Faire accepter les lieux de réduction des risques : un enjeu quotidien

Les professionnels de la Réduction des risques, qui accueillent et accompagnent les usagers de drogues, connaissent des difficultés à faire reconnaitre et accepter leur mission de Santé publique. Que ce soit par peur de la différence, des états de conscience modifiés, pour des raisons morales ou au regard de la loi, les riverains des dispositifs de RdR mettent en question la présence des usagers à leurs côtés. Pour leur répondre, la médiation sociale est inscrite au coeur des missions des Centres d'accueil et d'accompagnement à la réduction des risques des usagers de drogues (CAARUD), principal levier pour permettre l'acceptabilité des dispositifs. Quelles sont les formes données à la médiation mise en oeuvre par les professionnels de la RdR? Cette étude financée par la Direction générale de la santé (DGS) répond à cette question. Elle propose ainsi un état des lieux bibliographique des études, guides et observations faites autour de cette question, complété par le recueil détaillé des pratiques professionnelles dans un certain nombre de dispositifs de RdR. Enfin, une troisième et dernière partie reprend, sous forme de recommandations, les principaux enjeux liés à la mise en place d'un nouveau lieu d'accueil. Sont ici identifiées les étapes nécessaires à la mise en lien entre les dispositifs de RdR et leurs partenaires, qu'ils soient institutionnels (Agences régionales de santé, municipalités, communautés de communes, forces de l'ordre, services sociaux...) ou privés (bailleurs, commerçants, voisins...). Ce sont autant d'interlocuteurs de la médiation sociale, ressources pour permettre aux porteurs de projets de concevoir une démarche concertée d'implantation

Regulatory Role of Cell Division Rules on Tissue Growth Heterogeneity

The coordination of cell division and cell expansion are critical to normal development of tissues. In plants, cell wall mechanics and the there from arising cell shapes and mechanical stresses can regulate cell division and cell expansion and thereby tissue growth and morphology. Limited by experimental accessibility it remains unknown how cell division and expansion cooperatively affect tissue growth dynamics. Employing a cell-based two dimensional tissue simulation we investigate the regulatory role of a range of cell division rules on tissue growth dynamics and in particular on the spatial heterogeneity of growth. We find that random cell divisions only add noise to the growth and therefore increase growth heterogeneity, while cell divisions following the shortest new wall or along the direction of maximal mechanical stress reduce growth heterogeneity by actively enhancing the regulation of growth by mechanical stresses. Thus, we find that, beyond tissue geometry and topology, cell divisions affect the dynamics of growth, and that their signature is embedded in the statistics of tissue growth.Engineering and Applied Science

Comparison of Autografts vs. Allografts in the Surgical Repair of Pediatric Obstetrical Brachial Plexus Injuries

A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine.Obstetrical Brachial Plexus Injuries(OBPI) occur during delivery with a global incidence ranging from 0.2- 4% of live births, and generally, prognosis is excellent with spontaneous recovery in up to 95% of patients. For patients with OBPI that do not obtain a functional recovery by 4-6 months of life, treatment is primarily surgical in nature. Surgical treatment involves testing of the nerves to determine whether they remain connected distally and proximaly, removal of scar tissue/ neurolysis, and then bridging the nerve discontinuity or block with a nerve graft. Nerve grafting provide a three-dimensional extracellular matrix that promotes Schwann cell migration and axon regeneration. Historically, nerve graft was autograft using sural nerve. More recently, a decellularized processed cadaveric nerve allograft (Axogen) has been utilized in numerous peripheral nerve injury repairs, mostly in adults, but has not been reportedly used in pediatric OBPI. The aim of this study is to determine if using nerve allografts (Axogen) will have similar functional outcomes as compared to sural nerve autografts in reconstruction of the brachial plexus after OBPI.This item is part of the College of Medicine - Phoenix Scholarly Projects 2019 collection. For more information, contact the Phoenix Biomedical Campus Library at [email protected]

The self-organization of plant microtubules inside the cell volume yields their cortical localization, stable alignment, and sensitivity to external cues.

Many cell functions rely on the ability of microtubules to self-organize as complex networks. In plants, cortical microtubules are essential to determine cell shape as they guide the deposition of cellulose microfibrils, and thus control mechanical anisotropy of the cell wall. Here we analyze how, in turn, cell shape may influence microtubule behavior. Building upon previous models that confined microtubules to the cell surface, we introduce an agent model of microtubules enclosed in a three-dimensional volume. We show that the microtubule network has spontaneous aligned configurations that could explain many experimental observations without resorting to specific regulation. In particular, we find that the preferred cortical localization of microtubules emerges from directional persistence of the microtubules, and their interactions with each other and with the stiff wall. We also identify microtubule parameters that seem relatively insensitive to cell shape, such as length or number. In contrast, microtubule array anisotropy depends on local curvature of the cell surface and global orientation follows robustly the longest axis of the cell. Lastly, we find that geometric cues may be overcome, as the network is capable of reorienting toward weak external directional cues. Altogether our simulations show that the microtubule network is a good transducer of weak external polarity, while at the same time, easily reaching stable global configurations

An epidermis-driven mechanism positions and scales stem cell niches in plants.

How molecular patterning scales to organ size is highly debated in developmental biology. We explore this question for the characteristic gene expression domains of the plant stem cell niche residing in the shoot apical meristem. We show that a combination of signals originating from the epidermal cell layer can correctly pattern the key gene expression domains and notably leads to adaptive scaling of these domains to the size of the tissue. Using live imaging, we experimentally confirm this prediction. The identified mechanism is also sufficient to explain de novo stem cell niches in emerging flowers. Our findings suggest that the deformation of the tissue transposes meristem geometry into an instructive scaling and positional input for the apical plant stem cell niche.This work was funded by grants from the Gatsby Charitable Foundation (GAT3395/PR4) and the Swedish Research Council (VR2013-4632) to HJ; and by Gatsby Charitable Foundation grants GAT3272/C and GAT3273-PR1, the US National Institutes of Health (R01 GM104244), the Howard Hughes Medical Institute, and the Gordon and Betty Moore Foundation (GBMF3406) to EMM).This is the final version of the article. It first appeared from the American Association for the Advancement of Science via http://dx.doi.org/10.1126/sciadv.150098

Alignment between PIN1 Polarity and Microtubule Orientation in the Shoot Apical Meristem Reveals a Tight Coupling between Morphogenesis and Auxin Transport

Morphogenesis during multicellular development is regulated by intercellular signaling molecules as well as by the mechanical properties of individual cells. In particular, normal patterns of organogenesis in plants require coordination between growth direction and growth magnitude. How this is achieved remains unclear. Here we show that in Arabidopsis thaliana, auxin patterning and cellular growth are linked through a correlated pattern of auxin efflux carrier localization and cortical microtubule orientation. Our experiments reveal that both PIN1 localization and microtubule array orientation are likely to respond to a shared upstream regulator that appears to be biomechanical in nature. Lastly, through mathematical modeling we show that such a biophysical coupling could mediate the feedback loop between auxin and its transport that underlies plant phyllotaxis

Mechanical Stress Inference for Two Dimensional Cell Arrays

Many morphogenetic processes involve mechanical rearrangement of epithelial tissues that is driven by precisely regulated cytoskeletal forces and cell adhesion. The mechanical state of the cell and intercellular adhesion are not only the targets of regulation, but are themselves likely signals that coordinate developmental process. Yet, because it is difficult to directly measure mechanical stress {\it in vivo} on sub-cellular scale, little is understood about the role of mechanics of development. Here we present an alternative approach which takes advantage of the recent progress in live imaging of morphogenetic processes and uses computational analysis of high resolution images of epithelial tissues to infer relative magnitude of forces acting within and between cells. We model intracellular stress in terms of bulk pressure and interfacial tension, allowing these parameters to vary from cell to cell and from interface to interface. Assuming that epithelial cell layers are close to mechanical equilibrium, we use the observed geometry of the two dimensional cell array to infer interfacial tensions and intracellular pressures. Here we present the mathematical formulation of the proposed Mechanical Inverse method and apply it to the analysis of epithelial cell layers observed at the onset of ventral furrow formation in the {\it Drosophila} embryo and in the process of hair-cell determination in the avian cochlea. The analysis reveals mechanical anisotropy in the former process and mechanical heterogeneity, correlated with cell differentiation, in the latter process. The method opens a way for quantitative and detailed experimental tests of models of cell and tissue mechanics

Quantitative predictions on auxin-induced polar distribution of PIN proteins during vein formation in leaves

The dynamic patterning of the plant hormone auxin and its efflux facilitator the PIN protein are the key regulator for the spatial and temporal organization of plant development. In particular auxin induces the polar localization of its own efflux facilitator. Due to this positive feedback auxin flow is directed and patterns of auxin and PIN arise. During the earliest stage of vein initiation in leaves auxin accumulates in a single cell in a rim of epidermal cells from which it flows into the ground meristem tissue of the leaf blade. There the localized auxin supply yields the successive polarization of PIN distribution along a strand of cells. We model the auxin and PIN dynamics within cells with a minimal canalization model. Solving the model analytically we uncover an excitable polarization front that triggers a polar distribution of PIN proteins in cells. As polarization fronts may extend to opposing directions from their initiation site we suggest a possible resolution to the puzzling occurrence of bipolar cells, such we offer an explanation for the development of closed, looped veins. Employing non-linear analysis we identify the role of the contributing microscopic processes during polarization. Furthermore, we deduce quantitative predictions on polarization fronts establishing a route to determine the up to now largely unknown kinetic rates of auxin and PIN dynamics.Comment: 9 pages, 4 figures, supplemental information included, accepted for publication in Eur. Phys. J.

The zinc finger protein PtaZFP2 negatively controls stem growth and gene expression responsiveness to external mechanical loads in poplar

Mechanical cues are essential signals regulating plant growth and development. In response to wind, trees develop a thigmomorphogenetic response characterized by a reduction in longitudinal growth, an increase in diameter growth, and changes in mechanical properties. The molecular mechanisms behind these processes are poorly understood. In poplar, PtaZFP2, a C2H2 transcription factor, is rapidly up-regulated after stem bending. To investigate the function of PtaZFP2, we analyzed PtaZFP2-overexpressing poplars (Populus tremula 9 Populus alba). To unravel the genes downstream PtaZFP2, a transcriptomic analysis was performed. PtaZFP2-overexpressing poplars showed longitudinal and cambial growth reductions together with an increase in the tangent and hardening plastic moduli. The regulation level of mechanoresponsive genes was much weaker after stem bending in PtaZFP2-overexpressing poplars than in wild-type plants, showing that PtaZFP2 negatively modulates plant responsiveness to mechanical stimulation. Microarray analysis revealed a high proportion of down-regulated genes in PtaZFP2-overexpressing poplars. Among these genes, several were also shown to be regulated by mechanical stimulation. Our results confirmed the important role of PtaZFP2 during plant acclimation to mechanical load, in particular through a negative control of plant molecular responsiveness. This desensitization process could modulate the amplitude and duration of the plant response during recurrent stimuli

Photoprotection practices, knowledge and sun-related skin damage in Spanish beach handball players

Background. Outdoor sports are a risk activity for skin cancer, especially if adequate sun protection measures are not used. The aim of this study is to examine the photoprotection habits of outdoor (beach) handball players, and to determine the relation between duration of sports practice, photoprotection behaviour and sunrelated damage to the skin. Methods. This cross-sectional study is based on a health survey of sun exposure and protection habits and practices conducted among beach handball players in southern Spain. This survey provided data for a descriptive and comparative analysis, by groups and gender, of photoprotection and skin self-examination practices. Results. Among the whole sample, 76.9% had suffered at least one sunburn event during the last year. By groups, 73.97% of the older participants (Group I, University students) and 81.25% of the younger ones (Group II, youngers players) reported this outcome, and the difference was statistically significant (p D 0:003). With respect to photoprotection, 68.5% of the players in group I and 66.7% of those in group II used sun cream with a protection factor of 30 or higher, although 52.1% of group I and 35.4% of group II did not reapply it. As concerns self-examination, 94.5% of group I and 87.5% of group II had not examined their body for skin damage during the previous year. Medical examination revealed the presence of lentigines and freckles among many players, with no significant differences between the two groups. Conclusions. Beach handball players are highly exposed to the effects of ultraviolet radiation and often take insufficient measures of sun protection. Programmes should be designed and implemented to raise awareness among adolescent and young adult sport competitors of the risks of skin cancer associated with their sports activity and to encourage them to improve their photoprotection and skin monitoring practices