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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
    Electronic Resource
    Electronic Resource
    Regulation of methylammonium/ammonium transport in the unicellular cyanobacterium Synechococcus R-2 (PCC 7942) (1987)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 43 (1987), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The unicellular cyanobacterium Synechococcus R-2 (PCC 7942) took up 14CH3NH+3 at least 10 times faster after growth with NO−3 than with NH+4 as nitrogen source. When NH+4-grown cells were transferred to medium containing NO−3, the ability to accumulate 14CH3NH+3 required approximately 6 h for maximal expression. Chloramphenicol (50 μg · ml−1) completely prevented the rise in transport ability. Transport by nitrate-grown cells incubated in 2 mM NH4Cl or CH3NH3Cl, with or without NO−3, continued at high rates for 2–3 h, but fell to zero by about 5 h incubation in light. Methylammonium, or the γ-methyl glutamic amide derived from it, thus may also serve as a signal for repression; however, externally added glutamine stimulated rather than repressed 14CH3NH+3 transport. Changes in 14CH3NH+3 uptake rates brought about by NH+4 were confined to these slow effects, and to competition for entry into the cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1987.tb02160.x
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  • 3
    Electronic Resource
    Electronic Resource
    Phylogenetic origins of the plant mitochondrion based on a comparative analysis of 5S ribosomal RNA sequences (1985)
    Springer
    Journal of molecular evolution 22 (1985), S. 46-52 
    Details
    ISSN: 1432-1432
    Keywords: Symbiosis ; Plant mitochondria ; 5S RNA ; Evolution ; Purple bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The complete nucleotide sequences of 5S ribosomal RNAs fromRhodocyclus gelatinosa, Rhodobacter sphaeroides, andPseudomonas cepacia were determined. Comparisons of these 5S RNA sequences show that rather than being phylogenetically related to one another, the two photosynthetic bacterial 5S RNAs share more sequence and signature homology with the RNAs of two nonphotosynthetic strains.Rhodobacter sphaeroides is specifically related toParacoccus denitrificans andRc. gelatinosa is related toPs. cepacia.These results support earlier 16S ribosomal RNA studies and add two important groups to the 5S RNA data base. Unique 5S RNA structural features previously found inP. denitrificans are present also in the 5S RNA ofRb. sphaeroides; these provide the basis for subdivisional signatures. The immediate consequence of our obtaining these new sequences is that we are able to clarify the phylogenetic origins of the plant mitochondrion. In particular, we find a close phylogenetic relationship between the plant mitochondria and members of the alpha subdivision of the purple photosynthetic bacteria, namely,Rb. sphaeroides, P. denitrificans, andRhodospirillum rubrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02105804
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  • 4
    Electronic Resource
    Electronic Resource
    Permeability of ammonia, methylamine and ethylamine in the cyanobacterium,Synechococcus R-2 (Anacystis nidulans) PCC 7942 (1987)
    Springer
    The journal of membrane biology 95 (1987), S. 131-142 
    Details
    ISSN: 1432-1424
    Keywords: Synechococcus ; permeability ; ammonia ; methylamine ; ammonium transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Permeabilities of ammonia (NH3), methylamine (CH3NH2) and ethylamine (CH3CH2NH2) in the cyanobacterium (cyanophyte)Synechococcus R-2 (Anacystis nidulans) have been measured. Based on net uptake rates of DCMU (dichlorophenyldimethylurea) treated cells, the permeability of ammonia was 6.44±1.22 μm sec−1 (n=13). The permeabilities of methylamine and ethylamine, based on steady-state14C labeling were more than ten times that of ammonia (P methylamine=84.6±9.47 μm sec−1 (76),P ethylamine=109±11 μm sec−1 (55)). The apparent permeabilities based on net uptake rates of methylamine and ethylamine uptake were significantly lower, but this effect was partially reversible by ammonia, suggesting that net amine fluxes are rate limited by proton fluxes to an upper limit of about 700 nmol m−2 sec−1. Increasing concentrations of amines in alkaline conditions partially dissipated the pH gradient across the cell membrane, and this property could be used to calculate the relative permeabilities of different amines. The ratio of ethylamine to methylamine permeabilities was not significantly different from that calculated from the direct measurements of permeabilities; ammonia was much less effective in dissipating the pH gradient across the cell membrane than methylamine or ethylamine. An apparent permeability of ammonia of 5.7±0.9 μm sec−1 could be calculated from the permeability ratio of ammonia to methylamine and the experimentally measured permeability of methylamine. The permeability properties of ammonia and methylamine are very different; this poses problems in the interpretation of experiments where14C-methylamine is used as an ammonia analogue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869158
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  • 5
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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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  • 6
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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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  • 7
    Electronic Resource
    Electronic Resource
    Ruthenium nitrosyl complexes: Toxicity toEscherichia coli and yeasts and uptake by marine bacteria (1986)
    Springer
    Archives of environmental contamination and toxicology 15 (1986), S. 519-523 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The toxicity and possible accumulation of ruthenium nitrosyl complexes by marine bacteria and test organisms have been studied, A range of these complexes show no toxic effects towardsEscherichia coli K12 at concentrations of mM and below. Yeasts are more sensitive, showing effects on growth at 10 ΜM. The ruthenium nitrosyl complexes tested are unable to permeate the cytoplasmic membrane ofE. coli. This may account for their lack of toxicity. However, these compounds did not have significant inhibitory effects on Mg2+-ATPase activity in cell-extracts, I50 values lying in the range 2 to 125 Μmol(mg protein)−1. Marine bacteria are capable of taking up ruthenium complexes from simulated effluent, but this cannot be demonstrated in the presence of sediment which competes effectively for binding of complexes. There is minimal likelihood of concentration of ruthenium compounds from effluents by marine bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01056564
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  • 8
    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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