Abstract. We investigated the spatial distribution and seasonal variation of dissolved inorganic nitrogen in a large perturbed estuary, the Pearl River Estuary, based on three cruises conducted in winter (January 2005), summer (August 2005) and spring (March 2006). On-site incubation was also carried out for determining ammonium and nitrite oxidation rates (nitrification rates). We observed a year-round pattern of dramatic decrease in NH , accompanied by extremely high concentrations of ammonia (up to >800 µmol L −1 ) and nitrate (up to >300 µmol L −1 ). In summer, the upper estuary showed higher nitrification rates (ammonia oxidation rate ∼1.5-33.1 µmol N L −1 d −1 , nitrite oxidation rate ∼0.6-32.0 µmol N L −1 d −1 ) with lower concentrations of ammonia (<350 µmol L −1 ) and nitrate (<120 µmol L −1 ). The Most Probable Number test showed relatively lower nitrifier abundance in summer at most sampling stations, indicating a greater specific nitrification rate per cell in the warm season. Temperature appeared to control nitrification rates to a large degree in different seasons. Spatial variability of nitrification rates appeared to be controlled by a combination of many other factors such as nutrient concentrations, nitrifier abundance and dissolved oxygen (DO) concentrations. In addition to aerobic respiration, nitrification contributed significantly to the consumption of DO and production of free CO 2 at upper estuary. Nitrification-induced consumption accounted for up to approximately one third of the total waCorrespondence to: M. Dai (email@example.com) ter column community DO consumption in the upper estuary during the surveyed periods, boosting environmental stress on this large estuarine ecosystem.
BackgroundNumerous single nucleotide polymorphisms (SNPs) associated with complex diseases have been identified by genome-wide association studies (GWAS) and expression quantitative trait loci (eQTLs) studies. However, few of these SNPs have explicit biological functions. Recent studies indicated that the SNPs within the 3’UTR regions of susceptibility genes could affect complex traits/diseases by affecting the function of miRNAs. These 3’UTR SNPs are functional candidates and therefore of interest to GWAS and eQTL researchers.DescriptionWe developed a publicly available online database, MirSNP (http://cmbi.bjmu.edu.cn/mirsnp), which is a collection of human SNPs in predicted miRNA-mRNA binding sites. We identified 414,510 SNPs that might affect miRNA-mRNA binding. Annotations were added to these SNPs to predict whether a SNP within the target site would decrease/break or enhance/create an miRNA-mRNA binding site. By applying MirSNP database to three brain eQTL data sets, we identified four unreported SNPs (rs3087822, rs13042, rs1058381, and rs1058398), which might affect miRNA binding and thus affect the expression of their host genes in the brain. We also applied the MirSNP database to our GWAS for schizophrenia: seven predicted miRNA-related SNPs (p < 0.0001) were found in the schizophrenia GWAS. Our findings identified the possible functions of these SNP loci, and provide the basis for subsequent functional research.ConclusionMirSNP could identify the putative miRNA-related SNPs from GWAS and eQTLs researches and provide the direction for subsequent functional researches.
We examined the dynamics of dissolved inorganic nitrogen (DIN, nitrate + nitrite), dissolved inorganic phosphorus (DIP), and silicate (Si(OH) 4 ) in the northern shelf of the South China Sea in summer, which is under a complex hydrodynamic scheme largely shaped by river plume and coastal upwelling, along with the enhanced biological consumption of nutrients therein. The Pearl River plume, with high nutrient concentrations (, 0.1-14.2 mmol L 21 for DIN, , 0.02-0.10 mmol L 21 for DIP, and , 0.2-18.9 mmol L 21 for Si(OH) 4 ), occupied a large area of the middle shelf (salinity , 33.5). The nearshore area had high nutrient concentrations apparently sourced from subsurface nutrient-replete waters through wind-driven coastal upwelling. These nutrient levels were significantly elevated relative to those on the oligotrophic outer shelf where DIN, DIP, and Si(OH) 4 concentrations dropped to , 0.1 mmol L 21 , , 0.02-0.03 mmol L 21, and , 2.0 mmol L 21, respectively. A three end-member mixing model was constructed based on potential temperature and salinity conservation to assess biological consumption of inorganic nutrients, which was denoted by D and defined by the deviation from conservative mixing. In the coastal upwelling zone and deep chlorophyll maximum layer, the nutrient uptake ratio DDIN : DDIP was 16.7, which is the classic Redfield ratio. In contrast, in the river plume the uptake ratio was 61.3 6 8.7. We believed that an alternative non-DIP source likely contributed to this higher DIN : DIP consumption ratio in the river plume regime. Meanwhile, Si(OH) 4 showed predominant consumption in the river plume and a combination of regeneration and consumption along the path of the coastal upwelling current.
A novel graphene oxide (GO)-based nanofiltration membrane on a highly porous polyacrylonitrile nanofibrous mat (GO@PAN) is prepared for water treatment applications. GO with large lateral size (more than 200 μm) is first synthesized through an improved Hummers method and then assembled on a highly porous nanofibrous mat by vacuum suction method. The prepared GO@PAN membrane is characterized by scanning electron microscopy, transmission electron microscopy, Raman spectrum, X-ray diffraction, and so forth. The results show that graphene oxide can form a barrier on the top of a PAN nanofibrous mat with controllable thickness. The obtained graphene oxide layer exhibits "ideal" pathways (hydrophobic nanochannel) for water molecules between the well-stacked GO nanosheets. Water flux under an extremely low external pressure (1.0 bar) significantly increased due to the unique structure of the GO layer and nanofibrous support. Furthermore, the GO@PAN membrane shows high rejection performance (nearly 100% rejection of Congo red and 56.7% for Na2SO4). A hydrophilic-hydrophobic "gate"-nanochannel model is presented for explaining the water diffusion mechanism through the GO layer. This method for fabrication of the GO membrane on a highly porous support may provide many new opportunities for high performance nanofiltration applications.
Abstract. We assess the relative contributions of different sources of organic matter, marine vs. terrestrial, to oxygen consumption in an emerging hypoxic zone in the lower Pearl River Estuary (PRE), a large eutrophic estuary located in Southern China. Our cruise, conducted in July 2014, consisted of two legs before and after the passing of Typhoon Rammasun, which completely de-stratified the water column. The stratification recovered rapidly, within 1 day after the typhoon. We observed algal blooms in the upper layer of the water column and hypoxia underneath in bottom water during both legs. Repeat sampling at the initial hypoxic station showed severe oxygen depletion down to 30 µmol kg −1 before the typhoon and a clear drawdown of dissolved oxygen after the typhoon. Based on a three endmember mixing model and the mass balance of dissolved inorganic carbon and its isotopic composition, the δ 13 C of organic carbon remineralized in the hypoxic zone was −23.2 ± 1.1 ‰. We estimated that 65 ± 16 % of the oxygen-consuming organic matter was derived from marine sources, and the rest (35 ± 16 %) was derived from the continent. In contrast to a recently studied hypoxic zone in the East China Sea off the Changjiang Estuary where marine organic matter dominated oxygen consumption, here terrestrial organic matter significantly contributed to the formation and maintenance of hypoxia. How varying amounts of these organic matter sources drive oxygen consumption has important implications for better understanding hypoxia and its mitigation in bottom waters.
Severe sepsis associated with overproduction of tumor necrosis factor α and reactive oxygen species leads to energy depletion and cellular damage. Both reactive oxygen species and damaged organelles induce autophagy for recycling nutrients to combat pathological stress. To study whether autophagy plays a beneficial role in the pathogenesis of renal failure during sepsis, rats were subjected to cecal ligation and puncture (CLP) or sham operation. Temporal relationship of autophagy and renal dysfunction were examined in vivo. The results showed that the level of lipidated microtubule-associated protein light chain 3 (LC3-II), a marker of autophagy, elevated transiently at 3 h but declined at 9 h until 18 h after CLP. Light chain 3 aggregation in renal tissue showed a similar trend to the change of LC3-II protein. High levels of blood urea nitrogen and creatinine as well as low tubular sodium reabsorption occurred at 18 h after CLP. The distribution of autophagy located primarily in angiotensin-converting enzyme-positive, which is concentrated in proximal tubule, but calbindin D28k (calcium-binding protein D28K, a marker of distal tubule)-negative cells in renal cortex. Therefore, NRK-52E (proximal tubule epithelial cell line) cells were used to further examine cell viability and DNA fragmentation after silencing or inducing autophagy. We found that knockdown of Atg7 (autophagy-related gene 7) exaggerates, whereas preincubation of rapamycin (an autophagy inducer) diminishes tumor necrosis factor α-induced cell death. These results suggest that the decline of sepsis-induced autophagy contributes to the proximal tubular dysfunction, and maintenance of sufficient autophagy prevents cell death. These data open prospects for therapies that activate autophagy during sepsis.
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