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  • Astrophysics  (14)
  • Inorganic, Organic and Physical Chemistry  (10)
  • Cell & Developmental Biology  (5)
  • Lunar and Planetary Science and Exploration; Life Sciences (General)  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Glycogen breakdown in cleaving xenopus embryos is limited by ADP (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 32 (1992), S. 354-362 
    Details
    ISSN: 1040-452X
    Keywords: Glycolysis, Embryos, Metabolism, Pyruvate kinase, Malic enzyme ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Xenopus eggs contain large stores of glycogen, but this glycogen is not glycolytically processed during cleavage. The Embden-Meyerhof pathway is inhibited by the absence of pyruvate kinase activity in vivo, and lactate and pyruvate are present at relatively low levels. In the late blastula, just preceding gastrulation, lactate levels increase, indicating the onset of glycogen breakdown and glycolytic flux. Glycolysis from microinjected [14C]glucose-6-phosphate could be transiently activated, however, by the coinjection of ADP into fertilized eggs, and constitutively activated by the injection of the ATPase potato apyrase, indicating the presence of all enzymes necessary for glycolytic activity. The isozyme profiles of pyruvate kinase and malic enzyme, two enzymes involved in carbon metabolism during cleavage or in the subsequent activation of glycogen breakdown, do not change between the egg and gastrula stages. These data suggest that the activation of glycogen breakdown and glycolysis in the late blastula is probably not a result of new gene activity but may be the metabolic consequence of increased free ADP that is then able to support the pyruvate kinase reaction.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080320408
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and modification of D7 protein during Xenopusoocyte maturation (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 32 (1992), S. 293-301 
    Details
    ISSN: 1040-452X
    Keywords: Maternal mRNA ; Oocyte maturation ; Protein modification ; MPF ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The Xenopus maternal mRNA D7 is translationally repressed during oogenesis, only becoming recruited into polysomes during oocyte maturation, with D7 protein being detectable for the first time prior to germinal vesicle breakdown (GVBD). The synthesis of D7 protein was found to be induced by a variety of maturation-promoting agents including cyclin, c-mos and crude preparations of MPF. D7 protein induced by all these agents is post-translationally modified and exists as a number of variants of differing molecular weight. In contrast to endogenous D7 mRNA, D7 RNA injected into the stage VI oocyte is efficiently translated, resulting in the accumulation of predominantly unmodified D7 polypeptides, which become increasingly modified during oocyte maturation to produce a pattern of polypeptides similar to those derived from endogenous D7 mRNA. Thus, the system that results in the post-translational modification of the D7 protein is itself activated during oocyte maturation. The nature of the protein modification is not known but does not appear to be phosphorylation. The translation of exogenous D7 RNA in the stage VI oocyte does not lead to translational derepression of endogenous D7 mRNA.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080320315
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  • 3
    Electronic Resource
    Electronic Resource
    Functions of maternal mRNA in early development (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 26 (1990), S. 261-297 
    Details
    ISSN: 1040-452X
    Keywords: Egg mRNA ; Translational control ; Drosophila ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In this review, the types of mRNAs found in oocytes and eggs of several animal species, particularly Drosophila, marine invertebrates, frogs, and mice, are described. The roles that proteins derived from these mRNAs play in early development are discussed, and connections between maternally inherited information and embryonic pattern are sought. Comparisons between genetically identified maternally expressed genes in Drosophila and maternal mRNAs biochemically characterized in other species are made when possible. Regulation of the meiotic and early embryonic cell cycles is reviewed, and translational control of maternal mRNA following maturation and/or fertilization is discussed with regard to specific mRNAs.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080260310
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  • 4
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    The Laboratory Production of Complex Organic Molecules in Simulated Interstellar Ices (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Much of the volatiles in interstellar dense clouds exist in ices surrounding dust grains. Their low temperatures preclude most chemical reactions, but ionizing radiation can drive reactions that produce a suite of new species, many of which are complex organics. The Astrochemistry Lab at NASA Ames studies the UV radiation processing of interstellar ice analogs to better identify the resulting products and establish links between interstellar chemistry, the organics in meteorites, and the origin of life on Earth. Once identified, the spectral properties of the products can be quantified to assist with the search for these species in space. Of particular interest are findings that UV irradiation of interstellar ice analogs produces molecules of importance in current living organisms, including quinones, amphiphiles, and amino acids.
    Keywords: Astrophysics
    Type: Proceedings of the NASA Laboratory Astrophysics Workshop; 198-200; NASA/CP-2002-211863
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  • 5
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    Prebiotic Synthesis of Methionine and Other Sulfur-Containing Organic Compounds on the Primitive Earth: A Contemporary Reassessment Based on an Unpublished 1958 Stanley Miller Experiment (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Original extracts from an unpublished 1958 experiment conducted by the late Stanley L. Miller were recently found and analyzed using modern state-of-the-art analytical methods. The extracts were produced by the action of an electric discharge on a mixture of methane (CH4), hydrogen sulfide (H2S), ammonia (NH3), and carbon dioxide (CO2). Racemic methionine was farmed in significant yields, together with other sulfur-bearing organic compounds. The formation of methionine and other compounds from a model prebiotic atmosphere that contained H2S suggests that this type of synthesis is robust under reducing conditions, which may have existed either in the global primitive atmosphere or in localized volcanic environments on the early Earth. The presence of a wide array of sulfur-containing organic compounds produced by the decomposition of methionine and cysteine indicates that in addition to abiotic synthetic processes, degradation of organic compounds on the primordial Earth could have been important in diversifying the inventory of molecules of biochemical significance not readily formed from other abiotic reactions, or derived from extraterrestrial delivery.
    Keywords: Inorganic, Organic and Physical Chemistry
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  • 6
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    The Interstellar Production of Biologically Important Organics (2000)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: One of the primary tasks of the Astrochemistry Laboratory at Ames Research Center is to use laboratory simulations to study the chemical processes that occur in dense interstellar clouds. Since new stars are formed in these clouds, their materials may be responsible for the delivery of organics to new habitable planets and may play important roles in the origin of life. These clouds are extremely cold (less than 50 kelvin), and most of the volatiles in these clouds are condensed onto dust grains as thin ice mantles. These ices are exposed to cosmic rays and ultraviolet (UV) photons that break chemical bonds and result in the production of complex molecules when the ices are warmed (as they would be when incorporated into a star-forming region). Using cryovacuum systems and UV lamps, this study simulates the conditions of these clouds and studies the resulting chemistry. Some of the areas of progress made in 1999 are described below. It shows some of the types of molecules that may be formed in the interstellar medium. Laboratory simulations have already confirmed that many of these compounds are made under these conditions.
    Keywords: Astrophysics
    Type: Research and Technology 1999; 116-117; NASA/TM-2000-209618
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  • 7
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    Synthesis of Large Molecules in Cometary Ice Analogs: Physical Properties Related to Self-Assembly Processes (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The combination of realistic laboratory simulations and infrared observations have revolutionized our understanding of interstellar dust and ice-the main component of comets. Since comets and carbonaceous micrometeorites may have been important sources of volatiles and carbon compounds on the early Earth, their organic composition may be related to the origin of life. Ices on grains in molecular clouds contain a variety of simple molecules. The D/H ratios of the comets Hale-Bopp and Hyakutake are consistent with a primarily interstellar ice mixture. Within the cloud and especially in the presolar nebula through the early solar system, these icy grains would have been photoprocessed by the ultraviolet producing more complex species such as hexamethylenetetramine, polyoxymethylenes, and simple keones. We reported at the 1999 Bioastronomy meeting laboratory simulations studied to identify the types of molecules which could have been generated in pre-cometary ices. Experiments were conducted by forming a realistic interstellar mixed-molecular ice (H2O, CH3OH, NH3 and CO) at approximately 10 K under high vacuum irradiated with UV light from a hydrogen plasma lamp. The gas mixture was typically 100:50:1:1, however when different ratios were used material with similar characteristics was still produced. The residue that remained after warming to room temperature was analyzed by HPLC, and by several mass spectrometric methods. This material contains a rich mixture of complex compounds with mass spectral profiles resembling those found in IDPs and meteorites. Surface tension measurements show that an amphiphilic component is also present. These species do not appear in various controls or in unphotolyzed samples. Residues from the simulations were also dispersed in aqueous media for microscopy. The organic material forms 10-40 gm diameter droplets that fluoresce at 300-450 nm under UV excitation. These droplets have a morphology and internal structure which appear strikingly similar to those produced by extracts of the Murchison meteorite. Together, these results suggest a link between organic material photochemically synthesized on the cold grains in dense, interstellar molecular clouds and compounds that may have contributed to the organic inventory of the primitive Earth. For example, the amphiphilic properties of such compounds permit self-assembly into the membranous boundary structures that required for the first forms of cellular life.
    Keywords: Astrophysics
    Type: 1999 Meeting o BioAstronomy; Aug 01, 1999; Khilua, HI; United States
    Format: text
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  • 8
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    The Production of Amino Acids in Interstellar Ices: Implications for Meteoritic Organics (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Indigenous amino acids have been detected in a number of meteorites, over 70 in the Murchison meteorite alone. It has been generally accepted that the amino acids in meteorites formed in liquid water on an asteroid or comet parent-body. However, the water in the Murchison meteorite, for example, was depleted of deuterium, making the distribution of deuterium in organic acids in Murchison difficult to explain. Similarly, occasional but consistent meteoritic biases for non-terrestrial L amino acids cannot be reasonably rationalized by liquid water parent-body reactions. We will present the results of a laboratory demonstration showing that the amino acids glycine, alanine, and serine should result from the UV (ultraviolet) photolysis of interstellar ice grains. This suggests that some meteoritic amino acids may be the result of interstellar ice photochemistry, rather than having formed by reactions in liquid water. We will describe some of the potential implications of these findings for the organic materials found in primitive meteorites, in particular how interstellar ice synthesis might more easily accommodate the presence and distribution of deuterium, and the meteoritic bias for L amino acids.
    Keywords: Astrophysics
    Type: 65th Annual Meeting of the Meteoritical Society; Jul 21, 2002 - Jul 26, 2002; Los Angeles, CA; United States
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  • 9
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    Formation of Prebiotic Molecules in Interstellar and Cometary Ices (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: We report here on our lab studies of ice photochemistry of large organic molecules under cometary conditions. We focus on polycyclic aromatic hydrocarbons (PAHs), their photoproducts, and their similarities to molecules seen in living systems today. We note that these kinds of compounds are seen in meteorites and we propose an explanation for both their formation and their observed deuterium enrichments.
    Keywords: Astrophysics
    Type: Bioastronomy Conference 1999: A New Era in the Search for Life in the Universe; Aug 02, 1999 - Aug 06, 1999; Kohala Coast, HI; United States
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  • 10
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    The Amino Acid Composition of the Sutter's Mill Carbonaceous Chondrite (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In contrast to the Murchison meteorite which had a complex distribution of amino acids with a total C2 to Cs amino acid abundance of approx.14,000 parts-per-billion (ppb) [2], the Sutters Mill meteorite was found to be highly depleted in amino acids. Much lower abundances (approx.30 to 180 ppb) of glycine, beta-alanine, L-alanine and L-serine were detected in SM2 above procedural blank levels indicating that this meteorite sample experienced only minimal terrestrial amino acid contamination after its fall to Earth. Carbon isotope measurements will be necessary to establish the origin of glycine and beta-alanine in SM2. Other non-protein amino acids that are rare on Earth, yet commonly found in other CM meteorites such as aaminoisobutyric acid (alpha-AIB) and isovaline, were not identified in SM2. However, traces of beta-AIB (approx.1 ppb) were detected in SM2 and could be" extraterrestrial in origin. The low abundances of amino acids in the Sutter's Mill meteorite is consistent with mineralogical evidence that at least some parts of the Sutter's Mill meteorite parent body experienced extensive aqueous and/or thermal alteration.
    Keywords: Astrophysics
    Type: GSFC.OVPR.6657.2012 , 75th Annual Meeting of the Meteoritical Society; Aug 12, 2012 - Aug 17, 2012; Cairns; Australia
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