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

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

Real-Time PCR Screening for 16S rRNA Mutations Associated with Resistance to Tetracycline in Helicobacter pylori

The effectiveness of recommended first-line therapies for Helicobacter pylori infections is decreasing due to the occurrence of resistance to metronidazole and/or clarithromycin. Quadruple therapies, which include tetracycline and a bismuth salt, are useful alternative regimens. However, resistance to tetracycline, mainly caused by mutations in the 16S rRNA genes (rrnA and rrnB) affecting nucleotides 926 to 928, are already emerging and can impair the efficacies of such second-line regimens. Here, we describe a novel real-time PCR for the detection of 16S rRNA gene mutations associated with tetracycline resistance. Our PCR method was able to distinguish between wild-type strains and resistant strains exhibiting single-, double, or triple-base-pair mutations. The method was applicable both to DNA extracted from pure cultures and to DNA extracted from fresh or frozen H. pylori-infected gastric biopsy samples. We therefore conclude that this real-time PCR is an excellent method for determination of H. pylori tetracycline resistance even when live bacteria are no longer available

Diuretics in pediatrics: Current knowledge and future prospects

This review summarizes current knowledge on the pharmacology, pharmacokinetics, pharmacodynamics, and clinical application of the most commonly used diuretics in children. Diuretics are frequently prescribed drugs in children. Their main indication is to reduce fluid overload in acute and chronic disease states such as congestive heart failure and renal failure. As with most drugs used in children, optimal dosing schedules are largely unknown and empirical. This is undesirable as it can potentially result in either under- or over-treatment with the possibility of unwanted effects. The pharmacokinetics of diuretics vary in the different pediatric age groups as well as in different disease states. To exert their action, all diuretics, except spironolactone, have to reach the tubular lumen by glomerular filtration and/or proximal tubular secretion. Therefore, renal maturation and function influence drug delivery and consequently pharmacodynamics. Currently advised doses for diuretics are largely based on adult pharmacokinetic and pharmacodynamic studies. Therefore, additional pharmacokinetic and pharmacodynamic studies for the different pediatric age groups are necessary to develop dosing regimens based on pharmacokinetic and pharmacodynamic models for all routes of administration