1,720,983 research outputs found
Under-estimation of 210 Pb in industrial radioactive scales
No full textLead-210 (210Pb) can be present at high activity concentrations, in residues arising from the petroleum, mineral processing and chemical industries. Although 210Pb itself poses a low radiological risk, the nuclide decays via 210Bi to the alpha emitting and highly radiotoxic 210Po. Therefore, rapid, accurate determination of 210Pb is essential for assessing the radiological risk to plant operators and appropriate sentencing of waste. Unfortunately, direct measurement of 210Pb by gamma spectrometry is hindered by its weak gamma-ray emission at 46.5 keV, which is readily attenuated by mineral matrices. This paper demonstrates the extent to which 210Pb can be underestimated during routine analysis by an inter-laboratory exercise involving five accredited laboratories and a wide range of scales from diverse industrial sources. Two methods of addressing errors in 210Pb analysis are highlighted; the first, involving lithium tetraborate fusion prior to gamma spectrometry shows promise but is not suitable for all 210Pb-containing phases. The second method, requiring calculation of matrix attenuation factors for a representative fingerprint sample, was applied successfully to deposits from the steel and gas industries. However, its wider application depends on detailed chemical and mineralogical characterisation for each of the major categories of mineral scale found and at present, there is an acute lack of suitable certified reference materials
Ratio of lethal and edema factors in rabbit systemic anthrax
No full textBacillus anthracis secretes two binary toxins: lethal toxin (PA + LF) and edema toxin (PA + EF) that play a major role in the pathogenesis of anthrax. Their activities can synergize or interfere among each other, depending on the cell type. It is therefore fundamental to know their concentration ratio in vivo. Here, we report the first determination of the concentration ratio of anthrax toxin components LF/EF in the serum of rabbits infected with B. anthracis spores
BPH Obstruction: a linear classifier for the obstruction detection
No full textThe aim of the study was to collect the pressure-flow data in 100 Benign Prostatic Hyperplasia (BPH) patients (pts) and to develop a linear classifier for the detection of BPH obstruction. Finally, the data have been used for the evaluation of both the best parameters describing the BPH obstruction and for the evaluation of the error probabilities that non-obstructed patients are treated and viceversa
Tyrosine-728 and glutamic acid-735 are essential for the metalloproteolytic activity of the lethal factor of Bacillus anthracis
No full textThe lethal factor (LF) of Bacillus anthracis is a Zn2+-endopeptidase specific for the MAPK-kinase family of proteins. The catalytic zinc atom is coordinated by a first shell of residues including the two histidines and the glutamate of the zinc-binding motif HExxH and by Glu-735. A characteristic feature of LF is the presence, within the second shell of residues, of a tyrosine (Tyr-728) in close proximity (3.3 A) to the zinc atom. To investigate the role of Tyr-728 and Glu-735, LF mutants with one or both of these two residues replaced by Ala were cloned, expressed, and purified from Escherichia coli. A fourth mutant was obtained by replacing Tyr-728 with Phe. Spectroscopic analysis of these mutants indicates that they fold in the same way as the parental molecule and that zinc stabilizes the structure of LF. These mutants have neither proteolytic activity nor in vivo toxicity. The possible role of Tyr-728 in catalysis is discussed
cAMP imaging of cells treated with pertussis toxin, cholera toxin, and anthrax edema toxin
No full textThe enzymatic activity of the three most Studied bacterial toxins that increase the cytosolic cAMP level: pertussis toxin (PT), cholera toxin (CT), and anthrax edema toxin (ET), was imaged by fluorescence videomicroscopy. Three different cell lines were transfected with a fluorescence resonance energy transfer biosensor based on the PKA regulatory and catalytic subunits fused to CFP and YFP, respectively. Real-time imaging of cells expressing this cAMP biosensor provided time and space resolved Pictures of the toxins action. The time course of the PT-induced cAMP increase suggests that its active subunit enters the cytosol more rapidly than that deduced by biochemical experiments. ET generated cAMP concentration gradients decreasing from the nucleus to the cell periphery. On the contrary, CT, which acts on the plasma membrane adenylate cyclase, did not. The potential of imaging methods in studying the mode of entry and the intracellular action of bacterial toxins is discussed
Cell entry and cAMP imaging of anthrax edema toxin
No full textThe entry and enzymatic activity of the anthrax edema factor (EF) in different cell types was studied by monitoring EF-induced changes in intracellular cAMP with biochemical and microscopic methods. cAMP was imaged in live cells, transfected with a fluorescence resonance energy transfer biosensor based on the protein kinase A regulatory and catalytic subunits fused to CFP and YFP, respectively. The cAMP biosensor was located either in the cytosol or was membrane-bound owing to the addition of a tag determining its myristoylation/palmitoylation. Real-time imaging of cells expressing the cAMP biosensors provided the time course of EF catalytic activity and an indication of its subcellular localization. Bafilomycin A1, an inhibitor of the vacuolar ATPase proton pump, completely prevented EF activity, even when added long after the toxin. The time course of appearance of the adenylate cyclase activity and of bafilomycin A1 action suggests that EF enters the cytosol from late endosomes. EF remains associated to these compartments and its activity shows a perinuclear localization generating intracellular cAMP concentration gradients from the cell centre to the periphery
Molecular characterization of "Candidatus Phytoplasma mali" strains in outbreaks of apple proliferation in north eastern Italy, Hungary, and Serbia.
Full text linkDuring 2005-2008 apple plants showing proliferation symptoms were observed in diverse cvs in different areas of north eastern Italy, Hungary and Serbia. Leaves and young shoots were collected from June to October in orchards with epidemic presence of apple proliferation, and in others where the symptomatic plants were present in a scattered way. PCR/RFLP analyses carried out on R16F2/R2 amplicons showed that all the samples were infected with ‘Candidatus Phytoplasma mali’. Further strain characterization was carried out using RFLP analyses with HpaII and FauI on almost full ribosomal DNA plus spacer region, AluI on rpl22-s3 genes, and RcaI and HincII on AP13/AP10 amplicons from representative samples collected in these geographic areas. Analyses of 16S plus spacer region distinguished two phytoplasma profiles (P-I and P-II). P-I was detected in reference strains AP, AT1, AT2, in samples from Serbia, and in the majority of samples from Trentino. The P-II profile was prevalent in samples from Veneto, and both profiles were identified in samples from Hungary, in some cases together. The analyses of rpl22-s3 genes allow to identify in all the samples showing P-I profile the presence of phytoplasmas belonging to rpX-A subgroup, while in samples showing P-II profile it was possible to distinguish the other three described rp subgroups. In the majority of samples from Veneto region phytoplasmas belonging to rpX-D subgroup were identified, while rpX-B and X-C subgroups were identified in a few samples from Trentino and Veneto regions respectively. Further RFLP characterization on AP13/AP10 amplicons differentiates among strains belonging to rpX-A subgroup: the Serbian samples show AP profiles, while those from Trentino show AT-2 profiles. In the samples from Hungary the presence of AT1, AT2, and AP profiles was identified. The combined use of these molecular markers allows differentiating ‘Ca. P. mali’ strains according with geographical and epidemic distribution
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