Article

Heavy metal-induced differential gene expression of metallothionein in Javanese medaka, Oryzias javanicus

Southern Coastal Environment Research Division, Korea Ocean Research and Development Institute, Geoje, 656-830, Korea.
Marine Biotechnology (Impact Factor: 3.15). 12/2006; 8(6):654-62. DOI: 10.1007/s10126-006-6046-0
Source: PubMed

ABSTRACT A metallothionein (MT) gene was isolated for the first time from Javanese medaka, Oryzias javanicus, which shows high adaptability from freshwater to seawater. The full-length cDNA of MT from O. javanicus (OjaMT) comprises 349 bp, excluding the poly(A)+ stretch, and codes for a total of 60 amino acids. The positions of cysteine residues are highly conserved. The pattern of OjaMT expression induced by six heavy metals was analyzed via real-time quantitative polymerase chain reaction (PCR). The level of hepatic OjaMT mRNA was increased in a dose-dependent manner by Ag, Cd, Cu, and Zn after 24 h of exposure. However, after Cr and Ni exposure, a significant decrease in OjaMT levels was observed. Cadmium-induced OjaMT expression was detectable in fishes as young as 3 months. After Cd exposure, OjaMT induction was prominent in intestine and liver and moderate in muscle and gill. OjaMT mRNA levels could represent a good biomarker for monitoring heavy metals in seawater.

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    • "Java medaka is widely distributed in the coastal areas of Peninsular Malaysia and they are available all year round. It has been utilized in several ecotoxicological studies (Imai et al., 2005, 2007; Ismail and Yusof, 2011; Koyama et al., 2006; Woo et al., 2006; Yu et al., 2006). In this study, we used the early life stages of the fish to investigate their responses after exposure to glyphosate-based herbicide. "
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    ABSTRACT: Glyphosate is globally a widely used herbicide, yet there is little information on their toxicity to marine fishes. Java medaka, a small tropical fish native to coastal areas in several Southeast Asian countries, is viewed as a suitable candidate for toxicity test and thus was used for this study. Java medaka adults were cultured in the laboratory and the fertilized eggs of the F2 generation were exposed to different concentrations of glyphosate-based herbicide (100, 200, 300, 400 and 500ppm) until they hatched. The survival and hatching rates of the embryos, changes in the heart rate and morphological impairments were recorded. Generally, survival and hatching percentage decreased as glyphosate concentration increased. Absence of pectoral fin(s) and cornea, permanently bent tail, irregular shaped abdomen, and cell disruption in the fin, head and abdomen are among the common teratogenic effects observed. Furthermore, risk factor also increased with the increased in glyphosate concentrations.
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    • "Letters above the bars show the level of statistical difference between the bars radical damage. These data support other data using medaka fish which reveal complex interactions between metals (Tilton et al. 2003; Woo et al. 2006; Barjhoux et al. 2012). Little et al. (2007) looked at cobalt toxicity in combination with UV and found that if the fish were UV adapted, the cobalt–UV combined exposure was relatively less toxic than cobalt alone but if the two exposures were given without prior UV adaptation, then the combination was more toxic than the additive effect should be. "
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    ABSTRACT: Very little is known about the combined effects of low doses of heavy metals and radiation. However, such "multiple stressor" exposure is the reality in the environment. In the work reported in this paper, fish were exposed to cobalt 60 gamma irradiation with or without copper or aluminum in the water. Doses of radiation ranged from 4 to 75 mGy delivered over 48 or 6 h. Copper doses ranged from 10 to 80 μg/L for the same time period. The aluminum dose was 250 μg/L. Gills and skin were removed from the fish after exposure and explanted in tissue culture flasks for investigation of bystander effects of the exposures using a stress signal reporter assay, which has been demonstrated to be a sensitive indicator of homeostatic perturbations in cells. The results show complex synergistic interactions of radiation and copper. Gills on the whole produce more toxic bystander signals than skin, but the additivity scores show highly variable results which depend on dose and time of exposure. The impacts of low doses of copper and low doses of radiation are greater than additive, medium levels of copper alone have a similar level of effect of bystander signal toxicity to the low dose. The addition of radiation stress, however, produces clear protective effects in the reporters treated with skin-derived medium. Gill-derived medium from the same fish did not show protective effects. Radiation exposure in the presence of 80 μg/L led to highly variable results, which due to animal variation were not significantly different from the effect of copper alone. The results are stressor type, stressor concentration and time dependent. Clearly co-exposure to radiation and heavy metals does not always lead to simple additive effects.
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    • "Indeed, MREs are known to stimulate expression and to inhibit or decrease expression (Haq et al., 2003). The downregulation of metallothioneins after exposure to metals has already been observed by Woo et al. (2006). They observed a downregulation after exposure to nickel and chrome. "
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