined traverses and progressively added diverse operational aspects, such as proper usage of sampling tools, photo-documentation of pertinent features and rocks, simulation of space-suit mobility, and use of a roving vehicle. These exercises also provided simulations and practice for all major science support functions that would reside in Mission Control during the actual mission. This combined training of surface explorers and ground support will be indispensable in rendering future planetary surface operations as effi cient and scientifi cally rewarding as Apollo. © 2011 The Geological Society of America.