Statics and Dynamics of Adhesion between Two Soap Bubbles

9 pagesInternational audienceAn original set-up is used to study the adhesive properties of two hemispherical soap bubbles put into contact. The contact angle at the line connecting the three films is extracted by image analysis of the bubbles profiles. After the initial contact, the angle rapidly reaches a static value slightly larger than the standard $120$\textdegree\ angle expected from Plateau rule. This deviation is consistent with previous experimental and theoretical studies: it can be quantitatively predicted by taking into account the finite size of the Plateau border (the liquid volume trapped at the vertex) in the free energy minimization. The visco-elastic adhesion properties of the bubbles are further explored by measuring the deviation $\Delta \theta_d(t)$ of the contact angle from the static value as the distance between the two bubbles supports is sinusoidally modulated. It is found to linearly increase with $\Delta r_c/r_c$ where $r_c$ is the radius of the central film and $\Delta r_c$ the amplitude of modulation of this length induced by the displacement of the supports. The in-phase and out-of-phase components of $\Delta \theta_d(t)$ with the imposed modulation frequency are systematically probed, which reveals a transition from a viscous to an elastic response of the system with a crossover pulsation of the order $1$rad.s$^{-1}$. Independent interfacial rheological measurements, obtained from an oscillating bubble experiment, allow us to develop a model of dynamic adhesion which is confronted to our experimental results. The relevance of such adhesive dynamic properties to the rheology of foams is briefly discussed using a perturbative approach to the Princen 2D model of foams

Length-dependent anisotropic scaling of spindle shape

Spindle length varies dramatically across species and during early development to segregate chromosomes optimally. Both intrinsic factors, such as regulatory molecules, and extrinsic factors, such as cytoplasmic volume, determine spindle length scaling. However, the properties that govern spindle shape and whether these features can be modulated remain unknown. Here, we analyzed quantitatively how the molecular players which regulate microtubule dynamics control the kinetics of spindle formation and shape. We find that, in absence of Clasp1 and Clasp2, spindle assembly is biphasic due to unopposed inward pulling forces from the kinetochore-fibers and that kinetochore-fibers also alter spindle geometry. We demonstrate that spindle shape scaling is independent of the nature of the molecules that regulate dynamic microtubule properties, but is dependent on the steady-state metaphase spindle length. The shape of the spindle scales anisotropically with increasing length. Our results suggest that intrinsic mechanisms control the shape of the spindle to ensure the efficient capture and alignment of chromosomes independently of spindle length

Voltage-gated sodium channels: new targets in cancer therapy?

Early detection and treatment of cancers have increased survival and improved clinical outcome. The development of metastases is often associated with a poor prognostic of survival. Finding early markers of metastasis and developing new therapies against their development is a great challenge. Since a few years, there is more evidence that ionic channels are involved in the oncogenic process. Among these, voltage-gated sodium channels expressed in non-nervous or non-muscular organs are often associated with the metastatic behaviour of different cancers. The aim of this review is to describe the current knowledge on the functional expression of voltage-gated sodium channels and their biological roles in different cancers such as prostate, breast, lung (small cells and non-small cells) and leukaemia. In the conclusion, we develop conceptual approaches to understand how such channels can be involved in the metastatic process and conclude that blockers targeted toward these channels are promising new therapeutic solutions against metastatic cancers

Dietary long-chain omega-3 fatty acids of marine origin: a comparison of their protective effects on coronary heart disease and breast cancers.

The relationship between high fish consumption and low mortality following coronary heart disease (CHD) and low incidence of breast cancer was first mentioned 3 decades ago. The fishes of interest are rich in omega-3 long-chain polyunsaturated fatty acids (omega-3 LC-PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which could be the active nutrients. The current consensus about cardioprotection is that omega-3 LC-PUFAs would mainly exert antiarrhythmic effects. One of the proposed mechanisms is that circulating non-esterified LC-PUFAs partition into cardiac cells membrane phospholipids and exert a direct effect on ionic channels and/or modify intracellular calcium homeostasis. In another hypothesis, changes in the metabolism of phosphoinositides would be involved and lead to the differential activation of PKC isoforms. As compared to the mechanisms proposed for the cardioprotective effects of omega-3 LC-PUFAs, less is known about the molecular mechanisms involved in breast cancers prevention. Some proposed mechanisms such as the modulation of phosphoinositides metabolism and/or modulation of intracellular calcium homeostasis, are common to both pathologies. Other hypotheses involve the alteration of the cellular redox status induced by highly peroxidizable polyunsaturated fatty acids (FA), or the modulation of gene expression, both phenomena being tightly linked to apoptosis. In this review, we report and compare some proposed mechanisms for the involvement of omega-3 LC-PUFAs in both cardiac and breast cancer protection. Deliberately, we chose to discuss only the mechanisms, which are less described in other reviews such as ionic channels in cancer, calcium homeostasis, PKC activation or matrix metalloproteinases in both cancer and cardiac models. The leitmotiv along this review is that cardio- and cancero-protective effects use common pathways. Comparison of the cellular effects might therefore help to highlight the "protective" pathways

Voltage-gated sodium channels potentiate the invasive capacities of human non-small-cell lung cancer cell lines.

Ionic channel activity is involved in fundamental cellular behaviour and participates in cancerous features such as proliferation, migration and invasion which in turn contribute to the metastatic process. In this study, we investigated the expression and role of voltage-gated sodium channels in non-small-cell lung cancer cell lines. Functional voltage-gated sodium channels expression was investigated in normal and non-small-cell lung cancer cell lines. The measurement, in patch-clamp conditions, of tetrodotoxin-inhibitable sodium currents indicated that the strongly metastatic cancerous cell lines H23, H460 and Calu-1 possess functional sodium channels while normal and weakly metastatic cell lines do not. While all the cell lines expressed mRNA for numerous sodium channel isoforms, only H23, H460 and Calu-1 cells had a 250 kDa protein corresponding to the functional channel. The other cell lines also had another protein of 230 kDa which is not addressed to the membrane and might act as a dominant negative isoform to prevent channel activation. At the membrane potential of these cells, channels are partially open. This leads to a continuous entry of sodium, disrupting sodium homeostasis and down-stream signaling pathways. Inhibition of the channels by tetrodotoxin was responsible for a 40-50% reduction of in vitro invasion. These experiments suggest that the functional expression of voltage-gated sodium channels might be an integral component of the metastatic process in non-small-cell lung cancer cells probably through its involvement in the regulation of intracellular sodium homeostasis. These channels could serve both as novel markers of the metastatic phenotype and as potential new therapeutic targets

Community standards for open cell migration data

Cell migration research has become a high-content field. However, the quantitative information encapsulated in these complex and high-dimensional datasets is not fully exploited owing to the diversity of experimental protocols and non-standardized output formats. In addition, typically the datasets are not open for reuse. Making the data open and Findable, Accessible, Interoperable, and Reusable (FAIR) will enable meta-analysis, data integration, and data mining. Standardized data formats and controlled vocabularies are essential for building a suitable infrastructure for that purpose but are not available in the cell migration domain. We here present standardization efforts by the Cell Migration Standardisation Organisation (CMSO), an open community-driven organization to facilitate the development of standards for cell migration data. This work will foster the development of improved algorithms and tools and enable secondary analysis of public datasets, ultimately unlocking new knowledge of the complex biological process of cell migration

P2X7 Receptor Promotes Mouse Mammary Cancer Cell Invasiveness and Tumour Progression, and Is a Target for Anticancer Treatment

The P2X7 receptor is an ATP-gated cation channel with a still ambiguous role in cancer progression, proposed to be either pro- or anti-cancerous, depending on the cancer or cell type in the tumour. Its role in mammary cancer progression is not yet defined. Here, we show that P2X7 receptor is functional in highly aggressive mammary cancer cells, and induces a change in cell morphology with fast F-actin reorganization and formation of filopodia, and promotes cancer cell invasiveness through both 2- and 3-dimensional extracellular matrices in vitro. Furthermore, P2X7 receptor sustains Cdc42 activity and the acquisition of a mesenchymal phenotype. In an immunocompetent mouse mammary cancer model, we reveal that the expression of P2X7 receptor in cancer cells, but not in the host mice, promotes tumour growth and metastasis development, which were reduced by treatment with specific P2X7 antagonists. Our results demonstrate that P2X7 receptor drives mammary tumour progression and represents a pertinent target for mammary cancer treatment

Publishing and sharing multi-dimensional image data with OMERO

Imaging data are used in the life and biomedical sciences to measure the molecular and structural composition and dynamics of cells, tissues, and organisms. Datasets range in size from megabytes to terabytes and usually contain a combination of binary pixel data and metadata that describe the acquisition process and any derived results. The OMERO image data management platform allows users to securely share image datasets according to specific permissions levels: data can be held privately, shared with a set of colleagues, or made available via a public URL. Users control access by assigning data to specific Groups with defined membership and access rights. OMERO’s Permission system supports simple data sharing in a lab, collaborative data analysis, and even teaching environments. OMERO software is open source and released by the OME Consortium at www.openmicroscopy.org

Metadata management for high content screening in OMERO

High content screening (HCS) experiments create a classic data management challenge—multiple, large sets of heterogeneous structured and unstructured data, that must be integrated and linked to produce a set of “final” results. These different data include images, reagents, protocols, analytic output, and phenotypes, all of which must be stored, linked and made accessible for users, scientists, collaborators and where appropriate the wider community. The OME Consortium has built several open source tools for managing, linking and sharing these different types of data. The OME Data Model is a metadata specification that supports the image data and metadata recorded in HCS experiments. Bio-Formats is a Java library that reads recorded image data and metadata and includes support for several HCS screening systems. OMERO is an enterprise data management application that integrates image data, experimental and analytic metadata and makes them accessible for visualization, mining, sharing and downstream analysis. We discuss how Bio-Formats and OMERO handle these different data types, and how they can be used to integrate, link and share HCS experiments in facilities and public data repositories. OME specifications and software are open source and are available at https://www.openmicroscopy.org