Effects of metals on chromosomes of higher organisms.
TL;DR: 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.
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.
Citations
More filters
TL;DR: Studies on genotoxicity of metals discussed in this review showed that genotoxic effects could be in part responsible for metal phytotoxicity, deserving further examination to elucidate the underlying mechanisms.
624 citations
TL;DR: In this article, the authors present the results of studies on the recent developments in the utilization of plant growth promoting rhizobacteria for direct application in soils contaminated with heavy metals under a wide range of agro-ecological conditions with a view to restore contaminated soils and consequently, promote crop productivity in metal-polluted soils across the globe and their significance in phytoremediation.
Abstract: Pollution of the biosphere by the toxic metals is a global threat that has accelerated dramatically since the beginning of industrial revolution. The primary source of this pollution includes the industrial operations such as mining, smelting, metal forging, combustion of fossil fuels and sewage sludge application in agronomic practices. The metals released from these sources accumulate in soil and in turn, adversely affect the microbial population density and physico-chemical properties of soils, leading to the loss of soil fertility and yield of crops. The heavy metals in general cannot be biologically degraded to more or less toxic products and hence, persist in the environment. Conventional methods used for metal detoxification produce large quantities of toxic products and are cost-effective. The advent of bioremediation technology has provided an alternative to conventional methods for remediating the metal-poisoned soils. In metal-contaminated soils, the natural role of metal-tolerant plant growth promoting rhizobacteria in maintaining soil fertility is more important than in conventional agriculture, where greater use of agrochemicals minimize their significance. Besides their role in metal detoxification/removal, rhizobacteria also promote the growth of plants by other mechanisms such as production of growth promoting substances and siderophores. Phytoremediation is another emerging low-cost in situ technology employed to remove pollutants from the contaminated soils. The efficiency of phytoremediation can be enhanced by the judicious and careful application of appropriate heavy-metal tolerant, plant growth promoting rhizobacteria including symbiotic nitrogen-fixing organisms. This review presents the results of studies on the recent developments in the utilization of plant growth promoting rhizobacteria for direct application in soils contaminated with heavy metals under a wide range of agro-ecological conditions with a view to restore contaminated soils and consequently, promote crop productivity in metal-polluted soils across the globe and their significance in phytoremediation.
522 citations
Cites background from "Effects of metals on chromosomes of..."
...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. 2007a, 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 ......
[...]
TL;DR: The chemical nature of chromium compounds and how these properties impact upon the interactions ofchromium with cellular and genetic targets, including animal and human hosts, are discussed.
Abstract: Chromium, like many transition metal elements, is essential to life at low concentrations yet toxic to many systems at higher concentrations. In addition to the overt symptoms of acute chromium tox...
504 citations
TL;DR: Differential tolerance of plant genotypes exposed to zinc toxicity is a promising approach to enrich the authors' understanding of zinc tolerance in plants and may help in interdisciplinary studies to assess the ecological significance of metal stress.
Abstract: Zinc toxicity and problems with regard to tolerance and ecological significance are briefly discussed. Differential tolerance of plant genotypes exposed to zinc toxicity is a promising approach to enrich our understanding of zinc tolerance in plants. Knowledge concerning the physiology and biochemistry with regard to phytotoxicity, uptake and transport of zinc and tolerance and its characterization are also discussed. The cytotoxic effects of zinc on plants are elucidated. The major change was seen in the nucleus of the root tip cells due to zinc toxicity. The chromatin material was highly condensed and some of the cortical cells showed disruption and dilation of nuclear membrane in presence of 7.5 mM zinc. The cytoplasm became structureless, disintegration of cell organelles and the development of vacuoles were also observed. The number of nucleoli also increased in response to zinc resulting in the synthesis of new protein involved in heavy metal tolerance. This review may help in interdisciplinary studies to assess the ecological significance of metal stress.
387 citations
TL;DR: This review summarizes current information on the genotoxicity of arsenic, chromium, nickel, beryllium and cadmium compounds and their possible roles in carcinogenesis.
346 citations
References
More filters
Book•
31 Jan 2014
TL;DR: This book discusses the development and validation of short-term assays designed to detect the mutagenic effects of environmental chemicals, and the detection of mutagens in human feces as an approach to the discovery of causes of colon cancer.
Abstract: This book discusses the development and validation of short-term assays designed to detect the mutagenic effects of environmental chemicals. Topics considered include the grasshopper neuroblast short-term assay for evaluating the effects of environmental chemicals on chromosomes and cell kinetics, a comparison of the mutagenic responses of lung-derived and skin-derived human diploid fibroblast populations, the L-arabinose resistance test with Salmonella typhimurium, the Bacillus subtilis multigene sporulation test for the detection of environmental mutagens, the L5178Y/TK gene mutation assay system, the induction of bacteriophage lambda by DNA-interacting chemicals, the granuloma pouch assay, the use of multiply marked Escherichia coli K12 strains in the host-mediated assay, and the detection of mutagens in human feces as an approach to the discovery of causes of colon cancer.
1,480 citations
TL;DR: This article centers on the properties and dynamics of the endocytic vacuole membrane and stresses observations on cultured mouse macrophages with which the authors are most familier.
Abstract: The study of endocytosis has traditionally focused on the contents of endocytic vacuoles, i.e., extracellular fluid, dissolved solutes, and macromolecules or particles which specifically or nonspecifically bind to the plasma membrane (PM). Substances that are endocytosed include important nutrients, toxins, effector molecules (growth factors, hormones, antibodies), enzymes, and pathogens. This article centers on the properties and dynamics of the endocytic vacuole membrane. In many instances we will stress observations on cultured mouse macrophages with which we are most familier. We will emphasize four points: (a) Movement of vesicles is rapid such that endocytosed membrane and contents move from one cellular compartment to another in seconds to minutes. (b) Vesicular movement requires the interiorization and flow of large amounts of PM) (c) In many instances, internalized PM must recycle or return intact to the cell surface. (d) During recycling, contents and membrane components can be sorted from one another; e.g., endocytosed contents can accumulate within the cell while the container (membrane) can move into and out of the cell after one or more fusion events with other endocytic vacuoles, lysosomes (Ly), or Golgi apparatus. While it has been difficult to obtain direct evidence, the literature is replete with examples in which rapid membrane flow and recycling readily explains the data. Two of the more striking examples derive from studies of pinocytosis in cultured ceils. Fibroblasts, for instance, interiorize the equivalent of 50% of their surface area and 5-10% of their cell volume during each hour of pinocytic activity. Yet, the overall dimensions of the cells and the vacuolar system remain constant throughout hours, even days, of endocytic activity. Since it is unlikely that internalized PM is rapidly degraded, it was proposed that
1,413 citations
873 citations
TL;DR: The most important recommendations in this report are: (1) at least 500 PCE should be examined from each of 8 animals to detect an increase of about 4‰ (per thousand) PCE when the background is less than 4 per 1000, and (2) the highest possible doses should be used.
Abstract: There are many possible micronucleus assays involving different test organisms and tissues. Because micronuclei arise from chromosomal fragments or chromosomes that are not incorporated into daughter nuclei at the time of cell division, the assay detects both clastogens and agents that affect the spindle apparatus. We know of no case in which micronuclei and chromosomal breakage (or loss) have been shown to occur independently of one another in any dividing cell population. This relationship is so close that false-positives and false-negatives (insofar as the detection of tissue-specific chromosome damage is concerned) should be determined primarily by the statistics of sampling. The production of micronuclei in various experimental organisms has been reviewed. Although there are several promising experimental approaches such as the use of meiotic plant cells or human cells in culture, only one form of the assay, the in vivo mammalian bone-marrow polychromatic erythrocyte (PCE) assay, has been sufficiently developed to be considered a standard assay. More than 150 chemicals have been tested in this assay, with varying degrees of rigor. The data from the literature have been summarized and evaluated in light of the work Group's recommendations for an adequate test. The standards for an adequate test are an important part of the recommendations. These standards, although based on the most recent information available to us, are subject to change because this assay is still evolving. The most important recommendations in this report are: (1) at least 500 PCE should be examined from each of 8 animals to detect an increase of about 4‰ (per thousand) PCE when the background is less than 4 per 1000, (2) sampling should be extended to at least 72 h after the initial treatment, with sampling intervals no greater than 24 h, and (3) the highest possible doses should be used. The success rate of the assay to detect chemicals designated by the Environmental Protection Agency (EPA) as carcinogens is difficult to estimate for several reasons. First, few chemicals designated as noncarcinogens were studied, although in routine testing noncarcinogens are expected to be much more common than carcinogens. Hence, the rate of false-positives (insofar as the detection of cancer is concerned), which ought to be one of the strongest features of the assays, could not be estimated. Second, few chemicals have been tested as rigorously as this report recommends. Hence, the rate of false-negatives is almost certainly overestimated. (It is, nevertheless, obvious that false-negatives are to be expected for any tissue-specific in vivo assay like the micronucleus assay. For example diethylnitrosamine, which produces chromosomal aberrations, micronuclei, and cancer in the liver, is not detected in the bone-marrow micronucleus assay.) Third, many carcinogens are species-specific and this fact has not been taken into account. Considering these caveats, the uncorrected detection rate of the chemicals designated as carcinogens by EPA is about 50%. We believe that this would have been significantly higher had all tests been performed according to the test criteria. Further improvements in the assay are to be expected and these may lead to improvements in its success rate. Recent developments are discussed.
750 citations
TL;DR: Sister Chromatid Exchanges-Spontaneous or Induced?
Abstract: EARLY RESULTS 1 83 Sister Chromatid Exchange in Meiosis 1 83 Sister Chromatid Exchange in Somatic Cells 1 84 Isolabeling 1 86 Sister Chromatid Exchanges-Spontaneous or Induced? 1 86 RESULTS FROM NEW METHODS FOR DETECTING SISTER CHROMA TID EXCHANGES 1 86 Reasons for Differential Staining 1 87 Harlequin Chromosomes and Chromosome Structure 1 89 Multiple sister chromatid exchanges 1 90 Autoradiographic image spread 1 90 Labeling for more than one replication cycle 1 90 The Question 0/ Spontaneous Levels 0/ Sister Chromatid Exchanges 1 9 1 Location 0/ Sister Chromosome Exchanges in the Chromosome 1 93 Sister Chromatid Exchanges and Human Genetic Diseases 1 93 Sister Chromatid Exchanges as Indicators 0/ Mutagenic Carcinogens 1 94 Lesions Responsible for Sister Chromatid Exchange Formation 1 96 CONCLUSION 1 97
557 citations