Copper-dependent iron assimilation pathway in the model photosynthetic eukaryote chlamydomonas reinhardtii

The unicellular green alga Chlamydomonas reinhardtii is a valuable model for studying metal metabolism in a photosynthetic background. A search of the Chlamydomonas expressed sequence tag database led to the identification of several components that form a copper-dependent iron assimilation pathway related to the high-affinity iron uptake pathway defined originally for Saccharomyces cerevisiae. They include a multicopper ferroxidase (encoded by Fox1), an iron permease (encoded by Ftr1), a copper chaperone (encoded by Atx1), and a copper-transporting ATPase. A cDNA, Fer1, encoding ferritin for iron storage also was identified. Expression analysis demonstrated that Fox1 and Ftr1 were coordinately induced by iron deficiency, as were Atx1 and Fer1, although to lesser extents. In addition, Fox1 abundance was regulated at the posttranscriptional level by copper availability. Each component exhibited sequence relationship with its yeast, mammalian, or plant counterparts to various degrees; Atx1 of C. reinhardtii is also functionally related with respect to copper chaperone and antioxidant activities. Fox1 is most highly related to the mammalian homologues hephaestin and ceruloplasmin; its occurrence and pattern of expression in Chlamydomonas indicate, for the first time, a role for copper in iron assimilation in a photosynthetic species. Nevertheless, growth of C. reinhardtii under copper- and iron-limiting conditions showed that, unlike the situation in yeast and mammals, where copper deficiency results in a secondary iron deficiency, copper-deficient Chlamydomonas cells do not exhibit symptoms of iron deficiency. We propose the existence of a copper-independent iron assimilation pathway in this organism.

Facilitated heterogeneous photodegradation of dissolved organic matter by particulate iron

The photochemical degradation of dissolved organic matter (DOM) derived from the leaves of River Red Gum (Eucalyptus camaldulensis) was examined, with a particular focus on the photochemical generation of CO₂, consumption of O₂, and the effect of particulate iron minerals on these photochemical reactions. Solutions of leaf leachate were irradiated with ultraviolet and visible light in the presence and absence of amorphous iron oxides. Addition of fresh iron oxide was found to increase the rate of photodegradation of the organic matter by up to an order of magnitude compared to the reactions without added iron oxide. The ratio of CO₂ produced to O₂ consumed was ~1:1 in both the presence and absence of iron oxyhydroxide. The reactivity of the iron oxides was dependent on the preparation method and decreased with increased storage time. These results suggest that photochemical reactions on particle surfaces should be considered when examining carbon transformation in aquatic ecosystems, especially at sites with potential for the production of iron oxyhydroxides.

How the west was lost? Hamersley Iron, the birthplace of a decade of De-Unionisation

Given the focus of recent years on Rio Tinto's battles with the Australian union movement over its (largely successful) attempt to de-unionise its diverse mining and manufacturing operations, this paper examines how the company first introduced its 'staff employment system at Hamersley Iron in 1993. The success of this venture clearly provided a template for its replication throughout its many other operations over the following years. Though no doubt assisted by changed legal and political environments, this paper argues that it was ultimately the demonstration of managerial determination and a hesitant union leadership which led to the de-unionisation at Hamersley Iron. As the union movement/makes a renewed attempt to attract workers back to the fold, there are valuable lessons to be learnt from its earlier mistakes.

Chronological changes in tissue copper, zinc and iron in the toxic milk mouse and effects of copper loading

The toxic milk (tx) mouse is a rodent model for Wilson disease, an inherited disorder of copper overload. Here we assessed the effect of copper accumulation in the tx mouse on zinc and iron metabolism. Copper, zinc and iron concentrations were determined in the liver, kidney, spleen and brain of control and copper-loaded animals by atomic absorption spectroscopy. Copper concentration increased dramatically in the liver, and was also significantly higher in the spleen, kidney and brain of control tx mice in the first few months of life compared with normal DL mice. Hepatic zinc was increased with age in the tx mouse, but zinc concentrations in the other organs were normal. Liver and kidney iron concentrations were significantly lower at birth in tx mice, but increased quickly to be comparable with control mice by 2 months of age. Iron concentration in the spleen was significantly higher in tx mice, but was lower in 5 day old tx pups. Copper-loading studies showed that normal DL mice ingesting 300 mg/l copper in their diet for 3 months maintained normal liver, kidney and brain copper, zinc and iron levels. Copper-loading of tx mice did not increase the already high liver copper concentrations, but spleen and brain copper concentrations were increased. Despite a significant elevation of copper in the brain of the copper-loaded tx mice no behavioural changes were observed. The livers of copper-loaded tx mice had a lower zinc concentration than control tx mice, whilst the kidney had double the concentration of iron suggesting that there was increased erythrocyte hemolysis in the copper-loaded mutants.

Photodegradation, interaction with iron oxides and bioavailability of dissolved organic matter from forested floodplain sources

Photochemical degradation of dissolved organic matter (DOM) can influence food webs by altering the availability of carbon to microbial communities, and may be particularly important following periods of high DOM input (e.g. flooding of forested floodplains). Iron oxides can facilitate these reactions, but their influence on subsequent organic products is poorly understood. Degradation experiments with billabong (= oxbow lake) water and river red gum (Eucalyptus camaldulensis) leaf leachate were conducted to assess the importance of these reactions in floodplain systems. Photochemical degradation of DOM in sunlight-irradiated quartz tubes (with and without amorphous iron oxide) was studied using gas chromatography and UV-visible spectroscopy. Photochemical reactions generated gaseous products and small organic acids. Bioavailability of billabong DOM increased following irradiation, whereas that of leaf leachate was not significantly altered. Fluorescence excitation-emission spectra suggested that the humic component of billabong organic matter was particularly susceptible to degradation, and the source of DOM influenced the changes observed. The addition of amorphous iron oxide increased rates of photochemical degradation of leachate and billabong DOM. The importance of photochemical reactions to aquatic systems will depend on the source of the DOM and its starting bioavailability, whereas inputs of freshly formed iron oxides will accelerate the processes.

'Iron-saturated' lactoferrin is a potent natural adjuvant for augmenting cancer chemotherapy

Bovine lactoferrin (bLf), an iron-containing natural defence protein found in bodily secretions, has been reported to inhibit carcinogenesis and the growth of tumours. Here, we investigated whether natural bLf and iron-saturated forms of bLf differ in their ability to augment cancer chemotherapy. bLf was supplemented into the diet of C57BL/6 mice that were subsequently challenged subcutaneously with tumour cells, and treated by chemotherapy. Chemotherapy eradicated large (0.6 cm diameter) EL-4 lymphomas in mice that had been fed iron-saturated bLf (here designated Lf(+)) for 6 weeks prior to chemotherapy, but surprisingly not in mice that were fed lesser iron-saturated forms of bLf, including apo-bLf (4% iron saturated), natural bLf (approximately 15% iron saturated) and 50% iron-saturated bLf. Lf(+)-fed mice bearing either EL-4, Lewis lung carcinoma or B16 melanoma tumours completely rejected their tumours within 3 weeks following a single injection of either paclitaxel, doxorubicin, epirubicin or fluorouracil, whereas mice fed the control diet were resistant to chemotherapy. Lf(+) had to be fed to mice for more than 2 weeks prior to chemotherapy to be wholly effective in eradicating tumours from all mice, suggesting that it acts as a competence factor. It significantly reduced tumour vascularity and blood flow, and increased antitumour cytotoxicity, tumour apoptosis and the infiltration of tumours by leukocytes. Lf(+) bound to the intestinal epithelium and was preferentially taken up within Peyer's patches. It increased the production of Th1 and Th2 cytokines within the intestine and tumour, including TNF, IFN-gamma, as well as nitric oxide that have been reported to sensitize tumours to chemotherapy. Importantly, it restored both red and white peripheral blood cell numbers depleted by chemotherapy, potentially fortifying the mice against cancer. In summary, bLf is a potent natural adjuvant and fortifying agent for augmenting cancer chemotherapy, but needs to be saturated with iron to be effective.

Quality of life related to oral versus subcutaneous iron chelation: a time trade-off study

Objective: To investigate the utility associated with subcutaneous infusion (deferoxamine) compared with once-daily oral administration (deferasirox) of iron chelation therapy.

Methods: Interviews using the time trade-off technique were used to estimate preferences (utility) for health states by finding the point at which respondents were indifferent between a longer but lower quality of life (QoL) and a shorter time in full health. Participants (n = 110) were community-based, 51% women, median age 35 years, from four regions in Sydney, Australia. Respondents rated three health states involving equal outcomes for people with thalassemia but with different treatment modalities for iron chelation; an "anchor state" describing a patient receiving iron chelation without administration mode specified, anchor state plus iron chelation via subcutaneous infusion, and anchor state plus iron chelation through once-daily oral medication.

Results: On an interval scale between 0 (death) and 1 (full health), median (interquartile range) utility of 0.80 (0.65–0.95) for the anchor state, 0.66 (0.45–0.87) for subcutaneous infusion, and 0.93 (0.80–0.97) for once-daily oral administration was obtained. The mean (median) difference of 0.23 (0.27) between the two treatments was statistically significant (Wilcoxon-signed rank test, P < 0.001). Subcutaneous infusion was associated with a mean (median) utility 0.13 (0.14) lower than the anchor state (P < 0.001), and once-daily oral treatment had a utility 0.10 (0.13) higher (P < 0.001).

Conclusion: Community respondents associate oral administration of an iron chelator such as deferasirox with enhanced QoL compared with subcutaneous treatment. Assuming equal safety and efficacy, QoL gains from once-daily oral treatment compared with subcutaneous infusion are significant.

Incorporation of oxygen into the succinate co-product of iron(II) and 2-oxoglutarate dependent oxygenases from bacteria, plants and humans.

The ferrous iron and 2-oxoglutarate (2OG) dependent oxygenases catalyse two electron oxidation reactions by coupling the oxidation of substrate to the oxidative decarboxylation of 2OG, giving succinate and carbon dioxide coproducts. The evidence available on the level of incorporation of one atom from dioxygen into succinate is inconclusive. Here, we demonstrate that five members of the 2OG oxygenase family, AlkB from Escherichia coli, anthocyanidin synthase and flavonol synthase from Arabidopsis thaliana, and prolyl hydroxylase domain enzyme 2 and factor inhibiting hypoxia-inducible factor-1 from Homo sapiens all incorporate a single oxygen atom, almost exclusively derived from dioxygen, into the succinate co-product.

Casting yield improvement in graphite iron castings

A well designed runner and feeding system should produce castings with minimal defects and low pour weight. This thesis investigates how the filling regime and solidification of the mould influences defects in the castings produced from that mould. Design guidelines to reduce such defects are proposed and tested. An existing shrinkage fault in a Grey Iron disc brake casting is simulated using a commercial finite-difference computer program. Three criteria are used to predict the defect and the effect of changes to the feeder geometry. Critical Fraction Solidification analysis is used to determine whether the feeder remains in liquid contact with the casting during solidification and this approach is shown to correctly predict the presence or absence of porosity* The feeder block is extended below the ingate of the casting to improve liquid contact between the casting and feeder without significantly increasing the feeder mass. Plant trials confirm the change to the feeder eliminates the porosity defect. The runner system and mould venting for a thin walled Ductile Iron casting are investigated. Trials show that by setting the total mould vent area to be greater than the net ingate area of the castings, the cold-shut frequency is halved. A method for runner system design based on peak linear flow velocity in the runner during mould filling is proposed. A new pressurised runner system produces castings with significantly fewer defects and reduced pour weight when runner areas are designed to maintain peak velocity below 1 m/s. Peak velocity and magnesium levels are demonstrated to be critical factors in the elimination of cold-shut defects. A pressurised runner system is also shown to isolate inclusion defects from castings more effectively than an unpressurised system. From this work, a technique is proposed which allows the yield of an existing runner and feeder system for iron castings to be improved with confidence in the results.

A population-based study of the effect of the HFE C282Y and H63D mutations on iron metabolism

The C282Y and H63D mutations in the HFE gene are important causes of hemochromatosis. In the elderly, these mutations might be associated with increased morbidity because of the lifelong accumulation of iron. In a population-based sample of the elderly, we determined the value of genotyping for HFE mutations to screen for subclinical hemochromatosis. HFE genotype frequencies were determined in a random group of 2095 subjects (55 years and over). In this random group, we selected within the six genotype groups a total of 342 individuals and measured their serum transferrin saturation, iron and ferritin levels. We also estimated the heritability and parameters needed to evaluate screening, including the sensitivity, specificity, positive and negative predictive values (PPV, NPV) of HFE genotypes. Iron parameters were significantly increased in subjects homozygous, heterozygous or compound heterozygous. The effect of the mutations was more pronounced in men than in women. For the H63D mutation, an allele dose effect was observed. The HFE gene explained about 5% of the variability in serum iron indices. The PPV for hemochromatosis for the C282Y homozygous was 100% in men and 67% in women. The NPV of the wild-type allele was 97% for both men and women. The sensitivity of both mutations was 70% for men and 52% for women and the specificity was 62% for men and 64% for women. Our study shows that the HFE C282Y and H63D are determinants of iron parameters in the elderly and will be effective in detecting individuals at high risk of hemochromatosis. However, when screening based on these two mutations, some individuals with subclinical hemochromatosis will be missed.

Effect of NbC and TiC precipitation on shape memory in an iron-based alloy

This paper examines the effects of TiC and NbC precipitation and prior cold rolling on the shape memory behaviour of an iron-based alloy. A precipitate-free alloy was used as a reference to investigate the relative contributions of prior-deformation and precipitation on shape memory. Heat treatment of the Nb- and Ti-containing alloys at 700 °C and 800 °C resulted in carbide precipitates between 120 nm and 220 nm in diameter. Bend testing of these samples showed a marginal increase in shape memory compared to the precipitate-free alloy. Under these conditions TiC precipitation exhibited slightly better shape memory than for NbC. However, this small increase was over-shadowed by the marked increase in shape memory that can be produced by subjecting the alloys to cold rolling followed by recovery annealing. When processed in this way, fine carbides are formed in the Ti- and Nb-containing alloys during the heat treatment. For particles >25 nm in diameter the shape memory is unaffected, but, it was found that small <5 nm particles have a detrimental effect on shape memory due to pinning of the martensite plates, thereby inhibiting their reversion to austenite. The optimum shape memory was observed in the precipitate-free alloy after cold rolling and recovery annealing.

β-Thalassaemia : emergence of new and improved iron chelators for treatment

β-Thalassaemia is an inherited blood disorder which through repeated blood transfusions and enhanced iron uptake from the gastrointestinal tract, results in marked iron overload. Untreated, the iron accumulation results in the dysfunction of vital organs such as the heart and liver. At present, the most effective treatment for β-thalassaemia is the use of the iron chelator, desferrioxamine, which is expensive, orally inactive and requires long subcutaneous infusions. In this concise review, we will focus on novel chelators which show therapeutic potential to replace desferrioxamine. Furthermore, we will discuss the potential of combined iron chelation therapy and the principle that, in the future, the use of more than just one chelator may be beneficial in tailoring individual iron chelation regimens.