Regulation of Pom cluster dynamics in Myxococcus xanthus

Precise positioning of the cell division site is essential for the correct segregation of the genetic material into the two daughter cells. In the bacterium Myxococcus xanthus, the proteins PomX and PomY form a cluster on the chromosome that performs a biased random walk to midcell and positively regulates cell division there. PomZ, an ATPase, is necessary for tethering of the cluster to the nucleoid and regulates its movement towards midcell. It has remained unclear how the cluster dynamics change when the biochemical parameters, such as the attachment rates of PomZ to the nucleoid and the cluster, the ATP hydrolysis rate of PomZ or the mobility of PomZ dimers interacting with the nucleoid and cluster, are varied. To answer these questions, we investigate a one-dimensional model that includes the nucleoid, the Pom cluster and the PomZ protein. We find that a mechanism based on the diffusive PomZ fluxes on the nucleoid into the cluster can explain the latter's midnucleoid localization for a broad parameter range. Furthermore, there is an ATP hydrolysis rate that minimizes the time the cluster needs to reach midnucleoid. If the dynamics of PomZ dimers on the nucleoid is slow relative to the cluster's velocity, we observe oscillatory cluster movements around midnucleoid. To understand midnucleoid localization, we developed a semi-analytical approach that dissects the net movement of the cluster into its components: the difference in PomZ fluxes into the cluster from either side, the force exerted by a single PomZ dimer on the cluster and the effective friction coefficient of the cluster. Importantly, we predict that the Pom cluster oscillates around midnucleoid if the diffusivity of PomZ on the nucleoid is reduced. A similar approach to that applied here may also prove useful for cargo localization in ParABS systems.Comment: 17 pages, 6 figures, 10 pages supplemental material (including 12 figures and 1 table

Was denken deutsche Ökonomen? Eine empirische Auswertung einer Internetbefragung unter den Mitgliedern des Vereins für Socialpolitik im Sommer 2006

This article presents the results of a survey among the members of the "Verein f¨ur Socialpolitik", the association of German speaking economists, containing questions on schools of thought, economic role models and policy issues. A probit analysis is used to identify to what extent ideological preferences or personal facts determine the respondent's opinion. Some of the questions were already asked a quarter of a century ago so that it is possible to track the changes in view among economists. One of the most important findings is that neoclassical economics has become more strongly accepte

Theory of Active Intracellular Transport by DNA-relaying

The spatiotemporal organization of bacterial cells is crucial for the active segregation of replicating chromosomes. In several species, including Caulobacter crescentus, the ATPase ParA binds to DNA and forms a gradient along the long cell axis. The ParB partitioning complex on the newly replicated chromosome translocates up this ParA gradient, thereby contributing to chromosome segregation. A DNA-relay mechanism - deriving from the elasticity of the fluctuating chromosome - has been proposed as the driving force for this cargo translocation, but a mechanistic theoretical description remains elusive. Here, we propose a minimal model to describe force generation by the DNA-relay mechanism over a broad range of operational conditions. Conceptually, we identify four distinct force-generation regimes characterized by their dependence on chromosome fluctuations. These relay force regimes arise from an interplay of the imposed ParA gradient, chromosome fluctuations, and an emergent friction force due chromosome-cargo interactions.Comment: Formatting issues in the figures and references have been resolve

Full length interleukin 33 aggravates radiation-induced skin reaction

The interleukin (IL)-1 family member IL-33 has been described as intracellular alarmin with broad roles in wound healing, skin inflammation but also autoimmunity. Its dichotomy between full length (fl) IL-33 and the mature (m) form of IL-33 and its release by necrosis is still not fully understood. Here, we compare functional consequences of both forms in the skin in vivo, and therefore generated two lines of transgenic mice which selectively overexpress mmIL-33 and flmIL-33 in basal keratinocytes. Transgene mRNA was expressed at high level in skin of both lines but not in organs due to the specific K14 promoter. We could demonstrate that transgenic overexpression of mmIL-33 in murine keratinocytes leads to a spontaneous skin inflammation as opposed to flmIL-33. K14-mmIL-33 mice synthesize and secrete high amounts of mmIL-33 along with massive cutaneous manifestations, like increased epidermis and dermis thickness, infiltration of mast cells in the epidermis and dermis layers and marked hyperkeratosis. Using skin inflammation models such as IL-23 administration, imiquimod treatment, or mechanical irritation did not lead to exacerbated inflammation in the K14-flmIL-33 strain. As radiation induces a strong dermatitis due to apoptosis and necrosis, we determined the effect of fractionated radiation (12 Gy, 4 times). In comparison to wild-type mice, an increase in ear thickness in flmIL-33 transgenic mice was observed 25 days after irradiation. Macroscopic examination showed more severe skin symptoms in irradiated ears compared to controls. In summary, secreted mmIL-33 itself has a potent capacity in skin inflammation whereas fl IL-33 is limited due to its intracellular retention. During tissue damage, fl IL-33 exacerbated radiation-induced skin reaction

Personalentwicklung für Wissenschaftler/innen - Professionalisierung von Selbst-, Führungs- und Lehrkompetenzen

Die zunehmende Professionalisierung des Wissenschaftsbetriebes wirkt sich auch auf die Anforderungen an Wissenschaftlerinnen und Wissenschaftler aus. Um multiplen und wachsenden Rollenanforderungen gerecht werden zu können, wird eine Erweiterung und Professionalisierung der eigenen Kompetenzen notwendig. Am Beispiel des LMU Center for Leadership and People Management soll aufgezeigt werden, wie mit Hilfe professioneller Personalentwicklungsmaßnahmen dabei sowohl die wissenschaftliche Exzellenz an Hochschulen gezielt gefördert als auch ein wichtiger Beitrag zu Innovation und Organisationsentwicklung geleistet werden kann. Ziel des Beitrages ist es, ein Bewusstsein für die Notwendigkeit von Personalentwicklung an Hochschulen zu schaffen und zugleich anderen Universitäten Hilfestellung bei der Implementierung ähnlicher Maßnahmen zu bieten. 02.11.2011 | Silke Weisweiler, Tanja Peter, Claudia Peus & Dieter Frey (München

Constraining the radio jet proper motion of the high-redshift quasar J2134-0419 at z = 4.3

To date, PMN J2134-0419 (at a redshift z = 4.33) is the second most distant quasar known with a milliarcsecond-scale morphology permitting direct estimates of the jet proper motion. Based on two-epoch observations, we constrained its radio jet proper motion using the very long baseline interferometry (VLBI) technique. The observations were conducted with the European VLBI Network (EVN) at 5 GHz on 1999 November 26 and 2015 October 6. We imaged the central 10-pc scale radio jet emission and modeled its brightness distribution. By identifying a jet component at both epochs separated by 15.86 yr, a proper motion of μ = 0.035 ± 0.023 mas yr-1 is found. It corresponds to an apparent superluminal speed of βa = 4.1 ± 2.7 c. Relativistic beaming at both epochs suggests that the jet viewing angle with respect to the line of sight is smaller than 20°, with a minimum bulk Lorentz factor Γ = 4.3. The small value of the proper motion is in good agreement with the expectations from the cosmological interpretation of the redshift and the current cosmological model. Additionally we analyzed archival Very Large Array observations of J2143-0419 and found indication of a bent jet extending to ˜30 kpc

Digitale Teilhabe

Das Themenheft Digitale Teilhabe beschäftigt sich zentral mit den Potentialen der Nutzung der neuen Informations- und Kommunikationstechnologien durch benachteiligte Menschen. Im Leitartikel wird der Versuch unternommen, mögliche theoretische Anknüpfungspunkte und Forschungsfragen für weitere Studien- und Forschungsarbeiten in dem noch jungen Themenfeld der Digitalen Teilhabe zu identifizieren. Hierzu wird zunächst das zugrunde liegende Verständnis von Behinderung/Benachteiligung diskutiert und inklusive (Medien-)Bildung als Teil der Persönlichkeitsbildung skizziert. In verschiedenen Diskursen bzw. Disziplinen werden dann theoretische Anknüpfungspunkte für weitere Forschungsarbeiten benannt. Die Idee für das Themenheft ist im Rahmen des Projekts "Begleitforschung im PIKSL-Labor" des Zentrums für Planung und Evaluation Sozialer Dienste der Uni Siegen (ZPE) entstanden. Das PIKSL-Projekt zielt darauf ab, Menschen mit Behinderungen moderne Kommunikationstechnologien zugänglich zu machen, um ihnen Teilhabemöglichkeiten zu erleichtern und zugleich die personale Abhängigkeit von professioneller Unterstützung zu reduzieren. Der inter- und transdisziplinäre Ansatz von PIKSL wird durch die Vielfalt der Artikel in dem Heft deutlich: Digitale Teilhabe wird nicht alleine aus (medien-)pädagogischer bzw. sozialwissenschaftlicher Perspektive betrachtet. Die Besonderheit liegt in der Kooperation unterschiedlicher Disziplinen wie Soziale Arbeit, Kunst und Webdesign