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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physicochemical measurements ought to offer an opportunity to make significant progress in nutritional evaluation. Therefore, this possibility has continued to be explored, and in this short review paper, particular attention will be given to presenting preliminary results from recent studies in this laboratory involving simultaneous use of stable isotope tracers and of imaging techniques involving positron emission tomography (PET)
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Because there has been substantial discussion previously, as well as elsewhere in these workshop proceedings, on the use of stable isotope tracer techniques in protein nutritional metabolic research (Halliday and Rennie, 1982; Matthews and Bier, 1983; Waterlow et al., 1978; Young et al., 1991) , the major focus of attention in this paper will be with respect to PET.
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Figure 10-2 The two-pool model that is used widely to calculate rates of whole body protein synthesis and degradation (turnover) from data obtained with stable isotope (e.g., 15N or 13C)
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considered in brief. This is done to help the informed reader, who may nevertheless be unfamiliar with PET, to perhaps better appreciate both its advantages and limitations.
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Figure 10-4 Annihilation of positron and electron produces two 0.511-MeV gamma photons. υ, neutrino; , antineutrino.
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Figure 10-5 Schematic diagram of the principle of annihilation coincidence detection. SOURCE: Hoffman and Phelps, "Positron emission tomography: Principles and quantitation" in Positron Emission Tomography and Autoradiography: Principles and Applications for the Brain, 1986, pp.
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as a tracer to measure the glucose metabolic rate in the same organ. These nuclides are produced within a cyclotron whose design varies, and this determines cost and production capability (Fowler and Wolf, 1986)
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TABLE 10-3 Some Positron-Labeled Compounds that Have Been Synthesized for Biomedical Studies Compound Labeled Precursor [11C] Amino Acids L-[1-11C]
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Figure 10-6 A general outline of one route of synthesis of L-[11C-methyl] methionine.
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Figure 10-7 Outline of the metabolism of arginine, with reference to the cooperative involvement of the skeletal musculature intestines, kidney, and liver. SOURCE: Adapted from Brusilow and Horwich (1989)
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disease, including cardiovascular and arteriosclerotic disease and cancers at some organ sites. For these various reasons a detailed, quantitative understanding of the regional distribution of protein and amino acid utilization and of the ways by which imbalances between protein synthesis and breakdown occur in the major organs will be required if more effective nutritional-pharmacological strategies for attenuating these losses and for improving upon the tools used for assessment of nutritional status are to be developed.
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from simultaneous studies using A-V difference measurements during primed constant infusion of L-[1-13C-methyl-2H3] methionine (13C-2H3 -Met)
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muscle as already noted above, k2,3 is taken to reflect the rate of total protein synthesis in this tissue (PSR = Protein Synthetic Rate)
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Figure 10-9 Relationship between the estimate of PSRs determined by PET for hind limb and paraspinal muscle.
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TABLE 10-5 Rates of Protein Synthesis and Breakdown in the Whole Body and Hind Leg of Dogs Given a Constant Intravenous Infusion of L-[2H3-methyl-1-13C] Methionine Parameter Value Whole body (g·kg-1·day-1)
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of the PET methodology include: (1) an exposure of the subject to ionizing radiation, (2)
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methyl] histidine given into the vein, followed by compartment modeling of the plasma tracer data.
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research community, even in the United States, and so it will probably remain a valuable technique at a limited number of academic research centers during the foreseeable future. Finally, in preparing this paper the authors were asked to address a number of questions that relate to the technology discussed, and these, together with their brief answers, are presented in Table 10-6.
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References Astrup, A., and N.J. Christensen 1992 Role of the sympathetic nervous system in obese and postobese subjects.
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Faulkner, D.B., K.J. Kearfott, and R.G.
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Huang, S-C., R.E. Carson, E.J.
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Mudd, S.H., J.D. Finkelstein, F
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Smith, K., and M.J. Rennie 1990 Protein turnover and amino acid metabolism in skeletal muscle.
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Yarasheski, K.E., J.A. Campbell, K
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DONALD McCORMICK: I am thinking of cases where you have a carbon and a nitrogen, and you generate an azide that is very toxic. VERNON YOUNG: Oh, but the actual amount is so small.
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