Colorimetric Determination Of Urea Research Articles

Colorimetric determination of urea using diacetyl monoxime with strong acids.

Urea is a byproduct of the urea cycle in metabolism and is excreted through urine and sweat. Ammonia, which is toxic at low levels, is converted to the safe storage form of urea, which represents the largest efflux of nitrogen from many organisms. Urea is an important nitrogen source in agriculture, is added to many industrial products, and is a large component in wastewater. The enzyme urease hydrolyzes urea to ammonia and bicarbonate. This reaction is microbially mediated in soils, hydroponic solutions, and wastewater recycling and is catalyzed in vivo in plants using native urease, making measurement of urea environmentally important. Both direct and indirect methods to measure urea exist. This protocol uses diacetyl monoxime to directly determine the concentration of urea in solution. The protocol provides repeatable results and stable reagents with good color stability and simple measurement techniques for use in any lab with a spectrophotometer. The reaction between diacetyl monoxime and urea in the presence of sulfuric acid, phosphoric acid, thiosemicarbazide, and ferric chloride produces a chromophore with a peak absorbance at 520 nm and a linear relationship between concentration and absorbance from 0.4 to 5.0 mM urea in this protocol. The lack of detectable interferences makes this protocol suitable for the determination of millimolar levels of urea in wastewater streams and hydroponic solutions.

Arginase inhibition prevents the low shear stress-induced development of vulnerable atherosclerotic plaques in ApoE−/− mice

AimsWall shear stress differentially regulates the arginase pathway in carotid arteries perfused ex vivo. Specific patterns of wall shear stress can locally determine atherosclerotic plaque size and composition in vivo. The present work investigates the effects of arginase inhibition on shear stress induced plaque composition. Methods and resultsCarotid arteries of apolipoprotein E deficient mice were exposed to high (HSS), low (LSS) and oscillatory (OSS) shear stress conditions by the placement of a local shear stress modifier device for 9 weeks with or without the administration of the arginase inhibitor N-ω-Hydroxy-nor-L-arginine (nor-Noha) (10 mg/kg, i.p., 5 days/week). Carotid arginase activity was measured by colorimetric determination of urea. Atherosclerotic plaque size and composition, arginase expression and cellular localization were assessed by immunohistochemistry. Arginase activity was significantly increased in both LSS and OSS regions as compared to HSS. In the lesions, arginase II isoform co-localized preferentially with EC. Inhibition of arginase by nor-Noha decreased arginase activity and reduced plaque size in both LSS and OSS regions. Arginase inhibition affected mainly the composition of plaques developed in LSS regions by decreasing the total vascular ROS, the number of macrophages, apoptosis rate, lipid and collagen contents. ConclusionsArginase activity is modulated by patterns of wall shear stress in vivo. Chronic inhibition of vascular arginase decreased the size of atherosclerotic lesions in both OSS and LSS regions, whereas changes on plaque composition were more pronounced in plaques induced by LSS. We identified wall shear stress as a key biomechanical regulator of arginase during plaque formation and stability.

The effect of monotherapy and combined therapy with NSC-631570 (Ukrain) on growth of low- and high-metastasizing B16 melanoma in mice

NSC-631570 (ukrain) is a semisynthetic derivative of the Chelidonium majus alcaloids and the alkylans thiotepa. It exerts a selective cytotoxic effect on tumor cells in vitro and in vivo and shows the ability to modulate immunocyte functions. Purpose. The aim of our work was to carry out a comparative investigation of the effects of NSC-631570 alone or in combination with pathogen-associated molecules (PAM) on the growth of low- and high-metastasizing melanoma B16 in mice. NSC-631570 was administered intravenously and PAM intramuscularly to tumor-bearing mice seven times every third day, starting from the second day after the transplantation of tumor cells. The effect of monotherapy and combined therapy on tumor growth was evaluated by the indices of tumor growth inhibition in experimental animals. Cell cycle distribution of cancer cells was determined by flow cytometry. TAP1 and TAP2 expression was evaluated by RT-PCR. The metabolic activity of phagocytes was determined by NBT-test, phagocytosis was tested by flow cytometry, and arginase activity was estimated by colorimetric determination of urea. Combined therapy and monotherapy with NSC-631570 resulted in significant inhibition of tumor growth in melanoma-bearing mice. Monotherapy with Ukrain was more effective in mice with high-metastasizing tumors. The therapeutic efficacy of NSC-631570 used in combination with PAM was more expressed in mice with low-metastasizing melanoma. The effectiveness of monotherapy and combined therapy with NSC-631570 in the treatment of melanoma B16 depends on the biological properties of the tumor and the immune state of the organism.

Regulation of arginase pathway in response to wall shear stress

ObjectiveAlterations of wall shear stress can predispose the endothelium to the development of atherosclerotic plaques. Ample evidence indicates that arginase expression and/or activity correlates with several risk factors for cardiovascular disease including atherosclerosis. We investigated the regulation of arginase pathway in response to distinct patterns of wall shear stress. MethodsIsolated porcine endothelial cells and carotid arterial segments were perfused under unidirectional high shear stress (HSS) or oscillatory shear stress (OSS) for 1 and 3 days. Arginase I and II expression, cellular localization and enzyme activity were, respectively, assessed by Western blot, immunohistochemistry and colorimetric determination of urea. The contribution of arginase to the processes of endothelial dysfunction, cell proliferation and arterial remodeling induced by OSS was evaluated by administration of the arginase inhibitor N-ω-hydroxy-nor-l-arginine (nor-Noha). ResultsOnly arginase II isoform was detected on porcine carotid endothelial cells and on carotid artery. Exposure of arteries to OSS increased arginase II expression and activity as compared to HSS. Inhibition of arginase by nor-Noha improved NO-dependent endothelial function and decreased total vascular ROS formation in arteries submitted to OSS. In addition, inhibition of arginase activity decreased smooth muscle cell proliferation rate with no effect on collagen content after OSS. ConclusionsExposure of carotid artery to oscillatory flow induced a more pronounced activation of arginase as compared to HSS. Inhibition of arginase in arteries exposed to OSS improved NO-dependent endothelial function and decrease smooth muscle cell proliferation rate, both processes are important for the focal development of atherosclerotic plaque.

Colorimetric Determination of Urea in Potable Water using Diacetyldioxime and different Oxidising Agents

Colorimetric Determination of Urea in Potable Water using Diacetyldioxime and different Oxidising Agents

Colorimetric Determination of Urea in Wine

A colorimetric method for the analysis of urea in wine and juices, capable of accurately estimating the urea content at concentrations as low as 1 mg/L, is described. Nitrogen compounds other than carbamido compounds do not interfere with the reaction.

Colorimetric Determination of Urea in Soil Extracts Using an Automated System

AbstractA method is described for using an automated system to determine urea in 2M KCl soil extracts that contain a urease inhibitor (phenylmercuric acetate). The method is sensitive and precise and allows 90–120 extracts to be analysed per day.

Extraction and Colorimetric Determination of Urea in Plants

(1975). Extraction and Colorimetric Determination of Urea in Plants. Acta Agriculturae Scandinavica: Vol. 25, No. 2, pp. 109-112.

A rapid method of evaluating different compounds as inhibitors of urease activity in soils

A simple method of studying the abilities of different compounds to inhibit urease activity in soils is described. It involves determination of the effect of the test compound on the amount of urea hydrolyzed by incubation of soils with urea and toluene at 37°C for 5 hr, urea hydrolysis being estimated by colorimetric determination of urea in the extracts obtained by treatment of the incubated samples with 2 M KC1 containing a urease inhibitor (phenylmercuric acetate). The method is rapid and precise, and it is readily adapted for studies of the rate of inactivation of urease inhibitors in soils.

Extraction and Colorimetric Determination of Urea in Soils

AbstractA simple colorimetric method of determining urea in soils is described. The soil sample is extracted with 2M KCl containing a urease inhibitor (phenylmercuric acetate), and the extract is analyzed for urea by measurement of the red color formed when an aliquot is heated with diacetyl monoxime and thiosemicarbazide under acidic couditions (phosphoric acid‐sulfuric acid medium). The method is sensitive and precise, and it gives quantitative recovery of urea added to soils. The extraction performed is satisfactory for determination of exchangeable ammonium, nitrite, and nitrate by steam distillation methods.

Colorimetric Determination of Urea in Feeds (Report of AOAC Committee)

Abstract The colorimetric DMAB method for urea in feeds was improved with regard to sampling, color reading, and calibration, and the revised method was again studied collaboratively in comparison with the official enzymatic method. Validity of the data was tested by Youden's ranking method. It is recommended that the DMAB method be adopted as official, first action.

Colorimetric Determination of Urea in Feeds

Abstract A collaborative study was undertaken this year on the DMAB method for the colorimetric determination of urea in dry corn samples, which was compared with method 22.023-22.024. The DMAB method uses p-dimethylami-nobenzaldehyde as the color producer for spectrophotometry measurement. Mean values showed excellent recovery by both the official procedure and the DMAB procedure. Over-all standard deviation and coefficient of variation for all three dry corn samples containing urea indicated greater precision and accuracy by the DMAB procedure; collaborators expressed preference for this method. Further work is recommended to finalize the determination of urea in feeds.

Colorimetric Determination of Urea in Feeds

Colorimetric Determination of Urea in Feeds

Studies of Separation and Determination of Cyanamide Derivatives.IV-V. V. A New Colorimetric Determination of Urea

Studies of Separation and Determination of Cyanamide Derivatives.IV-V. V. A New Colorimetric Determination of Urea

Colorimetric Determination of Urea

Colorimetric Determination of Urea

THE COLORIMETRIC DETERMINATION OF UREA IN THE BLOOD OF NORMAL AND UREMIC RATS

THE COLORIMETRIC DETERMINATION OF UREA IN THE BLOOD OF NORMAL AND UREMIC RATS