Chelation, lead

Schwartz BS John Hopkins University School of Hygiene Public Health, Baltimore, MD Study of the relations among BLLS, DMSA-chelatable lead, bone lead, and health effects (heme synthesis, renal early biologic effects and function, blood pressure, and CNS and PNS function) in lead workers in South Korea National Institute of Environmental Health Sciences... 

Alessio L. 1988. Relationships between "chelatable lead" and the indicators of exposure and effect in current and past occupational life. Sci Total Environ 71 293-299. 

Chemical antagonism results when two drugs combine with each other chemically and the activity of one or both is blocked. For example, dimer-caprol chelates lead and reduces the toxicity of this heavy metal. Compeli-... 

B Diastereomeric mixed chelate complexes, where the selector ligand is strongly bound to a support. The (.S ,.V)-chelate may be more stable than the (S,f )-chelate leading to longer retention in a chromatographic system. 

Salt and chelate formation with edetate (ethylenediaminetetraacetate, EDTA). A In a solution of calcium disodium salt of EDTA, the sodium and hydrogen ions are chemically and biologically available. B In solutions of calcium disodium edetate, calcium is bound by coordinate-covalent bonds with nitrogens as well as by the usual ionic bonds. C In the lead-edetate chelate, lead is incorporated into five heterocyclic rings. 

Coatinas/Sealers/ Passivators/Cleaners Chelated Lead Brightener 13.5 80 2 4+... 

WTI has had systems operating on the following electronic and circuit board solutions acid copper plating, chelated lead brightening, and nickel sulfamate plating. Tin-lead fluoboric and electroless copper systems are to be installed in June, 1989. The systems have been or are to be installed at Cray Research, Control Data and Vitramon (a Thomas and Betts subsidiary). 

Another compound used to treat lead poisoning is British anti-Lewisite (BAL), originally developed to treat arsenic-containing poison gas Lewisite. As shown in Figure 10.6, BAL chelates lead through its sulfhydryl groups, and the chelate is excreted through the kidney and bile. 

In the most congested case, (Ru(terpy )(dmp)(CH3SCH3)2+), the photosubstitution quantum yield was shown to be

room temperature in pyridine, which is an extremely high value in ruthenium(II) photochemistry. The control of the bulkiness of the spectator chelates, leading to the control of the congestion of the complex and, hence, to the efficiency of ligand photoexpulsion, is a specific feature of the Ru(terpy)(phen)(L)2+ core. This... 

Unithiol (dimercaptopropanesulphonate, DMPS) effectively chelates lead and mercury it is well tolerated. 

Penicillamine (dimethylcysteine) is a metabolite of penicillin that contains SH groups it may be used to chelate lead and also copper (see Hepatolenticular degeneration). Its principal use is for rheumatoid arthritis (see Index). 

In severe lead poisoning sodium calciumedetate is commonly used to initiate lead excretion. It chelates lead from bone and the extracellular space and urinary lead excretion of diminishes over 5 days thereafter as the extracellular store is exhausted. Subsequently symptoms (colic and encephalopathy) may worsen and this has been attributed to redistribution of lead from bone to brain. Dimercaprol is more effective than sodium calciumedetate at chelating lead from the soft tissues such as brain, which is the rationale for combined therapy with sodium calciumedetate. More recently succimer (2,3-dimercaptosuccinic acid, DMSA), a water-soluble analogue of dimercaprol, has been increasingly used instead. Succimer has a high affinity for lead, is suitable for administration by mouth and is better tolerated (has a wider therapeutic index) than dimercaprol. It is licenced for such use in the USA but not the UK. 

D-Penicillamine, a chelating agent that can be administered orally, is currently used to chelate lead on an experimental basis. Individuals who are allergic to penicillin may experience adverse reactions to this agent toxic effects have been reported in as many as 20% of the patients treated with this compound. 

Schwartz BS, Lee BK, Lee GS, et al Associations of blood lead, dimercaptosuccinic acid-chelatable lead, and tibia lead with neurobehavioral test scores in South Korean lead workers. Am J Epidemiol 153 453 464, 2001 Sherman JD Case reports based on the review-of-systems approach, in Chemical Exposure and Disease. Edited by Sherman JD. New York, Van Nostrand Reinhold, 1988, pp 97-137... 

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