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  • The changes of serum testosterone level and hepatic Microsome Enzyme activity of crucian carp (Carassius carassius) exposed to a sublethal dosage of pentachlorophenol.
    Ecotoxicology and environmental safety, 2007
    Co-Authors: Min Zhang, Daqiang Yin, Fanxiang Kong
    Abstract:

    Abstract Pentachlorophenol (PCP), which was reported to be a typical persistent organic pollutant and environmental endocrine disruptor, may cause threat to aquatic species. In this study, serum testosterone concentration, activity of liver Microsome ethoxyresorufin O-deethylase (EROD) and glutathione S-tranferases (GST) of crucian carp (Carassius carassius) exposed to PCP for 7 and 15 d, respectively, were examined. The results showed that testosterone concentration was induced remarkably after 7 d (P

  • Altered serum levels of sex steroids and biotransformation Enzyme activities by long-term alachlor exposure in crucian carp (Carassius auratus).
    Bulletin of environmental contamination and toxicology, 2007
    Co-Authors: Hua Liu, Min Zhang, J. Tao, H. Ding, W. Jiang
    Abstract:

    In the past several decades, a variety of environmental chemicals such as pesticides have been found to be responsible for detrimental reproductive effects in wildlife and human. These compounds, termed as endocrine disruptors (EDs), can alter endocrine function and subsequently may disrupt growth, development and reproduction (Colborn et al. 1993). Alachlor (Fig. 1) [2-chloro-N-(2, 6-diethyl phenyl)-N-(methoxymethyl) acetamide] is a commercialized effective pre-emergence and post-emergence herbicide in control of most grasses, most annuals and some broad leaved plants (Hayes and Laws 1991). It is a selective systemic herbicide, absorbed by germinating shoots and roots, works by interfering with the ability of plant to produce protein and by interfering with root elongation process. It has been used in the United States, Europe, Asia and other places in the world (Donaldson et al. 2002). Because of its widespread use, alachlor has been found in both surface water and groundwater in different countries (Barcelo et al. 1996; Spalding et al. 2003). And the presence of alachlor in freshwater is likely to pose health hazards to non-target aquatic organisms and human (Chesters et al. 1989). Therefore, the aquatic ecological risk from this herbicide becomes an important worldwide concern (Gammon et al. 2005). Alachlor is classified as the carcinogen of B2 group and known as a highly toxic EDs (USEPA 1985). The potential toxicity of alachlor has been studied in a series of rodent chronic bioassays in mouse, rat, monkey, and isolated hepatocytes (Bonfant et al. 1992; Meisner et al. 1992). However, there has been a limited investigation of its endocrine disrupting effect in fish, which may be directly affected by this herbicide as they live in the surrounding aquatic environment near farmland. So far, only few studies have yet been performed by using crucian carp as an environmentally sensitive freshwater species. The aim of this study is to investigate the endocrine disrupting effect including perturbation of the endocrine parameters and phase II biotransformation Enzymes activities in response to long-term alachlor exposure. The serum hormonal levels of serum sex steroids (testosterone and 17b-estradiol) and activities of hepatic Microsome Enzymes (glutathione S-transferase (GST) and UDP-glucuronosyltransferase (UDPGT) are evaluated. The relationship between the levels of serum sex steroids and hepatic Microsome Enzyme activities is discussed.

  • Effects of four chlorobenzenes on serum sex steroids and hepatic Microsome Enzyme activities in crucian carp, Carassius auratus
    Chemosphere, 2004
    Co-Authors: Yu Qian, Daqiang Yin, Wang Jun, Min Zhang
    Abstract:

    Abstract Four chlorobenzenes (chlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, p -chloro-methylbenzene) were administrated to the crucian carps ( Carassius auratus ) by peritoneal injections in the laboratory for 30 days. Serum testosterone and 17β-estradiol concentrations were detected using radioimmunology assay (RIA), and the activities of two hepatic Microsome Enzymes, glutathione s-transferase (GST) and UDP-glucuronosyltransferase (UDPGT), were measured using the modified methods as described by Habig and Owens. Results showed that the four chlorobenzenes caused significant increases in serum testosterone concentration in the crucian carps ( P P p -chloro-methylbenzene resulted in a marked inhibition to UDPGT activity in crucian carp ( P

Daqiang Yin - One of the best experts on this subject based on the ideXlab platform.

Yu Qian - One of the best experts on this subject based on the ideXlab platform.

Fanxiang Kong - One of the best experts on this subject based on the ideXlab platform.

Takashi Hamasaki - One of the best experts on this subject based on the ideXlab platform.

  • Enzymatic formation of G-group aflatoxins and biosynthetic relationship between G- and B-group aflatoxins.
    Applied and environmental microbiology, 1999
    Co-Authors: Kimiko Yabe, Miki Nakamura, Takashi Hamasaki
    Abstract:

    We detected biosynthetic activity for aflatoxins G1 and G2 in cell extracts of Aspergillus parasiticus NIAH-26. We found that in the presence of NADPH, aflatoxins G1 and G2 were produced from O-methylsterigmatocystin and dihydro-O-methylsterigmatocystin, respectively. No G-group aflatoxins were produced from aflatoxin B1, aflatoxin B2, 5-methoxysterigmatocystin, dimethoxysterigmatocystin, or sterigmatin, confirming that B-group aflatoxins are not the precursors of G-group aflatoxins and that G- and B-group aflatoxins are independently produced from the same substrates (O-methylsterigmatocystin and dihydro-O-methylsterigmatocystin). In competition experiments in which the cell-free system was used, formation of aflatoxin G2 from dihydro-Omethylsterigmatocystin was suppressed when O-methylsterigmatocystin was added to the reaction mixture, whereas aflatoxin G1 was newly formed. This result indicates that the same Enzymes can catalyze the formation of aflatoxins G1 and G2. Inhibition of G-group aflatoxin formation by methyrapone, SKF-525A, or imidazole indicated that a cytochrome P-450 monooxygenase may be involved in the formation of G-group aflatoxins. Both the Microsome fraction and a cytosol protein with a native mass of 220 kDa were necessary for the formation of G-group aflatoxins. Due to instability of the Microsome fraction, G-group aflatoxin formation was less stable than B-group aflatoxin formation. The ordA gene product, which may catalyze the formation of B-group aflatoxins, also may be required for G-group aflatoxin biosynthesis. We concluded that at least three reactions, catalyzed by the ordA gene product, an unstable Microsome Enzyme, and a 220-kDa cytosol protein, are involved in the enzymatic formation of G-group aflatoxins from either O-methylsterigmatocystin or dihydro-O-methylsterigmatocystin. Aflatoxin B1 (AFB1), AFB2, AFG1, and AFG2 are toxic, carcinogenic secondary metabolites that are produced by some strains of Aspergillus flavus, Aspergillus parasiticus, Aspergillus nomius, and Aspergillus tamarii (10). The biosynthetic pathway consists of more than 18 Enzyme steps from acetyl coEnzyme A (2, 4‐6, 9, 25, 27, 30‐35, 37). Many of the genes involved in aflatoxin biosynthesis have been isolated, and most of them are clustered (reviewed in references 26 and 28). The pathway leading to the formation of G-group aflatoxins has not been determined yet because the Enzyme activities required to synthesize these compounds have not been detected in cell-free systems. AFB1 and AFG1 contain dihydrobisfuran rings, and AFB2 and AFG2 contain tetrahydrobisfuran rings. In vivo feeding experiments have shown that AFB1 and AFG1 are produced from O-methylsterigmatocystin (OMST) and that AFB2 and AFG2 are produced from dihydro-O-methylsterigmatocystin (DHOMST) (4, 6, 30). Also, AFB1 and AFB2 are independently produced from OMST and DHOMST, respectively, through common reactions in in vitro cell-free systems (4, 30). The biosynthetic pathway(s) associated with the formation of G-group aflatoxins has been controversial for a long time. All known G-group aflatoxin-producing strains also produce B-group aflatoxins (18). No mutants that produce only Ggroup aflatoxins have been isolated in mutagenesis experiments performed with aflatoxigenic strains (3, 36). Low levels of conversion of radioactive AFB1 to other aflatoxins, including AFG1, have been obtained by using a cell-free homogenate (22). These results are consistent with the hypothesis that Ggroup aflatoxins may be produced from B-group aflatoxins. However, some researchers have reported that in feeding experiments radioactive AFB1 is converted to other aflatoxins (16, 22), while other workers have not observed this (11, 17). Despite these differences, it is generally assumed that G-group aflatoxins are produced from B-group aflatoxins by insertion of oxygen into a C-C bond through a Baeyer-Villigar reaction (9, 27).