Effects of metals on chromosomes of higher organisms

Abstract

An analysis of the available data on the clastogenic effects of metals and their compounds on higher organisms indicates some general trends. Following chronic exposure to subtoxic doses, a decrease in mitotic frequency and an increase in the number of chromosomal abnormalities are observed. These effects are usually directly proportional to the dose applied and the duration of treatment within the threshold limits. Recovery after acute treatment is inversely related to the dosage. The ultimate expression of the effects depends on certain factors, including the mode and vehicle of administration; the form administered; the test system used; the rate of detoxification, distribution, and retention in the different tissues; and interaction with foreign and endogenous substances as well as the mode of action with the biological macromolecules. In mammals, the clastogenic activity of the metals within each vertical group of the periodic table is directly proportional to the increase in atomic weight, electropositivity, and solubility of the metallic cations in water and lipids, except for Li and Ba. This pattern of inherent cytotoxicity increases with successive periods in the horizontal level. It is enhanced by the formation of covalent and coordinate covalent complexes by heavy metals with the biological macromolecules. In plants, the solubility of the metals in water is of much greater importance. The degree of dissociation of metallic salts and the rate of absorption affect significantly the frequency of chromosomal aberrations. In assessing the effects of environmental metal pollution, the presence of other metals and toxic chemicals and the level of nutrition should be taken into account, since in nature, metals occur in combination and these factors modify the cytotoxic effects to a significant extent.

Role of plant growth promoting rhizobacteria in the remediation of metal contaminated soils

“…Once accumulated in the soils, the toxic metals inversely affect the microbial compositions, including plant growth promoting rhizobacteria (PGPR) in the rhizosphere, and their metabolic activities. In addition, the elevated concentration of metals in soils and their uptake by plants adversely affect the growth, symbiosis and consequently the yields of crops (Moftah 2000;Wani et al 2007aWani et al , 2008a by disintegrating cell organelles, and disrupting the membranes (Sresty and Madhava Rao 1999), acting as genotoxic substance (Sharma and Talukdar 1987) disrupting the physiological process, such as, photosynthesis (Van Assche and Clijstersters 1990; Wani et al 2007b), or by inactivating the respiration, protein synthesis and carbohydrate metabolism (Shakolnik 1984). The remediation of metal-contaminated soils thus becomes important, as these soils usually cover large areas that are rendered unsuitable for sustainable agriculture.…”

Genotoxic studies of vanadium pentoxide (V2O5) in male mice. II. Effects in several mouse tissues

“…Vanadium is widely distributed in human tissues and is toxic when ingested in large doses [1]; the most toxic forms of vanadium to mammals are the pentavalent form compounds [14]. Vanadium poisoning is known to occur in particular by inhalation of vanadium-rich dust and it may cause irritation and clinical symptoms of the respiratory tract [15].…”

Genotoxic effects of heavy metals in rat hepatocytes

“…For example, methods used to explore carcinogenesis in vitro have been extensively applied to metal compounds. Various endpoints have been examined, e.g., mutagenesis in mammalian cells, chromosomal damage and sister chromatid exchange, cell transformation, DNA strand breaks, DNA-protein crosslinks and DNA polymerase infidelity [for reviews, see Sunderman (1984); Hansen and Stern (1984); Sharma and Talukder (1987)]. Among prominent findings obtained using such systems, the mutagenicity of hexavalent Cr, which is quite potent in various assays, as well as that of Cd, Hg and Pb, provide valuable examples (Arlauskas et al, 1985;Babich et al, 1985).…”