Peroxyacetyl nitrate (PAN) in the urban atmosphere.

Peroxyacetyl nitrate (PAN) in air has been well known as the indicator of photochemical smog due to its frequent occurrences in Seoul metropolitan area. This study was implemented to assess the distribution characteristics of atmospheric PAN in association with relevant parameters measured concurrently. During a full year period in 2011, PAN was continuously measured at hourly intervals at two monitoring sites, Gwang Jin (GJ) and Gang Seo (GS) in the megacity of Seoul, South Korea. The annual mean concentrations of PAN during the study period were 0.64±0.49 and 0.57±0.46 ppb, respectively. The seasonal trends of PAN generally exhibited dual peaks in both early spring and fall, regardless of sites. Their diurnal trends were fairly comparable to each other. There was a slight time lag (e.g., 1 h) in the peak occurrence pattern between O3 and PAN, as the latter trended to peak after the maximum UV irradiance period (16:00 (GJ) and 17:00 (GS)). The concentrations of PAN generally exhibited strong correlations with particulates. The results of this study suggest that PAN concentrations were affected sensitively by atmospheric stability, the wet deposition of NO2, wind direction, and other factors.

Comparison of different methods to quantify fat classes in bakery products.

The definition of fat differs in different countries; thus whether fat is listed on food labels depends on the country. Some countries list crude fat content in the 'Fat' section on the food label, whereas other countries list total fat. In this study, three methods were used for determining fat classes and content in bakery products: the Folch method, the automated Soxhlet method, and the AOAC 996.06 method. The results using these methods were compared. Fat (crude) extracted by the Folch and Soxhlet methods was gravimetrically determined and assessed by fat class using capillary gas chromatography (GC). In most samples, fat (total) content determined by the AOAC 996.06 method was lower than the fat (crude) content determined by the Folch or automated Soxhlet methods. Furthermore, monounsaturated fat or saturated fat content determined by the AOAC 996.06 method was lowest. Almost no difference was observed between fat (crude) content determined by the Folch method and that determined by the automated Soxhlet method for nearly all samples. In three samples (wheat biscuits, butter cookies-1, and chocolate chip cookies), monounsaturated fat, saturated fat, and trans fat content obtained by the automated Soxhlet method was higher than that obtained by the Folch method. The polyunsaturated fat content obtained by the automated Soxhlet method was not higher than that obtained by the Folch method in any sample.

Monitoring of polyaromatic hydrocarbons and volatile organic compounds in two major traffic tunnels in Seoul, Korea.

To describe the fundamental aspects of air quality in tunnel environments, field campaigns were conducted to measure polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and some criteria pollutants from two tunnel sites of Nam San (NS) and Hong Ji (HJ) gates in Seoul, Korea. The total PAH values (ngm(-3)) for the NS tunnel (137.8 +/- 10.9) were notably higher than the HJ counterpart (91.3 +/- 7.82), while the total VOC exhibited a reversed pattern with a notable enhancement in the HJ tunnel (178.5 +/- 174.7 ppbC) relative to the NS tunnel (112.5 +/- 64.1 ppbC). A line of evidence, including the molecular diagnostic ratios of PAHs, indicates the relative dominance of diesel vehicles in the NS tunnel compared to the HJ site. The PAHs with high ring numbers (n > 6, such as benzo(g, h, i)perylene and indeno(1,2,3-cd)pyrene) were preferentially enriched in the particle phase, whereas their low ring number counterparts (n = 2-3) were in the gas phase. The results of our study suggest the possibility that the relative source processes for each tunnel site are characterized by the relative dominance of either diesel (NS) or gasoline-powered vehicles (HJ).

Antimicrobial resistance profiles among Escherichia coli strains isolated from commercial and cooked foods.

A total of 4330 food samples of which microbiological standard for Escherichia coli is negative in Korea were determined for the frequency of E. coli. Ninety six samples (2.2%) were positive for E. coli. Detection rate of E. coli varied significantly by food type and ranged from 0.3% to 10.9%. Seasoned raw meat (yukhoe) and cold bean-soup had the highest prevalence for E. coli (10.9%) followed by gimbap (5.2%), meat broth for cold noodle (2.9%) and sprout (2.1%). E. coli isolates (n=96) were investigated for their phenotypic and genotypic antimicrobial resistance patterns. Seventeen E. coli isolates (17.7%) were resistant to one or more antimicrobial agents tested. High rates of resistance to the following drugs were observed: tetracycline (15.6%), streptomycin (12.5%), ampicillin (10.4%), nalidixic acid (9.4%) and ticarcillin (9.4%). All ampicillin resistant isolates were screened for extended-spectrum ß-lactamase (ESBL) production by the combination disk test. None of the E. coli isolates produced ESBLs. Seventeen out of 96 E. coli isolates which were resistant to at least one antibiotic were investigated by PCR for the presence of 3 classes of antimicrobial resistance genes (tetracycline, aminoglycosides and beta-lactams). The tetracycline resistance genes tetA and tetB were found in 7 and 5 isolates, respectively. The aminoglycoside resistance genes, strA/B, aphA1, aadA and aac(3)-IV were found in 9, 5, 2 and 2 isolates, respectively. The beta-lactam resistance gene, bla(TEM) was found in 7 isolates. Results of this study show that 13 E. coli isolates were multidrug resistant (to three or more antibiotics) and 12 isolates carried at least one antimicrobial resistance gene. These isolates can act as the reservoir for antimicrobial resistance genes and facilitate the dissemination of these genes to other pathogenic and commensal bacteria. Adequate intervention to reduce microbial contamination of these foods is strongly recommended.

Determination of the esculetin contents of medicinal plants by liquid chromatography-tandem mass spectrometry.

We developed a LC-MS/MS method for the determination of esculetin contents in medicinal plants. The analysis was performed using multiple reaction monitoring in negative mode, and an XBridge™ C(18) column (2.1 × 100 mm, 3.5 µm) was used. Methanol and 0.1% formic acid were used for gradient analysis. The calibration curve showed good linearity (r(2) > 0.9993). The limits of detection and quantitation were 0.02 and 0.07 ng/mL, respectively. The intra-day and inter-day precisions were 1.5-6.8 and 2.0-5.3%, respectively, and the accuracy was 102.0-110.2%. The contents of esculetin in 35 different plants were determined, and Fraxini Cortex showed the highest content of esculetin (761-5475 mg/kg). In Mori Folium and Artemisiae Capillaris Herba, 5.2-21.5 and 7.0-17.6 mg/kg of esculetin were found, respectively. In other medicinal plants, no esculetin was detected, or it was present at a concentration less than 10 mg/kg. The analysis method appears to be simple, sensitive and reproducible. Contrary to expectations based on traditional medical knowledge, although Artemisiae Capillaris Herba contains a large amount of esculetin, it appears from this study that Fraxini Cortex contains a greater amount. The pharmacological effects of esculetin isolated from medicinal plants should be investigated as part of new medicines development.

Pinus densiflora leaf essential oil induces apoptosis via ROS generation and activation of caspases in YD-8 human oral cancer cells.

The leaf of Pinus (P.) densiflora, a pine tree widely distributed in Asian countries, has been used as a traditional medicine. In the present study, we investigated the anticancer activity of essential oil, extracted by steam distillation, from the leaf of P. densiflora in YD-8 human oral squamous cell carcinoma (OSCC) cells. Treatment of YD-8 cells with P. densiflora leaf essential oil (PLEO) at 60 µg/ml for 8 h strongly inhibited proliferation and survival and induced apoptosis. Notably, treatment with PLEO led to generation of ROS, activation of caspase-9, PARP cleavage, down-regulation of Bcl-2, and phosphorylation of ERK-1/2 and JNK-1/2 in YD-8 cells. Treatment with PLEO, however, did not affect the expression of Bax, XIAP and GRP78. Importantly, pharmaco-logical inhibition studies demonstrated that treatment with vitamin E (an anti-oxidant) or z-VAD-fmk (a pan-caspase inhibitor), but not with PD98059 (an ERK-1/2 inhibitor) or SP600125 (a JNK-1/2 inhibitor), strongly suppressed PLEO-induced apoptosis in YD-8 cells and reduction of their survival. Vitamin E treatment further blocked activation of caspase-9 and Bcl-2 down-regulation induced by PLEO. Thus, these results demonstrate firstly that PLEO has anti-proliferative, anti-survival and pro-apoptotic effects on YD-8 cells and the effects are largely due to the ROS-dependent activation of caspases.

Antimicrobial resistance and resistance genes in Escherichia coli strains isolated from commercial fish and seafood.

The purpose of this study was to investigate the antimicrobial resistance and to characterize the implicated genes in Escherichia coli isolated from commercial fish and seafood. Fish and seafood samples (n=2663) were collected from wholesale and retail markets in Seoul, Korea between 2005 and 2008. A total of 179 E. coli isolates (6.7%) from those samples were tested for resistance to a range of antimicrobial agents. High rates of resistance to the following drugs were observed: tetracycline (30.7%), streptomycin (12.8%), cephalothin (11.7%), ampicillin (6.7%) and ticarcillin (6.1%). No resistances to amikacin, amoxicillin/clavulanic acid and cefoxitin were observed. Seventy out of 179 isolates which were resistant to one or more drugs were investigated by PCR for the presence of 3 classes of antimicrobial resistance genes (tetracycline, aminoglycosides and beta-lactams), class 1, 2 and 3 integrons. Gene cassettes of classes 1 and 2 integrons were further characterized by amplicon sequencing. The tetracycline resistance genes tetB and tetD were found in 29 (41.4%) isolates and 14 (20%) isolates, respectively. The beta-lactam resistance gene, bla(TEM) was found in 15 (21.4%) isolates. The aminoglycoside resistance gene, aadA was found in 18 (25.7%) isolates. Class 1 integron was detected in 41.4% (n=29) of the isolates, while only 2.9% (n=2) of the isolates were positive for the presence of class 2 integron. Two different gene cassettes arrangements were identified in class 1 integron-positive isolates: dfrA12-aadA2 (1.8 kb, five isolates) and aadB-aadA2 (1.6 kb, four isolates). One isolate containing class 2 integron presented the dfrA1-sat-aadA1 gene cassette array. These data suggest that commercial fish and seafood may act as the reservoir for multi-resistant bacteria and facilitate the dissemination of the resistance genes.

Total mercury, methylmercury and ethylmercury in marine fish and marine fishery products sold in Seoul, Korea.

In 2009, a survey of 177 samples of fish and fishery products from the markets in Seoul was carried out to investigate total mercury and organic mercury (methylmercury) concentrations and to establish a correlation, if any, between total and organic mercury levels. Concentrations of total and organic mercury in canned tuna ranged 0.001-2.581 and 0.003-1.307 mg/kg, respectively; those for fish, such as cod or salmon, ranged 0.012-2.529 and 0.021-0.507 mg/kg, respectively. Ethylmercury was not detected. More than 50% of total mercury in the samples existed as organic mercury. The correlation coefficients (r(2)) between total mercury and methylmercury concentrations of fish and fishery products found to have methylmercury were 0.844 and 0.976, respectively, which was statistically significant. There was a higher correlation in fishery products than in fish. Although there was no product in which mercury exceeded the standard set by the Food Code in 2008, with the exception of marlin steak, a processed food, which contained 1.307 mg/kg methylmercury. None exceeded the provisional tolerable weekly intake (PTWI) for mercury. Collectively, the results indicate that fish or fishery products marketed in Seoul, with the exception of marlin, have low levels of total or organic mercury and, thus, intake of these products is not a risk to public health.