Ohr Protects Corynebacterium glutamicum against Organic Hydroperoxide Induced Oxidative Stress

Ohr, a bacterial protein encoded by the Organic Hydroperoxide Resistance (ohr) gene, plays a critical role in resistance to organic hydroperoxides. In the present study, we show that the Cys-based thiol-dependent Ohr of Corynebacterium glutamicum decomposes organic hydroperoxides more efficiently than hydrogen peroxide. Replacement of either of the two Cys residues of Ohr by a Ser residue resulted in drastic loss of activity. The electron donors supporting regeneration of the peroxidase activity of the oxidized Ohr of C. glutamicum were principally lipoylated proteins (LpdA and Lpd/SucB). A Δohr mutant exhibited significantly decreased resistance to organic hydroperoxides and marked accumulation of reactive oxygen species (ROS) in vivo; protein carbonylation was also enhanced notably. The resistance to hydrogen peroxide also decreased, but protein carbonylation did not rise to any great extent. Together, the results unequivocally show that Ohr is essential for mediation of organic hydroperoxide resistance by C. glutamicum.     

Structural and functional characterization of the Pseudomonas hydroperoxide resistance protein Ohr

Bacteria have developed complex strategies to detoxify and repair damage caused by reactive oxygen species. These compounds, produced during bacterial aerobic respiration as well as by the host immune system cells as a defense mechanism against the pathogenic microorganisms, have the ability to damage nucleic acids, proteins and phospholipid membranes. Here we describe the crystal structure of Pseudomonas aeruginosa Ohr, a member of a recently discovered family of organic hydroperoxide resistance proteins. Ohr is a tightly folded homodimer, with a novel alpha/beta fold, and contains two active sites located at the monomer interface on opposite sides of the molecule. Using in vitro assays, we demonstrate that Ohr functions directly as a hydroperoxide reductase, converting both inorganic and organic hydroperoxides to less toxic metabolites. Site-directed mutagenesis confirms that the two conserved cysteines in each active site are essential for catalytic activity. We propose that the Ohr catalytic mechanism is similar to that of the structurally unrelated peroxiredoxins, directly utilizing highly reactive cysteine thiol groups to elicit hydroperoxide reduction.     

Welsh I am

With developments in genetics, researchers are increasingly able to address historical issues surrounding human migration and provenance by studying present populations. Nigel Williams reports on one of the latest studies looking at a crucial period of British history.     

Vergleichende phasenmikroskopische Untersuchungen am Deckepithel der Leberkapsel und am Aortenendothel

Zusammenfassung Die Deckepithelien der Leberkapsel und das Aortenendothel bilden in den tiefen Schichten ein syncytiales Netzwerk. Oberflächlich besitzen diese Zellen homogene, hyaloplasmatische Deckplatten, die beim Aortenendothel in Ringerlösung stark quellen können.Die Strukturen der Grenzschichten der Zellen werden auf Grund der phasenmikroskopischen Untersuchungen näher analysiert und mit den vorliegenden Befunden an fixierten und versilberten Präparaten verglichen.Für das Deckepithel der Leberkapsel und den Endothelbelag der Aorta wird ein feingewebliches dreidimensionales Modell entworfen.Im Verband des Aortenendothels werden sehr große, oft mehrkernige Endothelzellen beschrieben und erstmalig abgebildet, die in ihrem Zytoplasma eiweißhaltige Einschlüsse besitzen. Für diese Zellen wird der Name große Einschlußendothelien vorgeschlagen.Herrn Professor Dr. Wolfgang Heubner zum 75. Geburtstag gewidmet.     

Pflanzensoziologie am Scheideweg

Ohne Zusammenfassung J. Braun-Blanquet zum 90. Geburtstag gewidmet     

Beobachtungen am Mornellregenpfeifer

Ohne Zusammenfassung     

Catecholaminnachweis am Paraffinschnitt

Ohne ZusammenfassungMit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Kastrationsversuche am Truthahn

Ohne Zusammenfassung     

Histochemische Untersuchungen am Fettgewebe

Zusammenfassung Mit histochemischen Methoden wurde die Ausstattung isolierter Fettzellen mit hydrolytischen Enzymen untersucht. Alkalische Phosphatase konnte in den Fettzellen nicht nachgewiesen werden, dagegen fand sich eine geringe Aktivität der sauren Phosphatase, sowie eine starke Aktivität der -Naphthyl-Azetat-Esterase. An Zupfpräparaten des epididymalen Fettgewebes konnten mit Ausnahme der sauren Phosphatase identische Befunde erhoben werden. Durch die Anwendung dieser histochemischen Methoden sind die Fettzellen von den anderen Zellen des Fettorganes abzugrenzen. Die -Naphthyl-Azetat-Esterase eignet sich zur selektiven Darstellung der Fettzellen, da sie lediglich in diesen Zellen im gesamten Zytoplasma eine starke Aktivität besitzt.

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Histochemical investigations on adipose tissue

Summary Hydrolytic enzymes in isolated fat cells were investigated by histochemical methods. Alkaline phosphatase was not detected in isolated fat cells, while it was possible to find acid phosphatase and esterase. The latter had a high activity. In teased fragments of the epididymal adipose tissue the same enzymatic pattern except acid phosphatase could be demonstrated. These observations made it possible to separate the fat cells from other cells of the adipose tissue. By demonstrating -naphthyl-acetat-esterase it is possible to determine selective fat cells, for only these cells exhibit activity within the entire cytoplasm.

     

Elektronenmikroskopische Untersuchungen am Ammonshorn

Zusammenfassung Vergleichende phasenkontrast- und elektronenmikroskopische Untersuchungen der Moosfaserschicht des Ammonshorns des Kaninchens ergaben:Im Phasenkonstrastbild hebt sich die Moosfaserschicht besonders deutlich ab. Der infrapyramidale Trakt der Moosfasern ist fast ebenso lang wie der suprapyramidale Trakt.In der Moosfaserschicht sind nach einer Nachfixierung mit OsO₄ die apikalen und basalen Dendriten der Pyramidenzellen nahezu vollständig von kontraststärkeren Strukturen umgeben als im übrigen Gewebe. Diese sind elektronenmikroskopisch eindeutig als die synaptischen Endformationen der Moosfasern zu identifizieren. Die synaptischen Endformationen der Moosfasern enthalten größere Mengen dicht gelagerter synaptischer Vesikel, außerdem Vesikel, die ein osmiophiles Zentrum besitzen. Die Befunde werden im Zusammenhang mit dem verstärkten Zinkgehalt der Moosfaserschicht diskutiert.

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Summary Comparative phase- and electron microscopical investigations have been carried out on the hippocampal layer of mossy fibres of the rabbit.The phase contrast microscope allows a particularly distinct demonstration of the layer of mossy fibres. The infrapyramidal tract of the mossy fibres is of approximately the same length as the suprapyramidal tract.After postfixation with OsO₄ it is seen that the apical and basal dendrites of pyramidal cells in the mossy fibre layer are almost entirely surrounded by darker structures, which are more clearly definable than in the surrounding tissue. Electron microscopically these structures could definitely be identified as the boutons of the mossy fibres. The synaptic endings of the mossy fibres contain larger masses of more densely packed synaptic vesicles and also a moderate number of vesicles, which include an osmiophilic centre. Our results are discussed with regard to the increased zinc content of hippocampal mossy fiber layer.

     

In Memoríam

In hysterical abdominal distention the symptoms may so closely simulate those of obstruction of the bowel that needless laparotomy is carried out.CLUES THAT INDICATE HYSTERICAL DISTENTION RATHER THAN ORGANIC CAUSE ARE: (1) History of vomiting but without dehydration; (2) complaint of severe pain although temperature, pulse and the number of leukocytes in the blood all are normal; (3) normal tympanic quality of the abdomen; (4) distention out of proportion to the amount of gas observed in x-ray examination; (5) pronounced lordosis caused by thrusting the abdomen forward; and (6) remission of distention when the patient is under general anesthesia. It must be remembered, however, that even when there is strong suspicion of hysterical cause, distention may actually be due to obstruction. In the case herein reported, obstructive adhesion finally did occur after the patient had had numerous exploratory operations in which the viscera were observed to be normal.     

Entwickelungsphysiologische Studien am Triton-Ei

Ohne Zusammenfassung