Z.H. Zhang

Impact of tillage erosion on water erosion in a hilly landscape.

Little has been known of the interaction between tillage erosion and water erosion, while the two erosion processes was independently studied. Can tillage-induced soil redistribution lead to exaggerated (or retarded) runoff flow and sediment concentrations in steeply sloping fields? A series of simulated tillage and artificial rainfall events were applied to rectangular runoff plots (2m×8m) with a slope of 15° to examine the impacts of tillage erosion intensities on water erosion in the Yangtze Three Gorges Reservoir Area, China. Mean flow velocity, effective/critical shear stress, and soil erodibility factor K were calculated to analyze the differences in hydrodynamic characteristics induced by tillage. Our experimental results suggest that mean runoff rates were 2.26, 1.19, and 0.65Lmin(-1) and that mean soil detachment rates were 1.53, 1.01, and 0.61gm(-2)min(-1) during the 70-min simulated rainfall events for 52-, 31-, and 10-year tillage, respectively. A significant difference (P<0.05) in cumulative detachment amounts was found among different tillage intensities. Compared with the soil flux of 0kgm(-1), cumulative detachment amounts for the soil fluxes of 9.86 and 24.72kgm(-1) increased by 40.02% and 100.94%, respectively, during the 30-min rainfall event. The results imply that soil and water losses tended to increase with increasing tillage intensity. A significant difference in mean flow velocity occurred near the upper and lower slope boundaries of the field, while significant differences (P<0.05) in runoff depth and effective shear stress were observed among different slope positions. Soil erodibility factor K for the soil fluxes of 9.86 and 24.72kgm(-1) were 2.40 and 5.11 times higher, respectively, than that for the soil flux of 0kgm(-1). As tillage intensity increased, critical shear stress trended to gradually decrease for all soil fluxes. Our results indicate that tillage erosion increases soil erodibility and delivers the soil for water erosion in sloping fields, accelerating water erosion.

Immunomodulated signaling in macrophages: Studies on activation of Raf-1, MAPK, cPLA2 and secretion of IL-12

Little is known about the mechanism and signal transduction by LPS-mediated immunomodulation of murine peritoneal macrophages. It is found that the signal molecules of the down-stream of Ras, Raf-1, MAPK p44, and MAPK p42 are phosphorylated, and cPLA2 is activated with a significant increase of the release of [ H3 ] AA by macrophages in response to LPS and PMA. Compared with the very recent finding that LPS and PMA trigger the activation and translocation of PKC-α and PKC-ε, these findings suggest that there is a connection between PKC signaling pathway and the Raf-1/MAPK pathway and that the activation of these main signaling events may be closely related to the secretion of IL-12 during LPS-induced modulation of macrophages.

Heat shock response downregulates IL-18 expression in the murine macrophage cell line, RAW264.7

Heat shock response is a self-defense mechanism for protection of cells and organisms from a wide range of harmful Stressors. Recent studies revealed that it is involved in the regulation of cytokines expression. IL-18 is an important cytokine in mediating immune response. We studied LPS-induced IL-18 expression in heat shock treated RAW264.7 murine macrophages. Our results show that the heat shock response significantly inhibited the expression of LPS-induced pro-inflammatory cytokine IL-18. Further research on the down-regulation mechanism shows that this inhibitory effect is correlated to the great suppression of the binding activity of AP-1, which is a transcription factor binding to the promoter of IL-18 (−1120 to −1083) and regulates the transcription of IL-18. Meanwhile, we observed that the phosphorylation of JNK, which is AP-1 upstream kinase, was greatly decreased. These results confirmed that the down-regulation effect on IL-18 production in heat shock response is related to the suppression of the JNK/AP-1 signaling pathway.

Promoting effect of IFN-γ on the expression of LPS-induced IL-12 p40 and p35 mRNA in murine suppressor macrophages

We detected the expression of IL-12 p40/p35 mRNA by semi-quantitative RT-PCR and silver staining, and studied the molecular interaction between the IL-12 expression and the NF-eB activation induced by LPS and IFN-γ/LPS in murine peritoneal suppressor macrophages (MPSMs). It was found that IFN-γ strongly enhanced the LPS-induced IL-12 p40 and p35 mRNA expression. Both p40 and p35 mRNA levels were approximately equal. IFN-a also greatly promoted the LPS-induced secretion of IL-12 p70 in MPSMs. The Proteasome Inhibitor I (PSI) could block the expression of IL-12 p40 and p35 mRNA, and the degradation of IκBα induced by LPS or LPS/IFN-γ. EMSA showed that LPS could augment the NF-κB binding activity to p40 promoter DNA. However, IFN-γ could neither enhance the LPS-induced NF-κB activity nor promote the degradation of IκBα. Taken together, the data suggest: (i) IFN-γ/LPS could strongly induce the expression of IL-12 p40 and p35 mRNA; both the expression levels were equal; this phenomenon coincided with the high-level secretion of IL-12 p70 induced by IFN-γ/LPS; (ii) NF-κB signal pathway is essential for IFN-γ/LPS to induce IL-12 mRNA expression; (iii) by blocking the degradation of IκB, the PSI suppresses the IL-12 p40/p35 mRNA expression induced by LPS and IFN-γ/LPS; (iv) NF-κB signal may not be involved in the mechanism by which IFN-γ enhanced the expression of the LPS-induced IL-12 p40/p35 mRNA.

Effect of thermal injury on LPS-mediated Toll signaling pathways by murine peritoneal macrophages: inhibition of DNA-binding of transcription factor AP-1 and NF-κB and gene expression of c-fos and IL-12p40

Thermal injury is able to induce the immune functional inhibition in the host, but the mechanisms are largely unknown. The available evidence indicates that macrophages play an important role in immune regulations and host defenses. Thus, studies of the effect of thermal injury on macrophages are essential. Transcriptional factors of AP-1 (activator protein-1) and NF-κB (nuclear factor-κB) are critical members of signal transduction pathways. These transcriptional factors have been shown to be necessary for a variety of expressions of cytokine genes. In this investigation, the effect of thermal injury on AP-1 and NF-κB was studied using a model for the murine thermal injury. Our findings indicated that thermal injury mediated the inhibition of AP-1 and NF-κB DNA binding activities and c-fos and IL-12 p40 gene expressions in response to LPS.

Effect of tillage erosion on the distribution of CaCO3, phosphorus and the ratio of CaCO3/available phosphorus in the slope landscape

Little is known about the effect of tillage erosion on the distribution of CaCO3, phosphorus and changes in the ratio of CaCO3/available phosphorus (AP) in the hillslope landscape. The aims of the present study were to elucidate the mechanisms underlying changes in CaCO3 and AP concentrations induced by tillage erosion along slope transects and to reconstruct the historical changes in CaCO3 in soil layers at different landscape positions. Two adjacent slopes were selected from the Sichuan Basin, China, one with downslope tillage (Slope 1) and the other with upslope tillage (Slope 2) for 29 years. Then, consecutive downslope tillage by hoeing was applied five and 20 times on Slope 1. Under normal tillage (both downslope and upslope) conditions, CaCO3 concentrations increased exponentially with soil depth. However, the mixing effect of consecutive tillage (five and 20 tills) changed the vertical CaCO3 distribution patterns. For downslope tillage, the topsoil layer CaCO3 concentration was significantly lower at the toeslope than at other slope positions, but there were no significant differences between toeslope and other slope positions for upslope tillage. Consecutive tillage with five and 20 tills increased CaCO3 concentrations in the topsoil layer by 27.7% and 30.8% respectively compared with downslope tillage, but AP concentrations decreased by 26.1% and 29.0% respectively. Under normal tillage, AP concentrations decreased with increasing CaCO3 concentrations due to the adsorption and precipitation of AP by CaCO3, but this relationship disappeared after consecutive tillage. After consecutive tillage with five and 20 tills, the mean CaCO3/AP ratios of the topsoil layer were 93.5% and 88.4% greater than those for downslope tillage respectively, whereas there were no significant differences between downslope and upslope tillage. In conclusion, tillage is a process of CaCO3 replenishment and AP dilution in the surface layer of soil derived from carbonate-rich bedrocks.

Complete mitochondrial genome of Drosophila albomicans

Abstract Drosophila albomicans has been widely used as an important animal model for chromosome evolution. In this study, the mitochondrial genome sequence of this species is determined and described for the first time. The mitochondrial genome (15 849 bp) encompasses two rRNA, 22 tRNA, and 13 protein-coding genes. Genome content and structure are similar to those reported from other Drosophila mitochondrial genomes. Phylogeny analysis indicates that D. albomicans have a closer genetic relationship with Drosophil aincompta and Drosophil alittoralis. This mitochondrial genome is potentially important for studying molecular evolution and conservation genetics in Drosophila genus.