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  • 1975-1979  (5)
  • Molecular Cell Biology  (2)
  • Photosynthesis  (2)
  • Apical ectodermal ridge  (1)
  • 1
    Electronic Resource
    Electronic Resource
    The early history of oxygen and ozone in the atmosphere (1978)
    Springer
    Pure and applied geophysics 117 (1978), S. 498-512 
    Details
    ISSN: 1420-9136
    Keywords: History of atmosphere ; Oxygen ; Ozone ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract There may have been three stages in the growth of oxygen in the terrestrial atmosphere. Prior to the origin of photosynthesis the only source of oxygen was photolysis of water vapor followed by escape of hydrogen to space. The rate of this process was probably less than the rate of release of reduced gases (principally hydrogen) from volcanoes, so the oxygen partial pressure was held to negligibly low values by photochemical reactions with an excess of hydrogen. The photosynthetic source of oxygen was probably in operation as long ago as 3.8 billion years. It released oxygen to the ocean. Presumably most of this oxygen was destroyed in the ocean as long as its rate of supply was less than the rate of supply of readily oxidizable material (principally Fe2+) provided by the weathering of rocks. This phase appears to have lasted until about 2 billion years ago, during which period most banded iron formations were deposited. During this period the production of oxygen by algae was limited by competition with photosynthetic bacteria, which preempted the supply of nutrient phosphorus as long as reduced chemicals were available in the environment. Once the photosynthetic oxygen source exceeded the rate of supply of reduced minerals exposed by erosion and weathering, the accumulation of oxygen in the ocean and atmosphere could be controlled only by reaction of oxygen with reduced organic material. This is the stabilization mechanism that operates today. It seems unlikely that oxygen could be consumed at a significant rate by this process until oxygen levels sufficiently high to support respiration had been achieved. I therefore suggest that atmospheric oxygen rose rapidly from essentially zero to approximately its present value (within a factor of 10) when the photosynthetic source of oxygen rose above the weathering source of reduced minerals, probably about 2 billion years ago. The ozone layer and the ultraviolet screen were absent prior to this time and essentially fully developed after this time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876630
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Oxygen and hydrogen in the primitive atmosphere (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 222-231 
    Details
    ISSN: 1420-9136
    Keywords: Photolysis ; Photosynthesis ; Primitive Atmosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract From time to time there appears in the literature the assertion that photolysis of water vapor could have maintained an appreciable concentration of oxygen in the primitive (prebiological) atmosphere. The implausibility of this assertion is argued in this paper. By itself, photolysis does not provide a source of oxygen because it is usually followed by recombination of the products of photolysis. Only the escape to space (at a much smaller rate) of the hydrogen produced by photolysis of water results in a net source of oxygen. The oxidation state of the primitive atmosphere depended on the relative magnitudes of this net source of oxygen and a volcanic source of hydrogen and other reduced gases. Today the volcanic source of reduced gases is approximately equal to the oxygen source provided by photolysis followed by escape. The oxygen source depends on the mixing ratio of water vapor in the stratosphere, which ultimately determines the rate of escape of hydrogen produced from water vapor. Its magnitude may not have been very different in the past. The volcanic source of hydrogen, on the other hand, is likely to have been much larger when the earth was tectonically young. Hydrogen was therefore released to the primitive atmosphere more rapidly than oxygen, probably. Photochemical reactions with the excess hydrogen maintained oxygen mixing ratios at negligibly small levels. The hydrogen mixing ratio was determined by a balance between the volcanic source (reduced by recombination with oxygen) and escape to space. In time, either because of decline of the volcanic source of hydrogen or because of addition of a biological source of oxygen, the input of oxygen to the atmosphere rose above the input of hydrogen. The oxidation state of the atmosphere changed rapidly. Volcanic hydrogen was now consumed by photochemical reactions with excess oxygen, while the oxygen mixing ratio was determined by a balance between the source (reduced by recombination with volcanic hydrogen) and consumption in reactions with reduced material at the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01636879
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  • 3
    Electronic Resource
    Electronic Resource
    Studies of malformation syndromes of man XXXXIA: anatomical studies in the Hanhart syndrome —A pathogenetic hypothesis (1976)
    Springer
    European journal of pediatrics 122 (1976), S. 1-17 
    Details
    ISSN: 1432-1076
    Keywords: Aglossia ; Adactylia ; Apical ectodermal ridge ; Ectoderm-mesoderm interaction ; “Ektodermring” ; Embryology ; Gross anatomical defects ; Hanhart's syndrome ; Imperforate anus ; Limb abnormalities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two infants with the Hanhart syndrome, i.e. micrognathia, microglossia, terminal deficiency of all limbs and imperforate anus in one, were dissected and studied in detail. The interrelationships of the muscular and skeletal defects suggested that they were the result of incomplete rather than abnormal morphogenesis. We speculate that the oral and limb abnormalities resulted from deficient mesodermal proliferation caused by disturbances in the ectodermal-mesodermal interactions beginning about the 4th week of development. The imperforate anus may also relate to the proposed defect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00445029
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  • 4
    Electronic Resource
    Electronic Resource
    Cell surface receptors and their dynamics on toxin-treated malignant cells (1976)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 4 (1976), S. 15-26 
    Details
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The binding, mobility, and mode of cell entry of the plant toxin ricin (or RCAII) were investigated on susceptible and partially resistant murine cell lines. When susceptible cells (SV40-transformed 3T3 fibroblast cells and BW5147 lymphoma cells) were examined, ricin bound rapidly, induced endocytosis, and entered the cell cytoplasm via broken endocytotic vesicles to inhibit cell protein synthesis, as found previously (1). Addition of lactose within 15 min after initial ricin binding prevented toxicity. After this time lactose addition no longer blocked the inhibition of protein synthesis.In a partially resistant lymphoma (BW5147/RCA3) that shows only a slight reduction in the total number of ricin-binding sites, ricin bound rapidly to the cell surface, but was endocytosed significantly less at low ricin doses compared to its parental line, indicating a possible difference in cell surface behavior. The exposed surface proteins on the BW5147 parental and BW5147/RCA3 resistant lines were examined by 125I-labeling utilizing lactoperoxidase-catalyzed iodination. The radiolabeled components were solubilized and separated by slab gel electrophoresis in sodium dodecyl sulfate. Autoradiograms of the slab gels indicated that two surface components of approximately 80,000 and 35,000 mol wt were much less exposed or were missing on the resistant line.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400040103
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  • 5
    Electronic Resource
    Electronic Resource
    Ricinus communis toxin-mediated inhibition of protein synthesis in cell-free extracts of a toxin-resistant variant mouse lymphoma cell line (1976)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 515-520 
    Details
    ISSN: 0091-7419
    Keywords: mutant RCAII ; ricin ; toxin ; protein synthesis ; variant cell line ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Ricinus communis agglutinin II (RCAII, ricin, toxin) at low concentrations inhibits protein synthesis in cell-free extracts, but not in intact cells, of an RCAII-resistant mouse lymphoma variant cell line. The concentration dependence of the inhibition by RCAII was the same in cell-free extracts of both RCAII-resistant variant and RCAII-sensitive parental cells, while intact parental cells are 250 times more sensitive to RCAII toxicity. The onset of RCAII inhibition of cell-free protein synthesis was extremely rapid in both cases, being complete in a few minutes. Under these condidtions RCAII inhibits protein synthesis in intact RCAII-sensitive parental cells, but maximal inhibition requires several hours to occur. These results support our previous electron microscopic observations that the variant cells are defective in the uptake of RCAII by endocytosis at low toxin concentrations.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400050408
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