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NASA NTRS1985

The evolution of chromospheric activity and the spin-down of solar-type stars

IUE data for 31 solar-type stars are compared with observations of T Tauri stars in order to determine whether the pattern of main sequence chromospheric decay shown by stars older than about 100 million yr extends back to ages of 100 million yr appropriate for T Tauri stars. An analysis of the time decay of stellar ultraviolet and X-ray emission establishes a relationship between emission level and axial rotation, which is expressed in terms of the Rossby parameter. It is shown that the intensity of ultraviolet chromospheric and transition region lines of solar-type stars declines with age. The activity-age relation for main sequence stars older than about 100 million yr is fitted best by an exponential law whose rate of falloff with age depends on temperature.

Simon, T.↗

NASA NTRSDate not supplied

Efficacy of Dried Plum to Countermeasure Simulated Spaceflight Exposure

Human exploration of the space environment has been a topic of interest for decades; however, the threat to physiological health posed by ionizing radiation and microgravity effects remains a concern. Previous research utilizing combined hindlimb unloading and irradiation to simulate spaceflight effects found that a dried plum diet can mitigate adverse effects of simulated spaceflight on skeletal health. Though the mechanism is not fully understood we believe this protective effect is due to its high antioxidant capacity and polyphenolic content. This study seeks to extend these findings to investigate if dried plum is an effective countermeasure in other tissues relating to aging and neurotoxicity. Male C57BL/6 J mice were assigned to one of eight groups (n = 10/group) and were fed either a controlled diet or dried plum diet, underwent normal loading or hindlimb unloading as well as exposure 2 Gy gamma radiation or sham exposure. At the end of the experiment, mice were euthanized, and RNA was extracted from brain and bone marrow tissue and PCR was employed to analyze significant changes in gene expression profiles. Analysis of five house-keeping genes revealed genes B2M (neurotoxicity) and GUSB (aging) to be the most stable genes across all treatments and were used to find the fold change within our genes of interest. Through this, and analysis via ANOVA, we were able to identify genes with significant altered expression levels within brain and bone marrow tissues related to neurotoxicity and aging. Considering previous research, we hypothesize that the dried plum diet’s antioxidative properties ameliorated the oxidative stress from irradiation and microgravity via altered levels of gene expression. Identified expression changes will provide insights into molecular mechanisms behind the observed protective effects. These findings present potential avenues for future interventions to alleviate negative impacts of spaceflight on astronaut health.

Faisal Ahmad↗

NASA NTRSDate not supplied

The Efficacy of Dried Plum to Counter Spaceflight Microgravity and Radiation

Faisal Ahmad↗

NASA NTRS1994

The anemia of primary autonomic failure and its reversal with recombinant erythropoietin

OBJECTIVE: To determine if chronic sympathetic deprivation is associated with anemia and a low erythropoietin response. DESIGN: Survey of the prevalence and characteristics of anemia in patients with severe primary autonomic failure. SETTING: A referral service for autonomic failure in a tertiary teaching hospital. PATIENTS: 84 patients with primary autonomic failure who had symptomatic orthostatic hypotension. INTERVENTION: Open-label trial with human recombinant erythropoietin. RESULTS: Anemia was present in 32 of 84 patients (38%; 95% Cl, 27% to 50%). Plasma norepinephrine levels, measured in patients standing upright, were lower in the patient group with lower hemoglobin levels. Mean values in 22 patients with a hemoglobin level of less than 120 g/L were as follows: hemoglobin, 108 g/L (range, 87 to 118 g/L); hematocrit, 0.33; corrected reticulocyte counts, 0.008; mean corpuscular volume, 89 fL (89 microns 3); serum iron, 16.5 mumol/L (92 micrograms/dL); total iron binding capacity, 43.3 mumol/L (242 micrograms/dL); ferritin, 184 micrograms/L; serum vitamin B12, 410 pmol/L (556 pg/mL); and serum folate, 22.7 nmol/L (10 ng/mL). No relation was found between serum erythropoietin and blood hemoglobin levels. In seven of nine patients with autonomic failure who had hemoglobin levels less than 120 g/L, serum erythropoietin levels decreased below the 95% confidence interval corresponding to patients with iron deficiency anemia. Therapy with recombinant erythropoietin improved mean hemoglobin levels (from 108 to 133 g/L) in all patients treated (n = 5) at relatively low doses (25 to 50 units/kg body weight, subcutaneously, three times a week). CONCLUSIONS: Our data support the hypothesis that the sympathetic nervous system stimulates erythropoiesis in humans because anemia is a frequent occurrence in patients with severe autonomic failure and is associated with a blunted erythropoietin response.

Clinical Trial↗

NASA NTRS2011

Disturbances in the Isotopic Record of Asuka 881394

Asuka 881394 is a unique achondrite with a granulitic texture, very calcic approximately An(sub 98) plagioclase, and pigeonite that has not inverted to orthopyroxene. First thought to be a eucrite, recent Oisotopic studies show it has a closer affinity to angrites . Initial isotopic studies provided evidence for now extinct A-26, Mn-53, and Sm-146. A recent study confirmed an early chronology with an absolute Pb-207 - Pb-206 age of 4566.5 +/- 0.2 Ma, a new measurement of the Al-Mg formation interval as 3.7 +/- 0.1 Ma since Al-26/Al-27 = approximately 4.63 x 10(exp -5) for the E60 CAI, and a Mn-Cr formation interval of -6.0 +/- 0.2 Ma relative to LEW86010 ("LEW"). Absolute ages relative to age anchors presented by were 4563.4 +/- 0.2 Ma by Al- Mg and 4564.6 +/- 0.5 Ma by Mn-Cr. These ages are in good, but not perfect, agreement with the Pb-207 - Pb-206 age. Perhaps the most direct comparison of the early chronology of A881394 as determined by various workers is provided by reported Al-26/Al-27 values of 1.18 +/- 0.14, 1.28 +/- 0.07, and 2.1 +/- 0.4 x 10(exp -6). Analyses of mineral separates by TIMS and MC-ICPMS6] agree well, but the higher value obtained by in situ SIMS analysis is significant in light of the slight inconsistency between absolute ages inferred from the short-lived chronometers and the Pb-207 - Pb-206 age. We examine the possibility that inconsistencies in the earliest fine-scale chronology of Asuka 881394 may be related to isotopic "disturbances" observed in Ar-39 - Ar-40, Rb-97 - Sr-87, and Sm-147 - Nd-143 chronometers.

Nyquist, L. E.↗

NASA NTRS2001

Thermal and Mechanical Testing of Neoprene Gloves Used in a Space Shuttle Microgravity Glove Box Experiment

Neoprene gloves are used in a Space Shuttle Microgravity Glove Box (MGBX) experiment. In 1999, significant corrosion was observed in the work area and on the outer surface of the left glove ring. Analysis of the corrosion products showed that they contained chlorine. The Neoprene gloves used in this glove box were obtained in 1995, with a recommended shelf life of 3 years. After storage of these gloves in a cabinet drawer until 1999, significant signs of corrosion were also observed in the drawer. Mechanical and thermal properties were determined on samples cut from the finger and sleeve areas of the "good" and "bad" gloves. This data showed significant aging of the left-hand glove, particularly in the sleeve area. Thermal analysis data by DSC and TGA was complimentary to tensile data in showing this aging. However, this test data did not pinpoint the cause of the left-hand glove aging, or of the corrosion products.

Wingard, Charles Doug↗

NASA NTRS1997

Anterior segment sparing to reduce charged particle radiotherapy complications in uveal melanoma

PURPOSE: The purpose of this investigation is to delineate the risk factors in the development of neovascular glaucoma (NVG) after helium-ion irradiation of uveal melanoma patients and to propose treatment technique that may reduce this risk. METHODS AND MATERIALS: 347 uveal melanoma patients were treated with helium-ions using a single-port treatment technique. Using univariate and multivariate statistics, the NVG complication rate was analyzed according to the percent of anterior chamber in the radiation field, tumor size, tumor location, sex, age, dose, and other risk factors. Several University of California San Francisco-Lawrence Berkeley National Laboratory (LBNL) patients in each size category (medium, large, and extralarge) were retrospectively replanned using two ports instead of a single port. By using appropriate polar and azimuthal gaze angles or by treating patients with two ports, the maximum dose to the anterior segment of the eye can often be reduced. Although a larger volume of anterior chamber may receive a lower dose by using two ports than a single port treatment. We hypothesize that this could reduce the level of complications that result from the irradiation of the anterior chamber of the eye. Dose-volume histograms were calculated for the lens, and compared for the single and two-port techniques. RESULTS: NVG developed in 121 (35%) patients. The risk of NVG peaked between 1 and 2.5 years posttreatment. By univariate and multivariate analysis, the percent of lens in the field was strongly correlated with the development of NVG. Other contributing factors were tumor height, history of diabetes, and vitreous hemorrhage. Dose-volume histogram analysis of single-port vs. two-port techniques demonstrate that for some patients in the medium and large category tumor groups, a significant decrease in dose to the structures in the anterior segment of the eye could have been achieved with the use of two ports. CONCLUSION: The development of NVG after helium-ion irradiation is correlated to the amount of lens, anterior chamber in the treatment field, tumor height, proximity to the fovea, history of diabetes, and the development of vitreous hemorrhage. Although the influence of the higher LET deposition of helium-ions is unclear, this study suggests that by reducing the dose to the anterior segment of the eye may reduce the NVG complications. Based on this retrospective analysis of LBNL patients, we have implemented techniques to reduce the amount of the anterior segment receiving a high dose in our new series of patients treated with protons using the cyclotron at the UC Davis Crocker Nuclear Laboratory (CNL).

NASA Discipline Radiation Health↗

NASA NTRS1980

Age related changes in the bone tissue under conditions of hypokinesia

Microroentgenography of nine young people, aged 24-29, before and after hypokinesia (16-37 days strict bed rest), showed that the heel bone density of those with initially high bone density generally decreased and that of those with initially low bone density generally increased. X-ray structural analysis of the femurs of 25 corpses of accidentally killed healthy people, aged 18-70, data are presented and discussed, with the conclusion that the bone hydroxyapatite crystal structure stabilizes by ages 20 to 25, is stable from ages 25 to 60 and decreases in density after age 60. It is concluded that bone tissue structure changes, both with age, and in a comparatively short time in hypokinesia.

Podrushnyak, E. P.↗

NASA NTRS1991

K/T age for the popigai impact event

The multi-ringed POPIGAI structure, with an outer ring diameter of over 100 km, is the largest impact feature currently recognized on Earth with an Phanerozoic age. The target rocks in this relatively unglaciated region consist of upper Proterozoic through Mesozoic platform sediments and igneous rocks overlying Precambrian crystalline basement. The reported absolute age of the Popigai impact event ranges from 30.5 to 39 Ma. With the intent of refining this age estimate, a melt-breccia (suevite) sample from the inner regions of the Popigai structure was prepared for total fusion and step-wise heating Ar-40/Ar-39 analysis. Although the total fusion and step-heating experiments suggest some degree of age heterogeneity, the recurring theme is an age of around 64 to 66 Ma.

Deino, A. L.↗

NASA NTRS1994

The metallicity of M4: Accurate spectroscopic fundamental parameters for four giants

High-quality spectra, covering the wavelength range 5480 to 7080 A, have been obtained for four giant stars in the intermediate-metallicity CN-bimodal globular cluster M4 (NGC 6121). We have employed a model atmosphere analysis that is entirely independent from cluster parameters, such as distance, age, and reddening, in order to derive accurate values for the stellar parameters effective temperature, surface gravity, and microturbulence, and for the abundance of iron relative to the Sun, (Fe/H), and of calcium, Ca/H, for each of the four stars. Detailed radiative transfer and statistical equilibrium calculations carried out for iron and calcium suggest that departures from local thermodynamic equilibrium are not significant for the purposes of our analysis. The spectroscopically derived effective temperatures for our program stars are hotter by about 200 K than existing photometric calibrations suggest. We conclude that this is due partly to the uncertain reddening of M4 and to the existing photometric temperature calibration for red giants being too cool by about 100 K. Comparison of our spectroscopic and existing photometric temperatures supports the prognosis of a significant east-west gradient in the reddening across M4. Our derived iron abundances are slightly higher than previous high-resolution studies suggested; the differences are most probably due to the different temperature scale and choice of microturbulent velocities adopted by earlier workers. The resulting value for the metallicity of M4 is (Fe/H )(sub M4) = -1.05 + or - 0.15. Based on this result, we suggest that metallicities derived in previous high-dispersion globular cluster abundance analyses could be too low by 0.2 to 0.3 dex. Our calcium abundances suggest an enhancement of calcium, an alpha element, over iron, relative to the Sun, in M4 of (Ca/H) = 0.23.

Drake, J. J.↗

NASA NTRS2009

On the Influence of Anthropogenic Forcings on Changes in the Stratospheric Mean Age

A common feature of stratospheric simulations of the past or future is an increase in tropical upwelling and a decrease in mean age. Possible causes or these changes include (1) increases in tropical sea surface temperatures (SSTs) driven by increases in well-mixed greenhouse gases (WMGHGs), (2) the direct radiative effect of increases in WMGHGs, and (3) changes in ozone. Here we examine a suite of simulations from the Goddard Earth Observing System chemistry-climate model (GEOS CCM) to isolate the relative role of these three factors. Our analysis indicates that all three factors cause changes in the mean age, but the relative impact of each factor depends on the time period analyzed. Over the past 30-40 years ozone depletion is the major factor causing the decrease in mean age, with negligible changes due to direct radiative impact of WMGHG's. However, ozone is predicted to recover back to 1970 levels during the next 50-60 years, and this causes an increase in the mean age, whereas the continued increase in SSTs from increased levels of WMGHGs and the direct radiative impact of WMGHGs will still cause a decrease in the mean age. The net impact of these factors will still result in a decreasing mean age although the rate will be smaller than that of the past. The decreases in mean age are primarily caused by increases in upwelling in the tropical lower stratosphere. The increased upwelling from both increased tropical SSTs and polar ozone loss appears to be related to changes in zonal winds and increases in wave activity propagating into the stratosphere. The different contributions of changes in SSTs, WMGHGs, and ozone to the circulation of the stratosphere may help explain the large spread in the rate of change of tropical upwelling seen in previous studies.

Oman, Luke↗

NASA NTRS1987

Age-related disappearance of Mayer-like heart rate waves

The effect of age on the principal spectral components of heart rate obtained immediately after passive upright tilt was investigated in human subjects who underwent a 60-deg tilt over 9 sec. Two groups were examined, the first of which consisting of healthy male subjects aged 22-26 years, while the second was comprised of subjects aged 65-84 years on no medication; radiograms were recorded continuously beginning just prior to tilt until 3 min posttilt. The results of spectral analysis showed that elderly subjects did not exhibit the Mayer-like heart rate waves (the 0.07-0.09 Hz oscillations) that were present in the spectra of young subjects immediately after passive upright tilt. The findings are consistent with the concept of a 'dysautonomia of aging'. It is suggested that postural stress testing with spectral analysis of heart rate fluctuations may provide a useful way of assessing physiologic vs chronologic age.

Jarisch, W. R.↗

NASA NTRS2017

Bone and Cartilage Degeneration in Mice Following Long-Duration Spaceflight: The Role of Bone Marrow Stem Cells

The detrimental effects of mechanical unloading in microgravity, including the musculo-skeletal system, are well documented. However, the effects of mechanical unloading on joint health and the interaction between bone and cartilage specifically, are less well known. Our ongoing studies with the mouse bone model have identified the failure of normal stem cell-based tissue regeneration, in addition to tissue degeneration, as a significant concern for long-duration spaceflight, especially in the mesenchymal and hematopoietic tissue lineages. Furthermore, we have identified the cell cycle arrest molecule, CDKN1ap21, as specifically up-regulated during spaceflight exposure and localized to osteoprecursors on the bone surface and chondroprogenitors in articular cartilage that are both required for normal tissue regeneration. The 30-day BionM1 and 37-day Rodent Research 1 (RR1) missions enabled the possibility of studying these effects in long-duration microgravity experiments. We hypothesized that the inhibition of stem cell-based tissue regeneration in short-duration spaceflight would continue during long-duration spaceflight resulting in significant tissue alterations and we specifically studied the hip joint (pelvis and proximal femur) to elucidate these effects. To test this hypothesis we analyzed bone and bone marrow stem cells using techniques including high-resolution Microcomputed Tomography (MicroCT), in-vivo differentiation and migration assays, and whole transcriptome expression profiling. We found that exposure to spaceflight for 30 days results in a significant decrease in bone volume fraction (-31), trabecular thickness (-14) and trabecular number (-20). Similar decrements in bone volume fraction (-27), trabecular number (-13) and trabecular thickness (-17) were found in female mice exposed to 37 days spaceflight. Furthermore, high-resolution MicroCT and immunohistochemical analysis of spaceflight tissues revealed a severe disruption of the epiphyseal boundary, resulting in endochondral ossification of the femoral head and perforation of articular cartilage by bone. This suggests that spaceflight in microgravity may cause rapid induction of an aging-like phenotype with signs of osteoarthritic disease in the hip joint. Microarray analysis also revealed that the top pathways altered during spaceflight include activation of matrix metalloproteinases, oxidative stress signaling and inflammation in both whole bone tissue and isolated bone marrow stem cells. In conclusion, the observed inhibition of stem cell-based tissue regeneration persists during long-duration spaceflight. Furthermore, spaceflight mice exhibit disruption of the epiphyseal boundary and endochondral ossification of the femoral head, and an inhibition of stem cell based tissue regeneration, which, taken together, may indicate onset of an accelerated aging phenotype with signs of osteoarthritic disease.

Cartilage↗

NASA NTRS1997

Chemical and Thermal Analysis

Work during the past three years has included significant research in several areas aimed at further clarification of the aging and chemical failure mechanism of thermoplastics (PVDF or Tefzel) for pipes. Among the areas investigated were the crystallinity changes associated with both the Coflon and Tefzel after various simulated environmental exposures using X-Ray diffraction analysis. We have found that significant changes in polymer crystallinity levels occur as a function of the exposures. These crystallinity changes may have important consequences on the fracture, fatigue, tensile, and chemical resistance of the materials. We have also noted changes in the molecular weight distribution and the increased crosslinking of the Coflon material using Gel Permeation Chromatographic Analysis. Again these changes may result in variations in the mechanical and chemical properties in the material. We conducted numerous analytical studies with methods including X-ray Diffraction, Gel Permeation Chromatography, Fourier Transform Infrared Spectroscopy, and Differential Scanning Calorimetry. We investigated a plethora of aged samples of both Tefzel and Coflon that were forwarded from MERL. Pressurized tests were performed on powdered PVDF in a modified Fluid A, which we will call A-2. In this case the ethylene diamine concentration was increased to 3 percent in methanol. Coflon pipe sections and powdered Coflon were exposed in pressure cells at 1700 psi at three separate test temperatures.

Bulluck, J. W.↗

NASA NTRS2017

Characterizing Fractures Across the Astronaut Corps: Preliminary Findings from Population-Level Analysis

Despite evidence of bone loss during spaceflight and operational countermeasures to mitigate this loss, the subsequent risk of fracture among astronauts is not known. The physiologic process of diminished bone density and bone recovery during or following spaceflight is multifactorial. Such factors as age, sex, fracture history, and others may combine to increase fracture risk among astronauts. As part of the 2016 Bone Research and Clinical Advisory Panel (RCAP), the authors analyzed data collected on 338 NASA astronauts to describe the demographics, bone-relevant characteristics, and fracture history of the astronaut population. The majority of the population are male (n=286, 84.6%), have flown at least one mission (n=306, 90.5%), and were between the ages of 30 and 49 at first mission (n=296, 96.7% of those with at least one mission). Of the 338 astronauts, 241 (71.3%) experienced a fracture over the course of their lifetime. One hundred and five (43.5%) of these 241 astronauts only experienced a fracture prior to being selected into the Astronaut Corps, whereas 53 (22.0%) only experienced a fracture after selection as an astronaut. An additional 80 astronauts (33.2%) had both pre- and post-selection fractures. The remaining 3 astronauts had a fracture of unknown date, which could not be categorized as pre- or post-selection. Among the 133 astronauts with at least one post-selection fracture, males comprised 90.2% (n=120) compared to 84.5% of the entire Corps, and females accounted for 9.8% (n=13) compared to 15.4% of the Corps. Ninety-seven of the 133 astronauts with post-selection fractures (72.9%) had one fracture event, 22 (16.5%) had two fractures, and 14 (10.5%) had three or more fractures. Some astronauts with multiple fractures suffered these in a single event, such as an automobile accident. The 133 astronauts with a post-selection fracture accounted for a total of 188 fracture events. One hundred and four (78.2%) of astronauts with post-selection fractures experienced those fractures following their first mission (mean 12.7 +/- 11.1 years following first mission; range 14.0 days - 50.6 years). Additional analyses are ongoing and include examination of fracture history, skeletal site, mechanism, and type of fracture, age at time of fracture, time from spaceflight to fracture, as well as multivariable analysis comparing fracture events to non-events. The results of such analyses may reveal trends in risk factors for fracture among the astronaut corps that have yet to be systematically described through a corps-wide approach.

Rossi, Meredith M.↗

NASA NTRS1993

Zinc and copper balances in healthy adult males during and after 17 wk of bed rest

The effects of long-term bed rest on zinc and copper balances were measured in seven healthy men. Volunteers aged 22-54 y (mean +/- SD, 34 +/- 12 y), 168-185 cm in height (173 +/- 5 cm), and 64-86 kg in weight (74 +/- 9 kg) remained on a metabolic ward for 29 wk. Subjects were ambulatory during weeks 1-5, remained in continuous bed rest for weeks 6-22, and were reambulated during weeks 23-29. Copper and zinc were measured in weekly urine and fecal composites. Dietary intakes provided (mean +/- SD) 19.2 +/- 1.2 mumol Cu (1.22 +/- 0.08 mg), 211 +/- 11 mumol Zn (13.81 +/- 0.72 mg), 25.2 +/- 1.2 mmol Ca (1011 +/- 46 mg), 1086 +/- 46 mmol N (15.21 +/- 0.65 g), and 48.1 +/- 1.4 mmol K (1489 +/- 44 mg)/d. Bed rest increased fecal zinc excretion and decreased zinc balance, whereas copper balance was unchanged. Reambulation decreased fecal zinc excretion and increased both zinc and copper balances. These results suggest that during long-term bed rest or space flight, individuals will lose total body zinc and will retain more zinc and copper when they reambulate.

Non-NASA Center↗

NASA NTRS1983

Crosscutting relations and relative ages of ridges and faults in the Tharsis region of Mars

The results of a detailed photogeologic analysis and classification of ridge-fault cross-cutting relationships on ridged plains units of the Tharsis region is reported. The problems involved in using the morphology of ridge-fault intersections to determine relative timing of structural events are discussed. The implications of using intersection angles as well as morphology to determine possible age relationships for the tectonic history of the region are presented. It is concluded that the major ridge-forming events in the Tharsis region were roughly coincident with, and possibly prior to, the extensional events that produced the faulting of the Tempe and Mareotis regions, the Coprates and Memnonia regions, and the rifting of the Valles Marineris. The compressional events that formed most of the ridges are restricted in time both by their relationship to regional extensional events and by the age of the units on which they formed.

Watters, T. R.↗

NASA NTRS1997

Analysis of strontium metabolism in humans on the basis of the Techa river data

Age and sex features of strontium metabolism have been analyzed on studies of the population residing on the banks of the Techa river which was contaminated by fission products during the years 1949-1956. Measurements of 90Sr body burden have been performed since 1974 using a whole-body counter, and these have made it possible to estimate age-specific long-term retention and elimination rates for men and women. Regarding the retention that correlated with the respective maturation ages, distinct sex differences have been observed for adolescents, whereas only postmenopausal women showed a sharp increase of their elimination rates. There were no differences concerning the reproductive ages. Our experimental findings have a clear physiological interpretation and can be used to develop metabolic models for bone-seeking radionuclides.

NASA Discipline Radiation Health↗