The effect of drying and urea treatment on nutritional and anti-nutritional components of browses collected during wet and dry seasons

Fibre, crude protein and tannin concentrations were measured in browse species from the semi-arid region of Northeast Brazil during the dry and wet seasons. The effects of oven-, sun- and shade-drying and of urea treatment were also determined. Crude protein (CP) content varied from 103 to 161 g/kg dry matter (DM) and the browses had similar CP content in the two seasons (during 2002) (102-161 and 107-153 g/kg DM in the wet and dry seasons, respectively). Total tannin concentrations ranged from 13 to 201 g/kg DM amongst the browses and were higher in the dry season. A 30-d treatment with urea reduced extractable tannins significantly (P < 0.05). The urea treatment was also most effective at reducing the in vitro effects of tannins compared to the other drying treatments. This was demonstrated by measuring the effect of polyethylene glycol (PEG) on gas production. Addition of PEG increased gas production of oven- (81.4%), sun- (78.5%) and shade-dried (76.7%) samples much more compared to urea treated samples (10.9%). (c) 2005 Elsevier B.V. All rights reserved.

Evaluation of milk urea nitrogen as a diagnostic of protein feeding

An evaluation of milk urea nitrogen (MUN) as a diagnostic of protein feeding in dairy cows was performed using mean treatment data (n = 306) from 50 production trials conducted in Finland (n = 48) and Sweden (n = 2). Data were used to assess the effects of diet composition and certain animal characteristics on MUN and to derive relationships between MUN and the efficiency of N utilization for milk production and urinary N excretion. Relationships were developed using regression analysis based on either models of fixed factors or using mixed models that account for between-experiment variations. Dietary crude protein (CP) content was the best single predictor of MUN and accounted for proportionately 0.778 of total variance [ MUN (mg/dL) = -14.2 + 0.17 x dietary CP content (g/kg dry matter)]. The proportion of variation explained by this relationship increased to 0.952 when a mixed model including the random effects of study was used, but both the intercept and slope remained unchanged. Use of rumen degradable CP concentration in excess of predicted requirements, or the ratio of dietary CP to metabolizable energy as single predictors, did not explain more of the variation in MUN (R-2 = 0.767 or 0.778, respectively) than dietary CP content. Inclusion of other dietary factors with dietary CP content in bivariate models resulted in only marginally better predictions of MUN (R-2 = 0.785 to 0.804). Closer relationships existed between MUN and dietary factors when nutrients (CP to metabolizable energy) were expressed as concentrations in the diet, rather than absolute intakes. Furthermore, both MUN and MUN secretion (g/d) provided more accurate predictions of urinary N excretion (R-2 = 0.787 and 0.835, respectively) than measurements of the efficiency of N utilization for milk production (R-2 = 0.769). It is concluded that dietary CP content is the most important nutritional factor influencing MUN, and that measurements of MUN can be utilized as a diagnostic of protein feeding in the dairy cow and used to predict urinary N excretion.

Urea-N,N-dimethylacetamide (1/1)

Urea forms a 1:1 solvate with N,N-dimethylacetamide (DMA) [systematic name: diaminomethanal- N,N-dimethylacetamide (1/1), C4H9NO center dot CH4N2O] with both molecules positioned on a twofold axis, giving rise to rotational disorder of the DMA molecule. The molecules display a layered structure in which urea molecules form hydrogen-bonded ribbons bounded by molecules of solvent.

Effects of the Allosteric Antagonist 1-(4-Chlorophenyl)-3-[3-(6-pyrrolidin-1-ylpyridin-2-yl)phenyl]urea (PSNCBAM-1) on CB1 Receptor Modulation in the Cerebellum

PSNCBAM-1 has recently been described as a cannabinoid CB1 receptor allosteric antagonist associated with hypophagic effects in vivo; however, PSNCBAM-1 effects on CB1 ligand-mediated modulation of neuronal excitability remain unknown. Here, we investigate PSNCBAM-1 actions on CB1 receptor-stimulated [35S]GTPγS binding in cerebellar membranes and on CB1 ligand modulation of presynaptic CB1 receptors at inhibitory interneurone-Purkinje cell (IN-PC) synapses in the cerebellum using whole-cell electrophysiology. PSNCBAM-1 caused non-competitive antagonism in [35S]GTPγS binding studies, with higher potency against the CB receptor agonist CP55940 than for WIN55,212-2 (WIN55). In electrophysiological studies, WIN55 and CP55940 reduced miniature inhibitory postsynaptic currents (mIPSCs) frequency, but not amplitude. PSNCBAM-1 application alone had no effect on mIPSCs; however, PSNCBAM-1 pre-treatment revealed agonist-dependent functional antagonism, abolishing CP55940-induced reductions in mIPSC frequency, but having no clear effect on WIN55 actions. The CB1 antagonist/inverse agonist AM251 increased mIPSC frequency beyond control, this effect was reversed by PSNCBAM-1. PSNCBAM-1 pre-treatment also attenuated AM251 effects. Thus, PSNCBAM-1 reduced CB1 receptor ligand functional efficacy in the cerebellum. The differential effect of PSNCBAM-1 on CP55940 versus WIN55 actions in [35S]GTPγS binding and electrophysiological studies and the attenuation of AM251 effects are consistent with the ligand-dependency associated with allosteric modulation. These data provide the first description of functional PSNCBAM-1 allosteric antagonist effects on neuronal excitability in the mammalian CNS. PSNCBAM-1 allosteric antagonism may provide viable therapeutic alternatives to orthosteric CB1 antagonists/inverse agonists in the treatment of CNS disease.

Urea organogelators: synthesis and properties

A series of aromatic ureas have been synthesised and found to exhibit strong gelation or even supergelation characteristics in organic solvents to afford colourless or translucent gel materials. The synthesis of these materials, assessment of their gelation characteristics and rheological properties are reported in this paper.

Effects of dietary urea levels on milk protein fractions of Holstein cows

The aim of this study was to evaluate the effects of substituting soybean meal for urea on milk protein fractions (casein, whey protein and non-protein nitrogen) of dairy cows in three dietary levels. Nine mid-lactation Holstein cows were used in a 3 x 3 Latin square arrangement, composed of 3 treatments, 3 periods of 21 days each, and 3 squares. The treatments consisted of three different diets fed to lactating cows, which were randomly assigned to three groups of three animals: (A) no urea inclusion, providing 100% of crude protein (CP), rumen undegradable protein (RUP) and rumen degradable protein (RDP) requirements, using soybean meal and sugarcane as roughage; (B) urea inclusion at 7.5 g/kg DM in partial substitution of soybean meal CP equivalent; (C) urea inclusion at 15 g/kg DM in partial substitution of soybean meal CP equivalent. Rations were isoenergetic and isonitrogenous-1 60 g/kg DM of crude protein and 6.40 MJ/kg DM of net energy for lactation. When the data were analyzed by simple polynomial regression, no differences were observed among treatments in relation to milk CP content, true protein, casein, whey protein, non-casein and non-protein nitrogen, or urea. The milk true protein:crude protein and casein:true protein ratios were not influenced by substituting soybean meal for urea in the diet. Based on the results it can be concluded that the addition of urea up to 15 g/kg of diet dry matter in substitution of soybean meal did not alter milk protein concentration casein, whey protein and its non-protein fractions, when fed to lactating dairy cows. (c) 2007 Elsevier B.V. All rights reserved.

Direct action of aldosterone on bicarbonate reabsorption in in vivo cortical proximal tubule

Pergher PS, Leite-Dellova D, de Mello-Aires M. Direct action of aldosterone on bicarbonate reabsorption in in vivo cortical proximal tubule. Am J Physiol Renal Physiol 296: F1185-F1193, 2009. First published February 18, 2009; doi:10.1152/ajprenal.90217.2008.-The direct action of aldosterone (10(-12) M) on net bicarbonate reabsorption (J(HCO3)(-)) was evaluated by stationary microperfusion of an in vivo middle proximal tubule (S2) of rat kidney, using H ion-sensitive microelectrodes. Aldosterone in luminally perfused tubules caused a significant increase in J(HCO3)(-) from a mean control value of 2.84 +/- 0.08 [49/19 (n degrees of measurements/n degrees of tubules)] to 4.20 +/- 0.15 nmol.cm(-2).s(-1) (58/10). Aldosterone perfused into peritubular capillaries also increased J(HCO3)(-), compared with basal levels during intact capillary perfusion with blood. In addition, in isolated perfused tubules aldosterone causes a transient increase of cytosolic free calcium ([Ca(2+)](i)), monitored fluorometrically. In the presence of ethanol ( in similar concentration used to prepare the hormonal solution), spironolactone (10(-6) M, a mineralocorticoid receptor antagonist), actinomycin D (10(-6) M, an inhibitor of gene transcription), or cycloheximide (40 mM, an inhibitor of protein synthesis), the J(HCO3)(-) and the [Ca(2+)](i) were not different from the control value; these drugs also did not prevent the stimulatory effect of aldosterone on J(HCO3)(-) and on [Ca(2+)](i). However, in the presence of RU 486 alone [10(-6) M, a classic glucocorticoid receptor (GR) antagonist], a significant decrease on J(HCO3)(-) and on [Ca(2+)](i) was observed; this antagonist also inhibited the stimulatory effect of aldosterone on J(HCO3)(-) and on [Ca(2+)](i). These studies indicate that luminal or peritubular aldosterone (10(-12) M) has a direct nongenomic stimulatory effect on J(HCO3)(-) and on [Ca(2+)](i) in proximal tubule and that probably GR participates in this process. The data also indicate that endogenous aldosterone stimulates J(HCO3)(-) in middle proximal tubule.

Effect of urea and glycine fuels on the combustion reaction synthesis of Mn-Zn ferrites: Evaluation of morphology and magnetic properties

The goal of this study is to evaluate the influence of the urea and glycine fuels on the synthesis of Mn-Zn ferrite by combustion reaction The morphology and magnetic properties of the resulting powders were investigated. The powders were characterized by X-ray diffraction (XRD), nitrogen adsorption (BET), scanning and transmission electron microscopy (SEM and TEM), and magnetic measurement of M x H curves. The X-lay diffraction patterns indicated that the samples containing urea resulted in the formation of crystalline powders and the presence of hematite as a secondary phase The samples containing glycine presented only the formation of crystalline and monophases (Mn,Zn)Fe(2)O(4). The average crystallite size was 18 and 35 nm and saturation magnetization was 3.6 and 75 emu/g, respectively, for the samples containing urea and glycine. The samples synthesized with glycine fuel showed better magnetic properties for application as soft magnetic devices. (C) 2009 Elsevier B.V All rights reserved

Structural effects and hydrogen bonds on N,N `-di(methoxycarbonylsulfenyl)urea, [CH(3)OC(O)SNH](2)CO, studied by experimental and theoretical methods

Pure N,N`-di(methoxycarbonylsulfenyl)urea, [CH(3)OC(O)SNH](2)CO, is quantitatively prepared by the hydrolysis reaction of CH(3)OC(O)SNCO and characterized by (1)H NMR, GC-MS and FTIR spectroscopy techniques. Structural and conformational properties are analyzed using a combined approach with data obtained from X-ray diffraction, vibrational spectra and theoretical calculation methods. The IR and Raman spectra for normal and deuterated species are reported. The crystal structure of [CH(3)OC(O)SNH](2)CO was determined by X-ray diffraction methods. The substance crystallizes in the orthorhombic P2(1)2(1)2 space group with a = 9.524(2), b = 12.003(1), c = 4.481 (1) angstrom, and Z = 2 moieties in the unit cell. The molecule is sited on a twofold crystallographic axis (C(2)) parallel to c and shows the anti-anti conformation (S-N single bonds antiperiplanar with respect to the opposite C-N single bonds in sulfenyl-urea-sic group). Neighboring molecules are arranged in a chain motif that extends along the C(2)-axis and is held by bifurcated NH center dot center dot center dot O center dot center dot center dot HN intermolecular bonds. A local planar symmetry is observed in the crystal for the central -SN(H)C(O)N(H)S- skeleton. Experimental and calculated data allow to trace this structural feature to the occurrence of N-H center dot center dot center dot O=C hydrogen bonding interactions. Calculated vibrational and structural properties are in good agreement with the experimentally determined features. (C) 2008 Elsevier B.V. All rights reserved.

Urea amperometric biosensors based on a multifunctional bipolymeric layer: Comparing enzyme immobilization methods

This paper outlines the results obtained with biosensors designed for urea amperometric detection. The incorporation of urease into a bipolymeric substrate consisting of poly(pyrrole) and poly(5-amino-1-naphthol) was performed through four different approaches: direct adsorption, entrapment in cellulose acetate layer. cross-linking with glutaraldehyde, and also covalent attachment to the polymeric matrix. Poly(pyrrole) acts as amperometric transducer in these biosensors, while poly(5-amino-1-naphthol) drastically reduces the interference signal of agents such as ascorbic and uric acids. The biosensors containing urease covalently attached to the substrate provided interesting results in terms of sensitivity towards urea (0.50 mu A cm(-2) mmol(-1) L), lifetime (20 days) and short response times, due to the enzyme immobilization method used. All biosensors analyzed showed also a wide linear concentration range (up to 100 mmol L(-1)) and low detection limits (0.22-0.58 mmol L(-1)). (C) 2009 Elsevier B.V. All rights reserved.

Electrocatalytic oxidation of urea by nanostructured nickel/cobalt hydroxide electrodes

The present paper describes the catalytic oxidation of urea performed by nickel hydroxide and nickel/cobalt hydroxide modified electrodes by using both electrodeposited films and nanoparticles. The incorporation of Co foreign atoms leads to a slight increase in sensitivity besides the shift in redox process, avoiding the oxygen reaction. Nanostructured Ni80Co20(OH)(2) was synthesized by sonochemical route producing 5 nm diameter particles characterized by high-resolution transmission electron microscopy (HRTEM) being immobilized onto electrode by using the electrostatic Layer-by-layer technique, yielding attractive modified electrodes for sensor development. (C) 2007 Elsevier Ltd. All rights reserved.

Monitoring urea levels during haemodialysis with a pulsed-flow chemiluminescence analyser

We have developed a rapid and robust method for the determination of urea in spent haemodialysis fluid as a measure of the efficiency of haemodialysis treatments. A novel flow analysis instrument (which generates a pulsed solution flow) was coupled with a chemiluminescence detection system, based on the oxidation of urea with hypobromite. The ‘pulsed-flow chemiluminescence analyser’ exhibited high precision (1.6% relative standard deviation (R.S.D.) for a 1×10−5 M urea standard, n=10) and good limit of detection (9×10−7 M, S/N=3) as a result of the rapid and reproducible mixing of small volumes of reagent and sample at the point of detection. The proposed chemiluminescence technique and an established urease-based laboratory procedure were compared, and showed a very similar trend for the change in urea concentration during a typical haemodialysis treatment. The relative chemiluminescence response from the oxidation of species with similar structure has revealed the inherent selectivity of the light producing pathway, but a positive interference was obtained from protein when this technique was applied to the determination of urea in serum samples. Arginine was identified as the predominant source of this interference.

Analytical methodology for the determination of urea: current practice and future trends

The determination of urea is important in a wide range of fields, including clinical diagnostics, environmental monitoring and food science. Numerous analytical techniques have been developed for the determination of urea, with no single technique dominant in all areas because of the diversity of applications. An overview of the existing analytical methodologies for urea is presented, and some new approaches are discussed, particularly those based on chemiluminescence detection to improve the sensitivity and the selectivity for the determination of this important analyte.