Effect of wind,thermal convection,and variation in flight strategies on the daily rhythm and flight paths of migrating raptors at Georgia's Black Sea coast

Every autumn, large numbers of raptors migrate through geographical convergence zones to avoid crossing large bodies of water. At coastal convergence zones, raptors may aggregate along coastlines because of convective or wind conditions. However, the effect of wind and thermal convection on migrating raptors may vary depending on local landscapes and weather, and on the flight strategies of different raptors. From 20 August to 14 October 2008 and 2009, we studied the effect of cloud development and crosswinds on the flight paths of raptors migrating through the eastern Black Sea convergence zone, where coastal lowlands at the foothills of the Pontic Mountains form a geographical bottleneck 5‐km‐wide near Batumi, the capital of the Independent Republic of Ajaria in southwestern Georgia. To identify key correlates of local aggregation, we examined diurnal variation in migration intensity and coastal aggregation of 11 species of raptors categorized based on size and flight strategies. As reported at other convergence zones, migration intensity of large obligate‐soaring species peaked during the core period of thermal activity at mid‐day. When clouds developed over interior mountains and limited thermal convection, these large obligate‐soaring species aggregated near the coast. However, medium‐sized soaring migrants that occasionally use flapping flight did not aggregate at the coast when clouds over the mountains weakened thermal convection. Numbers of alternate soaring‐flapping harriers (Circus spp.) peaked during early morning, with these raptors depending more on flapping flight during a time of day with poor thermal convection. Small sparrowhawks (Accipiter spp.) aggregated at the coast during periods when winds blew offshore, suggesting aggregation caused by wind drift. Thus, weather conditions, including cloud cover and wind speed and direction, can influence the daily rhythm and flight paths of migrating raptors and, therefore, should be accounted for before inferring population trends from migration counts.     

High resolution imaging of collagen organisation and synthesis using a versatile collagen specific probe

Collagen is the protein primarily responsible for the load-bearing properties of tissues and collagen architecture is one of the main determinants of the mechanical properties of tissues. Visualisation of changes in collagen three-dimensional structure is essential in order to improve our understanding of collagen fibril formation and remodelling, e.g. in tissue engineering experiments. A recently developed collagen probe, based on a natural collagen binding protein (CNA35) conjugated to a fluorescent dye, showed to be much more specific to collagen than existing fluorescent techniques currently used for collagen visualisation in live tissues. In this paper, imaging with this fluorescent CNA35 probe was compared to imaging with second harmonic generation (SHG) and the imaging of two- and three-dimensional collagen organisation was further developed. A range of samples (cell culture, blood vessels and engineered tissues) was imaged to illustrate the potential of this collagen probe. This images of collagen organisation showed improved detail compared to images generated with SHG, which is currently the most effective method for viewing three-dimensional collagen organisation in tissues. In conclusion, the fluorescent CNA35 probe allows easy access to high resolution imaging of collagen, ranging from very young fibrils to more mature collagen fibres. Furthermore, this probe enabled real-time visualisation of collagen synthesis in cell culture, which provides new opportunities to study collagen synthesis and remodelling.     

Polymer-based scaffold designs for in situ vascular tissue engineering: controlling recruitment and differentiation behavior of endothelial colony forming cells

In situ vascular tissue engineering has been proposed as a promising approach to fulfill the need for small-diameter blood vessel substitutes. The approach comprises the use of a cell-free instructive scaffold to guide and control cell recruitment, differentiation, and tissue formation at the locus of implantation. Here we review the design parameters for such scaffolds, with special emphasis on differentiation of recruited ECFCs into the different lineages that constitute the vessel wall. Next to defining the target properties of the vessel, we concentrate on the target cell source, the ECFCs, and on the environmental control of the fate of these cells within the scaffold. The prospects of the approach are discussed in the light of current technical and biological hurdles.     

Information propagation within the Genetic Network of Saccharomyces cerevisiae

Background  

A gene network's capacity to process information, so as to bind past events to future actions, depends on its structure and logic. From previous and new microarray measurements in Saccharomyces cerevisiae following gene deletions and overexpressions, we identify a core gene regulatory network (GRN) of functional interactions between 328 genes and the transfer functions of each gene. Inferred connections are verified by gene enrichment.     

Viscoelastic properties of single attached cells under compression

The viscoelastic properties of single, attached C2C12 myoblasts were measured using a recently developed cell loading device. The device allows global compression of an attached cell, while simultaneously measuring the associated forces. The viscoelastic properties were examined by performing a series of dynamic experiments over two frequency decades (0.1-10 Hz) and at a range of axial strains (approximately 10-40%). Confocal laser scanning microscopy was used to visualize the cell during these experiments. To analyze the experimentally obtained force-deformation curves, a nonlinear viscoelastic model was developed. The nonlinear viscoelastic model was able to describe the complete series of dynamic experiments using only a single set of parameters, yielding an elastic modulus of 2120 +/- 900 Pa for the elastic spring, an elastic modulus of 1960 +/- 1350 for the nonlinear spring, and a relaxation time constant of 0.3 +/- 0.12 s. To our knowledge, it is the first time that the global viscoelastic properties of attached cells have been quantified over such a wide range of strains. Furthermore, the experiments were performed under optimal environmental conditions and the results are, therefore, believed to reflect the viscoelastic mechanical behavior of cells, such as would be present in vivo.     

DELAYED URIC ACID ACCUMULATION IN PLASMA PROVIDES ADDITIONAL ANTI-OXIDANT PROTECTION AGAINST IRON-TRIGGERED OXIDATIVE STRESS AFTER A WINGATE TEST

Reactive oxygen species are produced during anaerobic exercise mostly by Fe ions released into plasma and endothelial/muscle xanthine oxidase activation that generates uric acid (UA) as the endpoint metabolite. Paradoxically, UA is considered a major antioxidant by virtue of being able to chelate pro-oxidative iron ions. This work aimed to evaluate the relationship between UA and plasma markers of oxidative stress following the exhaustive Wingate test. Plasma samples of 17 male undergraduate students were collected before, 5 and 60 min after maximal anaerobic effort for the measurement of total iron, haem iron, UA, ferric-reducing antioxidant activity in plasma (FRAP), and malondialdehyde (MDA, biomarker of lipoperoxidation). Iron and FRAP showed similar kinetics in plasma, demonstrating an adequate pro-/antioxidant balance immediately after exercise and during the recovery period (5–60 min). Slight variations of haem iron concentrations did not support a relevant contribution of rhabdomyolysis or haemolysis for iron overload following exercise. UA concentration did not vary immediately after exercise but rather increased 29% during the recovery period. Unaltered MDA levels were concomitantly measured. We propose that delayed UA accumulation in plasma is an auxiliary antioxidant response to post-exercise (iron-mediated) oxidative stress, and the high correlation between total UA and FRAP in plasma (R-Square = 0.636; p = 0.00582) supports this hypothesis.     

Calcium-permeable channels in plant cells

Calcium signal transduction is a central mechanism by which plants sense and respond to endogenous and environmental stimuli. Cytosolic Ca(2+) elevation is achieved via two cellular pathways, Ca(2+) influx through Ca(2+) channels in the plasma membrane and Ca(2+) release from intracellular Ca(2+) stores. Because of the significance of Ca(2+) channels in cellular signaling, interaction with the environment and developmental processes in plants, a great deal of effort has been invested in recent years with regard to these important membrane proteins. Because of limited space, in this review we focus on recent findings giving insight into both the molecular identity and physiological function of channels that have been suggested to be responsible for the elevation in cytosolic Ca(2+) level, including cyclic nucleotide gated channels, glutamate receptor homologs, two-pore channels and mechanosensitive Ca(2+) -permeable channels. We provide an overview of the regulation of these Ca(2+) channels and their physiological roles and discuss remaining questions.     

The proton cycle of a deciduous forest ecosystem in the Netherlands and its implications for soil acidification

Investigations into the proton cycle of a forest ecosystem in the Netherlands revealed an intermediate rate of soil acidification: 4.5 × 10² keq km^-2 yr^-1 of which 2/3 is caused by external proton sources. The high retention of NH₄-N in the biomass is the dominant source of protons. This retention of accounts for 90% of the external and for 59% of the total proton source, while atmospheric input of free acidity only accounts for 4% of total proton production. Next to this, Ca release by weathering is the main proton sink, accounting for 72% to total proton consumption. The proton transfer processes have caused very acid conditions of the upper soil horizons (pH 2.9–3.5) which resulted in the mobilization of aluminium as inorganic monomeric (toxic) Al up to maximum concentrations of 1500 μmol L^-1 (40 mg Al³⁺ L^-1).     

Plasma free amino acid profiles and nutrition proteins in chronic renal failure; effect of dialysis treatment

Summary A well preserved nutritional status is beneficial in chronically uremic patients for slowing the pace of deterioration of renal function, and delaying the need for dialysis therapy. The purpose of this study was to assess the nutritional profile of 10 patients in a steady state of advanced CRF, and of 15 patients with terminal renal failure immediately prior to their first hemodialysis session (J0), and 7, 14, 45, 60, days post start of dialysis. Patients were 18 to 65 years old with total plasma proteins 60g/1. Plasma concentrations of amino acids, nutrition proteins, apolipoproteins A1, and B were evaluated. Non inflammatory reaction was evaluated by determination of alpha-1-acid glycoprotein, and C reactive protein. The data (mean ± 1 SD) were compared with mean values of 15 healthy individuals.     

Colorful Protein-Based Fluorescent Probes for Collagen Imaging

Real-time visualization of collagen is important in studies on tissue formation and remodeling in the research fields of developmental biology and tissue engineering. Our group has previously reported on a fluorescent probe for the specific imaging of collagen in live tissue in situ, consisting of the native collagen binding protein CNA35 labeled with fluorescent dye Oregon Green 488 (CNA35-OG488). The CNA35-OG488 probe has become widely used for collagen imaging. To allow for the use of CNA35-based probes in a broader range of applications, we here present a toolbox of six genetically-encoded collagen probes which are fusions of CNA35 to fluorescent proteins that span the visible spectrum: mTurquoise2, EGFP, mAmetrine, LSSmOrange, tdTomato and mCherry. While CNA35-OG488 requires a chemical conjugation step for labeling with the fluorescent dye, these protein-based probes can be easily produced in high yields by expression in E. coli and purified in one step using Ni²⁺-affinity chromatography. The probes all bind specifically to collagen, both in vitro and in porcine pericardial tissue. Some first applications of the probes are shown in multicolor imaging of engineered tissue and two-photon imaging of collagen in human skin. The fully-genetic encoding of the new probes makes them easily accessible to all scientists interested in collagen formation and remodeling.