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Creatinine, urea, uric acid, water and electrolytes renal handling in the healthy oldest old  

PubMed Central

Renal physiology in the healthy oldest old has the following characteristics, in comparison with the renal physiology in the young: a reduced creatinine clearance, tubular pattern of creatinine back-filtration, preserved proximal tubule sodium reabsorption and uric acid secretion, reduced sodium reabsorption in the thick ascending loop of Henle, reduced free water clearance, increased urea excretion, presence of medulla hypotonicity, reduced urinary dilution and concentration capabilities, and finally a reduced collecting tubules response to furosemide which expresses a reduced potassium excretion in this segment due to a sort of aldosterone resistance. All physiological changes of the aged kidney are the same in both genders.

Musso, Carlos Guido; Alvarez Gregori, Joaquin; Jauregui, Jose Ricardo; Macias Nunez, Juan Florencio



Plasma urea, creatinine and uric acid concentrations in relation to feeding in peregrine falcons (Falco peregrinus)  

Microsoft Academic Search

Significant post?prandial increases in plasma uric acid and plasma urea concentrations were observed in peregrine falcons. Post?prandial uric acid concentrations were similar to those in birds suffering from hyperuricaemia and gout and were well above the theoretical limit of solubility of sodium urate in plasma. It is not clear why under normal circumstances no urate deposits occur in peregrine falcons

J. T. Lumeij; J. D. Remple



Urea, creatinine, uric acid, and phosphate spaces and their relationship to total body water during chronic hemodialysis  

SciTech Connect

The authors determined total body water (TBW) with tritium in 11 patients on chronic hemodialysis and compared this space to that estimated by 60% of body weight, and removal spaces of urea, creatinine, uric acid, and phosphate (PO4). The latter spaces were determined by dividing the total amount of substance (measured in total dialysate) by pre- minus post-dialysis concentrations. Body water X 0.6 was more than 10% less than the tritium space, and showed a maximal variation of 10 liters, or 24%. The removal space of urea was 80% of the tritium space, but correlated closely with it. The difference between total body water and urea removal space was variable and dependent on fluid excess (edema) in the patients. Creatinine, uric acid, and phosphate removal spaces were highly variable and not correlated to total body water. The authors suggest that actual measured TBW should be used, rather than estimations using BW X 0.6, for V in K X T/V, where K = clearance, T = duration of dialysis, and V = the removal space of urea. Furthermore, one may need to introduce a correction factor for urea removal space over TBW in the equation to allow better quantification of dialysis in edematous patients and during very fast dialyses.

Ericsson, F.; Odar-Cederloef, I.E.; Eriksson, C.G.; Lindgren, S.; Kjellstrand, C.M.



Effect of Kapalabhati on blood urea, creatinine and tyrosine.  


The present study conducted on twelve normal healthy male subjects showed decrease in blood urea, increase in creatinine and tyrosine after one minute of Kapalabhati, a fast-breathing technique of Hatha Yoga (120 respiratory strokes (min.). From biochemical point of view the practice of Kapalabhati seems to promote decarboxylation and oxidation mechanisms due to which quieting of respiratory centres is achieved, which is also the prerequisite for the practice of Pranayama, another important technique of Yoga. PMID:2399804

Desai, B P; Gharote, M L



Qualitative and quantitative analysis of uric acid, creatine and creatinine together with carbohydrates in biological material by HPTLC  

Microsoft Academic Search

Summary  In clinical diagnosis creatine, creatinine and uric acid are important parameters for the evaluation of renal diseases, and\\u000a are partially responsible for gout and the formation of renal calculi. The determination of various carbohydrates, especially\\u000a glucose, in urine and serum serves as an indicator of diabetes and other carbohydrate anomalies. A simple, rapid and economic\\u000a method for the simultaneous screening

R. Klausl; W. Fischer; H. E. Hauck



High versus low protein diets to mink--postprandial plasma urea and creatinine response, osmotic load and pattern of nitrogen and electrolyte excretion.  


Nitrogen balance, pattern of excretion of nitrogenous end-products, endogenous urinary N excretion, postprandial plasma urea and creatinine, osmotic load, urinary electrolyte excretion and water intake/output relationships were studied in 12 adult female mink fed a high protein diet (HP; n = 6) providing about 155 g protein/kg or a low protein diet (LP; n = 6) providing about 95 g protein/kg. Two balance periods of each 3 d were used and diets were fed raw or cooked. After the last balance period followed a 48 h fasting period. Postprandial plasma urea and creatinine were studied for 48 h following a test meal given after an overnight fast. Osmotic load was determined based on collection of non-acidified urine carried out during 48 h. Level of protein supply did not affect N balance, being close to zero, whereas slightly negative balances were achieved for fasting animals. Protein supply was clearly reflected in excretion of urinary urea and allantoin but not in creatinine and uric acid. Endogenous urinary N excretion was estimated by a second order regression equation giving an intercept of 280 mg/kg0.75. Post-prandial plasma urea concentrations were strongly influenced by protein supply, HP animals having substantially higher peaks than LP animals, but values returned to fasting values within 24 h after the test meal. Plasma creatinine followed a biphasic pattern with a peak about 2 h after feeding and a nadir approximately 6 h after feeding. Physical form of diet influenced postprandial urea, animals fed raw diets having a higher peak, but not creatinine. The HP diet provided almost the double osmotic load of the LP diet and a corresponding increase in urine volume. The resulting water balances were identical irrespective of diet, showing that water intake/output relationships are very accurately regulated. PMID:11851022

Tauson, A H; Hansen, N E; Wamberg, S



Gender, Degree of Obesity, and Discrepancy Between Urea and Creatinine Clearance in Peritoneal Dialysis  

Microsoft Academic Search

The effect of gender and degree of obesity on the size indicators V. used to normalize urea clearance (Kt\\/Vur), and body surface area (BSA), used to normalize creatinine clear- ance (Ccr), in pcnitoncab dialysis was studied by: (1) mathe- matical comparison of the formulae used to estimate V (Watson and Hume) with the Dubois formula used to estimate BSA in



Adaptive Bayesian Approach to Clinical Trial Renal Impairment Biomarker Signal from Urea and Creatinine  

PubMed Central

A major concern with the identification of renal toxicity using the traditional biomarkers, urea and creatinine, is that toxicity signal definitions are not sensitive to medically important changes in these biomarkers. Traditional renal signal definitions for urea and creatinine have not adequately identified drugs that have generated important medical issues later in development. Here, two clinical trial databases with a posteriori known drug induced renal impairment were analyzed for the presence of a renal impairment biomarker signal from urea (590 patients; age 26-92, median 65) and creatinine (532 patients; age 26-97, median 65). Data was analyzed retrospectively using multiple definitions for the biomarker signal to include values outside stratified reference intervals, values exceeding twofold increases from baseline, values classified by the 2009 NIAID renal toxicity table, change from baseline represented as a Z-score based on intra-individual biological variations, and an adaptive Bayesian methodology that generalizes population- with individual-based methods for evaluating a biomarker signal. The data demonstrated that the adaptive Bayesian methodology generated a prominent drug induced signal for renal impairment at the first visit after drug administration. The signal was directly related to dose and time of drug administration. All other data analysis methods produced none or significantly weaker signals than the adaptive Bayesian approach. Interestingly, serum creatinine and urea are able to detect early kidney dysfunction when the biomarker signal is personalized.

Sottas, Pierre-Edouard; Kapke, Gordon F.; Leroux, Jean-Marc



The effects of a probiotic on blood urea nitrogen and creatinine concentrations in large felids.  


Chronic kidney disease is a common finding in older captive exotic felids. The purpose of this study was to evaluate the effectiveness of a probiotic to reduce blood urea nitrogen and creatinine in large felids. Fifteen adult, large felids (6 tigers [Panthera tigris], 5 lions [Panthera leo], 3 cougars [Puma concolor], and 1 leopard [Panthera pardus]) were administered a probiotic twice daily after a baseline complete blood cell count and plasma chemistry panel was obtained. Plasma chemistry values were rechecked at 2 mo (n = 14) and 6 mo (n = 9). There was no significant change in blood urea nitrogen over time; however, there was a significant change in creatinine over time (P = 0.04). Creatinine concentration decreased significantly between 2 and 6 mo (P = 0.02), and a decrease was seen between 0 and 6 mo, but this change was not significant (P = 0.05). There was no significant difference noted for creatinine concentration between 0 and 2 mo (P = 0.35). This probiotic may be helpful in large felids with elevated creatinine concentrations because of chronic kidney disease; however, further studies are warranted. PMID:22950314

McCain, Stephanie; Allender, Matthew C; Schumacher, Juergen; Ramsay, Edward



Creatinine, blood urea nitrogen and thyroid hormone levels before and after haemodialysis.  


A study was carried out on 57 patients with chronic renal failure in a hospital in Kerman city, Islamic Republic of Iran. Blood samples were taken before and after haemodialysis to measure blood urea nitrogen and serum creatinine, triiodothyronine (T3) and thyroxine (T4) levels. Findings revealed that before dialysis T4 in 11 cases and T3 in 29 cases were lower than the normal range, but after haemodialysis only 3 cases for T4 and 15 cases for T3 were lower than normal levels. The remaining cases reverted to normal state. We suggest that a feedback relationship exists between the major end catabolic products (creatinine and blood urea nitrogen) and thyroid hormone serum levels. PMID:17037243

Shamsadini, S; Darvish-Moghaddam, S; Abdollahi, H; Fekri, A R; Ebrahimi, H A


Development of a biparametric bioanalyser for creatinine and urea. Validation of the determination of biochemical parameters associated with hemodialysis.  


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:9764511

Jurkiewicz, M; Alegret, S; Almirall, J; García, M; Fàbregas, E



Changes in Serum Electrolytes, Urea, and Creatinine in Aloe Vera-treated Rats  

PubMed Central

This study was carried out to investigate the effect of Aloe vera extract (AvE) on serum electrolytes, urea, and creatinine as indices of renal function in Sprague-Dawley rats. Twelve male Sprague-Dawley rats weighing between 80 and 130 g were used. Rats were divided into two groups: The control and the test groups (n=6). The test group received 1 ml of AvE daily for 28 days. Both the groups fed on standard rat chow and water ad libitum. The results showed a decrease in serum levels of sodium, and potassium, but an increase in the serum levels of bicarbonate, urea, and creatinine in the test group. The changes seen were, however, statistically insignificant, except for the serum levels of sodium and creatinine (P<0.05). It is thus concluded that AvE impairs renal handling of electrolytes with consequent hyponatremia and hypercreatinemia. However, this might be of therapeutic value in conditions associated with hypernatremia.

Saka, WA; Akhigbe, RE; Popoola, OT; Oyekunle, OS



Changes in Serum Electrolytes, Urea, and Creatinine in Aloe Vera-treated Rats.  


This study was carried out to investigate the effect of Aloe vera extract (AvE) on serum electrolytes, urea, and creatinine as indices of renal function in Sprague-Dawley rats. Twelve male Sprague-Dawley rats weighing between 80 and 130 g were used. Rats were divided into two groups: The control and the test groups (n=6). The test group received 1 ml of AvE daily for 28 days. Both the groups fed on standard rat chow and water ad libitum. The results showed a decrease in serum levels of sodium, and potassium, but an increase in the serum levels of bicarbonate, urea, and creatinine in the test group. The changes seen were, however, statistically insignificant, except for the serum levels of sodium and creatinine (P<0.05). It is thus concluded that AvE impairs renal handling of electrolytes with consequent hyponatremia and hypercreatinemia. However, this might be of therapeutic value in conditions associated with hypernatremia. PMID:22754258

Saka, Wa; Akhigbe, Re; Popoola, Ot; Oyekunle, Os



Estimation of amino acids, urea and uric acid in tasar silkworm, Antheraea mylitta Drury.  


The tasar silkworm, Antheraea mylitta Drury, Andhra local ecorace is an exclusive race of Andhra Pradesh. It is on the verge of extinction due to difficulty of acclimatisation at breeding and rearing stages. As an attempt to protect this race, a method of total indoor rearing has been done. In this context, the estimation of free amino acids, excretory products- urea and uric acid were compared during the fourth and fifth instars of tasar silkworm, reared under outdoor and indoor conditions. The study has revealed that amino acids decreased in the fat body in outdoor and indoor reared larvae in contrast to that in the haemolymph where it has gradually increased from first to third crops. This is an important finding as it reveals that indoor worms seem to adopt proteolytic activity in the haemolymph. Secondly, in the fifth instar the excretory products are more compared to fourth instar in the indoor reared worms. During fifth instar, formation of nitrogenous products lessens as silk synthesis enhances. The present study reveals that decrease in uric acid in fifth instar implies increase in growth rate and silk synthesis in both outdoor and indoor worms. The findings of the present investigation is helpful in the conservation and protection of the A. mylitta, Andhra local ecorace. PMID:19297987

Shamitha, G; Rao, A Purushotham



Microchip capillary electrophoresis with electrochemical detector for precolumn enzymatic analysis of glucose, creatinine, uric acid and ascorbic acid in urine and serum  

Microsoft Academic Search

An integrated multiple-enzymatic assay was performed on a (microchip capillary electrophoresis) ?CE–EC chip capable of precise intake of sample or reagents in nanoliters. Incorporating multiple-enzyme assay into the ?CE chip is relatively new—rendering simultaneous analysis of creatinine and uric acid a snap.Added to the list of merits in this study are the enhanced sensitivity down to 1?M and a broader

Hui-Ling Lee; Show-Chuen Chen



[Simultaneous determination of creatinine, pseudouridine and uric acid in serum and urine by high performance liquid chromatography].  


In this paper a sensitive, rapid and simple HPLC method for the simultaneous determination of creatinine (Cr), pseudouridine (Pu) and uric acid(UA) has been established. We have evaluated clinical value of the method in the early diagnosis of diabetic nephropathy (DN). Separation was obtained using Shim-pack CLC-ODS 15 x 0.6 cm column and mobile phase of buffer solution of phosphate (pH 3.0, 0.02 mol/L) with flow rate of 1 mL/min. Detection was performed with UV detector at an automatic adjustment of wavelength. The recoveries of Cr, Pu and UA were 101.4%, 104.9% and 105.0% respectively. The calibration curves were linear within the concentration range of 8.6-274.6 mumol/L for Cr, 0.72-22.93 mumol/L for Pu and 19.1-612.7 mumol/L for UA (n = 6, r > 0.999, p < 0.01). The CV for within day and between day measurements were < 2.5% and < 5.0% respectively. In addition, Pu, Cr and UA were simultaneously determined in serum and urine of 39 patients with diabetic mellitus (DM). 15 patients with nephrotic syndrome (NS) and 53 normal subjects by the method. Results include: 1. the levels of serum Pu in all DM patients (100%) with microalbuminuria (MiAU) and macroalbuminuria (MaAU) were greater than maximum of normal subjects (X + 2S). In addition, in 9 DM patients (41%) with normal albuminuria (NAU) the levels were also greater than the maximum. 2. In patients with DM, there was no correlation between the serum Pu and the urinary albumin excretion (UAE), whereas the serum Pu correlated closely with the serum Cr. However, the incidence for serum Pu increase was significantly greater in patients. 3. The levels of serum Pu in patients with NS were greater than those in control subjects and patients with DM. Conclusion is that the determination of serum Pu could be used as sensitivity index for the early diagnosis of DN. PMID:11326982

Peng, Z; Wang, C; Li, C; Gao, Q; Wang, Z; Zhang, G; Zhang, J; Li, X; Peng, J



Differences in Blood Urea and Creatinine Concentrations in Earthed and Unearthed Subjects during Cycling Exercise and Recovery  

PubMed Central

Contact of humans with the earth, either directly (e.g., with bare feet) or using a metal conductor, changes their biochemical parameters. The effects of earthing during physical exercise are unknown. This study was carried out to evaluate selected biochemical parameters in subjects who were earthed during cycling. In a double-blind, crossover study, 42 participants were divided into two groups and earthed during exercise and recovery. One group was earthed in the first week during 30 minutes of cycling exercise and during recovery, and a second group was earthed in the second week. A double-blind technique was applied. Blood samples were obtained before each training session, after 15 and 30 minutes of exercise, and after 40 minutes of recovery. Significantly lower blood urea levels were observed in subjects earthed during exercise and relaxation. These significant differences were noted in both groups earthed at the beginning of exercise (P < 0.0001), after 15 (P < 0.0001) and 30 minutes (P < 0.0001) of exercise, and after 40 minutes of relaxation (P < 0.0001). Creatinine concentrations in earthed subjects during exercise were unchanged. Conclusions. Earthing during exercise lowers blood urea concentrations and may inhibit hepatic protein catabolism or increase renal urea excretion. Exertion under earthing may result in a positive protein balance.

Sokal, Pawel; Jastrzebski, Zbigniew; Jaskulska, Ewelina; Sokal, Karol; Jastrzebska, Maria; Radziminski, Lukasz; Dargiewicz, Robert; Zielinski, Piotr



Differences in Blood Urea and Creatinine Concentrations in Earthed and Unearthed Subjects during Cycling Exercise and Recovery.  


Contact of humans with the earth, either directly (e.g., with bare feet) or using a metal conductor, changes their biochemical parameters. The effects of earthing during physical exercise are unknown. This study was carried out to evaluate selected biochemical parameters in subjects who were earthed during cycling. In a double-blind, crossover study, 42 participants were divided into two groups and earthed during exercise and recovery. One group was earthed in the first week during 30 minutes of cycling exercise and during recovery, and a second group was earthed in the second week. A double-blind technique was applied. Blood samples were obtained before each training session, after 15 and 30 minutes of exercise, and after 40 minutes of recovery. Significantly lower blood urea levels were observed in subjects earthed during exercise and relaxation. These significant differences were noted in both groups earthed at the beginning of exercise (P < 0.0001), after 15 (P < 0.0001) and 30 minutes (P < 0.0001) of exercise, and after 40 minutes of relaxation (P < 0.0001). Creatinine concentrations in earthed subjects during exercise were unchanged. Conclusions. Earthing during exercise lowers blood urea concentrations and may inhibit hepatic protein catabolism or increase renal urea excretion. Exertion under earthing may result in a positive protein balance. PMID:24066011

Sokal, Pawe?; Jastrz?bski, Zbigniew; Jaskulska, Ewelina; Sokal, Karol; Jastrz?bska, Maria; Radzimi?ski, Lukasz; Dargiewicz, Robert; Zieli?ski, Piotr



Catabolism in critical illness: estimation from urea nitrogen appearance and creatinine production during continuous renal replacement therapy.  


Thirty-eight intensive care unit (ICU) patients (26 men and 12 women with a mean age of 57.0 +/- 16.6 years) with acute renal failure (ARF) treated by venovenous continuous renal replacement therapy (CRRT) were evaluated while in relatively steady metabolic control. Twenty-seven were undergoing continuous venovenous hemodialysis, nine were undergoing continuous venovenous hemodiafiltration, and two were undergoing continuous venovenous hemofiltration. Periods of analysis varied between 24 and 408 hours (mean duration, 82.7 +/- 70.6 hours; median, 72 hours). Their mean Acute Physiology and Chronic Health Evaluation II (APACHE II) score within 24 hours of admission to the ICU was 21.3 +/- 6.3 and survival rate was 31.6%. Urea nitrogen and creatinine concentrations were determined every 6 to 12 hours in both serum (Cun and Cc, respectively) and effluent (spent dialysate and/or ultrafiltrate). The mean effluent rate was 1,472 +/- 580 mL/h and blood flow rate, 166 +/- 32 mL/min. Urine was collected daily for urea nitrogen and creatinine measurement. Urea nitrogen appearance rate (UnA) and creatinine production rate (Pc), calculated from urea nitrogen (UnMR) and creatinine mass removal (CMR) from both the effluent and the urine, using Garred mass balance equations and the Forbes-Bruining formula, allowed normalized protein catabolic rate (nPCR) and estimates of lean body mass (LBM) to be derived. Creatinine metabolic degradation rate (Dc), estimated by the Mitch formula, was included in the calculation. The lowest body weight recorded during the study period was considered as dry weight (BW). The creatinine index (CI) was also obtained. For each parameter, the results are presented as mean, median, and range values: UnMRe (from effluent), 13.6 +/- 7.2, 12.5, 1.6 to 32.6 mg/min; UnMRu (from urine), 0.13 +/- 0.40, 0, 0 to 2.30 mg/min; UnA, 13.6 +/- 7.0, 12.5, 3.8 to 32.1 mg/min; nPCR, 1.75 +/- 0.82, 1.60, 0.61 to 4.23 g/kg/d; CMRe (from effluent), 942.0 +/- 362.3, 918.0, 211.2 to 1,641.6 mg/d; CMRu (from urine), 44.4 +/- 138.8, 0, 0 to 698.5 mg/d; Dc, 94.6 +/- 49.9, 81.9, 31.0 to 294.1 mg/d; Pc total, 1,067.1 +/- 409.7, 1,053.7, 261.5 to 1,988.2 mg/d; LBM, 38.3 +/- 11.9, 37.9, 15.0 to 65.0 kg; LBM/BW ratio, 49.5% +/- 14.0%, 50.3%, 22.5% to 86.0%; and CI, 13.7 +/- 4.7, 14.2, 4.1 to 25.8 mg/kg/d. When Pc was estimated from the Cockcroft-Gault equations (as Pc'), the mean value for Pc and Pc' was similar (1,067.1 +/- 409.7 v 1,284.9 +/- 484.1 mg/d), but there were relatively large differences for the majority of cases. A positive correlation was observed between UnA and Pc (R = 0.42). Serum albumin and LBM/BW correlated poorly (R = 0.20). Outcome was weakly related to UnA and to nPCR (R = 0.29 and R = 0.31, respectively). Urea nitrogen appearance appears widely variable in critically ill ARF patients. This simple approach can provide useful information for an easy estimate of net protein catabolism in critically ill patients with ARF undergoing CRRT. PMID:9740161

Leblanc, M; Garred, L J; Cardinal, J; Pichette, V; Nolin, L; Ouimet, D; Geadah, D



Spectrophotometric simultaneous determination of orotic acid, creatinine and uric acid by orthogonal signal correction-partial least squares in spiked real samples.  


An orthogonal signal correction-partial least squares (OSC-PLS) method was developed for the simultaneous spectrophotometric determination of orotic acid (OA), creatinine (CRE), and uric acid (UA) in spiked real samples. By multivariate calibration methods, such as PLS regression, it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. The effect of OSC used to remove the information unrelated to the target variables is studied. In this study, the calibration model is based on absorption spectra in the 220-320 nm rang for 36 different mixtures of OA, CRE and UA. Calibration matrices contained 1.74-47.00 of OA, 1.13-33.95 of CRE, and 1.68-28.58 of UA in µg/ml. The number of principal component for OA, CRE, and UA with OSC were 3, 4, and 4, and 4, 6, and 5, without OSC, respectively. The evaluation of the prediction errors for the prediction set reveals that the OSC-treated data give substantially lower root mean square error of prediction (RMSEP) values than the original data. The RMSEP for OA, CRE, and UA with OSC were 0.69, 0.20, and 0.53 and 0.80, 0.69, and 0.73 without OSC, respectively. The proposed method was applied for the simultaneous determination of OA, CRE, and UA in spiked biological fluids with satisfactory results. PMID:22371390

Khajehsharifi, Habiboallah; Tavallali, Hossein; Shekoohi, Manzar; Sadeghi, Maasumeh



A multi-functional electrochemical sensing system using microfluidic technology for the detection of urea and creatinine.  


This study presents a new microfluidic system capable of precise measurements of two important biomarkers, urea and creatinine, automatically. In clinical applications, high levels of these two biomarkers are early indicators of nephropathy or renal failure and should be monitored on a regular basis. The microfluidic system is composed of a microfluidic chip, a control circuit system, a compressed air source and several electromagnetic valves to form a handheld system. The microfluidic chip is fabricated by using micro-electromechanical systems and microfluidic techniques comprising electrochemical sensor arrays and polydimethylsiloxane-based microfluidic structures such as micropumps/micromixers, normally closed valves and microchannels. The microfluidic system performs a variety of critical processes including sample pretreatment, mixing, transportation and detection on a single chip. The experimental results show that the entire procedure takes approximately 40 min, which is much faster than the traditional method (more than 6 h). Furthermore, the total sample volume consumed in each operation is only 0.1 mL, which is significantly less than that required in a large system (5 mL). The developed automatic microfluidic system may provide a powerful platform for further clinical applications. PMID:21437917

Huang, Chao-June; Lin, Jiun-Lin; Chen, Ping-Hong; Syu, Mei-Jywan; Lee, Gwo-Bin



Effective diffusion volume flow rates (Qe) for urea, creatinine, and inorganic phosphorous (Qeu, Qecr, QeiP) during hemodialysis.  


In vivo solute clearances can be estimated from dialyzer blood (Qb) and dialysate (Qd) flow rates and a solute- and dialyzer-specific overall permeability membrane area product (KoA). However, these calculations require knowledge of the flow rate of the effective solute distribution volume in the flowing bloodstream (Qe) in order to calculate in vivo clearances and KoAs. We have determined Qe for urea, creatinine, and inorganic phosphorus from changes in concentrations across the blood compartment and mass balance between the blood and dialysate streams. We made four serial measurements over one dialysis in 23 patients and found that Qeu equals the total blood water flow rate, Qecr equals the plasma water flow rate plus 61% of red cell water flow rate, and QeiP is limited to the plasma water flow rate. Equations are derived to calculate Qe for each of these solutes from Qb and hematocrit and in vivo KoAs for each solute were calculated. PMID:14629609

Gotch, Frank A; Panlilio, Froilan; Sergeyeva, Olga; Rosales, Laura; Folden, Tom; Kaysen, George; Levin, Nathan


High versus low protein diets to mink?postprandial plasma urea and creatinine response, osmotic load and pattern of nitrogen and electrolyte excretion  

Microsoft Academic Search

Nitrogen balance, pattern of excretion of nitrogenous end?products, endogenous urinary N excretion, postprandial plasma urea and creatinine, osmotic load, urinary electrolyte excretion and water intake\\/output relationships were studied in 12 adult female mink fed a high protein diet (HP; n=6) providing about 155g protein\\/kg or a low protein diet (LP; n=6) providing about 95 g protein\\/kg. Two balance periods of

N. E. Hansen; S. Wamberg



Serum Uric Acid in Smokers  

PubMed Central

Objectives To demonstrate the possible effect of smoking on serum uric acid. Methods Subjects enrolled in study were divided into two groups; nonsmokers and smokers, each with 60 male volunteers of the same social class and dietary habit without history of alcohol consumption, diabetes mellitus, hyperuricemia and gout, renal, joint, lung or heart diseases. Fasting blood and random urine samples were obtained from both groups for measurement of uric acid and creatinine. Calculation of both urine uric acid/urine creatinine ratio and fraction excretion of uric acid were done. The results were statistically evaluated by standard statistical methods. Results No significant differences in the age, serum creatinine, spot urine uric acid/urine creatinine ratio and fraction excretion of uric acid between the two groups, serum uric acid was significantly lower in smokers. In smokers there was significant negative correlation of smoking status (average number of cigarette smoked/day, duration of smoking and cumulative amount of smoking) with serum uric acid. Conclusion After exclusion of other factors affecting uric acid level, the significant low serum uric acid level in smokers was attributed to reduce endogenous production as a result of chronic exposure to cigarette smoke that is a significant source of oxidative stress. As this reduction is proportionate with smoking status and predisposes to cardiovascular disease, it is, therefore, recommended for smokers to stop or reduce smoking and introduce serum uric acid estimation as routine test since its cheap and simple to reflect their antioxidant level. Keywords Smokers; Uric acid; CVD.

Hanna, Bassam E.; Hamed, Jamal M.; Touhala, Luma M.



[The blood urea nitrogen/creatinine ratio in localizing the bleeding site in pediatric patients with gastrointestinal hemorrhage].  


The reliability of the blood urea nitrogen/creatinine (B/C) ratio in localizing the bleeding site in pediatric patients with gastrointestinal hemorrhages was evaluated retrospectively. Supplementary experiments on rats and rabbits were also conducted. The study population included 69 children ranging in age from 6 days to 16 years (mean age, 7y8m) with successful radiographic, endoscopic, and surgical identification of the bleeding site. Patients with renal disease, liver disease and coagulopathy were excluded. The upper gastrointestinal bleeding site was segregated from the lower one defined by the ligament of Treitz. For the 38 upper gastrointestinal bleeders, B/C values ranged from 7.8-69.0 (mean 28.8 +/- 15.4 SD). For the 31 lower gastrointestinal bleeders the values ranged from 4.3-28.5 (mean 18.9 +/- 6.9 SD). A significant difference between the two groups was noted after (p less than 0.01) analysis. No patients with lower gastrointestinal bleeding had values higher than 30. In the group of 17 bleeders with a value higher than 30, 8 patients were examined again from 2-5 days after they had been identified as having bleeding to prove that the bleeding had stopped. At the time of identification of no-bleeding, B/C values were calculated at under 30 in every patient. There was no significant correlation between Hb (g/dl) and B/C. With respect to our experiments on animals, the B/C ratio was evaluated in rats with gastric or small intestinal ulcers. Though B/C was 34.4 +/- 4.4 under normal conditions, it increased significantly to 114.0 +/- 8.8 in rats with gastrointestinal ulcers, while in those with small intestinal ulcers B/C did not increase significantly (40.3 +/- 12.3). Twenty ml of blood from ear veins of rabbits was infused into a) stomach b) small intestine (no-hemolysis blood) c) small intestine (hemolysis blood). For a) and c), B/C increased in a similar pattern. For b) the increase was small. Infusing 5 ml, 10 ml, and 15 ml of the whole blood into the stomach indicated that the volume of blood did not influence the change of B/C values, while the infusion of 3 ml of serum caused only a small increase. According to these studies the increase in the B/C ratio after upper gastrointestinal hemorrhage has been postulated to result from the procedure in which the hemorrhage blood is fragmented or hemolyzed by HCl and digestive enzymes in the gastric juices; and consequently the BUN in red blood cells as well as in serum is rapidly absorbed from the upper small intestine. Volume of blood has little influence upon B/C.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2229328

Kikai, Y; Matsuoka, K



Serum Uric Acid Levels among Nigerians with Essential Hypertension.  


There is an ongoing debate on the role of serum uric acid as an independent risk factor for hypertension and renal disease. This study determined the serum uric acid levels of Nigerians with essential hypertension and also evaluated the association between serum uric acid levels and blood pressure of these patients. A retrospective case-control study of three hundred and fifty one patients with essential hypertension seen at the hypertension clinic of Aminu Kano Teaching Hospital, Kano between January 2004 and December 2008. The control group comprised of one hundred apparently healthy non hypertensive subjects. The clinical characteristics including blood pressure measurement, serum uric acid, urea, creatinine, lipid profile and glucose were evaluated.The mean systolic and diastolic blood pressures of the male patients were 156mmHg and 101mmHg respectively, while those of the male controls were 120 ± 6.0 and 80 ± 5 respectively. The mean serum uric acid, fasting blood glucose, urea and creatinine were 483umol/L, 5.7mmol/L,6.61mmol/L, 93umol/l respectively compared to those of the male controls which were 326 ±10?mol/l, 5.0± 0.5mmol/l, 4.2± 0.12mmol/l, 5.16mmol/l ± 0.12 and 69±2.71?mol/l respectively. The mean systolic and diastolic blood pressures of the female patients were 158mmHg and 101mmHg, while those of the female controls were 101±2 and 62±9 respectively. The mean serum uric acid, fasting blood glucose, urea and creatinine of the female patients were 434umol/L, 5.3mmol/L 6.20mmol/L, and 88umol/L respectively while those for the female controls were 290±9?mol/l, 4.8±0.5mmol/l, 5.02±0.28 mmol/l, 62±0.36?mol/l respectively. Hyperuricaemia was observed in 59.3% of the male study patients and 62% of the female study patients. Serum uric acid correlated positively with both systolic blood pressure (r=0.192, p<0.001) and diastolic blood pressure (r=0.216; p<0.001). Hyperuricaemia is common among Nigerian patients with essential hypertension and there is an association between serum uric acid level and blood pressure. Further studies on the pathophysiologic significance of hyperuricaemia in these patients are recommended. PMID:23955405

Emokpae, Abiodun M; Abdu, Aliyu



Investigation of the efficacy of 99 mTc-DTPA scintigraphic GFR measurement with Gates method in the detection of cisplatin-induced nephrotoxicity in comparison with plasma urea and creatinine measurement.  


In this study, we investigated the efficacy of 99mTc-DTPA scintigraphic analysis of GFR with the Gates method in comparison with the measurement of plasma urea and creatinine, in the detection of nephrotoxicity occurred in patients treated with cisplatin.Twenty-six male patients with a mean age of 26.73±6.39 years (age range 15-42) who had seminomatous and nonseminomatous testicular carcinoma were included in our study. The patients received cisplatin with a dose of 20 mg/m2 per day for five consecutive days repeated every 21 days. Before starting chemotherapy, immediately after the end of four cycles of chemotherapy and 7 months after the beginning of chemotherapy, plasma urea and creatinine levels were measured and simultaneously scintigraphic GFR estimation using 99 mTc-DTPA with the Gates method was performed. In the measurements done immediately after the chemotherapy, in 18 of the 26 patients GFR levels decreased, in 4 of the 8 remaining patients GFR did not change, and in 4 patients there was an increase in the GFR levels. The changes in the averages of the plasma urea and creatinine levels between measurements done before and after the chemotherapy were not statistically significant. The decrease in the average of the GFR values immediately after chemotherapy, in comparison to the average of GFR values measured before chemotherapy, was found to be statistically significant with paired sample t test analysis (P<0.009 with 95% CI). We concluded that scintigraphic GFR measurement using the Gates method with 99mTc-DTPA is a suitable method in the diagnosis of nephrotoxicity occuring due to cisplatine. PMID:20467916

Özülker, Filiz; Özülker, Tamer; Uzun, Aysun Küçüköz; Özpaçac?, Tevfik



Correlating the amount of urea, creatinine, and glucose in urine from patients with diabetes mellitus and hypertension with the risk of developing renal lesions by means of Raman spectroscopy and principal component analysis  

NASA Astrophysics Data System (ADS)

Patients with diabetes mellitus and hypertension (HT) diseases are predisposed to kidney diseases. The objective of this study was to identify potential biomarkers in the urine of diabetic and hypertensive patients through Raman spectroscopy in order to predict the evolution to complications and kidney failure. Urine samples were collected from control subjects (CTR) and patients with diabetes and HT with no complications (lower risk, LR), high degree of complications (higher risk, HR), and doing blood dialysis (DI). Urine samples were stored frozen (-20°C) before spectral analysis. Raman spectra were obtained using a dispersive spectrometer (830-nm, 300-mW power, and 20-s accumulation). Spectra were then submitted to principal component analysis (PCA) followed by discriminant analysis. The first PCA loading vectors revealed spectral features of urea, creatinine, and glucose. It has been found that the amounts of urea and creatinine decreased as disease evoluted from CTR to LR/HR and DI (PC1, p<0.05), and the amount of glucose increased in the urine of LR/HR compared to CTR (PC3, p<0.05). The discriminating model showed better overall classification rate of 70%. These results could lead to diagnostic information of possible complications and a better disease prognosis.

Bispo, Jeyse Aliana Martins; de Sousa Vieira, Elzo Everton; Silveira, Landulfo; Fernandes, Adriana Barrinha



Uric acid test (image)  


Uric acid urine test is performed to check for the amount of uric acid in urine. Urine is collected over a 24 ... testing. The most common reason for measuring uric acid levels is in the diagnosis or treatment of ...


Serumurinezuur Spiegels bij Ouderen; Correlaten en Gevolgen van Verhoogd Serumurinezuur (Serum Uric Acid Levels in the Elderly; Correlates and Consequences of Increased Serum Uric Acid).  

National Technical Information Service (NTIS)

In 460 apparently healthy Dutch elderly, ages 65-79, serum uric acid correlates were separately studied for men and women by way of linear regression analyses. Diuretic therapy, total serum cholesterol (women only) and creatinine clearance were correlated...

H. Eshuis H. Loenen



Prediction of Creatinine Clearance from Serum Creatinine  

Microsoft Academic Search

A formula has been developed to predict creatinine clearance (Ccr) from serum creatinine (Scr) in adult males: Ccr = (140 – age) (wt kg)\\/72 × Scr(mg\\/100ml) (15% less in females). Derivation included the relationship found between age and 24-hour creatinine excretion\\/kg in 249 patients aged 18–92. Values for Ccr were predicted by this formula and four other methods and the

Donald W. Cockcroft; Henry Gault



Uric acid nephrolithiasis.  


Uric acid is the end-product of purine nucleotide metabolism in man. The renal handling of urate is a complicated process, resulting in a fractional clearance of 8.2-10.3%. The anhydrous form is thermodynamically the most stable uric acid crystal. Uric acid is a weak acid that ionizes with a Pka at pH 5.75. At the normal acidic region, uric acid solubility is strongly increased by urinary pH. The prevalence of uric acid stones varies between countries, reflecting climatic, dietary, and ethnical differences, ranging from 2.1% (in Texas) to 37.7% (in Iran). The risk for uric acid stone formation correlates with the degree of uric acid supersaturation in the urine, depending on uric acid concentration and urinary pH. Hyperuricosuria is the major risk factor, the most common cause being increased purine intake in the diet. Acquired and hereditary diseases accompanied by hyperuricosuria and stone disease include: gout, in strong correlation with the amount of uric acid excreted, myelo- and lymphoproliferative disorders, multiple myeloma, secondary polycythemia, pernicious anemia and hemolytic disorders, hemoglobinopathies and thalassemia, the complete or partial deficiency of HGPRT, superactivity of PRPP synthetase, and hereditary renal hypouricemia. A common denominator in patients with idiopathic and gouty stone formers is a low urinary pH. Uric acid nephrolithiasis is indicated in the presence of a radiolucent stone, a persistent undue urine acidity and uric acid crystals in fresh urine samples. A radiolucent stone in combination with normal or acidic pH should raise the possibility of urate stones.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7783706

Halabe, A; Sperling, O



Overweight, insulin resistance and blood pressure (parameters of the metabolic syndrome) in uric acid urolithiasis.  


Overweight, arterial hypertension and disturbances of the carbohydrate metabolism are important parameters of the metabolic syndrome (MS). The most important factor regarding renal pathophysiology is insulin resistance resulting in alterations of urine acidification and low urine pH. Since low urine pH is the main risk factor for uric acid urolithiasis (UAU), UAU may be regarded as a renal manifestation of the MS. So far, there are only few data on the prevalence of parameters of the MS in UAU patients especially with regard to the severity of the disease and recurrence rate, respectively. The objective of this study was to know more about the prevalence of different parameters of the MS and their importance for the natural history of this type of renal stone disease using a total number of 167 consecutive patients with pure UA stones. Stone analysis was performed by polarization microscopy and X-ray diffraction. The following parameters were measured: age, sex, systolic and diastolic arterial blood pressure (RRs and RRd), number of stone episodes, diabetes mellitus (DM); serum: creatinine, calcium, sodium, potassium, uric acid, glucose; urine: pH-profiles, citrate, calcium, uric acid, ammonia, urea, and creatinine. The following results were obtained (means ± standard deviations): age 61 ± 13 years, BMI 30 ± 6 kg/m(2), BP 147/84 ± 22/13 mmHg, number of stone episodes 1.8 ± 1.2, DM 32%; serum: creatinine 1.3 ± 0.6 mg/dl, glucose 136 ± 52 mg/dl, UA 6.3 ± 1.8 mg/dl, calcium 2.4 ± 1.3 mmol/l, sodium 134 ± 18 mmol/l, potassium 4.1 ± 0.4 mmol/l; urine: pH 5.87 ± 0.27, volume 2.4 ± 1.1 l/d, calcium 3.5 ± 2.5 mmol/d, UA 3.9 ± 2.4 mmol/d, citrate 1.3 ± 1.1 mmol/d, ammonia 41 ± 26 mmol/d, urea 390 ± 176 mmol/d. A significant positive correlation could be found for BMI and urea excretion, BMI correlated negatively with RRs and RRd. There was no significant correlation between BMI, urine pH, citrate, ammonia and UA in serum and urine. Undue acidity and hyperuricosuria were found in two-thirds of the UAU patients, increased urea excretion and decreased excretion of ammonia in less than 25%, Hyperuricemia in 37%. There was no significant correlation between the number of stone episodes and any other parameter studied. Overweight, arterial hypertension and DM as parameters of the MS are frequent in many patients with UAU. However, these parameters do explain the pathogenesis in two-thirds of the patients. The severity of the disease and the recurrence are not influenced by the presence of these metabolic parameters. Therefore, MS is no prognostic factor in UAU. PMID:21866382

Strohmaier, Walter Ludwig; Wrobel, Beate Maria; Schubert, Gernot



Uric acid - blood  


... blood. High levels of uric acid can cause gout or kidney disease. Your doctor may also order ... hyperuricemia) may be due to: Acidosis Alcoholism Diabetes Gout Hypoparathyroidism Lead poisoning Leukemia Nephrolithiasis Polycythemia vera Renal ...


Uric acid nephrolithiasis.  


Uric acid nephrolithiasis may be the final manifestation of various pathophysiological processes. Recent advances in renal urate transport have elucidated mechanisms by which hyperuricosuria occurs. However, in most uric acid stone formers the primary pathophysiologic defect is an excessively acidic urine pH rather than hyperuricosuria. Insulin resistance may contribute to the development of acidic urine by augmenting endogenous acid production and decreasing renal ammonium excretion. Medical management strategies focus primarily on alkali treatment or decreasing hyperuricosuria. PMID:17678984

Cameron, Mary Ann; Sakhaee, Khashayar



[Uric acid nephrolithiasis].  


Uric acid nephrolithiasis is frequent accounting for 10% of urinary stones in industrialized countries. Its frequency will increase in the next decades because of the ageing and the increasing prevalence of obesity and type 2 diabetes mellitus. The pathophysiologic defect is an excessively acidic urine pH rather than hyperuricosuria. Undissociated uric acid is poorly soluble in acidic urines (pH < 5.5) but solubility increases when sodium urate forms at higher pH. Insulin resistance may contribute to the development of acidic urine because of higher net acid excretion. Because uric acid kidney stones are radiolucent, diagnosis is based on echography and tomodensitometry. Medical management strategies focus primarily on alkali treatment and/or decreasing hyper-uricosuria. PMID:21563421

Dussol, Bertrand



Effects of cilnidipine on serum uric acid level and urinary nitrogen monoxide excretion in patients with hypertension.  


The effects of cilnidipine on the serum uric acid level and urinary NO excretion in hypertensive patients were investigated. Blood and urine samples of 16 hypertensive outpatients were collected before and 2 months after cilnidipine therapy (10 mg). The serum uric acid level decreased significantly after cilnidipine treatment, while the uric acid-creatinine clearance ratio was unaffected. The cilnidipine medication produced a significant increase in urinary NO excretion, although amlodipine did not change it significantly. Therefore, cilnidipine has a profound antihypertensive effect and may reduce the serum uric acid level and increase NO production in the kidney. PMID:22681507

Hamada, Toshihiro; Yamada, Kensaku; Mizuta, Einosuke; Watanabe, Arisa; Osaki, Tomohiro; Ishida, Katsunori; Hasegawa, Akira; Sakata, Shinji; Mishima, Mutsuo; Ogino, Kazuhide; Nosaka, Yoshihito; Miyazaki, Satoshi; Ohtahara, Akira; Ninomiya, Haruaki; Kato, Masahiko; Yoshida, Akio; Taniguchi, Shin-ichi; Yamamoto, Kazuhiro; Hisatome, Ichiro



False estimates of elevated creatinine.  


One of the most common reasons for a nephrology consult is an elevated creatinine. An elevation in the serum creatinine concentration usually reflects a reduction in the glomerular filtration rate (GFR). Given the association of elevated creatinine and risk of cardiovascular mortality, it is important to keep in mind that at times the elevation of the creatinine is not representative of a true reduction in GFR. There are various causes of factitious elevation of creatinine. They can be broadly grouped into increased production of creatinine, interference with the assay and decreased tubular secretion of creatinine. PMID:22745616

Samra, Manpreet; Abcar, Antoine C



Pathophysiology of uric acid nephrolithiasis.  


Humans although a predominantly ureotylic organism, has preserved the ability to excrete nitrogen as uric acid and ammonia. An imbalance between these two secondary modes of nitrogen excretion has resulted in uric acid precipitation in human urine. Uric acid nephrolithiasis can arise from diverse etiologies all with distinct underlying defects converging to one or more of three defects of hyperuricosuria, acidic urine pH, and low urinary volume, originating from secondary, genetic or heretofore undefined (idiopathic) causes. A subset of idiopathic uric acid nephrolithiasis (gouty diathesis) may be the "tip of the icebergp" of a broader systemic illness characterized by insulin resistance. A novel renal manifestation of insulin resistance is a mild defect in ammonium excretion, which is not severe enough to disturb acid-base homeostasis, but is sufficient to set up the chemical milieu for uric acid nephrolithiasis. PMID:12474637

Moe, Orson W; Abate, Nicola; Sakhaee, Khashayar



Long-term activation of semicarbazide-sensitive amine oxidase lowers circulating levels of uric acid in diabetic conditions.  


Uric acid is involved in nitrogenous waste in animals, together with ammonia and urea. Uric acid has also antioxidant properties and is a surrogate marker of metabolic syndrome. We observed that the elevated plasma uric acid of high-fat fed mice was normalized by benzylamine treatment. Indeed, benzylamine is the reference substrate of semicarbazide-sensitive amine oxidase (SSAO), an enzyme highly expressed in fat depots and vessels, which generates ammonia when catalysing oxidative deamination. Ammonia interferes with uric acid metabolism/solubility. Our aim was therefore to investigate whether the lowering action of benzylamine on uric acid was related to an improvement of diabetic complications, or was connected with SSAO-dependent ammonia production. First, we observed that benzylamine administration lowered plasma uric acid in diabetic db/db mice while it did not modify uric acid levels in normoglycemic and lean mice. In parallel, benzylamine improved the glycemic control in diabetic but not in normoglycemic mice, while plasma urea remained unaltered. Then, uric acid plasma levels were measured in mice invalidated for AOC3 gene, encoding for SSAO. These mice were unable to oxidize benzylamine but were not diabetic and exhibited unaltered plasma uric levels. Therefore, activated or abolished ammonia production by SSAO was without influence on uric acid in the context of normoglycemia. Our observations confirm that plasma uric acid increases with diabetes and can be normalized when glucose tolerance is improved. They also show that uric acid, a multifunctional metabolite at the crossroads of nitrogen waste and of antioxidant defences, can be influenced by SSAO, in a manner apparently related to changes in glucose homeostasis. PMID:22480418

Carpéné, C; Desquesnes, A; Gomez-Ruiz, A; Iffiú-Soltész, Z; Le Gonidec, S; Mercader, J




Microsoft Academic Search

SUMMARY Acute renal failure is a syndrome that usually runs with an increase in creatinine and urea plasma levels. However, there are clinical situations in which this syndrome may run with an increase in plasma creatinine keeping normal the urea one. In this report we present a case of acute renal failure with normal plasma urea level secondary to an

Musso CG; Vilas M; Fernandez Otero L; Jauregui R; Imperiali N; Algranati L; Rev Electron Biomed; Electron J Biomed



[Vesical uric acid lithiasis in a child with renal hypouricemia].  


We report a 12-month-old boy with renal hypouricemia who presented with crying due to obstructing vesicourethral uric acid stones. Metabolic study revealed persistent acidic urine with normal blood pH, and hypouricemia (1.4-1.7 mg/dl) with an increased ratio of uric acid clearance to creatinine clearance (24-32 %). Pyrazinamide produced no response but the patient showed a positive response to benzbromarone. These findings were consistent with a presecretory defect. No other tubular dysfunctions, such as renal glycosuria, aminoaciduria or phosphaturia were found. The patient underwent surgical treatment and was subsequently treated with potassium citrate. After a 2-year follow-up, he remains asymptomatic, despite persistent hyperuricosuria. To our knowledge, this is the youngest reported case of renal hypouricemia and lithiasis. PMID:11676906

Martín Hernández, E; Aparicio López, C; Alvarez Calatayud, G; García Herrera, M A



The relationship between uric acid and potassium in normal subjects.  

PubMed Central

The serum uric acid concentration in normal healthy subjects has been studied in relation to sex, height, weight, lean body mass measured from total body potassium and predicted from the Hume-Weyers formula (1971), total body potassium, plasma potassium and urea, and packed cell volume. The strongest correlation was found with sex, but height, weight, total body potassium, lean body mass (measured and predicted) also correlated significantly with serum uric acid concentration. However, when the sex variable was removed, the other factors lost their significant correlation. Finally, total red blood cell and plasma volumes were predicted (Hume and Goldberg, 1964) and from these an estimate of total plasma uric acid, total plasma potassium, and total red blood cell potassium obtained. Measured total body potassium was found to correlate well with total plasma potassium and total red blood cell potassium independent of sex. Total plasma uric acid correlated well with measured total body potassium when both sexes were considered and when separated into male and female groups the males retained a significant correlation as did the female group.

Kennedy, A C; Boddy, K; King, P C; Brennan, J; Anderson, J A; Buchanan, W W



Spreadsheet use to calculate creatinine clearance from serum creatinine.  


Spreadsheets may be created to include the Cockcroft-Gault Formula (CGF) for creatinine-based estimation of glomerular filtration rate. Creatinine clearance (CrCl) provides a more accurate method for perioperative risk assessment of renal function than serum creatinine. CrCl may be used to develop guidelines for renal protective management strategies during cardiopulmonary bypass. CGF uses serum creatinine, age, kilogram weight, sex, and "logical test" functions within the spreadsheet to calculate the CrCl. Implementation of spreadsheets has the potential for numerous other calculations and may provide an accurate and consistent method of clinical perfusion management. PMID:18293814

Shrewsberry, Timothy W; Banoub, Ashraf; Fleming, Kevin; Snyder, Holly; Stehlik, James



NAG, GGT, creatinine, urea and creatinine clearance before and after ESWL  

Microsoft Academic Search

N-acetyl-beta glucosaminidase (NAG) and gamma-glutamyltransferase (GGT) were measured in the urine and serum before, 24 hours\\u000a and one week after extracorporeal shock wave lithotripsy in 25 patients. Although ESWL is the preferred method in the treatment\\u000a of kidney stones, its effect on renal parenchymal cells has not been sufficiently elucidated.\\u000a \\u000a Since radiographic methods remain inadequate in the estimation and management

Ö. Erkizan; A. R. Ayder; S. Minareci; M. Lekili; Ç. Dincel



Uric acid provides antioxidant protection against ozone-induced damage for nucleobase, membranes and erythrocytes  

SciTech Connect

The ozone-induced degradation rates of various purine bases, hydroxylated purine compounds, pyrimidine bases, and uric acid were compared. Of the compounds examined, uric acid was the one most readily degraded while the parent compounds, purine and pyrimidine, were the ones most resistant to ozonation. When the breakdown of hydroxylated purines was studied, it was determined that the more OH substituents on the purine, the more readily it was degraded. Because of the preferential attack by ozone on uric acid in solutions containing a nucleic acid base plus uric acid, the presence of the uric acid had a sparing effect on the base. This effect was readily apparent for guanine, thymine, and uracil which were the bases more labile to ozone. Two of the ozonation products of uric acid were identified as allantoin and urea. Ozonation of bovine and swine erythrocyte suspensions resulted in oxidation of oxyhemoglobin to methemoglobin, formation of thiobarbituric acid-reactive materials-a measure of lipid oxidation- and lysis of the red cells. Each of these changes was inhibited by the presence of uric acid in the solution during ozonation.

Meadows, J.R.



Uric acid stones and hyperuricosuria.  


Recent work has highlighted the strong relationships among obesity, diabetes, and the metabolic syndrome as causes of low urinary pH. Low urinary pH in turn is the major urinary risk factor for uric acid stones. Unlike calcium stones, uric acid stones can be dissolved and easily prevented with adequate urinary alkalinization. Recognizing the relevant risk factors should lead to increased identification of these radiolucent stones. The cornerstone of therapy is raising urinary pH; xanthine dehydrogenase inhibitors should be used only when urinary alkalinization cannot be achieved. PMID:23089277

Mehta, Tapan H; Goldfarb, David S



Hypouricemia and tubular transport of uric acid.  


Hypouricemia is defined when a serum urate concentration is less than or equal 2.0mg/dl. Differential diagnosis is made by fractional uric acid excretion with the identification of urate transporters and intracellular proteins involved in the tubular transport of uric acid. This review examines current knowledge on uric acid tubular transport and the various clinical situations of hypouricemia. PMID:21270912

Esparza Martín, N; García Nieto, V



Uric Acid: The Oxidant-Antioxidant Paradox  

Microsoft Academic Search

Uric acid, despite being a major antioxidant in the human plasma, both correlates and predicts development of obesity, hypertension, and cardiovascular disease, conditions associated with oxidative stress. While one explanation for this paradox could be that a rise in uric acid represents an attempted protective response by the host, we review the evidence that uric acid may function either as

Yuri Y. Sautin; Richard J. Johnson



Urinary excretion of minerals, oxalate, and uric acid in north Indian children  

Microsoft Academic Search

.   Urinary excretion of calcium, magnesium, phosphate, uric acid, oxalate, and creatinine was measured in 208 children (aged\\u000a 8?–?15 years, 124 boys, 84 girls), living in a residential school near New Delhi. Levels were reduced compared with those\\u000a reported from developed countries. The 95th percentile value of 24-h creatinine excretion was 33.4 mg\\/kg, calcium 2.2 mg\\/kg,\\u000a magnesium 2.9 mg\\/kg, phosphate

Hani A. Sweid; Arvind Bagga; Meera Vaswani; Vandita Vasudev; R. K. Ahuja; R. N. Srivastava



Renal hypouricemia in school-aged children: screening of serum uric acid level before physical training  

Microsoft Academic Search

We present two cases of a 12-year-old Japanese boy and a 14-year-old Japanese girl who had exercise-induced acute renal failure (ARF). They experienced general fatigue, nausea\\/vomiting, and vague discomfort in the abdomen after physical exercise at school. In case of the boy, abdominal pain subsided, but renal dysfunction lasted 17 days, with peak levels of creatinine 9.4 mg\\/dl and uric acid

Akio Nakamura; Ryo Niimi; Yukishige Yanagawa



Uric acid transport and disease  

PubMed Central

Uric acid is the metabolic end product of purine metabolism in humans. It has antioxidant properties that may be protective but can also be pro-oxidant, depending on its chemical microenvironment. Hyperuricemia predisposes to disease through the formation of urate crystals that cause gout, but hyperuricemia, independent of crystal formation, has also been linked with hypertension, atherosclerosis, insulin resistance, and diabetes. We discuss here the biology of urate metabolism and its role in disease. We also cover the genetics of urate transport, including URAT1, and recent studies identifying SLC2A9, which encodes the glucose transporter family isoform Glut9, as a major determinant of plasma uric acid levels and of gout development.

So, Alexander; Thorens, Bernard





... and Glomerular Filtration Rate: Perception and Reality ( Clinical Chemistry , June 2010) » See all Article Sources Article Sources « ... Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 362- ...


Diminished creatinine clearance in anorexia nervosa: reversal with weight gain  

Microsoft Academic Search

To assess whether patients with anorexia nervosa have abnormalities in creatinine clearance, we measured plasma creatinine concentration, urinary creatinine excretion, and creatinine clearance in 10 patients with anorexia nervosa before and during treatment. Urinary creatinine excretion and creatinine clearance were diminished in all patients. Nine patients had significant decreases in their plasma creatinine and creatinine clearance was increased even when

F Boag; J Weerakoon; J Ginsburg; C W Havard; P Dandona



Uric Acid, Hypertension, and CKD among Alaska Eskimos--the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) Study  

PubMed Central

It is unknown what role uric acid may play in the increasing cardiovascular disease (CVD) among Alaska Eskimos. Uric acid is associated with both hypertension (HTN) and chronic kidney disease (CKD). We analyzed 1078 Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) participants. Estimated glomerular filtration rate (eGFR) was calculated from serum creatinine measures using the MDRD equation. CKD was defined by an eGFR of <60ml/min/1.73m2. We adjusted for age, sex, education, diabetes, hypertension (or eGFR), obesity, lipids, and smoking status; 7% (n=75) had prevalent CKD. eGFR decreased with increasing tertiles of serum uric acid. (p<0.001) Uric acid was independently associated with prevalent CKD (Adjusted Odds Ratio [OR] and 95% confidence interval [CI] of 2.04 (1.62–2.56), respectively). 21% (n=230) had prevalent HTN; Uric acid was independently associated with prevalent HTN (Adjusted OR 1.2, 95% CI 1.1–1.5). Uric acid is independently associated with prevalent CKD and HTN in this population.

Jolly, Stacey E.; Mete, Mihriye; Wang, Hong; Zhu, Jianhui; Ebbesson, Sven O.E.; Voruganti, V. Saroja; Comuzzie, Anthony G.; Howard, Barbara V.; Umans, Jason G.




SciTech Connect

Urea SCR is currently the only proven NOX aftertreatment for diesel engines - high NOX reduction possible - some SCR catalyst systems are robust against fuel sulfur - durability has been demonstrated - many systems in the field - long history in other markets - Major limitations to acceptance - distribution of urea solution to end user - ensuring that urea solution is added to vehicle.

Bunting, Bruce G.



Evaluation of Dietary Nitrogen Utilization in Dairy Cows Based on Urea Concentrations in Blood, Urine and Milk, and on Urinary Concentration of Purine Derivatives  

Microsoft Academic Search

The effects of level and degradability of dietary protein on urea in blood, urine and milk, and on the urinary purine derivatives and creatinine in dairy cows, were studied. Diurnal variation in urinary concentration of urea, allantoin and creatinine was also studied. A total of 24 multiparous lactating dairy cows were selected from a production experiment and divided into two

Horacio Leandro Gonda; Jan Erik Lindberg



Urea metabolism in plants.  


Urea is a plant metabolite derived either from root uptake or from catabolism of arginine by arginase. In agriculture, urea is intensively used as a nitrogen fertilizer. Urea nitrogen enters the plant either directly, or in the form of ammonium or nitrate after urea degradation by soil microbes. In recent years various molecular players of plant urea metabolism have been investigated: active and passive urea transporters, the nickel metalloenzyme urease catalyzing the hydrolysis of urea, and three urease accessory proteins involved in the complex activation of urease. The degradation of ureides derived from purine breakdown has long been discussed as a possible additional metabolic source for urea, but an enzymatic route for the complete hydrolysis of ureides without a urea intermediate has recently been described for Arabidopsis thaliana. This review focuses on the proteins involved in plant urea metabolism and the metabolic sources of urea but also addresses open questions regarding plant urea metabolism in a physiological and agricultural context. The contribution of plant urea uptake and metabolism to fertilizer urea usage in crop production is still not investigated although globally more than half of all nitrogen fertilizer is applied to crops in the form of urea. Nitrogen use efficiency in crop production is generally well below 50% resulting in economical losses and creating ecological problems like groundwater pollution and emission of nitric oxides that can damage the ozone layer and function as greenhouse gasses. Biotechnological approaches to improve fertilizer urea usage bear the potential to increase crop nitrogen use efficiency. PMID:21421389

Witte, Claus-Peter



Urinary phosphate\\/creatinine, calcium\\/creatinine, and magnesium\\/creatinine ratios in a healthy pediatric population  

Microsoft Academic Search

Objective: To determine reference values for urinary phosphate\\/creatinine (Cr) concentration ratios and to complete reference values for urinary calcium\\/creatinine and magnesium\\/creatinine ratios in the second morning urine sample of healthy infants, children, and adolescents.Design: Urinary P\\/Cr, Ca\\/Cr, and Mg\\/Cr ratios were determined from the second morning urine sample. Two urine samples were obtained 1 week apart from most subjects to

Vera Matos; Guy van Melle; Olivier Boulat; Michèle Markert; Claude Bachmann; Jean-Pierre Guignard



Uric acid, hyperuricemia and vascular diseases.  


Uric acid is the product of purine metabolism. It is known that hyperuricemia, defined as high levels of blood uric acid, is the major etiological factor of gout. A number of epidemiological reports have increasingly linked hyperuricemia with cardiovascular and neurological diseases. Studies highlighting the pathogenic mechanisms of uric acid point to an inflammatory response as the primary mechanism for inducing gout and possibly contributing to uric acid's vascular effects. Monosodium urate (MSU) crystals induce an inflammatory reaction, which are recognized by toll-like receptors (TLRs). These TLRs then activate NALP3 inflammasome. MSU also triggers neutrophil activation and further produces immune mediators, which lead to a proinflammatory response. In addition, soluble uric acid can also mediate the generation of free radicals and function as a pro-oxidant. This review summarizes the epidemiological studies of hyperuricemia and cardiovascular disease, takes a brief look at hyperuricemia and its role in neurological diseases, and highlights the studies of the advanced pathological mechanisms of uric acid and inflammation. PMID:22201767

Jin, Ming; Yang, Fan; Yang, Irene; Yin, Ying; Luo, Jin Jun; Wang, Hong; Yang, Xiao-Feng



[Surface-enhanced Raman spectroscopic analysis of uric acid].  


Based on Ag nanoparticles as the surface-enhanced Raman spectroscopy (SERS)-active nanostructure, the SERS of uric acid was presented in the paper. The absorption spectroscopies of uric acid and the mixture of silver colloids and uric acid were measured. The possible enhancing mechanism of the uric acid on silver colloid was speculated. The characteristic SERS bands of uric acid were tentatively assigned. The influence of absorption time and different ion on the SERS of uric acid were also discussed. The SERS spectral intensity changes linearly with the uric acid concentration, which indicated that the SERS might provide a new kind of direct and fast detecting method for the detection of uric acid. The detection limit of uric acid in silver sol is found to be 1 mg/L. PMID:22826955

Feng, Shangyuan; Lin, Duo; Li, Yongzeng; Huang, Zufang; Wu, Yan'an; Wang, Yue; Lin, Juqiang; Chen, Rong



Quantitation of Creatinine in Biological Fluids.  

National Technical Information Service (NTIS)

This overview covers the literature through 1980 and presents the state of the art of creatinine analysis. In the short space of three years (1939-1941) the biosynthesis of creatine, the precursor of creatinine, was elucidated. These studies showed that t...

B. E. Hindman F. Moya



Uric acid and inflammatory markers  

PubMed Central

Aims The role of uric acid (UA) in the process of atherosclerosis and atherotrombosis is controversial. Epidemiological studies have recently shown that UA may be a risk factor for cardiovascular diseases and a negative prognostic marker for mortality in subjects with pre-existing heart failure. Methods and results We evaluate a relationship between UA levels and several inflammatory markers in 957 subjects, free of severe renal failure, from a representative Italian cohort of persons aged 65–95. Plasma levels of UA and white blood cell (WBC) and neutrophil count, C-reactive protein, interleukin-1 receptor antagonist (IL-1ra), interleukin-6 (IL-6), soluble IL-6 receptor (sIL-6r), interleukin-18 (IL-18), and tumor necrosis factor-? (TNF-?) were measured. Complete information on potential confounders was collected using standard methods. WBC (P = 0.0001), neutrophils (P < 0.0001), C-reactive protein (P < 0.0001), IL-1ra (P < 0.0001), IL-6 (P = 0.0004), sIL-6r (P = 0.002), IL-18 (P < 0.0001), TNF-? (P = 0.0008), and the percentage of subjects with abnormally high levels of C-reactive protein (P = 0.004) and IL-6 (P = <0.0001) were significantly higher across UA quintiles. After adjustment for age, sex, behaviour- and disease-related confounders, results were virtually unchanged. In subjects with UA within the normal range, UA was significantly and independently associated with neutrophils count, C-reactive protein, IL-6, IL-1ra, IL-18, and TNF-?, whereas non-significant trends were observed for WBC (P = 0.1) and sIL-6r (P = 0.2). Conclusion A positive and significant association between UA and several inflammatory markers was found in a large population-based sample of older persons and in a sub-sample of participants with normal UA. Accordingly, the prevalence of abnormally high levels of C-reactive protein and IL-6 increased significantly across UA quintiles.

Ruggiero, Carmelinda; Cherubini, Antonio; Ble, Alessandro; Bos, Angelo J.G.; Maggio, Marcello; Dixit, Vishwa D.; Lauretani, Fulvio; Bandinelli, Stefania; Senin, Umberto; Ferrucci, Luigi



Uric acid deposits in symbiotic marine algae.  


The symbiosis between cnidarians and dinoflagellate algae is not understood at the cell or molecular level, yet this relationship is responsible for the formation of thousands of square kilometres of coral reefs. We have investigated the nature of crystalline material prominent within marine algal symbionts of Aiptasia sp. anemones. This material, which has historically been considered to be calcium oxalate, is shown to be uric acid. We demonstrate that these abundant uric acid stores can be mobilized rapidly, thereby allowing the algal symbionts to flourish in an otherwise N-poor environment. This is the first report of uric acid accumulation by symbiotic marine algae. These data provide new insight and considerations for understanding the physiological basis of algal symbioses, and represent a new and previously unconsidered aspect of N metabolism in cnidarian, and a variety of other, marine symbioses. PMID:19021889

Clode, Peta L; Saunders, Martin; Maker, Garth; Ludwig, Martha; Atkins, Craig A



Uric acid protects erythrocytes from ozone-induced changes  

SciTech Connect

Uric acid effectively reduced hemolysis and methemoglobin formation in bovine and swine erythrocytes bubbled with ozone in vitro. In bovine erythrocytes, formation of thiobarbituric acid-reactive material was inhibited by uric acid, but there was little immediate protection for the swine cells. Antioxidant protection was due to preferential degradation of the uric acid by ozone. These results provide evidence to support the hypothesis that in plasma, uric acid can provide antioxidant protection for erythrocytes.

Meadows, J.; Smith, R.C.



Cardiovascular Drugs and Serum Uric Acid  

Microsoft Academic Search

Uric acid (UA) is the final product of purine catabolism in man, and it is excreted mainly by the kidneys when renal function is not impaired. Consequently, serum (S) UA increases as a function of purine intake, and it varies inversely to uricosuria. The latter variable diminishes in response to low-sodium intakes and vice versa. Insofar as the diet is

Ariel J. Reyes



Uric acid, evolution and primitive cultures.  


Hypertension is epidemic and currently affects 25% of the world's population and is a major cause of stroke, congestive heart failure, and end-stage renal disease. Interestingly, there is evidence that the increased frequency of hypertension is a recent event in human history and correlates with dietary changes associated with Westernization. In this article, we review the evidence that links uric acid to the cause and epidemiology of hypertension. Specifically, we review the evidence that the mutation of uricase that occurred in the Miocene that resulted in a higher serum uric acid in humans compared with most other mammals may have occurred as a means to increase blood pressure in early hominoids in response to a low-sodium and low-purine diet. We then review the evidence that the epidemic of hypertension that evolved with Westernization was associated with an increase in the intake of red meat with a marked increase in serum uric acid levels. Indeed, gout and hyperuricemia should be considered a part of the obesity, type 2 diabetes, and hypertension epidemic that is occurring worldwide. Although other mechanisms certainly contribute to the pathogenesis of hypertension, the possibility that serum uric acid level may have a major role is suggested by these studies. PMID:15660328

Johnson, Richard J; Titte, Srinivas; Cade, J Robert; Rideout, Bruce A; Oliver, William J



Uric acid stones following hepatic transplantation.  


We report the case of a 52 year old man with a history of insulin-requiring diabetes and hepatitis B with cirrhosis who received an orthotopic liver transplant. One year later he developed renal colic and was found to have a 3 mm stone at the left ureterovesical junction. Numerous other stones formed and infrared spectroscopy analysis demonstrated all to be composed of 100% uric acid. Urine collections demonstrated a low urine pH of 5.1 without hyperuricosuria. His stones were effectively prevented with potassium citrate therapy. Few incidence data are available for uric acid stone occurrence in solid organ recipients. Calcineurin inhibitors are thought to often cause hyperuricemia on the basis of decreased urate excretion. However, this effect would not be expected to cause hyperuricosuria nor uric acid stones. This class of drugs may also be associated with low urine pH, perhaps on the basis of hypoaldosteronism, but the contribution of such a syndrome to uric acid stone formation is not established. PMID:15565437

Hwang, Mei-Tsuey; Goldfarb, David S



Urine alkalization facilitates uric acid excretion  

Microsoft Academic Search

BACKGROUND: Increase in the incidence of hyperuricemia associated with gout as well as hypertension, renal diseases and cardiovascular diseases has been a public health concern. We examined the possibility of facilitated excretion of uric acid by change in urine pH by managing food materials. METHODS: Within the framework of the Japanese government's health promotion program, we made recipes which consist

Aya Kanbara; Masayuki Hakoda; Issei Seyama



Detection of Interstellar Urea  

Microsoft Academic Search

Urea, a molecule discovered in human urine by H. M. Rouelle in 1773, has a significant role in prebiotic chemistry. Previous BIMA observations have suggested that interstellar urea [(NH2)2CO] is a compact hot core molecule such as other large molecules (e.g. methyl formate and acetic acid). We have conducted an extensive search for urea toward the high mass hot molecular

Hsin-Lun Kuo; Anthony J. Remijan; Lewis E. Snyder; Leslie W. Looney; Douglas N. Friedel; Francis J. Lovas; Benjamin J. McCall; Jan M. Hollis



Determinants of Urea Production and Mineral Retention in Parenterally Fed Preterm Infants  

PubMed Central

Objective: To determine how weight for gestational age affects urea and mineral excretion by preterm infants receiving total parenteral nutrition (TPN). Study Design: Daily urine samples were collected from all preterm infants given high calcium TPN, providing 30 kcal/g amino acids, during its first 44 months of use, and from all those given standard TPN, providing 25 kcal/g amino acids, over the previous 24 months. Urine urea and mineral excretion were measured as follows: Urea excretion mmol/kg/day = Urine urea/urine creatinine X creatinine production Creatinine production ?mol/kg/day = -2.07 + 2.34 X gestational age in weeks Results: High calcium TPN was evaluated in 52 infants. Urea excretion did not rise with increasing TPN intake. During the first week, urea excretion increased with weight for gestational age, with higher rates in above average than below average weight infants. It also increased with gestational age in above average but not below average weight infants. Below average weight infants had lower potassium and phosphate excretion than those above average. Standard TPN was evaluated in 20 infants. Urea excretion increased with TPN intake to higher levels than on high calcium, and also increased with weight for gestational age. Conclusion: Urea excretion was simple to measure, with remarkably consistent daily results in individuals. Below 30 weeks gestation infants on TPN providing 30 kcal/g amino acids had urea excretion < 0.1 g urea N/kg/day, < 3.5 mmol/kg/day if below average weight, and < 0.12 g urea N/kg/day, < 4.3 mmol/kg/day if above average weight. Below average weight infants retained more potassium and phosphate during the first week than those above average, and their greater requirements were provided by the TPN.

Aiken, Christopher Geoffrey Alexander



The Alkalizer Citrate Reduces Serum Uric Acid Levels and Improves Renal Function in Hyperuricemic Patients Treated with the Xanthine Oxidase Inhibitor Allopurinol  

PubMed Central

Hyperuricemia, an integral component of metabolic syndrome, is a major health problem causing gout and renal damage. Urine alkalizers like citrate preparations facilitate renal excretion of the uric acid, but its supportive effect on xanthine oxidase inhibitors has not been tested as yet. We thus performed a randomized, prospective study, employing patients with elevated serum uric acid levels (?7.0 mg/dL), or those treated for hyperuricemia. They were randomly enrolled into two study groups: the allopurinol monotherapy (MT) group or combination treatment (CT) group with allopurinol and a citrate preparation. Allopurinol (100 to 200 mg/day) in the absence or presence of a citrate preparation (3 g/day) was administered for 12 weeks and levels of serum uric acid, its urinary clearance (Cua), and the renal glomerular filtration rates assessed with the creatinine clearance (Ccr) were evaluated before and after the treatment. Serum levels of uric acid decreased significantly in both groups, while the change observed was much greater in CT group. Cua was significantly increased in CT group but not in MT group. Ccr was not altered in both groups in general, whereas it was significantly increased in a fraction of CT group with decreased renal function. These results indicate that an additional use of citrate preparations with xanthine oxidase inhibitors is beneficial for patients with hyperuricemia, reducing circulating uric acid and improving their glomerular filtration rates.

Saito, Jun; Matsuzawa, Yoko; Ito, Hiroko; Omura, Masao; Ito, Yuzuru; Yoshimura, Koichiro; Yajima, Yuki; Kino, Tomoshige; Nishikawa, Tetsuo



Uric acid and chronic kidney disease: A time to act?  

PubMed Central

A role for uric acid in the pathogenesis and progression of renal disease had been proposed almost a century ago, but, too hastily dismissed in the early eighties. A body of evidence, mostly accumulated during the last decade, has led to a reappraisal of the influence of uric acid on hypertension, cardiovascular, and renal disease. The focus of this review will be solely on the relationship between serum uric acid and renal function and disease. We will review experimental evidence derived from animal and human studies, evidence gathered from a number of epidemiological studies, and from the few (up to now) studies of uric-acid-lowering therapy. Some space will be also devoted to the effects of uric acid in special populations, such as diabetics and recipients of kidney allografts. Finally we will briefly discuss the challenges of a trial of uric-acid-lowering treatment, and the recent suggestions on how to conduct such a trial.

Bellomo, Gianni



Creatinine distribution dynamics in the dog  

PubMed Central

The dynamics of the distribution of creatinine infused into 5 anesthetized, heparinized dogs in moderate diuresis were analyzed in terms of the simplest serial compartmental model (4 chambers with passive exchanges) which would describe the data accurately. During 3-hr experiments, the intravenous infusion rate was continuously varied over a wide range, resulting in large variations in arterial plasma concentration (measured continuously by AutoAnalyzer), thus providing an exacting test of the model. Input into first chamber of the model was the experimental rate of creatinine infusion. Output, also from this chamber, was determined by matching the integral of the product of clearance times the concentration of the first chamber (delayed 2 min) to the observed creatinine output measured over 10-min periods. The concentration in this chamber, after passing through a dispersive delay line analogous to the AutoAnalyzer, was matched to the observed AutoAnalyzer record by varying the volumes of the chambers and the passive exchange rates. This simple model provides an accurate description of the observed creatinine concentration and output and therefore can be used either as a building block in more extensive descriptive systems or as a basis for summarizing and comparing data obtained under varied physiological or pathological conditions.

Heppner, Richard L.; Harvey, R. B.; Bassingthwaighte, J. B.



Interdialytic creatinine change versus predialysis creatinine as indicators of nutritional status in maintenance hemodialysis  

PubMed Central

Background. Protein–energy wasting is common in patients on maintenance hemodialysis and is strongly associated with poor quality of life and mortality. However, clinical assessment of protein–energy wasting remains difficult. Predialysis creatinine levels are associated with mortality risk but may be influenced by both muscle mass and dialysis dose. This might be overcome by examining the rate of rise in creatinine between dialysis sessions. Methods. We conducted an observational cohort study among 81 patients on maintenance hemodialysis at our Veterans Affairs unit. Predialysis serum creatinine and change in serum creatinine between midweek dialysis sessions served as the predictor variables of interest and clinically available proxies of nutritional status and time to mortality served as the outcome variables. Linear regression and Cox proportional hazards models evaluated relationships, respectively. Results. The mean age of the study participants was 63 ± 10 years, 77 (95%) were male, mean body mass index was 27 ± 6 kg/m2 and 69% had diabetes. Median follow-up time was 13 months, during which 12 patients (15%) died. Interdialytic change in serum creatinine showed a strong direct correlation with predialysis serum creatinine (R = 0.96). Higher levels of both markers were associated with younger age, less residual urine volume and higher serum albumin, serum phosphorus and normalized protein catabolic rate (P < 0.05 for all). Both markers were approximately equally strongly associated with mortality. For example, compared to the highest predialysis creatinine tertile, participants in the lowest tertile (<6 mg/dL) had 5.5-fold [95% confidence interval (CI) 1.1, 26.6] higher risk of death. Similarly, participants in the lowest tertile of interdialytic change in creatinine (change <3.7 mg/dL/48 h), had 5.0-fold (95% CI 1.0, 24.4) higher death risk. Conclusions. Predialysis creatinine and interdialytic change in creatinine are both strongly associated with proxies of nutritional status and mortality in hemodialysis patients and are highly correlated. Interdialytic change in creatinine provided little additional information about nutritional status or mortality risk above and beyond predialysis creatinine levels alone.

Walther, Carl P.; Carter, Caitlin Wise; Low, Chai L.; Williams, Peter; Rifkin, Dena E.; Steiner, Robert W.



[Renal regulation of the excretion of urea in fasting camels].  


Experiments were performed with young two-humped camels exposed to 36-hour starvation with free access to water. The renal functions were measured by the standard clearance method. In spite of the administration of 20 micrograms DDAVP, a higher urine flow rate was recorded in the camels subjected to control measurements (feed intake) than in the fasting period (1.45 +/- 0.06 vs. 0.96 +/- 0.06 ml . min-1, P less than less than 0.001). On the second day of fasting the camels had a significantly reduced glomerular filtration rate (GFR 317.5 +/- 23.2 vs. 170.2 +/- 17.4 ml . min-1, P less than 0.001), urea output (700.5 +/- 62.9 vs. 352.2 +/- 64.7 mumol . min-1, P less than 0.005), and fractional excretion of urea (26.9 +/- 2.8 vs. 17.9 +/- 1.7%, P less than 0.01), whereas their tubular resorption. of urea (Reab urea/GFR) increased (6.28 +/- 0.61 vs. 9.12 +/- 0.82 mumol . ml-1, P less than 0.02). No significant difference was found in the concentration of urea in plasma in the fed camels and in fasting camels (8.55 +/- 0.64 vs. 11.18 +/- 1.09 mmol . l-1, N. S.). The creatinine inulin clearance ratio (C creat/Cin) was 0.92 +/- 0.07 when the animals were fed and 1.17 +/- 0.05 when the animals starved (P less than 0.001); this suggests that the clearance of endogenous creatinine is not suitable for GFR measurement in camels under different conditions of nutrition. The kidneys of camels regulate the excretion of urea during short-time fasting mainly through the reduction of glomerular filtration rate and just partly through an increased tubular resorption. PMID:6438869

Leng, L; Bod'a, K; Tasenov, K T; Karinbaev, R S; Makasev, E K; Rachimberdiev, S A; Tlegenov, D K; Jurgalieva, L A



Urinary calcium and uric acid excretion in children with vesicoureteral reflux.  


Urolithiasis is relatively common in children, and identifiable predisposing factors for stone formation, including metabolic and structural derangements, can be established in most cases. Vesicoureteral reflux (VUR) is a common cause of kidney stone formation. The pathophysiological mechanism of urolithiasis in reflux is related to urinary tract infection and urinary stasis, both of which promote urinary crystal formation, but metabolic causes, such as crystallurias (mostly hypercalciuria), may also be involved in this process. However, few studies on urinary calcium and uric acid excretion in children with VUR have been conducted. We have studied the frequency of hypercalciuria and hyperuricosuria in children with VUR and compared the results with those from a control group. The VUR group comprised 108 children with VUR (19 boys, 89 girls; age range 3 months to 12 years), and the control group comprised 110 healthy children without any history of reflux or urinary tract infection (30 boys, 80 girls; age range 2 months to 12 years). Fasting urine was analyzed for the calcium/creatinine (Ca/Cr) and uric acid/creatinine (UA/Cr) ratios. Hypercalciuria was more frequently diagnosed in the VUR patients than in the control group (21.3 vs. 3.6%; P?=?0.0001). Significant differences between the two groups were also found for the mean Ca/Cr and UA/Cr ratios (P?=?0.0001 and P?=?0.0001, respectively). No differences were found in the urinary Ca/Cr or UA/Cr ratios related to VUR grading or unilateral/bilateral VUR in the patient group, with the exception of those for hypercalciuria and mild VUR (P?=?0.03). The association of urinary stones and microlithiasis in the VUR group was 29.6%. Our results demonstrate that the frequency of hypercalciuria and hyperuricosuria was higher in pediatric patients with VUR than in healthy children. Knowing this relationship, preventive and therapeutic interventions for stone formation in VUR could be greatly expanded. PMID:21814729

Madani, Abbas; Kermani, Nooshin; Ataei, Neamatollah; Esfahani, Seyed Taher; Hajizadeh, Niloufar; Khazaeipour, Zahra; Rafiei, Sima



Creatinine Inhibits D-Amino Acid Oxidase  

Microsoft Academic Search

Inhibition of D-amino acid oxidase (DAO) activity by various uremic retention products and guanidino compounds was investigated. Creatinine (CTN) was found to inhibit DAO at a similar concentration in the sera of uremic patients. The inhibition was competitive and the Ki value was 2.7 mM. Moreover, CTN was shown to interact with flavin adenine dinucleotide (FAD), a coenzyme of DAO.

Y. Nohara; J. Suzuki; T. Kinoshita; M. Watanabe



[Uric acid metabolism in children with hyperuricosuria].  


We treated 39 children with hyperuricosuria (18 boys and 21 girls aged between 6 and 11 years). Treatment consisted of increased fluid intake, low salt and low purine diet and urine alkalization up to pH 6.5-6.8. We have selected two groups of patients with different uric acid [UA] metabolism parameters. In group I (21 children) mean value of serum UA was 2.52 mg/dL, mean urine UA excretion was 13.11 mg/kg/d and UA FE was 21.51%. In group II (18 children) mean value of serum UA was 4.7 mg/dL, mean urine UA excretion was 12.8 mg/kg/d and UA FE was 10.9%. In group I, treatment did not normalize uricosuria (13.57 mg/kg/d), urine pH was elevated (6.56). In group II uricosuria was diminished (8.37 mg/kg/d), urine pH was 6.37. 1. Disturbances of tubular secretion may be suspected in some children with hyperuricosuria and without hypouricemia. 2. The maintenance of urine pH within normal values is the basic of treatment in children with hyperuricosuria. 3. In children suspected of tubular transport disturbances appropriate tests of uric acid metabolism should be performed. PMID:10897600

Gadomska-Prokop, K; Konopielko, Z



Distribution Patterns of Uric Acid in Coronary Artery Disease  

Microsoft Academic Search

The uric acid levels in each of 335 cardiac patients were studied over a period of more than 3 months from the onset of the acute stage of coronary heart disease. Comparison was made with uric acid values obtained from a group of 316 normal subjects. Male patients with arteriosclerotic coronary artery disease with infarction generally exhibited rising concentrations of

Morris London; Mary Hums


Uric acid calculi: types, etiology and mechanisms of formation.  


The study of the composition and structure of 41 stones composed of uric acid was complemented by in vitro investigation of the crystallization of uric acid. Uric acid dihydrate (UAD) precipitates from synthetic urine under physiological conditions when the medium is supersaturated with respect to this compound, though uric acid anhydrous (UAA) represents the thermodynamically stable form. Solid UAD in contact with liquid transforms into UAA within 2 days. This transition is accompanied by development of hexagonal bulky crystals of UAA and appearance of cracks in the UAD crystals. Uric acid calculi can be classified into two groups, differing in outer appearance and inner structure. Type I includes stones with a little central core and a compact columnar UAA shell and stones with interior structured in alternating densely non-columnar layers developed around a central core; both of them are formed mainly by crystalline growth at low uric acid supersaturation. Type II includes porous stones without inner structure and stones formed by a well developed outermost layer with an inner central cavity; this type of stones is formed mainly by sedimentation of uric acid crystals generated at higher uric acid supersaturation. PMID:11074067

Grases, F; Villacampa, A I; Costa-Bauzá, A; Söhnel, O



Nasal secretion of the ozone scavenger uric acid  

SciTech Connect

Uric acid, an important scavenger of ozone, has been identified as the major low molecular weight antioxidant in baseline and cholinergically induced nasal secretions. The purpose of this study was to determine the specific tissue source of uric acid in airway secretions. The secretion of uric acid is increased by cholinergic stimulation and correlates closely with the secretion of lactoferrin (a nasal glandular protein), suggesting that submucosal glands are involved. Indeed, nasal turbinate tissue was found to contain uric acid. However, careful analysis of nasal turbinate tissue failed to reveal the presence of xanthine oxidase, the enzyme responsible for uric acid synthesis. These data suggest that uric acid might be taken up secondarily by glands from plasma. This possibility was strengthened by the observation that lowering the plasma urate level with probenecid concomitantly lowered urate secretion. These findings are consistent with the hypotheses that the principal source of uric acid in nasal secretions is plasma and that uric acid is taken up, concentrated, and secreted by nasal glands.

Peden, D.B.; Swiersz, M.; Ohkubo, K.; Hahn, B.; Emery, B.; Kaliner, M.A. (Univ. of North Carolina, Chapel Hill (United States))



Clinical and biochemical aspects of uric acid overproduction  

Microsoft Academic Search

Purine nucleotides are synthesized and degraded through a regulated series of reactions which end in the formation of uric acid. Increased uric acid synthesis may be the result of two major pathophysiological disorders: increasedde novo purine synthesis and enhanced purine nucleotide degradation, both of which may be the result of an increased or decreased enzyme activity. In addition, some conditions

J. García Puig; F. Antón Mateos



Chemiresistor urea sensor  


A sensor to detect and quantify urea in fluids resulting from hemodialysis procedures, and in blood and other body fluids. The sensor is based upon a chemiresistor, which consists of an interdigitated array of metal fingers between which a resistance measured. The interdigitated array is fabricated on a suitable substrate. The surface of the array of fingers is covered with a coating containing the enzyme urease which catalyzes the hydrolysis of urea to form the ammonium ion, the bicarbonate ion, and hydroxide-chemical products which provide the basis for the measured signal. In a typical application, the sensor could be used at bedside, in conjunction with an appropriate electronics/computer system, in order to determine the hemodialysis endpoint. Also, the chemiresistor used to detect urea, can be utilized with a reference chemiresistor which does not contain urease, and connected in a differential measurement arrangement, such that the reference chemiresistor would cancel out any fluctuations due to background effects.

Glass, Robert S. (Livermore, CA)



Effect of dietary protein variation in terms of net truly digested intestinal protein (DVE) and rumen degraded protein balance (OEB) on the concentrations and excretion of urinary creatinine, purine derivatives and microbial N supply in sheep: comparison with the prediction from the DVE\\/OEB model  

Microsoft Academic Search

This study examined (1) the effects of dietary protein variation in terms of net truly digestible intestinal protein (DVE value) and rumen degraded protein balance (OEB value) on the concentrations and daily excretion of urinary products (creatinine, allantoin, combined value for uric acid, hypoxanthine and xanthine, total purine derivatives (PD)) and microbial N supply in sheep; (2) the relationship between

P. Yu; L. Boon-ek; B. J. Leury; A. R. Egan



Reverse iontophoresis of urea in health and chronic kidney disease: a potential diagnostic and monitoring tool?  

PubMed Central

Background Patients with chronic kidney disease (CKD) need regular monitoring, usually by blood urea and creatinine measurements, needing venepuncture, frequent attendances and a healthcare professional, with significant inconvenience. Noninvasive monitoring will potentially simplify and improve monitoring. We tested the potential of transdermal reverse iontophoresis of urea in patients with CKD and healthy controls. Methods Using a MIC 2® Iontophoresis Controller, reverse iontophoresis was applied on the forearm of five healthy subjects (controls) and 18 patients with CKD for 3–5 h. Urea extracted at the cathode was measured and compared with plasma urea. Results Reverse iontophoresis at 250 ?A was entirely safe for the duration. Cathodal buffer urea linearly correlated with plasma urea after 2 h (r = 0·82, P < 0·0001), to 3·5 h current application (r = 0·89, P = 0·007). The linear equations y = 0·24x + 1 and y = 0·21x + 4·63 predicted plasma urea (y) from cathodal urea after 2 and 3 h, respectively. Cathodal urea concentration in controls was significantly lower than in patients with CKD after a minimum current application of 2 h (P < 0·0001), with the separation between the two groups becoming more apparent with longer application (P = 0·003). A cathodal urea cut-off of 30 ?M gave a sensitivity of 83·3% and positive predictive value of 87% CKD. During haemodialysis, the fall in cathodal urea was able to track that of blood urea. Conclusion Reverse iontophoresis is safe, can potentially discriminate patients with CKD and healthy subjects and is able to track blood urea changes on dialysis. Further development of the technology for routine use can lead to an exciting opportunity for its use in diagnostics and monitoring.

Ebah, Leonard M; Read, Ian; Sayce, Andrew; Morgan, Jane; Chaloner, Christopher; Brenchley, Paul; Mitra, Sandip



Reductive alkylation of urea: A practical route to substituted ureas  

Microsoft Academic Search

Conditions are disclosed for the formation of either mono- or di-substituted ureas by reductive alkylation, which are readily adaptable to large scale preparations. Dehydrating agents such as acetyl chloride or trimethylsilyl chloride effectively promote the condensation of ureas and aldehydes. Reduction of the adducts affords the mono- or di-substituted ureas in high yields.

Daqiang Xu; Lech Ciszewski; Tangqing Li; Olijan Repi?; Thomas J. Blacklock



Increase in serum creatinine in a patient on continuous peritoneal dialysis: potential mechanisms and management.  


A large elevation in serum creatinine (S(Cr)) on an unchanged peritoneal dialysis (PD) schedule is usually caused by a decrease in total creatinine clearance (C(Cr)), but may also reflect an increase in creatinine (Cr) production. A meticulously compliant 43-year-old man with lupus nephritis on automated nocturnal PD plus an additional daytime exchange developed a rise in S(Cr) to 16.73 mg/dL from 8.06 mg/dL after starting fenofibrate, while total C(Cr) decreased only to 61.5 L/1.73 m2 from 77.4 m2 weekly. Creatinine excretion was 16.4 mg/(kg x 24 h) pre-fenofibrate. It increased to a high of 26.2 mg/(kg x 24 h) during the period of fenofibrate intake and returned to 21.9 mg/ (kg x 24 h) 2 months after discontinuation of that drug. The patient's age, weight, height, body mass index, 24-h drain and urine volumes, total Kt/V urea, serum urea nitrogen, urea nitrogen excretion, and (for the pre-fenofibrate period) S(Cr), Cr excretion, estimated Cr production, and measured-to-predicted Cr excretion (using a formula developed in PD patients) were within the 95% confidence intervals (CIs) obtained in a control group of 24 other men on similar PD schedules. The patient's Cr excretion and production were above the 95% CIs of the control group while he was on fenofibrate, and they returned toward or within the 95% CIs after cessation of the drug. The patient's serum creatine phosphokinase was not elevated while he was taking fenofibrate. A thorough investigation of the potential mechanisms of a rise in S(Cr) during the course of PD is warranted to determine if the rise is disproportional to any fall in total C(Cr). In the latter case, Cr excretion and production should be evaluated, and if elevated, conditions potentially causing the rise in Cr production (fenofibrate in this patient) should be sought, and appropriate therapeutic interventions should be implemented. PMID:23311210

Xu, Zhi; Gabaldon, Darlene; Wiggins, Brenda; Rondon-Berrios, Helbert; VanderJagt, Dorothy J; Tzamaloukas, Antonios H



Urea Process Analytical Study.  

National Technical Information Service (NTIS)

In an effort to help determine the feasibility of the Urea process for production of the amine fuels, AFRPL established an in-house program to develop a useful analytical technique for monitoring the critical DMU to UDMH reaction. It was the absence of su...

L. A. Dee S. G. Wax



[The fibrinolytic system in uric acid dysmetabolism].  


The subjects of the study were 50 first-degree relatives of patients with uric acid (UA) dysmetabolism. The subjects were divided into three groups: 15 with hyperuricosuria and normal UA blood level (group 1), 17--with hyperuricosuria and hyperuricemia (group 2), and 18--with hyperuricemia and lowered UA clearance (group 3). All of them displayed inhibited urine fibrinolytic activity (UFA) and reduced urokinase activity. The degree of UFA inhibition correlated with urokinase activity (r = 0.60) and grew from group 1 to group 3; the subjects in the latter had maximal manifestations of tubulointerstitial nephritis, which suggests that disorder of the local fibrinolytic mechanisms plays an important role in the development and progress of urate tubulointerstitial renal lesion. No changes of blood fibrinolysis were observed. PMID:16320701

Podorol'skaia, L V; Shcherbak, A V; Andreenko, G V; Lysenko, L V; Balkarov, I M



Role of uric acid in multiple sclerosis.  


In the past decade, a growing number of evidence has implicated free radicals in a variety of pathophysiological conditions including aging, cancer, and coronary heart disease. Analyses of different aspects of multiple sclerosis (MS) pathology with respect to oxidative damage have also revealed evidence of free radical injury to the central nervous system (CNS), although attempts to protect the CNS using various antioxidants have met with only moderate success. Several recent studies have reported lower levels of uric acid (UA), a major scavenger of reactive nitrogen species, in MS patients, while other studies found no such correlation. Here, we discuss these studies as well as current efforts to manipulate serum UA levels in MS patients. PMID:18219824

Spitsin, S; Koprowski, H



Increased creatinine clearance in polytrauma patients with normal serum creatinine: a retrospective observational study  

Microsoft Academic Search

Introduction  The aim of this study, performed in an intensive care unit (ICU) population with a normal serum creatinine, was to estimate\\u000a urinary creatinine clearance (CLCR) in a population of polytrauma patients (PT) through a comparison with a population of non trauma patients (NPT).\\u000a \\u000a \\u000a \\u000a \\u000a Methods  This was a retrospective, observational study in a medical and surgical ICU in a university hospital. A

Vincent Minville; Karim Asehnoune; Stephanie Ruiz; Audrey Breden; Bernard Georges; Thierry Seguin; Ivan Tack; Acil Jaafar; Sylvie Saivin; Olivier Fourcade; Kamran Samii; Jean Marie Conil



First trimester uric acid and adverse pregnancy outcomes  

PubMed Central

BACKGROUND The association of elevated serum uric acid with the development of hypertension is established outside of pregnancy. We investigated whether first trimester uric acid was associated with the development of the following: gestational hypertension or preeclampsia, these outcomes stratified by presence of hyperuricemia at delivery since this denotes more severe disease, preterm birth or small for gestational age (SGA). METHODS Uric acid was measured in 1541 banked maternal plasma samples from a prior prospective cohort study that were collected at a mean gestational age of 9.0 (± 2.5) weeks. Polytomous regressions were performed and adjusted for parity and pre-pregnancy body mass index. RESULTS First trimester uric acid in the highest quartile (>3.56 mg/dL) compared to lowest three quartiles was associated with an increased risk of developing preeclampsia (adjusted OR = 1.82; 95% CI, 1.03–3.21) but not gestational hypertension. In women with hypertensive disease complicated by hyperuricemia at delivery, high first trimester uric acid was associated with a 3.22-fold increased risk of hyperuricemic gestational hypertension and a 3.65-fold increased risk of hyperuricemic preeclampsia. High first trimester uric acid was not associated with gestational hypertension or preeclampsia without hyperuricemia at delivery, preterm birth, or SGA. In women who developed hypertensive disease, elevated uric acid at delivery was only partly explained by elevated uric acid in the first trimester (r2 = .23). CONCLUSIONS First trimester elevated uric acid was associated with later preeclampsia and more strongly with preeclampsia and gestational hypertension with hyperuricemia.

Laughon, S.K.; Catov, J.; Powers, R.W.; Roberts, J.M.; Gandley, R.E.



Major contribution of tubular secretion to creatinine clearance in mice  

PubMed Central

This study was performed to quantify the fraction of excreted creatinine not attributable to creatinine filtration for accurately determining the glomerular filtration rate in mice. To measure this we compared creatinine filtration with the simultaneous measurement of inulin clearance using both single-bolus fluorescein isothiocyanate (FITC)-inulin elimination kinetics and standard FITC-inulin infusion. During anesthesia, creatinine filtration was found to be systematically higher than inulin clearance in both male and female C57BL/6J mice. The secretion fraction was significantly less in female mice. Administration of either cimetidine or para-aminohippuric acid, competitors of organic cation and anion transport respectively, significantly reduced the secretion fraction in male and female mice and both significantly increased the plasma creatinine level. Creatinine secretion in both genders was not mediated by the organic cation transporters OCT1 or OCT 2 since secretion fraction levels were identical in FVB wild-type and OCT1/2 knockout mice. Thus, secretion accounts for about 50 and 35% of excreted creatinine in male and female mice, respectively. Increasing plasma creatinine threefold by infusion further increased the secretion fraction. Renal organic anion transporter 1 mRNA expression was higher in male than in female mice, reflecting the gender difference in creatinine secretion. Hence we show that there is a major secretory contribution to creatinine excretion mediated through the organic anion transport system. This feature adds to problems associated with measuring endogenous creatinine filtration in mice.

Eisner, Christoph; Faulhaber-Walter, Robert; Wang, Yaohui; Leelahavanichkul, Asada; Yuen, Peter S.T.; Mizel, Diane; Star, Robert A.; Briggs, Josephine P.; Levine, Mark; Schnermann, Jurgen



Renal Excretion of Uric Acid. Alterations during Stressful Underwater Demolition Team Training.  

National Technical Information Service (NTIS)

Serum uric acid and 24-hour uric acid excretion were determined in 16 men during various phases of U.S. Navy Underwater Demolition Team training activities. Elevations of serum uric acid were associated with decreases in uric acid clearance and decreases ...

L. M. Zir W. B. McHugh R. H. Rahe R. J. Arthur R. T. Rubin



Quinine and Urea  

NSDL National Science Digital Library

The WebWare molecules of the month are discussed in two laboratory articles in this issue. Quinine is studied in the article "A Fluorimetric Approach to Studying the Effects of Ionic Strength on Reaction Rates: An Undergraduate Steady-State Fluorescence Laboratory Experiment" by Stephen W. Bigger, Peter J. Watkins, and Bruce Verity. Urea, a typical protein denaturant, is used as a cosolvent in the article "Transfer Free Energy and the Hydrophobic Effect" by Joseph M. Serafin.


21 CFR 862.1775 - Uric acid test system.  

Code of Federal Regulations, 2013 CFR




Uric Acid as a Mediator of Diabetic Nephropathy  

PubMed Central

Despite the advances in the management of patients with diabetes, diabetic nephropathy (DN) remains the most common cause of end stage renal disease (ESRD) in the US and worldwide. Inflammation and endothelial dysfunction appear to play a central role in the onset and the progression of DN. Recent evidence has emerged in the last decade to suggest uric acid is an inflammatory factor and may play a role in endothelial dysfunction. This has lead our group and others to explore the role of uric acid in the onset and progression of DN. In this review, we will highlight some of the animal and human studies that implicate uric acid in DN. Based on the evidence we review, we conclude the need for properly planned randomized controlled studies to lower uric acid levels and assess the impact of such therapy on diabetic kidney disease.

Jalal, Diana I.; Maahs, David M; Hovind, Peter; Nakagawa, Takahiko



Relationship Between Serum Cystatin C and Creatinine or Dialysis Adequacy in Patients on Chronic Maintenance Hemodialysis  

PubMed Central

Background Glomerular filtration rate (GFR) is widely estimated by serum creatinine based equations such as Cockcroft-Gault (CG) standardized for body surface, and an abbreviated formula derived from MDRD (modification of diet in renal disease) study. However, some studies suggested that creatinine based estimation of GFR formula can be replaced by cystatin C based formula. Objectives The aim of this study was to determine whether cystatin C based equation could be used as an indicator for renal function in hemodialysis patients compared to MDRD equation; and whether cystatin C, a dialyzable molecule, was related to Kt/V, the marker for dialysis adequacy. Patients and Methods In this cross-sectional study, 98 patients on chronic hemodialysis were included. Plasma levels of urea and creatinine were measured before and after dialysis, and cystatin C was measured before dialysis. GFR was calculated and compared. Results The mean age of patients was 55.50 ± 16.10 (24-86) years and 66 cases were male (67.3%). The GFR was estimated at 6.05 ± 2.36 and 5.83 ± 2.19 cc/min by MDRD and cystatin C based formulas, respectively, with a significant correlation (r = 0.51; P < 0.001). Serum cystatin C level was 9.74 ± 2.47 mg/L which showed significant reverse correlation with both MDRD (r = -0.46; P < 0.001) and cystatin C based formulas (r = -0.87; P < 0.001). Neither creatinine nor serum cystatin C showed correlation with Kt/V, as the marker of dialysis adequacy. Conclusions Serum cystatin C may be considered as an indicator of renal function in patients under maintenance hemodialysis.

Khorgami, Zhinoos; Abdollahi, Alireza; Soleimani, Samaneh; Ahamadi, Farrokhlagha; Mahdavi-Mazdeh, Mitra



Inactivation of Nitric Oxide by Uric Acid  

PubMed Central

The 1980 identification of nitric oxide (NO) as an endothelial cell-derived relaxing factor resulted in an unprecedented biomedical research of NO and established NO as one of the most important cardiovascular, nervous and immune system regulatory molecule. A reduction in endothelial cell NO levels leading to “endothelial dysfunction” has been identified as a key pathogenic event preceding the development of hypertension, metabolic syndrome, and cardiovascular disease. The reduction in endothelial NO in cardiovascular disease has been attributed to the action of oxidants that either directly react with NO or uncouple its substrate enzyme. In this report, we demonstrate that uric acid (UA), the most abundant antioxidant in plasma, reacts directly with NO in a rapid irreversible reaction resulting in the formation of 6-aminouracil and depletion of NO. We further show that this reaction occurs preferentially with NO even in the presence of oxidants peroxynitrite and hydrogen peroxide and that the reaction is at least partially blocked by glutathione. This study shows a potential mechanism by which UA may deplete NO and cause endothelial dysfunction, particularly under conditions of oxidative stress in which UA is elevated and intracellular glutathione is depleted.

Gersch, Christine; Palii, Sergiu P.; Kim, Kyung Mee; Angerhofer, Alexander; Johnson, Richard J.; Henderson, George N.



Elevated plasma creatinine due to creatine ethyl ester use.  


Creatine is a nutritional supplement widely used in sport, physical fitness training and bodybuilding. It is claimed to enhance performance. We describe a case in which serum creatinine is elevated due to the use of creatine ethyl esther. One week after withdrawal, the plasma creatinine had normalised. There are two types of creatine products available: creatine ethyl esther (CEE) and creatine monohydrate (CM). Plasma creatinine is not elevated in all creatine-using subjects. CEE , but not CM, is converted into creatinine in the gastrointestinal tract. As a result the use of CEE may be associated with elevated plasma creatinine levels. Since plasma creatinine is a widely used marker for renal function, the use of CEE may lead to a false assumption of renal failure. PMID:21411845

Velema, M S; de Ronde, W



21 CFR 862.1225 - Creatinine test system.  

Code of Federal Regulations, 2013 CFR




Application of creatinine-sensitive biosensor for hemodialysis control.  


The highly sensitive and selective potentiometric biosensor for creatinine determination has been developed by us earlier. In it, pH-sensitive field effect transistors were used as transducer and immobilized creatinine deiminase (EC a biosensitive element. In the work presented, we optimized this biosensor for creatinine analysis in real samples of dialysate in patients with renal failure. The optimized version of biosensor was applied for on-line monitoring of the level of creatinine in the patient's dialysate fluid in the course of dialysis session. High correlation between the biosensor analysis and traditional Jaffe method was demonstrated. PMID:22459582

Zinchenko, O A; Marchenko, S V; Sergeyeva, T A; Kukla, A L; Pavlyuchenko, A S; Krasyuk, E K; Soldatkin, A P; El'skaya, A V



The shape of urea  

Microsoft Academic Search

The shape of the urea molecule has been studied by analysing the microwave spectra of several isotopic species, yielding rs coordinates of all atoms except that of C, the latter being derived from first-moment equations, and by ab initio molecular-orbital calculations at the MP26-311++G(d,p) level. The derived bond lengths and angles are: r(CO), 1.221 Å; r(CN), 1.378 Å; r(NH(5)), 0.998

Peter D. Godfrey; Ronald D. Brown; Andrew N. Hunter



Serum uric acid level in acute stroke patients  

PubMed Central

Background The role of uric acid as a risk factor for vascular disease and acute stroke is controversial and there is little information about it. In this study, we determined serum uric acid levels in patients with acute stroke and assessed its relationship with cerebrovascular risk factors. Methods In this cross sectional study, we assessed patients with acute stroke who were admitted in Firoozgar Hospital from September 2010 to March 2011. Clinical records of patients and their serum uric acid level was investigated. Finally, collected data were analyzed using SPSS software Ver.16. Results Fifty five patients with acute stroke were evaluated who 25 of these patients (45.5%) were female and 30 of them (54.5%) were male. The mean age of patients was 67±14 years. Mean serum uric acid levels in the patients studied 5.94±1.70 mg/dl, and about half of the patients (47.3%) were hyperuricemic. There was a significant negative correlation between age of patients and their serum uric acid level (p=0.04, R =-0.27). Uric acid level was significantly higher in men than women (p=0.03). Hyperuricemia was associated with increased amounts of triglycerides and Low-density lipoprotein (LDL) cholesterol (p=0.03, p=0.02). In patients with acute stroke, there was no significant association between serum uric acid level and diabetes mellitus, hypertension, history of ischemic heart disease, smoking, prescription rTPA, and type of stroke. Conclusion Due to the high prevalence of hyperuricemia in patients with acute stroke, and its accompanying increase in triglyceride and LDL cholesterol levels, it can be considered as a risk factor for acute stroke.

Khuzan, Mahbubeh; Najimi, Neda; Motamed, Mohamad R.; Fereshtehnejad, Seyed-Mohammad



Uric acid and chronic kidney disease: which is chasing which?  


Serum uric acid is commonly elevated in subjects with chronic kidney disease (CKD), but was historically viewed as an issue of limited interest. Recently, uric acid has been resurrected as a potential contributory risk factor in the development and progression of CKD. Most studies documented that an elevated serum uric acid level independently predicts the development of CKD. Raising the uric acid level in rats can induce glomerular hypertension and renal disease as noted by the development of arteriolosclerosis, glomerular injury and tubulointerstitial fibrosis. Pilot studies suggest that lowering plasma uric acid concentrations may slow the progression of renal disease in subjects with CKD. While further clinical trials are necessary, uric acid is emerging as a potentially modifiable risk factor for CKD. Gout was considered a cause of CKD in the mid-nineteenth century [1], and, prior to the availability of therapies to lower the uric acid level, the development of end-stage renal disease was common in gouty patients. In their large series of gouty subjects Talbott and Terplan found that nearly 100% had variable degrees of CKD at autopsy (arteriolosclerosis, glomerulosclerosis and interstitial fibrosis) [2]. Additional studies showed that during life impaired renal function occurred in half of these subjects [3]. As many of these subjects had urate crystals in their tubules and interstitium, especially in the outer renal medulla, the disease became known as gouty nephropathy. The identity of this condition fell in question as the presence of these crystals may occur in subjects without renal disease; furthermore, the focal location of the crystals could not explain the diffuse renal scarring present. In addition, many subjects with gout also had coexistent conditions such as hypertension and vascular disease, leading some experts to suggest that the renal injury in gout was secondary to these latter conditions rather than to uric acid per se [4]. Indeed, gout was removed from the textbooks as a cause of CKD, and the common association of hyperuricemia with CKD was solely attributed to the retention of serum uric acid that is known to occur as the glomerular filtration rate falls. Renewed interest in uric acid as a cause of CKD occurred when it was realized that invalid assumptions had been made in the arguments to dismiss uric acid as a risk factor for CKD [5]. The greatest assumption was that the mechanism by which uric acid would cause kidney disease would be via the precipitation as crystals in the kidney, similar to the way it causes gout. However, when laboratory animals with CKD were made hyperuricemic, the renal disease progressed rapidly despite an absence of crystals in the kidney [6]. Since this seminal study, there has been a renewed interest in the potential role uric acid may have in both acute and CKD. We briefly review some of the major advances that have occurred in this field in the last 15 years. PMID:23543594

Johnson, Richard J; Nakagawa, Takahiko; Jalal, Diana; Sánchez-Lozada, Laura Gabriela; Kang, Duk-Hee; Ritz, Eberhard



Purine metabolism of uric acid urolithiasis induced in newborn piglets.  


To clarify the relationship between uric acid urolithiasis and purine catabolites in newborn piglets, the incidence of uric acid urolithiasis and the plasma concentrations of xanthine, hypoxanthine, uric acid and allantoin were examined in 32 piglets. The newborn piglets were divided into two groups: normal (over 1.2 kg, n = 18, group N) and low body weight (below 0.9 kg, n = 14, group L). The animals in both groups were given water (non-nutrition, n = 11, treatment W), artificial milk (normal nutrition, n = 12, treatment M), or a combination of water and allopurinol (prophylactic treatment for the urolithiasis, n = 9, treatment A), during the first 60-hr of birth. At necropsy, the incidence of urolithiasis was higher in the piglets that received treatment W than those in the treatment M or A in both the N and L groups. In group L, the plasma xanthine, hypoxanthine and uric acid concentrations were markedly increased in the piglets that underwent treatment W compared with the treatment M. In both the N and L groups, the plasma allantoin concentration was higher in the treatment W piglets as compared with the treatment M piglets. These results suggested that the occurrence of uric acid urolithiasis in the newborn piglets is attributable to increased purine catabolites due to a starvational condition after birth. PMID:9524944

Kakino, J; Sato, R; Naito, Y



Uric Acid nephrolithiasis: recent progress and future directions.  


The prevalence of urolithiasis has been increasing for the past few decades in industrialized nations. Uric acid calculi account for a significant percentage of urinary stones. Certain risk factors may be involved in the pathogenesis of uric acid nephrolithiasis, including hyperuricosuria, low urinary volume, and persistently low urinary pH. Patients with medical conditions that promote profound hyperuricosuria are at high risk of developing uric acid calculi. These conditions include chronic diarrheal states; myeloproliferative disorders; insulin resistance, including diabetes mellitus; and monogenic metabolic disorders, such as Lesch-Nyhan syndrome. Computed tomography can provide a definitive diagnosis. Except in cases in which there is severe obstruction, progressive azotemia, serious infection, or unremitting pain, the initial treatment of patients with uric acid nephrolithiasis should be medical dissolution therapy because this approach is successful in the majority of cases. A thorough review of the epidemiology and pathophysiology of uric acid nephrolithiasis is crucial for the diagnosis, treatment, and prevention of stones in patients with this condition. PMID:17396168

Ngo, Tin C; Assimos, Dean G



Allopurinol, uric acid, and oxidative stress in cardiorenal disease.  


In humans, the hepatic end product of purine metabolism is uric acid. Serum uric acid levels physiologically and gradually rise during human lifetime. Hyperuricemia also arises from excess dietary purine or ethanol intake, decreased renal excretion of uric acid, tumor lysis in lymphoma, leukemia or solid tumors, and sometimes pharmacotherapy. The definition of hyperuricemia is currently arbitrary. Hyperuricemia is associated with chronic kidney disease, arterial hypertension, coronary artery and heart disease, cerebrovascular disease and diabetes mellitus. Xanthine oxidase, a hepatic enzyme, catalyzes the production of uric acid, nitric oxide, and reactive oxygen species, which potentially damage deoxyribonucleic acid, ribonucleic acid and proteins, inactivate enzymes, oxidize amino acids and convert poly-unsaturated fatty acids to lipids. This is believed to contribute to atherosclerosis, endothelial dysfunction, renovascular hypertension, and cardiovascular disease. Xanthine oxidase inhibition efficiently blocks uric acid generation, and this improves glomerular filtration rates, systemic blood pressure, and cerebro-cardiovascular outcomes. Here, data from animal, in vivo, retro- and prospective, and interventional studies are reported. PMID:21547469

Riegersperger, Markus; Covic, Adrian; Goldsmith, David



Separation methods applicable to urinary creatine and creatinine  

Microsoft Academic Search

Urinary creatinine has been analyzed for many years as an indicator of glomerular filtration rate. More recently, interest in studying the uptake of creatine as a result of creatine supplementation, a practice increasingly common among bodybuilders and athletes, has lead to a need to measure urinary creatine concentrations. Creatine levels are of the same order of magnitude as creatinine levels

Truis Smith-Palmer



Low serum urea level in dehydrated patients with central diabetes insipidus.  


Dehydrated patients usually present with an elevated serum urea level, owing in part to increased renal reabsorption of urea mediated by antidiuretic hormone (ADH). We carried out a study to examine whether, during dehydration, the variations in the serum urea level could discriminate patients with central diabetes insipidus (CDI) from those with dehydration not due to CDI. We studied retrospectively 27 episodes of dehydration in 23 patients with CDI and 14 episodes in 14 patients without CDI. The mean serum urea level was 2.9 mmol/L in the CDI group and 15.4 mmol/L in the patients without CDI (p less than 0.001); the mean serum sodium level was 155 mmol/L in both groups. All the patients with CDI had a sodium/urea ratio greater than 24.2, whereas the ratio was less than 21.7 in all the patients without CDI. In the patients with CDI a positive correlation was found between the magnitude of diuresis and the percentage decrease in the serum urea level compared with the level before dehydration (p less than 0.001). In the patients with CDI the serum urea level returned to the level before dehydration after the administration of vasopressin; a striking increase in the clearance of urea, which exceeded the creatinine clearance, was observed during dehydration in the three patients in whom clearance studies were done. The results suggest that serum urea values can be used to distinguish patients dehydrated because of CDI from those with hypertonic dehydration but without ADH deficiency and that during dehydration the net reabsorption of urea is dependent on the renal action of ADH. PMID:3179869

Comtois, R; Bertrand, S; Beauregard, H; Vinay, P



Dicarboxylic Acid-Urea Complexes.  

National Technical Information Service (NTIS)

A study of the reaction of several acids with urea resulted in a series of compounds of varying stoichiometry and structure. The acids having the structure HO2C(CH2)nCO2H produced saltlike compounds with urea when n = 0 and 1 and H-bonded complexes for n ...

J. Radell B. W. Brodman J. J. Domanski



Urea kinetic modeling for CRRT  

Microsoft Academic Search

Urea kinetic modeling (UKM) for dialysis quantification and prescription, although widely used in chronic renal failure (CRF), has been largely absent in the acute setting. A quantitative approach to prescription of continuous renal replacement therapies (CRRTs) for acute renal failure (ARF) based on UKM is presented. For patients with a relatively constant urea generation rate, G, who are receiving a

Laurie Garred; Martine Leblanc; Bernard Canaud



Serum Uric Acid and Non-Alcoholic Fatty Liver Disease in Non-Diabetic Chinese Men  

PubMed Central

Increased serum uric acid (SUA) levels may be involved in the development of non-alcoholic fatty liver disease (NAFLD) in men presenting with metabolic syndrome (MetS) and/or insulin resistance. We aimed to determine the independent relationship between SUA and NAFLD in non-diabetic Chinese male population, and to explore the determinants of SUA levels among indexes of adiposity, lipid, and genotypes pertaining to triglycerides metabolism, inflammation, oxidative stress, and SUA concentrations. A total of 1440 men, classified depending on the presence of ultrasonographically detected NAFLD, underwent a complete healthy checkup program. Genotypes were extracted from our previously established genome-wide association study database. After adjusting for age, smoking, drinking, body mass index, homeostasis model assessment of insulin resistance, C-reactive protein, creatinine, alanine aminotransferase (ALT) and components of metabolic syndrome, the odds ratio for NAFLD, comparing the highest with the lowest SUA quartile, was 2.81 (95% confidence interval 1.66–4.76). A stepwise multivariate linear regression analysis (R2?=?0.238, P<0.001) retained age, waist circumference, serum creatinine, triglycerides, the Q141K variant in ABCG2 (rs2231142) and NAFLD as significant predictors of SUA levels (all P<0.001). Besides, ALT and Met196Arg variant in TNFRSF1B (rs1061622) additionally associated with SUA among individuls with NAFLD. Our data suggest that in Chinese men, elevated SUA is significantly associated with NAFLD, independent of insulin resistance and other metabolic disorders, such as central obesity or hypertriglyceridemia. Meanwhile, among subjects with NAFLD, index of liver damage, such as elevated ALT combined with genetic susceptibility to inflammation associated with increased SUA levels.

Tan, Aihua; Gao, Yong; Liang, Zhengjia; Shi, Deyi; Huang, Zhang; Zhang, Haiying; Yang, Xiaobo; Lu, Zheng; Wu, Chunlei; Liao, Ming; Sun, Yu; Qin, Xue; Hu, Yanling; Li, Li; Peng, Tao; Li, Zhixian; Yang, Xiaoli; Mo, Zengnan



Serum uric acid and non-alcoholic fatty liver disease in non-diabetic Chinese men.  


Increased serum uric acid (SUA) levels may be involved in the development of non-alcoholic fatty liver disease (NAFLD) in men presenting with metabolic syndrome (MetS) and/or insulin resistance. We aimed to determine the independent relationship between SUA and NAFLD in non-diabetic Chinese male population, and to explore the determinants of SUA levels among indexes of adiposity, lipid, and genotypes pertaining to triglycerides metabolism, inflammation, oxidative stress, and SUA concentrations. A total of 1440 men, classified depending on the presence of ultrasonographically detected NAFLD, underwent a complete healthy checkup program. Genotypes were extracted from our previously established genome-wide association study database. After adjusting for age, smoking, drinking, body mass index, homeostasis model assessment of insulin resistance, C-reactive protein, creatinine, alanine aminotransferase (ALT) and components of metabolic syndrome, the odds ratio for NAFLD, comparing the highest with the lowest SUA quartile, was 2.81 (95% confidence interval 1.66-4.76). A stepwise multivariate linear regression analysis (R(2)?=?0.238, P<0.001) retained age, waist circumference, serum creatinine, triglycerides, the Q141K variant in ABCG2 (rs2231142) and NAFLD as significant predictors of SUA levels (all P<0.001). Besides, ALT and Met196Arg variant in TNFRSF1B (rs1061622) additionally associated with SUA among individuls with NAFLD. Our data suggest that in Chinese men, elevated SUA is significantly associated with NAFLD, independent of insulin resistance and other metabolic disorders, such as central obesity or hypertriglyceridemia. Meanwhile, among subjects with NAFLD, index of liver damage, such as elevated ALT combined with genetic susceptibility to inflammation associated with increased SUA levels. PMID:23935829

Xie, Yuanliang; Wang, Mengjie; Zhang, Youjie; Zhang, Shijun; Tan, Aihua; Gao, Yong; Liang, Zhengjia; Shi, Deyi; Huang, Zhang; Zhang, Haiying; Yang, Xiaobo; Lu, Zheng; Wu, Chunlei; Liao, Ming; Sun, Yu; Qin, Xue; Hu, Yanling; Li, Li; Peng, Tao; Li, Zhixian; Yang, Xiaoli; Mo, Zengnan



[Metabolism of purine nucleotides and the production of uric acid].  


The molecular and biochemical aspects of purine nucleotide biosynthesis through de novo and salvage pathways, the production of uric acid, and their regulation mechanisms are reviewed for further understanding of hyperuricemia and gout. The metabolic rate of purine nucleotide biosynthesis is chiefly determined by the regulation of the de novo pathway, especially amidophosphoribosyltransferase and PRPP synthetase, and the accumulation of uric acid results from the acceleration of de novo biosynthesis and catabolism of purine nucleotide or the decrease in urinary excretion of uric acid. Moreover, several enzyme mutations of purine nucleotide metabolism are also clinically important including gout with hyperactive HPRT and the deficiency of HPRT (Lesch-Nyhan syndrome), adenylosuccinate lyase, xanthine oxidase, APRT, PNP, or ADA (SCID) with gene therapy. PMID:8976090

Yamaoka, T; Itakura, M



Uric Acid and Insulin Sensitivity and Risk of Incident Hypertension  

PubMed Central

Background Uric acid, insulin sensitivity, and endothelial dysfunction may be important in the development of hypertension. Corresponding circulating biomarkers are associated with risk of hypertension in many studies. However, because these factors may be interrelated, whether they independently influence risk is unknown. Methods Among 1,496 young women who did not have hypertension at baseline, we prospectively analyzed the association between fasting plasma levels of uric acid, insulin, triglycerides, the insulin sensitivity index, two biomarkers associated with endothelial dysfunction (homocysteine and soluble intercellular adhesion molecule-1), and the odds of incident hypertension. Odds ratios were adjusted for standard risk factors, and then for all biomarkers, plus estimated glomerular filtration rate and total cholesterol. The population attributable risk was estimated for biomarkers significantly associated with hypertension. Results All biomarkers were associated with incident hypertension after adjustment for standard hypertension risk factors. However, after simultaneously controlling for all biomarkers, eGFR, and total cholesterol, only uric acid and insulin were independently associated with incident hypertension. Comparing the highest to lowest quartile of uric acid, the OR was 1.89 (1.26-2.82). A similar comparison yielded an OR=2.03 (1.35-3.05) for insulin. Using an estimated basal incidence rate of 14.6 per 1000/year, 30.8% of all hypertension occurring in young women annually is associated with uric acid levels ?3.4 mg/dL. For insulin levels ?2.9 ?IU/mL, this proportion is 24.2%. Conclusions Differences in uric acid and insulin robustly and substantially influence the risk of developing hypertension among young women. Measuring these biomarkers in clinical practice may identify higher risk individuals.

Forman, John P.; Choi, Hyon; Curhan, Gary C.



Urinary creatinine to serum creatinine ratio and renal failure index in dogs infected with Babesia canis.  


Urinary creatinine to serum creatinine (UCr/SCr) ratio and renal failure index (RFI) are useful indices of renal damage. Both UCr/SCr ratio and RFI are used in differentiation between prerenal azotaemia and acute tubular necrosis. In this work the authors calculated the UCr/SCr ratio and RFI in dogs infected with Babesia canis and the values of these indices in azotaemic dogs infected with the parasite. The results of this study showed significantly lower UCr/SCr ratio in dogs infected with B. canis than in healthy dogs. Moreover, in azotaemic dogs infected with B. canis the UCr/SCr ratio was significantly lower and the RFI was significantly higher than in non-azotaemic dogs infected with B. canis. The calculated correlation between RFI and duration of the disease before diagnosis and treatment was high, positive and statistically significant (r = 0.89, p < 0.001). The results of this study showed that during the course of canine babesiosis caused by B. canis in Poland acute tubular necrosis may develop. PMID:23990425

Zygner, Wojciech; Gójska-Zygner, Olga; Weso?owska, Agnieszka; W?drychowicz, Halina



Urea transport in the kidney.  


Urea transport proteins were initially proposed to exist in the kidney in the late 1980s when studies of urea permeability revealed values in excess of those predicted by simple lipid-phase diffusion and paracellular transport. Less than a decade later, the first urea transporter was cloned. Currently, the SLC14A family of urea transporters contains two major subgroups: SLC14A1, the UT-B urea transporter originally isolated from erythrocytes; and SLC14A2, the UT-A group with six distinct isoforms described to date. In the kidney, UT-A1 and UT-A3 are found in the inner medullary collecting duct; UT-A2 is located in the thin descending limb, and UT-B is located primarily in the descending vasa recta; all are glycoproteins. These transporters are crucial to the kidney's ability to concentrate urine. UT-A1 and UT-A3 are acutely regulated by vasopressin. UT-A1 has also been shown to be regulated by hypertonicity, angiotensin II, and oxytocin. Acute regulation of these transporters is through phosphorylation. Both UT-A1 and UT-A3 rapidly accumulate in the plasma membrane in response to stimulation by vasopressin or hypertonicity. Long-term regulation involves altering protein abundance in response to changes in hydration status, low protein diets, adrenal steroids, sustained diuresis, or antidiuresis. Urea transporters have been studied using animal models of disease including diabetes mellitus, lithium intoxication, hypertension, and nephrotoxic drug responses. Exciting new animal models are being developed to study these transporters and search for active urea transporters. Here we introduce urea and describe the current knowledge of the urea transporter proteins, their regulation, and their role in the kidney. PMID:23737200

Klein, Janet D; Blount, Mitsi A; Sands, Jeff M



Monodispersed molecularly imprinted polymer for creatinine by modified precipitation polymerization.  


A monodispersed molecularly imprinted polymer (MIP) for creatinine was prepared by modified precipitation polymerization. The retention and molecular-recognition properties of the prepared MIP were evaluated by the hydrophilic interaction chromatography mode using a mixture of ammonium acetate buffer and acetonitrile as a mobile phase in liquid chromatography. The MIP had a specific recognition ability for creatinine, while other structurally related compounds, such as hydantoin, 1-methylhydantoin, 2-pyrrolidone, N-hydroxysuccinimide and creatine, could not be recognized on the MIP. In addition to shape recognition, hydrophilic interactions could work for the recognition of creatinine on the MIP. PMID:22498455

Haginaka, Jun; Miura, Chitose; Funaya, Noriko; Matsunaga, Hisami



Simultaneous determination of creatine and creatinine using amperometric biosensors.  


In order to determine creatine and creatinine amperometric biosensors were proposed. A bienzymatic biosensor based on creatinase (CI) and sarcosine oxidase (SO) was used for the assay of creatine and a trienzymatic biosensor based on CI, SO and creatininase (CA) for the assay of creatinine. The linear concentration ranges are of pmol l(-1) to nmol l(-1) magnitude order, with very low limits of detection. The biosensors proved high reliability for determination of creatine and creatinine as raw material, and in the pharmaceutical formulation. PMID:18969149

Stefan, Raluca-Ioana; Bokretsion, Rahel Girmai; van Staden, Jacobus F; Aboul-Enein, Hassan Y



Serum Uric Acid Level and Endothelial Dysfunction in Patients with Nondiabetic Chronic Kidney Disease  

Microsoft Academic Search

Background: An elevated serum uric acid level is strongly associated with endothelial dysfunction and inflammation, both of which are common in chronic kidney disease (CKD). We hypothesized that endothelial dysfunction in subjects with CKD would correlate with uric acid levels. Materials and Methods: We evaluated the association between serum uric acid level and ultrasonographic flow-mediated dilatation (FMD) in 263 of

Mehmet Kanbay; Mahmut Ilker Yilmaz; Alper Sonmez; Faruk Turgut; Mutlu Saglam; Erdinc Cakir; Mujdat Yenicesu; Adrian Covic; Diana Jalal; Richard J. Johnson



Analyses of Uric Acid in Urine and Reconstituted Serum by Capillary Electrophoresis  

Microsoft Academic Search

Capillary electrophoresis was used to analyze uric acid in urine. Among several buffers tested, phosphate buffer was found to yield the best results, in close agreement with enzymatic assays utilizing urate oxidase. Ascorbic acid, gentisic acid, caffeine, theophylline, theobromine, glucose, acetyl salicylic acid and acetaminophen did not interfere with the uric acid determination. Analyses of uric acid concentrations in reconstituted

Claude Masson; John H. T. Luong; An-Lac Nguyen



Elevated Uric Acid Increases Blood Pressure in the Rat by a Novel Crystal-Independent Mechanism  

Microsoft Academic Search

An elevation in circulating serum uric acid is strongly associated with the development of hypertension and renal disease, but whether uric acid has a causal role or whether it simply indicates patients at risk for these complications remains controversial. We tested the hypothesis that uric acid may have a causal role in the development of hypertension and renal disease by

Marilda Mazzali; Jeremy Hughes; Yoon-Goo Kim; J. Ashley Jefferson; Duk-Hee Kang; Katherine L. Gordon; Hui Y. Lan; Salah Kivlighn; Richard J. Johnson


Nitric oxide inhibits prooxidant actions of uric acid during copper-mediated LDL oxidation  

Microsoft Academic Search

Interactions between uric acid and physiologically relevant fluxes of nitric oxide (NO) during copper-mediated low-density lipoprotein (LDL) oxidation were evaluated. In the absence of NO, a dual pro- and antioxidant action of uric acid was evident: low concentrations of uric acid enhanced lipid oxidation and ?-tocopherol consumption, while its protective role was observed at higher concentrations. The prooxidant effects of

Silvia M Sanguinetti; Carlos Batthyány; Andrés Trostchansky; Horacio Botti; Graciela I López; Regina L. W Wikinski; Homero Rubbo; Laura E Schreier



Uric Acid in Hypertension and Renal Disease: The Chicken or the Egg?  

Microsoft Academic Search

After uric acid was recognized as the causative factor in gout, increased prevalence of renal disease and hypertension in this patient population caught the attention of the medical community. Thus, it has been proposed that uric acid might have caused these disorders. However, uric acid suffered a long period of ignorance in which it was considered a metabolically inert substance.

Mehmet Kanbay; Yalcin Solak; Ekrem Dogan; Miguel A. Lanaspa; Adrian Covic



Optical Online Monitoring of Uric Acid Removal during Dialysis  

Microsoft Academic Search

This study estimates the total removal of uric acid (TRUA) by online UV absorbance measurements in the spent dialysate in two different dialysis centers in Estonia and Sweden. Sixteen dialysis patients were included. All dialysate was collected that gave the reference for TRUA. Two regression models were investigated: one for each patient (UV1) and one for the entire material (UV2).

Jana Jerotskaja; Fredrik Uhlin; Ivo Fridolin; Kai Lauri; Merike Luman; Anders Fernström



Uric acid elimination in the urine. Pathophysiological implications.  


Uric acid, a weak organic acid, has very low pH-dependent solubility in aqueous solutions. About 70% of urate elimination occurs in urine, the kidney standing as a major determinant of plasma levels. The complex renal handling results in a fractional clearance of less than 10%. Recently identified urate-specific transporter/channels are involved in tubular handling and extracellular transport. Extracellular fluid, rather than urine output, is the main regulator of urate excretion. A number of interfering agents, including widely used drugs such as aspirin, losartan, diuretics, may decrease or increase urate elimination. Hyperuricemia induced by hypouricosuria often accompanies the metabolic syndrome, and insulin resistance has been hypothesized as the common underlying defect. Hyperuricosuria, associated with dehydration or exercise, results in acute uric acid nephropathy, and causes an obstructive acute renal failure (ARF). This reversible ARF can be prevented by forced hydration with bicarbonate or saline solutions. Renal hypouricemia, due to mutations of urate transporter, is a rare cause of exercise-induced ARF. The existence of chronic urate nephropathy, gouty nephropathy, is still under discussion. Uric acid nephrolithiasis results from supersaturation, strongly influenced by low urine pH, rather than altered urate turnover. Alkali and fluid intake prove successful in managing uric acid stones. PMID:15604613

Marangella, Martino



Elevated serum uric acid — a facet of hyperinsulinaemia  

Microsoft Academic Search

Summary  In a representative sample of the adult Jewish population in Israel (n=1016) excluding known diabetic patients and individuals on antihypertensive medications, serum uric acid showed a positive association with plasma insulin response (sum of 1- and 2-hour post glucose load levels) in both males (r=0.316, pr=0.236, pp

M. Modan; H. Halkin; A. Karasik; A. Lusky



Uric Acid and Long-term Outcomes in CKD  

PubMed Central

Background Hyperuricemia is prevalent in chronic kidney disease (CKD); however data are limited on the relationship of uric acid levels with long term outcomes in this patient population. Study Design Cohort Study Setting & Participants The Modification of Diet in Renal Disease (MDRD) Study was a randomized controlled trial (N=840), conducted 1989–1993, to examine the effects of strict blood pressure control and dietary protein restriction on progression of stage 3–4 CKD. This analysis included 838 patients. Predictor Uric acid Outcomes & Measurements The study evaluated the association of baseline uric acid levels with all-cause mortality, cardiovascular (CVD) mortality, and kidney failure. Results Mean (SD) age was 52 (12) years, glomerular filtration rate was 33 (12) ml/min/1.73m2, and uric acid was 7.63 (1.66) mg/dl. During a median follow-up of 10 years, 208 (25%) participants died of any cause, 127 (15%) from CVD, and 553 (66%) reached kidney failure. In multivariate models, the highest tertile of uric acid was associated with increased risk of all-cause (HR, 1.57 [95% CI, 1.07–2.32]) mortality, a trend towards CVD mortality (HR, 1.47 [95% CI, 0.90–2.39]) and no association with kidney failure (HR, 1.20 [95% CI, 0.95–1.51), compared to the lowest tertile. In continuous analyses, a 1-mg/dl higher uric acid was associated with 17% increased risk of all-cause (HR, 1.17 [95% CI, 1.05–1.30]), and 16% increased risk of CVD mortality (HR, 1.16 [95% CI, 1.01–1.33]), but was not associated with kidney failure (HR, 1.02 [95% CI, 0.97–1.07]). Limitations Primary analyses were based on single measurement of uric acid. The results are primarily generalizable to relatively young white patients with predominantly non-diabetic CKD. Conclusions In stage 3–4 CKD, hyperuricemia appears to be an independent risk factor for all-cause and CVD mortality but not kidney failure.

Madero, Magdalena; Sarnak, Mark J; Wang, Xuelei; Greene, Tom; Beck, Gerald J; Kusek, John W; Collins, Allan J; Levey, Andrew S; Menon, Vandana



Reaction of picrate with creatinine and cepha antibiotics.  


The concentration of creatinine in serum, which is used to estimate glomerular filtration rate, is measured by reaction with alkaline picrate, but this reaction is not specific for creatinine. Although several other cephalosporin antibiotics have been reported not to react with picrate, we reacted picrate with creatinine, cefoxitin, penicillin, and eight different cephalosporins, and found that all compounds reacted with picrate and showed superimposable spectrophotograms with absorption maxima at 485 nm. From these results we conclude that the color-absorbing moiety of the product is the picrate molecule. Further, the structure common to creatinine and the cephalosporins, cefoxitin, or penicillin is the carbonyl group attached to a nitrogen and a carbon atom. We postulate that the carbonyl group with the adjacent carbon and nitrogen atoms is probably the chemical moiety that reacts with picrate to absorb energy at 485 nm. PMID:6478596

Kroll, M H; Hagengruber, C; Elin, R J



The relationship between hyperuricemia and the risk of contrast-induced acute kidney injury after percutaneous coronary intervention in patients with relatively normal serum creatinine  

PubMed Central

OBJECTIVES: Hyperuricemia is a risk factor for contrast-induced acute kidney injury in patients with chronic kidney disease. This study evaluated the value of hyperuricemia for predicting the risk of contrast-induced acute kidney injury in patients with relatively normal serum creatinine who were undergoing percutaneous coronary interventions. METHODS AND RESULTS: A total of 788 patients with relatively normal baseline serum creatinine (<1.5 mg/dL) undergoing percutaneous coronary intervention were prospectively enrolled and divided into a hyperuricemic group (n?=?211) and a normouricemic group (n?=?577). Hyperuricemia is defined as a serum uric acid level>7 mg/dL in males and >6 mg/dL in females. The incidence of contrast-induced acute kidney injury was significantly higher in the hyperuricemic group than in the normouricemic group (8.1% vs. 1.4%, p<0.001). In-hospital mortality and the need for renal replacement therapy were significantly higher in the hyperuricemic group. According to a multivariate analysis (adjusting for potential confounding factors) the odds ratio for contrast-induced acute kidney injury in the hyperuricemic group was 5.38 (95% confidence interval, 1.99-14.58; p?=?0.001) compared with the normouricemic group. The other risk factors for contrast-induced acute kidney injury included age >75 years, emergent percutaneous coronary intervention, diuretic usage and the need for an intra-aortic balloon pump. CONCLUSION: Hyperuricemia was significantly associated with the risk of contrast-induced acute kidney injury in patients with relatively normal serum creatinine after percutaneous coronary interventions. This observation will help to generate hypotheses for further prospective trials examining the effect of uric acid-lowering therapies for preventing contrast-induced acute kidney injury.

Liu, Yong; Tan, Ning; Chen, Jiyan; Zhou, Yingling; Chen, Liling; Chen, Shiqun; Chen, Zhujun; Li, Liwen



Modest serum creatinine elevation affects adverse outcome after general surgery  

Microsoft Academic Search

Modest serum creatinine elevation affects adverse outcome after general surgery.BackgroundModest preoperative serum creatinine elevation (1.5 to 3.0 mg\\/dL) has been recently shown to be independently associated with morbidity and mortality after cardiac surgery. It is important to know if this association can be applied more broadly to general surgery cases.MethodsMultivariable logistic regression analyses of 46 risk variables in 49,081 cases

Maureen M O'Brien; Ralph Gonzales; A Laurie Shroyer; Gary K Grunwald; Jennifer Daley; William G Henderson; Shukri F Khuri; Robert J Anderson



Spot Urine Osmolality\\/Creatinine Ratio in Healthy Humans  

Microsoft Academic Search

Background: Spot urine albumin\\/creatinine ratio is a reliable estimate of 24-hour urine albumin excretion. In a pilot study, we observed that the spot urine osmolality\\/creatinine ratio (Uosm\\/Ucr) in healthy adults is reproducible. Therefore, we postulated that Uosm\\/Ucr of a spot urine sample may give an overall estimate of urinary excretion of solutes, renal concentrating ability and body hydration status. Method:

Srini Godevithanage; Piyumi P. Kanankearachchi; Mahanama P. Dissanayake; Thilak A. Jayalath; Nimal Chandrasiri; Rangani P. Jinasena; Ranjith P. V. Kumarasiri; Chulananda D. A. Goonasekera



Dietary protein-induced increases in urinary calcium are accompanied by similar increases in urinary nitrogen and urinary urea: a controlled clinical trial.  


To determine the usefulness of urinary urea as an index of dietary protein intake, 10 postmenopausal women were enrolled in and completed a randomized, double-blind, cross-over feeding trial from September 2008 to May 2010 that compared 10 days of a 45-g whey supplement with 10 days of a 45-g maltodextrin control. Urinary nitrogen, urinary calcium, urinary urea, and bone turnover markers were measured at days 0, 7, and 10. Paired sample t tests, Pearson's correlation statistic, and simple linear regression were used to assess differences between treatments and associations among urinary metabolites. Urinary nitrogen/urinary creatinine rose from 12.3±1.7 g/g (99.6±13.8 mmol/mmol) to 16.8±2.2 g/g (135.5±17.8 mmol/mmol) with whey supplementation, but did not change with maltodextrin. Whey supplementation caused urinary calcium to rise by 4.76±1.84 mg (1.19±0.46 mmol) without a change in bone turnover markers. Because our goal was to estimate protein intake from urinary nitrogen/urinary creatinine, we used our data to develop the following equation: protein intake (g/day)=71.221+1.719×(urinary nitrogen, g)/creatinine, g) (R=0.46, R(2)=0.21). As a more rapid and less costly alternative to urinary nitrogen/urinary creatinine, we next determined whether urinary urea could predict protein intake and found that protein intake (g/day)=63.844+1.11×(urinary urea, g/creatinine, g) (R=0.58, R(2)=0.34). These data indicate that urinary urea/urinary creatinine is at least as good a marker of dietary protein intake as urinary nitrogen and is easier to quantitate in nutrition intervention trials. PMID:23438496

Bihuniak, Jessica D; Simpson, Christine A; Sullivan, Rebecca R; Caseria, Donna M; Kerstetter, Jane E; Insogna, Karl L



Evaporation of urea at atmospheric pressure.  


Aqueous urea solution is widely used as reducing agent in the selective catalytic reduction of NO(x) (SCR). Because reports of urea vapor at atmospheric pressure are rare, gaseous urea is usually neglected in computational models used for designing SCR systems. In this study, urea evaporation was investigated under flow reactor conditions, and a Fourier transform infrared (FTIR) spectrum of gaseous urea was recorded at atmospheric pressure for the first time. The spectrum was compared to literature data under vacuum conditions and with theoretical spectra of monomolecular and dimeric urea in the gas phase calculated with the density functional theory (DFT) method. Comparison of the spectra indicates that urea vapor is in the monomolecular form at atmospheric pressure. The measured vapor pressure of urea agrees with the thermodynamic data obtained under vacuum reported in the literature. Our results indicate that considering gaseous urea will improve the computational modeling of urea SCR systems. PMID:21381736

Bernhard, Andreas M; Czekaj, Izabela; Elsener, Martin; Wokaun, Alexander; Kröcher, Oliver



Nitric oxide inhibits prooxidant actions of uric acid during copper-mediated LDL oxidation.  


Interactions between uric acid and physiologically relevant fluxes of nitric oxide ((?)NO) during copper-mediated low-density lipoprotein (LDL) oxidation were evaluated. In the absence of (?)NO, a dual pro- and antioxidant action of uric acid was evident: low concentrations of uric acid enhanced lipid oxidation and alpha-tocopherol consumption, while its protective role was observed at higher concentrations. The prooxidant effects of uric acid were mostly related to its copper-reducing ability to form Cu(+), an initiator of lipid oxidation processes. While the prooxidant action of uric acid was completely inhibited by (?)NO, the antioxidant action of (?)NO was slightly counterbalanced by uric acid. Enhancement of alpha-tocopherol consumption by uric acid was inhibited in the presence of (?)NO while additive antioxidant effects between (?)NO and uric acid were observed in conditions where uric acid spared alpha-tocopherol. Altogether, these results suggest that in the artery wall, the (?)NO/uric acid pair may exert antioxidant actions on LDL, even if increased amounts of redox active copper were available at conditions favoring prooxidant activities of uric acid. PMID:15001394

Sanguinetti, Silvia M; Batthyány, Carlos; Trostchansky, Andrés; Botti, Horacio; López, Graciela I; Wikinski, Regina L W; Rubbo, Homero; Schreier, Laura E



Iodine and creatinine testing in urine dried on filter paper.  


Iodine deficiency is a world-wide health problem. A simple, convenient, and inexpensive method to monitor urine iodine levels would have enormous benefit in determining an individual's recent iodine intake or in identifying populations at risk for iodine deficiency or excess. Current methods used to monitor iodine levels require collection of a large volume of urine and its transport to a testing laboratory, both of which are inconvenient and impractical in parts of the world lacking refrigerated storage and transportation. To circumvent these limitations we developed and validated methods to collect and measure iodine and creatinine in urine dried on filter paper strips. We tested liquid urine and liquid-extracted dried urine for iodine and creatinine in a 96-well format using Sandell-Kolthoff and Jaffe reactions, respectively. Our modified dried urine iodine and creatinine assays correlated well with established liquid urine methods (iodine: R(2)=0.9483; creatinine: R(2)=0.9782). Results demonstrate that the dried urine iodine and creatinine assays are ideal for testing the iodine status of individuals and for wide scale application in iodine screening programs. PMID:23374216

Zava, Theodore T; Kapur, Sonia; Zava, David T



Two novel creatinine adducts of andrographolide in human urine.  


Andrographolide is a major labdane diterpenoid of the traditional Chinese and Ayurvedic medicine. Andrographis paniculate (Burm) Nees, is used in clinical situations in China mainly to treat fever, cold, and inflammation. In our previous study, fifteen metabolites of andrographolide were identified in human urine. However, there are still two other unknown metabolites. The aim of this study was to elucidate the structures of these two metabolites. 3. The two metabolites which are probably epimers were identified as creatinine adducts, and their structures were determined to be 14-deoxy-12-(creatinine-5-yl)-andrographolide-19-O-?-D-glucuronide A (Metabolite 1) and 14-deoxy-12-(creatinine-5-yl)-andrographolide-19-O-?-D-glucuronide B (Metabolite 2) by means of spectroscopic evidences. 4. It is for the first time that the formation of creatinine adducts as a novel metabolic pathway is reported. The mechanism was presumed that ?-carbon (C-12) of ?, ?-unsaturated carbonyl was attacked by a 5-anion intermediate of creatinine formed through elimination of a proton, followed by the double bond migration from 12(13) to 13(14) and elimination of the hydroxyl group at C-14. PMID:22568631

Qiu, Feng; Cui, Liang; Chen, Lixia; Sun, Jiawen; Yao, Xinsheng



Effect of sex hormones on uric acid metabolism in rats  

Microsoft Academic Search

Summary  The effects of sex hormones on purine metabolism were investigated in rats. No influence on purine synthesis was shown by\\u000a the injection of estrogen and androgen. The plasma urate levels were significantly lowered from 2.431.04 mg\\/100 ml to 1.530.57\\u000a mg\\/100 ml by the injection of progesterone. Urinary excretion of uric acid plus allantoin was slightly reduced. These results\\u000a suggested that

Y. Nishida; I. Akaoka; T. Nishizawa



The Role of Uric Acid and Other Crystals in Osteoarthritis  

Microsoft Academic Search

Clinicians have long assumed that an association exists between crystal arthropathies and the presence of osteoarthritis (OA).\\u000a However, studies establishing an independent association between calcium pyrophosphate or uric acid crystal disease and OA\\u000a are sparse. Even less is known about a possible pathogenic relationship. Whereas some studies suggest that the relationships\\u000a between crystals and OA may not be incidental and

Johannes Nowatzky; Rennie Howard; Michael H. Pillinger; Svetlana Krasnokutsky



Chronic Hyperuricemia, Uric Acid Deposit and Cardiovascular Risk  

PubMed Central

Hyperuricemia is commonly associated with traditional risk factors such as dysglicemia, dyslipidemia, central obesity and abnormal blood pressure, i.e. the metabolic syndrome. Concordantly, recent studies have revived the controversy over the role of circulating uric acid, hyperuricemia, and gout as an independent prognostic factor for cardiovascular morbidity and mortality. In this regard, different studies also evaluated the possible role of xanthine inhibitors in inducing blood pressure reduction, increment in flow-mediated dilation, and improved cardiovascular prognosis in various patient settings. The vast majority of these studies have been conducted with either allopurinol or its active metabolite oxypurinol, i.e. two purine-like non-selective inhibitors of xanthine oxidase. More recently, the role of uric acid as a risk factor for cardiovascular disease and the possible protective role exerted by reduction of hyperuricemia to normal level have been evaluated by the use of febuxostat, a selective, non purine-like xanthine oxidase inhibitor. In this review, we will report current evidence on hyperuricemia in cardiovascular disease. The value of uric acid as a biomarker and as a potential therapeutic target for tailored old and novel “cardiometabolic” treatments will be also discussed.

Grassi, Davide; Ferri, Livia; Desideri, Giovambattista; Giosia, Paolo Di; Cheli, Paola; Pinto, Rita Del; Properzi, Giuliana; Ferri, Claudio



Non-enzymatic cyclization of creatine ethyl ester to creatinine.  


Creatine ethyl ester was incubated at 37 degrees C in both water and phosphate-buffered saline and the diagnostic methylene resonances in the (1)H NMR spectrum were used to identify the resultant products. It was found that mild aqueous conditions result in the cyclization of creatine ethyl ester to provide inactive creatinine as the exclusive product, and this transformation becomes nearly instantaneous as the pH approaches 7.4. This study demonstrates that mild non-enzymatic conditions are sufficient for the cyclization of creatine ethyl ester into creatinine, and together with previous results obtained under enzymatic conditions suggests that there are no physiological conditions that would result in the production of creatine. It is concluded that creatine ethyl ester is a pronutrient for creatinine rather than creatine under all physiological conditions encountered during transit through the various tissues, thus no ergogenic effect is to be expected from supplementation. PMID:19660433

Giese, Matthew W; Lecher, Carl S



Random urine protein creatinine ratio as a preadmission test in hypertensive pregnancies with urinary protein creatinine ratio.  


To evaluate the value of random urinary protein creatinine ratio in prediction of 24h proteinuria in hypertensive pregnancies. Method: Random urine samples and routine 24h urine collections were collected from hypertensive pregnant women (n=100). Reliability of random urinary protein-creatinine ratio was assessed by receiver operator characteristic (ROC) curve to detect significant proteinuria (?300mg/day) using 24h. Urine protein as a gold standard. Forty six patients (46%) had significant proteinuria. The random protein creatinine ratio was correlated to 24h urine protein excretion (r(2)=0.777, P<0.001) Area under ROC curve to predict proteinuria was 0.926 (95% CI: 0.854-0.995, P<0.001). A cut off value of 0.22mg/mg for protein creatinine ratio best predicted significant proteinuria with sensitivity, specificity, positive and negative predictive values of 87%, 92.6%, 90.6% and 89.3% respectively. Random urinary protein creatinine ratio is a simple inexpensive and excellent alternative to 24h urine collection. It's helpful in diagnosis of preeclampsia and can be used as a pre admission test in PIH cases. PMID:21598214

Eslamian, Laleh; Behnam, Fariba; Tehrani, Zahra Foroohesh; Jamal, Ashraf; Marsoosi, Vajiheh



Effect of urea supplemented and urea treated straw based diet on milk urea concentration in crossbred Karan-Fries cows  

Microsoft Academic Search

The study was undertaken to evaluate the effect of urea supplemented and urea treated straw based diet on milk urea concentration. Six multiparous crossbred Karan-Fries (Holstein Friesian ? Tharparkar) cows were blocked into three groups of nearly equal body weight, DIM, milk yield and milk fat content and were randomized into a 3 ? 3 Latin square design with 3-week

Arindam Dhali; Ram Kumar Mehla; Sunil Kumar Sirohi



Serum Uric Acid Levels Are Associated with Polymorphism in the SAA1 Gene in Chinese Subjects  

PubMed Central

Objective Serum uric acid (SUA) is a cardiovascular risk marker associated with inflammation. The serum amyloid A protein (SAA) is an inflammatory factor and is associated with cardiovascular disease (CVD). However, the relationship between genetic polymorphisms of SAA and SUA levels has not been studied. The objective of this study was to investigate the association between SUA levels and SAA genetic polymorphisms. Methods All participants were selected from subjects participating in the Cardiovascular Risk Survey (CRS) study. The single nucleotide polymorphism (SNP) rs12218 of the SAA1 gene was genotyped by using the polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) method. The association of SUA levels with genotypes was assessed by using the general liner mode. Results The SNP rs12218 was associated with SUA levels by analyses of a dominate model (P?=?0.002) and additive model (P?=?0.005), and the difference remained significant after adjustment of sex, age, obesity, ethnicity, HDL-C, alcohol intake, smoking, and creatinine (P?=?0.006 and P?=?0.023, respectively). The TT genotype was associated with an increased SUA concentration of 39.34 mmol/L (95% confidence interval [CI], 3.61–75.06, P?=?0.031) compared with the CC genotype, and the TT genotype was associated with an increased SUA concentration of 2.48 mmol/L (95% CI, 6.86–38.10; P?=?0.005) compared with the CT genotype. Conclusions The rs12218 SNP in the SAA1 gene was associated with SUA levels in Chinese subjects, indicating that carriers of the T allele of rs12218 have a high risk of hyperuricemia.

Xie, Xiang; Ma, Yi-Tong; Yang, Yi-Ning; Li, Xiao-Mei; Fu, Zhen-Yan; Zheng, Ying-Ying; Ma, Xiang; Chen, Bang-Dang; Liu, Fen; Huang, Ying; Yu, Zi-Xiang; Chen, You



The relationship between serum uric acid and chronic kidney disease among Appalachian adults  

PubMed Central

Background. Higher serum uric acid (SUA) levels have been shown to be associated with cardiovascular disease. SUA levels are also associated with hypertension, a strong risk factor for chronic kidney disease (CKD). However, it is unclear whether SUA is independently associated with CKD. We examined the hypothesis that higher SUA levels are positively associated with CKD. Methods. We analysed data from the C8 Health Study, a population-based study of Appalachian adults aged ?18 years and free of cardiovascular disease (n = 49,295, 53% women). SUA was examined as gender-specific quartiles. The outcome of interest was CKD (n = 2,980), defined as an estimated glomerular filtration rate of <60 mL/min/1.73 m2 from serum creatinine. Results. Overall, we observed a clear positive association between increasing quartiles of SUA and CKD, independent of confounders. Compared with the lowest quartile of SUA (referent), the multivariable odds ratios (95% confidence interval) for quartiles 2–4, respectively, of CKD were 1.53 (1.31, 1.78), 2.16 (1.86 2.50) and 4.67 (4.07, 5.36); P-trend < 0.0001. This observed positive association persisted in separate analysis among men (P-trend < 0.0001) and women (P-trend < 0.0001). Conclusions. In conclusion, higher SUA levels are positively associated with CKD, suggesting that at least part of the reported association between SUA and cardiovascular disease may be mediated by CKD.

Cain, Loretta; Shankar, Anoop; Ducatman, Alan M.; Steenland, Kyle



Urea Biosynthesis Using Liver Slices  

ERIC Educational Resources Information Center

|Presented is a practical scheme to enable introductory biology students to investigate the mechanism by which urea is synthesized in the liver. The tissue-slice technique is discussed, and methods for the quantitative analysis of metabolites are presented. (Author/SL)|

Teal, A. R.



Triiodothyronine Administration Affects urea Synthesis in Rats  

Microsoft Academic Search

ABSTRACT The purpose of the present study was,to elucidate the mechanism,by which,thyroid hormone alters urea synthesis. The relative importance of urea cycle enzyme activities, substrate levels or the levels of urea cycle intermediates on urea production was investi gated in a set of four experiments in which rats were fed a diet supplemented with 6-propyl-2-thiouracil (PTU, a thyroid inhibitor) and

Kazotoshi Hayase; Goro Yonekawa; Akira Yoshida


Update on the Pathophysiology and Management of Uric Acid Renal Stones  

Microsoft Academic Search

Idiopathic uric acid nephrolithiasis appears to be increasing in prevalence. While it has long been known that low urine pH\\u000a is associated with uric acid stones, only recently has the pathophysiological basis for this disease emerged. Excessively\\u000a acidic urine is the decisive risk for uric acid lithogenesis, and patients with diabetes and the metabolic syndrome often\\u000a hold the company of

Jon-Emile S. Kenny; David S. Goldfarb



Soluble Neuroprotective Antioxidant Uric Acid Analogs Ameliorate Ischemic Brain Injury in Mice  

Microsoft Academic Search

Uric acid is a major antioxidant in the blood of humans that can protect cultured neurons against oxidative and metabolic\\u000a insults. However, uric acid has a very low solubility which compromises its potential clinical use for neurodegenerative disorders.\\u000a Here we describe the synthesis, characterization and preclinical development of neuroprotective methyl- and sulfur-containing\\u000a analogs of uric acid with increased solubility. In vitro

Frank Haberman; Sung-Chun Tang; Thiruma V. Arumugam; Dong-Hoon Hyun; Qian-Sheng Yu; Roy G. Cutler; Zhihong Guo; Harold W. Holloway; Nigel H. Greig; Mark P. Mattson



Quantum computations of the UV–visible spectra of uric acid and its anions  

Microsoft Academic Search

UV–visible spectra of uric acid as a function of pH have been studied and compared with experimental data. Different quantum methodologies have been employed: CIS–ZINDO, CIS–HF and TD-DFT. Solvent effects were modeled using the COSMO model. To account for the change in maximum absorbance along a variation of pH, different forms of uric acid have been taken into account: uric

Muhannad Altarsha; Gérald Monard; Bertrand Castro



An amperometric sensor for uric acid based on ordered mesoporous carbon-modified pyrolytic graphite electrode  

Microsoft Academic Search

A novel amperometric sensor for uric acid based on ordered mesoporous carbon modified pyrolytic graphite electrode was developed.\\u000a Uric acid oxidation was easily catalyzed by this electrode in a phosphate buffer solution at pH 7.0, with an anodic potential\\u000a decrease about 140 mV compared to bare pyrolytic graphite electrode. The uric acid level was determined by the amperometric\\u000a method, at

Yonggen Ma; Guangzhi Hu; Shijun Shao; Yong Guo



Petroleum Pollution Bioremediation Using Water-Insoluble Uric Acid as the Nitrogen Source  

PubMed Central

The biodegradation of hydrocarbon pollutants in open systems is limited by the availability of a utilizable nitrogen source. This limitation can be overcome by using uric acid. Enrichment cultures grown on crude oil-uric acid media yielded mixed and pure cultures that degraded petroleum. In a simulated open system, uric acid bound to crude oil and was available for bacterial growth and petroleum biodegradation.

Koren, Omry; Knezevic, Vishnia; Ron, Eliora Z.; Rosenberg, Eugene



Anaerobic degradation of uric acid via pyrimidine derivatives by selenium-starved cells of Clostridium purinolyticum  

Microsoft Academic Search

Clostridium purinolyticum decomposed uric acid via pyrimidine derivatives under selenium starvation conditions. Products were acetate, formate, glycine, ammonia, and CO2. 4,5-Diaminouracil could be identified as an intermediate after converting the labile substance into 6,7-dimethyllumazine. The breakdown of uric acid was inhibited by EDTA. High-pressure liquid chromatography methods have been developed for the simultaneous determination of uric acid, 4,5-diaminouracil, and 6,7-dimethyllumazine.

Peter Dfirre; Jan R. Andreesen



Petroleum pollution bioremediation using water-insoluble uric acid as the nitrogen source.  


The biodegradation of hydrocarbon pollutants in open systems is limited by the availability of a utilizable nitrogen source. This limitation can be overcome by using uric acid. Enrichment cultures grown on crude oil-uric acid media yielded mixed and pure cultures that degraded petroleum. In a simulated open system, uric acid bound to crude oil and was available for bacterial growth and petroleum biodegradation. PMID:14532103

Koren, Omry; Knezevic, Vishnia; Ron, Eliora Z; Rosenberg, Eugene



Nonenzymatic cyclization of creatine ethyl ester to creatinine  

Microsoft Academic Search

Creatine ethyl ester was incubated at 37°C in both water and phosphate-buffered saline and the diagnostic methylene resonances in the 1H NMR spectrum were used to identify the resultant products. It was found that mild aqueous conditions result in the cyclization of creatine ethyl ester to provide inactive creatinine as the exclusive product, and this transformation becomes nearly instantaneous as

Matthew W. Giese; Carl S. Lecher



Evaluation of creatinine phosphokinase in screening patients for malignant hyperpyrexia  

Microsoft Academic Search

Evidence is presented that serum creatinine phosphokinase (CPK) activity is of no direct value in screening patients for susceptibility to malignant hyperpyrexia and does not correlate with halothane-induced muscle contracture or the presence of myopathy. Widely differing CPK values were found at different times in the same people. In most \\

F R Ellis; I M Clarke; M Modgill; S Currie; D G Harriman



CCQM-K12: The determination of creatinine in serum  

Microsoft Academic Search

A Key Comparison on the determination of creatinine in human serum organized by the Consultative Committee on Amount of Substance (CCQM) was carried out in 2001. To address the measurement traceability needs of the clinical chemistry community, the CCQM is undertaking Key Comparisons to document the capabilities of national metrology institutes (NMIs) that provide measurement services in this area. This

Michael J Welch; Curtis P Phinney; Reenie M Parris; Willie E May; Gwi Suk Heo; Andre Henrion; Gavin OConner; Heinz Schimmel



Granulation of Urea in a Pan Granulator  

Microsoft Academic Search

Urea granulation is favored over prilling due to the problems associated with prilling. Tumbling agglomeration technique is employed in pan granulator. Product with wide size range can be produced by playing with only few parameters like binders (water and urea solution), ratio of binders, rpm of pan, granulation time and angle of inclination. Urea granulation is studied at laboratory scale

U. Irshad; M. N. Sharif; R. U. Khan; Z. H. Rizvi


In vitro oxidation of uric acid in serum by methylene blue.  


Methylene blue oxidizes uric acid to allantoin in vitro, analogous to the reaction between uric acid and phosphotungstate, although the rate is considerably slower. The reaction requires oxygen and produces hydrogen peroxide. As little as 10 micromol of methylene blue per liter in a serum sample will produce a measurable difference in the apparent uric acid concentration within 4 h at room temperature. Methylene blue may be administered for various medical reasons. If uric acid is to be measured in such sera, the procedure should be performed within 30 min, whatever method of analysis is used. PMID:3940703

Andranovich, T; Kelner, M J



Impulsivity is Associated with Uric Acid: Evidence from Humans and Mice.  


BACKGROUND: The ability to control impulses varies greatly, and difficulty with impulse control can have severe consequences; in the extreme, it is the defining feature of many psychiatric disorders. Evidence from disparate lines of research suggests that uric acid is elevated in psychiatric disorders characterized by high impulsivity, such as attention-deficit/hyperactivity disorder and bipolar disorder. The present research tests the hypothesis that impulsivity is associated with higher uric acid in humans and mice. METHODS: Using two longitudinal, nonclinical community samples (total n = 6883), we tested whether there is an association between uric acid and normal variation in trait impulsivity measured with the Revised NEO Personality Inventory. We also examined the effect of uric acid on behavior by comparing wild-type mice, which naturally have low levels of uric acid, with mice genetically modified to accumulate high levels of uric acid. RESULTS: In both human samples, the emotional aspects of trait impulsivity, specifically impulsiveness and excitement seeking, were associated with higher levels of uric acid concurrently and when uric acid was measured 3 to 5 years later. Consistent with the human data, the genetically modified mice displayed significantly more exploratory and novelty-seeking behavior than the wild-type mice. CONCLUSIONS: Higher uric acid was associated with impulsivity in both humans and mice. The identification of biological markers of impulsivity may lead to a better understanding of the physiological mechanisms involved in impulsivity and may suggest potential targets for therapeutic intervention. PMID:23582268

Sutin, Angelina R; Cutler, Roy G; Camandola, Simonetta; Uda, Manuela; Feldman, Neil H; Cucca, Francesco; Zonderman, Alan B; Mattson, Mark P; Ferrucci, Luigi; Schlessinger, David; Terracciano, Antonio



Relationship between Uric Acid Levels and Diagnostic and Prognostic Outcomes in Acute Heart Failure  

PubMed Central

Objectives We evaluated the association of plasma uric acid alone and in combination with b-type natriuretic peptide (BNP) for emergency department (ED) diagnosis and 30-day prognosis in patients evaluated for acute heart failure (AHF). Methods We prospectively enrolled 322 adult ED patients with suspected AHF. Wilcoxon rank sum test, multivariable logistic regression and likelihood ratio (LR) tests were used for statistical analyses. Results Uric acid’s diagnostic utility was poor and failed to show significant associations with 30-day clinical outcomes. Uric acid also did not add significantly to BNP results. Conclusion Among ED patients with suspected AHF, uric acid has poor diagnostic and prognostic utility.

Henry-Okafor, Queen; Collins, Sean P.; Jenkins, Cathy A.; Miller, Karen F.; Maron, David J.; Naftilan, Allen J.; Weintraub, Neal; Fermann, Gregory J.; McPherson, John; Menon, Santosh; Sawyer, Douglas B.; Storrow, Alan B.



A general photonic crystal sensing motif: creatinine in bodily fluids.  


We developed a new sensing motif for the detection and quantification of creatinine, which is an important small molecule marker of renal dysfunction. This novel sensor motif is based on our intelligent polymerized crystalline colloidal array (IPCCA) materials, in which a three-dimensional crystalline colloidal array (CCA) of monodisperse, highly charged polystyrene latex particles are polymerized within lightly cross-linked polyacrylamide hydrogels. These composite hydrogels are photonic crystals in which the embedded CCA diffracts visible light and appears intensely colored. Volume phase transitions of the hydrogel cause changes in the CCA lattice spacings which change the diffracted wavelength of light. We functionalized the hydrogel with two coupled recognition modules, a creatinine deiminase (CD) enzyme and a 2-nitrophenol (2NPh) titrating group. Creatinine within the gel is rapidly hydrolyzed by the CD enzyme in a reaction which releases OH(-). This elevates the steady-state pH within the hydrogel as compared to the exterior solution. In response, the 2NPh is deprotonated. The increased solubility of the phenolate species as compared to that of the neutral phenols causes a hydrogel swelling which red-shifts the IPCCA diffraction. This photonic crystal IPCCA senses physiologically relevant creatinine levels, with a detection limit of 6 microM, at physiological pH and salinity. This sensor also determines physiological levels of creatinine in human blood serum samples. This sensing technology platform is quite general. It may be used to fabricate photonic crystal sensors for any species for which there exists an enzyme which catalyzes it to release H(+) or OH(-). PMID:14995215

Sharma, Anjal C; Jana, Tushar; Kesavamoorthy, Rasu; Shi, Lianjun; Virji, Mohamed A; Finegold, David N; Asher, Sanford A



Uric acid decreases NO production and increases arginase activity in cultured pulmonary artery endothelial cells  

PubMed Central

Elevated levels of serum uric acid (UA) are commonly associated with primary pulmonary hypertension but have generally not been thought to have any causal role. Recent experimental studies, however, have suggested that UA may affect various vasoactive mediators. We therefore tested the hypothesis that UA might alter nitric oxide (NO) levels in pulmonary arterial endothelial cells (PAEC). In isolated porcine pulmonary artery segments (PAS), UA (7.5 mg/dl) inhibits acetylcholine-induced vasodilation. The incubation of PAEC with UA caused a dose-dependent decrease in NO and cGMP production stimulated by bradykinin or Ca2+-ionophore A23187. We explored cellular mechanisms by which UA might cause reduced NO production focusing on the effects of UA on the l-arginine-endothelial NO synthase (eNOS) and l-arginine-arginase pathways. Incubation of PAEC with different concentrations of UA (2.5–15 mg/dl) for 24 h did not affect l-[3H]arginine uptake or activity/expression of eNOS. However, PAEC incubated with UA (7.5 mg/dl; 24 h) released more urea in culture media than control PAEC, suggesting that arginase activation might be involved in the UA effect. Kinetic analysis of arginase activity in PAEC lysates and rat liver and kidney homogenates demonstrated that UA activated arginase by increasing its affinity for l-arginine. An inhibitor of arginase (S)-(2-boronoethyl)-l-cysteine prevented UA-induced reduction of A23187-stimulated cGMP production by PAEC and abolished UA-induced inhibition of acetylcholine-stimulated vasodilation in PAS. We conclude that UA-induced arginase activation is a potential mechanism for reduction of NO production in PAEC.

Zharikov, Sergey; Krotova, Karina; Hu, Hanbo; Baylis, Chris; Johnson, Richard J.; Block, Edward R.; Patel, Jawaharlal



Serum uric acid and hypertension: the Olivetti heart study.  


The association between serum uric acid and hypertension was evaluated in a sample of male workers in southern Italy enrolled in the Olivetti Heart Study, an ongoing longitudinal epidemiological investigation on risk factors for coronary heart disease carried out at the Olivetti factory in the suburban area of Naples. Participants were screened at baseline (1975) and at five year (1980) and 12 year (1987) follow-up examinations. The present report focuses on 619 male workers for whom information on coronary heart disease risk factors was available both at baseline and 12 year follow-up examination. At baseline, after excluding hypertensive participants (systolic blood pressure (SBP) > or = 140 mmHg and/or diastolic blood pressure (DBP), > or = 90 mmHg and/or on antihypertensive therapy; n = 72), serum uric acid was positively and significantly related to age, SBP, DBP, body mass index (BMI), serum total cholesterol (CHOL) and serum triglycerides (TG) in 547 normotensive participants. At 12 year follow-up examination, hypertension was defined by SBP > or = 140 mmHg and/or DBP > or = 90 mmHg and/or being on antihypertensive therapy. Multiple logistic regression analysis showed an independent positive association between serum uric acid levels and development of hypertension (RR = 1.23, 95% CI = 1.07-1.39; p = 0.011) after adjustment for age, BMI, CHOL and TG. Furthermore, according to more severe degrees of hypertension (SBP > or = 160 mmHg and/or DBP > or = 95 mmHg and/or being on antihypertensive therapy), the relative risk to develop hypertension was still significant (RR = 1.19; CI = 1.01-1.38; p = 0.051).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7807497

Jossa, F; Farinaro, E; Panico, S; Krogh, V; Celentano, E; Galasso, R; Mancini, M; Trevisan, M



How does urea really denature myoglobin?  

NASA Astrophysics Data System (ADS)

This study reports on a model for denaturation of myoglobin by urea for concentrations ranging from 0.1 M to 15 M. The experimental data from quartz crystal microbalance (QCM), circular dichroism (CD) and dilational rheology are examined with respect to a 'structure-breaking effect' of urea on the aqueous phase. Even at urea concentrations >10 M, native conformation of the protein is retained through a restabilization of the hydrophobic association. Our study shows that any proposed denaturation mechanism of large biomolecules requires very high concentrations of urea and the association of urea with protein-water system is based on enhancement of hydrophobic interactions.

Muthuselvi, L.; Miller, Reinhard; Dhathathreyan, A.



Ontogeny of rabbit proximal tubule urea permeability.  


Urea transport in the proximal tubule is passive and is dependent on the epithelial permeability. The present study examined the maturation of urea permeability (P(urea)) in in vitro perfused proximal convoluted tubules (PCT) and basolateral membrane vesicles (BLMV) from rabbit renal cortex. Urea transport was lower in neonatal than adult PCT at both 37 and 25 degrees C. The PCT P(urea) was also lower in the neonates than the adults (37 degrees C: 45.4 +/- 10.8 vs. 88.5 +/- 15.2 x 10(-6) cm/s, P < 0.05; 25 degrees C: 28.5 +/- 6.9 vs. 55.3 +/- 10.4 x 10(-6) cm/s; P < 0.05). The activation energy for PCT P(urea) was not different between the neonatal and adult groups. BLMV P(urea) was determined by measuring vesicle shrinkage, due to efflux of urea, using a stop-flow instrument. Neonatal BLMV P(urea) was not different from adult BLMV P(urea) at 37 degrees C [1.14 +/- 0.05 x 10(-6) vs. 1.25 +/- 0.05 x 10(-6) cm/s; P = not significant (NS)] or 25 degrees C (0.94 +/- 0.06 vs. 1.05 +/- 0.10 x 10(-6) cm/s; P = NS). There was no effect of 250 microM phloretin, an inhibitor of the urea transporter, on P(urea) in either adult or neonatal BLMV. The activation energy for urea diffusion was also identical in the neonatal and adult BLMV. These findings in the BLMV are in contrast to the brush-border membrane vesicles (BBMV) where we have previously demonstrated that urea transport is lower in the neonate than the adult. Urea transport is lower in the neonatal proximal tubule than the adult. This is due to a lower rate of apical membrane urea transport, whereas basolateral urea transport is the same in neonates and adults. The lower P(urea) in neonatal proximal tubules may play a role in overall urea excretion and in developing and maintaining a high medullary urea concentration and thus in the ability to concentrate the urine during renal maturation. PMID:11353675

Quigley, R; Lisec, A; Baum, M



Aquaporin-9 and urea transporter-A gene deletions affect urea transmembrane passage in murine hepatocytes.  


In mammals, the majority of nitrogen from protein degradation is disposed of as urea. Several studies have partly characterized expression of urea transporters (UTs) in hepatocytes, where urea is produced. Nevertheless, the contribution of these proteins to hepatocyte urea permeability (P(urea)) and their role in liver physiology remains unknown. The purpose of this study was to biophysically examine hepatocyte urea transport. We hypothesized that the water, glycerol, and urea channel aquaporin-9 (AQP9) is involved in hepatocyte urea release. Stopped-flow light-scattering measurements determined that the urea channel inhibitors phloretin and dimethylurea reduced urea permeability of hepatocyte basolateral membranes by 70 and 40%, respectively. In basolateral membranes isolated from AQP9(-/-) and UT-A1/3(-/-) single-knockout and AQP9(-/-):UT-A1/3(-/-) double-knockout mice, P(urea) was decreased by 30, 40, and 76%, respectively, compared with AQP9(+/-):UT-A1/3(+/-) mice. However, expression analysis by RT-PCR did not identify known UT-A transcripts in liver. High-protein diet followed by 24-h fasting affected the concentrations of urea and ammonium ions in AQP9(-/-) mouse liver and plasma without generating an apparent tissue-to-plasma urea gradient. We conclude that AQP9 and unidentified UT-A urea channels constitute primary but redundant urea facilitators in murine hepatocytes. PMID:23042941

Jelen, Sabina; Gena, Patrizia; Lebeck, Janne; Rojek, Aleksandra; Praetorius, Jeppe; Frøkiaer, Jørgen; Fenton, Robert A; Nielsen, Søren; Calamita, Giuseppe; Rützler, Michael



[Diagnostic value of the determination of blood urea in dehydrated patients with and without central diabetes insipidus].  


Dehydrated patients usually present with an elevated serum urea level, owing in part to increased renal reabsorption of urea mediated by antidiuretic hormone (ADH). This study was carried out in order to examine whether, during dehydration, the variations in the serum urea level could discriminate patients with central diabetes insipidus (CDI) from those with dehydration due to other causes. We studied retrospectively 27 episodes of dehydration in 23 patients with CDI and 14 episodes in 14 patients without CDI. The mean serum urea level was 2.9 mmol/L in the CDI group and 15.4 mmol/L in the patients without CDI (p less than 0.001) while the mean serum sodium level was 155 mmol/L in both groups. During dehydration, patients with CDI decreased their serum urea level (4.0 +/- 2.3 vs 2.9 +/- 1.5 mmol/L, p less than 0.001). In addition, a positive correlation was found in the patients with CDI between the magnitude of diuresis and the percentage decrease in the serum urea level compared with the level before dehydration (r = 0.70, p less than 0.001). A striking increase in the clearance of urea (0.8 +/- 1 vs 2.1 +/- 1 ml/s, P less than 0.01), which exceeded the creatinine clearance (1.8 +/- 0.5 ml/s), was observed during dehydration in the six patients in whom clearance studies were done. Therefore, our results suggest that serum urea values can be used to distinguish patients dehydrated because of CDI from those with hypertonic dehydration but without ADH deficiency and that during dehydration the reabsorption of urea is mainly dependent on the renal action of ADH. PMID:2075636

Comtois, R; Bertrand, S; Beauregard, H; Vinay, P


Extra-Renal Elimination of Uric Acid via Intestinal Efflux Transporter BCRP/ABCG2  

PubMed Central

Urinary excretion accounts for two-thirds of total elimination of uric acid and the remainder is excreted in feces. However, the mechanism of extra-renal elimination is poorly understood. In the present study, we aimed to clarify the mechanism and the extent of elimination of uric acid through liver and intestine using oxonate-treated rats and Caco-2 cells as a model of human intestinal epithelium. In oxonate-treated rats, significant amounts of externally administered and endogenous uric acid were recovered in the intestinal lumen, while biliary excretion was minimal. Accordingly, direct intestinal secretion was thought to be a substantial contributor to extra-renal elimination of uric acid. Since human efflux transporter BCRP/ABCG2 accepts uric acid as a substrate and genetic polymorphism causing a decrease of BCRP activity is known to be associated with hyperuricemia and gout, the contribution of rBcrp to intestinal secretion was examined. rBcrp was confirmed to transport uric acid in a membrane vesicle study, and intestinal regional differences of expression of rBcrp mRNA were well correlated with uric acid secretory activity into the intestinal lumen. Bcrp1 knockout mice exhibited significantly decreased intestinal secretion and an increased plasma concentration of uric acid. Furthermore, a Bcrp inhibitor, elacridar, caused a decrease of intestinal secretion of uric acid. In Caco-2 cells, uric acid showed a polarized flux from the basolateral to apical side, and this flux was almost abolished in the presence of elacridar. These results demonstrate that BCRP contributes at least in part to the intestinal excretion of uric acid as extra-renal elimination pathway in humans and rats.

Hosomi, Atsushi; Nakanishi, Takeo; Fujita, Takuya; Tamai, Ikumi



Characterization of the complete uric acid degradation pathway in the fungal pathogen Cryptococcus neoformans.  


Degradation of purines to uric acid is generally conserved among organisms, however, the end product of uric acid degradation varies from species to species depending on the presence of active catabolic enzymes. In humans, most higher primates and birds, the urate oxidase gene is non-functional and hence uric acid is not further broken down. Uric acid in human blood plasma serves as an antioxidant and an immune enhancer; conversely, excessive amounts cause the common affliction gout. In contrast, uric acid is completely degraded to ammonia in most fungi. Currently, relatively little is known about uric acid catabolism in the fungal pathogen Cryptococcus neoformans even though this yeast is commonly isolated from uric acid-rich pigeon guano. In addition, uric acid utilization enhances the production of the cryptococcal virulence factors capsule and urease, and may potentially modulate the host immune response during infection. Based on these important observations, we employed both Agrobacterium-mediated insertional mutagenesis and bioinformatics to predict all the uric acid catabolic enzyme-encoding genes in the H99 genome. The candidate C. neoformans uric acid catabolic genes identified were named: URO1 (urate oxidase), URO2 (HIU hydrolase), URO3 (OHCU decarboxylase), DAL1 (allantoinase), DAL2,3,3 (allantoicase-ureidoglycolate hydrolase fusion protein), and URE1 (urease). All six ORFs were then deleted via homologous recombination; assaying of the deletion mutants' ability to assimilate uric acid and its pathway intermediates as the sole nitrogen source validated their enzymatic functions. While Uro1, Uro2, Uro3, Dal1 and Dal2,3,3 were demonstrated to be dispensable for virulence, the significance of using a modified animal model system of cryptococcosis for improved mimicking of human pathogenicity is discussed. PMID:23667704

Lee, I Russel; Yang, Liting; Sebetso, Gaseene; Allen, Rebecca; Doan, Thi H N; Blundell, Ross; Lui, Edmund Y L; Morrow, Carl A; Fraser, James A



Characterization of the Complete Uric Acid Degradation Pathway in the Fungal Pathogen Cryptococcus neoformans  

PubMed Central

Degradation of purines to uric acid is generally conserved among organisms, however, the end product of uric acid degradation varies from species to species depending on the presence of active catabolic enzymes. In humans, most higher primates and birds, the urate oxidase gene is non-functional and hence uric acid is not further broken down. Uric acid in human blood plasma serves as an antioxidant and an immune enhancer; conversely, excessive amounts cause the common affliction gout. In contrast, uric acid is completely degraded to ammonia in most fungi. Currently, relatively little is known about uric acid catabolism in the fungal pathogen Cryptococcus neoformans even though this yeast is commonly isolated from uric acid-rich pigeon guano. In addition, uric acid utilization enhances the production of the cryptococcal virulence factors capsule and urease, and may potentially modulate the host immune response during infection. Based on these important observations, we employed both Agrobacterium-mediated insertional mutagenesis and bioinformatics to predict all the uric acid catabolic enzyme-encoding genes in the H99 genome. The candidate C. neoformans uric acid catabolic genes identified were named: URO1 (urate oxidase), URO2 (HIU hydrolase), URO3 (OHCU decarboxylase), DAL1 (allantoinase), DAL2,3,3 (allantoicase-ureidoglycolate hydrolase fusion protein), and URE1 (urease). All six ORFs were then deleted via homologous recombination; assaying of the deletion mutants' ability to assimilate uric acid and its pathway intermediates as the sole nitrogen source validated their enzymatic functions. While Uro1, Uro2, Uro3, Dal1 and Dal2,3,3 were demonstrated to be dispensable for virulence, the significance of using a modified animal model system of cryptococcosis for improved mimicking of human pathogenicity is discussed.

Lee, I. Russel; Yang, Liting; Sebetso, Gaseene; Allen, Rebecca; Doan, Thi H. N.; Blundell, Ross; Lui, Edmund Y. L.; Morrow, Carl A.; Fraser, James A.



Uric acid as one of the important factors in multifactorial disorders--facts and controversies.  


With considering serum concentration of the uric acid in humans we are observing hyperuricemia and possible gout development. Many epidemiological studies have shown the relationship between the uric acid and different disorders such are obesity, metabolic syndrome, hypertension and coronary artery disease. Clinicians and investigators recognized serum uric acid concentration as very important diagnostic and prognostic factor of many multifactorial disorders. This review presented few clinical conditions which are not directly related to uric acid, but the concentrations of uric acid might have a great impact in observing, monitoring, prognosis and therapy of such disorders. Uric acid is recognized as a marker of oxidative stress. Production of the uric acid includes enzyme xanthine oxidase which is involved in producing of radical-oxigen species (ROS). As by-products ROS have a significant role in the increased vascular oxidative stress and might be involved in atherogenesis. Uric acid may inhibit endothelial function by inhibition of nitric oxide-function under conditions of oxidative stress. Down regulation of nitric oxide and induction of endothelial dysfunction might also be involved in pathogenesis of hypertension. The most important and well evidenced is possible predictive role of uric acid in predicting short-term outcome (mortality) in acute myocardial infarction (AMI) patients and stroke. Nephrolithiasis of uric acid origin is significantly more common among patients with the metabolic syndrome and obesity. On contrary to this, uric acid also acts is an "antioxidant", a free radical scavenger and a chelator of transitional metal ions which are converted to poorly reactive forms. PMID:22384520

Pasalic, Daria; Marinkovic, Natalija; Feher-Turkovic, Lana



Urea biosensor for hemodialysis monitoring  


An electrochemical sensor capable of detecting and quantifying urea in fluids resulting from hemodialysis procedures. The sensor is based upon measurement of the pH change produced in an aqueous environment by the products of the enzyme-catalyzed hydrolysis of urea. The sensor may be fabricated using methods amenable to mass fabrication, resulting in low-cost sensors and thus providing the potential for disposable use. In a typical application, the sensor could be used in treatment centers, in conjunction with an appropriate electronics/computer system, in order to determine the hemodialysis endpoint. The sensor can also be utilized to allow at-home testing to determine if dialysis was necessary. Such a home monitor is similar, in principle, to devices used for blood glucose testing by diabetics, and would require a blood droplet sample by using a finger prick.

Glass, Robert S. (Livermore, CA)



SERS quantitative urine creatinine measurement of human subject  

Microsoft Academic Search

SERS method for biomolecular analysis has several potentials and advantages over traditional biochemical approaches, including less specimen contact, non-destructive to specimen, and multiple components analysis. Urine is an easily available body fluid for monitoring the metabolites and renal function of human body. We developed surface-enhanced Raman scattering (SERS) technique using 50nm size gold colloidal particles for quantitative human urine creatinine

Tsuei Lian Wang; Hui-hua K. Chiang; Hui-hsin Lu; Yung-da Hung



HPLC Method for the Assay of Creatinine in Urine  

Microsoft Academic Search

A simple and rapid HPLC method has been developed for the determination of creatinine in urine.Urine was diluted (1:50 v\\/v) with water and injected directly. The chromatographic separation was accomplished with butylamine-phosphoric acid buffer at a flow rate of 1.2 ml\\/min. The HPLC column was a cartridge packed with 3 ?m Econosphere C18. The UV detection wavelength was 230 nm.

D. H. Catlin; B. Starcevic



UV-induced effects on chlorination of creatinine.  


Ultraviolet (UV) irradiation is commonly employed for water treatment in swimming pools to complement conventional chlorination, and to reduce the concentration of inorganic chloramine compounds. The approach of combining UV irradiation and chlorination has the potential to improve water quality, as defined by microbial composition. However, relatively little is known about the effects of this process on water chemistry. To address this issue, experiments were conducted to examine the effects of sequential UV254 irradiation/chlorination, as will occur in recirculating system of swimming pools, on disinfection byproduct (DBP) formation. Creatinine, which is present in human sweat and urine, was selected as the target precursor for these experiments. Enhanced formation of dichloromethylamine (CH3NCl2) and inorganic chloramines was observed to result from post-chlorination of UV-irradiated samples. Chlorocreatinine was found to be more sensitive to UV254 irradiation than creatinine; UV254 irradiation of chlorocreatinine resulted in opening of the ring structure, thereby yielding a series of intermediates that were more susceptible to free chlorine attack than their parent compound. The quantum yields for photodegradation of creatinine and chlorocreatinine at 254 nm were estimated at 0.011 ± 0.002 mol/E and 0.144 ± 0.011 mol/E, respectively. The N-Cl bond was found to be common to UV-sensitive chlorinated compounds (e.g., inorganic chloramines, CH3NCl2, and chlorocreatinine); compounds that were less susceptible to UV-based attack generally lacked the N-Cl bond. This suggested that the N-Cl bond is susceptible to UV254 irradiation, and cleavage of the N-Cl bond appears to open or promote reaction pathways that involve free chlorine, thereby enhancing formation of some DBPs and promoting loss of free chlorine. Proposed reaction mechanisms to describe this behavior based on creatinine as a precursor are presented. PMID:23863372

Weng, Shih Chi; Li, Jing; Wood, Karl V; Kenttämaa, Hilkka I; Williams, Peggy E; Amundson, Lucas M; Blatchley, Ernest R



High plasma uric acid concentration: causes and consequences  

PubMed Central

High plasma uric acid (UA) is a precipitating factor for gout and renal calculi as well as a strong risk factor for Metabolic Syndrome and cardiovascular disease. The main causes for higher plasma UA are either lower excretion, higher synthesis or both. Higher waist circumference and the BMI are associated with higher insulin resistance and leptin production, and both reduce uric acid excretion. The synthesis of fatty acids (tryglicerides) in the liver is associated with the de novo synthesis of purine, accelerating UA production. The role played by diet on hyperuricemia has not yet been fully clarified, but high intake of fructose-rich industrialized food and high alcohol intake (particularly beer) seem to influence uricemia. It is not known whether UA would be a causal factor or an antioxidant protective response. Most authors do not consider the UA as a risk factor, but presenting antioxidant function. UA contributes to > 50% of the antioxidant capacity of the blood. There is still no consensus if UA is a protective or a risk factor, however, it seems that acute elevation is a protective factor, whereas chronic elevation a risk for disease.



Effects of Marine Corps Officer Candidate School Training on Serum Uric Acid Levels.  

National Technical Information Service (NTIS)

Serum uric acid levels were measured in successful Marine Corps Officer Candidate School students before and after the 12 weeks' intensive physical training. There was a significant fall in the serum uric acid level of 52 subjects from 6.01 mg percent to ...

L. H. Cronau P. J. Rasch J. W. Hamby H. J. Burns



Effect of insulin on renal sodium and uric acid handling in essential hypertension  

Microsoft Academic Search

In normal subjects, insulin decreases the urinary excretion of sodium, potassium, and uric acid. We tested whether these renal effects of insulin are altered in insulin resistant hypertension. In 37 patients with essential hypertension, we measured the changes in urinary excretion of sodium, potassium, and uric acid in response to physiological euglycemic hyperinsulinemia (by using the insulin clamp technique at

Elza Muscelli; Andrea Natali; Stefano Bianchi; Roberto Bigazzi; Alfredo Quiñones Galvan; Anna Maria Sironi; Silvia Frascerra; Demetrio Ciociaro; Ele Ferrannini; E. Ferrannini



The influence of dairy products on plasma uric acid in women  

Microsoft Academic Search

Elevated levels of plasma uric acid have been linked to increased risk of cardiovascular diseases and their complications. As dairy proteins have been found to decrease plasma uric acid without increasing glomerular filtration rate, a sample of postmenopausal women living in Montreal was studied to investigate the nature of this relationship. Participants (158 Roman Catholic nuns) were randomly assigned to

Parviz Ghadirian; Bryna Shatenstein; Maurice Verdy; Pavel Hamet



Uric acid modulates vascular endothelial function through the down regulation of nitric oxide production.  


Endothelial dysfunction characterized by decreased nitric oxide (NO) bioavailability is the first stage of coronary artery disease. It is known that one of the factors associated with an increased risk of coronary artery disease is a high plasma level of uric acid. However, causative associations between hyperuricaemia and cardiovascular risk have not been definitely proved. In this work, we tested the effect of uric acid on endothelial NO bioavailability. Electrochemical measurement of NO production in acetylcholine-stimulated human umbilical endothelial cells (HUVECs) revealed that uric acid markedly decreases NO release. This finding was confirmed by organ bath experiments on mouse aortic segments. Uric acid dose-dependently reduced endothelium-dependent vasorelaxation. To reveal the mechanism of decreasing NO bioavailability we tested the effect of uric acid on reactive oxygen species production by HUVECs, on arginase activity, and on acetylcholine-induced endothelial NO synthase phosphorylation. It was found that uric acid increases arginase activity and reduces endothelial NO synthase phosphorylation. Interestingly, uric acid significantly increased intracellular superoxide formation. In conclusion, uric acid decreases NO bioavailability by means of multiple mechanisms. This finding supports the idea of a causal association between hyperuricaemia and cardiovascular risk. PMID:23136942

Papežíková, I; Pekarová, M; Kolá?ová, H; Klinke, A; Lau, D; Baldus, S; Lojek, A; Kubala, L



Serum uric acid as an index of impaired oxidative metabolism in chronic heart failure  

Microsoft Academic Search

Background Elevated serum uric acid concentrations have been observed in clinical conditions associated with hypoxia. Since chronic heart failure is a state of impaired oxidative metabolism, we sought to determine whether serum uric acid concentrations correlate with measures of functional capacity and disease severity. Methods Fifty nine patients with a diagnosis of chronic heart failure due to coronary heart disease

F. Leyva; S. Anker; J. W. Swan; T.-P. Chua; J. C. Stevensonf; A. J. S. Coats


Elevation of the Serum Uric Acid Level Preceding the Clinical Manifestation of Preeclampsia in Twin Pregnancies  

Microsoft Academic Search

To assess changes in the serum uric acid level in the third trimester of twin pregnancies, a total of 152 consecutive women with twin pregnancies were examined. Serum uric acid levels were analyzed in the women at varying gestational weeks in the presence or absence of preeclampsia. A receiver operating characteristic curve was used to determine the optimal cutoff value

Toshimitsu Koike; Hisanori Minakami; Takeshi Takayama; Shuichi Ogawa; Tomoyuki Kuwata; Ikuo Sato



Poly( o-aminophenol)-modified bienzyme carbon paste electrode for the detection of uric acid  

Microsoft Academic Search

A reagentless uric acid selective biosensor constructed by immobilising uricase and horseradish peroxidase (HRP) in carbon paste without the addition of an electron transfer mediator is described. The response of the electrode is based on the enzymatic reduction of hydrogen peroxide in the presence of uric acid. Uricase and HRP were dispersed in the carbon paste and the optimum paste

E. Miland; A. J. Miranda Ordieres; P. Tuñón Blanco; M. R. Smyth; C. Ó. Fágáin



Uric Acid secretion from adipose tissue and its increase in obesity.  


Obesity is often accompanied by hyperuricemia. However, purine metabolism in various tissues, especially regarding uric acid production, has not been fully elucidated. Here we report, using mouse models, that adipose tissue could produce and secrete uric acid through xanthine oxidoreductase (XOR) and that the production was enhanced in obesity. Plasma uric acid was elevated in obese mice and attenuated by administration of the XOR inhibitor febuxostat. Adipose tissue was one of major organs that had abundant expression and activities of XOR, and adipose tissues in obese mice had higher XOR activities than those in control mice. 3T3-L1 and mouse primary mature adipocytes produced and secreted uric acid into culture medium. The secretion was inhibited by febuxostat in a dose-dependent manner or by gene knockdown of XOR. Surgical ischemia in adipose tissue increased local uric acid production and secretion via XOR, with a subsequent increase in circulating uric acid levels. Uric acid secretion from whole adipose tissue was increased in obese mice, and uric acid secretion from 3T3-L1 adipocytes was increased under hypoxia. Our results suggest that purine catabolism in adipose tissue could be enhanced in obesity. PMID:23913681

Tsushima, Yu; Nishizawa, Hitoshi; Tochino, Yoshihiro; Nakatsuji, Hideaki; Sekimoto, Ryohei; Nagao, Hirofumi; Shirakura, Takashi; Kato, Kenta; Imaizumi, Keiichiro; Takahashi, Hiroyuki; Tamura, Mizuho; Maeda, Norikazu; Funahashi, Tohru; Shimomura, Iichiro



Simultaneous determination of uric acid metabolites allantoin, 6-aminouracil, and triuret in human urine using liquid chromatography-mass spectrometry.  


Uric acid (UA) can be directly converted to allantoin enzymatically by uricase in most mammals except humans or by reaction with superoxide. UA can react directly with nitric oxide to generate 6-aminouracil and with peroxynitrite to yield triuret; both of these metabolites have been identified in biological samples. We now report a validated high-performance liquid chromatography and tandem mass spectrometry method for the determination of these urinary UA metabolites. Urine samples were diluted 10-fold, filtered and directly injected onto HPLC for LC-MS/MS analysis. The urinary metabolites of UA were separated using gradient HPLC. Identification and quantification of UA urinary metabolites was performed with electrospray in positive ion mode by selected-reaction monitoring (SRM). Correlation coefficients were 0.991-0.999 from the calibration curve. The intra- and inter-day precision (R.S.D., %) of the metabolites ranged from 0.5% to 13.4% and 2.5-12.2%, respectively. In normal individuals (n=21), urinary allantoin, 6-aminouracil and triuret, were 15.30 (+/-8.96), 0.22 (+/-0.12), and 0.12 (+/-0.10) microg/mg of urinary creatinine (mean (+/-S.D.)), respectively. The new method was used to show that smoking, which can induce oxidative stress, is associated with elevated triuret levels in urine. Thus, the method may be helpful in identifying pathways of oxidative stress in biological samples. PMID:19081307

Kim, Kyung Mee; Henderson, George N; Frye, Reginald F; Galloway, Cheryl D; Brown, Nancy J; Segal, Mark S; Imaram, Witcha; Angerhofer, Alexander; Johnson, Richard J



Simultaneous determination of uric acid metabolites allantoin, 6-aminouracil, and triuret in human urine using liquid chromatography-mass spectrometry  

PubMed Central

Uric acid (UA) can be directly converted to allantoin enzymatically by uricase in most mammals except humans or by reaction with superoxide. UA can react directly with nitric oxide to generate 6-aminouracil and with peroxynitrite to yield triuret; both of these metabolites have been identified in biological samples. We now report a validated high-performance liquid chromatography and tandem mass spectrometry method for the determination of these urinary UA metabolites. Urine samples were diluted 10-fold, filtered and directly injected onto HPLC for LC–MS/MS analysis. The urinary metabolites of UA were separated using gradient HPLC. Identification and quantification of UA urinary metabolites was performed with electrospray in positive ion mode by selected-reaction monitoring (SRM). Correlation coefficients were 0.991–0.999 from the calibration curve. The intra-and inter-day precision (R.S.D., %) of the metabolites ranged from 0.5% to 13.4% and 2.5–12.2%, respectively. In normal individuals (n = 21), urinary allantoin, 6-aminouracil and triuret, were 15.30 (±8.96), 0.22 (±0.12), and 0.12 (±0.10) ?g/mg of urinary creatinine (mean (±S.D.)), respectively. The new method was used to show that smoking, which can induce oxidative stress, is associated with elevated triuret levels in urine. Thus, the method may be helpful in identifying pathways of oxidative stress in biological samples.

Kim, Kyung Mee; Henderson, George N.; Frye, Reginald F.; Galloway, Cheryl D.; Brown, Nancy J.; Segal, Mark S.; Imaram, Witcha; Angerhofer, Alexander; Johnson, Richard J.



Effect of vitamin E therapy on serum uric acid in DOCA-salt-treated rats.  


Uric acid is considered as an antioxidant in the blood. Despite its proposed protective properties, elevated plasma uric acid has been associated with hypertension in a variety of disorders. The purpose of this study was to investigate the relationship between the increase of arterial blood pressure and the changes in serum uric acid, measured during the gradual development of experimental hypertension in deoxycorticosterone (DOCA)-salt-treated rats. Blood pressure was monitored by tail-cuff method, urinary and plasma uric acid was measured by autoanalyzer during the induction of hypertension in 1-, 2-, 3- and 4-week DOCA-salt-treated Sprague-Dawley rats. Vitamin E (200 mg/kg/day/gavage) was co-administered with DOCA-salt for 4 weeks. From the first week of DOCA-salt treatment, rats exhibited marked increases in blood pressure. DOCA-salt treatment also resulted in a significant increase in serum uric acid and a significant decrease in urinary uric acid at the end of the first week. These changes in serum and urinary uric acid remained until the 4th week of DOCA-salt treatment but blood pressure continued to increase throughout the study. Vitamin E treatment increased urinary excretion of uric acid and decreased blood pressure and serum uric acid in DOCA-salt-treated rats. These data suggest that enhanced serum uric acid may be a contributing factor to the onset of hypertension in DOCA-salt-treated rats. A uricosuric effect is suggested for vitamin E in the treatment of hypertension. PMID:21616780

Seifi, B; Kadkhodaee, Mehri; Zahmatkesh, M



Serum uric acid levels in normal pregnancy with observations on the renal excretion of urate in pregnancy  

Microsoft Academic Search

Serum uric acid estimations were performed in 106 healthy pregnant women during early, middle, and late pregnancy, using an automated colorimetric method. The mean serum uric acid level was significantly lower during early and middle pregnancy than that of 64 age-matched female controls. The serum uric acid level was not significantly different in late pregnancy from the control group. Studies

James A. Boyle; Stuart Campbell; Anne M. Duncan; William R. Greig; W. Watson Buchanan



The effect of a vegetarian and different omnivorous diets on urinary risk factors for uric acid stone formation  

Microsoft Academic Search

Summary. Background: About 10–15% of all urinary stones are composed of uric acid. A high urinary uric acid excretion, a low urine volume and an acidic urinary pH value are suggested to be the most important risk factors for uric acid stone formation. Aim of the study: The effect of a vegetarian diet and different omnivorous diets on the risk

Roswitha Siener; Albrecht Hesse



Uric Acid: A Novel Risk Factor for Acute Kidney Injury in High-Risk Cardiac Surgery Patients?  

Microsoft Academic Search

Background: Uric acid has been reported to be a risk factor for the development of chronic kidney disease; however, no study has examined whether uric acid may confer a risk for acute kidney injury. Methods: We investigated the relation between serum uric acid and the incidence of postoperative acute kidney injury in patients undergoing high-risk cardiovascular surgery (cardiac valve and

A. Ahsan Ejaz; Thomas M. Beaver; Michiko Shimada; Puneet Sood; Vijaykumar Lingegowda; Jesse D. Schold; Tad Kim; Richard J. Johnson



Urea Transformation of Wetland Microbial Communities  

Microsoft Academic Search

Transformation of urea to ammonium is an important link in the nitrogen cycle in soil and water. Although microbial nitrogen\\u000a transformations, such as nitrification and denitrification, are well studied in freshwater sediment and epiphytic biofilm\\u000a in shallow waters, information about urea transformation in these environments is scarce. In this study, urea transformation\\u000a of sedimentary, planktonic, and epiphytic microbial communities was

Ann-Karin Thorén



Substituted Ureas. Methods of Synthesis and Applications  

NASA Astrophysics Data System (ADS)

Systematic data on the method of synthesis of ureas by the interaction of compounds containing the amino-group with organic isocyanates, of amines and alkyl halides with alkali metal cyanates, and of primary and secondary amines with phosgene, carbon dioxide, urea, or nitrourea and by the carbonylation of amines are presented. The reactions involving the alkylation of urea and its interaction with various compounds containing functional groups are considered. The advantages and disadvantages of various methods are noted. The principal and practical applications of substituted ureas, including their applications as additives to organic materials, are discussed. The bibliography includes 314 references.

Vishnyakova, T. P.; Golubeva, I. A.; Glebova, E. V.



Rapid urea broth test for yeasts.  

PubMed Central

A rapid, miniaturized, urea broth test useful for detecting urease activity of yeasts was compared to Christensen urea agar. All urease-producing yeasts tested were positive on both media; however, 60% were reactive in the urea R broth within 30 min, and the remainder were reactive within 4 h. This urea multiwell test may be useful as a rapid screening method for detecting urease-producing yeasts recovered from clinical specimens and as an adjunct test with other rapid methods of yeast identification. Images

Roberts, G D; Horstmeier, C D; Land, G A; Foxworth, J H



Rapid and Accurate Estimation of Creatinine Clearance in the Muscle-Wasted Elderly by Computed Tomography  

Microsoft Academic Search

To develop a new method for accurately predicting creatinine clearance (Ccr) in the debilitated elderly without urine collections, the total muscle volume of both thighs (MV thigh), as a new predictive parameter, was calculated using computed tomography in 68 debilitated patients aged 61–92 years. A regression line between 24-hour urinary creatinine excretion and MV thigh was divided by serum creatinine

Masaki Sanaka; Kikuo Takano; Kazuro Shimakura; Yuichi Koike; Satoru Mineshita



Spectroscopic characterization of urea aqueous solutions: experimental phase diagram of the urea-water binary system.  


Raman spectroscopy was used to analyze mixtures of urea and water in order to identify the influence of the urea concentration on the solution's freezing point. Our approach consisted in the analysis of urea aqueous solutions and the determination of their phase transitions at low temperatures. Hence, Raman spectra of these solutions were acquired in a -30 to 10 °C temperature range. This enabled us to build the experimental phase diagram of the urea-water binary system. PMID:24067578

Durickovic, Ivana; Thiébaud, Laura; Bourson, Patrice; Kauffmann, Thomas; Marchetti, Mario



A technique for predicting urea release from coated urea in wetland soil  

Microsoft Academic Search

A simple technique for measuring urea release from different coated urea fertilizer materials in simulated wetland soil has been developed and tested. The laboratory soil system used simulates physical, chemical, and microbiological environments of wetland soils under field conditions. Laboratory and field values for urea release are in good agreement.

N. K. Savant; J. R. Clemmons; A. F. James



Higher serum uric acid and lipoprotein(a) are correlated with coronary spasm.  


It has been reported that a major cause of coronary vasospastic angina (VSA) is endothelial dysfunction of the coronary artery. On the other hand, some studies showed that serum uric acid and lipoprotein(a) are correlated with endothelial dysfunction. Thus, we examined whether uric acid and lipoprotein(a), are correlated with VSA. Four hundred forty-one patients with suspected VSA who underwent a coronary angiogram with acetylcholine provocation (ACh test) during an 8-year period were enrolled. We divided them into a VSA group, who showed coronary spasm by the ACh test, and an atypical chest pain (ACP) group, who showed negative ACh test. We compared serum markers between the two groups, including low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, high-sensitivity C-reactive protein (hs-CRP), lipoprotein(a), fibrinogen, total plasminogen activator inhibitor-1, and uric acid. Uric acid, hs-CRP, and lipoprotein(a) were significantly higher in the VSA group than in the ACP group (all P < 0.05) while there were no significant differences in the other parameters. Multivariate analyses identified uric acid and lipoprotein(a) as significant independent markers for VSA. Uric acid and lipoprotein(a) are correlated with VSA, and medical intervention to decrease uric acid and lipoprotein(a) might be effective in controlling VSA. PMID:23552902

Nishino, Masami; Mori, Naoki; Yoshimura, Takahiro; Nakamura, Daisuke; Lee, Yasuharu; Taniike, Masayuki; Makino, Nobuhiko; Kato, Hiroyasu; Egami, Yasuyuki; Shutta, Ryu; Tanouchi, Jun; Yamada, Yoshio



Uric acid deposits and estivation in the invasive apple-snail, Pomacea canaliculata.  


The physiological ability to estivate is relevant for the maintenance of population size in the invasive Pomacea canaliculata. However, tissue reoxygenation during arousal from estivation poses the problem of acute oxidative stress. Uric acid is a potent antioxidant in several systems and it is stored in specialized tissues of P. canaliculata. Changes in tissue concentration of thiobarbituric acid reactive substances (TBARS), uric acid and allantoin were measured during estivation and arousal in P. canaliculata. Both TBARS and uric acid increased two-fold during 45 days estivation, probably as a consequence of concomitant oxyradical production during uric acid synthesis by xanthine oxidase. However, after arousal was induced, uric acid and TBARS dropped to or near baseline levels within 20 min and remained low up to 24h after arousal induction, while the urate oxidation product allantoin continuously rose to a maximum at 24h after induction, indicating the participation of uric acid as an antioxidant during reoxygenation. Neither uric acid nor allantoin was detected in the excreta during this 24h period. Urate oxidase activity was also found in organs of active snails, but activity shut down during estivation and only a partial and sustained recovery was observed in the midgut gland. PMID:21182978

Giraud-Billoud, Maximiliano; Abud, María A; Cueto, Juan A; Vega, Israel A; Castro-Vazquez, Alfredo



Serum uric acid correlates with extracellular superoxide dismutase activity in patients with chronic heart failure.  


Increased serum uric acid has been identified as an independent risk factor for cardiovascular disease. However, because of its antioxidant capacity, uric acid may play a beneficial role in endothelial function. This paradoxical relationship between uric acid and endothelial function in chronic heart failure patients remains poorly understood. Thirty-eight chronic heart failure patients (New York Heart Association functional class II-III, mean age 58+/-10 years and mean left ventricular ejection fraction 25+/-8%) and twelve age-and-sex-matched healthy controls were studied. Chronic heart failure patients showed higher uric acid levels (7.3+/-2.3 mg/dL vs. 6.1+/-0.2 mg/dL, p<0.05) and lower extracellular superoxide dismutase activity (136+/-36 U ml(-1) min(-1) vs. 203+/-61 U ml(-1) min(-1), p<0.01) and endothelium-dependent vasodilatation (4.0+/-1.6% v. 9.1+/-3.0%, p<0.01) when compared with control subjects. In chronic heart failure patients, correlations between both uric acid levels and extracellular superoxide dismutase activity (r=0.45; p<0.01), and uric acid and endothelium-dependent vasodilatation (r=0.35; p=0.03) were detected. These correlations were not observed in healthy individuals, suggesting a positive effect of uric acid on endothelial function partially mediated by modulation of extracellular superoxide dismutase activity in chronic heart failure. PMID:18559296

Alcaino, Hernan; Greig, Douglas; Chiong, Mario; Verdejo, Hugo; Miranda, Rodrigo; Concepcion, Roberto; Vukasovic, José Luis; Diaz-Araya, Guillermo; Mellado, Rosemarie; Garcia, Lorena; Salas, Daniela; Gonzalez, Leticia; Godoy, Ivan; Castro, Pablo; Lavandero, Sergio



Prognostic value of uric acid in patients with acute coronary syndromes.  


The association between uric acid and cardiovascular disease is incompletely understood. In particular, the prognostic value of uric acid in patients with acute coronary syndromes who undergo percutaneous coronary intervention has not been studied. This study included 5,124 patients with acute coronary syndromes who underwent percutaneous coronary intervention: 1,629 with acute ST-segment elevation myocardial infarction, 1,332 with acute non-ST-segment elevation myocardial infarction, and 2,163 with unstable angina. The primary end point was 1-year mortality. Patients were divided into quartiles according to uric acid level as follows: quartile 1, 1.3 to <5.3 mg/dl; quartile 2, 5.3 to <6.3 mg/dl; quartile 3, 6.3 to <7.5 mg/dl; and quartile 4, 7.5 to 18.4 mg/dl. There were 450 deaths during follow-up: 80 deaths in quartile 1, 77deaths in quartile 2, 72 deaths in quartile 3, and 221 deaths in quartile 4 of uric acid (Kaplan-Meier estimates of 1-year mortality 6.4%, 6.2%, 5.6%, and 17.4%, respectively; unadjusted hazard ratio 3.05, 95% confidence interval 2.54 to 3.67, p <0.001 for fourth vs first quartile of uric acid). After adjustment for traditional cardiovascular risk factors, renal function, and inflammatory status, the association between uric acid and mortality remained significant, with a 12% increase in the adjusted risk for 1-year mortality for every 1 mg/dl increase in the uric acid level. Uric acid improved the discriminatory power of the predictive model regarding 1-year mortality (absolute integrated discrimination improvement 0.008, p = 0.005). In conclusion, elevated levels of uric acid are an independent predictor of 1-year mortality across the whole spectrum of patients with acute coronary syndromes treated with percutaneous coronary intervention. PMID:22325088

Ndrepepa, Gjin; Braun, Siegmund; Haase, Hans-Ullrich; Schulz, Stefanie; Ranftl, Sabine; Hadamitzky, Martin; Mehilli, Julinda; Schömig, Albert; Kastrati, Adnan



Serum uric acid: a forgotten prognostic marker in acute coronary syndromes?  

PubMed Central

Background: Serum uric acid (UA) has been shown to be an independent predictor of outcome in the general population and in patients with heart failure. There are, however, limited data regarding the prognostic value of UA in the context of acute coronary syndromes (ACS) particularly in medium-term follow up and the available results are contradictory. Materials and methods: Study of consecutive patients admitted with an ACS (with and without ST-segment elevation) at a single-centre coronary care unit. Primary endpoint was all-cause mortality at 1-year follow up. We evaluated if serum UA is an independent predictor of outcome and if it has any added value on top of GRACE risk score for risk prediction. Results: We included 683 patients, mean age 64±13 years, 69% males. In-hospital and 1-year mortality were 4.5 and 7.6% respectively. The best cut-off of UA to predict 1-year mortality was 6.25 mg/dl (sensitivity 59%, specificity 72%) and 30.2% of the patients had an increased UA according to this cut off. Independent predictors of UA were male gender (?= 0.078), body mass index (?=0.163), diuretics before admission (?=0.142), and admission serum creatinine (?=0.403). One-year mortality was significantly higher in patients with increased UA (15.5 vs. 4.2%, p<0.001; log rank, p<0.001). After adjustment, both increased UA as a categorical variable (HR 2.25, 95% CI 1.23–4.13, p=0.008) and as a continuous variable (HR 1.26, 95% CI 1.13–1.41, p<0.001) are independent predictors of mortality. The AUC increases only slightly after inclusion of UA in the model with GRACE risk score (from 0.78 to 0.79, p=0.350). Both models had a good fit; however, model fit worsened after inclusion of UA. Overall, the inclusion of UA in the original was associated with an improvement in both the net reclassification improvement (continuous NRI=44%), and the integrated discrimination improvement (IDI=0.052) suggesting effective reclassification. Conclusions: Serum UA is an independent predictor of all-cause mortality in medium-term after the whole spectrum of ACS and has an added value for risk stratification.

Lousinha, Ana; Labandeiro, Jorge; Miranda, Fernando; Papoila, Ana L; Oliveira, Jose A; Ferreira, Maria L; Ferreira, Rui C



Urea in rainwater and atmospheric aerosol  

NASA Astrophysics Data System (ADS)

The measurement of urea (CO(NH 2) 2) in rainwater samples from predominantly marine-influenced locations in Bermuda, and Ireland, and in rains and aqueous aerosol extracts from a rural site at UEA, Norwich indicates that urea is not generally a major contributor to atmospheric water-soluble organic nitrogen. At UEA, where anthropogenic and natural sources of urea are expected to be most intense, urea accounts for <10% of rainwater dissolved organic nitrogen (DON), and <1% of the water-soluble fraction of aerosol organic nitrogen. The analysis of size-segregated aerosol samples indicates that the size distribution of urea is quite different from those of ammonium and nitrate. In the less anthropogenically impacted Atlantic sites, rainwater urea was below the detection limits of the colorimetric method used in this study, consistent with expected dilution processes or reaction of urea during transport. However, in a small set of rain samples collected in Tahiti, urea concentrations ranged from 1 to 8 ?mol l -1, accounting for >40% of the DON measured in those samples. This may be a consequence of strong local sources, or it could possibly result from the partial breakdown of other DON compounds to urea during sample transport and storage. However, the similarity in urea concentrations observed in Pacific samples in this present study and in a previous one ( Timperley et al., 1985, Canadian Journal of Fisheries and Aquatic Science42, 1171-1177) suggests that this may reflect a difference in rain chemistry between Atlantic and Pacific rains, perhaps resulting from differences in levels of agricultural urea usage between Asia and the rest of the world.

Cornell, S. E.; Jickells, T. D.; Thornton, C. A.


Gender-dependent impacts of body mass index and moderate alcohol consumption on serum uric acid—an index of oxidant stress status?  

Microsoft Academic Search

Uric acid seems to be causally involved in a variety of medical disorders involving oxidative stress. Although alcohol abuse and obesity are known to increase serum uric acid, the interactions between moderate drinking, adiposity, and uric acid metabolism have remained poorly understood. We examined serum uric acid concentrations from 2062 apparently healthy volunteers (970 men, 1092 women) reporting either no

Päivikki I. Alatalo; Heidi M. Koivisto; Johanna P. Hietala; Risto S. Bloigu; Onni J. Niemelä



Urea Transporter Physiology Studied in Knockout Mice  

PubMed Central

In mammals, there are two types of urea transporters; urea transporter (UT)-A and UT-B. The UT-A transporters are mainly expressed in kidney epithelial cells while UT-B demonstrates a broader distribution in kidney, heart, brain, testis, urinary tract, and other tissues. Over the past few years, multiple urea transporter knockout mouse models have been generated enabling us to explore the physiological roles of the different urea transporters. In the kidney, deletion of UT-A1/UT-A3 results in polyuria and a severe urine concentrating defect, indicating that intrarenal recycling of urea plays a crucial role in the overall capacity to concentrate urine. Since UT-B has a wide tissue distribution, multiple phenotypic abnormalities have been found in UT-B null mice, such as defective urine concentration, exacerbated heart blockage with aging, depression-like behavior, and earlier male sexual maturation. This review summarizes the new insights of urea transporter functions in different organs, gleaned from studies of urea transporter knockout mice, and explores some of the potential pharmacological prospects of urea transporters.

Li, Xuechen; Chen, Guangping; Yang, Baoxue



Automated analytical biosystem for urea monitoring  

Microsoft Academic Search

The present work describes the construction and automation of a flow injection (FI) system for on-line monitoring of urea. The FI system comprises a nylon column on the wall of which the enzyme urease is covalently immobilized. Urea is hydrolyzed to ammonium and hydrogen carbonate ions in the presence of urease. The final measurement is done by an ammonium ion

M. Jurkiewicz; M. Del Valle; S. Alegret; E. Martínez-Fábregas



76 FR 15339 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

...Review)] Solid Urea From Russia and Ukraine AGENCY: United States International Trade...duty orders on solid urea from Russia and Ukraine...duty orders on solid urea from Russia and Ukraine would be likely to lead to...



75 FR 74746 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

...Review)] Solid Urea From Russia and Ukraine AGENCY: United States International Trade...duty orders on solid urea from Russia and Ukraine...duty orders on solid urea from Russia and Ukraine would be likely to lead to...



The Three Investigators Study. Serum Uric Acid, Cholesterol and Cortisol Variability during Stresses of Everday Life.  

National Technical Information Service (NTIS)

Serum uric acid, cholesterol, and cortisol variability were studied, semi-weekly, over three to six months' time in three medical investigators as they underwent the stresses of everyday life. These men maintained diaries of their life events, with partic...

R. H. Rahe R. T. Rubin R. J. Arthur



Serum Uric Acid and Cholesterol Variability: A Comprehensive View of Underwater Demolition Team Training.  

National Technical Information Service (NTIS)

One-third of a Navy underwater demolition team training class (32 men) was investigated by thrice weekly psychological assessment and serum uric acid and cholesterol determinations until they either dropped from training or graduated. In general, signific...

R. H. Rahe R. T. Rubin R. J. Arthur B. R. Clark



Serum Uric Acid Is a Determinant of Metabolic Syndrome in a Population-Based Study  

Microsoft Academic Search

Background: Determination of serum uric acid concentrations and role in risk of metabolic syndrome (MS) were investigated in 1877 participants in a cross-sectional population-based study including a brief follow-up.Methods: The MS was identified by modified criteria of the Adult Treatment Panel III, and coronary heart disease (CHD) by clinical findings and Minnesota coding of resting electrocardiograms. Uric acid concentrations were

Altan Onat; Hüseyin Uyarel; Ahmet Karabulut; Sinan Albayrak; Ibrahim Sar?; Mehmet Yaz?c?; Ibrahim Kele?



Cuticle Reflectivity and Optical Activity in Scarab Beetles: The Role of Uric Acid  

Microsoft Academic Search

The iridescent cuticle of certain Ruteline scarab beetles, which is a form optically active and selectively reflects circularly polarized light, incorporates an NH4OH-extractable component The ultraviolet absorption spectrum of this component, together with its chromatographic and refractive properties, identify it as uric acid (2,6,8-trihydroxypurine). All species of Plusiotis examined have uric acid in their reflecting layers, as do several species

S. Caveney



Association Between Uric Acid Levels and Obstructive Sleep Apnea Syndrome in a Large Epidemiological Sample  

PubMed Central

Introduction Recurrent hypoxia, which is associated with obstructive sleep apnea syndrome (OSAS), leads to an increase in the degradation of adenosine triphosphatase into xanthine, which in turn increases uric acid concentrations. Objective The current study aimed to determine whether an association exists between OSAS and uric acid levels in the peripheral blood from a representative population of Sao Paulo (Brazil). Methods A population-based survey adopting a probabilistic 3-stage cluster sample of Sao Paulo was used to represent the population according to gender, age, and socioeconomic class. A total of 1,042 volunteers underwent polysomnography recordings for OSAS diagnosis, blood pressure assessment, and biochemical blood analysis, and answered questionnaires. Results Uric acid levels were correlated with most important risk factors for OSAS, such as AHI, desaturation time and index, minimum oxyhemoglobin saturation (SpO2), blood pressure, cholesterol, BMI, triglycerides and arousal, and with OSAS itself. Also, uric acid was increased in OSAS volunteers even after controlling for all confounders. Hyperuricemic volunteers presented lower mean and minimum SpO2 and increased desaturation index. Importantly, minimum SpO2 was a significant predictor of uric acid levels, which in turn was considered an independent predictor for OSAS in the binary logistic model. However, a ROC curve analysis for establishing cut-off points for uric acid levels as a biomarker of OSAS revealed moderate sensitivity and specificity. Conclusion A strong association was found between uric acid levels and OSAS in a representative sample of the population of Sao Paulo. Although they do not qualify for a biomarker alone, uric acid levels may be involved in OSAS severity and should be considered in sleep apnea management in the future.

Hirotsu, Camila; Tufik, Sergio; Guindalini, Camila; Mazzotti, Diego R.; Bittencourt, Lia R.; Andersen, Monica L.



Genetic influence on variation in serum uric acid in American Indians: the strong heart family study  

Microsoft Academic Search

Hyperuricemia is associated with the metabolic syndrome, gout, renal and cardiovascular disease (CVD). American Indians have\\u000a high rates of CVD and 25% of individuals in the strong heart family study (SHFS) have high serum uric acid levels. The aim\\u000a of this study was to investigate the genetic determinants of serum uric acid variation in American Indian participants of\\u000a the SHFS.

V. Saroja Voruganti; Harald H. H. Göring; Amy Mottl; Nora Franceschini; Karin Haack; Sandra Laston; Laura Almasy; Richard R. Fabsitz; Elisa T. Lee; Lyle G. Best; Richard B. Devereux; Barbara V. Howard; Jean W. MacCluer; Anthony G. Comuzzie; Jason G. Umans; Shelley A. Cole



Uric Acid Spherulites in the Reflector Layer of Firefly Light Organ  

PubMed Central

Background In firefly light organs, reflector layer is a specialized tissue which is believed to play a key role for increasing the bioluminescence intensity through reflection. However, the nature of this unique tissue remains elusive. In this report, we investigated the role, fine structure and nature of the reflector layer in the light organ of adult Luciola cerata. Principal Findings Our results indicated that the reflector layer is capable of reflecting bioluminescence, and contains abundant uric acid. Electron microscopy (EM) demonstrated that the cytosol of the reflector layer's cells is filled with densely packed spherical granules, which should be the uric acid granules. These granules are highly regular in size (?700 nm in diameter), and exhibit a radial internal structure. X-ray diffraction (XRD) analyses revealed that an intense single peak pattern with a d-spacing value of 0.320 nm is specifically detected in the light organ, and is highly similar to the diffraction peak pattern and d-spacing value of needle-formed crystals of monosodium urate monohydrate. However, the molar ratio evaluation of uric acid to various cations (K+, Na+, Ca2+ and Mg2+) in the light organ deduced that only a few uric acid molecules were in the form of urate salts. Thus, non-salt uric acid should be the source of the diffraction signal detected in the light organ. Conclusions In the light organ, the intense single peak diffraction signal might come from a unique needle-like uric acid form, which is different from other known structures of non-salt uric acid form. The finding of a radial structure in the granules of reflector layer implies that the spherical uric acid granules might be formed by the radial arrangement of needle-formed packing matter.

Goh, King-Siang; Sheu, Hwo-Shuenn; Hua, Tzu-En; Kang, Mei-Hua; Li, Chia-Wei



Uric acid: Its relationship to renal hemodynamics and the renal renin-angiotensin system  

Microsoft Academic Search

Reports relating hyperuricemia and hypertension have been fieled for many decades. Nevertheless, controversy remains concerning\\u000a serum uric acid concentration as an independent risk factor underlying coronary heart disease (CHD) and essential hypertension\\u000a or as an indirect marker of renovascular involvement. Earlier studies in normotensive subjects and hypertensive patients demonstrated\\u000a that serum uric acid concentration was closely related to intrarenal hemodynamic

Xiaoyan Zhou; Luis Matavelli; Edward D. Frohlich



Spectrofluorimetric determination of uric acid based on its activation of catalytic oxidation of pyronine Y  

Microsoft Academic Search

A novel kinetic spectrofluorimetric method for the determination of uric acid based on the activation effect of uric acid\\u000a on the Cu(II) ion catalyzed oxidation of pyronine Y by hydrogen peroxide was developed. The influence of different buffer\\u000a solutions was tested and the Britton-Robinson buffer solution with pH 2.2 was found to be the optimum. The detection limit\\u000a and the

Suling Feng; Xueping Liu



Inverse association between coffee drinking and serum uric acid concentrations in middle-aged Japanese males  

Microsoft Academic Search

Consumption of caffeine-rich beverages, which have diuretic properties, may decrease serum uric acid concentrations. We examined cross-sectionally the relationship of coffee and green tea consumption to serum uric acid concentrations in 2240 male self-defence officials who received a pre-retirement health examination at four hospitals of the Self-Defence Forces between 1993 and 1994. The mean levels of coffee and green tea

C. Kiyohara; S. Kono; S. Honjo; I. Todoroki; Y. Sakurai; M. Nishiwaki; H. Hamad; H. Nishikawa; H. Koga; S. Ogawa; K. Nakagawa


The GLUT9 Gene Is Associated with Serum Uric Acid Levels in Sardinia and Chianti Cohorts  

Microsoft Academic Search

High serum uric acid levels elevate pro-inflammatory–state gout crystal arthropathy and place individuals at high risk for cardiovascular morbidity and mortality. Genome-wide scans in the genetically isolated Sardinian population identified variants associated with serum uric acid levels as a quantitative trait. They mapped within GLUT9, a Chromosome 4 glucose transporter gene predominantly expressed in liver and kidney. SNP rs6855911 showed

Siguang Li; Serena Sanna; Andrea Maschio; Fabio Busonero; Gianluca Usala; Antonella Mulas; Sandra Lai; Mariano Dei; Marco Orrù; Giuseppe Albai; Stefania Bandinelli; David Schlessinger; Edward Lakatta; Angelo Scuteri; Samer S Najjar; Jack Guralnik; Silvia Naitza; Laura Crisponi; Antonio Cao; Gonçalo Abecasis; Luigi Ferrucci; Manuela Uda; Wei-Min Chen; Ramaiah Nagaraja



The GLUT9 Gene Is Associated with Serum Uric Acid Levels in Sardinia and Chianti Cohorts  

Microsoft Academic Search

High serum uric acid levels elevate pro-inflammatory-state gout crystal arthropathy and place individuals at high risk for cardiovascular morbidity and mortality. Genome-wide scans in the genetically isolated Sardinian population identified variants associated with serum uric acid levels as a quantitative trait. They mapped within GLUT9 ,a Chromosome 4 glucose transporter gene predominantly expressed in liver and kidney. SNP rs6855911 showed

Siguang Li; Serena Sanna; Andrea Maschio; Fabio Busonero; Gianluca Usala; Antonella Mulas; Sandra Lai; Mariano Dei; Marco Orrù; Giuseppe Albai; Stefania Bandinelli; David Schlessinger; Edward Lakatta; Angelo Scuteri; Samer S. Najjar; Jack Guralnik; Silvia Naitza; Laura Crisponi; Antonio Cao; Gonçalo Abecasis; Luigi Ferrucci; Manuela Uda; Wei-Min Chen; Ramaiah Nagaraja



Plasmodium falciparum-Derived Uric Acid Precipitates Induce Maturation of Dendritic Cells  

PubMed Central

Malaria is characterized by cyclical fevers and high levels of inflammation, and while an early inflammatory response contributes to parasite clearance, excessive and persistent inflammation can lead to severe forms of the disease. Here, we show that Plasmodium falciparum-infected erythrocytes contain uric acid precipitates in the cytoplasm of the parasitophorous vacuole, which are released when erythrocytes rupture. Uric acid precipitates are highly inflammatory molecules that are considered a danger signal for innate immunity and are the causative agent in gout. We determined that P. falciparum-derived uric acid precipitates induce maturation of human dendritic cells, increasing the expression of cell surface co-stimulatory molecules such as CD80 and CD86, while decreasing human leukocyte antigen-DR expression. In accordance with this, uric acid accounts for a significant proportion of the total stimulatory activity induced by parasite-infected erythrocytes. Moreover, the identification of uric acid precipitates in P. falciparum- and P. vivax-infected erythrocytes obtained directly from malaria patients underscores the in vivo and clinical relevance of our findings. Altogether, our data implicate uric acid precipitates as a potentially important contributor to the innate immune response to Plasmodium infection and may provide a novel target for adjunct therapies.

van de Hoef, Diana L.; Coppens, Isabelle; Holowka, Thomas; Ben Mamoun, Choukri; Branch, OraLee; Rodriguez, Ana



Uric acid is a danger signal of increasing risk for osteoarthritis through inflammasome activation  

PubMed Central

Uric acid (UA) is known to activate the NLRP3 (Nacht, leucine-rich repeat and pyrin domain containing protein 3) inflammasome. When activated, the NLRP3 (also known as NALP3) inflammasome leads to the production of IL-18 and IL-1?. In this cohort of subjects with knee osteoarthritis (OA), synovial fluid uric acid was strongly correlated with synovial fluid IL-18 and IL-1?. Synovial fluid uric acid and IL-18 were strongly and positively associated with OA severity as measured by both radiograph and bone scintigraphy, and synovial fluid IL-1? was associated with OA severity but only by radiograph. Furthermore, synovial fluid IL-18 was associated with a 3-y change in OA severity, on the basis of the radiograph. We conclude that synovial fluid uric acid is a marker of knee OA severity. The correlation of synovial fluid uric acid with the two cytokines (IL-18 and IL-1?) known to be produced by uric acid-activated inflammasomes and the association of synovial fluid IL-18 with OA progression, lend strong support to the potential involvement of the innate immune system in OA pathology and OA progression.

Denoble, Anna E.; Huffman, Kim M.; Stabler, Thomas V.; Kelly, Susan J.; Hershfield, Michael S.; McDaniel, Gary E.; Coleman, R. Edward; Kraus, Virginia B.



Genotype-based changes in serum uric acid affect blood pressure  

PubMed Central

Elevated serum levels of uric acid consistently correlate with hypertension, but the directionality of the association remains debated. To help define this relationship, we used a controlled setting within a homogeneous Amish community and the Mendelian randomization of a nonsynonymous coding single-nucleotide polymorphism, rs16890979 (Val253Ile), in the SLC2A9 gene. This gene expresses the GLUT9 transporter that also transports uric acid and is associated with lower serum uric acid levels. We studied the unconfounded association between genotype and blood pressure in 516 Amish adults, each placed for 6 days on standardized diets, first with high sodium, followed by low sodium, with an intervening washout period. Blood pressure, measured using 24-h ambulatory monitoring, during both diet periods was used as the primary outcome. All participants were free of diuretic or other antihypertensive medications and the relationships between GLUT9 genotype and both serum uric acid and blood pressure were assessed. Each copy of the GLUT9 minor Ile allele was found to confer a significant 0.44 mg/dl reduction in serum uric acid and was associated with a significant mean decrease in the systolic blood pressure of 2.2 and 1.5 mm Hg on the high- and low-sodium diet, respectively. Thus, a Mendelian randomization analysis using variants in the GLUT9 gene indicates that a decrease in serum uric acid has a causal effect of lowering blood pressure.

Parsa, Afshin; Brown, Eric; Weir, Matthew R.; Fink, Jeffrey C.; Shuldiner, Alan R.; Mitchell, Braxton D.; McArdle, Patrick F.



An amperometric biosensor for uric acid determination prepared from uricase immobilized in polypyrrole film.  


In order to prepare a biosensor for the determination of uric acid, electropolymerization of pyrrole on Pt surface was carried out with an electrochemical cell containing pyrrole, ferrocene (as a electron mediator) and tetrabutylammonium tetrafluoroborat in acetonitrile by cyclic voltammetry between 0.0 and 1.0 V (vs. Ag/AgCl) at a scan rate of 50 mV/s upon Pt electrode. Uricase was immobilized by a glutaraldehyde/gelatine croslinking procedure on to polypyrrole film after the electropolymerization processes. The response of the biosensor against uric acid was measured after 330 seconds following the application of a constant potential of +0.7 V (vs. Ag/AgCl). The resulting biosensor exhibits excellent electrocatalysis for the uric acid. The amperometric determination is based on the electrochemical detection of H2O2, which is generated in enzymatic reaction of uric acid. The sensor responds to uric acid with a detection limit of 5.0 x 10(-7) M. The sensor remains relatively stable for 5 weeks. Interference effect were investigated on the amperometric response of the biosensor. Determination of uric acid was carried out in the biological fluids by biosensor. PMID:16809136

Cete, Servet; Ya?ar, Ahmet; Arslan, Fatma



Genotype-based changes in serum uric acid affect blood pressure.  


Elevated serum levels of uric acid consistently correlate with hypertension, but the directionality of the association remains debated. To help define this relationship, we used a controlled setting within a homogeneous Amish community and the Mendelian randomization of a nonsynonymous coding single-nucleotide polymorphism, rs16890979 (Val253Ile), in the SLC2A9 gene. This gene expresses the GLUT9 transporter that also transports uric acid and is associated with lower serum uric acid levels. We studied the unconfounded association between genotype and blood pressure in 516 Amish adults, each placed for 6 days on standardized diets, first with high sodium, followed by low sodium, with an intervening washout period. Blood pressure, measured using 24-h ambulatory monitoring, during both diet periods was used as the primary outcome. All participants were free of diuretic or other antihypertensive medications and the relationships between GLUT9 genotype and both serum uric acid and blood pressure were assessed. Each copy of the GLUT9 minor Ile allele was found to confer a significant 0.44?mg/dl reduction in serum uric acid and was associated with a significant mean decrease in the systolic blood pressure of 2.2 and 1.5?mm?Hg on the high- and low-sodium diet, respectively. Thus, a Mendelian randomization analysis using variants in the GLUT9 gene indicates that a decrease in serum uric acid has a causal effect of lowering blood pressure. PMID:22189840

Parsa, Afshin; Brown, Eric; Weir, Matthew R; Fink, Jeffrey C; Shuldiner, Alan R; Mitchell, Braxton D; McArdle, Patrick F



Serum uric Acid: an early indicator of oxidative stress in Beta thalassemia population.  


Iron induced alteration in the redox balance is a major complication in the beta thalassemia major patients receiving regular blood transfusion. Variable degrees of association between uric acid level with the free iron and its storage form ferritin in thalassemic patients are suggested to play a significant role in this alteration by an unclear mechanism. In the present study, we made an effort to analyze the association of serum uric acid with oxidative stress and to evaluate the predictive value of serum iron, serum ferritin and serum uric acid level on oxidative stress induced lipid peroxidation in beta thalassemic patients. For this we assayed these parameters in 61 patients of ? thalassemia major and 51 age and sex matched controls of a rural area of West Bengal. Serum TBARS, serum Uric acid, serum Ferritin and serum Iron levels were significantly higher in the patient group (p<0.001 for all of them). Significant correlations existed between serum levels of TBARS, Uric acid, Ferritin and Iron levels in the patient group whereas only serum TBARS levels showed significant correlation with serum iron level in the control group. Regression analysis revealed that uric acid levels have a better predictive value (?=0.3, p=0.001) than serum ferritin value (?=0.013, p=0.871) for indicating TBARS production. PMID:23982550

Dasgupta, S; Dasgupta, A; Mukhopadhayay, T; Bhattacharya, S; Swaika, B; Banarjee, U; Chakrabarty, P



Impact of urea on detergent micelle properties.  


Co-solvents, such as urea, can entail drastic changes in the micellization behavior of detergents. We present a systematic quantification of the impact of urea on the critical micellar concentration, the micellization thermodynamics, and the micelle size in three homologous series of commonly used non-ionic alkyl detergents. To this end, we performed demicellization experiments by isothermal titration calorimetry and hydrodynamic size measurements by dynamic light scattering on alkyl maltopyranosides, cyclohexyl alkyl maltopyranosides, and alkyl glucopyranosides at urea concentrations of 0-8 M. For all detergents studied, we found that the critical micellar concentration increases exponentially because the absolute Gibbs free energy of micellization decreases linearly over the entire urea concentration range, as does the micelle size. In contrast, the enthalpic and entropic contributions to micellization reveal more complex, nonlinear dependences on urea concentration. Both free energy and size changes are more pronounced for long-chain detergents, which bury more apolar surface area upon micelle formation. The Gibbs free energy increments per methylene group within each detergent series depend on urea concentration in a linear fashion, although they result from the entropic term for alkyl maltosides but are of enthalpic origin for cyclohexyl alkyl maltosides. We compare our results to transfer free energies of amino acid side chains, relate them to protein-folding data, and discuss how urea-induced changes in detergent micelle properties affect in vitro investigations on membrane proteins. PMID:23745835

Broecker, Jana; Keller, Sandro



Triiodothyronine administration affects urea synthesis in rats.  


The purpose of the present study was to elucidate the mechanism by which thyroid hormone alters urea synthesis. The relative importance of urea cycle enzyme activities, substrate levels or the levels of urea cycle intermediates on urea production was investigated in a set of four experiments in which rats were fed a diet supplemented with 6-propyl-2-thiouracil (PTU, a thyroid inhibitor) and treated with triiodothyronine (T3). Compared with that of normal or control rats, the plasma level of T3 was significantly lower in rats fed a diet containing PTU only and elevated in rats given PTU + T3. Urinary excretion of urea and the liver content of ornithine in rats given PTU + T3 were significantly lower than in rats given PTU only. The liver level of ornithine was closely correlated to the excretion of urea in the present study. Fractional rates of protein synthesis in liver, kidney and small intestine were lower in the hypothyroid group. However, most free amino acid concentrations, except ornithine in liver and plasma and the activity of hepatic argininosuccinate synthetase (EC of hypothyroid rats, were significantly reduced as compared with those of control or hyperthyroid rats. The results indicate that the increased hepatic ornithine content in the hypothyroid rats may be one of the regulatory factors causing changes in urea synthesis. PMID:2051240

Hayase, K; Yonekawa, G; Yokogoshi, H; Yoshida, A



Use of the Albumin\\/Creatinine Ratio to Detect Microalbuminuria: Implications of Sex and Race  

Microsoft Academic Search

The recommended albumin (g)\\/creatinine (mg) ra- tio (ACR) (30 g\\/mg) to detect microalbuminuria does not account for sex or racial differences in creatinine excretion. In a nationally representative sample of subjects, the distribution of urine albumin and creatinine concentrations was examined by using one ACR value (30 g\\/mg) and sex-specific cut- points (17 g\\/mg in men and 25 g\\/mg in



Urea release from silicate- and polymer-coated urea in water and a simulated wetland soil  

Microsoft Academic Search

Urea release rates in water (38°C) and in a simulated wetland soil system under greenhouse conditions from silicate- and polymer-coated urea (SPCU) materials have been studied. The SPCU materials were prepared by the Korea Advanced Institute of Science and Technology (KAIST), Seoul, Korea, in cooperation with the International Fertilizer Development Center (IFDC). Average urea release (\\u000a$$\\\\overline {UR} $$\\u000a)

NK Savant; AF James; GH McClellan



Urea reduction ratio that considers effects of ultrafiltration and intradialytic urea generation  

Microsoft Academic Search

We modified the urea reduction ratio (URR) equation to correct the effects of ultrafiltration and intradialytic urea generation on the delivered dose of hemodialysis: muRR = 1?R1+2?UFBW+0.01?t×100% where mURR is modified URR, R is postdialysis plasma urea nitrogen (PUN) to predialysis PUN ratio, UF is ultrafiltrate volume in liters, BW is postdialysis body weight in kilograms, and t is dialysis

Yuk Lun Cheng; Koon Shing Choi; Ka Foon Chau; Chun Sang Li; Cheen Unn Yung; Alex W Yu; Kwan Keung Wong



Differentiation of uric acid versus non-uric acid kidney stones in the presence of iodine using dual-energy CT  

NASA Astrophysics Data System (ADS)

In this study, the feasibility of differentiating uric acid from non-uric acid kidney stones in the presence of iodinated contrast material was evaluated using dual-energy CT (DECT). Iodine subtraction was accomplished with a commercial three material decomposition algorithm to create a virtual non-contrast (VNC) image set. VNC images were then used to segment stone regions from tissue background. The DE ratio of each stone was calculated using the CT images acquired at two different energies with DECT using the stone map generated from the VNC images. The performance of DE ratio-based stone differentiation was evaluated at five different iodine concentrations (21, 42, 63, 84 and 105 mg/ml). The DE ratio of stones in iodine solution was found larger than those obtained in non-iodine cases. This is mainly caused by the partial volume effect around the boundary between the stone and iodine solution. The overestimation of the DE ratio leads to substantial overlap between different stone types. To address the partial volume effect, an expectation-maximization (EM) approach was implemented to estimate the contribution of iodine and stone within each image pixel in their mixture area. The DE ratio of each stone was corrected to maximally remove the influence of iodine solutions. The separation of uric-acid and non-uric-acid stone was improved in the presence of iodine solution.

Wang, J.; Qu, M.; Leng, S.; McCollough, C. H.



Neurological implications of urea cycle disorders  

Microsoft Academic Search

Summary  The urea cycle disorders constitute a group of rare congenital disorders caused by a deficiency of the enzymes or transport\\u000a proteins required to remove ammonia from the body. Via a series of biochemical steps, nitrogen, the waste product of protein\\u000a metabolism, is removed from the blood and converted into urea. A consequence of these disorders is hyperammonaemia, resulting\\u000a in central

A. L. Gropman; M. Summar; J. V. Leonard



Detection of Interstellar Urea with Carma  

Microsoft Academic Search

Urea, a molecule discovered in human urine by H. M. Rouelle in 1773, has a significant role in prebiotic chemistry. Previous BIMA observations have suggested that interstellar urea [(NH_2)_2CO] is a compact hot core molecule such as other large molecules, e.g. methyl formate and acetic acid (2009, 64th OSU Symposium On Molecular Spectroscopy, WI05). We have conducted an extensive search

H.-L. Kuo; L. E. Snyder; D. N. Friedel; L. W. Looney; B. J. McCall; A. J. Remijan; F. J. Lovas; J. M. Hollis



Reversible denaturation of cyclosporin synthetase by urea  

Microsoft Academic Search

The reversible denaturation of the multifunctional polypeptide, cyclosporin synthetase, by urea was analyzed. It is possible to discriminate between at least two stages of enzyme denaturation. While at low urea concentration (up to 0.8 M) cyclosporin A formation is inhibited, synthesis of the diketopiperazine cyclo-(d-alanyl-N-methylleucyl), a molecule representing a partial sequence of cyclosporin A is still detectable. At higher concentrations

Joachim Dittmann; François Vaillant; Horst Kleinkauf; Alfons Lawen



Ammonia and Urea Permeability of Mammalian Aquaporins  

Microsoft Academic Search

The humanaquaporins,AQP3,AQP7, AQP8,AQP9, and possibly AQP10, are permeable to ammonia, and AQP7, AQP9, and possibly AQP3,\\u000a are permeable to urea. In humans, these aquaporins supplement the ammonia transport of the Rhesus (Rh) proteins and the urea\\u000a transporters (UTs). The mechanism by which ammonium is transported by aquaporins is not fully resolved. A comparison of transport\\u000a equations, models, and experimental data

Thomas Litman; Rikke Søgaard; Thomas Zeuthen


Influence of urea on polyvinyl alcohol molecular superstructure formation  

NASA Astrophysics Data System (ADS)

Whiskers up to 1 cm in length were grown in polyvinyl alcohol (PVA) and urea solution. Raman and IR spectra discover an interaction between PVA and urea molecules. Optical and electronic microscopy data show that urea influences on PVA molecular superstructure formation. PVA whiskers prepared in urea solution can be used for organic semiconductors production which properties are determined by arrangement of polymer macromolecules.

Prosanov, I. Yu.; Matvienko, A. A.; Bokhonov, B. B.



The Effects of Fructose Intake on Serum Uric Acid Vary among Controlled Dietary Trials1234  

PubMed Central

Hyperuricemia is linked to gout and features of metabolic syndrome. There is concern that dietary fructose may increase uric acid concentrations. To assess the effects of fructose on serum uric acid concentrations in people with and without diabetes, we conducted a systematic review and meta-analysis of controlled feeding trials. We searched MEDLINE, EMBASE, and the Cochrane Library for relevant trials (through August 19, 2011). Analyses included all controlled feeding trials ?7 d investigating the effect of fructose feeding on uric acid under isocaloric conditions, where fructose was isocalorically exchanged with other carbohydrate, or hypercaloric conditions, and where a control diet was supplemented with excess energy from fructose. Data were aggregated by the generic inverse variance method using random effects models and expressed as mean difference (MD) with 95% CI. Heterogeneity was assessed by the Q statistic and quantified by I2. A total of 21 trials in 425 participants met the eligibility criteria. Isocaloric exchange of fructose for other carbohydrate did not affect serum uric acid in diabetic and nondiabetic participants [MD = 0.56 ?mol/L (95% CI: ?6.62, 7.74)], with no evidence of inter-study heterogeneity. Hypercaloric supplementation of control diets with fructose (+35% excess energy) at extreme doses (213–219 g/d) significantly increased serum uric acid compared with the control diets alone in nondiabetic participants [MD = 31.0 mmol/L (95% CI: 15.4, 46.5)] with no evidence of heterogeneity. Confounding from excess energy cannot be ruled out in the hypercaloric trials. These analyses do not support a uric acid-increasing effect of isocaloric fructose intake in nondiabetic and diabetic participants. Hypercaloric fructose intake may, however, increase uric acid concentrations. The effect of the interaction of energy and fructose remains unclear. Larger, well-designed trials of fructose feeding at “real world” doses are needed.

Wang, D. David; Sievenpiper, John L.; de Souza, Russell J.; Chiavaroli, Laura; Ha, Vanessa; Cozma, Adrian I.; Mirrahimi, Arash; Yu, Matthew E.; Carleton, Amanda J.; Di Buono, Marco; Jenkins, Alexandra L.; Leiter, Lawrence A.; Wolever, Thomas M. S.; Beyene, Joseph; Kendall, Cyril W. C.; Jenkins, David J. A.



[The features of uric acid metabolism in women in climacterium].  


The purpose of the study was to establish the prevalence of uric acid (UA) metabolism disturbances as a possible risk factor of urate nephropathy in women of various age groups. The authors carried out a retrospective analysis of 757 case histories and performed uricemia and uricosuria screening in women aged 18 to 69 years. The study revealed significant age-dependent elevation of uricemia, with hyperuricemia (HUE) at the age of 60 to 69 years old. The study also found age-dependent increase of HUE rate with its significant elevation in postmenopausal women (older than 50 years), compared with HUE rate in reproductive age women (18 to 49 years old) -37.9% vs. 11.4%. For the first time the researchers established UA excretion level and found a significant tendency of uricosuria to decrease with age (p < 0.016 between the groups of 40 to 49 and 50 to 59 years old). The highest rate of hyperuricosuria was revealed in women of 40 to 49 years old (22.2%), while in women of 18 to 29 and 60 to 69 years old it was 10.1% to 12.1%. For the first time the authors established the rate of hypouricosuria in women, which culminated in women older than 50 (22% of cases). The increase of HUE rate, which is most prominent in postmenopausal women, is associated with the decrease in UA excretion, accompanied by the decrease of hyperuricosuria rate and increase of hypouricosuria rate. Taking into account high prevalence of UA metabolism disturbances in women older than 50, menopause may be considered a risk factor of HUE and urate nephropathy. PMID:15984582

Solov'eva, O A; Balkarov, I M; Smetnik, V P; Eliseeva, N A; Lebedeva, M V; Shovskaia, T N; Aleksandrovskaia, T N



Marking Renal Injury: Can We Move Beyond Serum Creatinine?  

PubMed Central

Acute kidney injury (AKI) is a prevalent and devastating condition associated with significant morbidity and mortality. Despite marked improvements in clinical care, the outcomes for subjects with AKI have shown limited improvement in the past 50 years. A major factor inhibiting clinical progress in this field has been inability to accurately predict and diagnose early kidney dysfunction. The current gold-standard clinical and biochemical criteria for diagnosis of AKI, Risk Injury Failure Loss End-stage renal disease (RIFLE), and its modification, Acute Kidney Injury Network (AKIN) criteria, rely on urine output and serum creatinine (SCr) which are insensitive, non-specific, and late markers of disease. The recent development of a variety of analytical mass spectrometry (MS) based platforms have enabled separation, characterization, detection, and quantification of proteins (proteomics) and metabolites (metabolomics). These high-throughput platforms have raised hopes of identifying novel protein and metabolite markers, and recent efforts have led to several promising novel markers of AKI. However, substantial challenges remain including need to systematically evaluate incremental performance of these markers over and beyond current clinical and biochemical criteria for AKI. Here, we discuss the basic issues surrounding AKI biomarker development, highlight the most promising markers currently under development, and discuss the barriers towards wide-spread clinical implementation of these markers.

Slocum, Jessica L.; Heung, Michael; Pennathur, Subramaniam



Uric Acid Stimulates Fructokinase and Accelerates Fructose Metabolism in the Development of Fatty Liver  

PubMed Central

Excessive dietary fructose intake may have an important role in the current epidemics of fatty liver, obesity and diabetes as its intake parallels the development of these syndromes and because it can induce features of metabolic syndrome. The effects of fructose to induce fatty liver, hypertriglyceridemia and insulin resistance, however, vary dramatically among individuals. The first step in fructose metabolism is mediated by fructokinase (KHK), which phosphorylates fructose to fructose-1-phosphate; intracellular uric acid is also generated as a consequence of the transient ATP depletion that occurs during this reaction. Here we show in human hepatocytes that uric acid up-regulates KHK expression thus leading to the amplification of the lipogenic effects of fructose. Inhibition of uric acid production markedly blocked fructose-induced triglyceride accumulation in hepatocytes in vitro and in vivo. The mechanism whereby uric acid stimulates KHK expression involves the activation of the transcription factor ChREBP, which, in turn, results in the transcriptional activation of KHK by binding to a specific sequence within its promoter. Since subjects sensitive to fructose often develop phenotypes associated with hyperuricemia, uric acid may be an underlying factor in sensitizing hepatocytes to fructose metabolism during the development of fatty liver.

Lanaspa, Miguel A.; Sanchez-Lozada, Laura G.; Cicerchi, Christina; Li, Nanxing; Roncal-Jimenez, Carlos A.; Ishimoto, Takuji; Le, Myphuong; Garcia, Gabriela E.; Thomas, Jeffrey B.; Rivard, Christopher J.; Andres-Hernando, Ana; Hunter, Brandi; Schreiner, George; Rodriguez-Iturbe, Bernardo; Sautin, Yuri Y.; Johnson, Richard J.



The GLUT9 Gene Is Associated with Serum Uric Acid Levels in Sardinia and Chianti Cohorts  

PubMed Central

High serum uric acid levels elevate pro-inflammatory–state gout crystal arthropathy and place individuals at high risk for cardiovascular morbidity and mortality. Genome-wide scans in the genetically isolated Sardinian population identified variants associated with serum uric acid levels as a quantitative trait. They mapped within GLUT9, a Chromosome 4 glucose transporter gene predominantly expressed in liver and kidney. SNP rs6855911 showed the strongest association (p = 1.84 × 10?16), along with eight others (p = 7.75 × 10?16 to 6.05 × 10?11). Individuals homozygous for the rare allele of rs6855911 (minor allele frequency = 0.26) had 0.6 mg/dl less uric acid than those homozygous for the common allele; the results were replicated in an unrelated cohort from Tuscany. Our results suggest that polymorphisms in GLUT9 could affect glucose metabolism and uric acid synthesis and/or renal reabsorption, influencing serum uric acid levels over a wide range of values.

Maschio, Andrea; Busonero, Fabio; Usala, Gianluca; Mulas, Antonella; Lai, Sandra; Dei, Mariano; Orru, Marco; Albai, Giuseppe; Bandinelli, Stefania; Schlessinger, David; Lakatta, Edward; Scuteri, Angelo; Najjar, Samer S; Guralnik, Jack; Naitza, Silvia; Crisponi, Laura; Cao, Antonio; Abecasis, Goncalo; Ferrucci, Luigi; Uda, Manuela; Chen, Wei-Min; Nagaraja, Ramaiah



Gut bacteria recycle uric acid nitrogen in termites: A strategy for nutrient conservation  

PubMed Central

Reticulitermes flavipes termites synthesize uric acid via purine-nucleoside phosphorylase (purine-nucleoside: orthophosphate ribosyltransferase, EC and xanthine dehydrogenase (xanthine:NAD+ oxidoreductase, EC, but their tissues lack uricase (urate:oxygen oxidoreductase, EC or any other enzyme that degrades uric acid. Nevertheless, uricolysis occurs in termites, but as an anaerobic process mediated by hindgut bacteria. 14C-Tracer experiments showed that termites transport uric acid from the site of synthesis and storage (fat body tissue) to the site of degradation (hindgut microbiota) via Malpighian tubules. Moveover, [1,3-15N]uric acid dissimilated by gut bacteria in vivo leads to assimilation of 15N into termite tissues. NH3, a product of uricolysis, is a potential N source for termites, either directly via glutamine synthetase [L-glutamate:ammonia ligase (ADP-forming), EC] activity of fat body tissue or indirectly through microbe assimilation. Symbiotic recycling of uric acid N appears to be important to N conservation in these oligonitrotrophic insects.

Potrikus, Catherine J.; Breznak, John A.



Uric Acid Induces Renal Inflammation via Activating Tubular NF-?B Signaling Pathway  

PubMed Central

Inflammation is a pathologic feature of hyperuricemia in clinical settings. However, the underlying mechanism remains unknown. Here, infiltration of T cells and macrophages were significantly increased in hyperuricemia mice kidneys. This infiltration of inflammatory cells was accompanied by an up-regulation of TNF-?, MCP-1 and RANTES expression. Further, infiltration was largely located in tubular interstitial spaces, suggesting a role for tubular cells in hyperuricemia-induced inflammation. In cultured tubular epithelial cells (NRK-52E), uric acid, probably transported via urate transporter, induced TNF-?, MCP-1 and RANTES mRNA as well as RANTES protein expression. Culture media of NRK-52E cells incubated with uric acid showed a chemo-attractive ability to recruit macrophage. Moreover uric acid activated NF-?B signaling. The uric acid-induced up-regulation of RANTES was blocked by SN 50, a specific NF-?B inhibitor. Activation of NF-?B signaling was also observed in tubule of hyperuricemia mice. These results suggest that uric acid induces renal inflammation via activation of NF-?B signaling.

Zhou, Yang; Fang, Li; Jiang, Lei; Wen, Ping; Cao, Hongdi; He, Weichun; Dai, Chunsun; Yang, Junwei



Soluble neuroprotective antioxidant uric acid analogs ameliorate ischemic brain injury in mice.  


Uric acid is a major antioxidant in the blood of humans that can protect cultured neurons against oxidative and metabolic insults. However, uric acid has a very low solubility which compromises its potential clinical use for neurodegenerative disorders. Here we describe the synthesis, characterization and preclinical development of neuroprotective methyl- and sulfur-containing analogs of uric acid with increased solubility. In vitro and cell culture screening identified 1,7-dimethyluric acid (mUA2) and 6,8-dithiouric acid (sUA2) as two analogs with high antioxidant and neuroprotective activities. When administered intravenously in mice, uric acid analogs mUA2 and sUA2 lessened damage to the brain and improved functional outcome in an ischemia-reperfusion mouse model of stroke. Analogs sUA2 and mUA2 were also effective in reducing damage to the cerebral cortex when administered up to 4 h after stroke onset in a permanent middle cerebral artery occlusion mouse model. These findings suggest a therapeutic potential for soluble analogs of uric acid in the treatment of stroke and related neurodegenerative conditions. PMID:17999205

Haberman, Frank; Tang, Sung-Chun; Arumugam, Thiruma V; Hyun, Dong-Hoon; Yu, Qian-Sheng; Cutler, Roy G; Guo, Zhihong; Holloway, Harold W; Greig, Nigel H; Mattson, Mark P



Etiopathogenesis of uric acid and ammonium urate uroliths in non-Dalmatian dogs.  


The etiopathogenesis of uric acid, sodium acid urate, and ammonium acid urate uroliths in non-Dalmatian dogs appears to be a complex phenomenon. It may involve one or more pathologic and/or physiologic processes acting independently or in concert to increase urinary concentration of lithogenic substances that result in initiation, growth, and retention of urate uroliths. Increased urine uric acid concentration and/or urinary excretion of uric acid appear to be primary predisposing factors in urate lithogenesis. Specific disorders resulting in hyperuricuria may involve abnormalities of increased synthesis, diminished biodegradation, and/or enhance excretion of uric acid. In addition, ammonium ion, hydrogen ion, and other organic and inorganic urine constituents appear to have major influences on urate urolith formation. Unfortunately, many specific disorders of uric acid metabolism and other factors promoting or inhibiting urate urolith formation remain poorly characterized in the majority of non-Dalmatian dogs with urate urolithiasis. Growing awareness of the significance of urate uroliths in non-Dalmatian dogs should encourage further investigation into the identification, characterization, and quantitation of parameters influencing urate lithogenesis. Results of such studies are required for development of practical and effective strategies for treatment and prevention of canine urate urolithiasis. PMID:3518203

Kruger, J M; Osborne, C A



Effects of Urea on M 4Lactate Dehydrogenase from Elasmobranchs and Urea-Accumulating Australian Desert Frogs  

Microsoft Academic Search

We measured the effect of urea on M4-lactate dehydrogenase (M4-LDH) from elasmobranchs and Australian desert frogs (urea accumulators) and from two animals that do not accumulate urea, the axolotl and the rabbit. An analysis of the effect of urea on the Kd(NADH), V, V\\/Km(pyr) and V\\/Km(NADH) shows that in all cases the major effect of urea was on the binding

Caroline J Fuery; Paul V Attwood; Philip C Withers; Paul H Yancey; John Baldwin; Michael Guppy



Winter Wheat and Maize Response to Urea Ammonium Nitrate and a New Urea Formaldehyde Polymer Fertilizer  

Technology Transfer Automated Retrieval System (TEKTRAN)

Slow release nitrogen (N) fertilizers have potential to improve yield and nitrogen use efficiency (NUE) in winter wheat (Triticum aestivum L.) and maize (Zea mays L.). A slow release urea formaldehyde polymer (UFP) was compared with conventional aqueous urea-ammonium nitrate (UAN) [(NH2)2CO, NH4NO3]...


Factors affecting N release of urea from reactive layer coated urea  

Microsoft Academic Search

An experimental fertilizer called reactive layer coated urea (RLCU) has been developed by coating urea with a mixture of diisocyanate and polyol in the presence of a catalyst. The hard, durable layer that is formed on the granule conveys slow-release character to the product. A series of soil incubation tests were conducted under simulated upland conditions for periods up to

C. B. Christianson



Transfer of Pasteurella ureae Jones 1962 to the Genus Actinobacillus Brumpt 1910: Actinobacillus ureae comb. nov  

Microsoft Academic Search

By using the renaturation method for deoxyribonucleic acid (DNA)-DNA hybridization (2), we have found that the species Pasteurella ureae consists of strains that are inter- related at DNA binding levels of more than 90% and that this species is confined to human hosts (9). The species most closely related to P. ureae (as revealed by DNA binding, using the same



Relation between serum creatinine and body mass index in elite athletes of different sport disciplines  

Microsoft Academic Search

Objectives: To document the relation between serum creatinine concentration and body mass index in elite athletes from five different sports, and to study potential differences among athletes performing different sports with different features and requirements.Methods: Before the start of the competitive season, serum creatinine was measured in 151 elite athletes from five different sports: rugby (n = 44), soccer (n

G Banfi; M Del Fabbro



Variability of Creatinine Measurements in Clinical Laboratories: Results from the CRIC Study  

Microsoft Academic Search

Objectives: Estimating equations using serum creatinine (SCr) are often used to assess glomerular filtration rate (GFR). Such creatinine (Cr)-based formulae may produce biased estimates of GFR when using Cr measurements that have not been calibrated to reference laboratories. In this paper, we sought to examine the degree of this variation in Cr assays in several laboratories associated with academic medical

Marshall Joffe; Chi-yuan Hsu; Harold I. Feldman; Matthew Weir; J. R. Landis; L. Lee Hamm



Treatment of Severe Hypothyroidism Reduced Serum Creatinine Levels in Two Chronic Renal Failure Patients  

Microsoft Academic Search

Short-term hypothyroidism has been associated with a reversible rise in serum creatinine levels in patients with normal renal function. A remarkable decline in serum creatinine levels associated with a treatment of severe and prolonged hypothyroidism has rarely been reported so far. We present here 2 patients with chronic renal failure in whom treatment for hypothyroidism resulted in a significant and

Hajime Nakahama; Katsuhiko Sakaguchi; Yoshio Horita; Osamu Sasaki; Satoko Nakamura; Takashi Inenaga; Shuichi Takishita




Microsoft Academic Search

.Objectives: To identify the most advantageous formula for estimating creatinine clearance (CCr) and to establish a dose of dialysis that will ensure minimal acceptable levels of creatinine clearance in patients on continuous peritoneal dialysis (CPD). .Design: Analysis of all CCr studies performed in CPD patients over 40 months. .Setting: All four dialysis units following CPD patients in one city. One

Antonios H. Tzamaloukas; Glen H. Murata; Deepak Malhotra; Lucy FOX; Richard S. Goldman; Pratap S. Avasthi



Is uric acid an indicator of metabolic syndrome in the first-degree relatives of patients with type 2 diabetes?  

PubMed Central

Background: To determine whether uric acid levels are associated with the components of metabolic syndrome and whether uric acid is a significant factor for development of metabolic syndrome in the first-degree relatives of type 2 diabetic patients as high risk group. Materials and Methods: A total of 694 (182 male and 512 female, aged 30-69 years) first-degree relatives of type 2 diabetic patients during 2007-2011 were enrolled. The height, weight, waist circumference, blood pressure, fasting plasma glucose, lipid profile and uric acid concentrations were measured. Metabolic syndrome was defined by NCEP-ATP III. Results: Uric acid was associated with waist circumference, blood pressure, triglyceride and HDL-cholesterol level in both sexes (r = 0.1-0.3, P < 0.05). The prevalence of metabolic syndrome in the fourth quartile of uric acid (64.4% of male and 60.2% of female population) was significantly more than those in the first (25.5% of male and 31.2% of female population) and second quartiles (33.3% of male and 32.0% of female population). The mean of uric acid in people with metabolic syndrome was significantly higher than in those without (6.6 ± 1.2 mg/dL vs. 5.8 ± 1.2 mg/dL; P = 0.0001). The age-adjusted odds ratios (95% confidence interval) of uric acid for metabolic syndrome in univariate analysis were [1.60 (1.23-2.07); P = 0.008] for men and [1.61 (1.34-1.92); P = 0.0001] for women but the effect of uric acid in multivariate logistic regression was not significant. Conclusions: Uric acid is associated with majority of the metabolic syndrome components. People with metabolic syndrome have higher uric acid levels. However, uric acid probably is not an independent factor to predict the metabolic syndrome.

Salehidoost, Rezvan; Aminorroaya, Ashraf; Zare, Maryam; Amini, Massoud



Association of plasma uric acid with ischaemic heart disease and blood pressure: mendelian randomisation analysis of two large cohorts  

PubMed Central

Objectives To assess the associations between both uric acid levels and hyperuricaemia, with ischaemic heart disease and blood pressure, and to explore the potentially confounding role of body mass index. Design Mendelian randomisation analysis, using variation at specific genes (SLC2A9 (rs7442295) as an instrument for uric acid; and FTO (rs9939609), MC4R (rs17782313), and TMEM18 (rs6548238) for body mass index). Setting Two large, prospective cohort studies in Denmark. Participants We measured levels of uric acid and related covariables in 58?072 participants from the Copenhagen General Population Study and 10?602 from the Copenhagen City Heart Study, comprising 4890 and 2282 cases of ischaemic heart disease, respectively. Main outcome Blood pressure and prospectively assessed ischaemic heart disease. Results Estimates confirmed known observational associations between plasma uric acid and hyperuricaemia with risk of ischaemic heart disease and diastolic and systolic blood pressure. However, when using genotypic instruments for uric acid and hyperuricaemia, we saw no evidence for causal associations between uric acid, ischaemic heart disease, and blood pressure. We used genetic instruments to investigate body mass index as a potentially confounding factor in observational associations, and saw a causal effect on uric acid levels. Every four unit increase of body mass index saw a rise in uric acid of 0.03 mmol/L (95% confidence interval 0.02 to 0.04), and an increase in risk of hyperuricaemia of 7.5% (3.9% to 11.1%). Conclusion By contrast with observational findings, there is no strong evidence for causal associations between uric acid and ischaemic heart disease or blood pressure. However, evidence supports a causal effect between body mass index and uric acid level and hyperuricaemia. This finding strongly suggests body mass index as a confounder in observational associations, and suggests a role for elevated body mass index or obesity in the development of uric acid related conditions.



Adjusting for Urinary Creatinine Overestimates Arsenic Concentrations in Diabetics  

PubMed Central

Background/Aims Arsenic (As) is linked to insulin resistance in animal studies, but the effect of low-level As exposure on the prevalence of diabetes in humans is uncertain. An optimal method to report inorganic As in humans has not been established. Measurements of As in spot urine are usually adjusted to creatinine (Cr). However, urinary Cr is an independent variable in diabetes. Our aims are to optimize reporting of urinary As in the setting of diabetes and insulin resistance. Methods Urinary inorganic As was measured in 24-hour or first-void spot urine from diabetic (n = 31) and non-diabetic (n = 12) subjects and normalized to Cr or specific gravity (SG). The relation of normalized urinary inorganic As to glycemia and surrogate measures of insulin resistance was investigated. Blood pressure, waist circumference, and glycated hemoglobin were also assessed. Homeostasis model assessment was used to determine insulin resistance. Results A strong correlation was found between spot urinary As adjusted to Cr (R2 = 0.82) or SG (R2 = 0.61) to 24-hour urinary As (p < 0.001), while non-adjusted urinary As did not correlate well (R2 = 0.03, p = 0.46). Adjusting for Cr revealed significant differences in total 24-hour urinary As when comparing diabetic to normal subjects. In contrast, no differences were found when As was adjusted to SG using either 24-hour or spot urine. Moreover, adjusted urinary spot or 24-hour As measures did not correlate with measures of glycemia or insulin resistance. Conclusions: Urinary Cr is an independent variable in diabetes, therefore adjusting spot As for SG is preferred.

Yassine, Hussein; Kimzey, Michael J.; Galligan, Michael A.; Gandolfi, A. Jay; Stump, Craig S.; Lau, Serrine S.



Caught red-handed: uric acid is an agent of inflammation  

PubMed Central

Inflammation occurs in response to both pathogenic insult and tissue damage under sterile conditions, with the latter contributing to the pathogenesis of many diseases. Although several endogenous substances, including uric acid, have been suggested to alert the body to danger and to stimulate inflammation, little is known about their contribution to such responses in vivo. In this issue of the JCI, Kono et al. use newly generated mice with reduced levels of uric acid to investigate its role as an endogenous signal of tissue damage in inflammatory responses to hepatic injury. They find that uric acid is released from dying tissues and induces inflammation to cell death but is not involved in the response to microbial molecules or sterile irritant particles. I believe this to be the first report of an endogenous danger signal acting as a physiological regulator of inflammation.

Shi, Yan



Stable isotope ratios and uric acid preservation in termites belonging to three feeding habits in Thailand.  


Nitrogen and carbon stable isotope ratios and uric acid concentrations in termites sampled from a dry evergreen forest in Thailand, were determined across three kinds of feeding habits. Feeding habits of Microcerotermes crassus, which is an abundant wood-feeder, and Dicuspiditermes makhamensis, a common soil-feeding termite, were confirmed by isotopic signatures. Lichen feeding termites (Hospitalitermes birmanicus, H. bicolor and H. ataramensis) were characterized by low delta15N values, suggesting that they assimilated nitrogen deposited from the atmosphere. There was also a significant difference in uric acid concentrations between termites representing different feeding habits. No significant relationships were found between uric acid concentrations and delta15N or delta13C in Hospitalitermes. However, delta15N values were correlated with C/N ratios in H. birmanicus, except in one colony of H. ataramensis. delta13C values in both species were negatively correlated with C/N ratios. PMID:11501704

Tayasu, I; Hyodo, F; Takematsu, Y; Sugimoto, A; Inoue, T; Kirtibutr, N; Abe, T



Evolutionary aspects of urea utilization by fungi  

PubMed Central

The higher fungi exhibit a dichotomy with regard to urea utilization. The hemiascomycetes use urea amidolyase (DUR1,2) whereas all other higher fungi use the nickel-containing urease. Urea amidolyase is an energy dependent biotin-containing enzyme. It likely arose prior to the Euascomycete/Hemiascomycete divergence ca. 350 million years ago by insertion of an unknown gene into one copy of a duplicated methylcrotonyl CoA carboxylase (MccA). The dichotomy between urease and urea amidolyase coincides precisely with that for the Ni/Co transporter (Nic1p) which is present in the higher fungi that use urease and absent in those that do not. We suggest that the selective advantage for urea amidolyase is that it allowed the hemiascomycetes to jettison all Ni2+ and Co2+ dependent metabolism and thus to have two fewer transition metals whose concentrations need to be regulated. Also, the absence of MccA in the hemiascomycetes coincides with and may explain their production of fusel alcohols.

Navarathna, Dhammika H.M.L.P.; Harris, Steven D.; Roberts, David D.; Nickerson, Kenneth W.



Regulation of Renal Urea Transport by Vasopressin  

PubMed Central

Terrestrial life would be miserable without the ability to concentrate urine. Production of concentrated urine requires complex interactions among the nephron segments and vasculature in the kidney medulla. In addition to water channels (aquaporins) and sodium transporters, urea transporters are critically important to the theories proposed to explain the physiologic processes occurring when urine is concentrated. Vasopressin (anti-diuretic hormone) is the key hormone regulating the production of concentrated urine. Vasopressin rapidly increases water and urea transport in the terminal inner medullary collecting duct (IMCD). Vasopressin rapidly increases urea permeability in the IMCD through increases in phosphorylation and apical plasma-membrane accumulation of the urea transporter A1 (UT-A1). Vasopressin acts through two cAMP-dependent signaling pathways in the IMCD: protein kinase A and exchange protein activated by cAMP Epac. Protein kinase A phosphorylates UT-A1 at serines 486 and 499. In summary, vasopressin regulates urea transport acutely by increasing UT-A1 phosphorylation and the apical plasma-membrane accumulation of UT-A1 through two cAMP-dependent pathways.

Sands, Jeff M.; Blount, Mitsi A.; Klein, Janet D.



A role for the organic anion transporter OAT3 in renal creatinine secretion in mice  

PubMed Central

Tubular secretion of the organic cation, creatinine, limits its value as a marker of glomerular filtration rate (GFR) but the molecular determinants of this pathway are unclear. The organic anion transporters, OAT1 and OAT3, are expressed on the basolateral membrane of the proximal tubule and transport organic anions but also neutral compounds and cations. Here, we demonstrate specific uptake of creatinine into mouse mOat1- and mOat3-microinjected Xenopus laevis oocytes at a concentration of 10 ?M (i.e., similar to physiological plasma levels), which was inhibited by both probenecid and cimetidine, prototypical competitive inhibitors of organic anion and cation transporters, respectively. Renal creatinine clearance was consistently greater than inulin clearance (as a measure of GFR) in wild-type (WT) mice but not in mice lacking OAT1 (Oat1?/?) and OAT3 (Oat3?/?). WT mice presented renal creatinine net secretion (0.23 ± 0.03 ?g/min) which represented 45 ± 6% of total renal creatinine excretion. Mean values for renal creatinine net secretion and renal creatinine secretion fraction were not different from zero in Oat1?/? (?0.03 ± 0.10 ?g/min; ?3 ± 18%) and Oat3?/? (0.01 ± 0.06 ?g/min; ?6 ± 19%), with greater variability in Oat1?/?. Expression of OAT3 protein in the renal membranes of Oat1?/? mice was reduced to ?6% of WT levels, and that of OAT1 in Oat3?/? mice to ?60%, possibly as a consequence of the genes for Oat1 and Oat3 having adjacent chromosomal locations. Plasma creatinine concentrations of Oat3?/? were elevated in clearance studies under anesthesia but not following brief isoflurane anesthesia, indicating that the former condition enhanced the quantitative contribution of OAT3 for renal creatinine secretion. The results are consistent with a contribution of OAT3 and possibly OAT1 to renal creatinine secretion in mice.

Eraly, Satish A.; Rao, Satish Ramachandra; Gerasimova, Maria; Rose, Michael; Nagle, Megha; Anzai, Naohiko; Smith, Travis; Sharma, Kumar; Nigam, Sanjay K.; Rieg, Timo



Uric Acid Levels and All-Cause and Cardiovascular Mortality in the Hemodialysis Population  

PubMed Central

Summary Background and objectives Hyperuricemia is associated with hypertension, coronary artery disease, and chronic kidney disease. However, there are no specific data on the relationship of uric acid to cardiovascular disease in the chronic hemodialysis setting. Design, setting, participants, & measurements Data from 5827 patients on chronic hemodialysis from six countries affiliated with the Dialysis Outcomes and Practice Patterns Study (DOPPS) were analyzed. All laboratory data were based upon the initial cross-section of patients in DOPPS I and II. Cox regression was used to calculate the hazard ratio (HR) of all-cause and cardiovascular (CV) mortality with adjustments for case-mix including 14 classes of comorbidity. Results There were no clinically significant differences in baseline characteristics between those who had measured uric acid (n = 4637) and those who did not (n = 1190). Uric acid level was associated with lower all-cause mortality (HR: 0.95, 95% confidence interval [CI]: 0.90 to 1.00 per 1 mg/dl higher uric acid level) and CV mortality (HR: 0.92, 95% CI: 0.86 to 0.99). When analyzed as a dichotomous variable, the adjusted HR at uric acid ?8.2 mg/dl compared with >8.2 mg/dl was 1.24 (95% CI: 1.03 to 1.49) for all-cause mortality and 1.54 (95% CI: 1.15 to 2.07) for CV mortality. Conclusions Higher uric acid levels were associated with lower risk of all-cause and CV mortality in the hemodialysis population. These results are in contrast to the association of hyperuricemia with higher cardiovascular risk in the general population and should be the subject of further research.

Latif, Walead; Karaboyas, Angelo; Tong, Lin; Winchester, James F.; Arrington, Charlotte J.; Pisoni, Ronald L.; Marshall, Mark R.; Kleophas, Werner; Levin, Nathan W.; Sen, Ananda; Robinson, Bruce M.



Uric acid levels predict survival in men with amyotrophic lateral sclerosis.  


Elevated uric acid levels have recently been found to be associated with slower disease progression in Parkinson's disease, Huntington's disease, multiple system atrophy, and mild cognitive impairment. The aim of this study is to determine whether serum uric acid levels predict survival in amyotrophic lateral sclerosis (ALS). A total of 251 people with ALS enrolled in two multicenter clinical trials were included in our analysis. The main outcome measure was survival time, which was calculated as time to death, tracheostomy, or permanent assistive ventilation, with any event considered a survival endpoint. Cox proportional hazards models were used to estimate the hazard ratio (HR) of reaching a survival endpoint according to baseline uric acid levels after adjusting for markers of disease severity (FVC, total ALSFRS-R score, time since symptom onset, diagnostic delay, BMI, bulbar vs. spinal onset, age, and riluzole use). There was a dose-dependent survival advantage in men, but not women, with higher baseline uric acid levels (logrank test: p = 0.018 for men, p = 0.81 for women). There was a 39% reduction in risk of death during the study for men with each 1 mg/dl increase in uric acid levels (adjusted HR: 0.61, 95% CI 0.39-0.96, p = 0.03). This is the first study to demonstrate that serum uric acid is associated with prolonged survival in ALS, after adjusting for markers of disease severity. Similar to previous reports in Parkinson's disease, this association was seen in male subjects only. PMID:22323210

Paganoni, Sabrina; Zhang, May; Quiroz Zárate, Alejandro; Jaffa, Matthew; Yu, Hong; Cudkowicz, Merit E; Wills, Anne-Marie



Uric Acid as a Prognostic Factor for Survival Time: A Prospective Cohort Study of Terminally Ill Cancer Patients  

Microsoft Academic Search

The aim of this prospective cohort study was to determine whether serum uric acid level is useful as a predictor of survival in terminally ill cancer patients. One hundred eighteen terminally ill cancer patients, including 63 (53.4%) males, were categorized into four groups by serum uric acid levels and followed up until death or to the end of the study.

Hyun-Sik Shin; Hye-Ree Lee; Duk-Chul Lee; Jae-Yong Shim; Kyung-Hee Cho; Sang-Yeon Suh



Comparative semiempirical and ab initio study of the structural and chemical properties of uric acid and its anions  

Microsoft Academic Search

Semiempirical, density functional theory (DFT), and ab initio calculations have been performed to assess the relative stabilities of 15 possible tautomer forms of neutral uric acid, and of the different urate mono- and dianion forms. These methods have also been used to compute ionization potentials (IPs) for uric acid and its derived anions. Overall, we have found that semiempirical calculations,

Muhannad Altarsha; Gérald Monard; Bertrand Castro



Increased fluid intake and adequate dietary modification may be enough for the successful treatment of uric acid stone.  


Uric acid stones are the most readily dissolvable of all types of urinary stones. The present paper describes two patients with uric acid stones in kidney and ureter, whom we have treated successfully only by a combination of increased fluid intake and adequate dietary modification. PMID:23503881

Chae, Ji Yun; Kim, Jong Wook; Kim, Jin Wook; Yoon, Cheol Yong; Park, Hong Seok; Moon, Du Geon; Oh, Mi Mi



Association of three genetic loci with uric acid concentration and risk of gout: a genome-wide association study  

Microsoft Academic Search

Background: Hyperuricaemia, a highly heritable trait, is a key risk factor for gout. We aimed to identify novel genes associated with serum uric acid concentration and gout. Methods: Genome-wide association studies were done for serum uric acid in 7699 participants in the Framingham cohort and in 4148 participants in the Rotterdam cohort. Genome-wide significant single nucleotide polymorphisms (SNPs) were replicated

Abbas Dehghan; Anna Köttgen; Qiong Yang; Shih-Jen Hwang; WH Linda Kao; Fernando Rivadeneira; Eric Boerwinkle; Daniel Levy; Albert Hofman; Brad C Astor; Emelia J Benjamin; Cornelia M van Duijn; Jacqueline C Witteman; Josef Coresh; Caroline S Fox



Serum uric acid is associated with microalbuminuria and subclinical atherosclerosis in men with type 2 diabetes mellitus  

Microsoft Academic Search

Hyperuricemia has been reported to be associated with increased risk of renal insufficiency as well as cardiovascular events. The aim of this study was to evaluate the relationships between serum uric acid concentration and degree of urinary albumin excretion as well as markers of subclinical atherosclerosis in men with type 2 diabetes mellitus. Serum uric acid concentrations were measured in

Michiaki Fukui; Muhei Tanaka; Emi Shiraishi; Ichiko Harusato; Hiroko Hosoda; Mai Asano; Mayuko Kadono; Goji Hasegawa; Toshikazu Yoshikawa; Naoto Nakamura



Monodisperse, molecularly imprinted polymers for creatinine by modified precipitation polymerization and their applications to creatinine assays for human serum and urine.  


Molecularly imprinted polymers (MIPs) for creatinine were prepared by modified precipitation polymerization using methacrylic acid as a functional monomer and divinylbenzene as a crosslinker. The prepared MIPs were monodispersed with a narrow particle size distribution. Binding experiments and Scatchard analyses revealed that two classes of binding sites, high- and low-affinity sites, were formed on the MIPs. The retention and molecular-recognition properties of the MIPs were evaluated by hydrophilic interaction chromatography using a mixture of ammonium acetate buffer and acetonitrile as a mobile phase. With an increase of acetonitrile content, the retention factor of creatinine was increased on the MIP. In addition to shape recognition, hydrophilic interactions seemed to enhance the recognition of creatinine on the MIP. The MIPs' molecular-recognition ability was specific for creatinine; the structurally related compounds such as hydantoin, 1-methylhydantoin, 2-pyrrolidone, N-hydroxysuccinimide and creatine were not recognized. Furthermore, the creatinine concentrations in human serum and urine were successfully determined by direct injection of the deproteinized serum and diluted urine samples onto the MIP. PMID:23973759

Miura, Chitose; Funaya, Noriko; Matsunaga, Hisami; Haginaka, Jun



A perfusion study of the handling of urea and urea analogues by the gills of the dogfish shark (Squalus acanthias)  

PubMed Central

The branchial mechanism of urea retention in elasmobranchs was investigated using an in vitro isolated-perfused head preparation, as well as in vivo samples, in the spiny dogfish shark. Both in vivo and in control saline perfusions containing 350 mmol L?1 urea, calculated intracellular urea concentrations in gill epithelial cells were close to extracellular concentrations. Urea efflux to the external water fell only non-significantly, and calculated gill intracellular urea concentration did not change when perfusate urea concentration was reduced from 350 to 175 mmol?L?1 with osmotic compensation by 175 mmol L?1 mannitol. However, when the urea analogues thiourea or acetamide were present in the perfusate at concentrations equimolar (175 mmol L?1) to those of urea (175 mmol L?1), urea efflux rates were increased 4-fold and 6.5-fold respectively, and calculated gill intracellular urea concentrations were depressed by about 55%. Analogue efflux rates were similar to urea efflux rates. Previous studies have argued that either the basolateral or apical membranes provided the limiting permeability barrier, and/or that a back-transporter on the basolateral membranes of gill cells is responsible for urea retention. The present results provide new evidence that the apical membrane is the limiting factor in maintaining gill urea impermeability, and raise the prospect that a urea back-transporter, which can be competitively inhibited by thiourea and acetamide, operates at the apical membrane.

Liew, Hon Jung; De Boeck, Gudrun; Walsh, Patrick J.



Wood plastic composite at different urea concentrations  

NASA Astrophysics Data System (ADS)

Wood plastic composite (WPC) has been prepared with a low grade wood simul (Salmalia malabarica) of Bangladesh under Co-60 gamma irradiation using MMA as the bulk monomer combined with methanol as the swelling solvent at different urea concentrations. Effect of a second solute such as NVP, TPGDA and TMPTA in the impregnating solution is evaluated. NVP appears to be the best co-additive/second solute among all the additives used to yield the composite with the highest polymer loading (PL) and tensile strength (TS) at 0.5% urea concentration.

Husain, M. M.; Khan, Mubarak A.; Ali, K. M. Idriss; Hasan, A. J. M. Moynul



Colorimetric test-systems for creatinine detection based on composite molecularly imprinted polymer membranes.  


An easy-to-use colorimetric test-system for the efficient detection of creatinine in aqueous samples was developed. The test-system is based on composite molecularly imprinted polymer (MIP) membranes with artificial receptor sites capable of creatinine recognition. A thin MIP layer was created on the surface of microfiltration polyvinylidene fluoride (PVDF) membranes using method of photo-initiated grafting polymerization. The MIP layer was obtained by co-polymerization of a functional monomer (e.g. 2-acrylamido-2-methyl-1-propanesulfonic acid, itaconic acid or methacrylic acid) with N, N'-methylenebisacrylamide as a cross-linker. The choice of the functional monomer was based on the results of computational modeling. The creatinine-selective composite MIP membranes were used for measuring creatinine in aqueous samples. Creatinine molecules were selectively adsorbed by the MIP membranes and quantified using color reaction with picrates. The intensity of MIP membranes staining was proportional to creatinine concentration in an analyzed sample. The colorimetric test-system based on the composite MIP membranes was characterized with 0.25 mM detection limit and 0.25-2.5mM linear dynamic range. Storage stability of the MIP membranes was estimated as at least 1 year at room temperature. As compared to the traditional methods of creatinine detection the developed test-system is characterized by simplicity of operation, small size and low cost. PMID:23498699

Sergeyeva, T A; Gorbach, L A; Piletska, E V; Piletsky, S A; Brovko, O O; Honcharova, L A; Lutsyk, O D; Sergeeva, L M; Zinchenko, O A; El'skaya, A V



Association between Vitamin D Insufficiency and Elevated Serum Uric Acid among Middle-Aged and Elderly Chinese Han Women  

PubMed Central

Background Association between vitamin D insufficiency and hyperuricemia has not been reported so far. We aimed to study the association of vitamin D insufficiency with elevated serum uric acid among middle-aged and elderly Chinese Han women. Methods We collected data from participants residing in Jinchang district of Suzhou from January to May, 2010. Serum uric acid, 25-hydroxy vitamin D and other traditional biomarkers including fasting plasma glucose and blood lipids were determined in 1726 women aged above 30 years. Association between vitamin D insufficiency and elevated uric acid was analyzed in premenopausal and postmenopausal women, respectively. Results Among postmenopausal women, 25-hydroxy vitamin D level of participants with elevated uric acid was lower than that of those with normal uric acid (median [interquartile range]: 35[28–57] vs 40[32–58], µg/L; P?=?0.006). Elevated uric acid was more prevalent in participants with vitamin D insufficiency compared to those without vitamin D insufficiency (16.50% vs 8.08%; P<0.001). Association between vitamin D insufficiency and elevated uric acid was not significant among premenopausal women. However, participants with vitamin D insufficiency were more likely to have elevated uric acid compared with those without vitamin D insufficiency among postmenopausal women (OR, 95% CI: 2.38, 1.47–3.87). Moreover, after excluding individuals with diabetes and/or hypertension, the association of vitamin D insufficiency with elevated uric acid was still significant (OR, 95% CI: 2.48, 1.17–5.44). Conclusions Vitamin D insufficiency was significantly associated with elevated uric acid among postmenopausal Chinese Han women. This study suggested that a clinical trial should be conducted to confirm the association of vitamin D insufficiency with hyperuricemia.

Li, Chao; Chao, Xiangqin; Zhang, Qiu; Zhang, Yonghong



Tautomeric equilibrium of creatinine and creatininium cation in aqueous solutions explored by Raman spectroscopy and density functional theory calculations  

NASA Astrophysics Data System (ADS)

The Raman spectral studies of creatinine with pH dependence were performed to explore the effects of pH values on the Raman spectroscopy of creatinine. Firstly, we calculated vibrational spectra by DFT to derive the equilibrium geometries and protonated form of creatinine. Comparing simulated and observed Raman spectra of creatinine in aqueous solution at pH 2, it is found the theoretical predicted spectra agree well with those of the experiment while seven water molecules are aggregated around the creatinine. Additionally, the tautomeric equilibrium of creatinine in aqueous solutions was studied and two tautomers are found to coexist by comparing its experimental and calculated Raman spectra. A water dimer being used to solvate creatinine would make the thermodynamic energy favor convert from the imino tautomer to the amino tautomer. Besides, the molecular electrostatic potential (MEP) analysis of the creatinine further confirms their discrepancies of typical experimental Raman spectra at different pH values.

Gao, Jiao; Hu, Yongjun; Li, Shaoxin; Zhang, Yanjiao; Chen, Xue




Microsoft Academic Search

A mathematical model is proposed for the urea prilling process of a commercial plant. In this model the prilling process has been simulated by simultaneous solution of the continuity, hydrodynamic, mass and energy transfer equations. Particle trajectory, temperature and moisture distribution of the particles and of the cooling air along the height of the tower was calculated from the mathematical




Distribution of Urea in the Baltic Sea.  

National Technical Information Service (NTIS)

The vertical distribution of urea has been determined during a five-year period (from June 1976 to May 1981) at 21 different stations in the Baltic Sea on samples collected during 20 cruises. Results show pronounced seasonal variations with the highest co...

J. C. Valderrama



Urea-catalyzed construction of oxazinanes.  


Highly functionalized oxazinanes are efficiently prepared through urea-catalyzed formal [3 + 3] cycloaddition reactions of nitrones and nitrocyclopropane carboxylates. The reaction system is general with respect to both the nitrocyclopropane carboxylates and nitrones enabling the preparation of a large family of oxazinanes, typically in high yield. This method affords access to enantioenriched oxazinane products through chirality transfer from enantioenriched nitrocyclopropane carboxylates. PMID:23907178

Hardman, Andrea M; So, Sonia S; Mattson, Anita E



Foliar urea fertilization of cereals: A review  

Microsoft Academic Search

It has been suggested that there are several potential benefits of providing nitrogen to cereals via the foliage as urea solution. These include: reduced nitrogen losses through denitrification and leaching compared with nitrogen fertilizer applications to the soil; the ability to provide nitrogen when root activity is impaired e.g., in saline or dry conditions, and uptake late in the season

M. J. Gooding; W. P. Davies



Free Radical Scavenging, DNA Protection, and Inhibition of Lipid Peroxidation Mediated by Uric Acid  

Microsoft Academic Search

Uric acid (UA) has been proposed to be the dominant antioxidant in birds. The objective of this study was to investigate the quenching effect of varying concentrations of UA, including those found in avian plasma, on specific reactive oxygen species (ROS) and to determine the ability of UA to protect DNA and cellular membranes from ROS-mediated damage. Hydroxyl (•OH) and

Beth Stinefelt; Stephen S. Leonard; Kenneth P. Blemings; Xianglin Shi; Hillar Klandorf



Nitrogen-doped zinc oxide thin films biosensor for determination of uric acid.  


Nitrogen-doped zinc oxide thin films (ZnO:N) have been realized as a potential matrix for the development of a uric acid biosensor. The correlation between the change in property of the ZnO film with N doping concentration and its biosensing response has been studied. The nitrogen dopant in a ZnO film alters its defects profile, thus improving the charge transfer characteristics and resulting in an enhanced peak oxidation current in the cyclic voltammogram in comparison to that of the pure ZnO film. The studies reveal that the bio-electrode based on the nitrogen-doped ZnO thin film matrix exhibits better sensitivity (1.1 mA mM(-1) cm(-2)) with linearity over a wide range (0.05 mM to 1.0 mM) of uric acid concentration. A comparatively low value (0.10 mM) of the Michaelis-Menten constant (Km) indicates high affinity of the immobilized uricase towards uric acid. The proposed ZnO:N thin films matrix-based uric acid-biosensor has good reproducibility, a long shelf-life (20 weeks) and high selectivity. PMID:23730688

Jindal, Kajal; Tomar, Monika; Gupta, Vinay



A selective voltammetric method for uric acid detection at Nafion(R)-coated carbon paste electrodes.  


A square-wave voltammetric method together with Nafion(R)-coated carbon paste electrodes were used for the selective determination of uric acid in the presence of a high concentration of ascorbic acid. Since the oxidation potential of uric acid is about 200 mV more positive than that of ascorbic acid at the Nafion(R)-coated carbon paste electrode, the selectivity can be greatly improved simply by applying an electrolysis potential of +0.4 V vs. Ag/AgCl where only ascorbic acid is oxidised. The acceptable tolerance of ascorbic acid concentration for the determination of uric acid is as high as 1.5 mM. With 30 s of electrolysis time, a linear calibration curve is obtained over the 0-50 muM range in 0.05 M citrate buffer solution, pH 4.0, with slope (muA/muM) and correlation coefficient of 0.34 and 0.9984, respectively. The detection limit (3sigma) is 0.25 muM. The practical analytical utility is illustrated by selective measurements of uric acid in human urine without any preliminary treatment. PMID:18967265

Zen, J M; Hsu, C T



Study of carbon nanotube modified biosensors for monitoring uric acid and total cholesterol in blood  

Microsoft Academic Search

The carbon nanotube modified biosensors for respectively monitoring uric acid (UA) and total cholesterol in blood were studied. The transducers were based on two screen-printed carbon electrodes, a carbon working electrode and a reference electrode. For UA sensors, uricase was immobilized on the surface of electrodes together with potassium ferrocyanide as electron transfer mediator. For cholesterol sensors, the corresponding enzyme

Hui Xu; Guang Li; Min Fu; You Wang; Jun Liu



Uric acid in chronic heart failure: a marker of chronic inflammation  

Microsoft Academic Search

Background Chronic heart failure is associated with hyperuricaemia and elevations in circulating markers of inflammation. Activation of xanthine oxidase, through free radical release, causes leukocyte and endothelial cell acti- vation. Associations could therefore be expected between serum uric acid level, as a marker of increased xanthine oxidase activity, and markers of inflammation. We have explored these associations in patients with

F. Leyva; S. D. Anker; I. F. Godsland; M. Teixeira; P. G. Hellewell; W. J. Kox; P. A. Poole-Wilson; A. J. S. Coats



Can Cerebrospinal Fluid Uric Acid Levels Differentiate Intraventricular Hemorrhage from Traumatic Tap?  

Microsoft Academic Search

Objective: To measure blood and cerebrospinal fluid (CSF) uric acid (UA) levels of neonates with intraventricular hemorrhage (IVH), and to examine whether or not UA can be used to differentiate traumatic tap from IVH. Material and Methods: The control group (n = 19, group I) consisted of neonates presenting with signs requiring analysis of CSF but whose CSF indices proved

K. Mutlu Hayran



Evaluation of Renal Handling of Uric Acid in Essential Hypertension: Hyperuricemia Related to Decreased Urate Secretion  

Microsoft Academic Search

The tubular transport of urate was studied in 40 hypertensive patients and in 20 normal subjects by means of pyrazinamide and benzbromarone tests. There was a marked decrease in urate excretion per nephron in hyperuricemic patients with essential hypertension. Serum uric acid correlated inversely with fractional excretion of urate (r = -0.7450, p < 0.001). Presecretory and postsecretory reabsorption of

A. Tykarski



Serum Uric Acid, Hyperuricemia and Body Mass Index in Children and Adolescents with Intellectual Disabilities  

ERIC Educational Resources Information Center

The aims of the preset study were to describe the profile of serum uric acid, the prevalence of hyperuricemia and its risk factors among children and adolescents with intellectual disabilities. We conducted a cross-sectional study of 941 children and adolescents with intellectual disabilities (aged 4-18 years) who participated in annual health…

Lin, Jin-Ding; Lin, Pei-Ying; Lin, Lan-Ping; Hsu, Shang-Wei; Yen, Chia-Feng; Fang, Wen-Hui; Wu, Sheng-Ru; Chien, Wu-Chien; Loh, Ching-Hui; Chu, Cordia M.



Uric Acid Oxidation by Peroxynitrite: Multiple Reactions, Free Radical Formation, and Amplification of Lipid Oxidation  

Microsoft Academic Search

Uric acid has been considered to be an efficient scavenger of peroxynitrite but the reaction between urate and peroxynitrite has been only partially characterized. Also, previous studies have indicated that urate may increase peroxynitrite-mediated oxidation of low density lipoprotein (LDL). Here, we examined the reaction between urate and peroxynitrite by combining kinetic, oxygen consumption, spin trapping, and product identification studies;

Célio X. C. Santos; Edson I. Anjos; Ohara Augusto



Uric acid deposits and estivation in the invasive apple-snail, Pomacea canaliculata  

Microsoft Academic Search

The physiological ability to estivate is relevant for the maintenance of population size in the invasive Pomacea canaliculata. However, tissue reoxygenation during arousal from estivation poses the problem of acute oxidative stress. Uric acid is a potent antioxidant in several systems and it is stored in specialized tissues of P. canaliculata. Changes in tissue concentration of thiobarbituric acid reactive substances

Maximiliano Giraud-Billoud; María A. Abud; Juan A. Cueto; Israel A. Vega; Alfredo Castro-Vazquez



Short-term vitamin D receptor activation increases serum creatinine due to increased production with no effect on the glomerular filtration rate  

Microsoft Academic Search

Vitamin D receptor activation has been associated with increased serum creatinine and reduced estimated glomerular filtration rates, raising concerns that its use may be detrimental to kidney function. Here we studied the effect of vitamin D receptor activation on serum creatinine, creatinine generation, and its clearance. We measured baseline serum creatinine and 24-h urine creatinine in 16 patients with chronic

Rajiv Agarwal; Jennifer E Hynson; Tyler J W Hecht; Robert P Light; Arjun D Sinha



Diagnostic accuracy of urinary spot protein:creatinine ratio for proteinuria in hypertensive pregnant women: systematic review  

Microsoft Academic Search

Objective To review the spot protein:creatinine ratio and albumin:creatinine ratio as diagnostic tests for significant proteinuria in hypertensive pregnant women.Design Systematic review.Data sources Medline and Embase, the Cochrane Library, reference lists, and experts.Review methods Literature search (1980-2007) for articles of the spot protein:creatinine ratio or albumin:creatinine ratio in hypertensive pregnancy, with 24 hour proteinuria as the comparator.Results 13 studies concerned

Anne-Marie Côté; Mark A Brown; Elaine Lam; Peter von Dadelszen; Tabassum Firoz; Robert M Liston; Laura A Magee



A test of improved force field parameters for urea: molecular-dynamics simulations of urea crystals.  


Molecular-dynamics (MD) simulations of urea crystals of different shapes (cubic, rectangular prismatic, and sheet) have been performed using our previously published force field for urea. This force field has been validated by calculating values for the cohesive energy, sublimation temperature, and melting point from the MD data. The cohesive energies computed from simulations of cubic and rectangular prismatic urea crystals in vacuo at 300 K agreed very well with the experimental sublimation enthalpies reported at 298 K. We also found very good agreement between the melting points as observed experimentally and from simulations. Annealing the crystals just below the melting point leads to reconstruction to form crystal faces that are consistent with experimental observations. The simulations reveal a melting mechanism that involves surface (corner/edge) melting well below the melting point, and rotational disordering of the urea molecules in the corner/edge regions of the crystal, which then facilitates the translational motion of these molecules. PMID:22281810

Özp?nar, Gül Alt?nba?; Beierlein, Frank R; Peukert, Wolfgang; Zahn, Dirk; Clark, Timothy




PubMed Central

The extent of urea denaturation depends on the concentration of protein and urea and also on the temperature of the solution. Egg albumin solutions (0.9 per cent) are not denatured by 20 per cent urea, denature slowly with 25 per cent urea, and denature rapidly with 35 per cent urea at room temperature. At a higher temperature 30 per cent urea is rapidly effective. Denaturation of the egg albumin molecule by radiation or by heat is accompanied by structural changes as evidenced by optical rotation values, but is not accompanied by association or dissociation of the molecule in the pH range outside the zone in which aggregation follows denaturation. Denaturation of the egg albumin molecule by urea produces no change in optical rotation until the concentration of urea is high enough to dissociate the molecule. In the presence of urea a urea-protein complex is formed in which the protein is denatured but cannot flocculate because of the dispersive action of the urea. This prevents flocculation of proteins exposed to radiation and subsequent heating to 40° C. as the urea-protein complex is not broken down at a temperature of 40° C. The presence of urea therefore prevents the flocculation of proteins denatured by radiation. The urea-protein complex is broken down by heating to 55–58° C. so that the molecules aggregate at a temperature below the temperature of rapid heat denaturation. This appears to be an acceleration of heat denaturation or a lowering of the heat denaturation temperature, but in reality is an effect of heat on the urea-protein complex which frees the urea-denatured protein and permits its aggregation.

Clark, Janet H.



Influence of urea on polyvinyl alcohol molecular superstructure formation  

Microsoft Academic Search

Whiskers up to 1 cm in length were grown in polyvinyl alcohol (PVA) and urea solution. Raman and IR spectra discover an interaction\\u000a between PVA and urea molecules. Optical and electronic microscopy data show that urea influences on PVA molecular superstructure\\u000a formation. PVA whiskers prepared in urea solution can be used for organic semiconductors production which properties are determined\\u000a by

I. Yu. Prosanov; A. A. Matvienko; B. B. Bokhonov



Sensitive Specialization Analysis of Urea in Human Blood by Surface Acoustic Wave Urea Sensor System  

Microsoft Academic Search

A novel and sensitive enzymatic method for the determination of micro amounts of urea in human blood has been developed based on the surface acoustic wave (SAW) urea sensor system, which was prepared by combining a SAW device with urease (E.C. extracted directly from watermelon seeds. The Michaelis constant and maximum rate of the urease were estimated as 1.77

Liu Dezhong; Ge Kai; Chen Kang; Nie Lihua; Yao Shouzhuo



The role of creatinine and histidine in Benedict's qualitative test for reducing sugar in urine  

PubMed Central

The statement made in some standard textbooks that Benedict's qualitative test gives a green, yellow, or orange-red precipitate with pure solutions of glucose of varying strength has been shown to be incorrect. Pure solutions of glucose give only a bright red precipitate at all concentrations. These changes in the colour of the suspensions are observed with urinary glucose only. The difference in the action of glucose in water and in urine has been shown to be mostly due to creatinine and to a small extent to the histidine content of urine. The colour of the precipitate depends not only on the concentration of glucose but also on that of creatinine. An increase in concentration of creatinine tends to make the precipitate more yellow. Histidine has a similar though much smaller effect. Attention has been drawn to possible errors in the semi-quantitative assay of urinary glucose by Benedict's test arising out of variation in concentration of creatinine and histidine.

Sur, B. K.; Shukla, R. K.; Agashe, V. S.



Estimation of the flow of microbial nitrogen to the duodenum using urinary uric acid or allantoin.  


Data were collected from six experiments using duodenally cannulated Holstein dairy cows (88 combinations of cow and period) to evaluate the relationship between urinary purine metabolites and microbial N flow. Experiments evaluated the effects of dietary factors on microbial N production, which included 1) varying concentrations of ruminally degradable protein and nonstructural carbohydrates, 2) supplemental sources of protected amino acids, 3) grass silage treated with fibrolytic enzymes, 4) bacterial inoculation of corn silage, and 5) ruminal starch availability as affected by corn silages of varying maturity. The coefficient of determination for individual experiments that measured the relationship between microbial N flow and allantoin or uric acid excretion in urine ranged from 0.01 to 0.68 and 0.02 to 0.82, respectively. Across all experiments, the coefficients of determination between microbial N flow and allantoin or uric acid excretion in urine were r2 = 0.002 and 0.11, respectively. Removal of data from one experiment improved the overall coefficient of determination between microbial N flow and urinary uric acid to r2 = 0.32. Urinary allantoin excretion across experiments was negatively correlated with microbial N flow, but urinary allantoin excretion within experiments was positively correlated with microbial N flow. Uric acid excretion in urine was positively correlated with microbial N flow across and within experiments, except for one experiment. Our data demonstrate that uric acid excretion in urine can be used to predict microbial N production, except in early lactation, and that urinary allantoin excretion cannot be used to predict microbial N production accurately among cows at different stages of lactation. PMID:9785232

Johnson, L M; Harrison, J H; Riley, R E



21 CFR 176.320 - Sodium nitrate-urea complex.  

Code of Federal Regulations, 2013 CFR

... 3 2013-04-01 2013-04-01 false Sodium nitrate-urea complex. 176.320 Section...Components of Paper and Paperboard § 176.320 Sodium nitrate-urea complex. Sodium nitrate-urea complex may be safely...



Adaptation of Lactating Cows to Rations Containing Urea  

Microsoft Academic Search

Effects of a progressive change in 6 wk from a urea-free concentrate to one providing .34 (medium) or .66 g (high) urea\\/kg body weight on jugular blood composition and animal performance were studied with 27 cows. Consumption of dry matter was not affected even at the high rate of urea intake. Milk produc- tion was maximum when after 6 wk

P. R. Narasimhalu; R. J. Belzile; G. J. Brisson; W. B. Holtman



76 FR 77015 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

...Review)] Solid Urea From Russia and Ukraine Determination On the basis of the record...duty orders on solid urea from Russia and Ukraine would be likely to lead to continuation...entitled Solid Urea from Russia and Ukraine: Investigation Nos. 731-TA-...




EPA Science Inventory

Rajender S. Varma* and Yong-Jin Kim Cyclic ureas are useful intermediates for a variety of pharmaceuticals and pesticides. One of the attractive approaches for the synthesis of cyclic ureas uses condensation of diamines with urea as a carbonyl source under dynamic evacuation. ...


Synergetic Effects of Nanoporous Support and Urea on Enzyme Activity  

SciTech Connect

Here we report that synergetic effects of functionalized nanoporous support and urea on enzyme activity enhancement. Even in 8.0 M urea, the specific activity of GI entrapped in FMS was still higher than the highest specific activity of GI free in solution, indicating the strong tolerance of GI in FMS to the high concentration of urea.

Lei, Chenghong; Shin, Yongsoon; Liu, Jun; Ackerman, Eric J.



Selective inhibition of urea transport by oxidizing agents  

Microsoft Academic Search

Summary Urea and water transport across the toad bladder epithelial cell appears to take place through independent vasopressin-stimulated pathways. Agents such as chromate, for example, when added to the luminal bathing medium, inhibit urea transport without inhibiting osmotic water flow, providing evidence for such independent pathways. In the present study, selective inhibition of urea transport is shown for permanganate and

Nicholas Franki; Roland Einhorn; Richard M. Hays



Assessment of dialysis adequacy using the dialysate urea monitor: preliminary experience of the dialysate urea monitor.  


Numerous studies have identified a strong linkage between the delivered dialysis dose (Kt/V) and the survival of hemodialysis (HD) patients. However, the current method used to calculate Kt/V requires multiple blood samples and the process is complex and time consuming. We evaluate the performance of a recently developed on-line monitor (Biostat 1000 dialysate urea monitor, Baxter) that measures the urea concentration in the effluent dialysate and displays Kt/V and nPCR immediately after hemodialysis. To verify the performance of the urea monitor, we selected 21 hemodialysis patients, calculated their Kt/V and nPCR values from blood samples obtained during each hemodialysis, and compared the results with data obtained using the urea monitor. The Kt/V and nPCR values calculated by the urea monitor were both significantly correlated with those obtained using blood samples (R = 0.804, p < 0.001 in Kt/V and R = 0.749, p < 0.001 in nPCR). Our results suggest that the urea monitor may be used for on-line assessment of dialysis adequacy and obviates the need for blood sampling. PMID:9415936

Lee, W C; Tsai, C J; Huang, C C; Lee, C C; Chien, Y S; Hu, S A; Wu, C H



[Methods of urine analysis for creatinine after long period of storage].  


Our investigations showed that n-cresol (4-methylphenol) stabilized urine and preserves urinal creatinine as long as for 50-d storage at room temperature. This antimicrobial biochemical stabilizer is the core of a novel method of delayed creatinine quantification in urine. It can be useful in metabolic investigations of cosmonauts and nuclear submarine crews, members of alpine, desert, deep-water, Arctic and Antarctic expeditions and in many other cases when samples cannot be analyzed immediately. PMID:11385990

Pishak, V P; Iarmol'chuk, S G



Trypsin\\/creatinine clearance ratio and serum immunoreactive trypsin in digestive and pancreatic diseases  

Microsoft Academic Search

Summary  The behavior of trypsin\\/creatinine clearance ratio (Ctr\\/Ccr) and serum immunoreactive trypsin (IRT) was evaluated in a total of 168 subjects with pancreatic cancer, chronic pancreatitis\\u000a and non-pancreatic digestive diseases. Amylase\\/creatinine clearance ratio (Cam\\/Ccr) and serum amylase levels were also evaluated in order to establish their possible relationship with Ctr\\/Ccr and IRT values. Elevated Ctr\\/Ccr and IRT values were observed in

Giuseppe Del Favero; Carlo Fabris; Piero Bonvicini; Antonio Piccoli; Ugo Baccaglini; Sergio Pedrazzoli; Angelo Burlina; Remo Naccarato



Association of microalbuminuria and the urine albumin-to-creatinine ratio with systemic disease in cats  

Microsoft Academic Search

OBJECTIVE: To determine the diagnostic usefulness of semiquantitative and quantitative microalbuminuria assays and urine albumin-to-creatinine (UAC) ratio for detecting disease in cats. DESIGN: Prospective study. ANIMALS: 441 cats evaluated at a veterinary teaching hospital. PROCEDURES: Urine samples from cats for which a complete medical record was available were included. Urine dipstick results, urine protein-to-creatinine ratios (cutoffs, 0.1 and 0.4), semiquantitative

Jacqueline C. Whittemore; Zona Miyoshi; Wayne A. Jensen; Steven V. Radecki; Michael R. Lappin



Creatine and creatinine evolution during the processing of dry-cured ham  

Microsoft Academic Search

Dry-curing of ham involves many biochemical reactions that depend on the processing conditions. The aim of this study was to evaluate the effect of the dry-cured processing on the concentration of creatine, creatinine and the creatinine\\/creatine ratio. Dry-cured hams under study were salted using three different salt mixtures (100% NaCl; NaCl and KCl at 50% each; and 55% NaCl, 25%

Leticia Mora; Aleida S. Hernández-Cázares; Miguel Angel Sentandreu; Fidel Toldrá



Serum creatinine is associated with coronary disease risk even in the absence of metabolic disorders.  


Abstract Background. In view of recent evidence that serum creatinine and dysfunctional apolipoprotein (apo)A-I may serve as inflammation mediators in people with enhanced inflammation, we studied whether or not these molecules were interrelated and associated with coronary heart disease (CHD) likelihood even in subjects without metabolic syndrome (MetS) or type-2 diabetes. Methods. Among unselected middle-aged Turkish adults with available serum apo A-I, lipoprotein(a) and creatinine measurements, 697 participants (designated as 'healthy') were enrolled, after exclusion of the stated metabolic disorders. CHD was identified in 87 subjects, roughly half during 3.1 years' follow-up. Results. 'Healthy' individuals were overweight and had partly impaired fasting glucose but otherwise normal serum creatinine and other biochemical measurements. Being consistent with lacking anti-inflammatory activity, apoA-I was linearly and positively associated with apoB, in women further with creatinine. Logistic regression analyses showed that, beyond age, not non-HDL-cholesterol, systolic blood pressure and smoking status, but serum creatinine in each sex (OR in men 1.63 [95% CI 1.14; 2.31]) and CRP in women were significantly associated with CHD likelihood. The combined highest and lowest creatinine quartiles in women displayed an OR 2.14 (1.02; 4.51) compared with the intermediate quartiles, after similar adjustments. Conclusion. Elevated creatinine levels within normal range, linked to apoA-I dysfunctionality, are independently associated with CHD likelihood even in non-diabetic subjects without MetS. In such women the lowest creatinine quartile is also linked to CHD risk. PMID:24094290

Onat, Altan; Yüksel, Hüsniye; Can, Günay; Köro?lu, Bayram; Kaya, Ay?em; Altay, Servet



Urinary protein:creatinine ratio in rabbits in relation to their serological status to Encephalitozoon cuniculi  

Microsoft Academic Search

The concentrations of protein and creatinine were measured in urine samples from 74 healthy domestic pet rabbits, 54 of them seronegative to Encephalitozoon cuniculi and 20 seropositive. The calculated reference range for the urinary protein:creatinine ratio (UPC) of E cuniculi-seronegative rabbits was 0·11 to 0·40. There was no significant variation in the UPC due to the bodyweight, breed, sex, neutered

B. Reusch; J. K. Murray; K. Papasouliotis; S. P. Redrobe



[Calcium antagonists: current and future applications based on new evidence. The mechanisms on lowering serum uric acid level by calcium channel blockers].  


In hypertensive subjects, their serum uric acid levels tend to be higher because of decreasing urinary secretion or overproduction of uric acid. Among calcium channel blockers (CCBs) , long acting nifedipine and cilnidipine reveal serum uric acid lowering action. They decrease the production of uric acid precursor in skeletal muscles under anaerobic condition induced by hypertension or insulin resistance. Hyperuricemia is considered to be a risk factor of not only gout but also renal and cardiovascular diseases, thus, it is important to use CCBs without adverse effect on uric acid metabolisms. PMID:20048433

Mizuta, Einosuke; Hamada, Toshihiro; Igawa, Osamu; Shigemasa, Chiaki; Hisatome, Ichiro



Association between serum uric acid and the metabolic syndrome among a middle- and old-age Chinese population.  


Our aim was to study whether there is causal association between serum uric acid and metabolic syndrome (MetS). A cross-sectional study was performed, including a total of 27,009 subjects (23,345 subjects having uric acid data) from the Dongfeng-Tongji Cohort study. The MetS was defined by the International Diabetes Foundation criteria of 2005. Association analysis was performed by logistic regression. A genetic risk score was calculated by adding the uric acid increasing alleles in two SNPs (rs11722228 in SLC2A9 and rs2231142 in ABCG2) which were identified from our genome-wide association study on uric acid levels. The causal association was examined by mendelian randomization analysis. Among a middle- and old-age Chinese population, serum uric acid concentrations were strongly associated with the risk of MetS and its several components (P < 0.0001). The effects were stronger in women than in men. Despite the lack of statistical significance, both SNPs exhibited a trend with increased MetS risk (rs11722228, OR = 1.06, 95 % CI 0.99-1.14; rs2231142, OR = 1.02, 95 % CI 0.95-1.10), consistent with their increasing uric acid effects. Each additional uric acid increasing allele in the genetic risk score was associated with 3 % increased MetS risk (OR = 1.03, 95 % CI 0.98-1.09; P = 0.23). Further adjustment for serum uric acid attenuated the trend of individual SNP and genetic risk score with increased MetS risk (all OR < 1.0). These findings suggested that serum uric acid was associated with MetS risk in a middle- and old-age Chinese population. Whether this association was causal remained to be investigated in the future studies. PMID:23864233

Dai, Xiayun; Yuan, Jing; Yao, Ping; Yang, Binyao; Gui, Lixuan; Zhang, Xiaomin; Guo, Huan; Wang, Youjie; Chen, Weihong; Wei, Sheng; Miao, Xiaoping; Li, Xiulou; Min, Xinwen; Yang, Handong; Fang, Weimin; Liang, Yuan; Hu, Frank B; Wu, Tangchun; He, Meian



Urea transformation and the adaptability of three leafy vegetables to urea as a source of nitrogen in hydroponic culture  

Microsoft Academic Search

Substitution of urea for commonly used nitrate fertilizers in hydroponic culture of vegetables would not only avoid excessive accumulation of nitrate in plants but would also reduce the cost of production. This substitution, however, might have adverse effects, such as a dramatic decrease in solution pH, reduced nutrient uptake and possibly urea toxicity per se. Differences in adaptability to urea

Jian Luo; Zhaohuang Lian; Xiaolong Yan



No evidence for a causal link between uric acid and type 2 diabetes: a Mendelian randomisation approach  

Microsoft Academic Search

Aims\\/hypothesis  Epidemiological and experimental evidence suggests that uric acid has a role in the aetiology of type 2 diabetes. Using a\\u000a Mendelian randomisation approach, we investigated whether there is evidence for a causal role of serum uric acid for development\\u000a of type 2 diabetes.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  We examined the associations of serum-uric-acid-raising alleles of eight common variants recently identified in genome-wide\\u000a association studies

R. Pfister; D. Barnes; R. Luben; N. G. Forouhi; M. Bochud; K.-T. Khaw; N. J. Wareham; C. Langenberg


Salvage of blood urea nitrogen in sheep is highly dependent on plasma urea concentration and the efficiency of capture within the digestive tract  

Microsoft Academic Search

The aims of this study were 1) to deter- mine whether transfer of blood urea to the gastrointes- tinal tract (GIT) or the efficiency of capture of urea N within the GIT is more limiting for urea N salvage, and 2) to establish the relationship between plasma urea concentration and recycling of urea N to the GIT. We used an

N. E. Sunny; S. L. Owens; R. L. Baldwin VI; S. W. El-Kadi; R. A. Kohn; B. J. Bequette



Urea formaldehyde foam insulation: defusing a timebomb  

SciTech Connect

With the onset of the energy crisis in the 1970's, thousands of homeowners insulated their homes with Urea Formaldehyde Foam Insulation (UFFI). The discovery that UFFI releases formaldehyde, a carcinogen and irritant, prompted various state and federal responses to this problem. This Note reviews those responses and concludes that a ban on the sale of UFFI, coupled with a removal and repurchase program, is the most effective solution from the standpoint of consumer health.

Fox, E.M.



Benzobisoxazole fluorophore vicariously senses amines, ureas, anions.  


A benzobisoxazole-based cruciform fluorophore forms fluorescent complexes with simple boronic acids. Through the changes of their fluorescence emission colours, these complexes can sense and qualitatively distinguish among structurally similar organic nitrogen compounds (amines and ureas) and small organic and inorganic anions. Preliminary results suggest that the intensity of this hybrid sensor's fluorescent response to chloride anions can be quantitatively correlated to chloride concentration. PMID:22983092

Lim, Jaebum; Miljani?, Ognjen Š



Urea Induced Denaturation of Pre-Q1 Riboswitch  

NASA Astrophysics Data System (ADS)

Urea, a polar molecule with a large dipole moment, not only destabilizes the folded RNA structures, but can also enhance the folding rates of large ribozymes. Unlike the mechanism of urea-induced unfolding of proteins, which is well understood, the action of urea on RNA has barely been explored. We performed extensive all atom molecular dynamics (MD) simulations to determine the molecular underpinnings of urea-induced RNA denaturation. Urea displays its denaturing power in both secondary and tertiary motifs of the riboswitch (RS) structure. Our simulations reveal that the denaturation of RNA structures is mainly driven by the hydrogen bonds and stacking interactions of urea with the bases. Through detailed studies of the simulation trajectories, we found that geminate pairs between urea and bases due to hydrogen bonds and stacks persist only ~ (0.1-1) ns, which suggests that urea-base interaction is highly dynamic. Most importantly, the early stage of base pair disruption is triggered by penetration of water molecules into the hydrophobic domain between the RNA bases. The infiltration of water into the narrow space between base pairs is critical in increasing the accessibility of urea to transiently disrupted bases, thus allowing urea to displace inter base hydrogen bonds. This mechanism, water-induced disruption of base-pairs resulting in the formation of a "wet" destabilized RNA followed by solvation by urea, is the exact opposite of the two-stage denaturation of proteins by urea. In the latter case, initial urea penetration creates a dry-globule, which is subsequently solvated by water penetration leading to global protein unfolding. Our work shows that the ability to interact with both water and polar, non-polar components of nucleotides makes urea a powerful chemical denaturant for nucleic acids.

Yoon, Jeseong; Thirumalai, Devarajan; Hyeon, Changbong



Urea-Induced Denaturation of PreQ1-Riboswitch.  


Urea, a polar molecule with a large dipole moment, not only destabilizes folded RNA structures but can also enhance the folding rates of large ribozymes. Unlike the mechanism of urea-induced unfolding of proteins, which is well understood, the action of urea on RNA has barely been explored. We performed extensive all-atom molecular dynamics simulations to determine the molecular underpinnings of urea-induced RNA denaturation. Urea displays its denaturing power in both secondary and tertiary motifs of the riboswitch structure. Our simulations reveal that the denaturation of RNA structures is mainly driven by the hydrogen-bonding and stacking interactions of urea with the bases. Through detailed studies of the simulation trajectories, we found that geminate pairs between urea and bases due to hydrogen bonds and stacks persist only ?0.1-1 ns, which suggests that the urea-base interaction is highly dynamic. Most importantly, the early stage of base-pair disruption is triggered by penetration of water molecules into the hydrophobic domain between the RNA bases. The infiltration of water into the narrow space between base pairs is critical in increasing the accessibility of urea to transiently disrupted bases, thus allowing urea to displace inter-base hydrogen bonds. This mechanism-water-induced disruption of base pairs resulting in the formation of a "wet" destabilized RNA followed by solvation by urea-is the exact opposite of the two-stage denaturation of proteins by urea. In the latter case, initial urea penetration creates a dry globule, which is subsequently solvated by water, leading to global protein unfolding. Our work shows that the ability to interact with both water and polar or nonpolar components of nucleotides makes urea a powerful chemical denaturant for nucleic acids. PMID:23863126

Yoon, Jeseong; Thirumalai, D; Hyeon, Changbong




PubMed Central

The title complex, [NiCl2(CH4N2S)2], has been synthesized from the previously reported (diamino­methyl­idene)sulfonium chloride–thio­urea (3/2) salt [Zouihri (2012b ?). Acta Cryst. E68, o257]. The NiII ion is coordinated in a distorted tetra­hedral geometry by two mol­ecules of thio­urea [Ni—S = 2.3079?(7) and 2.3177?(6)?Å] and two chloride anions [Ni—Cl = 2.2516?(7) and 2.2726?(7)?Å]. The bond angles at the Ni atom lie between 96.69?(2) and 115.40?(3)°, while the dihedral angle between the mean planes of the two thio­urea ligands is 6.36?(15)°. The crystal structure is characterized by intra- and inter­molecular N—H?Cl hydrogen bonds, which lead to the formation of two-dimensional networks lying parallel to the ab plane. The networks are linked via classical N—H?Cl and N—H?S hydrogen bonds, forming a three-dimensional arrangement.

Zouihri, Hafid



Serum uric acid levels in normal pregnancy with observations on the renal excretion of urate in pregnancy  

PubMed Central

Serum uric acid estimations were performed in 106 healthy pregnant women during early, middle, and late pregnancy, using an automated colorimetric method. The mean serum uric acid level was significantly lower during early and middle pregnancy than that of 64 age-matched female controls. The serum uric acid level was not significantly different in late pregnancy from the control group. Studies of the daily urinary urate excretion in 31 pregnant women showed normal urinary urate excretion in early pregnancy and enhanced renal loss of urate in middle and late pregnancy. It appears that the renal clearance of urate in pregnancy is high, especially in the middle period when the serum level is low in spite of the increased production of uric acid by the foetus.

Boyle, James A.; Campbell, Stuart; Duncan, Anne M.; Greig, William R.; Buchanan, W. Watson



Hypothesis: Could Excessive Fructose Intake and Uric Acid Cause Type 2 Diabetes?  

PubMed Central

We propose that excessive fructose intake (>50 g/d) may be one of the underlying etiologies of metabolic syndrome and type 2 diabetes. The primary sources of fructose are sugar (sucrose) and high fructose corn syrup. First, fructose intake correlates closely with the rate of diabetes worldwide. Second, unlike other sugars, the ingestion of excessive fructose induces features of metabolic syndrome in both laboratory animals and humans. Third, fructose appears to mediate the metabolic syndrome in part by raising uric acid, and there are now extensive experimental and clinical data supporting uric acid in the pathogenesis of metabolic syndrome. Fourth, environmental and genetic considerations provide a potential explanation of why certain groups might be more susceptible to developing diabetes. Finally, we discuss the counterarguments associated with the hypothesis and a potential explanation for these findings. If diabetes might result from excessive intake of fructose, then simple public health measures could have a major impact on improving the overall health of our populace.

Johnson, Richard J.; Perez-Pozo, Santos E.; Sautin, Yuri Y.; Manitius, Jacek; Sanchez-Lozada, Laura Gabriela; Feig, Daniel I.; Shafiu, Mohamed; Segal, Mark; Glassock, Richard J.; Shimada, Michiko; Roncal, Carlos; Nakagawa, Takahiko



Structure-activity relationships of alloxan-like compounds derived from uric acid.  

PubMed Central

The diabetogenic activity of a range of alloxan-like compounds derived from uric acid has been investigated. The classes of derivatives were: 5-substituted-isouric acids; 4,5-disubstituted-4, 5-dihydrouric acids; 5-substituted-pseudouric acids; salts of dehydro-uramil hydrate; salts of dehydro-isouramil hydrate; alloxan derivatives. Compounds were tested by intravenous injection into rats and diabetogenic activity assessed by production of persistent hyperglycaemia and glycosuria. The only essential structural feature common to all active compounds was the presence of a quinonoid pyrimidine system or its hydrated equivalent. The presence of the five-membered ring of uric acid (or an opened form thereof) did not abolish and in some compounds enhanced diabetogenic activity.

Ashcroft, S. J.; Harrison, D. E.; Poje, M.; Rocic, B.



[Inherited disorders of uric acid metabolism--classification, enzymatic- and DNA-diagnosis].  


Uric acid is the end product of purine metabolism in human. Then, the enzymatic abnormalities, concerning purine metabolism, cause disorders of uric acid metabolism including hyperuricemia and hypouricemia. The superactivity of 5-phosphoribosyl-pyrophosphate (PRPP) synthetase and deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) caused hyperuricemia. In glycogen storage diseases of type I, III, V, and VII, decreased energy supply induces hyperuricemia by accelerating ATP degradation. Deficiencies of xanthine oxidase (XO), purine nucleoside phosphorylase (PNP), and PRPP were reported causing hypouricemia. Many methods for DNA-diagnosis were developed including Southern blot, Northern blot, PCR-SSCP (polymerase chain reaction-single strand conformation polymorphism), PCR-RFLP (restriction fragment length polymorphism), and allele specific oligonucleotide hybridization etc. PMID:8976110

Iwahana, H; Itakura, M



Technical note: variation in muscle mass in wild chimpanzees: application of a modified urinary creatinine method.  


Individual body size and composition are important variables for a variety of questions about the behavioral ecology and life histories of non-human primates. Standard methodologies for obtaining body mass involve either capture, which poses risks to the subject, or provisioning, which can disrupt the processes being studied. There are no methods currently available to assess body composition from living animals in the wild. Because of its derivation in muscle, the amount of creatinine that an individual excretes in 24 hours is a reliable and frequently used indicator of relative muscle mass in humans and laboratory animals. Although it is not feasible to collect 24-hour urine samples from wild primates, we apply here a simple method to approximate muscle mass variation from collections of spot urine samples. Specific gravity (SG), an alternative method for assessing urinary water content, is both highly correlated to creatinine and free of mass-dependent effects. Individuals with greater muscle mass should excrete more creatinine for a given SG. We examine this relationship in a dataset of 12,598 urine samples from wild chimpanzees in the Kibale National Park, Uganda. As expected from known differences in body composition, the slope of the relationship between SG and creatinine is significantly greater in adult males than adult females and in adults versus immature individuals. Growth curves generated through this method closely approximate published weight curves for wild chimpanzees. Consistent with the role of testosterone in muscle anabolism, urinary testosterone predicted relative creatinine excretion among adult male chimpanzees. PMID:23077085

Emery Thompson, Melissa; Muller, Martin N; Wrangham, Richard W



Accumulation of allantoin and uric acid in plasma of exercising trotters.  


Plasma concentrations of hypoxanthine, uric acid, and allantoin, which are breakdown products of adenine nucleotides, were measured in Standardbred and Finnhorse trotters during and after an exercise test on a high-speed treadmill, after an incremental exercise test performed on a racetrack, and after a racing competition. Fiber-type composition of the middle gluteal muscle and the muscle concentrations of adenine nucleotides and inosine monophosphate were measured after the racetrack test. Changes in the concentration of hypoxanthine were not observed in any of the tests. Peak concentration of uric acid was measured between 5 and 30 minutes after exercise, and it was three- to tenfold higher than the value at rest. The variability can be explained by intensity of the exercise test and variation among horses. The concentration of allantoin after exercise was 2 to 3 times as high as that at rest, depending on the intensity of the exercise, although the absolute increase was about 10 times as high as the increase in the concentration of uric acid. Peak values of allantoin for the treadmill and the racetrack tests were obtained 4 to 6 minutes after exercise and < 30 minutes after the races. Peak concentration of allantoin correlated positively with the percentage of type-II (IIA+IIB) fibers in the middle gluteal muscle. Significant correlations were not observed between plasma concentration of uric acid or allantoin and muscle concentrations of adenosine triphosphate (ATP) or inosine monophosphate. It can be concluded that in horses, breakdown of ATP during and after exercise continues until allantoin is produced.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8291774

Räsänen, L A; Myllymäki, T; Hyyppä, S; Maisi, P; Pösö, A R



Simultaneous determination of uric acid and ascorbic acid at a ferrocenium–thioglycollate modified electrode  

Microsoft Academic Search

Self-assembled monolayers (SAMS) of chemisorbed thioglycollate on a gold electrode surface have been used as a base interface\\u000a for the electrostatic adsorption of ferrocenium ion. Electrochemical impedance spectra (EIS) and cyclic voltammetry (CV) were\\u000a used to evaluate the electrochemical properties of the supramolecular film. The bare gold electrode failed to distinguish\\u000a the oxidation peaks of ascorbic acid (AA) and uric

Bin Fang; Shoufeng Jiao; Maoguo Li; Haisheng Tao



Association of Serum Uric Acid With Aortic Stiffness and Pressure in a Chinese Workplace Setting  

Microsoft Academic Search

BackgroundIn the present analysis, we investigated the association of serum uric acid with aortic stiffness and pressure as measured by carotid–femoral pulse wave velocity (cf-PWV) and central systolic blood pressure (SBP), respectively.MethodsOur study was conducted in the framework of cardiovascular health examinations for the employees of a factory and their family members (ages 15–79 years). We performed arterial measurements using

Xin Chen; Yan Li; Chang-Sheng Sheng; Qi-Fang Huang; Yang Zheng; Ji-Guang Wang



Serum Uric Acid and Cognitive Function in Community-Dwelling Older Adults  

Microsoft Academic Search

Among possible markers of age-related cognitive decline, uric acid (UA) is controversial because it has antioxidant properties but is increased in diseases that often lead to cognitive impairment. In this study of 96 elderly adults, participants with mildly elevated (but normal) serum UA were 2.7 to 5.9 times more likely to score in the lowest quartile of the sample on

David J. Schretlen; Anjeli B. Inscore; H. A. Jinnah; Vani Rao; Barry Gordon; Godfrey D. Pearlson



Preliminary investigations on a new disposable potentiometric biosensor for uric acid  

Microsoft Academic Search

In this paper, uricase, catalase, and electron mediator were coimmobilized on the surface of the tin oxide (SnO2)\\/indium tin oxide (ITO) glass, to develop a disposable potentiometric uric acid biosensor. The SnO2 \\/ ITO glass was employed as a pH sensor, fabricated by sputtering SnO2 thin films on the ITO glass. 3-Glycidyloxypropyltrimethoxysilane (GPTS) was utilized to immobilize uricase, catalase and

Cheng Wei Liao; Jung Chuan Chou; Tai Ping Sun; Shen Kan Hsiung; Jui Hsiang Hsieh



Characterisation of Genome-Wide Association Epistasis Signals for Serum Uric Acid in Human Population Isolates  

Microsoft Academic Search

Genome-wide association (GWA) studies have identified a number of loci underlying variation in human serum uric acid (SUA) levels with the SLC2A9 gene having the largest effect identified so far. Gene-gene interactions (epistasis) are largely unexplored in these GWA studies. We performed a full pair-wise genome scan in the Italian MICROS population (n = 1201) to characterise epistasis signals in

Wenhua Wei; Gibran Hemani; Andrew A. Hicks; Veronique Vitart; Claudia Cabrera-Cardenas; Pau Navarro; Jennifer Huffman; Caroline Hayward; Sara A. Knott; Igor Rudan; Peter P. Pramstaller; Sarah H. Wild; James F. Wilson; Harry Campbell; Malcolm G. Dunlop; Nicholas Hastie; Alan F. Wright; Chris S. Haley



Non-invasive and transdermal measurement of blood uric acid level in human by electroporation and reverse iontophoresis  

PubMed Central

The aim of this study was to find out the optimum combination of electroporation (EP) and reverse iontophoresis (RI) on noninvasive and transdermal determination of blood uric acid level in humans. EP is the use of high-voltage electric pulse to create nano-channels on the stratum corneum, temporarily and reversibly. RI is the use of small current to facilitate both charged and uncharged molecule transportation across the skin. It is believed that the combination of these two techniques has additional benefits on the molecules’ extraction across the human skin. In vitro studies using porcine skin and diffusion cell have indicated that the optimum mode for transdermal uric acid extraction is the combination of RI with symmetrical biphasic direct current (current density = 0.3 mA/cm2; phase duration = 180 s) and EP with 10 pulses per second (voltage = 100 V/cm2; pulse width = 1 ms). This optimum mode was applied to six human subjects. Uric acid was successfully extracted through the subjects’ skin into the collection solution. A good correlation (r2 = 0.88) between the subject’s blood uric acid level and uric acid concentrations in collection solutions was observed. The results suggest that it may be possible to noninvasively and transdermally determine blood uric acid levels.

Lee, Chih-Kuei; Ching, Congo Tak-Shing; Sun, Tai-Ping; Tsai, Chun-Lang; Huang, Wei; Huang, Hsin-Hung; Kuo, Jen-Fu; Lai, Li-Hang; Chien, Mei-Ya; Tseng, Hsin-Hui; Pan, Hui-Tzu; Huang, Shiow-Yuan; Shieh, Hsiu-Li; Liu, Wei-Hao; Liu, Chia-Ming; Huang, Hsin-Wei



Progesterone increases glomerular filtration rate, urinary kallikrein excretion and uric acid clearance in normal women.  


In pregnancy there is a rise in glomerular filtration rate (GFR), plasma aldosterone levels, uric acid clearance and urinary kallikrein excretion. In toxemia all the above parameters tend to decrease. Progesterone has a diuretic effect which is usually related to aldosterone antagonism. We administered progesterone to normal women and observed that GFR, uric acid clearance and kallikrein excretion increased significantly, GFR from 103.0 +/- 13.7 ml/min to 118.0 +/- 18.0 ml/min (P less than 0.01), uric acid clearance from 9.0 +/- 3.6 ml/min to 14.3 +/- 4.0 ml/min (P less than 0.01), and urinary kallikrein excretion from 165 +/- 156 mU to 432 +/- 220 mU (P less than 0.01). Natriuresis and potassium excretion also increased from 15.9 +/- 6.4 mEq to 33.4 +/- 10.9 mEq (P less than 0.01) and from 7.6 +/- 2.7 mEq to 14.0 +/- 5.4 mEq, (P less than 0.01), respectively, suggesting that in this situation aldosterone antagonism is not relevant to explain the diuretic effects of progesterone. PMID:3179582

Atallah, A N; Guimarães, J A; Gebara, M; Sustovich, D R; Martinez, T R; Camano, L



Creatinine measurements often yielded false estimates of progression in chronic renal failure  

SciTech Connect

In 9 of 22 observation periods (lasting an average of 15 months) in 17 patients with moderate to severe chronic renal failure (GFR 4 to 23 ml/min), rates of progression as estimated from the linear regression on time of 24-hour creatinine clearance (b1) differed significantly from rates of progression as estimated from the regression on time of urinary clearance of 99mTc-DTPA (b2), during all or part of the period of observation. b1 exceeded b2 in four cases and was less than b2 in the other five. Thus there were gradual changes in the fractional tubular secretion of creatinine in individual patients, in both directions. Owing to these changes, measurements of creatinine clearance gave erroneous impressions of the rate or existence of progression during all or a portion of the period of observation in nearly half of these patients. In the 22 studies as a group, using the entire periods of observation, b1 indicated significantly more rapid progression (by 0.18 +/- 0.06 ml/min/month, P less than 0.01) than did b2, and had a significantly greater variance. Measurements of progression based on the rate of change of reciprocal plasma creatinine (multiplied by an average rate of urinary creatinine excretion in each study) were equally misleading, even though less variable. We conclude that sequential creatinine measurements are often misleading as measures of progression and should, when feasible, be replaced by urinary clearance of isotopes in following patients with chronic renal failure.

Walser, M.; Drew, H.H.; LaFrance, N.D.



Protein stabilization by urea and guanidine hydrochloride.  


The urea, guanidine hydrochloride, salt, and temperature dependence of the rate of dissociation of CO from a nonequilibrium state of CO-bound native ferrocytochrome c has been studied at pH 7. The heme iron of ferrocytochrome c in the presence of denaturing concentrations of guanidine hydrochloride (GdnHCl) and urea prepared in 0.1 M phosphate, pH 7, binds CO. When the unfolded protein solution is diluted 101-fold into CO-free folding buffer, the protein chain refolds completely, leaving the CO molecule bonded to the heme iron. Subsequently, slow thermal dissociation of the CO molecule yields to the heme coordination of the native M80 ligand. Thus, the reaction monitors the rate of thermal conversion of the CO-liganded native ferrocytochrome c to the M80-liganded native protein. The rate of this reaction, k(diss), shows a characteristic dependence on the presence of nondenaturing concentrations of the denaturants in the reaction medium. The rate decreases by approximately 1.9-3-fold as the concentration of GdnHCl in the refolding medium increases from nearly 0 to approximately 2.1 M. Similarly, the rate decreases by 1.8-fold as the urea concentration is raised from 0.l to approximately 5 M. At still higher concentrations of the denaturants the denaturing effect sets in, the protein is destabilized, and hence the CO dissociation rate increases sharply. The activation energy of the reaction, E(a), increases when the denaturant concentration in the reaction medium is raised: from 24.1 to 28.3 kcal mol(-1) for a 0.05-2.1 M rise in GdnHCl and from 25.2 to 26.9 kcal mol(-1) for a 0.1-26.9 M increase in urea. Corresponding to these increases in denaturant concentrations are also increases in the activation entropy, S(diss)/R, where R is the gas constant of the reaction. The denaturant dependence of these kinetic and thermodynamic parameters of the CO dissociation reaction suggests that binding interactions with GdnHCl and urea can increase the structural and energetic stability of ferrocytochrome c up to the limit of the subdenaturing concentrations of the additives. NaCl and Na(2)SO(4), which stabilize proteins through their salting-in effect, also decrease the rate with a corresponding increase in activation entropy of CO dissociation from CO-bound native ferrocytochrome c, lending support to the view that low concentrations of GdnHCl and urea stabilize proteins. These results have direct relevance to the understanding and interpretation of the free energy-denaturant relationship and protein folding chevrons. PMID:12416983

Bhuyan, Abani K



Cimetidine administration and tubular creatinine secretion in patients with compensated cirrhosis.  


Cimetidine inhibits the tubular secretion of creatinine, without altering the glomerular filtration rate (GFR). During cimetidine administration the creatinine/inulin clearance ratio approaches unity in patients with renal failure. We determined the clearance of lithium (an index of fluid delivery to the distal nephron), inulin (a measure of the actual GFR) and creatinine during cimetidine administration to investigate the occurrence of tubular creatinine secretion in patients with compensated cirrhosis. A total of 12 patients with Child-Pugh A cirrhosis were studied initially. The subjects consumed a stable diet containing 100 mmol of sodium. On successive days, 9 h creatinine clearances were measured, first without and then with the oral administration of cimetidine (400 mg as a priming dose, followed by 200 mg every 3 h). During the first study day, 4 h renal lithium clearance was also calculated. A further group of five patients with fully compensated cirrhosis underwent the measurement (on successive days) of plasma inulin clearance, first without and then with the oral administration of cimetidine (same schedule of drug administration). Cimetidine administration unmasked a marked overestimation of GFR when calculated as creatinine clearance (baseline, 138+/-20 ml/min; +cimetidine, 89+/-13 ml/min; P<0.01). Consequently, during cimetidine administration the calculated lithium fractional excretion (a measure of the fraction of filtered sodium load that is delivered to the loop of Henle) rose from 21.4+/-13.2% to 32.3+/-18.9% (P<0.05), and the ratio between absolute distal tubular sodium reabsorption and filtered sodium load rose from 20.6+/-13.1% to 31.6+/-19.3% (P<0.01). Cimetidine caused no significant decrease in the actual GFR (i.e. inulin clearance) when administered to the second group of patients with compensated cirrhosis. Our data demonstrate significant tubular secretion of creatinine in patients with compensated cirrhosis and, consequently, a marked overestimation of GFR and filtered sodium load and an underestimation of the fractional distal tubular sodium reabsorption when these parameters are calculated by means of the traditional creatinine and lithium clearance computation. The true GFR (measured as inulin clearance) is unaffected by cimetidine administration. PMID:11749665

Sansoè, Giovanni; Ferrari, Alberto; Castellana, Carmen Nives; Bonardi, Lorenzo; Villa, Erica; Manenti, Federico



Cloning and characterization of the vasopressin-regulated urea transporter  

Microsoft Academic Search

UREA is the principal end product of nitrogen metabolism in mammals1. Movement of urea across cell membranes was originally thought to occur by lipid-phase permeation, but recent studies have revealed the existence of specialized transporters with a low affinity for urea (Km > 200 mM)2. Here we report the isolation of a complementary DNA from rabbit renal medulla that encodes

Guofeng You; Craig P. Smith; Yoshikatsu Kanai; Wen-Sen Lee; Matthias Stelzner; Matthias A. Hediger



Reversible inhibition of urea exchange in rat hepatocytes.  

PubMed Central

Urea exchange is enhanced in renal collecting duct cells and erythrocytes by transporters which can be inhibited by phloretin and urea analogs such as thiourea. In this study, evidence for a comparable transporter was found in rat livers perfused with solutions which contained no red cells and in suspensions of hepatocytes. Bolus injections containing 125I-albumin (intravascular indicator), 99mTc-DTPA (extracellular indicator), 3HOH (water indicator), and [14C]urea were administered into the portal vein and fluid was collected from the hepatic vein. Under control conditions, [14C]urea and 3HOH emerged from the hepatic vein at nearly the same rate. However when the perfusate contained 2.5 mM phloretin (equivalent to 0.058 mM phloretin not bound to albumin), the amount of [14C]urea which had been recovered in the hepatic venous outflow by the time of peak 125I-albumin concentrations exceeded 3HOH recovery by a factor of 2.31 +/- 0.23 (n = 7). When the perfusate contained 200 mM thiourea, the comparable recovery of [14C]urea from the hepatic veins exceeded that of 3HOH by a factor of 3.48 +/- 0.44 (n = 7). These effects were at least partially reversible and suggested inhibition of urea transporters in hepatocytes. This conclusion was supported by studies of unloading of [14C]urea from hepatocytes which were exposed to unlabeled solutions: in the presence of phloretin, the amount of [14C]urea remaining within hepatocytes at 4 s was approximately twice that remaining in hepatocytes which had not been exposed to phloretin. Rapid transport of urea out of hepatocytes may increase urea synthesis and minimize cellular swelling due to urea accumulation.

Effros, R M; Jacobs, E; Hacker, A; Ozker, K; Murphy, C



Multicompartment urea kinetics in well-dialyzed children  

Microsoft Academic Search

Multicompartment urea kinetics in well-dialyzed children.BackgroundWe have reported catch-up growth with hemodialysis (HD) of approximately 15 hours\\/week. Without an equilibrated post-treatment blood urea nitrogen, the variable-volume single-pool (VVSP) model will not account for urea rebound, inflating the estimated HD dose (Kdt\\/V). A two-pool model (FVDP) predicts rebound, but requires fixed compartment volumes for the equations to be solvable in closed

Atul Sharma; Pauline Espinosa; Lorraine Bell; Alex Tom; Celia Rodd



Urea determination using pH–enzyme electrode  

Microsoft Academic Search

A pH-membrane electrode with n-tridodecylamine (TDDA) as the hydrogen-ion-selective ionophore was used for the construction of a potentiometric biosensor for urea determination. The electrode was enzymatically modified by covalent binding of urease molecules directly to the surface of the potentiometric membrane. Incorporation of the urea biosensor into simple double-channel flow injection analysis (FIA) system allows reproducible urea determination in a

Robert Koncki; Agnieszka Chudzik; Izabela Walcerz



14C-urea breath test in C pylori gastritis  

Microsoft Academic Search

14C-urea breath test was used to detect Campylobacter pylori colonisation in 129 consecutive non-ulcer dyspepsia patients. Fasting patients were given 3 microCi (110 kBq) of 14C-labelled urea after a test meal. Breath samples were collected at 10 minute intervals for 90 minutes and the C-14 activity was counted on a liquid scintillation analyser. Urea derived 14CO2 appears in the exhaled

E A Rauws; E A Royen; W Langenberg; J V Woensel; A A Vrij; G N Tytgat



Urea formaldehyde foam: a dangerous insulation  

SciTech Connect

Insulating a home with urea formaldehyde foam can lead to severe health problems due to poisoning from formaldehyde gas. Respiratory problems, allergies, memory loss, and mental problems can result from exposure to foam insulation fumes. Research is now under way at the Chemical Industry Inst., Univ. of Washington, and other institutions to learn more about the health effects of formaldehyde foam and to develop possible remedies to these problems. Several states are either banning or controlling the use of this type of home insulation.

Keough, C.



New potent calcimimetics: II. Discovery of benzothiazole trisubstituted ureas.  


Following the identification of trisubstituted ureas as a promising new chemical series of allosteric modulators of the calcium sensing receptor (CaSR), we further explored the SAR around the urea substitution, leading to the discovery of benzothiazole urea compound 13. This compound is a potent calcimimetic with an EC50=20 nM (luciferase assay). Evaluated in an in vivo model of chronic renal failure (short term and long term in 5/6 nephrectomized rats), benzothiazole urea 13 significantly decreased PTH levels after oral administration while keeping calcemia within the normal range. PMID:23499504

Deprez, Pierre; Temal, Taoues; Jary, Hélène; Auberval, Marielle; Lively, Sarah; Guédin, Denis; Vevert, Jean-Paul



The Protein and Non-Protein Nitrogen Fractions in Milk. I. Methods of Analysis1  

Microsoft Academic Search

While the major part of the nitrogen in milk is accounted by casein, albumin, globulin and proteoses-peptones, milk also contains nitrogen in the form of am- monia, urea, creatinine, creatine, uric acid and amino acids, and mere traces in the form of vitamins, enzymes, phospholipids and cerebrosides. The non-pro- tein nitrogen components of milk have not been studied extensively. They

K. M. Shahani; H. H. Sommer



Guppies, toadfish, lungfish, coelacanths and frogs: a scenario for the evolution of urea retention in fishes  

Microsoft Academic Search

The question of how (and why) the ureosmotic strategy, characteristic of Latimeria chalumnae and the chondrichthians evolved is addressed. There are three requirements for ureosmotic regulation: urea synthesis via the ornithine-urea cycle, urea tolerance involving biochemical and physiological adjustments, and urea retention that requires renal, branchial, metabolic and reproductive adaptations. Several examples of lower vertebrates in which urea plays a

Robert W. Griffith



Effect of urea and urea-gamma treatments on cellulose degradation of Thai rice straw and corn stalk  

NASA Astrophysics Data System (ADS)

Cellulose degradation of 20% urea treated and 20% urea-10kGy gamma treated Thai rice straw and corn stalk showed that combination effect of urea and gamma radiation gave a higher % decrease in neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), cellulose, hemicellulose, and lignin and cutin in comparison with urea effect only for both room temperature storage and room temperature +258K storage. The results also indicated that cellulose degradation proceeded with time, even at 258K. A drastic drop to less than half of the original contents in NDF, ADF, and ADL could not be obtained in this study.

Banchorndhevakul, Siriwattana




Microsoft Academic Search

While the best way to identify microalbuminuria is to determine albumin excretion rate (AER) in a 24 h urine sample. Published data have shown that calculation of an albumin\\/creatinine ratio (ACR) in a spot urine sample has reasonable rate of sensitivity and specificity. We aimed to evaluate the effect of daily exercise on ACR and estimate the best time for

Ercan Tuncel; Erdinc Erturk; Canan Ersoy; Sinem Kiyici; Cevdet Duran; Nesrin Kuru; Sazi Imamoglu



Platinum Accumulation in the Kidney and Changes in Creatinine Clearance following Chemotherapy with Cisplatin in Humans  

Microsoft Academic Search

To evaluate the effects of repeated administration of cisplatin on kidney platinum (Pt) accumulation and renal function, Pt content in the kidney was determined in 31 autopsy cases and changes in creatinine clearance (Co) were retrospectively assessed in 26 of 31 autopsy cases. There was no significant correlation between the cumulative dose of cisplatin and Pt content in the kidney.

Jiro Uozumi; Toyofumi Ueda; Tetsuo Yasumasu; Yasuhiro Koikawa; Seiji Naito; Joichi Kumazawa; Toshiharu Kamura; Hitoo Nakano; Katsuo Sueishi



Effect of alcohol consumption on estimated glomerular filtration rate and creatinine clearance rate  

Microsoft Academic Search

Background. Moderate alcohol consumption is widely recognized as beneficial in the prevention of cardio- vascular disease, yet the renal effects of alcohol intake are still controversial. The present study is designed to investigate the influence of alcohol consumption on calculated creatinine clearance rate (CCr) and glomerular filtration rate (GFR) in a Southern Taiwan Pai-Wan aboriginal community with a high prevalence

Fu-Mei Chung; Yi-Hsin Yang; Tien-Yu Shieh; Shyi-Jang Shin; Jack C.-R. Tsai; Yau-Jiunn Lee



Urinary Creatinine as an Index of Urinary Excretion of Estrogen in Cows Prepartum and Postpartum1  

Microsoft Academic Search

Urine was collected from 55 cows via indwelling urinary catheters for periods of 12 h on different days (28 days prepartum to 60 days postpartum). Ex- cretion of urinary creatinine (mg\\/h per kg bodyweight) among Holsteins increased from .94 on day 28 prepartum to 1.14 on day .5 postpartum and then decreased to .82 on days 30 to 45 of

R. E. Erb; A. H. Surve; R. D. Randel; H. A. Garverick



Urinary corticoid : creatinine ratios in dogs with pituitary-dependent hypercortisolism during trilostane treatment  

Microsoft Academic Search

Background: The adrenocorticotropic hormone (ACTH) stimulation test is used to evaluate trilostane treatment in dogs with hypercortisolism. Hypothesis: The urinary corticoid : creatinine ratio (UCCR) is a good alternative to the ACTH stimulation test to determine optimal trilostane dose. Animals: Eighteen dogs with pituitary-dependent hypercortisolism. Methods: In this prospective study, the dose of trilostane was judged to be optimal on

S. Galac; J. J. C. W. M. Buijtels; H. S. Kooistra



KEY COMPARISON: CCQM-K12: The determination of creatinine in serum  

Microsoft Academic Search

A Key Comparison on the determination of creatinine in human serum organized by the Consultative Committee on Amount of Substance (CCQM) was carried out in 2001. To address the measurement traceability needs of the clinical chemistry community, the CCQM is undertaking Key Comparisons to document the capabilities of national metrology institutes (NMIs) that provide measurement services in this area. This

Michael J. Welch; Curtis P. Phinney; Reenie M. Parris; Willie E. May; Gwi Suk Heo; Andre Henrion; Gavin O'Conner; Heinz Schimmel




EPA Science Inventory

We studied urine cotinine excretion in 27 children who attended a research day care center to determine the extent of correlation between urine cotinine-creatinine ratios (CCR) and intensity of nicotine exposure in the home. verage nicotine levels in home air were determined by a...


The relationship of plasma urea nitrogen with growth traits and age at first estrus in gilts.  


Gilts that reach puberty at an earlier age with more backfat have greater lifetime productivity. Increased growth rates generally promote earlier age at first estrus; however, an association of age at first estrus with discrete measures of body fatness remains controversial. We tested the hypothesis that metabolic state as determined by concentrations of plasma urea nitrogen (PUN), which reflect lean tissue growth, were correlated with age at first estrus. Blood samples were collected from gilts (n = 337) at 102, 123, and 145 d of age during development. Concentrations of albumin, creatinine, glucose, and PUN were determined. Body weight and backfat thickness were determined at each time point. From 130 to 240 d of age, gilts were monitored for first pubertal estrus. Concentrations of creatinine increased whereas concentrations of glucose decreased with increasing age (P < 0.0001). Concentrations of albumin and PUN remained relatively stable throughout development. Average daily BW gain (r = 0.22) and change in backfat thickness (r = 0.29) had a positive phenotypic correlation (P < 0.0001) with PUN at 145 d of age. Concentrations of PUN at 102 and 123 d of age were not phenotypically correlated with pubertal age, but there was a moderately negative phenotypic correlation (r = -0.22; P < 0.0001) of PUN at 145 d of age with age at first estrus along with a negative genetic correlation (r = -0.42). The relationship of PUN with age at first estrus shifted from liner to quadratic with advancing age. These data demonstrate that near the age at which gilts are selected for entry into the breeding unit, those with greater PUN have increased BW and backfat thickness and display pubertal estrus earlier but that PUN does not account for additional variation in age at first estrus beyond growth rate or backfat. It is concluded that PUN can be used to select gilts with increased efficiency of nutrient use without negatively impacting pubertal development. PMID:23572260

Lents, C A; Rempel, L A; Klindt, J; Wise, T; Nonneman, D; Freking, B A



Predicting urinary creatinine excretion and its usefulness to identify incomplete 24 h urine collections.  


Studies using 24 h urine collections need to incorporate ways to validate the completeness of the urine samples. Models to predict urinary creatinine excretion (UCE) have been developed for this purpose; however, information on their usefulness to identify incomplete urine collections is limited. We aimed to develop a model for predicting UCE and to assess the performance of a creatinine index using para-aminobenzoic acid (PABA) as a reference. Data were taken from the European Food Consumption Validation study comprising two non-consecutive 24 h urine collections from 600 subjects in five European countries. Data from one collection were used to build a multiple linear regression model to predict UCE, and data from the other collection were used for performance testing of a creatinine index-based strategy to identify incomplete collections. Multiple linear regression (n 458) of UCE showed a significant positive association for body weight (? = 0·07), the interaction term sex × weight (? = 0·09, reference women) and protein intake (? = 0·02). A significant negative association was found for age (? = -0·09) and sex (? = -3·14, reference women). An index of observed-to-predicted creatinine resulted in a sensitivity to identify incomplete collections of 0·06 (95 % CI 0·01, 0·20) and 0·11 (95 % CI 0·03, 0·22) in men and women, respectively. Specificity was 0·97 (95 % CI 0·97, 0·98) in men and 0·98 (95 % CI 0·98, 0·99) in women. The present study shows that UCE can be predicted from weight, age and sex. However, the results revealed that a creatinine index based on these predictions is not sufficiently sensitive to exclude incomplete 24 h urine collections. PMID:22136756

De Keyzer, Willem; Huybrechts, Inge; Dekkers, Arnold L M; Geelen, Anouk; Crispim, Sandra; Hulshof, Paul J M; Andersen, Lene F; ?eh??ková, Irena; Ruprich, Ji?í; Volatier, Jean-Luc; Van Maele, Georges; Slimani, Nadia; van't Veer, Pieter; de Boer, Evelien; De Henauw, Stefaan



Evidence that the Adverse Effect of Urea Fertilizer on Seed Germination in Soil is Due to Ammonia Formed through Hydrolysis of Urea by Soil Urease  

Microsoft Academic Search

Studies using seeds of wheat (Triticum aestivum L.), rye (Secale cereale L.), barley (Hordeum vulgare L.), and corn (Zea mays L.) indicated that the adverse effect of urea fertilizer on seed germination in soil is due to ammonia formed through hydrolysis of urea by soil urease and is not due to urea itself, to urea fertilizer impurities such as biuret,

John M. Bremner; Michael J. Krogmeier



Separation and simultaneous determination of uric acid and ascorbic acid on a dynamically modified poly(dimethylsiloxane) microchip.  


Poly(dimethylsiloxane) microfluidic channels alternately modified by poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate) were successfully used to separate uric acid and ascorbic acid. Results show that uric acid and ascorbic acid can be well separated and detected simultaneously in modified microchips coupled with in-channel electrochemical detection. Under the optimal conditions, the linear ranges of uric acid and ascorbic acid were both from 25 to 600 microM, with the correlation coefficients of 0.997 and 0.996, respectively. The detection limits were 8 microM for uric acid and 5 microM for ascorbic acid. Factors influencing separation and detection, including buffer solution, detection potential and separation voltage, were investigated and optimized. In addition, the dependences of the current response on sensitivity and reproducibility were studied, and the stability of the device was also evaluated in detail. This method was successfully used to determine uric acid and ascorbic acid in human urine. PMID:18071227

Qiu, Jianding; Hu, Pengfei; Liang, Ruping



Lessons from comparative physiology: could uric acid represent a physiologic alarm signal gone awry in western society?  

PubMed Central

Uric acid has historically been viewed as a purine metabolic waste product excreted by the kidney and gut that is relatively unimportant other than its penchant to crystallize in joints to cause the disease gout. In recent years, however, there has been the realization that uric acid is not biologically inert but may have a wide range of actions, including being both a pro- and anti-oxidant, a neurostimulant, and an inducer of inflammation and activator of the innate immune response. In this paper, we present the hypothesis that uric acid has a key role in the foraging response associated with starvation and fasting. We further suggest that there is a complex interplay between fructose, uric acid and vitamin C, with fructose and uric acid stimulating the foraging response and vitamin C countering this response. Finally, we suggest that the mutations in ascorbate synthesis and uricase that characterized early primate evolution were likely in response to the need to stimulate the foraging “survival” response and might have inadvertently had a role in accelerating the development of bipedal locomotion and intellectual development. Unfortunately, due to marked changes in the diet, resulting in dramatic increases in fructose- and purine-rich foods, these identical genotypic changes may be largely responsible for the epidemic of obesity, diabetes and cardiovascular disease in today’s society.

Sautin, Yuri Y.; Oliver, William J.; Roncal, Carlos; Mu, Wei; Sanchez-Lozada, L. Gabriela; Rodriguez-Iturbe, Bernardo; Nakagawa, Takahiko; Benner, Steven A.



Nitrification and Anammox with Urea as the Energy Source  

Microsoft Academic Search

Urea is present in many ecosystems and can be used as an energy source by chemolithotrophic aerobic ammonia oxidizing bacteria (AOB). Thus the utilization of urea in comparison to ammonia, by AOB as well as anaerobic ammonia oxidizing (Anammox) bacteria was investigated, using enrichments cultures, inoculated with activated sludge, and molecular ecological methods. In batch enrichment cultures grown with ammonia

A. Olav Sliekers; Suzanne Haaijer; Markus Schmid; Harry Harhangi; Karin Verwegen; J. Gijs Kuenen; Mike S. M. Jetten



Final report of the safety assessment of Urea.  


Although Urea is officially described as a buffering agent, humectant, and skin-conditioning agent-humectant for use in cosmetic products, there is a report stating that Urea also is used in cosmetics for its desquamating and antimicrobial action. In 2001, the Food and Drug Administration (FDA) reported that Urea was used in 239 formulations. Concentrations of use for Urea ranged from 0.01% to 10%. Urea is generally recognized as safe by FDA for the following uses: side-seam cements for food contact; an inhibitor or stabilizer in pesticide formulations and formulations applied to animals; internal sizing for paper and paperboard and surface sizing and coating of paper and paper board that contact water-in-oil dairy emulsions, low-moisture fats and oils, moist bakery products, dry solids with surface containing no free fats or oil, and dry solids with the surface of fat or oil; and to facilitate fermentation of wine. Urea is the end product of mammalian protein metabolism and the chief nitrogenous compound of urine. Urea concentrations in muscle, liver, and fetuses of rats increased after a subcutaneous injection of Urea. Urea diffused readily through the placenta and into other maternal and fetal organs. The half-life of Urea injected into rabbits was on the order of several hours, and the reutilization rate was 32.2% to 88.8%. Urea given to rats by a bolus injection or continuous infusion resulted in distribution to the following brain regions: frontal lobe, caudate nucleus, hippocampus, thalamus plus hypothalamus, pons and white matter (corpus callosum). The permeability constant after treatment with Urea of whole skin and the dermis of rabbits was 2.37 +/- 0.13 (x 10(6)) and 1.20 +/- 0.09 (x10(3)) cm/min, respectively. The absorption of Urea across normal and abraded human skin was 9.5% +/- 2.3% and 67.9% +/- 5.6%, respectively. Urea increased the skin penetration of other compounds, including hydrocortisone. No toxicity was observed for Urea at levels as high as 2000 mg/kg in acute oral studies using female rats or mice. No signs of toxicity were observed in male piglets dosed orally with up to 4 g/kg Urea for 5 days. Dogs dosed orally with 5 to 30 g/L Urea for 4 to 10 days had signs of toxicity, including weakness, anorexia, vomiting and retching, diarrhea and a decreased body temperature, which led to a deep torpor or coma. No significant microscopic changes were observed in the skin of male nude mice dermally exposed to 100% Urea for 24 h. No observable effect on fetal development was seen in rats and mice dosed orally with an aqueous solution of Urea (2000 mg/kg) on days 10 and 12 of gestation. The mean number of implants, live fetuses, percent fetal resorptions, mean fetal weight, and percent fetuses malformed were comparable to control group. A detergent containing 15% Urea was injected into pregnant ICR-JCl mice and dams and fetuses had no significant differences when compared to control animals. Urea given orally did not enhance the developmental toxicity of N-nitrosomethylurea. Female Sprague-Dawley rats injected in the uterine horn with 0.05 ml Urea on day 3 (preimplantation) or on day 7 (post implantation) exhibited no maternal mortality or morbidity; a dose-dependent reduction in embryo survival was seen with preimplantation treatment. Urea injected intra-amniotically induces mid-trimester abortions in humans. Urea was not genotoxic in several bacterial and mammalian assays; although in assays where Urea was used at a high concentration, genotoxicity was found, many in in vitro assays. Urea is commonly used in studies of DNA because it causes uncoiling of DNA molecules. Urea was not carcinogenic in Fisher 344 rats or C57B1/6 mice fed diets containing up to 4.5% Urea. Exposure of normal human skin to 60% Urea produced no significant irritation in one study, but 5% Urea was slightly irritating and 20% Urea was irritating in other reports. Burning sensations are the most frequently reported effect of Urea used alone or with other agents in treatment of diseased skin. Overall, there are few reports of sensiti



Molecular Basis of the Apparent Near Ideality of Urea Solutions.  

SciTech Connect

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Activity coefficients of urea solutions are calculated to explore the mechanism of its solution properties, which form the basis for its well-known use as a strong protein denaturant. We perform free energy simulations of urea solutions in different urea concentrations using two urea models (OPLS and KBFF models) to calculate and decompose the activity coefficients. For the case of urea, we clarify the concept of the ideal solution in different concentration scales and standard states and its effect on our subsequent analysis. The analytical form of activity coefficients depends on the concentration units and standard states. For both models studied, urea displays a weak concentration dependence for excess chemical potential. However, for the OPLS force-field model, this results from contributions that are independent of concentration to the van der Waals and electrostatic components whereas for the KBFF model those components are nontrivial but oppose each other. The strong ideality of urea solutions in some concentration scales (incidentally implying a lack of water perturbation) is discussed in terms of recent data and ideas on the mechanism of urea denaturation of proteins.

Kokubo, Hironori; Rosgen, Jorg; Bolen, D Wayne; Pettitt, Bernard M.



A structural basis for the interaction of urea with lysozyme.  

PubMed Central

The effect of urea on the crystal structure of hen egg-white lysozyme has been investigated using X-ray crystallography. High resolution structures have been determined from crystals grown in the presence of 0, 0.7, 2, 3, 4, and 5 M urea and from crystals soaked in 9 M urea. All the forms are essentially isomorphous with the native type II crystals, and the derived structures exhibit excellent geometry and RMS differences from ideality in bond distances and angles. Comparison of the urea complex structures with the native enzyme (type II form, at 1.5 A resolution) indicates that the effect of urea is minimal over the concentration range studied. The mean difference in backbone conformation between the native enzyme and its urea complexes varies from 0.18 to 0.49 A. Conformational changes are limited to flexible surface loops (Thr 69-Asn 74, Ser 100-Asn 103), the active site loop (Asn 59-Cys 80), and the C-terminus (Cys 127-Leu 129). Urea molecules are bound to distinct sites on the surface of the protein. One molecule is bound to the active site cleft's C subsite, at all concentrations, in a fashion analogous to that of the N-acetyl substituent of substrate and inhibitor sugars normally bound to this site. Occupation of this subsite by urea alone does not appear to induce the conformational changes associated with inhibitor binding.

Pike, A. C.; Acharya, K. R.



Urinary Urea Nitrogen as an Indicator of Pregnancy Risk.  

National Technical Information Service (NTIS)

The purpose of this investigation was to assess the amount of protein in the diets of pregnant women as reflected by the urinary urea nitrogen/cretinine nitrogen (UN/CN) and urea nitrogen/total nitrogen (UN/TN) ratios and to relate protein intake to pregn...

F. J. Zlatnik



Factors Associated with Milk Urea Concentrations in Ontario Dairy Cows  

Microsoft Academic Search

All DHI test-day data, including milk urea concentra- tions measured by infrared test method, were collected from 60 commercial Ontario Holstein dairy herds for a 13-mo period between December 1, 1995, and December 31, 1996. The objectives of this study were to describe the relationships between milk urea concentrations and seasonal factors, sampling factors, cow factors, and test- day production

S. M. Godden; K. D. Lissemore; D. F. Kelton; K. E. Leslie; J. S. Walton; J. H. Lumsden



Substrate Selectivity of YgfU, a Uric Acid Transporter from Escherichia coli*  

PubMed Central

The ubiquitous nucleobase-ascorbate transporter (NAT/NCS2) family includes more than 2,000 members, but only 15 have been characterized experimentally. Escherichia coli has 10 members, of which the uracil permease UraA and the xanthine permeases XanQ and XanP are functionally known. Of the remaining members, YgfU is closely related in sequence and genomic locus with XanQ. We analyzed YgfU and showed that it is a proton-gradient dependent, low-affinity (Km 0.5 mm), and high-capacity transporter for uric acid. It also shows a low capacity for transport of xanthine at 37 °C but not at 25 °C. Based on the set of positions delineated as important from our previous Cys-scanning analysis of permease XanQ, we subjected YgfU to rationally designed site-directed mutagenesis. The results show that the conserved His-37 (TM1), Glu-270 (TM8), Asp-298 (TM9), and Gln-318 and Asn-319 (TM10) are functionally irreplaceable, and Thr-100 (TM3) is essential for the uric acid selectivity because its replacement with Ala allows efficient uptake of xanthine. The key role of these residues is corroborated by the conservation pattern and homology modeling on the recently described x-ray structure of permease UraA. In addition, site-specific replacements at TM8 (S271A, M274D, V282S) impair expression in the membrane, and V320N (TM10) inactivates the permease, whereas R327G (TM10) or S426N (TM14) reduces the affinity for uric acid (4-fold increased Km). Our study shows that comprehensive analysis of structure-function relationships in a newly characterized transporter can be accomplished with relatively few site-directed replacements, based on the knowledge available from Cys-scanning mutagenesis of a prototypic homolog.

Papakostas, Konstantinos; Frillingos, Stathis



Quantification of tissue uric acid levels in a Harris's hawk with visceral gout.  


A young, captive-bred Harris's hawk, Parabuteo unicinctus, exhibited high fever and apparent paralysis of one leg shortly before death. Postmortem examination revealed milky white kidneys, white crystalline deposits in the pericardial sack, and white crystals in one intertarsal joint. Uric acid concentrations determined for the kidneys, heart muscle, skeletal muscle, and scrapings from the pericardial sack (20 mg) and intertarsal joint (2 mg) were, respectively, 12,200, 200, 110, 20,700, and 43,000 mg/100 g tissue. Compared with a healthy hawk, concentrations were elevated by a factor of 50 in the kidneys, 37 in skeletal muscle, and 18 in cardiac muscle. PMID:22017058

Herbert, Jack D; Coulson, Jennifer O; Coulson, Thomas D



[Irreversible inactivation of Chlorella glutamine synthetase by urea].  


The effect of urea on Chlorella glutamine synthetase (E. C. activity and tertiary structure is investigated. Urea is found to inhibit the activity of glutamine synthetase, the inhibitory effect being independent on the time. The enzyme molecule relax and changes its affinity to ammonium under the effect of urea at concentrations of 1.0-4.0 M. Higher concentrations of urea (5,0 M and more) produce a dissociation of the enzyme molecule into monomers without any intermediate forms. Monomers do not possess any synthetase and transferase activities. Substrates and cofactors do not protect the enzyme from the effect of urea and do not stimulate the emzyme reactivation and reaggregation after its dissotiation. The data obtained are discussed from the viewpoint of the regulation of Chlorella glutamine synthetase activity in vivo. PMID:26431

Rasulov, A S; Evstigneeva, Z G; Kretovich, W L



Brain swelling after dialysis: old urea or new osmoles?  


The pathogenesis of brain swelling and neurological deterioration after rapid hemodialysis (dialysis disequilibrium syndrome) is controversial. The "reverse urea hypothesis" suggests that hemodialysis removes urea more slowly from the brain than from the plasma, creating an osmotic gradient that results in cerebral edema. The "idiogenic osmole hypothesis" proposes that an osmotic gradient between brain and plasma develops during rapid dialysis because of newly formed brain osmoles. In this review, the experimental basis for the two hypotheses are critically examined. Based on what is known about the physiology of urea and water diffusion across the blood-brain barrier, and empiric observations of brain solute composition after experimental hemodialysis, we conclude that the "reverse urea hypothesis" remains a viable explanation for dialysis disequilibrium and that rapid reduction of a high urea level in and of itself predisposes to this condition. PMID:8712203

Silver, S M; Sterns, R H; Halperin, M L



Functionalized multilayered graphene platform for urea sensor.  


Multilayered graphene (MLG) is an interesting material for electrochemical sensing and biosensing because of its very large 2D electrical conductivity and large surface area. We propose a less toxic, reproducible, and easy method for producing functionalized multilayer graphene from multiwalled carbon nanotubes (MWCNTs) in mass scale using only concentrated H(2)SO(4)/HNO(3). Electron microscopy results show the MLG formation, whereas FTIR and XPS data suggest its carboxylic and hydroxyl-functionalized nature. We utilize this functionalized MLG for the fabrication of a novel amperometric urea biosensor. This biosensor shows linearity of 10-100 mg dL(-1), sensitivity of 5.43 ?A mg(-1) dL cm(-2), lower detection limit of 3.9 mg dL(-1), and response time of 10 s. Our results suggest that MLG is a promising material for electrochemical biosensing applications. PMID:22117758

Srivastava, Rajesh K; Srivastava, Saurabh; Narayanan, Tharangattu N; Mahlotra, Bansi D; Vajtai, Robert; Ajayan, Pulickel M; Srivastava, Anchal



Expressing the Modification of Diet in Renal Disease Study Equation for Estimating Glomerular Filtration Rate with Standardized Serum Creatinine Values  

Microsoft Academic Search

Purpose: We sought to reexpress the 4-variable Modifi- cation of Diet in Renal Disease (MDRD) Study equation for estimation of glomerular filtration rate (GFR) using serum creatinine (Scr) standardized to reference methods. Methods: Serum specimens included creatinine refer- ence materials prepared by the College of American Pathologists (CAP), traceable to primary reference ma- terial at the NIST, with assigned values

Andrew S. Levey; Josef Coresh; Tom Greene; Jane Marsh; Lesley A. Stevens


Preliminary Findings of Serum Creatinine and Estimated Glomerular Filtration Rate (eGFR) in Adolescents with Intellectual Disabilities  

ERIC Educational Resources Information Center

|The present study aimed to describe the kidney function profile--serum creatinine and estimated glomerular filtration rate (eGFR), and to examine the relationships of predisposing factors to abnormal serum creatinine in people with intellectual disabilities (ID). Data were collected by a cross-sectional study of 827 aged 15-18 years adolescents…

Lin, Jin-Ding; Lin, Lan-Ping; Hsieh, Molly; Lin, Pei-Ying



Calibration and random variation of the serum creatinine assay as critical elements of using equations to estimate glomerular filtration rate  

Microsoft Academic Search

Equations using serum creatinine level, age, sex, and other patient characteristics often are used to estimate glomerular filtration rate (GFR) in both clinical practice and research studies. However, the critical dependence of these equations on serum creatinine assay calibration often is overlooked, and the reproducibility of estimated GFR is rarely discussed. We address these issues in frozen samples from 212

Josef Coresh; Brad C. Astor; Geraldine McQuillan; John Kusek; Tom Greene; Frederick Van Lente; Andrew S. Levey



Vibrational and theoretical studies of urea and magnesium-urea complexes  

Microsoft Academic Search

.   The molecular structure and IR spectra of urea, H2NCONH2, in gas phase and in acetonitrile solution, as well as of the two complexes [MgU4Cl2] and [MgU6]Cl2 have been observed. The influence of environmental changes to geometry and spectra are shown. Various basis sets have been\\u000a employed to safeguard the validity of the reported findings, using polarization functions for all

S. G. Raptis; J. Anastassopoulou; T. Theophanides



Ethylated Urea - Ether - Modified Urea - Formaldehyde Resins, Part I: Structural and Physicochemical Properties  

Microsoft Academic Search

First, phenol - formaldehyde (PF) and urea - formaldehyde (UFII) resins were separately conventionally prepared in our laboratory. Also, UF resin synthesized from the acid modified synthesis procedure was synthesized in a purely acid medium of pH 1.0, FU molar ratio of 1.0 and at 50oC (one-stage acid modified-synthesis procedure). Subsequently, the UF resin II was modified during synthesis by

Mathew Obichukwu EDOGA


Desymmetrization of meso-2,5-Diallylpyrrolidinyl Ureas through Asymmetric Palladium-Catalyzed Carboamination: Stereocontrolled Synthesis of Bicyclic Ureas.  


Lost symmetry: Fused bicyclic ureas are enantioselectively obtained through Pd-catalyzed desymmetrizing carboaminations of meso-2,5-diallylpyrrolidinyl ureas. The reactions generate a C?N and a C?C bond, and afford products with three stereocenters. One of these products was transformed to a tricyclic guanidine and then to 9-epi-batzelladine?K over several steps. PMID:23824590

Babij, Nicholas R; Wolfe, John P



Treatment of wastewater polluted with urea by counter-current thermal hydrolysis in an industrial urea plant  

Microsoft Academic Search

In this paper, the removal of urea from industrial wastewater by thermal hydrolysis was studied via modeling and simulation of counter-current urea thermal hydrolysis reactor. The features of our proposed model are (1) the use of Nakamura equation of state to predict the vapor fugacity coefficients and UNIQUAC equation to describe the non-ideality of liquid phase, (2) the use of

M. M. Barmaki; M. R. Rahimpour; A. Jahanmiri



Analytic Validation of an Infrared Milk Urea Assay and Effects of Sample Acquisition Factors on Milk Urea Results  

Microsoft Academic Search

The objective of this study was to determine if milk samples, as they are routinely collected by Ontario Dairy Herd Improvement, would yield accurate milk urea results with an infrared assay. This investigation involved analytic validation of the infrared assay and assessment of the effect of DHI routine sample acquisi- tion factors on milk urea results. Analytic validation of an

S. M. Godden; K. D. Lissemore; D. F. Kelton; J. H. Lumsden; K. E. Leslie; J. S. Walton



Nitrogen balance and partitioning of some nitrogen catabolites in milk and urine of lactating cows  

Microsoft Academic Search

After calving, two groups of four cows were fed fescue hay (10 kg\\/d) and a concentrate (8 kg\\/d) containing 0 or 20 g kg?1 urea in order to induce different rumen microbial growth: the partition between the urine and milk excretion of allantoin, uric acid, creatinine and urea was examined. After 21 d of lactation, individual feed intakes, total faeces

P. Susmel; M. Spanghero; B. Stefanon; C. R. Mills



Kidney function estimated from serum creatinine and cystatin C and peripheral arterial disease in NHANES 1999-2002  

PubMed Central

Aims Serum cystatin C, a novel marker of kidney function, is reported to be superior to serum creatinine as a risk factor for atherosclerotic disease, but associations may vary across vascular beds. Methods and results A cross-sectional study of chronic kidney disease (CKD) and peripheral arterial disease (PAD) in 3089 adult participants aged 40+ from the 1999–2002 National Health and Nutrition Examination Survey (NHANES). Kidney function, assessed by estimated glomerular filtration rate (eGFR), was determined from serum creatinine and cystatin C using established equations. Peripheral arterial disease defined by an ankle brachial index <0.90. Glomerular filtration rate estimated using cystatin C was more strongly associated with PAD compared with eGFR using serum creatinine before and after multivariable adjustment. Further, after adjustment for cystatin C, kidney function based on serum creatinine was no longer significantly associated with PAD. However, cystatin C remained significantly associated with PAD even after adjustment for GFR estimated by serum creatinine. Compared with optimal kidney function (eGFRserum creatinine ?60, eGFRcystatin C >90), the odds ratio for PAD was 3.11 (95% confidence interval 1.26–7.64) for preclinical CKD (eGFRserum creatinine ?60, eGFRcystatin C <76.7) and 5.07 (3.01–8.52) for ‘confirmed’ CKD (eGFRserum creatinine <60, eGFRcystatin C <60). Conclusion Chronic kidney disease was strongly and independently associated with PAD. Cystatin C was a more potent marker of lower extremity PAD when compared with the serum creatinine equation currently used in clinical practice. Our results suggest that cystatin C may have clinical utility when combined with serum creatinine in evaluation of individuals who may have PAD.

Selvin, Elizabeth; Kottgen, Anna; Coresh, Josef



Microdialytical monitoring of uric and ascorbic acids in the brains of patients after severe brain injury and during neurovascular surgery  

PubMed Central

OBJECTIVES—Microdialysis has been extensively used to monitor brain metabolism in the extracellular fluid of patients with severe head injury, to detect the onset of secondary ischaemic damage. The aim was to investigate whether concentrations of uric and ascorbic acids were altered in such patients. Both these compounds play a part in free radical metabolism, which is accelerated after ischaemia and brain injury.?METHODS—Patients with aneurysm or bypass operations were monitored intraoperatively to assess concentrations in minimally disturbed tissue. Afterwards, 13 patients with severe head trauma were monitored for up to 13 days in the intensive care unit.?RESULTS—Intraoperatively, concentrations of both ascorbic and uric acids were significantly higher in the bypass group than in patients with aneurysm, which might be attributed to chronic ischaemic conditions caused by the unilateral occlusion of the carotid artery. In the patients with trauma, mean values of uric acid, varying between 6 µM and 180 µM, did not correlate with type of injury (contusion or diffuse) or duration of monitoring time. Patients who died had significantly higher concentrations of uric acid than those with a good outcome. Ascorbic acid could be detected only intermittently, probably due to technical problems. Concentrations of these two compounds could not be correlated with clinical findings during the course of monitoring.?CONCLUSIONS—Although uric and ascorbic acids are influenced by ischaemic conditions—for example, in bypass patients, neither compound is suitable for monitoring for free radical activity after severe head injury. Patients with a bad outcome tended to have higher concentrations of uric acid.??

Langemann, H; Feuerstein, T; Mendelowitsch, A; Gratzl, O



Carbon-Pt nanoparticles modified TiO2 nanotubes for simultaneous detection of dopamine and uric acid.  


The present work describes sensing application of modified TiO2 nanotubes having carbon-Pt nanoparticles for simultaneous detection of dopamine and uric acid. The TiO2 nanotubes electrode was prepared using anodizing method, followed by electrodeposition of Pt nanoparticles onto the tubes. Carbon was deposited by decomposition of polyethylene glycol in a tube furnace to improve the conductivity. The C-Pt-TiO2 nanotubes modified electrode was characterized by cyclic voltammetry and differential pulse voltammetry methods. The modified electrode displayed high sensitivity towards the oxidation of dopamine and uric acid in a phosphate buffer solution (pH 7.00). The electro-oxidation currents of dopamine and uric acid were linearly related to the concentration over a wide range of 3.5 x 10(-8) M to 1 x 10(-5) M and 1 x 10(-7) M to 3 x 10(-5) M respectively. The limit of detection was determined as 2 x 10(-10) M for dopamine at signal-to-noise ratio of 3. The interference of uric acid was also investigated. Electro-oxidation currents of dopamine in the presence of fix amount of uric acid represented a linear behaviour towards successive addition of dopamine in range of 1 x 10(-7) M to 1 x 10(-5) M. Furthermore, in a solution containing dopamine, uric acid and ascorbic acid the overlapped oxidation peaks of dopamine and ascorbic acid could be easily separated by using C-Pt-TiO2 nanotubes modified electrode. PMID:22103066

Mahshid, Sara; Luo, Shenglian; Yang, Lixia; Mahshid, Sahar Sadat; Askari, Masoud; Dolati, Abolghasem; Cai, Qingyun



Renal metabolism of uric acid in type I insulin-dependent diabetic patients: relation to metabolic compensation.  


Patients with insulin-dependent diabetes mellitus and poor glycemic control show hypouricemia with hyperuricosuria. In the present study, we have evaluated whether a good glycemic control influences the renal handling of uric acid. Sixteen patients (8 male, mean age 22.4 +/- 7.2 years) were studied under two situations, poor glycemic control (glycemia > 11 mmol/L and HbA1 c > 10%) and good glycemic control (glycemia < 6 mmol/L and HbA1 c < 8.5%). A group of 16 normal subjects served as the control group (8 male, mean age 21.9 +/- 9.1 years). In the poor glycemic control phase, patients showed lower plasma uric acid levels (0.18 +/- 0.06 mmol/L) and higher fractional urinary excretion of uric acid (16.1 +/- 9.3%) than the controls (0.28 +/- 0.06 and 8.2 +/- 1.9%, respectively). When a good glycemic control was reached, plasma uric acid increased (0.22 +/- 0.05), but it was still lower than that of the controls and fractional excretion of UA was normalized. Plasma uric acid was inversely correlated to glycemia (r = -0.34, p < 0.05) and to HbA1 c (r = -0.56, p < 0.0008) and fractional excretion of uric acid was directly correlated to glycemia (r = 0.39, p < 0.03) and HbA1 c (r = 0.73, p < 0.00005). These results indicate that the hypouricemia and hyperuricosuria of insulin-dependent diabetes mellitus is corrected by an adequate glycemic control, suggesting that these alterations are of a functional origin and due to a defective metabolic control. PMID:9405981

González-Sicilia, L; García-Estañ, J; Martínez-Blázquez, A; Fernández-Pardo, J; Quiles, J L; Hernández, J



Uric acid renal handling: spontaneous changes and influence of a thiazide alone or associated with triamterene.  


The spontaneous changes in renal handling of uric acid, the consequences of methyclothiazide (M) and of a combination of M with three doses of triamterene (25, 50, 75 mg) were assessed in eight normal men, in a ten-week placebo controlled, double-blind study. In untreated subjects, significant correlations were found between blood uric acid (bUA) and UAV, between bUA and FeUA, between FeUA and plasma renin activity (PRA) and between bUA and PRA. Spontaneous variations in bUA and UAV were shown to be predominantly dependent on changes in sodium status. All diuretics significantly increased bUA and decreased FeUA. Under diuretics, bUA kept correlations with FeUA and PRA similar to that observed in untreated subjects indicating that the changes were dependent only on variations in renal transport induced by changes in sodium status. Addition of triamterene to methyclothiazide significantly lessened the thiazide induced abnormalities in UA. PMID:3410590

Labeeuw, M; Pozet, N; Aissa, A H; Zech, P Y; Sassard, J; Laville, M



[Influence of acute administration of ramipril on the excretion of uric acid].  


The influence of a new ACEI, Ramipril (R) on renal handling of UA was investigated. 13 hypertensives with normal renal function received either R (10 mg p.o.) or placebo (P). Arterial pressure (AP), GFR (Inulin clearance), Renal Plasma Flow (RPF, PAH clearance), UA urinary excretion (UAV) and fractional clearance (FeAU: UA clearance/GFR) were studied for seven hours after drug administration. GFR remained stable in all cases. R had no effect on sodium excretion rate. Compared to P, R significantly increased UAV by 25 p. 100, FeAU by 32 p. 100, RPF by 26.5 p. 100 and decreased mean arterial pressure (MAP) by 10 p. 100. ACE activity was maximally suppressed at 2 hours. More than 80 p. 100 of the maximal changes in UAU and FeAU were observed within the first two hours, while a progressive increase in RPF up to the fifth hour, and a progressive fall in MAP up to the fourth hour was evident. Except for PAM, all these changes were still present at the end of the study (seventh hour). In conclusion, Ramipril increases the fractional excretion of uric acid. This effect is observed independently of any change in sodium balance and preceeds by two to three hours the changes in renal hemodynamics. The simultaneous changes in FeAU and in ACE activity indicate that the effect on uric acid excretion is presumably due to the fall in angiotensin concentration. PMID:2959232

Labeeuw, M; Pozet, N; Zech, P Y; Hadj-Aissa, A; Finaz de Villaine, J; Laville, M



Enzyme-entrapped mesoporous silica for treatment of uric acid disorders.  


Gout is an abnormality in the body resulting in the accumulation of uric acid mainly in joints. Dissolution of uric acid crystals into soluble allantoin by the enzyme uricase might provide a better alternative for the treatment of gout. This work aims to investigate the feasibility of a transdermal patch loaded with uricase for better patient compliance. Mesoporous silica (SBA-15) was chosen as the matrix for immobilisation of uricase. Highly oriented mesoporous SBA-15 was synthesized, characterized and uricase was physisorbed in the mesoporous material. The percentage adsorption and release of enzyme in borate buffer was monitored. The release followed linear kinetics and greater than 80% enzyme activity was retained indicating the potential of this system as an effective enzyme immobilization matrix. The enzyme permeability was studied with Wistar rat skin and human cadaver skin. It was found that in case of untreated rat skin 10% of enzyme permeated through skin in 100 h. The permeation increased by adding permeation enhancer (combination of oleic acid in propylene glycol (OA in PG)). The permeation enhancement was studied under two concentrations of OA in PG (1%, 5%) in both rat and human cadaver skin and it was found that 1% OA in PG showed better result in rat skin and 5% OA in PG showed good results in human cadaver skin. PMID:23802423

Muthukoori, Shanthini; Narayanan, Naagarajan; Chandra, Manuguri Sesha Sarath; Sethuraman, Swaminathan; Krishnan, Uma Maheswari



Prooxidant and antioxidant properties of human serum ultrafiltrates toward LDL: important role of uric acid.  


Oxidized LDL is present within atherosclerotic lesions, demonstrating a failure of antioxidant protection. A normal human serum ultrafiltrate of Mr below 500 was prepared as a model for the low Mr components of interstitial fluid, and its effects on LDL oxidation were investigated. The ultrafiltrate (0.3%, v/v) was a potent antioxidant for native LDL, but was a strong prooxidant for mildly oxidized LDL when copper, but not a water-soluble azo initiator, was used to oxidize LDL. Adding a lipid hydroperoxide to native LDL induced the antioxidant to prooxidant switch of the ultrafiltrate. Uric acid was identified, using uricase and add-back experiments, as both the major antioxidant and prooxidant within the ultrafiltrate for LDL. The ultrafiltrate or uric acid rapidly reduced Cu2+ to Cu+. The reduction of Cu2+ to Cu+ may help to explain both the antioxidant and prooxidant effects observed. The decreased concentration of Cu2+ would inhibit tocopherol-mediated peroxidation in native LDL, and the generation of Cu+ would promote the rapid breakdown of lipid hydroperoxides in mildly oxidized LDL into lipid radicals. The net effect of the low Mr serum components would therefore depend on the preexisting levels of lipid hydroperoxides in LDL. These findings may help to explain why LDL oxidation occurs in atherosclerotic lesions in the presence of compounds that are usually considered to be antioxidants. PMID:12562831

Patterson, Rebecca A; Horsley, Elizabeth T M; Leake, David S



Increased urinary uric acid excretion: a finding in Indian stone formers.  


Many studies have been done to determine the risk factors associated with urolithiasis so that preventive measures can be undertaken to prevent stone formation. However the exact aetiology of urinary stones still remains elusive. A prospective control study of epidemiological factors that influence urinary stone formation was done to determine the aetiology of urinary stones. Patients with stone disease had a significantly higher body mass index. 24-h urine excretion of uric acid and phosphate was found to be significantly higher in stone patients as compared to controls. The intake of non-vegetarian food was significantly higher amongst stone formers. Stone patients had a significantly higher consumption of curd and cheese as compared to controls. There was a significant correlation noted between stone formation and a positive family and past history of stone disease. The results indicate that obese patients, especially those with a family history of stone disease, should be counselled on weight loss. Individuals with a past history of stone disease should be advised to reduce their dietary intake of foods rich in uric acid (meat, liver and beans). PMID:19921166

Sinha, Tapan; Karan, S C; Kotwal, Atul



Uric acid as a danger signal in gout and its comorbidities  

PubMed Central

Uric acid is a waste product of purine catabolism. This molecule comes to clinical attention when it nucleates to form crystals of monosodium urate (MSU) in joints or other tissues and thereby causes the inflammatory disease of gout. Patients with gout also frequently suffer from a number of co-morbid conditions including hypertension, diabetes mellitus and cardiovascular disease. Why MSU crystals trigger inflammation and are associated with comorbidities of gout has been unclear, but recent studies provide new insights these issues. Rather than simply being a waste product, uric acid could serve a pathophysiological role as a local alarm signal that alerts the immune system to cell injury and helps to trigger both innate and adaptive immune responses. The inflammatory component of these immune responses is caused when urate crystals trigger both inflammasome-dependent and independent pathways to generate the proinflammatory cytokine IL-1. The resulting bioactive IL-1 stimulates the inflammation of gout and might contribute to the development of other comorbidities. Surprisingly, the same mechanisms underlie the inflammatory response to a number of irritant particles, many of which also cause disease. These new insights help to explain the pathogenesis of gout and point to potential new therapeutic targets for this and other sterile inflammatory diseases.

Rock, Kenneth L.; Kataoka, Hiroshi; Lai, Jiann-Jyh



Serum glutathione S-transferase concentrations and creatinine clearance after sevoflurane anaesthesia.  


The effects of sevoflurane and isoflurane on serum glutathione S-transferase concentrations and creatinine clearance were compared in 50 ASA I-III patients aged over 18 years undergoing body surface surgery of 1-3 h predicted duration. Patients randomly received sevoflurane (n = 24) or isoflurane (n = 26) in nitrous oxide and oxygen (FIO2 = 0.4) via a nonrebreathing system. Fluids were standardised and patient's lungs ventilated to normocapnia. Expired concentration of anaesthetic agent was adjusted to maintain systolic arterial pressure between 70 and 100% of baseline. Patients received significantly less (p < 0.05) sevoflurane (1.0 MAC-h) than isoflurane (1.5 MAC-h). Using serum glutathione S-transferase concentrations and creatinine clearance as markers of hepatic and renal function respectively, no statistically significant differences were identified between the groups. PMID:9059093

Darling, J R; Murray, J M; McBride, D R; Trinick, T R; Fee, J P



[Could cystatine C replace creatinine as a market of glomerular filtration rate?].  


Measurement of glomerular filtartion rate (GFR) is crucial for the detection and follow-up of an early renal impairment. Inulin clearance or radio-isotopes are the gold standard but they cannot be used routinely. Serum creatinine and creatinine clearance are the most widely used, but they lack sensibility to detect an early renal impairment and in cases of obesity, malnutrition or advanced age. Looking for a more reliable marker is necessary and cystatin C seems to be interesting. This molecule is constantly produced by nucleated cells, then freely filtrated and catabolized in the proximal tube. Clinical studies showed that cystatin C might be a more reliable marker of GFR in determined groups of patients. Moreover this molecule may have an other interest as a predictive risk factor or mortality, especially for cardiovascular events. PMID:16562601

Chollet-Dallon, E; Stoermann-Chopard, C; Martin, P Y



Uric acid: A new look at an old risk marker for cardiovascular disease, metabolic syndrome, and type 2 diabetes mellitus: The urate redox shuttle  

Microsoft Academic Search

BACKGROUND: The topical role of uric acid and its relation to cardiovascular disease, renal disease, and hypertension is rapidly evolving. Its important role both historically and currently in the clinical clustering phenomenon of the metabolic syndrome (MS), type 2 diabetes mellitus (T2DM), atheroscleropathy, and non-diabetic atherosclerosis is of great importance. RESULTS: Uric acid is a marker of risk and it

Melvin R Hayden; Suresh C Tyagi



Differential changes in serum uric acid concentrations in sibutramine promoted weight loss in diabetes: results from four weeks of the lead-in period of the SCOUT trial  

Microsoft Academic Search

BACKGROUND AND AIMS: Elevated levels of serum uric acid are associated with an increased risk of cardiovascular morbidity and mortality. The response of uric acid to weight loss therapy (lifestyle plus sibutramine) in an overweight and obese cardiovascular high risk population was studied. METHODS AND RESULTS: Data from a four week single-blind lead-in period of the Sibutramine Cardiovascular OUTcomes (SCOUT)

Charlotte Andersson; Peter Weeke; Bente Brendorp; Lars Køber; Emil L Fosbøl; Arya M Sharma; Nick Finer; Ian D Caterson; Richard A Rode; Philip T James; Christian Torp-Pedersen



Salvage of blood urea nitrogen in sheep is highly dependent on plasma urea concentration and the efficiency of capture within the digestive tract.  


The aims of this study were 1) to determine whether transfer of blood urea to the gastrointestinal tract (GIT) or the efficiency of capture of urea N within the GIT is more limiting for urea N salvage, and 2) to establish the relationship between plasma urea concentration and recycling of urea N to the GIT. We used an i.v. urea infusion model in sheep to elevate the urea entry rate and plasma concentrations, thus avoiding direct manipulation of the rumen environment that otherwise occurs when feeding additional N. Four growing sheep (28.1 +/- 0.6 kg of BW) were fed a low-protein (6.8% CP, DM basis) diet and assigned to 4 rates of i.v. urea infusion (0, 3.8, 7.5, or 11.3 g of urea N/d; 10-d periods) in a balanced 4 x 4 Latin square design. Nitrogen retention (d 6 to 9), urea kinetics([(15)N2]urea infusion over 80 h), and plasma AA were determined. Urea infusion increased apparent total tract digestibility of N (29.9 to 41.3%) and DM (47.5 to 58.9%), and N retention (1.45 to 5.46 g/d). The plasma urea N entry rate increased (5.1 to 21.8 g/d) with urea infusion, as did the amount of urea N entering the GIT (4.1 to 13.2 g/d). Urea N transfer to the GIT increased with plasma urea concentration, but the increases were smaller at greater concentrations of plasma urea. Anabolic use of urea N within the GIT also increased with urea infusion (1.43 to 2.98 g/d; P = 0.003), but anabolic use as a proportion of GIT entry was low and decreased (35 to 22%; P = 0.003) with urea infusions. Consequently, much (44 to 67%) of the urea N transferred to the GIT returned to the liver for resynthesis of urea (1.8 to 9.2 g/d; P < 0.05). The present results suggest that transfer of blood urea to the GIT is 1) highly related to blood urea concentration, and 2) less limiting for N retention than is the efficiency of capture of recycled urea N by microbes within the GIT. PMID:17202392

Sunny, N E; Owens, S L; Baldwin, R L; El-Kadi, S W; Kohn, R A; Bequette, B J



Response of renal orotic acid and creatinine to treatments affecting metabolic protein supply of ruminants  

Microsoft Academic Search

90 urine samples obtained in three lamb trials and one experiment using adult wethers were analyzed for their contents of orotic acid and creatinine. The average daily excretion of orotic acid accounted for 0.5 mg to 1.5 mg (35 ?g to 130 ?g\\/W) with a high individual variation. Correlation coefficients between orotic acid and other urinary constituents were low indicating

M. Kreuzer; Eva Vertesy; M. Kirchgessner



Urinary protein and albumin excretion corrected by creatinine and specific gravity  

Microsoft Academic Search

Timed urine collections are difficult to use in clinical practice owing to inaccurate collections making calculations of the 24-h albumin or protein excretion questionable. One of our goals was to assess the ‘correction’ of urinary albumin and (or) protein excretion by dividing these by either the creatinine concentration or the term, (specific gravity?1)×10011Note that the term, (SG-1)×100 increases with the

David J. Newman; Michael J. Pugia; John A. Lott; Jane F. Wallace; Andrew M. Hiar



Diagnostic accuracy of urinary protein-to-creatinine ratio in a tertiary referral centre  

Microsoft Academic Search

BackgroundThe gold standard for diagnosing proteinuria in pregnancy is ?300 mg of protein in a 24-h urine collection.1 Practical considerations have reduced the utility of this investigation and National Institute for Health and Clinical Excellence have recommended that a diagnosis of significant proteinuria can be made using a spot urinary protein-to-creatinine ratio (PCR).2 Given the reported variation in protein assay

S J Wang; J Myers



Adjustment of Creatinine-Adjusted Value to Urine Flow Rate in Lead Workers  

Microsoft Academic Search

Two male lead workers, aged 57 and 51 y, were studied to compare the urinary flow\\/creatinine-adjusted values published earlier by Araki et al. and by Greenberg and Levine. We collected 24-h urine samples once a month for 31 mo and 16 mo for workers 1 and 2, respectively. The workers' urinary excretions of lead, delta-aminolevulinic acid, and coproporphyrin were measured.

Fumihiro Sata; Shunichi Araki



Inflammation and dietary protein intake exert competing effects on serum albumin and creatinine in hemodialysis patients  

Microsoft Academic Search

Inflammation and dietary protein intake exert competing effects on serum albumin and creatinine in hemodialysis patients.BackgroundCross-sectional studies have shown an inverse correlation between serum C-reactive protein (CRP) and serum albumin concentration in hemodialysis patients. The net effects of inflammation and dietary protein intake on nutritional markers over time are unknown.MethodsTo explore the effects of CRP and normalized protein catabolic rate

George A Kaysen; Glenn M Chertow; Rohini Adhikarla; Belinda Young; Claudio Ronco; Nathan W Levin



Renal clearance of pancreatic and salivary amylase relative to creatinine in patients with chronic renal insufficiency  

Microsoft Academic Search

Pancreatic and salivary amylase\\/creatinine clearance ratios in patients with various degrees of renal impairment were compared with those obtained for control subjects. In chronic renal insufficiency (mean GFR 30 ml\\/min +\\/- 15 SD; n = 13) the clearance ratios for pancreatic (mean 3.5 +\\/- 1.85 SD) and salivary (mean 2.3 +\\/- 1.3 SD) amylase were significantly higher (P less than

J B Keogh; K F McGeeney; M I Drury; T B Counihan; M D ODonnell



Electrochemical and Spectroscopic Studies of Co(CREATININE)2Cl2  

Microsoft Academic Search

The electrochemical behavior of Co(creatinine)2Cl2 was investigated by cyclic voltammetry in organic solvents (DMSO and DMF) and in aqueous solution. Analysis of the results indicates that the electroactive species depend on the nature of the solvent. In DMF a single reduction process Co(II)\\/Co(I) is observed. In DMSO the redox behavior of the complex changes with the scan rate and a

B. S. Parajón Costa; A. C. González Baró; E. J. Baran



A New Equation for Estimating Renal Function Using Age, Body Weight and Serum Creatinine  

Microsoft Academic Search

Background: Many formulas have been developed to estimate glomerular filtration rate (GFR). The aim of our study was to propose a new, more reliable equation. Methods: The study considered 530 subjects (training sample) with M\\/F 280\\/250, age 57.1 ± 17.4, creatinine clearance (CrCl) 55.2 ± 38.2 (range 2.1–144.0) for the development the new equation. A linear model was used to

Giovambattista Virga; Flavio Gaspari; Karl Thomaseth; Marilena Cara; Stefania Mastrosimone; Vittorio Rossi



Creatol, a Creatinine Metabolite, as a Useful Determinant of Renal Function  

Microsoft Academic Search

Analysis of creatoi (CTL, 5-hydroxycreatinine), an oxidative creatinine (Cr) metabolite, in serum and urine of human subjects has indicated that CTL is a useful determinant of renal function. The existence itself of serum CTL (s-CTL) could be a diagnostic sign for chronic renal failure (CRF): in all normal subjects, s-CTL was undetectable, but s-CTL was detectable in sera of all

Ko Nakamura; Kazuharu Ienaga; Koji Nakano; Masahiko Nakai; Yoshio Nakamura; Goji Hasegawa; Manabu Sawada; Motoharu Kondo; Hiroshi Mori; Takahiro Kanatsuna



Novel cardiac protective effects of urea: from shark to rat  

PubMed Central

This study was carried out to investigate novel cardioprotective effects of urea and the underlying mechanisms. The cardiac functions under oxidative stress were evaluated using Langendorff perfused isolated heart.Isolated dogfish shark hearts tolerated the oxidative stress generated by electrolysis (10?mA, 1?min) of the perfusion solution (n=4), and also showed normal cardiac functions during post-ischaemia reperfusion (n=4). The high concentration of urea (350?mM) in the heart perfusate was indispensable for maintaining the normal cardiac functions of the shark heart.Urea at 3–300?mM (n=4 for each group) protected the isolated rat heart against both electrolysis-induced heart damage and post-ischaemia reperfusion-induced cardiac injury.A concentration-dependent scavenging effect of urea (3–300?mM, n=4 for each group) against electrolysis-induced reactive oxygen species was also demonstrated in vitro.Urea derivatives as hydroxyurea, dimethylurea, and thiourea had antioxidant cardioprotective effect against the electrolysis-induced cardiac dysfunction of rat heart, but were not as effective as urea in suppressing the post-ischaemia reperfusion injury.Our results suggest that urea and its derivatives are potential antioxidant cardioprotective agents against oxidative stress-induced myocardium damage including the post-ischaemia reperfusion-induced injury.

Wang, Xintao; Wu, Lingyun; Aouffen, M'hamed; Mateescu, Mircea-Alexandru; Nadeau, Reginald; Wang, Rui



Aqueous urea solution destabilizes Abeta(16-22) oligomers.  


We use long multiple trajectories generated by molecular dynamics simulations to probe the stability of oligomers of Abeta(16-22) (KLVFFAE) peptides in aqueous urea solution. High concentration of urea promotes the formation of beta-strand structures in Abeta(16-22) monomers, whereas in water they adopt largely compact random coil structures. The tripeptide system, which forms stable antiparallel beta-sheet structure in water, is destabilized in urea solution. The enhancement of beta-strand content in the monomers and the disruption of oligomeric structure occur largely by direct interaction of urea with the peptide backbone. Our simulations suggest that the oligomer unbinding dynamics is determined by two opposing effects, namely, by the increased propensity of monomers to form beta-strands and the rapid disruption of the oligomers. The qualitative conclusions are affirmed by using two urea models. Because the proposed destabilization mechanism depends largely on hydrogen bond formation between urea and the peptide backbone, we predict that high urea concentration will destabilize oligomers of other amyloidogenic peptides as well. PMID:15465917

Klimov, D K; Straub, John E; Thirumalai, D



A sensitive method for determining nitrogen-15 isotope in urea  

Microsoft Academic Search

A method is presented in which the 15N?at.% of urea is determined with high precision on liquid samples containing as little as 10?nmol of urea. The method involves\\u000a removal of interference from NH4\\u000a \\u000a + initially present in the sample by cation exchange. Urea in the sample is subsequently hydrolyzed to NH4\\u000a \\u000a + by the enzyme urease. Liberated NH4\\u000a \\u000a + is

S. Rysgaard; N. Risgaard-Petersen



Chroman and tetrahydroquinoline ureas as potent TRPV1 antagonists.  


Novel chroman and tetrahydroquinoline ureas were synthesized and evaluated for their activity as TRPV1 antagonists. It was found that aryl substituents on the 7- or 8-position of both bicyclic scaffolds imparted the best in vitro potency at TRPV1. The most potent chroman ureas were assessed in chronic and acute pain models, and compounds with the ability to cross the blood-brain barrier were shown to be highly efficacious. The tetrahydroquinoline ureas were found to be potent CYP3A4 inhibitors, but replacement of bulky substituents at the nitrogen atom of the tetrahydroisoquinoline moiety with small groups such as methyl can minimize the inhibition. PMID:21315587

Schmidt, Robert G; Bayburt, Erol K; Latshaw, Steven P; Koenig, John R; Daanen, Jerome F; McDonald, Heath A; Bianchi, Bruce R; Zhong, Chengmin; Joshi, Shailen; Honore, Prisca; Marsh, Kennan C; Lee, Chih-Hung; Faltynek, Connie R; Gomtsyan, Arthur



Predictive model for segmented poly(urea)  

NASA Astrophysics Data System (ADS)

Segmented poly(urea) has been shown to be of significant benefit in protecting vehicles from blast and impact and there have been several experimental studies to determine the mechanisms by which this protective function might occur. One suggested route is by mechanical activation of the glass transition. In order to enable design of protective structures using this material a constitutive model and equation of state are needed for numerical simulation hydrocodes. Determination of such a predictive model may also help elucidate the beneficial mechanisms that occur in polyurea during high rate loading. The tool deployed to do this has been Group Interaction Modelling (GIM) - a mean field technique that has been shown to predict the mechanical and physical properties of polymers from their structure alone. The structure of polyurea has been used to characterise the parameters in the GIM scheme without recourse to experimental data and the equation of state and constitutive model predicts response over a wide range of temperatures and strain rates. The shock Hugoniot has been predicted and validated against existing data. Mechanical response in tensile tests has also been predicted and validated.

Gould, P. J.; Cornish, R.; Frankl, P.; Lewtas, I.



Urea as a cosurfactant in enhanced oil recovery processes  

SciTech Connect

A surfactant system useful for oil recovery comprising salt water, a surfactant, such as a petroleum sulfonate, and urea. Optionally, a C/sub 3/ to C/sub 8/ alcohol is additionally present as a cosurfactant.

Stapp, P. R.; Chaney, M. B.



Urea as an Ice Nucleant for Supercooled Clouds.  

National Technical Information Service (NTIS)

Urea was observed to have extraordinary ice-nucleating properties in laboratory and natural clouds. Ice nucleation was induced in laboratory clouds at temperatures as warm as +6C. The nucleation mechanism involves the high endothermic heat of solution and...

R. G. Knollenberg



Photodegradation of MDI Based Polyurethane/Urea Elastomers.  

National Technical Information Service (NTIS)

A series of polyurethane urea and polyurea elastomers based on MDI, a chain extender such as ethylene glycol or ethylene diamine, and polyethylene glycol oligomers or amine end capped modified polyethylene glycol oligomers were synthesized and characteriz...

C. E. Hoyle H. Shah K. Moussa P. Berry I. B. Rufus



Reinvestigation of growth of thiourea urea zinc sulfate crystal.  


Reinvestigation of the growth of thiourea urea zinc sulfate crystal is reported. Aqueous reaction of thiourea, urea and zinc sulfate in 1:1:1mol ratio results in the formation of the well known [Zn(tu)3(SO4)] (1) (tu=thiourea) crystal and not the 'so called' novel semiorganic nonlinear optical thiourea urea zinc sulfate (2) crystal, as claimed by Redrothu Hanumantha Rao, S. Kalainathan, Spectroscopic investigation, nucleation, growth, optical, thermal and second harmonic studies of novel semi-organic nonlinear optical crystal - Thiourea urea zinc sulfate, Spectrochim. Acta A97 (2012) 456-463. In this work, we demonstrate the usefulness of elemental analytical data, infrared and NMR spectra and X-ray powder pattern, for accurate product characterization. PMID:24060627

Srinivasan, Bikshandarkoil R; Naik, Teja A; Tylczy?ski, Zbigniew; Priolkar, K R



21 CFR 862.1770 - Urea nitrogen test system.  

Code of Federal Regulations, 2013 CFR




Urea biosensors based on PVC membrane containing palmitic acid.  


A new urea biosensor was prepared by immobilizing urease with four different procedures on poly(vinylchloride) (PVC) ammonium membrane electrode containing palmitic acid by using nonactine as an ammonium-ionophore. The analytical characteristics were investigated and were compared those of the biosensor prepared by using carboxylated PVC. The effect of pH, buffer concentration, temperature, urease concentration, stirring rate and enzyme immobilization procedures on the response to urea of the enzyme electrode were investigated. The linear working range and sensitivity of the biosensor were also determined. The urea biosensor prepared by using the PVC membranes containing palmitic acid showed more effective performance than those of the carboxylated PVC based biosensors. Additionally, urea assay in serum was successfully carried out by using the standard addition method. PMID:16152697

Karaku?, Emine; Pekyardimci, Sule; Esma, Kiliç



Highly sensitive urea sensing with ion-irradiated polymer foils  

NASA Astrophysics Data System (ADS)

Recently we prepared urea-sensors by attaching urease to the inner walls of etched ion tracks within thin polymer foil. Here, alternative track-based sensor configurations are examined where the enzyme remained in solution. The conductivities of systems consisting of two parallel irradiated polymer foils and confining different urea/urease mixtures in between were examined. The correlations between conductivity and urea concentration differed strongly for foils with unetched and etched tracks, which points at different sensing mechanisms - tentatively attributed to the adsorption of enzymatic reaction products on the latent track entrances and to the enhanced conductivity of reaction product-filled etched tracks, respectively. All examined systems enable in principle, urea sensing. They point at the possibility of sensor cascade construction for more sensitive or selective sensor systems.

Fink, Dietmar; Muñoz Hernandez, Gerardo; Alfonta, Lital



Simultaneous determination of uric acid metabolites allantoin, 6-aminouracil, and triuret in human urine using liquid chromatography–mass spectrometry  

Microsoft Academic Search

Uric acid (UA) can be directly converted to allantoin enzymatically by uricase in most mammals except humans or by reaction with superoxide. UA can react directly with nitric oxide to generate 6-aminouracil and with peroxynitrite to yield triuret; both of these metabolites have been identified in biological samples. We now report a validated high-performance liquid chromatography and tandem mass spectrometry

Kyung Mee Kim; George N. Henderson; Reginald F. Frye; Cheryl D. Galloway; Nancy J. Brown; Mark S. Segal; Witcha Imaram; Alexander Angerhofer; Richard J. Johnson



Intake of Added Sugar and Sugar-Sweetened Drink and Serum Uric Acid Concentration in US Men and Women  

Technology Transfer Automated Retrieval System (TEKTRAN)

Fructose-induced hyperuricemia might have a causal role in metabolic syndrome, hypertension, and other chronic disease. However, no study has investigated whether sugar added to foods or sugar-sweetened beverages, which are major sources of fructose, are associated with serum uric acid concentration...


Potential role of uric acid in metabolic syndrome, hypertension, kidney injury, and cardiovascular diseases: is it time for reappraisal?  


Elevated serum uric acid concentration is a common laboratory finding in subjects with metabolic syndrome/obesity, hypertension, kidney disease and cardiovascular events. Hyperuricemia has been attributed to hyperinsulinemia in metabolic syndrome and to decreased uric acid excretion in kidney dysfunction, and is not acknowledged as a main mediator of metabolic syndrome, renal disease, and cardiovascular disorder development. However, more recent investigations have altered this traditional view and shown, by providing compelling evidence, to support an independent link between hyperuricemia and increased risk of metabolic syndrome, diabetes, hypertension, kidney disease and cardiovascular disorders. However, despite these new findings, controversy regarding the exact role of uric acid in inducing these diseases remains to be unfolded. Furthermore, recent data suggest that the high-fructose diet in the United State, as a major cause of hyperuricemia, may be contributing to the metabolic syndrome/obesity epidemic, diabetes, hypertension, kidney disease and cardiovascular disorder. Our focus in this review is to discuss the available evidence supporting a role for uric acid in the development of metabolic syndrome, hypertension, renal disease, and cardiovascular disorder; and the potential pathophysiology mechanisms involved. PMID:23588856

Soltani, Zohreh; Rasheed, Kashaf; Kapusta, Daniel R; Reisin, Efrain



Determination of uric acid in human saliva by high-performance liquid chromatography with amperometric electrochemical detection  

Microsoft Academic Search

The aim of the present study is to establish a highly sensitive method for the determination of uric acid (UA) in human saliva. The monitoring of UA levels in less invasive biological samples such as saliva is suggested for the diagnosis and therapy of gout, hyperuricemia, and the Lesch–Nyhan syndrome, and for detecting such conditions as alcohol dependence, obesity, diabetes,

Koichi Inoue; Tatsuya Namiki; Yusuke Iwasaki; Yoshihiro Yoshimura; Hiroyuki Nakazawa



A longitudinal study of the influence of shift work on serum uric acid levels in workers at a telecommunications company  

Microsoft Academic Search

Background Hyperuricemia is a lifestyle-related disease. Although there have been many previous reports about the association of serum uric acid (UA) levels with lifestyle, including eating habits and alcohol intake, there has been no report of a longitudinal study of the relationship between serum UA levels and shift work. Aims To clarify the influence of shift work on serum UA

Mirei Uetani; Yasushi Suwazono; Etsuko Kobayashi; Takeya Inaba; Mitsuhiro Oishi; Koji Nogawa



Intrinsic reactivity of uric acid with dioxygen: Towards the elucidation of the catalytic mechanism of urate oxidase  

Microsoft Academic Search

Urate oxidase catalyzes the transformation of uric acid in 5-hydroxyisourate, an unstable compound which is latter decomposed into allantoïn. Crystallographic data have shown that urate oxidase binds a dianion urate species deprotonated in N3 and N7, while kinetics experiments have highlighted the existence of several intermediates during catalysis. We have employed a quantum mechanical approach to analyze why urate oxidase

Muhannad Altarsha; Bertrand Castro; Gérald Monard



Menopause, postmenopausal hormone use and serum uric acid levels in US women – The Third National Health and Nutrition Examination Survey  

Microsoft Academic Search

INTRODUCTION: Despite the substantial prevalence of gout in the ageing female population, female hormonal influence has not been comprehensively examined. We evaluated and quantified the potential independent association between menopause, postmenopausal hormone use and serum uric acid levels in a nationally representative sample of women. METHODS: Using data from 7662 women aged 20 years and older in the Third National

A Elisabeth Hak; Hyon K Choi



A vasodilating ?1 blocker celiprolol inhibits muscular release of uric acid precursor in patients with essential hypertension.  


Although nonvasodilating ?1 blockers increase the levels of uric acid in serum, it is not known whether vasodilating ?1 blockers have a similar effect. In the present study, we evaluated the effect of celiprolol on the release of hypoxanthine, a uric acid precursor, from muscles after an exercise. We used the semi-ischemic forearm test to examine the release of lactate (?LAC), ammonia (?Amm), and hypoxanthine (?HX) before and 4, 10, and 60 min after an exercise in 18 hypertensive patients as well as 4 normotensive subjects. Before celiprolol treatment, all the levels of ?HX and ?Amm, and ?LAC were increased by semi-ischemic exercise in hypertensive patients, and the increases were remarkably larger than those in normotensive subjects. Celiprolol decreased both systolic and diastolic pressure. It also decreased the levels of ?HX and ?Amm without changes in ?LAC after an exercise. These findings also were confirmed by summation of each metabolite (??Metabolites). Celiprolol caused a marginal decrease of serum uric acid, but the difference was not statistically significant. On the other hand, nonvasodilating ?1 blockers did not suppress the levels of ?HX and ?Amm, whereas they significantly increased ?LAC after an exercise. Celiprolol improved energy metabolism in skeletal muscles. It suppressed HX production and consequently did not adversely affect serum uric acid levels. PMID:22893261

Mizuta, E; Utami, S B; Ohtahara, A; Endo, S; Mishima, M; Hasegawa, A; Yamada, K; Kato, M; Yamamoto, K; Ogino, K; Ninomiya, H; Miyazaki, S; Hamada, T; Taniguchi, S-i; Cheng, J; Hisatome, I



Prevalence of hyperuricemia and relation of serum uric acid with cardiovascular risk factors in a developing country  

Microsoft Academic Search

BACKGROUND: The prevalence of hyperuricemia has rarely been investigated in developing countries. The purpose of the present study was to investigate the prevalence of hyperuricemia and the association between uric acid levels and the various cardiovascular risk factors in a developing country with high average blood pressures (the Seychelles, Indian Ocean, population mainly of African origin). METHODS: This cross-sectional health

D Conen; V Wietlisbach; P Bovet; C Shamlaye; W Riesen; F Paccaud; M Burnier



Vitamin C, Uric Acid, and Glutathione Gradients in Murine Stratum Corneum and their Susceptibility to Ozone Exposure  

Microsoft Academic Search

The stratum corneum has been recognized as the main cutaneous oxidation target of atmospheric ozone (O3), a major part of photochemical smog. This study reports the presence and distribution of vitamin C, glutathione, and uric acid in murine stratum corneum, and evaluates their susceptibility to acute environmental exposure to O3. Based on tape stripping and a modified extraction method with

Stefan Udo Weber; Jens J. Thiele; Caroll E. Cross; Lester Packer



Concentration of uric acid removed during dialysis. Estimated by multi wavelength and processed ultra violet absorbance spectra.  


The aim of this study was to estimate the concentration of uric acid (UA) optically by using original and processed ultra violet (UV) absorbance spectra's of the spent dialysate. Also the effect of using several wavelengths for estimation was examined. PMID:21097101

Jerotskaja, Jana; Uhlin, Fredrik; Lauri, Kai; Tanner, Risto; Luman, Merike; Fridolin, Ivo



Luminometric single step urea assay using ATP-hydrolyzing urease  

Microsoft Academic Search

An automatic enzyme kinetic luminometric method for determination of small quantities of urea in biological fluids and in microdialysates is presented. The method is based on the ATP-hydrolyzing urease reaction (urea amidohydrolase (ATP-hydrolyzing); EC, moni- tored by a luciferin-luciferase ATP reaction. The assay range is 100 pmol to 50 nmol with a detection limit of 5 mmol\\/L in the

Birgitta Naslund; Lars Stahle; Arne Lundin; Bjorn Anderstam; Peter Arner; Jonas Bergstrom


Mechanism of urea effect on percutaneous absorption of clonidine  

Microsoft Academic Search

The urea effect on skin permeation of clonidine was investigated to reduce a log time and to increase a permeability. ICR\\u000a mouse skin and human skin were used and were assumed to be a two-layer membrane consisted of stratum corneum and viable epidermis.\\u000a The urea acted as a skin denaturant and humectant in the whole epidermis. Also it enhanced the

Young Rho Byun; Seo Young Jeong; Young Ha Kim



Urea loading enhances postfreeze performance of frog skeletal muscle  

Microsoft Academic Search

The wood frog (Rana sylvatica) is a terrestrial hibernator that can accumulate urea as an osmoprotectant in autumn and winter. This study tested the hypothesis\\u000a that elevated urea can also function as a cryoprotectant in this freeze-tolerant species. Performance characteristics (threshold\\u000a stimulus voltage, maximal isometric twitch and tetanic contraction forces, and ½ fatigue time) of isolated gastrocnemius muscles\\u000a were measured

Jon P. Costanzo; Marina Marjanovic; Elizabeth A. Fincel; Richard E. Lee Jr



Reliability of haemodialysis urea kinetic modelling in children  

Microsoft Academic Search

The reliability of urea kinetic modelling (UKM) in paediatric haemodialysis was tested by comparing results of the classic variable volume model (UKM3), a recently introduced two-sample modification of this (UKM2) and direct quantification by a partial dialysate collection method (PDC). Urea generation rate (G) was also found from a 1-week collection of dialysate and urine (OWC). Nine children aged 2–18

Tom Buurl; Mark G. Bradbury; Stephen W. Smye; J. Trevor Brocklebank



Measurement of urea and ammonium concentrations in gastric juice  

Microsoft Academic Search

AIM--To study the effect of known interference in the measurement of urea and ammonium concentrations in samples of gastric juice. METHODS--The effect of pH and ammonium concentration on the o-pthalaldehyde method, the diacetylmonoxime method, a Berthelot linked method and an enzymatic urease method for the measurement of urea in gastric juice was therefore conducted. An enzymatic method of the measurement

W D Neithercut; A M el Nujumi; K E McColl



Agronomic performance of urea briquette applicator in transplanted rice  

Microsoft Academic Search

Field trials were conducted in the Philippines and India during 1989 and 1990 seasons to study comparative yield responses of transplanted rice (Oryza sativa L.) to pillow-shaped urea briquettes (UB) deep placed by an applicator (prototype developed by IFDC) and by hand immediately after transplanting. The applicator-placed UB consistently increased grain yields over the split-applied prilled urea, and the additional

N. K. Savant; P. S. Ongkingco; F. D. Garcia; S. S. Dhane; R. R. Khadse; S. A. Chavan; K. S. Rao



Fractionation of urea-pretreated squid visceral oil ethyl esters  

Microsoft Academic Search

Ethyl esters of squid (Illex argentinus) visceral oil contained 11.8% eicosapentaenoic acid (EPA) and 14.9% docosahexaenoic acid (DHA). The esters were treated with\\u000a urea to increase the contents of EPA and DHA. The non-urea complexing ethyl esters of squid visceral oil contained 28.2% EPA\\u000a and 35.6% DHA. This mixture was fractionated by molecular distillation to further increase the EPA or

Lucy Sun Hwang



Solid-state urea biosensor based on the differential method  

Microsoft Academic Search

In this paper, the solid-state urea biosensor was successfully fabricated based on the differential method, which contains three parts: the SnO2\\/ITO glass electrode used as the pseudoreference electrode; the SnO2\\/ITO glass electrode used as the contrast electrode; and the urease\\/SnO2\\/ITO glass electrode used as the enzyme electrode. Correspondingly, this solid-state urea biosensor was fabricated based on the SnO2\\/ITO glass electrode,

Chung-We Pan; Jung-Chuan Chou; Tai-Ping Sun; Shen-Kan Hsiung



Curing process of phenol-urea-formaldehyde-tannin (PUFT) adhesives  

Microsoft Academic Search

Summary  Phenol-urea-formaldehyde-tannin (PUFT) adhesives have been prepared by copolymerization at room temperature of pine bark tannins\\u000a with phenol-urea-formaldehyde (PUF) prepolymers prepared under varying operating conditions. Differential scanning calorimetry\\u000a (DSC) and dynamic mechanical analysis (DMA) have been used to analyse the curing of prepolymers and adhesives. DSC curves\\u000a were obtained at three different heating rates and, by means of the Model Free

G. Vázquez; F. López-Suevos; J. González-Alvarez; G. Antorrena



Urea Metabolism in Beef Steers Fed Tall Fescue, Orchardgrass, or Gamagrass Hays  

Technology Transfer Automated Retrieval System (TEKTRAN)

Two experiments were conducted to assess effects of endophyte treatments (Exp. 1), forage species, and supplementation (Exp. 2) on urea production, excretion, and recycling in beef steers. Infusion of 15,15N-urea and enrichment of urea in urine samples were used to calculate urea N entry and recyc...


Use of sucrose fatty acid esters in foliar application of urea  

Microsoft Academic Search

Although urea is a good source of nitrogen for foliar application of nitrogen, only a small amount of the urea supplied can be absorbed by the leaves. To increase the absorption of urea by the leaves, the surface must first be wetted to enable urea to penetrate the leaf cuticle or stomata (Frank 1967). The ability of a liquid to

Won Kae Choi; Motoki Ikeda; Yoshio Yamada



Proteins and Amino Acids Triiodothyronine Administration Affects urea Synthesis in Rats  

Microsoft Academic Search

The purpose of the present study was to elucidate the mechanism by which thyroid hormone alters urea synthesis. The relative importance of urea cycle enzyme activities, substrate levels or the levels of urea cycle intermediates on urea production was investi gated in a set of four experiments in which rats were fed a diet supplemented with 6-propyl-2-thiouracil (PTU, a thyroid



NiO nanoparticle-based urea biosensor.  


NiO nanoparticles (NiO-NPs) have been exploited successfully for the fabrication of a urea biosensor. A thin film of NiO nanoparticles deposited on an indium tin oxide (ITO) coated glass substrate serves as an efficient matrix for the immobilisation of urease (Ur), the specific enzyme for urea detection. The prepared bioelectrode (Ur/NiO-NP/ITO/glass) is utilised for urea sensing using cyclic voltammetry and UV-visible spectroscopy. NiO nanoparticles act as electro-catalytic species that are based on the shuttling of electrons between Ni(2+) and Ni(3+) in the octahedral site and result in an enhanced electrochemical current response. The prepared bioelectrode (Ur/NiO-NPs/ITO/glass) exhibits a high sensitivity of 21.3 ?A/(mM (*) cm(2)) and a good linearity in a wide range (0.83-16.65 Mm) of urea concentrations with fast response time of 5s. The low value of the Michaelis-Menten constant (K(m)=0.34 mM) indicates the high affinity of Ur towards the analyte (urea). The high catalytic activity, along with the redox behaviour of NiO-NPs, makes it an efficient matrix for the realisation of a urea biosensor. PMID:22947517

Tyagi, Manisha; Tomar, Monika; Gupta, Vinay


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