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  • 1
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Chronic treatment with the adenosine receptor antagonist caffeine evokes an up-regulation of A1 adenosine receptors and increased coupling of the receptor to G proteins in rat brain membranes. However, chronic agonist exposure has not been explored. Primary cultures of cerebellar granule cells were exposed chronically to A1 adenosine receptor agonists and antagonists. Exposure to the A1 adenosine receptor agonist N6-cyclopentyladenosine resulted in (1) a time- and concentration-dependent reduction in the density of receptors labeled by 1,3-[3H]dipropyl-8-cyclopentylxanthine, (2) an enhanced ability of guanyl nucleotides to decrease the fraction of A1 adenosine receptor sites displaying high affinity for 2-chloroadenosine, and (3) a functional uncoupling of receptors from adenylyl cyclase (EC 4.6.1.1). The adenosine antagonists caffeine and 8-p-sulfophenyltheophylline produced alterations in A1 adenosine receptor homeostasis that were antipodal to those associated with agonist treatment. Antagonist exposure (1) increased the density of A1 adenosine receptors in cerebellar granule cell membranes, (2) blunted the effect of guanyl nucleotides on receptor coupling to G proteins, and (3) increased the functional coupling of receptors to adenylyl cyclase inhibition. Forskolin treatment of cerebellar granule cells did not affect receptor density, suggesting that cyclic AMP is not involved in the regulation of A1 adenosine receptor expression.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Public health nursing 15 (1998), S. 0 
    ISSN: 1525-1446
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract Three hundred seventy-nine youths from an inner city elementary school were surveyed to determine their perceptions of their neighborhood. Using a qualitative, word association format, older students responded to 20 descriptive words (e.g., dirty, safe, quiet, dangerous) while younger youths drew pictures in response to three words (safe, sad, happy). Using content analysis techniques, findings indicated that the youths found neighborhood areas and residents that were perceived as safe, quiet, beautiful, friendly, fun/happy, and helpful. However, safety issues and a dirty, noisy neighborhood also emerged as major themes. Collaborative initiatives focusing on cleaning up the neighborhood and reducing violence are suggested, as are areas of intervention and further research.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1399-0047
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: Diffraction-quality crystals have been obtained of the integral membrane protein ferric enterobactin receptor (FepA) from the outer membrane of Escherichia coli. Crystals were grown using the zwitterionic detergent lauryldimethylamine oxide (LDAO), the precipitants polyethylene glycol (PEG) 1000 and sodium chloride, and the additive heptane-1,2,3-triol; they have the symmetry of the orthorhomic space group C2221 with a = 112.2, b = 137.2 and c = 135.4 Å and diffract to 2.5 Å resolution. The crystals were flash-cooled and a preliminary data set was collected at 103 K. The crystals are suitable for three-dimensional structure analysis.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] The entry and exit of water from cells is a fundamental process of life. Recognition of the high water permeability of red blood cells led to the proposal that specialized water pores exist in the plasma membrane. Expression in Xenopus oocytes and functional studies of an erythrocyte integral ...
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature structural biology 2 (1995), S. 730-732 
    ISSN: 1072-8368
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Medizin
    Notizen: [Auszug] Sir—The plasma membranes of mammalian red cells and renal proximal tubules, the intestinal epithelium of sap-sucking insects, and the vacuolar membranes of plants are highly permeable to water molecules due to the presence of water-selective pores known as the aquaporins (reviewed in refs 1, ...
    Materialart: Digitale Medien
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  • 6
    ISSN: 1072-8368
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Medizin
    Notizen: [Auszug] Integral outer membrane receptors for iron chelates and vitamin B 12 carry out specific ligand transport against a concentration gradient. Energy for active transport is obtained from the proton–motive force of the inner membrane through physical interaction with ...
    Materialart: Digitale Medien
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  • 7
    ISSN: 1572-9354
    Schlagwort(e): combinatorial optimization ; integer linear programming ; constraint programming
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract Many discrete optimization problems can be formulated as either integer linear programming problems or constraint satisfaction problems. Although ILP methods appear to be more powerful, sometimes constraint programming can solve these problems more quickly. This paper describes a problem in which the difference in performance between the two approaches was particularly marked, since a solution could not be found using ILP. The problem arose in the context of organizing a “progressive party” at a yachting rally. Some yachts were to be designated hosts; the crews of the remaining yachts would then visit the hosts for six successive half-hour periods. A guest crew could not revisit the same host, and two guest crews could not meet more than once. Additional constraints were imposed by the capacities of the host yachts and the crew sizes of the guests. Integer linear programming formulations which included all the constraints resulted in very large models, and despite trying several different strategies, all attempts to find a solution failed. Constraint programming was tried instead and solved the problem very quickly, with a little manual assistance. Reasons for the success of constraint programming in this problem are identified and discussed.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-0991
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Pierce's disease (PD, Xylella fastidiosa) of grapevine is the primary pathogen limiting vinifera grape production in Florida and other regions of the southeastern United States. Quick and accurate detection of PD strains is essential for PD studies and control. A unique random amplified polymorphic DNA (PD1-1-2) was isolated from a PD strain from Florida. Fragment PD1-1-2 was cloned, sequenced, and found to be 1005 bp in length. PCR primers were designed to utilize these sequence data for PD strain detection. One primer set (XF176f–XF954r) amplified a 779-bp DNA fragment from 34 PD strains including seven pathotypes of X. fastidiosa, but not from strains of Xanthomonas campestris pv. campestris, Xan. vesicatoria or Escherichia coli. A second primer set (XF176f and XF686r) amplified a 511-bp fragment specific to 98 PD strains, but not from strains of citrus variegated chlorosis, mulberry leaf scorch, oak leaf scorch, periwinkle wilt, phony peach, or plum leaf scald. Sequence analysis indicated that RAPD fragment PD1-1-2 contains a Ser-tRNA gene. The PD-specific region includes a TaqI restriction site (TCGA) and is 150 bp downstream of the Ser-tRNA gene.
    Materialart: Digitale Medien
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  • 9
    ISSN: 0730-2312
    Schlagwort(e): assembly of type I collagen ; COOH-terminal propeptide ; pepsin-resistant heterotrimers ; interspecies collagen molecule ; thermal stability ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Procollagen (Type I) contains a noncollagenous COOH-terminal propeptide (C-propeptide) hypothesized to be important in directing chain association and alignment during assembly. We previously expressed human pro-α2(I) cDNA in rat liver epithelial cells, W8, that produce only pro-α1(I) trimer collagen (Lim et al. [1994] MatrixBiol. 14: 21-30). In the resulting cell lines, α2(I) assembled with α1(I) forming heterotrimers. Using this cell system, we investigated the importance of the COOH-terminal propeptide sequence of the pro-α2(I) chain for normal assembly of type I collagen. Full-length human pro-α2(I) cDNA was cloned into expression vectors with a premature stop signal eliminating the final 10 amino acids. No triple-helical molecules containing α2(I) were detected in transfected W8 cells, although pro-α2(I) mRNA was detected. Additional protein analysis demonstrated that these cells synthesize small amounts of truncated pro-α2(I) chains detected by immunoprecipitation with a pro-α2(I) antibody. In addition, since the human-rat collagen was less thermostable than normal intraspecies collagen, wild-type and C-terminal truncated mouse cDNAs were expressed in mouse D2 cells, which produced only type I trimers. Results from both systems were consistent, suggesting that the last 10 amino acid residues of the pro-α2(I) chain are important for formation of stable type I collagen. J. Cell. Biochem. 71:216-232, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 10
    ISSN: 0730-2312
    Schlagwort(e): skin ; lung ; CAT gene expression ; α1(I) collagen promoter ; TGF-β ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Transgenic mice containing a rat collagen α1(I) promoter (3.6 kilobases) fused to the reporter gene chloramphenicol acetyl transferase (CAT) express the reporter gene parallel to endogenous gene in most connective tissues other than vascular tissue [Pavlin et al. (1992): J Cell Biol 116:227-236; Bedalov et al. (1994): J Biol Chem 269:4903-4909]. We have challenged transgenic mice with subcutaneous injections of transforming growth factor-β (TGF-β) or intratracheal instillation of bleomycin. In situ hybridization studies of skin revealed increased CAT expression in the papillary dermis of TGF-β treated animals. In contrast, α1(I) collagen mRNA was expressed throughout the dermis including granulation tissue and reticular dermis. Therefore, the transgenic promoter responds to TGF-β in a subset of dermal fibroblasts. Endotracheal instillation of bleomycin induces lung fibrosis which is thought to be mediated in part by TGF-β. CAT gene expression in lungs was increased 6-8-fold at 2 weeks post bleomycin treatment. In situ hybridization studies revealed focal areas of cells expressing both CAT and collagen genes in the interstitium. However, most regions, especially around airways, contained a subset of cells expressing the endogenous gene with little or no CAT expression as judged by in situ hybridization. These cells could be myofibroblasts that require additional cis-acting elements to activate α1(I) collagen gene expression similar to smooth muscle cells. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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