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Radiocarbon (14C) measurement of water-soluble organic carbon (WSOC) in ambient aerosols is a quantitative tool for unambiguously distinguishing fossil and non-fossil sources. In this study, a fast and reliable method for measuring 14C in micro-scale (μg) WSOC aerosol samples is successfully developed, which includes three steps: (1) extraction (2) freeze drying, and (3) online 14C analysis of CO2 from WSOC combustion. Procedure blanks are carefully assessed by measuring high-purity water and reference materials. Accurate 14C results could be obtained for WSOC with only 10 μg C, and thus the potential applications are substantially broadened because much less filter material is needed compared to previous reported methods. This method is applied to aerosols samples collected during winter from Switzerland and China. The results demonstrate that non-fossil sources are important if not dominant contributors of WSOC. These non-fossil components are consistently enriched in WSOC compared to bulk OC and water-insoluble OC for all samples, due to high water solubility of primary and secondary biomass burning aerosols. However, the presence of fossil WSOC is still considerable indicating a substantial contribution of secondary OC (SOC) formed from precursors emitted by fossil emissions. Larger fossil contributions to WSOC is found in China than in Switzerland and previously reported values in Europe, USA and South Asia, which may be attributed to higher fossil-derived SOC formation in China. [ABSTRACT FROM AUTHOR]

Purpose Observe how specific small RNA interference (siRNA) aimed at TPX2 gene suppresses TPX2 gene expression in esophageal cancer EC9706 cells and the effect on esophageal cancer cell growth and invasion ability. Methods Transfect TPX2 siRNA into EC9706 cells via lipofectamin 2000. The experiments were divided into three groups, a negative control, a blank control and an siRNA interference group (24 h, 48 h, 72 h, 96 h). We examined RNA and protein level alteration of the TPX2 gene after TPX2 siRNA transfection by RT-PCR and Western blot analysis. Detection of how TPX2 siRNA influences EC9706 cell proliferation was done by MTT, cell apoptosis monitored through Tunel assay, in vitro invasion ability via Boyden chamber and cell cycle change by flow cytometry. Results After effective siRNA transfection, TPX2 mRNA and protein expression level in siRNA interference group were (0.31 ± 0.08, 0.39 ± 0.12),72 h after transfection, significantly lower than blank control group (1.00 ± 0.01) and negative control group (0.98 ± 0.11), ( F = 71.182, t 1 = 8.17, t 2 = 7.90, P < 0.05); MTT results demonstrated that cell growth and proliferation were inhibited and the inhibition rate was up to 35.4% ( P < 0.05) compared with the control group. TUNEL results indicated that cell apoptosis index in siRNA interference group was 18.28 ± 0.35, higher than that in blank control group (4.07 ± 0.26)and negative control group (4.13 ± 0.22), ( F = 244.5, t 1 = 60.61, t 2 = 53.32, P < 0.01). Boyden chamber results showed that the transmembrane cell number was 45.30 ± 8.08 in siRNA interference group, less than blank control group (121.90 ± 7.83), ( F = 122.46, t 1 = 11.81, t 2 = 10.47, P < 0.01); besides, in siRNA interference group cell invasion inhibition rate was 71.42 ± 9.12, higher than negative control group (5.65 ± 3.55), ( t = 14.256, P < 0.01). Flow cytometry results illustrated that more EC9706 cells went into apoptosis and cell cycle arrested in S phase. Similar results were obtained by in vivo transplantation, as TPX2 siRNA transfection significantly reduced tumor growth of the xenograft in nude mice. Conclusion siRNA could effectively inhibit the invasion and metastasis of EC9706 cells, promote the apoptosis of tumor cells and may become a new approach for treatment of esophageal carcinoma. [ABSTRACT FROM AUTHOR]