Effect of short-term nitrogen deposition on dry-wet seasonal variation of soil respiration in degraded Poa pratensis alpine meadow of the Napahai, Yunnan, China.

To explore the coupling of dry-wet seasonal variations of soil respiration with their environmental factors in the alpine meadow under the background of increasing nitrogen (N) deposition, we conducted an experiment in the typical degraded Poa pratensis meadow in the Napahai, Yunnan. There were four treatments, i.e., control (0 g·m-2·a-1), low (5 g·m-2·a-1), medium (10 g·m-2·a-1), and high (15 g·m-2·a-1) levels. We examined the effects of aboveground biomass, plant diversity, and soil physicochemical properties on soil respiration. The results showed that N deposition significantly promoted soil respiration. Compared with that in the control, soil respiration rates increased by 21.9%-53.9% and 27.3%-51.2% in dry and wet seasons, respectively. The maximum value of soil respiration rate was recorded in the medium N treatment. N deposition dramatically elevated aboveground biomass (52.2%-66.4%). Plant diversity declined with increasing N addition levels, with the maximum value (13.5%-24.2%) being recorded in high treatment in wet season. The values of ammonium nitrogen, organic matter, microbial biomass carbon and nitrogen, temperature and moisture in the three N treatments were elevated by 14.3%-333.5% compared with the control, while those of soil pH were decreased by 9.0%-34.6%. Results of the structural equation modelling showed that plant biomass, Shannon diversity, microbial biomass, soil temperature, and moisture showed a positive effect on soil respiration, while bulk density had a negative effect. Soil nitrogen pool and pH were main factors driving soil CO2 emissions, accounting for 55.7% and 45.1% of the variations, respectively. Therefore, short-term atmospheric N deposition stimulated soil respiration primarily via altering soil pH and nitrogen pool components in the degraded alpine meadow.

Effects of vegetation and soil changes on microbial biomass carbon and nitrogen in the Napahai meadow under N deposition.

To explore the responses of soil microorganisms to short-term nitrogen deposition in alpine meadow, we set three treatments of low nitrogen (5 g N·m-2·a-1), medium nitrogen (10 g N·m-2·a-1), and high nitrogen (15 g N·m-2·a-1) addition to investigate the effects of nitrogen-deposition induced alterations in plant diversity and soil physicochemical properties on microbial biomass carbon (MBC) and nitrogen (MBN) in a typical alpine meadow community of Carex nubigena in Napahai. The results showed that nitrogen addition significantly increased soil MBC, MBN, and their quotients, with the increases of MBC being as high as 139.3% under medium nitrogen treatment. Both MBC and MBN showed significant decreases along the soil layer, with a reduction of 24.1% to 75.1%. Nitrogen addition significantly increased aboveground biomass and reduced Shannon and Simpson indices by 6.6%-65.4%. Nitrogen addition significantly decreased soil pH, increased the contents of organic matter, total nitrogen, ammonium nitrogen and nitrate nitrogen, with the highest reduction (7.0%-511.1%) being observed in medium nitrogen treatment. Soil pH increased while other physical and chemical indicators significantly decreased with the increases of soil layer, with a variation range of 19.5%-91.2%. Results of structural equation model showed that microbial biomass was significantly positively correlated with ammonium nitrogen, nitrate nitrogen and organic matter, but negatively correlated with pH and Shannon index. The interaction of plant and soil physicochemical properties explained 55%-77% of the variations in MBC, MBN and their quotient. Soil physicochemical properties had the highest effect value (0.56-0.95) on MBC, MBN and their quotients, followed by plant diversity and aboveground biomass. Therefore, nitrogen deposition increased soil MBC and MBN and their quotient, primarily through improving soil nutrient availability and plant aboveground biomass, whereas MBC and MBN and their quotient were suppressed by high-level nitrogen deposition due to soil acidification and plant diversity losses.

The effect of peer victimization on adolescents' revenge: the roles of hostility attribution bias and rumination tendency.

Although previous studies revealed that peer victimization was closely related to revenge, mechanisms underlying this association have been unclear. The purpose of this study is to examine the mediating role of hostility attribution bias (HAB) and the moderating role of rumination tendency in the relationship between peer victimization and revenge. The data were collected from 6,622 adolescents. The PROCESS macro of SPSS 26.0 was used to examine the hypotheses. The results show that peer victimization positively associates with revenge. Hostile attribution bias play a partial mediating role between peer victimization and revenge. Both the direct effect of peer victimization on revenge and the first half of the mediating effect of HAB are moderated by rumination tendencies. Specifically, both direct and indirect effects of peer victimization on revenge are stronger in individuals with concrete experiential rumination (CER) tendency than in those with abstract analytic rumination (AAR) tendency.

[Synergistic anti-tumor effect of obatoclax and MG-132 in esophageal cancer cell line CaES-17].

OBJECTIVE: To explore whether MG-132 could enhance the anti-tumor activity of obatoclax against esophageal cancer cell line CaES-17. METHODS: MTT assay was used to determine the cytotoxicity of obatoclax and MG-132 in CaES-17 cells. The IC(50) of obatoclax and MG-132 were used to determine the molar ratio (1:2.4) of the two drugs for combined treatment of the cells. The concentrations of obatoclax and MG-132 ranged from 1/8 IC(50) to 4 IC(50) after serial dilution, and their combination index (CI) was calculated using CompuSyn software. The expression of ubiquitin and the cleavage of PARP, caspase-9, phospho-histone H3 and phospho-aurora A/B/C in the exposed cells were examined with Western blotting; the cell apoptosis was measured by flow cytometry with Annexin V staining, and the percentage of cells in each cell cycle phase was also determined by flow cytometry. RESULTS: The CI of obatoclax and MG-132 was 0.296 for a 50% inhibition of Caes-17 cells and was 0.104 for a 95% inhibition. The cells treated with obatoclax or MG-132 alone showed increased expression of ubiquitin and cleavage of PARP and caspase-9. Compared with the cells treated with obatoclax or MG-132 alone, the cells with a combined treatment exhibited significantly increased expression of ubiquitin, cleavage of PARP and caspase-9, and expression of phospho-Histone H3 (P<0.05). The combined treatment of the cells also resulted in significantly increased expression of phospho-Aurora A/B/C compared with obatoclax treatment alone. The cells with the combined treatment showed significantly higher percentages of apoptotic cells and cells in sub-G(1) and G(2)/M phases compared with the cells treated with either of the drugs (P<0.05). CONCLUSION: Obatoclax combined with MG-132 shows a significant synergistic anti-tumor effect against esophageal cancer CaES-17 cells by inducing apoptosis and cell cycle arrest.

Frequency- and state-dependent blockade of human ether-a-go-go-related gene K+ channel by arecoline hydrobromide.

BACKGROUND: The rapidly activating delayed rectifier potassium current (I(Kr)), whose pore-forming alpha subunit is encoded by the human ether-a-go-go-related gene (hERG), is a key contributor to the third phase of action potential repolarization. The aim of this study was to investigate the effect and mechanism of arecoline hydrobromide induced inhibition of hERG K(+) current (I(hERG)). METHODS: Transient transfection of hERG channel cDNA plasmid pcDNA3.1 into the cultured HEK293 cells was performed using Lipofectamine. A standard whole-cell patch-clamp technique was used to record the I(hERG) before and after the exposure to arecoline. RESULTS: Arecoline decreased the amplitude and the density of the I(hERG) in a concentration-dependent manner (IC(50) = 9.55 mmol/L). At test potential of +60 mV, the magnitude of I(hERG) tail at test pulse of -40 mV was reduced from (151.7 ± 6.2) pA/pF to (84.4 ± 7.6) pA/pF (P < 0.01, n = 20) and the magnitude of I(hERG) tail at test pulse of -110 mV was reduced from (-187.5 ± 9.8) pA/pF to (-97.6 ± 12.6) pA/pF (P < 0.01, n = 20). The blockade of arecoline in the open and inactivated state was significant in a state-dependent manner. The maximal blockade was achieved in the inactivated state. Studies of gating mechanism showed that the steady-state activation curve of I(hERG) was significantly negatively shifted by arecoline. Time constants of activation were shortened. Steady-state inactivation curve and time constants of fast inactivation were not significantly affected by arecoline. Furthermore, the inhibition of I(hERG) by arecoline was characterized markedly by a frequency-dependent manner from 0.03 to 1.00 Hz pulse. CONCLUSION: Arecoline could potently block I(hERG) in both frequency and state-dependent manner.