Heavy metals toxicity studies

Atkins, J.M., Schreoder, J.A., Brower, D.L., and Aposhian, H.V. Evaluation of Drosophila melanogaster as an alternative animal for studying heavy metal toxicity. Toxicologist, 11(1) 39, 1991. 

Zinc efflux is mediated by a zinc exporter known as ZntA (Zn + transport or tolerance), a membrane protein which was identified through studies of bacterial strains that were hypersensitive to zinc and cadmium. Sequence inspection revealed that ZntA was a member of the family of cation transport P-type ATPases, a major family of ion-translocating membrane proteins in which ATPase activity in one portion of the protein is used to phophorylate an aspartate within a highly conserved amino acid sequence, DKTG, in another portion of the protein. The cysteine rich N-terminus of these soft metal transport proteins contains several metal-binding sites. How the chemical energy released by ATP hydrolysis results in metal ion transport is not yet known, in part because there is only partial information about the structures of these proteins. The bacterial zinc exporter also pumps cadmium and lead and is therefore also involved in protection from heavy metal toxicity (see Metal Ion Toxicity). 

Several classes of molecules are involved in metal homeostasis. Metallothioneins (MTs) are a family of cysteine-rich metal-binding proteins that in mammals appear to function in Zn homeostasis and protect against heavy metal toxicity and oxidative stress60. Glutathione (GSH) is a sulfhydryl-rich tripeptide that is generally involved in the protection of cells against toxicants and in the metabolism of xenobiotics71. MTs and GSH are found in fish, and their expression and functions have been conveniently studied with piscine cell lines. 

This chapter presents experimental data on the involvement of oxygen radicals and hydrogen peroxide H2O2 in the catalytic conversion of L-arginine to NO and the modification of this process by various transition and heavy metals. In addition to the role of the NO pathway in the pathophysiology of various disorders such as cancer, hypertension, and inflammation, our study envisions the involvement of the NOS system in the mechanism of toxicity of some of heavy metal toxicant via redox potential alterations. 

Metabonomics has already been applied in fields outside human and other mammalian systems. For example, studies in the environmental pollution field have highlighted the potential benefits of this approach by studies of caterpillar hemo-lymph [38] and earthworm biochemical changes as a result of soil pollution by model toxic substances [39]. In addition, a study of heavy metal toxicity (As + and Cd +) in wild rodents living on polluted sites has been concluded successfully [40]. In terms of monitoring water quality, one study has evaluated adverse effects in abalone using NMR-based metabonomics [41]. 

Lafaye A, Junot C, Ramounet-Le Gall B, Fritsch P, Tabet JC, Ezan E. Metabolite profiling in rat urine by liquid chromatography/electrospray ion trap mass spectrometry. Application to the study of heavy metal toxicity. Rapid Commun Mass Spectrom 2003 17 2541-2549. 

Cobalt is one of the heavy metal toxic pollutants that is present in trace amounts in natural waters, the amount usually being less than 1 g/L. Consequently, its removal by adsorption using suitable adsorbents has been studied by a number of... 

In summary, the impact of diet and nutrition status of the infant on the toxicity of heavy metals is not capable of precise definition at this time. There are significant animal data that provide sound bases for hypotheses about the relationships between nutrition and heavy metal toxicities. Limited clinical studies in humans tend to confirm the hypotheses about the roles of nutrition in heavy metal toxicity drawn from animal studies. 

The name dust , is used in a variety of ways, and with different meanings. These range from the material that accumulates on the earth s surface, such as on streets and in living and working environments, to the particulate material suspended in the atmosphere. In this paper I wish to consider these two materials in terms of their chemical composition, sources and relationship between them. The names used for the two materials will be surface dust and atmospheric dust . The word aerosol may also be used for atmospheric dust but it more properly applies to the finer particles of atmospheric dust and includes liquid aerosol (i). Botfi surface and atmospheric dusts are increasingly seen to be a hazard to human beings as they are a source of intake of toxic materials such as heavy metals. For this reason study is important of the composition and sources of the dusts. 

The emption of Mount St. Helens on May 18, 1980, provided geologists with a unique opportunity to study the action of volcanos. Gas samples from the plume were collected and analyzed for toxic heavy metals. To collect mercury (Hg), gas samples were passed over a piece of gold metal, which binds Hg atoms veiy tightly. The mass of the metal increased as it absorbed Hg from the plume. From a plume-gas sample containing 200 g of ash, 3.60 ft g of Hg was deposited on the gold. How many moles of mercury were present in the gas sample How many atoms is this ... 

Bioremediation also has its limitations. Some chemicals are not amenable to biodegradation, for instance, heavy metals, radionuclides, and some chlorinated compounds. In some cases, the microbial metabolism of the contaminants may produce toxic metabolites. Bioremediation is a scientifically intensive procedure that must be tailored to site-specific conditions, and usually requires treatability studies to be conducted on a small scale before the actual cleanup of a site.13 The treatability procedure is important, as it establishes the extent of degradation and evaluates the potential use of a selected microorganism for bioremediation. A precise estimate on vessel size or area involved, speed of reaction, and economics can therefore be determined at the laboratory stage. 

Emissions of actually and potentially dangerous toxic elements may influence the human and ecosystem health on local, regional and global scales. Accumulation of toxic metals may be in soils, waters, bottom sediments and biota. For example, the accumulation of heavy metals in the upper layers of bottom sediments and glaciers occurring during the 20th century is shown in many recent studies. 

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