Detection of Cytolethal Distending Toxin Activity and cdt Genes in Actinobacillus Actinomycetemcomitans Isolates From Geographically Diverse Populations

A cytolethal distending toxin (CDT) found in Actinobacillus actinomycetemcomitans inhibits the eukaryotic cell cycle, which may contribute to the pathogenic potential of the bacterium. The presence of the cdtABC genes and CDT activity were examined in 40 clinical isolates of A. actinomycetemcomitans from Brazil, Kenya, Japan and Sweden. Thirty-nine of 40 cell lysates caused distension of Chinese hamster ovary cells. At least one of the cdt genes was detected in all strains examined. The three cdt genes were detected, by PCR, in 34 DNA samples. DNA from one strain from Kenya did not yield amplicons of the cdtA and cdtB genes and did not express toxic activity. Restriction analysis was performed on every amplicon obtained. PCR-RFLP patterns revealed that the three cdt genes were conserved. These data provided evidence that the cdt genes are found and expressed in the majority of the A. actinomycetemcomitans isolates. Although a quantitative difference in cytotoxicity was observed, indicating variation in expression of CDT among strains, no clear relationship between CDT activity and periodontal status was found

Ionized o-, m-, and p-Difluorobenzene Dissociate Through Ring-Opened Intermediates: A TPEPICO Investigation

Threshold photoelectron photoion coincidence (TPEPICO) experiments have shown that o-, m-, and p-difluorobenzene ions dissociate via a common, ring-opened intermediate and not via ionized p-difluorobenzene. Rice-Ramsperger-Kassel-Marcus (RRKM) modeling of the experimental breakdown curves yields activation energies for the initial isomerization of 4.48 ± 0.05, 4.55 ± 0.05, and 4.68 ± 0.05 eV for o-, m-, and p-difluorobenzene, respectively. These values place each ion at a similar absolute energy and thus similar transition states. A large positive ΔS‡ for each ion (ca 100 J K−1 mol−1) suggests a ring-opened structure for these transition states

Intra-annual patterns of tracheid size in the Mediterranean tree Juniperus thurifera as an indicator of seasonal water stress

Because climate can affect xylem cell anatomy, series of intra-annual cell anatomical features have the potential to retrospectively supply seasonal climatic information. In this study, we explored the ability to extract information about water stress conditions from tracheid features of the Mediterranean conifer Juniperus thurifera L. Tracheidograms of four climatic years from two drought-sensitive sites in Spain were compared to evaluate whether it is possible to link intra-annual cell size patterns to seasonal climatic conditions. Results indicated site-specific anatomical adjustment such as smaller and thicker tracheids at the dryer site but also showed a strong climatic imprint on the intra-annual pattern of tracheid size. Site differences in cell size reflected expected structural adjustments against cavitation failures. Differences between intra-annual patterns, however, indicated a response to seasonal changes in water availability whereby cells formed under drought conditions were smaller and thicker, and vice versa. This relationship was more manifest and stable at the dryer sit

Possible origins of macroscopic left-right asymmetry in organisms

I consider the microscopic mechanisms by which a particular left-right (L/R) asymmetry is generated at the organism level from the microscopic handedness of cytoskeletal molecules. In light of a fundamental symmetry principle, the typical pattern-formation mechanisms of diffusion plus regulation cannot implement the "right-hand rule"; at the microscopic level, the cell's cytoskeleton of chiral filaments seems always to be involved, usually in collective states driven by polymerization forces or molecular motors. It seems particularly easy for handedness to emerge in a shear or rotation in the background of an effectively two-dimensional system, such as the cell membrane or a layer of cells, as this requires no pre-existing axis apart from the layer normal. I detail a scenario involving actin/myosin layers in snails and in C. elegans, and also one about the microtubule layer in plant cells. I also survey the other examples that I am aware of, such as the emergence of handedness such as the emergence of handedness in neurons, in eukaryote cell motility, and in non-flagellated bacteria.Comment: 42 pages, 6 figures, resubmitted to J. Stat. Phys. special issue. Major rewrite, rearranged sections/subsections, new Fig 3 + 6, new physics in Sec 2.4 and 3.4.1, added Sec 5 and subsections of Sec

Canada-Africa Relations in Changing Core-Periphery Dynamics: A Chance to "Come Back" Differently

The Department of Foreign Affairs Canada sees the dynamism at play across the African continent as calling out for Canadian engagement. Africa in the twenty-first century is no longer the continent emerging from colonial rule; it seeks new forms of relationships with international partners. The African Development Bank, for instance, has identified five priorities for inclusive growth on the continent. The challenges are huge, as is the potential for transformative change. But the conditions for international collaboration in achieving these goals have changed; African leaders are seeking new forms of associations and teamwork. Canada has an opportunity to "come back" differently if it can look beyond its narrow mining interests and become an active partner working with public authorities in need of new and bold international partnerships. Unfortunately, Trudeau's "Canada is back" campaign does not look set to change the status quo. And, in a world where the political economic power is moving east, African countries do not have much reason to listen to Canada

Gamma ray studies of neutron-rich sdf shell nuclei produced in heavy ion collisions

Reanalysis of ichproductsofbinaryreactio nsof$34S, S36, and Cl37 beams on Gd160 targets. Gates set on known amma$raysin$A∼160 products selected individual react ion channels and identified coincident amma$raysin$A∼36 partner products. Transfers of protons from projectile to target and of neutrons from target to projectile were generally favored, leading to excited neutron-rich light nuclei, including some difficult to reach by other means. Notable results include the observation of amma$raycascadesupthehigh e stknownyraststatesinfour$N=20 isotones. In two N=19 nuclei, Si33 and P34, the two N=22 nuclei, S38 and Cl39, previously unknown yrast states were identified

Superdeformed band in Dy154

A superdeformed band has been found in the Dy154 (N=88) nucleus. The dynamic moment of inertia is identical to that of the yrast superdeformed band of Dy152 and the transition energies are similar to those of an excited superdeformed band in Dy153. It is proposed that the two valence neutrons above the N=86 shell gap occupy the deformation-driving [514]9/2 orbital

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter