Iron-induced lipid peroxidation and inhibition of dopamine synthesis in striatum synaptosomes

Crude striatum synaptosomes (P₂ fraction) from Fisher 344 female rats were incubated in the presence of ADP-chelated Fe³⁺ (0.5–50 M) and ascorbate (250 M). Intrasynaptosomal conversion of tyrosine to dopamine (DA) was measured by¹⁴CO₂ evolution froml-[1-¹⁴C]tyrosine in the absence of added cofactors and DOPA decarboxylase. Malondialdehyde (MDA) was measured as an index of lipid peroxidation. A concentration-dependent inhibition of DA synthesis by ADP-Fe³⁺/ascorbate was found with 50% inhibition occurring at 2.5 M Fe³⁺ concentration. This was accompanied by marked accumulation of MDA. Ascorbate or ADP alone did not affect DA synthesis and ADP-Fe³⁺ in the absence of exogenous ascorbate was effective only above 25 M. Exogenously added MDA did not inhibit DA synthesis. Purified synaptosomes were isolated from peroxidized and control P₂ fractions using sucrose gradients. Membrane microviscosity of the purifled synaptosomes was assessed by nitroxyl spin labels of stearic acid using electron paramagetic resonance techniques. There was a significant increase in membrane microviscosity as a result of ADP-Fe³⁺/ascorbate induced peroxidation. Maleimide nitroxide spin-label binding to protein sulhydryls was significantly modified by peroxidation of striatum synaptosomes. The weakly immobilized component of the sulhydryl spin-label (w) was drastically decreased whereas the strongly immobilized component (s) was modified less, thus leading to a marked reduction of w/s ratio. The exposure of striatum synaptosomes to the peroxidizing system resulted in a significant increase in total iron and in a 25% decrease in protein sulhydryl content. It is concluded that ironinduced damage to the DA synthetic system is mediated by alterations of the structural properties of nerve ending membranes.     

Genetic studies on the acidification capacity of sunflower roots induced under iron stress

Under stress of iron deficiency roots of sunflower (Helianthus annuus L.) increase proton efflux which acidifies the root medium, increase the ferric reducing capacity and the exudation of phenolic compounds. Differences have been found previously among sunflower inbred lines in the capacity of their roots to lower pH and it was also found that this character is under genetic control.This work presents the results of an inheritance study made by crossing two genotypes, one (CMS HA 89) without acidification capacity and another (RHA 271) with it. Plants were grown individually in 75 mL vessels with an aerated solution low in iron. After 4 days, solutions were changed to one without iron and the pH of the medium was measured during the following days. Results from F₁, F₂, and backcross generations can be explained with two pairs of alleles controlling the character, being the relation between alleles of complete dominance at both gene pairs, but either gene, when dominant is epistatic to the other.     

Genotypical differences among graminaceous species in release of phytosiderophores and uptake of iron phytosiderophores

Graminaceous species can enhance iron (Fe) acquisition from sparingly soluble inorganic Fe(III) compounds by release of phytosiderophores (PS) which mobilize Fe(III) by chelation. In most graminaceous species Fe deficiency increases the rate of PS release from roots by a factor of 10–20, but in some species, for example sorghum, this increase is much less. The chemical nature of PS can differ between species and even cultivars.The various PS are similarly effective as the microbial siderophore Desferal (ferrioxamine B methane sulfonate) in mobilizing Fe(III) from a calcareous soil. Under the same conditions the synthetic chelator DTPA (diaethylenetriamine pentaacetic acid) is ineffective.The rate of Fe(III)PS uptake by roots of graminaceous species increases by a factor of about 5 under Fe deficiency. In contrast, uptake of Fe from both synthetic and microbial Fe(III) chelates is much lower and not affected by the Fe nutritional status of the plants. This indicates that in graminaceous species under Fe deficiency a specific uptake system for FePS is activated. In contrast, the specific uptake system for FePS is absent in dicots. In a given graminaceous species the uptake rates of the various FePS are similar, but vary between species by a factor of upto 3. In sorghum, despite the low rate of PS release, the rate of FePS uptake is particularly high.The results indicate that release of PS and subsequent uptake of FePS are under different genetic control. The high susceptibility of sorghum to Fe deficiency (lime-chlorosis) is most probably caused by low rates of PS release in the early seedling stage. Therefore in sorghum, and presumably other graminaceous species also, an increase in resistance to lime chlorosis could be best achieved by breeding for cultivars with high rates of PS release. In corresponding screening procedures attention should be paid to the effects of iron nutritional status and daytime on PS release as well as on rapid microbial degradation of PS.     

Iron nutrition of a hydroponic strawberry culture (Fragaria vesca L.) supplied with different Fe chelates

Several indexes are used to determine the iron nutritional status of plants, but their effectiveness depends either on the plant growth conditions in natural environments or on the assay conditions. This research was conducted to test different indexes of the iron nutritional status of a hydroponic strawberry culture where treatments mainly differed in the source of the iron applied: Fe-EDTA, Fe-EDDHA and Fe-polyflavonoid. Macro and micronutrient concentrations in the nutrient solutions, leaf and vascular tissues were measured. Fe concentration in the nutrient solution during the course of the experiment was considered in relation to the stability of the different chelates. Both Fe concentration and total Fe content of leaves reflected the effect of the treatments; Fe/Mn ratio was significant as a diagnosis index. Other element ratios as P/Fe and K/Ca are not well related with the iron nutrition symptoms observed. Fe²⁺ concentration measured in leaves was not directly affected by the different chelate treatments.     

Effects of copper aspirinate and aspirin on tissue copper,zinc, and iron concentrations following chronic oral treatment in the adjuvant arthritic rat

Concentrations of copper, zinc, and iron were analyzed and compared in a number of tissues of adjuvant arthritic rats following 22 d of chronic treatment (per os) with either vehicle, aspirin or copper aspirinate, at doses of 100 mg/kg, 200 mg/kg, or 400 mg/kg. Such chronic treatment resulted in a negative balance in copper, zinc, and iron in many tissues. Among the tissues examined, liver and kidney exhibited the greatest changes in metal concentrations; brain and skeletal muscle exhibited the least. Arthritis-induced changes in the concentrations of all three metals in the liver were reversed upon treatment with aspirin. Treatment with copper aspirinate, on the other hand, resulted in an extremely high accumulation of copper in the liver. Arthritis-induced changes in copper, zinc, and iron concentrations in the pancreas and copper concentration in the plasma were generally not reversed upon treatment with either aspirin or copper aspirinate. Among the three metals examined, the degree of change observed as a result of drug treatments was greatest for iron and least for zinc. Finally, it appeared that the effects of aspirin and copper aspirinate on tissue metal concentrations were independent of the antiarthritic effects of these compounds.     

DNA Single Strand Breakage by H2O2 and Ferric or Cupric Ions: Its Modulation by Histidine

The role of histidine on DNA breakage induced by hydrogen peroxide (H₂O₂) and ferric ions or by H₂O₂ and cupric ions was studied on purified DNA. L-histidine slightly reduced DNA breakage by H₂O₂ and Fe³⁺ but greatly inhibited DNA breakage by H₂O₂ and Cu²⁺. However, only when histidine was present, the addition of EDTA to H₂O₂ and Fe³⁺ exhibited a bimodal dose response curve depending on the chelator metal ratio. The enhancing effect of histidine on the rate of DNA degradation by H₂O₂ was maximal at a chelator metal ratio between 0.2 and 0.5, and was specific for iron. When D-histidine replaced L-histidine, the same pattern of EDTA dose response curve was observed. Superoxide dismutase greatly inhibited the rate of DNA degradation induced by H₂O₂, Fe³⁺, EDTA and L-histidine involving the superoxide radical.

These studies suggest that the enhancing effect of histidine on the rate of DNA degradation by H₂O₂ and Fe³⁺ is mediated by an oxidant which could be a ferrous-dioxygen-ferric chelate complex or a chelate-ferryl ion.     

Utilization of Iron Sources and Its Possible Roles in the Pathogenesis of Vibrio parahaemolyticus

Vibrio parahaemolyticus is an important enteropathogen in Japan, Taiwan and other coastal regions. The influence of the regulation of iron on the pathogenesis of this pathogen has not been well characterized. The growth of pathogenic and non-pathogenic strains of V. parahaemolyticus on iron-limited agar plates was stimulated by ferritin, lactoferrin and transferrin at 30 μM , and also by hemin, hemoglobin and ferric ammonium citrate at 100 μM . Spontaneous iron-utilizing mutant strains (mutants) were derived from a clinical strain, ST550. Compared with the parent strain, lowered virulence was demonstrated for these mutants, as assayed by adult mouse and suckling mouse models. The in vivo growth and enterotoxigenicity of these mutants were also lower in the suckling mice. Adherence of the mutants to excised mouse intestine was lower as demonstrated by scanning electron microscopy. The iron-regulated outer membrane protein profile also changed in selected mutants. These results indicate that iron-regulated outer membrane proteins and other unknown factors associated with iron utilization may have profound influences, besides iron acquisition, on the pathogenesis of V. parahaemolyticus.     

Study of the role of iron in the anticryptococcal activity of human serum and fluconazole

Anticryptococcal activity of human serum and apotransferrin in RPMI 1640 was studied in vitro. The effects of varying concentrations of FeCl₃ on this activity was investigated. Possible synergy of serum and apotransferrin with fluconazole was also measured. The fungistatic activity of human serum, whether lyophilized, stored at 4 °C, fresh frozen or purchased from commercial sources vs. Cryptococcus neoformans was comparable. There was no significant loss of fungistatic activity after freezing and thawing the serum up to 10 times. The fungistatic activity of human serum was similar when tested in different tissue culture media with the exception of Medium 199. The addition of apotransferrin (2.0 or 0.2 mg/ml) to RPMI 1640 had an inhibitory effect on cryptococcal growth. This effect was reversed by 20 M of FeCl₃ at both apotransferrin concentrations. By contrast, addition of FeCl₃ to human serum and RPMI 1640 did not reverse inhibition of growth. Fluconazole synergized with the human serum preparations described, but not with pooled commercial serum, for fungicidal activity. Synergistic activity of fluconazole and human serum was not affected by the addition of FeCl₃. Apotransferrin did not show any synergistic fungicidal activity with fluconazole.     

Biogeochemical cycling of sulfur and iron in sediments of a south-east Asian mangrove,Phuket Island,Thailand

Benthic sulfate reduction and sediment pools of sulfur and iron were examined during January 1992 at 3 stations in the Ao Nam Bor mangrove, Phuket, Thailand. Patterns of sulfate reduction rates (0–53 cm) reflected differences in physical and biological conditions at the 3 stations, and highest rates were found at the vegetated site within the mangrove (Rhizophora apiculata) forest. Due to extended oxidation of mangrove sediments, a large portion of the added³⁵S-label was recovered in the chromium reducible pools (FeS₂ and S⁰) (41–91% of the reduced sulfur). Pyrite was the most important inorganic sulfur component, attaining pool sizes 50–100 times higher than acid volatile pools (FeS). HCl-extractable (0.5 M HCl) iron pools, including Fe(II)_HCl and Fe(III)_HCl, were generally low and Fe(III)_HCl was only present in the upper surface layers (0–5 cm). Maximum concentrations of dissolved Fe²⁺ (35–285 M) occurred just about the depth where dissolved H₂S accumulated. Furthermore Fe²⁺ and H₂S coexisted only where concentrations of both were low. There was an accumulation of organic sulfur in the deep sediment at 2 stations in the inner part of the mangrove. The reoxidation of reduced sulfides was rapid, and storage of sulfur was minor in the upper sediment layers, where factors like bioturbation, the presence of roots, or tidal mixing enhance oxidation processes.Author of correspondence.     

Diversity of siderophore genes encoding biosynthesis of 2,3-dihydroxybenzoic acid in Aeromonas spp.

Most species of the genus Aeromonas produce the siderophore amonabactin, although two species produce enterobactin, the siderophore of many enteric bacteria. Both siderophores contain 2,3-dihydroxybenzoic acid (2,3-DHB). Siderophore genes (designated aebC, -E, -B and -A, for aeromonad enterobactin biosynthesis) that complemented mutations in the enterobactin genes of the Escherichia coli 2,3-DHB operon, entCEBA(P15), were cloned from an enterobactin-producing isolate of the Aeromonas spp. Mapping of the aeromonad genes suggested a gene order of aebCEBA, identical to that of the E. coli 2,3-DHB operon. Gene probes for the aeromonad aebCE genes and for amoA (the entC-equivalent gene previously cloned from an amonabactin-producing Aeromonas spp.) did not cross-hybridize. Gene probes for the E. coli 2,3-DHB genes entCEBA did not hybridize with Aeromonas spp. DNA. Therefore, in the genus Aeromonas, 2,3-DHB synthesis is encoded by two distinct gene groups; one (amo) is present in the amonabactin-producers, while the other (aeb) occurs in the enterobactin-producers. Each of these systems differs from (but is functionally related to) the E. coli 2,3-DHB operon. These genes may have diverged from an ancestral group of 2,3-DHB genes.