Relationship between climatic conditions and the relative abundance of modern C<inf>3</inf> and C<inf>4</inf> plants in three regions around the North Pacific

Using -24‰ and -14‰ as the endpoints of stable carbon isotopic composition of total organic carbon (δ13CTOC) of surface soil under pure C3 and C4 vegetation, and surface soil δ13CTOC data from eastern China, Australia and the Great Plains of North America, we estimate the relative abundance of C3/C4 plants (i. e., the ratio of C3 or C4 biomass to local primary production) in modern vegetation for each region. The relative abundance of modern C3/C4 vegetation from each region is compared to the corresponding climatic parameters (mean annual temperature and precipitation) to explore the relationship between relative C4 abundance and climate. The results indicate that temperature controls the growth of C4 plants. However, even where temperature is high enough for the growth of C4 plants, they will only dominate the landscape when precipitation declines as temperatures increase. Our results are consistent with those of other investigations of the geographic distribution of modern C4 plant species. Therefore, our results provide an important reference for interpretation of past C3/C4 relative abundance records in these three regions. © 2010 Science China Press and Springer-Verlag Berlin Heidelberg

Paleoclimatic implications of an 850-year oxygen-isotope record from the northern Tibetan Plateau

Oxygen-isotope records from the sediments of hydrologically-closed lakes are commonly interpreted in terms of changing effective precipitation. We compare an 850-year-long oxygen-isotope record derived from ostracode carbonate from the sediments of Sugan Lake, in the northern Tibetan Plateau, with tree-ring and ice core evidence for changing temperature, precipitation and isotopic composition of the lake's inflow. Taking into account all of these independent records, we show that variations in the carbonate delta O-18 values could not have been the result of varying effective precipitation alone: changes in water temperature and in the delta O-18 of source waters also played a significant role. Where independent records of temperature, precipitation or the isotopic composition of input waters are unavailable, care should be taken to avoid simplistic interpretations of carbonate stable isotope records, as these may contribute to incorrect paleoclimatic reconstructions

Anomalous tqγtq\gamma coupling effects in exclusive radiative B-meson decays

The top-quark FCNC processes will be searched for at the CERN LHC, which are correlated with the B-meson decays. In this paper, we study the effects of top-quark anomalous interactions $tq\gamma$ in the exclusive radiative $B\to K^*\gamma$ and $B\to\rho\gamma$ decays. With the current experimental data of the branching ratios, the direct CP and the isospin asymmetries, bounds on the coupling $\kappa_{tcR}^{\gamma}$ from $B\to K^*\gamma$ and $\kappa_{tuR}^{\gamma}$ from $B\to \rho\gamma$ decays are derived, respectively. The bound on $|\kappa_{tcR}^{\gamma}|$ from ${\mathcal B}(B\to K^{*}\gamma)$ is generally compatible with that from ${\mathcal B}(B\to X_{s}\gamma)$. However, the isospin asymmetry $\Delta(K^{*}\gamma)$ further restrict the phase of $\kappa_{tcR}^{\gamma}$, and the combined bound results in the upper limit, $\mathcal B(t\to c\gamma)<0.21$, which is lower than the CDF result. For real $\kappa_{tcR}^{\gamma}$, the upper bound on $\mathcal B(t\to c\gamma)$ is about of the same order as the $5\sigma$ discovery potential of ATLAS with an integrated luminosity of $10 {\rm fb}^{-1}$. For $B\to\rho\gamma$ decays, the NP contribution is enhanced by a large CKM factor $|V_{ud}/V_{td}|$, and the constraint on $tu\gamma$ coupling is rather restrictive, $\mathcal B(t\to u\gamma)<1.44\times 10^{-5}$. With refined measurements to be available at the LHCb and the future super-B factories, we can get close correlations between $B\to V \gamma$ and the rare $t\to q\gamma$ decays, which will be studied directly at the LHC ATLAS and CMS.Comment: 25 pages, 15 figures, pdflate

Cytokinesis in bloodstream stage Trypanosoma brucei requires a family of katanins and spastin

Microtubule severing enzymes regulate microtubule dynamics in a wide range of organisms and are implicated in important cell cycle processes such as mitotic spindle assembly and disassembly, chromosome movement and cytokinesis. Here we explore the function of several microtubule severing enzyme homologues, the katanins (KAT80, KAT60a, KAT60b and KAT60c), spastin (SPA) and fidgetin (FID) in the bloodstream stage of the African trypanosome parasite, Trypanosoma brucei. The trypanosome cytoskeleton is microtubule based and remains assembled throughout the cell cycle, necessitating its remodelling during cytokinesis. Using RNA interference to deplete individual proteins, we show that the trypanosome katanin and spastin homologues are non-redundant and essential for bloodstream form proliferation. Further, cell cycle analysis revealed that these proteins play essential but discrete roles in cytokinesis. The KAT60 proteins each appear to be important during the early stages of cytokinesis, while downregulation of KAT80 specifically inhibited furrow ingression and SPA depletion prevented completion of abscission. In contrast, RNA interference of FID did not result in any discernible effects. We propose that the stable microtubule cytoskeleton of T. brucei necessitates the coordinated action of a family of katanins and spastin to bring about the cytoskeletal remodelling necessary to complete cell divisio

MegaSNPHunter: a learning approach to detect disease predisposition SNPs and high level interactions in genome wide association study

<p>Abstract</p> <p>Background</p> <p>The interactions of multiple single nucleotide polymorphisms (SNPs) are highly hypothesized to affect an individual's susceptibility to complex diseases. Although many works have been done to identify and quantify the importance of multi-SNP interactions, few of them could handle the genome wide data due to the combinatorial explosive search space and the difficulty to statistically evaluate the high-order interactions given limited samples.</p> <p>Results</p> <p>Three comparative experiments are designed to evaluate the performance of MegaSNPHunter. The first experiment uses synthetic data generated on the basis of epistasis models. The second one uses a genome wide study on Parkinson disease (data acquired by using Illumina HumanHap300 SNP chips). The third one chooses the rheumatoid arthritis study from Wellcome Trust Case Control Consortium (WTCCC) using Affymetrix GeneChip 500K Mapping Array Set. MegaSNPHunter outperforms the best solution in this area and reports many potential interactions for the two real studies.</p> <p>Conclusion</p> <p>The experimental results on both synthetic data and two real data sets demonstrate that our proposed approach outperforms the best solution that is currently available in handling large-scale SNP data both in terms of speed and in terms of detection of potential interactions that were not identified before. To our knowledge, MegaSNPHunter is the first approach that is capable of identifying the disease-associated SNP interactions from WTCCC studies and is promising for practical disease prognosis.</p

Establishment of a canine model of cardiac memory using endocardial pacing via internal jugular vein

<p>Abstract</p> <p>Background</p> <p>Development of experimental animal models has played an important role in understanding the mechanisms of cardiac memory. The purpose of this study was to evaluate a new canine model of cardiac memory using endocardial ventricular pacing via internal jugular vein.</p> <p>Methods</p> <p>Twelve Beagle dogs underwent placement of a permanent ventricular pacemaker mimicking the use of pacemakers in humans and induction of cardiac memory by endocardial ventricular pacing.</p> <p>Results</p> <p>Cardiac memory was achieved in 11 of 12 attempts overall. Procedural mortality due to cardiac tamponade (n = 1) occurred in the first attempt. The T-wave memory persisted for 96 ± 17 minutes and 31 ± 6 days in the short-term and long-term cardiac memory groups, respectively. There were no significant differences in the heart rate, blood pressure and echocardiographic parameters in the animals between before and after ventricular pacing in the short-term and long-term cardiac memory groups. No significant pathologic changes with the light microscopy were found in the present study in all dogs.</p> <p>Conclusion</p> <p>The model does require surgery but is not as invasive as an open-chest model. This canine model can serve as a useful tool for studying mechanisms of cardiac memory.</p

miR-K12-7-5p Encoded by Kaposi's Sarcoma-Associated Herpesvirus Stabilizes the Latent State by Targeting Viral ORF50/RTA

Seventeen miRNAs encoded by Kaposi's sarcoma-associated herpesvirus (KSHV) have been identified and their functions have begun to be characterized. Among these miRNAs, we report here that miR-K12-7 directly targets the replication and transcription activator (RTA) encoded by open reading frame 50. We found that miR-K12-7 targeted the RTA 3′ untranslated region (RTA3′UTR) in a seed sequence-dependent manner. miR-K12-7-5p derived from miR-K12-7 mediates the inhibition of RTA expression, and the mutation of the seed match site totally abrogated the inhibitory effect of miR-K12-7 on RTA3′UTR. The inhibition of RTA expression by miR-K12-7 was further confirmed in the latently KSHV-infected 293/Bac36 cell line through transient transfection of miR-K12-7 expression plasmid or specific inhibitor of miR-K12-7-5p, respectively. The transient transfection of miR-K12-7 into 293/Bac36 cells reduced RTA expression and the expression of the downstream early genes regulated by RTA, and also the production of progeny virus was significantly reduced after treatment with chemical inducers. Our study revealed that another miRNA, miR-K12-7-5p, targets the viral immediate early gene RTA and that this miRNA contributes to the maintenance of viral latency

Analyzing Thioflavin T Binding to Amyloid Fibrils by an Equilibrium Microdialysis-Based Technique

A new approach for the determination of the amyloid fibril – thioflavin T (ThT) binding parameters (the number of binding modes, stoichiometry, and binding constants of each mode) is proposed. This approach is based on the absorption spectroscopy determination of the concentration of free and bound to fibril dye in solutions, which are prepared by equilibrium microdialysis. Furthermore, the proposed approach allowed us, for the first time, to determine the absorption spectrum, molar extinction coefficient, and fluorescence quantum yield of the ThT bound to fibril by each binding modes. This approach is universal and can be used for determining the binding parameters of any dye interaction with a receptor, such as ANS binding to proteins in the molten globule state or to protein amorphous aggregates