Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.3.4.6 (urease)
 7,490 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A strategy for the multifunctionalization of the FIA biosensor was developed. The described multifunctional FIA system offers a fast and simple method for the simultaneous determination of ammonia, creatinine, and urea. The hydrolysis of creatinine by creatinine deiminase (CRDI) or of urea by urease forms ammonia, which is amperometrically detected by an oxygen electrode, based on an enzyme conversion system, glutamate dehydrogenase (GLDH)/glutamate oxidase (GLOD). The split of the stream into three after sample injection and confluence before the GLDH reactor resulted in a three-channel system, into which were set three parallel columns, respectively, filled with immobilized CRDI, urease, and CPG. A triple-peak recording was obtained by putting two delay coils at the channels involving CRDI and urease. Thus the interfering of the endogenous ammonia on the creatinine and urea assay is simultaneously compensated. Furthermore, the problem of great difference in concentration between urea and the other two components is resolved by taking advantage of the differentiated dilution effect for each channel caused from the split-stream, flow-injection system. Linear calibration ranges for ammonia, creatinine, and urea were 0.1-5, 0.2-10, and 2-40 mM, respectively. One run was finished within 5 minutes, and the system was reproducibility good (3 to 5%). The results of the urine assay obtained by the present method will be described in the near future.
 ...
PMID:A multifunctional flow-injection biosensor for the simultaneous determination of ammonia, creatinine, and urea. 778 57

A new sensor for the on-line measurement of urea in the dialysate output is described. The sensor is based on a differential measurement of conductivity changes induced by the urease-catalyzed hydrolysis of urea. The use of screen printing for the batch-fabrication of the basic transducers results in cheap disposable devices. In addition, the sensor has been designed to fit into a standard male luer-adapter, and can be plugged directly into the dialysate line. The in vitro response is linear to urea concentrations exceeding 6620mM. A resolution of 20020 microM has been achieved with a baseline stability of 50 microM/hr. Interferences caused by fluctuations in the ionic strength and the consequent conductivity changes are effectively suppressed by the differential sensor pair. The efficiency of this suppression is expressed in a common mode rejection ratio of typically 40 to 50. Preliminary ex vivo results show the feasibility of the concept. The sensor principle is not restricted to urea but can be extended to other molecules of interest for hemodialysis monitoring, such as creatinine and L- and D-amino acids.
 ...
PMID:A disposable urea sensor for continuous monitoring of hemodialysis efficiency. 826 58

A two-step method for assaying creatinine in serum and urine samples, suitable with automated analyzers, is reported. Reagent 1, for the first step, contains a blanking system [creatine amidinohydrolase (CRTase), urease, glutamate dehydrogenase, NADPH, and 2-oxoglutarate] and a NADPH-regenerating system [Mg(2+)-dependent isocitrate dehydrogenase (ICD), MgCl2, and excess isocitrate]. Reagent 2, for the second step, contains the metal-chelating reagent trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid (CyDTA) and a trigger system [creatinine amidohydrolase (CRNase)]. When a specimen is mixed with reagent 1, all the creatine, urea, and NH3 present are removed by the blanking and NADPH systems. On adding reagent 2, CyDTA inactivates ICD to inhibit the NADPH system. Simultaneously, the creatinine (1 mol) in the specimen is hydrolyzed into creatine by CRNase, and then releases NADP+ (2 mol) through the blanking system. Our optimized method can determine creatinine linearly up to 500 mg/L, with within-day CVs < 1.2% and day-to-day CVs < 2.7%.
 ...
PMID:Enzymatic rate assay of creatinine in serum and urine. 840 98

The objective of the study was to evaluate the prevalence of Helicobacter pylori in patients with different degrees of renal function. Two hundred and twenty consecutive patients requiring gastroscopy for upper intestinal symptoms were enrolled in the study: group I (normal renal function, n = 127), group II (chronic renal failure, creatinine clearance > 5 < 90 ml/min, n = 59), and group III (hemodialysis therapy, n = 34). On endoscopy, biopsy specimens were taken for analysis of H. pylori infection by urease test and histology. The prevalence of H. pylori in patients with renal dysfunction proved to be significantly lower than that in patients with normal renal function (22.6% vs 37%, P < 0.05). The incidence of ulcer disease in patients with normal renal function was higher than that in uremic patients (14.2% vs 10.8%, not significant). These findings indicate that uremic patients seem to be partly protected against H. pylori infection.
 ...
PMID:Significantly lower prevalence of Helicobacter pylori in uremic patients than in patients with normal renal function. 857 29

The effect of aminoglycosides on renal function was evaluated in 30 full-term infants who were treated within 24 h of birth with either amikacin (10 infants, group A), gentamicin (9 infants, group B), or netilmicin (10 infants, group C). Renal function was assessed before, during, and 48 h after discontinuation of therapy by measuring the plasma creatinine concentration (PCr), the fractional excretion of sodium (FENa), potassium, magnesium, phosphate (FEP), uric acid, and the urinary excretion of calcium (UCA/UCr ratio) immediately before (trough) and after (peak) the infusion of the aminoglycosides. The results were compared with 10 control newborns who did not receive antibiotics. Significant alterations in renal function were observed only during therapy with gentamicin (group B). These consisted of a sustained elevation of FENa and UCa/UCr ratio throughout therapy, a latent increase in FEP on the 7th day (P < 0.05), and lack of the normal postnatal decline of PCr in 3 of 9 infants (P < 0.01). These abnormalities persisted up to 2 days after discontinuation of therapy. Therapeutic doses of gentamicin may result in significant electrolyte disturbances in sick full-term infants.
 ...
PMID:Effect of aminoglycoside therapy on renal function in full-term infants. 897 4

Electrochemical principle of ion-selective electrodes (ISEs) based on the ion-transfer reactions across a polarizable organic or oil/aqueous or water interface is described; the amperometric ISE and the potentiometric ISE are addressed. Electrochemical sensors and biosensors based on amperometric ISEs are discussed in some details. Amperometric sensors for monitoring ammonia (and other volatile amines) can be constructed on the basis of amperometric ammonium-ISE, where the pulse amperometric technique can successfully be employed. Urea and creatinine biosensors can also be fabricated by immobilizing urease or creatinine deiminase, respectively, on the surface of the amperometric ammonia sensor. Some favored characteristics of amperometric ISE-based sensors and biosensors are discussed with reference to the sensors and biosensors described.
 ...
PMID:Coupling of enzyme reactions to the charge transfer at the interface of two immiscible solvents. 900 14

Cis-urocanic acid (cis-UCA), a mediator of immunosuppression, is formed from trans-UCA upon UV-exposure of the skin. This study describes a liquid chromatographic method for the simultaneous quantification of cis- and trans-UCA in skin, urine and plasma of nonirradiated volunteers. It also describes cis- and trans-UCA kinetics in UV-irradiated volunteers. New procedures to remove interfering substances from urine and plasma are reported. Normal levels of cis-UCA in skin, urine and plasma of nonirradiated volunteers were 0.5 nmol/cm2, 0.03 mumol/mmol creatinine (median 0.00) and undetectable and those of trans-UCA were 17.1 nmol/cm2, 1.36 mumol/ mmol creatinine and 0.5 microM, respectively. Upon single total body UVB (290-320 nm) exposures of 250 J/m2, epidermal cis-UCA levels immediately reached a maximum and returned to basic levels 3 weeks later. The cis-UCA levels in urine reached a maximum in 5-12 h postirradiation and reached baseline values in 8-12 days. Additionally, a single total body UVA (320-400 nm) irradiation of 200 kJ/m2 yielded a similar pattern. The kinetics of cis-UCA in plasma could not be followed due to low concentrations; however, that of skin and urine was informative in relation to solar exposures and phototherapy.
 ...
PMID:Prolonged increase of cis-urocanic acid levels in human skin and urine after single total-body ultraviolet exposures. 907 46

The reference values of common blood chemistry analytes in healthy population, aged newborn to 80 years, of Rawalpindi Islamabad area were determined at AFIP, Rawalpindi. A total of 2115 healthy subjects, 1206 males and 909 females, were included in the study. Plasma glucose was analysed by GOD/POD, serum cholesterol by CHOD/PAP, triglycerides by GPO/PAP, urea by urease/GLDH, creatinine by Jaffe' rate reaction, uric acid by uricase, total bilirubin by Jendrassik and Grof, total protein by biuret, alanine transaminase (ALT) by optimized IFCC and alkaline phosphatase (AP) by optimized DGKC method. The between batch CVs of all the parameters were within acceptable quality goals. The reference values were calculated using 2.5 and 97.5 percentiles as lower and upper limits (95% CI). In healthy adult males the reference values were: fasting plasma glucose, 3.6-6.0 mmol/l; serum cholesterol; 3.2-6.6 mmol/l; triglycerides, 0.6-2.3 mmol/l; urea, 2.8-6.4 mmol/l; creatinine, 65-132 umol/l; uric acid, 164-430 umol/l; total bilirubin, 5-18 umol/l; total protein, 57-83 g/l; ALT, 15-45 U/l and AP, 185-620 U/l. The values in adult females, children and elderly subjects were slightly different than adult males. The reference values of our population show mild to moderate differences from the other Asian, European and American populations. It is recommended that reference values of different biochemical investigations should be established in various areas of Pakistan to make appropriate use of such investigations.
 ...
PMID:Reference values of common blood chemistry analytes in healthy population of Rawalpindi-Islamabad area. 930 Nov 67

The construction and evaluation of an automated urea and creatinine biparametric biosystem using flow injection analysis (FIA) are described. The biosystem uses enzyme reactions that hydrolyse urea and creatinine producing ammonium ions. The enzymes used were creatinine deiminase and urease, which are immobilized covalently in flow reactors. The reactor with creatinine deiminase has the enzyme immobilized on controlled-pore glass beads, whereas urease is immobilized on a nylon open tubular reactor. Detection is realised with a flow-through ammonium ion-selective electrode with an inner solid-state contact (graphite-epoxy composite). Ammonium ions are separated from alkali ion interferents through a gas-diffusion cell. The bioanalyser is fully automated using software and electronics developed ex profeso in our laboratories. The analyser was validated off-line by measuring urea and creatinine from discrete effluent samples from hemodialysis equipment. Results agreed with concurrent analyses realised using hospital laboratory methods. There were no significant differences between the two sets of results at the 95% confidence level. Finally, the biparametric bioanalyser was validated on-line by measuring creatinine and urea levels in artificial kidney effluents. These measurements were useful in the determination of key biochemical parameters of clinical interest such as the mass of urea and creatinine extracted from the patient as well as the initial concentration of creatinine and urea in blood plasma. When the results of the bioanalyser were compared with those yielded by the usual methods, they showed no significant differences at the 95% confidence level when determining the mass of the analytes extracted by the hemodialyser or when determining the urea concentration in blood plasma. However, when measuring the creatinine concentration in blood plasma using the developed bioanalyser, significant differences appeared.
 ...
PMID:Development of a biparametric bioanalyser for creatinine and urea. Validation of the determination of biochemical parameters associated with hemodialysis. 976 11

The abilities of different types of organosilanes, in particular of polymers with: 1) completely or 2) partially hydrophobical surfaces; 3) regular changes of part of silicium ions by metal ions; 4) preliminary aminosilanization were studied for sorption of ammonia ions, urea, cholesterol, creatinine, albumin, IgG, haemoglobin and myoglobin. Polymethylsiloxane was used as haemosorbent for directed sorption of myoglobin and haemoglobin from solution and blood. It didn't hemolysate red cells. The high efficiency of those organosilanes for sorption of haemoproteins it was shown. Organosilanes were very good as membrane for immobilization of urease and IgG-specific antibodies to create enzyme sensor and immunosensor based on the ionsensitive field effect transistors. The advantages and possibilities of organosilane usage as haemosorbents in the field of medicine of catastrophes as well as for sensor technology are discussed.
 ...
PMID:[Study of sorption properties of organosilanes to be used as the basis for hemosorbents and diagnostic enzyme and immunosensors]. 984 81


<< Previous 1 2 3 4 5 Next >>