Resistance to Ca2+-induced opening of the permeability transition pore differs in mitochondria from glycolytic and oxidative muscles

This study determined whether susceptibility to opening of the permeability transition pore (PTP) varies according to muscle phenotype represented by the slow oxidative soleus (Sol) and superficial white gastrocnemius (WG). Threshold for Ca2+-induced mitochondrial Ca2+ release following PTP opening was determined with a novel approach using permeabilized ghost myofibers. Threshold values for PTP opening were approximately threefold higher in fibers from WG compared with those from Sol (124+/-47 vs. 30.4+/-6.8 pmol Ca2+/mU citrate synthase). A similar phenomenon was also observed in isolated mitochondria (threshold: 121+/-60 vs. 40+/-10 nmol Ca2+/mg protein in WG and Sol), indicating that this was linked to differences in mitochondrial factors between the two muscles. The resistance of WG fibers to PTP opening was not related to the expression of putative protein modulators (cyclophilin D, adenylate nucleotide translocator-1, and voltage-dependent anion channels) or to difference in respiratory properties and occurred despite the fact that production of reactive oxygen species, which promote pore opening, was higher than in the Sol. However, endogenous matrix Ca2+ measured in mitochondria isolated under resting baseline conditions was approximately twofold lower in the WG than in the Sol (56+/-4 vs. 111+/-11 nmol/mg protein), which significantly accounted for the resistance of WG. Together, these results reveal fiber type differences in the sensitivity to Ca2+-induced PTP opening, which may constitute a physiological mechanism to adapt mitochondria to the differences in Ca2+ dynamics between fiber types.     

Methylated DNA/RNA in Body Fluids as Biomarkers for Lung Cancer

DNA/RNA methylation plays an important role in lung cancer initiation and progression. Liquid biopsy makes use of cells, nucleotides and proteins released from tumor cells into body fluids to help with cancer diagnosis and prognosis. Methylation of circulating tumor DNA (ctDNA) has gained increasing attention as biomarkers for lung cancer. Here we briefly introduce the biological basis and detection method of ctDNA methylation, and review various applications of methylated DNA in body fluids in lung cancer screening, diagnosis, prognosis, monitoring and treatment prediction. We also discuss the emerging role of RNA methylation as biomarkers for cancer.     

Enhancement of the direct antimicrobial activity of Lysep3 against <Emphasis Type="Italic">Escherichia coli</Emphasis> by inserting cationic peptides into its C terminus

Phage lysins are considered promising antimicrobials against resistant bacterial infections. Some lysins have been reported for the prevention and treatment of Gram-positive bacterial infection. Gram-negative bacterial phage lysins, however, can only destroy the bacterial cell wall from inside because of the obstruction of the bacterial outer membrane that prevents direct hydrolysis of the bacterial wall peptidoglycan from the outside, severely restricting the development of lysins against Gram-negative bacteria. In this study, genetic engineering techniques were used to fuse a 5 cationic amino acid polypeptide (KRKRK), a 10 cationic amino acid polypeptide (KRKRKRKRKR), a 15 cationic amino acid polypeptide (KRKRKRKRKRKRKRK), and a polypeptide including both cationic and hydrophobic amino acids (KRKRKFFVAIIP) to the C-terminus of the Escherichia coli phage lysin Lysep3 to obtain four fusion lysins (5aa, 10aa, 15aa, Mix). The bactericidal effects of those four lysins on E. coli were then compared in vitro. Our results showed that the fusion of hydrophobic and positively charged amino acids, Mix, can kill E. coli effectively; the fusion of positively charged amino acids alone at the C-terminus (5aa, 10aa, 15aa) also showed bactericidal activity against E. coli from the outside, with the bactericidal activity gradually increasing with the positive charge at the C-terminus of the lysin. Collectively, improving the positive charge at the C-terminus of E. coli bacteriophage lysin Lysep3 increases its bactericidal ability from outside E. coli, providing a new practical method for the development of anti-Gram-negative bacterial lysins.     

SPHK1 (sphingosine kinase 1) induces epithelial-mesenchymal transition by promoting the autophagy-linked lysosomal degradation of CDH1/E-cadherin in hepatoma cells

SPHK1 (sphingosine kinase 1), a regulator of sphingolipid metabolites, plays a causal role in the development of hepatocellular carcinoma (HCC) through augmenting HCC invasion and metastasis. However, the mechanism by which SPHK1 signaling promotes invasion and metastasis in HCC remains to be clarified. Here, we reported that SPHK1 induced the epithelial-mesenchymal transition (EMT) by accelerating CDH1/E-cadherin lysosomal degradation and facilitating the invasion and metastasis of HepG2 cells. Initially, we found that SPHK1 promoted cell migration and invasion and induced the EMT process through decreasing the expression of CDH1, which is an epithelial marker. Furthermore, SPHK1 accelerated the lysosomal degradation of CDH1 to induce EMT, which depended on TRAF2 (TNF receptor associated factor 2)-mediated macroautophagy/autophagy activation. In addition, the inhibition of autophagy recovered CDH1 expression and reduced cell migration and invasion through delaying the degradation of CDH1 in SPHK1-overexpressing cells. Moreover, the overexpression of SPHK1 produced intracellular sphingosine-1-phosphate (S1P). In response to S1P stimulation, TRAF2 bound to BECN1/Beclin 1 and catalyzed the lysine 63-linked ubiquitination of BECN1 for triggering autophagy. The deletion of the RING domain of TRAF2 inhibited autophagy and the interaction of BECN1 and TRAF2. Our findings define a novel mechanism responsible for the regulation of the EMT via SPHK1-TRAF2-BECN1-CDH1 signal cascades in HCC cells. Our work indicates that the blockage of SPHK1 activity to attenuate autophagy may be a promising strategy for the prevention and treatment of HCC.     

PALM成像中激光强度和定位精度相关性的研究

近十年来,基于单分子定位的PALM成像技术快速发展,将显微镜的分辨率提高到了2-25nm。本文发现PALM成像过程中采用的激发光强度与成像的定位精度之间有密切的联系。我们分别选择了PALM成像使用的光激活荧光蛋白、光转换荧光蛋白和光开关荧光蛋白中最常用的荧光蛋白进行验证。实验发现伴随激光强度的增加,大部分荧光蛋白的光子数先升高然后趋于饱和,背景噪声几乎线性升高。进一步分析发现荧光蛋白的定位误差随着激光强度增强先降低后升高,因此选用合适的激光强度在PALM成像实验中至关重要。如何提高PALM成像的分辨率一直是科学家研究的热点,本研究内容可以指导研究人员在PALM成像中选用合适的激发光强度,从而得到高分辨率的图像。     

基于元胞自动机的城市空间动态模拟

城市空间动态的模拟与预测可以为城市可持续发展规划与管理提供重要的参考依据。SLEUTH元胞自动机模型在城市空间模拟中较强的适用性和可移植性,该模型通过对历史数据的蒙特卡洛迭代自动寻找城市增长误差最小的参数组合,解决了传统元胞自动机模型中转换规则不易确定的问题。以武汉市为研究案例,运用SLEUTH模型进行了城市空间动态模拟与情景预测。2007年至2011年的城市空间模拟结果显示,模拟结果与实际历史数据可以获得良好的空间匹配度,Lee-Sallee形状指数均在0.6以上,显示SLEUTH元胞自动机模型经过本地化校正后具有较强的适用性和满意的模拟精度。进而,设置了现状趋势、基本保护、严格保护等3种情景对武汉2025年城市空间动态进行了预测,结果显示,各情景模式下城市居住用地均明显增长,农业用地、林地、水域等均有所减少;现状趋势情景和基本保护情景下农田、林地、水域减少的幅度较大,会加剧区域的生境破碎、耕地功能下降、水资源匮乏、湖滨湿地萎缩等生态问题,说明这两种情景不能有效满足城市生态系统健康和可持续发展的需要。严格保护情景下,城市居住用地扩张的程度得到了明显的控制,水域和林地得到了有效的保护,对于重要的自然生态系统组分保护及其服务能力维持可以起到显著作用。     

诱导多能干细胞技术在药物研发领域中的前景

由于基础研究环境和临床环境之间存在的转化差异,使得药物在临床阶段取得成功仍然具有挑战性。诱导多能干(iPS)细胞的诞生为药物研发领域带来了新的希望,使研究者能在体外人性化各种药理学和毒理学模型。人iPS衍生细胞的可获得性,特别是可以定向分化成特定的功能性细胞、组织和器官,一方面为疾病机制研究与细胞治疗提供了全新的途径。另一方面,转化研究中的生物标记物提供了评估临床前基础研究环境和临床环境下毒理学及药理学影响的可衡量的指标,而iPS细胞给生物标记物的研究带来了全新的思路。从转化研究的角度概述了基于iPS细胞药物发现的现行策略,阐明了iPS细胞的潜力以及生物标志物在药物发现和发展整个过程中的作用,突出在该领域有待改进的地方,以期为进一步相关性研究提供一定参考,为新药研发提供新的思路与方法。     

昆虫次生内共生菌Rickettsia研究进展

Rickettsia隶属于变形菌纲Proteobacteria的α亚群立克次体科Rickettsiaceae革兰氏阴性菌,是形态多样的次生真核细胞内共生菌。Rickettsia的功能是多样的,在一些宿主中为营养共生菌,在另一些宿主中为生殖调控因子,或以昆虫为载体的植物病原菌,此外,Rickettsia还能增强宿主抗药性,提高宿主抵御天敌、高温或者其它致死因素的能力。本综述主要从Rickettsia的起源、分类、在昆虫体内的分布、传播方式、与昆虫生殖调控的关系以及基因组进化等方面,简述Rickettsia的研究进展,重点提出了Rickettsia研究中一些尚未解决的问题,期望通过这些研究进一步明确Rickettsia与昆虫之间的互作关系。     

星星草光合蒸腾季节变化与气候因子的关系

本项研究工作在测定天然星星草和人工种植生长一至三年星星草光合蒸腾特性季节变化的同时,测定了日照量、气温、地温、相对湿度,降雨量和蒸发量等气候因子的季节变化,并采用相关系数和通径系数分析方法分析了星星草光合蒸腾特性季节变休与气候因子的关系。     

Photosynthetic regulation of C4 desert plant Haloxylon ammodendron under drought stress

About 20-year-old desert plants of C₄ species, Haloxylon ammodendron, growing at the southern edge of the Badain Jaran Desert in China, were selected to study the photosynthetic characteristics and changes in chlorophyll fluorescence when plants were subject to a normal arid environment (AE), moist atmospheric conditions during post-rain (PR), and the artificial supplement of soil water (SW). Results showed that under high radiation, in the AE, the species down-regulated its net assimilation rate (A) and maximum photochemical efficiency of PS II (Fv/Fm), indicating photoinhibition. However, under the PR and SW environments, A was up-regulated, with a unimodal diurnal course of A and a small diurnal change in Fv/Fm, suggesting no photoinhibition. When the air humidity or SW content was increased, the light compensation points were reduced; light saturation points were enhanced; while light saturated rate of CO₂ assimilation (A _max) and apparent quantum yield of CO₂ assimilation (Φ_C) increased. Φ_C was higher while the A _max was reduced under PR relative to the SW treatment. It was concluded that under high-radiation conditions drought stress causes photoinhibition of H. ammodendron. Increasing air humidity or soil moisture content can reduce photoinhibition and increase the efficiency of solar energy use.