Physical mechanisms of red blood cell splenic filtration.

The splenic interendothelial slits fulfill the essential function of continuously filtering red blood cells (RBCs) from the bloodstream to eliminate abnormal and aged cells. To date, the process by which 8 [Formula: see text]m RBCs pass through 0.3 [Formula: see text]m-wide slits remains enigmatic. Does the slit caliber increase during RBC passage as sometimes suggested? Here, we elucidated the mechanisms that govern the RBC retention or passage dynamics in slits by combining multiscale modeling, live imaging, and microfluidic experiments on an original device with submicron-wide physiologically calibrated slits. We observed that healthy RBCs pass through 0.28 [Formula: see text]m-wide rigid slits at 37 °C. To achieve this feat, they must meet two requirements. Geometrically, their surface area-to-volume ratio must be compatible with a shape in two tether-connected equal spheres. Mechanically, the cells with a low surface area-to-volume ratio (28% of RBCs in a 0.4 [Formula: see text]m-wide slit) must locally unfold their spectrin cytoskeleton inside the slit. In contrast, activation of the mechanosensitive PIEZO1 channel is not required. The RBC transit time through the slits follows a [Formula: see text]1 and [Formula: see text]3 power law with in-slit pressure drop and slip width, respectively. This law is similar to that of a Newtonian fluid in a two-dimensional Poiseuille flow, showing that the dynamics of RBCs is controlled by their cytoplasmic viscosity. Altogether, our results show that filtration through submicron-wide slits is possible without further slit opening. Furthermore, our approach addresses the critical need for in vitro evaluation of splenic clearance of diseased or engineered RBCs for transfusion and drug delivery.

Mechanical instability and interfacial energy drive biofilm morphogenesis.

Surface-attached bacterial communities called biofilms display a diversity of morphologies. Although structural and regulatory components required for biofilm formation are known, it is not understood how these essential constituents promote biofilm surface morphology. Here, using Vibrio cholerae as our model system, we combine mechanical measurements, theory and simulation, quantitative image analyses, surface energy characterizations, and mutagenesis to show that mechanical instabilities, including wrinkling and delamination, underlie the morphogenesis program of growing biofilms. We also identify interfacial energy as a key driving force for mechanomorphogenesis because it dictates the generation of new and the annihilation of existing interfaces. Finally, we discover feedback between mechanomorphogenesis and biofilm expansion, which shapes the overall biofilm contour. The morphogenesis principles that we discover in bacterial biofilms, which rely on mechanical instabilities and interfacial energies, should be generally applicable to morphogenesis processes in tissues in higher organisms.

Self-organization of red blood cell suspensions under confined 2D flows.

Dynamic self-organized structures with long-range order have been observed in emulsions and suspensions of particles under confined flows. Here, experiments on red blood cell suspensions under quasi-2D confined flows and numerical simulations were combined to explore long-distance self-organization as a function of the channel width, red blood cell concentration and flow rate. They reveal and quantitatively describe the existence of red blood cell long-range alignments and heterogeneous cross-stream concentration profiles characterized by red blood cell-enriched bands parallel to the flow. Numerical simulations show that, in addition to the degree of lateral confinement, the key factor for the structural self-organization of a suspension of particles under a confined flow is the deformability of the constituent particles.

Bacterial Biofilm Material Properties Enable Removal and Transfer by Capillary Peeling.

Biofilms, surface-attached communities of bacterial cells, are a concern in health and in industrial operations because of persistent infections, clogging of flows, and surface fouling. Extracellular matrices provide mechanical protection to biofilm-dwelling cells as well as protection from chemical insults, including antibiotics. Understanding how biofilm material properties arise from constituent matrix components and how these properties change in different environments is crucial for designing biofilm removal strategies. Here, using rheological characterization and surface analyses of Vibrio cholerae biofilms, it is discovered how extracellular polysaccharides, proteins, and cells function together to define biofilm mechanical and interfacial properties. Using insight gained from our measurements, a facile capillary peeling technology is developed to remove biofilms from surfaces or to transfer intact biofilms from one surface to another. It is shown that the findings are applicable to other biofilm-forming bacterial species and to multiple surfaces. Thus, the technology and the understanding that have been developed could potentially be employed to characterize and/or treat biofilm-related infections and industrial biofouling problems.

Targeted Delivery of Toxoplasma gondii Antigens to Dendritic Cells Promote Immunogenicity and Protective Efficiency against Toxoplasmosis.

Toxoplasmosis is a major public health problem and the development of a human vaccine is of high priority. Efficient vaccination against Toxoplasma gondii requires both a mucosal and systemic Th1 immune response. Moreover, dendritic cells play a critical role in orchestrating the innate immune functions and driving specific adaptive immunity to T. gondii. In this study, we explore an original vaccination strategy that combines administration via mucosal and systemic routes of fusion proteins able to target the major T. gondii surface antigen SAG1 to DCs using an antibody fragment single-chain fragment variable (scFv) directed against DEC205 endocytic receptor. Our results show that SAG1 targeting to DCs by scFv via intranasal and subcutaneous administration improved protection against chronic T. gondii infection. A marked reduction in brain parasite burden is observed when compared with the intranasal or the subcutaneous route alone. DC targeting improved both local and systemic humoral and cellular immune responses and potentiated more specifically the Th1 response profile by more efficient production of IFN-γ, interleukin-2, IgG2a, and nasal IgA. This study provides evidence of the potential of DC targeting for the development of new vaccines against a range of Apicomplexa parasites.

European College of Orthodontics: Commission of affiliation and titularisation.

Date of birth: 2/8/1982; sex: male. A. PRETREATMENT RECORDS: 25 years; 7/3/2008. DIAGNOSIS: Very severe Class III malocclusion in adult dentition in hyperdivergent facial pattern; Sagittal dimension: skeletal and dental Class II, severe alveolar retrusion of the mandibular incisors, negative overjet (-11mm); transverse dimension: Class III-related bilateral crossbite with no transverse maxillary deficiency; vertical dimension: incisor overbite, increased height of the lower facial third; Teeth missing prior to treatment: 16-26. TREATMENT PLAN: Appliances or procedures: multi-bracket bi-maxillary appliance and maxillofacial surgery; arch decompensation; maxillofacial surgery; fixed retainers; beginning of treatment: 26 years; 10/01/2009. B. POSTTREATMENT RECORDS: 17/2/2011; 28 years. DURATION OF ACTIVE TREATMENT: 25 months. RETENTION: Maxillary: 17/2/2011; mandibular: 17/2/2011. C. POST-RETENTION RECORDS: (1 year minimum): 25/04/2016; 33 years; duration of retention: lifelong. Post-retention duration: 5years and 2months.

[A particular temporomandibular disorder: the temporomandibular joint ankylosis. Basic and clinical concepts]. / Un trouble temporo-mandibulaire particulier : l'ankylose. Notions fondamentales et cliniques.

Ankylosis of the temporomandibular joint mostly affects children and young adults. Although it is rare, it is an extremely debilitating disease whose effects on growth, morphological development and personal development are significant. To manage this disorder, it is essential to be informed about the causes, about the anatomical shapes it presents and about its symptoms. This knowledge will also help us choose the most appropriate therapy, that may nevertheless result in failures and in relapses requiring prosthetic rehabilitation.

[SIBSytem: innovation for bracket bonding?]. / SIBSystem : une innovation dans le domaine du collage des attaches orthodontiques?

The orthodontic bracket placement has known two major improvements these last fifty years: first with the ability of bonding brackets directly on the enamel (Newmann 1965); second with the indirect bonding procedure introduced by Silvermann and Cohen in 1972. If we put aside the technological evolutions of bonding materials (brackets and adhesives), few refinements have occurred regarding the protocols in this period of time. Furthermore, direct bonding procedure seems to be used by a majority of orthodontists despite the rapidity, accuracy and ergonomics promised by indirect bonding protocol. The main originality of the system detailed in this article is to bond orthodontic brackets in a virtually predetermined position with indirect bonding advantages but with the efficiency of direct bonding because the adhesive is applied directly on the bracket base without pre-bonding necessity. This innovation has been allowed by the use of up-to-date CFAO technology. The article first describes the two components of the SIBSystem (SIBClip and SIBTray) and details the manufacturing stages. The clinical use is then evoked as well as the cautions and limits of this innovative bonding system.

[Upper central incisors and asymmetry: a significant orthodontic challenge]. / Incisives centrales maxillaires et symétrie : un enjeu orthodontique majeur.

In any assessment of the esthetic characteristics of a smile the central incisors play a decisive role. Moreover, correction of their malpositions and, especially, their asymmetry, is one of the principal reasons patients consult orthodontists. The etiology of this asymmetry may be vertical, with one incisor more erupted than its mate or horizontal, with a mid-line discrepancy, and can be objectified by a clinical examination and supplementary studies, especially radiological as a means of helping orthodontists adopt the most appropriate treatment plan. In accordance with the etiopathogenesis of the malocclusion, alveolo-dental trauma, skeletal asymmetry, or asymmetry of arches, the orthodontic treatment may be undertaken on three levels, with the teeth themselves by extrusion, intrusion, or rotation; regionally with the arches by retraction of teeth en masse; or globally at the skeletal level with maxillo-facial surgery. The complexity of some treatment in relation to the coordination of different levels of therapeutic action is intensified by the occasional necessity of obtaining collaboration of other specialists like general dentists, periodontists, and maxillo-facial surgeons. In such cases the initial treatment plan takes on increased importance, as does the choice of collaborating colleagues. However, once successfully completed these complicated treatments become a source of great satisfaction both for practitioners and for patients because of the enormous improvement that has been obtained.

[Supraclusion origins]. / La genèse de la supraclusion.

Orthodontists often observe the clinical sign of supraclusion, or deep overbite, in their patients, a condition that is difficult to correct and that relapses frequently. In order to treat it with the most appropriate therapy, orthodontists should have a precise understanding of its etiology, which can be skeletal, neuromuscular, or dental and may often result from an intricate web of factors. In preparing their diagnoses, orthodontists should examine the possible mechanisms of its installation and evaluate them in an architectural cephalometric analysis of the oral prehensile complex.

[Diagnosis and treatment of temporo-mandibular disorders in orthodontics]. / Détection et thérapeutique des troubles temporo-mandibulaires en orthodontie.

Orthodontists are fully prepared to treat the problems of occlusion that they are called upon to deal with every day. On the other hand temporo-mandibular joint disorders present more obscure difficulties from the point of view of detection and diagnosis as well the management of their treatment. That is why a profound understanding of the anatomical and physiological functioning of the temporo-mandibular joint has become indispensable for today's orthodontists who are now asked to detect and diagnose an assortment of TMJ disturbances whose etiology may vary greatly. By performing a rigorous diagnostic procedure, based on a thorough clinical examination supported by careful axiographic and radiological studies, of temporo-mandibular malfunctioning and its underlying etiological causes, which are primarily dento-alveolar and occlusal in nature, orthodontists will be able to adopt an appropriate therapeutic approach that might be purely orthodontic or multi-disciplinary and carried out with the collaboration of specialists in occlusion, oral surgery, and even osteopathy.

[Does dysfunctional swallowing influence posture?]. / La déglutition dysfonctionnelle a-t-elle une influence sur la posture ?

Swallowing is one of the first functions to be set up in utero for vital reasons. Physiological and psychic maturation then occur to lead from a dysfunctional to a functional state. Nevertheless, for certain individuals, maturation is incomplete, and swallowing remains dysfunctional. The clinical literature has already proven the incidence of a dental change of occlusion and the consequences of a lingual dysfunction upon posture. This work proposes to show that the posture can be affected by dysfunctional deglutition because of the lack of dental contacts during this function and because of the lingual dysfunction which characterizes it. We studied a population of 20 young adults, divided into two groups: a group of subjects presenting with a functional swallowing, and a group of subjects presenting with a dysfunctional swallowing. The experimental protocol includes four conditions: mandibular rest, cognitive task of articulation, functional swallowing, dysfunctional swallowing. Their effect on the posture is evaluated by means of a standardized stabilometric platform, and is supplemented by an electromyographic study of a manducator muscle (the masseter) and of a muscle of the cephalic posture (the sternocleidomastoid). The results show that swallowing would have the same postural effects as the cognitive task by increasing the postural oscillations and the energy spent by the postural system. Furthermore, the deglutition would have increased effects when it corresponds to a forced deglutition for the subject.