Liver Transplantation for Primary Sclerosing Cholangitis (PSC) With or Without Inflammatory Bowel Disease (IBD)-A European Society of Organ Transplantation (ESOT) Consensus Statement

Primary sclerosing cholangitis (PSC) is the classical hepatobiliary manifestation of inflammatory bowel disease (IBD) and a lead indication for liver transplantation (LT) in the western world. In this article, we present a Consensus Statement on LT practice, developed by a dedicated Guidelines' Taskforce of the European Society of Organ Transplantation (ESOT). The overarching goal is to provide practical guidance on commonly debated topics, including indications and timing of LT, management of bile duct stenosis in patients on the transplant waiting list, technical aspects of transplantation, immunosuppressive strategies post-transplant, timing and extension of intestinal resection and futility criteria for re-transplantation.

Synapses do not facilitate prion-like transfer of alpha-synuclein: a quantitative study in reconstructed unidirectional neural networks

Alpha-synuclein (aSyn) aggregation spreads between cells and underlies the progression of neuronal lesions in the brain of patients with synucleinopathies such as Parkinson's diseases. The mechanisms of cell-to-cell propagation of aggregates, which dictate how aggregation progresses at the network level, remain poorly understood. Notably, while prion and prion-like spreading is often simplistically envisioned as a "domino-like" spreading scenario where connected neurons sequentially propagate protein aggregation to each other, the reality is likely to be more nuanced. Here, we demonstrate that the spreading of preformed aSyn aggregates is a limited process that occurs through molecular sieving of large aSyn seeds. We further show that this process is not facilitated by synaptic connections. This was achieved through the development and characterization of a new microfluidic platform that allows reconstruction of binary fully oriented neuronal networks in vitro with no unwanted backward connections, and through the careful quantification of fluorescent aSyn aggregates spreading between neurons. While this allowed us for the first time to extract quantitative data of protein seeds dissemination along neural pathways, our data suggest that prion-like dissemination of proteinopathic seeding aggregates occurs very progressively and leads to highly compartmentalized pattern of protein seeding in neural networks.

Surface Tension and Neuronal Sorting in Magnetically Engineered Brain-Like Tissue

Engineered 3D brain-like models have advanced the understanding of neurological mechanisms and disease, yet their mechanical signature, while fundamental for brain function, remains understudied. The surface tension for instance controls brain development and is a marker of cell-cell interactions. Here, 3D magnetic brain-like tissue spheroids composed of intermixed primary glial and neuronal cells at different ratios are engineered. Remarkably, the two cell types self-assemble into a functional tissue, with the sorting of the neuronal cells toward the periphery of the spheroids, whereas the glial cells constitute the core. The magnetic fingerprint of the spheroids then allows their deformation when placed under a magnetic field gradient, at a force equivalent to a 70 g increased gravity at the spheroid level. The tissue surface tension and elasticity can be directly inferred from the resulting deformation, revealing a transitional dependence on the glia/neuron ratio, with the surface tension of neuronal tissue being much lower. The results suggest an underlying mechanical contribution to the exclusion of the neurons toward the outer spheroid region, and depict the glia/neuron organization as a sophisticated mechanism that should in turn influence tissue development and homeostasis relevant in the neuroengineering field.

Mitochondria: At the crossroads between mechanobiology and cell metabolism

Metabolism and mechanics are two key facets of structural and functional processes in cells, such as growth, proliferation, homeostasis and regeneration. Their reciprocal regulation has been increasingly acknowledged in recent years: external physical and mechanical cues entail metabolic changes, which in return regulate cell mechanosensing and mechanotransduction. Since mitochondria are pivotal regulators of metabolism, we review here the reciprocal links between mitochondrial morphodynamics, mechanics and metabolism. Mitochondria are highly dynamic organelles which sense and integrate mechanical, physical and metabolic cues to adapt their morphology, the organization of their network and their metabolic functions. While some of the links between mitochondrial morphodynamics, mechanics and metabolism are already well established, others are still poorly documented and open new fields of research. First, cell metabolism is known to correlate with mitochondrial morphodynamics. For instance, mitochondrial fission, fusion and cristae remodeling allow the cell to fine-tune its energy production through the contribution of mitochondrial oxidative phosphorylation and cytosolic glycolysis. Second, mechanical cues and alterations in mitochondrial mechanical properties reshape and reorganize the mitochondrial network. Mitochondrial membrane tension emerges as a decisive physical property which regulates mitochondrial morphodynamics. However, the converse link hypothesizing a contribution of morphodynamics to mitochondria mechanics and/or mechanosensitivity has not yet been demonstrated. Third, we highlight that mitochondrial mechanics and metabolism are reciprocally regulated, although little is known about the mechanical adaptation of mitochondria in response to metabolic cues. Deciphering the links between mitochondrial morphodynamics, mechanics and metabolism still presents significant technical and conceptual challenges but is crucial both for a better understanding of mechanobiology and for potential novel therapeutic approaches in diseases such as cancer.

Spatial confinement: A spur for axonal growth

The concept of spatial confinement is the basis of cell positioning and guidance in in vitro studies. In vivo, it reflects many situations faced during embryonic development. In vitro, spatial confinement of neurons is achieved using different technological approaches: adhesive patterning, topographical structuring, microfluidics and the use of hydrogels. The notion of chemical or physical frontiers is particularly central to the behaviors of growth cones and neuronal processes under confinement. They encompass phenomena of cell spreading, boundary crossing, and path finding on surfaces with different adhesive properties. However, the most universal phenomenon related to confinement, regardless of how it is implemented, is the acceleration of neuronal growth. Overall, a bi-directional causal link emerges between the shape of the growth cone and neuronal elongation dynamics, both in vivo and in vitro. The sensing of adhesion discontinuities by filopodia and the subsequent spatial redistribution and size adaptation of these actin-rich filaments seem critical for the growth rate in conditions in which adhesive contacts and actin-associated clutching forces dominate. On the other hand, the involvement of microtubules, specifically demonstrated in 3D hydrogel environments and leading to ameboid-like locomotion, could be relevant in a wider range of growth situations. This review brings together a literature collected in distinct scientific fields such as development, mechanobiology and bioengineering that highlight the consequences of confinement and raise new questions at different cellular scales. Its ambition is to stimulate new research that could lead to a better understanding of what gives neurons their ability to establish and regulate their exceptional size.

Bending stiffness of Candida albicans hyphae as a proxy of cell wall properties

The cell wall is a key component of fungi. It constitutes a highly regulated viscoelastic shell which counteracts internal cell turgor pressure. Its mechanical properties thus contribute to define cell morphology. Measurements of the elastic moduli of the fungal cell wall have been carried out in many species including Candida albicans, a major human opportunistic pathogen. They mainly relied on atomic force microscopy, and mostly considered the yeast form. We developed a parallelized pressure-actuated microfluidic device to measure the bending stiffness of hyphae. We found that the cell wall stiffness lies in the MPa range. We then used three different ways to disrupt cell wall physiology: inhibition of beta-glucan synthesis, a key component of the inner cell wall; application of a hyperosmotic shock triggering a sudden decrease of the hyphal diameter; deletion of two genes encoding GPI-modified cell wall proteins resulting in reduced cell wall thickness. The bending stiffness values were affected to different extents by these environmental stresses or genetic modifications. Overall, our results support the elastic nature of the cell wall and its ability to remodel at the scale of the entire hypha over minutes.

Poly-l-lysine/Laminin Surface Coating Reverses Glial Cell Mechanosensitivity on Stiffness-Patterned Hydrogels

Brain tissues demonstrate heterogeneous mechanical properties, which evolve with aging and pathologies. The observation in these tissues of smooth to sharp rigidity gradients raises the question of brain cell responses to both different values of rigidity and their spatial variations, in dependence on the surface chemistry they are exposed to. Here, we used recent techniques of hydrogel photopolymerization to achieve stiffness texturing down to micrometer resolution in polyacrylamide hydrogels. We investigated primary neuron adhesion and orientation as well as glial cell proliferative properties on these rigidity-textured hydrogels for two adhesive coatings: fibronectin or poly-l-lysine/laminin. Our main observation is that glial cell adhesion and proliferation is favored on the stiffer regions when the adhesive coating is fibronectin and on the softer ones when it consists of poly-l-lysine/laminin. This behavior was unchanged by the presence or the absence of neuronal cells. In addition, glial cells were not confined by sharp, micron-scaled gradients of rigidity. Our observations suggest that rigidity sensing could involve adhesion-related pathways that profoundly depend on surface chemistry.

Compromised nuclear envelope integrity drives TREX1-dependent DNA damage and tumor cell invasion

Although mutations leading to a compromised nuclear envelope cause diseases such as muscular dystrophies or accelerated aging, the consequences of mechanically induced nuclear envelope ruptures are less known. Here, we show that nuclear envelope ruptures induce DNA damage that promotes senescence in non-transformed cells and induces an invasive phenotype in human breast cancer cells. We find that the endoplasmic reticulum (ER)-associated exonuclease TREX1 translocates into the nucleus after nuclear envelope rupture and is required to induce DNA damage. Inside the mammary duct, cellular crowding leads to nuclear envelope ruptures that generate TREX1-dependent DNA damage, thereby driving the progression of in situ carcinoma to the invasive stage. DNA damage and nuclear envelope rupture markers were also enriched at the invasive edge of human tumors. We propose that DNA damage in mechanically challenged nuclei could affect the pathophysiology of crowded tissues by modulating proliferation and extracellular matrix degradation of normal and transformed cells.

Sex Hormones in Men with Abdominal Aortic Aneurysm

BACKGROUND

Abdominal aortic aneurysm (AAA) primarily affects elderly men. The impact of sex on aneurysm development has been associated with an effect of sex hormones, through mechanisms that are not fully understood. This study aimed to examine the association between levels of sex hormones and the occurrence of AAA in elderly men.

METHODS

A prospective case-control study was conducted including 452, 65-year old men participating in screening for AAA, 2013-2019; 230 men with AAA and 222 men with an aortic diameter<30mm (controls). Questionnaires and blood samples were collected and stored consecutively. Serum levels of total testosterone, estradiol, progesterone, luteinizing hormone and sex hormone binding globulin were analyzed by electrochemiluminescent immunoassays. Multivariable logistic regression analysis was used to assess the association of sex hormones with AAA.

RESULTS

The median aneurysm diameter was 33mm. Men with AAA had higher estradiol and progesterone levels than controls (93pmol/L vs. 84pmol/L, p=.003 and 0.41nmol/L vs. 0.17nmol/L, p<.001). Testosterone levels were lower in men with AAA than in controls (13nmol/L vs. 14nmol/L, p=.026). AAA was associated with detectable levels of progesterone(OR 6.69, 95%CI 3.86-11.47), smoking(OR 5.26, 95%CI 3.12-8.85), coronary heart disease(OR 4.06, 95%CI 1.92-8.58) and body mass index>25(OR 2.26, 95%CI 1.34-3.82).

CONCLUSION

The observed higher levels of estradiol and progesterone in men with AAA, suggest an impact of sex hormones on aneurysm development. The association between progesterone levels and aortic diameter, stress the importance of focusing on the potential effect of this unconsidered female sex hormone on aneurysm formation.

Conversion therapy in patients with colorectal liver metastases

BACKGROUND

The occurrence of colorectal liver metastases (CRLM) impairs prognosis, yet long-term survival can be achieved by enabling liver resection. This study aims to describe factors associated with conversion therapy leading to liver surgery and treatment outcome.

METHODS

A retrospective cohort study was conducted including all patients with CRLM discussed at multidisciplinary team conference at Karolinska University Hospital, Stockholm, Sweden, from 2013 to 2018. Factors associated with conversion therapy and outcome following conversion therapy were analysed with logistic regression and survival analyses.

RESULTS

Out of 1023 patients with CRLM, 100 patients (10%) received conversion chemotherapy, out of whom 31 patients (31%) subsequently underwent liver resection. Patients in whom conversion chemotherapy resulted in liver resection were younger (median age 61 vs. 66 years, p = .024), less likely to have a KRAS/NRAS-mutated primary tumours (25% vs. 53%, p = .039) and more likely to have received anti-EGFR agents (32% vs. 4%, p = .001) than patients progressing during conversion chemotherapy. The median OS for patients treated with conversion chemotherapy leading to liver resection was 24 months, compared to 14 months for patients progressing during conversion chemotherapy, p < .001. The OS for patients progressing during conversion chemotherapy was similar to patients given palliative chemotherapy, approximately 13 months.

CONCLUSION

Conversion therapy offers a survival benefit in selected patients. Despite treatment advances, the majority of patients undergoing conversion chemotherapy never become eligible for curative treatment.

Neuronal growth from a volume perspective

Microfluidic-based fluorescent exclusion method allows to tackle the issue of neuronal growth from a volume perspective. Based on this technology, we studied the two main actin-rich structures accompanying the early stages of neuron development, i.e. growth cones, located at the tip of growing neuronal processes, and propagative actin waves. Our work reveals that growth cones tend to loose volume during their forward motion, as do actin waves during their journey from the cell body to the tip of neuronal processes, before the total transfer of their remaining volume to the growth cone. Actin waves seem thus to supply material to increasingly distant growth cones as neurons develop. In addition, our work may suggest the existence of a membrane recycling phenomena associated to actin waves as a pulsatile anterograde source of material and by a continuous retrograde transport.

Cellular and Subcellular Contact Guidance on Microfabricated Substrates

Topography of the extracellular environment is now recognized as a major biophysical regulator of cell behavior and function. The study of the influence of patterned substrates on cells, named contact guidance, has greatly benefited from the development of micro and nano-fabrication techniques, allowing the emergence of increasingly diverse and elaborate engineered platforms. The purpose of this review is to provide a comprehensive view of the process of contact guidance from cellular to subcellular scales. We first classify and illustrate the large diversity of topographies reported in the literature by focusing on generic cellular responses to diverse topographical cues. Subsequently, and in a complementary fashion, we adopt the opposite approach and highlight cell type-specific responses to classically used topographies (arrays of pillars or grooves). Finally, we discuss recent advances on the key subcellular and molecular players involved in topographical sensing. Throughout the review, we focus particularly on neuronal cells, whose unique morphology and behavior have inspired a large body of studies in the field of topographical sensing and revealed fascinating cellular mechanisms. We conclude by using the current understanding of the cell-topography interactions at different scales as a springboard for identifying future challenges in the field of contact guidance.

Parallelized Manipulation of Adherent Living Cells by Magnetic Nanoparticles-Mediated Forces

The remote actuation of cellular processes such as migration or neuronal outgrowth is a challenge for future therapeutic applications in regenerative medicine. Among the different methods that have been proposed, the use of magnetic nanoparticles appears to be promising, since magnetic fields can act at a distance without interactions with the surrounding biological system. To control biological processes at a subcellular spatial resolution, magnetic nanoparticles can be used either to induce biochemical reactions locally or to apply forces on different elements of the cell. Here, we show that cell migration and neurite outgrowth can be directed by the forces produced by a switchable parallelized array of micro-magnetic pillars, following the passive uptake of nanoparticles. Using live cell imaging, we first demonstrate that adherent cell migration can be biased toward magnetic pillars and that cells can be reversibly trapped onto these pillars. Second, using differentiated neuronal cells we were able to induce events of neurite outgrowth in the direction of the pillars without impending cell viability. Our results show that the range of forces applied needs to be adapted precisely to the cellular process under consideration. We propose that cellular actuation is the result of the force on the plasma membrane caused by magnetically filled endo-compartments, which exert a pulling force on the cell periphery.

Fluid shear stress coupled with narrow constrictions induce cell type-dependent morphological and molecular changes in SK-BR-3 and MDA-MB-231 cells

Cancer mortality mainly arises from metastases, due to cells that escape from a primary tumor, circulate in the blood as circulating tumor cells (CTCs), permeate across blood vessels and nest in distant organs. It is still unclear how CTCs overcome the harsh conditions of fluid shear stress and mechanical constraints within the microcirculation. Here, a minimal model of the blood microcirculation was established through the fabrication of microfluidic channels comprising constrictions. Metastatic breast cancer cells of epithelial-like and mesenchymal-like phenotypes were flowed into the microfluidic device. These cells were visualized during circulation and analyzed for their dynamical behavior, revealing long-lived plastic deformations and significant differences in biomechanics between cell types. γ-H2AX staining of cells retrieved post-circulation showed significant increase of DNA damage response in epithelial-like SK-BR-3 cells, while gene expression analysis of key regulators of epithelial-to-mesenchymal transition revealed significant changes upon circulation. This work thus documents first results of the changes at the cellular, subcellular and molecular scales induced by the two main mechanical stimuli arising from circulatory conditions, and suggest a significant role of this still elusive step of the metastatic cascade in cancer cells heterogeneity and aggressiveness.

Reconstruction of directed neuronal networks in a microfluidic device with asymmetric microchannels

Microfluidic devices for controlling neuronal connectivity in vitro are extremely useful tools for deciphering pathological and physiological processes occurring in neuronal networks. These devices allow the connection between different neuronal populations located into separate culture chambers through axon-selective microchannels. In order to implement specific features of brain connectivity such as directionality, it is necessary to control axonal growth orientation in these devices. Among the various strategies proposed to achieve this goal, one of the most promising and easily reproducible is the use of asymmetric microchannels. We present here a general protocol and several guidelines for the design, production and testing of a new paradigm of asymmetric microchannels geometries based on a "return to sender" strategy. In this method, axons are either allowed to travel between the emitting and receiving chambers within straight microchannels (forward direction), or are rerouted toward their initial location through curved microchannels (reverse direction). We introduce variations of these "arches" microchannels and evaluate their respective axonal filtering capacities. Importantly, one of these variants presents an almost complete filtration of axonal growth in the non-permissive direction while allowing robust axonal invasion in the other one, with a selectivity ratio as high as 99.7%.

High-resolution Volume Imaging of Neurons by the Use of Fluorescence eXclusion Method and Dedicated Microfluidic Devices

Volume is an important parameter regarding physiological and pathological characteristics of neurons at different time scales. Neurons are quite unique cells regarding their extended ramified morphologies and consequently raise several methodological challenges for volume measurement. In the particular case of in vitro neuronal growth, the chosen methodology should include sub-micrometric axial resolution combined with full-field observation on time scales from minutes to hours or days. Unlike other methods like cell shape reconstruction using confocal imaging, electrically-based measurements or Atomic Force Microscopy, the recently developed Fluorescence eXclusion method (FXm) has the potential to fulfill these challenges. However, although being simple in its principle, implementation of a high-resolution FXm for neurons requires multiple adjustments and a dedicated methodology. We present here a method based on the combination of fluorescence exclusion, low-roughness multi-compartments microfluidic devices, and finally micropatterning to achieve in vitro measurements of local neuronal volume. The high resolution provided by the device allowed us to measure the local volume of neuronal processes (neurites) and the volume of some specific structures involved in neuronal growth, such as growth cones (GCs).

Geometrical Determinants of Neuronal Actin Waves

Hippocampal neurons produce in their early stages of growth propagative, actin-rich dynamical structures called actin waves. The directional motion of actin waves from the soma to the tip of neuronal extensions has been associated with net forward growth, and ultimately with the specification of neurites into axon and dendrites. Here, geometrical cues are used to control actin wave dynamics by constraining neurons on adhesive stripes of various widths. A key observable, the average time between the production of consecutive actin waves, or mean inter-wave interval (IWI), was identified. It scales with the neurite width, and more precisely with the width of the proximal segment close to the soma. In addition, the IWI is independent of the total number of neurites. These two results suggest a mechanistic model of actin wave production, by which the material conveyed by actin waves is assembled in the soma until it reaches the threshold leading to the initiation and propagation of a new actin wave. Based on these observations, we formulate a predictive theoretical description of actin wave-driven neuronal growth and polarization, which consistently accounts for different sets of experiments.

Transient microfluidic compartmentalization using actionable microfilaments for biochemical assays, cell culture and organs-on-chip

We report here a simple yet robust transient compartmentalization system for microfluidic platforms. Cylindrical microfilaments made of commercially available fishing lines are embedded in a microfluidic chamber and employed as removable walls, dividing the chamber into several compartments. These partitions allow tight sealing for hours, and can be removed at any time by longitudinal sliding with minimal hydrodynamic perturbation. This allows the easy implementation of various functions, previously impossible or requiring more complex instrumentation. In this study, we demonstrate the applications of our strategy, firstly to trigger chemical diffusion, then to make surface co-coating or cell co-culture on a two-dimensional substrate, and finally to form multiple cell-laden hydrogel compartments for three-dimensional cell co-culture in a microfluidic device. This technology provides easy and low-cost solutions, without the use of pneumatic valves or external equipment, for constructing well-controlled microenvironments for biochemical and cellular assays.

Asymmetric axonal edge guidance: a new paradigm for building oriented neuronal networks

We present a novel kind of directional axon guides for brain-on-a-chip applications. Contrarily to previous works, the directionality in our design is created by rerouting axons growing in the unwanted direction back to their original compartment while leaving the other growth direction unaffected. This design yields state-of-the-art levels of directionality without the disadvantages of previously reported technologies.

In-mold patterning and actionable axo-somatic compartmentalization for on-chip neuron culture

Oriented neuronal networks with controlled connectivity are required for many applications ranging from studies of neurodegeneration to neuronal computation. To build such networks in vitro, an efficient, directed and long lasting guidance of axons toward their target is a pre-requisite. The best guidance achieved so far, however, relies on confining axons in enclosed microchannels, making them poorly accessible for further investigation. Here we describe a method providing accessible and highly regular arrays of axons, emanating from somas positioned in distinct compartments. This method combines the use of a novel removable partition, allowing soma positioning outside of the axon guidance patterns, and in-mold patterning (iMP), a hybrid method combining chemical and mechanical cell positioning clues applied here for the first time to neurons. The axon guidance efficiency of iMP is compared to that of conventional patterning methods, e.g. micro-contact printing (chemical constraints by a poly-l-lysine motif) and micro-grooves (physical constraints by homogeneously coated microstructures), using guiding tracks of different widths and spacing. We show that iMP provides a gain of 10 to 100 in axon confinement efficiency on the tracks, yielding mm-long, highly regular, and fully accessible on-chip axon arrays. iMP also allows well-defined axon guidance from small populations of several neurons confined at predefined positions in μm-sized wells. iMP will thus open new routes for the construction of complex and accurately controlled neuronal networks.

Small RNA Deep-Sequencing Analyses Reveal a New Regulator of Virulence in Agrobacterium fabrum C58

Novel ways of regulating Ti plasmid functions were investigated by studying small RNAs (sRNAs) that are known to act as posttranscriptional regulators in plant pathogenic bacteria. sRNA-seq analyses of Agrobacterium fabrum C58 allowed us to identify 1,108 small transcripts expressed in several growth conditions that could be sRNAs. A quarter of them were confirmed by bioinformatics or by biological experiments. Antisense RNAs represent 24% of the candidates and they are over-represented on the pTi (with 62% of pTi sRNAs), suggesting differences in the regulatory mechanisms between the essential and accessory replicons. Moreover, a large number of these pTi antisense RNAs are transcribed opposite to those genes involved in virulence. Others are 5'- and 3'-untranslated region RNAs and trans-encoded RNAs. We have validated, by rapid amplification of cDNA ends polymerase chain reaction, the transcription of 14 trans-encoded RNAs, among which RNA1111 is expressed from the pTiC58. Its deletion decreased the aggressiveness of A. fabrum C58 on tomatoes, tobaccos, and kalanchoe, suggesting that this sRNA activates virulence. The identification of its putative target mRNAs (6b gene, virC2, virD3, and traA) suggests that this sRNA may coordinate two of the major pTi functions, the infection of plants and its dissemination among bacteria.

Nanoscale surface topography reshapes neuronal growth in culture

Neurons are sensitive to topographical cues provided either by in vivo or in vitro environments on the micrometric scale. We have explored the role of randomly distributed silicon nanopillars on primary hippocampal neurite elongation and axonal differentiation. We observed that neurons adhere on the upper part of nanopillars with a typical distance between adhesion points of about 500 nm. These neurons produce fewer neurites, elongate faster, and differentiate an axon earlier than those grown on flat silicon surfaces. Moreover, when confronted with a differential surface topography, neurons specify an axon preferentially on nanopillars. As a whole, these results highlight the influence of the physical environment in many aspects of neuronal growth.

Tuning the adhesive geometry of neurons: length and polarity control

Neurons acquire their functional and morphological axo-dendritic polarity by extending, from competing minor processes (neurites), one long axon among numerous dendrites. We employed complementary sets of micropatterns built from 2 and 6 μm wide stripes of various lengths to constrain hippocampal neuron shapes. Using these geometries, we have (i) limited the number of neuronal extensions to obtain a minimal in vitro system of bipolar neurons and (ii) controlled the neurite width during growth by the generation of a progressive cell shape asymmetry on either side of the cellular body. From this geometrical approach, we gained a high level of control of each neurite length and of the localization of axonal specification. To analyze these results, we developed a model based on a width and polarization dependent neurite elongation rate and on the existence of a critical neurite length that sets the axonal fate. Our data on the four series of micro-patterns developed for this study are described by a single set of growth parameters, well supported by experiments. The control of neuronal shapes by adhesive micro-patterns thereby offers a novel paradigm to follow the dynamical process of neurite lengthening and competition through the process of axonal polarization.

How morphological constraints affect axonal polarity in mouse neurons

Neuronal differentiation is under the tight control of both biochemical and physical information arising from neighboring cells and micro-environment. Here we wished to assay how external geometrical constraints applied to the cell body and/or the neurites of hippocampal neurons may modulate axonal polarization in vitro. Through the use of a panel of non-specific poly-L-lysine micropatterns, we manipulated the neuronal shape. By applying geometrical constraints on the cell body we provided evidence that centrosome location was not predictive of axonal polarization but rather follows axonal fate. When the geometrical constraints were applied to the neurites trajectories we demonstrated that axonal specification was inhibited by curved lines. Altogether these results indicated that intrinsic mechanical tensions occur during neuritic growth and that maximal tension was developed by the axon and expressed on straight trajectories. The strong inhibitory effect of curved lines on axon specification was further demonstrated by their ability to prevent formation of multiple axons normally induced by cytochalasin or taxol treatments. Finally we provided evidence that microtubules were involved in the tension-mediated axonal polarization, acting as curvature sensors during neuronal differentiation. Thus, biomechanics coupled to physical constraints might be the first level of regulation during neuronal development, primary to biochemical and guidance regulations.

Neuronal architectures with axo-dendritic polarity above silicon nanowires

An approach is developped to gain control over the polarity of neuronal networks at the cellular level by physically constraining cell development by the use of micropatterns. It is demonstrated that the position and path of individual axons, the cell extension that propagates the neuron output signal, can be chosen with a success rate higher than 85%. This allows the design of small living computational blocks above silicon nanowires.

Ruminococcin C, a new anti-Clostridium perfringens bacteriocin produced in the gut by the commensal bacterium Ruminococcus gnavus E1

When colonizing the digestive tract of mono-associated rats, Ruminococcus gnavus E1 - a bacterium isolated from human faeces - produced a trypsin-dependent anti-Clostridium perfringens substance collectively named Ruminococcin C (RumC). RumC was isolated from the caecal contents of E1-monocontaminated rats and found to consist of two antimicrobial fractions: a single peptide (RumCsp) of 4235 Da, and a mixture of two other peptides (RumCdp) with distinct molecular masses of 4324 Da and 4456 Da. Both RumCsp and RumCdp were as effective as metronidazole in combating C. perfringens and their activity spectra against different pathogens were established. Even if devoid of synergistic activity, the combination of RumCsp and RumCdp was observed to be much more resistant to acidic pH and high temperature than each fraction tested individually. N-terminal sequence analysis showed that the primary structures of these three peptides shared a high degree of homology, but were clearly distinct from previously reported amino acid sequences. Amino acid composition of the three RumC peptides did not highlight the presence of any Lanthionine residue. However, Edman degradation could not run beyond the 11th amino acid residue. Five genes encoding putative pre-RumC-like peptides were identified in the genome of strain E1, confirming that RumC was a bacteriocin. This is the first time that a bacteriocin produced in vivo by a human commensal bacterium was purified and characterized.

Living cell imaging by far-field fibered interference scanning optical microscopy

We report on the imaging of biological cells including living neurons by a dedicated fibered interferometric scanning optical microscope. The topography and surface roughness of mouse fibroblasts and hippocampal neurons are clearly revealed. This straightforward far-field technique allows fast, high resolution observation of samples in liquids without lengthy alignment procedures or costly components.

Microtubule targeting agents: from biophysics to proteomics

This review explores various aspects of the interaction between microtubule targeting agents and tubulin, including binding site, affinity, and drug resistance. Starting with the basics of tubulin polymerization and microtubule targeting agent binding, we then highlight how the three-dimensional structures of drug-tubulin complexes obtained on stabilized tubulin are seeded by precise biological and biophysical data. New avenues opened by thermodynamics analysis, high throughput screening, and proteomics for the molecular pharmacology of these drugs are presented. The amount of data generated by biophysical, proteomic and cellular techniques shed more light onto the microtubule-tubulin equilibrium and tubulin-drug interaction. Combining these approaches provides new insight into the mechanism of action of known microtubule interacting agents and rapid in-depth characterization of next generation molecules targeting the interaction between microtubules and associated modulators of their dynamics. This will facilitate the design of improved and/or alternative chemotherapies targeting the microtubule cytoskeleton.

Magneto-optical setup for in situ strain and transport measurements on superconductors

A recently developed magneto-optical (MO) imaging setup for investigations on superconductors is reported. The main originality of our setup is its ability to combine both strain and transport measurements in the temperature range of 6-300 K with magneto-optical observations. We give here some theoretical considerations on the cryostat conception, which is a key point of our setup. In particular, the thermal and mechanical aspects are discussed. A detailed description of the MO setup and of the associated strain apparatus is given. Additionally, an example of MO strain and transport study on DyBCO coated conductors is given. Evidence of Luders Bands formation under strain in the Hastelloy is revealed by the field penetration inside cracks in the DyBCO and MgO layers. A correlation between the damaging morphology and the critical current at 70 K versus strain has been established.

[Evaluation of the analytical performances of CRP Diasys reagent on Roche Hitachi 917]

C reactive protein, the most sensible acute phase protein of inflammation and the labororatory should perform CRP testing on a continous 24 hour basis. The measurement is mainly performed by immunoturbimetry and immunonephelemetry methods available on multiparametric biochemical analyzer. In this study, we evaluated the analytical performances, precision and exactitude, of the CRP Diasys reagent on Roche Hitachi 917. The results were compared to those obtained with a CRP latex immunoassay (Roche). The reagent showed high analytical characteristics and especially a significant precision in a large range of CRP levels including low levels between 1 and 3 mg/L. Although this reagent is not considered as a high-sensitive CRP reagent, the measurement quality obtained in the 1-3 mg/L range allows an utilization as a cardiovascular risk predictor.

Structure-function relationships in the carboxylic-ester-hydrolase superfamily. Disulfide bridge arrangement in porcine intestinal glycerol-ester hydrolase

CNBr fragments from porcine intestinal glycerol-ester hydrolase were separated by SDS/PAGE under reducing and nonreducing conditions, and their amino-acid sequences were analysed. Two intra-chain disulfide bridges were identified, namely Cys70-Cys99 (loop A) and Cys256-Cys267 (loop B). As the Cys71 sulfhydryl group could not be alkylated with iodoacetamide, it is suggested that the residue is blocked rather than being present in the free form. The two disulfide bridges of intestinal glycerol-ester hydrolase are present in the cholinesterase family, although the enzyme showed only about 35% identity with these proteins. Furthermore, the finding that glycerol-ester hydrolase was partly inactivated under reducing conditions suggests that one or both disulfide bridges are important for the enzyme conformation. Lastly, glycerol-ester hydrolase was also found to hydrolyse cholinergic substrates, although residues Trp86 and Asp74 which are considered to be the main constituents of the 'anionic' subsite responsible for substrate binding in cholinesterases were absent from loop A. Other amino-acid residues in the glycerol-ester hydrolase may therefore be responsible for the binding of cholinergic substrates to the enzyme.

Purification and molecular cloning of porcine intestinal glycerol-ester hydrolase--evidence for its identity with carboxylesterase

A glycerol-ester hydrolase was purified to homogeneity from porcine intestinal mucosa using a partial delipidation method and an eight-step purification procedure. The isolation scheme used gave a 483-fold purification, resulting in a pure enzyme with a specific activity on tributyrin of 290 micromol x min(-1) x mg(-1). The molecular mass of the enzyme was estimated at 240 kDa, based on the results of size-exclusion chromatography, and at 60 kDa, as determined by SDS/PAGE analysis. The isoelectric focusing data obtained indicated that only one isoform with a pI of 5.1 was present. Complete identity was found to exist between the N-terminal sequence of the first 25 amino acid residues and that of a porcine liver carboxylesterase. A full-length cDNA coding for the enzyme was isolated from pig small intestine. We observed that the corresponding protein originally named intestinal glycerol-ester hydrolase definitely belongs to the carboxylesterase family. The deduced amino acid sequence consisted of 565 residues and showed 97% identity with that of porcine liver carboxylesterase and more than 50% identity with those of other carboxylesterases from different mammalian species.

Comparative quantitative analysis of sucrose and related compounds using ion exchange and reverse phase chromatographic methods

Two analytical methods of sugar determination, namely ion exchange chromatography on an anionic resin coupled with electrochemical detection, and reverse phase chromatography on Nucleosil-NH2 resin equipped with a light scattering detector were tested and compared as regards their rapidity, sensitivity and accuracy with sucrose, fructose, glucose, raffinose, maltose, arabinose, fucose, rhamnose and xylose. Excellent resolution and highly reproducible results were obtained in both cases. Greater sensitivity up to the picomolar range was possible however only with ion exchange chromatography. Reverse phase chromatography was successfully applied to the time course of sucrose hydrolysis under chemical (acid) and enzymatic (invertase) conditions. The hydrolysis was monitored by determining sucrose degradation and the corresponding formation of glucose and fructose.

Evaluation of a new automated ELISA test for von Willebrand factor using two monoclonal antibodies

A new automated quantitative enzyme linked immunosorbent assay (ELISA) for the detection of human von Willebrand factor (vWF), VIDAS vWF, has been developed for use on the VIDAS analyser (bioMérieux). The two-step capture/tag test relies on two monoclonal antibodies (mAbs), the second one being labelled with alkaline phosphatase. The lower limit of detection of the assay is < 1 IU/dl, and the upper limit of detection is 120 IU/dl. There is no hook effect for concentrations up to 1100 IU/dl. Intra- and inter-assay precision ranges from 3% and 5%. Assays are performed preferentially using citrated plasma and in these conditions the 95% confidence intervals for normal values are 52-154 IU/dl and 60-200 IU/dl for O blood group and non-O blood group subjects, respectively. Using the lower limits of the normal range as the cut-off level, all patients tested with type 1 (n = 29) or 3 (n = 2) von Willebrand disease (vWD) would be accurately classified with the new ELISA. Comparing the VIDAS test with a conventional ELISA gave a good correlation and comparable results with type 1 and 3 vWD patients (n = 31; r = 0.99; y = 0.99x + 0.24), type 2A and 2B vWD patients (n = 20; r = 0.99; y = 1.05x-1.65) and normal subjects (n = 204; r = 0.94; y = 1.06x-2.6).

VIDAS D-dimer: fast quantitative ELISA for measuring D-dimer in plasma

VIDAS D-dimer (bioMérieux) is a new quantitative ELISA for D-dimer determination designed for the VIDAS automated system. The test contains single-dose, ready-to-use reagents and is completed within 35 min. Quantitative results are obtained from a calibration curve stored in the software of the system and expressed as fibrinogen equivalent units. The two-step capture/tag test relies on two complementary monoclonal anti-D-dimer antibodies, the second one being labeled with alkaline phosphatase. The upper limit of the measuring range is 1000 micrograms/L and the lower detection limit is <50 micrograms/L, which is below the lower limit of the reference interval (68-494 micrograms/L). Reproducibility (CV) within and between runs ranges from 5% to 7%. There is no interference from heparin, bilirubin, hemoglobin, fibrinogen degradation products, or plasma turbidity. Comparison with a conventional ELISA (y) gave good correlation (r= 0.91, n= 579) and comparable results (y= 1.35x - 148, S(y/x)= 750), especially for D-dimer concentrations ranging from 0 to 1000 micrograms/L (y= 1.09x - 10.6, r= 0.88, S(y/x)= 170).

VIDAS D-dimer: fast quantitative ELISA for measuring D-dimer in plasma

VIDAS D-dimer (bioMérieux) is a new quantitative ELISA for D-dimer determination designed for the VIDAS automated system. The test contains single-dose, ready-to-use reagents and is completed within 35 min. Quantitative results are obtained from a calibration curve stored in the software of the system and expressed as fibrinogen equivalent units. The two-step capture/tag test relies on two complementary monoclonal anti-D-dimer antibodies, the second one being labeled with alkaline phosphatase. The upper limit of the measuring range is 1000 micrograms/L and the lower detection limit is &lt;50 micrograms/L, which is below the lower limit of the reference interval (68-494 micrograms/L). Reproducibility (CV) within and between runs ranges from 5% to 7%. There is no interference from heparin, bilirubin, hemoglobin, fibrinogen degradation products, or plasma turbidity. Comparison with a conventional ELISA (y) gave good correlation (r= 0.91, n= 579) and comparable results (y= 1.35x - 148, S(y/x)= 750), especially for D-dimer concentrations ranging from 0 to 1000 micrograms/L (y= 1.09x - 10.6, r= 0.88, S(y/x)= 170).

Comparative clinical trial of AMO Vitrax and Healon use in extracapsular cataract extraction

This randomized, single-masked, multicenter clinical trial, comprising 95 patients enrolled at five sites, evaluated the performance of AMO Vitrax and Healon viscoelastic materials during cataract surgery. Patients were examined preoperatively and at one day, four days, one month, and three months postoperatively. The following measurements were recorded and analyzed: percentage of endothelial cell loss from preoperative to three months postoperative; change in intraocular pressure (IOP) from preoperative to 24 hours postoperatively; postoperative corrected visual acuity; subjective assessment of ability of viscoelastic to create and maintain tissue space; intraocular transparency; ease of evacuation. Three months postoperatively, endothelial cell loss was 4.9% (+/- 8.3%) for the AMO Vitrax group and 6.3% (+/- 10.5%) for the Healon group. One day postoperatively, IOP decreased by 1.6 mm Hg and increased by +1.1 mm Hg, respectively. Postoperative visual acuities were similar between the two groups at three months. Subjective assessment of transparency was higher for Healon. Assessment of tissue space maintenance was similar between the two materials. Healon was rated as slightly easier to evacuate.