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At least 973 records · Page 54Linked to original sources
PubMed1999

[Evaluation of a fast urease test for the detection of Helicobacter pylori].

Helicobacter Pylori colonize the gastric mucosa and their adaptation to this environment is related with its high activity urease. This enzyme hydrolyzes the gastric urea, neutralizing the acid environment of the bacteria. Based on that reaction numerous presumptive diagnosis tests, have been developed using a solution of urea (usually 6%) with a pH indicator (usually 0.05% fenol-red); nevertheless, the color changes are so light that some persons do not detect it. For that reason, a modification of that reaction was proposed using a mix of pH indicators (0.05% fenolred and 0.002 bromothymol blue) which induces a color change from light green to deep purple. Also, the reaction of urease was evaluated using only bromothymol blue. The reaction using fenol red as indicator showed the higher values for sensitivity of 58.8% and the specificity of 66.6%; whereas using only bromothymol-blue those values were 46 y 71.4% respectively. The efficiency of the test using fenol-red or the mix of this bromothymol- was 64.2 y 62.2%, respectively; however, the mix of indicators induce a change color easily detected, because of changes from ligh-green to deep-purple.

Bromthymol Blue↗
PubMed2000

Selection of putative immunogenic peptides by molecular modelling of the urease of Helicobacter pylori.

Computational methods such as molecular modelling are becoming an increasingly useful means of rationalising experimental data and creating a hypothesis that can suggest new experiments. In this report we discuss the application of molecular modelling methods to aid the selection of feasible peptide epitopes of the urease enzyme from Helicobacter pylori, an important vaccine candidate. Surface exposure was chosen as a criterion for the selection of three peptides which each had different levels of accessibility according to the 3D model. Antibodies raised against these peptides were analysed for their immunoreactivity with the holo enzyme. Only one anti-peptide antibody showed good reactivity with the urease. Our findings emphasise that surface exposure of peptide is not the only important criterion for the selection of immunogenic peptides.

Enzyme-Linked Immunosorbent Assay↗
PubMed2001

[Ureasic activity in soy products. Proposal of a new method].

The evaluation of residual ureasic activity in soy products is usually employed as an indicator of the efficiency of the inhibition treatments. The purpose of this study is to compare the AACC method (22-90), based on differences of pH, with an assay where ureasic activity is measured by its hydrolytic action on urea and quantification of the ammonium produced with Berthelot reaction. Twenty different samples of soy bean flour with and without thermal inactivation treatments were assessed with the two methods. The new method has a good correlation with that of the AACC--r = 0.9416 (p < 0.0001). It also presents a better specificity because it measures the concentration of the reaction product and shows a more amplified answer than the increase of pH.

Flour↗
PubMed1975

Interpretation of the kinetics of consecutive enzyme-catalyzed reactions. Studies on the arginase-urease system.

Physiocochemical properties of beef liver arginase are reported, particular attention being given to its state of aggregation in the concentration range encountered in enzymic assays. It is shown that a species of molecular weight 114,000 is the operational kinetic unit. Evidence is also provided that arginase does not associate heterogeneously with urease, and therefore, in the absence of macromolecular interactions, the arginase-urease couple provides a suitable experimental system to test the applicability of theory previously developed to guide the interpretation of coupled assay results. Application of the theory led to values of the Michaelis constant and maximal velocity describing the first reaction in the sequence, catalyzed by arginase, which agreed within experimental error with the corresponding values obtained by studying the arginase-catalyzed reaction alone. Comment is also made on the product inhibition of arginase by ornithine, which must be considered in the comparison of experimental results describing the time course of a coupled assay with theoretical solutions obtained by numerical integration.

Animals↗
PubMed2002

Evaluation of a locally-made urease test for detecting Helicobacter pylori infection.

We studied the efficacy of a home-made urease test (HUT) in the detection of Helicobacter pylori (HP) infection in patients undergoing upper gastrointestinal endoscopy. In the first phase of the study, two antral biopsies each were obtained from 43 patients for urease tests using the CLOtest and a home-made buffered 2% urea solution with phenol red as indicator at pH 6.8 (2% HUT). Twenty-six patients (60.5%) were HP positive, both by the 2% HUT and CLOtest with 100% concordance. In the second phase of the study three antral biopsies each and blood were obtained from 42 patients for the determination of HP status using a 10% HUT and a combination of culture and serology. Twenty-three patients (54.8%) were HP positive using the 10% HUT, while 32 patients (76.2%) were positive using the combination of 2 tests. Compared to this the sensitivity and specificity of the 10% HUT were 72% and 100% respectively. The CLOtest produced a colour change in a shorter time than the 2% and 10% HUT (median 1 hour versus 10 hours versus 16 hours p < 0.0001). In the third phase of the study, we observed that by doubling the biopsy size, the time required to obtain a colour change was significantly reduced (median 4.5 hours versus 10 hours p < 0.05). The HUT is easy to prepare, cheap, sufficiently sensitive and it is reliable enough to start treatment when positive. With 100% concordance and 1% the cost per test when compared to the commercially available CLOtest; the 10% HUT is hereby recommended for the detection of UP infection in our region.

Adult↗
PubMed1979

[Evaluation of urease and beta-glucosidase activity for the practical identification of mycobacteria (author's transl)].

The urease and the beta-glucosidase for the identification of the mycobacteria were evaluated using 1,019 strains received for reference purposes in this laboratory in 1978. We found that the urease test was useful in the differential identification of BCG which, contrary to Mycobacterium bovis, gave a strong positive reaction in 3 h. The test was also useful to discriminate M. scrofulaceum from pigmented strains of M. avium. The beta-glucosidase test discriminated between M. tuberculosis and M. bovis and was useful to distinguish the niacine-positive strains of M. africanum which were usually negative in this test. The beta-glucosidase test was particularly useful in the differential identification of M. fortuitum and M. chelonei. In this report, the frequency distribution of the species which were submitted to this laboratory in 1978 was also shown and the results obtained for each of the conventional test procedures was presented.

Glucosidases↗
PubMed2002

The effect of blood on rapid urease test for Helicobacter pylori detection: an in vitro study.

The sensitivity of rapid urease test (RUT) for detecting Helicobacter pylori (H. pylori) is limited in patients presented with bleeding peptic ulcers. Blood contents are potentially responsible for the lack of sensitivity of RUT in patients with upper gastrointestinal bleeding. This study was designed to determine the efficacy of RUT in detecting H. pylori when exposed to the patients' own blood at varying durations. Four gastric antral biopsy specimens were collected from dyspeptic patients who underwent gastroscopic examination. The first specimen was immediately placed into the urea broth as the control group. The second, third and fourth specimens were immersed in the patients' own blood for one, two and four hours respectively before testing for the RUT. The results of these RUT were compared to those of the control group. Gastric antral biopsy specimens tested with the RUT of twenty patients were evaluated in this study. The 1-hour RUT and 2-hour RUT was not significantly different in sensitivity (92.31% vs 100%: p>0.05, 84.62% vs 100%: p>0.05 respectively) and accuracy (95.0% vs 100%: p>0.05, 90.0% vs 100%: p>0.05 respectively) compared to the unexposed blood RUT for H. pylori diagnosis. However, the study demonstrated that the 4-hour RUT had significantly lower sensitivity (53.85% vs 100%: p<0.05) and accuracy (70.00% vs 100%: p<0.05) than that of the unexposed blood RUT for H. pylori diagnosis. It is concluded that exposure of gastric biopsy specimens to their own blood for four hours significantly decreased the sensitivity of the biopsy rapid urease test for H. pylori detection.

Biopsy, Needle↗
PubMed2002

[Effect of elevated atmospheric CO2 on soil urease and phosphatase activities].

The response of soil urease and phosphatase activities at different rice growth stages to free air CO2 enrichment (FACE) was studied. The results showed that comparing with the ambient atmospheric CO2 concentration (370 mumol.mol-1), FACE (570 mumol.mol-1) significantly increased the urease activity of 0-5 cm soil layer at the vigorous growth stage of rice, whole that of 5-10 cm layer had no significant change during the whole growing season. Phosphatase activity of 0-5 cm and 5-10 cm soil layers significantly increased, and the peak increment was at the vigorous growth stage of rice.

Air↗
PubMed1992

[Diagnosis of Helicobacter pylori infection. Rapid urease test, microscopy of smears and culture from ventricular biopsy compared with the 14C-urea breath test].

By employing the 14C-urea breath test as the reference method we determined the specificity and sensitivity of three bioptic methods for diagnosis of Helicobacter pylori infection in 103 subjects. All biopsy specimens were obtained from the gastric antrum. For culture the specificity was 100%. Its applicability was reduced, however, by a low sensitivity (73.8%) and a delay of several days before the final result was available. Microscopy of Loeffler-stained biopsy smears yielded a specificity of 100% and a sensitivity of 92.9%, but the method was regarded time-consuming. The rapid urease test yielded a specificity of 98.4% and a sensitivity of 85.7%. Being quick, simple and inexpensive the rapid urease test is well suited for routine use in gastroscopy.

Bacteriological Techniques↗
PubMed2004

[The reaction mechanism of metolachlor and S-isomer with urease].

The binding of metolachlor and S-Isomer to urease in aqueous solution was studied using UV difference spectrum and fluorescence spectrum. According to the results of the UV difference spectrum curve, the UV difference adsorption deltaA changed rapidly when herbicide concentration increased from 0.0 to 1.6 micromol x L(-1) x UV difference spectra were red-shifted and absorb-peaks became lower. It was shown that herbicide can quench the urease fluorescence mainly through a static quenching procedure. The binding constant K and the number of binding site n were calculated according to the fluorescence quenching results. For metolachlor, K = 1.49 x 10(3) L x mol(-1) and n was 0.84; for S-isomer, K=2.22 x 10(3) L x mol(-1) and n was 0.89.

Acetamides↗
PubMedDate not supplied

[Quantitative urease test for Helicobacter pylori infection in patients with gastric and duodenal ulcer].

The monitoring for the presence of H. pylori carrier state in a group of patients with gastric and duodenal ulcer was carried out with subsequent determination of the relationship between the intensity of the urease activity of the bioptic specimen of the mucous membrane and the severity of the course of the disease. For this purpose we developed the scheme for the evaluation of the severity of the disease with quantitative criteria. The data obtained in this work showed no correlation between the severity of this disease and usease activity. Still the method of the quantitative determination of the urease activity of the bioptic specimen made it possible to evaluate the rate of the production of hydroxyl anions by a given H. pylori strain and thus quickly establish the presence of carrier state.

Adolescent↗
PubMed2005

[Study on the reaction mechanism of chloroacetanilide herbicides with urease using fluorescence spectrum and high-performance liquid chromatography].

The relationship between excess thermodynamic function and binding to urease of four chloroacetanilide herbicides was studied using high-performance liquid chromatography and fluorescence spectrum. The linear relationship between the composition of mobile phase of RP-HPLC and the capacity factor of chloroacetanilide herbicides has been obtained. The excess thermodynamic enthalpy (deltaH* ) of acetochlor, pretilachlor, butachlor and metolachlor was determined, and the binding constant K and the number of binding sites with urease were calculated. The relationship between excess thermodynamic function and the binding constant K was suggested.

Acetamides↗
PubMed2005

Comparison of 13C- urea blood test to 13C-breath test and rapid urease test for the diagnosis of Helicobacter pylori infection.

At present, the available methods to diagnose active H. pylori infection are endoscopy with biopsy for histology, culture, rapid urease tests, 13C or 14C urea breath test, urine antibody and the stool antigen test. The aims of this study were to simplify the 13C urea test by measuring 13C in blood rather than breath, and to evaluate the usefulness of the 13C urea blood test for the diagnosis of H. pylori infection. Patients who underwent upper endoscopy for standard clinical indications (e.g. dyspepsia, abdominal pain) were enrolled. A total of 161 patients (93F, 68M, mean age 47 +/- 14.2) were evaluated; 50 (31%) of them were H. pylori positive, and 111(69%) were H. pylori negative. H. pylori infection was diagnosed with a rapid urease test (CLO-test) and 13C urea breath test (UBT). Performance characteristics for the 13C urea blood test for diagnosis and evaluation of H. pylori eradication were calculated using UBT and CLO as gold standards. The fifty H. pylori-positive patients were treated with triple antibiotic therapy for two weeks. Four weeks after finishing antibiotic therapy patients were retested with a commercial UBT and urea blood test. The 13C blood test had sensitivities of 92 and 98% and specificities of 96 and 100% as compared with urea breath test and CLO, respectively. We conclude that the 13C urea blood test is highly sensitive and specific for the initial diagnosis and control of eradication of H. pylori infection.

Adolescent↗
PubMed1991

[ELISA for detection of anti-urease antibodies of Campylobacter pylori and its application].

The urease extracted from 6 strains of Helicobacter pylori (HP) was used as antigen to detect sera anti-urease antibodies of HP in 136 patients with gastric diseases and 13 persons with normal gastric mucosa by enzyme-linked immunosorbent assay (ELISA). The antigen proved to be pure and specific for ELISA. For a titre of 450EU or over 450EU the test had a sensitivity of 91.96% and a specificity of 86.49%. The results of the ELISA showed excellent correlation with microbiological detection of HP and histological examination of the antrum. The level of sera antibody showed a relation to the bacterial amount of HP in gastric mucosa, but no connection with the severity of gastritis. While ELISA may be effective for the serodiagnosis of HP infection and is able to distinguish patients with normal antrum mucosa from those with gastritis. The test does not help to distinguish those with antrum gastritis from those with peptic ulcer. It also provides a reliable method for epidemiological investigation of HP infection.

Adolescent↗
PubMed1977

[Assay of aminoglycosides in serum using the urease method (author's transl)].

The urease method developed by Noone et al. for rapid bioassay of aminoglycoside antibiotics in serum is described in detail. The accuracy of the method was improved by using a BM 1-09 electrode assembly (Metrohm, CH-9100 Herisau, Switzerland) in conjunction with a digital pH-Meter (Metrohm E 500). The mean difference between spiked serum samples and measured concentrations was +0.37 +/-0.78 microgram/ml. The coefficient of determination between the urease and agar diffusion method was 0.94. Disadvantages of the method are a low sensitivity at concentrations below 1.5 microgram/ml and a large serum sample (1.5 ml). Advantages are its simplicity and rapidity.

Aminoglycosides↗
PubMed1990

Relative merits of various rapid biopsy urease tests for diagnosis of Helicobacter pylori (Campylobacter pylori).

Three rapid urease tests, i.e., liquid urea broth containing phenol red as indicator, liquid urea broth containing bromothymol blue as indicator and CLO gel were compared in 109 patients of dyspepsia for the diagnosis of Campylobacter pylori (Helicobacter pylori) infection. Mean time taken for positive reaction in liquid broth with phenol was 3 minutes (range 0.6 to 5.3 minutes) with bromothymol blue was 3.5 minutes (range 0.4 to 5.5 minutes) while with CLO gel it was 101 minutes (range 11-261 minutes). There was no difference in results of liquid urea broth containing phenol red and bromothymol blue. The difference in timing of urea broth containing phenol red and bromothymol blue was statistically significant as compared to CLO gel (p less than 0.05). Rapid urease tests employing liquid urea broth are quick, simple and reliable for the diagnosis of Helicobacer pylori infection.

Adolescent↗
PubMed1987

Campylobacter pyloridis gastritis I: Detection of urease as a marker of bacterial colonization and gastritis.

A method to detect the presence of Campylobacter pyloridis in dyspeptic patients is described. The test procedure involves placing a gastric pinch biopsy into a small amount of a solution containing urea and a pH indicator in the well of a microtiter tray. The method depends on the ability of C. pyloridis to hydrolyse urea and release an alkaline product (ammonia). The "microtiter biopsy urease test" is 100% specific for C. pyloridis and has a 91% sensitivity after 18 h reaction time. Seventy-five percent of positive biopsies had a reaction time of less than 1 h. The test may be used to predict the presence of antral gastritis; as well as marking the presence of the bacterium; with a positive predictive value of 96% and a negative predictive value of 73%. There was a positive correlation between the biopsy urease test results and the grades of both chronic and active antral gastritis. This test is simple and can be performed in the endoscopy clinic as the formulation of the reagent obviates the need for aseptic techniques.

Ammonia↗