Improved initial osteoblast functions on amino-functionalized titanium surfaces

Adhesion and spreading of cells on biomaterials are integrin-mediated processes. But recent findings indicate a key role of the cell membrane associated matrix substance hyaluronan (HA) in interface interactions. Because HA is a negatively charged molecule we assume that a biomaterial surface with an opposed charge could boost the first contact of the cell to the surface. Polished cp titanium (R(a)=0.19 microm) was coated with an amino-group containing plasma polymer (Ti PPA). For this purpose, a microwave excited, pulsed, low-pressure plasma was used. Additionally, collagen was immobilized on Ti PPA with polyethylene glycol diacid (PEG-DA), catalyzed by carbodiimide (CDI). The physico-chemical surface analytical techniques like XPS, FT-IR, water contact angle and zeta-potential verified the retention of the allylamine precursor structure. Human osteoblasts were cultured in serum-free Dulbecco's modified Eagle medium (DMEM). Adhesion and cell cycle phases were calculated by flow cytometry. Spreading and actin cytoskeleton were visualized by confocal microscopy. Gene expression of osteogenic markers was detected by real-time RT-PCR. Ti PPA is significantly advantageous concerning initial adhesion and spreading during the first hours of the cell contact to the surface. The proliferation of osteoblasts is positively influenced. Gene expression of the differentiation marker bone sialoprotein was upregulated after 24h. Our results demonstrate that functionalization of titanium with positively charged amino-groups is sufficiently enough to significantly improve initial steps of the cellular contact to the material surface.     

Selenoproteins of the thyroid gland: expression, localization and possible function of glutathione peroxidase 3

The thyroid gland has an exceptionally high selenium content, even during selenium deficiency. At least 11 selenoproteins are expressed, which may be involved in the protection of the gland against the high amounts of H2O2 produced during thyroid hormone biosynthesis. As determined here by in situ hybridization and Northern blotting experiments, glutathione peroxidases (GPx) 1 and 4 and selenoprotein P were moderately expressed, occurring selectively in the follicular cells and in leukocytes of germinal follicles of thyroids affected by Hashimoto's thyroiditis. Selenoprotein 15 was only marginally expressed and distributed over all cell types. GPx3 mRNA was exclusively localized to the thyrocytes, showed the highest expression levels and was down-regulated in 5 of 6 thyroid cancer samples as compared to matched normal controls. GPx3 could be extracted from thyroidal colloid by incubation with 0.5% sodium dodecyl sulfate indicating that this enzyme is (i) secreted into the follicular lumen and (ii) loosely attached to the colloidal thyroglobulin. These findings are consistent with a role of selenoproteins in the protection of the thyroid from possible damage by H2O2. Particularly, GPx3 might use excess H2O2 and catalyze the polymerization of thyroglobulin to the highly cross-linked storage form present in the colloid.     

A systematic approach for testing expression of human full-length proteins in cell-free expression systems

Background  

The growing field of proteomics and systems biology is resulting in an ever increasing demand for purified recombinant proteins for structural and functional studies. Here, we show a systematic approach to successfully express a full-length protein of interest by using cell-free and cell-based expression systems.     

Drosophila ASPP regulates C-terminal Src kinase activity

Src-family kinases (SFKs) control a variety of biological processes, from cell proliferation and differentiation to cytoskeletal rearrangements. Abnormal activation of SFKs has been implicated in a wide variety of cancers and is associated with metastatic behavior (Yeatman, 2004). SFKs are maintained in an inactive state by inhibitory phosphorylation of their C-terminal region by C-terminal Src kinase (Csk). We have identified Drosophila Ankyrin-repeat, SH3-domain, and Proline-rich-region containing Protein (dASPP) as a regulator of Drosophila Csk (dCsk) activity. dASPP is the homolog of the mammalian ASPP proteins, which are known to bind to and stimulate the proapoptotic function of p53. We show that dASPP is a positive regulator of dCsk. First, dASPP loss-of-function strongly enhances the specific phenotypes of dCsk mutants in wing epithelial cells. Second, dASPP interacts physically with dCsk to potentiate the inhibitory phosphorylation of Drosophila Src (dSrc). Our results suggest a role for dASPP in maintaining epithelial integrity through dCsk regulation.     

Boden – ein unterschätzter Lebensraum

Soil – an underestimated biotope The soil is a biotope with high species abundances and richness. It is, furthermore, a location where important ecosystem services are realized. Recent research projects on the origin and development of soil animal communities, on the heterogeneous interactions within the soil nutrient net and the distribution of soil animals show the different ecological traits and adaptabilities of the world beneath our feet. So research contributes to maintain the eco‐resource of soil and its sustainable use.     

Substantial variation in leaf senescence times among 1360 temperate woody plant species: implications for phenology and ecosystem processes

Background and Aims Autumn leaf senescence marks the end of the growing season in temperate ecosystems. Its timing influences a number of ecosystem processes, including carbon, water and nutrient cycling. Climate change is altering leaf senescence phenology and, as those changes continue, it will affect individual woody plants, species and ecosystems. In contrast to spring leaf out times, however, leaf senescence times remain relatively understudied. Variation in the phenology of leaf senescence among species and locations is still poorly understood.Methods Leaf senescence phenology of 1360 deciduous plant species at six temperate botanical gardens in Asia, North America and Europe was recorded in 2012 and 2013. This large data set was used to explore ecological and phylogenetic factors associated with variation in leaf senescence.Key Results Leaf senescence dates among species varied by 3 months on average across the six locations. Plant species tended to undergo leaf senescence in the same order in the autumns of both years at each location, but the order of senescence was only weakly correlated across sites. Leaf senescence times were not related to spring leaf out times, were not evolutionarily conserved and were only minimally influenced by growth habit, wood anatomy and percentage colour change or leaf drop. These weak patterns of leaf senescence timing contrast with much stronger leaf out patterns from a previous study.Conclusions The results suggest that, in contrast to the broader temperature effects that determine leaf out times, leaf senescence times are probably determined by a larger or different suite of local environmental effects, including temperature, soil moisture, frost and wind. Determining the importance of these factors for a wide range of species represents the next challenge for understanding how climate change is affecting the end of the growing season and associated ecosystem processes.