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PubMed2000

Rapid urease test is less sensitive than histology in diagnosing Helicobacter pylori infection in patients with non-variceal upper gastrointestinal bleeding.

BACKGROUND AND AIMS: The validity of the rapid urease (CLO) test to diagnose Helicobacter pylori infection in patients with bleeding ulcers has been questioned. The aim of this paper is to evaluate the validity of the CLO test in comparison with histology in diagnosing H. pylori infection in patients with acute upper gastrointestinal bleeding (UGB), irrespective of non-steroidal anti-inflammatory drug (NSAID) use. METHODS: Upper gastrointestinal endoscopy was performed within 24 h of admission for all patients with UGB admitted to the Department of Pathophysiology, Medical School, Athens, for a period of 12 months. Patients with variceal bleeding, previous gastric operation, recent treatment with proton pump inhibitors (< 2 months) and those with a history of H. pylori eradication therapy were excluded from the study. At least four biopsies (two from the antrum and two from the body) were obtained for the CLO test and histology (modified Giemsa). RESULTS: Seventy-two consecutive patients (aged 18-90 years, 51 men, 21 women) were included. Forty-six patients (64%) used NSAID. Thirty-two patients (44%) were found to be positive for H. pylori infection by the CLO test, while 44 patients (61%) were found to be positive on histology (P<0.045, 95% CI, 0.004-0.331). The sensitivity and specificity of the CLO test were 68 and 93% respectively; positive and negative predictive values were 94 and 65%, respectively. The age of the patient and visible blood in the stomach did not influence results of either the CLO or histology. CONCLUSIONS: The CLO test, performed within 24 h of hospital admission in patients with UGB, irrespective of NSAID use, is unreliable for the detection of H. pylori infection. The age of the patient and the presence of blood in the stomach do not seem to influence these results.

Adolescent↗
PubMed1997

An in vitro comparison of urease-induced encrustation of JJ stents in human urine.

OBJECTIVE: To report the results of a comparative study of in vitro encrustation of five different types of JJ stents in human urine. MATERIALS AND METHODS: Samples of five JJ stents (polyurethane, silicone, Percuflex, C-Flex and hydrogel-coated C-Flex) were immersed for 24 h at 37 degrees C in fresh human urine supplemented with urease, and the surface photographed and dried. The crystals formed on the stents were dissolved in hydrochloric acid and the calcium and magnesium concentrations determined. RESULTS: Large crystals were deposited on the surface of the hydrogel-coated C-Flex stent and significantly higher levels of calcium and magnesium salts were obtained after acidic dissolution. There were no differences in crystal deposition among the remaining stents. CONCLUSION: Hydrogel-coated stents have an higher risk of becoming encrusted in vitro than do uncoated stents made of the same substrate polymer or made of different materials. These results emphasize the need for the regular follow-up of patients with hydrophilic stents in place.

Crystallization↗
PubMed2002

Cloning and sequencing of 16S rDNA and 16S-23S rDNA internal spacer region (ISR) from urease-positive thermophilic Campylobacter (UPTC).

AIMS: To clone and sequence the 16S rDNA and 16S-23S rDNA internal spacer region (ISR) from urease-positive thermophilic Campylobacter (UPTC). METHODS AND RESULTS: The primer sets for 16S rDNA and 16S-23S rDNA ISR amplified almost the full length of 16S rDNA and 16S-23S rDNA ISR. About 1500 bp for 16S rDNA and about 720 bp for 16S-23S rDNA ISR of the rrn operon of four strains of UPTC were identified after molecular cloning and sequencing. CONCLUSIONS: The four strains and CCUG18267 of UPTC showed approximately 99% sequence homology of 16S rDNA to each other, 96-97% to Camp. coli, 97-98% to Camp. jejuni and 97-98% to Camp. lari. SIGNIFICANCE AND IMPACT OF THE STUDY: For the first time, the nucleotide sequence of 16S-23S rDNA ISR of UPTC has been analysed. The sequence of ISR was almost identical among the four strains of UPTC. It is interesting that the UPTC intercistronic tRNAs demonstrated an order of tRNA of 5'-16S-tRNAAla-tRNAIle-23S-3' in the organisms.

Campylobacter↗
PubMed2002

flaA-like sequences containing internal termination codons (TAG) in urease-positive thermophilic Campylobacter isolated in Japan.

AIMS: To demonstrate two flaA-like sequences containing two internal termination codons (TAG) in two Japanese strains of urease-positive thermophilic Campylobacter (UPTC). METHODS AND RESULTS: A primer pair of A1 and A2, which ought to generate a product of approx. 1700 bp of the flaA gene for Campylobacter jejuni, was used to amplify products of approx. 1450 bp for two Japanese strains of UPTC, CF89-12 and CF89-14. After molecular cloning and sequencing, the nucleotide sequences of the amplicons from the two strains were found to be 1461 bp in length and to have nucleotide sequence differences in relation to each other at four nucleotide positions, respectively. CONCLUSIONS: Nucleotide and amino acid sequence alignment and homology analysis demonstrated that the polymerase chain reaction (PCR) amplicons from the two Japanese strains have approx. 83% nucleotide and 80% amino acid sequence homology to the possible open reading frame of the flaA gene of UPTC NCTC 12892. SIGNIFICANCE AND IMPACT OF THE STUDY: Surprisingly, both PCR amplicons from the Japanese UPTC have two internal termination codons (TAG) at nucleotide positions from 775 to 777 and 817 to 819, respectively.

Amino Acid Sequence↗
PubMed1999

Colonization and tissue tropism of Helicobacter pylori and a novel urease-negative Helicobacter species in ICR mice are independent of route of exposure.

BACKGROUND: In humans, Helicobacter pylori is known to colonize the stomach and to induce persistent gastritis; selected reports also suggest it causes extragastric disease, including hepatitis. H. pylori and a novel urease-negative Helicobacter sp. induce gastritis and typhlocolitis, respectively, when inoculated orally into mice. Experimental typhlocolitis and hepatitis have been caused by intraperitoneal (i.p.) injection of H. hepaticus, H. bilis, and the novel Helicobacter spp. However, the route by which i.p.-inoculated organisms localize to specific areas of the gastrointestinal system is unknown. MATERIALS AND METHODS: To determine whether Helicobacter spp. can be isolated from blood, can preferentially colonize specific tissues, and can cause pathological changes, we inoculated 6-week-old outbred mice orally or intraperitoneally with H. pylori or a novel Helicobacter sp. RESULTS: When these mice were inoculated by the i.p. route, H. pylori was cultured from lungs, spleen, liver, cecum, and stomach on day 1 after inoculation, from liver and stomach mucosa on day 3 after inoculation, and from the stomach on day 30 after inoculation, suggesting preferential colonization of the stomach. After inoculation by the i.p. route, the novel intestinal Helicobacter sp. was cultured from the blood, lungs, spleen, liver, kidneys, cecum, and feces but not from stomach mucosa on day 1 after inoculation. By day 30 after inoculation, the novel Helicobacter sp. was cultured from cecum and feces only, suggesting that it had preferentially colonized the lower bowel. By the i.p. route, the novel Helicobacter sp. induced hepatitis that persisted for 30 days after inoculation. Though mice inoculated intraperitoneally with H. pylori developed an acute hepatitis, the liver lesion began to resolve 30 days after inoculation. Mice inoculated orally with either H. pylori or the novel Helicobacter sp. did not have hepatitis on day 30 after inoculation but developed 100% colonization of stomach and cecum, respectively. CONCLUSION: The isolation of H. pylori and the novel Helicobacter sp. from multiple tissues infers that a transient helicobacter bacteremia occurs when Helicobacter spp. are injected intraperitoneally, but organisms are cleared rapidly from nontarget tissues and preferentially colonize specific regions of the gastrointestinal tract.

Animals↗
PubMed2000

Nic1p, a relative of bacterial transition metal permeases in Schizosaccharomyces pombe, provides nickel ion for urease biosynthesis.

The Schizosaccharomyces pombe genome sequencing project identified an open reading frame (O74869 and O74912, named Nic1p in the present study) with significant similarity to members of a family of bacterial transition metal permeases. These uptake systems transport Ni(2+) ion with extremely high affinity across the bacterial cytoplasmic membrane, but they differ in selectivity toward divalent transition metal cations. An S. pombe mutant harboring an interrupted nic1 allele (nic1-1) was strongly impaired in (63)Ni(2+) uptake in the presence of a high molar ratio of Mg(2+) relative to Ni(2+), conditions that reflect the natural situation. Under these conditions, the nic1-1 mutant contained only background activities of the nickel-dependent cytoplasmic enzyme urease and could not catabolize urea. Among a series of divalent transition metal cations tested (Cd(2+), Co(2+), Cu(2+), Mn(2+), and Zn(2+)), only Co(2+) caused considerable inhibition of Nic1p-mediated Ni(2+) uptake. On the other hand, experiments with (57)Co(2+) (at nm concentrations) did not show significant differences in Co(2+) uptake between the nic1-1 mutant and the parental strain. Our data suggest that Nic1p acts as a plasma-membrane nickel transporter in fission yeast, a finding that invites searches for isologous counterparts in higher eukaryotes.

Amino Acid Sequence↗
PubMed2002

First isolation of urease-positive thermophilic Campylobacter (UPTC) from crows (Corvus levaillantii) in Japan.

Two strains of urease-positive thermophilic Campylobacter (UPTC), designated YC98-1 and YC98-2, were identified by biochemical characterization after isolation from the intestinal contents of crows around Yokohama City, Japan, in 1998. The biochemical characteristics of these strains were identical to those of strains described previously. Pulsed-field gel electrophoresis (PFGE) after separate digestion with ApaI, SalI, and SmaI of the genomic DNA from the two strains indicated that respective PFGE profiles were distinctly different and distinguishable from each other. This is the first report of the isolation of UPTC from crows (Corvus levaillantii).

Animals↗
PubMed1999

Decreased sensitivity of the ultrarapid urease test for diagnosing Helicobacter pylori in patients with chronic renal failure.

Fifty patients with chronic renal failure and 50 asymptomatic healthy volunteers were studied to determine the prevalence of Helicobacter pylori in the two groups and to compare the results of ultrarapid urease test (URUT) and gastric histology for detecting H. pylori infection. Four gastric antral biopsy specimens were taken. Two specimens were used for the URUT and two were processed routinely. Sections were stained with H&E and Loeffler's methylene blue. Histological examination showed presence of H. pylori in 56% of patients with chronic renal failure (CRF) and in 78% of the controls. The difference was statistically significant (p < 0.05). The URUT was positive in only 16% of patients with CRF compared to 74% in the controls (p < 0.0001). The sensitivity and overall diagnostic accuracy of the URUT to diagnose H. pylori infection were 94.8 and 96%, respectively, in controls but were only 29 and 60%, respectively, in patients with CRF. It is concluded that the prevalence of H. pylori is significantly less in patients with CRF and that the URUT is less sensitive than gastric histology for diagnosing H. pylori infection in these patients.

Adolescent↗
PubMed1998

Diagnosis of Helicobacter pylori infection after gastric surgery for peptic ulcer: is the rapid urease test useful?

BACKGROUND: The usefulness of the rapid urease test (RUT) in diagnosing Helicobacter pylori infection after peptic ulcer surgery is unknown. METHODS: Patients who had undergone peptic ulcer surgery were offered endoscopic examination if they presented with dyspepsia or gastrointestinal bleeding. Biopsy specimens were taken for RUT and histology from the corpus and the stoma in patients who had undergone partial gastrectomy or from the corpus and the antrum in patients who had undergone vagotomy. Histologic examination using haematoxylin and eosin stain and Warthin-Starry stain were used as the gold standard. RESULTS: Ninety patients were studied (69 had partial gastrectomy and 21 had vagotomy). Forty-three patients (32 in the partial gastrectomy group and 11 in the vagotomy group) were positive for H. pylori by histology. The respective sensitivity of RUT was 59% (stoma) and 75% (corpus) in the partial gastrectomy group (P = 0.36) and 55% (antrum) and 73% (corpus) in the vagotomy group (P = 0.51). CONCLUSIONS: RUT is not sensitive for detecting H. pylori after acid reduction surgery.

Biopsy↗
PubMed2004

Phenotypic characterisation of flagellin and flagella of urease-positive thermophilic campylobacters.

In this study, flagellin is purified biochemically from eight urease-positive thermophilic camplylobacters (UPTC) isolated from river water, sea water and mussels, and purified also from two isolates of Campylobacter jejuni and C. coli and fractionated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Results showed that no flagellin components were detected in the two Japanese UPTC isolates (CF89-12 and CF89-14) and the two UPTC NCTC strains (NCTC12893 and NCTC12894). Flagellin components, each consisting of a single peptide, with a heterogeneous molecular mass of approximately 52-63 kDa were demonstrated in the other four UPTC isolates (NCTC12892, NCTC12895, NCTC12896 and NI15F [from Northern Ireland]) and the two Japanese isolates of C. jejuni (JCM2013 and C. coli 27). The approximate molecular mass of flagellin from the flagellin-positive UPTC isolates was smaller than those of C. jejuni and C. coli. Flagella were not detected by electron microscopy in the four flagellin-negative UPTC isolates but they were detected in the four flagellin-positive UPTC isolates and the two isolates of C. jejuni and C. coli. Thus, significant phenotypic diversity for flagellin, which must be due to genotypic variations, was demonstrated among the UPTC isolates.

Campylobacter↗
PubMed2004

Acetohydroxamate inhibition of the activity of urease from dehusked seeds of water melon (Citrullus vulgaris).

Urease from the seeds of watermelon (Citrullus vulgaris) was purified to apparent homogeneity, using two acetone fractionation steps, heat treatment at 48 degrees C and gel filtration through Sephadex G-200. Effect of acetohydroxamic acid (AHA) on the activity of the homogeneous enzyme preparation (sp. act. 3000 +/- 550U/mg protein) was investigated. AHA exhibited a concentration-dependent inhibition both in the presence and absence of the substrate. The inhibition was uncompetitive and the Ki was 2.5 mM. Binding of AHA with the enzyme was reversible, as 63% activity could be restored by dialysis. Time-dependent inhibition revealed a monophasic inhibition of the activity. Addition of beta-mercaptoethanol (ME) gradually abolished the inhibition. Pre-treatment of native enzyme with 8.0 mM ME for 5 min at 30 degrees C exhibited protection against AHA-induced inhibition. The significance of these observations is discussed.

Citrullus↗
PubMed2006

New natural urease inhibitors from Ranunculus repens.

Phytochemical investigations on the chloroform and ethyl acetate soluble fractions of the roots of Ranunculus repens led to the isolation of methyl 3,4,5-trihydroxybenzoate 1, R(+)- 4-methoxydalbergione 2 and R(+)-dalbergiophenol 3. The structures of these compounds were established through spectral studies including 1D and 2D NMR experiments and by comparison with literature data. These compounds showed potent inhibitory activity against urease.

Benzoates↗
PubMed2006

A new Bacillus pasteurii urease inhibitor from Euphorbia decipiens.

Inhibition of Bacillus pasteurii urease enzyme by 3,7,15-tri-O-acetyl-5-O-nicotinoyl-13,14-dihydroxymyrsinol (1), a diterpene ester with a myrsinol-type skeleton, isolated from Euphorbia decipiens Boiss. and Buhse, was un-competitive consistent with the molecular docking results. The Ki value was 117.40 +/- 0.7 microM.

Bacillus↗
PubMed2006

Novel urease inhibitors from Daphne oleoids.

Phytochemical investigations on the chloroform and ethyl acetate soluble fractions of the roots of the Daphne oleoids led to the isolation of the coumarin glycosides 1-6. Compound 5 with IC50 values 22.05 and 26.30 microM repectively, was found to be the most active of these compounds when screened against Bacillus pasteurii and jack bean urease enzymes in a concentration-dependent fashion.

Daphne↗
PubMed2003

Arginine selective biosensor based on arginase-urease immobilized in gelatin.

Arginase and urease enzymes were immobilized on the surface of pH electrode by using gelatin membrane which is then cross-linked with glutaraldehyde. Sensor response was maximum when 2.5 mM, Tris-HCl buffer (pH 8.5) was used at 25 degrees C. The biosensor response depends linearly on arginine concentration between 0.025-0.310 mM with response time 10 min. Furthermore, application of the system for the arginine detection in serum samples was also tested.

Arginase↗
PubMed1990

Intracellular vacuolization caused by the urease of Helicobacter pylori.

Tissue culture cells were exposed to supernatants of Helicobacter pylori for 24 h at 37 degrees C in the presence of various quantities of urea. In the normal human stomach the concentration of urea is less than or equal to 4 mmol/l, and in the presence of this low concentration up to 10% of Vero cells showed intracellular vacuolization. In the presence of 7.5 mmol/l urea, 25% of the cells showed vacuolization. With 30 mmol/l urea, the final pH was 7.6, indicating that vacuolization was not due to change of pH. The first report of vacuolization of tissue culture cells by H. pylori was in a system without added urea but with concentrated bacterial supernatant; 30% of H. pylori strains demonstrated a cytotoxic effect. In those experiments fetal calf serum was used; it contains 6 mmol/l urea but was used at a concentration of 10%. A urease inhibitor, acetohydroxamic acid, caused a 75% drop in the number of cells showing vacuolization, and ammonia caused vacuolization. Thus the urea of H. pylori probably causes this vacuolization.

Animals↗
PubMed1984

Effect of dietary nickel on growth, urease activity, blood parameters and tissue mineral concentrations in the neonatal pig.

Day-old pigs were individually fed a low nickel (0.16 ppm) liquid milk-based diet supplemented with either 0, 5 or 25 ppm nickel on a dry matter basis for a 21-day period. At the end of the liquid feeding period, five pigs per treatment were killed, and the remaining five were fed a dried skim milk-based diet (0.12 ppm nickel) with similar levels of added nickel for an additional 28 days. Dietary nickel did not affect animal gain, liver cholesterol, serum protein concentrations or bacterial urease activity in the gastrointestinal tract. The addition of 5 ppm nickel to the basal dry diet reduced ammonia concentrations in the cecum by 33%. Pigs receiving the high level of nickel had decreased serum alkaline phosphatase and increased serum glucose at 49 days, compared to controls. Animals receiving 5 ppm nickel had higher liver iron and zinc concentrations than controls at 21 days but not at 49 days. Control pigs had lower kidney and lung nickel concentrations than animals receiving 5 ppm nickel at 21 days but not at 49 days. Increasing dietary nickel from 5 to 25 ppm resulted in increased concentrations of nickel in serum, kidney, lung, spleen and muscle. These results suggest that 0.12-0.16 ppm nickel is adequate for growth of neonatal pigs fed milk-based diets. However, additional nickel may improve the iron and zinc status of the young pig.

Alkaline Phosphatase↗
PubMed1984

Amino acid sequence around a cysteine residue in the active center of jack bean urease.

Cysteine residues in the active center of jack bean urease [EC 3.5.1.5] were modified with 14C-labeled diazonium-1H-tetrazole (DHT). The labeled enzyme was carboxymethylated with iodoacetic acid, and then hydrolyzed with trypsin. The tryptic digest was subjected to gel filtration on Sephadex G-50, yielding two radioactive fractions. The [14C]DHT-labeled peptide having a lower molecular weight, which was determined to be approximately 1,000 by the method of gel filtration, was further purified to homogeneity by ion-exchange chromatography on DEAE-Sephadex A-25. [14C]DHT-labeled cysteine was identified as cysteic acid after performic acid oxidation, and the amino acid sequence of the low-molecular-weight [14C]DHT-labeled peptide was determined to be Phe-Glu-Pro-Gly-Asp-Cys-Asn-Ser-Thr-Phe-Lys.

Amino Acid Sequence↗