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  • 1
    Electronic Resource
    Electronic Resource
    The presence of an extracellular matrix between cells involved in the determination of the mesoderm bands in embryos ofPatella vulgata (Mollusca, gastropoda) (1986)
    Springer
    Development genes and evolution 195 (1986), S. 265-275 
    Details
    ISSN: 1432-041X
    Keywords: Extracellular matrix ; Mollusca ; Mesoderm determination ; Lectins ; Cell contacts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In 32-cell stage embryos ofPatella vulgata one of the macromeres contacts the animal micromeres, and as a result is induced to differentiate into the stem cell of the mesodermal cell line. In this study we show the presence of an extracellular matrix (ECM) between these two interacting cell types. The ECM appears to be formed by the micromeres during the 32-cell stage. Staining experiments with alcian blue and tannic acid indicate that in contains glycoconjugates, possibly in the form of proteoglycans. The characteristics of the ECM were examined further by fluorescein isothiocyanate (FITC)-lectin labelling. Of 17 lectins tested, concanavalin A (ConA), succinyl-ConA, LCH-B (Lens culinaris) and PEA (Pisum sativum) showed a positive labelling of the ECM. These results are in accordance with the electron microscopic data. The appearance of the ECM at this specific stage and place suggests that it might play an important role in the induction of the mesodermal cell line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02438960
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  • 2
    Electronic Resource
    Electronic Resource
    Hypoaldosteronism in piglets induced by carbadox (1986)
    Springer
    Cellular and molecular life sciences 42 (1986), S. 1247-1249 
    Details
    ISSN: 1420-9071
    Keywords: Carbadox ; aldosterone ; adrenal damage ; zona glomerulosa ; electrolyte homeostasis ; pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An exploratory study was made of the mechanisms underlying the toxic action of carbadox in young pigs: dehydration, loss of appetite and at autopsy seemingly specific and selective structural alterations of the glomerular zone of the adrenal cortex. Administration of carbadox in the feed, in dosages of 150 ppm (approximately 6 mg·kg−1 b.wt·day−1) caused a rapid decline in the plasma aldosterone levels (to 10% of control) followed by significant changes in the sodium and potassium levels in blood. Characteristic for the toxic action of carbadox are the rapid and seemingly selective and specific alterations in the aldosterone-releasing zona glomerulosa of the adrenals. Our results indicate that with carbadox a functional and possibly reversible extirpation of the adrenal zona glomerulosa can be achieved in pigs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01946407
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  • 3
    Electronic Resource
    Electronic Resource
    Der Einfluß der Krümmunǵ des Luftspaltes auf die Zusatzverluste im massiven Rotoreisen von Synchronmaschinen (1969)
    Springer
    Electrical engineering 53 (1969), S. 45-52 
    Details
    ISSN: 1432-0487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Description / Table of Contents: Contents The surface losses in unlaminated rotors of synchronous machines are calculated. In order to take into account the curvature, cylindrical polar coordinates are used for the air gap. On the other hand the rotor is described in Cartesian coordinates as the depth of penetration of the fields in the solid rotor is small. By this means very simple results can be achieved in spite of considering the curvature. The influences of the curvature on the surface losses are discussed in an example.
    Notes: Übersicht Es werden die Zusatzverluste im massiven Eisen des Rotors von Synchronmaschinen berechnet. Um die Krümmung zu berücksichtigen, werden für den Luftspalt Zylinderkoordinaten verwendet. Wegen der geringen Eindringtiefe der Felder im massiven Eisen wird dagegen der Rotor in kartesischen Koordinaten dargestellt. Auf diese Weise erhält man trotz Berücksichtigung der Krümmung sehr einfache Ergebnisse. Der Einfluß der Krümmung auf die Zusatzverluste wird anhand eines Beispiels gezeigt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01407214
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  • 4
    Electronic Resource
    Electronic Resource
    Security of Quantum Key Distribution against All Collective Attacks
    Springer
    Algorithmica 34 (NaN), S. 372-388 
    Details
    ISSN: 1432-0541
    Keywords: Key words. Quantum cryptography, Key distribution, Security, Information versus disturbance.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. Security of quantum key distribution against sophisticated attacks is among the most important issues in quantum information theory. In this work we prove security against a very important class of attacks called collective attacks (under a compatible noise model) which use quantum memories and gates, and which are directed against the final key. This work was crucial for a full proof of security (against the joint attack) recently obtained by Biham, Boyer, Boykin, Mor, and Roychowdhury [1].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00453-002-0973-6
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  • 5
    Electronic Resource
    Electronic Resource
    Reactive Phosphonic Acids as Prebiotic Carriers of Phosphorus (1997)
    Springer
    Journal of molecular evolution 44 (1997), S. 237 -241 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Prebiotic chemistry — Nucleotide analogues — Phosphonic acids — Photochemistry — Ribose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Phosphonic acids are the only phosphorus-containing organic compounds detected in the Murchison meteorite. We earlier described the synthesis of methyl-, hydroxymethyl-, and 1-hydroxyethyl phosphonic acids using sodium phosphite as a source of phosphite radicals. We now show that ultraviolet irradiation of dilute aqueous solutions of acetylene in the presence of sodium phosphite leads to the synthesis of vinyl phosphonic acid. At neutral to basic pH, vinyl phosphonic acid reacts under photochemical conditions to produce phosphonoacetaldehyde and 2-hydroxyethyl phosphonic acid as the major products, as well as smaller yields of 1-hydroxyethyl phosphonic acid, phosphonoacetic acid, and ethyl phosphonic acid. Of these products, phosphonoacetaldehyde is particularly interesting as a potential precursor of prebiotic carbohydrate derivatives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006140
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  • 6
    Electronic Resource
    Electronic Resource
    Mineral Catalysis of a Potentially Prebiotic Aldol Condensation (1998)
    Springer
    Journal of molecular evolution 47 (1998), S. 501-507 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Aldol condensation — Chemical evolution — Origin of life — Double-layer hydroxide minerals — Phosphonic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Minerals may have played a significant role in chemical evolution. In the course of investigating the chemistry of phosphonoacetaldehyde (PAL), an analogue of glycolaldehyde phosphate, we have observed a striking case of catalysis by the layered hydroxide mineral hydrotalcite ([Mg2Al(OH)6][Cl.nH2O]). In neutral or moderately basic aqueous solutions, PAL is unreactive even at a concentration of 0.1 M. In the presence of a large excess of NaOH (2 M), the compound undergoes aldol condensation to produce a dimer containing a C3–C4 double-bond. In dilute neutral solutions and in the presence of the mineral, however, condensation takes place rapidly, to produce a dimer which is almost exclusively the C2–C3 unsaturated product.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00006406
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  • 7
    Electronic Resource
    Electronic Resource
    The prebiotic synthesis of carbohydrates: A reassessment (1993)
    Springer
    Journal of molecular evolution 36 (1993), S. 101-106 
    Details
    ISSN: 1432-1432
    Keywords: Prebiotic chemistry ; Formose reaction ; Carbohydrates ; Formaldehyde ; Minerals ; Pentaerythritol ; UV irradiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Questions concerning the significance of previous work on the formose reaction have led us to reexamine the question of the prebiotic synthesis of sugars. The results of new experiments lead to the following conclusions: The formose reaction is a geochemically plausible reaction which depends on neither basic conditions nor on the presence of trace amounts of carbohydrate impurities. However, this process is not a plausible source of ribose nor of any other individual sugar. In contrast to the nonspecific formation of complex mixtures of sugars via the formose reaction, the reduced sugar pentaerythritol is formed with great selectivity by the ultraviolet irradiation of 0.1 M formaldehyde. This compound may have played an important role in chemical evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166245
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  • 8
    Electronic Resource
    Electronic Resource
    31P Nuclear magnetic resonance studies of ethanol inhibition in Zymomonas mobilis (1993)
    Springer
    Archives of microbiology 159 (1993), S. 484-490 
    Details
    ISSN: 1432-072X
    Keywords: Zymomonas ; Glucose catabolism ; Ethanol inhibition ; 31P NMR in vivo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ethanol inhibition of glucose catabolism in Zymomonas mobilis was investigated using 31P NMR spectroscopy in vivo and of perchloric acid extracts from cell suspensions incubated with 0, 5 and 10% (w/v) ethanol. In vivo 31P NMR experiments revealed slower glucose utilization and decreased levels of nucleoside triphosphates in the presence of 10% ethanol as compared to controls. Using 31P NMR spectroscopy of perchloric acid extracts, intracellular accumulation of 3.4 mM 3-phosphoglycerate was found when 10% ethanol was present in the medium. No accumulation of this metabolite occurred in cells incubated with 0 and 5% ethanol. Enzyme assays confirmed that phosphoglycerate-mutase and enolase were inhibited 31 and 40%, respectively, in the presence of 10% ethanol in the test system. Therefore, under the conditions used the decrease in the fermentative activity of Z. mobilis at high ethanol concentrations is due to inhibition of phosphoglycerate-mutase and enolase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00288598
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  • 9
    Electronic Resource
    Electronic Resource
    Propionate oxidation in Escherichia coli: evidence for operation of a methylcitrate cycle in bacteria (1997)
    Springer
    Archives of microbiology 168 (1997), S. 428-436 
    Details
    ISSN: 1432-072X
    Keywords: Key words Escherichia coli ; Propionate oxidation ; 13C and 2H-labeling ; Methylcitrate cycle ; Glyoxylate ; cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Escherichia coli grew in a minimal medium on propionate as the sole carbon and energy source. Initially a lag phase of 4–7 days was observed. Cells adapted to propionate still required 1–2 days before growth commenced. Incorporation of (2-13C), (3-13C) or (2H3)propionate into alanine revealed by NMR that propionate was oxidized to pyruvate without randomisation of the carbon skeleton and excluded pathways in which the methyl group was transiently converted to a methylene group. Extracts of propionate-grown cells contained a specific enzyme that catalyses the condensation of propionyl-CoA with oxaloacetate, most probably to methylcitrate. The enzyme was purified and identified as the already-known citrate synthase II. By 2-D gel electrophoresis, the formation of a second propionate-specific enzyme with sequence similarities to isocitrate lyases was detected. The genes of both enzymes were located in a putative operon with high identities (at least 76% on the protein level) with the very recently discovered prp operon from Salmonella typhimurium. The results indicate that E. coli oxidises propionate to pyruvate via the methylcitrate cycle known from yeast. The 13C patterns of aspartate and glutamate are consistent with the further oxidation of pyruvate to acetyl-CoA. Oxaloacetate is predominantly generated via the glyoxylate cycle rather than by carboxylation of phosphoenolpyruvate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050518
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  • 10
    Electronic Resource
    Electronic Resource
    Metabolic state of Zymomonas mobilis in glucose-, fructose-, and xylose-fed continuous cultures as analysed by 13C- and 31P-NMR spectroscopy (1999)
    Springer
    Archives of microbiology 171 (1999), S. 371-385 
    Details
    ISSN: 1432-072X
    Keywords: Key wordsZymomonas mobilis ; Metabolic flux ; analysis ; Sugar phosphates ; Glucose ; Fructose ; Xylose ; 13C-NMR ; In vivo 31P-NMR ; Rate-limiting step
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The reasons for the well-known significantly different behaviour of the anaerobic, gram-negative, ethanologenic bacterium Zymomonas mobilis during growth on fructose (i.e. decreased growth and ethanol yields, increased by-product formation) as compared to that on its second natural substrate, glucose, have remained unexplained. A xylose-fermenting recombinant strain of Z. mobilis that was recently constructed in our laboratory also unexpectedly displayed an increased formation of by-products and a strongly reduced growth rate as compared to the parent strain. Therefore, a comprehensive study employing recently developed NMR-based methods for the in vivo analysis of intracellular phosphorylated pool sizes and metabolic fluxes was undertaken to enable a global characterization of the intracellular metabolic state of Z. mobilis during growth on 13C-labelled glucose, fructose and xylose in defined continuous cultures. The 13C-NMR flux analysis indicated that ribose 5-phosphate is synthesized via the nonoxidative pentose phosphate pathway in Z. mobilis, and it identified a metabolic bottleneck in the recombinant xylose-fermenting Z. mobilis strain at the level of heterologous xylulokinase. The 31P-NMR analyses revealed a global alteration of the levels of intracellular phosphorylated metabolites during growth on fructose as compared to that on glucose. The results suggest that this is primarily caused by an elevated concentration of intracellular fructose 6-phosphate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050724
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