Structure à conserver et aménagement à prévoir pour le conservation de la loutre en Région wallonne

Learning material (2012)

La loutre d’Europe est un mammifère protégé devenu rare en Région wallonne. Autrefois, l’espèce était pourtant présente sur l’ensemble des réseaux hydrographiques du pays. Très exigeante par rapport à la ... [more ▼]

La loutre d’Europe est un mammifère protégé devenu rare en Région wallonne. Autrefois, l’espèce était pourtant présente sur l’ensemble des réseaux hydrographiques du pays. Très exigeante par rapport à la qualité de son habitat et de sa nourriture, la loutre constitue un excellent témoin de l’état de santé de nos rivières. Mais si la population de loutre d’Europe paraît chez nous aujourd’hui au bord de l’extinction, on constate que d’autres populations européennes sont en pleine progression, notamment à partir de la France (Massif central) et de l’Allemagne. Elle gagne du terrain chaque année, amenuisant la distance qui nous sépare des autres populations européennes. Ce guide propose l’identification des abris potentiels pour la loutre ainsi que des aménagements des cours d’eau propices à son retour, puisqu’on pourrait l’espérer, à partir des populations européennes, d’ici 15 ou 20 ans. [less ▲]

Structure and behavior of rat primary and secondary Schwann cells in vitro

in Experimental Cell Research (1981), 131(2), 283-297

The structure and motility of isolated rat primary (I) Schwann cells (SC) have been compared to that of subcultured (II) SC during and after mitotic stimulation. I SC contain myelin components which ... [more ▼]

The structure and motility of isolated rat primary (I) Schwann cells (SC) have been compared to that of subcultured (II) SC during and after mitotic stimulation. I SC contain myelin components which persist for 2 weeks in serum-free medium while they rapidly disappear in medium containing serum and high glucose concentration. These components were never detected in II SC. Both I SC and II SC after their mitotic phase are spindle-shaped, contain many intermediate and actin filaments, have no basement membrane but show intense migratory and undulatory activities. Rare fibroblasts in I cultures are recognized by their extremely variable shape, the presence of Thy 1.1 antigen in their membrane and their intense edge ruffling alternating with abrupt translocation. In contrast, I SC movements consist of intracellular translocation of nuclei along SC processes, which retract and extend constantly, and in slow rhythmic undulation episodes (2.3 ± 0.2/min) alternating with migration at 135 ± 50 μ/h. The total number of these episodes per day in serum-free medium is rigorously identical for different cells (166.3 ± 0.2) and this uniformity of frequency suggests a genotypic basis. Cycles, consisting of an undulation episode followed by a resting interval, have mean durations of 8.6 ± 4.1 min and a sharp peak of occurrence at 6 min, with exponential distribution of the longer periods. Motility of II SC is considerably inhibited during mitotic stimulation by cholera toxin and a pituitary extract while SC phenotype has changed to a flat multipolar cell with prominent Golgi and ribosomes. Migration is reduced to 24 ± 2 μ/h and only 2% of the SC show pulsations of the same periodicity as the I SC undulations. A dramatic increase in pulsation frequency occurs 6–12 h after removal of mitogenic factors when 80% of II SC start pulsating twice as fast for 2–3 days. When mitoses cease, SC quickly recover their SC phenotype with rhythmic undulations while migration speed increased to 92 ± 20 μ/h. Thus, in spite of dramatic modification of shape, structure and behavior during mitotic stimulation, SC subsequently recover their unique motility pattern which might be essential for their myelinating function [less ▲]

Structure and bonding in liquid tellurium

in Physical Review. B, Condensed Matter and Materials Physics (1996), 53(1), 206-211211

The atomic structure and bonding mechanism in liquid tellurium have been investigated by a tight-binding Monte Carlo simulation. On melting, the chain structure of the crystal is preserved in spite of ... [more ▼]

The atomic structure and bonding mechanism in liquid tellurium have been investigated by a tight-binding Monte Carlo simulation. On melting, the chain structure of the crystal is preserved in spite of some significant changes in the local atomic environment. A third covalent bond appears with a bond length (widely distributed around 3.15 Aring) intermediate between those characteristic of the crystal. A short-long alternation of the bonds takes place within the chains, in agreement with the most recent extended X-ray-absorption fine structure measurements. In addition, the bond angle within the chains is reduced. Our calculations clearly prove that these effects are due to the electronic interaction between the lone pair orbitals. The subsequent broadening of the lone pair band is responsible for the semiconductor to metal transition that takes place upon melting. [less ▲]

Structure and development of cochlear afferent innervation in mammals.

in American Journal of Physiology - Cell Physiology (2011), 301(4), 750-61

In mammals, sensorineural deafness results from damage to the auditory receptors of the inner ear, the nerve pathways to the brain or the cortical area that receives sound information. In this review, we ... [more ▼]

In mammals, sensorineural deafness results from damage to the auditory receptors of the inner ear, the nerve pathways to the brain or the cortical area that receives sound information. In this review, we first focused on the cellular and molecular events taking part to spiral ganglion axon growth, extension to the organ of Corti, and refinement. In the second half, we considered the functional maturation of synaptic contacts between sensory hair cells and their afferent projections. A better understanding of all these processes could open insights into novel therapeutic strategies aimed to re-establish primary connections from sound transducers to the ascending auditory nerve pathways. [less ▲]

Structure and dynamics of cationic surfactants intercalated in synthetic clays

in Langmuir (2004), 20(7), 2982-2985

Structure and evolution of Lake Hazar pull-apart Basin along the East Anatolian Fault

in Basin Research (2010)

The Hazar Basin is a 25 km-long, 7 km-wide and 216 m-deep depression located on the central section of the East Anatolian Fault zone (eastern Turkey) and predominantly overlain by Lake Hazar. This basin ... [more ▼]

The Hazar Basin is a 25 km-long, 7 km-wide and 216 m-deep depression located on the central section of the East Anatolian Fault zone (eastern Turkey) and predominantly overlain by Lake Hazar. This basin has been described previously as a pull-apart basin because of its rhombic shape and an apparent fault step-over between the main fault traces situated at the southwestern and northeastern ends of the lake. However, detailed structural investigation beneath Lake Hazar has not been undertaken previously to verify this interpretation. Geophysical and sedimentological data from Lake Hazar were collected during field campaigns in 2006 and 2007. The analysis of this data reveals that the main strand of the East Anatolian Fault (the Master Fault) is continuous across the Hazar Basin, connecting the two segments previously assumed to be the sidewall faults of a pull-apart structure. In the northeastern part of the lake, an asymmetrical subsiding sub-basin, bounded by two major faults, is cross-cut by the Master Fault, which forms a releasing bend within the lake. Comparison of the structure revealed by this study with analogue models produced for transtensional step-overs suggests that the Hazar Basin structure represents a highly evolved pull-apart basin, to the extent that the previous asperity has been bypassed by a linking fault. The absence of a step-over structure at the Hazar Basin means that no significant segmentation boundary is recognised on the East Anatolian Fault between Palu and Sincik. Therefore, this fault segment is capable of causing larger earthquakes than recognised previously. [less ▲]

Structure and expression of growth hormone genes by recombinant DNA technology

in Gross, Erhard; Meienhofer, Johannes (Eds.) Peptides: Structure and biological function (1979)

Structure and functional analysis of a tilapia (Oreochromis mossambicus) growth hormone gene: activation and repression by pituitary transcription factor Pit-1

in DNA & Cell Biology (1999), 18(6), 489-502

A gene encoding the Tilapia mossambica (Oreochromis mossambicus) growth hormone (tiGH) was isolated and sequenced. The gene spans 5.6 kb, including 3.7 kb of 5' and 0.2 kb of 3' flanking sequences and a 1 ... [more ▼]

A gene encoding the Tilapia mossambica (Oreochromis mossambicus) growth hormone (tiGH) was isolated and sequenced. The gene spans 5.6 kb, including 3.7 kb of 5' and 0.2 kb of 3' flanking sequences and a 1.7-kb transcription unit comprised of six exons and five introns. The gene and the 5' flanking region contain several potential binding sites for Pit-1, a key transcription activator of mammalian GH genes. One of these (-57/-42) is highly conserved in fish GH genes. It activates transcription in pituitary cells and binds Pit-1. Transfection of luciferase reporter plasmids containing either the -3602/+19 tiGH sequence or one of its 5' deletion mutants (-2863/, -1292/, and -463/+19) resulted in strong activity in Pit-1-producing rat pituitary GC cells. A dose-dependent activation of the tiGH promoter was achieved in nonpituitary fish EPC and monkey COS cells cotransfected with a rat Pit-1 expression vector, demonstrating the crucial role played by Pit-1 as an activator of the tiGH gene. Fusion of the tiGH promoter with the beta-galactosidase gene led to transient expression specifically in the nervous system of microinjected zebrafish embryos. The activity of the tiGH promoter in GC and EPC cells was strongly repressed by extending its 3' end from +19 to +40, a sequence in which a Pit-1-binding site was identified using gel retardation assays. Point mutations of the site that suppressed Pit-1 binding in vitro restored full tiGH promoter activity. Thus, a Pit-1-binding site located in the 5' untranslated region mediates Pit-1-dependent repression of the tiGH gene. [less ▲]

Structure and Lattice Dynamics of Thermoelectric Complex Chalcogenides

Doctoral thesis (2012)

The goal of this work is to characterize the structure and lattice dynamics of complex chalcogenide alloys. Particular interest is paid to the system AgPbmSbTem+2 (LAST-m), AgSbTe2 and the binaries PbTe ... [more ▼]

The goal of this work is to characterize the structure and lattice dynamics of complex chalcogenide alloys. Particular interest is paid to the system AgPbmSbTem+2 (LAST-m), AgSbTe2 and the binaries PbTe, SnTe and GeTe. Synchrotron radiation studies including high energy X-ray di raction and nuclear inelastic scattering, and macroscopic measurements of heat capacity and elastic constants were performed. A new resonant ultrasound spectroscopy setup with capable of performing measurements from room temperature to 1073K was built for mechanical characterization of the thermoelectric alloys at their working temperatures. The rst chapter presents a brief review of relevant information on thermoelectricity and on the materials under study. The characterization methods including heat capacity, resonant ultrasound spectroscopy, X-ray di raction and nuclear inelastic scattering are introduced. Not as an exhaustive review, but rather in order to give the reader a basic level of understanding and a sense of the acessible information. The introduction is followed by three chapters which address the experimental studies of lattice dynamics in chalcogenide alloys. Chapter 2 describes the lattice dynamics in the compounds GeTe, SnTe and PbTe studied by 119Sn and 125Te nuclear inelastic scattering. The obtained partial density of phonon states were compared with published theoretical calculations, and the resulting vibrational properties were found to be in good agreement with these reports. Additionally, the phase purity and structure were characterized by high energy X-ray di raction. The atomic arrangement, rhombohedral for GeTe and cubic for SnTe and PbTe, is seem to a ect the density of phonon states, with the NaCl-type structure having a softer character in comparison with the rhombohedral structure. In Chapter 3, the lattice dynamics of a polycrystalline AgSbTe2 sample was investigated by 121Sb and 125Te nuclear inelastic scattering, at low temperatures. For this compound, the phonon modes have energies below 25meV and a sound velocity of vs =1490(30) m/s was determined. A simple temperature independent estimation of the lattice thermal conductivity of AgSbTe2 yielded L =0.50 0.05Wm􀀀1K􀀀1. The low Debye temperature, D =150(15)K combined with the short phonon lifetime and the low sound velocity are found to be key factors for the low thermal conductivity in AgSbTe2 and are related to the good thermoelectric performance in AgSbTe2 and AgSbTe2containing systems. Chapter 4 is dedicated to the study of the average and local structure in bulk AgPb18SbTe20 alloy, by a combined Rietveld and Pair Distribution Function analysis. The strong in uence of the synthesis conditions on the lattice parameters and on the composition and the concentration of nanoclusters in LAST-18 is con- rmed. Moreover, the 121Sb and 125Te partial density of phonons states were obtained by nuclear inelastic scattering in order to separately characterize the lattice dynamics from the matrix and the nanoinclusions. Additional characterization of the elastic properties and lattice governed properties were performed by resonance ultrasound spectroscopy, heat capacity and thermal expansion measurements. The nal chapter is dedicated to the resonant ultrasound spectroscopy technique, and the process of building up this bu er-rods high-temperature measurement system are presented. Advantages and disadvantages, as well as limitations and di culties are discussed. Using the \mode-tracking" method, the mechanical behavior of a PbTe and a Niobium sample, from room temperature to 523K and from room temperature to 973 K, respectively, were investigated. [less ▲]

Structure and orientation of apo B-100 peptides into a lipid bilayer.

in Journal of Protein Chemistry (1994), 13(1), 77-88

Peptides corresponding to lipid binding domains of Apo B-100 were synthesized, purified, and incubated with dimyristoylphosphatidylcholine (DMPC) liposomes. The secondary structure of the apo B-100 ... [more ▼]

Peptides corresponding to lipid binding domains of Apo B-100 were synthesized, purified, and incubated with dimyristoylphosphatidylcholine (DMPC) liposomes. The secondary structure of the apo B-100 peptide-lipid complexes was evaluated by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Those peptides belonging to the hydrophobic "core" domain of apo B-100 when associated with phospholipids were rich in beta sheet structure; a predominant alpha helical conformation was shown to be associated with one peptide located in a surface region of apo B-100. IR dichroic spectra revealed, in the case of the "core" peptides, that the beta sheet component is the only oriented structure with respect to the phospholipid acyl chains. This orientation of the beta sheet was recently found in LDL particles after proteolytic digestion by trypsin (Goormaghtigh, E., Cabiaux, V., De Meutter, J., Rosseneu, M., and Ruysschaert, J. M., 1993, Biochemistry 32, 6104-6110). Altogether, the data suggest that beta sheet, present in a high proportion in the native apo B-100, is probably another protein structure in addition to the amphipathic helix which strongly interacts with the lipid outer layer surrounding the LDL particle. [less ▲]