Mechanically mineral toxicity

Animals encounter poison in the plants they eat, from other animals that use poisons in attack and for protection, and from toxin-producing bacteria and fungi. Animals are exposed to toxic metals released from minerals, and even the oxygen that all animals depend on is a very poisonous gas. Leakage of mineral oil, with many toxic and lipohilic substances, is also an old challenge that organisms had to adapt to. Substances produced inside the animal (e.g., ammonia, epoxides, phenolic substances) may also be toxic. Animals must therefore have many protection mechanisms against toxic substances in order to survive and reproduce. 

Kinraide, T.B., 1998. Three mechanisms for the calcium alleviation of mineral toxicities. Plant Physiol. 118, 513-520. 

As for other biological substances, states of dynamic equiUbrium exist for the various mineral nutrients as well as mechanisms whereby a system can adjust to varying amounts of these minerals in the diet. In forms usually found in foods, and under circumstances of normal human metaboHsm, most nutrient minerals are not toxic when ingested orally. Amounts considerably greater than the recommended dietary allowances (RDAs) can generally be eaten without concern for safety (Table 1) (3). 

Mossman, B.T. and Marsh, J.P. (1985). Mechanisms of cell toxic injury by asbestos fibres role of oxygen free radicals. In In vitro Effects of Mineral Dusts (eds. E.G. Beck and J. Bignon) pp. 66-81. Springer Verlag, Berlin. 

Root exudation of extraordinary high amounts of specific carboxy lutes (e.g ci-u-ate, malate. oxalate, pbytosiderophores) in response to nutritional deficiency stress or Al toxicity in some plant species cannot simply be attributed to diffusion processes. The controlled release of these compounds, involved in mobilization of mineral nutrients and in detoxification of Al. may be mediated by more specific mechanisms. Inhibitory effects by exogenous application of various anion chan-... 

Mineral Oil Hydraulic Fluids. No specific methods were located for interfering with the mechanism of action for toxic effects produced by mineral oil hydraulic fluids. Unstable alveoli and distal airways have been proposed as major factors in the respiratory symptoms that occur after the ingestion of other petroleum-derived materials. Continuous positive airway pressure or continuous negative chest wall pressure, as well as the application of supplemental oxygen, have been recommended to counteract the resultant pneumonitis (Eade et al. 1974 Klein and Simon 1986). 

Coprecipitation is a partitioning process whereby toxic heavy metals precipitate from the aqueous phase even if the equilibrium solubility has not been exceeded. This process occurs when heavy metals are incorporated into the structure of silicon, aluminum, and iron oxides when these latter compounds precipitate out of solution. Iron hydroxide collects more toxic heavy metals (chromium, nickel, arsenic, selenium, cadmium, and thorium) during precipitation than aluminum hydroxide.38 Coprecipitation is considered to effectively remove trace amounts of lead and chromium from solution in injected wastes at New Johnsonville, Tennessee.39 Coprecipitation with carbonate minerals may be an important mechanism for dealing with cobalt, lead, zinc, and cadmium. 

Bacteria and their composites with soil minerals or organic matter are capable of taking up a wide range and variety of toxic metals in soil environments. Research done over the last decade or so has greatly improved our understanding of the mechanisms on biosorption of metals and bacte-ria-metal-soil component interactions. However, more studies from molecular level are needed in order to enhance the ability of bacteria and their association with soil components to remediate toxic metals-contaminated soils. The focus of future investigations should be on the mechanisms by which metals are sorbed and bound by bacterial cell surfaces and bacteria-soil/mineral composites. In this connection, X-ray absorption spectroscopy (XAS) is a promising technique because it can provide information about... 

Little is known about the effects of 2,3-benzofuran exposure on humans. The principal adverse health effects noted in animals associated with oral exposure to 2,3-benzofuran are kidney and liver damage (NTP 1989). In the kidney, 2,3-benzofuran causes injury to the tubular cells, with degeneration, necrosis, and mineralization. In the liver, damage due to 2,3-benzofuran is usually characterized by focal necrosis of hepatocytes. However, the mechanism(s) associated with this damage are unknown. A better understanding of the mechanism of action of 2,3-benzofuran may make it possible to develop effective methods to reduce toxic effects caused by exposure. 

Biodegradation, hydrolysis, and sorption influence the environmental fate of LAS, AS, and AES. Primary degradation of surfactants is important because this process usually results in loss of surfactancy and reduced toxicity (5, 6). Complete mineralization ensures that persistent intermediates will not be formed and that biodegradation will be an effective mass-removal mechanism in the environment. Sorption and association of surfactants with particles or dissolved organic substances are processes that decrease bioavailability and can be correlated with decreased surfactant toxicity (7). 

Metal complexation by carboxylates is, on the other hand, an important mechanism to exclude uptake of toxic elements, such as Al3+, in plant species and cultivars adapted to acid mineral soils. The release is restricted to the apical root zones, which are most susceptible to the toxic effects of aluminum (Ma, 2000 Brimecombe et al., 2007). 

Indicates the pore space available for water and roots influenced by soil composition (mineral content, mineral type, and organic matter) and soil texture Affects adsorption of the chemical Affects the surface area where adsorption can take place Influences partitioning and availability of chemicals Affects ability of a soil to transmit water or air Dictates the porosity of the soil Affects the form, reactivity, solubility, availability, and toxicity of some contaminants Affects the toxicity of some substances (mainly heavy metals) with binding or antagonistic mechanisms, for example, by alkaline-earth metals and aluminum Organic matter content, type, and % carbon Influences soil sorption properties for heavy metals and... 

The search for the exact sites of ion and compound deposition in plants and the nature of the chemical species involved has been carried out with a number of aims The elucidation of various mechanisms of phytochemical importance mineral uptake and utilisation toxicity and tolerance exhibited by many individual species and the study of plants that accumulate or hyperaccumulate metals. The literature for a number of individual elements to the late 1970s has been reviewed (Farago, 1981) and the phytochemistry of metal hyperaccumulators has been reviewed by Baker and Brooks (1989). 

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