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Sample records for actin-rich membrane protrusions

  1. Lgr4 and Lgr5 drive the formation of long actin-rich cytoneme-like membrane protrusions

    PubMed Central

    Snyder, Joshua C.; Rochelle, Lauren K.; Marion, Sébastien; Lyerly, H. Kim; Barak, Larry S.; Caron, Marc G.

    2015-01-01

    ABSTRACT Embryonic development and adult tissue homeostasis require precise information exchange between cells and their microenvironment to coordinate cell behavior. A specialized class of ultra-long actin-rich filopodia, termed cytonemes, provides one mechanism for this spatiotemporal regulation of extracellular cues. We provide here a mechanism whereby the stem-cell marker Lgr5, and its family member Lgr4, promote the formation of cytonemes. Lgr4- and Lgr5-induced cytonemes exceed lengths of 80 µm, are generated through stabilization of nascent filopodia from an underlying lamellipodial-like network and functionally provide a pipeline for the transit of signaling effectors. As proof-of-principle, we demonstrate that Lgr5-induced cytonemes act as conduits for cell signaling by demonstrating that the actin motor and filopodial cargo carrier protein myosin X (Myo10) and the G-protein-coupled receptor (GPCR) signaling effector β-arrestin-2 (Arrb2) transit into cytonemes. This work delineates a biological function for Lgr4 and Lgr5 and provides the rationale to fully investigate Lgr4 and Lgr5 function and cytonemes in mammalian stem cell and cancer stem cell behavior. PMID:25653388

  2. Human Papillomavirus Type 16 Entry: Retrograde Cell Surface Transport along Actin-Rich Protrusions

    PubMed Central

    Schelhaas, Mario; Ewers, Helge; Rajamäki, Minna-Liisa; Day, Patricia M.; Schiller, John T.; Helenius, Ari

    2008-01-01

    The lateral mobility of individual, incoming human papillomavirus type 16 pseudoviruses (PsV) bound to live HeLa cells was studied by single particle tracking using fluorescence video microscopy. The trajectories were computationally analyzed in terms of diffusion rate and mode of motion as described by the moment scaling spectrum. Four distinct modes of mobility were seen: confined movement in small zones (30–60 nm in diameter), confined movement with a slow drift, fast random motion with transient confinement, and linear, directed movement for long distances. The directed movement was most prominent on actin-rich cell protrusions such as filopodia or retraction fibres, where the rate was similar to that measured for actin retrograde flow. It was, moreover, sensitive to perturbants of actin retrograde flow such as cytochalasin D, jasplakinolide, and blebbistatin. We found that transport along actin protrusions significantly enhanced HPV-16 infection in sparse tissue culture, cells suggesting a role for in vivo infection of basal keratinocytes during wound healing. PMID:18773072

  3. Physical model for membrane protrusions during spreading.

    PubMed

    Chamaraux, F; Ali, O; Keller, S; Bruckert, F; Fourcade, B

    2008-01-01

    During cell spreading onto a substrate, the kinetics of the contact area is an observable quantity. This paper is concerned with a physical approach to modeling this process in the case of ameboid motility where the membrane detaches itself from the underlying cytoskeleton at the leading edge. The physical model we propose is based on previous reports which highlight that membrane tension regulates cell spreading. Using a phenomenological feedback loop to mimic stress-dependent biochemistry, we show that the actin polymerization rate can be coupled to the stress which builds up at the margin of the contact area between the cell and the substrate. In the limit of small variation of membrane tension, we show that the actin polymerization rate can be written in a closed form. Our analysis defines characteristic lengths which depend on elastic properties of the membrane-cytoskeleton complex, such as the membrane-cytoskeleton interaction, and on molecular parameters, the rate of actin polymerization. We discuss our model in the case of axi-symmetric and non-axi-symmetric spreading and we compute the characteristic time scales as a function of fundamental elastic constants such as the strength of membrane-cytoskeleton adherence. PMID:18824791

  4. Tetraspanins regulate the protrusive activities of cell membrane

    SciTech Connect

    Bari, Rafijul; Guo, Qiusha; Zhongnan Hospital, Wuhan University, Wuhan ; Xia, Bing; Zhang, Yanhui H.; Giesert, Eldon E.; Levy, Shoshana; Zheng, Jie J.; Zhang, Xin A.

    2011-12-02

    Highlights: Black-Right-Pointing-Pointer Tetraspanins regulate microvillus formation. Black-Right-Pointing-Pointer Tetraspanin CD81 promotes microvillus formation. Black-Right-Pointing-Pointer Tetraspanin CD82 inhibits microvillus formation. Black-Right-Pointing-Pointer Based on this study, we extrapolated a general cellular mechanism for tetraspanins. Black-Right-Pointing-Pointer Tetraspanins engage various functions by regulating membrane protrusion morphogenesis. -- Abstract: Tetraspanins have gained increased attention due to their functional versatility. But the universal cellular mechanism that governs such versatility remains unknown. Herein we present the evidence that tetraspanins CD81 and CD82 regulate the formation and/or development of cell membrane protrusions. We analyzed the ultrastructure of the cells in which a tetraspanin is either overexpressed or ablated using transmission electron microscopy. The numbers of microvilli on the cell surface were counted, and the radii of microvillar tips and the lengths of microvilli were measured. We found that tetraspanin CD81 promotes the microvillus formation and/or extension while tetraspanin CD82 inhibits these events. In addition, CD81 enhances the outward bending of the plasma membrane while CD82 inhibits it. We also found that CD81 and CD82 proteins are localized at microvilli using immunofluorescence. CD82 regulates microvillus morphogenesis likely by altering the plasma membrane curvature and/or the cortical actin cytoskeletal organization. We predict that membrane protrusions embody a common morphological phenotype and cellular mechanism for, at least some if not all, tetraspanins. The differential effects of tetraspanins on microvilli likely lead to the functional diversification of tetraspanins and appear to correlate with their functional propensity.

  5. Solvent-exposed lipid tail protrusions depend on lipid membrane composition and curvature.

    PubMed

    Tahir, Mukarram A; Van Lehn, Reid C; Choi, S H; Alexander-Katz, Alfredo

    2016-06-01

    The stochastic protrusion of hydrophobic lipid tails into solution, a subclass of hydrophobic membrane defects, has recently been shown to be a critical step in a number of biological processes like membrane fusion. Understanding the factors that govern the appearance of lipid tail protrusions is critical for identifying membrane features that affect the rate of fusion or other processes that depend on contact with solvent-exposed lipid tails. In this work, we utilize atomistic molecular dynamics simulations to characterize the likelihood of tail protrusions in phosphotidylcholine lipid bilayers of varying composition, curvature, and hydration. We distinguish two protrusion modes corresponding to atoms near the end of the lipid tail or near the glycerol group. Through potential of mean force calculations, we demonstrate that the thermodynamic cost for inducing a protrusion depends on tail saturation but is insensitive to other bilayer structural properties or hydration above a threshold value. Similarly, highly curved vesicles or micelles increase both the overall frequency of lipid tail protrusions as well as the preference for splay protrusions, both of which play an important role in driving membrane fusion. In multi-component bilayers, however, the incidence of protrusion events does not clearly depend on the mismatch between tail length or tail saturation of the constituent lipids. Together, these results provide significant physical insight into how system components might affect the appearance of protrusions in biological membranes, and help explain the roles of composition or curvature-modifying proteins in membrane fusion. PMID:26828121

  6. Normal mammary epithelial cells promote carcinoma basement membrane invasion by inducing microtubule-rich protrusions

    PubMed Central

    Lee, Meng-Horng; Wu, Pei-Hsun; Gilkes, Daniele; Aifuwa, Ivie; Wirtz, Denis

    2015-01-01

    Recent work suggests that the dissemination of tumor cells may occur in parallel with, and even preceed, tumor growth. The mechanism for this early invasion is largely unknown. Here, we find that mammary epithelial cells (MECs) induce neighboring breast carcinoma cells (BCCs) to cross the basement membrane by secreting soluble laminin. Laminin continuously produced by MECs induce long membrane cellular protrusions in BCCs that promote their contractility and invasion into the surrounding matrix. These protrusions depend on microtubule bundles assembled de novo through laminin-integrin β1 signaling. These results describe how non-cancerous MECs can actively participate in the invasive process of BCCs. PMID:26334095

  7. Fluxes of Water through Aquaporin 9 Weaken Membrane-Cytoskeleton Anchorage and Promote Formation of Membrane Protrusions

    PubMed Central

    Karlsson, Thommie; Bolshakova, Anastasia; Magalhães, Marco A. O.; Loitto, Vesa M.; Magnusson, Karl-Eric

    2013-01-01

    All modes of cell migration require rapid rearrangements of cell shape, allowing the cell to navigate within narrow spaces in an extracellular matrix. Thus, a highly flexible membrane and a dynamic cytoskeleton are crucial for rapid cell migration. Cytoskeleton dynamics and tension also play instrumental roles in the formation of different specialized cell membrane protrusions, viz. lamellipodia, filopodia, and membrane blebs. The flux of water through membrane-anchored water channels, known as aquaporins (AQPs) has recently been implicated in the regulation of cell motility, and here we provide novel evidence for the role of AQP9 in the development of various forms of membrane protrusion. Using multiple imaging techniques and cellular models we show that: (i) AQP9 induced and accumulated in filopodia, (ii) AQP9-associated filopodial extensions preceded actin polymerization, which was in turn crucial for their stability and dynamics, and (iii) minute, local reductions in osmolarity immediately initiated small dynamic bleb-like protrusions, the size of which correlated with the reduction in osmotic pressure. Based on this, we present a model for AQP9-induced membrane protrusion, where the interplay of water fluxes through AQP9 and actin dynamics regulate the cellular protrusive and motile activity of cells. PMID:23573219

  8. The Metalloprotease Mpl Supports Listeria monocytogenes Dissemination through Resolution of Membrane Protrusions into Vacuoles.

    PubMed

    Alvarez, Diego E; Agaisse, Hervé

    2016-06-01

    Listeria monocytogenes is an intracellular pathogen that disseminates within the intestinal epithelium through acquisition of actin-based motility and formation of plasma membrane protrusions that project into adjacent cells. The resolution of membrane protrusions into vacuoles from which the pathogen escapes results in bacterial spread from cell to cell. This dissemination process relies on the mlp-actA-plcB operon, which encodes ActA, a bacterial nucleation-promoting factor that mediates actin-based motility, and PlcB, a phospholipase that mediates vacuole escape. Here we investigated the role of the metalloprotease Mpl in the dissemination process. In agreement with previous findings showing that Mpl is required for PlcB activation, infection of epithelial cells with the ΔplcB or Δmpl strains resulted in the formation of small infection foci. As expected, the ΔplcB strain displayed a strong defect in vacuole escape. However, the Δmpl strain showed an unexpected defect in the resolution of protrusions into vacuoles, in addition to the expected but mild defect in vacuole escape. The Δmpl strain displayed increased levels of ActA on the bacterial surface in protrusions. We mapped an Mpl-dependent processing site in ActA between amino acid residues 207 to 238. Similar to the Δmpl strain, the ΔactA207-238 strain displayed increased levels of ActA on the bacterial surface in protrusions. Although the ΔactA207-238 strain displayed wild-type actin-based motility, it formed small infection foci and failed to resolve protrusions into vacuoles. We propose that, in addition to its role in PlcB processing and vacuole escape, the metalloprotease Mpl is required for ActA processing and protrusion resolution. PMID:27068088

  9. Dynamic Localization of G-actin During Membrane Protrusion in Neuronal Motility

    PubMed Central

    Lee, Chi Wai; Vitriol, Eric A.; Shim, Sangwoo; Wise, Ariel L.; Velayutham, Radhi P.; Zheng, James Q.

    2013-01-01

    Summary Background Actin-based cell motility is fundamental for the development, function, and malignant events of eukaryotic organisms. During neural development, axonal growth cones depend on rapid assembly and disassembly of actin filaments (F-actin) for their guided extension to specific targets for wiring. Monomeric globular actin (G-actin) is the building block for F-actin but is not considered to play a direct role in spatiotemporal control of actin dynamics in cell motility. Results Here we report that a pool of G-actin dynamically localizes to the leading edge of growth cones and neuroblastoma cells to spatially elevate the G-/F-actin ratio that drives membrane protrusion and cell movement. Loss of G-actin localization leads to the cessation and retraction of membrane protrusions. Moreover, G-actin localization occurs asymmetrically in growth cones during attractive turning. Finally, we identify the actin monomer binding proteins profilin and thymosin β4 as key molecules that localize actin monomers to the leading edge of lamellipodia for their motility. Conclusions Our results suggest that dynamic localization of G-actin provides a novel mechanism to regulate the spatiotemporal actin dynamics underlying membrane protrusion in cell locomotion and growth cone chemotaxis. PMID:23746641

  10. Formation of Mitochondrial Outer Membrane Derived Protrusions and Vesicles in Arabidopsis thaliana.

    PubMed

    Yamashita, Akihiro; Fujimoto, Masaru; Katayama, Kenta; Yamaoka, Shohei; Tsutsumi, Nobuhiro; Arimura, Shin-Ichi

    2016-01-01

    Mitochondria are dynamic organelles that have inner and outer membranes. In plants, the inner membrane has been well studied but relatively little is known about the outer membrane. Here we report that Arabidopsis cells have mitochondrial outer membrane-derived structures, some of which protrude from the main body of mitochondria (mitochondrial outer-membrane protrusions; MOPs), while others form vesicle-like structures without a matrix marker. The latter vesicle-like structures are similar to some mammalian MDVs (mitochondrial-derived vesicles). Live imaging demonstrated that a plant MDV budded off from the tip of a MOP. MDVs were also observed in the drp3a drp3b double mutant, indicating that they could be formed without the mitochondrial fission factors DRP3A and DRP3B. Double staining studies showed that the MDVs were not peroxisomes, endosomes, Golgi apparatus or trans-Golgi network (TGN). The numbers of MDVs and MOPs increased in senescent leaves and after dark treatment. Together, these results suggest that MDVs and MOPs are related to leaf senescence. PMID:26752045

  11. The formin FMNL3 assembles plasma membrane protrusions that participate in cell–cell adhesion

    PubMed Central

    Gauvin, Timothy J.; Young, Lorna E.; Higgs, Henry N.

    2015-01-01

    FMNL3 is a vertebrate-specific formin protein previously shown to play a role in angiogenesis and cell migration. Here we define the cellular localization of endogenous FMNL3, the dynamics of GFP-tagged FMNL3 during cell migration, and the effects of FMNL3 suppression in mammalian culture cells. The majority of FMNL3 localizes in a punctate pattern, with >95% of these puncta being indistinguishable from the plasma membrane by fluorescence microscopy. A small number of dynamic cytoplasmic FMNL3 patches also exist, which enrich near cell–cell contact sites and fuse with the plasma membrane at these sites. These cytoplasmic puncta appear to be part of larger membranes of endocytic origin. On the plasma membrane, FMNL3 enriches particularly in filopodia and membrane ruffles and at nascent cell–cell adhesions. FMNL3-containing filopodia occur both at the cell–substratum interface and at cell–cell contacts, with the latter being 10-fold more stable. FMNL3 suppression by siRNA has two major effects: decrease in filopodia and compromised cell–cell adhesion in cells migrating as a sheet. Overall our results suggest that FMNL3 functions in assembly of actin-based protrusions that are specialized for cell–cell adhesion. PMID:25428984

  12. Formation of Mitochondrial Outer Membrane Derived Protrusions and Vesicles in Arabidopsis thaliana

    PubMed Central

    Yamashita, Akihiro; Fujimoto, Masaru; Katayama, Kenta; Yamaoka, Shohei; Tsutsumi, Nobuhiro; Arimura, Shin-ichi

    2016-01-01

    Mitochondria are dynamic organelles that have inner and outer membranes. In plants, the inner membrane has been well studied but relatively little is known about the outer membrane. Here we report that Arabidopsis cells have mitochondrial outer membrane-derived structures, some of which protrude from the main body of mitochondria (mitochondrial outer-membrane protrusions; MOPs), while others form vesicle-like structures without a matrix marker. The latter vesicle-like structures are similar to some mammalian MDVs (mitochondrial-derived vesicles). Live imaging demonstrated that a plant MDV budded off from the tip of a MOP. MDVs were also observed in the drp3a drp3b double mutant, indicating that they could be formed without the mitochondrial fission factors DRP3A and DRP3B. Double staining studies showed that the MDVs were not peroxisomes, endosomes, Golgi apparatus or trans-Golgi network (TGN). The numbers of MDVs and MOPs increased in senescent leaves and after dark treatment. Together, these results suggest that MDVs and MOPs are related to leaf senescence. PMID:26752045

  13. Mechanisms of leading edge protrusion in interstitial migration

    NASA Astrophysics Data System (ADS)

    Wilson, Kerry; Lewalle, Alexandre; Fritzsche, Marco; Thorogate, Richard; Duke, Tom; Charras, Guillaume

    2013-12-01

    While the molecular and biophysical mechanisms underlying cell protrusion on two-dimensional substrates are well understood, our knowledge of the actin structures driving protrusion in three-dimensional environments is poor, despite relevance to inflammation, development and cancer. Here we report that, during chemotactic migration through microchannels with 5 μm × 5 μm cross-sections, HL60 neutrophil-like cells assemble an actin-rich slab filling the whole channel cross-section at their front. This leading edge comprises two distinct F-actin networks: an adherent network that polymerizes perpendicular to cell-wall interfaces and a ‘free’ network that grows from the free membrane at the cell front. Each network is polymerized by a distinct nucleator and, due to their geometrical arrangement, the networks interact mechanically. On the basis of our experimental data, we propose that, during interstitial migration, medial growth of the adherent network compresses the free network preventing its retrograde movement and enabling new polymerization to be converted into forward protrusion.

  14. The F-BAR domain of srGAP2 induces membrane protrusions required for neuronal migration and morphogenesis

    PubMed Central

    Guerrier, Sabrice; Coutinho-Budd, Jaeda; Sassa, Takayuki; Gresset, Aurélie; Jordan, Nicole Vincent; Cheng, Ken; Jin, Wei-Lin; Frost, Adam; Polleux, Franck

    2009-01-01

    SUMMARY During brain development, proper neuronal migration and morphogenesis is critical for the establishment of functional neural circuits. Here we report that srGAP2 negatively regulates neuronal migration and induces neurite outgrowth and branching through the ability of its F-BAR domain to induce filopodia-like membrane protrusions resembling those induced by I-BAR domains in vivo and in vitro. Previous work has suggested that in non-neuronal cells, filopodia dynamics decreases the rate of cell migration and the persistence of leading edge protrusions. srGAP2 knockdown reduces leading process branching and increases the rate of neuronal migration in vivo. Overexpression of srGAP2 or its F-BAR domain has the opposite effects, increasing leading process branching and decreasing migration. These results (1) suggest that F-BAR domains are functionally diverse and (2) highlight the functional importance of proteins directly regulating membrane deformation for proper neuronal migration and morphogenesis. PMID:19737524

  15. SNARE and regulatory proteins induce local membrane protrusions to prime docked vesicles for fast calcium-triggered fusion

    PubMed Central

    Bharat, Tanmay A M; Malsam, Jörg; Hagen, Wim J H; Scheutzow, Andrea; Söllner, Thomas H; Briggs, John A G

    2014-01-01

    Synaptic vesicles fuse with the plasma membrane in response to Ca2+ influx, thereby releasing neurotransmitters into the synaptic cleft. The protein machinery that mediates this process, consisting of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) and regulatory proteins, is well known, but the mechanisms by which these proteins prime synaptic membranes for fusion are debated. In this study, we applied large-scale, automated cryo-electron tomography to image an in vitro system that reconstitutes synaptic fusion. Our findings suggest that upon docking and priming of vesicles for fast Ca2+-triggered fusion, SNARE proteins act in concert with regulatory proteins to induce a local protrusion in the plasma membrane, directed towards the primed vesicle. The SNAREs and regulatory proteins thereby stabilize the membrane in a high-energy state from which the activation energy for fusion is profoundly reduced, allowing synchronous and instantaneous fusion upon release of the complexin clamp. PMID:24493260

  16. APC/β-catenin-rich complexes at membrane protrusions regulate mammary tumor cell migration and mesenchymal morphology

    PubMed Central

    2013-01-01

    Background The APC tumor suppressor is mutated or downregulated in many tumor types, and is prominently localized to punctate clusters at protrusion tips in migratory cells, such as in astrocytes where it has been implicated in directed cell motility. Although APC loss is considered an initiating event in colorectal cancer, for example, it is less clear what role APC plays in tumor cell motility and whether loss of APC might be an important promoter of tumor progression in addition to initiation. Methods The localization of APC and β-catenin was analyzed in multiple cell lines, including non-transformed epithelial lines treated with a proteasome inhibitor or TGFβ to induce an epithelial-to-mesenchymal transition (EMT), as well as several breast cancer lines, by immunofluorescence. APC expression was knocked down in 4T07 mammary tumor cells using lentiviral-mediated delivery of APC-specific short-hairpin (sh) RNAs, and assessed using quantitative (q) reverse-transcriptase (RT)-PCR and western blotting. Tumor cell motility was analyzed by performing wound-filling assays, and morphology via immunofluorescence (IF) and phase-contrast microscopy. Additionally, proliferation was measured using BrdU incorporation, and TCF reporter assays were performed to determine β-catenin/TCF-mediated transcriptional activity. Results APC/β-catenin-rich complexes were observed at protrusion ends of migratory epithelial cells treated with a proteasome inhibitor or when EMT has been induced and in tumor cells with a mesenchymal, spindle-like morphology. 4T07 tumor cells with reduced APC levels were significantly less motile and had a more rounded morphology; yet, they did not differ significantly in proliferation or β-catenin/TCF transcriptional activity. Furthermore, we found that APC/β-catenin-rich complexes at protrusion ends were dependent upon an intact microtubule cytoskeleton. Conclusions These findings indicate that membrane protrusions with APC/β-catenin-containing puncta

  17. Lipid tail protrusions mediate the insertion of nanoparticles into model cell membranes.

    PubMed

    Van Lehn, Reid C; Ricci, Maria; Silva, Paulo H J; Andreozzi, Patrizia; Reguera, Javier; Voïtchovsky, Kislon; Stellacci, Francesco; Alexander-Katz, Alfredo

    2014-01-01

    Recent work has demonstrated that charged gold nanoparticles (AuNPs) protected by an amphiphilic organic monolayer can spontaneously insert into the core of lipid bilayers to minimize the exposure of hydrophobic surface area to water. However, the kinetic pathway to reach the thermodynamically stable transmembrane configuration is unknown. Here, we use unbiased atomistic simulations to show the pathway by which AuNPs spontaneously insert into bilayers and confirm the results experimentally on supported lipid bilayers. The critical step during this process is hydrophobic-hydrophobic contact between the core of the bilayer and the monolayer of the AuNP that requires the stochastic protrusion of an aliphatic lipid tail into solution. This last phenomenon is enhanced in the presence of high bilayer curvature and closely resembles the putative pre-stalk transition state for vesicle fusion. To the best of our knowledge, this work provides the first demonstration of vesicle fusion-like behaviour in an amphiphilic nanoparticle system. PMID:25042518

  18. Protrusion force microscopy reveals oscillatory force generation and mechanosensing activity of human macrophage podosomes.

    PubMed

    Labernadie, Anna; Bouissou, Anaïs; Delobelle, Patrick; Balor, Stéphanie; Voituriez, Raphael; Proag, Amsha; Fourquaux, Isabelle; Thibault, Christophe; Vieu, Christophe; Poincloux, Renaud; Charrière, Guillaume M; Maridonneau-Parini, Isabelle

    2014-01-01

    Podosomes are adhesion structures formed in monocyte-derived cells. They are F-actin-rich columns perpendicular to the substrate surrounded by a ring of integrins. Here, to measure podosome protrusive forces, we designed an innovative experimental setup named protrusion force microscopy (PFM), which consists in measuring by atomic force microscopy the deformation induced by living cells onto a compliant Formvar sheet. By quantifying the heights of protrusions made by podosomes onto Formvar sheets, we estimate that a single podosome generates a protrusion force that increases with the stiffness of the substratum, which is a hallmark of mechanosensing activity. We show that the protrusive force generated at podosomes oscillates with a constant period and requires combined actomyosin contraction and actin polymerization. Finally, we elaborate a model to explain the mechanical and oscillatory activities of podosomes. Thus, PFM shows that podosomes are mechanosensing cell structures exerting a protrusive force. PMID:25385672

  19. Protrusion force microscopy reveals oscillatory force generation and mechanosensing activity of human macrophage podosomes

    NASA Astrophysics Data System (ADS)

    Labernadie, Anna; Bouissou, Anaïs; Delobelle, Patrick; Balor, Stéphanie; Voituriez, Raphael; Proag, Amsha; Fourquaux, Isabelle; Thibault, Christophe; Vieu, Christophe; Poincloux, Renaud; Charrière, Guillaume M.; Maridonneau-Parini, Isabelle

    2014-11-01

    Podosomes are adhesion structures formed in monocyte-derived cells. They are F-actin-rich columns perpendicular to the substrate surrounded by a ring of integrins. Here, to measure podosome protrusive forces, we designed an innovative experimental setup named protrusion force microscopy (PFM), which consists in measuring by atomic force microscopy the deformation induced by living cells onto a compliant Formvar sheet. By quantifying the heights of protrusions made by podosomes onto Formvar sheets, we estimate that a single podosome generates a protrusion force that increases with the stiffness of the substratum, which is a hallmark of mechanosensing activity. We show that the protrusive force generated at podosomes oscillates with a constant period and requires combined actomyosin contraction and actin polymerization. Finally, we elaborate a model to explain the mechanical and oscillatory activities of podosomes. Thus, PFM shows that podosomes are mechanosensing cell structures exerting a protrusive force.

  20. Differing and isoform-specific roles for the formin DIAPH3 in plasma membrane blebbing and filopodia formation

    PubMed Central

    Stastna, Jana; Pan, Xiaoyu; Wang, Haicui; Kollmannsperger, Alina; Kutscheidt, Stefan; Lohmann, Volker; Grosse, Robert; Fackler, Oliver T

    2012-01-01

    Plasma membrane (PM) blebs are dynamic actin-rich cell protrusions that occur, e.g., during cytokinesis, amoeboid cell motility and cell attachment. Using a targeted siRNA screen against 21 actin nucleation factors, we identify a novel and essential role of the human diaphanous formin DIAPH3 in PM blebbing during cell adhesion. Suppression of DIAPH3 inhibited blebbing to promote rapid cell spreading involving β1-integrin. Multiple isoforms of DIAPH3 were detected on the mRNA and protein level of which isoforms 3 and 7 were the largest and most abundant isoforms that however did not induce formation of actin-rich protrusions. Rather, PM blebbing specifically involved the low abundance isoform 1 of DIAPH3 and activation of isoform 7 by deletion of the diaphanous-autoregulatory domain caused the formation of filopodia. Dimerization and actin assembly activity were essential for induction of specific cell protrusions by DIAPH3 isoforms 1 and 7. Our data suggest that the N-terminal region comprising the GTPase-binding domain determined the subcellular localization of the formin as well as its protrusion activity between blebs and filopodia. We propose that isoform-selective actin assembly by DIAPH3 exerts specific and differentially regulated functions during cell adhesion and motility. PMID:22184005

  1. ELMO recruits actin cross-linking family 7 (ACF7) at the cell membrane for microtubule capture and stabilization of cellular protrusions.

    PubMed

    Margaron, Yoran; Fradet, Nadine; Côté, Jean-François

    2013-01-11

    ELMO and DOCK180 proteins form an evolutionarily conserved module controlling Rac GTPase signaling during cell migration, phagocytosis, and myoblast fusion. Here, we identified the microtubule and actin-binding spectraplakin ACF7 as a novel ELMO-interacting partner. A C-terminal polyproline segment in ELMO and the last spectrin repeat of ACF7 mediate a direct interaction between these proteins. Co-expression of ELMO1 with ACF7 promoted the formation of long membrane protrusions during integrin-mediated cell spreading. Quantification of membrane dynamics established that coupling of ELMO and ACF7 increases the persistence of the protruding activity. Mechanistically, we uncovered a role for ELMO in the recruitment of ACF7 to the membrane to promote microtubule capture and stability. Functionally, these effects of ELMO and ACF7 on cytoskeletal dynamics required the Rac GEF DOCK180. In conclusion, our findings support a role for ELMO in protrusion stability by acting at the interface between the actin cytoskeleton and the microtubule network. PMID:23184944

  2. Dynamic Membrane Remodeling at Invadopodia Differentiates Invadopodia from Podosomes

    PubMed Central

    Artym, Vira V.; Matsumoto, Kazue; Mueller, Susette C.; Yamada, Kenneth M.

    2011-01-01

    Invadopodia are specialized actin-rich protrusions of metastatic tumor and transformed cells with crucial functions in ECM degradation and invasion. Although early electron microscopy studies described invadopodia as long filament-like protrusions of the cell membrane adherent to the matrix, fluorescence microscopy studies have focused on invadopodia as actin-cortactin aggregates localized to areas of ECM degradation. The absence of a clear conceptual integration of these two descriptions of invadopodial structure has impeded understanding of the regulatory mechanisms that govern invadopodia. To determine the relationship between the membrane filaments identified by electron microscopy and the actin-cortactin aggregates of invadopodia, we applied rapid live-cell high-resolution TIRF microscopy to examine cell membrane dynamics at the cortactin core of the invadopodia of human carcinoma cells. We found that cortactin docking to the cell membrane adherent to 2D fibronectin matrix initiates invadopodium assembly associated with the formation of a invadopodial membrane process that extends from a ventral cell membrane lacuna toward the ECM. The tip of the invadopodial process flattens as it interacts with the 2D matrix, and it undergoes constant rapid ruffling and dynamic formation of filament-like protrusions as the invadopodium matures. To describe this newly discovered dynamic relationship between the actin-cortactin core and invadopodial membranes, we propose a model of the invadopodial complex. Using TIRF microscopy, we also established that – in striking contrast to the invadopodium – membrane at the podosome of a macrophage fails to form any process- or filament-like membrane protrusions. Thus, the undulation and ruffling of the invadopodial membrane together with the formation of dynamic filament-like extensions from the invadopodial cortactin core defines invadopodia as invasive superstructures that are distinct from the podosomes. PMID:20656375

  3. Endothelial Surface Protrusion by a Point Force.

    PubMed

    Chen, Yong; Lu, Lan; Shao, Jin-Yu

    2016-03-01

    During leukocyte rolling on the endothelium, surface protrusion and membrane tether extraction occur consecutively on leukocytes. Both surface protrusion and tether extraction of leukocytes stabilize leukocyte rolling. Tethers can also be extracted from endothelial cells (ECs), but surface protrusion of ECs has never been confirmed to exist. In this study, we examined EC surface protrusion with the micropipette aspiration technique. We found that, like leukocytes, surface protrusion on an EC did exist when a point force was imposed. Both the protrusional stiffness and the crossover force of EC surface protrusion were dependent on the force loading rate and the cytoskeletal integrity, but neither of them was dependent on tumor necrosis factor α stimulation. Temperature (37°C) affected the protrusional stiffness only at small force loading rates. When a neutrophil was employed to directly impose the pulling force on the EC, simultaneous surface protrusion from both cells occurred, and it can be modeled as two springs connected in series, although the spring constants should be adjusted according to the force loading rate. Therefore, EC surface protrusion is an important aspect of leukocyte rolling, and it should not be ignored when leukocyte rolling stability is studied systematically. PMID:26958891

  4. CD81 is essential for the formation of membrane protrusions and regulates Rac1-activation in adhesion-dependent immune cell migration.

    PubMed

    Quast, Thomas; Eppler, Felix; Semmling, Verena; Schild, Cora; Homsi, Yahya; Levy, Shoshana; Lang, Thorsten; Kurts, Christian; Kolanus, Waldemar

    2011-08-18

    CD81 (TAPA-1) is a member of the widely expressed and evolutionary conserved tetraspanin family that forms complexes with a variety of other cell surface receptors and facilitates hepatitis C virus entry. Here, we show that CD81 is specifically required for the formation of lamellipodia in migrating dendritic cells (DCs). Mouse CD81(-/-) DCs, or murine and human CD81 RNA interference knockdown DCs lacked the ability to form actin protrusions, thereby impairing their motility dramatically. Moreover, we observed a selective loss of Rac1 activity in the absence of CD81, the latter of which is exclusively required for integrin-dependent migration on 2-dimensional substrates. Neither integrin affinity for substrate nor the size of basal integrin clusters was affected by CD81 deficiency in adherent DCs. However, the use of total internal reflection fluorescence microscopy revealed an accumulation of integrin clusters above the basal layer in CD81 knockdown cells. Furthermore, β1- or β2-integrins, actin, and Rac are strongly colocalized at the leading edge of DCs, but the very fronts of these cells protrude CD81-containing membranes that project outward from the actin-integrin area. Taken together, these data suggest a thus far unappreciated role for CD81 in the mobilization of preformed integrin clusters into the leading edge of migratory DCs on 2-dimensional surfaces. PMID:21677313

  5. The initiation of post-synaptic protrusions

    PubMed Central

    Hotulainen, Pirta; Saarikangas, Juha

    2016-01-01

    ABSTRACT The post-synaptic spines of neuronal dendrites are highly elaborate membrane protrusions. Their anatomy, stability and density are intimately linked to cognitive performance. The morphological transitions of spines are powered by coordinated polymerization of actin filaments against the plasma membrane, but how the membrane-associated polymerization is spatially and temporally regulated has remained ill defined. Here, we discuss our recent findings showing that dendritic spines can be initiated by direct membrane bending by the I-BAR protein MIM/Mtss1. This lipid phosphatidylinositol (PI(4,5)P2) signaling-activated membrane bending coordinated spatial actin assembly and promoted spine formation. From recent advances, we formulate a general model to discuss how spatially concentrated protein-lipid microdomains formed by multivalent interactions between lipids and actin/membrane regulatory proteins might launch cell protrusions. PMID:27489575

  6. Myosin Va facilitates the distribution of secretory granules in the F-actin rich cortex of PC12 cells.

    PubMed

    Rudolf, Rüdiger; Kögel, Tanja; Kuznetsov, Sergei A; Salm, Thorsten; Schlicker, Oliver; Hellwig, Andrea; Hammer, John A; Gerdes, Hans-Hermann

    2003-04-01

    Neuroendocrine secretory granules, the storage organelles for neuropeptides and hormones, are formed at the trans-Golgi network, stored inside the cell and exocytosed upon stimulation. Previously, we have reported that newly formed secretory granules of PC12 cells are transported in a microtubule-dependent manner from the trans-Golgi network to the F-actin-rich cell cortex, where they undergo short directed movements and exhibit a homogeneous distribution. Here we provide morphological and biochemical evidence that myosin Va is associated with secretory granules. Expression of a dominant-negative tail domain of myosin Va in PC12 cells led to an extensive clustering of secretory granules close to the cell periphery, a loss of their cortical restriction and a strong reduction in their motility in the actin cortex. Based on this data we propose a model that implies a dual transport system for secretory granules: after microtubule-dependent delivery to the cell periphery, secretory granules exhibit a myosin Va-dependent transport leading to their restriction and even dispersal in the F-actin-rich cortex of PC12 cells. PMID:12615975

  7. The mechanics of cell protrusion

    NASA Astrophysics Data System (ADS)

    Danuser, Gaudenz

    2006-03-01

    The protrusion of the cell edge is the first step in a cycle of molecular processes that drive cell movements during development, immune responses, wound healing and many other physiological functions. It is also the earliest pathological event observed during metastasis of cancer. Textbook models associate protrusion with the assembly of an actin polymer network subadjacent to the cell plasma membrane. However, for this process to be transformed into edge advancement, polymerization-induced forces need to be balanced by adhesion complexes that link the actin network to the extracellular domain. Also, the effectiveness of network assembly in mediating forward movement of the cell edge depends on how contraction forces pull the network in the cell front retrogradly towards the cell center. Thus, what is observed in a microscope as cell protrusion reflects the kinematic output of at least three space- and time-modulated mechanisms of force generation. The coordination of these machineries is thought to be regulated by a complex network of mechano-chemical signals. Our goal is to establish the contributions of each those mechanisms and their control by reconstructing the spatiotemporal distribution of intracellular forces via inverse dynamics and molecular intervention with the relevant signalling pathways. To this end, we have developed quantitative Fluorescent Speckle Microscopy (qFSM) which provides high-resolution spatiotemporal measurements of actin network deformation and material properties in migrating cells. In addition, qFSM delivers maps of cytoskeleton assembly and disassembly, so that we can infer the plasticity of the material in situ. Together, this data allows us to deduce intracellular force distributions from the constitutive laws of strain and stress in the actin polymer network. Using this approach we discovered that unperturbed cells protrude in a dynamic steady state where periodic patterns of network assembly, adhesion formation, and

  8. Device for cutting protrusions

    DOEpatents

    Bzorgi, Fariborz M.

    2011-07-05

    An apparatus for clipping a protrusion of material is provided. The protrusion may, for example, be a bolt head, a nut, a rivet, a weld bead, or a temporary assembly alignment tab protruding from a substrate surface of assembled components. The apparatus typically includes a cleaver having a cleaving edge and a cutting blade having a cutting edge. Generally, a mounting structure configured to confine the cleaver and the cutting blade and permit a range of relative movement between the cleaving edge and the cutting edge is provided. Also typically included is a power device coupled to the cutting blade. The power device is configured to move the cutting edge toward the cleaving edge. In some embodiments the power device is activated by a momentary switch. A retraction device is also generally provided, where the retraction device is configured to move the cutting edge away from the cleaving edge.

  9. Powered protrusion cutter

    DOEpatents

    Bzorgi, Fariborz M.

    2010-03-09

    An apparatus for clipping a protrusion of material is provided. The protrusion may, for example, be a bolt head, a nut, a rivet, a weld bead, or a temporary assembly alignment tab protruding from a substrate surface of assembled components. The apparatus typically includes a cleaver having a cleaving edge and a cutting blade having a cutting edge. Generally, a mounting structure configured to confine the cleaver and the cutting blade and permit a range of relative movement between the cleaving edge and the cutting edge is provided. Also typically included is a power device coupled to the cutting blade. The power device is configured to move the cutting edge toward the cleaving edge. In some embodiments the power device is activated by a momentary switch. A retraction device is also generally provided, where the retraction device is configured to move the cutting edge away from the cleaving edge.

  10. Role of major sperm protein (MSP) in the protrusion and retraction of Ascaris sperm.

    PubMed

    Roberts, Thomas M; Stewart, Murray

    2012-01-01

    Nematode sperm offer a unique perspective for investigating amoeboid cell motility. These cells display the hallmark features of amoeboid movement but power their locomotion with a cytoskeleton composed of major sperm protein (MSP) filaments in place of the familiar actin cytoskeleton found in other crawling cells. Thus, properties of sperm can be compared to those of actin-rich cells to identify the shared features that are essential to motility. Sperm are simple cells in which cytoskeletal dynamics are tightly coupled to protrusion of the leading edge and retraction of the cell body. These features have facilitated reconstitution of both protrusion and retraction in cell-free extracts and enabled identification of accessory components in the motility apparatus as well as elucidation of the mechanical basis of movement. Six MSP accessory proteins have been isolated including four components of the sperm cytoskeleton and two enzymes that play key roles in regulating cytoskeletal dynamics and locomotion. Analysis of this versatile in vitro motility system has identified motor-independent mechanisms for protrusion and retraction that are based on changes in filament-packing density. These changes result in expansion and contraction of the MSP-filament network that generate the forces for movement. We discuss how the mechanisms of motility that operate in nematode sperm may contribute generally to the movement of crawling cells. PMID:22608562

  11. Tongue protrusion in burned bodies.

    PubMed

    Bohnert, Michael; Hejna, Petr

    2016-09-01

    Protrusion of the tongue is a common, though often neglected finding in fire fatalities. According to a study recently published by Bernitz et al., it is an indicator of vital burning. This statement has been doubted repeatedly. Retrospective analysis of 61 fire fatalities from our own autopsy material did not show any statistically significant increased incidence of tongue protrusion in deaths with vital exposure to heat. Similarly, there was no correlation with the degree of destruction by the fire in general or the extent of cervical burning. Further prospective studies seem to be necessary also with regard to the pathophysiological processes. PMID:26987317

  12. The Calponin Family Member CHDP-1 Interacts with Rac/CED-10 to Promote Cell Protrusions

    PubMed Central

    Zhang, Jingyan; Liu, Jia-Jia; Wang, Yingchun; Ding, Mei

    2016-01-01

    Eukaryotic cells extend a variety of surface protrusions to direct cell motility. Formation of protrusions is mediated by coordinated actions between the plasma membrane and the underlying actin cytoskeleton. Here, we found that the single calponin homology (CH) domain-containing protein CHDP-1 induces the formation of cell protrusions in C. elegans. CHDP-1 is anchored to the cortex through its amphipathic helix. CHDP-1 associates through its CH domain with the small GTPase Rac1/CED-10, which is a key regulator of the actin cytoskeleton. CHDP-1 preferentially binds to the GTP-bound active form of the CED-10 protein and preserves the membrane localization of GTP-CED-10. Hence, by coupling membrane expansion to Rac1-mediated actin dynamics, CHDP-1 promotes the formation of cellular protrusions in vivo. PMID:27415421

  13. The Calponin Family Member CHDP-1 Interacts with Rac/CED-10 to Promote Cell Protrusions.

    PubMed

    Guan, Liying; Ma, Xuehua; Zhang, Jingyan; Liu, Jia-Jia; Wang, Yingchun; Ding, Mei

    2016-07-01

    Eukaryotic cells extend a variety of surface protrusions to direct cell motility. Formation of protrusions is mediated by coordinated actions between the plasma membrane and the underlying actin cytoskeleton. Here, we found that the single calponin homology (CH) domain-containing protein CHDP-1 induces the formation of cell protrusions in C. elegans. CHDP-1 is anchored to the cortex through its amphipathic helix. CHDP-1 associates through its CH domain with the small GTPase Rac1/CED-10, which is a key regulator of the actin cytoskeleton. CHDP-1 preferentially binds to the GTP-bound active form of the CED-10 protein and preserves the membrane localization of GTP-CED-10. Hence, by coupling membrane expansion to Rac1-mediated actin dynamics, CHDP-1 promotes the formation of cellular protrusions in vivo. PMID:27415421

  14. Actin Grips: Circular Actin-Rich Cytoskeletal Structures that Mediate the Wrapping of Polymeric Microfibers by Endothelial Cells

    PubMed Central

    Jones, Desiree; Park, DoYoung; Anghelina, Mirela; Pecot, Thierry; Machiraju, Raghu; Xue, Ruipeng; Lannutti, John; Thomas, Jessica; Cole, Sara; Moldovan, Leni; Moldovan, Nicanor I.

    2015-01-01

    Interaction of endothelial-lineage cells with three-dimensional substrates was much less studied than that with flat culture surfaces. We investigated the in vitro attachment of both mature endothelial cells (ECs) and of less differentiated EC colony-forming cells to poly-e-capro-lactone (PCL) fibers with diameters in 5–20 μm range (‘scaffold microfibers’, SMFs). We found that notwithstanding the poor intrinsic adhesiveness to PCL, both cell types completely wrapped the SMFs after long-term cultivation, thus attaining a cylindrical morphology. In this system, both EC types grew vigorously for more than a week and became increasingly more differentiated, as shown by multiplexed gene expression. Three-dimensional reconstructions from multiphoton confocal microscopy images using custom software showed that the filamentous (F) actin bundles took a conspicuous ring-like organization around the SMFs. Unlike the classical F-actin-containing stress fibers, these rings were not associated with either focal adhesions or intermediate filaments. We also demonstrated that plasma membrane boundaries adjacent to these circular cytoskeletal structures were tightly yet dynamically apposed to the SMFs, for which reason we suggest to call them ‘actin grips’. In conclusion, we describe a particular form of F-actin assembly with relevance for cytoskeletal organization in response to biomaterials, for endothelial-specific cell behavior in vitro and in vivo, and for tissue engineering. PMID:25818446

  15. Actin is not required for nanotubular protrusions of primary astrocytes grown on metal nano-lawn.

    PubMed

    Gimsa, Ulrike; Iglic, Ales; Fiedler, Stefan; Zwanzig, Michael; Kralj-Iglic, Veronika; Jonas, Ludwig; Gimsa, Jan

    2007-01-01

    We used sub-micron metal rod decorated surfaces, 'nano-lawn' structures, as a substrate to study cell-to-cell and cell-to-surface interactions of primary murine astrocytes. These cells form thin membranous tubes with diameters of less than 100 nm and a length of several microns, which make contact to neighboring cells and the substrate during differentiation. While membrane protrusions grow on top of the nano-lawn pillars, nuclei sink to the bottom of the substrate. We observed gondola-like structures along those tubes, suggestive of their function as transport vehicles. Elements of the cytoskeleton such as actin fibers are commonly believed to be essential for triggering the onset and growth of tubular membrane protrusions. A rope-pulling mechanism along actin fibers has recently been proposed to account for the transport or exchange of cellular material between cells. We present evidence for a complementary mechanism that promotes growth and stabilization of the observed tubular protrusions of cell membranes. This mechanism does not require active involvement of actin fibers as the formation of membrane protrusions could not be prevented by suppressing polymerization of actin by latrunculin B. Also theoretically, actin fibers are not essential for the growing and stability of nanotubes since curvature-driven self-assembly of interacting anisotropic raft elements is sufficient for the spontaneous formation of thin nano-tubular membrane protrusions. PMID:17520481

  16. Electrical assembly having heat sink protrusions

    SciTech Connect

    Rinehart, Lawrence E.; Romero, Guillermo L.

    2009-04-21

    An electrical assembly, comprising a heat producing semiconductor device supported on a first major surface of a direct bond metal substrate that has a set of heat sink protrusions supported by its second major surface. In one preferred embodiment the heat sink protrusions are made of the same metal as is used in the direct bond copper.

  17. 16 CFR 1511.4 - Protrusions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... orientation of the hinge axis shall be horizontal. A plane surface shall be applied to any protrusion from the... direction along the axis of the nipple. The normal of the plane surface shall be maintained parallel to the axis of the nipple. Any protrusion shall be allowed to flex or rotate about its hinge as the...

  18. Filopodia and Viruses: An Analysis of Membrane Processes in Entry Mechanisms

    PubMed Central

    Chang, Kenneth; Baginski, John; Hassan, Samer F.; Volin, Michael; Shukla, Deepak; Tiwari, Vaibhav

    2016-01-01

    Filopodia are thin, actin rich bundles protruding from cell plasma membranes, serving physiological purposes, such as probing the environment and facilitating cell-to-cell adhesion. Recent studies have highlighted that actively polymerized filopodial-protrusions are exploited during virus entry, trafficking, spread, and the development of clinical pathology of viral diseases. These observations have caused a surge in investigation of the key determinants of filopodial induction and their influence on cell topography including receptor expression for viral entry. It is now very clear that filopodia can provide unique opportunities for many viruses to invade host cells vertically during primary infection, or horizontally during virus spread from cell-to-cell. These emerging concepts can explain the unprecedented ability of viruses to invade both nearby and long-distant host cells, a feature that may directly contribute to viral tropism. In this review, we summarize the significance of filopodia in viral diseases and discuss future therapeutic possibilities to precisely target filopodial-flyovers to prevent or control infectious diseases. PMID:27014223

  19. Morphogenesis of protrusions from confined lipid bilayers mediated by mechanics

    NASA Astrophysics Data System (ADS)

    Arroyo, Marino; Staykova, Margarita; Rahimi, Mohammad; Stone, Howard A.

    2012-02-01

    Biological membranes adopt a wide range of shapes that structure and give functionality to cells, compartmentalizing the cytosol, forming organelles, or regulating their area. The formation, stabilization, and remodeling of these structures is generally attributed to localized forces or to biochemical processes (insertion of proteins, active compositional regulation). Noting that in the crowded intra and extra-cellular environments membranes are highly constrained, we explore to what extent can mechanics explain the shape of protrusions out of confined membranes. For this purpose, we developed an in-vitro system coupling a lipid bilayer to the strain-controlled deformation of an elastic sheet (Staykova et al, PNAS 108, 2011). We show that upon contracting the elastic support, tubular or spherical protrusions grow out of the adhered membrane, which can be reversibly controlled with strain and osmolarity without resorting to localized forces or chemical alterations of the bilayer. The morphologies produced by our minimal system are ubiquitous in cells, suggesting mechanics may be a simple and generic organizing principle. We can understand most of our observations in terms of a phase diagram accounting for elasticity, adhesion, and the limited amount of area and volume available.

  20. Measurement of Lamellipodial Protrusion by Optical Trapping

    NASA Astrophysics Data System (ADS)

    Sakai, Ken'ichi; Kohmoto, Sogo; Nobezawa, Daisuke; Ikeda, Sho-ichi; Miyata, Hidetake

    2015-02-01

    Lamellipodial protrusion is a fundamental step in cell locomotion. This important process is driven by actin polymerization, but its physical aspect has not yet been fully investigated. We previously studied the lamellipodial protrusion of Swiss 3T3 fibroblast cells at 33 ms temporal resolution and 10 nm accuracy by probing the motion of the cell edge with a 1 µm bead held in an optical trap. In that study, we found a transient mode of protrusion and analyzed the time variation of the protrusion velocity. In this study, we analyzed the power spectra of the fluctuations of a trap-held bead during the protrusion and found cell-specific fluctuations. The maximal amplitude of the fluctuations was 23 nm, which was estimated from the power of the fluctuations accumulated over 1.9 and 7.6 Hz. This value was significantly larger than that of the fluctuations of the trap-held bead that is not in contact with the cell edge (14 nm). The amplitude of the fluctuation of the probing bead showed a positive correlation with the cell edge velocity, suggesting that the cell-specific fluctuations play an important role in the lamellipodial protrusion.

  1. Septins guide microtubule protrusions induced by actin-depolymerizing toxins like Clostridium difficile transferase (CDT).

    PubMed

    Nölke, Thilo; Schwan, Carsten; Lehmann, Friederike; Østevold, Kristine; Pertz, Olivier; Aktories, Klaus

    2016-07-12

    Hypervirulent Clostridium difficile strains, which are associated with increased morbidity and mortality, produce the actin-ADP ribosylating toxin Clostridium difficile transferase (CDT). CDT depolymerizes actin, causes formation of microtubule-based protrusions, and increases pathogen adherence. Here, we show that septins (SEPT) are essential for CDT-induced protrusion formation. SEPT2, -6, -7, and -9 accumulate at predetermined protrusion sites and form collar-like structures at the base of protrusions. The septin inhibitor forchlorfenuron or knockdown of septins inhibits protrusion formation. At protrusion sites, septins colocalize with the GTPase Cdc42 (cell division control protein 42) and its effector Borg (binder of Rho GTPases), which act as up-stream regulators of septin polymerization. Precipitation and surface plasmon resonance studies revealed high-affinity binding of septins to the microtubule plus-end tracking protein EB1, thereby guiding incoming microtubules. The data suggest that CDT usurps conserved regulatory principles involved in microtubule-membrane interaction, depending on septins, Cdc42, Borgs, and restructuring of the actin cytoskeleton. PMID:27339141

  2. Subcellular and Dynamic Coordination between Src Activity and Cell Protrusion in Microenvironment

    PubMed Central

    Zhuo, Yue; Qian, Tongcheng; Wu, Yiqian; Seong, Jihye; Gong, Ya; Ma, Hongwei; Wang, Yingxiao; Lu, Shaoying

    2015-01-01

    Migration of endothelial cells is essential for wound healing and angiogenesis. Src kinase activity plays important roles at the protrusions of migrating endothelial cells. However, the spatiotemporal coordination between Src kinase activity and the protrusion of cell edge remains unclear. Therefore, we investigate these coordinated molecular events at the initiation of cell migration, by integrating microfabrication, fluorescence resonance energy transfer (FRET)-based biosensors, and automated computational image analysis. We demonstrate that the physical release of restrictive micropattern triggered a significant decrease of Src activity at the protrusive edge of endothelial cells. Computational cross-correlation analysis reveals that the decrease of Src activity occurred earlier in time, and was well-coordinated with the protrusion of cell edge in polarized cells, but not in non-polarized cells. These results suggest that the spatiotemporal control of Src kinase activity is well-coordinated with cell polarization and protrusion in endothelial cells upon the release of physical constraint, as that experienced by endothelial cells sprouting from stiff tumor micro-environment during angiogenesis. Therefore, our integrative approach enabled the discovery of a new model where Src is de-activated in coordination with membrane protrusion, providing important insights into the regulation of endothelial migration and angiogenesis. PMID:26261043

  3. Subcellular and Dynamic Coordination between Src Activity and Cell Protrusion in Microenvironment

    NASA Astrophysics Data System (ADS)

    Zhuo, Yue; Qian, Tongcheng; Wu, Yiqian; Seong, Jihye; Gong, Ya; Ma, Hongwei; Wang, Yingxiao; Lu, Shaoying

    2015-08-01

    Migration of endothelial cells is essential for wound healing and angiogenesis. Src kinase activity plays important roles at the protrusions of migrating endothelial cells. However, the spatiotemporal coordination between Src kinase activity and the protrusion of cell edge remains unclear. Therefore, we investigate these coordinated molecular events at the initiation of cell migration, by integrating microfabrication, fluorescence resonance energy transfer (FRET)-based biosensors, and automated computational image analysis. We demonstrate that the physical release of restrictive micropattern triggered a significant decrease of Src activity at the protrusive edge of endothelial cells. Computational cross-correlation analysis reveals that the decrease of Src activity occurred earlier in time, and was well-coordinated with the protrusion of cell edge in polarized cells, but not in non-polarized cells. These results suggest that the spatiotemporal control of Src kinase activity is well-coordinated with cell polarization and protrusion in endothelial cells upon the release of physical constraint, as that experienced by endothelial cells sprouting from stiff tumor micro-environment during angiogenesis. Therefore, our integrative approach enabled the discovery of a new model where Src is de-activated in coordination with membrane protrusion, providing important insights into the regulation of endothelial migration and angiogenesis.

  4. Subcellular and Dynamic Coordination between Src Activity and Cell Protrusion in Microenvironment.

    PubMed

    Zhuo, Yue; Qian, Tongcheng; Wu, Yiqian; Seong, Jihye; Gong, Ya; Ma, Hongwei; Wang, Yingxiao; Lu, Shaoying

    2015-01-01

    Migration of endothelial cells is essential for wound healing and angiogenesis. Src kinase activity plays important roles at the protrusions of migrating endothelial cells. However, the spatiotemporal coordination between Src kinase activity and the protrusion of cell edge remains unclear. Therefore, we investigate these coordinated molecular events at the initiation of cell migration, by integrating microfabrication, fluorescence resonance energy transfer (FRET)-based biosensors, and automated computational image analysis. We demonstrate that the physical release of restrictive micropattern triggered a significant decrease of Src activity at the protrusive edge of endothelial cells. Computational cross-correlation analysis reveals that the decrease of Src activity occurred earlier in time, and was well-coordinated with the protrusion of cell edge in polarized cells, but not in non-polarized cells. These results suggest that the spatiotemporal control of Src kinase activity is well-coordinated with cell polarization and protrusion in endothelial cells upon the release of physical constraint, as that experienced by endothelial cells sprouting from stiff tumor micro-environment during angiogenesis. Therefore, our integrative approach enabled the discovery of a new model where Src is de-activated in coordination with membrane protrusion, providing important insights into the regulation of endothelial migration and angiogenesis. PMID:26261043

  5. Teneurin-4 promotes cellular protrusion formation and neurite outgrowth through focal adhesion kinase signaling

    PubMed Central

    Suzuki, Nobuharu; Numakawa, Tadahiro; Chou, Joshua; de Vega, Susana; Mizuniwa, Chihiro; Sekimoto, Kaori; Adachi, Naoki; Kunugi, Hiroshi; Arikawa-Hirasawa, Eri; Yamada, Yoshihiko; Akazawa, Chihiro

    2014-01-01

    Teneurin-4 (Ten-4), a transmembrane protein, is highly expressed in the central nervous system; however, its cellular and molecular function in neuronal differentiation remains unknown. In this study, we aimed to elucidate the function of Ten-4 in neurite outgrowth. Ten-4 expression was induced during neurite outgrowth of the neuroblastoma cell line Neuro-2a. Ten-4 protein was localized at the neurite growth cones. Knockdown of Ten-4 expression in Neuro-2a cells decreased the formation of the filopodia-like protrusions and the length of individual neurites. Conversely, overexpression of Ten-4 promoted filopodia-like protrusion formation. In addition, knockdown and overexpression of Ten-4 reduced and elevated the activation of focal adhesion kinase (FAK) and Rho-family small GTPases, Cdc42 and Rac1, key molecules for the membranous protrusion formation downstream of FAK, respectively. Inhibition of the activation of FAK and neural Wiskott-Aldrich syndrome protein (N-WASP), which is a downstream regulator of FAK and Cdc42, blocked protrusion formation by Ten-4 overexpression. Further, Ten-4 colocalized with phosphorylated FAK in the filopodia-like protrusion regions. Together, our findings show that Ten-4 is a novel positive regulator of cellular protrusion formation and neurite outgrowth through the FAK signaling pathway.—Suzuki, N., Numakawa, T., Chou, J., de Vega, S., Mizuniwa, C., Sekimoto, K., Adachi, N., Kunugi, H., Arikawa-Hirasawa, E., Yamada, Y., Akazawa, C. Teneurin-4 promotes cellular protrusion formation and neurite outgrowth through focal adhesion kinase signaling. PMID:24344332

  6. Coxsackievirus B3-Induced Cellular Protrusions: Structural Characteristics and Functional Competence▿†

    PubMed Central

    Paloheimo, Outi; Ihalainen, Teemu O.; Tauriainen, Sisko; Välilehto, Outi; Kirjavainen, Sanna; Niskanen, Einari A.; Laakkonen, Johanna P.; Hyöty, Heikki; Vihinen-Ranta, Maija

    2011-01-01

    Virus-induced alterations in cell morphology play important roles in the viral life cycle. To examine the intracellular events of coxsackievirus B3 (CVB3) infection, green monkey kidney (GMK) cells were either inoculated with the virus or transfected with the viral RNA. Various microscopic and flow cytometric approaches demonstrated the emergence of CVB3 capsid proteins at 8 h posttransfection, followed by morphological transformation of the cells. The morphological changes included formation of membranous protrusions containing viral capsids, together with microtubules and actin. Translocation of viral capsids into these protrusions was sensitive to cytochalasin D, suggesting the importance of actin in the process. Three-dimensional (3D) live-cell imaging demonstrated frequent contacts between cellular protrusions and adjacent cells. Markedly, in spite of an increase in the cellular viral protein content starting 8 h postinfection, no significant decrease in cell viability or increase in the amount of early apoptotic markers was observed by flow cytometry by 28 h postinfection. Comicroinjection of viral RNA and fluorescent dextran in the presence of neutralizing virus antibody suggested that these protrusions mediated the spread of infection from one cell to another prior to virus-induced cell lysis. Altogether, the CVB3-induced cellular protrusions could function as a hitherto-unknown nonlytic mechanism of cell-to-cell transmission exploited by enteroviruses. PMID:21525342

  7. Prominin-2 expression increases protrusions, decreases caveolae and inhibits Cdc42 dependent fluid phase endocytosis

    SciTech Connect

    Singh, Raman Deep Schroeder, Andreas S.; Scheffer, Luana; Holicky, Eileen L.; Wheatley, Christine L.; Marks, David L. Pagano, Richard E.

    2013-05-10

    Highlights: •Prominin-2 expression induced protrusions that co-localized with lipid raft markers. •Prominin-2 expression decreased caveolae, caveolar endocytosis and increased pCav1. •Prominin-2 expression inhibited fluid phase endocytosis by inactivation of Cdc42. •These endocytic effects can be reversed by adding exogenous cholesterol. •Caveolin1 knockdown restored fluid phase endocytosis in Prominin2 expressing cells. -- Abstract: Background: Membrane protrusions play important roles in biological processes such as cell adhesion, wound healing, migration, and sensing of the external environment. Cell protrusions are a subtype of membrane microdomains composed of cholesterol and sphingolipids, and can be disrupted by cholesterol depletion. Prominins are pentaspan membrane proteins that bind cholesterol and localize to plasma membrane (PM) protrusions. Prominin-1 is of great interest as a marker for stem and cancer cells, while Prominin-2 (Prom2) is reportedly restricted to epithelial cells. Aim: To characterize the effects of Prom-2 expression on PM microdomain organization. Methods: Prom2-fluorescent protein was transfected in human skin fibroblasts (HSF) and Chinese hamster ovary (CHO) cells for PM raft and endocytic studies. Caveolae at PM were visualized using transmission electron microscopy. Cdc42 activation was measured and caveolin-1 knockdown was performed using siRNAs. Results: Prom2 expression in HSF and CHO cells caused extensive Prom2-positive protrusions that co-localized with lipid raft markers. Prom2 expression significantly decreased caveolae at the PM, reduced caveolar endocytosis and increased caveolin-1 phosphorylation. Prom2 expression also inhibited Cdc42-dependent fluid phase endocytosis via decreased Cdc42 activation. Effects on endocytosis were reversed by addition of cholesterol. Knockdown of caveolin-1 by siRNA restored Cdc42 dependent fluid phase endocytosis in Prom2-expressing cells. Conclusions: Prom2 protrusions primarily

  8. ERK reinforces actin polymerization to power persistent edge protrusion during motility

    PubMed Central

    Mendoza, Michelle C.; Vilela, Marco; Juarez, Jesus E.; Blenis, John; Danuser, Gaudenz

    2016-01-01

    Cells move through perpetual protrusion and retraction cycles at the leading edge. These cycles are coordinated with substrate adhesion and retraction of the cell rear. Here, we tracked spatial and temporal fluctuations in the molecular activities of individual moving cells to elucidate how extracellular regulated kinase (ERK) signaling controlled the dynamics of protrusion and retraction cycles. ERK is activated by many cell-surface receptors and we found that ERK signaling specifically reinforced cellular protrusions so that they translated into rapid, sustained forward motion of the leading edge. Using quantitative fluorescent speckle microscopy (qFSM) and cross-correlation analysis, we showed that ERK controlled the rate and timing of actin polymerization by promoting the recruitment of the actin nucleator Arp2/3 to the leading edge. Arp2/3 activity generates branched actin networks that can produce pushing force. These findings support a model in which surges in ERK activity induced by extracellular cues enhance Arp2/3-mediated actin polymerization to generate protrusion power phases with enough force to counteract increasing membrane tension and to promote sustained motility. PMID:25990957

  9. Identification and characterization of espin, an actin-binding protein localized to the F-actin-rich junctional plaques of Sertoli cell ectoplasmic specializations.

    PubMed

    Bartles, J R; Wierda, A; Zheng, L

    1996-06-01

    Ectoplasmic specializations are membrane-cytoskeletal assemblages found in Sertoli cells at sites of attachment to elongate spermatids or neighboring Sertoli cells. They are characterized in part by the presence of a unique junctional plaque which contains a narrow layer of parallel actin bundles sandwiched between the Sertoli cell plasma membrane and an affiliated cistern of endoplasmic reticulum. Using a monoclonal antibody, we have identified 'espin,' a novel actin-binding protein localized to ectoplasmic specializations. By immunogold electron microscopy, espin was localized to the parallel actin bundles of ectoplasmic specializations at sites where Sertoli cells contacted the heads of elongate spermatids. The protein was also detected at the sites of ectoplasmic specializations between neighboring Sertoli cells. Espin exhibits an apparent molecular mass of approximately 110 kDa in SDS gels. It is encoded by an approximately 2.9 kb mRNA, which was found to be specific to testis among the 11 rat organs and tissues examined. On the basis of cDNA sequence, espin is predicted to be an 836 amino acid protein which contains 8 ankyrin-like repeats in its N-terminal third, a potential P-loop, two proline-rich peptides and two peptides which contain clusters of multiple glutamates bracketed by arginines, lysines and glutamines in a pattern reminiscent of the repetitive motif found in the protein trichohyalin. The ankyrin-like repeats and a 66 amino acid peptide in the C terminus show significant sequence similarity to proteins encoded by the forked gene of Drosophila. A fusion protein containing the C-terminal 378 amino acids of espin was found to bind with high affinity (Kd = approximately 10 nM) to F-actin in vitro with a stoichiometry of approximately 1 espin per 6 actin monomers. When expressed by transfected NRK fibroblasts, the same C-terminal fragment of espin was observed to decorate actin fibers or cables. On the basis of its structure, localization and

  10. The Class II Phosphatidylinositol 3-Phosphate Kinase PIK3C2A Promotes Shigella flexneri Dissemination through Formation of Vacuole-Like Protrusions

    PubMed Central

    Dragoi, Ana-Maria

    2015-01-01

    Intracellular pathogens such as Shigella flexneri and Listeria monocytogenes achieve dissemination in the intestinal epithelium by displaying actin-based motility in the cytosol of infected cells. As they reach the cell periphery, motile bacteria form plasma membrane protrusions that resolve into vacuoles in adjacent cells, through a poorly understood mechanism. Here, we report on the role of the class II phosphatidylinositol 3-phosphate kinase PIK3C2A in S. flexneri dissemination. Time-lapse microscopy revealed that PIK3C2A was required for the resolution of protrusions into vacuoles through the formation of an intermediate membrane-bound compartment that we refer to as a vacuole-like protrusion (VLP). Genetic rescue of PIK3C2A depletion with RNA interference (RNAi)-resistant cDNA constructs demonstrated that VLP formation required the activity of PIK3C2A in primary infected cells. PIK3C2A expression was required for production of phosphatidylinositol 3-phosphate [PtdIns(3)P] at the plasma membrane surrounding protrusions. PtdIns(3)P production was not observed in the protrusions formed by L. monocytogenes, whose dissemination did not rely on PIK3C2A. PIK3C2A-mediated PtdIns(3)P production in S. flexneri protrusions was regulated by host cell tyrosine kinase signaling and relied on the integrity of the S. flexneri type 3 secretion system (T3SS). We suggest a model of S. flexneri dissemination in which the formation of VLPs is mediated by the PIK3C2A-dependent production of the signaling lipid PtdIns(3)P in the protrusion membrane, which relies on the T3SS-dependent activation of tyrosine kinase signaling in protrusions. PMID:25667265

  11. Gap junctions are selectively associated with interlocking ball-and-sockets but not protrusions in the lens

    PubMed Central

    Biswas, Sondip K.; Lee, Jai Eun; Brako, Lawrence; Jiang, Jean X.

    2010-01-01

    Purpose Ball-and-sockets and protrusions are specialized interlocking membrane domains between lens fibers of all species studied. Ball-and-sockets and protrusions are similar in their shape, size, and surface morphology, and are traditionally believed to play a key role in maintaining fiber-to-fiber stability. Here, we evaluate the hypothesis that ball-and-sockets and protrusions possess important structural and functional differences during fiber cell differentiation and maturation. Methods Intact lenses of leghorn chickens (E7 days to P62 weeks old) and rhesus monkeys (1.5–20 years old) were studied with SEM, freeze-fracture TEM, freeze-fracture immunogold labeling (FRIL), and filipin cytochemistry for membrane cholesterol detection. Results SEM showed that ball-and-sockets were distributed along the long and short sides of hexagonal fiber cells, whereas protrusions were located along the cell corners, from superficial to deep cortical regions in both chicken and monkey lenses. Importantly, by freeze-fracture TEM, we discovered the selective association of gap junctions with all ball-and-sockets examined, but not with protrusions, in both species. In the embryonic chicken lens (E18), the abundant distribution of ball-and-socket gap junctions was regularly found in an approximate zone extending at least 300 μm deep from the equatorial surface of the superficial cortical fibers. Many ball-and-socket gap junctions often protruded deeply into neighboring cells. However, in the mature fibers of monkey lenses, several ball-and-sockets exhibited only partial occupancy of gap junctions with disorganized connexons, possibly due to degradation of gap junctions during fiber maturation and aging. FRIL analysis confirmed that both connexin46 (Cx46) and connexin50 (Cx50) antibodies specifically labeled ball-and-socket gap junctions, but not protrusions. Furthermore, filipin cytochemistry revealed that the ball-and-socket gap junctions contained different amounts of

  12. Regulation of cell protrusions by small GTPases during fusion of the neural folds

    PubMed Central

    Rolo, Ana; Savery, Dawn; Escuin, Sarah; de Castro, Sandra C; Armer, Hannah EJ; Munro, Peter MG; Molè, Matteo A; Greene, Nicholas DE; Copp, Andrew J

    2016-01-01

    Epithelial fusion is a crucial process in embryonic development, and its failure underlies several clinically important birth defects. For example, failure of neural fold fusion during neurulation leads to open neural tube defects including spina bifida. Using mouse embryos, we show that cell protrusions emanating from the apposed neural fold tips, at the interface between the neuroepithelium and the surface ectoderm, are required for completion of neural tube closure. By genetically ablating the cytoskeletal regulators Rac1 or Cdc42 in the dorsal neuroepithelium, or in the surface ectoderm, we show that these protrusions originate from surface ectodermal cells and that Rac1 is necessary for the formation of membrane ruffles which typify late closure stages, whereas Cdc42 is required for the predominance of filopodia in early neurulation. This study provides evidence for the essential role and molecular regulation of membrane protrusions prior to fusion of a key organ primordium in mammalian development. DOI: http://dx.doi.org/10.7554/eLife.13273.001 PMID:27114066

  13. Cortactin Branches Out: Roles in Regulating Protrusive Actin Dynamics

    PubMed Central

    Ammer, Amanda Gatesman; Weed, Scott A.

    2008-01-01

    Since its discovery in the early 1990’s, cortactin has emerged as a key signaling protein in many cellular processes, including cell adhesion, migration, endocytosis, and tumor invasion. While the list of cellular functions influenced by cortactin grows, the ability of cortactin to interact with and alter the cortical actin network is central to its role in regulating these processes. Recently, several advances have been made in our understanding of the interaction between actin and cortactin, providing insight into how these two proteins work together to provide a framework for normal and altered cellular function. This review examines how regulation of cortactin through post-translational modifications and interactions with multiple binding partners elicits changes in cortical actin cytoskeletal organization, impacting the regulation and formation of actin-rich motility structures. PMID:18615630

  14. Cdc42 is required for EGF-stimulated protrusion and motility in MTLn3 carcinoma cells

    PubMed Central

    El-Sibai, Mirvat; Nalbant, Peri; Pang, Huan; Flinn, Rory J.; Sarmiento, Corina; Macaluso, Frank; Cammer, Michael; Condeelis, John S.; Hahn, Klaus M.; Backer, Jonathan M.

    2014-01-01

    Summary Cdc42 plays a central role in regulating the actin cytoskeleton and maintaining cell polarity. Here, we show that Cdc42 is crucial for epidermal growth factor (EGF)-stimulated protrusion in MTLn3 carcinoma cells. When stimulated with EGF, carcinoma cells showed a rapid increase in activated Cdc42 that is primarily localized to the protruding edge of the cells. siRNA-mediated knockdown of Cdc42 expression caused a decrease in EGF-stimulated protrusion and reduced cell motility in time-lapse studies. These changes were correlated with a decrease in barbed-end formation and Arp2/3 localization at the cell edge, and a marked defect in actin filament branching, as revealed by rotary-shadowing scanning electron microscopy. Upstream of Arp2/3, Cdc42 knockdown inhibited EGF-stimulated activation of PI 3-kinase at early (within 1 minute) but not late (within 3 minutes) time points. Membrane targeting of N-WASP, WAVE2 and IRSp53 were also inhibited. Effects on WAVE2 were not owing to Rac1 inhibition, because WAVE2 recruitment is unaffected by Rac1 knockdown. Our data suggest that Cdc42 activation is crucial for the regulation of actin polymerization in carcinoma cells, and required for both EGF-stimulated protrusion and cell motility independently of effects on Rac. PMID:17855387

  15. A mechanism of leading-edge protrusion in the absence of Arp2/3 complex

    PubMed Central

    Suraneni, Praveen; Fogelson, Ben; Rubinstein, Boris; Noguera, Philippe; Volkmann, Niels; Hanein, Dorit; Mogilner, Alex; Li, Rong

    2015-01-01

    Cells employ protrusive leading edges to navigate and promote their migration in diverse physiological environments. Classical models of leading-edge protrusion rely on a treadmilling dendritic actin network that undergoes continuous assembly nucleated by the Arp2/3 complex, forming ruffling lamellipodia. Recent work demonstrated, however, that, in the absence of the Arp2/3 complex, fibroblast cells adopt a leading edge with filopodia-like protrusions (FLPs) and maintain an ability to move, albeit with altered responses to different environmental signals. We show that formin-family actin nucleators are required for the extension of FLPs but are insufficient to produce a continuous leading edge in fibroblasts lacking Arp2/3 complex. Myosin II is concentrated in arc-like regions of the leading edge in between FLPs, and its activity is required for coordinated advancement of these regions with formin-generated FLPs. We propose that actomyosin contraction acting against membrane tension advances the web of arcs between FLPs. Predictions of this model are verified experimentally. The dependence of myosin II in leading-edge advancement helps explain the previously reported defect in directional movement in the Arpc3-null fibroblasts. We provide further evidence that this defect is cell autonomous during chemotaxis. PMID:25568333

  16. Differential regulation of protrusion and polarity by PI(3)K during neutrophil motility in live zebrafish

    PubMed Central

    Yoo, Sa Kan; Deng, Qing; Cavnar, Peter J.; Wu, Yi I.; Hahn, Klaus M.; Huttenlocher, Anna

    2010-01-01

    Summary Cell polarity is crucial for directed migration. Here we show that phosphoinositide 3-kinase (PI(3)K) mediates neutrophil migration in vivo by differentially regulating cell protrusion and polarity. The dynamics of PI(3)K products PI(3,4,5)P3-PI(3,4)P2 during neutrophil migration were visualized in living zebrafish, revealing that PI(3)K activation at the leading edge is critical for neutrophil motility in intact tissues. A genetically encoded photoactivatable Rac was used to demonstrate that localized activation of Rac is sufficient to direct migration with precise temporal and spatial control in vivo. Similar stimulation of PI(3)K-inhibited cells did not direct migration. Localized Rac activation rescued membrane protrusion but not anteroposterior polarization of F-actin dynamics of PI(3)K-inhibited cells. Uncoupling Rac-mediated protrusion and polarization suggests a paradigm of two-tiered PI(3)K-mediated regulation of cell motility. This work provides new insight into how cell signaling at the front and back of the cell is coordinated during polarized cell migration in intact tissues within a multicellular organism. PMID:20159593

  17. Nanoscale segregation of actin nucleation and elongation factors determines dendritic spine protrusion

    PubMed Central

    Chazeau, Anaël; Mehidi, Amine; Nair, Deepak; Gautier, Jérémie J; Leduc, Cécile; Chamma, Ingrid; Kage, Frieda; Kechkar, Adel; Thoumine, Olivier; Rottner, Klemens; Choquet, Daniel; Gautreau, Alexis; Sibarita, Jean-Baptiste; Giannone, Grégory

    2014-01-01

    Actin dynamics drive morphological remodeling of neuronal dendritic spines and changes in synaptic transmission. Yet, the spatiotemporal coordination of actin regulators in spines is unknown. Using single protein tracking and super-resolution imaging, we revealed the nanoscale organization and dynamics of branched F-actin regulators in spines. Branched F-actin nucleation occurs at the PSD vicinity, while elongation occurs at the tip of finger-like protrusions. This spatial segregation differs from lamellipodia where both branched F-actin nucleation and elongation occur at protrusion tips. The PSD is a persistent confinement zone for IRSp53 and the WAVE complex, an activator of the Arp2/3 complex. In contrast, filament elongators like VASP and formin-like protein-2 move outwards from the PSD with protrusion tips. Accordingly, Arp2/3 complexes associated with F-actin are immobile and surround the PSD. Arp2/3 and Rac1 GTPase converge to the PSD, respectively, by cytosolic and free-diffusion on the membrane. Enhanced Rac1 activation and Shank3 over-expression, both associated with spine enlargement, induce delocalization of the WAVE complex from the PSD. Thus, the specific localization of branched F-actin regulators in spines might be reorganized during spine morphological remodeling often associated with synaptic plasticity. PMID:25293574

  18. Effects of vortex generator on cylindrical protrusion aerodynamics

    NASA Astrophysics Data System (ADS)

    Vignesh Ram, P. S.; Setoguchi, Toshiaki; Kim, Heuy Dong

    2016-02-01

    Experimental and numerical studies were carried out to evaluate the effect of vortex generator on a small cylindrical protrusion at Mach number 2.0. The experiments were performed using the supersonic blow down wind tunnel on different heights of cylindrical protrusion with vortex generator placed ahead of them. The upstream and downstream flow around the cylindrical protrusion is influenced by vortex generator as is observed using both visualization and pressure measurement techniques. Numerical studies using three dimensional steady implicit formulations with standard k-ω turbulence model was performed. Results obtained through the present computation are compared with the experimental results at Mach 2.0. Good agreements between computation and experimental results have been achieved. The results indicate that the aerodynamic drag acting on cylindrical protrusion can be reduced by adopting vortex generator.

  19. Measuring Actin Flow in 3D Cell Protrusions

    PubMed Central

    Chiu, Chi-Li; Digman, Michelle A.; Gratton, Enrico

    2013-01-01

    Actin dynamics is important in determining cell shape, tension, and migration. Methods such as fluorescent speckle microscopy and spatial temporal image correlation spectroscopy have been used to capture high-resolution actin turnover dynamics within cells in two dimensions. However, these methods are not directly applicable in 3D due to lower resolution and poor contrast. Here, we propose to capture actin flow in 3D with high spatial-temporal resolution by combining nanoscale precise imaging by rapid beam oscillation and fluctuation spectroscopy techniques. To measure the actin flow along cell protrusions in cell expressing actin-eGFP cultured in a type I collagen matrix, the laser was orbited around the protrusion and its trajectory was modulated in a clover-shaped pattern perpendicularly to the protrusion. Orbits were also alternated at two positions closely spaced along the protrusion axis. The pair cross-correlation function was applied to the fluorescence fluctuation from these two positions to capture the flow of actin. Measurements done on nonmoving cellular protrusion tips showed no pair-correlation at two orbital positions indicating a lack of flow of F-actin bundles. However, in some protrusions, the pair-correlation approach revealed directional flow of F-actin bundles near the protrusion surface with flow rates in the range of ∼1 μm/min, comparable to results in two dimensions using fluorescent speckle microscopy. Furthermore, we found that the actin flow rate is related to the distance to the protrusion tip. We also observed collagen deformation by concomitantly detecting collagen fibers with reflectance detection during these actin motions. The implementation of the nanoscale precise imaging by rapid beam oscillation method with a cloverleaf-shaped trajectory in conjunction with the pair cross-correlation function method provides a quantitative way of capturing dynamic flows and organization of proteins during cell migration in 3D in conditions of

  20. A continuum model of protrusion of pseudopod in leukocytes.

    PubMed Central

    Zhu, C; Skalak, R

    1988-01-01

    The morphology of human leukocytes, the biochemistry of actin polymerization, and the theory of continuum mechanics are used to model the pseudopod protrusion process of leukocytes. In the proposed model, the pseudopod is considered as a porous solid of F-actin network, the pores of which are full of aqueous solution. G-actin is considered as a "solute" transported by convection and diffusion in the fluid phase. The pseudopod grows as actin filaments elongate at their barbed ends at the tip of the pseudopod. The driving force of extension is hypothesized as being provided by the actin polymerization. It is assumed that elongation of actin filaments, powered by chemical energy liberated from the polymerization reaction, does mechanical work against opposing pressure on the membrane. This also gives rise to a pressure drop in the fluid phase at the tip of the pseudopod, which is formulated by an equation relating the work done by actin polymerization to the local state of pressure. The pressure gradient along the pseudopod drives the fluid filtration through the porous pseudopod according to Darcy's Law, which in turn brings more actin monomers to the growing tip. The main cell body serves as a reservoir of G-actin. A modified first-order equation is used to describe the kinetics of polymerization. The rate of pseudopod growth is modulated by regulatory proteins. A one-dimensional moving boundary problem based on the proposed mechanism has been constructed and approximate solutions have been obtained. Comparison of the solutions with experimental data shows that the model is compatible with available observations. The model is also applicable to growth of other cellular systems such as elongation of acrosomal process in sperm cells. Images FIGURE 1 FIGURE 4 PMID:3233268

  1. Influence of bimaxillary protrusion on the perception of smile esthetics

    PubMed Central

    Almutairi, Terki K.; Albarakati, Sahar F.; Aldrees, Abdullah M.

    2015-01-01

    Objectives: To evaluate the impact of bimaxillary protrusion on smile esthetics as perceived by dental professionals and laypersons. Methods: One hundred and fifty evaluators, equally distributed into their respective panels (orthodontists, general dentists, and laypersons), participated in this cross-sectional study conducted in April to December 2012 in Riyadh, Saudi Arabia. The patient sample consisted of 14 female patients divided equally into 2 groups: bimaxillary protrusion patients, and patients who have had 4-premolar extraction treatment. Two standardized photographs (frontal and three-quarter close-up smile views), and a lateral cephalogram were taken for each patient. The evaluators were asked to rate the attractiveness of each photo according to a 100-mm visual analog scale. These esthetic ratings were correlated with the patients’ cephalometric measurements. Results: The bimaxillary protrusion group was rated significantly as less attractive than the treatment group by each evaluator panel. Panel comparison showed that laypeople were less receptive of bimaxillary protrusion than dental professionals. Frontal and three-quarter views of the same smiles were not similarly rated for esthetic perceptions. Correlational analysis revealed that the dentoalveolar measurement with the highest significant negative correlation to the smile esthetics was the upper incisors to palatal plane (U1-PP) angle. Conclusion: Patients with bimaxillary protrusion were found to be less attractive than patients who were treated for the condition. This was especially evident among the laypersons. An increase in the upper incisor inclination, as well as a decrease in the interincisal angle compounds the bimaxillary effect. PMID:25630010

  2. Local force induced conical protrusions of phagocytic cells.

    PubMed

    Vonna, Laurent; Wiedemann, Agnès; Aepfelbacher, Martin; Sackmann, Erich

    2003-03-01

    Magnetic tweezers were used to study the passive and active response of macrophages to local centripetal nanonewton forces on beta1 integrins. Superparamagnetic beads coated with the beta1-integrin-binding protein invasin were attached to J774 murine macrophages to mimic phagocytosis of bacterial pathogens. Forces exceeding approximately 0.5 nN induce the active formation of trumpet-like protrusions resembling pseudopodia after an initial elastic deflection and a response time of approximately 30 seconds. The speed of advancement of the protrusion is =0.065+/-0.020 micro m second(-1) and is force independent. After saturation (after about 100 seconds) the protrusion stops abruptly and is completely retracted again against forces exceeding 5 nN with an effective relaxation time of approximately 30 seconds. The active protrusion is tentatively attributed to the growth of the actin cortex in the direction of the force, and evidence for the involvement of actin is provided by the finding that Latrunculin A abolishes the activated cone growth. The growth is assumed to be activated by cell signaling mediated by the invasin-specific integrins (exhibiting beta1 chains) and could play a role in phagocytic and protrusive events during immune response by macrophages. PMID:12571276

  3. CFD simulations to study the effects of wall protrusions on microfluidic mixing

    NASA Astrophysics Data System (ADS)

    Sarkar, Sourav; Singh, K. K.; Shankar, V.; Shenoy, K. T.

    2015-08-01

    In this study the effects of different types of wall protrusions on microfluidic mixing are studied using computational fluid dynamics (CFD) simulations. Two new protrusions, single first bracket protrusions and double opposite first bracket protrusions (DOFBPs), are conceptualized, evaluated through CFD simulations and compared to protrusions having standard geometrical shapes, e.g. rectangular protrusions, triangular protrusions and semicircular protrusions. In the range of Reynolds numbers covered in this study, the microchannel having an opposed T-junction and DOFBPs is found to provide good mixing. A hybrid approach relying on the modification of microfluidic junctions as well as wall protrusions for enhancing microfluidic mixing is also evaluated. The microchannel based on the hybrid approach of an OA 10°-20°-165° WY-junction and DOFBPs is also found to provide very good mixing for a wide range of Reynolds numbers.

  4. Jet through a wall protrusion in a cross-flow

    NASA Technical Reports Server (NTRS)

    Hong, S. K.; Murthy, S. N. B.; Warner, C. F.

    1984-01-01

    The flow interactions between a jet issuing out of a protrusion in a wall and a crosswise flow are of interest because of the manner in which the spreading and mixing of the jet are affected by the flow separation, formation of vortices and recirculation zones and the associated flow instabilities. In combustors and in aircraft void spaces adjoining fuel tanks such interactions determine flame stability and propagation characteristics. Results from flow visualization and from predictions based on a three-dimensional viscous flow code are utilized to show the effects of several flow and geometrical parameters on the processes occuring in the vicinity of the protrusion and the jet.

  5. The Shigella flexneri Type 3 Secretion System Is Required for Tyrosine Kinase-Dependent Protrusion Resolution, and Vacuole Escape during Bacterial Dissemination

    PubMed Central

    Kuehl, Carole J.; Dragoi, Ana-Maria; Agaisse, Hervé

    2014-01-01

    Shigella flexneri is a human pathogen that triggers its own entry into intestinal cells and escapes primary vacuoles to gain access to the cytosolic compartment. As cytosolic and motile bacteria encounter the cell cortex, they spread from cell to cell through formation of membrane protrusions that resolve into secondary vacuoles in adjacent cells. Here, we examined the roles of the Type 3 Secretion System (T3SS) in S. flexneri dissemination in HT-29 intestinal cells infected with the serotype 2a strain 2457T. We generated a 2457T strain defective in the expression of MxiG, a central component of the T3SS needle apparatus. As expected, the ΔmxiG strain was severely affected in its ability to invade HT-29 cells, and expression of mxiG under the control of an arabinose inducible expression system (ΔmxiG/pmxiG) restored full infectivity. In this experimental system, removal of the inducer after the invasion steps (ΔmxiG/pmxiG (Ara withdrawal)) led to normal actin-based motility in the cytosol of HT-29 cells. However, the time spent in protrusions until vacuole formation was significantly increased. Moreover, the number of formed protrusions that failed to resolve into vacuoles was also increased. Accordingly, the ΔmxiG/pmxiG (Ara withdrawal) strain failed to trigger tyrosine phosphorylation in membrane protrusions, a signaling event that is required for the resolution of protrusions into vacuoles. Finally, the ΔmxiG/pmxiG (Ara withdrawal) strain failed to escape from the formed secondary vacuoles, as previously reported in non-intestinal cells. Thus, the T3SS system displays multiple roles in S. flexneri dissemination in intestinal cells, including the tyrosine kinase signaling-dependent resolution of membrane protrusions into secondary vacuoles, and the escape from the formed secondary vacuoles. PMID:25405985

  6. Mandible protrusion and decrease of TMJ sounds: an electrovibratographic examination.

    PubMed

    Garcia, Alicio Rosalino; Folli, Sérgio; Zuim, Paulo Renato Junqueira; de Sousa, Valdir

    2008-01-01

    This study quantified by, electrovibratography, the amount of mandible protrusion required to decrease significantly temporomandibular joint (TMJ) vibratory energy as an aid in the diagnosis of the recapture of anteriorly displaced disk. Eighteen patients diagnosed as having anterior disk displacement with reduction and TMJ clicking were submitted to electrovibratographic examination at the first appointment and treated with a stabilizing appliance and anterior positioning appliance with 1 to 5 mm protrusion. Vibratory energy was checked in each of these positions. Baseline data were used as control. At the first appointment, the patients had vibrations with more elevated intensities at the middle and late phases of the mouth opening cycle. At only one clinical step, mandible protrusion was obtained with the anterior repositioning appliance, ranging from 1 to 5 mm protusion. At each new position, a new electrovibratographic exam was made. After the 5-mm mandibular projection, only 2 patients presented vibration, with means between 0.6 and 2.8 Hz. Data were analyzed statistically by ANOVA and Tukey's test (alpha=0.05). The outcomes of this study indicate that 3 mm is the minimum amount of mandible protrusion to significantly decrease the TMJ vibratory energy and to recapture the displaced articular disk. PMID:18438565

  7. Shear flow-induced formation of tubular cell protrusions in multiple myeloma cells

    PubMed Central

    Porat, Ziv; Yaron, Itamar; Katz, Ben-Zion; Kam, Zvi; Geiger, Benjamin

    2011-01-01

    Exposure of live cells to shear flow induces major changes in cell shape, adhesion to the extracellular matrix, and migration. In the present study, we show that exposure of cultured multiple myeloma (MM) cells to shear flow of 4–36 dynes/cm2 triggers the extension of long tubular protrusions (denoted FLow-Induced Protrusions, or FLIPs) in the direction of the flow. These FLIPs were found to be rich in actin, contain few or no microtubules and, apart from endoplasmic reticulum (ER)-like membranal structures, are devoid of organelles. Studying the dynamics of this process revealed that FLIPs elongate at their tips in a shear force-dependent manner, and retract at their bases. Examination of this force dependence revealed considerable heterogeneity in the mechanosensitivity of individual cells, most likely reflecting the diversity of the malignant B-cell population. The mechanisms underlying FLIP formation following mechanical perturbation, and their relevance to the cellular trafficking of MM cells, are discussed. PMID:21344380

  8. Protrusive and Contractile Forces of Spreading Human Neutrophils.

    PubMed

    Henry, Steven J; Chen, Christopher S; Crocker, John C; Hammer, Daniel A

    2015-08-18

    Human neutrophils are mediators of innate immunity and undergo dramatic shape changes at all stages of their functional life cycle. In this work, we quantified the forces associated with a neutrophil's morphological transition from a nonadherent, quiescent sphere to its adherent and spread state. We did this by tracking, with high spatial and temporal resolution, the cell's mechanical behavior during spreading on microfabricated post-array detectors printed with the extracellular matrix protein fibronectin. Two dominant mechanical regimes were observed: transient protrusion and steady-state contraction. During spreading, a wave of protrusive force (75 ± 8 pN/post) propagates radially outward from the cell center at a speed of 206 ± 28 nm/s. Once completed, the cells enter a sustained contractile state. Although post engagement during contraction was continuously varying, posts within the core of the contact zone were less contractile (-20 ± 10 pN/post) than those residing at the geometric perimeter (-106 ± 10 pN/post). The magnitude of the protrusive force was found to be unchanged in response to cytoskeletal inhibitors of lamellipodium formation and myosin II-mediated contractility. However, cytochalasin B, known to reduce cortical tension in neutrophils, slowed spreading velocity (61 ± 37 nm/s) without significantly reducing protrusive force. Relaxation of the actin cortical shell was a prerequisite for spreading on post arrays as demonstrated by stiffening in response to jasplakinolide and the abrogation of spreading. ROCK and myosin II inhibition reduced long-term contractility. Function blocking antibody studies revealed haptokinetic spreading was induced by β2 integrin ligation. Neutrophils were found to moderately invaginate the post arrays to a depth of ∼1 μm as measured from spinning disk confocal microscopy. Our work suggests a competition of adhesion energy, cortical tension, and the relaxation of cortical tension is at play at the onset of

  9. Is orthodontics an option in the management of bimaxillary protrusion?

    PubMed

    Dawjee, S M; Becker, P J; Hlongwa, P

    2010-10-01

    Successful orthodontic treatment is based on a clear perception by the clinician of a patient's facial preference and treatment needs. Bimaxillary protrusion is a normal facial trait seen in the Black population and the most acceptable bimaxillary facial profile in a sample of Black subjects was determined by Beukes et al in 2007. Variations from this ideal profile may require extractions as part of orthodontic treatment in order to attain the ideal. The objective of this study was to determine whether Black subjects with bimaxillary protrusion would want to change their facial profile to the ideal and at what financial cost. A sample of 586 school learners and 321 university students were presented with four silhouetted profiles of varying degrees of bimaxillary protrusion. One of the silhouette profiles represented the ideal and treatment procedures required to achieve this ideal were explained to the sample. They were then requested to answer a questionnaire that would assist in identifying their perception of their own profile and their desire to change their appearance. The ideal silhouette was confirmed to be the most attractive (91.51%) and the sample felt that any severe deviations from this ideal profile should be treated. The financial cost of treatment was found to be a concern, as more subjects (62.84%) would undergo the required treatment if it were free. Many subjects (43.55%) would be prepared to pay for the necessary treatment to achieve the ideal profile. Females were found to be more definite in their decision making, reflecting a greater awareness about their aesthetic appearance than their male counterparts. Findings from this study can serve as an essential tool to assist both orthodontists and maxillofacial surgeons in the treatment planning and management of Black patients with bimaxillary protrusion. PMID:21180286

  10. Protrusive and Contractile Forces of Spreading Human Neutrophils

    PubMed Central

    Henry, Steven J.; Chen, Christopher S.; Crocker, John C.; Hammer, Daniel A.

    2015-01-01

    Human neutrophils are mediators of innate immunity and undergo dramatic shape changes at all stages of their functional life cycle. In this work, we quantified the forces associated with a neutrophil’s morphological transition from a nonadherent, quiescent sphere to its adherent and spread state. We did this by tracking, with high spatial and temporal resolution, the cell’s mechanical behavior during spreading on microfabricated post-array detectors printed with the extracellular matrix protein fibronectin. Two dominant mechanical regimes were observed: transient protrusion and steady-state contraction. During spreading, a wave of protrusive force (75 ± 8 pN/post) propagates radially outward from the cell center at a speed of 206 ± 28 nm/s. Once completed, the cells enter a sustained contractile state. Although post engagement during contraction was continuously varying, posts within the core of the contact zone were less contractile (−20 ± 10 pN/post) than those residing at the geometric perimeter (−106 ± 10 pN/post). The magnitude of the protrusive force was found to be unchanged in response to cytoskeletal inhibitors of lamellipodium formation and myosin II-mediated contractility. However, cytochalasin B, known to reduce cortical tension in neutrophils, slowed spreading velocity (61 ± 37 nm/s) without significantly reducing protrusive force. Relaxation of the actin cortical shell was a prerequisite for spreading on post arrays as demonstrated by stiffening in response to jasplakinolide and the abrogation of spreading. ROCK and myosin II inhibition reduced long-term contractility. Function blocking antibody studies revealed haptokinetic spreading was induced by β2 integrin ligation. Neutrophils were found to moderately invaginate the post arrays to a depth of ∼1 μm as measured from spinning disk confocal microscopy. Our work suggests a competition of adhesion energy, cortical tension, and the relaxation of cortical tension is at play at the

  11. Membrane tubulation from giant lipid vesicles in alternating electric fields.

    PubMed

    Antonova, K; Vitkova, V; Meyer, C

    2016-01-01

    We report on the formation of tubular membrane protrusions from giant unilamellar vesicles in alternating electric fields. The construction of the experimental chamber permitted the application of external AC fields with strength of dozens of V/mm and kHz frequency during relatively long time periods (several minutes). Besides the vesicle electrodeformation from quasispherical to prolate ellipsoidal shape, the formation of long tubular membrane protrusions with length of up to several vesicle diameters, arising from the vesicular surface in the field direction, was registered and analyzed. The threshold electric field at which the electro-induced protrusions appeared was lower than the field strengths inducing membrane electroporation. PMID:26871107

  12. Lipid merging, protrusion and vesicle release triggered by shrinking/swelling of poly(N-isopropylacrylamide) microgel particles

    NASA Astrophysics Data System (ADS)

    Dou, Yujiang; Li, Jingliang; Yuan, Bing; Yang, Kai

    2014-03-01

    Cell membrane changes its morphology during many physiological processes with the assistance of a solid support, such as the cytoskeleton, under an environmental stimulus. Here, a novel type of stimuli-responsive lipogel was fabricated, mimicking the changes of cell membrane. The lipogel was prepared from poly(N-isopropylacrylamide) (pNIPAM) microgel particle and phospholipid by a solvent-exchange method. The temperature dependent volume phase transition of pNIPAM triggers reversible transformation of the lipogel between a lipid vesicle-coated sun-like structure and a contracted hybrid sphere, through lipid merging and protrusion processes, respectively. By contrast, the salt induced pNIPAM phase transition leads to an irreversible vesicle release behaviour. The lipogel creates a unique platform for studying cell membrane behaviour and provides promising candidates in drug delivery and controlled release applications.

  13. Management of severe pain due to lumbar disk protrusion.

    PubMed

    Conroy, Liam

    2015-03-01

    Lumbar intervertebral disk protrusion can cause excruciating pain in severe cases, which can be exacerbated by activity such as sitting down and straining at stool. Acute sciatica due to disk rupture will improve within 1 to 3 months. The efficacy of drugs used for the management of sciatica in primary care is unclear. Severe cases can require opioid analgesia, however people taking opioids for pain relief frequently present with opioid-induced bowel dysfunction. The use of transforaminal steroid injections is a controversial issue and repeat steroid injections should be considered in light of the risk-benefit profile of the individual patient. PMID:25643230

  14. [Two Cases of Ruptured Cerebral Aneurysm Complicated with Delayed Coil Protrusion after Coil Embolization].

    PubMed

    Furukawa, Takashi; Ogata, Atsushi; Ebashi, Ryo; Takase, Yukinori; Masuoka, Jun; Kawashima, Masatou; Abe, Tatsuya

    2016-07-01

    We report two cases of delayed coil protrusion after coil embolization for ruptured cerebral aneurysms. Case 1:An 82-year-old woman with a subarachnoid hemorrhage due to a ruptured small anterior communicating artery aneurysm underwent successful coil embolization. Eighteen days after the procedure, coil protrusion from the aneurysm into the right anterior cerebral artery was observed without any symptoms. Further coil protrusion did not develop after 28 days. Case 2:A 78-year-old woman with a subarachnoid hemorrhage due to a ruptured small left middle cerebral artery aneurysm underwent successful coil embolization. Twenty days after the procedure, coil protrusion from the aneurysm into the left middle cerebral artery was observed, with a transient ischemic attack. Further coil protrusion did not develop. Both patients recovered with antithrombotic treatment. Even though delayed coil protrusion after coil embolization is rare, it should be recognized as a long-term complication of coil embolization for cerebral aneurysms. PMID:27384117

  15. Retreatment of a transfer patient with bialveolar protrusion with mini bone-plate anchorage.

    PubMed

    Bilodeau, John E

    2014-10-01

    A 40-year-old black woman, with pretorqued, preangulated appliances on the maxillary teeth, transferred with chief concerns of missing teeth and her orthodontic progress. She had bialveolar protrusion and edentulous areas in both the maxilla and the mandible. After records were made and her desires assessed, she was retreated with the extraction of 3 premolars. Her protrusion was reduced and all edentulous spaces were closed. The facial change was evident due to the reduction of the protrusion. PMID:25263153

  16. Asymmetric formation of coated pits on dorsal and ventral surfaces at the leading edges of motile cells and on protrusions of immobile cells

    PubMed Central

    Kural, Comert; Akatay, Ahmet Ata; Gaudin, Raphaël; Chen, Bi-Chang; Legant, Wesley R.; Betzig, Eric; Kirchhausen, Tom

    2015-01-01

    Clathrin/AP2-coated vesicles are the principal endocytic carriers originating at the plasma membrane. In the experiments reported here, we used spinning-disk confocal and lattice light-sheet microscopy to study the assembly dynamics of coated pits on the dorsal and ventral membranes of migrating U373 glioblastoma cells stably expressing AP2 tagged with enhanced green fluorescence (AP2-EGFP) and on lateral protrusions from immobile SUM159 breast carcinoma cells, gene-edited to express AP2-EGFP. On U373 cells, coated pits initiated on the dorsal membrane at the front of the lamellipodium and at the approximate boundary between the lamellipodium and lamella and continued to grow as they were swept back toward the cell body; coated pits were absent from the corresponding ventral membrane. We observed a similar dorsal/ventral asymmetry on membrane protrusions from SUM159 cells. Stationary coated pits formed and budded on the remainder of the dorsal and ventral surfaces of both types of cells. These observations support a previously proposed model that invokes net membrane deposition at the leading edge due to an imbalance between the endocytic and exocytic membrane flow at the front of a migrating cell. PMID:25851602

  17. Excitable actin dynamics in lamellipodial protrusion and retraction.

    PubMed

    Ryan, Gillian L; Petroccia, Heather M; Watanabe, Naoki; Vavylonis, Dimitrios

    2012-04-01

    Many animal cells initiate crawling by protruding lamellipodia, consisting of a dense network of actin filaments, at their leading edge. We imaged XTC cells that exhibit flat lamellipodia on poly-L-lysine-coated coverslips. Using active contours, we tracked the leading edge and measured the total amount of F-actin by summing the pixel intensities within a 5-μm band. We observed protrusion and retraction with period 130-200 s and local wavelike features. Positive (negative) velocities correlated with minimum (maximum) integrated actin concentration. Approximately constant retrograde flow indicated that protrusions and retractions were driven by fluctuations of the actin polymerization rate. We present a model of these actin dynamics as an excitable system in which a diffusive, autocatalytic activator causes actin polymerization; F-actin accumulation in turn inhibits further activator accumulation. Simulations of the model reproduced the pattern of actin polymerization seen in experiments. To explore the model's assumption of an autocatalytic activation mechanism, we imaged cells expressing markers for both F-actin and the p21 subunit of the Arp2/3 complex. We found that integrated Arp2/3-complex concentrations spike several seconds before spikes of F-actin concentration. This suggests that the Arp2/3 complex participates in an activation mechanism that includes additional diffuse components. Response of cells to stimulation by fetal calf serum could be reproduced by the model, further supporting the proposed dynamical picture. PMID:22500749

  18. A novel multilayer immunoisolating encapsulation system overcoming protrusion of cells

    PubMed Central

    Bhujbal, Swapnil V.; de Haan, Bart; Niclou, Simone P.; de Vos, Paul

    2014-01-01

    Application of alginate-microencapsulated therapeutic cells is a promising approach for diseases that require a local and constant supply of therapeutic molecules. However most conventional alginate microencapsulation systems are associated with low mechanical stability and protrusion of cells which is associated with higher surface roughness and limits their clinical application. Here we have developed a novel multilayer encapsulation system that prevents cells from protruding from capsules. The system was tested using a therapeutic protein with anti-tumor activity overexpressed in mammalian cells. The cell containing core of the multilayer capsule was formed by flexible alginate, creating a cell sustaining environment. Surrounded by a poly-L-lysine layer the flexible core was enveloped in a high-G alginate matrix that is less flexible and has higher mechanical stability, which does not support cell survival. The cells in the core of the multilayer capsule did not show growth impairment and protein production was normal for periods up to 70 days in vitro. The additional alginate layer also lowered the surface roughness compared to conventional cell containing alginate-PLL capsules. Our system provides a solution for two important, often overlooked phenomena in cell encapsulation: preventing cell protrusion and improving surface roughness. PMID:25358640

  19. Cranial thoracic disc protrusions in three German Shepherd dogs.

    PubMed

    Gaitero, Lluís; Añor, Sònia

    2009-11-01

    Although intervertebral disc degeneration can occur at any level of the spine, cervical and thoraco-lumbar discs are more commonly affected. The presence of the inter-capital ligament between the rib heads results in an extremely low incidence of cranial thoracic intervertebral disc herniation. In this case series, the clinical, radiological, and surgical findings, as well as the post-operative outcome, in three German Shepherd dogs with T2-T3 disc protrusions is reported. These dogs had chronic progressive paraparesis and lumbar myelography and post-myelographic computerised tomography revealed ventrolateral, extra-dural spinal cord compressions over the T2-T3 intervertebral disc. All animals exhibited transient deterioration in their clinical signs and one developed unilateral Horner's syndrome following T2-T3 hemi-dorsal laminectomy. Subsequently two of the dogs improved progressively and neurological dysfunction had completely resolved by 2 months. To the authors' knowledge, this is the first case series describing T2-T3 disc protrusions in the dog. PMID:18691916

  20. The Rise of Jaw Protrusion in Spiny-Rayed Fishes Closes the Gap on Elusive Prey.

    PubMed

    Bellwood, David R; Goatley, Christopher H R; Bellwood, Orpha; Delbarre, Daniel J; Friedman, Matt

    2015-10-19

    Jaw protrusion is one of the most important innovations in vertebrate feeding over the last 400 million years [1, 2]. Protrusion enables a fish to rapidly decrease the distance between itself and its prey [2, 3]. We assessed the evolution and functional implications of jaw protrusion in teleost fish assemblages from shallow coastal seas since the Cretaceous. By examining extant teleost fishes, we identified a robust morphological predictor of jaw protrusion that enabled us to predict the extent of jaw protrusion in fossil fishes. Our analyses revealed increases in both average and maximum jaw protrusion over the last 100 million years, with a progressive increase in the potential impact of fish predation on elusive prey. Over this period, the increase in jaw protrusion was initially driven by a taxonomic restructuring of fish assemblages, with an increase in the proportion of spiny-rayed fishes (Acanthomorpha), followed by an increase in the extent of protrusion within this clade. By increasing the ability of fishes to catch elusive prey [2, 4], jaw protrusion is likely to have fundamentally changed the nature of predator-prey interactions and may have contributed to the success of the spiny-rayed fishes, the dominant fish clade in modern oceans [5]. PMID:26455299

  1. Open source software for quantification of cell migration, protrusions, and fluorescence intensities

    PubMed Central

    Barry, David J.; Durkin, Charlotte H.; Abella, Jasmine V.

    2015-01-01

    Cell migration is frequently accompanied by changes in cell morphology (morphodynamics) on a range of spatial and temporal scales. Despite recent advances in imaging techniques, the application of unbiased computational image analysis methods for morphodynamic quantification is rare. For example, manual analysis using kymographs is still commonplace, often caused by lack of access to user-friendly, automated tools. We now describe software designed for the automated quantification of cell migration and morphodynamics. Implemented as a plug-in for the open-source platform, ImageJ, ADAPT is capable of rapid, automated analysis of migration and membrane protrusions, together with associated fluorescently labeled proteins, across multiple cells. We demonstrate the ability of the software by quantifying variations in cell population migration rates on different extracellular matrices. We also show that ADAPT can detect and morphologically profile filopodia. Finally, we have used ADAPT to compile an unbiased description of a “typical” bleb formed at the plasma membrane and quantify the effect of Arp2/3 complex inhibition on bleb retraction. PMID:25847537

  2. Self-organization of protrusions and polarity during eukaryotic chemotaxis

    PubMed Central

    Graziano, Brian R.; Weiner, Orion D.

    2014-01-01

    Many eukaryotic cells regulate their polarity and motility in response to external chemical cues. While we know many of the linear connections that link receptors with downstream actin polymerization events, we have a much murkier understanding of the higher order positive and negative feedback loops that organize these processes in space and time. Importantly, physical forces and actin polymerization events don't simply act downstream of chemotactic inputs but are rather involved in a web of reciprocal interactions with signaling components to generate self-organizing pseudopods and cell polarity. Here we focus on recent progress and open questions in the field, including the basic unit of actin organization, how cells regulate the number and speed of protrusions, and 2D vs. 3D migration. PMID:24998184

  3. Real-time monitoring of cell protrusion dynamics by impedance responses.

    PubMed

    Gagliardi, Paolo Armando; Puliafito, Alberto; di Blasio, Laura; Chianale, Federica; Somale, Desiana; Seano, Giorgio; Bussolino, Federico; Primo, Luca

    2015-01-01

    Cellular protrusions are highly dynamic structures involved in fundamental processes, including cell migration and invasion. For a cell to migrate, its leading edge must form protrusions, and then adhere or retract. The spatial and temporal coordination of protrusions and retraction is yet to be fully understood. The study of protrusion dynamics mainly relies on live-microscopy often coupled to fluorescent labeling. Here we report the use of an alternative, label-free, quantitative and rapid assay to analyze protrusion dynamics in a cell population based on the real-time recording of cell activity by means of electronic sensors. Cells are seeded on a plate covered with electrodes and their shape changes map into measured impedance variations. Upon growth factor stimulation the impedance increases due to protrusive activity and decreases following retraction. Compared to microscopy-based methods, impedance measurements are suitable to high-throughput studies on different cell lines, growth factors and chemical compounds. We present data indicating that this assay lends itself to dissect the biochemical signaling pathways controlling adhesive protrusions. Indeed, we show that the protrusion phase is sustained by actin polymerization, directly driven by growth factor stimulation. Contraction instead mainly relies on myosin action, pointing at a pivotal role of myosin in lamellipodia retraction. PMID:25976978

  4. Independently evolved upper jaw protrusion mechanisms show convergent hydrodynamic function in teleost fishes.

    PubMed

    Staab, Katie Lynn; Holzman, Roi; Hernandez, L Patricia; Wainwright, Peter C

    2012-05-01

    A protrusible upper jaw has independently evolved multiple times within teleosts and has been implicated in the success of two groups in particular: Acanthomorpha and Cypriniformes. We use digital particle image velocimetry (DPIV) to compare suction feeding flow dynamics in a representative of each of these clades: goldfish and bluegill. Using DPIV, we contrast the spatial pattern of flow, the temporal relationship between flow and head kinematics, and the contribution of jaw protrusion to the forces exerted on prey. As expected, the spatial patterns of flow were similar in the two species. However, goldfish were slower to reach maximal kinematic excursions, and were more flexible in the relative timing of jaw protrusion, other jaw movements and suction flows. Goldfish were also able to sustain flow speeds for a prolonged period of time as compared with bluegill, in part because goldfish generate lower peak flow speeds. In both species, jaw protrusion increased the force exerted on the prey. However, slower jaw protrusion in goldfish resulted in less augmentation of suction forces. This difference in force exerted on prey corresponds with differences in trophic niches and feeding behavior of the two species. The bluegill uses powerful suction to capture insect larvae whereas the goldfish uses winnowing to sort through detritus and sediment. The kinethmoid of goldfish may permit jaw protrusion that is independent of lower jaw movement, which could explain the ability of goldfish to decouple suction flows (due to buccal expansion) from upper jaw protrusion. Nevertheless, our results show that jaw protrusion allows both species to augment the force exerted on prey, suggesting that this is a fundamental benefit of jaw protrusion to suction feeders. PMID:22496281

  5. Morphological change of self-organized protrusions of fluoropolymer surface by ion beam irradiation

    NASA Astrophysics Data System (ADS)

    Kitamura (Ogawa), Akane; Kobayashi, Tomohiro; Satoh, Takahiro; Koka, Masashi; Kamiya, Tomihiro; Suzuki, Akihiro; Terai, Takayuki

    2013-07-01

    Polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP) are typical fluoropolymers displaying several desirable technological properties such as electrical insulation and high chemical resistance. When their surfaces are irradiated with ion beams, dense micro-protrusions formed after the emergence and spread of micropores across the entire irradiated area, allowing culture cells to spread on the top of the protrusions. In this study, we investigate the morphological changes introduced in the fluoropolymer surfaces by ion beams as the energy of the beams is increased. When an FEP sample was irradiated with a nitrogen ion beam with an energy of less than 350 keV at 1.0 μA/cm2, protrusions were formed with a density between 2 × 107/cm2 and 2 × 108/cm2. However, at energies higher than 350 keV, the protrusions became sparse, and the density dropped to 5 × 102/cm2. Protrusions appeared sporadically during irradiation at high energies, and the top of the protrusions appeared as spots inside the sample, which were difficult to etch and became elongated as the erosion of the surface progressed. Erosion was caused by sputtering of FEP molecules and evaporation at notably elevated temperatures on the surface. Analysis based on attenuated total reflectance/Fourier transform infrared spectroscopy showed the presence of Cdbnd C bonds as well as -COOH, -Cdbnd O, and -OH bonds on all irradiated samples. Their concentration on the surface densely covered with micro-protrusions was higher than that on the surface with sparse protrusions after irradiation at energies exceeding 350 keV. Thus, we determined a suitable range for the ion energy for creating FEP surfaces densely covered with protrusions.

  6. MAXIMUM PROTRUSIVE TONGUE FORCE IN HEALTHY YOUNG ADULTS.

    PubMed

    Berbert, Monalise Costa Batista; Brito, Vivian Garro; Furlan, Renata Maria Moreira Moraes; Perilo, Tatiana Vargas De Castro; Valentim, Amanda Freitas; Barroso, Márcio Falcão Santos; De Las Casas, Estevam Barbosa; Motta, Andréa Rodrigues

    2014-11-01

    In clinical speech-language pathology practice, tongue force is usually evaluated qualitatively. Perception and practical experience are used to classify this force. The Biomechanical Engineering Group from the Federal University of Minas Gerais developed an instrument to quantify tongue force. The purposes of this study were to quantify maximum tongue protrusion force in Brazilian subjects with normal tongue strength and to compare force values between gender groups. In total, 105 subjects, 43 men and 62 women, aged from 18 to 29 years, with normal tongue strength according to qualitative evaluation, underwent quantitative evaluation by using the instrument. The mean of the maximum tongue force values of all participants was 17.58 ± 7.95 N. There were significant differences in the median values for maximum tongue forces between the genders, with higher values observed for men. In intersubject comparisons, high variation coefficients were evident due to the variability among individuals. However, the study suggested that the instrument could be an interesting tool for intrasubject comparisons, especially during the follow-up. PMID:27295848

  7. Protrusive waves guide 3D cell migration along nanofibers

    PubMed Central

    Guetta-Terrier, Charlotte; Monzo, Pascale; Zhu, Jie; Long, Hongyan; Venkatraman, Lakshmi; Zhou, Yue; Wang, PeiPei; Chew, Sing Yian; Mogilner, Alexander

    2015-01-01

    In vivo, cells migrate on complex three-dimensional (3D) fibrous matrices, which has made investigation of the key molecular and physical mechanisms that drive cell migration difficult. Using reductionist approaches based on 3D electrospun fibers, we report for various cell types that single-cell migration along fibronectin-coated nanofibers is associated with lateral actin-based waves. These cyclical waves have a fin-like shape and propagate up to several hundred micrometers from the cell body, extending the leading edge and promoting highly persistent directional movement. Cells generate these waves through balanced activation of the Rac1/N-WASP/Arp2/3 and Rho/formins pathways. The waves originate from one major adhesion site at leading end of the cell body, which is linked through actomyosin contractility to another site at the back of the cell, allowing force generation, matrix deformation and cell translocation. By combining experimental and modeling data, we demonstrate that cell migration in a fibrous environment requires the formation and propagation of dynamic, actin based fin-like protrusions. PMID:26553933

  8. Increased cellular apoptosis susceptibility (CSE1L/CAS) protein expression promotes protrusion extension and enhances migration of MCF-7 breast cancer cells

    SciTech Connect

    Tai, Cheng-Jeng; Shen, Shing-Chuan; Lee, Woan-Ruoh; Liao, Ching-Fong; Deng, Win-Ping; Chiou, Hung-Yi; Hsieh, Cheng-I; Tung, Jai-Nien; Chen, Ching-Shyang; Chiou, Jeng-Fong; Li, Li-Tzu; Lin, Chuang-Yu; Hsu, Chung-Huei; Jiang, Ming-Chung

    2010-10-15

    Microtubules are part of cell structures that play a role in regulating the migration of cancer cells. The cellular apoptosis susceptibility (CSE1L/CAS) protein is a microtubule-associated protein that is highly expressed in cancer. We report here that CSE1L regulates the association of {alpha}-tubulin with {beta}-tubulin and promotes the migration of MCF-7 breast cancer cells. CSE1L was associated with {alpha}-tubulin and {beta}-tubulin in GST (glutathione S-transferase) pull-down and immunoprecipitation assays. CSE1L-GFP (green fluorescence protein) fusion protein experiments showed that the N-terminal of CSE1L interacted with microtubules. Increased CSE1L expression resulted in decreased tyrosine phosphorylation of {alpha}-tubulin and {beta}-tubulin, increased {alpha}-tubulin and {beta}-tubulin association, and enhanced assembly of microtubules. Cell protrusions or pseudopodia are temporary extensions of the plasma membrane and are implicated in cancer cell migration and invasion. Increased CSE1L expression increased the extension of MCF-7 cell protrusions. In vitro migration assay showed that enhanced CSE1L expression increased the migration of MCF-7 cells. Our results indicate that CSE1L plays a role in regulating the extension of cell protrusions and promotes the migration of cancer cells.

  9. Spatio-temporal co-ordination of RhoA, Rac1 and Cdc42 activation during prototypical edge protrusion and retraction dynamics

    PubMed Central

    Martin, Katrin; Reimann, Andreas; Fritz, Rafael D.; Ryu, Hyunryul; Jeon, Noo Li; Pertz, Olivier

    2016-01-01

    The three canonical Rho GTPases RhoA, Rac1 and Cdc42 co-ordinate cytoskeletal dynamics. Recent studies indicate that all three Rho GTPases are activated at the leading edge of motile fibroblasts, where their activity fluctuates at subminute time and micrometer length scales. Here, we use a microfluidic chip to acutely manipulate fibroblast edge dynamics by applying pulses of platelet-derived growth factor (PDGF) or the Rho kinase inhibitor Y-27632 (which lowers contractility). This induces acute and robust membrane protrusion and retraction events, that exhibit stereotyped cytoskeletal dynamics, allowing us to fairly compare specific morphodynamic states across experiments. Using a novel Cdc42, as well as previously described, second generation RhoA and Rac1 biosensors, we observe distinct spatio-temporal signaling programs that involve all three Rho GTPases, during protrusion/retraction edge dynamics. Our results suggest that Rac1, Cdc42 and RhoA regulate different cytoskeletal and adhesion processes to fine tune the highly plastic edge protrusion/retraction dynamics that power cell motility. PMID:26912264

  10. Responses of tumor cell pseudopod protrusion to changes in medium osmolality.

    PubMed

    You, J; Aznavoorian, S; Liotta, L A; Dong, C

    1996-04-01

    The potential involvement of osmotically generated force in protrusion of tumor cell pseudopods was examined during a micropipette assay. Experiments were performed on single A2058 melanoma cells activated by a micropipette filled with soluble type IV collagen. Previous observations suggested that tumor cell pseudopod protrusion induced by type IV collagen took place in distinct, separable phases: an initial bleb (first phase) caused by localized Ca2+-activated actin filament severing resulting in an osmotic flux followed by an extension with an irregular shape (second phase) which required G protein-mediated actin polymerization (Dong et al., 1994, Microvasc. Res., 47:55-67). Presently we studied cell pseudopod protrusion in response to the changes in chemoattractant osmolality. Reduction of attractant osmolality by 20-25% from its baseline value (297 mmol/ kg) resulted in an increase in pseudopod length by 50% apparent in the initial phase. Increases in attractant osmolality by 25-30% from the baseline value arrested pseudopod protrusion significantly during both initial and later phases. Using a dual-pipette method, such osmotic influence on the cell pseudopod protrusion was shown to be only a local effect in a small region where the cell surface was stimulated by the micropipette. While forces derived from actin polymerization and osmotic pressure have been proposed to cause protrusion in general, our results suggested that osmotically generated force is more apparent in the initial phase of the pseudopod formation. PMID:8698833

  11. Global Analysis of mRNA, Translation, and Protein Localization: Local Translation Is a Key Regulator of Cell Protrusions

    PubMed Central

    Mardakheh, Faraz K.; Paul, Angela; Kümper, Sandra; Sadok, Amine; Paterson, Hugh; Mccarthy, Afshan; Yuan, Yinyin; Marshall, Christopher J.

    2015-01-01

    Summary Polarization of cells into a protrusive front and a retracting cell body is the hallmark of mesenchymal-like cell migration. Many mRNAs are localized to protrusions, but it is unclear to what degree mRNA localization contributes toward protrusion formation. We performed global quantitative analysis of the distributions of mRNAs, proteins, and translation rates between protrusions and the cell body by RNA sequencing (RNA-seq) and quantitative proteomics. Our results reveal local translation as a key determinant of protein localization to protrusions. Accordingly, inhibition of local translation destabilizes protrusions and inhibits mesenchymal-like morphology. Interestingly, many mRNAs localized to protrusions are translationally repressed. Specific cis-regulatory elements within mRNA UTRs define whether mRNAs are locally translated or repressed. Finally, RNAi screening of RNA-binding proteins (RBPs) enriched in protrusions revealed trans-regulators of localized translation that are functionally important for protrusions. We propose that by deciphering the localized mRNA UTR code, these proteins regulate protrusion stability and mesenchymal-like morphology. PMID:26555054

  12. Modeling the Excess Cell Surface Stored in a Complex Morphology of Bleb-Like Protrusions.

    PubMed

    Kapustina, Maryna; Tsygankov, Denis; Zhao, Jia; Wessler, Timothy; Yang, Xiaofeng; Chen, Alex; Roach, Nathan; Elston, Timothy C; Wang, Qi; Jacobson, Ken; Forest, M Gregory

    2016-03-01

    Cells transition from spread to rounded morphologies in diverse physiological contexts including mitosis and mesenchymal-to-amoeboid transitions. When these drastic shape changes occur rapidly, cell volume and surface area are approximately conserved. Consequently, the rounded cells are suddenly presented with a several-fold excess of cell surface whose area far exceeds that of a smooth sphere enclosing the cell volume. This excess is stored in a population of bleb-like protrusions (BLiPs), whose size distribution is shown by electron micrographs to be skewed. We introduce three complementary models of rounded cell morphologies with a prescribed excess surface area. A 2D Hamiltonian model provides a mechanistic description of how discrete attachment points between the cell surface and cortex together with surface bending energy can generate a morphology that satisfies a prescribed excess area and BLiP number density. A 3D random seed-and-growth model simulates efficient packing of BLiPs over a primary rounded shape, demonstrating a pathway for skewed BLiP size distributions that recapitulate 3D morphologies. Finally, a phase field model (2D and 3D) posits energy-based constitutive laws for the cell membrane, nematic F-actin cortex, interior cytosol, and external aqueous medium. The cell surface is equipped with a spontaneous curvature function, a proxy for the cell surface-cortex couple, that is a priori unknown, which the model "learns" from the thin section transmission electron micrograph image (2D) or the "seed and growth" model image (3D). Converged phase field simulations predict self-consistent amplitudes and spatial localization of pressure and stress throughout the cell for any posited stationary morphology target and cell compartment constitutive properties. The models form a general framework for future studies of cell morphological dynamics in a variety of biological contexts. PMID:27015526

  13. Modeling the Excess Cell Surface Stored in a Complex Morphology of Bleb-Like Protrusions

    PubMed Central

    Wessler, Timothy; Yang, Xiaofeng; Chen, Alex; Roach, Nathan; Elston, Timothy C.; Wang, Qi; Jacobson, Ken; Forest, M. Gregory

    2016-01-01

    Cells transition from spread to rounded morphologies in diverse physiological contexts including mitosis and mesenchymal-to-amoeboid transitions. When these drastic shape changes occur rapidly, cell volume and surface area are approximately conserved. Consequently, the rounded cells are suddenly presented with a several-fold excess of cell surface whose area far exceeds that of a smooth sphere enclosing the cell volume. This excess is stored in a population of bleb-like protrusions (BLiPs), whose size distribution is shown by electron micrographs to be skewed. We introduce three complementary models of rounded cell morphologies with a prescribed excess surface area. A 2D Hamiltonian model provides a mechanistic description of how discrete attachment points between the cell surface and cortex together with surface bending energy can generate a morphology that satisfies a prescribed excess area and BLiP number density. A 3D random seed-and-growth model simulates efficient packing of BLiPs over a primary rounded shape, demonstrating a pathway for skewed BLiP size distributions that recapitulate 3D morphologies. Finally, a phase field model (2D and 3D) posits energy-based constitutive laws for the cell membrane, nematic F-actin cortex, interior cytosol, and external aqueous medium. The cell surface is equipped with a spontaneous curvature function, a proxy for the cell surface-cortex couple, that is a priori unknown, which the model “learns” from the thin section transmission electron micrograph image (2D) or the “seed and growth” model image (3D). Converged phase field simulations predict self-consistent amplitudes and spatial localization of pressure and stress throughout the cell for any posited stationary morphology target and cell compartment constitutive properties. The models form a general framework for future studies of cell morphological dynamics in a variety of biological contexts. PMID:27015526

  14. The value of accurate clinical assessment in the surgical management of the lumbar disc protrusion.

    PubMed

    Kerr, R S; Cadoux-Hudson, T A; Adams, C B

    1988-02-01

    One hundred patients with lumbar disc protrusions were studied. Thirty six "control" patients were admitted in the same time period with low back pain and sciatica but with subsequently "normal" myelograms and no surgery. The aim of this paper was to relate history and clinical signs to the myelograms and surgical findings. Ninety nine per cent of our patients presented with sciatica (controls 94%). The most frequently found sign in patients with a disc protrusion was reduction of ipsilateral straight leg raising (98%). However, 55% of controls also showed this sign. There were three signs that, when present, particularly indicated a disc protrusion; "crossed straight leg raising" (pain on contralateral straight leg raising), measured calf wasting and impaired ankle reflex: the latter being especially indicative of an L5-S1 disc protrusion. There were two further important signs, weakness of dorsiflexion of the foot and scoliosis of the lumbar spine. However, such signs occurred in about half the patients and so clinical diagnosis in the remaining half depended on obtaining a good history of sciatica, and paying due regard to severity of the pain, the mobility of the patient, the ability and desire to work and the overall personality. Satisfactory results of surgery simply depend on finding and removing a definite disc protrusion. Using these methods of selection, 98% have returned to their original employment, 86% within 3 months of the operation. For a patient with no abnormal signs and a normal myelogram, surgical treatment should not be advised. PMID:3346682

  15. Mandibular advancement and obstructive sleep apnoea: a method for determining effective mandibular protrusion.

    PubMed

    Dort, L C; Hadjuk, E; Remmers, J E

    2006-05-01

    The objectives of the study were to test the hypotheses that it is possible, during routine polysomnography (PSG), to prospectively identify favourable candidates for mandibular repositioning appliance (MRA) therapy in the treatment of obstructive sleep apnoea (OSA) and to accurately estimate an optimal protrusive distance at which to fabricate the MRA. A series of subjects underwent a remotely controlled mandibular positioner (RCMP) test during PSG monitoring. The ability of the RCMP test to eliminate OSA and the target protrusion at which that occurred was compared with the success of a custom oral MRA in the 33 subjects who completed the protocol. The RCMP test was a success in 15 subjects and a failure in 18 subjects. Appliance therapy was initiated in 38 subjects and completed in 33. MRA therapy was successful at target protrusion in 80% of subjects who had a successful RCMP test and failed in 78% of those who failed the RCMP test. In conclusion the remotely controlled mandibular positioner test outcome demonstrated a statistically significant association with mandibular repositioning appliance outcome. The target protrusion determined during the remotely controlled mandibular positioner test was the effective therapeutic protrusion in subjects with a successful remotely controlled mandibular positioner test. PMID:16707396

  16. Self-organization of waves and pulse trains by molecular motors in cellular protrusions.

    PubMed

    Yochelis, A; Ebrahim, S; Millis, B; Cui, R; Kachar, B; Naoz, M; Gov, N S

    2015-01-01

    Actin-based cellular protrusions are an ubiquitous feature of cells, performing a variety of critical functions ranging from cell-cell communication to cell motility. The formation and maintenance of these protrusions relies on the transport of proteins via myosin motors, to the protrusion tip. While tip-directed motion leads to accumulation of motors (and their molecular cargo) at the protrusion tip, it is observed that motors also form rearward moving, periodic and isolated aggregates. The origins and mechanisms of these aggregates, and whether they are important for the recycling of motors, remain open puzzles. Motivated by novel myosin-XV experiments, a mass conserving reaction-diffusion-advection model is proposed. The model incorporates a non-linear cooperative interaction between motors, which converts them between an active and an inactive state. Specifically, the type of aggregate formed (traveling waves or pulse-trains) is linked to the kinetics of motors at the protrusion tip which is introduced by a boundary condition. These pattern selection mechanisms are found not only to qualitatively agree with empirical observations but open new vistas to the transport phenomena by molecular motors in general. PMID:26335545

  17. Self-organization of waves and pulse trains by molecular motors in cellular protrusions

    PubMed Central

    Yochelis, A.; Ebrahim, S.; Millis, B.; Cui, R.; Kachar, B.; Naoz, M.; Gov, N. S.

    2015-01-01

    Actin-based cellular protrusions are an ubiquitous feature of cells, performing a variety of critical functions ranging from cell-cell communication to cell motility. The formation and maintenance of these protrusions relies on the transport of proteins via myosin motors, to the protrusion tip. While tip-directed motion leads to accumulation of motors (and their molecular cargo) at the protrusion tip, it is observed that motors also form rearward moving, periodic and isolated aggregates. The origins and mechanisms of these aggregates, and whether they are important for the recycling of motors, remain open puzzles. Motivated by novel myosin-XV experiments, a mass conserving reaction-diffusion-advection model is proposed. The model incorporates a non-linear cooperative interaction between motors, which converts them between an active and an inactive state. Specifically, the type of aggregate formed (traveling waves or pulse-trains) is linked to the kinetics of motors at the protrusion tip which is introduced by a boundary condition. These pattern selection mechanisms are found not only to qualitatively agree with empirical observations but open new vistas to the transport phenomena by molecular motors in general. PMID:26335545

  18. PAK-PIX interactions regulate adhesion dynamics and membrane protrusion to control neurite outgrowth.

    PubMed

    Santiago-Medina, Miguel; Gregus, Kelly A; Gomez, Timothy M

    2013-03-01

    The roles of P21-activated kinase (PAK) in the regulation of axon outgrowth downstream of extracellular matrix (ECM) proteins are poorly understood. Here we show that PAK1-3 and PIX are expressed in the developing spinal cord and differentially localize to point contacts and filopodial tips within motile growth cones. Using a specific interfering peptide called PAK18, we found that axon outgrowth is robustly stimulated on laminin by partial inhibition of PAK-PIX interactions and PAK function, whereas complete inhibition of PAK function stalls axon outgrowth. Furthermore, modest inhibition of PAK-PIX stimulates the assembly and turnover of growth cone point contacts, whereas strong inhibition over-stabilizes adhesions. Point mutations within PAK confirm the importance of PIX binding. Together our data suggest that regulation of PAK-PIX interactions in growth cones controls neurite outgrowth by influencing the activity of several important mediators of actin filament polymerization and retrograde flow, as well as integrin-dependent adhesion to laminin. PMID:23321640

  19. Bleb Nucleation through Membrane Peeling

    NASA Astrophysics Data System (ADS)

    Alert, Ricard; Casademunt, Jaume

    2016-02-01

    We study the nucleation of blebs, i.e., protrusions arising from a local detachment of the membrane from the cortex of a cell. Based on a simple model of elastic linkers with force-dependent kinetics, we show that bleb nucleation is governed by membrane peeling. By this mechanism, the growth or shrinkage of a detached membrane patch is completely determined by the linker kinetics, regardless of the energetic cost of the detachment. We predict the critical nucleation radius for membrane peeling and the corresponding effective energy barrier. These may be typically smaller than those predicted by classical nucleation theory, implying a much faster nucleation. We also perform simulations of a continuum stochastic model of membrane-cortex adhesion to obtain the statistics of bleb nucleation times as a function of the stress on the membrane. The determinant role of membrane peeling changes our understanding of bleb nucleation and opens new directions in the study of blebs.

  20. 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

  1. Surgical treatment of cervical disc protrusion causing intracranial hypotension following chiropractic manipulation.

    PubMed

    Wilson, David; Steel, Timothy; Sutton, Ian

    2015-09-01

    We describe a woman with intracranial hypotension provoked by a combination of calcified disc protrusion and chiropractic manipulation who required surgical intervention for definitive treatment. Intracranial hypotension is a rare but increasingly well recognized cause of orthostatic headache that arises due to spinal cerebrospinal fluid leakage from meningeal diverticula or dural perforations. PMID:26067544

  2. Imitation of Tongue Protrusion in Human Neonates: Specificity of the Response in a Large Sample

    ERIC Educational Resources Information Center

    Nagy, Emese; Pilling, Karen; Orvos, Hajnalka; Molnar, Peter

    2013-01-01

    Although a large body of evidence has accumulated on the young human infant's ability to imitate, the phenomenon has failed to gain unanimous acceptance. Imitation of tongue protrusion, the most tested gesture to date, was examined in a sample of 115 newborns in the first 5 days of life in 3 seating positions. An ethologically based…

  3. Human neutrophil surface protrusion under a point load: location independence and viscoelasticity

    PubMed Central

    Xu, Gang; Shao, Jin-Yu

    2008-01-01

    Mechanical properties of neutrophils have been recognized as key contributors to stabilizing neutrophil rolling on the endothelium during the inflammatory response. In particular, accumulating evidence suggests that surface protrusion and tether extraction from neutrophils facilitate stable rolling by relieving the disruptive forces on adhesive bonds. Using a customized optical trap setup, we applied piconewton-level pulling forces on targeted receptors that were located either on the microvillus tip (CD162) or intermicrovillus surface of neutrophils (CD18 and CD44). Under a constant force-loading rate, there always occurred an initial tent-like surface protrusion that was terminated either by rupture of the adhesion or by a “yield” or “crossover” to tether extraction. The corresponding protrusional stiffness of neutrophils was found to be between 0.06 and 0.11 pN/nm, depending on the force-loading rate and the cytoskeletal integrity, but not on the force location, the medium osmolality, nor the temperature increase from 22°C to 37°C. More importantly, we found that neutrophil surface protrusion was accompanied by force relaxation and hysteresis. In addition, the crossover force did not change much in the range of force-loading rates studied, and the protrusional stiffness of lymphocytes was similar to that of neutrophils. These results show that neutrophil surface protrusion is essentially viscoelastic, with a protrusional stiffness that stems primarily from the actin cortex, and the crossover force is independent of the receptor-cytoskeleton interaction. PMID:18815230

  4. Effect of Tongue Exercise on Protrusive Force and Muscle Fiber Area in Aging Rats

    ERIC Educational Resources Information Center

    Connor, Nadine P.; Russell, John A.; Wang, Hao; Jackson, Michelle A.; Mann, Laura; Kluender, Keith

    2009-01-01

    Purpose: Age-related changes in tongue function may contribute to dysphagia in elderly people. The authors' purpose was to investigate whether aged rats that have undergone tongue exercise would manifest increased protrusive tongue forces and increased genioglossus (GG) muscle fiber cross-sectional areas. Method: Forty-eight young adult,…

  5. Moesin is activated in cardiomyocytes in experimental autoimmune myocarditis and mediates cytoskeletal reorganization with protrusion formation.

    PubMed

    Miyawaki, Akimitsu; Mitsuhara, Yusuke; Orimoto, Aya; Nakayasu, Yusuke; Tsunoda, Shin-Ichi; Obana, Masanori; Maeda, Makiko; Nakayama, Hiroyuki; Yoshioka, Yasuo; Tsutsumi, Yasuo; Fujio, Yasushi

    2016-08-01

    Acute myocarditis is a self-limiting disease. Most patients with myocarditis recover without cardiac dysfunction in spite of limited capacity of myocardial regeneration. Therefore, to address intrinsic reparative machinery of inflamed hearts, we investigated the cellular dynamics of cardiomyocytes in response to inflammation using experimental autoimmune myocarditis (EAM) model. EAM was induced by immunization of BALB/c mice with α-myosin heavy chain peptides twice. The inflammatory reaction was evoked with myocardial damage with the peak at 3 wk after the first immunization (EAM3w). Morphological and functional restoration started from EAM3w, when active protrusion formation, a critical process of myocardial healing, was observed in cardiomyocytes. Shotgun proteomics revealed that cytoskeletal proteins were preferentially increased in cardiomyocytes at EAM3w, compared with preimmunized (EAM0w) hearts, and that moesin was the most remarkably upregulated among them. Immunoblot analyses demonstrated that the expression of both total and phosphorylated moesin was upregulated in isolated cardiomyocytes from EAM3w hearts. Immunofluorescence staining showed that moesin was localized at cardiomyocyte protrusions at EAM3w. Adenoviral vectors expressing wild-type, constitutively active and inactive form of moesin (wtMoesin, caMoesin, and iaMoesin, respectively) were transfected in neonatal rat cardiomyocytes. The overexpression of wtMoesin and caMoesin resulted in protrusion formation, while not iaMoesin. Finally, we found that cardiomyocyte protrusions were accompanied by cell-cell contact formation. The expression of moesin was upregulated in cardiomyocytes under inflammation, inducing protrusion formation in a phosphorylation-dependent fashion. Moesin signal could be a novel therapeutic target that stimulates myocardial repair by promoting contact formation of cardiomyocytes. PMID:27342875

  6. Premaxillary movements in cyprinodontiform fishes: an unusual protrusion mechanism facilitates "picking" prey capture.

    PubMed

    Ferry-Graham, Lara A; Gibb, Alice C; Hernandez, L Patricia

    2008-01-01

    Premaxillary protrusion is hypothesized to confer a number of feeding advantages to teleost fishes; however, most proposed advantages relate to enhanced stealth or suction production during prey capture. Cyprinodontiformes exhibit an unusual form of premaxillary protrusion where the descending process of the premaxilla does not rotate anteriorly to occlude the sides of the open mouth during prey capture. Instead, the premaxilla is protruded such that it gives the impression of a beak during prey capture. We quantified premaxillary kinematics during feeding in four cyprinodontiform taxa and compared them with three percomorph taxa to identify any performance consequences of this protrusion mechanism. Individual prey capture events were recorded using digital high-speed video at 250-500 frames per second (n >or= 4 individuals, >or= 4 strikes per individual). Species differed in the timing of movement and the maximum displacement of the premaxilla during the gape cycle and in the contribution of the premaxilla to jaw closing. Cyprinodontiform taxa produced less premaxillary protrusion than the percomorph taxa, and were consistently slower in the time to maximum gape. Further, it appears cyprinodontiforms can alter the contribution of the premaxilla to mouth closure on an event-specific basis. We were able to demonstrate that, within at least one species, this variability is associated with the location of the prey (bottom vs. water column). Cyprinodontiform upper jaw movements likely reflect increased dexterity associated with a foraging ecology where prey items are "picked" from a variety of locations: the bottom, water column, or surface. We postulate that dexterity requires slow, precisely controlled jaw movements; thus, may be traded off for some aspects of suction-feeding performance, such as protrusion distance and speed. PMID:18619823

  7. Correlations of O3 therapeutic targets and imaging localization in lumbar intervertebral disc protrusion

    PubMed Central

    Xu, Fenghe; Yin, Yanwei; Liu, Chuansheng; Yi, Yusheng; Yu, Junmin; Kou, Dewei; Wang, Shijie

    2015-01-01

    Objective: This study aims to investigate correlations between the effects of O3 target-injection treatment and imaging localization in lumbar intervertebral disc protrusion (LIDP). Methods: 164 LIDP patients were divided into 3 groups: group A, the protrusion located at level I-III, region 1-2, domain a-b; group B, the protrusion located at level I-III, region 1-2, domain c-d; group C: the protrusion located at level I-III, region 3-4, domain a-b. The patients were treated with LIDP O3-target treatment + blocking therapy with epidural anti-inflammatory analgesic liquid. Results: Among the 164 LIDP patients, 95 patients (57.93%) exhibited the significant effectiveness after the treatment; 64 cases (39.02%) exhibited the effectiveness. The results of functional improvements revealed that 50 cases (53.76%) of sagittal plane and 54 cases of horizontal plane (55.67%) in the group A, 33 cases (35.48%) and 31 cases (31.96%) in the group C respectively were significantly better than those in the group B (10 cases, 10.75%; 12 cases, 12.37%) (P < 0.05). The visual analogue scale (VAS) scores 1 week and 1 month after the treatment in the three groups were significantly decreased than those before the treatment (P < 0.05). The intergroup comparison revealed that the A group (1 week 2.28 ± 0.85, 1 month 1.21 ± 0.27) and C (2.79 ± 0.98, 1.38 ± 0.55) were significantly better than the B group (3.92 ± 1.14, 2.53 ± 0.51) (P < 0.05). Conclusions: The O3 target-injection treatment exhibited the best effects in treating the LIDP patients with the protrusion located at level I-III, region 1-2, domain a-b. PMID:26309586

  8. Early carbon mobilization and radicle protrusion in maize germination

    PubMed Central

    Sánchez-Linares, Luis; Gavilanes-Ruíz, Marina; Díaz-Pontones, David; Guzmán-Chávez, Fernando; Calzada-Alejo, Viridiana; Zurita-Villegas, Viridiana; Luna-Loaiza, Viridiana; Moreno-Sánchez, Rafael; Bernal-Lugo, Irma; Sánchez-Nieto, Sobeida

    2012-01-01

    Considerable amounts of information is available on the complex carbohydrates that are mobilized and utilized by the seed to support early seedling development. These events occur after radicle has protruded from the seed. However, scarce information is available on the role of the endogenous soluble carbohydrates from the embryo in the first hours of germination. The present work analysed how the soluble carbohydrate reserves in isolated maize embryos are mobilized during 6–24 h of water imbibition, an interval that exclusively embraces the first two phases of the germination process. It was found that sucrose constitutes a very significant reserve in the scutellum and that it is efficiently consumed during the time in which the adjacent embryo axis is engaged in an active metabolism. Sucrose transporter was immunolocalized in the scutellum and in vascular elements. In parallel, a cell-wall invertase activity, which hydrolyses sucrose, developed in the embryo axis, which favoured higher glucose uptake. Sucrose and hexose transporters were active in the embryo tissues, together with the plasma membrane H+-ATPase, which was localized in all embryo regions involved in both nutrient transport and active cell elongation to support radicle extension. It is proposed that, during the initial maize germination phases, a net flow of sucrose takes place from the scutellum towards the embryo axis and regions that undergo elongation. During radicle extension, sucrose and hexose transporters, as well as H+-ATPase, become the fundamental proteins that orchestrate the transport of nutrients required for successful germination. PMID:22611232

  9. Exo70 Generates Membrane Curvature for Morphogenesis and Cell Migration

    PubMed Central

    Zhao, Yuting; Liu, Jianglan; Yang, Changsong; Capraro, Benjamin R.; Baumgart, Tobias; Bradley, Ryan P.; Ramakrishnan, N.; Xu, Xiaowei; Radhakrishnan, Ravi; Svitkina, Tatyana; Guo, Wei

    2013-01-01

    Dynamic shape changes of the plasma membrane are fundamental to many processes ranging from morphogenesis and cell migration to phagocytosis and viral propagation. Here we demonstrate that Exo70, a component of the exocyst complex, induces tubular membrane invaginations towards the lumen of synthetic vesicles in vitro and generates protrusions on the surface of cells. Biochemical analyses using Exo70 mutants and independent molecular dynamics simulations based on Exo70 structure demonstrate that Exo70 generates negative membrane curvature through an oligomerization-based mechanism. In cells, the membrane-deformation function of Exo70 is required for protrusion formation and directional cell migration. Exo70 thus represents a membrane-bending protein that may couple actin dynamics and plasma membrane remodeling for morphogenesis. PMID:23948253

  10. Electrokinetic effects near a membrane

    NASA Astrophysics Data System (ADS)

    Lacoste, David

    2009-03-01

    We discuss the electrostatic and electrokinetic contribution to the elastic moduli of a cell or artificial membrane placed in an electrolyte and driven by a DC electric field. The field drives ion currents across the membrane, through specific channels, pumps or natural pores. In steady state, charges accumulate in the Debye layers close to the membrane, modifying the membrane elastic moduli. We first study a model of a membrane of zero thickness, later generalizing this treatment to allow for a finite thickness and finite dielectric constant. Our results clarify and extend the results presented in [D. Lacoste, M. Cosentino Lagomarsino, and J. F. Joanny, Europhys. Lett., 77, 18006 (2007)], by providing a physical explanation for a destabilizing term proportional to kps^3 in the fluctuation spectrum, which we relate to a nonlinear (E^2) electro-kinetic effect called induced-charge electro-osmosis (ICEO). Recent studies of ICEO have focused on electrodes and polarizable particles, where an applied bulk field is perturbed by capacitive charging of the double layer and drives flow along the field axis toward surface protrusions; we predict similar ICEO flows around driven membranes, due to curvature-induced tangential fields within a non-equilibrium double layer, which hydrodynamically enhance protrusions.

  11. Effect of microscale protrusions on local fluid flow and mass transport in the presence of forced convection

    SciTech Connect

    Matzen, G.W.

    1997-01-01

    Three-dimensional creeping flow around single, axisymmetric protrusions is studied numerically using the boundary-integral technique. Emphasis is placed upon cylindrical protrusions on plane walls for various height-to-radius (h-to-a) aspect ratios, but cones and sections of spheres protruding from plane walls are also briefly examined. The presented items include shear-stress distributions, shear-stress contours, extents of the fluid-flow disturbance, total forces and torques on the cylinders, streamlines, and skin-friction lines. Also included is a discussion of flow topology around axisymmetric geometries. No flow reversal is observed for cylindrical protrusions with aspect ratios greater than 2.4 to 2.6. At higher aspect ratios, the fluid tends to be swept around cylindrical protrusions with little vertical motion. At lower aspect ratios, the strength of the recirculation increases, and the recirculation region becomes wider in the transverse direction and narrower in the flow direction. Also, the recirculation pattern begins to resemble the closed streamline patterns in two-dimensional flow over square ridges. However, unlike two-dimensional flow, closed streamline patterns are not observed. For arbitrary axisymmetric geometries, the extent of the fluid-flow disturbance can be estimated with the total force that is exerted on the protrusion. When the same force is exerted on protrusions with different aspect ratios, the protrusion with the higher aspect ratio tends to have a greater disturbance in the flow direction and a smaller disturbance in the transverse direction. The total force exerted on cylindrical protrusions with rounded corners is only slightly lower than the total force exerted on cylindrical protrusions with sharp corners.

  12. Closed membrane shapes with attached BAR domains subject to external force of actin filaments.

    PubMed

    Mesarec, Luka; Góźdź, Wojciech; Iglič, Veronika Kralj; Kralj, Samo; Iglič, Aleš

    2016-05-01

    Membrane deformations induced by attached BAR superfamily domains could trigger or facilitate the growth of plasma membrane protrusions. The BAR domain family consists of BAR, F-BAR and I-BAR domains, each enforcing a different local curvature when attached to the membrane surface. Our theoretical study mainly focuses on the role of I-BAR in the membrane tubular deformations generated or stabilised by actin filaments. The influence of the area density of membrane attached BAR domains and their intrinsic curvature on the closed membrane shapes (vesicles) was investigated numerically. We derived an analytical approximative expression for the critical relative area density of BARs at which the membrane tubular protrusions on vesicles are most prominent. We have shown that the BARs with a higher intrinsic curvature induce thinner and longer cylindrical protrusions. The average orientation of the membrane attached BARs is altered when the vesicle shape is subjected to external force of growing actin rod-like structure inside a vesicle. The average orientation angle of membrane attached BARs may indicate whether the actin filaments are just stabilising the protrusion or generating it by stretching the vesicle. PMID:26854580

  13. Changing gears from chemical adhesion of cells to flat substrata toward engulfment of micro-protrusions by active mechanisms

    NASA Astrophysics Data System (ADS)

    Hai, Aviad; Kamber, Dotan; Malkinson, Guy; Erez, Hadas; Mazurski, Noa; Shappir, Joseph; Spira, Micha E.

    2009-12-01

    Microelectrode arrays increasingly serve to extracellularly record in parallel electrical activity from many excitable cells without inflicting damage to the cells by insertion of microelectrodes. Nevertheless, apart from rare cases they suffer from a low signal to noise ratio. The limiting factor for effective electrical coupling is the low seal resistance formed between the plasma membrane and the electronic device. Using transmission electron microscope analysis we recently reported that cultured Aplysia neurons engulf protruding micron size gold spines forming tight apposition which significantly improves the electrical coupling in comparison with flat electrodes (Hai et al 2009 Spine-shaped gold protrusions improve the adherence and electrical coupling of neurons with the surface of micro-electronic devices J. R. Soc. Interface 6 1153-65). However, the use of a transmission electron microscope to measure the extracellular cleft formed between the plasma membrane and the gold-spine surface may be inaccurate as chemical fixation may generate structural artifacts. Using live confocal microscope imaging we report here that cultured Aplysia neurons engulf protruding spine-shaped gold structures functionalized by an RGD-based peptide and to a significantly lesser extent by poly-l-lysine. The cytoskeletal elements actin and associated protein cortactin are shown to organize around the stalks of the engulfed gold spines in the form of rings. Neurons grown on the gold-spine matrix display varying growth patterns but maintain normal electrophysiological properties and form functioning synapses. It is concluded that the matrices of functionalized gold spines provide an improved substrate for the assembly of neuro-electronic hybrids.

  14. Heterotypic and homotypic associations between ezrin and moesin, two putative membrane-cytoskeletal linking proteins.

    PubMed Central

    Gary, R; Bretscher, A

    1993-01-01

    Ezrin and moesin are components of actin-rich cell surface structures that are thought to function as membrane-cytoskeletal linking proteins. Here we show that a stable complex of ezrin and moesin can be isolated from cultured cells by immunoprecipitation with specific antibodies. The capacity of these two proteins to interact directly was confirmed with a blot-overlay procedure in which biotin-tagged proteins in solution were incubated with immobilized binding partners. In addition to the heterotypic association of ezrin and moesin, homotypic binding of ezrin to ezrin and of moesin to moesin was also demonstrated in vitro. These results suggest mechanisms by which ezrin and moesin might participate in dynamic aspects of cortical cytoskeletal structure. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:8248180

  15. Treatment of Bi-maxillary Protrusion with Impacted Maxillary and Mandibular Canines: Case Report.

    PubMed

    Shdrma, Vipul Kumar; Yadav, Kirti; Nagar, Amit; Tandon, Pradeep; Chaturvedi, Thakur Prasad

    2016-01-01

    Bi-maxillary protrusion in adolescent patients has traditionally been treated by extraction of the four first premolars and retraction ofthe anterior teeth. The ectopic eruption of the maxiIlary permanent canines is a frequently encountered clinical problem. Orthodontic treatment of the impacted teeth remains a challenge for clinicians. If it is associated with other dental and skeletalproblems, there will be further complications to the treatment plan. In such cases, if we extract canines, then problems with this approach are restricted to anatomical and functional limitations ofpremolars substitution of canines. Here, we are presenting a case report of bi-maxillary dento-alveolar protrusion with the impacted maxillary and mandibular left canines and its management. PMID:27319045

  16. Accurate determination of relative metatarsal protrusion with a small intermetatarsal angle: a novel simplified method.

    PubMed

    Osher, Lawrence; Blazer, Marie Mantini; Buck, Stacie; Biernacki, Tomasz

    2014-01-01

    Several published studies have explained in detail how to measure relative metatarsal protrusion on the plain film anteroposterior pedal radiograph. These studies have demonstrated the utility of relative metatarsal protrusion measurement in that it correlates with distal forefoot deformity or pathologic features. The method currently preferred by practitioners in podiatric medicine and surgery often presents one with the daunting challenge of obtaining an accurate measurement when the intermetatarsal 1-2 angle is small. The present study illustrates a novel mathematical solution to this problem that is simple to master, relatively quick to perform, and yields accurate results. Our method was tested and proven by 4 trained observers with varying degrees of clinical skill who independently measured the same 10 radiographs. PMID:24933656

  17. Study on different surgical approaches for acute Lumber disk protrusion combined with Cauda Equina Syndrome

    PubMed Central

    Shen, Lianbing; Fang, Liangqin; Qiu, Yihua; Xing, Shunming; Chen, Dechun; He, Xiang; Wang, Jinxin; Lai, Jing; Shi, Guohua; Zhang, Jiefeng; Liao, Teng; Tan, Junming

    2014-01-01

    To compare the long and short term effectiveness and complications of different surgical approaches for Lumber disk protrusion combined with Cauda Equina Syndrome and find a better surgical method for the disease. In this study, follow up records of 144 patients received conventional laminectomy and minimally invasive decompression and fenestration 48 hours within acute injury of lumber disk protrusion combined with Cauda Equina Syndrome were analyzed. Surgical outcome immediately and 3, 6, 12, 36 months after the surgery were compared to evaluate the effectiveness two different approaches. The results indicated that there are no significant differences regarding age, sexual proportion, body mass index (BMI), visual analogue scale of pain (VAS) score as well as Frankel scores before the surgery, and significant differences VAS score as well as Frankel scores immediately after the surgery. In conclusion, minimally invasive decompression and fenestration can be of the same effectiveness and less complications comparing with the conventional laminectomy. PMID:25674258

  18. Human Newborns Match Tongue Protrusion of Disembodied Human and Robotic Mouths

    ERIC Educational Resources Information Center

    Soussignan, Robert; Courtial, Alexis; Canet, Pierre; Danon-Apter, Gisele; Nadel, Jacqueline

    2011-01-01

    No evidence had been provided so far of newborns' capacity to give a matching response to 2D stimuli. We report evidence from 18 newborns who were presented with three types of stimuli on a 2D screen. The stimuli were video-recorded displays of tongue protrusion shown by: (a) a human face, (b) a human tongue from a disembodied mouth, and (c) an…

  19. Atmospheric effects on radiometry from zenith of a plane with dark vertical protrusions

    NASA Technical Reports Server (NTRS)

    Otterman, J.

    1983-01-01

    Effects of an optically thin plane-parallel scattering atmosphere on radiometric imaging from the zenith of a specific surface-type are analyzed. The surface model was previously developed to describe arid steppe, where the sparse vegetation forms dark vertical protrusions from the bright soil-plane. The analysis is in terms of the surface reflectivity to the zenith r sub p for the direct beam, which is formulated as r sub p = r sub i exp (-s tan theta sub 0), where v sub i is the Lambert law reflectivity of the soil, the protrusions parameters s is the projection on a vertical plane of protrusions per unit area and theta sub 0 is the zenith angle. The surface reflectivity r sub p is approximately equal to that for the global irradiance (which is directly measured in the field) only for a narrow range of the solar zenith angles. The effects of the atmosphere when imaging large uniform areas of this type are comparable to those in imaging a Lambert surface with a reflectivity r sub p. Thus, the effects can be approximated by those in the case of a dark Lambert surface (analyzed previously), inasmuch as r sub p is smaller than the soil reflectivity r sub i for any off-zenith illumination. The surface becomes effectively darker with increasing solar zenith angle. Adjacency effects of a reflection from one area and scattering in the instantaneous field of view (object pixel) are analyzed as cross radiance and cross irradiance.

  20. Thermal pole tip protrusion finite element analysis of thin film inductive recording heads

    NASA Astrophysics Data System (ADS)

    Yan, Wentao

    2002-05-01

    In recent low flying height hard disk drives, the head write current causes thermal protrusion of the pole tip region that results in head-disk contact. Finite element analysis is performed in this work to study the temperature and displacement fields in heads during writing. Three-dimensional steady-state thermal-structural analysis of a head in air and over a disk is presented. Complex head geometry is modeled. Velocity slip and temperature jump boundary conditions are used in formulating heat transfer through the air bearing. Moreover, transient analysis of head thermal protrusion is presented. Step direct current is applied. Snapshots of the temperature field as well as temperature and displacement time functions of several locations in the head are exhibited. It is found that head protrusion first occurs at the pole tip, then spreads to the trailing end of the slider. For the head-disk interface studied, it takes 0.6 ms for the head to come in contact with the disk after writing starts.

  1. Protrusion of hepatocellular carcinoma is a predictor of early recurrence in hepatectomy patients after spontaneous rupture

    PubMed Central

    Han, Seung Rim; Choi, Gyu-Seong; Park, Jae Berm; Kwon, Choon Hyuck David; Kim, Sung Joo; Joh, Jae-Won

    2016-01-01

    Purpose The factors related to early-onset tumor recurrence in patients with spontaneously ruptured hepatocellular carcinoma (HCC) after hepatectomy remain unclear. The aims of the present study were to compare characteristics between early and late recurrence groups in spontaneously ruptured HCC patients who received curative hepatectomy and to identify risk factors for mortality. Methods We selected 19 patients who had been diagnosed with spontaneously ruptured HCC and who were treated with curative liver resection between 1998 and 2013. The 19 patients were divided into 2 groups: the early recurrence group of patients who experienced tumor recurrence within 12 months after hepatectomy, and the late recurrence group of patients who experienced recurrence after 12 months or who did not experience recurrence. Results The median tumor size was 7.4 cm, and there were no cases of postoperative mortality. Patient survival rates at 1, 3, and 5 years were 78.9%, 58.6%, and 58.6%, respectively. The incidence of tumor protrusion in the early recurrence group was higher than that in the late recurrence group (100% vs. 30%, respectively, P = 0.003). There were no statistically significant differences in other factors between the 2 groups. Multivariate analysis showed that greater than 30% protrusion of the tumor was a predictor of patient survival. Conclusion The results from the present study suggests that spontaneously ruptured HCC patients with protrusion should be frequently monitored after hepatectomy in order to achieve early detection of tumor recurrence and improve survival. PMID:27433460

  2. Numerical investigation of root canal irrigation adopting innovative needles with dimple and protrusion.

    PubMed

    Li, Ping; Zhang, Di; Xie, Yonghui; Lan, Jibing

    2013-01-01

    As important passive flow control methods, dimples and protrusions have been successfully implemented via geometric modifications to manipulate flow fields to get a desired flow parameters enhancement. In this research, two novel needles were proposed based on a prototype by means of the dimple and protrusion, and flow patterns within a root canal during final irrigation with these needles were numerically investigated. The calculation cases consistent with the clinically realistic irrigant flow rates, which are 0.02, 0.16 and 0.26 mL s(-1) are marked as case A, B and C, respectively. The characteristic parameters to estimate irrigation efficiency, such as shearing effect, mean apical pressure, irrigation replacement and fluid agitation, were compared and the optimal geometry in every calculation case was obtained. As shown from the results, flow rates and needle geometries were the causes of irrigation parameters variations. The sum of shear stress, irrigation replacement and fluid agitation were equal in the low flow rate case A, however, the needle with a protrusion on its tip had advantages in the three irrigation characteristic parameters above in calculation case B, and the needle with a dimple on its tip had advantages in calculation case C. Furthermore, the needles proposed did not give rise to the risk of irrigant extrusion. These needles can be better choices at larger flow rates. Therefore, needle geometry optimizations utilizing passive flow control methods are worthy to be investigated in the root canal irrigation enhancement. PMID:23957591

  3. Friction-induced nanofabrication method to produce protrusive nanostructures on quartz

    NASA Astrophysics Data System (ADS)

    Song, Chenfei; Li, Xiaoying; Yu, Bingjun; Dong, Hanshan; Qian, Linmao; Zhou, Zhongrong

    2011-12-01

    In this paper, a new friction-induced nanofabrication method is presented to fabricate protrusive nanostructures on quartz surfaces through scratching a diamond tip under given normal loads. The nanostructures, such as nanodots, nanolines, surface mesas and nanowords, can be produced on the target surface by programming the tip traces according to the demanded patterns. The height of these nanostructures increases with the increase of the number of scratching cycles or the normal load. Transmission electron microscope observations indicated that the lattice distortion and dislocations induced by the mechanical interaction may have played a dominating role in the formation of the protrusive nanostructures on quartz surfaces. Further analysis reveals that during scratching, a contact pressure ranged from 0.4 P y to P y ( P y is the critical yield pressure of quartz) is apt to produce protuberant nanostructures on quartz under the given experimental conditions. Finally, it is of great interest to find that the protrusive nanostructures can be selectively dissolved in 20% KOH solution. Since the nanowords can be easily 'written' by friction-induced fabrication and 'erased' through selective etching on a quartz surface, this friction-induced method opens up new opportunities for future nanofabrication.

  4. Local extracellular matrix alignment directs cellular protrusion dynamics and migration through Rac1 and FAK.

    PubMed

    Carey, Shawn P; Goldblatt, Zachary E; Martin, Karen E; Romero, Bethsabe; Williams, Rebecca M; Reinhart-King, Cynthia A

    2016-08-01

    Cell migration within 3D interstitial microenvironments is sensitive to extracellular matrix (ECM) properties, but the mechanisms that regulate migration guidance by 3D matrix features remain unclear. To examine the mechanisms underlying the cell migration response to aligned ECM, which is prevalent at the tumor-stroma interface, we utilized time-lapse microscopy to compare the behavior of MDA-MB-231 breast adenocarcinoma cells within randomly organized and well-aligned 3D collagen ECM. We developed a novel experimental system in which cellular morphodynamics during initial 3D cell spreading served as a reductionist model for the complex process of matrix-directed 3D cell migration. Using this approach, we found that ECM alignment induced spatial anisotropy of cells' matrix probing by promoting protrusion frequency, persistence, and lengthening along the alignment axis and suppressing protrusion dynamics orthogonal to alignment. Preference for on-axis behaviors was dependent upon FAK and Rac1 signaling and translated across length and time scales such that cells within aligned ECM exhibited accelerated elongation, front-rear polarization, and migration relative to cells in random ECM. Together, these findings indicate that adhesive and protrusive signaling allow cells to respond to coordinated physical cues in the ECM, promoting migration efficiency and cell migration guidance by 3D matrix structure. PMID:27384462

  5. Protrusion of the tongue in bodies burned after death: Two cases of arson to cover homicide.

    PubMed

    Nikolić, Slobodan; Živković, Vladimir

    2015-10-01

    In the forensic assessment of burned bodies, the question of whether the victim was exposed to fire before or after death is of crucial importance. Many authors consider tongue protrusion in cases of burned bodies to be a post-mortem phenomenon. Deep-heating effects of fire are sufficient to cook muscle. The muscle becomes shortened by dehydration and protein denaturation. Exposure to heat causes flexion of the extremities on the contraction of muscles and tendons - heat rigour. The flexors, being bulkier than the extensors, contract more and force the limbs into the position of general flexion. The genioglossus is the major muscle of the tongue and is responsible for protruding or sticking out the tongue: by means of its inferior fibres, it draws the root of the tongue forward and protrudes the apex from the mouth. Similar to the action of limb flexors exposed to heat and the appearance of post-mortem general flexion of a burned body due to heat rigour, perhaps the geniglossus could be shortened by heat, causing post-mortem tongue protrusion to appear as heat rigour of the tongue. In this paper, we present two such cases of protrusion of the tongue in bodies burned after death - cases of arson to cover homicide. PMID:25013164

  6. A lipid bound actin meshwork organizes liquid phase separation in model membranes

    PubMed Central

    Honigmann, Alf; Sadeghi, Sina; Keller, Jan; Hell, Stefan W; Eggeling, Christian; Vink, Richard

    2014-01-01

    The eukaryotic cell membrane is connected to a dense actin rich cortex. We present FCS and STED experiments showing that dense membrane bound actin networks have severe influence on lipid phase separation. A minimal actin cortex was bound to a supported lipid bilayer via biotinylated lipid streptavidin complexes (pinning sites). In general, actin binding to ternary membranes prevented macroscopic liquid-ordered and liquid-disordered domain formation, even at low temperature. Instead, depending on the type of pinning lipid, an actin correlated multi-domain pattern was observed. FCS measurements revealed hindered diffusion of lipids in the presence of an actin network. To explain our experimental findings, a new simulation model is proposed, in which the membrane composition, the membrane curvature, and the actin pinning sites are all coupled. Our results reveal a mechanism how cells may prevent macroscopic demixing of their membrane components, while at the same time regulate the local membrane composition. DOI: http://dx.doi.org/10.7554/eLife.01671.001 PMID:24642407

  7. Electrical and chemical characteristics of probe-induced two-dimensional SiO{sub x} protrusion layers

    SciTech Connect

    Lin, Jin-Han; Chiu, Hsien-Che; Lin, Yu-Rong; Wen, Teng-Kai; Patil, Ranjit A.; Devan, Rupesh S.; Ma, Yuan-Ron; Chen, Chia-Hao; Shiu, Hung-Wei; Liou, Yung

    2013-01-21

    Three two-dimensional SiO{sub x} (x {identical_to} O/Si content ratio and x > 2) protrusion layers of {approx}0.5, {approx}4, and {approx}6 nm high were induced on a native SiO{sub 2} layer by atomic force microscopy (AFM) probes. X-ray photoemission spectroscopy (XPS) was used to reveal the elemental quantity of the photoelectrons, Si 2p core-levels, and Si oxidation states in the three SiO{sub x} protrusion layers and native SiO{sub 2} layer. Pt-coated conductive AFM probes were also exploited to acquire the rectifying current-voltage (IV) characteristics of the three SiO{sub x} protrusion layers and the native SiO{sub 2} layer, indicating all the three SiO{sub x} protrusion layers to be good Schottky diodes.

  8. Case of Severe Maxillary Protrusion Accompanied by Crowding and Scissor Bite.

    PubMed

    Katada, Hidenori; Sueishi, Kenji

    2015-01-01

    This case involved a 30-year-old woman who visited our hospital with the main complaint of protrusion of the maxillary incisors and upper and lower lips. She had difficulty closing her lips, and a chin button was observed when the lips were closed. The skeletal pattern showed maxillary protrusion and mandibular retrusion, and the mandible showed severe high angle. Labial inclination of both the maxillary and mandibular incisors was found, as well as crowding. In addition, the maxillary left second molar showed buccal displacement, and scissor bite was evident in the left second molar region. The bilateral molar relationship was cusp-to-cusp class II malocclusion. Angle class II maxillary protrusion accompanied by crowding and left second molar scissor bite was diagnosed. Surgical orthodontic treatment was judged as the best approach to treat the jaw deformities. However, in line with the wishes of the patient, treatment was undertaken using implant anchors instead. Straight-wire brackets with a 0.022-inch slot were fitted. A lingual arch was placed in the mandible and plate-type implant anchors in the first molar region of the maxilla. Almost no change was observed in skeletal pattern as no surgery was performed. The maxillary incisors moved back 10 mm, however, and the mandibular incisors showed an improvement of 4 mm from L1 to APo. The upper and lower lips consequently moved back 7 mm with respect to the E-line. Active treatment required 3 years and 6 months. Esthetic and functional improvements were achieved. PMID:26657523

  9. EVALUATION OF MAGNETIC RESONANCE IMAGING GUIDELINES FOR DIFFERENTIATION BETWEEN THORACOLUMBAR INTERVERTEBRAL DISK EXTRUSIONS AND INTERVERTEBRAL DISK PROTRUSIONS IN DOGS.

    PubMed

    De Decker, Steven; Gomes, Sergio A; Packer, Rowena Ma; Kenny, Patrick J; Beltran, Elsa; Parzefall, Birgit; Fenn, Joe; Nair, Devi; Nye, George; Volk, Holger A

    2016-09-01

    Four MRI variables have recently been suggested to be independently associated with a diagnosis of thoracolumbar intervertebral disk extrusion or protrusion. Midline intervertebral disk herniation, and partial intervertebral disk degeneration were associated with intervertebral disk protrusion, while presence of a single intervertebral disk herniation and disk material dispersed beyond the boundaries of the intervertebral disk space were associated with intervertebral disk extrusion. The aim of this retrospective, cross-sectional study was to determine whether using these MRI variables improves differentiation between thoracolumbar intervertebral disk extrusions and protrusions. Eighty large breed dogs with surgically confirmed thoracolumbar intervertebral disk extrusions or protrusions were included. Randomized MRI studies were presented on two occasions to six blinded observers, which were divided into three experience categories. During the first assessment, observers made a presumptive diagnosis of thoracolumbar intervertebral disk extrusion or protrusion without guidelines. During the second assessment they were asked to make a presumptive diagnosis with the aid of guidelines. Agreement was evaluated by Kappa-statistics. Diagnostic accuracy significantly improved from 70.8 to 79.6% and interobserver agreement for making a diagnosis of intervertebral disk extrusion or intervertebral disk protrusion improved from fair (κ = 0.27) to moderate (κ = 0.41) after using the proposed guidelines. Diagnostic accuracy was significantly influenced by degree of observer experience. Intraobserver agreement for the assessed variables ranged from fair to excellent and interobserver agreement ranged from fair to moderate. The results of this study suggest that the proposed imaging guidelines can aid in differentiating thoracolumbar intervertebral disk extrusions from protrusions. PMID:27374979

  10. Vertebral stabilisation and selective decompression for the management of triple thoracolumbar disc protrusions.

    PubMed

    McKee, W M; Downes, C J

    2008-10-01

    Triple adjacent thoracolumbar disc protrusions causing moderate to severe spinal cord compression were diagnosed by magnetic resonance imaging in two German shepherd dogs with marked paraparesis and pelvic limb ataxia. Both cases were managed by selective hemilaminectomy, partial annulectomy and bilateral quadruple vertebral body stabilisation using novel canine locking fixation plates (SOP). The stabilisation of multiple vertebrae in the thoracolumbar spine was possible because the plates could be contoured with six degrees of freedom. Spinal pain resolved and neurological function improved in both dogs. Screw breakage was evident in one dog five months following surgery. PMID:18631222

  11. The Dictyostelium type V myosin MyoJ is responsible for the cortical association and motility of contractile vacuole membranes.

    PubMed

    Jung, Goeh; Titus, Margaret A; Hammer, John A

    2009-08-24

    The contractile vacuole (CV) complex in Dictyostelium is a tubulovesicular osmoregulatory organelle that exhibits extensive motility along the actin-rich cortex, providing a useful model for investigating myosin-dependent membrane transport. Here, we show that the type V myosin myoJ localizes to CV membranes and is required for efficient osmoregulation, the normal accumulation of CV membranes in the cortex, and the conversion of collapsed bladder membranes into outwardly radiating cortical CV tubules. Complementation of myoJ-null cells with a version of myoJ containing a shorter lever arm causes these radiating tubules to move at a slower speed, confirming myoJ's role in translocating CV membranes along the cortex. MyoJ-null cells also exhibit a dramatic concentration of CV membranes around the microtubule-organizing center. Consistently, we demonstrate that CV membranes also move bi-directionally on microtubules between the cortex and the centrosome. Therefore, myoJ cooperates with plus and minus end-directed microtubule motors to drive the normal distribution and dynamics of the CV complex in Dictyostelium. PMID:19687255

  12. Space closure with loop mechanics for treatment of bimaxillary protrusion: a case report.

    PubMed

    Sanjay, N; Rajesh, R N G; Scindia, Rajat; Ajith, Sreedevi D

    2015-05-01

    This case report intends to highlight the space closure with tear drop loop mechanics for bimaxillary protrusion. Loops can be fabricated in a sectional or full arch wire, and closing loops are usually used in loop mechanics for extraction space closure. The major advantage of loop mechanics is the lack of friction between the bracket and arch wire during space closure. An adult patient with bimaxillary protrusion reported to the clinic. The patient was treated successfully by maximum retraction of maxillary and mandibular anterior teeth after extraction of all first premolars. Space closure was begun using a moment differential between posterior and anterior segments created by a Tear drop loop. Anterior teeth were moved with bodily movement, and no anchorage loss of the posterior segments was seen using a Tear drop loop spring. A stable result with normal over jet and overbite was achieved with retraction of maxillary and mandibular anterior teeth. With a Tear drop loop, individual biomechanical responses can be achieved, and it is possible to calculate force magnitude for every patient. PMID:26028908

  13. FMNL2 drives actin-based protrusion and migration downstream of Cdc42.

    PubMed

    Block, Jennifer; Breitsprecher, Dennis; Kühn, Sonja; Winterhoff, Moritz; Kage, Frieda; Geffers, Robert; Duwe, Patrick; Rohn, Jennifer L; Baum, Buzz; Brakebusch, Cord; Geyer, Matthias; Stradal, Theresia E B; Faix, Jan; Rottner, Klemens

    2012-06-01

    Cell migration entails protrusion of lamellipodia, densely packed networks of actin filaments at the cell front. Filaments are generated by nucleation, likely mediated by Arp2/3 complex and its activator Scar/WAVE. It is unclear whether formins contribute to lamellipodial actin filament nucleation or serve as elongators of filaments nucleated by Arp2/3 complex. Here we show that the Diaphanous-related formin FMNL2, also known as FRL3 or FHOD2, accumulates at lamellipodia and filopodia tips. FMNL2 is cotranslationally modified by myristoylation and regulated by interaction with the Rho-guanosine triphosphatase Cdc42. Abolition of myristoylation or Cdc42 binding interferes with proper FMNL2 activation, constituting an essential prerequisite for subcellular targeting. In vitro, C-terminal FMNL2 drives elongation rather than nucleation of actin filaments in the presence of profilin. In addition, filament ends generated by Arp2/3-mediated branching are captured and efficiently elongated by the formin. Consistent with these biochemical properties, RNAi-mediated silencing of FMNL2 expression decreases the rate of lamellipodia protrusion and, accordingly, the efficiency of cell migration. Our data establish that the FMNL subfamily member FMNL2 is a novel elongation factor of actin filaments that constitutes the first Cdc42 effector promoting cell migration and actin polymerization at the tips of lamellipodia. PMID:22608513

  14. Space Closure with Loop Mechanics for Treatment of Bimaxillary Protrusion: A Case Report

    PubMed Central

    Sanjay, N; Rajesh, R N G; Scindia, Rajat; Ajith, Sreedevi D

    2015-01-01

    This case report intends to highlight the space closure with tear drop loop mechanics for bimaxillary protrusion. Loops can be fabricated in a sectional or full arch wire, and closing loops are usually used in loop mechanics for extraction space closure. The major advantage of loop mechanics is the lack of friction between the bracket and arch wire during space closure. An adult patient with bimaxillary protrusion reported to the clinic. The patient was treated successfully by maximum retraction of maxillary and mandibular anterior teeth after extraction of all first premolars. Space closure was begun using a moment differential between posterior and anterior segments created by a Tear drop loop. Anterior teeth were moved with bodily movement, and no anchorage loss of the posterior segments was seen using a Tear drop loop spring. A stable result with normal over jet and overbite was achieved with retraction of maxillary and mandibular anterior teeth. With a Tear drop loop, individual biomechanical responses can be achieved, and it is possible to calculate force magnitude for every patient. PMID:26028908

  15. Hydrodynamic investigation of fluvial sediment transport with Soil Protrusion Apparatus (SPA)

    NASA Astrophysics Data System (ADS)

    Jayaratne, Ravindra; Salim, Sarik

    2014-11-01

    In order to understand sediment transport process based on knowledge of their soil properties and hydrodynamic behaviour a series of 2D laboratory controlled small-scale experiments were conducted using the Ahlborn sediment mobile bed tank (4.0×0.6×0.2 m). Experiments were conducted in smooth and rough bed conditions with purposely-built Soil Protrusion Apparatus (SPA) to measure the basic parameters on which erosion depends. Sediment deposition patterns in equilibrium stage associated with different bed roughness and particle size distributionswere fundamentally investigated. Extended physical modelling of crescent zones also included analysing their grain size distribution. Dimensional analysis and multiple linear regression methodswere employed to derive a simple empirical relationship for erosion rate (ER) in terms of the shear stress (τs), average grain diameter (d50) and soil protrusion (z) for smooth and rough sediment bed conditions. These analyses also suggest ways to refine empirical models, examining transport rates to explore the limits of erosion and deposition influences in shallow flow conditions.

  16. Protrusions Beyond the Blast Waves of Young Type Ia Supernova Remnants: Hydrodynamic Instabilities or Ejecta Bullets?

    NASA Astrophysics Data System (ADS)

    Dyer, Ashton; Blondin, J. M.; Reynolds, S. P.

    2014-01-01

    High resolution imaging of two young Type Ia supernova remnants (SNRs), Tycho and SN 1006, has revealed several morphological features which have resisted explanation with numerical simulations. One such feature is the presence of shocked ejecta blobs protruding beyond the mean forward shock radius. Two current theories explain the presence of such ejecta: highly dense ejecta shrapnel produced in the explosion penetrating the forward shock, or plumes generated by hydrodynamic instabilities long after the initial explosion. We investigate the shrapnel theory through hydrodynamic simulations in 2D and 3D of the evolution of dense ejecta clumps embedded in an exponential density profile, appropriate for Type Ia supernovae. We use high-resolution 2D simulations to identify relevant clump parameters which we investigate further in 3D. In contradiction to some former work, we find that sufficiently resolved clumps in 2D models shatter upon collision with the forward shock, yielding new protrusion features. In both 2D and 3D, shrapnel is capable of penetrating the forward shock, but the resultant protrusions in 3D simulations vary significantly from those in similar 2D runs, implying 2D simulations may not be an accurate method of investigating the shrapnel theory. We compare the our simulations with Chandra observations of projections seen in Tycho and SN 1006. This work was performed as part of NC State University's Undergraduate Research in Computational Astrophysics (URCA) program, an REU program supported by the National Science Foundation through award AST-1032736.

  17. Extraction of the lateral incisors to treat maxillary protrusion: quantitative evaluation of the stomatognathic functions.

    PubMed

    Ishihara, Yoshihito; Kuroda, Shingo; Sumiyoshi, Kumi; Takano-Yamamoto, Teruko; Yamashiro, Takashi

    2013-03-01

    To treat morphological abnormalities, impaction, and severe malposition of the teeth, the lateral incisors are sometimes extracted, followed by orthodontic space closure. This procedure often requires special consideration, not only with regard to esthetics but also for functional issues. However, thus far, few reports that have performed a functional evaluation in such cases. The purpose of this article is to report the successful treatment of an adult patient with a Class II division 1 malocclusion who was treated with extraction of the upper lateral incisors. The female patient, aged 23 years and 6 months, had a chief complaint of maxillary incisal protrusion and crooked teeth. In this patient, the upper lateral incisors were extracted to fulfill the patient's strong request, followed by orthodontic treatment using edgewise appliances. A high-pull J-hook headgear on the lower dental arch was used to prevent further labial inclination of the lower incisors. The total active treatment period was 37 months. The resulting occlusion and a satisfactory facial profile were maintained during a 4-year retention period. Additionally, this treatment did not affect the stomatognathic functions as assessed by the following criteria: range of the incisal path or condylar motion during maximal open-close movement, protrusive excursion, lateral excursion, and the chewing test. In conclusion, extraction of the upper lateral incisors can be an effective treatment choice when the upper lateral incisors are dwarfed, are nonvital, or demonstrate severe malposition. PMID:22908948

  18. Skeletal anchorage for orthodontic correction of maxillary protrusion with adult periodontitis.

    PubMed

    Fukunaga, Tomohiro; Kuroda, Shingo; Kurosaka, Hiroshi; Takano-Yamamoto, Teruko

    2006-01-01

    Because the number of adult patients seeking orthodontic treatment is increasing, orthodontists are becoming more likely to encounter patients with adult periodontitis. However, it is sometimes difficult to establish anchorage because of poor periodontal tissues in patients with adult periodontitis. This article reports the successful use of skeletal anchorage to treat a maxillary protrusion case complicated by severe adult periodontitis. A female patient aged 50 years seven months showed a skeletal Class II jaw base relationship. A spacing of five mm in the upper anterior teeth with an overjet of 7.5 mm and overbite of four mm was observed. She had generalized horizontal bone loss in both arches, with vertical bone loss in the posterior segment. After periodontal treatment, miniplates were placed in the zygomatic process, and retraction and intrusion of the maxillary incisors were performed. After active treatment for 21 months, the upper incisors had been inclined 9.5 degrees lingually, intruded two mm at the apex, and good anterior occlusion was achieved. Acceptable occlusion and periodontal tissue were maintained after a retention period of two years. Our results suggest that skeletal anchorage is useful for retraction and intrusion of upper incisors in cases of maxillary protrusion with severe adult periodontitis. PMID:16448285

  19. Mitochondrial outer membrane forms bridge between two mitochondria in Arabidopsis thaliana.

    PubMed

    Yamashita, Akihiro; Fujimoto, Masaru; Katayama, Kenta; Tsutsumi, Nobuhiro; Arimura, Shin-Ichi

    2016-05-01

    Mitochondria are double-membrane organelles that move around and change their shapes dynamically. In plants, the dynamics of the outer membrane is not well understood. We recently demonstrated that mitochondria had tubular protrusions of the outer membrane with little or no matrix, called MOPs (mitochondrial outer-membrane protrusions; MOPs). Here we show that a MOP can form a bridge between two mitochondria in Arabidopsis thaliana. The bridge does not appear to involve the inner membranes. Live imaging revealed stretching of the MOP bridge, demonstrating the flexibility of the outer membrane. Mitochondria frequently undergo fission and fusion. These observations raise the possibility that MOPs bridges have a role in these processes. PMID:27031262

  20. The More the Tubular: Dynamic Bundling of Actin Filaments for Membrane Tube Formation

    PubMed Central

    Weichsel, Julian; Geissler, Phillip L.

    2016-01-01

    Tubular protrusions are a common feature of living cells, arising from polymerization of stiff protein filaments against a comparably soft membrane. Although this process involves many accessory proteins in cells, in vitro experiments indicate that similar tube-like structures can emerge without them, through spontaneous bundling of filaments mediated by the membrane. Using theory and simulation of physical models, we have elaborated how nonequilibrium fluctuations in growth kinetics and membrane shape can yield such protrusions. Enabled by a new grand canonical Monte Carlo method for membrane simulation, our work reveals a cascade of dynamical transitions from individually polymerizing filaments to highly cooperatively growing bundles as a dynamical bottleneck to tube formation. Filament network organization as well as adhesion points to the membrane, which bias filament bending and constrain membrane height fluctuations, screen the effective attractive interactions between filaments, significantly delaying bundling and tube formation. PMID:27384915

  1. The More the Tubular: Dynamic Bundling of Actin Filaments for Membrane Tube Formation.

    PubMed

    Weichsel, Julian; Geissler, Phillip L

    2016-07-01

    Tubular protrusions are a common feature of living cells, arising from polymerization of stiff protein filaments against a comparably soft membrane. Although this process involves many accessory proteins in cells, in vitro experiments indicate that similar tube-like structures can emerge without them, through spontaneous bundling of filaments mediated by the membrane. Using theory and simulation of physical models, we have elaborated how nonequilibrium fluctuations in growth kinetics and membrane shape can yield such protrusions. Enabled by a new grand canonical Monte Carlo method for membrane simulation, our work reveals a cascade of dynamical transitions from individually polymerizing filaments to highly cooperatively growing bundles as a dynamical bottleneck to tube formation. Filament network organization as well as adhesion points to the membrane, which bias filament bending and constrain membrane height fluctuations, screen the effective attractive interactions between filaments, significantly delaying bundling and tube formation. PMID:27384915

  2. Protein-Induced Modulation of Chloroplast Membrane Morphology

    PubMed Central

    Machettira, Anu B.; Groß, Lucia E.; Tillmann, Bodo; Weis, Benjamin L.; Englich, Gisela; Sommer, Maik S.; Königer, Martina; Schleiff, Enrico

    2012-01-01

    Organelles are surrounded by membranes with a distinct lipid and protein composition. While it is well established that lipids affect protein functioning and vice versa, it has been only recently suggested that elevated membrane protein concentrations may affect the shape and organization of membranes. We therefore analyzed the effects of high chloroplast envelope protein concentrations on membrane structures using an in vivo approach with protoplasts. Transient expression of outer envelope proteins or protein domains such as CHUP1-TM–GFP, outer envelope protein of 7 kDa–GFP, or outer envelope protein of 24 kDa–GFP at high levels led to the formation of punctate, circular, and tubular membrane protrusions. Expression of inner membrane proteins such as translocase of inner chloroplast membrane 20, isoform II (Tic20-II)–GFP led to membrane protrusions including invaginations. Using increasing amounts of DNA for transfection, we could show that the frequency, size, and intensity of these protrusions increased with protein concentration. The membrane deformations were absent after cycloheximide treatment. Co-expression of CHUP1-TM–Cherry and Tic20-II–GFP led to membrane protrusions of various shapes and sizes including some stromule-like structures, for which several functions have been proposed. Interestingly, some structures seemed to contain both proteins, while others seem to contain one protein exclusively, indicating that outer and inner envelope dynamics might be regulated independently. While it was more difficult to investigate the effects of high expression levels of membrane proteins on mitochondrial membrane shapes using confocal imaging, it was striking that the expression of the outer membrane protein Tom20 led to more elongate mitochondria. We discuss that the effect of protein concentrations on membrane structure is possibly caused by an imbalance in the lipid to protein ratio and may be involved in a signaling pathway regulating membrane

  3. GIT1 Phosphorylation on Serine 46 by PKD3 Regulates Paxillin Trafficking and Cellular Protrusive Activity*

    PubMed Central

    Huck, Bettina; Kemkemer, Ralf; Franz-Wachtel, Mirita; Macek, Boris; Hausser, Angelika; Olayioye, Monilola A.

    2012-01-01

    The continuous assembly and disassembly of focal adhesions is required for efficient cell spreading and migration. The G-protein-coupled receptor kinase-interacting protein 1 (GIT1) is a multidomain protein whose dynamic localization to sites of cytoskeletal remodeling is critically involved in the regulation of these processes. Here we provide evidence that the subcellular localization of GIT1 is regulated by protein kinase D3 (PKD3) through direct phosphorylation on serine 46. GIT1 phosphorylation on serine 46 was abrograted by PKD3 depletion, thereby identifying GIT1 as the first specific substrate for this kinase. A GIT1 S46D phosphomimetic mutant localized to motile, paxillin-positive cytoplasmic complexes, whereas the phosphorylation-deficient GIT1 S46A was enriched in focal adhesions. We propose that phosphorylation of GIT1 on serine 46 by PKD3 represents a molecular switch by which GIT1 localization, paxillin trafficking, and cellular protrusive activity are regulated. PMID:22893698

  4. Penetrating keratoplasty for treatment of corneal protrusion in a great horned owl (Bubo virginianus).

    PubMed

    Andrew, Stacy E; Clippinger, Tracy L; Brooks, Dennis E; Helmick, Kelly E

    2002-09-01

    A young adult great horned owl (Bubo virginianus) was examined following presumed trauma. The owl had soft tissue injury to its left wing as well as corneal protrusion, lens subluxation, and iridodialysis of the right eye. The bird's eye was treated surgically with a large, rectangular penetrating keratoplasty. Following escape from housing, the bird was found with partial wound dehiscence and iris prolapse 12 days post operation. Surgical repair was performed and healing progressed for 14 days, at which time the transplant dehisced and the globe was exenterated. The patient rehabilitated well until escaping from its cage again 4 weeks later, at which time it sustained an open comminuted humeral fracture and was euthanized. PMID:12236872

  5. Successful treatment of Class II malocclusion with bidental protrusion using standard edgewise prescription.

    PubMed

    Ayaz, Mohd; Kharbanda, Om Prakash

    2016-01-01

    This case report deals with the successful orthodontic treatment of a 14-year-old female patient having Class II malocclusion with bidental protrusion using standard edgewise prescription. She reported with forwardly placed upper front teeth and difficulty in closing lips. She had prognathic maxilla, retrognathic mandible, and full cusp Class II molar and canine relation bilaterally with overjet of 7 mm. She was in cervical vertebrae maturation indicator Stage IV. The case was treated by fixed extraction mechanotherapy. Interarch Class II mechanics was used to retract the upper incisor and to mesialize the lower molars. Simultaneously, Class I mechanics was used to upright lower incisors. Tip back bend, curve of Spee, and extra palatal root torque were incorporated in upper archwire to maintain molars in upright position and prevent extrusion and deepening of bite, respectively. There was satisfactory improvement in facial profile at the end of 24 months. After a follow-up of 6 months, occlusion was stable. PMID:27041906

  6. Successful treatment of Class II malocclusion with bidental protrusion using standard edgewise prescription

    PubMed Central

    Ayaz, Mohd; Kharbanda, Om Prakash

    2016-01-01

    This case report deals with the successful orthodontic treatment of a 14-year-old female patient having Class II malocclusion with bidental protrusion using standard edgewise prescription. She reported with forwardly placed upper front teeth and difficulty in closing lips. She had prognathic maxilla, retrognathic mandible, and full cusp Class II molar and canine relation bilaterally with overjet of 7 mm. She was in cervical vertebrae maturation indicator Stage IV. The case was treated by fixed extraction mechanotherapy. Interarch Class II mechanics was used to retract the upper incisor and to mesialize the lower molars. Simultaneously, Class I mechanics was used to upright lower incisors. Tip back bend, curve of Spee, and extra palatal root torque were incorporated in upper archwire to maintain molars in upright position and prevent extrusion and deepening of bite, respectively. There was satisfactory improvement in facial profile at the end of 24 months. After a follow-up of 6 months, occlusion was stable. PMID:27041906

  7. Effects of tongue-hold swallows on suprahyoid muscle activation according to the relative tongue protrusion length: a preliminary study.

    PubMed

    Oh, Jong-Chi

    2016-01-01

    Tongue-hold swallow (THS) is a therapeutic maneuver used to increase the posterior pharyngeal wall motion during swallowing. This maneuver has also been reported to result in increased activation of the suprahyoid muscles. The hypothesis of this study was that the degree of suprahyoid muscle activation would depend on the tongue protrusion-length. The aim of this study was to investigate the activation levels of the suprahyoid muscles by surface electromyography (sEMG) while performing the THS maneuver at three tongue-protrusion lengths. Suprahyoid muscle activity during THSs was recorded in 25 adult volunteers (17 women and 8 men; age range 20-38 years). To record the activity of the suprahyoid muscles while the participants performed the maneuver, surface wireless EMG electrodes separated by a distance of 1 cm were placed on the skin on both sides of the midline under the chin. Each activity was recorded three times. Data analysis was performed by repeated-measures analysis of variance. Our results revealed that participants exhibited greater electrical activity during THS with 2/3rd or maximal tongue protrusion as compared to THS with 1/3rd tongue protrusion (p ≤ 0.001). To maximize the therapeutic effect of the THS maneuver, it is advised to protrude the tongue maximally as long as swallowing is possible. PMID:27504242

  8. The Diaphanous-Related Formins Promote Protrusion Formation and Cell-to-Cell Spread of Listeria monocytogenes

    PubMed Central

    Fattouh, Ramzi; Kwon, Hyunwoo; Czuczman, Mark A.; Copeland, John W.; Pelletier, Laurence; Quinlan, Margot E.; Muise, Aleixo M.; Higgins, Darren E.; Brumell, John H.

    2015-01-01

    The Gram-positive bacterium Listeria monocytogenes is a facultative intracellular pathogen whose virulence depends on its ability to spread from cell to cell within an infected host. Although the actin-related protein 2/3 (Arp2/3) complex is necessary and sufficient for Listeria actin tail assembly, previous studies suggest that other actin polymerization factors, such as formins, may participate in protrusion formation. Here, we show that Arp2/3 localized to only a minor portion of the protrusion. Moreover, treatment of L. monocytogenes–infected HeLa cells with a formin FH2-domain inhibitor significantly reduced protrusion length. In addition, the Diaphanous-related formins 1–3 (mDia1–3) localized to protrusions, and knockdown of mDia1, mDia2, and mDia3 substantially decreased cell-to-cell spread of L. monocytogenes. Rho GTPases are known to be involved in formin activation. Our studies also show that knockdown of several Rho family members significantly influenced bacterial cell-to-cell spread. Collectively, these findings identify a Rho GTPase–formin network that is critically involved in the cell-to-cell spread of L. monocytogenes. PMID:25281757

  9. The diaphanous-related formins promote protrusion formation and cell-to-cell spread of Listeria monocytogenes.

    PubMed

    Fattouh, Ramzi; Kwon, Hyunwoo; Czuczman, Mark A; Copeland, John W; Pelletier, Laurence; Quinlan, Margot E; Muise, Aleixo M; Higgins, Darren E; Brumell, John H

    2015-04-01

    The Gram-positive bacterium Listeria monocytogenes is a facultative intracellular pathogen whose virulence depends on its ability to spread from cell to cell within an infected host. Although the actin-related protein 2/3 (Arp2/3) complex is necessary and sufficient for Listeria actin tail assembly, previous studies suggest that other actin polymerization factors, such as formins, may participate in protrusion formation. Here, we show that Arp2/3 localized to only a minor portion of the protrusion. Moreover, treatment of L. monocytogenes-infected HeLa cells with a formin FH2-domain inhibitor significantly reduced protrusion length. In addition, the Diaphanous-related formins 1-3 (mDia1-3) localized to protrusions, and knockdown of mDia1, mDia2, and mDia3 substantially decreased cell-to-cell spread of L. monocytogenes. Rho GTPases are known to be involved in formin activation. Our studies also show that knockdown of several Rho family members significantly influenced bacterial cell-to-cell spread. Collectively, these findings identify a Rho GTPase-formin network that is critically involved in the cell-to-cell spread of L. monocytogenes. PMID:25281757

  10. Remotely Controlled Mandibular Protrusion during Sleep Predicts Therapeutic Success with Oral Appliances in Patients with Obstructive Sleep Apnea

    PubMed Central

    Remmers, John; Charkhandeh, Shouresh; Grosse, Joshua; Topor, Zbigniew; Brant, Rollin; Santosham, Peter; Bruehlmann, Sabina

    2013-01-01

    Study Objectives: The present study addresses the need for a validated tool that prospectively identifies favorable candidates for oral appliance therapy in treatment of obstructive sleep apnea. The objective of the study was to evaluate the ability of a mandibular titration study, performed with a remotely controlled mandibular positioner (RCMP), to predict treatment outcome with a mandibular repositioning appliance (MRA) and to predict an effective target protrusive position (ETPP). Design: A prospective, blinded, outcome study. Setting: Standard clinical care with tests performed in the polysomnographic laboratory. Participants: Consecutive patients (n = 67) recruited from a sleep center or a dental practice using broad inclusion criteria (age 21-80 years; AHI > 10/h; BMI < 40 kg/m2). Interventions: Therapeutic outcome with a mandibular protruding oral appliance was predicted following a mandibular protrusive titration study in the polysomnographic laboratory using a remotely controlled positioner and prospectively established predictive rules. An ETPP was also prospectively determined for participants predicted to be therapeutically successful with MRA therapy. All participants were blindly treated with a MRA, at either the predicted ETPP or a sham position, and therapeutic outcome was compared against prediction. Measurements and Results: At the final protrusive position, standard predictive parameters (sensitivity, specificity, positive and negative predictive values) showed statistically significant predictive accuracy (P < 0.05) in the range of 83% to 94%. The predicted ETPP provided an efficacious protrusive position in 87% of participants predicted to be therapeutically successful with MRA therapy (P < 0.05). Conclusions: Using prospectively established rules for interpreting the polysomnographic data, the mandibular titration study predicted mandibular repositioning appliance therapeutic outcome with significant accuracy, particularly with regard to

  11. CLINICAL AND MAGNETIC RESONANCE IMAGING CHARACTERISTICS OF THORACOLUMBAR INTERVERTEBRAL DISK EXTRUSIONS AND PROTRUSIONS IN LARGE BREED DOGS.

    PubMed

    Gomes, Sergio A; Volk, Holger A; Packer, Rowena Ma; Kenny, Patrick J; Beltran, Elsa; De Decker, Steven

    2016-07-01

    Treatment recommendations differ for dogs with intervertebral disk extrusion vs. intervertebral disk protrusion. The aim of this retrospective, cross-sectional study was to determine whether clinical and magnetic resonance imaging (MRI) variables could be used to predict a diagnosis of thoracolumbar intervertebral disk extrusion or protrusion in dogs. Dogs were included if they were large breed dogs, had an MRI study of the thoracolumbar or lumbar vertebral column, had undergone spinal surgery, and had the type of intervertebral disk herniation (intervertebral disk extrusion or protrusion) clearly stated in surgical reports. A veterinary neurologist unaware of surgical findings reviewed MRI studies and recorded number, location, degree of degeneration and morphology of intervertebral disks, presence of nuclear clefts, disk space narrowing, extent, localization and lateralization of herniated disk material, degree of spinal cord compression, intraparenchymal intensity changes, spondylosis deformans, spinal cord swelling, spinal cord atrophy, vertebral endplate changes, and presence of extradural hemorrhage. Ninety-five dogs were included in the sample. Multivariable statistical models indicated that longer duration of clinical signs (P = 0.01), midline instead of lateralized disk herniation (P = 0.007), and partial instead of complete disk degeneration (P = 0.01) were associated with a diagnosis of intervertebral disk protrusion. The presence of a single intervertebral herniation (P = 0.023) and dispersed intervertebral disk material not confined to the disk space (P = 0.06) made a diagnosis of intervertebral disk extrusion more likely. Findings from this study identified one clinical and four MRI variables that could potentially facilitate differentiating intervertebral disk extrusions from protrusions in dogs. PMID:27038182

  12. Plasmonic gratings with nano-protrusions made by glancing angle deposition for single-molecule super-resolution imaging

    NASA Astrophysics Data System (ADS)

    Chen, B.; Wood, A.; Pathak, A.; Mathai, J.; Bok, S.; Zheng, H.; Hamm, S.; Basuray, S.; Grant, S.; Gangopadhyay, K.; Cornish, P. V.; Gangopadhyay, S.

    2016-06-01

    Super-resolution imaging has been advantageous in studying biological and chemical systems, but the required equipment and platforms are expensive and unable to observe single-molecules at the high (μM) fluorophore concentrations required to study protein interaction and enzymatic activity. Here, a plasmonic platform was designed that utilized an inexpensively fabricated plasmonic grating in combination with a scalable glancing angle deposition (GLAD) technique using physical vapor deposition. The GLAD creates an abundance of plasmonic nano-protrusion probes that combine the surface plasmon resonance (SPR) from the periodic gratings with the localized SPR of these nano-protrusions. The resulting platform enables simultaneous imaging of a large area without point-by-point scanning or bulk averaging for the detection of single Cyanine-5 molecules in dye concentrations ranging from 50 pM to 10 μM using epifluorescence microscopy. Combining the near-field plasmonic nano-protrusion probes and super-resolution technique using localization microscopy, we demonstrate the ability to resolve grain sizes down to 65 nm. This plasmonic GLAD grating is a cost-effective super-resolution imaging substrate with potential applications in high-speed biomedical imaging over a wide range of fluorescent concentrations.Super-resolution imaging has been advantageous in studying biological and chemical systems, but the required equipment and platforms are expensive and unable to observe single-molecules at the high (μM) fluorophore concentrations required to study protein interaction and enzymatic activity. Here, a plasmonic platform was designed that utilized an inexpensively fabricated plasmonic grating in combination with a scalable glancing angle deposition (GLAD) technique using physical vapor deposition. The GLAD creates an abundance of plasmonic nano-protrusion probes that combine the surface plasmon resonance (SPR) from the periodic gratings with the localized SPR of these nano-protrusions

  13. Protrusive Activity Guides Changes in Cell-Cell Tension during Epithelial Cell Scattering

    PubMed Central

    Maruthamuthu, Venkat; Gardel, Margaret L.

    2014-01-01

    Knowing how epithelial cells regulate cell-matrix and cell-cell adhesions is essential to understand key events in morphogenesis as well as pathological events such as metastasis. During epithelial cell scattering, epithelial cell islands rupture their cell-cell contacts and migrate away as single cells on the extracellular matrix (ECM) within hours of growth factor stimulation, even as adhesion molecules such as E-cadherin are present at the cell-cell contact. How the stability of cell-cell contacts is modulated to effect such morphological transitions is still unclear. Here, we report that in the absence of ECM, E-cadherin adhesions continue to sustain substantial cell-generated forces upon hepatocyte growth factor (HGF) stimulation, consistent with undiminished adhesion strength. In the presence of focal adhesions, constraints that preclude the spreading and movement of cells at free island edges also prevent HGF-mediated contact rupture. To explore the role of cell motion and cell-cell contact rupture, we examine the biophysical changes that occur during the scattering of cell pairs. We show that the direction of cell movement with respect to the cell-cell contact is correlated with changes in the average intercellular force as well as the initial direction of cell-cell contact rupture. Our results suggest an important role for protrusive activity resulting in cell displacement and force redistribution in guiding cell-cell contact rupture during scattering. PMID:25099795

  14. Local anesthetics inhibit kinesin motility and microtentacle protrusions in human epithelial and breast tumor cells.

    PubMed

    Yoon, Jennifer R; Whipple, Rebecca A; Balzer, Eric M; Cho, Edward H; Matrone, Michael A; Peckham, Michelle; Martin, Stuart S

    2011-10-01

    Detached breast tumor cells produce dynamic microtubule protrusions that promote reattachment of cells and are termed tubulin microtentacles (McTNs) due to their mechanistic distinctions from actin-based filopodia/invadopodia and tubulin-based cilia. McTNs are enriched with vimentin and detyrosinated α-tubulin, (Glu-tubulin). Evidence suggests that vimentin and Glu-tubulin are cross-linked by kinesin motor proteins. Using known kinesin inhibitors, Lidocaine and Tetracaine, the roles of kinesins in McTN formation and function were tested. Live-cell McTN counts, adhesion assays, immunofluorescence, and video microscopy were performed to visualize inhibitor effects on McTNs. Viability and apoptosis assays were used to confirm the non-toxicity of the inhibitors. Treatments of human non-tumorigenic mammary epithelial and breast tumor cells with Lidocaine or Tetracaine caused rapid collapse of vimentin filaments. Live-cell video microscopy demonstrated that Tetracaine reduces motility of intracellular GFP-kinesin and causes centripetal collapse of McTNs. Treatment with Tetracaine inhibited the extension of McTNs and their ability to promote tumor cell aggregation and reattachment. Lidocaine showed similar effects but to a lesser degree. Our current data support a model in which the inhibition of kinesin motor proteins by Tetracaine leads to the reductions in McTNs, and provides a novel mechanism for the ability of this anesthetic to decrease metastatic progression. PMID:21069453

  15. Actin cytoskeletal remodeling with protrusion formation is essential for heart regeneration in Hippo-deficient mice

    PubMed Central

    Morikawa, Yuka; Zhang, Min; Heallen, Todd; Leach, John; Tao, Ge; Xiao, Yang; Bai, Yan; Li, Wei; Willerson, James T.; Martin, James F.

    2015-01-01

    The mammalian heart regenerates poorly, and damage commonly leads to heart failure. Hippo signaling is an evolutionarily conserved kinase cascade that regulates organ size during development and prevents adult mammalian cardiomyocyte regeneration by inhibiting the transcriptional coactivator Yap, which also responds to mechanical signaling in cultured cells to promote cell proliferation. To identify Yap target genes that are activated during cardiomyocyte renewal and regeneration, we performed Yap chromatin immunoprecipitation sequencing (ChIP-Seq) and mRNA expression profiling in Hippo signaling-deficient mouse hearts. We found that Yap directly regulated genes encoding cell cycle progression proteins, as well as genes encoding proteins that promote F-actin polymerization and that link the actin cytoskeleton to the extracellular matrix. Included in the latter group were components of the dystrophin glycoprotein complex (DGC), a large molecular complex that, when defective, results in muscular dystrophy in humans. Cardiomyocytes near scar tissue of injured Hippo signaling-deficient mouse hearts showed cellular protrusions suggestive of cytoskeletal remodeling. The hearts of mdx mutant mice, which lack functional dystrophin and are a model for muscular dystrophy, showed impaired regeneration and cytoskeleton remodeling, but normal cardiomyocyte proliferation after injury. Our data showed that, in addition to genes encoding cell cycle progression proteins, Yap regulated genes that enhance cytoskeletal remodeling Thus, blocking the Hippo pathway input to Yap may tip the balance so that Yap responds to the mechanical changes associated with heart injury to promote repair. PMID:25943351

  16. ER-endosome contact sites in endosome positioning and protrusion outgrowth.

    PubMed

    Raiborg, Camilla; Wenzel, Eva M; Pedersen, Nina M; Stenmark, Harald

    2016-04-15

    The endoplasmic reticulum (ER) makes abundant contacts with endosomes, and the numbers of contact sites increase as endosomes mature. It is already clear that such contact sites have diverse compositions and functions, but in this mini-review we will focus on two particular types of ER-endosome contact sites that regulate endosome positioning. Formation of ER-endosome contact sites that contain the cholesterol-binding protein oxysterol-binding protein-related protein 1L (ORP1L) is coordinated with loss of the minus-end-directed microtubule motor Dynein from endosomes. Conversely, formation of ER-endosome contact sites that contain the Kinesin-1-binding protein Protrudin results in transfer of the plus-end-directed microtubule motor Kinesin-1 from ER to endosomes. We discuss the possibility that formation of these two types of contact sites is coordinated as a 'gear-shift' mechanism for endosome motility, and we review evidence that Kinesin-1-mediated motility of late endosomes (LEs) to the cell periphery promotes outgrowth of neurites and other protrusions. PMID:27068952

  17. Megabirnavirus structure reveals a putative 120-subunit capsid formed by asymmetrical dimers with distinctive large protrusions.

    PubMed

    Miyazaki, Naoyuki; Salaipeth, Lakha; Kanematsu, Satoko; Iwasaki, Kenji; Suzuki, Nobuhiro

    2015-08-01

    Rosellinia necatrix megabirnavirus 1 (RnMBV1) W779 is a bi-segmented dsRNA virus and a strain of the type species Rosellinia necatrix megabirnavirus 1 of the family Megabirnaviridae. RnMBV1 causes severe reduction of both mycelial growth of Rosellinia necatrix in synthetic medium and fungal virulence to plant hosts, and thus has strong potential for virocontrol (biological control using viruses) of white rot. The structure of RnMBV1 was examined by cryo-electron microscopy and three-dimensional reconstruction at 15.7 Å resolution. The diameter of the RnMBV1 capsid was 520 Å, and the capsid was composed of 60 asymmetrical dimers in the T = 1 (so-called T = 2) lattice that is well conserved among dsRNA viruses. However, RnMBV1 has putatively 120 large protrusions with a width of ∼ 45 Å and a height of ∼ 50 Å on the virus surface, making it distinguishable from the other dsRNA viruses. PMID:25968130

  18. Antero-posterior lingual sliding retraction system for orthodontic correction of hyperdivergent Class II protrusion

    PubMed Central

    2014-01-01

    Background This report introduces a lingual bonded retraction system (Kinematics of Lingual Bar on Non-Paralleling Technique, KILBON) for efficient sliding mechanics combined with vertical control of the anterior and posterior teeth, which is suitable for Class II hyperdivergent patients. Methods Design and biomechanics of the KILBON System were described. Two adults with hyperdivergent class II malocclusion were treated with the KILBON system and temporary skeletal anchorage devices (TSADs) on the palate. The first patient was treated with conventional KILBON system on the upper arch and detailed with lingual appliances. The second patient showed the modified design of the KILBON when applied to a low palatal vault. Results A large amount of intrusion and retraction of the anterior teeth and simultaneous intrusion of the posterior segment were achieved in short treatment time. Concomitant counterclockwise rotation of the mandible improved the esthetic profile. Periodontal support without dehiscence or bone loss was confirmed on anterior region in spite of large amount of retraction. Conclusions This report presented a lingual retraction system that provides simple and effective vertical and sagittal control of both anterior and posterior teeth. The biomechanics are dependable for correcting a dentoalveolar protrusion in a patient with Class II hyperdivergent skeletal pattern. PMID:24897979

  19. Spontaneous Regression of Herniated Lumbar Disc with New Disc Protrusion in the Adjacent Level.

    PubMed

    Hakan, Tayfun; Gürcan, Serkan

    2016-01-01

    Spontaneous regression of herniated lumbar discs was reported occasionally. The mechanisms proposed for regression of disc herniation are still incomplete. This paper describes and discusses a case of spontaneous regression of herniated lumbar discs with a new disc protrusion in the adjacent level. A 41-year-old man was admitted with radiating pain and numbness in the left lower extremity with a left posterolateral disc extrusion at L5-S1 level. He was admitted to hospital with low back pain due to disc herniation caudally immigrating at L4-5 level three years ago. He refused the surgical intervention that was offered and was treated conservatively at that time. He had no neurological deficit and a history of spontaneous regression of the extruded lumbar disc; so, a conservative therapy, including bed rest, physical therapy, nonsteroidal anti-inflammatory drugs, and analgesics, was advised. In conclusion, herniated lumbar disc fragments may regress spontaneously. Reports are prone to advise conservative treatment for extruded or sequestrated lumbar disc herniations. However, these patients should be followed up closely; new herniation at adjacent/different level may occur. Furthermore, it is important to know which herniated disk should be removed and which should be treated conservatively, because disc herniation may cause serious complications as muscle weakness and cauda equine syndrome. PMID:27429818

  20. Exploratory Calibration of Adjustable-Protrusion Surface-Obstacle (APSO) Skin Friction Vector Gage

    NASA Technical Reports Server (NTRS)

    Hakkinen, Raimo J.; Neubauer, Jeremy S.; Hamory, Philip J.; Bui, Trong T.; Noffz, Gregory K.; Young, Ron (Technical Monitor)

    2003-01-01

    The design of an adjustable-protrusion surface-obstacle (APSO) skin friction vector gage is presented. Results from exploratory calibrations conducted in laminar and turbulent boundary layers at the Washington University Low-Speed Wind Tunnel and for turbulent boundary layers at speeds up to Mach 2 on the ceiling of the NASA Glenn Research Center 8- X 6-ft Supersonic Wind Tunnel are also discussed. The adjustable-height gage was designed to yield both the magnitude and direction of the surface shear stress vector and to measure the local static pressure distribution. Results from the NASA test show good correlation for subsonic and low supersonic conditions covering several orders of magnitude in terms of the adopted similarity variables. Recommendations for future work in this area consist of identifying the physical parameters responsible for the disagreement between the university and NASA data sets, developing a compressibility correction specific to the APSO geometry, and examining the effect that static pressure distribution and skewed boundary layers have on the results from the APSO.

  1. Spontaneous Regression of Herniated Lumbar Disc with New Disc Protrusion in the Adjacent Level

    PubMed Central

    Gürcan, Serkan

    2016-01-01

    Spontaneous regression of herniated lumbar discs was reported occasionally. The mechanisms proposed for regression of disc herniation are still incomplete. This paper describes and discusses a case of spontaneous regression of herniated lumbar discs with a new disc protrusion in the adjacent level. A 41-year-old man was admitted with radiating pain and numbness in the left lower extremity with a left posterolateral disc extrusion at L5-S1 level. He was admitted to hospital with low back pain due to disc herniation caudally immigrating at L4-5 level three years ago. He refused the surgical intervention that was offered and was treated conservatively at that time. He had no neurological deficit and a history of spontaneous regression of the extruded lumbar disc; so, a conservative therapy, including bed rest, physical therapy, nonsteroidal anti-inflammatory drugs, and analgesics, was advised. In conclusion, herniated lumbar disc fragments may regress spontaneously. Reports are prone to advise conservative treatment for extruded or sequestrated lumbar disc herniations. However, these patients should be followed up closely; new herniation at adjacent/different level may occur. Furthermore, it is important to know which herniated disk should be removed and which should be treated conservatively, because disc herniation may cause serious complications as muscle weakness and cauda equine syndrome. PMID:27429818

  2. Bin2 Is a Membrane Sculpting N-BAR Protein That Influences Leucocyte Podosomes, Motility and Phagocytosis

    PubMed Central

    Sánchez-Barrena, María José; Vallis, Yvonne; Clatworthy, Menna R.; Doherty, Gary J.; Veprintsev, Dmitry B.; Evans, Philip R.; McMahon, Harvey T.

    2012-01-01

    Cell motility, adhesion and phagocytosis are controlled by actin and membrane remodelling processes. Bridging integrator-2 (Bin2) also called Breast cancer-associated protein 1 (BRAP1) is a predicted N-BAR domain containing protein with unknown function that is highly expressed in leucocytic cells. In the present study we solved the structure of Bin2 BAR domain and studied its membrane binding and bending properties in vitro and in vivo. Live-cell imaging experiments showed that Bin2 is associated with actin rich structures on the plasma membrane, where it was targeted through its N-BAR domain. Pull-down experiments and immunoprecipitations showed that Bin2 C-terminus bound SH3 domain containing proteins such as Endophilin A2 and α-PIX. siRNA of endogenous protein led to decreased cell migration, increased phagocytosis and reduced podosome density and dynamics. In contrast, overexpression of Bin2 led to decreased phagocytosis and increased podosome density and dynamics. We conclude that Bin2 is a membrane-sculpting protein that influences podosome formation, motility and phagocytosis in leucocytes. Further understanding of this protein may be key to understand the behaviour of leucocytes under physiological and pathological conditions. PMID:23285027

  3. Rewiring neuronal microcircuits of the brain via spine head protrusions--a role for synaptopodin and intracellular calcium stores.

    PubMed

    Verbich, David; Becker, Denise; Vlachos, Andreas; Mundel, Peter; Deller, Thomas; McKinney, R Anne

    2016-01-01

    Neurological diseases associated with neuronal death are also accompanied by axonal denervation of connected brain regions. In these areas, denervation leads to a decrease in afferent drive, which may in turn trigger active central nervous system (CNS) circuitry rearrangement. This rewiring process is important therapeutically, since it can partially recover functions and can be further enhanced using modern rehabilitation strategies. Nevertheless, the cellular mechanisms of brain rewiring are not fully understood. We recently reported a mechanism by which neurons remodel their local connectivity under conditions of network-perturbance: hippocampal pyramidal cells can extend spine head protrusions (SHPs), which reach out toward neighboring terminals and form new synapses. Since this form of activity-dependent rewiring is observed only on some spines, we investigated the required conditions. We speculated, that the actin-associated protein synaptopodin, which is involved in several synaptic plasticity mechanisms, could play a role in the formation and/or stabilization of SHPs. Using hippocampal slice cultures, we found that ~70 % of spines with protrusions in CA1 pyramidal neurons contained synaptopodin. Analysis of synaptopodin-deficient neurons revealed that synaptopodin is required for the stability but not the formation of SHPs. The effects of synaptopodin could be linked to its role in Ca(2+) homeostasis, since spines with protrusions often contained ryanodine receptors and synaptopodin. Furthermore, disrupting Ca(2+) signaling shortened protrusion lifetime. By transgenically reintroducing synaptopodin on a synaptopodin-deficient background, SHP stability could be rescued. Overall, we show that synaptopodin increases the stability of SHPs, and could potentially modulate the rewiring of microcircuitries by making synaptic reorganization more efficient. PMID:27102112

  4. Three-dimensional matrix fiber alignment modulates cell migration and MT1-MMP utility by spatially and temporally directing protrusions.

    PubMed

    Fraley, Stephanie I; Wu, Pei-Hsun; He, Lijuan; Feng, Yunfeng; Krisnamurthy, Ranjini; Longmore, Gregory D; Wirtz, Denis

    2015-01-01

    Multiple attributes of the three-dimensional (3D) extracellular matrix (ECM) have been independently implicated as regulators of cell motility, including pore size, crosslink density, structural organization, and stiffness. However, these parameters cannot be independently varied within a complex 3D ECM protein network. We present an integrated, quantitative study of these parameters across a broad range of complex matrix configurations using self-assembling 3D collagen and show how each parameter relates to the others and to cell motility. Increasing collagen density resulted in a decrease and then an increase in both pore size and fiber alignment, which both correlated significantly with cell motility but not bulk matrix stiffness within the range tested. However, using the crosslinking enzyme Transglutaminase II to alter microstructure independently of density revealed that motility is most significantly predicted by fiber alignment. Cellular protrusion rate, protrusion orientation, speed of migration, and invasion distance showed coupled biphasic responses to increasing collagen density not predicted by 2D models or by stiffness, but instead by fiber alignment. The requirement of matrix metalloproteinase (MMP) activity was also observed to depend on microstructure, and a threshold of MMP utility was identified. Our results suggest that fiber topography guides protrusions and thereby MMP activity and motility. PMID:26423227

  5. Plasmonic gratings with nano-protrusions made by glancing angle deposition for single-molecule super-resolution imaging.

    PubMed

    Chen, B; Wood, A; Pathak, A; Mathai, J; Bok, S; Zheng, H; Hamm, S; Basuray, S; Grant, S; Gangopadhyay, K; Cornish, P V; Gangopadhyay, S

    2016-06-16

    Super-resolution imaging has been advantageous in studying biological and chemical systems, but the required equipment and platforms are expensive and unable to observe single-molecules at the high (μM) fluorophore concentrations required to study protein interaction and enzymatic activity. Here, a plasmonic platform was designed that utilized an inexpensively fabricated plasmonic grating in combination with a scalable glancing angle deposition (GLAD) technique using physical vapor deposition. The GLAD creates an abundance of plasmonic nano-protrusion probes that combine the surface plasmon resonance (SPR) from the periodic gratings with the localized SPR of these nano-protrusions. The resulting platform enables simultaneous imaging of a large area without point-by-point scanning or bulk averaging for the detection of single Cyanine-5 molecules in dye concentrations ranging from 50 pM to 10 μM using epifluorescence microscopy. Combining the near-field plasmonic nano-protrusion probes and super-resolution technique using localization microscopy, we demonstrate the ability to resolve grain sizes down to 65 nm. This plasmonic GLAD grating is a cost-effective super-resolution imaging substrate with potential applications in high-speed biomedical imaging over a wide range of fluorescent concentrations. PMID:27250765

  6. Three-dimensional matrix fiber alignment modulates cell migration and MT1-MMP utility by spatially and temporally directing protrusions

    NASA Astrophysics Data System (ADS)

    Fraley, Stephanie I.; Wu, Pei-Hsun; He, Lijuan; Feng, Yunfeng; Krisnamurthy, Ranjini; Longmore, Gregory D.; Wirtz, Denis

    2015-10-01

    Multiple attributes of the three-dimensional (3D) extracellular matrix (ECM) have been independently implicated as regulators of cell motility, including pore size, crosslink density, structural organization, and stiffness. However, these parameters cannot be independently varied within a complex 3D ECM protein network. We present an integrated, quantitative study of these parameters across a broad range of complex matrix configurations using self-assembling 3D collagen and show how each parameter relates to the others and to cell motility. Increasing collagen density resulted in a decrease and then an increase in both pore size and fiber alignment, which both correlated significantly with cell motility but not bulk matrix stiffness within the range tested. However, using the crosslinking enzyme Transglutaminase II to alter microstructure independently of density revealed that motility is most significantly predicted by fiber alignment. Cellular protrusion rate, protrusion orientation, speed of migration, and invasion distance showed coupled biphasic responses to increasing collagen density not predicted by 2D models or by stiffness, but instead by fiber alignment. The requirement of matrix metalloproteinase (MMP) activity was also observed to depend on microstructure, and a threshold of MMP utility was identified. Our results suggest that fiber topography guides protrusions and thereby MMP activity and motility.

  7. Three-dimensional matrix fiber alignment modulates cell migration and MT1-MMP utility by spatially and temporally directing protrusions

    PubMed Central

    Fraley, Stephanie I.; Wu, Pei-hsun; He, Lijuan; Feng, Yunfeng; Krisnamurthy, Ranjini; Longmore, Gregory D.; Wirtz, Denis

    2015-01-01

    Multiple attributes of the three-dimensional (3D) extracellular matrix (ECM) have been independently implicated as regulators of cell motility, including pore size, crosslink density, structural organization, and stiffness. However, these parameters cannot be independently varied within a complex 3D ECM protein network. We present an integrated, quantitative study of these parameters across a broad range of complex matrix configurations using self-assembling 3D collagen and show how each parameter relates to the others and to cell motility. Increasing collagen density resulted in a decrease and then an increase in both pore size and fiber alignment, which both correlated significantly with cell motility but not bulk matrix stiffness within the range tested. However, using the crosslinking enzyme Transglutaminase II to alter microstructure independently of density revealed that motility is most significantly predicted by fiber alignment. Cellular protrusion rate, protrusion orientation, speed of migration, and invasion distance showed coupled biphasic responses to increasing collagen density not predicted by 2D models or by stiffness, but instead by fiber alignment. The requirement of matrix metalloproteinase (MMP) activity was also observed to depend on microstructure, and a threshold of MMP utility was identified. Our results suggest that fiber topography guides protrusions and thereby MMP activity and motility. PMID:26423227

  8. Transoral protrusion of a peritoneal catheter due to gastric perforation 10 years after a ventriculoperitoneal shunting: case report and review of the literature.

    PubMed

    Yilmaz, Muhammet Bahadır; Egemen, Emrah; Tonge, Mehmet; Kaymaz, Memduh

    2013-01-01

    Various complications following ventriculoperitoneal (VP) shunting have been reported but transoral protrusion of peritoneal catheter is a very rare situation. This case is the first adult with a transoral VP shunt protrusion in available literature. A 47-year-old female with pseudotumor cerebri admitted after the peritoneal catheter protruded from her mouth during retching. Endoscopic examination showed a catheter inside stomach entered through the anterior surface. The patient was treated via VP shunt extraction and remained stable. Extrusion of peritoneal catheter through vagina, anus, scrotal skin or gastrostomy wound is well-known. However transoral protrusion should be considered as a very rare complication of VP shunting, especially in an adult. We present a rare case of transoral protrusion of a peritoneal catheter 10 years after ventriculo-peritoneal shunting procedure and review of the literature through this article. PMID:23546921

  9. Targeted Disruption of Shp2 in Chondrocytes Leads to Metachondromatosis With Multiple Cartilaginous Protrusions

    PubMed Central

    Kim, Harry KW; Feng, Gen-Sheng; Chen, Di; King, Philip D; Kamiya, Nobuhiro

    2014-01-01

    Metachondromatosis is a benign bone disease predominantly observed in the hands and feet of children or young adults demonstrating two different manifestations: a cartilage-capped bony outgrowth on the surface of the bone called exostosis and ectopic cartilaginous nodules inside the bone called enchondroma. Recently, it has been reported that loss-of-function mutations of the SHP2 gene, which encodes the SHP2 protein tyrosine phosphatase, are associated with metachondromatosis. The purpose of this study was to investigate the role of SHP2 in postnatal cartilage development, which is largely unknown. We disrupted Shp2 during the postnatal stage of mouse development in a chondrocyte-specific manner using a tamoxifen-inducible system. We found tumor-like nodules on the hands and feet within a month after the initial induction. The SHP2-deficient mice demonstrated an exostosis-like and enchondroma-like phenotype in multiple bones of the hands, feet, and ribs as assessed by X-ray and micro-computed tomography (CT). Histological assessment revealed the disorganization of the growth plate cartilage, a cartilaginous protrusion from the epiphyseal bone, and ectopic cartilage nodules within the bones, which is consistent with the pathological features of metachondromatosis in humans (ie, both exostosis and enchondroma). At molecular levels, we observed an abundant expression of Indian hedgehog protein (IHH) and fibroblast growth factor 2 (FGF2) and impaired expression of mitogen-activated protein kinases (MAPK) in the affected cartilage nodules in the SHP2-deficient mice. In summary, we have generated a mouse model of metachondromatosis that includes manifestations of exostosis and enchondroma. This study provides a novel model for the investigation of the pathophysiology of the disease and advances the understanding of metachondromatosis. This model will be useful to identify molecular mechanisms for the disease cause and progression as well as to develop new therapeutic

  10. On fragmenting, densely mineralised acellular protrusions into articular cartilage and their possible role in osteoarthritis.

    PubMed

    Boyde, A; Davis, G R; Mills, D; Zikmund, T; Cox, T M; Adams, V L; Niker, A; Wilson, P J; Dillon, J P; Ranganath, L R; Jeffery, N; Jarvis, J C; Gallagher, J A

    2014-10-01

    High density mineralised protrusions (HDMP) from the tidemark mineralising front into hyaline articular cartilage (HAC) were first described in Thoroughbred racehorse fetlock joints and later in Icelandic horse hock joints. We now report them in human material. Whole femoral heads removed at operation for joint replacement or from dissection room cadavers were imaged using magnetic resonance imaging (MRI) dual echo steady state at 0.23 mm resolution, then 26-μm resolution high contrast X-ray microtomography, sectioned and embedded in polymethylmethacrylate, blocks cut and polished and re-imaged with 6-μm resolution X-ray microtomography. Tissue mineralisation density was imaged using backscattered electron SEM (BSE SEM) at 20 kV with uncoated samples. HAC histology was studied by BSE SEM after staining block faces with ammonium triiodide solution. HDMP arise via the extrusion of an unknown mineralisable matrix into clefts in HAC, a process of acellular dystrophic calcification. Their formation may be an extension of a crack self-healing mechanism found in bone and articular calcified cartilage. Mineral concentration exceeds that of articular calcified cartilage and is not uniform. It is probable that they have not been reported previously because they are removed by decalcification with standard protocols. Mineral phase morphology frequently shows the agglomeration of many fine particles into larger concretions. HDMP are surrounded by HAC, are brittle, and show fault lines within them. Dense fragments found within damaged HAC could make a significant contribution to joint destruction. At least larger HDMP can be detected with the best MRI imaging ex vivo. PMID:25132002

  11. EB1-recruited microtubule +TIP complexes coordinate protrusion dynamics during 3D epithelial remodeling

    PubMed Central

    Gierke, Sarah; Wittmann, Torsten

    2012-01-01

    SUMMARY Background Epithelial remodeling, in which apical-basal polarized cells switch to a migratory phenotype, plays a central role in development and disease of multicellular organisms. Although dynamic microtubules (MTs) are required for directed migration on flat surfaces, how MT dynamics are controlled or contribute to epithelial remodeling in a more physiological three-dimensional (3D) environment is not understood. We use confocal live cell imaging to analyze MT function and dynamics during 3D epithelial morphogenesis and remodeling of polarized Madin-Darby canine kidney (MDCK) epithelial cells that undergo partial epithelial-to-mesenchymal transition (EMT) in response to hepatocyte growth factor (HGF). Results We find that HGF treatment increases MT growth rate before morphological changes are evident, and that large numbers of MTs grow into HGF-induced cell extensions independent of centrosome reorientation. Using lentivirus-mediated shRNA, we demonstrate that EB1, an adaptor protein that mediates recruitment of numerous other +TIP proteins to growing MT plus ends, is required for this HGF-induced MT reorganization. We further show that protrusion and adhesion dynamics are disorganized, and that vesicular trafficking to the tip of HGF-induced cell extensions is disrupted in EB1-depleted cells. Conclusions We conclude that EB1-mediated interactions with growing MTs are important to coordinate cell shape changes and directed migration into the surrounding extracellular matrix during epithelial remodeling in a physiological 3D environment. In contrast, EB1 is not required for the establishment or maintenance of apical-basal cell polarity, suggesting different functions of +TIPs and MTs in different types of cell polarity. PMID:22483942

  12. Comparison of Mallampati test with lower jaw protrusion maneuver in predicting difficult laryngoscopy and intubation

    PubMed Central

    Ul Haq, Muhammad Irfan; Ullah, Hameed

    2013-01-01

    Background: Failure to maintain a patent airway is one of the commonest causes of anesthesia-related morbidity and mortality. Many protocols, algorithms, and different combinations of tested methods for airway assessment have been developed to predict difficult laryngoscopy and intubation. The reported incidence of a difficult intubation varies from 1.5% to 13%. The objective of this study was to compare Mallampati test (MT) with lower jaw protrusion (LJP) maneuver in predicting difficult laryngoscopy and intubation. Materials and Methods: Seven hundred and sixty patients were included in the study. All the patients underwent MT and LJP maneuver for their airway assessment. After a standardized technique of induction of anesthesia, primary anesthetist performed laryngoscopy and graded it according to the grades described by Cormack and Lehane. Sensitivity, specificity, accuracy, and positive predictive value (PPV) and negative predictive value (NPV) were calculated for both these tests with 95% confidence interval (CI) using conventional laryngoscopy as gold standard. Area under curve was also calculated for both, MT and LJP maneuver. A P < 0.05 was taken as significant. Results: LJP maneuver had higher sensitivity (95.9% vs. 27.1%), NPV (98.7% vs. 82.0%), and accuracy (90.1% vs. 80.3%) when compared to MT in predicting difficult laryngoscopy and intubation. Both tests, however, had similar specificity and PPV. There was marked difference in the positive and negative likelihood ratio between LJP and MT. Similarly, the area under the curve favored LJP maneuver over MT. Conclusion: The results of this study show that LJP maneuver is a better test to predict difficult laryngoscopy and tracheal intubation. We recommend the addition of this maneuver to the routine preoperative evaluation of airway. PMID:24106353

  13. Cdc42 and Actin Control Polarized Expression of TI-VAMP Vesicles to Neuronal Growth Cones and Their Fusion with the Plasma MembraneV⃞

    PubMed Central

    Alberts, Philipp; Rudge, Rachel; Irinopoulou, Theano; Danglot, Lydia; Gauthier-Rouvière, Cécile; Galli, Thierry

    2006-01-01

    Tetanus neurotoxin-insensitive vesicle-associated membrane protein (TI-VAMP)-mediated fusion of intracellular vesicles with the plasma membrane is crucial for neurite outgrowth, a pathway not requiring synaptobrevin-dependent exocytosis. Yet, it is not known how the TI-VAMP membrane trafficking pathway is regulated or how it is coordinated with cytoskeletal dynamics within the growth cone that guide neurite outgrowth. Here, we demonstrate that TI-VAMP, but not synaptobrevin 2, concentrates in the peripheral, F-actin-rich region of the growth cones of hippocampal neurons in primary culture. Its accumulation correlates with and depends upon the presence of F-actin. Moreover, acute stimulation of actin remodeling by homophilic activation of the adhesion molecule L1 induces a site-directed, actin-dependent recruitment of the TI-VAMP compartment. Expression of a dominant-positive mutant of Cdc42, a key regulator of cell polarity, stimulates formation of F-actin- and TI-VAMP-rich filopodia outside the growth cone. Furthermore, we report that Cdc42 activates exocytosis of pHLuorin tagged TI-VAMP in an actin-dependent manner. Collectively, our data suggest that Cdc42 and regulated assembly of the F-actin network control the accumulation and exocytosis of TI-VAMP-containing membrane vesicles in growth cones to coordinate membrane trafficking and actin remodeling during neurite outgrowth. PMID:16381811

  14. Interventricular membranous septal aneurysm: CT and MR manifestations.

    PubMed

    Carcano, Carolina; Kanne, Jeffrey P; Kirsch, Jacobo

    2016-02-01

    Advanced cardiac imaging is a valuable method to investigate cardiac malformations. The detection of the interventricular membranous septum has clinical significance due to thrombogenic and arrythmogenic predisposition, as well as a role in obstructing the pulmonary flow. This review describes six clinical presentations in which advanced cardiac imaging has been the tool for evaluation, with special emphasis in CT angiography and cardiac MRI sequences. Teaching Points • The interventricular membranous septum can predispose patients to thrombogenic and arrythmogenic events. • Subpulmonic stenosis relates to the protrusion of the aneurysm into the right ventricle • During surgery, ventricular pressures of the opened heart become balanced, making the aneurysm less evident. PMID:26687514

  15. Membrane Tension Acts Through PLD2 and mTORC2 to Limit Actin Network Assembly During Neutrophil Migration

    PubMed Central

    Diz-Muñoz, Alba; Thurley, Kevin; Chintamen, Sana; Altschuler, Steven J.; Fletcher, Daniel A.; Weiner, Orion D.

    2016-01-01

    For efficient polarity and migration, cells need to regulate the magnitude and spatial distribution of actin assembly. This process is coordinated by reciprocal interactions between the actin cytoskeleton and mechanical forces. Actin polymerization-based protrusion increases tension in the plasma membrane, which in turn acts as a long-range inhibitor of actin assembly. These interactions form a negative feedback circuit that limits the magnitude of membrane tension in neutrophils and prevents expansion of the existing front and the formation of secondary fronts. It has been suggested that the plasma membrane directly inhibits actin assembly by serving as a physical barrier that opposes protrusion. Here we show that efficient control of actin polymerization-based protrusion requires an additional mechanosensory feedback cascade that indirectly links membrane tension with actin assembly. Specifically, elevated membrane tension acts through phospholipase D2 (PLD2) and the mammalian target of rapamycin complex 2 (mTORC2) to limit actin nucleation. In the absence of this pathway, neutrophils exhibit larger leading edges, higher membrane tension, and profoundly defective chemotaxis. Mathematical modeling suggests roles for both the direct (mechanical) and indirect (biochemical via PLD2 and mTORC2) feedback loops in organizing cell polarity and motility—the indirect loop is better suited to enable competition between fronts, whereas the direct loop helps spatially organize actin nucleation for efficient leading edge formation and cell movement. This circuit is essential for polarity, motility, and the control of membrane tension. PMID:27280401

  16. Membrane Tension Acts Through PLD2 and mTORC2 to Limit Actin Network Assembly During Neutrophil Migration.

    PubMed

    Diz-Muñoz, Alba; Thurley, Kevin; Chintamen, Sana; Altschuler, Steven J; Wu, Lani F; Fletcher, Daniel A; Weiner, Orion D

    2016-06-01

    For efficient polarity and migration, cells need to regulate the magnitude and spatial distribution of actin assembly. This process is coordinated by reciprocal interactions between the actin cytoskeleton and mechanical forces. Actin polymerization-based protrusion increases tension in the plasma membrane, which in turn acts as a long-range inhibitor of actin assembly. These interactions form a negative feedback circuit that limits the magnitude of membrane tension in neutrophils and prevents expansion of the existing front and the formation of secondary fronts. It has been suggested that the plasma membrane directly inhibits actin assembly by serving as a physical barrier that opposes protrusion. Here we show that efficient control of actin polymerization-based protrusion requires an additional mechanosensory feedback cascade that indirectly links membrane tension with actin assembly. Specifically, elevated membrane tension acts through phospholipase D2 (PLD2) and the mammalian target of rapamycin complex 2 (mTORC2) to limit actin nucleation. In the absence of this pathway, neutrophils exhibit larger leading edges, higher membrane tension, and profoundly defective chemotaxis. Mathematical modeling suggests roles for both the direct (mechanical) and indirect (biochemical via PLD2 and mTORC2) feedback loops in organizing cell polarity and motility-the indirect loop is better suited to enable competition between fronts, whereas the direct loop helps spatially organize actin nucleation for efficient leading edge formation and cell movement. This circuit is essential for polarity, motility, and the control of membrane tension. PMID:27280401

  17. Structural Features of Membrane Fusion between Influenza Virus and Liposome as Revealed by Quick-Freezing Electron Microscopy

    PubMed Central

    Kanaseki, Toku; Kawasaki, Kazunori; Murata, Masayuki; Ikeuchi, Yoko; Ohnishi, Shun-ichi

    1997-01-01

    The structure of membrane fusion intermediates between the A/PR/8(H1N1) strain of influenza virus and a liposome composed of egg phosphatidylcholine, cholesterol, and glycophorin was studied using quick-freezing electron microscopy. Fusion by viral hemagglutinin protein was induced at pH 5.0 and 23°C. After a 19-s incubation under these conditions, small protrusions with a diameter of 10–20 nm were found on the fractured convex faces of the liposomal membranes, and small pits complementary to the protrusions were found on the concave faces. The protrusions and pits corresponded to fractured parts of outward bendings of the lipid bilayer or “microprotrusions of the lipid bilayer.” At the loci of the protrusions and pits, liposomal membranes had local contacts with viral membranes. In many cases both the protrusions and the pits were aligned in regular polygonal arrangements, which were thought to reflect the array of hemagglutinin spikes on the viral surface. These structures were induced only when the medium was acidic with the virus present. Based on these observations, it was concluded that the microprotrusions of the lipid bilayer are induced by hemagglutinin protein. Furthermore, morphological evidence for the formation of the “initial fusion pore” at the microprotrusion was obtained. The protrusion on the convex face sometimes had a tiny hole with a diameter of <4 nm in the center. The pits transformed into narrow membrane connections <10 nm in width, bridging viruses and liposomes. The structures of the fusion pore and fusion neck with larger sizes were also observed, indicating growth of the protrusions and pits to distinct fusion sites. We propose that the microprotrusion of the lipid bilayer is a fusion intermediate induced by hemagglutinin protein, and suggest that the extraordinarily high curvature of this membrane structure is a clue to the onset of fusion. The possible architecture of the fusion intermediate is discussed with regard to the

  18. Infantile Perianal Pyramidal Protrusion with Coexisting Perineal and Perianal Hemangiomas: A Fortuitous Association or Incomplete PELVIS Syndrome?

    PubMed Central

    Verma, Shyam B; Wollina, Uwe

    2014-01-01

    Two cases of infantile perianal pyramidal protrusions (IPPP), one pyramidal in shape and one leaf shaped, are being described by us. Both were notable for coexisting hemangiomas in the close vicinity. To the best of our knowledge we are reporting these two variants of IPPP with the associated neighboring hemangiomas for the first time in Indian dermatologic literature. We suggest that this presentation may be a part of one of the syndromes that comprise anorectal malformations with hemangiomas like PELVIS syndrome and others mentioned in the table. PMID:24470664

  19. Bovine binder-of-sperm protein BSP1 promotes protrusion and nanotube formation from liposomes

    SciTech Connect

    Lafleur, Michel; Courtemanche, Lesley; Karlsson, Goeran; Edwards, Katarina; Schwartz, Jean-Louis; Manjunath, Puttaswamy

    2010-08-27

    Research highlights: {yields} Binder-of-sperm protein 1 (BSP1) modifies the morphology of lipidic vesicles inducing bead necklace-like and thread-like structures. {yields} In the presence of multilamellar liposomes, BSP1 leads to the formation of long nanotubes. {yields} The insertion of BSP1 in the external lipid leaflet of membranes induces local changes in bilayer curvature. -- Abstract: Binder-of-sperm (BSP) proteins interact with sperm membranes and are proposed to extract selectively phosphatidylcholine and cholesterol from these. This change in lipid composition is a key step in sperm capacitation. The present work demonstrates that the interactions between the protein BSP1 and model membranes composed with phosphatidylcholine lead to drastic changes in the morphology of the lipidic self-assemblies. Using cryo-electron microscopy and fluorescence microscopy, we show that, in the presence of the protein, the lipid vesicles elongate, and form bead necklace-like structures that evolve toward small vesicles or thread-like structures. In the presence of multilamellar vesicles, where a large reservoir of lipid is available, the presence of BSP proteins lead to the formation of long nanotubes. Long spiral-like threads, associated with lipid/protein complexes, are also observed. The local curvature of lipid membranes induced by the BSP proteins may be involved in lipid domain formation and the extraction of some lipids during the sperm maturation process.

  20. Controlled synthesis and investigation of the mechanism of formation of hollow hemispherical protrusions on laurate anion-intercalated Zn/Al layered double hydroxide hybrid films.

    PubMed

    Yue, Caili; Chen, Hongyun; Xu, Sailong; Zhang, Fazhi

    2012-11-01

    Films of laurate (La) anion-intercalated zinc-aluminum layered double hydroxides (ZnAl-La-LDHs) with hollow hemispherical protrusions on the surface of the hybrid film have been conveniently prepared by an ion-exchange reaction of a nitrate-containing LDH film previously grown in situ on a porous anodic alumina/aluminum (PAO/Al) substrate. No template is required to form the hemispherical protrusions, thus avoiding a complicated template removal process. The dimensions, morphology, and resistance to bursting of the hollow hemispherical protrusions can be easily tuned by varying the experimental conditions such as sodium laurate concentration, reaction time, and reaction temperature. The evolution of the hollow protrusions was investigated by scanning electron microscopy (SEM), and a "bubble template-reconfiguration assembly" mechanism, in which air bubbles on the film surface act as a template, has been proposed to explain their formation. When the ion-exchange reaction was carried out on a film that had been treated by ultrasound to eliminate surface air bubbles, no hemispherical protrusions were formed, which is consistent with the proposed mechanism. PMID:22840873

  1. Test of the movement expansion model: Anticipatory vowel lip protrusion and constriction in French and English speakers

    PubMed Central

    Noiray, Aude; Cathiard, Marie-Agnès; Ménard, Lucie; Abry, Christian

    2011-01-01

    The modeling of anticipatory coarticulation has been the subject of longstanding debates for more than 40 yr. Empirical investigations in the articulatory domain have converged toward two extreme modeling approaches: a maximal anticipation behavior (Look-ahead model) or a fixed pattern (Time-locked model). However, empirical support for any of these models has been hardly conclusive, both within and across languages. The present study tested the temporal organization of vocalic anticipatory coarticulation of the rounding feature from [i] to [u] transitions for adult speakers of American English and Canadian French. Articulatory data were synchronously recorded using an Optotrak for lip protrusion and a dedicated Lip-Shape-Tracking-System for lip constriction. Results show that (i) protrusion is an inconsistent parameter for tracking anticipatory rounding gestures across individuals, more specifically in English; (ii) labial constriction (between-lip area) is a more reliable correlate, allowing for the description of vocalic rounding in both languages; (iii) when tested on the constriction component, speakers show a lawful anticipatory behavior expanding linearly as the intervocalic consonant interval increases from 0 to 5 consonants. The Movement Expansion Model from Abry and Lallouache [(1995a) Bul. de la Comm. Parlée 3, 85–99; (1995b) Proceedings of ICPHS4, 152–155.] predicted such a regular behavior, i.e., a lawful variabilitywith a speaker-specific expansion rate, which is not language-specific. PMID:21303015

  2. Examination of unsteady flow in a mildly curved vessel with stent-like wall protrusions: A tale of two vessels

    NASA Astrophysics Data System (ADS)

    Prince, Chekema; Peterson, Sean D.

    2014-11-01

    New stent designs allow for better conformity to the vessel curvature, maintaining the complex primary and secondary flow patterns present in the native vessel. Despite design improvements, stent induced alterations in local vascular geometry are inevitable and have been associated with stent failure due to in-stent restenosis (ISR). The objective of this study is to elucidate the unsteady flow physics induced by stent implantation, accounting in particular for vessel curvature. The present study focuses on the investigation of unsteady flow through mildly curved vessels with protrusion patterns that emulate current stent designs using computational fluid dynamics (CFD). The modeled geometries include various protrusion frequencies, heights, and widths. Two different arterial velocities waveforms, mimicking the coronary and carotid artery environment, will be considered. A detailed examination of the flow environment induced by the stent presence will be correlated with derived parameters from the flow behavior, such as critical wall shear stress typically associated with ISR development. Specifically, the role of secondary flow in the convective transport of ISR stimuli to the vessel wall will be explored.

  3. Contralateral dominance of corticomuscular coherence for both sides of the tongue during human tongue protrusion: an MEG study.

    PubMed

    Maezawa, Hitoshi; Mima, Tatsuya; Yazawa, Shogo; Matsuhashi, Masao; Shiraishi, Hideaki; Hirai, Yoshiyuki; Funahashi, Makoto

    2014-11-01

    Sophisticated tongue movements contribute to speech and mastication. These movements are regulated by communication between the bilateral cortex and each tongue side. The functional connection between the cortex and tongue was investigated using oscillatory interactions between whole-head magnetoencephalographic (MEG) signals and electromyographic (EMG) signals from both tongue sides during human tongue protrusion compared to thumb data. MEG-EMG coherence was observed at 14-36 Hz and 2-10 Hz over both hemispheres for each tongue side. EMG-EMG coherence between tongue sides was also detected at the same frequency bands. Thumb coherence was detected at 15-33 Hz over the contralateral hemisphere. Tongue coherence at 14-36 Hz was larger over the contralateral vs. ipsilateral hemisphere for both tongue sides. Tongue cortical sources were located in the lower part of the central sulcus and were anterior and inferior to the thumb areas, agreeing with the classical homunculus. Cross-correlogram analysis showed the MEG signal preceded the EMG signal. The cortex-tongue time lag was shorter than the cortex-thumb time lag. The cortex-muscle time lag decreased systematically with distance. These results suggest that during tongue protrusions, descending motor commands are modulated by bilateral cortical oscillations, and each tongue side is dominated by the contralateral hemisphere. PMID:25038437

  4. Cytosolic pressure provides a propulsive force comparable to actin polymerization during lamellipod protrusion

    NASA Astrophysics Data System (ADS)

    Manoussaki, Daphne; Shin, William D.; Waterman, Clare M.; Chadwick, Richard S.

    2015-07-01

    Does cytosolic pressure facilitate f-actin polymerization to push the leading edge of a cell forward during self-propelled motion? AFM force-distance (f-d) curves obtained from lamellipodia of live cells often exhibit a signal from which the tension, bending modulus, elastic modulus and thickness in the membrane-cortex complex can be estimated close to the contact point. These measurements permit an estimate of the cytosolic pressure via the canonical Laplace force balance. The deeper portion of the f-d curve allows estimation of the bulk modulus of the cytoskeleton after removal of the bottom effect artifact. These estimates of tension, pressure, cortex thickness and elastic moduli imply that cytosolic pressure both pushes the membrane forward and compresses the actin cortex rearward to facilitate f-actin polymerization. We also estimate that cytosolic pressure fluctuations, most likely induced by myosin, provide a propulsive force comparable to that provided by f-actin polymerization in a lamellipod.

  5. Membrane stabilizer

    DOEpatents

    Mingenbach, William A.

    1988-01-01

    A device is provided for stabilizing a flexible membrane secured within a frame, wherein a plurality of elongated arms are disposed radially from a central hub which penetrates the membrane, said arms imposing alternately against opposite sides of the membrane, thus warping and tensioning the membrane into a condition of improved stability. The membrane may be an opaque or translucent sheet or other material.

  6. Regulation of membrane-shape transitions induced by I-BAR domains.

    PubMed

    Chen, Zhiming; Shi, Zheng; Baumgart, Tobias

    2015-07-21

    I-BAR proteins are well-known actin-cytoskeleton adaptors and have been observed to be involved in the formation of plasma membrane protrusions (filopodia). I-BAR proteins contain an all-helical, crescent-shaped IRSp53-MIM domain (IMD) dimer that is believed to be able to couple with a membrane shape. This coupling could involve the sensing and even the generation of negative plasma membrane curvature. Indeed, the in vitro studies have shown that IMDs can induce inward tubulation of liposomes. While N-BAR domains, which generate positive membrane curvature, have received a considerable amount of attention from both theory and experiments, the mechanisms of curvature coupling through IMDs are comparatively less studied and understood. Here we used a membrane-shape stability assay developed recently in our lab to quantitatively characterize IMD-induced membrane-shape transitions. We determined a membrane-shape stability diagram for IMDs that reveals how membrane tension and protein density can comodulate the generation of IMD-induced membrane protrusions. From comparison to analytical theory, we determine three key parameters that characterize the curvature coupling of IMD. We find that the curvature generation capacity of IMDs is significantly stronger compared to that of endophilin, an N-BAR protein known to be involved in plasma membrane shape transitions. Contrary to N-BAR domains, where amphipathic helix insertion is known to promote its membrane curvature generation, for IMDs we find that amphipathic helices inhibit membrane shape transitions, consistent with the inverse curvature that IMDs generate. Importantly, in both of these types of BAR domains, electrostatic interactions affect membrane-binding capacity, but do not appear to affect the curvature generation capacity of the protein. These two types of BAR domain proteins show qualitatively similar membrane shape stability diagrams, suggesting an underlying ubiquitous mechanism by which peripheral proteins

  7. Dynamic recruitment of the curvature-sensitive protein ArhGAP44 to nanoscale membrane deformations limits exploratory filopodia initiation in neurons

    PubMed Central

    Galic, Milos; Tsai, Feng-Chiao; Collins, Sean R; Matis, Maja; Bandara, Samuel; Meyer, Tobias

    2014-01-01

    In the vertebrate central nervous system, exploratory filopodia transiently form on dendritic branches to sample the neuronal environment and initiate new trans-neuronal contacts. While much is known about the molecules that control filopodia extension and subsequent maturation into functional synapses, the mechanisms that regulate initiation of these dynamic, actin-rich structures have remained elusive. Here, we find that filopodia initiation is suppressed by recruitment of ArhGAP44 to actin-patches that seed filopodia. Recruitment is mediated by binding of a membrane curvature-sensing ArhGAP44 N-BAR domain to plasma membrane sections that were deformed inward by acto-myosin mediated contractile forces. A GAP domain in ArhGAP44 triggers local Rac-GTP hydrolysis, thus reducing actin polymerization required for filopodia formation. Additionally, ArhGAP44 expression increases during neuronal development, concurrent with a decrease in the rate of filopodia formation. Together, our data reveals a local auto-regulatory mechanism that limits initiation of filopodia via protein recruitment to nanoscale membrane deformations. DOI: http://dx.doi.org/10.7554/eLife.03116.001 PMID:25498153

  8. Mechanism of Actin Network Attachment to Moving Membranes

    PubMed Central

    Co, Carl; Wong, Derek T.; Gierke, Sarah; Chang, Vicky; Taunton, Jack

    2007-01-01

    Summary Actin filament networks exert protrusive and attachment forces on membranes and thereby drive membrane deformation and movement. Here, we show that N-WASP WH2 domains play a previously unanticipated role in vesicle movement by transiently attaching actin filament barbed ends to the membrane. To dissect the attachment mechanism, we reconstituted the propulsive motility of lipid-coated glass beads using purified soluble proteins. N-WASP WH2 mutants assembled actin comet tails and initiated movement, but the comet tails catastrophically detached from the membrane. When presented on the surface of a lipid-coated bead, WH2 domains were sufficient to maintain comet tail attachment. In v-Src-transformed fibroblasts, N-WASP WH2 mutants were severely defective in the formation of circular podosome arrays. In addition to creating an attachment force, interactions between WH2 domains and barbed ends may locally amplify signals for dendritic actin nucleation. PMID:17350575

  9. Protrusion-localized STAT3 mRNA promotes metastasis of highly metastatic hepatocellular carcinoma cells in vitro

    PubMed Central

    Liu, Yan-hong; Jin, Jia-lu; Wang, Yu-zhe; Tan, Ying; Zhou, Ying-ying; Peng, Ting; Li, Feng; Liang, Wan-dong; Chartrand, Pascal; Jiang, Yu-yang; Shen, Zhi-fa

    2016-01-01

    Aim: Recent evidence shows that localization of mRNAs and their protein products at cellular protrusions plays a decisive function in the metastasis of cancer cells. The aim of this study was to identify the variety of proteins encoded by protrusion-localized mRNAs and their roles in the metastasis and invasion of liver cancer cells. Methods: Highly metastatic hepatocellular carcinoma cell line HCCLM3 and non-metastatic hepatocellular carcinoma cell line SMMC-7721 were examined. Cell protrusions (Ps) were separated from cell bodies (CB) using a Boyden chamber assay; total mRNA population in CB and Ps fractions was analyzed using high-throughput direct RNA sequencing. The localization of STAT3 mRNA and protein at Ps was confirmed using RT-qPCR, RNA FISH, and immunofluorescence assays. Cell migration capacity and invasiveness of HCCLM3 cells were evaluated using MTT, wound healing migration and in vitro invasion assays. The interaction between Stat3 and growth factor receptors was explored with co-immunoprecipitation assays. Results: In HCCLM3 cells, 793 mRNAs were identified as being localized in the Ps fraction according to a cut-off value (Ps/CB ratio) >1.6. The Ps-localized mRNAs could be divided into 4 functional groups, and were all closely related to the invasive and metastatic properties. STAT3 mRNA accumulated in the Ps of HCCLM3 cells compared with non-metastatic SMMC-7721 cells. Treatment of HCCLM3 cells with siRNAs against STAT3 mRNA drastically decreased the cell migration and invasion. Moreover, Ps-localized Stat3 was found to interact with pseudopod-enriched platelet-derived growth factor receptor tyrosine kinase (PDGFRTK) in a growth factor-dependent manner. Conclusion: This study reveals STAT3 mRNA localization at the Ps of metastatic hepatocellular carcinoma HCCLM3 cells by combining application of genome-wide and gene specific description and functional analysis. PMID:27133294

  10. Cytosolic pressure provides a propulsive force comparable to actin polymerization during lamellipod protrusion.

    PubMed

    Manoussaki, Daphne; Shin, William D; Waterman, Clare M; Chadwick, Richard S

    2015-01-01

    Does cytosolic pressure facilitate f-actin polymerization to push the leading edge of a cell forward during self-propelled motion? AFM force-distance (f-d) curves obtained from lamellipodia of live cells often exhibit a signal from which the tension, bending modulus, elastic modulus and thickness in the membrane-cortex complex can be estimated close to the contact point. These measurements permit an estimate of the cytosolic pressure via the canonical Laplace force balance. The deeper portion of the f-d curve allows estimation of the bulk modulus of the cytoskeleton after removal of the bottom effect artifact. These estimates of tension, pressure, cortex thickness and elastic moduli imply that cytosolic pressure both pushes the membrane forward and compresses the actin cortex rearward to facilitate f-actin polymerization. We also estimate that cytosolic pressure fluctuations, most likely induced by myosin, provide a propulsive force comparable to that provided by f-actin polymerization in a lamellipod. PMID:26197304

  11. BMP Signals Promote Proepicardial Protrusion Necessary for Recruitment of Coronary Vessel and Epicardial Progenitors to the Heart

    PubMed Central

    Ishii, Yasuo; Garriock, Robert J.; Navetta, Alicia M.; Coughlin, Laura E.; Mikawa, Takashi

    2010-01-01

    SUMMARY The coronary vessels and epicardium arise from an extracardiac rudiment called the proepicardium. Failed fusion of the proepicardium to the heart results in severe coronary and heart defects. However, it is unknown how the proepicardium protrudes toward and attaches to the looping heart tube. Here we show that ectopic expression of BMP ligands in the embryonic myocardium can cause proepicardial cells to target aberrant regions of the heart. Additionally, misexpression of a BMP antagonist, Noggin, suppresses proepicardium protrusion and contact with the heart. Finally, proepicardium explant preferentially expands toward a co-cultured heart segment. This preference can be mimicked by BMP2/4 and suppressed by Noggin. These results support a model in which myocardium-derived BMP signals regulate the entry of coronary progenitors to the specific site of the heart by directing their morphogenetic movement. PMID:20708592

  12. Bottom Feeding and Beyond: How the Premaxillary Protrusion of Cypriniforms Allowed for a Novel Kind of Suction Feeding.

    PubMed

    Hernandez, L Patricia; Staab, Katie Lynn

    2015-07-01

    While much of the functional work on suction feeding has involved members of Acanthopterygii, an earlier cypriniform radiation led to over 3200 species filling nearly every freshwater trophic niche. Within the great majority of acanthomorph clades that have been investigated suction feeding and the underlying morphology responsible for the generation of rapid suction have been largely conserved. This conserved feeding-apparatus is often associated with increasing the force experienced by the prey item, thus making a strike on elusive prey more effective. Cypriniforms' trophic anatomy is comprised of a number of novelties used for benthic feeding, which characterized early members of this clade. The modified cypriniform structure of the oral jaws represents a situation in which a particular type of suction feeding allowed for probing the benthos with a more functionally maneuverable anatomy. Requisite evolutionary modifications included origin and elongation of a median kinethmoid, duplications of certain divisions of the muscles of the adductor mandibulae, and origin of a dorsal, intra-buccal muscular palatal organ used in winnowing detritus. The elongated kinethmoid (coupled with modified adductor muscles) allowed for a type of premaxillary protrusion that decoupled the upper and lower jaws, enabled premaxillary protrusions with a closed mouth, and facilitated benthic feeding by increasing functional flexibility. The resultant flow of fluid generated by cypriniforms is also quite flexible, with multiple instances of peak flow in a single feeding event. This greatly modified morphology allowed for a degree of kinematic maneuverability not seen within most acanthomorphs. Later cypriniform radiations into piscivorous, insectivorous, or planktivorous feeding guilds were associated with shortening of the kinethmoid and with simplified morphology of the adductor, likely involving an emphasis on ram feeding. Although this suite of morphological novelties seemingly

  13. A novel approach to pseudopodia proteomics: excimer laser etching, two-dimensional difference gel electrophoresis, and confocal imaging

    PubMed Central

    Mimae, Takahiro; Ito, Akihiko; Hagiyama, Man; Nakanishi, Jun; Hosokawa, Yoichiroh; Okada, Morihito; Murakami, Yoshinori; Kondo, Tadashi

    2014-01-01

    Pseudopodia are actin-rich ventral cellular protrusions shown to facilitate the migration and metastasis of tumor cells. Here, we present a novel approach to perform pseudopodia proteomics. Tumor cells growing on porous membranes extend pseudopodia into the membrane pores. In our method, cell bodies are removed by horizontal ablation at the basal cell surface with the excimer laser while pseudopodia are left in the membrane pores. For protein expression profiling, whole cell and pseudopodia proteins are extracted with a lysis buffer, labeled with highly sensitive fluorescent dyes, and separated by two-dimensional gel electrophoresis. Proteins with unique expression patterns in pseudopodia are identified by mass spectrometry. The effects of the identified proteins on pseudopodia formation are evaluated by measuring the pseudopodia length in cancer cells with genetically modified expression of target proteins using confocal imaging. This protocol allows global identification of pseudopodia proteins and evaluation of their functional significance in pseudopodia formation within one month. PMID:25309719

  14. SMN affects membrane remodelling and anchoring of the protein synthesis machinery.

    PubMed

    Gabanella, Francesca; Pisani, Cinzia; Borreca, Antonella; Farioli-Vecchioli, Stefano; Ciotti, Maria Teresa; Ingegnere, Tiziano; Onori, Annalisa; Ammassari-Teule, Martine; Corbi, Nicoletta; Canu, Nadia; Monaco, Lucia; Passananti, Claudio; Di Certo, Maria Grazia

    2016-02-15

    Disconnection between membrane signalling and actin networks can have catastrophic effects depending on cell size and polarity. The survival motor neuron (SMN) protein is ubiquitously involved in assembly of spliceosomal small nuclear ribonucleoprotein particles. Other SMN functions could, however, affect cellular activities driving asymmetrical cell surface expansions. Genes able to mitigate SMN deficiency operate within pathways in which SMN can act, such as mRNA translation, actin network and endocytosis. Here, we found that SMN accumulates at membrane protrusions during the dynamic rearrangement of the actin filaments. In addition to localization data, we show that SMN interacts with caveolin-1, which mediates anchoring of translation machinery components. Importantly, SMN deficiency depletes the plasma membrane of ribosomes, and this correlates with the failure of fibroblasts to extend membrane protrusions. These findings strongly support a relationship between SMN and membrane dynamics. We propose that SMN could assembly translational platforms associated with and governed by the plasma membrane. This activity could be crucial in cells that have an exacerbated interdependence of membrane remodelling and local protein synthesis. PMID:26743087

  15. Membrane stabilizer

    DOEpatents

    Mingenbach, W.A.

    1988-02-09

    A device is provided for stabilizing a flexible membrane secured within a frame, wherein a plurality of elongated arms are disposed radially from a central hub which penetrates the membrane, said arms imposing alternately against opposite sides of the membrane, thus warping and tensioning the membrane into a condition of improved stability. The membrane may be an opaque or translucent sheet or other material. 10 figs.

  16. A CFD study of steady flow of a Newtonian and non-Newtonian fluid through a mildly curved tube with stent-like wall protrusions patterns

    NASA Astrophysics Data System (ADS)

    Prince, Chekema; Peterson, Sean D.

    2012-11-01

    Early stent designs caused vessel straightening post-implantation and motivated the exploration of flow in the stent vicinity using straight pipe models with stent-like protrusion patterns. Recent advancements in stent design allow the device to better conform to the native vessel curvature. The present study focuses on the investigation of steady flow through mildly curved pipes with protrusion patterns that emulate current stent designs using computational fluid dynamics (CFD). The modeled geometries include various protrusion frequencies, heights, and widths with flow behavior within the range of physiologically relevant Dean numbers. The results are compared to smooth wall curved pipe models as well as straight pipe protrusion studies. Differences in flow behavior pre/post stent implantation will be discussed. Particular attention will be paid to flow characteristics, such as wall shear stress (WSS) magnitude and WSS gradients, indicative of potential stent failure. Newtonian and non-Newtonian fluid models will be utilized to discuss their impact on flow patterns. The study findings can be used to optimize stent design to mitigate flow conditions associated with stent failure.

  17. Quantitative Three-Dimensional Ultrasound Analysis of Tongue Protrusion, Grooving and Symmetry: Data from 12 Normal Speakers and a Partial Glossectomee

    ERIC Educational Resources Information Center

    Bressmann, Tim; Thind, Parveen; Uy, Catherine; Bollig, Carmen; Gilbert, Ralph W.; Irish, Jonathan C.

    2005-01-01

    The functional determinants for a good speech outcome after a partial tongue resection and reconstruction are not well established. The purpose of the present study was to assess the protrusion, grooving and symmetry of the tongue during sustained speech sound production using three-dimensional ultrasound. The participants were twelve normal…

  18. Automatic Prompting and Positive Attention to Reduce Tongue Protrusion and Head Tilting by Two Adults with Severe to Profound Intellectual Disabilities

    ERIC Educational Resources Information Center

    Lancioni, Giulio E.; Singh, Nirbhay N.; O'Reilly, Mark F.; Sigafoos, Jeff; Didden, Robert; Pichierri, Sabrina

    2010-01-01

    This study assessed a simple behavioral strategy for reducing stereotypic tongue protrusion and forward head tilting displayed by a woman and a man with severe to profound intellectual disabilities. The strategy involved (a) auditory prompting (i.e., verbal encouragements to keep the tongue in the mouth or the head upright) delivered automatically…

  19. Membrane Elastic Properties and Cell Function

    PubMed Central

    Pontes, Bruno; Ayala, Yareni; Fonseca, Anna Carolina C.; Romão, Luciana F.; Amaral, Racκele F.; Salgado, Leonardo T.; Lima, Flavia R.; Farina, Marcos; Viana, Nathan B.; Moura-Neto, Vivaldo; Nussenzveig, H. Moysés

    2013-01-01

    Recent studies indicate that the cell membrane, interacting with its attached cytoskeleton, is an important regulator of cell function, exerting and responding to forces. We investigate this relationship by looking for connections between cell membrane elastic properties, especially surface tension and bending modulus, and cell function. Those properties are measured by pulling tethers from the cell membrane with optical tweezers. Their values are determined for all major cell types of the central nervous system, as well as for macrophage. Astrocytes and glioblastoma cells, which are considerably more dynamic than neurons, have substantially larger surface tensions. Resting microglia, which continually scan their environment through motility and protrusions, have the highest elastic constants, with values similar to those for resting macrophage. For both microglia and macrophage, we find a sharp softening of bending modulus between their resting and activated forms, which is very advantageous for their acquisition of phagocytic functions upon activation. We also determine the elastic constants of pure cell membrane, with no attached cytoskeleton. For all cell types, the presence of F-actin within tethers, contrary to conventional wisdom, is confirmed. Our findings suggest the existence of a close connection between membrane elastic constants and cell function. PMID:23844071

  20. Membrane Supply and Demand Regulates F-Actin in a Cell Surface Reservoir.

    PubMed

    Figard, Lauren; Wang, Mengyu; Zheng, Liuliu; Golding, Ido; Sokac, Anna Marie

    2016-05-01

    Cells store membrane in surface reservoirs of pits and protrusions. These membrane reservoirs facilitate cell shape change and buffer mechanical stress, but we do not know how reservoir dynamics are regulated. During cellularization, the first cytokinesis in Drosophila embryos, a reservoir of microvilli unfolds to fuel cleavage furrow ingression. We find that regulated exocytosis adds membrane to the reservoir before and during unfolding. Dynamic F-actin deforms exocytosed membrane into microvilli. Single microvilli extend and retract in ∼20 s, while the overall reservoir is depleted in sync with furrow ingression over 60-70 min. Using pharmacological and genetic perturbations, we show that exocytosis promotes microvillar F-actin assembly, while furrow ingression controls microvillar F-actin disassembly. Thus, reservoir F-actin and, consequently, reservoir dynamics are regulated by membrane supply from exocytosis and membrane demand from furrow ingression. PMID:27165556

  1. Pinkbar is an epithelial-specific BAR domain protein that generates planar membrane structures

    SciTech Connect

    Pykäläinen, Anette; Boczkowska, Malgorzata; Zhao, Hongxia; Saarikangas, Juha; Rebowski, Grzegorz; Jansen, Maurice; Hakanen, Janne; Koskela, Essi V.; Peränen, Johan; Vihinen, Helena; Jokitalo, Eija; Salminen, Marjo; Ikonen, Elina; Dominguez, Roberto; Lappalainen, Pekka

    2013-05-29

    Bin/amphipysin/Rvs (BAR)-domain proteins sculpt cellular membranes and have key roles in processes such as endocytosis, cell motility and morphogenesis. BAR domains are divided into three subfamilies: BAR- and F-BAR-domain proteins generate positive membrane curvature and stabilize cellular invaginations, whereas I-BAR-domain proteins induce negative curvature and stabilize protrusions. We show that a previously uncharacterized member of the I-BAR subfamily, Pinkbar, is specifically expressed in intestinal epithelial cells, where it localizes to Rab13-positive vesicles and to the plasma membrane at intercellular junctions. Notably, the BAR domain of Pinkbar does not induce membrane tubulation but promotes the formation of planar membrane sheets. Structural and mutagenesis analyses reveal that the BAR domain of Pinkbar has a relatively flat lipid-binding interface and that it assembles into sheet-like oligomers in crystals and in solution, which may explain its unique membrane-deforming activity.

  2. Molecular modeling of membrane responses to the adsorption of rotating nanoparticles: promoted cell uptake and mechanical membrane rupture.

    PubMed

    Yue, Tongtao; Zhang, Xianren; Huang, Fang

    2015-01-21

    Recently, a unique dynamic magnetic field was developed to induce the rotational movement of superparamagnetic iron oxide nanoparticles. This technique has been applied to remotely control both cellular internalization and apoptosis. Therefore, a thorough understanding of how a lipid membrane responds to the introduction of rotating NPs is quite important to promote the applications of this technique in a variety of biomedical area. Here, we performed Dissipative Particle Dynamics (DPD) simulations to systematically investigate the interaction mechanism between lipid membranes and rotating NPs. Two kinds of membrane responses are observed. One is the promoted cell uptake and the other is the mechanical membrane rupture. The promoting effect of NP rotation on the cell uptake is ascribed to the enhanced membrane monolayer protrusion, which can wrap the NP from the top side. Meanwhile, the rotating NP exerts a shearing force on the membrane. Accordingly, the membrane undergoes a local distortion around the NP. If the shearing force exceeds a critical value, the local membrane distortion develops into a mechanical rupture. A number of factors, like NP size, NP shape, ligand density and rotation speed, are critical in both of the above membrane responses. PMID:25388826

  3. Membrane tension and membrane fusion.

    PubMed

    Kozlov, Michael M; Chernomordik, Leonid V

    2015-08-01

    Diverse cell biological processes that involve shaping and remodeling of cell membranes are regulated by membrane lateral tension. Here we focus on the role of tension in driving membrane fusion. We discuss the physics of membrane tension, forces that can generate the tension in plasma membrane of a cell, and the hypothesis that tension powers expansion of membrane fusion pores in late stages of cell-to-cell and exocytotic fusion. We propose that fusion pore expansion can require unusually large membrane tensions or, alternatively, low line tensions of the pore resulting from accumulation in the pore rim of membrane-bending proteins. Increase of the inter-membrane distance facilitates the reaction. PMID:26282924

  4. Membrane tethering

    PubMed Central

    Chia, Pei Zhi Cheryl

    2014-01-01

    Membrane trafficking depends on transport vesicles and carriers docking and fusing with the target organelle for the delivery of cargo. Membrane tethers and small guanosine triphosphatases (GTPases) mediate the docking of transport vesicles/carriers to enhance the efficiency of the subsequent SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-mediated fusion event with the target membrane bilayer. Different classes of membrane tethers and their specific intracellular location throughout the endomembrane system are now well defined. Recent biochemical and structural studies have led to a deeper understanding of the mechanism by which membrane tethers mediate docking of membrane carriers as well as an appreciation of the role of tethers in coordinating the correct SNARE complex and in regulating the organization of membrane compartments. This review will summarize the properties and roles of membrane tethers of both secretory and endocytic systems. PMID:25343031

  5. Electrostatic and electrokinetic contributions to the elastic moduli of a driven membrane

    NASA Astrophysics Data System (ADS)

    Lacoste, D.; Menon, G. I.; Bazant, M. Z.; Joanny, J. F.

    2009-03-01

    We discuss the electrostatic contribution to the elastic moduli of a cell or artificial membrane placed in an electrolyte and driven by a DC electric field. The field drives ion currents across the membrane, through specific channels, pumps or natural pores. In steady state, charges accumulate in the Debye layers close to the membrane, modifying the membrane elastic moduli. We first study a model of a membrane of zero thickness, later generalizing this treatment to allow for a finite thickness and finite dielectric constant. Our results clarify and extend the results presented by D. Lacoste, M. Cosentino Lagomarsino, and J.F. Joanny (EPL 77, 18006 (2007)), by providing a physical explanation for a destabilizing term proportional to k ⊥ 3 in the fluctuation spectrum, which we relate to a nonlinear (E2) electrokinetic effect called induced-charge electro-osmosis (ICEO). Recent studies of ICEO have focused on electrodes and polarizable particles, where an applied bulk field is perturbed by capacitive charging of the double layer and drives the flow along the field axis toward surface protrusions; in contrast, we predict “reverse” ICEO flows around driven membranes, due to curvature-induced tangential fields within a nonequilibrium double layer, which hydrodynamically enhance protrusions. We also consider the effect of incorporating the dynamics of a spatially dependent concentration field for the ion channels.

  6. Higher-order assemblies of BAR domain proteins for shaping membranes.

    PubMed

    Suetsugu, Shiro

    2016-06-01

    Most cellular organelles contain lipid bilayer membranes. The earliest characterization of cellular organelles was performed by electron microscopy observation of such membranes. However, the precise mechanisms for shaping the membrane in particular subcellular organelles is poorly understood. Classically, the overall cellular shape, i.e. the shape of the plasma membrane, was thought to be governed by the reorganization of cytoskeletal components such as actin and microtubules. The plasma membrane contains various submicron structures such as clathrin-coated pits, caveolae, filopodia and lamellipodia. These subcellular structures are either invaginations or protrusions and are associated with the cytoskeleton. Therefore, it could be hypothesized that there are membrane-binding proteins that cooperates with cytoskeleton in shaping of plasma membrane organelles. Proteins with the Bin-Amphiphysin-Rvs (BAR) domain connect a variety of membrane shapes to actin filaments. The BAR domains themselves bend the membranes by their rigidity and then mold the membranes into tubules through their assembly as spiral polymers, which are thought to be involved in the various submicron structures. Membrane tubulation by polymeric assembly of the BAR domains is supposed to be regulated by binding proteins, binding lipids and the mechanical properties of the membrane. This review gives an overview of BAR protein assembly, describes the significance of the assembly and discusses how to study the assembly in the context of membrane and cellular morphology. The technical problems encountered in microscopic observation of BAR domain assembly are also discussed. PMID:26884618

  7. Mobility of membrane-trapped particles

    NASA Astrophysics Data System (ADS)

    Masoud, Hassan; Stone, Howard

    2015-11-01

    The translation or diffusion of particles along membranes or interfaces is of interest because it is a model system for describing basic features of interfacial hydrodynamics. It is also important in cellular signalling in biology and biophysics, and it can be used to deduce the rheological properties of surface films. Here, we consider the translational mobility of spherical and oblate spheroidal particles protruding into the surrounding subphase liquid. Both the subphase and surface film contribute to the resistance experienced by the particle, which is calculated as a function of the degree of protrusion as well as the viscosity contrast between the surface film and the surrounding fluid. The calculations are based on a combination of a perturbation expansion involving the particle shape and the Lorentz reciprocal theorem. It appears that just considering one term of the expansions is in very good agreement with available analytical and numerical results.

  8. Numerical prediction of the performance of horizontal sand filters as the pitch of the spiral protrusion changes.

    PubMed

    Mossad, Ruth; Aral, Hal

    2013-01-01

    The height of vertical sand filters are limited due to their structural cost. A horizontal sand filter may offer a better alternative; however, flow channels to the least resistance zone generated at the top of the filter as the sand gets wet and settles. A horizontal sand filter, internally baffled with spiral protrusion, is numerically modelled to study the effect of these spirals in reducing the channelling and enhancing the filter's effectiveness. Three different spiral pitches, 1.0, 0.75, and 0.5 m have been numerically modelled using Ansys FLUENT software. The parameters investigated were the power needed to run a flow rate through the horizontal filter and the residence time. The results show that as the spiral pitch decreases, the channelling reduces while the power increases. The power needed to pump a given flow rate of water in a 10 m long horizontal filter in all three cases investigated was less than the power needed to pump the same flow rate to the top of a 10 m long vertically standing sand filter. Results also showed that the time required for the flow to traverse through the sand filter increases in a nonlinear fashion as the pitch size decreases; however, the effectiveness of the filter increases. PMID:23676395

  9. Dementia with Lewy bodies presenting marked tongue protrusion and bite due to lingual dystonia: A case report.

    PubMed

    Shiga, Yuji; Kanaya, Yuhei; Kono, Ryuhei; Takeshima, Shinichi; Shimoe, Yutaka; Kuriyama, Masaru

    2016-06-22

    We report the patient of a 53-year-old woman who developed subacute-onset marked tonge protrusion and bite. She was diagnosed as dementia with Lewy bodies (DLB) from the clinical features including progressive cognitive decline, visual hallucinations, parkinsonism, and severe insomnia and depression, and the radiological finding of low dopamine transported uptake in basal ganglia by Dat SCAN and low blood circulation in occipital lobe of cerebrum. The patient received 600 mg doses of levodopa for over a year, followed by rotigotine and ropinirole with a rapid increase of dosage. It is believed that these treatments stimulated and sensitized dopamine D1 receptors, thereby inducing lingual dystonia. Furthermore, the patient demonstrated dyspnea and attacks of apnea caused by the closure of bilateral vocal cords due to laryngeal dyskinesia. After initiation of the neuroleptic, olanzapine, for a short duration, the high dose of levodopa overlapped with neuroleptic sensitivity, suggesting DOPA-induced dystonia and dyskinesia. This interaction can sometimes lead to lethal adverse events, and must be considered very important when treating patients with DLB. PMID:27212676

  10. Interference of wedge-shaped protrusions on the faces of a Griffith crack in biaxial stress. Final report

    SciTech Connect

    Boulet, J.A.M.

    1992-04-01

    An initial investigation of the influence of protrusion interference on the fracture toughness required to prevent unstable propagation of a Griffith crack in a brittle material is described. The interference is caused by relative shear displacement of the crack faces when subjected to remote biaxial stress with neither principal stress parallel to the crack. It is shown that for room temperature cracks smaller than about one centimeter in silicon carbide, or about one millimeter in silicon nitride, the presence of interference changes the fracture stress. A mathematical model based on linear elasticity solutions and including multiple interference sites at arbitrarily specified positions on the crack is presented. Computations of the change in required fracture toughness and its dependence on wedge geometry (size and vertex angle), applied stresses (orientation and magnitude), and location of the interference site are discussed. Results indicate that a single interference site has only a slight effect on required toughness. However, the influence of interference increases monotonically with the number of interference sites. The two-dimensional model described herein is not accurate when the interference sites are closely spaced.

  11. Rubisco decrease is involved in chloroplast protrusion and Rubisco-containing body formation in soybean (Glycine max.) under salt stress.

    PubMed

    He, Yi; Yu, Chenliang; Zhou, Li; Chen, Yue; Liu, Ao; Jin, Junhua; Hong, Jian; Qi, Yanhua; Jiang, Dean

    2014-01-01

    Salt stress often induces declination of net photosynthetic rate (Pn), partially resulted from Rubisco degradation. The chloroplast protrusions (CPs) is one of the pathways of Rubisco exclusion from chloroplasts. To explore the relationship between the Rubisco contents and CPs under salt stress, Pn, maximum photochemical efficiency of PSII (F(v)/F(m)), carboxylation efficiency (CE) and concentration of Rubisco, number of CPs and Rubisco-containing Body (RCBs) were investigated with two differently salt-responding varieties in this experiment. We observed that 150 mM salt treatment resulted in not only significant decrease in Pn, CE and Rubisco content, but also obvious increase in the number of CPs and RCBs in salt-sensitive variety. Under salt stress formation of CPs resulted in production of much more RCBs, which could immigrate into and combine with vacuole. It may be a kind of important mechanism for rapid degradation of Rubisco under salt stress. Our conclusion provides a new sight for how Rubisco can be fast degraded under salt stress. PMID:24291158

  12. High Density Infill in Cracks and Protrusions from the Articular Calcified Cartilage in Osteoarthritis in Standardbred Horse Carpal Bones

    PubMed Central

    Laverty, Sheila; Lacourt, Mathieu; Gao, Chan; Henderson, Janet E.; Boyde, Alan

    2015-01-01

    We studied changes in articular calcified cartilage (ACC) and subchondral bone (SCB) in the third carpal bones (C3) of Standardbred racehorses with naturally-occurring repetitive loading-induced osteoarthritis (OA). Two osteochondral cores were harvested from dorsal sites from each of 15 post-mortem C3 and classified as control or as showing early or advanced OA changes from visual inspection. We re-examined X-ray micro-computed tomography (µCT) image sets for the presence of high-density mineral infill (HDMI) in ACC cracks and possible high-density mineralized protrusions (HDMP) from the ACC mineralizing (tidemark) front (MF) into hyaline articular cartilage (HAC). We hypothesized and we show that 20-µm µCT resolution in 10-mm diameter samples is sufficient to detect HDMI and HDMP: these are lost upon tissue decalcification for routine paraffin wax histology owing to their predominant mineral content. The findings show that µCT is sufficient to discover HDMI and HDMP, which were seen in 2/10 controls, 6/9 early OA and 8/10 advanced OA cases. This is the first report of HDMI and HDMP in the equine carpus and in the Standardbred breed and the first to rely solely on µCT. HDMP are a candidate cause for mechanical tissue destruction in OA. PMID:25927581

  13. Reaching for far-flung antigen: How solid-core podosomes of dendritic cells transform into protrusive structures

    PubMed Central

    Baranov, Maksim V; ter Beest, Martin; van den Bogaart, Geert

    2014-01-01

    We recently identified a novel role for podosomes in antigen sampling. Podosomes are dynamic cellular structures that consist of point-like concentrations of actin surrounded by integrins and adaptor proteins such as vinculin and talin. Podosomes establish cellular contact with the extracellular matrix (ECM) and facilitate cell migration via ECM degradation. In our recent paper, we studied podosomes of human dendritic cells (DCs), major antigen presenting cells (APC) that take-up, process, and present foreign antigen to naive T-cells. We employed gelatin-impregnated porous polycarbonate filters to demonstrate that the mechanosensitive podosomes of DCs selectively localize to regions of low-physical resistance such as the filter pores. After degradation of the gelatin, podosomes increasingly protrude into the lumen of these pores. These protrusive podosome-derived structures contain several endocytic and early endosomal markers such as clathrin, Rab5, and VAMP3, and, surprisingly, also contain C-type lectins, a type of pathogen recognition receptors (PRRs). Finally, we performed functional uptake experiments to demonstrate that these PRRs facilitate uptake of antigen from the opposite side of the filter. Our data provide mechanistic insight in how dendritic cells sample for antigen across epithelial barriers for instance from the lumen of the lung and gut. PMID:26843902

  14. High density infill in cracks and protrusions from the articular calcified cartilage in osteoarthritis in standardbred horse carpal bones.

    PubMed

    Laverty, Sheila; Lacourt, Mathieu; Gao, Chan; Henderson, Janet E; Boyde, Alan

    2015-01-01

    We studied changes in articular calcified cartilage (ACC) and subchondral bone (SCB) in the third carpal bones (C3) of Standardbred racehorses with naturally-occurring repetitive loading-induced osteoarthritis (OA). Two osteochondral cores were harvested from dorsal sites from each of 15 post-mortem C3 and classified as control or as showing early or advanced OA changes from visual inspection. We re-examined X-ray micro-computed tomography (µCT) image sets for the presence of high-density mineral infill (HDMI) in ACC cracks and possible high-density mineralized protrusions (HDMP) from the ACC mineralizing (tidemark) front (MF) into hyaline articular cartilage (HAC). We hypothesized and we show that 20-µm µCT resolution in 10-mm diameter samples is sufficient to detect HDMI and HDMP: these are lost upon tissue decalcification for routine paraffin wax histology owing to their predominant mineral content. The findings show that µCT is sufficient to discover HDMI and HDMP, which were seen in 2/10 controls, 6/9 early OA and 8/10 advanced OA cases. This is the first report of HDMI and HDMP in the equine carpus and in the Standardbred breed and the first to rely solely on µCT. HDMP are a candidate cause for mechanical tissue destruction in OA. PMID:25927581

  15. Target-specific mechanics of phagocytosis: protrusive neutrophil response to zymosan differs from the uptake of antibody-tagged pathogens

    PubMed Central

    Lee, Cheng-Yuk; Herant, Marc; Heinrich, Volkmar

    2011-01-01

    The physical mechanisms that control target-specific responses of human neutrophils to distinct immune threats are poorly understood. Using dual-micropipette manipulation, we have quantified and compared the time courses of neutrophil phagocytosis of two different targets: zymosan (a prominent model of fungal infection), and antibody-coated (Fc) particles. Our single-live-cell/single-target approach exposes surprising differences between these two forms of phagocytosis. Unlike the efficient uptake of 3-μm Fc targets (within ~66 seconds), the engulfment of similarly sized zymosan is slow (~167 seconds), mainly due to the formation of a characteristic pedestal that initially pushes the particle outwards by ~1 μm. Despite a roughly twofold difference in maximum cortical tensions, the top ‘pull-in’ speeds of zymosan and Fc targets are indistinguishable at ~33 nm/second. Drug inhibition shows that both actin as well as myosin II partake in the regulation of neutrophil cortical tension and cytoplasmic viscosity; other than that, myosin II appears to play a minor role in both forms of phagocytosis. Remarkably, an intact actin cytoskeleton is required to suppress, in antibody-mediated phagocytosis, the initially protrusive deformation that distinguishes the neutrophil response to zymosan. PMID:21385838

  16. Nanopore formation process in artificial cell membrane induced by plasma-generated reactive oxygen species.

    PubMed

    Tero, Ryugo; Yamashita, Ryuma; Hashizume, Hiroshi; Suda, Yoshiyuki; Takikawa, Hirofumi; Hori, Masaru; Ito, Masafumi

    2016-09-01

    We investigated morphological change of an artificial lipid bilayer membrane induced by oxygen radicals which were generated by non-equilibrium atmospheric pressure plasma. Neutral oxygen species, O((3)Pj) and O2((1)Δg), were irradiated of a supported lipid bilayer existing under a buffer solution at various conditions of dose time and distances, at which the dose amounts of the oxygen species were calculated quantitatively. Observation using an atomic force microscope and a fluorescence microscope revealed that dose of the neutral oxygen species generated nanopores with the diameter of 10-50 nm in a phospholipid bilayer, and finally destructed the bilayer structure. We found that protrusions appeared on the lipid bilayer surface prior to the formation of nanopores, and we attributed the protrusions to the precursor of the nanopores. We propose a mechanism of the pore formation induced by lipid oxidation on the basis of previous experimental and theoretical studies. PMID:27216034

  17. Listeria monocytogenes exploits efferocytosis to promote cell-to-cell spread

    PubMed Central

    Czuczman, Mark A.; Fattouh, Ramzi; van Rijn, Jorik; Canadien, Veronica; Osborne, Suzanne; Muise, Aleixo M.; Kuchroo, Vijay K.; Higgins, Darren E.; Brumell, John H.

    2014-01-01

    Efferocytosis, the process by which dying/dead cells are removed by phagocytosis, plays an important role in development, tissue homeostasis and innate immunity1. Efferocytosis is mediated, in part, by receptors that bind to exofacial phosphatidylserine (PS) on cells or cellular debris after loss of plasma membrane asymmetry. Here we show that a bacterial pathogen, Listeria monocytogenes (Lm), can exploit efferocytosis to promote cell-to-cell spread during infection. These bacteria can escape the phagosome in host cells using the pore-forming toxin Listeriolysin O (LLO) and two phospholipases C2. Expression of the cell surface protein ActA allows Lm to activate host actin regulatory factors and undergo actin-based motility in the cytosol, eventually leading to formation of actin-rich protrusions at the cell surface. We show that protrusion formation is associated with plasma membrane damage due to LLO’s pore-forming activity. LLO also promotes the release of bacteria-containing protrusions from the host cell, generating membrane-derived vesicles with exofacial PS. The PS-binding receptor TIM-4 contributes to efficient cell-to-cell spread by Lm in macrophages in vitro and growth of these bacteria is impaired in TIM-4−/− mice. Thus, Lm promotes its dissemination in a host by exploiting efferocytosis. Our study suggests that PS-targeted therapeutics may be useful in the fight against infections by Lm and other bacteria that utilize similar strategies of cell-to-cell spread during infection. PMID:24739967

  18. 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

  19. T-Stenting-and-Small-Protrusion Technique for Bifurcation Stenoses After End-to-Side Anastomosis of Transplant Renal Artery and External Iliac Artery: Report of Two Cases

    SciTech Connect

    Chen, Yong Ye, Peng; Jiang, Wen-jin; Ma, Shuo-yi Zhao, Jian-bo Zeng, Qing-le

    2015-10-15

    Bifurcation stenoses after end-to-side anastomosis of transplant renal artery (TRA) and external iliac artery (EIA), including stenoses at the anastomosis and the iliac artery proximal to the TRA, are rare. In the present article, we report two successfully managed cases of bifurcation stenoses after end-to-side anastomosis of the TRA and EIA using the technique of T-stenting and small protrusion (TAP stenting)

  20. Molecular design for growth of supramolecular membranes with hierarchical structure.

    PubMed

    Zha, R Helen; Velichko, Yuri S; Bitton, Ronit; Stupp, Samuel I

    2016-02-01

    Membranes with hierarchical structure exist in biological systems, and bio-inspired building blocks have been used to grow synthetic analogues in the laboratory through self-assembly. The formation of these synthetic membranes is initiated at the interface of two aqueous solutions, one containing cationic peptide amphiphiles (PA) and the other containing the anionic biopolymer hyaluronic acid (HA). The membrane growth process starts within milliseconds of interface formation and continues over much longer timescales to generate robust membranes with supramolecular PA-HA nanofibers oriented orthogonal to the interface. Computer simulation indicates that formation of these hierarchically structured membranes requires strong interactions between molecular components at early time points in order to generate a diffusion barrier between both solutions. Experimental studies using structurally designed PAs confirm simulation results by showing that only PAs with high ζ potential are able to yield hierarchically structured membranes. Furthermore, the chemical structure of such PAs must incorporate residues that form β-sheets, which facilitates self-assembly of long nanofibers. In contrast, PAs that form low aspect ratio nanostructures interact weakly with HA and yield membranes that exhibit non-fibrous fingering protrusions. Furthermore, experimental results show that increasing HA molecular weight decreases the growth rate of orthogonal nanofibers. This result is supported by simulation results suggesting that the thickness of the interfacial contact layer generated immediately after initiation of self-assembly increases with polymer molecular weight. PMID:26649980

  1. Membrane Processes.

    PubMed

    Pellegrin, Marie-Laure; Sadler, Mary E; Greiner, Anthony D; Aguinaldo, Jorge; Min, Kyungnan; Zhang, Kai; Arabi, Sara; Burbano, Marie S; Kent, Fraser; Shoaf, Robert

    2015-10-01

    This review, for literature published in 2014, contains information related to membrane processes for municipal and industrial applications. This review is a subsection of the Treatment Systems section of the annual Water Environment Federation literature review and covers the following topics: pretreatment, membrane bioreactor (MBR) configuration, design, nutrient removal, operation, industrial treatment, fixed film and anaerobic membrane systems, reuse, microconstituents removal, membrane technology advances, membrane fouling, and modeling. Other sub-sections of the Treatment Systems section that might relate to this literature review include: Biological Fixed-Film Systems, Activated Sludge and Other Aerobic Suspended Culture Processes, Anaerobic Processes, Water Reclamation and Reuse. The following sections might also have related information on membrane processes: Industrial Wastes, Hazardous Wastes, and Fate and Effects of Pollutants. PMID:26420079

  2. Membrane Processes.

    PubMed

    Pellegrin, Marie-Laure; Burbano, Marie S; Sadler, Mary E; Diamond, Jason; Baker, Simon; Greiner, Anthony D; Arabi, Sara; Wong, Joseph; Doody, Alexandra; Padhye, Lokesh P; Sears, Keith; Kistenmacher, Peter; Kent, Fraser; Tootchi, Leila; Aguinaldo, Jorge; Saddredini, Sara; Schilling, Bill; Min, Kyungnan; McCandless, Robert; Danker, Bryce; Gamage, Neranga P; Wang, Sunny; Aerts, Peter

    2016-10-01

    This review, for literature published in 2015, contains information related to membrane processes for municipal and industrial applications. This review is a subsection of the Treatment Systems section of the annual Water Environment Federation literature review and covers the following topics: pretreatment, membrane bioreactor (MBR) configuration, design, nutrient removal, operation, industrial treatment, anaerobic membrane systems, reuse, microconstituents removal, membrane technology advances, membrane fouling, and modeling. Other sub-sections of the Treatment Systems section that might relate to this literature review include: Biological Fixed-Film Systems, Activated Sludge and Other Aerobic Suspended Culture Processes, Anaerobic Processes, Water Reclamation and Reuse. The following sections might also have related information on membrane processes: Industrial Wastes, Hazardous Wastes, and Fate and Effects of Pollutants. PMID:27620084

  3. Multicomponent membranes

    DOEpatents

    Kulprathipanja, Santi; Kulkarni, Sudhir S.; Funk, Edward W.

    1988-01-01

    A multicomponent membrane which may be used for separating various components which are present in a fluid feed mixture comprises a mixture of a plasticizer such as a glycol and an organic polymer cast upon a porous organic polymer support. The membrane may be prepared by casting an emulsion or a solution of the plasticizer and polymer on the porous support, evaporating the solvent and recovering the membrane after curing.

  4. Randomized clinical trial comparing lumbar percutaneous hydrodiscectomy with lumbar open microdiscectomy for the treatment of lumbar disc protrusions and herniations

    PubMed Central

    Cristante, Alexandre Fogaça; Rocha, Ivan Diasda; Marcon, Raphael Martus; de Barros Filho, Tarcísio Eloy Pessoa

    2016-01-01

    OBJECTIVES: Hydrodiscectomy is a new technique used for percutaneous spinal discectomy that employs a high-intensity stream of water for herniated disc ablation and tissue aspiration. No previous clinical study has examined the effects of percutaneous hydrodiscectomy. The aim of this study is to evaluate the outcomes of hydrodiscectomy compared to open microdiscectomy regarding pain, function, satisfaction, complications and recurrence rates. METHODS: In this randomized clinical trial, patients referred to our tertiary hospital for lumbar back pain were recruited and included in the study if they had disc protrusion or small herniation in only one level, without neurological deficits and with no resolution after six weeks of conservative treatment. One group underwent open microdiscectomy, and the other group underwent percutaneous microdiscectomy via hydrosurgery. Function was evaluated using the Oswestry Disability Index and pain was assessed using a visual analog scale. Evaluations were performed preoperatively, and then during the first week and at one, three, six and twelve months postoperatively. Personal satisfaction was verified. Clinicaltrials.gov: NCT01367860. RESULTS: During the study period, 20 patients were included in each arm and 39 completed one-year of follow-up (one patient died of unrelated causes). Both groups exhibited equal improvement on the visual analog scale and Oswestry evaluations after treatment, without any significant differences. The improvement in the lumbar visual analog scale score was not significant in the hydrodiscectomy group (p=0.138). The rates of infection, pain, recurrence and satisfaction were similar between the two groups. CONCLUSION: Percutaneous hydrodiscectomy was demonstrated to be as effective as open microdiscectomy for reducing pain. The rates of complications and recurrence of herniation were similar between groups. Patient satisfaction with the treatment was also similar between groups. PMID:27276397

  5. MYADM regulates Rac1 targeting to ordered membranes required for cell spreading and migration.

    PubMed

    Aranda, Juan F; Reglero-Real, Natalia; Kremer, Leonor; Marcos-Ramiro, Beatriz; Ruiz-Sáenz, Ana; Calvo, María; Enrich, Carlos; Correas, Isabel; Millán, Jaime; Alonso, Miguel A

    2011-04-15

    Membrane organization into condensed domains or rafts provides molecular platforms for selective recruitment of proteins. Cell migration is a general process that requires spatiotemporal targeting of Rac1 to membrane rafts. The protein machinery responsible for making rafts competent to recruit Rac1 remains elusive. Some members of the MAL family of proteins are involved in specialized processes dependent on this type of membrane. Because condensed membrane domains are a general feature of the plasma membrane of all mammalian cells, we hypothesized that MAL family members with ubiquitous expression and plasma membrane distribution could be involved in the organization of membranes for cell migration. We show that myeloid-associated differentiation marker (MYADM), a protein with unique features within the MAL family, colocalizes with Rac1 in membrane protrusions at the cell surface and distributes in condensed membranes. MYADM knockdown (KD) cells had altered membrane condensation and showed deficient incorporation of Rac1 to membrane raft fractions and, similar to Rac1 KD cells, exhibited reduced cell spreading and migration. Results of rescue-of-function experiments by expression of MYADM or active Rac1L61 in cells knocked down for Rac1 or MYADM, respectively, are consistent with the idea that MYADM and Rac1 act on parallel pathways that lead to similar functional outcomes. PMID:21325632

  6. Patterned ion exchange membranes for improved power production in microbial reverse-electrodialysis cells

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Geise, Geoffrey M.; Luo, Xi; Hou, Huijie; Zhang, Fang; Feng, Yujie; Hickner, Michael A.; Logan, Bruce E.

    2014-12-01

    Power production in microbial reverse-electrodialysis cells (MRCs) can be limited by the internal resistance of the reverse electrodialysis stack. Typical MRC stacks use non-conductive spacers that block ion transport by the so-called spacer shadow effect. These spacers can be relatively thick compared to the membrane, and thus they increase internal stack resistance due to high solution (ohmic) resistance associated with a thick spacer. New types of patterned anion and cation exchange membranes were developed by casting membranes to create hemispherical protrusions on the membranes, enabling fluid flow between the membranes without the need for a non-conductive spacer. The use of the patterned membrane decreased the MRC stack resistance by ∼22 Ω, resulting in a 38% increase in power density from 2.50 ± 0.04 W m-2 (non-patterned membrane with a non-conductive spacer) to 3.44 ± 0.02 W m-2 (patterned membrane). The COD removal rate, coulombic efficiency, and energy efficiency of the MRC also increased using the patterned membranes compared to the non-patterned membranes. These results demonstrate that these patterned ion exchange membranes can be used to improve performance of an MRC.

  7. Formation of membrane ridges and scallops by the F-BAR protein Nervous Wreck

    PubMed Central

    Becalska, Agata N.; Kelley, Charlotte F.; Berciu, Cristina; Stanishneva-Konovalova, Tatiana B.; Fu, Xiaofeng; Wang, ShiYu; Sokolova, Olga S.; Nicastro, Daniela; Rodal, Avital A.

    2013-01-01

    Eukaryotic cells are defined by extensive intracellular compartmentalization, which requires dynamic membrane remodeling. FER/Cip4 homology-Bin/amphiphysin/Rvs (F-BAR) domain family proteins form crescent-shaped dimers, which can bend membranes into buds and tubules of defined geometry and lipid composition. However, these proteins exhibit an unexplained wide diversity of membrane-deforming activities in vitro and functions in vivo. We find that the F-BAR domain of the neuronal protein Nervous Wreck (Nwk) has a novel higher-order structure and membrane-deforming activity that distinguishes it from previously described F-BAR proteins. The Nwk F-BAR domain assembles into zigzags, creating ridges and periodic scallops on membranes in vitro. This activity depends on structural determinants at the tips of the F-BAR dimer and on electrostatic interactions of the membrane with the F-BAR concave surface. In cells, Nwk-induced scallops can be extended by cytoskeletal forces to produce protrusions at the plasma membrane. Our results define a new F-BAR membrane-deforming activity and illustrate a molecular mechanism by which positively curved F-BAR domains can produce a variety of membrane curvatures. These findings expand the repertoire of F-BAR domain mediated membrane deformation and suggest that unique modes of higher-order assembly can define how these proteins sculpt the membrane. PMID:23761074

  8. Membrane-Sculpting BAR Domains Generate Stable Lipid Microdomains

    PubMed Central

    Zhao, Hongxia; Michelot, Alphée; Koskela, Essi V.; Tkach, Vadym; Stamou, Dimitrios; Drubin, David G.; Lappalainen, Pekka

    2014-01-01

    SUMMARY Bin-Amphiphysin-Rvs (BAR) domain proteins are central regulators of many cellular processes involving membrane dynamics. BAR domains sculpt phosphoinositide-rich membranes to generate membrane protrusions or invaginations. Here, we report that, in addition to regulating membrane geometry, BAR domains can generate extremely stable lipid microdomains by “freezing” phosphoinositide dynamics. This is a general feature of BAR domains, because the yeast endocytic BAR and Fes/CIP4 homology BAR (F-BAR) domains, the inverse BAR domain of Pinkbar, and the eisosomal BAR protein Lsp1 induced phosphoinositide clustering and halted lipid diffusion, despite differences in mechanisms of membrane interactions. Lsp1 displays comparable low diffusion rates in vitro and in vivo, suggesting that BAR domain proteins also generate stable phosphoinositide microdomains in cells. These results uncover a conserved role for BAR superfamily proteins in regulating lipid dynamics within membranes. Stable microdomains induced by BAR domain scaffolds and specific lipids can generate phase boundaries and diffusion barriers, which may have profound impacts on diverse cellular processes. PMID:24055060

  9. An Effector Domain Mutant of Arf6 Implicates Phospholipase D in Endosomal Membrane RecyclingD⃞

    PubMed Central

    Jovanovic, Olivera A.; Brown, Fraser D.; Donaldson, Julie G.

    2006-01-01

    In this study, we investigated the role of phospholipase D (PLD) in mediating Arf6 function in cells. Expression of Arf6 mutants that are defective in activating PLD, Arf6N48R and Arf6N48I, inhibited membrane recycling to the plasma membrane (PM), resulting in an accumulation of tubular endosomal membranes. Additionally, unlike wild-type Arf6, neither Arf6 mutant could generate protrusions or recruit the Arf6 GTPase activating protein (GAP) ACAP1 onto the endosome in the presence of aluminum fluoride. Remarkably, all of these phenotypes, including accumulated tubular endosomes, blocked recycling, and failure to make protrusions and recruit ACAP effectively, could be recreated in either untransfected cells or cells expressing wild-type Arf6 by treatment with 1-butanol to inhibit the formation of phosphatidic acid (PA), the product of PLD. Moreover, most of the defects present in cells expressing Arf6N48R or N48I could be reversed by treatment with agents expected to elevate PA levels in cells. Together, these observations provide compelling evidence that Arf6 stimulation of PLD is required for endosomal membrane recycling and GAP recruitment. PMID:16280360

  10. Tks5-dependent, Nox-mediated Generation of Reactive Oxygen Species is Necessary for Invadopodia Formation*

    PubMed Central

    Diaz, Begoña; Shani, Gidon; Pass, Ian; Anderson, Diana; Quintavalle, Manuela; Courtneidge, Sara A.

    2009-01-01

    Invadopodia are actin-rich membrane protrusions of cancer cells which facilitate pericellular proteolysis and invasive behavior. We show here that reactive oxygen species (ROS) generated by the NADPH oxidase (Nox) system are necessary for invadopodia formation and function. The invadopodia protein Tks5 is structurally related to p47phox, a Nox component in phagocytic cells. Knockdown of Tks5 reduces total ROS levels in cancer cells. Furthermore, Tks5 and p22phox can associate with each other, suggesting that Tks5 is part of the Nox complex. Tyrosine phosphorylation of Tks5 and Tks4, but not other Src substrates, is reduced by Nox inhibition. We propose that Tks5 facilitates the production of ROS necessary for invadopodia formation, and that in turn ROS modulates Tks5 tyrosine phosphorylation in a positive feedback loop. PMID:19755709

  11. Crystalline Membranes

    NASA Technical Reports Server (NTRS)

    Tsapatsis, Michael (Inventor); Lai, Zhiping (Inventor)

    2008-01-01

    In certain aspects, the invention features methods for forming crystalline membranes (e.g., a membrane of a framework material, such as a zeolite) by inducing secondary growth in a layer of oriented seed crystals. The rate of growth of the seed crystals in the plane of the substrate is controlled to be comparable to the rate of growth out of the plane. As a result, a crystalline membrane can form a substantially continuous layer including grains of uniform crystallographic orientation that extend through the depth of the layer.

  12. Biological membranes

    PubMed Central

    Watson, Helen

    2015-01-01

    Biological membranes allow life as we know it to exist. They form cells and enable separation between the inside and outside of an organism, controlling by means of their selective permeability which substances enter and leave. By allowing gradients of ions to be created across them, membranes also enable living organisms to generate energy. In addition, they control the flow of messages between cells by sending, receiving and processing information in the form of chemical and electrical signals. This essay summarizes the structure and function of membranes and the proteins within them, and describes their role in trafficking and transport, and their involvement in health and disease. Techniques for studying membranes are also discussed. PMID:26504250

  13. Membranous nephropathy

    MedlinePlus

    ... to reduce cholesterol and triglyceride levels (most often statins) may be recommended. A low-salt diet may ... of membranous nephropathy Your symptoms get worse or don't go away You develop new symptoms You have ...

  14. Interaction of myosin VI and its binding partner DOCK7 plays an important role in NGF-stimulated protrusion formation in PC12 cells.

    PubMed

    Sobczak, Magdalena; Chumak, Vira; Pomorski, Paweł; Wojtera, Emilia; Majewski, Łukasz; Nowak, Jolanta; Yamauchi, Junji; Rędowicz, Maria Jolanta

    2016-07-01

    DOCK7 (dedicator of cytokinesis 7) is a guanidine nucleotide exchange factor (GEF) for Rac1 GTPase that is involved in neuronal polarity and axon generation as well in Schwann cell differentiation and myelination. Recently, we identified DOCK7 as the binding partner of unconventional myosin VI (MVI) in neuronal-lineage PC12 cells and postulated that this interaction could be important in vivo [Majewski et al. (2012) Biochem Cell Biol., 90:565-574]. Herein, we found that MVI-DOCK7 interaction takes also place in other cell lines and demonstrated that MVI cargo domain via its RRL motif binds to DOCK7 C-terminal M2 and DHR2 domains. In MVI knockdown cells, lower Rac1 activity and a decrease of DOCK7 phosphorylation on Tyr1118 were observed, indicating that MVI could contribute to DOCK7 activity. MVI and DOCK7 co-localization was maintained during NGF-stimulated PC12 cell differentiation and observed also in the outgrowths. Also, during differentiation an increase in phosphorylation of DOCK7 as well as of its downstream effector JNK kinase was detected. Interestingly, overexpression of GFP-tagged MVI cargo domain (GFP-GT) impaired protrusion formation indicating that full length protein is important for this process. Moreover, a transient increase in Rac activity observed at 5min of NGF-stimulated differentiation of PC12 cells (overexpressing either GFP or GFP-MVI) was not detected in cells overexpressing the cargo domain. These data indicate that MVI-DOCK7 interaction could have functional implications in the protrusion outgrowth, and full length MVI seems to be important for delivery and maintenance of DOCK7 along the protrusions, and exerting its GEF activity. PMID:27018747

  15. Protrusive intrusion, dehydration and polymorphism in minerals as possible reason of seismic activity, relation between ophiolite belts and seismic zonation of the territory of Armenia

    NASA Astrophysics Data System (ADS)

    Harutyunyan, A. V.; Petrosyan, H. M.

    2010-05-01

    In the basis of multiple geological and geophysical data, also on the results of investigations seismic and density properties of rocks at high termobaric conditions, we proposed the petrophisical section and model of evolution of Earth crust of the territory of Armenia. On the proposed model the following interrelated problems are debated: forming of ophiolite belts and volcanic centers, genesis of hydrocarbons by organic and inorganic ways, and also reasons of originating of seismic centers. The reasons of originating of seismic centers in different depths of Earth crust, are miscellaneous. According to the model of Earth crust evolution the ophiolite belts are formed due to permanent protrusive intrusion of serpentinized masses from the foot of the crust (35-50km) into upper horizons. It is natural to assume, that the permanent intrusion of serpentinizd masses through deep faults has drastically occurred accompanying with seismic shakings. This process encourages the development of deep faults. The protrusive intrusion of serpentinized masse accompanied with partial dehydration of serpentinites and serpentinized ultrabasites and new mineral formation. The processes was accompanied also with drastic change of seismic waves and volumes up to 30%. Experiments at high termobaric conditions show, that some minerals undergone polymorphous transformations, accompanied with phase change and drastic change of rocks volume. Particularly plastic calcite, included in the composition of metamorphic rocks to run into the cracks expends and diversifies them. The process described cause some general effects similar to those of the process of dilatancy. Therefore, the protrusive intrusion of serpentinized masses into upper horizons, it dehydrations and polymorphous transformations in different minerals, may be cause of geo-dynamic processes at different depths of Earth crust. It may be assumed, that those processes permanently occur nowadays as well. Comparing the maps of

  16. Formation of chloroplast protrusions and catalase activity in alpine Ranunculus glacialis under elevated temperature and different CO2/O2 ratios.

    PubMed

    Buchner, Othmar; Moser, Tim; Karadar, Matthias; Roach, Thomas; Kranner, Ilse; Holzinger, Andreas

    2015-11-01

    Chloroplast protrusions (CPs) have frequently been observed in plants, but their significance to plant metabolism remains largely unknown. We investigated in the alpine plant Ranunculus glacialis L. treated under various CO2 concentrations if CP formation is related to photorespiration, specifically focusing on hydrogen peroxide (H2O2) metabolism. Immediately after exposure to different CO2 concentrations, the formation of CPs in leaf mesophyll cells was assessed and correlated to catalase (CAT) and ascorbate peroxidase (APX) activities. Under natural irradiation, the relative proportion of chloroplasts with protrusions (rCP) was highest (58.7 %) after exposure to low CO2 (38 ppm) and was lowest (3.0 %) at high CO2 (10,000 ppm). The same relationship was found for CAT activity, which decreased from 34.7 nkat mg(-1) DW under low CO2 to 18.4 nkat mg(-1) DW under high CO2, while APX activity did not change significantly. When exposed to natural CO2 concentration (380 ppm) in darkness, CP formation was significantly lower (18.2 %) compared to natural solar irradiation (41.3 %). In summary, CP formation and CAT activity are significantly increased under conditions that favour photorespiration, while in darkness or at high CO2 concentration under light, CP formation is significantly lower, providing evidence for an association between CPs and photorespiration. PMID:25701381

  17. Vocal anatomy, tongue protrusion behaviour and the acoustics of rutting roars in free-ranging Iberian red deer stags (Cervus elaphus hispanicus)

    PubMed Central

    Frey, Roland; Volodin, Ilya; Volodina, Elena; Carranza, Juan; Torres-Porras, Jerónimo

    2012-01-01

    Roaring in rutting Iberian red deer stags Cervus elaphus hispanicus is unusual compared to other subspecies of red deer, which radiated from the Iberian refugium after the last glacial maximum. In all red deer stags, the larynx occupies a permanent low mid-neck resting position and is momentarily retracted almost down to the rostral end of the sternum during the production of rutting calls. Simultaneous with the retraction of the larynx, male Iberian red deer pronouncedly protrude the tongue during most of their rutting roars. This poses a mechanical challenge for the vocal tract (vt) and for the hyoid apparatus, as tongue and larynx are strongly pulled in opposite directions. This study (i) examines the vocal anatomy and the acoustics of the rutting roars in free-ranging male C. e. hispanicus; (ii) establishes a potential mechanism of simultaneous tongue protrusion and larynx retraction by applying a two-dimensional model based on graphic reconstructions in single video frames of unrestrained animals; and (iii) advances a hypothesis of evaporative cooling by tongue protrusion in the males of a subspecies of red deer constrained to perform all of the exhausting rutting activities, including acoustic display, in a hot and arid season. PMID:22257361

  18. Broadening the Spectrum of Actin-Based Protrusive Activity Mediated by Arp2/3 Complex-Facilitated Polymerization: Motility of Cytoplasmic Ridges and Tubular Projections

    PubMed Central

    Henson, John H.; Gianakas, Anastasia D.; Henson, Lauren H.; Lakin, Christina L.; Voss, Meagen K.; Bewersdorf, Joerg; Oldenbourg, Rudolf; Morris, Robert L.

    2014-01-01

    Arp2/3 complex-facilitated actin polymerization plays an essential role in a variety of cellular functions including motility, adherence, endocytosis and trafficking. In the present study we employ the sea urchin coelomocyte experimental model system to test the hypotheses that Arp2/3 complex-nucleated actin assembly mediates the motility of two unusual cellular protrusions; the cytoplasmic ridges present during coelomocyte spreading, and inducible, tubular-shaped, and neurite-like projections. Our investigations couple pharmacological manipulation employing inhibitors of actin polymerization and the Arp2/3 complex with a wide array of imaging methods including digitally enhanced phase contrast, DIC and polarization light microscopy of live cells; conventional, confocal and super-resolution light microscopy of fluorescently labeled cells; and scanning and transmission electron microscopy. Taken together, the results of this study indicate that Arp2/3 complex-facilitated actin polymerization underlies the motility of coelomocyte cytoplasmic ridges and tubular projections, that these processes are related to each other, and that they have been preliminarily identified in other cell types. The results also highlight the broad spectrum of actin-based protrusive activities dependent on the Arp2/3 complex and provide additional insights into the pervasive nature of this ubiquitous actin nucleator. Furthermore we provide the first evidence of a possible mechanistic difference between the impacts of the small molecule drugs BDM and CK666 on the Arp2/3 complex. PMID:25111797

  19. Membrane magic

    SciTech Connect

    Buecker, B.

    2005-09-01

    The Kansas Power and Light Co.'s La Cyne generating station has found success with membrane filtration water pretreatment technology. The article recounts the process followed in late 2004 to install a Pall Aria 4 microfilter in Unit 1 makeup water system at the plant to produce cleaner water for reverse osmosis feed. 2 figs., 2 photos.

  20. F-actin-rich contractile endothelial pores prevent vascular leakage during leukocyte diapedesis through local RhoA signalling

    PubMed Central

    Heemskerk, Niels; Schimmel, Lilian; Oort, Chantal; van Rijssel, Jos; Yin, Taofei; Ma, Bin; van Unen, Jakobus; Pitter, Bettina; Huveneers, Stephan; Goedhart, Joachim; Wu, Yi; Montanez, Eloi; Woodfin, Abigail; van Buul, Jaap D.

    2016-01-01

    During immune surveillance and inflammation, leukocytes exit the vasculature through transient openings in the endothelium without causing plasma leakage. However, the exact mechanisms behind this intriguing phenomenon are still unknown. Here we report that maintenance of endothelial barrier integrity during leukocyte diapedesis requires local endothelial RhoA cycling. Endothelial RhoA depletion in vitro or Rho inhibition in vivo provokes neutrophil-induced vascular leakage that manifests during the physical movement of neutrophils through the endothelial layer. Local RhoA activation initiates the formation of contractile F-actin structures that surround emigrating neutrophils. These structures that surround neutrophil-induced endothelial pores prevent plasma leakage through actomyosin-based pore confinement. Mechanistically, we found that the initiation of RhoA activity involves ICAM-1 and the Rho GEFs Ect2 and LARG. In addition, regulation of actomyosin-based endothelial pore confinement involves ROCK2b, but not ROCK1. Thus, endothelial cells assemble RhoA-controlled contractile F-actin structures around endothelial pores that prevent vascular leakage during leukocyte extravasation. PMID:26814335

  1. F-actin-rich contractile endothelial pores prevent vascular leakage during leukocyte diapedesis through local RhoA signalling.

    PubMed

    Heemskerk, Niels; Schimmel, Lilian; Oort, Chantal; van Rijssel, Jos; Yin, Taofei; Ma, Bin; van Unen, Jakobus; Pitter, Bettina; Huveneers, Stephan; Goedhart, Joachim; Wu, Yi; Montanez, Eloi; Woodfin, Abigail; van Buul, Jaap D

    2016-01-01

    During immune surveillance and inflammation, leukocytes exit the vasculature through transient openings in the endothelium without causing plasma leakage. However, the exact mechanisms behind this intriguing phenomenon are still unknown. Here we report that maintenance of endothelial barrier integrity during leukocyte diapedesis requires local endothelial RhoA cycling. Endothelial RhoA depletion in vitro or Rho inhibition in vivo provokes neutrophil-induced vascular leakage that manifests during the physical movement of neutrophils through the endothelial layer. Local RhoA activation initiates the formation of contractile F-actin structures that surround emigrating neutrophils. These structures that surround neutrophil-induced endothelial pores prevent plasma leakage through actomyosin-based pore confinement. Mechanistically, we found that the initiation of RhoA activity involves ICAM-1 and the Rho GEFs Ect2 and LARG. In addition, regulation of actomyosin-based endothelial pore confinement involves ROCK2b, but not ROCK1. Thus, endothelial cells assemble RhoA-controlled contractile F-actin structures around endothelial pores that prevent vascular leakage during leukocyte extravasation. PMID:26814335

  2. [Membranous nephropathy].

    PubMed

    Mercadal, Lucile

    2013-12-01

    Membranous nephropathy is characterized by immune complex deposits on the outer side of the glomerular basement membrane. Activation of complement and of oxidation lead to basement membrane lesions. The most frequent form is idiopathic. At 5 and 10 years, renal survival is around 90 and 65% respectively. A prognostic model based on proteinuria, level and duration, progression of renal failure in a few months can refine prognosis. The urinary excretion of C5b-9, β2 and α1 microglobuline and IgG are strong predictors of outcome. Symptomatic treatment is based on anticoagulation in case of nephrotic syndrome, angiotensin conversion enzyme inhibitors, angiotensin II receptor blockers and statins. Immunosuppressive therapy should be discussed for patients having a high risk of progression. Corticoids alone has no indication. Treatment should include a simultaneous association or more often alternating corticoids and alkylant agent for a minimum of 6 months. Adrenocorticoid stimulating hormone and steroids plus mycophenolate mofetil may be equally effective. Steroids plus alkylant decrease the risk of end stage renal failure. Cyclosporine and tacrolimus decrease proteinuria but are associated with a high risk of recurrence at time of withdrawal and are nephrotoxic. Rituximab evaluated on open studies needs further evaluations to define its use. PMID:24315535

  3. A novel mechanism of generating extracellular vesicles during apoptosis via a beads-on-a-string membrane structure

    PubMed Central

    Atkin-Smith, Georgia K.; Tixeira, Rochelle; Paone, Stephanie; Mathivanan, Suresh; Collins, Christine; Liem, Michael; Goodall, Katharine J.; Ravichandran, Kodi S.; Hulett, Mark D.; Poon, Ivan K.H.

    2015-01-01

    Disassembly of apoptotic cells into smaller fragments (a form of extracellular vesicle called apoptotic bodies) can facilitate removal of apoptotic debris and intercellular communication. However, the mechanism underpinning this process is unclear. While observing monocytes undergoing apoptosis by time-lapse microscopy, we discovered a new type of membrane protrusion that resembles a ‘beads-on-a-string' structure. Strikingly, the ‘beads' are frequently sheared off the ‘string' to form apoptotic bodies. Generation of apoptotic bodies via this mechanism can facilitate a sorting process and results in the exclusion of nuclear contents from apoptotic bodies. Mechanistically, generation of ‘beads-on-a-string' protrusion is controlled by the level of actomyosin contraction and apoptopodia formation. Furthermore, in an unbiased drug screen, we identified the ability of sertraline (an antidepressant) to block the formation of ‘beads-on-a-string' protrusions and apoptotic bodies. These data uncover a new mechanism of apoptotic body formation in monocytes and also compounds that can modulate this process. PMID:26074490

  4. Breakdown of interlocking domains may contribute to formation of membranous globules and lens opacity in ephrin-A5(-/-) mice.

    PubMed

    Biswas, Sondip; Son, Alexander; Yu, Qili; Zhou, Renping; Lo, Woo-Kuen

    2016-04-01

    Ephrin-A5, a ligand of the Eph family of receptor tyrosine kinases, plays a key role in lens fiber cell packing and cell-cell adhesion, with approximately 87% of ephrin-A5(-/-) mice develop nuclear cataracts. Here, we investigated the extensive formation of light-scattering globules associated with breakdown of interlocking protrusions during lens opacification in ephrin-A5(-/-) mice. Lenses from wild-type (WT) and ephrin-A5(-/-) mice between 2 and 21 weeks old were studied with light and electron microscopy, immunofluorescence labeling, freeze-fracture TEM and filipin cytochemistry for membrane cholesterol detection. Lens opacities with various densities were first observed in ephrin-A5(-/-) mice at around 60 days old. Dense cataracts in the mutant lenses were seen primarily in the nuclear region surrounded by transparent cortices from all eyes examined. We confirmed that a majority of nuclear cataracts were dislocated posteriorly and ruptured the thinner posterior lens capsule. SEM analysis indicated that numerous interlocking protrusions and wavy ridge-and-valley membrane surfaces in deep cortical and nuclear fibers did not cause lens opacity in both transparent ephrin-A5(-/-) and WT mice. In contrast, abundant isolated membranous globules of approximately 1000 nm in size were distributed randomly along the intact fiber cells during early stage of all ephrin-A5(-/-) cataracts examined. A further examination using both SEM and TEM revealed that isolated globules were generated from the disintegrated interlocking protrusions originally located along the corners of hexagonal fiber cells. Freeze-fracture TEM further revealed the association of square-array aquaporin junctions with both isolated globules and interlocking membrane domains. This study reports for the first time that disrupted interlocking protrusions are the source of numerous large membranous globules that contribute to light scattering and nuclear cataracts in the ephrin-A5(-/-) mice. Our results

  5. Three-dimensional evaluation of upper anterior alveolar bone dehiscence after incisor retraction and intrusion in adult patients with bimaxillary protrusion malocclusion*

    PubMed Central

    Guo, Qing-yuan; Zhang, Shi-jie; Liu, Hong; Wang, Chun-ling; Wei, Fu-lan; Lv, Tao; Wang, Na-na; Liu, Dong-xu

    2011-01-01

    Objective: The purpose of this study was to evaluate three-dimensional (3D) dehiscence of upper anterior alveolar bone during incisor retraction and intrusion in adult patients with maximum anchorage. Methods: Twenty adult patients with bimaxillary dentoalveolar protrusion had the four first premolars extracted. Miniscrews were placed to provide maximum anchorage for upper incisor retraction and intrusion. A computed tomography (CT) scan was performed after placement of the miniscrews and treatment. The 3D reconstructions of pre- and post-CT data were used to assess the dehiscence of upper anterior alveolar bone. Results: The amounts of upper incisor retraction at the edge and apex were (7.64±1.68) and (3.91±2.10) mm, respectively, and (1.34±0.74) mm of upper central incisor intrusion. Upper alveolar bone height losses at labial alveolar ridge crest (LAC) and palatal alveolar ridge crest (PAC) were 0.543 and 2.612 mm, respectively, and the percentages were (6.49±3.54)% and (27.42±9.77)%, respectively. The shape deformations of LAC-labial cortex bending point (LBP) and PAC-palatal cortex bending point (PBP) were (15.37±5.20)° and (6.43±3.27)°, respectively. Conclusions: Thus, for adult patients with bimaxillary protrusion, mechanobiological response of anterior alveolus should be taken into account during incisor retraction and intrusion. Pursuit of maximum anchorage might lead to upper anterior alveolar bone loss. PMID:22135148

  6. The Threefold Protrusions of Adeno-Associated Virus Type 8 Are Involved in Cell Surface Targeting as Well as Postattachment Processing

    PubMed Central

    Raupp, Christina; Naumer, Matthias; Müller, Oliver J.; Gurda, Brittney L.; Agbandje-McKenna, Mavis

    2012-01-01

    Adeno-associated virus (AAV) has attracted considerable interest as a vector for gene therapy owing its lack of pathogenicity and the wealth of available serotypes with distinct tissue tropisms. One of the most promising isolates for vector development, based on its superior gene transfer efficiency to the liver in small animals compared to AAV type 2 (AAV2), is AAV8. Comparison of the in vivo gene transduction of rAAV2 and rAAV8 in mice showed that single amino acid exchanges in the 3-fold protrusions of AAV8 in the surface loops comprised of residues 581 to 584 and 589 to 592 to the corresponding amino acids of AAV2 and vice versa had a strong influence on transduction efficiency and tissue tropism. Surprisingly, not only did conversion of AAV8 to AAV2 cap sequences increase the transduction efficiency and change tissue tropism but so did the reciprocal conversion of AAV2 to AAV8. Insertion of new peptide motifs at position 590 in AAV8 also enabled retargeting of AAV8 capsids to specific tissues, suggesting that these sequences can interact with receptors on the cell surface. However, a neutralizing monoclonal antibody that binds to amino acids 588QQNTA592 of AAV8 does not prevent cell binding and virus uptake, indicating that this region is not necessary for receptor binding but rather that the antibody interferes with an essential step of postattachment processing in which the 3-fold protrusion is also involved. This study supports a multifunctional role of the 3-fold region of AAV capsids in the infection process. PMID:22718833

  7. Intra-observer reliability for measuring first and second toe and metatarsal protrusion distance using palpation-based tests: a test-retest study

    PubMed Central

    2014-01-01

    Background Measurement of first and second metatarsal and toe protrusion is frequently used to explain foot problems using x-rays, osteological measurements or palpation-based tests. Length differences could be related to the appearance of problems in the foot. A test-retest design was conducted in order to establish the intra-rater reliability of three palpation-based tests. Methods 202 feet of physical therapy students and teachers of the CEU San Pablo University of Madrid, 39 men and 62 women, were measured using three different tests. Data were analysed using SPSS version 15.0. Mean, SD and 95% CI were calculated for each variable. A normal distribution of quantitative data was assessed using the Kolmogorov-Smirnov test. The test-retest intra-rater reliability was assessed using an Intraclass Correlation Coefficient (ICC). The Standard Error Mean (SEM) and the Minimal Detectable Change (MDC) were also obtained. Results All the ICC values showed a high degree of reliability (Test 1 = 0.97, Test 2 = 0.86 and Test 3 = 0.88) as did the SEM (Test 1 = 0.07, Test 2 = 0.10 and Test 3 = 0.11) and the MDC (Test 1 = 0.21, Test 2 = 0.30 and Test 3 = 0.31). Conclusions Reliability of measuring first and second metatarsal and toe protrusion using the three palpation-based tests showed a high degree of reliability. PMID:25729437

  8. Lipid membranes for membrane proteins.

    PubMed

    Kukol, Andreas

    2015-01-01

    The molecular dynamics (MD) simulation of membrane proteins requires the setup of an accurate representation of lipid bilayers. This chapter describes the setup of a lipid bilayer system from scratch using generally available tools, starting with a definition of the lipid molecule POPE, generation of a lipid bilayer, energy minimization, MD simulation, and data analysis. The data analysis includes the calculation of area and volume per lipid, deuterium order parameters, self-diffusion constant, and the electron density profile. PMID:25330959

  9. Omniphobic Membrane for Robust Membrane Distillation

    SciTech Connect

    Lin, SH; Nejati, S; Boo, C; Hu, YX; Osuji, CO; Ehmelech, M

    2014-11-01

    In this work, we fabricate an omniphobic microporous membrane for membrane distillation (MD) by modifying a hydrophilic glass fiber membrane with silica nanoparticles followed by surface fluorination and polymer coating. The modified glass fiber membrane exhibits an anti-wetting property not only against water but also against low surface tension organic solvents that easily wet a hydrophobic polytetrafluoroethylene (PTFE) membrane that is commonly used in MD applications. By comparing the performance of the PTFE and omniphobic membranes in direct contact MD experiments in the presence of a surfactant (sodium dodecyl sulfate, SDS), we show that SDS wets the hydrophobic PTFE membrane but not the omniphobic membrane. Our results suggest that omniphobic membranes are critical for MD applications with feed waters containing surface active species, such as oil and gas produced water, to prevent membrane pore wetting.

  10. The flatness of Lamellipodia explained by the interaction between actin dynamics and membrane deformation.

    PubMed

    Schmeiser, Christian; Winkler, Christoph

    2015-09-01

    The crawling motility of many cell types relies on lamellipodia, flat protrusions spreading on flat substrates but (on cells in suspension) also growing into three-dimensional space. Lamellipodia consist of a plasma membrane wrapped around an oriented actin filament meshwork. It is well known that the actin density is controlled by coordinated polymerization, branching, and capping processes, but the mechanisms producing the small aspect ratios of lamellipodia (hundreds of nm thickness vs. several μm lateral and inward extension) remain unclear. The main hypothesis of this work is a strong influence of the local geometry of the plasma membrane on the actin dynamics. This is motivated by observations of co-localization of proteins with I-BAR domains (like IRSp53) with polymerization and branching agents along the membrane. The I-BAR domains are known to bind to the membrane and to prefer and promote membrane curvature. This hypothesis is translated into a stochastic mathematical model where branching and capping rates, and polymerization speeds depend on the local membrane geometry and branching directions are influenced by the principal curvature directions. This requires the knowledge of the deformation of the membrane, being described in a quasi-stationary approximation by minimization of a modified Helfrich energy, subject to the actin filaments acting as obstacles. Simulations with this model predict pieces of flat lamellipodia without any prescribed geometric restrictions. PMID:26002996

  11. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Hodgdon, R. B.; Waite, W. A.

    1980-01-01

    The efforts on the synthesis of polymer anion redox membranes were mainly concentrated in two areas, membrane development and membrane fabrication. Membrane development covered the preparation and evaluation of experimental membranes systems with improved resistance stability and/or lower permeability. Membrane fabrication covered the laboratory scale production of prime candidate membranes in quantities of up to two hundred and sizes up to 18 inches x 18 inches (46 cm x 46 cm). These small (10 in x 11 in) and medium sized membranes were mainly for assembly into multicell units. Improvements in processing procedures and techniques for preparing such membrane sets lifted yields to over 90 percent.

  12. Selecting a Roof Membrane.

    ERIC Educational Resources Information Center

    Waldron, Larry W.

    1990-01-01

    Offers a brief synopsis of the unique characteristics of the following roof membranes: (1) built-up roofing; (2) elastoplastic membranes; (3) modified bitumen membranes; (4) liquid applied membranes; and (5) metal roofing. A chart compares the characteristics of the raw membranes only. (MLF)

  13. Magnetic Membrane System

    DOEpatents

    McElfresh, Michael W.; ; Lucas, Matthew S.

    2004-12-30

    The present invention provides a membrane with magnetic particles. In one embodiment the membrane is created by mixing particles in a non-magnetic base. The membrane may act as an actuator, a sensor, a pump, a valve, or other device. A magnet is operatively connected to the membrane. The magnet acts on and changes the shape of the membrane.

  14. Membrane Systems in Cyanobacteria

    SciTech Connect

    Liberton, Michelle L.; Pakrasi, Himadri B.

    2008-01-01

    Cyanobacteria are photosynthetic prokaryotes with highly differentiated membrane systems. In addition to a Gram-negative-type cell envelope with plasma membrane and outer membrane separated by a periplasmic space, cyanobacteria have an internal system of thylakoid membranes where the fully functional electron transfer chains of photosynthesis and respiration reside. The presence of different membrane systems lends these cells a unique complexity among bacteria. Cyanobacteria must be able to reorganize the membranes, synthesize new membrane lipids, and properly target proteins to the correct membrane system. The outer membrane, plasma membrane, and thylakoid membranes each have specialized roles in the cyanobacterial cell. Understanding the organization, functionality, protein composition and dynamics of the membrane systems remains a great challenge in cyanobacterial cell biology.

  15. Three-dimensional organization of nascent rod outer segment disk membranes

    PubMed Central

    Volland, Stefanie; Hughes, Louise C.; Kong, Christina; Burgess, Barry L.; Linberg, Kenneth A.; Luna, Gabriel; Zhou, Z. Hong; Fisher, Steven K.; Williams, David S.

    2015-01-01

    The vertebrate photoreceptor cell contains an elaborate cilium that includes a stack of phototransductive membrane disks. The disk membranes are continually renewed, but how new disks are formed remains poorly understood. Here we used electron microscope tomography to obtain 3D visualization of the nascent disks of rod photoreceptors in three mammalian species, to gain insight into the process of disk morphogenesis. We observed that nascent disks are invariably continuous with the ciliary plasma membrane, although, owing to partial enclosure, they can appear to be internal in 2D profiles. Tomographic analyses of the basal-most region of the outer segment show changes in shape of the ciliary plasma membrane indicating an invagination, which is likely a first step in disk formation. The invagination flattens to create the proximal surface of an evaginating lamella, as well as membrane protrusions that extend between adjacent lamellae, thereby initiating a disk rim. Immediately distal to this initiation site, lamellae of increasing diameter are evident, indicating growth outward from the cilium. In agreement with a previous model, our data indicate that mature disks are formed once lamellae reach full diameter, and the growth of a rim encloses the space between adjacent surfaces of two lamellae. This study provides 3D data of nascent and mature rod photoreceptor disk membranes at unprecedented z-axis depth and resolution, and provides a basis for addressing fundamental questions, ranging from protein sorting in the photoreceptor cilium to photoreceptor electrophysiology. PMID:26578801

  16. Disentangling Membrane Dynamics and Cell Migration; Differential Influences of F-actin and Cell-Matrix Adhesions

    PubMed Central

    Kowalewski, Jacob M.; Shafqat-Abbasi, Hamdah; Jafari-Mamaghani, Mehrdad; Endrias Ganebo, Bereket; Gong, Xiaowei

    2015-01-01

    Cell migration is heavily interconnected with plasma membrane protrusion and retraction (collectively termed “membrane dynamics”). This makes it difficult to distinguish regulatory mechanisms that differentially influence migration and membrane dynamics. Yet such distinctions may be valuable given evidence that cancer cell invasion in 3D may be better predicted by 2D membrane dynamics than by 2D cell migration, implying a degree of functional independence between these processes. Here, we applied multi-scale single cell imaging and a systematic statistical approach to disentangle regulatory associations underlying either migration or membrane dynamics. This revealed preferential correlations between membrane dynamics and F-actin features, contrasting with an enrichment of links between cell migration and adhesion complex properties. These correlative linkages were often non-linear and therefore context-dependent, strengthening or weakening with spontaneous heterogeneity in cell behavior. More broadly, we observed that slow moving cells tend to increase in area, while fast moving cells tend to shrink, and that the size of dynamic membrane domains is independent of cell area. Overall, we define macromolecular features preferentially associated with either cell migration or membrane dynamics, enabling more specific interrogation and targeting of these processes in future. PMID:26248038

  17. Chloroplast protrusions in leaves of Ranunculus glacialis L. respond significantly to different ambient conditions, but are not related to temperature stress.

    PubMed

    Moser, Tim; Holzinger, Andreas; Buchner, Othmar

    2015-07-01

    The occurrence of chloroplast protrusions (CPs) in leaves of Ranunculus glacialis L. in response to different environmental conditions was assessed. CPs occur highly dynamically. They do not contain thylakoids and their physiological function is still largely unknown. Controlled in situ sampling showed that CP formation follows a pronounced diurnal rhythm. Between 2 and 27 °C the relative proportion of chloroplasts with CPs (rCP) showed a significant positive correlation to leaf temperature (TL; 0.793, P < 0.01), while irradiation intensity had a minor effect on rCP. In situ shading and controlled laboratory experiments confirmed the significant influence of TL. Under moderate irradiation intensity, an increase of TL up to 25 °C significantly promoted CP formation, while a further increase to 37 °C led to a decrease. Furthermore, rCP values were lower in darkness and under high irradiation intensity. Gas treatment at 2000 ppm CO2/2% O2 led to a significant decrease of rCP, suggesting a possible involvement of photorespiration in CP formation. Our findings demonstrate that in R. glacialis, CPs are neither a rare phenomenon nor a result of heat or light stress; on the contrary, they seem to be most abundant under moderate temperature and non-stress irradiation conditions. PMID:25393014

  18. Listeria monocytogenes exploits efferocytosis to promote cell-to-cell spread.

    PubMed

    Czuczman, Mark A; Fattouh, Ramzi; van Rijn, Jorik M; Canadien, Veronica; Osborne, Suzanne; Muise, Aleixo M; Kuchroo, Vijay K; Higgins, Darren E; Brumell, John H

    2014-05-01

    Efferocytosis, the process by which dying or dead cells are removed by phagocytosis, has an important role in development, tissue homeostasis and innate immunity. Efferocytosis is mediated, in part, by receptors that bind to exofacial phosphatidylserine (PS) on cells or cellular debris after loss of plasma membrane asymmetry. Here we show that a bacterial pathogen, Listeria monocytogenes, can exploit efferocytosis to promote cell-to-cell spread during infection. These bacteria can escape the phagosome in host cells by using the pore-forming toxin listeriolysin O (LLO) and two phospholipase C enzymes. Expression of the cell surface protein ActA allows L. monocytogenes to activate host actin regulatory factors and undergo actin-based motility in the cytosol, eventually leading to formation of actin-rich protrusions at the cell surface. Here we show that protrusion formation is associated with plasma membrane damage due to LLO's pore-forming activity. LLO also promotes the release of bacteria-containing protrusions from the host cell, generating membrane-derived vesicles with exofacial PS. The PS-binding receptor TIM-4 (encoded by the Timd4 gene) contributes to efficient cell-to-cell spread by L. monocytogenes in macrophages in vitro and growth of these bacteria is impaired in Timd4(-/-) mice. Thus, L. monocytogenes promotes its dissemination in a host by exploiting efferocytosis. Our results indicate that PS-targeted therapeutics may be useful in the fight against infections by L. monocytogenes and other bacteria that use similar strategies of cell-to-cell spread during infection. PMID:24739967

  19. Composite sensor membrane

    DOEpatents

    Majumdar, Arun; Satyanarayana, Srinath; Yue, Min

    2008-03-18

    A sensor may include a membrane to deflect in response to a change in surface stress, where a layer on the membrane is to couple one or more probe molecules with the membrane. The membrane may deflect when a target molecule reacts with one or more probe molecules.

  20. Re-analysis of protein data reveals the germination pathway and up accumulation mechanism of cell wall hydrolases during the radicle protrusion step of seed germination in Podophyllum hexandrum- a high altitude plant

    PubMed Central

    Dogra, Vivek; Bagler, Ganesh; Sreenivasulu, Yelam

    2015-01-01

    Podophyllum hexandrum Royle is an important high-altitude plant of Himalayas with immense medicinal value. Earlier, it was reported that the cell wall hydrolases were up accumulated during radicle protrusion step of Podophyllum seed germination. In the present study, Podophyllum seed Germination protein interaction Network (PGN) was constructed by using the differentially accumulated protein (DAP) data set of Podophyllum during the radicle protrusion step of seed germination, with reference to Arabidopsis protein–protein interaction network (AtPIN). The developed PGN is comprised of a giant cluster with 1028 proteins having 10,519 interactions and a few small clusters with relevant gene ontological signatures. In this analysis, a germination pathway related cluster which is also central to the topology and information dynamics of PGN was obtained with a set of 60 key proteins. Among these, eight proteins which are known to be involved in signaling, metabolism, protein modification, cell wall modification, and cell cycle regulation processes were found commonly highlighted in both the proteomic and interactome analysis. The systems-level analysis of PGN identified the key proteins involved in radicle protrusion step of seed germination in Podophyllum. PMID:26579141

  1. Outer-Inner Membrane Vesicles Naturally Secreted by Gram-Negative Pathogenic Bacteria

    PubMed Central

    Pérez-Cruz, Carla; Delgado, Lidia; López-Iglesias, Carmen; Mercade, Elena

    2015-01-01

    Outer-inner membrane vesicles (O-IMVs) were recently described as a new type of membrane vesicle secreted by the Antarctic bacterium Shewanella vesiculosa M7T. Their formation is characterized by the protrusion of both outer and plasma membranes, which pulls cytoplasmic components into the vesicles. To demonstrate that this is not a singular phenomenon in a bacterium occurring in an extreme environment, the identification of O-IMVs in pathogenic bacteria was undertaken. With this aim, a structural study by Transmission Electron Microscopy (TEM) and Cryo-transmission electron microscopy (Cryo-TEM) was carried out, confirming that O-IMVs are also secreted by Gram-negative pathogenic bacteria such as Neisseria gonorrhoeae, Pseudomonas aeruginosa PAO1 and Acinetobacter baumannii AB41, in which they represent between 0.23% and 1.2% of total vesicles produced. DNA and ATP, which are components solely found in the cell cytoplasm, were identified within membrane vesicles of these strains. The presence of DNA inside the O-IMVs produced by N. gonorrhoeae was confirmed by gold DNA immunolabeling with a specific monoclonal IgM against double-stranded DNA. A proteomic analysis of N. gonorrhoeae-derived membrane vesicles identified proteins from the cytoplasm and plasma membrane. This confirmation of O-IMV extends the hitherto uniform definition of membrane vesicles in Gram-negative bacteria and explains the presence of components in membrane vesicles such as DNA, cytoplasmic and inner membrane proteins, as well as ATP, detected for the first time. The production of these O-IMVs by pathogenic Gram-negative bacteria opens up new areas of study related to their involvement in lateral gene transfer, the transfer of cytoplasmic proteins, as well as the functionality and role of ATP detected in these new vesicles. PMID:25581302

  2. Loss of the F-BAR protein CIP4 reduces platelet production by impairing membrane-cytoskeleton remodeling

    PubMed Central

    Chen, Yolande; Aardema, Jorie; Kale, Sayali; Whichard, Zakary L.; Awomolo, Arinola; Blanchard, Elisabeth; Chang, Brian; Myers, David R.; Ju, Lining; Tran, Reginald; Reece, David; Christensen, Hilary; Boukour, Siham; Debili, Najet; Strom, Ted S.; Rawlings, David; Vázquez, Francisco X.; Voth, Gregory A.; Zhu, Cheng; Kahr, Walter H. A.; Lam, Wilbur A.

    2013-01-01

    Megakaryocytes generate platelets through extensive reorganization of the cytoskeleton and plasma membrane. Cdc42 interacting protein 4 (CIP4) is an F-BAR protein that localizes to membrane phospholipids through its BAR domain and interacts with Wiskott-Aldrich Syndrome Protein (WASP) via its SRC homology 3 domain. F-BAR proteins promote actin polymerization and membrane tubulation. To study its function, we generated CIP4-null mice that displayed thrombocytopenia similar to that of WAS− mice. The number of megakaryocytes and their progenitors was not affected. However, the number of proplatelet protrusions was reduced in CIP4-null, but not WAS−, megakaryocytes. Electron micrographs of CIP4-null megakaryocytes showed an altered demarcation membrane system. Silencing of CIP4, not WASP, expression resulted in fewer proplatelet-like extensions. Fluorescence anisotropy studies showed that loss of CIP4 resulted in a more rigid membrane. Micropipette aspiration demonstrated decreased cortical actin tension in megakaryocytic cells with reduced CIP4 or WASP protein. These studies support a new biophysical mechanism for platelet biogenesis whereby CIP4 enhances the complex, dynamic reorganization of the plasma membrane (WASP independent) and actin cortex network (as known for WASP and cortical actin) to reduce the work required for generating proplatelets. CIP4 is a new component in the highly coordinated system of megakaryocytic membrane and cytoskeletal remodeling affecting platelet production. PMID:23881916

  3. Arrangement of Photosystem II and ATP Synthase in Chloroplast Membranes of Spinach and Pea[W][OA

    PubMed Central

    Daum, Bertram; Nicastro, Daniela; Austin, Jotham; McIntosh, J. Richard; Kühlbrandt, Werner

    2010-01-01

    We used cryoelectron tomography to reveal the arrangements of photosystem II (PSII) and ATP synthase in vitreous sections of intact chloroplasts and plunge-frozen suspensions of isolated thylakoid membranes. We found that stroma and grana thylakoids are connected at the grana margins by staggered lamellar membrane protrusions. The stacking repeat of grana membranes in frozen-hydrated chloroplasts is 15.7 nm, with a 4.5-nm lumenal space and a 3.2-nm distance between the flat stromal surfaces. The chloroplast ATP synthase is confined to minimally curved regions at the grana end membranes and stroma lamellae, where it covers 20% of the surface area. In total, 85% of the ATP synthases are monomers and the remainder form random assemblies of two or more copies. Supercomplexes of PSII and light-harvesting complex II (LHCII) occasionally form ordered arrays in appressed grana thylakoids, whereas this order is lost in destacked membranes. In the ordered arrays, each membrane on either side of the stromal gap contains a two-dimensional crystal of supercomplexes, with the two lattices arranged such that PSII cores, LHCII trimers, and minor LHCs each face a complex of the same kind in the opposite membrane. Grana formation is likely to result from electrostatic interactions between these complexes across the stromal gap. PMID:20388855

  4. Membrane tubule formation by banana-shaped proteins with or without transient network structure.

    PubMed

    Noguchi, Hiroshi

    2016-01-01

    In living cells, membrane morphology is regulated by various proteins. Many membrane reshaping proteins contain a Bin/Amphiphysin/Rvs (BAR) domain, which consists of a banana-shaped rod. The BAR domain bends the biomembrane along the rod axis and the features of this anisotropic bending have recently been studied. Here, we report on the role of the BAR protein rods in inducing membrane tubulation, using large-scale coarse-grained simulations. We reveal that a small spontaneous side curvature perpendicular to the rod can drastically alter the tubulation dynamics at high protein density, whereas no significant difference is obtained at low density. A percolated network is intermediately formed depending on the side curvature. This network suppresses tubule protrusion, leading to the slow formation of fewer tubules. Thus, the side curvature, which is generated by protein-protein and membrane-protein interactions, plays a significant role in tubulation dynamics. We also find that positive surface tensions and the vesicle membrane curvature can stabilize this network structure by suppressing the tubulation. PMID:26863901

  5. Membrane tubule formation by banana-shaped proteins with or without transient network structure

    NASA Astrophysics Data System (ADS)

    Noguchi, Hiroshi

    2016-02-01

    In living cells, membrane morphology is regulated by various proteins. Many membrane reshaping proteins contain a Bin/Amphiphysin/Rvs (BAR) domain, which consists of a banana-shaped rod. The BAR domain bends the biomembrane along the rod axis and the features of this anisotropic bending have recently been studied. Here, we report on the role of the BAR protein rods in inducing membrane tubulation, using large-scale coarse-grained simulations. We reveal that a small spontaneous side curvature perpendicular to the rod can drastically alter the tubulation dynamics at high protein density, whereas no significant difference is obtained at low density. A percolated network is intermediately formed depending on the side curvature. This network suppresses tubule protrusion, leading to the slow formation of fewer tubules. Thus, the side curvature, which is generated by protein-protein and membrane-protein interactions, plays a significant role in tubulation dynamics. We also find that positive surface tensions and the vesicle membrane curvature can stabilize this network structure by suppressing the tubulation.

  6. Membrane shrinkage and cortex remodelling are predicted to work in harmony to retract blebs

    PubMed Central

    Woolley, Thomas E.; Gaffney, Eamonn A.; Goriely, Alain

    2015-01-01

    Numerous cell types undergo an oscillatory form of dynamics known as blebbing, whereby pressure-driven spherical protrusions of membrane (known as blebs) expand and contract over the cell's surface. Depending on the cell line, blebs play important roles in many different phenomena including mitosis and locomotion. The expansion phase of cellular blebbing has been mathematically modelled in detail. However, the active processes occurring during the retraction phase are not so well characterized. It is thought that blebs retract because a cortex reforms inside, and adheres to, the bleb membrane. This cortex is retracted into the cell and the attached bleb membrane follows. Using a computational model of a cell's membrane, cortex and interconnecting adhesions, we demonstrate that cortex retraction alone cannot account for bleb retraction and suggest that the mechanism works in tandem with membrane shrinking. Further, an emergent hysteresis loop is observed in the intracellular pressure, which suggests a potential mechanism through which a secondary bleb can be initiated as a primary bleb contracts. PMID:26587278

  7. Membrane shrinkage and cortex remodelling are predicted to work in harmony to retract blebs.

    PubMed

    Woolley, Thomas E; Gaffney, Eamonn A; Goriely, Alain

    2015-07-01

    Numerous cell types undergo an oscillatory form of dynamics known as blebbing, whereby pressure-driven spherical protrusions of membrane (known as blebs) expand and contract over the cell's surface. Depending on the cell line, blebs play important roles in many different phenomena including mitosis and locomotion. The expansion phase of cellular blebbing has been mathematically modelled in detail. However, the active processes occurring during the retraction phase are not so well characterized. It is thought that blebs retract because a cortex reforms inside, and adheres to, the bleb membrane. This cortex is retracted into the cell and the attached bleb membrane follows. Using a computational model of a cell's membrane, cortex and interconnecting adhesions, we demonstrate that cortex retraction alone cannot account for bleb retraction and suggest that the mechanism works in tandem with membrane shrinking. Further, an emergent hysteresis loop is observed in the intracellular pressure, which suggests a potential mechanism through which a secondary bleb can be initiated as a primary bleb contracts. PMID:26587278

  8. Src1 is a Protein of the Inner Nuclear Membrane Interacting with the Dictyostelium Lamin NE81

    PubMed Central

    Batsios, Petros; Ren, Xiang; Baumann, Otto; Larochelle, Denis A.; Gräf, Ralph

    2016-01-01

    The nuclear envelope (NE) consists of the outer and inner nuclear membrane (INM), whereby the latter is bound to the nuclear lamina. Src1 is a Dictyostelium homologue of the helix-extension-helix family of proteins, which also includes the human lamin-binding protein MAN1. Both endogenous Src1 and GFP-Src1 are localized to the NE during the entire cell cycle. Immuno-electron microscopy and light microscopy after differential detergent treatment indicated that Src1 resides in the INM. FRAP experiments with GFP-Src1 cells suggested that at least a fraction of the protein could be stably engaged in forming the nuclear lamina together with the Dictyostelium lamin NE81. Both a BioID proximity assay and mis-localization of soluble, truncated mRFP-Src1 at cytosolic clusters consisting of an intentionally mis-localized mutant of GFP-NE81 confirmed an interaction of Src1 and NE81. Expression GFP-Src11–646, a fragment C-terminally truncated after the first transmembrane domain, disrupted interaction of nuclear membranes with the nuclear lamina, as cells formed protrusions of the NE that were dependent on cytoskeletal pulling forces. Protrusions were dependent on intact microtubules but not actin filaments. Our results indicate that Src1 is required for integrity of the NE and highlight Dictyostelium as a promising model for the evolution of nuclear architecture. PMID:26999214

  9. Correlation of cell membrane dynamics and cell motility

    PubMed Central

    2011-01-01

    Background Essential events of cell development and homeostasis are revealed by the associated changes of cell morphology and therefore have been widely used as a key indicator of physiological states and molecular pathways affecting various cellular functions via cytoskeleton. Cell motility is a complex phenomenon primarily driven by the actin network, which plays an important role in shaping the morphology of the cells. Most of the morphology based features are approximated from cell periphery but its dynamics have received none to scant attention. We aim to bridge the gap between membrane dynamics and cell states from the perspective of whole cell movement by identifying cell edge patterns and its correlation with cell dynamics. Results We present a systematic study to extract, classify, and compare cell dynamics in terms of cell motility and edge activity. Cell motility features extracted by fitting a persistent random walk were used to identify the initial set of cell subpopulations. We propose algorithms to extract edge features along the entire cell periphery such as protrusion and retraction velocity. These constitute a unique set of multivariate time-lapse edge features that are then used to profile subclasses of cell dynamics by unsupervised clustering. Conclusions By comparing membrane dynamic patterns exhibited by each subclass of cells, correlated trends of edge and cell movements were identified. Our findings are consistent with published literature and we also identified that motility patterns are influenced by edge features from initial time points compared to later sampling intervals. PMID:22372978

  10. Correlative Light and Electron Microscopy Reveals the HAS3-Induced Dorsal Plasma Membrane Ruffles

    PubMed Central

    Rilla, Kirsi; Koistinen, Arto

    2015-01-01

    Hyaluronan is a linear sugar polymer synthesized by three isoforms of hyaluronan synthases (HAS1, 2, and 3) that forms a hydrated scaffold around cells and is an essential component of the extracellular matrix. The morphological changes of cells induced by active hyaluronan synthesis are well recognized but not studied in detail with high resolution before. We have previously found that overexpression of HAS3 induces growth of long plasma membrane protrusions that act as platforms for hyaluronan synthesis. The study of these thin and fragile protrusions is challenging, and they are difficult to preserve by fixation unless they are adherent to the substrate. Thus their structure and regulation are still partly unclear despite careful imaging with different microscopic methods in several cell types. In this study, correlative light and electron microscopy (CLEM) was utilized to correlate the GFP-HAS3 signal and the surface ultrastructure of cells in order to study in detail the morphological changes induced by HAS3 overexpression. Surprisingly, this method revealed that GFP-HAS3 not only localizes to ruffles but in fact induces dorsal ruffle formation. Dorsal ruffles regulate diverse cellular functions, such as motility, regulation of glucose metabolism, spreading, adhesion, and matrix degradation, the same functions driven by active hyaluronan synthesis. PMID:26448759

  11. Correlative Light and Electron Microscopy Reveals the HAS3-Induced Dorsal Plasma Membrane Ruffles.

    PubMed

    Rilla, Kirsi; Koistinen, Arto

    2015-01-01

    Hyaluronan is a linear sugar polymer synthesized by three isoforms of hyaluronan synthases (HAS1, 2, and 3) that forms a hydrated scaffold around cells and is an essential component of the extracellular matrix. The morphological changes of cells induced by active hyaluronan synthesis are well recognized but not studied in detail with high resolution before. We have previously found that overexpression of HAS3 induces growth of long plasma membrane protrusions that act as platforms for hyaluronan synthesis. The study of these thin and fragile protrusions is challenging, and they are difficult to preserve by fixation unless they are adherent to the substrate. Thus their structure and regulation are still partly unclear despite careful imaging with different microscopic methods in several cell types. In this study, correlative light and electron microscopy (CLEM) was utilized to correlate the GFP-HAS3 signal and the surface ultrastructure of cells in order to study in detail the morphological changes induced by HAS3 overexpression. Surprisingly, this method revealed that GFP-HAS3 not only localizes to ruffles but in fact induces dorsal ruffle formation. Dorsal ruffles regulate diverse cellular functions, such as motility, regulation of glucose metabolism, spreading, adhesion, and matrix degradation, the same functions driven by active hyaluronan synthesis. PMID:26448759

  12. The Short Stature Homeobox 2 (Shox2)-bone Morphogenetic Protein (BMP) Pathway Regulates Dorsal Mesenchymal Protrusion Development and Its Temporary Function as a Pacemaker during Cardiogenesis*

    PubMed Central

    Sun, Cheng; Yu, Diankun; Ye, Wenduo; Liu, Chao; Gu, Shuping; Sinsheimer, Nathan R.; Song, Zhongchen; Li, Xihai; Chen, Chun; Song, Yingnan; Wang, Shusheng; Schrader, Laura; Chen, YiPing

    2015-01-01

    The atrioventricular (AV) junction plays a critical role in chamber septation and transmission of cardiac conduction pulses. It consists of structures that develop from embryonic dorsal mesenchymal protrusion (DMP) and the embryonic AV canal. Despite extensive studies on AV junction development, the genetic regulation of DMP development remains poorly understood. In this study we present evidence that Shox2 is expressed in the developing DMP. Intriguingly, this Shox2-expressing domain possesses a pacemaker-specific genetic profile including Hcn4 and Tbx3. This genetic profile leads to nodal-like electrophysiological properties, which is gradually silenced as the AV node becomes matured. Phenotypic analyses of Shox2−/− mice revealed a hypoplastic and defectively differentiated DMP, likely attributed to increased apoptosis, accompanied by dramatically reduced expression of Bmp4 and Hcn4, ectopic activation of Cx40, and an aberrant pattern of action potentials. Interestingly, conditional deletion of Bmp4 or inhibition of BMP signaling by overexpression of Noggin using a Shox2-Cre allele led to a similar DMP hypoplasia and down-regulation of Hcn4, whereas activation of a transgenic Bmp4 allele in Shox2−/− background attenuated DMP defects. Moreover, the lack of Hcn4 expression in the DMP of mice carrying Smad4 conditional deletion and direct binding of pSmad1/5/8 to the Hcn4 regulatory region further confirm the Shox2-BMP genetic cascade in the regulation of DMP development. Our results reveal that Shox2 regulates DMP fate and development by controlling BMP signaling through the Smad-dependent pathway to drive tissue growth and to induce Hcn4 expression and suggest a temporal pacemaking function for the DMP during early cardiogenesis. PMID:25488669

  13. Sheet Membrane Spacesuit Water Membrane Evaporator

    NASA Technical Reports Server (NTRS)

    Bue, Grant; Trevino, Luis; Zapata, Felipe; Dillion, Paul; Castillo, Juan; Vonau, Walter; Wilkes, Robert; Vogel, Matthew; Frodge, Curtis

    2013-01-01

    A document describes a sheet membrane spacesuit water membrane evaporator (SWME), which allows for the use of one common water tank that can supply cooling water to the astronaut and to the evaporator. Test data showed that heat rejection performance dropped only 6 percent after being subjected to highly contaminated water. It also exhibited robustness with respect to freezing and Martian atmospheric simulation testing. Water was allowed to freeze in the water channels during testing that simulated a water loop failure and vapor backpressure valve failure. Upon closing the backpressure valve and energizing the pump, the ice eventually thawed and water began to flow with no apparent damage to the sheet membrane. The membrane evaporator also serves to de-gas the water loop from entrained gases, thereby eliminating the need for special degassing equipment such as is needed by the current spacesuit system. As water flows through the three annular water channels, water evaporates with the vapor flowing across the hydrophobic, porous sheet membrane to the vacuum side of the membrane. The rate at which water evaporates, and therefore, the rate at which the flowing water is cooled, is a function of the difference between the water saturation pressure on the water side of the membrane, and the pressure on the vacuum side of the membrane. The primary theory is that the hydrophobic sheet membrane retains water, but permits vapor pass-through when the vapor side pressure is less than the water saturation pressure. This results in evaporative cooling of the remaining water.

  14. Methanotroph outer membrane preparation.

    PubMed

    Karlsen, Odd A; Berven, Frode S; Jensen, Harald B; Fjellbirkeland, Anne

    2011-01-01

    All presently known methanotrophs are gram-negative bacteria suggesting that they are surrounded by a two-layered membrane: an inner or cytoplasmic membrane and an outer membrane. In the methanotroph Methylococcus capsulatus (Bath), separation of the two membranes has allowed studies on protein and lipid composition of the outer membrane. Its outer membrane can be isolated from purified cell envelopes by selective solubilization of the inner membranes with the detergent Triton X-100. The proteins associated with the outer membrane can further be fractionated into integral and tightly associated proteins and peripheral loosely associated proteins. We present here protocols for this fractionation and show how the proteins associated with the outer leaflet of the outer membrane can be isolated and identified by whole-cell biotin surface labeling. PMID:21419921

  15. Membrane selectivity in pervaporation

    SciTech Connect

    Kujawski, W.

    1996-06-01

    A qualitative description is presented of pervaporation which discusses the initial preferential sorption into the membrane, diffusion of liquid, phase transition from liquid to vapor phase, followed by diffusion of vapors and fast desorption from the other side of the membrane. The overall separation of each pervaporation step was calculated in terms of separation factor {alpha}. The results show that in the case of hydrophilic membranes (i.e., dense polyamide-6 membrane and ion-exchange membrane PESS-1) and water-ethanol mixtures, the phase transition step decreases the overall separation. Also, diffusion through the membrane is unfavorable to water at a low concentration range.

  16. Ionene membrane battery separator

    NASA Technical Reports Server (NTRS)

    Moacanin, J.; Tom, H. Y.

    1969-01-01

    Ionic transport characteristics of ionenes, insoluble membranes from soluble polyelectrolyte compositions, are studied for possible application in a battery separator. Effectiveness of the thin film of separator membrane essentially determines battery lifetime.

  17. Composite zeolite membranes

    DOEpatents

    Nenoff, Tina M.; Thoma, Steven G.; Ashley, Carol S.; Reed, Scott T.

    2002-01-01

    A new class of composite zeolite membranes and synthesis techniques therefor has been invented. These membranes are essentially defect-free, and exhibit large levels of transmembrane flux and of chemical and isotopic selectivity.

  18. Hybrid adsorptive membrane reactor

    DOEpatents

    Tsotsis, Theodore T.; Sahimi, Muhammad; Fayyaz-Najafi, Babak; Harale, Aadesh; Park, Byoung-Gi; Liu, Paul K. T.

    2011-03-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  19. Supertubes and Superconducting Membranes

    SciTech Connect

    Cordero, Ruben; Miguel-Pilar, Zelin

    2007-02-09

    We show the equivalence between configurations that arise from string theory of type IIA, called supertubes, and superconducting membranes at the bosonic level. We find equilibrium and oscillating configurations for a tubular membrane carrying a current along its axis.

  20. Premature rupture of membranes

    MedlinePlus

    ... When the water breaks early, it is called premature rupture of membranes (PROM). Most women will go ... th week of pregnancy, it is called preterm premature rupture of membranes (PPROM). The earlier your water ...

  1. Hybrid adsorptive membrane reactor

    NASA Technical Reports Server (NTRS)

    Tsotsis, Theodore T. (Inventor); Sahimi, Muhammad (Inventor); Fayyaz-Najafi, Babak (Inventor); Harale, Aadesh (Inventor); Park, Byoung-Gi (Inventor); Liu, Paul K. T. (Inventor)

    2011-01-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  2. Supported inorganic membranes

    DOEpatents

    Sehgal, Rakesh; Brinker, Charles Jeffrey

    1998-01-01

    Supported inorganic membranes capable of molecular sieving, and methods for their production, are provided. The subject membranes exhibit high flux and high selectivity. The subject membranes are substantially defect free and less than about 100 nm thick. The pores of the subject membranes have an average critical pore radius of less than about 5 .ANG., and have a narrow pore size distribution. The subject membranes are prepared by coating a porous substrate with a polymeric sol, preferably under conditions of low relative pressure of the liquid constituents of the sol. The coated substrate is dried and calcined to produce the subject supported membrane. Also provided are methods of derivatizing the surface of supported inorganic membranes with metal alkoxides. The subject membranes find use in a variety of applications, such as the separation of constituents of gaseous streams, as catalysts and catalyst supports, and the like.

  3. Induction of Membrane Ceramides: A Novel Strategy to Interfere with T Lymphocyte Cytoskeletal Reorganisation in Viral Immunosuppression

    PubMed Central

    Harms, Harry; Krohne, Georg; Gulbins, Erich; Schneider-Schaulies, Sibylle

    2009-01-01

    Silencing of T cell activation and function is a highly efficient strategy of immunosuppression induced by pathogens. By promoting formation of membrane microdomains essential for clustering of receptors and signalling platforms in the plasma membrane, ceramides accumulating as a result of membrane sphingomyelin breakdown are not only essential for assembly of signalling complexes and pathogen entry, but also act as signalling modulators, e. g. by regulating relay of phosphatidyl-inositol-3-kinase (PI3K) signalling. Their role in T lymphocyte functions has not been addressed as yet. We now show that measles virus (MV), which interacts with the surface of T cells and thereby efficiently interferes with stimulated dynamic reorganisation of their actin cytoskeleton, causes ceramide accumulation in human T cells in a neutral (NSM) and acid (ASM) sphingomyelinase–dependent manner. Ceramides induced by MV, but also bacterial sphingomyelinase, efficiently interfered with formation of membrane protrusions and T cell spreading and front/rear polarisation in response to β1 integrin ligation or αCD3/CD28 activation, and this was rescued upon pharmacological or genetic ablation of ASM/NSM activity. Moreover, membrane ceramide accumulation downmodulated chemokine-induced T cell motility on fibronectin. Altogether, these findings highlight an as yet unrecognised concept of pathogens able to cause membrane ceramide accumulation to target essential processes in T cell activation and function by preventing stimulated actin cytoskeletal dynamics. PMID:19834551

  4. Composite fuel cell membranes

    DOEpatents

    Plowman, Keith R.; Rehg, Timothy J.; Davis, Larry W.; Carl, William P.; Cisar, Alan J.; Eastland, Charles S.

    1997-01-01

    A bilayer or trilayer composite ion exchange membrane suitable for use in a fuel cell. The composite membrane has a high equivalent weight thick layer in order to provide sufficient strength and low equivalent weight surface layers for improved electrical performance in a fuel cell. In use, the composite membrane is provided with electrode surface layers. The composite membrane can be composed of a sulfonic fluoropolymer in both core and surface layers.

  5. Composite fuel cell membranes

    DOEpatents

    Plowman, K.R.; Rehg, T.J.; Davis, L.W.; Carl, W.P.; Cisar, A.J.; Eastland, C.S.

    1997-08-05

    A bilayer or trilayer composite ion exchange membrane is described suitable for use in a fuel cell. The composite membrane has a high equivalent weight thick layer in order to provide sufficient strength and low equivalent weight surface layers for improved electrical performance in a fuel cell. In use, the composite membrane is provided with electrode surface layers. The composite membrane can be composed of a sulfonic fluoropolymer in both core and surface layers.

  6. Meniscus membranes for separations

    DOEpatents

    Dye, Robert C.; Jorgensen, Betty; Pesiri, David R.

    2004-01-27

    Gas separation membranes, especially meniscus-shaped membranes for gas separations are disclosed together with the use of such meniscus-shaped membranes for applications such as thermal gas valves, pre-concentration of a gas stream, and selective pre-screening of a gas stream. In addition, a rapid screening system for simultaneously screening polymer materials for effectiveness in gas separation is provided.

  7. Meniscus Membranes For Separation

    DOEpatents

    Dye, Robert C.; Jorgensen, Betty; Pesiri, David R.

    2005-09-20

    Gas separation membranes, especially meniscus-shaped membranes for gas separations are disclosed together with the use of such meniscus-shaped membranes for applications such as thermal gas valves, pre-concentration of a gas stream, and selective pre-screening of a gas stream. In addition, a rapid screening system for simultaneously screening polymer materials for effectiveness in gas separation is provided.

  8. Cadmium sulfide membranes

    DOEpatents

    Spanhel, Lubomir; Anderson, Marc A.

    1992-07-07

    A method is described for the creation of novel q-effect cadmium sulfide membranes. The membranes are made by first creating a dilute cadmium sulfide colloid in aqueous suspension and then removing the water and excess salts therefrom. The cadmium sulfide membrane thus produced is luminescent at room temperature and may have application in laser fabrication.

  9. Cadmium sulfide membranes

    DOEpatents

    Spanhel, Lubomir; Anderson, Marc A.

    1991-10-22

    A method is described for the creation of novel q-effect cadmium sulfide membranes. The membranes are made by first creating a dilute cadmium sulfide colloid in aqueous suspension and then removing the water and excess salts therefrom. The cadmium sulfide membrane thus produced is luminescent at room temperature and may have application in laser fabrication.

  10. Polyphosphazene semipermeable membranes

    DOEpatents

    Allen, Charles A.; McCaffrey, Robert R.; Cummings, Daniel G.; Grey, Alan E.; Jessup, Janine S.; McAtee, Richard E.

    1988-01-01

    A semipermeable, inorganic membrane is disclosed; the membrane is prepared from a phosphazene polymer and, by the selective substitution of the constituent groups bound to the phosphorous in the polymer structure, the selective passage of fluid from a feedstream can be controlled. Resistance to high temperatures and harsh chemical environments is observed in the use of the phosphazene polymers as semipermeable membranes.

  11. Water vapor diffusion membranes

    NASA Technical Reports Server (NTRS)

    Holland, F. F., Jr.; Smith, J. K.

    1974-01-01

    The program is reported, which was designed to define the membrane technology of the vapor diffusion water recovery process and to test this technology using commercially available or experimental membranes. One membrane was selected, on the basis of the defined technology, and was subjected to a 30-day demonstration trial.

  12. Membrane tubule formation by banana-shaped proteins with or without transient network structure

    PubMed Central

    Noguchi, Hiroshi

    2016-01-01

    In living cells, membrane morphology is regulated by various proteins. Many membrane reshaping proteins contain a Bin/Amphiphysin/Rvs (BAR) domain, which consists of a banana-shaped rod. The BAR domain bends the biomembrane along the rod axis and the features of this anisotropic bending have recently been studied. Here, we report on the role of the BAR protein rods in inducing membrane tubulation, using large-scale coarse-grained simulations. We reveal that a small spontaneous side curvature perpendicular to the rod can drastically alter the tubulation dynamics at high protein density, whereas no significant difference is obtained at low density. A percolated network is intermediately formed depending on the side curvature. This network suppresses tubule protrusion, leading to the slow formation of fewer tubules. Thus, the side curvature, which is generated by protein–protein and membrane–protein interactions, plays a significant role in tubulation dynamics. We also find that positive surface tensions and the vesicle membrane curvature can stabilize this network structure by suppressing the tubulation. PMID:26863901

  13. Graphene microsheets enter cells through spontaneous membrane penetration at edge asperities and corner sites

    PubMed Central

    Li, Yinfeng; Yuan, Hongyan; von dem Bussche, Annette; Creighton, Megan; Hurt, Robert H.; Kane, Agnes B.; Gao, Huajian

    2013-01-01

    Understanding and controlling the interaction of graphene-based materials with cell membranes is key to the development of graphene-enabled biomedical technologies and to the management of graphene health and safety issues. Very little is known about the fundamental behavior of cell membranes exposed to ultrathin 2D synthetic materials. Here we investigate the interactions of graphene and few-layer graphene (FLG) microsheets with three cell types and with model lipid bilayers by combining coarse-grained molecular dynamics (MD), all-atom MD, analytical modeling, confocal fluorescence imaging, and electron microscopic imaging. The imaging experiments show edge-first uptake and complete internalization for a range of FLG samples of 0.5- to 10-μm lateral dimension. In contrast, the simulations show large energy barriers relative to kBT for membrane penetration by model graphene or FLG microsheets of similar size. More detailed simulations resolve this paradox by showing that entry is initiated at corners or asperities that are abundant along the irregular edges of fabricated graphene materials. Local piercing by these sharp protrusions initiates membrane propagation along the extended graphene edge and thus avoids the high energy barrier calculated in simple idealized MD simulations. We propose that this mechanism allows cellular uptake of even large multilayer sheets of micrometer-scale lateral dimension, which is consistent with our multimodal bioimaging results for primary human keratinocytes, human lung epithelial cells, and murine macrophages. PMID:23840061

  14. Organization of acetylcholine receptors in quick-frozen, deep-etched, and rotary-replicated Torpedo postsynaptic membrane.

    PubMed

    Heuser, J E; Salpeter, S R

    1979-07-01

    The receptor-rich postsynaptic membrane of the elasmobranch electric organ was fixed by quick-freezing and then viewed by freeze-fracture, deep-etching and rotary-replication. Traditional freeze-fracture revealed a distinct, geometrical pattern of shallow 8.5-nm bumps on the E fracture-face, similar to the lattice which has been seen before in chemically fixed material, but seen less clearly than after quick-freezing. Fracture plus deep-etching brought into view on the true outside of this membrane a similar geometrical pattern of 8.5-nm projections rising out of the membrane surface. The individual projections looked like structures that have been seen in negatively stained or deep-etched membrane fragments and have been identified as individual acetylcholine receptor molecules. The surface protrusions were twice as abundant as the large intramembrane particles that characterize the fracture faces of this membrane, which have also been considered to be receptor molecules. Particle counts have always been too low to match the estimates of postsynaptic receptor density derived from physiological and biochemical studies; counts of surface projections, however, more closely matched these estimates. Rotary-replication of quick-frozen, etched postsynaptic membranes enhanced the visibility of these surface protuberances and illustrated that they often occur in dimers, tetramers, and ordered rows. The variations in these surface patterns suggested that in vivo, receptors in the postsynaptic membrane may tend to pack into "liquid crystals" which constantly appear, flow, and disappear in the fluid environment of the membrane. Additionally, deep-etching revealed a distinct web of cytoplasmic filaments beneath the postsynaptic membrane, and revealed the basal lamina above it; and delineated possible points of contact between these structures and the membrane proper. PMID:479296

  15. Course 6: Physics of Composite Cell Membrane and Actin Based Cytoskeleton

    NASA Astrophysics Data System (ADS)

    Sackmann, E.; Bausch, A. R.; Vonna, L.

    1 Architecture of composite cell membranes 1.1 The lipid/protein bilayer is a multicomponent smectic phase with mosaic like architecture 1.2 The spectrin/actin cytoskeleton as hyperelastic cell stabilizer 1.3 The actin cortex: Architecture and function 2 Physics of the actin based cytoskeleton 2.1 Actin is a living semiflexible polymer 2.2 Actin network as viscoelastic body 2.3 Correlation between macroscopic viscoelasticity and molecular 3 Heterogeneous actin gels in cells and biological function 3.1 Manipulation of actin gels 3.2 Control of organization and function of actin cortex by cell signalling 4 Micromechanics and microrheometry of cells 5 Activation of endothelial cells: On the possibility of formation of stress fibers as phase transition of actin-network triggered by cell signalling pathways 6 On cells as adaptive viscoplastic bodies 7 Controll of cellular protrusions controlled by actin/myosin cortex

  16. Tracking Membrane Protein Association in Model Membranes

    PubMed Central

    Reffay, Myriam; Gambin, Yann; Benabdelhak, Houssain; Phan, Gilles; Taulier, Nicolas; Ducruix, Arnaud; Hodges, Robert S.; Urbach, Wladimir

    2009-01-01

    Membrane proteins are essential in the exchange processes of cells. In spite of great breakthrough in soluble proteins studies, membrane proteins structures, functions and interactions are still a challenge because of the difficulties related to their hydrophobic properties. Most of the experiments are performed with detergent-solubilized membrane proteins. However widely used micellar systems are far from the biological two-dimensions membrane. The development of new biomimetic membrane systems is fundamental to tackle this issue. We present an original approach that combines the Fluorescence Recovery After fringe Pattern Photobleaching technique and the use of a versatile sponge phase that makes it possible to extract crucial informations about interactions between membrane proteins embedded in the bilayers of a sponge phase. The clear advantage lies in the ability to adjust at will the spacing between two adjacent bilayers. When the membranes are far apart, the only possible interactions occur laterally between proteins embedded within the same bilayer, whereas when membranes get closer to each other, interactions between proteins embedded in facing membranes may occur as well. After validating our approach on the streptavidin-biotinylated peptide complex, we study the interactions between two membrane proteins, MexA and OprM, from a Pseudomonas aeruginosa efflux pump. The mode of interaction, the size of the protein complex and its potential stoichiometry are determined. In particular, we demonstrate that: MexA is effectively embedded in the bilayer; MexA and OprM do not interact laterally but can form a complex if they are embedded in opposite bilayers; the population of bound proteins is at its maximum for bilayers separated by a distance of about 200 Å, which is the periplasmic thickness of Pseudomonas aeruginosa. We also show that the MexA-OprM association is enhanced when the position and orientation of the protein is restricted by the bilayers. We

  17. Elastic membranes in confinement

    NASA Astrophysics Data System (ADS)

    Bostwick, Joshua; Miksis, Michael; Davis, Stephen

    2014-11-01

    An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and DNA, have finer internal structure in which a membrane (or elastic member) is geometrically ``confined'' by another object. We study the shape stability of elastic membranes in a ``confining'' box and introduce repulsive van der Waals forces to prevent the membrane from intersecting the wall. We aim to define the parameter space associated with mitochondria-like deformations. We compare the confined to `unconfined' solutions and show how the structure and stability of the membrane shapes changes with the system parameters.

  18. Separation membrane development

    SciTech Connect

    Lee, M.W.

    1998-08-01

    A ceramic membrane has been developed to separate hydrogen from other gases. The method used is a sol-gel process. A thin layer of dense ceramic material is coated on a coarse ceramic filter substrate. The pore size distribution in the thin layer is controlled by a densification of the coating materials by heat treatment. The membrane has been tested by permeation measurement of the hydrogen and other gases. Selectivity of the membrane has been achieved to separate hydrogen from carbon monoxide. The permeation rate of hydrogen through the ceramic membrane was about 20 times larger than Pd-Ag membrane.

  19. Three dimensional microscopic surface profiles of membranes reconstructed from freeze etching electrol micrographs.

    PubMed

    Krbecek, R; Gebhardt, C; Gruler, H; Sackmann, E

    1979-06-13

    A method of three-dimensional reconstruction of the surface profile of artificial and natural membranes from freeze quenched electron micrographs is presented. The method is based on the analysis of the variation in thickness of platinum layers, deposited under an oblique angle. In essence, it is reminiscent of the method of Eratosthenes to measure the earth's radius. The thickness of etch-like protrusions of membranes could be determined to an accuracy of about 3 A. True distances on curved surfaces rather than projections of distances are obtained. The method has been applied to both model membranes and biological membranes. The essential results are: 1. Detailed information on the symmetry and the molecular structure of the crystalline phases of dimyristoyl phosphatidylcholine was obtained. The microscopic surface profile of the ripple structure observed between the pretransition and the main transition was analysed. In accordance with a previous model we found that the ripple structure is caused by the spontaneous curvature of the monolayers. The surface profiles of the ripple structure and of the low temperature biaxial phase could be clearly distinguished. 2. The sizes and shapes of lipid domains formed by both thermically and charge-induced lateral phase separation were determined. This showed that the visual inspection of electron micrographs may lead to a considerable underestimation of the domain size. Conclusions may be drawn concerning the different phases formed upon lateral phase separation. 3. As a biological example, yeast cell membranes were studied. The method allows one to distinguish between different membrane-bound proteins by measuring the width-to-height ratio of the particles. The deformation of the lipid layer in the environment of the proteins may be determined. This deformation contains information about lipid-mediated long-range interactions between membrane proteins. PMID:378255

  20. Feedback Interactions of Polymerized Actin with the Cell Membrane: Waves, Pulses, and Oscillations

    NASA Astrophysics Data System (ADS)

    Carlsson, Anders

    Polymerized filaments of the protein actin have crucial functions in cell migration, and in bending the cell membrane to drive endocytosis or the formation of protrusions. The nucleation and polymerization of actin filaments are controlled by upstream agents in the cell membrane, including nucleation-promoting factors (NPFs) that activate the Arp2/3 complex to form new branches on pre-existing filaments. But polymerized actin (F-actin) also feeds back on the assembly of NPFs. We explore the effects of the resulting feedback loop of F-actin and NPFs on two phenomena: actin pulses that drive endocytosis in yeast, and actin waves traveling along the membrane of several cell types. In our model of endocytosis in yeast, the actin network is grown explicitly in three dimensions, exerts a negative feedback interaction on localized patch of NPFs in the membrane, and bends the membrane by exerting a distribution of forces. This model explains observed actin and NPF pulse dynamics, and the effects of several interventions including i) NPF mutations, ii) inhibition of actin polymerization, and iii) deletion of a protein that allows F-actin to bend the cell membrane. The model predicts that mutation of the active region of an NPF will enhance the accumulation of that NPF, and we confirm this prediction by quantitative fluorescence microscopy. For actin waves, we treat a similar model, with NPFs distributed over a larger region of the cell membrane. This model naturally generates actin waves, and predicts a transition from wave behavior to spatially localized oscillations when NPFs are confined to a small region. We also predict a transition from waves to static polarization as the negative-feedback coupling between F-actin and the NPFs is reduced. Supported by NIGMS Grant R01 GM107667.

  1. Membrane Flotation Assay

    PubMed Central

    Vogt, Dorothee A; Ott, Melanie

    2016-01-01

    Many postitive-stranded RNA viruses, such as Hepatitis C virus (HCV), highjack cellular membranes, including the Golgi, ER, mitchondria, lipid droplets, and utilize them for replication of their RNA genome or assembly of new virions. By investigating how viral proteins associate with cellular membranes we will better understand the roles of cellular membranes in the viral life cycle. Our lab has focused specifically on the role of lipid droplets and lipid-rich membranes in the life cycle of HCV. To analyze the role of lipid-rich membranes in HCV RNA replication, we utilized a membrane flotation assay based on an 10–20–30% iodixanol density gradient developed by Yeaman et al. (2001). This gradient results in a linear increase in density over almost the entire length of the gradient, and membrane particles are separated in the gradient based on their buoyant characteristics. To preserve membranes in the lysate, cells are broken mechanically in a buffer lacking detergent. The cell lysate is loaded on the bottom of the gradient, overlaid with the gradient, and membranes float up as the iodixanol gradient self-generates. The lipid content of membranes and the concentration of associated proteins will determine the separation of different membranes within the gradient. After centrifugation, fractions can be sampled from the top of the gradient and analyzed using standard SDS-PAGE and western blot analysis for proteins of interest.

  2. Water Membrane Evaporator

    NASA Technical Reports Server (NTRS)

    Ungar, Eugene K.; Almlie, Jay C.

    2010-01-01

    A water membrane evaporator (WME) has been conceived and tested as an alternative to the contamination-sensitive and corrosion-prone evaporators currently used for dissipating heat from space vehicles. The WME consists mainly of the following components: An outer stainless-steel screen that provides structural support for the components mentioned next; Inside and in contact with the stainless-steel screen, a hydrophobic membrane that is permeable to water vapor; Inside and in contact with the hydrophobic membrane, a hydrophilic membrane that transports the liquid feedwater to the inner surface of the hydrophobic membrane; Inside and in contact with the hydrophilic membrane, an annular array of tubes through which flows the spacecraft coolant carrying the heat to be dissipated; and An inner exclusion tube that limits the volume of feedwater in the WME. In operation, a pressurized feedwater reservoir is connected to the volume between the exclusion tube and the coolant tubes. Feedwater fills the volume, saturates the hydrophilic membrane, and is retained by the hydrophobic membrane. The outside of the WME is exposed to space vacuum. Heat from the spacecraft coolant is conducted through the tube walls and the water-saturated hydrophilic membrane to the liquid/vapor interface at the hydrophobic membrane, causing water to evaporate to space. Makeup water flows into the hydrophilic membrane through gaps between the coolant tubes.

  3. Catalytic membranes beckon

    SciTech Connect

    Caruana, C.M.

    1994-11-01

    Chemical engineers here and abroad are finding that the marriage of catalysts and membranes holds promise for faster and more specific reactions, although commercialization of this technology is several years away. Catalytic membrane reactors (CMRs) combine a heterogeneous catalyst and a permselective membrane. Reactions performed by CMRs provide higher yields--sometimes as much as 50% higher--because of better reaction selectivity--as opposed to separation selectivity. CMRs also can work at very high temperatures, using ceramic materials that would not be possible with organic membranes. Although the use of CMRs is not widespread presently, the development of new membranes--particularly porous ceramic and zeolite membranes--will increase the potential to improve yields of many catalytic processes. The paper discusses ongoing studies, metal and advanced materials for membranes, the need for continued research, hydrogen recovery from coal-derived gases, catalytic oxidation of sulfides, CMRs for water purification, and oxidative coupling of methane.

  4. Phosphatidic acid is required for the constitutive ruffling and macropinocytosis of phagocytes.

    PubMed

    Bohdanowicz, Michal; Schlam, Daniel; Hermansson, Martin; Rizzuti, David; Fairn, Gregory D; Ueyama, Takehiko; Somerharju, Pentti; Du, Guangwei; Grinstein, Sergio

    2013-06-01

    Macrophages and dendritic cells continuously survey their environment in search of foreign particles and soluble antigens. Such surveillance involves the ongoing extension of actin-rich protrusions and the consequent formation of phagosomes and macropinosomes. The signals inducing this constitutive cytoskeletal remodeling have not been defined. We report that, unlike nonphagocytic cells, macrophages and immature dendritic cells have elevated levels of phosphatidic acid (PA) in their plasma membrane. The plasmalemmal PA is synthesized by phosphorylation of diacylglycerol, which is in turn generated by a G protein-stimulated phospholipase C. Inhibition of diacylglycerol kinase activity results in the detachment of T-cell lymphoma invasion and metastasis-inducing protein 1 (TIAM1)-a Rac guanine exchange factor-from the plasma membrane, thereby depressing Rac activity and abolishing the constitutive ruffling and macropinocytosis that characterize macrophages and immature dendritic cells. Accumulation of PA and binding of TIAM1 to the membrane require the activity of phosphatidylinositol-4,5-bisphosphate 3-kinase. Thus a distinctive, constitutive pathway of PA biosynthesis promotes the actin remodeling required for immune surveillance. PMID:23576545

  5. Polymers at membranes

    NASA Astrophysics Data System (ADS)

    Breidenich, Markus

    2000-11-01

    The surface of biological cells consists of a lipid membrane and a large amount of various proteins and polymers, which are embedded in the membrane or attached to it. We investigate how membranes are influenced by polymers, which are anchored to the membrane by one end. The entropic pressure exerted by the polymer induces a curvature, which bends the membrane away from the polymer. The resulting membrane shape profile is a cone in the vicinity of the anchor segment and a catenoid far away from it. The perturbative calculations are confirmed by Monte-Carlo simulations. An additional attractive interaction between polymer and membrane reduces the entropically induced curvature. In the limit of strong adsorption, the polymer is localized directly on the membrane surface and does not induce any pressure, i.e. the membrane curvature vanishes. If the polymer is not anchored directly on the membrane surface, but in a non-vanishing anchoring distance, the membrane bends towards the polymer for strong adsorption. In the last part of the thesis, we study membranes under the influence of non-anchored polymers in solution. In the limit of pure steric interactions between the membrane and free polymers, the membrane curves towards the polymers (in contrast to the case of anchored polymers). In the limit of strong adsorption the membrane bends away from the polymers. Die Oberfläche biologischer Zellen besteht aus einer Lipidmembran und einer Vielzahl von Proteinen und Polymeren, die in die Membran eingebaut sind. Die Beeinflussung der Membran durch Polymere, die mit einem Ende an der Membran verankert sind, wird im Rahmen dieser Arbeit anhand eines vereinfachten biomimetischen Systems studiert. Der entropische Druck, den das Polymer durch Stöße auf die Membran ausübt, führt dazu, dass sich die Membran vom Polymer weg krümmt. Die resultierende Membranform ist ein Kegel in der Nähe des Ankers und ein Katenoid in grossem Abstand vom Ankerpunkt. Monte Carlo-Simulationen best

  6. Membrane with supported internal passages

    NASA Technical Reports Server (NTRS)

    Gonzalez-Martin, Anuncia (Inventor); Salinas, Carlos E. (Inventor); Cisar, Alan J. (Inventor); Hitchens, G. Duncan (Inventor); Murphy, Oliver J. (Inventor)

    2000-01-01

    The invention provides an improved proton exchange membrane for use in electrochemical cells having internal passages parallel to the membrane surface comprising permanent tubes preferably placed at the ends of the fluid passages. The invention also provides an apparatus and process for making the membrane, membrane and electrode assemblies fabricated using the membrane, and the application of the membrane and electrode assemblies to a variety of devices, both electrochemical and otherwise. The passages in the membrane extend from one edge of the membrane to another and allow fluid flow through the membrane and give access directly to the membrane.

  7. Poxvirus Membrane Biogenesis

    PubMed Central

    2015-01-01

    Poxviruses differ from most DNA viruses by replicating entirely within the cytoplasm. The first discernible viral structures are crescents and spherical immature virions containing a single lipoprotein membrane bilayer with an external honeycomb lattice. Because this viral membrane displays no obvious continuity with a cellular organelle, a de novo origin was suggested. Nevertheless, transient connections between viral and cellular membranes could be difficult to resolve. Despite the absence of direct evidence, the intermediate compartment (ERGIC) between the endoplasmic reticulum (ER) and Golgi apparatus and the ER itself were considered possible sources of crescent membranes. A break-through in understanding poxvirus membrane biogenesis has come from recent studies of the abortive replication of several vaccinia virus null mutants. Novel images showing continuity between viral crescents and the ER and the accumulation of immature virions in the expanded ER lumen provide the first direct evidence for a cellular origin of this poxvirus membrane. PMID:25728299

  8. Poxvirus membrane biogenesis.

    PubMed

    Moss, Bernard

    2015-05-01

    Poxviruses differ from most DNA viruses by replicating entirely within the cytoplasm. The first discernible viral structures are crescents and spherical immature virions containing a single lipoprotein membrane bilayer with an external honeycomb lattice. Because this viral membrane displays no obvious continuity with a cellular organelle, a de novo origin was suggested. Nevertheless, transient connections between viral and cellular membranes could be difficult to resolve. Despite the absence of direct evidence, the intermediate compartment (ERGIC) between the endoplasmic reticulum (ER) and Golgi apparatus and the ER itself were considered possible sources of crescent membranes. A break-through in understanding poxvirus membrane biogenesis has come from recent studies of the abortive replication of several vaccinia virus null mutants. Novel images showing continuity between viral crescents and the ER and the accumulation of immature virions in the expanded ER lumen provide the first direct evidence for a cellular origin of this poxvirus membrane. PMID:25728299

  9. Substituted polyacetylene separation membrane

    DOEpatents

    Pinnau, Ingo; Morisato, Atsushi

    1998-01-13

    A separation membrane useful for gas separation, particularly separation of C.sub.2+ hydrocarbons from natural gas. The invention encompasses the membrane itself, methods of making it and processes for using it. The membrane comprises a polymer having repeating units of a hydrocarbon-based, disubstituted polyacetylene, having the general formula: ##STR1## wherein R.sub.1 is chosen from the group consisting of C.sub.1 -C.sub.4 alkyl and phenyl, and wherein R.sub.2 is chosen from the group consisting of hydrogen and phenyl. In the most preferred embodiment, the membrane comprises poly(4-methyl-2-pentyne) ›PMP!. The membrane exhibits good chemical resistance and has super-glassy properties with regard to separating certain large, condensable permeant species from smaller, less-condensable permeant species. The membranes may also be useful in other fluid separations.

  10. Substituted polyacetylene separation membrane

    DOEpatents

    Pinnau, I.; Morisato, Atsushi

    1998-01-13

    A separation membrane is described which is useful for gas separation, particularly separation of C{sub 2+} hydrocarbons from natural gas. The invention encompasses the membrane itself, methods of making it and processes for using it. The membrane comprises a polymer having repeating units of a hydrocarbon-based, disubstituted polyacetylene, having the general formula shown in the accompanying diagram, wherein R{sub 1} is chosen from the group consisting of C{sub 1}-C{sub 4} alkyl and phenyl, and wherein R{sub 2} is chosen from the group consisting of hydrogen and phenyl. In the most preferred embodiment, the membrane comprises poly(4-methyl-2-pentyne) [PMP]. The membrane exhibits good chemical resistance and has super-glassy properties with regard to separating certain large, condensable permeant species from smaller, less-condensable permeant species. The membranes may also be useful in other fluid separations. 4 figs.

  11. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Alexander, S.; Hodgdon, R. B.

    1977-01-01

    The objective of NAS 3-20108 was the development and evaluation of improved anion selective membranes useful as efficient separators in a redox power storage cell system being constructed. The program was divided into three parts, (a) optimization of the selected candidate membrane systems, (b) investigation of alternative membrane/polymer systems, and (c) characterization of candidate membranes. The major synthesis effort was aimed at improving and optimizing as far as possible each candidate system with respect to three critical membrane properties essential for good redox cell performance. Substantial improvements were made in 5 candidate membrane systems. The critical synthesis variables of cross-link density, monomer ratio, and solvent composition were examined over a wide range. In addition, eight alternative polymer systems were investigated, two of which attained candidate status. Three other alternatives showed potential but required further research and development. Each candidate system was optimized for selectivity.

  12. Differing strategies of patterning of follicular cells in higher and lower brachycerans (Diptera: Brachycera).

    PubMed

    Tworzydlo, Waclaw; Jablonska, Anna; Kisiel, Elzbieta; Bilinski, Szczepan M

    2005-10-01

    In all higher dipterans (Brachycera), including the fruitfly, Drosophila melanogaster, each egg chamber (ovarian follicle) consists of a group (clone) of germ cells (one oocyte and 15 accompanying nurse cells) that is surrounded by a layer of somatic mesodermal follicular cells (FCs). As oogenesis progresses the initially uniform FCs diversify into several morphologically and functionally distinct subpopulations. In D. melanogaster some of these subpopulations, e.g., border, centripetal, and dorsolateral cells, undertake coordinated migration or rearrangement over the surface of the germ cells. During the final stages of oogenesis these subpopulations participate in the formation of a complex, regionally specialized eggshell. In representatives of lower brachycerans (Orthorrhapha), only FCs that undertake active, directed migration are the border cells. These cells originate at the anterior pole of the ovarian follicle and migrate between the nurse cells to the anterior pole of the oocyte. Reduced motility of FCs in lower brachycerans results in the absence of certain FC subpopulations in their egg chambers and subsequent simplicity of their eggshells. We found that the lack of some FC subpopulations coincided with the appearance of lamellipodium-like protrusions of the oocyte. These protrusions penetrated between the apposing membranes of nurse and FCs and partially enveloped the nurse cell compartment. Analysis of whole-mount preparations stained with rhodamine-conjugated phalloidin revealed that the protrusions contained microfilaments and that their tips were equipped with actin-rich filopodium-like processes. We also found that in some lower brachycerans (representatives of the family Rhagionidae), the FCs located at the posterior pole of the oocyte, became enlarged and morphologically similar to the anterior border cells. These findings indicate that in higher dipterans the processes leading to the formation of a functional egg are variable and often markedly

  13. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Hodgdon, R. B.; Waite, W. A.; Alexander, S. S.

    1984-01-01

    Two polymer ion exchange membranes were synthesized to fulfill the needs of both electrical resistivity and anolyte/catholyte separation for utility load leveling utilizing the DOE/NASA mixed electrolyte REDOX battery. Both membranes were shown to meet mixed electrolyte utility load leveling criteria. Several modifications of an anion exchange membrane failed to meet utility load leveling REDOX battery criteria using the unmixed electrolyte REDOX cell.

  14. Anion permselective membrane

    NASA Astrophysics Data System (ADS)

    Hodgdon, R. B.; Waite, W. A.; Alexander, S. S.

    1984-07-01

    Two polymer ion exchange membranes were synthesized to fulfill the needs of both electrical resistivity and anolyte/catholyte separation for utility load leveling utilizing the DOE/NASA mixed electrolyte REDOX battery. Both membranes were shown to meet mixed electrolyte utility load leveling criteria. Several modifications of an anion exchange membrane failed to meet utility load leveling REDOX battery criteria using the unmixed electrolyte REDOX cell.

  15. Siloxane-grafted membranes

    DOEpatents

    Friesen, Dwayne T.; Obligin, Alan S.

    1989-01-01

    Composite cellulosic semipermeable membranes are disclosed which are the covalently bonded reaction product of an asymmetric cellulosic semipermeable membrane and a polysiloxane containing reactive functional groups. The two reactants chemically bond by ether, ester, amide or acrylate linkages to form a siloxane-grafted cellulosic membrane having superior selectivity and flux stability. Selectivity may be enhanced by wetting the surface with a swelling agent such as water.

  16. Polyarylether composition and membrane

    DOEpatents

    Hung, Joyce; Brunelle, Daniel Joseph; Harmon, Marianne Elisabeth; Moore, David Roger; Stone, Joshua James; Zhou, Hongyi; Suriano, Joseph Anthony

    2010-11-09

    A composition including a polyarylether copolymer is provided. The copolymer includes a polyarylether backbone; and a sulfonated oligomeric group bonded to the polyarylether suitable for use as a cation conducting membrane. Method of bonding a sulfonated oligomeric group to the polyarylether backbone to form a polyarylether copolymer. The membrane may be formed from the polyarylether copolymer composition. The chain length of the sulfonated oligomeric group may be controlled to affect or control the ion conductivity of the membrane.

  17. Siloxane-grafted membranes

    DOEpatents

    Friesen, D.T.; Obligin, A.S.

    1989-10-31

    Composite cellulosic semipermeable membranes are disclosed which are the covalently bonded reaction product of an asymmetric cellulosic semipermeable membrane and a polysiloxane containing reactive functional group. The two reactants chemically bond by ether, ester, amide or acrylate linkages to form a siloxane-grafted cellulosic membrane having superior selectivity and flux stability. Selectivity may be enhanced by wetting the surface with a swelling agent such as water.

  18. Proteins causing membrane fouling in membrane bioreactors.

    PubMed

    Miyoshi, Taro; Nagai, Yuhei; Aizawa, Tomoyasu; Kimura, Katsuki; Watanabe, Yoshimasa

    2015-01-01

    In this study, the details of proteins causing membrane fouling in membrane bioreactors (MBRs) treating real municipal wastewater were investigated. Two separate pilot-scale MBRs were continuously operated under significantly different operating conditions; one MBR was a submerged type whereas the other was a side-stream type. The submerged and side-stream MBRs were operated for 20 and 10 days, respectively. At the end of continuous operation, the foulants were extracted from the fouled membranes. The proteins contained in the extracted foulants were enriched by using the combination of crude concentration with an ultrafiltration membrane and trichloroacetic acid precipitation, and then separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). The N-terminal amino acid sequencing analysis of the proteins which formed intensive spots on the 2D-PAGE gels allowed us to partially identify one protein (OmpA family protein originated from genus Brevundimonas or Riemerella anatipestifer) from the foulant obtained from the submerged MBR, and two proteins (OprD and OprF originated from genus Pseudomonas) from that obtained from the side-stream MBR. Despite the significant difference in operating conditions of the two MBRs, all proteins identified in this study belong to β-barrel protein. These findings strongly suggest the importance of β-barrel proteins in developing membrane fouling in MBRs. PMID:26360742

  19. Biomolecular membrane protein crystallization

    NASA Astrophysics Data System (ADS)

    Reddy Bolla, Jani; Su, Chih-Chia; Yu, Edward W.

    2012-07-01

    Integral membrane proteins comprise approximately 30% of the sequenced genomes, and there is an immediate need for their high-resolution structural information. Currently, the most reliable approach to obtain these structures is X-ray crystallography. However, obtaining crystals of membrane proteins that diffract to high resolution appears to be quite challenging, and remains a major obstacle in structural determination. This brief review summarizes a variety of methodologies for use in crystallizing these membrane proteins. Hopefully, by introducing the available methods, techniques, and providing a general understanding of membrane proteins, a rational decision can be made about now to crystallize these complex materials.

  20. Plant cell membranes

    SciTech Connect

    Packer, L.; Douce, R.

    1987-01-01

    The contents of this book are: Cells, Protoplasts, Vacuoles and Liposomes; Tonoplasts; Nuclei, Endolplasmic Reticulum, and Plasma Membrane; Peroxisomes; Plastids; Teneral Physical and Biochemical Methods; and Mitochondira.

  1. Drugging Membrane Protein Interactions.

    PubMed

    Yin, Hang; Flynn, Aaron D

    2016-07-11

    The majority of therapeutics target membrane proteins, accessible on the surface of cells, to alter cellular signaling. Cells use membrane proteins to transduce signals into cells, transport ions and molecules, bind cells to a surface or substrate, and catalyze reactions. Newly devised technologies allow us to drug conventionally "undruggable" regions of membrane proteins, enabling modulation of protein-protein, protein-lipid, and protein-nucleic acid interactions. In this review, we survey the state of the art of high-throughput screening and rational design in drug discovery, and we evaluate the advances in biological understanding and technological capacity that will drive pharmacotherapy forward against unorthodox membrane protein targets. PMID:26863923

  2. Membrane Tension Control

    NASA Technical Reports Server (NTRS)

    Su, Ji (Inventor); Harrison, Joycelyn S. (Inventor)

    2005-01-01

    An electrostrictive polymer actuator comprises an electrostrictive polymer with a tailorable Poisson's ratio. The electrostrictive polymer is electroded on its upper and lower surfaces and bonded to an upper material layer. The assembly is rolled tightly and capped at its ends. In a membrane structure having a membrane, a supporting frame and a plurality of threads connecting the membrane to the frame, an actuator can be integrated into one or more of the plurality of threads. The electrostrictive polymer actuator displaces along its longitudinal axis, thereby affecting movement of the membrane surface.

  3. Gas separation membranes

    DOEpatents

    Schell, William J.

    1979-01-01

    A dry, fabric supported, polymeric gas separation membrane, such as cellulose acetate, is prepared by casting a solution of the polymer onto a shrinkable fabric preferably formed of synthetic polymers such as polyester or polyamide filaments before washing, stretching or calendering (so called griege goods). The supported membrane is then subjected to gelling, annealing, and drying by solvent exchange. During the processing steps, both the fabric support and the membrane shrink a preselected, controlled amount which prevents curling, wrinkling or cracking of the membrane in flat form or when spirally wound into a gas separation element.

  4. Anion exchange membrane

    DOEpatents

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  5. A Non-sulfated Chondroitin Stabilizes Membrane Tubulation in Cnidarian Organelles*

    PubMed Central

    Adamczyk, Patrizia; Zenkert, Claudia; Balasubramanian, Prakash G.; Yamada, Shuhei; Murakoshi, Saori; Sugahara, Kazuyuki; Hwang, Jung Shan; Gojobori, Takashi; Holstein, Thomas W.; Özbek, Suat

    2010-01-01

    Membrane tubulation is generally associated with rearrangements of the cytoskeleton and other cytoplasmic factors. Little is known about the contribution of extracellular matrix components to this process. Here, we demonstrate an essential role of proteoglycans in the tubulation of the cnidarian nematocyst vesicle. The morphogenesis of this extrusive organelle takes place inside a giant post-Golgi vesicle, which topologically represents extracellular space. This process includes the formation of a complex collagenous capsule structure that elongates into a long tubule, which invaginates after its completion. We show that a non-sulfated chondroitin appears as a scaffold in early morphogenesis of all nematocyst types in Hydra and Nematostella. It accompanies the tubulation of the vesicle membrane forming a provisional tubule structure, which after invagination matures by collagen incorporation. Inhibition of chondroitin synthesis by β-xylosides arrests nematocyst morphogenesis at different stages of tubule outgrowth resulting in retention of tubule material and a depletion of mature capsules in the tentacles of hydra. Our data suggest a conserved role of proteoglycans in the stabilization of a membrane protrusion as an essential step in organelle morphogenesis. PMID:20538610

  6. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Hodgdon, R. B.; Waite, W. A.

    1982-01-01

    The synthesis and fabrication of polymeric anion permselective membranes for redox systems are discussed. Variations of the prime candidate anion membrane formulation to achieve better resistance and/or lower permeability were explored. Processing parameters were evaluated to lower cost and fabricate larger sizes. The processing techniques to produce more membranes per batch were successfully integrated with the fabrication of larger membranes. Membranes of about 107 cm x 51 cm were made in excellent yield. Several measurements were made on the larger sample membranes. Among the data developed were water transport and transference numbers for these prime candidate membranes at 20 C. Other work done on this system included characterization of a number of specimens of candidate membranes which had been returned after service lives of up to sixteen months. Work with new polymer constituents, with new N.P.'s, catalysts and backing fabrics is discussed. Some work was also done to evaluate other proportions of the ingredients of the prime candidate system. The adoption of a flow selectivity test at elevated temperature was explored.

  7. Membrane in cancer cells

    SciTech Connect

    Galeotti, T.; Cittadini, A.; Neri, G.; Scarpa, A.

    1988-01-01

    This book contains papers presented at a conference on membranes in cancer cells. Topics covered include Oncogenies, hormones, and free-radical processes in malignant transformation in vitro and Superoxide onion may trigger DNA strand breaks in human granulorytes by acting as a membrane target.

  8. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, M.A.; Guangyao Sheng.

    1993-05-04

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  9. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  10. Polymide gas separation membranes

    DOEpatents

    Ding, Yong; Bikson, Benjamin; Nelson, Joyce Katz

    2004-09-14

    Soluble polyamic acid salt (PAAS) precursors comprised of tertiary and quaternary amines, ammonium cations, sulfonium cations, or phosphonium cations, are prepared and fabricated into membranes that are subsequently imidized and converted into rigid-rod polyimide articles, such as membranes with desirable gas separation properties. A method of enhancing solubility of PAAS polymers in alcohols is also disclosed.

  11. Membrane module assembly

    DOEpatents

    Kaschemekat, Jurgen

    1994-01-01

    A membrane module assembly adapted to provide a flow path for the incoming feed stream that forces it into prolonged heat-exchanging contact with a heating or cooling mechanism. Membrane separation processes employing the module assembly are also disclosed. The assembly is particularly useful for gas separation or pervaporation.

  12. Membrane module assembly

    DOEpatents

    Kaschemekat, J.

    1994-03-15

    A membrane module assembly is described which is adapted to provide a flow path for the incoming feed stream that forces it into prolonged heat-exchanging contact with a heating or cooling mechanism. Membrane separation processes employing the module assembly are also disclosed. The assembly is particularly useful for gas separation or pervaporation. 2 figures.

  13. Membrane Transport Phenomena (MTP)

    NASA Technical Reports Server (NTRS)

    Mason, Larry W.

    1996-01-01

    The development of the seal between the membrane and the Fluid Optical Cells (FOC) has been a high priority activity. This seal occurs at an interface in the instrument where three key functions must be realized: (1) physical membrane support, (2) fluid sealing, and (3) unobscured optical transmission.

  14. Permeable membrane experiment

    NASA Technical Reports Server (NTRS)

    Slavin, Thomas J.; Cao, Tuan Q.; Kliss, Mark H.

    1993-01-01

    The purpose of the Permeable Membrane Experiment is to gather flight data on three areas of membrane performance that are influenced by the presence of gravity. These areas are: (1) Liquid/gas phase separation, (2) gas bubble interference with diffusion through porous membranes and (3) wetting characteristics of hydrophilic membrane surfaces. These data are important in understaning the behavior of membrane/liquid/gas interfaces where surface tension forces predominate. The data will be compared with 1-g data already obtained and with predicted micrograviity behavior. The data will be used to develop designs for phase separation and plant nutrient delivery systems and will be available to the life support community for use in developing technologies which employ membranes. A conceptual design has been developed to conduct three membrane experiments, in sequence, aboard a single Complex Autonomous Payload (CAP) carrier to be carried in the Shuttle Orbiter payload bay. One experiment is conducted for each of the three membrane performance areas under study. These experiments are discussed in this paper.

  15. Viral Membrane Scission

    PubMed Central

    Rossman, Jeremy S.; Lamb, Robert A.

    2014-01-01

    Virus budding is a complex, multistep process in which viral proteins make specific alterations in membrane curvature. Many different viral proteins can deform the membrane and form a budding virion, but very few can mediate membrane scission to complete the budding process. As a result, enveloped viruses have developed numerous ways of facilitating membrane scission, including hijacking host cellular scission machinery and expressing their own scission proteins. These proteins mediate scission in very different ways, though the biophysical mechanics underlying their actions may be similar. In this review, we explore the mechanisms of membrane scission and the ways in which enveloped viruses use these systems to mediate the release of budding virions. PMID:24099087

  16. Ion-conducting membranes

    DOEpatents

    Masel, Richard L.; Chen, Qingmei; Liu, Zengcai; Kutz, Robert

    2016-06-21

    An ion conducting polymeric composition mixture comprises a copolymer of styrene and vinylbenzyl-R.sub.s. R.sub.s is selected from the group consisting of imidazoliums and pyridiniums. The composition contains 10%-90% by weight of vinylbenzyl-R.sub.s. The composition can further comprise a polyolefin comprising substituted polyolefins, a polymer comprising cyclic amine groups, a polymer comprising at least one of a phenylene group and a phenyl group, a polyamide, and/or the reaction product of a constituent having two carbon-carbon double bonds. The composition can be in the form of a membrane. In a preferred embodiment, the membrane is a Helper Membrane that increases the faradaic efficiency of an electrochemical cell into which the membrane is incorporated, and also allows product formation at lower voltages than in cells without the Helper Membrane.

  17. Anton permselective membrane

    NASA Technical Reports Server (NTRS)

    Alexander, S. S.; Hodgdon, R. B.; Waite, W. A.

    1979-01-01

    Experimental composite membranes were synthesized on a lab scale consisting of a thin layer of anion permselective resin supported by and bonded to a porous physically strong and conductive substrate film. These showed good selectivity and also substantially lower electrical resistivities than the homogenous candidate membranes optimized in the previous contract. A wide range of resin porosities were examined for three candidate membrane systems, CDIL, CP4L, and A3L to identify the formulation giving the best overall redox cell performance. Candidate anion membranes showed large increases in resistivity after a short time of immersion in concentrated FeCl/HCl solution. Largely on the basis of resistance stability the CDIL formulation was selected as prime candidate and about thirty-five membranes (one foot square) were produced for experimental static and dynamic evaluation.

  18. Elastic membranes in confinement.

    PubMed

    Bostwick, J B; Miksis, M J; Davis, S H

    2016-07-01

    An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and coiled DNA, have fine internal structure in which a membrane (or elastic member) is geometrically 'confined' by another object. Here, the two-dimensional shape of an elastic membrane in a 'confining' box is studied by introducing a repulsive confinement pressure that prevents the membrane from intersecting the wall. The stage is set by contrasting confined and unconfined solutions. Continuation methods are then used to compute response diagrams, from which we identify the particular membrane mechanics that generate mitochondria-like shapes. Large confinement pressures yield complex response diagrams with secondary bifurcations and multiple turning points where modal identities may change. Regions in parameter space where such behaviour occurs are then mapped. PMID:27440257

  19. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2002-04-01

    This report covers the following tasks: Task 1--Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints; Task 2--Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability; Task 3--Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres; Task 4--Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures; Task 5--Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability; and Task 6--Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  20. Membrane projection lithography

    DOEpatents

    Burckel, David Bruce; Davids, Paul S; Resnick, Paul J; Draper, Bruce L

    2015-03-17

    The various technologies presented herein relate to a three dimensional manufacturing technique for application with semiconductor technologies. A membrane layer can be formed over a cavity. An opening can be formed in the membrane such that the membrane can act as a mask layer to the underlying wall surfaces and bottom surface of the cavity. A beam to facilitate an operation comprising any of implantation, etching or deposition can be directed through the opening onto the underlying surface, with the opening acting as a mask to control the area of the underlying surfaces on which any of implantation occurs, material is removed, and/or material is deposited. The membrane can be removed, a new membrane placed over the cavity and a new opening formed to facilitate another implantation, etching, or deposition operation. By changing the direction of the beam different wall/bottom surfaces can be utilized to form a plurality of structures.

  1. Alterations of Red Cell Membrane Properties in Nneuroacanthocytosis

    PubMed Central

    Siegl, Claudia; Hamminger, Patricia; Jank, Herbert; Ahting, Uwe; Bader, Benedikt; Danek, Adrian; Gregory, Allison; Hartig, Monika; Hayflick, Susan; Hermann, Andreas; Prokisch, Holger; Sammler, Esther M.; Yapici, Zuhal; Prohaska, Rainer; Salzer, Ulrich

    2013-01-01

    Neuroacanthocytosis (NA) refers to a group of heterogenous, rare genetic disorders, namely chorea acanthocytosis (ChAc), McLeod syndrome (MLS), Huntington’s disease-like 2 (HDL2) and pantothenate kinase associated neurodegeneration (PKAN), that mainly affect the basal ganglia and are associated with similar neurological symptoms. PKAN is also assigned to a group of rare neurodegenerative diseases, known as NBIA (neurodegeneration with brain iron accumulation), associated with iron accumulation in the basal ganglia and progressive movement disorder. Acanthocytosis, the occurrence of misshaped erythrocytes with thorny protrusions, is frequently observed in ChAc and MLS patients but less prevalent in PKAN (about 10%) and HDL2 patients. The pathological factors that lead to the formation of the acanthocytic red blood cell shape are currently unknown. The aim of this study was to determine whether NA/NBIA acanthocytes differ in their functionality from normal erythrocytes. Several flow-cytometry-based assays were applied to test the physiological responses of the plasma membrane, namely drug-induced endocytosis, phosphatidylserine exposure and calcium uptake upon treatment with lysophosphatidic acid. ChAc red cell samples clearly showed a reduced response in drug-induced endovesiculation, lysophosphatidic acid-induced phosphatidylserine exposure, and calcium uptake. Impaired responses were also observed in acanthocyte-positive NBIA (PKAN) red cells but not in patient cells without shape abnormalities. These data suggest an “acanthocytic state” of the red cell where alterations in functional and interdependent membrane properties arise together with an acanthocytic cell shape. Further elucidation of the aberrant molecular mechanisms that cause this acanthocytic state may possibly help to evaluate the pathological pathways leading to neurodegeneration. PMID:24098554

  2. Alterations of red cell membrane properties in neuroacanthocytosis.

    PubMed

    Siegl, Claudia; Hamminger, Patricia; Jank, Herbert; Ahting, Uwe; Bader, Benedikt; Danek, Adrian; Gregory, Allison; Hartig, Monika; Hayflick, Susan; Hermann, Andreas; Prokisch, Holger; Sammler, Esther M; Yapici, Zuhal; Prohaska, Rainer; Salzer, Ulrich

    2013-01-01

    Neuroacanthocytosis (NA) refers to a group of heterogenous, rare genetic disorders, namely chorea acanthocytosis (ChAc), McLeod syndrome (MLS), Huntington's disease-like 2 (HDL2) and pantothenate kinase associated neurodegeneration (PKAN), that mainly affect the basal ganglia and are associated with similar neurological symptoms. PKAN is also assigned to a group of rare neurodegenerative diseases, known as NBIA (neurodegeneration with brain iron accumulation), associated with iron accumulation in the basal ganglia and progressive movement disorder. Acanthocytosis, the occurrence of misshaped erythrocytes with thorny protrusions, is frequently observed in ChAc and MLS patients but less prevalent in PKAN (about 10%) and HDL2 patients. The pathological factors that lead to the formation of the acanthocytic red blood cell shape are currently unknown. The aim of this study was to determine whether NA/NBIA acanthocytes differ in their functionality from normal erythrocytes. Several flow-cytometry-based assays were applied to test the physiological responses of the plasma membrane, namely drug-induced endocytosis, phosphatidylserine exposure and calcium uptake upon treatment with lysophosphatidic acid. ChAc red cell samples clearly showed a reduced response in drug-induced endovesiculation, lysophosphatidic acid-induced phosphatidylserine exposure, and calcium uptake. Impaired responses were also observed in acanthocyte-positive NBIA (PKAN) red cells but not in patient cells without shape abnormalities. These data suggest an "acanthocytic state" of the red cell where alterations in functional and interdependent membrane properties arise together with an acanthocytic cell shape. Further elucidation of the aberrant molecular mechanisms that cause this acanthocytic state may possibly help to evaluate the pathological pathways leading to neurodegeneration. PMID:24098554

  3. Fendiline inhibits proliferation and invasion of pancreatic cancer cells by interfering with ADAM10 activation and β-catenin signaling

    PubMed Central

    Woods, Neha; Trevino, Jose; Coppola, Domenico; Chellappan, Srikumar; Yang, Shengyu; Padmanabhan, Jaya

    2015-01-01

    ADAM10 (A Disintegrin and Metalloprotease Domain 10) affects the pathophysiology of various cancers, and we had shown that inhibition of ADAM10 sensitizes pancreatic cancer cells to gemcitabine. ADAM10 is activated in response to calcium influx, and here we examined if calcium channel blockers (CCB) would impede ADAM10 activation and affect biology of pancreatic cancer cells. We find that the CCB, fendiline, significantly reduces proliferation, migration, invasion, and anchorage independent growth of pancreatic cancer cells. This was associated with ADAM10 inhibition and its localization at the actin-rich membrane protrusions. Further, fendiline-treated cells formed cadherin-catenin positive tight adherens junctions and elicited defective protein trafficking and recycling. Furthermore, the expression of β-catenin target genes, cyclinD1, c-Myc and CD44, were significantly decreased, suggesting that fendiline might prevent cell proliferation and migration by inhibiting ADAM10 function, cadherin proteolysis and stabilization of cadherin-catenin interaction at the plasma membrane. This will subsequently diminish β-catenin intracellular signaling and repress TCF/LEF target gene expression. Supporting this notion, RNAi-directed downregulation of ADAM10 in cancer cells decreased the expression of cyclinD1, c-Myc and CD44. Furthermore, analysis of human pancreatic tumor tissue microarrays and lysates showed elevated levels of ADAM10, suggesting that aberrant activation of ADAM10 plays a fundamental role in growth and metastasis of PDACs and inhibiting this pathway might be a viable strategy to combat PDACs. PMID:26440150

  4. The art of cellular communication: tunneling nanotubes bridge the divide

    PubMed Central

    Gurke, Steffen; Barroso, João F. V.

    2008-01-01

    The ability of cells to receive, process, and respond to information is essential for a variety of biological processes. This is true for the simplest single cell entity as it is for the highly specialized cells of multicellular organisms. In the latter, most cells do not exist as independent units, but are organized into specialized tissues. Within these functional assemblies, cells communicate with each other in different ways to coordinate physiological processes. Recently, a new type of cell-to-cell communication was discovered, based on de novo formation of membranous nanotubes between cells. These F-actin-rich structures, referred to as tunneling nanotubes (TNT), were shown to mediate membrane continuity between connected cells and facilitate the intercellular transport of various cellular components. The subsequent identification of TNT-like structures in numerous cell types revealed some structural diversity. At the same time it emerged that the direct transfer of cargo between cells is a common functional property, suggesting a general role of TNT-like structures in selective, long-range cell-to-cell communication. Due to the growing number of documented thin and long cell protrusions in tissue implicated in cell-to-cell signaling, it is intriguing to speculate that TNT-like structures also exist in vivo and participate in important physiological processes. PMID:18386044

  5. Ordered ceramic membranes

    SciTech Connect

    Anderson, M.A.; Hill, C.G. Jr.; Zeltner, W.A.

    1991-10-01

    Ceramic membranes have been formed from colloidal sols coated on porous clay supports. These supported membranes have been characterized in terms of their permeabilities and permselectivities to various aqueous test solutions. The thermal stabilities and pore structures of these membranes have been characterized by preparing unsupported membranes of the correpsonding material and performing N{sub 2} adsorption-desorption and X-ray diffraction studies on these membranes. To date, membranes have been prepared from a variety of oxides, including TiO{sub 2}, SiO{sub 2}, ZrO{sub 2}, and Al{sub 2}O{sub 3}, as well as Zr-, Fe-, and Nb-doped TiO{sub 2}. In many of these membranes pore diameters are less than 2 nm, while in others the pore diameters are between 3 and 5 nm. Procedures for fabricating porous clay supports with reproducible permeabilities for pure water are also discussed. 30 refs., 59 figs., 22 tabs.

  6. Hollow fiber catalytic membranes

    SciTech Connect

    Ma, Yi Hua; Moser, W.; Shelekhin, A.; Pien, Shyhing

    1993-09-01

    The objective of the present research is to investigate the possibility of the enhancement of the H{sub 2}S thermal decomposition in the IGCC system by employing the hollow fiber catalytic membrane reactor. To accomplish the objective, the following major components in the analysis of the high temperature membrane reactor must be investigated: high-temperature stability of the porous glass membrane; catalytic properties of MoS{sub 2} and of the porous glass membrane; catalytic decomposition of H{sub 2}S in a packed bed reactor; catalytic decomposition of 100%, 8.6%, and 1.1% H{sub 2}S gas mixtures in the membrane reactor. The study has been shown that the conversion of the H{sub 2}S can be increased in the packed bed membrane reactor compared to the equilibrium conversion on the shell side. The development of a mathematical model for the proposed process is in progress. The model will enable optimization of the H{sub 2}S decomposition. These conditions include selectivity factors and pressure drop across the membrane.

  7. Supported double membranes

    PubMed Central

    Murray, David H.; Tamm, Lukas K.; Kiessling, Volker

    2009-01-01

    Planar model membranes, like supported lipid bilayers and surface-tethered vesicles, have been proven to be useful tools for the investigation of complex biological functions in a significantly less complex membrane environment. In this study, we introduce a supported double membrane system that should be useful for studies that target biological processes in the proximity of two lipid bilayers such as the periplasm of bacteria and mitochondria or the small cleft between pre-and postsynaptic neuronal membranes. Large unilamellar vesicles (LUV) were tethered to a preformed supported bilayer by a biotin-streptavidin tether. We show from single particle tracking (SPT) experiments that these vesicle are mobile above the plane of the supported membrane. At higher concentrations, the tethered vesicles fuse to form a second continuous bilayer on top of the supported bilayer. The distance between the two bilayers was determined by fluorescence interference contrast (FLIC) microscopy to be between 16 and 24 nm. The lateral diffusion of labeled lipids in the second bilayer was very similar to that in supported membranes. SPT experiments with reconstituted syntaxin-1A show that the mobility of transmembrane proteins was not improved when compared with solid supported membranes. PMID:19236921

  8. Electroporation of cell membranes.

    PubMed

    Tsong, T Y

    1991-08-01

    Electric pulses of intensity in kilovolts per centimeter and of duration in microseconds to milliseconds cause a temporary loss of the semipermeability of cell membranes, thus leading to ion leakage, escape of metabolites, and increased uptake by cells of drugs, molecular probes, and DNA. A generally accepted term describing this phenomenon is "electroporation." Other effects of a high-intensity electric field on cell membranes include membrane fusions, bleb formation, cell lysis... etc. Electroporation and its related phenomena reflect the basic bioelectrochemistry of cell membranes and are thus important for the study of membrane structure and function. These phenomena also occur in such events as electric injury, electrocution, and cardiac procedures involving electric shocks. Electroporation has found applications in: (a) introduction of plasmids or foreign DNA into living cells for gene transfections, (b) fusion of cells to prepare heterokaryons, hybridoma, hybrid embryos... etc., (c) insertion of proteins into cell membranes, (d) improving drug delivery and hence effectiveness in chemotherapy of cancerous cells, (e) constructing animal model by fusing human cells with animal tissues, (f) activation of membrane transporters and enzymes, and (g) alteration of genetic expression in living cells. A brief review of mechanistic studies of electroporation is given. PMID:1912274

  9. Electroporation of cell membranes.

    PubMed Central

    Tsong, T Y

    1991-01-01

    Electric pulses of intensity in kilovolts per centimeter and of duration in microseconds to milliseconds cause a temporary loss of the semipermeability of cell membranes, thus leading to ion leakage, escape of metabolites, and increased uptake by cells of drugs, molecular probes, and DNA. A generally accepted term describing this phenomenon is "electroporation." Other effects of a high-intensity electric field on cell membranes include membrane fusions, bleb formation, cell lysis... etc. Electroporation and its related phenomena reflect the basic bioelectrochemistry of cell membranes and are thus important for the study of membrane structure and function. These phenomena also occur in such events as electric injury, electrocution, and cardiac procedures involving electric shocks. Electroporation has found applications in: (a) introduction of plasmids or foreign DNA into living cells for gene transfections, (b) fusion of cells to prepare heterokaryons, hybridoma, hybrid embryos... etc., (c) insertion of proteins into cell membranes, (d) improving drug delivery and hence effectiveness in chemotherapy of cancerous cells, (e) constructing animal model by fusing human cells with animal tissues, (f) activation of membrane transporters and enzymes, and (g) alteration of genetic expression in living cells. A brief review of mechanistic studies of electroporation is given. PMID:1912274

  10. Catalytic nanoporous membranes

    DOEpatents

    Pellin, Michael J; Hryn, John N; Elam, Jeffrey W

    2013-08-27

    A nanoporous catalytic membrane which displays several unique features Including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity. Also provided is a method for producing a catalytic membrane having flow-through pores and discreet catalytic clusters adhering to the inside surfaces of the pores.

  11. Nanoengineered membrane electrode assembly interface

    DOEpatents

    Song, Yujiang; Shelnutt, John A

    2013-08-06

    A membrane electrode structure suitable for use in a membrane electrode assembly (MEA) that comprises membrane-affixed metal nanoparticles whose formation is controlled by a photochemical process that controls deposition of the metal nanoparticles using a photocatalyst integrated with a polymer electrolyte membrane, such as an ionomer membrane. Impregnation of the polymer membrane with the photocatalyst prior to metal deposition greatly reduces the required amount of metal precursor in the deposition reaction solution by restricting metal reduction substantially to the formation of metal nanoparticles affixed on or near the surface of the polymer membrane with minimal formation of metallic particles not directly associated with the membrane.

  12. CENTRIFUGAL MEMBRANE FILTRATION

    SciTech Connect

    Daniel J. Stepan; Bradley G. Stevens; Melanie D. Hetland

    1999-10-01

    The overall project consists of several integrated research phases related to the applicability, continued development, demonstration, and commercialization of the SpinTek centrifugal membrane filtration process. Work performed during this reporting period consisted of Phase 2 evaluation of the SpinTek centrifugal membrane filtration technology and Phase 3, Technology Partnering. During Phase 1 testing conducted at the EERC using the SpinTek ST-IIL unit operating on a surrogate tank waste, a solids cake developed on the membrane surface. The solids cake was observed where linear membrane velocities were less than 17.5 ft/s and reduced the unobstructed membrane surface area up to 25%, reducing overall filtration performance. The primary goal of the Phase 2 research effort was to enhance filtration performance through the development and testing of alternative turbulence promoter designs. The turbulence promoters were designed to generate a shear force across the entire membrane surface sufficient to maintain a self-cleaning membrane capability and improve filtration efficiency and long-term performance. Specific Phase 2 research activities included the following: System modifications to accommodate an 11-in.-diameter, two-disk rotating membrane assembly; Development and fabrication of alternative turbulence promoter designs; Testing and evaluation of the existing and alternative turbulence promoters under selected operating conditions using a statistically designed test matrix; and Data reduction and analysis; The objective of Phase 3 research was to demonstrate the effectiveness of SpinTek's centrifugal membrane filtration as a pretreatment to remove suspended solids from a liquid waste upstream of 3M's WWL cartridge technology for the selective removal of technetium (Tc).

  13. Membrane photobiophysics and photochemistry

    NASA Astrophysics Data System (ADS)

    Ti Tien, H.

    Life, as we know it, depends on solar energy, in particular in the visible range of the solar spectrum. However, visible light alone is useless to the living organism unless a means is available for its capture, transformation, and utilization. Nature, through its long evolution, has perfected a process known as photosynthesis by which visible light is transduced into electrical/ chemical energy. However, the heart of Nature's energy transducer is the thylakoid membrane whose molecular organization was not known until early in the 1960s. Then it was established that the bilayer lipid membrane was central to the design of the thylakoid membrane. To explain the light-driven reactions from water oxidation to carbon dioxide reduction, the so-called Z-scheme was proposed. Concurrent with the establishment of Mitchell's Chemiosmotic Hypothesis for electron transfer and phosphorylation, the experimental bilayer lipid membrane (BLM) system was developed in 1960. But what are the fundamental biophysical mechanisms involved in the phototransduction via pigmented bilayer lipid membrane-based transducers? One of the main purposes of this review is to consider these questions. A second main purpose is to introduce to the reader the experimental aspects of lipid bilayers in the investigation of photoactive biomembranes. The areas covered in this review include a brief summary of the laws of photochemistry relevant to membrane photobiophysics and photobiology. The current exploitation of the BLM system in relation to the thylakoid membrane and to the visual receptor membrane will be considered in turn. The purple membrane of H. Halobium is then discussed. Consideration will also be given to dye-sensitized BLMs, semiconducting BLMs, and BLMs formed from liquid crystals. A common characteristic in the topics covered in this review is the desire to stimulate further studies in the use of the BLM system, not only for the fundamental understanding of biomembranes, but also towards

  14. A computer simulation approach to quantify the true area and true area compressibility modulus of biological membranes

    SciTech Connect

    Chacón, Enrique; Tarazona, Pedro; Bresme, Fernando

    2015-07-21

    We present a new computational approach to quantify the area per lipid and the area compressibility modulus of biological membranes. Our method relies on the analysis of the membrane fluctuations using our recently introduced coupled undulatory (CU) mode [Tarazona et al., J. Chem. Phys. 139, 094902 (2013)], which provides excellent estimates of the bending modulus of model membranes. Unlike the projected area, widely used in computer simulations of membranes, the CU area is thermodynamically consistent. This new area definition makes it possible to accurately estimate the area of the undulating bilayer, and the area per lipid, by excluding any contributions related to the phospholipid protrusions. We find that the area per phospholipid and the area compressibility modulus features a negligible dependence with system size, making possible their computation using truly small bilayers, involving a few hundred lipids. The area compressibility modulus obtained from the analysis of the CU area fluctuations is fully consistent with the Hooke’s law route. Unlike existing methods, our approach relies on a single simulation, and no a priori knowledge of the bending modulus is required. We illustrate our method by analyzing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers using the coarse grained MARTINI force-field. The area per lipid and area compressibility modulus obtained with our method and the MARTINI forcefield are consistent with previous studies of these bilayers.

  15. Metabolic regulation of neutrophil spreading, membrane tubulovesicular extensions (cytonemes) formation and intracellular pH upon adhesion to fibronectin

    SciTech Connect

    Galkina, Svetlana I. . E-mail: galkina@genebee.msu.su; Sud'ina, Galina F.; Klein, Thomas

    2006-08-01

    Circulating leukocytes have a round cell shape and roll along vessel walls. However, metabolic disorders can lead them to adhere to the endothelium and spread (flatten). We studied the metabolic regulation of adhesion, spreading and intracellular pH (pHi) of neutrophils (polymorphonuclear leukocytes) upon adhesion to fibronectin-coated substrata. Resting neutrophils adhered and spread on fibronectin. An increase in pHi accompanied neutrophil spreading. Inhibition of oxidative phosphorylation or inhibition of P- and F-type ATPases affected neither neutrophil spreading nor pHi. Inhibition of glucose metabolism or V-ATPase impaired neutrophil spreading, blocked the increase in the pHi and induced extrusion of membrane tubulovesicular extensions (cytonemes), anchoring cells to substrata. Omission of extracellular Na{sup +} and inhibition of chloride channels caused a similar effect. We propose that these tubulovesicular extensions represent protrusions of exocytotic trafficking, supplying the plasma membrane of neutrophils with ion exchange mechanisms and additional membrane for spreading. Glucose metabolism and V-type ATPase could affect fusion of exocytotic trafficking with the plasma membrane, thus controlling neutrophil adhesive state and pHi. Cl{sup -} efflux through chloride channels and Na{sup +} influx seem to be involved in the regulation of the V-ATPase by carrying out charge compensation for the proton-pumping activity and through V-ATPase in regulation of neutrophil spreading and pHi.

  16. Cyclic membrane separation process

    DOEpatents

    Bowser, John

    2004-04-13

    A cyclic process for controlling environmental emissions of volatile organic compounds (VOC) from vapor recovery in storage and dispensing operations of liquids maintains a vacuum in the storage tank ullage. In one of a two-part cyclic process ullage vapor is discharged through a vapor recovery system in which VOC are stripped from vented gas with a selectively gas permeable membrane. In the other part, the membrane is inoperative while gas pressure rises in the ullage. Ambient air is charged to the membrane separation unit during the latter part of the cycle.

  17. Rotating bubble membrane radiator

    DOEpatents

    Webb, Brent J.; Coomes, Edmund P.

    1988-12-06

    A heat radiator useful for expelling waste heat from a power generating system aboard a space vehicle is disclosed. Liquid to be cooled is passed to the interior of a rotating bubble membrane radiator, where it is sprayed into the interior of the bubble. Liquid impacting upon the interior surface of the bubble is cooled and the heat radiated from the outer surface of the membrane. Cooled liquid is collected by the action of centrifical force about the equator of the rotating membrane and returned to the power system. Details regarding a complete space power system employing the radiator are given.

  18. Cholesterol dynamics in membranes.

    PubMed Central

    Yeagle, P L; Albert, A D; Boesze-Battaglia, K; Young, J; Frye, J

    1990-01-01

    Time-resolved fluorescence anisotropy of the sterol analogue, cholestatrienol, and 13C nuclear magnetic resonance (NMR) spin lattice relaxation time (T1c) measurements of [13C4] labeled cholesterol were exploited to determine the correlation times characterizing the major modes of motion of cholesterol in unsonicated phospholipid multilamellar liposomes. Two modes of motion were found to be important: (a) rotational diffusion and (b) time dependence of the orientation of the director for axial diffusion, or "wobble." From the time-resolved fluorescence anisotropy decays of cholestatrienol in egg phosphatidylcholine (PC) bilayers, a value for tau perpendicular, the correlation time for wobble, of 0.9 x 10(-9) s and a value for S perpendicular, the order parameter characterizing the same motion, of 0.45 s were calculated. Both tau perpendicular and S perpendicular were relatively insensitive to temperature and cholesterol content of the membranes. The T1c measurements of [13C4] labeled cholesterol did not provide a quantitative determination of tau parallel, the correlation time for axial diffusion. T1c from the lipid hydrocarbon chains suggested a value for tau perpendicular similar to that for cholesterol. Steady-state anisotropy measurements and time-resolved anisotropy measurements of cholestatrienol were used to probe sterol behavior in a variety of pure and mixed lipid multilamellar liposomes. Both the lipid headgroups and the lipid hydrocarbons chains contributed to the determination of the sterol environment in the membrane, as revealed by these fluorescence measurements. In particular, effects of the phosphatidylethanolamine (PE) headgroup and of multiple unsaturation in the lipid hydrocarbon chains were observed. However, while the steady-state anisotropy was sensitive to these factors, the time-resolved fluorescence analysis indicated that tau perpendicular was not strongly affected by the lipid composition of the membrane. S perpendicular may be increased

  19. Neural Membrane Signaling Platforms

    PubMed Central

    Wallace, Ron

    2010-01-01

    Throughout much of the history of biology, the cell membrane was functionally defined as a semi-permeable barrier separating aqueous compartments, and an anchoring site for proteins. Little attention was devoted to its possible regulatory role in intracellular molecular processes and neuron electrical signaling. This article reviews the history of membrane studies and the current state of the art. Emphasis is placed on natural and artificial membrane studies of electric field effects on molecular organization, especially as these may relate to impulse propagation in neurons. Implications of these studies for new designs in artificial intelligence are briefly examined. PMID:20640161

  20. Composite metal membrane

    DOEpatents

    Peachey, Nathaniel M.; Dye, Robert C.; Snow, Ronny C.; Birdsell, Stephan A.

    1998-01-01

    A composite metal membrane including a first metal layer of Group IVB met or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof is provided together with a process for the recovery of hydrogen from a gaseous mixture including contacting a hydrogen-containing gaseous mixture with a first side of a nonporous composite metal membrane including a first metal of Group IVB metals or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof, and, separating hydrogen from a second side of the nonporous composite metal membrane.

  1. Composite metal membrane

    DOEpatents

    Peachey, N.M.; Dye, R.C.; Snow, R.C.; Birdsell, S.A.

    1998-04-14

    A composite metal membrane including a first metal layer of Group IVB met or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof is provided together with a process for the recovery of hydrogen from a gaseous mixture including contacting a hydrogen-containing gaseous mixture with a first side of a nonporous composite metal membrane including a first metal of Group IVB metals or Group VB metals, the first metal layer sandwiched between two layers of an oriented metal of palladium, platinum or alloys thereof, and, separating hydrogen from a second side of the nonporous composite metal membrane.

  2. Cyclic membrane separation process

    DOEpatents

    Nemser, Stuart M.

    2005-05-03

    A cyclic process for controlling environmental emissions of volatile organic compounds (VOC) from vapor recovery in storage and dispensing operations of liquids maintains a vacuum in the storage tank ullage. In the first part of a two-part cyclic process ullage vapor is discharged through a vapor recovery system in which VOC are stripped from vented gas with a selectively gas permeable membrane. In the second part, the membrane is inoperative while gas pressure rises in the ullage. In one aspect of this invention, a vacuum is drawn in the membrane separation unit thus reducing overall VOC emissions.

  3. PERSISTENT PUPILLARY MEMBRANE OR ACCESSORY IRIS MEMBRANE?.

    PubMed

    Gavriş, Monica; Horge, Ioan; Avram, Elena; Belicioiu, Roxana; Olteanu, Ioana Alexandra; Kedves, Hanga

    2015-01-01

    Frequently, in literature and curent practice, accessory iris membrane (AIM) and persistant pupillary membrane (PPM) are confused. Both AIM and PPM are congenital iris anomalies in which fine or thick iris strands arrise form the collarette and obscure the pupil. AIM, which is also called iris duplication, closely resembles the normal iris tissue in color and thickness and presents a virtual second pseudopupil aperture in the centre while PPM even in its extreme forms presents as a translucent or opaque membranous structure that extends across the pupil and has no pseudopupil. Mydriatiscs, laser treatment or surgery is used to clear the visual axis and optimize visual development. Surgical intervention is reserved for large, dense AIMs and PPMs. Our patient, a 29 year old male, has come with bilateral dense AIM, bilateral compound hyperopic astigmatism, BCVA OD = 0.6, BCVA OS = 0.4, IOP OU = 17 mmHg. To improve the visual acuity of the patient we decided to do a bilateral membranectomy, restoring in this way transparency of the visual axis. After surgery, the visual acuity improved to BCVA OD= 0.8, BCVA OS=0.8. PMID:26978889

  4. Novel Catalytic Membrane Reactors

    SciTech Connect

    2009-02-01

    This factsheet describes a research project that will focus on the development and application of nonporous high gas flux perfluoro membranes with high temperature rating and excellent chemical resistance.

  5. Hydrogen transport membranes

    DOEpatents

    Mundschau, Michael V.

    2005-05-31

    Composite hydrogen transport membranes, which are used for extraction of hydrogen from gas mixtures are provided. Methods are described for supporting metals and metal alloys which have high hydrogen permeability, but which are either too thin to be self supporting, too weak to resist differential pressures across the membrane, or which become embrittled by hydrogen. Support materials are chosen to be lattice matched to the metals and metal alloys. Preferred metals with high permeability for hydrogen include vanadium, niobium, tantalum, zirconium, palladium, and alloys thereof. Hydrogen-permeable membranes include those in which the pores of a porous support matrix are blocked by hydrogen-permeable metals and metal alloys, those in which the pores of a porous metal matrix are blocked with materials which make the membrane impervious to gases other than hydrogen, and cermets fabricated by sintering powders of metals with powders of lattice-matched ceramic.

  6. Protein mediated membrane adhesion

    NASA Astrophysics Data System (ADS)

    Carlson, Andreas; Mahadevan, L.

    2015-05-01

    Adhesion in the context of mechanical attachment, signaling, and movement in cellular dynamics is mediated by the kinetic interactions between membrane-embedded proteins in an aqueous environment. Here, we present a minimal theoretical framework for the dynamics of membrane adhesion that accounts for the kinetics of protein binding, the elastic deformation of the membrane, and the hydrodynamics of squeeze flow in the membrane gap. We analyze the resulting equations using scaling estimates to characterize the spatiotemporal features of the adhesive patterning and corroborate them using numerical simulations. In addition to characterizing aspects of cellular dynamics, our results might also be applicable to a range of phenomena in physical chemistry and materials science where flow, deformation, and kinetics are coupled to each other in slender geometries.

  7. Ultrasonic Membrane Processing

    NASA Astrophysics Data System (ADS)

    Kentish, Sandra; Ashokkumar, Muthupandian

    A membrane is a sermipermeable material that permits the passage of some molecules while retaining others. Ultrasound can enhance membrane operation through the asymmetric collapse of cavitating bubbles and through the turbulence associated with acoustic streaming. The added turbulence can lead to a looser, more porous fouling cake layer and may agglomerate fine particles, reducing pore blockage and cake compaction.These effects are dependent upon the ultrasonic intensity, the operating pressure, crossflow velocity and solids concentration.Membrane cleaning can also be enhanced by the use of ultrasound, but this application may not be economic when used in isolation. One of the greatest challenges facing the technology is the generation of a uniform acoustic field across the entire membrane surface in a full-scale module.

  8. Membrane separation technology

    SciTech Connect

    Stookey, D.J.; Patton, C.J.; Malcolm, G.L.

    1986-01-01

    Membrane separations of interest here are not to be confused with barrier separations of the type employed in the uranium enrichment plant at Oak Ridge, Tennessee. There isotopes of uranium hexafluoride were separated by the free-molecular or Knudsen flow of the gas mixture through the pores and orifices created within a porous nickel media which was sometimes referred to as a membrane. In barrier separation, an enrichment of gases of differing molecular weights is accomplished by the differing gaseous diffusion rates within the porous media. By contrast the membranes of interest here are thin, dense, continuous films, typically formed from polymers. The separation of species is accomplished by the dissolution of the gases in the polymer and their diffusion across the solid film thickness under a concentration gradient according to Fick's law. This process is commonly referred to as membrane permeation.

  9. Drugging Membrane Protein Interactions

    PubMed Central

    Yin, Hang; Flynn, Aaron D.

    2016-01-01

    The majority of therapeutics target membrane proteins, accessible on the surface of cells, to alter cellular signaling. Cells use membrane proteins to transduce signals into cells, transport ions and molecules, bind the cell to a surface or substrate, and catalyze reactions. Newly devised technologies allow us to drug conventionally “undruggable” regions of membrane proteins, enabling modulation of protein–protein, protein–lipid, and protein–nucleic acid interactions. In this review, we survey the state of the art in high-throughput screening and rational design in drug discovery, and we evaluate the advances in biological understanding and technological capacity that will drive pharmacotherapy forward against unorthodox membrane protein targets. PMID:26863923

  10. Evaporative Cooling Membrane Device

    NASA Technical Reports Server (NTRS)

    Lomax, Curtis (Inventor); Moskito, John (Inventor)

    1999-01-01

    An evaporative cooling membrane device is disclosed having a flat or pleated plate housing with an enclosed bottom and an exposed top that is covered with at least one sheet of hydrophobic porous material having a thin thickness so as to serve as a membrane. The hydrophobic porous material has pores with predetermined dimensions so as to resist any fluid in its liquid state from passing therethrough but to allow passage of the fluid in its vapor state, thereby, causing the evaporation of the fluid and the cooling of the remaining fluid. The fluid has a predetermined flow rate. The evaporative cooling membrane device has a channel which is sized in cooperation with the predetermined flow rate of the fluid so as to produce laminar flow therein. The evaporative cooling membrane device provides for the convenient control of the evaporation rates of the circulating fluid by adjusting the flow rates of the laminar flowing fluid.

  11. Structures of membrane proteins

    PubMed Central

    Vinothkumar, Kutti R.; Henderson, Richard

    2010-01-01

    In reviewing the structures of membrane proteins determined up to the end of 2009, we present in words and pictures the most informative examples from each family. We group the structures together according to their function and architecture to provide an overview of the major principles and variations on the most common themes. The first structures, determined 20 years ago, were those of naturally abundant proteins with limited conformational variability, and each membrane protein structure determined was a major landmark. With the advent of complete genome sequences and efficient expression systems, there has been an explosion in the rate of membrane protein structure determination, with many classes represented. New structures are published every month and more than 150 unique membrane protein structures have been determined. This review analyses the reasons for this success, discusses the challenges that still lie ahead, and presents a concise summary of the key achievements with illustrated examples selected from each class. PMID:20667175

  12. Fuel cell membrane humidification

    DOEpatents

    Wilson, Mahlon S.

    1999-01-01

    A polymer electrolyte membrane fuel cell assembly has an anode side and a cathode side separated by the membrane and generating electrical current by electrochemical reactions between a fuel gas and an oxidant. The anode side comprises a hydrophobic gas diffusion backing contacting one side of the membrane and having hydrophilic areas therein for providing liquid water directly to the one side of the membrane through the hydrophilic areas of the gas diffusion backing. In a preferred embodiment, the hydrophilic areas of the gas diffusion backing are formed by sewing a hydrophilic thread through the backing. Liquid water is distributed over the gas diffusion backing in distribution channels that are separate from the fuel distribution channels.

  13. Supported membrane nanodevices.

    PubMed

    Anrather, Dorothea; Smetazko, Michaela; Saba, Miriam; Alguel, Yilmaz; Schalkhammer, Thomas

    2004-01-01

    Supported membrane nanodevices are based on natural or artificial ion channels embedded in a lipid membrane deposited on a chip wafer. Membrane conductance is modulated by biorecognitive events, with the use of intrinsic binding sites of the ion channel or via artificial sites fused to the channel protein. Artificial ion gates are constructed by coupling a specific ligand for the analyte near the channel entrance or a site important to triggering channel conformation. The binding event leads to the closure of the ion channel or induces a conformational change of the channel, reducing the ion flux. The signal transduced from the device is the decrease in the ion flux-induced electron current at a silver-silver chloride electrode at ultimate single-molecule sensitivity. Among the natural ion channels, gramicidin A, a transport antibiotic, was found to be most suitable, and thus was used by AMBRI, Australia, to set up prototypes of membrane biochips, using self-association of the dimer. Covalent dimerization-based devices, developed by the Vienna group, make use of the down-regulation of the permanently open membrane-spanning bisgramicidine ion channel. The reactive group at the C-terminus, a hydroxy group, allows precise coupling of the analyte-binding moiety in gramicidin as well as bisgramicidin. The device is set up with bilayer membranes deposited on apertures of a hydrophobic frame structure produced via microlithography, facing an aqueous or hydro-gel micro-environment on both sides, constructing black lipid membranes or patch-clamp devices "on chip." The setup of the device needs gel membrane supports that allow membrane formation and contribute to the stability of the bilayer by exposure of functional groups that promote electrostatic interaction and formation of hydrogen bridges and enable the introduction of covalent spacers and anchors. Photo-cross-linked polyvinylpyrrolidone and polyacrylamide, electropolymerized polydiaminobenzene and coated agarose, as

  14. Microprobes aluminosilicate ceramic membranes

    DOEpatents

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Methods have been developed to make mixed alumina-silicate and aluminosilicate particulate microporous ceramic membranes. One method involves the making of separate alumina and silica sols which are then mixed. Another method involves the creation of a combined sol with aluminosilicate particles. The resulting combined alumina and silica membranes have high surface area, a very small pore size, and a very good temperature stability.

  15. [Candidiasis of mucous membranes].

    PubMed

    Khmel'nitskiĭ, O K

    2000-01-01

    The author presents a new concept of complex relationship between the organism and Candida. According to this concept there is transformation of Candida carriage into invasive candidiasis of the mucous membranes. The idea is formulated on mixed-mycocenosis as association of fungal, bacterial, protozoic and viral biota. For the first time the notion of intermediate preinvasive form of candidiasis is given and clinical, morphological criteria of differential diagnosis between candida carriage, preinvasive and invasive candidiasis of mucous membranes are presented. PMID:11198119

  16. Membrane separation of hydrocarbons

    DOEpatents

    Funk, Edward W.; Kulkarni, Sudhir S.; Chang, Y. Alice

    1986-01-01

    Mixtures of heavy oils and light hydrocarbons may be separated by passing the mixture over a polymeric membrane which comprises a polymer capable of maintaining its integrity in the presence of hydrocarbon compounds at temperature ranging from about ambient to about 100.degree. C. and pressures ranging from about 50 to about 1000 psi. The membranes which possess pore sizes ranging from about 10 to about 500 Angstroms are cast from a solvent solution and recovered.

  17. Membrane reference electrode

    DOEpatents

    Redey, L.; Bloom, I.D.

    1988-01-21

    A reference electrode utilizes a small thin, flat membrane of a highly conductive glass placed on a small diameter insulator tube having a reference material inside in contact with an internal voltage lead. When the sensor is placed in a non-aqueous ionic electrolytic solution, the concentration difference across the glass membrane generates a low voltage signal in precise relationship to the concentration of the species to be measured, with high spatial resolution. 2 figs.

  18. Battery utilizing ceramic membranes

    DOEpatents

    Yahnke, Mark S.; Shlomo, Golan; Anderson, Marc A.

    1994-01-01

    A thin film battery is disclosed based on the use of ceramic membrane technology. The battery includes a pair of conductive collectors on which the materials for the anode and the cathode may be spin coated. The separator is formed of a porous metal oxide ceramic membrane impregnated with electrolyte so that electrical separation is maintained while ion mobility is also maintained. The entire battery can be made less than 10 microns thick while generating a potential in the 1 volt range.

  19. Exploring membrane respiratory chains.

    PubMed

    Marreiros, Bruno C; Calisto, Filipa; Castro, Paulo J; Duarte, Afonso M; Sena, Filipa V; Silva, Andreia F; Sousa, Filipe M; Teixeira, Miguel; Refojo, Patrícia N; Pereira, Manuela M

    2016-08-01

    Acquisition of energy is central to life. In addition to the synthesis of ATP, organisms need energy for the establishment and maintenance of a transmembrane difference in electrochemical potential, in order to import and export metabolites or to their motility. The membrane potential is established by a variety of membrane bound respiratory complexes. In this work we explored the diversity of membrane respiratory chains and the presence of the different enzyme complexes in the several phyla of life. We performed taxonomic profiles of the several membrane bound respiratory proteins and complexes evaluating the presence of their respective coding genes in all species deposited in KEGG database. We evaluated 26 quinone reductases, 5 quinol:electron carriers oxidoreductases and 18 terminal electron acceptor reductases. We further included in the analyses enzymes performing redox or decarboxylation driven ion translocation, ATP synthase and transhydrogenase and we also investigated the electron carriers that perform functional connection between the membrane complexes, quinones or soluble proteins. Our results bring a novel, broad and integrated perspective of membrane bound respiratory complexes and thus of the several energetic metabolisms of living systems. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi. PMID:27044012

  20. Catalytic nanoporous membranes

    DOEpatents

    Pellin, Michael J.; Hryn, John N.; Elam, Jeffrey W.

    2009-12-01

    A nanoporous catalytic membrane which displays several unique features including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity.

  1. The Excitable Membrane

    PubMed Central

    Offner, Franklin F.

    1972-01-01

    The model of the excitable membrane assumes common channels for Na+ and K+; the two ion species interact within the pores through their electrostatic forces. The electric field varies across the membrane and with time, as a result of ionic redistribution. Ionic flow is primarily controlled by energy barriers at the two interfaces and by Ca++ adsorption at the external interface. When the membrane is polarized, the high electric field at the external interface acting on the membrane fixed charge keeps the effective channel diameter small, so that only dihydrated ions can cross the interface. The higher energy required to partially dehydrate Na+ accounts for its lower permeability when polarized. Depolarized, the channel entrance can expand, permitting quadrihydrated ions to pass; the large initial Na+ flow is the result of the large concentration ratio across the interface. The effect at the internal interface is symmetric; Na+ crosses with greater difficulty when the membrane is depolarized. Na+ inactivation occurs when the ion distribution within the membrane has assumed its new steady-state value. Calculations based on parameters consistent with physicochemical data agree generally with a wide range of experiments. The model does not obey the two fundamental Hodgkin-Huxley (HH) postulates (independence principle, ion flow proportional to thermodynamic potential). In several instances the model predicts experimental results which are not predicted by the HH equations. ImagesFIGURE 12 PMID:4655662

  2. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-10-01

    This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  3. Fractal reconstruction of rough membrane surface related with membrane fouling in a membrane bioreactor.

    PubMed

    Zhang, Meijia; Chen, Jianrong; Ma, Yuanjun; Shen, Liguo; He, Yiming; Lin, Hongjun

    2016-09-01

    In this paper, fractal reconstruction of rough membrane surface with a modified Weierstrass-Mandelbrot (WM) function was conducted. The topography of rough membrane surface was measured by an atomic force microscopy (AFM), and the results showed that the membrane surface was isotropous. Accordingly, the fractal dimension and roughness of membrane surface were calculated by the power spectrum method. The rough membrane surface was reconstructed on the MATLAB platform with the parameter values acquired from raw AFM data. The reconstructed membrane was much similar to the real membrane morphology measured by AFM. The parameters (including average roughness and root mean square (RMS) roughness) associated with membrane morphology for the model and real membrane were calculated, and a good match of roughness parameters between the reconstructed surface and real membrane was found, indicating the feasibility of the new developed method. The reconstructed membrane surface can be potentially used for interaction energy evaluation. PMID:27318159

  4. Composite membranes for fluid separations

    DOEpatents

    Blume, Ingo; Peinemann, Klaus-Viktor; Pinnau, Ingo; Wijmans, Johannes G.

    1991-01-01

    A method for designing and making composite membranes having a microporous support membrane coated with a permselective layer. The method involves calculating the minimum thickness of the permselective layer such that the selectivity of the composite membrane is close to the intrinsic selectivity of the permselective layer. The invention also provides high performance membranes with optimized properties.

  5. Composite membranes for fluid separations

    DOEpatents

    Blume, Ingo; Peinemann, Klaus-Viktor; Pinnau, Ingo; Wijmans, Johannes G.

    1992-01-01

    A method for designing and making composite membranes having a microporous support membrane coated with a permselective layer. The method involves calculating the minimum thickness of the permselective layer such that the selectivity of the composite membrane is close to the intrinsic selectivity of the perselective layer. The invention also provides high performance membranes with optimized properties.

  6. Composite membranes for fluid separations

    DOEpatents

    Blume, Ingo; Peinemann, Klaus-Viktor; Pinnau, Ingo; Wijmans, Johannes G.

    1990-01-01

    A method for designing and making composite membranes having a microporous support membrane coated with a permselective layer. The method involves calculating the minimum thickness of the permselective layer such that the selectivity of the composite membrane is close to the intrinsic selectivity of the permselective layer. The invention also provides high performance membranes with optimized properties.

  7. Handbook of industrial membrane technology

    SciTech Connect

    Porter, M.C.

    1989-01-01

    This book emphasizes the use of synthetic membranes for separations involving industrial or municipal process streams. In addition to the classic membrane processes-microfiltration, ultrafiltration, reverse osmosis, gas separation, and electrodialysis-chapters on enzyme membrane reactors, membrane fermentors and coupled transport membranes are included. The preparation of synthetic membranes and process design and optimization are also covered. Most of the membrane processes are pressure driven, the notable exception being electrodialysis, by which ions are separated under the influence of an electric field. In addition, coupled transport covers processes driven under the influence of a concentration gradient.

  8. Oxygen Transport Ceramic Membranes

    SciTech Connect

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-11-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In the current research, the electrical conductivity and Seebeck coefficient were measured as a function of temperature in air. Based on these measurements, the charge carrier concentration, net acceptor dopant concentration, activation energy of conduction and mobility were estimated. The studies on the fracture toughness of the LSFT and dual phase membranes at room temperature have been completed and reported previously. The membranes that are exposed to high temperatures at an inert and a reactive atmosphere undergo many structural and chemical changes which affects the mechanical properties. To study the effect of temperature on the membranes when exposed to an inert environment, the membranes (LAFT and Dual phase) were heat treated at 1000 C in air and N{sub 2} atmosphere and hardness and fracture toughness of the membranes were studied after the treatment. The indentation method was used to find the fracture toughness and the effect of the heat treatment on the mechanical properties of the membranes. Further results on the investigation of the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appears to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. 2-D modeling of oxygen movement has been undertaken in order to fit isotope data. The model will serve to study ''frozen'' profiles in patterned or composite membranes.

  9. Tectorial Membrane Stiffness Gradients

    PubMed Central

    Richter, Claus-Peter; Emadi, Gulam; Getnick, Geoffrey; Quesnel, Alicia; Dallos, Peter

    2007-01-01

    The mammalian inner ear processes sound with high sensitivity and fine resolution over a wide frequency range. The underlying mechanism for this remarkable ability is the “cochlear amplifier”, which operates by modifying cochlear micromechanics. However, it is largely unknown how the cochlea implements this modification. Although gradual improvements in experimental techniques have yielded ever-better descriptions of gross basilar membrane vibration, the internal workings of the organ of Corti and of the tectorial membrane have resisted exploration. Although measurements of cochlear function in mice with a gene mutation for α-tectorin indicate the tectorial membrane's key role in the mechanoelectrical transformation by the inner ear, direct experimental data on the tectorial membrane's physical properties are limited, and only a few direct measurements on tectorial micromechanics are available. Using the hemicochlea, we are able to show that a tectorial membrane stiffness gradient exists along the cochlea, similar to that of the basilar membrane. In artificial perilymph (but with low calcium), the transversal and radial driving point stiffnesses change at a rate of –4.0 dB/mm and −4.9 dB/mm, respectively, along the length of the cochlear spiral. In artificial endolymph, the stiffness gradient for the transversal component was –3.4 dB/mm. Combined with the changes in tectorial membrane dimensions from base to apex, the radial stiffness changes would be able to provide a second frequency-place map in the cochlea. Young's modulus, which was obtained from measurements performed in the transversal direction, decreased by −2.6 dB/mm from base to apex. PMID:17496047

  10. Membrane Bending by Protein Crowding

    NASA Astrophysics Data System (ADS)

    Stachowiak, Jeanne

    2014-03-01

    From endosomes and synaptic vesicles to the cristae of the mitochondria and the annulus of the nuclear pore, highly curved membranes are fundamental to the structure and physiology of living cells. The established view is that specific families of proteins are able to bend membranes by binding to them. For example, inherently curved proteins are thought to impose their structure on the membrane surface, while membrane-binding proteins with hydrophobic motifs are thought to insert into the membrane like wedges, driving curvature. However, computational models have recently revealed that these mechanisms would require specialized membrane-bending proteins to occupy nearly 100% of a curved membrane surface, an improbable physiological situation given the immense density and diversity of membrane-bound proteins, and the low expression levels of these specialized proteins within curved regions of the membrane. How then does curvature arise within the complex and crowded environment of cellular membranes? Our recent work using proteins involved in clathrin-mediated endocytosis, as well as engineered protein-lipid interactions, has suggested a new hypothesis - that lateral pressure generated by collisions between membrane-bound proteins can drive membrane bending. Specifically, by correlating membrane bending with quantitative optical measurements of protein density on synthetic membrane surfaces and simple physical models of collisions among membrane-bound proteins, we have demonstrated that protein-protein steric interactions can drive membrane curvature. These findings suggest that a simple imbalance in the concentration of membrane-bound proteins across a membrane surface can drive a membrane to bend, providing an efficient mechanism by which essentially any protein can contribute to shaping membranes.

  11. Micron-scale plasma membrane curvature is recognized by the septin cytoskeleton.

    PubMed

    Bridges, Andrew A; Jentzsch, Maximilian S; Oakes, Patrick W; Occhipinti, Patricia; Gladfelter, Amy S

    2016-04-11

    Cells change shape in response to diverse environmental and developmental conditions, creating topologies with micron-scale features. Although individual proteins can sense nanometer-scale membrane curvature, it is unclear if a cell could also use nanometer-scale components to sense micron-scale contours, such as the cytokinetic furrow and base of neuronal branches. Septins are filament-forming proteins that serve as signaling platforms and are frequently associated with areas of the plasma membrane where there is micron-scale curvature, including the cytokinetic furrow and the base of cell protrusions. We report here that fungal and human septins are able to distinguish between different degrees of micron-scale curvature in cells. By preparing supported lipid bilayers on beads of different curvature, we reconstitute and measure the intrinsic septin curvature preference. We conclude that micron-scale curvature recognition is a fundamental property of the septin cytoskeleton that provides the cell with a mechanism to know its local shape. PMID:27044896

  12. CENTRIFUGAL MEMBRANE FILTRATION

    SciTech Connect

    William A. Greene; Patricia A. Kirk; Richard Hayes; Joshua Riley

    2005-10-28

    SpinTek Membrane Systems, Inc., the developer of a centrifugal membrane filtration technology, has engineered and developed a system for use within the U.S. Department of Energy (DOE) Environmental Management (EM) Program. The technology uses supported microporous membranes rotating at high rpm, under pressure, to separate suspended and colloidal solids from liquid streams, yielding a solids-free permeate stream and a highly concentrated solids stream. This is a crosscutting technology that falls under the Efficient Separations and Processing Crosscutting Program, with potential application to tank wastes, contaminated groundwater, landfill leachate, and secondary liquid waste streams from other remediation processes, including decontamination and decommissioning systems. SpinTek II High Shear Rotary Membrane Filtration System is a unique compact crossflow membrane system that has large, demonstrable advantages in performance and cost compared to currently available systems: (1) High fluid shear prevents membrane fouling even with very high solids content; hazardous and radioactive components can be concentrated to the consistency of a pasty slurry without fouling. (2) Induced turbulence and shear across the membrane increases membrane flux by a factor of ten over existing systems and allows operation on fluids not otherwise treatable. (3) Innovative ceramic membrane and mechanical sealing technology eliminates compatibility problems with aggressive DOE waste streams. (4) System design allows rapid, simple disassembly for inspection or complete decontamination. (5) Produces colloidal- and suspended-solids-free filtrate without the addition of chemicals. The first phase of this project (PRDA maturity stage 5) completed the physical scale-up of the SpinTek unit and verified successful scale-up with surrogate materials. Given successful scale-up and DOE concurrence, the second phase of this project (PRDA maturity stage 6) will provide for the installation and

  13. Small scale membrane mechanics

    PubMed Central

    Rangamani, Padmini; Benjamini, Ayelet; Agrawal, Ashutosh; Smit, Berend; Oster, George

    2014-01-01

    Large scale changes to lipid bilayer shapes are well represented by the Helfrich model. However, there are membrane processes that take place at smaller length scales that this model cannot address. In this work, we present a one-dimensional continuum model that captures the mechanics of the lipid bilayer membrane at the length scale of the lipids themselves. The model is developed using the Cosserat theory of surfaces with lipid orientation, or ‘tilt’, as the fundamental degree of freedom. The Helfrich model can be recovered as a special case when the curvatures are small and the lipid tilt is everywhere zero. We use the tilt model to study local membrane deformations in response to a protein inclusion. Parameter estimates and boundary conditions are obtained from a coarse-grained molecular model using dissipative particle dynamics (DPD) to capture the same phenomenon. The continuum model is able to reproduce the membrane bending, stretch and lipid tilt as seen in the DPD model. The lipid tilt angle relaxes to the bulk tilt angle within 5–6 nm from the protein inclusion. Importantly, for large tilt gradients induced by the proteins, the tilt energy contribution is larger than the bending energy contribution. Thus, the continuum model of tilt accurately captures behaviors at length scales shorter than the membrane thickness. PMID:24081650

  14. Lidocaine induces ROCK-dependent membrane blebbing and subsequent cell death in rabbit articular chondrocytes.

    PubMed

    Maeda, Tsutomu; Toyoda, Futoshi; Imai, Shinji; Tanigawa, Hitoshi; Kumagai, Kousuke; Matsuura, Hiroshi; Matsusue, Yoshitaka

    2016-05-01

    Local anesthetics are administered intraarticularly for pain control in orthopedic clinics and surgeries. Although previous studies have shown that local anesthetics can be toxic to chondrocytes, the underlying cellular mechanisms remain unclear. The present study investigates acute cellular responses associated with lidocaine-induced toxicity to articular chondrocytes. Rabbit articular chondrocytes were exposed to lidocaine and their morphological changes were monitored with live cell microscopy. The viability of chondrocytes was evaluated using a fluorescence based LIVE/DEAD assay. Acute treatment of chondrocytes with lidocaine (3-30 mM) induced spherical protrusions on the cell surface (so called "membrane blebbing") in a time- and concentration-dependent manner. The concentration-response relationship for the lidocaine effect was shifted leftward by elevating extracellular pH, as expected for the non-ionized lidocaine being involved in the bleb formation. ROCK (Rho-kinase) inhibitors Y-27632 and fasudil completely prevented the lidocaine-induced membrane blebbing, suggesting that ROCK activation is required for bleb formation. Caspase-3 levels were unchanged by 10 mM lidocaine (p = 0.325) and a caspase inhibitor z-VAD-fmk did not affect the lidocaine-induced blebbing (p = 0.964). GTP-RhoA levels were significantly increased (p < 0.001), but Rho inhibitor-1 failed to suppress the membrane blebbing (p = 0.875). Lidocaine (30 mM) reduced the cell viability of isolated chondrocytes (p < 0.001) and in situ chondrocytes (p < 0.001). The chondrotoxicity was attenuated by pretreatment of cells with ROCK inhibitors or a myosin-II inhibitor blebbistatin (p < 0.001). These findings suggest that lidocaine induces ROCK-dependent membrane blebbing and thereby produces a cytotoxic effect on chondrocytes. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:754-762, 2016. PMID:26519731

  15. Viral membrane fusion

    PubMed Central

    Harrison, Stephen C.

    2015-01-01

    Membrane fusion is an essential step when enveloped viruses enter cells. Lipid bilayer fusion requires catalysis to overcome a high kinetic barrier; viral fusion proteins are the agents that fulfill this catalytic function. Despite a variety of molecular architectures, these proteins facilitate fusion by essentially the same generic mechanism. Stimulated by a signal associated with arrival at the cell to be infected (e.g., receptor or co-receptor binding, proton binding in an endosome), they undergo a series of conformational changes. A hydrophobic segment (a “fusion loop” or “fusion peptide”) engages the target-cell membrane and collapse of the bridging intermediate thus formed draws the two membranes (virus and cell) together. We know of three structural classes for viral fusion proteins. Structures for both pre- and postfusion conformations of illustrate the beginning and end points of a process that can be probed by single-virion measurements of fusion kinetics. PMID:25866377

  16. Altering morphology of membranes

    SciTech Connect

    Narayan, R.S.

    1987-01-01

    The use of membranes in industrial gas processing and separation has been on the increase in the last eight years, especially since the successful introduction and commercialization of PRISM separators by Monsanto in 1979. Since that time, a number of gas separation applications have been successfully applied on an industrial scale. Separation of hydrogen from N/sub 2/ and hydrocarbons using membranes have become commonplace, and separation of carbon dioxide from hydrocarbons is gaining increasing acceptance. More recently, the separation of nitrogen from oxygen from air has been gaining considerable attention. The economic benefits of using membranes for on-site generation of N/sub 2/ containing less than 5% O/sub 2/ for inert blanketing such as, product storage, packaging, on board ships, airplanes and oil/gas production platforms, etc., are demonstrated to be significant.

  17. Permeability across lipid membranes.

    PubMed

    Shinoda, Wataru

    2016-10-01

    Molecular permeation through lipid membranes is a fundamental biological process that is important for small neutral molecules and drug molecules. Precise characterization of free energy surface and diffusion coefficients along the permeation pathway is required in order to predict molecular permeability and elucidate the molecular mechanisms of permeation. Several recent technical developments, including improved molecular models and efficient sampling schemes, are illustrated in this review. For larger penetrants, explicit consideration of multiple collective variables, including orientational, conformational degrees of freedom, are required to be considered in addition to the distance from the membrane center along the membrane normal. Although computationally demanding, this method can provide significant insights into the molecular mechanisms of permeation for molecules of medical and pharmaceutical importance. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg. PMID:27085977

  18. Outer membrane protein purification.

    PubMed

    Arigita, C; Jiskoot, W; Graaf, M R; Kersten, G F

    2001-01-01

    The major outer membrane proteins (OMPs) from Neisseria meningitidis, which are expressed at high levels, are subdivided in five classes based on molecular weight (1,2) (see Table 1). Table 1 Major Meningococcal Outer-Membrane Proteins Outer-membrane proteins Name Molecular maass Function/characteristics Class 1 PorA 44-47 kDa Porin Class 2/3 PorB 37-42 kDa Porin Class 4 Rmp Reductionmodifiableprotein, unknown Class 5 Opa 26-30 kDa Adhesion,opacity protein Opc 25 kDa Invasion, opacity protein Iron-regulated proteins Mirp 37 kDa Iron acquisition (?);majoriron-regulatedprotein FrpB 70 kDa Ferric enterobactin receptor (also FetA) Adapted from ref. (1). PMID:21336748

  19. Oxygen Transport Ceramic Membranes

    SciTech Connect

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2006-05-01

    In this quarter a systematic analysis on the decomposition behavior of the OTM membranes at air and nitrogen were initiated to understand the structural and stoichiometric changes associated with elevated temperatures. Evaluation of the flexural strengths using 4-point bend test was also started for the dual phase membranes. Initial results on the synthesis of dual phase composite materials have been obtained. The measurements have focused on the compatibility of mixed conductors with the pure ionic conductors yttria stabilized zirconia (YSZ) and gadolinium doped ceria (GDC). The initial results obtained for three different mixed conductors suggest that (GDC) is the better choice. A new membrane permeation system has been designed and tested and sintering studies of biphasic systems are in progress.

  20. Hybrid Filter Membrane

    NASA Technical Reports Server (NTRS)

    Laicer, Castro; Rasimick, Brian; Green, Zachary

    2012-01-01

    Cabin environmental control is an important issue for a successful Moon mission. Due to the unique environment of the Moon, lunar dust control is one of the main problems that significantly diminishes the air quality inside spacecraft cabins. Therefore, this innovation was motivated by NASA s need to minimize the negative health impact that air-suspended lunar dust particles have on astronauts in spacecraft cabins. It is based on fabrication of a hybrid filter comprising nanofiber nonwoven layers coated on porous polymer membranes with uniform cylindrical pores. This design results in a high-efficiency gas particulate filter with low pressure drop and the ability to be easily regenerated to restore filtration performance. A hybrid filter was developed consisting of a porous membrane with uniform, micron-sized, cylindrical pore channels coated with a thin nanofiber layer. Compared to conventional filter media such as a high-efficiency particulate air (HEPA) filter, this filter is designed to provide high particle efficiency, low pressure drop, and the ability to be regenerated. These membranes have well-defined micron-sized pores and can be used independently as air filters with discreet particle size cut-off, or coated with nanofiber layers for filtration of ultrafine nanoscale particles. The filter consists of a thin design intended to facilitate filter regeneration by localized air pulsing. The two main features of this invention are the concept of combining a micro-engineered straight-pore membrane with nanofibers. The micro-engineered straight pore membrane can be prepared with extremely high precision. Because the resulting membrane pores are straight and not tortuous like those found in conventional filters, the pressure drop across the filter is significantly reduced. The nanofiber layer is applied as a very thin coating to enhance filtration efficiency for fine nanoscale particles. Additionally, the thin nanofiber coating is designed to promote capture of

  1. Functional membranes. Present and future

    NASA Technical Reports Server (NTRS)

    Kunitake, T.

    1982-01-01

    The present situation and the future development of the functional membrane are discussed. It is expected that functional membranes will play increasingly greater roles in the chemical industry of the coming decade. These membranes are formed from polymer films, liquid membranes or bilayer membranes. The two most important technologies based on the polymeric membrane are reverse osmosis and ion exchange. The liquid membrane is used for separation of ionic species; an extension of the solvent extraction process. By using appropriate ligands and ionophores, highly selective separations are realized. The active transport is made possible if the physical and chemical potentials are applied to the transport process. More advanced functional membranes may be designed on the basis of the synthetic bilayer membrane.

  2. Supported microporous ceramic membranes

    DOEpatents

    Webster, E.; Anderson, M.

    1993-12-14

    A method for the formation of microporous ceramic membranes onto a porous support includes placing a colloidal suspension of metal or metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane useful for ultrafiltration, reverse osmosis, or molecular sieving having mean pore sizes less than 100 Angstroms. 4 figures.

  3. Supported microporous ceramic membranes

    DOEpatents

    Webster, Elizabeth; Anderson, Marc

    1993-01-01

    A method for permformation of microporous ceramic membranes onto a porous support includes placing a colloidal suspension of metal or metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane useful for ultrafiltration, reverse osmosis, or molecular sieving having mean pore sizes less than 100 Angstroms.

  4. Battery utilizing ceramic membranes

    DOEpatents

    Yahnke, M.S.; Shlomo, G.; Anderson, M.A.

    1994-08-30

    A thin film battery is disclosed based on the use of ceramic membrane technology. The battery includes a pair of conductive collectors on which the materials for the anode and the cathode may be spin coated. The separator is formed of a porous metal oxide ceramic membrane impregnated with electrolyte so that electrical separation is maintained while ion mobility is also maintained. The entire battery can be made less than 10 microns thick while generating a potential in the 1 volt range. 2 figs.

  5. The RalB Small GTPase Mediates Formation of Invadopodia through a GTPase-Activating Protein-Independent Function of the RalBP1/RLIP76 Effector

    PubMed Central

    Neel, Nicole F.; Rossman, Kent L.; Martin, Timothy D.; Hayes, Tikvah K.; Yeh, Jen Jen

    2012-01-01

    Our recent studies implicated key and distinct roles for the highly related RalA and RalB small GTPases (82% sequence identity) in pancreatic ductal adenocarcinoma (PDAC) tumorigenesis and invasive and metastatic growth, respectively. How RalB may promote PDAC invasion and metastasis has not been determined. In light of known Ral effector functions in regulation of actin organization and secretion, we addressed a possible role for RalB in formation of invadopodia, actin-rich membrane protrusions that contribute to tissue invasion and matrix remodeling. We determined that a majority of KRAS mutant PDAC cell lines exhibited invadopodia and that expression of activated K-Ras is both necessary and sufficient for invadopodium formation. Invadopodium formation was not dependent on the canonical Raf-MEK-ERK effector pathway and was instead dependent on the Ral effector pathway. However, this process was more dependent on RalB than on RalA. Surprisingly, RalB-mediated invadopodium formation was dependent on RalBP1/RLIP76 but not Sec5 and Exo84 exocyst effector function. Unexpectedly, the requirement for RalBP1 was independent of its best known function as a GTPase-activating protein for Rho small GTPases. Instead, disruption of the ATPase function of RalBP1 impaired invadopodium formation. Our results identify a novel RalB-mediated biochemical and signaling mechanism for invadopodium formation. PMID:22331470

  6. The CD44s splice isoform is a central mediator for invadopodia activity.

    PubMed

    Zhao, Pu; Xu, Yilin; Wei, Yong; Qiu, Qiong; Chew, Teng-Leong; Kang, Yibin; Cheng, Chonghui

    2016-04-01

    The ability for tumor cells to spread and metastasize to distant organs requires proteolytic degradation of extracellular matrix (ECM). This activity is mediated by invadopodia, actin-rich membrane protrusions that are enriched for proteases. However, the mechanisms underlying invadopodia activity are not fully understood. Here, we report that a specific CD44 splice isoform, CD44s, is an integral component in invadopodia. We show that CD44s, but not another splice isoform CD44v, is localized in invadopodia. Small hairpin (sh)RNA-mediated depletion of CD44s abolishes invadopodia activity, prevents matrix degradation and decreases tumor cell invasiveness. Our results suggest that CD44s promotes cortactin phosphorylation and recruits MT1-MMP (also known as MMP14) to sites of matrix degradation, which are important activities for invadopodia function. Importantly, we show that depletion of CD44s inhibits breast cancer cell metastasis to the lung in animals. These findings suggest a crucial mechanism underlying the role of the CD44s splice isoform in breast cancer metastasis. PMID:26869223

  7. The cancer-testis antigens SPANX-A/C/D and CTAG2 promote breast cancer invasion

    PubMed Central

    Prechtl, Amanda M.; Dang, Tuyen T.; Whitehurst, Angelique W.; Pearson, Gray W.

    2016-01-01

    Genes that are normally biased towards expression in the testis are often induced in tumor cells. These gametogenic genes, known as cancer-testis antigens (CTAs), have been extenstively investigated as targets for immunotherapy. However, despite their frequent detection, the degree to which CTAs support neoplastic invasion is poorly understood. Here, we find that the CTA genes SPANX-A/C/D and CTAG2 are coordinately induced in breast cancer cells and regulate distinct features of invasive behavior. Our functional analysis revealed that CTAG2 interacts with Pericentrin at the centrosome and is necessary for directional migration. Conversely, SPANX-A/C/D interacts with Lamin A/C at the inner nuclear membrane and is required for the formation of actin-rich cellular protrusions that reorganize the extracellular matrix. Importantly, SPANX-A/C/D was required for breast cancer cells to spontaneously metastasize to the lung, demonstrating that CTA reactivation can be critical for invasion dependent phenotypes in vivo. Moreover, elevated SPANX-A/C/D expression in breast cancer patient tumors correlated with poor outcome. Together, our results suggest that distinct CTAs promote tumor progression by regulating complementary cellular functions that are integrated together to induce invasive behavior. PMID:26895102

  8. Rapid Remodeling of Invadosomes by Gi-coupled Receptors: DISSECTING THE ROLE OF Rho GTPases.

    PubMed

    Kedziora, Katarzyna M; Leyton-Puig, Daniela; Argenzio, Elisabetta; Boumeester, Anja J; van Butselaar, Bram; Yin, Taofei; Wu, Yi I; van Leeuwen, Frank N; Innocenti, Metello; Jalink, Kees; Moolenaar, Wouter H

    2016-02-26

    Invadosomes are actin-rich membrane protrusions that degrade the extracellular matrix to drive tumor cell invasion. Key players in invadosome formation are c-Src and Rho family GTPases. Invadosomes can reassemble into circular rosette-like superstructures, but the underlying signaling mechanisms remain obscure. Here we show that Src-induced invadosomes in human melanoma cells (A375M and MDA-MB-435) undergo rapid remodeling into dynamic extracellular matrix-degrading rosettes by distinct G protein-coupled receptor agonists, notably lysophosphatidic acid (LPA; acting through the LPA1 receptor) and endothelin. Agonist-induced rosette formation is blocked by pertussis toxin, dependent on PI3K activity and accompanied by localized production of phosphatidylinositol 3,4,5-trisphosphate, whereas MAPK and Ca(2+) signaling are dispensable. Using FRET-based biosensors, we show that LPA and endothelin transiently activate Cdc42 through Gi, concurrent with a biphasic decrease in Rac activity and differential effects on RhoA. Cdc42 activity is essential for rosette formation, whereas G12/13-mediated RhoA-ROCK signaling suppresses the remodeling process. Our results reveal a Gi-mediated Cdc42 signaling axis by which G protein-coupled receptors trigger invadosome remodeling, the degree of which is dictated by the Cdc42-RhoA activity balance. PMID:26740622

  9. Supervillin Reorganizes the Actin Cytoskeleton and Increases Invadopodial Efficiency

    PubMed Central

    Crowley, Jessica L.; Smith, Tara C.; Fang, Zhiyou; Takizawa, Norio

    2009-01-01

    Tumor cells use actin-rich protrusions called invadopodia to degrade extracellular matrix (ECM) and invade tissues; related structures, termed podosomes, are sites of dynamic ECM interaction. We show here that supervillin (SV), a peripheral membrane protein that binds F-actin and myosin II, reorganizes the actin cytoskeleton and potentiates invadopodial function. Overexpressed SV induces redistribution of lamellipodial cortactin and lamellipodin/RAPH1/PREL1 away from the cell periphery to internal sites and concomitantly increases the numbers of F-actin punctae. Most punctae are highly dynamic and colocalize with the podosome/invadopodial proteins, cortactin, Tks5, and cdc42. Cortactin binds SV sequences in vitro and contributes to the formation of enhanced green fluorescent protein (EGFP)-SV induced punctae. SV localizes to the cores of Src-generated podosomes in COS-7 cells and with invadopodia in MDA-MB-231 cells. EGFP-SV overexpression increases average numbers of ECM holes per cell; RNA interference-mediated knockdown of SV decreases these numbers. Although SV knockdown alone has no effect, simultaneous down-regulation of SV and the closely related protein gelsolin reduces invasion through ECM. Together, our results show that SV is a component of podosomes and invadopodia and that SV plays a role in invadopodial function, perhaps as a mediator of cortactin localization, activation state, and/or dynamics of metalloproteinases at the ventral cell surface. PMID:19109420

  10. Mechanical interplay between invadopodia and the nucleus in cultured cancer cells.

    PubMed

    Revach, Or-Yam; Weiner, Allon; Rechav, Katya; Sabanay, Ilana; Livne, Ariel; Geiger, Benjamin

    2015-01-01

    Invadopodia are actin-rich membrane protrusions through which cells adhere to the extracellular matrix and degrade it. In this study, we explored the mechanical interactions of invadopodia in melanoma cells, using a combination of correlative light and electron microscopy. We show here that the core actin bundle of most invadopodia interacts with integrin-containing matrix adhesions at its basal end, extends through a microtubule-rich cytoplasm, and at its apical end, interacts with the nuclear envelope and indents it. Abolishment of invadopodia by microtubules or src inhibitors leads to the disappearance of these nuclear indentations. Based on the indentation profile and the viscoelastic properties of the nucleus, the force applied by invadopodia is estimated to be in the nanoNewton range. We further show that knockdown of the LINC complex components nesprin 2 or SUN1 leads to a substantial increase in the prominence of the adhesion domains at the opposite end of the invadopodia. We discuss this unexpected, long-range mechanical interplay between the apical and basal domains of invadopodia, and its possible involvement in the penetration of invadopodia into the matrix. PMID:25820462

  11. Invertebrate and Vertebrate Class III Myosins Interact with MORN Repeat-Containing Adaptor Proteins

    PubMed Central

    Mecklenburg, Kirk L.; Freed, Stephanie A.; Raval, Manmeet; Quintero, Omar A.; Yengo, Christopher M.; O'Tousa, Joseph. E.

    2015-01-01

    In Drosophila photoreceptors, the NINAC-encoded myosin III is found in a complex with a small, MORN-repeat containing, protein Retinophilin (RTP). Expression of these two proteins in other cell types showed NINAC myosin III behavior is altered by RTP. NINAC deletion constructs were used to map the RTP binding site within the proximal tail domain of NINAC. In vertebrates, the RTP ortholog is MORN4. Co-precipitation experiments demonstrated that human MORN4 binds to human myosin IIIA (MYO3A). In COS7 cells, MORN4 and MYO3A, but not MORN4 and MYO3B, co-localize to actin rich filopodia extensions. Deletion analysis mapped the MORN4 binding to the proximal region of the MYO3A tail domain. MYO3A dependent MORN4 tip localization suggests that MYO3A functions as a motor that transports MORN4 to the filopodia tips and MORN4 may enhance MYO3A tip localization by tethering it to the plasma membrane at the protrusion tips. These results establish conserved features of the RTP/MORN4 family: they bind within the tail domain of myosin IIIs to control their behavior. PMID:25822849

  12. Hypoxia-Induced Invadopodia Formation Involves Activation of NHE-1 by the p90 Ribosomal S6 Kinase (p90RSK)

    PubMed Central

    Lucien, Fabrice; Brochu-Gaudreau, Karine; Arsenault, Dominique; Harper, Kelly; Dubois, Claire M.

    2011-01-01

    The hypoxic and acidic microenvironments in tumors are strongly associated with malignant progression and metastasis, and have thus become a central issue in tumor physiology and cancer treatment. Despite this, the molecular links between acidic pH- and hypoxia-mediated cell invasion/metastasis remain mostly unresolved. One of the mechanisms that tumor cells use for tissue invasion is the generation of invadopodia, which are actin-rich invasive plasma membrane protrusions that degrade the extracellular matrix. Here, we show that hypoxia stimulates the formation of invadopodia as well as the invasive ability of cancer cells. Inhibition or shRNA-based depletion of the Na+/H+ exchanger NHE-1, along with intracellular pH monitoring by live-cell imaging, revealed that invadopodia formation is associated with alterations in cellular pH homeostasis, an event that involves activation of the Na+/H+ exchange rate by NHE-1. Further characterization indicates that hypoxia triggered the activation of the p90 ribosomal S6 kinase (p90 RSK), which resulted in invadopodia formation and site-specific phosphorylation and activation of NHE-1. This study reveals an unsuspected role of p90RSK in tumor cell invasion and establishes p90RS kinase as a link between hypoxia and the acidic microenvironment of tumors. PMID:22216126

  13. Ultrastructure of the fetal membranes of the oviparous kingsnake, Lampropeltis getula (Colubridae) as revealed by scanning electron microscopy.

    PubMed

    Kim, Young K; Blackburn, Daniel G

    2015-12-01

    In reptilian sauropsids, fetal (extraembryonic) membranes that line the eggshell sustain developing embryos by providing for gas exchange and uptake of water and eggshell calcium. However, a scarcity of morphological studies hinders an understanding of functional specializations and their evolution. In kingsnakes (Lampropeltis getula), scanning electron microscopy reveals two major fetal membranes: the chorioallantois and yolk sac omphalopleure. In early development, the chorioallantois contains tall chorionic epithelial cells, avascular connective tissue, and enlarged allantoic epithelial cells. During its maturation, the chorionic and allantoic epithelia thin dramatically and become underlain by a rich network of allantoic capillaries, yielding a membrane ideally suited for respiratory gas exchange. Yolk sac development initially is like that of typical lizards and snakes, forming an avascular omphalopleure, isolated yolk mass (IYM), and yolk cleft. However, unlike the situation in most squamates studied, the omphalopleure becomes transformed into a "secondary chorioallantois" via three asynchronous events: flattening of the epithelium, regression of the IYM, and vascularization by the allantois. Progressive expansion of chorioallantois parallels growing embryonic needs for gas exchange. In early through mid-development, external surfaces of both the chorionic and omphalopleure epithelium show an abundance of irregular surface protrusions that possibly increase surface area for water absorption. We postulate that the hypertrophied allantoic epithelial cells produce allantoic fluid, a viscous substance that facilitates water uptake and storage. Our findings are consistent with a previous study on the corn snake Pantherophis guttatus, but include new observations and novel functional hypotheses relevant to a reconstruction of basal squamate patterns. PMID:26335135

  14. TOM1L1 drives membrane delivery of MT1-MMP to promote ERBB2-induced breast cancer cell invasion

    PubMed Central

    Chevalier, Clément; Collin, Guillaume; Descamps, Simon; Touaitahuata, Heiani; Simon, Valérie; Reymond, Nicolas; Fernandez, Laurent; Milhiet, Pierre-Emmanuel; Georget, Virginie; Urbach, Serge; Lasorsa, Laurence; Orsetti, Béatrice; Boissière-Michot, Florence; Lopez-Crapez, Evelyne; Theillet, Charles; Roche, Serge; Benistant, Christine

    2016-01-01

    ERBB2 overexpression in human breast cancer leads to invasive carcinoma but the mechanism is not clearly understood. Here we report that TOM1L1 is co-amplified with ERBB2 and defines a subgroup of HER2+/ER+ tumours with early metastatic relapse. TOM1L1 encodes a GAT domain-containing trafficking protein and is a SRC substrate that negatively regulates tyrosine kinase signalling. We demonstrate that TOM1L1 upregulation enhances the invasiveness of ERBB2-transformed cells. This pro-tumoural function does not involve SRC, but implicates membrane-bound membrane-type 1 MMP (MT1-MMP)-dependent activation of invadopodia, membrane protrusions specialized in extracellular matrix degradation. Mechanistically, ERBB2 elicits the indirect phosphorylation of TOM1L1 on Ser321. The phosphorylation event promotes GAT-dependent association of TOM1L1 with the sorting protein TOLLIP and trafficking of the metalloprotease MT1-MMP from endocytic compartments to invadopodia for tumour cell invasion. Collectively, these results show that TOM1L1 is an important element of an ERBB2-driven proteolytic invasive programme and that TOM1L1 amplification potentially enhances the metastatic progression of ERBB2-positive breast cancers. PMID:26899482

  15. Characterization of TtALV2, an Essential Charged Repeat Motif Protein of the Tetrahymena thermophila Membrane Skeleton

    PubMed Central

    El-Haddad, Houda; Przyborski, Jude M.; Kraft, Lesleigh G. K.; McFadden, Geoffrey I.; Waller, Ross F.

    2013-01-01

    Alveolins are a recently described class of proteins common to all members of the superphylum Alveolata that are characterized by conserved charged repeat motifs (CRMs) but whose exact function remains unknown. We have analyzed the smaller of the two alveolins of Tetrahymena thermophila, TtALV2. The protein localizes to dispersed, broken patches arranged between the rows of the longitudinal microtubules. Macronuclear knockdown of Ttalv2 leads to multinuclear cells with no apparent cell polarity and randomly occurring cell protrusions, either by interrupting pellicle integrity or by disturbing cytokinesis. Correct association of TtALV2 with the alveoli or the pellicle is complex and depends on both the termini as well as the charged repeat motifs of the protein. Proteins containing similar CRMs are a dominant part of the ciliate membrane cytoskeleton, suggesting that these motifs may play a more general role in mediating membrane attachment and/or cytoskeletal association. To better understand their integration into the cytoskeleton, we localized a range of CRM-based fusion proteins, which suggested there is an inherent tendency for proteins with CRMs to be located in the peripheral cytoskeleton, some nucleating as filaments at the basal bodies. Even a synthetic protein, mimicking the charge and repeat pattern of these proteins, directed a reporter protein to a variety of peripheral cytoskeletal structures in Tetrahymena. These motifs might provide a blueprint for membrane and cytoskeleton affiliation in the complex pellicles of Alveolata. PMID:23606287

  16. Characterization of TtALV2, an essential charged repeat motif protein of the Tetrahymena thermophila membrane skeleton.

    PubMed

    El-Haddad, Houda; Przyborski, Jude M; Kraft, Lesleigh G K; McFadden, Geoffrey I; Waller, Ross F; Gould, Sven B

    2013-06-01

    Alveolins are a recently described class of proteins common to all members of the superphylum Alveolata that are characterized by conserved charged repeat motifs (CRMs) but whose exact function remains unknown. We have analyzed the smaller of the two alveolins of Tetrahymena thermophila, TtALV2. The protein localizes to dispersed, broken patches arranged between the rows of the longitudinal microtubules. Macronuclear knockdown of Ttalv2 leads to multinuclear cells with no apparent cell polarity and randomly occurring cell protrusions, either by interrupting pellicle integrity or by disturbing cytokinesis. Correct association of TtALV2 with the alveoli or the pellicle is complex and depends on both the termini as well as the charged repeat motifs of the protein. Proteins containing similar CRMs are a dominant part of the ciliate membrane cytoskeleton, suggesting that these motifs may play a more general role in mediating membrane attachment and/or cytoskeletal association. To better understand their integration into the cytoskeleton, we localized a range of CRM-based fusion proteins, which suggested there is an inherent tendency for proteins with CRMs to be located in the peripheral cytoskeleton, some nucleating as filaments at the basal bodies. Even a synthetic protein, mimicking the charge and repeat pattern of these proteins, directed a reporter protein to a variety of peripheral cytoskeletal structures in Tetrahymena. These motifs might provide a blueprint for membrane and cytoskeleton affiliation in the complex pellicles of Alveolata. PMID:23606287

  17. The interactions of peripheral membrane proteins with biological membranes

    SciTech Connect

    Johs, Alexander; Whited, A. M.

    2015-01-01

    The interactions of peripheral proteins with membrane surfaces are critical to many biological processes, including signaling, recognition, membrane trafficking, cell division and cell structure. On a molecular level, peripheral membrane proteins can modulate lipid composition, membrane dynamics and protein-protein interactions. Biochemical and biophysical studies have shown that these interactions are in fact highly complex, dominated by several different types of interactions, and have an interdependent effect on both the protein and membrane. Here we examine three major mechanisms underlying the interactions between peripheral membrane proteins and membranes: electrostatic interactions, hydrophobic interactions, and fatty acid modification of proteins. While experimental approaches continue to provide critical insights into specific interaction mechanisms, emerging bioinformatics resources and tools contribute to a systems-level picture of protein-lipid interactions. Through these recent advances, we begin to understand the pivotal role of protein-lipid interactions underlying complex biological functions at membrane interfaces.

  18. Mitigated membrane fouling of anammox membrane bioreactor by microbiological immobilization.

    PubMed

    Zhang, Zuotao; Liu, Sitong; Miyoshi, Taro; Matsuyama, Hideto; Ni, Jinren

    2016-02-01

    In this study, membrane fouling behavior of anammox MBR with or without carriers made by magnetic porous carbon microspheres was investigated. The results show that Trans Membrane Pressure was an order of magnitude lower after 50days due to use of carriers, which did not directly contact with membrane surface. Scanning Electron Microscope analysis indicates that abundance of anammox bacteria formed biofilm on membrane surface. Fourier transform infrared spectroscopy combined with amino acids contents analysis for membrane surface deposition show that metabolite released by anammox bacteria contains more hydrophobic groups than hydrophilic, which was considered as important reason for its abundant existence on hydrophobic membrane surface. Microbiological immobilization not only reduces biological membrane fouling, but also mitigates organic fouling including organic matter containing COO, hydrophobic groups (CH3, CH2 and CH etc), as well as inorganic deposition. Our finding provides an effective method for mitigating MBR membrane fouling in anammox process. PMID:26687491

  19. The interactions of peripheral membrane proteins with biological membranes

    DOE PAGESBeta

    Johs, Alexander; Whited, A. M.

    2015-01-01

    The interactions of peripheral proteins with membrane surfaces are critical to many biological processes, including signaling, recognition, membrane trafficking, cell division and cell structure. On a molecular level, peripheral membrane proteins can modulate lipid composition, membrane dynamics and protein-protein interactions. Biochemical and biophysical studies have shown that these interactions are in fact highly complex, dominated by several different types of interactions, and have an interdependent effect on both the protein and membrane. Here we examine three major mechanisms underlying the interactions between peripheral membrane proteins and membranes: electrostatic interactions, hydrophobic interactions, and fatty acid modification of proteins. While experimental approachesmore » continue to provide critical insights into specific interaction mechanisms, emerging bioinformatics resources and tools contribute to a systems-level picture of protein-lipid interactions. Through these recent advances, we begin to understand the pivotal role of protein-lipid interactions underlying complex biological functions at membrane interfaces.« less

  20. Enzyme catalytic membrane based on a hybrid mesoporous membrane.

    PubMed

    Fu, Wensheng; Yamaguchi, Akira; Kaneda, Hideaki; Teramae, Norio

    2008-02-21

    Immobilization of glucose oxidase (GOD) within a hybrid mesoporous membrane with 12 nm pore diameter was successfully achieved, resulting in catalytically high efficiency during flow of a glucose solution across the membrane. PMID:18253526

  1. Effective rigidity of membranes

    NASA Astrophysics Data System (ADS)

    Peliti, L.

    1986-12-01

    The role of thermal fluctuations of shape (undulations) in reducing the effective rigidity of membranes is reviewed. The consequences of this effect on vesicle size distribution and on the structure of microemulsions, as well as on other physical phenomena, are sketched.

  2. Improved ion exchange membrane

    NASA Technical Reports Server (NTRS)

    Rembaum, A.; Yen, S. P. S.; Klein, E.

    1975-01-01

    Membrane, made from commercially-available hollow fibers, is used in reverse osmosis, or dialysis. Fiber has skin layers which pass only small molecules. Macromolecules cannot penetrate skin. Fibers can also be used to remove other undesirable anions, such as phosphate, sulfate, carbonate, and uranium in form of uranium-sulfate complex.

  3. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2003-01-01

    In the present quarter, the possibility of using a more complex interfacial engineering approach to the development of reliable and stable oxygen transport perovskite ceramic membranes/metal seals is discussed. Experiments are presented and ceramic/metal interactions are characterized. Crack growth and fracture toughness of the membrane in the reducing conditions are also discussed. Future work regarding this approach is proposed are evaluated for strength and fracture in oxygen gradient conditions. Oxygen gradients are created in tubular membranes by insulating the inner surface from the reducing environment by platinum foils. Fracture in these test conditions is observed to have a gradient in trans and inter-granular fracture as opposed to pure trans-granular fracture observed in homogeneous conditions. Fracture gradients are reasoned to be due to oxygen gradient set up in the membrane, variation in stoichiometry across the thickness and due to varying decomposition of the parent perovskite. The studies are useful in predicting fracture criterion in actual reactor conditions and in understanding the initial evolution of fracture processes.

  4. Electrodichroism of Purple Membrane

    PubMed Central

    Papp, E.; Fricsovszky, G.; Meszéna, G.

    1986-01-01

    The dichroism of purple membrane suspension was measured in dc and ac electric fields. From these measurements three parameters can be obtained: the permanent dipole moment, μ, the electrical polarizability, α, and the retinal angle, δ, (relative to the membrane normal). The functional dependence of the dichroism on the electric field is analyzed. There is a small decrease (∼2°) in retinal angle going from dark adapted to the light adapted form. No measurable difference in μ, α, and δ was found under the photocycle. The dichroism was measured in two different salt solutions (KCl and CaCl2) in the range 0-10 mM. The retinal angle increases from 64° to 68° with increasing ionic strength going through a minimum. This is attributed to the changing (decreasing) inner electric field in the membrane. The polarizability, α, consists of two parts. One component is related to the polarization of the purple membrane and the second component to the ionic cloud. The second component decreases with ion concentration approximately as κ-3 (κ is the Debye parameter) in agreement with a model calculation for the polarization of the ionic cloud. The origin of the slightly ionic strength dependent permanent dipole moment is not well understood. PMID:19431673

  5. Hydrogen-Selective Membrane

    DOEpatents

    Collins, John P.; Way, J. Douglas

    1995-09-19

    A hydrogen-selective membrane comprises a tubular porous ceramic support having a palladium metal layer deposited on an inside surface of the ceramic support. The thickness of the palladium layer is greater than about 10 .mu.m but typically less than about 20 .mu.m. The hydrogen permeation rate of the membrane is greater than about 1.0 moles/m.sup.2.s at a temperature of greater than about 500.degree. C. and a transmembrane pressure difference of about 1,500 kPa. Moreover, the hydrogen-to-nitrogen selectivity is greater than about 600 at a temperature of greater than about 500.degree. C. and a transmembrane pressure of about 700 kPa. Hydrogen can be separated from a mixture of gases using the membrane. The method may include the step of heating the mixture of gases to a temperature of greater than about 400.degree. C. and less than about 1000.degree. C. before the step of flowing the mixture of gases past the membrane. The mixture of gases may include ammonia. The ammonia typically is decomposed to provide nitrogen and hydrogen using a catalyst such as nickel. The catalyst may be placed inside the tubular ceramic support. The mixture of gases may be supplied by an industrial process such as the mixture of exhaust gases from the IGCC process.

  6. Hydrogen-selective membrane

    DOEpatents

    Collins, J.P.; Way, J.D.

    1995-09-19

    A hydrogen-selective membrane comprises a tubular porous ceramic support having a palladium metal layer deposited on an inside surface of the ceramic support. The thickness of the palladium layer is greater than about 10 {micro}m but typically less than about 20 {micro}m. The hydrogen permeation rate of the membrane is greater than about 1.0 moles/m{sup 2}s at a temperature of greater than about 500 C and a transmembrane pressure difference of about 1,500 kPa. Moreover, the hydrogen-to-nitrogen selectivity is greater than about 600 at a temperature of greater than about 500 C and a transmembrane pressure of about 700 kPa. Hydrogen can be separated from a mixture of gases using the membrane. The method may include the step of heating the mixture of gases to a temperature of greater than about 400 C and less than about 1000 C before the step of flowing the mixture of gases past the membrane. The mixture of gases may include ammonia. The ammonia typically is decomposed to provide nitrogen and hydrogen using a catalyst such as nickel. The catalyst may be placed inside the tubular ceramic support. The mixture of gases may be supplied by an industrial process such as the mixture of exhaust gases from the IGCC process. 9 figs.

  7. Hydrogen-selective membrane

    DOEpatents

    Collins, John P.; Way, J. Douglas

    1997-01-01

    A hydrogen-selective membrane comprises a tubular porous ceramic support having a palladium metal layer deposited on an inside surface of the ceramic support. The thickness of the palladium layer is greater than about 10 .mu.m but typically less than about 20 .mu.m. The hydrogen permeation rate of the membrane is greater than about 1.0 moles/m.sup.2. s at a temperature of greater than about 500.degree. C. and a transmembrane pressure difference of about 1,500 kPa. Moreover, the hydrogen-to-nitrogen selectivity is greater than about 600 at a temperature of greater than about 500.degree. C. and a transmembrane pressure of about 700 kPa. Hydrogen can be separated from a mixture of gases using the membrane. The method may include the step of heating the mixture of gases to a temperature of greater than about 400.degree. C. and less than about 1000.degree. C. before the step of flowing the mixture of gases past the membrane. The mixture of gases may include ammonia. The ammonia typically is decomposed to provide nitrogen and hydrogen using a catalyst such as nickel. The catalyst may be placed inside the tubular ceramic support. The mixture of gases may be supplied by an industrial process such as the mixture of exhaust gases from the IGCC process.

  8. Hydrogen-selective membrane

    DOEpatents

    Collins, J.P.; Way, J.D.

    1997-07-29

    A hydrogen-selective membrane comprises a tubular porous ceramic support having a palladium metal layer deposited on an inside surface of the ceramic support. The thickness of the palladium layer is greater than about 10 {micro}m but typically less than about 20 {micro}m. The hydrogen permeation rate of the membrane is greater than about 1.0 moles/m{sup 2} s at a temperature of greater than about 500 C and a transmembrane pressure difference of about 1,500 kPa. Moreover, the hydrogen-to-nitrogen selectivity is greater than about 600 at a temperature of greater than about 500 C and a transmembrane pressure of about 700 kPa. Hydrogen can be separated from a mixture of gases using the membrane. The method may include the step of heating the mixture of gases to a temperature of greater than about 400 C and less than about 1000 C before the step of flowing the mixture of gases past the membrane. The mixture of gases may include ammonia. The ammonia typically is decomposed to provide nitrogen and hydrogen using a catalyst such as nickel. The catalyst may be placed inside the tubular ceramic support. The mixture of gases may be supplied by an industrial process such as the mixture of exhaust gases from the IGCC process. 9 figs.

  9. Membrane Transfer Phenomena (MTP)

    NASA Technical Reports Server (NTRS)

    Mason, Larry

    1996-01-01

    Progress has been made in several areas of the definition, design, and development of the Membrane Transport Apparatus (MTA) instrument and associated sensors and systems. Progress is also reported in the development of software modules for instrument control, experimental image and data acquisition, and data analysis.

  10. Membrane humidity control investigation

    NASA Technical Reports Server (NTRS)

    Elam, J.; Ruder, J.; Strumpf, H.

    1974-01-01

    The basic performance data on a hollow fiber membrane unit that removes water from a breathing gas loop by diffusion is presented. Using available permeability data for cellulose acetate, a preliminary design was made of a dehumidifier unit that would meet the problem statement.

  11. Composite oxygen transport membrane

    SciTech Connect

    Christie, Gervase Maxwell; Lane, Jonathan A.

    2014-08-05

    A method of producing a composite oxygen ion membrane and a composite oxygen ion membrane in which a porous fuel oxidation layer and a dense separation layer and optionally, a porous surface exchange layer are formed on a porous support from mixtures of (Ln.sub.1-xA.sub.x).sub.wCr.sub.1-yB.sub.yO.sub.3-.delta. and a doped zirconia. In the porous fuel oxidation layer and the optional porous surface exchange layer, A is Calcium and in the dense separation layer A is not Calcium and, preferably is Strontium. Preferred materials are (La.sub.0.8Ca.sub.0.2).sub.0.95Cr.sub.0.5Mn.sub.0.5O.sub.3-.delta. for the porous fuel oxidation and optional porous surface exchange layers and (La.sub.0.8Sr.sub.0.2).sub.0.95Cr.sub.0.5Fe.sub.0.5O.sub.3-.delta. for the dense separation layer. The use of such materials allows the membrane to sintered in air and without the use of pore formers to reduce membrane manufacturing costs. The use of materials, as described herein, for forming the porous layers have application for forming any type of porous structure, such as a catalyst support.

  12. Life, death and membrane bilayers.

    PubMed

    Hulbert, A J

    2003-07-01

    Membrane bilayers are essential elements of life, and the synthesis of the hydrocarbons that make up membrane bilayers may have preceded the appearance of life on Earth. Membrane-associated processes are significant components of metabolism, and the acyl composition of membrane bilayers is associated with metabolic activity in a predictable manner. This has resulted in the "membrane pacemaker" theory of metabolism, which proposes that the relative balance between monounsaturated and long-chain polyunsaturated acyl chains in membrane bilayers is a fundamental determinant of metabolic rate of a species. The omega-3 polyunsaturated docosahexaenoate is an especially important component of membranes in this regard. Whilst it is suggested that the physical properties of membrane polyunsaturates are important with respect to their influence on metabolic rate, it is their chemistry that is important in aging. Membrane acyl composition is related to maximum lifespan in mammals and birds, probably via their role in lipid peroxidation. Calorie restriction modifies acyl composition of membrane bilayers and is associated with decreased membrane lipid peroxidation and lifespan extension. The membrane pacemaker theory of metabolism has given birth to the membrane pacemaker hypothesis of aging, which will require further investigation. PMID:12796449

  13. Dialysis membranes for blood purification.

    PubMed

    Sakai, K

    2000-01-01

    All of the artificial membranes in industrial use, such as a reverse-osmosis membrane, dialysis membrane, ultrafiltration membrane, microfiltration membrane and gas separation membrane, also have therapeutic applications. The most commonly used artificial organ is the artificial kidney, a machine that performs treatment known as hemodialysis. This process cleanses the body of a patient with renal failure by dialysis and filtration, simple physicochemical processes. Hemodialysis membranes are used to remove accumulated uremic toxins, excess ions and water from the patient via the dialysate, and to supply (deficit) insufficient ions from the dialysate. Dialysis membranes used clinically in the treatment of patients with renal failure account for by far the largest volume of membranes used worldwide; more than 70 million square meters are used a year. Almost all dialyzers now in use are of the hollow-fiber type. A hollow-fiber dialyzer contains a bundle of approximately 10000 hollow fibers, each with an inner diameter of about 200 microm when wet. The membrane thickness is about 20-45 microm, and the length is 160-250 mm. The walls of the hollow fibers function as the dialysis membrane. Various materials, including cellulose-based materials and synthetic polymers, are used for dialysis membranes. This paper reviews blood purification, hemodialysis and dialysis membranes. PMID:10898241

  14. HYDROGEN SEPARATION MEMBRANES

    SciTech Connect

    Donald P. McCollor; John P. Kay

    1999-08-01

    A likely membrane for future testing of high-temperature hydrogen separation from a gasification product stream was targeted as an inorganic analog of a dense-metal membrane, where the hydrogen would dissolve into and diffuse through the membrane structure. An amorphous membrane such as zinc sulfide appeared to be promising. Previously, ZnS film coating tests had been performed using an electron-beam vacuum coating instrument, with zinc films successfully applied to glass substrates. The coatings appeared relatively stable in air and in a simple simulated gasification atmosphere at elevated temperature. Because the electron-beam coating instrument suffered irreparable breakdown, several alternative methods were tested in an effort to produce a nitrogen-impermeable, hydrogen-permeable membrane on porous sintered steel substrates. None of the preparation methods proved successful in sealing the porous substrate against nitrogen gas. To provide a nitrogen-impermeable ZnS material to test for hydrogen permeability, two ZnS infrared sample windows were purchased. These relatively thick ''membranes'' did not show measurable permeation of hydrogen, either due to lack of absorption or a negligible permeation rate due to their thickness. To determine if hydrogen was indeed adsorbed, thermogravimetric and differential thermal analyses tests were performed on samples of ZnS powder. A significant uptake of hydrogen gas occurred, corresponding to a maximum of 1 mole H{sub 2} per 1 mole ZnS at a temperature of 175 C. The hydrogen remained in the material at ambient temperature in a hydrogen atmosphere, but approximately 50% would be removed in argon. Reheating in a hydrogen atmosphere resulted in no additional hydrogen uptake. Differential scanning calorimetry indicated that the hydrogen uptake was probably due to the formation of a zinc-sulfur-hydrogen species resulting in the formation of hydrogen sulfide. The zinc sulfide was found to be unstable above approximately 200 C

  15. Selective permeability of PVA membranes. I - Radiation-crosslinked membranes

    NASA Technical Reports Server (NTRS)

    Katz, M. G.; Wydeven, T., Jr.

    1981-01-01

    The water and salt transport properties of ionizing radiation crosslinked poly(vinyl alcohol) (PVA) membranes were investigated. The studied membranes showed high permeabilities and low selectivities for both water and salt. The results were found to be in accord with a modified solution-diffusion model for transport across the membranes, in which pressure-dependent permeability coefficients are employed.

  16. Selective Permeability of PVA Membranes. I: Radiation-Crosslinked Membranes

    NASA Technical Reports Server (NTRS)

    Katz, Moshe G.; Wydeven, Theodore, Jr.

    1981-01-01

    The water and salt transport properties of ionizing radiation crosslinked poly(vinyl alcohol) (PVA) membranes were investigated. The studied membranes showed high permeabilities and low selectivities for both water and salt. The results were found to be in accord with a modified solution-diffusion model for transport across the membranes, in which pressure-dependent permeability coefficients are employed.

  17. Process of treating cellulosic membrane and alkaline with membrane separator

    NASA Technical Reports Server (NTRS)

    Hoyt, H. E.; Pfluger, H. L. (Inventor)

    1970-01-01

    The improvement of water-soluble cellulose ether membranes for use as separators in concentrated alkaline battery cells is discussed. The process of contacting membranes with an aqueous alkali solution of concentration less than that of the alkali solution to be used in the battery but above that at which the membrane is soluble is described.

  18. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2001-12-01

    Conversion of natural gas to liquid fuels and chemicals is a major goal for the Nation as it enters the 21st Century. Technically robust and economically viable processes are needed to capture the value of the vast reserves of natural gas on Alaska's North Slope, and wean the Nation from dependence on foreign petroleum sources. Technologies that are emerging to fulfill this need are all based syngas as an intermediate. Syngas (a mixture of hydrogen and carbon monoxide) is a fundamental building block from which chemicals and fuels can be derived. Lower cost syngas translates directly into more cost-competitive fuels and chemicals. The currently practiced commercial technology for making syngas is either steam methane reforming (SMR) or a two-step process involving cryogenic oxygen separation followed by natural gas partial oxidation (POX). These high-energy, capital-intensive processes do not always produce syngas at a cost that makes its derivatives competitive with current petroleum-based fuels and chemicals. This project has the following 6 main tasks: Task 1--Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. Task 2--Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. Task 3--Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. Task 4--Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. Task 5--Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. Task 6--Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  19. Bioanalysis with Potentiometric Membrane Electrodes.

    ERIC Educational Resources Information Center

    Rechnitz, G. A.

    1982-01-01

    Discusses major themes and interrelationships common to bioselective potentiometric membrane electrodes including the nature of bioselective electrodes, applications, and future prospects. Includes tables on traditional ion-selective membrane electrodes, nontraditional electrodes, and typical biocatalytic potentiometric electrodes. (Author/JN)

  20. Ion Channels in Nerve Membranes

    ERIC Educational Resources Information Center

    Ehrenstein, Gerald

    1976-01-01

    Discusses research that indicates that nerve membranes, which play a key role in the conduction of impulses, are traversed by protein channels with ion pathways opened and closed by the membrane electric field. (Author/MLH)

  1. Membrane Cells for Brine Electrolysis.

    ERIC Educational Resources Information Center

    Tingle, M.

    1982-01-01

    Membrane cells were developed as alternatives to mercury and diaphragm cells for the electrolysis of brine. Compares the three types of cells, focusing on the advantages and disadvantages of membrane cells. (JN)

  2. Structural Analysis of the Roles of Influenza A Virus Membrane-Associated Proteins in Assembly and Morphology

    PubMed Central

    Chlanda, Petr; Schraidt, Oliver; Kummer, Susann; Riches, James; Oberwinkler, Heike; Prinz, Simone; Kräusslich, Hans-Georg

    2015-01-01

    ABSTRACT The assembly of influenza A virus at the plasma membrane of infected cells leads to release of enveloped virions that are typically round in tissue culture-adapted strains but filamentous in strains isolated from patients. The viral proteins hemagglutinin (HA), neuraminidase (NA), matrix protein 1 (M1), and M2 ion channel all contribute to virus assembly. When expressed individually or in combination in cells, they can all, under certain conditions, mediate release of membrane-enveloped particles, but their relative roles in virus assembly, release, and morphology remain unclear. To investigate these roles, we produced membrane-enveloped particles by plasmid-derived expression of combinations of HA, NA, and M proteins (M1 and M2) or by infection with influenza A virus. We monitored particle release, particle morphology, and plasma membrane morphology by using biochemical methods, electron microscopy, electron tomography, and cryo-electron tomography. Our data suggest that HA, NA, or HANA (HA plus NA) expression leads to particle release through nonspecific induction of membrane curvature. In contrast, coexpression with the M proteins clusters the glycoproteins into filamentous membrane protrusions, which can be released as particles by formation of a constricted neck at the base. HA and NA are preferentially distributed to differently curved membranes within these particles. Both the budding intermediates and the released particles are morphologically similar to those produced during infection with influenza A virus. Together, our data provide new insights into influenza virus assembly and show that the M segment together with either of the glycoproteins is the minimal requirement to assemble and release membrane-enveloped particles that are truly virus-like. IMPORTANCE Influenza A virus is a major respiratory pathogen. It assembles membrane-enveloped virus particles whose shapes vary from spherical to filamentous. Here we examine the roles of individual

  3. Active membrane phased array radar

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; Del Castillo, Linda; Huang, John; Sadowy, Greg; Hoffman, James; Smith, Phil; Hatake, Toshiro; Derksen, Chuck; Lopez, Bernardo; Caro, Ed

    2005-01-01

    We have developed the first membrane-based active phased array in L-band (1.26GHz). The array uses membrane compatible Transmit/Receive (T/R) modules (membrane T/R) for each antenna element. We use phase shifters within each T/R module for electronic beam steering. We will discuss the T/R module design and integration with the membrane, We will also present transmit and receive beam-steering results for the array.

  4. Fuel cell with ionization membrane

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T. (Inventor)

    2007-01-01

    A fuel cell is disclosed comprising an ionization membrane having at least one area through which gas is passed, and which ionizes the gas passing therethrough, and a cathode for receiving the ions generated by the ionization membrane. The ionization membrane may include one or more openings in the membrane with electrodes that are located closer than a mean free path of molecules within the gas to be ionized. Methods of manufacture are also provided.

  5. Pretreatment and Membrane Hydrophilic Modification to Reduce Membrane Fouling

    PubMed Central

    Sun, Wen; Liu, Junxia; Chu, Huaqiang; Dong, Bingzhi

    2013-01-01

    The application of low pressure membranes (microfiltration/ultrafiltration) has undergone accelerated development for drinking water production. However, the major obstacle encountered in its popularization is membrane fouling caused by natural organic matter (NOM). This paper firstly summarizes the two factors causing the organic membrane fouling, including molecular weight (MW) and hydrophilicity/hydrophobicity of NOM, and then presents a brief introduction of the methods which can prevent membrane fouling such as pretreatment of the feed water (e.g., coagulation, adsorption, and pre-oxidation) and membrane hydrophilic modification (e.g., plasma modification, irradiation grafting modification, surface coating modification, blend modification, etc.). Perspectives of further research are also discussed. PMID:24956947

  6. Focus issue: signaling across membranes.

    PubMed

    Gough, Nancy R

    2005-12-01

    This week's issues of Science and Science's STKE focus on movement of molecules and information across cellular membranes. Science highlights the mechanisms by which proteins, ions, and DNA cross the membranes of eukaryotic and prokaryotic cells. STKE addresses how information is transmitted across cell membranes to allow cells to communicate with each other and to respond to signals in their environments. PMID:16333016

  7. Bioenergetics: Proton fronts on membranes

    NASA Astrophysics Data System (ADS)

    Agmon, Noam; Gutman, Menachem

    2011-11-01

    Proton migration on membranes is a crucial step in the bioenergetics of the cell. It has typically been regarded as slow successive proton transfers between ionizable moieties within the membrane, but recent measurements suggest fast lateral diffusion in the membrane's hydration layer.

  8. Natural convection immersion cooling of an array of vertically oriented heated protrusions in an enclosure filled with a dielectric liquid: Effects of enclosure width, Prandtl number and component orientation

    NASA Astrophysics Data System (ADS)

    Matthews, Scott T.

    1991-12-01

    The natural convection heat transfer characteristics of a 3 x 3 array of vertically oriented heated protrusions, immersed in a dielectric liquid, were investigated. Aluminum blocks, 24 x 8 x 6 mm, were used to simulate 20 pin dual in-line packages. Surface temperature measurements of the components were made by imbedding copper-constantan thermocouples below the surface of each component face. A constant heat flux was provided to each component using an Inconel foil heating element. Power supplied to each component varied from 0.115 to 2.90 W. The aluminum blocks were mounted on a plexiglass substrate to form a 3 x 3 array of simulated electronic components. The circuit board containing the components was placed in a rectangular, plexiglass enclosure with inner dimensions: L = 203.2 mm H = 152.0 mm W = 82.6 mm, and a wall thickness of 25.4 mm. The upper boundary was maintained at 10 C, while all other exterior surfaces were insulated. The chamber width, measured from the surface of the circuit board to the opposite, inner wall of the enclosure, was varied from 42 to 7 mm by inserting plexiglass spacers into the enclosure. Two dielectric liquids, FC-75 and FC-43, were used as working fluids. Nondimensional data from this study was combined with the data obtained for a horizontal component orientation, to develop an empirical correlation which predicts the Nusselt number as a function of Rayleigh number, Prandtl number, component orientation, and chamber width.

  9. Superhydrophobicity on transparent fluorinated ethylene propylene films with nano-protrusion morphology by Ar + O{sub 2} plasma etching: Study of the degradation in hydrophobicity after exposure to the environment

    SciTech Connect

    Gupta, Nitant; Kavya, M. V.; Singh, Yogesh R. G.; Jyothi, J.; Barshilia, Harish C.

    2013-10-28

    Fluorinated ethylene propylene (FEP) films were made superhydrophobic by Ar + O{sub 2} plasma etching process. Field emission scanning electron microscopy and atomic force microscopy studies of the plasma-treated FEP samples detected the presence of uniformly distributed nano-protrusions exhibiting a low surface roughness necessary for maintaining the transparency of the samples. In fact, optical transmittance measurements showed an improvement in the transparency of FEP samples after plasma treatment. The X-ray photoelectron spectroscopic analysis showed the presence of –CF{sub x}–O–CF{sub x}– (x = 1, 2, or 3) linkages in both untreated and plasma-treated samples which explains the hydrophilic nature (contact angle below 90{sup ∘}) of the untreated sample. Fourier transform infrared spectroscopy showed no changes in the bulk properties of the plasma-treated samples. Moreover, exposure to the environment caused the surfaces to lose their superhydrophobic property in an indefinite amount of time. This has been further studied through a water immersion experiment and explained through the wetting state transition from Cassie state to Wenzel state.

  10. Membrane tension and peripheral protein density mediate membrane shape transitions

    PubMed Central

    Shi, Zheng; Baumgart, Tobias

    2015-01-01

    Endocytosis is a ubiquitous eukaryotic membrane budding, vesiculation, and internalization process fulfilling numerous roles including compensation of membrane area increase after bursts of exocytosis. The mechanism of the coupling between these two processes to enable homeostasis is not well understood. Recently, an ultrafast endocytosis (UFE) pathway was revealed with a speed significantly exceeding classical clathrin-mediated endocytosis (CME). Membrane tension reduction is a potential mechanism by which endocytosis can be rapidly activated at remote sites. Here we provide experimental evidence for a mechanism whereby membrane tension reduction initiates membrane budding and tubulation mediated by endocytic proteins such as endophilin A1. We find that shape instabilities occur at well-defined membrane tensions and surface densities of endophilin. From our data, we obtain a membrane shape stability diagram that shows remarkable consistency with a quantitative model. This model applies to all laterally diffusive curvature coupling proteins and therefore a wide range of endocytic proteins. PMID:25569184

  11. Membrane tension and peripheral protein density mediate membrane shape transitions.

    PubMed

    Shi, Zheng; Baumgart, Tobias

    2015-01-01

    Endocytosis is a ubiquitous eukaryotic membrane budding, vesiculation and internalization process fulfilling numerous roles including compensation of membrane area increase after bursts of exocytosis. The mechanism of the coupling between these two processes to enable homeostasis is not well understood. Recently, an ultrafast endocytosis (UFE) pathway was revealed with a speed significantly exceeding classical clathrin-mediated endocytosis (CME). Membrane tension reduction is a potential mechanism by which endocytosis can be rapidly activated at remote sites. Here, we provide experimental evidence for a mechanism whereby membrane tension reduction initiates membrane budding and tubulation mediated by endocytic proteins, such as endophilin A1. We find that shape instabilities occur at well-defined membrane tensions and surface densities of endophilin. From our data, we obtain a membrane shape stability diagram that shows remarkable consistency with a quantitative model. This model applies to all laterally diffusive curvature-coupling proteins and therefore a wide range of endocytic proteins. PMID:25569184

  12. Membrane tension and peripheral protein density mediate membrane shape transitions

    NASA Astrophysics Data System (ADS)

    Shi, Zheng; Baumgart, Tobias

    2015-01-01

    Endocytosis is a ubiquitous eukaryotic membrane budding, vesiculation and internalization process fulfilling numerous roles including compensation of membrane area increase after bursts of exocytosis. The mechanism of the coupling between these two processes to enable homeostasis is not well understood. Recently, an ultrafast endocytosis (UFE) pathway was revealed with a speed significantly exceeding classical clathrin-mediated endocytosis (CME). Membrane tension reduction is a potential mechanism by which endocytosis can be rapidly activated at remote sites. Here, we provide experimental evidence for a mechanism whereby membrane tension reduction initiates membrane budding and tubulation mediated by endocytic proteins, such as endophilin A1. We find that shape instabilities occur at well-defined membrane tensions and surface densities of endophilin. From our data, we obtain a membrane shape stability diagram that shows remarkable consistency with a quantitative model. This model applies to all laterally diffusive curvature-coupling proteins and therefore a wide range of endocytic proteins.

  13. Regulation of Salmonella-induced membrane ruffling by SipA differs in strains lacking other effectors.

    PubMed

    Perrett, Charlotte A; Jepson, Mark A

    2009-03-01

    The Salmonella pathogenicity island 1 (SPI-1) type three secretion system (TTSS) is essential for Salmonella invasion of host cells through its triggering of actin-dependent membrane ruffles. The SPI-1 effectors SipA, SopE, SopE2 and SopB all have actin regulating activities and contribute to invasion. The precise role of actin regulation by SipA in Salmonella invasion remains controversial since divergent data have been presented regarding the relationship between SipA and membrane ruffling. We hypothesized that the contribution of SipA to membrane ruffling and invasion might vary between Salmonella strains. We compared the effects of SipA deletion on Salmonella enterica serovar Typhimurium (S. Typhimurium) strains that possess or lack SopE. Loss of SipA reduced invasion in the early stages of infection by SopE(+) and SopE(-) strains but the number of membrane ruffles elicited was unaffected. Salmonella strains lacking both SipA and SopE induced ruffles with very different morphology from those induced by wild-type strains or ones lacking single effectors, including the presence of highly dynamic finger-like protrusions and numerous filopodia. A similar phenotype was found for sipA(-)sopE(-), sipA(-)sopE2(-) and sipA(-)sopB(-) mutants. Thus, SipA plays a more prominent role in induction of invasion-competent membrane ruffles by Salmonella lacking a full complement of SPI-1 effectors. PMID:19046340

  14. Recycling of used perfluorosulfonic acid membranes

    DOEpatents

    Grot, Stephen; Grot, Walther

    2007-08-14

    A method for recovering and recycling catalyst coated fuel cell membranes includes dissolving the used membranes in water and solvent, heating the dissolved membranes under pressure and separating the components. Active membranes are produced from the recycled materials.

  15. NASA In-step: Permeable Membrane Experiment

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Viewgraphs on the Permeable Membrane Experiment are presented. An experiment overview is given. The Membrane Phase Separation Experiment, Membrane Diffusion Interference Experiment, and Membrane Wetting Experiment are described. Finally, summary and conclusions are discussed.

  16. Membrane bioreactors for water reclamation.

    PubMed

    Tao, G; Kekre, K; Wei, Z; Lee, T C; Viswanath, B; Seah, H

    2005-01-01

    Singapore has been using dual membrane technology (MF/UF RO) to produce high-grade water (NEWater) from secondary treated sewage. Membrane bioreactor (MBR) has very high potential and will lead to the further improvement of the productivity and quality of high-grade water. This study was focused on the technical feasibility of MBR system for water reclamation in Singapore, making a comparison between various membrane systems available and to get operational experience in terms of membrane cleaning and other issues. Three MBR plants were built at Bedok Water Reclamation Plant with a design flow of 300 m3/day each. They were commissioned in March 2003. Three different types of submerged membranes were tested. They are Membrane A, plate sheet membrane with pore size of 0.4 microm; Membrane B, hollow fibre membrane with pore size of 0.4 microm; and Membrane C, hollow fibre membrane with pore size of 0.035 microm. The permeate quality of all the three MBR Systems were found equivalent to or better than that of the conventional tertiary treatment by ultrafiltration. MBR permeate TOC was about 2 mg/l lower than UF permeate TOC. GC-MS, GC-ECD and HPLC scan results show that trace organic contaminants in MBR permeate and UF permeate were in the same range. MBR power consumption can be less than 1 kwh/m3. Gel layer or dynamic membrane generated on the submerged membrane surface played an important role for the lower MBR permeate TOC than the supernatant TOC in the membrane tank. Intensive chemical cleaning can temporarily remove this layer. During normal operation conditions, the formation of dynamic membrane may need one day to obtain the steady low TOC levels in MBR permeate. PMID:16004005

  17. The First Cell Membranes

    NASA Technical Reports Server (NTRS)

    Deamer, David; Dworkin, Jason P.; Sandford, Scott A.; Bernstein, Max P.; Allamandola, Louis J.

    2004-01-01

    Organic compounds are synthesized in the interstellar medium and can be delivered to planetary surfaces such as the early Earth, where they mix with endogenous organic mixtures. Some of these compounds are amphiphilic, having polar and non-polar groups on the same molecule. Amphiphilic compounds spontaneously self-assembly into more complex structures such as bimolecular layers, which in turn form closed membranous vesicles. The first forms of cellular life required self-assembled membranes that were likely to be available on the prebiotic Earth. Laboratory simulations show that such vesicles readily encapsulate functional macromolecules, including nucleic acids and polymerases. A goal of future investigations is to fabricate artificial cells as models of the origin of life.

  18. Membrane separation of hydrocarbons

    DOEpatents

    Chang, Y. Alice; Kulkarni, Sudhir S.; Funk, Edward W.

    1986-01-01

    Mixtures of heavy oils and light hydrocarbons may be separated by passing the mixture through a polymeric membrane. The membrane which is utilized to effect the separation comprises a polymer which is capable of maintaining its integrity in the presence of hydrocarbon compounds and which has been modified by being subjected to the action of a sulfonating agent. Sulfonating agents which may be employed will include fuming sulfuric acid, chlorosulfonic acid, sulfur trioxide, etc., the surface or bulk modified polymer will contain a degree of sulfonation ranging from about 15 to about 50%. The separation process is effected at temperatures ranging from about ambient to about 100.degree. C. and pressures ranging from about 50 to about 1000 psig.

  19. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2003-01-01

    In the present quarter, experiments are presented on ceramic/metal interactions of Zirconia/Ni-B-Si system and with a thin Ti coating deposited on zirconia surface. Processing of perovskites of LSC, LSF and LSCF composition for evaluation of mechanical properties as a function of environment are begun. The studies are to be in parallel with LSFCO composition to characterize the segregation of cations and slow crack growth in environmental conditions. La{sub 1-x}Sr{sub x}FeO{sub 3-d} has also been characterized for paramagnetic ordering at room temperature and the evolution of magnetic moments as a function of temperature are investigated. Investigation on the thermodynamic properties of the membrane materials are continued to develop a complete model for the membrane transport.

  20. Oxygen Transport Ceramic Membranes

    SciTech Connect

    S. Bandopadhyay; N. Nagabhushana; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-02-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. Thermogravimetric analysis (TGA) was carried out on La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} to investigate oxygen deficiency ({delta}) of the sample. The TGA was performed in a controlled atmosphere using oxygen, argon, carbon monoxide and carbon dioxide with adjustable gas flow rates. In this experiment, the weight loss and gain of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} was directly measured by TGA. The weight change of the sample was evaluated at between 600 and 1250 C in air or 1000 C as a function of oxygen partial pressure. The oxygen deficiencies calculated from TGA data as a function of oxygen activity and temperature will be estimated and compared with that from neutron diffraction measurement in air. The LSFT and LSFT/CGO membranes were fabricated from the powder obtained from Praxair Specialty Ceramics. The sintered membranes were subjected to microstructure analysis and hardness analysis. The LSFT membrane is composed of fine grains with two kinds of grain morphology. The grain size distribution was characterized using image analysis. In LSFT/CGO membrane a lot of grain pullout was observed from the less dense, porous phase. The hardness of the LSFT and dual phase membranes were studied at various loads. The hardness values obtained from the cross section of the membranes were also compared to that of the values obtained from the surface. An electrochemical cell has been designed and built for measurements of the Seebeck coefficient as a function of temperature and pressure. Measurements on La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} as a function of temperature an oxygen partial pressure are reported. Further analysis of the dilatometry data obtained previously is presented. A series of isotope transients

  1. Membrane Protein Prediction Methods

    PubMed Central

    Punta, Marco; Forrest, Lucy R.; Bigelow, Henry; Kernytsky, Andrew; Liu, Jinfeng; Rost, Burkhard

    2007-01-01

    We survey computational approaches that tackle membrane protein structure and function prediction. While describing the main ideas that have led to the development of the most relevant and novel methods, we also discuss pitfalls, provide practical hints and highlight the challenges that remain. The methods covered include: sequence alignment, motif search, functional residue identification, transmembrane segment and protein topology predictions, homology and ab initio modeling. Overall, predictions of functional and structural features of membrane proteins are improving, although progress is hampered by the limited amount of high-resolution experimental information available. While predictions of transmembrane segments and protein topology rank among the most accurate methods in computational biology, more attention and effort will be required in the future to ameliorate database search, homology and ab initio modeling. PMID:17367718

  2. Characterization and expression of plasma and tonoplast membrane aquaporins in primed seed of Brassica napus during germination under stress conditions.

    PubMed

    Gao, Y P; Young, L; Bonham-Smith, P; Gusta, L V

    1999-07-01

    Two aquaporin genes were isolated from a cDNA library of canola (Brassica napus L.). The first aquaporin, BnPIP1 of 1094 bp, encoding a putative polypeptide of 287 amino acids with a predicted molecular mass of 30.4 kDa and a pI of 7.8, belongs to the family of plasma membrane intrinsic protein (PIPs) aquaporins. The B. napus aquaporin showed 85-94% identity to the Arabidopsis thaliana PIPs. ABA priming of seed induced high levels of BnPIP1 transcript which remained after subsequent re-drying of the seed. The second aquaporin, Bny-TIP2 of 1020 bp, encoded a putative polypeptide of 253 amino acids with a predicted molecular mass of 25.8 kDa and a pI of 5.8. Bngamma-TIP2 showed 83-90% identity to gamma-TIP genes from a variety of plant species. Bngamma-TIP2 was expressed only when radicle protrusion occurred in either untreated or primed seeds. Seeds primed with PEG or ABA germinated earlier and showed a higher final percentage of germination than unprimed seed, particularly under salt and osmotic stresses at low temperature. Transcripts of both BnPIP1 and Bngamma-TIP2 genes were present earlier during germination of primed seeds than non-primed seed. From these results, we conclude that BnPIP1 is related to the water transportation required for enzymatic metabolism of storage nutrients at the early stages of canola seed germination whereas Bngamma-TIP2 expression is related to cell growth associated with radicle protrusion. Priming induced the expression of BnPIP1 but had no effect on Bngamma-TIP2. PMID:10480387

  3. HSPES membrane electrode assembly

    NASA Technical Reports Server (NTRS)

    Kindler, Andrew (Inventor); Yen, Shiao-Ping (Inventor)

    2000-01-01

    An improved fuel cell electrode, as well as fuel cells and membrane electrode assemblies that include such an electrode, in which the electrode includes a backing layer having a sintered layer thereon, and a non-sintered free-catalyst layer. The invention also features a method of forming the electrode by sintering a backing material with a catalyst material and then applying a free-catalyst layer.

  4. Bioselective Membrane Electrode Probes

    NASA Astrophysics Data System (ADS)

    Rechnitz, Garry A.

    1981-10-01

    The use of intact bacterial cells or tissue slices of plant and animal origin as immobilized biocatalysts has extended the possible range of potentiometric bioselective membrane electrodes beyond that of conventional enzyme electrodes. The use of such materials as biocatalysts offers advantages in situations where isolated enzymes are not available or where multistep reaction paths are required. The resulting bioselective electrodes also offer exceptional ease of preparation, time stability, and low cost.

  5. Membrane Transport Phenomena (MTP)

    NASA Technical Reports Server (NTRS)

    Mason, Larry W.

    1997-01-01

    The third semi-annual period of the MTP project has been involved with performing experiments using the Membrane Transport Apparatus (MTA), development of analysis techniques for the experiment results, analytical modeling of the osmotic transport phenomena, and completion of a DC-9 microgravity flight to test candidate fluid cell geometries. Preparations were also made for the MTP Science Concept Review (SCR), held on 13 June 1997 at Lockheed Martin Astronautics in Denver. These activities are detailed in the report.

  6. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-07-01

    This is the fourth quarterly report on a new study to develop a ceramic membrane/metal joint. The first experiments using the La-Sr-Fe-O ceramic are reported. Some of the analysis performed on the samples obtained are commented upon. A set of experiments to characterize the mechanical strength and thermal fatigue properties of the joints has been designed and begun. Finite element models of joints used to model residual stresses are described.

  7. Challenges in plasma membrane phosphoproteomics

    PubMed Central

    Orsburn, Benjamin C; Stockwin, Luke H; Newton, Dianne L

    2011-01-01

    The response to extracellular stimuli often alters the phosphorylation state of plasma membrane-associated proteins. In this regard, generation of a comprehensive membrane phosphoproteome can significantly enhance signal transduction and drug mechanism studies. However, analysis of this subproteome is regarded as technically challenging, given the low abundance and insolubility of integral membrane proteins, combined with difficulties in isolating, ionizing and fragmenting phosphopeptides. In this article, we highlight recent advances in membrane and phosphoprotein enrichment techniques resulting in improved identification of these elusive peptides. We also describe the use of alternative fragmentation techniques, and assess their current and future value to the field of membrane phosphoproteomics. PMID:21819303

  8. Water vapor diffusion membrane development

    NASA Technical Reports Server (NTRS)

    Tan, M. K.

    1976-01-01

    A total of 18 different membranes were procured, characterized, and tested in a modified bench-scale vapor diffusion water reclamation unit. Four membranes were selected for further studies involving membrane fouling. Emphasis was placed on the problem of flux decline due to membrane fouling. This is discussed in greater details under "Summary and Discussion on Membrane Fouling Studies" presented in pages 47-51. The system was also investigated for low temperature application on wash-water where the permeated water is not recovered but vented into space vacuum.

  9. Premature rupture of membranes.

    PubMed Central

    Poma, P. A.

    1996-01-01

    The management of patients with premature rupture of membranes has changed markedly in the past several years. The basis for this is a combination of a better understanding of newborn physiology, improved neonatal care, refinements in antibiotic therapy, and the widespread use of maternal and fetal monitoring. The best outcome for both mother and infant undoubtedly reflects data based on a combination of factors, among which are gestational age survival, evidence of fetal distress, presence or absence of labor and sepsis, and of course, the cervical condition as it is related to labor-readiness. An important recent advance is the recognition that an active observation management program is associated with less morbidity and mortality than the classic management course of delivery within 12 hours of membrane rupture. The fact that preterm premature rupture of membranes tends to recur in subsequent pregnancies offers an opportunity for prevention. Moreover, advances in perinatal and neonatal care will continue to improve the outcomes of these women and their children. PMID:8583489

  10. Novel Catalytic Membrane Reactors

    SciTech Connect

    Stuart Nemser, PhD

    2010-10-01

    There are many industrial catalytic organic reversible reactions with amines or alcohols that have water as one of the products. Many of these reactions are homogeneously catalyzed. In all cases removal of water facilitates the reaction and produces more of the desired chemical product. By shifting the reaction to right we produce more chemical product with little or no additional capital investment. Many of these reactions can also relate to bioprocesses. Given the large number of water-organic compound separations achievable and the ability of the Compact Membrane Systems, Inc. (CMS) perfluoro membranes to withstand these harsh operating conditions, this is an ideal demonstration system for the water-of-reaction removal using a membrane reactor. Enhanced reaction synthesis is consistent with the DOE objective to lower the energy intensity of U.S. industry 25% by 2017 in accord with the Energy Policy Act of 2005 and to improve the United States manufacturing competitiveness. The objective of this program is to develop the platform technology for enhancing homogeneous catalytic chemical syntheses.

  11. Viral membrane fusion

    SciTech Connect

    Harrison, Stephen C.

    2015-05-15

    Membrane fusion is an essential step when enveloped viruses enter cells. Lipid bilayer fusion requires catalysis to overcome a high kinetic barrier; viral fusion proteins are the agents that fulfill this catalytic function. Despite a variety of molecular architectures, these proteins facilitate fusion by essentially the same generic mechanism. Stimulated by a signal associated with arrival at the cell to be infected (e.g., receptor or co-receptor binding, proton binding in an endosome), they undergo a series of conformational changes. A hydrophobic segment (a “fusion loop” or “fusion peptide”) engages the target-cell membrane and collapse of the bridging intermediate thus formed draws the two membranes (virus and cell) together. We know of three structural classes for viral fusion proteins. Structures for both pre- and postfusion conformations of illustrate the beginning and end points of a process that can be probed by single-virion measurements of fusion kinetics. - Highlights: • Viral fusion proteins overcome the high energy barrier to lipid bilayer merger. • Different molecular structures but the same catalytic mechanism. • Review describes properties of three known fusion-protein structural classes. • Single-virion fusion experiments elucidate mechanism.

  12. Lipid exchange between membranes.

    PubMed Central

    Jähnig, F

    1984-01-01

    The exchange of lipid molecules between vesicle bilayers in water and a monolayer forming at the water surface was investigated theoretically within the framework of thermodynamics. The total number of exchanged molecules was found to depend on the bilayer curvature as expressed by the vesicle radius and on the boundary condition for exchange, i.e., whether during exchange the radius or the packing density of the vesicles remains constant. The boundary condition is determined by the rate of flip-flop within the bilayer relative to the rate of exchange between bi- and monolayer. If flip-flop is fast, exchange is independent of the vesicle radius; if flip-flop is slow, exchange increases with the vesicle radius. Available experimental results agree with the detailed form of this dependence. When the theory was extended to exchange between two bilayers of different curvature, the direction of exchange was also determined by the curvatures and the boundary conditions for exchange. Due to the dependence of the boundary conditions on flip-flop and, consequently, on membrane fluidity, exchange between membranes may partially be regulated by membrane fluidity. PMID:6518251

  13. Painted supported lipid membranes

    PubMed Central

    Florin, E.-L.; Gaub, H. E.

    1993-01-01

    We report herein measurements on a novel type of supported lipid films, which we call painted supported membranes (PSM). These membranes are formed in a self-assembly process on alkylated gold films from an organic solution. The formation process was investigated with surface plasmon resonance microscopy. The optical and electrical properties of the films were determined for various types of lipids and as a function of temperature by means of cyclic voltammetry and potential relaxation after charge injection. We could show that these films exhibit an extraordinarily high specific resistivity which, depending on the lipid, may be as high as 109 ohm/cm2. We could also show that due to this low conductivity, an electrical polarization across the PSM relaxes with characteristic time constants of up to 20 min. The electrical properties together with their high mechanical stability and accessibility to surface sensitive techniques make these films well suitable model membranes for optical and electrical investigations. Examples for such applications are given in the subsequent article by Seifert et al. ImagesFIGURE 3FIGURE 4 PMID:19431873

  14. Virus separation using membranes.

    PubMed

    Grein, Tanja A; Michalsky, Ronald; Czermak, Peter

    2014-01-01

    Industrial manufacturing of cell culture-derived viruses or virus-like particles for gene therapy or vaccine production are complex multistep processes. In addition to the bioreactor, such processes require a multitude of downstream unit operations for product separation, concentration, or purification. Similarly, before a biopharmaceutical product can enter the market, removal or inactivation of potential viral contamination has to be demonstrated. Given the complexity of biological solutions and the high standards on composition and purity of biopharmaceuticals, downstream processing is the bottleneck in many biotechnological production trains. Membrane-based filtration can be an economically attractive and efficient technology for virus separation. Viral clearance, for instance, of up to seven orders of magnitude has been reported for state of the art polymeric membranes under best conditions.This chapter summarizes the fundamentals of virus ultrafiltration, diafiltration, or purification with adsorptive membranes. In lieu of an impractical universally applicable protocol for virus filtration, application of these principles is demonstrated with two examples. The chapter provides detailed methods for production, concentration, purification, and removal of a rod-shaped baculovirus (Autographa californica M nucleopolyhedrovirus, about 40 × 300 nm in size, a potential vector for gene therapy, and an industrially important protein expression system) or a spherical parvovirus (minute virus of mice, 22-26 nm in size, a model virus for virus clearance validation studies). PMID:24297430

  15. Microtechnologies for membrane protein studies

    PubMed Central

    Suzuki, Hiroaki

    2008-01-01

    Despite the rapid and enormous progress in biotechnologies, the biochemical analysis of membrane proteins is still a difficult task. The presence of the large hydrophobic region buried in the lipid bilayer membrane (transmembrane domain) makes it difficult to analyze membrane proteins in standard assays developed for water-soluble proteins. To handle membrane proteins, the lipid bilayer membrane may be used as a platform to sustain their functionalities. Relatively slow progress in developing micro total analysis systems (μTAS) for membrane protein analysis directly reflects the difficulty of handling lipid membranes, which is a common problem in bulk measurement technologies. Nonetheless, researchers are continuing to develop efficient and sensitive analytical microsystems for the study of membrane proteins. Here, we review the latest developments, which enable detection of events caused by membrane proteins, such as ion channel current, membrane transport, and receptor/ligand interaction, by utilizing microfabricated structures. High-throughput and highly sensitive detection systems for membrane proteins are now becoming a realistic goal. Although most of these systems are still in the early stages of development, we believe this field will become one of the most important applications of μTAS for pharmaceutical and clinical screenings as well as for basic biochemical research. PMID:18335213

  16. Solid-state membrane module

    DOEpatents

    Gordon, John Howard; Taylor, Dale M.

    2011-06-07

    Solid-state membrane modules comprising at least one membrane unit, where the membrane unit has a dense mixed conducting oxide layer, and at least one conduit or manifold wherein the conduit or manifold comprises a dense layer and at least one of a porous layer and a slotted layer contiguous with the dense layer. The solid-state membrane modules may be used to carry out a variety of processes including the separating of any ionizable component from a feedstream wherein such ionizable component is capable of being transported through a dense mixed conducting oxide layer of the membrane units making up the membrane modules. For ease of construction, the membrane units may be planar.

  17. CHARMM-GUI Membrane Builder toward realistic biological membrane simulations.

    PubMed

    Wu, Emilia L; Cheng, Xi; Jo, Sunhwan; Rui, Huan; Song, Kevin C; Dávila-Contreras, Eder M; Qi, Yifei; Lee, Jumin; Monje-Galvan, Viviana; Venable, Richard M; Klauda, Jeffery B; Im, Wonpil

    2014-10-15

    CHARMM-GUI Membrane Builder, http://www.charmm-gui.org/input/membrane, is a web-based user interface designed to interactively build all-atom protein/membrane or membrane-only systems for molecular dynamics simulations through an automated optimized process. In this work, we describe the new features and major improvements in Membrane Builder that allow users to robustly build realistic biological membrane systems, including (1) addition of new lipid types, such as phosphoinositides, cardiolipin (CL), sphingolipids, bacterial lipids, and ergosterol, yielding more than 180 lipid types, (2) enhanced building procedure for lipid packing around protein, (3) reliable algorithm to detect lipid tail penetration to ring structures and protein surface, (4) distance-based algorithm for faster initial ion displacement, (5) CHARMM inputs for P21 image transformation, and (6) NAMD equilibration and production inputs. The robustness of these new features is illustrated by building and simulating a membrane model of the polar and septal regions of E. coli membrane, which contains five lipid types: CL lipids with two types of acyl chains and phosphatidylethanolamine lipids with three types of acyl chains. It is our hope that CHARMM-GUI Membrane Builder becomes a useful tool for simulation studies to better understand the structure and dynamics of proteins and lipids in realistic biological membrane environments. PMID:25130509

  18. Membranes, methods of making membranes, and methods of separating gases using membranes

    DOEpatents

    Ho, W. S. Winston

    2012-10-02

    Membranes, methods of making membranes, and methods of separating gases using membranes are provided. The membranes can include at least one hydrophilic polymer, at least one cross-linking agent, at least one base, and at least one amino compound. The methods of separating gases using membranes can include contacting a gas stream containing at least one of CO.sub.2, H.sub.2S, and HCl with one side of a nonporous and at least one of CO.sub.2, H.sub.2S, and HCl selectively permeable membrane such that at least one of CO.sub.2, H.sub.2S, and HCl is selectively transported through the membrane.

  19. Influences of Membrane Mimetic Environments on Membrane Protein Structures

    PubMed Central

    Zhou, Huan-Xiang; Cross, Timothy A.

    2013-01-01

    The number of membrane protein structures in the Protein Data Bank is becoming significant and growing. Here, the transmembrane domain structures of the helical membrane proteins are evaluated to assess the influences of the membrane mimetic environments. Toward this goal, many of the biophysical properties of membranes are discussed and contrasted with those of the membrane mimetics commonly used for structure determination. Although the mimetic environments can perturb the protein structures to an extent that potentially gives rise to misinterpretation of functional mechanisms, there are also many structures that have a native-like appearance. From this assessment, an initial set of guidelines is proposed for distinguishing native-like from nonnative-like membrane protein structures. With experimental techniques for validation and computational methods for refinement and quality assessment and enhancement, there are good prospects for achieving native-like structures for these very important proteins. PMID:23451886

  20. Chemical degradation mechanisms of membranes for alkaline membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Choe, Yoong-Kee; Henson, Neil J.; Kim, Yu Seung

    2015-12-01

    Chemical degradation mechanisms of membranes for alkaline membrane fuel cells have been investigated using density functional theory (DFT). We have elucidated that the aryl-ether moiety of membranes is one of the weakest site against attack of hydroxide ions. The results of DFT calculations for hydroxide initiated aryl-ether cleavage indicated that the aryl-ether cleavage occurred prior to degradation of cationic functional group. Such a weak nature of the aryl-ether group arises from the electron deficiency of the aryl group as well as the low bond dissociation energy. The DFT results suggests that removal of the aryl-ether group in the membrane should enhance the stability of membranes under alkaline conditions. In fact, an ether fee poly(phenylene) membrane exhibits excellent stability against the attack from hydroxide ions.

  1. Chemical degradation mechanisms of membranes for alkaline membrane fuel cells

    SciTech Connect

    Choe, Yoong-Kee; Henson, Neil J.; Kim, Yu Seung

    2015-12-31

    Chemical degradation mechanisms of membranes for alkaline membrane fuel cells have been investigated using density functional theory (DFT). We have elucidated that the aryl-ether moiety of membranes is one of the weakest site against attack of hydroxide ions. The results of DFT calculations for hydroxide initiated aryl-ether cleavage indicated that the aryl-ether cleavage occurred prior to degradation of cationic functional group. Such a weak nature of the aryl-ether group arises from the electron deficiency of the aryl group as well as the low bond dissociation energy. The DFT results suggests that removal of the aryl-ether group in the membrane should enhance the stability of membranes under alkaline conditions. In fact, an ether fee poly(phenylene) membrane exhibits excellent stability against the attack from hydroxide ions.

  2. Pervaporation from a dense membrane: roles of permeant-membrane interactions, Kelvin effect, and membrane swelling.

    PubMed

    Sharma, Ashutosh; Thampi, Sumesh P; Suggala, Satyanarayana V; Bhattacharya, Prashant K

    2004-05-25

    Dense polymeric membranes with extremely small pores in the form of free volume are used widely in the pervaporative separation of liquid mixtures. The membrane permeation of a component followed by its vaporization on the opposite face is governed by the solubility and downstream pressure. We measured the evaporative flux of pure methanol and 2-propanol using dense membranes with different free volumes and different affinities (wettabilities and solubilities) for the permeant. Interestingly, the evaporative flux for different membranes vanished substantially (10-75%) below the equilibrium vapor pressure in the bulk. The discrepancy was larger for a smaller pore size and for more wettable membranes (higher positive spreading coefficients). This observation, which cannot be explained by the existing (mostly solution-diffusion type) models ofpervaporation, suggests an important role for the membrane-permeant interactions in nanopores that can lower the equilibrium vapor pressure. The pore sizes, as estimated from the positron annihilation, ranged from 0.2 to 0.6 nm for the dry membranes. Solubilities of methanol in different composite membranes were estimated from the Flory-Huggins theory. The interaction parameter was obtained from the surface properties measured by the contact angle goniometry in conjunction with the acid-base theory of polar surface interactions. For the membranes examined, the increase in the "wet" pore volume due to membrane swelling correlates almost linearly with the solubility of methanol in these membranes. Indeed, the observations are found to be consistent with the lowering of the equilibrium vapor pressure on the basis of the Kelvin equation. Thus, a higher solubility or selectivity of a membrane also implies stronger permeant-membrane interactions and a greater retention of the permeant by the membrane, thus decreasing its evaporative flux. This observation has important implications for the interpretation of existing experiments and in

  3. Oxygen Transport Ceramic Membranes

    SciTech Connect

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-08-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In the previous research, the reference point of oxygen occupancy was determined and verified. In the current research, the oxygen occupancy was investigated at 1200 C as a function of oxygen activity and compared with that at 1000 C. The cause of bumps at about 200 C was also investigated by using different heating and cooling rates during TGA. The fracture toughness of LSFT and dual phase membranes at room temperature is an important mechanical property. Vicker's indentation method was used to evaluate this toughness. Through this technique, a K{sub Ic} (Mode-I Fracture Toughness) value is attained by means of semi-empirical correlations between the indentation load and the length of the cracks emanating from the corresponding Vickers indentation impression. In the present investigation, crack propagation behavior was extensively analyzed in order to understand the strengthening mechanisms involved in the non-transforming La based ceramic composites. Cracks were generated using Vicker's indenter and used to identify and evaluate the toughening mechanisms involved. Preliminary results of an electron microscopy study of the origin of the slow kinetics on reduction of ferrites have been obtained. The slow kinetics appear to be related to a non-equilibrium reduction pathway that initially results in the formation of iron particles. At long times, equilibrium can be reestablished with recovery of the perovskite phase. Modeling of the isotopic transients on operating membranes (LSCrF-2828 at 900 C) and a ''frozen'' isotope profile have been analyzed in conjunction with a 1-D model to reveal the gradient in oxygen diffusivity through the membrane under conditions of high chemical gradients.

  4. Proteins interacting with Membranes: Protein Sorting and Membrane Shaping

    NASA Astrophysics Data System (ADS)

    Callan-Jones, Andrew

    2015-03-01

    Membrane-bound transport in cells requires generating membrane curvature. In addition, transport is selective, in order to establish spatial gradients of membrane components in the cell. The mechanisms underlying cell membrane shaping by proteins and the influence of curvature on membrane composition are active areas of study in cell biophysics. In vitro approaches using Giant Unilamellar Vesicles (GUVs) are a useful tool to identify the physical mechanisms that drive sorting of membrane components and membrane shape change by proteins. I will present recent work on the curvature sensing and generation of IRSp53, a protein belonging to the BAR family, whose members, sharing a banana-shaped backbone, are involved in endocytosis. Pulling membrane tubes with 10-100 nm radii from GUVs containing encapsulated IRSp53 have, unexpectedly, revealed a non-monotonic dependence of the protein concentration on the tube as a function of curvature. Experiments also show that bound proteins alter the tube mechanics and that protein phase separation along the tube occurs at low tensions. I will present accompanying theoretical work that can explain these findings based on the competition between the protein's intrinsic curvature and the effective rigidity of a membrane-protein patch.

  5. Protein-Induced Membrane Curvature Alters Local Membrane Tension

    PubMed Central

    Rangamani, Padmini; Mandadap, Kranthi K.; Oster, George

    2014-01-01

    Adsorption of proteins onto membranes can alter the local membrane curvature. This phenomenon has been observed in biological processes such as endocytosis, tubulation, and vesiculation. However, it is not clear how the local surface properties of the membrane, such as membrane tension, change in response to protein adsorption. In this article, we show that the partial differential equations arising from classical elastic model of lipid membranes, which account for simultaneous changes in shape and membrane tension due to protein adsorption in a local region, cannot be solved for nonaxisymmetric geometries using straightforward numerical techniques; instead, a viscous-elastic formulation is necessary to fully describe the system. Therefore, we develop a viscous-elastic model for inhomogeneous membranes of the Helfrich type. Using the newly available viscous-elastic model, we find that the lipids flow to accommodate changes in membrane curvature during protein adsorption. We show that, at the end of protein adsorption process, the system sustains a residual local tension to balance the difference between the actual mean curvature and the imposed spontaneous curvature. We also show that this change in membrane tension can have a functional impact such as altered response to pulling forces in the presence of proteins. PMID:25099814

  6. Electrically Conductive Porous Membrane

    NASA Technical Reports Server (NTRS)

    Burke, Kenneth Alan (Inventor)

    2014-01-01

    The present invention relates to an electrically conductive membrane that can be configured to be used in fuel cell systems to act as a hydrophilic water separator internal to the fuel cell, or as a water separator used with water vapor fed electrolysis cells, or as a water separator used with water vapor fed electrolysis cells, or as a capillary structure in a thin head pipe evaporator, or as a hydrophobic gas diffusion layer covering the fuel cell electrode surface in a fuel cell.

  7. Supported liquid membranes

    SciTech Connect

    Danesi, P.R.

    1984-01-01

    The possibility of utilizing thin layers of organic solutions of solvent extraction reagents, immobilized on microporous inert supports interposed between two aqueous solutions, for selectively removing metal ions from a mixture represents an attractive alternative to liquid-liquid extraction. A detailed knowledge of the liquid-liquid extraction equilibria and mass transfer kinetics is required to understand and to describe quantitatively the rate laws which control the permeation of metal species through Supported Liquid Membranes (SLM) and to exploit them for separation processes. This paper attempts to understand the mechanism of transport through SLM.

  8. [Juvenile idiopathic epiretinal membrane].

    PubMed

    Kontopoulou, K; Krause, S; Fili, S; Hayvazov, S; Schilling, H; Kohlhaas, M

    2016-07-01

    Idiopathic epiretinal membrane (iERM) is very rare in adolescent patients. The pathogenesis remains unclear although the role of hyalocytes is of major importance. The clinical features in young patients are different from those in older patients. We describe a case of iERM in a 15-year-old girl who presented with metamorphopsia of the right eye. This case report presents the basis for the decision for surgical treatment as well as the clinical features at follow-up examination 9 months after surgery. PMID:26458892

  9. Oxygen Transport Ceramic Membranes

    SciTech Connect

    S. Bandopadhyay; N. Nagabhushana; X.-D Zhou; Q. Cai; J. Yang; W.B. Yelon; W.J. James; H.U. Anderson; Alan Jacobson; C.A. Mims

    2004-05-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped LSF. In this report, in situ neutron diffraction was used to characterize the chemical and structural properties of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} (here after as L2SF55T) specimen, which was subject to measurements of neutron diffraction from room temperature to 900 C. It was found that space group of R3c yielded a better refinement than a cubic structure of Pm3m. Oxygen occupancy was nearly 3 in the region from room temperature to 700 C, above which the occupancy decreased due to oxygen loss. Dense OTM bars provided by Praxair were loaded to fracture at varying stress rates. Studies were done at room temperature in air and at 1000 C in a specified environment to evaluate slow crack growth behavior. The X-Ray data and fracture mechanisms points to non-equilibrium decomposition of the LSFCO OTM membrane. The non-equilibrium conditions could probably be due to the nature of the applied stress field (stressing rates) and leads to transition in crystal structures and increased kinetics of decomposition. The formations of a Brownmillerite or Sr2Fe2O5 type structures, which are orthorhombic are attributed to the ordering of oxygen vacancies. The cubic to orthorhombic transitions leads to 2.6% increase in strains and thus residual stresses generated could influence the fracture behavior of the OTM membrane. Continued investigations on the thermodynamic properties (stability and phase-separation behavior) and total conductivity of prototype membrane materials were carried out. The data are needed together with the kinetic information to develop a complete model for the membrane transport. Previously characterization, stoichiometry and conductivity measurements for samples of La{sub 0.2}Sr{sub 0.8}Fe{sub 0.55}Ti{sub 0.45}O{sub 3-{delta}} were reported. In this report

  10. Molecularly Imprinted Membranes

    PubMed Central

    Trotta, Francesco; Biasizzo, Miriam; Caldera, Fabrizio

    2012-01-01

    Although the roots of molecularly imprinted polymers lie in the beginning of 1930s in the past century, they have had an exponential growth only 40–50 years later by the works of Wulff and especially by Mosbach. More recently, it was also proved that molecular imprinted membranes (i.e., polymer thin films) that show recognition properties at molecular level of the template molecule are used in their formation. Different procedures and potential application in separation processes and catalysis are reported. The influences of different parameters on the discrimination abilities are also discussed. PMID:24958291

  11. Gas separations using inorganic membranes

    SciTech Connect

    Egan, B.Z.; Singh, S.P.N.; Fain, D.E.; Roettger, G.E.; White, D.E.

    1992-04-01

    This report summarizes the results from a research and development program to develop, fabricate, and evaluate inorganic membranes for separating gases at high temperatures and pressures in hostile process environments encountered in fossil energy conversion processes such as coal gasification. The primary emphasis of the research was on the separation and recovery of hydrogen from synthesis gas. Major aspects of the program included assessment of the worldwide research and development activity related to gas separations using inorganic membranes, identification and selection of candidate membrane materials, fabrication and characterization of membranes using porous membrane technology developed at the Oak Ridge K-25 Site, and evaluation of the separations capability of the fabricated membranes in terms of permeabilities and fluxes of gases.

  12. An Arp2/3 nucleated F-actin shell fragments nuclear membranes at nuclear envelope breakdown in starfish oocytes.

    PubMed

    Mori, Masashi; Somogyi, Kálmán; Kondo, Hiroshi; Monnier, Nilah; Falk, Henning J; Machado, Pedro; Bathe, Mark; Nédélec, François; Lénárt, Péter

    2014-06-16

    Animal cells disassemble and reassemble their nuclear envelopes (NEs) upon each division. Nuclear envelope breakdown (NEBD) serves as a major regulatory mechanism by which mixing of cytoplasmic and nuclear compartments drives the complete reorganization of cellular architecture, committing the cell for division. Breakdown is initiated by phosphorylation-driven partial disassembly of the nuclear pore complexes (NPCs), increasing their permeability but leaving the overall NE structure intact. Subsequently, the NE is rapidly broken into membrane fragments, defining the transition from prophase to prometaphase and resulting in complete mixing of cyto- and nucleoplasm. However, the mechanism underlying this rapid NE fragmentation remains largely unknown. Here, we show that NE fragmentation during NEBD in starfish oocytes is driven by an Arp2/3 complex-nucleated F-actin "shell" that transiently polymerizes on the inner surface of the NE. Blocking the formation of this F-actin shell prevents membrane fragmentation and delays entry of large cytoplasmic molecules into the nucleus. We observe spike-like protrusions extending from the F-actin shell that appear to "pierce" the NE during the fragmentation process. Finally, we show that NE fragmentation is essential for successful reproduction, because blocking this process in meiosis leads to formation of aneuploid eggs. PMID:24909322

  13. Glass is a Viable Substrate for Precision Force Microscopy of Membrane Proteins

    PubMed Central

    Chada, Nagaraju; Sigdel, Krishna P.; Gari, Raghavendar Reddy Sanganna; Matin, Tina Rezaie; Randall, Linda L.; King, Gavin M.

    2015-01-01

    Though ubiquitous in optical microscopy, glass has long been overlooked as a specimen supporting surface for high resolution atomic force microscopy (AFM) investigations due to its roughness. Using bacteriorhodopsin from Halobacterium salinarum and the translocon SecYEG from Escherichia coli, we demonstrate that faithful images of 2D crystalline and non-crystalline membrane proteins in lipid bilayers can be obtained on microscope cover glass following a straight-forward cleaning procedure. Direct comparison between AFM data obtained on glass and on mica substrates show no major differences in image fidelity. Repeated association of the ATPase SecA with the cytoplasmic protrusion of SecYEG demonstrates that the translocon remains competent for binding after tens of minutes of continuous AFM imaging. This opens the door for precision long-timescale investigations of the active translocase in near-native conditions and, more generally, for integration of high resolution biological AFM with many powerful optical techniques that require non-birefringent substrates. PMID:26228793

  14. When plasmonics meets membrane technology

    NASA Astrophysics Data System (ADS)

    Politano, A.; Cupolillo, A.; Di Profio, G.; Arafat, H. A.; Chiarello, G.; Curcio, E.

    2016-09-01

    In this review, we present the applications of thermoplasmonics in membrane processes. We discuss the influence of the heat capacity of the solvent, the amount of plasmonic nanoparticles in the membrane, the intensity of the light source and the transmembrane flow rate on the increase of permeability. Remarkably, thermoplasmonic effects do not involve any noticeable loss of membrane rejection. Herein, we consider application feasibilities, including application fields, requirements of feed, alternatives of light sources, promising thermoplasmonic nanoparticles and scaling up issues.

  15. When plasmonics meets membrane technology.

    PubMed

    Politano, A; Cupolillo, A; Di Profio, G; Arafat, H A; Chiarello, G; Curcio, E

    2016-09-14

    In this review, we present the applications of thermoplasmonics in membrane processes. We discuss the influence of the heat capacity of the solvent, the amount of plasmonic nanoparticles in the membrane, the intensity of the light source and the transmembrane flow rate on the increase of permeability. Remarkably, thermoplasmonic effects do not involve any noticeable loss of membrane rejection. Herein, we consider application feasibilities, including application fields, requirements of feed, alternatives of light sources, promising thermoplasmonic nanoparticles and scaling up issues. PMID:27414212

  16. Supported liquid membrane electrochemical separators

    SciTech Connect

    Pemsler, J. Paul; Dempsey, Michael D.

    1986-01-01

    Supported liquid membrane separators improve the flexibility, efficiency and service life of electrochemical cells for a variety of applications. In the field of electrochemical storage, an alkaline secondary battery with improved service life is described in which a supported liquid membrane is interposed between the positive and negative electrodes. The supported liquid membranes of this invention can be used in energy production and storage systems, electrosynthesis systems, and in systems for the electrowinning and electrorefining of metals.

  17. Oxygen Transport Ceramic Membranes

    SciTech Connect

    S. Bandopadhyay; T. Nithyanantham; X.-D Zhou; Y-W. Sin; H.U. Anderson; Alan Jacobson; C.A. Mims

    2005-05-01

    The present quarterly report describes some of the investigations on the structural properties of dense OTM bars provided by Praxair and studies on newer composition of Ti doped Ti-substituted perovskites, La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Ti{sub x}O{sub 3}, with 0 {le} x {le} 0.20, were investigated by neutron diffraction, magnetization, electric resistivity, and magnetoresistance (MR) measurements. All samples show a rhombohedral structure (space group R3C) from 10 K to room temperature. At room temperature, the cell parameters a, c and the unit cell volume increase with increasing Ti content. However, at 10 K, the cell parameter a has a maximum value for x = 0.10, and decreases for x > 0.10, while the unit cell volume remains nearly constant for x > 0.10. The average (Mn,Ti)-O bond length increases up to x = 0.15, and the (Mn,Ti)-O-(Mn,Ti) bond angle decreases with increasing Ti content to its minimum value at x = 0.15 at room temperature. Below the Curie temperature TC, the resistance exhibits metallic behavior for the x {le} 0.05 samples. A metal (semiconductor) to insulator transition is observed for the x {ge} 0.10 samples. A peak in resistivity appears below TC for all samples, and shifts to a lower temperature as x increases. The substitution of Mn by Ti decreases the 2p-3d hybridization between O and Mn ions, reduces the bandwidth W, and increases the electron-phonon coupling. Therefore, the TC shifts to a lower temperature and the resistivity increases with increasing Ti content. A field-induced shift of the resistivity maximum occurs at x {le} 0.10 compounds. The maximum MR effect is about 70% for La{sub 0.7}Sr{sub 0.3}Mn{sub 0.8}Ti{sub 0.2}O{sub 3}. The separation of TC and the resistivity maximum temperature T{sub {rho},max} enhances the MR effect in these compounds due to the weak coupling between the magnetic ordering and the resistivity as compared with La{sub 0.7}Sr{sub 0.3}MnO{sub 3}. The bulk densities of the membranes were determined using the

  18. Catalytic Membrane Sensors

    SciTech Connect

    Boyle, T.J.; Brinker, C.J.; Gardner, T.J.; Hughes, R.C.; Sault, A.G.

    1998-12-01

    The proposed "catalytic membrane sensor" (CMS) was developed to generate a device which would selectively identify a specific reagent in a complex mixture of gases. This was to be accomplished by modifying an existing Hz sensor with a series of thin films. Through selectively sieving the desired component from a complex mixture and identifying it by decomposing it into Hz (and other by-products), a Hz sensor could then be used to detect the presence of the select component. The proposed "sandwich-type" modifications involved the deposition of a catalyst layered between two size selective sol-gel layers on a Pd/Ni resistive Hz sensor. The role of the catalyst was to convert organic materials to Hz and organic by-products. The role of the membraneo was to impart both chemical specificity by molecukir sieving of the analyte and converted product streams, as well as controlling access to the underlying Pd/Ni sensor. Ultimately, an array of these CMS elements encompassing different catalysts and membranes were to be developed which would enable improved selectivity and specificity from a compiex mixture of organic gases via pattern recognition methodologies. We have successfully generated a CMS device by a series of spin-coat deposited methods; however, it was determined that the high temperature required to activate the catalyst, destroys the sensor.

  19. Impact on floating membranes

    NASA Astrophysics Data System (ADS)

    Vandenberghe, Nicolas; Duchemin, Laurent

    2016-05-01

    When impacted by a rigid body, a thin elastic membrane with negligible bending rigidity floating on a liquid pool deforms. Two axisymmetric waves radiating from the impact point propagate. First, a longitudinal wave front, associated with in-plane deformation of the membrane and traveling at constant speed, separates an outward stress-free domain from a stretched domain. Then, in the stretched domain a dispersive transverse wave travels at a speed that depends on the local stretching rate. The dynamics is found to be self-similar in time. Using this property, we show that the wave dynamics is similar to the capillary waves that propagate at a liquid-gas interface but with a surface tension coefficient that depends on impact speed. During wave propagation, we observe the development of a buckling instability that gives rise to radial wrinkles. We address the dynamics of this fluid-body system, including the rapid deceleration of an impactor of finite mass, an issue that may have applications in the domain of absorption of impact energy.

  20. A Molecular Look at Membranes.

    PubMed

    Berkowitz, Max

    2016-01-01

    Due to the recent advances in computer hardware and software, we can now use molecular dynamics and Monte Carlo computer simulation techniques to study systems with large conformational spaces. It is demonstrated here that computer simulations allow us to get a glimpse at the structural and dynamical properties of membranes and also at the interaction of membranes with other molecules. Specifically two examples are considered: (1) structural properties of lipid rafts in model membranes and (2) interaction of model membranes with an antimicrobial peptide, melittin. PMID:26781828