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Query: UMLS:C0240066 (iron deficiency)
 7,156 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Young mycelia of the fungus Neurospora crassa contain a soluble NADH-linked sideramine reductase, which may be responsible for liberating iron in vivo from accumulated sideramines during iron-deficient cultivation. The enzymes can be assayed using a soluble supernatant fraction, EDTA, and an atmosphere of pure nitrogen. The enzyme is stable without loss of activity up to 45 degrees C and has an optimum of activity at pH 7.0. Besides coprogen (Km = 100 micrometer, V=2.8 nmol/min per mg protein), some other ferrichrome-type compounds are reduced. However, ferrichrome, ferrirubin coprogen B and ferrioxamine are poor substrates. When the mucelia were grown in a medium containing 10(-5) M ferri iron, the activity of the reductase was found to be only 30% of that found under low iron conditions. The enzyme is inhibited by oxygen, SH-alkylating agents and partly by some detergents. Unlike the reductase of N. crassa, the corresponding enzyme from Aspergillus fumigatus revealed low reduction of coprogen and high reduction of ferrichrome, indicating genusdependent specificities of sideramine reduction enzymes in fungi. The participation of acids of the citric acid cycle as natural iron acceptors during strong iron deficiency is studied and confirmed by iron uptake measurements on isolated mitochondria.
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PMID:Enzymatic release of iron from sideramines in fungi. NADH:sideramine oxidoreductase in Neurospora crassa. 14 35

Iron acquisition by symbiotic Rhizobium spp. is essential for nitrogen fixation in the legume root nodule symbiosis. Rhizobium leguminosarum 116, an ineffective mutant strain with a defect in iron acquisition, was isolated after nitrosoguanidine mutagenesis of the effective strain 1062. The pop-1 mutation in strain 116 imparted to it a complex phenotype, characteristic of iron deficiency: the accumulation of porphyrins (precursors of hemes) so that colonies emitted a characteristic pinkish-red fluorescence when excited by UV light, reduced levels of cytochromes b and c, and wild-type growth on high-iron media but low or no growth in low-iron broth and on solid media supplemented with the iron scavenger dipyridyl. Several iron(III)-solubilizing agents, such as citrate, hydroxyquinoline, and dihydroxybenzoate, stimulated growth of 116 on low-iron solid medium; anthranilic acid, the R. leguminosarum siderophore, inhibited low-iron growth of 116. The initial rate of 55Fe uptake by suspensions of iron-starved 116 cells was 10-fold less than that of iron-starved wild-type cells. Electron microscopic observations revealed no morphological abnormalities in the small, white nodules induced by 116. Nodule cortical cells were filled with vesicles containing apparently normal bacteroids. No premature degeneration of bacteroids or of plant cell organelles was evident. We mapped pop-1 by R plasmid-mediated conjugation and recombination to the ade-27-rib-2 region of the R. leguminosarum chromosome. No segregation of pop-1 and the symbiotic defect was observed among the recombinants from these crosses. Cosmid pKN1, a pLAFR1 derivative containing a 24-kilobase-pair fragment of R. leguminosarum DNA, conferred on 116 the ability to grow on dipyridyl medium and to fix nitrogen symbiotically. These results indicate that the insert cloned in pKN1 encodes an element of the iron acquisition system of R. leguminosarum that is essential for symbiotic nitrogen fixation.
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PMID:A Rhizobium leguminosarum mutant defective in symbiotic iron acquisition. 240 49

A sophisticated appreciation of the role of nutrition in athletic performance has been made possible by increasing knowledge of the physiology of exercise. The nutritional issues of training are of primary importance, since this occupies most of the athlete's effort. The nutritional support of an intense daily training programme includes an appropriately high energy intake, predominantly in the form of carbohydrate in order to continually replenish muscle glycogen stores. Recent review of the protein needs of athletes indicates that requirements may be substantially above those of sedentary subjects, to account for the oxidation of amino acids during exercise as well as the retention of nitrogen during periods of muscle building. However, these increased requirements are likely to be met by the generous protein intakes anticipated in a high energy diet. The same would seem to hold true for micronutrient considerations, although there is no evidence that vitamin requirements are considerably increased by exercise. Nevertheless, a high energy diet chosen from a sufficiently varied range of foods should allow micronutrient intakes well in excess of population recommended dietary intake levels. Current interest is focused on the mineral status of athletes, particularly that of iron and calcium. In the case of iron, there is a possibility that the increased level of loss by some endurance athletes will not be met by their usual dietary patterns. Screening for early signs of iron deficiency, and appropriate supplementation and dietary counselling seem warranted in high risk groups. Competition poses the challenge of identifying possible factors limiting performance, and taking steps to delay or reduce these. Of paramount importance is body temperature regulation through the maintenance of hydration levels. This issue has long been recognised, but recent studies of gastric emptying and the benefits of carbohydrate supplementation during exercise have caused an update of the advice to athletes regarding fluid intake during exercise. It now seems possible to simultaneously achieve fluid and carbohydrate requirements for endurance exercise within a wide range of choice of beverages containing up to 10% carbohydrate. Concern about the adequacy of carbohydrate fuel stores in endurance exercise situations is also well known. The recognition that training achieves various physiological adaptations to enhance the lifespan of fuel stores has taken away some of the attention previously focussed on carbohydrate-loading techniques.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Sports nutrition. Approaching the nineties. 267 59

Cultures of Streptomyces griseus grown under phosphate-limiting conditions produced a complex of green products. Three of these were separated from the mixture and characterized. One was identified as viridomycin A, the ferrous chelate of 4-hydroxy-3-nitrosobenzaldehyde; the second (actinoviridin A) was the corresponding carboxylic acid chelate and the third (viridomycin E) was a hybrid chelate containing both the aldehyde and acid ligands. Only two out of nine strains of S. griseus examined produced viridomycins and the ligands were biosynthesized only in media from which phosphate had been exhausted. Optimization of the production medium showed that fructose and alanine were the most favorable carbon and nitrogen sources and that relatively high concentrations of ferrous ions were necessary. The results suggest that viridomycins are not produced by S. griseus as iron scavengers in response to iron deficiency but as secondary metabolites that are stabilized adventitiously in the broth by metal ion chelation.
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PMID:Characterization of new viridomycins and requirements for production in cultures of Streptomyces griseus. 368 25

Eighty-five consecutive general hospital patients requiring total parenteral nutrition (TPN) were prospectively studied in order to evaluate the safety and efficacy of a '3-in-1' nutrient mixture. All formulas were individualized to estimated requirements (average composition nitrogen 14 g, glucose 350 g, fat 50 g), mixed in the hospital pharmacy, contained within 3-litre EVA plastic bags, and given to the patients as a continuous 24-hour infusion. The average duration of TPN was 19 days per patient (range 8 - 84 days). Judging by nitrogen balance and plasma protein concentrations, the system was effective in maintaining or improving nutritional status in patients in a relatively stable condition but not in those who were critically ill (e.g. those in an intensive care unit). Development of magnesium and iron deficiencies was common during the period of TPN (25% of patients developing magnesium deficiency and 40% developing iron deficiency) despite daily supplementation with commercial trace element mixtures, but these states were easily corrected by high-dose administration. 'Creaming' of less than 5 mm on the surface of the emulsion was common, whereas that of more than 10 mm was rare (12 bags) and invariably associated with excessive addition of polyvalent cation or glucose. Deposition of lipid on the internal surface of the catheter was a common problem after 2 weeks' continuous administration. Temporary problems with faulty bag connections resulted in excessive catheter sepsis (14%) due to Staphylococcus epidermidis. Mild reversible disturbances in liver function occurred in one-third of the patients. The system appears safe and effective for the management of most patients requiring long-term TPN.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Clinical evaluation of a '3-in-1' intravenous nutrient solution. 392 69

The expression of ferredoxin-NADP+ reductase (FNR) from Anabaena sp. PCC 7119 in heterocysts and vegetative cells has been quantified. Specific reductase activity in heterocysts was approximately 10 times higher than in vegetative cells, corresponding to the increased FNR protein content. This was confirmed by immunoquantification of the FNR protein from whole filaments of Anabaena sp. PCC 7120 grown in media with and without combined nitrogen. Transcription of the petH gene was markedly enhanced in the absence of combined nitrogen. This suggests that the increased RNA level is mainly responsible for the up-regulation of FNR in heterocysts. As has been observed for nif genes, iron deficiency also increased transcription of petH. Characterization of the FNR purified from isolated heterocysts showed no detectable differences from the enzyme from vegetative cells. Although nitrogen stress was a key regulatory factor, localization of the petH gene in the genomic map of Anabaena PCC 7120 showed that this gene is not physically associated with the nif cluster.
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PMID:Expression of ferredoxin-NADP+ reductase in heterocysts from Anabaena sp. 864 99

The treatment efficacy of erythropoietin (EPO) in end-stage renal disease (ESRD) can be limited by deficiencies of iron, folate, or vitamin B12, by hyperparathyroidism, or by aluminum intoxication. Since EPO costs are significant, this study attempted to determine the cost-effectiveness of performing a panel of screening tests for anemia before starting EPO. Anemia screening was performed prospectively in 48 new-onset ESRD patients at the Ralph H. Johnson Veterans Affairs Medical Center before EPO treatment was started. Serum iron, transferrin, folate, vitamin B12, parathyroid hormone, and aluminum levels were determined, and transferrin saturation (Tfsat) was calculated at the first dialysis session. At presentation for dialysis, the mean hematocrit was 0.264 +/- 0.036 and the mean blood urea nitrogen was 32 +/- 2 mmol/L. Eighteen patients (37.5%) had a serum iron level lower than 7 micromol/L, suggesting iron deficiency. Twenty-five patients (52%) had Tfsat less than 0.20, consistent with overt iron deficiency. No patient was found to be vitamin B12 deficient, to be aluminum intoxicated, or to have significant hyperparathyroidism. One patient had folate deficiency. A cost-effectiveness analysis was performed assuming that (1) EPO would be given at an average starting dose of 6,000 U/wk at a cost of $14/2,000 U of EPO; (2) that without screening 1 month would elapse before a poor response was identified; and (3) that the failure to treat aluminum intoxication and hyperparathyroidism or to replete iron, vitamin B12, or folate deficiency would significantly impair the response to EPO. The Tfsat screen had a cost-effectiveness ratio of 0.2019, saving approximately $5.00 in EPO use for each dollar of test administration. All other screens had cost-effectiveness ratios greater than 1.0, indicating that their testing costs exceeded dollar savings in EPO use. In conclusion, iron deficiency is common in anemic patients starting dialysis, but other causes of anemia are not. It is imperative that current clinical practices be influenced by cost-effectiveness considerations. Given the cost of laboratory screens, and the relative ineffectiveness of the other screens examined here to identify factors known to impair the response to EPO, anemia screening before initiating EPO therapy should be limited to tests to identify iron deficiency.
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PMID:A cost-effectiveness analysis of anemia screening before erythropoietin in patients with end-stage renal disease. 915 97

Anemia in chronic renal failure is predominantly caused by diminished erythropoietin synthesis by diseased kidneys. While iron deficiency is often stated as a cause of anemia in chronic renal failure prior to end-stage renal disease, its relative contribution is debated. It is speculated that rather than frank 'iron deficiency', many patients with chronic renal failure may indeed have impaired utilization of iron. We analyzed 139 consecutive patients with chronic renal failure starting maintenance hemodialysis to determine the relationship between hematocrit, measures of renal function (blood urea nitrogen and serum creatinine concentration), and measures of iron availability (serum transferrin saturation, serum iron level and serum ferritin). The 139 study subjects (60 men, 79 women) comprised 116 blacks (83%), 15 hispanics (11%), and 8 whites (6%) of a mean age 56 +/- 15 years. Only 23 (17%) of 139 subjects had positive hemoccult stool test for blood. Their mean hematocrit was 24 +/- 4.5%, mean blood urea nitrogen concentration was 121 +/- 38, mean serum creatinine concentration was 12.6 +/- 5.2 mg/dl, mean serum transferrin saturation was 22 +/- 14%, mean serum ferritin level was 235 +/- 194 U/l, mean serum iron level was 55 +/- 40 U/l, and mean total iron binding capacity was 254 +/- 93%. Multiple regression analysis with hematocrit as the outcome variable, and blood urea nitrogen level, serum creatinine concentration, serum albumin concentration, serum transferrin saturation, and serum ferritin level as the independent variables, showed an inverse correlation between hematocrit and serum creatinine concentration (p = 0.002). We conclude that in patients with chronic renal failure starting uremia therapy, anemia does not correlate with any of the commonly measured indices of body iron stores. We infer that impaired utilization of iron may be a significant factor in the anemia of chronic renal failure.
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PMID:Relative contributions of body iron status and uremia severity to anemia in patients with advanced chronic renal failure. 937 26

Impaired erythropoiesis in continuous ambulatory peritoneal dialysis (CAPD) or continuous cyclic peritoneal dialysis (CCPD) patients receiving recombinant human erythropoietin (rHuEPO) is most often secondary to iron deficiency, either as a result of poor intestinal absorption or failure to take oral supplements as prescribed. The inconvenience of giving intravenous (i.v.) iron dextran (ID) to CAPD/CCPD patients precluded its use in this population. We therefore examined the efficacy of bolus intraperitoneal (i.p.) iron dextran (1000 mg) on erythropoiesis in a pilot study of 14 CAPD/CCPD patients. The patients ranged in age from 23-81 years, and all had iron deficiency (transferrin saturation 6%-23%; mean: 15.2% +/- 1.34%). Of the 14 patients studied, 13 were receiving rHuEPO. Pre-treatment hematocrit (Hct) ranged from 21%-38% (mean: 30.2% +/- 1.37%). After infusion of 2 L Dianeal (Baxter Healthcare Corp., Deerfield, Illinois, U.S.A.), 500 mg of undiluted ID was administered directly into the Tenckhoff catheter and subsequently flushed with 30 mm3 normal saline. The peritoneal dialysis (PD) exchange containing ID then dwelled for a period not < 6 hours before standard PD resumed. A second 500 mg dose ID was given to each patient by the same protocol 3-86 days later (mean: 14 days). No complications were seen. No patient complained of abdominal pain or other subjective symptoms during infusion or during the dwell. Repeat iron studies done 1-7 months post ID (mean: 2.8 months) showed a 1.1-fold to 4.9-fold increase (mean: 1.4-fold) in mean iron levels (40.4 +/- 3.9 mg/dL versus 57.5 +/- 5.5 mg/dL, p = 0.036); a 1.1-fold to 5.2-fold increase (mean: 1.6-fold) in mean transferrin saturation (15.2% +/- 1.3% versus 24.5% +/- 2.6%, p = 0.008); a 1.01-fold to 1.60-fold increase (mean: 1.12-fold) in mean Hct (30.2% +/- 1.37% versus 33.8% +/- 1.5%; p = 0.042). The mean dose of rHuEPO was statistically unchanged (170.0 +/- 47.4 U/kg body weight versus 178.8 +/- 49.6 U/kg body weight per week; p = 0.841). Peritoneal equilibration test (PET) score 1-4 months post ID (mean: 2 months) was 0.778 +/- 0.02 compared with a PET score at baseline of 0.767 +/- 0.03 (p = 0.734). No significant delta was observed in blood urea nitrogen (BUN) or creatinine values. We conclude that use of bolus i.p. ID is safe, effective, and convenient, and demonstrates no short-term negative effect on peritoneal membrane integrity. Long-term effects have yet to be determined.
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PMID:Use of bolus intraperitoneal iron dextran in continuous ambulatory peritoneal dialysis or continuous cyclic peritoneal dialysis patients receiving recombinant human erythropoietin. 1068 73

Marine fixation of atmospheric nitrogen is believed to be an important source of biologically useful nitrogen to ocean surface waters, stimulating productivity of phytoplankton and so influencing the global carbon cycle. The majority of nitrogen fixation in tropical waters is carried out by the marine cyanobacterium Trichodesmium, which supplies more than half of the new nitrogen used for primary production. Although the factors controlling marine nitrogen fixation remain poorly understood, it has been thought that nitrogen fixation is limited by iron availability in the ocean. This was inferred from the high iron requirement estimated for growth of nitrogen fixing organisms and the higher apparent densities of Trichodesmium where aeolian iron inputs are plentiful. Here we report that nitrogen fixation rates in the central Atlantic appear to be independent of both dissolved iron levels in sea water and iron content in Trichodesmium colonies. Nitrogen fixation was, instead, highly correlated to the phosphorus content of Trichodesmium and was enhanced at higher irradiance. Furthermore, our calculations suggest that the structural iron requirement for the growth of nitrogen-fixing organisms is much lower than previously calculated. Although iron deficiency could still potentially limit growth of nitrogen-fixing organisms in regions of low iron availability-for example, in the subtropical North Pacific Ocean-our observations suggest that marine nitrogen fixation is not solely regulated by iron supply.
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PMID:Phosphorus limitation of nitrogen fixation by Trichodesmium in the central Atlantic Ocean. 1133 77


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