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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ccd locus of the F plasmid codes for two gene products, CcdA and CcdB, which contribute to the plasmid's high stability by post-segregational killing of plasmid-free bacteria. Like the quinolones, the CcdB protein is a poison of the DNA-topoisomerase II complexes, while CcdA acts as an antidote against CcdB. in addition to these poison-antipoison properties, the CcdA and CcdB proteins act together at transcription level to repress their own synthesis. In this work, we have isolated, in vivo., and characterized several non-killer CcdB mutants. All missense mutations which inactivate CcdB killer activity are located in the region coding for the last three C-terminal residues. However, the resulting mutant CcdB proteins retain their auto-regulatory properties. We conclude that the last three C-terminal residues of CcdB play a key role in poisoning but are not involved in repressor formation.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Der Onkologe 3 (1997), S. 99-104 
    ISSN: 1433-0415
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The purpose of the present study was to test the effects of synthetic atrial natriuretic peptide (ANP) on renal haemodynamics and excretory capacities of salt and water in the rat during an ‘acute volumic stress’, which was induced by brisk disturbances of the circulatory volume.2. To this end, 29 anaesthetized male Wistar rats were rapidly injected with 1 mL of 0.85% NaCl, repeated twice at 60 s intervals. The injectates contained no ANP (n = 5) or 1 × 0.25 (n = 6), 3 × 0.25 (n = 6), 1 × 2.5 (n = 6) or 3 × 2.5 μg (n = 6) ANP, added to the first injectate only (1 ×) or to each injectate (3 ×). Renal blood flow (RBF) was continuously measured with an electromagnetic flow transducer.3. Renal blood flow increased transiently (approximately 30 s) by approximately 13% (P 〈 0.05) during each injection of saline without ANP. Addition of 0.25 or 2.5 μg ANP to the first injectate enhanced RBF by 21 and 35%, respectively (both P 〈 0.05), but did not modify the time sequence. Furthermore, addition of 0.25 μg ANP to the second and third injectate produced an almost similar change in RBF at the end of each injection (ΔRBF = 20 and 17%, respectively). In contrast, the addition of 2.5 μg ANP to the second and third injectate did not produce the same changes in RBF observed at the end of the first injection. The amplitude of the change in RBF was then similar to the increase in RBF induced by 1 mL saline without ANP. Mean arterial pressure (MAP) did not change significantly during repeated injections of saline alone or with addition of 0.25 μg ANP to the first injectate. However, MAP decreased significantly (by 5, 9 and 9 mmHg) after the injection of 3 × 0.25, 1 × 2.5 or 3 × 2.5 μg ANP, respectively.4. Sodium excretion was rapidly increased from 2.600±0.654 to 9.330±1.322 μmol/min after injection of 3 × 1 mL of 0.85% NaCl (P 〈 0.05). Thereafter, sodium excretion remained enhanced throughout the experiment, so that 70% of the sodium load injected was recovered at the end of the experiment. Atrial natriuretic peptide added to the injectates further elevated the maximal responses in diuresis and natriuresis induced by saline injections without ANP (P 〈 0.001). A maximal effect was observed after the addition of 2.5 μg ANP to the first saline solution. When the amount of sodium excreted was calculated by integrating the areas under the curve of the natriuretic responses, a relationship was established as a function of the amount of ANP added to the saline solutions. It was characterized by a threshold in the presence of 2.5 μg ANP added to the first injectate when the integration period was limited to 4 min 30 s and 14 min 30 s after starting the first injection of the varying test solutions. When the integration period was extended until the end of the experiment (2 h), the amount of sodium excreted in each group was further enhanced, especially after injection of 3 × 1 mL of 0.85% NaCl without ANP or with 1 × 0.25 and 3 × 0.25 μg ANP. Differences in sodium excretion between groups were attenuated (P 〈 0.054, ANOVA).5. In conclusion, our results demonstrate differential effects of synthetic ANP on renal vascular reactivity and excretory capacity. These effects were superimposed on changes induced by acute volumic stress. In particular, effects of saline injections on renal vascular compliance were amplified in the presence of ANP added in varying amounts to the injectates. This amplification was limited to 2.5 μg ANP.
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 378 (1995), S. 68-70 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Investigation of the genetics, gonads, genitalia or hormone level of transsexuals has not, so far, produced any results that explain their status1'2. In experimental animals, however, the same gonadal hormones that prenatally determine the morphology of the genitalia also influence the morphology ...
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] EPR-1 is an activation-dependent molecule of relative molecular mass 62,000 (Mr 62K) which participates in protease-depen-dent mechanisms of lymphocyte co-stimulation8'9. Anti-EPR-1 mAb 2E1 (ref. 8) nearly completely inhibited lymphocyte proliferation in vitro that was stimulated by soluble or ...
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  • 6
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] To the editor: Cisgenesis (more commonly called intragenesis) and transgenesis are two technically similar approaches to create genetic variability through gene-splicing technology. Cisgenic plants are defined as plants that have been genetically modified with one or more genes (including introns ...
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  • 7
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Fusarium oxysporum f. sp. lycopersici is the causal agent of tomato wilt disease. In order to identify genes involved in its pathogenicity, we performed insertional mutagenesis. Mutant N40 had lost its pathogenicity completely, when tested in bioassays with tomato seedlings. Molecular characterization of mutant N40 revealed that the plasmid insertion had occurred in a gene that codes for a 60.2 kDa protein containing an F-box motif. The gene was therefore designated as FRP1 (F-box protein required for pathogenicity). Targeted FRP1 disruptants had lost their pathogenicity completely, and became fully virulent again upon re-introduction of the FRP1 gene. This confirmed that the FRP1 gene is required for pathogenesis. In a yeast two-hybrid assay Frp1 interacts with Skp1, suggesting involvement of an SCF ubiquitin ligase complex in pathogenicity. FRP1 is constitutively expressed during infection and under different culture conditions. Although growth, spore formation and germination on artificial media were not impaired, confocal laser scanning microscopy of a GFP-marked mutant N40 and a GFP-marked targeted FRP1 disruptant revealed that they were unable to colonize the roots.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 340-340 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
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  • 9
    ISSN: 1573-4846
    Keywords: electrochromism ; coating ; nanoparticle ; sol-gel material ; WO3 ; Nb2O5 ; TiO2 ; CeO2 ; Fe2O3 ; mixed compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Electrochromism is defined as the persistent but reversible optical change (usually transmission) produced electrochemically. The preparation by the sol-gel process of thin films made of amorphous or crystalline nanoparticles of WO3, V2O5, Nb2O5, TiO2, CeO2, Fe2O3 and mixed compounds such as WO3-TiO2, CeO2-TiO2, CeO2-SnO2, have opened remarkable new opportunities for obtaining electrochromic layers exhibiting large optical transmission variation in the UV, visible or infrared range and acceptable kinetics under H+ or Li+ insertion. In this paper we give an overview of what has been recently achieved in this field, with emphasis for cathodic electrochromic coatings of Nb2O5 and TiO2 composition. Finally we stress the future developments in this fast growing field.
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  • 10
    ISSN: 1573-4846
    Keywords: sol-gel ; Nb2O5 ; film ; photoconductivity ; photoelectrochemistry ; semiconductor ; solar cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural, optical, electro and photoelectrochemical properties of amorphous and crystalline sol-gel Nb2O5 coatings have been determined. The coatings are n-type semiconductor with indirect allowed transition and present an overall low quantum efficiency (φ 〈 4%) for UV light to electric conversion. The photoconducting behavior of the coatings is discussed within the framework of the Gärtner and Södergren models. Improvement can be foreseen if Nb2O5 coatings can be made of 10–20 nm size nanoparticles.
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