Selenium status assessment

Determination of the effective functioning of particular enzymes or metabolic pathways potentially may be useful in demonstrating adequacy of provision. Enzymes in plasma that may be helpful in this regard are glutathione peroxidase as an index of selenium status, and red cell enzymes, such as transketolase (thiamine), glutathione reductase (riboflavin) or transaminase (pyridoxine), or glutathione peroxidase (selenium) are all widely used. Methyltetrahydrofolate reductase is involved in metabolism of homocysteine, hence assessment of plasma homocysteine is a useful measure of... 

Selenium toxicity may occur when patients receive doses exceeding 200 mcg/kg per day for prolonged periods. Selenium status may be assessed by measuring plasma selenium concentrations, which will reflect recent selenium intake. Decreased concentrations may indicate selenium deficiency, but reductions also have been observed in patients with malignancies, liver failure, and pregnancy. Assays that... 

Janghorbani M, Martin RF, Kasper LJ, et al. 1990c. The selenite-exchangeable metabolic pool in humans A new concept for the assessment of selenium status. Am J Clin Nutr 51(4) 670-677. 

Thomson CD. 1991. Clinical consequences and assessment of low selenium status. New Zealand Medical Journal 104(919) 376-377. 

Levander OA (1985) Considerations on the assessment of selenium status. Fed Proc 44 2579—2583. 

Resource managers and aquatic biologists need data on selenium concentrations in water, food-chain organisms, and fish and wildlife tissues in order to adequately assess the overall selenium status and health of aquatic ecosystems. Because selenium is depurated rapidly in aquatic birds, resource managers should... 

This is documented by the discovery of essential functions for the "new trace elements in the past seven years (I) and by the increasing knowledge of marginal or pronoimced deficiencies in humans of such elements as iron (2), zinc (3), chromium (4), and perhaps copper (5) and selenium (6), Although some of these deficiencies occur only in special age and sex groups or under unusual conditions, their existence has aroused public and scientific concern for the exact definition of human trace element needs and for the assessment of trace element nutritional status. These two major challenges for human trace element research cannot be met without proper analytical support. I will attempt to describe the present status of trace element analysis as it relates to nutrition research and to point out some new concepts that might well influence the future direction of trace element analysis. 

The selenium data are presented in Chapter 111 and Appendix E. Unless otherwise indicated, they refer to standard conditions cf. Section 11.3) and 298.15K (25°C) and are provided with an uncertainty which should correspond to the 95% confidence level (see Appendix C). Thermodynamic parameters (formation data and entropies) that could be evaluated from reaction data with selected TDB auxiliary data in Chapter IV are denoted as selected and presented in Chapter III. When use of non-TDB auxiliary data had to be resorted to in the evaluation, the result is denoted as adopted and presented in Appendix E. The difference in the status between a selected and an adopted value thus depends entirely on the background of the auxiliary data used in the assessment. 

Selenium stable isotopes Selenium is recognized as an essential trace element for humans. Se status is determined by dietary Se intake and its bioavail-ability. Se bioavailability can be estimated by assessing absorption and retention of Se stable isotopes. These studies require analytical techniques that allow precise and accurate determination of stable isotope ratios at low levels of total selenium. 

Glutathione reductase has selenium at the catalytic site, as a selenocysteine residue (section 11.15.2.5) this explains the role of selenium as an antioxidant nutrient. Glutathione reductase is a flavoprotein, and is especially sensitive to riboflavin (vitamin B ) depletion as discussed in section 11.7.4.1, measurement of glutathione reductase is used as a means of assessing riboflavin status. 

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