Basic kinematics of the saddle and rider in high-level dressage horses trotting on a treadmill

REASONS FOR PERFORMING STUDY: A comprehensive kinematic description of rider and saddle movements is not yet present in the scientific literature. OBJECTIVE: To describe saddle and rider movements in a group of high-level dressage horses and riders. METHOD: Seven high-level dressage horses and riders were subjected to kinematic measurements while performing collected trot on a treadmill. For analysis a rigid body model for the saddle and core rider segments, projection angles of the rider's extremities and the neck and trunk of the horse, and distances between markers selected to indicate rider position were used. RESULTS: For a majority of the variables measured it was possible to describe a common pattern for the group. Rotations around the transverse axis (pitch) were generally biphasic for each diagonal. During the first half of stance the saddle rotated anti-clockwise and the rider's pelvis clockwise viewed from the right and the rider's lumbar back extended. During the later part of stance and the suspension phase reverse pitch rotations were observed. Rotations of the saddle and core rider segments around the longitudinal (roll) and vertical axes (yaw) changed direction only around time of contact of each diagonal. CONCLUSION: The saddles and riders of high-level dressage horses follow a common movement pattern at collected trot. The movements of the saddle and rider are clearly related to the movements of the horse and saddle movements also seem to be influenced by the rider. POTENTIAL RELEVANCE: Knowledge about rider and saddle movements can further our understanding of, and hence possibilities to prevent, orthopaedic injuries related to the exposure of the horse to a rider and saddle

Les relations structurales entre birnavirus et autres virus icosaédriques à ARN

International audienceLes particules des virus à ARN double brin (ARNdb) sont compétentes pour la transcription et doivent traverser une membrane cellulaire pour fonctionner dans le cytoplasme de la cellule cible. Parmi ces virus, les birnavirus sont singuliers car ils possèdent une simple capside icosaédrique de triangulation T \= 13 et ne contiennent pas la capside interne caractéristique observée dans la plupart de ces virus. Nous avons récemment élucidé la structure de sous-particules virales ainsi que de particules virales complètes d’un birnavirus aviaire [1]. Nos résultats révèlent des relations structurales inattendues entre virus icosaédriques et nous permettent de proposer un lien phylogénétique entre certains virus à ARNdb et des virus à ARN de polarité positive

Broad-spectrum non-toxic antiviral nanoparticles with a virucidal inhibition mechanism

Viral infections kill millions yearly. Available antiviral drugs are virus-specific and active against a limited panel of human pathogens. There are broad-spectrum substances that prevent the first step of virus-cell interaction by mimicking heparan sulfate proteoglycans (HSPG), the highly conserved target of viral attachment ligands (VALs). The reversible binding mechanism prevents their use as a drug, because, upon dilution, the inhibition is lost. Known VALs are made of closely packed repeating units, but the aforementioned substances are able to bind only a few of them. We designed antiviral nanoparticles with long and flexible linkers mimicking HSPG, allowing for effective viral association with a binding that we simulate to be strong and multivalent to the VAL repeating units, generating forces (190 pN) that eventually lead to irreversible viral deformation. Virucidal assays, electron microscopy images, and molecular dynamics simulations support the proposed mechanism. These particles show no cytotoxicity, and in vitro nanomolar irreversible activity against herpes simplex virus (HSV), human papilloma virus, respiratory syncytial virus (RSV), dengue and lenti virus. They are active ex vivo in human cervicovaginal histocultures infected by HSV-2 and in vivo in mice infected with RSV

Pore Formation by T3SS Translocators: Liposome Leakage Assay

International audienceGram-negative bacteria utilize a dedicated membrane-embedded apparatus, the type III secretion system (T3SS), to inject proteins into host cells. The passage of the proteins across the target membrane is accomplished by a proteinaceous pore-the translocon-formed within the host-cell cytoplasmic membrane. Translocators bound to their chaperones can be expressed in Escherichia coli and subsequently dissociated from the chaperone by guanidine treatment. The pore formation properties of the translocators can then be studied by an in-vitro liposome leakage assay. Sulforhodamine-B is encapsulated within lipid vesicles during liposome preparation. At high concentration, this fluorochrome exhibits self-quenching limiting fluorescence emission. Upon pore formation, liposome leakage leads to the dilution of Sulforhodamine-B in the medium and fluorescence emission increases. Alternatively, fluorochromes coupled to large dextran molecules can be encapsulated in order to estimate pore dimensions. Here we describe protein expression and purification, dye-liposome preparation, and leakage assay conditions