Science.gov

Sample records for cell polarization processes

  1. Cell polarity

    PubMed Central

    Romereim, Sarah M

    2011-01-01

    Despite extensive genetic analysis of the dynamic multi-phase process that transforms a small population of lateral plate mesoderm into the mature limb skeleton, the mechanisms by which signaling pathways regulate cellular behaviors to generate morphogenetic forces are not known. Recently, a series of papers have offered the intriguing possibility that regulated cell polarity fine-tunes the morphogenetic process via orienting cell axes, division planes and cell movements. Wnt5a-mediated non-canonical signaling, which may include planar cell polarity, has emerged as a common thread in the otherwise distinct signaling networks that regulate morphogenesis in each phase of limb development. These findings position the limb as a key model to elucidate how global tissue patterning pathways direct local differences in cell behavior that, in turn, generate growth and form. PMID:22064549

  2. Cell polarity: mechanochemical patterning.

    PubMed

    Goehring, Nathan W; Grill, Stephan W

    2013-02-01

    Nearly every cell type exhibits some form of polarity, yet the molecular mechanisms vary widely. Here we examine what we term 'chemical systems' where cell polarization arises through biochemical interactions in signaling pathways, 'mechanical systems' where cells polarize due to forces, stresses and transport, and 'mechanochemical systems' where polarization results from interplay between mechanics and chemical signaling. To reveal potentially unifying principles, we discuss mathematical conceptualizations of several prototypical examples. We suggest that the concept of local activation and global inhibition - originally developed to explain spatial patterning in reaction-diffusion systems - provides a framework for understanding many cases of cell polarity. Importantly, we find that the core ingredients in this framework - symmetry breaking, self-amplifying feedback, and long-range inhibition - involve processes that can be chemical, mechanical, or even mechanochemical in nature. PMID:23182746

  3. Polar processing project

    NASA Astrophysics Data System (ADS)

    Tom, C. N.; Davies, W. J.; Goycochea, J. F.

    1993-09-01

    The purpose of this project was to explore the use of polar processing techniques in SIGINT-related signal processing applications. An investigation of ways to apply the CORDIC arithmetic algorithm to signal processing problems, and an application of the TMC2330 Coordinate Transformer chip in a coprocessor or accelerator board for a Sun workstation are covered.

  4. Optimization of Spin-Polarization of Helium-3 Target Cell by Thermal Convection Processes

    NASA Astrophysics Data System (ADS)

    Karthas, Stacy

    2013-10-01

    Polarized Helium-3 (3He) is an effective polarized neutron target that has been used in particle accelerators like the Thomas Jefferson National Accelerator Facility (TJNAF) for the past three decades to study properties of the neutron. Due to the spin structure of its nucleons, the nucleus of 3He can be approximated as a single polarized neutron. The previous generations of 3He targets have reached their limit in polarization and are not ideal for use as targets with the 12 GeV update at TJNAF due to large polarization gradients. The new target cell uses thermal convection to transfer polarized gas to the target chamber quickly. The focus of this project was to study the effects of the new convection system, at various gas velocities, on Adiabatic Fast Passage (AFP) polarization loss that results from measuring the polarization of 3He with Nuclear Magnetic Resonance (NMR). Gas velocities were varied by using a Kapton flexible heater to induce thermal convection. This target cell loses less than one percent of its polarization by measurement when convection is induced at a gas velocity under 6 cm/min thereby verifying the possible use of convection induction for the future experiments. Research conducted at Thomas Jefferson National Accelerator Facility funded through a grant from NSF by the Old Dominion University Research Experience for Undergraduates Program.

  5. Wnt-Dependent Control of Cell Polarity in Cultured Cells.

    PubMed

    Runkle, Kristin B; Witze, Eric S

    2016-01-01

    The secreted ligand Wnt5a regulates cell polarity and polarized cell movement during development by signaling through the poorly defined noncanonical Wnt pathway. Cell polarity regulates most aspects of cell behavior including the organization of apical/basolateral membrane domains of epithelial cells, polarized cell divisions along a directional plane, and front rear polarity during cell migration. These characteristics of cell polarity allow coordinated cell movements required for tissue formation and organogenesis during embryonic development. Genetic model organisms have been used to identify multiple signaling pathways including Wnt5a that are required to establish cell polarity and regulate polarized cell behavior. However, the downstream signaling events that regulate these complex cellular processes are still poorly understood. The methods below describe assays to study Wnt5a-induced cell polarity in cultured cells, which may facilitate our understanding of these complex signaling pathways. PMID:27590152

  6. Mitotic internalization of planar cell polarity proteins preserves tissue polarity.

    PubMed

    Devenport, Danelle; Oristian, Daniel; Heller, Evan; Fuchs, Elaine

    2011-08-01

    Planar cell polarity (PCP) is the collective polarization of cells along the epithelial plane, a process best understood in the terminally differentiated Drosophila wing. Proliferative tissues such as mammalian skin also show PCP, but the mechanisms that preserve tissue polarity during proliferation are not understood. During mitosis, asymmetrically distributed PCP components risk mislocalization or unequal inheritance, which could have profound consequences for the long-range propagation of polarity. Here, we show that when mouse epidermal basal progenitors divide PCP components are selectively internalized into endosomes, which are inherited equally by daughter cells. Following mitosis, PCP proteins are recycled to the cell surface, where asymmetry is re-established by a process reliant on neighbouring PCP. A cytoplasmic dileucine motif governs mitotic internalization of atypical cadherin Celsr1, which recruits Vang2 and Fzd6 to endosomes. Moreover, embryos transgenic for a Celsr1 that cannot mitotically internalize exhibit perturbed hair-follicle angling, a hallmark of defective PCP. This underscores the physiological relevance and importance of this mechanism for regulating polarity during cell division. PMID:21743464

  7. Symmetry breaking mechanism for epithelial cell polarization

    NASA Astrophysics Data System (ADS)

    Veglio, A.; Gamba, A.; Nicodemi, M.; Bussolino, F.; Serini, G.

    2009-09-01

    In multicellular organisms, epithelial cells form layers separating compartments responsible for different physiological functions. At the early stage of epithelial layer formation, each cell of an aggregate defines an inner and an outer side by breaking the symmetry of its initial state, in a process known as epithelial polarization. By integrating recent biochemical and biophysical data with stochastic simulations of the relevant reaction-diffusion system, we provide evidence that epithelial cell polarization is a chemical phase-separation process induced by a local bistability in the signaling network at the level of the cell membrane. The early symmetry breaking event triggering phase separation is induced by adhesion-dependent mechanical forces localized in the point of convergence of cell surfaces when a threshold number of confluent cells is reached. The generality of the emerging phase-separation scenario is likely common to many processes of cell polarity formation.

  8. Cell Polarity Proteins in Breast Cancer Progression.

    PubMed

    Rejon, Carlis; Al-Masri, Maia; McCaffrey, Luke

    2016-10-01

    Breast cancer, one of the leading causes of cancer related death in women worldwide, is a heterogeneous disease with diverse subtypes that have different properties and prognoses. The developing mammary gland is a highly proliferative and invasive tissue, and some of the developmental programs may be aberrantly activated to promote breast cancer progression. In the breast, luminal epithelial cells exhibit apical-basal polarity, and the failure to maintain this organizational structure, due to disruption of polarity complexes, is implicated in promoting hyperplasia and tumors. Therefore, understanding the mechanisms underlying loss of polarity will contribute to our knowledge of the early stages leading to the pathogenesis of the disease. In this review, we will discuss recent findings that support the idea that loss of apical-basal cell polarity is a crucial step in the acquisition of the malignant phenotype. Oncogene induced loss of tissue organization shares a conserved cellular mechanism with developmental process, we will further describe the role of the individual polarity complexes, the Par, Crumbs, and Scribble, to couple cell division orientation and cell growth. We will examine symmetric or asymmetric cell divisions in mammary stem cell and their contribution to the development of breast cancer subtypes and cancer stem cells. Finally, we will highlight some of the recent advances in our understanding of the molecular mechanisms by which changes in epithelial polarity programs promote invasion and metastasis through single cell and collective cell modes. J. Cell. Biochem. 117: 2215-2223, 2016. © 2016 Wiley Periodicals, Inc. PMID:27362918

  9. The cell biology of planar cell polarity

    PubMed Central

    2014-01-01

    Planar cell polarity (PCP) refers to the coordinated alignment of cell polarity across the tissue plane. Key to the establishment of PCP is asymmetric partitioning of cortical PCP components and intercellular communication to coordinate polarity between neighboring cells. Recent progress has been made toward understanding how protein transport, endocytosis, and intercellular interactions contribute to asymmetric PCP protein localization. Additionally, the functions of gradients and mechanical forces as global cues that bias PCP orientation are beginning to be elucidated. Together, these findings are shedding light on how global cues integrate with local cell interactions to organize cellular polarity at the tissue level. PMID:25349257

  10. Profiling Signaling Polarity in Chemotactic Cells

    SciTech Connect

    Wang, Yingchun; Ding, Shi-Jian; Wang, Wei; Jacobs, Jon M.; Qian, Weijun; Moore, Ronald J.; Yang, Feng; Camp, David G.; Smith, Richard D.; Klemke, Richard L.

    2007-05-15

    While directional movement requires morphological polarization characterized by formation of a leading pseudopodium at the front and a trailing rear at the back, little is known about how protein networks are spatially integrated to regulate this process. Here, we utilize a unique pseudopodial purification system and quantitative proteomics and phosphoproteomics to map the spatial relationship of 3509 proteins and 228 distinct sites of phosphorylation in polarized cells. Networks of signaling proteins, metabolic pathways, actin regulatory proteins, and kinase-substrate cascades were found to partition to different poles of the cell including components of the Ras/ERK pathway. Also, several novel proteins were found to be differentially phosphorylated at the front or rear of polarized cells and to localize to distinct subcellular structures. Our findings provide insight into the spatial organization of signaling networks that control cell movement and provide a comprehensive profile of proteins and their sites of phosphorylation that control cell polarization.

  11. Integrins and epithelial cell polarity

    PubMed Central

    Lee, Jessica L.; Streuli, Charles H.

    2014-01-01

    ABSTRACT Cell polarity is characterised by differences in structure, composition and function between at least two poles of a cell. In epithelial cells, these spatial differences allow for the formation of defined apical and basal membranes. It has been increasingly recognised that cell–matrix interactions and integrins play an essential role in creating epithelial cell polarity, although key gaps in our knowledge remain. This Commentary will discuss the mounting evidence for the role of integrins in polarising epithelial cells. We build a model in which both inside-out signals to polarise basement membrane assembly at the basal surface, and outside-in signals to control microtubule apical–basal orientation and vesicular trafficking are required for establishing and maintaining the orientation of epithelial cell polarity. Finally, we discuss the relevance of the basal integrin polarity axis to cancer. This article is part of a Minifocus on Establishing polarity. For further reading, please see related articles: ‘ERM proteins at a glance’ by Andrea McClatchey (J. Cell Sci. 127, 3199–3204). ‘Establishment of epithelial polarity – GEF who's minding the GAP?’ by Siu Ngok et al. (J. Cell Sci. 127, 3205–3215). PMID:24994933

  12. Tissue morphodynamics: Translating planar polarity cues into polarized cell behaviors.

    PubMed

    Devenport, Danelle

    2016-07-01

    The ability of cells to collectively orient and align their behaviors is essential in multicellular organisms for unidirectional cilia beating, collective cell movements, oriented cell divisions, and asymmetric cell fate specification. The planar cell polarity pathway coordinates a vast and diverse array of collective cell behaviors by intersecting with downstream pathways that regulate cytoskeletal dynamics and intercellular signaling. How the planar polarity pathway translates directional cues to produce polarized cell behaviors is the focus of this review. PMID:26994528

  13. Polarized Cell Division of Chlamydia trachomatis.

    PubMed

    Abdelrahman, Yasser; Ouellette, Scot P; Belland, Robert J; Cox, John V

    2016-08-01

    Bacterial cell division predominantly occurs by a highly conserved process, termed binary fission, that requires the bacterial homologue of tubulin, FtsZ. Other mechanisms of bacterial cell division that are independent of FtsZ are rare. Although the obligate intracellular human pathogen Chlamydia trachomatis, the leading bacterial cause of sexually transmitted infections and trachoma, lacks FtsZ, it has been assumed to divide by binary fission. We show here that Chlamydia divides by a polarized cell division process similar to the budding process of a subset of the Planctomycetes that also lack FtsZ. Prior to cell division, the major outer-membrane protein of Chlamydia is restricted to one pole of the cell, and the nascent daughter cell emerges from this pole by an asymmetric expansion of the membrane. Components of the chlamydial cell division machinery accumulate at the site of polar growth prior to the initiation of asymmetric membrane expansion and inhibitors that disrupt the polarity of C. trachomatis prevent cell division. The polarized cell division of C. trachomatis is the result of the unipolar growth and FtsZ-independent fission of this coccoid organism. This mechanism of cell division has not been documented in other human bacterial pathogens suggesting the potential for developing Chlamydia-specific therapeutic treatments. PMID:27505160

  14. Polarized Cell Division of Chlamydia trachomatis

    PubMed Central

    Abdelrahman, Yasser; Ouellette, Scot P.; Belland, Robert J.; Cox, John V.

    2016-01-01

    Bacterial cell division predominantly occurs by a highly conserved process, termed binary fission, that requires the bacterial homologue of tubulin, FtsZ. Other mechanisms of bacterial cell division that are independent of FtsZ are rare. Although the obligate intracellular human pathogen Chlamydia trachomatis, the leading bacterial cause of sexually transmitted infections and trachoma, lacks FtsZ, it has been assumed to divide by binary fission. We show here that Chlamydia divides by a polarized cell division process similar to the budding process of a subset of the Planctomycetes that also lack FtsZ. Prior to cell division, the major outer-membrane protein of Chlamydia is restricted to one pole of the cell, and the nascent daughter cell emerges from this pole by an asymmetric expansion of the membrane. Components of the chlamydial cell division machinery accumulate at the site of polar growth prior to the initiation of asymmetric membrane expansion and inhibitors that disrupt the polarity of C. trachomatis prevent cell division. The polarized cell division of C. trachomatis is the result of the unipolar growth and FtsZ-independent fission of this coccoid organism. This mechanism of cell division has not been documented in other human bacterial pathogens suggesting the potential for developing Chlamydia-specific therapeutic treatments. PMID:27505160

  15. ΔF508 CFTR processing correction and activity in polarized airway and non-airway cell monolayers

    PubMed Central

    Rowe, SM; Pyle, LC; Jurkevante, A; Varga, K; Collawn, J; Sloane, PA; Woodworth, B; Mazur, M; Fulton, J; Fan, L; Li, Y; Fortenberry, J; Sorscher, EJ; Clancy, JP

    2010-01-01

    We examined the activity of ΔF508 cystic fibrosis transmembrane conductance regulator (CFTR) stably expressed in polarized cystic fibrosis bronchial epithelial cells (CFBE41o−) human airway cells and Fisher Rat Thyroid (FRT) cells following treatment with low temperature and a panel of small molecule correctors of ΔF508 CFTR misprocessing. Corr-4a increased ΔF508 CFTR-dependent Cl− conductance in both cell types, whereas treatment with VRT-325 or VRT-640 increased activity only in FRT cells. Total currents stimulated by forskolin and genistein demonstrated similar dose/response effects to Corr-4a treatment in each cell type. When examining the relative contribution of forskolin and genistein to total stimulated current, CFBE41o− cells had smaller forskolin-stimulated Isc following either low temperature or corr-4a treatment (10–30% of the total Isc produced by the combination of both CFTR agonists). In contrast, forskolin consistently contributed greater than 40% of total Isc in ΔF508 CFTR expressing FRT cells corrected with low temperature, and corr-4a treatment preferentially enhanced forskolin dependent currents only in FRT cells (60% of total Isc). ΔF508 CFTR cDNA transcript levels, ΔF508 CFTR C band levels, or cAMP signaling did not account for the reduced forskolin response in CFBE41o− cells. Treatment with non-specific inhibitors of phosphodiesterases (papaverine) or phosphatases (endothall) did not restore ΔF508 CFTR activation by forskolin in CFBE41o− cells, indicating that the Cl− transport defect in airway cells is distal to cAMP or its metabolism. The results identify important differences in ΔF508 CFTR activation in polarizing epithelial models of CF, and have important implications regarding detection of rescued of ΔF508 CFTR in vivo. PMID:20226262

  16. A gas cell for stopping, storing and polarizing radioactive particles

    NASA Astrophysics Data System (ADS)

    Sytema, A.; van den Berg, J. E.; Böll, O.; Chernowitz, D.; Dijck, E. A.; Grasdijk, J. O.; Hoekstra, S.; Jungmann, K.; Mathavan, S. C.; Meinema, C.; Mohanty, A.; Müller, S. E.; Nuñez Portela, M.; Onderwater, C. J. G.; Pijpker, C.; Willmann, L.; Wilschut, H. W.

    2016-06-01

    A radioactive beam of 20Na is stopped in a gas cell filled with Ne gas. The stopped particles are polarized by optical pumping. The degree of polarization that can be achieved is studied. A maximum polarization of 50% was found. The dynamic processes in the cell are described with a phenomenological model.

  17. Polarized cytokinesis in vacuolate cells of Arabidopsis

    PubMed Central

    Cutler, Sean R.; Ehrhardt, David W.

    2002-01-01

    The view of plant-cell cytokinesis commonly depicted in textbooks is of a symmetrical process, with the phragmoplast initiating in the center of the cell and growing outward to the parental cell membrane. In contrast to this picture, we observe that cell-plate development in Arabidopsis shoot cells is highly polarized along the plane of division. Three-dimensional live-cell imaging reveals that the mitotic spindle and phragmoplast are laterally displaced, and that the growing cell plate anchors on one side of the cell at an early stage of cytokinesis. Growth of phragmoplast across the cell creates a new partition in its wake, giving the visual effect of a curtain being pulled across the cell. Throughout this process, the advancing front of the phragmoplast is in intimate contact with the parental wall, suggesting that short-range interactions between the phragmoplast and plasma membrane may play important roles in guiding the cell plate throughout much of its development. Polarized cytokinesis was observed in a wide variety of vacuolate shoot cells and in some small root cells, implying that it is not solely a function of cell size. This mode of cytokinesis may provide a mechanically robust mechanism for cell-plate formation in large cells and suggests a simple explanation for the occurrence of cell wall stubs observed upon drug treatment or in cytokinetic mutants. PMID:11880633

  18. Organic photovoltaic cells with controlled polarization sensitivity

    SciTech Connect

    Awartani, Omar; O'Connor, Brendan T.; Kudenov, Michael W.

    2014-03-03

    In this study, we demonstrate linearly polarized organic photovoltaic cells with a well-controlled level of polarization sensitivity. The polarized devices were created through the application of a large uniaxial strain to the bulk heterojunction poly(3-hexylthiophene):Phenyl-C61-butyric acid methyl ester (P3HT:PCBM) film and printing the plastically deformed active layer onto a PEDOT:PSS and indium tin oxide coated glass substrate. The P3HT:PCBM layer is processed such that it is able to accommodate high strains (over 100%) without fracture. After printing the strained films, thermal annealing is used to optimize solar cell performance while maintaining polarization sensitivity. A dichroic ratio and short circuit current ratio of ≈6.1 and ≈1.6 were achieved, respectively.

  19. Processing Polarity Items: Contrastive Licensing Costs

    ERIC Educational Resources Information Center

    Saddy, Douglas; Drenhaus, Heiner; Frisch, Stefan

    2004-01-01

    We describe an experiment that investigated the failure to license polarity items in German using event-related brain potentials (ERPs). The results reveal distinct processing reflexes associated with failure to license positive polarity items in comparison to failure to license negative polarity items. Failure to license both negative and…

  20. Cell Polarization and Cytokinesis in Budding Yeast

    PubMed Central

    Bi, Erfei; Park, Hay-Oak

    2012-01-01

    Asymmetric cell division, which includes cell polarization and cytokinesis, is essential for generating cell diversity during development. The budding yeast Saccharomyces cerevisiae reproduces by asymmetric cell division, and has thus served as an attractive model for unraveling the general principles of eukaryotic cell polarization and cytokinesis. Polarity development requires G-protein signaling, cytoskeletal polarization, and exocytosis, whereas cytokinesis requires concerted actions of a contractile actomyosin ring and targeted membrane deposition. In this chapter, we discuss the mechanics and spatial control of polarity development and cytokinesis, emphasizing the key concepts, mechanisms, and emerging questions in the field. PMID:22701052

  1. Physical processes in spin polarized plasmas

    SciTech Connect

    Kulsrud, R.M.; Valeo, E.J.; Cowley, S.

    1984-05-01

    If the plasma in a nuclear fusion reactor is polarized, the nuclear reactions are modified in such a way as to enhance the reactor performance. We calculate in detail the modification of these nuclear reactions by different modes of polarization of the nuclear fuel. We also consider in detail the various physical processes that can lead to depolarization and show that they are by and large slow enough that a high degree of polarization can be maintained.

  2. The interdependence of the Rho GTPases and apicobasal cell polarity

    PubMed Central

    Mack, Natalie Ann; Georgiou, Marios

    2014-01-01

    Signaling via the Rho GTPases provides crucial regulation of numerous cell polarization events, including apicobasal (AB) polarity, polarized cell migration, polarized cell division and neuronal polarity. Here we review the relationships between the Rho family GTPases and epithelial AB polarization events, focusing on the 3 best-characterized members: Rho, Rac and Cdc42. We discuss a multitude of processes that are important for AB polarization, including lumen formation, apical membrane specification, cell-cell junction assembly and maintenance, as well as tissue polarity. Our discussions aim to highlight the immensely complex regulatory mechanisms that encompass Rho GTPase signaling during AB polarization. More specifically, in this review we discuss several emerging common themes, that include: 1) the need for Rho GTPase activities to be carefully balanced in both a spatial and temporal manner through a multitude of mechanisms; 2) the existence of signaling feedback loops and crosstalk to create robust cellular responses; and 3) the frequent multifunctionality that exists among AB polarity regulators. Regarding this latter theme, we provide further discussion of the potential plasticity of the cell polarity machinery and as a result the possible implications for human disease. PMID:25469537

  3. The interdependence of the Rho GTPases and apicobasal cell polarity.

    PubMed

    Mack, Natalie Ann; Georgiou, Marios

    2014-01-01

    Signaling via the Rho GTPases provides crucial regulation of numerous cell polarization events, including apicobasal (AB) polarity, polarized cell migration, polarized cell division and neuronal polarity. Here we review the relationships between the Rho family GTPases and epithelial AB polarization events, focusing on the 3 best-characterized members: Rho, Rac and Cdc42. We discuss a multitude of processes that are important for AB polarization, including lumen formation, apical membrane specification, cell-cell junction assembly and maintenance, as well as tissue polarity. Our discussions aim to highlight the immensely complex regulatory mechanisms that encompass Rho GTPase signaling during AB polarization. More specifically, in this review we discuss several emerging common themes, that include: 1) the need for Rho GTPase activities to be carefully balanced in both a spatial and temporal manner through a multitude of mechanisms; 2) the existence of signaling feedback loops and crosstalk to create robust cellular responses; and 3) the frequent multifunctionality that exists among AB polarity regulators. Regarding this latter theme, we provide further discussion of the potential plasticity of the cell polarity machinery and as a result the possible implications for human disease. PMID:25469537

  4. Sterol-Rich Membrane Domains Define Fission Yeast Cell Polarity.

    PubMed

    Makushok, Tatyana; Alves, Paulo; Huisman, Stephen Michiel; Kijowski, Adam Rafal; Brunner, Damian

    2016-05-19

    Cell polarization is crucial for the functioning of all organisms. The cytoskeleton is central to the process but its role in symmetry breaking is poorly understood. We study cell polarization when fission yeast cells exit starvation. We show that the basis of polarity generation is de novo sterol biosynthesis, cell surface delivery of sterols, and their recruitment to the cell poles. This involves four phases occurring independent of the polarity factor cdc42p. Initially, multiple, randomly distributed sterol-rich membrane (SRM) domains form at the plasma membrane, independent of the cytoskeleton and cell growth. These domains provide platforms on which the growth and polarity machinery assembles. SRM domains are then polarized by the microtubule-dependent polarity factor tea1p, which prepares for monopolar growth initiation and later switching to bipolar growth. SRM polarization requires F-actin but not the F-actin organizing polarity factors for3p and bud6p. We conclude that SRMs are key to cell polarization. PMID:27180904

  5. Apicobasal polarity of brain endothelial cells.

    PubMed

    Worzfeld, Thomas; Schwaninger, Markus

    2016-02-01

    Normal brain homeostasis depends on the integrity of the blood-brain barrier that controls the access of nutrients, humoral factors, and immune cells to the CNS. The blood-brain barrier is composed mainly of brain endothelial cells. Forming the interface between two compartments, they are highly polarized. Apical/luminal and basolateral/abluminal membranes differ in their lipid and (glyco-)protein composition, allowing brain endothelial cells to secrete or transport soluble factors in a polarized manner and to maintain blood flow. Here, we summarize the basic concepts of apicobasal cell polarity in brain endothelial cells. To address potential molecular mechanisms underlying apicobasal polarity in brain endothelial cells, we draw on investigations in epithelial cells and discuss how polarity may go awry in neurological diseases. PMID:26661193

  6. Epithelial Cell Polarity Determinant CRB3 in Cancer Development

    PubMed Central

    Li, Pingping; Mao, Xiaona; Ren, Yu; Liu, Peijun

    2015-01-01

    Cell polarity, which is defined as asymmetry in cell shape, organelle distribution and cell function, is essential in numerous biological processes, including cell growth, cell migration and invasion, molecular transport, and cell fate. Epithelial cell polarity is mainly regulated by three conserved polarity protein complexes, the Crumbs (CRB) complex, partitioning defective (PAR) complex and Scribble (SCRIB) complex. Research evidence has indicated that dysregulation of cell polarity proteins may play an important role in cancer development. Crumbs homolog 3 (CRB3), a member of the CRB complex, may act as a cancer suppressor in mouse kidney epithelium and mouse mammary epithelium. In this review, we focus on the current data available on the roles of CRB3 in cancer development. PMID:25552927

  7. Processing of polarized light by squid photoreceptors.

    PubMed

    Saidel, W M; Lettvin, J Y; MacNichol, E F

    Behavioural tests have demonstrated that cephalopods can discriminate light polarized in different planes, and the receptors have been localized by electrophysiological studies of the eye. Discrimination of the plane of polarization is a consequence of both the structure of the microvilli in the outer segments of the photoreceptors and the orientation of the photosensitive chromophore on these membranes. However, between the depolarizing receptor response resulting from photoreception and the behaviour of the animal, nothing is known about neuronal processing of polarized light by cephalopods. Here we show that some squid photoreceptors discriminate the plane of polarization within the spike train, and that any particular plane is seen as a variable intensity. Given the well known orthogonal orientation of microvilli in outer segments of adjacent photoreceptors and the physiological preference for one of two mutually perpendicular planes of polarization by single photoreceptors, we conclude that cephalopod vision is based on two complementary views of the world, each determined by the transformation of polarization-sensitive receptors into complementary intensity scales. A visual system based on this transformation would lead to enhanced contrast underwater and visualization of object details obscured by confounding highlights. PMID:6877374

  8. Rebuilding cytoskeleton roads: Active-transport-induced polarization of cells

    NASA Astrophysics Data System (ADS)

    Hawkins, R. J.; Bénichou, O.; Piel, M.; Voituriez, R.

    2009-10-01

    Many cellular processes require a polarization axis which generally initially emerges as an inhomogeneous distribution of molecular markers in the cell. We present a simple analytical model of a general mechanism of cell polarization taking into account the positive feedback due to the coupled dynamics of molecular markers and cytoskeleton filaments. We find that the geometry of the organization of cytoskeleton filaments, nucleated on the membrane (e.g., cortical actin) or from a center in the cytoplasm (e.g., microtubule asters), dictates whether the system is capable of spontaneous polarization or polarizes only in response to external asymmetric signals. Our model also captures the main features of recent experiments of cell polarization in two considerably different biological systems, namely, mating budding yeast and neuron growth cones.

  9. Mechanics and polarity in cell motility

    NASA Astrophysics Data System (ADS)

    Ambrosi, D.; Zanzottera, A.

    2016-09-01

    The motility of a fish keratocyte on a flat substrate exhibits two distinct regimes: the non-migrating and the migrating one. In both configurations the shape is fixed in time and, when the cell is moving, the velocity is constant in magnitude and direction. Transition from a stable configuration to the other one can be produced by a mechanical or chemotactic perturbation. In order to point out the mechanical nature of such a bistable behaviour, we focus on the actin dynamics inside the cell using a minimal mathematical model. While the protein diffusion, recruitment and segregation govern the polarization process, we show that the free actin mass balance, driven by diffusion, and the polymerized actin retrograde flow, regulated by the active stress, are sufficient ingredients to account for the motile bistability. The length and velocity of the cell are predicted on the basis of the parameters of the substrate and of the cell itself. The key physical ingredient of the theory is the exchange among actin phases at the edges of the cell, that plays a central role both in kinematics and in dynamics.

  10. International Polar Orbiter Processing Package (IPOPP)

    NASA Astrophysics Data System (ADS)

    Overton, J.; Fesenger, G.; Reed, B.; Thomas, W.

    2009-12-01

    In 1994, the United States merged its two polar-orbiting operational environmental satellite programs operated by the Department of Commerce and the Department of Defense respectively into a single system which is called the National Polar-orbiting Operational Environmental Satellite System (NPOESS). NPOESS is a tri-agency program comprised of the Department of Defense, the Department of Commerce and the National Aeronautics and Space Administration. NPOESS is managed by the Integrated Program Office (IPO) that is staffed by personnel from the three sponsoring agencies. The IPO is working with prime contractor Northrop Grumman Aerospace Systems (NGAS) and its subcontractors to develop, launch, and operate NPOESS. The first NPOESS satellite which is planned for 2013 will be preceded by a risk reduction mission named the NPOESS Preparatory Project (NPP) that is planned for launch in 2010. The International Polar Orbiter Processing Package (IPOPP) is a software package that will enable the Direct Readout user community to smoothly transition from the Earth Observing System (EOS) to the NPOESS. IPOPP will host US Government sanctioned algorithms that will enable the Direct Broadcast (DB) community to process, visualize, and evaluate Polar Orbiter Sensor and Environmental Data Records (starting with the Moderate Resolution Imaging Spectroradiometer (MODIS) and the NPP missions). The IPOPP development approach is to start with a framework that uses a Science Processing Algorithm (SPA) wrapping technique that allows a modular implementation to envelop sensor unique algorithms thus making IPOPP a multi-mission processing package. As a multi-platform processing package, IPOPP will meet the high expectations of the Direct Broadcast community for mission continuity from EOS to NPOESS, enable a global feedback loop for NPP Cal/Val campaigns, and initiate the role of the research to operations provider for the Direct Readout Mission.

  11. Defective planar cell polarity in polycystic kidney disease.

    PubMed

    Fischer, Evelyne; Legue, Emilie; Doyen, Antonia; Nato, Faridabano; Nicolas, Jean-François; Torres, Vicente; Yaniv, Moshe; Pontoglio, Marco

    2006-01-01

    Morphogenesis involves coordinated proliferation, differentiation and spatial distribution of cells. We show that lengthening of renal tubules is associated with mitotic orientation of cells along the tubule axis, demonstrating intrinsic planar cell polarization, and we demonstrate that mitotic orientations are significantly distorted in rodent polycystic kidney models. These results suggest that oriented cell division dictates the maintenance of constant tubule diameter during tubular lengthening and that defects in this process trigger renal tubular enlargement and cyst formation. PMID:16341222

  12. Lobe cell convection and polar cap precipitation

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Peria, W. J.; Bonnell, J. W.; Su, Y.-J.; Ergun, R. E.; Tung, Y.-K.; Parks, G. K.; Carlson, C. W.

    2003-05-01

    The characteristic electric and magnetic field signature of lobe cells as observed by the low-altitude FAST satellite in 55 dawn-dusk passes are compared with Polar ultraviolet images of polar cap auroral activity. Initial results from 34 events of UV image coverage suggest that there is an intimate coupling between the sunward convection flow of the lobe cell and transpolar auroral arcs or diffuse polar cap precipitation in ˜62% of these cases. However, in some cases where the field signatures are suggestive of lobe cell convection, there is no detectable particle precipitation either in Polar UVI or the FAST data sets. Moreover, the presence of lobe cells coincide with UV data intensifications in the premidnight 2000-2400 MLT sector and/or the postnoon 1500 MLT region in ˜59% of all cases with UVI coverage. The magnetic local time dependence of the lobe cells and polar cap precipitation on the interplanetary magnetic field (IMF) are examined using the upstream Wind monitor. The relative importance of the IMF By and Bz components are investigated and compared with the predictions of the antiparallel merging model and strongly suggests a connection with the magnetospheric sash, as is further implied by the mapping of magnetic field lines using the [2002] (T01) model. It was also noted that a majority of lobe cell events occurred during enhanced AE index substorm-like conditions and that generally stronger AE indices are measured for stronger IMF By magnitudes during these events.

  13. Genetic control of polar cell expansion in Arabidopsis thaliana

    SciTech Connect

    Schiefelbein, J.; Ford, S. ); Somerville, C. )

    1990-05-01

    Certain plant cells, like root hairs and pollen tubes, exhibit polar cell growth, with expansion limited to the tip of the growing cell. In order to understand the mechanisms regulating polar cell expansion, we are studying the process of root hair elongation in Arabidopsis thaliana. By visually screening roots from 12,000 mutagenized Arabidopsis seedlings on Petri dishes, more than 40 root hair mutants have been identified. We have focused our attention on mutants that possess nuclear recessive mutations in three genes (RHD2, RHD3, and RDH4) that appear to be involved in controlling polar cell growth in root hairs. We are currently using cellular, genetic, and molecular approaches to understand these genes' normal roles in root hair elongation.

  14. Kif26b controls endothelial cell polarity through the Dishevelled/Daam1-dependent planar cell polarity-signaling pathway.

    PubMed

    Guillabert-Gourgues, Aude; Jaspard-Vinassa, Beatrice; Bats, Marie-Lise; Sewduth, Raj N; Franzl, Nathalie; Peghaire, Claire; Jeanningros, Sylvie; Moreau, Catherine; Roux, Etienne; Larrieu-Lahargue, Frederic; Dufourcq, Pascale; Couffinhal, Thierry; Duplàa, Cecile

    2016-03-15

    Angiogenesis involves the coordinated growth and migration of endothelial cells (ECs) toward a proangiogenic signal. The Wnt planar cell polarity (PCP) pathway, through the recruitment of Dishevelled (Dvl) and Dvl-associated activator of morphogenesis (Daam1), has been proposed to regulate cell actin cytoskeleton and microtubule (MT) reorganization for oriented cell migration. Here we report that Kif26b-a kinesin-and Daam1 cooperatively regulate initiation of EC sprouting and directional migration via MT reorganization. First, we find that Kif26b is recruited within the Dvl3/Daam1 complex. Using a three-dimensional in vitro angiogenesis assay, we show that Kif26b and Daam1 depletion impairs tip cell polarization and destabilizes extended vascular processes. Kif26b depletion specifically alters EC directional migration and mislocalized MT organizing center (MTOC)/Golgi and myosin IIB cell rear enrichment. Therefore the cell fails to establish a proper front-rear polarity. Of interest, Kif26b ectopic expression rescues the siDaam1 polarization defect phenotype. Finally, we show that Kif26b functions in MT stabilization, which is indispensable for asymmetrical cell structure reorganization. These data demonstrate that Kif26b, together with Dvl3/Daam1, initiates cell polarity through the control of PCP signaling pathway-dependent activation. PMID:26792835

  15. Cellular Polarization and Contractility in Collective Cell Migration

    NASA Astrophysics Data System (ADS)

    Utuje, Kazage J. Christophe; Notbohm, Jacob; Banerjee, Shiladitya; Gweon, Bomi; Jang, Hwanseok; Park, Yongdoo; Shin, Jennifer; Butler, James P.; Fredberg, Jeffrey J.; Marchetti, M. Cristina

    Collective cell migration drives many biological processes such as metastasis, morphogenesis and wound healing. These coordinated motions are driven by active forces. The physical nature of these forces and the mechanisms by which they generate collective cell migration are still not fully understood. We have developed a minimum physical model of a cell monolayer as an elastic continuum whose deformation field is coupled to two internal degrees of freedom: the concentration of a chemical signal, controlling cell Contractility, and the polarization field controlling the direction of local cell motion. By combining theory with experiments, we show that these two internal variables account for the sloshing waves and the systematic deviations of the direction of cell polarization from that of local cell velocity observed in confined cell monolayers. KJCU and MCM were supported by the Simons Foundation.

  16. Module level solutions to solar cell polarization

    DOEpatents

    Xavier, Grace , Li; Bo

    2012-05-29

    A solar cell module includes interconnected solar cells, a transparent cover over the front sides of the solar cells, and a backsheet on the backsides of the solar cells. The solar cell module includes an electrical insulator between the transparent cover and the front sides of the solar cells. An encapsulant protectively packages the solar cells. To prevent polarization, the insulator has resistance suitable to prevent charge from leaking from the front sides of the solar cells to other portions of the solar cell module by way of the transparent cover. The insulator may be attached (e.g., by coating) directly on an underside of the transparent cover or be a separate layer formed between layers of the encapsulant. The solar cells may be back junction solar cells.

  17. Adaptation of core mechanisms to generate cell polarity

    PubMed Central

    Nelson, W. James

    2012-01-01

    Cell polarity is defined as asymmetry in cell shape, protein distributions and cell functions. It is characteristic of single-cell organisms, including yeast and bacteria, and cells in tissues of multi-cell organisms such as epithelia in worms, flies and mammals. This diversity raises several questions: do different cell types use different mechanisms to generate polarity, how is polarity signalled, how do cells react to that signal, and how is structural polarity translated into specialized functions? Analysis of evolutionarily diverse cell types reveals that cell-surface landmarks adapt core pathways for cytoskeleton assembly and protein transport to generate cell polarity. PMID:12700771

  18. Modeling the Control of Planar Cell Polarity

    PubMed Central

    Axelrod, Jeffrey D.; Tomlin, Claire J.

    2016-01-01

    A growing list of medically important developmental defects and disease mechanisms can be traced to disruption of the Planar Cell Polarity (PCP) pathway. The PCP system polarizes cells in epithelial sheets along an axis orthogonal to their apical-basal axis. Studies in the fruitfly, Drosophila, have led to the concept of a modular system controlling PCP. The components of the PCP signaling modules, and the effector systems with which they interact, function together to produce emergent patterns. Experimental methods allow the manipulation of individual PCP signaling molecules in specified groups of cells; these interventions not only perturb the polarization of the targeted cells at a subcellular level, but also perturb patterns of polarity at the multicellular level, often affecting nearby cells in characteristic ways. These kinds of experiments should, in principle, allow one to infer the architecture within and between modules, but the relationships between molecular interactions and tissue-level pattern are sufficiently complex that they defy intuitive understanding. Mathematical modeling has been an important tool to address these problems. This review explores the emergence of a local signaling hypothesis, and describes how a local intercellular signal, coupled with a directional cue, can give rise to global pattern. We will discuss the critical role mathematical modeling has played in guiding and interpreting experimental results, and speculate about future roles for mathematical modeling of PCP. Mathematical models at varying levels of abstraction have and are expected to continue contributing in distinct ways to understanding the regulation of PCP signaling. PMID:21755606

  19. ROS Regulation of Polar Growth in Plant Cells.

    PubMed

    Mangano, Silvina; Juárez, Silvina Paola Denita; Estevez, José M

    2016-07-01

    Root hair cells and pollen tubes, like fungal hyphae, possess a typical tip or polar cell expansion with growth limited to the apical dome. Cell expansion needs to be carefully regulated to produce a correct shape and size. Polar cell growth is sustained by oscillatory feedback loops comprising three main components that together play an important role regulating this process. One of the main components are reactive oxygen species (ROS) that, together with calcium ions (Ca(2+)) and pH, sustain polar growth over time. Apoplastic ROS homeostasis controlled by NADPH oxidases as well as by secreted type III peroxidases has a great impact on cell wall properties during cell expansion. Polar growth needs to balance a focused secretion of new materials in an extending but still rigid cell wall in order to contain turgor pressure. In this review, we discuss the gaps in our understanding of how ROS impact on the oscillatory Ca(2+) and pH signatures that, coordinately, allow root hair cells and pollen tubes to expand in a controlled manner to several hundred times their original size toward specific signals. PMID:27208283

  20. ROS Regulation of Polar Growth in Plant Cells1[OPEN

    PubMed Central

    Mangano, Silvina; Juárez, Silvina Paola Denita

    2016-01-01

    Root hair cells and pollen tubes, like fungal hyphae, possess a typical tip or polar cell expansion with growth limited to the apical dome. Cell expansion needs to be carefully regulated to produce a correct shape and size. Polar cell growth is sustained by oscillatory feedback loops comprising three main components that together play an important role regulating this process. One of the main components are reactive oxygen species (ROS) that, together with calcium ions (Ca2+) and pH, sustain polar growth over time. Apoplastic ROS homeostasis controlled by NADPH oxidases as well as by secreted type III peroxidases has a great impact on cell wall properties during cell expansion. Polar growth needs to balance a focused secretion of new materials in an extending but still rigid cell wall in order to contain turgor pressure. In this review, we discuss the gaps in our understanding of how ROS impact on the oscillatory Ca2+ and pH signatures that, coordinately, allow root hair cells and pollen tubes to expand in a controlled manner to several hundred times their original size toward specific signals. PMID:27208283

  1. Search for Polarization Effects in the Antiproton Production Process

    DOE PAGESBeta

    Grzonka, D.; Kilian, K.; Ritman, J.; Sefzick, T.; Oelert, W.; Diermaier, M.; Widmann, E.; Zmeskal, J.; Głowacz, B.; Moskal, P.; et al

    2015-01-01

    For the production of a polarized antiproton beam, various methods have been suggested including the possibility that antiprotons may be produced polarized which will be checked experimentally. The polarization of antiprotons produced under typical conditions for antiproton beam preparation will be measured at the CERN/PS. If the production process creates some polarization, a polarized antiproton beam could be prepared by a rather simple modification of the antiproton beam facility. The detection setup and the expected experimental conditions are described.

  2. Lobe Cell Convection and Polar cap Precipitation

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Peria, W. J.; Su, Y.; Ergun, R. E.; Tung, Y.; Parks, G.; Carlson, C. W.

    2002-12-01

    The characteristic electric and magnetic field signature of lobe cells as observed by the low-altitude FAST satellite are compared with Polar ultraviolet images of polar cap auroral activity. Initial results from 55 events suggest that there is an intimate coupling between the sunward convection flow of the lobe cell and transpolar auroral arcs or diffuse polar cap precipitation. Moreover, the presence of lobe cells coincide with UV data intensifications in the premidnight 2100-2400 MLT sector and/or the postnoon 1500 MLT region in ~54% of all cases with UVI coverage. The magnetic local time dependence of the lobe cells and polar cap precipitation on the interplanetary magnetic field (IMF) are examined using the upstream Wind monitor. The relative importance of the IMF By and Bz components are investigated and compared with the predictions of the antiparallel merging model and strongly suggests a connection with the magnetospheric sash, as is further implied by the mapping of magnetic field lines using the Tsyganenko [2002] (T01) model. It was also noted that a majority of events occurred during enhanced AE index substorm-like conditions and that generally stronger AE indices are measured for stronger IMF By magnitudes.

  3. Epithelial organization, cell polarity and tumorigenesis.

    PubMed

    McCaffrey, Luke Martin; Macara, Ian G

    2011-12-01

    Epithelial cells comprise the foundation for the majority of organs in the mammalian body, and are the source of approximately 90% of all human cancers. Characteristically, epithelial cells form intercellular adhesions, exhibit apical/basal polarity, and orient their mitotic spindles in the plane of the epithelial sheet. Defects in these attributes result in the tissue disorganization associated with cancer. Epithelia undergo self-renewal from stem cells, which might in some cases be the cell of origin for cancers. The PAR polarity proteins are master regulators of epithelial organization, and are closely linked to signaling pathways such as Hippo, which orchestrate proliferation and apoptosis to control organ size. 3D ex vivo culture systems can now faithfully recapitulate epithelial organ morphogenesis, providing a powerful approach to study both normal development and the initiating events in carcinogenesis. PMID:21782440

  4. Mechanochemical Pattern Formation in the Polarization of the One-Cell C. Elegans Embryo

    NASA Astrophysics Data System (ADS)

    Bois, Justin S.; Grill, Stephan W.

    2013-12-01

    Cellular polarity refers to the uneven distribution of certain proteins and nucleic acids on one half of a cell versus the other. Polarity establishment is often an essential process in the development, being responsible for cell differentiation upon division of the polarized cell. The one cell embryo of the nematode Caenorhabditis elegans is a classic model system for the study of polarity. Interestingly, distribution of polarity proteins is accompanied by directional movements of the cell cytoskeleton in this system. In addition to undergoing diffusion, the polarity proteins are transported by these movements. Thus, polarization is achieved by both mechanical and chemical means. We discuss our current understanding of this process in the C. elegans model system. We also discuss more general consequences of mechanochemical coupling in morphogenesis.

  5. Observing planar cell polarity in multiciliated mouse airway epithelial cells

    PubMed Central

    Vladar, Eszter K.; Lee, Yin Loon; Stearns, Tim; Axelrod, Jeffrey D.

    2015-01-01

    The concerted movement of cilia propels inhaled contaminants out of the lungs, safeguarding the respiratory system from toxins, pathogens, pollutants, and allergens. Motile cilia on the multiciliated cells (MCCs) of the airway epithelium are physically oriented along the tissue axis for directional motility, which depends on the planar cell polarity (PCP) signaling pathway. The MCCs of the mouse respiratory epithelium have emerged as an important model for the study of motile ciliogenesis and the PCP signaling mechanism. Unlike other motile ciliated or planar polarized tissues, airway epithelial cells are relatively easily accessible and primary cultures faithfully model many of the essential features of the in vivo tissue. There is growing interest in understanding how cells acquire and polarize motile cilia due to the impact of mucociliary clearance on respiratory health. Here, we present methods for observing and quantifying the planar polarized orientation of motile cilia both in vivo and in primary culture airway epithelial cells. We describe how to acquire and evaluate electron and light microscopy images of ciliary ultrastructural features that reveal planar polarized orientation. Furthermore, we describe the immunofluorescence localization of PCP pathway components as a simple readout for airway epithelial planar polarization and ciliary orientation. These methods can be adapted to observe ciliary orientation in other multi- and monociliated cells and to detect PCP pathway activity in any tissue or cell type. PMID:25837385

  6. Coordinated process of polarized growth in filamentous fungi.

    PubMed

    Takeshita, Norio

    2016-09-01

    Filamentous fungi are extremely polarized organisms, exhibiting continuous growth at their hyphal tips. The hyphal form is related to their pathogenicity in animals and plants, and their high secretion ability for biotechnology. Polarized growth requires a sequential supply of proteins and lipids to the hyphal tip. This transport is managed by vesicle trafficking via the actin and microtubule cytoskeleton. Therefore, the arrangement of the cytoskeleton is a crucial step to establish and maintain the cell polarity. This review summarizes recent findings unraveling the mechanism of polarized growth with special emphasis on the role of actin and microtubule cytoskeleton and polarity marker proteins. Rapid insertions of membranes via highly active exocytosis at hyphal tips could quickly dilute the accumulated polarity marker proteins. Recent findings by a super-resolution microscopy indicate that filamentous fungal cells maintain their polarity at the tips by repeating transient assembly and disassembly of polarity sites. PMID:27121747

  7. Studies of 3He polarization losses during NMR and EPR measurment and Polarized 3He target cell lifetime

    NASA Astrophysics Data System (ADS)

    An, Peibo

    2014-09-01

    The 3He target cell polarized by spin-exchange optical pumping(SEOP) is used as a neutron substitute to study the inner structure of the neutron. In our lab, nuclear-magnetic-resonance(NMR) is used to measure the relative polarization and electron-paramagnetic-resonance(EPR) is used to measure the spin exchange EPR frequency shift parameter of potassium and rubidium in our target cell presented in magnetic fields. The alkali in the cell is used to facilitate the polarization of 3He. The first part of my work presents the study of the polarization losses of the cell during both NMR and EPR. With the help of improved RF coils, we keep the background noise received by pickup coils reasonably low, but three other kinds of losses are inevitable: losses during Adiabatic Fast Passage (AFP) sweep, losses due to flux change caused by different cell orientation with respect to RF fields and physical losses. Fortunately there is only flux change in NMR measurements. The second part of my work presents the study of cell lifetime improvement. The polarization decreases in a process called relaxation exponentially. The lifetime of a cell is how long it can keep its polarization. The typical lifetime of cells produced in our lab is about 22 hours. With a newly designed vacuum system. The 3He target cell polarized by spin-exchange optical pumping(SEOP) is used as a neutron substitute to study the inner structure of the neutron. In our lab, nuclear-magnetic-resonance(NMR) is used to measure the relative polarization and electron-paramagnetic-resonance(EPR) is used to measure the spin exchange EPR frequency shift parameter of potassium and rubidium in our target cell presented in magnetic fields. The alkali in the cell is used to facilitate the polarization of 3He. The first part of my work presents the study of the polarization losses of the cell during both NMR and EPR. With the help of improved RF coils, we keep the background noise received by pickup coils reasonably low, but

  8. Dynamic membrane patterning, signal localization and polarity in living cells.

    PubMed

    Zamparo, M; Chianale, F; Tebaldi, C; Cosentino-Lagomarsino, M; Nicodemi, M; Gamba, A

    2015-02-01

    We review the molecular and physical aspects of the dynamic localization of signaling molecules on the plasma membranes of living cells. At the nanoscale, clusters of receptors and signaling proteins play an essential role in the processing of extracellular signals. At the microscale, "soft" and highly dynamic signaling domains control the interaction of individual cells with their environment. At the multicellular scale, individual polarity patterns control the forces that shape multicellular aggregates and tissues. PMID:25563791

  9. TRPM7 Regulates Polarized Cell Movements

    PubMed Central

    Su, Li-Ting; Liu, Wei; Chen, Hsiang-Chin; González-Pagán, Omayra; Habas, Raymond; Runnels, Loren W.

    2012-01-01

    SYNOPSIS TRPM7 is a Ca2+ and Mg2+ permeant ion channel in possession of its own kinase domain. As a kinase, the protein has been linked to the control of actomyosin contractility, whereas the channel has been found to regulate cell adhesion as well as cellular Mg2+ homeostasis. Here we show that depletion of TRPM7 by RNA interference in fibroblasts alters cell morphology, the cytoskeleton, and the ability of cells to form lamellipodia and to execute polarized cell movements. A pulldown purification assay revealed that knockdown of TRPM7 prevents cells from activating Rac and Cdc42 when stimulated to migrate into a cellular wound. Re-expression of TRPM7 reverses these phenotypic changes, as does, unexpectedly, expression of a kinase-inactive mutant of TRPM7. Surprisingly, expression of the Mg2+ transporter SLC41A2 is also effective restoring the change in cell morphology, disruption of the cytoskeleton, and directional cell motility caused by depletion of the channel-kinase. These data uncover an essential role for Mg2+ in TRPM7's control over the cytoskeleton and its ability to regulate polarized cell movements. PMID:21208190

  10. Arabidopsis  SABRE and CLASP interact to stabilize cell division plane orientation and planar polarity

    PubMed Central

    Pietra, Stefano; Gustavsson, Anna; Kiefer, Christian; Kalmbach, Lothar; Hörstedt, Per; Ikeda, Yoshihisa; Stepanova, Anna N.; Alonso, Jose M.; Grebe, Markus

    2013-01-01

    The orientation of cell division and the coordination of cell polarity within the plane of the tissue layer (planar polarity) contribute to shape diverse multicellular organisms. The root of Arabidopsis thaliana displays regularly oriented cell divisions, cell elongation and planar polarity providing a plant model system to study these processes. Here we report that the SABRE protein, which shares similarity with proteins of unknown function throughout eukaryotes, has important roles in orienting cell division and planar polarity. SABRE localizes at the plasma membrane, endomembranes, mitotic spindle and cell plate. SABRE stabilizes the orientation of CLASP-labelled preprophase band microtubules predicting the cell division plane, and of cortical microtubules driving cell elongation. During planar polarity establishment, sabre is epistatic to clasp at directing polar membrane domains of Rho-of-plant GTPases. Our findings mechanistically link SABRE to CLASP-dependent microtubule organization, shedding new light on the function of SABRE-related proteins in eukaryotes. PMID:24240534

  11. Roles of regulated internalization in the polarization of cell surface receptors

    PubMed Central

    Tian, Wei; Cao, Youfang; Ismael, Amber; Stone, David

    2016-01-01

    Cell polarization, the generation of cellular asymmetries, is a fundamental biological process. Polarity of different molecules can arise through several mechanisms. Among these, internalization has been shown to play an important role in the polarization of cell surface receptors. The internalization of cell surface receptors can be upregulated upon ligand binding. Additional regulatory mechanism can downregulate the internalization process. Here we describe a general model, which incorporates these two opposing processes, to study the role of internalization in the establishment of cell polarity. We find that the competition between these two processes is sufficient to induce receptor polarization. Our results show that regulated internalization provides additional regulation on polarization as well. In addition, we discuss applications of our model to the yeast system, which shows the capability and potential of the model. PMID:25570171

  12. Process control system using polarizing interferometer

    DOEpatents

    Schultz, T.J.; Kotidis, P.A.; Woodroffe, J.A.; Rostler, P.S.

    1994-02-15

    A system for nondestructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading. 38 figures.

  13. Process control system using polarizing interferometer

    DOEpatents

    Schultz, Thomas J.; Kotidis, Petros A.; Woodroffe, Jaime A.; Rostler, Peter S.

    1994-01-01

    A system for non-destructively measuring an object and controlling industrial processes in response to the measurement is disclosed in which an impulse laser generates a plurality of sound waves over timed increments in an object. A polarizing interferometer is used to measure surface movement of the object caused by the sound waves and sensed by phase shifts in the signal beam. A photon multiplier senses the phase shift and develops an electrical signal. A signal conditioning arrangement modifies the electrical signals to generate an average signal correlated to the sound waves which in turn is correlated to a physical or metallurgical property of the object, such as temperature, which property may then be used to control the process. External, random vibrations of the workpiece are utilized to develop discernible signals which can be sensed in the interferometer by only one photon multiplier. In addition the interferometer includes an arrangement for optimizing its sensitivity so that movement attributed to various waves can be detected in opaque objects. The interferometer also includes a mechanism for sensing objects with rough surfaces which produce speckle light patterns. Finally the interferometer per se, with the addition of a second photon multiplier is capable of accurately recording beam length distance differences with only one reading.

  14. Methods for studying planar cell polarity.

    PubMed

    Olofsson, Jessica; Axelrod, Jeffrey D

    2014-06-15

    Planar cell polarity (PCP) is the polarity of epithelial cells in the plane orthogonal to the apical-basal axis, and is controlled by a partially defined signaling system. PCP related signaling also plays roles in cell migration, tissue re-organization and stem cell differentiation during embryonic development, and later, in regeneration and repair. Aberrant signaling has been linked to a broad range of pathophysiologies including cancer, developmental defects, and neurological disorders. The deepest mechanistic insights have come from studies of PCP in Drosophila. In this chapter we review tools and methods to study PCP signaling in Drosophila epithelia, where it was found to involve asymmetric protein localization that is coordinated between adjacent cells. Such signaling has been most extensively studied in wing, eye, and abdomen, but also in other tissues such as leg and notum. In the adult fly, PCP is manifested in the coordinated direction of hairs and bristles, as well as the organization of ommatidia in the eye. The polarity of these structures is preceded by asymmetric localization of PCP signaling proteins at the apical junctions of epithelial cells. Based on genetic and molecular criteria, the proteins that govern PCP can be divided into distinct modules, including the core module, the Fat/Dachsous/Four-jointed (Fat/Ds/Fj) module (often referred to as the 'global' module) as well as tissue specific effector modules. Different tissues and tissue regions differ in their sensitivity to disturbances in the various modules of the PCP signaling system, leading to controversies about the interactions among the modules, and emphasizing the value of studying PCP in multiple contexts. Here, we review methods including those generally applicable, as well as some that are selectively useful for analyses of PCP in eye (including eye discs), wing (including wing discs), pupal and adult abdomen, and the cuticle of larvae and embryos. PMID:24680701

  15. Physical processes in polar stratospheric ice clouds

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.; Turco, Richard; Jordan, Joseph

    1988-01-01

    A one dimensional model of cloud microphysics was used to simulate the formation and evolution of polar stratospheric ice clouds. Some of the processes which are included in the model are outlined. It is found that the clouds must undergo preferential nucleation upon the existing aerosols just as do tropospheric cirrus clouds. Therefore, there is an energy barrier between stratospheric nitric acid particles and ice particles implying that nitric acid does not form a continuous set of solutions between the trihydrate and ice. The Kelvin barrier is not significant in controlling the rate of formation of ice particles. It was found that the cloud properties are sensitive to the rate at which the air parcels cool. In wave clouds, with cooling rates of hundreds of degrees per day, most of the existing aerosols nucleate and become ice particles. Such clouds have particles with sizes on the order of a few microns, optical depths on order of unity and are probably not efficient at removing materials from the stratosphere. In clouds which form with cooling rates of a few degrees per day or less, only a small fraction of the aerosols become cloud particles. In such clouds the particle radius is larger than 10 microns, the optical depths are low and water vapor is efficiently removed. Seasonal simulations show that the lowest water vapor mixing ratio is determined by the lowest temperature reached, and that the time when clouds disappear is controlled by the time when temperatures begin to rise above the minimum values.

  16. Self-Polarization of Cells in Elastic Gels

    NASA Astrophysics Data System (ADS)

    Zemel, Assaf; Safran, Samuel

    2008-03-01

    The shape of a cell as well as the rigidity and geometry of its surroundings play an important role in vital cellular processes. The contractile activity of cells provides a generic means by which cells may sense and respond to mechanical features. The matrix stresses, that depend on the elasticity and geometry of cells, feedback on the cells and influence their activity. This suggests a mechanical mechanism by which cells control their shape and forces. We present a quantitative, mechanical model that predicts that cells in an elastic medium can self-polarize to form well ordered stress fibers. We focus on both single cells in a gel, as well as on an ensemble of cells that is confined to some region within the gel. While the magnitude of the cellular forces is found to increase monotonically with the matrix rigidity the anisotropy of the forces, and thus the ability of the cells to polarize, is predicted to depend non-monotonically on the medium's rigidity. We discuss these results with experimental findings and with the observation of an optimal medium elasticity for cell function and differentiation.

  17. Process for determining the polarity of a crude oil

    SciTech Connect

    de Andrade Bruning, I.M.R.

    1989-12-26

    This patent describes a process for determining the relative polarity of a crude oil or fraction thereof. It comprises: contacting a known test substance with a stationary phase of the crude oil or fraction in a gas chromatography column, and measuring the interaction between the test substance and the oil; contacting the known test substance with a stationary phase of a non-polar second substance in a gas chromatography column and measuring the interaction between the test substance and the non-polar second substance; and determining the polarity of the crude oil relative to the non-polar second substance from the measurements obtained.

  18. Auxin regulation of cell polarity in plants.

    PubMed

    Pan, Xue; Chen, Jisheng; Yang, Zhenbiao

    2015-12-01

    Auxin is well known to control pattern formation and directional growth at the organ/tissue levels via the nuclear TIR1/AFB receptor-mediated transcriptional responses. Recent studies have expanded the arena of auxin actions as a trigger or key regulator of cell polarization and morphogenesis. These actions require non-transcriptional responses such as changes in the cytoskeleton and vesicular trafficking, which are commonly regulated by ROP/Rac GTPase-dependent pathways. These findings beg for the question about the nature of auxin receptors that regulate these responses and renew the interest in ABP1 as a cell surface auxin receptor, including the work showing auxin-binding protein 1 (ABP1) interacts with the extracellular domain of the transmembrane kinase (TMK) receptor-like kinases in an auxin-dependent manner, as well as the debate on this auxin binding protein discovered about 40 years ago. This review highlights recent work on the non-transcriptional auxin signaling mechanisms underscoring cell polarity and shape formation in plants. PMID:26599954

  19. Cellular mechanisms for cargo delivery and polarity maintenance at different polar domains in plant cells

    PubMed Central

    Łangowski, Łukasz; Wabnik, Krzysztof; Li, Hongjiang; Vanneste, Steffen; Naramoto, Satoshi; Tanaka, Hirokazu; Friml, Jiří

    2016-01-01

    The asymmetric localization of proteins in the plasma membrane domains of eukaryotic cells is a fundamental manifestation of cell polarity that is central to multicellular organization and developmental patterning. In plants, the mechanisms underlying the polar localization of cargo proteins are still largely unknown and appear to be fundamentally distinct from those operating in mammals. Here, we present a systematic, quantitative comparative analysis of the polar delivery and subcellular localization of proteins that characterize distinct polar plasma membrane domains in plant cells. The combination of microscopic analyses and computational modeling revealed a mechanistic framework common to diverse polar cargos and underlying the establishment and maintenance of apical, basal, and lateral polar domains in plant cells. This mechanism depends on the polar secretion, constitutive endocytic recycling, and restricted lateral diffusion of cargos within the plasma membrane. Moreover, our observations suggest that polar cargo distribution involves the individual protein potential to form clusters within the plasma membrane and interact with the extracellular matrix. Our observations provide insights into the shared cellular mechanisms of polar cargo delivery and polarity maintenance in plant cells. PMID:27462465

  20. Cellular mechanisms for cargo delivery and polarity maintenance at different polar domains in plant cells.

    PubMed

    Łangowski, Łukasz; Wabnik, Krzysztof; Li, Hongjiang; Vanneste, Steffen; Naramoto, Satoshi; Tanaka, Hirokazu; Friml, Jiří

    2016-01-01

    The asymmetric localization of proteins in the plasma membrane domains of eukaryotic cells is a fundamental manifestation of cell polarity that is central to multicellular organization and developmental patterning. In plants, the mechanisms underlying the polar localization of cargo proteins are still largely unknown and appear to be fundamentally distinct from those operating in mammals. Here, we present a systematic, quantitative comparative analysis of the polar delivery and subcellular localization of proteins that characterize distinct polar plasma membrane domains in plant cells. The combination of microscopic analyses and computational modeling revealed a mechanistic framework common to diverse polar cargos and underlying the establishment and maintenance of apical, basal, and lateral polar domains in plant cells. This mechanism depends on the polar secretion, constitutive endocytic recycling, and restricted lateral diffusion of cargos within the plasma membrane. Moreover, our observations suggest that polar cargo distribution involves the individual protein potential to form clusters within the plasma membrane and interact with the extracellular matrix. Our observations provide insights into the shared cellular mechanisms of polar cargo delivery and polarity maintenance in plant cells. PMID:27462465

  1. Prion Infection of Epithelial Rov Cells Is a Polarized Event

    PubMed Central

    Paquet, Sophie; Sabuncu, Elifsu; Delaunay, Jean-Louis; Laude, Hubert; Vilette, Didier

    2004-01-01

    During prion infections, the cellular glycosylphosphatidylinositol-anchored glycoprotein PrP is converted into a conformational isoform. This abnormal conformer is thought to recruit and convert the normal cellular PrP into a likeness of itself and is proposed to be the infectious agent. We investigated the distribution of the PrP protein on the surface of Rov cells, an epithelial cell line highly permissive to prion multiplication, and we found that PrP is primarily expressed on the apical side. We further show that prion transmission to Rov cells is much more efficient if infectivity contacts the apical side, indicating that the apical and basolateral sides of Rov cells are not equally competent for prion infection and adding prions to the list of the conventional infectious agents (viruses and bacteria) that infect epithelial cells in a polarized manner. These data raise the possibility that apically expressed PrP may be involved in this polarized process of infection. This would add further support for a crucial role of PrP at the cell surface in prion infection of target cells. PMID:15194791

  2. A comparison of polarization image processing across different platforms

    NASA Astrophysics Data System (ADS)

    York, Timothy; Powell, Samuel; Gruev, Viktor

    2011-10-01

    Division-of-focal-plane (DoFP) polarimeters for the visible spectrum hold the promise of being able to capture both the angle and degree of linear polarization in real-time and at high spatial resolution. These sensors are realized by monolithic integration of CCD imaging elements with metallic nanowire polarization filter arrays at the focal plane of the sensor. These sensors capture large amounts of raw polarization data and present unique computational challenges as they aim to provide polarimetric information at high spatial and temporal resolutions. The image processing pipeline in a typical DoFP polarimeter is: per-pixel calibration, interpolation of the four sub-sampled polarization pixels, Stokes parameter estimation, angle and degree of linear polarization estimation, and conversion from polarization domain to color space for display purposes. The entire image processing pipeline must operate at the same frame rate as the CCD polarization imaging sensor (40 frames per second) or higher in order to enable real-time extraction of the polarization properties from the imaged environment. To achieve the necessary frame rate, we have implemented and evaluated the image processing pipeline on three different platforms: general purpose CPU, graphics processing unit (GPU), and an embedded FPGA. The computational throughput, power consumption, precision and physical limitations of the implementations on each platform are described in detail and experimental data is provided.

  3. Prkci is required for a non-autonomous signal that coordinates cell polarity during cavitation.

    PubMed

    Mah, In Kyoung; Soloff, Rachel; Izuhara, Audrey K; Lakeland, Daniel L; Wang, Charles; Mariani, Francesca V

    2016-08-01

    Polarized epithelia define boundaries, spaces, and cavities within organisms. Cavitation, a process by which multicellular hollow balls or tubes are produced, is typically associated with the formation of organized epithelia. In order for these epithelial layers to form, cells must ultimately establish a distinct apical-basal polarity. Atypical PKCs have been proposed to be required for apical-basal polarity in diverse species. Here we show that while cells null for the Prkci isozyme exhibit some polarity characteristics, they fail to properly segregate apical-basal proteins, form a coordinated ectodermal epithelium, or participate in normal cavitation. A failure to cavitate could be due to an overgrowth of interior cells or to an inability of interior cells to die. Null cells however, do not have a marked change in proliferation rate and are still capable of undergoing cell death, suggesting that alterations in these processes are not the predominant cause of the failed cavitation. Overexpression of BMP4 or EZRIN can partially rescue the phenotype possibly by promoting cell death, polarity, and differentiation. However, neither is sufficient to provide the required cues to generate a polarized epithelium and fully rescue cavitation. Interestingly, when wildtype and Prkci(-/-) ES cells are mixed together, a polarized ectodermal epithelium forms and cavitation is rescued, likely due to the ability of wildtype cells to produce non-autonomous polarity cues. We conclude that Prkci is not required for cells to respond to these cues, though it is required to produce them. Together these findings indicate that environmental cues can facilitate the formation of polarized epithelia and that cavitation requires the proper coordination of multiple basic cellular processes including proliferation, differentiation, cell death, and apical-basal polarization. PMID:27312576

  4. Mapping cellular processes in the mesenchyme during palatal development in the absence of Tbx1 reveals complex proliferation changes and perturbed cell packing and polarity.

    PubMed

    Brock, Lara J; Economou, Andrew D; Cobourne, Martyn T; Green, Jeremy B A

    2016-03-01

    The 22q11 deletion syndromes represent a spectrum of overlapping conditions including cardiac defects and craniofacial malformations. Amongst the craniofacial anomalies that are seen, cleft of the secondary palate is a common feature. Haploinsufficiency of TBX1 is believed to be a major contributor toward many of the developmental structural anomalies that occur in these syndromes, and targeted deletion of Tbx1 in the mouse reproduces many of these malformations, including cleft palate. However, the cellular basis of this defect is only poorly understood. Here, palatal development in the absence of Tbx1 has been analysed, focusing on cellular properties within the whole mesenchymal volume of the palatal shelves. Novel image analyses and data presentation tools were applied to quantify cell proliferation rates, including regions of elevated as well as reduced proliferation, and cell packing in the mesenchyme. Also, cell orientations (nucleus-Golgi axis) were mapped as a potential marker of directional cell movement. Proliferation differed only subtly between wild-type and mutant until embryonic day (E)15.5 when proliferation in the mutant was significantly lower. Tbx1(-/-) palatal shelves had slightly different cell packing than wild-type, somewhat lower before elevation and higher at E15.5 when the wild-type palate has elevated and fused. Cell orientation is biased towards the shelf distal edge in the mid-palate of wild-type embryos but is essentially random in the Tbx1(-/-) mutant shelves, suggesting that polarised processes such as directed cell rearrangement might be causal for the cleft phenotype. The implications of these findings in the context of further understanding Tbx1 function during palatogenesis and of these methods for the more general analysis of genotype-phenotype functional relationships are discussed. PMID:26689739

  5. Airway epithelial homeostasis and planar cell polarity signaling depend on multiciliated cell differentiation

    PubMed Central

    Vladar, Eszter K.; Nayak, Jayakar V.; Milla, Carlos E.; Axelrod, Jeffrey D.

    2016-01-01

    Motile airway cilia that propel contaminants out of the lung are oriented in a common direction by planar cell polarity (PCP) signaling, which localizes PCP protein complexes to opposite cell sides throughout the epithelium to orient cytoskeletal remodeling. In airway epithelia, PCP is determined in a 2-phase process. First, cell-cell communication via PCP complexes polarizes all cells with respect to the proximal-distal tissue axis. Second, during ciliogenesis, multiciliated cells (MCCs) undergo cytoskeletal remodeling to orient their cilia in the proximal direction. The second phase not only directs cilium polarization, but also consolidates polarization across the epithelium. Here, we demonstrate that in airway epithelia, PCP depends on MCC differentiation. PCP mutant epithelia have misaligned cilia, and also display defective barrier function and regeneration, indicating that PCP regulates multiple aspects of airway epithelial homeostasis. In humans, MCCs are often sparse in chronic inflammatory diseases, and these airways exhibit PCP dysfunction. The presence of insufficient MCCs impairs mucociliary clearance in part by disrupting PCP-driven polarization of the epithelium. Consistent with defective PCP, barrier function and regeneration are also disrupted. Pharmacological stimulation of MCC differentiation restores PCP and reverses these defects, suggesting its potential for broad therapeutic benefit in chronic inflammatory disease. PMID:27570836

  6. Superresolution microscopy reveals a dynamic picture of cell polarity maintenance during directional growth

    PubMed Central

    Ishitsuka, Yuji; Savage, Natasha; Li, Yiming; Bergs, Anna; Grün, Nathalie; Kohler, Daria; Donnelly, Rebecca; Nienhaus, G. Ulrich; Fischer, Reinhard; Takeshita, Norio

    2015-01-01

    Polar (directional) cell growth, a key cellular mechanism shared among a wide range of species, relies on targeted insertion of new material at specific locations of the plasma membrane. How these cell polarity sites are stably maintained during massive membrane insertion has remained elusive. Conventional live-cell optical microscopy fails to visualize polarity site formation in the crowded cell membrane environment because of its limited resolution. We have used advanced live-cell imaging techniques to directly observe the localization, assembly, and disassembly processes of cell polarity sites with high spatiotemporal resolution in a rapidly growing filamentous fungus, Aspergillus nidulans. We show that the membrane-associated polarity site marker TeaR is transported on microtubules along with secretory vesicles and forms a protein cluster at that point of the apical membrane where the plus end of the microtubule touches. There, a small patch of membrane is added through exocytosis, and the TeaR cluster gets quickly dispersed over the membrane. There is an incessant disassembly and reassembly of polarity sites at the growth zone, and each new polarity site locus is slightly offset from preceding ones. On the basis of our imaging results and computational modeling, we propose a transient polarity model that explains how cell polarity is stably maintained during highly active directional growth. PMID:26665168

  7. Superresolution microscopy reveals a dynamic picture of cell polarity maintenance during directional growth.

    PubMed

    Ishitsuka, Yuji; Savage, Natasha; Li, Yiming; Bergs, Anna; Grün, Nathalie; Kohler, Daria; Donnelly, Rebecca; Nienhaus, G Ulrich; Fischer, Reinhard; Takeshita, Norio

    2015-11-01

    Polar (directional) cell growth, a key cellular mechanism shared among a wide range of species, relies on targeted insertion of new material at specific locations of the plasma membrane. How these cell polarity sites are stably maintained during massive membrane insertion has remained elusive. Conventional live-cell optical microscopy fails to visualize polarity site formation in the crowded cell membrane environment because of its limited resolution. We have used advanced live-cell imaging techniques to directly observe the localization, assembly, and disassembly processes of cell polarity sites with high spatiotemporal resolution in a rapidly growing filamentous fungus, Aspergillus nidulans. We show that the membrane-associated polarity site marker TeaR is transported on microtubules along with secretory vesicles and forms a protein cluster at that point of the apical membrane where the plus end of the microtubule touches. There, a small patch of membrane is added through exocytosis, and the TeaR cluster gets quickly dispersed over the membrane. There is an incessant disassembly and reassembly of polarity sites at the growth zone, and each new polarity site locus is slightly offset from preceding ones. On the basis of our imaging results and computational modeling, we propose a transient polarity model that explains how cell polarity is stably maintained during highly active directional growth. PMID:26665168

  8. Front-Rear Polarization by Mechanical Cues: From Single Cells to Tissues.

    PubMed

    Ladoux, Benoit; Mège, René-Marc; Trepat, Xavier

    2016-06-01

    Directed cell migration is a complex process that involves front-rear polarization, characterized by cell adhesion and cytoskeleton-based protrusion, retraction, and contraction of either a single cell or a cell collective. Single cell polarization depends on a variety of mechanochemical signals including external adhesive cues, substrate stiffness, and confinement. In cell ensembles, coordinated polarization of migrating tissues results not only from the application of traction forces on the extracellular matrix but also from the transmission of mechanical stress through intercellular junctions. We focus here on the impact of mechanical cues on the establishment and maintenance of front-rear polarization from single cell to collective cell behaviors through local or large-scale mechanisms. PMID:26920934

  9. Competition of two distinct actin networks for actin defines a bistable switch for cell polarization

    PubMed Central

    Lomakin, Alexis J.; Lee, Kun-Chun; Han, Sangyoon J.; Bui, D A.; Davidson, Michael; Mogilner, Alex; Danuser, Gaudenz

    2015-01-01

    Symmetry-breaking polarization enables functional plasticity of cells and tissues and is yet not well understood. Here we show that epithelial cells, hard-wired to maintain a static morphology and to preserve tissue organization, can spontaneously switch to a migratory polarized phenotype upon relaxation of the actomyosin cytoskeleton. We find that myosin-II engages actin in the formation of cortical actomyosin bundles and thus makes it unavailable for deployment in the process of dendritic growth normally driving cell motility. At low contractility regimes epithelial cells polarize in a front-back manner due to emergence of actin retrograde flows powered by dendritic polymerization of actin. Coupled to cell movement, the flows transport myosin-II from the front to the back of the cell, where the motor locally “locks” actin in contractile bundles. This polarization mechanism could be employed by embryonic and cancer epithelial cells in microenvironments where high contractility-driven cell motion is inefficient. PMID:26414403

  10. Getting to the root of plant iron uptake and cell-cell transport: Polarity matters!

    PubMed Central

    Dubeaux, Guillaume; Zelazny, Enric; Vert, Grégory

    2015-01-01

    Plasma membrane proteins play pivotal roles in mediating responses to endogenous and environmental cues. Regulation of membrane protein levels and establishment of polarity are fundamental for many cellular processes. In plants, IRON-REGULATED TRANSPORTER 1 (IRT1) is the major root iron transporter but is also responsible for the absorption of other divalent metals such as manganese, zinc and cobalt. We recently uncovered that IRT1 is polarly localized to the outer plasma membrane domain of plant root epidermal cells upon depletion of its secondary metal substrates. The endosome-recruited FYVE1 protein interacts with IRT1 in the endocytic pathway and plays a crucial role in the establishment of IRT1 polarity, likely through its recycling to the cell surface. Our work sheds light on the mechanisms of radial transport of nutrients across the different cell types of plant roots toward the vascular tissues and raises interesting parallel with iron transport in mammals. PMID:26479146

  11. Positioning of polarity formation by extracellular signaling during asymmetric cell division.

    PubMed

    Seirin Lee, Sungrim

    2016-07-01

    Anterior-posterior (AP) polarity formation of cell membrane proteins plays a crucial role in determining cell asymmetry, which ultimately generates cell diversity. In Caenorhabditis elegans, a single fertilized egg cell (P0), its daughter cell (P1), and the germline precursors (P2 and P3 cells) form two exclusive domains of different PAR proteins on the membrane along the anterior-posterior axis. However, the phenomenon of polarity reversal has been observed in which the axis of asymmetric cell division of the P2 and P3 cells is formed in an opposite manner to that of the P0 and P1 cells. The extracellular signal MES-1/SRC-1 has been shown to induce polarity reversal, but the detailed mechanism remains elusive. Here, using a mathematical model, I explore the mechanism by which MES-1/SRC-1 signaling can induce polarity reversal and ultimately affect the process of polarity formation. I show that a positive correlation between SRC-1 and the on-rate of PAR-2 is the essential mechanism underlying polarity reversal, providing a mathematical basis for the orientation of cell polarity patterns. PMID:27086039

  12. At the heart of cell polarity and the cytoskeleton.

    PubMed

    Gotta, Monica

    2005-05-01

    Researchers working on cell polarity and cytoskeletal processes met at a Keystone meeting in Coeur d'Alene, Idaho in March to present and discuss the newest findings in these rapidly moving fields. The unexpectedly warm weather and the lack of snow favored discussions at this very interactive meeting. To fill the 6 hr break in the afternoon, walks in the beautiful surroundings and shopping trips were organized, during which microtubules, PAR proteins, and small G proteins were the guests of honor. PMID:15926249

  13. Entry of genital Chlamydia trachomatis into polarized human epithelial cells.

    PubMed Central

    Wyrick, P B; Choong, J; Davis, C H; Knight, S T; Royal, M O; Maslow, A S; Bagnell, C R

    1989-01-01

    To study the initial invasion process(es) of genital chlamydiae, a model system consisting of hormonally maintained primary cultures of human endometrial gland epithelial cells (HEGEC), grown in a polarized orientation on collagen-coated filters, was utilized. After Chlamydia trachomatis inoculation of the apical surface of polarized HEGEC, chlamydiae were readily visualized, by transmission electron microscopy, in coated pits and coated vesicles. This was true for HEGEC maintained in physiologic concentrations of estrogen (proliferative phase) and of estrogen plus progesterone (secretory phase), despite the finding that association of chlamydiae with secretory-phase HEGEC is significantly reduced (P = 0.025; A.S. Maslow, C.H. Davis, J. Choong, and P.B. Wyrick, Am. J. Obstet. Gynecol. 159:1006-1014, 1988). In contrast, chlamydiae were rarely observed in the clathrin-associated structures if the HEGEC were cultured on plastic surfaces. The same pattern of coated pit versus noncoated pit entry was reproducible in HeLa cells. The quantity of coated pits associated with isolated membrane sheets derived from HeLa cells, grown on poly-L-lysine-coated cover slips in medium containing the female hormones, was not significantly different as monitored by radiolabeling studies and by laser scanning microscopy. These data suggest that culture conditions which mimic in vivo cellular organization may enhance entry into coated pits for some obligate intracellular pathogens. Images PMID:2744852

  14. Synthetic aperture radar processing with polar formatted subapertures

    SciTech Connect

    Doerry, A.W.

    1994-10-01

    Synthetic Aperture Radar (SAR) uses the motion of a small real antenna to synthesize a larger aperture, and thereby achieve very fine azimuth resolution. Efficient SAR image formation requires modelling the radar echo and compensating (focusing) the delay and phase for various positions in the target scene. Polar-Format processing is one successful algorithm developed to process large scenes at fine resolutions, but is still limited, especially at resolutions near a wavelength. This paper shows how using tiers of subapertures can overcome the limitations of Polar-Format processing and increase the focused scene size substantially while using only efficient vector multiplies and Fast Fourier Transforms.

  15. Measurement of dynamic variations of polarized light in processed meat due to aging

    NASA Astrophysics Data System (ADS)

    Abubaker, Hamed M.; Tománek, Pavel; Grmela, Lubomír

    2011-05-01

    The propagation of laser light in biological tissues is of growing importance in many medical and food applications. This problem is seriously studied in live science. The biological tissues consist of cells which dimensions are bigger than wavelength of visible light and display large compositional variations, inhomogeneities, and anisotropic structures. Therefore a Mie scattering of transmitted or backscattered light occurs and different polarization states arise. The changes of polarization state due to the multiple scattering of light in the biological cellular tissues also allow measure the freshness of processed victuals. The transmitted and backscattered laser light exhibits multiple scattering on the thin slice of sample. The phenomenon is different if the cellular tissues are living or dead. In the case of meat, there are temporal and dynamic changes not only as a result of chemical process, but also geometric deformations due to the water evaporation from intracellular and extracellular sites. The polarization measurement shows the changes in polarization orientation due to the muscle orientation and meat aging. Two types of measurements were provided: a) Measurement of polarized light reflected and twice transmitted forward and backward through the biological tissue samples - meat slice attached on sample holder mirror. b) Measurement of polarized light transmitted through the biological tissue sample. The relationship between polarization changes and meat freshness, and a dynamic temporal behavior of polarization states in the aged meat is reported.

  16. The acetylenic tricyclic bis(cyano enone), TBE-31, targets microtubule dynamics and cell polarity in migrating cells.

    PubMed

    Chan, Eddie; Saito, Akira; Honda, Tadashi; Di Guglielmo, Gianni M

    2016-04-01

    Cell migration is dependent on the microtubule network for structural support as well as for the proper delivery and positioning of polarity proteins at the leading edge of migrating cells. Identification of drugs that target cytoskeletal-dependent cell migration and protein transport in polarized migrating cells is important in understanding the cell biology of normal and tumor cells and can lead to new therapeutic targets in disease processes. Here, we show that the tricyclic compound TBE-31 directly binds to tubulin and interferes with microtubule dynamics, as assessed by end binding 1 (EB1) live cell imaging. Interestingly, this interference is independent of in vitro tubulin polymerization. Using immunofluorescence microscopy, we also observed that TBE-31 interferes with the polarity of migratory cells. The polarity proteins Rac1, IQGAP and Tiam1 were localized at the leading edge of DMSO-treated migrating cell, but were observed to be in multiple protrusions around the cell periphery of TBE-31-treated cells. Finally, we observed that TBE-31 inhibits the migration of Rat2 fibroblasts with an IC50 of 0.75 μM. Taken together, our results suggest that the inhibition of cell migration by TBE-31 may result from the improper maintenance of cell polarity of migrating cells. PMID:26775215

  17. History and current processes of the Martian polar layered deposits

    NASA Astrophysics Data System (ADS)

    Byrne, Shane

    2003-12-01

    The Martian polar layered deposits constitute a detailed record of geologically recent environmental conditions. In this thesis I examine processes that have affected this history over timescales ranging from ˜102 to ˜107 Martian years. To complete the work in this thesis I developed a geographic database of the Martian polar regions to enable comparisons of different datasets spread over different missions. I report on the discovery of a large sand rich unit underlying the northern polar layered deposits. The presence of this unit suggests there once existed a radically different polar environment where there was no polar cap. A major new question now arises of where that water went during this time period and how the old polar cap (if there was one) was removed. I describe analysis and modeling of evolving landforms on the southern residual CO2 cap. This modeling suggests that these landforms are underlain by a water ice layer. THEMIS observations were used to confirm this hypothesis. This limits the size of the residual CO2 cap reservoir to no more than 5% of the current atmosphere, which puts an important constraint on models of atmospheric evolution. Analysis of the size distribution coupled with this modeling indicates a uniform age for a large group of these features, implying some environmental change on the order of Martian centuries ago. I examined geomorphologic evidence for flow processes at the margin of the south polar layered deposits. Indications of multiple episodes of previous flow are seen. However much evidence of brittle processes such as faulting, slumping and landsliding is also present. This leads to the conclusion that, during some periods, flow of the layered deposits is incapable of relieving the gravitationally generated stresses within the ice sheet. The evidence suggests that periods where flow was possible occurred intermittently and were separated by periods in which sublimation-based retreat of the ice dominated.

  18. Inversion by P4: polarization-picture post-processing.

    PubMed

    Schechner, Yoav Y

    2011-03-12

    Polarization may be sensed by imaging modules. This is done in various engineering systems as well as in biological systems, specifically by insects and some marine species. However, polarization per pixel is usually not the direct variable of interest. Rather, polarization-related data serve as a cue for recovering task-specific scene information. How should polarization-picture post-processing (P(4)) be done for the best scene understanding? Answering this question is not only helpful for advanced engineering (computer vision), but also to prompt hypotheses as to the processing occurring within biological systems. In various important cases, the answer is found by a principled expression of scene recovery as an inverse problem. Such an expression relies directly on a physics-based model of effects in the scene. The model includes analysis that depends on the different polarization components, thus facilitating the use of these components during the inversion, in a proper, even if non-trivial, manner. We describe several examples for this approach. These include automatic removal of path radiance in haze or underwater, overcoming partial semireflections and visual reverberations; three-dimensional recovery and distance-adaptive denoising. The resulting inversion algorithms rely on signal-processing methods, such as independent component analysis, deconvolution and optimization. PMID:21282167

  19. PLEKHG3 enhances polarized cell migration by activating actin filaments at the cell front.

    PubMed

    Nguyen, Trang Thi Thu; Park, Wei Sun; Park, Byung Ouk; Kim, Cha Yeon; Oh, Yohan; Kim, Jin Man; Choi, Hana; Kyung, Taeyoon; Kim, Cheol-Hee; Lee, Gabsang; Hahn, Klaus M; Meyer, Tobias; Heo, Won Do

    2016-09-01

    Cells migrate by directing Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division control protein 42 (Cdc42) activities and by polymerizing actin toward the leading edge of the cell. Previous studies have proposed that this polarization process requires a local positive feedback in the leading edge involving Rac small GTPase and actin polymerization with PI3K likely playing a coordinating role. Here, we show that the pleckstrin homology and RhoGEF domain containing G3 (PLEKHG3) is a PI3K-regulated Rho guanine nucleotide exchange factor (RhoGEF) for Rac1 and Cdc42 that selectively binds to newly polymerized actin at the leading edge of migrating fibroblasts. Optogenetic inactivation of PLEKHG3 showed that PLEKHG3 is indispensable both for inducing and for maintaining cell polarity. By selectively binding to newly polymerized actin, PLEKHG3 promotes local Rac1/Cdc42 activation to induce more local actin polymerization, which in turn promotes the recruitment of more PLEKHG3 to induce and maintain cell front. Thus, autocatalytic reinforcement of PLEKHG3 localization to the leading edge of the cell provides a molecular basis for the proposed positive feedback loop that is required for cell polarization and directed migration. PMID:27555588

  20. Gamma-ray burst polarization via Compton scattering process

    SciTech Connect

    Chang, Zhe; Lin, Hai-Nan; Jiang, Yunguo

    2014-03-01

    Synchrotron radiation and Compton scattering are widely accepted as the most likely emission mechanisms of some astrophysical phenomena, such as gamma-ray bursts (GRBs) and active galactic nuclei. The measurement of the polarization of photons provides a useful tool to distinguish different emission mechanisms and structures of the emission region. Based on the differential cross section of a polarized photon scattered by an unpolarized electron of any initial momentum, we derive an analytical formula of polarization for beamed photons scattered by isotropic electrons with a power-law distribution. Numerical calculations are carried out in four special cases: electrons at rest, Thomson limit, head-on collision, and monochromatic electrons. It is found that the maximum polarization can be as high as 100% for low energy photons, if the electrons are at rest. Although polarization is highly suppressed due to the isotropic electrons, a maximum value of ∼10%-20% can still be achieved. The Compton scattering process can be used to explain the polarization of GRB 041219A and GRB 100826A.

  1. Gamma-Ray Burst Polarization via Compton Scattering Process

    NASA Astrophysics Data System (ADS)

    Chang, Zhe; Lin, Hai-Nan; Jiang, Yunguo

    2014-03-01

    Synchrotron radiation and Compton scattering are widely accepted as the most likely emission mechanisms of some astrophysical phenomena, such as gamma-ray bursts (GRBs) and active galactic nuclei. The measurement of the polarization of photons provides a useful tool to distinguish different emission mechanisms and structures of the emission region. Based on the differential cross section of a polarized photon scattered by an unpolarized electron of any initial momentum, we derive an analytical formula of polarization for beamed photons scattered by isotropic electrons with a power-law distribution. Numerical calculations are carried out in four special cases: electrons at rest, Thomson limit, head-on collision, and monochromatic electrons. It is found that the maximum polarization can be as high as 100% for low energy photons, if the electrons are at rest. Although polarization is highly suppressed due to the isotropic electrons, a maximum value of ~10%-20% can still be achieved. The Compton scattering process can be used to explain the polarization of GRB 041219A and GRB 100826A.

  2. Early-time dynamics of actomyosin polarization in cells of confined shape in elastic matrices.

    PubMed

    Nisenholz, Noam; Botton, Mordechai; Zemel, Assaf

    2014-04-14

    The cell shape and the rigidity of the extracellular matrix have been shown to play an important role in the regulation of cytoskeleton structure and force generation. Elastic stresses that develop by actomyosin contraction feedback on myosin activity and govern the anisotropic polarization of stress fibers in the cell. We theoretically study the consequences that the cell shape and matrix rigidity may have on the dynamics and steady state polarization of actomyosin forces in the cell. Actomyosin forces are assumed to polarize in accordance with the stresses that develop in the cytoskeleton. The theory examines this self-polarization process as a relaxation response determined by two distinct susceptibility factors and two characteristic times. These reveal two canonical polarization responses to local variations in the elastic stress: an isotropic response, in which actomyosin dipolar stress isotropically changes in magnitude, and an orientational response, in which actomyosin forces orient with no net change in magnitude. Actual polarization may show up as a superimposition of the two mechanisms yielding different phases in the polarization response as observed experimentally. The cell shape and elastic moduli of the surroundings are shown to govern both the dynamics of the process as well as the steady-state. We predict that in the steady-state, beyond a critical matrix rigidity, spherical cells exert maximal force, and below that rigidity, elongated or flattened cells exert more force. Similar behaviors are reflected in the rate of the polarization process. The theory is also applicable to study the elastic response of whole cell aggregates in a gel. PMID:24623163

  3. Proceedings of the Polar Processes on Mars Workshop

    NASA Technical Reports Server (NTRS)

    Haberle, Robert M.

    1988-01-01

    Included in this publication is a collection of abstracts from the NASA-sponsored workshop, Polar Processes on Mars, which was held at the Sunnyvale Hilton Hotel, Sunnyvale, California, on 12 to 13 May 1988. Support for the workshop came from NASA's Planetary Geology and Geophysics program managed by Dr. Jospeh Boyce. The workshop is one of a series identified by MECA (an acronym for Mars: Evolution of its Climate and Atmosphere) as being worthy of focused research, but one for which it was not possible to hold during the project's lifetime. Consequently, it was held after the project ended. The MECA project was part of the Mars Data Analysis program. The workshop consisted of four sessions: The Polar Caps, Dynamics/Atmospheric Processes, Polar Geology, and Future Measurements. To put things into perspective, each of the first three sessions began with a review. All sessions were scheduled to allow ample time for discussion. A brief review of each session is provided.

  4. Proceedings of the Polar Processes on Mars Workshop

    NASA Astrophysics Data System (ADS)

    Haberle, Robert M.

    1988-12-01

    Included in this publication is a collection of abstracts from the NASA-sponsored workshop, Polar Processes on Mars, which was held at the Sunnyvale Hilton Hotel, Sunnyvale, California, on 12 to 13 May 1988. Support for the workshop came from NASA's Planetary Geology and Geophysics program managed by Dr. Jospeh Boyce. The workshop is one of a series identified by MECA (an acronym for Mars: Evolution of its Climate and Atmosphere) as being worthy of focused research, but one for which it was not possible to hold during the project's lifetime. Consequently, it was held after the project ended. The MECA project was part of the Mars Data Analysis program. The workshop consisted of four sessions: The Polar Caps, Dynamics/Atmospheric Processes, Polar Geology, and Future Measurements. To put things into perspective, each of the first three sessions began with a review. All sessions were scheduled to allow ample time for discussion. A brief review of each session is provided.

  5. Polarization and molecular information transmission in the cell

    NASA Astrophysics Data System (ADS)

    Valdez-Gomez, Adriano; Ramirez-Santiago, Guillermo

    2012-02-01

    During chemotaxis, pseudopodia are extended at the leading edge and retracted at the back of the cell. Efficient chemotaxis is the result of a refined interplay between signaling modules to transmit and integrate spatial information such as PtdIns(3,4,5)P3. The localization of PtdIns(3,4,5)P3 is expected to depend on the distributions or activities of PI3Ks, PTEN, and 5-phosphatases. The spatial signals spread relatively slowly so that high local concentrations of PIP3 in the plasma membrane appear in patches. These gradients induce localization of PIP3 and PTEN to the front and back of the cell, respectively. To simulate this polarization process that involves the action of seven reaction-channels inside the cell we carried out extensive stochastic simulations using Gilliespie algorithm. The simulations were done on a square cell with ten thousand sites (100x100) emulating a square cell with side 10>μm long. We found that there are localized patches of PIP3 at the active receptors and segregation of PTEN on the opposite side of the cell. When we block the reaction-channel, PTEN + PIP3 ->PIP2 that involves the production of PIP2 we obtained a five-fold increase in the concentration of PIP3. This finding appears to be consistent with the o

  6. Postnatal Refinement of Auditory Hair Cell Planar Polarity Deficits Occurs in the Absence of Vangl2

    PubMed Central

    Copley, Catherine O.; Duncan, Jeremy S.; Liu, Chang; Cheng, Haixia

    2013-01-01

    The distinctive planar polarity of auditory hair cells is evident in the polarized organization of the stereociliary bundle. Mutations in the core planar cell polarity gene Van Gogh-like 2 (Vangl2) result in hair cells that fail to properly orient their stereociliary bundles along the mediolateral axis of the cochlea. The severity of this phenotype is graded along the length of the cochlea, similar to the hair cell differentiation gradient, suggesting that an active refinement process corrects planar polarity phenotypes in Vangl2 knock-out (KO) mice. Because Vangl2 gene deletions are lethal, Vangl2 conditional knock-outs (CKOs) were generated to test this hypothesis. When crossed with Pax2–Cre, Vangl2 is deleted from the inner ear, yielding planar polarity phenotypes similar to Vangl2 KOs at late embryonic stages except that Vangl2 CKO mice are viable and do not have craniorachischisis like Vangl2 KOs. Quantification of planar polarity deficits through postnatal development demonstrates the activity of a Vangl2-independent refinement process that rescues the planar polarity phenotype within 10 d of birth. In contrast, the Pax2–Cre;Vangl2 CKO has profound changes in the shape and distribution of outer pillar cell and Deiters' cell phalangeal processes that are not corrected during the period of planar polarity refinement. Auditory brainstem response analyses of adult mice show a 10–15 dB shift in auditory threshold, and distortion product otoacoustic emission measurements indicate that this mild hearing deficit is of cochlear origin. Together, these data demonstrate a Vangl2-independent refinement mechanism that actively reorients auditory stereociliary bundles and reveals an unexpected role of Vangl2 during supporting cell morphogenesis. PMID:23986237

  7. Regulation of actin assembly by microtubules in fission yeast cell polarity.

    PubMed

    Chang, Fred; Feierbach, Becket; Martin, Sophie

    2005-01-01

    It has been speculated that microtubule plus ends function to regulate the actin cytoskeleton in processes such as cytokinesis, cell polarization and cell migration. In the fission yeast Schizosaccharomyces pombe, interphase microtubules regulate cell polarity through proteins such as tea1p, a kelch repeat protein, and for3p, a formin that nucleates actin cable assembly at cell tips. Here, we review recent progress on understanding tea1p regulation and function. Microtubules may govern the localization of tea1p by transporting it on the plus ends of microtubules and depositing it directly onto the cell tip when the microtubule catastrophes. The interaction of tea1p with the CLIP170 protein tip1p is responsible for its localization at growing microtubule plus ends. Tea1p may regulate cell polarity by associating with large 'polarisome' complexes that include for3p. For3p is present at both cell tips, but is not on the microtubules. Tea1p is needed to localize the formin to establish polarized cell growth at cell tips that have not grown previously. These studies begin to elucidate a molecular pathway for how microtubules contribute to the proper spatial regulation of actin assembly and polarized cell growth. PMID:16355535

  8. Induction of CD4+ Regulatory and Polarized Effector/helper T Cells by Dendritic Cells

    PubMed Central

    2016-01-01

    Dendritic cells (DCs) are considered to play major roles during the induction of T cell immune responses as well as the maintenance of T cell tolerance. Naive CD4+ T cells have been shown to respond with high plasticity to signals inducing their polarization into effector/helper or regulatory T cells. Data obtained from in vitro generated bone-marrow (BM)-derived DCs as well as genetic mouse models revealed an important but not exclusive role of DCs in shaping CD4+ T cell responses. Besides the specialization of some conventional DC subsets for the induction of polarized immunity, also the maturation stage, activation of specialized transcription factors and the cytokine production of DCs have major impact on CD4+ T cells. Since in vitro generated BM-DCs show a high diversity to shape CD4+ T cells and their high similarity to monocyte-derived DCs in vivo, this review reports data mainly on BM-DCs in this process and only touches the roles of transcription factors or of DC subsets, which have been discussed elsewhere. Here, recent findings on 1) the conversion of naive into anergic and further into Foxp3− regulatory T cells (Treg) by immature DCs, 2) the role of RelB in steady state migratory DCs (ssmDCs) for conversion of naive T cells into Foxp3+ Treg, 3) the DC maturation signature for polarized Th2 cell induction and 4) the DC source of IL-12 for Th1 induction are discussed. PMID:26937228

  9. Process and apparatus for measuring degree of polarization and angle of major axis of polarized beam of light

    DOEpatents

    Decker, Derek E.; Toeppen, John S.

    1994-01-01

    Apparatus and process are disclosed for calibrating measurements of the phase of the polarization of a polarized beam and the angle of the polarized optical beam's major axis of polarization at a diagnostic point with measurements of the same parameters at a point of interest along the polarized beam path prior to the diagnostic point. The process is carried out by measuring the phase angle of the polarization of the beam and angle of the major axis at the point of interest, using a rotatable polarizer and a detector, and then measuring these parameters again at a diagnostic point where a compensation apparatus, including a partial polarizer, which may comprise a stack of glass plates, is disposed normal to the beam path between a rotatable polarizer and a detector. The partial polarizer is then rotated both normal to the beam path and around the axis of the beam path until the detected phase of the beam polarization equals the phase measured at the point of interest. The rotatable polarizer at the diagnostic point may then be rotated manually to determine the angle of the major axis of the beam and this is compared with the measured angle of the major axis of the beam at the point of interest during calibration. Thereafter, changes in the polarization phase, and in the angle of the major axis, at the point of interest can be monitored by measuring the changes in these same parameters at the diagnostic point.

  10. A Predictive Model for Yeast Cell Polarization in Pheromone Gradients

    PubMed Central

    Calvez, Vincent; Voituriez, Raphaël; Gonçalves-Sá, Joana; Guo, Chin-Lin; Jiang, Xingyu; Murray, Andrew; Meunier, Nicolas

    2016-01-01

    Budding yeast cells exist in two mating types, a and α, which use peptide pheromones to communicate with each other during mating. Mating depends on the ability of cells to polarize up pheromone gradients, but cells also respond to spatially uniform fields of pheromone by polarizing along a single axis. We used quantitative measurements of the response of a cells to α-factor to produce a predictive model of yeast polarization towards a pheromone gradient. We found that cells make a sharp transition between budding cycles and mating induced polarization and that they detect pheromone gradients accurately only over a narrow range of pheromone concentrations corresponding to this transition. We fit all the parameters of the mathematical model by using quantitative data on spontaneous polarization in uniform pheromone concentration. Once these parameters have been computed, and without any further fit, our model quantitatively predicts the yeast cell response to pheromone gradient providing an important step toward understanding how cells communicate with each other. PMID:27077831

  11. A Predictive Model for Yeast Cell Polarization in Pheromone Gradients.

    PubMed

    Muller, Nicolas; Piel, Matthieu; Calvez, Vincent; Voituriez, Raphaël; Gonçalves-Sá, Joana; Guo, Chin-Lin; Jiang, Xingyu; Murray, Andrew; Meunier, Nicolas

    2016-04-01

    Budding yeast cells exist in two mating types, a and α, which use peptide pheromones to communicate with each other during mating. Mating depends on the ability of cells to polarize up pheromone gradients, but cells also respond to spatially uniform fields of pheromone by polarizing along a single axis. We used quantitative measurements of the response of a cells to α-factor to produce a predictive model of yeast polarization towards a pheromone gradient. We found that cells make a sharp transition between budding cycles and mating induced polarization and that they detect pheromone gradients accurately only over a narrow range of pheromone concentrations corresponding to this transition. We fit all the parameters of the mathematical model by using quantitative data on spontaneous polarization in uniform pheromone concentration. Once these parameters have been computed, and without any further fit, our model quantitatively predicts the yeast cell response to pheromone gradient providing an important step toward understanding how cells communicate with each other. PMID:27077831

  12. The final cut: cell polarity meets cytokinesis at the bud neck in S. cerevisiae.

    PubMed

    Juanes, Maria Angeles; Piatti, Simonetta

    2016-08-01

    Cell division is a fundamental but complex process that gives rise to two daughter cells. It includes an ordered set of events, altogether called "the cell cycle", that culminate with cytokinesis, the final stage of mitosis leading to the physical separation of the two daughter cells. Symmetric cell division equally partitions cellular components between the two daughter cells, which are therefore identical to one another and often share the same fate. In many cases, however, cell division is asymmetrical and generates two daughter cells that differ in specific protein inheritance, cell size, or developmental potential. The budding yeast Saccharomyces cerevisiae has proven to be an excellent system to investigate the molecular mechanisms governing asymmetric cell division and cytokinesis. Budding yeast is highly polarized during the cell cycle and divides asymmetrically, producing two cells with distinct sizes and fates. Many components of the machinery establishing cell polarization during budding are relocalized to the division site (i.e., the bud neck) for cytokinesis. In this review we recapitulate how budding yeast cells undergo polarized processes at the bud neck for cell division. PMID:27085703

  13. Modified Polar-Format Software for Processing SAR Data

    NASA Technical Reports Server (NTRS)

    Chen, Curtis

    2003-01-01

    HMPF is a computer program that implements a modified polar-format algorithm for processing data from spaceborne synthetic-aperture radar (SAR) systems. Unlike prior polar-format processing algorithms, this algorithm is based on the assumption that the radar signal wavefronts are spherical rather than planar. The algorithm provides for resampling of SAR pulse data from slant range to radial distance from the center of a reference sphere that is nominally the local Earth surface. Then, invoking the projection-slice theorem, the resampled pulse data are Fourier-transformed over radial distance, arranged in the wavenumber domain according to the acquisition geometry, resampled to a Cartesian grid, and inverse-Fourier-transformed. The result of this process is the focused SAR image. HMPF, and perhaps other programs that implement variants of the algorithm, may give better accuracy than do prior algorithms for processing strip-map SAR data from high altitudes and may give better phase preservation relative to prior polar-format algorithms for processing spotlight-mode SAR data.

  14. Reciprocal and dynamic polarization of planar cell polarity core components and myosin

    PubMed Central

    Newman-Smith, Erin; Kourakis, Matthew J; Reeves, Wendy; Veeman, Michael; Smith, William C

    2015-01-01

    The Ciona notochord displays planar cell polarity (PCP), with anterior localization of Prickle (Pk) and Strabismus (Stbm). We report that a myosin is polarized anteriorly in these cells and strongly colocalizes with Stbm. Disruption of the actin/myosin machinery with cytochalasin or blebbistatin disrupts polarization of Pk and Stbm, but not of myosin complexes, suggesting a PCP-independent aspect of myosin localization. Wash out of cytochalasin restored Pk polarization, but not if done in the presence of blebbistatin, suggesting an active role for myosin in core PCP protein localization. On the other hand, in the pk mutant line, aimless, myosin polarization is disrupted in approximately one third of the cells, indicating a reciprocal action of core PCP signaling on myosin localization. Our results indicate a complex relationship between the actomyosin cytoskeleton and core PCP components in which myosin is not simply a downstream target of PCP signaling, but also required for PCP protein localization. DOI: http://dx.doi.org/10.7554/eLife.05361.001 PMID:25866928

  15. Planar cell polarity links axes of spatial dynamics in neural-tube closure.

    PubMed

    Nishimura, Tamako; Honda, Hisao; Takeichi, Masatoshi

    2012-05-25

    Neural-tube closure is a critical step of embryogenesis, and its failure causes serious birth defects. Coordination of two morphogenetic processes--convergent extension and neural-plate apical constriction--ensures the complete closure of the neural tube. We now provide evidence that planar cell polarity (PCP) signaling directly links these two processes. In the bending neural plates, we find that a PCP-regulating cadherin, Celsr1, is concentrated in adherens junctions (AJs) oriented toward the mediolateral axes of the plates. At these AJs, Celsr1 cooperates with Dishevelled, DAAM1, and the PDZ-RhoGEF to upregulate Rho kinase, causing their actomyosin-dependent contraction in a planar-polarized manner. This planar-polarized contraction promotes simultaneous apical constriction and midline convergence of neuroepithelial cells. Together our findings demonstrate that PCP signals confer anisotropic contractility on the AJs, producing cellular forces that promote the polarized bending of the neural plate. PMID:22632972

  16. Influence of cell shape, inhomogeneities and diffusion barriers in cell polarization models

    NASA Astrophysics Data System (ADS)

    Giese, Wolfgang; Eigel, Martin; Westerheide, Sebastian; Engwer, Christian; Klipp, Edda

    2015-12-01

    In silico experiments bear the potential for further understanding of biological transport processes by allowing a systematic modification of any spatial property and providing immediate simulation results. Cell polarization and spatial reorganization of membrane proteins are fundamental for cell division, chemotaxis and morphogenesis. We chose the yeast Saccharomyces cerevisiae as an exemplary model system which entails the shuttling of small Rho GTPases such as Cdc42 and Rho, between an active membrane-bound form and an inactive cytosolic form. We used partial differential equations to describe the membrane-cytosol shuttling of proteins. In this study, a consistent extension of a class of 1D reaction-diffusion systems into higher space dimensions is suggested. The membrane is modeled as a thin layer to allow for lateral diffusion and the cytosol is modeled as an enclosed volume. Two well-known polarization mechanisms were considered. One shows the classical Turing-instability patterns, the other exhibits wave-pinning dynamics. For both models, we investigated how cell shape and diffusion barriers like septin structures or bud scars influence the formation of signaling molecule clusters and subsequent polarization. An extensive set of in silico experiments with different modeling hypotheses illustrated the dependence of cell polarization models on local membrane curvature, cell size and inhomogeneities on the membrane and in the cytosol. In particular, the results of our computer simulations suggested that for both mechanisms, local diffusion barriers on the membrane facilitate Rho GTPase aggregation, while diffusion barriers in the cytosol and cell protrusions limit spontaneous molecule aggregations of active Rho GTPase locally.

  17. Characterization of PEM fuel cell degradation by polarization change curves

    NASA Astrophysics Data System (ADS)

    Bezmalinovic, Dario; Simic, Boris; Barbir, Frano

    2015-10-01

    Polarization change curves, defined as a difference between the polarization curve at the beginning of life and the actual polarization curve after the cell has been operational for some time, were used to analyze degradation of a PEM fuel cell exposed to voltage cycling as an accelerated stress test for electrocatalyst degradation. Degradation, i.e., loss of voltage was due to increase of activation losses and increase of resistance in the catalyst layer, both most likely due to the loss of catalyst electrochemically active area. The results of the polarization change curves analysis correspond to the findings of the periodic individual tests performed during the accelerated stress test, such as electrochemical impedance spectroscopy, cyclic voltammetry and linear sweep voltammetry. Therefore, this method has potential to be used as a relatively quick and simple, yet effective, degradation diagnostic tool.

  18. Feedback Mechanisms in a Mechanical Model of Cell Polarization

    PubMed Central

    Wang, Xinxin; Carlsson, Anders E.

    2014-01-01

    Directed cell migration requires a spatially polarized distribution of polymerized actin. We develop and treat a mechanical model of cell polarization based on polymerization and depolymerization of actin filaments at the two ends of a cell, modulated by forces at either end that are coupled by the cell membrane. We solve this model using both a simulation approach that treats filament nucleation, polymerization, and depolymerization stochastically, and a rate-equation approach based on key properties such as the number of filaments N and the number of polymerized subunits F at either end of the cell. The rate-equation approach agrees closely with the stochastic approach at steady state and, when appropriately generalized, also predicts the dynamic behavior accurately. The calculated transitions from symmetric to polarized states show that polarization is enhanced by a high free-actin concentration, a large pointed-end off-rate, a small barbed-end off-rate, and a small spontaneous nucleation rate. The rate-equation approach allows us to perform a linear-stability analysis to pin down the key interactions that drive the polarization. The polarization is driven by a positive-feedback loop having two interactions. First, an increase in F at one side of the cell lengthens the filaments and thus reduces the decay rate of N (increasing N); second, increasing N enhances F because the force per growing filament tip is reduced. We find that the transitions induced by changing system properties result from supercritical pitchfork bifurcations. The filament lifetime depends strongly on the average filament length, and this effect is crucial for obtaining polarization correctly. PMID:25313164

  19. Kif26b controls endothelial cell polarity through the Dishevelled/Daam1-dependent planar cell polarity–signaling pathway

    PubMed Central

    Guillabert-Gourgues, Aude; Jaspard-Vinassa, Beatrice; Bats, Marie-Lise; Sewduth, Raj N.; Franzl, Nathalie; Peghaire, Claire; Jeanningros, Sylvie; Moreau, Catherine; Roux, Etienne; Larrieu-Lahargue, Frederic; Dufourcq, Pascale; Couffinhal, Thierry; Duplàa, Cecile

    2016-01-01

    Angiogenesis involves the coordinated growth and migration of endothelial cells (ECs) toward a proangiogenic signal. The Wnt planar cell polarity (PCP) pathway, through the recruitment of Dishevelled (Dvl) and Dvl-associated activator of morphogenesis (Daam1), has been proposed to regulate cell actin cytoskeleton and microtubule (MT) reorganization for oriented cell migration. Here we report that Kif26b—a kinesin—and Daam1 cooperatively regulate initiation of EC sprouting and directional migration via MT reorganization. First, we find that Kif26b is recruited within the Dvl3/Daam1 complex. Using a three-dimensional in vitro angiogenesis assay, we show that Kif26b and Daam1 depletion impairs tip cell polarization and destabilizes extended vascular processes. Kif26b depletion specifically alters EC directional migration and mislocalized MT organizing center (MTOC)/Golgi and myosin IIB cell rear enrichment. Therefore the cell fails to establish a proper front–rear polarity. Of interest, Kif26b ectopic expression rescues the siDaam1 polarization defect phenotype. Finally, we show that Kif26b functions in MT stabilization, which is indispensable for asymmetrical cell structure reorganization. These data demonstrate that Kif26b, together with Dvl3/Daam1, initiates cell polarity through the control of PCP signaling pathway–dependent activation. PMID:26792835

  20. A Modeling Approach to Study the Effect of Cell Polarization on Keratinocyte Migration

    PubMed Central

    Fuhr, Matthias Jörg; Meyer, Michael; Fehr, Eric; Ponzio, Gilles

    2015-01-01

    The skin forms an efficient barrier against the environment, and rapid cutaneous wound healing after injury is therefore essential. Healing of the uppermost layer of the skin, the epidermis, involves collective migration of keratinocytes, which requires coordinated polarization of the cells. To study this process, we developed a model that allows analysis of live-cell images of migrating keratinocytes in culture based on a small number of parameters, including the radius of the cells, their mass and their polarization. This computational approach allowed the analysis of cell migration at the front of the wound and a reliable identification and quantification of the impaired polarization and migration of keratinocytes from mice lacking fibroblast growth factors 1 and 2 – an established model of impaired healing. Therefore, our modeling approach is suitable for large-scale analysis of migration phenotypes of cells with specific genetic defects or upon treatment with different pharmacological agents. PMID:25671585

  1. Apicobasal polarity controls lymphocyte adhesion to hepatic epithelial cells.

    PubMed

    Reglero-Real, Natalia; Alvarez-Varela, Adrián; Cernuda-Morollón, Eva; Feito, Jorge; Marcos-Ramiro, Beatriz; Fernández-Martín, Laura; Gómez-Lechón, Maria José; Muntané, Jordi; Sandoval, Pilar; Majano, Pedro L; Correas, Isabel; Alonso, Miguel A; Millán, Jaime

    2014-09-25

    Loss of apicobasal polarity is a hallmark of epithelial pathologies. Leukocyte infiltration and crosstalk with dysfunctional epithelial barriers are crucial for the inflammatory response. Here, we show that apicobasal architecture regulates the adhesion between hepatic epithelial cells and lymphocytes. Polarized hepatocytes and epithelium from bile ducts segregate the intercellular adhesion molecule 1 (ICAM-1) adhesion receptor onto their apical, microvilli-rich membranes, which are less accessible by circulating immune cells. Upon cell depolarization, hepatic ICAM-1 becomes exposed and increases lymphocyte binding. Polarized hepatic cells prevent ICAM-1 exposure to lymphocytes by redirecting basolateral ICAM-1 to apical domains. Loss of ICAM-1 polarity occurs in human inflammatory liver diseases and can be induced by the inflammatory cytokine tumor necrosis factor alpha (TNF-α). We propose that adhesion receptor polarization is a parenchymal immune checkpoint that allows functional epithelium to hamper leukocyte binding. This contributes to the haptotactic guidance of leukocytes toward neighboring damaged or chronically inflamed epithelial cells that expose their adhesion machinery. PMID:25242329

  2. A Molecular Switch for the Orientation of Epithelial Cell Polarization

    PubMed Central

    Bryant, David M.; Roignot, Julie; Datta, Anirban; Overeem, Arend W.; Kim, Minji; Yu, Wei; Peng, Xiao; Eastburn, Dennis J.; Ewald, Andrew J.; Werb, Zena; Mostov, Keith E.

    2014-01-01

    SUMMARY The formation of epithelial tissues containing lumens requires not only the apical-basolateral polarization of cells, but also the coordinated orientation of this polarity such that the apical surfaces of neighboring cells all point toward the central lumen. Defects in extracellular matrix (ECM) signaling lead to inverted polarity so that the apical surfaces face the surrounding ECM. We report a molecular switch mechanism controlling polarity orientation. ECM signals through a β1-integrin/FAK/p190RhoGAP complex to down-regulate a RhoA/ROCK/Ezrin pathway at the ECM interface. PKCβII phosphorylates the apical identity-promoting Podocalyxin/NHERF1/Ezrin complex, removing Podocalyxin from the ECM-abutting cell surface and initiating its transcytosis to an apical membrane initiation site for lumen formation. Inhibition of this switch mechanism results in the retention of Podocalyxin at the ECM interface and the development instead of collective front-rear polarization and motility. Thus, ECM-derived signals control the morphogenesis of epithelial tissues by controlling the collective orientation of epithelial polarization. PMID:25307480

  3. Balloon cell melanoma: a case report with polarized and non-polarized dermatoscopy and dermatopathology.

    PubMed

    Maher, James; Cameron, Alan; Wallace, Sharon; Acosta-Rojas, Rafael; Weedon, David; Rosendahl, Cliff

    2014-01-01

    Balloon cell melanoma is a rare melanoma subtype, with only one previous case with dermatoscopy published. It is often non-pigmented, leading to diagnostic difficulty, and there is a tendency for lesions to be thick at diagnosis. We report a case of balloon cell melanoma on the forearm of a 61-year-old man with both polarized and non-polarized dermatoscopy and dermatopathology. It presented as a firm pale nodule with focal eccentric pigmentation. The clinical images evoke a differential diagnosis of dermatofibroma, dermal nevus, Spitz nevus and basal cell carcinoma as well as melanoma. This melanoma was partially pigmented due to a small, pigmented superficial spreading component on the edge of the non-pigmented balloon cell nodule, prompting further evaluation. In retrospect there was the clue to malignancy of polarizing-specific white lines (chrysalis structures) and polymorphous vessels, including a pattern of dot vessels. The reticular lines exclude basal cell carcinoma, polarizing-specific white lines are inconsistent with the diagnosis of dermal nevus and their eccentric location is inconsistent with both Spitz nevus and dermatofibroma. Excision biopsy was performed, revealing a superficial spreading melanoma with two distinct invasive components, one of atypical non-mature epithelioid cells and the other an amelanotic nodular component, comprising more than 50% of the lesion, characterized by markedly distended epithelioid melanocytes showing pseudo-xanthomatous cytoplasmic balloon cell morphology. A diagnosis of balloon cell melanoma, Breslow thickness 1.9 mm, mitotic rate 3 per square millimeter was rendered. Wide local excision was performed, as was sentinel lymph node biopsy, which was negative. PMID:24520518

  4. Polarized Fluorescence Microscopy to Study Cytoskeleton Assembly and Organization in Live Cells.

    PubMed

    McQuilken, Molly; Mehta, Shalin B; Verma, Amitabh; Harris, Grant; Oldenbourg, Rudolf; Gladfelter, Amy S

    2015-01-01

    The measurement of not only the location but also the organization of molecules in live cells is crucial to understanding diverse biological processes. Polarized light microscopy provides a nondestructive means to evaluate order within subcellular domains. When combined with fluorescence microscopy and GFP-tagged proteins, the approach can reveal organization within specific populations of molecules. This unit describes a protocol for measuring the architectural dynamics of cytoskeletal components using polarized fluorescence microscopy and OpenPolScope open-access software (http://www.openpolscope.org). The protocol describes installation of linear polarizers or a liquid crystal (LC) universal compensator, calibration of the system, polarized fluorescence imaging, and analysis. The use of OpenPolScope software and hardware allows for reliable, user-friendly image acquisition to measure and analyze polarized fluorescence. PMID:26061244

  5. Polarized Fluorescence Microscopy to Study Cytoskeleton Assembly and Organization in live cells

    PubMed Central

    McQuilken, Molly; Mehta, Shalin B.; Verma, Amitabh; Harris, Grant; Oldenbourg, Rudolf; Gladfelter, Amy S.

    2015-01-01

    The measurement of not only the location but also the organization of molecules in live cells is crucial to understanding diverse biological processes. Polarized light microscopy provides a nondestructive means to evaluate order within subcellular domains. When combined with fluorescence microscopy and GFP-tagged proteins, the approach can reveal organization within specific populations of molecules. This unit describes a protocol for measuring the architectural dynamics of cytoskeletal components using polarized fluorescence microscopy and OpenPolScope open-access software (www.openpolscope.org). The protocol describes installation of linear polarizers or a liquid crystal (LC) universal compensator, calibration of the system, polarized fluorescence imaging, and analysis. The use of OpenPolScope software and hardware allows for reliable, user-friendly image acquisition to measure and analyze polarized fluorescence. PMID:26061244

  6. LKB1 Regulates Pancreatic β Cell Size, Polarity, and Function

    PubMed Central

    Granot, Zvi; Swisa, Avital; Magenheim, Judith; Stolovich-Rain, Miri; Fujimoto, Wakako; Manduchi, Elisabetta; Miki, Takashi; Lennerz, Jochen K.; Stoeckert, Christian J.; Meyuhas, Oded; Seino, Susumu; Permutt, M. Alan; Piwnica-Worms, Helen; Bardeesy, Nabeel; Dor, Yuval

    2009-01-01

    Summary Pancreatic β cells, organized in the islets of Langerhans, sense glucose and secrete appropriate amounts of insulin. We have studied the roles of LKB1, a conserved kinase implicated in the control of cell polarity and energy metabolism, in adult β cells. LKB1-deficient β cells show a dramatic increase in insulin secretion in vivo. Histologically, LKB1-deficient β cells have striking alterations in the localization of the nucleus and cilia relative to blood vessels, suggesting a shift from hepatocyte-like to columnar polarity. Additionally, LKB1 deficiency causes a 65% increase in β cell volume. We show that distinct targets of LKB1 mediate these effects. LKB1 controls β cell size, but not polarity, via the mTOR pathway. Conversely, the precise position of the β cell nucleus, but not cell size, is controlled by the LKB1 target Par1b. Insulin secretion and content are restricted by LKB1, at least in part, via AMPK. These results expose a molecular mechanism, orchestrated by LKB1, for the coordinated maintenance of β cell size, form, and function. PMID:19808022

  7. Matrix rigidity optimizes the polarization of stem cells

    NASA Astrophysics Data System (ADS)

    Zemel, Assaf; Rehfeldt, Florian; Brown, Andre; Discher, Dennis; Safran, Samuel

    2009-03-01

    We present a theoretical model and experiments to explain the non-monotonic dependence of stress-fiber polarization in stem cells on matrix rigidity. The theory generalizes the treatment of elastic inclusions to ``living'' inclusions (cells) whose active polarizability, unlike non-living matter, depends on the feedback of cellular forces that develop in response to matrix stresses. We demonstrate experimentally that the stress fibers in adult mesenchymal stem cells, generally orient parallel to the long axis of the cells, with an anisotropy that depends non-monotonically on substrate stiffness. Consistent with these experiments, our theory predicts that the magnitude of the cellular force increases monotonically with the matrix rigidity while the polarization anisotropy shows a maximum that depends on the cell shape and the elastic modulus of the medium. These findings offer a mechanical correlate for the observation that stem cell differentiation optimizes in a range of matrix rigidities that depends on the tissue type.

  8. Carbon Dioxide Convection in the Martian Polar Night and Its Implications for Polar Processes

    NASA Technical Reports Server (NTRS)

    Colaprete, A.; Haberle, R. M.

    2003-01-01

    Each Martian year nearly 30% of the atmosphere is exchanged with the polar ice caps. This exchange occurs through a combination of direct surface condensation and atmospheric precipitation of carbon dioxide. It has long been thought the amount of condensation within the polar night is maintained by a balance between diabatic processes such as radiative cooling and latent heating from condensing CO2. This assumption manifests itself in Mars General Circulation Models (GCM) in such a way as to never allow the atmospheric temperature to dip below the saturation temperature of CO2. However, observations from Mars Global Surveyor (MGS) Radio Science (RS) and the Thermal Emission Spectrometer (TES) have demonstrated this assumption to be, at best, approximate. Both RS and TES observations within the polar nights of both poles indicate substantial supersaturated regions with respect to CO2. The observed temperature profiles suggest conditionally unstable regions containing planetary significant amounts of potential convective energy. Presented here are estimates of the total planetary inventory of convective available potential energy (CAPE) and the potential convective energy flux (PCEF). The values for CAPE and PCEF are derived from RS temperature profiles and compared to Mars GCM results using a new convective CO2 cloud model that allows for the formation of CAPE.

  9. Coordinating cell polarity and cell cycle progression: what can we learn from flies and worms?

    PubMed Central

    Noatynska, Anna; Tavernier, Nicolas; Gotta, Monica; Pintard, Lionel

    2013-01-01

    Spatio-temporal coordination of events during cell division is crucial for animal development. In recent years, emerging data have strengthened the notion that tight coupling of cell cycle progression and cell polarity in dividing cells is crucial for asymmetric cell division and ultimately for metazoan development. Although it is acknowledged that such coupling exists, the molecular mechanisms linking the cell cycle and cell polarity machineries are still under investigation. Key cell cycle regulators control cell polarity, and thus influence cell fate determination and/or differentiation, whereas some factors involved in cell polarity regulate cell cycle timing and proliferation potential. The scope of this review is to discuss the data linking cell polarity and cell cycle progression, and the importance of such coupling for asymmetric cell division. Because studies in model organisms such as Caenorhabditis elegans and Drosophila melanogaster have started to reveal the molecular mechanisms of this coordination, we will concentrate on these two systems. We review examples of molecular mechanisms suggesting a coupling between cell polarity and cell cycle progression. PMID:23926048

  10. Competition for actin between two distinct F-actin networks defines a bistable switch for cell polarization.

    PubMed

    Lomakin, Alexis J; Lee, Kun-Chun; Han, Sangyoon J; Bui, Duyen A; Davidson, Michael; Mogilner, Alex; Danuser, Gaudenz

    2015-11-01

    Symmetry-breaking polarization enables functional plasticity of cells and tissues and is yet not well understood. Here we show that epithelial cells, hard-wired to maintain a static morphology and to preserve tissue organization, can spontaneously switch to a migratory polarized phenotype after relaxation of the actomyosin cytoskeleton. We find that myosin II engages actin in the formation of cortical actomyosin bundles and thus makes it unavailable for deployment in the process of dendritic growth normally driving cell motility. Under low-contractility regimes, epithelial cells polarize in a front-back manner owing to the emergence of actin retrograde flows powered by dendritic polymerization of actin. Coupled to cell movement, the flows transport myosin II from the front to the back of the cell, where the motor locally 'locks' actin in contractile bundles. This polarization mechanism could be employed by embryonic and cancer epithelial cells in microenvironments where high-contractility-driven cell motion is inefficient. PMID:26414403

  11. A protein interaction map for cell polarity development

    PubMed Central

    Drees, Becky L.; Sundin, Bryan; Brazeau, Elizabeth; Caviston, Juliane P.; Chen, Guang-Chao; Guo, Wei; Kozminski, Keith G.; Lau, Michelle W.; Moskow, John J.; Tong, Amy; Schenkman, Laura R.; McKenzie, Amos; Brennwald, Patrick; Longtine, Mark; Bi, Erfei; Chan, Clarence; Novick, Peter; Boone, Charles; Pringle, John R.; Davis, Trisha N.; Fields, Stanley; Drubin, David G.

    2001-01-01

    Many genes required for cell polarity development in budding yeast have been identified and arranged into a functional hierarchy. Core elements of the hierarchy are widely conserved, underlying cell polarity development in diverse eukaryotes. To enumerate more fully the protein–protein interactions that mediate cell polarity development, and to uncover novel mechanisms that coordinate the numerous events involved, we carried out a large-scale two-hybrid experiment. 68 Gal4 DNA binding domain fusions of yeast proteins associated with the actin cytoskeleton, septins, the secretory apparatus, and Rho-type GTPases were used to screen an array of yeast transformants that express ∼90% of the predicted Saccharomyces cerevisiae open reading frames as Gal4 activation domain fusions. 191 protein–protein interactions were detected, of which 128 had not been described previously. 44 interactions implicated 20 previously uncharacterized proteins in cell polarity development. Further insights into possible roles of 13 of these proteins were revealed by their multiple two-hybrid interactions and by subcellular localization. Included in the interaction network were associations of Cdc42 and Rho1 pathways with proteins involved in exocytosis, septin organization, actin assembly, microtubule organization, autophagy, cytokinesis, and cell wall synthesis. Other interactions suggested direct connections between Rho1- and Cdc42-regulated pathways; the secretory apparatus and regulators of polarity establishment; actin assembly and the morphogenesis checkpoint; and the exocytic and endocytic machinery. In total, a network of interactions that provide an integrated response of signaling proteins, the cytoskeleton, and organelles to the spatial cues that direct polarity development was revealed. PMID:11489916

  12. A protein interaction map for cell polarity development.

    PubMed

    Drees, B L; Sundin, B; Brazeau, E; Caviston, J P; Chen, G C; Guo, W; Kozminski, K G; Lau, M W; Moskow, J J; Tong, A; Schenkman, L R; McKenzie, A; Brennwald, P; Longtine, M; Bi, E; Chan, C; Novick, P; Boone, C; Pringle, J R; Davis, T N; Fields, S; Drubin, D G

    2001-08-01

    Many genes required for cell polarity development in budding yeast have been identified and arranged into a functional hierarchy. Core elements of the hierarchy are widely conserved, underlying cell polarity development in diverse eukaryotes. To enumerate more fully the protein-protein interactions that mediate cell polarity development, and to uncover novel mechanisms that coordinate the numerous events involved, we carried out a large-scale two-hybrid experiment. 68 Gal4 DNA binding domain fusions of yeast proteins associated with the actin cytoskeleton, septins, the secretory apparatus, and Rho-type GTPases were used to screen an array of yeast transformants that express approximately 90% of the predicted Saccharomyces cerevisiae open reading frames as Gal4 activation domain fusions. 191 protein-protein interactions were detected, of which 128 had not been described previously. 44 interactions implicated 20 previously uncharacterized proteins in cell polarity development. Further insights into possible roles of 13 of these proteins were revealed by their multiple two-hybrid interactions and by subcellular localization. Included in the interaction network were associations of Cdc42 and Rho1 pathways with proteins involved in exocytosis, septin organization, actin assembly, microtubule organization, autophagy, cytokinesis, and cell wall synthesis. Other interactions suggested direct connections between Rho1- and Cdc42-regulated pathways; the secretory apparatus and regulators of polarity establishment; actin assembly and the morphogenesis checkpoint; and the exocytic and endocytic machinery. In total, a network of interactions that provide an integrated response of signaling proteins, the cytoskeleton, and organelles to the spatial cues that direct polarity development was revealed. PMID:11489916

  13. Towards Hybrid Quantum Information Processing with Polar Molecules

    NASA Astrophysics Data System (ADS)

    Rabl, Peter

    2008-05-01

    With the ongoing miniaturization of on-chip traps for atoms and ions it is timely to think about coherent interfaces between AMO and solid state systems with potential applications for new hybrid implementations for quantum computers. In this talk I will discuss a potential scenario, where ensembles of polar molecules serve as long-lived quantum memories for superconducting qubits and quantum information is transmitted via a high-Q microwave cavity. Polar molecules combine the exceptional features of a large electric dipole moment and long-lived rotational states with level splittings in the GHz regime. When trapped close to the surface of a chip this combination allows strong interactions with coherent solid state devices, e.g., superconducting microwave cavities or Josephson qubits. I will first introduce the system consisting of a single polar molecule coupled to a stripline cavity which realizes a cavity QED system in the microwave regime and discuss applications for quantum information processing, state detection and new cavity-assisted cooling schemes for polar molecules. I will then switch to molecular ensemble qubits where quantum information is encoded in collective spin or rotational excitations of an ensemble of N molecules. Ensemble qubits benefit from a collectively enhanced coupling ˜√N which allows quantum state transfer between the molecules and, e.g., a charge qubit on a timescale that is compatible with typical coherence times in a solid state environment. With the goal to protect ensemble qubits from collisions, I will finally discuss a scenario, where molecules are prepared in a crystalline phase under 1D trapping conditions and dipole moments aligned by an external field.

  14. High voltage processing of the SLC polarized electron gun

    SciTech Connect

    Saez, P.; Clendenin, J.; Garden, C.; Hoyt, E.; Klaisner, L.; Prescott, C.; Schultz, D.; Tang, H.

    1993-04-01

    The SLC polarized electron gun operates at 120 kV with very low dark current to maintain the ultra high vacuum (UHV). This strict requirement protects the extremely sensitive photocathode from contaminants caused by high voltage (HV) activity. Thorough HV processing is thus required x-ray sensitive photographic film, a nanoammeter in series with gun power supply, a radiation meter, a sensitive residual gas analyzer and surface x-ray spectrometry were used to study areas in the gun where HV activity occurred. By reducing the electric field gradients, carefully preparing the HV surfaces and adhering to very strict clean assembly procedures, we found it possible to process the gun so as to reduce both the dark current at operating voltage and the probability of HV discharge. These HV preparation and processing techniques are described.

  15. Local Pheromone Release from Dynamic Polarity Sites Underlies Cell-Cell Pairing during Yeast Mating.

    PubMed

    Merlini, Laura; Khalili, Bita; Bendezú, Felipe O; Hurwitz, Daniel; Vincenzetti, Vincent; Vavylonis, Dimitrios; Martin, Sophie G

    2016-04-25

    Cell pairing is central for many processes, including immune defense, neuronal connection, hyphal fusion, and sexual reproduction. How does a cell orient toward a partner, especially when faced with multiple choices? Fission yeast Schizosaccharomyces pombe P and M cells, which respectively express P and M factor pheromones [1, 2], pair during the mating process induced by nitrogen starvation. Engagement of pheromone receptors Map3 and Mam2 [3, 4] with their cognate pheromone ligands leads to activation of the Gα protein Gpa1 to signal sexual differentiation [3, 5, 6]. Prior to cell pairing, the Cdc42 GTPase, a central regulator of cell polarization, forms dynamic zones of activity at the cell periphery at distinct locations over time [7]. Here we show that Cdc42-GTP polarization sites contain the M factor transporter Mam1, the general secretion machinery, which underlies P factor secretion, and Gpa1, suggesting that these are sub-cellular zones of pheromone secretion and signaling. Zone lifetimes scale with pheromone concentration. Computational simulations of pair formation through a fluctuating zone show that the combination of local pheromone release and sensing, short pheromone decay length, and pheromone-dependent zone stabilization leads to efficient pair formation. Consistently, pairing efficiency is reduced in the absence of the P factor protease. Similarly, zone stabilization at reduced pheromone levels, which occurs in the absence of the predicted GTPase-activating protein for Ras, leads to reduction in pairing efficiency. We propose that efficient cell pairing relies on fluctuating local signal emission and perception, which become locked into place through stimulation. PMID:27020743

  16. Dressed spin of polarized {sup 3}He in a cell

    SciTech Connect

    Chu, P.-H.; Esler, A. M.; Peng, J. C.; Beck, D. H.; Chandler, D. E.; Clayton, S.; Williamson, S.; Yoder, J.; Hu, B.-Z.; Ngan, S. Y.; Sham, C. H.; So, L. H.

    2011-08-15

    We report a measurement of the modification of the effective precession frequency of polarized {sup 3}He atoms in response to a dressing field in a room-temperature cell. The {sup 3}He atoms were polarized using the metastability spin-exchange method. An oscillating dressing field was then applied perpendicular to the constant magnetic field. Modification of the {sup 3}He effective precession frequency was observed over a broad range of the amplitude and frequency of the dressing field. The observed effects are compared with calculations based on quantum optics formalism.

  17. Dressed spin of polarized 3He in a cell

    NASA Astrophysics Data System (ADS)

    Chu, P.-H.; Esler, A. M.; Peng, J. C.; Beck, D. H.; Chandler, D. E.; Clayton, S.; Hu, B.-Z.; Ngan, S. Y.; Sham, C. H.; So, L. H.; Williamson, S.; Yoder, J.

    2011-08-01

    We report a measurement of the modification of the effective precession frequency of polarized 3He atoms in response to a dressing field in a room-temperature cell. The 3He atoms were polarized using the metastability spin-exchange method. An oscillating dressing field was then applied perpendicular to the constant magnetic field. Modification of the 3He effective precession frequency was observed over a broad range of the amplitude and frequency of the dressing field. The observed effects are compared with calculations based on quantum optics formalism.

  18. Tropospheric entrainment as a source of ground level aerosols within the polar Antarctic cell

    NASA Astrophysics Data System (ADS)

    Humphries, R. S.; Schofield, R.; Keywood, M.; Wilson, S. R.; Klekociuk, A. R.; Paton-Walsh, C.

    2013-12-01

    The Antarctic region is a pristine environment without any significant anthropogenic influence. Measurements of aerosols in this environment therefore allow the study of natural aerosol properties and formation mechanisms in polar conditions, and also allow insight into polar atmospheric dynamics. Measurements in this region have been limited primarily to continental and coastal locations where permanent stations exist, with only one other measurement campaign passing through the sea ice region. The MAPS campaign (Measurements of Aerosols and Precursors during SIPEXII) occurred as part of SIPEX II (Sea Ice Physics and Ecosystems eXperiment II) voyage in Spring, 2012, and produced the first sea-ice focused aerosol dataset aimed at characterizing new particle formation processes in the pack ice off the coast of East Antarctica (~65°S, 120°E). Numerous atmospheric parameters and species were measured, including the number of aerosol particles in the 3-10 nm size range, the range associated with new particle formation. During the latitudinal transect through the sea ice, these measurements were used to identify the polar front - the boundary between the Polar cell and the Ferrel cell. Nuclei concentrations showed a clear and sudden change with latitude, averaging 51cm-3 north of the front in the Ferrel cell, and 766 cm-3 south of the front, in the Polar cell region. The latitudinal location of the polar front was also confirmed by wind directions which reflected global circulation patterns (Ferrel cell westerlies and Polar cell easterlies). Background aerosol populations in the Polar cell fluctuated significantly (3-10 nm particle concentrations ranged between 153 cm-3 to 2312 cm-3) but displayed no growth indicators, suggesting transport. Back-trajectories revealed that air parcels often descended from the free-troposphere within the previous 24-48 hrs. It is proposed that particle formation occurs in the free troposphere from precursors uplifted at the polar front

  19. Noise filtering tradeoffs in spatial gradient sensing and cell polarization response

    PubMed Central

    2011-01-01

    Background Cells sense chemical spatial gradients and respond by polarizing internal components. This process can be disrupted by gradient noise caused by fluctuations in chemical concentration. Results We investigated how external gradient noise affects spatial sensing and response focusing on noise-filtering and the resultant tradeoffs. First, using a coarse-grained mathematical model of gradient-sensing and cell polarity, we characterized three negative consequences of noise: Inhibition of the extent of polarization, degradation of directional accuracy, and production of a noisy output polarization. Next, we explored filtering strategies and discovered that a combination of positive feedback, multiple signaling stages, and time-averaging produced good results. There was an important tradeoff, however, because filtering resulted in slower polarization. Simulations demonstrated that a two-stage filter-amplifier resulted in a balanced outcome. Then, we analyzed the effect of noise on a mechanistic model of yeast cell polarization in response to gradients of mating pheromone. This analysis showed that yeast cells likely also combine the above three filtering mechanisms into a filter-amplifier structure to achieve impressive spatial-noise tolerance, but with the consequence of a slow response time. Further investigation of the amplifier architecture revealed two positive feedback loops, a fast inner and a slow outer, both of which contributed to noise-tolerant polarization. This model also made specific predictions about how orientation performance depended upon the ratio between the gradient slope (signal) and the noise variance. To test these predictions, we performed microfluidics experiments measuring the ability of yeast cells to orient to shallow gradients of mating pheromone. The results of these experiments agreed well with the modeling predictions, demonstrating that yeast cells can sense gradients shallower than 0.1% μm-1, approximately a single receptor

  20. Processing TOVS Polar Pathfinder data using the distributed batch controller

    NASA Astrophysics Data System (ADS)

    Duff, James; Salem, Kenneth M.; Schweiger, Axel; Livny, Miron

    1997-09-01

    The distributed batch controller (DBC) supports scientific batch data processing. Batch jobs are distributed by the DBC over a collection of computing resources. Since these resources may be widely scattered the DBC is well suited for collaborative research efforts whose resources may not be centrally located. The DBC provides its users with centralized monitoring and control of distributed batch jobs. Version 1 of the DBC is currently being used by the TOVS Polar Pathfinder project to generate Arctic atmospheric temperature and humidity profiles. Profile generating jobs are distributed and executed by the DBC on workstation clusters located at several sites across the US. This paper describes the data processing requirements of the TOVS Polar Pathfinder project, and how the DBC is being used to meet them. It also describes Version 2 of the DBC. DBC V2 is implemented in Java, and utilizes a number of advanced Java features such as threads and remote method invocation. It incorporates a number of functional enhancements. These include a flexible mechanism supporting interoperation of the DBC with a wider variety of execution resources and an improved user interface.

  1. Planar Cell Polarity Signaling in Collective Cell Movements During Morphogenesis and Disease

    PubMed Central

    Muñoz-Soriano, Verónica; Belacortu, Yaiza; Paricio, Nuria

    2012-01-01

    Collective and directed cell movements are crucial for diverse developmental processes in the animal kingdom, but they are also involved in wound repair and disease. During these processes groups of cells are oriented within the tissue plane, which is referred to as planar cell polarity (PCP). This requires a tight regulation that is in part conducted by the PCP pathway. Although this pathway was initially characterized in flies, subsequent studies in vertebrates revealed a set of conserved core factors but also effector molecules and signal modulators, which build the fundamental PCP machinery. The PCP pathway in Drosophila regulates several developmental processes involving collective cell movements such as border cell migration during oogenesis, ommatidial rotation during eye development, and embryonic dorsal closure. During vertebrate embryogenesis, PCP signaling also controls collective and directed cell movements including convergent extension during gastrulation, neural tube closure, neural crest cell migration, or heart morphogenesis. Similarly, PCP signaling is linked to processes such as wound repair, and cancer invasion and metastasis in adults. As a consequence, disruption of PCP signaling leads to pathological conditions. In this review, we will summarize recent findings about the role of PCP signaling in collective cell movements in flies and vertebrates. In addition, we will focus on how studies in Drosophila have been relevant to our understanding of the PCP molecular machinery and will describe several developmental defects and human disorders in which PCP signaling is compromised. Therefore, new discoveries about the contribution of this pathway to collective cell movements could provide new potential diagnostic and therapeutic targets for these disorders. PMID:23730201

  2. A combined binary interaction and phenotypic map of C. elegans cell polarity proteins

    PubMed Central

    Koorman, Thijs; Lemmens, Irma; Ramalho, João J.; Nieuwenhuize, Susan; van den Heuvel, Sander; Tavernier, Jan; Nance, Jeremy; Boxem, Mike

    2015-01-01

    The establishment of cell polarity is an essential process for the development of multicellular organisms and the functioning of cells and tissues. Here, we combine large-scale protein interaction mapping with systematic phenotypic profiling to study the network of physical interactions that underlies polarity establishment and maintenance in the nematode Caenorhabditis elegans. Using a fragment-based yeast two-hybrid strategy, we identified 439 interactions between 296 proteins, as well as the protein regions that mediate these interactions. Phenotypic profiling of the network resulted in the identification of 100 physically interacting protein pairs for which RNAi-mediated depletion caused a defect in the same polarity-related process. We demonstrate the predictive capabilities of the network by showing that the physical interaction between the RhoGAP PAC-1 and PAR-6 is required for radial polarization of the C. elegans embryo. Our network represents a valuable resource of candidate interactions that can be used to further our insight into cell polarization. PMID:26780296

  3. Iron repletion relocalizes hephaestin to a proximal basolateral compartment in polarized MDCK and Caco2 cells

    SciTech Connect

    Lee, Seung-Min; Attieh, Zouhair K.; Son, Hee Sook; Chen, Huijun; Bacouri-Haidar, Mhenia; Vulpe, Chris D.

    2012-05-11

    Highlights: Black-Right-Pointing-Pointer Hephaestin localizes in the perinuclear space in non-polarized cells. Black-Right-Pointing-Pointer Hephaestin localizes in the perinuclear space in iron deficient and polarized cells. Black-Right-Pointing-Pointer Hephaestin with apical iron moves near to basolateral membrane of polarized cells. Black-Right-Pointing-Pointer Peri-basolateral location of hephaestin is accessible to the extracellular space. Black-Right-Pointing-Pointer Hephaestin is involved in iron mobilization from the intestine to circulation. -- Abstract: While intestinal cellular iron entry in vertebrates employs multiple routes including heme and non-heme routes, iron egress from these cells is exclusively channeled through the only known transporter, ferroportin. Reduced intestinal iron export in sex-linked anemia mice implicates hephaestin, a ferroxidase, in this process. Polarized cells are exposed to two distinct environments. Enterocytes contact the gut lumen via the apical surface of the cell, and through the basolateral surface, to the body. Previous studies indicate both local and systemic control of iron uptake. We hypothesized that differences in iron availability at the apical and/or basolateral surface may modulate iron uptake via cellular localization of hephaestin. We therefore characterized the localization of hephaestin in two models of polarized epithelial cell lines, MDCK and Caco2, with varying iron availability at the apical and basolateral surfaces. Our results indicate that hephaestin is expressed in a supra-nuclear compartment in non-polarized cells regardless of the iron status of the cells and in iron deficient and polarized cells. In polarized cells, we found that both apical (as FeSO{sub 4}) and basolateral iron (as the ratio of apo-transferrin to holo-transferrin) affect mobilization of hephaestin from the supra-nuclear compartment. We find that the presence of apical iron is essential for relocalization of hephaestin to a

  4. Effect of EHF-radiation polarization on yeast cells

    SciTech Connect

    Golant, M.B.; Mudrik, D.G.; Kruglyakova, O.P.

    1994-07-01

    It is known that millimeter-wave radiation can cause numerous changes in living organisms. The detection of changes in the states of living organisms is a very complex task, since a complete biological examination is extremely complicated if not practically impossible. As a result, some important aftereffects could be undiscovered. Here we present experimental data on the effects of EHF radiation with left and right circular polarization on a yeast cell culture (Saccharomyces Carlsbergensis). EHF circular polarizers were specially prepared for this. The radiation had a fixed frequency f = 42.19 GHz, power p = 0.12 mW/cm{sup 2}, and 1-hr exposure time. If cell division cycles are synchronized by synchronization of the generated or EHF oscillations under the influence of external coherent EHF radiation, it follows that EHF oscillations chiefly with left circular polarization are excited in the cells. On the other hand, the examined results can be considered evidence that objects with the dimensions of cells are the primary receivers of EHF radiation in the cell culture. A ratio value d{sub mol}/{lambda} {approx} 10{sup -6} is too low to produce space dispersion at the molecular level.

  5. The variable polarity plasma arc welding process: Characteristics and performance

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Zhu, G. J.

    1991-01-01

    Significant advantages of the Variable Polarity Plasma Arc (VPPA) Welding Process include faster welding, fewer repairs, less joint preparation, reduced weldment distortion, and absence of porosity. The power distribution was analyzed for an argon plasma gas flow constituting the fluid in the VPPA Welding Process. The major heat loss at the torch nozzle is convective heat transfer; in the space between the outlet of the nozzle and the workpiece; radiative heat transfer; and in the keyhole in the workpiece, convective heat transfer. The power absorbed at the workpiece produces the molten puddle that solidifies into the weld bead. Crown and root widths, and crown and root heights of the weld bead are predicted. The basis is provided for an algorithm for automatic control of VPPA welding machine parameters to obtain desired weld bead dimensions.

  6. Satellite Cells in Muscular Dystrophy - Lost in Polarity.

    PubMed

    Chang, Natasha C; Chevalier, Fabien P; Rudnicki, Michael A

    2016-06-01

    Recent findings employing the mdx mouse model for Duchenne muscular dystrophy (DMD) have revealed that muscle satellite stem cells play a direct role in contributing to disease etiology and progression of DMD, the most common and severe form of muscular dystrophy. Lack of dystrophin expression in DMD has critical consequences in satellite cells including an inability to establish cell polarity, abrogation of asymmetric satellite stem-cell divisions, and failure to enter the myogenic program. Thus, muscle wasting in dystrophic mice is not only caused by myofiber fragility but is exacerbated by intrinsic satellite cell dysfunction leading to impaired regeneration. Despite intense research and clinical efforts, there is still no effective cure for DMD. In this review we highlight recent research advances in DMD and discuss the current state of treatment and, importantly, how we can incorporate satellite cell-targeted therapeutic strategies to correct satellite cell dysfunction in DMD. PMID:27161598

  7. A dual role for planar cell polarity genes in ciliated cells.

    PubMed

    Boutin, Camille; Labedan, Paul; Dimidschstein, Jordane; Richard, Fabrice; Cremer, Harold; André, Philipp; Yang, Yingzi; Montcouquiol, Mireille; Goffinet, Andre M; Tissir, Fadel

    2014-07-29

    In the nervous system, cilia dysfunction perturbs the circulation of the cerebrospinal fluid, thus affecting neurogenesis and brain homeostasis. A role for planar cell polarity (PCP) signaling in the orientation of cilia (rotational polarity) and ciliogenesis is established. However, whether and how PCP regulates cilia positioning in the apical domain (translational polarity) in radial progenitors and ependymal cells remain unclear. By analysis of a large panel of mutant mice, we show that two PCP signals are operating in ciliated cells. The first signal, controlled by cadherin, EGF-like, laminin G-like, seven-pass, G-type receptor (Celsr) 2, Celsr3, Frizzled3 (Fzd3) and Van Gogh like2 (Vangl2) organizes multicilia in individual cells (single-cell polarity), whereas the second signal, governed by Celsr1, Fzd3, and Vangl2, coordinates polarity between cells in both radial progenitors and ependymal cells (tissue polarity). Loss of either of these signals is associated with specific defects in the cytoskeleton. Our data reveal unreported functions of PCP and provide an integrated view of planar polarization of the brain ciliated cells. PMID:25024228

  8. Structure of polarization-resolved conoscopic patterns of planar oriented liquid crystal cells

    SciTech Connect

    Kiselev, A. D. Vovk, R. G.

    2010-05-15

    The geometry of distributions of the polarization of light in conoscopic patterns of planar oriented nematic and cholesteric liquid crystal (LC) cells is described in terms of the polarization singularities including C-points (points of circular polarization) and L lines (lines of linear polarization). Conditions for the formation of polarization singularities (C-points) in an ensemble of conoscopic patterns parametrized by the polarization azimuth and ellipticity of the incident light wave have been studied. A characteristic feature of these conditions is selectivity with respect to the polarization parameters of the incident light wave. The polarization azimuth and ellipticity are determining parameters for nematic and cholesteric LC cells, respectively.

  9. Spectral induced polarization for monitoring electrokinetic remediation processes

    NASA Astrophysics Data System (ADS)

    Masi, Matteo; Losito, Gabriella

    2015-12-01

    Electrokinetic remediation is an emerging technology for extracting heavy metals from contaminated soils and sediments. This method uses a direct or alternating electric field to induce the transport of contaminants toward the electrodes. The electric field also produces pH variations, sorption/desorption and precipitation/dissolution of species in the porous medium during remediation. Since heavy metal mobility is pH-dependent, the accurate control of pH inside the material is required in order to enhance the removal efficiency. The common approach for monitoring the remediation process both in laboratory and in the field is the chemical analysis of samples collected from discrete locations. The purpose of this study is the evaluation of Spectral Induced Polarization as an alternative method for monitoring geochemical changes in the contaminated mass during remediation. The advantage of this technique applied to field-scale is to offer higher resolution mapping of the remediation site and lower cost compared to the conventional sampling procedure. We carried out laboratory-scale electrokinetic remediation experiments on fine-grained marine sediments contaminated by heavy metal and we made Spectral Induced Polarization measurements before and after each treatment. Measurements were done in the frequency range 10- 3-103 Hz. By the deconvolution of the spectra using the Debye Decomposition method we obtained the mean relaxation time and total chargeability. The main finding of this work is that a linear relationship exists between the local total chargeability and pH, with good agreement. The observed behaviour of chargeability is interpreted as a direct consequence of the alteration of the zeta potential of the sediment particles due to pH changes. Such relationship has a significant value for the interpretation of induced polarization data, allowing the use of this technique for monitoring electrokinetic remediation at field-scale.

  10. Initiation of Hippo signaling is linked to polarity rather than to cell position in the pre-implantation mouse embryo.

    PubMed

    Anani, Shihadeh; Bhat, Shivani; Honma-Yamanaka, Nobuko; Krawchuk, Dayana; Yamanaka, Yojiro

    2014-07-01

    In the mouse embryo, asymmetric divisions during the 8-16 cell division generate two cell types, polar and apolar cells, that are allocated to outer and inner positions, respectively. This outer/inner configuration is the first sign of the formation of the first two cell lineages: trophectoderm (TE) and inner cell mass (ICM). Outer polar cells become TE and give rise to the placenta, whereas inner apolar cells become ICM and give rise to the embryo proper and yolk sac. Here, we analyze the frequency of asymmetric divisions during the 8-16 cell division and assess the relationships between cell polarity, cell and nuclear position, and Hippo signaling activation, the pathway that initiates lineage-specific gene expression in 16-cell embryos. Although the frequency of asymmetric divisions varied in each embryo, we found that more than six blastomeres divided asymmetrically in most embryos. Interestingly, many apolar cells in 16-cell embryos were located at outer positions, whereas only one or two apolar cells were located at inner positions. Live imaging analysis showed that outer apolar cells were eventually internalized by surrounding polar cells. Using isolated 8-cell blastomeres, we carefully analyzed the internalization process of apolar cells and found indications of higher cortical tension in apolar cells than in polar cells. Last, we found that apolar cells activate Hippo signaling prior to taking inner positions. Our results suggest that polar and apolar cells have intrinsic differences that establish outer/inner configuration and differentially regulate Hippo signaling to activate lineage-specific gene expression programs. PMID:24948601

  11. Minimal model for spontaneous cell polarization and edge activity in oscillating, rotating and migrating cells

    NASA Astrophysics Data System (ADS)

    Raynaud, Franck; Ambühl, Mark E.; Gabella, Chiara; Bornert, Alicia; Sbalzarini, Ivo F.; Meister, Jean-Jacques; Verkhovsky, Alexander B.

    2016-04-01

    How cells break symmetry and organize activity at their edges to move directionally is a fundamental question in cell biology. Physical models of cell motility commonly incorporate gradients of regulatory proteins and/or feedback from the motion itself to describe the polarization of this edge activity. These approaches, however, fail to explain cell behaviour before the onset of polarization. We use polarizing and moving fish epidermal cells as a model system to bridge the gap between cell behaviours before and after polarization. Our analysis suggests a novel and simple principle of self-organizing cell activity, in which local cell-edge dynamics depends on the distance from the cell centre, but not on the orientation with respect to the front-back axis. We validate this principle with a stochastic model that faithfully reproduces a range of cell-migration behaviours. Our findings indicate that spontaneous polarization, persistent motion and cell shape are emergent properties of the local cell-edge dynamics controlled by the distance from the cell centre.

  12. Evolutionary adaptation after crippling cell polarization follows reproducible trajectories

    PubMed Central

    Laan, Liedewij; Koschwanez, John H; Murray, Andrew W

    2015-01-01

    Cells are organized by functional modules, which typically contain components whose removal severely compromises the module's function. Despite their importance, these components are not absolutely conserved between parts of the tree of life, suggesting that cells can evolve to perform the same biological functions with different proteins. We evolved Saccharomyces cerevisiae for 1000 generations without the important polarity gene BEM1. Initially the bem1∆ lineages rapidly increase in fitness and then slowly reach >90% of the fitness of their BEM1 ancestors at the end of the evolution. Sequencing their genomes and monitoring polarization reveals a common evolutionary trajectory, with a fixed sequence of adaptive mutations, each improving cell polarization by inactivating proteins. Our results show that organisms can be evolutionarily robust to physiologically destructive perturbations and suggest that recovery by gene inactivation can lead to rapid divergence in the parts list for cell biologically important functions. DOI: http://dx.doi.org/10.7554/eLife.09638.001 PMID:26426479

  13. Rap1 integrates tissue polarity, lumen formation, and tumorigenicpotential in human breast epithelial cells

    SciTech Connect

    Itoh, Masahiko; Nelson, Celeste M.; Myers, Connie A.; Bissell,Mina J.

    2006-09-29

    Maintenance of apico-basal polarity in normal breast epithelial acini requires a balance between cell proliferation, cell death, and proper cell-cell and cell-extracellular matrix signaling. Aberrations in any of these processes can disrupt tissue architecture and initiate tumor formation. Here we show that the small GTPase Rap1 is a crucial element in organizing acinar structure and inducing lumen formation. Rap1 activity in malignant HMT-3522 T4-2 cells is appreciably higher than in S1 cells, their non-malignant counterparts. Expression of dominant-negative Rap1 resulted in phenotypic reversion of T4-2 cells, led to formation of acinar structures with correct apico-basal polarity, and dramatically reduced tumor incidence despite the persistence of genomic abnormalities. The resulting acini contained prominent central lumina not observed when other reverting agents were used. Conversely, expression of dominant-active Rap1 in T4-2 cells inhibited phenotypic reversion and led to increased invasiveness and tumorigenicity. Thus, Rap1 acts as a central regulator of breast architecture, with normal levels of activation instructing apical polarity during acinar morphogenesis, and increased activation inducing tumor formation and progression to malignancy.

  14. Membrane aging during cell growth ascertained by Laurdan generalized polarization.

    PubMed

    Parasassi, T; Di Stefano, M; Ravagnan, G; Sapora, O; Gratton, E

    1992-10-01

    The sensitivity of the fluorescent probe Laurdan to the phase state of lipids has been utilized to detect modifications in the composition and physical state of cell membranes during cell growth. In phospholipid vesicles, the Laurdan emission spectrum shows a 50-nm red shift by passing from the gel to the liquid-crystalline phase. The Generalized Polarization (GP) value has been used for the data treatment instead of the ratiometric method common in investigations utilizing other fluorescent probes that display spectral sensitivity to medium properties. The GP value can be measured easily and quickly and possesses all the properties of "classical" polarization, including the additivity rule. Once Laurdan limiting GP values have been established for the gel and the liquid-crystalline phase of lipids, the quantitative determination of coexisting phases in natural samples is possible. In the present work the observation of a relevant decrease in the fractional intensity of the liquid-crystalline phase in K562 cell membranes during 5 days of asynchronous growth is reported. A decrease in the "fluidity" of cell membranes in K562 cells kept in culture for several months is also reported. The procedure developed for labeling cell membranes with Laurdan is reported and the influence of cell metabolism on fluorescence parameters is discussed. Also discussed is the influence of cholesterol on Laurdan GP. PMID:1397095

  15. High efficiency solar cell processing

    NASA Technical Reports Server (NTRS)

    Ho, F.; Iles, P. A.

    1985-01-01

    At the time of writing, cells made by several groups are approaching 19% efficiency. General aspects of the processing required for such cells are discussed. Most processing used for high efficiency cells is derived from space-cell or concentrator cell technology, and recent advances have been obtained from improved techniques rather than from better understanding of the limiting mechanisms. Theory and modeling are fairly well developed, and adequate to guide further asymptotic increases in performance of near conventional cells. There are several competitive cell designs with promise of higher performance ( 20%) but for these designs further improvements are required. The available cell processing technology to fabricate high efficiency cells is examined.

  16. Cytokinesis-Based Constraints on Polarized Cell Growth in Fission Yeast

    PubMed Central

    Bohnert, K. Adam; Gould, Kathleen L.

    2012-01-01

    The rod-shaped fission yeast Schizosaccharomyces pombe, which undergoes cycles of monopolar-to-bipolar tip growth, is an attractive organism for studying cell-cycle regulation of polarity establishment. While previous research has described factors mediating this process from interphase cell tips, we found that division site signaling also impacts the re-establishment of bipolar cell growth in the ensuing cell cycle. Complete loss or targeted disruption of the non-essential cytokinesis protein Fic1 at the division site, but not at interphase cell tips, resulted in many cells failing to grow at new ends created by cell division. This appeared due to faulty disassembly and abnormal persistence of the cell division machinery at new ends of fic1Δ cells. Moreover, additional mutants defective in the final stages of cytokinesis exhibited analogous growth polarity defects, supporting that robust completion of cell division contributes to new end-growth competency. To test this model, we genetically manipulated S. pombe cells to undergo new end take-off immediately after cell division. Intriguingly, such cells elongated constitutively at new ends unless cytokinesis was perturbed. Thus, cell division imposes constraints that partially override positive controls on growth. We posit that such constraints facilitate invasive fungal growth, as cytokinesis mutants displaying bipolar growth defects formed numerous pseudohyphae. Collectively, these data highlight a role for previous cell cycles in defining a cell's capacity to polarize at specific sites, and they additionally provide insight into how a unicellular yeast can transition into a quasi-multicellular state. PMID:23093943

  17. [Polar coordinates representation based leukocyte segmentation of microscopic cell images].

    PubMed

    Gu, Guanghua; Cui, Dong; Hao, Lianwang

    2010-12-01

    We propose an algorithm for segmentation of the overlapped leukocyte in the microscopic cell image. The histogram of the saturation channel in the cell image is smoothed to obtain the meaningful global valley point by the fingerprint smoothing method, and then the nucleus can be segmented. A circular region, containing the entire regions of the leukocyte, is marked off according to the equivalent sectional radius of the nucleus. Then, the edge of the overlapped leukocyte is represented by polar coordinates. The overlapped region by the change of the polar angle of the edge pixels is determined, and the closed edge of the leukocyte integrating the gradient information of the overlapped region is reconstructed. Finally, the leukocyte is exactly extracted. The experimental results show that our method has good performance in terms of recall ratio, precision ratio and pixel error ratio. PMID:21374971

  18. Cell Division Resets Polarity and Motility for the Bacterium Myxococcus xanthus

    PubMed Central

    Harvey, Cameron W.; Madukoma, Chinedu S.; Mahserejian, Shant; Alber, Mark S.

    2014-01-01

    Links between cell division and other cellular processes are poorly understood. It is difficult to simultaneously examine division and function in most cell types. Most of the research probing aspects of cell division has experimented with stationary or immobilized cells or distinctly asymmetrical cells. Here we took an alternative approach by examining cell division events within motile groups of cells growing on solid medium by time-lapse microscopy. A total of 558 cell divisions were identified among approximately 12,000 cells. We found an interconnection of division, motility, and polarity in the bacterium Myxococcus xanthus. For every division event, motile cells stop moving to divide. Progeny cells of binary fission subsequently move in opposing directions. This behavior involves M. xanthus Frz proteins that regulate M. xanthus motility reversals but is independent of type IV pilus “S motility.” The inheritance of opposing polarity is correlated with the distribution of the G protein RomR within these dividing cells. The constriction at the point of division limits the intracellular distribution of RomR. Thus, the asymmetric distribution of RomR at the parent cell poles becomes mirrored at new poles initiated at the site of division. PMID:25157084

  19. Gravity-induced PIN transcytosis for polarization of auxin fluxes in gravity-sensing root cells

    PubMed Central

    Kleine-Vehn, Jürgen; Ding, Zhaojun; Jones, Angharad R.; Tasaka, Masao; Morita, Miyo T.; Friml, Jiří

    2010-01-01

    Auxin is an essential plant-specific regulator of patterning processes that also controls directional growth of roots and shoots. In response to gravity stimulation, the PIN3 auxin transporter polarizes to the bottom side of gravity-sensing root cells, presumably redirecting the auxin flux toward the lower side of the root and triggering gravitropic bending. By combining live-cell imaging techniques with pharmacological and genetic approaches, we demonstrate that PIN3 polarization does not require secretion of de novo synthesized proteins or protein degradation, but instead involves rapid, transient stimulation of PIN endocytosis, presumably via a clathrin-dependent pathway. Moreover, gravity-induced PIN3 polarization requires the activity of the guanine nucleotide exchange factors for ARF GTPases (ARF-GEF) GNOM-dependent polar-targeting pathways and might involve endosome-based PIN3 translocation from one cell side to another. Our data suggest that gravity perception acts at several instances of PIN3 trafficking, ultimately leading to the polarization of PIN3, which presumably aligns auxin fluxes with gravity vector and mediates downstream root gravitropic response. PMID:21135243

  20. Planar cell polarity protein Celsr1 regulates endothelial adherens junctions and directed cell rearrangements during valve morphogenesis.

    PubMed

    Tatin, Florence; Taddei, Andrea; Weston, Anne; Fuchs, Elaine; Devenport, Danelle; Tissir, Fadel; Makinen, Taija

    2013-07-15

    Planar cell polarity (PCP) signaling controls tissue morphogenesis by coordinating collective cell behaviors. We show a critical role for the core PCP proteins Celsr1 and Vangl2 in the complex morphogenetic process of intraluminal valve formation in lymphatic vessels. We found that valve-forming endothelial cells undergo elongation, reorientation, and collective migration into the vessel lumen as they initiate valve leaflet formation. During this process, Celsr1 and Vangl2 are recruited from endothelial filopodia to discrete membrane domains at cell-cell contacts. Celsr1- or Vangl2-deficient mice show valve aplasia due to failure of endothelial cells to undergo rearrangements and adopt perpendicular orientation at valve initiation sites. Mechanistically, we show that Celsr1 regulates dynamic cell movements by inhibiting stabilization of VE-cadherin and maturation of adherens junctions. These findings reveal a role for PCP signaling in regulating adherens junctions and directed cell rearrangements during vascular development. PMID:23792146

  1. Fine-scale dissection of the subdomains of polarity protein BASL in stomatal asymmetric cell division

    PubMed Central

    Zhang, Ying; Bergmann, Dominique C.; Dong, Juan

    2016-01-01

    Cell polarity is a prerequisite for asymmetric cell divisions (ACDs) that generate cell type diversity during development of multicellular organisms. In Arabidopsis, stomatal lineage ACDs are regulated by the plant-specific protein BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL). BASL exhibits dynamic subcellular localization, accumulating initially in the nucleus, but then additionally in a highly polarized crescent at the cell cortex before division. BASL polarization requires a phosphorylation-mediated activation process, but how this is achieved remains unknown. In this study, we performed a fine-scale dissection of BASL protein subdomains and elucidated a nuclear localization sequence for nuclear import and a critical FxFP motif for cortical polarity formation, respectively. Artificially tethering BASL subdomains to the plasma membrane suggests that novel protein partner/s might exist and bind to an internal region of BASL. In addition, we suspect the existence of a protein degradation mechanism associated with the amino terminal domain of BASL that accounts for restricting its predominant expression to the stomatal lineage cells of the epidermis. Taken together, our results revealed that BASL, through its distinct subdomains, integrates multiple regulatory inputs to provide a mechanism that promotes difference during stomatal lineage ACDs. PMID:27422992

  2. Dynamics of cell polarity in tissue morphogenesis: a comparative view from Drosophila and Ciona

    PubMed Central

    Veeman, Michael T.; McDonald, Jocelyn A.

    2016-01-01

    Tissues in developing embryos exhibit complex and dynamic rearrangements that shape forming organs, limbs, and body axes. Directed migration, mediolateral intercalation, lumen formation, and other rearrangements influence the topology and topography of developing tissues. These collective cell behaviors are distinct phenomena but all involve the fine-grained control of cell polarity. Here we review recent findings in the dynamics of polarized cell behavior in both the Drosophila ovarian border cells and the Ciona notochord. These studies reveal the remarkable reorganization of cell polarity during organ formation and underscore conserved mechanisms of developmental cell polarity including the Par/atypical protein kinase C (aPKC) and planar cell polarity pathways. These two very different model systems demonstrate important commonalities but also key differences in how cell polarity is controlled in tissue morphogenesis. Together, these systems raise important, broader questions on how the developmental control of cell polarity contributes to morphogenesis of diverse tissues across the metazoa. PMID:27303647

  3. Planar cell polarity protein localization in the secretory ameloblasts of rat incisors.

    PubMed

    Nishikawa, Sumio; Kawamoto, Tadafumi

    2012-05-01

    The localization of the planar cell polarity proteins Vang12, frizzled-3, Vang11, and Celsr1 in the rat incisors was examined using immunocytochemistry. The results showed that Vang12 was localized at two regions of the Tomes' processes of inner enamel-secretory ameloblasts in rat incisors: a proximal and a distal region. In contrast, frizzled-3 was localized at adherens junctions of the proximal and distal areas of inner enamel- and outer enamel-secretory ameloblasts, where N-cadherin and β-catenin were localized. frizzled-3 was also localized in differentiating inner enamel epithelial cells. Vang11 was localized sparsely in differentiating preameloblasts and extensively at the cell boundary of stratum intermedium. Celsr1 was not localized in ameloblasts but localized in odontoblasts extensively. These results suggest the involvement of planar cell polarity proteins in odontogenesis. PMID:22378702

  4. A biomechanical model for cell polarization and intercalation during Drosophila germband extension

    NASA Astrophysics Data System (ADS)

    Lan, Haihan; Wang, Qiming; Fernandez-Gonzalez, Rodrigo; Feng, James J.

    2015-10-01

    Germband extension during Drosophila development features the merging of cells along the dorsal-ventral (DV) axis and their separation along the anterior-posterior (AP) axis. This intercalation process involves planar cell polarity, anisotropic contractile forces along cell edges, and concerted cell deformation and movement. Although prior experiments have probed each of these factors separately, the connection among them remains unclear. This paper presents a chemo-mechanical model that integrates the three factors into a coherent framework. The model predicts the polarization of Rho-kinase, myosin and Bazooka downstream of an anisotropic Shroom distribution. In particular, myosin accumulates on cell edges along the DV axis, causing them to contract into a vertex. Subsequently, medial myosin in the cells anterior and posterior to the vertex helps to elongate it into a new edge parallel to the body axis. Thus, the tissue extends along the AP axis and narrows in the transverse direction through neighbor exchange. Model predictions of the polarity of the proteins and cell and tissue deformation are in good agreement with experimental observations.

  5. Neuronal polarization.

    PubMed

    Takano, Tetsuya; Xu, Chundi; Funahashi, Yasuhiro; Namba, Takashi; Kaibuchi, Kozo

    2015-06-15

    Neurons are highly polarized cells with structurally and functionally distinct processes called axons and dendrites. This polarization underlies the directional flow of information in the central nervous system, so the establishment and maintenance of neuronal polarization is crucial for correct development and function. Great progress in our understanding of how neurons establish their polarity has been made through the use of cultured hippocampal neurons, while recent technological advances have enabled in vivo analysis of axon specification and elongation. This short review and accompanying poster highlight recent advances in this fascinating field, with an emphasis on the signaling mechanisms underlying axon and dendrite specification in vitro and in vivo. PMID:26081570

  6. Volatile and polar compounds in Rosadamascena Mill 1803 cell suspension.

    PubMed

    Pavlov, Atanas; Popov, Simeon; Kovacheva, Elena; Georgiev, Milen; Ilieva, Mladenka

    2005-07-21

    Studies were conducted on low molecular metabolites (volatiles and polar compounds) produced by Rosa damascena Mill 1803 cell suspension culture, cultivated under different regimes: as a free suspension (in flasks and in bioreactor) and in a two-phase system (in the presence of Amberlite XAD-4 as a second phase). It was established that the main groups of volatiles were hydrocarbons and free acids and their esters and only traces of terpenoids were found. The main components of polar fraction were free acids, especially amino acids and oxidized acids. Depending on the culture conditions, significant differences were established in the amounts of all compounds under study in biomasses, culture media and adsorbed on the second phase (Amberlite XAD-4). PMID:15899533

  7. Chimera proteins with affinity for membranes and microtubule tips polarize in the membrane of fission yeast cells

    PubMed Central

    Recouvreux, Pierre; Sokolowski, Thomas R.; Grammoustianou, Aristea; ten Wolde, Pieter Rein; Dogterom, Marileen

    2016-01-01

    Cell polarity refers to a functional spatial organization of proteins that is crucial for the control of essential cellular processes such as growth and division. To establish polarity, cells rely on elaborate regulation networks that control the distribution of proteins at the cell membrane. In fission yeast cells, a microtubule-dependent network has been identified that polarizes the distribution of signaling proteins that restricts growth to cell ends and targets the cytokinetic machinery to the middle of the cell. Although many molecular components have been shown to play a role in this network, it remains unknown which molecular functionalities are minimally required to establish a polarized protein distribution in this system. Here we show that a membrane-binding protein fragment, which distributes homogeneously in wild-type fission yeast cells, can be made to concentrate at cell ends by attaching it to a cytoplasmic microtubule end-binding protein. This concentration results in a polarized pattern of chimera proteins with a spatial extension that is very reminiscent of natural polarity patterns in fission yeast. However, chimera levels fluctuate in response to microtubule dynamics, and disruption of microtubules leads to disappearance of the pattern. Numerical simulations confirm that the combined functionality of membrane anchoring and microtubule tip affinity is in principle sufficient to create polarized patterns. Our chimera protein may thus represent a simple molecular functionality that is able to polarize the membrane, onto which additional layers of molecular complexity may be built to provide the temporal robustness that is typical of natural polarity patterns. PMID:26831106

  8. Chimera proteins with affinity for membranes and microtubule tips polarize in the membrane of fission yeast cells.

    PubMed

    Recouvreux, Pierre; Sokolowski, Thomas R; Grammoustianou, Aristea; Ten Wolde, Pieter Rein; Dogterom, Marileen

    2016-02-16

    Cell polarity refers to a functional spatial organization of proteins that is crucial for the control of essential cellular processes such as growth and division. To establish polarity, cells rely on elaborate regulation networks that control the distribution of proteins at the cell membrane. In fission yeast cells, a microtubule-dependent network has been identified that polarizes the distribution of signaling proteins that restricts growth to cell ends and targets the cytokinetic machinery to the middle of the cell. Although many molecular components have been shown to play a role in this network, it remains unknown which molecular functionalities are minimally required to establish a polarized protein distribution in this system. Here we show that a membrane-binding protein fragment, which distributes homogeneously in wild-type fission yeast cells, can be made to concentrate at cell ends by attaching it to a cytoplasmic microtubule end-binding protein. This concentration results in a polarized pattern of chimera proteins with a spatial extension that is very reminiscent of natural polarity patterns in fission yeast. However, chimera levels fluctuate in response to microtubule dynamics, and disruption of microtubules leads to disappearance of the pattern. Numerical simulations confirm that the combined functionality of membrane anchoring and microtubule tip affinity is in principle sufficient to create polarized patterns. Our chimera protein may thus represent a simple molecular functionality that is able to polarize the membrane, onto which additional layers of molecular complexity may be built to provide the temporal robustness that is typical of natural polarity patterns. PMID:26831106

  9. Topographic cell instructive patterns to control cell adhesion, polarization and migration

    PubMed Central

    Ventre, Maurizio; Natale, Carlo Fortunato; Rianna, Carmela; Netti, Paolo Antonio

    2014-01-01

    Topographic patterns are known to affect cellular processes such as adhesion, migration and differentiation. However, the optimal way to deliver topographic signals to provide cells with precise instructions has not been defined yet. In this work, we hypothesize that topographic patterns may be able to control the sensing and adhesion machinery of cells when their interval features are tuned on the characteristic lengths of filopodial probing and focal adhesions (FAs). Features separated by distance beyond the length of filopodia cannot be readily perceived; therefore, the formation of new adhesions is discouraged. If, however, topographic features are separated by a distance within the reach of filopodia extension, cells can establish contact between adjacent topographic islands. In the latter case, cell adhesion and polarization rely upon the growth of FAs occurring on a specific length scale that depends on the chemical properties of the surface. Topographic patterns and chemical properties may interfere with the growth of FAs, thus making adhesions unstable. To test this hypothesis, we fabricated different micropatterned surfaces displaying feature dimensions and adhesive properties able to interfere with the filopodial sensing and the adhesion maturation, selectively. Our data demonstrate that it is possible to exert a potent control on cell adhesion, elongation and migration by tuning topographic features’ dimensions and surface chemistry. PMID:25253035

  10. The Rac-GAP Bcr is a novel regulator of the Par complex that controls cell polarity

    PubMed Central

    Narayanan, Anjana S.; Reyes, Steve B.; Um, Kyongmi; McCarty, Joseph H.; Tolias, Kimberley F.

    2013-01-01

    Cell polarization is essential for many biological processes, including directed cell migration, and loss of polarity contributes to pathological conditions such as cancer. The Par complex (Par3, Par6, and PKCζ) controls cell polarity in part by recruiting the Rac-specific guanine nucleotide exchange factor T-lymphoma invasion and metastasis 1 (Tiam1) to specialized cellular sites, where Tiam1 promotes local Rac1 activation and cytoskeletal remodeling. However, the mechanisms that restrict Par-Tiam1 complex activity to the leading edge to maintain cell polarity during migration remain unclear. We identify the Rac-specific GTPase-activating protein (GAP) breakpoint cluster region protein (Bcr) as a novel regulator of the Par-Tiam1 complex. We show that Bcr interacts with members of the Par complex and inhibits both Rac1 and PKCζ signaling. Loss of Bcr results in faster, more random migration and striking polarity defects in astrocytes. These polarity defects are rescued by reducing PKCζ activity or by expressing full-length Bcr, but not an N-terminal deletion mutant or the homologous Rac-GAP, Abr, both of which fail to associate with the Par complex. These results demonstrate that Bcr is an integral member of the Par-Tiam1 complex that controls polarized cell migration by locally restricting both Rac1 and PKCζ function. PMID:24152735

  11. A Three-Dimensional Cell Culture Model To Study Enterovirus Infection of Polarized Intestinal Epithelial Cells.

    PubMed

    Drummond, Coyne G; Nickerson, Cheryl A; Coyne, Carolyn B

    2016-01-01

    Despite serving as the primary entry portal for coxsackievirus B (CVB), little is known about CVB infection of the intestinal epithelium, owing at least in part to the lack of suitable in vivo models and the inability of cultured cells to recapitulate the complexity and structure associated with the gastrointestinal (GI) tract. Here, we report on the development of a three-dimensional (3-D) organotypic cell culture model of Caco-2 cells to model CVB infection of the gastrointestinal epithelium. We show that Caco-2 cells grown in 3-D using the rotating wall vessel (RWV) bioreactor recapitulate many of the properties of the intestinal epithelium, including the formation of well-developed tight junctions, apical-basolateral polarity, brush borders, and multicellular complexity. In addition, transcriptome analyses using transcriptome sequencing (RNA-Seq) revealed the induction of a number of genes associated with intestinal epithelial differentiation and/or intestinal processes in vivo when Caco-2 cells were cultured in 3-D. Applying this model to CVB infection, we found that although the levels of intracellular virus production were similar in two-dimensional (2-D) and 3-D Caco-2 cell cultures, the release of infectious CVB was enhanced in 3-D cultures at early stages of infection. Unlike CVB, the replication of poliovirus (PV) was significantly reduced in 3-D Caco-2 cell cultures. Collectively, our studies show that Caco-2 cells grown in 3-D using the RWV bioreactor provide a cell culture model that structurally and transcriptionally represents key aspects of cells in the human GI tract and can thus be used to expand our understanding of enterovirus-host interactions in intestinal epithelial cells. IMPORTANCE Coxsackievirus B (CVB), a member of the enterovirus family of RNA viruses, is associated with meningitis, pericarditis, diabetes, dilated cardiomyopathy, and myocarditis, among other pathologies. CVB is transmitted via the fecal-oral route and encounters the

  12. A Three-Dimensional Cell Culture Model To Study Enterovirus Infection of Polarized Intestinal Epithelial Cells

    PubMed Central

    Drummond, Coyne G.

    2015-01-01

    ABSTRACT Despite serving as the primary entry portal for coxsackievirus B (CVB), little is known about CVB infection of the intestinal epithelium, owing at least in part to the lack of suitable in vivo models and the inability of cultured cells to recapitulate the complexity and structure associated with the gastrointestinal (GI) tract. Here, we report on the development of a three-dimensional (3-D) organotypic cell culture model of Caco-2 cells to model CVB infection of the gastrointestinal epithelium. We show that Caco-2 cells grown in 3-D using the rotating wall vessel (RWV) bioreactor recapitulate many of the properties of the intestinal epithelium, including the formation of well-developed tight junctions, apical-basolateral polarity, brush borders, and multicellular complexity. In addition, transcriptome analyses using transcriptome sequencing (RNA-Seq) revealed the induction of a number of genes associated with intestinal epithelial differentiation and/or intestinal processes in vivo when Caco-2 cells were cultured in 3-D. Applying this model to CVB infection, we found that although the levels of intracellular virus production were similar in two-dimensional (2-D) and 3-D Caco-2 cell cultures, the release of infectious CVB was enhanced in 3-D cultures at early stages of infection. Unlike CVB, the replication of poliovirus (PV) was significantly reduced in 3-D Caco-2 cell cultures. Collectively, our studies show that Caco-2 cells grown in 3-D using the RWV bioreactor provide a cell culture model that structurally and transcriptionally represents key aspects of cells in the human GI tract and can thus be used to expand our understanding of enterovirus-host interactions in intestinal epithelial cells. IMPORTANCE Coxsackievirus B (CVB), a member of the enterovirus family of RNA viruses, is associated with meningitis, pericarditis, diabetes, dilated cardiomyopathy, and myocarditis, among other pathologies. CVB is transmitted via the fecal-oral route and

  13. Polarization information processing and software system design for simultaneously imaging polarimetry

    NASA Astrophysics Data System (ADS)

    Wang, Yahui; Liu, Jing; Jin, Weiqi; Wen, Renjie

    2015-08-01

    Simultaneous imaging polarimetry can realize real-time polarization imaging of the dynamic scene, which has wide application prospect. This paper first briefly illustrates the design of the double separate Wollaston Prism simultaneous imaging polarimetry, and then emphases are put on the polarization information processing methods and software system design for the designed polarimetry. Polarization information processing methods consist of adaptive image segmentation, high-accuracy image registration, instrument matrix calibration. Morphological image processing was used for image segmentation by taking dilation of an image; The accuracy of image registration can reach 0.1 pixel based on the spatial and frequency domain cross-correlation; Instrument matrix calibration adopted four-point calibration method. The software system was implemented under Windows environment based on C++ programming language, which realized synchronous polarization images acquisition and preservation, image processing and polarization information extraction and display. Polarization data obtained with the designed polarimetry shows that: the polarization information processing methods and its software system effectively performs live realize polarization measurement of the four Stokes parameters of a scene. The polarization information processing methods effectively improved the polarization detection accuracy.

  14. A mechanism for cell motility by active polar gels

    PubMed Central

    Marth, W.; Praetorius, S.; Voigt, A.

    2015-01-01

    We analyse a generic motility model, with the motility mechanism arising by contractile stress due to the interaction of myosin and actin. A hydrodynamic active polar gel theory is used to model the cytoplasm of a cell and is combined with a Helfrich-type model to account for membrane properties. The overall model allows consideration of the motility without the necessity for local adhesion. Besides a detailed numerical approach together with convergence studies for the highly nonlinear free boundary problem, we also compare the induced flow field of the motile cell with that of classical squirmer models and identify the motile cell as a puller or pusher, depending on the strength of the myosin–actin interactions. PMID:25926698

  15. Challenge for lowering concentration polarization in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Shimada, Hiroyuki; Suzuki, Toshio; Yamaguchi, Toshiaki; Sumi, Hirofumi; Hamamoto, Koichi; Fujishiro, Yoshinobu

    2016-01-01

    In the scope of electrochemical phenomena, concentration polarization at electrodes is theoretically inevitable, and lowering the concentration overpotential to improve the performance of electrochemical cells has been a continuing challenge. Electrodes with highly controlled microstructure, i.e., high porosity and uniform large pores are therefore essential to achieve high performance electrochemical cells. In this study, state-of-the-art technology for controlling the microstructure of electrodes has been developed for realizing high performance support electrodes of solid oxide fuel cells (SOFCs). The key is controlling the porosity and pore size distribution to improve gas diffusion, while maintaining the integrity of the electrolyte and the structural strength of actual sized electrode supports needed for the target application. Planar anode-supported SOFCs developed in this study realize 5 μm thick dense electrolyte (yttria-stabilized zirconia: YSZ) and the anode substrate (Ni-YSZ) of 53.6 vol.% porosity with a large median pore diameter of 0.911 μm. Electrochemical measurements reveal that the performance of the anode-supported SOFCs improves with increasing anode porosity. This Ni-YSZ anode minimizes the concentration polarization, resulting in a maximum power density of 3.09 W cm-2 at 800 °C using humidified hydrogen fuel without any electrode functional layers.

  16. Coordination of planar cell polarity pathways through Spiny-legs

    PubMed Central

    Ambegaonkar, Abhijit A; Irvine, Kenneth D

    2015-01-01

    Morphogenesis and physiology of tissues and organs requires planar cell polarity (PCP) systems that orient and coordinate cells and their behaviors, but the relationship between PCP systems has been controversial. We have characterized how the Frizzled and Dachsous-Fat PCP systems are connected through the Spiny-legs isoform of the Prickle-Spiny-legs locus. Two different components of the Dachsous-Fat system, Dachsous and Dachs, can each independently interact with Spiny-legs and direct its localization in vivo. Through characterization of the contributions of Prickle, Spiny-legs, Dachsous, Fat, and Dachs to PCP in the Drosophila wing, eye, and abdomen, we define where Dachs-Spiny-legs and Dachsous-Spiny-legs interactions contribute to PCP, and provide a new understanding of the orientation of polarity and the basis of PCP phenotypes. Our results support the direct linkage of PCP systems through Sple in specific locales, while emphasizing that cells can be subject to and must ultimately resolve distinct, competing PCP signals. DOI: http://dx.doi.org/10.7554/eLife.09946.001 PMID:26505959

  17. Polarizing intestinal epithelial cells electrically through Ror2.

    PubMed

    Cao, Lin; McCaig, Colin D; Scott, Roderick H; Zhao, Siwei; Milne, Gillian; Clevers, Hans; Zhao, Min; Pu, Jin

    2014-08-01

    The apicobasal polarity of enterocytes determines where the brush border membrane (apical membrane) will form, but how this apical membrane faces the lumen is not well understood. The electrical signal across the epithelium could serve as a coordinating cue, orienting and polarizing enterocytes. Here, we show that applying a physiological electric field to intestinal epithelial cells, to mimic the natural electric field created by the transepithelial potential difference, polarized phosphorylation of the actin-binding protein ezrin, increased expression of intestinal alkaline phosphatase (ALPI, a differentiation marker) and remodeled the actin cytoskeleton selectively on the cathode side. In addition, an applied electric field also activated ERK1/2 and LKB1 (also known as STK11), key molecules in apical membrane formation. Disruption of the tyrosine protein kinase transmembrane receptor Ror2 suppressed activation of ERK1/2 and LKB1 significantly, and subsequently inhibited apical membrane formation in enterocytes. Our findings indicate that the endogenous electric field created by the transepithelial potential difference might act as an essential coordinating signal for apical membrane formation at a tissue level, through activation of LKB1 mediated by Ror2-ERK signaling. PMID:24928904

  18. Polarizing intestinal epithelial cells electrically through Ror2

    PubMed Central

    Cao, Lin; McCaig, Colin D.; Scott, Roderick H.; Zhao, Siwei; Milne, Gillian; Clevers, Hans; Zhao, Min; Pu, Jin

    2014-01-01

    ABSTRACT The apicobasal polarity of enterocytes determines where the brush border membrane (apical membrane) will form, but how this apical membrane faces the lumen is not well understood. The electrical signal across the epithelium could serve as a coordinating cue, orienting and polarizing enterocytes. Here, we show that applying a physiological electric field to intestinal epithelial cells, to mimic the natural electric field created by the transepithelial potential difference, polarized phosphorylation of the actin-binding protein ezrin, increased expression of intestinal alkaline phosphatase (ALPI, a differentiation marker) and remodeled the actin cytoskeleton selectively on the cathode side. In addition, an applied electric field also activated ERK1/2 and LKB1 (also known as STK11), key molecules in apical membrane formation. Disruption of the tyrosine protein kinase transmembrane receptor Ror2 suppressed activation of ERK1/2 and LKB1 significantly, and subsequently inhibited apical membrane formation in enterocytes. Our findings indicate that the endogenous electric field created by the transepithelial potential difference might act as an essential coordinating signal for apical membrane formation at a tissue level, through activation of LKB1 mediated by Ror2–ERK signaling. PMID:24928904

  19. Mesenchymal Stromal Cells Affect Disease Outcomes via Macrophage Polarization

    PubMed Central

    Zheng, Guoping; Ge, Menghua; Qiu, Guanguan; Shu, Qiang; Xu, Jianguo

    2015-01-01

    Mesenchymal stromal cells (MSCs) are multipotent and self-renewable cells that reside in almost all postnatal tissues. In recent years, many studies have reported the effect of MSCs on the innate and adaptive immune systems. MSCs regulate the proliferation, activation, and effector function of T lymphocytes, professional antigen presenting cells (dendritic cells, macrophages, and B lymphocytes), and NK cells via direct cell-to-cell contact or production of soluble factors including indoleamine 2,3-dioxygenase, prostaglandin E2, tumor necrosis factor-α stimulated gene/protein 6, nitric oxide, and IL-10. MSCs are also able to reprogram macrophages from a proinflammatory M1 phenotype toward an anti-inflammatory M2 phenotype capable of regulating immune response. Because of their capacity for differentiation and immunomodulation, MSCs have been used in many preclinical and clinical studies as possible new therapeutic agents for the treatment of autoimmune, degenerative, and inflammatory diseases. In this review, we discuss the central role of MSCs in macrophage polarization and outcomes of diseases such as wound healing, brain/spinal cord injuries, and diseases of heart, lung, and kidney in animal models. PMID:26257791

  20. Mesenchymal Stromal Cells Affect Disease Outcomes via Macrophage Polarization.

    PubMed

    Zheng, Guoping; Ge, Menghua; Qiu, Guanguan; Shu, Qiang; Xu, Jianguo

    2015-01-01

    Mesenchymal stromal cells (MSCs) are multipotent and self-renewable cells that reside in almost all postnatal tissues. In recent years, many studies have reported the effect of MSCs on the innate and adaptive immune systems. MSCs regulate the proliferation, activation, and effector function of T lymphocytes, professional antigen presenting cells (dendritic cells, macrophages, and B lymphocytes), and NK cells via direct cell-to-cell contact or production of soluble factors including indoleamine 2,3-dioxygenase, prostaglandin E2, tumor necrosis factor-α stimulated gene/protein 6, nitric oxide, and IL-10. MSCs are also able to reprogram macrophages from a proinflammatory M1 phenotype toward an anti-inflammatory M2 phenotype capable of regulating immune response. Because of their capacity for differentiation and immunomodulation, MSCs have been used in many preclinical and clinical studies as possible new therapeutic agents for the treatment of autoimmune, degenerative, and inflammatory diseases. In this review, we discuss the central role of MSCs in macrophage polarization and outcomes of diseases such as wound healing, brain/spinal cord injuries, and diseases of heart, lung, and kidney in animal models. PMID:26257791

  1. Trafficking of epidermal growth factor receptor ligands in polarized epithelial cells.

    PubMed

    Singh, Bhuminder; Coffey, Robert J

    2014-01-01

    A largely unilamellar epithelial layer lines body cavities and organ ducts such as the digestive tract and kidney tubules. This polarized epithelium is composed of biochemically and functionally separate apical and basolateral surfaces. The epidermal growth factor receptor (EGFR) signaling pathway is a critical regulator of epithelial homeostasis and is perturbed in a number of epithelial disorders. It is underappreciated that in vivo EGFR signaling is most often initiated by cell-surface delivery and processing of one of seven transmembrane ligands, resulting in release of the soluble form that binds EGFR. In polarized epithelial cells, EGFR is restricted largely to the basolateral surface, and apical or basolateral ligand delivery therefore has important biological consequences. In vitro approaches have been used to study the biosynthesis, cell-surface delivery, proteolytic processing, and release of soluble EGFR ligands in polarized epithelial cells. We review these results, discuss their relevance to normal physiology, and demonstrate the pathophysiological consequences of aberrant trafficking. These studies have uncovered a rich diversity of apico-basolateral trafficking mechanisms among the EGFR ligands, provided insights into the pathogenesis of an inherited magnesium-wasting disorder of the kidney (isolated renal hypomagnesemia), and identified a new mode of EGFR ligand signaling via exosomes. PMID:24215440

  2. Trafficking of Epidermal Growth Factor Receptor Ligands in Polarized Epithelial Cells

    PubMed Central

    Singh, Bhuminder; Coffey, Robert J.

    2014-01-01

    A largely unilamellar epithelial layer lines body cavities and organ ducts such as the digestive tract and kidney tubules. This polarized epithelium is composed of biochemically and functionally separate apical and basolateral surfaces. The epidermal growth factor receptor (EGFR) signaling pathway is a critical regulator of epithelial homeostasis and is perturbed in a number of epithelial disorders. It is underappreciated that in vivo EGFR signaling is most often initiated by cell-surface delivery and processing of one of seven transmembrane ligands, resulting in release of the soluble form that binds EGFR. In polarized epithelial cells, EGFR is restricted largely to the basolateral surface, and apical or basolateral ligand delivery therefore has important biological consequences. In vitro approaches have been used to study the biosynthesis, cell-surface delivery, proteolytic processing, and release of soluble EGFR ligands in polarized epithelial cells. We review these results, discuss their relevance to normal physiology, and demonstrate the pathophysiological consequences of aberrant trafficking. These studies have uncovered a rich diversity of apico-basolateral trafficking mechanisms among the EGFR ligands, provided insights into the pathogenesis of an inherited magnesium-wasting disorder of the kidney (isolated renal hypomagnesemia), and identified a new mode of EGFR ligand signaling via exosomes. PMID:24215440

  3. Studies of interactive plasma processes in the polar cusp

    NASA Technical Reports Server (NTRS)

    Waite, J. Hunter, Jr.

    1992-01-01

    Progress during the reporting period is presented. Several distinctly different areas of research are presently being pursued: (1) studies of the thermal structure of polar outflows; (2) Prognoz data analysis; and (3) Ulysses Jupiter encounter.

  4. Polar process and world climate /A brief overview/

    NASA Technical Reports Server (NTRS)

    Goody, R.

    1980-01-01

    A review is presented of events relating polar regions to the world climate, the mechanisms of sea ice and polar ice sheets, and of two theories of the Pleistocene Ice Ages. The sea ice which varies over time scales of one or two years and the polar ice sheets with time changes measured in tens or hundreds of thousands of years introduce two distinct time constants into global time changes; the yearly Arctic sea ice variations affect northern Europe and have some effect over the entire Northern Hemisphere; the ice-albedo coupling in the polar ice sheets is involved in major climatic events such as the Pleistocene ice ages. It is concluded that climate problems require a global approach including the atmosphere, the oceans, and the cryosphere.

  5. Cell Fate Determination and the Switch from Diffuse Growth to Planar Polarity in Arabidopsis Root Epidermal Cells

    PubMed Central

    Balcerowicz, Daria; Schoenaers, Sébastjen; Vissenberg, Kris

    2015-01-01

    Plant roots fulfill important functions as they serve in water and nutrient uptake, provide anchorage of the plant body in the soil and in some species form the site of symbiotic interactions with soil-living biota. Root hairs, tubular-shaped outgrowths of specific epidermal cells, significantly increase the root’s surface area and aid in these processes. In this review we focus on the molecular mechanisms that determine the hair and non-hair cell fate of epidermal cells and that define the site on the epidermal cell where the root hair will be initiated (=planar polarity determination). In the model plant Arabidopsis, trichoblast and atrichoblast cell fate results from intra- and intercellular position-dependent signaling and from complex feedback loops that ultimately regulate GL2 expressing and non-expressing cells. When epidermal cells reach the end of the root expansion zone, root hair promoting transcription factors dictate the establishment of polarity within epidermal cells followed by the selection of the root hair initiation site at the more basal part of the trichoblast. Molecular players in the abovementioned processes as well as the role of phytohormones are discussed, and open areas for future experiments are identified. PMID:26779192

  6. Dchs1–Fat4 regulation of polarized cell behaviours during skeletal morphogenesis

    PubMed Central

    Mao, Yaopan; Kuta, Anna; Crespo-Enriquez, Ivan; Whiting, Danielle; Martin, Tina; Mulvaney, Joanna; Irvine, Kenneth D.; Francis-West, Philippa

    2016-01-01

    Skeletal shape varies widely across species as adaptation to specialized modes of feeding and locomotion, but how skeletal shape is established is unknown. An example of extreme diversity in the shape of a skeletal structure can be seen in the sternum, which varies considerably across species. Here we show that the Dchs1–Fat4 planar cell polarity pathway controls cell orientation in the early skeletal condensation to define the shape and relative dimensions of the mouse sternum. These changes fit a model of cell intercalation along differential Dchs1–Fat4 activity that drives a simultaneous narrowing, thickening and elongation of the sternum. Our results identify the regulation of cellular polarity within the early pre-chondrogenic mesenchyme, when skeletal shape is established, and provide the first demonstration that Fat4 and Dchs1 establish polarized cell behaviour intrinsically within the mesenchyme. Our data also reveal the first indication that cell intercalation processes occur during ventral body wall elongation and closure. PMID:27145737

  7. Glycoprotein E of Varicella-Zoster Virus Enhances Cell-Cell Contact in Polarized Epithelial Cells

    PubMed Central

    Mo, Chengjun; Schneeberger, Eveline E.; Arvin, Ann M.

    2000-01-01

    Varicella-zoster virus (VZV) infection involves the cell-cell spread of virions, but how viral proteins interact with the host cell membranes that comprise intercellular junctions is not known. Madin-Darby canine kidney (MDCK) cells were constructed to express the glycoproteins gE, gI, or gE/gI constitutively and were used to examine the effects of these VZV glycoproteins in polarized epithelial cells. At low cell density, VZV gE induced partial tight junction (TJ) formation under low-calcium conditions, whether expressed alone or with gI. Although most VZV gE was intracellular, gE was also shown to colocalize with the TJ protein ZO-1 with or without concomitant expression of gI. Freeze fracture electron microscopy revealed normal TJ strand morphology in gE-expressing MDCK cells. Functionally, the expression of gE was associated with a marked acceleration in the establishment of maximum transepithelial electrical resistance (TER) in MDCK-gE cells; MDCK-gI and MDCK-gE/gI cells exhibited a similar pattern of early TER compared to MDCK cells, although peak resistances were lower than those of gE alone. VZV gE expression altered F-actin organization and lipid distribution, but coexpression of gI modulated these effects. Two regions of the gE ectodomain, amino acids (aa) 278 to 355 and aa 467 to 498, although lacking Ca2+ binding motifs, exhibit similarities with corresponding regions of the cell adhesion molecules, E-cadherin and desmocollin. These observations suggest that VZV gE and gE/gI may contribute to viral pathogenesis by facilitating epithelial cell-cell contacts. PMID:11070038

  8. Implementation of polarization processes in a charge transport model applied on poly(ethylene naphthalate) films

    NASA Astrophysics Data System (ADS)

    Hoang, M.-Q.; Le Roy, S.; Boudou, L.; Teyssedre, G.

    2016-06-01

    One of the difficulties in unravelling transport processes in electrically insulating materials is the fact that the response, notably charging current transients, can have mixed contributions from orientation polarization and from space charge processes. This work aims at identifying and characterizing the polarization processes in a polar polymer in the time and frequency-domains and to implement the contribution of the polarization into a charge transport model. To do so, Alternate Polarization Current (APC) and Dielectric Spectroscopy measurements have been performed on poly(ethylene naphthalene 2,6-dicarboxylate) (PEN), an aromatic polar polymer, providing information on polarization mechanisms in the time- and frequency-domain, respectively. In the frequency-domain, PEN exhibits 3 relaxation processes termed β, β* (sub-glass transitions), and α relaxations (glass transition) in increasing order of temperature. Conduction was also detected at high temperatures. Dielectric responses were treated using a simplified version of the Havriliak-Negami model (Cole-Cole (CC) model), using 3 parameters per relaxation process, these parameters being temperature dependent. The time dependent polarization obtained from the CC model is then added to a charge transport model. Simulated currents issued from the transport model implemented with the polarization are compared with the measured APCs, showing a good consistency between experiments and simulations in a situation where the response comes essentially from dipolar processes.

  9. MMP28 promotes macrophage polarization toward M2 cells and augments pulmonary fibrosis

    PubMed Central

    Gharib, Sina A.; Johnston, Laura K.; Huizar, Isham; Birkland, Timothy P.; Hanson, Josiah; Wang, Ying; Parks, William C.; Manicone, Anne M.

    2014-01-01

    Members of the MMP family function in various processes of innate immunity, particularly in controlling important steps in leukocyte trafficking and activation. MMP28 (epilysin) is a member of this family of proteinases, and we have found that MMP28 is expressed by macrophages and regulates their recruitment to the lung. We hypothesized that MMP28 regulates other key macrophage responses, such as macrophage polarization. Furthermore, we hypothesized that these MMP28-dependent changes in macrophage polarization would alter fibrotic responses in the lung. We examined the gene expression changes in WT and Mmp28−/− BMDMs, stimulated with LPS or IL-4/IL-13 to promote M1 and M2 cells, respectively. We also collected macrophages from the lungs of Pseudomonas aeruginosa-exposed WT and Mmp28−/− mice to evaluate changes in macrophage polarization. Lastly, we evaluated the macrophage polarization phenotypes during bleomycin-induced pulmonary fibrosis in WT and Mmp28−/− mice and assessed mice for differences in weight loss and total collagen levels. We found that MMP28 dampens proinflammatory macrophage function and promots M2 programming. In both in vivo models, we found deficits in M2 polarization in Mmp28−/− mice. In bleomycin-induced lung injury, these changes were associated with reduced fibrosis. MMP28 is an important regulator of macrophage polarization, promoting M2 function. Loss of MMP28 results in reduced M2 polarization and protection from bleomycin-induced fibrosis. These findings highlight a novel role for MMP28 in macrophage biology and pulmonary disease. PMID:23964118

  10. Basics of Polar-Format algorithm for processing Synthetic Aperture Radar images.

    SciTech Connect

    Doerry, Armin Walter

    2012-05-01

    The purpose of this report is to provide a background to Synthetic Aperture Radar (SAR) image formation using the Polar Format (PFA) processing algorithm. This is meant to be an aid to those tasked to implement real-time image formation using the Polar Format processing algorithm.

  11. Modeling Yeast Cell Polarization Induced by Pheromone Gradients

    NASA Astrophysics Data System (ADS)

    Yi, Tau-Mu; Chen, Shanqin; Chou, Ching-Shan; Nie, Qing

    2007-07-01

    Yeast cells respond to spatial gradients of mating pheromones by polarizing and projecting up the gradient toward the source. It is thought that they employ a spatial sensing mechanism in which the cell compares the concentration of pheromone at different points on the cell surface and determines the maximum point, where the projection forms. Here we constructed the first spatial mathematical model of the yeast pheromone response that describes the dynamics of the heterotrimeric and Cdc42p G-protein cycles, which are linked in a cascade. Two key performance objectives of this system are (1) amplification—converting a shallow external gradient of ligand to a steep internal gradient of protein components and (2) tracking—following changes in gradient direction. We used simulations to investigate amplification mechanisms that allow tracking. We identified specific strategies for regulating the spatial dynamics of the protein components (i.e. their changing location in the cell) that would enable the cell to achieve both objectives.

  12. Mass Wasting Processes in Vesta's South Polar Region

    NASA Astrophysics Data System (ADS)

    Otto, K.; Jaumann, R.; Krohn, K.; Preusker, F.; Roatsch, T.; Stephan, K.; Sykes, M. V.; Schenk, P.; Raymond, C. A.; Russell, C. T.

    2012-12-01

    Images of Asteroid Vesta taken by the Dawn framing camera give insight to a wide range of geologic phenomena on Vesta's surface. In this abstract we focus on the evidence of different types of gravity-driven mass wasting that can be seen on Vesta with an emphasis on the south polar region where the formation of the giant impact basin of Rheasilvia (1, 2) caused significant mass movements and lateral displacement. During the formation of the impact basin various processes such as uplift and stretching moved material of the impact site (3). The remnant are fault scarps, ridges, and uplift features inside the Rheasilvia basin (2). Beside these mass movements, there are also three types of debris movement associated with the Rheasilvia impact basin: block slumping of solid material, granular landslides, and flow-like features. They all occur on the rim of the basin and the central peak with slopes varying from 10° to 40°. The movement, however, is in different directions. While the block slumping and landslides occur on the steep slopes of the crater wall facing inward, the flow-like movements go outward from the crater rim on less steep slopes. The block slumping is most prominent in the region between 80° and 120° east and 50° and 60° south (4). The slump blocks in a rotational movement showing multiple scarps and ridges. Landslides on the steep slopes inward of Rheasilvia have a length to height ratio of about 1. The flow-like features occur in the region between 50° and 90° east and 20° to 40° south. They are in a relatively young area and have a length to height ratio up to 35. Additionally, many small elongate depressions of about 1.5 km length can be found near the central peak of Rheasilvia. They are mainly arranged parallel to the slope with a slight curvature and are related to instability of granular material on a slope. References: (1) Jaumann et al., Science 336, 687 (2012); (2) Schenk et al., Science 336, 694 (2012); (3) Melosh, Impact Cratering

  13. Rear Polarization of the Microtubule-Organizing Center in Neointimal Smooth Muscle Cells Depends on PKCα, ARPC5, and RHAMM

    PubMed Central

    Silverman-Gavrila, Rosalind; Silverman-Gavrila, Lorelei; Hou, Guangpei; Zhang, Ming; Charlton, Milton; Bendeck, Michelle P.

    2011-01-01

    Directed migration of smooth muscle cells (SMCs) from the media to the intima in arteries occurs during atherosclerotic plaque formation and during restenosis after angioplasty or stent application. The polarized orientation of the microtubule-organizing center (MTOC) is a key determinant of this process, and we therefore investigated factors that regulate MTOC polarity in vascular SMCs. SMCs migrating in vivo from the medial to the intimal layer of the rat carotid artery following balloon catheter injury were rear polarized, with the MTOC located posterior of the nucleus. In tissue culture, migrating neointimal cells maintained rear polarization, whereas medial cells were front polarized. Using phosphoproteomic screening and mass spectrometry, we identified ARPC5 and RHAMM as protein kinase C (PKC)-phosphorylated proteins associated with rear polarization of the MTOC in neointimal SMCs. RNA silencing of ARPC5 and RHAMM, PKC inhibition, and transfection with a mutated nonphosphorylatable ARPC5 showed that these proteins regulate rear polarization by organizing the actin and microtubule cytoskeletons in neointimal SMCs. Both ARPC5 and RHAMM, in addition to PKC, were required for migration of neointimal SMCs. PMID:21281821

  14. Complex polar machinery required for proper chromosome segregation in vegetative and sporulating cells of Bacillus subtilis

    PubMed Central

    Kloosterman, Tomas G.; Lenarcic, Rok; Willis, Clare R.; Roberts, David M.; Hamoen, Leendert W.; Errington, Jeff

    2016-01-01

    Summary Chromosome segregation is an essential process of cell multiplication. In prokaryotes, segregation starts with the newly replicated sister origins of replication, oriCs, which move apart to defined positions in the cell. We have developed a genetic screen to identify mutants defective in placement of oriC during spore development in the Gram‐positive bacterium Bacillus subtilis. In addition to the previously identified proteins Soj and DivIVA, our screen identified several new factors involved in polar recruitment of oriC: a reported regulator of competence ComN, and the regulators of division site selection MinD and MinJ. Previous work implicated Soj as an important regulator of oriC positioning in the cell. Our results suggest a model in which the DivIVA‐interacting proteins ComN and MinJ recruit MinD to the cell pole, and that these proteins work upstream of Soj to enable oriC placement. We show that these proteins form a polar complex, which acts in parallel with but distinct from the sporulation‐specific RacA pathway of oriC placement, and also functions during vegetative growth. Our study further shows that MinD has two distinct cell cycle roles, in cell division and chromosome segregation, and highlights that cell probably use multiple parallel mechanisms to ensure accurate chromosome segregation. PMID:27059541

  15. Cortical PAR polarity proteins promote robust cytokinesis during asymmetric cell division.

    PubMed

    Jordan, Shawn N; Davies, Tim; Zhuravlev, Yelena; Dumont, Julien; Shirasu-Hiza, Mimi; Canman, Julie C

    2016-01-01

    Cytokinesis, the physical division of one cell into two, is thought to be fundamentally similar in most animal cell divisions and driven by the constriction of a contractile ring positioned and controlled solely by the mitotic spindle. During asymmetric cell divisions, the core polarity machinery (partitioning defective [PAR] proteins) controls the unequal inheritance of key cell fate determinants. Here, we show that in asymmetrically dividing Caenorhabditis elegans embryos, the cortical PAR proteins (including the small guanosine triphosphatase CDC-42) have an active role in regulating recruitment of a critical component of the contractile ring, filamentous actin (F-actin). We found that the cortical PAR proteins are required for the retention of anillin and septin in the anterior pole, which are cytokinesis proteins that our genetic data suggest act as inhibitors of F-actin at the contractile ring. Collectively, our results suggest that the cortical PAR proteins coordinate the establishment of cell polarity with the physical process of cytokinesis during asymmetric cell division to ensure the fidelity of daughter cell formation. PMID:26728855

  16. Cortical PAR polarity proteins promote robust cytokinesis during asymmetric cell division

    PubMed Central

    Jordan, Shawn N.; Davies, Tim; Zhuravlev, Yelena; Dumont, Julien; Shirasu-Hiza, Mimi

    2016-01-01

    Cytokinesis, the physical division of one cell into two, is thought to be fundamentally similar in most animal cell divisions and driven by the constriction of a contractile ring positioned and controlled solely by the mitotic spindle. During asymmetric cell divisions, the core polarity machinery (partitioning defective [PAR] proteins) controls the unequal inheritance of key cell fate determinants. Here, we show that in asymmetrically dividing Caenorhabditis elegans embryos, the cortical PAR proteins (including the small guanosine triphosphatase CDC-42) have an active role in regulating recruitment of a critical component of the contractile ring, filamentous actin (F-actin). We found that the cortical PAR proteins are required for the retention of anillin and septin in the anterior pole, which are cytokinesis proteins that our genetic data suggest act as inhibitors of F-actin at the contractile ring. Collectively, our results suggest that the cortical PAR proteins coordinate the establishment of cell polarity with the physical process of cytokinesis during asymmetric cell division to ensure the fidelity of daughter cell formation. PMID:26728855

  17. VANGL2 regulates membrane trafficking of MMP14 to control cell polarity and migration.

    PubMed

    Williams, B Blairanne; Cantrell, V Ashley; Mundell, Nathan A; Bennett, Andrea C; Quick, Rachel E; Jessen, Jason R

    2012-05-01

    Planar cell polarity (PCP) describes the polarized orientation of cells within the plane of a tissue. Unlike epithelial PCP, the mechanisms underlying PCP signaling in migrating cells remain undefined. Here, the establishment of PCP must be coordinated with dynamic changes in cell adhesion and extracellular matrix (ECM) organization. During gastrulation, the membrane type-1 matrix metalloproteinase (MT1-MMP or MMP14) is required for PCP and convergence and extension cell movements. We report that the PCP protein Vang-like 2 (VANGL2) regulates the endocytosis and cell-surface availability of MMP14 in manner that is dependent on focal adhesion kinase. We demonstrate that zebrafish trilobite/vangl2 mutant embryos exhibit increased Mmp14 activity and decreased ECM. Furthermore, in vivo knockdown of Mmp14 partially rescues the Vangl2 loss-of-function convergence and extension phenotype. This study identifies a mechanism linking VANGL2 with MMP14 trafficking and suggests that establishment of PCP in migrating gastrula cells requires regulated proteolytic degradation or remodeling of the ECM. Our findings implicate matrix metalloproteinases as downstream effectors of PCP and suggest a broadly applicable mechanism whereby VANGL2 affects diverse morphogenetic processes. PMID:22357946

  18. VANGL2 regulates membrane trafficking of MMP14 to control cell polarity and migration

    PubMed Central

    Williams, B. Blairanne; Cantrell, V. Ashley; Mundell, Nathan A.; Bennett, Andrea C.; Quick, Rachel E.; Jessen, Jason R.

    2012-01-01

    Planar cell polarity (PCP) describes the polarized orientation of cells within the plane of a tissue. Unlike epithelial PCP, the mechanisms underlying PCP signaling in migrating cells remain undefined. Here, the establishment of PCP must be coordinated with dynamic changes in cell adhesion and extracellular matrix (ECM) organization. During gastrulation, the membrane type-1 matrix metalloproteinase (MT1-MMP or MMP14) is required for PCP and convergence and extension cell movements. We report that the PCP protein Vang-like 2 (VANGL2) regulates the endocytosis and cell-surface availability of MMP14 in manner that is dependent on focal adhesion kinase. We demonstrate that zebrafish trilobite/vangl2 mutant embryos exhibit increased Mmp14 activity and decreased ECM. Furthermore, in vivo knockdown of Mmp14 partially rescues the Vangl2 loss-of-function convergence and extension phenotype. This study identifies a mechanism linking VANGL2 with MMP14 trafficking and suggests that establishment of PCP in migrating gastrula cells requires regulated proteolytic degradation or remodeling of the ECM. Our findings implicate matrix metalloproteinases as downstream effectors of PCP and suggest a broadly applicable mechanism whereby VANGL2 affects diverse morphogenetic processes. PMID:22357946

  19. Complex polar machinery required for proper chromosome segregation in vegetative and sporulating cells of Bacillus subtilis.

    PubMed

    Kloosterman, Tomas G; Lenarcic, Rok; Willis, Clare R; Roberts, David M; Hamoen, Leendert W; Errington, Jeff; Wu, Ling J

    2016-07-01

    Chromosome segregation is an essential process of cell multiplication. In prokaryotes, segregation starts with the newly replicated sister origins of replication, oriCs, which move apart to defined positions in the cell. We have developed a genetic screen to identify mutants defective in placement of oriC during spore development in the Gram-positive bacterium Bacillus subtilis. In addition to the previously identified proteins Soj and DivIVA, our screen identified several new factors involved in polar recruitment of oriC: a reported regulator of competence ComN, and the regulators of division site selection MinD and MinJ. Previous work implicated Soj as an important regulator of oriC positioning in the cell. Our results suggest a model in which the DivIVA-interacting proteins ComN and MinJ recruit MinD to the cell pole, and that these proteins work upstream of Soj to enable oriC placement. We show that these proteins form a polar complex, which acts in parallel with but distinct from the sporulation-specific RacA pathway of oriC placement, and also functions during vegetative growth. Our study further shows that MinD has two distinct cell cycle roles, in cell division and chromosome segregation, and highlights that cell probably use multiple parallel mechanisms to ensure accurate chromosome segregation. PMID:27059541

  20. A Par-1-Par-3-Centrosome Cell Polarity Pathway and Its Tuning for Isotropic Cell Adhesion.

    PubMed

    Jiang, Tao; McKinley, R F Andrew; McGill, Melanie A; Angers, Stephane; Harris, Tony J C

    2015-10-19

    To form regulated barriers between body compartments, epithelial cells polarize into apical and basolateral domains and assemble adherens junctions (AJs). Despite close links with polarity networks that generate single polarized domains, AJs distribute isotropically around the cell circumference for adhesion with all neighboring cells [1-3]. How AJs avoid the influence of polarity networks to maintain their isotropy has been unclear. In established epithelia, trans cadherin interactions could maintain AJ isotropy [4], but AJs are dynamic during epithelial development and remodeling [5, 6], and thus specific mechanisms may control their isotropy. In Drosophila, aPKC prevents hyper-polarization of junctions as epithelia develop from cellularization to gastrulation [7]. Here, we show that aPKC does so by inhibiting a positive feedback loop between Bazooka (Baz)/Par-3, a junctional organizer [5, 8-10], and centrosomes. Without aPKC, Baz and centrosomes lose their isotropic distributions and recruit each other to single plasma membrane (PM) domains. Surprisingly, our loss- and gain-of-function analyses show that the Baz-centrosome positive feedback loop is driven by Par-1, a kinase known to phosphorylate Baz and inhibit its basolateral localization [8, 11, 12]. We find that Par-1 promotes the positive feedback loop through both centrosome microtubule effects and Baz phosphorylation. Normally, aPKC attenuates the circuit by expelling Par-1 from the apical domain at gastrulation. The combination of local activation and global inhibition is a common polarization strategy [13-16]. Par-1 seems to couple both effects for a potent Baz polarization mechanism that is regulated for the isotropy of Baz and AJs around the cell circumference. PMID:26455305

  1. Non-invasive imaging of cellulose microfibril orientation within plant cell walls by polarized Raman microspectroscopy.

    PubMed

    Sun, Lan; Singh, Seema; Joo, Michael; Vega-Sanchez, Miguel; Ronald, Pamela; Simmons, Blake A; Adams, Paul; Auer, Manfred

    2016-01-01

    Cellulose microfibrils represent the major scaffold of plant cell walls. Different packing and orientation of the microfibrils at the microscopic scale determines the macroscopic properties of cell walls and thus affect their functions with a profound effect on plant survival. We developed a polarized Raman microspectroscopic method to determine cellulose microfibril orientation within rice plant cell walls. Employing an array of point measurements as well as area imaging and subsequent Matlab-assisted data processing, we were able to characterize the distribution of cellulose microfibril orientation in terms of director angle and anisotropy magnitude. Using this approach we detected differences between wild type rice plants and the rice brittle culm mutant, which shows a more disordered cellulose microfibril arrangement, and differences between different tissues of a wild type rice plant. This novel non-invasive Raman imaging approach allows for quantitative assessment of cellulose fiber orientation in cell walls of herbaceous plants, an important advancement in cell wall characterization. PMID:26137889

  2. Studies of interactive plasma processes in the polar cusp

    NASA Technical Reports Server (NTRS)

    Waite, J. Hunter, Jr.

    1992-01-01

    The final report for NAGW-1657 (SwRI Project 15-2783) is presented. Several distinctly different areas of research are discussed: (1) studies of the thermal structure of polar outflows; (2) Prognoz-8 data analysis; and (3) the Ulysses Jupiter encounter.

  3. Interhemispheric Differences in Dentifrication and Related Processes Affecting Polar Ozone

    NASA Technical Reports Server (NTRS)

    Santee, M. L.; Read, W. G.; Waters, J. W.; Froidevaux, L.; Manney, G. L.; Flower, D. A.; Jarnot, R. F.; Harwood, R. S.; Peckham, G. E.

    1994-01-01

    The severe depletion of stratospheric ozone over Antarctica in late winter and early spring is caused by enhanced CLO abundances arising from heterogeneous reactions on polar stratospheric clouds (PSCs). CLO abundances comparable to those over Antarctica have also been observed throughout the Arctic Vortex, but the accompanying loss of Arctic ozone has been much less severe.

  4. Polar format statistical image processing based fiber optic pressure sensors

    NASA Astrophysics Data System (ADS)

    Alver, Muhammed B.; Toker, Onur; Fidanboylu, Kemal

    2014-09-01

    This paper presents detailed study on the development of a fiber optic sensor system to design a pressure sensor with different sensor configurations. The sensor used in the experiments is based on modal power distribution (MPD) technique. MPD technique is spatial modulation of the modal power in multimode fibers. Stress measurements and CCD camera based techniques were investigated in this research. Differently from earlier MPD works, all of the data gathered from CCD camera are used instead of using some part of the data, the ring shaped pictures taken from the CCD camera converted to polar coordinates, and so stripe shaped pictures are obtained. Four different features are calculated from these converted pictures. R component of the center of mass in the polar form is the first feature. It is calculated because it was expected to decrease monotonically with respect to increasing applied pressure. Second and third features are ring thickness in polar form with taking brightness of each pixel into account and ring thickness in polar form without taking brightness of each pixel into account. These features are calculated to analyze the effect of each pixel's brightness. It was expected for these two features that there will not be a big margin between them. Fourth feature is the ratio between third feature and first feature. A MATLAB code is written to correlate these features and applied force to the sensor. Various experiments conducted to analyze this correlation. Pictures are taken from CCD camera with 1 kg steps and from the written MATLAB code, graphics of each feature versus the applied force are generated. Experimental results showed that, the sensitivity of the proposed sensor is much higher than sensors that uses only some part of the collected data in earlier MPD studies. Furthermore, results are almost exactly the same that what was expected for the four proposed features. Results also showed that converting pictures to the polar form increases the

  5. Dystroglycan loss disrupts polarity and beta-casein induction inmammary epithelial cells by perturbing laminin anchoring

    SciTech Connect

    Weir, M. Lynn; Oppizzi, Maria Luisa; Henry, Michael D.; Onishi,Akiko; Campbell, Kevin P.; Bissell, Mina J.; Muschler, John L.

    2006-02-17

    Precise contact between epithelial cells and their underlying basement membrane is critical to the maintenance of tissue architecture and function. To understand the role that the laminin receptor dystroglycan (DG) plays in these processes, we assayed cell responses to laminin-111 following conditional ablation of DG expression in cultured mammary epithelial cells (MECs). Strikingly, DG loss disrupted laminin-111-induced polarity and {beta}-casein production, and abolished laminin assembly at the step of laminin binding to the cell surface. DG re-expression restored these deficiencies. Investigations of mechanism revealed that DG cytoplasmic sequences were not necessary for laminin assembly and signaling, and only when the entire mucin domain of extracellular DG was deleted did laminin assembly not occur. These results demonstrate that DG is essential as a laminin-111 co-receptor in MECs that functions by mediating laminin anchoring to the cell surface, a process that allows laminin polymerization, tissue polarity, and {beta}-casein induction. The observed loss of laminin-111 assembly and signaling in DG-/-MECs provides insights into the signaling changes occurring in breast carcinomas and other cancers, where DG's laminin-binding function is frequently defective.

  6. Interaction of Motility, Directional Sensing, and Polarity Modules Recreates the Behaviors of Chemotaxing Cells

    PubMed Central

    Shi, Changji; Huang, Chuan-Hsiang; Devreotes, Peter N.; Iglesias, Pablo A.

    2013-01-01

    Chemotaxis involves the coordinated action of separable but interrelated processes: motility, gradient sensing, and polarization. We have hypothesized that these are mediated by separate modules that account for these processes individually and that, when combined, recreate most of the behaviors of chemotactic cells. Here, we describe a mathematical model where the modules are implemented in terms of reaction-diffusion equations. Migration and the accompanying changes in cellular morphology are demonstrated in simulations using a mechanical model of the cell cortex implemented in the level set framework. The central module is an excitable network that accounts for random migration. The response to combinations of uniform stimuli and gradients is mediated by a local excitation, global inhibition module that biases the direction in which excitability is directed. A polarization module linked to the excitable network through the cytoskeleton allows unstimulated cells to move persistently and, for cells in gradients, to gradually acquire distinct sensitivity between front and back. Finally, by varying the strengths of various feedback loops in the model we obtain cellular behaviors that mirror those of genetically altered cell lines. PMID:23861660

  7. The Cdc42 Effector Kinase PAK4 Localizes to Cell-Cell Junctions and Contributes to Establishing Cell Polarity

    PubMed Central

    Selamat, Widyawilis; Tay, Pei-Ling Felicia; Baskaran, Yohendran; Manser, Ed

    2015-01-01

    The serine/threonine kinase PAK4 is a Cdc42 effector whose role is not well understood; overexpression of PAK4 has been associated with some cancers, and there are reports that correlate kinase level with increased cell migration in vitro. Here we report that PAK4 is primarily associated with cell-cell junctions in all the cell lines we tested, and fails to accumulate at focal adhesions or at the leading edge of migrating cells. In U2OS osteosarcoma and MCF-7 breast cancer cell lines, PAK4 depletion did not affect collective cell migration, but affected cell polarization. By contrast, Cdc42 depletion (as reported by many studies) caused a strong defect in junctional assembly in multiple cells lines. We also report that the depletion of PAK4 protein or treatment of cells with the PAK4 inhibitor PF-3758309 can lead to defects in centrosome reorientation (polarization) after cell monolayer wounding. These experiments are consistent with PAK4 forming part of a conserved cell-cell junctional polarity Cdc42 complex. We also confirm β-catenin as a target for PAK4 in these cells. Treatment of cells with PF-3758309 caused inhibition of β-catenin Ser-675 phosphorylation, which is located predominantly at cell-cell junctions. PMID:26068882

  8. The Cdc42 Effector Kinase PAK4 Localizes to Cell-Cell Junctions and Contributes to Establishing Cell Polarity.

    PubMed

    Selamat, Widyawilis; Tay, Pei-Ling Felicia; Baskaran, Yohendran; Manser, Ed

    2015-01-01

    The serine/threonine kinase PAK4 is a Cdc42 effector whose role is not well understood; overexpression of PAK4 has been associated with some cancers, and there are reports that correlate kinase level with increased cell migration in vitro. Here we report that PAK4 is primarily associated with cell-cell junctions in all the cell lines we tested, and fails to accumulate at focal adhesions or at the leading edge of migrating cells. In U2OS osteosarcoma and MCF-7 breast cancer cell lines, PAK4 depletion did not affect collective cell migration, but affected cell polarization. By contrast, Cdc42 depletion (as reported by many studies) caused a strong defect in junctional assembly in multiple cells lines. We also report that the depletion of PAK4 protein or treatment of cells with the PAK4 inhibitor PF-3758309 can lead to defects in centrosome reorientation (polarization) after cell monolayer wounding. These experiments are consistent with PAK4 forming part of a conserved cell-cell junctional polarity Cdc42 complex. We also confirm β-catenin as a target for PAK4 in these cells. Treatment of cells with PF-3758309 caused inhibition of β-catenin Ser-675 phosphorylation, which is located predominantly at cell-cell junctions. PMID:26068882

  9. Hook2, a microtubule-binding protein, interacts with Par6α and controls centrosome orientation during polarized cell migration.

    PubMed

    Pallesi-Pocachard, Emilie; Bazellieres, Elsa; Viallat-Lieutaud, Annelise; Delgrossi, Marie-Hélène; Barthelemy-Requin, Magali; Le Bivic, André; Massey-Harroche, Dominique

    2016-01-01

    Polarity protein complexes function during polarized cell migration and a subset of these proteins localizes to the reoriented centrosome during this process. Despite these observations, the mechanisms behind the recruitment of these polarity complexes such as the aPKC/PAR6α complex to the centrosome are not well understood. Here we identify Hook2 as an interactor for the aPKC/PAR6α complex that functions to localize this complex at the centrosome. We first demonstrate that Hook2 is essential for the polarized Golgi re-orientation towards the migration front. Depletion of Hook2 results in a decrease of PAR6α at the centrosome during cell migration, while overexpression of Hook2 in cells induced the formation of aggresomes with the recruitment of PAR6α, aPKC and PAR3. In addition, we demonstrate that the interaction between the C-terminal domain of Hook2 and the aPKC-binding domain of PAR6α localizes PAR6α to the centrosome during cell migration. Our data suggests that Hook2, a microtubule binding protein, plays an important role in the regulation of PAR6α recruitment to the centrosome to bridge microtubules and the aPKC/PAR complex. This data reveals how some of the polarity protein complexes are recruited to the centrosome and might regulate pericentriolar and microtubule organization and potentially impact on polarized migration. PMID:27624926

  10. Epithelial cell polarity genes are required for neural tube closure.

    PubMed

    Doudney, Kit; Stanier, Philip

    2005-05-15

    Human neural tube defects (NTD) are a heterogeneous group that exhibit complex inheritance, making it difficult to identify the underlying cause. Due to the uniform genetic background, inbred mouse strains are a more amenable target for genetic studies. We investigated the loop-tail (Lp) mouse as a model for the severe NTD, craniorachischisis. A homozygous point mutation was identified in the transmembrane protein Vangl2, which in Drosophila has been shown to function in the planar cell polarity (PCP) pathway. Morphological analysis of the Lp mice shows that the defect results from an abnormally broad floor plate, most likely through a failure in convergent extension. The elevated neural folds remain too far apart to contact, inhibiting neural tube closure. Recently, two other mouse mutants (crash and circletail) were described with a similar phenotype to Lp and were investigated as potentially new alleles. Mapping studies, however, showed that both mutants segregated to distinct loci. In the crash (Crsh) mouse, a mutation was identified in Celsr1, a seven pass transmembrane receptor that encodes a protein orthologous to Drosophila Flamingo. Like Vangl2, this gene also functions in the PCP pathway. While in circletail, a point mutation was identified introducing a premature stop codon into the apical-basal cell polarity gene scribble (Scrb1). We subsequently demonstrated a genetic interaction between all three genes, where double heterozygotes exhibit the same homozygous NTD phenotype. This strongly suggests both a candidate gene pathway and that interaction between independent recessive alleles may be a possible explanation for the complex inheritance in severe human NTD. PMID:15800847

  11. Self-organized spatiotemporal patterns of PIP3 and PTEN during spontaneous cell polarization

    NASA Astrophysics Data System (ADS)

    Knoch, Fabian; Tarantola, Marco; Rappel, Wouter-Jan; Bodenschatz, Eberhard

    2014-03-01

    During spontaneous cell polarization of Dictyostelium discoideum cells, PIP3 (phosphatidylinositol (3,4,5)-triphoshpate) and PTEN (phosphatase tensin homolog) have been identified as key signaling molecules, which govern the process of polarization in a self-organized manner. Gerisch et al. have shown that randomly triggered excitable PIP3 waves regulate the anti-correlated PTEN concentration. Here we show that this requires a switch-like dynamics of the overall membrane bound PTEN concentration in combination with two species of PTEN differing in their dephosphorylation rates. A quantitative modeling with a coupled reaction-diffusion system shows excellent agreement with experimental results and predicts a ratio σ of dephosphorylation rates acting on PIP3 of σ ~ 80 - 100. Our quantitative analysis suggests that surface-attached cell membrane spanning PIP3 waves are necessary for resetting the global actin network. This is evidenced by the experimentally observed delay between polarization-cycles also quantitatively captured by our analysis. Max Planck Society and Center for Theoretical Biological Physics.

  12. Basic science track. Entry and release of canine coronavirus from polarized epithelial cells.

    PubMed

    Pratelli, Annamaria

    2011-01-01

    Virus entry into and release from epithelial cells are polarized as a result of the distribution of the viral receptors. In order to establish the polarity of entry and release of CCoV from epithelial cells, the interactions of the virus with A72 and CrFK cells grown on permeable supports was evaluated, and the amount of infective virus in the apical and in the basolateral media was determined and compared. Infection of A72 cells after different times post seeding demonstrated that CCoV grow after infection from both apical and basolateral sides. In CrFK cells, CCoV was observed in both compartments only in the later phase of the infection. To establish the reciprocal binding of CCoV on plasma membrane, A72 cells on a permeable support were preincubated with a mAb specific for CCoV. Infection from the apical side was blocked by mAb applied to that side; in contrast, such treatment on the basolateral side had no effect on the infectious process. Similarly, the low levels of CCoV observed after basolateral exposure to virus was abolished following mAb treatment of that side. The identification of CCoV into the basolateral medium could play an important role in the viral pathogenesis. PMID:21344143

  13. Noncanonical Wnt signaling pathways in C. elegans converge on POP-1/TCF and control cell polarity.

    PubMed

    Herman, Michael A; Wu, Mingfu

    2004-05-01

    In the nematode Caenorhabditis elegans, a canonical Wnt signaling pathway controls a cell migration whereas noncanonical Wnt pathways control the polarities of individual cells. Despite the differences in the identities and interactions among canonical and noncanonical Wnt pathway components, as well as the processes they regulate, almost all C. elegans Wnt pathways involve the sole Tcf homolog, POP-1. Intriguingly, POP-1 is asymmetrically distributed between the daughters of an asymmetric cell division, with the anterior sister cell usually having a higher level of nuclear POP-1 than its posterior sister. At some divisions, asymmetric distribution of POP-1 is controlled by noncanonical Wnt signaling, but at others the asymmetry is generated independently. Recent experiments suggest that despite this elaborate anterior-posterior POP-1 asymmetry, the quantity of POP-1 protein may have less to do with the subsequent determination of fate than does the quality of the POP-1 protein in the cell. In this review, we will embark on a quest to understand Quality (1), at least from the standpoint of the effect POP/Tcf quality has on the control of cell polarity in C. elegans. PMID:14977564

  14. Requirement of Phosphoinositides Containing Stearic Acid To Control Cell Polarity

    PubMed Central

    Laquel, Patricia; Testet, Eric; Tuphile, Karine; Fouillen, Laetitia; Bessoule, Jean-Jacques

    2015-01-01

    Phosphoinositides (PIPs) are present in very small amounts but are essential for cell signaling, morphogenesis, and polarity. By mass spectrometry, we demonstrated that some PIPs with stearic acyl chains were strongly disturbed in a psi1Δ Saccharomyces cerevisiae yeast strain deficient in the specific incorporation of a stearoyl chain at the sn-1 position of phosphatidylinositol. The absence of PIPs containing stearic acid induced disturbances in intracellular trafficking, although the total amount of PIPs was not diminished. Changes in PIPs also induced alterations in the budding pattern and defects in actin cytoskeleton organization (cables and patches). Moreover, when the PSI1 gene was impaired, a high proportion of cells with bipolar cortical actin patches that occurred concomitantly with the bipolar localization of Cdc42p was specifically found among diploid cells. This bipolar cortical actin phenotype, never previously described, was also detected in a bud9Δ/bud9Δ strain. Very interestingly, overexpression of PSI1 reversed this phenotype. PMID:26711260

  15. Design and implementation of the parallel processing system of multi-channel polarization images

    NASA Astrophysics Data System (ADS)

    Li, Zhi-yong; Huang, Qin-chao

    2013-08-01

    Compared with traditional optical intensity image processing, polarization images processing has two main problems. One is that the amount of data is larger. The other is that processing tasks is more complex. To resolve these problems, the parallel processing system of multi-channel polarization images is designed by the multi-DSP technique. It contains a communication control unit (CCU) and a data processing array (DPA). CCU controls communications inside and outside the system. Its logics are designed by a FPGA chip. DPA is made up of four Digital Signal Processor (DSP) chips, which are interlinked by the loose coupling method. DPA implements processing tasks including images registration and images synthesis by parallel processing methods. The polarization images parallel processing model is designed on multi levels including the system task, the algorithm and the operation. Its program is designed by the assemble language. While the polarization image resolution is 782x582 pixels, the pixel data length is 12 bits in the experiment. After it received 3 channels of polarization image simultaneously, this system implements parallel task to acquire the target polarization characteristics. Experimental results show that this system has good real-time and reliability. The processing time of images registration is 293.343ms while the registration accuracy achieves 0.5 pixel. The processing time of images synthesis is 3.199ms.

  16. Planar cell polarity-mediated induction of neural stem cell expansion during axolotl spinal cord regeneration.

    PubMed

    Rodrigo Albors, Aida; Tazaki, Akira; Rost, Fabian; Nowoshilow, Sergej; Chara, Osvaldo; Tanaka, Elly M

    2015-01-01

    Axolotls are uniquely able to mobilize neural stem cells to regenerate all missing regions of the spinal cord. How a neural stem cell under homeostasis converts after injury to a highly regenerative cell remains unknown. Here, we show that during regeneration, axolotl neural stem cells repress neurogenic genes and reactivate a transcriptional program similar to embryonic neuroepithelial cells. This dedifferentiation includes the acquisition of rapid cell cycles, the switch from neurogenic to proliferative divisions, and the re-expression of planar cell polarity (PCP) pathway components. We show that PCP induction is essential to reorient mitotic spindles along the anterior-posterior axis of elongation, and orthogonal to the cell apical-basal axis. Disruption of this property results in premature neurogenesis and halts regeneration. Our findings reveal a key role for PCP in coordinating the morphogenesis of spinal cord outgrowth with the switch from a homeostatic to a regenerative stem cell that restores missing tissue. PMID:26568310

  17. Study of cellular dynamics on polarized CoCrMo alloy using time-lapse live-cell imaging.

    PubMed

    Haeri, Morteza; Gilbert, Jeremy L

    2013-11-01

    The physico-chemical processes and phenomena occurring at the interface of metallic biomedical implants and the body dictate their successful integration in vivo. Changes in the surface potential and the associated redox reactions at metallic implants can significantly influence several aspects of biomaterial/cell interactions such as cell adhesion and survival in vitro. Accordingly, there is a voltage viability range (voltages which do not compromise cellular viability of the cells cultured on the polarized metal) for metallic implants. We report on cellular dynamics (size, polarity, movement) and temporal changes in the number and total area of focal adhesion complexes in transiently transfected MC3T3-E1 pre-osteoblasts cultured on CoCrMo alloy surfaces polarized at the cathodic and anodic edges of its voltage viability range (-400 and +500 mV (Ag/AgCl), respectively). Nucleus dynamics (size, circularity, movement) and the release of reactive oxygen species (ROS) were also studied on the polarized metal at -1000, -400 and +500 mV (Ag/AgCl). Our results show that at -400 mV, where reduction reactions dominate, a gradual loss of adhesion occurs over 24 h while cells shrink in size during this time. At +500 mV, where oxidation reactions dominate (i.e. metal ions form, including Cr6+), cells become non-viable after 5h without showing any significant changes in adhesion behavior right before cell death. Nucleus size of cells at -1000 mV decreased sharply within 15 min after polarization, which rendered the cells completely non-viable. No significant amount of ROS release by cells was detected on the polarized CoCrMo at any of these voltages. PMID:23831720

  18. PHENOTYPE AND POLARIZATION OF AUTOLOGOUS T CELLS BY BIOMATERIAL-TREATED DENDRITIC CELLS

    PubMed Central

    Park, Jaehyung; Gerber, Michael H.; Babensee, Julia E.

    2014-01-01

    Given the central role of dendritic cells (DCs) in directing T cell phenotypes, the ability of biomaterial-treated DCs to dictate autologous T cell phenotype was investigated. Here, we demonstrate that differentially biomaterial-treated DCs differentially directed autologous T cell phenotype and polarization, depending on the biomaterial used to pre-treat the DCs. Immature DCs (iDCs) were derived from human peripheral blood monocytes, and treated with biomaterial films of alginate, agarose, chitosan, hyaluronic acid, or 75:25 poly(lactic-co-glycolic acid) (PLGA), followed by co-culture of these biomaterial-treated DCs and autologous T cells. When autologous T cells were co-cultured with DCs treated with biomaterial film/antigen (ovalbumin, OVA) combinations, different biomaterial films induced differential levels of T cell marker (CD4, CD8, CD25, CD69) expression, as well as differential cytokine profiles [interferon (IFN)-γ, interleukin (IL)-12p70, IL-10, IL-4] in the polarization of T helper types. Dendritic cells treated with agarose films/OVA induced CD4+CD25+FoxP3+ (T regulatory cells) expression, comparable to untreated iDCs, on autologous T cells in the DC-T co-culture system. Furthermore, in this co-culture, agarose treatment induced release of IL-12p70 and IL-10 at higher levels, as compared to DC treatment with other biomaterial films/OVA, suggesting Th1 and Th2 polarization, respectively. Dendritic cells treated with PLGA film/OVA treatment induced release of IFN-γ at higher levels compared to that observed for co-cultures with iDCs or DCs treated with all other biomaterial films. These results indicate that DC treatment with different biomaterial films has potential as a tool for immunomodulation by directing autologous T cell responses. PMID:24616366

  19. Preferential Budding of Vesicular Stomatitis Virus from the Basolateral Surface of Polarized Epithelial Cells Is Not Solely Directed by Matrix Protein or Glycoprotein

    PubMed Central

    Drokhlyansky, Eugene; Soh, Timothy K.

    2015-01-01

    Vesicular stomatitis virus has been shown to bud basolaterally, and the matrix protein, but not glycoprotein, was proposed to mediate this asymmetry. Using polarized T84 monolayers, we demonstrate that no single viral protein is sufficient for polarized budding. Particles are released from the apical and basolateral surfaces and are indistinguishable, indicating that there is no apical assembly defect. We propose that aspects of host cell polarity create a more efficient budding process at the basolateral surface. PMID:26339064

  20. Solar cell module lamination process

    DOEpatents

    Carey, Paul G.; Thompson, Jesse B.; Aceves, Randy C.

    2002-01-01

    A solar cell module lamination process using fluoropolymers to provide protection from adverse environmental conditions and thus enable more extended use of solar cells, particularly in space applications. A laminate of fluoropolymer material provides a hermetically sealed solar cell module structure that is flexible and very durable. The laminate is virtually chemically inert, highly transmissive in the visible spectrum, dimensionally stable at temperatures up to about 200.degree. C. highly abrasion resistant, and exhibits very little ultra-violet degradation.

  1. Sequential development of apical-basal and planar polarities in aggregating epitheliomuscular cells of Hydra.

    PubMed

    Seybold, Anna; Salvenmoser, Willi; Hobmayer, Bert

    2016-04-01

    Apical-basal and planar cell polarities are hallmarks of metazoan epithelia required to separate internal and external environments and to regulate trans- and intracellular transport, cytoskeletal organization, and morphogenesis. Mechanisms of cell polarization have been intensively studied in bilaterian model organisms, particularly in early embryos and cultured cells, while cell polarity in pre-bilaterian tissues is poorly understood. Here, we have studied apical-basal and planar polarization in regenerating (aggregating) clusters of epitheliomuscular cells of Hydra, a simple representative of the ancestral, pre-bilaterian phylum Cnidaria. Immediately after dissociation, single epitheliomuscular cells do not exhibit cellular polarity, but they polarize de novo during aggregation. Reestablishment of the Hydra-specific epithelial bilayer is a result of short-range cell sorting. In the early phase of aggregation, apical-basal polarization starts with an enlargement of the epithelial apical-basal diameter and by the development of belt-like apical septate junctions. Specification of the basal pole of epithelial cells occurs shortly later and is linked to synthesis of mesoglea, development of hemidesmosome-like junctions, and formation of desmosome-like junctions connecting the basal myonemes of neighbouring cells. Planar polarization starts, while apical-basal polarization is already ongoing. It is executed gradually starting with cell-autonomous formation, parallelization, and condensation of myonemes at the basal end of each epithelial cell and continuing with a final planar alignment of epitheliomuscular cells at the tissue level. Our findings reveal that epithelial polarization in Hydra aggregates occurs in defined steps well accessible by histological and ultrastructural techniques and they will provide a basis for future molecular studies. PMID:26921448

  2. Polarity Proteins as Regulators of Cell Junction Complexes: Implications for Breast Cancer

    PubMed Central

    Bazzoun, Dana; Lelièvre, Sophie; Talhouk, Rabih

    2013-01-01

    The epithelium of multicellular organisms possesses a well-defined architecture, referred to as polarity that coordinates the regulation of essential cell features. Polarity proteins are intimately linked to the protein complexes that make the tight, adherens and gap junctions; they contribute to the proper localization and assembly of these cell-cell junctions within cells and consequently to functional tissue organization. The establishment of cell-cell junctions and polarity are both implicated in the regulation of epithelial modifications in normal and cancer situations. Uncovering the mechanisms through which cell-cell junctions and epithelial polarization are established and how their interaction with the microenvironment direct cell and tissue organization has opened new venues for the development of cancer therapies. In this review, we focus on the breast epithelium to highlight how polarity and cell-cell junction proteins interact together in normal and cancerous contexts to regulate major cellular mechanisms such as migration. The impact of these proteins on epigenetic mechanisms responsible for resetting cells towards oncogenesis is discussed in light of increasing evidence that tissue polarity modulates chromatin function. Finally, we give an overview of recent breast cancer therapies that target proteins involved in cell-cell junctions. PMID:23458609

  3. Loss of Cell Adhesion Increases Tumorigenic Potential of Polarity Deficient Scribble Mutant Cells

    PubMed Central

    Waghmare, Indrayani

    2016-01-01

    Epithelial polarity genes are important for maintaining tissue architecture, and regulating growth. The Drosophila neoplastic tumor suppressor gene scribble (scrib) belongs to the basolateral polarity complex. Loss of scrib results in disruption of its growth regulatory functions, and downregulation or mislocalization of Scrib is correlated to tumor growth. Somatic scribble mutant cells (scrib-) surrounded by wild-type cells undergo apoptosis, which can be prevented by introduction of secondary mutations that provide a growth advantage. Using genetic tools in Drosophila, we analyzed the phenotypic effects of loss of scrib in different growth promoting backgrounds. We investigated if a central mechanism that regulates cell adhesion governs the growth and invasive potential of scrib mutant cells. Here we show that increased proliferation, and survival abilities of scrib- cells in different genetic backgrounds affect their differentiation, and intercellular adhesion. Further, loss of scrib is sufficient to cause reduced cell survival, activation of the JNK pathway and a mild reduction of cell adhesion. Our data show that for scrib cells to induce aggressive tumor growth characterized by loss of differentiation, cell adhesion, increased proliferation and invasion, cooperative interactions that derail signaling pathways play an essential role in the mechanisms leading to tumorigenesis. Thus, our study provides new insights on the effects of loss of scrib and the modification of these effects via cooperative interactions that enhance the overall tumorigenic potential of scrib deficient cells. PMID:27327956

  4. The Influence of Local Geometric Effects on Mars Polar Processes

    NASA Technical Reports Server (NTRS)

    Hecht, M. H.

    2005-01-01

    Using simple, qualitative heat balance models, this paper addresses textures and structures that will result from the evolution of volatile layers by accretion and by ablation. Such phenomena may have global implications that are not apparent when only flat or sloped surfaces are modeled. In general, structures such as mounds or depressions formed out of volatile materials will evolve in shape such that the growth or retreat of any particular surface will be maximized. It can be shown that the local radius of curvature is proportional to the growth or retreat rate. For example, icy surfaces will tend to form facets that face the dominant sun direction. Two such cases are evaluated: a) Features associated with condensation of volatiles, include cold-trapping and redistribution, such as the concentration of frost around the Viking 2 lander [1]. Here I will focus on textures that likely result from the formation of seasonal CO2 deposits. b) Features associated with sublimation of volatiles, such as those described by Ingersoll et. al. [2] result in textured surfaces that affect both the apparent emissivity and albedo. Similar calculations have been performed with respect to the "Swiss cheese" features on the South Polar Cap [3]. Here, I evaluate the likely sublimation rates from optimal ice scarp structures and their implications for the long-term evolution of the polar caps and formation of layered terrain.

  5. Salmonella enterica Invasion of Polarized Epithelial Cells Is a Highly Cooperative Effort

    PubMed Central

    Lorkowski, Martin; Felipe-López, Alfonso; Danzer, Claudia A.; Hansmeier, Nicole

    2014-01-01

    The invasion of polarized epithelial cells by Salmonella enterica requires the cooperative activity of the Salmonella pathogenicity island 1 (SPI1)-encoded type III secretion system (T3SS) and the SPI4-encoded adhesin SiiE. The invasion of polarized cells is more efficient than that of nonpolarized cells, and we observed the formation of clusters of bacteria on infected cells. Here we demonstrate that the invasion of polarized cells is a highly cooperative activity. Using a novel live-cell imaging approach, we visualized the cooperative entry of multiple bacteria into ruffles induced on the apical surfaces of polarized cells. The induction of membrane ruffles by activity of Salmonella enables otherwise noninvasive mutant strains to enter polarized host cells. Bacterial motility and chemotaxis were of lower importance for cooperativity in polarized-cell invasion. We propose that cooperative invasion is a key factor for the very efficient entry into polarized cells and a factor contributing to epithelial damage and intestinal inflammation. PMID:24711567

  6. A polarized cell model for Chikungunya virus infection: entry and egress of virus occurs at the apical domain of polarized cells.

    PubMed

    Lim, Pei Jin; Chu, Justin Jang Hann

    2014-02-01

    Chikungunya virus (CHIKV) has resulted in several outbreaks in the past six decades. The clinical symptoms of Chikungunya infection include fever, skin rash, arthralgia, and an increasing incidence of encephalitis. The re-emergence of CHIKV with more severe pathogenesis highlights its potential threat on our human health. In this study, polarized HBMEC, polarized Vero C1008 and non-polarized Vero cells grown on cell culture inserts were infected with CHIKV apically or basolaterally. Plaque assays, viral binding assays and immunofluorescence assays demonstrated apical entry and release of CHIKV in polarized HBMEC and Vero C1008. Drug treatment studies were performed to elucidate both host cell and viral factors involved in the sorting and release of CHIKV at the apical domain of polarized cells. Disruption of host cell myosin II, microtubule and microfilament networks did not disrupt the polarized release of CHIKV. However, treatment with tunicamycin resulted in a bi-directional release of CHIKV, suggesting that N-glycans of CHIKV envelope glycoproteins could serve as apical sorting signals. PMID:24587455

  7. EGFR signaling promotes self-renewal through the establishment of cell polarity in Drosophila follicle stem cells.

    PubMed

    Castanieto, Angela; Johnston, Michael J; Nystul, Todd G

    2014-01-01

    Epithelial stem cells divide asymmetrically, such that one daughter replenishes the stem cell pool and the other differentiates. We found that, in the epithelial follicle stem cell (FSC) lineage of the Drosophila ovary, epidermal growth factor receptor (EGFR) signaling functions specifically in the FSCs to promote the unique partially polarized state of the FSC, establish apical-basal polarity throughout the lineage, and promote FSC maintenance in the niche. In addition, we identified a novel connection between EGFR signaling and the cell-polarity regulator liver kinase B1 (LKB1), which indicates that EGFR signals through both the Ras-Raf-MEK-Erk pathway and through the LKB1-AMPK pathway to suppress apical identity. The development of apical-basal polarity is the earliest visible difference between FSCs and their daughters, and our findings demonstrate that the EGFR-mediated regulation of apical-basal polarity is essential for the segregation of stem cell and daughter cell fates. PMID:25437306

  8. Gamma-Ray Polarization of the Synchrotron Self-compton Process from a Highly Relativistic Jet

    NASA Astrophysics Data System (ADS)

    Chang, Zhe; Lin, Hai-Nan

    2014-11-01

    The high polarization observed in the prompt phase of some gamma-ray bursts invites extensive study of the emission mechanism. In this paper, we investigate the polarization properties of the synchrotron self-Compton (SSC) process from a highly relativistic jet. A magnetic-dominated, baryon-loaded jet ejected from the central engine travels with a large Lorentz factor. Shells with slightly different velocities collide with each other and produce shocks. The shocks accelerate electrons to a power-law distribution and, at the same time, magnify the magnetic field. Electrons move in the magnetic field and produce synchrotron photons. Synchrotron photons suffer from the Compton scattering (CS) process and then are detected by an observer located slightly off-axis. We analytically derive the formulae of photon polarization in the SSC process in two magnetic configurations: a magnetic field in the shock plane and perpendicular to the shock plane. We show that photons induced by the SSC process can be highly polarized, with the maximum polarization Π ~ 24% in the energy band [0.5, 5] MeV. The polarization depends on the viewing angles, peaking in the plane perpendicular to the magnetic field. In the energy band [0.05, 0.5] MeV, in which most γ-ray polarimeters are active, the polarization is about twice that in the Thomson limit, reaching Π ~ 20%. This implies that the Klein-Nishina effect, which is often neglected in the literature, should be carefully considered.

  9. Gamma-ray polarization of the synchrotron self-compton process from a highly relativistic jet

    SciTech Connect

    Chang, Zhe; Lin, Hai-Nan

    2014-11-01

    The high polarization observed in the prompt phase of some gamma-ray bursts invites extensive study of the emission mechanism. In this paper, we investigate the polarization properties of the synchrotron self-Compton (SSC) process from a highly relativistic jet. A magnetic-dominated, baryon-loaded jet ejected from the central engine travels with a large Lorentz factor. Shells with slightly different velocities collide with each other and produce shocks. The shocks accelerate electrons to a power-law distribution and, at the same time, magnify the magnetic field. Electrons move in the magnetic field and produce synchrotron photons. Synchrotron photons suffer from the Compton scattering (CS) process and then are detected by an observer located slightly off-axis. We analytically derive the formulae of photon polarization in the SSC process in two magnetic configurations: a magnetic field in the shock plane and perpendicular to the shock plane. We show that photons induced by the SSC process can be highly polarized, with the maximum polarization Π ∼ 24% in the energy band [0.5, 5] MeV. The polarization depends on the viewing angles, peaking in the plane perpendicular to the magnetic field. In the energy band [0.05, 0.5] MeV, in which most γ-ray polarimeters are active, the polarization is about twice that in the Thomson limit, reaching Π ∼ 20%. This implies that the Klein-Nishina effect, which is often neglected in the literature, should be carefully considered.

  10. Dysregulation of cell polarity proteins synergize with oncogenes or the microenvironment to induce invasive behavior in epithelial cells.

    PubMed

    Chatterjee, Samit; Seifried, Laurie; Feigin, Michael E; Gibbons, Don L; Scuoppo, Claudio; Lin, Wei; Rizvi, Zain H; Lind, Evan; Dissanayake, Dilan; Kurie, Jonathan; Ohashi, Pam; Muthuswamy, Senthil K

    2012-01-01

    Changes in expression and localization of proteins that regulate cell and tissue polarity are frequently observed in carcinoma. However, the mechanisms by which changes in cell polarity proteins regulate carcinoma progression are not well understood. Here, we report that loss of polarity protein expression in epithelial cells primes them for cooperation with oncogenes or changes in tissue microenvironment to promote invasive behavior. Activation of ErbB2 in cells lacking the polarity regulators Scribble, Dlg1 or AF-6, induced invasive properties. This cooperation required the ability of ErbB2 to regulate the Par6/aPKC polarity complex. Inhibition of the ErbB2-Par6 pathway was sufficient to block ErbB2-induced invasion suggesting that two polarity hits may be needed for ErbB2 to promote invasion. Interestingly, in the absence of ErbB2 activation, either a combined loss of two polarity proteins, or exposure of cells lacking one polarity protein to cytokines IL-6 or TNFα induced invasive behavior in epithelial cells. We observed the invasive behavior only when cells were plated on a stiff matrix (Matrigel/Collagen-1) and not when plated on a soft matrix (Matrigel alone). Cells lacking two polarity proteins upregulated expression of EGFR and activated Akt. Inhibition of Akt activity blocked the invasive behavior identifying a mechanism by which loss of polarity promotes invasion of epithelial cells. Thus, we demonstrate that loss of polarity proteins confers phenotypic plasticity to epithelial cells such that they display normal behavior under normal culture conditions but display aggressive behavior in response to activation of oncogenes or exposure to cytokines. PMID:22529912

  11. Effect of dust particle polarization on scattering processes in complex plasmas

    SciTech Connect

    Kodanova, S. K.; Ramazanov, T. S.; Bastykova, N. Kh.; Moldabekov, Zh. A.

    2015-06-15

    Screened interaction potentials in dusty plasmas taking into account the polarization of dust particles have been obtained. On the basis of screened potentials scattering processes for ion-dust particle and dust particle-dust particle pairs have been studied. In particular, the scattering cross section is considered. The scattering processes for which the dust grain polarization is unimportant have been found. The effect of zero angle dust particle-dust particle scattering is predicted.

  12. The polarity protein Par3 regulates APP trafficking and processing through the endocytic adaptor protein Numb.

    PubMed

    Sun, Miao; Asghar, Suwaiba Z; Zhang, Huaye

    2016-09-01

    The processing of amyloid precursor protein (APP) into β-amyloid peptide (Aβ) is a key step in the pathogenesis of Alzheimer's disease (AD), and trafficking dysregulations of APP and its secretases contribute significantly to altered APP processing. Here we show that the cell polarity protein Par3 plays an important role in APP processing and trafficking. We found that the expression of full length Par3 is significantly decreased in AD patients. Overexpression of Par3 promotes non-amyloidogenic APP processing, while depletion of Par3 induces intracellular accumulation of Aβ. We further show that Par3 functions by regulating APP trafficking. Loss of Par3 decreases surface expression of APP by targeting APP to the late endosome/lysosome pathway. Finally, we show that the effects of Par3 are mediated through the endocytic adaptor protein Numb, and Par3 functions by interfering with the interaction between Numb and APP. Together, our studies show a novel role for Par3 in regulating APP processing and trafficking. PMID:27072891

  13. Role of the Polycystins in Cell Migration, Polarity, and Tissue Morphogenesis

    PubMed Central

    Nigro, Elisa Agnese; Castelli, Maddalena; Boletta, Alessandra

    2015-01-01

    Cystic kidney diseases (CKD) is a class of disorders characterized by ciliary dysfunction and, therefore, belonging to the ciliopathies. The prototype CKD is autosomal dominant polycystic kidney disease (ADPKD), whose mutated genes encode for two membrane-bound proteins, polycystin-1 (PC-1) and polycystin-2 (PC-2), of unknown function. Recent studies on CKD-associated genes identified new mechanisms of morphogenesis that are central for establishment and maintenance of proper renal tubular diameter. During embryonic development in the mouse and lower vertebrates a convergent-extension (CE)-like mechanism based on planar cell polarity (PCP) and cellular intercalation is involved in “sculpting” the tubules into a narrow and elongated shape. Once the appropriate diameter is established, further elongation occurs through oriented cell division (OCD). The polycystins (PCs) regulate some of these essential processes. In this review we summarize recent work on the role of PCs in regulating cell migration, the cytoskeleton, and front-rear polarity. These important properties are essential for proper morphogenesis of the renal tubules and the lymphatic vessels. We highlight here several open questions and controversies. Finally, we try to outline some of the next steps required to study these processes and their relevance in physiological and pathological conditions. PMID:26529018

  14. Terrestrial photovoltaic cell process testing

    NASA Technical Reports Server (NTRS)

    Burger, D. R.

    1985-01-01

    The paper examines critical test parameters, criteria for selecting appropriate tests, and the use of statistical controls and test patterns to enhance PV-cell process test results. The coverage of critical test parameters is evaluated by examining available test methods and then screening these methods by considering the ability to measure those critical parameters which are most affected by the generic process, the cost of the test equipment and test performance, and the feasibility for process testing.

  15. Shroom3 functions downstream of planar cell polarity to regulate myosin II distribution and cellular organization during neural tube closure

    PubMed Central

    McGreevy, Erica M.; Vijayraghavan, Deepthi; Davidson, Lance A.; Hildebrand, Jeffrey D.

    2015-01-01

    ABSTRACT Neural tube closure is a critical developmental event that relies on actomyosin contractility to facilitate specific processes such as apical constriction, tissue bending, and directional cell rearrangements. These complicated processes require the coordinated activities of Rho-Kinase (Rock), to regulate cytoskeletal dynamics and actomyosin contractility, and the Planar Cell Polarity (PCP) pathway, to direct the polarized cellular behaviors that drive convergent extension (CE) movements. Here we investigate the role of Shroom3 as a direct linker between PCP and actomyosin contractility during mouse neural tube morphogenesis. In embryos, simultaneous depletion of Shroom3 and the PCP components Vangl2 or Wnt5a results in an increased liability to NTDs and CE failure. We further show that these pathways intersect at Dishevelled, as Shroom3 and Dishevelled 2 co-distribute and form a physical complex in cells. We observed that multiple components of the Shroom3 pathway are planar polarized along mediolateral cell junctions in the neural plate of E8.5 embryos in a Shroom3 and PCP-dependent manner. Finally, we demonstrate that Shroom3 mutant embryos exhibit defects in planar cell arrangement during neural tube closure, suggesting a role for Shroom3 activity in CE. These findings support a model in which the Shroom3 and PCP pathways interact to control CE and polarized bending of the neural plate and provide a clear illustration of the complex genetic basis of NTDs. PMID:25596276

  16. Influence of polar solvents on photovoltaic performance of Monascusred dye-sensitized solar cell

    NASA Astrophysics Data System (ADS)

    Lee, Jae Wook; Kim, Tae Young; Ko, Hyun Seok; Han, Shin; Lee, Suk-Ho; Park, Kyung Hee

    Dye-sensitized solar cells (DSSCs) were assembled using natural dyes extracted from Monascus red pigment as a sensitizer. In this work, we studied the adsorption characteristics for harvesting sunlight and the electrochemical behavior for electron transfer in Monascus red DSSC using different solvents. The effect of polar aprotic and protic solvents including water, ethanol, and dimethylsulfoxide (DMSO) used in the sensitization process was investigated for the improvement in conversion efficiency of a cell. As for the Monascus red dye-sensitized electrode in DMSO solvent, the solar cell yields a short-circuit current density (Jsc) of 1.23 mA/cm2, a photovoltage (Voc) of 0.75 V, and a fill factor of 0.72, corresponding to an energy conversion efficiency (η) of 0.66%.

  17. 10.6% Certified Colloidal Quantum Dot Solar Cells via Solvent-Polarity-Engineered Halide Passivation.

    PubMed

    Lan, Xinzheng; Voznyy, Oleksandr; García de Arquer, F Pelayo; Liu, Mengxia; Xu, Jixian; Proppe, Andrew H; Walters, Grant; Fan, Fengjia; Tan, Hairen; Liu, Min; Yang, Zhenyu; Hoogland, Sjoerd; Sargent, Edward H

    2016-07-13

    Colloidal quantum dot (CQD) solar cells are solution-processed photovoltaics with broad spectral absorption tunability. Major advances in their efficiency have been made via improved CQD surface passivation and device architectures with enhanced charge carrier collection. Herein, we demonstrate a new strategy to improve further the passivation of CQDs starting from the solution phase. A cosolvent system is employed to tune the solvent polarity in order to achieve the solvation of methylammonium iodide (MAI) and the dispersion of hydrophobic PbS CQDs simultaneously in a homogeneous phase, otherwise not achieved in a single solvent. This process enables MAI to access the CQDs to confer improved passivation. This, in turn, allows for efficient charge extraction from a thicker photoactive layer device, leading to a certified solar cell power conversion efficiency of 10.6%, a new certified record in CQD photovoltaics. PMID:27351104

  18. Bioinspired Polarization Imaging Sensors: From Circuits and Optics to Signal Processing Algorithms and Biomedical Applications

    PubMed Central

    York, Timothy; Powell, Samuel B.; Gao, Shengkui; Kahan, Lindsey; Charanya, Tauseef; Saha, Debajit; Roberts, Nicholas W.; Cronin, Thomas W.; Marshall, Justin; Achilefu, Samuel; Lake, Spencer P.; Raman, Baranidharan; Gruev, Viktor

    2015-01-01

    In this paper, we present recent work on bioinspired polarization imaging sensors and their applications in biomedicine. In particular, we focus on three different aspects of these sensors. First, we describe the electro–optical challenges in realizing a bioinspired polarization imager, and in particular, we provide a detailed description of a recent low-power complementary metal–oxide–semiconductor (CMOS) polarization imager. Second, we focus on signal processing algorithms tailored for this new class of bioinspired polarization imaging sensors, such as calibration and interpolation. Third, the emergence of these sensors has enabled rapid progress in characterizing polarization signals and environmental parameters in nature, as well as several biomedical areas, such as label-free optical neural recording, dynamic tissue strength analysis, and early diagnosis of flat cancerous lesions in a murine colorectal tumor model. We highlight results obtained from these three areas and discuss future applications for these sensors. PMID:26538682

  19. Flotillins Are Involved in the Polarization of Primitive and Mature Hematopoietic Cells

    PubMed Central

    Rajendran, Lawrence; Beckmann, Julia; Magenau, Astrid; Boneberg, Eva-Maria; Gaus, Katharina; Viola, Antonella; Giebel, Bernd; Illges, Harald

    2009-01-01

    Background Migration of mature and immature leukocytes in response to chemokines is not only essential during inflammation and host defense, but also during development of the hematopoietic system. Many molecules implicated in migratory polarity show uniform cellular distribution under non-activated conditions, but acquire a polarized localization upon exposure to migratory cues. Methodology/Principal Findings Here, we present evidence that raft-associated endocytic proteins (flotillins) are pre-assembled in lymphoid, myeloid and primitive hematopoietic cells and accumulate in the uropod during migration. Furthermore, flotillins display a polarized distribution during immunological synapse formation. Employing the membrane lipid-order sensitive probe Laurdan, we show that flotillin accumulation in the immunological synapse is concomittant with membrane ordering in these regions. Conclusions Together with the observation that flotillin polarization does not occur in other polarized cell types such as polarized epithelial cells, our results suggest a specific role for flotillins in hematopoietic cell polarization. Based on our results, we propose that in hematopoietic cells, flotillins provide intrinsic cues that govern segregation of certain microdomain-associated molecules during immune cell polarization. PMID:20027317

  20. A self-propelled particle model with experimentally quantified cell polarization

    NASA Astrophysics Data System (ADS)

    Passucci, Giuseppe; Brasch, Megan E.; Deakin, Nicholas O.; Turner, Christopher E.; Henderson, James H.; Manning, M. Lisa

    2015-03-01

    Self-propelled particle (SPP) models have been used extensively to study collective cell motion, but they do not always accurately capture the long-time behavior observed in experiments. Furthermore, the equation for polarization in these models is not experimentally well-constrained. Therefore we developed a novel method for quantifying polarization in Hs578T breast carcinoma cells in a wound healing geometry. During cell movement, the nucleus orients toward the anterior of a cell while the Golgi body orients towards the posterior; we simultaneously imaged and tracked the Golgi and nuclei and constructed a polarization vector defined by the Golgi-nuclei axis. We find that cells in the bulk are not highly polarized, while those on the edge are highly polarized outward perpendicular to the wound edge. We also study the temporal correlations between a cell's internal polarization determined by the Golgi-nuclei axis and the polarization of its motion determined from nuclei displacements. We incorporate these polarization dynamics into a SPP model, and compare wound healing and long-time diffusion in the model to the experiments. These SPP equations can also be coarse-grained to generate a continuum model.

  1. Wdr1-mediated cell shape dynamics and cortical tension are essential for epidermal planar cell polarity

    PubMed Central

    Pasolli, H. Amalia; Chai, Sophia; Nikolova, Maria; Stokes, Nicole; Fuchs, Elaine

    2015-01-01

    During mouse development, core planar cell polarity (PCP) proteins become polarized in the epidermal plane to guide angling/morphogenesis of hair follicles. How PCP is established is poorly understood. Here, we identify a key role for Wdr1 (also known as Aip1), an F-actin-binding protein that enhances cofilin/destrin-mediated F-actin disassembly. We show that cofilin and destrin function redundantly in developing epidermis, but their combined depletion perturbs cell adhesion, cytokinesis, apicobasal polarity and PCP. Although Wdr1 depletion accentuates single-loss-of-cofilin/destrin phenotypes, alone it resembles core PCP mutations. Seeking a mechanism, we find that Wdr1 and cofilin/destrin-mediated actomyosin remodelling are essential for generating or maintaining cortical tension within the developing epidermal sheet and driving the cell shape and planar orientation changes that accompany establishment of PCP in mammalian epidermis. Our findings suggest intriguing evolutionary parallels but mechanistic modifications to the distal wing hinge-mediated mechanical forces that drive cell shape change and orient PCP in the Drosophila wing disc. PMID:25915128

  2. PrPC Undergoes Basal to Apical Transcytosis in Polarized Epithelial MDCK Cells

    PubMed Central

    Arkhipenko, Alexander; Syan, Sylvie; Victoria, Guiliana Soraya

    2016-01-01

    The Prion Protein (PrP) is an ubiquitously expressed glycosylated membrane protein attached to the external leaflet of the plasma membrane via a glycosylphosphatidylinositol anchor (GPI). While the misfolded PrPSc scrapie isoform is the infectious agent of prion disease, the cellular isoform (PrPC) is an enigmatic protein with unclear function. Of interest, PrP localization in polarized MDCK cells is controversial and its mechanism of trafficking is not clear. Here we investigated PrP traffic in MDCK cells polarized on filters and in three-dimensional MDCK cysts, a more physiological model of polarized epithelia. We found that, unlike other GPI-anchored proteins (GPI-APs), PrP undergoes basolateral-to-apical transcytosis in fully polarized MDCK cells. Following this event full-length PrP and its cleavage fragments are segregated in different domains of the plasma membrane in polarized cells in both 2D and 3D cultures. PMID:27389581

  3. PrPC Undergoes Basal to Apical Transcytosis in Polarized Epithelial MDCK Cells.

    PubMed

    Arkhipenko, Alexander; Syan, Sylvie; Victoria, Guiliana Soraya; Lebreton, Stéphanie; Zurzolo, Chiara

    2016-01-01

    The Prion Protein (PrP) is an ubiquitously expressed glycosylated membrane protein attached to the external leaflet of the plasma membrane via a glycosylphosphatidylinositol anchor (GPI). While the misfolded PrPSc scrapie isoform is the infectious agent of prion disease, the cellular isoform (PrPC) is an enigmatic protein with unclear function. Of interest, PrP localization in polarized MDCK cells is controversial and its mechanism of trafficking is not clear. Here we investigated PrP traffic in MDCK cells polarized on filters and in three-dimensional MDCK cysts, a more physiological model of polarized epithelia. We found that, unlike other GPI-anchored proteins (GPI-APs), PrP undergoes basolateral-to-apical transcytosis in fully polarized MDCK cells. Following this event full-length PrP and its cleavage fragments are segregated in different domains of the plasma membrane in polarized cells in both 2D and 3D cultures. PMID:27389581

  4. The BASL Polarity Protein Controls a MAPK Signaling Feedback Loop in Asymmetric Cell Division

    PubMed Central

    Zhang, Ying; Wang, Pengcheng; Shao, Wanchen; Zhu, Jian-Kang; Dong, Juan

    2015-01-01

    SUMMARY Cell polarization is linked to fate determination during asymmetric division of plant stem cells, but the underlying molecular mechanisms remain unknown. In Arabidopsis, BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL) is polarized to control stomatal asymmetric division. A MITOGEN-ACTIVATED PROTEIN KINASE (MAPK) cascade determines terminal stomatal fate by promoting the degradation of the lineage determinant SPEECHLESS (SPCH). Here we demonstrate that a positive feedback loop between BASL and the MAPK pathway constitutes a polarity module at the cortex. Cortical localization of BASL requires phosphorylation mediated by MPK3/6. Phosphorylated BASL functions as a scaffold and recruits the MAPKKK YODA and MPK3/6 to spatially concentrate signaling at the cortex. Activated MPK3/6 reinforces the feedback loop by phosphorylating BASL, and inhibits stomatal fate by phosphorylating SPCH. Polarization of the BASL-MAPK signaling feedback module represents a mechanism connecting cell polarity to fate differentiation during asymmetric stem cell division in plants. PMID:25843888

  5. T Cells' Immunological Synapses Induce Polarization of Brain Astrocytes In Vivo and In Vitro: A Novel Astrocyte Response Mechanism to Cellular Injury

    PubMed Central

    Barcia, Carlos; Sanderson, Nicholas S. R.; Barrett, Robert J.; Wawrowsky, Kolja; Kroeger, Kurt M.; Puntel, Mariana; Liu, Chunyan; Castro, Maria G.; Lowenstein, Pedro R.

    2008-01-01

    Background Astrocytes usually respond to trauma, stroke, or neurodegeneration by undergoing cellular hypertrophy, yet, their response to a specific immune attack by T cells is poorly understood. Effector T cells establish specific contacts with target cells, known as immunological synapses, during clearance of virally infected cells from the brain. Immunological synapses mediate intercellular communication between T cells and target cells, both in vitro and in vivo. How target virally infected astrocytes respond to the formation of immunological synapses established by effector T cells is unknown. Findings Herein we demonstrate that, as a consequence of T cell attack, infected astrocytes undergo dramatic morphological changes. From normally multipolar cells, they become unipolar, extending a major protrusion towards the immunological synapse formed by the effector T cells, and withdrawing most of their finer processes. Thus, target astrocytes become polarized towards the contacting T cells. The MTOC, the organizer of cell polarity, is localized to the base of the protrusion, and Golgi stacks are distributed throughout the protrusion, reaching distally towards the immunological synapse. Thus, rather than causing astrocyte hypertrophy, antiviral T cells cause a major structural reorganization of target virally infected astrocytes. Conclusions Astrocyte polarization, as opposed to hypertrophy, in response to T cell attack may be due to T cells providing a very focused attack, and thus, astrocytes responding in a polarized manner. A similar polarization of Golgi stacks towards contacting T cells was also detected using an in vitro allogeneic model. Thus, different T cells are able to induce polarization of target astrocytes. Polarization of target astrocytes in response to immunological synapses may play an important role in regulating the outcome of the response of astrocytes to attacking effector T cells, whether during antiviral (e.g. infected during HIV, HTLV-1

  6. A Molecular Probe for the Detection of Polar Lipids in Live Cells.

    PubMed

    Bader, Christie A; Shandala, Tetyana; Carter, Elizabeth A; Ivask, Angela; Guinan, Taryn; Hickey, Shane M; Werrett, Melissa V; Wright, Phillip J; Simpson, Peter V; Stagni, Stefano; Voelcker, Nicolas H; Lay, Peter A; Massi, Massimiliano; Plush, Sally E; Brooks, Douglas A

    2016-01-01

    Lipids have an important role in many aspects of cell biology, including membrane architecture/compartment formation, intracellular traffic, signalling, hormone regulation, inflammation, energy storage and metabolism. Lipid biology is therefore integrally involved in major human diseases, including metabolic disorders, neurodegenerative diseases, obesity, heart disease, immune disorders and cancers, which commonly display altered lipid transport and metabolism. However, the investigation of these important cellular processes has been limited by the availability of specific tools to visualise lipids in live cells. Here we describe the potential for ReZolve-L1™ to localise to intracellular compartments containing polar lipids, such as for example sphingomyelin and phosphatidylethanolamine. In live Drosophila fat body tissue from third instar larvae, ReZolve-L1™ interacted mainly with lipid droplets, including the core region of these organelles. The presence of polar lipids in the core of these lipid droplets was confirmed by Raman mapping and while this was consistent with the distribution of ReZolve-L1™ it did not exclude that the molecular probe might be detecting other lipid species. In response to complete starvation conditions, ReZolve-L1™ was detected mainly in Atg8-GFP autophagic compartments, and showed reduced staining in the lipid droplets of fat body cells. The induction of autophagy by Tor inhibition also increased ReZolve-L1™ detection in autophagic compartments, whereas Atg9 knock down impaired autophagosome formation and altered the distribution of ReZolve-L1™. Finally, during Drosophila metamorphosis fat body tissues showed increased ReZolve-L1™ staining in autophagic compartments at two hours post puparium formation, when compared to earlier developmental time points. We concluded that ReZolve-L1™ is a new live cell imaging tool, which can be used as an imaging reagent for the detection of polar lipids in different intracellular

  7. A Molecular Probe for the Detection of Polar Lipids in Live Cells

    PubMed Central

    Bader, Christie A.; Shandala, Tetyana; Carter, Elizabeth A.; Ivask, Angela; Guinan, Taryn; Hickey, Shane M.; Werrett, Melissa V.; Wright, Phillip J.; Simpson, Peter V.; Stagni, Stefano; Voelcker, Nicolas H.; Lay, Peter A.; Massi, Massimiliano; Brooks, Douglas A.

    2016-01-01

    Lipids have an important role in many aspects of cell biology, including membrane architecture/compartment formation, intracellular traffic, signalling, hormone regulation, inflammation, energy storage and metabolism. Lipid biology is therefore integrally involved in major human diseases, including metabolic disorders, neurodegenerative diseases, obesity, heart disease, immune disorders and cancers, which commonly display altered lipid transport and metabolism. However, the investigation of these important cellular processes has been limited by the availability of specific tools to visualise lipids in live cells. Here we describe the potential for ReZolve-L1™ to localise to intracellular compartments containing polar lipids, such as for example sphingomyelin and phosphatidylethanolamine. In live Drosophila fat body tissue from third instar larvae, ReZolve-L1™ interacted mainly with lipid droplets, including the core region of these organelles. The presence of polar lipids in the core of these lipid droplets was confirmed by Raman mapping and while this was consistent with the distribution of ReZolve-L1™ it did not exclude that the molecular probe might be detecting other lipid species. In response to complete starvation conditions, ReZolve-L1™ was detected mainly in Atg8-GFP autophagic compartments, and showed reduced staining in the lipid droplets of fat body cells. The induction of autophagy by Tor inhibition also increased ReZolve-L1™ detection in autophagic compartments, whereas Atg9 knock down impaired autophagosome formation and altered the distribution of ReZolve-L1™. Finally, during Drosophila metamorphosis fat body tissues showed increased ReZolve-L1™ staining in autophagic compartments at two hours post puparium formation, when compared to earlier developmental time points. We concluded that ReZolve-L1™ is a new live cell imaging tool, which can be used as an imaging reagent for the detection of polar lipids in different intracellular

  8. The variable polarity plasma arc welding process: Its application to the Space Shuttle external tank

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.; Bayless, O. E., Jr.; Jones, C. S., III; Munafo, A. P.; Wilson, W. A.

    1983-01-01

    The technical history of the variable polarity plasma arc (VPPA) welding process being introduced as a partial replacement for the gas shielded tungsten arc process in assembly welding of the space shuttle external tank is described. Interim results of the weld strength qualification studies, and plans for further work on the implementation of the VPPA process are included.

  9. Capture and sorting of multiple cells by polarization-controlled three-beam interference

    NASA Astrophysics Data System (ADS)

    Hou, Yu; Wang, Zuobin; Hu, Yaowei; Li, Dayou; Qiu, Renxi

    2016-03-01

    For the capture and sorting of multiple cells, a sensitive and highly efficient polarization-controlled three-beam interference set-up has been developed. With the theory of superposition of three beams, simulations on the influence of polarization angle upon the intensity distribution and the laser gradient force change with different polarization angles have been carried out. By controlling the polarization angle of the beams, various intensity distributions and different sizes of dots are obtained. We have experimentally observed multiple optical tweezers and the sorting of cells with different polarization angles, which are in accordance with the theoretical analysis. The experimental results have shown that the polarization angle affects the shapes and feature sizes of the interference patterns and the trapping force.

  10. Novel role for the midbody in primary ciliogenesis by polarized epithelial cells.

    PubMed

    Bernabé-Rubio, Miguel; Andrés, Germán; Casares-Arias, Javier; Fernández-Barrera, Jaime; Rangel, Laura; Reglero-Real, Natalia; Gershlick, David C; Fernández, José J; Millán, Jaime; Correas, Isabel; Miguez, David G; Alonso, Miguel A

    2016-08-01

    The primary cilium is a membrane protrusion that is crucial for vertebrate tissue homeostasis and development. Here, we investigated the uncharacterized process of primary ciliogenesis in polarized epithelial cells. We show that after cytokinesis, the midbody is inherited by one of the daughter cells as a remnant that initially locates peripherally at the apical surface of one of the daughter cells. The remnant then moves along the apical surface and, once proximal to the centrosome at the center of the apical surface, enables cilium formation. The physical removal of the remnant greatly impairs ciliogenesis. We developed a probabilistic cell population-based model that reproduces the experimental data. In addition, our model explains, solely in terms of cell area constraints, the various observed transitions of the midbody, the beginning of ciliogenesis, and the accumulation of ciliated cells. Our findings reveal a biological mechanism that links the three microtubule-based organelles-the midbody, the centrosome, and the cilium-in the same cellular process. PMID:27458130

  11. Comparisons of polar processing diagnostics from 34 years of the ERA-Interim and MERRA reanalyses

    NASA Astrophysics Data System (ADS)

    Lawrence, Z. D.; Manney, G. L.; Minschwaner, K.; Santee, M. L.; Lambert, A.

    2015-04-01

    We present a comprehensive comparison of polar processing diagnostics derived from the National Aeronautics and Space Administration (NASA) Modern Era Retrospective-analysis for Research and Applications (MERRA) and the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis (ERA-Interim). We use diagnostics that focus on meteorological conditions related to stratospheric chemical ozone loss based on temperatures, polar vortex dynamics, and air parcel trajectories to evaluate the effects these reanalyses might have on polar processing studies. Our results show that the agreement between MERRA and ERA-Interim changes significantly over the 34 years from 1979 to 2013 in both hemispheres and in many cases improves. By comparing our diagnostics during five time periods when an increasing number of higher-quality observations were brought into these reanalyses, we show how changes in the data assimilation systems (DAS) of MERRA and ERA-Interim affected their meteorological data. Many of our stratospheric temperature diagnostics show a convergence toward significantly better agreement, in both hemispheres, after 2001 when Aqua and GOES (Geostationary Operational Environmental Satellite) radiances were introduced into the DAS. Other diagnostics, such as the winter mean volume of air with temperatures below polar stratospheric cloud formation thresholds (VPSC) and some diagnostics of polar vortex size and strength, do not show improved agreement between the two reanalyses in recent years when data inputs into the DAS were more comprehensive. The polar processing diagnostics calculated from MERRA and ERA-Interim agree much better than those calculated from earlier reanalysis data sets. We still, however, see fairly large differences in many of the diagnostics in years prior to 2002, raising the possibility that the choice of one reanalysis over another could significantly influence the results of polar processing studies. After 2002, we see overall

  12. Auxin efflux carrier activity and auxin accumulation regulate cell division and polarity in tobacco cells.

    PubMed

    Petrásek, Jan; Elckner, Miroslav; Morris, David A; Zazímalová, Eva

    2002-12-01

    Division and growth of most types of in vitro-cultured plant cells require an external source of auxin. In such cultures, the ratio of external to internal auxin concentration is crucial for the regulation of the phases of the standard growth cycle. In this report the internal concentration of auxin in suspension-cultured cells of Nicotiana tabacum L., strain VBI-0, was manipulated either (i) by increasing 10-fold the normal concentration of 1-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid in the external medium; or (ii) by addition 1-N-naphthylphthalamic acid (NPA; an inhibitor of auxin efflux and of auxin efflux carrier traffic). Both treatments delayed the onset of cell division for 6-7 days without loss of cell viability. In both cases, cell division activity subsequently resumed coincident with a reduction in the ability of cells to accumulate [(3)H]NAA from an external medium. Following renewed cell division, a significant proportion of the NPA-treated cells but not those grown at high auxin concentration, exhibited changes in the orientation of new cell divisions and loss of polarity. We conclude that cell division, but not cell elongation, is prevented when the internal auxin concentration rises above a critical threshold value and that the directed traffic of auxin efflux carriers to the plasma membrane may regulate the orientation of cell divisions. PMID:12447544

  13. New circular polarization selective surface concepts based on the Pierrot cell using printed circuit technology

    NASA Astrophysics Data System (ADS)

    Lopez, Humberto Israel

    This M.A.Sc. thesis focuses on finding an alternative method of constructing a circular polarization selective surface (CPSS) based on the Pierrot cell using the standard printed circuit technology. This technique uses a folded flexible substrate, which enables the implementation of the 3D Pierrot cells on a single metal layer defined with precision printed circuit board techniques, without the need for metalized via holes. Different topologies of the CPSS are analyzed in order to make the CPSS more efficient in terms of bandwidth and independence on the direction of propagation of the incident wave. A left-hand CPSS is designed to illustrate the benefits of the proposed approach. The first approach is a simple Pierrot unit cell CPSS which is optimized to have good reflection and transmission coefficients. A prototype is built and then characterized in a test bench operating in the K-band. For the fabricated prototype, the transmission coefficients of plane waves at normal incidence in the right-hand and the left-hand circular polarizations are --0.48 dB and --24 dB respectively. The bandwidth for which the transmission coefficient of the incident left-handed incident wave is greater than --3 dB was of 17.6%. These results are in good agreement with simulations results obtained with HFSS. A second variant considered is a Pierrot cell with a series load in the middle segment. With this cell it is possible to equalize the frequencies giving a better operation in the right- and left-handed circular polarized waves. There is an improvement for the co-pol to cross-pol ratio for the RHCP waves of 10 dB at 20 GHz. The added load does not affect the performance for the left-hand circular polarization, as expected. The third modification is a Pierrot cell at 90 degrees. This cell is designed to allow the combination of two Pierrot cells working at different frequencies on the same substrate in order to increase the frequency bandwidth of the CPSS. Unfortunately, the axial

  14. Polarized electroabsorption spectra and light soaking of solar cells based on hydrogenated amorphous silicon

    NASA Astrophysics Data System (ADS)

    Jiang, Lin; Wang, Qi; Schiff, E. A.; Guha, S.; Yang, J.

    1998-03-01

    We present grazing-incidence measurements of polarized electroabsorption spectra in p-i-n solar cells based on hydrogenated amorphous silicon (a-Si:H). We find a significantly stronger polarization dependence in the present measurements compared with earlier work based on electroabsorption detected using coplanar electrodes on a-Si:H thin films. We do not find any significant dependence of the polarized electroabsorption upon light soaking, although this effect was found in previous work with coplanar electrodes.

  15. Features of the processes of ion heating in polar boundary of the night auroral oval

    NASA Astrophysics Data System (ADS)

    Chugunin, Dmitriy; Lutsenko, Volt; Romantsova, Tatiana; Mogilevsky, Mikhail; Moiseenko, Irina

    Investigation of the processes of ion heating in polar boundary of the night auroral oval measured by INTERBALL-2 (Auroral probe) is presented. Measurements of particles and waves were made on altitude about 20000 км. Feature of the orbits was the satellite slid along auroral oval and stay long time in the auroral zone. It were cases chosen when the polar boundary moved and passed through satellite. Particular attention is given to ions heating at this border and to ion heating position in relation to polar boundary of particle precipitation.

  16. Proceedings of a Workshop on Polar Stratospheric Clouds: Their Role in Atmospheric Processes

    NASA Technical Reports Server (NTRS)

    Hamill, P. (Editor); Mcmaster, L. R. (Editor)

    1984-01-01

    The potential role of polar stratospheric clouds in atmospheric processes was assessed. The observations of polar stratospheric clouds with the Nimbus 7 SAM II satellite experiment were reviewed and a preliminary analysis of their formation, impact on other remote sensing experiments, and potential impact on climate were presented. The potential effect of polar stratospheric clouds on climate, radiation balance, atmospheric dynamics, stratospheric chemistry and water vapor budget, and cloud microphysics was assessed. Conclusions and recommendations, a synopsis of materials and complementary material to support those conclusions and recommendations are presented.

  17. Dkk-1 Inhibits Intestinal Epithelial Cell Migration by Attenuating Directional Polarization of Leading Edge Cells

    PubMed Central

    Koch, Stefan; Capaldo, Christopher T.; Samarin, Stanislav; Nava, Porfirio; Neumaier, Irmgard; Skerra, Arne; Sacks, David B.; Parkos, Charles A.

    2009-01-01

    Wnt signaling pathways regulate proliferation, motility, and survival in a variety of human cell types. Dickkopf-1 (Dkk-1) is a secreted Wnt antagonist that has been proposed to regulate tissue homeostasis in the intestine. In this report, we show that Dkk-1 is secreted by intestinal epithelial cells after wounding and that it inhibits cell migration by attenuating the directional orientation of migrating epithelial cells. Dkk-1 exposure induced mislocalized activation of Cdc42 in migrating cells, which coincided with a displacement of the polarity protein Par6 from the leading edge. Consequently, the relocation of the microtubule organizing center and the Golgi apparatus in the direction of migration was significantly and persistently inhibited in the presence of Dkk-1. Small interfering RNA-induced down-regulation of Dkk-1 confirmed that extracellular exposure to Dkk-1 was required for this effect. Together, these data demonstrate a novel role of Dkk-1 in the regulation of directional polarization of migrating intestinal epithelial cells, which contributes to the effect of Dkk-1 on wound closure in vivo. PMID:19776352

  18. Dishevelled is essential for neural connectivity and planar cell polarity in planarians.

    PubMed

    Almuedo-Castillo, Maria; Saló, Emili; Adell, Teresa

    2011-02-15

    The Wingless/Integrated (Wnt) signaling pathway controls multiple events during development and homeostasis. It comprises multiple branches, mainly classified according to their dependence on β-catenin activation. The Wnt/β-catenin branch is essential for the establishment of the embryonic anteroposterior (AP) body axis throughout the phylogenetic tree. It is also required for AP axis establishment during planarian regeneration. Wnt/β-catenin-independent signaling encompasses several different pathways, of which the most extensively studied is the planar cell polarity (PCP) pathway, which is responsible for planar polarization of cell structures within an epithelial sheet. Dishevelled (Dvl) is the hub of Wnt signaling because it regulates and channels the Wnt signal into every branch. Here, we analyze the role of Schmidtea mediterranea Dvl homologs (Smed-dvl-1 and Smed-dvl-2) using gene silencing. We demonstrate that in addition to a role in AP axis specification, planarian Dvls are involved in at least two different β-catenin-independent processes. First, they are essential for neural connectivity through Smed-wnt5 signaling. Second, Smed-dvl-2, together with the S. mediterranea homologs of Van-Gogh (Vang) and Diversin (Div), is required for apical positioning of the basal bodies of epithelial cells. These data represent evidence not only of the function of the PCP network in lophotrocozoans but of the involvement of the PCP core elements Vang and Div in apical positioning of the cilia. PMID:21282632

  19. Prickle1 stunts limb growth through alteration of cell polarity and gene expression

    PubMed Central

    Yang, Tian; Bassuk, Alexander G.; Fritzsch, Bernd

    2014-01-01

    Background Wnt/PCP signaling plays a critical role in multiple developmental processes, including limb development. Wnt5a, a ligand of the PCP pathway, signals through the Ror2/Vangl2 or the Vangl2/Ryk complex to regulate limb development along the proximal-distal axis in mice. Based on the interaction between Van Gogh and Prickle in Drosophila, we hypothesized the vertebrate Prickle1 have similar function as Vangl2 in limb development. Results We show Prickle1 is expressed in the skeletal condensates that will differentiate into chondrocytes and later form bones. Disrupted Prickle1 function in Prickle1C251X/C251X mouse mutants alters expression of genes such as Bmp4, Fgf8, Vangl2 and Wnt5a. These expression changes correlate with shorter and wider bones in the limbs and loss of one phalangeal segment in digits 2-5 of Prickle1C251X mutants. These growth defects along the proximal-distal axis are also associated with increased cell death in the growing digit tip, reduced cell death in the interdigital membrane and disrupted chondrocyte polarity. Conclusions We suggest Prickle1 is part of the Wnt5a/PCP signaling, regulating cell polarity and affecting expression of multiple factors to stunt limb growth through altered patterns of gene expression, including the PCP genes Wnt5a and Vangl2. PMID:23913870

  20. Polar/apolar compounds induce leukemia cell differentiation by modulating cell-surface potential.

    PubMed Central

    Arcangeli, A; Carlà, M; Del Bene, M R; Becchetti, A; Wanke, E; Olivotto, M

    1993-01-01

    The mechanism of action of polar/apolar inducers of cell differentiation, such as dimethyl sulfoxide and hexamethylene-bisacetamide, is still obscure. In this paper evidence is provided that their effects on murine erythroleukemia cells are modulated by various extracellular cations as a precise function of the cation effects on membrane surface potential. The interfacial effects of the inducers were directly measured on the charged electrode, showing that both dimethyl sulfoxide and hexamethylene-bisacetamide, at the effective concentrations for cell differentiation and within the physiological range of charge density, adsorb at the charged surface and produce a potential shift. A linear correlation was found between this shift and the inducer effects on cell differentiation. Besides offering a different interpretation of the mechanism of action of the inducers, these findings indicate that surface potential has a signaling function. They may also be relevant to cancer treatments based on tumor-cell commitment to terminal differentiation. Images Fig. 1 PMID:8516337

  1. Polarization Processes of Nanocomposite Silicate-EVA and PP Materials

    NASA Astrophysics Data System (ADS)

    Montanari, Gian Carlo; Palmieri, Fabrizio; Testa, Luigi; Motori, Antonio; Saccani, Andrea; Patuelli, Francesca

    Recent works indicate that polypropylene (PP) and ethylene-vinylacetate (EVA) filled by nanosilicates may present low content of space charge and high electric strength. Investigations are being made to explain nanocomposite behaviour and characterize their electrical, thermal and mechanical properties. In this paper, the results of broad-band dielectric spectroscopy performed on EVA and PP filled by layered nanosized silicates are reported. Isochronal and isothermal curves of complex permittivity, as well as activation energies of the relaxation processes, are presented and discussed. Nanostructuration gives rise to substantial changes in the polarisation and dielectric loss behaviour. While the relaxation process of EVA, associated with glass transition of the material amorphous phase, results unchanged from base to nanostructured material, nanocomposites EVA and PP have shown the rise of a new process at higher temperatures respect to the typical host material processes, as well as a different distribution of relaxation processes. Changes in space charge accumulation in relation to the effectiveness of the purification process performed upon nanostructured materials are also reported: while the dispersion of the clean clays leads to a reduction of the space charge, especially at high fields, an unclean filler gives rise to significant homo-charge accumulation and interfacial polarisation phenomena.

  2. Cell shape, spreading symmetry, and the polarization of stress-fibers in cells

    NASA Astrophysics Data System (ADS)

    Zemel, A.; Rehfeldt, F.; Brown, A. E. X.; Discher, D. E.; Safran, S. A.

    2010-05-01

    The active regulation of cellular forces during cell adhesion plays an important role in the determination of cell size, shape, and internal structure. While on flat, homogeneous and isotropic substrates some cells spread isotropically, others spread anisotropically and assume elongated structures. In addition, in their native environment as well as in vitro experiments, the cell shape and spreading asymmetry can be modulated by the local distribution of adhesive molecules and topography of the environment. We present a simple elastic model and experiments on stem cells to explain the variation of cell size with the matrix rigidity. In addition, we predict the experimental consequences of two mechanisms of acto-myosin polarization and focus here on the effect of the cell spreading asymmetry on the regulation of the stress-fiber alignment in the cytoskeleton. We show that when cell spreading is sufficiently asymmetric the alignment of acto-myosin forces in the cell increases monotonically with the matrix rigidity; however, in general this alignment is non-monotonic, as shown previously. These results highlight the importance of the symmetry characteristics of cell spreading in the regulation of cytoskeleton structure and suggest a mechanism by which different cell types may acquire different morphologies and internal structures in different mechanical environments.

  3. Building cortical polarity in a cell line: identification of an Aurora-A/PinsLINKER spindle orientation pathway

    PubMed Central

    Johnston, Christopher A.; Hirono, Keiko; Prehoda, Kenneth E.; Doe, Chris Q.

    2009-01-01

    SUMMARY Asymmetric cell division is intensely studied because it can generate cellular diversity as well as maintain stem cell populations. Asymmetric cell division requires mitotic spindle alignment with intrinsic or extrinsic polarity cues, but mechanistic detail of this process is lacking. Here we develop a method to construct cortical polarity in a normally unpolarized cell line, and use this method to characterize Partner of Inscuteable (Pins; LGN/AGS3 in mammals)-dependent spindle orientation. We identify a previously unrecognized evolutionarily-conserved Pins domain (PinsLINKER) that requires Aurora-A phosphorylation to recruit Discs large (Dlg; PSD-95/hDlg in mammals) and promote partial spindle orientation. The well-characterized PinsTPR domain has no function alone, but placing the PinsTPR in cis to the PinsLINKER gives dynein-dependent precise spindle orientation. This "induced cortical polarity" assay is suitable for rapid identification of the proteins, domains, and amino acids regulating spindle orientation or cell polarity. PMID:19766567

  4. A polarization-based frequency scanning interferometer and the signal processing acceleration method based on parallel processing architecture

    NASA Astrophysics Data System (ADS)

    Lee, Seung Hyun; Kim, Min Young

    FSI system, one of the most promising optical surface measurement techniques, generally results in superior optical performance comparing with other 3-dimensional measuring methods as its hardware structure is fixed in operation and only the light frequency is scanned in a specific spectral band without vertical scanning of the target surface or the objective lens. FSI system collects a set of images of interference fringe by changing the frequency of light source. After that, it transforms intensity data of acquired image into frequency information, and calculates the height profile of target objects with the help of frequency analysis based on FFT. However, it still suffers from optical noise from target surface and relatively long processing time due to the number of images acquired in frequency scanning phase. First, a polarization-based frequency scanning interferometry (PFSI) is proposed for optical noise robustness. It consists of tunable laser for light source, λ/4 plate in front of reference mirror, λ/4 plate in front of target object, polarizing beam splitter, polarizer in front of image sensor, polarizer in front of the fiber coupled light source, λ/2 plate between PBS and polarizer of the light source. Using the proposed system, we can solve the problem low contrast of acquired fringe image by using polarization technique. Also, we can control light distribution of object beam and reference beam. Second, the signal processing acceleration method is proposed for PFSI, based on parallel processing architecture, which consists of parallel processing hardware and software such as GPU (Graphic Processing Unit) and CUDA (Compute Unified Device Architecture). As a result, the processing time reaches into tact time level of real-time processing. Finally, the proposed system is evaluated in terms of accuracy and processing speed through a series of experiment and the obtained results show the effectiveness of the proposed system and method.

  5. von Willebrand factor multimerization and the polarity of secretory pathways in endothelial cells.

    PubMed

    Lopes da Silva, Mafalda; Cutler, Daniel F

    2016-07-14

    The von Willebrand factor (VWF) synthesized and secreted by endothelial cells is central to hemostasis and thrombosis, providing a multifunctional adhesive platform that brings together components needed for these processes. VWF secretion can occur from both apical and basolateral sides of endothelial cells, and from constitutive, basal, and regulated secretory pathways, the latter two via Weibel-Palade bodies (WPB). Although the amount and structure of VWF is crucial to its function, the extent of VWF release, multimerization, and polarity of the 3 secretory pathways have only been addressed separately, and with conflicting results. We set out to clarify these relationships using polarized human umbilical vein endothelial cells (HUVECs) grown on Transwell membranes. We found that regulated secretion of ultra-large (UL)-molecular-weight VWF predominantly occurred apically, consistent with a role in localized platelet capture in the vessel lumen. We found that constitutive secretion of low-molecular-weight (LMW) VWF is targeted basolaterally, toward the subendothelial matrix, using the adaptor protein complex 1 (AP-1), where it may provide the bulk of collagen-bound subendothelial VWF. We also found that basally-secreted VWF is composed of UL-VWF, released continuously from WPBs in the absence of stimuli, and occurs predominantly apically, suggesting this could be the main source of circulating plasma VWF. Together, we provide a unified dataset reporting the amount and multimeric state of VWF secreted from the constitutive, basal, and regulated pathways in polarized HUVECs, and have established a new role for AP-1 in the basolateral constitutive secretion of VWF. PMID:27106123

  6. Enhanced plasmid DNA utilization in transiently transfected CHO-DG44 cells in the presence of polar solvents.

    PubMed

    Rajendra, Yashas; Balasubramanian, Sowmya; Kiseljak, Divor; Baldi, Lucia; Wurm, Florian M; Hacker, David L

    2015-01-01

    Although the protein yields from transient gene expression (TGE) with Chinese hamster ovary (CHO) cells have recently improved, the amount of plasmid DNA (pDNA) needed for transfection remains relatively high. We describe a strategy to reduce the pDNA amount by transfecting CHO-DG44 cells with 0.06 μg pDNA/10(6) cells (10% of the optimal amount) in the presence of nonspecific (filler) DNA and various polar solvents including dimethylsufoxide, dimethyl formamide, acetonitrile, dimethyl acetamide (DMA), and hexamethyl phosphoramide (HMP). All of the polar solvents with the exception of HMP increased the production of a recombinant antibody in comparison to the untreated control transfection. In the presence of 0.25% DMA, the antibody yield in a 7-day batch culture was 500 mg/L. This was fourfold higher than the yield from the untreated control transfection. Mechanistic studies revealed that the polar solvents did not affect polyethylenimine-mediated pDNA delivery into cells or nuclei. The steady-state transgene mRNA level was elevated in the presence of each of the polar solvents tested, while the transgene mRNA half-life remained the same. These results indicated that the polar solvents enhanced transgene transcription. When screening a panel of recombinant antibodies and Fc-fusion proteins for production in the presence of the polar solvents, the highest increase in yield was observed following DMA addition for 11 of the 12 proteins. These results are expected to enhance the applicability of high-yielding TGE processes with CHO-DG44 cells by decreasing the amount of pDNA required for transfection. PMID:26260195

  7. Cyclooxygenase-2 inhibition attenuates hypoxic cancer cells induced m2-polarization of macrophages.

    PubMed

    Dubey, P; Shrivastava, R; Tripathi, C; Jain, N K; Tewari, B N; Lone, M-U-D; Baghel, K S; Kumar, V; Misra, S; Bhadauria, S; Bhatt, M L B

    2014-01-01

    Tumor-associated macrophages (TAMs), represent a major subpopulation of tumor infiltrating immune cells. These alternatively activated M2-polarized macrophages are well known for their pro-tumor functions. Owing to their established role in potentiating tumor-neovasculogenesis and metastasis, TAMs have emerged as promising target for anti-cancer immunotherapy. One of the key TAMs related phenomenon that is amenable to therapeutic intervention is their phenotype switching into alternatively activated M2-polarized macrophages. Hindering macrophage polarization towards a pro-tumor M2 phenotype, or better still reprogramming the M2 like TAMs towards M1 subtype is being considered a beneficial anti-cancer strategy. Hypoxic tumor milieu has been proposed as one of the most plausible factor governing M2-polarization of macrophages. We recently demonstrated that hypoxic tumor cells imparted a pro—angiogenic M2 skewed phenotype to macrophages. Furthermore, sizeable body of data indicates for participation of cyclooxygenase-2 (COX-2) in macrophage polarization. Concordantly, inhibition of COX-2 is associated with impaired macrophage polarization. Prompted by this in the current study we decided to explore if inhibition of COX-2 activity via chemical inhibitors may prevent hypoxic cancer cell induced M2-polarization of macrophages. We observed that treatment with Flunixin meglumine, an established preferential inhibitor of COX-2 activity markedly inhibited hypoxic cancer cell induced of M2-polarization of macrophages thereby indicating for usage of COX-2 inhibition as possible anti-cancer treatment modality. PMID:25210855

  8. Identification of Genes Required for Normal Pheromone-Induced Cell Polarization in Saccharomyces Cerevisiae

    PubMed Central

    Chenevert, J.; Valtz, N.; Herskowitz, I.

    1994-01-01

    In response to mating pheromones, cells of the yeast Saccharomyces cerevisiae adopt a polarized ``shmoo'' morphology, in which the cytoskeleton and proteins involved in mating are localized to a cell-surface projection. This polarization is presumed to reflect the oriented morphogenesis that occurs between mating partners to facilitate cell and nuclear fusion. To identify genes involved in pheromone-induced cell polarization, we have isolated mutants defective in mating to an enfeebled partner and studied a subset of these mutants. The 34 mutants of interest are proficient for pheromone production, arrest in response to pheromone, mate to wild-type strains, and exhibit normal cell polarity during vegetative growth. The mutants were divided into classes based on their morphological responses to mating pheromone. One class is unable to localize cell-surface growth in response to mating factor and instead enlarges in a uniform manner. These mutants harbor special alleles of genes required for cell polarization during vegetative growth, BEM1 and CDC24. Another class of mutants forms bilobed, peanut-like shapes when treated with pheromone and defines two genes, PEA1 and PEA2. PEA1 is identical to SPA2. A third class forms normally shaped but tiny shmoos and defines the gene TNY1. A final group of mutants exhibits apparently normal shmoo morphology. The nature of their mating defect is yet to be determined. We discuss the possible roles of these gene products in establishing cell polarity during mating. PMID:8013906

  9. Polarization diversity of human CD4+ stem cell memory T cells.

    PubMed

    Takeshita, Masaru; Suzuki, Katsuya; Kassai, Yoshiaki; Takiguchi, Maiko; Nakayama, Yusuke; Otomo, Yuki; Morita, Rimpei; Miyazaki, Takahiro; Yoshimura, Akihiko; Takeuchi, Tsutomu

    2015-07-01

    T cells are considered to develop through three stages, from naïve T (Tn) into central memory T (Tcm) and finally into effector memory T (Tem). Among the subsets of Tn, stem cell memory T (Tscm) were recently found to be the least developed memory subset. While this subset was revealed to possess self-reproducibility and multipotentiality, little is known about the relationship between development and polarity. We conducted transcriptome analysis of human CD4(+) T subsets and found that Tscm was a clearly distinct subset, located between Tn and Tcm. Surface antigen analysis and differentiation assay showed that the flexibility of polarity and the cytokine production progressively changed as the differentiation of CD4(+) T cells advanced. Interestingly, we found that most cells of the CD45RO(-)CCR7(+)CCR6(+) subset, hitherto considered the naïve precursor of Th17, were in fact Tscm. These findings may advance our understanding of the highly heterogeneous human helper T cells. PMID:25931384

  10. Some comments about polarization in deep inelastic processes

    SciTech Connect

    Bajpai, R.P.

    1983-01-01

    One can fit baryon production in deep inelastic processes in terms of baryon fragmentation functions. It appears that for z > 0.3, the individual quark materializes into a baryon by picking up the appropriate diquark. The spin and isospin properties of the diquark will give definite asymmetry in baryon production in terms of only three unknown parameters. 4 references, 1 table.

  11. Planar cell polarity effector gene Intu regulates cell fate-specific differentiation of keratinocytes through the primary cilia.

    PubMed

    Dai, D; Li, L; Huebner, A; Zeng, H; Guevara, E; Claypool, D J; Liu, A; Chen, J

    2013-01-01

    Genes involved in the planar cell polarity (PCP) signaling pathway are essential for a number of developmental processes in mammals, such as convergent extension and ciliogenesis. Tissue-specific PCP effector genes of the PCP signaling pathway are believed to mediate PCP signals in a tissue- and cell type-specific manner. However, how PCP signaling controls the morphogenesis of mammalian tissues remains unclear. In this study, we investigated the role of inturned (Intu), a tissue-specific PCP effector gene, during hair follicle formation in mice. Tissue-specific disruption of Intu in embryonic epidermis resulted in hair follicle morphogenesis arrest because of the failure of follicular keratinocyte to differentiate. Targeting Intu in the epidermis resulted in almost complete loss of primary cilia in epidermal and follicular keratinocytes, and a suppressed hedgehog signaling pathway. Surprisingly, the epidermal stratification and differentiation programs and barrier function were not affected. These results demonstrate that tissue-specific PCP effector genes of the PCP signaling pathway control the differentiation of keratinocytes through the primary cilia in a cell fate- and context-dependent manner, which may be critical in orchestrating the propagation and interpretation of polarity signals established by the core PCP components. PMID:22935613

  12. Long-term trends of the Polar and Arctic cells influencing the Arctic climate since 1989

    NASA Astrophysics Data System (ADS)

    Qian, Weihong; Wu, Kaijun; Leung, Jeremy Cheuk-Hin; Shi, Jian

    2016-03-01

    The strengthening and broadening trends of the Hadley cell have been revealed, while the existence of the Arctic cell has also been confirmed in previous studies. This study extends previous strengthening trend analyses of the Hadley cell to the Polar and Arctic cells in the Northern Hemisphere and explores their climate influences. Results show that the Polar cell experienced an abrupt change from a slow to a rapid strengthening trend in 1989, while the Arctic cell showed an insignificant strengthening trend and a significant weakening trend successively. The strengthening subsidence flow associated with the Polar and Arctic cells can partly explain the warming surface air temperature and declining sea ice concentration through the increasing tropospheric height and temperature trends. These results provide new insights for understanding the interdecadal relationship between atmospheric circulation and climate change in the Arctic region.

  13. Industrial processes with animal cells.

    PubMed

    Kretzmer, G

    2002-07-01

    Industrial processes involving animal cells for the production of useful products still seem to be rather uncommon. Nevertheless, during the last four decades of the last century the number of relevant processes has increased from production of virus vaccines to monoclonal antibodies and finally complex structured glycoproteins. As soon as cell lines became permanent and culture medium changed from purely biological fluids to more or less defined chemical media, large-scale cultivation could begin. The developments of the 1970s - fusion of cells to form hybridomas, and genetic engineering - triggered a second wave of products. Monoclonal antibodies and recombinant proteins for diagnosis and therapy set new challenges for the inventors. Historically, there has been no straightforward process development since the product dictates the process operation. Therefore, the scale of production covers the whole range from small multiple-unit reactors (flasks or roller bottles) up to 10,000-l single-unit batch reactors. Products with high value and small demand can be produced in multiple-unit systems whereas "bulk" products for vaccination and therapy may need large-scale bioreactors to be cost effective. All the different systems have their advantages and disadvantages and significant challenges that curb the development of effective perfusion cultures still remain. PMID:12111138

  14. Planar cell polarity-mediated induction of neural stem cell expansion during axolotl spinal cord regeneration

    PubMed Central

    Rost, Fabian; Nowoshilow, Sergej; Chara, Osvaldo; Tanaka, Elly M

    2015-01-01

    Axolotls are uniquely able to mobilize neural stem cells to regenerate all missing regions of the spinal cord. How a neural stem cell under homeostasis converts after injury to a highly regenerative cell remains unknown. Here, we show that during regeneration, axolotl neural stem cells repress neurogenic genes and reactivate a transcriptional program similar to embryonic neuroepithelial cells. This dedifferentiation includes the acquisition of rapid cell cycles, the switch from neurogenic to proliferative divisions, and the re-expression of planar cell polarity (PCP) pathway components. We show that PCP induction is essential to reorient mitotic spindles along the anterior-posterior axis of elongation, and orthogonal to the cell apical-basal axis. Disruption of this property results in premature neurogenesis and halts regeneration. Our findings reveal a key role for PCP in coordinating the morphogenesis of spinal cord outgrowth with the switch from a homeostatic to a regenerative stem cell that restores missing tissue. DOI: http://dx.doi.org/10.7554/eLife.10230.001 PMID:26568310

  15. Polarization Sensitive THz TDS and Fabrication of Alignment Cells for Solution Phase THz Spectroscopy

    NASA Astrophysics Data System (ADS)

    George, Deepu Koshy

    sense that it makes use of the polarization state of THz pulse which is also the case for the alignment spectroscopy. PMOTS technique detects the rotation and change in ellipticity to the incident polarization from which the hall coefficients of the sample can be calculated. The final section deals with the fabrication of Dynamical Alignment Terahertz Spectroscopy cells for solution phase measurements. Design, fabrication and process optimization are detailed. Micro-fabrication based on optical lithography and SU-8 negative photoresist has been explored.

  16. Responses of hair follicle–associated structures to loss of planar cell polarity signaling

    PubMed Central

    Chang, Hao; Nathans, Jeremy

    2013-01-01

    The mammalian hair follicle unit consists of a central follicle and a series of associated structures: sebaceous glands, arrector pili muscles, Merkel cells, and sensory nerve endings. The architecture of this multicellular structure is highly polarized with respect to the body axes. Previous work has implicated Frizzled6 (Fz6)-mediated planar cell polarity (PCP) signaling in the initial specification of hair follicle orientation. Here we investigate the origin of polarity information among structures within the hair follicle unit. Merkel cell clusters appear to have direct access to Fz6-based polarity information, and they lose polarity in the absence of Fz6. By contrast, the other follicle-associated structures likely derive some or all of their polarity cues from hair follicles, and as a result, their orientations closely match that of their associated follicle. These experiments reveal the interplay between global and local sources of polarity information for coordinating the spatial arrangement of diverse multicellular structures. They also highlight the utility of mammalian skin as a system for quantitative analyses of biological polarity. PMID:23431170

  17. Reciprocity between Regulatory T Cells and Th17 Cells: Relevance to Polarized Immunity in Leprosy.

    PubMed

    Sadhu, Soumi; Khaitan, Binod Kumar; Joshi, Beenu; Sengupta, Utpal; Nautiyal, Arvind Kumar; Mitra, Dipendra Kumar

    2016-01-01

    T cell defect is a common feature in lepromatous or borderline lepromatous leprosy (LL/BL) patients in contrast to tuberculoid or borderline tuberculoid type (TT/BT) patients. Tuberculoid leprosy is characterized by strong Th1-type cell response with localized lesions whereas lepromatous leprosy is hallmarked by its selective Mycobacterium leprae specific T cell anergy leading to disseminated and progressive disease. FoxP3+ Regulatory T cells (Treg) which are essential for maintaining peripheral tolerance, preventing autoimmune diseases and limiting chronic inflammatory diseases also dampen proinflammatory T cells that include T helper 17 (Th17) cells. This study is aimed at evaluating the role of Treg cells in influencing other effector T cells and its relationship with the cytokine polarized state in leprosy patients. Peripheral blood mononuclear cells from of BT/TT (n = 15) and BL/LL (n = 15) patients were stimulated with M. leprae antigen (WCL) in presence of golgi transport inhibitor monensin for FACS based intracellular cytokine estimation. The frequency of Treg cells showed >5-fold increase in BL/LL in comparison to BT/TT and healthy contacts. These cells produced suppressive cytokine, IL-10 in BL/LL as opposed to BT/TT (p = 0.0200) indicating their suppressive function. The frequency of Th17 cells (CD4, CD45RO, IL-17) was, however, higher in BT/TT. Significant negative correlation (r = -0.68, P = 0.03) was also found between IL-10 of Treg cells and IL-17+ T cells in BL/LL. Blocking IL-10/TGF-β restored the IL-17+ T cells in BL/LL patients. Simultaneously, presence of Th17 related cytokines (TGF-β, IL-6, IL-17 and IL-23) decreased the number of FoxP3+ Treg cells concomitantly increasing IL-17 producing CD4+ cells in lepromatous leprosy. Higher frequency of Programmed Death-1/PD-1+ Treg cells and its ligand, PDL-1 in antigen presenting cells (APCs) was found in BL/LL patients. Inhibition of this pathway led to rescue of IFN-γ and IL-17 producing T cells

  18. Reciprocity between Regulatory T Cells and Th17 Cells: Relevance to Polarized Immunity in Leprosy

    PubMed Central

    Sadhu, Soumi; Khaitan, Binod Kumar; Joshi, Beenu; Sengupta, Utpal; Nautiyal, Arvind Kumar; Mitra, Dipendra Kumar

    2016-01-01

    T cell defect is a common feature in lepromatous or borderline lepromatous leprosy (LL/BL) patients in contrast to tuberculoid or borderline tuberculoid type (TT/BT) patients. Tuberculoid leprosy is characterized by strong Th1-type cell response with localized lesions whereas lepromatous leprosy is hallmarked by its selective Mycobacterium leprae specific T cell anergy leading to disseminated and progressive disease. FoxP3+ Regulatory T cells (Treg) which are essential for maintaining peripheral tolerance, preventing autoimmune diseases and limiting chronic inflammatory diseases also dampen proinflammatory T cells that include T helper 17 (Th17) cells. This study is aimed at evaluating the role of Treg cells in influencing other effector T cells and its relationship with the cytokine polarized state in leprosy patients. Peripheral blood mononuclear cells from of BT/TT (n = 15) and BL/LL (n = 15) patients were stimulated with M. leprae antigen (WCL) in presence of golgi transport inhibitor monensin for FACS based intracellular cytokine estimation. The frequency of Treg cells showed >5-fold increase in BL/LL in comparison to BT/TT and healthy contacts. These cells produced suppressive cytokine, IL-10 in BL/LL as opposed to BT/TT (p = 0.0200) indicating their suppressive function. The frequency of Th17 cells (CD4, CD45RO, IL-17) was, however, higher in BT/TT. Significant negative correlation (r = -0.68, P = 0.03) was also found between IL-10 of Treg cells and IL-17+ T cells in BL/LL. Blocking IL-10/TGF-β restored the IL-17+ T cells in BL/LL patients. Simultaneously, presence of Th17 related cytokines (TGF-β, IL-6, IL-17 and IL-23) decreased the number of FoxP3+ Treg cells concomitantly increasing IL-17 producing CD4+ cells in lepromatous leprosy. Higher frequency of Programmed Death-1/PD-1+ Treg cells and its ligand, PDL-1 in antigen presenting cells (APCs) was found in BL/LL patients. Inhibition of this pathway led to rescue of IFN-γ and IL-17 producing T cells

  19. {sup 3}He polarization via optical pumping in a birefringent cell

    SciTech Connect

    Masuda, Y.; Ino, T.; Skoy, V.R.; Jones, G.L.

    2005-08-01

    A sapphire cell was used to obtain a high {sup 3}He nuclear polarization by means of spin-exchange optical pumping. The phase-shift difference between ordinary and extraordinary rays is well controlled using the thickness of the birefringent sapphire window so that a high circular polarization is obtained in the cell. Neutron transmission through the polarized {sup 3}He gas was measured as a function of neutron energy. A large {sup 3}He polarization of 63{+-}1% was obtained at a {sup 3}He pressure of 3.1 atm. Neutron polarizations of 97 and 90 % were obtained with transmission rates of 15 and 22 % at 10 and 20 meV, respectively.

  20. Control of vertebrate core planar cell polarity protein localization and dynamics by Prickle 2

    PubMed Central

    Butler, Mitchell T.; Wallingford, John B.

    2015-01-01

    Planar cell polarity (PCP) is a ubiquitous property of animal tissues and is essential for morphogenesis and homeostasis. In most cases, this fundamental property is governed by a deeply conserved set of ‘core PCP’ proteins, which includes the transmembrane proteins Van Gogh-like (Vangl) and Frizzled (Fzd), as well as the cytoplasmic effectors Prickle (Pk) and Dishevelled (Dvl). Asymmetric localization of these proteins is thought to be central to their function, and understanding the dynamics of these proteins is an important challenge in developmental biology. Among the processes that are organized by the core PCP proteins is the directional beating of cilia, such as those in the vertebrate node, airway and brain. Here, we exploit the live imaging capabilities of Xenopus to chart the progressive asymmetric localization of fluorescent reporters of Dvl1, Pk2 and Vangl1 in a planar polarized ciliated epithelium. Using this system, we also characterize the influence of Pk2 on the asymmetric dynamics of Vangl1 at the cell cortex, and we define regions of Pk2 that control its own localization and those impacting Vangl1. Finally, our data reveal a striking uncoupling of Vangl1 and Dvl1 asymmetry. This study advances our understanding of conserved PCP protein functions and also establishes a rapid, tractable platform to facilitate future in vivo studies of vertebrate PCP protein dynamics. PMID:26293301

  1. Wg and Wnt4 provide long-range directional input to planar cell polarity orientation in Drosophila

    PubMed Central

    Wu, Jun; Roman, Angel-Carlos; Carvajal-Gonzalez, Jose Maria; Mlodzik, Marek

    2013-01-01

    Planar cell polarity (PCP) is cellular polarity within the plane of an epithelial tissue or organ. PCP is established through interactions of the core Frizzled(Fz)/PCP factors and although their molecular interactions are beginning to be understood, the upstream input providing directional bias/polarity axis remains unknown. Among core PCP genes, Fz is unique as it regulates PCP both cell-autonomously and non-autonomously, with the extra-cellular domain of Fz acting as a ligand for Van-Gogh (Vang). We demonstrate in Drosophila wings that Wg and dWnt4 provide instructive regulatory input for PCP axis determination, establishing polarity axes along their graded distribution and perpendicular to their expression domain borders. Loss-of-function studies reveal that Wg/dWnt4 act redundantly in PCP determination. They affect PCP by modulating the intercellular interaction between Fz and Vang, which is thought to be a key step in setting up initial polarity, thus providing directionality to the PCP process. PMID:23912125

  2. Active self-polarization of contractile cells in asymmetrically shaped domains.

    PubMed

    Zemel, A; Safran, S A

    2007-08-01

    Mechanical forces generated by contractile cells allow the cells to sense their environment and to interact with other cells. By locally pulling on their environment, cells can sense and respond to mechanical features such as the local stress (or strain), the shape of a cellular domain, and the surrounding rigidity; at the same time, they also modify the mechanical state of the system. This creates a mechanical feedback loop that can result in self-polarization of cells. In this paper, we present a quantitative mechanical model that predicts the self-polarization of cells in spheroidally shaped domains, comprising contractile cells and an elastic matrix, that are embedded in a three-dimensional, cell-free gel. The theory is based on a generalization of the known results for passive inclusions in solids to include the effects of cell activity. We use the active cellular susceptibility tensor presented by Zemel [Phys. Rev. Lett. 97, 128103 (2006)] to calculate the polarization response and hence the elastic stress field developed by the cells in the cellular domain. The cell polarization is analyzed as a function of the shape and the elastic moduli of the cellular domain compared with the cell-free surrounding material. Consistent with experiment, our theory predicts the development of a stronger contractile force for cells in a gel that is surrounded by a large, cell-free material whose elastic modulus is stiffer than that of the gel that contains the cells. This provides a quantitative explanation of the differences in the development of cellular forces as observed in free and fixed gels. In the case of an asymmetrically shaped (spheroidal) domain of cells, we show that the anisotropic elastic field within the domain leads to a spontaneous self-polarization of the cells along the long axis of the domain. PMID:17930063

  3. Polarity determination in breast tissue: Desmosomal adhesion, myoepit helial cells, and laminin 1

    SciTech Connect

    Bissell, Mina J.; Bilder, David

    2003-06-05

    In all epithelial organs, apicobasal polarity determines functional integrity and contributes to the maintenance of tissue and organ specificity. In the breast, the functional unit is a polar double-layered tube consisting of luminal epithelial cells surrounded by myoepithelial cells and a basement membrane. It is far from clear how this double-layered structure is established and how polarity is maintained. Two recent papers have shed some light onto this intriguing problem in mammary gland biology. The results point to desmosomes and laminin 1 as having crucial roles. However, some questions remain.

  4. Myosin Id is required for planar cell polarity in ciliated tracheal and ependymal epithelial cells.

    PubMed

    Hegan, Peter S; Ostertag, Eric; Geurts, Aron M; Mooseker, Mark S

    2015-10-01

    In wild type (WT) tracheal epithelial cells, ciliary basal bodies are oriented such that all cilia on the cell surface beat in the same upward direction. This precise alignment of basal bodies and, as a result, the ciliary axoneme, is termed rotational planar cell polarity (PCP). Rotational PCP in the multi-ciliated epithelial cells of the trachea is perturbed in rats lacking myosin Id (Myo1d). Myo1d is localized in the F-actin and basal body rich subapical cortex of the ciliated tracheal epithelial cell. Scanning and transmission electron microscopy of Myo1d knock out (KO) trachea revealed that the unidirectional bending pattern is disrupted. Instead, cilia splay out in a disordered, often radial pattern. Measurement of the alignment axis of the central pair axonemal microtubules was much more variable in the KO, another indicator that rotational PCP is perturbed. The asymmetric localization of the PCP core protein Vangl1 is lost. Both the velocity and linearity of cilia-driven movement of beads above the tracheal mucosal surface was impaired in the Myo1d KO. Multi-ciliated brain ependymal epithelial cells exhibit a second form of PCP termed translational PCP in which basal bodies and attached cilia are clustered at the anterior side of the cell. The precise asymmetric clustering of cilia is disrupted in the ependymal cells of the Myo1d KO rat. While basal body clustering is maintained, left-right positioning of the clusters is lost. PMID:26446290

  5. Effects of polar oil related hydrocarbons on steroidogenesis in vitro in H295R cells.

    PubMed

    Knag, Anne Christine; Verhaegen, Steven; Ropstad, Erik; Mayer, Ian; Meier, Sonnich

    2013-06-01

    Oil pollution from various sources, including exploration, production and transportation, is a growing global concern. Of particular concern is the environmental impact of produced water (PW), the main waste discharge from oil and gas platforms. In this study, we have investigated the potential of polar hydrocarbon pollutants to disrupt or modulate steroidogenesis in vitro, using a human adrenocortical carcinoma cell line, the H295R assay. Effects of two of the major groups of compounds found in the polar fraction of crude oil and PW; alkylphenols (C(2)- and C(3)-AP) and naphthenic acids (NAs), as well as the polar fraction of PW as a whole has been assessed. Endpoints include hormone (cortisol, estradiol, progesterone, testosterone) production at the functional level and key genes for steroidogenesis (17β-HSD1, 17β-HSD4, 3β-HSD2, ACTHR, CYP11A1, CYP11B1, CYP11B2, CYP17, CYP19, CYP21, DAX1, EPHX, HMGR, SF1, STAR) and metabolism (CYP1A) at the molecular level. All compounds induced the production of both estradiol and progesterone in exposed H295R cells, while the C(3)-AP and NAs decreased the production of testosterone. Exposure to C(2)-AP caused an up-regulation of DAX1 and EPHX, while exposure to NAs caused an up-regulation of ACTHR. All compounds caused an up-regulation of CYP1A1. The results indicated that these hydrocarbon pollutants, including PW, have the potential to disrupt the vitally important process of steroidogenesis. PMID:23561572

  6. Polarization fluctuation dominated electrical transport processes of polymer-based ferroelectric field effect transistors

    NASA Astrophysics Data System (ADS)

    Senanayak, Satyaprasad P.; Guha, S.; Narayan, K. S.

    2012-03-01

    Ferroelectric field effect transistors (FE-FETs) consisting of tunable dielectric layers are utilized to investigate interfacial transport processes. Large changes in the dielectric constant as a function of temperature are observed in FE-FETs in conjunction with the ferroelectric to paraelectric transition. The devices offer a test bed to evaluate specific effects of polarization on the electrical processes. FE-FETs have dominant contributions from polarization fluctuation rather than static dipolar disorder prevalent in high k paraelectric dielectric-based FETs. Additionally, photo-excitation measurements in the depletion mode reveal clear features in the FET response at different temperatures, indicative of different transport regimes.

  7. Porcine aminopeptidase N mediated polarized infection by porcine epidemic diarrhea virus in target cells

    SciTech Connect

    Cong, Yingying; Li, Xiaoxue; Bai, Yunyun; Lv, Xiaonan; Herrler, Georg; Enjuanes, Luis; Zhou, Xingdong; Qu, Bo; Meng, Fandan; Cong, Chengcheng; Ren, Xiaofeng; Li, Guangxing

    2015-04-15

    Infection of polarized intestinal epithelial cells by porcine epidemic diarrhea virus (PEDV) was characterized. Indirect immunofluorescence assay, real-time PCR, and transmission electron microscopy confirmed PEDV can be successfully propagated in immortalized swine small intestine epithelial cells (IECs). Infection involved porcine aminpeptidase N (pAPN), a reported cellular receptor for PEDV, transient expression of pAPN and siRNA targeted pAPN increased and decreased the infectivity of PEDV in IECs, respectively. Subsequently, polarized entry into and release from both Vero E6 and IECs was analyzed. PEDV entry into polarized cells and pAPN grown on membrane inserts occurs via apical membrane. The progeny virus released into the medium was also quantified which demonstrated that PEDV is preferentially released from the apical membrane. Collectively, our data demonstrate that pAPN, the cellular receptor for PEDV, mediates polarized PEDV infection. These results imply the possibility that PEDV infection may proceed by lateral spread of virus in intestinal epithelial cells. - Highlights: • PEDV infection of polarized intestinal epithelial cells (IECs) was characterized. • Porcine aminpeptidase N (pAPN) facilitated PEDV infection in IECs. • PEDV entry into and release from polarized cell via its apical membrane. • PEDV infection may proceed by lateral spread of virus in IECs.

  8. Polarization of cells and soft objects driven by mechanical interactions: Consequences for migration and chemotaxis

    NASA Astrophysics Data System (ADS)

    Leoni, M.; Sens, P.

    2015-02-01

    We study a generic model for the polarization and motility of self-propelled soft objects, biological cells, or biomimetic systems, interacting with a viscous substrate. The active forces generated by the cell on the substrate are modeled by means of oscillating force multipoles at the cell-substrate interface. Symmetry breaking and cell polarization for a range of cell sizes naturally "emerge" from long range mechanical interactions between oscillating units, mediated both by the intracellular medium and the substrate. However, the harnessing of cell polarization for motility requires substrate-mediated interactions. Motility can be optimized by adapting the oscillation frequency to the relaxation time of the system or when the substrate and cell viscosities match. Cellular noise can destroy mechanical coordination between force-generating elements within the cell, resulting in sudden changes of polarization. The persistence of the cell's motion is found to depend on the cell size and the substrate viscosity. Within such a model, chemotactic guidance of cell motion is obtained by directionally modulating the persistence of motion, rather than by modulating the instantaneous cell velocity, in a way that resembles the run and tumble chemotaxis of bacteria.

  9. Plasma membrane protein polarity and trafficking in RPE cells: Past, present and future

    PubMed Central

    Lehmann, Guillermo L.; Benedicto, Ignacio; Philp, Nancy J.; Rodriguez-Boulan, Enrique

    2015-01-01

    The retinal pigment epithelium (RPE) comprises a monolayer of polarized pigmented epithelial cells that is strategically interposed between the neural retina and the fenestrated choroid capillaries. The RPE performs a variety of vectorial transport functions (water, ions, metabolites, nutrients and waste products) that regulate the composition of the subretinal space and support the functions of photoreceptors (PRs) and other cells in the neural retina. To this end, RPE cells display a polarized distribution of channels, transporters and receptors in their plasma membrane (PM) that is remarkably different from that found in conventional extra-ocular epithelia, e.g. intestine, kidney, and gall bladder. This characteristic PM protein polarity of RPE cells depends on the interplay of sorting signals in the RPE PM proteins and sorting mechanisms and biosynthetic/recycling trafficking routes in the RPE cell. Although considerable progress has been made in our understanding of the RPE trafficking machinery, most available data have been obtained from immortalized RPE cell lines that only partially maintain the RPE phenotype and by extrapolation of data obtained in the prototype Madin–Darby Canine Kidney (MDCK) cell line. The increasing availability of RPE cell cultures that more closely resemble the RPE in vivo together with the advent of advanced live imaging microscopy techniques provides a platform and an opportunity to rapidly expand our understanding of how polarized protein trafficking contributes to RPE PM polarity. PMID:25152359

  10. Cu₂ZnSnS(4x)Se(4(1-x)) solar cells from polar nanocrystal inks.

    PubMed

    van Embden, Joel; Chesman, Anthony S R; Della Gaspera, Enrico; Duffy, Noel W; Watkins, Scott E; Jasieniak, Jacek J

    2014-04-01

    A facile ligand exchange method for dispersing Cu2ZnSnS4 (CZTS) nanocrystals (NCs) in environmentally benign polar solvents, such as ethanol or n-propanol, at high concentrations (up to 200 mg/mL) is demonstrated. This approach has been applied to CZTS nanocrystals synthesized via scalable, noninjection methods to formulate colloidally stable inks that are suitable for the solution processing of solar cell devices. Unlike other inks currently used to fabricate NC solar cells, the CZTS nanocrystal ink developed here circumvents the need for hydrazine, pyridine, or thiol coordinating solvents. By combining our polar CZTS inks with optimized selenization procedures, substrate CZTSSe solar cells have been successfully fabricated with device efficiencies of 7.7%. PMID:24690032

  11. The influence of polar heterogeneous processes on reactive chlorine at middle latitudes - Three dimensional model implications

    NASA Astrophysics Data System (ADS)

    Douglass, Anne R.; Rood, Richard B.; Kaye, Jack A.; Stolarki, Richard S.; Allen, Dale J.

    1991-01-01

    Three-dimensional model calculations with the NASA/GSFC chemistry and transport model have been designed to consider the impact of heterogeneous processes occurring on polar stratospheric clouds (PSCs) in the Arctic vortex on the HCl distribution. By examining the HCl concentration for a calculation with PSCs relative to a calculation with gas phase chemistry only, the impact of polar processing on reactive chlorine species at middle latitudes is inferred. Results from the chemistry and transport model reproduce basic features of the ClO measurements (Toohey et al., 1991), which were made on the ferry flights of the ER-2 from Stavanger, Norway to Moffett Field, California via Wallops Island, Virginia on February 20 and 21, 1989. The model indicates that perturbed air which is contained within the polar vortex during winter is not homogeneously mixed, and that the ferry flights were made through air with the largest conversion of HCl to reactive chlorine that is seen at middle latitudes.

  12. Regulation of cell polarity determinants by the Retinoblastoma tumor suppressor protein.

    PubMed

    Payankaulam, Sandhya; Yeung, Kelvin; McNeill, Helen; Henry, R William; Arnosti, David N

    2016-01-01

    In addition to their canonical roles in the cell cycle, RB family proteins regulate numerous developmental pathways, although the mechanisms remain obscure. We found that Drosophila Rbf1 associates with genes encoding components of the highly conserved apical-basal and planar cell polarity pathways, suggesting a possible regulatory role. Here, we show that depletion of Rbf1 in Drosophila tissues is indeed associated with polarity defects in the wing and eye. Key polarity genes aPKC, par6, vang, pk, and fmi are upregulated, and an aPKC mutation suppresses the Rbf1-induced phenotypes. RB control of cell polarity may be an evolutionarily conserved function, with important implications in cancer metastasis. PMID:26971715

  13. Regulation of cell polarity determinants by the Retinoblastoma tumor suppressor protein

    PubMed Central

    Payankaulam, Sandhya; Yeung, Kelvin; McNeill, Helen; Henry, R. William; Arnosti, David N.

    2016-01-01

    In addition to their canonical roles in the cell cycle, RB family proteins regulate numerous developmental pathways, although the mechanisms remain obscure. We found that Drosophila Rbf1 associates with genes encoding components of the highly conserved apical–basal and planar cell polarity pathways, suggesting a possible regulatory role. Here, we show that depletion of Rbf1 in Drosophila tissues is indeed associated with polarity defects in the wing and eye. Key polarity genes aPKC, par6, vang, pk, and fmi are upregulated, and an aPKC mutation suppresses the Rbf1-induced phenotypes. RB control of cell polarity may be an evolutionarily conserved function, with important implications in cancer metastasis. PMID:26971715

  14. Mammalian aPKC/Par polarity complex mediated regulation of epithelial division orientation and cell fate

    SciTech Connect

    Vorhagen, Susanne; Niessen, Carien M.

    2014-11-01

    Oriented cell division is a key regulator of tissue architecture and crucial for morphogenesis and homeostasis. Balanced regulation of proliferation and differentiation is an essential property of tissues not only to drive morphogenesis but also to maintain and restore homeostasis. In many tissues orientation of cell division is coupled to the regulation of differentiation producing daughters with similar (symmetric cell division, SCD) or differential fate (asymmetric cell division, ACD). This allows the organism to generate cell lineage diversity from a small pool of stem and progenitor cells. Division orientation and/or the ratio of ACD/SCD need to be tightly controlled. Loss of orientation or an altered ratio can promote overgrowth, alter tissue architecture and induce aberrant differentiation, and have been linked to morphogenetic diseases, cancer and aging. A key requirement for oriented division is the presence of a polarity axis, which can be established through cell intrinsic and/or extrinsic signals. Polarity proteins translate such internal and external cues to drive polarization. In this review we will focus on the role of the polarity complex aPKC/Par3/Par6 in the regulation of division orientation and cell fate in different mammalian epithelia. We will compare the conserved function of this complex in mitotic spindle orientation and distribution of cell fate determinants and highlight common and differential mechanisms in which this complex is used by tissues to adapt division orientation and cell fate to the specific properties of the epithelium.

  15. The Variable Polarity Plasma Arc Welding Process: Its Application to the Space Shuttle External Tank

    NASA Technical Reports Server (NTRS)

    Nunes, A. C., Jr.; Bayless, E. O., Jr.; Wilson, W. A.

    1984-01-01

    This report describes progress in the implementation of the Variable Polarity Plasma Arc Welding (VPPAW) process at the External Tank (ET) assembly facility. Design allowable data has been developed for thicknesses up to 1.00 in. More than 24,000 in. of welding on liquid oxygen and liquid hydrogen cylinders has been made without an internal defect.

  16. Wavefront curvature limitations and compensation to polar format processing for synthetic aperture radar images.

    SciTech Connect

    Doerry, Armin Walter

    2006-01-01

    Limitations on focused scene size for the Polar Format Algorithm (PFA) for Synthetic Aperture Radar (SAR) image formation are derived. A post processing filtering technique for compensating the spatially variant blurring in the image is examined. Modifications to this technique to enhance its robustness are proposed.

  17. Cell Processing Engineering for Regenerative Medicine : Noninvasive Cell Quality Estimation and Automatic Cell Processing.

    PubMed

    Takagi, Mutsumi

    2016-01-01

    The cell processing engineering including automatic cell processing and noninvasive cell quality estimation of adherent mammalian cells for regenerative medicine was reviewed. Automatic cell processing necessary for the industrialization of regenerative medicine was introduced. The cell quality such as cell heterogeneity should be noninvasively estimated before transplantation to patient, because cultured cells are usually not homogeneous but heterogeneous and most protocols of regenerative medicine are autologous system. The differentiation level could be estimated by two-dimensional cell morphology analysis using a conventional phase-contrast microscope. The phase-shifting laser microscope (PLM) could determine laser phase shift at all pixel in a view, which is caused by the transmitted laser through cell, and might be more noninvasive and more useful than the atomic force microscope and digital holographic microscope. The noninvasive determination of the laser phase shift of a cell using a PLM was carried out to determine the three-dimensional cell morphology and estimate the cell cycle phase of each adhesive cell and the mean proliferation activity of a cell population. The noninvasive discrimination of cancer cells from normal cells by measuring the phase shift was performed based on the difference in cytoskeleton density. Chemical analysis of the culture supernatant was also useful to estimate the differentiation level of a cell population. A probe beam, an infrared beam, and Raman spectroscopy are useful for diagnosing the viability, apoptosis, and differentiation of each adhesive cell. PMID:25373455

  18. Regulation of cochlear convergent extension by the vertebrate planar cell polarity pathway is dependent on p120-catenin.

    PubMed

    Chacon-Heszele, Maria F; Ren, Dongdong; Reynolds, Albert B; Chi, Fanglu; Chen, Ping

    2012-03-01

    The vertebrate planar cell polarity (PCP) pathway consists of conserved PCP and ciliary genes. During development, the PCP pathway regulates convergent extension (CE) and uniform orientation of sensory hair cells in the cochlea. It is not clear how these diverse morphogenetic processes are regulated by a common set of PCP genes. Here, we show that cellular contacts and geometry change drastically and that the dynamic expression of N-cadherin and E-cadherin demarcates sharp boundaries during cochlear extension. The conditional knockout of a component of the adherens junctions, p120-catenin, leads to the reduction of E-cadherin and N-cadherin and to characteristic cochlear CE defects but not misorientation of hair cells. The specific CE defects in p120-catenin mutants are in contrast to associated CE and hair cell misorientation defects observed in common PCP gene mutants. Moreover, the loss-of-function of a conserved PCP gene, Vangl2, alters the dynamic distribution of N-cadherin and E-cadherin in the cochlea and causes similar abnormalities in cellular morphology to those found in p120-catenin mutants. Conversely, we found that Pcdh15 interacts genetically with PCP genes to regulate the formation of polar hair bundles, but not CE defects in the cochlea. Together, these results indicate that the vertebrate PCP pathway regulates CE and hair cell polarity independently and that a p120-catenin-dependent mechanism regulates CE of the cochlea. PMID:22318628

  19. The APC tumor suppressor is required for epithelial cell polarization and three-dimensional morphogenesis.

    PubMed

    Lesko, Alyssa C; Goss, Kathleen H; Yang, Frank F; Schwertner, Adam; Hulur, Imge; Onel, Kenan; Prosperi, Jenifer R

    2015-03-01

    The Adenomatous Polyposis Coli (APC) tumor suppressor has been previously implicated in the control of apical-basal polarity; yet, the consequence of APC loss-of-function in epithelial polarization and morphogenesis has not been characterized. To test the hypothesis that APC is required for the establishment of normal epithelial polarity and morphogenesis programs, we generated APC-knockdown epithelial cell lines. APC depletion resulted in loss of polarity and multi-layering on permeable supports, and enlarged, filled spheroids with disrupted polarity in 3D culture. Importantly, these effects of APC knockdown were independent of Wnt/β-catenin signaling, but were rescued with either full-length or a carboxy (c)-terminal segment of APC. Moreover, we identified a gene expression signature associated with APC knockdown that points to several candidates known to regulate cell-cell and cell-matrix communication. Analysis of epithelial tissues from mice and humans carrying heterozygous APC mutations further supports the importance of APC as a regulator of epithelial behavior and tissue architecture. These data also suggest that the initiation of epithelial-derived tumors as a result of APC mutation or gene silencing may be driven by loss of polarity and dysmorphogenesis. PMID:25578398

  20. Polar delivery in plants; commonalities and differences to animal epithelial cells

    PubMed Central

    Kania, Urszula; Fendrych, Matyáš; Friml, Jiří

    2014-01-01

    Although plant and animal cells use a similar core mechanism to deliver proteins to the plasma membrane, their different lifestyle, body organization and specific cell structures resulted in the acquisition of regulatory mechanisms that vary in the two kingdoms. In particular, cell polarity regulators do not seem to be conserved, because genes encoding key components are absent in plant genomes. In plants, the broad knowledge on polarity derives from the study of auxin transporters, the PIN-FORMED proteins, in the model plant Arabidopsis thaliana. In animals, much information is provided from the study of polarity in epithelial cells that exhibit basolateral and luminal apical polarities, separated by tight junctions. In this review, we summarize the similarities and differences of the polarization mechanisms between plants and animals and survey the main genetic approaches that have been used to characterize new genes involved in polarity establishment in plants, including the frequently used forward and reverse genetics screens as well as a novel chemical genetics approach that is expected to overcome the limitation of classical genetics methods. PMID:24740985

  1. Dynamics of Cdc42 network embodies a Turing-type mechanism of yeast cell polarity.

    PubMed

    Goryachev, Andrew B; Pokhilko, Alexandra V

    2008-04-30

    Complex biochemical networks can be understood by identifying their principal regulatory motifs and mode of action. We model the early phase of budding yeast cellular polarization and show that the biochemical processes in the presumptive bud site comprise a Turing-type mechanism. The roles of the prototypical activator and substrate are played by GTPase Cdc42 in its active and inactive states, respectively. We demonstrate that the nucleotide cycling of Cdc42 converts cellular energy into a stable cluster of activated Cdc42. This energy drives a continuous membrane-cytoplasmic exchange of the cluster components to counteract diffusive spread of the cluster. This exchange explains why only one bud forms per cell cycle, because the winner-takes-all competition of candidate sites inevitably selects a single site. PMID:18381072

  2. Specific polar subpopulations of astral microtubules control spindle orientation and symmetric neural stem cell division.

    PubMed

    Mora-Bermúdez, Felipe; Matsuzaki, Fumio; Huttner, Wieland B

    2014-01-01

    Mitotic spindle orientation is crucial for symmetric vs asymmetric cell division and depends on astral microtubules. Here, we show that distinct subpopulations of astral microtubules exist, which have differential functions in regulating spindle orientation and division symmetry. Specifically, in polarized stem cells of developing mouse neocortex, astral microtubules reaching the apical and basal cell cortex, but not those reaching the central cell cortex, are more abundant in symmetrically than asymmetrically dividing cells and reduce spindle orientation variability. This promotes symmetric divisions by maintaining an apico-basal cleavage plane. The greater abundance of apical/basal astrals depends on a higher concentration, at the basal cell cortex, of LGN, a known spindle-cell cortex linker. Furthermore, newly developed specific microtubule perturbations that selectively decrease apical/basal astrals recapitulate the symmetric-to-asymmetric division switch and suffice to increase neurogenesis in vivo. Thus, our study identifies a novel link between cell polarity, astral microtubules, and spindle orientation in morphogenesis. PMID:24996848

  3. Yeast Rrp14p is a nucleolar protein involved in both ribosome biogenesis and cell polarity

    PubMed Central

    Yamada, Hiroko; Horigome, Chihiro; Okada, Takafumi; Shirai, Chiharu; Mizuta, Keiko

    2007-01-01

    We previously cloned RRP14/YKL082c, whose product exhibits two-hybrid interaction with Ebp2p, a regulatory factor of assembly of 60S ribosomal subunits. Depletion of Rrp14p results in shortage of 60S ribosomal subunits and retardation of processing from 27S pre-rRNA to 25S rRNA. Furthermore, 35S pre-rRNA synthesis appears to decline in Rrp14p-depleted cells. Rrp14p interacts with regulatory factors of 60S subunit assembly and also with Utp11p and Faf1p, which are regulatory factors required for assembly of 40S ribosomal subunits. We propose that Rrp14p is involved in ribosome synthesis from the beginning of 35S pre-rRNA synthesis to assembly of the 60S ribosomal subunit. Disruption of RRP14 causes an extremely slow growth rate of the cell, a severe defect in ribosome synthesis, and a depolarized localization of cortical actin patches throughout the cell cycle. These results suggest that Rrp14p has dual functions in ribosome synthesis and polarized cell growth. PMID:17804645

  4. The reduction half cell in biomaterials corrosion: oxygen diffusion profiles near and cell response to polarized titanium surfaces.

    PubMed

    Gilbert, J L; Zarka, L; Chang, E; Thomas, C H

    1998-11-01

    Mechanically assisted corrosion processes can greatly increase the oxidation currents generated in passivating alloy systems like Co-Cr and titanium due to oxide film disruption. When oxide films are abraded, repassivation and ionic dissolution both occur at rates that are orders of magnitude higher than undisrupted surfaces. The excess electrons generated by these anodic processes must be consumed in corresponding reduction reactions that include the reduction of oxygen. If large enough, these reduction reactions may locally deplete the concentration of solution-dissolved oxygen and, in turn, affect cell behavior in the vicinity of the implant surface. To date, this hypothesis has not been tested. In the present study, a scanning electrochemical microscope was used to measure oxygen concentration profiles in vitro near a planar titanium electrode polarized to different voltages representative of those attainable by titanium undergoing mechanically assisted corrosion. The potentials investigated ranged from 0 mV to -1000 mV (AgCl). The oxygen concentration as a function of distance from the titanium surface was measured using a platinum-iridium microelectrode and an amperometric technique. Also, preliminary experiments were performed to assess the response of rat calvarial osteoblast-rich cells cultured for 2 h on titanium samples polarized to two different potentials (0 mV and -1000 mV versus AgCl). The results of this study indicate that oxygen concentrations near titanium surfaces are affected by sample potentials out to probe-sample distances as great as 500 microm. Within 2 microm of the surface, oxygen concentrations decreased by 15 to 25% for sample potentials between -100 and -500 mV. At potentials more negative than -600 mV, the oxygen concentration dropped rapidly to near zero by -900 mV. The cell experiments showed a statistically significant difference in the amount of cell spreading, as measured by projected cell area, between the two groups (p < 0

  5. Real time polarization sensor image processing on an embedded FPGA/multi-core DSP system

    NASA Astrophysics Data System (ADS)

    Bednara, Marcus; Chuchacz-Kowalczyk, Katarzyna

    2015-05-01

    Most embedded image processing SoCs available on the market are highly optimized for typical consumer applications like video encoding/decoding, motion estimation or several image enhancement processes as used in DSLR or digital video cameras. For non-consumer applications, on the other hand, optimized embedded hardware is rarely available, so often PC based image processing systems are used. We show how a real time capable image processing system for a non-consumer application - namely polarization image data processing - can be efficiently implemented on an FPGA and multi-core DSP based embedded hardware platform.

  6. Radially polarized annular beam generated through a second-harmonic-generation process.

    PubMed

    Sato, Shunichi; Kozawa, Yuichi

    2009-10-15

    A radially polarized beam with an annular intensity pattern was generated through a second-harmonic-generation process by focusing an azimuthally polarized Ti:sapphire pulsed laser beam to a c-cut beta-barium borate (BBO) crystal. The annular intensity pattern of the second-harmonic wave had a nearly sixfold symmetry as a result of the nonlinear susceptibility tensor of the BBO crystal. The width of the annulus was as narrow as less than 1/40th of its radius. PMID:19838261

  7. Climatic anomalous patterns associated with the Arctic and Polar cell strength variations

    NASA Astrophysics Data System (ADS)

    Qian, Weihong; Wu, Kaijun; Leung, Jeremy Cheuk-Hin

    2016-03-01

    The Arctic cell as a reversed and closed loop next to the Polar cell has been recently revealed in the Northern Hemisphere (NH). In this paper, we study the interannual variability of the Arctic and Polar cell strengths during 1979-2012, and their influence on surface air temperature (SAT), precipitation, and sea-ice concentration (SIC) at mid- and high-latitudes of the NH. We show that there is a significant negative correlation between the Arctic and Polar cell strengths. Both the Arctic and Polar cell strengths can well indicate the recurring climatic anomalies of SAT, precipitation, and SIC in their extreme winters. The surface large-scale cold-warm and dry-wet anomalous patterns in these extreme winters are directly linked with the vertical structure of height and temperature anomalies in the troposphere. Results suggest that the past climatic anomalies are better indicated by the strength anomalies of the Polar and Arctic cells than the traditional indices of mid-high latitude pattern such as the Arctic Oscillation and North Atlantic Oscillation. This study illustrates a three-dimensional picture of atmospheric variable anomalies in the troposphere that result in surface climatic anomalies.

  8. A Novel Human Cytomegalovirus Glycoprotein, gpUS9, Which Promotes Cell-to-Cell Spread in Polarized Epithelial Cells, Colocalizes with the Cytoskeletal Proteins E-Cadherin and F-Actin

    PubMed Central

    Maidji, Ekaterina; Tugizov, Sharof; Abenes, Gerardo; Jones, Thomas; Pereira, Lenore

    1998-01-01

    Processes by which human herpesviruses penetrate and are released from polarized epithelial cells, which have distinct apical and basolateral membrane domains differing in protein and lipid content, are poorly understood. We recently reported that human cytomegalovirus (CMV) mutants with deletions of the gene US9 formed wild-type plaques in cultures of human fibroblasts but were impaired in the capacity for cell-to-cell spread in polarized human retinal pigment epithelial cells. Unlike the glycoproteins that are required for infection, the protein encoded by CMV US9 plays an accessory role by promoting dissemination of virus across cell-cell junctions of polarized epithelial cells. To identify the product and investigate its specialized functions, we selected Madine-Darby canine kidney II (MDCK) epithelial cells that constitutively express CMV US9 or, as a control, US8. The gene products, designated gpUS9 and gpUS8, were glycosylated proteins of comparable molecular masses but differed considerably in intracellular distribution and solubility. Immunofluorescence laser scanning confocal microscopy indicated that, like gpUS8, gpUS9 was present in the endoplasmic reticulum and Golgi compartments of nonpolarized cells. In polarized epithelial cells, gpUS9 also accumulated along lateral membranes, colocalizing with cadherin and actin, and was insoluble in Triton X-100, a property shared with proteins that associate with the cytoskeleton. We hypothesize that gpUS9 may enhance the dissemination of CMV in infected epithelial tissues by associating with the cytoskeletal matrix. PMID:9621030

  9. Polarized Human Embryonic Stem Cell-Derived Retinal Pigment Epithelial Cell Monolayers Have Higher Resistance to Oxidative Stress-Induced Cell Death Than Nonpolarized Cultures

    PubMed Central

    Hsiung, Jamie; Zhu, Danhong

    2015-01-01

    Oxidative stress-mediated injury to the retinal pigment epithelium (RPE) is a major factor involved in the pathogenesis of age-related macular degeneration (AMD), the leading cause of blindness in the elderly. Human embryonic stem cell (hESC)-derived RPE cells are currently being evaluated for their potential for cell therapy in AMD patients through subretinal injection of cells in suspension and subretinal placement as a polarized monolayer. To gain an understanding of how transplanted RPE cells will respond to the highly oxidatively stressed environment of an AMD patient eye, we compared the survival of polarized and nonpolarized RPE cultures following oxidative stress treatment. Polarized, nonpolarized/confluent, nonpolarized/subconfluent hESC-RPE cells were treated with H2O2. Terminal deoxynucleotidyl transferase dUTP nick end labeling stains revealed the highest amount of cell death in subconfluent hESC-RPE cells and little cell death in polarized hESC-RPE cells with H2O2 treatment. There were higher levels of proapoptotic factors (phosphorylated p38, phosphorylated c-Jun NH2-terminal kinase, Bax, and cleaved caspase 3 fragments) in treated nonpolarized RPE—particularly subconfluent cells—relative to polarized cells. On the other hand, polarized RPE cells had constitutively higher levels of cell survival and antiapoptotic signaling factors such as p-Akt and Bcl-2, as well as antioxidants superoxide dismutase 1 and catalase relative to nonpolarized cells, that possibly contributed to polarized cells’ higher tolerance to oxidative stress compared with nonpolarized RPE cells. Subconfluent cells were particularly sensitive to oxidative stress-induced apoptosis. These results suggest that implantation of polarized hESC-RPE monolayers for treating AMD patients with geographic atrophy should have better survival than injections of hESC-RPE cells in suspension. PMID:25411476

  10. Epidermal wound repair is regulated by the planar cell polarity signaling pathway.

    PubMed

    Caddy, Jacinta; Wilanowski, Tomasz; Darido, Charbel; Dworkin, Sebastian; Ting, Stephen B; Zhao, Quan; Rank, Gerhard; Auden, Alana; Srivastava, Seema; Papenfuss, Tony A; Murdoch, Jennifer N; Humbert, Patrick O; Parekh, Vishwas; Boulos, Nidal; Weber, Thomas; Zuo, Jian; Cunningham, John M; Jane, Stephen M

    2010-07-20

    The mammalian PCP pathway regulates diverse developmental processes requiring coordinated cellular movement, including neural tube closure and cochlear stereociliary orientation. Here, we show that epidermal wound repair is regulated by PCP signaling. Mice carrying mutant alleles of PCP genes Vangl2, Celsr1, PTK7, and Scrb1, and the transcription factor Grhl3, interact genetically, exhibiting failed wound healing, neural tube defects, and disordered cochlear polarity. Using phylogenetic analysis, ChIP, and gene expression in Grhl3(-)(/-) mice, we identified RhoGEF19, a homolog of a RhoA activator involved in PCP signaling in Xenopus, as a direct target of GRHL3. Knockdown of Grhl3 or RhoGEF19 in keratinocytes induced defects in actin polymerization, cellular polarity, and wound healing, and re-expression of RhoGEF19 rescued these defects in Grhl3-kd cells. These results define a role for Grhl3 in PCP signaling and broadly implicate this pathway in epidermal repair. PMID:20643356

  11. Epidermal wound repair is regulated by the planar cell polarity signaling pathway

    PubMed Central

    Caddy, Jacinta; Wilanowski, Tomasz; Darido, Charbel; Dworkin, Sebastian; Ting, Stephen B.; Zhao, Quan; Rank, Gerhard; Auden, Alana; Srivastava, Seema; Papenfuss, Tony A.; Murdoch, Jennifer N.; Humbert, Patrick O.; Boulos, Nidal; Weber, Thomas; Zuo, Jian; Cunningham, John M.; Jane, Stephen M.

    2010-01-01

    SUMMARY The mammalian PCP pathway regulates diverse developmental processes requiring coordinated cellular movement, including neural tube closure and cochlear stereociliary orientation. Here, we show that epidermal wound repair is regulated by PCP signaling. Mice carrying mutant alleles of PCP genes Vangl2, Celsr1, PTK7, and Scrb1, and the transcription factor Grhl3, interact genetically, exhibiting failed wound healing, neural tube defects and disordered cochlear polarity. Using phylogenetic analysis, ChIP, and gene expression in Grhl3−/− mice, we identified RhoGEF19, a homologue of a RhoA activator involved in PCP signaling in Xenopus, as a direct target of GRHL3. Knockdown of Grhl3 or RhoGEF19 in keratinocytes induced defects in actin polymerisation, cellular polarity and wound healing, and re-expression of RhoGEF19 rescued these defects in Grhl3-kd cells. These results define a role for Grhl3 in PCP signaling, and broadly implicate this pathway in epidermal repair. PMID:20643356

  12. Correlation processing of polarization inhomogenous images in laser diagnostics of biological tissues

    NASA Astrophysics Data System (ADS)

    Trifonyuk, L.

    2012-10-01

    The model of interaction of laser radiation with biological tissue as a two-component amorphous-crystalline matrix was proposed. The processes of formation of polarization of laser radiation are considered, taking into account birefringence network protein fibrils. Measurement of the coordinate distribution of polarization states in the location of the laser micropolarimetr was conducted .The results of investigating the interrelation between the values of correlation (correlation area, asymmetry coefficient and autocorrelation function excess) and fractal (dispersion of logarithmic dependencies of power spectra) parameters are presented. They characterize the coordinate distributions of polarization azimuth of laser images of histological sections of women's reproductive sphere tissues and pathological changes in human organism. The diagnostic criteria of the prolapse of the vaginal tissue arising are determined.

  13. Azimuthal asymmetries in single polarized proton-proton Drell-Yan processes

    SciTech Connect

    Lu Zhun; Ma Boqiang; Zhu Jiacai

    2011-10-01

    We study the azimuthal asymmetries in proton-proton Drell-Yan processes with one incident proton being transversely or longitudinally polarized. We consider particularly the asymmetries contributed by the leading-twist chiral-odd quark distributions. We analyze the asymmetries with sin(2{phi}+{phi}{sub S}) and sin(2{phi}-{phi}{sub S}) modulations in transverse single polarized p{sup {up_arrow}p} Drell-Yan and sin2{phi} asymmetries in longitudinal single polarized p{sup {yields}p} Drell-Yan at the Relativistic Heavy Ion Collider, the Japan Proton Accelerator Research Complex, E906 (Fermi Lab), and the Nuclotron-based Ion Collider Facility (Joint Institute for Nuclear Research). We show that the measurements of the asymmetries in those facilities can provide valuable information of the chiral-odd structure of the nucleon both in the valence and sea regions.

  14. Roles of planar cell polarity pathways in the development of neural [correction of neutral] tube defects.

    PubMed

    Wu, Gang; Huang, Xupei; Hua, Yimin; Mu, Dezhi

    2011-01-01

    Neural tube defects (NTDs) are the second most common birth defect in humans. Despite many advances in the understanding of NTDs and the identification of many genes related to NTDs, the fundamental etiology for the majority of cases of NTDs remains unclear. Planar cell polarity (PCP) signaling pathway, which is important for polarized cell movement (such as cell migration) and organ morphogenesis through the activation of cytoskeletal pathways, has been shown to play multiple roles during neural tube closure. The disrupted function of PCP pathway is connected with some NTDs. Here, we summarize our current understanding of how PCP factors affect the pathogenesis of NTDs. PMID:21864354

  15. Polarity Protein Complex Scribble/Lgl/Dlg and Epithelial Cell Barriers

    PubMed Central

    Su, Wen-Hui; Mruk, Dolores D.; Wong, Elissa W.P.; Lui, Wing-Yee; Cheng, C. Yan

    2014-01-01

    The Scribble polarity complex or module is one of the three polarity modules that regulate cell polarity in multiple epithelia including blood-tissue barriers. This protein complex is composed of Scribble, Lethal giant larvae (Lgl) and Discs large (Dlg), which are well conserved across species from fruitflies and worms to mammals. Originally identified in Drosophila and C. elegans where the Scribble complex was found to work with the Par-based and Crumbs-based polarity modules to regulate apicobasal polarity and asymmetry in cells and tissues during embryogenesis, their mammalian homologs have all been identified in recent years. Components of the Scribble complex are known to regulate multiple cellular functions besides cell polarity, which include cell proliferation, assembly and maintenance of adherens junction (AJ) and tight junction (TJ), and they are also tumor suppressors. Herein, we provide an update on the Scribble polarity complex and how this protein complex modulates cell adhesion with some emphasis on its role in Sertoli cell blood-testis barrier (BTB) function. It should be noted that this is a rapidly developing field, in particular the role of this protein module in blood-tissue barriers, and this short chapter attempts to provide the information necessary for investigators studying reproductive biology and blood-tissue barriers to design future studies. We also include results of recent studies from flies and worms since this information will be helpful in planning experiments for future functional studies in the testis to understand how Scribble-based proteins regulate BTB dynamics and spermatogenesis. PMID:23397623

  16. Barley disease susceptibility factor RACB acts in epidermal cell polarity and positioning of the nucleus

    PubMed Central

    Scheler, Björn; Schnepf, Vera; Galgenmüller, Carolina; Ranf, Stefanie; Hückelhoven, Ralph

    2016-01-01

    RHO GTPases are regulators of cell polarity and immunity in eukaryotes. In plants, RHO-like RAC/ROP GTPases are regulators of cell shaping, hormone responses, and responses to microbial pathogens. The barley (Hordeum vulgare L.) RAC/ROP protein RACB is required for full susceptibility to penetration by Blumeria graminis f.sp. hordei (Bgh), the barley powdery mildew fungus. Disease susceptibility factors often control host immune responses. Here we show that RACB does not interfere with early microbe-associated molecular pattern-triggered immune responses such as the oxidative burst or activation of mitogen-activated protein kinases. RACB also supports rather than restricts expression of defence-related genes in barley. Instead, silencing of RACB expression by RNAi leads to defects in cell polarity. In particular, initiation and maintenance of root hair growth and development of stomatal subsidiary cells by asymmetric cell division is affected by silencing expression of RACB. Nucleus migration is a common factor of developmental cell polarity and cell-autonomous interaction with Bgh. RACB is required for positioning of the nucleus near the site of attack from Bgh. We therefore suggest that Bgh profits from RACB’s function in cell polarity rather than from immunity-regulating functions of RACB. PMID:27056842

  17. Dystrophin expression in muscle stem cells regulates their polarity and asymmetric division

    PubMed Central

    Dumont, Nicolas A.; Wang, Yu Xin; von Maltzahn, Julia; Pasut, Alessandra; Bentzinger, C. Florian; Brun, Caroline E.; Rudnicki, Michael A.

    2016-01-01

    Dystrophin is expressed in differentiated myofibers where it is required for sarcolemmal integrity, and loss-of-function mutations in its gene result in Duchenne Muscular Dystrophy (DMD), a disease characterized by progressive and severe skeletal muscle degeneration. Here we found that dystrophin is also highly expressed in activated muscle stem cells (also known as satellite cells) where it associates with the Ser/Thr kinase Mark2 (also known as Par1b), an important regulator of cell polarity. In the absence of dystrophin, expression of Mark2 protein is downregulated, resulting in the inability to polarize Pard3 to the opposite side of the cell. Consequently, the number of asymmetric divisions is strikingly reduced in dystrophin-deficient satellite cells, while also displaying a loss of polarity, abnormal division patterns including centrosome amplification, impaired mitotic spindle orientation, and prolonged cell divisions. Altogether, these intrinsic defects strongly reduce the generation of myogenic progenitors needed for proper muscle regeneration. Therefore, we conclude that dystrophin has an essential role in the regulation of satellite cell polarity and asymmetric division. Our findings indicate that muscle wasting in DMD is not only caused by myofiber fragility, but is also exacerbated by impaired regeneration due to intrinsic satellite cell dysfunction. PMID:26569381

  18. Barley disease susceptibility factor RACB acts in epidermal cell polarity and positioning of the nucleus.

    PubMed

    Scheler, Björn; Schnepf, Vera; Galgenmüller, Carolina; Ranf, Stefanie; Hückelhoven, Ralph

    2016-05-01

    RHO GTPases are regulators of cell polarity and immunity in eukaryotes. In plants, RHO-like RAC/ROP GTPases are regulators of cell shaping, hormone responses, and responses to microbial pathogens. The barley (Hordeum vulgare L.) RAC/ROP protein RACB is required for full susceptibility to penetration by Blumeria graminis f.sp. hordei (Bgh), the barley powdery mildew fungus. Disease susceptibility factors often control host immune responses. Here we show that RACB does not interfere with early microbe-associated molecular pattern-triggered immune responses such as the oxidative burst or activation of mitogen-activated protein kinases. RACB also supports rather than restricts expression of defence-related genes in barley. Instead, silencing of RACB expression by RNAi leads to defects in cell polarity. In particular, initiation and maintenance of root hair growth and development of stomatal subsidiary cells by asymmetric cell division is affected by silencing expression of RACB. Nucleus migration is a common factor of developmental cell polarity and cell-autonomous interaction with Bgh RACB is required for positioning of the nucleus near the site of attack from Bgh We therefore suggest that Bgh profits from RACB's function in cell polarity rather than from immunity-regulating functions of RACB. PMID:27056842

  19. A dynamic intracellular distribution of Vangl2 accompanies cell polarization during zebrafish gastrulation

    PubMed Central

    Roszko, Isabelle; S. Sepich, Diane; Jessen, Jason R.; Chandrasekhar, Anand; Solnica-Krezel, Lilianna

    2015-01-01

    During vertebrate gastrulation, convergence and extension movements elongate embryonic tissues anteroposteriorly and narrow them mediolaterally. Planar cell polarity (PCP) signaling is essential for mediolateral cell elongation underlying these movements, but how this polarity arises is poorly understood. We analyzed the elongation, orientation and migration behaviors of lateral mesodermal cells undergoing convergence and extension movements in wild-type zebrafish embryos and mutants for the Wnt/PCP core component Vangl2 (Trilobite). We demonstrate that Vangl2 function is required at the time when cells transition to a highly elongated and mediolaterally aligned body. vangl2 mutant cells fail to undergo this transition and to migrate along a straight path with high net speed towards the dorsal midline. Instead, vangl2 mutant cells exhibit an anterior/animal pole bias in cell body alignment and movement direction, suggesting that PCP signaling promotes effective dorsal migration in part by suppressing anterior/animalward cell polarity and movement. Endogenous Vangl2 protein accumulates at the plasma membrane of mesenchymal converging cells at the time its function is required for mediolaterally polarized cell behavior. Heterochronic cell transplantations demonstrated that Vangl2 cell membrane accumulation is stage dependent and regulated by both intrinsic factors and an extracellular signal, which is distinct from PCP signaling or other gastrulation regulators, including BMP and Nodals. Moreover, mosaic expression of fusion proteins revealed enrichment of Vangl2 at the anterior cell edges of highly mediolaterally elongated cells. These results demonstrate that the dynamic Vangl2 intracellular distribution is coordinated with and necessary for the changes in convergence and extension cell behaviors during gastrulation. PMID:26062934

  20. Transcriptome Analysis of Soybean Leaf Abscission Identifies Transcriptional Regulators of Organ Polarity and Cell Fate

    PubMed Central

    Kim, Joonyup; Yang, Jinyoung; Yang, Ronghui; Sicher, Richard C.; Chang, Caren; Tucker, Mark L.

    2016-01-01

    Abscission, organ separation, is a developmental process that is modulated by endogenous and environmental factors. To better understand the molecular events underlying the progression of abscission in soybean, an agriculturally important legume, we performed RNA sequencing (RNA-seq) of RNA isolated from the leaf abscission zones (LAZ) and petioles (Non-AZ, NAZ) after treating stem/petiole explants with ethylene for 0, 12, 24, 48, and 72 h. As expected, expression of several families of cell wall modifying enzymes and many pathogenesis-related (PR) genes specifically increased in the LAZ as abscission progressed. Here, we focus on the 5,206 soybean genes we identified as encoding transcription factors (TFs). Of the 5,206 TFs, 1,088 were differentially up- or down-regulated more than eight-fold in the LAZ over time, and, within this group, 188 of the TFs were differentially regulated more than eight-fold in the LAZ relative to the NAZ. These 188 abscission-specific TFs include several TFs containing domains for homeobox, MYB, Zinc finger, bHLH, AP2, NAC, WRKY, YABBY, and auxin-related motifs. To discover the connectivity among the TFs and highlight developmental processes that support organ separation, the 188 abscission-specific TFs were then clustered based on a >four-fold up- or down-regulation in two consecutive time points (i.e., 0 and 12 h, 12 and 24 h, 24 and 48 h, or 48 and 72 h). By requiring a sustained change in expression over two consecutive time intervals and not just one or several time intervals, we could better tie changes in TFs to a particular process or phase of abscission. The greatest number of TFs clustered into the 0 and 12 h group. Transcriptional network analysis for these abscission-specific TFs indicated that most of these TFs are known as key determinants in the maintenance of organ polarity, lateral organ growth, and cell fate. The abscission-specific expression of these TFs prior to the onset of abscission and their functional

  1. Expression of Opacity Proteins Interferes with the Transmigration of Neisseria gonorrhoeae across Polarized Epithelial Cells.

    PubMed

    Stein, Daniel C; LeVan, Adriana; Hardy, Britney; Wang, Liang-Chun; Zimmerman, Lindsey; Song, Wenxia

    2015-01-01

    Neisseria gonorrhoeae (GC) establishes infection at the mucosal surface of the human genital tract, most of which is lined with polarized epithelial cells. GC can cause localized as well as disseminated infections, leading to various complications. GC constantly change their surface structures via phase and antigenic variation, which has been implicated as a means for GC to establish infection at various anatomic locations of male and female genital tracks. However, the exact contribution of each surface molecule to bacterial infectivity remains elusive due to their phase variation. Using a GC derivative that is genetically devoid of all opa genes (MS11∆Opa), this study shows that Opa expression interferes with GC transmigration across polarized human epithelial cells. MS11∆Opa transmigrates across polarized epithelial cells much faster and to a greater extent than MS11Opa+, while adhering at a similar level as MS11Opa+. When MS11Opa+, able to phase vary Opa expression, was inoculated, only those bacteria that turn off Opa expression transmigrate across the polarized epithelial monolayer. Similar to bacteria alone or co-cultured with non-polarized epithelial cells, MS11∆Opa fails to form large microcolonies at the apical surface of polarized epithelial cells. Apical inoculation of MS11Opa+, but not MS11∆Opa, induces the recruitment of the Opa host-cell receptor carcinoembryonic antigen-related cell adhesion molecules (CEACAMs) to the apical junction and the vicinity of bacterial adherent sites. Our results suggest that Opa expression limits gonococcal ability to invade into subepithelial tissues by forming tight interactions with neighboring bacteria and by inducing CEACAM redistribution to cell junctions. PMID:26244560

  2. Expression of Opacity Proteins Interferes with the Transmigration of Neisseria gonorrhoeae across Polarized Epithelial Cells

    PubMed Central

    Stein, Daniel C.; LeVan, Adriana; Hardy, Britney; Wang, Liang-Chun; Zimmerman, Lindsey; Song, Wenxia

    2015-01-01

    Neisseria gonorrhoeae (GC) establishes infection at the mucosal surface of the human genital tract, most of which is lined with polarized epithelial cells. GC can cause localized as well as disseminated infections, leading to various complications. GC constantly change their surface structures via phase and antigenic variation, which has been implicated as a means for GC to establish infection at various anatomic locations of male and female genital tracks. However, the exact contribution of each surface molecule to bacterial infectivity remains elusive due to their phase variation. Using a GC derivative that is genetically devoid of all opa genes (MS11∆Opa), this study shows that Opa expression interferes with GC transmigration across polarized human epithelial cells. MS11∆Opa transmigrates across polarized epithelial cells much faster and to a greater extent than MS11Opa+, while adhering at a similar level as MS11Opa+. When MS11Opa+, able to phase vary Opa expression, was inoculated, only those bacteria that turn off Opa expression transmigrate across the polarized epithelial monolayer. Similar to bacteria alone or co-cultured with non-polarized epithelial cells, MS11∆Opa fails to form large microcolonies at the apical surface of polarized epithelial cells. Apical inoculation of MS11Opa+, but not MS11∆Opa, induces the recruitment of the Opa host-cell receptor carcinoembryonic antigen–related cell adhesion molecules (CEACAMs) to the apical junction and the vicinity of bacterial adherent sites. Our results suggest that Opa expression limits gonococcal ability to invade into subepithelial tissues by forming tight interactions with neighboring bacteria and by inducing CEACAM redistribution to cell junctions. PMID:26244560

  3. Tethering of ICAM on target cells is required for LFA-1-dependent NK cell adhesion and granule polarization

    PubMed Central

    Gross, Catharina C.; Brzostowski, Joseph A.; Liu, Dongfang; Long, Eric O.

    2013-01-01

    αLβ2 integrin (LFA-1) has an important role in the formation of T cell and NK cell cytotoxic immunological synapses and in target cell killing. Binding of LFA-1 to ICAM on target cells promotes not only adhesion, but also polarization of cytolytic granules in NK cells. Here we tested whether LFA-1-dependent NK cell responses are regulated by the distribution and mobility of ICAM at the surface of target cells. We show that depolymerization of F-actin in NK-sensitive target cells abrogated LFA-1-dependent conjugate formation and granule polarization in primary NK cells. Degranulation, which is not controlled by LFA-1, was not impaired. Fluorescence recovery after photobleaching experiments and particle tracking by total internal reflection fluorescence microscopy revealed that ICAM-1 and ICAM-2 were distributed in largely immobile clusters. ICAM clusters were maintained and became highly mobile after actin depolymerization. Moreover, reducing ICAM-2 mobility on an NK-resistant target cell through expression of ezrin, an adapter molecule that tethers proteins to the actin cytoskeleton, enhanced LFA-1-dependent adhesion and granule polarization. Finally, while NK cells kept moving over freely diffusible ICAM-1 on a lipid bilayer, they bound and spread over solid-phase ICAM-1. We conclude that tethering, rather than clustering of ICAM promotes proper signaling by LFA-1 in NK cells. Our findings suggest that the lateral diffusion of integrin ligands on cells may be an important determinant of susceptibility to lysis by cytotoxic lymphocytes. PMID:20675589

  4. EGFR signaling promotes self-renewal through the establishment of cell polarity in Drosophila follicle stem cells

    PubMed Central

    Castanieto, Angela; Johnston, Michael J; Nystul, Todd G

    2014-01-01

    Epithelial stem cells divide asymmetrically, such that one daughter replenishes the stem cell pool and the other differentiates. We found that, in the epithelial follicle stem cell (FSC) lineage of the Drosophila ovary, epidermal growth factor receptor (EGFR) signaling functions specifically in the FSCs to promote the unique partially polarized state of the FSC, establish apical–basal polarity throughout the lineage, and promote FSC maintenance in the niche. In addition, we identified a novel connection between EGFR signaling and the cell-polarity regulator liver kinase B1 (LKB1), which indicates that EGFR signals through both the Ras–Raf–MEK–Erk pathway and through the LKB1–AMPK pathway to suppress apical identity. The development of apical–basal polarity is the earliest visible difference between FSCs and their daughters, and our findings demonstrate that the EGFR-mediated regulation of apical–basal polarity is essential for the segregation of stem cell and daughter cell fates. DOI: http://dx.doi.org/10.7554/eLife.04437.001 PMID:25437306

  5. Ultrasonic pulse detection with split spectrum processing and consecutive polarity coincidence

    SciTech Connect

    Ericsson, L.; Stepinski, T.; Dahlgren, S.

    1995-08-01

    The subject of signal processing for material noise reduction has been addressed in a large number of papers during the last decade. Several processing algorithms have been proposed, of which the Split Spectrum Processing (SSP) probably is the most renowned. The SSP technique is based on a synthetic frequency diversity approach, i.e. a filter bank is applied in order to obtain a set of signals with decorrelated noise components. Provided that the target echoes meet certain requirements, they will remain correlated in the generated set of signals. Target echo extraction may then be implemented using a suitable correlation measure. Simple target extractors such as Polarity Thresholding and Amplitude Minimization have been suggested and proven successful if the processing parameters had been correctly tuned. However, parameter tuning is not a trivial matter and relevant echoes may be lost due to the parameter sensitivity. In the paper a new target extraction algorithm, which avoids the requirement for a priori knowledge of frequency range, is introduced. The algorithm, referred to as Consecutive Polarity Coincidence, makes explicit use of the pulse characteristics of the target echo in order to implement local bandwidth estimation. If desired, a gating signal could be constructed by comparing the calculated bandwidth with a user defined threshold. Setting the threshold equal to the frequency range utilized for processing will generate a gating signal identical to the one obtained when using conventional Polarity Thresholding.

  6. Differential regulation of the Hippo pathway by adherens junctions and apical-basal cell polarity modules.

    PubMed

    Yang, Chih-Chao; Graves, Hillary K; Moya, Ivan M; Tao, Chunyao; Hamaratoglu, Fisun; Gladden, Andrew B; Halder, Georg

    2015-02-10

    Adherens junctions (AJs) and cell polarity complexes are key players in the establishment and maintenance of apical-basal cell polarity. Loss of AJs or basolateral polarity components promotes tumor formation and metastasis. Recent studies in vertebrate models show that loss of AJs or loss of the basolateral component Scribble (Scrib) cause deregulation of the Hippo tumor suppressor pathway and hyperactivation of its downstream effectors Yes-associated protein (YAP) and Transcriptional coactivator with PDZ-binding motif (TAZ). However, whether AJs and Scrib act through the same or independent mechanisms to regulate Hippo pathway activity is not known. Here, we dissect how disruption of AJs or loss of basolateral components affect the activity of the Drosophila YAP homolog Yorkie (Yki) during imaginal disc development. Surprisingly, disruption of AJs and loss of basolateral proteins produced very different effects on Yki activity. Yki activity was cell-autonomously decreased but non-cell-autonomously elevated in tissues where the AJ components E-cadherin (E-cad) or α-catenin (α-cat) were knocked down. In contrast, scrib knockdown caused a predominantly cell-autonomous activation of Yki. Moreover, disruption of AJs or basolateral proteins had different effects on cell polarity and tissue size. Simultaneous knockdown of α-cat and scrib induced both cell-autonomous and non-cell-autonomous Yki activity. In mammalian cells, knockdown of E-cad or α-cat caused nuclear accumulation and activation of YAP without overt effects on Scrib localization and vice versa. Therefore, our results indicate the existence of multiple, genetically separable inputs from AJs and cell polarity complexes into Yki/YAP regulation. PMID:25624491

  7. Diacylglycerol kinase-α controls T cell polarity by shaping diacylglycerol accumulation at the immune synapse

    PubMed Central

    Chauveau, Anne; Le Floc’h, Audrey; Bantilan, Niels S.; Koretzky, Gary A.; Huse, Morgan

    2016-01-01

    Polarization of the T cell microtubule-organizing center (MTOC) to the immunological synapse maintains the specificity of effector responses by enabling directional secretion toward the antigen-presenting cell. MTOC reorientation is guided by a sharp gradient of diacylglycerol that is centered at the synapse. Here, we used a single cell photoactivation approach to demonstrate that diacylglycerol kinase-α (DGK-α) controls T cell polarity by limiting the diffusion of diacylglycerol. DGK-α deficient T cells exhibited enlarged synaptic diacylglycerol accumulations and impaired MTOC reorientation. By contrast, T cells lacking the related isoform DGK-ζ did not display polarization defects. We also found that DGK-α localized preferentially to the periphery of the synapse, suggesting that it constrains the scope of diacylglycerol accumulation from the outside. Phosphoinositide 3-kinase activity was required for this peripheral localization pattern, establishing an intriguing link between diacylglycerol and phosphatidylinositol signaling during T cell activation. These results reveal a previously unappreciated function of DGK-α and provide insight into the mechanisms of lymphocyte polarity. PMID:25161317

  8. Identification of the arabidopsis RAM/MOR signalling network: adding new regulatory players in plant stem cell maintenance and cell polarization

    PubMed Central

    Zermiani, Monica; Begheldo, Maura; Nonis, Alessandro; Palme, Klaus; Mizzi, Luca; Morandini, Piero; Nonis, Alberto; Ruperti, Benedetto

    2015-01-01

    Background and Aims The RAM/MOR signalling network of eukaryotes is a conserved regulatory module involved in co-ordination of stem cell maintenance, cell differentiation and polarity establishment. To date, no such signalling network has been identified in plants. Methods Genes encoding the bona fide core components of the RAM/MOR pathway were identified in Arabidopsis thaliana (arabidopsis) by sequence similarity searches conducted with the known components from other species. The transcriptional network(s) of the arabidopsis RAM/MOR signalling pathway were identified by running in-depth in silico analyses for genes co-regulated with the core components. In situ hybridization was used to confirm tissue-specific expression of selected RAM/MOR genes. Key Results Co-expression data suggested that the arabidopsis RAM/MOR pathway may include genes involved in floral transition, by co-operating with chromatin remodelling and mRNA processing/post-transcriptional gene silencing factors, and genes involved in the regulation of pollen tube polar growth. The RAM/MOR pathway may act upstream of the ROP1 machinery, affecting pollen tube polar growth, based on the co-expression of its components with ROP-GEFs. In silico tissue-specific co-expression data and in situ hybridization experiments suggest that different components of the arabidopsis RAM/MOR are expressed in the shoot apical meristem and inflorescence meristem and may be involved in the fine-tuning of stem cell maintenance and cell differentiation. Conclusions The arabidopsis RAM/MOR pathway may be part of the signalling cascade that converges in pollen tube polarized growth and in fine-tuning stem cell maintenance, differentiation and organ polarity. PMID:26078466

  9. Silicon film solar cell process

    NASA Technical Reports Server (NTRS)

    Hall, R. B.; Mcneely, J. B.; Barnett, A. M.

    1984-01-01

    The most promising way to reduce the cost of silicon in solar cells while still maintaining performance is to utilize thin films (10 to 20 microns thick) of crystalline silicon. The method of solution growth is being employed to grow thin polycrystalline films of silicon on dissimilar substrates. The initial results indicate that, using tin as the solvent, this growth process only requires operating temperatures in the range of 800 C to 1000 C. Growth rates in the range of 0.4 to 2.0 microns per minute and grain sizes in the range of 20 to 100 microns were achieved on both quartz and coated steel substrates. Typically, an aspect ratio of two to three between the width and the Si grain thickness is seen. Uniform coverage of Si growth on quartz over a 2.5 x 2.5 cm area was observed.

  10. Polarization birefringence measurements for characterizing the myocardium, including healthy, infarcted, and stem-cell-regenerated tissues

    NASA Astrophysics Data System (ADS)

    Wood, Michael F. G.; Ghosh, Nirmalya; Wallenburg, Marika A.; Li, Shu-Hong; Weisel, Richard D.; Wilson, Brian C.; Li, Ren-Ke; Vitkin, I. Alex

    2010-07-01

    Myocardial infarction leads to structural remodeling of the myocardium, in particular to the loss of cardiomyocytes due to necrosis and an increase in collagen with scar formation. Stem cell regenerative treatments have been shown to alter this remodeling process, resulting in improved cardiac function. As healthy myocardial tissue is highly fibrous and anisotropic, it exhibits optical linear birefringence due to the different refractive indices parallel and perpendicular to the fibers. Accordingly, changes in myocardial structure associated with infarction and treatment-induced remodeling will alter the anisotropy exhibited by the tissue. Polarization-based linear birefringence is measured on the myocardium of adult rat hearts after myocardial infarction and compared with hearts that had received mesenchymal stem cell treatment. Both point measurement and imaging data show a decrease in birefringence in the region of infarction, with a partial rebound back toward the healthy values following regenerative treatment with stem cells. These results demonstrate the ability of optical polarimetry to characterize the micro-organizational state of the myocardium via its measured anisotropy, and the potential of this approach for monitoring regenerative treatments of myocardial infarction.

  11. The dual effects of polar methanolic extract of Hypericum perforatum L. in bladder cancer cells

    NASA Astrophysics Data System (ADS)

    Nseyo, U. O.; Nseyo, O. U.; Shiverick, K. T.; Medrano, T.; Mejia, M.; Stavropoulos, N.; Tsimaris, I.; Skalkos, D.

    2007-02-01

    Introduction and background: We have reported on the polar methanolic fraction (PMF) of Hypericum Perforatum L as a novel photosensitizing agent for photodynamic therapy (PDT) and photodynamic diagnosis (PDD). PMF has been tested in human leukemic cells, HL-60 cells, cord blood hemopoietic progenitor cells, bladder cancers derived from metastatic lymph node (T-24) and primary papillary bladder lesion (RT-4). However, the mechanisms of the effects of PMF on these human cell lines have not been elucidated. We have investigated mechanisms of PMF + light versus PMF-alone (dark experiment) in T-24 human bladder cancer cells. Methods: PMF was prepared from an aerial herb of HPL which was brewed in methanol and extracted with ether and methanol. Stock solutions of PMF were made in DSMO and stored in dark conditions. PMF contains 0.57% hypericin and 2.52% hyperforin. The T24 cell line was obtained from American Type Culture Collection (ATCC). In PDT treatment, PMF (60μg/ml) was incubated with cells, which were excited with laser light (630nm) 24 hours later. Apoptosis was determined by DNA fragmentation/laddering assay. DNA isolation was performed according to the manufacture's instructions with the Kit (Oncogene Kit#AM41). Isolated DNA samples were separated by electrophoresis in 1.5% in agarose gels and bands were visualized by ethidium bromide labeling. The initial cell cycle analysis and phase distribution was by flow cytometry. DNA synthesis was measured by [3H] thymidine incorporation, and cell cycle regulatory proteins were assayed by Western immunoblot. Results: The results of the flow cytometry showed PMF +light induced significant (40%) apoptosis in T24 cells, whereas Light or PMF alone produced little apoptosis. The percentage of cells in G 0/G I phase was decreased by 25% and in G2/M phase by 38%. The main impact was observed on the S phase which was blocked by 78% from the specific photocytotoxic process. DNA laddering analysis showed that PMF (60

  12. Wnt7a Activates the Planar Cell Polarity Pathway to Drive the Symmetric Expansion of Satellite Stem Cells

    PubMed Central

    Le Grand, Fabien; Jones, Andrew E.; Seale, Vanessa; Scimè, Anthony; Rudnicki, Michael A.

    2009-01-01

    Summary Satellite cells in skeletal muscle are a heterogeneous population of stem cells and committed progenitors. We found that quiescent satellite stem cells expressed the Wnt-receptor Fzd7, and that its candidate ligand Wnt7a was upregulated during regeneration. Notably, Wnt7a markedly stimulated the symmetric expansion of satellite stem cells but did not affect the growth or differentiation of myoblasts. Silencing of Fzd7 abrogated Wnt7a binding and stimulation of stem cell expansion. Wnt7a signaling induced the polarized distribution of the planar cell polarity effector Vangl2. Silencing of Vangl2 inhibited Wnt7a action on satellite stem cell expansion. Wnt7a overexpression enhanced muscle regeneration and increased both the number of satellite cells and the proportion of satellite stem cells. Muscle lacking Wnt7a exhibited a marked decrease in satellite cell number following regeneration. Therefore, Wnt7a signaling through the planar cell polarity pathway controls the homeostatic level of satellite stem cells and hence regulates the regenerative potential of muscle. PMID:19497282

  13. Sequential regulation of developmental events during polar morphogenesis in Caulobacter crescentus: assembly of pili on swarmer cells requires cell separation.

    PubMed Central

    Sommer, J M; Newton, A

    1988-01-01

    Pili, along with the flagellum and DNA bacteriophage receptors, are structural markers for polar morphogenesis in Caulobacter crescentus. Pili act as primary receptors for a number of small, C. crescentus-specific DNA and RNA bacteriophages, and the timing of pilus-dependent adsorption of bacteriophage phiCb5 in synchronized cell populations has led to the general conclusion that pili are formed coordinately with the flagellum and other polar surface structures in the predivisional cell. The use of rotary platinum shadow casting and electron microscopy as a direct assay for formation of flagella and pili in synchronous cell cultures now shows, however, that when expressed as fractions of the swarmer cell cycle, flagella are assembled on the predivisional cells at approximately 0.8 and that pili are assembled on the new swarmer cells at approximately 0.1 of the next cell cycle. Adsorption of pilus-specific bacteriophage phiCb5 prevented the loss of pili from swarmer cells during development, which suggests that these structures are retracted at the time of stalk formation. Examination of temperature-sensitive cell division mutants showed that the assembly of pili depends on completion of cell separation. These results indicate that the stage-specific events required for polar morphogenesis in C. crescentus occur sequentially, rather than coordinately in the cell cycle, and that the timing of these events reflects the order of underlying cell cycle steps. Images PMID:2891681

  14. Polar stimulation and constrained cell migration in microfluidic channels†

    PubMed Central

    Agrawal, Nitin; Mitchison, Timothy; Toner, Mehmet

    2010-01-01

    Asymmetrical delivery of stimuli to moving cells for perturbing spatially-heterogeneous intracellular signaling is an experimental challenge not adequately met by existing technologies. Here, we report a robust microfluidic platform allowing localized treatment of the front and/or back of moving cells which crawl through narrow channels that they completely occlude. The enabling technical element for this study is a novel design for precise, passive balancing of flow inside the microfluidic device by contacting two fluid streams before splitting them again. The microchannels constrain cell morphology and induce qualitative and quantitative changes in neutrophil chemotaxis that mimic cells crawling through tissues. PMID:18030401

  15. Epithelia suspended in collagen gels can lose polarity and express characteristics of migrating mesenchymal cells.

    PubMed

    Greenburg, G; Hay, E D

    1982-10-01

    This study of epithelial-mesenchymal transformation and epithelial cell polarity in vitro reveals that environmental conditions can have a profound effect on the epithelial phenotype, cell shape, and polarity as expressed by the presence of apical and basal surfaces. A number of different adult and embryonic epithelia were suspended within native collagen gels. Under these conditions, cells elongate, detach from the explants, and migrate as individual cells within the three-dimensional lattice, a previously unknown property of well-differentiated epithelia. Epithelial cells from adult and embryonic anterior lens were studied in detail. Elongated cells derived from the apical surface develop pseudopodia and filopodia characteristic of migratory cells and acquire a morphology and ultrastructure virtually indistinguishable from that of mesenchymal cells in vivo. It is concluded from these experiments that the three-dimensional collagen gel can promote dissociation, migration, and acquisition of secretory organelles by differentiated epithelial cells, and can abolish the apical-basal cell polarity characteristic of the original epithelium. PMID:7142291

  16. Rab11b Regulates the Apical Recycling of the Cystic Fibrosis Transmembrane Conductance Regulator in Polarized Intestinal Epithelial Cells

    PubMed Central

    Silvis, Mark R.; Bertrand, Carol A.; Ameen, Nadia; Golin-Bisello, Franca; Butterworth, Michael B.; Bradbury, Neil A.

    2009-01-01

    The cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP/PKA-activated anion channel, undergoes efficient apical recycling in polarized epithelia. The regulatory mechanisms underlying CFTR recycling are understood poorly, yet this process is required for proper channel copy number at the apical membrane, and it is defective in the common CFTR mutant, ΔF508. Herein, we investigated the function of Rab11 isoforms in regulating CFTR trafficking in T84 cells, a colonic epithelial line that expresses CFTR endogenously. Western blotting of immunoisolated Rab11a or Rab11b vesicles revealed localization of endogenous CFTR within both compartments. CFTR function assays performed on T84 cells expressing the Rab11a or Rab11b GDP-locked S25N mutants demonstrated that only the Rab11b mutant inhibited 80% of the cAMP-activated halide efflux and that only the constitutively active Rab11b-Q70L increased the rate constant for stimulated halide efflux. Similarly, RNAi knockdown of Rab11b, but not Rab11a, reduced by 50% the CFTR-mediated anion conductance response. In polarized T84 monolayers, adenoviral expression of Rab11b-S25N resulted in a 70% inhibition of forskolin-stimulated transepithelial anion secretion and a 50% decrease in apical membrane CFTR as assessed by cell surface biotinylation. Biotin protection assays revealed a robust inhibition of CFTR recycling in polarized T84 cells expressing Rab11b-S25N, demonstrating the selective requirement for the Rab11b isoform. This is the first report detailing apical CFTR recycling in a native expression system and to demonstrate that Rab11b regulates apical recycling in polarized epithelial cells. PMID:19244346

  17. Alkali-metal-atom polarization imaging in high-pressure optical-pumping cells

    NASA Astrophysics Data System (ADS)

    Baranga, A. Ben-Amar; Appelt, S.; Erickson, C. J.; Young, A. R.; Happer, W.

    1998-09-01

    We present a detailed experimental analysis of Rb-polarization imaging in high-pressure gas cells. The Rb vapor in these cells is optically pumped by high-power diode-laser arrays. We present images for high (35 G) and low (4 G) magnetic fields and for different He and Xe buffer-gas mixtures. We demonstrate that high-field imaging provides an absolute measurement of the Rb-polarization distribution in the cell, based on the fact that a spin-temperature distribution of the hyperfine magnetic sublevels is established in high-pressure buffer gases. A survey of various mechanisms that broaden the Rb magnetic-resonance lines is presented. These broadening mechanisms determine the limits of the spatial resolution achievable for images of the Rb-polarization distribution.

  18. Wnt5a functions in planar cell polarity regulation in mice

    PubMed Central

    Qian, Dong; Jones, Chonnettia; Rzadzinska, Agnieszka; Mark, Sharayne; Zhang, Xiaohui; Steel, Karen P; Dai, Xing; Chen, Ping

    2007-01-01

    Planar cell polarity (PCP) refers to the polarization of cells within the plane of a cell sheet. A distinctive epithelial PCP in vertebrates is the uniform orientation of stereociliary bundles of the sensory hair cells in the mammalian cochlea. In addition to establishing epithelial PCP, planar polarization is also required for convergent extension (CE), a polarized cellular movement that occurs during neural tube closure and cochlear extension. Studies in Drosophila and vertebrates have revealed a conserved PCP pathway, including Frizzled (Fz) receptors. Here we use the cochlea as a model system to explore the involvement of known ligands of Fz, Wnt morphogens, in PCP regulation. We show that Wnt5a forms a reciprocal expression pattern with a Wnt antagonist, the secreted frizzled-related protein 3 (Sfrp3 or Frzb), along the axis of planar polarization in the cochlear epithelium. We further demonstrate that Wnt5a antagonizes Frzb in regulating cochlear extension and stereociliary bundle orientation in vitro, and that Wnt5a−/− animals have a shortened and widened cochlea. Finally, we show that Wnt5a is required for proper subcellular distribution of a PCP protein, Ltap/Vangl2, and that Wnt5a interacts genetically with Ltap/Vangl2 for uniform orientation of stereocilia, cochlear extension, and neural tube closure. Together, these findings demonstrate that Wnt5a functions in PCP regulation in mice. PMID:17433286

  19. Polarized neural stem cells derived from adult bone marrow stromal cells develop a rosette-like structure.

    PubMed

    Darabi, Shahram; Tiraihi, Taki; Ruintan, Atefeh; Abbaszadeh, Hojatt Allah; Delshad, AliReza; Taheri, Taher

    2013-09-01

    Bone marrow stromal cells (BMSCs) were reported to form floating aggregation of cells with expression of nestin, a marker for neural stem cells (NSCs). The purpose of this investigation is to evaluate the morphology and the molecular markers expressed by NSCs derived from these neurospheres. The BMSCs were isolated from Sprague Dawley rats and evaluated for osteogenesis, lipogenesis, and expression of fibronectin, CD90, CD106, CD31, and Oct4. The BMSCs were cultured with Dulbecco's modified Eagle's medium (DMEM)/F12 containing 15% fetal bovine serum, then with DMEM/F12 containing 2% B27, basic fibroblast growth factor, and epidermal growth factor. The cell aggregates or spheres were stained with acridine orange, which showed that the neurospheres comprised aggregated cells at either premitotic/postsynthetic (PS), postmitotic/presynthetic (PM) phases of cell cycle, or a mixture of both. The NSCs harvested from the neurospheres were polar with eccentric nucleus, and at either a PS or a PM cell cycle phases, some cells at the latter phase tended to form rosette-like structures. The cells were immunostained for molecular markers such as nestin, neurofilament 68 (NF68), NF160, and NF200 and glial fibrillary acidic protein (GFAP). Myelin basic protein (MBP), the pluripotency (Oct4, Nanog, and SOX2), and the differentiation genes (NeuroD1, Tubb4, and Musashi I) were also evaluated using reverse transcription polymerase chain reaction (RT-PCR). Nestin, NF68, NF160, NF200, GFAP, O4, and N-cadherin were expressed in the NSCs. The percentage of immunoreactive cells to nestin was significantly higher than that of the other neuronal markers. MBP was not expressed in BMSCs, neurospheres, and NSCs. The neurospheres were immunoreactive to GFAP. RT-PCR showed the expression of NeuroD1 and Musashi I. The pluripotency gene (SOX2) was expressed in NSCs. Oct4 and Nanog were expressed in BMSCs, while Oct4 and SOX2 were expressed in the neurosphere. This indicates that a pluripotency

  20. Polar Processes in a 50-year Simulation of Stratospheric Chemistry and Transport

    NASA Technical Reports Server (NTRS)

    Kawa, S.R.; Douglass, A. R.; Patrick, L. C.; Allen, D. R.; Randall, C. E.

    2004-01-01

    The unique chemical, dynamical, and microphysical processes that occur in the winter polar lower stratosphere are expected to interact strongly with changing climate and trace gas abundances. Significant changes in ozone have been observed and prediction of future ozone and climate interactions depends on modeling these processes successfully. We have conducted an off-line model simulation of the stratosphere for trace gas conditions representative of 1975-2025 using meteorology from the NASA finite-volume general circulation model. The objective of this simulation is to examine the sensitivity of stratospheric ozone and chemical change to varying meteorology and trace gas inputs. This presentation will examine the dependence of ozone and related processes in polar regions on the climatological and trace gas changes in the model. The model past performance is base-lined against available observations, and a future ozone recovery scenario is forecast. Overall the model ozone simulation is quite realistic, but initial analysis of the detailed evolution of some observable processes suggests systematic shortcomings in our description of the polar chemical rates and/or mechanisms. Model sensitivities, strengths, and weaknesses will be discussed with implications for uncertainty and confidence in coupled climate chemistry predictions.

  1. Microdissection studies on the polarity of unequal division in grasshopper neuroblasts. I. Subsequent divisions in neuroblast-type cells produced against the polarity by micromanipulation.

    PubMed

    Yamashiki, N; Kawamura, K

    1986-09-01

    Equal or unequal division against the polarity of normal division was induced in grasshopper neuroblasts by means of a microdissection technique. The subsequent cell divisions were traced in order to analyse the factors that determine the polarity. Daughter cells of two types (neuroblast-type and ganglion cell type) were produced by operations in which the mitotic apparatus was rotated or shifted. Cell types were classified by such characteristics as nuclear shape, mitotic activity, and inequality or equality of the subsequent cytokinesis. It became evident that the fate of daughter cells was determined simply by the cytoplasmic volume. In 27 cases out of 40 microdissecting operations, both sister cells were recognized as of neuroblast type. Mitosis of these neuroblast-type sister cells proceeded asynchronously. The time required for neuroblast-type cells to reach metaphase of the second division depended on their volume. It is considered that the polarity of unequal division in grasshopper neuroblasts may be maintained by a joint action of the cap cells attaching to one of the polar regions of the cell and the cortex differentiated in the previous cell division. PMID:3743651

  2. Localized Patch Clamping of Plasma Membrane of a Polarized Plant Cell 1

    PubMed Central

    Taylor, Alison R.; Brownlee, Colin

    1992-01-01

    We used an ultraviolet laser to rupture a small region of cell wall of a polarized Fucus spiralis rhizoid cell and gained localized access to the plasma membrane at the growing apex. Careful control of cell turgor enabled a small portion of plasma membrane-bound cytoplasm to be exposed. Gigaohm seals allowing single-channel recordings were obtained with a high success rate using this method with conventional patch clamp techniques. ImagesFigure 1 PMID:16669092

  3. Mitotic Control of Planar Cell Polarity by Polo-like Kinase 1.

    PubMed

    Shrestha, Rezma; Little, Katherine A; Tamayo, Joel V; Li, Wenyang; Perlman, David H; Devenport, Danelle

    2015-06-01

    During cell division, polarized epithelial cells employ mechanisms to preserve cell polarity and tissue integrity. In dividing cells of the mammalian skin, planar cell polarity (PCP) is maintained through the bulk internalization, equal segregation, and polarized recycling of cortical PCP proteins. The dramatic redistribution of PCP proteins coincides precisely with cell-cycle progression, but the mechanisms coordinating PCP and mitosis are unknown. Here we identify Plk1 as a master regulator of PCP dynamics during mitosis. Plk1 interacts with core PCP component Celsr1 via a conserved polo-box domain (PBD)-binding motif, localizes to mitotic endosomes, and directly phosphorylates Celsr1. Plk1-dependent phosphorylation activates the endocytic motif specifically during mitosis, allowing bulk recruitment of Celsr1 into endosomes. Inhibiting Plk1 activity blocks PCP internalization and perturbs PCP asymmetry. Mimicking dileucine motif phosphorylation is sufficient to drive Celsr1 internalization during interphase. Thus, Plk1-mediated phosphorylation of Celsr1 ensures that PCP redistribution is precisely coordinated with mitotic entry. PMID:26004507

  4. Caveolin-1 Orchestrates TCR Synaptic Polarity, Signal Specificity, and Function in CD8 T Cells

    PubMed Central

    Tomassian, Tamar; Humphries, Lisa A.; Liu, Scot D.; Silva, Oscar; Brooks, David G.; Miceli, M. Carrie

    2013-01-01

    TCR engagement triggers the polarized recruitment of membrane, actin, and transducer assemblies within the T cell–APC contact that amplify and specify signaling cascades and Teffector activity. We report that caveolin-1, a scaffold that regulates polarity and signaling in nonlymphoid cells, is required for optimal TCR-induced actin polymerization, synaptic membrane raft polarity, and function in CD8, but not CD4, T cells. In CD8+ T cells, caveolin-1 ablation selectively impaired TCR-induced NFAT-dependent NFATc1 and cytokine gene expression, whereas caveolin-1 re-expression promoted NFATc1 gene expression. Alternatively, caveolin-1 ablation did not affect TCR-induced NF-κB–dependent Iκbα expression. Cav-1−/− mice did not efficiently promote CD8 immunity to lymphocytic choriomeningitis virus, nor did cav-1−/− OT-1+ CD8+ T cells efficiently respond to Listeria mono-cytogenes-OVA after transfer into wild-type hosts. Therefore, caveolin-1 is a T cell-intrinsic orchestrator of TCR-mediated membrane polarity and signal specificity selectively employed by CD8 T cells to customize TCR responsiveness. PMID:21849673

  5. Mitotic Control of Planar Cell Polarity by Polo-like Kinase 1

    PubMed Central

    Shrestha, Rezma; Little, Katherine A.; Tamayo, Joel V.; Li, Wenyang; Perlman, David H.; Devenport, Danelle

    2015-01-01

    SUMMARY During cell division, polarized epithelial cells employ mechanisms to preserve cell polarity and tissue integrity. In dividing cells of the mammalian skin, planar cell polarity (PCP) is maintained through the bulk internalization, equal segregation, and polarized recycling of cortical PCP proteins. The dramatic redistribution of PCP proteins coincides precisely with cell cycle progression, but the mechanisms coordinating PCP and mitosis are unknown. Here we identify Plk1 as a master regulator of PCP dynamics during mitosis. Plk1 interacts with core PCP component, Celsr1, via a conserved polo-box domain (PBD) binding motif, localizes to mitotic endosomes and directly phosphorylates Celsr1. Plk1-dependent phosphorylation activates the endocytic motif specifically during mitosis, allowing bulk recruitment of Celsr1 into endosomes. Inhibiting Plk1 activity blocks PCP internalization and perturbs PCP asymmetry. Mimicking dileucine motif phosphorylation is sufficient to drive Celsr1 internalization during interphase. Thus, Plk1-mediated phosphorylation of Celsr1 ensures PCP redistribution is precisely coordinated with mitotic entry. PMID:26004507

  6. Information processing in parallel through directionally resolved molecular polarization components in coherent multidimensional spectroscopy

    NASA Astrophysics Data System (ADS)

    Yan, Tian-Min; Fresch, Barbara; Levine, R. D.; Remacle, F.

    2015-08-01

    We propose that information processing can be implemented by measuring the directional components of the macroscopic polarization of an ensemble of molecules subject to a sequence of laser pulses. We describe the logic operation theoretically and demonstrate it by simulations. The measurement of integrated stimulated emission in different phase matching spatial directions provides a logic decomposition of a function that is the discrete analog of an integral transform. The logic operation is reversible and all the possible outputs are computed in parallel for all sets of possible multivalued inputs. The number of logic variables of the function is the number of laser pulses used in sequence. The logic function that is computed depends on the chosen chromophoric molecular complex and on its interactions with the solvent and on the two time intervals between the three pulses and the pulse strengths and polarizations. The outputs are the homodyne detected values of the polarization components that are measured in the allowed phase matching macroscopic directions, kl, k l = ∑ i l i k i where ki is the propagation direction of the ith pulse and {li} is a set of integers that encodes the multivalued inputs. Parallelism is inherently implemented because all the partial polarizations that define the outputs are processed simultaneously. The outputs, which are read directly on the macroscopic level, can be multivalued because the high dynamical range of partial polarization measurements by nonlinear coherent spectroscopy allows for fine binning of the signals. The outputs are uniquely related to the inputs so that the logic is reversible.

  7. A one-dimensional model of PCP signaling: polarized cell behavior in the notochord of the ascidian Ciona

    PubMed Central

    Kourakis, Matthew J.; Reeves, Wendy; Newman-Smith, Erin; Maury, Benoit; Abdul-Wajid, Sarah; Smith, William C.

    2014-01-01

    Despite its importance in development and physiology the planar cell polarity (PCP) pathway remains one of the most enigmatic signaling mechanisms. The notochord of the ascidian Ciona provides a unique model for investigating the PCP pathway. Interestingly, the notochord appears to be the only embryonic structure in Ciona activating the PCP pathway. Moreover, the Ciona notochord as a single-file array of forty polarized cells is a uniquely tractable system for the study of polarization dynamics and the transmission of the PCP pathway. Here, we test models for propagation of a polarizing signal, interrogating temporal, spatial and signaling requirements. A simple cell-cell relay cascading through the entire length of the notochord is not supported; instead a more complex mechanism is revealed, with interactions influencing polarity between neighboring cells, but not distant ones. Mechanisms coordinating notochord-wide polarity remain elusive, but appear to entrain general (i.e., global) polarity even while local interactions remain important. However, this global polarizer does not appear to act as a localized, spatially-restricted determinant. Coordination of polarity along the long axis of the notochord requires the PCP pathway, a role we demonstrate is temporally distinct from this pathway’s earlier role in convergent extension and intercalation. We also reveal polarity in the notochord to be dynamic: a cell’s polarity state can be changed and then restored, underscoring the Ciona notochord’s amenability for in vivo studies of PCP. PMID:25173874

  8. Polarization controlled intensity noise correlation and squeezing of four-wave mixing processes in rubidium vapor

    NASA Astrophysics Data System (ADS)

    Li, Changbiao; Jiang, Zihai; Wang, Xiuxiu; Ahmed, Irfan; Raza, Faizan; Yang, Yiheng; Zhang, Yanpeng

    2016-05-01

    We observed four-wave mixing (FWM) processes in a double-Λ level of rubidium atomic system with electromagnetically induced transparency window having different polarization. The Autler-Townes splitting of FWM induced by the polarized multi-dark-state is observed. And the two-stage line shape of correlation that exhibits a sharp peak and a broad peak is also studied. The sharp peak and the broad peak are from the correlation of two spontaneous parametric FWMs and that of the vertical component and horizontal component of two coherent FWMs. Moreover we demonstrate that the intensity noise correlation and intensity-difference squeezing can be well modulated by the relative initial phase and nonlinear phase shift. Meanwhile, we also found the following of correlation (anti-correlation) by intensity-difference squeezing (anti-squeezing). The associated results may be applicable in all-optical communication and optical information processing on photonic chips.

  9. Measuring Glass Thickness of a Reference Cell Used in a Polarized 3HE Experiment

    SciTech Connect

    Justis, N.; Chen, J.

    2005-01-01

    Studies of the spin structure of the neutron are often conducted using a polarized 3He target due to its close spin resemblance to that of a free neutron. Experiments are conducted by bombarding polarized 3He nuclei with high-energy electrons from a linear accelerator. The polarized 3He gas is contained in a glass tube-like cell called the target cell. In addition to the target cell, a reference cell is also used for calibration purposes. The thickness of each cell must be accurately determined for the analysis of the scattering data of the experiment. The thickness of a reference cell was determined by using a tunable infrared laser to create a thin-film interference pattern by reflecting the laser light off of the glass cell. The intensity of the pattern is known to vary sinusoidally as the wavelength of the laser changes. Such variation was recorded as an array of numbers by a LabView program at 26 different points on the cell. Each of the 26 sets of data were fit to an equation containing the thickness variable to determine the thickness of the glass. The cell side, or wall, thickness ranged from 1.42 mm to 1.65 mm, with an uncertainty of less than 5% in every case. End, or window, thickness measurements were also successfully taken, but have yet to be fitted to the derived equation.

  10. Transepithelial pressure pulses induce nucleotide release in polarized MDCK cells.

    PubMed

    Praetorius, H A; Frøkiaer, J; Leipziger, J

    2005-01-01

    The release of nucleotides is involved in mechanosensation in various epithelial cells. Intriguingly, kidney epithelial cells are absolutely dependent on the primary cilium to sense changes in apical laminar flow. During fluid passage, the renal epithelial cells are subjected to various mechanical stimuli in addition to changes in the laminar flow rate. In the distal part of the collecting duct, the epithelial cells are exposed to pressure changes and possibly distension during papillary contractions. The aim of the present study was to determine whether nucleotide release contributes to mechanosensation in kidney epithelial cells, thereby establishing whether pressure changes are sufficient to produce nucleotide-mediated responses. Madin-Darby canine kidney (MDCK) cells grown on permeable supports were mounted in a closed double perfusion chamber on an inverted microscope. The intracellular Ca(2+) concentration ([Ca(2+)](i)) was monitored with the Ca(2+)-sensitive fluorescence probe fluo 4. Transepithelial pressure pulses of 30-80 mm Hg produced a transient increase in [Ca(2+)](i) of MDCK cells. This response is independent of the primary cilium, since it is readily observed in immature cells that do not yet express primary cilia. The amplitudes of the pressure-induced Ca(2+) transients varied with the applied chamber pressure in a quantity-dependent manner. The ATPase apyrase and the P2Y antagonist suramin significantly reduced the pressure-induced Ca(2+) transients. Applying apyrase or suramin to both sides of the preparation simultaneously nearly abolished the pressure-induced Ca(2+) response. In conclusion, these observations suggest that rapid pressure changes induce both apical and basolateral nucleotide release that contribute to mechanosensation in kidney epithelial cells. PMID:15367389

  11. Polarization and Hyperfine Transitions of Metastable ^129Xe in Discharge Cells

    NASA Astrophysics Data System (ADS)

    Xia, Tian; Morgan, Steven; Jau, Yuan-Yu; Happer, William

    2010-03-01

    The polarization and relaxation rates of metastable ^129Xe atoms are measured with magnetic resonance spectroscopy, at both microwave frequencies, where δF = 1 transitions are induced between the sublevels, and at radiofrequencies, corresponding to δF = 0 transitions. The nuclear spin polarization of the resonant velocity group is measured to be 22±2%. However, the relaxation rate of spin polarization is much larger than the velocity changing rate, the narrow line pumping laser produces spin polarization only for atoms with resonant velocity. The relaxation of metastable xenon atoms is dominated by depolarizing collisions with ground state atoms, with lesser contributions from metastability exchange collisions. We also measure the pressure broadening coefficient of the relaxation rate by varying the temperature of the cryogenic part of the cell.

  12. Theoretical description of transverse measurements of polarization in optically-pumped Rb vapor cells

    NASA Astrophysics Data System (ADS)

    Dreiling, Joan; Tupa, Dale; Norrgard, Eric; Gay, Timothy

    2012-06-01

    In optical pumping of alkali-metal vapors, the polarization of the atoms is typically determined by probing along the entire length of the pumping beam, resulting in an averaged value of polarization over the length of the cell. Such measurements do not give any information about spatial variations of the polarization along the pump beam axis. Using a D1 probe beam oriented perpendicular to the pumping beam, we have demonstrated a heuristic method for determining the polarization along the pump beam's axis. Adapting a previously developed theory [1], we provide an analysis of the experiment which explains why this method works. The model includes the effects of Rb density, buffer gas pressure, and pump detuning. [4pt] [1] E.B. Norrgard, D. Tupa, J.M. Dreiling, and T.J. Gay, Phys. Rev. A 82, 033408 (2010).

  13. Cellulose synthesis in two secondary cell wall processes in a single cell type

    PubMed Central

    Mendu, Venugopal; Stork, Jozsef; Harris, Darby; DeBolt, Seth

    2011-01-01

    Plant cells have a rigid cell wall that constrains internal turgor pressure yet extends in a regulated and organized manner to allow the cell to acquire shape. The primary load-bearing macromolecule of a plant cell wall is cellulose, which forms crystalline microfibrils that are organized with respect to a cell's function and shape requirements. A primary cell wall is deposited during expansion whereas secondary cell wall is synthesized post expansion during differentiation. A complex form of asymmetrical cellular differentiation occurs in Arabidopsis seed coat epidermal cells, where we have recently shown that two secondary cell wall processes occur that utilize different cellulose synthase (CESA) proteins. One process is to produce pectinaceous mucilage that expands upon hydration and the other is a radial wall thickening that reinforced the epidermal cell structure. Our data illustrate polarized specialization of CESA5 in facilitating mucilage attachment to the parent seed and CESA2, CESA5 and CESA9 in radial cell wall thickening and formation of the columella. Herein, we present a model for the complexity of cellulose biosynthesis in this highly differentiated cell type with further evidence supporting each cellulosic secondary cell wall process. PMID:22057330

  14. Trophoblast glycoprotein promotes pancreatic ductal adenocarcinoma cell metastasis through Wnt/planar cell polarity signaling.

    PubMed

    He, Ping; Jiang, Shuheng; Ma, Mingze; Wang, Yang; Li, Rongkun; Fang, Fang; Tian, Guangang; Zhang, Zhigang

    2015-07-01

    Trophoblast glycoprotein (TPBG), a 72 kDa glycoprotein was identified using a monoclonal antibody, which specifically binds human trophoblast. The expression of TPBG in normal tissues is limited; however, it is upregulated in numerous types of cancer. When TPBG is expressed at a high level, this usually indicates a poor clinical outcome. In the present study, it was demonstrated that TPBG was more commonly observed in human pancreatic ductal adenocarcinoma (PDAC) compared with normal pancreatic tissue. Immunohistochemical analysis of PDAC tissue microarrays indicated that the expression of TPBG in PDAC tissues was closely correlated with the tumor-node-metastasis stage of the tumor. Silencing of TPBG in PDAC cell lines resulted in a decreased ability of cancer cell migration and invasion. Further investigation demonstrated that the Wnt/planar cell polarity signaling pathway was suppressed, as the expression of Wnt5a and the activation of c-Jun N-terminal kinase was inhibited following TPBG knockdown. In conclusion, the present study provided evidence that TPBG is involved in PDAC metastasis, and that TPBG and its associated signaling pathways may be a suitable target for PDAC therapy. PMID:25738465

  15. Comparing the O+ and H+ Escape Fluxes from Fluid and Particle-in-Cell Solutions of the Polar Wind

    NASA Astrophysics Data System (ADS)

    Eccles, J. V.; Schunk, R. W.; Barakat, A. R.

    2015-12-01

    There are different theoretical descriptions of the terrestrial polar wind. Fluid models of mass, momentum, and energy equations can be used to solve the field-aligned flow of H+ and O+ ions from the ionosphere into the earth's magnetosphere. Particle-in-cell (PIC) codes, which include kinetic processes, have also treated polar wind flow between an active ionospheric boundary condition and the outflow boundary into the magnetosphere. In study, we compare the O+ and H+ escape fluxes from the USU Ionosphere-Plasmasphere Model (IPM) [Schunk et al., 2003] with the escape fluxes from the macroscopic PIC solution of the Generalized Polar Wind (GPW) Model of Barakat and Schunk [2006]. The IPM model results at 1500km are used to supply the time-varying boundary conditions to the GPW model. The escape flux comparisons will be made at the 2.5 Re, which is a typical boundary condition radius for fluxes into MHD magnetosphere models. Classical fluid codes generate escape fluxes driven by the pressure gradients in the ionosphere, while the PIC code has additional energization processes for the polar wind fluxes. Differencing the two escape flux solutions at 2.5 Re will quantify the importance of the additional energization processes within the PIC GPW model. We will make the comparisons of escape fluxes using the model results of 4 different storm periods: an idealized storm period, April 5-8, 2000, 2002 September 27 to October 4, and 2002 October 22-29. These storm periods were chosen for the collaborative studies of the Outflow Measuring Modeling, and Merging GEM focus group. Barakat, A. R. and R. W. Schunk (2006), A three-dimensional model of the generalized polar wind, J. Geophys. Res., 111, A12314, doi:10.1029/2006JA011662. Schunk, R. W., J. V. Eccles, J. J. Sojka, D. C. Thompson, and L. Zhu (2003), Assimilation Ionosphere Model (AIM), Final report, Space Environment Corporation, Providence, Utah.

  16. Near-IR Auroral Processes in the Polar Regions of Jupiter

    NASA Astrophysics Data System (ADS)

    Kim, S. J.

    2011-10-01

    Recently, 3 micron auroral emission lines of CH4, C2H2, and C2H6 from the south polar auroral region of Jupiter were detected [1]. In order to understand the auroral processes producing these emissions, we constructed an electron precipitation model for the auroral atmosphere including H2, He, H, and the hydrocarbon molecules. We present preliminary results for the mixing ratios of these molecules in the stratosphere, which are consistent with the observed auroral emission intensities.

  17. Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes

    NASA Astrophysics Data System (ADS)

    Hansen, C. J.; Byrne, S.; Portyankina, G.; Bourke, M.; Dundas, C.; McEwen, A.; Mellon, M.; Pommerol, A.; Thomas, N.

    2013-08-01

    Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels ("araneiform" terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.

  18. Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes

    USGS Publications Warehouse

    Hansen, C.J.; Byrne, S.; Portyankina, G.; Bourke, M.; Dundas, C.; McEwen, A.; Mellon, M.; Pommerol, A.; Thomas, N.

    2013-01-01

    Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels (“araneiform” terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.

  19. Wnt4 Enhances Murine Hematopoietic Progenitor Cell Expansion Through a Planar Cell Polarity-Like Pathway

    PubMed Central

    Heinonen, Krista M.; Vanegas, Juan Ruiz; Lew, Deborah; Krosl, Jana; Perreault, Claude

    2011-01-01

    Background While the role of canonical (β-catenin-mediated) Wnt signaling in hematolymphopoiesis has been studied extensively, little is known of the potential importance of non-canonical Wnt signals in hematopoietic cells. Wnt4 is one of the Wnt proteins that can elicit non-canonical pathways. We have previously shown that retroviral overexpression of Wnt4 by hematopoietic cells increased thymic cellularity as well as the frequency of early thymic progenitors and bone marrow hematopoietic progenitor cells (HPCs). However, the molecular pathways responsible for its effect in HPCs are not known. Methodology/Principal Findings Here we report that Wnt4 stimulation resulted in the activation of the small GTPase Rac1 as well as Jnk kinases in an HPC cell line. Jnk activity was necessary, while β-catenin was dispensable, for the Wnt4-mediated expansion of primary fetal liver HPCs in culture. Furthermore, Jnk2-deficient and Wnt4 hemizygous mice presented lower numbers of HPCs in their bone marrow, and Jnk2-deficient HPCs showed increased rates of apoptosis. Wnt4 also improved HPC activity in a competitive reconstitution model in a cell-autonomous, Jnk2-dependent manner. Lastly, we identified Fz6 as a receptor for Wnt4 in immature HPCs and showed that the absence of Wnt4 led to a decreased expression of four polarity complex genes. Conclusions/Significance Our results establish a functional role for non-canonical Wnt signaling in hematopoiesis through a pathway involving Wnt4, Fz6, Rac1 and Jnk kinases. PMID:21541287

  20. Polarization compensator for optical communications

    NASA Technical Reports Server (NTRS)

    Fitzmaurice, M. W.; Abshire, J. B. (Inventor)

    1976-01-01

    An optical data communication system is provided whereby two orthogonal polarization states of a light beam carrier correspond to digital states. In such a system, automatic polarization compensation is provided by applying a dither modulating voltage to a cell exhibiting the electro-optic effect. The cell controls the relative phase of electric field components of an input light beam enabling the dither frequency component of the difference of the instantaneous powers in the two polarization states to be coherently detected. A signal derived from the coherent detection process is fed back to the cell via an integrator to form polarization bias compensating servo loop ot Type 1.

  1. Ovarian cancer stem-like cells elicit the polarization of M2 macrophages.

    PubMed

    Zhang, Qing; Cai, Da-Jun; Li, Bin

    2015-06-01

    Ovarian cancer is a life‑threatening disease in females worldwide. The polarization of macrophages is crucial in oncogenesis and the development of ovarian cancer. Increasing evidence has supported the correlation between ovarian cancer stem‑like cells (OCSCs) and macrophages, however, whether OCSCs can affect the polarization of macrophages and the underlying mechanisms involved remain to be elucidated. To examine the interplay between OCSCs and macrophages, a co‑culture system was used to detect the effect of OCSCs on macrophage polarization. The expression of cluster of differentiation 206+ and the secretion of interleukin‑10 were significantly increased and the production of tumor necrosis factor‑α was suppressed, confirming macrophage polarization to M2 macrophages. Further investigation of the macrophages in a Transwell culture system with OCSCs revealed polarization to the M2 macrophages to a similar extent, indicating that the cytokines of the OCSCs, rather than direct cell‑cell contact, are important for the polarization of M2 macrophages. Furthermore, the expression levels of chemokine (C‑C motif) ligand (CCL)2, cyclooxygenase (COX)‑2 and prostaglandin E2 (PGE2) were increased in the Transwell system and the inhibition of COX‑2, but not CCL2, significantly decreased the polarization of the M2 macrophages. In addition, mechanistic analysis revealed the importance of the COX‑2/PGE2 pathway in OCSCs to activate Janus kinase (JAK) signaling in macrophages to elicit M2 polarization. These findings provided the first evidence, to the best of our knowledge, that OCSCs are capable of altering macrophages into the M2 phenotype via the overexpression of COX‑2 and the increased production of PGE2 cytokines and that the JAK signaling pathway in macrophages is important for this alteration. The present study provided evidence supporting possible molecular targets for cancer treatment. PMID:25672286

  2. M2 polarized macrophages induced by CSE promote proliferation, migration, and invasion of alveolar basal epithelial cells.

    PubMed

    Fu, Xiao; Shi, Hengfei; Qi, Yue; Zhang, Weiyun; Dong, Ping

    2015-09-01

    Cigarette smoking plays an important role in the genesis of lung cancer, and tumor-associated macrophages (TAMs) are believed to accelerate the process. We therefore sought to clarify the relationship between cigarette smoking, TAMs and tumorigenesis. We treated macrophages (THP-1) with cigarette smoke extract (CSE) and found that the mRNA levels of IL-6, IL-10, IL-12 and TNF-α decreased, while TGF-β mRNA levels increased. CSE significantly inhibited the phagocytic ability of macrophages, as assessed by flow cytometric analysis of FITC-dextran internalization. JAK2/STAT3 was significantly activated by CSE, as determined by Western blot analysis. When the scavenger receptor CD163, a specific marker of M2 macrophages, was analyzed by flow cytometry, its expression was significantly increased. After inducing M2 polarization of THP-1 cells, we co-cultured macrophages and alveolar basal epithelial cells (A549). The proliferation of A549 cells was detected by the MTT assay and cell cycle analysis, while their migration and invasion were detected by scratch wound assay and transwell assay. The results showed that the proliferation, migration and invasion of A549 cells were significantly promoted by M2 macrophages but were slightly inhibited by CSE. In conclusion, we demonstrated that macrophage M2 polarization induced by CSE promotes proliferation, migration, and invasion of alveolar basal epithelial cells. PMID:26253658

  3. Tea4p links microtubule plus ends with the formin for3p in the establishment of cell polarity.

    PubMed

    Martin, Sophie G; McDonald, W Hayes; Yates, John R; Chang, Fred

    2005-04-01

    Microtubules regulate actin-based processes such as cell migration and cytokinesis, but molecular mechanisms are not understood. In the fission yeast Schizosaccharomyces pombe, microtubule plus ends regulate cell polarity in part by transporting the kelch repeat protein tea1p to cell ends. Here, we identify tea4p, a SH3 domain protein that binds directly to tea1p. Like tea1p, tea4p localizes to growing microtubule plus ends and to cortical sites at cell ends, and it is necessary for the establishment of bipolar growth. Tea4p binds directly to and recruits the formin for3p, which nucleates actin cable assembly. During "new end take off" (NETO), formation of a protein complex that includes tea1p, tea4p, and for3p is necessary and sufficient for the establishment of cell polarity and localized actin assembly at new cell ends. Our results suggest a molecular mechanism for how microtubule plus ends regulate the spatial distribution of actin assembly. PMID:15809031

  4. Polarity protein Par3 controls B-cell receptor dynamics and antigen extraction at the immune synapse.

    PubMed

    Reversat, Anne; Yuseff, Maria-Isabel; Lankar, Danielle; Malbec, Odile; Obino, Dorian; Maurin, Mathieu; Penmatcha, Naga Venkata Gayathri; Amoroso, Alejandro; Sengmanivong, Lucie; Gundersen, Gregg G; Mellman, Ira; Darchen, François; Desnos, Claire; Pierobon, Paolo; Lennon-Duménil, Ana-Maria

    2015-04-01

    B-cell receptor (BCR) engagement with surface-tethered antigens leads to the formation of an immune synapse, which facilitates antigen uptake for presentation to T-lymphocytes. Antigen internalization and processing rely on the early dynein-dependent transport of BCR-antigen microclusters to the synapse center, as well as on the later polarization of the microtubule-organizing center (MTOC). MTOC repositioning allows the release of proteases and the delivery of MHC class II molecules at the synapse. Whether and how these events are coordinated have not been addressed. Here we show that the ancestral polarity protein Par3 promotes BCR-antigen microcluster gathering, as well as MTOC polarization and lysosome exocytosis, at the synapse by facilitating local dynein recruitment. Par3 is also required for antigen presentation to T-lymphocytes. Par3 therefore emerges as a key molecule in the coupling of the early and late events needed for efficient extraction and processing of immobilized antigen by B-cells. PMID:25631815

  5. Polarity protein Par3 controls B-cell receptor dynamics and antigen extraction at the immune synapse

    PubMed Central

    Reversat, Anne; Yuseff, Maria-Isabel; Lankar, Danielle; Malbec, Odile; Obino, Dorian; Maurin, Mathieu; Penmatcha, Naga Venkata Gayathri; Amoroso, Alejandro; Sengmanivong, Lucie; Gundersen, Gregg G.; Mellman, Ira; Darchen, François; Desnos, Claire; Pierobon, Paolo; Lennon-Duménil, Ana-Maria

    2015-01-01

    B-cell receptor (BCR) engagement with surface-tethered antigens leads to the formation of an immune synapse, which facilitates antigen uptake for presentation to T-lymphocytes. Antigen internalization and processing rely on the early dynein-dependent transport of BCR–antigen microclusters to the synapse center, as well as on the later polarization of the microtubule-organizing center (MTOC). MTOC repositioning allows the release of proteases and the delivery of MHC class II molecules at the synapse. Whether and how these events are coordinated have not been addressed. Here we show that the ancestral polarity protein Par3 promotes BCR–antigen microcluster gathering, as well as MTOC polarization and lysosome exocytosis, at the synapse by facilitating local dynein recruitment. Par3 is also required for antigen presentation to T-lymphocytes. Par3 therefore emerges as a key molecule in the coupling of the early and late events needed for efficient extraction and processing of immobilized antigen by B-cells. PMID:25631815

  6. Development and localization of reverse-polarity mechanotransducer channels in cochlear hair cells.

    PubMed

    Beurg, Maryline; Goldring, Adam C; Ricci, Anthony J; Fettiplace, Robert

    2016-06-14

    Cochlear hair cells normally detect positive deflections of their hair bundles, rotating toward their tallest edge, which opens mechanotransducer (MT) channels by increased tension in interciliary tip links. After tip-link destruction, the normal polarity of MT current is replaced by a mechanically sensitive current evoked by negative bundle deflections. The "reverse-polarity" current was investigated in cochlear hair cells after tip-link destruction with BAPTA, in transmembrane channel-like protein isoforms 1/2 (Tmc1:Tmc2) double mutants, and during perinatal development. This current is a natural adjunct of embryonic development, present in all wild-type hair cells but declining after birth with emergence of the normal-polarity current. Evidence indicated the reverse-polarity current seen developmentally was a manifestation of the same ion channel as that evident under abnormal conditions in Tmc mutants or after tip-link destruction. In all cases, sinusoidal fluid-jet stimuli from different orientations suggested the underlying channels were opened not directly by deflections of the hair bundle but by deformation of the apical plasma membrane. Cell-attached patch recording on the hair-cell apical membrane revealed, after BAPTA treatment or during perinatal development, 90-pS stretch-activated cation channels that could be blocked by Ca(2+) and by FM1-43. High-speed Ca(2+) imaging, using swept-field confocal microscopy, showed the Ca(2+) influx through the reverse-polarity channels was not localized to the hair bundle, but distributed across the apical plasma membrane. These reverse-polarity channels, which we propose to be renamed "unconventional" mechanically sensitive channels, have some properties similar to the normal MT channels, but the relationship between the two types is still not well defined. PMID:27162344

  7. Electronic polarization-division demultiplexing based on digital signal processing in intensity-modulation direct-detection optical communication systems.

    PubMed

    Kikuchi, Kazuro

    2014-01-27

    We propose a novel configuration of optical receivers for intensity-modulation direct-detection (IM · DD) systems, which can cope with dual-polarization (DP) optical signals electrically. Using a Stokes analyzer and a newly-developed digital signal-processing (DSP) algorithm, we can achieve polarization tracking and demultiplexing in the digital domain after direct detection. Simulation results show that the power penalty stemming from digital polarization manipulations is negligibly small. PMID:24515206

  8. Proliferative effects of apical, but not basal, matrix metalloproteinase-7 activity in polarized MDCK cells

    SciTech Connect

    Harrell, Permila C.; McCawley, Lisa J.; Fingleton, Barbara; McIntyre, J. Oliver; Matrisian, Lynn M. . E-mail: lynn.matrisian@vanderbilt.edu

    2005-02-15

    Matrix metalloproteinase-7 (MMP-7) is primarily expressed in glandular epithelium. Therefore, its mechanism of action may be influenced by its regulated vectorial release to either the apical and/or basolateral compartments, where it would act on its various substrates. To gain a better understanding of where MMP-7 is released in polarized epithelium, we have analyzed its pattern of secretion in polarized MDCK cells expressing stably transfected human MMP-7 (MDCK-MMP-7), and HCA-7 and Caco2 human colon cancer cell lines. In all cell lines, latent MMP-7 was secreted to both cellular compartments, but was 1.5- to 3-fold more abundant in the basolateral compartment as compared to the apical. However, studies in the MDCK system demonstrated that MMP-7 activity was 2-fold greater in the apical compartment of MDCK-MMP-7{sup HIGH}-polarized monolayers, which suggests the apical co-release of an MMP-7 activator. In functional assays, MMP-7 over-expression increased cell saturation density as a result of increased cell proliferation with no effect on apoptosis. Apical MMP-7 activity was shown to be responsible for the proliferative effect, which occurred, as demonstrated by media transfer experiments, through cleavage of an apical substrate and not through the generation of a soluble factor. Taken together, our findings demonstrate the importance of MMP-7 secretion in relation to its mechanism of action when expressed in a polarized epithelium.

  9. Phosphatidylinositol 4,5-bisphosphate Directs Spermatid Cell Polarity and Exocyst Localization in Drosophila

    PubMed Central

    Fabian, Lacramioara; Wei, Ho-Chun; Rollins, Janet; Noguchi, Tatsuhiko; Blankenship, J. Todd; Bellamkonda, Kishan; Polevoy, Gordon; Gervais, Louis; Guichet, Antoine; Fuller, Margaret T.

    2010-01-01

    During spermiogenesis, Drosophila melanogaster spermatids coordinate their elongation in interconnected cysts that become highly polarized, with nuclei localizing to one end and sperm tail growth occurring at the other. Remarkably little is known about the signals that drive spermatid polarity and elongation. Here we identify phosphoinositides as critical regulators of these processes. Reduction of plasma membrane phosphatidylinositol 4,5-bisphosphate (PIP2) by low-level expression of the PIP2 phosphatase SigD or mutation of the PIP2 biosynthetic enzyme Skittles (Sktl) results in dramatic defects in spermatid cysts, which become bipolar and fail to fully elongate. Defects in polarity are evident from the earliest stages of elongation, indicating that phosphoinositides are required for establishment of polarity. Sktl and PIP2 localize to the growing end of the cysts together with the exocyst complex. Strikingly, the exocyst becomes completely delocalized when PIP2 levels are reduced, and overexpression of Sktl restores exocyst localization and spermatid cyst polarity. Moreover, the exocyst is required for polarity, as partial loss of function of the exocyst subunit Sec8 results in bipolar cysts. Our data are consistent with a mechanism in which localized synthesis of PIP2 recruits the exocyst to promote targeted membrane delivery and polarization of the elongating cysts. PMID:20237161

  10. A new source of Southern Ocean and Antarctic aerosol from tropospheric polar cell chemistry of sea ice emissions

    NASA Astrophysics Data System (ADS)

    Humphries, R. S.; Klekociuk, A. R.; Schofield, R.; Robinson, A. D.; Harris, N. R. P.; Keywood, M.; Ward, J.; Galbally, I.; Molloy, S.; Thomas, A.; Wilson, S. R.

    2014-12-01

    The Antarctic region is a pristine environment with minimal anthropogenic influence. Aerosol measurements in this environment allow the study of natural aerosols and polar atmospheric dynamics. Measurements in this region have been limited primarily to continental and coastal locations where permanent stations exist, with a handful of measurements in the sea ice region. The MAPS campaign (Measurements of Aerosols and Precursors during SIPEXII) occurred as part of SIPEX II (Sea Ice Physics and Ecosystems eXperiment II) voyage in Spring, 2012, and produced the first Antarctic pack-ice focused aerosol dataset aimed at characterizing new particle formation processes off the coast of East Antarctica (~65°S, 120°E). Numerous atmospheric parameters and species were measured, including the number of aerosol particles in the 3-10 nm size range, the range associated with nucleating particle formation. A latitudinal transect through the sea ice identified the Polar Front from sudden changes in nucleating particle concentrations, averaging 51cm-3 north of the front in the Ferrel cell, and 766 cm-3 south of the front, in the Polar cell region. The Polar Front location was also confirmed by meteorological and back-trajectory data. Background aerosol populations in the Polar cell fluctuated significantly but displayed no growth indicators, suggesting transport. Back-trajectories revealed that air parcels often descended from the free-troposphere within the previous 24-48 hrs. It is proposed that particle formation occurs in the free troposphere from precursors uplifted at the polar front region which, being a sea-ice/ocean region, is a significant precursor source. After tropospheric formation, populations descending at the poles are transported northward and reach the sea ice surface, missing continental stations. Current measurements of Antarctic aerosol suggest very low loading which may be explained by these circulation patterns and may underestimate total regional loading

  11. Epoxyeicosatrienoic Acids Affect Electrolyte Transport in Renal Tubular Epithelial Cells: Dependence on Cyclooxygenase and Cell Polarity

    PubMed Central

    Nüsing, Rolf M.; Schweer, Horst; Fleming, Ingrid; Zeldin, Darryl C.; Wegmann, Markus

    2007-01-01

    We investigated the effects of epoxyeicosatrienoic acids (EETs) on ion transport in the polarized renal distal tubular cell line, MDCK C7. Of the four EET regioisomers (5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET) studied, only apical, but not basolateral, application of 5,6-EET increased short circuit current (Isc) with kinetics similar to those of arachidonic acid. The ion transport was blocked by preincubation with the cyclooxygenase inhibitor indomethacin or with the chloride channel blocker NPPB. Further, both a Cl−-free bath solution and the Ca2+ antagonist verapamil blocked 5,6-EET-induced ion transport. Although the presence of the PGE2 receptors EP2, EP3, and EP4 was demonstrated, apically added PGE2 was ineffective and basolaterally added PGE2 caused a different kinetics in ion transport compared to 5,6-EET. Moreover, PGE2 sythesis in MDCK C7 cells was unaffected by 5,6-EET treatment. GC/MS/MS analysis of cell supernatants revealed the presence of the biologically inactive 5,6-dihydroxy-PGE1 in 5,6-EET-treated cells, but not in control cells. Indomethacin suppressed the formation of 5,6-dihydroxy-PGE1. 5,6-epoxy-PGE1 the precursor of 5,6-dihydroxy-PGE1, caused a similar ion transport as 5,6-EET. Cytochrome P450 enzymes homolog to human CYP2C8, CYP2C9, and CYP2J2 protein were detected immunologically in the MDCK C7 cells. Our findings suggest that 5,6-EET affects Cl-transport in renal distal tubular cells independent of PGE2 but by a mechanism, dependent on its conversion to 5,6-epoxy-PGE1 by cyclooxygenase. We suggest a role for this P450 epoxygenase product in the regulation of electrolyte transport, especially as a saluretic compound acting from the luminal side of tubular cells in the mammalian kidney. PMID:17494091

  12. Epoxyeicosatrienoic acids affect electrolyte transport in renal tubular epithelial cells: dependence on cyclooxygenase and cell polarity.

    PubMed

    Nüsing, Rolf M; Schweer, Horst; Fleming, Ingrid; Zeldin, Darryl C; Wegmann, Markus

    2007-07-01

    We investigated the effects of epoxyeicosatrienoic acids (EETs) on ion transport in the polarized renal distal tubular cell line, Madin-Darby canine kidney (MDCK) C7. Of the four EET regioisomers (5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET) studied, only apical, but not basolateral, application of 5,6-EET increased short-circuit current (I(sc)) with kinetics similar to those of arachidonic acid. The ion transport was blocked by preincubation with the cyclooxygenase inhibitor indomethacin or with the chloride channel blocker NPPB. Furthermore, both a Cl(-)-free bath solution and the Ca(2+) antagonist verapamil blocked 5,6-EET-induced ion transport. Although the presence of the PGE(2) receptors EP2, EP3, and EP4 was demonstrated, apically added PGE(2) was ineffective and basolaterally added PGE(2) caused a different kinetics in ion transport compared with 5,6-EET. Moreover, PGE(2) synthesis in MDCK C7 cells was unaffected by 5,6-EET treatment. GC/MS/MS analysis of cell supernatants revealed the presence of the biologically inactive 5,6-dihydroxy-PGE(1) in 5,6-EET-treated cells, but not in control cells. Indomethacin suppressed the formation of 5,6-dihydroxy-PGE(1). 5,6-Epoxy-PGE(1), the precursor of 5,6-dihydroxy-PGE(1), caused a similar ion transport as 5,6-EET. Cytochrome P-450 enzymes homolog to human CYP2C8, CYP2C9, and CYP2J2 protein were detected immunologically in the MDCK C7 cells. Our findings suggest that 5,6-EET affects Cl(-) transport in renal distal tubular cells independent of PGE(2) but by a mechanism, dependent on its conversion to 5,6-epoxy-PGE(1) by cyclooxygenase. We suggest a role for this P450 epoxygenase product in the regulation of electrolyte transport, especially as a saluretic compound acting from the luminal side of tubular cells in the mammalian kidney. PMID:17494091

  13. The Rho GTPase Cdc42 regulates hair cell planar polarity and cellular patterning in the developing cochlea

    PubMed Central

    Kirjavainen, Anna; Laos, Maarja; Anttonen, Tommi; Pirvola, Ulla

    2015-01-01

    Hair cells of the organ of Corti (OC) of the cochlea exhibit distinct planar polarity, both at the tissue and cellular level. Planar polarity at tissue level is manifested as uniform orientation of the hair cell stereociliary bundles. Hair cell intrinsic polarity is defined as structural hair bundle asymmetry; positioning of the kinocilium/basal body complex at the vertex of the V-shaped bundle. Consistent with strong apical polarity, the hair cell apex displays prominent actin and microtubule cytoskeletons. The Rho GTPase Cdc42 regulates cytoskeletal dynamics and polarization of various cell types, and, thus, serves as a candidate regulator of hair cell polarity. We have here induced Cdc42 inactivation in the late-embryonic OC. We show the role of Cdc42 in the establishment of planar polarity of hair cells and in cellular patterning. Abnormal planar polarity was displayed as disturbances in hair bundle orientation and morphology and in kinocilium/basal body positioning. These defects were accompanied by a disorganized cell-surface microtubule network. Atypical protein kinase C (aPKC), a putative Cdc42 effector, colocalized with Cdc42 at the hair cell apex, and aPKC expression was altered upon Cdc42 depletion. Our data suggest that Cdc42 together with aPKC is part of the machinery establishing hair cell planar polarity and that Cdc42 acts on polarity through the cell-surface microtubule network. The data also suggest that defects in apical polarization are influenced by disturbed cellular patterning in the OC. In addition, our data demonstrates that Cdc42 is required for stereociliogenesis in the immature cochlea. PMID:25770185

  14. Compartmentalized microchannel array for high-throughput analysis of single cell polarized growth and dynamics

    PubMed Central

    Geng, Tao; Bredeweg, Erin L.; Szymanski, Craig J.; Liu, Bingwen; Baker, Scott E.; Orr, Galya; Evans, James E.; Kelly, Ryan T.

    2015-01-01

    Interrogating polarized growth is technologically challenging due to extensive cellular branching and uncontrollable environmental conditions in conventional assays. Here we present a robust and high-performance microfluidic system that enables observations of polarized growth with enhanced temporal and spatial control over prolonged periods. The system has built-in tunability and versatility to accommodate a variety of scientific applications requiring precisely controlled environments. Using the model filamentous fungus, Neurospora crassa, our microfluidic system enabled direct visualization and analysis of cellular heterogeneity in a clonal fungal cell population, nuclear distribution and dynamics at the subhyphal level, and quantitative dynamics of gene expression with single hyphal compartment resolution in response to carbon source starvation and exchange. Although the microfluidic device is demonstrated on filamentous fungi, the technology is immediately extensible to a wide array of other biosystems that exhibit similar polarized cell growth, with applications ranging from bioenergy production to human health. PMID:26530004

  15. Compartmentalized microchannel array for high-throughput analysis of single cell polarized growth and dynamics

    SciTech Connect

    Geng, Tao; Bredeweg, Erin L.; Szymanski, Craig J.; Liu, Bingwen; Baker, Scott E.; Orr, Galya; Evans, James E.; Kelly, Ryan T.

    2015-11-04

    Here, interrogating polarized growth is technologically challenging due to extensive cellular branching and uncontrollable environmental conditions in conventional assays. Here we present a robust and high-performance microfluidic system that enables observations of polarized growth with enhanced temporal and spatial control over prolonged periods. The system has built-in tunability and versatility to accommodate a variety of science applications requiring precisely controlled environments. Using the model filamentous fungus, Neurospora crassa, this microfluidic system enabled direct visualization and analysis of cellular heterogeneity in a clonal fungal cell population, nuclear distribution and dynamics at the subhyphal level, and quantitative dynamics of gene expression with single hyphal compartment resolution in response to carbon source starvation and exchange experiments. Although the microfluidic device is demonstrated on filamentous fungi, our technology is immediately extensible to a wide array of other biosystems that exhibit similar polarized cell growth with applications ranging from bioenergy production to human health.

  16. Compartmentalized microchannel array for high-throughput analysis of single cell polarized growth and dynamics

    DOE PAGESBeta

    Geng, Tao; Bredeweg, Erin L.; Szymanski, Craig J.; Liu, Bingwen; Baker, Scott E.; Orr, Galya; Evans, James E.; Kelly, Ryan T.

    2015-11-04

    Here, interrogating polarized growth is technologically challenging due to extensive cellular branching and uncontrollable environmental conditions in conventional assays. Here we present a robust and high-performance microfluidic system that enables observations of polarized growth with enhanced temporal and spatial control over prolonged periods. The system has built-in tunability and versatility to accommodate a variety of science applications requiring precisely controlled environments. Using the model filamentous fungus, Neurospora crassa, this microfluidic system enabled direct visualization and analysis of cellular heterogeneity in a clonal fungal cell population, nuclear distribution and dynamics at the subhyphal level, and quantitative dynamics of gene expression withmore » single hyphal compartment resolution in response to carbon source starvation and exchange experiments. Although the microfluidic device is demonstrated on filamentous fungi, our technology is immediately extensible to a wide array of other biosystems that exhibit similar polarized cell growth with applications ranging from bioenergy production to human health.« less

  17. Polarized Dendritic Cells as Cancer Vaccines: Directing Effector-type T Cells to Tumors

    PubMed Central

    Kalinski, Pawel; Okada, Hideho

    2010-01-01

    Ex-vivo-generation and antigen loading of dendritic cells (DCs) from cancer patients helps to bypass the dysfunction of endogenous DCs. It also allows to control the process of DC maturation and to imprint in maturing DCs several functions essential for induction of effective forms of cancer immunity. Recent reports from several groups including ours demonstrate that distinct conditions of DC generation and maturation can prime DCs for preferential interaction with different (effector versus regulatory) subsets of immune cells. Moreover, differentially-generated DCs have been shown to imprint different effector mechanisms in CD4+ and CD8+ T cells (delivery of “signal three”) and to induce their different homing properties (delivery of “signal four”). These developments allow for selective induction of tumor-specific T cells with desirable effector functions and tumor-relevant homing properties and to direct the desirable types of immune cells to tumors. PMID:20409732

  18. Inducing self-rotation of cells with natural and artificial melanin in a linearly polarized alternating current electric field

    PubMed Central

    Ouyang, Mengxing; Ki Cheung, Wing; Liang, Wenfeng; Mai, John D.; Keung Liu, Wing; Jung Li, Wen

    2013-01-01

    The phenomenon of self-rotation observed in naturally and artificially pigmented cells under an applied linearly polarized alternating current (non-rotating) electrical field has been investigated. The repeatable and controllable rotation speeds of the cells were quantified and their dependence on dielectrophoretic parameters such as frequency, voltage, and waveform was studied. Moreover, the rotation behavior of the pigmented cells with different melanin content was compared to quantify the correlation between self-rotation and the presence of melanin. Most importantly, macrophages, which did not originally rotate in the applied non-rotating electric field, began to exhibit self-rotation that was very similar to that of the pigmented cells, after ingesting foreign particles (e.g., synthetic melanin or latex beads). We envision the discovery presented in this paper will enable the development of a rapid, non-intrusive, and automated process to obtain the electrical conductivities and permittivities of cellular membrane and cytoplasm in the near future. PMID:24404075

  19. The data processing of the temporarily and spatially mixed modulated polarization interference imaging spectrometer.

    PubMed

    Jian, Xiaohua; Zhang, Chunmin; Zhang, Lin; Zhao, Baochang

    2010-03-15

    Based on the basic imaging theory of the temporally and spatially mixed modulated polarization interference imaging spectrometer (TSMPIIS), a method of interferogram obtaining and processing under polychromatic light is presented. Especially, instead of traditional Fourier transform spectroscopy, according to the unique imaging theory and OPD variation of TSMPIIS, the spectrum is reconstructed respectively by wavelength. In addition, the originally experimental interferogram obtained by TSMPIIS is processed in this new way, the satisfying result of interference data and reconstructed spectrum prove that the method is very precise and feasible, which will great improve the performance of TSMPIIS. PMID:20389583

  20. Spillage of Lunar Polar Crater Volatiles onto Adjacent Terrains: The Case for Dynamic Processes

    NASA Technical Reports Server (NTRS)

    Farrell, William M.; Hurley, D M.

    2015-01-01

    We present an investigation of the release and transport of lunar polar crater volatiles onto topside regions surrounding the cold traps. The volatiles are liberated via surface energization processes associated with the harsh space environment, including solar wind plasma sputtering and impact vaporization. We find that some fraction of these volatiles can migrate from crater floors onto topside regions (those regions directly adjacent to and above the polar crater floors), and that these surrounding terrains should contain a sampling of the material originating within the crater itself. It is concluded that the nature of the volatile content on crater floors can be obtained by sampling the surface volatiles that have migrated or "spilled out" onto the adjacent terrain. This "spillage" effect could make human or robotic prospecting for crater resources significantly easier, since an assessment may not require direct entry into the very harsh polar crater environment. We also suggest that there are dynamic processes actively operating on the crater floors, and we estimate their source rates assuming dynamic equilibrium of the observed water frost and our modeled loss rates.

  1. Dissociating space charge processes from orientation polarization in poly(ethylene naphthalate) films

    NASA Astrophysics Data System (ADS)

    Hoang, M.-Q.; Boudou, L.; Le Roy, S.; Teyssedre, G.

    2014-11-01

    Thermo-stimulated depolarization current (TSDC) measurements and space charge measurements were performed on poly(ethylene naphthalene 2,6-dicarboxylate) (PEN), an aromatic and polar polyester. The aim is to develop an understanding of the dipolar and conduction processes at play in this material and in particular to understand the effects of temperature. For the TSDC measurements, when polarizing at 130 and 170 °C, the sub-glass transition and the glass transition relaxations are observed. However, in the case of a polarization temperature of 170 °C, one more current peak, labelled ρ peak, is observed at temperatures above the glass transition. This peak is not only of dipolar origin and could be associated with charge detrapping in the material. To unravel the mechanisms behind this process, a TSDC was combined with space charge measurements using the pulsed electroacoustic method (PEA) and the partial heating method was used. It is shown that the ρ peak is predominantly associated with the release of the negative charge build-up in the material.

  2. Spillage of lunar polar crater volatiles onto adjacent terrains: The case for dynamic processes

    NASA Astrophysics Data System (ADS)

    Farrell, W. M.; Hurley, D. M.; Zimmerman, M. I.

    2015-05-01

    We present an investigation of the release and transport of lunar polar crater volatiles onto topside regions surrounding the cold traps. The volatiles are liberated via surface energization processes associated with the harsh space environment, including solar wind plasma sputtering and impact vaporization. We find that some fraction of these volatiles can migrate from crater floors onto topside regions (those regions directly adjacent to and above the polar crater floors), and that these surrounding terrains should contain a sampling of the material originating within the crater itself. It is concluded that the nature of the volatile content on crater floors can be obtained by sampling the surface volatiles that have migrated or "spilled out" onto the adjacent terrain. This "spillage" effect could make human or robotic prospecting for crater resources significantly easier, since an assessment may not require direct entry into the very harsh polar crater environment. We also suggest that there are dynamic processes actively operating on the crater floors, and we estimate their source rates assuming dynamic equilibrium of the observed water frost and our modeled loss rates.

  3. Simple system for evaluating retardation of liquid crystal cells using grating type liquid crystal polarization splitters

    NASA Astrophysics Data System (ADS)

    Honma, Michinori; Nose, Toshiaki

    2016-04-01

    We propose a unique optical system for measuring the retardation of birefringent films using a pair of liquid crystal (LC) gratings; that is, the examined birefringent films are inserted between two LC gratings. Because the LC grating functions as a polarization beam splitter for circularly polarized light, the proposed system is optically equivalent to the measurement system using a pair of two circular polarizers. First, the polarization splitting performance of the LC grating is discussed. It is found that a sufficiently high voltage (such that the retardation is less than a half wavelength) has to be applied for the almost pure circularly polarized diffracted light. Next, the measurement of the retardation of a homogeneous LC cell as an examined birefringent film was demonstrated using the proposed method. The proposed method is revealed to have the same measurement performance as that of the conventional method using a pair of linear polarizers and has an advantage that there is no need for the optic axis of the test birefringent specimen to be set at a specific angle.

  4. Cell polarity pathways converge and extend to regulate neural tube closure.

    PubMed

    Zohn, Irene E; Chesnutt, Catherine R; Niswander, Lee

    2003-09-01

    Neural tube defects, such as spinabifida, craniorachischisis and anencephaly, are some of the most common birth defects in humans. Recent studies in mouse model systems suggest that craniorachischisis is associated with mutations in genes that regulate cell polarity. Using Xenopus as a model system, Wallingford and Harland have now shed light on the mechanism by which these pathways affect neural tube closure. PMID:12946622

  5. The young and happy marriage of membrane traffic and cell polarity

    PubMed Central

    Thompson, Barry J; Perez, Franck; Vaccari, Thomas

    2012-01-01

    The ESF–EMBO meeting on ‘Cell Polarity and Membrane Traffic' took place in Poland in April 2012. It brought together scientists from two once separate fields and highlighted their emerging interdependence. The wealth of scientific insights and discoveries presented laid a path for future research. PMID:22777496

  6. Porcine aminopeptidase N mediated polarized infection by porcine epidemic diarrhea virus in target cells.

    PubMed

    Cong, Yingying; Li, Xiaoxue; Bai, Yunyun; Lv, Xiaonan; Herrler, Georg; Enjuanes, Luis; Zhou, Xingdong; Qu, Bo; Meng, Fandan; Cong, Chengcheng; Ren, Xiaofeng; Li, Guangxing

    2015-04-01

    Infection of polarized intestinal epithelial cells by porcine epidemic diarrhea virus (PEDV) was characterized. Indirect immunofluorescence assay, real-time PCR, and transmission electron microscopy confirmed PEDV can be successfully propagated in immortalized swine small intestine epithelial cells (IECs). Infection involved porcine aminpeptidase N (pAPN), a reported cellular receptor for PEDV, transient expression of pAPN and siRNA targeted pAPN increased and decreased the infectivity of PEDV in IECs, respectively. Subsequently, polarized entry into and release from both Vero E6 and IECs was analyzed. PEDV entry into polarized cells and pAPN grown on membrane inserts occurs via apical membrane. The progeny virus released into the medium was also quantified which demonstrated that PEDV is preferentially released from the apical membrane. Collectively, our data demonstrate that pAPN, the cellular receptor for PEDV, mediates polarized PEDV infection. These results imply the possibility that PEDV infection may proceed by lateral spread of virus in intestinal epithelial cells. PMID:25681796

  7. Polarized exocyst-mediated vesicle fusion directs intracellular lumenogenesis within the C. elegans excretory cell

    PubMed Central

    Armenti, Stephen T.; Chan, Emily; Nance, Jeremy

    2015-01-01

    Lumenogenesis of small seamless tubes occurs through intracellular membrane growth and directed vesicle fusion events. Within the C. elegans excretory cell, which forms seamless intracellular tubes (canals) that mediate osmoregulation, lumens grow in length and diameter when vesicles fuse with the expanding lumenal surface. Here, we show that lumenal vesicle fusion depends on the small GTPase RAL-1, which localizes to vesicles and acts through the exocyst vesicle-tethering complex. Loss of either the exocyst or RAL-1 prevents excretory canal lumen extension. Within the excretory canal and other polarized cells, the exocyst co-localizes with the PAR polarity proteins PAR-3, PAR-6 and PKC-3. Using early embryonic cells to determine the functional relationships between the exocyst and PAR proteins, we show that RAL-1 recruits the exocyst to the membrane, while PAR proteins concentrate membrane-localized exocyst proteins to a polarized domain. These findings reveal that RAL-1 and the exocyst direct the polarized vesicle fusion events required for intracellular lumenogenesis of the excretory cell, suggesting mechanistic similarities in the formation of topologically distinct multicellular and intracellular lumens. PMID:25102190

  8. Polarized exocyst-mediated vesicle fusion directs intracellular lumenogenesis within the C. elegans excretory cell.

    PubMed

    Armenti, Stephen T; Chan, Emily; Nance, Jeremy

    2014-10-01

    Lumenogenesis of small seamless tubes occurs through intracellular membrane growth and directed vesicle fusion events. Within the Caenorhabditis elegans excretory cell, which forms seamless intracellular tubes (canals) that mediate osmoregulation, lumens grow in length and diameter when vesicles fuse with the expanding lumenal surface. Here, we show that lumenal vesicle fusion depends on the small GTPase RAL-1, which localizes to vesicles and acts through the exocyst vesicle-tethering complex. Loss of either the exocyst or RAL-1 prevents excretory canal lumen extension. Within the excretory canal and other polarized cells, the exocyst co-localizes with the PAR polarity proteins PAR-3, PAR-6 and PKC-3. Using early embryonic cells to determine the functional relationships between the exocyst and PAR proteins, we show that RAL-1 recruits the exocyst to the membrane, while PAR proteins concentrate membrane-localized exocyst proteins to a polarized domain. These findings reveal that RAL-1 and the exocyst direct the polarized vesicle fusion events required for intracellular lumenogenesis of the excretory cell, suggesting mechanistic similarities in the formation of topologically distinct multicellular and intracellular lumens. PMID:25102190

  9. Comparison study of distinguishing cancerous and normal prostate epithelial cells by confocal and polarization diffraction imaging

    NASA Astrophysics Data System (ADS)

    Jiang, Wenhuan; Lu, Jun Qing; Yang, Li V.; Sa, Yu; Feng, Yuanming; Ding, Junhua; Hu, Xin-Hua

    2016-07-01

    Accurate classification of malignant cells from benign ones can significantly enhance cancer diagnosis and prognosis by detection of circulating tumor cells (CTCs). We have investigated two approaches of quantitative morphology and polarization diffraction imaging on two prostate cell types to evaluate their feasibility as single-cell assay methods toward CTC detection after cell enrichment. The two cell types have been measured by a confocal imaging method to obtain their three-dimensional morphology parameters and by a polarization diffraction imaging flow cytometry (p-DIFC) method to obtain image texture parameters. The support vector machine algorithm was applied to examine the accuracy of cell classification with the morphology and diffraction image parameters. Despite larger mean values of cell and nuclear sizes of the cancerous prostate cells than the normal ones, it has been shown that the morphologic parameters cannot serve as effective classifiers. In contrast, accurate classification of the two prostate cell types can be achieved with high classification accuracies on measured data acquired separately in three measurements. These results provide strong evidence that the p-DIFC method has the potential to yield morphology-related "fingerprints" for accurate and label-free classification of the two prostate cell types.

  10. Targeting a Plk1-Controlled Polarity Checkpoint in Therapy-Resistant Glioblastoma-Propagating Cells.

    PubMed

    Lerner, Robin G; Grossauer, Stefan; Kadkhodaei, Banafsheh; Meyers, Ian; Sidorov, Maxim; Koeck, Katharina; Hashizume, Rintaro; Ozawa, Tomoko; Phillips, Joanna J; Berger, Mitchel S; Nicolaides, Theodore; James, C David; Petritsch, Claudia K

    2015-12-15

    The treatment of glioblastoma (GBM) remains challenging in part due to the presence of stem-like tumor-propagating cells that are resistant to standard therapies consisting of radiation and temozolomide. Among the novel and targeted agents under evaluation for the treatment of GBM are BRAF/MAPK inhibitors, but their effects on tumor-propagating cells are unclear. Here, we characterized the behaviors of CD133(+) tumor-propagating cells isolated from primary GBM cell lines. We show that CD133(+) cells exhibited decreased sensitivity to the antiproliferative effects of BRAF/MAPK inhibition compared to CD133(-) cells. Furthermore, CD133(+) cells exhibited an extended G2-M phase and increased polarized asymmetric cell divisions. At the molecular level, we observed that polo-like kinase (PLK) 1 activity was elevated in CD133(+) cells, prompting our investigation of BRAF/PLK1 combination treatment effects in an orthotopic GBM xenograft model. Combined inhibition of BRAF and PLK1 resulted in significantly greater antiproliferative and proapoptotic effects beyond those achieved by monotherapy (P < 0.05). We propose that PLK1 activity controls a polarity checkpoint and compensates for BRAF/MAPK inhibition in CD133(+) cells, suggesting the need for concurrent PLK1 inhibition to improve antitumor activity against a therapy-resistant cell compartment. PMID:26573800

  11. Comparison study of distinguishing cancerous and normal prostate epithelial cells by confocal and polarization diffraction imaging.

    PubMed

    Jiang, Wenhuan; Lu, Jun Qing; Yang, Li V; Sa, Yu; Feng, Yuanming; Ding, Junhua; Hu, Xin-Hua

    2016-07-01

    Accurate classification of malignant cells from benign ones can significantly enhance cancer diagnosis and prognosis by detection of circulating tumor cells (CTCs). We have investigated two approaches of quantitative morphology and polarization diffraction imaging on two prostate cell types to evaluate their feasibility as single-cell assay methods toward CTC detection after cell enrichment. The two cell types have been measured by a confocal imaging method to obtain their three-dimensional morphology parameters and by a polarization diffraction imaging flow cytometry (p-DIFC) method to obtain image texture parameters. The support vector machine algorithm was applied to examine the accuracy of cell classification with the morphology and diffraction image parameters. Despite larger mean values of cell and nuclear sizes of the cancerous prostate cells than the normal ones, it has been shown that the morphologic parameters cannot serve as effective classifiers. In contrast, accurate classification of the two prostate cell types can be achieved with high classification accuracies on measured data acquired separately in three measurements. These results provide strong evidence that the p-DIFC method has the potential to yield morphology-related “fingerprints” for accurate and label-free classification of the two prostate cell types. PMID:26616011

  12. A protein targeting signal that functions in polarized epithelial cells in vivo.

    PubMed Central

    Ali, S; Hall, J; Hazlewood, G P; Hirst, B H; Gilbert, H J

    1996-01-01

    Eukaryotic membrane-associated polypeptides often contain a glycosylphosphatidylinositol (GPI) anchor that signals the attachment of GPI lipids to these proteins. The GPI anchor can function as a basolateral or apical targeting signal in mammalian cells cultured in vitro, although the function of the GPI anchor in vivo remains to be elucidated. In this study we have evaluated the effect of fusing a GPI anchor sequence to a prokaryotic reporter protein on the cellular location of the polypeptide in polarized epithelial cells of transgenic mice. The bacterial enzyme, when fused to a eukaryotic signal peptide, was secreted through the basolateral membrane of small-intestinal enterocytes; however, when the enzyme was lined to the GPI anchor sequence the polypeptide was redirected to the apical surface of the epithelial cells. These data provide the first direct evidence that the GPI anchor functions as an apical membrane protein sorting signal in polarized epithelial cells in vivo. PMID:8645168

  13. Enhanced metabolic and redox activity of vascular aquatic plant Lemna valdiviana under polarization in Direct Photosynthetic Plant Fuel Cell.

    PubMed

    Hubenova, Yolina; Mitov, Mario

    2015-12-01

    In this study, duckweed species Lemna valdiviana was investigated as a photoautotrophycally grown biocatalyst in recently developed Direct Photosynthetic Plant Fuel Cell. Stable current outputs, reaching maximum of 226±11 mА/m(2), were achieved during the operating period. The electricity production is associated with electrons generated through the light-dependent reactions in the chloroplasts as well as the respiratory processes in the mitochondria and transferred to the anode via endogenous electron shuttle, synthesized by the plants as a specific response to the polarization. In parallel, a considerable increase in the content of proteins (47%) and reserve carbohydrates (44%) of duckweeds grown under polarization conditions was established by means of biochemical analyses. This, combined with the electricity generation, makes the technology a feasible approach for the duckweed farming. PMID:25129413

  14. Polarity establishment, morphogenesis, and cultured plant cells in space

    NASA Technical Reports Server (NTRS)

    Krikorian, Abraham D.

    1989-01-01

    Plant development entails an orderly progression of cellular events both in terms of time and geometry. There is only circumstantial evidence that, in the controlled environment of the higher plant embryo sac, gravity may play a role in embryo development. It is still not known whether or not normal embryo development and differentiation in higher plants can be expected to take place reliably and efficiently in the micro g space environment. It seems essential that more attention be given to studying aspects of reproductive biology in order to be confident that plants will survive seed to seed to seed in a space environment. Until the time arrives when successive generations of plants can be grown, the best that can be done is utilize the most appropriate systems and begin, piece meal, to accumulate information on important aspects of plant reproduction. Cultured plant cells can play an important role in these activities since they can be grown so as to be morphogenetically competent, and thus can simulate those embryogenic events more usually identified with fertilized eggs in the embryo sac of the ovule in the ovary. Also, they can be manipulated with relative ease. The extreme plasticity of such demonstrably totipotent cell systems provides a means to test environmental effects such as micro g on a potentially free-running entity. The successful manipulation and management of plant cells and propagules in space also has significance for exploitation of biotechnologies in space since such systems, perforce, are an important vehicle whereby many genetic engineering manipulations are achieved.

  15. Hybrid T-helper cells: stabilizing the moderate center in a polarized system.

    PubMed

    Huang, Sui

    2013-01-01

    Polarization of cell phenotypes, a common strategy to achieve cell type diversity in metazoa, results from binary cell-fate decisions in the branching pedigree of development. Such "either-or" fate decisions are controlled by two opposing cell fate-determining transcription factors. Each of the two distinct "master regulators" promotes differentiation of its respective sister lineage. But they also suppress one other, leading to their mutually exclusive expression in the two ensuing lineages. Thus, promiscuous coexistence of the antagonist regulators in the same cell, the hallmark of the common "undecided" progenitor of two sister lineages, is considered unstable. This antagonism ensures robust polarization into two discretely distinct cell types. But now the immune system's T-helper (Th) cells and their two canonical subtypes, Th1 and Th2 cells, tell a different story, as revealed in three papers recently published in PLOS Biology. The intermediate state that co-expresses the two opposing master regulators of the Th1 and Th2 subtypes, T-bet and Gata3, is highly stable and is not necessarily an undecided precursor. Instead, the Th1/Th2 hybrid cell is a robust new type with properties of both Th1 and Th2 cells. These hybrid cells are functionally active and possess the benefit of moderation: self-limitation of effector T cell function to prevent excessive inflammation, a permanent risk in host defense that can cause tissue damage or autoimmunity. Gene regulatory network analysis suggests that stabilization of the intermediate center in a polarizing system can be achieved by minor tweaking of the architecture of the mutual suppression gene circuit, and thus is a design option readily available to evolution. PMID:23976879

  16. Phosphorylation of Rab11-FIP2 regulates polarity in MDCK cells

    PubMed Central

    Lapierre, Lynne A.; Avant, Kenya M.; Caldwell, Cathy M.; Oztan, Asli; Apodaca, Gerard; Knowles, Byron C.; Roland, Joseph T.; Ducharme, Nicole A.; Goldenring, James R.

    2012-01-01

    The Rab11 effector Rab11-family interacting protein 2 (Rab11-FIP2) regulates transcytosis through its interactions with Rab11a and myosin Vb. Previous studies implicated Rab11-FIP2 in the establishment of polarity in Madin–Darby canine kidney (MDCK) cells through phosphorylation of Ser-227 by MARK2. Here we examine the dynamic role of Rab11-FIP2 phosphorylation on MDCK cell polarity. Endogenous Rab11-FIP2 phosphorylated on Ser-227 coalesces on vesicular plaques during the reestablishment of polarity after either monolayer wounding or calcium switch. Whereas expression of the nonphosphorylatable Rab11-FIP2(S227A) elicits a loss in lumen formation in MDCK cell cysts grown in Matrigel, the putative pseudophosphorylated Rab11-FIP2(S227E) mutant induces the formation of cysts with multiple lumens. On permeable filters, Rab11-FIP2(S227E)–expressing cells exhibit alterations in the composition of both the adherens and tight junctions. At the adherens junction, p120 catenin and K-cadherin are retained, whereas the majority of the E-cadherin is lost. Although ZO-1 is retained at the tight junction, occludin is lost and the claudin composition is altered. Of interest, the effects of Rab11-FIP2 on cellular polarity did not involve myosin Vb or Rab11a. These results indicate that Ser-227 phosphorylation of Rab11-FIP2 regulates the composition of both adherens and tight junctions and is intimately involved in the regulation of polarity in epithelial cells. PMID:22553350

  17. Development and localization of reverse-polarity mechanotransducer channels in cochlear hair cells

    PubMed Central

    Beurg, Maryline; Goldring, Adam C.; Ricci, Anthony J.; Fettiplace, Robert

    2016-01-01

    Cochlear hair cells normally detect positive deflections of their hair bundles, rotating toward their tallest edge, which opens mechanotransducer (MT) channels by increased tension in interciliary tip links. After tip-link destruction, the normal polarity of MT current is replaced by a mechanically sensitive current evoked by negative bundle deflections. The “reverse-polarity” current was investigated in cochlear hair cells after tip-link destruction with BAPTA, in transmembrane channel-like protein isoforms 1/2 (Tmc1:Tmc2) double mutants, and during perinatal development. This current is a natural adjunct of embryonic development, present in all wild-type hair cells but declining after birth with emergence of the normal-polarity current. Evidence indicated the reverse-polarity current seen developmentally was a manifestation of the same ion channel as that evident under abnormal conditions in Tmc mutants or after tip-link destruction. In all cases, sinusoidal fluid-jet stimuli from different orientations suggested the underlying channels were opened not directly by deflections of the hair bundle but by deformation of the apical plasma membrane. Cell-attached patch recording on the hair-cell apical membrane revealed, after BAPTA treatment or during perinatal development, 90-pS stretch-activated cation channels that could be blocked by Ca2+ and by FM1-43. High-speed Ca2+ imaging, using swept-field confocal microscopy, showed the Ca2+ influx through the reverse-polarity channels was not localized to the hair bundle, but distributed across the apical plasma membrane. These reverse-polarity channels, which we propose to be renamed “unconventional” mechanically sensitive channels, have some properties similar to the normal MT channels, but the relationship between the two types is still not well defined. PMID:27162344

  18. Regulation of neuronal migration by Dchs1-Fat4 planar cell polarity

    PubMed Central

    Zakaria, Sana; Mao, Yaopan; Kuta, Anna; de Sousa, Catia Ferreira; Gaufo, Gary O.; McNeill, Helen; Hindges, Robert; Guthrie, Sarah

    2014-01-01

    Summary Planar-cell polarity (PCP) describes the polarisation of cell structures and behaviors within the plane of a tissue. PCP is essential for the generation of tissue architecture during embryogenesis and for post-natal growth and tissue repair, yet how it is oriented to coordinate cell polarity remains poorly understood [1]. In Drosophila, PCP is mediated via the Frizzled-Flamingo (Fz-PCP) and Dachsous-Fat (Fat-PCP) pathways [1-3]. Fz-PCP is conserved in vertebrates but an understanding in vertebrates of whether and how Fat-PCP polarizes cells, and its relationship to Fz-PCP signaling, is lacking. Mutations in human FAT4 and DCHS1 cause Van Maldergem syndrome, characterized by severe neuronal abnormalities indicative of altered neuronal migration [4]. Here, we investigate the role and mechanisms of Fat-PCP during neuronal migration using the murine facial branchiomotor neurons (FBM) as a model. We find that Fat4 and Dchs1, key components of Fat-PCP signaling, are expressed in complementary gradients and are required for the collective tangential migration of FBM and for their PCP. Fat4 and Dchs1 are required intrinsically within the FBM and extrinsically within the neuroepithelium. Remarkably, Fat-PCP and Fz-PCP regulate FBM migration along orthogonal axes. Disruption of the Dchs1 gradients by mosaic inactivation of Dchs1 alters FBM polarity and migration. This study implies that PCP in vertebrates can be regulated via gradients of Fat4 and Dchs1 expression, which establish intracellular polarity across FBM cells during their migration. Our results also identify Fat-PCP as a novel neuronal guidance system, and reveal that Fat-PCP and Fz-PCP can act along orthogonal axes. PMID:24998526

  19. Polarized trafficking of the sorting receptor SorLA in neurons and MDCK cells.

    PubMed

    Klinger, Stine C; Højland, Anne; Jain, Shweta; Kjolby, Mads; Madsen, Peder; Svendsen, Anna Dorst; Olivecrona, Gunilla; Bonifacino, Juan S; Nielsen, Morten S

    2016-07-01

    The sorting receptor SorLA is highly expressed in neurons and is also found in other polarized cells. The receptor has been reported to participate in the trafficking of several ligands, some of which are linked to human diseases, including the amyloid precursor protein, TrkB, and Lipoprotein Lipase (LpL). Despite this, only the trafficking in nonpolarized cells has been described so far. Due to the many differences between polarized and nonpolarized cells, we examined the localization and trafficking of SorLA in epithelial Madin-Darby canine kidney (MDCK) cells and rat hippocampal neurons. We show that SorLA is mainly found in sorting endosomes and on the basolateral surface of MDCK cells and in the somatodendritic domain of neurons. This polarized distribution of SorLA respectively depends on an acidic cluster and an extended version of this cluster and involves the cellular adaptor complex AP-1. Furthermore, we show that SorLA can mediate transcytosis across a tight cell layer. PMID:27192064

  20. Fluorescence generalized polarization of cell membranes: a two-photon scanning microscopy approach.

    PubMed Central

    Yu, W; So, P T; French, T; Gratton, E

    1996-01-01

    We use the lipophilic fluorescence probe Laurdan to study cell membranes. The generalized polarization (GP) of Laurdan-labeled cells contains useful information about membrane fluidity and polarity. A high GP is usually associated with low fluidity, low polarity, or high cholesterol content of the membranes, and a low GP is the opposite. We have combined the GP method and two-photon fluorescence microscopy to provide an alternative approach to study cell membranes. Using two-photon excitation in a conventional microscope offers great advantages for studying biological samples. These advantages include efficient background rejection, low photodamage, and improved depth discrimination. We performed GP measurements on mouse fibroblast cells and observed that both intensity and GP images are not spatially uniform. We tested for possible GP artifacts arising from cellular autofluorescence and lifetime quenching, using a procedure for background fluorescence subtraction and by direct lifetime measurements in the microscope. GP measured in a single cell displays a broad distribution, and the GP of 40 different cells grown on the same cover glass is also statistically distributed. The correlations between intensity and GP images were analyzed, and no monotonic dependence between the two was found. By digitally separating high and low GP values, we found that high GP values often associate with the regions of the plasma membrane and low GP values link with the nuclear membranes. Our results also show local GP variations within the plasma and nuclear membranes. Images FIGURE 1 FIGURE 3 FIGURE 5 FIGURE 6 FIGURE 7 PMID:8789081

  1. The role of G protein-coupled receptors in cochlear planar cell polarity.

    PubMed

    Sun, Jinpeng; Zhang, Daolai; Wang, Yanfei; Lin, Hal; Yu, Xiao; Xu, Zhigang

    2016-08-01

    Planar cell polarity (PCP) is defined as the coordinated alignment of cell polarity across the tissue plane, which is important for the integration of cells into tissues. One of the best examples of PCP is in the cochlear epithelium. Several core PCP proteins have been identified to play important roles in PCP regulation, in which these proteins form complexes and associate with the cell membrane asymmetrically, mediating intercellular PCP signal transduction. Among the core PCP proteins are two G protein-coupled receptors (GPCRs), Celsr and Frizzled, both of which have been shown to play important roles in cochlear PCP regulation. Celsr and Frizzled genes are expressed in the cochlear sensory epithelium, and Frizzled1, 2, 3 and 6 show asymmetric localizations on the cell membrane of hair cells or supporting cells. In the animal model, Celsr1, Frizzled2 and Frizzled3/6 mutant or knockout mice have profound cochlear PCP deficits. Downstream of GPCR signaling, Gαi was shown to asymmetrically localize on the apical surface of hair cells, together with LGN and mInsc, Gαi controls cochlear PCP in a cell-autonomous way. Inactivity of Gαi, LGN or mInsc results in PCP deficits in the mouse cochlea. We hypothesize that GPCR-Gαi coupling plays a pivotal role in cochlear PCP regulation via connecting the intercellular PCP signals with cell-autonomous PCP machinery. Further investigations are needed to fully understand the mechanism of cochlear PCP regulation. PMID:26921719

  2. Photoreceptors in the crayfish compound eye: electrical interactions between cells as related to polarized-light sensitivity

    PubMed Central

    Muller, Kenneth J.

    1973-01-01

    1. The sensitivity to plane-polarized light and the electrical interactions of photoreceptors were examined with intracellular and extracellular micro-electrodes in excised compound eyes of the crayfish. 2. There are two types of photoreceptor: each photoreceptor cell responds best to polarized light when the electric-vector of the light is oriented in one of two orthogonal directions. Seven cells, representing each type, are grouped together to form ommatidia. 3. In each ommatidium, cells that are sensitive to the same orientation of the electric-vector of polarized light are coupled electrically. Cells having orthogonal polarized-light sensitivities are not coupled. 4. Nearly all cells studied were sensitive to orange light. A few cells of both types were found that were sensitive to blue light. Blue-sensitive cells were not coupled to orange-sensitive cells. 5. The photocurrents of both cell types produce negative extracellular potentials which can be greater than 10 mV when measured near the photoreceptive membranes within ommatidia. Evidence suggests that the extracellular potentials produced by one type of cell can effectively reduce the receptor potentials recorded in the other cell type. It is proposed that such a mutual non-synaptic interaction can make a cell more sensitive to the orientation of polarized-light than would be predicted from the cell's differential absorption of polarized light (i.e. its dichroic ratio). ImagesAB PMID:4759681

  3. Signaling through the G-protein-coupled receptor Rickets is important for polarity, detachment, and migration of the border cells in Drosophila.

    PubMed

    Anllo, Lauren; Schüpbach, Trudi

    2016-06-15

    Cell migration plays crucial roles during development. An excellent model to study coordinated cell movements is provided by the migration of border cell clusters within a developing Drosophila egg chamber. In a mutagenesis screen, we isolated two alleles of the gene rickets (rk) encoding a G-protein-coupled receptor. The rk alleles result in border cell migration defects in a significant fraction of egg chambers. In rk mutants, border cells are properly specified and express the marker Slbo. Yet, analysis of both fixed as well as live samples revealed that some single border cells lag behind the main border cell cluster during migration, or, in other cases, the entire border cell cluster can remain tethered to the anterior epithelium as it migrates. These defects are observed significantly more often in mosaic border cell clusters, than in full mutant clusters. Reduction of the Rk ligand, Bursicon, in the border cell cluster also resulted in migration defects, strongly suggesting that Rk signaling is utilized for communication within the border cell cluster itself. The mutant border cell clusters show defects in localization of the adhesion protein E-cadherin, and apical polarity proteins during migration. E-cadherin mislocalization occurs in mosaic clusters, but not in full mutant clusters, correlating well with the rk border cell migration phenotype. Our work has identified a receptor with a previously unknown role in border cell migration that appears to regulate detachment and polarity of the border cell cluster coordinating processes within the cells of the cluster themselves. PMID:27130192

  4. Laser-assisted solar cell metallization processing

    NASA Technical Reports Server (NTRS)

    Rohatgi, A.; Gupta, S.; Mcmullin, P. G.; Palaschak, P. A.

    1985-01-01

    Laser-assisted processing techniques for producing high-quality solar cell metallization patterns are being investigated, developed, and characterized. The tasks comprising these investigations are outlined.

  5. Energy requirements of the switchable polarity solvent forward osmosis (SPS-FO) water purification process

    SciTech Connect

    Wendt, Daniel S.; Orme, Christopher J.; Mines, Gregory L.; Wilson, Aaron D.

    2015-08-01

    A model was developed to estimate the process energy requirements of a switchable polarity solvent forward osmosis (SPS FO) system for water purification from aqueous NaCl feed solution concentrations ranging from 0.5 to 4.0 molal at an operational scale of 480 m3/day (feed stream). The model indicates recovering approximately 90% of the water from a feed solution with NaCl concentration similar to seawater using SPS FO would have total equivalent energy requirements between 2.4 and 4.3 kWh per m3 of purified water product. The process is predicted to be competitive with current costs for disposal/treatment of produced water from oil and gas drilling operations. As a result, once scaled up the SPS FO process may be a thermally driven desalination process that can compete with the cost of seawater reverse osmosis.

  6. Energy requirements of the switchable polarity solvent forward osmosis (SPS-FO) water purification process

    DOE PAGESBeta

    Wendt, Daniel S.; Orme, Christopher J.; Mines, Gregory L.; Wilson, Aaron D.

    2015-08-01

    A model was developed to estimate the process energy requirements of a switchable polarity solvent forward osmosis (SPS FO) system for water purification from aqueous NaCl feed solution concentrations ranging from 0.5 to 4.0 molal at an operational scale of 480 m3/day (feed stream). The model indicates recovering approximately 90% of the water from a feed solution with NaCl concentration similar to seawater using SPS FO would have total equivalent energy requirements between 2.4 and 4.3 kWh per m3 of purified water product. The process is predicted to be competitive with current costs for disposal/treatment of produced water from oilmore » and gas drilling operations. As a result, once scaled up the SPS FO process may be a thermally driven desalination process that can compete with the cost of seawater reverse osmosis.« less

  7. In Vitro Polarization of Colonoids to Create an Intestinal Stem Cell Compartment

    PubMed Central

    Attayek, Peter J.; Ahmad, Asad A.; Wang, Yuli; Williamson, Ian; Sims, Christopher E.; Magness, Scott T.; Allbritton, Nancy L.

    2016-01-01

    The polarity of proliferative and differentiated cellular compartments of colonic crypts is believed to be specified by gradients of key mitogens and morphogens. Indirect evidence demonstrates a tight correlation between Wnt- pathway activity and the basal-luminal patterning; however, to date there has been no direct experimental manipulation demonstrating that a chemical gradient of signaling factors can produce similar patterning under controlled conditions. In the current work, colonic organoids (colonoids) derived from cultured, multicellular organoid fragments or single stem cells were exposed in culture to steep linear gradients of two Wnt-signaling ligands, Wnt-3a and R-spondin1. The use of a genetically engineered Sox9-Sox9EGFP:CAGDsRED reporter gene mouse model and EdU-based labeling enabled crypt patterning to be quantified in the developing colonoids. Colonoids derived from multicellular fragments cultured for 5 days under a Wnt-3a or a combined Wnt-3a and R-spondin1 gradient were highly polarized with proliferative cells localizing to the region of the higher morphogen concentration. In a Wnt-3a gradient, Sox9EGFP polarization was 7.3 times greater than that of colonoids cultured in the absence of a gradient; and the extent of EdU polarization was 2.2 times greater than that in the absence of a gradient. Under a Wnt-3a/R-spondin1 gradient, Sox9EGFP polarization was 8.2 times greater than that of colonoids cultured in the absence of a gradient while the extent of EdU polarization was 10 times greater than that in the absence of a gradient. Colonoids derived from single stem cells cultured in Wnt-3a/R-spondin1 gradients were most highly polarized demonstrated by a Sox9EGFP polarization 20 times that of colonoids grown in the absence of a gradient. This data provides direct evidence that a linear gradient of Wnt signaling factors applied to colonic stem cells is sufficient to direct patterning of the colonoid unit in culture. PMID:27100890

  8. Polarization of Diploid Daughter Cells Directed by Spatial Cues and GTP Hydrolysis of Cdc42 in Budding Yeast

    PubMed Central

    Narayan, Monisha; Chou, Ching-Shan; Park, Hay-Oak

    2013-01-01

    Cell polarization occurs along a single axis that is generally determined by a spatial cue. Cells of the budding yeast exhibit a characteristic pattern of budding, which depends on cell-type-specific cortical markers, reflecting a genetic programming for the site of cell polarization. The Cdc42 GTPase plays a key role in cell polarization in various cell types. Although previous studies in budding yeast suggested positive feedback loops whereby Cdc42 becomes polarized, these mechanisms do not include spatial cues, neglecting the normal patterns of budding. Here we combine live-cell imaging and mathematical modeling to understand how diploid daughter cells establish polarity preferentially at the pole distal to the previous division site. Live-cell imaging shows that daughter cells of diploids exhibit dynamic polarization of Cdc42-GTP, which localizes to the bud tip until the M phase, to the division site at cytokinesis, and then to the distal pole in the next G1 phase. The strong bias toward distal budding of daughter cells requires the distal-pole tag Bud8 and Rga1, a GTPase activating protein for Cdc42, which inhibits budding at the cytokinesis site. Unexpectedly, we also find that over 50% of daughter cells lacking Rga1 exhibit persistent Cdc42-GTP polarization at the bud tip and the distal pole, revealing an additional role of Rga1 in spatiotemporal regulation of Cdc42 and thus in the pattern of polarized growth. Mathematical modeling indeed reveals robust Cdc42-GTP clustering at the distal pole in diploid daughter cells despite random perturbation of the landmark cues. Moreover, modeling predicts different dynamics of Cdc42-GTP polarization when the landmark level and the initial level of Cdc42-GTP at the division site are perturbed by noise added in the model. PMID:23437206

  9. Concomitant use of polarization and positive phase contrast microscopy for the study of microbial cells.

    PubMed

    Žižka, Zdeněk; Gabriel, Jiří

    2015-11-01

    Polarization and positive phase contrast microscope were concomitantly used in the study of the internal structure of microbial cells. Positive phase contrast allowed us to view even the fine cell structure with a refractive index approaching that of the surrounding environment, e.g., the cytoplasm, and transferred the invisible phase image to a visible amplitude image. With polarization microscopy, crossed polarizing filters together with compensators and a rotary stage showed the birefringence of different cell structures. Material containing algae was collected in ponds in Sýkořice and Zbečno villages (Křivoklát region). The objects were studied in laboratory microscopes LOMO MIN-8 Sankt Petersburg and Polmi A Carl Zeiss Jena fitted with special optics for positive phase contrast, polarizers, analyzers, compensators, rotary stages, and digital SLR camera Nikon D 70 for image capture. Anisotropic granules were found in the cells of flagellates of the order Euglenales, in green algae of the orders Chlorococcales and Chlorellales, and in desmid algae of the order Desmidiales. The cell walls of filamentous algae of the orders Zygnematales and Ulotrichales were found to exhibit significant birefringence; in addition, relatively small amounts of small granules were found in the cytoplasm. A typical shape-related birefringence of the cylindrical walls and the septa between the cells differed in intensity, which was especially apparent when using a Zeiss compensator RI-c during its successive double setting. In conclusion, the anisotropic granules found in the investigated algae mostly showed strong birefringence and varied in number, size, and location of the cells. Representatives of the order Chlorococcales contained the highest number of granules per cell, and the size of these granules was almost double than that of the other monitored microorganisms. Very strong birefringence was exhibited by cell walls of filamentous algae; it differed in the intensity

  10. A theory of elementary photophysical processes with the participation of excess electrons in polar liquids

    NASA Astrophysics Data System (ADS)

    Misurkin, I. A.; Titov, S. V.

    2008-10-01

    The main concepts of the new theory of processes with the participation of excess electrons in polar liquids are considered. The theory takes into account that (1) polar liquids are electrostatically inhomogeneous (local potentials on molecules are different) and (2) a molecule can accept an electron for a short time to produce an anion in an unstable state with a certain energy and lifetime. A discrete model of a substance consisting of molecules with constant dipole moments is used. Excess electrons in a liquid are described by energy distribution density, and the behavior of electrons, by quantum mechanics equations. The experimental data on the photoionization of water and aqueous solutions of salts and the low threshold energy of photons (˜6.5 eV) at which solvated electrons appear in water are explained. The absorption spectra of water with excess electrons at the first and subsequent time moments after their photogeneration are reproduced theoretically. The dependence of the photoemission of solvated electrons from potassium-ammonia solutions on the energy of photons is interpreted. The continuous spectrum of spontaneous radiation of solvated electrons in liquid ammonia and water is calculated. The optical absorption spectra of solvated electrons in such polar liquids as water and ammonia are reproduced.

  11. Complete all-optical processing polarization-based binary logic gates and optical processors.

    PubMed

    Zaghloul, Y A; Zaghloul, A R M

    2006-10-16

    We present a complete all-optical-processing polarization-based binary-logic system, by which any logic gate or processor can be implemented. Following the new polarization-based logic presented in [Opt. Express 14, 7253 (2006)], we develop a new parallel processing technique that allows for the creation of all-optical-processing gates that produce a unique output either logic 1 or 0 only once in a truth table, and those that do not. This representation allows for the implementation of simple unforced OR, AND, XOR, XNOR, inverter, and more importantly NAND and NOR gates that can be used independently to represent any Boolean expression or function. In addition, the concept of a generalized gate is presented which opens the door for reconfigurable optical processors and programmable optical logic gates. Furthermore, the new design is completely compatible with the old one presented in [Opt. Express 14, 7253 (2006)], and with current semiconductor based devices. The gates can be cascaded, where the information is always on the laser beam. The polarization of the beam, and not its intensity, carries the information. The new methodology allows for the creation of multiple-input-multiple-output processors that implement, by itself, any Boolean function, such as specialized or non-specialized microprocessors. Three all-optical architectures are presented: orthoparallel optical logic architecture for all known and unknown binary gates, singlebranch architecture for only XOR and XNOR gates, and the railroad (RR) architecture for polarization optical processors (POP). All the control inputs are applied simultaneously leading to a single time lag which leads to a very-fast and glitch-immune POP. A simple and easy-to-follow step-by-step algorithm is provided for the POP, and design reduction methodologies are briefly discussed. The algorithm lends itself systematically to software programming and computer-assisted design. As examples, designs of all binary gates, multiple

  12. Evaluation of Surface Sorption Processes Using Spectral Induced Polarization and a (22)Na Tracer.

    PubMed

    Hao, Na; Moysey, Stephen M J; Powell, Brian A; Ntarlagiannis, Dimitrios

    2015-08-18

    We investigate mechanisms controlling the complex electrical conductivity of a porous media using noninvasive spectral induced polarization (SIP) measurements of a silica gel during a pH dependent surface adsorption experiment. Sorption of sodium on silica gel surfaces was monitored as the pH of a column was equilibrated at 5.0 and then successively raised to 6.5 and 8.0, but the composition of the 0.01 M NaCl solution was otherwise unchanged. SIP measurements show an increase in the imaginary conductivity of the sample (17.82 ± 0.07 μS/cm) in response to the pH change, interpreted as deprotonation of silanol groups on the silica gel surface followed by sorption of sodium cations. Independent measurements of Na(+) accumulation on grain surfaces performed using a radioactive (22)Na tracer support the interpretation of pH-dependent sorption as a dominant process controlling the electrical properties of the silica gel (R(2) = 0.99) and confirms the importance of grain polarization (versus membrane polarization) in influencing SIP measurements of silicate minerals. The number of surface sorption sites estimated by fitting a mechanistic, triple-layer model for the complex conductivity to the SIP data (13.22 × 10(16) sites/m(2)) was 2.8 times larger than that estimated directly by a (22)Na mass balance (5.13 × 10(16) sites/m(2)), suggesting additional contributions to polarization exist. PMID:26191613

  13. Unloading Versus Driven Processes Derived from Auroral Energy Deposition and Polar Cap Size

    NASA Technical Reports Server (NTRS)

    Brittnacher, M. J.; Parks, G. K.; Fillingim, M. O.; Elsen, R.; Chua, D.; Germany, G. A.; Spann, J. F., Jr.

    1998-01-01

    The intensity of far ultraviolet auroral emissions at all local times during the three substorm phases has been monitored by the Ultraviolet Imager (UVI) on the Polar spacecraft for many substorms. Changes in the energy flux and characteristic energy of the precipitating electrons can be derived from these observations by modeling of the spectral emission processes. The global and local energy deposition is a new parameter that can be used in substorm studies since it provides a measure of energy transfer from the tail to the ionosphere due to precipitating electrons at a time resolution of three minutes. The polar cap area and area of auroral emissions can also be determined at high time resolution during substorms from the UVI images. An example of a substorm that appears to be driven by solar wind dynamic pressure alone will be presented. The polar cap area and other parameters do not indicate a growth phase prior to substorm onset. In another example, the slow growth phase followed by a very rapid increase in energy deposition during the expansion phase will be shown. This substorm was preceded by a southward IMF orientation. In these two examples, the role the solar wind in determining polar cap area is discussed. The time development of the area of auroral emissions is also discussed in relation to substorm phase and energy deposition. If the auroral emissions occur on closed field lines then the area of auroral emissions may provide an indication of changes in the thickness of the plasma sheet during each substorm phase.

  14. Paraxial protocadherin coordinates cell polarity during convergent extension via Rho A and JNK

    PubMed Central

    Unterseher, Frank; Hefele, Joerg A; Giehl, Klaudia; De Robertis, Eddy M; Wedlich, Doris; Schambony, Alexandra

    2004-01-01

    Convergent extension movements occur ubiquitously in animal development. This special type of cell movement is controlled by the Wnt/planar cell polarity (PCP) pathway. Here we show that Xenopus paraxial protocadherin (XPAPC) functionally interacts with the Wnt/PCP pathway in the control of convergence and extension (CE) movements in Xenopus laevis. XPAPC functions as a signalling molecule that coordinates cell polarity of the involuting mesoderm in mediolateral orientation and thus selectively promotes convergence in CE movements. XPAPC signals through the small GTPases Rho A and Rac 1 and c-jun N-terminal kinase (JNK). Loss of XPAPC function blocks Rho A-mediated JNK activation. Despite common downstream components, XPAPC and Wnt/PCP signalling are not redundant, and the activity of both, XPAPC and PCP signalling, is required to coordinate CE movements. PMID:15297873

  15. Solvent polarity and nanoscale morphology in bulk heterojunction organic solar cells: A case study

    SciTech Connect

    Thomas, Ajith; Elsa Tom, Anju; Ison, V. V. E-mail: praveen@materials.iisc.ernet.in; Rao, Arun D.; Varman, K. Arul; Ranjith, K.; Ramamurthy, Praveen C. E-mail: praveen@materials.iisc.ernet.in; Vinayakan, R.

    2014-03-14

    Organic bulk heterojunction solar cells were fabricated under identical experimental conditions, except by varying the solvent polarity used for spin coating the active layer components and their performance was evaluated systematically. Results showed that presence of nitrobenzene-chlorobenzene composition governs the morphology of active layer formed, which is due to the tuning of solvent polarity as well as the resulting solubility of the P3HT:PCBM blend. Trace amount of nitrobenzene favoured the formation of better organised P3HT domains, as evident from conductive AFM, tapping mode AFM and surface, and cross-sectional SEM analysis. The higher interfacial surface area thus generated produced cells with high efficiency. But, an increase in the nitrobenzene composition leads to a decrease in cell performance, which is due to the formation of an active layer with larger size polymer domain networks with poor charge separation possibility.

  16. The polarity protein Baz forms a platform for the centrosome orientation during asymmetric stem cell division in the Drosophila male germline

    PubMed Central

    Inaba, Mayu; Venkei, Zsolt G; Yamashita, Yukiko M

    2015-01-01

    Many stem cells divide asymmetrically in order to balance self-renewal with differentiation. The essence of asymmetric cell division (ACD) is the polarization of cells and subsequent division, leading to unequal compartmentalization of cellular/extracellular components that confer distinct cell fates to daughter cells. Because precocious cell division before establishing cell polarity would lead to failure in ACD, these two processes must be tightly coupled; however, the underlying mechanism is poorly understood. In Drosophila male germline stem cells, ACD is prepared by stereotypical centrosome positioning. The centrosome orientation checkpoint (COC) further serves to ensure ACD by preventing mitosis upon centrosome misorientation. In this study, we show that Bazooka (Baz) provides a platform for the correct centrosome orientation and that Baz-centrosome association is the key event that is monitored by the COC. Our work provides a foundation for understanding how the correct cell polarity may be recognized by the cell to ensure productive ACD. DOI: http://dx.doi.org/10.7554/eLife.04960.001 PMID:25793442

  17. Thimerosal compromises human dendritic cell maturation, IL-12 production, chemokine release, and T-helper polarization

    PubMed Central

    Loison, Emily; Gougeon, Marie-Lise

    2014-01-01

    Thimerosal is a preservative used in multidose vials of vaccine formulations to prevent bacterial and fungal contamination. We recently reported that nanomolar concentrations of thimerosal induce cell cycle arrest of human T cells activated via the TCR and inhibition of proinflammatory cytokine production, thus interfering with T-cell functions. Given the essential role of dendritic cells (DCs) in T-cell polarization and vaccine immunity, we studied the influence of non-toxic concentrations of thimerosal on DC maturation and functions. Ex-vivo exposure of human monocyte-derived DCs to nanomolar concentrations of thimerosal prevented LPS-induced DC maturation, as evidenced by the inhibition of morphological changes and a decreased expression of the maturation markers CD86 and HLA-DR. In addition thimerosal dampened their proinflammatory response, in particular the production of the Th1 polarizing cytokine IL-12, as well as TNF-α and IL-6. DC-dependent T helper polarization was altered, leading to a decreased production of IFN-γ IP10 and GM-CSF and increased levels of IL-8, IL-9, and MIP-1α. Although multi-dose vials of vaccines containing thimerosal remain important for vaccine delivery, our results alert about the ex-vivo immunomodulatory effects of thimerosal on DCs, a key player for the induction of an adaptive response PMID:25424939

  18. Microtubules Regulate Migratory Polarity through Rho/ROCK Signaling in T Cells

    PubMed Central

    Takesono, Aya; Heasman, Sarah J.; Wojciak-Stothard, Beata; Garg, Ritu; Ridley, Anne J.

    2010-01-01

    Background Migrating leukocytes normally have a polarized morphology with an actin-rich lamellipodium at the front and a uropod at the rear. Microtubules (MTs) are required for persistent migration and chemotaxis, but how they affect cell polarity is not known. Methodology/Principal Findings Here we report that T cells treated with nocodazole to disrupt MTs are unable to form a stable uropod or lamellipodium, and instead often move by membrane blebbing with reduced migratory persistence. However, uropod-localized receptors and ezrin/radixin/moesin proteins still cluster in nocodazole-treated cells, indicating that MTs are required specifically for uropod stability. Nocodazole stimulates RhoA activity, and inhibition of the RhoA target ROCK allows nocodazole-treated cells to re-establish lamellipodia and uropods and persistent migratory polarity. ROCK inhibition decreases nocodazole-induced membrane blebbing and stabilizes MTs. The myosin inhibitor blebbistatin also stabilizes MTs, indicating that RhoA/ROCK act through myosin II to destabilize MTs. Conclusions/Significance Our results indicate that RhoA/ROCK signaling normally contributes to migration by affecting both actomyosin contractility and MT stability. We propose that regulation of MT stability and RhoA/ROCK activity is a mechanism to alter T-cell migratory behavior from lamellipodium-based persistent migration to bleb-based migration with frequent turning. PMID:20098744

  19. Gaalas/Gaas Solar Cell Process Study

    NASA Technical Reports Server (NTRS)

    Almgren, D. W.; Csigi, K. I.

    1980-01-01

    Available information on liquid phase, vapor phase (including chemical vapor deposition) and molecular beam epitaxy growth procedures that could be used to fabricate single crystal, heteroface, (AlGa) As/GaAs solar cells, for space applications is summarized. A comparison of the basic cost elements of the epitaxy growth processes shows that the current infinite melt LPE process has the lower cost per cell for an annual production rate of 10,000 cells. The metal organic chemical vapor deposition (MO-CVD) process has the potential for low cost production of solar cells but there is currently a significant uncertainty in process yield, i.e., the fraction of active material in the input gas stream that ends up in the cell. Additional work is needed to optimize and document the process parameters for the MO-CVD process.

  20. Planar cell polarity genes, Celsr1-3, in neural development.

    PubMed

    Feng, Jia; Han, Qi; Zhou, Libing

    2012-06-01

    flamingo is among the 'core' planar cell-polarity genes, protein of which belongs to a unique cadherin subfamily. In contrast to the classic cadherins, composed of several extracellular cadherin repeats, one transmembrane domain and one cytoplasmic segment linked to catenin binding, Drosophila Flamingo has seven transmembrane segments and a cytoplasmic tail with no catenin-binding sequence. In Drosophila, Flamingo has pleotropic roles in controlling epithelial polarity and neuronal morphogenesis. Three mammalian orthologs of flamingo, Celsr1-3, are widely expressed in the nervous system. Recent work has shown that Celsr1-3 play important roles in neural development, such as in axon guidance, neuronal migration, and cilium polarity. Celsr1-3 single-gene knockout mice exhibit different phenotypes, but there are cooperative interactions among these genes. PMID:22622831

  1. Recording of polarization holograms in a liquid crystal cell with a photosensitive chalcogenide orientation layer [Invited].

    PubMed

    Sheremet, Nina; Kurioz, Yuriy; Slyusarenko, Kostyantyn; Trunov, Michael; Reznikov, Yuriy

    2013-08-01

    Polarization gratings have been recorded in a combined liquid crystal (LC) cell made of a substrate covered with a photosensitive chalcogenide orientation layer and a reference substrate covered with a rubbed polyimide film. The gratings are formed due to the spatially modulated light-induced easy orientation axis on the chalcogenide surface recorded by two beams with opposite circular polarizations. The gratings are permanent, but they can be erased by one of the recording beams and re-recorded. The diffraction intensity of the circularly polarized light is achromatic and does not depend on the birefringence of the LC. The diffraction efficiency of the grating is of the order of a few percents. Application of an ac field causes a strong increase of the diffraction efficiency up to 45%. PMID:23913086

  2. Active and Selective Transcytosis of Cell-Free Human Immunodeficiency Virus through a Tight Polarized Monolayer of Human Endometrial Cells

    PubMed Central

    Hocini, Hakim; Becquart, Pierre; Bouhlal, Hicham; Chomont, Nicolas; Ancuta, Petronela; Kazatchkine, Michel D.; Bélec, Laurent

    2001-01-01

    We report that both primary and laboratory-adapted infectious human immunodeficiency virus type 1 (HIV-1) isolates in a cell-free form are capable of transcytosis through a tight and polarized monolayer of human endometrial cells. Trancytosis of cell-free HIV occurs in a strain-selective fashion and appears to be dependent on interactions between HIV envelope glycoproteins and lectins on the apical membrane of the epithelial cells. These findings provide new insights into the initial events occurring during heterosexual transmission of the virus. PMID:11333919

  3. Ultrastructural analyses of somatic embryo initiation, development and polarity establishment from mesophyll cells of Dactylis glomerata

    NASA Technical Reports Server (NTRS)

    Vasilenko, A.; McDaniel, J. K.; Conger, B. V.

    2000-01-01

    Somatic embryos initiate and develop directly from single mesophyll cells in in vitro-cultured leaf segments of orchardgrass (Dactylis glomerata L.). Embryogenic cells establish themselves in the predivision stage by formation of thicker cell walls and dense cytoplasm. Electron microscopy observations for embryos ranging from the pre-cell-division stage to 20-cell proembryos confirm previous light microscopy studies showing a single cell origin. They also confirm that the first division is predominantly periclinal and that this division plane is important in establishing embryo polarity and in determining the embryo axis. If the first division is anticlinal or if divisions are in random planes after the first division, divisions may not continue to produce an embryo. This result may produce an embryogenic cell mass, callus formation, or no structure at all. Grant numbers: NAGW-3141, NAG10-0221.

  4. The planar cell polarity protein VANGL2 coordinates remodeling of the extracellular matrix.

    PubMed

    Williams, B Blairanne; Mundell, Nathan; Dunlap, Julie; Jessen, Jason

    2012-07-01

    Understanding how planar cell polarity (PCP) is established, maintained, and coordinated in migrating cell populations is an important area of research with implications for both embryonic morphogenesis and tumor cell invasion. We recently reported that the PCP protein Vang-like 2 (VANGL2) regulates the endocytosis and cell surface level of membrane type-1 matrix metalloproteinase (MMP14 or MT1-MMP). Here, we further discuss these findings in terms of extracellular matrix (ECM) remodeling, cell migration, and zebrafish gastrulation. We also demonstrate that VANGL2 function impacts the focal degradation of ECM by human cancer cells including the formation or stability of invadopodia. Together, our findings implicate MMP14 as a downstream effector of VANGL2 signaling and suggest a model whereby the regulation of pericellular proteolysis is a fundamental aspect of PCP in migrating cells. PMID:23060953

  5. The planar cell polarity protein VANGL2 coordinates remodeling of the extracellular matrix

    PubMed Central

    Williams, B. Blairanne; Mundell, Nathan; Dunlap, Julie; Jessen, Jason

    2012-01-01

    Understanding how planar cell polarity (PCP) is established, maintained, and coordinated in migrating cell populations is an important area of research with implications for both embryonic morphogenesis and tumor cell invasion. We recently reported that the PCP protein Vang-like 2 (VANGL2) regulates the endocytosis and cell surface level of membrane type-1 matrix metalloproteinase (MMP14 or MT1-MMP). Here, we further discuss these findings in terms of extracellular matrix (ECM) remodeling, cell migration, and zebrafish gastrulation. We also demonstrate that VANGL2 function impacts the focal degradation of ECM by human cancer cells including the formation or stability of invadopodia. Together, our findings implicate MMP14 as a downstream effector of VANGL2 signaling and suggest a model whereby the regulation of pericellular proteolysis is a fundamental aspect of PCP in migrating cells. PMID:23060953

  6. Polar processing and development of the 2004 Antarctic ozone hole : first results from MLS on Aura

    NASA Technical Reports Server (NTRS)

    Santee, M. L.; Manney, G. L.; Livesey, N. J.; Froidevaux, L.; MacKenzie, I. A.; Pumphrey, H. C.; Read, W. G.; Schwartz, M. J.; Waters, J. W.; Harwood, R. S.

    2005-01-01

    The Microwave Limb Sounder (MLS) on Aura is providing an extensive data set on stratospheric winter polar processing, including the first daily global observations of HCl, together with simultaneous measurements of ClO, HNO3, H2O, O3, N2O, and temperature (among others). We present first results charting the evolution of these quantities during the 2004 Antarctic late winter. MLS observations of chlorine deactivation and ozone loss during this period are shown to be consistent with results from the SLIMCAT chemical transport model.

  7. Photon emission asymmetry in the elementary process of bremsstrahlung from transversely polarized electrons

    SciTech Connect

    Mergl, E.; Prinz, H.; Schroeter, C.D.; Nakel, W. )

    1992-08-10

    By using an electron-phonon coincidence method the photon emission asymmetry in the elementary process of bremsstrahlung from transversely polarized electrons was measured for fixed directions of the outgoing electrons and coplanar geometry. For an electron beam of 300 keV incident on a gold target, emission asymmetries up to 35% were found. Even in the case of no deflection of the decelerated outgoing electrons a nonzero photon emission asymmetry was observed. The measurements are a proper test for theories going beyond the first Born approximation.

  8. Ultrathin organic solar cells with graphene doped by ferroelectric polarization.

    PubMed

    Kim, Keumok; Bae, Sang-Hoon; Toh, Chee Tat; Kim, Hobeom; Cho, Jeong Ho; Whang, Dongmok; Lee, Tae-Woo; Özyilmaz, Barbaros; Ahn, Jong-Hyun

    2014-03-12

    Graphene has been employed as transparent electrodes in organic solar cells (OSCs) because of its good physical and optical properties. However, the electrical conductivity of graphene films synthesized by chemical vapor deposition (CVD) is still inferior to that of conventional indium tin oxide (ITO) electrodes of comparable transparency, resulting in a lower performance of OSCs. Here, we report an effective method to improve the performance and long-term stability of graphene-based OSCs using electrostatically doped graphene films via a ferroelectric polymer. The sheet resistance of electrostatically doped few layer graphene films was reduced to ∼70 Ω/sq at 87% optical transmittance. Such graphene-based OSCs exhibit an efficiency of 2.07% with a superior stability when compared to chemically doped graphene-based OSCs. Furthermore, OSCs constructed on ultrathin ferroelectric film as a substrate of only a few micrometers show extremely good mechanical flexibility and durability and can be rolled up into a cylinder with 7 mm diameter. PMID:24521002

  9. An efficient means to mitigate wavefront curvature effects in polar format processed SAR imagery

    NASA Astrophysics Data System (ADS)

    Linnehan, Robert; Yasuda, Mark; Doerry, Armin

    2012-06-01

    Synthetic aperture radar (SAR) images processed using the polar format algorithm (PFA) may exhibit distortion if the curvature of the spherical wavefronts are not accounted for. The distortion manifests in geometric shifts and defocusing of targets, and intensifies as distances between pixels and the scene reference position increase. In this work, we demonstrate a method to mitigate the effects of wavefront curvature by applying localized (space-variant) phase corrections to sub-regions selected from the polar format processed image. The modified sub-images are then reassembled into a full image. To minimize discontinuities in the reconstructed image, the spatially variant phase adjustments are made to regions larger than the sub-images, and pared down before being reinserted into the complete image. The result is a SAR process that retains the efficiency of the PFA, yet avoids scene size limitations due to wavefront curvature distortions. The method is illustrated and validated using simulations and real data collected by the General Atomics Aeronautical Systems, Inc. (GA-ASI) Lynx® Multi-mode Radar System.

  10. On-chip nanostructures for polarization imaging and multispectral sensing using dedicated layers of modified CMOS processes

    NASA Astrophysics Data System (ADS)

    Junger, Stephan; Tschekalinskij, Wladimir; Verwaal, Nanko; Weber, Norbert

    2011-03-01

    Sub-wavelength gratings and hole arrays in metal films are applicable for polarization and spectral selective sensors, respectively. We demonstrate the fabrication of wire grid polarizers using standard complementary metal-oxide semiconductor (CMOS) processes. Extraordinary optical transmission of hole arrays was achieved by using the dedicated layer of a modified CMOS process. The structures were simulated using the finite-difference time-domain (FDTD) method and fabricated using the work flow of integrated circuits. A high-speed polarization image sensor with a pixel size of 6 μm was designed and demonstrated, and multispectral sensing was implemented using nanostructures with different spectral filter performances on a single chip.

  11. Mesenchymal stem cells alleviate experimental asthma by inducing polarization of alveolar macrophages.

    PubMed

    Song, Xiaolian; Xie, Shuanshuan; Lu, Kun; Wang, Changhui

    2015-04-01

    The reparative and immunoregulatory properties of mesenchymal stromal cells (MSCs) have made them attractive candidates for cellular therapy. However, the underlying mechanism of the effects of transplanted MSCs on allergic asthma remains elusive. Here, we show that administration of MSCs isolated from human bone marrow provoked a pronounced polarization in alveolar macrophages to M2 subtypes, rather than induced an increase in the total macrophage number, and efficiently inhibited hallmark features of asthma, including airway hyperresponsiveness and eosinophilic accumulation. Moreover, transforming growth factor beta (TGF-β) signaling pathway appeared to mediate the effects of MSCs on macrophage polarization and subsequently the inhibition of hallmark features of asthma. Inhibition of TGF-β signaling was sufficient to inhibit the macrophage polarization in response to MSCs and consequently reserved the inhibitory effects of macrophage polarization on hallmark features of asthma. Collectively, our data demonstrate that human MSCs have immunosuppressive activity on asthma, which is mediated by TGF-β-signaling-dependent alveolar macrophage polarization. PMID:24958014

  12. Process for preparing organoclays for aqueous and polar-organic systems

    DOEpatents

    Chaiko, David J.

    2001-01-01

    A process for preparing organoclays as thixotropic agents to control the rheology of water-based paints and other aqueous and polar-organic systems. The process relates to treating low-grade clay ores to achieve highly purified organoclays and/or to incorporate surface modifying agents onto the clay by adsorption and/or to produce highly dispersed organoclays without excessive grinding or high shear dispersion. The process involves the treatment of impure, or run-of-mine, clay using an aqueous biphasic extraction system to produce a highly dispersed clay, free of mineral impurities and with modified surface properties brought about by adsorption of the water-soluble polymers used in generating the aqueous biphasic extraction system. This invention purifies the clay to greater than 95%.

  13. Hybrid K-Rb Spin Exchange Optical Pumping Cells for the Polarization of ^3He

    NASA Astrophysics Data System (ADS)

    Couture, Alex; Daniels, Tim; Arnold, Charles; Clegg, Tom

    2006-11-01

    We are transitioning from polarizing ^3He using optical pumping cells charged with pure Rb to using a mixture of Rb and K, lean in Rb. The reason for this is the spin exchange efficiency between K and ^3He is an order of magnitude greater than that of Rb and ^3He. Also the spin exchange cross section between Rb and K is very large, which leads to a very fast rate of polarization transfer from Rb to K. Thus by optically pumping using a standard 795 nm Rb laser on a hybrid K-Rb cell, we can obtain significant improvements in spin-up time as well as improvements in overall polarization.[1] We produce hybrid pumping cells at TUNL using a filling station consisting of an oven and a turbo pumping station to bake out and pump away any impurities in the cells. The alkali metals are introduced into the pumping cells from a Y-shaped manifold with a separate retort for each alkali. We are able to determine the ratio of K to Rb in the vapor using white light absorption spectroscopy. Light from a halogen light bulb is incident upon the heated cell and enters a spectrometer beyond. We examine the relative sizes of the D1 and D2 absorption lines for the two alkali metals. We will have data comparing hybrid cells to pure Rb cells, GE-180 cells to Pyrex, and are working to obtain comparative performance data for spectrally unnarrowed and narrowed lasers. Our latest results will be reported. [1] E. Babcock, et al. (2003) Phys. Rev. Letter Vol. 91, Num.12, 123003

  14. Polarization independent beam fanning using a multi-domain liquid crystal cell.

    PubMed

    Ren, Hongwen; Wu, Shin-Tson

    2009-07-01

    Polarization independent beam fanning using a multi-domain liquid crystal (LC) cell is demonstrated experimentally. In the neighboring domains, the LC directors are aligned in orthogonal directions. To prove concepts, two hybrid-aligned LC cells with four and six domains were fabricated. Applying a voltage across the LC layer will change the phase difference between the neighboring domains. When the phase difference is 2mpi (m is an integer), the LC cell will not disturb the incident beam. However, if the phase shift is (2m + 1)pi, the outgoing beam will fan out into several beams; the number of fanout beams is equal to the domain number. PMID:19582068

  15. Positioning of centrioles is a conserved readout of Frizzled planar cell polarity signalling.

    PubMed

    Carvajal-Gonzalez, Jose Maria; Roman, Angel-Carlos; Mlodzik, Marek

    2016-01-01

    Planar cell polarity (PCP) signalling is a well-conserved developmental pathway regulating cellular orientation during development. An evolutionarily conserved pathway readout is not established and, moreover, it is thought that PCP mediated cellular responses are tissue-specific. A key PCP function in vertebrates is to regulate coordinated centriole/cilia positioning, a function that has not been associated with PCP in Drosophila. Here we report instructive input of Frizzled-PCP (Fz/PCP) signalling into polarized centriole positioning in Drosophila wings. We show that centrioles are polarized in pupal wing cells as a readout of PCP signalling, with both gain and loss-of-function Fz/PCP signalling affecting centriole polarization. Importantly, loss or gain of centrioles does not affect Fz/PCP establishment, implicating centriolar positioning as a conserved PCP-readout, likely downstream of PCP-regulated actin polymerization. Together with vertebrate data, these results suggest a unifying model of centriole/cilia positioning as a common downstream effect of PCP signalling from flies to mammals. PMID:27021213

  16. Positioning of centrioles is a conserved readout of Frizzled planar cell polarity signalling

    PubMed Central

    Carvajal-Gonzalez, Jose Maria; Roman, Angel-Carlos; Mlodzik, Marek

    2016-01-01

    Planar cell polarity (PCP) signalling is a well-conserved developmental pathway regulating cellular orientation during development. An evolutionarily conserved pathway readout is not established and, moreover, it is thought that PCP mediated cellular responses are tissue-specific. A key PCP function in vertebrates is to regulate coordinated centriole/cilia positioning, a function that has not been associated with PCP in Drosophila. Here we report instructive input of Frizzled-PCP (Fz/PCP) signalling into polarized centriole positioning in Drosophila wings. We show that centrioles are polarized in pupal wing cells as a readout of PCP signalling, with both gain and loss-of-function Fz/PCP signalling affecting centriole polarization. Importantly, loss or gain of centrioles does not affect Fz/PCP establishment, implicating centriolar positioning as a conserved PCP-readout, likely downstream of PCP-regulated actin polymerization. Together with vertebrate data, these results suggest a unifying model of centriole/cilia positioning as a common downstream effect of PCP signalling from flies to mammals. PMID:27021213

  17. Host cell polarity proteins participate in innate immunity to Pseudomonas aeruginosa infection.

    PubMed

    Tran, Cindy S; Eran, Yoni; Ruch, Travis R; Bryant, David M; Datta, Anirban; Brakeman, Paul; Kierbel, Arlinet; Wittmann, Torsten; Metzger, Ross J; Mostov, Keith E; Engel, Joanne N

    2014-05-14

    The mucosal epithelium consists of polarized cells with distinct apical and basolateral membranes that serve as functional and physical barriers to external pathogens. The apical surface of the epithelium constitutes the first point of contact between mucosal pathogens, such as Pseudomonas aeruginosa, and their host. We observed that binding of P. aeruginosa aggregates to the apical surface of polarized cells led to the striking formation of an actin-rich membrane protrusion with inverted polarity, containing basolateral lipids and membrane components. Such protrusions were associated with a spatially localized host immune response to P. aeruginosa aggregates that required bacterial flagella and a type III secretion system apparatus. Host protrusions formed de novo underneath bacterial aggregates and involved the apical recruitment of a Par3/Par6α/aPKC/Rac1 signaling module for a robust, spatially localized host NF-κB response. Our data reveal a role for spatiotemporal epithelial polarity changes in the activation of innate immune responses. PMID:24832456

  18. Exocyst requirement for endocytic traffic directed toward the apical and basolateral poles of polarized MDCK cells.

    PubMed

    Oztan, Asli; Silvis, Mark; Weisz, Ora A; Bradbury, Neil A; Hsu, Shu-Chan; Goldenring, James R; Yeaman, Charles; Apodaca, Gerard

    2007-10-01

    The octameric exocyst complex is associated with the junctional complex and recycling endosomes and is proposed to selectively tether cargo vesicles directed toward the basolateral surface of polarized Madin-Darby canine kidney (MDCK) cells. We observed that the exocyst subunits Sec6, Sec8, and Exo70 were localized to early endosomes, transferrin-positive common recycling endosomes, and Rab11a-positive apical recycling endosomes of polarized MDCK cells. Consistent with its localization to multiple populations of endosomes, addition of function-blocking Sec8 antibodies to streptolysin-O-permeabilized cells revealed exocyst requirements for several endocytic pathways including basolateral recycling, apical recycling, and basolateral-to-apical transcytosis. The latter was selectively dependent on interactions between the small GTPase Rab11a and Sec15A and was inhibited by expression of the C-terminus of Sec15A or down-regulation of Sec15A expression using shRNA. These results indicate that the exocyst complex may be a multipurpose regulator of endocytic traffic directed toward both poles of polarized epithelial cells and that transcytotic traffic is likely to require Rab11a-dependent recruitment and modulation of exocyst function, likely through interactions with Sec15A. PMID:17686995

  19. Myosin light chain kinase regulates cell polarization independently of membrane tension or Rho kinase

    PubMed Central

    Lou, Sunny S.; Diz-Muñoz, Alba; Weiner, Orion D.; Fletcher, Daniel A.

    2015-01-01

    Cells polarize to a single front and rear to achieve rapid actin-based motility, but the mechanisms preventing the formation of multiple fronts are unclear. We developed embryonic zebrafish keratocytes as a model system for investigating establishment of a single axis. We observed that, although keratocytes from 2 d postfertilization (dpf) embryos resembled canonical fan-shaped keratocytes, keratocytes from 4 dpf embryos often formed multiple protrusions despite unchanged membrane tension. Using genomic, genetic, and pharmacological approaches, we determined that the multiple-protrusion phenotype was primarily due to increased myosin light chain kinase (MLCK) expression. MLCK activity influences cell polarity by increasing myosin accumulation in lamellipodia, which locally decreases protrusion lifetime, limiting lamellipodial size and allowing for multiple protrusions to coexist within the context of membrane tension limiting protrusion globally. In contrast, Rho kinase (ROCK) regulates myosin accumulation at the cell rear and does not determine protrusion size. These results suggest a novel MLCK-specific mechanism for controlling cell polarity via regulation of myosin activity in protrusions. PMID:25918227

  20. The clathrin adaptor AP-1 complex and Arf1 regulate planar cell polarity in vivo

    PubMed Central

    Mendoza, Meg; Dussert, Aurore; Collu, Giovanna; Roman, Angel-Carlos; Weber, Ursula; Ciruna, Brian; Mlodzik, Marek

    2015-01-01

    A key step in generating planar cell polarity (PCP) is the formation of restricted junctional domains containing Frizzled/Dishevelled/Diego (Fz/Dsh/Dgo) or Van Gogh/Prickle (Vang/Pk) complexes within the same cell, stabilized via Flamingo (Fmi) across cell membranes. Although models have been proposed for how these complexes acquire and maintain their polarized localization, the machinery involved in moving core PCP proteins around cells remains unknown. We describe the AP-1 adaptor complex and Arf1 as major regulators of PCP protein trafficking in vivo. AP-1 and Arf1 disruption affects the accumulation of Fz/Fmi and Vang/Fmi complexes in the proximo–distal axis, producing severe PCP phenotypes. Using novel tools, we demonstrate a direct and specific Arf1 involvement in Fz trafficking in vivo. Moreover, we uncover a conserved Arf1 PCP function in vertebrates. Our data support a model whereby the trafficking machinery plays an important part during PCP establishment, promoting formation of polarized PCP-core complexes in vivo. PMID:25849195

  1. Shear stress–induced endothelial cell polarization is mediated by Rho and Rac but not Cdc42 or PI 3-kinases

    PubMed Central

    Wojciak-Stothard, Beata; Ridley, Anne J.

    2003-01-01

    Shear stress induces endothelial polarization and migration in the direction of flow accompanied by extensive remodeling of the actin cytoskeleton. The GTPases RhoA, Rac1, and Cdc42 are known to regulate cell shape changes through effects on the cytoskeleton and cell adhesion. We show here that all three GTPases become rapidly activated by shear stress, and that each is important for different aspects of the endothelial response. RhoA was activated within 5 min after stimulation with shear stress and led to cell rounding via Rho-kinase. Subsequently, the cells respread and elongated within the direction of shear stress as RhoA activity returned to baseline and Rac1 and Cdc42 reached peak activation. Cell elongation required Rac1 and Cdc42 but not phosphatidylinositide 3-kinases. Cdc42 and PI3Ks were not required to establish shear stress–induced polarity although they contributed to optimal migration speed. Instead, Rho and Rac1 regulated directionality of cell movement. Inhibition of Rho or Rho-kinase did not affect the cell speed but significantly increased cell displacement. Our results show that endothelial cells reorient in response to shear stress by a two-step process involving Rho-induced depolarization, followed by Rho/Rac-mediated polarization and migration in the direction of flow. PMID:12719476

  2. Coupling Mechanical Deformations and Planar Cell Polarity to Create Regular Patterns in the Zebrafish Retina

    PubMed Central

    Salbreux, Guillaume; Barthel, Linda K.; Raymond, Pamela A.; Lubensky, David K.

    2012-01-01

    The orderly packing and precise arrangement of epithelial cells is essential to the functioning of many tissues, and refinement of this packing during development is a central theme in animal morphogenesis. The mechanisms that determine epithelial cell shape and position, however, remain incompletely understood. Here, we investigate these mechanisms in a striking example of planar order in a vertebrate epithelium: The periodic, almost crystalline distribution of cone photoreceptors in the adult teleost fish retina. Based on observations of the emergence of photoreceptor packing near the retinal margin, we propose a mathematical model in which ordered columns of cells form as a result of coupling between planar cell polarity (PCP) and anisotropic tissue-scale mechanical stresses. This model recapitulates many observed features of cone photoreceptor organization during retinal growth and regeneration. Consistent with the model's predictions, we report a planar-polarized distribution of Crumbs2a protein in cone photoreceptors in both unperturbed and regenerated tissue. We further show that the pattern perturbations predicted by the model to occur if the imposed stresses become isotropic closely resemble defects in the cone pattern in zebrafish lrp2 mutants, in which intraocular pressure is increased, resulting in altered mechanical stress and ocular enlargement. Evidence of interactions linking PCP, cell shape, and mechanical stresses has recently emerged in a number of systems, several of which show signs of columnar cell packing akin to that described here. Our results may hence have broader relevance for the organization of cells in epithelia. Whereas earlier models have allowed only for unidirectional influences between PCP and cell mechanics, the simple, phenomenological framework that we introduce here can encompass a broad range of bidirectional feedback interactions among planar polarity, shape, and stresses; our model thus represents a conceptual framework

  3. Dual functions for the Schizosaccharomyces pombe inositol kinase Ipk1 in nuclear mRNA export and polarized cell growth.

    PubMed

    Sarmah, Bhaskarjyoti; Wente, Susan R

    2009-02-01

    The inositol 1,3,4,5,6-pentakisphosphate (IP(5)) 2-kinase (Ipk1) catalyzes the production of inositol hexakisphosphate (IP(6)) in eukaryotic cells. Previous studies have shown that IP(6) is required for efficient nuclear mRNA export in the budding yeast Saccharomyces cerevisiae. Here, we report the first functional analysis of ipk1(+) in Schizosaccharomyces pombe. S. pombe Ipk1 (SpIpk1) is unique among Ipk1 orthologues in that it harbors a novel amino (N)-terminal domain with coiled-coil structural motifs similar to those of BAR (Bin-amphiphysin-Rvs) domain proteins. Mutants with ipk1(+) deleted (ipk1Delta) had mRNA export defects as well as pleiotropic defects in polarized growth, cell morphology, endocytosis, and cell separation. The SpIpk1 catalytic carboxy-terminal domain was required to rescue these defects, and the mRNA export block was genetically linked to SpDbp5 function and, likely, IP(6) production. However, the overexpression of the N-terminal domain alone also inhibited these functions in wild-type cells. This revealed a distinct noncatalytic function for the N-terminal domain. To test for connections with other inositol polyphosphates, we also analyzed whether the loss of asp1(+) function, encoding an IP(6) kinase downstream of Ipk1, had an effect on ipk1Delta cells. The asp1Delta mutant alone did not block mRNA export, and its cell morphology, polarized growth, and endocytosis defects were less severe than those of ipk1Delta cells. Moreover, ipk1Delta asp1Delta double mutants had altered inositol polyphosphate levels distinct from those of the ipk1Delta mutant. This suggested novel roles for asp1(+) upstream of ipk1(+). We propose that IP(6) production is a key signaling linchpin for regulating multiple essential cellular processes. PMID:19047361

  4. Process of making solar cell module

    DOEpatents

    Packer, M.; Coyle, P.J.

    1981-03-09

    A process is presented for the manufacture of solar cell modules. A solution comprising a highly plasticized polyvinyl butyral is applied to a solar cell array. The coated array is dried and sandwiched between at last two sheets of polyvinyl butyral and at least two sheets of a rigid transparent member. The sandwich is laminated by the application of heat and pressure to cause fusion and bonding of the solar cell array with the rigid transparent members to produce a solar cell module.

  5. Quantum-state storage and processing for polarization qubits in an inhomogeneously broadened Λ-type three-level medium

    NASA Astrophysics Data System (ADS)

    Viscor, D.; Ferraro, A.; Loiko, Yu.; Mompart, J.; Ahufinger, V.

    2011-10-01

    We address the propagation of a single-photon pulse with two polarization components, i.e., a polarization qubit, in an inhomogeneously broadened “phaseonium” Λ-type three-level medium. We combine some of the nontrivial propagation effects characteristic for this kind of coherently prepared systems and the controlled reversible inhomogeneous broadening technique to propose several quantum information-processing applications, such as a protocol for polarization qubit filtering and sieving as well as a tunable polarization beam splitter. Moreover, we show that by imposing a spatial variation of the atomic coherence phase, an efficient quantum memory for the incident polarization qubit can be also implemented in Λ-type three-level systems.

  6. In the dark: A review of ecosystem processes during the Arctic polar night

    NASA Astrophysics Data System (ADS)

    Berge, Jørgen; Renaud, Paul E.; Darnis, Gerald; Cottier, Finlo; Last, Kim; Gabrielsen, Tove M.; Johnsen, Geir; Seuthe, Lena; Weslawski, Jan Marcin; Leu, Eva; Moline, Mark; Nahrgang, Jasmine; Søreide, Janne E.; Varpe, Øystein; Lønne, Ole Jørgen; Daase, Malin; Falk-Petersen, Stig

    2015-12-01

    Several recent lines of evidence indicate that the polar night is key to understanding Arctic marine ecosystems. First, the polar night is not a period void of biological activity even though primary production is close to zero, but is rather characterized by a number of processes and interactions yet to be fully understood, including unanticipated high levels of feeding and reproduction in a wide range of taxa and habitats. Second, as more knowledge emerges, it is evident that a coupled physical and biological perspective of the ecosystem will redefine seasonality beyond the "calendar perspective". Third, it appears that many organisms may exhibit endogenous rhythms that trigger fitness-maximizing activities in the absence of light-based cues. Indeed a common adaptation appears to be the ability to utilize the dark season for reproduction. This and other processes are most likely adaptations to current environmental conditions and community and trophic structures of the ecosystem, and may have implications for how Arctic ecosystems can change under continued climatic warming.

  7. The RHIC polarized H- ion source

    NASA Astrophysics Data System (ADS)

    Zelenski, A.; Atoian, G.; Raparia, D.; Ritter, J.; Steski, D.

    2016-02-01

    A novel polarization technique had been successfully implemented for the Relativistic Heavy Ion Collider (RHIC) polarized H- ion source upgrade to higher intensity and polarization. In this technique, a proton beam inside the high magnetic field solenoid is produced by ionization of the atomic hydrogen beam (from external source) in the He-gaseous ionizer cell. Further proton polarization is produced in the process of polarized electron capture from the optically pumped Rb vapor. The use of high-brightness primary beam and large cross sections of charge-exchange cross sections resulted in production of high intensity H- ion beam of 85% polarization. The source very reliably delivered polarized beam in the RHIC Run-2013 and Run-2015. High beam current, brightness, and polarization resulted in 75% polarization at 23 GeV out of Alternating Gradient Synchrotron (AGS) and 60%-65% beam polarization at 100-250 GeV colliding beams in RHIC.

  8. The RHIC polarized H⁻ ion source.

    PubMed

    Zelenski, A; Atoian, G; Raparia, D; Ritter, J; Steski, D

    2016-02-01

    A novel polarization technique had been successfully implemented for the Relativistic Heavy Ion Collider (RHIC) polarized H(-) ion source upgrade to higher intensity and polarization. In this technique, a proton beam inside the high magnetic field solenoid is produced by ionization of the atomic hydrogen beam (from external source) in the He-gaseous ionizer cell. Further proton polarization is produced in the process of polarized electron capture from the optically pumped Rb vapor. The use of high-brightness primary beam and large cross sections of charge-exchange cross sections resulted in production of high intensity H(-) ion beam of 85% polarization. The source very reliably delivered polarized beam in the RHIC Run-2013 and Run-2015. High beam current, brightness, and polarization resulted in 75% polarization at 23 GeV out of Alternating Gradient Synchrotron (AGS) and 60%-65% beam polarization at 100-250 GeV colliding beams in RHIC. PMID:26932068

  9. CAMSAP3 orients the apical-to-basal polarity of microtubule arrays in epithelial cells.

    PubMed

    Toya, Mika; Kobayashi, Saeko; Kawasaki, Miwa; Shioi, Go; Kaneko, Mari; Ishiuchi, Takashi; Misaki, Kazuyo; Meng, Wenxiang; Takeichi, Masatoshi

    2016-01-12

    Polarized epithelial cells exhibit a characteristic array of microtubules that are oriented along the apicobasal axis of the cells. The minus-ends of these microtubules face apically, and the plus-ends face toward the basal side. The mechanisms underlying this epithelial-specific microtubule assembly remain unresolved, however. Here, using mouse intestinal cells and human Caco-2 cells, we show that the microtubule minus-end binding protein CAMSAP3 (calmodulin-regulated-spectrin-associated protein 3) plays a pivotal role in orienting the apical-to-basal polarity of microtubules in epithelial cells. In these cells, CAMSAP3 accumulated at the apical cortices, and tethered the longitudinal microtubules to these sites. Camsap3 mutation or depletion resulted in a random orientation of these microtubules; concomitantly, the stereotypic positioning of the nucleus and Golgi apparatus was perturbed. In contrast, the integrity of the plasma membrane was hardly affected, although its structural stability was decreased. Further analysis revealed that the CC1 domain of CAMSAP3 is crucial for its apical localization, and that forced mislocalization of CAMSAP3 disturbs the epithelial architecture. These findings demonstrate that apically localized CAMSAP3 determines the proper orientation of microtubules, and in turn that of organelles, in mature mammalian epithelial cells. PMID:26715742

  10. Twisted nematic liquid crystal cell characterization using rotating polarizers including full-field cell gap thickness measurement

    NASA Astrophysics Data System (ADS)

    Dev, Kapil; Prakarsa, Andy; Jiang, Yin Xi; Lee, Hooi Leng; Asundi, Anand

    2009-12-01

    Liquid crystal cells have always been an important part of commercially available displays, modulators and projectors. In this paper, Jones matrix representation including four independent parameters for twisted nematic liquid crystal (TN-LC) cell has been demonstrated. The physical parameters of the TN-LC cell such as twist angle, birefringence and director orientation at the input face of cell has been calculated using intensity transmittance of an experimental set-up that includes circularly polarized light and TN-LC cell sandwiched between two polarizers. The physical parameters have been calculated without any ambiguity using three different wavelengths. The knowledge from above measurement gives the general information about the birefringence and hence liquid crystal cell gap thickness. To acquire full-field liquid crystal cell gap thickness measurement phase shift polariscope has been adopted. The four phase shifted images through the rotating analyzer gives the full-field cell gap thickness measurement. The experimental results have been compared with the commercial point wise measurement and are in good agreement.

  11. Twisted nematic liquid crystal cell characterization using rotating polarizers including full-field cell gap thickness measurement

    NASA Astrophysics Data System (ADS)

    Dev, Kapil; Prakarsa, Andy; Jiang, Yin Xi; Lee, Hooi Leng; Asundi, Anand

    2010-03-01

    Liquid crystal cells have always been an important part of commercially available displays, modulators and projectors. In this paper, Jones matrix representation including four independent parameters for twisted nematic liquid crystal (TN-LC) cell has been demonstrated. The physical parameters of the TN-LC cell such as twist angle, birefringence and director orientation at the input face of cell has been calculated using intensity transmittance of an experimental set-up that includes circularly polarized light and TN-LC cell sandwiched between two polarizers. The physical parameters have been calculated without any ambiguity using three different wavelengths. The knowledge from above measurement gives the general information about the birefringence and hence liquid crystal cell gap thickness. To acquire full-field liquid crystal cell gap thickness measurement phase shift polariscope has been adopted. The four phase shifted images through the rotating analyzer gives the full-field cell gap thickness measurement. The experimental results have been compared with the commercial point wise measurement and are in good agreement.

  12. Opposite-polarity motors activate one another to trigger cargo transport in live cells.

    PubMed

    Ally, Shabeen; Larson, Adam G; Barlan, Kari; Rice, Sarah E; Gelfand, Vladimir I

    2009-12-28

    Intracellular transport is typically bidirectional, consisting of a series of back and forth movements. Kinesin-1 and cytoplasmic dynein require each other for bidirectional transport of intracellular cargo along microtubules; i.e., inhibition or depletion of kinesin-1 abolishes dynein-driven cargo transport and vice versa. Using Drosophila melanogaster S2 cells, we demonstrate that replacement of endogenous kinesin-1 or dynein with an unrelated, peroxisome-targeted motor of the same directionality activates peroxisome transport in the opposite direction. However, motility-deficient versions of motors, which retain the ability to bind microtubules and hydrolyze adenosine triphosphate, do not activate peroxisome motility. Thus, any pair of opposite-polarity motors, provided they move along microtubules, can activate one another. These results demonstrate that mechanical interactions between opposite-polarity motors are necessary and sufficient for bidirectional organelle transport in live cells. PMID:20038680

  13. Opposite-polarity motors activate one another to trigger cargo transport in live cells

    PubMed Central

    Ally, Shabeen; Larson, Adam G.; Barlan, Kari; Rice, Sarah E.

    2009-01-01

    Intracellular transport is typically bidirectional, consisting of a series of back and forth movements. Kinesin-1 and cytoplasmic dynein require each other for bidirectional transport of intracellular cargo along microtubules; i.e., inhibition or depletion of kinesin-1 abolishes dynein-driven cargo transport and vice versa. Using Drosophila melanogaster S2 cells, we demonstrate that replacement of endogenous kinesin-1 or dynein with an unrelated, peroxisome-targeted motor of the same directionality activates peroxisome transport in the opposite direction. However, motility-deficient versions of motors, which retain the ability to bind microtubules and hydrolyze adenosine triphosphate, do not activate peroxisome motility. Thus, any pair of opposite-polarity motors, provided they move along microtubules, can activate one another. These results demonstrate that mechanical interactions between opposite-polarity motors are necessary and sufficient for bidirectional organelle transport in live cells. PMID:20038680

  14. Interaction of red blood cells with a polarized electrode: evidence of long-range intermolecular forces.

    PubMed Central

    Gingell, D; Fornes, J A

    1976-01-01

    We have investigated the electrostatic interaction of glutaraldehyde-fixed human red cells with a polarizable electrode carrying a defined surface charge density which can be varied continuously through a wide range. Cells in a dilute salt solution are unable to adhere to the electrode at high negative charge, but at lower negative charge densities they are reversibly adherent and can be forced off by increasing the negative polarization. Near zero electrode charge they become irreversibly stuck to the electrode and cannot be evicted even at maximum electrode polarization. Calculation of the electrostatic repulsive force using measured charge densities indicates the existence of an attractive force which may be acting over several hundred angstroms. PMID:822894

  15. Line up and listen: planar cell polarity regulation in the mammalian inner ear

    PubMed Central

    Rida, Padmashree C. G.; Chen, Ping

    2009-01-01

    The inner ear sensory organs possess extraordinary structural features necessary to conduct mechanosensory transduction for hearing and balance. Their structural beauty has fascinated scientists since the dawn of modern science and ensured a rigorous pursuit of the understanding of mechanotransduction. Sensory cells of the inner ear display unique structural features that underlie their mechanosensitivity and resolution, and represent perhaps the most distinctive form of a type of cellular polarity, known as planar cell polarity (PCP). Until recently, however, it was not known how the precise PCP of the inner ear sensory organs was achieved during development. Here, we review the PCP of the inner ear and recent advances in the quest for an understanding of its formation. PMID:19508855

  16. Human B cells induce dendritic cell maturation and favour Th2 polarization by inducing OX-40 ligand

    PubMed Central

    Maddur, Mohan S.; Sharma, Meenu; Hegde, Pushpa; Stephen-Victor, Emmanuel; Pulendran, Bali; Kaveri, Srini V.; Bayry, Jagadeesh

    2015-01-01

    Dendritic cells (DCs) play a critical role in immune homeostasis by regulating the functions of various immune cells, including T and B cells. Notably, DCs also undergo education on reciprocal signalling by these immune cells and environmental factors. Various reports demonstrated that B cells have profound regulatory functions, although only few reports have explored the regulation of human DCs by B cells. Here we demonstrate that activated but not resting B cells induce maturation of DCs with distinct features to polarize Th2 cells that secrete interleukin (IL)-5, IL-4 and IL-13. B-cell-induced maturation of DCs is contact dependent and implicates signalling of B-cell activation molecules CD69, B-cell-activating factor receptor, and transmembrane activator and calcium-modulating cyclophilin ligand interactor. Mechanistically, differentiation of Th2 cells by B-cell-matured DCs is dependent on OX-40 ligand. Collectively, our results suggest that B cells have the ability to control their own effector functions by enhancing the ability of human DCs to mediate Th2 differentiation. PMID:24910129

  17. Polycystin-1 is a microtubule-driven desmosome-associated component in polarized epithelial cells

    SciTech Connect

    Basora, Nuria; Tetreault, Marie-Pier; Boucher, Marie-Pierre; Herring, Elizabeth; Beaulieu, Jean-Francois

    2010-05-15

    In this study, we have analyzed the expression and localization of polycystin-1 in intestinal epithelial cells, a system lacking primary cilia. Polycystin-1 was found to be expressed in the epithelium of the small intestine during development and levels remained elevated in the adult. Dual-labelling indirect immunofluorescence revealed polycystin-1 at sites of cell-cell contact co-localizing with the desmosomes both in situ as well as in polarized Caco-2/15 cells. In unpolarized cultures of Caco-2/15 cells, polycystin-1 was recruited to the cell surface early during initiation of cell junction assembly. In isolated Caco-2/15 cells and HIEC-6 cell cultures, where junctional complexes are absent, polycystin-1 was found predominantly associated with the cytoskeletal elements of the intermediate filaments and microtubule networks. More precisely, polycystin-1 was seen as brightly labelled puncta decorating the keratin-18 positive filaments as well as the {beta}-tubulin positive microtubules, which was particularly obvious in the lamellipodia. Treatment with the microtubule-disrupting agent, nocodazole, eliminated the microtubule association of polycystin-1 but did not seem to affect its association with keratin or the desmosomes. Taken together these data suggest that polycystin-1 is involved with the establishment of cell-cell junctions in absorptive intestinal epithelial cells and exploits the microtubule-based machinery in order to be transported to the plasma membrane.

  18. RacA-Mediated ROS Signaling Is Required for Polarized Cell Differentiation in Conidiogenesis of Aspergillus fumigatus

    PubMed Central

    Chi, Myoung-Hwan; Craven, Kelly D.

    2016-01-01

    Conidiophore development of fungi belonging to the genus Aspergillus involves dynamic changes in cellular polarity and morphogenesis. Synchronized differentiation of phialides from the subtending conidiophore vesicle is a good example of the transition from isotropic to multi-directional polarized growth. Here we report a small GTPase, RacA, which is essential for reactive oxygen species (ROS) production in the vesicle as well as differentiation of phialides in Aspergillus fumigatus. We found that wild type A. fumigatus accumulates ROS in these conidiophore vesicles and that null mutants of racA did not, resulting in the termination of conidiophore development in this early vesicle stage. Further, we found that stress conditions resulting in atypical ROS accumulation coincide with partial recovery of phialide emergence but not subsequent apical dominance of the phialides in the racA null mutant, suggesting alternative means of ROS generation for the former process that are lacking in the latter. Elongation of phialides was also suppressed by inhibition of NADPH-oxidase activity. Our findings provide not only insights into role of ROS in fungal cell polarity and morphogenesis but also an improved model for the developmental regulatory pathway of conidiogenesis in A. fumigatus. PMID:26890813

  19. Enhanced biological processes associated with alopecia in polar bears (Ursus maritimus).

    PubMed

    Bowen, Lizabeth; Miles, A Keith; Stott, Jeffrey; Waters, Shannon; Atwood, Todd

    2015-10-01

    Populations of wildlife species worldwide experience incidents of mass morbidity and mortality. Primary or secondary drivers of these events may escape classical detection methods for identifying microbial insults, toxin exposure, or additional stressors. In 2012, 28% of polar bears sampled in a study in the southern Beaufort Sea region of Alaska had varying degrees of alopecia that was concomitant with reduced body condition. Concurrently, elevated numbers of sick or dead ringed seals were detected in the southern Beaufort, Chukchi, and Bering seas in 2012, resulting in the declaration of an unusual mortality event (UME) by the National Oceanic and Atmospheric Administration (NOAA). The primary and possible ancillary causative stressors of these events are unknown, and related physiological changes within individual animals have been undetectable using classical diagnostic methods. Here we present an emerging technology as a potentially guiding investigative approach aimed at elucidating the circumstances responsible for the susceptibility of certain polar bears to observed conditions. Using transcriptomic analysis we identified enhanced biological processes including immune response, viral defense, and response to stress in polar bears with alopecia. Our results support an alternative mechanism of investigation into the causative agents that, when used proactively, could serve as an early indicator for populations and species at risk. We suggest that current or classical methods for investigation into events of unusual morbidity and mortality can be costly, sometimes unfocused, and often inconclusive. Advances in technology allow for implementation of a holistic system of surveillance and investigation that could provide early warning of health concerns in wildlife species important to humans. PMID:26005754

  20. Enhanced biological processes associated with alopecia in polar bears (Ursus maritimus)

    USGS Publications Warehouse

    Bowen, Lizabeth; Miles, A. Keith; Stott, Jeffrey L.; Waters, Shannon C.; Atwood, Todd C.

    2015-01-01

    Populations of wildlife species worldwide experience incidents of mass morbidity and mortality. Primary or secondary drivers of these events may escape classical detection methods for identifying microbial insults, toxin exposure, or additional stressors. In 2012, 28% of polar bears sampled in a study in the southern Beaufort Sea region of Alaska had varying degrees of alopecia that was concomitant with reduced body condition. Concurrently, elevated numbers of sick or dead ringed seals were detected in the southern Beaufort, Chukchi, and Bering seas in 2012, resulting in the declaration of an unusual mortality event (UME) by the National Oceanic and Atmospheric Administration (NOAA). The primary and possible ancillary causative stressors of these events are unknown, and related physiological changes within individual animals have been undetectable using classical diagnostic methods. Here we present an emerging technology as a potentially guiding investigative approach aimed at elucidating the circumstances responsible for the susceptibility of certain polar bears to observed conditions. Using transcriptomic analysis we identified enhanced biological processes including immune response, viral defense, and response to stress in polar bears with alopecia. Our results support an alternative mechanism of investigation into the causative agents that, when used proactively, could serve as an early indicator for populations and species at risk. We suggest that current or classical methods for investigation into events of unusual morbidity and mortality can be costly, sometimes unfocused, and often inconclusive. Advances in technology allow for implementation of a holistic system of surveillance and investigation that could provide early warning of health concerns in wildlife species important to humans.

  1. Accessory human cytomegalovirus glycoprotein US9 in the unique short component of the viral genome promotes cell-to-cell transmission of virus in polarized epithelial cells.

    PubMed Central

    Maidji, E; Tugizov, S; Jones, T; Zheng, Z; Pereira, L

    1996-01-01

    Human cytomegalovirus (CMV) encodes accessory glycoproteins that are dispensable for virus growth in nonpolarized cells in culture. We report that CMV deletion mutants lacking the gene for accessory glycoprotein US9 in the unique short component of the viral genome are impaired in plaque formation in polarized human retinal pigment epithelial (ARPE-19) cells. Comparison of CMV deletion mutants in US9 with herpes simplex virus type 1 deletion mutants lacking glycoproteins gE and gI showed that both of these mutants are impaired in altering junctional complexes and increasing paracellular permeability in polarized ARPE-19 cells cultured on permeable filter supports. Results of functional studies indicate that CMV US9 and homologs of gE have analogous roles in promoting virus spread across lateral membranes of polarized epithelial cells. PMID:8970961

  2. Bone morphogenetic protein 7 polarizes THP-1 cells into M2 macrophages.

    PubMed

    Rocher, Crystal; Singla, Reetu; Singal, Pawan K; Parthasarathy, Sampath; Singla, Dinender K

    2012-07-01

    It was hypothesized that monocyte treatment with bone morphogenetic protein 7 (BMP7) would significantly enhance monocyte polarization into M2 macrophages as well as increasing the levels of anti-inflammatory cytokines. In a cell culture system using monocytes (human acute monocytic leukemia cell line THP-1), we studied the effects of BMP7 on monocytes polarizing into M2 macrophages. The data demonstrate that THP-1 cells contain a BMP type II receptor (BMPR2), and that its activation is significantly (p < 0.05) increased following treatment with BMP7. Furthermore, there was an increase of M2 macrophages, BMPR2, and anti-inflammatory cytokines interleukin (IL)-10 and IL-1ra compared with the respective controls. Moreover, treatment with BMP7 caused a significant (p < 0.05) decrease in the levels of pro-inflammatory cytokines IL-6, tumour necrosis factor (TNF-α), and monocyte chemotactic protein-1 (MCP-1), compared with the controls. In conclusion, we suggest for the first time that BMP7 has a unique potential to polarize monocytes into M2 macrophages, required for tissue repair, which will have significant applications for the treatment of atherosclerosis. PMID:22720873

  3. The Ski2-family helicase Obelus regulates Crumbs alternative splicing and cell polarity

    PubMed Central

    Vichas, Athea; Laurie, Matthew T.

    2015-01-01

    Alternative splicing can have profound consequences for protein activity, but the functions of most alternative splicing regulators are not known. We show that Obelus, a conserved Ski2-family helicase, is required for cell polarity and adherens junction organization in the Drosophila melanogaster embryo. In obelus mutants, epithelial cells display an expanded apical domain, aggregation of adherens junctions at the cell membrane, and microtubule-dependent defects in centrosome positioning. Through whole-genome transcriptome analysis, we found that Obelus is required for the alternative splicing of a small number of transcripts in the early embryo, including the pre-mRNA that encodes the apical polarity protein Crumbs. In obelus mutants, inclusion of an alternative exon results in increased expression of a Crumbs isoform that contains an additional epidermal growth factor–like repeat in the extracellular domain. Overexpression of this alternative Crumbs isoform recapitulates the junctional aggregation and centrosome positioning defects of obelus mutants. These results indicate that regulation of Crumbs alternative splicing by the Obelus helicase modulates epithelial polarity during development. PMID:26644515

  4. Knockin' on pollen's door: live cell imaging of early polarization events in germinating Arabidopsis pollen

    PubMed Central

    Vogler, Frank; Konrad, Sebastian S. A.; Sprunck, Stefanie

    2015-01-01

    Pollen tubes are an excellent system for studying the cellular dynamics and complex signaling pathways that coordinate polarized tip growth. Although several signaling mechanisms acting in the tip-growing pollen tube have been described, our knowledge on the subcellular and molecular events during pollen germination and growth site selection at the pollen plasma membrane is rather scarce. To simultaneously track germinating pollen from up to 12 genetically different plants we developed an inexpensive and easy mounting technique, suitable for every standard microscope setup. We performed high magnification live-cell imaging during Arabidopsis pollen activation, germination, and the establishment of pollen tube tip growth by using fluorescent marker lines labeling either the pollen cytoplasm, vesicles, the actin cytoskeleton or the sperm cell nuclei and membranes. Our studies revealed distinctive vesicle and F-actin polarization during pollen activation and characteristic growth kinetics during pollen germination and pollen tube formation. Initially, the germinating Arabidopsis pollen tube grows slowly and forms a uniform roundish bulge, followed by a transition phase with vesicles heavily accumulating at the growth site before switching to rapid tip growth. Furthermore, we found the two sperm cells to be transported into the pollen tube after the phase of rapid tip growth has been initiated. The method presented here is suitable to quantitatively study subcellular events during Arabidopsis pollen germination and growth, and for the detailed analysis of pollen mutants with respect to pollen polarization, bulging, or growth site selection at the pollen plasma membrane. PMID:25954283

  5. The Ski2-family helicase Obelus regulates Crumbs alternative splicing and cell polarity.

    PubMed

    Vichas, Athea; Laurie, Matthew T; Zallen, Jennifer A

    2015-12-01

    Alternative splicing can have profound consequences for protein activity, but the functions of most alternative splicing regulators are not known. We show that Obelus, a conserved Ski2-family helicase, is required for cell polarity and adherens junction organization in the Drosophila melanogaster embryo. In obelus mutants, epithelial cells display an expanded apical domain, aggregation of adherens junctions at the cell membrane, and microtubule-dependent defects in centrosome positioning. Through whole-genome transcriptome analysis, we found that Obelus is required for the alternative splicing of a small number of transcripts in the early embryo, including the pre-mRNA that encodes the apical polarity protein Crumbs. In obelus mutants, inclusion of an alternative exon results in increased expression of a Crumbs isoform that contains an additional epidermal growth factor-like repeat in the extracellular domain. Overexpression of this alternative Crumbs isoform recapitulates the junctional aggregation and centrosome positioning defects of obelus mutants. These results indicate that regulation of Crumbs alternative splicing by the Obelus helicase modulates epithelial polarity during development. PMID:26644515

  6. Ciliary proteins Bbs8 and Ift20 promote planar cell polarity in the cochlea.

    PubMed

    May-Simera, Helen L; Petralia, Ronald S; Montcouquiol, Mireille; Wang, Ya-Xian; Szarama, Katherine B; Liu, Yun; Lin, Weichun; Deans, Michael R; Pazour, Gregory J; Kelley, Matthew W

    2015-02-01

    Primary cilia have been implicated in the generation of planar cell polarity (PCP). However, variations in the severity of polarity defects in different cilia mutants, coupled with recent demonstrations of non-cilia-related actions of some cilia genes, make it difficult to determine the basis of these polarity defects. To address this issue, we evaluated PCP defects in cochlea from a selection of mice with mutations in cilia-related genes. Results indicated notable PCP defects, including mis-oriented hair cell stereociliary bundles, in Bbs8 and Ift20 single mutants that are more severe than in other cilia gene knockouts. In addition, deletion of either Bbs8 or Ift20 results in disruptions in asymmetric accumulation of the core PCP molecule Vangl2 in cochlear cells, suggesting a role for Bbs8 and/or Ift20, possibly upstream of core PCP asymmetry. Consistent with this, co-immunoprecipitation experiments indicate direct interactions of Bbs8 and Ift20 with Vangl2. We observed localization of Bbs and Ift proteins to filamentous actin as well as microtubules. This could implicate these molecules in selective trafficking of membrane proteins upstream of cytoskeletal reorganization, and identifies new roles for cilia-related proteins in cochlear PCP. PMID:25605782

  7. Characterization of a pancreatic islet cell tumor in a polar bear (Ursus maritimus).

    PubMed

    Fortin, Jessica S; Benoit-Biancamano, Marie-Odile

    2014-01-01

    Herein, we report a 25-year-old male polar bear suffering from a pancreatic islet cell tumor. The aim of this report is to present a case of this rare tumor in a captive polar bear. The implication of potential risk factors such as high carbohydrate diet or the presence of amyloid fibril deposits was assessed. Necropsy examination revealed several other changes, including nodules observed in the liver, spleen, pancreas, intestine, and thyroid glands that were submitted for histopathologic analysis. Interestingly, the multiple neoplastic nodules were unrelated and included a pancreatic islet cell tumor. Immunohistochemistry of the pancreas confirmed the presence of insulin and islet amyloid polypeptide (IAPP) within the pancreatic islet cells. The IAPP gene was extracted from the paraffin-embedded liver tissue and sequenced. IAPP cDNA from the polar bear exhibits some differences as compared to the sequence published for several other species. Different factors responsible for neoplasms in bears such as diet, infectious agents, and industrial chemical exposure are reviewed. This case report raised several issues that further studies may address by evaluating the prevalence of cancers in captive or wild animals. PMID:25273481

  8. Tumor cell-activated CARD9 signaling contributes to metastasis-associated macrophage polarization.

    PubMed

    Yang, M; Shao, J-H; Miao, Y-J; Cui, W; Qi, Y-F; Han, J-H; Lin, X; Du, J

    2014-08-01

    Macrophages are critical immune effector cells of the tumor microenvironment that promote seeding, extravasation and persistent growth of tumor cells in primary tumors and metastatic sites. Tumor progression and metastasis are affected by dynamic changes in the specific phenotypes of macrophage subpopulations; however, the mechanisms by which tumor cells modulate macrophage polarization remain incompletely understood. Caspase recruitment domain-containing protein 9 (CARD9) is a central adaptor protein of innate immune responses to extracellular pathogens. We report that increased CARD9 expression is primarily localized in infiltrated macrophages and significantly associated with advanced histopathologic stage and the presence of metastasis. Using CARD9-deficient (CARD9(-/-)) mice, we show that bone marrow-derived CARD9 promotes liver metastasis of colon carcinoma cells. Mechanistic studies reveal that CARD9 contributes to tumor metastasis by promoting metastasis-associated macrophage polarization through activation of the nuclear factor-kappa B signaling pathway. We further demonstrate that tumor cell-secreted vascular endothelial growth factor facilitates spleen tyrosine kinase activation in macrophages, which is necessary for formation of the CARD9-B-cell lymphoma/leukemia 10-mucosa-associated lymphoid tissue lymphoma translocation protein 1 complex. Taken together, our results indicating that CARD9 is a regulator of metastasis-associated macrophages will lead to new insights into evolution of the microenvironments supporting tumor metastasis, thereby providing targets for anticancer therapies. PMID:24722209

  9. Polarity, cell division, and out-of-equilibrium dynamics control the growth of epithelial structures

    PubMed Central

    Cerruti, Benedetta; Puliafito, Alberto; Shewan, Annette M.; Yu, Wei; Combes, Alexander N.; Little, Melissa H.; Chianale, Federica; Primo, Luca; Serini, Guido; Mostov, Keith E.; Celani, Antonio

    2013-01-01

    The growth of a well-formed epithelial structure is governed by mechanical constraints, cellular apico-basal polarity, and spatially controlled cell division. Here we compared the predictions of a mathematical model of epithelial growth with the morphological analysis of 3D epithelial structures. In both in vitro cyst models and in developing epithelial structures in vivo, epithelial growth could take place close to or far from mechanical equilibrium, and was determined by the hierarchy of time-scales of cell division, cell–cell rearrangements, and lumen dynamics. Equilibrium properties could be inferred by the analysis of cell–cell contact topologies, and the nonequilibrium phenotype was altered by inhibiting ROCK activity. The occurrence of an aberrant multilumen phenotype was linked to fast nonequilibrium growth, even when geometric control of cell division was correctly enforced. We predicted and verified experimentally that slowing down cell division partially rescued a multilumen phenotype induced by altered polarity. These results improve our understanding of the development of epithelial organs and, ultimately, of carcinogenesis. PMID:24145168

  10. Universal polarization terahertz phase controllers using randomly aligned liquid crystal cells with graphene electrodes.

    PubMed

    Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro; Ono, Hiroshi

    2015-04-01

    We present a universal polarization terahertz (THz) phase controller using a randomly aligned liquid crystal (LC) cell with graphene electrodes. The LC cell was fabricated using a nematic LC and two quartz substrates that were coated with a monolayer of graphene as the transparent electrode. The LC in the cell was prepared without any alignment treatments and was randomly aligned. The size of the random domains and the width of the disclination lines in the LC layer were several tens of microns. These textures disappeared when an alternating voltage was applied to the LC through the graphene layers. Using a THz time domain spectroscopic technique, we investigated the complex transmittance of the LC cell. The LC cell was highly transparent in the THz frequency range, and there was little change in the transmittance with the applied voltage. This indicated that the scattering loss originating in the randomly aligned LC molecules was small for the THz waves. We also demonstrated that the THz phase shift could be controlled by the applied voltage. The amplitude of the phase shift was explained by the ordinary and extraordinary refractive indices of the LC. These LC cells with graphene electrodes can be used to realize universal polarization THz phase controllers because of the random alignment. PMID:25831380

  11. A polarized Ca2+, diacylglycerol, and STIM1 signaling system regulates directed cell migration

    PubMed Central

    Tsai, Feng-Chiao; Seki, Akiko; Yang, Hee Won; Hayer, Arnold; Carrasco, Silvia; Malmersjö, Seth; Meyer, Tobias

    2014-01-01

    Ca2+ signals control cell migration by regulating forward movement and cell adhesion. However, it is not well understood how Ca2+-regulatory proteins and second messengers are spatially organized in migrating cells. Here we show that receptor tyrosine kinase and phospholipase C signaling are restricted to the front of migrating endothelial leader cells, triggering local Ca2+ pulses, local depletion of Ca2+ in the endoplasmic reticulum, and local activation of STIM1, supporting pulsatile front retraction and adhesion. At the same time, the mediator of store-operated Ca2+ influx STIM1 is transported by microtubule plus ends to the front. Furthermore, higher Ca2+ pump rates in the front relative to the back of the plasma membrane enable effective local Ca2+ signaling by locally decreasing basal Ca2+. Finally, polarized phospholipase C signaling generates a diacylglycerol gradient towards the front that promotes persistent forward migration. Thus, cells employ an integrated Ca2+ control system with polarized Ca2+ signaling proteins and second messengers to synergistically promote directed cell migration. PMID:24463606

  12. Segregation of leading-edge and uropod components into specific lipid rafts during T cell polarization

    PubMed Central

    Gómez-Moutón, Concepción; Abad, Jose Luis; Mira, Emilia; Lacalle, Rosa Ana; Gallardo, Eduard; Jiménez-Baranda, Sonia; Illa, Isabel; Bernad, Antonio; Mañes, Santos; Martínez-A., Carlos

    2001-01-01

    Redistribution of specialized molecules in migrating cells develops asymmetry between two opposite cell poles, the leading edge and the uropod. We show that acquisition of a motile phenotype in T lymphocytes results in the asymmetric redistribution of ganglioside GM3- and GM1-enriched raft domains to the leading edge and to the uropod, respectively. This segregation to each cell pole parallels the specific redistribution of membrane proteins associated to each raft subfraction. Our data suggest that raft partitioning is a major determinant for protein redistribution in polarized T cells, as ectopic expression of raft-associated proteins results in their asymmetric redistribution, whereas non-raft-partitioned mutants of these proteins are distributed homogeneously in the polarized cell membrane. Both acquisition of a migratory phenotype and SDF-1α-induced chemotaxis are cholesterol depletion-sensitive. Finally, GM3 and GM1 raft redistribution requires an intact actin cytoskeleton, but is insensitive to microtubule disruption. We propose that membrane protein segregation not only between raft and nonraft domains but also between distinct raft subdomains may be an organizational principle that mediates redistribution of specialized molecules needed for T cell migration. PMID:11493690

  13. Actin flows in cell migration: from locomotion and polarity to trajectories.

    PubMed

    Callan-Jones, Andrew C; Voituriez, Raphaël

    2016-02-01

    Eukaryotic cell movement is characterized by very diverse migration modes. Recent studies show that cells can adapt to environmental cues, such as adhesion and geometric confinement, thereby readily switching their mode of migration. Among this diversity of motile behavior, actin flows have emerged as a highly conserved feature of both mesenchymal and amoeboid migration, and have also been identified as key regulators of cell polarity. This suggests that the various observed migration modes are continuous variations of elementary locomotion mechanisms, based on a very robust physical property of the actin/myosin system - its ability to sustain flows at the cell scale. This central role of actin/myosin flows is shown to affect the large scale properties of cell trajectories. PMID:26827283

  14. An experimental set-up to apply polarization modulation to infrared reflection absorption spectroscopy for improved in situ studies of atmospheric corrosion processes

    SciTech Connect

    Wiesinger, R.; Schade, U.; Kleber, Ch.; Schreiner, M.

    2014-06-15

    A new set-up for improved monitoring of atmospheric corrosion processes in situ and in real-time is presented. To characterize chemical structures of thin films on metal surfaces surface sensitive analytical techniques are required. One possible technique is Infrared Reflection Absorption Spectroscopy (IRRAS) which has become an established method to investigate surface corrosion films of thicknesses less than 200 nm. However, there are limitations related to the sensitivity of these measurements, in case of investigating ultrathin films or absorption bands of interest, surface species are superimposed by atmospheric background absorption, which changes during in situ measurements in ambient atmospheres. These difficulties of in situ surface reflection measurements can be eliminated by availing the polarization selectivity of adsorbed surface species. At grazing angles of incidence the absorption of p-polarized infrared radiation by thin surface films on metals is enhanced, while the absorption of s-polarized light by this film is nearly zero. This different behavior of the polarization properties leads to strong selection rules at the surface and can therefore be used to identify molecules adsorbed on metal surfaces. Polarization Modulation (PM) of the infrared (IR) light takes advantage of this disparity of polarization on sample surfaces and in combination with IRRAS yielding a very sensitive and surface-selective method for obtaining IR spectra of ultra-thin films on metal surfaces. An already existing in situ IRRAS/Quartz Crystal Microbalance weathering cell was combined with PM and evaluated according to its applicability to study in situ atmospheric corrosion processes. First real-time measurements on silver samples exposed to different atmospheres were performed showing the advantage of PM-IRRAS compared to conventional IRRAS for such investigations.

  15. An experimental set-up to apply polarization modulation to infrared reflection absorption spectroscopy for improved in situ studies of atmospheric corrosion processes.

    PubMed

    Wiesinger, R; Schade, U; Kleber, Ch; Schreiner, M

    2014-06-01

    A new set-up for improved monitoring of atmospheric corrosion processes in situ and in real-time is presented. To characterize chemical structures of thin films on metal surfaces surface sensitive analytical techniques are required. One possible technique is Infrared Reflection Absorption Spectroscopy (IRRAS) which has become an established method to investigate surface corrosion films of thicknesses less than 200 nm. However, there are limitations related to the sensitivity of these measurements, in case of investigating ultrathin films or absorption bands of interest, surface species are superimposed by atmospheric background absorption, which changes during in situ measurements in ambient atmospheres. These difficulties of in situ surface reflection measurements can be eliminated by availing the polarization selectivity of adsorbed surface species. At grazing angles of incidence the absorption of p-polarized infrared radiation by thin surface films on metals is enhanced, while the absorption of s-polarized light by this film is nearly zero. This different behavior of the polarization properties leads to strong selection rules at the surface and can therefore be used to identify molecules adsorbed on metal surfaces. Polarization Modulation (PM) of the infrared (IR) light takes advantage of this disparity of polarization on sample surfaces and in combination with IRRAS yielding a very sensitive and surface-selective method for obtaining IR spectra of ultra-thin films on metal surfaces. An already existing in situ IRRAS/Quartz Crystal Microbalance weathering cell was combined with PM and evaluated according to its applicability to study in situ atmospheric corrosion processes. First real-time measurements on silver samples exposed to different atmospheres were performed showing the advantage of PM-IRRAS compared to conventional IRRAS for such investigations. PMID:24985826

  16. An experimental set-up to apply polarization modulation to infrared reflection absorption spectroscopy for improved in situ studies of atmospheric corrosion processes

    NASA Astrophysics Data System (ADS)

    Wiesinger, R.; Schade, U.; Kleber, Ch.; Schreiner, M.

    2014-06-01

    A new set-up for improved monitoring of atmospheric corrosion processes in situ and in real-time is presented. To characterize chemical structures of thin films on metal surfaces surface sensitive analytical techniques are required. One possible technique is Infrared Reflection Absorption Spectroscopy (IRRAS) which has become an established method to investigate surface corrosion films of thicknesses less than 200 nm. However, there are limitations related to the sensitivity of these measurements, in case of investigating ultrathin films or absorption bands of interest, surface species are superimposed by atmospheric background absorption, which changes during in situ measurements in ambient atmospheres. These difficulties of in situ surface reflection measurements can be eliminated by availing the polarization selectivity of adsorbed surface species. At grazing angles of incidence the absorption of p-polarized infrared radiation by thin surface films on metals is enhanced, while the absorption of s-polarized light by this film is nearly zero. This different behavior of the polarization properties leads to strong selection rules at the surface and can therefore be used to identify molecules adsorbed on metal surfaces. Polarization Modulation (PM) of the infrared (IR) light takes advantage of this disparity of polarization on sample surfaces and in combination with IRRAS yielding a very sensitive and surface-selective method for obtaining IR spectra of ultra-thin films on metal surfaces. An already existing in situ IRRAS/Quartz Crystal Microbalance weathering cell was combined with PM and evaluated according to its applicability to study in situ atmospheric corrosion processes. First real-time measurements on silver samples exposed to different atmospheres were performed showing the advantage of PM-IRRAS compared to conventional IRRAS for such investigations.

  17. NKp46 Clusters at the Immune Synapse and Regulates NK Cell Polarization

    PubMed Central

    Hadad, Uzi; Thauland, Timothy J.; Martinez, Olivia M.; Butte, Manish J.; Porgador, Angel; Krams, Sheri M.

    2015-01-01

    Natural killer (NK) cells play an important role in first-line defense against tumor and virus-infected cells. The activity of NK cells is tightly regulated by a repertoire of cell surface expressed inhibitory and activating receptors. NKp46 is a major NK cell-activating receptor that is involved in the elimination of target cells. NK cells form different types of synapses that result in distinct functional outcomes: cytotoxic, inhibitory, and regulatory. Recent studies revealed that complex integration of NK receptor signaling controls cytoskeletal rearrangement and other immune synapse-related events. However, the distinct nature by which NKp46 participates in NK immunological synapse formation and function remains unknown. In this study, we determined that NKp46 forms microclusters structures at the immune synapse between NK cells and target cells. Over-expression of human NKp46 is correlated with increased accumulation of F-actin mesh at the immune synapse. Concordantly, knock-down of NKp46 in primary human NK cells decreased recruitment of F-actin to the synapse. Live cell imaging experiments showed a linear correlation between NKp46 expression and lytic granules polarization to the immune synapse. Taken together, our data suggest that NKp46 signaling directly regulates the NK lytic immune synapse from early formation to late function. PMID:26441997

  18. Polarity mechanisms such as contact inhibition of locomotion regulate persistent rotational motion of mammalian cells on micropatterns

    PubMed Central

    Camley, Brian A.; Zhang, Yunsong; Zhao, Yanxiang; Li, Bo; Ben-Jacob, Eshel; Levine, Herbert; Rappel, Wouter-Jan

    2014-01-01

    Pairs of endothelial cells on adhesive micropatterns rotate persistently, but pairs of fibroblasts do not; coherent rotation is present in normal mammary acini and kidney cells but absent in cancerous cells. Why? To answer this question, we develop a computational model of pairs of mammalian cells on adhesive micropatterns using a phase field method and study the conditions under which persistent rotational motion (PRM) emerges. Our model couples the shape of the cell, the cell’s internal chemical polarity, and interactions between cells such as volume exclusion and adhesion. We show that PRM can emerge from this minimal model and that the cell-cell interface may be influenced by the nucleus. We study the effect of various cell polarity mechanisms on rotational motion, including contact inhibition of locomotion, neighbor alignment, and velocity alignment, where cells align their polarity to their velocity. These polarity mechanisms strongly regulate PRM: Small differences in polarity mechanisms can create significant differences in collective rotation. We argue that the existence or absence of rotation under confinement may lead to insight into the cell’s methods for coordinating collective cell motility. PMID:25258412

  19. Dual-Specificity Phosphatase 4 Regulates STAT5 Protein Stability and Helper T Cell Polarization*

    PubMed Central

    Liao, Fang-Hsuean; Chan, Yi-Chiao; Huang, Ching-Yu

    2015-01-01

    Immune responses are critically regulated by the functions of CD4 helper T cells. Based on their secreted cytokines, helper T cells are further categorized into different subsets like Treg or Th17 cells, which suppress or promote inflammatory responses, respectively. Signals from IL-2 activate the transcription factor STAT5 to promote Treg but suppress Th17 cell differentiation. Our previous results found that the deficiency of a dual-specificity phosphatase, DUSP4, induced STAT5 hyper-activation, enhanced IL-2 signaling, and increased T cell proliferation. In this report, we examined the effects of DUSP4 deficiency on helper T cell differentiation and STAT5 regulation. Our in vivo data showed that DUSP4 mice were more resistant to the induction of autoimmune encephalitis, while in vitro differentiations revealed enhanced iTreg and reduced Th17 polarization in DUSP4-deficient T cells. To study the cause of this altered helper T cell polarization, we performed luciferase reporter assays and confirmed that, as predicted by our previous report, DUSP4 over-expression suppressed the transcription factor activity of STAT5. Surprisingly, we also found that DUSP4-deficient T but not B cells exhibited elevated STAT5 protein levels, and over-expressed DUSP4 destabilized STAT5 in vitro; moreover, this destabilization required the phosphatase activity of DUSP4, and was insensitive to MG132 treatment. Finally, domain-mapping results showed that both the substrate-interacting and the phosphatase domains of DUSP4 were required for its optimal interaction with STAT5, while the coiled-coil domain of STAT5 appeared to hinder this interaction. Our data thus provide the first genetic evidence that DUSP4 is important for helper T cell development. In addition, they also help uncover the novel, DUSP4-mediated regulation of STAT5 protein stability. PMID:26710253

  20. Wideband Reception and Processing for Dual-Polarization Radars with Dual Transmitters

    SciTech Connect

    Choudhury, Sutanay; Chandrasekar, V.

    2007-01-01

    Improving the estimation accuracy and reducing the time required for measurement are governing goals for any radar design. Polarimetric weather radar measures the polarization covariance matrix of the signal returns from precipitation volumes in addition to the Doppler parameters. Increasing the equivalent number of independent samples in any estimation process results in decrease in the standard deviation of estimates. Oversampling pulsed Doppler radar returns at a rate larger than the pulse bandwidth, whitening the range samples and subsequent averaging have been pursued as a potential way to decrease the measured standard deviation of signal parameters estimates. It has been shown that the application of oversampling, whitening and subsequent averaging improves the quality of reflectivity and mean velocity estimates in agreement with theory; Oversampled data collected from CSU-CHILL radar are analyzed to evaluate the performance of dual-polarization parameter estimators such as differential reflectivity and differential phase. The reasons that may limit the improvement in estimation quality of polarimetric parameters are investigated. It is demonstrated that the observation of the variability of range signals within subpulses is important for obtaining maximum variance reduction through whitening. Accurate measurement of the amplitude and phase of the transmitted pulse is critically important for effective whitening of the received waveform. The differential phase pattern between the transmit pulses is found to be critical for obtaining unbiased and accurate estimates of polarimetric parameters through whitening. CSU-CHILL radar's transmit pulse sampling capability is used to evaluate the impact of waveforms on oversampling and estimation.

  1. Comparison of clinical grade type 1 polarized and standard matured dendritic cells for cancer immunotherapy.

    PubMed

    Hansen, Morten; Hjortø, Gertrud Malene; Donia, Marco; Met, Özcan; Larsen, Niels Bent; Andersen, Mads Hald; thor Straten, Per; Svane, Inge Marie

    2013-01-11

    Monocyte-derived dendritic cells (DCs) used for immunotherapy e.g. against cancer are commonly matured by pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) and prostaglandin E(2) although the absence of Toll-like receptor mediated activation prevents secretion of IL-12 from DCs and subsequent efficient induction of type 1 effector T cells. Standard matured clinical grade DCs "sDCs" were compared with DCs matured with either of two type 1 polarizing maturation cocktails; the alpha-type-1 DCs "αDC1s" (TNF-α, IL-1β, IFN-γ, IFN-α, Poly(I:C)) and "mDCs" (monophosphoryl lipid A (MPL), IFN-γ) or a mixed cocktail - "mpDCs", containing MPL, IFN-γ and PGE(2). αDC1s and mDCs secreted IL-12 directly and following re-stimulation with CD40L-expressing cells and they mainly secreted the T effector cell attracting chemokines CXCL10 and CCL5 as opposed to sDCs that mainly secreted CCL22, known to attract regulatory T cells. αDC1s and mDCs were functionally superior to sDCs as they polarized naïve CD4(+) T cells most efficiently into T helper type 1 effector cells and primed more functional MART-1 specific CD8(+) T cells although with variation between donors. αDC1s and mDCs were transiently less capable of CCL21-directed transwell migration than standard matured DCs, likely due to their increased secretion of CCL19, which mediate internalization of CCR7. mpDCs were intermediate between standard and polarized DCs both in terms of IL-12 secretion and transwell migratory ability but functionally they resembled sDCs and strikingly had the highest expression of the inhibitory molecules PD-L1 and CD25. Thus, further studies with type 1 polarized DCs are warranted for use in immunotherapy, but when combined with PGE(2) as in mpDCs, they seems to be less optimal for maturation of DCs. PMID:23200882

  2. Cell culture processes for monoclonal antibody production

    PubMed Central

    Li, Feng; Vijayasankaran, Natarajan; Shen, Amy (Yijuan); Kiss, Robert

    2010-01-01

    Animal cell culture technology has advanced significantly over the last few decades and is now generally considered a reliable, robust and relatively mature technology. A range of biotherapeutics are currently synthesized using cell culture methods in large scale manufacturing facilities that produce products for both commercial use and clinical studies. The robust implementation of this technology requires optimization of a number of variables, including (1) cell lines capable of synthesizing the required molecules at high productivities that ensure low operating cost; (2) culture media and bioreactor culture conditions that achieve both the requisite productivity and meet product quality specifications; (3) appropriate on-line and off-line sensors capable of providing information that enhances process control; and (4) good understanding of culture performance at different scales to ensure smooth scale-up. Successful implementation also requires appropriate strategies for process development, scale-up and process characterization and validation that enable robust operation and ensure compliance with current regulations. This review provides an overview of the state-of-the art technology in key aspects of cell culture, e.g., generation of highly productive cell lines and optimization of cell culture process conditions. We also summarize the current thinking on appropriate process development strategies and process advances that might affect process development. PMID:20622510

  3. Polarization- and wavelength-sensitive sub-wavelength structures fabricated in the metal layers of deep submicron CMOS processes

    NASA Astrophysics Data System (ADS)

    Junger, Stephan; Tschekalinskij, Wladimir; Verwaal, Nanko; Weber, Norbert

    2010-05-01

    Sub-wavelength structures in metal films have interesting optical properties that can be implemented for sensing applications: gratings act as wire grid polarizer, hole arrays with enhanced transmission can be used as spectral filters. This paper demonstrates the feasibility of these nanostructures using 180 nm and 90 nm complementary metal-oxide semiconductor (CMOS) processes. The metal layers of the process can be used for optical nanostructures with feature sizes down to 100 nm. We describe the design and simulation of these metal structures using the finite-difference timedomain (FDTD) method. The spectral response of the test structures was measured for different polarizations, where the gratings showed typical features of wire grid polarizers. Using a 180 nm CMOS image sensor process, an image sensor with 6 μm pixel size was designed and fabricated with different polarization selective structures allowing for polarization imaging. A polarization camera using this image sensor is demonstrated, visualizing stress birefringence as an application example. Finally, first results on the fabrication of hole arrays with a period of 320 nm are presented, showing color filters with enhanced transmission.

  4. Mycobacterium tuberculosislpdC, Rv0462, induces dendritic cell maturation and Th1 polarization

    SciTech Connect

    Heo, Deok Rim; Shin, Sung Jae; Kim, Woo Sik; Noh, Kyung Tae; Park, Jin Wook; Son, Kwang Hee; Park, Won Sun; Lee, Min-Goo; Kim, Daejin; Shin, Yong Kyoo; Jung, In Duk; Park, Yeong-Min

    2011-08-05

    Highlights: {yields} Treatment with Rv0462 induces the expression of surface molecules and the production of cytokines in DCs. {yields} Rv0462 induces the activation of MAPKs. {yields} Rv0462-treated DCs enhances the proliferation of CD4{sup +} T cells. -- Abstract: Mycobacterium tuberculosis, the etiological factor of pulmonary tuberculosis, causes significant morbidity and mortality worldwide. Activation of host immune responses for containment of mycobacterial infections involves participation of innate immune cells, such as dendritic cells (DCs). In this study, we demonstrated that the gene encoding lipoamide dehydrogenase C (lpdC) from M. tuberculosis, Rv0462, induce maturation and activation of DCs involved in the MAPKs signaling pathway. Moreover, Rv0462-treated DCs activated naive T cells, polarized CD4{sup +} and CD8{sup +} T cells to secrete IFN-{gamma} in syngeneic mixed lymphocyte reactions, which would be expected to contribute to Th1 polarization of the immune response. Our results suggest that Rv0462 can contribute to the innate and adaptive immune responses during tuberculosis infection, and thus modulate the clinical course of tuberculosis.

  5. Evolutionarily conserved sites in yeast tropomyosin function in cell polarity, transport and contractile ring formation

    PubMed Central

    Cranz-Mileva, Susanne; MacTaggart, Brittany; Russell, Jacquelyn; Hitchcock-DeGregori, Sarah E.

    2015-01-01

    ABSTRACT Tropomyosin is a coiled-coil protein that binds and regulates actin filaments. The tropomyosin gene in Schizosaccharomyces pombe, cdc8, is required for formation of actin cables, contractile rings, and polar localization of actin patches. The roles of conserved residues were investigated in gene replacement mutants. The work validates an evolution-based approach to identify tropomyosin functions in living cells and sites of potential interactions with other proteins. A cdc8 mutant with near-normal actin affinity affects patch polarization and vacuole fusion, possibly by affecting Myo52p, a class V myosin, function. The presence of labile residual cell attachments suggests a delay in completion of cell division and redistribution of cell patches following cytokinesis. Another mutant with a mild phenotype is synthetic negative with GFP-fimbrin, inferring involvement of the mutated tropomyosin sites in interaction between the two proteins. Proteins that assemble in the contractile ring region before actin do so in a mutant cdc8 strain that cannot assemble condensed actin rings, yet some cells can divide. Of general significance, LifeAct-GFP negatively affects the actin cytoskeleton, indicating caution in its use as a biomarker for actin filaments. PMID:26187949

  6. Topological control of the Caulobacter cell cycle circuitry by a polarized single-domain PAS protein

    PubMed Central

    Sanselicio, Stefano; Bergé, Matthieu; Théraulaz, Laurence; Radhakrishnan, Sunish Kumar; Viollier, Patrick H.

    2015-01-01

    Despite the myriad of different sensory domains encoded in bacteria, only a few types are known to control the cell cycle. Here we use a forward genetic screen for Caulobacter crescentus motility mutants to identify a conserved single-domain PAS (Per-Arnt-Sim) protein (MopJ) with pleiotropic regulatory functions. MopJ promotes re-accumulation of the master cell cycle regulator CtrA after its proteolytic destruction is triggered by the DivJ kinase at the G1-S transition. MopJ and CtrA syntheses are coordinately induced in S-phase, followed by the sequestration of MopJ to cell poles in Caulobacter. Polarization requires Caulobacter DivJ and the PopZ polar organizer. MopJ interacts with DivJ and influences the localization and activity of downstream cell cycle effectors. Because MopJ abundance is upregulated in stationary phase and by the alarmone (p)ppGpp, conserved systemic signals acting on the cell cycle and growth phase control are genetically integrated through this conserved single PAS-domain protein. PMID:25952018

  7. T cell receptor reversed polarity recognition of a self-antigen major histocompatibility complex.

    PubMed

    Beringer, Dennis X; Kleijwegt, Fleur S; Wiede, Florian; van der Slik, Arno R; Loh, Khai Lee; Petersen, Jan; Dudek, Nadine L; Duinkerken, Gaby; Laban, Sandra; Joosten, Antoinette; Vivian, Julian P; Chen, Zhenjun; Uldrich, Adam P; Godfrey, Dale I; McCluskey, James; Price, David A; Radford, Kristen J; Purcell, Anthony W; Nikolic, Tatjana; Reid, Hugh H; Tiganis, Tony; Roep, Bart O; Rossjohn, Jamie

    2015-11-01

    Central to adaptive immunity is the interaction between the αβ T cell receptor (TCR) and peptide presented by the major histocompatibility complex (MHC) molecule. Presumably reflecting TCR-MHC bias and T cell signaling constraints, the TCR universally adopts a canonical polarity atop the MHC. We report the structures of two TCRs, derived from human induced T regulatory (iT(reg)) cells, complexed to an MHC class II molecule presenting a proinsulin-derived peptide. The ternary complexes revealed a 180° polarity reversal compared to all other TCR-peptide-MHC complex structures. Namely, the iT(reg) TCR α-chain and β-chain are overlaid with the α-chain and β-chain of MHC class II, respectively. Nevertheless, this TCR interaction elicited a peptide-reactive, MHC-restricted T cell signal. Thus TCRs are not 'hardwired' to interact with MHC molecules in a stereotypic manner to elicit a T cell signal, a finding that fundamentally challenges our understanding of TCR recognition. PMID:26437244

  8. A novel monoclonal antibody against the second extracellular loop of occludin disrupts epithelial cell polarity.

    PubMed

    Tokunaga, Yuichi; Kojima, Takashi; Osanai, Makoto; Murata, Masaki; Chiba, Hideki; Tobioka, Hirotoshi; Sawada, Norimasa

    2007-07-01

    The tight junction (TJ) regulates epithelial cell polarity and paracellular permeability. In the present study, to investigate whether the second extracellular loop of occludin affects the localization of carcinoembryonic antigen (CEA) and CD26 expressed on apical membranes, and the fence function of the TJ, the human intestinal epithelial cell line T84 was treated with the monoclonal anti-occludin antibody (MAb) 1H8, corresponding to the second extracellular loop of occludin. In T84 cells treated with MAb 1H8, occludin disappeared, and CEA and CD26 were observed to diffuse from the apical membrane to the basolateral membrane. Furthermore, a decrease in the fence function of TJ was observed without changes in the TJ strands and barrier function. When T84 cells precultured in low calcium (Ca) medium were recultured in normal Ca medium in the presence of MAb 1H8, recruitment of occludin to the apical-most membranes and recovery in distribution of CEA and CD26 were markedly retarded compared with the control. These results suggested that MAb 1H8 against the second extracellular loop of occludin selectively affected formation of the apical/basolateral intramembrane diffusion barrier and that the second extracellular loop of occludin plays a crucial role in the maintenance of epithelial cell polarity by the TJ. PMID:17371936

  9. Th17 polarization of memory Th cells in early arthritis: the vasoactive intestinal peptide effect.

    PubMed

    Jimeno, Rebeca; Leceta, Javier; Garín, Marina; Ortiz, Ana M; Mellado, Mario; Rodríguez-Frade, Jose Miguel; Martínez, Carmen; Pérez-García, Selene; Gomariz, Rosa P; Juarranz, Yasmina

    2015-08-01

    Several studies in humans indicate the implication of Th17 cells in RA. Therapies targeting their pathogenicity, as well as their plasticity to the Th17/1 phenotype, could ameliorate the progression of the pathology. The neuroendocrine environment has a major impact on the differentiation of lymphoid cells. VIP is present in the microenvironment of the joint, and its known therapeutic effects are supported by several studies on RA. We examine the ability of VIP to modulate the differentiation of Th17 cells. Peripheral blood CD4(+)CD45RO(+) T cells from HD and eRA patients were expanded under Th17-polarizing conditions in the presence of TGF-β. After 7 days, the higher IL-17A, IL-21, and IL-9 levels and lower IL-22 levels indicate the nonpathogenic profile for Th17 cells in HD. In contrast, Th17 cells from eRA patients produced significantly more IL-22 and IFN-γ, and these cells show a more Th17/1 profile, indicating a pathogenic phenotype. Interestingly, when VIP was present in the Th17 conditioned medium, increased levels of IL-10 and IL-9 were detected in HD and eRA patients. VIP also reduced the levels of IL-22 in eRA patients. These data suggest that VIP reduces the pathogenic profile of the Th17-polarized cells. This effect was accompanied by an increased in the Treg/Th17 profile, as shown by the increase levels of Foxp3. In conclusion, this report addresses a novel and interesting question on the effect of VIP on human Th17 cells and adds clinical relevance by analyzing, in parallel, HD and eRA patients. PMID:25957307

  10. [Targeting of type IV carbonic anhydrases in Capan-1 human pancreatic duct cells is concomitant of the polarization].

    PubMed

    Mairal, A; Fanjul, M; Hollande, E

    1996-01-01

    Carbonic anhydrases II and IV play an essential role in the synthesis and secretion of HCO3- ions in pancreatic duct cells. Secretion of these ions is regulated by the CFTR (cystic fibrosis transmembrane conductance regulator) chloride channel. In the present study, the expression of carbonic anhydrases IV and their targeting to plasma membranes were examined during the growth of human pancreatic duct cells in vitro. Human cancerous pancreatic duct cells of Capan-1 cell line which polarize during their growth were used. We show that: a) these cells express carbonic anhydrases IV continuously during growth in culture, and the expression depends on the stage of growth and the conformation of the cells; b) carbonic anhydrases IV are seen in the cytoplasm in non-polarized cells, but become progressively anchored to plasma membranes as the cells polarize, being targeted to the apical membranes of polarized cells; c) the subcellular distribution of carbonic anhydrases IV indicates that these enzymes are synthetized in rough endoplasmic reticulum and then transported towards the plasma membrane using the classical secretory pathway through the Golgi apparatus. The results indicated that targeting of carbonic anhydrases IV in Capan-1 cells is linked to cellular polarization. PMID:8881572

  11. A Comparative Study of the T Cell Stimulatory and Polarizing Capacity of Human Primary Blood Dendritic Cell Subsets

    PubMed Central

    Sittig, Simone P.; Bakdash, Ghaith; Weiden, Jorieke; Sköld, Annette E.; Tel, Jurjen; Figdor, Carl G.; de Vries, I. Jolanda M.

    2016-01-01

    Dendritic cells (DCs) are central players of immune responses; they become ac