Biosynthetic pathways of Vibrio succinogenes growing with fumarate as terminal electron acceptor and sole carbon source

1. With fumarate as the terminal electron acceptor and either H₂ or formate as donor, Vibrio succinogenes could grow anaerobically in a mineral medium using fumarate as the sole carbon source. Both the growth rate and the cell yield were increased when glutamate was also present in the medium.
2. Glutamate was incorporated only into the amino acids of the glutamate family (glutamate, glutamine, proline and arginine) of the protein. The residual cell constituents were synthesized from fumarate.
3. Pyruvate and phosphoenolpyruvate, as the central intermediates of most of the cell constituents, were formed through the action of malic enzyme and phosphoenolpyruvate synthetase. Fructose-1,6-bisphosphate aldolase was present in the bacterium suggesting that this enzyme is involved in carbohydrate synthesis.
4. In the absence of added glutamate the amino acids of the glutamate family were synthesized from fumarate via citrate. The enzymes involved in glutamate synthesis were present.
5. During growth in the presence of glutamate, net reducing equivalents were needed for cell synthesis. Glutamate and not H₂ or formate was used as the source of these reducing equivalents. For this purpose part of the glutamate was oxidized to yield succinate and CO₂.
6. The α-ketoglutarate dehydrogenase involved in this reaction was found to use ferredoxin as the electron acceptor. The ferredoxin of the bacterium was reoxidized by means of a NADP-ferredoxin oxidoreductase. Enzymes catalyzing the reduction of NAD, NADP or ferredoxin by H₂ or formate were not detected in the bacterium.

     

Der Serotoninstoffwechsel in einzelnen Hirnteilen vom Tupaia (Tupaia belangeri) bei soziopsychischem Stress

Zusammenfassung Bei sozialem Stress nehmen die Konzentrationen von Serotonin (5-HT) und 5-Hydroxyindolessigsäure (5-HIAA) in den einzelnen Hirnteilen von Tupaias zu. Diese Zunahme läßt sich durch eine erhöhte Stoffwechselgeschwindigkeit (turnover) erklären.Die Änderungen in der Stoffwechselgeschwindigkeit der einzelnen Hirnteile hängen von der Art der sozialen Belastung ab.Schon Kampf mit Unterwerfung (zweimal täglich) führt zu einem schnelleren Stoffwechsel des 5-HT in allen Hirnteilen. Belastet man die Tiere außer durch Kampf noch dadurch, daß sie das Tier, das sie besiegt hat, zwischen den Kampfpausen sehen können, so wird der Stoffwechsel des 5-HT in einzelnen Hirnteilen (Septum, Frontaler Cortex) nochmals erhöht.Eine mögliche funktioneile Bedeutung dieser Veränderungen wurde diskutiert.

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Serotonin metabolism in discrete brain areas and sociopsychic stress in tupaia (Tupaia belangeri)

Summary The physiological state of the animals depends not only on ecological factors. It is also determined by the social interactions of the animals. Some of these social interactions are harmful to the physiological state of the individuals. The aim of this work was to separate the physical loads of social interactions from the mere psychic ones and to correlate them with neurochemical changes. For this purpose the concentration levels of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were measured in discrete brain areas.To separate the psychic from the physical loads male tupaias (Tupaia belangeri) were exposed two times a day (at 9.30 and 13.30 h) for two minutes to the attacks of an experienced fighter. The animals were defeated during these attacks. One group of the defeated animals was in optical contact with the experienced fighter throughout the day (12 hours; Stresstiere). The other group of the defeated animals was optically separated from the experienced fighter after each fight (Kampftiere).After four days the animals were decapitated at 15.00 h, 5.5 hours after the last fight (on the fourth day the animals were not allowed to fight at 13.30 h). Animals which had not fought were decapitated at the same time and served as controls. 5-HT and 5-HIAA levels were estimated within two days after decapitation.During the test the animals lose body weight. Animals who are only exposed to attacks (Kampftiere) loose 2.8±2.8%; animals who are exposed to attacks and optical contact with the experienced fighter (Stresstiere) lose 11.8±3.4%.The concentration levels of 5-HT and 5-HIAA in both groups are elevated compared with controls. This fact indicates a higher turnover of these substances. The concentration levels are most elevated in parts of the brain of defeated animals exposed to continuous optical contact with the experienced fighter (Stresstiere). These differences are most prominent in the septum and the frontal cortex (s. p. 60).A model for the physiological meaning of these changes is discussed. It was assumed that the activity of the brain is controlled by a system which is functionally analogous to the peripheral autonomous nervous system. 5-HT and norepinephrine should act on antagonistic branches of such a system in central nervous system. Under stress conditions the activity of both branches should be enhanced.

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Herrn Prof. Dr. H. Autrum möchte ich für die Überlassung des Themas, für sein stetes Interesse und anregende Diskussionen danken. Die Untersuchungen wurden durch Sachbeihilfen gefördert, die die Deutsche Forschungsgemeinschaft Herrn Prof. Dr. H. Autrum zur Verfügung stellte.

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Der Firma Sharp & Dohme GmbH danke ich für die kostenlose Überlassung von 15 g Probenecid.     

Benzotriazonine as a new core structure for the design of CCK‐receptor antagonists

The search for heterocyclic scaffolds for the design of non‐peptidic and highly selective agonists or antagonists of peptide hormone receptors led to 4‐N‐benzyl‐2,3,4,5,6,7‐hexahydro‐1H‐1,4,7‐benzotriazonin‐2,6‐dione with a 9‐membered core structure as a new low mass lead compound that exhibits submicromolar antagonistic activity at the CCK‐A receptor with a 54‐fold selectivity over the CCK‐B/gastrin receptor. Copyright © 1999 European Peptide Society and John Wiley & Sons, Ltd.     

<Emphasis Type="Italic">ZWILLE</Emphasis> buffers meristem stability in<Emphasis Type="Italic"> Arabidopsis thaliana</Emphasis>

The shoot apical meristem of higher plants consists of a population of stem cells at the tip of the plant body that continuously gives rise to organs such as leaves and flowers. Cells that leave the meristem differentiate and must be replaced to maintain the integrity of the meristem. The balance between differentiation and maintenance is governed both by the environment and the developmental status of the plant. In order to respond to these different stimuli, the meristem has to be plastic thus ensuring the stereotypic shape of the plant body. Meristem plasticity requires the ZWILLE (ZLL) gene. In zll mutant embryos, the apical cells are misspecified causing a variability of the meristems size and function. Using specific antibodies against ZLL, we show that the zll phenotype is due to the complete absence of the ZLL protein. In immunohistochemical experiments we confirm the observation that ZLL is solely localized in vascular tissue. For a better understanding of the role of ZLL in meristem stability, we analysed the genetic interactions of ZLL with WUSCHEL (WUS) and the CLAVATA1, 2 and 3 (CLV) genes that are involved in size regulation of the meristem. In a zll loss-of-function background wus has a negative effect whereas clv mutations have a positive effect on meristem size. We propose that ZLL buffers meristem stability non-cell-autonomously by ensuring the critical number of apical cells required for proper meristem function.Edited by G. JürgensAn erratum to this article can be found at     

Experimental Helicobacter pylori infection induces antral-predominant, chronic active gastritis in hispid cotton rats (Sigmodon hispidus)

BACKGROUND: The hispid cotton rat has proven to be an excellent animal model for a variety of human infectious disease agents. This study was performed to evaluate the use of the cotton rat as a model of Helicobacter pylori infection. MATERIALS AND METHODS: Thirty-eight inbred cotton rats were orogastrically inoculated with a human strain of H. pylori. Twenty-eight control cotton rats were dosed with vehicle only. Animals were sacrificed at 2, 4, 12, 26, or 38 weeks after inoculation for bacterial and histologic and immunologic examinations. RESULTS: Helicobacter pylori was cultured from the glandular stomach of 89% of the infected cotton rats. The level of colonization was consistently high (approximately 10(4-6) colony-forming units/g tissue). Histologically, the spiral bacteria were demonstrated on the epithelial surface and in the foveolae of the gastric mucosa with highest numbers in the antrum. H. pylori infection was associated with antral-predominant, chronic active gastritis which progressively increased in severity over time. By week 26 of infection, moderate antral gastritis had developed with frequent involvement of the submucosa and formation of lymphocytic aggregates. Splenic T cells from infected cotton rats expressed mRNAs for interferon-gamma, interleukin-4, interleukin-6, and interleukin-10 following in vitro stimulation with H. pylori. Serum levels of H. pylori-specific immunoglobulin G were significantly elevated after 12 weeks of infection. CONCLUSIONS: The H. pylori-infected cotton rat represents a novel animal model that should prove useful for studies of H. pylori-induced chronic active gastritis and factors affecting gastric colonization by this pathogen.     

The electrochemical proton potential generated by the sulphur respiration of Wolinella succinogenes

Wolinella succinogenes grown on formate and elemental sulphur was found to use the polysulphide derivatives 2,2-tetrathiobispropionate (R₂S₄) or pentathionate (S₅O ₆ ⁼ ) as acceptors for formate oxidation. The specific activities of formate oxidation with these acceptors were similar to those with elemental sulphur. The main reaction products of R₂S₄ reduction were 2,2-dithiobispropionate (R₂S₂) and sulphide. Pentathionate was converted to thiosulphate and some elemental sulphur. The electrochemical proton potential across the cytoplasmic membrane of the bacterium was measured in the steady state of electron transport from formate to R₂S₄. The electrical proportion () of the determined through the distribution of labeled tetraphenylphosphonium cation was obtained as 0.17 Volt. The was zero, when a protonophore was present. The pH-difference across the membrane was negligible. Thus the generated by sulphur respiration is close to that measured earlier with fumarate as the terminal acceptor of electron transport.Abbreviations DMO 5,5-dimethyloxazolidine-2,4-dione - R₂S_n (n=2–5) 2,2-polythiobispropionate - TTFB 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazol - TPP tetraphenylphosphonium cation     

S/T Phosphorylation of DLL1 Is Required for Full Ligand Activity In Vitro but Dispensable for DLL1 Function In Vivo during Embryonic Patterning and Marginal Zone B Cell Development

Interaction of Notch receptors with Delta- and Serrate-type ligands is an evolutionarily conserved mechanism that mediates direct communication between adjacent cells and thereby regulates multiple developmental processes. Posttranslational modifications of both receptors and ligands are pivotal for normal Notch pathway function. We have identified by mass spectrometric analysis two serine and one threonine phosphorylation sites in the intracellular domain of the mouse Notch ligand DLL1. Phosphorylation requires cell membrane association of DLL1 and occurs sequentially at the two serine residues. Phosphorylation of one serine residue most likely by protein kinase B primes phosphorylation of the other serine. A DLL1 variant, in which all three identified phosphorylated serine/threonine residues are mutated to alanine and valine, was more stable than wild-type DLL1 but had reduced relative levels on the cell surface and was more effectively cleaved in the extracellular domain. In addition, the mutant variant activated Notch1 significantly less efficient than wild-type DLL1 in a coculture assay in vitro. Mice, however, whose endogenous DLL1 was replaced with the phosphorylation-deficient triple mutant developed normally, suggesting compensatory mechanisms under physiological conditions in vivo.