[en] The structure of brain-derived neurotrophic factor (BDNF) gene is complex, which is composed of eight non-coding exons and one coding exon, each of them has its own unique promoter. Multiple BDNF transcripts have distinct functional properties and epigenetic modulation of BDNF gene transcription is implicated in the neurological disorders. In the present study, rat models with amyloid-β (Aβ) intrahippocampal injection and PC12 cells were used to explore the role of DNA methylation in the promoters of BDNF exon Ⅳ and exon Ⅵ in BDNF suppression caused by Aβ. We found that Aβ inhibited BDNF expression accompanying with hypermethylation in BDNF exon Ⅳ promoter, meanwhile, S-adenosylmethionine (SAM), primary methyl donor, reversed the low BDNF expression through demethylation in BDNF exon Ⅳ promoter. No methylation change was observed in BDNF exon Ⅵ promoter. The alteration of DNA methylation caused by Aβ or SAM was mediated by DNA methyltransferase 3A (DNMT3A). These data suggest that methylation change in BDNF exon Ⅳ is involved in the regulation of BDNF expression by Aβ or SAM, and further support the view of specific epigenetic modifications of a certain BDNF gene transcript.

[en] This study investigates observed and modeled contributions of global sea surface temperature (SST) to China winter climate trends in 1960–2014, including increased precipitation, warming through about 1997, and cooling since then. Observations and Atmospheric Model Intercomparison Project (AMIP) simulations with prescribed historical SST and sea ice show that tropical Indian Ocean (TIO) warming and increasing rainfall causes diabatic heating that generates a tropospheric wave train with anticyclonic 500-hPa height anomaly centers in the TIO or equatorial western Pacific (TIWP) and northeastern Eurasia (EA) and a cyclonic anomaly over China, referred to as the TIWP-EA wave train. The cyclonic anomaly causes Indochina moisture convergence and southwesterly moist flow that enhances South China precipitation, while the northern anticyclone enhances cold surges, sometimes causing severe ice storms. AMIP simulations show a 1960–1997 China cooling trend by simulating increasing instead of decreasing Arctic 500-hPa heights that move the northern anticyclone into Siberia, but enlarge the cyclonic anomaly so it still simulates realistic China precipitation trend patterns. A separate idealized TIO SST warming simulation simulates the TIWP-EA feature more realistically with correct precipitation patterns and supports the TIWP-EA teleconnection as the primary mechanism for long-term increasing precipitation in South China since 1960. Coupled Model Intercomparison Project (CMIP) experiments simulate a reduced TIO SST warming trend and weak precipitation trends, so the TIWP-EA feature is absent and strong drying is simulated in South China for 1960–1997. These simulations highlight the need for accurately modeled SST to correctly attribute regional climate trends.

[en] This study examines Northern Hemisphere winter (DJFM) atmospheric responses to opposite strong phases of interdecadal (low frequency, LF) Pacific sea surface temperature (SST) forcing, which resembles El Niño-Southern Oscillation (ENSO) on a longer time scale, in observations and GFDL and CAM4 model simulations. Over the Pacific–North America (PNA) sector, linear observed responses of 500-hPa height (Z500) anomalies resemble the PNA teleconnection pattern, but show a PNA-like nonlinear response because of a westward Z500 shift in the negative (LF−) relative to the positive LF (LF+) phase. Significant extratropical linear responses include a North Atlantic Oscillation (NAO)-like Z500 anomaly, a dipole-like Z500 anomaly over northern Eurasia associated with warming over mid-high latitude Eurasia, and a Southern Annular anomaly pattern associated with warming in southern land areas. Significant nonlinear Z500 responses also include a NAO-like anomaly pattern. Models forced by LF+ and LF− SST anomalies reproduce many aspects of observed linear and nonlinear responses over the Pacific–North America sector, and linear responses over southern land, but not in the North Atlantic–European sector and Eurasia. Both models simulate PNA-like linear responses in the North Pacific–North America region similar to observed, but show larger PNA-like LF+ responses, resulting in a PNA nonlinear response. The nonlinear PNA responses result from both nonlinear western tropical Pacific rainfall changes and extratropical transient eddy feedbacks. With LF tropical Pacific forcing only (LFTP+ and LFTP−, climatological SST elsewhere), CAM4 simulates a significant NAO response to LFTP−, including a linear negative and nonlinear positive NAO response.

[en] Nanostructured titania-based solid-phase microextraction (SPME) fibers were fabricated through the in situ oxidation of titanium wires with H₂O₂ (30%, w/w) at 80 deg. C for 24 h. The obtained SPME fibers possess a ∼1.2 μm thick nanostructured coating consisting of ∼100 nm titania walls and 100-200 nm pores. The use of these fibers for headspace SPME coupled with gas chromatography with electron capture detection (GC-ECD) resulted in improved analysis of dichlorodiphenyltrichloroethane (DDT) and its degradation products. The presented method to detect DDT and its degradation products has high sensitivity (0.20-0.98 ng L^-1), high precision (relative standard deviation R.S.D. = 9.4-16%, n = 5), a wide linear range (5-5000 ng L^-1), and good linearity (coefficient of estimation R² = 0.991-0.998). As the nanostructured titania was in situ formed on the surface of a titanium wire, the coating was uniformly and strongly adhered on the titanium wire. Because of the inherent chemical stability of the titania coating and the mechanical durability of the titanium wire substrate, this new SPME fiber exhibited long life span (over 150 times)