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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Maladjustment of kidneys to microgravity: Design of measures to reduce the loss of calcium

Losses of skeletal calcium and body fluids occur during prolonged exposure to microgravity. The kidney plays a major role in regulating the physiological functions involved. Relative to this regulatory function, the kidney performs three operations: filtration of blood plasma through the glomeruli, reabsorption, and secretion of fluid and electrolytes so that needed components are retained and only waste is eliminated in the urine. Using data published in Biomedical Results from Skylab, researchers performed new calculations that reflect more directly the operations of the kidney in the handling of calcium, sodium, chloride, potassium and phosphate during space flight. These calculations revealed that the fraction of filtered calcium that was rejected by renal tubules and excreted in the urine increased by 71 percent, from 1.77 percent (preflight) to 3.02 percent (inflight) of the filtered load. This represents a large absolute increase because the total filtered amount is huge. Because the tubular rejection fraction of other ions increased relatively less than that of calcium, researchers postulate the inflight development of a specific renal defect that causes an excessive loss of calcium in urine and thereby contributes to the weakening of bones.

Nechay, Bohdan R.↗
NASA NTRS1992

Effects of microgravity or simulated launch on testicular function in rats

Reproductive toxicology and cellular and molecular biology approaches were used to evaluate testicular function in rats from Cosmos 2044. It is found that concentrations of testosterone in testicular tissue or peripheral blood plasma were reduced in flight rates to less than 20 percent of values for simulated-launch or vivarium controls. Spermatogenesis was essentially normal in flight rats, but production of testosterone was severely depressed.

Amann, R. P.↗
NASA NTRS1994

Experiment K-7-16: Effects of Microgravity or Simulated Launch on Testicular Function in Rats

Fixed or frozen testicular tissues from five rats per group were analyzed by: subjective and quantitative evaluations of spermatogenesis; Northern-blot analysis for expression of selected genes; quantification of testosterone and receptors for LH; and morphometric analysis of Leydig cells. Based on observations of fixed tissue, it was evident that some rats in the flight and vivarium groups had testicular abnormalities unassociated with treatment, and probably existing when they were assigned randomly to the four treatment groups; the simulated-launch group contained no abnormal rat. Lesions induced in testes of caudal-elevation rats precluded discernment of any pre-existing abnormality. Considering rats without pre-existing abnormalities, diameter of seminiferous tubules and numbers of germ cells per tubule cross section were lower (E less than 0.05) in flight rats than in simulated-launch or vivarium rats. However, ratios of germ cells to each other, or to Sertoli cells, and number of homogenization-resistant spermatids did not differ from values for simulated-launch or vivarium controls. There was no effect of flight on normal expression of testis-specific hsp gene products, or evidence for production of stress-inducible transcripts of the hsp70 or hsp90 genes. Concentration of receptors for rLH in testicular tissue, and surface densities of smooth endoplasmic reticulum and peroxisomes in Leydig cells, were similar in flight and simulated-launch rats. However, concentrations of testosterone in testicular tissue or peripheral blood plasma were reduced (P less than 0.05) in flight rats to less than 20 percent of values for simulated-launch or vivarium controls. Thus, spermatogenesis was essentially normal in flight rats, but production of testosterone was severely depressed. Sequela of reduced androgen production on turnover of muscle and bone should be considered when interpreting data from mammals exposed to microgravity.

Amann, R. P.↗
NASA NTRS1992

Effects of Microgravity or Simulated Launch on Testicular Function in Rats

Testes from flight rats on COSMOS 2044 and simulated-launch, vivarium, or caudal-elevation control rats (5/group) were analyzed by subjective and quantitative methods. On the basis of observations of fixed tissue, it was evident that some rats had testicular abnormalities unassociated with treatment and probably existing when they were assigned randomly to the four treatment groups. Considering rats without preexisting abnormalities, diameter of seminiferous tubules and numbers of germ cells per tubule cross section were lower (P less than 0.05) in flight than in simulated-launch or vivarium rats. However, ratios of germ cells to each other or to Sertoli cells and number of homogenization-resistant spermatids did not differ from values for simulated-launch or vivarium controls. Expression of testis-specific gene products was not greatly altered by flight. Furthermore, there was no evidence for production of stress-inducible transcripts of the hsp7O or hsp9O genes. Concentration of receptors for rat luteinizing hormone in testicular tissue and surface density of smooth endoplasmic reticulum in Leydig cells were similar in flight and simulated-launch rats. However, concentrations of testosterone in testicular tissue or peripheral blood plasma were reduced (P less than 0.05) in flight rats to less than 20% of values for simulated-launch or vivarium controls. Thus spermatogenesis was essentially normal in flight rats, but production of testosterone was severely depressed. Exposure to microgravity for more than 2 wk might result in additional changes. Sequelae of reduced androgen production associated with microgravity on turnover of muscle and bone should be considered.

Amann, R. P.↗
NASA NTRSDate not supplied

Cardiovascular Responses to Simulated Spaceflight: Molecular Signatures and Surrogate Outputs to Measure CVD Risk

During extended space missions beyond low Earth orbit, astronauts will encounter prolonged periods of weightlessness and low dose space radiation. Previous studies have shown that exposure to small doses of high LET radiation (< 50 cGy) can lead to both short-term and long-term alterations in heart function, structure and underlying molecular mechanisms. In this study, we aim to identify the molecular signature associated with the cardiovascular response to simulated galactic cosmic radiation (5-ion GCR) alone or in combination with simulated weightlessness at time intervals relevant to mission length and recovery. Additionally, we aim to determine whether sex impacts cardiovascular responses to these spaceflight factors. Our overarching goal is to enhance our understanding of the cardiovascular risks associated with extended space missions and the clinical endpoints they suggest. We hypothesize that exposure to simulated space radiation leads to enduring alterations in the transcriptome, redox signaling and cytokine environment of cardiovascular tissue, some which have known links with reduced cardiovascular performance, aging, and increased risk of cardiovascular disease (CVD). Furthermore, we posit that simulated space radiation exposure in combination with simulated microgravity exacerbates cardiovascular deficits compared to single factor exposure. Female and male C57BL/6J mice, aged 23-24 weeks, were exposed to a single dose of 5, 15, or 50 cGy of 5-ion GCR, or sham-treated (0 cGy). Euthanasia was performed at 14 days and ~4 months post-irradiation. Hearts, aorta and blood plasma were collected shortly thereafter. RNA-sequencing of left ventricles at ~4 months post-GCR exposure revealed sex differences in the heart transcriptome with a few genes showing radiation-dependent changes in expression levels. Notably, some of the differentially expressed genes in 15 and 50 cGy GCR groups are known to play roles in the development of CVD. Analysis of protein levels of a subset of inflammatory cytokines in the heart indicated sex differences but no differences between sham and 50 cGy groups. Results also showed correlations among differentially expressed genes and a subset of inflammatory cytokines, with some correlations altered by GCR exposure. These findings suggest that GCR exposure can modify protein and gene networks linked to inflammation and CVD progression. In the aorta, telomere lengths were comparable across treatment groups sexes. Mitochondrial copy number is a biomarker for mitochondrial function with decreased copy numbers associated with cardiometabolic disease traits. Mitochondrial copy numbers of aorta also showed no sex nor dose differences. In a second study, mice underwent one week of simulated microgravity by hindlimb unloading (HU) and then exposed to a single dose of 15 cGy of 5-ion GCR. HU was conducted for an additional two weeks following GCR exposure. Single factor exposure groups (HU or GCR only) also were included in the study. Euthanasia was then performed and the same tissues were collected. Protein levels of select inflammatory cytokines in the heart showed sex-dependent differences in expression. In the aorta, telomere lengths and mitochondrial copy number also showed sex differences. In summary, our results indicate differences between sexes in biomarkers related to cardiovascular health. Exposure to 5-ion GCR or HU, alone or in combination, did not result in changes in most of the cardiovascular biomarkers that were examined. However, in the heart, simulated space radiation at doses of 15 and 50 cGy led to long-term alterations in the expression levels of a small group of genes known to be associated with the progression of CVD. The long-term transcriptomic changes resulting from exposure to simulated space radiation should be carefully investigated to mitigate adverse cardiovascular events during and after deep space missions. Our results also highlight the importance of sex-specific strategies in monitoring and maintaining cardiovascular health during and after deep space missions.

cardiovascular↗
NASA NTRS2024

Crew State and Risk Model Development to Predict Hydration Status During Extravehicular Activity Training Events

Introduction: Hydration is critical for optimal human health and performance and dehydration can lead to impaired cardiovascular function, thermal dysregulation, decreased blood plasma volume, and cognitive impacts, particularly during physical activity. Prolonged and repeated extravehicular activities (EVA) without sufficiently available drinking water may increase risk for dehydration, which could impair crew health and impact mission success. Understanding hydration needs and potential effects on health and performance are necessary to optimize crew well-being and enable successful EVA objectives. This study aims to develop a model of hydration status during EVA using water balance techniques. Methods: Water balance measures were collected on 15 healthy astronauts who performed ≈6-hour simulated microgravity extravehicular activity (EVA) training in the NASA Neutral Buoyancy Laboratory (NBL). Data collected included pre-and post-EVA nude body weight (BW), maximum absorption garment (MAG) weight, Disposable In-suit Drink Bag (DIDB) weight, urine specific gravity (USG), and extra pre-EVA intake (W). Variables were combined to create the water balance model as pre-EVA (Hn)= BWn+ MAGn+ DIDBn+ Wnand post EVA (Hn+1) = BWn+1+ MAGn+1+ DIDBn+1. Urine specific gravity values were used to refine water balance measures into hydration categories: Hydrated, Marginally Hydrated, and Dehydrated. Results: Pre-EVA modeling indicated53% of crew were hydrated, 20% were marginally hydrated, and 27% were dehydrated. Alternately, Hn+1 showed 13% of crew remained hydrated, 47% were marginally hydrated, and 40% were dehydrated at the end of the EVA. Furthermore, 75% of the crewmembers who started sufficiently hydrated finished the run marginally hydrated or dehydrated. According to USG indices presented by Casa and Lawrence, et al. (2000), only 25% of the crew started and remained hydrated throughout the EVA, and those who were dehydrated at the outset stayed dehydrated. Conclusion: Model outcomes assessing hydration status during 6-hour simulated microgravity EVAs demonstrate the necessity to further address hydration requirements for optimal human performance during spaceflight and EVA. This study enables additional baseline development of the Crew State and Risk Model Hydration, Nutrition, and Waste Management component that aims to provide individualized crew state and risk predictions during EVAs. Reference: Casa, D. J., Armstrong, L. E., et al. (2000). National Athletic Trainers’ Association Position Statement: Fluid Replacement for Athletes. Journal of Athletic Training, 35:212-224.

L Cooper↗
NASA NTRS1996

Destruction of newly released red blood cells in space flight

Space flight results in a rapid change in total blood volume, plasma volume, and red blood cell mass because the space to contain blood is decreased. The plasma volume and total blood volume decreases during the first hours in space and remain at a decreased level for the remainder of the flight. During the first several hours following return to earth, plasma volume and total blood volume increase to preflight levels. During the first few days in space recently produced red blood cells disappear from the blood resulting in a decrease in red blood cell mass of 10-15%. Red cells 12 d old or older survive normally and production of new cells continues at near preflight levels. After the first few days in space, the red cell mass is stable at the decreased level. Following return to earth the hemoglobin and red blood cell mass concentrations decrease reflecting the increase in plasma volume. The erythropoietin levels increase responding to "postflight anemia"; red cell production increases, and the red cell mass is restored to preflight levels after several weeks.

STS-58 Shuttle Project↗
NASA NTRS1985

Blood pressure and plasma renin activity as predictors of orthostatic intolerance

The effect of 3 h standing, followed by a period of head-up tilt (HUT) on physiological response (orthostatic tolerance, blood pressure and heart rate), as well as on plasma vasopressin (PVP) and renin activity (PRA) were studied in 13 dehydrated (to 2.4 pct loss of body weight) subjects. Seven subjects showed signs of orthostatic intolerance (INT), manifested by sweating, pallor, nausea and dizziness. Prior to these symptoms, the INT subjects exhibited lower systolic (SP) and pulse (PP) pressures, and an elevated PRA, compared to the tolerant (TOL) subjects. HUT has aggravated increases of RPA in the INT subjects and caused an increase, higher than in TOL subjects, in PVP, while rehydration has greatly attenuated the PVP response to the HUT and decreased the PRA response. It is concluded that dehydration, together with measurements of SP, PP and PRA, may serve as a means of predicting orthostatic intolerance and may provide a physiological model for studying the causes of intolerance.

Harrison, M. H.↗
NASA NTRS1995

Catecholaminergic effects of prolonged head-down bed rest

Prolonged head-down bed rest (HDBR) provides a model for examining responses to chronic weightlessness in humans. Eight healthy volunteers underwent HDBR for 2 wk. Antecubital venous blood was sampled for plasma levels of catechols [norepinephrine (NE), epinephrine, dopamine, dihydroxyphenylalanine, dihydroxyphenylglycol, and dihydroxyphenylacetic acid] after supine rest on a control (C) day and after 4 h and 7 and 14 days of HDBR. Urine was collected after 2 h of supine rest during day C, 2 h before HDBR, and during the intervals 1-4, 4-24, 144-168 (day 7), and 312-336 h (day 14) of HDBR. All subjects had decreased plasma and blood volumes (mean 16%), atriopeptin levels (31%), and peripheral venous pressure (26%) after HDBR. NE excretion on day 14 of HDBR was decreased by 35% from that on day C, without further trends as HDBR continued, whereas plasma levels were only variably and nonsignificantly decreased. Excretion rates of dihydroxyphenylglycol and dihydroxyphenylalanine decreased slightly during HDBR; excretion rates of epinephrine, dopamine, and dihydroxyphenylacetic acid and plasma levels of catechols were unchanged. The results suggest that HDBR produces sustained inhibition of sympathoneural release, turnover, and synthesis of NE without affecting adrenomedullary secretion or renal dopamine production. Concurrent hypovolemia probably interferes with detection of sympathoinhibition by plasma levels of NE and other catechols in this setting. Sympathoinhibition, despite decreased blood volume, may help to explain orthostatic intolerance in astronauts returning from spaceflights.

Non-NASA Center↗
NASA NTRS1995

Capillary Pressure Balance with Repeated Head-Up Tilt in Humans

We measured blood density (BD). plasma density (PD) and hematocrit (Ht) during repeated 70 deg head-up tilt (HUT) consisting of a pre-drink period with two supine (P and P3) and two HUT (P2 and P4) phases of 45 min each. At the end of P4 test subjects (N=8) drank 10 ml/kg body weight of isotonic (290 mOsm/kg) sodium chloride (ISO) or hypotonic (<10 mOsm/kg) unsweetened us (HYP), or nothing (control: CON). The following periods continued the supine (P5, P7) / upright (P6) sequence. Mass density of plasma and whole blood using a "mechanical oscillation" technique were measured from ear lobe blood. Tilting altered (p<0.001) BD, PD, and Ht in all consecutive Phases. BD and PD were different (p<0.05) between CON. HYP. and ISO Phases 6 and 7. The computed mass density of fluid (FD). which moved between intra. and extravascular compartments. averaged 1008 g/l and was the same in any conditions. In the non-drink treatment (P3, P5, P7), supine PV steadly decreased when compared to P1. Tilt-induced PV shifts ranged from 9.7 to 16.7% when compared to PV du. ring the respective previous Phases. After drinking, PV increased above CON values at the end of Phase 7 by 12.9% with ISO, and by 6.6% with HYP. Progressive hemoconcentration. occurred during non-drink supine; isotonic saline ingestion increased supine PV a control level but did not stop or reverse the decrease of upright hemoconcentration. Upright density values were not slowed with repeated upright tilting; decreased fluid loss occurred in consecutive upright periods. Upright capillary pressure balance was achieved with diminished plasma volume loss during repeated tilting.

Hinghofer-Szalkay, H. G.↗
NASA NTRS1995

Effects of chronic elevated levels of CO2 on the concentration of blood cellular elements and plasma corticosterone in the male rat

The mean CO2 concentration on the Space Shuttle is 0.3% and has reached 0.7%, for extended periods of time. Following space flight, it has been shown that both humans and animals have significant changes in red blood cell counts (RBC) and white blood cell counts (WBC). In other studies, where no significant change did occur in the total WBC, a significant change did occur in the distribution of WBC. WBC are affected by circulating levels of glucocorticoids, which often increase when animals or humans are exposed to adverse and/or novel stimuli (e.g. elevated CO2 levels or weightlessness). The purpose of this study was to determine if elevations in CO2 concentration produce changes in total WBC and/or their distribution.

Alexander, R. A.↗