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  • 2005-2009  (116)
  • 1995-1999  (84)
  • 1965-1969  (16)
  • 1940-1944
  • 1900-1904
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  • 11
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In the yeast Saccharomyces cerevisiae, growth with a non-fermentable carbon source requires co-ordinate transcriptional activation of gluconeogenic structural genes by an upstream activation site (UAS) element, designated CSRE (carbon source-responsive element). The zinc cluster protein encoded by CAT8 is necessary for transcriptional derepression mediated by a CSRE. Expression of CAT8 as well as transcriptional activation by Cat8p is regulated by the carbon source, requiring a functional Cat1p (= Snf1p) protein kinase. The importance of both regulatory levels was investigated by construction of CAT8 variants with a constitutive transcriptional activation domain (INO2TAD) and/or a carbon source-independent promoter (MET25 ). Whereas a reporter gene driven by a CSRE-dependent synthetic minimal promoter showed a 40-fold derepression with wild-type CAT8, an almost constitutive expression was found with a MET25–CAT8–INO2TAD fusion construct due to a dramatically increased gene activation under conditions of glucose repression. Similar results were obtained with the mRNA of the isocitrate lyase gene ICL1 and at the level of ICL enzyme activity. Taking advantage of a Cat8p size variant, we demonstrate its binding to the CSRE. Our data show that carbon source-dependent transcriptional activation by Cat8p is the most important mechanism affecting the regulated expression of gluconeogenic structural genes.
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  • 12
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ACS1 gene, encoding one out of two acetyl-CoA synthetase isoenzymes of Saccharomyces cerevisiae, is strictly regulated at the transcriptional level by the carbon source of the medium. While ACS1 is poorly expressed in the presence of a high glucose concentration, a several hundred-fold derepression occurs with ethanol as the sole carbon source or under conditions of sugar limitation. The molecular mechanism responsible for the carbon source control of ACS1 turned out to be highly complex. A carbon source-responsive element (CSRE), previously identified upstream of gluconeogenic structural genes, and a binding site of the alcohol dehydrogenase regulator, Adr1p, together mediate about 80% of the derepressed gene activity. Binding of Adr1p synthesized by Escherichia coli to the ACS1 control region was shown by an electrophoretic mobility shift assay. In addition to these activating elements, two URS1 motifs confer negative control on the ACS1 promoter. The URS1 element was found to be a constitutive repression site, which is most effective from a downstream position with respect to an upstream activation site (UAS). In a mutant lacking the URS1-binding factor, Ume6p, ACS1 expression was partially glucose insensitive. Ume6p must counteract transcription factors that are constitutively active. Site-directed mutagenesis of Abf1p binding sites in the ACS1 promoter significantly reduced gene expression in the ume6 mutant, grown under repressing conditions. Thus, a functional balance of the pleiotropic positive factor Abf1p and the negative factor Ume6p is in part responsible for glucose repression of ACS1. The combined influence of the regulated UAS elements, CSRE and Adr1p binding site, mediates a strong increase in ACS1 expression under derepressing conditions.
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  • 13
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Regulated expression of structural genes involved in yeast phospholipid biosynthesis is mediated by inositol/choline-responsive element (ICRE) upstream motifs, bound by the heterodimeric activator complex Ino2 + Ino4. Gene repression occurs in the presence of sufficient inositol and choline, requiring an intact Opi1 repressor which binds to Ino2. For a better understanding of interactions among regulators, we mapped an 18 aa repressor interaction domain (RID, aa 118–135) within Ino2 necessary and sufficient for binding by Opi1. By alanine scanning mutagenesis of the entire RID we were able to identify nine residues critical for Opi1-dependent repression of Ino2 function. Consequently, the corresponding dominant Ino2 variants conferred constitutive expression of an ICRE-dependent reporter gene and were no longer inhibited even by overproduction of Opi1. Interestingly, Ino2 RID partially overlaps with transcriptional activation domain TAD2. As certain mutations exclusively affect repression while others affect both repression and activation, both functions of Ino2 can be functionally uncoupled. Correspondingly, we mapped the RID–binding activator interaction domain (AID, aa 321–380) at the C-terminus of Opi1 and introduced missense mutations at selected positions. An Opi1 variant simultaneously mutated at three highly conserved positions showed complete loss of repressor function, confirming RID–AID interaction as the crucial step of regulated expression of ICRE-dependent genes.
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  • 14
    Electronic Resource
    Electronic Resource
    PO Box 1354, 9600 Garsington Road, Oxford OX4 2XG, UK. : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 28 (2005), S. 0 
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A procedure for non-destructive inspection by taking into account the effects of stochastic fatigue crack growth is presented. For this purpose a Markoff chain model is used to update the crack statistics, allowing an efficient computational implementation and a clear account of the involved concepts. In this context, perfect and imperfect removal of cracks, respectively, are considered, which represent idealizations defining bounds for actual situations.
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  • 15
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The higher plant Arabidopsis thaliana (Arabidopsis) is an important model for identifying plant genes and determining their function. To assist biological investigations and to define chromosome structure, a coordinated effort to sequence the Arabidopsis genome was initiated in late 1996. Here we ...
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  • 16
    Electronic Resource
    Electronic Resource
    Bradford : Emerald
    Circuit world 22 (1996), S. 10-15 
    ISSN: 0305-6120
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Tape ball grid array (TBGA) packages offer many of theadvantages of plastic BGAs, namely excellent durability, improved board space utilisation and ease ofsurface mount assembly along with the associated yield improvements. TBGA packages go a stepfurther, however, and offer the added benefits of improved signal integrity, better heat dissipation, andextendability to higher pin counts. This paper outlines the design and material selection process toproduce a low-cost TBGA which allows the wire bonding of a die. This type of packageoffers an attractive solution for applications requiring mid to high I/O capability and good electricaland thermal properties. Preliminary results have demonstrated the feasibility of wire bonding to thispackage at temperatures up to 200°C.
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  • 17
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS immunology and medical microbiology 20 (1998), S. 0 
    ISSN: 1574-695X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Macrophage cells play a central role during infection with Listeria monocytogenes by both providing a major habitat for bacterial multiplication and presenting bacterial antigens to the immune system. In this study, we investigated the influence of L. monocytogenes infection on the expression of MHC class I and class II genes in two murine macrophage cell lines. Steady-state levels of I-Aβ chain mRNA were decreased in both resting J774A.1 and P388D1 macrophages infected with L. monocytogenes whereas reduction of H-2K mRNA was only observed in P388D1 cells. In addition, L. monocytogenes suppressed induction of MHC class I and class II mRNAs in response to γ-interferon as well as the maintenance of the induced state in activated P388D1 macrophages. Exposure to the non-pathogenic species L. innocua or a deletion mutant of L. monocytogenes, which lacks the lecithinase operon, did not cause a reduction in H-2K and I-Aβ mRNA levels nor suppress expression of Ia antigens. Inhibition of MHC gene expression may represent an important part of the cross-talk between L. monocytogenes and the macrophage that probably influences the efficiency of a T cell-mediated immune response and thus the outcome of a listerial infection.
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  • 18
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 157 (1997), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In this study we show that protein tyrosine kinases and also protein tyrosine phosphatases are involved in the uptake of Listeria monocytogenes by J774 macrophages to a different extent than in the uptake of inert latex beads. In addition, protein tyrosine kinases are necessary for the intracellular growth and survival of L. monocytogenes. The expression of the MAP kinase phosphatase MKP-1, a protein tyrosine phosphatase, is induced upon infection, and phagocytosis of L. monocytogenes by J774 cells overexpressing the MKP-1 protein is reduced compared to control cells. The decreased phagocytosis of L. monocytogenes as a result of the MKP-1 overexpression in J774 macrophages suggests that the activation of the MAP kinase(s) ERK-1 and/or ERK-2 is an essential requirement for the uptake of L. monocytogenes by J774 macrophages.
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Archive of applied mechanics 69 (1999), S. 765-784 
    ISSN: 1432-0681
    Keywords: Key words Finite elements, statistical equivalent linearization, component-mode synthesis, complex modal analysis, random eigenvalue problem, hysteresis, damping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary This paper focuses on the stochastic dynamic response of structures modeled by finite elements with a relatively large number of degrees of freedom. FE models with nonlinearities and uncertain (stochastic) system properties are discussed. It is shown that component mode synthesis can be used most advantageously to solve the issue of computational efficiency and feasibility. The stochastic response due to stochastic loading of large FE models with nonlinear elements is determined by statistical equivalent linearization (EQL). The developed component-mode synthesis allows to determine the complex modal properties of arbitrary large linearized finite element models. Nonsymmetric structural matrices, as a result of the EQL, and filters for modeling of filtered white noise can be treated by the suggested approach. Since the efficiency of the procedure is nearly independent of the number of degrees-of-freedom (DOF) involved, statistical equivalent linearization becomes applicable for arbitrary detailed FE models. Furthermore, the dynamic response of FE models with uncertain or stochastic system properties is discussed. In this case, Monte Carlo simulation is suggested as the most appropriate approach for FE models. The paper focuses on the random eigenvalue problem for large FE systems as the computationally most demanding part of the dynamic analysis. Component-mode synthesis is used to provide in an efficient manner all the eigenvalue solutions of the FE system needed by the Monte Carlo simulation.
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Microchimica acta 54 (1966), S. 742-750 
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary In the determination of materials that are present in very small amounts, it is necessary above all to learn the error of the individual steps of the analysis. The greatest partial error governs the total error of the procedure and usually is due to the inhomogeneity of the material being examined. Only with knowledge of the total error can a decision be reached as to whether the analysis has informational worth, and what apparatus is necessary. The concepts: error, precision, and accuracy are defined and the problem is made clear on the basis of several examples.
    Abstract: Résumé Dans le cas de l'analyse de substances se trouvant en très petites quantités, il est indispensable, en première ligne, d'établir l'erreur intervenant dans chaque étape de l'analyse. L'erreur partielle la plus grande l'emporte sur l'erreur totale du procédé. Elle est due, la plupart du temps, au manque d'homogénéité dû corps étudié. Les notions d'erreur, de précision et d'exactitude se trouvent définies et le problème est rendu explicite à l'aide d'exemples.
    Notes: Zusammenfassung Bei der Analyse von Stoffen, die in sehr geringen Gehalten vorliegen, ist es in erster Linie notwendig, die Fehler der einzelnen Analysenschritte festzustellen. Der größte Teilfehler beherrscht den Gesamtfehler des Verfahrens und ist meist in der Inhomogenität des zu untersuchenden Materials begründet. Erst bei Kenntnis des Gesamtfehlers kann entschieden werden, ob der Analyse Aussagekraft zukommt und welche Apparate notwendig sind. Die Begriffe Fehler, Genauigkeit und Richtigkeit werden definiert und das Problem an Hand einiger Beispiele deutlich gemacht.
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