Determination of the Rate of Urea Synthesis from Serial Measurements of Plasma Urea Concentration after an Alanine Load: Theoretical and Methodological Aspects

1985 ◽  
Vol 68 (2) ◽  
pp. 201-208 ◽  
Author(s):  
D. Geiseler ◽  
J. D. S. Kay ◽  
V. G. Oberholzer ◽  
J. W. T. Seakins ◽  
M. Hjelm
Keyword(s):  
Isotopic Analysis ◽  
Urea Synthesis ◽  
Experimental Conditions ◽  
Maximum Increase ◽  
Plasma Urea ◽  
Desk Computer ◽  
Plasma Urea Concentration ◽  
Methodological Aspects ◽  
Serial Measurements

1. A method is described by which the rate of synthesis of urea can be calculated from the change of plasma concentration of urea after an alanine load. 2. The results can be expressed in terms of f, the maximum increase in the rate of urea synthesis, and t, the time at which urea synthesis reaches its maximum. 3. These parameters are calculated by an algebraic curve-fitting technique which is suitable for a desk computer. 4. The method removes the need for isotopic analysis and urine collections. 5. The effect of various errors and experimental conditions on the calculated synthesis parameters is investigated.

Digestion and nitrogen conservation in cattle and buffaloes given rice straw with or without molasses

1992 ◽  
Vol 119 (2) ◽  
pp. 255-263 ◽  
Author(s):  
N. Abdullah ◽  
J. V. Nolan ◽  
M. Mahyuddin ◽  
S. Jalaludin
Keyword(s):  
Rice Straw ◽  
The Body ◽  
Synthesis Rate ◽  
Urea Synthesis ◽  
Total Volatile ◽  
Plasma Urea ◽  
Rumen Ph ◽  
Swamp Buffaloes ◽  
Nitrogen Conservation ◽  
Plasma Urea Concentration

SUMMARYUsing [14C]urea, the rates of urea synthesis in the body, excretion in the urine and degradation in the rumen and gut were compared in 20-month-old Kedah-Kelantan cattle and swamp buffaloes at the Universiti Pertanian Malaysia, Malaysia in 1987. The animals were fed rice straw or straw plus molasses.The buffaloes were heavier than the cattle and had higher straw and nitrogen intakes, although these intakes did not differ significantly when compared on the basis of metabolic liveweight (W0·75).Rumen pH in the buffaloes was lower, whereas ammonia and total volatile fatty acid (VFA) concentrations were higher than in the cattle. Total VFA concentration was lower when the diet contained molasses. Rumen bicarbonate kinetics did not differ significantly between species or diets.There were no significant differences between species in plasma urea concentration, or urea synthesis rate per W0·75, or endogenous urea movement into the rumen per W0·75.The buffaloes consumed more water and discharged twice as much urine as the cattle, but nevertheless excreted less urea per W0·75, and a larger fraction of their endogenously produced urea entered the gut. Movement of urea into the rumen per W0·75 was lower when the diet contained molasses.

scholarly journals Substrate and pH effects on glutamine synthesis in rat liver. Consequences for acid-base regulation

1991 ◽  
Vol 278 (3) ◽  
pp. 709-714 ◽  
Author(s):  
M K Almond ◽  
A Smith ◽  
R D Cohen ◽  
R A Iles ◽  
G Flynn
Keyword(s):  
Ph Effects ◽  
Urea Synthesis ◽  
Acid Base ◽  
Plasma Urea ◽  
Net Uptake ◽  
Male Wistar Rats ◽  
Glutamine Synthesis ◽  
Ph Range ◽  
Plasma Urea Concentration ◽  
Glutamine Uptake

Switching in acidosis of hepatic nitrogen disposal from urea synthesis to NH4+ and net glutamine production was demonstrated in the isolated perfused livers of starved male Wistar rats. Lactate was preferred to glucose as the substrate for the carbon skeleton of glutamine synthesized over the pH range 6.9-7.5. This is necessary if the switch away from a proton-producing process (ureagenesis) in acidosis is to constitute an acid-base regulating system intrinsic to the liver. Glutamine balance shifted with pH from marked net uptake to small net output under acidotic conditions (pH 7.5-6.9), an effect due solely to a decrease in glutamine uptake. NH4+ uptake by the liver had a linear relationship with pH, being markedly decreased in acidosis because glutamine synthesis was insufficient to compensate for the decreased incorporation into urea. Animals rendered chronically acidotic showed a lower central venous plasma urea concentration and a raised NH4+ concentration, but their livers synthesized no more glutamine when perfused at an acidotic pH than did normal livers. We conclude that perivenous hepatocytes may not be efficient scavengers of NH4+ ions, which must be partly disposed of elsewhere by non-proton-generating pathways if inhibition of ureagenesis is to represent a hepatic acid-base regulating system.

The nitrogen metabolism of sheep consuming Flinders grass (Iseilema spp.), Mitchell grass (Astrebla spp.) and mixed native pasture

1978 ◽  
Vol 29 (3) ◽  
pp. 595 ◽  
Author(s):  
BW Norton ◽  
RM Murray ◽  
KW Entwistle ◽  
JV Nolan ◽  
FM Ball ◽  
...  
Keyword(s):  
Digestive Tract ◽  
Nitrogen Metabolism ◽  
Nutritive Value ◽  
The Body ◽  
Urea Synthesis ◽  
Plasma Urea ◽  
Native Pasture ◽  
Nitrogen Conservation ◽  
Plasma Urea Concentration ◽  
Energy Balances

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.

Antithrombin-mediated Inhibition of Factor Vlla-Tissue Factor Complex by the Synthetic Pentasaccharide Representing the Heparin Binding Site to Antithrombin

1996 ◽  
Vol 76 (01) ◽  
pp. 005-008 ◽  
Author(s):  
Jean Claude Lormeau ◽  
Jean Pascal Herault ◽  
Jean Marc Herbert
Keyword(s):  
Binding Site ◽  
Tissue Factor ◽  
Residual Activity ◽  
Coagulation Factors ◽  
Heparin Binding ◽  
Experimental Conditions ◽  
First Order ◽  
Heparin Binding Site ◽  
Coagulant Activity

SummaryWe examined the effect of the synthetic pentasaccharide representing the minimal binding site of heparin to antithrombin on the antithrombin-mediated inactivation of factor Vila bound to tissue factor. This effect was compared to the effect of unfractionated heparin. Using purified recombinant human coagulation factors and either a clotting or an amidolytic assay for the determination of the residual activity of factor Vila, we showed that the pentasaccharide was an efficient antithrombin-dependent inhibitor of the coagulant activity of tissue factor-factor Vila complex. In our experimental conditions, assuming a mean MW of 14,000 for heparin, the molar pseudo-first order rate constants for ATIII-mediated FVIIa inhibition by ATIII-binding heparin and by the synthetic pentasaccharide were found to be similar with respective values of 104,000 ± 10,500 min-1 and 112,000 ± 12,000 min-1 (mean ± s.e.m., n = 3)

Determination of alcohols in mixtures by 19F NMR spectroscopy using hexefluoroacetone reagent

1982 ◽  
Vol 47 (7) ◽  
pp. 1973-1978 ◽  
Author(s):  
Jiří Karhan ◽  
Zbyněk Ksandr ◽  
Jiřina Vlková ◽  
Věra Špatná
Keyword(s):  
Standard Deviation ◽  
Nmr Spectroscopy ◽  
Standard Method ◽  
Internal Standard ◽  
Internal Standard Method ◽  
Concentration Region ◽  
Experimental Conditions ◽  
Curve Method ◽  
Sample Preparation Procedure

The determination of alcohols by 19F NMR spectroscopy making use of their reaction with hexafluoroacetone giving rise to hemiacetals was studied on butanols. The calibration curve method and the internal standard method were used and the results were mutually compared. The effects of some experimental conditions, viz. the sample preparation procedure, concentration, spectrometer setting, and electronic integration, were investigated; the conditions, particularly the concentrations, proved to have a statistically significant effect on the results of determination. For the internal standard method, the standard deviation was 0.061 in the concentration region 0.032-0.74 mol l-1. The method was applied to a determination of alcohols in the distillation residue from an oxo synthesis.

scholarly journals Software-guided microscale flow calorimeter for efficient acquisition of thermokinetic data

2021 ◽  
Author(s):  
Timothy Aljoscha Frede ◽  
Marlene Dietz ◽  
Norbert Kockmann
Keyword(s):  
Design Of Experiments ◽  
Process Development ◽  
Reaction Conditions ◽  
Experimental Conditions ◽  
Flow Calorimeter ◽  
Microscale Flow ◽  
Increased Sensitivity ◽  
Important Time ◽  
Optimal Reaction

AbstractFast chemical process development is inevitably linked to an optimized determination of thermokinetic data of chemical reactions. A miniaturized flow calorimeter enables increased sensitivity when examining small amounts of reactants in a short time compared to traditional batch equipment. Therefore, a methodology to determine optimal reaction conditions for calorimetric measurement experiments was developed and is presented in this contribution. Within the methodology, short-cut calculations are supplemented by computational fluid dynamics (CFD) simulations for a better representation of the hydrodynamics within the microreactor. This approach leads to the effective design of experiments. Unfavourable experimental conditions for kinetics experiments are determined in advance and therefore, need not to be considered during design of experiments. The methodology is tested for an instantaneous acid-base reaction. Good agreement of simulations was obtained with experimental data. Thus, the prediction of the hydrodynamics is enabled and the first steps towards a digital twin of the calorimeter are performed. The flow rates proposed by the methodology are tested for the determination of reaction enthalpy and showed that reasonable experimental settings resulted. Graphical abstract A methodology is suggested to evaluate optimal reaction conditions for efficientacquisition of kinetic data. The experimental design space is limited by thestepwise determination of important time scales based on specified input data.

Genome-wide association for plasma urea concentration in sheep

2021 ◽  
Vol 248 ◽  
pp. 104483
Author(s):  
Taiana Cortez de Souza ◽  
Tatiana Cortez de Souza ◽  
Gregorí Alberto Rovadoscki ◽  
Luiz Lehmann Coutinho ◽  
Gerson Barreto Mourão ◽  
...  
Keyword(s):  
Urea Concentration ◽  
Genome Wide Association ◽  
Plasma Urea ◽  
Genome Wide ◽  
Plasma Urea Concentration

scholarly journals Apparent Young’s Modulus of the Adhesive in Numerical Modeling of Adhesive Joints

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 328
Author(s):  
Kamil Anasiewicz ◽  
Józef Kuczmaszewski
Keyword(s):  
Numerical Model ◽  
Young’S Modulus ◽  
Adhesive Joint ◽  
Young's Modulus ◽  
Precise Determination ◽  
Adhesive Joints ◽  
Experimental Conditions ◽  
Element Simulation ◽  
Joint Material

This article is an evaluation of the phenomena occurring in adhesive joints during curing and their consequences. Considering changes in the values of Young’s modulus distributed along the joint thickness, and potential changes in adhesive strength in the cured state, the use of a numerical model may make it possible to improve finite element simulation effects and bring their results closer to experimental data. The results of a tensile test of a double overlap adhesive joint sample, performed using an extensometer, are presented. This test allowed for the precise determination of the shear modulus G of the cured adhesive under experimental conditions. Then, on the basis of the research carried out so far, a numerical model was built, taking the differences observed in the properties of the joint material into account. The stress distribution in a three-zone adhesive joint was analyzed in comparison to the standard numerical model in which the adhesive in the joint was treated as isotropic. It is proposed that a joint model with three-zones, differing in the Young’s modulus values, is more accurate for mapping the experimental results.

scholarly journals Quantitative determination of organic adsorption capacity in the Palaeozoic shales from South China

2021 ◽  
pp. 014459872098303
Author(s):  
Sibo Wang ◽  
Zhiguang Song ◽  
Jia Xia ◽  
Yuan Gao ◽  
YaoPing Wang ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
Clear Understanding ◽  
Soluble Organic Matter ◽  
Maximum Increase ◽  
Immature Oil ◽  
Methane Sorption ◽  
Oil Shales ◽  
The Impact ◽  
Total Adsorption

In this study, the methane adsorption capacity of kerogen isolated from the Cambrian, Silurian, and Permian shales and the impact of soluble organic matter (SOM) on the adsorption capacity of these shales were investigated. The results reveal that 1) the adsorption capacity of kerogen varies in a broad range, from 14.48 to 23.22 cm3/g for the Cambrian kerogens, from 15.50 to 36.06 cm3/g for the Silurian kerogens, and from 10.71 to 11.15 cm3/g for the Permian kerogens; 2) the kerogen adsorption accounts for 33.67–70.23% of the total adsorption capacity of these Palaeozoic extracted shales, demonstrating that kerogen is the primary adsorbing substance in shales; 3) the adsorption isotherms of kerogen in highly mature Cambrian and Silurian shales are similar to those of Triassic coal, while the isotherms of kerogen in the relatively immature Permian shales are similar to those of the immature oil shales; and 4) the SOM demonstrates a significant impact on the adsorption capacity of shales as the removal of SOM can cause a maximum increase of 34.29% or a decrease of 23.36% in the total adsorption capacity of shales. However, there is no clear understanding of the impact of SOM on the methane sorption of shales.

Factors affecting in vitro and in vivo antioxidant effects. Experimental conditions and nature of oxidants determine antioxidant efficacy

2021 ◽  
pp. 1-9
Author(s):  
Etsuo Niki
Keyword(s):  
Biological Molecules ◽  
Experimental Conditions ◽  
Factors Affecting ◽  
Beneficial Effects ◽  
Multiple Oxidants ◽  
Antioxidant Effects

Reactive oxygen and nitrogen species have been implicated in the onset and progression of various diseases and the role of antioxidants in the maintenance of health and prevention of diseases has received much attention. The action and effect of antioxidants have been studied extensively under different reaction conditions in multiple media. The antioxidant effects are determined by many factors. This review aims to discuss several important issues that should be considered for determination of experimental conditions and interpretation of experimental results in order to understand the beneficial effects and limit of antioxidants against detrimental oxidation of biological molecules. Emphasis was laid on cell culture experiments and effects of diversity of multiple oxidants on antioxidant efficacy.

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