Ecouter et dire en médecine, une approche psycho-sociale : utiliser la simulation pour former les futurs médecins à la relation thérapeutique

Les « simulations relationnelles » sont assurées par un docteur en psychologie sociale et un médecin ; menées dans un cabinet de médecine générale spécialement recréé pour les étudiants médecins. Les séquences avec patients simulés sont regardées en direct, débriefées et ré visionnées. La formation est réalisée sur quatre promotions de 180 futurs médecins répartis en groupes (9 à 14 étudiants) de 4e ou 5e année. L’objectif est de produire une analyse réflexive et rétrospective sur l’activité du médecin généraliste tout en protégeant les apprenants. La formation exposée ici est réalisée pour quatre promotions de 180 futurs médecins répartis en groupes (9 à 14 étudiants) de 4ème ou 5ème année. L’objectif est, tout en protégeant les apprenants, de susciter une analyse réflexive et rétrospective de l’activité du médecin (avec la production d’une synthèse collective écrite sur les situations abordées).In Switzerland, men predominate in higher education science courses. However, biology courses are attended primarily by women. The little success of affirmative actions targeting girls and women in science invites us to re-examine the way these subjects are taught in Geneva primary school. We will show that only biology seems to occupy a proper place in the real curriculum. Put science back in the general knowledge could be a way to attract women in science

Integrity of H1 helix in prion protein revealed by molecular dynamic simulations to be especially vulnerable to changes in the relative orientation of H1 and its S1 flank

In the template-assistance model, normal prion protein (PrPC), the pathogenic cause of prion diseases such as Creutzfeldt-Jakob (CJD) in human, Bovine Spongiform Encephalopathy (BSE) in cow, and scrapie in sheep, converts to infectious prion (PrPSc) through an autocatalytic process triggered by a transient interaction between PrPC and PrPSc. Conventional studies suggest the S1-H1-S2 region in PrPC to be the template of S1-S2 $\beta$-sheet in PrPSc, and the conformational conversion of PrPC into PrPSc may involve an unfolding of H1 in PrPC and its refolding into the $\beta$-sheet in PrPSc. Here we conduct a series of simulation experiments to test the idea of transient interaction of the template-assistance model. We find that the integrity of H1 in PrPC is vulnerable to a transient interaction that alters the native dihedral angles at residue Asn$^{143}$, which connects the S1 flank to H1, but not to interactions that alter the internal structure of the S1 flank, nor to those that alter the relative orientation between H1 and the S2 flank.Comment: A major revision on statistical analysis method has been made. The paper now has 23 pages, 11 figures. This work was presented at 2006 APS March meeting session K29.0004 at Baltimore, MD, USA 3/13-17, 2006. This paper has been accepted for pubcliation in European Biophysical Journal on Feb 2, 200

Dynamic Diagnosis of Familial Prion Diseases Supports the β2-α2 Loop as a Universal Interference Target

[Background] Mutations in the cellular prion protein associated to familial prion disorders severely increase the likelihood of its misfolding into pathogenic conformers. Despite their postulation as incompatible elements with the native fold, these mutations rarely modify the native state structure. However they variably have impact on the thermodynamic stability and metabolism of PrPC and on the properties of PrPSc aggregates. To investigate whether the pathogenic mutations affect the dynamic properties of the HuPrP(125-229) α-fold and find possible common patterns of effects that could help in prophylaxis we performed a dynamic diagnosis of ten point substitutions.[Methodology/Principal Findings] Using all-atom molecular dynamics simulations and novel analytical tools we have explored the effect of D178N, V180I, T183A, T188K, E196K, F198S, E200K, R208H, V210I and E211Q mutations on the dynamics of HuPrP(125-228) α-fold. We have found that while preserving the native state, all mutations produce dynamic changes which perturb the coordination of the α2-α3 hairpin to the rest of the molecule and cause the reorganization of the patches for intermolecular recognition, as the disappearance of those for conversion inhibitors and the emergence of an interaction site at the β2-α2 loop region.[Conclusions/Significance] Our results suggest that pathogenic mutations share a common pattern of dynamical alterations that converge to the conversion of the β2-α2 loop into an interacting region that can be used as target for interference treatments in genetic diseases.This work was supported in parts by grants BFU2009-07971 from the MICINN (MG), FundaciÃ3n Cien (MG); Fondazione Cariplo (GC) and AIRC (GC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. No additional external funding received for this study.Peer reviewe

Scratching the surface : bacterial cell envelopes at the nanoscale

The bacterial cell envelope is essential for viability, the environmental gatekeeper and first line of defense against external stresses. For most bacteria, the envelope biosynthesis is also the site of action of some of the most important groups of antibiotics. It is a complex, often multicomponent structure, able to withstand the internally generated turgor pressure. Thus, elucidating the architecture and dynamics of the cell envelope is important, to unravel not only the complexities of cell morphology and maintenance of integrity but also how interventions such as antibiotics lead to death. To address these questions requires the capacity to visualize the cell envelope in situ via high-spatial resolution approaches. In recent years, atomic force microscopy (AFM) has brought novel molecular insights into the assembly, dynamics, and functions of bacterial cell envelopes. The ultrafine resolution and physical sensitivity of the technique have revealed a wealth of ultrastructural features that are invisible to traditional optical microscopy techniques or imperceptible in their true physiological state by electron microscopy. Here, we discuss recent progress in our use of AFM imaging for understanding the architecture and dynamics of the bacterial envelope. We survey recent studies that demonstrate the power of the technique to observe isolated membranes and live cells at (sub)nanometer resolution and under physiological conditions and to track in vitro structural dynamics in response to growth or to drugs

Monitoring Alzheimer Amyloid Peptide Aggregation by EPR

Plaques containing the aggregated β-Amyloid (Aβ) peptide in the brain are the main indicators of Alzheimer’s disease. Fibrils, the building blocks of plaques, can also be produced in vitro and consist of a regular arrangement of the peptide. The initial steps of fibril formation are not well understood and could involve smaller aggregates (oligomers) of Aβ. Such oligomers have even been implicated as the toxic agents. Here, a method to study oligomers on the time scale of aggregation is suggested. We have labeled the 40 residue Aβ peptide variant containing an N-terminal cysteine (cys-Aβ) with the MTSL [1-oxyl-2,2,5,5-tetramethyl-Δ-pyrroline-3-methyl] methanethiosulfonate spin label (SL-Aβ). Fibril formation in solutions of pure SL-Aβ and of SL-Aβ mixed with Aβ was shown by Congo-red binding and electron microscopy. Continuous-wave 9 GHz electron paramagnetic resonance reveals three fractions of different spin-label mobility: one attributed to monomeric Aβ, one to a multimer (8–15 monomers), and the last one to larger aggregates or fibrils. The approach, in principle, allows detection of oligomers on the time scale of aggregation

Methionine Sulfoxides on Prion Protein Helix-3 Switch on the α-Fold Destabilization Required for Conversion

BACKGROUND: The conversion of the cellular prion protein (PrP(C)) into the infectious form (PrP(Sc)) is the key event in prion induced neurodegenerations. This process is believed to involve a multi-step conformational transition from an alpha-helical (PrP(C)) form to a beta-sheet-rich (PrP(Sc)) state. In addition to the conformational difference, PrP(Sc) exhibits as covalent signature the sulfoxidation of M213. To investigate whether such modification may play a role in the misfolding process we have studied the impact of methionine oxidation on the dynamics and energetics of the HuPrP(125-229) alpha-fold. METHODOLOGY/PRINCIPAL FINDINGS: Using molecular dynamics simulation, essential dynamics, correlated motions and signal propagation analysis, we have found that substitution of the sulfur atom of M213 by a sulfoxide group impacts on the stability of the native state increasing the flexibility of regions preceding the site of the modification and perturbing the network of stabilizing interactions. Together, these changes favor the population of alternative states which maybe essential in the productive pathway of the pathogenic conversion. These changes are also observed when the sulfoxidation is placed at M206 and at both, M206 and M213. CONCLUSIONS/SIGNIFICANCE: Our results suggest that the sulfoxidation of Helix-3 methionines might be the switch for triggering the initial alpha-fold destabilization required for the productive pathogenic conversion

Synthetic prions with novel strain-specified properties

Prions are infectious proteins that possess multiple self-propagating structures. The information for strains and structural specific barriers appears to be contained exclusively in the folding of the pathological isoform, PrP(Sc). Many recent studies determined that de novo prion strains could be generated in vitro from the structural conversion of recombinant (rec) prion protein (PrP) into amyloidal structures. Our aim was to elucidate the conformational diversity of pathological recPrP amyloids and their biological activities, as well as to gain novel insights in characterizing molecular events involved in mammalian prion conversion and propagation. To this end we generated infectious materials that possess different conformational structures. Our methodology for the prion conversion of recPrP required only purified rec full-length mouse (Mo) PrP and common chemicals. Neither infected brain extracts nor amplified PrP(Sc) were used. Following two different in vitro protocols recMoPrP converted to amyloid fibrils without any seeding factor. Mouse hypothalamic GT1 and neuroblastoma N2a cell lines were infected with these amyloid preparations as fast screening methodology to characterize the infectious materials. Remarkably, a large number of amyloid preparations were able to induce the conformational change of endogenous PrPC to harbor several distinctive proteinase-resistant PrP forms. One such preparation was characterized in vivo habouring a synthetic prion with novel strain specified neuropathological and biochemical properties

The Physical Relationship between Infectivity and Prion Protein Aggregates Is Strain-Dependent

Prions are unconventional infectious agents thought to be primarily composed of PrPSc, a multimeric misfolded conformer of the ubiquitously expressed host-encoded prion protein (PrPC). They cause fatal neurodegenerative diseases in both animals and humans. The disease phenotype is not uniform within species, and stable, self-propagating variations in PrPSc conformation could encode this ‘strain’ diversity. However, much remains to be learned about the physical relationship between the infectious agent and PrPSc aggregation state, and how this varies according to the strain. We applied a sedimentation velocity technique to a panel of natural, biologically cloned strains obtained by propagation of classical and atypical sheep scrapie and BSE infectious sources in transgenic mice expressing ovine PrP. Detergent-solubilized, infected brain homogenates were used as starting material. Solubilization conditions were optimized to separate PrPSc aggregates from PrPC. The distribution of PrPSc and infectivity in the gradient was determined by immunoblotting and mouse bioassay, respectively. As a general feature, a major proteinase K-resistant PrPSc peak was observed in the middle part of the gradient. This population approximately corresponds to multimers of 12–30 PrP molecules, if constituted of PrP only. For two strains, infectivity peaked in a markedly different region of the gradient. This most infectious component sedimented very slowly, suggesting small size oligomers and/or low density PrPSc aggregates. Extending this study to hamster prions passaged in hamster PrP transgenic mice revealed that the highly infectious, slowly sedimenting particles could be a feature of strains able to induce a rapidly lethal disease. Our findings suggest that prion infectious particles are subjected to marked strain-dependent variations, which in turn could influence the strain biological phenotype, in particular the replication dynamics