For iron poisoning

Deferoxamine is isolated from Streptomycespilosus. It binds iron avidly but essential trace metals poorly. Furthermore, while competing for loosely bound iron in iron-carrying proteins (hemosiderin and ferritin), it fails to compete for biologically chelated iron, as in microsomal and mitochondrial cytochromes and hemoproteins. Consequently, it is the chelator of choice for iron poisoning (Chapters 33 and 59). Deferoxamine plus hemodialysis may also be useful in the treatment of aluminum toxicity in renal failure. Deferoxamine is poorly absorbed when administered orally and may increase iron absorption when given by this route. It should therefore be administered intramuscularly or, preferably, intravenously. It is believed to be metabolized, but the pathways are unknown. The iron-chelator complex is excreted in the urine, often turning the urine an orange-red color. 

Respiratory distress and interstitial infiltrates have also been reported in children receiving deferoxamine for iron poisoning or refractory cancers (24,25). 

The standard antidote for iron poisoning is desferrioxamine B (//.6) (deferoxamine) (Keberle, 1964), which must be injected. Other ironchelating agents undergoing trial are rhodotorulic acid (i/./o), cheaply made from yeast but still requiring injection, 2,3-dihydroxybenzoic acid which is part of the enterochelin molecule (//.y) and is active orally, and ethylenediamine-fe 5(2-hydroxyphenylacetic acid) which is related to EDTA. 

In the treatment of poisoning by lead or other metal ions, higher concentrations of chelant can be safely obtained in humans by administering Na2CaEDTA rather than Na EDTA. The metal ion is bound by displacing small amounts of Ca " that the body can tolerate. Use of Na EDTA would result in calcium chelation and thus serious depletion of calcium in the body fluids (44). Removal of iron in Cooley s anemia is accompHshed by using chelants that are relatively specific for iron (45). 

At this point, the system was tested with catalyst for activation and FTS, in the hopes that the seal leak rates would be impeded by the presence of small catalyst particles. The FTFE 20-B catalyst (L-3950) (Fe, 50.2% Cu, 4.2% K, 1.5% and Si, 2.4%) was utilized. This is part of the batch used for LaPorte FTS run II.20 The catalyst was activated at 543 K with CO at a space velocity (SV) of 9 sl/h/g catalyst for 48 h. A total of 1,100 g of catalyst was taken and 7.9 L of C30 oil was used as the start-up solvent. At the end of the activation period, an attempt was made for Fischer-Tropsch synthesis at 503 K, 175 psig, syngas SV = 9 sl/h/g catalyst, and H2/CO = 0.7. However, the catalyst was found to be completely inactive for Fischer-Tropsch synthesis. Potential reasons for catalyst poisoning under present experimental conditions were investigated. Sulfur and fluorine are known to poison iron-based Fischer-Tropsch catalysts.21,22 Since the stator of the pump is... 

Iron is an essential element, for humans and for many forms of life, but even a modest excess can be toxic as the human body does not have an effective iron excretion mechanism. It is therefore necessary to maintain an appropriate level of iron in the body, to supply iron in absorbable form if it is deficient (anemia) and to remove iron if present in excess. Inorganic coordination chemistry plays an important role in dealing with these complementary conditions of deficiency and of excess. The latter condition is much more common than often supposed, for there are a number of conditions, such as hemochromatosis and thallasemia, where the build-up of iron in essential organs is eventually lethal. Mild iron poisoning is not infrequent in children, while even iron fortification of foodstuffs can have adverse effects. Mild iron poisoning can be treated with bicarbonate or phosphate, which presumably complex and precipitate the iron. ... 

Under FCCU operating conditions, almost 100% of the metal contaminants in the feed (such as nickel, vanadium, iron and copper porphyrins) are decomposed and deposited on the catalyst (2). The most harmful of these contaminants are vanadium and nickel. The deleterious effect of the deposited vanadium on catalyst performance and the manner in which vanadium is deposited on the cracking catalyst differ from those of nickel. The effect of vanadium on the catalyst performance is primarily a decrease in catalyst activity while the major effect of nickel is a selectivity change reflected in increased coke and gas yields (3). Recent laboratory studies (3-6) show that nickel distributes homogeneously over the catalyst surface while vanadium preferentially deposits on and reacts destructively with the zeolite. A mechanism for vanadium poisoning involving volatile vanadic acid as the... 

It is indicated in metallic intoxication due to arsenic, mercury, gold, bismuth, lead, nickel, thallium and antimony in conjunction with sodium calcium edetate for lead poisoning. It is also useful in hepatolenticular degeneration (Wilson s disease). It is contraindicated in iron and cadmium poisoning. 

Deferoxamine (see also Chapters 58 and 59) Chelates excess iron Reduces the toxicity associated with acute or chronic iron overload Treatment of acute iron poisoning and for inherited or acquired hemochromatosis that is not adequately treated by phlebotomy Preferred route of administration is IM or SC Toxicity Rapid IV administration may cause hypotension acute respiratory distress has been observed with long infusions neurotoxicity and increased susceptibility to certain infections has occurred with longterm use... 

Exactly the opposite problem may occur for plants whose roots are growing in anaerobic media. In Hooded soils the roots may be exposed to high levels of irontll). posing potential problems of iron toxicity. Rice plants and water lilies with roots in anaerobic soils transport dioxygen (from the air or photosynthesis, or both) to the periphery of the roots where it oxidizes the iron(II) to irondll). In (his case the insolubility of Irondll) hydroxide is utilized to protect the plant from iron poisoning.113 A similar problem from too much iron occurs in parts of sub-Saharan Africa. 

The stability constants of the FeIU siderophore complexes are some of the largest known, e.g. the ferrichrome and ferrioxamine E complexes have log values of the order 29 and 32 respectively as compared to a value of 25 for Fe(edta). So strong are these complexes that microbes have been observed to leach iron from stainless steel vessels. Not surprisingly the siderophores also find use in treating cases of iron poisoning and for the elimination of iron from cases of thalassaemia.84 Complexation of Fe11 is considerably weaker than that of FeIU and this is probably utilized for the release of the iron within the cells. 

The mechanism of hydrogen evolution has been investigated by impedance measurements [371] and hydrogen-tritium kinetic isotope effects [375]. The effect of halides dissolved in solution has been studied [372, 376] these ions increase the overpotential in the sequence Cl- Adsorption isotherms for halides have been derived. They conform to the Temkin adsorption model with partial charge transfer. The lateral interaction between adsorbed particles has been calculated. It is higher for Br- than for I- and increases with overpotential on account of the weakening in the metal-halide bond. Thus, halides are substantial poisons for hydrogen evolution on iron. Poisons also include metal ions such as Cd2+, Zn2+, and Mn2+ [26]. 

One strong point of SIMS is its ability to detect elements that are present in trace amounts, and as such the technique is highly suited to the detection of poisons on a catalyst caused by contaminants in the reactor feed. Chlorine, for example, poisons the iron catalyst used in ammonia synthesis because it suppresses the dissociation of nitrogen molecules. Plog et al. [18] used SIMS to show that chlorine impurities may coordinate to potassium promoters, as evidenced by a KCI2- signal, or to iron, visible by an FeCh- peak. The SIMS intensity ratio... 

In addition to transformation by corrodable metals (such as Fe° and Zn°), bimetallic combinations of a catalytic metal with a corrodable metal (such as Pd/Fe or Ni/Fe) have also been shown to transform a variety of contaminants. In most cases, rates of transformation by bimetallic combinations have been significantly faster than those observed for iron metal alone [26,96,135-139]. Not only have faster transformation rates been observed with bimetallic combinations, but, in some cases, transformation of highly recalcitrant compounds, such as polychlorinated biphenyls (PCBs), chlorinated phenols, and DDT has been achieved [24,140,141]. The mechanism responsible for the enhanced reactivity with bimetallic combinations is still unclear however, it has been suggested that electrochemical effects, catalytic hydrogenation, or intercalation of H2 may be responsible. A likely limitation to the full-scale application of bimetallic combinations to groundwater remediation is deactivation of the catalytic surface either by poisoning (e.g., by sulfide) or by formation of thick oxide films [136,142,143]. 

Antidotes for cyanide poisoning (B). Cyanide ions (CN ) enter the organism in the form of hydrocyanic acid (HCN) the latter can be inhaled, released from cyanide salts in the acidic stomach juice, or enzymatically liberated from bitter almonds in the gastrointestinal tract. The lethal dose of HCN can be as low as 50 mg. CN binds with high af nity to trivalent iron and thereby arrests utilization of oxygen via mitochondrial cytochrome oxidases of the respiratory chain. Internal asphyxiation (histotoxic hypoxia) ensues while erythrocytes remain charged with 02 (venous blood colored bright red). 

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