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PubMed1999

Incidence of Epstein-Barr virus in astronaut saliva during spaceflight.

BACKGROUND: Astronauts experience psychological and physical stresses that may result in reactivation of latent viruses during space-flight, potentially increasing the risk of disease among crewmembers. HYPOTHESIS: The shedding of Epstein-Barr virus (EBV) in the saliva of astronauts will increase during spaceflight. METHODS: A total of 534 saliva specimens were collected from 11 EBV-seropositive astronauts before, during, and after four space shuttle missions. The presence of EBV DNA in saliva, assessed by polymerase chain reaction (PCR), was used to determine shedding patterns before, during, and after space-flight. RESULTS: EBV DNA was detected more frequently before flight than during (p < 0.001) or after (p < 0.01) flight. No significant difference between the inflight and postflight periods was detected in the frequency of occurrence of EBV DNA. CONCLUSIONS: The increased frequency of shedding of EBV before flight suggests that stress levels may be greater before launch than during or after spaceflight.

Analysis of Variance↗
PubMed2000

Exercise thermoregulation in men after 1 and 24-hours of 6 degrees head-down tilt.

BACKGROUND: Exercise thermoregulation is dependent on heat loss by increased skin blood flow (convective and conductive heat loss) and through enhanced sweating (evaporative heat loss). Reduction of plasma volume (PV), increased plasma osmolality, physical deconditioning, and duration of exposure to simulated and actual microgravity reduces the ability to thermoregulate during exercise. HYPOTHESIS: We hypothesized that 24 h of head down tilt (HDT24) would alter thermoregulatory responses to a submaximal exercise test and result in a higher exercise rectal temperature (Tre) when compared with exercise Tre after 1 h of head down tilt (HDT1). METHODS: Seven men (31+/-SD 6 yr, peak oxygen uptake (VpO2peak) of 44+/-6 ml x kg(-1) x min(-1)) were studied during 70 min of supine cycling at 58+/-SE 1.5% VO2peak at 22.0 degrees C Tdb and 47% rh. RESULTS: Relative to pre-tilt sitting chair rest data, HDT1 resulted in a 6.1+/-0.9% increase and HDT24 in a 4.3+/-2.3% decrease in PV (delta = 10.4% between experiments, p<0.05) while plasma osmolality remained unchanged (NS). Pre-exercise Tre was elevated after HDT24 (36.71 degrees C +/-0.06 HDT1 vs. 36.93 degrees C+/-0.11 HDT24, p<0.05). The 70 min of exercise did not alter this relationship (p<0.05) with respective end exercise increases in Tre to 38.01 degrees C and 38.26 degrees C (degrees = 1.30 degrees C (HDT1) and 1.33 degrees C (HDT24)). While there were no pre-exercise differences in mean skin temperature (Tsk), a significant (p<0.05) time x treatment interaction occurred during exercise: after min 30 in HDT24 the Tsk leveled off at 31.1 degrees C, while it continued to increase reaching 31.5 degrees C at min 70 in HDT1. A similar response (NS) occurred in skin blood velocity. Neither local sweating rates nor changes in body weight during exercise of -1.63+/-0.24 kg (HDT1) or - 1.33+/-0.09 kg (HDT24) were different (NS) between experiments. CONCLUSION: While HDT24 resulted in elevated pre-exercise Tre, reduced PV, attenuation of Tsk and skin blood velocity during exercise, the absolute increase in exercise Tre was not altered. But if sweat rate and cutaneous vascular responses were similar at different core temperatures (unchanged thermoregulation), the Tre offset could have been caused by the HDT-induced hypovolemia.

Adult↗
PubMedDate not supplied

Effects of proton and gamma radiation on lymphocyte populations and acute response to antigen.

BACKGROUND: The clinical use of proton radiation in the management of cancer, as well as benign disorders, is rapidly increasing. The major goal of this study was to compare the effects of proton and gamma (60Co) radiation on cell-mediated and humoral immunological parameters. MATERIALS AND METHODS: C57BL/6 mice were exposed to a single dose of 3 Gray (Gy) protons or gamma-rays and intraperitoneally injected 1 day later with sheep red blood cells (sRBC). On 4, 10, 15, and 29 days after exposure, subsets from each group were euthanised; nonirradiated controls (with and without sRBC injection) were included. Body and relative spleen weights, leukocyte counts, spontaneous blastogenesis, lymphocyte populations, and anti-sRBC titers were evaluated. RESULTS: The data showed significant depression (p < 0.05) in nearly all assays on days 4 and 10 after irradiation. B lymphocytes (CD19+) were the most radiosensitive, although reconstitution back to normal levels was observed by day 15. T cell (CD3+) and T helper cell (CD4+) recovery was evident by day 29, whereas the T cytotoxic cell (CD8+) count remained significantly below normal. Natural killer cells (NK1.1+) were relatively radioresistant. Anti-sRBC antibody production was slow and low titers were obtained after irradiation. No significant differences were noted between the two types of radiation. CONCLUSIONS: Taken together, the data show that whole-body irradiation with protons or gamma-rays, at the dose employed, results in marked, but transient, immunosuppression. However, at the time points of testing and with the assays used, little or no differences were found between the two forms of radiation.

Animals↗
PubMed1989

Screened hydrogenic radial integrals.

The screened hydrogenic radial integral both for discrete-discrete and discrete-continuum transitions is expressed in forms suitable for obtaining closed-form expressions for specific transitions. Two effective charge parameters Zi and Zf, respectively, for the initial state and for the final state are retained in these formulas. As examples, explicit expressions for a few transitions are derived and a method for obtaining a series for a discrete-discrete radial integral, suitable for large final-state principal quantum numbers, is indicated.

Electrons↗
PubMed1984

Activity of calcium activated protease in skeletal muscles and its changes in atrophy and stretch.

The reduction of protein content in skeletal muscle undergoing disuse-induced atrophy is correlated with accelerated rates of protein degradation and reduced rates of protein synthesis. It is not known in what manner myofibers are partially disassembled during disuse atrophy to fibers of smaller diameter; nor is it known which proteases are responsible for this morphological change in contractile protein mass. Dayton and colleagues have suggested that the Ca(2+)-activated protease (CaP) may initiate myofibril degradation. The discovery of a form of CaP that is activatable by nanomolar concentrations of Ca2+ indicates that CaP activity may be regulated by physiological concentrations of Ca2+. The enhancement of proteolysis by the Ca2+ ionophore A23187, reported by Etlinger, is consistent with a significant role for CaP in protein degradation. It was of interest, therefore, to measure the levels of CaP activity and the CaP inhibitor in extracts obtained from skeletal muscles of rat and chicken limbs undergoing disuse atrophy or stretch hypertrophy, respectively.

Animals↗
PubMed1988

Differential oscillator strengths and dipole polarizabilities for transitions of the helium sequence.

The dipole radial integral for an initial discrete 1s state and a final continuum state has been calculated under the screened hydrogenic model. In this model, single-electron hydrogenic wave functions are employed and the initial and the final states are treated by two different effective-charge parameters. Numerical values of differential oscillator strengths for transitions from 1s 21S to the continuum for the helium sequence ions are obtained. Also calculated are the dipole polarizabilities, which are found to be in excellent agreement with the results of other authors.

Electrons↗
PubMed2002

Physiological changes, sleep, and morning mood in an isolated environment.

BACKGROUND: Previous isolation studies have shown increased 24-h urine volumes and body weight gains in subjects. This project examined those and other physiological variables in relationship to sleep motor activity, subjective sleep quality, mood, and complaints during confinement. METHODS: Six male and two female subjects lived for 7 d in the National Space Development Agency of Japan's isolation chamber, which simulates the interior of the Japanese Experiment Module. Each 24-h period included 6 h of sleep, 3 meals, and 20 min of exercise. Each morning, subjects completed Sleep Sensation and Complaint Index questionnaires. Catecholamine and creatinine excretion, urine volume, and body weight were measured on the 2 d before and 2 d after confinement, and sleep motor activity was measured during confinement. RESULTS: Confinement produced no significant change in body weight, urine volume, or questionnaire results. In contrast, epinephrine, norepinephrine, and sleep motor activity exhibited significant differences during confinement (p < 0.05). Higher nocturnal norepinephrine excretion correlated with higher sleep motor activity. CONCLUSION: The 24-h epinephrine values were slightly higher than normal throughout the experiment, but lower than for subjects working under time-stress. High sympathetic activity (as indicated by norepinephrine) may have interfered with sleep.

Adult↗
PubMed2002

Smooth pursuit deficits in space flights of variable length.

The maintenance of stable vision is a primary function of the neurovestibular and sensory-motor systems. There is, however, strong evidence suggesting that space flight results in a modification of the central nervous system and subsequent control of ocular-motor responses. These changes effect those neural mechanisms which are responsible for holding images steady on the retina during brief, self-initiated, head rotations or during the voluntary pursuit of moving targets. Recent studies have shown significant saccadic intrusions in both of these experimental paradigms, including an inability to null the vestibulo-ocular reflex (VOR) during the head/eye pursuit task. The maintenance of vision, while not entirely stable, both inflight and immediately postflight is now believed to be due to neural strategies that evolve for the purpose of assisting in directing the moving target onto the retina.

NASA Center JSC↗
PubMed2003

The response of Dahl salt-sensitive and salt-resistant female rats to a space flight model.

Vitamin D metabolism in the Dahl salt-sensitive (S) rat, a model of salt-induced hypertension, differs from that in the Dahl salt-resistant (R) rat. We have tested the hypothesis that differences in vitamin D metabolism would render the Dahl S rat more susceptible than the Dahl R rat to the effects of a space flight model. Dahl female rats were tail suspended (hind limb unloaded) for 28 days, while fed a low salt (3 g/kg sodium chloride) diet. Plasma 25-OHD concentrations of S rats were significantly lower than that of R rats. Plasma 1,25-(OH)2D concentration was 50% lower in unloaded than in loaded S rats, but was unaffected in unloaded R rats. The left soleus muscle weight and breaking strength of the left femur (torsion test) were 50% and 25% lower in unloaded than in loaded S and R rats. The mineral content of the left femur, however, was significantly lower (by 11%) only in unloaded S rats. We conclude that female S rats are more vulnerable than female R rats to decreases in plasma 1,25-(OH)2D concentration and femur mineral content during hind limb unloading, but equally vulnerable to muscle atrophy and reduced breaking strength of the femur.

Animals↗
PubMed2003

Antibody binding in altered gravity: implications for immunosorbent assay during space flight.

A single antibody-incubation step of an indirect, enzyme-linked immunosorbent assay (ELISA) was performed during microgravity, Martian gravity (0.38 G) and hypergravity (1.8 G) phases of parabolic flight, onboard the NASA KC-135 aircraft. Antibody-antigen binding occurred within 15 seconds; the level of binding did not differ between microgravity, Martian gravity and 1 G (Earth's gravity) conditions. During hypergravity and 1 G, antibody binding was directly proportional to the fluid volume (per microtiter well) used for incubation; this pattern was not observed during microgravity. These effects in microgravity may be due to "fluid spread" within the chamber (observed during microgravity with digital photography), leading to greater fluid-surface contact and subsequently antibody-antigen contact. In summary, these results demonstrate that: i) ELISA antibody-incubation and washing steps can be successfully performed by human operators during microgravity, Martian gravity and hypergravity; ii) there is no significant difference in antibody binding between microgravity, Martian gravity and 1 G conditions; and iii) a smaller fluid volume/well (and therefore less antibody) was required for a given level of binding during microgravity. These conclusions indicate that reduced gravity would not present a barrier to successful operation of immunosorbent assays during spaceflight.

Antigen-Antibody Reactions↗
PubMed1989

Changes in volume, muscle compartment, and compliance of the lower extremities in man following 30 days of exposure to simulated microgravity.

The purpose of these experiments was to test the hypothesis that reduced size of the leg muscle compartment following exposure to long-duration microgravity would be associated with increased leg compliance. Eight men, 31-45 years of age, were measured for vascular compliance of the calf and serial circumferences of the thigh and calf before, during and after 30 d of continuous 6 degrees head-down bedrest. Cross-sectional areas (CSA) of muscle, fat, and bone compartments in the thigh and calf were determined pre- and post-bedrest by computed tomography. Calculated leg volumes decreased (p less than 0.05) in the calf by 9.9% and in the thigh by 4.5% from pre- to post-bedrest. Muscle compartment CSA also decreased (p less than 0.05) in both calf (-4.8%) and thigh (-8.1%); leg compliance (vol%/mm Hg x 100) increased (p less than 0.05) from 3.9 +/- 0.7 to 4.9 +/- 0.5. Calf compliance measured before and after bedrest was inversely related to calf muscle compartment CSA (r = -0.61, p less than 0.05) and the percent decrease in calf muscle compartment CSA from pre- to post-bedrest was inversely correlated with an increase in calf compliance (r = -0.72, p less than 0.05). Increased leg compliance following long-duration spaceflight is associated with reduced size of the leg muscle compartment.

Adipose Tissue↗
PubMed2002

Complexities in ETS-domain transcription factor function and regulation: lessons from the TCF (ternary complex factor) subfamily. The Colworth Medal Lecture.

The ETS-domain transcription factor family can be divided into a series of subfamilies. Elk-1 represents the founding member of the ternary complex factor (TCF) subfamily. By focusing on the TCF subfamily, we can demonstrate the complexities that exist in the function and regulation of ETS-domain transcription factors. This article focuses on Elk-1 in detail and summarizes the functions of other TCFs. The key themes covered include the domain structure of the TCFs, the mechanisms of complex formation with serum response factor, regulation of TCFs by mitogen-activated protein kinase cascades, and transcriptional regulatory properties of the TCFs. Finally, the emerging role of the TCFs in vivo is discussed. A picture is developing indicating that, while these proteins exhibit significant sequence and functional conservation, key differences in their structure and regulation are being identified which may relate to unique functions of these proteins in vivo.

Amino Acid Sequence↗
PubMedDate not supplied

Communicating bioastronautics research to students, families and the nation.

The National Space Biomedical Research Institute (NSBRI) is supporting the National Aeronautics and Space Administration's (NASA) education mission through a comprehensive Education and Public Outreach Program (EPOP) that communicates the excitement and significance of space biology to schools, families, and lay audiences. The EPOP is comprised of eight academic institutions: Baylor College of Medicine, Massachusetts Institute of Technology, Morehouse School of Medicine, Mount Sinai School of Medicine, Texas A&M University, University of Texas Medical Branch Galveston, Rice University, and the University of Washington. This paper describes the programs and products created by the EPOP to promote space life science education in schools and among the general public. To date, these activities have reached thousands of teachers and students around the US and have been rated very highly.

Biological Science Disciplines↗