Molecular cloning and comparative analysis of fibrinogen-related proteins from the soft tick Ornithodoros moubata and the hard tick Ixodes ricinus

Among disease-vectors, the evolution of the tick innate immune system is still lagging when compared to insects. Such an investigation, which was initiated, by first cloning and sequencing lectins associated in the innate immunity of invertebrates and having fibrinogen related domains, helped in the sequencing of cDNA encoding for OMFREP from the soft tick, Ornithodoros moubata. Also obtained were Ixoderin A and Ixoderin B cDNA sequences from the hard tick Ixodes ricinus. Tissue-specific expression of OMFREP showed that it was present primarily in the hemocytes and salivary glands. Ixoderin A besides sharing a similar expression profile was also expressed in the midgut. Both showed significantly high homology to the lectin Dorin M, from O. moubata. Further, phylogenetic comparisons between these molecules of the soft and hard ticks showed their relatedness to Tachylectins 5A and 5B, involved in the innate immunity of Tachypleus tridentatus and ficolins from both vertebrates and invertebrates. Ixoderin B showing tissue-specific expression only in the salivary glands and the sequence displaying certain motif differences in homology point towards a possible function different from the other two molecules. This is the first report of lectin-like sequences, with a fibrinogen-domain, from the hard tick I. ricinus and a preliminary phylogenetic study of these tick sequences with related fibrinogen-domain containing sequences highlights a possible role for them in the innate immunity of the ticks.     

On the origin of eukaryotic cells and their endomembranes.

A novel hypothesis for the origin of eukaryotic cells is presented. It is assumed that the universal ancestor was bounded by two membranes of heterochiral lipid composition. We propose that the prokaryotic cells (the hypothetical host entity for alpha proteic-bacteria), though sharing a common ancestor with Archaea, was bounded by two membranes. The hypothesis suggests that an alpha proteic-bacterial symbiont was enclosed in the prokaryotic cells intermembrane space. In this view, the eukaryotic nuclear membrane and endomembrane system arose from the prokaryotic cells inner membrane while the eukaryotic plasma membrane arose from the prokaryotic cells outer membrane. The outlined scenario agrees with the view that engulfment of an alpha-proteic-bacterial cell by a host entity and its transformation to a mitochondrion was the driving force leading to the appearance of the first eukaryotic cell. The hypothesis seems to be consistent with the pre-cell theory, theory of membrane heredity, and the phagocytosis-late scenario.     

A threshold of mechanical strain intensity for the direct activation of osteoblast function exists in a murine maxilla loading model

The response to the mechanical loading of bone tissue has been extensively investigated; however, precisely how much strain intensity is necessary to promote bone formation remains unclear. Combination studies utilizing histomorphometric and numerical analyses were performed using the established murine maxilla loading model to clarify the threshold of mechanical strain needed to accelerate bone formation activity. For 7 days, 191 kPa loading stimulation for 30 min/day was applied to C57BL/6J mice. Two regions of interest, the AWAY region (away from the loading site) and the NEAR region (near the loading site), were determined. The inflammatory score increased in the NEAR region, but not in the AWAY region. A strain intensity map obtained from \(\upmu \hbox {CT}\) images was superimposed onto the images of the bone formation inhibitor, sclerostin-positive cell localization. The number of sclerostin-positive cells significantly decreased after mechanical loading of more than \(150\,{\upmu }{\upvarepsilon }\) in the AWAY region, but not in the NEAR region. The mineral apposition rate, which shows the bone formation ability of osteoblasts, was accelerated at the site of surface strain intensity, namely around \(170\,{\upmu }{\upvarepsilon }\), but not at the site of lower surface strain intensity, which was around \(80\,{\upmu }{\upvarepsilon }\) in the AWAY region, thus suggesting the existence of a strain intensity threshold for promoting bone formation. Taken together, our data suggest that a threshold of mechanical strain intensity for the direct activation of osteoblast function and the reduction of sclerostin exists in a murine maxilla loading model in the non-inflammatory region.     

Photosynthesis, leaf conductance and water relations of in vitro cultured grapevine rootstock in relation to acclimatisation

Leaf net CO₂ uptake and leaf photosynthetic capacity were investigated in micropropagated 41B grapevine rootstock (Vitis vinifera‘Chasselas’×Vitis berlandieri, Mill. De Gr.) plants grown in the presence of four sucrose concentrations (6.25, 12.5, 25.0 or 37.5 g l^?1). Sucrose concentration in the medium during growth in vitro did not affect the leaf photosynthetic performance of plants neither before nor after transplantation. The maximum photosynthetic rate, measured as CO₂-dependent O₂ evolution, was 7.3 µmol m^?2 s^?1 before transplanting and 15.4 µmol m^?2 s^?1 one month after transplantation. The maximum quantum yield of O₂ evolution (on the basis of incident light) was about 0.07 for all sucrose treatments both before and after transplantation. Dry biomass before transplanting was highest in plants grown with 25.0 or 37.5 g l^?1 sucrose in the medium. One month after transplantation the highest dry biomass was also observed for the same treatments. Survival of plants was 100% for all treatments. Leaf conductance to water vapour was always higher in plants before than after transplantation. Both before and after transplanting it increased with increasing light intensity and decreased slightly with increasing CO₂ molar ratio in in vitro plants. Stomata of plants before transplantation were unresponsive to vapour pressure deficit. In vitro plants experience an acute water stress when they are maintained with the whole root system in water and exposed to ambient controlled conditions in a growth chamber. However, there was no wilting of the leaves when similar plants with roots cut off were left in the same conditions. Hydraulic conductivity was low at both root and shoot-root connection levels. It is likely that water supply could be limiting during transplantation because of the low root and root-stem connection conductivity. Water uptake by roots rather than water loss from the shoots would be of primary importance for the maintenance of water balance during acclimatisation.     

High vegetation and environmental diversity during the Late Glacial and Early Holocene on the example of lowlands in the Czech Republic

The diversity of vegetation and the environment in the Late Glacial period in the Elbe region is illustrated by a comparison of three palynological localities. The localities differ in their history, profile lithology and position relative to the Elbe river. The Hrabanovská ?ernava profile holds a record of the development of a shallow lake, which was surrounded by a cold continental steppe in the Early Dryas. Evidence of a pine forest in the Late Glacial period is captured in the surroundings of the profile Chrást. The Mělnický úval — P?ívory locality is an interdune infill, where marl sediments redeposited in shallow water. The surrounding vegetation was diffuse and influenced by erosion. In the Early Holocene, the landscape was covered by an open birch-pine forest. Broad-leaved woody species appeared later. Localities in the Elbe region share a high proportion of Pinus throughout the Holocene as a result of the spread of drift and terrace sands. The human impact in the mid Holocene manifests as evidence of intensive charring of localities.     

Late-Glacial and Holocene Environmental History of an Oxbow Wetland in the Polabí Lowland (River Elbe,Czech Republic); a Context-Dependent Interpretation of a Multi-Proxy Analysis

This study presents a palaeoenvironmental reconstruction of an oxbow wetland covering the past 11,500 years. The origin of the oxbow lake and development of the floodplain wetland and changes of the surrounding vegetation are reconstructed using palaeobotanical analyses, radiocarbon dating, detailed sediment stratigraphy and micromorphology of samples taken from a former palaeomeander of the river Elbe in the Czech Republic. The sedimentary record of the section Chrast was chosen due to its exceptional position within the area of former oxbow lakes. Using a multi-proxy approach, we investigated how this environment reflected climatic changes during the Holocene. Our results show that the Chrast section covers the Late-Glacial to the Middle Holocene period, which is climatically very unstable and characterized by extensive vegetation and sedimentological changes. The macrofossil record provides detailed evidence of Allerød vegetation. The sedimentological record reflects changes in fluvial activity (meandering-braided transition in the channel pattern) during Late-Glacial/Holocene and postsedimentological changes (occurrence of a doplerite layer) in the middle Holocene. We follow three independent lines of interpretation: (a) a local autogenic environmental-succession process, (b) a regional process driven by climate change, and (c) the role of stochastic and indeterministic processes.