Research on Value Evaluation and Impact Mechanism of Water Ecological Services in Mountainous Cities: A Case Study of Xiangxi Prefecture

To have a more comprehensive understanding of the water ecological services of Xiangxi, the index system of water ecological service is constructed and the intensity of its influencing factors founded on the geographic detector model (GDM) is obtained in this paper. Then, the water ecological service index of eight cities in Xiangxi to evaluate the function level is determined. It is proved that: (a) The overall service value of water cultural function as a key factor in the construction of water ecological services, soil conservation value, and water supply value are relatively poor. (b) The value of the water ecological culture function type is the largest, with an overall value of 353.32 billion yuan. The value of water resources supply is the smallest, with a value of only 4.37 billion yuan, which indicates that human activities have a strong interference with the service function of the water ecosystem. (c) Based on GDM, four factors, including precipitation, resident population, sewage discharge, and water quality compliance rate, have a significant impact on water ecological services. Among them, per capita GDP(X7) > vegetation coverage (X6) > precipitation (X2) > resident population (X4), which further clearly explains the impact intensity of mountain climate basic conditions and human socio-economic activities on water ecological services. The results can offer a practical basis for the spatial development and protection of the water ecosystem to coordinate humans and the environment

Osteocalcin Induces Proliferation via Positive Activation of the PI3K/Akt, P38 MAPK Pathways and Promotes Differentiation Through Activation of the GPRC6A-ERK1/2 Pathway in C2C12 Myoblast Cells

Background/Aims: Sarcopenia is characterized by an age-related decline in skeletal muscle plus low muscle strength and/or physical performance. Despite the clinical significance of sarcopenia, the molecular pathways underlying sarcopenia remain elusive. The recent demonstration that undercarboxylated osteocalcin (ucOC) favours muscle function related to insulin sensitivity and glucose metabolism raises the question of whether this hormone may also regulate muscle mass. The present study explored the promotive effects of ucOC in proliferation and differentiation processes of C2C12 myoblasts as well as the possible signalling pathways involved. Methods: The effects of exogenous ucOC on C2C12 myoblasts proliferation were assessed using CCK8 and immunohistological staining assays. C2C12 cells were pretreated with PI3K/Akt or P38 MAPK inhibitors to investigate the possible involvement of the PI3K/Akt and P38 MAPK pathways in proliferation. The levels of Akt, phosphorylated-Akt (p-Akt), P38, and phosphorylated-P38 (p-P38) were measured by Western Blotting. The effects of ucOC on myoblast differentiation were quantified by morphological analysis. A silencing experiment was conducted in which the expression of GPRC6A in C2C12 myoblasts was modified. The expression of GPRC6A, myosin heavy chain (MyHC) and the related ERK1/2 signalling pathway in C2C12 myoblasts were monitored by qRT-PCR and Western Blotting. Results: We showed that treatment with exogenous ucOC stimulated the priming of C2C12 myoblasts proliferation. Inhibition of Akt phosphorylation by wortmannin or inhibition of P38 MAPK phosphorylation by SB203580 decreased C2C12 cell proliferation. Wortmannin also reduced P38 MAPK phosphorylation, whereas SB203580 did not affect Akt activation. Furthermore, ucOC promoted C2C12 myoblast differentiation. Inhibition of ERK1/2 phosphorylation with U0126 decreased C2C12 cell differentiation. Finally, GPRC6A expression was substantially increased after ucOC treatment of C2C12 cells. GPRC6A silencing inhibited Akt, P38 MAPK phosphorylation in C2C12 cells, and ERK1/2 phosphorylation in C2C12 myotubes; GPRC6A silencing also decreased cell proliferation, decreased cell differentiation, and downregulated MyHC expression. Conclusions: The present data suggest that ucOC induces myoblast proliferation via sequential activation of the PI3K/Akt and p38 MAPK pathways in C2C12 myoblast cells. Moreover, ucOC enhances myogenic differentiation via a mechanism involving GPRC6A-ERK1/2 signalling

Effects of Mn average oxidation state on the oxidation behaviors of As(III) and Cr(III) by vernadite

Vernadite is a poorly crystalline phyllomanganate that widely distributed in natural environments, and plays a pivotal role in the geochemical transformations of heavy metal and other pollutants. Though many works have done about the reaction mechanisms between vernadite-like minerals and As(III)/Cr(III), the effects of some basic structure characteristics of the mineral, such as Mn average oxidation state (AOS), on the oxidation of As (III)/Cr(III) are not fully understood. In this study, vernadite samples with different Mn AOSs but almost the same particle sizes (Ver and Ver20) were synthesized, characterized, and their reactivities towards As(III)/Cr(III) oxidation and As(V)/Cr(VI) adsorption were compared. It is found that Ver and Ver20 have almost the same point of zero charge (PZC), but ver20 has increased contents of layer Mn(III) at particle edges and interlayer Mn (III) and Mn(II), thus greatly reduced Mn AOS. Decrease in Mn AOS greatly reduces the oxidation capacity and initial reaction rate (K-obs) of this mineral towards As(III) on mineral-water interfaces. The apparent As(III) oxidation amount and K-obs by Ver are 202 +/- 8mmolkg(-1) and 0.3515 min(-1) while that by Ver20 are 162 +/- 7mmolkg(-1) and 0.0139 min(-1). The oxidation capacity and K-obs for Cr(III) by these vernadie samples are also decreased but in a less extent compared to that in As(III) oxidation, e.g. Cr(III) oxidized by Ver and Ver20 are 2895 +/- 47 and 1974 +/- 109 mmol kg(-1) and the K-obs are 0.0439 and 0.0169 min(-1) respectively. Adsorption density of As(V) or Cr(VI) on Ver20 is similar to 15-18% higher than that on Ver. These results suggest the more important role Mn AOS plays in As(III) oxidation than Cr(III) oxidation, and helps understand the geochemical behaviors of these toxic metals in natural environments mediated by Mn oxide minerals