Emerging Technologies for Nutrition Research Potential for Assessing Military Performance Capability (1997) / Chapter Skim
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Emerging Technologies for Nutrition Research, 1997 Pp.
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TABLE 8-1 Natural Abundance of Elements Commonly Found in Biological Substances Element Mass Abundance (%) Hydrogen 1 99.985 2 0.015 Carbon 12 98.89 13 1.11 14 *
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hardware and software, this instrumentation is more user friendly. For these reasons, the use of nonradioactive, stable isotope tracers as probes for in vivo nutrition and metabolic studies has increased enormously over the last 20 years.
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most biological questions lie at the site of the nutrient's metabolic effects, that is, within organs and cells. In some instances, this information can be obtained invasively by inserting sampling catheters into the site of interest.
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Figure 8-2 Generic representation of the isotopes of carbon and how they contribute to the determination of isotope content in a sample taken during a stable or radioisotope tracer experiment (see text)
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ANALYTICAL CONSIDERATIONS Although advances in magnetic resonance spectroscopy now permit limited noninvasive measurements of stable isotope tracers in vivo and a broad approach to in vitro measurements of selected stable nuclides in samples obtained during in vivo tracer experiments, mass spectrometry has been the most commonly used tool for quantifying samples containing stable, isotopically labeled substrates. This use is appropriate since mass spectrometry is the most rapid, sensitive, specific, and precise general analytical method available for this purpose.
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of capillary gas chromatography to the high isotope dilution and precision characteristics of gas isotope ratio mass spectrometry and is a valuable addition to the analytical repertoire (Goodman and Brenna, 1992; Yarasheski, 1992)
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TABLE 8-4 Measurement Precision of Selected Stable Nuclides by Gas Isotope Ratio Mass Spectrometry* Isotope Substance Atom % Excess Coefficient of Variation (%)
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product relationships in biological systems, as described more fully below. Lastly, because of their safety, several stable isotope tracers can be used simultaneously and repeatedly in the same subject, a luxury not available with radiotracers because of acceptable exposure limits.
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Figure 8-3 Mass isotopomer distribution patterns in egg white protein phenylalanine (A) and glutamine plus glutamate (B)
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glutamine and glutamate. Thus, this experiment illustrates the fact that careful consideration of the full isotopic information content of a synthesized product can contain significant information about the metabolism of its precursor.
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amply demonstrated by the large and ever-increasing number of such studies over the last two decades. This technique is now a widely accepted, basic method for human investigation applied in laboratories worldwide by individuals of vastly different types and degrees of basic education, training, and accomplishment.
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Hoyt, R.W., T.E. Jones, C.J.
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