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Gene expression levels of choriogenin, vitellogenin, and estrogen receptor were determined using a reverse transcription-polymerase chain reaction (RT-PCR) technique after exposure to estrogenic chemicals to compare the sensitivities of the biomarkers of endocrine disruption in medaka, Oryzias latipes. Mature male medaka were treated with a single dose of 100 μ/l of 17α-ethinylestradiol, nonylphenol, and bisphenol A for 6 days, then RNA was extracted from the livers of treated fish for RT-PCR. Primers of RT-PCR for choriogenin H and L, and estrogen receptor were synthesized based on previously known cDNA sequences, and primers for vitellogenin I and II were synthesized based on the partial cDNA which was sequenced in this study. When the five biomarker genes were amplified by RT-PCR under the same condition, the mRNA induction level of each gene was elevated with different sensitivities. Conclusively, choriogenin L, which is a precursor of zona radiata protein (ZI-3) with molecular weight of 49 kD, showed the most sensitive gene expression in all the treated groups.

The sequence of cytochrome P4501A (CYP1A) cDNA of medaka (Oryzias latipes) was determined, and its messenger ribonucleic acid (mRNA) regulation by beta-naphthoflavone (betaNF) was evaluated. The determined cDNA sequence contained 2,349 base pairs (bp), and the open reading frame contained a total of 1,563 bp encoding 521 predicted amino acids. The induction of CYP1A mRNA in medaka was evaluated using reverse transcription-polymerase chain reaction. The concentration-dependent induction of CYP1A mRNA in the liver was observed after exposure to betaNF at nominal concentrations of 20, 100, and 500 microg/L for 2 d. Time-dependent changes of CYP1A mRNA levels were also observed in the liver, gill, gut, and caudal fin tissues of medaka exposed to 100 microg/L of betaNF for 7 d. Our results showed that the degree of CYP1A mRNA induction in the gill, gut, and caudal fin after exposure to betaNF was relatively higher than that in the liver, possibly because of low basal levels of CYP1A mRNA in the gill, gut, and caudal fin of nonexposed fish. The induction of medaka CYP1A mRNA was also observed after exposure to an environmental sample, landfill leachate. The CYP1A mRNA inductions in the gill, gut, and caudal fin were also higher than that in the liver as shown in the betaNF-treated groups. These results show that CYP1A mRNA determination in the gill, gut, and caudal fin, which are in direct contact with the polluted water, may become a useful method for monitoring CYP1A-inducible chemicals.

The Chemical Accidents Response Information System (CARIS) was developed at the Center for Chemical Safety Management in South Korea in order to track and predict the dispersion of hazardous chemicals in the case of an accident or terrorist attack involving chemical companies. The main objective of CARIS is to facilitate an efficient emergency response to hazardous chemical accidents by rapidly providing key information in the decision-making process. In particular, the atmospheric modeling system implemented in CARIS, which is composed of a real-time numerical weather forecasting model and an air pollution dispersion model, can be used as a tool to forecast concentrations and to provide a wide range of assessments associated with various hazardous chemicals in real time. This article introduces the components of CARIS and describes its operational modeling system. Some examples of the operational modeling system and its use for emergency preparedness are presented and discussed. Finally, this article evaluates the current numerical weather prediction model for Korea.

The fish egg envelope has been known to consist of two distinct layers. The outer layer is thin and is formed around the oocytes during the later stage of previtellogenic development. The inner layer, called zona radiata, is thicker than outer layer and occupies most of the egg envelope. Zona radiata proteins of medaka (Oryzias latipes) consist of two major subunit groups, ZI-1,2 and ZI-3. The precursors of ZI-1,2 and ZI-3 have been named choriogenin H and choriogenin L, respectively. They are synthesized in the liver in response to estrogen, and then released into the blood stream and incorporated into the zona radiata in sexually matured female medaka. However, choriogenin is also induced in male medaka when the fish are exposed to estrogenic chemicals. Choriogenin can be suggested as a possible biomarker of endocrine disruption in fish, however, relatively little has been known about chorogenin gene expression by estrogenic chemicals. In this study, full sequence of choriogenin L DNA was identified, and measurement of choriogenin mRNA induction was established in medaka by use of RT-PCR technique. Also estrogenic effects of industrial chemicals were evaluated by this tool. When mature male medaka was treated with bisphenol A, nonylphenol, and 17alpha-ethinylestradiol for 6 days, respectively, the expression levels of choriogenin L and H mRNA were elevated in treated groups. The induction of choriogenin subunits expression by these chemicals showed a dose-dependent pattern and choriogenin L was found to be more sensitive than choriogenin H.

Zona radiata proteins of medaka (Oryzias latipes) consist of two major subunit groups, ZI-1,2 and ZI-3. The precursor of ZI-1,2, which is a glycoprotein with a molecular weight of 74,000 to 76,000 Da, is called choriogenin H, and the precursor of ZI-3, with a molecular weight of 49,000 Da, is called choriogenin L. The precursor proteins are synthesized in the liver in response to estrogen in sexually mature female medaka. However, they are also induced in the male medaka when fish are exposed to estrogenic chemicals. Therefore, choriogenin is known as a possible sensitive biomarker for endocrine disruption in fish. In this study, the choriogenin H cDNA sequence was reanalyzed and the genomic DNA sequence was newly analyzed. This was done for the selection of proper reverse transcription-polymerase chain reaction (RT-PCR) primers to measure the choriogenin mRNA induction by estrogenic chemicals. In the results, the full cDNA sequence was found to be 2,109 bp long and the size of the open reading frame (ORF) was found to be a total of 1,998 bp encoding 666 predicted amino acids, which was found to be different from previously reported cDNA sequence of medaka choriogenin. In the choriogenin H cDNA, a repetitive domain and a nonrepetitive domain were shown. Regarding the repetitive domain, seven complete repeats of the 45 bp of 5'-ccc cag tac cca tca aag cct cag ccc cct cag aat cct cag gtc-3' encoding PQYPSKPQPPQNPQV were found. Medaka choriogenin H gene was found to possess seven exons and six introns, and the total length was 2,643 bp long. The seven repetitive nucleotide residues described above existed in exon 1, which was found to be 1,033 bp long. Based on the full sequence information, proper primers were synthesized for RT-PCR to detect choriogenin H mRNA induction in male and juvenile medaka by 17alpha-ethinylestradiol, and this type of measurement system was found to be effective as a simple tool for the screening of endocrine-disrupting chemicals.