A monoclonal antibody marker for the exclusion-zone filaments of Trypanosoma brucei

<p>Abstract</p> <p>Background</p> <p><it>Trypanosoma brucei </it>is a haemoflagellate pathogen of man, wild animals and domesticated livestock in central and southern Africa. In all life cycle stages this parasite has a single mitochondrion that contains a uniquely organised genome that is condensed into a flat disk-like structure called the kinetoplast. The kinetoplast is essential for insect form procyclic cells and therefore is a potential drug target. The kinetoplast is unique in nature because it consists of novel structural proteins and thousands of circular, interlocking, DNA molecules (kDNA). Secondly, kDNA replication is critically timed to coincide with nuclear S phase and new flagellum biogenesis. Thirdly, the kinetoplast is physically attached to the flagellum basal bodies <it>via </it>a structure called the tripartite attachment complex (TAC). The TAC consists of unilateral filaments (within the mitochondrion matrix), differentiated mitochondrial membranes and exclusion-zone filaments that extend from the distal end of the basal bodies. To date only one protein, p166, has been identified to be a component of the TAC.</p> <p>Results</p> <p>In the work presented here we provide data based on a novel EM technique developed to label and characterise cytoskeleton structures in permeabilised cells without extraction of mitochondrion membranes. We use this protocol to provide data on a new monoclonal antibody reagent (Mab 22) and illustrate the precise localisation of basal body-mitochondrial linker proteins. Mab 22 binds to these linker proteins (exclusion-zone filaments) and provides a new tool for the characterisation of cytoskeleton mediated kinetoplast segregation.</p> <p>Conclusion</p> <p>The antigen(s) recognised by Mab 22 are cytoskeletal, insensitive to extraction by high concentrations of non-ionic detergent, extend from the proximal region of basal bodies and bind to the outer mitochondrial membrane. This protein(s) is the first component of the TAC exclusion-zone fibres to be identified. Mab 22 will therefore be important in characterising TAC biogenesis.</p

Irreversible Structural Transformation of five fold i-AlPdMn Quasicrystals after Ion Bombardment and Annealing

Five fold i-AlPdMn surface prepared under UHV by ion bombardment and annealing was so far considered to be bulk terminated. This result was substantially based on a quantitative LEED analyses [1]. Analysis of the specular rod in a X ray diffraction experiment at grazing incidence supported this result [2]. We present a new study of this surface by high resolution X ray diffraction at normal incidence. In this Bragg configuration the diffraction peak 18 – 29 for instance is at a photon energy of 2.873keV, the 72 – 116 reflection at 5.725keV. This results in an analyzed thickness of the sample surface of a few micrometers. The surface was cleaned by ion bombardment. During annealing (T≅880K), we clearly observed the progressive disappearance of the initial Bragg peak characteristic of the as cast bulk sample. Conversely a new Bragg peak grows at an energy position shifted by 1eV compared to the position of the original Bragg peak. This is a clear signature for an irreversible structural transformation which takes place on at least the micron thickness. On the transformed surface, both, a LEED pattern and a RHEED pattern, characteristic for a five fold surface were easily obtained. This high resolution experiment (the relative Bragg peak shift is 3ׁ10−4) was reproduced on samples from different initial compositions. This shows that five fold i-AlPdMn surface changes after preparation by ion bombardment and annealing at 900K on a micrometer thickness. This is not consistent with the conclusion that the surface is simply terminated by a cut of the original bulk. We conclude that a reorganization process of the quasicrystalline structure during annealing proceeds in the surface vicinity (probed depth is close to a few microns)

Dermal-Type Macrophages Expressing CD209/DC-SIGN Show Inherent Resistance to Dengue Virus Growth

Mosquito-transmitted pathogens are a major challenge to humans due to ever-increasing distribution of the vector worldwide. Dengue virus causes morbidity and mortality, and no anti-viral treatment or vaccine are currently available. The virus is injected into the skin when an infected mosquito probes for blood. Among the skin immunocytes, dendritic cells and macrophages are equipped with pathogen-sensing receptors. Our work has shown that dermal macrophages bind the dengue virus envelope protein. We demonstrate that monocyte-derived dermal macrophages are resistant to infection and present evidence that this is due to sequestration of the virus into fusion-incompetent intracellular vesicles. This identifies skin macrophages as the first innate immune cell potentially capable of protecting the human host from infection by dengue virus shortly after a mosquito bite. These findings have important implications for better understanding the early infection events of dengue virus and of other skin-penetrating pathogens

The Effect of Structural Complexity, Prey Density, and “Predator-Free Space” on Prey Survivorship at Created Oyster Reef Mesocosms

Interactions between predators and their prey are influenced by the habitat they occupy. Using created oyster (Crassostrea virginica) reef mesocosms, we conducted a series of laboratory experiments that created structure and manipulated complexity as well as prey density and “predator-free space” to examine the relationship between structural complexity and prey survivorship. Specifically, volume and spatial arrangement of oysters as well as prey density were manipulated, and the survivorship of prey (grass shrimp, Palaemonetes pugio) in the presence of a predator (wild red drum, Sciaenops ocellatus) was quantified. We found that the presence of structure increased prey survivorship, and that increasing complexity of this structure further increased survivorship, but only to a point. This agrees with the theory that structural complexity may influence predator-prey dynamics, but that a threshold exists with diminishing returns. These results held true even when prey density was scaled to structural complexity, or the amount of “predator-free space” was manipulated within our created reef mesocosms. The presence of structure and its complexity (oyster shell volume) were more important in facilitating prey survivorship than perceived refugia or density-dependent prey effects. A more accurate indicator of refugia might require “predator-free space” measures that also account for the available area within the structure itself (i.e., volume) and not just on the surface of a structure. Creating experiments that better mimic natural conditions and test a wider range of “predator-free space” are suggested to better understand the role of structural complexity in oyster reefs and other complex habitats

Biophysical analysis of the plant-specific GIPC sphingolipids reveals multiple modes of membrane regulation

The plant plasma membrane (PM) is an essential barrier between the cell and the external environment, controlling signal perception and transmission. It consists of an asymmetrical lipid bilayer made up of three different lipid classes: sphingolipids, sterols, and phospholipids. The glycosyl inositol phosphoryl ceramides (GIPCs), representing up to 40% of total sphingolipids, are assumed to be almost exclusively in the outer leaflet of the PM. However, their biological role and properties are poorly defined. In this study, we investigated the role of GIPCs in membrane organization. Because GIPCs are not commercially available, we developed a protocol to extract and isolate GIPC-enriched fractions from eudicots (cauliflower and tobacco) and monocots (leek and rice). Lipidomic analysis confirmed the presence of trihydroxylated long chain bases and 2-hydroxylated very long-chain fatty acids up to 26 carbon atoms. The glycan head groups of the GIPCs from monocots and dicots were analyzed by gas chromatograph–mass spectrometry, revealing different sugar moieties. Multiple biophysics tools, namely Langmuir monolayer, ζ-Potential, light scattering, neutron reflectivity, solid state 2H-NMR, and molecular modeling, were used to investigate the physical properties of the GIPCs, as well as their interaction with free and conjugated phytosterols. We showed that GIPCs increase the thickness and electronegativity of model membranes, interact differentially with the different phytosterols species, and regulate the gel-to-fluid phase transition during temperature variations. These results unveil the multiple roles played by GIPCs in the plant PM.Vers un modèle intégratif de la bicouche lipidique de la membrane plasmique végétaleDéveloppement d’une infrastructure française distribuée pour la métabolomique dédiée à l’innovatio

Spiritual quest in François Cheng's novel works

L’œuvre chengienne est traversée de bout en bout par des interrogations existentielles qui découlent des trois formes élémentaires du désir que François Cheng distingue en l’homme : « désir de réalisation, désir de dépassement, désir de transcendance. » (Cinq méditations sur la mort, p. 56). Ces interrogations, qui se retrouvent sans surprise dans son oeuvre romanesque, conduisent ses personnages à entreprendre une véritable quête spirituelle, terme que nous entendons à la fois comme quête de l’esprit et comme élancement de l’âme vers la surnature. Nous tâchons dans notre étude d’en dégager les tenants et les aboutissants, en montrant comment l’auteur parvient à relier de manière cohérente des spiritualités a priori différentes et sans oublier que les héros chengiens sont tous ancrés dans la culture chinoise qui n’a pas établi de distinction radicale entre transcendance et immanence, horizontalité et verticalité. Parce qu’il est fondamentalement en quête de sens, le héros est irrésistiblement poussé à entreprendre un cheminement (à la fois physique et intérieur), qui lui permet de se réconcilier à la fois avec lui-même et avec le monde, tout en faisant l’expérience d’une certaine Transcendance. Cette quête a pour corollaire une quête du féminin qui lui est indissociable, car la Femme, telle que la conçoit Cheng, est par excellence celle qui mène l’homme vers la spiritualité. C’est pourquoi l’éros chengien est un éros mystique, naturellement porté à se muer en Agapè. En somme, ce sont les trois ordres pascaliens qui se trouvent unifiés au terme de cette aventure, le troisième ordre ne supprimant pas les deux autres, mais leur permettant au contraire de se réaliser pleinement. C’est-à-dire que l’œuvre romanesque de François Cheng, de même que son œuvre poétique, n’est au fond qu’une célébration de la relianceQuestions of existence are running throughout Cheng’s works, from beginning to end. These questions derive from the three elementary forms of desire which François Cheng tells apart in human : desire to accomplish, desire to exceed and desire to transcend (Five Meditations on Death, p.56). These questions, which can be found unsurprisingly in his novel works, lead his characters to a true spiritual quest, a term we understand as a quest of spirit, and at the same time, as a march from soul to supernature. In our study, we try to analyse all the relevant factors, to show how the author had succeeded in relating the a priori different spiritualities in a coherent way, without neglecting the fact that Cheng’s heros are all rooted in a Chinese culture background, where the basic distinctions between transcendance and immanence, between horizontality and verticality have not been established yet. Because of his fundamental quest on meanings, the hero is irresistibly pushed to go through a progress (both physical and interior), which allows him to reconciliate with himself and with the world, while experiencing a certain kind of transcendance. This quest has resulted in the quest of the female, which is inseparable from him. Because according to Cheng, the women are the ones who excellently lead the men to spirituality. That’s why Cheng’s Eros is a mystical Eros, and is naturally turned into Agape. In summary, the three Pascal rules are unitied in the end of the adventure, the third one does not supress the two others, in contrary, it helps them to full fulfillment. This means that Cheng’s novel works as long as his poetry works, are in fact nothing but a celebration of connectio