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  • 1
    Electronic Resource
    Electronic Resource
    Pulse injection, 13C tracer studies of lactate metabolism in humans during rest and two levels of exercise (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 9 (1982), S. 310-314 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to determine the role of lactic acid as a metabolic substrate during exercise, the extent of its oxidation was studied using (13C)lactate under three different metabolic conditions in two subjects. During rest, easy exercise (work below the lactate inflection point), and hard exercise (work above the lactate inflection point), 100 mg of Na+-D,L(+)-2,3-(13C)lactate was injected via an indwelling catheter inserted in an antecubital vein. Blood as well as expired gas samples were collected up to 2 h post-injection. Subjects worked at average intensities of 53% and 74% VO2max during easy and hard exercise, respectively. During rest and easy exercise, blood lactate concentrations remained stable at 1-2 mM. During hard exercise, blood lactate increased to 3-4 times those observed at rest. Excretion of 13CO2 peaked much sooner and enrichment of 13C in CO2 was greater during both exercise intensities than during rest. Cumulative recovery of injected 13C as 13CO2 averaged 13.2 and 86.2% through 120 min during rest and easy exercise. Through 45 min of hard exercise, recovery of tracer as CO2 was the same as during a similar time point of easy exercise, 51.8%. The results support the contention that oxidation is the major fate of lactate during exercise.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200090708
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  • 2
    Electronic Resource
    Electronic Resource
    Geographical variations in the carbon isotope composition of the diet and hair in contemporary man (1982)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 9 (1982), S. 390-394 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Geographic variations in the carbon isotope composition of the human diet and human hair were investigated. The carbon isotopic composition of common foodstufls purchased in Chicago, USA, Tokyo, Japan and Munich, FRG, were determined by combustion and differential isotope ratio mass spectrometry. The dietary protein carbon for the United States (-18.1‰) was calculated to be enriched in 13C relative to the Japanese (-21.2‰) and the German (-23.6‰) diets. To a large degree, the differences reflected the consumption of corn-fed animal products in the United States and Japan, as well as seafood in Japan. The carbon isotopic composition of hair (-16.4, -18.0 and -20.4%) for the three respective populations correlated with the calculated values of the dietary protein, but were 2-3% enriched in 13C. Changes in the isotopic composition of beard hair were shown to record the changes in dietary composition in travelers visiting the respective regions.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200090906
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  • 3
    Electronic Resource
    Electronic Resource
    A simplified technique for collecting breath CO2 for isotope ratio mass spectrometry (1978)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 5 (1978), S. 29-31 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simplified technique of collecting breath CO2 for isotopic analysis has been developed. The subject breathes into a 3 I bag from which a 50 ml aliquot is transferred to an evacuated, septum-capped tube (Vacutainer®). The sample is later withdrawn and the CO2 is cryogenically purified. No isotope fractionation is observed in samples collected in this manner. Samples have been stored up to three months without any change in the isotope ratio.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200050106
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  • 4
    Electronic Resource
    Electronic Resource
    A microprocessor controlled mass spectrometer for the fully automated purification and isotopic analysis of breath carbon dioxideThis work was supported by the National Institutes of Health through grant AM 18741 and the US Department of Energy. The work was performed at both the University of Chicago and Argonne National Laboratory. This paper was presented in part at the Third International Conference on Stable Isotopes, Oak Brook, Illinois, USA (1978) and has appeared in abstract form in the conference proceedings. (1979)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 6 (1979), S. 350-355 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Breath tests that measure the oxidative utilization of 13C labeled substrates have been shown to be clinically useful, but have failed to gain wide acceptance because of the slow and costly isotopic analysis of the breath samples. Therefore we have developed a fully automated, microprocessor controlled CO2 purification and isotopic analysis system. The breath CO2 is cryogenically purified by passage through cold traps of -94°C and -196°C to condense water and CO2, respectively. The CO2 is introduced into a dual inlet, peak-stepping mass spectrometer and analyzed for isotopic content by comparison with a known standard. Thirty samples can be analyzed without operator intervention. Analysis time averages 14 minutes per sample, and the analysis has a precision of 0.3‰ which corresponds to 3 parts excess 13C per 106 parts CO2. The speed of analysis is comparable with scintillation counting and permits next day reporting of clinical breath test results. The precision is sufficient for clinical applications as it is less than the 0.7‰ isotopic variation in basal breath CO2.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200060809
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of metabolic fuel on the 13C/12C ratio of breath CO2 (1984)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 11 (1984), S. 557-561 
    Details
    ISSN: 0306-042X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Natural differences in 13C/12C ratios of various metabolic fuels can produce systematic changes in the 13C/12C ratio of breath CO2, and therefore introduce errors into 13CO2 breath tests. To gain insight into the potential problem, we compared 13C/12C ratios of plasma macronutrients to those of breath CO2 under conditions that should alter the percentages of carbohydrate and lipid being oxidized. In rats, 48 h of starvation decreased the 13C/12C ratio of breath CO2 by 3.5‰. At this time the 13C/12C ratio of breath CO2 was very similar to that of plasma lipids. In humans, 30 min of heavy exercise increased the breath 13CO2/12CO2 ratio by 1.3‰. These changes in breath 13C/12C ratios could be predicted from 13C/12C ratios of plasma macronutrients and the percentage of carbon dioxide derived from each macronutrient, but only when compared within the same populations. For example, the 13C/12C ratios of plasma macronutrients of residents of Chicago, Illinois (USA) and Tokyo (Japan) differed by 1-3‰. An empirical correction of 13CO2 breath test data is recommended when breath tests are run under conditions that will change metabolic fuel utilization.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200111103
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  • 6
    Electronic Resource
    Electronic Resource
    Intramolecular isotopic order in biologically produced acetic acid (1974)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1974), S. 172-174 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetic acid isolated from cider vinegar and inorganically synthesized glacial acetic acid have markedly different intramolecular isotopic distributions of the stable carbon isotopes. Carbon-12 is concentrated in the methyl group relative to the carboxyl group in the biologically produced acid. The reverse distribution is observed in the particular sample of glacial acetic acid examined here.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200010306
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  • 7
    Electronic Resource
    Electronic Resource
    Model for determining the influence of instrumental variations on the long-term precision of isotope dilution analyses (1980)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 7 (1980), S. 457-463 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isotope dilution calibration curves for the quantitative analysis of organic compounds are determined at one point in time. Future analyses of unknowns are then referred to that single calibration. However, between the time that the calibration was performed and the time that the unknowns are analyzed, numerous changes in mass spectrometric operating conditions have often occurred. These include changes in resolution, mass discrimination, fragmentation patterns due to temperature changes, and electrometer offset. These changes will alter the mass spectrometric response and may reduce the accuracy and precision of the analysis. In order to investigate the effect of the above variations, a mathematical model has been developed which permits the influence of the operating conditions to be quantitated. The mass spectrometric response - i.e. isotope ratio - was very sensitive to changes in operating conditions. Changes in the isotope ratios of mixtures that were comprised predominantly of either the natural abundance compound or the labeled compound varied by up to 50%. However, the use of data reduction procedures that include a correction term for the isotope ratio of either or both of the natural abundance or labeled compound reduced the errors to 5% or less.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200071103
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  • 8
    Electronic Resource
    Electronic Resource
    A review of the statistical considerations involved in the treatment of isotope dilution calibration data (1976)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 3 (1976), S. 265-271 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of linear regression analysis for the reduction of isotope dilution data is reviewed. The calculation of linear regression statistics is based upon four assumptions: zero variance in the independent variable, equal variance for all values of the dependent variable, linearity and continuity. Unfortunately, isotope dilution data often violate one or more of these assumptions, which results in the calculation of an inaccurate calibration line. The inaccuracies can be avoided through careful inspection of the data, including analyses of variance and linearity. Large differences in the variances of the dependent variable require the use of a weighted linear regression. Nonlinearity necessitates either discarding data in the nonlinear portion of the calibration or the calculation and use of atom % excess and dilution instead of the simple isotope ratios.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200030603
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  • 9
    Electronic Resource
    Electronic Resource
    Limits of detection of carbon-13 labelled drugs and their metabolites in human urineAbbreviation used: PDB = Belemnitella americana (‘Peedee Belemnite’). (1974)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1974), S. 345-349 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The precise isotopic analysis of carbon by means of differential comparison of CO2 samples is applied to neutral, acid c and basic extract fractions of human urine. It is shown that the standard deviation of the analytical procedure, including sample preparation steps, is about 1% or 0.001 atom % excess carbon-13, but depends some what on the fraction considered. Day to day variations (expressed as standard deviations) in the isotopic composition of the urine fractions are generally less than 2.8%, 1.4% and 3.9% for the neutral, acidica and basic fractions, respectively, although the effect of unusual dietary inputs can be recognized. The ingestion of 23 μg excess carbon-13 in the form of isotopically labelled aspirin is shown to perturb significantly the isotopic composition of the acidic urine fraction which, for a 24 hour collection period, had a mass of 570 mg C. Because only 0.01% of the fraction was consumed by isotopic analysis, further extensive analysis would be possible. It is concluded that carbon-13 tracer experiments generally should be arranged to provide at least 5 × 10-5 g excess 13C/g carbon in any fraction which is to be used for lable detection.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200010510
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  • 10
    Electronic Resource
    Electronic Resource
    Evaluation of isotope ratio (IR) mass spectrometry for the study of drug metabolism (1985)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1985), S. 502-506 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isotope ratio (IR) mass spectrometry was evaluated for the study of drug metabolism and balance using 13C,15N2- labelled antipyrine (AP) as a test drug. Rats were given 40 mg kg-1 (13C, 15N2)AP intraperitoneally. Breath, urine, faeces and blood were collected. Except for breath, samples were combusted in sealed quartz tubes. The resulting CO2 and N2 were analysed for excess 13C and 15N, relative to pre-dose samples, by IR mass spectrometry. In addition, blood levels of AP and cumulative excretion of urinary AP metabolites were determined by gas chromatography/mass spectrometry/selected ion monitoring (GC/MS/SIM) and high-performance liquid chromatography (HPLC) respectively. Excess 13C and 15N levels in blood were comparable with observed levels of AP, and urinary recoveries of 13C (42%) were in good agreement with those calculated from HPLC data (45%). N-Demethylation, one of the important pathways of AP metabolism, was most rapidly determined by excess 13CO2 excretion in breath (8%). The IR mass spectral analysis complemented gas chromatographic/mass spectrum and HPLC analyses, and was less complex.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200120911
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