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  • Plasma-Renin-Konzentration  (2)
  • Temperature adaptation  (2)
  • Toxaphene  (2)
  • Springer  (6)
  • Nature Publishing Group (NPG)
  • Oxford University Press
  • 2010-2014
  • 1995-1999  (4)
  • 1970-1974  (2)
  • 1955-1959
Document type
Publisher
  • Springer  (6)
  • Nature Publishing Group (NPG)
  • Oxford University Press
Years
  • 2010-2014
  • 1995-1999  (4)
  • 1970-1974  (2)
  • 1955-1959
Year
  • 1
    ISSN: 1432-1440
    Keywords: Plasma renin concentration ; radioimmunoassay ; angiotensin I ; Plasma-Renin-Konzentration ; radioimmunologischer Nachweis ; Angiotensin I
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Ein Radioimmunoassay für Angiotensin I und seine Anwendung für die Messung der Reninkonzentration im Plasma werden beschrieben. Die zur Herstellung von Angiotensinantikörpern und radioaktiv markiertem Angiotensin sowie zur Trennung von gebundenem und freiem Hormon benutzten Verfahren werden mitgeteilt. Die Empfindlichkeit der Methode erlaubt den Nachweis von zwanzig Pikogramm Angiotensin I. Zur Messung der Reninkonzentration wurde substratfreies Plasma mit Schafsubstrat im Überschuß versetzt und in Anwesenheit von Inhibitoren von „converting enzyme“ und Angiotensinasen bei 37°C inkubiert. Das gebildete Angiotensin wurde in 20 µl des proteinfreien Inkubationsgemisches bestimmt. Die initiale Geschwindigkeit der Angiotensinbildung wurde zur Berechnung der Reninkonzentration herangezogen. Als eine Einheit wurde die Reninmenge definiert, die ein Nanogramm Angiotensin I pro Stunde Inkubation bildet. Normalwerte unter kontrollierter natriumreicher und natriumarmer Diät wurden ermittelt. Die Empfindlichkeit der Methode erlaubt die Messung der Reninkonzentration im Plasma von Patienten mit primärem Aldosteronismus.
    Notes: Summary A radioimmunoassay for angiotensin I and its application to the measurement of plasma renin concentration are described. Outlined are the methods which were used to elicite antibodies against angiotensin I, to iodinate angiotensin I with iodine125, and to separate free from antibody-bound hormone. The method is sensitive enough to detect 20 picogrammes of angiotensin I. Substrate-free plasma was mixed with excess of sheep substrate. The mixture was incubated at 37°C in the presence of inhibitors of converting enzyme and angiotensinases. The generated angiotensin I was measured in 20 µl of the protein-free incubation mixture. The initial velocity of angiotensin generation was used to calculate the renin concentration. One unit was defined as the amount of renin which generates one nanogram of angiotensin per hour. Normal values of plasma renin concentration were obtained both during sodium loading and sodium depletion. The sensitivity of the method allows the measurement of plasma renin in patients with primary aldosteronism.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1440
    Keywords: Primary aldosteronism ; Plasma renin concentration ; Primärer Hyperaldosteronismus ; Plasma-Renin-Konzentration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 13 Patienten mit einem primären Hyperaldosteronismus wurde die Plasma-Renin-Konzentration unter Stimulations- und unter Suppressionsbedingungen gemessen. Eine hochempfindliche Methode zur Reninmessung, die sich eines Radioimmunoassays für Angiotensin I bediente, wurde verwandt. Bei jedem der Patienten ließ sich die Reninkonzentration im Plasma gut messen. Die Werte lagen hochsignifikant unter den Normbereichen, die unter denselben Bedingungen ermittelt worden waren. Am eindrücklichsten war der Unterschied zwischen normalen und pathologischen Werten unter Stimulationsbedingungen. Nach Kochsalzentzug stieg die Reninkonzentration zwar bei nahezu allen Patienten signifikant an, der Anstieg war jedoch subnormal, gemessen an dem gesunden Kontrollkollektiv. Renin ist auch beim primären Aldosteronismus im Plasma vorhanden und reagiert auf Stimulation qualitativ regelrecht, quantitativ jedoch subnormal.
    Notes: Summary Plasma renin concentration (PRC) was measured in thirteen patients with primary aldosteronism during high and low sodium intake. A highly sensitive method using a radioimmunoassay for angiotensin I was applied for the determinations of PRC. PRC was detectable in each patient. The values obtained were significantly lower than the normal ranges which were assessed under the same conditions. Most impressive was the difference between normal and pathological values during sodium deprivation. PRC rose in almost each patient after several days of dietary sodium restriction. The increase was subnormal, however, when compared with normal controls. Renin is present in plasma of patients with primary aldosteronism. It responds qualitatively normally, but quantitatively subnormally when stimulated by sodium deprivation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 165 (1995), S. 46-55 
    ISSN: 1432-136X
    Keywords: Citrate synthase ; Enzyme characteristics ; Temperature adaptation ; Isopod crustacea ; Euphausiid crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: 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.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 165 (1995), S. 56-61 
    ISSN: 1432-136X
    Keywords: Citrate synthase ; Enzyme regulation ; Temperature adaptation ; ATP inhibition ; Crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1612-1112
    Keywords: Gas chromatography-mass spectrometry ; Electron-capture negative ionization ; Toxaphene ; Seal blubber samples ; Antarctic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatography and electron-capture, negative-ionization, mass spectrometry (GC-ECNI-MS) in combination with a non-polar stationary phase (CP-Sil 2) was applied to study the composition of residues of the multicomponent toxaphene mixture in seal blubber from the Antarctic. In samples of the five Antarctic seal species eleven compounds of technical toxaphene (CTTs) were detected and six of them quantified by application of single standard compounds. Five abundant CTTs in seal blubber were included in the “Parlar 22 components standard” (commercially available) and one further was isolated and quantified for the first time. Finally, high levels of toxaphene were determined in Weddell seals and crabeaters confirming that toxaphene is a major organochlorine pollutant in the Antarctic.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Chiral stationary phases ; Enantioseparation ; Toxaphene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of the enantiomers of the compounds of technical toxaphene (CTTs) on heptakis(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-β-cyclodextrin (β-TBDM) has been studied by gas chromatography with electron-capture detection (GC-ECD). Enantiomers of eight of the nine CTTs under investigation were separated on this chiral stationary phase. Separations of the enantioners of CTTs have hitherto been achieved ontert-butyldimethylsilylated β-cyclodextrin (β-BSCD). The chiral resolution values and separation factors of the CTTs on β-TBDM have been compared with those obtained on β-BSCD. Although several components coeluted, enantioselective determination of three CTTs was possible in an extract of seal blubber. For each CTT the first-eluting enantiomer was enantioenriched. Enantioselective accumulation of2-endo, 3-exo,5-endo,6-exo,-8,8,9,10-octachlorobornane (B8-1412) in biota has been established for the first time.
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