Use of Metformin Alone Is Not Associated with Survival Outcomes of Colorectal Cancer Cell but AMPK Activator AICAR Sensitizes Anticancer Effect of 5-Fluorouracil through AMPK Activation

Colorectal cancer (CRC) is still the third most common cancer and the second most common causes of cancer-related death around the world. Metformin, a biguanide, which is widely used for treating diabetes mellitus, has recently been shown to have a suppressive effect on CRC risk and mortality, but not all laboratory studies suggest that metformin has antineoplastic activity. Here, we investigated the effect of metformin and AMPK activator AICAR on CRC cells proliferation. As a result, metformin did not inhibit cell proliferation or induce apoptosis for CRC cell lines in vitro and in vivo. Different from metformin, AICAR emerged antitumor activity and sensitized anticancer effect of 5-FU on CRC cells in vitro and in vivo. In further analysis, we show that AMPK activation may be a key molecular mechanism for the additive effect of AICAR. Taken together, our results suggest that metformin has not antineoplastic activity for CRC cells as a single agent but AMPK activator AICAR can induce apoptosis and enhance the cytotoxic effect of 5-FU through AMPK activation.     

不同刺激方式对在体和离体蛙腓肠肌单收缩影响的定量分析

目的:自编程定量分析不同电刺激方式对在体和离体蛙腓肠肌单收缩的影响。方法:实验分为四个组:间接刺激在体标本组(n=12),直接刺激在体标本组(n=8),间接刺激离体标本组(n=12),直接刺激离体标本组(n=8)。分别制备在体和离体蛙腓肠肌标本,施以间接电刺激(经坐骨神经)或直接电刺激(细针灸针刺激电极直接刺入腓肠肌中):强度从0 V开始,周期3 s,增量0.02 V,刺激150次;用生物机能实验系统(BL-420F)实时记录不同强度刺激对肌肉收缩的影响。后续通过自编程辅助处理分析肌肉收缩数据,对单收缩特征参数进行定量比较分析。结果:①对在体标本,与直接刺激比较:间接刺激的阈强度、半高强度和最适强度均更小(P<0.05);最大单收缩幅度更大,收缩期更长,上升斜率更小(P<0.05)。②对离体标本,与直接刺激比较:间接刺激的阈强度、半高强度和最适强度也均更小(P<0.05);最大单收缩幅度更大,收缩期更长,上升斜率更小(P<0.05)。③均采用间接刺激或直接刺激时,与离体标本比较,在体标本单收缩的各项参数均无差异(P>0.05)。结论:不论使用间接刺激或是直...     

A novel series of pyrazolylpiperidine N-type calcium channel blockers

Selective blockers of the N-type calcium channel have proven to be effective in animal models of chronic pain. However, even though intrathecally delivered synthetic ω-conotoxin MVIIA from Conus magnus (ziconotide [Prialt®]) has been approved for the treatment of chronic pain in humans, its mode of delivery and narrow therapeutic window have limited its usefulness. Therefore, the identification of orally active, small-molecule N-type calcium channel blockers would represent a significant advancement in the treatment of chronic pain. A novel series of pyrazole-based N-type calcium channel blockers was identified by structural modification of a high-throughput screening hit and further optimized to improve potency and metabolic stability. In vivo efficacy in rat models of inflammatory and neuropathic pain was demonstrated by a representative compound from this series.     

Effects of Differentiated Versus Undifferentiated Adipose Tissue-derived Stromal Cell Grafts on Functional Recovery After Spinal Cord Contusion

Controversies exist concerning the need for mesenchymal stromal cells (MSCs) to be transdifferentiated prior to their transplantation. In the present study, we compared the results of grafting into the rat contused spinal cord undifferentiated, adipose tissue-derived stromal cells (uADSCs) versus ADSCs induced by two different protocols to form differentiated nervous tissue. Using Basso, Beattie, and Bresnahan scores and grid tests, we found that three cell-treated groups, including uADSCs-treated, dADSCs induced by Protocol 1 (dADSC-P1)-treated, and dADSCs induced by Protocol 2 (dADSC-P2)-treated groups, significantly improved locomotor functional recovery in SCI rats, compared with the saline-treated group. Furthermore, functional recovery was better in the uADSC-treated and dADSC-P2-treated groups than in the dADSC-P1-treated group at week 12 postinjury (P < 0.05 for dADSC-P1 group vs. uADSCs or dADSC-P2 groups). Although both protocols could induce high percentages of cells expressing neural markers in vitro, few BrdU-labeled cells survived at the injury sites in the three cell-treated groups, and only a small percentage of BrdU-positive cells expressed neural markers. On the other hand, the number of NF200-positive axons in the uADSC-treated and dADSC-P2-treated groups was significantly larger than those in the dADSC-P1-treated and saline-treated control groups. Our results indicate that ADSCs are able to differentiate into neural-like cells in vitro and in vivo. However, neural differentiated ADSCs did not result in better functional recovery than undifferentiated ones, following SCI. In vitro neural transdifferentiation of ADSCs might therefore not be a necessary pretransplantation step. Furthermore, cellular replacement or integration might not contribute to the functional recovery of the injured spinal cord.     

A model of sequential branching in hierarchical cell fate determination

Multipotent stem or progenitor cells undergo a sequential series of binary fate decisions, which ultimately generate the diversity of differentiated cells. Efforts to understand cell fate control have focused on simple gene regulatory circuits that predict the presence of multiple stable states, bifurcations and switch-like transitions. However, existing gene network models do not explain more complex properties of cell fate dynamics such as the hierarchical branching of developmental paths. Here, we construct a generic minimal model of the genetic regulatory network controlling cell fate determination, which exhibits five elementary characteristics of cell differentiation: stability, directionality, branching, exclusivity, and promiscuous expression. We argue that a modular architecture comprising repeated network elements reproduces these features of differentiation by sequentially repressing selected modules and hence restricting the dynamics to lower dimensional subspaces of the high-dimensional state space. We implement our model both with ordinary differential equations (ODEs), to explore the role of bifurcations in producing the one-way character of differentiation, and with stochastic differential equations (SDEs), to demonstrate the effect of noise on the system. We further argue that binary cell fate decisions are prevalent in cell differentiation due to general features of the underlying dynamical system. This minimal model makes testable predictions about the structural basis for directional, discrete and diversifying cell phenotype development and thus can guide the evaluation of real gene regulatory networks that govern differentiation.     

Bradyrhizobium arachidis sp. nov., isolated from effective nodules of Arachis hypogaea grown in China

Twenty-three bacterial strains isolated from root nodules of Arachis hypogaea and Lablab purpureus grown in five provinces of China were classified as a novel group within the genus Bradyrhizobium by analyses of PCR-based RFLP of the 16S rRNA gene and 16S–23S IGS. To determine their taxonomic position, four representative strains were further characterized. The comparative sequence analyses of 16S rRNA and six housekeeping genes clustered the four strains into a distinctive group closely related to the defined species Bradyrhizobium liaoningense, Bradyrhizobium yuanmingense, Bradyrhizobium huanghuaihaiense, Bradyrhizobium japonicum and Bradyrhizobium daqingense. The DNA–DNA relatedness between the reference strain of the novel group, CCBAU 051107^T, and the corresponding type strains of the five mentioned species varied between 46.05% and 13.64%. The nodC and nifH genes of CCBAU 051107^T were phylogenetically divergent from those of the reference strains for the related species. The four representative strains could nodulate with A. hypogaea and L. purpureus. In addition, some phenotypic features differentiated the novel group from the related species. Based on all the results, we propose a new species Bradyrhizobium arachidis sp. nov. and designate CCBAU 051107^T (=CGMCC 1.12100^T = HAMBI 3281^T = LMG 26795^T) as the type strain, which was isolated from a root nodule of A. hypogaea and had a DNA G + C mol% of 60.1 (Tm).     

Pericentromeric effects shape the patterns of divergence, retention, and expression of duplicated genes in the paleopolyploid soybean

The evolutionary forces that govern the divergence and retention of duplicated genes in polyploids are poorly understood. In this study, we first investigated the rates of nonsynonymous substitution (Ka) and the rates of synonymous substitution (Ks) for a nearly complete set of genes in the paleopolyploid soybean (Glycine max) by comparing the orthologs between soybean and its progenitor species Glycine soja and then compared the patterns of gene divergence and expression between pericentromeric regions and chromosomal arms in different gene categories. Our results reveal strong associations between duplication status and Ka and gene expression levels and overall low Ks and low levels of gene expression in pericentromeric regions. It is theorized that deleterious mutations can easily accumulate in recombination-suppressed regions, because of Hill-Robertson effects. Intriguingly, the genes in pericentromeric regions-the cold spots for meiotic recombination in soybean-showed significantly lower Ka and higher levels of expression than their homoeologs in chromosomal arms. This asymmetric evolution of two members of individual whole genome duplication (WGD)-derived gene pairs, echoing the biased accumulation of singletons in pericentromeric regions, suggests that distinct genomic features between the two distinct chromatin types are important determinants shaping the patterns of divergence and retention of WGD-derived genes.     

槟榔黄化病组织RNA提取方法的比较

为了从发生黄化病的槟榔茎、叶、花中提取到完整的RNA,采用了CTAB法、Trizol法和异硫氰酸胍法提取槟榔黄化病组织RNA。从RNA的完整性、产率和纯度方面对这几种方法进行了比较,结果表明,异硫氰酸胍法所得RNA完整性较好,条带清晰无明显降解,OD260/OD280介于1.8-2.0之间,RNA得率较高,为120μg/g以上,并能成功进行反转录制备cDNA,表明该RNA可以进行后续分子生物学操作。     

荒漠草原“土岛”生境群落物种共存机制

经过长期破碎化, 荒漠草原原生硬质灰钙土斑块散布在广大沙化土地中, 形成类似“土岛”的土被结构。为揭示土岛生境的群落物种共存机制, 2016年在宁夏盐池县皖记沟村选取大(200-300 m²)、中(约100 m²)、小(约50 m²)土岛各3个开展调查, 采用Jaccard相异系数、物种生态位宽度和生态位重叠度、零模型、Meta分析, 综合计算和分析土岛内部与外部植物群落相似性、物种生态位宽度和生态位重叠、物种共存格局及其影响因子。研究发现, (1)随着破碎化加剧, 土岛内部植物多样性整体呈现下降趋势, 群落优势种从短花针茅(Stipa breviflora)转变为猪毛蒿(Artemisia scoparia)和短花针茅共优种, 土岛内外群落相似性增加。(2)土岛内外绝大多数物种生态位重叠较小, 生态位重叠在土岛内呈集中分布, 而土岛外则呈均匀发散分布。(3)环境过滤为主的生态过程决定了土岛生境群落物种的共存格局, 随着土岛面积减小, 环境因子对群落物种共存的调控强度降低, 关键性环境因子由土壤细砂粒和黏粒转变为粗砂粒, 显著性竞争物种共存格局在小岛出现。综上所述, 土岛生境对于维持草原物种具有重要作用, 环境过滤主导了荒漠草原物种共存格局。随着生境破碎化加剧或土岛面积减小, 物种共存格局及其调控因子发生转变。保护面积在200 m²以上的大土岛对于恢复荒漠草原区草原成分种和其物种多样性机制都十分必要。