Stable isotopic tracers

Rabinowitz M, Wetherill GW, Kopple JD. 1974. Studies of human lead metabolism by use of stable isotope tracers. Environ Health Perspect 7 145-153. 

R. R. Wolfe (1992) Radioactive and Stable Isotope Tracers in Biomedicine, p. 357, Wiley-Liss, New York. 

Sabatier, M., Pont, F., Arnaud, M. J., and Tumlund, J. R. (2003). A compartmental model of magnesium metabolism in healthy men based on two stable isotope tracers. Am.. Physiol. Regul. Integr. Comp. Physiol. 285, R656-R663. 

Wolfe RR (1992) Radioactive and stable isotope tracers in biomedicine Principle and practice of kinetic analysis. Whiley-Liss, New York... 

A multiple ion collector device is required for the simultaneous determination of separated ion beams in precise and accurate isotope ratio measurements in order to study, for example, isotope fine variation in Nature or during tracer experiments using enriched stable isotope tracers. In thermal ionization mass spectrometers or in ICP-MS, mostly a system of several Faraday cups (up to 16) and/or ion counters (electron multipliers) is applied. In the photographs in Figures 4.7 and 4.8 examples of multiple ion collector systems are shown from the mass spectrometers MC-ICP-MS... 

A large fraction of Emmett s research centered around iron catalysts and the application of both radioactive and stable isotopic tracers in catalysis. His studies of the iron-synthetic ammonia system led to conclusions that remain unchallenged to this day. 

Activation with 14 MeV neutrons has been used to determine the oxygen content of various metals such as beryllium 20>, Cl, F, O, Na, Si, and various rare earths in complex molten salt electrolytes 45>, the protein content of food products by means of the nitrogen content 46>, i60/180 and 14N/15N isotopic ratios in stable isotope tracer experiments 47,48), and in a wide variety of other applications. One application we... 

The role of metals and other elements in the health of humans, animals, and plants continues to be of great interest both on a routine basis and in research. Two recent reviews described the important impact of ICP-MS in biomedical research [227, 228]. ICP-MS provides the ability to measure multiple elements at ultratrace levels rapidly and to measure isotope ratios at low enough concentrations so that stable isotope tracers can be used for biomedical research [229]. Much remains unknown about the role of metals and their speciation on biological activity, in large part as a result of inadequate measurement techniques. 

Stable isotope tracers can be conveniently measured by using ICP-MS [259,260]. The low ICP-MS detection limits allow small amounts of stable isotope tracers to be given to subjects, including infants [261]. 

Food authentication, application of stable isotope tracers, characterization of complex metallobiomolecules, and investigation of their role in biological processes are all areas in which ICP-MS can play a more and more critical role. Speciation will continue to be a very dynamic field of investigation and the integration of speciation and metabolism studies with the use of stable isotopes as species-specific tracers is likely to become a research area of vital importance. On... 

P. B. Moser-Veillon, A. R. Mangels, K. Y. Patterson, C. Veillon, Utilization of two different chemical forms of selenium during lactation using stable isotope tracers an example of speciation in nutrition, Analyst, 117 (1992), 559D562. 

Direct measurement of dietary zinc availability in humans requires development of the stable isotope tracer methodology. Several aspects of this integrated methodology are considered and briefly discussed. These are analytical isotopic measurement methodology, consequences of the finite precision of isotopic measurements, validation of in vivo measurements, and several aspects of biological labeling of human foods. It is shown that Radiochemical Neutron Activation Analysis provides a suitable method for accurate measurement of the stable isotopes Zn,... 

Replacement of Metabolic Losses An alternative approach to determining vitamin requirements is to measure the loss from the body pool in a steady state. This requires estimation of the total body pool, and measurement of the fractional rate of loss from that pool, generally using radioactive or stable isotope tracers. Three problems can arise in such studies. 

Collaborative efforts with experts in nutrition and bioavailability have been carried out at NBS and have resulted in the use of TIMS for the measurement of stable Isotope tracers in adults and newborns(, J 0). Typical data for these efforts are summarized in Tables II and III for Ca and Zn isotopes For each of these elements optimum Isotope ratio precisions of about 0 1% (R S D )were achieved which permitted the resolution of extended term kinetic effects that would be impossible to achieve with less accurate and precise mass spectrometry. 

Physiologically important calcium flow rates can be determined using calcium isotopic tracers without resorting to classical metabolic balance methodology Calcium stable isotopic tracers are sufficiently benign to permit their use in studies of calcium metabolism in children The measurement techniques and clinical protocol for our studies of skeletal development in children are described ... 

Although the precision of El-MS abundance measurements is not comparable to that of TI-MS, the El mass spectrometer is much more widely available. More stable iron chelates that would permit GC sample introduction and reduce the memory effect problem would significantly improve the method. A potentially serious drawback of stable isotope tracers is that the amounts used are more in the range of substrate than tracer levels. A related question pertains to the validity of the extrinsic labeling technique when stable isotope tracers are used. In an ongoing study in our laboratory, we are attempting to compare the absorption of intrinsic and extrinsic stable iron isotope tracers. 

Over the past several years we have applied stable isotopic tracers to a vetriety of metabolic and nutritional problems in human subjects. This chapter will focus on examples of our studies of glucose metabolism. The general principle and vaUdatLon of the tracer techniques we have used will be presented first, followed by a review of some of our work examining the response to infused glucose. In these studies we used stable isotopes because of the... 

Indirect methods used to estimate DNF include the acetylene block method (S0rensen, 1978), metabolite stoichiometry (Dollar et al., 1991), or stable isotope tracers (Nielsen, 1992). Acetylene (C2H2) blocks the terminal step of DNF, the conversion of N2O to N2, and the DNF rate is estimated by quantifying the production of N2O on a gas chromatograph with an electron capture detector. Problems with the acetylene block technique include blockage of NTR (which means that rates of coupled NTR—DNF cannot be obtained), inefficacy at low N03 concentration, and interference by H2S. Sulfide appears to alleviate the acetylene block of nitrous oxide reductase and permit full reduction of N2O to N2. 

The use of stable isotopic tracers is based on following a labeled compound from one pool (the source pool) to another (the target pool) (Sheppard, 1962). The principles described below are the same regardless of whether one is measuring rates in the water column or sediment. What changes are the protocols used to isolate the different fractions prior to isotopic analysis. The basic equation to calculate the flux rate from one pool to another is ... 

Cobelli, C., TofFolo, G., Bier, D. M., and Nosadini, R. (1987). Models to interpret kinetic data in stable isotope tracer studies. Am. J. Physiol. 253, E551—E564. 

Amundson R. and Baisden W. T. (2000) Stable isotope tracers and mathematical models in soil organic matter studies. In Methods in Ecosystem Science (eds. O. E. Sala, R. B. Jackson, H. A. Mooney, and R. W. Howarth). Springer, New York, pp. 117-137. 

Williams A. E. (1997) Stable isotope tracers natural and anthropogenic recharge, Orange County, California. J. Hydrol. 201, 230-248. 

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