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.

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.

Effects of pH on Glucose Measurements With Handheld Glucose Meters and a Portable Glucose Analyzer for Point-of-Care Testing

2000 ◽  
Vol 124 (4) ◽  
pp. 577-582 ◽  
Author(s):  
Zuping Tang ◽  
Xiaogu Du ◽  
Richard F. Louie ◽  
Gerald J. Kost
Keyword(s):  
Glucose Level ◽  
Point Of Care ◽  
Diabetic Patients ◽  
Ph Effects ◽  
Acid Base ◽  
Glucose Levels ◽  
Glucose Testing ◽  
Ph Range ◽  
Control Samples

Abstract Objectives.—To determine pH effects on glucose measurements obtained with the latest generation of glucose devices, to quantitate changes in glucose measurements obtained over a wide pH range, and to assess the potential clinical risks of pH effects with use of point-of-care glucose testing. Design.—Paired differences of glucose measurements between pH-altered and parallel control samples with target pH 7.40 were calculated. Setting.—A pH range of 6.94 to 7.84 was used to evaluate pH effects on glucose measurements in vitro with 6 handheld glucose meters and a portable glucose analyzer at both normal, 4.81 mmol/L (86.6 mg/dL), and high, 11.16 mmol/L (201 mg/dL), glucose levels. Main Outcome Measures.—Glucose measurements obtained from test samples and control samples were compared by calculating paired differences, which were plotted against pH to show pH effects on glucose meter measurements. Results.—At the normal glucose level, different pH levels did not interfere significantly with glucose measurements. At the high glucose level, a trend whereby low pH decreased and high pH increased glucose measurements was observed on the Precision G and the Precision QID glucose meters. Conclusion.—Because of potential risk in diabetic patients with ketoacidosis and in other patients with acid-base disorders, we recommend that clinicians choose glucose devices carefully and interpret the measurements cautiously when point-of-care glucose testing is performed in critically ill patients with acidemia, alkalemia, or changing acid-base status.

Control of breathing in uremia: ventilatory response to CO2 after hemodialysis

1976 ◽  
Vol 41 (2) ◽  
pp. 216-222 ◽  
Author(s):  
R. W. Hamilton ◽  
P. E. Epstein ◽  
L. W. Henderson ◽  
N. H. Edelman ◽  
A. P. Fishman
Keyword(s):  
Carbon Dioxide ◽  
Ventilatory Response ◽  
Respiratory Alkalosis ◽  
Similar Increase ◽  
Acid Base ◽  
Plasma Urea ◽  
Acid Base Status ◽  
Uremic Patients ◽  
Plasma Urea Concentration ◽  
Ventilatory Response To Co2

The mechanisms responsible for the transient respiratory alkalosis which follows clinical hemodialysis were evaluated by studying the ventilatory response to carbon dioxide in chronic uremic patients, and in unanesthetized normal and chronic uremic goats. A significant increase in sensitivity to CO2 was found in acidotic uremic patients immediately (within 30 min) following hemodialysis (P less than 0.01). Sensitivity to CO2 returned to the predialysis value within 24 h. Lung volume and maximal breathing capacity were unchanged. A similar increase in sensitivity to CO2 was seen in nonacidotic uremic goats following hemodialysis. In the goats, these changes in sensitivity could not be explained by changes in cerebrospinal fluid acid-base status. Adding sufficient urea to the dialysate to prevent a fall in plasma urea concentration, eliminated this increase in sensitivity to CO2 in both uremic patients and goats. These results suggests that the transient respiratory alkalosis following hemodialysis is due to an increase in the sensitivity of the ventilatory response to carbon dioxide and is a consequence of dialysis-induced osmotic disequilibrium.

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.

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.

Grand-Reaction Method for Simulations of Ionization Equilibria and Ion Partitioning in a Broad Range of pH and Ionic Strength

2019 ◽  
Author(s):  
Jonas Landsgesell ◽  
Oleg Rud ◽  
Pascal Hebbeker ◽  
Raju Lunkad ◽  
Peter Košovan ◽  
...  
Keyword(s):  
Mean Field ◽  
Coarse Grained ◽  
Reactive System ◽  
Acid Base ◽  
Buffer Solution ◽  
Reaction Method ◽  
Ionization Equilibria ◽  
Coarse Grained Simulations ◽  
Ph Range ◽  
Weak Polyelectrolytes

We introduce the grand-reaction method for coarse-grained simulations of acid-base equilibria in a system coupled to a reservoir at a given pH and concentration of added salt. It can be viewed as an extension of the constant-pH method and the reaction ensemble, combining explicit simulations of reactions within the system, and grand-canonical exchange of particles with the reservoir. Unlike the previously introduced methods, the grand-reaction method is applicable to acid-base equilibria in the whole pH range because it avoids known artifacts. However, the method is more general, and can be used for simulations of any reactive system coupled to a reservoir of a known composition. To demonstrate the advantages of the grand-reaction method, we simulated a model system: A solution of weak polyelectrolytes in equilibrium with a buffer solution. By carefully accounting for the exchange of all constituents, the method ensures that all chemical potentials are equal in the system and in the multi-component reservoir. Thus, the grand-reaction method is able to predict non-monotonic swelling of weak polyelectrolytes as a function of pH, that has been known from mean-field predictions and from experiments but has never been observed in coarse-grained simulations. Finally, we outline possible extensions and further generalizations of the method, and provide a set of guidelines to enable safe usage of the method by a broad community of users.<br><br>

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

Role of acidosis in regulating hepatic nitrogen metabolism during fasting in conscious dog

1987 ◽  
Vol 252 (3) ◽  
pp. E313-E319
Author(s):  
E. Cersosimo ◽  
P. E. Williams ◽  
D. O'Donovan ◽  
D. B. Lacy ◽  
N. N. Abumrad
Keyword(s):  
Extraction Methods ◽  
Redox Potentials ◽  
Fick Principle ◽  
Dependent Component ◽  
Glutamine Synthesis ◽  
Lactate Utilization ◽  
Hepatic Portal ◽  
Beta Hydroxybutyrate ◽  
Glutamine Uptake

This study was designed to investigate the role that acidosis plays in the metabolic responses to fasting. Eighteen conscious dogs with surgically implanted catheters in the femoral artery and in the hepatic, portal, and renal veins were studied. Six were fasted for 24 h and 12 were fasted for 4 days (96 h). On the day of the study, six 4-day fasted dogs were infused intravenously with NaHCO3 (10 mumol X kg-1 X min-1) for 3 h, while the rest received saline and acted as controls. Splanchnic balances of glutamine, alanine, blood urea nitrogen, ammonia, lactate, beta-hydroxybutyrate, and acetoacetate were estimated using the Fick principle. Blood flow to the splanchnic and renal beds were estimated using indocyanine green and p-aminohippurate extraction methods, respectively. The infusion of NaHCO3 nearly abolished the base deficit associated with fasting and normalized arterial bicarbonate levels but did not alter blood pH. It suppressed but did not abolish hepatic glutamine output by 60%. This was associated with a shift in cytoplasmic and mitochondrial redox potentials of the hepatocyte as evident by a decrease in hepatic production of beta-hydroxybutyrate and an increase in hepatic production of acetoacetate and a decrease in hepatic lactate utilization. Concomitantly, renal glutamine uptake decreased. Glutamine release of skeletal muscle was unchanged. The data suggest that hepatic glutamine synthesis and release seen with 4-day fasting has two components: a bicarbonate-dependent component that is influenced by the redox potential of the hepatocyte and a bicarbonate-independent component, the nature of which is not yet clear.(ABSTRACT TRUNCATED AT 250 WORDS)

Urea Excretion in the Camel

1957 ◽  
Vol 188 (3) ◽  
pp. 477-484 ◽  
Author(s):  
Bodil Schmidt-Nielsen ◽  
Knut Schmidt-Nielsen ◽  
T. R. Houpt ◽  
S. A. Jarnum
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Urea Concentration ◽  
Nitrogen Excretion ◽  
Renal Tubules ◽  
Urea Clearance ◽  
Plasma Urea ◽  
Urea Excretion ◽  
Plasma Urea Concentration

The nitrogen excretion was studied in the one-humped camel, Camelus dromedarius. When a growing camel was maintained on a low N intake (dates and hay) the amount of N excreted in the form of urea, NH3 and creatinine decreased to 2–3 gm/day. This decrease was caused by a drop in urea excretion from 13 gm to 0.2–0.5 gm/day. Urea given intravenously during low N intake was not excreted but was retained. (The camel like other ruminants can utilize urea for microbial synthesis of protein.) The renal mechanism for urea excretion was investigated by measuring urea clearance and glomerular filtration rate during a period of 7 months. During normal N intake about 40% of the urea filtered in the glomeruli were excreted in the urine while during low N intake only 1–2% were excreted. The variations in urea clearance were independent of the plasma urea concentration and of glomerular filtration rate, but were related to N intake and rate of growth. No evidence of active tubular reabsorption of urea was found since the urine urea concentration at all times remained higher than the simultaneous plasma urea concentration. The findings are not in agreement with the current concept for the mechanism of urea excretion in mammals. It is concluded that the renal tubules must either vary their permeability to urea in a highly selective manner or secrete urea actively.

scholarly journals Utilization of Extract of Sambang Getih Leaves (Hemigraphis colorata. Hall. F) as a Acid-Base Indicator

2020 ◽  
Vol 9 (1) ◽  
pp. 7-15
Author(s):  
Eksari Ekasari ◽  
Purnama Ningsih
Keyword(s):  
Leaf Extract ◽  
Strong Acid ◽  
Weak Base ◽  
Acid Base ◽  
Strong Base ◽  
Unique Color ◽  
Acid Base Titration ◽  
Naoh Solution ◽  
Ph Range ◽  
Color Pigment

Getih sambang leaves (Hemigraphis Colorata. Hall. F) are plants that have a distinctive and unique color, namely the upper surface of the leaf is green and the bottom of the leaf is burgundy where sambang leaves contain anthocyanin compounds. Anthocyanin is the color pigment in plants that forms the basis of the use of natural indicators. This study aims to prove whether getih cucumber leaves can be used as an acid-base indicator, to determine the type of acid-base titration that is suitable for indicators of getih cucumber leaves, and to find out what the pH-changing color route of getih cucumber leaves is. The method used is extraction, namely maceration. Wee leaves are macerated by using methanol as a solvent for 24 hours. The extract was previously tested using HCl solution and NaOH solution as a test to prove the presence of anthocyanin. The results obtained in this study, getih sambang leaf extract can be used as an indicator of acid base, and also the type of acid-base titration that is suitable for use in the indicator of getih leaf extract extract precisely on the titration of strong-base strong acid, and strong weak base-acid It is best used as a substitute for the phenolphthalein indicator. In titration of strong and weak acids and bases, it is good to be used as a substitute for the indicator of methyl orange. The pH range obtained from the getih sambang leaf extract is pH 4-7 (red-purple).

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