Distribution of55Fe in juvenile adult lampreys,Petromyzon marinus L., following oral intubation of the isotope

Summary The capacity of a sanguivorous lamprey,Petromyzon marinus L., to deal with ingested iron was studied over time using autoradiography and scintillation counting of solubilized tissue samples after intubation of the oesophagus with a single dose of⁵⁵ferrous citrate. A highly efficient mechanism for absorption in the anterior intestine was recognized with 17% of the intubated radioactivity absorbed into the body after only 5 min, 66% by 3 h, and almost 80% by 21 h. Iron concentration in the epithelial cells of the anterior intestine may be a factor in restricting iron absorption during spontaneous feeding. A decline in total body radioactivity over the 15 days following iron intubation probably results from transport of the metal in the blood and release of radioiron from the mucous cells of the posterior intestine. The kidneys appear to play a smaller but still significant role in iron loss. Gradual increases in radioiron concentration (cpm g^–1 wet weight) and percent of total body radioactivity occur in the liver (2 to 26%), carcass (14 to 37%), and integument (4 to 12%) during the course of the experiment, indicating that these are the chief sites of iron storage during times of metal excess. However, eventually integument may also be a site of iron excretion. Significant fluctuations in radioiron concentration (cpm ml^–1) in whole blood during the 15 day period can be correlated with transport of the metal to sites of storage and excretion, and maybe with incorporation into haemoglobin and with erythropoietic activity. Feeding adult lampreys represent a valuable system, with both general and unique characters, for studying iron metabolism in vertebrates.     

Haematological studies on90Sr-90Y-toxicity

Summary Erythropoietic changes were observed, measured by⁵⁹Fe-uptake into red blood cells, and on radioiron turnover from blood plasma, at different time intervals (2–64 days) after treating adult female mice with varying activities of⁹⁰Sr-⁹⁰Y. Activities of 2.5 or 5.0 µCi radiostrontium per animal lead to a depression at time intervals of two and four days, at longer periods there was an overshoot. With activities of 0.5 or 1.0 µCi radiostrontium disturbances in the radioiron uptake are still observed, although these effects are not as pronounced as in experiments with higher burdens. In comparison with results obtained in experiments in which the plasma⁵⁹Fe-turnover was applied, even with an activity of 5 µCi radiostrontium per mouse, no deviation as against the untreated controls was detected.Dedicated to Prof. Dr. Hermann Muth, Homburg/Saar, on the occasion of his 65th birthday     

Treatment of menorrhagia during menstruation: randomised controlled trial of ethamsylate,mefenamic acid,and tranexamic acid.

OBJECTIVE: To compare the efficacy and acceptability of ethamsylate, mefenamic acid, and tranexamic acid for treating menorrhagia. DESIGN: Randomised controlled trial. SETTING: A university department of obstetrics and gynaecology. SUBJECTS: 76 women with dysfunctional uterine bleeding. INTERVENTIONS: Treatment for five days from day 1 of menses during three consecutive menstrual periods. 27 patients were randomised to take ethamsylate 500 mg six hourly, 23 patients to take mefenamic acid 500 mg eight hourly, and 26 patients to take tranexamic acid 1 g six hourly. MAIN OUTCOMES MEASURES: Menstrual loss measured by the alkaline haematin method in three control menstrual periods and three menstrual periods during treatment; duration of bleeding; patient''s estimation of blood loss; sanitary towel usage; the occurrence of dysmenorrhoea; and unwanted events. RESULTS: Ethamsylate did not reduce mean menstrual blood loss whereas mefenamic acid reduced blood loss by 20% (mean blood loss 186 ml before treatment, 148 ml during treatment) and tranexamic acid reduced blood loss by 54% (mean blood loss 164 ml before treatment, 75 ml during treatment). Sanitary towel usage was significantly reduced in patients treated with mefenamic acid and tranexamic acid. CONCLUSIONS: Tranexamic acid given during menstruation is a safe and highly effective treatment for excessive bleeding. Patients with dysfunctional uterine bleeding should be offered medical treatment with tranexamic acid before a decision is made about surgery.     

A simplified method for determination of radioactive iron in whole-blood samples

For studies on iron absorption in man radioisotopes represent an easy and simple tool However, measurement of the orbital electron emitting radioiron, 55Fe, in blood is difficult and insufficiently described in the literature. The present study describes a relatively simple method for simultaneous determination of 55Fe and 59Fe in blood, using a dry-ashing procedure and recrystallization of the remaining iron. The detection limit of the method permits measurements of 0.1 Bq/ml blood thus allowing detection of less than 1% absorption from a 40 kBq dose, which is ethically acceptable in humans. The overall recovery of radioiron from blood is more than 90%, and the coefficient of variation, as judged by the variation in the ratio 55Fe/59Fe is in the order of 4%. Combined with whole-body counting of 59Fe and direct gamma-counting of 59Fe on blood samples, this method represents a sensitive method for studying the intestinal absorption of 55Fe and 59Fe in man and at the same time allows estimation of the amount of radioiron located in the vascular compartment.     

EPR study of blood of anemic patients with urological cancer

Changes in Fe³⁺-transferrin (Fe-Tf) and Cu²⁺-ceruloplasmin (Cu-Cp) concentrations in venous blood sampled from anemic patients with urinary bladder and kidney cancer of stages I–IV were assessed using EPR spectroscopy. In malignancy-associated anemia, the paramagnetic Fe³⁺ concentration in Tf proved to be below the norm, while in anemic non-oncology patients the Tf iron saturation was normal. Moreover, in patients with malignancy-associated anemia the Cu-Cp on average was nearly twice higher than in healthy volunteers (p < 0.01). Thus, simultaneous EPR measurement of protein-borne paramagnetic centers (such as Fe-Tf and Cu-Cp) in the blood of anemic patients can be used as an express biomarker for urological cancer even at early stages of malignant growth.     

HMGB1 Mediates Anemia of Inflammation in Murine Sepsis Survivors

Patients surviving sepsis develop anemia, but the molecular mechanism is unknown. Here we observed that mice surviving polymicrobial gram-negative sepsis develop hypochromic, microcytic anemia with reticulocytosis. The bone marrow of sepsis survivors accumulates polychromatophilic and orthochromatic erythroblasts. Compensatory extramedullary erythropoiesis in the spleen is defective during terminal differentiation. Circulating tumor necrosis factor (TNF) and interleukin (IL)-6 are elevated for 5 d after the onset of sepsis, and serum high-mobility group box 1 (HMGB1) levels are increased from d 7 until at least d 28. Administration of recombinant HMGB1 to healthy mice mediates anemia with extramedullary erythropoiesis and significantly elevated reticulocyte counts. Moreover, administration of anti-HMGB1 monoclonal antibodies after sepsis significantly ameliorates the development of anemia (hematocrit 48.5 ± 9.0% versus 37.4 ± 6.1%, p < 0.01; hemoglobin 14.0 ± 1.7 versus 11.7 ± 1.2 g/dL, p < 0.01). Together, these results indicate that HMGB1 mediates anemia by interfering with erythropoiesis, suggesting a potential therapeutic strategy for anemia in sepsis.     

Isotope Ratio Measurements of Iron in Blood Samples by Multi-collector ICP-MS to Support Nutritional Investigations in Humans

With the perspective of embarking on a human study using a double iron (Fe) stable isotope tracer protocol to assess iron bioavailability, investigations were conducted on Fe isotope ratios in blood samples using a VG Axiom Multi-collector ICP-MS. The factors affecting the precision and accuracy of Fe isotopic ratios, such as spectral- and matrix-induced interferences and Fe recoveries from sample preparation, have been identified and optimized. Major polyatomic interferences (e.g., Ar-O, Ar-OH, and FeH) were significantly reduced by using an Aridus nebulizer and desolvating system. Isobaric metal (e.g., ⁵⁴Cr⁺ on ⁵⁴Fe⁺ and ⁵⁸Ni⁺ on ⁵⁸Fe⁺) interferences and Ca-oxides and hydroxides were quantitatively removed during chemical purification of blood samples and selective isolation of Fe by anion-exchange resin, after mineralization of the blood samples by microwave digestion. Quantitative recoveries of Fe from different steps of sample preparation were verified using whole blood reference material. Fe isotopic compositions of the samples were corrected for instrumental mass bias by the standard-sample bracketing method using the certified reference standard IRMM-014. External precisions on the order of 0.008–0.05 (% RSD), 0.007–0.015 (% RSD), and 0.03–0.09 (% RSD) were obtained for ⁵⁴Fe/⁵⁶Fe, ⁵⁷Fe/⁵⁶Fe, and ⁵⁸Fe/⁵⁶Fe, respectively, in the blood for three replicate measurements. The level of precision obtained in this work enables the detection of low enrichments of Fe in blood, which is highly desired in nutrition tracer studies.     

Molecular mechanisms of non‐transferrin‐bound and transferring‐bound iron uptake in primary hippocampal neurons

The molecular mechanisms of iron trafficking in neurons have not been elucidated. In this study, we characterized the expression and localization of ferrous iron transporters Zip8, Zip14 and divalent metal transporter 1 (DMT1), and ferrireductases Steap2 and stromal cell‐derived receptor 2 in primary rat hippocampal neurons. Steap2 and Zip8 partially co‐localize, indicating these two proteins may function in Fe³⁺ reduction prior to Fe²⁺ permeation. Zip8, DMT1, and Steap2 co‐localize with the transferrin receptor/transferrin complex, suggesting they may be involved in transferrin receptor/transferrin‐mediated iron assimilation. In brain interstitial fluid, transferring‐bound iron (TBI) and non‐transferrin‐bound iron (NTBI) exist as potential iron sources. Primary hippocampal neurons exhibit significant iron uptake from TBI (Transferrin‐⁵⁹Fe³⁺) and NTBI, whether presented as ⁵⁹Fe²⁺‐citrate or ⁵⁹Fe³⁺‐citrate; reductase‐independent ⁵⁹Fe²⁺ uptake was the most efficient uptake pathway of the three. Kinetic analysis of Zn²⁺ inhibition of Fe²⁺ uptake indicated that DMT1 plays only a minor role in the uptake of NTBI. In contrast, localization and knockdown data indicate that Zip8 makes a major contribution. Data suggest also that cell accumulation of ⁵⁹Fe from TBI relies at least in part on an endocytosis‐independent pathway. These data suggest that Zip8 and Steap2 play a major role in iron accumulation from NTBI and TBI by hippocampal neurons.

     

Validation of a questionnaire method for estimating extent of menstrual blood loss in young adult women.

The objective of this study was to validate two indirect methods for estimating the extent of menstrual blood loss against a reference method to determine which method would be most appropriate for use in a population of young adult women. Thirty-two women aged 18 to 29 years (mean +/- SD; 22.4 +/- 2.8) were recruited by poster in Dunedin (New Zealand). Data are presented for 29 women. A recall method and a record method for estimating extent of menstrual loss were validated against a weighed reference method. Spearman rank correlation coefficients between blood loss assessed by Weighed Menstrual Loss and Menstrual Record was rs = 0.47 (p = 0.012), and between Weighed Menstrual Loss and Menstrual Recall, was rs = 0.61 (p = 0.001). The Record method correctly classified 66% of participants into the same tertile, grossly misclassifying 14%. The Recall method correctly classified 59% of participants, grossly misclassifying 7%. Reference method menstrual loss calculated for surrogate categories demonstrated a significant difference between the second and third tertiles for the Record method, and between the first and third tertiles for the Recall method. The Menstrual Recall method can differentiate between low and high levels of menstrual blood loss in young adult women, is quick to complete and analyse, and has a low participant burden.     

59Fe study of red blood cells life span in glucose-6-phosphate dehydrogenase deficiency heterozygote

Summary In a presumptive heterozygote for congenital nonspherocytic hemolytic anemia caused by glucose-6-phosphate dehydrogenase deficiency, a fraction of short-living red blood cells was demonstrated by administration of nitrofurantoin in the 22nd day of the ⁵⁹Fe study of erythrocyte life span. A small percentage of deficient red blood cells in peripheral blood in this case (4%) may originate in the shorter life span of deficient cells and in the proportion of the deficient to normal red blood cells produced.     

Haematological and haematopoietic response to sodium chloride stress in a freshwater air-breathing fish Channapunctatus Bloch

Results of experiments to determine the sensitivity of Channa punciatus to different levels of sodium chloride (NaCl) (1.2, 3.2 and 6.2g 1⁻¹) are reported. It was found that C. punctatus which is otherwise considered a hardy fish is more sensitive to higher levels of sodium chloride stress. Thus 10% of the LC50 96 h value (1.2 g 1⁻¹ NaCl) was found stressful as evidenced by loss in body weight, while 25 and 50% of the LC50 96 h value (3.2 and 6.2 g 1⁻¹ NaCl) even resulted in mortality. Haematological and associated haematopoietic investigation confirmed stress symptoms in all the parameters tested. Thus microcytic hypochromic anemia together with leucopenia was indicated at the two higher sublethal levels, i.e., 25% and 50% of LC50 96 h value. Differential leucocyte count showed that leucopenia is mainly contributed by thrombocytic and neutrophilic decrease. Other cell types, viz., eosinophils, basophils, large and small lymphocytes, showed a relatively significant (P < 0.01) increase in number.
Haematopoietic studies revealed that the two penultimate stages in both RBC and neutrophil development closely follow the trend of their counterparts in the peripheral blood. However, the stem cells of both these cell types recorded significant increase under sodium chloride stress, which indicated homeostatic response. Biochemical studies revealed a depletion in blood glucose level as well as in liver and muscle glycogen reserves.
Restoration to normal control conditions after 6 weeks of exposure to different levels of sodium chloride stress resulted in a cessation of mortality (if any), gain in body weight and more or less normality in all the haematological parameters within a period of 2 weeks.     

Process for biological oxidation and control of dissolved iron in bioleach liquors

Iron has a central role in bioleaching and biooxidation processes. Fe²⁺ produced in the dissolution of sulfidic minerals is re-oxidized to Fe³⁺ mostly by biological action in acid bioleaching processes. To control the concentration of iron in solution, it is important to precipitate the excess as part of the process circuit. In this study, a bioprocess was developed based on a fluidized-bed reactor (FBR) for Fe²⁺ oxidation coupled with a gravity settler for precipitative removal of ferric iron. Biological iron oxidation and partial removal of iron by precipitation from a barren heap leaching solution was optimized in relation to the performance and retention time (τ_FBR) of the FBR. The biofilm in the FBR was dominated by Leptospirillum ferriphilum and “Ferromicrobium acidiphilum.” The FBR was operated at pH 2.0 ± 0.2 and at 37 °C. The feed was a barren leach solution following metal recovery, with all iron in the ferrous form. 98–99% of the Fe²⁺ in the barren heap leaching solution was oxidized in the FBR at loading rates below 10 g Fe²⁺/L h (τ_FBR of 1 h). The optimal performance with the oxidation rate of 8.2 g Fe²⁺/L h was achieved at τ_FBR of 1 h. Below the τ_FBR of 1 h the oxygen mass transfer from air to liquid limited the iron oxidation rate. The precipitation of ferric iron ranged from 5% to 40%. The concurrent Fe²⁺ oxidation and partial precipitative iron removal was maximized at τ_FBR of 1.5 h, with Fe²⁺ oxidation rate of 5.1 g Fe²⁺/L h and Fe³⁺ precipitation rate of 25 mg Fe³⁺/L h, which corresponded to 37% iron removal. The precipitates had good settling properties as indicated by the sludge volume indices of 3–15 mL/g but this step needs additional characterization of the properties of the solids and optimization to maximize the precipitation and to manage sludge disposal.     

A mouse model for β-thalassemia

A mutation that produces an absolute deficiency of normal β-major globin polypeptides has been recovered from a DBA/2J male mouse. Most mice homozygous for the deficiency survived to adulthood and reproduced but were smaller at birth than their littermates and demonstrated a hypochromic, microcytic anemia with severe anisocytosis, poikilocytosis, and reticulocytosis and the presence of inclusion bodies in a high proportion of circulating erythrocytes. Mice heterozygous for the deficiency demonstrated a mild reticulocytosis but were not clinically anemic. Analysis of globin chain synthesis in vitro by ³H-leucine incorporation revealed that β-globin synthesis was nearly normal (95%) in heterozygotes and about 75% of normal in deficiency homozygotes. Molecular characterization of the mutation by restriction analysis revealed a deletion of about 3.3 kb of DNA, including regulatory sequences and all coding blocks for β-major globin. Based on genetic and hematological criteria, mice homozygous for the mutant allele, designated Hbb^th-1, represent the first animal model of β-thalassemia (Cooley's anemia), a severe genetic disease of humans.     

A mutation in the gene for delta-aminolevulinic acid dehydratase (ALAD) causes hypochromic anemia in the medaka, Oryzias latipes

A genetic screen for mutations affecting embryogenesis in the medaka, Oryzias latipes, identified a mutant, whiteout (who), that exhibited hypochromic anemia. The who mutant initially had the normal number of blood cells, but it then gradually decreased during the embryonic and larval stages. The blood cells in the who mutants show an elongated morphology and little hemoglobin activity. Genetic mapping localized who to the vicinity of a LG12 marker, olgc1. By utilizing the highly conserved synteny between medaka and pufferfish, we identified a gene for delta-aminolevulinic acid dehydratase (ALAD), which is the second enzyme in the heme synthetic pathway, as a candidate for who. We found a missense mutation in the alad gene that was tightly linked to the who phenotype, strongly suggesting that the hypochromic anemia phenotype in the who mutant is caused by a loss of the alad function. Thus, who mutants represent a model for the human disease ALAD-deficiency porphyria.     

An analytical study of in vivo survival of limited populations of animal red blood cells tagged with radio-iron

Animal red blood cell in vivo survival curves, obtained by the radioiron tagging of populations of approximately the same age followed by the administration of non-radioactive iron to suppress radioiron reutilization, have been subjected to mathematical analysis on the basis of the three following assumptions:— (A) Red blood cells disappear from the circulation as the result of senescence: there is an average life span around which the life spans of individual cells are distributed in the usual way. (B) Red blood cells may be removed from the circulation by a process of random destruction which continuously removes a constant fraction of the cells present at any moment irrespective of age or other characteristics. (C) Under the conditions of the experiments described, a fraction of the radioiron, constant for each animal, is reutilized in new red cell formation when released by red cell destruction. This mathematical analysis indicates the following average life spans with the respective standard errors of the mean: dog 107 days ± 1.14; rabbit 67.6 days ± 1.94; cat 68.4 ± 1.50. The mathematical treatment presented has permitted a consideration of the theoretical variation of red cell life spans which was found in these experiments to be relatively small for all three species studied. In the rabbit and cat 2.5 per cent of tagged populations of red cells of the same age would theoretically have disappeared by senescence 17 days before the average life span was reached. The variation of red cell life in the dog was slightly less. Animals of the three species studied, in spite of apparently normal health, exhibited varying degrees of random destruction of both autogenous and transfused fresh normal homologous red cells. As yet, we have no explanation for this random loss of cells occurring in apparently healthy normal animals. The method of mathematical analysis presented is applicable to animal red cell survival studies employing radioiron in which differing rates of random destruction are operating in the removal of red cells.     

Referral for menstrual problems: cross sectional survey of symptoms,reasons for referral,and management

ObjectivesTo describe the menstrual experience of women referred for menstrual problems, in particular menorrhagia (excessive menstrual loss), and to assess associations with reasons for referral given by their general practitioners, the women''s understanding of the reasons for their attendance at the hospital clinics, and clinic outcome.DesignQuestionnaire survey, with partial review of case notes after 8 months.SettingThree hospital gynaecology clinics in Glasgow and Edinburgh.Participants952 women completed the questionnaire, and the first 665 were reviewed.ResultsOnly 38% (95% confidence interval 34% to 41%) of women reported excessive menstrual loss as a severe problem. However 60% (57-63%) gave it as reason for attending a clinic, and 76% (73-79%) of general practitioners gave it as reason for referral. Reason for referral was significantly biased towards bleeding (McNemar odds ratio 4.01, 3.0 to 5.3, P<0.001) and against pain (0.54, 0.4 to 0.7, P<0.001). Dysfunctional uterine bleeding was diagnosed in 37% (31-42%) of the 259 women who gave as reason for attendance something other than bleeding. Women who were economically disadvantaged differed in prevalence of the main diagnoses and were more likely to fail to reattend. Hysterectomy was associated with referral for bleeding (relative risk 4.9, 1.6 to 15.6, P<0.001) but not with the patient stating bleeding as the reason for clinic attendance.ConclusionsIntolerance of the volume of their bleeding is not a key feature among women attending clinics for bleeding problems. Broad menstrual complaint tends to be reframed as excessive bleeding at referral and during management. This may result in women receiving inappropriate care. Conceptualisation and assessment of menorrhagia requires reconsideration.

What is already known on this topic

Excessive menstrual loss (menorrhagia) is one of the commonest reasons for secondary referral of women, but there is no formalised clinical assessment in routine useManagement typically involves potent drugs or invasive surgery, with 60% of women having hysterectomy within 5 yearsMany women referred for menorrhagia have menstrual blood loss that is not excessive

What this study adds

Discordance exists between symptoms and both referral and diagnostic pathways, arising from a disproportionate focus on menstrual bleedingAmong women referred for menorrhagia, volume of bleeding is not a key symptomThis raises concerns about conceptualisation and assessment of menstrual complaint and the appropriateness of healthcare provision     

Kinetics of the liquid-phase oxidation of acid ferrous sulfate by the bacterium Thiobacillus ferrooxidens

The kinetics of the batch-wise liquid-phase oxidation of ferrous sulfate by the organism Thiobacillus ferrooxidans has been studied over a range of temperatures from 20°C to 31°C and in the presence of an abundant supply of oxygen, carbon dioxide, and other nutrients. The rate of oxidation was found to be accurately described by the equation where t = time hr, S = concentration of ferrous ions g Fe⁺⁺/1., μ_m = maximum specific growth rate of bacteria, hr^?1. Y = mass of bacteria produced per gram of iron oxidized g/g, K = saturation constant, g Fe⁺⁺/l., and X = concentration of bacteria g/1. The value for the maximum specific growth rate, μ_m, was found to vary from 0.12 hr^?1 at 20°C to 0.20 hr^?1 at 31°C, while the value for the saturation constant K varied randomly between 1 and 2 g/1. A method has also been described which permitted evaluation of the relevant rate constants μ_m and K without direct knowledge of the bacterial population. This method was found to yield values of μ_m and K which agreed with values determined accurately by a statistical regression analysis of the experimental data.     

Sfxn1 is essential for erythrocyte maturation via facilitating hemoglobin production in zebrafish

Previous reports revealed that mutation of mitochondrial inner-membrane located protein SFXN1 led to pleiotropic hematological and skeletal defects in mice, associated with the presence of hypochromic erythroid cell, iron overload in mitochondrion of erythroblast and the development of sideroblastic anemia (SA). However, the potential role of sfxn1 during erythrocyte differentiation and the development of anemia, especially the pathological molecular mechanism still remains elusive. In this study, the correlation between sfxn1 and erythroid cell development is explored through zebrafish in vivo coupled with human hematopoietic cells assay ex vivo. Both knockdown and knockout of sfxn1 result in hypochromic anemia phenotype in zebrafish. Further analyses demonstrate that the development of anemia attributes to the biosynthetic deficiency of hemoglobin, which is caused by the biosynthetic disorder of heme that associates with one?carbon (1C) metabolism process of mitochondrial branch in erythrocyte. Sfxn1 is also involved in the differentiation and maturation of erythrocyte in inducible human umbilical cord blood stem cells. In addition, we found that functional disruption of sfxn1 causes hypochromic anemia that is distinct from SA. These findings reveal that sfxn1 is genetically conserved and essential for the maturation of erythrocyte via facilitating the production of hemoglobin, which may provide a possible guidance for the future clinical treatment of sfxn1 mutation associated hematological disorders.     

Uptake of 5 9Fe from soluble 5 9Fe-humate complexes by cucumber and barley plants

The capability of cucumber (Cucumis sativus L., cv. Serpente cinese), a Strategy I plant and barley (Hordeum vulgaris L., cv. Europa), a Strategy II plant to use Fe complexed by a water-soluble humic fraction (WEHS) extracted from a peat, was studied. Uptake of ⁵⁹Fe from ⁵⁹Fe-WEHS by cucumber plants was higher at pH 6.0 than at pH 7.5. Roots of intact cucumber plants were able to reduce the Fe^III-WEHS complex either at pH 6.0 or 7.5, rates being higher in the assay medium buffered at pH 6.0. After supply of ⁵⁹Fe-WEHS, a large pool of root extraplasmatic ⁵⁹Fe was formed, which could be used to a large extent by Fe-deficient plants, particularly under acidic conditions. Uptake of ⁵⁹Fe from ⁵⁹Fe-WEHS by Fe-sufficient and Fe-deficient barley plants was examined during periods of high (morning) and low (evening) PS release. Uptake paralleled the diurnal rhythm of PS release. Furthermore, ⁵⁹Fe uptake was strongly enhanced by addition of PS to the uptake solution in both Fe-sufficient and Fe-deficient plants. High amount of root extraplasmatic ⁵⁹Fe was formed upon supply of Fe-WEHS, particularly in the evening experiment. Fe-deficient barley plants were able to utilize Fe from the root extraplasmatic pool, conceivably as a result of high rates of PS release. The results of the present work together with previous observations indicate that cucumber plants (Strategy I) utilize Fe complexed to WEHS, presumably via reduction of Fe^III-WEHS by the plasma membrane-bound reductase, while barley plants (Strategy II) use an indirect mechanism involving ligand exchange between WEHS and PS.