Possible mechanisms for strand-breaks in DNA induced by stirring

When aqueous solutions of DNA are stirred at room temperature, strand breaks occur extensively. Using various spin-traps, coupled with epr spectroscopy, we have shown that this does not proceed via homolysis. It is suggested that breaks occur by hydrolysis at strongly bent regions, momentarily induced by the stirring.     

Sierra Nevada mountain lake microbial communities are structured by temperature,resources and geographic location

Warming, eutrophication (nutrient fertilization) and brownification (increased loading of allochthonous organic matter) are three global trends impacting lake ecosystems. However, the independent and synergistic effects of resource addition and warming on autotrophic and heterotrophic microorganisms are largely unknown. In this study, we investigate the independent and interactive effects of temperature, dissolved organic carbon (DOC, both allochthonous and autochthonous) and nitrogen (N) supply, in addition to the effect of spatial variables, on the composition, richness, and evenness of prokaryotic and eukaryotic microbial communities in lakes across elevation and N deposition gradients in the Sierra Nevada mountains of California, USA. We found that both prokaryotic and eukaryotic communities are structured by temperature, terrestrial (allochthonous) DOC and latitude. Prokaryotic communities are also influenced by total and aquatic (autochthonous) DOC, while eukaryotic communities are also structured by nitrate. Additionally, increasing N availability was associated with reduced richness of prokaryotic communities, and both lower richness and evenness of eukaryotes. We did not detect any synergistic or antagonistic effects as there were no interactions among temperature and resource variables. Together, our results suggest that (a) organic and inorganic resources, temperature, and geographic location (based on latitude and longitude) independently influence lake microbial communities; and (b) increasing N supply due to atmospheric N deposition may reduce richness of both prokaryotic and eukaryotic microbes, probably by reducing niche dimensionality. Our study provides insight into abiotic processes structuring microbial communities across environmental gradients and their potential roles in material and energy fluxes within and between ecosystems.     

The early life history of two sympatric New Zealand octopuses: eggs and paralarvae of Octopus huttoni and Pinnoctopus cordiformis

This study combined morphological and morphometric information on egg clutches, egg capsules and paralarvae of two sympatric coastal octopuses from New Zealand waters, Octopus huttoni and Pinnoctopus cordiformis, to provide species-specific traits to identify their early life stages obtained from field surveys. Eggs of O. huttoni (2.5 mm length; 1 mm width) were entwined with one another forming strings that ranged from 11 to 25.8 mm in length. Eggs of P. cordiformis (6.4 mm length; 1.5 mm width) were significantly bigger than those of O. huttoni and were grouped in small clusters of about seven eggs. Paralarvae O. huttoni and P. cordiformis differed in hatching size (1.4 mm versus 3.1 mm mantle length), number of suckers per arm (four versus eight), number of lamellae per outer demibranch (five versus ten) and arrangements of chromatophores in the body surface (29 to 59 versus 91 to 179), respectively. The morphological traits described in hatchlings from the laboratory allowed comparisons with field-collected paralarvae, suggesting that such characters were reliable species-specific patterns to enable a consistent differentiation between the early life stages of these two sympatric species, even in the absence of the brooding female.     

The Src Homology 3 Domain-containing Guanine Nucleotide Exchange Factor Is Overexpressed in High-grade Gliomas and Promotes Tumor Necrosis Factor-like Weak Inducer of Apoptosis-Fibroblast Growth Factor-inducible 14-induced Cell Migration and Invasion via Tumor Necrosis Factor Receptor-associated Factor 2

Glioblastoma (GB) is the highest grade of primary adult brain tumors, characterized by a poorly defined and highly invasive cell population. Importantly, these invading cells are attributed with having a decreased sensitivity to radiation and chemotherapy. TNF-like weak inducer of apoptosis (TWEAK)-Fn14 ligand-receptor signaling is one mechanism in GB that promotes cell invasiveness and survival and is dependent upon the activity of multiple Rho GTPases, including Rac1. Here we report that Src homology 3 domain-containing guanine nucleotide exchange factor (SGEF), a RhoG-specific guanine nucleotide exchange factor, is overexpressed in GB tumors and promotes TWEAK-Fn14-mediated glioma invasion. Importantly, levels of SGEF expression in GB tumors inversely correlate with patient survival. SGEF mRNA expression is increased in GB cells at the invasive rim relative to those in the tumor core, and knockdown of SGEF expression by shRNA decreases glioma cell migration in vitro and invasion ex vivo. Furthermore, we showed that, upon TWEAK stimulation, SGEF is recruited to the Fn14 cytoplasmic tail via TRAF2. Mutation of the Fn14-TRAF domain site or depletion of TNF receptor-associated factor 2 (TRAF2) expression by siRNA oligonucleotides blocked SGEF recruitment to Fn14 and inhibited SGEF activity and subsequent GB cell migration. We also showed that knockdown of either SGEF or RhoG diminished TWEAK activation of Rac1 and subsequent lamellipodia formation. Together, these results indicate that SGEF-RhoG is an important downstream regulator of TWEAK-Fn14-driven GB cell migration and invasion.     

Production of endothelial progenitor cells obtained from human Wharton's jelly using different culture conditions

Endothelial progenitor cells (EPC) participate in revascularization and angiogenesis. EPC can be cultured in vitro from mononuclear cells of peripheral blood, umbilical cord blood or bone marrow; they also can be transdifferentiated from mesenchymal stem cells (MSC). We isolated EPCs from Wharton's jelly (WJ) using two methods. The first method was by obtaining MSC from WJ and characterizing them by flow cytometry and their adipogenic and osteogenic differentiation, then applying endothelial growth differentiating media. The second method was by direct culture of cells derived from WJ into endothelial differentiating media. EPCs were characterized by morphology, Dil-LDL uptake/UEA-1 immunostaining and testing the expression of endothelial markers by flow cytometry and RT-PCR. We found that MSC derived from WJ differentiated into endothelial-like cells using simple culture conditions with endothelium induction agents in the medium.     

羌活与宽叶羌活的群体遗传结构和种间分化研究

为了合理利用羌活和宽叶羌活的药用植物资源,同时保护其物种多样性,该研究利用SSR分子标记技术对羌活与宽叶羌活邻域及异域分布的23个自然种群,共计227个个体进行多样性和种间分化研究.结果显示:(1)两个物种具有中等水平的遗传多样性;羌活的平均等位基因数(Na)、有效等位基因数(Ne)和期望杂合度(He)分别为2.603...     

On the changes in the structure of two algal populations: species diversity and stability

Two assumptions were made: 1. when comparing two sample places in the same pond, the one taken nearer to the water edge will show a more diversified populations structure. 2. The population taken nearer to the water edge having a more diversified population structure will be more self-regulatory than the one taken from the open water.For each of those two assumptions a quantitative measure was proposed. The calculated coefficients did seem to confirm the assumptions.     

Effects of AQ4N and its reduction product on radiation-mediated DNA strand breakage

Supercoiled plasmid pBR322 DNA was irradiated in phosphate buffer by 60Co gamma-rays at a dose rate 19.26 Gy/min and total dose of 10 Gy in the presence of a bioreductive antitumour prodrug namely 1,4-bis [?2-(dimethylamino-N-oxide)ethyl? amino] 5, 8-dihydroxyanthracene-9,10-dione (AQ4N) and its DNA affinic reduction product 1,4-bis[?2(dimethylamino)ethyl? amino] 5,8-dihydroxyanthracene-9,10-dione (AQ4) under air and nitrogen. AQ4N and AQ4 were found to protect against radiation-induced plasmid single and double strand breakage as assessed by agarose gel electrophoresis. The differences between the two agents, and between atmospheres of air or nitrogen were negligible. It was also found that the protection efficiencies of the compounds were pH dependent and showed maximum protection at pH 6. These results indicate that protection of DNA by AQ4 and AQ4N against radiation damage is an indirect effect since both agents are equally effective despite major differences in their DNA affinity. It is likely that radiation-induced phosphate buffer radicals are intercepted by AQ4 and AQ4N in a pH-dependent process.     

Brassinosteroids do not undergo long-distance transport in pea. Implications for the regulation of endogenous brassinosteroid levels

It is widely accepted that brassinosteroids (BRs) are important regulators of plant growth and development. However, in comparison to the other classical plant hormones, such as auxin, relatively little is known about BR transport and its potential role in the regulation of endogenous BR levels in plants. Here, we show that end-pathway BRs in pea (Pisum sativum) occur in a wide range of plant tissues, with the greatest accumulation of these substances generally occurring in the young, actively growing tissues, such as the apical bud and young internodes. However, despite the widespread distribution of BRs throughout the plant, we found no evidence of long-distance transport of these substances between different plant tissues. For instance, we show that the maintenance of steady-state BR levels in the stem does not depend on their transport from the apical bud or mature leaves. Similarly, reciprocal grafting between the wild type and the BR-deficient lkb mutants demonstrates that the maintenance of steady-state BR levels in whole shoots and roots does not depend on either basipetal or acropetal transport of BRs between these tissues. Together, with results from (3)H-BR feeding studies, these results demonstrate that BRs do not undergo long-distance transport in pea. The widespread distribution of end-pathway BRs and the absence of long-distance BR transport between different plant tissues provide significant insight into the mechanisms that regulate BR homeostasis in plants.