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  • Temperature adaptation  (2)
  • As, Se, Hg  (1)
  • Plasma-Renin-Konzentration
  • Springer  (3)
  • Nature Publishing Group (NPG)
  • Oxford University Press
  • 2010-2014
  • 1995-1999  (3)
  • 1970-1974
  • 1955-1959
  • 1995  (3)
Publikationsart
Verlag/Herausgeber
  • Springer  (3)
  • Nature Publishing Group (NPG)
  • Oxford University Press
Erscheinungszeitraum
  • 2010-2014
  • 1995-1999  (3)
  • 1970-1974
  • 1955-1959
Jahr
  • 1
    ISSN: 1436-5073
    Schlagwort(e): flow injection ; As, Se, Hg ; estuarine sediment ; standard reference material ; microwave-oven digestion ; CVAAS ; FIA-AAS
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A flow-injection analysis atomic absorption spectrometric (FIA-AAS) method was developed for the determination of trace amounts of arsenic, selenium and mercury in a proposed estuarine sediment standard reference material (SRM 1646a). The samples were prepared in two manners: a) A wet digestion procedure with HNO3, H2SO4, and HClO4 using a reflux column and b) A microwave-oven digestion procedure utilizing HNO3, H2SO4, and HCl for As and Se, and HNO3 for Hg. Microwave-oven digestion provides results comparable to those found by reflux column digestion and reduces the sample preparation time by a factor of 10. The proposed method employing the microwave-oven digestion procedure coupled with FIA-AAS for As and Se, and FIA-CVAAS for Hg, has detection limits of 0.15 ng As/ml, O.17 ng Se/ml and 0.15 ng Hg/ml.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 165 (1995), S. 46-55 
    ISSN: 1432-136X
    Schlagwort(e): Citrate synthase ; Enzyme characteristics ; Temperature adaptation ; Isopod crustacea ; Euphausiid crustacea
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract The characteristics and properties chromatographically purified citrate synthase from the euphausiids Euphausia superba (Antarctica) and Meganyctiphanes norvegica (Scandinavian Kattegat and Mediterranean Sea) and from the isopods Serolis polita (Antarctica) and Idotea baltica (Baltic Sea) were used to elucidate biochemical mechanisms of temperature adaptation. Additionally, maintenance experiments were carried out on the euphausiids to determine mechanisms of short term acclimation. Temperature optima (between 37 and 45°C) were unrelated to genotypic cold adaptation, but the activation energy of the Antarctic krill E. superba (10.9 kJ · mol-1) was only a quarter of that in other species (41.8–45.1 kJ · mol-1). The minima of apparent Michaelis constants (total range: 4–20 μmol · 1-1 oxaloacetate; 7–45 μmol · 1-1 acetyl-coenzyme A) showed no relation to natural conditions, and no distinct pH optimum occurred at ambient temperatures. In contrast, apparent Michaelis constants and specific enzyme activities were related to maintenance temperatures in M. norvegica, but not in E. superba. The differences between M. norvegica and E. superba can be interpreted as adaptations to the changes in ambient temperature with regard to the respective steno- and eurythermic tolerances of these crustaceans.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of comparative physiology 165 (1995), S. 56-61 
    ISSN: 1432-136X
    Schlagwort(e): Citrate synthase ; Enzyme regulation ; Temperature adaptation ; ATP inhibition ; Crustacea
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Citrate synthase is a regulatory enzyme of the energy metabolism pathway controlling the citric acid cycle. It was studied in order to determine modes of enzyme regulation with regard to the life-style of the investigated species. Citrate synthase from crustaceans with different life-styles were compared: the pelagic euphausiids Euphausia superba from the Antarctic and Meganyctiphanes norvegica from the Scandinavian Kattegat and the Mediterranean were compared to the benthic isopods Serolis polita from the Antarctic and Idotea baltica from the Baltic. Citrate synthase was partly purified chromatographically and the influence of adenosine 5′-triphosphate on enzyme activity was examined. Mechanisms of inhibition and inhibitor constants were determined. Two different mechanisms of enzyme regulation by ATP were found. Citrate synthase from isopods was only competitively inhibited, while citrate synthase from euphausiids showed not only competitive inhibition but also activation by low concentrations of ATP. This activation is equivalent to the reversed methanism of uncompetitive inhibition. The ecophysiological relevances of the coupling of these mechanisms are discussed. The degree of competitive inhibition was different in the two groups of investigated crustaceans. Inhibitor constants were similar within the euphausiids but not in isopods, which showed higher or lower inhibition depending on the climatic zone: the colder the ambient temperature the lower the ATP inhibition. A possible mechanism of temperature adaptation through effects of varying inhibition constants is concluded.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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