植物生物量分配格局反映了环境对植物的选择和植物对环境的响应。在祁连山高寒退化草地,采用标准化主轴估计(standardized major axis estimation)方法,探讨甘肃臭草(Melica przewalskyi)茎、叶生物量变化及其分配策略对斑块不同发育阶...植物生物量分配格局反映了环境对植物的选择和植物对环境的响应。在祁连山高寒退化草地,采用标准化主轴估计(standardized major axis estimation)方法,探讨甘肃臭草(Melica przewalskyi)茎、叶生物量变化及其分配策略对斑块不同发育阶段(斑块形成、斑块扩散、斑块稳定及斑块衰退阶段)的响应。结果表明:随着甘肃臭草斑块的发育,甘肃臭草茎生物量积累呈先上升后下降趋势,茎生物量分配比例呈先下降后上升趋势;叶生物量积累及生物量分配比例在斑块形成、斑块扩散及斑块稳定阶段均呈逐渐上升趋势,斑块衰退阶段呈下降趋势;斑块形成阶段甘肃臭草茎叶生物量呈等速生长模式,斑块扩散及稳定阶段叶生物量的增长速度大于茎生物量的增长速度,斑块衰退阶段转为茎生物量的增长速度大于叶生物量的增长速度。随着斑块的发育,甘肃臭草由依靠增加叶干物质投入占领资源,转为减小叶生物量投入、提高茎生物量的增长速度。展开更多
Owing to their capacity for self-renewal and pluripotency, stem cells possess untold potential for revolutionizing the field of regenerative medicine through the development of novel therapeutic strategies for treatin...Owing to their capacity for self-renewal and pluripotency, stem cells possess untold potential for revolutionizing the field of regenerative medicine through the development of novel therapeutic strategies for treating cancer, diabetes, cardiovascular and neurodegenerative diseases. Central to developing these strategies is improving our understanding of biological mechanisms responsible for governing stem cell fate and self-renewal. Increasing attention is being given to the significance of metabolism, through the production of energy and generation of small molecules, as a critical regulator of stem cell functioning. Rapid advances in the field of metabolomics now allow for in-depth profiling of stem cells both in vitro and in vivo, providing a systems perspective on key metabolic and molecular pathways which influence stem cell biology. Understanding the analytical platforms and techniques that are currently used to study stem cell metabolomics, as well as how new insights can be derived from this knowledge, will accelerate new research in the field and improve future efforts to expand our understanding of the interplay between metabolism and stem cell biology.展开更多
Androgen doping in power sports is undeniably rampant worldwide. There is strong evidence that androgen administration in men increases skeletal muscle mass, maximal voluntary strength and muscle power. However, we do...Androgen doping in power sports is undeniably rampant worldwide. There is strong evidence that androgen administration in men increases skeletal muscle mass, maximal voluntary strength and muscle power. However, we do not have good experimental evidence to support the presumption that androgen administration improves physical function or athletic performance. Androgens do not increase specific force or whole body endurance measures. The anabolic effects of testosterone on the skeletal muscle are mediated through androgen receptor signaling. Testosterone promotes myogenic differentiation of multipotent mesenchymal stem cells and inhibits their differentiation into the adipogenic lineage. Testosterone binding to androgen receptor induces a conformational change in androgen receptor protein, causing it to associate with beta-catenin and TCF-4 and activate downstream Wnt target genes thus promoting myogenic differentiation. The adverse effects of androgens among athletes and recreational bodybuilders are under reported and include acne, deleterious changes in the cardiovascular risk factors, including a marked decrease in plasma high-density lipoproteins （HDL） cholesterol level, suppression of spermatogenesis resulting in infertility, increase in liver enzymes, hepatic neoplasms, mood and behavioral disturbances, and long term suppression of the endogenous hypothalamic-pituitary-gonadal axis. Androgens are often used in combination with other drugs which may have serious adverse events of their own. In spite of effective methods for detecting androgen doping, the policies for screening of athletes are highly variable in different countries and organizations and even existing policies are not uniformly enforced.展开更多
The objective was to examine the effects of optimal leaf nitrogen levels>2.0%and suboptimal levels<2.0%,nitrogen nutrition on net photo synthetic rate,stem diameter increment,height growth increment and acorn ma...The objective was to examine the effects of optimal leaf nitrogen levels>2.0%and suboptimal levels<2.0%,nitrogen nutrition on net photo synthetic rate,stem diameter increment,height growth increment and acorn mass of pedunculate oak during 2010 in the absence of drought stress and during 2011 under the impact of moderate drought stress.According to the results,moderate drought stress significantly reduced net photo synthetic rate,stem diameter increment and height growth increment,while acorn mass was not affected.Suboptimal nitrogen nutrition significantly reduced the net photo synthetic rate and stem diameter increment only in the wet year,acorn mass in both wet and dry years,while height growth increment was not significantly reduced by suboptimal nitrogen nutrition in either year.The results indicate that optimal nitrogen levels can stimulate photo synthetic rate and stem diameter increment of pedunculate oak only in the absence of moderate drought stress.Moreover,the results show that moderate drought stress is a more dominant stressor for photosynthesis and growth of pedunculate oak than suboptimal nitrogen nutrition,while for acorn development,it is the more dominant stressor.展开更多
The distinctive features of proteomics are large-scale and high throughput. The key techniques of proteomics are two-dimensional gel electrophoresis, mass spectrometry and bioinformatics. Stem cell can differentiate i...The distinctive features of proteomics are large-scale and high throughput. The key techniques of proteomics are two-dimensional gel electrophoresis, mass spectrometry and bioinformatics. Stem cell can differentiate into all kinds of cells, tissues and organs. There are many proteins and cytokines involved in the process of differentiation. Applying proteomics techniques to the research of the complex process of stem cell differentiation is of great importance to study the mechanism and applications of stem cell differentiation.展开更多
Human embryonic stem cells （hESC） not only hold great promise for the treatment of degenerative diseases but also provide a valuable tool for developmental studies. However, the clinical applications of hESC are at ...Human embryonic stem cells （hESC） not only hold great promise for the treatment of degenerative diseases but also provide a valuable tool for developmental studies. However, the clinical applications of hESC are at present limited by xeno-contamination during the in vitro derivation and propagation of these cells. In this review, we summarize the current methodologies for the derivation and the propagation of hESC in conditions that will eventually enable the generation of clinical-grade cells for future therapeutic applications.展开更多
叶片和茎的生长规律决定植物对光截取的模式以及与外界环境的物质交换面积,其生物量分配是研究植物生活史对策的一个重要途径。在石羊河上游高寒退化草地,采用标准化主轴估计(standardized major axis estimation,SMA)方法,研究了狼毒(S...叶片和茎的生长规律决定植物对光截取的模式以及与外界环境的物质交换面积,其生物量分配是研究植物生活史对策的一个重要途径。在石羊河上游高寒退化草地,采用标准化主轴估计(standardized major axis estimation,SMA)方法,研究了狼毒(Stellera chamaejasme)种群茎大小对茎与叶生物量分配的影响,以及对叶面积支持效率的影响。结果表明:狼毒种群茎干重与比叶重(LMA)、单叶面积、叶干重呈异速生长关系,SMA斜率分别为0.781(95%的置信区间,CI=0.71～0.94)、0.824(CI=0.77～0.95)和0.856(CI=0.79～0.99)。狼毒种群中较大茎的狼毒植株具有较高的叶生物量分配比例和叶面积支持效率,同时具有较高的比叶重,说明较大的狼毒采取以提高资源利用效率为主的适应策略,而相对较小的狼毒采取以快速生长为主的适应策略。展开更多
文摘植物生物量分配格局反映了环境对植物的选择和植物对环境的响应。在祁连山高寒退化草地,采用标准化主轴估计(standardized major axis estimation)方法,探讨甘肃臭草(Melica przewalskyi)茎、叶生物量变化及其分配策略对斑块不同发育阶段(斑块形成、斑块扩散、斑块稳定及斑块衰退阶段)的响应。结果表明:随着甘肃臭草斑块的发育,甘肃臭草茎生物量积累呈先上升后下降趋势,茎生物量分配比例呈先下降后上升趋势;叶生物量积累及生物量分配比例在斑块形成、斑块扩散及斑块稳定阶段均呈逐渐上升趋势,斑块衰退阶段呈下降趋势;斑块形成阶段甘肃臭草茎叶生物量呈等速生长模式,斑块扩散及稳定阶段叶生物量的增长速度大于茎生物量的增长速度,斑块衰退阶段转为茎生物量的增长速度大于叶生物量的增长速度。随着斑块的发育,甘肃臭草由依靠增加叶干物质投入占领资源,转为减小叶生物量投入、提高茎生物量的增长速度。
文摘Owing to their capacity for self-renewal and pluripotency, stem cells possess untold potential for revolutionizing the field of regenerative medicine through the development of novel therapeutic strategies for treating cancer, diabetes, cardiovascular and neurodegenerative diseases. Central to developing these strategies is improving our understanding of biological mechanisms responsible for governing stem cell fate and self-renewal. Increasing attention is being given to the significance of metabolism, through the production of energy and generation of small molecules, as a critical regulator of stem cell functioning. Rapid advances in the field of metabolomics now allow for in-depth profiling of stem cells both in vitro and in vivo, providing a systems perspective on key metabolic and molecular pathways which influence stem cell biology. Understanding the analytical platforms and techniques that are currently used to study stem cell metabolomics, as well as how new insights can be derived from this knowledge, will accelerate new research in the field and improve future efforts to expand our understanding of the interplay between metabolism and stem cell biology.
文摘Androgen doping in power sports is undeniably rampant worldwide. There is strong evidence that androgen administration in men increases skeletal muscle mass, maximal voluntary strength and muscle power. However, we do not have good experimental evidence to support the presumption that androgen administration improves physical function or athletic performance. Androgens do not increase specific force or whole body endurance measures. The anabolic effects of testosterone on the skeletal muscle are mediated through androgen receptor signaling. Testosterone promotes myogenic differentiation of multipotent mesenchymal stem cells and inhibits their differentiation into the adipogenic lineage. Testosterone binding to androgen receptor induces a conformational change in androgen receptor protein, causing it to associate with beta-catenin and TCF-4 and activate downstream Wnt target genes thus promoting myogenic differentiation. The adverse effects of androgens among athletes and recreational bodybuilders are under reported and include acne, deleterious changes in the cardiovascular risk factors, including a marked decrease in plasma high-density lipoproteins （HDL） cholesterol level, suppression of spermatogenesis resulting in infertility, increase in liver enzymes, hepatic neoplasms, mood and behavioral disturbances, and long term suppression of the endogenous hypothalamic-pituitary-gonadal axis. Androgens are often used in combination with other drugs which may have serious adverse events of their own. In spite of effective methods for detecting androgen doping, the policies for screening of athletes are highly variable in different countries and organizations and even existing policies are not uniformly enforced.
基金conducted as part of the research project“Reproductive physiology of pedunculate oak(Quercus robur L.)in Spa?va”fully supported and funded by“Croatian Forests Ltd”。
文摘The objective was to examine the effects of optimal leaf nitrogen levels>2.0%and suboptimal levels<2.0%,nitrogen nutrition on net photo synthetic rate,stem diameter increment,height growth increment and acorn mass of pedunculate oak during 2010 in the absence of drought stress and during 2011 under the impact of moderate drought stress.According to the results,moderate drought stress significantly reduced net photo synthetic rate,stem diameter increment and height growth increment,while acorn mass was not affected.Suboptimal nitrogen nutrition significantly reduced the net photo synthetic rate and stem diameter increment only in the wet year,acorn mass in both wet and dry years,while height growth increment was not significantly reduced by suboptimal nitrogen nutrition in either year.The results indicate that optimal nitrogen levels can stimulate photo synthetic rate and stem diameter increment of pedunculate oak only in the absence of moderate drought stress.Moreover,the results show that moderate drought stress is a more dominant stressor for photosynthesis and growth of pedunculate oak than suboptimal nitrogen nutrition,while for acorn development,it is the more dominant stressor.
基金This work was supported by the National Outstanding Youth Foundation of China (No. 30225038) and the National Key Research Project of China (No. 00CB510103).
文摘The distinctive features of proteomics are large-scale and high throughput. The key techniques of proteomics are two-dimensional gel electrophoresis, mass spectrometry and bioinformatics. Stem cell can differentiate into all kinds of cells, tissues and organs. There are many proteins and cytokines involved in the process of differentiation. Applying proteomics techniques to the research of the complex process of stem cell differentiation is of great importance to study the mechanism and applications of stem cell differentiation.
文摘Human embryonic stem cells （hESC） not only hold great promise for the treatment of degenerative diseases but also provide a valuable tool for developmental studies. However, the clinical applications of hESC are at present limited by xeno-contamination during the in vitro derivation and propagation of these cells. In this review, we summarize the current methodologies for the derivation and the propagation of hESC in conditions that will eventually enable the generation of clinical-grade cells for future therapeutic applications.
文摘叶片和茎的生长规律决定植物对光截取的模式以及与外界环境的物质交换面积,其生物量分配是研究植物生活史对策的一个重要途径。在石羊河上游高寒退化草地,采用标准化主轴估计(standardized major axis estimation,SMA)方法,研究了狼毒(Stellera chamaejasme)种群茎大小对茎与叶生物量分配的影响,以及对叶面积支持效率的影响。结果表明:狼毒种群茎干重与比叶重(LMA)、单叶面积、叶干重呈异速生长关系,SMA斜率分别为0.781(95%的置信区间,CI=0.71～0.94)、0.824(CI=0.77～0.95)和0.856(CI=0.79～0.99)。狼毒种群中较大茎的狼毒植株具有较高的叶生物量分配比例和叶面积支持效率,同时具有较高的比叶重,说明较大的狼毒采取以提高资源利用效率为主的适应策略,而相对较小的狼毒采取以快速生长为主的适应策略。
