Ecological effects of dams,alien fish,and physiochemical environmental factors on homogeneity/heterogeneity of fish community in four tributaries of the Pearl River in China

In this study, we aimed to characterize the fish community structure and identify the drivers contributing to homogenization/differentiation processes in four tributaries to the Pearl River, Guangxi Province, China, over the past few decades. We sampled 22 sites seasonally from 2013 through 2015, and these sites were selected based on archived records of previous sampling conducted in the 1980s. Jaccard's faunal similarity index, cluster analysis, and canonical correspondence analysis (CCA) were applied to describe the homogenization/differentiation of fish community and illustrate the potential effectors. The number of fish species present in three of the four sampled tributaries declined dramatically over the past 30 years, leading toward a trend of increased fish community homogeneity throughout the watershed. Results from multidimensional scaling and cluster analyses allowed us to divide the study area into two distinct ecoregions. Four species (yellow catfish Pelteobagrus fulvidraco, pond loach Misgurnus anguillicaudatus, Nile tilapia Oreochromis niloticus, and sharpbelly Hemiculter leucisculus) were considered to be indicative fish species contributing more than 5% of the dissimilarity between the two eco‐regions according to the results of similarity percentage procedure. Results from CCA revealed that pH and latitude corresponded with the dominant fish species of each respective tributary. More specifically, CCA results allowed us to classify dominant fish species into three distinct groups. The first group was mainly located in Guijiang characterized by higher latitudes and lower pH values, the second group was widespread in the four tributaries, and the last group was primarily distributed in Yujiang, Youjiang, and Zuojiang characterized by lower latitudes and higher pH values. Spatial differentiation of fish community structure and temporal homogeneity of species composition were attributed to the joint actions of human interventions including construction of dams and introductions of exotic fish species that led to habitat degeneration and fragmentation, and unequal interspecies competitions.     

苦杏仁对照提取物替代苦杏仁对照药材的可行性研究

目的：以对照药材技术要求为基础,以等量同质为原则,利用现代的提取制备技术,制备成质量稳定、均匀性好的苦杏仁对照提取物。通过考察不同的薄层系统,建立薄层鉴别用对照提取物的质量标准,供中药标准中薄层鉴别使用。并对其主要药效成分进行方法学考察,确保今后制备的对照提取物的一致性。方法：采用不同薄层色谱系统对苦杏仁对照提取物可替代对照药材进行定性研究;并用高效液相色谱法测定苦杏仁对照提取物中苦杏仁苷的含量。结果：在苦杏仁对照提取物薄层色谱中,展开剂：为甲苯－甲酸乙酯－甲醇－甲酸－水（6∶2∶0．4∶0．1∶0．1 ）,在与对照药材色谱相应位置上,显相同颜色的斑点。HPLC测定苦杏仁对照提取物中苦杏仁苷含量,苦杏仁苷线性范围461．7～15．39 mg／L（r＝0．9995）,平均回收率为101 ．1％（RSD＝2．15％）,该方法准确、可靠、专属性强,重复性好。结论：苦杏仁对照提取可替代对照药材进行定性鉴别。     

Endocytosis and exocytosis in hyphal growth

Two ancient processes, endocytosis and exocytosis, are employed by eukaryotic cells to shape their plasma membrane and interact with their environment. Filamentous fungi have adapted them to roles compatible with their unique ecological niche and morphology. These organisms are optimal systems in which to address questions such as how endocytosis is localized, how endocytosis and exocytosis interact, and how large molecules traverse eukaryotic cell walls. In the tips of filamentous (hyphal) cells, a ring of endocytosis encircles an apical crescent of exocytosis, suggesting that this area is able to support an endocytic recycling route, although both processes can occur in subapical regions as well. Endocytosis and exocytosis underlie growth, but also facilitate disease progression and secretion of industrially relevant compounds in these organisms. Here we highlight recent work on endocytosis and exocytosis in filamentous fungi.     

Global fit and structure optimization of flexible and rigid macromolecules and nanoparticles from analytical ultracentrifugation and other dilute solution properties

The calculation of hydrodynamic and other solution properties from structural information (size and shape or flexibility) of macromolecules and nanoparticles is feasible thanks to existing theories and computational tools. Here we review our recent advances in the inverse problem of extracting structural information from those properties. The concepts of equivalent radii and ratios of radii are particularly useful in global-fitting structural analysis, when one has to treat simultaneously with various properties, eventually for a series of samples. Based on the equivalent radii or their ratios, we define target functions that measure the adequacy of a given structure to fit a set of experimental properties. Structural determination is carried out by minimization of those target functions. We review a variety of examples. Some of them refer to the simple, yet important models like ellipsoids, cylinders and wormlike chains, whose structure is determined by optimization of the model parameters. In other, more complex cases, properties are calculated with computational tools like programs in the HYDRO suite. We have devised other tools to make the structure optimization from the results of those calculations in a quite direct, simple and systematic manner.     

Homogeneous immunoassay of polyclonal antibodies by use of antigen-coupled liposomes

Anti-cytochrome c and anti-myoglobin antibodies were assayed by use of immunoliposomes coupled with the antigens. Addition of complement under the existence of the antigens. Addition of complement under the existence of the antigen-antibody complex on the surface of the liposome caused lysis of the liposomes, which was proportional to the amount of the antigen-antibody complex formed as well as the concentration of complement added. Thus, the degree of marker release depended on the average association constant and also on its heterogeneity of the polyclonal antibodies, which shows that the results assayed by this method are correlated to the antibody ability to form the antigen-antibody complex (c) 1993 Wiley & Sons, Inc.     

Root and shoot elongation as an assessment of heavy metal toxicity and ‘Zn Equivalent Value’ of edible crops

Seeds of thirteen edible plant species were tested for their response to heavy metals during their early development. It was found that a short-term root elongation test of six days could be used to evaluate the degree of toxicity of aqueous samples containing heavy metals. Shoot elongation was found to be less sensitive to metals than root elongation.The seeds were sown in pots containing freshwater sand to which known concentrations of metal solutions were added. The relative toxicity of the three metals, copper, nickel and zinc, followed the pattern of Ni > Cu > Zn.Results on the relative toxicity of Zn : Cu: Ni to various plant species indicated that the ratios were species-specific. The Zn equivalent concept of Zn : Cu : Ni = 1 : 2 : 8 could not be applied to all the plant species tested.The root growth of seeds of Brassica parachinensis (flowering Chinese cabbage) placed on filter papers in petri dishes to which metal solutions were added were tested. The sensitivity ranking of the metals tested was found to be as follows: Ni > Cd > Cu > Al > Fe > Zn > Pb > Mn > Ag. There was no significant difference (p > 0.05) in percentage reduction in root elongation among the four different repeated trials.     

Rate-limiting Reactions Determining Different Activation Kinetics of Kv1.2and Kv2.1 Channels

To identify the mechanisms underlying the faster activation kinetics in Kv1.2 channels compared to Kv2.1 channels, ionic and gating currents were studied in rat Kv1.2 and human Kv2.1 channels heterologously expressed in mammalian cells. At all voltages the time course of the ionic currents could be described by an initial sigmoidal and a subsequent exponential component and both components were faster in Kv1.2 than in Kv2.1 channels. In Kv1.2 channels, the activation time course was more sigmoid at more depolarized potentials, whereas in Kv2.1 channels it was somewhat less sigmoid at more depolarized potentials. In contrast to the ionic currents, the ON gating currents were similarly fast for both channels. The main portion of the measured ON gating charge moved before the ionic currents were activated. The equivalent gating charge of Kv1.2 ionic currents was twice that of Kv2.1 ionic currents, whereas that of Kv1.2 ON gating currents was smaller than that of Kv2.1 ON gating currents. In conclusion, the different activation kinetics of Kv1.2 and Kv2.1 channels are caused by rate-limiting reactions that follow the charge movement recorded from the gating currents. In Kv1.2 channels, the reaction coupling the voltage-sensor movement to the pore opening contributes to rate limitation in a voltage-dependent fashion, whereas in Kv2.1 channels, activation is additionally rate-limited by a slow reaction in the subunit gating.     

Landscape connectivity dynamics based on network analysis in the Xishuangbanna Nature Reserve,China

Lack of landscape connectivity and habitat loss is major threats to biodiversity and ecosystem integrity in nature reserves aimed at conservation. In this study, we used structural pattern and functional connectivity metrics to analyze the spatial patterns and landscape connectivity of habitat patches for the Shangyong sub-reserve of the Xishuangbanna Nature Reserve from 1970, 1990, and 2000. On the basis of vegetation and land cover data, we applied the equivalent connected area ECA(PC) indicator to analyze the changes in forest connectivity. Four distance thresholds (2, 4, 8, 12 km) were considered to compare the patch importance of connectivity by dECA values. The results showed the declining trends of landscape connectivity measured by ECA(PC) index from 1970 to 2000. The importance of connectivity in each forest patch varied with the increment of dispersal distances at the patch level, and some important habitat patches, which exhibit a potential to enhance landscape connectivity, should be given more attention. The least-cost pathways based on network structure were displayed under four dispersal distances in three periods. The results showed that the number of paths among the fragments of forest patches exhibited radical increases for larger dispersal distances. Further correlation analyses of AWF, ECA (IIC), and ECA (PC) showed the weakest and least-frequent correlations with the structural pattern indices, while H presented more significant correlations with the PD fragmentation metric. Furthermore, Kendall's rank correlations between the forest patch area and functional connectivity indicators showed that dECA (PC) and dAWF indicators should provided the area-based prioritization of habitat patches. Moreover, the low-rank correlations showed that dF and dLCP can be considered as effective and appropriate indicators for the evaluation of habitat features and network patterns.     

单增李斯特菌vip基因缺失

单增李斯特菌(Listeria monocytogenes)是广泛存在于自然界及食物中的食源性致病菌,作为胞内寄生菌,它可以引起强烈的细胞免疫,是潜在的优良疫苗载体。vip是单增李斯特菌的毒力基因,与其侵袭能力密切相关。因此构建vip基因敲除株可为单增李斯特菌疫苗载体的研发打下重要基础。从单增李斯特菌EGDe基因组中扩增出vip基因上、下游序列,连接到穿梭载体pKSV7中得到敲除载体pKSV7-Δvip,将其以电穿孔的方式转入单增李斯特菌后,通过同源重组利用氯霉素和温度双重压力筛选得到vip基因的敲除突变株,并对敲除菌株的生长曲线进行分析发现vip敲除对细菌的生长没有显著影响,为进一步研究vip基因功能、单增李斯特的致病机制和疫苗载体的研发提供参考。     

Dosimetric and radiobiological comparison in head-and-neck radiotherapy using JO-IMRT and 3D-CRT

IntroductionDosimetric and radiobiological evaluations for the Jaws-only Intensity-modulated radiotherapy (JO-IMRT) technique for head and neck jaws-only intensity-modulated radiation therapy (JO-IMRT) and 3D conformal radiation therapy (3D-CRT). To compare the head-and-neck therapeutic approaches utilizing JO-IMRT and 3D-CRT techniques, different radiation dose indices were calculated, including: conformity index (CI), homogeneity index (HI), and radiobiological variables like Niemierko's equivalent uniform dose based tumor control probability (TCP) of planning target volume (PTV), normal tissue complication probability (NTCP) of organs at risk (OAR) (brainstem, spinal cord, and parotid grand).Materials and methodsTwenty-five nasopharynx patients were studied using the Prowess Panther Treatment Planning System (Prowess Inc). The results were compared with the dose distribution obtained using 3D-CRT.ResultsRegarding tumor coverage and CI, JO-IMRT showed better results than 3D-CRT. The average doses received by the PTVs were quite similar: 72.1 ± 0.8 Gy by 3D-CRT and 72.5 ± 0.6 Gy by JO-IMRT plans (p > 0.05). The mean doses received by the parotid gland were 56.7 ± 0.7 Gy by 3D-CRT and 26.8 ± 0.3 Gy by JO-IMRT (p > 0.05). The HI and CI were 0.13 ± 0.01 and 0.14 ± 0.05 and (p > 0.05) by 3D-CRT and 0.83 ± 0.05 and 0.73 ± 0.10 by JO-IMRT (p < 0.05). The average TCP of PTV was 0.82 ± 0.08 by 3D-CRT and 0.92 ± 0.02 by JO-IMRT. Moreover, the NTCP of the parotid glands, brain stem, and spinal cord were lower using the JO-IMRT than 3D-CRT plans. In comparison to the 3D-CRT approach, the JO-IMRT technique was able to boost dose coverage to the PTV, improve the target's CI and HI, and spare the parotid glands. This suggests the power of the JO-IMRT over 3D-CRT in head-and-neck radiotherapy.