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  • 1
    Electronic Resource
    Electronic Resource
    Pinocytosis and locomotion in amoebae (1979)
    Springer
    Protoplasma 100 (1979), S. 33-43 
    Details
    ISSN: 1615-6102
    Keywords: Amoeba proteus ; Ca++-binding sites ; Cytochemical demonstration ; Induced pinocytosis ; Plasma membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Different methods were used to demonstrate the existence of Ca++-binding sites (Ca++-bs) at the plasma membrane ofAmoeba proteus. In pinocytoting animals the number (indicated by the average distanced in nm) and size (average longitudinal axiss in nm) of Ca++-bs at the cytoplasmic surface of the cell membrane were significantly increased (d=162±15;n=41 ands=93±5;n=47) in comparison to controls (d=208 ±21;n=37 ands=59±8;n=45). The ratio of P: Ca obtained by X-ray microanalysis was in the range of 1.5. The differences observed in the two experimental groups of amoebae are explained by conformational changes in the molecular structure and an increased Ca++-permeability of the plasma membrane during induced pinocytosis. Microplasmodia of the acellular slime moldPhysarum polycephalum investigated for comparison were found to have no Ca++-bs at the interior cell surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276299
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Pinocytosis and locomotion of amoebae: XII. Dynamics and motive force generation during induced pinocytosis in A. proteus (1979)
    Springer
    Cell & tissue research 197 (1979), S. 263-279 
    Details
    ISSN: 1432-0878
    Keywords: Induced pinocytosis ; Dynamics ; Motive force generation ; Light and electron microscopy ; Amoeba proteus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The mechanism of induced pinocytosis was investigated in Amoeba proteus by light and electron microscopy. The application of nine different inducing substances revealed that pinocytotic channel formation, elongation, vesiculation, shortening and disappearance are the result of the successive or simultaneous action of both traction and pressure forces, which are produced by the contractile activity of a plasma membrane-associated layer of filaments ranging from a few hundred nm to several μ in thickness. The initial phase of channel formation is caused by traction forces according to the membrane flow concept, whereas channel elongation and vesiculation mainly result from pressure forces in conjunction with the extrusion of small hyaline pseudopodia. Shortening and disappearance of the pinocytotic channels are brought about by local contractions of the cortical filament layer in the basal region of the hyaline pseudopodia. Experiments using latex beads as marker particles together with inducing substances show that a rapid membrane turnover during pinocytosis can be excluded, and that the plasma membrane slides as an entire structure over the underlying cytoplasm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233919
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  • 3
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    The Viking biological investigation - General aspects (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The Viking biological investigation has tested four different hypotheses regarding the possible nature of Martian organisms. While significant results were obtained for each of these, tests of three of the hypotheses appear to indicate the absence of biology in the samples used, while the fourth is consistent with a biological interpretation. The original assumptions for each experiment and the experimental procedures that were utilized to test these assumptions are reviewed.
    Keywords: SPACE BIOLOGY
    Type: Journal of Geophysical Research; 82; Sept. 30
    Format: text
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  • 4
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    The Viking biological experiments on Mars (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The three biological experiments on board the Viking Mars Landers are discussed. The gas exchange experiment provided periodic measurements of the composition and quantity of gases from Martian surface material, either in a humid or a wet nutrient sampling mode. The labeled release experiment demonstrated that adding an aqueous solution of dilute radioactive compounds to Martian material caused a rapid release of labeled gas. The results of the pyrolytic release experiment remain difficult to interpret. Data from the first two experiments suggest that oxidants (including H2O2 and iron oxide) rather than biota may account for all the observed reactions.
    Keywords: SPACE BIOLOGY
    Type: Icarus; 34; June 197
    Format: text
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  • 5
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    General constraints on the Viking biology investigation (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper discusses some of the constraints pertaining to the Viking mission for detection of life on Mars, within which the Viking experiments were conceived, designed, and developed. The most important limitation to the entire study is the complete information about the nature of Mars, such as the chemical composition of the surface material of Mars and the exact identification of the constituents of that planet. Ways in which celestial mechanics places severe limitations on the Viking biology investigation are discussed. Major engineering constraints are examined relative to the accomodation of biology instrument inside the Viking lander and to the design of the instrument itself. Other constraints discussed concern the operational aspects of the mission and the testing program.
    Keywords: SPACE BIOLOGY
    Type: Origins of Life; 7; Aug. 197
    Format: text
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  • 6
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    The Viking mission search for life on Mars (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The scientific payload on the Viking Mars landers is described. Shortly after landing, two facsimile cameras capable of stereoscopic imaging will scan the landing site area in black and white, color, and infrared to reveal gross evidence of past or present living systems. A wide range mass spectrometer will record a complete mass spectrum for soil samples from mass 12 to mass 200 every 10.3 sec. Three experiments based on different assumptions on the nature of life on Mars, if it exists, will be carried out by the bio-lab. A pyrolytic release experiment is designed to measure photosynthetic or dark fixation of carbon dioxide or carbon monoxide into organic compounds. A labelled release experiment will test for metabolic activity during incubation of a surface sample moistened with a solution of radioactively labelled simple organic compounds. A gas exchange experiment will detect changes in the gaseous medium surrounding a soil sample as the result of metabolic activity. The hardware, function, and terrestrial test results of the bio-lab experiments are discussed.
    Keywords: SPACE BIOLOGY
    Type: Nature; 262; July 1
    Format: text
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  • 7
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    Simulation of the Viking biology experiments - An overview (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: In the present paper, ground-based investigations of the Viking Martian biology data, which have resulted in reasonable simulations of these data, are reviewed. These simulations, which in strong oxidants, UV-treated materials, iron-containing clays, or iron salts were used as Martian analogs, are capable of explaining the ambiguity between the GCMS (gas-chromatography mass-spectrometry) experiments, in which no organic compounds were found on Mars, and the Labeled Release experiments, in which added organics were decomposed.
    Keywords: SPACE BIOLOGY
    Type: Journal of Molecular Evolution; 14; Dec. 197
    Format: text
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  • 8
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    The Viking biological investigations - Review and status (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The three experimental approaches incorporated into the Viking biology instrument have yielded results that are most readily explained as nonbiological phenomena. The predominant view among investigators trying to simulate the Mars results is that the surface material of Mars contains strongly oxidizing compounds which would account for many of the more intense reactions seen on Mars. Other mechanisms are also currently being proposed and studied.
    Keywords: SPACE BIOLOGY
    Type: Origins of Life; 9; Dec. 197
    Format: text
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  • 9
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    Planetary protection issues for sample return missions (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Planetary protection (PP) issues for both a comet nucleus sample return (CNSR) mission and a Mars rover sample return (MRSR) mission are discussed, with special attention given to the PP requirements for such missions, the exobiology science objectives for the CNSR and MRSR missions, and a qualitative PP risk assessment for both mission types. A set of contamination control procedures for both missions is presented, which identify procedures for each of the mission phases (i.e., the prelaunch, launch, sample handling, transit vehicle, and earth return). Recommendations for further research and technology development are discussed.
    Keywords: SPACE BIOLOGY
    Type: Planetary Biology and Origins of Life, 20th, 21st, and 23rd, Espoo, Finland, July 18-29, 1988) Advances in Space Research (ISSN 0273-1177); 203-206
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  • 10
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    An exobiology science strategy for Mars exploration (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-04-02
    Description: Of all the other planets in the solar system, Mars remains the most promising for further elucidating concepts about chemical evolution and the origin of life. Exobiological objectives for Mars exploration include: determining the abundance and distribution of the biogenic elements and organic compounds, detecting evidence of an ancient biota on Mars, and determining whether indigenous organisms exist anywhere on the planet. Both approved and planned missions to Mars were evaluated for their potential to contribute to the understanding of these exobiology science objectives and an exploration strategy was developed for each objective.
    Keywords: SPACE BIOLOGY
    Type: Origins of Life and Evolution of the Biosphere (ISSN 0169-6149); 24; 2-4; p. 342-343
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