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  • 1
    Electronic Resource
    Electronic Resource
    Ammonia translocation in cyanobacteria (1991)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 88 (1991), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Ammonia is the inorganic nitrogen source preferentially used by most cyanobacteria. Moreover, even in nitrate utilizers or N2-fixers, ammonia is an obligate intracellular intermediate in nitrogen assimilation. It also affects the synthesis and the activation of several key enzymes in nitrogen metabolism such as nitrogenase, glutamine synthetase and nitrate reductase. The mechanism by which NH3/NH4+ enters different cyanobacteria (N2-fixers, non-fixers, neutrophilic) was thus studied. Using 14CH3NH3+, the convenient radioactive analog of ammonium, we have shown that the neutrophilic A. nidulans R-2 possibly possesses an active transport system for this cation. The conditions leading to repression and depression of this transport system have been studied; it appears that de novo protein synthesis is required for the acquisition of the transport ability. We have also provided evidence that methionine sulfoximine affects ammonium uptake only through its inhibition on glutamine synthetase, and found no support for the possible interaction of this inhibitor with the ammonium transporter. In the alkalophilic cyanobacterium Spirulina platensis, an active mechanism to translocate ammonium is probably not needed. Our data suggest that net uptake of ammonia to support optimal growth could be explained by a pH driven diffusion process.In all the different strains tested net ammonia uptake was observed only when conditions permit continuous amidation through the activity glutamine synthetase and inhibition of this enzyme by methionine sulfoximine caused the excretion of ammonia to the external medium. The weight of experimentation suggests that ammonia leaks from cells because of the inherent permeability of NH3, and that no specific carrier is involved in its release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1991.tb04953.x
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  • 2
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    Dianne Newell and Ralph Greenhill, "Survivals: Aspects of Industrial Archaeology in Ontario" (Book Review) (1991)
    Detroit, Mich. : Periodicals Archive Online (PAO)
    Technology and Culture. 32:2 (1991:Apr.) 414 
    Details
    ISSN: 0040-165X
    Topics: Technology
    Notes: BOOK REVIEWS
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:5129-1991-032-02-000020
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  • 3
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    Peter Mathias and John A. Davis, eds., "The First Industrial Revolutions" (Book Review) (1993)
    Detroit, Mich. : Periodicals Archive Online (PAO)
    Technology and Culture. 34:3 (1993:July) 682 
    Details
    ISSN: 0040-165X
    Topics: Technology
    Notes: BOOK REVIEWS
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:5129-1993-034-03-000022
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  • 4
    Electronic Resource
    Electronic Resource
    Chromatin structure changes suggest a compensatory response to c-myc gene amplification in malignant fibrous histiocytoma (1992)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 49 (1992), S. 148-156 
    Details
    ISSN: 0730-2312
    Keywords: c-myc transcription ; DNAse I hypersensitivity ; oncogenes ; sarcomas ; tumor cell lines ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Changes in chromatin structure as determined from DNAse I hypersensitive site analysis are associated with c-myc amplification and increased transcript/protein levels in malignant fibrous histiocytoma (MFH) cell lines. A DNAse I hypersensitive site near the PO promoter region was observed in one MFH cell line (UR HCL 1), and in normal fibroblasts (HFF), but not in an MFH cell line with an amplified c-myc gene (P3C). A DNAse I hypersensitive site exclusive to P3C amplified c-myc was identified slightly 3′ of exon one. No alterations in c-myc DNAse I hypersensitive site patterns were observed in HFF fibroblasts following serum release, when peak levels of c-myc transcript were induced. DNAse I hypersensitive site patterns associated with gene amplification may reflect a compensatory response by P3C cells to an abundance of c-myc transcript. Furthermore, elevated levels of protein in P3C cells provide additional evidence that amplified c-myc is an oncogene in MFHs.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240490207
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