Cheolmin Kim

Bioaccessibility of AhR-active PAHs in sediments contaminated by the Hebei Spirit oil spill: Application of Tenax extraction in effect-directed analysis

Bioaccessibility of toxic substances in sedimentary residual oil is a crucial factor that needs to be considered for accurate risk assessments posed by oil spills. However, information on oil weathering processes and bioaccessibility of residual oil is often not sufficient and clear. In the present study, bioaccessibility of aryl hydrocarbon receptor (AhR)-active polycyclic aromatic hydrocarbons (PAHs) in coastal sediments near the site of the Hebei Spirit oil spill (Korea, 2007) was assessed by Tenax extraction in effect-directed analysis (EDA). Sediment samples collected 6 years after the oil spill were extracted using Soxhlet or Tenax, and EDA was performed using a battery of H4IIE-luc bioassay and GC/MSD analysis. Concentrations of PAHs and alkyl-PAHs in Soxhlet extracts ranged from 210 to 53,000 μg kg(-1) dry mass. However, concentrations of PAHs and alkyl-PAHs in Tenax extracts were approximately 20-fold less compared to those in Soxhlet extracts. In Soxhlet and Tenax extracts, the major AhR-active PAHs were identified as C1-chrysene, C3-chrysene, and C4-phenanthrene. Concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalents (TEQ(PAHs)) explained 31% and 60% of the bioassay-derived TCDD-EQ concentrations in Soxhlet and Tenax extracts, respectively. Overall, bioaccessibility of PAHs and alkyl-PAHs in sedimentary residual oils depended on hydrophobicity (log K(ow)) and degree of weathering of crude oil. The results of the present study provide further evidence in support of the biological and ecological recoveries of oil spill sites.

In vitro and in vivo toxicities of sediment and surface water in an area near a major steel industry of Korea: Endocrine disruption, reproduction, or survival effects combined with instrumental analysis

The influence of industrial and/or municipal contaminant inputs on the aquatic environment of Pohang, Korea was investigated, with a focus on bioassay combined with instrumental analysis. Pohang is the most heavily populated city in Gyeongsangbuk-do province of Korea, with more than half a million residents, and also hosts the nations biggest steel manufacturer and related industries. Sediment (n=15) and surface water samples (n=17) were collected from Hyeongsan River which runs across the Pohang city, in two separate events, i.e., June 2010 and February 2011. Sediment samples were first Soxhlet-extracted (raw extract) and were measured for estrogenicity using H295R cell line, and also analyzed for alkylphenols (APs), bisphenol A (BPA), PAHs, and PCBs. For sediment samples which exhibited greatest effects in the cell line, further fractionation was performed into non-polar, mid-polar, and polar portions. In surface water samples, heavy metals were also analyzed. Among 15 sediment samples, station S2 near the steel industry complex and station M3 near the municipal area showed the greatest sex hormone changes, and these changes were generally explained by the fractions which contained APs and BPA. Principal component analysis (PCA) however suggests that chemicals that were not analyzed in the present study would better explain endocrine disruption capacity of sediments. In water samples, adverse effects on hatchability and growth of Japanese medaka fish, and on Daphnia reproduction were noted following exposure to six water samples collected from stations near industrial and municipal areas. Several heavy metals and nonylphenol (NP) concentrations exceeded surface water quality guidelines, suggesting adverse effects of contamination inputs from both industrial and municipal activities. Observed estrogenicities in stations such as S2 and M3 warrant further investigations on longer term ecosystem impacts near industrial and municipal areas. The levels of major organic chemicals in sediments are quite comparable to those reported in ~10 years ago, emphasizing a need for source control.

Thyroid hormone disrupting potentials of bisphenol A and its analogues - in vitro comparison study employing rat pituitary (GH3) and thyroid follicular (FRTL-5) cells

As adverse health effects of bisphenol A (BPA) become a growing public health concern, the chemicals substituting BPA have been increasingly used in everyday lives. BPA substitutes have been frequently detected in both environment and biota in increasing levels. However, very limited toxicological information is available for these chemicals. In the present study, thyroid disrupting effects of nine structural analogues of BPA were evaluated along with BPA, using rat pituitary (GH3) and thyroid follicular (FRTL-5) cells. Similar to BPA, its analogues caused significant down-regulation of tshβ, trα, trβ, dio1 or dio2 genes in GH3 cells, and some analogues, such as BPF, BPM or BPZ, showed even greater potency compared to BPA. In FRTL-5 cells, the genes responsible for hormone synthesis, e.g., pax8, nis, tg or tpo genes, exhibited over 1.5-fold up-regulation following exposure to BPA analogues, such as BPS. The effects on gene regulation was different by the cell line. Our results clearly show that the BPA substituting chemicals may influence thyroid hormone homeostasis by affecting thyroid regulation and hormone synthesis, often at lower doses compared to BPA. Thyroid effects of the BPA analogues deserve further investigations in experimental organisms and in human populations.

An effective resource management for variable bit rate video-on-demand server

Video on demand servers use compression techniques to reduce the storage and bandwidth requirements. The compression techniques make the bit rates of compressed video data significantly variable from frame to frame. Consequently, video on demand servers with a constant bit rate retrieval can not maximize the utilization of resources. It is possible that when variable bit rate video data is stored, accurate description of the bit rate changes could be computed a priori. We propose a resource management strategy of a video on demand server for variable bit rate continuous media. Given a fixed disk bandwidth and a fixed amount of buffer space, our strategy maximizes the system throughput of video on demand server. Results of trace driven simulations show the effectiveness of our strategy.

Reconnaissance of dioxin-like and estrogen-like toxicities in sediments of Taean, Korea-seven years after the Hebei Spirit oil spill

Oil spills near the coastlines may damage marine and intertidal ecosystem. Constituents of the oil have been reported to cause toxic consequences mediated by aryl hydrocarbon receptor (AhR), and estrogen receptor (ER). In the present study, AhR- and ER-mediated toxicities of coastal sediments of Taean were investigated seven years after Hebei Spirit oil spill (HSOS). Sediment samples were collected on June and October 2014 from seven locations along the Taean coastline, where signs of oil spill were detected. Sediment samples were extracted in Soxhlet extractors and further processed through activated silica gels to separate into four fractions; F1 (saturate hydrocarbons), F2 (aromatic hydrocarbons), F3 (resins and polar compounds), and F4 (residues). ER-mediated and AhR-mediated potencies (% E2max and % TCDDmax) of each fraction were determined using MVLN cells and H4IIE-luc cells, respectively. F2 and F3 fractions of Sinduri 1, Sinduri 2, and Sogeunri 1 samples showed greater AhR-mediated potencies (up to 107% TCDDmax). Chemical analysis revealed that PAH components are correlated with AhR-binding activities. The % E2max results varied by sample: While there was no noticeable induction of ER-dependent responses (<45%), some aromatics fractions (F2) exhibited the highest ER-mediated responses. Compared with previous reports from the same sites, both AhR-mediated and ER-mediated potencies have decreased over time. Nevertheless, AhR-mediated potencies could be identified in the environmental samples even after 7 years of the incident. Therefore, possible ecosystem implications of these findings should be further investigated.

Cloning metallothionein gene in Zacco platypus and its potential as an exposure biomarker against cadmium.

Zacco platypus, pale chub, is an indigenous freshwater fish of East Asia including Korea and has many useful characteristics as indicator species for water pollution. While utility of Z. platypus as an experimental species has been recognized, genetic-level information is very limited and warrants extensive research. Metallothionein (MT) is widely used and well-known biomarker for heavy metal exposure in many experimental species. In the present study, we cloned MT in Z. platypus and evaluated its utility as a biomarker for metal exposure. For this purpose, we sequenced complete complementary DNA (cDNA) of MT in Z. platypus and carried out phylogenetic analysis with its sequences. The transcription-level responses of MT gene following the exposure to CdCl2 were also assessed to validate the utility of this gene as an exposure biomarker. Analysis of cDNA sequence of MT gene demonstrated high conformity with those of other fish. MT messenger RNA (mRNA) expression and enzymatic MT content significantly increased following CdCl2 exposure in a concentration-dependent manner. The level of CdCl2 that resulted in significant MT changes in Z. platypus was within the range that was reported from other fish. The MT gene of Z. platypus sequenced in the present study can be used as a useful biomarker for heavy metal exposure in the aquatic environment of Korea and other countries where this freshwater fish species represents the ecosystem.

A new species of eriophyid mite Aceria zelkoviana sp. n. (Acari: Eriophyidae) associated with Zelkova Serrata makino (Ulmaceae) from Korea

Abstract A new species of gall-forming mite, Aceria zelkoviana sp. n. infesting Zelkova serrata Makino from Korea is described. Illustrations are given.