Mechanism study on the frequent variations of cell-bound microcystins in cyanobacterial blooms in Lake Taihu: Implications for water quality monitoring and assessments

Although Microcystis-based toxins have been intensively studied, previous studies using laboratory cultures of Microcystis strains are difficult to explain the phenomenon that microcystin concentrations and toxin variants in natural blooms differ widely and frequently within a short-term period. The present study was designed to unravel the mechanisms for the frequent variations of intracellular toxins related to the differences in cyanobacterial colonies during bloom seasons in Lake Taihu, China. Monitoring of Microcystis colonies during warm seasons indicated that the variations in microcystins in both concentrations and toxin species were associated with the frequent alteration of Microcystis colonies in Lake Taihu. High concentration of microcystins in the blooms was always associated with two Microcystis colonies, Microcystis flos-aquae and Microcystis aeruginosa, whereas when Microcystis wesenbergii was the dominant colonial type, the toxin production of the blooms was low. Additionally, environmental factors such as temperature and nutrition were also shown to have an effect on the toxin production of the blooms, and may also potentially influence the Microcystis species present. The results of the present study provides insight into a new consideration for quick water quality monitoring, assessment and risk alert in cyanobacterium- and toxin-contaminated freshwaters, which will be beneficial not only for water agencies but also for public health. (C) 2009 Elsevier Ltd. All rights reserved.

Temperature dependence of surface quantum dots grown under frequent growth interruption

We grow In-GaAs quantum dot (QD) at low growth rate with 70 times insertion of growth interruption in MBE system. It is found that because of the extreme growth condition, QDs exhibit a thick wetting layer, large QD height value and special surface morphology which is attributed to the In segregation effect. Temperature dependence of photoluminescence measurement shows that this kind of QDs has a good thermal stability which is explained in terms of a "group coupling" model put forward by us. (C) 2007 Elsevier B.V. All rights reserved.

Temperature dependence of surface quantum dots grown under frequent growth interruption

We grow InGaAs quantum dot (QD) at low growth rate with 70 times insertion of growth interruption in MBE system. It is found that because of the extreme growth condition, QDs exhibit a thick wetting layer, large QD height value and special surface morphology which is attributed to the enhanced adatom surface diffusion and In-segregation effect. Temperature dependence of photoluminescence measurement from surface QD shows that this kind of QD has good thermal stability which is explained in terms of the presence of surface oxide. The special distribution of QD may also play a role in this thermal character. (c) 2006 Elsevier B.V. All rights reserved.

maintaining only frequent itemsets to mine approximate frequent itemsets over online data streams

IEEE

Mechanism Analysis of Landslide of a Layered Slope Induced by Drawdown of Water Level

The frequent drawdown of water level of Yangtze River will greatly influence the stability of the widely existing slopes in the Three Gorges reservoir zone, especially those layered ones. Apart from the fluctuating speed of water level, the different geological materials will also play important roles in the failure of slopes. Thus, it must be first to study the mechanism of such a landslide caused by drawdown of water level.A new experimental setup is designed to study the performance of a layered slope under the drawdown of water level. The pattern of landslide of a layered slope induced by drawdown of water level has been explored by means of simulating experiments. The influence of fluctuating speed of water level on the stability of the layered slope is probed,especially the whole process of deformation and development of landslide of the slope versus time. The experimental results show that the slope is stable during the water level rising, and the sliding body occurs in the upper layer of the slope under a certain drawdown speed of water level. In the process of slope failure, some new small sliding body will develop on the main sliding body, and the result is that they speed up the disassembly of the whole slope.Based on the simulating experiment on landslide of a layered slope induced by drawdown of water level, the stress and displacement field of the slope are calculated.The seepage velocity, the pore water pressure, and the gradient of pore water head are also calculated for the whole process of drawdown of water level. The computing results are in good agreement with the experimental results. Accordingly, the mechanism of deformation and landslide of the layered slope induced by drawdown of water level is analyzed. It may provide basis for treating this kind of layered slopes in practical engineering.

Evolution of phenylalanyl-tRNA synthetase by domain losing

The gene duplication, fusion and horizontal transfer are the frequent events during evolution of many proteins, including the aminoacyl-tRNA synthetases (AARSs). However, in this work, it was shown that the main event during evolution of phenylalanyl-tRNA synthetase (PheRS) is a domain loss, and the function/activity of PheRS is not affected by domain losing. Generally, the size of genome and number of genes are increased during evolution from bacteria to eukaryote, but the interesting thing is that the type and number of PheRS domains in eukaryotae are obviously less than those in bacteria. The evolution of PheRS by domain losing seems to be related to the functional evolution of some AARSs from the multiple specificities to the single specificity.

Numbers of migratory waterbirds at Lake Lashihai, China

Between October 1999 and April 2000, WC surveyed the waterbirds at Lake Lashihai, China. A total of 52 species were recorded, of which one species was a resident, 34 were winter visitors, and 17 were passage migrants. Species richness was highest in November. Passage migrants mainly occurred in October, November, and April, and they stayed longer at the lake during their autumn migration than during the spring migration. The seasonal distribution pattern of total numbers of all waterbirds was bimodal. One peak occurred between late December and early January, and the other in middle March. The seasonal distribution patterns of 15 common species have been classified a. bimodal, unimodal, or irregular. The numbers of five common species were variable in middle winter, and their numerical Change in contiguous weeks were more than 30%, suggesting that local movements might be frequent.

Spatial and seasonal variations in benthic algal assemblages in streams in monsoonal Hong Kong

Samples from stone surfaces were collected in pools within four unpolluted hillstreams (two shaded and two unshaded) in monsoonal Hong Kong (lat. 23 degrees N) to elucidate the extent of spatial (within and among streams) and temporal (seasonal) variations in algal biomass and assemblage composition. Sampling continued for over 12 months, incorporating the dry season when streams were at baseflow, and the wet season when spates were frequent. We anticipated that algal biomass would be lower in shaded streams and during the wet season, with associated seasonal differences in assemblage composition or relative abundance of different growth forms (e. g. erect versus prostrate). Benthic chlorophyll a (a proxy for algal biomass) varied among streams from an annual mean of 11.0-22.3 mg m(-2). Dry-season standing stocks were 18% higher than during the wet season when spate-induced disturbance reduced algal standing stocks. Algal biomass varied significantly at the stream scale, but not at the pool scale, and was lower in unshaded streams, where standing stocks may have been limited by high densities of algivorous balitorid loaches (mainly Pseudogastromyzon myersi). An overriding effect of grazers on algal biomass could also have reduced variations resulting from spate-induced disturbance. Significant differences in assemblage composition among streams, which were dominated by diatoms and cyanobacteria (totally 82 taxa) were not systematically related to shading conditions. Seasonal variations in algal assemblages were statistically significant but rather minor, and did not involve major shifts in composition or growth form caused by spate-induced disturbance. The abundance of filamentous cyanobacteria in all the streams may have been due to 'gardening' by balitorid loaches that removed erect or stalked diatoms and favoured cyanobacteria that persist through basal regeneration of filaments. This explanation requires validation through manipulative experiments.

Identification of differentially expressed immune-relevant genes in Chinese soft-shelled turtle (Trionyx sinensis) infected with Aeromonas hydrophila

Expressed sequence tag (EST) analysis is an efficient tool for gene discovery and profiling gene expression. Aeromonas hydrophila, a ubiquitous waterborne bacterium, is one of the most frequent pathogens isolated from diseased aquatic organisms. In order to understand the molecular mechanism of anti-bacteria immune response in reptile, we have investigated the differentially expressed genes in Chinese soft-shelled turtle (Trionyx sinensis) experimentally infected with A. hydrophila by suppression subtractive hybridization (SSH). Forty-two genes were identified from more than 200 clones, of which 25 genes are found for the first time in reptiles, and classified into 6 categories: 18 in defense/immunity. 4 in catalysis, 2 in retrotransposon; 2 in cell signal transduction, 5 in cell metabolism, 10 in protein expression, and 1 in cell structure. Of the 42 differentially expressed genes, 6 genes, IL-8, serum amyloid A (SAA), CD9, CD59, activating transcription factor 4 (ATF4) and cathepsin L genes, were further observed to be up-regulated in the infected turtles by virtual Northern hybridization and RT-PCR assays. (C) 2008 Elsevier B.V. All rights reserved.

U19/Eaf2 knockout causes lung adenocarcinoma, B-cell lymphoma, hepatocellular carcinoma and prostatic intraepithelial neoplasia

Upregulated gene 19 (U19)/ELL-associated factor 2 (Eaf2) is a potential human tumor suppressor that exhibits frequent allelic loss and downregulation in high-grade prostate cancer. U19/Eaf2, along with its homolog Eaf1, has been reported to regulate transcriptional elongation via interaction with the eleven-nineteen lysine-rich leukemia (ELL) family of proteins. To further explore the tumor-suppressive effects of U19/Eaf2, we constructed and characterized a murine U19/Eaf2-knockout model. Homozygous or heterozygous deletion of U19/Eaf2 resulted in high rates of lung adenocarcinoma, B-cell lymphoma, hepato cellular carcinoma and prostate intraepithelial neoplasia. Within the mouse prostate, U19/Eaf2 defficiency enhanced cell proliferation and increased epithelial cell size. The knockout mice also exhibited cardiac cell hypertrophy. These data indicate a role for U19/Eaf2 in growth suppression and cell size control as well as argue for U19/Eaf2 as a novel tumor suppressor in multiple mouse tissues. The U19/Eaf2 knockout mouse also provides a unique animal model for three important cancers: lung adenocarcinoma, B-cell lymphoma and hepatocellular carcinoma.

Cloning, expression and characterization of aerolysin from Aeromonas hydrophila in Escherichia coli

Aerolysin is a toxin (protein in nature) secreted by the strains of Aeromonas spp. and plays all important role in the virulence of Aeromonas strains. It has also found several applications such as for detection of glycosylphosphatidylinositol (GPI)-anchored proteins etc. A. hydrophila is a ubiquitous Gram-negative bacterium which causes frequent harm to the aquaculture. To obtain a significant amount of recombinant aerolysin in the active form, in this study, we expressed the aerolysin in E. Coli Under the control of T7 RNase promoter. The coding region (AerA-W) of the aerA gene of A. hydrophila XS91-4-1. excluding partial coding region of the signal peptide was cloned into the vector pET32a and then transformed into E. coli b121. After optimizing the expression conditions, the recombinant protein AerA-W was expressed in a soluble form and purified using His-Bind resin affinity chromatography. Recombinant aerolysin showed hemolytic activity in the agar diffusive hemolysis test. Western blot analysis demonstrated good antigenicity of the recombinant protein.

FB1, an E2A fusion partner in childhood leukemia, interacts with U19/EAF2 and inhibits its transcriptional activity

Background: U19/EAF2 is a potential tumor suppressor exhibiting frequent down-regulation and allelic loss in advanced human prostate cancer specimens. U 19/EAF2 has also been identified as ELL-associated factor 2 (EAF2) based on its binding to ELL, a fusion partner of MLL in acute myeloid leukemia. U19/EAF2 is a putative transcription factor with a transactivation domain and capability of sequence-specific DNA binding. Methods: Yeast-two-hybrid-screening was used to identify U19/EAF2-binding partners. Co-immunoprecipitation and mammalian 1-hybrid assay were used to characterize a U19/EAF2-binding partner. Results: FB1, an E2A fusion partner in childhood leukemia, was identified as a binding-partner of U19/EAF2. FB1 also binds to EAF1, the only homologue of U19/EAF2. FB1 also interacts and co-localizes with ELL in the nucleus. Interestingly, FB1 inhibited the transcriptional activity of U19/EAF2 but not EAF1. Conclusions: FB1 is an important binding partner and a functional regulator of U19/EAF2, EAF1, and/or ELL. (c) 2007 Elsevier Ireland Ltd. All rights reserved.

Phylogenetic relationships of the Chinese sisorid catfishes: a nuclear intron versus mitochondrial gene approach

Several recent molecular phylogenetic studies of the sisorid catfishes (Sisoridae) have challenged some aspects of their traditional taxonomy and cladistic hypotheses of their phylogeny. However, disagreement with respect to relationships within this family in these studies highlights the need for additional data and analyses. Here we subjected 15 taxa representing 12 sisorids genera to comprehensive phylogenetic analyses using the second intron of low-copy nuclear S7 ribosomal protein (rpS7) gene and the mitochondrial 16S rRNA gene segments both individually and in combination. The competing sisorid topologies were then tested by using the approximately unbiased (AU) test and the Shimodaira-Hasegawa (SH) test. Our results support previously suggested polyphyly of Pareuchiloglanis. The genus Pseudecheneis is likely to be nested in the glyptosternoids and Glaridoglanis might be basal to the tribe Glyptosternini. However, justified by AU and SH test, the sister-group relationship between Pseudecheneis and the monophyletic glyptosternoids cannot be rejected based on the second intron of rpS7 gene and combined data analyses. It follows that both gene segments are not suitable for resolving the phylogenetic relationships within the sisorid catfishes. Overall, the second intron of rpS7 gene yielded poor phylogenetic performance when compared to 16S rRNA gene, the evolutionary hypothesis of which virtually agreed with the combined data analyses tree. This phenomenon can be explained by the insufficient length and fast saturation of substitutions in the second intron of rpS7 gene, due to substitution patterns such as frequent indels (insertion/deletion events) of bases in the sequences during the evolution.