Search Results - (Author, Cooperation:A. Voelker)

2014-06-14

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Atlantic Ocean ; *Climate Change ; Mediterranean Sea ; Paleontology ; *Seawater ; *Water Movements

1434-6036

PACS. 73.50.Bk General theory, scattering mechanisms - 72.10.Bg General formulation of transport theory - 72.15.Rn Quantum localization

Springer Online Journal Archives 1860-2000

Physics

Abstract: A time-dependent electric field gives rise to a stationary non-equilibrium current I (2) around a mesoscopic metal ring threaded by a magnetic flux. We show that this current, which is proportional to the intensity of the field, is closely related to the exchange part of the interaction contribution to the equilibrium persistent current, and that the corresponding non-linear conductivity directly measures the weak localization correction to the polarization. We explicitly calculate the disorder average of I (2) in the diffusive regime as function of the frequency of the electric field and the static flux piercing the ring, and suggest an experiment to test our theory.

Electronic Resource

1432-1440

Springer Online Journal Archives 1860-2000

Medicine

Zusammenfassung Es wird über die Therapie bei 3 Patientinnen mit PNH berichtet: Heparin als Dauertropfinfusion vermag in jedem Fall akute hämolytische Krisen zu unterbinden. Bluttransfusionen können unter Heparinschutz unbeschadet ausgeführt werden. Marcumar eignet sich besonders für die Behandlung im Intervall. Bei ausreichender Dosierung können hämolytische Krisen über Jahre unterdrückt werden. Die Frage der Splenektomie bei PNH wird diskutiert. Die Milz sollte nur bei Vorliegen einer echten Hypersplenie möglichst im hämolysefreien Intervall entfernt werden.

Electronic Resource

1432-1106

Calcium ; Hypoxia ; Medulla ; Potassium Rat

Springer Online Journal Archives 1860-2000

Medicine

Abstract Tissue oxygen (PO2), K+ (aKe), pH (pHe) and Ca2+ ([Ca2+]e) were measured in the region of the ventral respiratory group (VRG) in the in vitro brainstem-spinal cord preparation of neonatal rats. During tissue anoxia, elicited by superfusion of N2-gassed solutions, an initial increase in the frequency of respiratory activity, lasting between 2 and 12 min, turned into a frequency depression. During anoxia periods of up to 60 min, respiratory activity persisted in solutions containing CO2/bicarbonate, whereas a complete blockade was observed after 15–25 min in N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid- (Hepes)-buffered salines. After such anoxic apnea, respiratory rhythmicity could be reactivated by superfusion of hypoxic, CO2/bicarbonate-buffered solutions. In both types of hypoxic solutions, aKe increased by maximally 1.5mM, whereas an initial increase of pHe by up to 0.05 pH units turned, after 2–4 min, into an acidification which could exceed 0.5 pH units. In contrast, [Ca2+]e remained unaffected by anoxia. Addition of 2–5 mM cyanide (CN-) to oxygenated Hepes-buffered saline evoked an increase in PO2 in the VRG from 100 to more than 300 mmHg. The effects of CN- on respiratory activity, aKe and pHe were almost identical to those during anoxia. In oxygenated, CO2/bicarbonatefree solutions of different pH, however, an increase in pHe in the VRG led to a decrease in respiratory frequency, whereas a fall of pHe produced a frequency acceleration. A rise of aKe in the VRG by more than 2 mM as induced by superfusion of a 7 mM K+ solution led to a sustained increase of respiratory frequency. The results indicate that blockade of aerobic metabolism does not severely perturb K+ and Ca2+ homeostasis and that the biphasic response to anoxia is not directly related to the observed changes in PO2, aKe, pHe, or [Ca2+]e. In the respiratory network of neonatal mammals, CO2 might provide a stimulus for long-term maintenance of respiratory activity under oxygen depletion.

Electronic Resource

1617-4623

Key words Phenol degradation  ;  Transcriptional activator  ;  Promoter-up mutations  ;  Pseudomonas putida  ;  Escherichia coli

Springer Online Journal Archives 1860-2000

Biology

Abstract The activator-encoding gene phlR was identified upstream of the plasmid-encoded operon for phenol degradation in Pseudomonas putida strain H by cassette mutagenesis and DNA sequence analysis. The deduced amino acid sequence of PHLR shows high homology to DmpR of P. putida sp. CF600 and to the chromosomally encoded PhhR of P. putida P35X reported previously. Trans-activation of phenol degradation was observed when phlR was overexpressed in a phlR insertion mutant. Transconjugants of Escherichia coli carrying pPGH11, which contains the complete set of phl genes, are unable to grow on phenol as carbon source. However, two types of mutants were selected for further characterization that were able to metabolize phenol as sole source of carbon and energy. In both types of mutants enhanced expression of phlR is responsible for the Phl+ phenotype. In type I (pPGH13) a deletion of 1 bp made the −35 region and the spacing between the −35 and −10 regions of the phlR promoter more similar to the consensus structure. In type II (pPGH14) a duplication of the phlR 5′ region was identified that includes part of the −35 motif and reduces the spacing between the −35 and −10 regions. In addition, due to the duplication of part of phlR, the distance from the phlR promoter to the catabolic phl operon is increased. Different transcriptional start sites have been identified by primer extension analysis in clones harboring pPGH14 or the wild type phlR. Quantitative primer extension analysis revealed that the greatest amount of phlR transcript is expressed from the partial, phlR duplication. Growth on phenol and phenol hydroxylase activity reflect the high level of phlR transcript in E. coli transconjugants. Overexpression of PhlR was also observed when pPGH14 was transferred into P. putida, and results in earlier induction of the phenol degradation operon relative to the wild-type strain.

Electronic Resource

0075-4617

Chemistry ; Organic Chemistry

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Electronic Resource