Showing papers on "Urea published in 1978"
TL;DR: The attributes of ammonia and the epidemiological evidence comparing populations that maintain low intakes of unrefined carbohydrate with those that consume high intakes of protein, fat, and refined carbohydrates implicate ammonia in carcinogenesis and other disease processes.
226 citations
TL;DR: These studies indicated that urokinase, as well as trypsin, chymotrypsin), plasmin and thrombin forms complexes with alphaM, and the stability of thetrypsin-binding activity of the alpha2M preparations was studied under several storage situations.
Abstract: Alpha2-M (alpha2-macroglobulin) was purified from human plasma by two different procedures. As well as having no detectable impurities by the usual criteria for testing the homogeneity of protein preparations, these alpha2M preparations showed a single component, after reduction in urea, of 185000 daltons by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The molecular weight of the alpha2M was found to be 718000 by sedimentation equilibrium experiments using the gravimetrically determined -v of 0.731 ml/g. The interaction of several proteinases with alpha2M was studied by using a novel discontinuous polyacrylamide-gel system, which showed clear separation of the enzyme-complexed alpha2M from the free alpha2M. These studies indicated that urokinase, as well as trypsin, chymotrypsin, plasmin and thrombin forms complexes with alphaM. The cleavage of the 185000-dalton subunit to a 85000-dalton species on interaction of trypsin with alpha2M was demonstrated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis after reduction of the alpha2M-trypsin complex in urea. The amino acid composition, carbohydrate content, absorption coefficient at 280 nm, the specific refractive increment and the sedimentation coefficient for these alpha2M preparations were measured. The stability of the trypsin-binding activity of the alpha2M preparations was also studied under several storage situations.
223 citations
136 citations
TL;DR: In this paper, 35 N -phenyl- N "-(4-pyridyl)urea derivatives were synthesized and tested their cytokinin activity in the tobacco callus bioassay.
118 citations
TL;DR: It appears that the reate of endogenous catabolism of urea depends mainly on the activity of the gut flora which may be affected by dietary intake and clinical status of the subject.
98 citations
TL;DR: In this paper, 15 Holstein cows at various stages of lactation, fed corn-based diets that contained 9 to 14.5% crude protein were used in total collection digestibility and nitrogen balance trials to investigate the efficiency of nitrogen utilization from urea and soybean meal.
92 citations
Patent•
20 Jul 1978
TL;DR: In this paper, a method for preparing microcapsules comprising polymerizing urea and formaldehyde in the presence of an anionic polyelectrolyte and an ammonium salt of an acid was presented.
Abstract: A method for preparing microcapsules comprising polymerizing urea and formaldehyde in the presence of an anionic polyelectrolyte and an ammonium salt of an acid and forming a wall membrane of a urea/formaldehyde resin around droplets of a hydrophobic oily liquid.
90 citations
86 citations
TL;DR: Activity of the urea uptake system is elevated in nitrogen-starved cultures and elevated even further in the presence of urea or arginine, suggesting that both are subject to modulation by a complex set of interacting endogenous and exogenous factors.
Abstract: Chlamydomonas reinhardtii possesses a high affinity, highly specific carrier involved in uptake of exogenous arginine. Carrier-mediated uptake of other amino acids cannot be detected, even in cultures maintained on amino acids as a nitrogen source or starved for nitrogen. This fact may contribute to the difficulty of isolating strains auxotrophic for amino acids other than arginine; conventional selection media may not supply adequate quantities of amino acids to permit growth of auxotrophs. A urea carrier is also present in C. reinhardtii but is readily distinguished from the arginine carrier on the basis of kinetic properties and sensitivity to a range of structural analogs. Ammonia appears to play a major role in regulating (depressing) activity of the arginine uptake system. Activity of the urea uptake system is elevated in nitrogen-starved cultures and elevated even further in the presence of urea or arginine. Extensive, independent fluctuations in the two uptake systems observed in semisynchronous cultures suggest that both are subject to modulation by a complex set of interacting endogenous and exogenous factors.
84 citations
TL;DR: There was a significant negative correlation between the rate of transfer of plasma urea-N to the rumen and the concentration of rumen ammonia.
Abstract: 1. The rate of transfer of plasma urea-nitrogen to rumen ammonia was measured by infusion of 15NH4Cl and [15N]urea into sheep given brome grass (Bromus inermis) or lucerne (Medicago sativa) pellets. Urea was infused into the rumen or abomasum of two sheep given brome grass in order to increase the concentration of rumen ammonia. 2. From 6.2 to 9.8 g/d of plasma urea-N were transferred to the rumen of sheep given brome grass pellets and a measurement of 1.3 g nitrogen/d was obtained for a sheep given lucerne pellets. When urea was infused into the rumen of sheep given brome grass pellets the transfer was only 2.8--3.7 g N/d. 3. There was a significant negative correlation between the rate of transfer of plasma urea-N to the rumen and the concentration of rumen ammonia.
82 citations
TL;DR: The M4-lactate dehydrogenase of the freshwater elasmobranch,Potamotrygon sp.
Abstract: The kinetic properties — apparentKm of pyruvate, pyruvate inhibition pattern, and maximal velocity — of M4 (skeletal muscle) lactate dehydrogenases of marine elasmobranch fishes resemble those of the homologous lactate dehydrogenases of non-elasmobranchs only when physiological concentrations of urea (approximately 400 mM) are present in the assay medium. Urea increases the apparentKm of pyruvate to values typical of other vertebrates (Fig. 2), and reduces pyruvate inhibition to levels seen with other M4-lactate dehydrogenases (Fig. 3). Urea reduces the activation enthalpy of the reaction, and increasesVmax at physiological temperatures (Fig. 4).
Patent•
22 May 1978
TL;DR: Urea granules are prepared by spraying an aqueous urea solution having a urea concentration of 70-99.9% by weight on to fluidized urea nuclei in the form of droplets having a mean drop diameter of 20-120 μm as discussed by the authors.
Abstract: Urea granules are prepared by spraying an aqueous urea solution having a urea concentration of 70-99.9% by weight on to fluidized urea nuclei in the form of droplets having a mean drop diameter of 20-120 μm at a temperature at which the water is evaporated from the solution sprayed on to the nuclei and urea crystallizes on the nuclei to form granules having a desired size.
TL;DR: In this article, a 13C Fourier transform NMR was used to characterize a random chemical structure of ureaformaldehyde resins and reacted formaldehyde (e.g., methylol group, methylene group, and dimethylene ether group) was isolated.
Abstract: 13C Fourier transform NMR has been used to characterize a random chemical structure of ureaformaldehyde resins. By comparison of 13C chemical shifts with synthesized standard derivatives from urea and formaldehyde the analysis of reacted formaldehyde was completed. In a 13C spectrum of resin each signal due to reacted formaldehyde (e.g., methylol group, methylene group, and dimethylene ether group) was isolated.
Measurement of a 13C spectrum of resin by the gated decoupling of proton without nuclear Overhauser effect made a quantitative analysis of reacted formaldehyde possible. In this quantitative analysis a 13C quantity of carbonyl groups in urea residue can be directly compared with that of each combined formaldehyde.
TL;DR: From an examination of these two derivatives, it is clear that guanidine hydrochloride and urea unfold proteins by different mechanisms.
Abstract: Crystals of alpha-chymotrypsin (CHT) at equilibrium in solutions of 2.0 M guanidine hydrochloride and 3.0 M urea at pH 3.6 were prepared, three-dimensional X-ray intensities were measured, and difference electron-density maps were calculated and examined. The guanidine hydrochloride derivative displayed changes occurring exclusively on the surface of the protein. The difference peaks represented mostly small changes in various protein surface groups and in the adjacent solvent regions, and some displayed convincing evidence of binding of the guanidinium ion to the protein. The urea difference map likewise showed that changes had occurred on the surface of the protein, but also that numerous changes in the structure occurred in the hydrophobic interior of the CHT molecule. Further, the urea difference map contained evidence for two kinds of interactions of urea with protein groups. There are examples of bound urea either causing or accompanying structural changes and examples of urea binding with no accompanying changes to the protein. Examples of both kinds of binding were observed in both the surface regions and in the hydrophobic interior of the molecule. From an examination of these two derivatives, it is clear that guanidine hydrochloride and urea unfold proteins by different mechanisms.
TL;DR: In this paper, three trials were conducted to determine the usefulness of melamine as a dietary non-protein nitrogen (NPN) source for cattle, and the results indicated that melamine had little effect on the digestibility of dietary components.
Abstract: SUMMARY Three trials were conducted to determine the usefulness of melamine as a dietary non- protein nitrogen (NPN) source for cattle. Ruminally fistulated steers were fed diets in which the supplemental protein was provided by either cottonseed meal, urea or melamine. Rumen fluid was sampled for ammonia concen- tration periodically for 7 hr after feeding on six occasions during the first 49 days. After 88 days the steers fed cottonseed meal and mela- mine were fasted for 48 hr then refed and ruminal ammonia concentrations monitored. In vitro rumen ammonia concentrations produced by inoculation of either a cottonseed meal, urea, melamine or control (no supplemental nitrogen) substrate with rumen fluid from the steers fed either cottonseed meal or melamine were monitored. Results of these ammonia concentration trials indicated that melamine was slowly hydrolized in a ruminal environment. A 3 “ 3 replicated Latin square digestion and nitrogen balance trial was conducted using the three diets previously fed to the fistulated steers. Results indicated that melamine had little effect on the digestibility of dietary components. Melamine nitrogen was apparently digested to an extent equal to cottonseed meal nitrogen but not (P<.01) as completely as urea nitrogen. Larger (P<.05) amounts of nitrogen fractions other than ammonia and urea appeared in the urine when melamine was fed than when cottonseed meal or urea was fed. Nitrogen balance was lower (P<.05) for melamine than cottonseed meal and tended to be lower than for urea. Under the conditions of these trials, mela- mine may not be hydrolized in the rumen at a rate sufficient to promote maximum ruminal protein synthesis and incompletely hydrolized fractions may be absorbed and voided in the urine. These observations would tend to indicate that melamine may not be an acceptable NPN source for ruminants. (Key Words: Melamine, Urea, Non-Protein Nitrogen, Nitrogen Balance, Ruminal Ammonia, Protein Supplements, Beef Cattle.) INTRODUCTION There has been considerable interest in improving the utilization on non-protein nitrogen in ruminant diets. Basically, two approaches have been taken; optimizing urea utilization (Satter and Roffler, 1975; Burroughs
TL;DR: The experiments support the view that hepatic glutamate dehydrogenase can supply the required ammonia in urea synthesis for the carbamoyl phosphate synthase reaction (EC 2.7.2.5).
Abstract: The initial rate of incorporation of [15N]alanine into the 6-amino group of the adenine nucleotides in rat hepatocytes was about one-eighteenth of the rate of incorporation into urea Thus the purine nucleotide cycle cannot provide most of the ammonia needed in urea synthesis for the carbamoyl phosphate synthase reaction (EC 2725) On the other hand, contrary to the view expressed by McGivan & Chappell [(1975) FEBS Lett 52, 1–7], the experiments support the view that hepatic glutamate dehydrogenase can supply the required ammonia
TL;DR: The time course of the changes seems to indicate that conversion of T4 into T3 and rT3 is mediated by separate processes, and the effect of caloric restriction on the serum concentrations of thyroxine, 3,3',5-triiodothyronine (T3), urea, uric acid, creatinine, and bilirubin was studied.
Abstract: In nine obese but otherwise healthy subjects the effect of caloric restriction on the serum concentrations of thyroxine (T 4 ), 3,3′,5-triiodothyronine (T 3 ), 3,3′,5′-triiodothyronine (rT 3 ), urea, uric acid, creatinine, and bilirubin was studied. Blood was obtained before and 2, 4, and 6 wk after the subjects had changed to a chemically defined diet (31 g amino acids, 44 g carbohydrate, and 1.5 g fat; 300 kcal/day). A decline of body weight to 88% and of serum T 3 to 70% of the pretreatment values was observed. Creatinine and bilirubin increased to 115% and 163%, respectively. Uric acid and rT 3 showed a transient rise to 148% and 180%, respectively. Serum urea was lowest (72%) from the second until the fourth week. There was a highly significant correlation between serum rT 3 and uric acid ( r = 0.77, p ⪡ 0.001). The time course of the changes seems to indicate that conversion of T 4 into T 3 and rT 3 is mediated by separate processes.
TL;DR: The lower digestive tract was the major site of Urea degradation in sheep given these low protein diets, and the rate of urea transfer to this part of the digestive tractwas linearly related to the rateof urea synthesis in the body.
Abstract: Some aspects of nitrogen metabolism of sheep given Mitchell grass (Astrebla spp.), Flinders grass (Iseilema spp.) and mixed native pasture were investigated. All diets were of low nutritive value as demonstrated by negative nitrogen and energy balances in sheep on these diets. Studies of urea metabolism demonstrated a significant relationship between plasma urea concentration, the rate of irreversible loss of urea from plasma and the rate of urea degradation in the digestive tract. On average, 81% of the urea synthesized in the body was transferred to the digestive tract and degraded to ammonia and carbon dioxide. The proportion of urea degradation occurring intraruminally was estimated during an intravenous infusion of 14C urea by measuring the rate of appearance of 14CO2 in ruminal fluid, the proportion degraded post-ruminally being obtained by difference. Urea degraded in the rumen accounted for 7–13% of the total quantity degraded in the digestive tract, and the rate of urea transfer (0.55 ± 0.13 g nitrogen/day) was not related to the rate of urea synthesis in the body. The lower digestive tract was the major site of urea degradation in sheep given these low protein diets, and the rate of urea transfer to this part of the digestive tract was linearly related to the rate of urea synthesis in the body. The implications of these findings are discussed in relation to nitrogen conservation in sheep given low quality diets.
TL;DR: In this article, the compositions of nitrogen compounds excreted by P. cantonensis and B. pectinirostris in water and on land, and excretory organs of nitrogen were studied.
TL;DR: All three of the major human nitrogenous waste products--urea, creatinine, and uric acid--are significantly degraded by intestinal bacteria, and metabolites of these complex heterocyclic nitrogen compounds may well turn out to play a role in uremic toxicity.
TL;DR: 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.
Abstract: 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.
TL;DR: Nitrogen metabolism and hepatic function were comprehensively evaluated in 73 patients with cirrhosis, portal hypertension, and history of variceal hemorrhage, and in 18 normal controls.
Patent•
05 Jun 1978
TL;DR: In this article, aqueous urea solutions suitable for foliar application containing mineral or organic acids, or both, in the presence or absence of a pH buffer having pH values between about 6 and 7.6.
Abstract: Aqueous urea solutions particularly suited for foliar fertilization are disclosed. They are characterized by low phytotoxicity, low corrosivity, and improved toxicity stability and comprise urea nitrogen and between about 0.005 and about 0.1 molar equivalents per mole of urea of a pH buffer having a buffering point between about 6 and about 7.6. Also provided are aqueous urea solutions suitable for foliar application containing mineral or organic acids, or both, in the presence or absence of a pH buffer having pH values between about 6 and 7.6. Either solution is foliarly applied at substantially non-toxic rates of at least about 10 pounds of nitrogen per acre.
TL;DR: Early-weaned lambs were used to estimate the concentration of urea required to give the maximum intake and utilization of maize or barley with either a high (HPB) or low (LPB) protein content, and theoretical requirements for urea were calculated and compared with other predictions and with the experimentally determined values.
Abstract: 1. Early-weaned lambs were used to estimate the concentration of urea required to give the maximum intake and utilization of maize or barley with either a high (HPB) or low (LPB) protein content. 2. Approximately the same concentration of urea (7--11 g urea/kg feed) was required for maximum intake and feed utilization of both HPB and LPB. With maize there was no increase in intake, live weight gain, digestion and feed conversion as a result of adding more than 7 g urea/kg. 3. The proportion of protein degraded in the rumen was estimated by the synthetic fibre bag technique to be 0.69, 0.82 and 0.54 for HPB, LPB and maize respectively. The similarity in concentration of urea required for optimum utilization of LPB AND HPB might be explained by differences in the extent of degradation of protein in the rumen, but the lower concentration of urea required for maize cannot be similarly explained. 4. From estimates of yield of microbial protein in the rumen, the extent of rumen fermentation and the measured extent of protein degradation, theoretical requirements for urea were calculated and compared with other predictions and with the experimentally determined values. For barley, predicted values agreed reasonably well with experimental ones, but for maize all values, including those derived by a new system adopted by the Agricultural Research Council (ARC) Working Party, were too high.
TL;DR: In this paper, the authors used urease immobilized in an enzyme reactor to determine the amount of mercury in the mixture of urea and bicarbonate and ammonia, the latter being measured by an ammonia gas electrode.
TL;DR: The results indicate that the hepatic responses to ethanol and acetaldehyde are different if the livers are derived from fed or fasted donors, and it is not possible to ascribe the toxic effects of acetaldehyde or ethanol on albumin and urea synthesis to either agent, per se.
TL;DR: The α-Galactosidase from Saccharomyces carlsbergensis has been reported to be stable to both acidic and alkaline conditions as well as to heating to 50 °C as discussed by the authors.
TL;DR: The calcium binding in urea indicates that the spasmins within a single spasmoneme have different calcium affinities, and this difference in calcium-binding properties may be an important factor in the physiological function of the organelle.
Abstract: The proteins of the contractile spasmoneme from Vorticella convallaria, Carcheslium polypinum, and Zoothamnium geniculatum have been extracted in the detergent, sodium dodecyl sulfate (SDS), as well as urea and guanidine hydrochloride (GuCl). After SDS extraction, the molecular weight distribution of the proteins was examined by means of SDS-polyacrylamide gel electrophoresis. Significant amounts of material corresponding to the contractile proteins actin and tubulin are not present. The contractile organelles in the three species examined contain a group of closely related proteins of molecular weight near 20,000, which constitute a major part (40-60%) of the dry mass. The 20,000 mol wt proteins in Zoothamnium bind calcium with high affinity (pK congruent to 6) and are termed "spasmins." By means of urea polyacrylamide gel electrophorsis, it is demonstrated that in Carchesium and Zoothamnium certain spasmin components bind calcium even in the presence of 6 M urea. The binding of calcium in 6 M urea suggests a functional relationship between the spasmins and the calcium-binding proteins of striated muscle which behave similarly. The calcium binding in urea also indicates that the spasmins within a single spasmoneme have different calcium affinities, and this difference in calcium-binding properties may be an important factor in the physiological function of the organelle.