Iron enrichment studies

The first two unenclosed iron-enrichment studies were carried out in 1993 and 1995 in the Equatorial Pacific. In both, nanomolar concentrations of iron were induced in the surface layer by release of iron sulfate, the patches being labeled by SFg addition. The SEg(initial addition of iron, the tracer component was then used as a guide to keep track of the affected patch of ocean. Sampling could be reliably categorized as in or out the patch, even after all the measurable iron had disappeared from solution. In the second study, the main experiment included reseeding the patch with iron, but not tracer, twice after the initial release. Important secondary aims of the tracer component of the experiments have been the study of mixing rates both horizontally in the mixed layer, and vertically across the thermocline. 

SERIES Subarctic Ecosystem Response to Iron Enrichment Study SOFeX Southern Ocean Fe Experiment, including both North and South... 

There is a possibility that some milk constituents regulate the absorption of ions in the intestine. In studying manganese metabolism we turned to the low iron content in milk. Iron has received great attention in pediatric nutrition. The concern has been to prevent the anemia caused by iron deficiency earlier often found in childhood. Wide milk consumption by infants and young children makes this food an attractive vehicle for iron fortification. Iron-enriched proprietary milk substitutes can adequately prevent the anemia common to infants who subsist largely on low-iron mother s or cow s milk (53). 

Effect of Heat Processing on Bioavailability of Added Iron. Several studies in Table III measured directly the effect of heat processing on added iron. These studies compared processed foods to a control group of identical unprocessed food. Studies in Table 111 utilizing unprocessed controls include 15, 19, and 23. Other studies did not employ an unprocessed control, but used a reference dose to enable comparisons from study to study. Reference doses of ferrous sulfate (most animal assays) or ferrous ascorbate (most human tests) were frequently used. Preparation of ferrous ascorbate, usually a 2 1 molar ascorbic acid iron solution, has been detailed by Layrisse et al. (25). These controls enabled measurement of variation in iron absorption from subject to subject, important in view of greater absorption of an iron deficient versus an iron replete subject. When a reference dose was fed as a radiolabeled salt (55Fe), and on alternate times the test diet was fed with a different radiolabel (59Fe), errors due to variation in subject absorption were eliminated, as each subject served as its own control. The different availabilities of various iron sources from baked enriched rolls were established in this manner (17). 

Isotopically enriched iron tablets have been used to study absorption of iron from nutritional sources. Iron is a very problematic element for ICP-MS in biological samples because there are significant interferences from Ar-based and Ca-based molecular ions. Vanhaecke et compared sector-field ICP-MS with a collision cell ICP-MS for the determination of iron isotopes in semm The problem exists mostly because typical levels of calciumin semm are approximately 50 times higher than those of iron. This study found that sector-field ICP-MS at a mass resolution of 3000 allows accurate determination of iron isotope ratios in human serum but only Fe/ Fe ratios could be determined with sufficient accuracy and precision using CO as a reaction gas with a DRC-ICP-MS. This was due to the DRC-ICP-MS not being able to correct for both the argon and calcium interferences. 

An important advance on these studies was the possibility of isolating AORs from Fe enriched media with obvious interest for an iron-sulfur center site labeling, with enhanced sensitivity of the Mossbauer studies. The work developed with bacterial systems is advantageous as compared with mammalian systems for isotopic labeling and opens the possibility of a direct measurement of substrate binding. Spectra of the enzyme in oxidized, partially reduced, benzaldehyde-reacted, and fully reduced states were recorded at different temperatures and with variable externally applied magnetic fields (222). In the oxidized enzyme, the clusters are diamag-... 

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