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Biomedical subjects

G T Royle

Publications and source records attributed to G T Royle.

81 records · Page 5Linked to original sources
PubMed1982

Urea, glucose and alanine kinetics in man: effects of glucose infusion.

1. The simultaneous effects of an intravenous glucose infusion on plasma urea, glucose and alanine kinetics were investigated in normal post-absorptive man. 2. The primed constant intravenous infusion of compounds labelled with stable isotopes, [15N2]urea, [6-2H]glucose and [3-13C]alanine, was used. 3. The rate of appearance of glucose and urea in the plasma was rapidly reduced by the 17.7 mumol min-1 kg-1 glucose infusion. 4. In contrast, during the glucose infusion there was an increased rate of appearance of alanine in the plasma, and an increased percentage of glucose carbon atoms derived from alanine. 5. Reduced production of glucose and urea during the glucose infusion was not due to decreased gluconeogenesis from alanine.

Adult↗
PubMed1982

Isotopic analysis of leucine and urea metabolism in exercising humans.

We have used the primed constant infusion of di-[15N]urea and [1-13C]leucine to determine the effects of mild exercise (approx 30% Vo2max for 105 min) on urea production and leucine metabolism in human subjects. The oxidation of plasma leucine was distinguished from the oxidation of leucine that never entered the plasma pool ("intracellular" leucine) by means of determining the enrichment of alpha-ketoisocaproic acid (alpha-KICA). Total leucine oxidation increased from 0.38 +/0 0.05 to 1.41 +/- 0.14 micromol . kg-1 . min-1 during exercise due to increases in the oxidation of plasma leucine (150%) and intracellular leucine (600%). Plasma leucine flux decreased slightly, but not significantly (0.1 greater than P greater than 0.05), and the percent of alpha-KICA derived from plasma leucine dropped significantly (P less than 0.05) from 79.5 +/- 4.3 at rest to 62.0 +/- 5.3% over the last 30 min of exercise. Despite the increase in leucine oxidation during exercise, urea concentration and production did not change. Thus in exercise urea production does not accurately reflect all aspects of amino acid metabolism.

Adult↗
PubMed1982

Leucine and urea metabolism in acute human cold exposure.

Four healthy males voluntarily underwent acute cold exposure at 10 degrees C. Metabolic rate doubled for the 100-min exposure. [1-13C]leucine and [15N2]urea were used as tracers of protein metabolism via a primed constant infusion. Total and plasma transported leucine oxidation approximately doubled, but the oxidation of leucine derived from protein in the tissue where oxidation occurred ("intracellular oxidation") did not change as it did when the same subjects underwent mild exercise. Rate of appearance of urea and leucine in plasma were not significantly different between control and cold. Although the rate of protein synthesis calculated from the leucine data did not change, the rate of catabolism increased. Net protein catabolism based on the urea data agreed well with the leucine data at rest but did not exhibit a significant increase during exposure. However, net protein catabolism based on the leucine data did increase significantly during acute cold exposure. Further, there appears to be a qualitative difference in the protein catabolism associated with the voluntary muscular activity of exercise and muscular shivering aimed at thermogenesis.

Blood Proteins↗
PubMed1981

Alanine metabolism in patients with chronic infection.

Alanine matabolism was studied in surgical patients with chronic infection and non-infected control subjects by means of an intravenous infusion of alanine. Septic patients had low basal blood concentrations of alanine compared with control subjects but alanine half-life was similar in both groups. This suggests that low basal alanine concentration in the septic patients was due to decreased release from muscle rather than increased hepatic uptake. Alanine infusion in septic patients caused a fall in the blood concentration of ketone bodies which was initially raised. Similar increases in blood concentrations of glucose, lactate, pyruvate an insulin occurred in both septic and control patients after alanine infusion. Hyperketonaemia may limit muscle breakdown and alanine release in patients with chronic infection.

Abscess↗
PubMed1981

Glutamate metabolism in malnutrition and sepsis in man.

The metabolism of intravenous glutamate has been studied for its usefulness as a nutrient in intravenous feeding regimens. Intravenously infused monosodium L-glutamate was rapidly removed from the blood with a half-life of 10.7 and 9.1 min in healthy control and malnourished septic patients, respectively. Under the same conditions, alanine was metabolized much more slowly, with a half-life of 35 min (1). After the infusion of glutamate, blood lactate fell and glucose was increased in the control patients but not in the sick patients. Blood pyruvate, ketone bodies, glutamine, aspartate and alanine levels did not change after the infusion of glutamate in either group of patients. Increased urinary excretion of aspartate was observed in the control patients following the infusion of glutamate, but in the sick patients there was an increased excretion of glutamine. Insulin concentration in the blood rose after the infusion of glutamate in the control patients but not in the sick patients. Although the glutamate half-life life was similar in the two groups of patients, glutamate was metabolized differently in the sick. Deamination predominates over transamination. We conclude that glutamate, in the amounts provided in intravenous feeding, is safe, although its effectiveness may be less than previously thought.

Adult↗
PubMed1981

A simple system of parenteral nutrition.

The practical problems involved in the preparation and delivery of parenteral nutrition may result in such treatment being withheld from patients who would benefit from it. A simple and reliable system is described which has been developed to overcome the more common problems.

Catheters, Indwelling↗
PubMed1981

Techniques for investigating substrate metabolism in patients.

Studies of dynamic aspects of substrate metabolism in patients can be made with a variety of techniques. Methods include indirect calorimetry, substrate load tests, measurement of arteriovenous differences with use of the Fick principle, and isotope infusions. Recent developments in stable isotope methodology have made available safe techniques for accurate measurement of the turnover of plasma substrates in patients. The use of deuterated, 13C, and 15N isotopes enables the turnover of several substrates to be measured at the same time. It is hoped that the primed constant infusion of stable isotopes combined with indirect calorimetry will lead to a greater understanding of metabolism in ill patients.

Calorimetry, Indirect↗
PubMedDate not supplied

A new intravenous emulsion containing medium-chain triglyceride: studies of its metabolic effects in the perioperative period compared with a conventional long-chain triglyceride emulsion.

The effects of carbohydrate, lipid, and nitrogen metabolism of recently available lipid emulsions containing either 50% medium-chain triglyceride (MCT) and 50% long-chain triglyceride (LCT) or 100% LCT were compared in elective surgical patients. Postoperative urinary urea excretion was similar during isocaloric MCT/LCT and LCT infusions (1.9 mg/kg/min) and was decreased compared with a standard infusion of 5% glucose (1 mg/kg/min). Plasma glucose and insulin concentrations were similar during both lipid and low dose glucose infusions. However, plasma triglyceride and nonesterified fatty acid concentrations were decreased during the MCT/LCT infusion compared with the LCT infusion, suggesting that the MCT/LCT emulsion was cleared from the circulation faster than pure LCT. Ketone body concentrations were similar during all three infusions. MCT/LCT emulsion can be safely infused perioperatively and has similar nitrogen conserving properties to LCT in these circumstances.

Blood Glucose↗