生物复苏——大绝灭后生物演化历史的第一幕

生命史是一部生物界短期,快速剧变与长期,慢速稳定相互交替的历史。大绝灭（即集群绝灭）事件反映了全球环境的大突变,点断了地质历史中的生命记录及其发展历程,预示着生物界的演化出现了最有意义的飞跃,近年来尝试研究大绝灭后全球生物界的残存－复苏及其基本型式,并探索复苏的控制因素,标志着地质科学中一个重心的转移（即从大绝灭转向其后的生物残存与复苏的研究）。生物复苏揭示了大绝灭后生物演化历史的第一幕,其研究的     

青海湖裸鲤寄生舌状绦虫的空间格局研究

舌状绦虫裂头蚴只寄生在体长小于２２０ｍｍ的青海湖裸鲤中,其种群在宿主种群中呈聚集分布。其聚集分布的强度随寄生虫种群平均密度的增加而降低。由于舌状绦虫在宿主体腔生长,产生明显的空间拥挤效应,可能导致宿主死亡或被食鱼鸟类捕食而转移到终末宿主中。在体长小于１２０ｍｍ的宿主中,密度依赖的死亡过程可能是使聚集强度降低的原因;而体长１４０－２００ｍｍ的鱼中,则是非密度依赖的全死过程使聚集强度增加．     

Functional Roles of the Non-Catalytic Calcium-Binding Sites in the N-Terminal Domain of Human Peptidylarginine Deiminase 4

This study investigated the functional roles of the N-terminal Ca²⁺ ion-binding sites, in terms of enzyme catalysis and stability, of peptidylarginine deiminase 4 (PAD4). Amino acid residues located in the N-terminal Ca²⁺-binding site of PAD4 were mutated to disrupt the binding of Ca²⁺ ions. Kinetic data suggest that Asp155, Asp157 and Asp179, which directly coordinate Ca3 and Ca4, are essential for catalysis in PAD4. For D155A, D157A and D179A, the k _cat/K _m,BAEE values were 0.02, 0.63 and 0.01 s⁻¹mM⁻¹ (20.8 s⁻¹mM⁻¹ for WT), respectively. Asn153 and Asp176 are directly coordinated with Ca3 and indirectly coordinated with Ca5 via a water molecule. However, N153A displayed low enzymatic activity with a k _cat value of 0.3 s⁻¹ (13.3 s⁻¹ for wild-type), whereas D176A retained some catalytic power with a k _cat of 9.7 s⁻¹. Asp168 is the direct ligand for Ca5, and Ca5 coordination by Glu252 is mediated by two water molecules. However, mutation of these two residues to Ala did not cause a reduction in the k _cat/K _m,BAEE values, which indicates that the binding of Ca5 may not be required for PAD4 enzymatic activity. The possible conformational changes of these PAD4 mutants were examined. Thermal stability analysis of the PAD4 mutants in the absence or presence of Ca²⁺ indicated that the conformational stability of the enzyme is highly dependent on Ca²⁺ ions. In addition, the results of urea-induced denaturation for the N153, D155, D157 and D179 series mutants further suggest that the binding of Ca²⁺ ions in the N-terminal Ca²⁺-binding site stabilizes the overall conformational stability of PAD4. Therefore, our data strongly suggest that the N-terminal Ca²⁺ ions play critical roles in the full activation of the PAD4 enzyme.     

兰花蕉花部维管束系统的解剖学研究

兰花蕉花梗的维管束分散排列．子房基部的维管束排成两部分,外方为一轮大维管束环,中央为分散排列的小维管束区。前者的纸管束进入子房壁,后者进入子房的中轴,形成股座纸管束;及至延长都以后,股座维管束逐渐消失．子房壁上的维管束较易识别的有心皮背束、心皮背束伴束和隔膜束．三束心皮背束经延长部最终进入花柱和柱头．心皮背束指心皮背束务与其紧靠的大维管束,三枚心皮背束伴束最终分别进入三枚外轮雄蓝．三枚隔膜束中远轴面的两枚分别进入两校内轮雄蕊,而近轴面的一枚伴随着第六枚雄蓝的缺失最后进入唇瓣中央．子房壁其余的维管束进入延长部后,先向外分出一轮纸管束进入花幕,余下的中央部分排成一轮心形的线管来环．该环远轴面的维管束分为两半分别进入两枚侧生花瓣;近轴面即心形凹陷一侧初为两轮即外轮大的维管束与内轮小的维管束,后排成一轮并与近轴面的隔膜束一同进入唇瓣．兰花蕉的唇瓣既为花瓣成员,又含一枚缺失的雄蓝维管束,与姜目已报道的只来自退化雄蕊的竹芋科的兜状结构和美人蕉科、姜科、闭鞘姜科的唇瓣有明显区别．在旅人蕉科尚未有研究资料的情况下,作者根据已有资料,对姜目雄蕊维管束系统来源和结构进行比较,初步认为在姜目的系统演化上,兰花蕉科与芭蕉料更近．     

Polyclonal Antibodies in Microplates to Predict the Maximum Adsorption Activities of Enzyme/Mutants from Cell Lysates

With microplate-immobilized polyclonal antibodies against a starting enzyme or its active mutant bearing consistent accessible epitopes, the maximum activity of an adsorbed enzyme/mutant (Vs) was predicted for comparison to recognize weakly-positive mutants. Rabbit antisera against Escherichia coli alkaline phosphatase (ECAP) were fractionated with 33% ammonium sulfate to yield crude polyclonal antibodies for conventional immobilization in 96-well microplates. The response curve of the activities of ECAP/mutant adsorbed by the immobilized polyclonal antibodies to protein quantities from a cell lysate was fit to an approximation model to predict Vs. With 0.4 μg crude polyclonal antibody for immobilization, Vs was consistent for ECAP in cell lysates bearing fourfold differences in its apparent specific activities when its abundance was greater than 0.9%. The ratio of Vs of the mutant R168K to that of ECAP was 1.5?±?0.1 (n?=?2), consistent with that of their specific activities after affinity purification. Unfortunately, the prediction of Vs with polyclonal antibodies that saturated microplate wells was ineffective to Pseudomonas aeruginosa arylsulfatase bearing less than 2% specific activity of ECAP. Therefore, with microplate-immobilized polyclonal antibodies to adsorb enzyme/mutants from cell lysates, high-throughput prediction of Vs was practical to recognize weakly-positive mutants of starting enzymes bearing fairly-high activities.     

Impacts of climate variability on tree demography in second growth tropical forests: the importance of regional context for predicting successional trajectories

Naturally regenerating and restored second growth forests account for over 70% of tropical forest cover and provide key ecosystem services. Understanding climate change impacts on successional trajectories of these ecosystems is critical for developing effective large‐scale forest landscape restoration (FLR) programs. Differences in environmental conditions, species composition, dynamics, and landscape context from old growth forests may exacerbate climate impacts on second growth stands. We compile data from 112 studies on the effects of natural climate variability, including warming, droughts, fires, and cyclonic storms, on demography and dynamics of second growth forest trees and identify variation in forest responses across biomes, regions, and landscapes. Across studies, drought decreases tree growth, survival, and recruitment, particularly during early succession, but the effects of temperature remain unexplored. Shifts in the frequency and severity of disturbance alter successional trajectories and increase the extent of second growth forests. Vulnerability to climate extremes is generally inversely related to long‐term exposure, which varies with historical climate and biogeography. The majority of studies, however, have been conducted in the Neotropics hindering generalization. Effects of fire and cyclonic storms often lead to positive feedbacks, increasing vulnerability to climate extremes and subsequent disturbance. Fragmentation increases forests’ vulnerability to fires, wind, and drought, while land use and other human activities influence the frequency and intensity of fire, potentially retarding succession. Comparative studies of climate effects on tropical forest succession across biogeographic regions are required to forecast the response of tropical forest landscapes to future climates and to implement effective FLR policies and programs in these landscapes.     

Proteasome Inhibition-Induced Downregulation of Akt/GSK-3β Pathway Contributes to Abnormality of Tau in Hippocampal Slice

Proteasome inhibition can induce abnormal accumulation and phosphorylation of microtubule-associated protein tau. The major function of tau protein is to promote microtubules assembly and stabilization, and abnormal tau protein would disturb its microtubule-binding function. In this study, proteasome inhibitor MG132 was used to treat hippocampal slices to explore the role and mechanism of Akt/glycogen synthase kinase-3β (GSK-3β) in proteasome inhibition-induced tau abnormality. During the culture period, we measure the lactate dehydrogenase (LDH) content to assay the viability of hippocampal slices. Following 2.5 and 5 μM MG132 treatment for 6 h, we detected the expression, phosphorylation modification, and microtubule-binding function of tau protein of slices. We also analyzed the changed activities of glycogen synthase kinase-3β (GSK-3β) and protein kinase B (PKB/Akt) and the level of heat shock protein 90 (Hsp90) in the process. In addition, co-immunoprecipitation was used to investigate the interaction between Akt and Hsp90, Akt and protein phosphatase-2A (PP2A) in the MG132-treated organotypic hippocampal slices. Our results indicated that proteasome inhibition led to degradation obstacles and abnormal phosphorylation of tau protein. The downregulated Akt/GSK-3β signaling pathway might be responsible for the abnormal phosphorylation of tau protein at multiple sites which further reduced the microtubule-binding function of tau protein. Furthermore, proteasome inhibition decreased the binding capacity of Akt-Hsp90 while increased the Akt-PP2A binding ability which mediated Akt inactivity. This current study establishes a hippocampal slice model targeting Akt/GSK-3β signaling pathway to explore the pivotal role of proteasome inhibition in tau pathology.     

Risk Factors of Pneumothorax after Endobronchial Ultrasound-Guided Transbronchial Biopsy for Peripheral Lung Lesions

Background

The risk of endobronchial ultrasound-guided transbronchial biopsy-related pneumothorax is a major concern and warrants further studies. The aim of our study was to estimate the risk of pneumothorax after this procedure and identify its risk factors.

Methods

From 2007 to 2011, 399 patients who underwent endobronchial ultrasound-guided transbronchial biopsy for peripheral lung lesions were included in this study. The variables analyzed included patient factors, lesion factors and procedure factors. Multivariate logistic regression analysis was used to identify independent risk factors for pneumothorax.

Results

The incidence of pneumothorax was 3.3% (13/399). Chest tube placement was required for 31% (4/13) of pneumothoraces. Independent risk factors for pneumothorax included pulmonary emphysema (OR, 55.09; 95% CI, 9.37–324.03; p<0.001) and probe position adjacent to the lesion (OR, 17.01; 95% CI, 2.85–101.64; p = 0.002). The number of biopsy specimens, age, sex, history of prior lung surgery and lesion size, location and character did not influence the risk of pneumothorax in our analyses.

Conclusions

The risk of pneumothorax after endobronchial ultrasound-guided transbronchial biopsy is low. To further reduce the risk of pneumothorax, every effort should be made to advance the endobronchial ultrasound probe into the bronchus where it is imaged within the target lesion before embarking on transbronchial biopsy.     

Dissection of human MiRNA regulatory influence to subpathway

The global insight into the relationships between miRNAs and their regulatory influences remains poorly understood. And most of complex diseases may be attributed to certain local areas of pathway (subpathway) instead of the entire pathway. Here, we reviewed the studies on miRNA regulations to pathways and constructed a bipartite miRNAs and subpathways network for systematic analyzing the miRNA regulatory influences to subpathways. We found that a small fraction of miRNAs were global regulators, environmental information processing pathways were preferentially regulated by miRNAs, and miRNAs had synergistic effect on regulating group of subpathways with similar function. Integrating the disease states of miRNAs, we also found that disease miRNAs regulated more subpathways than nondisease miRNAs, and for all miRNAs, the number of regulated subpathways was not in proportion to the number of the related diseases. Therefore, the study not only provided a global view on the relationships among disease, miRNA and subpathway, but also uncovered the function aspects of miRNA regulations and potential pathogenesis of complex diseases. A web server to query, visualize and download for all the data can be freely accessed at http://bioinfo.hrbmu.edu.cn/miR2Subpath.