胡杨种子散布的时空分布格局

以额济纳胡杨为研究对象,对种子雨的散布时间、强度、散布距离以及种子雨和空气湿度、风之间的关系进行了研究。胡杨种子雨可以分为初始期、高峰期和消退期3个阶段,大部分的种子集中在高峰期落下。种子的散布主要受湿度和风的影响。湿度对种子雨的强度起主要作用,在一天之中,种子在湿度较低的中午和下午集中散落。应用一元线性回归模型对种子雨强度和相对湿度进行分析后表明二者之间存在显著的负相关关系。对种子的散播距离进行研究后发现,大部分种子落在母树附近,少部分种子能够进行长距离传播。风对种子的传播的方向和距离起决定性的作用,不同方向上的种子传播距离和强度相差很大。在顺风方向上,种子的传播距离最远,所有的长距离传播现象几乎都发生在这一方向上;而在主风向的垂直方向和逆风方向上,种子的散布距离较小,很少有种子能够进行长距离传播。对风的观测表明中午后和下午初的风力较强,而此时种子雨强度又最大,有利风力条件和高种子雨强度出现的同步性可能是促进胡杨种子进行长距离传播最有效的生物控制机制。由于胡杨种子在自然条件下的存活时间非常短暂,所以研究中不同胡杨母树林间种子散播时间的差异可能是胡杨种群内部为适应不同洪水期所表现出的风险分摊机制所造成的。     

肠道微生物与线粒体之间的互作

肠道微生物与肠道细胞线粒体功能之间的关系十分密切。一方面,肠道微生物可直接或通过短链脂肪酸、硫化氢和一氧化氮等代谢产物间接影响与线粒体相关的能量代谢过程,调节线粒体活性氧的产生,调控线粒体甚至整个机体的免疫反应。另一方面,肠道细胞线粒体功能紊乱和基因组的遗传变异也会影响肠道微生物的组成和功能。本文主要介绍了肠道微生物和线粒体之间的互作关系的最新研究进展,为靶向作用于肠道菌群和线粒体以调节肠道健康提供理论依据。     

Comprehensive analysis of mRNA‐level and miRNA‐level subpathway activities for identifying robust ovarian cancer prognostic signatures

Ovarian cancer (OvCa) causes the highest mortality among all gynaecologic cancers. A large number of mRNA‐ or miRNA‐based signatures were identified for OvCa patient prognosis. However, the comprehensive analysis of function‐level prognostic signatures is currently not considered in OvCa. In the present study, we respectively inferred subpathway activities from mRNA and miRNA levels based on high‐throughput expression profiles and reconstructed subpathways. Firstly, the activities of two tumour pathways were calculated and the difference between normal and tumour samples were analysed using multiple tumour types. Then, we calculated subpathway activities for OvCa based on the expression profiles from both mRNA and miRNA levels. Furthermore, based on these subpathway activity matrices, we performed bootstrap analysis to obtain sub‐training sets and utilized univariate method to identify robust OvCa prognostic subpathways. A comprehensive comparison of subpathway results between these two levels was performed. As a result, we observed subpathway mutual exclusion trend between the levels of mRNA and miRNA, which indicated the necessary of combining mRNA‐miRNA levels. Finally, by using ICGC data as testing sets, we utilized two strategies to verify survival predictive power of the mRNA‐miRNA combined subpathway signatures and performed comparisons with results from individual levels. It was confirmed that our framework displayed application to identify robust and efficient prognostic signatures for OvCa, and the combined signatures indeed exhibited advantages over individual ones. In the study, we took a step forward in relevant novel integrated functional signatures for OvCa prognosis.     

Leucine ureido derivatives as aminopeptidase N inhibitors using click chemistry. Part II

Aminopeptidase N (APN) has been proved to be deeply associated with cancer angiogenesis, metastasis and invasion. Therefore, APN gains increasing attention as a promising anti-tumor target. In the current study, we report the design, synthesis, biological evaluation and structure-activity relationship of one new series of leucine ureido derivatives containing the 1,2,3-triazole moiety. Among them, compound 31f was identified as the best APN inhibitor with IC₅₀ value being two orders of magnitude lower than that of the positive control bestatin. Compound 31f possessed selective cytotoxicity to several tumor cell lines over the normal cell line human umbilical vein endothelial cells (HUVECs). Notably, when combined with 5-fluorouracil (5-Fu), 31f exhibited synergistic anti-proliferation effect against several tumor cell lines. At the same concentration, 31f exhibited much better anti-angiogenesis activities than bestatin in the HUVECs capillary tube formation assay and the rat thoracic aorta rings test. In the in vitro anti-invasion assay, 31f also exhibited superior potency over bestatin. Moreover, considerable in vivo antitumor potencies of 31f alone or in combination with 5-Fu were observed without significant toxic signs in a mouse heptoma H22 tumor transplant model.     

Correction to: Managing biological invasions: the cost of inaction

Biological Invasions -     

人肠道产甲烷菌与肠道健康

摘要:肠道中甲烷菌可以在严格厌氧的条件下利用H2和碳源生成甲烷,约1/3的正常人体内都可以检测到甲烷。近年来,很多研究发现甲烷菌在维持肠道微生态稳定方面起积极作用,越来越多的研究关注甲烷菌发酵产物(甲烷)在肠道中的代谢,主要集中于甲烷菌与肠道功能失调之间的关系。IBS患者肠道甲烷菌数量常比正常人群少,并且肠道甲烷菌与肥胖症的发生有一定关系。本文对甲烷菌的产甲烷作用在肠道功能稳定方面的作用、甲烷与肠道疾病(肠易激综合症、结肠癌)以及甲烷菌和甲烷与肥胖症的关系进行概述,并从上述几个方面综述肠道产甲烷菌、甲烷与肠道健康的关系。     

The yeast mitochondrial citrate transport protein: characterization of transmembrane domain III residue involvement in substrate translocation

Previous examination of the accessibility of a panel of single-Cys mutants in transmembrane domain III (TMDIII) of the yeast mitochondrial citrate transport protein to hydrophilic, cysteine-specific methanethiosulfonate reagents, enabled identification of the water-accessible surface of this domain and suggested its potential participation in the formation of a portion of the substrate translocation pathway. To evaluate this idea, we conducted a detailed characterization of the functional properties of 20 TMDIII single-Cys substitution mutants. Kinetic studies indicate that the A118C, S123C, and K134C mutants displayed a 3- to 7-fold increase in K(m). Moreover, the A118C mutation caused a doubling of the V(max) value, whereas the S123C, E131C, and K134C mutations caused V(max) to dramatically decrease, resulting in a reduction of the catalytic efficiencies of these three mutants by >97%. Examination of the ability of citrate to protect against the inhibition mediated by sodium (2-sulfonatoethyl)methanethiosulfonate (MTSES) indicated that citrate conferred significant protection of cysteines substituted at eight water-accessible locations (i.e. Gly-115, Leu-116, Gly-117, Leu-121, Ser-123, Val-127, Glu-131, and Thr-135), but not at other sites. Importantly, similar levels of protection were observed at both 4 degrees C and 20 degrees C. The temperature independence of the protection indicates that substrate binding and/or occupancy of the transport pathway sterically blocks the access of MTSES to these sites, thereby providing direct protection, without involvement of a major protein conformational change. The significance of these extensive functional investigations is discussed in terms of the three-dimensional CTP homology model that we previously developed and a new model of the dimer interface.     

Concentration of phenolic compounds of Populus euphratica and soil water contents in Ejina oasis, Inner Mongolia, China

With colorimetric methods, the concentrations of total phenolics, flavonoids and condensed tannins were analyzed in 9 categories of organs in Populus euphratica, including lanceolate leaves, ovate leaves, green branches, branches (D < 5 mm in diameter), branches (5–10 mm in diameter), barks, roots (D < 2 mm in diameter), roots (2–5 mm in diameter) and roots (5–10 mm in diameter). The results showed that phenolic compounds were present throughout the collected organs with the higher total phenolics concentrations in barks (27.93 mg/g), and the mean total phenolics concentrations in two categories of leaves, three classes of roots and three classes of branches were 17.64, 16.72 and 12.19 mg/g, respectively. The higher flavonoids were present in barks (51.30 mg/g), and the mean flavonoid contents in two categories of leaves, three classes of roots and three classes of branches were 28.45, 39.99 and 23.67 mg/g, respectively. The higher condensed tannin contents were found in roots (mean = 22.10 mg/g for three categories of roots), and the average condensed tannin contents in barks, leaves in two categories and branches in three classes were 8.41, 4.03 and 4.47 mg/g, respectively. There was no significant difference between the phenolic compounds of lanceolate leaves and ovate leaves (P > 0.05). Phenolic compounds in branches decreased with the branches maturing, resulting in the following orders: green branches > branches (D < 5 mm) > branches (5–10 mm). Condensed tannins in roots increased with the root diameter decreasing, and the highest condensed tannin contents were found in small roots (D < 2 mm) (25.95 mg/g). By analyzing correlation between phenolic compounds in all collected organs and soil water contents, it was indicated that the phenolic compounds in ovate leaves had negative relation with soil water contents (P < 0.05), and the r values for total phenolics, flavonoids and condensed tannins were –0.949, –0.923 and –0.944, respectively. Data reported here revealed the variation of phenolic compounds in different organs of P. euphratica, and their relationships with the environmental factors in extremely arid areas were discussed.     

Kinetic study of corn straw pyrolysis: comparison of two different three-pseudocomponent models

With heating rates of 20, 50 and 100 K min(-1), the thermal decomposition of corn straw samples (corn stalks skins, corn stalks cores, corn bracts and corn leaves) were studied using thermogravimetric analysis. The maximum pyrolysis rates increased with the heating rate increasing and the temperature at the peak pyrolysis rate also increased. Assuming the addition of three independent parallel reactions, corresponding to three pseudocomponents linked to the hemicellulose, cellulose and lignin, two different three-pseudocomponent models were used to simulate the corn straw pyrolysis. Model parameters of pyrolysis were given. It was found that the three-pseudocomponent model with n-order kinetics was more accurate than the model with first-order kinetics at most cases. It showed that the model with n-order kinetics was more accurate to describe the pyrolysis of the hemicellulose.