Distribution characteristics and potential release risk of nitrogen in sediments in Lake Daihai, China.

Nitrogen (N) in sediments was a key element of lake eutrophication. The spatial distribution characteristics of four parts N in surface sediments were investigated by sequential extraction method, including free nitrogen (FN), exchangeable nitrogen (EN), hydrolyzable nitrogen (HN), and residual nitrogen (RN). Modified models were utilized to describe the adsorption isotherms of ammonia nitrogen (NH4+-N) in sediments and thus predict the risk of N release. The correlation between environmental factors and N concentration was discussed, as well as the migration or transformation and release risk of N between different mediums. The results showed that spatial variations characteristics of N fractions were influenced by the lake topography and surrounding human activities. The content of total nitrogen (TN) in the sediments was 933.4 ~ 3006.8 mg/kg, with an average of 1835 mg/kg. The HN, RN, FN, and EN in sediments accounted for 66.85%, 21.35%, 6.82%, and 4.92% of TN, respectively. There was a significant correlation between each fraction of N and TN and also between different fractions of N (p < 0.01). Fitting by modified Langmuir model indicated that the adsorbed amounts of N in the sediments at maximum (Qmax) was, from greatest to least, southeast lake (2905.3 mg/kg) > southwest lake (1415.4 mg/kg) ≈ north lake (1424.6 mg/kg). Environmental parameters (pH, DO, C/N, etc.) affected the occurrence fraction of nitrogen, which could cause the persistent and increased risk of sustained release of high concentrations of endogenous N. N pollution in sediment and interstitial water is severe, and the risk of endogenous N release will gradually increase in the future.

Geochemistry and release risk for nutrients in lake sediments based on diffusive gradients in thin films.

A comprehensive understanding of the mobility of both nitrogen (N) and phosphorus (P) and the inter-relationships between P, N, and iron (Fe) in sediments is important for controlling the "internal loadings" of nutrients in lakes. In this research, diffusive gradients in thin film (DGT) assemblies with binding layers (ZrO-AT, chelex, and ZrO) were designed for PO4-P, Fe, ammonium (NH4-N), and nitrate (NO3-N) at sediment/water interface (SWI) in Western Lake Taihu (China). The biogeochemical processes of N and P related to the physicochemical properties, the dynamic P transfer, the distribution characteristics of P microniches, and the estimation of the release risks in sediments in Western Lake Taihu were simultaneously revealed by the passive sampling technique-DGT with the high spatial resolutions (millimeter and sub-millimeter). Based on DGT concentration (CDGT) related to physicochemical properties in sediments, (1) P biogeochemical reactions included P release from Fe-bound P during Fe reduction, algae biomass decomposition, and phosphatase enzyme activity increased by NH4-N; (2) denitrification and dissimilatory nitrate reduction to ammonium (DNRA) led to exchangeable ammonium (NH4ex) enrichment and NH4-N release; anammox depleted NH4-N transfer; organic matter (OM) mineralization favored NH4-N release; and (3) aerobic nitrification led to NO3-N remobilization; denitrification and DNRA reduced NO3-N release. Redox status, OM, Fe, aluminum, or calcium influenced mobilization of nutrients. The numerical model of DGT-induced fluxes in sediments was used for dynamic P transfers with resupply types ("slow" ~ "fast") controlled by labile P pool, resupply constant, response time, and Dspt rate. The formation of P microniches in two dimensions was revealed. Sediment P release risk index (0.49 ~ 36.85 [lg (nmol cm-3 d-1)]) with "light" ~ "high" risks and diffusive fluxes across SWI (µg m-2 d-1) of 15.0 ~ 639 (PO4-P), - 1403 ~ 5010 (NH4-N), and - 1395 ~ 149 (NO3-N) were derived and lake management strategies were provided. The DGT technique provides the characterization of the mobilization of nutrients and evidence for biogeochemical processes at the fine spatial scales for control of internal loadings in sediments.

[Structural Characteristics of Zooplankton and Phytoplankton Communities and Its Relationship with Environmental Factors in Different Regions of Nanhu Lake in Jiaxing City].

Nanhu Lake is a red tourist attraction in Jiaxing city and the birthplace of the "Red Boat Spirit."To identify the influence of environmental factors on the distribution of plankton communities after ecological restoration in different regions, the environmental factors and plankton community in areas A, B, C, D, and S of Nanhu Lake were investigated in January 2021 after the completion of the ecological restoration projects. The concentrations of total nitrogen(TN), dissolved total nitrogen (DTN), ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3--N), total phosphorus (TP), and dissolved total phosphorus (DTP) in the ecological restoration areas were significantly lower, and the content of dissolved oxygen (DO) was significantly higher (P<0.05) than those in the non-restoration area. The main phytoplankton species in the study area belonged to Cyanophyta and Bacillariophyta, and the main zooplankton species were protozoans and rotifers. The phytoplankton biomass in the restored area was lower than that in the unrestored area, and the number of phytoplankton and zooplankton species increased. Clustering and principal coordinate analysis results showed significant differences in plankton communities among the restoration areas (P<0.05), and plankton structures in regions A and B were similar. Redundancy analysis (RDA) showed that the main environmental factors affecting the distribution of phytoplankton communities were DO, NO3--N, pH, and water temperature (WT). The main driving factors of zooplankton community distribution were DO, NO3--N, NH4+-N, and TP. The results clarified the phytoplankton community characteristics and environmental correlation in different regions of Nanhu Lake, which can provide data support and reference for water ecological restoration of the lake.

[Phosphorus Adsorption Characteristics and Loss Risk in Sediments of Lake Bay During the Overwinter Period of Cyanobacteria].

The overwinter period is the pre-stage of the algal bloom, and the endogenous phosphorus (P) in sediments is one of the main P sources of algal blooms during this period. Based on the investigation of the water quality and sediment pollutants during the overwinter period of cyanobacteria (recruitment period and dormancy period), this study analyzed the P release characteristics of sediments in the horizontal and vertical directions and clarified the P release risk of sediments and the change in microbial community structures. The results showed that the lake bay was moderately eutrophic in the two periods of the study area, and the water quality and sediment nitrogen and P pollution were more serious, and the chlorophyll a content (Chl-a) was still at a high level in the overwinter period. The pseudo-second order model and the modified Langmuir model could respectively describe the P kinetics and sorption isotherm behavior in the sediment. The theoretical maximum P sorption capacities (Qmax) of sediments were bottom layer>middle layer>surface layer, and the highest value was 1.648 mg·g-1 with the highest P sorption rate constant of the pseudo second-order kinetic model of 6.292 g·(mg·min)-1. Additionally, the P adsorption parameters (Qmax, NAP, and EPC0) were mainly affected by the physical and chemical properties of the sediment itself and the nutritional level of the lake bay. The surface sediments from the dormancy period mainly played the role of P sinks, and the part of sediments from the recruitment period played the role of P sources, in which existed the risk of endogenous P release. The analysis of the microbial community structure in sediments indicated that the microbial diversity in the sediments during the dormancy period was higher than that during the recruitment period, and some microbial categories with phosphate-solubilizing function of relative abundance was high.

The C-terminal cysteine-rich motif of NYE1/SGR1 is indispensable for its function in chlorophyll degradation in Arabidopsis.

KEY MESSAGE: The C-terminal cysteine-rich motif of NYE1/SGR1 affects chlorophyll degradation likely by mediating its self-interaction and conformational change, and somehow altering its Mg-dechelating activity in response to the changing redox potential. During green organ senescence in plants, the most prominent phenomenon is the degreening caused by net chlorophyll (Chl) loss. NON-YELLOWING1/STAY-GREEN1 (NYE1/SGR1) was recently reported to be able to dechelates magnesium (Mg) from Chl a to initiate its degradation, but little is known about the domain/motif basis of its functionality. In this study, we carried out a protein truncation assay and identified a conserved cysteine-rich motif (CRM, P-X3-C-X3-C-X-C2-F-P-X5-P) at its C terminus, which is essential for its function. Genetic analysis showed that all four cysteines in the CRM were irreplaceable, and enzymatic assays demonstrated that the mutation of each of the four cysteines affected its Mg-dechelating activity. The CRM plays a critical role in the conformational change and self-interaction of NYE1 via the formation of inter- and intra-molecular disulfide bonds. Our results may provide insight into how NYE1 responds to rapid redox changes during leaf senescence and in response to various environmental stresses.

Comparison among the microbial communities in the lake, lake wetland, and estuary sediments of a plain river network.

Sediment microbial communities from plain river networks exert different effects on pollutant transformation and migration in lake basins. In this study, we examined millions of Illumina reads (16S rRNA gene amplicons) to compare lake, lake wetland, and estuary bacterial communities through a technically consistent approach. Results showed that bacterial communities in the sampled lake sediments had the highest alpha-diversity (Group B), than in sampled lake wetland sediments and estuary sediments. Proteobacteria was the most abundant (more than 30%) phyla in all the sediments. The lake sediments had more Nitrospirae (1.63%-11.75%) and Acidobacteria (3.46%-10.21%) than the lake wetland and estuary sediments, and estuary sediments had a greater abundance of the phylum Firmicutes (mean of 22.30%). Statistical analysis (LEfSe) revealed that lake wetland sediments contained greater abundances of the class Anaerolineaceae, orders Xanthomonadales, Pseudomonadales, and genera Flavobacterium, Acinetobacter. The lake sediments had a distinct community of diverse primary producers, such as phylum Acidobacteria, order Ignavibacteriales, and families Nitrospiraceae, Hydrogenophilaceae. Total phosphorus and organic matter were the main factors influencing the bacterial communities in sediments from several parts of the lake wetland and river estuary (p < .05). The novel insights into basin pollution control in plain river networks may be obtained from microbial distribution in sediments from different basin regions.

Asiatic Acid Prevents Retinal Ganglion Cell Apoptosis in a Rat Model of Glaucoma.

Asiatic acid (AA), a pentacyclic triterpene derived from the tropical medicinal plant Centella asiatica, has been widely used as an antioxidant and anti-inflammatory agent. Evidence regarding the neuroprotective properties of AA is emerging. However, the protective effects of AA and its mechanism in glaucoma are poorly understood. In the current study, we investigate the neuroprotective effect and mechanism of AA on retinal ganglion cells (RGCs) in a rat model of glaucoma. Elevated intraocular pressure (IOP) was induced in adult rats by injecting microspheres into the anterior chamber. AA was intravitreally injected into glaucomatous rats. RGC densities were analyzed by evaluating surviving RGC number of the retinal flatmounts and retinal sections, and the apoptotic cell number were evaluated by analyzing retinal sections. RGC function was assessed by measuring the photopic negative response (PhNR). Retinal Bcl-2, Bax, and cleaved caspase-3 expression were determined using a Simple Western System, real-time PCR and immunofluorescence staining. AA reduced the loss of RGCs and decreased the apoptotic RGC number. AA exerted neuroprotective effects and ameliorated retinal dysfunction in impaired RGCs in a rat model of glaucoma. AA protected RGCs by upregulating the expression of the antiapoptotic protein Bcl-2 and downregulating the expression of the pro-apoptotic proteins Bax and caspase-3. This study has provided important evidence indicating that AA may be a potential therapeutic agent for glaucoma.

[Strategies of preserving urinary continence in transurethral plasmakinetic enucleation of the prostate for benign prostate hyperplasia].

OBJECTIVE: To explore the strategies of preserving urinary continence in transurethral plasmakinetic enucleation of the prostate (PKEP) for benign prostate hyperplasia (BPH). METHODS: We treated 65 BPH patients by PKEP with preservation of urinary continence (UC-PKEP), which involved protection of the external urethral sphincter in the beginning of surgery, proper preservation of the anterior lobe of the prostate to protect the internal urethral sphincter in the middle, and preservation of the integrity of the bladder neck towards the end. We compared the postoperative status of urinary continence of the patients with that of the 54 BPH cases treated by complete plasmakinetic enucleation of the prostate (Com-PKEP). RESULTS: All the operations were performed successfully with the urinary catheters removed at 5 days after surgery. In comparison with Com-PKEP, UC-PKEP achieved evidently lower incidence rates of urinary incontinence at 24 hours (31.49% vs 13.85%, P <0.05), 1 week (18.52% vs 4.62%, P <0.05), 2 weeks (14.81% vs 3.08%, P <0.05), 1 month (3.70% vs 1.54%, P >0.05), and 3 months (3.70% vs 0%, P >0.05) after catheter removal. Compared with the baseline, the maximum urinary flow rate (Qmax) was significantly improved postoperatively in both the Com-PKEP (ï¼»7.43 ± 3.26ï¼½ vs ï¼»20.58 ± 3.22ï¼½ ml, P <0.05) and the UC-PKEP group (ï¼»8.04 ± 2.28ï¼½ vs ï¼»20.66 ± 3.08ï¼½ ml, P <0.05). CONCLUSIONS: Transurethral PKEP is a safe and effective method for the management of BPH, during which the strategies of avoiding blunt or sharp damage to the external urethral sphincter in the beginning, properly preserving the anterior lobe of the prostate in the middle and preserving the integrity of the bladder neck towards the end may help to achieve rapid recovery of urinary continence.

The anti-aging effects of Ludwigia octovalvis on Drosophila melanogaster and SAMP8 mice.

We investigated the anti-aging effects of Ludwigia octovalvis (Jacq.) P. H. Raven (Onagraceae), an extract of which is widely consumed as a healthful drink in a number of countries. Using the fruit fly, Drosophila melanogaster, as a model organism, we demonstrated that L. octovalvis extract (LOE) significantly extended fly lifespan on a high, but not a low, calorie diet, indicating that LOE may regulate lifespan through a dietary restriction (DR)-related pathway. LOE also attenuated age-related cognitive decline in both flies and in the senescence-accelerated-prone 8 (SAMP8) mouse, without causing any discernable negative trade-offs, including water intake, food intake, fecundity, or spontaneous motor activity. LOE contained high levels of polyphenols and flavonoids, which possess strong DPPH radical scavenging activity, and was shown to attenuate paraquat-induced oxidative damage and lethality in flies. Gas chromatography-mass spectrometry (GC-MS) analyses identified 17 known molecules, of which ß-sitosterol and squalene were the two most abundant. We further demonstrated that ß-sitosterol was capable of extending lifespan, likely through activating AMP-activated protein kinase (AMPK) in the fat body of adult flies. Taken together, our data suggest that LOE is a potent anti-aging intervention with potential for treating age-related disorders.

[Correlation and path analysis of artemisininum content and related factor on Artemisiae annie in Three Gorges reservoir area].

OBJECTIVE: Study on the correlation and path analysis of artemisininum comtent and related factor on Artemisiae annie. In order to obtain high artemisininum content Artemisiae annie. METHODS: On the natural condition, choose 36 area where Artemisiae annie growth in three gorges reservoir area. The related factor on artemisininum content are studies through correlation and path analysis. RESULTS: The artemisininum content had significant correlations with biomass, over cover degree, K, P, and N in soil. P in soil had the nost positive influence on the artemisininum content with the direct path coefficinent 0.3439, over cover degree had the nost negative in fluence on the artemisininum content with the direct path coefficient -0.1421. The influence order of other factor was N in soil (0.3180), K in soil (0.2352), biomass ( -0.0084), and plant height (-0.0347). CONCLUSION: Artemisininum content in Artemisiae annie leaves are correlated with biomass, over cover degree, K in soil, P in soil, N in soil.