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  • 1
    Publication Date: 2013-08-31
    Description: A comparison study was conducted of the effects of continuous low dose-rate gamma irradiation on cell population kinetics of lymphoid tissue (white pulp) of the mouse spleen with findings as they relate to the mouse thymus. Experimental techniques employed included autoradiography and specific labeling with tritiated thymidine (TdR-(h-3)). The problem studied involved the mechanism of cell proliferation of lymphoid tissue of the mouse spleen and thymus under the stress of continuous irradiation at a dose rate of 10 roentgens (R) per day for 105 days (15 weeks). The aim was to determine whether or not a steady state or near-steady state of cell population could be established for this period of time, and what compensatory mechanisms of cell population were involved.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-CR-143262
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  • 2
    Publication Date: 2017-07-01
    Description: The effects of space flight on the production and characteristics of proteolytic enzymes are studied for a number of bacterial species isolated from crew members and spacecraft. Enzymatic make-up and cultural characteristics of bacteria isolated from spacecraft crew members are determined. The organism Aeromonas proteolytica and the proteolytic enzymes which it produces are used as models for future spacecraft experiments.
    Keywords: BIOSCIENCES
    Type: NASA-CR-125805
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  • 3
    Publication Date: 2005-11-30
    Description: The performance of the microbial response to space environment experiment is considered excellent by all investigators. For most microbial systems, only preliminary survival data are available at this time. None of the available data indicate space flight-mediated changes in cell viability or recovery. One quite important observation has been made at this early date, however. The eggs produced after mice had been infected with N. dubius larvae demonstrated a significant decrease in hatchability when compared to identical ground controls. Except for the fact that the Apollo 16 flight larvae had been on board the command module, treatment of the flown larvae and ground control larvae was the same; neither had been exposed to UV irradiation. The significance and implications of this finding are currently being studied.
    Keywords: BIOSCIENCES
    Type: Apollo 16 Prelim. Sci. Rept.; 6 p
    Format: text
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  • 4
    Publication Date: 2006-04-26
    Description: The bacterium Aeromonas proteolytica was selected for studying the effects of solar irradiation on extracellular enzymes because it produces an endopeptidase that is capable of degrading proteins and a hemolysin that is active in lysing human erythrocytes. Possible alterations in the rate of enzyme production in response to the test conditions are currently underway and are not available for this preliminary report. Completed viability studies are indicative that little difference exists among the survival curves derived for cells exposed to various components of ultraviolet irradiation in space.
    Keywords: BIOSCIENCES
    Type: NASA. Johnson Space Center Proc. of the Microbial Response to Space Environ. Symp.; p 137-151
    Format: text
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  • 5
    Publication Date: 2013-08-31
    Description: Cellular response and cell population kinetics were studied during lymphopoiesis in the thymus of the mouse under continuous gamma irradiation using autoradiographic techniques and specific labeling with tritiated thymidine. On the basis of tissue weights, it is concluded that the response of both the thymus and spleen to continuous low dose-rate irradiation is multiphasic. That is, alternating periods of steady state growth, followed by collapse, which in turn is followed by another period of homeostasis. Since there are two populations of lymphocytes - short lived and long-lived, it may be that different phases of steady state growth are mediated by different lymphocytes. The spleen is affected to a greater extent with shorter periods of steady-state growth than exhibited by the thymus.
    Keywords: BIOSCIENCES
    Type: NASA-CR-140114
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  • 6
    Publication Date: 2013-08-31
    Description: Preflight studies on Aeromonas proteolytica are reported to investigate the possibility of genetic alterations resulting in increased proteolysis in spacecraft environments. This organism may be present on human tissue and could pose medical problems if its endopeptidase and a hemolysin were to be produced in ususually high quantities or altered in such a way as to be more effective in their activities. Considered are: (1) Development of a nutrative holding medium for suspension of organisms; (2) the establishment of baseline information for the standardization of the assay for endopeptidase levels and hemolytic titers; (3) formulation of a method by which intracutaneous hemorrhage could be quantitated in guinea pig tissue; and (4) the responses of these organisms to parameters of spaceflight and experimentation.
    Keywords: BIOSCIENCES
    Type: NASA-CR-134328
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  • 7
    Publication Date: 2013-08-31
    Description: The problem studied involved cell proliferation in mice thymus undergoing irradiation at a dose rate of 10 roetgens/day for 105 days. Specifically, the aim was to determine wheather or not a steady state of cell population can be established for the indicated period of time and what compensatory mechanisms of cell population are involved.
    Keywords: BIOSCIENCES
    Type: NASA-CR-135723 , SASR-4
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  • 8
    Publication Date: 2013-08-31
    Description: A computer program for analyzing axisymmetric shells with inertial forces caused by rotation about the shell axis is developed by revising the STARS II shell program. The basic capabilities of the STARS II shell program, such as the treatment of the branched shells, stiffened wall construction, and thermal gradients, are retained.
    Keywords: STRUCTURAL MECHANICS
    Type: M-367 , NASA-TN-D-6485
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  • 9
    Publication Date: 2013-08-31
    Description: The mechanism of cell proliferation is studied in the lymphoid tissue of the mouse spleen under the stress of continuous irradiation at a dose-rate of 10 roentgens per day for 105 days. Autoradiography and specific labeling with tritiated thymidine were utilized. It was found that at least four compensatory mechanisms maintained a near-steady state of cellular growth: (1) an increase in the proportion of PAS-positive cells which stimulate mitotic activity, (2) maturation arrest of proliferating and differentiating cells which tend to replenish the cells damaged or destroyed by irradiation, (3) an increase in the proportion of cells proliferating, and (4) an increase in the proportion of precursor cells. The results are compared to previous findings observed in the thymus.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-CR-142068
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  • 10
    Publication Date: 2010-09-29
    Description: Computer program can be used to analyze any disk or shell of revolution of arbitrary cross section under inertial loads caused by rotation about shell axis and under various static loads, including thermal gradients. Geometric shapes incorporated in program are ellipsoidal, spherical, ogival, toroidal, conical, circular plate, cylindrical, and parabolic.
    Keywords: MATHEMATICS AND INFORMATION SCIENCES
    Type: MFS-21970
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