Showing papers on "Urea published in 1981"

The excretion of isotope in urea and ammonia for estimating protein turnover in man with (15N)glycine

Abstract: 1. Four normal adults were given [ 15 N]-glycine in a single dose either orally or intravenously. Rates of whole-body protein turnover were estimated from the excretion of 15 N in ammonia and in urea during the following 9 h. The rate derived from urea took account of the [ 15 N]urea retained in body water. 2. In postabsorptive subjects the rates of protein synthesis given by ammonia were equal to those from urea, when the isotope was given orally, but lower when an intravenous dose was given. 3. In subjects receiving equal portions of food every 2 h rates of synthesis calculated from ammonia were much lower than those from urea whether an oral or intravenous isotope was given. Comparison of rates obtained during the post-absorptive and absorptive periods indicated regulation by food intake primarily of synthesis when measurements were made on urea, but regulation primarily of breakdown when measurements were made on ammonia. 4. These inconsistencies suggest that changes in protein metabolism might be assessed better by correlating results given by different end-products, and it is suggested that the mean value given by urea and ammonia will be useful for this purpose.

Adaptation of nitrogen metabolism to hyperosmotic environment in Amphibia

Abstract: A large number of species of Amphibia, both Anura and Urodela, are capable of tolerating a moderately saline environment. Rana cancrivora, Bufo viridis, and Xenopus laevis are among the most euryhaline frogs so far studied. Rana cancrivora can tolerate undiluted seawater. In a saline environment, Amphibia show raised plasma sodium and chloride and raised intracellular potassium and chloride. In the adults, plasma and tissue urea are elevated, especially in the more euryhaline species. Free amino acids contribute negligibly to plasma osmolarity, but are very important in intracellular fluids. By these various means, the osmotic pressure of body fluids is always maintained at a higher level than that of the surroundings. Larval Amphibia, however, do not make urea; Rana cancrivora tadpoles can live in saltwater, but maintain the osmolarity of their body fluids below that of their surroundings. Adaptive responses to hyperosmolar environment include decreased skin sodium transport, greatly reduced urine flow, and release of posterior pituitary hormones. After the initial response, the release of these hormones declines, and urine flow increases. Accumulation of urea occurs slowly, but this substance plays an increasingly important role as adaptation proceeds. Accumulation is due initially to urea retention, and possibly to greater synthesis due to a high concentration of precursors of the urea cycle. In later stages of adaptation, increased urea synthesis is due to elevated levels of urea cycle enzymes, especially those that appear to have been rate-limiting. Liver glutamate dehydrogenase is also elevated. In animals subjected to pure osmotic stress, in solutions not containing sodium, responses are similar to, but not identical with, those caused by a medium containing sodium chloride.

Ammonia concentration and protein synthesis in the rumen

Abstract: The effect of rumen ammonia concentration on microbial protein synthesis and fermentation was studied in three separate experiments. In each experiment three separate sheep were fed semi-purified diets [designated A (‘concentrate’), B (‘roughageconcentrate’) or C (‘roughage’)] and infused intra-ruminally with five graded amounts of urea according to a randomised block design. Rumen ammonia concentrations remained low until the total nitrogen intake was about 10 g day−1 after which rumen ammonia concentration rose rapidly. Rumen and duodenal ammonia concentrations were linearly related (r=0.90, 0.98 and 0.84 for diets A, B and C, respectively; P< 0.001). Microbial protein production did not increase when rumen ammonia concentrations exceeded 2.8 mM for diet A, 6.0 mM for diet B and 1.6 mM for diet C. Diets A and C produced a propionate-type fermentation while diet B was characterised by an acetate-type fermentation. Rumen ammonia concentration had no apparent effect on either concentration or the molar proportions of volatile fatty acids. There were no systematic trends in digestibility in relation to rumen ammonia concentration.

Renal Function and Effects of Partial Rehydration During Diabetic Ketoacidosis

Abstract: Although diabetic ketoacidosis is characterized by increased renal excretion of glucose, ketone bodies, and nitrogenous compounds, there are few quantitative studies pertaining to renal function during this state. Therefore, renal function was studied in 10 adult patients in moderate to severe diabetic ketoacidosis before insulin administration. Admission plasma concentrations were: glucose 21.4 (9.2–39.4) mM or 386 (166–710) mg/dl, acetoacetate 3.0 (1.3–7.4) mM, beta-hydroxybutyrate 7.9 (2.9–15.2) mM, acetone 4.4 (1.3–8.9) mM, and HCO3 12.8 (9.5–17.8) mM. Arterial blood pH was 7.28 (7.21–7.38). Partial rehydration was achieved with 0.45% saline. Inulin was used to measure GFR. Renal clearance of acetoacetate, beta-hydroxybutyrate, acetone, glucose, and urinary excretion of nitrogenous compounds were determined. Partial rehydration reduced plasma glucose concentration, primarily because of renal excretion, amounting to 384 ± 73 μmol/min or 69 ± 13 mg/min. Partial rehydration had no effect on plasma ketone bodies, on bicarbonate or urea concentrations, or on arterial pH. Partial rehydration had no effect on ketone body or nitrogenous compound excretory rates. Reabsorptive rates of acetoacetate, beta-hydroxybutyrate, acetone, and glucose increased linearly with their filtered loads, and no maximal renal tubular transport rates were demonstrated for any ketone body or glucose. Because renal absorption of ketone bodies was less than 100%, ketonuria increased as filtered loads increase. Unlike ketone bodies, glucose reabsorptive rate was directly related to GFR. Total renal excretion of nitrogen in the forms of urea, ammonium, creatinine, and uric acid amounted to 16 ± 2 mg/min. This huge loss of body nitrogen reflected ongoing protein catabolism and not heightened renal excretion of preformed compounds, as the plasma concentrations of urea, creatinine, and uric acid did not change during the study. Urea nitrogen accounted for 12 ± 2 mg/min (72%) of the total nitrogen excreted. Ammonium excretion was markedly augmented, ranging from 76 to 537 μmol/min, and was inversely related to arterial pH. We conclude that the fall in plasma glucose concentration is primarily caused by renal glucose excretion, and that the absence of a maximal renal tubular reab-sorption rate for either acetoacetate (AcAc) or beta-hydroxybutyrate ( β -OHB) serves to mitigate urinary losses of sodium and potassium during diabetic ketoacidosis.

Time and mode of nitrogen fertilizer application to tropical wetland rice

Abstract: In experiments with transplanted rice (Oryza sativa L.) at the International Rice Research Institute, Philippines, two methods of split application of urea and ammonium sulfate were compared with deep, point placement (10 cm) of urea supergranules and broadcast application of a slow-release fertilizer sulfur-coated urea (SCU). Comparisons were made in the wet and dry seasons and were based on rice yield and N uptake. Urea- and ammonium-N concentrations and pH of the floodwater were measured to aid interpretation of the results. Split applications of urea were generally less efficient than ammonium sulfate. The split in which the initial fertilizer dose was broadcast and incorporated into the soil before transplanting was more effective than the split in which the fertilizer was broadcast directly into the floodwater 21 days after transplanting. Both split applications were inferior to the urea supergranules and SCU, in terms of both yield and N uptake efficiency; average apparent N recoveries ranged from 30% for the delayed split urea to 80% for the urea supergranule. Broadcast applications of urea and ammonium sulfate produced high floodwater concentrations of urea- and ammonium-N, which fell to zero within 4–5 days. Floodwater pH was as high as 9.3 and fluctuated diurnally due to heavy algal growth. Ammonia volatilization and algal immobilization of N in the floodwater were probably responsible for the poor efficiency of the split applications; the supergranules and SCU on the other hand produced low floodwater N concentrations and were efficiently used by the rice crop.

Method of purifying eicosapentaenoic acid and its esters

Abstract: A method of purifying eicosapentaenoic acid and esters of eicosapentaenoic acid comprising subjecting a mixture containing eicosapentaenoic acid or an ester of eicosapentaenoic acid to the following steps in either order: (1) urea treatment, where the treatment comprises contacting the mixture with a polar organic solvent containing dissolved urea whereby a solution containing the acid or ester is formed, precipitating urea crystals from the solution, and removing the urea crystals, and (2) fractional distillation.

Interactions in aqueous solutions of urea-like compounds. Heats of mixing of urea, monomethylurea and thiourea at 298.15 K

Abstract: The heats of mixing of aqueous solutions of monomethylurea, urea and thiourea were determined at 298.15 K and the excess enthalpies obtained were expressed in terms of pair- and triplet-interaction coefficients.The validity of the empirical rule: hij2≈hij hjj, relating the self- and cross-interaction coefficients, was tested for the solutes under examination, for which both hii, hjj < 0.

The Effect of N Fertilizer Source on Grain Yield, N Uptake, Soil pH, and Lime Requirement in No-Till Corn1

Abstract: The increasing use of no-till crop production with urea based N fertilizers in the Northeast makes it imperative that we obtain a more quantitative understanding of both the magnitude of apparent NH₃ losses from nonincorporated urea fertilizers in the field and of the factors that contribute to those losses. A 4-year field study was conducted on a Murrill silt loam (Typic Hapludult) to compare the yields and N uptake by no-till corn (Zea mays L.) receiving five rates of broadcast, unincorporated N (0 to 202 kg/ha) as NH₄NO₃, urea, urea-NH₄NO₃ solution (UAN), or (NH₄)₂SO₄. The effects of these sources on the soil pH of the 0 to 2.5 cm and 0 to 17 cm layers and on the lime requirement (LR) in the 0 to 17 an layer were also measured. In 2 of the 4 years, either urea, UAN, or both produced signifcantly lower yields and N uptake than the non-urea sources at the higher (101 and 202 kg/ha) N rates. Apparent N volatilization losses ranged from 0 to 35%. Comparing the results from this experiment with those from other field experiments reported in the literature where the effect of rainfall after N application on apparent N volatilization losses could be measured showed that the following observations applied to all: (1) there was insignificant NH, volatilization loss from unincorporated urea fertilizers if at least 10 mm of rain fell within 48 hours after fertilizer application; (2) if 10 mm or more rain fell 3 days after the urea was applied, volatilization losses were slight ( 30%). The pH in the surface 2.5 an of soil in the plots receiving 202 kg/ha/year of N as NH₄NO₃ urea, or UAN for 5 years was approximately 5.7 or one unit below that in the check. In the plots receiving this rate of (NH₄)₂SO₄, the soil pH in the 0 to 2.5 cm layer was 4.7. As expected, the 101 kg N/ha/year rate produced half was much lowering of pH as the 202 kg/ha rate. Lime requirement measurements in the surface 17 cm of soil receiving 202 kg N/ha/year for 5 years indicated that approximately 67% of the acidity theoretically produced in the nitrification of NH₄⁺ remained to be neutralized with the less acidifying sources (NH₄O₃, urea, and UAN) and that approximately 100% of that from (NH₄)₂SO₄ required neutralization.

Metabolic effects of short term food deprivation in the rat.

Abstract: The effects of food deprivation for up to 24 hours on plasma metabolic parameters in the rat have been studied. Liver dry weight and glycogen content dropped significantly from 3 hours of food deprivation onwards. Total muscle glycogen supplied about as much glycosyl residues or precursors as did the liver. Plasma glucose, urea, lactate and total and essential amino acids decreased significantly from 3 hours of fasting onwards. Glycerol, free significantly from 3 hours of fasting onwards. Glycerol, free fatty acids, beta-hydroxybutyrate and acetoacetate showed significant increases with fasting. Alanine, serine, arginine, threonine, aspartate plus asparagine and proline showed significant decreases with fasting. Several other amino acids showed almost no change with fasting. Lysine, leucine plus isoleucine and taurine showed biphasic changes in their concentrations with a minimum at 6 hours and a transient recovery at 12 hours of fasting Essential amino acids decreased more than the non essential ones. With fasting there is a shift in ammonia disposal with lower urea concentrations as nitrogen is better conserved. The results seem to suggest that there is a constant release of substrates, through liver and peripheral tissue proteolysis, that is counteracted by differential utilization of amino acids during fasting.

Effectiveness of ammonification through urea in improving the feeding value of rice straw in ruminants

Abstract: Eight male crossbred sheep with four in each batch were used to provide backup research for an integrated rural development project. The crude protein (CP) content of rice straw tree increased from 2.9% through various treatments with urea as follows: 3% and 5% urea in an earthen pit for 20 days, 5.9% CP and 6.7% CP respectively; 5% urea in an earthen pit for 40 days, 6.5% CP; 5% urea in a bamboo basket for 20 days, 7.1% CP. The intake of organic matter rose from 46.2g/kg W 0.71 /day. in untreated straw, to 51.7 with 3% urea. 60.9 with 5% urea treated for 20 days and 63.4 when treated with 5% urea for 40 days and fed 10% molasses ant 57.5 for straw treated with 5% urea in a bamboo basket. The organic matter and crude fibre digestibility increased from 45% and 65% in untreated straw to 54 and 65 with the 3% urea treatment, 56 and 60, 57 and 60 in straw treated with 5% urea and fed without and with 10% molasses and 56% and 64% in straw treated with 5% urea in a bamboo basket. The-nitrogen balance was found to be positive in the treatments with 5% urea. Calculated metabolizable energy MJ/kg DM increased from 6.93 in untreated straw to a maximum of 9.51 in straw treated with 5% urea and fed with 102 molasses. It is concluded that treatment of rice straw with ammonia through urea is possible under simple storage conditions. This is an essential step in bringing the method to the use of small farmers. Further studies are recommended.

Liquid-chromatographic determination of cimetidine, its known metabolites, and creatinine in serum and urine.

Abstract: We describe a liquid-chromatographic procedure for determination of cimetidine, its hydroxymethyl-, sulfoxide-, and guanyl urea metabolites, and creatinine in patients serum and urine. SKF 92374 is used as the internal standard. Protein in 0.5 mL of serum or diluted urine is precipitated with 2 mL of acetonitrile, the organic and aqueous phases are separated by adding 0.3-0.5 g of anhydrous K2HPO4. The organic phase is evaporated, and 0.5 mL of 50 mmol/L HCl is added. This solution is washed with 3 mL of water-saturated isoamyl alcohol, the aqueous phase is extracted with 3 mL of methylene chloride and enough K2HPO4 to saturate the solution. The methylene chloride is evaporated, the residue reconstituted with 100 microL of mobile phase, and a 25-microL aliquot injected onto the chromatographic column (Dupont Sil). The mobile phase is acetonitrile/methanol/water/ammonium hydroxide (1000/50/50/2, by vol). The column effluent is monitored at 228 nm. Lower limits of detection ranged from 0.05 mg/L for cimetidine to 0.2 mg/L for guanyl urea. We determined cimetidine and its principal metabolites in the serum of a patient receiving cimetidine for the treatment of Zollinger-Ellison syndrome, and have assessed use of the assay in a clinical setting.

Synergistic mixtures of phosphinothricine

Abstract: 1. Herbicidal compositions which comprise an amount of A) phosphinothricine derivatives of the formula see diagramm : EP0036106,P13,F3 in which R is hydrogen or (C1 -C4 )-alkyl, their salts with acids or bases of phosphinothricyl-alanyl-alanine, in combination with B) inorganic or organic ammonium salts of the formula see diagramm : EP0036106,P13,F4 in which R**1 to R**4 , being identical or different, each are hydrogen, or hydroxyethyl ; X is the anion of an inorganic or organic mono- or polybasic acid and n is 1, 2 or 3, or with the free bases from which the salts of the formula II are derived, or with urea or C) inorganic or organic chelating agents, with the proviso that, if R in formula I is hydrogen, the compound B is not a free base.

Germicidal absorbent body

Abstract: An absorbent body for collecting blood, faeces and urine contains a water-soluble copper salt which impedes bacterial growth, prevents the breaking-down of urea into ammonia and complex-binds ammonia so as to prevent the occurrence of unpleasant odor. Preferably copper acetate is used, in which even the acetate ion has germicidal effect.

Postprandial changes in plasma urea and creatinine concentrations in dogs.

Abstract: Changes in plasma urea and creatinine concentrations were compared in 6 dogs fed 3 meals (cooked meat, raw meat, and a soft-moist preparation) in a crossover fashion. Each meal produced changes in urea and creatinine values. Although increased urea values were seen after all meals, the effects on creatinine were varied; concentrations increased after feeding cooked meat, but decreased after consumption of raw meat or soft-moist food. Although the creatinine changes were less pronounced, the variable effect of diet complicates the interpretation of plasma creatinine concentration in evaluating renal function.

Noncorrosive urea-sulfuric acid compositions

Abstract: Improved, liquid, urea-sulfuric acid reaction product compositions, noncorrosive to carbon steel, contain about 5 to about 75 weight percent urea, about 5 to about 85 weight percent sulfuric acid, 0 to about 75 weight percent water, and a corrosion inhibiting amount of certain dialkylthioureas, in which the urea and sulfuric acid together constitute at least about 25 weight percent of the composition, the urea/sulfuric acid molar ratio of the composition is greater than 2 or less than 1, and a portion of the urea and sulfuric acid are present as monourea sulfate, diurea sulfate, or combinations thereof The compositions can also contain corrosion inhibiting amounts of one or more cupric ion-containing compounds sufficient to reduce the corrosivity of the composition to stainless steel

Methods of producing concentrated urea-sulfuric acid reaction products

Abstract: Stable concentrated solutions of urea and sulfuric acid containing mono- and/or diurea sulfates and less than 35 weight percent water, free of sulfamic acid and/or ammonium sulfamate, are produced by a unique process that involves the simultaneous and separate addition of urea, sulfuric acid and optionally water to a reaction zone at controlled rates and in stochiometric proportions equivalent to the composition of the desired product, and maintaining reaction temperatures below the incipient decomposition temperature for the particular composition. The heat generated by the highly exothermic reaction can be removed by cooling the liquid phase during the course of the reaction by direct air heat exchange with only nominal, if any, atmospheric emissions.

Noncorrosive urea-sulfuric acid reaction products

Abstract: Improved liquid, urea-sulfuric acid compositions noncorrosive to stainless steel contain about 5 to about 75 weight percent urea, about 5 to about 85 weight percent sulfuric acid, 0 to about 75 weight percent water and a corrosion inhibiting amount of a cupric ion-containing compound, in which the urea and sulfuric acid together comprise at least about 25 weight percent of the composition, and in which at least a portion of the urea and sulfuric acid are present as monourea sulfate, diurea sulfate or combinations thereof. The compositions may also contain amounts of selected dialkylthioureas sufficient to reduce their corrosivity to carbon steel.

Nitrogen recovery in soil and needle biomass after fertilization of a Scots pine stand, and growth responses obtained

Abstract: The distribution of fertilizer nitrogen in soil and needle biomass of an 120-year-old stand of Scots pine was studied over a period of six years. The nitrogen was applied as ammonium nitrate or urea and at rates of 150,300 and 600 kg N per hectare. The soil investigations showed that, at the lowest nitrogen application rate, 21 % of the ammonium nitrate and 49% of the urea nitrogen were immobilized in the soil in nonexchangeable form. For the corresponding treatments the losses by leaching were estimated to 3040% and 0-lo%, respectively. The accumulation of fertilizer nitrogen in the needle biomass culminated during the third growing season. Relative to control, the total nitrogen accumulation for the lowest ammonium nitrate and urea application rates then amounted to 174 and 134% respectively. As regards volume growth, the ammonium nitrate was greatly superior to urea at the two lowest nitrogen application rates. The dose of 600 kg N per hectare proved to be over-optimal as far as the ammonium nitrate source of nitrogen was concerned.

NaCl transport in mouse medullary thick ascending limbs. III. Modulation of the ADH effect by peritubular osmolality.

Abstract: We evaluated the effects of increasing bath osmolality on both the passive permeability properties and the ADH-dependent rates of net Cl- absorption in isolated mouse medullary thick ascending limbs of Henle (mTALH). Increases in both osmolality to 900 mosmol/kg H2O with 600 mM urea had no effect on either the electrical (PNa/PCl ratio, 1.7 and 1.9 with and without peritubular urea, respectively) or tracer (PNa, 0.21 and 0.22 micrometers . s-1 with and without peritubular urea, respectively) ionic permeability characteristics of the mTALH. However, this degree of urea bath hypertonicity reduced reversibly both JnetNaCl, the net rate of transepithelial NaCl absorption, and Ve, the spontaneous transepithelial voltage: JnetNaCl fell by 85% and Ve by 70%. Both of these latter effects could be accounted for quantitatively by an 85% reduction in tau NaCl, the rate of conservative transcellular NaCl transport. The inhibition of Ve by peritubular medium urea hypertonicity was not altered by supramaximal bath conc...

Method of producing urea-sulfuric acid reaction products

Abstract: Stable, urea-sulfuric acid reaction products of predetermined composition containing mono- and/or diurea sulfates and less than 35 weight percent water are produced from concentrated, urea-sulfuric acid reaction product feeds of different compositions by simultaneously and separately adding a selected feed solution and reactant urea and/or sulfuric acid, and optionally water, to a reaction zone in stoichiometric proportions so that the composition of the total feed to the reaction zone corresponds to the predetermined composition. Reaction temperature is maintained at a level below the incipient decomposition temperature of the predetermined composition, and the resulting products are essentially or completely free of sulfamic acid and/or ammonium sulfamate. Depending upon the relative proportions of unreacted sulfuric acid and urea in the total feed, the reaction may be exothermic or endothermic and, when desired, the otherwise endothermic reactions can be made exothermic by the reaction of excess urea and sulfuric acid to autogenously maintain the desired reaction temperature.

Renal inner medullary prostaglandin synthesis. A calcium-calmodulin-dependent process suppressed by urea.

Abstract: Previous studies have demonstrated that hyperosmolar NaCl and mannitol stimulate immunoreactive prostaglandin E (iPGE) production by slices of inner medulla (IM), whereas urea inhibits this process. In the present study, the roles of Ca2+ and calmodulin in the control of PGE synthesis in IM and the basis for the differential actions of solutes were examined. A23187 increased [14C]arachidonate (AA) release and iPGE accumulation in the presence but not in the absence of media Ca2+ whereas stimulation by hypertonic NaCl or mannitol was well expressed with Ca2+ or in Ca2+-free buffer containing 2 mM EGTA. Hypertonic urea and trifluoperazine (TFP), an inhibitor of actions of the Ca2+-CaM complex, suppressed increases in [14C]AA release and iPGE induced by A23187, NaCl, or mannitol. By contrast, increases in iPGE in response to exogenous AA were not altered by urea or TFP. Ca2+ (25-100 microM) increased acyl hydrolase (AH) activity in EGTA washed (4 degrees C) 100,000 g particulate fractions of IM threefold, thereby restoring AH activity to the higher basal values of particulate fractions not washed with EGTA. This action of Ca2+ was blocked by hypertonic urea of TFP, whereas AH activity was not influenced by NaCl or mannitol in the presence or absence of Ca2+. In contrast to their effects on AH activity, hypertonic urea and TFP did not alter conversion of AA to PGE2, PGF2 alpha, or PGD2 by IM microsomal fractions. Ca2+-induced increases in particulate AH were blunted after partial depletion of endogenous CaM-like activity. Ca2+ action was restored by addition of purified exogenous CaM, but not by addition of other small acidic proteins, including troponin C. The findings support a role for CaM in the regulation of PGE synthesis in the IM at the level of Ca2+-responsive AH activity. They further imply that urea suppresses PGE synthesis in IM through inhibition of AH and a reduction in the availability of endogenous AA for conversion to PGE.