Design of Biomembrane-Mimicking Substrates of Tunable Viscosity to Regulate Cellular Mechanoresponse

Indiana University-Purdue University Indianapolis (IUPUI)Tissue cells display mechanosensitivity in their ability to discern and respond to changes in the viscoelastic properties of their surroundings. By anchoring and pulling, cells are capable of translating mechanical stimuli into a biological response through a process known as mechanotransduction, a pathway believed to critically impact cell adhesion, morphology and multiple cellular processes from migration to differentiation. While previous studies on polymeric gels have revealed the influence of substrate elasticity on cellular shape and function, a lack of suitable substrates (i.e. with mobile cell-substrate linkers) has hindered research on the role of substrate viscosity. This work presents the successful design and characterization of lipid-bilayer based cell substrates of tunable viscosity affecting cell-substrate linker mobility through changes in viscous drag. Here, two complementary membrane systems were employed to span a wide range of viscosity. Single polymer-tethered lipid bilayers were used to generate subtle changes in substrate viscosity while multiple, polymer-interconnected lipid bilayer stacks were capable of producing dramatic changes in substrate viscosity. The homogeneity and integrity of these novel multibilayer systems in the presence of adherent cells was confirmed using optical microscopy techniques. Profound changes in cellular growth, phenotype and cytoskeletal organization confirm the ability of cells to sense changes in viscosity. Moreover, increased migration speeds coupled with rapid area fluctuations suggest a transition to a different migration mode in response to the dramatic changes in substrate viscosity

Functionalization of Polymeric Beads as Optical Reporters of Biomembrane Mimicking Cell Substrate Properties

poster abstractNovel biomembrane-mimicking cell substrates based on a polymer-tethered multi-lipid bilayer stack have been recently developed in the Naumann lab. These novel substrates have been shown to induce profound changes in cellular behavior dependent on the number of bilayers in the stack. However, the underlying mechanical substrate properties remain unclear. To overcome this problem, the central goal of my research is the development of a nanoparticle-based optical reporter that provides insight into the dynamic and viscoelastic properties of the multibilayer system. To achieve this goal, fluorescent polystyrene beads and magnetic polystyrene beads were functionalized for use in confocal microscopy and magnetic tweezers (MT) assays, respectively. Both kinds of beads were specifically tailored and functionalized to link the bilayer system to cellular adhesion proteins recognized by plated cells, thus acting as fluorescent cell-substrate linkages. To assure the correct surface functionalization of nanoparticles, Zetasizer assays were run on both kinds of beads to verify expected changes in hydrodynamic radius and zeta potential as reactions progressed. Fluorescent beads were specifically linked to lipid bilayers using maleimide-thiol coupling chemistry, thus allowing subsequent experiments in the presence of plated cells. As confirmed by analysis of cellular nanoparticle uptake, the cellular uptake kinetics of the newly synthesized fluorescent beads could be controlled through adjustment of nanoparticle coating composition. These results are significant because they validate the new nanobead design, which shows enhanced reporter efficiency for confocal microscopy and MT based assays

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Design of biomembrane-mimicking substrates of tunable viscosity to regulate cellular mechanoresponse

Tissue cells display mechanosensitivity in their ability to discern and respond to changes in the viscoelastic properties of their surroundings. By anchoring and pulling, cells are capable of translating mechanical stimuli into a biological response through a process known as mechanotransduction, a pathway believed to critically impact cell adhesion, morphology and multiple cellular processes from migration to differentiation. While previous studies on polymeric gels have revealed the influence of substrate elasticity on cellular shape and function, a lack of suitable substrates (i.e. with mobile cell-substrate linkers) has hindered research on the role of substrate viscosity. This work presents the successful design and characterization of lipid-bilayer based cell substrates of tunable viscosity affecting cell-substrate linker mobility through changes in viscous drag. Here, two complementary membrane systems were employed to span a wide range of viscosity. Single polymer-tethered lipid bilayers were used to generate subtle changes in substrate viscosity while multiple, polymer-interconnected lipid bilayer stacks were capable of producing dramatic changes in substrate viscosity. The homogeneity and integrity of these novel multibilayer systems in the presence of adherent cells was confirmed using optical microscopy techniques. Profound changes in cellular growth, phenotype and cytoskeletal organization confirm the ability of cells to sense changes in viscosity. Moreover, increased migration speeds coupled with rapid area fluctuations suggest a transition to a different migration mode in response to the dramatic changes in substrate viscosity

Tentatives de suicide aux urgences: Profil des facteurs de risque et corrélations avec les antécédents personnels.

6e Congrès de l'Encéphale, Paris, 24-26 Janvier 2008info:eu-repo/semantics/publishe

Substance abuse and addiction profile in 6600 patients admitted at a psychiatric emergency room

21st Congress of the European College of Neuropsychopharmacology (ECNP) Barcelona, Spain (Aug.30-Sept 3 2008)info:eu-repo/semantics/publishe

An Integrated Guaranteed- and Stochastic-Service Approach to Inventory Optimization in Supply Chains

Multi-echelon inventory optimization literature distinguishes stochastic- (SS) and guaranteed-service (GS) approaches as mutually exclusive frameworks. While the GS approach considers flexibility measures at the stages to deal with stockouts, the SS approach only relies on safety stock. Within a supply chain, flexibility levels might differ between stages rendering them appropriate candidates for one approach or the other. The existing approaches, however, require the selection of a single framework for the entire supply chain instead of a stage-wise choice. We develop an integrated hybrid-service (HS) approach which endogenously determines the overall cost-optimal approach for each stage and computes the required inventory levels. We present a dynamic programming optimization algorithm for serial supply chains that partitions the entire system into subchains of different types. From a numerical study we find that, besides implicitly choosing the better of the two pure frameworks, whose cost differences can be considerable, the HS approach enables additional pipeline and on-hand stock cost savings. We further identify drivers for the preferability of the HS approach

Étude du sentiment de dés-appartenance dans un échantillon de patients suicidaires hospitalisés

7e Congrès de l'Encéphale à Paris (22-24 Janvier 2009)info:eu-repo/semantics/publishe

Suivi ambulatoire par un médecin traitant et verbalisation des idées suicidaires précédents une tentative de suicide

7e Congrès de l'Encéphale à Paris (22-24 Janvier 2009)info:eu-repo/semantics/publishe