Magnetic Resonance Imaging Is More Sensitive Than PET for Detecting Treatment-Induced Cell Death-Dependent Changes in Glycolysis.

Metabolic imaging has been widely used to measure the early responses of tumors to treatment. Here, we assess the abilities of PET measurement of [18F]FDG uptake and MRI measurement of hyperpolarized [1-13C]pyruvate metabolism to detect early changes in glycolysis following treatment-induced cell death in human colorectal (Colo205) and breast adenocarcinoma (MDA-MB-231) xenografts in mice. A TRAIL agonist that binds to human but not mouse cells induced tumor-selective cell death. Tumor glycolysis was assessed by injecting [1,6-13C2]glucose and measuring 13C-labeled metabolites in tumor extracts. Injection of hyperpolarized [1-13C]pyruvate induced rapid reduction in lactate labeling. This decrease, which correlated with an increase in histologic markers of cell death and preceded decrease in tumor volume, reflected reduced flux from glucose to lactate and decreased lactate concentration. However, [18F]FDG uptake and phosphorylation were maintained following treatment, which has been attributed previously to increased [18F]FDG uptake by infiltrating immune cells. Quantification of [18F]FDG uptake in flow-sorted tumor and immune cells from disaggregated tumors identified CD11b+/CD45+ macrophages as the most [18F]FDG-avid cell type present, yet they represented <5% of the cells present in the tumors and could not explain the failure of [18F]FDG-PET to detect treatment response. MRI measurement of hyperpolarized [1-13C]pyruvate metabolism is therefore a more sensitive marker of the early decreases in glycolytic flux that occur following cell death than PET measurements of [18F]FDG uptake. SIGNIFICANCE: These findings demonstrate superior sensitivity of MRI measurement of hyperpolarized [1-13C]pyruvate metabolism versus PET measurement of 18F-FDG uptake for detecting early changes in glycolysis following treatment-induced tumor cell death

Relationships between the characteristics of soil and understory in a Pinus massoniana forest in southern China

Soil is the basis for vegetation growth, and vegetation in turn improves soil quality. Understanding the relationships between soil and vegetation characteristics is needed to rehabilitate degraded land and implement sustainable land use practices. In particular, it is important to uncover the relationship between natural vegetation restoration and key soil parameters for the improvement of restored ecological environments. This study analyzed the relationships between soil and understory characteristics of a P. massoniana forest in degraded red soil in southern China. Red soils in this area have been severely eroded. The soils were categorized into three groups whose attributes differed significantly and each group was distributed within a topographical type. Understory and soil characteristics were closely correlated, but restoration of the understory was only related to some key soil attributes (e.g. available potassium content, pH, soil water content, bacteria amounts, and urease and catalase activities). Our results provide insight into the relationships between soil and vegetation characteristics for natural revegetation in degraded land with severely eroded soil

Effect of Material Inhomogeneity on the Crack Tip Mechanical Field and SCC Growth Rate of 52M/316L Dissimilar Metal Welded Joints

The stress–strain conditions at the crack tip in dissimilar metal welded joints (DMWJ) are a critical factor influencing stress corrosion cracking (SCC) behavior. The processing technology and working environment of DMWJ lead to a randomly inhomogeneous distribution of material mechanical properties, making the crack tip mechanical field more complex. An inhomogeneous model was obtained using a combination of physical experiments and the elastic–plastic finite element method to understand the effect of this inhomogeneous distribution of mechanical properties on the direction of SCC growth and the growth rate in DMWJ and the impact of inhomogeneity on the SCC growth behavior was compared and analyzed. The findings demonstrate that Type I (opening mode) cracks are more likely to form due to the inhomogeneity of mechanical properties and are more likely to deflect toward the Alloy 52M region at the interface between Alloy 52M and 316L stainless steel. Additionally, the strain gradient at the crack tip increases with the degree of inhomogeneity, which has a bigger impact on the accuracy of SCC growth rate predictions

Relationship between topography and the distribution of understory vegetation in a Pinus massoniana forest in Southern China

The poor growth of understory vegetation and the severe losses of soil and water in Pinus massoniana forests have recently become serious concerns in an area in southern China with eroded red soil. The influence of topography on the spatial distribution of vegetation, however, has received little attention. This study combined several multivariate analyses to discern the complicated relationship between understory vegetation and topography. Thirty-six plots (10 m×10 m) were sampled in a field survey of the vegetation and topography in the central red-soil region. The distributions of the understory vegetation differed significantly amongst the topographies. Most plants grew in gullies, and few grew on ridges. The low coverage (25.2%) and number of species (5 per plot) of the vegetation on ridges was due to serious soil erosion. Surface curvature and slope aspect were the first and second most important topographic factors, respectively, affecting the distribution of the vegetation. The relationship between topography and distribution could be described by a linear model. Surface curvature or slope aspect alone, however, could only explain 22.2–59.2% of the variance in distribution. The adaptation of vegetation to specific topographies should be considered for restorations of P. massoniana forests in the study area. The results of this study will be helpful for selecting potential sites for seeding and vegetation restoration to improve the ecology of the study area. Further studies will be needed to identify the mechanism of the distribution of the understory vegetation in these P. massoniana forests

The potential capability of substituting chemical fertilizers with crop straw and human-livestock-poultry manure in areas with different topographic characteristics

Agricultural production and lifestyle are constrained by topography, causing notable under disparities in the composition, distribution, and environmental benefits of crop straw and human-livestock-poultry manure (CSHLPM) in areas with different topographic characteristics. Under the premise of the international consensus on sustainable development, it has become an objective requirement to improve the use of CSHLPM as fertilizer, and minimize the use of chemical fertilizers. Thus, an investigation was conducted to assess the difference in the quantity and composition of CSHLPM in plain, hill, and mountainous areas, taking Anhui Province of China as a case study, to evaluate the potential contribution of CSHLPM to farmland and identify the environmental benefits. The results show that the composition of CSHLPM in plain, hill, and mountainous areas varied greatly, and the reuse of CSHLPM in farmland could supplement, but not completely replace the use of chemical fertilizer to meet the needs of nutrients. In plain areas, CSHLPM did not provide the necessary amount of N and P2O5 for crop growth, whereas in mountainous areas, P2O5 was not available in adequate amounts for crop growth. Only in hilly areas can CSHLPM be used to completely replace chemical fertilizers and supply the necessary amounts of nutrients for crop growth. Based on the characteristics of different topographies, two constructive suggestions for improving the management strategy of CSHLPM were put forward: adjust the industrial structure of husbandry and planting, and specify the recommended ratios for mixing organic chemical fertilizers