Arsenic levels in the groundwater of Korea and the urinary excretion among contaminated area.

Drinking water is a main source of human exposure to arsenic. Hence, the determination of arsenic in groundwater is essential to assess its impact on public health. Here, we report arsenic levels in the groundwater of 722 sites covering all six major provinces of Korea. Water was sampled in two occasions (summer, 722 sites and winter, 636 sites) and the arsenic levels were measured with highly sensitive inductively coupled plasma-mass spectrometry method (limit of detection, 0.1 µg/l) to encompass the current drinking water standard (<10 µg/l). Seasonal variation was negligible, but the geographical difference was prominent. Total arsenic in groundwater ranged from 0.1 to 48.4 µg/l. A 88.0-89.0% of sites were <2.0 µg/l and the remaining ones generally did not exceed 10 µg/l (6.4-7.0%, 2.0-4.9 µg/l; 2.4-3.0%, 5.0-9.9 µg/l). However, some areas (1.0-9.2%) exhibited >10 µg/l. Notably, urinary arsenic excretion of people around these regions was markedly higher compared with non-contaminated areas (<5 µg/l) (79.7±5.2 µg/g (N=122) vs 68.4±5.4 µg/g (N=65) creatinine, P=0.052). All stratified analysis also revealed higher urinary excretion, where a statistically significant difference was noted for non-smokers (85.9±12.7 vs 54.0±6.3, P=0.030), suggesting that arsenic-contaminated groundwater may contribute to its systemic exposure.

Single-channel multiplexing without melting curve analysis in real-time PCR.

Multiplex real-time PCR with quantification of targets in a single fluorescence channel has been the demand in biotechnology industry. Here, we develop a novel analytical real-time PCR technique to detect multiple targets in a single fluorescence channel without melting curve analysis. In this technique, we show the intensity of the fluorescence signals of two discrete Tm targets is different at certain temperatures called detection temperatures, by which a high Tm target can be detected regardless of a low Tm target. We then identify the low Tm target by utilizing a change of the fluorescence signals between two different detection temperatures. Furthermore, it enables us to determine quantification of each target in a single channel, possibly facilitating convenient patient care for drug treatment in clinics.

Direct detection of lamivudine-resistant hepatitis B virus mutants by a multiplex PCR using dual-priming oligonucleotide primers.

Mutations in the YMDD motif of the hepatitis B virus (HBV) polymerase gene increase lamivudine resistance of HBV, highlighting the clinical importance of accurate and sensitive detection of HBV mutants. Using dual-priming oligonucleotide primer technology, an assay that can detect mutations at codons 180 (L528M) and 204 (YVDD, YIDD, and YSDD) by a single-step multiplex PCR was developed. This Seeplex Lami-DR assay was sufficiently sensitive to detect 10(3)HBV/ml and was able to detect minor mutants comprising as little as 2% of the viral population. Mutants were detected in 57 of 65 serum samples (88%) from patients with chronic hepatitis B who had been treated with lamivudine (median, 32 months; range, 1-83 months). The agreement with direct sequencing was only 38.5% (25/65). Discrepancies between these methods resulted from detection of additional mutants by the Seeplex Lami-DR assay, as confirmed by a novel verification analysis. This assay is not only highly accurate and sensitive, but is also simple and cost-effective, requiring no expensive probes, laborious sequencing procedures, or digestion with restriction enzymes. Accordingly, the Seeplex HBV Lami-DR assay should be considered as a first-line, cost-effective tool for detecting viral mutations in patients with chronic hepatitis B receiving lamivudine therapy.