61 research outputs found
NikR mediates nickel-responsive transcriptional induction of urease expression in Helicobacter pylori
The important human pathogen Helicobacter pylori requires the abundant
expression and activity of its urease enzyme for colonization of the
gastric mucosa. The transcription, expression, and activity of H. pylori
urease were previously demonstrated to be induced by nickel
supplementation of growth media. Here it is demonstrated that the HP1338
protein, an ortholog of the Escherichia coli nickel regulatory protein
NikR, mediates nickel-responsive induction of urease expression in H.
pylori. Mutation of the HP1338 gene (nikR) of H. pylori strain 26695
resulted in significant growth inhibition of the nikR mutant in the
presence of supplementation with NiCl(2) at > or =100 microM, whereas the
wild-type strain tolerated more than 10-fold-higher levels of NiCl(2).
Mutation of nikR did not affect urease subunit expression or urease enzyme
activity in unsupplemented growth media. However, the nickel-induced
increase in urease subunit expression and urease enzyme activity observed
in wild-type H. pylori was absent in the H. pylori nikR mutant. A similar
lack of nickel responsiveness was observed upon removal of a 19-bp
palindromic sequence in the ureA promoter, as demonstrated by using a
genomic ureA::lacZ reporter gene fusion. In conclusion, the H. pylori NikR
protein and a 19-bp operator sequence in the ureA promoter are both
essential for nickel-responsive induction of urease expression in H.
pylori
Transcriptional profiling of Helicobacter pylori Fur- and iron-regulated gene expression
Intracellular iron homeostasis is a necessity for almost all living
organisms, since both iron restriction and iron overload can result in
cell death. The ferric uptake regulator protein, Fur, controls iron
homeostasis in most Gram-negative bacteria. In the human gastric pathogen
Helicobacter pylori, Fur is thought to have acquired extra functions to
compensate for the relative paucity of regulatory genes. To identify H.
pylori genes regulated by iron and Fur, we used DNA array-based
transcriptional profiling with RNA isolated from H. pylori 26695 wild-type
and fur mutant cells grown in iron-restricted and iron-replete conditions.
Sixteen genes encoding proteins involved in metal metabolism, nitrogen
metabolism, motility, cell wall synthesis and cofactor synthesis displayed
iron-dependent Fur-repressed expression. Conversely, 16 genes encoding
proteins involved in iron storage, respiration, energy metabolism,
chemotaxis, and oxygen scavenging displayed iron-induced Fur-dependent
expression. Several Fur-regulated genes have been previously shown to be
essential for acid resistance or gastric colonization in animal models,
such as those encoding the hydrogenase and superoxide dismutase enzymes.
Overall, there was a partial overlap between the sets of genes regulated
by Fur and those previously identified as growth-phase, iron or acid
regulated. Regulatory patterns were confirmed for five selected genes
using Northern hybridization. In conclusion, H. pylori Fur is a versatile
regulator involved in many pathways essential for gastric colonization.
These findings further delineate the central role of Fur in regulating the
unique capacity of H. pylori to colonize the human stomach
The role of the ferric uptake regulator (Fur) in regulation of Helicobacter pylori iron uptake
Background. Availability of the essential nutrient iron is thought to vary greatly in the gastric mucosa, and thus the human gastric pathogen Helicobacter pylori requires regulatory responses to these environmental changes. Bacterial iron-responsive regulation is often mediated by Ferric Uptake Regulator (Fur) homologs, and in this study we have determined the role of H. pylori Fur in regulation of H. pylori iron uptake. Methods. Wild-type H. pylori and fur mutant derivatives were compared after growth in ironrestricted and iron-replete conditions. Iron-uptake was measured using 55Fe-labeled iron, whereas gene expression was mon
Differential regulation of amidase- and formamidase-mediated ammonia production by the Helicobacter pylori fur repressor.
The production of high levels of ammonia allows the human gastric pathogen
Helicobacter pylori to survive the acidic conditions in the human stomach.
H. pylori produces ammonia through urease-mediated degradation of urea,
but it is also able to convert a range of amide substrates into ammonia
via its AmiE amidase and AmiF formamidase enzymes. Here data are provided
that demonstrate that the iron-responsive regulatory protein Fur directly
and indirectly regulates the activity of the two H. pylori amidases. In
contrast to other amidase-positive bacteria, amidase and formamidase
enzyme activities were not induced by medium supplementation with their
respective substrates, acrylamide and formamide. AmiE protein expression
and amidase enzyme activity were iron-repressed in H. pylori 26695 but
constitutive in the isogenic fur mutant. This regulation was mediated at
the transcriptional level via the binding of Fur to the amiE promoter
region. In contrast, formamidase enzyme activity was not iron-repressed
but was significantly higher in the fur mutant. This effect was not
mediated at the transcriptional level, and Fur did not bind to the amiF
promoter region. These roles of Fur in regulation of the H. pylori
amidases suggest that the H. pylori Fur regulator may have acquired extra
functions to compensate for the absence of other regulatory systems
Communicable Diseases Prioritized for Surveillance and Epidemiological Research: Results of a Standardized Prioritization Procedure in Germany, 2011
To establish strategic priorities for the German national public health institute (RKI) and guide the institute's mid-term strategic decisions, we prioritized infectious pathogens in accordance with their importance for national surveillance and epidemiological research.We used the Delphi process with internal (RKI) and external experts and a metric-consensus approach to score pathogens according to ten three-tiered criteria. Additional experts were invited to weight each criterion, leading to the calculation of a median weight by which each score was multiplied. We ranked the pathogens according to the total weighted score and divided them into four priority groups.., Respiratory syncytial virus or Hantavirus) indicate a possible under-recognised importance within the current German public health framework. A process to strengthen respective surveillance systems and research has been started. The prioritization methodology has worked well; its modular structure makes it potentially useful for other settings
A Novel System of Cytoskeletal Elements in the Human Pathogen Helicobacter pylori
Pathogenicity of the human pathogen Helicobacter pylori relies upon its capacity to adapt to a hostile environment and to escape from the host response. Therefore, cell shape, motility, and pH homeostasis of these bacteria are specifically adapted to the gastric mucus. We have found that the helical shape of H. pylori depends on coiled coil rich proteins (Ccrp), which form extended filamentous structures in vitro and in vivo, and are differentially required for the maintenance of cell morphology. We have developed an in vivo localization system for this pathogen. Consistent with a cytoskeleton-like structure, Ccrp proteins localized in a regular punctuate and static pattern within H. pylori cells. Ccrp genes show a high degree of sequence variation, which could be the reason for the morphological diversity between H. pylori strains. In contrast to other bacteria, the actin-like MreB protein is dispensable for viability in H. pylori, and does not affect cell shape, but cell length and chromosome segregation. In addition, mreB mutant cells displayed significantly reduced urease activity, and thus compromise a major pathogenicity factor of H. pylori. Our findings reveal that Ccrp proteins, but not MreB, affect cell morphology, while both cytoskeletal components affect the development of pathogenicity factors and/or cell cycle progression
Recurrent differentiated thyroid cancer: Towards personalized treatment based on evaluation of tumor characteristics with PET (THYROPET Study): Study protocol of a multicenter observational cohort study
Background: After initial treatment of differentiated thyroid carcinoma (DTC) patients are followed with thyroglobulin (Tg) measurements to detect recurrences. In case of elevated levels of Tg and negative neck ultrasonography, patients are treated 'blindly' with Iodine-131 (131I). However, in up to 50% of patients, the post-therapy scan reveals no 131I-targeting of tumor lesions. Such patients derive no benefit from the blind therapy but are exposed to its toxicity. Alternatively, iodine-124 (124I) Positron Emission Tomography/Computed Tomography (PET/CT) has become available to visualize DTC lesions and without toxicity. In addition to this, 18F-fluorodeoxyglucose (18F-FDG) PET/CT detects the recurrent DTC phenotype, which lost the capacity to accumulate iodine. Taken together, the combination of 124I and 18F-FDG PET/CT has potential to stratify patients for treatment with 131I.Methods/Design: In a multicenter prospective observational cohort study the hypothesis that the combination of 124I and 18F-FDG PET/CT can avoid futile 131I treatments in patients planned for 'blind' therapy with 131I, is tested.One hundred patients planned for 131I undergo both 124I and 18F-FDG PET/CT after rhTSH stimulation. Independent of the outcome of the scans, all patients will subsequently receive, after thyroid hormone withdrawal, the 131I therapy. The post 131I therapeutic scintigraphy is compared with the outcome of the 124I and 18F-FDG PET/CT in order to evaluate the diagnostic value of the combined PET modalities.This study primary aims to reduce the number of futile 131I therapies. Secondary aims are the nationwide introduction of 124I PET/CT by a quality assurance and quality control (QA/QC) program, to correlate imaging outcome with histopathological features, to compare 124I PET/CT after rhTSH and after withdrawal of thyroid hormone, and to compare 124I and 131I dosimetry.Discussion: This study aims to evaluate the potential value of the combination of 124I and 18F-FDG PET/CT in the prevention of futile 131I therapies in patients with biochemically suspected recurrence of DTC. To our best knowledge no studies addressed this in a prospective cohort of patients. This is of great clinical importance as a futile 131I is a costly treatment associated with morbidity and therefore should be restricted to those likely to benefit from this treatment.Trial registration: Clinicaltrials.gov identifier: NCT01641679
Characteristics of contralateral carcinomas in patients with differentiated thyroid cancer larger than 1 cm
Purpose: Traditionally, total thyroidectomy has been advocated for patients with tumors larger than 1 cm. However, according to the ATA and NCCN guidelines (2015, USA), patients with tumors up to 4 cm are now eligible for lobectomy. A rationale for adhering to total thyroidectomy might be the presence of contralateral carcinomas. The purpose of this study was to describe the characteristics of contralateral carcinomas in patients with differentiated thyroid cancer (DTC) larger than 1 cm. Methods: A retrospective study was performed including patients from 17 centers in 5 countries. Adults diagnosed with DTC stage T1b-T3 N0-1a M0 who all underwent a total thyroidectomy were included. The primary endpoint was the presence of a contralateral carcinoma. Results: A total of 1
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