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Effects of Heavy Metals and Metalloids on Freshwater Communities
Published in Abhik Gupta, Heavy Metal and Metalloid Contamination of Surface and Underground Water, 2020
The Matylda stream in upper Silesia, southern Poland, had been receiving effluent waters from the Matylda Zn–Pb mine, which had resulted in high concentrations of Cd, Pb, and Zn in the fine-grained sediments. Contaminated sediments had also entered the inundated floodplain of the stream, fish ponds, and the associated wetlands. Though the chironomid community structure and species diversity were not visibly affected, genomic changes occurred in the sediment-inhabiting species. Chironomus riparius was found to have a large number of somatic chromosome alterations. The giant salivary gland chromosome, a unique feature of Chironomidae, showed high response to heavy metal pollution, and had somatic alterations, which included para- and pericentric inversions, deficiencies, amplifications, and deletions. The frequency of such alterations varied among the different species, thus showing species-specific differences (Szarek-Gwiazda et al. 2013).
Biological Responses of Mobile Phone Frequency Exposure
Published in Jitendra Behari, Radio Frequency and Microwave Effects on Biological Tissues, 2019
DNA damage caused by any endogenous and exogenous factors is under a constant repair process. Any imbalance or mistakes in damage and repair result in accumulation of former, causing apoptosis, ageing, or promotion of cancer. While damage to DNA strand has been confirmed by several workers (as detailed next), it is argued that its repair is an ongoing process and the damaged chromosomes can be reconstituted. However, this proposition is not without risk. There is no guarantee that these will replicate in the manner they were originally present. Pieces may be left out (deletions), joined in the backward (inversions), swapped between different parts of the chromosomes (translocations), or even attached to the wrong chromosome. The effect may also be frequency dependent in cases, the new arrangement can work for a while if most of the genes are still present and any metabolic deficiencies can often be made good by the surrounding cells. However, things may be different if it comes to meiosis. During meiosis, the chromosomes line up in pairs (one from each original parent) along their entire length so that corresponding parts are adjacent and can be exchanged. Malformed pairs are torn apart in the later stages of meiosis so that eggs or sperms have an incomplete or unbalanced set of genes, may not function properly, and so reduce fertility and other physiological functioning. There is a possibility that this may lead to permanent genetic damage, which though may not be visible in the first generation but may be seen thereafter.
Radiation and man
Published in R.J. Pentreath, Nuclear Power, Man and the Environment, 2019
Each chromosome is, in fact, an assemblage of discrete units of DNA called genes, the units being arranged in bead-like manner along the chromosome. In man the total number of different genes is estimated to be about 30 000. Radiations can cause structural damage to whole chromosomes resulting in their breakage and possible subsequent rejoining. This may result in changes to the sequence of the genes, effects known as inversions or translocations, or may even result in the absence or doubling of certain genes in that chromosome, effects referred to as deletions and duplications, respectively. Indeed the damage may be such as to result in a change of the number of chromosomes observed.
Recombinogenic, genotoxic, and cytotoxic effects of azathioprine using in vivo assays
Published in Journal of Toxicology and Environmental Health, Part A, 2021
A. V. D. Melo Bisneto, L. C. D. Oliveira, A. Silva Fernandes, L. S. Silva, J. H. Véras, C. G. Cardoso, Carolina R. E Silva, A. V. de Moraes Filho, C. C. Carneiro, L. Chen-Chen
Two distinct crosses were performed: [I] standard cross (ST): mwh males crossed with flare-3 virgin females and [II] high bioactivation cross (HB): mwh males crossed with ORR virgin females. HB cross is characterized by high levels of cytochrome P450 enzymes, whereas ST cross demonstrates basal levels of these enzymes (Graf et al. 1989; Graf and van Schaik 1992; Saner et al. 1996). Both crosses produced two types of descendants: (I) marked-heterozygous (MH) flies (mwh +/+ flr3) with phenotypically wild-type wings, enabling identification of mutagenic and recombinogenic events and (II) balanced heterozygous (BH) flies (mwh +/+ TM3, BdS) with phenotypically serrate wings, enabling the identification of mutation events due to multiple inversions on the TM3 chromosome, which blocks recombination events.
Relationship between viability and genotoxic effect of gamma rays delivered at different dose rates in somatic cells of Drosophila melanogaster
Published in Journal of Toxicology and Environmental Health, Part A, 2019
Elizabeth Jiménez, Emilio Pimentel, Martha P. Cruces, Araceli Amaya-Chavez
Somatic recombination has important implications in the estimation of the risk of developing cancer (Ramel et al. 1996). In the SMART test, if recombination takes place in the region of the chromosome between mwh and flr markers, two daughter cells arise: one expressing mwh phenotype and the other expressing the wild type phenotype are formed, these mwh spots are indistinguishable from those originating from point mutation or deletions. The method to estimate the proportion of induced mwh singles ascribable to mutation vs. recombination, is to compare the frequency of mwh singles in the mwh +/+ flr with mwh +/+ TM3, Ser individuals. The latter is taken as a measure of mutations, because, the products of mitotic recombination between the TM3 chromosome bearing multiple inversions and its structurally normal homolog are not viable (Zimmering et al. 1997). For this reason and in order to exclude the % of mwh spots resulting from mutation events, the wings of the mwh/TM3, Ser individuals were analyzed. Results from linear regression analysis (Figure 3), showed that the rate of somatic recombination-induction was significant dose-dependent increases with 5.1 and 32.9 Gy/hr. However somatic recombination-induction by 860.9 Gy/hr was not. Some investigators using doses at low DR found -reverse effects (Marin et al. 1991; Russell and Kelly 1981); however, results obtained in this investigation were contradictory.