Création d'un espace documentaire grand public au Muséum d'histoire naturelle de Genève

Ce travail a été réalisé dans le cadre d’un mandat pour le Service d'information documentaire spécialisé (SIDoS) du Muséum d’histoire naturelle de Genève. Celui-ci souhaite créer un nouvel espace documentaire qui soit dédié spécifiquement au grand public et qui propose des documents de vulgarisation sur les sujets du Muséum. Il vise à la réalisation d’un espace de type troisième lieu qui intègre des ressources originales. Le présent document expose en premier lieu le concept de troisième lieu et de son application au monde des bibliothèques. Il définit également le public du futur espace documentaire. Il présente ensuite un état de l’art du SIDoS, ainsi que des institutions similaires, d’après la littérature spécialisée et grâce aux réponses de questionnaires, afin d’établir une tendance des pratiques en bibliothèques de musées d’histoire naturelle. Il liste également les besoins et les attentes des différentes parties prenantes du projet d’espace documentaire, notamment par la synthèse d’entretiens. Enfin, ce travail émet une proposition détaillée d’espace documentaire grand public au Muséum d’histoire naturelle de Genève, intégrant des concepts originaux et répondant aux besoins de chacun, le tout dans un esprit de bibliothèque troisième lieu. La proposition englobe le type de services et de ressources à mettre en place à l’espace documentaire, mais expose également les aspects de mise en espace et d’esthétisme visant à proposer une solution la plus complète possible et pouvant être mise en place rapidement

Microscopic structural study of collagen aging in isolated fibrils using polarized second harmonic generation

International audiencePolarization resolved second harmonic generation (PSHG) is developed to study, at the microscopic scale, the impact of aging on the structure of type I collagen fibrils in two-dimensional coatings. A ribose-glycated collagen is also used to mimic tissue glycation usually described as an indicator of aging. PSHG images are analyzed using a generic approach of the molecular disorder information in collagen fibrils, revealing significant changes upon aging, with a direct correlation between molecular disorder and fibril diameters

3D collagen type I matrix inhibits the antimigratory effect of doxorubicin

<p>Abstract</p> <p>Background</p> <p>The cell microenvironment, especially extracellular matrix proteins, plays an important role in tumor cell response to chemotherapeutic drugs. The present study was designed to investigate whether this microenvironment can influence the antimigratory effect of an anthracycline drug, doxorubicin, when tumor cells are grown in a matrix of type I collagen, a three-dimensional (3D) context which simulates a natural microenvironment.</p> <p>Methods</p> <p>To this purpose, we studied the migratory parameters, the integrin expression, and the activation state of focal adhesion kinase (FAK) and GTPase RhoA involved in the formation of focal adhesions and cell movement. These parameters were evaluated at non toxic concentrations which did not affect HT1080 cell proliferation.</p> <p>Results</p> <p>We show that while doxorubicin decreased cell migration properties by 70% in conventional two-dimensional (2D) culture, this effect was completely abolished in a 3D one. Regarding the impact of doxorubicin on the focal adhesion complexes, unlike in 2D systems, the data indicated that the drug neither affected β1 integrin expression nor the state of phosphorylation of FAK and RhoA.</p> <p>Conclusion</p> <p>This study suggests the lack of antiinvasive effect of doxorubicin in a 3D environment which is generally considered to better mimic the phenotypic behaviour of cells <it>in vivo</it>. Consistent with the previously shown resistance to the cytotoxic effect in a 3D context, our results highlight the importance of the matrix configuration on the tumor cell response to antiinvasive drugs.</p

BMC Biology BMC Biology The toxoplasma-host cell junction is anchored to the cell cortex to sustain parasite invasive force

International audienceBackgroundThe public health threats imposed by toxoplasmosis worldwide and by malaria in sub-Saharan countries are directly associated with the capacity of their closely related causative agents Toxoplasma and Plasmodium, respectively to colonize and expand inside host cells. Therefore, deciphering how these two Apicomplexan protozoan parasites access their hosting cells has been highlighted as a high priority research with the relevant perspective of designing anti-invasive molecules to prevent diseases. Central to the mechanistic base of invasion for both genera is mechanical force, which is thought to be applied by the parasite at the interface between the two cells following assembly of a unique cell junction but this model lacks direct evidence and has been challenged by recent genetic and cell biology studies. In this work, using parasites expressing the fluorescent core component of this junction, we analyse characteristic features of the kinematics of penetration of more than 1000 invasion events.ResultsThe majority of invasion events occur with a typical forward rotational progression of the parasite through a static junction into a vacuole formed from the invaginating host cell plasma membrane, in which the parasite subsequently replicates. However, if parasites encounter resistance and if the junction is not strongly anchored to the host cell cortex, as when parasites do not secrete the toxofilin protein and therefore are unable to locally remodel the cortical actin cytoskeleton, the junction is capped backwards and travels retrogradely with the host cell membrane along the parasite surface as it is enclosed within a functional vacuole. Kinetic measurements of the invasive trajectories strongly support a similar parasite driven force in both static and capped junctions, both of which lead to successful invasion. However about 20% of toxofilin mutants fail to enter and eventually disengage from the host cell membrane while the secreted RON2 molecules are capped at the posterior pole before being cleaved and released in the medium. By contrast in cells characterized by low cortex tension and high cortical actin dynamics, junction capping and entry failure are drastically reduced.ConclusionThis kinematic analysis of pre-invasive and invasive T. gondii tachyzoite behaviors newly highlights that to invade cells, parasites need to engage their motor with the junction molecular complex where force is efficiently applied only upon proper anchorage to the host cell membrane and cortex

Using Bacterial Artificial Chromosomes in Leukemia Research: The Experience at the University Cytogenetics Laboratory in Brest, France

The development of the bacterial artificial chromosome (BAC) system was driven in part by the human genome project in order to construct genomic DNA libraries and physical maps for genomic sequencing. The availability of BAC clones has become a valuable tool for identifying cancer genes. We report here our experience in identifying genes located at breakpoints of chromosomal rearrangements and in defining the size and boundaries of deletions in hematological diseases. The methodology used in our laboratory consists of a three-step approach using conventional cytogenetics followed by FISH with commercial probes, then BAC clones. One limitation to the BAC system is that it can only accommodate inserts of up to 300 kb. As a consequence, analyzing the extent of deletions requires a large amount of material. Array comparative genomic hybridization (array-CGH) using a BAC/PAC system can be an alternative. However, this technique has limitations also, and it cannot be used to identify candidate genes at breakpoints of chromosomal rearrangements such as translocations, insertions, and inversions

Slow implementation of mifepristone medical termination of pregnancy in Quebec, Canada: a qualitative investigation.

Objectives: Mifepristone for first-trimester medical termination of pregnancy (MTOP) became available in Quebec in 2018, one year after the rest of Canada. Using the theory of the Diffusion of Innovation (DOI) and the transtheoretical model of change (TTM), we investigated factors influencing the implementation of mifepristone MTOP in Quebec.Material and Methods: Semi-structured interviews were conducted with 37 Quebec physicians in early 2018. Deductive thematic analysis guided by the theory of DOI explored facilitators and barriers to physicians' adoption of mifepristone MTOP. We then classified participants into five stages of mifepristone adoption based on the TTM. Follow-up data collection one year later assessed further adoption.Results: At baseline, three physicians provided mifepristone MTOP (Maintenance) and two were about to start (Action). Thirteen physicians at Preparation and Advanced Contemplation stages intended to start while, within the Slow Contemplation, two intended to start and ten were unsure. Seven had no intention to provide mifepristone MTOP (Pre-Contemplation). Major reported barriers were: complexity of local health care organisations, medical policy restrictions, lack of support, and general uncertainty. One year later, ten physicians provided mifepristone MTOP (including three at baseline) and nine still intended to, while seventeen did not intend to start provision. Seven of sixteen participants (44%) who worked in TOP clinics at baseline were still not providing MTOP with mifepristone one year later.Conclusion: Despite ideological support, mifepristone MTOP uptake in Quebec is slow and laborious, mainly due to restrictive medical policies, vested interests in surgical provision and administrative inertia

A microscopic and macroscopic study of aging collagen on its molecular structure, mechanical properties, and cellular response

During aging, collagen structure changes, detrimentally affecting tissues' biophysical and biomechanical properties due to an accumulation of advanced glycation end-products (AGEs). In this investigation, we conducted a parallel study of microscopic and macroscopic properties of different-aged collagens from newborn to 2-yr-old rats, to examine the effect of aging on fibrillogenesis, mechanical and contractile properties of reconstituted hydrogels from these collagens seeded with or without fibroblasts. In addition to fibrillogenesis of collagen under the conventional conditions, some fibrillogenesis was conducted alongside a 12-T magnetic field, and gelation rate and AGE content were measured. A nondestructive indentation technique and optical coherence tomography were used to determine the elastic modulus and dimensional changes, respectively. It was revealed that in comparison to younger specimens, older collagens exhibited higher viscosity, faster gelation rates, and a higher AGE-specific fluorescence. Exceptionally, only young collagens formed highly aligned fibrils under magnetic fields. The youngest collagen demonstrated a higher elastic modulus and contraction in comparison to the older collagen. We conclude that aging changes collagen monomer structure, which considerably affects the fibrillogenesis process, the architecture of the resulting collagen fibers and the global network, and the macroscopic properties of the formed constructs

The effect of collagen ageing on its structure and cellular behaviour

Collagen is the most important component in extracellular matrix (ECM) and plays a pivotal role in individual tissue function in mammals. During ageing, collagen structure changes, which can detrimentally affect its biophysical and biomechanical properties due to an accumulation of advanced glycation end-products (AGEs). AGEs have been linked to non-enzymatic cross-linking of proteins resulting in the alteration of mechanical properties of the tissue. In this study we investigate the influence of different aged collagens on the mechanical and contractile properties of reconstituted hydrogel constructs seeded with corneal stromal fibroblasts. A non-destructive indentation technique and optical coherence tomography (OCT) are used to determine the elastic modulus and dimensional changes respectively. It is revealed that the youngest collagen constructs have a higher elastic modulus and increased contraction compared to the older collagen. These results provide new insights into the relationship between collagen molecular structures and their biomechanical properties