Recovery of Infused [14C]Bicarbonate as Respiratory 14CO2 in Man

Clugston, Graeme; Garlick, Peter J.

doi:10.1042/cs0640231

Cited by 37 publications

(19 citation statements)

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“…Others have reported on the coefficient of variation of 'plateau' recovery, which takes into account C02 production, e.g. 1-3% [23] or 6% [9]. One study has reported on the coefficient of variation ( < 10%) associated with the measurement of C02 production [2], but many studies do not give such results (e.g.…”

Section: Period Of Infusionmentioning

confidence: 94%

“…No relationship was found between the priming dose and recovery of label, but the use of different protocols, which involved assessment of recovery over widely different periods of time, and the use of different methods to analyse the results, confounds interpretation. [8,9,11,12,15,16,25,29,30,321 and five of these whole-body calorimetry [9,11,12,15,251. Eight studies used a hood or a face mask to measure the COz production intermittently.…”

Section: Period Of Infusionmentioning

confidence: 99%

“…With continuous infusions, three different methods have been used. The first calculates the recovery at a given point in time (point recovery) by multiplying specific activity or change in enrichment of C02 at a given point in time by COz production at the same time point [2,3,9,16,18,20,25,29,30,341. The second method calculates recovery over a specified period of time (period recovery) [ l l , 12, 13, 271 and the third involves calculating recovery at an apparent plateau enrichment (or an apparent plateau recovery over a variable period of time) depending on the individual subject or individual study [l, 3, 8, 9, 15, 18, 20, 23, 26, 27, 30, 341. It is difficult to estimate the short-term differences or short-term variations in recovery obtained by using these different methods because of the frequent lack of reported data.…”

Section: Period Of Infusionmentioning

confidence: 99%

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Recovery of 13CO2 and 14CO2 in Human Bicarbonate Studies: A Critical Review with Original Data

Leijssen¹,

Elia²

1996

Clinical Science

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1. In order to establish biological and/or methodological explanations for the wide variability in recovery (50-100%) of labelled CO2 after administration of [13C]bicarbonate or [14C]bicarbonate, 34 human bicarbonate studies involving 480 subjects were analysed, and potential methodological issues were investigated in the laboratory. 2. Overall, continuous infusion studies reported a higher recovery than bolus studies (84 +/- 11% versus 69 +/- 12%; P < 0.001). No significant differences in recovery were found between 14C and 13C studies, children and adults, obese and lean subjects, or rest and exercise (steady state). Higher recoveries were found during feeding than during fasting (84 +/- 8% versus 74 +/- 7%; P < 0.001). Different methods used to analyse the results (0-10%) and different study protocols, which include differences in the duration of infusions and background drift in 13C enrichment (0-10%), contribute to the variability. 3. The laboratory studies suggest multiple sources of potential error, including loss of CO2 from the scintillation fluid (up to > 30%, but only in 14C studies in which the scintillation fluid is not alkalized), diffusion of CO2 through syringes and tubing (0 to > 10%), non-linearity of CO2 analysers (up to 8%), inaccuracies in the measurement of bicarbonate concentrations (13C studies) or the strength of CO2-trapping agents (14C studies; 0-8%). 4. It is concluded that much of the variability in the recovery of labelled bicarbonate is likely to be attributable to methodological differences, and that attention to these will ensure better interpretation of metabolic studies that involve oxidation of carbon-labelled substrates.

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Section: Period Of Infusionmentioning

confidence: 94%

Section: Period Of Infusionmentioning

confidence: 99%

Section: Period Of Infusionmentioning

confidence: 99%

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Recovery of 13CO2 and 14CO2 in Human Bicarbonate Studies: A Critical Review with Original Data

Leijssen¹,

Elia²

1996

Clinical Science

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“…The magnitude of the error introduced by retention of labelled CO2 has been re-examined (Clugston & Garlick, 1983;Irving, Wong, Wong, Boutton, Shulman, Lifschitz, Malphus, Helge & Klein, 1983). To avoid uncertainty some workers now routinely give a primed infusion of labelled bicarbonate before the amino acid infusion (Matthews et al 1980;Clague, Keir, Wright & Johnston, 1983).…”

Section: Methods Of Measuring Protein Turnover In the Living Animalmentioning

confidence: 99%

Protein Turnover With Special Reference to Man

1984

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This review is concerned with rates of N flux in the living animal rather than with mechanisms of protein synthesis and breakdown at the cellular level. Methods of measuring protein turnover in the whole body are discussed, with special emphasis on studies in man, and results obtained by different methods have been compared. Aspects of whole body protein turnover which are of physiological interest include its relation to body size, growth and development, energy metabolism and food intake. There are substantial increases in protein turnover in injury, and changes that occur in exercise are beginning to be explored. From the physiological point of view these results point the need for future research along two main lines. The first is that of regulation: a wide variety of hormones stimulate or repress protein synthesis and breakdown, with varying actions in different tissues. These effects, however, do not in themselves explain the mechanism by which a balance between synthesis and breakdown is maintained. Secondly, the fact that all cellular proteins are in a dynamic state poses questions about the relation between structure and function in tissues such as muscle and brain, which physiologists have hardly begun to tackle.

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“…We calculated the instantaneous rate of label oxidation (T; [32] for substrate labelled with a single 13 C per molecule. We used a bicarbonate retention factor of 86 per cent because previous studies in various mammal taxa consistently showed that bicarbonate retention was almost identical across taxa [38][39][40][41]. Any deviation between assumed and true bicarbonate retention factors may not affect the relative difference in our estimates of compound-specific oxidation rates because this constant applies to both calculations in the same way.…”

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confidence: 99%

The insectivorous batPipistrellus nathusiiuses a mixed-fuel strategy to power autumn migration

et al. 2012

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In contrast to birds, bats are possibly limited in their capacity to use body fat as an energy source for long migrations. Here, we studied the fuel choice of migratory Pipistrellus nathusii (approximate weight: 8 g) by analysing the stable carbon isotope ratio (d C V-PDB of insect prey and adipocyte triacylglycerols, suggesting a mixed-fuel use of P. nathusii during autumn migration. To clarify the origin of oxidized fatty acids, we performed feeding experiments with captive P. nathusii. After an insect diet, bat breath was enriched in 13 C relative to the bulk and fat portion of insects, but not deviating from the non-fat portion of insects, suggesting that bats oxidized exogenous proteins and carbohydrates, but not exogenous fatty acids. A feeding experiment with 13 C-labelled substrates confirmed these findings. In conclusion, migratory P. nathusii oxidized dietary proteins directly from insects captured en route in combination with endogenous fatty acids from adipocytes, and replenished their body reserves by routing dietary fatty acids to their body reserves.

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Recovery of Infused [14C]Bicarbonate as Respiratory 14CO2 in Man

Abstract: 1. Nine adult subjects (eight obese, one normal) were infused with NaH14CO3 for up to 36 h. 2. The recovery of label as respiratory 14CO2 was close to 90% throughout and did not change with feeding or with dietary composition.

Cited by 37 publications

References 0 publications

Recovery of 13CO2 and 14CO2 in Human Bicarbonate Studies: A Critical Review with Original Data

Recovery of 13CO2 and 14CO2 in Human Bicarbonate Studies: A Critical Review with Original Data

Protein Turnover With Special Reference to Man

The insectivorous batPipistrellus nathusiiuses a mixed-fuel strategy to power autumn migration

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