毛乌素沙地沙丘土壤含水量特点——兼论老固定沙地上油蒿衰退原因

土壤表面干沙层在冬春少雨季节较厚,流动沙地的又明显地大于固和地的。流动沙地地表干沙层以下的土壤含水量一般在于同深化度固定沙地的,特别是在报系密集分布的土层。科季或早春土壤含水量比较低,雨季的明显较高,雨季结束后,土层中的水分在重力的作用下会向深层运动,导致根系层土壤含水量下降。在植物生长季,缺少降雨时,因少地的土土壤水量会因植物的蒸腾消耗而变得很低（１％～２％）,而流动沙地的不受或受此影响很小。地     

论世界遗产地和生物圈保护区的关系

世界遗产地和生物圈保护区的概念都是在联合国教科文组织(UNESCO)主持下制定的,主要目的都在于保护世界的物种多样性和生态系统;彼此之间究竞有何异同,人们或许并不十分清楚,特别是许多生物圈保护区也包括在世界遗产名录中,这就常常造成某种混淆。实际上,两者具有不同的目的、目标、法律依据和管理原则,不应该有所混淆。本文就拟简略地探讨一下这个问题供有关方面参考。     

西藏色季拉山垂直植被带土壤细菌群落组成及功能潜势

研究青藏高原土壤微生物群落组成和功能的空间分布特征有助于深入理解典型高寒生态系统中土壤微生物的重要生态功能.本研究采用16S rDNA高通量测序方法,分析了西藏色季拉山4个不同海拔土壤细菌群落物种组成和功能潜势的变化特征及其驱动因子.结果 表明:随着海拔的升高,土壤细菌的丰富度和Shannon多样性指数显著降低;酸杆菌...     

大肠杆菌rhtA缺失对血红素合成的影响

【背景】Escherichia coli BL21(DE3)是基因工程的常用宿主,以C5途径合成5-氨基乙酰丙酸(5-Aminolevulinicacid,ALA),ALA是合成血红素的重要前体物质,但ALA分泌对血红素合成的影响尚不清楚。【目的】阐明参与ALA外运的RhtA在血红素合成途径中的作用。【方法】利用Red同源重组,敲除Escherichia coli BL21(DE3)的rhtA,同时构建重组质粒pEA过表达血红素合成途径中的关键酶基因hemA,检测分析血红素及其前体物质含量,以及血红素合成途径中10个关键基因的表达水平。【结果】敲除rhtA对菌体生长没有显著影响,敲除菌株BL21(DE3)Δrht A与原始菌株BL21(DE3)比较,ALA的胞外含量下降23%,血红素含量提高12%,尿卟啉III (Uroporphyrin III,UIII)、粪卟啉III (Coproporphyrin III,CIII)和原卟啉IX (Protoporphyrin IX,PPIX)的含量分别提高25%、15%和18%;敲除rhtA同时过表达hemA的菌株BL21(DE3)ΔrhtA/pEA与仅过表达hemA的菌株BL21(DE3)/pEA比较,胞外ALA减少了16%,血红素含量提高了24%,UIII和CIII含量分别提高55%和64%,PPIX含量显著增加,约为4.7倍。实时定量PCR结果表明,rhtA缺失后,hemC基因转录水平下调,其余9个基因转录水平均有不同程度的上调。【结论】rhtA敲除减少了ALA的外运,使得胞内血红素产量得到提高。     

Paradoxical role of β8 integrin on angiogenesis and vasculogenic mimicry in glioblastoma

Glioblastoma multiforme (GBM) is the most aggressive and highly vascularized brain tumor with poor prognosis. Endothelial cell-dependent angiogenesis and tumor cell-dependent Vasculogenic mimicry (VM) synergistically contribute to glioma vascularization and progression. However, the mechanism underlying GBM vascularization remains unclear. In this study, GBM stem cells (GSCs) were divided into high and low β8 integrin (ITGB8) subpopulations. Co-culture assays followed by Cell Counting Kit-8 (CCK-8), migration, Matrigel tube formation, and sprouting assays were conducted to assess the proliferative, migratory and angiogenic capacity of GBM cells and human brain microvascular endothelial cells (hBMECs). An intracranial glioma model was constructed to assess the effect of ITGB8 on tumor vascularization in vivo. Our results indicated that ITGB8 expression was elevated in GSCs and positively associated with stem cell markers in glioma tissues, and could be induced by hypoxia and p38 activation. ITGB8 in GSCs inhibited the angiogenesis of hBMECs in vitro, while it promoted the ability of network formation and expression of VM-related proteins. The orthotopic GBM model showed that ITGB8 contributed to decreased angiogenesis, meanwhile enhanced invasiveness and VM formation. Mechanistic studies indicated that ITGB8-TGFβ1 axis modulates VM and epithelial-mesenchymal transition (EMT) process via Smad2/3-RhoA signaling. Together, our findings demonstrated a differential role for ITGB8 in the regulation of angiogenesis and VM formation in GBM, and suggest that pharmacological inhibition of ITGB8 may represent a promising therapeutic strategy for treatment of GBM.Subject terms: Cancer stem cells, CNS cancer     

栗山天牛及其天敌花绒寄甲空间分布的地统计学分析

本文用地统计学的方法研究了栗山天牛及其天敌花绒寄甲的空间分布规律,结果表明:栗山天牛与花绒寄甲均呈聚集性分布,而且栗山天牛分布较多的样地,花绒寄甲也较多,花绒寄甲与栗山天牛有较强的跟随效应。栗山天牛与花绒寄甲的空间分布模型为球状+指数套合模型。栗山天牛和花绒寄甲空间分布在四个方向的变程均在100 m左右,而且在四个方向均比较集中。栗山天牛在东西方向聚集度最高,超过了0.8,而花绒寄甲在南北方向聚集度最高,2008年达到0.8452,2009年达到0.7230。研究还表明,2008年人工释放花绒寄甲后,其成虫在林间逐渐扩散,聚集度下降。     

Hemin with Peroxidase Activity Can Inhibit the Oxidative Damage Induced by Ultraviolet A

Excessive reactive oxygen species (ROS), a highly reactive substance that contains oxygen, induced by ultraviolet A (UVA) cause oxidative damage to skin. We confirmed that hemin can catalyze the reaction of tyrosine (Tyr) and hydrogen peroxide (H₂O₂). Catalysis was found to effectively reduce or eliminate oxidative damage to cells induced by H₂O₂ or UVA. The scavenging effects of hemin for other free-radical ROS were also evaluated through pyrogallol autoxidation, 1,1-diphenyl-2-picrylhydrazyl radical (DPPH·)-scavenging assays, and phenanthroline–Fe²⁺ assays. The results show that a mixture of hemin and tyrosine exhibits strong scavenging activities for H₂O₂, superoxide anion (O₂⁻·), DPPH·, and the hydroxyl radical (·OH). Furthermore, the inhibition of oxidative damage to human skin keratinocyte (HaCaT) cells induced by H₂O₂ or UVA was evaluated. The results show that catalysis can significantly reduce the ratio of cell apoptosis and death and inhibit the release of lactate dehydrogenase (LDH), as well as accumulation of malondialdehyde (MDA). Furthermore, the resistance to apoptosis was found to be enhanced. These results show that the mixture of hemin and tyrosine has a significantly protective effect against oxidative damage to HaCaT cells caused by UVA, suggesting it as a protective agent for combating UVA damage.     

The genomic basis of high-elevation adaptation in wild house mice (Mus musculus domesticus) from South America

Understanding the genetic basis of environmental adaptation in natural populations is a central goal in evolutionary biology. The conditions at high elevation, particularly the low oxygen available in the ambient air, impose a significant and chronic environmental challenge to metabolically active animals with lowland ancestry. To understand the process of adaptation to these novel conditions and to assess the repeatability of evolution over short timescales, we examined the signature of selection from complete exome sequences of house mice (Mus musculus domesticus) sampled across two elevational transects in the Andes of South America. Using phylogenetic analysis, we show that house mice colonized high elevations independently in Ecuador and Bolivia. Overall, we found distinct responses to selection in each transect and largely nonoverlapping sets of candidate genes, consistent with the complex nature of traits that underlie adaptation to low oxygen availability (hypoxia) in other species. Nonetheless, we also identified a small subset of the genome that appears to be under parallel selection at the gene and SNP levels. In particular, three genes (Col22a1, Fgf14, and srGAP1) bore strong signatures of selection in both transects. Finally, we observed several patterns that were common to both transects, including an excess of derived alleles at high elevation, and a number of hypoxia-associated genes exhibiting a threshold effect, with a large allele frequency change only at the highest elevations. This threshold effect suggests that selection pressures may increase disproportionately at high elevations in mammals, consistent with observations of some high-elevation diseases in humans.     

江苏省县域森林生态安全评价及空间计量分析

通过考察生态区位因素对森林生态安全的影响,建立评价指标体系,研究其空间相关性的内在效应机制,从而实现森林生态安全的评价与监测。以江苏省80个区县为研究对象,基于2000—2015年面板数据,运用熵权法、专家法及模糊物元法计算森林生态安全指数,然后结合气象类指标及地形类指标计算生态区位系数,再用该系数修正森林ESI,同时结合Arc GIS技术、空间相关性分析、SLM与SEM模型得出如下结论:(1)人口密度、单位面积能源消耗量、退耕还林面积占比等指标权重最大;(2)生态区位系数高值区主要分布在江苏南部少数地区,低值区主要分布在江苏东北部;(3)苏南地区森林生态安全状况整体好于苏北及中东部地区;(4) 2000—2015年,江苏省67.5%的区县森林ESI呈现出较明显下降趋势,反映出江苏省森林生态安全发展状况不容乐观;(5)江苏省县域森林ESI整体空间相关性显著(P≤0.01),但2000—2015年空间聚集程度有所下降,且Low-Low聚类显著性更强;(6)森林ESI在江苏省县域间为扩散效应与回流效应并存。     

LRP6 downregulation promotes cardiomyocyte proliferation and heart regeneration

The adult mammalian heart is thought to be a terminally differentiated organ given the postmitotic nature of cardiomyocytes. Consequently, the potential for cardiac repair through cardiomyocyte proliferation is extremely limited. Low-density lipoprotein receptor-related protein 6 (LRP6) is a Wnt co-receptor that is required for embryonic heart development. In this study we investigated the role of LRP6 in heart repair through regulation of cardiomyocyte proliferation. Lrp6 deficiency increased cardiomyocyte cell cycle activity in neonatal, juvenile and adult mice. Cardiomyocyte-specific deletion of Lrp6 in the mouse heart induced a robust regenerative response after myocardial infarction (MI), led to reduced MI area and improvement in left ventricular systolic function. In vivo genetic lineage tracing revealed that the newly formed cardiomyocytes in Lrp6-deficient mouse hearts after MI were mainly derived from resident cardiomyocytes. Furthermore, we found that the pro-proliferative effect of Lrp6 deficiency was mediated by the ING5/P21 signaling pathway. Gene therapy using the adeno-associated virus (AAV)9 miRNAi-Lrp6 construct promoted the repair of heart injury in mice. Lrp6 deficiency also induced the proliferation of human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). Our study identifies LRP6 as a critical regulator of cardiomyocyte proliferation, which may lead to the development of a novel molecular strategy to promote myocardial regeneration and repair.Subject terms: Cell-cycle exit, Cytokinesis