Tracer priming the bicarbonate pool

Allsop, John R.; Wolfe, Robert R.; Burke, John F.

doi:10.1152/jappl.1978.45.1.137

Cited by 209 publications

(90 citation statements)

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“…This is not necessarily true. In studies where 13 C-bicarbonate had been infused in human subjects the percentage of 13 CO 2 reported as recovered varied widely from approximately 50 to almost 100% (Irving et al, 1983;Allsop et al, 1978;Halliday, 1991). Furthermore, there is evidence to suggest that feeding or underfeeding could affect the amount of 13 CO 2 recovered (Wenham et al, 1991) in labelled experiments.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, there is evidence to suggest that feeding or underfeeding could affect the amount of 13 CO 2 recovered (Wenham et al, 1991) in labelled experiments. The bicarbonate correction factor has been used to account for this discrepancy (Allsop et al, 1978). More recently, Sidossis et al (1995) suggested that the use of the bicarbonate correction factor is invalid because it does not account for labelled ®xation, which occurs in many tissues through tricarboxylic acid cycle (TCA) exchange reactions.…”

Section: Discussionmentioning

confidence: 99%

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Dose-response relationship between fat ingestion and oxidation: quantitative estimation using whole-body calorimetry and 13C isotope ratio mass spectrometry

Coward

et al. 2001

Eur J Clin Nutr

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Objective: To determine dose-dependent relationship between ingested fat and its oxidation in the immediate post-prandial period in humans. Design: Subjects were randomly selected for the study at the Dunn Clinical Nutrition Centre, Cambridge, UK. Subjects ingested naturally enriched 13 C corn-oil doses (range 20 ± 140 g) in a whole-body indirect calorimeter, and were studied for 8 h. Ingested fat oxidation was estimated from the subject's breath 13 C enrichment and total carbon dioxide production. Total fat and carbohydrate oxidation were estimated from non-protein oxygen and carbon dioxide exchanges. Endogenous fat oxidation was estimated as the difference between total fat and ingested fat oxidation. Results: The amount of fat dose oxidized was nonlinearly related to the amount ingested. On average, 25.6 AE 2.7% of the mean fat dose was oxidized. A signi®cant (r 7 0.72, P`0.001) inverse correlation was found between the amount of fat dose and the proportion oxidized. Endogenous carbohydrate oxidation was negatively and signi®cantly correlated to fat dose oxidized (r 7 0.61, P`0.01), but it was not correlated to endogenous fat oxidation.Conclusions: There was a nonlinear relationship between amount of fat dose and its quantity that was oxidized in the immediate post-prandial period. The inverse relationship between the size of the fat load and the proportion that was oxidized post-prandially implies increased dietary fat storage beyond about 50 g in a normal resting adult. This has important implications for 13 CO 2 -based studies.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Dose-response relationship between fat ingestion and oxidation: quantitative estimation using whole-body calorimetry and 13C isotope ratio mass spectrometry

Coward

et al. 2001

Eur J Clin Nutr

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“…The experimental protocol was approved by the Institutional Ethical Committee. (4,19). After 2 h ofisotope equilibration, samples were drawn at 10-min intervals from 120 to 180 min for the determination of basal leucine and a-ketoisocaproic acid (a-KIC) specific activities, as well as hormone and substrate concentrations.…”

Section: Introductionmentioning

confidence: 99%

“…Expired air samples were collected at 15-min intervals and bubbled through a CO2 trapping solution (hyamine hydroxide/absolute ethanol/0. 1% phenolphthalein, 3:5:1) as described previously (4,19). The solution was titrated to trap 1 mmol CO2 per 3 ml of solution.…”

Section: Introductionmentioning

confidence: 99%

Combined pancreas and kidney transplantation normalizes protein metabolism in insulin-dependent diabetic-uremic patients.

Luzi¹,

Battezzati²,

Perseghin³

et al. 1994

J. Clin. Invest.

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In order to assess the combined and separate effects of pancreas and kidney transplant on whole-body protein metabolism, 9 insulin-dependent diabetic-uremic patients (IDDUP), 14 patients after combined kidney-pancreas transplantation (KPTx), and 6 insulin-dependent diabetic patients with isolated kidney transplant (K-Tx), were studied in the basal postabsorptive state and during euglycemic hyperinsulinemia (study 1). 11-14ClLeucine infusion and indirect calorimetry were utilized to assess leucine metabolism. The subjects were studied again with a combined infusion ofinsulin and amino acids, given to mimic postprandial amino acid levels (study 2). Amol* m-2. min-') (P = NS vs. CON). During hyperinsulinemia (study 1), IDDUP showed a defective decrease of leucine (42% vs. 53%; P < 0.05), BCAA (38% vs. 47%, P < 0.05), ELF (28% vs. 33%, P < 0.05), and LO (0% vs. 32%, P < 0.05) with respect to CON. Isolated kidney transplant reverted the defective inhibition of ELF (34%, P = NS vs. CON) of IDDUP, but not the inhibition of LO (18%, P < 0.05 vs. CON) by insulin. Combined kidney and pancreas transplantation normalized all kinetic parameters of insulin-mediated protein turnover. During combined hyperinsulinemia and hyperaminoacidemia (study 2), IDDUP showed a defective stimulation of NOLD

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“…where V CO 2 is the rate of CO 2 production (micromoles per kilogram per hour), 13 CO 2 MPE is the 13 C enrichment of expired CO 2 at steady state, and 0.8 is a constant representing the fractional recovery of 13 CO 2 obtained during 13 Cbicarbonate infusions in adults and newborns that corrects for the loss of the 13 C label (28,29). From the above, NOD leuc and RP leuc can then be determined using Equation 1 above.…”

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confidence: 99%

Effect of Low versus High Intravenous Amino Acid Intake on Very Low Birth Weight Infants in the Early Neonatal Period

Thureen

2003

Pediatric Research

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Greater protein intakes are required than have been commonly used to achieve fetal in utero protein accretion rates in preterm neonates. To study the efficacy and safety of more aggressive amino acid intake, we performed a prospective randomized study in 28 infants [mean wt, 946 Ϯ 40 g (SEM)] of 1 (low amino acid intake, LAA) versus 3 g·kg Ϫ1 ·d Ϫ1 (high amino acid intake, HAA) at 52.0 Ϯ 3.0 h of life. After a minimum of 12 h of parenteral nutrition, efficacy was determined by protein balance and was significantly lower in the LAA versus HAA groups by both nitrogen balance (Ϫ0. Abbreviations PN, parenteral nutrition LAA, low amino acid intake HAA, high amino acid intake Int leuc , leucine intake rate Q leuc , leucine flux rate Ox leuc , leucine oxidation rate NOD leuc , nonoxidative leucine disposal intake rate RP leuc , rate of leucine appearance from protein breakdown ELBW, extremely low birth weight BUN, blood urea nitrogen GCMS, gas chromatography-mass spectroscopyThe current standard for postnatal nutrition in all preterm infants is one that duplicates normal in utero fetal growth rates (1). Owing to advances in perinatal care, more very preterm infants are surviving. These infants have unique nutritional metabolic requirements for growth, predicted by low energy stores, high protein flux rate, and a high metabolic rate as a result of a relatively larger mass of metabolically active organs. Nevertheless, it is common practice in many neonatal intensive care units to limit nutrient administration, particularly amino acids, to ELBW or sick neonates in the early neonatal period because of concerns of substrate intolerance. Several studies suggest that this delay in nutrition results in postnatal malnutrition that produces measurable growth failure at hospital discharge (2-4).Although strategies to improve growth necessitate delivery of larger amounts of both energy and protein beginning shortly after birth, there are reasons to suggest that focusing on protein delivery may be particularly important. Throughout life, maximal weight-specific protein gain occurs before 32 wk gestation (5). Data from studies in fetal animal models suggest that amino acid metabolic rates may be a much more sensitive indicator than growth rate of adequate nutrition before term (6). Additionally, recent data suggest that long-term developmental outcome in the preterm may be correlated with early protein intake (7

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Tracer priming the bicarbonate pool

Cited by 209 publications

References 0 publications

Dose-response relationship between fat ingestion and oxidation: quantitative estimation using whole-body calorimetry and 13C isotope ratio mass spectrometry

Dose-response relationship between fat ingestion and oxidation: quantitative estimation using whole-body calorimetry and 13C isotope ratio mass spectrometry

Combined pancreas and kidney transplantation normalizes protein metabolism in insulin-dependent diabetic-uremic patients.

Effect of Low versus High Intravenous Amino Acid Intake on Very Low Birth Weight Infants in the Early Neonatal Period

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