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  • 1
    ISSN: 0275-1062
    Keywords: solar magnetic field-full-disk magnetic field
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The production of pectin lyase (Pnl) in Erwiniacarotovora ssp. carotovora strain 71 is induced by DNA-damaging agents such as mitomycin C (MC). This induction requires functions of recA, rdgA and rdgB genes. Based upon sequence homology, rdgA was predicted to encode a repressor and rdgB was presumed to specify a transcriptional activator. To elucidate the function of rdgA, the gene has been over-expressed in Escherichia coli, and the 30 kDa product purified by ammonium-sulphate precipitation, heparin–agarose chromatography and gel filtration. The results of gel mobility-shift and DNase I protection assays revealed that purified RdgA specifically binds the rdgA operator sequence located between the −10 and −35 boxes. The expression of a rdgA–lacZ gene fusion in E. coli MC4100 is suppressed upon overproduction of RdgA from a Ptac–rdgA construct induced by isopropyl-β-d-thiogalactopyranoside (IPTG). However, the suppression of rdgA–lacZ expression is relieved by MC in the RecA+E. coli strain MC4100, but not in its RecA− derivative, MC4160. An immunoblot analysis revealed RecA-dependent in vivo cleavage of the 30 kDa RdgA protein upon MC treatment. These results demonstrate that the transcription of rdgA is autoregulated, and strongly support the idea that proteolytic activity of RecA* is responsible for the derepression of rdgA expression.
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In most soft-rotting Erwinia spp., including E. carotovora sub sp. carotovora strain 71 (Ecc71), production of the plant cell wall degrading enzyme pectin lyase (PnI) is activated by DNA-damaging agents such as mitomycin C (MC). Induction of PnI production in Ecc71 requires a functional recA gene and the rdg locus DNA sequencing and RNA analyses revealed that the rdg locus contains two regulatory genes, rdgA and rdgB, in separate transcriptional units. There is high homology between RdgA and repressers of lambdoid phages, specially φ80. RdgB, however, has significant homology with transcriptional activators of Mu phage. Both RdgA and RdgB are also predicted to possess helix-turn-helix motifs. By replacing the rdgB promoter with the IPTG-inducible tac promoter, we have determined that rdgB by itself can activate PnI production in Escherichia coli. However, deletion analysis of rdg+ DNA indicated that, when driven by their native promoters, functions of both rdgA and rdgB are required for the induction of pnIA expression by MC treatment. While rdgB transcription occurs only after MC treatment, a substantial level of rdgA mRNA is detected in the absence of MC treatment. Moreover, upon induction with MC, a new rdgA mRNA species, initiated from a different start site, is produced at a high level. Thus, the two closely linked rdgA and rdgB genes, required for the regulation of PnI production, are expressed differently in Ecc71.
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  • 4
    ISSN: 1432-0509
    Keywords: Hepatic actinomycosis ; Portal vein occlusion ; Duodenobiliary reflux
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Hepatic actinomycosis with abdominal wall invasion was found by computed tomography (CT) in a 44-year-old woman. Occlusion of the main and right portal veins by the actinomycoma causing cavernous transformation was proven by angiography. Duodenobiliary reflux and communication between the biliary tree and the abscess were demonstrated by upper gastrointestinal radiography, percutaneous transhepatic cholangiogram, and CT. The imaging studies reflected the pathologic process of this disease. The unique feature of this case is that infection ascended through the duodenobiliary reflux; this should be considered one of the routes for the transmission of hepatic actinomycosis.
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spontaneous emission factor β is an important parameter for the characterization of semiconductor light emitting devices. In the analysis of superluminescent diodes, especially in the calculation of the optical intensity using rate equations, most authors have used the estimated value of β taken from laser diodes, despite the conceptual difference involved in each device. In this article, the spontaneous emission factor β for superluminescent diodes is discussed in detail, and a new method in calculating the average value of β is introduced. Based on this method, the values of β for gain-guided and index-guided structures are obtained. © 1999 American Institute of Physics.
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  • 6
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The enterobacterium Erwinia carotovora ssp. carotovora strain 71 (hereafter Ecc71) produces extracellular enzymes such as pectate lyase isozymes (Pels), cellulase (Cel), polygalacturonase (Peh) and protease (Prt). These enzymes degrade plant cell wall components and are largely responsible for the elicitation of soft-rot diseases in plants and plant products. Ecc71 also produces HarpinEcc, the elicitor of hypersensitive reaction (HR) and the quorum-sensing signal, N-(3-oxohexanoyl)-L-homoserine lactone (OHL). OHL controls extracellular enzyme and HarpinEcc production. The levels of these enzymes, as well as the expression of hrpNEcc, the structural gene for HarpinEcc, and ohlI, the gene specifying OHL synthesis, are negatively regulated by RsmA. rsmB, formerly aepH, on the other hand, positively regulates extracellular enzyme production. 6His–RsmA recombinant protein purified from E. coli binds rsmB RNA as indicated by gel mobility shift assays. rsmB comprises 547 bp DNA, which is transcribed from a single start site immediately after a σ70-like promoter. In Ecc71, two rsmB RNA species are detected: a full-length 479 base rsmB RNA and a 259 base rsmB′ RNA. rsmB′ DNA hybridizes with the 259 base and the 479 base transcripts. A 3′ RNase protection assay revealed that the 259 base and the 479 base RNA species end at the same position immediately after the putative rho-independent terminator. The expression of rsmB–lacZ transcriptional fusions established that the rsmB′ RNA is not produced because of the activation of an internal promoter. These data strongly suggest that the 259 base rsmB′ RNA is derived by processing of the primary rsmB RNA. In Ecc71, rsmB′ expression driven by the lac promoter causes overproduction of Pel, Peh, Cel and Prt, and accumulation of pel-1, peh-1, hrpNEcc and ohlI transcripts. By contrast, a plasmid with the rsmB′ DNA sequence deleted fails to cause overproduction of the extracellular enzymes in Ecc71. The rsmB′ effect also occurs in Escherichia coli as glycogen accumulation is stimulated in the presence of rsmB′. In vivo and in vitro translation as well as mutational analysis of rsmB′ have established that rsmB′ RNA does not yield a translational product. Therefore, we concluded that the rsmB′ RNA itself functions as the regulator. Indeed, the expression of rsmB′ DNA leads to neutralization of the negative effects of the RNA-binding protein, RsmA, in Ecc71 and Serratia marcescens strain SM274. We propose a model that explains how RsmA and rsmB control the expression of genes for extracellular enzymes.
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  • 7
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fragments of foreign antigens associated with class I molecules of the major histocompatibility complex (MHC) are presented at the cell surface to elicit an immune response. This presentation requires the coordinated expression of several genes contained in the MHC, including those encoding the ...
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Physics and Chemistry of Solids 55 (1994), S. 1227-1232 
    ISSN: 0022-3697
    Keywords: A. metals ; D. diffusion ; D. elastic properties ; D. phase equilibria ; D. thermodynamic properties
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-7217
    Keywords: breast cancer ; nude mice ; antiestrogens ; aromatase inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of antiestrogens, tamoxifen and ICI 182,780, and aromatase inhibitors, arimidex (anastrozole ZD1033) and letrozole (CGS 20,267), on the growth of tumors were studied in nude mice. In this model, estrogen dependent MCF-7 human breast cancer cells stably transfected with the aromatase gene were inoculated in four sites per mouse. Sufficient estrogen is produced from aromatization of androstenedione supplement (0.1 mg/mouse/day) by the cells to stimulate their proliferation, tumor formation, and maintain the uterus similar to that of the intact mouse. Once the tumors reached a measurable size, the mice were injected with antiestrogen or inhibitor for 35–56 days. Tumor volumes were measured weekly. At autopsy, the tumors were removed, cleaned, and weighed. Statistical data was determined from tumor weights. Both antiestrogens were effective in reducing tumor growth in these mice. Tamoxifen appears to be more effective than ICI 182,780, although the former stimulated the uterine weight whereas the pure antiestrogen did not. However, both aromatase inhibitors were more effective than the antiestrogens. Tumor regression was observed with letrozole. Thus, after-treatment tumor weights were less than those of a group of mice at the start of treatment. The aromatase inhibitors also reduced the weight of the uterus, suggesting that these compounds, as well as the pure antiestrogen, may not cause endometrial proliferation, unlike tamoxifen. These aromatase inhibitors may not only benefit patients who have relapsed from tamoxifen, but may be more effective in patients as first line agents for suppressing the effects of estrogen.
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  • 10
    ISSN: 1573-7217
    Keywords: breast cancer ; nude mice ; aromatase inhibitors ; antiestrogens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have previously established a model for postmenopausal, hormone‐dependent breast cancer in nude mice which is responsive to both antiestrogens and aromatase inhibitors. In this model, MCF‐7 human breast carcinoma cells transfected with the aromatase gene (MCF‐7CA) synthesize sufficient estrogen to form tumors in ovariectomized nude mice. In the present study we used this intratumoral aromatase model to investigate the effects on tumor growth of the new nonsteroidal aromatase inhibitors letrozole (CGS 20,267) and anastrozole (ZD 1033) and the antiestrogens tamoxifen (ICI 47,474) and faslodex (ICI 182,780). Furthermore, we determined whether the inhibition of estrogen synthesis together with inhibition of estrogen action would be more effective in controlling breast tumor growth. The results of our studies indicate that the aromatase inhibitors anastrozole and letrozole, as well as the new pure antiestrogen faslodex, have potent antitumor effects in the mouse model. In the treatment of mice with mammary tumors, letrozole was more effective in suppressing tumor growth than anastrozole. This was consistent with the Ki values of these inhibitors against placental aromatase and the IC50 values in cell culture (MCF‐7CA), which indicated the greater potency of letrozole as an aromatase inhibitor. Letrozole also had greater antitumor effects than tamoxifen and faslodex. The antitumor effect of letrozole was substantial, making it difficult to detect any additional effect on the tumors when letrozole was combined with the antiestrogens. However, the combined treatment of anastrozole + tamoxifen and anastrozole + faslodex also did not increase efficacy compared to the aromatase inhibitor alone. In addition, combining the two antiestrogens did not suppress tumor growth more effectively than faslodex alone. Our results show that treatment with the combinations of aromatase inhibitors with either tamoxifen or faslodex are not more effective in blocking estrogen stimulation of tumor growth than the aromatase inhibitors alone.
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