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  • 1
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Transcription of the Trichoderma longibrachiatum egl1 gene is induced in the presence of lactose and β-methylglucoside and repressed by glucose. A DNA fragment containing 722 bp upstream of the ATG codon has been sequenced. The gene has two major transcription start points (20 and 24 nucleotides upstream from the ATG codon) and several transcription termination points (located in a region around 130 nt downstream of the stop codon). Two 6-mer sequences (5′-CTGGAG-3′) separated by 16 bp are present in the egl1 gene promoter. These sequences match the Aspergillus nidulans consensus CreA binding site and might be implicated in carbon catabolite repression of egl1 transcription.
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  • 2
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The long-time effect of phosphinothricin (PPT) on gas exchange and nitrate metabolism in intact plants of lucerne (Medicago sativa L. cv. Aragón) was investigated. Photosynthetic CO2 uptake, stomatal conductance, and transpiration were measured with an Infra-Red Gas Analyzer (IRGA). Under photorespiratory conditions, CO2 uptake continuously decreased after PPT treatment. The decrease of photosynthesis led to an increase in the internal CO2 concentration, which in turn caused stomatal closure and a reduction of transpiration rate. Nitrate reduction from plants sprayed with PPT was assayed both in vitro and in vivo. In vivo nitrate reductase was measured with and without nitrate in the infiltration medium. Both types of nitrate reductase assays indicated that the enzyme was inhibited in plants treated with PPT; however, the enzyme appeared more affected when the in vivo assay was used than when the one in vitro was applied. The nitrate reduction was pronouncedly affected after 24 h of PPT treatment, when glutamine synthetase (GS, EC 6.3.1.2.) activity and gas exchange were inhibited by more than 60%. The data suggest that the inhibition of GS leads to inhibition of photosynthesis, which, in turn, means lack of NADPH and nitrate, the substrates for nitrate reductase. The inhibition of GS also leads to a high ammonia level, which will produce a secondary inhibition of nitrate reductase activity.
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  • 3
    ISSN: 1745-4565
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of the pH of the heating medium (which included several foods and buffers) on the thermal resistance (D and z-values) of spores of three Bacillus cereus strains was studied. Acidification from pH 7.0 to 4.0 produced a 5-fold decrease in D-values. Plots of log D vs pH gave straight lines, which made it possible to develop an equation to approximately predict the changes in heat sensitivity of B. cereus spores which occurred with changing pH. z-Values for two of the strains studied were not affected by acidification. On the other hand, with the strain ATCC 9818, a clear and statistically significant increase in z-value was observed as the pH decreased.
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  • 4
    ISSN: 1745-4565
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of the addition of starch, glucose, sodium chloride, sodium citrate, monopotassium phosphate and disodium phosphate to the recovery medium on apparent heat resistance of Bacillus cereus spores (ATCC 4342, 7004 and 9818) were investigated. Sodium citrate, monopotassium and disodium phosphate at concentrations of 0.1% were effective inhibitory agents for heat injured B. cereus spores especially for strain 9818, although only monopotassium and disodium phosphate caused a significant reduction (p 〈 0.05) in D-values obtained for strain 9818. Sodium chloride also had a marked effect on the recovery of heat injured spores. Concentration as low as 0.5% caused a significant reduction in the recovery rates for strains 9818 and 7004. In all cases, increasing the salt levels from 0.5 to 4% resulted in a progressive decrease in spore recovery. D-values gradually decreased as the salt content increased, although the concentrations which produced statistically significant differences (p 〈 0.05) varied among strains. The addition of starch at 0.1% resulted in a significant increase in the counts for strains 9818 and 7004. In contrast, glucose (0.1%), did not significantly modify the counts obtained Neither of these compounds affected decimal reduction times. No statistical significance (p〉0.05) differences were detected among z-values for the spores of the three strains recovered in the presence of different additives assayed. z-Values ranged from 6.67 to 8.32, with a mean value of 7.56 ± 0.46C.
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  • 5
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Aspergillus species included in section Nigri are common in plant products and processed food, such as grapes, cereals, coffee and derivatives, particularly in warm and tropical climates. Two of these species, A. carbonarius and A. niger, are known to produce ochratoxin A (OTA), a potent nephrotoxin and carcinogenic to human (group 2B). Recognition of the several species of this section is difficult and requires considerable expertise using conventional methods based on morphological features. In this work we describe rapid, sensitive and robust assays based on the PCR technique to discriminate the main species included in section Nigri: A. japonicus, A. heteromorphus, A. ellipticus and the two morphologically indistinguishable species of the A. niger aggregate: A. niger and A. tubingensis. The species-specific primers have been designed on the basis of ITS (internal transcribed spacers of rDNA units) sequence comparisons obtained from several Aspergillus strains and have been tested in a number of strains from different origins and hosts. These PCR assays, based on multi-copy sequences, are highly sensitive and specific and represent a good tool for an early detection of OTA-producing Aspergillus species in order to prevent OTA from entering the food chain.
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  • 6
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The reporter gene xylE (encoding catechol 2,3-dioxygenase) has been modified for a more rational use in Streptomyces. Two reporter fragments, one containing xylE, and the other containing also the upstream gene xylT (which encodes a soluble ferredoxin), have been constructed to allow precise fusion of regulatory regions to the reporter genes. Identical fusions of these xylE and xylTE reporter fragments to the Streptomyces dagA and tipA promoters, in low and high copy number plasmids, show that the levels of xylE mRNA and catechol 2,3-dioxygenase activities are significantly higher when xylT is present.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Kyklos 58 (2005), S. 0 
    ISSN: 1467-6435
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Sociology , Economics
    Notes: Are private firms more efficient than public ones? Does privatisation improve performance? In order to answer these questions, it is necessary to disentangle the impact of ownership and competition upon business performance. This paper presents empirical evidence relating to the hypothesis that public ownership and competition are determinants of firms' productivity. It concludes that public ownership has a significant negative effect on productivity and also that privatisation has a positive impact on efficiency. Furthermore, increased competition is found to have a positive effect on productivity. These results are interpreted as confirming that privatisation is effective as a means of increasing firms' efficiency, at least in a non-regulated and relatively competitive sector, such as manufacturing.
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  • 8
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Cytochrome c-oxidase type aa3 (EC 1.9.3.1.) was purified to homogeneity from vegetative Bacillus cereus by ion-exchange and hydroxylapatite chromatography in the presence of Triton X–100. Gel filtration analysis suggested a dimeric structure apparently 172kDa in size; however, only a monomer of 81kDa was detected when analysed by non-denaturing gel electrophoresis. Denaturing gel electrophoresis analysis of the protein showed the presence of two subunits (51 and 30kDa), Atomic absorption and visible spectroscopy showed typical aa3 redox centres with haem a iron and copper in a ratio of 22 nmol and 35ng-atom per mg protein, respectively. No haem c was found associated with the purified enzyme in the conditions reported here. Oxidase activity was fully reconstituted by phospholipids in the presence of N, N, N′ N′-tetramethyl-p-phenylenediamine or reduced yeast cytochrome c (but not horse cytochrome c) as electron donors. This activity was abolished by cyanide and carbon monoxide.
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  • 9
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The structure, genomic organization and transcription of the gene encoding histone H2B in the protozoan parasite Trypanosoma cruzi have been studied. This gene consists of a 746-nucleotlde unit, tandemly repeated at least 18 times in each of two clusters. DNA probes corresponding to histones H2B and H3 hybridized to different chromosomes revealing that the genes coding for these two histones are not physically linked in the genome of T. cruzi. The primary transcription product of the H2B gene is processed by trans-splicing and polyadenylation. Inhibition of DNA synthesis with aphidicolin resulted in the reduction of histone H2B mRNA to undetectable levels in about two hours, suggesting that its abundance is regulated throughout the cell cycle as it occurs in other eukaryotes. in addition, a concomitant inhibition of translation by cycloheximide reverted this effect indicating that de novo protein synthesis is required for RNA instability. Histone mRNA abundance was dependent on the life-cycle stage of T. cruzi: abundant in amastigotes and epimastigotes, the dividing forms in the host cell and the insect vector, respectively, white undetected in trypomastigotes, the parasite's non-dividing life stage.
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  • 10
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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