Prediction of the potential geographical distribution of Betula platyphylla Suk. in China under climate change scenarios.

Climate is a dominant factor affecting the potential geographical distribution of species. Understanding the impact of climate change on the potential geographic distribution of species, which is of great significance to the exploitation, utilization, and protection of resources, as well as ecologically sustainable development. Betula platyphylla Suk. is one of the most widely distributed temperate deciduous tree species in East Asia and has important economic and ecological value. Based on 231 species distribution data points of Betula platyphylla Suk. in China and 37 bioclimatic, soil, and topography variables (with correlation coefficients < 0.75), the potential geographical distribution pattern of Betula platyphylla Suk. under Representative Concentration Pathway (RCP) climate change scenarios at present and in the 2050s and 2070s was predicted using the MaxEnt model. We analyzed the main environmental variables affecting the distribution and change of suitable areas and compared the scope and change of suitable areas under different climate scenarios. This study found: (1) At present, the main suitable area for Betula platyphylla Suk. extends from northeastern to southwestern China, with the periphery area showing fragmented distribution. (2) Annual precipitation, precipitation of the warmest quarter, mean temperature of the warmest quarter, annual mean temperature, and precipitation of the driest month are the dominant environmental variables that affect the potential geographical distribution of Betula platyphylla Suk. (3) The suitable area for Betula platyphylla Suk. is expected to expand under global warming scenarios. In recent years, due to the impact of diseases and insect infestation, and environmental damage, the natural Betula platyphylla Suk. forest in China has gradually narrowed. This study accurately predicted the potential geographical distribution of Betula platyphylla Suk. under current and future climate change scenarios, which can provide the scientific basis for the cultivation, management, and sustainable utilization of Betula platyphylla Suk. resources.

Dynamic Changes, Spatiotemporal Differences and Factors Influencing the Urban Eco-Efficiency in the Lower Reaches of the Yellow River.

The measurement of eco-efficiency is an important tool to evaluate the level of urban sustainable development. Therefore; improving urban eco-efficiency in the lower reaches of the Yellow River ensures the implementation of ecological protection and high-quality development strategies in the Yellow River Basin. In this study; the dynamic changes of urban eco-efficiency and spatiotemporal differences in the lower reaches of the Yellow River were investigated using the Super-SBM (Super-Slack measure model) model with undesirable outputs and standard deviation ellipse. The STIRPAT (Stochastic Impacts by Regression Population; Affluence and Technology) model was introduced to analyze the factors affecting the change in urban eco-efficiency. The results showed that the overall urban eco-efficiency in the lower reaches of the Yellow River has not reached the optimal level. The overall eco-efficiency in the lower reaches of the Yellow River in Shandong Province was higher than that in Henan Province but the gap is narrowing. The spatial differentiation of urban eco-efficiency in the lower reaches of the Yellow River showed the following trends: "blooming in the middle and reverse development at both ends" in the high-value area and gradual decrease in the low-value area. From 2007 to 2018; a direction was notable with respect to the development of urban eco-efficiency in the lower reaches of the Yellow River; with the centripetal force weakening. Although the mean center of urban eco-efficiency located in Shandong Province; it notably shifted to the west during the study period. In terms of driving factors; affluence and technological progress play positive roles in driving eco-efficiency; while investment intensity; industrial structure; and foreign investment intensity hindered the optimization and improvement of urban eco-efficiency in the lower reaches of the Yellow River. The results of this study show that urban eco-efficiency in the lower reaches of the Yellow River is improving; but the regional coordination is poor. The main methods promoting the sustainable development in the study area include changing the mode of extensive investments and the introduction of foreign capital; which improve the energy efficiency and promote faster and better economic development.

Upfront eltrombopag monotherapy induces stable hematologic remission in pediatric patients with nonsevere idiopathic aplastic anemia.

Aplastic anemia (AA) is characterized by multilineage cytopenias and bone marrow hypocellularity. Severe AA can be treated with immunosuppressive therapy (IST) and/or allogeneic hematopoietic stem cell transplantation. The thrombopoietin agonist eltrombopag has been shown to induce hematopoietic recovery and transfusion independence in adults with refractory and relapsed AA. Recently, upfront eltrombopag therapy in patients with AA in combination with IST has shown efficacy. Data for its use without concurrent IST in pediatric patients with AA remain sparse. Here we report two pediatric patients with AA not meeting severe criteria who achieved hematologic response with upfront eltrombopag monotherapy.

Pre-treatment of synthetic elastomeric scaffolds by cardiac fibroblasts improves engineered heart tissue.

Native myocardium consists of several cell types, of which approximately one-third are myocytes and most of the nonmyocytes are fibroblasts. By analogy with monolayer culture in which fibroblasts were removed to prevent overgrowth, early attempts to engineer myocardium utilized cell populations enriched for cardiac myocytes (CMs; approximately 80-90% of total cells). We hypothesized that the pre-treatment of synthetic elastomeric scaffolds with cardiac fibroblasts (CFs) will enhance the functional assembly of the engineered cardiac constructs by creating an environment supportive of cardiomyocyte attachment and function. Cells isolated from neonatal rat ventricles were prepared to form three distinct populations: rapidly plating cells identified as CFs, slowly plating cells identified as CMs, and unseparated initial population of cells (US). The cell fractions (3 x 10(6) cells total) were seeded into poly(glycerol sebacate) scaffolds (highly porous discs, 5 mm in diameter x 2-mm thick) using Matrigeltrade mark, either separately (CM or CF), concurrently (US), or sequentially (CF pre-treatment followed by CM culture, CF + CM), and cultured in spinner flasks. The CF + CM group had the highest amplitude of contraction and the lowest excitation threshold, superior DNA content, and higher glucose consumption rate. The CF + CM group exhibited compact 100- to 200-mum thick layers of elongated myocytes aligned in parallel over layers of collagen-producing fibroblasts, while US and CM groups exhibited scattered and poorly elongated myocytes. The sequential co-culture of CF and CM on a synthetic elastomer scaffold thus created an environment supportive of cardiomyocyte attachment, differentiation, and contractile function, presumably due to scaffold conditioning by cultured fibroblasts. When implanted over the infarcted myocardium in a nude rat model, cell-free poly(glycerol sebacate) remained at the ventricular wall after 2 weeks of in vivo, and was vascularized.

Photocrosslinkable hydrogel for myocyte cell culture and injection.

Conventional treatment options for myocardial infarction are limited by the inability of mature myocardium to regenerate after injury. Although functional improvements after injection of cells and growth factors have been demonstrated, the clinical utility of this procedure has been hampered by poor cell localization, low survival, and rapid clearance of injected growth factors. The main objective of this study was to evaluate the applicability of a hydrogel, based on photocrosslinkable chitosan and acryloyl-poly(ethylene glycol)-RGDS (Az-chitosan/Acr-PEG-RGD) for myocyte cell culture and myocardial injection. Chitosan was modified with photoreactive azidobenzoic acid and Acr-PEG-RGD was synthesized by reacting YRGDS with an equimolar amount of acryloyl-PEG-N-hydroxysuccinimide. For injection and encapsulation each polymer was dissolved in Di-H(2)O (pH 6.4), the solutions were mixed and crosslinked by UV application (4 mW/cm(2)). C2C12 myoblasts proliferated and differentiated on hydrogels containing 5 mM RGD but not on the pure photocrosslinked chitosan. In vitro, the crosslinked hydrogels retained 80% of encapsulated VEGF for 24 days. Live/dead staining of neonatal rat cardiomyocytes encapsulated into Az-chitosan/Acr-PEG-RGD hydrogels indicated high cell viability upon UV crosslinking. Ex vivo, we localized the hydrogel on the surface and in the ventricle wall of an adult rat heart by brief (2 min) UV light application.

Oxygen gradients correlate with cell density and cell viability in engineered cardiac tissue.

For clinical utility, cardiac grafts should be thick and compact, and contain physiologic density of metabolically active, differentiated cells. This involves the need to control the levels of nutrients, and most critically oxygen, throughout the construct volume. Most culture systems involve diffusional transport within the constructs, a situation associated with gradients of oxygen concentration, cell density, cell viability, and function. The goal of our study was to measure diffusional gradients of oxygen in statically cultured cardiac constructs, and to correlate oxygen gradients to the spatial distributions of cell number and cell viability. Using microelectrodes, we measured oxygen distribution in a disc-shaped constructs (3.6 mm diameter, 1.8 mm thickness) based on neonatal rat cardiomyocytes cultured on collagen scaffolds for 16 days in static dishes. To rationalize experimental data, a mathematical model of oxygen distribution was derived as a function of cell density, viability, and spatial position within the construct. Oxygen concentration and cell viability decreased linearly and the live cell density decreased exponentially with the distance from the construct surface. Physiological density of live cells was present only within the first 128 microm of the construct thickness. Medium flow significantly increased oxygen concentration within the construct, correlating with the improved tissue properties observed for constructs cultured in convectively mixed bioreactors.