Linking fluorescent dissolved organic matters to microbial carbon metabolism in the overlying water during submerged macrophyte Potamogeton crispus L decomposition in the presence/absence of Vallisneria natans.

Multi-species submerged plants grow with succession patterns in the same habit and play an important role in the aquatic ecosystems. The decomposition of submerged plants in aquatic environments was a disturbance that affected the water quality and microbial community structures. However, the responses of the microbial community function in surface water to the disturbance remain poorly understood. In this study, the effects of submerged macrophyte Potamogeton crispus L decomposition on the water quality and microbial carbon metabolism functions (MCMF) in the overlying water were investigated in the presence/absence of Vallisneria natans. The result showed that the decomposition rapidly released a large amount of organic matter and nutrients into the overlying water. The presence of Vallisneria natans promoted the removal of dissolved organic carbon and fluorescent component C3, resulting in lower values of the percentage content of C3 (C3%). Under various decomposition processes, the MCMF changed over time and significantly negatively correlated with C3%. The functional diversity of MCMF significantly correlated with the fluorescence organic matters, such as the richness and Simpson index correlated with the amount of C1, C1+C2+C3, and C3%. But UV-visible absorption indexes and nutrients in the overlying water had no relationship with the MCMF, except for the total nitrogen correlated with the richness. These results suggested that under various decomposition conditions, the fluorescent dissolved organic matter could be used as an indicator for quick prediction of MCMF in surface water.

Propofol Attenuates Inflammatory Damage via Inhibiting NLRP1-Casp1-Casp6 Signaling in Ischemic Brain Injury.

Stroke is a common cerebrovascular disease. Inflammation-induced neuronal death is one of the key factors in stroke pathology. Propofol has been shown to ameliorate neuroinflammatory injury, but the exact mechanism of its neuroprotective role remains to be fully elucidated. In the present study, we found that inflammation was activated in ischemic cortical neurons, and the expression of nucleotide-binding domain, leucine-rich-repeat containing family, pyrin domain-containing 1 (NLRP1), NLRP3 inflammasome and effectors in primary cortical neurons increased. However, we found that propofol could inhibit the increased expression of NLRP1 and NLRP3 inflammasome induced by oxygen-glucose deprivation (OGD). Furthermore, the effector molecule caspase-1 (casp1) was revealed to be the downstream target of NLRP1 and propofol repressed the activation of caspase-1 via inhibiting NLRP1 in cortical neurons. Moreover, propofol inhibits caspase-6 activation in neurons through the NLRP1-caspase-1 pathway. Once the expression of caspase6 increases, propofol reduced its neuroprotective effect in OGD-treated cortical neurons. In the stroke middle cerebral artery occlusion (MCAO) model, infusion of caspase-6 inhibitors enhanced the protective effect of propofol on infarct size and neurological function. In conclusion, our results suggest that propofol plays a neuroprotective role in stroke by inhibiting the inflammatory pathway of NLRP1-caspase-1-caspase-6. Overall, these data suggest that propofol plays a key role in the inflammatory-dependent pathway after stroke, providing an important evidence for propofol as an effective strategy for neuroprotection in stroke.

Adsorption and molecular weight fractionation of dissolved organic matters with different origins on colloidal surface.

Dissolved organic matter (DOM) adsorption on colloid surface occurred ubiquitously in aquatic ecosystems, while variations in molecular weight (MW) distribution during adsorption remained poorly understood. In this study, the adsorption and MW fractionation of aquatic DOMs with different origins (e.g., macrophyte- and algae-derived, MDOM and ADOM, respectively) on colloid surface were examined using total organic carbon, absorption and fluorescence spectroscopy, and flow field flow fractionation (FlFFF) analysis. Both the total organic carbon and spectroscopic results showed the predominant adsorption of DOMs within the first 45 min, which behaved not synchronously with MW fractionation. Quantitative FlFFF analysis further indicated that the organic ligands with different MWs exhibited different adsorption affinities on colloid surface. It was found that 5-15 kDa and 50 kDã0.45 µm were preferential adsorption fraction for humic- and protein-like MDOM, respectively, while 0.3-2 kDa and 0.3-50 kDa were preferential adsorption fraction for humic- and protein-like ADOM, respectively. Therefore, the MW fractionation of DOMs upon adsorption was highly dependent on DOM origins as well as specific components. Results obtained herein can enlarge our insights into adsorption and the resultant behavior and fate of DOMs that were highly related with the MW fractionation in aquatic environments.

[Phosphorus threshold for the shift between grass- and algae-stable states in Dahong Harbor of Gehu Lake].

Taking the macrophytes remaining area in Dahong Harbor of Gehu Lake as test object, this paper studied the phosphorus threshold for the shift between grass- and algae-stable states under natural conditions. The correlation analysis on the environmental factors showed that the total phosphorous in water body had better liner relationships with phytoplankton chlorophyll a and Secchi depth, and principal component analysis indicated that total phosphorous and nitrogen in the water body were the two main components affecting the water quality, among which, total phosphorous was the maximum weight source and played a determinant role in the shift between grass- and algae-stable states. The Harbor was in grass-stable state in winter, shifted to grass-algae intermediate state in spring, and kept the intermediate state in summer and autumn. The total phosphorous threshold for grass-stable state shifting to grass-algae intermediate state was 61 microg x L(-1), and that for grass-algae intermediate state shifting to algae-stable state was 115 microg x L(-1). In order to make the ecosystem shift from algae-stable state to grass-stable state, some measures such as cutting and controlling the Lake's nutrient sources, removing the sediment rich in organic matter, and constructing submerged macrophytes areas should be adopted to make the total phosphorous threshold in the water body dropped to below 61 microg x L(-1).

[Dynamics model analysis of pollutants removal in aerated vertical-flow wetland].

Based on the dynamic model building of pollutants removal in aerated vertical-flow constructed wetland, data of the wetland under different aeration conditions were analysed. Different aeration conditions' k values were calculated, which represented the pollutants removal kinetic constants. The results demonstrate that the efficiency of pollutants removal is higher with the increasing gas-water ratio. The most favorable designing gas-water ratio of the aerated vertical-flow constructed wetland was chosen as 2 : 1 through analysis of curve fits by regression with kinetic constants values and gas-water ratio values. The corresponding k values of BOD5 and NH4(+) -N are 3.8 d(-1) and 4.1 d(-1) respectively.

[Oxygen transfer efficiency of four kinds substrates applied in artificial aeration vertical-flow wetland].

In subsurface flow constructed wetlands, artificial aeration plays an important role in enhancing the ability of pollutant removal. Oxygenation capacity of four substrates, limestone, vesuvianite, 500 grade ceramisite and high-strength ceramisite, are tested under three kinds of gas volume [0.19, 0.38, 0.76 m3 x (m2 x h)(-1)] in artificial aeration vertical-flow wetland. When the gas volume is 0.19 m3 x (m2 x h)(-1), the results demonstrate that the oxygen utilization of 500 grade ceramisite and high-strength ceramisite are highest as 14.39% and 14.21%, and the oxygen utilization of limestone and vesuvianite are 11.68% and 13.11% respectively. With the increase of aeration intensity, oxygen transfer efficiency parameter KLa rises accordingly. However, the oxygen utilization of vesuvianite and two other kinds of ceramisite decreases with the increase of aeration intensity. The oxygen utilization of vesuvianite, 500 grad ceramisite and high-strength ceramisite are lower as 7.67%, 10.46% and 10.77% respectively when the aeration intensity is 0.76 m3 x (m2 x h)(-1). On the contrary, the oxygen utilization of limestone get its maximum value of 14.04% as the aeration intensity is 0.38 m3 x (m2 x h)(-1).

[Spatial distribution and its environmental analysis of chironomid larvae in Fuxian Lake of Yunnan Province].

A field survey was made on the chironomid larvae in Fuxian Lake of Yunnan Province from June to July 2005. A total of 6 species belonging to 5 genera were collected, among which, Procladius choreus and Chironomous plumosus were the dominant species, with a sum of their relative density and of relative biomass being 94.9% and 97.5%, respectively. The average density of chironomid larvae in the lake was (275 +/- 333) ind x m(-2), and the average biomass was (0.642 +/- 0.763) g x m(-2) x P. choreus distributed all over the lake, C. plumosus mainly distributed in the water area at the south of Mingxingyudong, while other species distributed locally. Micropsectra sp., a typical species distributing in deep oligotrophic water, had an average distribution water depth of 107.2 m. The density of chironomid larvae had a significant positive correlation with water depth, and increased in the sequences of sand or gravel bottom < sand bottom < mud bottom, and submerged macrophyte area < no submerged macrophyte area. Compared with the survey data around 1980, the occurrence frequency and standing stock of chironomid larvae increased greatly, and the indicator species C. plumosus for eutrophic water appeared, indicating that the nutritional level of Fuxian Lake was being improved.