Les grès apto-albiens dans leur contexte paléomorphologique (Bassin subalpin méridional, S.E. France)

Mémoire HS n° 13 - Géologie Alpine : Le détritisme dans le Sud-Est de la France - Colloque Association des Géologues du Sud-est - Grenoble 11-12 décembre 1986La série apto-albienne, essentiellement marneuse, comporte dans les différentes zones du bassin subalpin de nombreuses venues gréseuses qu'il est possible d'interpréter d'un point de vue dynamique et paléomorphologique. L'utilisation des figures directionnelles (current marks) et des structures de glissement (slumps) permet de reconstituer, dans le bassin essentiellement E-W, des morphologies méridiennes, notamment le sillon du Buëch. Sur ses flancs se dessinent des vallées sous-marines profondément entaillées, et particulièrement celle de Ceüse, dont l'éventail à l'Aptien peut être très précisément restitué: 20 km de large et plus de 70 km de long : d'amont en aval les divers faciès (chenaux, lobes turbiditiques, séquences de slumps), s'organisent tant verticalement qu'horizontalement. Sur la bordure méridionale, les grès (albiens) correspondent d'une part à des faciès de plate-forme et d'autre part à des chenaux emplis de fluxoturbidites qui acheminent les venues détritiques jusqu'au bassin. Plusieurs mécanismes contrôlent ces venues : l'histoire des sources (difficiles à localiser) , celle du niveau marin (eustatisme) mais plus encore l'activité tectonique synsédimentaire et la fracturation induite au long des pentes, ainsi que la compaction précoce ; ces deux derniers mécanismes sont déchiffrables en particulier par l'analyse des sills et dykes sédimentaires gréseux qui, en divers sites, sont profondément infiltrés dans le massif argileux

Olistolithes et conglomérats au Lias-Dogger en relation avec l'activitè tectonique synsédimentaire

Mémoire HS n° 13 - Géologie Alpine : Le détritisme dans le Sud-Est de la France - Colloque Association des Géologues du Sud-est - Grenoble 11-12 décembre 1986Des exemples répartis dans le bassin montrent l'importance des démantèlements associés aux discontinuités majeures, en relation avec des situations tectoniques singulières: accidents pérennes structurant le bassin et zones diapiriques

Protection of organic matter by mineral matrix in a Cenomanian black shale

L'UMR CNRS 6531, Laboratoire de Géologie de la Matière Organique a été intégré dans l'ISTO - UMR6113 - CNRS-Université d'OrléansThree types of pathways (degradation-recondensation, natural sulphurization and selective preservation) are commonly considered for the formation of kerogen dispersed in sedimentary rocks. A fourth pathway has been recently put forward, however, from studies on Recent marine sediments, the so-called sorptive protection mechanism. This pathway is based on the adsorption of otherwise labile organic compounds onto minerals, thus preventing their diagenetic degradation and promoting their subsequent condensation into kerogen. The main results of the present study are derived from a combination of microscopic and pyrolytic methods applied on a Cenomanian kerogen. They provide (i) evidence, on an ancient material, for a crucial role of the mineral matrix both in organic matter (OM) preservation during kerogen formation and in kerogen stability once formed, (ii) indications that the dominant protective process likely involves physical protection by minerals, resulting from alternation of organic and clay nanolayers of approximately 100 nm in thickness, rather than OM adsorption as molecular monolayers and (iii) observations of the relatively poor stability of an isolated kerogen, contrary to the inertness commonly assumed for fossil macromolecular organic matter

Production of a bilayered self-assembled skin substitute using a tissue-engineered acellular dermal matrix

Our bilayered self-assembled skin substitutes (SASS) are skin substitutes showing a structure and functionality very similar to native human skin. These constructs are used, in life-threatening burn wounds, as permanent autologous grafts for the treatment of such affected patients even though their production is exacting. We thus intended to shorten their current production time to improve their clinical applicability. A self-assembled decellularized dermal matrix (DM) was used. It allowed the production of an autologous skin substitute from patient's cells. The characterization of SASS reconstructed using a decellularized dermal matrix (SASS-DM) was performed by histology, immunofluorescence, transmission electron microscopy, and uniaxial tensile analysis. Using the SASS-DM, it was possible to reduce the standard production time from about 8 to 4 and a half weeks. The structure, cell differentiation, and mechanical properties of the new skin substitutes were shown to be similar to the SASS. The decellularization process had no influence on the final microstructure and mechanical properties of the DM. This model, by enabling the production of a skin substitute in a shorter time frame without compromising its intrinsic tissue properties, represents a promising addition to the currently available burn and wound treatments

Impact of simulated brain interstitial fluid flow on the chemokine CXCL12 release from an alginate-based hydrogel in a new 3D in vitro model

ABSTRACT: Introduction: Extensive investigation has been undertaken regarding drug delivery systems for the management of glioblastoma multiforme (GBM). The infiltrative behavior of GBM cells within the brain tissue is primarily attributed to their heterogeneity, the movement of interstitial fluid (IFF), and the presence of chemokines. These factors contribute to the limited effectiveness of current conventional treatments. To address the dissemination of GBM cells, a proposed therapeutic approach involves utilizing a controlled release gradient of CXC-chemokine-ligand-12 (CXCL12). However, the impact of IFF on GBM cell migration within the brain underscores its critical importance as a significant parameter, which, surprisingly, has not been extensively studied in the context of localized drug delivery targeting the brain. Methods: Hydrogels are known for their inherent capacity to entrap various agents and exert precise control over their subsequent release. In the present investigation, we aimed to elucidate the release kinetics of CXCL12, whether in its free form or encapsulated within nanoparticles, from alginate-based hydrogels, both under static and dynamic conditions. To investigate the impact of convective forces mimicking the interstitial fluid flow (IFF) within the peritumoral environment of the brain, a three-dimensional in vitro model was developed. This model enabled the evaluation of CXCL12 release as a function of time and position, specifically accounting for the contribution of simulated IFF on the release behavior. Results: We first demonstrated that the release kinetic profiles under static culture conditions were independent of the initial mass loading and the predominant phenomenon occurring was diffusion. Subsequently, we investigated the release of CXCL12, which was loaded into Alginate/Chitosan-Nanoparticles (Alg/Chit-NPs) and embedded within an alginate hydrogel matrix. Mathematical modeling results also indicated the presence of electrostatic interactions between alginate and CXCL12. The Alg/Chit-NPs effectively slowed down the initial burst release, leading to a reduction in the diffusion coefficient of CXCL12. To further study the release behavior, we developed a perfusion bioreactor with a unique culture chamber designed to recapitulate the peritumoral environment and varied the fluid flow rates at 0.5 µL/min, 3 µL/min, 6.5 µL/min, and 10 µL/min. As the flow rate increased, the cumulative amount of released CXCL12 also increased for all three initial mass loadings. Beyond 3 µL/min, convection became the dominant mechanism governing CXCL12 release, whereas below this threshold, diffusion played a more prominent role. Conclusion: The indirect perfusion flow had a crucial impact on CXCL12 release and distribution inside the hydrogel in and against its direction. This system highlights the importance of considering the IFF in brain targeting delivery system and will be used in the future to study GBM cell behaviors in response to CXCL12 gradient