Microglial K(+) channel expression in young adult and aged mice.

The K(+) channel expression pattern of microglia strongly depends on the cells' microenvironment and has been recognized as a sensitive marker of the cells' functional state. While numerous studies have been performed on microglia in vitro, our knowledge about microglial K(+) channels and their regulation in vivo is limited. Here, we have investigated K(+) currents of microglia in striatum, neocortex and entorhinal cortex of young adult and aged mice. Although almost all microglial cells exhibited inward rectifier K(+) currents upon membrane hyperpolarization, their mean current density was significantly enhanced in aged mice compared with that determined in young adult mice. Some microglial cells additionally exhibited outward rectifier K(+) currents in response to depolarizing voltage pulses. In aged mice, microglial outward rectifier K(+) current density was significantly larger than in young adult mice due to the increased number of aged microglial cells expressing these channels. Aged dystrophic microglia exhibited outward rectifier K(+) currents more frequently than aged ramified microglia. The majority of microglial cells expressed functional BK-type, but not IK- or SK-type, Ca(2+) -activated K(+) channels, while no differences were found in their expression levels between microglia of young adult and aged mice. Neither microglial K(+) channel pattern nor K(+) channel expression levels differed markedly between the three brain regions investigated. It is concluded that age-related changes in microglial phenotype are accompanied by changes in the expression of microglial voltage-activated, but not Ca(2+) -activated, K(+) channels

The Long and Viscous Road: Uncovering Nuclear Diffusion Barriers in Closed Mitosis

During Saccharomyces cerevisiae closed mitosis, parental identity is sustained by the asymmetric segregation of ageing factors. Such asymmetry has been hypothesized to occur via diffusion barriers, constraining protein lateral exchange in cellular membranes. Diffusion barriers have been extensively studied in the plasma membrane, but their identity and organization within the nucleus remain unknown. Here, we propose how sphingolipid domains, protein rings, and morphological changes of the nucleus may coordinate to restrict protein exchange between nuclear lobes. Our spatial stochastic model is based on several lines of experimental evidence and predicts that, while a sphingolipid domain and a protein ring could constitute the barrier during early anaphase; a sphingolipid domain spanning the bridge between lobes during late anaphase would be entirely sufficient. Additionally, we explore the structural organization of plausible diffusion barriers. Our work shows how nuclear diffusion barriers in closed mitosis may be emergent properties of simple nanoscale biophysical interactions.Comment: 21 pages, 6 figures and supplementary material (including 8 additional figures and a Table

Anomalous Spin and Charge Dynamics of the 2D t-J Model at low doping

We present an exact diagonalization study of the dynamical spin and density correlation function of the 2D t-J model for hole doping < 25%. Both correlation functions show a remarkably regular, but completely different scaling behaviour with both hole concentration and parameter values: the density correlation function is consistent with that of bosons corresponding to the doped holes and condensed into the lowest state of the noninteracting band of width 8t, the spin correlation function is consistent with Fermions in a band of width J. We show that the spin bag picture gives a natural explanation for this unusual behaviour.Comment: Revtex-file, 4 PRB pages + 5 figures attached as uu-encoded ps-files Hardcopies of figures (or the entire manuscript) can also be obtained by e-mailing to: [email protected]

Validity of the rigid band picture for the t-J model

We present an exact diagonalization study of the doping dependence of the single particle Green's function in 16, 18 and 20 site clusters of t-J model. We find evidence for rigid-band behaviour starting from the half-filled case: upon doping, the topmost states of the quasiparticle band observed in the photoemisson spectrum at half-filling cross the chemical potential and reappear as the lowermost states of the inverse photoemission spectrum. Features in the inverse photoemission spectra which are inconsistent with rigid-band behaviour are shown to originate from the nontrivial point group symmetry of the ground state with two holes, which enforces different selection rules than at half-filling. Deviations from rigid band behaviour which lead to the formation of the `large Fermi surface' in the momentum distribution occur only at energies far from the chemical potential. A Luttinger Fermi surface and a nearest neighbor hopping band do not exist.Comment: Remarks: Revtex file + 7 figures attached as compressed postscript files Figures can also be obtained by ordinary mail on reques

Entwicklung von Populationen bei Mais (Zea mays L.) Selektionseffizienz und Leistungsfähigkeit

Maize is one of the most important crops around the world. Global players in seed production offer more than hundreds of different varieties. All of them are hybrids whereas open pollinated varieties (OPVs) are rare or extinct. In Germany (and many other European countries) no new OPVs are registered; efforts to do so failed in the past. The main advantage of OPVs is their phenotypic and genetic heterogeneity and thus their ability to adapt to different environmental conditions. This could be of utmost interest facing the complex challenge of climate change. Populations based on new breeding material were developed and tested in comparison to actual hybrids and landraces. While the new populations achieved about 80 % of the hybrid yield, landraces failed with only 65 %. The efficiency of selection methods needs to be improved

Direct current arc-plasma synthesis of B-C powder product

Measurement of blood oxygen saturation in biological tissue is of great interest for medical applications as it allows the detection of pathological alterations. Fibre based re-emission spectroscopy enables this parameter to be determined minimally-invasively in organ tissue inside the human body. In this report a measurement system for the contactless determination of blood oxygenation, as well as simulations regarding light diffusion in tissue are presented

Dynamics of an SO(5) symmetric ladder model

We discuss properties of an exactly SO(5) symmetric ladder model. In the strong coupling limit we demonstrate how the SO(3)-symmetric description of spin ladders in terms of bond Bosons can be upgraded to an SO(5)-symmetric bond-Boson model, which provides a particularly simple example for the concept of SO(5) symmetry. Based on this representation we show that antiferro- magnetism on one hand and superconductivity on the other hand can be understood as condensation of either magnetic or charged Bosons into an RVB vacuum. We identify exact eigenstates of a finite cluster with general multiplets of the SO(5) group, and present numerical results for the single particle spectra and spin/charge correlation functions of the SO(5)-symmetric model and identify `fingerprints' of SO(5) symmetry in these. In particluar we show that SO(5) symmetry implies a `generalized rigid band behavior' of the photoemission spectrum, i.e. spectra for the doped case are rigorously identical to spectra for spin-polarized states at half-filling. We discuss the problem of adiabatic continuity between the SO(5) symmetric ladder and the actual t-J ladder and demonstrate the feasibility of a `Landau mapping' between the two models.Comment: Revtex-file, 16 pages with 15 eps-figures. Hardcopies of Figures (or the entire manuscript) obtainable by e-mail request to [email protected]