Population repletion

The need to understand the chemical behavior of iron in foods is essential to a clear understanding of subsequent biological behavior. There are many factors which impinge upon the chemical status of iron in food with the physicochemical being only one. However, it is hoped that the interrelationship and importance of some of these factors might be considered more fully. In this way, a spirit of scientific cooperation might very well provide answers to the problems which seem to inhibit the existence of a population replete in terms of iron nutriture. 

However, as the upper pumped level population increases, that of the lower pumped level decreases (see Fig. 1), and so does that of the pair as a whole. That is, under the influence of the laser pumping, population of the pair is depleted. The reason for this is that the rate of energy transfer out of the upper pumped level (depletion of the pair population) is significantly faster than energy transfer into the lower pumped level (repletion). 

The FvIFm of 0.5 recorded for iron-replete cells was close to the maximum values measured in our lab, though they are lower than the values reported for natural populations that were dominated by Phaeocystis antarctica (Vaillancourt et al. 2003). Whereas our cultures were in good condition, the experimental conditions provided were certainly not the most optimal for growth P. antarctica. Maximum values for FvIFm were in fact achieved at more stable light conditions (pers. obs.). 

During the past two decades, essentiality of zinc for man has been established. Deficiency of zinc in man due to nutritional factors and several dls-seased states, has been recognized. A marginal deficiency of zinc appears to be prevalent in many segments of population in developed countries and more severe deficiencies are widespread in many parts of the world. In our experimental human model, a marginal deficiency of zinc was induced by dietary means. Loss of body weight (less than 10% in six months on zinc restricted diet), testicular hypofunction, hyperammonemia and a decrease in plasma, urinary and neutrophil zinc concentration were observed. Changes in zinc dependent enzymes such as deoxythymldine kinase in newly synthesized connective tissue and plasma alkaline phosphatase were also observed as a result of zinc restriction and repletion in our model. 

On the basis of depletion/repletion studies, the minimum adult requirement for riboflavin is 0.5 to 0.8 mg per day. In population studies, values of the EGR activation coefficient <1.3 are seen in subjects whose habitual intake of riboflavin is 1.2 to 1.5 mg per day. At intakes between 1.1 to 1.6 mg per day urinary excretion rises sharply, suggesting that tissue reserves are saturated. On the basis of such studies, reference intakes (see Table 7.6) are in the range of 1.2 to 1.6 mg per day (Bates, 1987a, 1987b). 

Hematopoiesis is the process of blood cell production that takes place in the bone marrow. Through a complex series of regulatory events, stem cells are differentiated into various types of cells, including red blood cells. Stem cell differentiation is responsive to exogenous stimuli and can be upregulated to resupply a deficient cell population. However, only a limited number of therapeutics (iron, hemin, or erythropoietin, for example) can stimulate Hb-replete red blood cell formation. Recognition of the poor bioavailability of many iron compounds or hemin compositions and the improved safety profile of a tHb relative to rmmodified Hb has renewed the interest in Hb administration as... 

Guidelines for potassium supplementation have been published by the National Council on Potassium in Clinical Practice (Table 50-3). These guidelines provide a comprehensive framework for potassium prophylaxis and replacement in many distinct patient populations. When deciding on appropriate pharmacotherapy to replete potassium, five factors must be considered (1) the patient s normal baseline potassium concentration (2) underlying medical conditions that may affect potassium balance (3) concomitant medications that may affect potassium balance (4) the patient s dietary and salt intake and (5) the patient s ability to comply with the therapeutic regimen. ... 

Meltzer HM, Norheim G, Bibow K, et al. 1990. The form of selenium determines the response to supplementation in a selenium replete population. Eur J Clin Nutr 44(6) 435-446. 

Meltzer HM, Norheim G, Loken EB, et al. 1992. Supplementation with wheat selenium induces a dose-dependent response in serum and urine of a Se-replete population. Br J Nutr 67(2) 287-294. 

The variation in urinary iodine excretion affects the reliability of estimates of population iodine nutrition. Low urinary iodine is seen in iodine-replete individuals due to random variation (Andersen et al., 2001). However, a high number of samples increases the reliability of the estimates of iodine excretion in a population, but what is the reh-ability of a study including a certain number of spot urine samples from a population ... 

In this table, admittedly crude calculations based on median UI excretion in the three study populations revealed a negative iodine balance of —30% and —28.5% in the Irish and UK study populations, respectively, with a positive balance of +8% in the iodine-replete Sri Lankan population. However, it must be emphasized that despite providing useful comparisons between iodine-replete regions and those... 

Hypothyroidism thus remains a significant source of morbidity in the American population. Within this iodine-replete population, relatively small differences in iodine intake do not appear to significantly affect the prevalence of this disorder. Although the risk of hypothyroidism associated with postpartum thyroiditis is significant, the most important subpopulation at risk for hypothyroidism appears to be the elderly. 

Donaldson C, Denning-Kendall P, Bradley B, et al. (2001). The CD34(-l-)CD38(neg) population is significantly increased in haemopoietic cell expansion cultures in serum-free compared to serum-replete conditions dissociation of phenotype and function. Bone Marrow Trans. 27 365-371. 

Delange et al. (Delange et al., 2002) determined the frequency distribution of urinary iodine in iodine-replete popnilations (schoolchildren and adults) and the proportion of concentrations <50 pg/1. The findings were as follows nineteen groups reported data from 48 popnilations with median urinary iodine concentrations >100 ig/l. The total population was 55 892, including 35 661 (64%) schoolchildren. Median urinary iodine concentrations were 111-540 (median 201) pg/1 for all populations, 100-199 ig/l in 23 (48%) populations and >/=200 jig/1 in 25 (52%). The frequencies of values <50 qg/1 were 0-20.8 (mean 4.8%) overall and 7.2% and 2.5% in populations with medians of 100-199 rg/l and >200 pg/1, respectively. The frequency reached 20% only in two places where iodine had been supplemented for <2 years. According to the authors conclusions the frequency of urinary iodine concentrations <50 Hg/1 in populations with median urinary iodine concentrations >/=100 rg/l has been overestimated, and the threshold of 100 qg/1 does not need to be increased. The main conclusion of the cited work was that in populations, median urinary iodine concentrations of 100-200 qg/1 indicate adequate iodine intake and optimal iodine nutrition. 

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