Evaluation of chemokine and cytokine profiles in osteoblast progenitors from umbilical cord blood stem cells by BIO-PLEX technology

We have used cytokine protein array to analyze the secretion of cytokines from an osteoblastic clone derived from human umbilical cord blood mesenchymal stem cells (MSCs) cultured in an osteogenic differentiation medium. The analysis demonstrated the unexpected ability of osteoblast committed cells and their early progenitors to produce significant amounts of a range of soluble immune mediators without in vitro exposure to clinically relevant bacterial pathogens. The cells were expanded and their osteogenic potential analyzed over 45 days of culture was revealed by the expression of osteoblast-specific markers (alkaline phosphatase and Runx2), and by matrix mineralization. Over this culture period, the cells secreted particularly high levels of IL-8, MCP-1 and VEGF, but did not express IL-2, IL-7, IL-17, eotaxin, G-CSF and IFN-gamma. These findings should encourage the use of human umbilical cord blood as a potential stem cells source for bone regeneration.     

Chromosome demise in the wake of ligase-deficient replication

Bacterial DNA ligases, NAD⁺‐dependent enzymes, are distinct from eukaryotic ATP‐dependent ligases, representing promising targets for broad‐spectrum antimicrobials. Yet, the chromosomal consequences of ligase‐deficient DNA replication, during which Okazaki fragments accumulate, are still unclear. Using ligA251(Ts), the strongest ligase mutant of Escherichia coli, we studied ligase‐deficient DNA replication by genetic and physical approaches. Here we show that replication without ligase kills after a short resistance period. We found that double‐strand break repair via RecA, RecBCD, RuvABC and RecG explains the transient resistance, whereas irreparable chromosomal fragmentation explains subsequent cell death. Remarkably, death is mostly prevented by elimination of linear DNA degradation activity of ExoV, suggesting that non‐allelic double‐strand breaks behind replication forks precipitate DNA degradation that enlarge them into allelic double‐strand gaps. Marker frequency profiling of synchronized replication reveals stalling of ligase‐deficient forks with subsequent degradation of the DNA synthesized without ligase. The mechanism that converts unsealed nicks behind replication forks first into repairable double‐strand breaks and then into irreparable double‐strand gaps may be behind lethality of any DNA damaging treatment.     

Wood anatomy and carbon‐isotope discrimination support long‐term hydraulic deterioration as a major cause of drought‐induced dieback

Hydraulic impairment due to xylem embolism and carbon starvation are the two proposed mechanisms explaining drought‐induced forest dieback and tree death. Here, we evaluate the relative role played by these two mechanisms in the long‐term by quantifying wood‐anatomical traits (tracheid size and area of parenchyma rays) and estimating the intrinsic water‐use efficiency (iWUE) from carbon isotopic discrimination. We selected silver fir and Scots pine stands in NE Spain with ongoing dieback processes and compared trees showing contrasting vigour (declining vs nondeclining trees). In both species earlywood tracheids in declining trees showed smaller lumen area with thicker cell wall, inducing a lower theoretical hydraulic conductivity. Parenchyma ray area was similar between the two vigour classes. Wet spring and summer conditions promoted the formation of larger lumen areas, particularly in the case of nondeclining trees. Declining silver firs presented a lower iWUE than conspecific nondeclining trees, but the reverse pattern was observed in Scots pine. The described patterns in wood anatomical traits and iWUE are coherent with a long‐lasting deterioration of the hydraulic system in declining trees prior to their dieback. Retrospective quantifications of lumen area permit to forecast dieback in declining trees 2–5 decades before growth decline started. Wood anatomical traits provide a robust tool to reconstruct the long‐term capacity of trees to withstand drought‐induced dieback.     

Rotifer Nervous System Visualized by FMRFamide and 5-HT Immunocytochemistry and Confocal Laser Scanning Microscopy

The characteristic ecology of floodplain lakes is in part due to their relatively strong water-level fluctuations. We analyzed the factors determining water-level fluctuations in 100 floodplain lakes (during non-flooded conditions) in the active floodplains of the Lower Rhine in the Netherlands. Furthermore, we explored the relationship between water-level fluctuations and macrophyte species richness, and analyzed the suitability of artificially created lakes for macrophyte vegetation. During non-flooded conditions along the Rhine, lake water-level fluctuations are largely driven by groundwater connection to the river. Hence, water-level fluctuations are largest in lakes close to the main channel in strongly fluctuating sectors of the river and smallest in isolated lakes. Additionally, water-level fluctuations are usually small in old lakes, mainly due to reduced groundwater hydraulic conductivity resulting from accumulated clay and silt on the bottom. Species richness of floating-leaved and emergent macrophytes was reduced at both small and large water-level fluctuations, whereas species richness of submerged macrophytes was reduced at small water-level fluctuations only. In addition, species richness of submerged macrophytes was higher in lakes that experienced drawdown, whereas no similar pattern was detected for floating-leaved and emergent macrophytes. The decline in amplitude of lake water-level with lake age implies that the number of hydrologically dynamic lakes will decrease over time. Therefore, we suggest that excavation of new lakes is essential to conserve the successional sequence of floodplain water bodies including conditions of high biodiversity. Shallow, moderately isolated, lakes with occasional bottom exposure have the highest potential for creating macrophyte-rich floodplain lakes along large lowland rivers. The water-level regime of such lakes can in part be designed, through choice of the location along the river, the distance away from the river and the depth profile of the lake.     

Arbuscular Mycorrhizal Symbiosis with Arundo donax Decreases Root Respiration and Increases Both Photosynthesis and Plant Biomass Accumulation

The effect of arbuscular mycorrhiza (AM) symbiosis on plant growth is associated with the balance between costs and benefits. A feedback regulation loop has been described in which the higher carbohydrate cost to plants for AM symbiosis is compensated by increases in their photosynthetic rates. Nevertheless, plant carbon balance depends both on photosynthetic carbon uptake and respiratory carbon consumption. The hypothesis behind this research was that the role of respiration in plant growth under AM symbiosis may be as important as that of photosynthesis. This hypothesis was tested in Arundo donax L. plantlets inoculated with Rhizophagus irregularis and Funneliformis mosseae. We tested the effects of AM inoculation on both photosynthetic capacity and in vivo leaf and root respiration. Additionally, analyses of the primary metabolism and ion content were performed in both leaves and roots. AM inoculation increased photosynthesis through increased CO₂ diffusion and electron transport in the chloroplast. Moreover, respiration decreased only in AM roots via the cytochrome oxidase pathway (COP) as measured by the oxygen isotope technique. This decline in the COP can be related to the reduced respiratory metabolism and substrates (sugars and tricarboxylic acid cycle intermediates) observed in roots.     

Lateral line scale types and review of their taxonomic distribution

The trunk canal of fishes is contained within a series of lateral line (LL) scales. To categorise LL scale structural types, and determine their distribution, an analysis of original data was undertaken using light and scanning electron microscopy in combination with a literature survey from over 1,000 species representative of most orders of bony fishes. Our categorisation of LL scales is based on the relationship between the tube, or ossified trunk canal segment, and associated scale. Tubular‐Scalar LL scales consist of a distinguishable tube and elasmoid scale in scale pockets. Four types occur only in species with elasmoid scales. Integrated LL scales do not develop in scale pockets, and their tube is enclosed or extended by a non‐elasmoid scale or spines. Integrated 1 and 2 LL scales co‐occur with ganoid and calcidermoid scales, and Integrated 3 LL scales occur when common scales are absent or elasmoid. Tubular LL scales are tubes only, occurring mainly in scaleless species or with calcidermoid and elasmoid scales. Non‐Tubular LL scales are composed only of a scale, co‐occurring mainly with cycloid scales. There is consistency of LL scale type in many orders, families and genera and the presence of different types within taxa can be meaningful.     

EZH2 is downstream of the pRB-E2F pathway, essential for proliferation and amplified in cancer

Recent experiments have demonstrated that the Polycomb group (PcG) gene EZH2 is highly expressed in metastatic prostate cancer and in lymphomas. EZH2 is a component of the PRC2 histone methyltransferase complex, which also contains EED and SUZ12 and is required for the silencing of HOX gene expression during embryonic development. Here we demonstrate that both EZH2 and EED are essential for the proliferation of both transformed and non-transformed human cells. In addition, the pRB-E2F pathway tightly regulates their expression and, consistent with this, we find that EZH2 is highly expressed in a large set of human tumors. These results raise the question whether EZH2 is a marker of proliferation or if it is actually contributing to tumor formation. Significantly, we propose that EZH2 is a bona fide oncogene, since we find that ectopic expression of EZH2 is capable of providing a proliferative advantage to primary cells and, in addition, its gene locus is specifically amplified in several primary tumors.     

Microbial structural diversity estimated by dilution-extinction of phenotypic traits and T-RFLP analysis along a land-use intensification gradient

The present work tested whether the relationship between functional traits and inoculum density reflected structural diversity in bacterial communities from a land-use intensification gradient applying a mathematical model. Terminal restriction fragment length polymorphism (T-RFLP) analysis was also performed to provide an independent assessment of species richness. Successive 10-fold dilutions of a soil suspension were inoculated onto Biolog GN(R) microplates. Soil bacterial density was determined by total cell and plate counts. The relationship between phenotypic traits and inoculum density fit the model, allowing the estimation of maximal phenotypic potential (Rmax) and inoculum density (KI) at which Rmax will be half-reduced. Though Rmax decreased with time elapsed since clearing of native vegetation, KI remained high in two of the disturbed sites. The genetic pool of bacterial community did not experience a significant reduction, but the active fraction responding in the Biolog assay was adversely affected, suggesting a reduction in the functional potential.