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  • 1
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 110 (2000), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Polyamines play an important role in the control of cell growth and cell division. In the unicellular green alga Chlamydomonas reinhardtii as in animal cells, biosynthesis of the 3 commonly occurring polyamines (putrescine, spermidine and spermine) is dependent on the activity of ornithine decarboxylase (ODC, EC 4.1.1.17) catalyzing the formation of putrescine, which is the precursor of the other two polyamines. Therefore, we have investigated the regulation of ODC activity during the cell cycle of Clamydomonas reinhardtii using synchronized cultures. A 2.5–3-fold increase in ODC activity was observed during the transition to the cell division phase. This up-regulation of ODC activity was not due to an increased level of ODC-mRNA as revealed by northern-blot analyses, but correlated with an increased half-life of this particular enzyme (from 1.1 to 3.2 h). Addition of the DNA topoisomerase II inhibitor nalidixic acid during the second half of the growth period caused a transient decrease of ODC activity and a considerable delay of cell divisions. After cell division, a down-regulation of ODC activity was observed which was faster in the dark than in the light and also correlated with changes of the ODC half-life.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 108 (2000), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The polyamines putrescine, spermidine and spermine are required for cell proliferation of both eukaryotic and prokaryotic organisms. In plant cells, putrescine, which is also the precursor of spermidine, is derived from ornithine by the action of ornithine decarboxylase (ODC, EC 4.1.1.17) or from arginine by arginine decarboxylase (ADC, EC 4.4.4.19). In the unicellular green alga Chlamydomonas reinhardtii, ODC activity exceeds ADC activity by orders of magnitude as shown in the present communication, indicating that biosynthesis of polyamines is controlled by ODC activity in this organism. ODC was localized in the cytosol and was found to consist of 50 kDa subunits as revealed by affinity labeling with [ 3H]difluoromethylornithine and subsequent SDS-PAGE and fluorography. Its activity was much higher in light- than in dark-adapted (starved) cells. After transfer from darkness to light, a rapid increase in ODC activity was observed. This light-induced increase in ODC activity could be completely abolished by addition of cycloheximide, an inhibitor of protein biosynthesis, but not by actinomycin D inhibition of transcription. Up-regulation of ODC activity after onset of illumination could be prevented by addition of the photosystem II inhibitor 3-(3′,4′-dichlorophenyl)-1,1-dimethyl-urea. ODC activity was found to be correlated with the ATP level both in light- and dark-adapted cells. ODC half-lives of 42 and 83 min were determined for dark- and light-adapted cells, respectively.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Langenbeck's archives of surgery 340 (1976), S. 219-226 
    ISSN: 1435-2451
    Keywords: Peptic jejunal ulcer ; Gastric secretion analysis ; Reresection ; Vagotomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Als Ursache für das Auftreten eines Ulcus pepticum jejuni (U.p.j.) nach Magenresektion wegen eines Ulcus duodeni kommen neben technischen Fehlern im Anastomosenbereich und dem seltenen gastrin-produzierenden Tumor eine Verlagerung von Antrum-Schleimhaut in das alkalische Milieu des Duodenalstumpfes, ein verstärkter Vagotonus sowie ein zu großer Magenrest infrage. Bei 17 von 32 Patienten mit einem U. p. j. aus dem Zeitraum von 1968–1972 wurden präoperative Magensaftanalysen unter Stimulation mit Gastrin-Pentapeptid, Histalog und durch eine Insulin-Hyperglykämie vorgenommen. Eine hohe Basalsekretion mit geringer Stimulierbarkeit besonders durch exogenes Gastrin sollte Veranlassung zur Nachresektion des Duodenalstumpfes geben. Eine erhebliche Sekretion auf einen Hypoglykämiereiz bei nur mäßiger Reaktion auf Histalog und Gastrin führte zur alleinigen Vagotomie, die gleichbleibende Antwort auf alle 3 Stimuli bei erhöhter Basalsekretion zur Nachresektion des Magens. Die letztere wurde zusätzlich mit einer Vagotomie kombiniert, wenn sich stark erhöhte Basal- und Stimulationswerte ergaben. Postoperative Kontrollen bestätigten bisher die Richtigkeit des Konzepts. Die immer noch in einer Größenordnung von 5–20 % gelegene Operationsletalität beim U.p.j. müßte sich durch gezielte Eingriffe senken lassen. Von den eigenen 32 Patienten des 5-Jahres-Zeitraums verloren wir einen.
    Notes: Summary The development of a peptic jejunal ulcer after partial gastrectomy may result either from a technical deficiency of the anastomotic region, a seldom-occurring gastrin producing tumor, a displacement of the pyloric antrum into the alkaline milieu of the duodenal stump, an abnormally high vagus tone, or from too low a resection. In 17 out of 32 patients with a peptic jejunal ulcer preoperative gastric secretion analysis were performed during consecutive stimulation of the gastric secretion by gastrin-pentapeptide, histalog, and insulin-induced hypoglycemia. A high basal secretion, which could only be minimally stimulated by exogenous gastrin, required the operative revision of the duodenal stump. A vagotomy was found to be sufficient in patients reacting strongly to hypoglycemia and moderately to gastrin-pentapeptide or histalog. A hypersecretion after stimulation by gastrin-pentapeptide, histalog as well as by hypoglycemia was an indication for a re-resection of the gastric stump. The latter was combined with vagotomy if both the basal and the stimulated secretion values were found to be increased to higher levels. Up to now the postoperative conditions of the patients seem to give support to the procedure applied. It should be possible to reduce the operative letality of the re-resection of peptic jejunal ulcers on the basis of the aforementioned careful selection. Out of the 32 patients of this study only one was lost.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Potential analysis 5 (1996), S. 109-138 
    ISSN: 1572-929X
    Keywords: Primary 47D07 ; Secondary 31C25 ; Dirichlet form ; measure perturbation ; substochastic semigroup ; capacity ; smooth measures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Perturbations of a Dirichlet form $$\mathfrak{h}$$ by measures μ are studied. The perturbed form $$\mathfrak{h}$$ −μ−+μ+ is defined for μ− in a suitable Kato class and μ+ absolutely continuous with respect to capacity. L p-properties of the corresponding semigroups are derived by approximating μ− by functions. For treating μ+, a criterion for domination of positive semigroups is proved. If the unperturbed semigroup has L p -L q -smoothing properties the same is shown to hold for the perturbed semigroup. If the unperturbed semigroup is holomorphic on L 1 the same is shown to be true for the perturbed semigroup, for a large class of measures.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archiv der Mathematik 28 (1977), S. 86-90 
    ISSN: 1420-8938
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Archiv der Mathematik 67 (1996), S. 308-311 
    ISSN: 1420-8938
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Mathematische Zeitschrift 188 (1985), S. 283-286 
    ISSN: 1432-1823
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Mathematische Zeitschrift 199 (1988), S. 115-117 
    ISSN: 1432-1823
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Mathematik 90 (1980), S. 153-161 
    ISSN: 1436-5081
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We generalize the Jörgens-Vidav semigroup perturbation theorem: If (U (t)), (V (t)) are s. c. semigroups, the generator of (V (t)) a bounded perturbation of the generator of (U (t)), and some remainder in the iteration series ofV (t) is strictly power compact, then the spectrum ofV (t) outside the spectral disc ofU (t) consists of eigenvalues of finite algebraic multiplicity. As a prerequisite, we show the invariance of components of the essential resolvent set of an operator under relatively power compact pertubations.
    Type of Medium: Electronic Resource
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