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  • Other Sources  (498)
  • 2010-2014  (117)
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  • 11
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    A short pulse of mechanical force induces gene expression and growth in MC3T3-E1 osteoblasts via an ERK 1/2 pathway (2003)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Physiological mechanical loading is crucial for maintenance of bone integrity and architecture. We have calculated the strain caused by gravity stress on osteoblasts and found that 4-30g corresponds to physiological levels of 40-300 microstrain. Short-term gravity loading (15 minutes) induced a 15-fold increase in expression of growth-related immediate early gene c-fos, a 5-fold increase in egr-1, and a 3-fold increase in autocrine bFGF. The non-growth-related genes EP-1, TGF-beta, and 18s were unaffected by gravity loading. Short-term physiological loading induced extracellular signal-regulated kinase (ERK 1/2) phosphorylation in a dose-dependent manner with maximum phosphorylation saturating at mechanical loading levels of 12g (p 〈 0.001) with no effect on total ERK. The phosphorylation of focal adhesion kinase (FAK) was unaffected by mechanical force. g-Loading did not activate P38 MAPK or c-jun N-terminal kinase (JNK). Additionally, a gravity pulse resulted in the localization of phosphorylated ERK 1/2 to the nucleus; this did not occur in unloaded cells. The induction of c-fos was inhibited 74% by the MEK1/2 inhibitor U0126 (p 〈 0.001) but was not affected by MEK1 or p38 MAPK-specific inhibitors. The long-term consequence of a single 15-minute gravity pulse was a 64% increase in cell growth (p 〈 0.001). U0126 significantly inhibited gravity-induced growth by 50% (p 〈 0.001). These studies suggest that short periods of physiological mechanical stress induce immediate early gene expression and growth in MC3T3-E1 osteoblasts primarily through an ERK 1/2-mediated pathway.
    Keywords: Life Sciences (General)
    Type: Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research (ISSN 0884-0431); Volume 18; 1; 58-66
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  • 12
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    X-ray spectroscopy of SNR E0102-72 with the ASCA satellite (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The Advanced Satellite for Cosmology and Astrophysics (ASCA) satellite has obtained a moderate-resolution energy spectrum of E0102-72, the brightest Supernova Remnant (SNR) in the Small Magellanic Cloud (SMC). This paper reports on the first results of the analysis of the high quality spectrum of E0102-72. The spectrum shows resolved emission lines of He-like K alpha, H-like K alpha and K beta from oxygen, neon, and magnesium. The intensity ratios of these lines cannot be explained by a multi-component plasma model with uniform abundances, but requires abundance inhomogeneity in the plasma. We demonstrate how the spectral capabilities of the ASCA SIS make available new diagnostics of X-ray plasmas in a state of non-equilibrium ionization. Some interpretation based on the spectral analysis is also given.
    Keywords: ASTROPHYSICS
    Type: PASJ: Publications of the Astronomical Society of Japan (ISSN 0004-6264); 46; 3; p. L121-L124
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  • 13
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    Microgravity modifies protein kinase C isoform translocation in the human monocytic cell line U937 and human peripheral blood T-cells (2002)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Individual protein kinase C (PKC) isoforms fulfill distinct roles in the regulation of the commitment to differentiation, cell cycle arrest, and apoptosis in both monocytes and T-cells. The human monocyte like cell line U937 and T-cells were exposed to microgravity, during spaceflight and the translocation (a critical step in PKC signaling) of individual isoforms to cell particulate fraction examined. PKC activating phorbol esters induced a rapid translocation of several PKC isoforms to the particulate fraction of U937 monocytes under terrestrial gravity (1 g) conditions in the laboratory. In microgravity, the translocation of PKC beta II, delta, and epsilon in response to phorbol esters was reduced in microgravity compared to 1 g, but was enhanced in weak hypergravity (1.4 g). All isoforms showed a net increase in particulate PKC following phorbol ester stimulation, except PKC delta which showed a net decrease in microgravity. In T-cells, phorbol ester induced translocation of PKC delta was reduced in microgravity, compared to 1 g, while PKC beta II translocation was not significantly different at the two g-levels. These data show that microgravity differentially alters the translocation of individual PKC isoforms in monocytes and T-cells, thus providing a partial explanation for the modifications previously observed in the activation of these cell types under microgravity.
    Keywords: Life Sciences (General)
    Type: Journal of cellular biochemistry (ISSN 0730-2312); Volume 87; 1; 39-50
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  • 14
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    Dayside ionospheric convection changes in response to long-period interplanetary magnetic field oscillations - Determination of the ionospheric phase velocity (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Ground magnetic field perturbations recorded by the CANOPUS magnetometer network in the 7 to 13 MLT sector are used to examine how reconfigurations of the dayside polar ionospheric flow take place in response to north-south changes of the IMF. During the 6-h interval in question, IMF Bz oscillates between +/- 7 nT with about a 1-h period. Corresponding variations in the ground magnetic disturbance are observed which we infer are due to changes in ionospheric flow. Cross correlation of the data obtained from two ground stations at 73.5 deg magnetic latitude, but separated by about 2 hours in MLT, shows that changes in the flow are initiated in the prenoon sector (about 10 MLT) and then spread outward toward dawn and dusk with a phase speed of about 5 km/s over the longitude range about 8 to 12 MLT, slowing to about 2 km/s outside this range. Cross correlating the data from these ground stations with IMP 8 IMF Bz records produces a MLT variation in the ground response delay relative to the IMF which is compatible with these deduced phase speeds.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 97; A12; p. 19,373-19,380.
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  • 15
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    X-ray evidence for particulate contamination on the AXAF VETA-1 mirrors (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: X-ray testing of the AXAF outer mirror pairs, in the VETA-1 configuration, reveals a point spread function (PSF) with unexpectedly large wings at low energies. Although the angular dependence in the wings of the PSF is close to that expected for diffractive scattering from surface roughness, the energy dependence differs substantially. Analyses of the observed X-ray PSF, images near ring focus, and single-quadrant images at conjugate focus suggest that the excess scattering observed at low X-ray energies results from diffractive scattering by relatively small grains (as small as a few tenths micrometer in radius). We develop a simple model for the contribution of scattering by particulates to the PSF. Merging this model with that for scattering by surface roughness, we fit the combined model to the observed energy-dependent PSF, in order to estimate parameters and associated uncertainties characterizing the grain-size distribution and the surface-roughness power spectral density. In particular, we find that the fractional coverage of the mirrors by particulates is approximately 1 x 10 exp -4 (for grain radii between 0.1 and 10 microns), and that the rms surface-roughness is approximately 0.7 nm (for spatial frequencies between 1/mm and 1000/mm).
    Keywords: OPTICS
    Type: In: Multilayer and grazing incidence X-ray(EUV optics for astronomy and projection lithography; Proceedings of the Meeting, San Diego, CA, July 19-22, 1992 (A93-39601 15-74); p. 171-182.
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  • 16
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    Calibration of the Energetic Gamma-Ray Experiment Telescope (EGRET) for the Compton Gamma-Ray Observatory (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The calibration of the (EGRET) prior to its launch aboard the Compton Gamma Ray Observatory, the continuing calibration after launch, and instrument-performance results based on calibrations and early postlaunch data, are described. Particular attention is given to the effective area, the annular resolution, and the energy resolution.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 86; 2; p. 629-656.
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  • 17
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    A practical approach to determining the uncertainty of a pressure measurement system (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The pressure measurement systems located at three propulsion component test stands at the Marshall Space Flight Center (MSFC) were evaluated for their specific measurement uncertainty levels. An elemental error source evaluation was performed to provide an analytical estimate of uncertainty. Applied loads tests were also conducted at the different MSFC test sites to derive an empirical estimate of uncertainty for the measurement system process. The analytical results are compared to those obtained empirically. The data from MFSC was also compared to data reported from other comparable test facilities. Methods for acquiring and processing the data from calibration, acquisition, and reduction error sources are also addressed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: International Instrumentation Symposium, 39th, Albuquerque, NM, May 2-6, 1993, Proceedings (A93-54351 24-35); p. 511-539.
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  • 18
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    Image analysis of the AXAF VETA-1 X-ray mirror (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Initial core scan data of the VETA-1 X-ray mirror proved disappointing, showing considerable unpredicted image structure and poor measured FWHM. 2-D core scans were performed, providing important insight into the nature of the distortion. Image deconvolutions using a raytraced model PSF was performed successfully to reinforce our conclusion regarding the origin of the astigmatism. A mechanical correction was made to the optical structure, and the minor was tested successfully (FWHM 0.22 arcsec) as a result.
    Keywords: OPTICS
    Type: In: Multilayer and grazing incidence X-ray(EUV optics for astronomy and projection lithography; Proceedings of the Meeting, San Diego, CA, July 19-22, 1992 (A93-39601 15-74); p. 136-151.
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  • 19
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    One joule output from a diode-array-pumped Nd:YAG laser with side-pumped rod geometry (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Output of 1.25 J per pulse (1.064 micron) with an absolute optical efficiency of 28 percent and corresponding electrical efficiency of 10 percent was demonstrated in a diode-array-pumped Nd:YAG laser using a side-pumped rod geometry in a master-oscillator/power-amplifier configuration. In Q-switched operation, an output of 0.75 J in a 17-ns pulse was obtained. The fundamental laser output was frequency doubled in KTP with 60 percent conversion efficiency to obtain 0.45 J in a 16-ns pulse at 532 nm. The output beam had high spatial quality with pointing stability better than 40 microrad and a shot-to-shot pulse energy fluctuation of less than +/-3 percent.
    Keywords: LASERS AND MASERS
    Type: IEEE Journal of Quantum Electronics (ISSN 0018-9197); 28; 4, Ap; 977-985
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  • 20
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    Cytoplasmic pH influences cytoplasmic calcium in MC3T3-E1 osteoblast cells (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We found that the cytoplasmic concentration of calcium (Cai) of MC3T3-E1 osteoblasts was influenced by the type of pH buffer we used in the perfusing medium, suggesting that intracellular pH (pHi) might influence Cai. To study this effect, the Cai and pHi were monitored as we applied various experimental conditions known to change pHi. Exposure to NH4Cl caused a transient increase in both pHi and Cai without a change in extracellular pH (pHo). Decreasing pHo and pHi by lowering the bicarbonate concentration of the medium decreased Cai, and increasing pHi by the removal of 5% CO2 increased Cai. Clamping pHi to known values with 10 microM nigericin, a potassium proton ionophore, also influenced Cai: acid pHi lowered Cai, whereas alkaline pHi increased it. The rise in Cai appears to be very sensitive to the extracellular concentration of calcium, suggesting the existence of a pH-sensitive calcium influx mechanism. We conclude that physiologic changes in pH could modulate Cai by controlling the influx of calcium ions and could change the time course of the Cai transient associated with hormonal activation.
    Keywords: Life Sciences (General)
    Type: Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research (ISSN 0884-0431); Volume 8; 6; 725-32
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