| 研究実績の概要 |
The manuscript has been published:
THOMPSON, L.A., DARWISH, W.S., IKENAKA, Y., NAKAYAMA, S.M., MIZUKAWA, H. and ISHIZUKA, M., 2017. Organochlorine pesticide contamination of foods in Africa: incidence and public health significance. Journal of Veterinary Medical Science, 79 (4), pp.751-764.
Further field samples of free-range chicken products in KwaZulu-Natal Province, where DDT is sprayed, were analysed for DDT and metabolites (DDTs). Median ∑DDTs was 6.1 ng/g ww in meat and 9,544 ng/g ww in eggs. Risk assessment based on national consumption values showed consumption of free-range chicken eggs carries a very high risk of developing cancer - a 179 chance in 10,000 at 25th percentile and 8,423 chance in 10,000 at 95th percentile (compared to 0.9 to 34.9 for free-range chicken meat). I have submitted these in a manuscript for peer-reviewed publication.
The main focus this year has been on analysis of samples from in vivo exposure of chicks with p,p’-DDT. Microarray analysis of liver samples identified 72 genes significantly down-regulated with exposure. These were different to those identified from field samples, suggesting confounding factors. Chemical analysis of livers confirmed metabolic conversion of DDT to DDD and DDE congeners from 1 dpe, with DDE becoming the predominant congener by 14 dpe.
The third arm of my research is cell culture. I have been using human breast cancer cell lines, as DDTs are excreted in human milk and have been linked to mammary tissue pathology. Exposure studies have been performed and gene expression assessment begun.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
Publication of the literature review conducted last year is useful as an introduction for my graduation thesis. The manuscript on data from free-range chicken contamination and human health risk assessment in South Africa is useful not only for my thesis, but also as information to be used by health authorities in countries with malaria in decision-making about use of DDT and advice to consumers about health risks from free-range products.
Time spent at the Okinawa Institute of Science & Technology (OIST) was very helpful in training of cell culture techniques, but unfortunately did not produce results that may be used towards publication or my PhD thesis. These skills are now being employed successfully in cell culture at the laboratory in Hokkaido University.
Microarray analysis from the in vivo study has provided some very interesting data, some of which was presented at the ASCM conference in Taiwan. This data is of interest to our understanding of DDT metabolism and effects in livestock birds, and also in wild birds exposed through environmental contamination.
Much of the other laboratory work is in progress - with sample preparation completed, analysis underway, and results expected in the near future.
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| 今後の研究の推進方策 |
The major thrust of my research this year is on validation of microarray results using qPCR. Liver samples extracted from in vivo exposed chickens will be analysed, enabling comparison with DDT concentration results in the organ.
Other analysis of chicken samples from the in vivo study will be conducted, starting with histopathological analysis of tissue samples. Also, metabolomics analysis will be performed on chicken serum samples.
Investigation is also ongoing into gene expression changes in the MCF-7 human breast cancer cell line after p,p’-DDT exposure. Chicken microarray results identified many genes linked to inflammation and immunity, and genes with similar functions in human cell lines will be selected for analysis in these samples.
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