Microarray and network-based identification of functional modules and pathways of active tuberculosis.

PubMed

Bian, Zhong-Rui; Yin, Juan; Sun, Wen; Lin, Dian-Jie

2017-04-01

Diagnose of active tuberculosis (TB) is challenging and treatment response is also difficult to efficiently monitor. The aim of this study was to use an integrated analysis of microarray and network-based method to the samples from publically available datasets to obtain a diagnostic module set and pathways in active TB. Towards this goal, background protein-protein interactions (PPI) network was generated based on global PPI information and gene expression data, following by identification of differential expression network (DEN) from the background PPI network. Then, ego genes were extracted according to the degree features in DEN. Next, module collection was conducted by ego gene expansion based on EgoNet algorithm. After that, differential expression of modules between active TB and controls was evaluated using random permutation test. Finally, biological significance of differential modules was detected by pathways enrichment analysis based on Reactome database, and Fisher's exact test was implemented to extract differential pathways for active TB. Totally, 47 ego genes and 47 candidate modules were identified from the DEN. By setting the cutoff-criteria of gene size >5 and classification accuracy ≥0.9, 7 ego modules (Module 4, Module 7, Module 9, Module 19, Module 25, Module 38 and Module 43) were extracted, and all of them had the statistical significance between active TB and controls. Then, Fisher's exact test was conducted to capture differential pathways for active TB. Interestingly, genes in Module 4, Module 25, Module 38, and Module 43 were enriched in the same pathway, formation of a pool of free 40S subunits. Significant pathway for Module 7 and Module 9 was eukaryotic translation termination, and for Module 19 was nonsense mediated decay enhanced by the exon junction complex (EJC). Accordingly, differential modules and pathways might be potential biomarkers for treating active TB, and provide valuable clues for better understanding of molecular mechanism of active TB. Copyright © 2017 Elsevier Ltd. All rights reserved.

Quantifying cadherin mechanotransduction machinery assembly/disassembly dynamics using fluorescence covariance analysis.

PubMed

Vedula, Pavan; Cruz, Lissette A; Gutierrez, Natasha; Davis, Justin; Ayee, Brian; Abramczyk, Rachel; Rodriguez, Alexis J

2016-06-30

Quantifying multi-molecular complex assembly in specific cytoplasmic compartments is crucial to understand how cells use assembly/disassembly of these complexes to control function. Currently, biophysical methods like Fluorescence Resonance Energy Transfer and Fluorescence Correlation Spectroscopy provide quantitative measurements of direct protein-protein interactions, while traditional biochemical approaches such as sub-cellular fractionation and immunoprecipitation remain the main approaches used to study multi-protein complex assembly/disassembly dynamics. In this article, we validate and quantify multi-protein adherens junction complex assembly in situ using light microscopy and Fluorescence Covariance Analysis. Utilizing specific fluorescently-labeled protein pairs, we quantified various stages of adherens junction complex assembly, the multiprotein complex regulating epithelial tissue structure and function following de novo cell-cell contact. We demonstrate: minimal cadherin-catenin complex assembly in the perinuclear cytoplasm and subsequent localization to the cell-cell contact zone, assembly of adherens junction complexes, acto-myosin tension-mediated anchoring, and adherens junction maturation following de novo cell-cell contact. Finally applying Fluorescence Covariance Analysis in live cells expressing fluorescently tagged adherens junction complex proteins, we also quantified adherens junction complex assembly dynamics during epithelial monolayer formation.

Mine or Theirs, Where Do Users Go? A Comparison of E-Journal Usage at the OhioLINK Electronic Journal Center Platform versus the Elsevier ScienceDirect Platform

ERIC Educational Resources Information Center

Swanson, Juleah

2015-01-01

This research provides librarians with a model for assessing and predicting which platforms patrons will use to access the same content, specifically comparing usage at the Ohio Library and Information Network (OhioLINK) Electronic Journal Center (EJC) and at Elsevier's ScienceDirect from 2007 to 2013. Findings show that in the earlier years, the…

Role Of Cathepsin C During Breast Cancer Metastasis

DTIC Science & Technology

2010-09-01

tumor histopathology is regulated by CSTC; however, in cathepsin C (Ctsc)-deficient mice, there is a significant reduction in the number of...hyaluronan. Glycobiology 14(11): 1108. 2. Ruffell B, Johnson P. (2006) Hyaluronan induces apoptosis through CD44 in activated lymphoma cells. EJC...tumors and lymphomas [16,17]. The ability of immune-deficient mice to reject and/or inhibit the growth of many, but not all cell lines is also impaired

Breaking into the epithelial apical–junctional complex — news from pathogen hackers

PubMed Central

Vogelmann, Roger; Amieva, Manuel R; Falkow, Stanley; Nelson, W James

2012-01-01

The epithelial apical–junctional complex is a key regulator of cellular functions. In addition, it is an important target for microbial pathogens that manipulate the cell to survive, proliferate and sometimes persist within a host. Out of a myriad of potential molecular targets, some bacterial and viral pathogens have selected a subset of protein targets at the apical–junctional complex of epithelial cells. Studying how microbes use these targets also teaches us about the inherent physiological properties of host molecules in the context of normal junctional structure and function. Thus, we have learned that three recently uncovered components of the apical–junctional complex of the Ig superfamily — junctional adhesion molecule, Nectin and the coxsackievirus and adenovirus receptor — are important regulators of junction structure and function and represent critical targets of microbial virulence gene products. PMID:15037310

Breaking into the epithelial apical-junctional complex--news from pathogen hackers.

PubMed

Vogelmann, Roger; Amieva, Manuel R; Falkow, Stanley; Nelson, W James

2004-02-01

The epithelial apical-junctional complex is a key regulator of cellular functions. In addition, it is an important target for microbial pathogens that manipulate the cell to survive, proliferate and sometimes persist within a host. Out of a myriad of potential molecular targets, some bacterial and viral pathogens have selected a subset of protein targets at the apical-junctional complex of epithelial cells. Studying how microbes use these targets also teaches us about the inherent physiological properties of host molecules in the context of normal junctional structure and function. Thus, we have learned that three recently uncovered components of the apical-junctional complex of the Ig superfamily--junctional adhesion molecule, Nectin and the coxsackievirus and adenovirus receptor--are important regulators of junction structure and function and represent critical targets of microbial virulence gene products.

Synergistic effect of ATP for RuvA-RuvB-Holliday junction DNA complex formation.

PubMed

Iwasa, Takuma; Han, Yong-Woon; Hiramatsu, Ryo; Yokota, Hiroaki; Nakao, Kimiko; Yokokawa, Ryuji; Ono, Teruo; Harada, Yoshie

2015-12-14

The Escherichia coli RuvB hexameric ring motor proteins, together with RuvAs, promote branch migration of Holliday junction DNA. Zero mode waveguides (ZMWs) constitute of nanosized holes and enable the visualization of a single fluorescent molecule under micromolar order of the molecules, which is applicable to characterize the formation of RuvA-RuvB-Holliday junction DNA complex. In this study, we used ZMWs and counted the number of RuvBs binding to RuvA-Holliday junction DNA complex. Our data demonstrated that different nucleotide analogs increased the amount of Cy5-RuvBs binding to RuvA-Holliday junction DNA complex in the following order: no nucleotide, ADP, ATPγS, and mixture of ADP and ATPγS. These results suggest that not only ATP binding to RuvB but also ATP hydrolysis by RuvB facilitates a stable RuvA-RuvB-Holliday junction DNA complex formation.

Distributed, Collaborative Human-Robotic Networks for Outdoor Experiments in Search, Identify and Track

DTIC Science & Technology

2011-01-11

and its variance σ2Ûi are determined. Ûi = ûi + Pu,EN (PEN )−1 [( Ejc Njc ) − ( êi n̂i )] (15) σ2 Ûi = Pui − P u,EN i ( PENi )−1 PEN,ui (16) where...screen; the operator can click a robot’s camera view to select it as the Focus Robot. The Focus Robot’s camera stream is enlarged and displayed in the

Dynamics between actin and the VE-cadherin/catenin complex

PubMed Central

Abu Taha, Abdallah; Schnittler, Hans-J

2014-01-01

Endothelial adherens junctions are critical for physiological and pathological processes such as differentiation, maintenance of entire monolayer integrity, and the remodeling. The endothelial-specific VE-cadherin/catenin complex provides the backbone of adherens junctions and acts in close interaction with actin filaments and actin/myosin-mediated contractility to fulfill the junction demands. The functional connection between the cadherin/catenin complex and actin filaments might be either directly through α-catenins, or indirectly e.g., via linker proteins such as vinculin, p120ctn, α-actinin, or EPLIN. However, both junction integrity and dynamic remodeling have to be contemporarily coordinated. The actin-related protein complex ARP2/3 and its activating molecules, such as N-WASP and WAVE, have been shown to regulate the lammellipodia-mediated formation of cell junctions in both epithelium and endothelium. Recent reports now demonstrate a novel aspect of the ARP2/3 complex and the nucleating-promoting factors in the maintenance of endothelial barrier function and junction remodeling of established endothelial cell junctions. Those mechanisms open novel possibilities; not only in fulfilling physiological demands but obtained information may be of critical importance in pathologies such as wound healing, angiogenesis, inflammation, and cell diapedesis. PMID:24621569

The complex between a four-way DNA junction and T7 endonuclease I

PubMed Central

Déclais, Anne-Cécile; Fogg, Jonathan M.; Freeman, Alasdair D.J.; Coste, Franck; Hadden, Jonathan M.; Phillips, Simon E.V.; Lilley, David M.J.

2003-01-01

The junction-resolving enzyme endonuclease I is selective for the structure of the DNA four-way (Holliday) junction. The enzyme binds to a four-way junction in two possible orientations, with a 4:1 ratio, opening the DNA structure at the centre and changing the global structure into a 90° cross of approximately coaxial helices. The nuclease cleaves the continuous strands of the junction in each orientation. Binding leads to pronounced regions of protection of the DNA against hydroxyl radical attack. Using all this information together with the known structure of the enzyme and the structure of the BglI–DNA complex, we have constructed a model of the complex of endonuclease I and a DNA junction. This shows how the enzyme is selective for the structure of a four-way junction, such that both continuous strands can be accommodated into the two active sites so that a productive resolution event is possible. PMID:12628932

Synaptopodin couples epithelial contractility to α-actinin-4–dependent junction maturation

PubMed Central

Kannan, Nivetha

2015-01-01

The epithelial junction experiences mechanical force exerted by endogenous actomyosin activities and from interactions with neighboring cells. We hypothesize that tension generated at cell–cell adhesive contacts contributes to the maturation and assembly of the junctional complex. To test our hypothesis, we used a hydraulic apparatus that can apply mechanical force to intercellular junction in a confluent monolayer of cells. We found that mechanical force induces α-actinin-4 and actin accumulation at the cell junction in a time- and tension-dependent manner during junction development. Intercellular tension also induces α-actinin-4–dependent recruitment of vinculin to the cell junction. In addition, we have identified a tension-sensitive upstream regulator of α-actinin-4 as synaptopodin. Synaptopodin forms a complex containing α-actinin-4 and β-catenin and interacts with myosin II, indicating that it can physically link adhesion molecules to the cellular contractile apparatus. Synaptopodin depletion prevents junctional accumulation of α-actinin-4, vinculin, and actin. Knockdown of synaptopodin and α-actinin-4 decreases the strength of cell–cell adhesion, reduces the monolayer permeability barrier, and compromises cellular contractility. Our findings underscore the complexity of junction development and implicate a control process via tension-induced sequential incorporation of junctional components. PMID:26504173

Density functional theory study on Herzberg-Teller contribution in Raman scattering from 4-aminothiophenol-metal complex and metal-4-aminothiophenol-metal junction

NASA Astrophysics Data System (ADS)

Liu, Shasha; Zhao, Xiuming; Li, Yuanzuo; Zhao, Xiaohong; Chen, Maodu

2009-06-01

Density functional theory (DFT) and time-dependent DFT calculations have been performed to investigate the Raman scattering spectra of metal-molecule complex and metal-molecule-metal junction architectures interconnected with 4-aminothiophenol (PATP) molecule. The simulated profiles of normal Raman scattering (NRS) spectra for the two complexes (Ag2-PATP and PATP-Au2) and the two junctions (Ag2-PATP-Au2 and Au2-PATP-Ag2) are similar to each other, but exhibit obviously different Raman intensities. Due to the lager static polarizabilities of the two junctions, which directly influence the ground state chemical enhancement in NRS spectra, the calculated normal Raman intensities of them are stronger than those of two complexes by the factor of 102. We calculate preresonance Raman scattering (RRS) spectra with incident light at 1064 nm, which is much lower than the S1 electronic transition energy of complexes and junctions. Ag2-PATP-Au2 and Au2-PATP-Ag2 junctions yield higher Raman intensities than those of Ag2-PATP and PATP-Au2 complexes, especially for b2 modes. This effect is mainly attributed to charge transfer (CT) between the metal gap and the PAPT molecule which results in the occurrence of CT resonance enhancement. The calculated pre-RRS spectra strongly depend on the electronic transition state produced by new structures. With excitation at 514.5 nm, the calculated pre-RRS spectra of two complexes and two junctions are stronger than those of with excitation at 1064 nm. A charge difference densities methodology has been used to visually describe chemical enhancement mechanism of RRS spectrum. This methodology aims at visualizing intermolecular CT which provides direct evidence of the Herzberg-Teller mechanism.

The heart of the matter: Outcome reporting bias and registration status in cardio-thoracic surgery.

PubMed

Wiebe, Jordan; Detten, Grant; Scheckel, Caleb; Gearhart, David; Wheeler, Denna; Sanders, Donald; Vassar, Matt

2017-01-15

Our objective is to compare registered outcomes to published reports; to evaluate for discrepancies favoring statistically significant outcomes; to examine funding source and likelihood of outcome reporting bias; and to evaluate for any temporal trends in outcome reporting bias. PubMed was searched for randomized controlled trials published between 2008 and 2015 from 4 high impact cardio-thoracic journals: European Journal of Cardio-thoracic Surgery (EJCS), The Journal of Cardiothoracic Surgery (JCS), The Journal of Thoracic and Cardiovascular Surgery (JTCS), and Annals of Cardiothoracic Surgery (ACS). Data was collected using a standardized extraction form. We reviewed 287 articles, of which 214 (74.6%) did not meet registration criteria. Of those 214, 94 (43.9%) were published in the EJCS, 34 (15.9%) in JCS, 86 (40.2%) in JTCS, and 0 (0%) in the ACS. Of the remaining 73 articles, 34 (46.6%) had a discrepancy between the primary outcome registered and the published outcome, and 11 of the 34 reported p-values favoring the change. We also found that 12 of the 73 registrations had updated primary outcomes from the initial report to the final report. The timing of registration was an incidental finding showing 14 (19.1%) articles retrospectively registered, 29 (39.7%) registered during patient enrollment, and 30 (41.1%) registered prospectively. The results indicated that selective outcome reporting is prevalent in cardio-thoracic surgery journals. The more concerning issue, however, is the lack of registration or provision of registration number for randomized controlled trials within these journals. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

An EMMPRIN-γ-catenin-Nm23 complex drives ATP production and actomyosin contractility at endothelial junctions.

PubMed

Moreno, Vanessa; Gonzalo, Pilar; Gómez-Escudero, Jesús; Pollán, Ángela; Acín-Pérez, Rebeca; Breckenridge, Mark; Yáñez-Mó, María; Barreiro, Olga; Orsenigo, Fabrizio; Kadomatsu, Kenji; Chen, Christopher S; Enríquez, José A; Dejana, Elisabetta; Sánchez-Madrid, Francisco; Arroyo, Alicia G

2014-09-01

Cell-cell adhesions are important sites through which cells experience and resist forces. In endothelial cells, these forces regulate junction dynamics and determine endothelial barrier strength. We identify the Ig superfamily member EMMPRIN (also known as basigin) as a coordinator of forces at endothelial junctions. EMMPRIN localization at junctions correlates with endothelial junction strength in different mouse vascular beds. Accordingly, EMMPRIN-deficient mice show altered junctions and increased junction permeability. Lack of EMMPRIN alters the localization and function of VE-cadherin (also known as cadherin-5) by decreasing both actomyosin contractility and tugging forces at endothelial cell junctions. EMMPRIN ensures proper actomyosin-driven maturation of competent endothelial junctions by forming a molecular complex with γ-catenin (also known as junction plakoglobin) and Nm23 (also known as NME1), a nucleoside diphosphate kinase, thereby locally providing ATP to fuel the actomyosin machinery. These results provide a novel mechanism for the regulation of actomyosin contractility at endothelial junctions and might have broader implications in biological contexts such as angiogenesis, collective migration and tissue morphogenesis by coupling compartmentalized energy production to junction assembly. © 2014. Published by The Company of Biologists Ltd.

An EMMPRIN–γ-catenin–Nm23 complex drives ATP production and actomyosin contractility at endothelial junctions

PubMed Central

Moreno, Vanessa; Gonzalo, Pilar; Gómez-Escudero, Jesús; Pollán, Ángela; Acín-Pérez, Rebeca; Breckenridge, Mark; Yáñez-Mó, María; Barreiro, Olga; Orsenigo, Fabrizio; Kadomatsu, Kenji; Chen, Christopher S.; Enríquez, José A.; Dejana, Elisabetta; Sánchez-Madrid, Francisco; Arroyo, Alicia G.

2014-01-01

ABSTRACT Cell–cell adhesions are important sites through which cells experience and resist forces. In endothelial cells, these forces regulate junction dynamics and determine endothelial barrier strength. We identify the Ig superfamily member EMMPRIN (also known as basigin) as a coordinator of forces at endothelial junctions. EMMPRIN localization at junctions correlates with endothelial junction strength in different mouse vascular beds. Accordingly, EMMPRIN-deficient mice show altered junctions and increased junction permeability. Lack of EMMPRIN alters the localization and function of VE-cadherin (also known as cadherin-5) by decreasing both actomyosin contractility and tugging forces at endothelial cell junctions. EMMPRIN ensures proper actomyosin-driven maturation of competent endothelial junctions by forming a molecular complex with γ-catenin (also known as junction plakoglobin) and Nm23 (also known as NME1), a nucleoside diphosphate kinase, thereby locally providing ATP to fuel the actomyosin machinery. These results provide a novel mechanism for the regulation of actomyosin contractility at endothelial junctions and might have broader implications in biological contexts such as angiogenesis, collective migration and tissue morphogenesis by coupling compartmentalized energy production to junction assembly. PMID:24994937

Endoplasmic reticulum-plasma membrane junctions: structure, function and dynamics.

PubMed

Okeke, Emmanuel; Dingsdale, Hayley; Parker, Tony; Voronina, Svetlana; Tepikin, Alexei V

2016-06-01

Endoplasmic reticulum (ER)-plasma membrane (PM) junctions are contact sites between the ER and the PM; the distance between the two organelles in the junctions is below 40 nm and the membranes are connected by protein tethers. A number of molecular tools and technical approaches have been recently developed to visualise, modify and characterise properties of ER-PM junctions. The junctions serve as the platforms for lipid exchange between the organelles and for cell signalling, notably Ca(2+) and cAMP signalling. Vice versa, signalling events regulate the development and properties of the junctions. Two Ca(2+) -dependent mechanisms of de novo formation of ER-PM junctions have been recently described and characterised. The junction-forming proteins and lipids are currently the focus of vigorous investigation. Junctions can be relatively short-lived and simple structures, forming and dissolving on the time scale of a few minutes. However, complex, sophisticated and multifunctional ER-PM junctions, capable of attracting numerous protein residents and other cellular organelles, have been described in some cell types. The road from simplicity to complexity, i.e. the transformation from simple 'nascent' ER-PM junctions to advanced stable multiorganellar complexes, is likely to become an attractive research avenue for current and future junctologists. Another area of considerable research interest is the downstream cellular processes that can be activated by specific local signalling events in the ER-PM junctions. Studies of the cell physiology and indeed pathophysiology of ER-PM junctions have already produced some surprising discoveries, likely to expand with advances in our understanding of these remarkable organellar contact sites. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

Epithelial junction formation requires confinement of Cdc42 activity by a novel SH3BP1 complex

PubMed Central

Elbediwy, Ahmed; Zihni, Ceniz; Terry, Stephen J.; Clark, Peter

2012-01-01

Epithelial cell–cell adhesion and morphogenesis require dynamic control of actin-driven membrane remodeling. The Rho guanosine triphosphatase (GTPase) Cdc42 regulates sequential molecular processes during cell–cell junction formation; hence, mechanisms must exist that inactivate Cdc42 in a temporally and spatially controlled manner. In this paper, we identify SH3BP1, a GTPase-activating protein for Cdc42 and Rac, as a regulator of junction assembly and epithelial morphogenesis using a functional small interfering ribonucleic acid screen. Depletion of SH3BP1 resulted in loss of spatial control of Cdc42 activity, stalled membrane remodeling, and enhanced growth of filopodia. SH3BP1 formed a complex with JACOP/paracingulin, a junctional adaptor, and CD2AP, a scaffolding protein; both were required for normal Cdc42 signaling and junction formation. The filamentous actin–capping protein CapZ also associated with the SH3BP1 complex and was required for control of actin remodeling. Epithelial junction formation and morphogenesis thus require a dual activity complex, containing SH3BP1 and CapZ, that is recruited to sites of active membrane remodeling to guide Cdc42 signaling and cytoskeletal dynamics. PMID:22891260

Selective binding of meiosis-specific yeast Hop1 protein to the holliday junctions distorts the DNA structure and its implications for junction migration and resolution.

PubMed

Tripathi, Pankaj; Anuradha, S; Ghosal, Gargi; Muniyappa, K

2006-12-08

Saccharomyces cerevisiae HOP1, which encodes a component of synaptonemal complex (SC), plays an important role in both gene conversion and crossing over between homologs, as well as enforces meiotic recombination checkpoint control over the progression of recombination intermediates. In hop1Delta mutants, meiosis-specific double-strand breaks (DSBs) are reduced to 10% of the wild-type level, and at aberrantly late times, these DSBs are processed into inter-sister recombination intermediates. However, the underlying mechanism by which Hop1 protein regulates these nuclear events remains obscure. Here we show that Hop1 protein interacts selectively with the Holliday junction, changes its global conformation and blocks the dissolution of the junction by a RecQ helicase. The Holliday junction-Hop1 protein complexes are significantly more stable at higher ionic strengths and molar excess of unlabeled competitor DNA than complexes containing other recombination intermediates. Structural analysis of the Holliday junction using 2-aminopurine fluorescence emission, DNase I footprinting and KMnO4 probing provide compelling evidence that Hop1 protein binding induces significant distortion at the center of the Holliday junction. We propose that Hop1 protein might coordinate the physical monitoring of meiotic recombination intermediates with the process of branch migration of Holliday junction.

Neogenin recruitment of the WAVE regulatory complex maintains adherens junction stability and tension

PubMed Central

Lee, Natalie K.; Fok, Ka Wai; White, Amanda; Wilson, Nicole H.; O'Leary, Conor J.; Cox, Hayley L.; Michael, Magdalene; Yap, Alpha S.; Cooper, Helen M.

2016-01-01

To maintain tissue integrity during epithelial morphogenesis, adherens junctions (AJs) must resist the mechanical stresses exerted by dynamic tissue movements. Junctional stability is dependent on actomyosin contractility within the actin ring. Here we describe a novel function for the axon guidance receptor, Neogenin, as a key component of the actin nucleation machinery governing junctional stability. Loss of Neogenin perturbs AJs and attenuates junctional tension. Neogenin promotes actin nucleation at AJs by recruiting the Wave regulatory complex (WRC) and Arp2/3. A direct interaction between the Neogenin WIRS domain and the WRC is crucial for the spatially restricted recruitment of the WRC to the junction. Thus, we provide the first example of a functional WIRS–WRC interaction in epithelia. We further show that Neogenin regulates cadherin recycling at the AJ. In summary, we identify Neogenin as a pivotal component of the AJ, where it influences both cadherin dynamics and junctional tension. PMID:27029596

Nutrient Intakes and Work Performance of Soldiers during Seven Days of Exercise at 7,200 Feet Ready-to-Eat Ration

DTIC Science & Technology

1986-09-19

100.000 *4 • D " ",4.. .4.’-’ FrteiuEncy of M1aE Fouds Consumed CLASS=khJlTS FCOOD NAM~E FOOD FREQUENCY CUM? FaL1 £EjcENlI CUM PER~CENT APPLESAUCE ...4 1/2 3/4 all JELLY 1/4 1/2 3/4 all PEANUT BUTTER 1/4 1/2 3/4 all FRUIT APPLESAUCE 1/4 1/2 3/4 all MIXED FRUITS 1/4 1/2 3/4 all PEACHES 1/4 1/2 3/4

Conserved tetramer junction in the kinetochore Ndc80 complex

PubMed Central

Valverde, Roberto; Ingram, Jessica; Harrison, Stephen C.

2016-01-01

Summary The heterotetrameric Ndc80 complex establishes connectivity along the principal longitudinal axis of a kinetochore. Its two heterodimeric subcomplexes, each with a globular end and a coiled-coil shaft, connect end-to-end to create a ∼600 Å long rod spanning the gap from centromere-proximal structures to spindle microtubules. Neither subcomplex has a known function on its own, but the heterotetrameric organization and the characteristics of the junction are conserved from yeast to man. We have determined crystal structures of two shortened (“dwarf”) Ndc80 complexes that contain the full tetramer junction and both globular ends. The junction connects two α-helical coiled coils through regions of four-chain and three-chain overlap. The complexity of its structure depends on interactions among conserved amino-acid residues, suggesting a binding site for additional cellular factor(s) not yet identified. PMID:27851957

Modulation of Intestinal Paracellular Transport by Bacterial Pathogens.

PubMed

Roxas, Jennifer Lising; Viswanathan, V K

2018-03-25

The passive and regulated movement of ions, solutes, and water via spaces between cells of the epithelial monolayer plays a critical role in the normal intestinal functioning. This paracellular pathway displays a high level of structural and functional specialization, with the membrane-spanning complexes of the tight junctions, adherens junctions, and desmosomes ensuring its integrity. Tight junction proteins, like occludin, tricellulin, and the claudin family isoforms, play prominent roles as barriers to unrestricted paracellular transport. The past decade has witnessed major advances in our understanding of the architecture and function of epithelial tight junctions. While it has been long appreciated that microbes, notably bacterial and viral pathogens, target and disrupt junctional complexes and alter paracellular permeability, the precise mechanisms remain to be defined. Notably, renewed efforts will be required to interpret the available data on pathogen-mediated barrier disruption in the context of the most recent findings on tight junction structure and function. While much of the focus has been on pathogen-induced dysregulation of junctional complexes, commensal microbiota and their products may influence paracellular permeability and contribute to the normal physiology of the gut. Finally, microbes and their products have become important tools in exploring host systems, including the junctional properties of epithelial cells. © 2018 American Physiological Society. Compr Physiol 8:823-842, 2018. Copyright © 2018 American Physiological Society. All rights reserved.

Signaling from the Podocyte Intercellular Junction to the Actin Cytoskeleton

PubMed Central

George, Britta; Holzman, Lawrence B.

2012-01-01

Observations of hereditary glomerular disease support the contention that podocyte intercellular junction proteins are essential for junction formation and maintenance. Genetic deletion of most of these podocyte intercellular junction proteins results in foot process effacement and proteinuria. This review focuses on the current understanding of molecular mechanisms by which podocyte intercellular junction proteins such as the Nephrin-Neph1-Podocin receptor complex coordinate cytoskeletal dynamics and thus intercellular junction formation, maintenance and injury-dependent remodeling. PMID:22958485

Neisseria gonorrhoeae breaches the apical junction of polarized epithelial cells for transmigration by activating EGFR

PubMed Central

Edwards, Vonetta L.; Wang, Liang-Chun; Dawson, Valerie; Stein, Daniel C.; Song, Wenxia

2017-01-01

Summary Neisseria gonorrhoeae initiates infection at the apical surface of columnar endocervical epithelial cells in the female reproductive tract. These cells provide a physical barrier against pathogens by forming continuous apical junctional complexes between neighbouring cells. This study examines the interaction of gonococci (GC) with polarized epithelial cells. We show that viable GC preferentially localize at the apical side of the cell–cell junction in polarized endometrial and colonic epithelial cells, HEC-1-B and T84. In GC-infected cells, continuous apical junctional complexes are disrupted, and the junction-associated protein β-catenin is redistributed from the apical junction to the cytoplasm and to GC adherent sites; however, overall cellular levels remain unchanged. This redistribution of junctional proteins is associated with a decrease in the ‘fence’ function of the apical junction but not its ‘gate’ function. Disruption of the apical junction by removing calcium increases GC transmigration across the epithelial monolayer. GC inoculation induces the phosphorylation of both epidermal growth factor receptor (EGFR) and β-catenin, while inhibition of EGFR kinase activity significantly reduces both GC-induced β-catenin redistribution and GC transmigration. Therefore, the gonococcus is capable of weakening the apical junction and polarity of epithelial cells by activating EGFR, which facilitates GC transmigration across the epithelium. PMID:23279089

Glutamine Supplementation Attenuates Ethanol-Induced Disruption of Apical Junctional Complexes in Colonic Epithelium and Ameliorates Gut Barrier Dysfunction and Fatty Liver in Mice

PubMed Central

Chaudhry, Kamaljit K.; Shukla, Pradeep K.; Mir, Hina; Manda, Bhargavi; Gangwar, Ruchika; Yadav, Nikki; McMullen, Megan; Nagy, Laura E.; Rao, RadhaKrishna

2015-01-01

Previous in vitro studies showed that glutamine (Gln) prevents acetaldehyde-induced disruption of tight junctions and adherens junctions in Caco-2 cell monolayers and human colonic mucosa. In the present study, we evaluated the effect of Gln supplementation on ethanol-induced gut barrier dysfunction and liver injury in mice in vivo. Ethanol feeding caused a significant increase in inulin permeability in distal colon. Elevated permeability was associated with a redistribution of tight junction and adherens junction proteins and depletion of detergent-insoluble fractions of these proteins, suggesting that ethanol disrupts apical junctional complexes in colonic epithelium and increases paracellular permeability. Ethanol-induced increase in colonic mucosal permeability and disruption of junctional complexes were most severe in mice fed Gln-free diet. Gln supplementation attenuated ethanol-induced mucosal permeability and disruption of tight junctions and adherens junctions in a dose-dependent manner, indicating the potential role of glutamine in nutritional intervention to alcoholic tissue injury. Gln supplementation dose-dependently elevated reduced-protein thiols in colon without affecting the level of oxidized-protein thiols. Ethanol feeding depleted reduced protein thiols and elevated oxidized protein thiols. Ethanol-induced protein thiol oxidation was most severe in mice fed Gln-free diet and absent in mice fed Gln-supplemented diet, suggesting that antioxidant effect is one of the likely mechanisms involved in Gln-mediated amelioration of ethanol-induced gut barrier dysfunction. Ethanol feeding elevated plasma transaminase and liver triglyceride, which was accompanied by histopathologic lesions in the liver; ethanol-induced liver damage was attenuated by Gln supplementation. These results indicate that Gln supplementation ameliorates alcohol-induced gut and liver injury. PMID:26365579

Molecular cell biology and physiology of solute transport

PubMed Central

Caplan, Michael J.; Seo-Mayer, Patricia; Zhang, Li

2010-01-01

Purpose of review An enormous body of research has been focused on exploring the mechanisms through which epithelial cells establish their characteristic polarity. It is clear that under normal circumstances cell–cell contacts mediated by the calcium-dependent adhesion proteins of the intercellular adhesion junctions are required to initiate complete polarization. Furthermore, formation of the tight, or occluding, junctions that limit paracellular permeability has long been thought to help to establish polarity by preventing the diffusion of membrane proteins between the two plasmalemmal domains. This review will discuss several selected kinases and protein complexes and highlight their relevance to transporting epithelial cell polarization. Recent findings Recent work has shed new light on the roles of junctional complexes in establishing and maintaining epithelial cell polarity. In addition, work from several laboratories, suggests that the formation of these junctions is tied to processes that regulate cellular energy metabolism. Summary Junctional complexes and energy sensing kinases constitute a novel class of machinery whose capacity to generate and modulate epithelial cell polarity is likely to have wide ranging and important physiological ramifications. PMID:18695392

VASP, zyxin and TES are tension-dependent members of Focal Adherens Junctions independent of the α-catenin-vinculin module.

PubMed

Oldenburg, Joppe; van der Krogt, Gerard; Twiss, Floor; Bongaarts, Annika; Habani, Yasmin; Slotman, Johan A; Houtsmuller, Adriaan; Huveneers, Stephan; de Rooij, Johan

2015-11-27

Mechanical forces are integrated at cadherin-based adhesion complexes to regulate morphology and strength of cell-cell junctions and organization of associated F-actin. A central mechanosensor at the cadherin complex is α-catenin, whose stretching recruits vinculin to regulate adhesion strength. The identity of the F-actin regulating signals that are also activated by mechanical forces at cadherin-based junctions has remained elusive. Here we identify the actin-regulators VASP, zyxin and TES as members of punctate, tensile cadherin-based junctions called Focal Adherens Junctions (FAJ) and show that they display mechanosensitive recruitment similar to that of vinculin. However, this recruitment is not altered by destroying or over-activating the α-catenin/vinculin module. Structured Illumination Microscopy (SIM) indicates that these tension sensitive proteins concentrate at locations within FAJs that are distinct from the core cadherin complex proteins. Furthermore, localization studies using mutated versions of VASP and zyxin indicate that these two proteins require binding to each other in order to localize to the FAJs. We conclude that there are multiple force sensitive modules present at the FAJ that are activated at distinct locations along the cadherin-F-actin axis and regulate specific aspects of junction dynamics.

VASP, zyxin and TES are tension-dependent members of Focal Adherens Junctions independent of the α-catenin-vinculin module

PubMed Central

Oldenburg, Joppe; van der Krogt, Gerard; Twiss, Floor; Bongaarts, Annika; Habani, Yasmin; Slotman, Johan A.; Houtsmuller, Adriaan; Huveneers, Stephan; de Rooij, Johan

2015-01-01

Mechanical forces are integrated at cadherin-based adhesion complexes to regulate morphology and strength of cell-cell junctions and organization of associated F-actin. A central mechanosensor at the cadherin complex is α-catenin, whose stretching recruits vinculin to regulate adhesion strength. The identity of the F-actin regulating signals that are also activated by mechanical forces at cadherin-based junctions has remained elusive. Here we identify the actin-regulators VASP, zyxin and TES as members of punctate, tensile cadherin-based junctions called Focal Adherens Junctions (FAJ) and show that they display mechanosensitive recruitment similar to that of vinculin. However, this recruitment is not altered by destroying or over-activating the α-catenin/vinculin module. Structured Illumination Microscopy (SIM) indicates that these tension sensitive proteins concentrate at locations within FAJs that are distinct from the core cadherin complex proteins. Furthermore, localization studies using mutated versions of VASP and zyxin indicate that these two proteins require binding to each other in order to localize to the FAJs. We conclude that there are multiple force sensitive modules present at the FAJ that are activated at distinct locations along the cadherin-F-actin axis and regulate specific aspects of junction dynamics. PMID:26611125

PLEKHA7 Recruits PDZD11 to Adherens Junctions to Stabilize Nectins.

PubMed

Guerrera, Diego; Shah, Jimit; Vasileva, Ekaterina; Sluysmans, Sophie; Méan, Isabelle; Jond, Lionel; Poser, Ina; Mann, Matthias; Hyman, Anthony A; Citi, Sandra

2016-05-20

PLEKHA7 is a junctional protein implicated in stabilization of the cadherin protein complex, hypertension, cardiac contractility, glaucoma, microRNA processing, and susceptibility to bacterial toxins. To gain insight into the molecular basis for the functions of PLEKHA7, we looked for new PLEKHA7 interactors. Here, we report the identification of PDZ domain-containing protein 11 (PDZD11) as a new interactor of PLEKHA7 by yeast two-hybrid screening and by mass spectrometry analysis of PLEKHA7 immunoprecipitates. We show that PDZD11 (17 kDa) is expressed in epithelial and endothelial cells, where it forms a complex with PLEKHA7, as determined by co-immunoprecipitation analysis. The N-terminal Trp-Trp (WW) domain of PLEKHA7 interacts directly with the N-terminal 44 amino acids of PDZD11, as shown by GST-pulldown assays. Immunofluorescence analysis shows that PDZD11 is localized at adherens junctions in a PLEKHA7-dependent manner, because its junctional localization is abolished by knock-out of PLEKHA7, and is rescued by re-expression of exogenous PLEKHA7. The junctional recruitment of nectin-1 and nectin-3 and their protein levels are decreased via proteasome-mediated degradation in epithelial cells where either PDZD11 or PLEKHA7 have been knocked-out. PDZD11 forms a complex with nectin-1 and nectin-3, and its PDZ domain interacts directly with the PDZ-binding motif of nectin-1. PDZD11 is required for the efficient assembly of apical junctions of epithelial cells at early time points in the calcium-switch model. These results show that the PLEKHA7-PDZD11 complex stabilizes nectins to promote efficient early junction assembly and uncover a new molecular mechanism through which PLEKHA7 recruits PDZ-binding membrane proteins to epithelial adherens junctions. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Transmembrane proteins of tight junctions.

PubMed

Chiba, Hideki; Osanai, Makoto; Murata, Masaki; Kojima, Takashi; Sawada, Norimasa

2008-03-01

Tight junctions contribute to the paracellular barrier, the fence dividing plasma membranes, and signal transduction, acting as a multifunctional complex in vertebrate epithelial and endothelial cells. The identification and characterization of the transmembrane proteins of tight junctions, claudins, junctional adhesion molecules (JAMs), occludin and tricellulin, have led to insights into the molecular nature of tight junctions. We provide an overview of recent progress in studies on these proteins and highlight their roles and regulation, as well as their functional significance in human diseases.

An UPF3-based nonsense-mediated decay in Paramecium.

PubMed

Contreras, Julia; Begley, Victoria; Macias, Sandra; Villalobo, Eduardo

2014-12-01

Nonsense-mediated decay recognises mRNAs containing premature termination codons. One of its components, UPF3, is a molecular link bridging through its binding to the exon junction complex nonsense-mediated decay and splicing. In protists UPF3 has not been identified yet. We report that Paramecium tetraurelia bears an UPF3 gene and that it has a role in nonsense-mediated decay. Interestingly, the identified UPF3 has not conserved the essential amino acids required to bind the exon junction complex. Though, our data indicates that this ciliate bears genes coding for core proteins of the exon junction complex. Copyright © 2014 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

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

PubMed Central

Bazzoun, Dana; Lelièvre, Sophie; Talhouk, Rabih

2013-01-01

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

Transition from slab to slabless: Results from the 1993 Mendocino triple junction seismic experiment

USGS Publications Warehouse

Beaudoin, B.C.; Godfrey, N.J.; Klemperer, S.L.; Lendl, C.; Trehu, A.M.; Henstock, T.J.; Levander, A.; Holl, J.E.; Meltzer, A.S.; Luetgert, J.H.; Mooney, W.D.

1996-01-01

Three seismic refraction-reflection profiles, part of the Mendocino triple junction seismic experiment, allow us to compare and contrast crust and upper mantle of the North American margin before and after it is modified by passage of the Mendocino triple junction. Upper crustal velocity models reveal an asymmetric Great Valley basin overlying Sierran or ophiolitic rocks at the latitude of Fort Bragg, California, and overlying Sierran or Klamath rocks near Redding, California. In addition, the upper crustal velocity structure indicates that Franciscan rocks underlie the Klamath terrane east of Eureka, California. The Franciscan complex is, on average, laterally homogeneous and is thickest in the triple junction region. North of the triple junction, the Gorda slab can be traced 150 km inboard from the Cascadia subduction zone. South of the triple junction, strong precritical reflections indicate partial melt and/or metamorphic fluids at the base of the crust or in the upper mantle. Breaks in these reflections are correlated with the Maacama and Bartlett Springs faults, suggesting that these faults extend at least to the mantle. We interpret our data to indicate tectonic thickening of the Franciscan complex in response to passage of the Mendocino triple junction and an associated thinning of these rocks south of the triple junction due to assimilation into melt triggered by upwelling asthenosphere. The region of thickened Franciscan complex overlies a zone of increased scattering, intrinsic attenuation, or both, resulting from mechanical mixing of lithologies and/or partial melt beneath the onshore projection of the Mendocino fracture zone. Our data reveal that we have crossed the southern edge of the Gorda slab and that this edge and/or the overlying North American crust may have fragmented because of the change in stress presented by the edge.

"The Art of Successful Publication" ECCO 13 workshop report.

PubMed

Smyth, John; Verweij, Jaap; D'Incalci, Maurizio; Balakrishnan, Lekshmy

2006-03-01

Having your work published in a good journal is the life-blood of research. Publications are the key element in scientific communication and influence future funding and cancer development for the authors. Every year more and more manuscripts are submitted and competition for acceptance is fierce. The editors of EJC recently held a workshop to discuss ways to improve manuscript writing, and this paper summarises their recommendations. Choose a title carefully, keep the introduction short, avoid confusing methods with results, and use figures wherever possible. Discuss only the relevance of new findings to published literature. Above all read the specific "instructions to authors" -- it is surprising how often this is ignored -- at peril!

Single-molecule analysis of diffusion and trapping of STIM1 and Orai1 at endoplasmic reticulum–plasma membrane junctions

PubMed Central

Wu, Minnie M.; Covington, Elizabeth D.; Lewis, Richard S.

2014-01-01

Following endoplasmic reticulum (ER) Ca2+ depletion, STIM1 and Orai1 complexes assemble autonomously at ER–plasma membrane (PM) junctions to trigger store-operated Ca2+ influx. One hypothesis to explain this process is a diffusion trap in which activated STIM1 diffusing in the ER becomes trapped at junctions through interactions with the PM, and STIM1 then traps Orai1 in the PM through binding of its calcium release-activated calcium activation domain. We tested this model by analyzing STIM1 and Orai1 diffusion using single-particle tracking, photoactivation of protein ensembles, and Monte Carlo simulations. In resting cells, STIM1 diffusion is Brownian, while Orai1 is slightly subdiffusive. After store depletion, both proteins slow to the same speeds, consistent with complex formation, and are confined to a corral similar in size to ER–PM junctions. While the escape probability at high STIM:Orai expression ratios is <1%, it is significantly increased by reducing the affinity of STIM1 for Orai1 or by expressing the two proteins at comparable levels. Our results provide direct evidence that STIM-Orai complexes are trapped by their physical connections across the junctional gap, but also reveal that the complexes are surprisingly dynamic, suggesting that readily reversible binding reactions generate free STIM1 and Orai1, which engage in constant diffusional exchange with extrajunctional pools. PMID:25057023

Heterocellular interaction enhances recruitment of {alpha} and {beta}-catenins and ZO-2 into functional gap-junction complexes and induces gap junction-dependant differentiation of mammary epithelial cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Talhouk, Rabih S.; Mroue, Rana; Mokalled, Mayssa

2008-11-01

Gap junctions (GJ) are required for mammary epithelial differentiation. Using epithelial (SCp2) and myoepithelial-like (SCg6) mouse-derived mammary cells, the role of heterocellular interaction in assembly of GJ complexes and functional differentiation ({beta}-casein expression) was evaluated. Heterocellular interaction is critical for {beta}-casein expression, independent of exogenous basement membrane or cell anchoring substrata. Functional differentiation of SCp2, co-cultured with SCg6, is more sensitive to GJ inhibition relative to homocellular SCp2 cultures differentiated by exogenous basement membrane. Connexin (Cx)32 and Cx43 levels were not regulated across culture conditions; however, GJ functionality was enhanced under differentiation-permissive conditions. Immunoprecipitation studies demonstrated association of junctional complexmore » components ({alpha}-catenin, {beta}-catenin and ZO-2) with Cx32 and Cx43, in differentiation conditions, and additionally with Cx30 in heterocellular cultures. Although {beta}-catenin did not shuttle between cadherin and GJ complexes, increased association between connexins and {beta}-catenin in heterocellular cultures was observed. This was concomitant with reduced nuclear {beta}-catenin, suggesting that differentiation in heterocellular cultures involves sequestration of {beta}-catenin in GJ complexes.« less

A perisynaptic ménage à trois between Dlg, DLin-7, and Metro controls proper organization of Drosophila synaptic junctions.

PubMed

Bachmann, André; Kobler, Oliver; Kittel, Robert J; Wichmann, Carolin; Sierralta, Jimena; Sigrist, Stephan J; Gundelfinger, Eckart D; Knust, Elisabeth; Thomas, Ulrich

2010-04-28

Structural plasticity of synaptic junctions is a prerequisite to achieve and modulate connectivity within nervous systems, e.g., during learning and memory formation. It demands adequate backup systems that allow remodeling while retaining sufficient stability to prevent unwanted synaptic disintegration. The strength of submembranous scaffold complexes, which are fundamental to the architecture of synaptic junctions, likely constitutes a crucial determinant of synaptic stability. Postsynaptic density protein-95 (PSD-95)/ Discs-large (Dlg)-like membrane-associated guanylate kinases (DLG-MAGUKs) are principal scaffold proteins at both vertebrate and invertebrate synapses. At Drosophila larval glutamatergic neuromuscular junctions (NMJs) DlgA and DlgS97 exert pleiotropic functions, probably reflecting a few known and a number of yet-unknown binding partners. In this study we have identified Metro, a novel p55/MPP-like Drosophila MAGUK as a major binding partner of perisynaptic DlgS97 at larval NMJs. Based on homotypic LIN-2,-7 (L27) domain interactions, Metro stabilizes junctional DlgS97 in a complex with the highly conserved adaptor protein DLin-7. In a remarkably interdependent manner, Metro and DLin-7 act downstream of DlgS97 to control NMJ expansion and proper establishment of synaptic boutons. Using quantitative 3D-imaging we further demonstrate that the complex controls the size of postsynaptic glutamate receptor fields. Our findings accentuate the importance of perisynaptic scaffold complexes for synaptic stabilization and organization.

Perfection and complexity in the lower Brazos River

NASA Astrophysics Data System (ADS)

Phillips, Jonathan D.

2007-11-01

The "perfect landscape" concept is based on the notion that any specific geomorphic system represents the combined, interacting effects of a set of generally applicable global laws and a set of geographically and historically contingent local controls. Because the joint probability of any specific combination of local and global controls is low, and the local controls are inherently idiosyncratic, the probability of existence of any given landscape is vanishingly small. A perfect landscape approach to geomorphic complexity views landscapes as circumstantial, contingent outcomes of deterministic laws operating in a specific environmental and historical context. Thus, explaining evolution of complex landscapes requires the integration of global and local approaches. Because perfection in this sense is the most important and pervasive form of complexity, the study of geomorphic complexity is not restricted to nonlinear dynamics, self-organization, or any other aspects of complexity theory. Beyond what can be achieved via complexity theory, the details of historical and geographic contexts must be addressed. One way to approach this is via synoptic analyses, where the relevant global laws are applied in specific situational contexts. A study of non-acute tributary junctions in the lower Brazos River, Texas illustrates this strategy. The application of generalizations about tributary junction angles, and of relevant theories, does not explain the unexpectedly high occurrence or the specific instances of barbed or straight junctions in the study area. At least five different causes for the development of straight or obtuse junction angles are evident in the lower Brazos. The dominant mechanism, however, is associated with river bank erosion and lateral channel migration which encroaches on upstream-oriented reaches of meandering tributaries. Because the tributaries are generally strongly incised in response to Holocene incision of the Brazos, the junctions are not readily reoriented to the expected acute angle. The findings are interpreted in the context of nonlinear divergent evolution, geographical and historical contingency, synoptic frameworks for generalizing results, and applicability of the dominant processes concept in geomorphology.

Carbon Nanotubes: Molecular Electronic Components

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Saini, Subhash; Menon, Madhu

1997-01-01

The carbon Nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale molecular electronic networks. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal graphene sheet, more complex joints require other mechanisms. In this work we explore structural characteristics of complex 3-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme. The study of pi-electron local densities of states (LDOS) of these junctions reveal many interesting features, most prominent among them being the defect-induced states in the gap.

Toxicants target cell junctions in the testis: Insights from the indazole-carboxylic acid model

PubMed Central

Cheng, C Yan

2014-01-01

There are numerous types of junctions in the seminiferous epithelium which are integrated with, and critically dependent on the Sertoli cell cytoskeleton. These include the basal tight junctions between Sertoli cells that form the main component of the blood–testis barrier, the basal ectoplasmic specializations (basal ES) and basal tubulobulbar complexes (basal TBC) between Sertoli cells; as well as apical ES and apical TBC between Sertoli cells and the developing spermatids that orchestrate spermiogenesis and spermiation. These junctions, namely TJ, ES, and TBC interact with actin microfilament-based cytoskeleton, which together with the desmosomal junctions that interact with the intermediate filament-based cytoskeleton plus the highly polarized microtubule-based cytoskeleton are working in concert to move spermatocytes and spermatids between the basal and luminal aspect of the seminiferous epithelium. In short, these various junctions are structurally complexed with the actin- and microtubule-based cytoskeleton or intermediate filaments of the Sertoli cell. Studies have shown toxicants (e.g., cadmium, bisphenol A (BPA), perfluorooctanesulfonate (PFOS), phthalates, and glycerol), and some male contraceptives under development (e.g., adjudin, gamendazole), exert their effects, at least in part, by targeting cell junctions in the testis. The disruption of Sertoli–Sertoli cell and Sertoli–germ cell junctions, results in the loss of germ cells from the seminiferous epithelium. Adjudin, a potential male contraceptive under investigation in our laboratory, produces loss of spermatids from the seminiferous tubules through disruption of the Sertoli cell spermatid junctions and disruption of the Sertoli cell cytoskeleton. The molecular and structural changes associated with adjudin administration are described, to provide an example of the profile of changes caused by disturbance of Sertoli-germ cell and also Sertoli cell-cell junctions. PMID:26413399

Formation of a PKCζ/β-catenin complex in endothelial cells promotes angiopoietin-1–induced collective directional migration and angiogenic sprouting

PubMed Central

Oubaha, Malika; Lin, Michelle I.; Margaron, Yoran; Filion, Dominic; Price, Emily N.; Zon, Leonard I.; Côté, Jean-François

2012-01-01

Angiogenic sprouting requires that cell-cell contacts be maintained during migration of endothelial cells. Angiopoietin-1 (Ang-1) and vascular endothelial growth factor act oppositely on endothelial cell junctions. We found that Ang-1 promotes collective and directional migration and, in contrast to VEGF, induces the formation of a complex formed of atypical protein kinase C (PKC)-ζ and β-catenin at cell-cell junctions and at the leading edge of migrating endothelial cells. This complex brings Par3, Par6, and adherens junction proteins at the front of migrating cells to locally activate Rac1 in response to Ang-1. The colocalization of PKCζ and β-catenin at leading edge along with PKCζ-dependent stabilization of cell-cell contacts promotes directed and collective endothelial cell migration. Consistent with these results, down-regulation of PKCζ in endothelial cells alters Ang-1–induced sprouting in vitro and knockdown in developing zebrafish results in intersegmental vessel defects caused by a perturbed directionality of tip cells and by loss of cell contacts between tip and stalk cells. These results reveal that PKCζ and β-catenin function in a complex at adherens junctions and at the leading edge of migrating endothelial cells to modulate collective and directional migration during angiogenesis. PMID:22936663

Experiments with d-wave Superconductors

NASA Astrophysics Data System (ADS)

Mannhart, J.; Hilgenkamp, H.; Hammerl, G.; Schneider, C. W.

2003-10-01

The predominant dx2-y2-wave pairing-symmetry of most high-Tc, superconductors provides the opportunity to fabricate Josephson junction circuits in which part of the junctions are biased by a phase difference of the superconducting order parameter of π. To explore the road to such π-electronics, we have fabricated and studied all-high-Tc dc superconducting quantum interference devices (dc SQUIDs) realized with thin film technology, of which the Josephson junctions consist of one standard junction and one junction with a π-phase shift. These π-SQUIDs provide clear evidence of the dx2-y2-wave symmetry of the order parameter, the amount of complex admixtures of other symmetry components being undetectably small. This seems to contradict other experiments, the results of which have been presented as evidence for an s-wave order parameter or for complex admixtures. Possible solutions to resolve this apparent contradiction are presented. In particular it is pointed out that even in the bulk of a superconductor the order parameter symmetry (the admixture of various symmetry components) may be spatially dependent.

Congestion relaxation due to density-dependent junction rules in TASEP network

NASA Astrophysics Data System (ADS)

Tannai, Takahiro; Nishinari, Katsuhiro

2017-09-01

We now consider a small network module of Totally Asymmetric Simple Exclusion Process with branching and aggregation points, and rules of junctions dependent on the densities of segments of the network module. We also focus on the interaction among junctions which are branching and aggregation. The interaction among junctions with density-dependent rules possesses more complexity than those with density-independent rules studied in the previous papers. In conclusion, we confirm the result that density-dependent rules enable vehicles to move more effectively than the density-independent rules.

Complexity in neuronal noise depends on network interconnectivity.

PubMed

Serletis, Demitre; Zalay, Osbert C; Valiante, Taufik A; Bardakjian, Berj L; Carlen, Peter L

2011-06-01

"Noise," or noise-like activity (NLA), defines background electrical membrane potential fluctuations at the cellular level of the nervous system, comprising an important aspect of brain dynamics. Using whole-cell voltage recordings from fast-spiking stratum oriens interneurons and stratum pyramidale neurons located in the CA3 region of the intact mouse hippocampus, we applied complexity measures from dynamical systems theory (i.e., 1/f(γ) noise and correlation dimension) and found evidence for complexity in neuronal NLA, ranging from high- to low-complexity dynamics. Importantly, these high- and low-complexity signal features were largely dependent on gap junction and chemical synaptic transmission. Progressive neuronal isolation from the surrounding local network via gap junction blockade (abolishing gap junction-dependent spikelets) and then chemical synaptic blockade (abolishing excitatory and inhibitory post-synaptic potentials), or the reverse order of these treatments, resulted in emergence of high-complexity NLA dynamics. Restoring local network interconnectivity via blockade washout resulted in resolution to low-complexity behavior. These results suggest that the observed increase in background NLA complexity is the result of reduced network interconnectivity, thereby highlighting the potential importance of the NLA signal to the study of network state transitions arising in normal and abnormal brain dynamics (such as in epilepsy, for example).

Evidence for differential changes of junctional complex proteins in murine neurocysticercosis dependent upon CNS vasculature.

PubMed

Alvarez, Jorge I; Teale, Judy M

2007-09-12

The delicate balance required to maintain homeostasis of the central nervous system (CNS) is controlled by the blood-brain barrier (BBB). Upon injury, the BBB is disrupted compromising the CNS. BBB disruption has been represented as a uniform event. However, our group has shown in a murine model of neurocysticercosis (NCC) that BBB disruption varies depending upon the anatomical site/vascular bed analyzed. In this study further understanding of the mechanisms of BBB disruption was explored in blood vessels located in leptomeninges (pial vessels) and brain parenchyma (parenchymal vessels) by examining the expression of junctional complex proteins in murine brain infected with Mesocestoides corti. Both pial and parenchymal vessels from mock infected animals showed significant colocalization of junctional proteins and displayed an organized architecture. Upon infection, the patterned organization was disrupted and in some cases, particular tight junction and adherens junction proteins were undetectable or appeared to be undergoing proteolysis. The extent and timing of these changes differed between both types of vessels (pial vessel disruption within days versus weeks for parenchymal vessels). To approach potential mechanisms, the expression and activity of matrix metalloproteinase-9 (MMP-9) were evaluated by in situ zymography. The results indicated an increase in MMP-9 activity at sites of BBB disruption exhibiting leukocyte infiltration. Moreover, the timing of MMP activity in pial and parenchymal vessels correlated with the timing of permeability disruption. Thus, breakdown of the BBB is a mutable process despite the similar structure of the junctional complex between pial and parenchymal vessels and involvement of MMP activity.

The Saccharomyces cerevisiae Mlh1-Mlh3 Heterodimer Is an Endonuclease That Preferentially Binds to Holliday Junctions*

PubMed Central

Ranjha, Lepakshi; Anand, Roopesh; Cejka, Petr

2014-01-01

MutLγ, a heterodimer of the MutL homologues Mlh1 and Mlh3, plays a critical role during meiotic homologous recombination. The meiotic function of Mlh3 is fully dependent on the integrity of a putative nuclease motif DQHAX2EX4E, inferring that the anticipated nuclease activity of Mlh1-Mlh3 is involved in the processing of joint molecules to generate crossover recombination products. Although a vast body of genetic and cell biological data regarding Mlh1-Mlh3 is available, mechanistic insights into its function have been lacking due to the unavailability of the recombinant protein complex. Here we expressed the yeast Mlh1-Mlh3 heterodimer and purified it into near homogeneity. We show that recombinant MutLγ is a nuclease that nicks double-stranded DNA. We demonstrate that MutLγ binds DNA with a high affinity and shows a marked preference for Holliday junctions. We also expressed the human MLH1-MLH3 complex and show that preferential binding to Holliday junctions is a conserved capacity of eukaryotic MutLγ complexes. Specific DNA recognition has never been observed with any other eukaryotic MutL homologue. MutLγ thus represents a new paradigm for the function of the eukaryotic MutL protein family. We provide insights into the mode of Holliday junction recognition and show that Mlh1-Mlh3 prefers to bind the open unstacked Holliday junction form. This further supports the model where MutLγ is part of a complex acting on joint molecules to generate crossovers in meiosis. PMID:24443562

The Saccharomyces cerevisiae Mlh1-Mlh3 heterodimer is an endonuclease that preferentially binds to Holliday junctions.

PubMed

Ranjha, Lepakshi; Anand, Roopesh; Cejka, Petr

2014-02-28

MutLγ, a heterodimer of the MutL homologues Mlh1 and Mlh3, plays a critical role during meiotic homologous recombination. The meiotic function of Mlh3 is fully dependent on the integrity of a putative nuclease motif DQHAX2EX4E, inferring that the anticipated nuclease activity of Mlh1-Mlh3 is involved in the processing of joint molecules to generate crossover recombination products. Although a vast body of genetic and cell biological data regarding Mlh1-Mlh3 is available, mechanistic insights into its function have been lacking due to the unavailability of the recombinant protein complex. Here we expressed the yeast Mlh1-Mlh3 heterodimer and purified it into near homogeneity. We show that recombinant MutLγ is a nuclease that nicks double-stranded DNA. We demonstrate that MutLγ binds DNA with a high affinity and shows a marked preference for Holliday junctions. We also expressed the human MLH1-MLH3 complex and show that preferential binding to Holliday junctions is a conserved capacity of eukaryotic MutLγ complexes. Specific DNA recognition has never been observed with any other eukaryotic MutL homologue. MutLγ thus represents a new paradigm for the function of the eukaryotic MutL protein family. We provide insights into the mode of Holliday junction recognition and show that Mlh1-Mlh3 prefers to bind the open unstacked Holliday junction form. This further supports the model where MutLγ is part of a complex acting on joint molecules to generate crossovers in meiosis.

Intestinal epithelial barrier function and tight junction proteins with heat and exercise

PubMed Central

Zuhl, Micah N.; Moseley, Pope L.

2015-01-01

A single layer of enterocytes and tight junctions (intercellular multiprotein complexes) form the intestinal epithelial barrier that controls transport of molecules through transcellular and paracellular pathways. A dysfunctional or “leaky” intestinal tight junction barrier allows augmented permeation of luminal antigens, endotoxins, and bacteria into the blood stream. Various substances and conditions have been shown to affect the maintenance of the intestinal epithelial tight junction barrier. The primary focus of the present review is to analyze the effects of exertional or nonexertional (passive hyperthermia) heat stress on tight junction barrier function in in vitro and in vivo (animals and humans) models. Our secondary focus is to review changes in tight junction proteins in response to exercise or hyperthermic conditions. Finally, we discuss some pharmacological or nutritional interventions that may affect the cellular mechanisms involved in maintaining homeostasis of the intestinal epithelial tight junction barrier during heat stress or exercise. PMID:26359485

Intestinal epithelial barrier function and tight junction proteins with heat and exercise.

PubMed

Dokladny, Karol; Zuhl, Micah N; Moseley, Pope L

2016-03-15

A single layer of enterocytes and tight junctions (intercellular multiprotein complexes) form the intestinal epithelial barrier that controls transport of molecules through transcellular and paracellular pathways. A dysfunctional or "leaky" intestinal tight junction barrier allows augmented permeation of luminal antigens, endotoxins, and bacteria into the blood stream. Various substances and conditions have been shown to affect the maintenance of the intestinal epithelial tight junction barrier. The primary focus of the present review is to analyze the effects of exertional or nonexertional (passive hyperthermia) heat stress on tight junction barrier function in in vitro and in vivo (animals and humans) models. Our secondary focus is to review changes in tight junction proteins in response to exercise or hyperthermic conditions. Finally, we discuss some pharmacological or nutritional interventions that may affect the cellular mechanisms involved in maintaining homeostasis of the intestinal epithelial tight junction barrier during heat stress or exercise. Copyright © 2016 the American Physiological Society.

Disruption of the Cdc42/Par6/aPKC or Dlg/Scrib/Lgl Polarity Complex Promotes Epithelial Proliferation via Overlapping Mechanisms

PubMed Central

Schimizzi, Gregory V.; Maher, Meghan T.; Loza, Andrew J.; Longmore, Gregory D.

2016-01-01

The establishment and maintenance of apical-basal polarity is a defining characteristic and essential feature of functioning epithelia. Apical-basal polarity (ABP) proteins are also tumor suppressors that are targeted for disruption by oncogenic viruses and are commonly mutated in human carcinomas. Disruption of these ABP proteins is an early event in cancer development that results in increased proliferation and epithelial disorganization through means not fully characterized. Using the proliferating Drosophila melanogaster wing disc epithelium, we demonstrate that disruption of the junctional vs. basal polarity complexes results in increased epithelial proliferation via distinct downstream signaling pathways. Disruption of the basal polarity complex results in JNK-dependent proliferation, while disruption of the junctional complex primarily results in p38-dependent proliferation. Surprisingly, the Rho-Rok-Myosin contractility apparatus appears to play opposite roles in the regulation of the proliferative phenotype based on which polarity complex is disrupted. In contrast, non-autonomous Tumor Necrosis Factor (TNF) signaling appears to suppress the proliferation that results from apical-basal polarity disruption, regardless of which complex is disrupted. Finally we demonstrate that disruption of the junctional polarity complex activates JNK via the Rho-Rok-Myosin contractility apparatus independent of the cortical actin regulator, Moesin. PMID:27454609

Disruption of the Cdc42/Par6/aPKC or Dlg/Scrib/Lgl Polarity Complex Promotes Epithelial Proliferation via Overlapping Mechanisms.

PubMed

Schimizzi, Gregory V; Maher, Meghan T; Loza, Andrew J; Longmore, Gregory D

2016-01-01

The establishment and maintenance of apical-basal polarity is a defining characteristic and essential feature of functioning epithelia. Apical-basal polarity (ABP) proteins are also tumor suppressors that are targeted for disruption by oncogenic viruses and are commonly mutated in human carcinomas. Disruption of these ABP proteins is an early event in cancer development that results in increased proliferation and epithelial disorganization through means not fully characterized. Using the proliferating Drosophila melanogaster wing disc epithelium, we demonstrate that disruption of the junctional vs. basal polarity complexes results in increased epithelial proliferation via distinct downstream signaling pathways. Disruption of the basal polarity complex results in JNK-dependent proliferation, while disruption of the junctional complex primarily results in p38-dependent proliferation. Surprisingly, the Rho-Rok-Myosin contractility apparatus appears to play opposite roles in the regulation of the proliferative phenotype based on which polarity complex is disrupted. In contrast, non-autonomous Tumor Necrosis Factor (TNF) signaling appears to suppress the proliferation that results from apical-basal polarity disruption, regardless of which complex is disrupted. Finally we demonstrate that disruption of the junctional polarity complex activates JNK via the Rho-Rok-Myosin contractility apparatus independent of the cortical actin regulator, Moesin.

Evolution of disorder in Mediator complex and its functional relevance

PubMed Central

Nagulapalli, Malini; Maji, Sourobh; Dwivedi, Nidhi; Dahiya, Pradeep; Thakur, Jitendra K.

2016-01-01

Mediator, an important component of eukaryotic transcriptional machinery, is a huge multisubunit complex. Though the complex is known to be conserved across all the eukaryotic kingdoms, the evolutionary topology of its subunits has never been studied. In this study, we profiled disorder in the Mediator subunits of 146 eukaryotes belonging to three kingdoms viz., metazoans, plants and fungi, and attempted to find correlation between the evolution of Mediator complex and its disorder. Our analysis suggests that disorder in Mediator complex have played a crucial role in the evolutionary diversification of complexity of eukaryotic organisms. Conserved intrinsic disordered regions (IDRs) were identified in only six subunits in the three kingdoms whereas unique patterns of IDRs were identified in other Mediator subunits. Acquisition of novel molecular recognition features (MoRFs) through evolution of new subunits or through elongation of the existing subunits was evident in metazoans and plants. A new concept of ‘junction-MoRF’ has been introduced. Evolutionary link between CBP and Med15 has been provided which explain the evolution of extended-IDR in CBP from Med15 KIX-IDR junction-MoRF suggesting role of junction-MoRF in evolution and modulation of protein–protein interaction repertoire. This study can be informative and helpful in understanding the conserved and flexible nature of Mediator complex across eukaryotic kingdoms. PMID:26590257

Human Heart Mitochondrial DNA Is Organized in Complex Catenated Networks Containing Abundant Four-way Junctions and Replication Forks*

PubMed Central

Pohjoismäki, Jaakko L. O.; Goffart, Steffi; Tyynismaa, Henna; Willcox, Smaranda; Ide, Tomomi; Kang, Dongchon; Suomalainen, Anu; Karhunen, Pekka J.; Griffith, Jack D.; Holt, Ian J.; Jacobs, Howard T.

2009-01-01

Analysis of human heart mitochondrial DNA (mtDNA) by electron microscopy and agarose gel electrophoresis revealed a complete absence of the θ-type replication intermediates seen abundantly in mtDNA from all other tissues. Instead only Y- and X-junctional forms were detected after restriction digestion. Uncut heart mtDNA was organized in tangled complexes of up to 20 or more genome equivalents, which could be resolved to genomic monomers, dimers, and linear fragments by treatment with the decatenating enzyme topoisomerase IV plus the cruciform-cutting T7 endonuclease I. Human and mouse brain also contained a population of such mtDNA forms, which were absent, however, from mouse, rabbit, or pig heart. Overexpression in transgenic mice of two proteins involved in mtDNA replication, namely human mitochondrial transcription factor A or the mouse Twinkle DNA helicase, generated abundant four-way junctions in mtDNA of heart, brain, and skeletal muscle. The organization of mtDNA of human heart as well as of mouse and human brain in complex junctional networks replicating via a presumed non-θ mechanism is unprecedented in mammals. PMID:19525233

Effects of 18beta-glycyrrhetinic acid on the junctional complex and steroidogenesis in rat adrenocortical cells.

PubMed

Huang, Shih-Horng; Wu, Jiahn-Chun; Hwang, Ra-Der; Yeo, Hui-Lin; Wang, Seu-Mei

2003-09-01

Cellular junctions play important roles in cell differentiation, signal transduction, and cell function. This study investigated their function in steroid secretion by adrenal cells. Immunofluorescence staining revealed the presence of gap junctions and adherens junctions between adrenal cells. The major gap junction protein, connexin43, was seen as a linear dotted pattern of the typical gap junction plaques, in contrast to alpha-, beta-, and gamma-catenin, which were seen as continuous, linear staining of cell-cell adherens junction. Treatment with 18beta-glycyrrhetinic acid, a gap junction inhibitor, reduced the immunoreactivity of these proteins in a time- and dose-dependent manner, and caused the gap junction and adherens junction to separate longitudinally from the cell-cell contact sites, indicating the structural interdependency of these two junctions. Interestingly, 18beta-glycyrrhetinic acid stimulated a two- to three-fold increase in steroid production in these adrenal cells lacking intact cell junctions. These data raise the question of the necessity for cell communication for the endocrine function of adrenal cells. Pharmacological analyses indicated that the steroidogenic effect of 18beta-glycyrrhetinic acid was partially mediated by extracellular signal-related kinase and calcium/calmodulin-dependent kinase, a pathway distinct from the protein kinase A signaling pathway already known to mediate steroidogenesis in adrenal cells. Copyright 2003 Wiley-Liss, Inc.

Fullerene Derived Molecular Electronic Devices

NASA Technical Reports Server (NTRS)

Menon, Madhu; Srivastava, Deepak; Saini, Subbash

1998-01-01

The carbon Nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale electronic devices. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal grapheme sheet, more complex joints require other mechanisms. In this work we explore structural and electronic properties of complex 3-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme.

Electro-Spark Deposited Coatings for Replacement of Chrome Electroplating

DTIC Science & Technology

2005-06-01

2.6 0.4 2.2 Thickness uniformity (A-F) 2.8/0.8 2.8/0.8 6.3/0 6.5/0.4 2 to 0 3.9/0.4 Coating integrity (A-F) A A- F C - D A- Defects/mm F D + F D + F B...or width of the wear scar (cm), h is the height or depth of the wear scar (cm), and c is the circumference of the wear scar (cm) where c = "rrd, and d ...inerS4C *2 Panelb MHC583010 -,,IN 3 4853 0.42 roiness 1)N32-15m x c -e sca. 3) &wN x Deb 1nQ withn sar Dein HxW 1).057n*~ 3)211200 12 ve 2 Panl 2 EJC .5 D

Celiac Disease: Role of the Epithelial Barrier.

PubMed

Schumann, Michael; Siegmund, Britta; Schulzke, Jörg D; Fromm, Michael

2017-03-01

In celiac disease (CD) a T-cell-mediated response to gluten is mounted in genetically predisposed individuals, resulting in a malabsorptive enteropathy histologically highlighted by villous atrophy and crypt hyperplasia. Recent data point to the epithelial layer as an under-rated hot spot in celiac pathophysiology to date. This overview summarizes current functional and genetic evidence on the role of the epithelial barrier in CD, consisting of the cell membranes and the apical junctional complex comprising sealing as well as ion and water channel-forming tight junction proteins and the adherens junction. Moreover, the underlying mechanisms are discussed, including apoptosis of intestinal epithelial cells, biology of intestinal stem cells, alterations in the apical junctional complex, transcytotic uptake of gluten peptides, and possible implications of a defective epithelial polarity. Current research is directed toward new treatment options for CD that are alternatives or complementary therapeutics to a gluten-free diet. Thus, strategies to target an altered epithelial barrier therapeutically also are discussed.

Cardiac myocyte diversity and a fibroblast network in the junctional region of the zebrafish heart revealed by transmission and serial block-face scanning electron microscopy.

PubMed

Lafontant, Pascal J; Behzad, Ali R; Brown, Evelyn; Landry, Paul; Hu, Norman; Burns, Alan R

2013-01-01

The zebrafish has emerged as an important model of heart development and regeneration. While the structural characteristics of the developing and adult zebrafish ventricle have been previously studied, little attention has been paid to the nature of the interface between the compact and spongy myocardium. Here we describe how these two distinct layers are structurally and functionally integrated. We demonstrate by transmission electron microscopy that this interface is complex and composed primarily of a junctional region occupied by collagen, as well as a population of fibroblasts that form a highly complex network. We also describe a continuum of uniquely flattened transitional cardiac myocytes that form a circumferential plate upon which the radially-oriented luminal trabeculae are anchored. In addition, we have uncovered within the transitional ring a subpopulation of markedly electron dense cardiac myocytes. At discrete intervals the transitional cardiac myocytes form contact bridges across the junctional space that are stabilized through localized desmosomes and fascia adherentes junctions with adjacent compact cardiac myocytes. Finally using serial block-face scanning electron microscopy, segmentation and volume reconstruction, we confirm the three-dimensional nature of the junctional region as well as the presence of the sheet-like fibroblast network. These ultrastructural studies demonstrate the previously unrecognized complexity with which the compact and spongy layers are structurally integrated, and provide a new basis for understanding development and regeneration in the zebrafish heart.

Crystal structure of RuvC resolvase in complex with Holliday junction substrate

PubMed Central

Górecka, Karolina M.; Komorowska, Weronika; Nowotny, Marcin

2013-01-01

The key intermediate in genetic recombination is the Holliday junction (HJ), a four-way DNA structure. At the end of recombination, HJs are cleaved by specific nucleases called resolvases. In Gram-negative bacteria, this cleavage is performed by RuvC, a dimeric endonuclease that belongs to the retroviral integrase superfamily. Here, we report the first crystal structure of RuvC in complex with a synthetic HJ solved at 3.75 Å resolution. The junction in the complex is in an unfolded 2-fold symmetrical conformation, in which the four arms point toward the vertices of a tetrahedron. The two scissile phosphates are located one nucleotide from the strand exchange point, and RuvC approaches them from the minor groove side. The key protein–DNA contacts observed in the structure were verified using a thiol-based site-specific cross-linking approach. Compared with known complex structures of the phage resolvases endonuclease I and endonuclease VII, the RuvC structure exhibits striking differences in the mode of substrate binding and location of the cleavage site. PMID:23980027

The lateral mobility of cell adhesion molecules is highly restricted at septate junctions in Drosophila.

PubMed

Laval, Monique; Bel, Christophe; Faivre-Sarrailh, Catherine

2008-07-18

A complex of three cell adhesion molecules (CAMs) Neurexin IV(Nrx IV), Contactin (Cont) and Neuroglian (Nrg) is implicated in the formation of septate junctions between epithelial cells in Drosophila. These CAMs are interdependent for their localization at septate junctions and e.g. null mutation of nrx IV or cont induces the mislocalization of Nrg to the baso-lateral membrane. These mutations also result in ultrastructural alteration of the strands of septate junctions and breakdown of the paracellular barrier. Varicose (Vari) and Coracle (Cora), that both interact with the cytoplasmic tail of Nrx IV, are scaffolding molecules required for the formation of septate junctions. We conducted photobleaching experiments on whole living Drosophila embryos to analyze the membrane mobility of CAMs at septate junctions between epithelial cells. We show that GFP-tagged Nrg and Nrx IV molecules exhibit very stable association with septate junctions in wild-type embryos. Nrg-GFP is mislocalized to the baso-lateral membrane in nrx IV or cont null mutant embryos, and displays increased mobile fraction. Similarly, Nrx IV-GFP becomes distributed to the baso-lateral membrane in null mutants of vari and cora, and its mobile fraction is strongly increased. The loss of Vari, a MAGUK protein that interacts with the cytoplasmic tail of Nrx IV, has a stronger effect than the null mutation of nrx IV on the lateral mobility of Nrg-GFP. The strands of septate junctions display a stable behavior in vivo that may be correlated with their role of paracellular barrier. The membrane mobility of CAMs is strongly limited when they take part to the multimolecular complex forming septate junctions. This restricted lateral diffusion of CAMs depends on both adhesive interactions and clustering by scaffolding molecules. The lateral mobility of CAMs is strongly increased in embryos presenting alteration of septate junctions. The stronger effect of vari by comparison with nrx IV null mutation supports the hypothesis that this scaffolding molecule may cross-link different types of CAMs and play a crucial role in stabilizing the strands of septate junctions.

The Peptidoglycan-Binding Protein SjcF1 Influences Septal Junction Function and Channel Formation in the Filamentous Cyanobacterium Anabaena.

PubMed

Rudolf, Mareike; Tetik, Nalan; Ramos-León, Félix; Flinner, Nadine; Ngo, Giang; Stevanovic, Mara; Burnat, Mireia; Pernil, Rafael; Flores, Enrique; Schleiff, Enrico

2015-06-30

Filamentous, heterocyst-forming cyanobacteria exchange nutrients and regulators between cells for diazotrophic growth. Two alternative modes of exchange have been discussed involving transport either through the periplasm or through septal junctions linking adjacent cells. Septal junctions and channels in the septal peptidoglycan are likely filled with septal junction complexes. While possible proteinaceous factors involved in septal junction formation, SepJ (FraG), FraC, and FraD, have been identified, little is known about peptidoglycan channel formation and septal junction complex anchoring to the peptidoglycan. We describe a factor, SjcF1, involved in regulation of septal junction channel formation in the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. SjcF1 interacts with the peptidoglycan layer through two peptidoglycan-binding domains and is localized throughout the cell periphery but at higher levels in the intercellular septa. A strain with an insertion in sjcF1 was not affected in peptidoglycan synthesis but showed an altered morphology of the septal peptidoglycan channels, which were significantly wider in the mutant than in the wild type. The mutant was impaired in intercellular exchange of a fluorescent probe to a similar extent as a sepJ deletion mutant. SjcF1 additionally bears an SH3 domain for protein-protein interactions. SH3 binding domains were identified in SepJ and FraC, and evidence for interaction of SjcF1 with both SepJ and FraC was obtained. SjcF1 represents a novel protein involved in structuring the peptidoglycan layer, which links peptidoglycan channel formation to septal junction complex function in multicellular cyanobacteria. Nonetheless, based on its subcellular distribution, this might not be the only function of SjcF1. Cell-cell communication is central not only for eukaryotic but also for multicellular prokaryotic systems. Principles of intercellular communication are well established for eukaryotes, but the mechanisms and components involved in bacteria are just emerging. Filamentous heterocyst-forming cyanobacteria behave as multicellular organisms and represent an excellent model to study prokaryotic cell-cell communication. A path for intercellular metabolite exchange appears to involve transfer through molecular structures termed septal junctions. They are reminiscent of metazoan gap junctions that directly link adjacent cells. In cyanobacteria, such structures need to traverse the peptidoglycan layers in the intercellular septa of the filament. Here we describe a factor involved in the formation of channels across the septal peptidoglycan layers, thus contributing to the multicellular behavior of these organisms. Copyright © 2015 Rudolf et al.

Holliday Junction Thermodynamics and Structure: Coarse-Grained Simulations and Experiments

NASA Astrophysics Data System (ADS)

Wang, Wujie; Nocka, Laura M.; Wiemann, Brianne Z.; Hinckley, Daniel M.; Mukerji, Ishita; Starr, Francis W.

2016-03-01

Holliday junctions play a central role in genetic recombination, DNA repair and other cellular processes. We combine simulations and experiments to evaluate the ability of the 3SPN.2 model, a coarse-grained representation designed to mimic B-DNA, to predict the properties of DNA Holliday junctions. The model reproduces many experimentally determined aspects of junction structure and stability, including the temperature dependence of melting on salt concentration, the bias between open and stacked conformations, the relative populations of conformers at high salt concentration, and the inter-duplex angle (IDA) between arms. We also obtain a close correspondence between the junction structure evaluated by all-atom and coarse-grained simulations. We predict that, for salt concentrations at physiological and higher levels, the populations of the stacked conformers are independent of salt concentration, and directly observe proposed tetrahedral intermediate sub-states implicated in conformational transitions. Our findings demonstrate that the 3SPN.2 model captures junction properties that are inaccessible to all-atom studies, opening the possibility to simulate complex aspects of junction behavior.

What happens in Josephson junctions at high critical current densities

NASA Astrophysics Data System (ADS)

Massarotti, D.; Stornaiuolo, D.; Lucignano, P.; Caruso, R.; Galletti, L.; Montemurro, D.; Jouault, B.; Campagnano, G.; Arani, H. F.; Longobardi, L.; Parlato, L.; Pepe, G. P.; Rotoli, G.; Tagliacozzo, A.; Lombardi, F.; Tafuri, F.

2017-07-01

The impressive advances in material science and nanotechnology are more and more promoting the use of exotic barriers and/or superconductors, thus paving the way to new families of Josephson junctions. Semiconducting, ferromagnetic, topological insulator and graphene barriers are leading to unconventional and anomalous aspects of the Josephson coupling, which might be useful to respond to some issues on key problems of solid state physics. However, the complexity of the layout and of the competing physical processes occurring in the junctions is posing novel questions on the interpretation of their phenomenology. We classify some significant behaviors of hybrid and unconventional junctions in terms of their first imprinting, i.e., current-voltage curves, and propose a phenomenological approach to describe some features of junctions characterized by relatively high critical current densities Jc. Accurate arguments on the distribution of switching currents will provide quantitative criteria to understand physical processes occurring in high-Jc junctions. These notions are universal and apply to all kinds of junctions.

Innovative architecture design for high performance organic and hybrid multi-junction solar cells

NASA Astrophysics Data System (ADS)

Li, Ning; Spyropoulos, George D.; Brabec, Christoph J.

2017-08-01

The multi-junction concept is especially attractive for the photovoltaic (PV) research community owing to its potential to overcome the Schockley-Queisser limit of single-junction solar cells. Tremendous research interests are now focused on the development of high-performance absorbers and novel device architectures for emerging PV technologies, such as organic and perovskite PVs. It has been predicted that the multi-junction concept is able to boost the organic and perovskite PV technologies approaching the 20% and 30% benchmarks, respectively, showing a bright future of commercialization of the emerging PV technologies. In this contribution, we will demonstrate innovative architecture design for solution-processed, highly functional organic and hybrid multi-junction solar cells. A simple but elegant approach to fabricating organic and hybrid multi-junction solar cells will be introduced. By laminating single organic/hybrid solar cells together through an intermediate layer, the manufacturing cost and complexity of large-scale multi-junction solar cells can be significantly reduced. This smart approach to balancing the photocurrents as well as open circuit voltages in multi-junction solar cells will be demonstrated and discussed in detail.

Evolution of disorder in Mediator complex and its functional relevance.

PubMed

Nagulapalli, Malini; Maji, Sourobh; Dwivedi, Nidhi; Dahiya, Pradeep; Thakur, Jitendra K

2016-02-29

Mediator, an important component of eukaryotic transcriptional machinery, is a huge multisubunit complex. Though the complex is known to be conserved across all the eukaryotic kingdoms, the evolutionary topology of its subunits has never been studied. In this study, we profiled disorder in the Mediator subunits of 146 eukaryotes belonging to three kingdoms viz., metazoans, plants and fungi, and attempted to find correlation between the evolution of Mediator complex and its disorder. Our analysis suggests that disorder in Mediator complex have played a crucial role in the evolutionary diversification of complexity of eukaryotic organisms. Conserved intrinsic disordered regions (IDRs) were identified in only six subunits in the three kingdoms whereas unique patterns of IDRs were identified in other Mediator subunits. Acquisition of novel molecular recognition features (MoRFs) through evolution of new subunits or through elongation of the existing subunits was evident in metazoans and plants. A new concept of 'junction-MoRF' has been introduced. Evolutionary link between CBP and Med15 has been provided which explain the evolution of extended-IDR in CBP from Med15 KIX-IDR junction-MoRF suggesting role of junction-MoRF in evolution and modulation of protein-protein interaction repertoire. This study can be informative and helpful in understanding the conserved and flexible nature of Mediator complex across eukaryotic kingdoms. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

Complex band structure and electronic transmission eigenchannels

NASA Astrophysics Data System (ADS)

Jensen, Anders; Strange, Mikkel; Smidstrup, Søren; Stokbro, Kurt; Solomon, Gemma C.; Reuter, Matthew G.

2017-12-01

It is natural to characterize materials in transport junctions by their conductance length dependence, β. Theoretical estimations of β are made employing two primary theories: complex band structure and density functional theory (DFT) Landauer transport. It has previously been shown that the β value derived from total Landauer transmission can be related to the β value from the smallest |ki| complex band; however, it is an open question whether there is a deeper relationship between the two. Here we probe the details of the relationship between transmission and complex band structure, in this case individual eigenchannel transmissions and different complex bands. We present calculations of decay constants for the two most conductive states as determined by complex band structure and standard DFT Landauer transport calculations for one semi-conductor and two molecular junctions. The molecular junctions show that both the length dependence of the total transmission and the individual transmission eigenvalues can be, almost always, found through the complex band structure. The complex band structure of the semi-conducting material, however, does not predict the length dependence of the total transmission but only of the individual channels, at some k-points, due to multiple channels contributing to transmission. We also observe instances of vertical bands, some of which are the smallest |ki| complex bands, that do not contribute to transport. By understanding the deeper relationship between complex bands and individual transmission eigenchannels, we can make a general statement about when the previously accepted wisdom linking transmission and complex band structure will fail, namely, when multiple channels contribute significantly to the transmission.

A Luminescent Cocaine Detection Platform Using a Split G-Quadruplex-Selective Iridium(III) Complex and a Three-Way DNA Junction Architecture.

PubMed

Ma, Dik-Lung; Wang, Modi; He, Bingyong; Yang, Chao; Wang, Wanhe; Leung, Chung-Hang

2015-09-02

In this study, a series of 10 in-house cyclometalated iridium(III) complexes bearing different auxiliary ligands were tested for their selectivity toward split G-quadruplex in order to construct a label-free switch-on cocaine detection platform employing a three-way junction architecture and a G-quadruplex motif as a signal output unit. Through two rounds of screening, we discovered that the iridium(III) complex 7 exhibited excellent selectivity toward the intermolecular G-quadruplex motif. A detection limit as low as 30 nM for cocaine can be achieved by this sensing approach with a linear relationship between luminescence intensity and cocaine concentration established from 30 to 300 nM. Furthermore, this sensing approach could detect cocaine in diluted oral fluid. We hope that our simple, signal-on, label-free oligonucleotide-based sensing method for cocaine using a three-way DNA junction architecture could act as a useful platform in bioanalytical research.

The Nuclear and Adherent Junction Complex Component Protein Ubinuclein Negatively Regulates the Productive Cycle of Epstein-Barr Virus in Epithelial Cells▿

PubMed Central

Gruffat, Henri; Lupo, Julien; Morand, Patrice; Boyer, Véronique; Manet, Evelyne

2011-01-01

The Epstein-Barr Virus (EBV) productive cycle is initiated by the expression of the viral trans-activator EB1 (also called Zebra, Zta, or BZLF1), which belongs to the basic leucine zipper transcription factor family. We have previously identified the cellular NACos (nuclear and adherent junction complex components) protein ubinuclein (Ubn-1) as a partner for EB1, but the function of this complex has never been studied. Here, we have evaluated the consequences of this interaction on the EBV productive cycle and find that Ubn-1 overexpression represses the EBV productive cycle whereas Ubn-1 downregulation by short hairpin RNA (shRNA) increases virus production. By a chromatin immunoprecipitation (ChIP) assay, we show that Ubn-1 blocks EB1-DNA interaction. We also show that in epithelial cells, relocalization and sequestration of Ubn-1 to the tight junctions of nondividing cells allow increased activation of the productive cycle. We propose a model in which Ubn-1 is a modulator of the EBV productive cycle: in proliferating epithelial cells, Ubn-1 is nuclear and inhibits activation of the productive cycle, whereas in differentiated cells, Ubn-1 is sequestrated to tight junctions, thereby allowing EB1 to fully function in the nucleus. PMID:21084479

Ca2+-dependent localization of integrin-linked kinase to cell junctions in differentiating keratinocytes.

PubMed

Vespa, Alisa; Darmon, Alison J; Turner, Christopher E; D'Souza, Sudhir J A; Dagnino, Lina

2003-03-28

Integrin complexes are necessary for proper proliferation and differentiation of epidermal keratinocytes. Differentiation of these cells is accompanied by down-regulation of integrins and focal adhesions as well as formation of intercellular adherens junctions through E-cadherin homodimerization. A central component of integrin adhesion complexes is integrin-linked kinase (ILK), which can induce loss of E-cadherin expression and epithelial-mesenchymal transformation when ectopically expressed in intestinal and mammary epithelia. In cultured primary mouse keratinocytes, we find that ILK protein levels are independent of integrin expression and signaling, since they remain constant during Ca(2+)-induced differentiation. In contrast, keratinocyte differentiation is accompanied by marked reduction in kinase activity in ILK immunoprecipitates and altered ILK subcellular distribution. Specifically, ILK distributes in close apposition to actin fibers along intercellular junctions in differentiated but not in undifferentiated keratinocytes. ILK localization to cell-cell borders occurs independently of integrin signaling and requires Ca(2+) as well as an intact actin cytoskeleton. Further, and in contrast to what is observed in other epithelial cells, ILK overexpression in differentiated keratinocytes does not promote E-cadherin down-regulation and epithelial-mesenchymal transition. Thus, novel tissue-specific mechanisms control the formation of ILK complexes associated with cell-cell junctions in differentiating murine epidermal keratinocytes.

Tropomyosin modulates erythrocyte membrane stability

PubMed Central

An, Xiuli; Salomao, Marcela; Guo, Xinhua; Gratzer, Walter; Mohandas, Narla

2007-01-01

The ternary complex of spectrin, actin, and 4.1R (human erythrocyte protein 4.1) defines the nodes of the erythrocyte membrane skeletal network and is inseparable from membrane stability under mechanical stress. These junctions also contain tropomyosin (TM) and the other actin-binding proteins, adducin, protein 4.9, tropomodulin, and a small proportion of capZ, the functions of which are poorly defined. Here, we have examined the consequences of selective elimination of TM from the membrane. We have shown that the mechanical stability of the membranes of resealed ghosts devoid of TM is grossly, but reversibly, impaired. That the decreased membrane stability of TM-depleted membranes is the result of destabilization of the ternary complex of the network junctions is demonstrated by the strongly facilitated entry into the junctions in situ of a β-spectrin peptide, containing the actin- and 4.1R-binding sites, after extraction of the TM. The stabilizing effect of TM is highly specific, in that it is only the endogenous isotype, and not the slightly longer muscle TM that can bind to the depleted membranes and restore their mechanical stability. These findings have enabled us identify a function for TM in elevating the mechanical stability of erythrocyte membranes by stabilizing the spectrin-actin-4.1R junctional complex. PMID:17008534

Junctional complexes in the inner cyst tissue of the cysticercoid of Hymenolepis diminuta (Cestoda).

PubMed

Richards, K S; Arme, C

1983-10-01

The inner cyst tissue development is anteriad and centripetal. The cells produce lamellar extensions which assume parallel alignment. The first contact points (approximately 4 days post-infection) establish heptalaminar (gap) junctions. Lamellar attenuation results in a decreased intercellular space, and at 5-6 days pentalaminar junctions (with fused outer plasmalemma leaflets to give an electron-dense, approximately 3 nm wide O-O line) occur. This is the first maturation (M1) stage. The O-O lines are permeable to lanthanum, and evidence of their possible transformation from heptalaminar junctions is presented. Continued lamellar attenuation, associated with scolex retraction and subsequent growth, results in cytoplasmic occlusion and contact between the inner leaflets of the same lamella. The resultant electron-dense I-I line is approximately 3 nm wide; the O-O line is now less electron-dense and thinner (approximately 2 nm). This final maturation (M2) stage, resembling vertebrate myelin, occurs over limited areas; closely adjacent regions either remaining at the M1 stage, or not displaying junctional complexes. Since in vivo and in vitro excystment can occur before the M2 stage, the inner cyst tissue is not considered to be protective against the definitive host. That the tissue may function in limiting nutrient flow, thus regulating the size of the presumptive adult, is discussed.

Intracellular Ca2+ release mediates cationic but not anionic poly(amidoamine) (PAMAM) dendrimer-induced tight junction modulation.

PubMed

Avaritt, Brittany R; Swaan, Peter W

2014-09-01

Poly(amidoamine) (PAMAM) dendrimers show great promise for utilization as oral drug delivery vehicles. These polymers are capable of traversing epithelial barriers, and have been shown to translocate by both transcellular and paracellular routes. While many proof-of-concept studies have shown that PAMAM dendrimers improve intestinal transport, little information exists on the mechanisms of paracellular transport, specifically dendrimer-induced tight junction modulation. Using anionic G3.5 and cationic G4 PAMAM dendrimers with known absorption enhancers, we investigated tight junction modulation in Caco-2 monolayers by visualization and mannitol permeability and compared dendrimer-mediated tight junction modulation to that of established permeation enhancers. [(14)C]-Mannitol permeability in the presence and absence of phospholipase C-dependent signaling pathway inhibitors was also examined and indicated that this pathway may mediate dendrimer-induced changes in permeability. Differences between G3.5 and G4 in tight junction protein staining and permeability with inhibitors were evident, suggesting divergent mechanisms were responsible for tight junction modulation. These dissimilarities are further intimated by the intracellular calcium release caused by G4 but not G3.5. Based on our results, it is apparent that the underlying mechanisms of dendrimer permeability are complex, and the complexities are likely a result of the density and sign of the surface charges of PAMAM dendrimers. The results of this study will have implications on the future use of PAMAM dendrimers for oral drug delivery.

Conformational trapping of mismatch recognition complex MSH2/MSH3 on repair-resistant DNA loops.

PubMed

Lang, Walter H; Coats, Julie E; Majka, Jerzy; Hura, Greg L; Lin, Yuyen; Rasnik, Ivan; McMurray, Cynthia T

2011-10-18

Insertion and deletion of small heteroduplex loops are common mutations in DNA, but why some loops are prone to mutation and others are efficiently repaired is unknown. Here we report that the mismatch recognition complex, MSH2/MSH3, discriminates between a repair-competent and a repair-resistant loop by sensing the conformational dynamics of their junctions. MSH2/MSH3 binds, bends, and dissociates from repair-competent loops to signal downstream repair. Repair-resistant Cytosine-Adenine-Guanine (CAG) loops adopt a unique DNA junction that traps nucleotide-bound MSH2/MSH3, and inhibits its dissociation from the DNA. We envision that junction dynamics is an active participant and a conformational regulator of repair signaling, and governs whether a loop is removed by MSH2/MSH3 or escapes to become a precursor for mutation.

Branched actin networks push against each other at adherens junctions to maintain cell-cell adhesion.

PubMed

Efimova, Nadia; Svitkina, Tatyana M

2018-05-07

Adherens junctions (AJs) are mechanosensitive cadherin-based intercellular adhesions that interact with the actin cytoskeleton and carry most of the mechanical load at cell-cell junctions. Both Arp2/3 complex-dependent actin polymerization generating pushing force and nonmuscle myosin II (NMII)-dependent contraction producing pulling force are necessary for AJ morphogenesis. Which actin system directly interacts with AJs is unknown. Using platinum replica electron microscopy of endothelial cells, we show that vascular endothelial (VE)-cadherin colocalizes with Arp2/3 complex-positive actin networks at different AJ types and is positioned at the interface between two oppositely oriented branched networks from adjacent cells. In contrast, actin-NMII bundles are located more distally from the VE-cadherin-rich zone. After Arp2/3 complex inhibition, linear AJs split, leaving gaps between cells with detergent-insoluble VE-cadherin transiently associated with the gap edges. After NMII inhibition, VE-cadherin is lost from gap edges. We propose that the actin cytoskeleton at AJs acts as a dynamic push-pull system, wherein pushing forces maintain extracellular VE-cadherin transinteraction and pulling forces stabilize intracellular adhesion complexes. © 2018 Efimova and Svitkina.

Lethality of cytochalasin B and other compounds isolated from fungus Aspergillus sp. (Trichocomaceae) endophyte of Bauhinia guianensis (Fabaceae).

PubMed

Feitosa, André de O; Dias, Amanda Cristina S; Ramos, Gisele da C; Bitencourt, Heriberto R; Siqueira, José Edson S; Marinho, Patrícia Santana B; Barison, Andersson; Ocampos, Fernanda M M; Marinho, Andrey Moacir do R

Endophytic fungi are fungi that colonize internal tissues of plants; several biologically active compounds have been isolated from these fungi. There are few studies of compounds isolated from endophytic fungi of Amazon plants. Thus, this study aimed the isolation and structural identification of ergosterol (1), ergosterol peroxide (2), mevalonolactone (3), cytochalasin B (4) and cytochalasin H (5) from Aspergillus sp. EJC 04, an endophytic fungus from Bauhinia guianensis. The cytochalasin B (4) and the diacetate derivative of cytochalasin B (4a) showed high lethality in the brine shrimp assay. This is the first occurrence of cytochalasins in Amazonian endophytic fungi from B. guianensis. Copyright © 2016 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Antibacterial activity of alkaloids produced by endophytic fungus Aspergillus sp. EJC08 isolated from medical plant Bauhinia guianensis.

PubMed

Pinheiro, Eduardo Antonio A; Carvalho, Josiwander Miranda; dos Santos, Diellem Cristina P; Feitosa, André de Oliveira; Marinho, Patrícia Santana B; Guilhon, Giselle Maria Skelding Pinheiro; de Souza, Afonso Duarte L; da Silva, Felipe Moura A; Marinho, Andrey Moacir do R

2013-01-01

Bauhinia guianensis is a typical plant in the Amazon region belonging to the family Leguminosea, used by local populations for the treatment of infectious and renal diseases. Previous work on the plant B. guianensis led to the isolation of substances with anti-inflammatory and analgesic activities. Thus, compounds isolated from B. guianensis with antimicrobial activities had not been identified. Given that there is a possibility of biological activity reported for a given plant being found in the endophytic fungi, we decided to isolate endophytic fungi from B. guianensis and test their antimicrobial activities. The alkaloids known as fumigaclavine C and pseurotin A were isolated by column chromatography and identified by 1D and 2D NMR techniques and mass spectrometry. The alkaloids are first reported as broad-spectrum antibacterial agents with good activity.

N-cadherin in adult rat cardiomyocytes in culture. II. Spatio-temporal appearance of proteins involved in cell-cell contact and communication. Formation of two distinct N-cadherin/catenin complexes.

PubMed

Hertig, C M; Butz, S; Koch, S; Eppenberger-Eberhardt, M; Kemler, R; Eppenberger, H M

1996-01-01

The spatio-temporal appearance and distribution of proteins forming the intercalated disc were investigated in adult rat cardiomyocytes (ARC). The 'redifferentiation model' of ARC involves extensive remodelling of the plasma membrane and of the myofibrillar apparatus. It represents a valuable system to elucidate the formation of cell-cell contact between cardiomyocytes and to assess the mechanisms by which different proteins involved in the cell-cell adhesion process are sorted in a precise manner to the sites of function. Appearance of N-cadherin, the catenins and connexin43 within newly formed adherens and gap junctions was studied. Here first evidence is provided for a formation of two distinct and separable N-cadherin/catenin complexes in cardiomyocytes. Both complexes are composed of N-cadherin and alpha-catenin which bind to either beta-catenin or plakoglobin in a mutually exclusive manner. The two N-cadherin/catenin complexes are assumed to be functionally involved in the formation of cell-cell contacts in ARC; however, the differential appearance and localization of the two types of complexes may also point to a specific role during ARC differentiation. The newly synthesized beta-catenin containing complex is more abundant during the first stages in culture after ARC isolation, while the newly synthesized plakoglobin containing complex progressively accumulates during the morphological changes of ARC. ARC formed a tissue-like pattern in culture whereby the new cell-cell contacts could be dissolved through Ca2+ depletion. Presence of cAMP and replenishment of Ca2+ content in the culture medium not only allowed reformation of cell-cell contacts but also affected the relative protein ratio between the two N-cadherin/catenin complexes, increasing the relative amount of newly synthesized beta-catenin over plakoglobin at a particular stage of ARC differentiation. The clustered N-cadherin/catenin complexes at the plasma membrane appear to be a prerequisite for the following gap junction formation; a temporal sequence of the appearance of adherens junction proteins and of gap junctions forming connexin-43 is suggested.

Preparation of Gap Junctions in Membrane Microdomains for Immunoprecipitation and Mass Spectrometry Interactome Analysis.

PubMed

Fowler, Stephanie; Akins, Mark; Bennett, Steffany A L

2016-01-01

Protein interaction networks at gap junction plaques are increasingly implicated in a variety of intracellular signaling cascades. Identifying protein interactions of integral membrane proteins is a valuable tool for determining channel function. However, several technical challenges exist. Subcellular fractionation of the bait protein matrix is usually required to identify less abundant proteins in complex homogenates. Sufficient solvation of the lipid environment without perturbation of the protein interactome must also be achieved. The present chapter describes the flotation of light and heavy liver tissue membrane microdomains to facilitate the identification and analysis of endogenous gap junction proteins and includes technical notes for translation to other integral membrane proteins, tissues, or cell culture models. These procedures are valuable tools for the enrichment of gap junction membrane compartments and for the identification of gap junction signaling interactomes.

Live-cell imaging of ER-PM contact architecture by a novel TIRFM approach reveals extension of junctions in response to store-operated Ca2+-entry.

PubMed

Poteser, Michael; Leitinger, Gerd; Pritz, Elisabeth; Platzer, Dieter; Frischauf, Irene; Romanin, Christoph; Groschner, Klaus

2016-10-19

Nanometer-spaced appositions between endoplasmic reticulum and plasma membrane (ER-PM junctions) stabilized by membrane-joining protein complexes are critically involved in cellular Ca 2+ -handling and lipid trafficking. ER-PM junctional architecture and plasticity associated with inter-membrane communication are as yet barely understood. Here, we introduce a method to precisely characterize ER-PM junction morphology and dynamics with high temporal resolution and minimal disturbance of junctional intermembrane communication. We show that expression of soluble cytosolic fluorophores in combination with TIRFM enables to delineate ER and PM distance in the range of 10-150 nm. Live-cell imaging of sub-plasmalemmal structures in RBL-2H3 mast cells by this method, designated as fluorescence density mapping (FDM), revealed profound dynamics of ER-PM contact sites in response to store-depletion. We report the existence of a Ca 2+ -dependent process that expands the junctional ER to enlarge its contact surface with the PM, thereby promoting and stabilizing STIM1-Orai1 competent ER-PM junctions.

Proteomic analysis of laser capture microscopy purified myotendinous junction regions from muscle sections

PubMed Central

2014-01-01

The myotendinous junction is a specialized structure of the muscle fibre enriched in mechanosensing complexes, including costameric proteins and core elements of the z-disc. Here, laser capture microdissection was applied to purify membrane regions from the myotendinous junctions of mouse skeletal muscles, which were then processed for proteomic analysis. Sarcolemma sections from the longitudinal axis of the muscle fibre were used as control for the specificity of the junctional preparation. Gene ontology term analysis of the combined lists indicated a statistically significant enrichment in membrane-associated proteins. The myotendinous junction preparation contained previously uncharacterized proteins, a number of z-disc costameric ligands (e.g., actinins, capZ, αB cristallin, filamin C, cypher, calsarcin, desmin, FHL1, telethonin, nebulin, titin and an enigma-like protein) and other proposed players of sarcomeric stretch sensing and signalling, such as myotilin and the three myomesin homologs. A subset were confirmed by immunofluorescence analysis as enriched at the myotendinous junction, suggesting that laser capture microdissection from muscle sections is a valid approach to identify novel myotendinous junction players potentially involved in mechanotransduction pathways. PMID:25071420

Kinase programs spatiotemporally regulate gap junction assembly and disassembly: effects on wound repair

PubMed Central

Solan, Joell L.; Lampe, Paul D.

2016-01-01

Gap junctions are highly ordered plasma membrane domains that are constantly assembled, remodeled and turned over due to the short half-life of connexins, the integral membrane proteins that form gap junctions. Connexin 43 (Cx43), by far the most widely expressed connexin, is phosphorylated at multiple serine residues in the cytoplasmic, C-terminal region allowing for exquisite cellular control over gap junctional communication. This is evident during epidermal wounding where spatiotemporal changes in connexin expression occur as cells are instructed whether to die, proliferate or migrate to promote repair. Early gap junctional communication is required for initiation of keratinocyte migration, but accelerated Cx43 turnover is also critical for proper wound healing at later stages. These events are controlled via a "kinase program" where sequential phosphorylation of Cx43 leads to reductions in Cx43’s half-life and significant depletion of gap junctions from the plasma membrane within several hours. The complex regulation of gap junction assembly and turnover affords several steps where intervention might speed wound healing. PMID:26706150

Kinase programs spatiotemporally regulate gap junction assembly and disassembly: Effects on wound repair.

PubMed

Solan, Joell L; Lampe, Paul D

2016-02-01

Gap junctions are highly ordered plasma membrane domains that are constantly assembled, remodeled and turned over due to the short half-life of connexins, the integral membrane proteins that form gap junctions. Connexin 43 (Cx43), by far the most widely expressed connexin, is phosphorylated at multiple serine residues in the cytoplasmic, C-terminal region allowing for exquisite cellular control over gap junctional communication. This is evident during epidermal wounding where spatiotemporal changes in connexin expression occur as cells are instructed whether to die, proliferate or migrate to promote repair. Early gap junctional communication is required for initiation of keratinocyte migration, but accelerated Cx43 turnover is also critical for proper wound healing at later stages. These events are controlled via a "kinase program" where sequential phosphorylation of Cx43 leads to reductions in Cx43's half-life and significant depletion of gap junctions from the plasma membrane within several hours. The complex regulation of gap junction assembly and turnover affords several steps where intervention might speed wound healing. Copyright © 2015 Elsevier Ltd. All rights reserved.

Resolution of model Holliday junctions by yeast endonuclease: effect of DNA structure and sequence.

PubMed Central

Parsons, C A; Murchie, A I; Lilley, D M; West, S C

1989-01-01

The resolution of Holliday junctions in DNA involves specific cleavage at or close to the site of the junction. A nuclease from Saccharomyces cerevisiae cleaves model Holliday junctions in vitro by the introduction of nicks in regions of duplex DNA adjacent to the crossover point. In previous studies [Parsons and West (1988) Cell, 52, 621-629] it was shown that cleavage occurred within homologous arm sequences with precise symmetry across the junction. In contrast, junctions with heterologous arm sequences were cleaved asymmetrically. In this work, we have studied the effect of sequence changes and base modification upon the site of cleavage. It is shown that the specificity of cleavage is unchanged providing that perfect homology is maintained between opposing arm sequences. However, in the absence of homology, cleavage depends upon sequence context and is affected by minor changes such as base modification. These data support the proposed mechanism for cleavage of a Holliday junction, which requires homologous alignment of arm sequences in an enzyme--DNA complex as a prerequisite for symmetrical cleavage by the yeast endonuclease. Images PMID:2653810

Structure and function of gap junction proteins: role of gap junction proteins in embryonic heart development.

PubMed

Ahir, Bhavesh K; Pratten, Margaret K

2014-01-01

Intercellular (cell-to-cell) communication is a crucial and complex mechanism during embryonic heart development. In the cardiovascular system, the beating of the heart is a dynamic and key regulatory process, which is functionally regulated by the coordinated spread of electrical activity through heart muscle cells. Heart tissues are composed of individual cells, each bearing specialized cell surface membrane structures called gap junctions that permit the intercellular exchange of ions and low molecular weight molecules. Gap junction channels are essential in normal heart function and they assist in the mediated spread of electrical impulses that stimulate synchronized contraction (via an electrical syncytium) of cardiac tissues. This present review describes the current knowledge of gap junction biology. In the first part, we summarise some relevant biochemical and physiological properties of gap junction proteins, including their structure and function. In the second part, we review the current evidence demonstrating the role of gap junction proteins in embryonic development with particular reference to those involved in embryonic heart development. Genetics and transgenic animal studies of gap junction protein function in embryonic heart development are considered and the alteration/disruption of gap junction intercellular communication which may lead to abnormal heart development is also discussed.

Generation of sub-femtoliter droplet by T-junction splitting on microfluidic chips

NASA Astrophysics Data System (ADS)

Yang, Yu-Jun; Feng, Xuan; Xu, Na; Pang, Dai-Wen; Zhang, Zhi-Ling

2013-03-01

In the paper, sub-femtoliter droplets were easily produced by droplet splitting at a simple T-junction with orifice, which did not need expensive equipments, complex photolithography skill, or high energy input. The volume of the daughter droplet was not limited by channel size but controlled by channel geometry and fluidic characteristic. Moreover, single bead sampling and bead quantification in different orders of magnitude of droplet volumes were investigated. The droplets split at our T-junction chip had small volume and monodispersed size and could be produced efficiently, orderly, and controllably.

Regulation of Endothelial Adherens Junctions by Tyrosine Phosphorylation

PubMed Central

Adam, Alejandro Pablo

2015-01-01

Endothelial cells form a semipermeable, regulated barrier that limits the passage of fluid, small molecules, and leukocytes between the bloodstream and the surrounding tissues. The adherens junction, a major mechanism of intercellular adhesion, is comprised of transmembrane cadherins forming homotypic interactions between adjacent cells and associated cytoplasmic catenins linking the cadherins to the cytoskeleton. Inflammatory conditions promote the disassembly of the adherens junction and a loss of intercellular adhesion, creating openings or gaps in the endothelium through which small molecules diffuse and leukocytes transmigrate. Tyrosine kinase signaling has emerged as a central regulator of the inflammatory response, partly through direct phosphorylation and dephosphorylation of the adherens junction components. This review discusses the findings that support and those that argue against a direct effect of cadherin and catenin phosphorylation in the disassembly of the adherens junction. Recent findings indicate a complex interaction between kinases, phosphatases, and the adherens junction components that allow a fine regulation of the endothelial permeability to small molecules, leukocyte migration, and barrier resealing. PMID:26556953

Carcinoembryonic antigen promotes colorectal cancer progression by targeting adherens junction complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bajenova, Olga, E-mail: o.bazhenova@spbu.ru; Department of Genetics and Biotechnology, St. Petersburg State University, St. Petersburg 199034; Department of Surgery and Biomedical Sciences, Creighton University, Omaha, NE 68178

2014-06-10

Oncomarkers play important roles in the detection and management of human malignancies. Carcinoembryonic antigen (CEA, CEACAM5) and epithelial cadherin (E-cadherin) are considered as independent tumor markers in monitoring metastatic colorectal cancer. They are both expressed by cancer cells and can be detected in the blood serum. We investigated the effect of CEA production by MIP101 colorectal carcinoma cell lines on E-cadherin adherens junction (AJ) protein complexes. No direct interaction between E-cadherin and CEA was detected; however, the functional relationships between E-cadherin and its AJ partners: α-, β- and p120 catenins were impaired. We discovered a novel interaction between CEA andmore » beta-catenin protein in the CEA producing cells. It is shown in the current study that CEA overexpression alters the splicing of p120 catenin and triggers the release of soluble E-cadherin. The influence of CEA production by colorectal cancer cells on the function of E-cadherin junction complexes may explain the link between the elevated levels of CEA and the increase in soluble E-cadherin during the progression of colorectal cancer. - Highlights: • Elevated level of CEA increases the release of soluble E-cadherin during the progression of colorectal cancer. • CEA over-expression alters the binding preferences between E-cadherin and its partners: α-, β- and p120 catenins in adherens junction complexes. • CEA produced by colorectal cancer cells interacts with beta-catenin protein. • CEA over-expression triggers the increase in nuclear beta-catenin. • CEA over-expression alters the splicing of p120 catenin protein.« less

Shear zone junctions: Of zippers and freeways

NASA Astrophysics Data System (ADS)

Passchier, Cees W.; Platt, John P.

2017-02-01

Ductile shear zones are commonly treated as straight high-strain domains with uniform shear sense and characteristic curved foliation trails, bounded by non-deforming wall rock. Many shear zones, however, are branched, and if movement on such branches is contemporaneous, the resulting shape can be complicated and lead to unusual shear sense arrangement and foliation geometries in the wall rock. For Y-shaped shear zone triple junctions with three joining branches and transport direction at a high angle to the branchline, only eight basic types of junction are thought to be stable and to produce significant displacement. The simplest type, called freeway junctions, have similar shear sense in all three branches. The other types show joining or separating behaviour of shear zone branches similar to the action of a zipper. Such junctions may have shear zone branches that join to form a single branch (closing zipper junction), or a single shear zone that splits to form two branches, (opening zipper junction). All categories of shear zone junctions show characteristic foliation patterns and deflection of markers in the wall rock. Closing zipper junctions are unusual, since they form a non-active zone with opposite deflection of foliations in the wall rock known as an extraction fault or wake. Shear zipper junctions can form domains of overprinting shear sense along their flanks. A small and large field example are given from NE Spain and Eastern Anatolia. The geometry of more complex, 3D shear zone junctions with slip parallel and oblique to the branchline is briefly discussed.

Gap junctions contain different amounts of cholesterol which undergo unique sequestering processes during fiber cell differentiation in the embryonic chicken lens.

PubMed

Biswas, Sondip K; Lo, Woo-Kuen

2007-03-09

To determine the possible changes in the distribution of cholesterol in gap junction plaques during fiber cell differentiation and maturation in the embryonic chicken lens. The possible mechanism by which cholesterol is removed from gap junction plaques is also investigated. Filipin cytochemistry in conjunction with freeze-fracture TEM was used to visualize cholesterol, as represented by filipin-cholesterol complexes (FCCs) in gap junction plaques. Quantitative analysis on the heterogeneous distribution of cholesterol in gap junction plaques was conducted from outer and inner cortical regions. A novel technique combining filipin cytochemistry with freeze-fracture replica immunogold labeling (FRIL) was used to label Cx45.6 and Cx56 antibodies in cholesterol-containing gap junctions. Filipin cytochemistry and freeze-fracture TEM and thin-section TEM were used to examine the appearance and nature of the cholesterol-containing vesicular structures associated with gap junction plaques. Chicken lens fibers contain cholesterol-rich, cholesterol-intermediate and cholesterol-free gap junction populations in both outer and inner cortical regions. Filipin cytochemistry and FRIL studies confirmed that cholesterol-containing junctions were gap junctions. Quantitative analysis showed that approximately 86% of gap junctions in the outer cortical zone were cholesterol-rich gap junctions, whereas approximately 81% of gap junctions in the inner cortical zone were cholesterol-free gap junctions. A number of pleiomorphic cholesterol-rich vesicles of varying sizes were often observed in the gap junction plaques. They appear to be involved in the removal of cholesterol from gap junction plaques through endocytosis. Gap junctions in the young fibers are enriched with cholesterol because they are assembled in the unique cholesterol-rich cell membranes in the lens. A majority of cholesterol-rich gap junctions in the outer young fibers are transformed into cholesterol-free ones in the inner mature fibers during fiber cell maturation. A distinct endocytotic process appears to be involved in removing cholesterol from the cholesterol-containing gap junctions, and it may play a major role in the transformation of cholesterol-rich gap junctions into cholesterol-free ones during fiber cell maturation.

Geodynamical simulation of the RRF triple junction

NASA Astrophysics Data System (ADS)

Wang, Z.; Wei, D.; Liu, M.; Shi, Y.; Wang, S.

2017-12-01

Triple junction is the point at which three plate boundaries meet. Three plates at the triple junction form a complex geological tectonics, which is a natural laboratory to study the interactions of plates. This work studies a special triple junction, the oceanic transform fault intersects the collinear ridges with different-spreading rates, which is free of influence of ridge-transform faults and nearby hotspots. First, we build 3-D numerical model of this triple junction used to calculate the stead-state velocity and temperature fields resulting from advective and conductive heat transfer. We discuss in detail the influence of the velocity and temperature fields of the triple junction from viscosity, spreading rate of the ridge. The two sides of the oceanic transform fault are different sensitivities to the two factors. And, the influence of the velocity mainly occurs within 200km of the triple junction. Then, we modify the model by adding a ridge-transform fault to above model and directly use the velocity structure of the Macquarie triple junction. The simulation results show that the temperature at both sides of the oceanic transform fault decreases gradually from the triple junction, but the temperature difference between the two sides is a constant about 200°. And, there is little effect of upwelling velocity away from the triple junction 100km. The model results are compared with observational data. The heat flux and thermal topography along the oceanic transform fault of this model are consistent with the observed data of the Macquarie triple junction. The earthquakes are strike slip distributed along the oceanic transform fault. Their depths are also consistent with the zone of maximum shear stress. This work can help us to understand the interactions of plates of triple junctions and help us with the foundation for the future study of triple junctions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Qiang; Zhou, Liping, E-mail: zhoulp@suda.edu.cn; Cheng, Jue-Fei

Electronic structures and coherent quantum transport properties are explored for spin-crossover molecule iron-benzene Fe(Bz){sub 2} using density functional theory combined with non-equilibrium Green’s function. High- and low-spin states are investigated for two different lead-molecule junctions. It is found that the asymmetrical T-shaped contact junction in the high-spin state behaves as an efficient spin filter while it has a smaller conductivity than that in the low-spin state. Large spin Seebeck effect is also observed in asymmetrical T-shaped junction. Spin-polarized properties are absent in the symmetrical H-shaped junction. These findings strongly suggest that both the electronic and contact configurations play significant rolesmore » in molecular devices and metal-benzene complexes are promising materials for spintronics and thermo-spintronics.« less

Carbon Nanotube Based Molecular Electronics

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Saini, Subhash; Menon, Madhu

1998-01-01

Carbon nanotubes and the nanotube heterojunctions have recently emerged as excellent candidates for nanoscale molecular electronic device components. Experimental measurements on the conductivity, rectifying behavior and conductivity-chirality correlation have also been made. While quasi-one dimensional simple heterojunctions between nanotubes with different electronic behavior can be generated by introduction of a pair of heptagon-pentagon defects in an otherwise all hexagon graphene sheet. Other complex 3- and 4-point junctions may require other mechanisms. Structural stability as well as local electronic density of states of various nanotube junctions are investigated using a generalized tight-binding molecular dynamics (GDBMD) scheme that incorporates non-orthogonality of the orbitals. The junctions investigated include straight and small angle heterojunctions of various chiralities and diameters; as well as more complex 'T' and 'Y' junctions which do not always obey the usual pentagon-heptagon pair rule. The study of local density of states (LDOS) reveal many interesting features, most prominent among them being the defect-induced states in the gap. The proposed three and four pointjunctions are one of the smallest possible tunnel junctions made entirely of carbon atoms. Furthermore the electronic behavior of the nanotube based device components can be taylored by doping with group III-V elements such as B and N, and BN nanotubes as a wide band gap semiconductor has also been realized in experiments. Structural properties of heteroatomic nanotubes comprising C, B and N will be discussed.

Apoptosis of enterocytes and nitration of junctional complex proteins promote alcohol-induced gut leakiness and liver injury.

PubMed

Cho, Young-Eun; Yu, Li-Rong; Abdelmegeed, Mohamed A; Yoo, Seong-Ho; Song, Byoung-Joon

2018-07-01

Binge alcohol exposure causes gut leakiness, contributing to increased endotoxemia and inflammatory liver injury, although the molecular mechanisms are still elusive. This study was aimed at investigating the roles of apoptosis of enterocytes and nitration followed by degradation of intestinal tight junction (TJ) and adherens junction (AJ) proteins in binge alcohol-induced gut leakiness. The levels of intestinal (ileum) junctional complex proteins, oxidative stress markers and apoptosis-related proteins in rodents, T84 colonic cells and autopsied human ileums were determined by immunoblot, immunoprecipitation, immunofluorescence, and mass-spectral analyses. Binge alcohol exposure caused apoptosis of gut enterocytes with elevated serum endotoxin and liver injury. The levels of intestinal CYP2E1, iNOS, nitrated proteins and apoptosis-related marker proteins were significantly elevated in binge alcohol-exposed rodents. Differential, quantitative mass-spectral analyses of the TJ-enriched fractions of intestinal epithelial layers revealed that several TJ, AJ and desmosome proteins were decreased in binge alcohol-exposed rats compared to controls. Consistently, the levels of TJ proteins (claudin-1, claudin-4, occludin and zonula occludens-1), AJ proteins (β-catenin and E-cadherin) and desmosome plakoglobin were very low in binge alcohol-exposed rats, wild-type mice, and autopsied human ileums but not in Cyp2e1-null mice. Additionally, pretreatment with specific inhibitors of CYP2E1 and iNOS prevented disorganization and/or degradation of TJ proteins in alcohol-exposed T84 colonic cells. Furthermore, immunoprecipitation followed by immunoblot confirmed that intestinal TJ and AJ proteins were nitrated and degraded via ubiquitin-dependent proteolysis, resulting in their decreased levels. These results demonstrated for the first time the critical roles of CYP2E1, apoptosis of enterocytes, and nitration followed by ubiquitin-dependent proteolytic degradation of the junctional complex proteins, in promoting binge alcohol-induced gut leakiness and endotoxemia, contributing to inflammatory liver disease. Binge alcohol exposure causes gut leakiness, contributing to increased endotoxemia and inflammatory liver injury. Our results demonstrated for the first time the critical roles of apoptosis of enterocytes and nitration followed by ubiquitin-dependent proteolytic degradation of the junctional complex proteins in promoting this gut leakiness and endotoxemia. These results provide insight into the molecular mechanisms of alcohol-induced inflammatory liver disease. Published by Elsevier B.V.

Gap junctional communication modulates gene transcription by altering the recruitment of Sp1 and Sp3 to connexin-response elements in osteoblast promoters

NASA Technical Reports Server (NTRS)

Stains, Joseph P.; Lecanda, Fernando; Screen, Joanne; Towler, Dwight A.; Civitelli, Roberto

2003-01-01

Loss-of-function mutations of gap junction proteins, connexins, represent a mechanism of disease in a variety of tissues. We have shown that recessive (gene deletion) or dominant (connexin45 overexpression) disruption of connexin43 function results in osteoblast dysfunction and abnormal expression of osteoblast genes, including down-regulation of osteocalcin transcription. To elucidate the molecular mechanisms of gap junction-sensitive transcriptional regulation, we systematically analyzed the rat osteocalcin promoter for sensitivity to gap junctional intercellular communication. We identified an Sp1/Sp3 containing complex that assembles on a minimal element in the -70 to -57 region of the osteocalcin promoter in a gap junction-dependent manner. This CT-rich connexin-response element is necessary and sufficient to confer gap junction sensitivity to the osteocalcin proximal promoter. Repression of osteocalcin transcription occurs as a result of displacement of the stimulatory Sp1 by the inhibitory Sp3 on the promoter when gap junctional communication is perturbed. Modulation of Sp1/Sp3 recruitment also occurs on the collagen Ialpha1 promoter and translates into gap junction-sensitive transcriptional control of collagen Ialpha1 gene expression. Thus, regulation of Sp1/Sp3 recruitment to the promoter may represent a potential general mechanism for transcriptional control of target genes by signals passing through gap junctions.

Dielectric properties of biological tissues in which cells are connected by communicating junctions

NASA Astrophysics Data System (ADS)

Asami, Koji

2007-06-01

The frequency dependence of the complex permittivity of biological tissues has been simulated using a simple model that is a cubic array of spherical cells in a parallel plate capacitor. The cells are connected by two types of communicating junctions: one is a membrane-lined channel for plasmodesmata in plant tissues, and the other is a conducting patch of adjoining plasma membranes for gap junctions in animal tissues. Both junctions provided similar effects on the dielectric properties of the tissue model. The model without junction showed a dielectric relaxation (called β-dispersion) that was expected from an interfacial polarization theory for a concentrated suspension of spherical cells. The dielectric relaxation was the same as that of the model in which neighbouring cells were connected by junctions perpendicular to the applied electric field. When neighbouring cells were connected by junctions parallel to the applied electric field or in all directions, a dielectric relaxation appeared at a lower frequency side in addition to the β-dispersion, corresponding to the so called α-dispersion. When junctions were randomly introduced at varied probabilities Pj, the low-frequency (LF) relaxation curve became broader, especially at Pj of 0.2-0.5, and its intensity was proportional to Pj up to 0.7. The intensity and the characteristic frequency of the LF relaxation both decreased with decreasing junction conductance. The simulations indicate that communicating junctions are important for understanding the LF dielectric relaxation in tissues.

The beneficial effects of cumulus cells and oocyte-cumulus cell gap junctions depends on oocyte maturation and fertilization methods in mice.

PubMed

Zhou, Cheng-Jie; Wu, Sha-Na; Shen, Jiang-Peng; Wang, Dong-Hui; Kong, Xiang-Wei; Lu, Angeleem; Li, Yan-Jiao; Zhou, Hong-Xia; Zhao, Yue-Fang; Liang, Cheng-Guang

2016-01-01

Cumulus cells are a group of closely associated granulosa cells that surround and nourish oocytes. Previous studies have shown that cumulus cells contribute to oocyte maturation and fertilization through gap junction communication. However, it is not known how this gap junction signaling affects in vivo versus in vitro maturation of oocytes, and their subsequent fertilization and embryonic development following insemination. Therefore, in our study, we performed mouse oocyte maturation and insemination using in vivo- or in vitro-matured oocyte-cumulus complexes (OCCs, which retain gap junctions between the cumulus cells and the oocytes), in vitro-matured, denuded oocytes co-cultured with cumulus cells (DCs, which lack gap junctions between the cumulus cells and the oocytes), and in vitro-matured, denuded oocytes without cumulus cells (DOs). Using these models, we were able to analyze the effects of gap junction signaling on oocyte maturation, fertilization, and early embryo development. We found that gap junctions were necessary for both in vivo and in vitro oocyte maturation. In addition, for oocytes matured in vivo, the presence of cumulus cells during insemination improved fertilization and blastocyst formation, and this improvement was strengthened by gap junctions. Moreover, for oocytes matured in vitro, the presence of cumulus cells during insemination improved fertilization, but not blastocyst formation, and this improvement was independent of gap junctions. Our results demonstrate, for the first time, that the beneficial effect of gap junction signaling from cumulus cells depends on oocyte maturation and fertilization methods.

Dbl3 drives Cdc42 signaling at the apical margin to regulate junction position and apical differentiation

PubMed Central

Zihni, Ceniz; Munro, Peter M.G.; Elbediwy, Ahmed; Keep, Nicholas H.; Terry, Stephen J.; Harris, John

2014-01-01

Epithelial cells develop morphologically characteristic apical domains that are bordered by tight junctions, the apical–lateral border. Cdc42 and its effector complex Par6–atypical protein kinase c (aPKC) regulate multiple steps during epithelial differentiation, but the mechanisms that mediate process-specific activation of Cdc42 to drive apical morphogenesis and activate the transition from junction formation to apical differentiation are poorly understood. Using a small interfering RNA screen, we identify Dbl3 as a guanine nucleotide exchange factor that is recruited by ezrin to the apical membrane, that is enriched at a marginal zone apical to tight junctions, and that drives spatially restricted Cdc42 activation, promoting apical differentiation. Dbl3 depletion did not affect junction formation but did affect epithelial morphogenesis and brush border formation. Conversely, expression of active Dbl3 drove process-specific activation of the Par6–aPKC pathway, stimulating the transition from junction formation to apical differentiation and domain expansion, as well as the positioning of tight junctions. Thus, Dbl3 drives Cdc42 signaling at the apical margin to regulate morphogenesis, apical–lateral border positioning, and apical differentiation. PMID:24379416

Measurement of Aharonov-Casher effect in a Josephson junction chain

NASA Astrophysics Data System (ADS)

Pop, Ioan Mihai; Lecocq, Florent; Pannetier, Bernard; Buisson, Olivier; Guichard, Wiebke

2011-03-01

We have recently measured the effect of superconducting phase-slips on the ground state of a Josephson junction chain and a rhombi chain. Here we report clear evidence of Aharonov-Casher effect in a chain of Josephson junctions. This phenomenon is the dual of the well known Aharonov-Bohm interference. Using a capacitively coupled gate to the islands of the chain, we induce oscillations of the supercurrent by tuning the polarization charges on the islands. We observe complex interference patterns for different quantum phase slip amplitudes, that we understand quantitatively as Aharonov-Casher vortex interferences. European STREP MIDAS.

Single-molecule FRET studies of the cooperative and non-cooperative binding kinetics of the bacteriophage T4 single-stranded DNA binding protein (gp32) to ssDNA lattices at replication fork junctions

PubMed Central

Lee, Wonbae; Gillies, John P.; Jose, Davis; Israels, Brett A.; von Hippel, Peter H.; Marcus, Andrew H.

2016-01-01

Gene 32 protein (gp32) is the single-stranded (ss) DNA binding protein of the bacteriophage T4. It binds transiently and cooperatively to ssDNA sequences exposed during the DNA replication process and regulates the interactions of the other sub-assemblies of the replication complex during the replication cycle. We here use single-molecule FRET techniques to build on previous thermodynamic studies of gp32 binding to initiate studies of the dynamics of the isolated and cooperative binding of gp32 molecules within the replication complex. DNA primer/template (p/t) constructs are used as models to determine the effects of ssDNA lattice length, gp32 concentration, salt concentration, binding cooperativity and binding polarity at p/t junctions. Hidden Markov models (HMMs) and transition density plots (TDPs) are used to characterize the dynamics of the multi-step assembly pathway of gp32 at p/t junctions of differing polarity, and show that isolated gp32 molecules bind to their ssDNA targets weakly and dissociate quickly, while cooperatively bound dimeric or trimeric clusters of gp32 bind much more tightly, can ‘slide’ on ssDNA sequences, and exhibit binding dynamics that depend on p/t junction polarities. The potential relationships of these binding dynamics to interactions with other components of the T4 DNA replication complex are discussed. PMID:27694621

Protein phosphatase 2A associates with and regulates atypical PKC and the epithelial tight junction complex

PubMed Central

Nunbhakdi-Craig, Viyada; Machleidt, Thomas; Ogris, Egon; Bellotto, Dennis; White, Charles L.; Sontag, Estelle

2002-01-01

Tight junctions (TJs) play a crucial role in the establishment of cell polarity and regulation of paracellular permeability in epithelia. Here, we show that upon calcium-induced junction biogenesis in Madin-Darby canine kidney cells, ABαC, a major protein phosphatase (PP)2A holoenzyme, is recruited to the apical membrane where it interacts with the TJ complex. Enhanced PP2A activity induces dephosphorylation of the TJ proteins, ZO-1, occludin, and claudin-1, and is associated with increased paracellular permeability. Expression of PP2A catalytic subunit severely prevents TJ assembly. Conversely, inhibition of PP2A by okadaic acid promotes the phosphorylation and recruitment of ZO-1, occludin, and claudin-1 to the TJ during junctional biogenesis. PP2A negatively regulates TJ assembly without appreciably affecting the organization of F-actin and E-cadherin. Significantly, inhibition of atypical PKC (aPKC) blocks the calcium- and serum-independent membrane redistribution of TJ proteins induced by okadaic acid. Indeed, PP2A associates with and critically regulates the activity and distribution of aPKC during TJ formation. Thus, we provide the first evidence for calcium-dependent targeting of PP2A in epithelial cells, we identify PP2A as the first serine/threonine phosphatase associated with the multiprotein TJ complex, and we unveil a novel role for PP2A in the regulation of epithelial aPKC and TJ assembly and function. PMID:12196510

Holding Tight: Cell Junctions and Cancer Spread.

PubMed

Knights, Alexander J; Funnell, Alister P W; Crossley, Merlin; Pearson, Richard C M

2012-01-01

Cell junctions are sites of intercellular adhesion that maintain the integrity of epithelial tissue and regulate signalling between cells. These adhesive junctions are comprised of protein complexes that serve to establish an intercellular cytoskeletal network for anchoring cells, in addition to regulating cell polarity, molecular transport and communication. The expression of cell adhesion molecules is tightly controlled and their downregulation is essential for epithelial-mesenchymal transition (EMT), a process that facilitates the generation of morphologically and functionally diverse cell types during embryogenesis. The characteristics of EMT are a loss of cell adhesion and increased cellular mobility. Hence, in addition to its normal role in development, dysregulated EMT has been linked to cancer progression and metastasis, the process whereby primary tumors migrate to invasive secondary sites in the body. This paper will review the current understanding of cell junctions and their role in cancer, with reference to the abnormal regulation of junction protein genes. The potential use of cell junction molecules as diagnostic and prognostic markers will also be discussed, as well as possible therapies for adhesive dysregulation.

C-terminal Src kinase (Csk) regulates the tricellular junction protein Gliotactin independent of Src

PubMed Central

Samarasekera, G. D. N. Gayathri; Auld, Vanessa Jane

2018-01-01

Tricellular junctions (TCJs) are uniquely placed permeability barriers formed at the corners of polarized epithelia where tight junctions in vertebrates or septate junctions (SJ) in invertebrates from three cells converge. Gliotactin is a Drosophila TCJ protein, and loss of Gliotactin results in SJ and TCJ breakdown and permeability barrier loss. When overexpressed, Gliotactin spreads away from the TCJs, resulting in disrupted epithelial architecture, including overproliferation, cell delamination, and migration. Gliotactin levels are tightly controlled at the mRNA level and at the protein level through endocytosis and degradation triggered by tyrosine phosphorylation. We identified C-terminal Src kinase (Csk) as a tyrosine kinase responsible for regulating Gliotactin endocytosis. Increased Csk suppresses the Gliotactin overexpression phenotypes by increasing endocytosis. Loss of Csk causes Gliotactin to spread away from the TCJ. Although Csk is known as a negative regulator of Src kinases, the effects of Csk on Gliotactin are independent of Src and likely occur through an adherens junction associated complex. Overall, we identified a new Src-independent role for Csk in the control of Gliotactin, a key tricellular junction protein. PMID:29167383

FSGS3/CD2AP is a barbed-end capping protein that stabilizes actin and strengthens adherens junctions

PubMed Central

Brieher, William M.

2013-01-01

By combining in vitro reconstitution biochemistry with a cross-linking approach, we have identified focal segmental glomerulosclerosis 3/CD2-associated protein (FSGS3/CD2AP) as a novel actin barbed-end capping protein responsible for actin stability at the adherens junction. FSGS3/CD2AP colocalizes with E-cadherin and α-actinin-4 at the apical junction in polarized Madin-Darby canine kidney (MDCK) cells. Knockdown of FSGS3/CD2AP compromised actin stability and decreased actin accumulation at the adherens junction. Using a novel apparatus to apply mechanical stress to cell–cell junctions, we showed that knockdown of FSGS3/CD2AP compromised adhesive strength, resulting in tearing between cells and disruption of barrier function. Our results reveal a novel function of FSGS3/CD2AP and a previously unrecognized role of barbed-end capping in junctional actin dynamics. Our study underscores the complexity of actin regulation at cell–cell contacts that involves actin activators, inhibitors, and stabilizers to control adhesive strength, epithelial behavior, and permeability barrier integrity. PMID:24322428

Tight junctions in inflammatory bowel diseases and inflammatory bowel disease associated colorectal cancer

PubMed Central

Landy, Jonathan; Ronde, Emma; English, Nick; Clark, Sue K; Hart, Ailsa L; Knight, Stella C; Ciclitira, Paul J; Al-Hassi, Hafid Omar

2016-01-01

Inflammatory bowel diseases are characterised by inflammation that compromises the integrity of the epithelial barrier. The intestinal epithelium is not only a static barrier but has evolved complex mechanisms to control and regulate bacterial interactions with the mucosal surface. Apical tight junction proteins are critical in the maintenance of epithelial barrier function and control of paracellular permeability. The characterisation of alterations in tight junction proteins as key players in epithelial barrier function in inflammatory bowel diseases is rapidly enhancing our understanding of critical mechanisms in disease pathogenesis as well as novel therapeutic opportunities. Here we give an overview of recent literature focusing on the role of tight junction proteins, in particular claudins, in inflammatory bowel diseases and inflammatory bowel disease associated colorectal cancer. PMID:27003989

Cell polarity, cell adhesion, and spermatogenesis: role of cytoskeletons

PubMed Central

Li, Linxi; Gao, Ying; Chen, Haiqi; Jesus, Tito; Tang, Elizabeth; Li, Nan; Lian, Qingquan; Ge, Ren-shan; Cheng, C. Yan

2017-01-01

In the rat testis, studies have shown that cell polarity, in particular spermatid polarity, to support spermatogenesis is conferred by the coordinated efforts of the Par-, Crumbs-, and Scribble-based polarity complexes in the seminiferous epithelium. Furthermore, planar cell polarity (PCP) is conferred by PCP proteins such as Van Gogh-like 2 (Vangl2) in the testis. On the other hand, cell junctions at the Sertoli cell–spermatid (steps 8–19) interface are exclusively supported by adhesion protein complexes (for example, α6β1-integrin-laminin-α3,β3,γ3 and nectin-3-afadin) at the actin-rich apical ectoplasmic specialization (ES) since the apical ES is the only anchoring device in step 8–19 spermatids. For cell junctions at the Sertoli cell–cell interface, they are supported by adhesion complexes at the actin-based basal ES (for example, N-cadherin-β-catenin and nectin-2-afadin), tight junction (occludin-ZO-1 and claudin 11-ZO-1), and gap junction (connexin 43-plakophilin-2) and also intermediate filament-based desmosome (for example, desmoglein-2-desmocollin-2). In short, the testis-specific actin-rich anchoring device known as ES is crucial to support spermatid and Sertoli cell adhesion. Accumulating evidence has shown that the Par-, Crumbs-, and Scribble-based polarity complexes and the PCP Vangl2 are working in concert with actin- or microtubule-based cytoskeletons (or both) and these polarity (or PCP) protein complexes exert their effects through changes in the organization of the cytoskeletal elements across the seminiferous epithelium of adult rat testes. As such, there is an intimate relationship between cell polarity, cell adhesion, and cytoskeletal function in the testis. Herein, we critically evaluate these recent findings based on studies on different animal models. We also suggest some crucial future studies to be performed. PMID:28928959

Visualisation of Multiple Tight Junctional Complexes in Human Airway Epithelial Cells.

PubMed

Buckley, Alysia G; Looi, Kevin; Iosifidis, Thomas; Ling, Kak-Ming; Sutanto, Erika N; Martinovich, Kelly M; Kicic-Starcevich, Elizabeth; Garratt, Luke W; Shaw, Nicole C; Lannigan, Francis J; Larcombe, Alexander N; Zosky, Graeme; Knight, Darryl A; Rigby, Paul J; Kicic, Anthony; Stick, Stephen M

2018-01-01

Apically located tight junctions in airway epithelium perform a fundamental role in controlling macromolecule migration through paracellular spaces. Alterations in their expression may lead to disruptions in barrier integrity, which subsequently facilitates entry of potential bacterial and other pathogens into the host. Furthermore, there is emerging evidence that the barrier integrity of the airway in certain airway inflammatory diseases may be altered. However, there is little consensus on the way this is assessed and measured and the type of cells used to achieve this. Here, we assessed four fixation methods including; (i) 4% ( v /v) paraformaldehyde; (ii) 100% methanol; (iii) acetone or; (iv) 1:1 methanol: acetone. Pre-extraction with Triton X-100 was also performed and assessed on cells prior to fixation with either methanol or paraformaldehyde. Cells were also permeabilized with 0.1% (v/v) Saponin in 1× TBS following fixation and subsequently stained for tight junction proteins. Confocal microscopy was then used to visualise, compare and evaluate staining intensity of the tight junctional complexes in order to determine a standardised workflow of reproducible staining. Positive staining was observed following methanol fixation for claudin-1 and ZO-1 tight junction proteins but no staining was detected for occludin in 16HBE14o- cells. Combinatorial fixation with methanol and acetone also produced consistent positive staining for both occludin and ZO-1 tight junction proteins in these cells. When assessed using primary cells cultured at air-liquid interface, similar positive staining for claudin-1 and ZO-1 was observed following methanol fixation, while similar positive staining for occludin and ZO-1 was observed following the same combinatorial fixation with methanol and acetone. The present study demonstrates the importance of a personalised approach to optimise staining for the visualisation of different tight junction proteins. Of significance, the workflow, once optimised, can readily be translated into primary airway epithelial cell air-liquid interface cultures where it can be used to assess barrier integrity in chronic lung diseases.

The adherens junction is lost during normal pregnancy but not during ovarian hyperstimulated pregnancy.

PubMed

Dowland, Samson N; Madawala, Romanthi J; Lindsay, Laura A; Murphy, Christopher R

2016-03-01

During early pregnancy in the rat, the luminal uterine epithelial cells (UECs) must transform to a receptive state to permit blastocyst attachment and implantation. The implantation process involves penetration of the epithelial barrier, so it is expected that the transformation of UECs includes alterations in the lateral junctional complex. Previous studies have demonstrated a deepening of the tight junction (zonula occludens) and a reduction in the number of desmosomes (macula adherens) in UECs at the time of implantation. However, the adherens junction (zonula adherens), which is primarily responsible for cell-cell adhesion, has been little studied during early pregnancy. This study investigated the adherens junction in rat UECs during the early stages of normal pregnancy and ovarian hyperstimulated (OH) pregnancy using transmission electron microscopy. The adherens junction is present in UECs at the time of fertilisation, but is lost at the time of blastocyst implantation during normal pregnancy. Interestingly, at the time of implantation after OH, adherens junctions are retained and may impede blastocyst penetration of the epithelium. The adherens junction anchors the actin-based terminal web, which is known to be disrupted in UECs during early pregnancy. However, artificial disruption of the terminal web, using cytochalasin D, did not cause removal of the adherens junction in UECs. This study revealed that adherens junction disassembly occurs during early pregnancy, but that this process does not occur during OH pregnancy. Such disassembly does not appear to depend on the disruption of the terminal web. Copyright © 2015 Elsevier GmbH. All rights reserved.

Gap Junctions

PubMed Central

Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

2013-01-01

Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981-2035, 2012. PMID:23723031

Droplet Traffic Control at a simple T junction

NASA Astrophysics Data System (ADS)

Panizza, Pascal; Engl, Wilfried; Colin, Annie; Ajdari, Armand

2006-03-01

A basic yet essential element of every traffic flow control is the effect of a junction where the flow is separated into several streams. How do pedestrians, vehicles or blood cells divide when they reach a junction? How does the outcome depend on their density? Similar fundamental questions hold for much simpler systems: in this paper, we have studied the behaviour of periodic trains of water droplets flowing in oil through a channel as they reach a simple, locally symmetric, T junction. Depending on their dilution, we observe that the droplets are either alternately partitioned between both outlets or sorted exclusively into the shortest one. We show that this surprising behaviour results from the hydrodynamic feed-back of drops in the two outlets on the selection process occurring at the junction. Our results offer a first guide for the design and modelling of droplet traffic in complex branched networks, a necessary step towards parallelized droplet-based ``lab-on-chip'' devices.

Epitaxial growth of mosaic diamond: Mapping of stress and defects in crystal junction with a confocal Raman spectroscopy

NASA Astrophysics Data System (ADS)

Shu, Guoyang; Dai, Bing; Ralchenko, V. G.; Khomich, A. A.; Ashkinazi, E. E.; Bolshakov, A. P.; Bokova-Sirosh, S. N.; Liu, Kang; Zhao, Jiwen; Han, Jiecai; Zhu, Jiaqi

2017-04-01

We studied defects and stress distributions in mosaic epitaxial diamond film using a confocal Raman spectroscopy, with a special attention to the junction area between the crystals. The mosaics was grown by microwave plasma CVD on closely arranged (1 0 0)-oriented HPHT type Ib substrates. The width of stress affected and defect enriched region around the junction show a tendency of extending with the film thickness, from ≈40 μm on the film-substrate interface to ≈250 μm in the layer 500 μm above the substrate, as found from the mosaics analysis in cross-section. The stress field around the junction demonstrates a complex pattern, with mixed domains of tensile and compressive stress, with maximum value of σ ≈ 0.6 GPa. A similar non-uniform pattern was observed for defect distribution as well. No sign of amorphous sp2 carbon in the junction zone was revealed.

p120 catenin associates with kinesin and facilitates the transport of cadherin–catenin complexes to intercellular junctions

PubMed Central

Chen, Xinyu; Kojima, Shin-ichiro; Borisy, Gary G.; Green, Kathleen J.

2003-01-01

p120 catenin (p120) is a component of adherens junctions and has been implicated in regulating cadherin-based cell adhesion as well as the activity of Rho small GTPases, but its exact roles in cell–cell adhesion are unclear. Using time-lapse imaging, we show that p120-GFP associates with vesicles and exhibits unidirectional movements along microtubules. Furthermore, p120 forms a complex with kinesin heavy chain through the p120 NH2-terminal head domain. Overexpression of p120, but not an NH2-terminal deletion mutant deficient in kinesin binding, recruits endogenous kinesin to N-cadherin. Disruption of the interaction between N-cadherin and p120, or the interaction between p120 and kinesin, leads to a delayed accumulation of N-cadherin at cell–cell contacts during calcium-initiated junction reassembly. Our analyses identify a novel role of p120 in promoting cell surface trafficking of cadherins via association and recruitment of kinesin. PMID:14610057

Virus interaction with the apical junctional complex.

PubMed

Gonzalez-Mariscal, Lorenza; Garay, Erika; Lechuga, Susana

2009-01-01

In order to infect pathogens must breach the epithelial barriers that separate the organism from the external environment or that cover the internal cavities and ducts of the body. Epithelia seal the passage through the paracellular pathway with the apical junctional complex integrated by tight and adherens junctions. In this review we describe how viruses like coxsackie, swine vesicular disease virus, adenovirus, reovirus, feline calcivirus, herpes viruses 1 and 2, pseudorabies, bovine herpes virus 1, poliovirus and hepatitis C use as cellular receptors integral proteins present at the AJC of epithelial cells. Interaction with these proteins contributes in a significant manner in defining the particular tropism of each virus. Besides these proteins, viruses exhibit a wide range of cellular co-receptors among which proteins present in the basolateral cell surface like integrins are often found. Therefore targeting proteins of the AJC constitutes a strategy that might allow viruses to bypass the physical barrier that blocks their access to receptors expressed on the basolateral surface of epithelial cells.

Basolateral junctions are sufficient to suppress epithelial invasion during Drosophila oogenesis.

PubMed

Szafranski, Przemyslaw; Goode, Scott

2007-02-01

Epithelial junctions play crucial roles during metazoan evolution and development by facilitating tissue formation, maintenance, and function. Little is known about the role of distinct types of junctions in controlling epithelial transformations leading to invasion of neighboring tissues. Discovering the key junction complexes that control these processes and how they function may also provide mechanistic insight into carcinoma cell invasion. Here, using the Drosophila ovary as a model, we show that four proteins of the basolateral junction (BLJ), Fasciclin-2, Neuroglian, Discs-large, and Lethal-giant-larvae, but not proteins of other epithelial junctions, directly suppress epithelial tumorigenesis and invasion. Remarkably, the expression pattern of Fasciclin-2 predicts which cells will invade. We compared the apicobasal polarity of BLJ tumor cells to border cells (BCs), an epithelium-derived cluster that normally migrates during mid-oogenesis. Both tumor cells and BCs differentiate a lateralized membrane pattern that is necessary but not sufficient for invasion. Independent of lateralization, derepression of motility pathways is also necessary, as indicated by a strong linear correlation between faster BC migration and an increased incidence of tumor invasion. However, without membrane lateralization, derepression of motility pathways is also not sufficient for invasion. Our results demonstrate that spatiotemporal patterns of basolateral junction activity directly suppress epithelial invasion by organizing the cooperative activity of distinct polarity and motility pathways.

Pre-crash scenarios at road junctions: A clustering method for car crash data.

PubMed

Nitsche, Philippe; Thomas, Pete; Stuetz, Rainer; Welsh, Ruth

2017-10-01

Given the recent advancements in autonomous driving functions, one of the main challenges is safe and efficient operation in complex traffic situations such as road junctions. There is a need for comprehensive testing, either in virtual simulation environments or on real-world test tracks. This paper presents a novel data analysis method including the preparation, analysis and visualization of car crash data, to identify the critical pre-crash scenarios at T- and four-legged junctions as a basis for testing the safety of automated driving systems. The presented method employs k-medoids to cluster historical junction crash data into distinct partitions and then applies the association rules algorithm to each cluster to specify the driving scenarios in more detail. The dataset used consists of 1056 junction crashes in the UK, which were exported from the in-depth "On-the-Spot" database. The study resulted in thirteen crash clusters for T-junctions, and six crash clusters for crossroads. Association rules revealed common crash characteristics, which were the basis for the scenario descriptions. The results support existing findings on road junction accidents and provide benchmark situations for safety performance tests in order to reduce the possible number parameter combinations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dissection of neuronal gap junction circuits that regulate social behavior in Caenorhabditis elegans.

PubMed

Jang, Heeun; Levy, Sagi; Flavell, Steven W; Mende, Fanny; Latham, Richard; Zimmer, Manuel; Bargmann, Cornelia I

2017-02-14

A hub-and-spoke circuit of neurons connected by gap junctions controls aggregation behavior and related behavioral responses to oxygen, pheromones, and food in Caenorhabditis elegans The molecular composition of the gap junctions connecting RMG hub neurons with sensory spoke neurons is unknown. We show here that the innexin gene unc-9 is required in RMG hub neurons to drive aggregation and related behaviors, indicating that UNC-9-containing gap junctions mediate RMG signaling. To dissect the circuit in detail, we developed methods to inhibit unc-9 -based gap junctions with dominant-negative unc-1 transgenes. unc-1(dn) alters a stomatin-like protein that regulates unc-9 electrical signaling; its disruptive effects can be rescued by a constitutively active UNC-9::GFP protein, demonstrating specificity. Expression of unc-1(dn) in RMG hub neurons, ADL or ASK pheromone-sensing neurons, or URX oxygen-sensing neurons disrupts specific elements of aggregation-related behaviors. In ADL, unc-1(dn) has effects opposite to those of tetanus toxin light chain, separating the roles of ADL electrical and chemical synapses. These results reveal roles of gap junctions in a complex behavior at cellular resolution and provide a tool for similar exploration of other gap junction circuits.

Dissection of neuronal gap junction circuits that regulate social behavior in Caenorhabditis elegans

PubMed Central

Jang, Heeun; Levy, Sagi; Flavell, Steven W.; Mende, Fanny; Latham, Richard; Zimmer, Manuel; Bargmann, Cornelia I.

2017-01-01

A hub-and-spoke circuit of neurons connected by gap junctions controls aggregation behavior and related behavioral responses to oxygen, pheromones, and food in Caenorhabditis elegans. The molecular composition of the gap junctions connecting RMG hub neurons with sensory spoke neurons is unknown. We show here that the innexin gene unc-9 is required in RMG hub neurons to drive aggregation and related behaviors, indicating that UNC-9–containing gap junctions mediate RMG signaling. To dissect the circuit in detail, we developed methods to inhibit unc-9–based gap junctions with dominant-negative unc-1 transgenes. unc-1(dn) alters a stomatin-like protein that regulates unc-9 electrical signaling; its disruptive effects can be rescued by a constitutively active UNC-9::GFP protein, demonstrating specificity. Expression of unc-1(dn) in RMG hub neurons, ADL or ASK pheromone-sensing neurons, or URX oxygen-sensing neurons disrupts specific elements of aggregation-related behaviors. In ADL, unc-1(dn) has effects opposite to those of tetanus toxin light chain, separating the roles of ADL electrical and chemical synapses. These results reveal roles of gap junctions in a complex behavior at cellular resolution and provide a tool for similar exploration of other gap junction circuits. PMID:28143932

Pelvi-ureteric junction obstruction related to crossing vessels: vascular anatomic variations and implication for surgical approaches.

PubMed

Panthier, Frédéric; Lareyre, Fabien; Audouin, Marie; Raffort, Juliette

2018-03-01

Pelvi-ureteric junction obstruction corresponds to an impairment of urinary transport that can lead to renal dysfunction if not treated. Several mechanisms can cause the obstruction of the ureter including intrinsic factors or extrinsic factors such as the presence of crossing vessels. The treatment of the disease relies on surgical approaches, pyeloplasty being the standard reference. The technique consists in removing the pathologic ureteric segment and renal pelvis and transposing associated crossing vessels if present. The vascular anatomy of the pelvi-ureteric junction is complex and varies among individuals, and this can impact on the disease development and its surgical treatment. In this review, we summarize current knowledge on vascular anatomic variations in the pelvi-ureteric junction. Based on anatomic characteristics, we discuss implications for surgical approaches during pyeloplasty and vessel transposition.

Connexins in Prostate Cancer Initiation and Progression

DTIC Science & Technology

2013-11-01

the Golgi Apparatus for Cargo Transport Prior to Complete Assembly. Mol.Biol.Cell, 17, 4105-4117. 79. Hunziker,W. and Geuze,H. (2011...tumor growth by inducing the assembly of other junctional and signaling complexes? Wild type connexins which form functional gap junctions and mutant...and influences the function of two other important proteins that have been shown to prevent the spread of cancer cells from prostate to distant organs

Planar Cell Polarity Pathway Regulates Nephrin Endocytosis in Developing Podocytes

PubMed Central

Babayeva, Sima; Rocque, Brittany; Aoudjit, Lamine; Zilber, Yulia; Li, Jane; Baldwin, Cindy; Kawachi, Hiroshi; Takano, Tomoko; Torban, Elena

2013-01-01

The noncanonical Wnt/planar cell polarity (PCP) pathway controls a variety of cell behaviors such as polarized protrusive cell activity, directional cell movement, and oriented cell division and is crucial for the normal development of many tissues. Mutations in the PCP genes cause malformation in multiple organs. Recently, the PCP pathway was shown to control endocytosis of PCP and non-PCP proteins necessary for cell shape remodeling and formation of specific junctional protein complexes. During formation of the renal glomerulus, the glomerular capillary becomes enveloped by highly specialized epithelial cells, podocytes, that display unique architecture and are connected via specialized cell-cell junctions (slit diaphragms) that restrict passage of protein into the urine; podocyte differentiation requires active remodeling of cytoskeleton and junctional protein complexes. We report here that in cultured human podocytes, activation of the PCP pathway significantly stimulates endocytosis of the core slit diaphragm protein, nephrin, via a clathrin/β-arrestin-dependent endocytic route. In contrast, depletion of the PCP protein Vangl2 leads to an increase of nephrin at the cell surface; loss of Vangl2 functions in Looptail mice results in disturbed glomerular maturation. We propose that the PCP pathway contributes to podocyte development by regulating nephrin turnover during junctional remodeling as the cells differentiate. PMID:23824190

Dynamics of Defects and Dopants in Complex Systems: Si and Oxide Surfaces and Interfaces

NASA Astrophysics Data System (ADS)

Kirichenko, Taras; Yu, Decai; Banarjee, Sanjay; Hwang, Gyeong

2004-10-01

Fabrication of forthcoming nanometer scale electronic devices faces many difficulties including formation of extremely shallow and highly doped junctions. At present, ultra-low-energy ion implantation followed by high-temperature thermal annealing is most widely used to fabricate such ultra-shallow junctions. In the process, a great challenge lies in achieving precise control of redistribution and electrical activation of dopant impurities. Native defects (such as vacancies and interstitials) generated during implantation are known to be mainly responsible for the TED and also influence significantly the electrical activation/deactivation. Defect-dopant dynamics is rather well understood in crystalline Si and SiO2. However, little is known about their diffusion and annihilation (or precipitation) at the surfaces and interfaces, despite its growing importance in determining junction profiles as device dimensions get smaller. In this talk, we will present our density functional theory calculation results on the atomic and electronic structure and dynamical behavior of native defects and dopant-defect complexes in disordered/strained Si and oxide systems, such as i) clean and absorbent-modified Si(100) surface and subsurface layers, ii) amorphous-crystalline Si interfaces and iii) amorphous SiO2/Si interfaces. The fundamental understanding and data is essential in developing a comprehensive kinetic model for junction formation, which would contribute greatly in improving current process technologies.

The tight junction protein ZO-2 and Janus kinase 1 mediate intercellular communications in vascular smooth muscle cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tkachuk, Natalia; Tkachuk, Sergey; Patecki, Margret

2011-07-08

Highlights: {yields} The tight junction protein ZO-2 associates with Jak1 in vascular smooth muscle cells via ZO-2 N-terminal fragment. {yields} Jak1 mediates ZO-2 tyrosine phosphorylation and ZO-2 localization to the sites of homotypic intercellular contacts. {yields} The urokinase receptor uPAR regulates ZO-2/Jak1 functional association. {yields} The ZO-2/Jak1/uPAR signaling complex is required for vascular smooth muscle cells functional network formation. -- Abstract: Recent evidence points to a multifunctional role of ZO-2, the tight junction protein of the MAGUK (membrane-associated guanylate kinase-like) family. Though ZO-2 has been found in cell types lacking tight junction structures, such as vascular smooth muscle cells (VSMC),more » little is known about ZO-2 function in these cells. We provide evidence that ZO-2 mediates specific homotypic cell-to-cell contacts between VSMC. Using mass spectrometry we found that ZO-2 is associated with the non-receptor tyrosine kinase Jak1. By generating specific ZO-2 constructs we further found that the N-terminal fragment of ZO-2 molecule is responsible for this interaction. Adenovirus-based expression of Jak1 inactive mutant demonstrated that Jak1 mediates ZO-2 tyrosine phosphorylation. By means of RNA silencing, expression of Jak1 mutant form and fluorescently labeled ZO-2 fusion protein we further specified that active Jak1, but not Jak1 inactive mutant, mediates ZO-2 localization to the sites of intercellular contacts. We identified the urokinase receptor uPAR as a pre-requisite for these cellular events. Functional requirement of the revealed signaling complex for VSMC network formation was confirmed in experiments using Matrigel and in contraction assay. Our findings imply involvement of the ZO-2 tight junction independent signaling complex containing Jak1 and uPAR in VSMC intercellular communications. This mechanism may contribute to vascular remodeling in occlusive cardiovascular diseases and in arteriogenesis.« less

Crystal structure of a Fanconi anemia-associated nuclease homolog bound to 5' flap DNA: basis of interstrand cross-link repair by FAN1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gwon, Gwang Hyeon; Kim, Youngran; Liu, Yaqi

2014-10-15

Fanconi anemia (FA) is an autosomal recessive genetic disorder caused by defects in any of 15 FA genes responsible for processing DNA interstrand cross-links (ICLs). The ultimate outcome of the FA pathway is resolution of cross-links, which requires structure-selective nucleases. FA-associated nuclease 1 (FAN1) is believed to be recruited to lesions by a monoubiquitinated FANCI–FANCD2 (ID) complex and participates in ICL repair. Here, we determined the crystal structure of Pseudomonas aeruginosa FAN1 (PaFAN1) lacking the UBZ (ubiquitin-binding zinc) domain in complex with 5' flap DNA. All four domains of the right-hand-shaped PaFAN1 are involved in DNA recognition, with each domainmore » playing a specific role in bending DNA at the nick. The six-helix bundle that binds the junction connects to the catalytic viral replication and repair (VRR) nuclease (VRR nuc) domain, enabling FAN1 to incise the scissile phosphate a few bases distant from the junction. The six-helix bundle also inhibits the cleavage of intact Holliday junctions. PaFAN1 shares several conserved features with other flap structure-selective nucleases despite structural differences. A clamping motion of the domains around the wedge helix, which acts as a pivot, facilitates nucleolytic cleavage. The PaFAN1 structure provides insights into how archaeal Holliday junction resolvases evolved to incise 5' flap substrates and how FAN1 integrates with the FA complex to participate in ICL repair.« less

Clustering and negative feedback by endocytosis in planar cell polarity signaling is modulated by ubiquitinylation of prickle.

PubMed

Cho, Bomsoo; Pierre-Louis, Gandhy; Sagner, Andreas; Eaton, Suzanne; Axelrod, Jeffrey D

2015-05-01

The core components of the planar cell polarity (PCP) signaling system, including both transmembrane and peripheral membrane associated proteins, form asymmetric complexes that bridge apical intercellular junctions. While these can assemble in either orientation, coordinated cell polarization requires the enrichment of complexes of a given orientation at specific junctions. This might occur by both positive and negative feedback between oppositely oriented complexes, and requires the peripheral membrane associated PCP components. However, the molecular mechanisms underlying feedback are not understood. We find that the E3 ubiquitin ligase complex Cullin1(Cul1)/SkpA/Supernumerary limbs(Slimb) regulates the stability of one of the peripheral membrane components, Prickle (Pk). Excess Pk disrupts PCP feedback and prevents asymmetry. We show that Pk participates in negative feedback by mediating internalization of PCP complexes containing the transmembrane components Van Gogh (Vang) and Flamingo (Fmi), and that internalization is activated by oppositely oriented complexes within clusters. Pk also participates in positive feedback through an unknown mechanism promoting clustering. Our results therefore identify a molecular mechanism underlying generation of asymmetry in PCP signaling.

Interaction of Ddc1 and RPA with single-stranded/double-stranded DNA junctions in yeast whole cell extracts: Proteolytic degradation of the large subunit of replication protein A in ddc1Δ strains.

PubMed

Sukhanova, Maria V; D'Herin, Claudine; Boiteux, Serge; Lavrik, Olga I

2014-10-01

To characterize proteins that interact with single-stranded/double-stranded (ss/ds) DNA junctions in whole cell free extracts of Saccharomyces cerevisiae, we used [(32)P]-labeled photoreactive partial DNA duplexes containing a 3'-ss/ds-junction (3'-junction) or a 5'-ss/ds-junction (5'-junction). Identification of labeled proteins was achieved by MALDI-TOF mass spectrometry peptide mass fingerprinting and genetic analysis. In wild-type extract, one of the components of the Ddc1-Rad17-Mec3 complex, Ddc1, was found to be preferentially photocrosslinked at a 3'-junction. On the other hand, RPAp70, the large subunit of the replication protein A (RPA), was the predominant crosslinking product at a 5'-junction. Interestingly, ddc1Δ extracts did not display photocrosslinking of RPAp70 at a 5'-junction. The results show that RPAp70 crosslinked to DNA with a 5'-junction is subject to limited proteolysis in ddc1Δ extracts, whereas it is stable in WT, rad17Δ, mec3Δ and mec1Δ extracts. The degradation of the RPAp70-DNA adduct in ddc1Δ extract is strongly reduced in the presence of the proteasome inhibitor MG 132. We also addressed the question of the stability of free RPA, using anti-RPA antibodies. The results show that RPAp70 is also subject to proteolysis without photocrosslinking to DNA upon incubation in ddc1Δ extract. The data point to a novel property of Ddc1, modulating the turnover of DNA binding proteins such as RPAp70 by the proteasome. Copyright © 2014 Elsevier B.V. All rights reserved.

Death of Neurons following Injury Requires Conductive Neuronal Gap Junction Channels but Not a Specific Connexin

PubMed Central

Fontes, Joseph D.; Ramsey, Jon; Polk, Jeremy M; Koop, Andre; Denisova, Janna V.; Belousov, Andrei B.

2015-01-01

Pharmacological blockade or genetic knockout of neuronal connexin 36 (Cx36)-containing gap junctions reduces neuronal death caused by ischemia, traumatic brain injury and NMDA receptor (NMDAR)-mediated excitotoxicity. However, whether Cx36 gap junctions contribute to neuronal death via channel-dependent or channel-independent mechanism remains an open question. To address this, we manipulated connexin protein expression via lentiviral transduction of mouse neuronal cortical cultures and analyzed neuronal death twenty-four hours following administration of NMDA (a model of NMDAR excitotoxicity) or oxygen-glucose deprivation (a model of ischemic injury). In cultures prepared from wild-type mice, over-expression and knockdown of Cx36-containing gap junctions augmented and prevented, respectively, neuronal death from NMDAR-mediated excitotoxicity and ischemia. In cultures obtained form from Cx36 knockout mice, re-expression of functional gap junction channels, containing either neuronal Cx36 or non-neuronal Cx43 or Cx31, resulted in increased neuronal death following insult. In contrast, the expression of communication-deficient gap junctions (containing mutated connexins) did not have this effect. Finally, the absence of ethidium bromide uptake in non-transduced wild-type neurons two hours following NMDAR excitotoxicity or ischemia suggested the absence of active endogenous hemichannels in those neurons. Taken together, these results suggest a role for neuronal gap junctions in cell death via a connexin type-independent mechanism that likely relies on channel activities of gap junctional complexes among neurons. A possible contribution of gap junction channel-permeable death signals in neuronal death is discussed. PMID:26017008

Single-molecule force-conductance spectroscopy of hydrogen-bonded complexes

NASA Astrophysics Data System (ADS)

Pirrotta, Alessandro; De Vico, Luca; Solomon, Gemma C.; Franco, Ignacio

2017-03-01

The emerging ability to study physical properties at the single-molecule limit highlights the disparity between what is observable in an ensemble of molecules and the heterogeneous contributions of its constituent parts. A particularly convenient platform for single-molecule studies are molecular junctions where forces and voltages can be applied to individual molecules, giving access to a series of electromechanical observables that can form the basis of highly discriminating multidimensional single-molecule spectroscopies. Here, we computationally examine the ability of force and conductance to inform about molecular recognition events at the single-molecule limit. For this, we consider the force-conductance characteristics of a prototypical class of hydrogen bonded bimolecular complexes sandwiched between gold electrodes. The complexes consist of derivatives of a barbituric acid and a Hamilton receptor that can form up to six simultaneous hydrogen bonds. The simulations combine classical molecular dynamics of the mechanical deformation of the junction with non-equilibrium Green's function computations of the electronic transport. As shown, in these complexes hydrogen bonds mediate transport either by directly participating as a possible transport pathway or by stabilizing molecular conformations with enhanced conductance properties. Further, we observe that force-conductance correlations can be very sensitive to small changes in the chemical structure of the complexes and provide detailed information about the behavior of single molecules that cannot be gleaned from either measurement alone. In fact, there are regions during the elongation that are only mechanically active, others that are only conductance active, and regions where both force and conductance changes as the complex is mechanically manipulated. The implication is that force and conductance provide complementary information about the evolution of molecules in junctions that can be used to interrogate basic structure-transport relations at the single-molecule limit.

CHRONIC PERIPHERAL NERVE COMPRESSION DISRUPTS PARANODAL AXOGLIAL JUNCTIONS

PubMed Central

Otani, Yoshinori; Yermakov, Leonid M.; Dupree, Jeffrey L.; Susuki, Keiichiro

2016-01-01

Introduction Peripheral nerves are often exposed to mechanical stress leading to compression neuropathies. The pathophysiology underlying nerve dysfunction by chronic compression is largely unknown. Methods We analyzed molecular organization and fine structures at and near nodes of Ranvier in a compression neuropathy model in which a silastic tube was placed around the mouse sciatic nerve. Results Immunofluorescence study showed that clusters of cell adhesion complex forming paranodal axoglial junctions were dispersed with frequent overlap with juxtaparanodal components. These paranodal changes occurred without internodal myelin damage. The distribution and pattern of paranodal disruption suggests that these changes are the direct result of mechanical stress. Electron microscopy confirmed loss of paranodal axoglial junctions. Discussion Our data show that chronic nerve compression disrupts paranodal junctions and axonal domains required for proper peripheral nerve function. These results provide important clues toward better understanding of the pathophysiology underlying nerve dysfunction in compression neuropathies. PMID:27463510

An all-perovskite p-n junction based on transparent conducting p -La 1-x Sr x CrO 3 epitaxial layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Yingge; Li, Chen; Zhang, Kelvin H. L.

2017-08-07

Transparent, conducting p -La 1-x Sr x CrO 3 epitaxial layers were deposited on Nb-doped SrTiO 3(001) by oxygen-assisted molecular beam epitaxy to form structurally coherent p-n junctions. X-ray photoelectron spectroscopy reveals a type II or “staggered” band alignment, with valence and conduction band offsets of 2.0 eV and 0.9 eV, respectively. Diodes fabricated from these heterojunctions exhibit rectifying behavior, and the I-V characteristics are different from those for traditional semiconductor p-n junctions. A rather large ideality factor is ascribed to the complex nature of the interface.

Modeling Intrajunction Dispersion at a Well-Mixed Tidal River Junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolfram, Phillip J.; Fringer, Oliver B.; Monsen, Nancy E.

In this paper, the relative importance of small-scale, intrajunction flow features such as shear layers, separation zones, and secondary flows on dispersion in a well-mixed tidal river junction is explored. A fully nonlinear, nonhydrostatic, and unstructured three-dimensional (3D) model is used to resolve supertidal dispersion via scalar transport at a well-mixed tidal river junction. Mass transport simulated in the junction is compared against predictions using a simple node-channel model to quantify the effects of small-scale, 3D intrajunction flow features on mixing and dispersion. The effects of three-dimensionality are demonstrated by quantifying the difference between two-dimensional (2D) and 3D model results.more » An intermediate 3D model that does not resolve the secondary circulation or the recirculating flow at the junction is also compared to the 3D model to quantify the relative sensitivity of mixing on intrajunction flow features. Resolution of complex flow features simulated by the full 3D model is not always necessary because mixing is primarily governed by bulk flow splitting due to the confluence–diffluence cycle. Finally, results in 3D are comparable to the 2D case for many flow pathways simulated, suggesting that 2D modeling may be reasonable for nonstratified and predominantly hydrostatic flows through relatively straight junctions, but not necessarily for the full junction network.« less

Modeling Intrajunction Dispersion at a Well-Mixed Tidal River Junction

DOE PAGES

Wolfram, Phillip J.; Fringer, Oliver B.; Monsen, Nancy E.; ...

2016-08-01

In this paper, the relative importance of small-scale, intrajunction flow features such as shear layers, separation zones, and secondary flows on dispersion in a well-mixed tidal river junction is explored. A fully nonlinear, nonhydrostatic, and unstructured three-dimensional (3D) model is used to resolve supertidal dispersion via scalar transport at a well-mixed tidal river junction. Mass transport simulated in the junction is compared against predictions using a simple node-channel model to quantify the effects of small-scale, 3D intrajunction flow features on mixing and dispersion. The effects of three-dimensionality are demonstrated by quantifying the difference between two-dimensional (2D) and 3D model results.more » An intermediate 3D model that does not resolve the secondary circulation or the recirculating flow at the junction is also compared to the 3D model to quantify the relative sensitivity of mixing on intrajunction flow features. Resolution of complex flow features simulated by the full 3D model is not always necessary because mixing is primarily governed by bulk flow splitting due to the confluence–diffluence cycle. Finally, results in 3D are comparable to the 2D case for many flow pathways simulated, suggesting that 2D modeling may be reasonable for nonstratified and predominantly hydrostatic flows through relatively straight junctions, but not necessarily for the full junction network.« less

Mechanism of synergistic activation of Arp2/3 complex by cortactin and N-WASP

PubMed Central

Helgeson, Luke A; Nolen, Brad J

2013-01-01

Nucleation promoting factors (NPFs) initiate branched actin network assembly by activating Arp2/3 complex, a branched actin filament nucleator. Cellular actin networks contain multiple NPFs, but how they coordinately regulate Arp2/3 complex is unclear. Cortactin is an NPF that activates Arp2/3 complex weakly on its own, but with WASP/N-WASP, another class of NPFs, potently activates. We dissect the mechanism of synergy and propose a model in which cortactin displaces N-WASP from nascent branches as a prerequisite for nucleation. Single-molecule imaging revealed that unlike WASP/N-WASP, cortactin remains bound to junctions during nucleation, and specifically targets junctions with a ∼160-fold increased on rate over filament sides. N-WASP must be dimerized for potent synergy, and targeted mutations indicate release of dimeric N-WASP from nascent branches limits nucleation. Mathematical modeling shows cortactin-mediated displacement but not N-WASP recycling or filament recruitment models can explain synergy. Our results provide a molecular basis for coordinate Arp2/3 complex regulation. DOI: http://dx.doi.org/10.7554/eLife.00884.001 PMID:24015358

Complex capacitance spectroscopy as a probe for oxidation process of AlO{sub x}-based magnetic tunnel junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, J.C.A.; Hsu, C.Y.; Taiwan SPIN Research Center, National Chung Cheng University, Chiayi, Taiwan

2004-12-13

Proper as well as under- and over-oxided CoFe-AlO{sub x}-CoFe magnetic tunnel junctions (MTJs) have been systematically investigated in a frequency range from 10{sup 2} to 10{sup 8} Hz by complex capacitance spectroscopy. The dielectric relaxation behavior of the MTJs remarkably disobeys the typical Cole-Cole arc law probably due to the existence of imperfectly blocked Schottky barrier in the metal-insulator interface. The dielectric relaxation response can be successfully modeled on the basis of Debye relaxation by incorporating an interfacial dielectric contribution. In addition, complex capacitance spectroscopy demonstrates significant sensitivity to the oxidation process of metallic Al layers, i.e., almost a fingerprintmore » of under, proper, and over oxidation. This technique provides a fast and simple method to inspect the AlO{sub x} barrier quality of MTJs.« less

Chromosome catastrophes involve replication mechanisms generating complex genomic rearrangements

PubMed Central

Liu, Pengfei; Erez, Ayelet; Sreenath Nagamani, Sandesh C.; Dhar, Shweta U.; Kołodziejska, Katarzyna E.; Dharmadhikari, Avinash V.; Cooper, M. Lance; Wiszniewska, Joanna; Zhang, Feng; Withers, Marjorie A.; Bacino, Carlos A.; Campos-Acevedo, Luis Daniel; Delgado, Mauricio R.; Freedenberg, Debra; Garnica, Adolfo; Grebe, Theresa A.; Hernández-Almaguer, Dolores; Immken, LaDonna; Lalani, Seema R.; McLean, Scott D.; Northrup, Hope; Scaglia, Fernando; Strathearn, Lane; Trapane, Pamela; Kang, Sung-Hae L.; Patel, Ankita; Cheung, Sau Wai; Hastings, P. J.; Stankiewicz, Paweł; Lupski, James R.; Bi, Weimin

2011-01-01

SUMMARY Complex genomic rearrangements (CGR) consisting of two or more breakpoint junctions have been observed in genomic disorders. Recently, a chromosome catastrophe phenomenon termed chromothripsis, in which numerous genomic rearrangements are apparently acquired in one single catastrophic event, was described in multiple cancers. Here we show that constitutionally acquired CGRs share similarities with cancer chromothripsis. In the 17 CGR cases investigated we observed localization and multiple copy number changes including deletions, duplications and/or triplications, as well as extensive translocations and inversions. Genomic rearrangements involved varied in size and complexities; in one case, array comparative genomic hybridization revealed 18 copy number changes. Breakpoint sequencing identified characteristic features, including small templated insertions at breakpoints and microhomology at breakpoint junctions, which have been attributed to replicative processes. The resemblance between CGR and chromothripsis suggests similar mechanistic underpinnings. Such chromosome catastrophic events appear to reflect basic DNA metabolism operative throughout an organism’s life cycle. PMID:21925314

Creating complex molecular topologies by configuring DNA four-way junctions

NASA Astrophysics Data System (ADS)

Liu, Di; Chen, Gang; Akhter, Usman; Cronin, Timothy M.; Weizmann, Yossi

2016-10-01

The realization of complex topologies at the molecular level represents a grand challenge in chemistry. This necessitates the manipulation of molecular interactions with high precision. Here we show that single-stranded DNA (ssDNA) knots and links can be created by utilizing the inherent topological properties that pertain to the DNA four-way junction, at which the two helical strands form a node and can be configured conveniently and connected for complex topological construction. Using this strategy, we produced series of ssDNA topoisomers with the same sequences. By finely designing the curvature and torsion, double-stranded DNA knots were accessed by hybridizing and ligating the complementary strands with the knotted ssDNA templates. Furthermore, we demonstrate the use of a constructed ssDNA knot both to probe the topological conversion catalysed by DNA topoisomerase and to study the DNA replication under topological constraint.

BLM and RMI1 alleviate RPA inhibition of TopoIIIα decatenase activity.

PubMed

Yang, Jay; Bachrati, Csanad Z; Hickson, Ian D; Brown, Grant W

2012-01-01

RPA is a single-stranded DNA binding protein that physically associates with the BLM complex. RPA stimulates BLM helicase activity as well as the double Holliday junction dissolution activity of the BLM-topoisomerase IIIα complex. We investigated the effect of RPA on the ssDNA decatenase activity of topoisomerase IIIα. We found that RPA and other ssDNA binding proteins inhibit decatenation by topoisomerase IIIα. Complex formation between BLM, TopoIIIα, and RMI1 ablates inhibition of decatenation by ssDNA binding proteins. Together, these data indicate that inhibition by RPA does not involve species-specific interactions between RPA and BLM-TopoIIIα-RMI1, which contrasts with RPA modulation of double Holliday junction dissolution. We propose that topoisomerase IIIα and RPA compete to bind to single-stranded regions of catenanes. Interactions with BLM and RMI1 enhance toposiomerase IIIα activity, promoting decatenation in the presence of RPA.

Global Structure of a Three-Way Junction in a Phi29 Packaging RNA Dimer Determined Using Site-Directed Spin Labeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xiaojun; Tung, Chang-Shung; Sowa, Glenna

2012-02-08

The condensation of bacteriophage phi29 genomic DNA into its preformed procapsid requires the DNA packaging motor, which is the strongest known biological motor. The packaging motor is an intricate ring-shaped protein/RNA complex, and its function requires an RNA component called packaging RNA (pRNA). Current structural information on pRNA is limited, which hinders studies of motor function. Here, we used site-directed spin labeling to map the conformation of a pRNA three-way junction that bridges binding sites for the motor ATPase and the procapsid. The studies were carried out on a pRNA dimer, which is the simplest ring-shaped pRNA complex and servesmore » as a functional intermediate during motor assembly. Using a nucleotide-independent labeling scheme, stable nitroxide radicals were attached to eight specific pRNA sites without perturbing RNA folding and dimer formation, and a total of 17 internitroxide distances spanning the three-way junction were measured using Double Electron-Electron Resonance spectroscopy. The measured distances, together with steric chemical constraints, were used to select 3662 viable three-way junction models from a pool of 65 billion. The results reveal a similar conformation among the viable models, with two of the helices (HT and HL) adopting an acute bend. This is in contrast to a recently reported pRNA tetramer crystal structure, in which HT and HL stack onto each other linearly. The studies establish a new method for mapping global structures of complex RNA molecules, and provide information on pRNA conformation that aids investigations of phi29 packaging motor and developments of pRNA-based nanomedicine and nanomaterial.« less

Innexin 3, a New Gene Required for Dorsal Closure in Drosophila Embryo

PubMed Central

Giuliani, Fabrizio; Giuliani, Giuliano; Bauer, Reinhard; Rabouille, Catherine

2013-01-01

Background Dorsal closure is a morphogenetic event that occurs during mid-embryogenesis in many insects including Drosophila, during which the ectoderm migrates on the extraembryonic amnioserosa to seal the embryo dorsally. The contribution of the ectoderm in this event has been known for a long time. However, amnioserosa tension and contractibility have recently been shown also to be instrumental to the closure. A critical pre-requisite for dorsal closure is integrity of these tissues that in part is mediated by cell-cell junctions and cell adhesion. In this regard, mutations impairing junction formation and/or adhesion lead to dorsal closure. However, no role for the gap junction proteins Innexins has so far been described. Results and Discussion Here, we show that Innexin 1, 2 and 3, are present in the ectoderm but also in the amnioserosa in plaques consistent with gap junctions. However, only the loss of Inx3 leads to dorsal closure defects that are completely rescued by overexpression of inx3::GFP in the whole embryo. Loss of Inx3 leads to the destabilisation of Inx1, Inx2 and DE-cadherin at the plasma membrane, suggesting that these four proteins form a complex. Accordingly, in addition to the known interaction of Inx2 with DE-cadherin, we show that Inx3 can bind to DE-cadherin. Furthermore, Inx3-GFP overexpression recruits DE-cadherin from its wildtype plasma membrane domain to typical Innexin plaques, strengthening the notion that they form a complex. Finally, we show that Inx3 stability is directly dependent on tissue tension. Taken together, we propose that Inx3 is a critical factor for dorsal closure and that it mediates the stability of Inx1, 2 and DE-cadherin by forming a complex. PMID:23894431

Cell polarity proteins and spermatogenesis.

PubMed

Gao, Ying; Xiao, Xiang; Lui, Wing-Yee; Lee, Will M; Mruk, Dolores; Cheng, C Yan

2016-11-01

When the cross-section of a seminiferous tubule from an adult rat testes is examined microscopically, Sertoli cells and germ cells in the seminiferous epithelium are notably polarized cells. For instance, Sertoli cell nuclei are found near the basement membrane. On the other hand, tight junction (TJ), basal ectoplasmic specialization (basal ES, a testis-specific actin-rich anchoring junction), gap junction (GJ) and desmosome that constitute the blood-testis barrier (BTB) are also located near the basement membrane. The BTB, in turn, divides the epithelium into the basal and the adluminal (apical) compartments. Within the epithelium, undifferentiated spermatogonia and preleptotene spermatocytes restrictively reside in the basal compartment whereas spermatocytes and post-meiotic spermatids reside in the adluminal compartment. Furthermore, the heads of elongating/elongated spermatids point toward the basement membrane with their elongating tails toward the tubule lumen. However, the involvement of polarity proteins in this unique cellular organization, in particular the underlying molecular mechanism(s) by which polarity proteins confer cellular polarity in the seminiferous epithelium is virtually unknown until recent years. Herein, we discuss latest findings regarding the role of different polarity protein complexes or modules and how these protein complexes are working in concert to modulate Sertoli cell and spermatid polarity. These findings also illustrate polarity proteins exert their effects through the actin-based cytoskeleton mediated by actin binding and regulatory proteins, which in turn modulate adhesion protein complexes at the cell-cell interface since TJ, basal ES and GJ utilize F-actin for attachment. We also propose a hypothetical model which illustrates the antagonistic effects of these polarity proteins. This in turn provides a unique mechanism to modulate junction remodeling in the testis to support germ cell transport across the epithelium in particular the BTB during the epithelial cycle of spermatogenesis. Copyright © 2016 Elsevier Ltd. All rights reserved.

A Cul-3-BTB ubiquitylation pathway regulates junctional levels and asymmetry of core planar polarity proteins

PubMed Central

Strutt, Helen; Searle, Elizabeth; Thomas-MacArthur, Victoria; Brookfield, Rosalind; Strutt, David

2013-01-01

The asymmetric localisation of core planar polarity proteins at apicolateral junctions is required to specify cell polarity in the plane of epithelia. This asymmetric distribution of the core proteins is proposed to require amplification of an initial asymmetry by feedback loops. In addition, generation of asymmetry appears to require the regulation of core protein levels, but the importance of such regulation and the underlying mechanisms is unknown. Here we show that ubiquitylation acts through more than one mechanism to control core protein levels in Drosophila, and that without this regulation cellular asymmetry is compromised. Levels of Dishevelled at junctions are regulated by a Cullin-3-Diablo/Kelch ubiquitin ligase complex, the activity of which is most likely controlled by neddylation. Furthermore, activity of the deubiquitylating enzyme Fat facets is required to maintain Flamingo levels at junctions. Notably, ubiquitylation does not alter the total cellular levels of Dishevelled or Flamingo, but only that of the junctional population. When junctional core protein levels are either increased or decreased by disruption of the ubiquitylation machinery, their asymmetric localisation is reduced and this leads to disruption of planar polarity at the tissue level. Loss of asymmetry by altered core protein levels can be explained by reference to feedback models for amplification of asymmetry. PMID:23487316

Analysis of the Intrinsically Disordered N-Terminus of the DNA Junction-Resolving Enzyme T7 Endonuclease I: Identification of Structure Formed upon DNA Binding

PubMed Central

2016-01-01

The four-way (Holliday) DNA junction of homologous recombination is processed by the symmetrical cleavage of two strands by a nuclease. These junction-resolving enzymes bind to four-way junctions in dimeric form, distorting the structure of the junction in the process. Crystal structures of T7 endonuclease I have been determined as free protein, and the complex with a DNA junction. In neither crystal structure was the N-terminal 16-amino acid peptide visible, yet deletion of this peptide has a marked effect on the resolution process. Here we have investigated the N-terminal peptide by inclusion of spin-label probes at unique sites within this region, studied by electron paramagnetic resonance. Continuous wave experiments show that these labels are mobile in the free protein but become constrained on binding a DNA junction, with the main interaction occurring for residues 7–10 and 12. Distance measurements between equivalent positions within the two peptides of a dimer using PELDOR showed that the intermonomeric distances for residues 2–12 are long and broadly distributed in the free protein but are significantly shortened and become more defined on binding to DNA. These results suggest that the N-terminal peptides become more organized on binding to the DNA junction and nestle into the minor grooves at the branchpoint, consistent with the biochemical data indicating an important role in the resolution process. This study demonstrates the presence of structure within a protein region that cannot be viewed by crystallography. PMID:27387136

TNF-α Signals Through PKCζ/NF-κB to Alter the Tight Junction Complex and Increase Retinal Endothelial Cell Permeability

PubMed Central

Aveleira, Célia A.; Lin, Cheng-Mao; Abcouwer, Steven F.; Ambrósio, António F.; Antonetti, David A.

2010-01-01

OBJECTIVE Tumor necrosis factor-α (TNF-α) and interleukin-1 beta (IL-1β) are elevated in the vitreous of diabetic patients and in retinas of diabetic rats associated with increased retinal vascular permeability. However, the molecular mechanisms underlying retinal vascular permeability induced by these cytokines are poorly understood. In this study, the effects of IL-1β and TNF-α on retinal endothelial cell permeability were compared and the molecular mechanisms by which TNF-α increases cell permeability were elucidated. RESEARCH DESIGN AND METHODS Cytokine-induced retinal vascular permeability was measured in bovine retinal endothelial cells (BRECs) and rat retinas. Western blotting, quantitative real-time PCR, and immunocytochemistry were performed to determine tight junction protein expression and localization. RESULTS IL-1β and TNF-α increased BREC permeability, and TNF-α was more potent. TNF-α decreased the protein and mRNA content of the tight junction proteins ZO-1 and claudin-5 and altered the cellular localization of these tight junction proteins. Dexamethasone prevented TNF-α–induced cell permeability through glucocorticoid receptor transactivation and nuclear factor-kappaB (NF-κB) transrepression. Preventing NF-κB activation with an inhibitor κB kinase (IKK) chemical inhibitor or adenoviral overexpression of inhibitor κB alpha (IκBα) reduced TNF-α–stimulated permeability. Finally, inhibiting protein kinase C zeta (PKCζ) using both a peptide and a novel chemical inhibitor reduced NF-κB activation and completely prevented the alterations in the tight junction complex and cell permeability induced by TNF-α in cell culture and rat retinas. CONCLUSIONS These results suggest that PKCζ may provide a specific therapeutic target for the prevention of vascular permeability in retinal diseases characterized by elevated TNF-α, including diabetic retinopathy. PMID:20693346

Involvement of the interaction of afadin with ZO-1 in the formation of tight junctions in Madin-Darby canine kidney cells.

PubMed

Ooshio, Takako; Kobayashi, Reiko; Ikeda, Wataru; Miyata, Muneaki; Fukumoto, Yuri; Matsuzawa, Naomi; Ogita, Hisakazu; Takai, Yoshimi

2010-02-12

Tight junctions (TJs) and adherens junctions (AJs) are major junctional apparatuses in epithelial cells. Claudins and junctional adhesion molecules (JAMs) are major cell adhesion molecules (CAMs) at TJs, whereas cadherins and nectins are major CAMs at AJs. Claudins and JAMs are associated with ZO proteins, whereas cadherins are associated with beta- and alpha-catenins, and nectins are associated with afadin. We previously showed that nectins first form cell-cell adhesions where the cadherin-catenin complex is recruited to form AJs, followed by the recruitment of the JAM-ZO and claudin-ZO complexes to the apical side of AJs to form TJs. It is not fully understood how TJ components are recruited to the apical side of AJs. We studied the roles of afadin and ZO-1 in the formation of TJs in Madin-Darby canine kidney (MDCK) cells. Before the formation of TJs, ZO-1 interacted with afadin through the two proline-rich regions of afadin and the SH3 domain of ZO-1. During and after the formation of TJs, ZO-1 dissociated from afadin and associated with JAM-A. Knockdown of afadin impaired the formation of both AJs and TJs in MDCK cells, whereas knockdown of ZO-1 impaired the formation of TJs, but not AJs. Re-expression of full-length afadin restored the formation of both AJs and TJs in afadin-knockdown MDCK cells, whereas re-expression of afadin-DeltaPR1-2, which is incapable of binding to ZO-1, restored the formation of AJs, but not TJs. These results indicate that the transient interaction of afadin with ZO-1 is necessary for the formation of TJs in MDCK cells.

Involvement of the Interaction of Afadin with ZO-1 in the Formation of Tight Junctions in Madin-Darby Canine Kidney Cells*

PubMed Central

Ooshio, Takako; Kobayashi, Reiko; Ikeda, Wataru; Miyata, Muneaki; Fukumoto, Yuri; Matsuzawa, Naomi; Ogita, Hisakazu; Takai, Yoshimi

2010-01-01

Tight junctions (TJs) and adherens junctions (AJs) are major junctional apparatuses in epithelial cells. Claudins and junctional adhesion molecules (JAMs) are major cell adhesion molecules (CAMs) at TJs, whereas cadherins and nectins are major CAMs at AJs. Claudins and JAMs are associated with ZO proteins, whereas cadherins are associated with β- and α-catenins, and nectins are associated with afadin. We previously showed that nectins first form cell-cell adhesions where the cadherin-catenin complex is recruited to form AJs, followed by the recruitment of the JAM-ZO and claudin-ZO complexes to the apical side of AJs to form TJs. It is not fully understood how TJ components are recruited to the apical side of AJs. We studied the roles of afadin and ZO-1 in the formation of TJs in Madin-Darby canine kidney (MDCK) cells. Before the formation of TJs, ZO-1 interacted with afadin through the two proline-rich regions of afadin and the SH3 domain of ZO-1. During and after the formation of TJs, ZO-1 dissociated from afadin and associated with JAM-A. Knockdown of afadin impaired the formation of both AJs and TJs in MDCK cells, whereas knockdown of ZO-1 impaired the formation of TJs, but not AJs. Re-expression of full-length afadin restored the formation of both AJs and TJs in afadin-knockdown MDCK cells, whereas re-expression of afadin-ΔPR1–2, which is incapable of binding to ZO-1, restored the formation of AJs, but not TJs. These results indicate that the transient interaction of afadin with ZO-1 is necessary for the formation of TJs in MDCK cells. PMID:20008323

Extracorporeal shock wave therapy in treatment of delayed bone-tendon healing.

PubMed

Wang, Lin; Qin, Ling; Lu, Hong-bin; Cheung, Wing-hoi; Yang, Hu; Wong, Wan-nar; Chan, Kai-ming; Leung, Kwok-sui

2008-02-01

Extracorporeal shock wave therapy is indicated for treatment of chronic injuries of soft tissues and delayed fracture healing and nonunion. No investigation has been conducted to study the effect of shock wave on delayed healing at the bone-tendon junction. Shock wave promotes osteogenesis, regeneration of fibrocartilage zone, and remodeling of healing tissue in delayed healing of bone-tendon junction surgical repair. Controlled laboratory study. Twenty-eight mature rabbits were used for establishing a delayed healing model at the patella-patellar tendon complex after partial patellectomy and then divided into control and shock wave groups. In the shock wave group, a single shock wave treatment was given at week 6 postoperatively to the patella-patellar tendon healing complex. Seven samples were harvested at week 8 and 7 samples at week 12 for radiologic, densitometric, histologic, and mechanical evaluations. Radiographic measurements showed 293.4% and 185.8% more new bone formation at the patella-patellar tendon healing junction in the shock wave group at weeks 8 and 12, respectively. Significantly better bone mineral status was found in the week 12 shock wave group. Histologically, the shock wave group showed more advanced remodeling in terms of better alignment of collagen fibers and thicker and more mature regenerated fibrocartilage zone at both weeks 8 and 12. Mechanical testing showed 167.7% and 145.1% higher tensile load and strength in the shock wave group at week 8 and week 12, respectively, compared with controls. Extracorporeal shock wave promotes osteogenesis, regeneration of fibrocartilage zone, and remodeling in the delayed bone-to-tendon healing junction in rabbits. These results provide a foundation for future clinical studies toward establishment of clinical indication for treatment of delayed bone-to-tendon junction healing.

Secret handshakes: cell-cell interactions and cellular mimics.

PubMed

Cohen, Daniel J; Nelson, W James

2018-02-01

Cell-cell junctions, acting as 'secret handshakes', mediate cell-cell interactions and make multicellularity possible. Work over the previous century illuminated key players comprising these junctions including the cadherin superfamily, nectins, CAMs, connexins, notch/delta, lectins, and eph/Ephrins. Recent work has focused on elucidating how interactions between these complex and often contradictory cues can ultimately give rise to large-scale organization in tissues. This effort, in turn, has enabled bioengineering advances such as cell-mimetic interfaces that allow us to better probe junction biology and to develop new biomaterials. This review details exciting, recent developments in these areas as well as providing both historical context and a discussion of some topical challenges and opportunities for the future. Copyright © 2018 Elsevier Ltd. All rights reserved.

Transmembrane protein PERP is a component of tessellate junctions and of other junctional and non-junctional plasma membrane regions in diverse epithelial and epithelium-derived cells.

PubMed

Franke, Werner W; Heid, Hans; Zimbelmann, Ralf; Kuhn, Caecilia; Winter-Simanowski, Stefanie; Dörflinger, Yvette; Grund, Christine; Rickelt, Steffen

2013-07-01

Protein PERP (p53 apoptosis effector related to PMP-22) is a small (21.4 kDa) transmembrane polypeptide with an amino acid sequence indicative of a tetraspanin character. It is enriched in the plasma membrane and apparently contributes to cell-cell contacts. Hitherto, it has been reported to be exclusively a component of desmosomes of some stratified epithelia. However, by using a series of newly generated mono- and polyclonal antibodies, we show that protein PERP is not only present in all kinds of stratified epithelia but also occurs in simple, columnar, complex and transitional epithelia, in various types of squamous metaplasia and epithelium-derived tumors, in diverse epithelium-derived cell cultures and in myocardial tissue. Immunofluorescence and immunoelectron microscopy allow us to localize PERP predominantly in small intradesmosomal locations and in variously sized, junction-like peri- and interdesmosomal regions ("tessellate junctions"), mostly in mosaic or amalgamated combinations with other molecules believed, to date, to be exclusive components of tight and adherens junctions. In the heart, PERP is a major component of the composite junctions of the intercalated disks connecting cardiomyocytes. Finally, protein PERP is a cobblestone-like general component of special plasma membrane regions such as the bile canaliculi of liver and subapical-to-lateral zones of diverse columnar epithelia and upper urothelial cell layers. We discuss possible organizational and architectonic functions of protein PERP and its potential value as an immunohistochemical diagnostic marker.

Exploring motorcyclist injury severity resulting from various crash configurations at T-junctions in the United Kingdom--an application of the ordered probit models.

PubMed

Pai, Chih-Wei; Saleh, Wafaa

2007-03-01

The fact that motorcycle users tend to be more vulnerable to injuries than those using other motorized vehicles may act synergistically with the complexity of conflicting movements between vehicles and motorcycles to increase injury severity in a junction-type accident. A junction-type collision tends to be more severe than a non-junction case due to the fact that some of the injurious crashes such as angle-collision commonly occur. Existing studies have applied several statistical modeling techniques to examine influential factors on the occurrences of different crashes among motorized vehicles but surprisingly very little has empirically explored whether a particular crash type, resulting from a junction-type accident, is more injurious to motorcyclists. This article attempts to investigate whether a particular collision is more deadly to motorcyclists conditioned on crash occurrence at T-junctions in the U.K., while controlling for environment, vehicle, and demographic factors. The statistical modeling technique employed is the ordered probit models using the data extracted from the STATS19 accident injury database (1999-2004). The modeling found determinants of injury severity among motorcyclists at T-junctions in the U.K. For example, an approach-turn/head-on collision is much more injurious to motorcyclists; and, those riding in early morning (i.e., 0000-0659) are more likely to be severely injured. This study offers a guideline for future research, as well as insight into potential prevention strategies that might help moderate motorcyclist injuries.

Intercellular communication via gap junctions affected by mechanical load in the bovine annulus fibrosus.

PubMed

Desrochers, Jane; Duncan, Neil A

2014-01-01

Cells in the intervertebral disc, as in other connective tissues including tendon, ligament and bone, form interconnected cellular networks that are linked via functional gap junctions. These cellular networks may be necessary to affect a coordinated response to mechanical and environmental stimuli. Using confocal microscopy with fluorescence recovery after photobleaching methods, we explored the in situ strain environment of the outer annulus of an intact bovine disc and the effect of high-level flexion on gap junction signalling. The in situ strain environment in the extracellular matrix of the outer annulus under high flexion load was observed to be non-uniform with the extensive cellular processes remaining crimped sometimes at flexion angles greater than 25°. A significant transient disruption of intercellular communication via functional gap junctions was measured after 10 and 20 min under high flexion load. This study illustrates that in healthy annulus fibrosus tissue, high mechanical loads can impede the functioning of the gap junctions. Future studies will explore more complex loading conditions to determine whether losses in intercellular communication can be permanent and whether gap junctions in aged and degenerated tissues become more susceptible to load. The current research suggests that cellular structures such as gap junctions and intercellular networks, as well as other cell-cell and cell-matrix interconnections, need to be considered in computational models in order to fully understand how macroscale mechanical signals are transmitted across scales to the microscale and ultimately into a cellular biosynthetic response in collagenous tissues.

Bovine dairy complex lipids improve in vitro measures of small intestinal epithelial barrier integrity.

PubMed

Anderson, Rachel C; MacGibbon, Alastair K H; Haggarty, Neill; Armstrong, Kelly M; Roy, Nicole C

2018-01-01

Appropriate intestinal barrier maturation is essential for absorbing nutrients and preventing pathogens and toxins from entering the body. Compared to breast-fed infants, formula-fed infants are more susceptible to barrier dysfunction-associated illnesses. In infant formula dairy lipids are usually replaced with plant lipids. We hypothesised that dairy complex lipids improve in vitro intestinal epithelial barrier integrity. We tested milkfat high in conjugated linoleic acid, beta serum (SureStart™Lipid100), beta serum concentrate (BSC) and a ganglioside-rich fraction (G600). Using Caco-2 cells as a model of the human small intestinal epithelium, we analysed the effects of the ingredients on trans-epithelial electrical resistance (TEER), mannitol flux, and tight junction protein co-localisation. BSC induced a dose-dependent improvement in TEER across unchallenged cell layers, maintained the co-localisation of tight junction proteins in TNFα-challenged cells with increased permeability, and mitigated the TEER-reducing effects of lipopolysaccharide (LPS). G600 also increased TEER across healthy and LPS-challenged cells, but it did not alter the co-location of tight junction proteins in TNFα-challenged cells. SureStart™Lipid100 had similar TEER-increasing effects to BSC when added at twice the concentration (similar lipid concentration). Ultimately, this research aims to contribute to the development of infant formulas supplemented with dairy complex lipids that support infant intestinal barrier maturation.

Multiple Rap1 effectors control Epac1-mediated tightening of endothelial junctions.

PubMed

Pannekoek, Willem-Jan; Vliem, Marjolein J; Bos, Johannes L

2018-02-17

Epac1 and Rap1 mediate cAMP-induced tightening of endothelial junctions. We have previously found that one of the mechanisms is the inhibition of Rho-mediated tension in radial stress fibers by recruiting the RhoGAP ArhGAP29 in a complex containing the Rap1 effectors Rasip1 and Radil. However, other mechanisms have been proposed as well, most notably the induction of tension in circumferential actin cables by Cdc42 and its GEF FGD5. Here, we have investigated how Rap1 controls FGD5/Cdc42 and how this interconnects with Radil/Rasip1/ArhGAP29. Using endothelial barrier measurements, we show that Rho inhibition is not sufficient to explain the barrier stimulating effect of Rap1. Indeed, Cdc42-mediated tension is induced at cell-cell contacts upon Rap1 activation and this is required for endothelial barrier function. Depletion of potential Rap1 effectors identifies AF6 to mediate Rap1 enhanced tension and concomitant Rho-independent barrier function. When overexpressed in HEK293T cells, AF6 is found in a complex with FGD5 and Radil. From these results we conclude that Rap1 utilizes multiple pathways to control tightening of endothelial junctions, possibly through a multiprotein effector complex, in which AF6 functions to induce tension in circumferential actin cables.

Bovine dairy complex lipids improve in vitro measures of small intestinal epithelial barrier integrity

PubMed Central

MacGibbon, Alastair K. H.; Haggarty, Neill; Armstrong, Kelly M.; Roy, Nicole C.

2018-01-01

Appropriate intestinal barrier maturation is essential for absorbing nutrients and preventing pathogens and toxins from entering the body. Compared to breast-fed infants, formula-fed infants are more susceptible to barrier dysfunction-associated illnesses. In infant formula dairy lipids are usually replaced with plant lipids. We hypothesised that dairy complex lipids improve in vitro intestinal epithelial barrier integrity. We tested milkfat high in conjugated linoleic acid, beta serum (SureStart™Lipid100), beta serum concentrate (BSC) and a ganglioside-rich fraction (G600). Using Caco-2 cells as a model of the human small intestinal epithelium, we analysed the effects of the ingredients on trans-epithelial electrical resistance (TEER), mannitol flux, and tight junction protein co-localisation. BSC induced a dose-dependent improvement in TEER across unchallenged cell layers, maintained the co-localisation of tight junction proteins in TNFα-challenged cells with increased permeability, and mitigated the TEER-reducing effects of lipopolysaccharide (LPS). G600 also increased TEER across healthy and LPS-challenged cells, but it did not alter the co-location of tight junction proteins in TNFα-challenged cells. SureStart™Lipid100 had similar TEER-increasing effects to BSC when added at twice the concentration (similar lipid concentration). Ultimately, this research aims to contribute to the development of infant formulas supplemented with dairy complex lipids that support infant intestinal barrier maturation. PMID:29304106

Exploiting the Gastric Epithelial Barrier: Helicobacter pylori's Attack on Tight and Adherens Junctions.

PubMed

Backert, Steffen; Schmidt, Thomas P; Harrer, Aileen; Wessler, Silja

2017-01-01

Highly organized intercellular tight and adherens junctions are crucial structural components for establishing and maintenance of epithelial barrier functions, which control the microbiota and protect against intruding pathogens in humans. Alterations in these complexes represent key events in the development and progression of multiple infectious diseases as well as various cancers. The gastric pathogen Helicobacter pylori exerts an amazing set of strategies to manipulate these epithelial cell-to-cell junctions, which are implicated in changing cell polarity, migration and invasive growth as well as pro-inflammatory and proliferative responses. This chapter focuses on the H. pylori pathogenicity factors VacA, CagA, HtrA and urease, and how they can induce host cell signaling involved in altering cell-to-cell permeability. We propose a stepwise model for how H. pylori targets components of tight and adherens junctions in order to disrupt the gastric epithelial cell layer, giving fresh insights into the pathogenesis of this important bacterium.

Dlg3 Trafficking and Apical Tight Junction Formation Is Regulated by Nedd4 and Nedd4-2 E3 Ubiquitin Ligases

PubMed Central

Van Campenhout, Claude A.; Eitelhuber, Andrea; Gloeckner, Christian J.; Giallonardo, Patrizia; Gegg, Moritz; Oller, Heide; Grant, Seth G.N.; Krappmann, Daniel; Ueffing, Marius; Lickert, Heiko

2011-01-01

Summary The Drosophila Discs large (Dlg) scaffolding protein acts as a tumor suppressor regulating basolateral epithelial polarity and proliferation. In mammals, four Dlg homologs have been identified; however, their functions in cell polarity remain poorly understood. Here, we demonstrate that the X-linked mental retardation gene product Dlg3 contributes to apical-basal polarity and epithelial junction formation in mouse organizer tissues, as well as to planar cell polarity in the inner ear. We purified complexes associated with Dlg3 in polarized epithelial cells, including proteins regulating directed trafficking and tight junction formation. Remarkably, of the four Dlg family members, Dlg3 exerts a distinct function by recruiting the ubiquitin ligases Nedd4 and Nedd4-2 through its PPxY motifs. We found that these interactions are required for Dlg3 monoubiquitination, apical membrane recruitment, and tight junction consolidation. Our findings reveal an unexpected evolutionary diversification of the vertebrate Dlg family in basolateral epithelium formation. PMID:21920314

Kondo blockade due to quantum interference in single-molecule junctions

PubMed Central

Mitchell, Andrew K.; Pedersen, Kim G. L.; Hedegård, Per; Paaske, Jens

2017-01-01

Molecular electronics offers unique scientific and technological possibilities, resulting from both the nanometre scale of the devices and their reproducible chemical complexity. Two fundamental yet different effects, with no classical analogue, have been demonstrated experimentally in single-molecule junctions: quantum interference due to competing electron transport pathways, and the Kondo effect due to entanglement from strong electronic interactions. Here we unify these phenomena, showing that transport through a spin-degenerate molecule can be either enhanced or blocked by Kondo correlations, depending on molecular structure, contacting geometry and applied gate voltages. An exact framework is developed, in terms of which the quantum interference properties of interacting molecular junctions can be systematically studied and understood. We prove that an exact Kondo-mediated conductance node results from destructive interference in exchange-cotunneling. Nonstandard temperature dependences and gate-tunable conductance peaks/nodes are demonstrated for prototypical molecular junctions, illustrating the intricate interplay of quantum effects beyond the single-orbital paradigm. PMID:28492236

Binding configurations and intramolecular strain in single-molecule devices.

PubMed

Rascón-Ramos, Habid; Artés, Juan Manuel; Li, Yuanhui; Hihath, Joshua

2015-05-01

The development of molecular-scale electronic devices has made considerable progress over the past decade, and single-molecule transistors, diodes and wires have all been demonstrated. Despite this remarkable progress, the agreement between theoretically predicted conductance values and those measured experimentally remains limited. One of the primary reasons for these discrepancies lies in the difficulty to experimentally determine the contact geometry and binding configuration of a single-molecule junction. In this Article, we apply a small-amplitude, high-frequency, sinusoidal mechanical signal to a series of single-molecule devices during junction formation and breakdown. By measuring the current response at this frequency, it is possible to determine the most probable binding and contact configurations for the molecular junction at room temperature in solution, and to obtain information about how an applied strain is distributed within the molecular junction. These results provide insight into the complex configuration of single-molecule devices, and are in excellent agreement with previous predictions from theoretical models.

The role of apical cell-cell junctions and associated cytoskeleton in mechanotransduction.

PubMed

Sluysmans, Sophie; Vasileva, Ekaterina; Spadaro, Domenica; Shah, Jimit; Rouaud, Florian; Citi, Sandra

2017-04-01

Tissues of multicellular organisms are characterised by several types of specialised cell-cell junctions. In vertebrate epithelia and endothelia, tight and adherens junctions (AJ) play critical roles in barrier and adhesion functions, and are connected to the actin and microtubule cytoskeletons. The interaction between junctions and the cytoskeleton is crucial for tissue development and physiology, and is involved in the molecular mechanisms governing cell shape, motility, growth and signalling. The machineries which functionally connect tight and AJ to the cytoskeleton comprise proteins which either bind directly to cytoskeletal filaments, or function as adaptors for regulators of the assembly and function of the cytoskeleton. In the last two decades, specific cytoskeleton-associated junctional molecules have been implicated in mechanotransduction, revealing the existence of multimolecular complexes that can sense mechanical cues and translate them into adaptation to tensile forces and biochemical signals. Here, we summarise the current knowledge about the machineries that link tight and AJ to actin filaments and microtubules, and the molecular basis for mechanotransduction at epithelial and endothelial AJ. © 2017 Société Française des Microscopies and Société de Biologie Cellulaire de France. Published by John Wiley & Sons Ltd.

Interlocked positive and negative feedback network motifs regulate β-catenin activity in the adherens junction pathway

PubMed Central

Klinke, David J.; Horvath, Nicholas; Cuppett, Vanessa; Wu, Yueting; Deng, Wentao; Kanj, Rania

2015-01-01

The integrity of epithelial tissue architecture is maintained through adherens junctions that are created through extracellular homotypic protein–protein interactions between cadherin molecules. Cadherins also provide an intracellular scaffold for the formation of a multiprotein complex that contains signaling proteins, including β-catenin. Environmental factors and controlled tissue reorganization disrupt adherens junctions by cleaving the extracellular binding domain and initiating a series of transcriptional events that aim to restore tissue homeostasis. However, it remains unclear how alterations in cell adhesion coordinate transcriptional events, including those mediated by β-catenin in this pathway. Here were used quantitative single-cell and population-level in vitro assays to quantify the endogenous pathway dynamics after the proteolytic disruption of the adherens junctions. Using prior knowledge of isolated elements of the overall network, we interpreted these data using in silico model-based inference to identify the topology of the regulatory network. Collectively the data suggest that the regulatory network contains interlocked network motifs consisting of a positive feedback loop, which is used to restore the integrity of adherens junctions, and a negative feedback loop, which is used to limit β-catenin–induced gene expression. PMID:26224311

Early detection of a two-long-terminal-repeat junction molecule in the cytoplasm of recombinant murine leukemia virus-infected cells.

PubMed

Serhan, Fatima; Penaud, Magalie; Petit, Caroline; Leste-Lasserre, Thierry; Trajcevski, Stéphane; Klatzmann, David; Duisit, Ghislaine; Sonigo, Pierre; Moullier, Philippe

2004-06-01

We showed that a U5-U3 junction was reproducibly detected by a PCR assay as early as 1 to 2 h postinfection with a DNase-treated murine leukemia virus (MLV)-containing supernatant in aphidicolin-arrested NIH 3T3 cells, as well as in nonarrested cells. Such detection is azidothymidine sensitive and corresponded to neosynthesized products of the reverse transcriptase. This observation was confirmed in two additional human cell lines, TE671 and ARPE-19. Using cell fractionation combined with careful controls, we found that a two-long-terminal-repeat (two-LTR) junction molecule was detectable in the cytoplasm as early as 2 h post virus entry. Altogether, our data indicated that the neosynthesized retroviral DNA led to the early formation of structures including true two-LTR junctions in the cytoplasm of MLV-infected cells. Thus, the classical assumption that two-LTR circles are a mitosis-dependent dead-end product accumulating in the nucleus must be reconsidered. MLV-derived products containing a two-LTR junction can no longer be used as an exclusive surrogate for the preintegration complex nuclear translocation event.

Alpha-catenin-dependent recruitment of the centrosomal protein CAP350 to adherens junctions allows epithelial cells to acquire a columnar shape.

PubMed

Gavilan, Maria P; Arjona, Marina; Zurbano, Angel; Formstecher, Etienne; Martinez-Morales, Juan R; Bornens, Michel; Rios, Rosa M

2015-03-01

Epithelial morphogenesis involves a dramatic reorganisation of the microtubule cytoskeleton. How this complex process is controlled at the molecular level is still largely unknown. Here, we report that the centrosomal microtubule (MT)-binding protein CAP350 localises at adherens junctions in epithelial cells. By two-hybrid screening, we identified a direct interaction of CAP350 with the adhesion protein α-catenin that was further confirmed by co-immunoprecipitation experiments. Block of epithelial cadherin (E-cadherin)-mediated cell-cell adhesion or α-catenin depletion prevented CAP350 localisation at cell-cell junctions. Knocking down junction-located CAP350 inhibited the establishment of an apico-basal array of microtubules and impaired the acquisition of columnar shape in Madin-Darby canine kidney II (MDCKII) cells grown as polarised epithelia. Furthermore, MDCKII cystogenesis was also defective in junctional CAP350-depleted cells. CAP350-depleted MDCKII cysts were smaller and contained either multiple lumens or no lumen. Membrane polarity was not affected, but cortical microtubule bundles did not properly form. Our results indicate that CAP350 may act as an adaptor between adherens junctions and microtubules, thus regulating epithelial differentiation and contributing to the definition of cell architecture. We also uncover a central role of α-catenin in global cytoskeleton remodelling, in which it acts not only on actin but also on MT reorganisation during epithelial morphogenesis.

Mechanics of flow and sediment transport in delta distributary channels

USGS Publications Warehouse

Nelson, Jonathan M.; Kinzel, Paul J.; Duc Toan, Duong; Shimizu, Yasuyuki; McDonald, Richard R.

2011-01-01

boundary conditions. Over time, the pattern of erosion and deposition in the distributary channels gives rise to variations in the amount of water and sediment routed into them. In the simplest case, this results in channel switching on deltas, but in a more general sense these dynamics produce a rich suite of interesting morphologic change contributing both to the evolution of the channel distributary network and the overall evolution of the delta. As part of a study to develop a better understanding of these processes, we conducted a field study measuring the detailed morphology of the Hong-Luoc junction on the Red River downstream of Hanoi, Vietnam. This junction was selected for such a study because it has a 1,000-year history, modern observations suggest that it is currently switching (changing the proportion of sediment and streamflow provided to each of the distributary channels), and hydrologic configuration of the junction allows for the study of two bifurcations and one confluence in a single junction complex. In this paper, our morphologic observations are used in computational flow models to show how flow and sediment transport changes as a function of total discharge upstream of the junction. This is a key component of understanding how the junction attains stability over a range of flows or how imbalances in the distribution of flow and sediment transport lead to destabilization of the channel bifurcation.

Induction of stable ER–plasma-membrane junctions by Kv2.1 potassium channels

PubMed Central

Fox, Philip D.; Haberkorn, Christopher J.; Akin, Elizabeth J.; Seel, Peter J.; Krapf, Diego; Tamkun, Michael M.

2015-01-01

ABSTRACT Junctions between cortical endoplasmic reticulum (cER) and the plasma membrane are a subtle but ubiquitous feature in mammalian cells; however, very little is known about the functions and molecular interactions that are associated with neuronal ER–plasma-membrane junctions. Here, we report that Kv2.1 (also known as KCNB1), the primary delayed-rectifier K+ channel in the mammalian brain, induces the formation of ER–plasma-membrane junctions. Kv2.1 localizes to dense, cell-surface clusters that contain non-conducting channels, indicating that they have a function that is unrelated to membrane-potential regulation. Accordingly, Kv2.1 clusters function as membrane-trafficking hubs, providing platforms for delivery and retrieval of multiple membrane proteins. Using both total internal reflection fluorescence and electron microscopy we demonstrate that the clustered Kv2.1 plays a direct structural role in the induction of stable ER–plasma-membrane junctions in both transfected HEK 293 cells and cultured hippocampal neurons. Glutamate exposure results in a loss of Kv2.1 clusters in neurons and subsequent retraction of the cER from the plasma membrane. We propose Kv2.1-induced ER–plasma-membrane junctions represent a new macromolecular plasma-membrane complex that is sensitive to excitotoxic insult and functions as a scaffolding site for both membrane trafficking and Ca2+ signaling. PMID:25908859

Alpha-catenin-Dependent Recruitment of the Centrosomal Protein CAP350 to Adherens Junctions Allows Epithelial Cells to Acquire a Columnar Shape

PubMed Central

Zurbano, Angel; Formstecher, Etienne; Martinez-Morales, Juan R.; Bornens, Michel; Rios, Rosa M.

2015-01-01

Epithelial morphogenesis involves a dramatic reorganisation of the microtubule cytoskeleton. How this complex process is controlled at the molecular level is still largely unknown. Here, we report that the centrosomal microtubule (MT)-binding protein CAP350 localises at adherens junctions in epithelial cells. By two-hybrid screening, we identified a direct interaction of CAP350 with the adhesion protein α-catenin that was further confirmed by co-immunoprecipitation experiments. Block of epithelial cadherin (E-cadherin)-mediated cell-cell adhesion or α-catenin depletion prevented CAP350 localisation at cell-cell junctions. Knocking down junction-located CAP350 inhibited the establishment of an apico-basal array of microtubules and impaired the acquisition of columnar shape in Madin-Darby canine kidney II (MDCKII) cells grown as polarised epithelia. Furthermore, MDCKII cystogenesis was also defective in junctional CAP350-depleted cells. CAP350-depleted MDCKII cysts were smaller and contained either multiple lumens or no lumen. Membrane polarity was not affected, but cortical microtubule bundles did not properly form. Our results indicate that CAP350 may act as an adaptor between adherens junctions and microtubules, thus regulating epithelial differentiation and contributing to the definition of cell architecture. We also uncover a central role of α-catenin in global cytoskeleton remodelling, in which it acts not only on actin but also on MT reorganisation during epithelial morphogenesis. PMID:25764135

Cellular Organization and Cytoskeletal Regulation of the Hippo Signaling Network

PubMed Central

Sun, Shuguo; Irvine, Kenneth D.

2016-01-01

The Hippo signaling network integrates diverse upstream signals to control cell fate decisions and regulate organ growth. Recent studies have provided new insights into the cellular organization of Hippo signaling, its relationship to cell-cell junctions, and how the cytoskeleton modulates Hippo signaling. Cell-cell junctions serve as platforms for Hippo signaling by localizing scaffolding proteins that interact with core components of the pathway. Interactions of Hippo pathway components with cell-cell junctions and the cytoskeleton also suggest potential mechanisms for the regulation of the pathway by cell contact and cell polarity. As our understanding of the complexity of Hippo signaling increases, a future challenge will be to understand how the diverse inputs into the pathway are integrated, and to define their respective contributions in vivo. PMID:27268910

Cross reactive arrays of three-way junction sensors for steroid determination

NASA Technical Reports Server (NTRS)

Stojanovic, Milan N. (Inventor); Nikic, Dragan B. (Inventor); Landry, Donald (Inventor)

2008-01-01

This invention provides analyte sensitive oligonucleotide compositions for detecting and analyzing analytes in solution, including complex solutions using cross reactive arrays of analyte sensitive oligonucleotide compositions.

The long journey of botulinum neurotoxins into the synapse.

PubMed

Rummel, Andreas

2015-12-01

Botulinum neurotoxins (BoNT) cause the disease botulism, a flaccid paralysis of the muscle. They are also very effective, widely used medicines applied locally in sub-nanogram quantities. BoNTs are released together with several non-toxic, associated proteins as progenitor toxin complexes (PCT) by Clostridium botulinum to become highly potent oral poisons ingested via contaminated food. They block the neurotransmission in susceptible animals and humans already in nanogram quantities due to their specific ability to enter motoneurons and to cleave only selected neuronal proteins involved in neuroexocytosis. BoNTs have developed a sophisticated strategy to passage the gastrointestinal tract and to be absorbed in the intestine of the host to finally attack neurons. A non-toxic non-hemagglutinin (NTNHA) forms a binary complex with BoNT to protect it from gastrointestinal degradation. This binary M-PTC is one component of the bi-modular 14-subunit ∼760 kDa large progenitor toxin complex. The other component is the structurally and functionally independent dodecameric hemagglutinin (HA) complex which facilitates the absorption on the intestinal epithelium by glycan binding. Subsequent to its transcytosis the HA complex disrupts the tight junction of the intestinal barrier from the basolateral side by binding to E-cadherin. Now, the L-PTC can also enter the circulation by paracellular routes in much larger quantities. From here, the dissociated BoNTs reach the neuromuscular junction and accumulate via interaction with polysialo gangliosides, complex glycolipids, on motoneurons at the neuromuscular junction. Subsequently, additional specific binding to luminal segments of synaptic vesicles proteins like SV2 and synaptotagmin leads to their uptake. Finally, the neurotoxins shut down the synaptic vesicle cycle, which they had exploited before to enter their target cells, via specific cleavage of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins, which constitute the core components of the cellular membrane fusion machinery. Copyright © 2015 Elsevier Ltd. All rights reserved.

Humidity-controlled rectification switching in ruthenium-complex molecular junctions

NASA Astrophysics Data System (ADS)

Atesci, Huseyin; Kaliginedi, Veerabhadrarao; Celis Gil, Jose A.; Ozawa, Hiroaki; Thijssen, Joseph M.; Broekmann, Peter; Haga, Masa-aki; van der Molen, Sense Jan

2018-02-01

Although molecular rectifiers were proposed over four decades ago1,2, until recently reported rectification ratios (RR) were rather moderate2-11 (RR 101). This ceiling was convincingly broken using a eutectic GaIn top contact12 to probe molecular monolayers of coupled ferrocene groups (RR 105), as well as using scanning tunnelling microscopy-break junctions13-16 and mechanically controlled break junctions17 to probe single molecules (RR 102-103). Here, we demonstrate a device based on a molecular monolayer in which the RR can be switched by more than three orders of magnitude (between RR 100 and RR ≥ 103) in response to humidity. As the relative humidity is toggled between 5% and 60%, the current-voltage (I-V) characteristics of a monolayer of di-nuclear Ru-complex molecules reversibly change from symmetric to strongly asymmetric (diode-like). Key to this behaviour is the presence of two localized molecular orbitals in series, which are nearly degenerate in dry circumstances but become misaligned under high humidity conditions, due to the displacement of counter ions (PF6-). This asymmetric gating of the two relevant localized molecular orbital levels results in humidity-controlled diode-like behaviour.

The central element of the synaptonemal complex in mice is organized as a bilayered junction structure.

PubMed

Hernández-Hernández, Abrahan; Masich, Sergej; Fukuda, Tomoyuki; Kouznetsova, Anna; Sandin, Sara; Daneholt, Bertil; Höög, Christer

2016-06-01

The synaptonemal complex transiently stabilizes pairing interactions between homologous chromosomes during meiosis. Assembly of the synaptonemal complex is mediated through integration of opposing transverse filaments into a central element, a process that is poorly understood. We have, here, analyzed the localization of the transverse filament protein SYCP1 and the central element proteins SYCE1, SYCE2 and SYCE3 within the central region of the synaptonemal complex in mouse spermatocytes using immunoelectron microscopy. Distribution of immuno-gold particles in a lateral view of the synaptonemal complex, supported by protein interaction data, suggest that the N-terminal region of SYCP1 and SYCE3 form a joint bilayered central structure, and that SYCE1 and SYCE2 localize in between the two layers. We find that disruption of SYCE2 and TEX12 (a fourth central element protein) localization to the central element abolishes central alignment of the N-terminal region of SYCP1. Thus, our results show that all four central element proteins, in an interdependent manner, contribute to stabilization of opposing N-terminal regions of SYCP1, forming a bilayered transverse-filament-central-element junction structure that promotes synaptonemal complex formation and synapsis. © 2016. Published by The Company of Biologists Ltd.

Acetylcholine attenuated TNF-α-induced intracellular Ca2+ overload by inhibiting the formation of the NCX1-TRPC3-IP3R1 complex in human umbilical vein endothelial cells.

PubMed

Zhao, Ming; Jia, Hang-Huan; Liu, Long-Zhu; Bi, Xue-Yuan; Xu, Man; Yu, Xiao-Jiang; He, Xi; Zang, Wei-Jin

2017-06-01

The endoplasmic reticulum (ER) forms discrete junctions with the plasma membrane (PM) that play a critical role in the regulation of Ca 2+ signaling during cellular bioenergetics, apoptosis and autophagy. We have previously confirmed that acetylcholine can inhibit ER stress and apoptosis after inflammatory injury. However, limited research has focused on the effects of acetylcholine on ER-PM junctions. In this work, we evaluated the structure and function of the supramolecular sodium-calcium exchanger 1 (NCX1)-transient receptor potential canonical 3 (TRPC3)-inositol 1,4,5-trisphosphate receptor 1 (IP3R1) complex, which is involved in regulating Ca 2+ homeostasis during inflammatory injury. The width of the ER-PM junctions of human umbilical vein endothelial cells (HUVECs) was measured in nanometres using transmission electron microscopy and a fluorescent probe for Ca 2+ . Protein-protein interactions were assessed by immunoprecipitation. Ca 2+ concentration was measured using a confocal microscope. An siRNA assay was employed to silence specific proteins. Our results demonstrated that the peripheral ER was translocated to PM junction sites when induced by tumour necrosis factor-alpha (TNF-α) and that NCX1-TRPC3-IP3R1 complexes formed at these sites. After down-regulating the protein expression of NCX1 or IP3R1, we found that the NCX1-mediated inflow of Ca 2+ and the release of intracellular Ca 2+ stores were reduced in TNF-α-treated cells. We also observed that acetylcholine attenuated the formation of NCX1-TRPC3-IP3R1 complexes and maintained calcium homeostasis in cells treated with TNF-α. Interestingly, the positive effects of acetylcholine were abolished by the selective M3AChR antagonist darifenacin and by AMPK siRNAs. These results indicate that acetylcholine protects endothelial cells from TNF-alpha-induced injury, [Ca 2+ ] cyt overload and ER-PM interactions, which depend on the muscarinic 3 receptor/AMPK pathway, and that acetylcholine may be a new inhibitor for suppressing [Ca 2+ ] cyt overload. Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermodynamic characterization of a triple-helical three-way junction containing a Hoogsteen branch point.

PubMed

Hüsler, P L; Klump, H H

1995-09-10

We have designed a Hoogsteen (HG) triple-helical three-way junction (ternary complex) constructed from three 33-mer oligonucleotides based on the same subset of sequences used for the Watson-Crick (WC) triple-helical three-way junction, characterized previously (P. L. Hüsler and H. H. Klump (1994) Arch. Biochem. Biophys., 313, 29-38). The junction differs primarily in the assembly of the branch point and the ends of the arms. The three oligonucleotides can each fold into a WC hairpin, linked by a four-member cytosine loop, each containing a homo-pyrimidine 10-mer single-strand extension. On lowering the pH (between 6 and 4), the extensions mutually associate to one of the other hairpins via Hoogsteen (HG) hydrogen bonding. Collectively, this process results in the formation of the branch point and the triple-helical arms. The HG triple-helical three-way junction is characterized by gel electrophoresis, circular dichroism, uv melting, and differential scanning calorimetry. The junction undergoes thermal unfolding in two distinct temperature regions. In the temperature range 15 to 50 degrees C loss of HG base pairing results in the dissociation of the three-way junction. Between 55 and 95 degrees C the resulting hairpins undergo further successive unfolding. The overall calorimetric unfolding enthalpy and entropy changes associated with the loss of HG base pairing are approximately equal to the sum of the enthalpy and entropy changes associated with the dissociation of the HG base pairing in the isolated arms (170.6 kcal.mol-1; 540.1 cal.mol-1.K-1). It is apparent from these results that in the proximity of the branch point the structure is not perturb or strain. This result is contrary to the results obtained for the WC triple-helical three-way and for three-way junctions constructed from canonical double-helical DNA. Complete folding of the junction requires either high Na+ (600 mM) ion concentrations or 40-60 mM Mg2+.

Functional asymmetry and plasticity of electrical synapses interconnecting neurons through a 36-state model of gap junction channel gating

PubMed Central

Kraujalis, Tadas; Maciunas, Kestutis

2017-01-01

We combined the Hodgkin–Huxley equations and a 36-state model of gap junction channel gating to simulate electrical signal transfer through electrical synapses. Differently from most previous studies, our model can account for dynamic modulation of junctional conductance during the spread of electrical signal between coupled neurons. The model of electrical synapse is based on electrical properties of the gap junction channel encompassing two fast and two slow gates triggered by the transjunctional voltage. We quantified the influence of a difference in input resistances of electrically coupled neurons and instantaneous conductance–voltage rectification of gap junctions on an asymmetry of cell-to-cell signaling. We demonstrated that such asymmetry strongly depends on junctional conductance and can lead to the unidirectional transfer of action potentials. The simulation results also revealed that voltage spikes, which develop between neighboring cells during the spread of action potentials, can induce a rapid decay of junctional conductance, thus demonstrating spiking activity-dependent short-term plasticity of electrical synapses. This conclusion was supported by experimental data obtained in HeLa cells transfected with connexin45, which is among connexin isoforms expressed in neurons. Moreover, the model allowed us to replicate the kinetics of junctional conductance under different levels of intracellular concentration of free magnesium ([Mg2+]i), which was experimentally recorded in cells expressing connexin36, a major neuronal connexin. We demonstrated that such [Mg2+]i-dependent long-term plasticity of the electrical synapse can be adequately reproduced through the changes of slow gate parameters of the 36-state model. This suggests that some types of chemical modulation of gap junctions can be executed through the underlying mechanisms of voltage gating. Overall, the developed model accounts for direction-dependent asymmetry, as well as for short- and long-term plasticity of electrical synapses. Our modeling results demonstrate that such complex behavior of the electrical synapse is important in shaping the response of coupled neurons. PMID:28384220

Expression of TM4SF10, a Claudin/EMP/PMP22 family cell junction protein, during mouse kidney development and podocyte differentiation.

PubMed

Bruggeman, Leslie A; Martinka, Scott; Simske, Jeffrey S

2007-02-01

Cell junctions in the nephron are highly specialized to perform specific and distinct filtration and reabsorption functions. The mature kidney forms complex cell junctions including slit diaphragms that prevent the passage of serum proteins into the filtrate, and tubule cell junctions that regulate specific paracellular ion reuptake. We have investigated the expression of TM4SF10 (Trans-Membrane tetra(4)-Span Family 10) in mouse kidneys. TM4SF10 is the vertebrate orthologue of Caenorhabditis elegans VAB-9, a tetraspan adherens junction protein in the PMP22/EMP/Claudin family of proteins. We found that TM4SF10 localizes at the basal-most region of podocyte precursors before the capillary loop stage, at some tubule precursors, and at the ureteric bud junction with S-shaped bodies. Overall expression of TM4SF10 peaked at postnatal day 4 and was virtually absent in adult kidneys. The very limited expression of TM4SF10 protein that persisted into adulthood was restricted to a few tubule segments but remained localized to the basal region of lateral membranes. In undifferentiated cultured podocytes, TM4SF10 localized to the perinuclear region and translocated to the cell membrane after Cadherin appearance at cell-cell contacts. TM4SF10 colocalized with ZO1 and p120ctn in undifferentiated confluent podocytes and also colocalized with the tips of actin filaments at cell contacts. Upon differentiation of cultured podocytes, TM4SF10 protein disappeared from cell contacts and expression ceased. These results suggest that TM4SF10 functions during differentiation of podocytes and may participate in the maturation of cell junctions from simple adherens junctions to elaborate slit diaphragms. TM4SF10 may define a new class of Claudin-like proteins that function during junctional development.

A novel reduced symmetry oxide (Mg3B2O6) for magnetic tunnel junctions based on FeCo or Fe leads

NASA Astrophysics Data System (ADS)

Stewart, Derek

2010-03-01

Magnetic tunnel junctions with high TMR values, such as FeMgOFe, capitalize on spin filtering in the oxide due to the band symmetry of incident electrons. However, these structures rely on magnetic leads and oxide regions of the same cubic symmetry class. This raises the question of whether reducing the oxide symmetry can enhance spin filtering. A new magnetic tunnel junction (FeCoMg3B2O6FeCo) is presented that uses a reduced symmetry oxide region (orthorhombic) to filter spins between two cubic magnetic leads. Symmetry analysis of coupling between states in the cubic leads and the orthorhombic oxide indicates that majority carrier tunneling through the oxide should be favored over minority carriers. Complex band structure analysis of Mg3B2O6 shows that the relevant evanescent states in the band gap are due to boron p states and that there is sufficient difference in the decay rates of the imaginary bands for spin filtering to occur. Electronic transport calculations through a FeMg3B2O6Fe magnetic tunnel junction are also performed to address the possible influence of interface states. Some recent experimental studies of FeCoBMgOFeCoB junctions, with B diffusion into the MgO region, indicate that this new type of junction may have already been fabricated. The prospect of developing a general class of magnetic tunnel junctions based on reduced symmetry oxides is also examined.

A new method to synthesize complicated multi-branched carbon nanotubes with controlled architecture and composition.

PubMed

Wei, Dacheng; Liu, Yunqi; Cao, Lingchao; Fu, Lei; Li, Xianglong; Wang, Yu; Yu, Gui; Zhu, Daoben

2006-02-01

Here we develop a simple method by using flow fluctuation to synthesize arrays of multi-branched carbon nanotubes (CNTs) that are far more complex than those previously reported. The architectures and compositions can be well controlled, thus avoiding any template or additive. A branching mechanism of fluctuation-promoted coalescence of catalyst particles is proposed. This finding will provide a hopeful approach to the goal of CNT-based integrated circuits and be valuable for applying branched junctions in nanoelectronics and producing branched junctions of other materials.

Resonant tunneling via a Ru-dye complex using a nanoparticle bridge junction.

PubMed

Nishijima, Satoshi; Otsuka, Yoichi; Ohoyama, Hiroshi; Kajimoto, Kentaro; Araki, Kento; Matsumoto, Takuya

2018-06-15

Nonlinear current-voltage (I-V) characteristics is an important property for the realization of information processing in molecular electronics. We studied the electrical conduction through a Ru-dye complex (N-719) on a 2-aminoethanethiol (2-AET) monolayer in a nanoparticle bridge junction system. The nonlinear I-V characteristics exhibited a threshold voltage at around 1.2 V and little temperature dependence. From the calculation of the molecular states using density functional theory and the energy alignment between the electrodes and molecules, the conduction mechanism in this system was considered to be resonant tunneling via the HOMO level of N-719. Our results indicate that the weak electronic coupling of electrodes and molecules is essential for obtaining nonlinear I-V characteristics with a clear threshold voltage that reflect the intrinsic molecular state.

Resonant tunneling via a Ru–dye complex using a nanoparticle bridge junction

NASA Astrophysics Data System (ADS)

Nishijima, Satoshi; Otsuka, Yoichi; Ohoyama, Hiroshi; Kajimoto, Kentaro; Araki, Kento; Matsumoto, Takuya

2018-06-01

Nonlinear current–voltage (I–V) characteristics is an important property for the realization of information processing in molecular electronics. We studied the electrical conduction through a Ru–dye complex (N-719) on a 2-aminoethanethiol (2-AET) monolayer in a nanoparticle bridge junction system. The nonlinear I–V characteristics exhibited a threshold voltage at around 1.2 V and little temperature dependence. From the calculation of the molecular states using density functional theory and the energy alignment between the electrodes and molecules, the conduction mechanism in this system was considered to be resonant tunneling via the HOMO level of N-719. Our results indicate that the weak electronic coupling of electrodes and molecules is essential for obtaining nonlinear I–V characteristics with a clear threshold voltage that reflect the intrinsic molecular state.

Free energy landscapes of RNA/RNA complexes: with applications to snRNA complexes in spliceosomes.

PubMed

Cao, Song; Chen, Shi-Jie

2006-03-17

We develop a statistical mechanical model for RNA/RNA complexes with both intramolecular and intermolecular interactions. As an application of the model, we compute the free energy landscapes, which give the full distribution for all the possible conformations, for U4/U6 and U2/U6 in major spliceosome and U4atac/U6atac and U12/U6atac in minor spliceosome. Different snRNA experiments found contrasting structures, our free energy landscape theory shows why these structures emerge and how they compete with each other. For yeast U2/U6, the model predicts that the two distinct experimental structures, the four-helix junction structure and the helix Ib-containing structure, can actually coexist and specifically compete with each other. In addition, the energy landscapes suggest possible mechanisms for the conformational switches in splicing. For instance, our calculation shows that coaxial stacking is essential for stabilizing the four-helix junction in yeast U2/U6. Therefore, inhibition of the coaxial stacking possibly by protein-binding may activate the conformational switch from the four-helix junction to the helix Ib-containing structure. Moreover, the change of the energy landscape shape gives information about the conformational changes. We find multiple (native-like and misfolded) intermediates formed through base-pairing rearrangements in snRNA complexes. For example, the unfolding of the U2/U6 undergoes a transition to a misfolded state which is functional, while in the unfolding of U12/U6atac, the functional helix Ib is found to be the last one to unfold and is thus the most stable structural component. Furthermore, the energy landscape gives the stabilities of all the possible (functional) intermediates and such information is directly related to splicing efficiency.

Cellular Organization and Cytoskeletal Regulation of the Hippo Signaling Network.

PubMed

Sun, Shuguo; Irvine, Kenneth D

2016-09-01

The Hippo signaling network integrates diverse upstream signals to control cell fate decisions and regulate organ growth. Recent studies have provided new insights into the cellular organization of Hippo signaling, its relationship to cell-cell junctions, and how the cytoskeleton modulates Hippo signaling. Cell-cell junctions serve as platforms for Hippo signaling by localizing scaffolding proteins that interact with core components of the pathway. Interactions of Hippo pathway components with cell-cell junctions and the cytoskeleton also suggest potential mechanisms for the regulation of the pathway by cell contact and cell polarity. As our understanding of the complexity of Hippo signaling increases, a future challenge will be to understand how the diverse inputs into the pathway are integrated and to define their respective contributions in vivo. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of lactobacilli on paracellular permeability in the gut.

PubMed

Ahrne, Siv; Hagslatt, Marie-Louise Johansson

2011-01-01

Paracellular permeability is determined by the complex structures of junctions that are located between the epithelial cells. Already in 1996, it was shown that the human probiotic strain Lactobacillus plantarum 299v and the rat-originating strain Lactobacillus reuteri R2LC could reduce this permeability in a methotrexate-induced colitis model in the rat. Subsequently, many animal models and cell culture systems have shown indications that lactobacilli are able to counteract increased paracellular permeability evoked by cytokines, chemicals, infections, or stress. There have been few human studies focusing on the effect of lactobacilli on intestinal paracellular permeability but recently it has been shown that they could influence the tight junctions. More precisely, short-term administration of L. plantarum WCSF1 to healthy volunteers increased the relocation of occludin and ZO-1 into the tight junction area between duodenal epithelial cells.

HfO2 and SiO2 as barriers in magnetic tunneling junctions

NASA Astrophysics Data System (ADS)

Shukla, Gokaran; Archer, Thomas; Sanvito, Stefano

2017-05-01

SiO2 and HfO2 are both high-k, wide-gap semiconductors, currently used in the microelectronic industry as gate barriers. Here we investigate whether the same materials can be employed to make magnetic tunnel junctions, which in principle can be amenable for integration in conventional Si technology. By using a combination of density functional theory and the nonequilibrium Green's functions method for quantum transport we have studied the transport properties of Co [0001 ] /SiO2[001 ] /Co [0001 ] and Fe [001 ] /HfO2[001 ] /Fe [001 ] junctions. In both cases we found a quite large magnetoresistance, which is explained through the analysis of the real band structure of the magnets and the complex one of the insulator. We find that there is no symmetry spin filtering for the Co-based junction since the high transmission Δ2' band crosses the Fermi level, EF, for both spin directions. However, the fact that Co is a strong ferromagnet makes the orbital contribution to the two Δ2' spin subbands different, yielding magnetoresistance. In contrast for the Fe-based junction symmetry filtering is active for an energy window spanning between the Fermi level and 1 eV below EF, with Δ1 symmetry contributing to the transmission.

Tunable ohmic environment using Josephson junction chains

NASA Astrophysics Data System (ADS)

Rastelli, Gianluca; Pop, Ioan M.

2018-05-01

We propose a scheme to implement a tunable, wide frequency-band dissipative environment using a double chain of Josephson junctions. The two parallel chains consist of identical superconducting quantum interference devices (SQUIDs), with magnetic-flux tunable inductance, coupled to each other at each node via a capacitance much larger than the junction capacitance. Thanks to this capacitive coupling, the system sustains electromagnetic modes with a wide frequency dispersion. The internal quality factor of the modes is maintained as high as possible, and the damping is introduced by a uniform coupling of the modes to a transmission line, itself connected to an amplification and readout circuit. For sufficiently long chains, containing several thousands of junctions, the resulting admittance is a smooth function versus frequency in the microwave domain, and its effective dissipation can be continuously monitored by recording the emitted radiation in the transmission line. We show that by varying in situ the SQUIDs' inductance, the double chain can operate as a tunable ohmic resistor in a frequency band spanning up to 1 GHz, with a resistance that can be swept through values comparable to the resistance quantum Rq=h /(4 e2) ≃6.5 kΩ . We argue that the circuit complexity is within reach using current Josephson junction technology.

Multijunction solar cell design revisited: disruption of current matching by atmospheric absorption bands: Disruption of current matching by atmospheric absorption bands

DOE PAGES

McMahon, William E.; Friedman, Daniel J.; Geisz, John F.

2017-05-23

This paper re-examines the impact of atmospheric absorption bands on series-connected multijunction cell design, motivated by the numerous local efficiency maxima that appear as the number of junctions is increased. Some of the local maxima are related to the bottom subcell bandgap and are already well understood: As the bottom subcell bandgap is varied, a local efficiency maximum is produced wherever the bottom cell bandgap crosses an atmospheric absorption band. The optimal cell designs at these local maxima are generally current matched, such that all subcells have nearly the same short-circuit current. We systematically describe additional local maxima that occurmore » wherever an upper subcell bandgap encounters an atmospheric absorption band. Moreover, these local maxima are not current matched and become more prevalent as the number of junctions increases, complicating the solution space for five-junction and six-junction designs. A systematic framework for describing this complexity is developed, and implications for numerical convergence are discussed.« less

Drosophila Big bang regulates the apical cytocortex and wing growth through junctional tension.

PubMed

Tsoumpekos, Giorgos; Nemetschke, Linda; Knust, Elisabeth

2018-03-05

Growth of epithelial tissues is regulated by a plethora of components, including signaling and scaffolding proteins, but also by junctional tension, mediated by the actomyosin cytoskeleton. However, how these players are spatially organized and functionally coordinated is not well understood. Here, we identify the Drosophila melanogaster scaffolding protein Big bang as a novel regulator of growth in epithelial cells of the wing disc by ensuring proper junctional tension. Loss of big bang results in the reduction of the regulatory light chain of nonmuscle myosin, Spaghetti squash. This is associated with an increased apical cell surface, decreased junctional tension, and smaller wings. Strikingly, these phenotypic traits of big bang mutant discs can be rescued by expressing constitutively active Spaghetti squash. Big bang colocalizes with Spaghetti squash in the apical cytocortex and is found in the same protein complex. These results suggest that in epithelial cells of developing wings, the scaffolding protein Big bang controls apical cytocortex organization, which is important for regulating cell shape and tissue growth. © 2018 Tsoumpekos et al.

Cervicothoracic junction thrust manipulation in the multimodal management of a patient with temporomandibular disorder.

PubMed

Jayaseelan, Dhinu J; Tow, Nancy S

2016-05-01

Temporomandibular disorder (TMD) is a common condition that can be difficult to manage in physical therapy. A number of interventions, such as manual therapy, therapeutic exercise, and patient education have typically been used in some combination. However, the evidence regarding thrust manipulation of not only the local but also adjacent segments is sparse. Specifically, the use of cervicothoracic (CT) junction thrust manipulation has not previously been described in the management of individuals with TMD. In this case report, CT junction thrust manipulation, in addition to locally directed manual therapy, exercise, and postural education, was associated with immediate improvements in neck and jaw symptoms and function in a complex patient with TMD. The patient was seen for seven visits over the course of 2 months and demonstrated clinically significant changes in the neck disability index (NDI), the numeric rating of pain scale (NPRS), and the global rating of change (GROC) scale. The purpose of this report is to describe the successful physical therapy management of a patient with TMD utilizing manual therapy, including CT junction thrust manipulation, education, and exercise.

Cervicothoracic junction thrust manipulation in the multimodal management of a patient with temporomandibular disorder

PubMed Central

Jayaseelan, Dhinu J.; Tow, Nancy S.

2016-01-01

Temporomandibular disorder (TMD) is a common condition that can be difficult to manage in physical therapy. A number of interventions, such as manual therapy, therapeutic exercise, and patient education have typically been used in some combination. However, the evidence regarding thrust manipulation of not only the local but also adjacent segments is sparse. Specifically, the use of cervicothoracic (CT) junction thrust manipulation has not previously been described in the management of individuals with TMD. In this case report, CT junction thrust manipulation, in addition to locally directed manual therapy, exercise, and postural education, was associated with immediate improvements in neck and jaw symptoms and function in a complex patient with TMD. The patient was seen for seven visits over the course of 2 months and demonstrated clinically significant changes in the neck disability index (NDI), the numeric rating of pain scale (NPRS), and the global rating of change (GROC) scale. The purpose of this report is to describe the successful physical therapy management of a patient with TMD utilizing manual therapy, including CT junction thrust manipulation, education, and exercise. PMID:27559278

Multijunction solar cell design revisited: disruption of current matching by atmospheric absorption bands: Disruption of current matching by atmospheric absorption bands

DOE Office of Scientific and Technical Information (OSTI.GOV)

McMahon, William E.; Friedman, Daniel J.; Geisz, John F.

This paper re-examines the impact of atmospheric absorption bands on series-connected multijunction cell design, motivated by the numerous local efficiency maxima that appear as the number of junctions is increased. Some of the local maxima are related to the bottom subcell bandgap and are already well understood: As the bottom subcell bandgap is varied, a local efficiency maximum is produced wherever the bottom cell bandgap crosses an atmospheric absorption band. The optimal cell designs at these local maxima are generally current matched, such that all subcells have nearly the same short-circuit current. We systematically describe additional local maxima that occurmore » wherever an upper subcell bandgap encounters an atmospheric absorption band. Moreover, these local maxima are not current matched and become more prevalent as the number of junctions increases, complicating the solution space for five-junction and six-junction designs. A systematic framework for describing this complexity is developed, and implications for numerical convergence are discussed.« less

One-pot growth of two-dimensional lateral heterostructures via sequential edge-epitaxy

NASA Astrophysics Data System (ADS)

Sahoo, Prasana K.; Memaran, Shahriar; Xin, Yan; Balicas, Luis; Gutiérrez, Humberto R.

2018-01-01

Two-dimensional heterojunctions of transition-metal dichalcogenides have great potential for application in low-power, high-performance and flexible electro-optical devices, such as tunnelling transistors, light-emitting diodes, photodetectors and photovoltaic cells. Although complex heterostructures have been fabricated via the van der Waals stacking of different two-dimensional materials, the in situ fabrication of high-quality lateral heterostructures with multiple junctions remains a challenge. Transition-metal-dichalcogenide lateral heterostructures have been synthesized via single-step, two-step or multi-step growth processes. However, these methods lack the flexibility to control, in situ, the growth of individual domains. In situ synthesis of multi-junction lateral heterostructures does not require multiple exchanges of sources or reactors, a limitation in previous approaches as it exposes the edges to ambient contamination, compromises the homogeneity of domain size in periodic structures, and results in long processing times. Here we report a one-pot synthetic approach, using a single heterogeneous solid source, for the continuous fabrication of lateral multi-junction heterostructures consisting of monolayers of transition-metal dichalcogenides. The sequential formation of heterojunctions is achieved solely by changing the composition of the reactive gas environment in the presence of water vapour. This enables selective control of the water-induced oxidation and volatilization of each transition-metal precursor, as well as its nucleation on the substrate, leading to sequential edge-epitaxy of distinct transition-metal dichalcogenides. Photoluminescence maps confirm the sequential spatial modulation of the bandgap, and atomic-resolution images reveal defect-free lateral connectivity between the different transition-metal-dichalcogenide domains within a single crystal structure. Electrical transport measurements revealed diode-like responses across the junctions. Our new approach offers greater flexibility and control than previous methods for continuous growth of transition-metal-dichalcogenide-based multi-junction lateral heterostructures. These findings could be extended to other families of two-dimensional materials, and establish a foundation for the development of complex and atomically thin in-plane superlattices, devices and integrated circuits.

10. ELECTRICAL SWITCHING STATION FOR IRON MOUNTAIN BRINGS ELECTRICITY FROM ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

10. ELECTRICAL SWITCHING STATION FOR IRON MOUNTAIN BRINGS ELECTRICITY FROM HOOVER DAM COMPLEX. - Iron Mountain Pump Plant, South of Danby Lake, north of Routes 62 & 177 junction, Rice, San Bernardino County, CA

MLC-based penumbra softener of EDW borders to reduce junction inhomogeneities.

PubMed

Szpala, Stanislaw; Kohli, Kirpal

2017-05-01

Junctions of fields are known to be susceptible to developing cold or hot spots in the presence of even small geometrical misalignments. Reduction of these dose inhomogeneities can be accomplished through decreasing the dose gradients in the penumbra, but currently it cannot be done for enhanced dynamic wedges (EDW). An MLC-based penumbra softener was developed in the developer mode of TrueBeam linacs to reduce dose gradients across the side border of EDWs. The movement of each leaf was individually synchronized with the movement of the dynamic Y jaw to soften the penumbra in the same manner along the entire field border, in spite of the presence of the dose gradient of the EDW. Junction homogeneity upon field misalignment for side-matched EDWs was examined with the MV imager. The fluence inhomogeneities were reduced from about 30% per mm of shift of the field borders for the conventional EDW to about 2% per mm for the softened-penumbra plan. The junction in a four-field monoisocentric breast plan delivered to the Rando phantom was assessed with film. The dose inhomogeneities across the junction in the superior-inferior direction were reduced from about 20% to 25% per mm for the conventional fields to about 5% per mm. The dose near the softened junction of the breast plan with no shifts did not deviate from the conventional plan by more than about 4%. The newly-developed softened-penumbra junction of EDW (and/or open) fields was shown to reduce sensitivity to misalignments without increasing complexity of the planning or delivery. This methodology needs to be adopted by the manufacturers for clinical use. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Relationships between junction temperature, electroluminescence spectrum and ageing of light-emitting diodes

NASA Astrophysics Data System (ADS)

Vaskuri, Anna; Kärhä, Petri; Baumgartner, Hans; Kantamaa, Olli; Pulli, Tomi; Poikonen, Tuomas; Ikonen, Erkki

2018-04-01

We have developed spectral models describing the electroluminescence spectra of AlGaInP and InGaN light-emitting diodes (LEDs) consisting of the Maxwell-Boltzmann distribution and the effective joint density of states. One spectrum at a known temperature for one LED specimen is needed for calibrating the model parameters of each LED type. Then, the model can be used for determining the junction temperature optically from the spectral measurement, because the junction temperature is one of the free parameters. We validated the models using, in total, 53 spectra of three red AlGaInP LED specimens and 72 spectra of three blue InGaN LED specimens measured at various current levels and temperatures between 303 K and 398 K. For all the spectra of red LEDs, the standard deviation between the modelled and measured junction temperatures was only 2.4 K. InGaN LEDs have a more complex effective joint density of states. For the blue LEDs, the corresponding standard deviation was 11.2 K, but it decreased to 3.5 K when each LED specimen was calibrated separately. The method of determining junction temperature was further tested on white InGaN LEDs with luminophore coating and LED lamps. The average standard deviation was 8 K for white InGaN LED types. We have six years of ageing data available for a set of LED lamps and we estimated the junction temperatures of these lamps with respect to their ageing times. It was found that the LEDs operating at higher junction temperatures were frequently more damaged.

Conductivity of Langmuir-Blodgett films of a disk-shaped liquid-crystalline molecule-DNA complex studied by current-sensing atomic force microscopy.

PubMed

Nayak, Alpana; Suresh, K A

2008-08-01

We have studied the electrical conductivity in monolayer films of an ionic disk-shaped liquid-crystal molecule, pyridinium tethered with hexaalkoxytriphenylene (PyTp), and its complex with DNA by current-sensing atomic force microscopy (CS-AFM). The pure PyTp and PyTp-DNA complex monolayer films were first formed at the air-water interface and then transferred onto conducting substrates by the Langmuir-Blodgett (LB) technique to study the nanoscale electron transport through these films. The conductive tip of CS-AFM, the LB film, and the metal substrate form a nanoscopic metal-LB film-metal (M-LB-M) junction. We have measured the current-voltage (I-V) characteristics for the M-LB-M junction using CS-AFM and have analyzed the data quantitatively. We find that the I-V curves fit well to the Fowler-Nordheim (FN) model, suggesting electron tunneling to be a possible mechanism for electron transport in our system. Further, analysis of the I-V curves based on the FN model yields the barrier heights of PyTp-DNA complex and pure PyTp films. Electron transport studies of films of ionic disk-shaped liquid-crystal molecules and their complex with DNA are important from the point of view of their applications in organic electronics.

Conductivity of Langmuir-Blodgett films of a disk-shaped liquid-crystalline molecule-DNA complex studied by current-sensing atomic force microscopy

NASA Astrophysics Data System (ADS)

Nayak, Alpana; Suresh, K. A.

2008-08-01

We have studied the electrical conductivity in monolayer films of an ionic disk-shaped liquid-crystal molecule, pyridinium tethered with hexaalkoxytriphenylene (PyTp), and its complex with DNA by current-sensing atomic force microscopy (CS-AFM). The pure PyTp and PyTp-DNA complex monolayer films were first formed at the air-water interface and then transferred onto conducting substrates by the Langmuir-Blodgett (LB) technique to study the nanoscale electron transport through these films. The conductive tip of CS-AFM, the LB film, and the metal substrate form a nanoscopic metal-LB film-metal (M-LB-M) junction. We have measured the current-voltage (I-V) characteristics for the M-LB-M junction using CS-AFM and have analyzed the data quantitatively. We find that the I-V curves fit well to the Fowler-Nordheim (FN) model, suggesting electron tunneling to be a possible mechanism for electron transport in our system. Further, analysis of the I-V curves based on the FN model yields the barrier heights of PyTp-DNA complex and pure PyTp films. Electron transport studies of films of ionic disk-shaped liquid-crystal molecules and their complex with DNA are important from the point of view of their applications in organic electronics.

A four-way junction with triple-helical arms: design, characterization, and stability.

PubMed

Makube, N; Klump, H H

2000-05-01

The formation of the four-way junction containing four triple-helical arms has been demonstrated using chemical methods (polyacrylamide gel electrophoresis and chemical footprinting using OsO(4) as a probe) and physical methods (UV absorbance melting and DSC). The junction J(T1T3) was assembled from two 20-mer purine strands and two 44-mer pyrimidine strands. To determine the contribution of the different arms to the stability of the complete structure of J(T1T3), the junction was compared to two simplified substructures, J(T1) and J(T3), respectively. Common to these complexes is the underlying double-helical four-way junction Js. Addition of Na(+) had a profound effect on stabilizing and subsequently folding the junctions into the stacked X-structures. The following results support the structure present: (i) The native polyacrylamide electrophoresis exhibits only a single band(s) corresponding to one species present when all four single strands are mixed in equal amounts. (ii) OsO(4) modifications were investigated at pH 5.0 and in the presence of 10 mM Mg(2+) and 100 mM Na(+). There is no cleavage of thymine residues at the branch point and throughout the structure. (iii) The thermal unfolding of J(T1) and J(T3) illustrates that the triple-helical arms are more stable than the double-helical arms which are contained in these junctions and that J(T1T3) with four triple-helical arms is slightly more stable than J(T1) and J(T3). (iv) The calorimetric transition enthalpies determined for the arms of J(T1T3) are comparable to those associated with the unfolding of its corresponding arms in J(T1) and J(T3). The results also illustrate that the formation of the junctions is not restricted by the pH, [Na(+)], sequence composition of the arms, and/or the loop position. Copyright 2000 Academic Press.

Alternative splicing regulated by butyrate in bovine epithelial cells.

PubMed

Wu, Sitao; Li, Congjun; Huang, Wen; Li, Weizhong; Li, Robert W

2012-01-01

As a signaling molecule and an inhibitor of histone deacetylases (HDACs), butyrate exerts its impact on a broad range of biological processes, such as apoptosis and cell proliferation, in addition to its critical role in energy metabolism in ruminants. This study examined the effect of butyrate on alternative splicing in bovine epithelial cells using RNA-seq technology. Junction reads account for 11.28 and 12.32% of total mapped reads between the butyrate-treated (BT) and control (CT) groups. 201,326 potential splicing junctions detected were supported by ≥ 3 junction reads. Approximately 94% of these junctions conformed to the consensus sequence (GT/AG) while ~3% were GC/AG junctions. No AT/AC junctions were observed. A total of 2,834 exon skipping events, supported by a minimum of 3 junction reads, were detected. At least 7 genes, their mRNA expression significantly affected by butyrate, also had exon skipping events differentially regulated by butyrate. Furthermore, COL5A3, which was induced 310-fold by butyrate (FDR <0.001) at the gene level, had a significantly higher number of junction reads mapped to Exon#8 (Donor) and Exon#11 (Acceptor) in BT. This event had the potential to result in the formation of a COL5A3 mRNA isoform with 2 of the 69 exons missing. In addition, 216 differentially expressed transcript isoforms regulated by butyrate were detected. For example, Isoform 1 of ORC1 was strongly repressed by butyrate while Isoform 2 remained unchanged. Butyrate physically binds to and inhibits all zinc-dependent HDACs except HDAC6 and HDAC10. Our results provided evidence that butyrate also regulated deacetylase activities of classical HDACs via its transcriptional control. Moreover, thirteen gene fusion events differentially affected by butyrate were identified. Our results provided a snapshot into complex transcriptome dynamics regulated by butyrate, which will facilitate our understanding of the biological effects of butyrate and other HDAC inhibitors.

Atlantoaxial dislocation in a patient with nonsyndromic symmetrical dwarfism: Report of a rare case

PubMed Central

Ram, Duvuru; Madhugiri, Venkatesh S.; Roopesh Kumar, V. R.; Gulati, Reena; Sasidharan, Gopalakrishnan M.; Gundamaneni, Sudheer Kumar

2015-01-01

Congenital anomalies of the craniovertebral junction (CVJ) are complex developmental defects. We describe a patient with atlantoaxial dislocation (AAD) and short stature whose morphopathologydid not fit into any of the previously described syndromic constellations. The patient underwent a reduction of the AAD followed by fixation with C1-C2 transarticular screws. Although numerous syndromes have been linked to both dwarfism and craniovertebral junction anomalies, this patient did not fit into any of these patterns. It is possible that this may be one of the many as yet unrecognized patterns of congenital anomalies. PMID:25788820

Force transmission in epithelial tissues.

PubMed

Vasquez, Claudia G; Martin, Adam C

2016-03-01

In epithelial tissues, cells constantly generate and transmit forces between each other. Forces generated by the actomyosin cytoskeleton regulate tissue shape and structure and also provide signals that influence cells' decisions to divide, die, or differentiate. Forces are transmitted across epithelia because cells are mechanically linked through junctional complexes, and forces can propagate through the cell cytoplasm. Here, we review some of the molecular mechanisms responsible for force generation, with a specific focus on the actomyosin cortex and adherens junctions. We then discuss evidence for how these mechanisms promote cell shape changes and force transmission in tissues. © 2016 Wiley Periodicals, Inc.

Foramen Magnum Meningioma: a Case Report and Review of Literature.

PubMed

Jurinovic, Pavao; Bulicic, Ana Repic; Marcic, Marino; Mise, Nikolina Ivica; Titlic, Marina; Suljic, Enra

2016-02-01

Meningiomas are slow-growing benign tumors that arise at any location where arachnoid cells reside. Although meningiomas account for a sizable proportion of all primary intracranial neoplasms (14.3-19%), only 1.8 to 3.2% arise at the foramen magnum. Their indolent development at the craniocervical junction makes clinical diagnosis complex and often leads to a long interval between onset of symptoms and diagnosis. We report a case of a 79-year-old male patient, presented with ataxia and sense of threatening fainting during verticalization. Magnetic resonance imaging revealed the presence of meningioma in the right side of craniospinal junction.

Equivalent electron fluence for space qualification of shallow junction heteroface GaAs solar cells

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Stock, L. V.

1984-01-01

It is desirable to perform qualification tests prior to deployment of solar cells in space power applications. Such test procedures are complicated by the complex mixture of differing radiation components in space which are difficult to simulate in ground test facilities. Although it has been shown that an equivalent electron fluence ratio cannot be uniquely defined for monoenergetic proton exposure of GaAs shallow junction cells, an equivalent electron fluence test can be defined for common spectral components of protons found in space. Equivalent electron fluence levels for the geosynchronous environment are presented.

Method for shallow junction formation

DOEpatents

Weiner, K.H.

1996-10-29

A doping sequence is disclosed that reduces the cost and complexity of forming source/drain regions in complementary metal oxide silicon (CMOS) integrated circuit technologies. The process combines the use of patterned excimer laser annealing, dopant-saturated spin-on glass, silicide contact structures and interference effects creates by thin dielectric layers to produce source and drain junctions that are ultrashallow in depth but exhibit low sheet and contact resistance. The process utilizes no photolithography and can be achieved without the use of expensive vacuum equipment. The process margins are wide, and yield loss due to contact of the ultrashallow dopants is eliminated. 8 figs.

Method for shallow junction formation

DOEpatents

Weiner, Kurt H.

1996-01-01

A doping sequence that reduces the cost and complexity of forming source/drain regions in complementary metal oxide silicon (CMOS) integrated circuit technologies. The process combines the use of patterned excimer laser annealing, dopant-saturated spin-on glass, silicide contact structures and interference effects creates by thin dielectric layers to produce source and drain junctions that are ultrashallow in depth but exhibit low sheet and contact resistance. The process utilizes no photolithography and can be achieved without the use of expensive vacuum equipment. The process margins are wide, and yield loss due to contact of the ultrashallow dopants is eliminated.

Y-junctions based on circular depressed-cladding waveguides fabricated with femtosecond pulses in Nd:YAG crystal: A route to integrate complex photonic circuits in crystals

NASA Astrophysics Data System (ADS)

Ajates, Javier G.; Romero, Carolina; Castillo, Gabriel R.; Chen, Feng; Vázquez de Aldana, Javier R.

2017-10-01

We have designed and fabricated photonic structures such as, Y-junctions (one of the basic building blocks for construction any integrated photonic devices) and Mach-Zehnder interferometers, based on circular depressed-cladding waveguides by direct femtosecond laser irradiation in Nd:YAG crystal. The waveguides were optically characterized at 633 nm, showing nearly mono-modal behaviour for the selected waveguide radius (9 μm). The effect of the splitting angle in the Y structures was investigated finding a good preservation of the modal profiles up to more than 2°, with 1 dB of additional losses in comparison with straight waveguides. The dependence with polarization of these splitters keeps in a reasonable low level. Our designs pave the way for the fabrication of arbitrarily complex 3D photonic circuits in crystals with cladding waveguides.

Pictures of Processes: Automated Graph Rewriting for Monoidal Categories and Applications to Quantum Computing

NASA Astrophysics Data System (ADS)

Kumar, Bhupendra

Light assisted or driven fuel generation by carbon dioxide and proton reduction can be achieved by a p-type semiconductor/liquid junction. There are four different types of schemes which are typically used for carbon dioxide and proton reduction for fuel generation applications. In these systems, the semiconductor can serve the dual role of a catalyst and a light absorber. Specific electrocatalysts (heterogeneous and homogeneous) can be driven by p-type semiconductor where it works only as light absorber in order to achieve better selectivity and faster rates of catalysis. The p-type semiconductor/molecular catalyst junction is primarily explored in this dissertation for CO2 and proton photoelectrochemical reduction. A general principle for the operation of p-type semiconductor/molecular junctions is proposed and validated for several molecular catalysts in contact with p-Si photocathode. It is also shown that the light assisted homogeneous and heterogeneous catalysis can coexist. This principle is extended to achieve direct conversion of CO 2 to methanol on Platinum nanoparticles decorated p-Si in aqueous medium through pyridine/pyridinium system for CO2 reduction. An open circuit voltage higher than 600 mV is achieved for p-Si/Re(bipy-tBu)(CO) 3Cl [where bipy-tBu = 4,4'- tert-butyl-2,2'-bipyridine] (Re-catalyst) junction. The photoelectrochemical conversion of CO2 to CO using a p-Si/Re-catalyst junction is obtained at 100 % Faradaic efficiency. The homogeneous catalytic current density for CO2 by p-Si/Re-catalyst junction under illumination scales linearly with illumination intensity (both polychromatic and monochromatic). This indicates that the homogeneous catalysis is light driven for the p-Si/Re-catalyst junction system up to light intensities approaching one sun. The photoelectrochemical reduction of other active members of Re(bipyridyl)(CO)3Cl molecular catalyst family is also observed on illuminated p-Si photocathode. Effects of surface modification and nanowire morphology of the p-Si photocathode on the homogeneous catalytic reduction of CO2 by using p-Si/Re-catalyst junction are also described in this dissertation. For phenyl ethyl modified p-Si photocathode, the rate of homogeneous catalysis for CO2 reduction by Re-catalyst is three times greater than glassy carbon electrode and six times greater than the hexyl modified and the hydrogen terminated p-Si photocathodes. When hexyl modified p-Si nanowires are used as photocathode, the homogeneous catalytic current density increased by a factor of two compared to planar p-Si (both freshly etched and hexyl modified) photocathode. A successful light assisted generation of syngas (H2:CO = 2:1) from CO2 and water is achieved by using p-Si/Re-catalyst. In this system, water is reduced heterogeneously on p-Si surface and CO2 is reduced homogeneously by Re-catalyst. The same principle is extended to the homogeneous proton reduction by using p-Si/[FeFe] complex junction where [FeFe] complex [Fe2(micro-bdt)(CO) 6] (bdt = benzene-1,2-dithiolate)] is a proton reduction molecular catalyst. A short circuit quantum efficiency of 79 % with 100 % Faradaic efficiency and 600 mV open circuit are achieved by using p-Si/[FeFe] complex for proton reduction with 300 mM perchloric acid as a proton source. Cobalt difluororyl-diglyoximate (Co-catalyst) is a proton reduction catalyst with only 200 mV of overpotential for the hydrogen evolution reaction (HRE). The Co-catalyst is photoelectrochemically reduced with a photovoltage of 470 mV on illuminated p-Si photocathode. For p-Si photocathodes, the overpotential for proton reduction is over 1 V. In principle, p-Si/Co-catalyst junction can reduce proton to hydrogen homogeneously at underpotential. In a concluding effort, a wireless monolithic dual face single photoelectrode (multi junction photovoltaic cell which can generate a voltage higher 1.7 V) based photochemical cell is proposed for direct conversion of solar energy into liquid fuel. In this device, the two faces of the multijunction photoelectrode are serve as an anode and a cathode for water oxidation and fuel generation, respectively, and are separated by proton exchange membrane.

RhoGTPase signalling at epithelial tight junctions: Bridging the GAP between polarity and cancer.

PubMed

Zihni, Ceniz; Terry, Stephen James

2015-07-01

The establishment and maintenance of epithelial polarity must be correctly controlled for normal development and homeostasis. Tight junctions (TJ) in vertebrates define apical and basolateral membrane domains in polarized epithelia via bi-directional, complex signalling pathways between TJ themselves and the cytoskeleton they are associated with. RhoGTPases are central to these processes and evidence suggests that their regulation is coordinated by interactions between GEFs and GAPs with junctional, cytoplasmic adapter proteins. In this InFocus review we determine that the expression, localization or stability of a variety of these adaptor proteins is altered in various cancers, potentially representing an important mechanistic link between loss of polarity and cancer. We focus here, on two well characterized RhoGTPases Cdc42 and RhoA who's GEFs and GAPs are predominantly localized to TJ via cytoplasmic adaptor proteins. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Effect of Lactobacilli on Paracellular Permeability in the Gut

PubMed Central

Ahrne, Siv; Hagslatt, Marie-Louise Johansson

2011-01-01

Paracellular permeability is determined by the complex structures of junctions that are located between the epithelial cells. Already in 1996, it was shown that the human probiotic strain Lactobacillus plantarum 299v and the rat-originating strain Lactobacillus reuteri R2LC could reduce this permeability in a methotrexate-induced colitis model in the rat. Subsequently, many animal models and cell culture systems have shown indications that lactobacilli are able to counteract increased paracellular permeability evoked by cytokines, chemicals, infections, or stress. There have been few human studies focusing on the effect of lactobacilli on intestinal paracellular permeability but recently it has been shown that they could influence the tight junctions. More precisely, short-term administration of L. plantarum WCSF1 to healthy volunteers increased the relocation of occludin and ZO-1 into the tight junction area between duodenal epithelial cells. PMID:22254077

Quantum-statistical theory of microwave detection using superconducting tunnel junctions

NASA Astrophysics Data System (ADS)

Deviatov, I. A.; Kuzmin, L. S.; Likharev, K. K.; Migulin, V. V.; Zorin, A. B.

1986-09-01

A quantum-statistical theory of microwave and millimeter-wave detection using superconducting tunnel junctions is developed, with a rigorous account of quantum, thermal, and shot noise arising from fluctuation sources associated with the junctions, signal source, and matching circuits. The problem of the noise characterization in the quantum sensitivity range is considered and a general noise parameter Theta(N) is introduced. This parameter is shown to be an adequate figure of merit for most receivers of interest while some devices can require a more complex characterization. Analytical expressions and/or numerically calculated plots for Theta(N) are presented for the most promising detection modes including the parametric amplification, heterodyne mixing, and quadratic videodetection, using both the quasiparticle-current and the Cooper-pair-current nonlinearities. Ultimate minimum values of Theta(N) for each detection mode are compared and found to be in agreement with limitations imposed by the quantum-mechanical uncertainty principle.

Paranodal reorganization results in the depletion of transverse bands in the aged central nervous system

PubMed Central

Shepherd, Mark N.; Pomicter, Anthony D.; Velazco, Cristine S.; Henderson, Scott C.; Dupree, Jeffrey L.

2012-01-01

Paranodal axo-glial junctional complexes anchor the myelin sheath to the axon and breakdown of these complexes presumably facilitates demyelination. Myelin deterioration is also prominent in the aging central nervous system (CNS); however, the stability of the paranodal complexes in the aged CNS has not been examined. Here, we show that transverse bands, prominent components of paranodal junctions, are significantly reduced in the aged CNS; however, the number of paired clusters of both myelin and axonal paranodal proteins is not altered. Ultrastructural analyses also reveal that thicker myelin sheaths display a “piling” of paranodal loops, the cytoplasm-containing sacs that demarcate the paranode. Loops involved in piling are observed throughout the paranode and are not limited to loops positioned in either the nodal- or juxtanodal-most regions. Here, we propose that as myelination continues, previously anchored loops lose their transverse bands and recede away from the axolemma. Newly juxtaposed loops then lose their transverse bands, move laterally to fill in the gap left by the receded loops and finally reform their transverse bands. This paranodal reorganization results in conservation of paranodal length, which may be important in maintaining ion channel spacing and axonal function. Furthermore, we propose that transverse band reformation is less efficient in the aged CNS, resulting in the significant reduction of these junctional components. Although demyelination was not observed, we propose that loss of transverse bands facilitates myelin degeneration and may predispose the aged CNS to a poorer prognosis following a secondary insult. PMID:20888080

Trans splicing in Leishmania enriettii and identification of ribonucleoprotein complexes containing the spliced leader and U2 equivalent RNAs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, S.I.; Wirth, D.F.

1988-06-01

The 5' ends of Leishmania mRNAs contain an identical 35-nucleotide sequence termed the spliced leader (SL) or 5' mini-exon. The SL sequence is at the 5' end of an 85-nucleotide primary transcript that contains a consensus eucaryotic 5' intron-exon splice junction immediately 3' to the SL. The SL is added to protein-coding genes immediately 3' to a consensus eucaryotic 3' intron-exon splice junction. The authors' previous work demonstrated possible intermediates in discontinuous mRNA processing that contain the 50 nucleotides of the SL primary transcript 3' to the SL, the SL intron sequence (SLIS). These RNAs have a 5' terminus atmore » the splice junction of the SL and the SLIS. The authors examined a Leishmania nuclear extract for these RNAs in ribonucleoprotein (RNP) particles. Density centrifugation analysis showed that the SL RNA is predominately in RNP complexes at 60S, while the SLIS-containing RNAs are in complexes at 40S. They also demonstrated that the SLIS can be released from polyadenylated RNA by incubation with a HeLa cell extract containing debranching enzymatic activity. These data suggested that Leishmania enriettii mRNAs are assembled by bimolecular or trans splicing as has been recently demonstrated for Trypanosoma brucei. Furthermore, they determined the partial sequence of the Leishmania U2 equivalent RNA and demonstrated that it cosediments with the SL RNA at 60S in a nuclear extract. These RNP particles may be analogous to so-called spliceosomes that have been demonstrated in other systems.« less

The Anatomic Midpoint of the Attachment of the Medial Patellofemoral Complex.

PubMed

Tanaka, Miho J; Voss, Andreas; Fulkerson, John P

2016-07-20

The medial patellofemoral ligament varies in attachment of its fibers to the patella and vastus intermedius tendon. Our aim was to identify and describe its anatomic midpoint. To account for the variability of the attachment site, we refer to it as the medial patellofemoral complex. Using AutoCAD software, we identified the midpoint of the medial patellofemoral complex attachment on photographs of 31 cadaveric knee dissections. The midpoint was referenced relative to the superior articular surface of the patella (P1) and was described in terms of the percentage of the patellar articular length distal to this point. A second point, at the junction of the medial border of the vastus intermedius tendon with the superior articular border of the patella, was identified (P2). The distances of the midpoint to P1 and P2 were calculated and were compared using paired t tests. Twenty-five images had appropriate quality and landmarks for digital analysis. The midpoint of the medial patellofemoral complex was located a mean (and standard deviation) of 2.3% ± 15.8% of the patellar articular length distal to the superior pole and was at or proximal to P1 in 12 knees. In all knees, the midpoint was at or proximal to P2. After exclusion of 2 knees with vastus intermedius tendon attachments only, the medial patellofemoral complex midpoint was closer to P2 (5.3% ± 8.6% of the patellar articular length) than to P1 (9.3% ± 8.5% of the patellar articular length) (p = 0.06). The midpoint of the medial patellofemoral complex was 2.3% of the articular length distal to the superior pole of the patella. Additionally, we describe an anatomic landmark at the junction of the medial border of the vastus intermedius tendon and the articular border of the patella that approximates the midpoint of this complex. Our study shows that the anatomic midpoint of the attachment of the medial patellofemoral complex is proximal to the junction of the medial vastus intermedius tendon and the articular border of the patella, suggesting that graft placement may be more anatomic on the vastus intermedius tendon rather than on the patella. Copyright © 2016 by The Journal of Bone and Joint Surgery, Incorporated.

A Homozygous Mutation in the Tight-Junction Protein JAM3 Causes Hemorrhagic Destruction of the Brain, Subependymal Calcification, and Congenital Cataracts

PubMed Central

Mochida, Ganeshwaran H.; Ganesh, Vijay S.; Felie, Jillian M.; Gleason, Danielle; Hill, R. Sean; Clapham, Katie Rose; Rakiec, Daniel; Tan, Wen-Hann; Akawi, Nadia; Al-Saffar, Muna; Partlow, Jennifer N.; Tinschert, Sigrid; Barkovich, A. James; Ali, Bassam; Al-Gazali, Lihadh; Walsh, Christopher A.

2010-01-01

The tight junction, or zonula occludens, is a specialized cell-cell junction that regulates epithelial and endothelial permeability, and it is an essential component of the blood-brain barrier in the cerebrovascular endothelium. In addition to functioning as a diffusion barrier, tight junctions are also involved in signal transduction. In this study, we identified a homozygous mutation in the tight-junction protein gene JAM3 in a large consanguineous family from the United Arab Emirates. Some members of this family had a rare autosomal-recessive syndrome characterized by severe hemorrhagic destruction of the brain, subependymal calcification, and congenital cataracts. Their clinical presentation overlaps with some reported cases of pseudo-TORCH syndrome as well as with cases involving mutations in occludin, another component of the tight-junction complex. However, massive intracranial hemorrhage distinguishes these patients from others. Homozygosity mapping identified the disease locus in this family on chromosome 11q25 with a maximum multipoint LOD score of 6.15. Sequence analysis of genes in the candidate interval uncovered a mutation in the canonical splice-donor site of intron 5 of JAM3. RT-PCR analysis of a patient lymphoblast cell line confirmed abnormal splicing, leading to a frameshift mutation with early termination. JAM3 is known to be present in vascular endothelium, although its roles in cerebral vasculature have not been implicated. Our results suggest that JAM3 is essential for maintaining the integrity of the cerebrovascular endothelium as well as for normal lens development in humans. PMID:21109224

Ultrastructural changes in cardiac myocytes from Boxer dogs with arrhythmogenic right ventricular cardiomyopathy

PubMed Central

Oxford, Eva M.; Danko, Charles G.; Kornreich, Bruce G.; Maass, Karen; Hemsley, Shari A.; Raskolnikov, Dima; Fox, Philip R.; Delmar, Mario; Moïse, N. Sydney

2011-01-01

Objectives We sought to quantify the number and length of desmosomes, gap junctions, and adherens junctions in arrhythmogenic right ventricular cardiomyopathy (ARVC) and non-ARVC dogs, and to determine if ultrastructural changes existed. Animals Hearts from 8 boxer dogs afflicted with histopathologically confirmed ARVC and 6 dogs without ARVC were studied. Methods Quantitative transmission electron microscopy (TEM) and Western blot semi-quantification of α-actinin were used to study the intercalated disc and sarcomere of the right and left ventricles. Results When ARVC dogs were compared to non-ARVC dogs reductions in the number of desmosomes (P = 0.04), adherens junctions (P = 0.04) and gap junctions (P = 0.02) were found. The number of gap junctions (P = 0.04) and adherens junctions (P = 0.04) also were reduced in the left ventricle, while the number of desmosomes was not (P = 0.88). A decrease in the length of desmosomal complexes within LV samples (P=0.04) was found. These findings suggested disruption of proteins providing attachment of the cytoskeleton to the intercalated disc. Immunoblotting did not demonstrate a quantitative reduction in the amount of α-actinin in ARVC afflicted samples. All boxers with ARVC demonstrated the presence of electron dense material originating from the Z band and extending into the sarcomere, apparently at the expense of the cytoskeletal structure. Conclusions These results emphasize the importance of structural integrity of the intercalated disc in the pathogenesis of ARVC. In addition, observed abnormalities in sarcomeric structure suggest a novel link between ARVC and the actin-myosin contractile apparatus. PMID:21636338

System-level simulation of liquid filling in microfluidic chips.

PubMed

Song, Hongjun; Wang, Yi; Pant, Kapil

2011-06-01

Liquid filling in microfluidic channels is a complex process that depends on a variety of geometric, operating, and material parameters such as microchannel geometry, flow velocity∕pressure, liquid surface tension, and contact angle of channel surface. Accurate analysis of the filling process can provide key insights into the filling time, air bubble trapping, and dead zone formation, and help evaluate trade-offs among the various design parameters and lead to optimal chip design. However, efficient modeling of liquid filling in complex microfluidic networks continues to be a significant challenge. High-fidelity computational methods, such as the volume of fluid method, are prohibitively expensive from a computational standpoint. Analytical models, on the other hand, are primarily applicable to idealized geometries and, hence, are unable to accurately capture chip level behavior of complex microfluidic systems. This paper presents a parametrized dynamic model for the system-level analysis of liquid filling in three-dimensional (3D) microfluidic networks. In our approach, a complex microfluidic network is deconstructed into a set of commonly used components, such as reservoirs, microchannels, and junctions. The components are then assembled according to their spatial layout and operating rationale to achieve a rapid system-level model. A dynamic model based on the transient momentum equation is developed to track the liquid front in the microchannels. The principle of mass conservation at the junction is used to link the fluidic parameters in the microchannels emanating from the junction. Assembly of these component models yields a set of differential and algebraic equations, which upon integration provides temporal information of the liquid filling process, particularly liquid front propagation (i.e., the arrival time). The models are used to simulate the transient liquid filling process in a variety of microfluidic constructs and in a multiplexer, representing a complex microfluidic network. The accuracy (relative error less than 7%) and orders-of-magnitude speedup (30 000X-4 000 000X) of our system-level models are verified by comparison against 3D high-fidelity numerical studies. Our findings clearly establish the utility of our models and simulation methodology for fast, reliable analysis of liquid filling to guide the design optimization of complex microfluidic networks.

House Dust Mite Der p 1 Effects on Sinonasal Epithelial Tight Junctions

PubMed Central

Henriquez, Oswaldo A.; Beste, Kyle Den; Hoddeson, Elizabeth K.; Parkos, Charles A.; Nusrat, Asma; Wise, Sarah K.

2013-01-01

Background Epithelial permeability is highly dependent upon the integrity of tight junctions, cell-cell adhesion complexes located at the apical aspect of the lateral membrane of polarized epithelial cells. We hypothesize that sinonasal epithelial exposure to Der p 1 house dust mite antigen decreases expression of tight junction proteins (TJPs), representing a potential mechanism for increased permeability and presentation of antigens across the sinonasal epithelial layer. Methods Confluent cultured primary human sinonasal epithelial cells were exposed to recombinant Der p 1 antigen versus control, and transepithelial resistance measurements were performed over 24 hours. Antibody staining for a panel of tight junction proteins was examined with immunofluorescence/confocal microscopy and Western blotting. Tissue for these experiments was obtained from 4 patients total. Results Der p 1 exposed sinonasal cells showed a marked decrease in transepithelial resistance when compared to control cells. In addition, results of Western immunoblot and immunofluorescent labeling demonstrated decreased expression of TJPs claudin-1 and junction adhesion molecule-A (JAM-A) in Der p 1 exposed cultured sinonasal cells versus controls. Conclusion Der p 1 antigen exposure decreases sinonasal epithelium TJP expression, most notably seen in JAM-A and claudin-1 in these preliminary experiments. This decreased TJP expression likely contributes to increased epithelial permeability and represents a potential mechanism for transepithelial antigen exposure in allergic rhinitis. PMID:23592402

A unified framework for spiking and gap-junction interactions in distributed neuronal network simulations.

PubMed

Hahne, Jan; Helias, Moritz; Kunkel, Susanne; Igarashi, Jun; Bolten, Matthias; Frommer, Andreas; Diesmann, Markus

2015-01-01

Contemporary simulators for networks of point and few-compartment model neurons come with a plethora of ready-to-use neuron and synapse models and support complex network topologies. Recent technological advancements have broadened the spectrum of application further to the efficient simulation of brain-scale networks on supercomputers. In distributed network simulations the amount of spike data that accrues per millisecond and process is typically low, such that a common optimization strategy is to communicate spikes at relatively long intervals, where the upper limit is given by the shortest synaptic transmission delay in the network. This approach is well-suited for simulations that employ only chemical synapses but it has so far impeded the incorporation of gap-junction models, which require instantaneous neuronal interactions. Here, we present a numerical algorithm based on a waveform-relaxation technique which allows for network simulations with gap junctions in a way that is compatible with the delayed communication strategy. Using a reference implementation in the NEST simulator, we demonstrate that the algorithm and the required data structures can be smoothly integrated with existing code such that they complement the infrastructure for spiking connections. To show that the unified framework for gap-junction and spiking interactions achieves high performance and delivers high accuracy in the presence of gap junctions, we present benchmarks for workstations, clusters, and supercomputers. Finally, we discuss limitations of the novel technology.

A unified framework for spiking and gap-junction interactions in distributed neuronal network simulations

PubMed Central

Hahne, Jan; Helias, Moritz; Kunkel, Susanne; Igarashi, Jun; Bolten, Matthias; Frommer, Andreas; Diesmann, Markus

2015-01-01

Contemporary simulators for networks of point and few-compartment model neurons come with a plethora of ready-to-use neuron and synapse models and support complex network topologies. Recent technological advancements have broadened the spectrum of application further to the efficient simulation of brain-scale networks on supercomputers. In distributed network simulations the amount of spike data that accrues per millisecond and process is typically low, such that a common optimization strategy is to communicate spikes at relatively long intervals, where the upper limit is given by the shortest synaptic transmission delay in the network. This approach is well-suited for simulations that employ only chemical synapses but it has so far impeded the incorporation of gap-junction models, which require instantaneous neuronal interactions. Here, we present a numerical algorithm based on a waveform-relaxation technique which allows for network simulations with gap junctions in a way that is compatible with the delayed communication strategy. Using a reference implementation in the NEST simulator, we demonstrate that the algorithm and the required data structures can be smoothly integrated with existing code such that they complement the infrastructure for spiking connections. To show that the unified framework for gap-junction and spiking interactions achieves high performance and delivers high accuracy in the presence of gap junctions, we present benchmarks for workstations, clusters, and supercomputers. Finally, we discuss limitations of the novel technology. PMID:26441628

Identification of vibrational signatures from short chains of interlinked molecule-nanoparticle junctions obtained by inelastic electron tunnelling spectroscopy

NASA Astrophysics Data System (ADS)

Jafri, S. H. M.; Löfås, H.; Fransson, J.; Blom, T.; Grigoriev, A.; Wallner, A.; Ahuja, R.; Ottosson, H.; Leifer, K.

2013-05-01

Short chains containing a series of metal-molecule-nanoparticle nanojunctions are a nano-material system with the potential to give electrical signatures close to those from single molecule experiments while enabling us to build portable devices on a chip. Inelastic electron tunnelling spectroscopy (IETS) measurements provide one of the most characteristic electrical signals of single and few molecules. In interlinked molecule-nanoparticle (NP) chains containing typically 5-7 molecules in a chain, the spectrum is expected to be a superposition of the vibrational signatures of individual molecules. We have established a stable and reproducible molecule-AuNP multi-junction by placing a few 1,8-octanedithiol (ODT) molecules onto a versatile and portable nanoparticle-nanoelectrode platform and measured for the first time vibrational molecular signatures at complex and coupled few-molecule-NP junctions. From quantum transport calculations, we model the IETS spectra and identify vibrational modes as well as the number of molecules contributing to the electron transport in the measured spectra.Short chains containing a series of metal-molecule-nanoparticle nanojunctions are a nano-material system with the potential to give electrical signatures close to those from single molecule experiments while enabling us to build portable devices on a chip. Inelastic electron tunnelling spectroscopy (IETS) measurements provide one of the most characteristic electrical signals of single and few molecules. In interlinked molecule-nanoparticle (NP) chains containing typically 5-7 molecules in a chain, the spectrum is expected to be a superposition of the vibrational signatures of individual molecules. We have established a stable and reproducible molecule-AuNP multi-junction by placing a few 1,8-octanedithiol (ODT) molecules onto a versatile and portable nanoparticle-nanoelectrode platform and measured for the first time vibrational molecular signatures at complex and coupled few-molecule-NP junctions. From quantum transport calculations, we model the IETS spectra and identify vibrational modes as well as the number of molecules contributing to the electron transport in the measured spectra. Electronic supplementary information (ESI) available: Methods and materials. Details of the ab initio calculation of molecular vibrations and inelastic spectra of ODT between two Au electrodes. A model of carrier transport through the molecular junctions. See DOI: 10.1039/c3nr00505d

A comprehensive study of extended tetrathiafulvalene cruciform molecules for molecular electronics: synthesis and electrical transport measurements.

PubMed

Parker, Christian R; Leary, Edmund; Frisenda, Riccardo; Wei, Zhongming; Jennum, Karsten S; Glibstrup, Emil; Abrahamsen, Peter Bæch; Santella, Marco; Christensen, Mikkel A; Della Pia, Eduardo Antonio; Li, Tao; Gonzalez, Maria Teresa; Jiang, Xingbin; Morsing, Thorbjørn J; Rubio-Bollinger, Gabino; Laursen, Bo W; Nørgaard, Kasper; van der Zant, Herre; Agrait, Nicolas; Nielsen, Mogens Brøndsted

2014-11-26

Cruciform-like molecules with two orthogonally placed π-conjugated systems have in recent years attracted significant interest for their potential use as molecular wires in molecular electronics. Here we present synthetic protocols for a large selection of cruciform molecules based on oligo(phenyleneethynylene) (OPE) and tetrathiafulvalene (TTF) scaffolds, end-capped with acetyl-protected thiolates as electrode anchoring groups. The molecules were subjected to a comprehensive study of their conducting properties as well as their photophysical and electrochemical properties in solution. The complex nature of the molecules and their possible binding in different configurations in junctions called for different techniques of conductance measurements: (1) conducting-probe atomic force microscopy (CP-AFM) measurements on self-assembled monolayers (SAMs), (2) mechanically controlled break-junction (MCBJ) measurements, and (3) scanning tunneling microscopy break-junction (STM-BJ) measurements. The CP-AFM measurements showed structure-property relationships from SAMs of series of OPE3 and OPE5 cruciform molecules; the conductance of the SAM increased with the number of dithiafulvene (DTF) units (0, 1, 2) along the wire, and it increased when substituting two arylethynyl end groups of the OPE3 backbone with two DTF units. The MCBJ and STM-BJ studies on single molecules both showed that DTFs decreased the junction formation probability, but, in contrast, no significant influence on the single-molecule conductance was observed. We suggest that the origins of the difference between SAM and single-molecule measurements lie in the nature of the molecule-electrode interface as well as in effects arising from molecular packing in the SAMs. This comprehensive study shows that for complex molecules care should be taken when directly comparing single-molecule measurements and measurements of SAMs and solid-state devices thereof.

Protein myozap--a late addition to the molecular ensembles of various kinds of adherens junctions.

PubMed

Rickelt, Steffen; Kuhn, Caecilia; Winter-Simanowski, Stefanie; Zimbelmann, Ralf; Frey, Norbert; Franke, Werner Wilhelm

2011-12-01

The protein myozap, a polypeptide of 54 kDa, has recently been identified as a component of the cytoplasmic plaques of the composite junctions (areae compositae) in the myocardiac intercalated disks and of the adherens junctions (AJs) in vascular endothelia. Now we report that using very sensitive new antibodies and drastic localization methods, we have also identified this protein as a component of the AJ plaques in simple and complex epithelia, in the adluminal cell layer of the transitional epithelium of the urinary tract and in certain cell layers of diverse stratified epithelia, including gingiva, tongue, pharynx and esophagus, cervix, vagina and epidermis. Myozap has not been identified in desmosomal and tight junction plaques. We have also detected protein myozap in AJ structures of carcinomas. The discovery of a novel major protein in AJ plaques now calls for re-examinations of molecular interactions in AJ formation and maintenance and also offers a new marker for diagnostic immunocytochemistry. We also discuss the need for progressive unravelling, extractive treatments and buffer rinses of sections and cultured cells to reveal obscured or masked antigens, before definitive negative conclusions in immunohistochemistry can be made.

Gap Junction Coupling and Calcium Waves in the Pancreatic Islet

PubMed Central

Benninger, Richard K. P.; Zhang, Min; Head, W. Steven; Satin, Leslie S.; Piston, David W.

2008-01-01

The pancreatic islet is a highly coupled, multicellular system that exhibits complex spatiotemporal electrical activity in response to elevated glucose levels. The emergent properties of islets, which differ from those arising in isolated islet cells, are believed to arise in part by gap junctional coupling, but the mechanisms through which this coupling occurs are poorly understood. To uncover these mechanisms, we have used both high-speed imaging and theoretical modeling of the electrical activity in pancreatic islets under a reduction in the gap junction mediated electrical coupling. Utilizing islets from a gap junction protein connexin 36 knockout mouse model together with chemical inhibitors, we can modulate the electrical coupling in the islet in a precise manner and quantify this modulation by electrophysiology measurements. We find that after a reduction in electrical coupling, calcium waves are slowed as well as disrupted, and the number of cells showing synchronous calcium oscillations is reduced. This behavior can be reproduced by computational modeling of a heterogeneous population of β-cells with heterogeneous levels of electrical coupling. The resulting quantitative agreement between the data and analytical models of islet connectivity, using only a single free parameter, reveals the mechanistic underpinnings of the multicellular behavior of the islet. PMID:18805925

Bias Selective Operation of Sb-Based Two-Color Photodetectors

NASA Technical Reports Server (NTRS)

Abedin, M. N.; Refaat, Tamer F.; Bhat, Ishwara B.; Xiao, Yegao; Johnson, David G.

2006-01-01

Multicolor detectors have a strong potential to replace conventional single-color detectors in application dealing with the simultaneous detection of more than one wavelength. This will lead to the reduction of heavy and complex optical components now required for spectral discrimination for multi-wavelengths applications. This multicolor technology is simpler, lighter, compact and cheaper with respect to the single-color ones. In this paper, Sb-based two-color detectors fabrication and characterization are presented. The color separation is achieved by fabricating dual band pn junction on a GaSb substrate. The first band consists of an InGaAsSb pn junction for long wavelength detection, while the second band consists of a GaSb pn junction for shorter wavelength detection. Three metal contacts were deposited to access the individual junctions. Surface morphology of multi-layer thin films and also device characteristics of quasi-dual band photodetector were characterized using standard optical microscope and electro-optic techniques respectively. Dark current measurements illustrated the diode behavior of both lattice-matched detector bands. Spectral response measurements indicated either independent operation of both detectors simultaneously, or selective operation of one detector, by the polarity of the bias voltage, while serially accessing both devices.

Role of Non-Myocyte Gap Junctions and Connexin Hemichannels in Cardiovascular Health and Disease: Novel Therapeutic Targets?

PubMed

Johnson, Robert D; Camelliti, Patrizia

2018-03-15

The heart is a complex organ composed of multiple cell types, including cardiomyocytes and different non-myocyte populations, all working closely together to determine the hearts properties and maintain normal cardiac function. Connexins are abundantly expressed proteins that form plasma membrane hemichannels and gap junctions between cells. Gap junctions are intracellular channels that allow for communication between cells, and in the heart they play a crucial role in cardiac conduction by coupling adjacent cardiomyocytes. Connexins are expressed in both cardiomyocytes and non-myocytes, including cardiac fibroblasts, endothelial cells, and macrophages. Non-myocytes are the largest population of cells in the heart, and therefore it is important to consider what roles connexins, hemichannels, and gap junctions play in these cell types. The aim of this review is to provide insight into connexin-based signalling in non-myocytes during health and disease, and highlight how targeting these proteins could lead to the development of novel therapies. We conclude that connexins in non-myocytes contribute to arrhythmias and adverse ventricular remodelling following myocardial infarction, and are associated with the initiation and development of atherosclerosis. Therefore, therapeutic interventions targeting these connexins represent an exciting new research avenue with great potential.

Experiments with BECs in a Painted Potential: Atom SQUID, Matter Wave Bessel Beams, and Matter Wave Circuits

NASA Astrophysics Data System (ADS)

Boshier, Malcolm; Ryu, Changhyun; Blackburn, Paul; Blinova, Alina; Henderson, Kevin

2014-05-01

The painted potential is a time-averaged optical dipole potential which is able to create arbitrary and dynamic two dimensional potentials for Bose Einstein condensates (BECs). This poster reports three recent experiments using this technique. First, we have realized the dc atom SQUID geometry of a BEC in a toroidal trap with two Josephson junctions. We observe Josephson effects, measure the critical current of the junctions, and find dynamic behavior that is in good agreement with the simple Josephson equations for a tunnel junction with the ideal sinusoidal current-phase relation expected for the parameters of the experiment. Second, we have used free expansion of a rotating toroidal BEC to create matter wave Bessel beams, which are of interest because perfect Bessel beams (plane waves with amplitude profiles described by Bessel functions) propagate without diffraction. Third, we have realized the basic circuit elements necessary to create complex matter wave circuits. We launch BECs at arbitrary velocity along straight waveguides, propagate them around curved waveguides and stadium-shaped waveguide traps, and split them coherently at y-junctions that can also act as switches. Supported by LANL/LDRD.

Rab14 and Its Exchange Factor FAM116 Link Endocytic Recycling and Adherens Junction Stability in Migrating Cells

PubMed Central

Linford, Andrea; Yoshimura, Shin-ichiro; Bastos, Ricardo Nunes; Langemeyer, Lars; Gerondopoulos, Andreas; Rigden, Daniel J.; Barr, Francis A.

2012-01-01

Summary Rab GTPases define the vesicle trafficking pathways underpinning cell polarization and migration. Here, we find that Rab4, Rab11, and Rab14 and the candidate Rab GDP-GTP exchange factors (GEFs) FAM116A and AVL9 are required for cell migration. Rab14 and its GEF FAM116A localize to and act on an intermediate compartment of the transferrin-recycling pathway prior to Rab11 and after Rab5 and Rab4. This Rab14 intermediate recycling compartment has specific functions in migrating cells discrete from early and recycling endosomes. Rab14-depleted cells show increased N-cadherin levels at junctional complexes and cannot resolve cell-cell junctions. This is due to decreased shedding of cell-surface N-cadherin by the ADAM family protease ADAM10/Kuzbanian. In FAM116A- and Rab14-depleted cells, ADAM10 accumulates in a transferrin-positive endocytic compartment, and the cell-surface level of ADAM10 is correspondingly reduced. FAM116 and Rab14 therefore define an endocytic recycling pathway needed for ADAM protease trafficking and regulation of cell-cell junctions. PMID:22595670

Foramen Magnum Meningioma: a Case Report and Review of Literature

PubMed Central

Jurinovic, Pavao; Bulicic, Ana Repic; Marcic, Marino; Mise, Nikolina Ivica; Titlic, Marina; Suljic, Enra

2016-01-01

Introduction: Meningiomas are slow-growing benign tumors that arise at any location where arachnoid cells reside. Although meningiomas account for a sizable proportion of all primary intracranial neoplasms (14.3–19%), only 1.8 to 3.2% arise at the foramen magnum. Their indolent development at the craniocervical junction makes clinical diagnosis complex and often leads to a long interval between onset of symptoms and diagnosis. Case report: We report a case of a 79-year-old male patient, presented with ataxia and sense of threatening fainting during verticalization. Magnetic resonance imaging revealed the presence of meningioma in the right side of craniospinal junction. PMID:27041817

Actin filament curvature biases branching direction

NASA Astrophysics Data System (ADS)

Wang, Evan; Risca, Viviana; Chaudhuri, Ovijit; Chia, Jia-Jun; Geissler, Phillip; Fletcher, Daniel

2012-02-01

Actin filaments are key components of the cellular machinery, vital for a wide range of processes ranging from cell motility to endocytosis. Actin filaments can branch, and essential in this process is a protein complex known as the Arp2/3 complex, which nucleate new ``daughter'' filaments from pre-existing ``mother'' filaments by attaching itself to the mother filament. Though much progress has been made in understanding the Arp2/3-actin junction, some very interesting questions remain. In particular, F-actin is a dynamic polymer that undergoes a wide range of fluctuations. Prior studies of the Arp2/3-actin junction provides a very static notion of Arp2/3 binding. The question we ask is how differently does the Arp2/3 complex interact with a straight filament compared to a bent filament? In this study, we used Monte Carlo simulations of a surface-tethered worm-like chain to explore possible mechanisms underlying the experimental observation that there exists preferential branch formation by the Arp2/3 complex on the convex face of a curved filament. We show that a fluctuation gating model in which Arp2/3 binding to the actin filament is dependent upon a rare high-local-curvature shape fluctuation of the filament is consistent with the experimental data.

Preferential V beta gene usage and lack of junctional sequence conservation among human T cell receptors specific for a tetanus toxin- derived peptide: evidence for a dominant role of a germline-encoded V region in antigen/major histocompatibility complex recognition

PubMed Central

1992-01-01

To investigate the structural and genetic basis of the T cell response to defined peptide/major histocompatibility (MHC) class II complexes in humans, we established a large panel of T cell clones (61) from donors of different HLA-DR haplotypes and reactive with a tetanus toxin- derived peptide (tt830-844) recognized in association with most DR molecules (universal peptide). By using a bacterial enterotoxin-based proliferation assay and cDNA sequencing, we found preferential use of a particular V beta region gene segment, V beta 2.1, in three of the individuals studied (64%, n = 58), irrespective of whether the peptide was presented by the DR6wcI, DR4w4, or DRw11.1 and DRw11.2 alleles, demonstrating that shared MHC class II antigens are not required for shared V beta gene use by T cell receptors (TCRs) specific for this peptide. V alpha gene use was more heterogeneous, with at least seven different V alpha segments derived from five distinct families encoding alpha chains able to pair with V beta 2.1 chains to form a tt830-844/DR- specific binding site. Several cases were found of clones restricted to different DR alleles that expressed identical V beta and (or very closely related) V alpha gene segments and that differed only in their junctional sequences. Thus, changes in the putative complementary determining region 3 (CDR3) of the TCR may, in certain cases, alter MHC specificity and maintain peptide reactivity. Finally, in contrast to what has been observed in other defined peptide/MHC systems, a striking heterogeneity was found in the junctional regions of both alpha and beta chains, even for TCRs with identical V alpha and/or V beta gene segments and the same restriction. Among 14 anti-tt830-844 clones using the V beta 2.1 gene segment, 14 unique V beta-D-J beta junctions were found, with no evident conservation in length and/or amino acid composition. One interpretation for this apparent lack of coselection of specific junctional sequences in the context of a common V element, V beta 2.1, is that this V region plays a dominant role in the recognition of the tt830-844/DR complex. PMID:1371303

Magnetic resonance imaging features of complex Chiari malformation variant of Chiari 1 malformation.

PubMed

Moore, Hannah E; Moore, Kevin R

2014-11-01

Complex Chiari malformation is a subgroup of Chiari 1 malformation with distinct imaging features. Children with complex Chiari malformation are reported to have a more severe clinical phenotype and sometimes require more extensive surgical treatment than those with uncomplicated Chiari 1 malformation. We describe reported MR imaging features of complex Chiari malformation and evaluate the utility of craniometric parameters and qualitative anatomical observations for distinguishing complex Chiari malformation from uncomplicated Chiari 1 malformation. We conducted a retrospective search of the institutional imaging database using the keywords "Chiari" and "Chiari 1" to identify children imaged during the 2006-2011 time period. Children with Chiari 2 malformation were excluded after imaging review. We used the first available diagnostic brain or cervical spine MR study for data measurement. Standard measurements and observations were made of obex level (mm), cerebellar tonsillar descent (mm), perpendicular distance to basion-C2 line (pB-C2, mm), craniocervical angle (degrees), clivus length, and presence or absence of syringohydromyelia, basilar invagination and congenital craniovertebral junction osseous anomalies. After imaging review, we accessed the institutional health care clinical database to determine whether each subject clinically met criteria for Chiari 1 malformation or complex Chiari malformation. Obex level and craniocervical angle measurements showed statistically significant differences between the populations with complex Chiari malformation and uncomplicated Chiari 1 malformation. Cerebellar tonsillar descent and perpendicular distance to basion-C2 line measurements trended toward but did not meet statistical significance. Odontoid retroflexion, craniovertebral junction osseous anomalies, and syringohydromyelia were all observed proportionally more often in children with complex Chiari malformation than in those with Chiari 1 malformation. Characteristic imaging features of complex Chiari malformation, especially obex level, permit its distinction from the more common uncomplicated Chiari 1 malformation.

Drosophila Symplekin localizes dynamically to the histone locus body and tricellular junctions.

PubMed

Tatomer, Deirdre C; Rizzardi, Lindsay F; Curry, Kaitlin P; Witkowski, Alison M; Marzluff, William F; Duronio, Robert J

2014-01-01

The scaffolding protein Symplekin is part of multiple complexes involved in generating and modifying the 3' end of mRNAs, including cleavage-polyadenylation, histone pre-mRNA processing and cytoplasmic polyadenylation. To study these functions in vivo, we examined the localization of Symplekin during development and generated mutations of the Drosophila Symplekin gene. Mutations in Symplekin that reduce Symplekin protein levels alter the efficiency of both poly A(+) and histone mRNA 3' end formation resulting in lethality or sterility. Histone mRNA synthesis takes place at the histone locus body (HLB) and requires a complex composed of Symplekin and several polyadenylation factors that associates with the U7 snRNP. Symplekin is present in the HLB in the early embryo when Cyclin E/Cdk2 is active and histone genes are expressed and is absent from the HLB in cells that have exited the cell cycle. During oogenesis, Symplekin is preferentially localized to HLBs during S-phase in endoreduplicating follicle cells when histone mRNA is synthesized. After the completion of endoreplication, Symplekin accumulates in the cytoplasm, in addition to the nucleoplasm, and localizes to tricellular junctions of the follicle cell epithelium. This localization depends on the RNA binding protein ypsilon schachtel. CPSF-73 and a number of mRNAs are localized at this same site, suggesting that Symplekin participates in cytoplasmic polyadenylation at tricellular junctions.

Phosphorylation on Ser-279 and Ser-282 of connexin43 regulates endocytosis and gap junction assembly in pancreatic cancer cells

PubMed Central

Johnson, Kristen E.; Mitra, Shalini; Katoch, Parul; Kelsey, Linda S.; Johnson, Keith R.; Mehta, Parmender P.

2013-01-01

The molecular mechanisms regulating the assembly of connexins (Cxs) into gap junctions are poorly understood. Using human pancreatic tumor cell lines BxPC3 and Capan-1, which express Cx26 and Cx43, we show that, upon arrival at the cell surface, the assembly of Cx43 is impaired. Connexin43 fails to assemble, because it is internalized by clathrin-mediated endocytosis. Assembly is restored upon expressing a sorting-motif mutant of Cx43, which does not interact with the AP2 complex, and by expressing mutants that cannot be phosphorylated on Ser-279 and Ser-282. The mutants restore assembly by preventing clathrin-mediated endocytosis of Cx43. Our results also document that the sorting-motif mutant is assembled into gap junctions in cells in which the expression of endogenous Cx43 has been knocked down. Remarkably, Cx43 mutants that cannot be phosphorylated on Ser-279 or Ser-282 are assembled into gap junctions only when connexons are composed of Cx43 forms that can be phosphorylated on these serines and forms in which phosphorylation on these serines is abolished. Based on the subcellular fate of Cx43 in single and contacting cells, our results document that the endocytic itinerary of Cx43 is altered upon cell–cell contact, which causes Cx43 to traffic by EEA1-negative endosomes en route to lysosomes. Our results further show that gap-junctional plaques formed of a sorting motif–deficient mutant of Cx43, which is unable to be internalized by the clathrin-mediated pathway, are predominantly endocytosed in the form of annular junctions. Thus the differential phosphorylation of Cx43 on Ser-279 and Ser-282 is fine-tuned to control Cx43’s endocytosis and assembly into gap junctions. PMID:23363606

On-line focusing of flavin derivatives using Dynamic pH junction-sweeping capillary electrophoresis with laser-induced fluorescence detection.

PubMed

Britz-McKibbin, Philip; Otsuka, Koji; Terabe, Shigeru

2002-08-01

Simple yet effective methods to enhance concentration sensitivity is needed for capillary electrophoresis (CE) to become a practical method to analyze trace levels of analytes in real samples. In this report, the development of a novel on-line preconcentration technique combining dynamic pH junction and sweeping modes of focusing is applied to the sensitive and selective analysis of three flavin derivatives: riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). Picomolar (pM) detectability of flavins by CE with laser-induced fluorescence (LIF) detection is demonstrated through effective focusing of large sample volumes (up to 22% capillary length) using a dual pH junction-sweeping focusing mode. This results in greater than a 1,200-fold improvement in sensitivity relative to conventional injection methods, giving a limit of detection (S/N = 3) of approximately 4.0 pM for FAD and FMN. Flavin focusing is examined in terms of analyte mobility dependence on buffer pH, borate complexation and SDS interaction. Dynamic pH junction-sweeping extends on-line focusing to both neutral (hydrophobic) and weakly acidic (hydrophilic) species and is considered useful in cases when either conventional sweeping or dynamic pH junction techniques used alone are less effective for certain classes of analytes. Enhanced focusing performance by this hyphenated method was demonstrated by greater than a 4-fold reduction in flavin bandwidth, as compared to either sweeping or dynamic pH junction, reflected by analyte detector bandwidths <0.20 cm. Novel on-line focusing strategies are required to improve sensitivity in CE, which may be applied toward more effective biochemical analysis methods for diverse types of analytes.

Nonlinear Gap Junctions Enable Long-Distance Propagation of Pulsating Calcium Waves in Astrocyte Networks

PubMed Central

Goldberg, Mati; De Pittà, Maurizio; Volman, Vladislav; Berry, Hugues; Ben-Jacob, Eshel

2010-01-01

A new paradigm has recently emerged in brain science whereby communications between glial cells and neuron-glia interactions should be considered together with neurons and their networks to understand higher brain functions. In particular, astrocytes, the main type of glial cells in the cortex, have been shown to communicate with neurons and with each other. They are thought to form a gap-junction-coupled syncytium supporting cell-cell communication via propagating Ca2+ waves. An identified mode of propagation is based on cytoplasm-to-cytoplasm transport of inositol trisphosphate (IP3) through gap junctions that locally trigger Ca2+ pulses via IP3-dependent Ca2+-induced Ca2+ release. It is, however, currently unknown whether this intracellular route is able to support the propagation of long-distance regenerative Ca2+ waves or is restricted to short-distance signaling. Furthermore, the influence of the intracellular signaling dynamics on intercellular propagation remains to be understood. In this work, we propose a model of the gap-junctional route for intercellular Ca2+ wave propagation in astrocytes. Our model yields two major predictions. First, we show that long-distance regenerative signaling requires nonlinear coupling in the gap junctions. Second, we show that even with nonlinear gap junctions, long-distance regenerative signaling is favored when the internal Ca2+ dynamics implements frequency modulation-encoding oscillations with pulsating dynamics, while amplitude modulation-encoding dynamics tends to restrict the propagation range. As a result, spatially heterogeneous molecular properties and/or weak couplings are shown to give rise to rich spatiotemporal dynamics that support complex propagation behaviors. These results shed new light on the mechanisms implicated in the propagation of Ca2+ waves across astrocytes and the precise conditions under which glial cells may participate in information processing in the brain. PMID:20865153

Fatigue crack propagation path across the dentinoenamel junction complex in human teeth.

PubMed

Dong, X D; Ruse, N D

2003-07-01

The human tooth structures should be understood clearly to improve clinically used restorative materials. The dentinoenamel junction (DEJ) plays a key role in resisting crack propagation in teeth. The aim of this study was to determine the fracture toughness of the enamel-DEJ-dentin complex and to investigate the influence of the DEJ on the fatigue crack propagation path across it by characterizing fatigue-fractured enamel-DEJ-dentin complexes using optical and scanning electron microscopy. The results of this study showed that the fracture toughness of the enamel-DEJ-dentin complex was 1.50 +/- 0.28 Mpa x m(1/2). Based on the results of this investigation, it was concluded that the DEJ complex played a critical role in resisting crack propagation from enamel into dentin. The DEJ complex is, approximately, a 100 to 150 microm broad region at the interface between enamel and dentin. The toughening mechanism of the DEJ complex may be explained by the fact that crack paths were deflected as cracks propagated across it. Understanding the mechanism of crack deflection could help in improving dentin-composite as well as ceramic-cement interfacial qualities with the aim to decrease the risk of clinical failure of restorations. Both can be viewed as being composed from a layer of material of high strength and hardness bonded to a softer but tougher substratum (dentin). The bonding agent or the luting cement layer may play the critical role of the DEJ in improving the strength of these restorations in clinical situations. Copyright 2003 Wiley Periodicals, Inc.

Protein tyrosine phosphatase σ targets apical junction complex proteins in the intestine and regulates epithelial permeability

PubMed Central

Murchie, Ryan; Guo, Cong-Hui; Persaud, Avinash; Muise, Aleixo; Rotin, Daniela

2014-01-01

Protein tyrosine phosphatase (PTP)σ (PTPRS) was shown previously to be associated with susceptibility to inflammatory bowel disease (IBD). PTPσ−/− mice exhibit an IBD-like phenotype in the intestine and show increased susceptibility to acute models of murine colitis. However, the function of PTPσ in the intestine is uncharacterized. Here, we show an intestinal epithelial barrier defect in the PTPσ−/− mouse, demonstrated by a decrease in transepithelial resistance and a leaky intestinal epithelium that was determined by in vivo tracer analysis. Increased tyrosine phosphorylation was observed at the plasma membrane of epithelial cells lining the crypts of the small bowel and colon of the PTPσ−/− mouse, suggesting the presence of PTPσ substrates in these regions. Using mass spectrometry, we identified several putative PTPσ intestinal substrates that were hyper–tyrosine-phosphorylated in the PTPσ−/− mice relative to wild type. Among these were proteins that form or regulate the apical junction complex, including ezrin. We show that ezrin binds to and is dephosphorylated by PTPσ in vitro, suggesting it is a direct PTPσ substrate, and identified ezrin-Y353/Y145 as important sites targeted by PTPσ. Moreover, subcellular localization of the ezrin phosphomimetic Y353E or Y145 mutants were disrupted in colonic Caco-2 cells, similar to ezrin mislocalization in the colon of PTPσ−/− mice following induction of colitis. Our results suggest that PTPσ is a positive regulator of intestinal epithelial barrier, which mediates its effects by modulating epithelial cell adhesion through targeting of apical junction complex-associated proteins (including ezrin), a process impaired in IBD. PMID:24385580

Impact of the structural integrity of the three-way junction of adenovirus VAI RNA on PKR inhibition

PubMed Central

Dzananovic, Edis; Astha; Chojnowski, Grzegorz; Deo, Soumya; Booy, Evan P.; Padilla-Meier, Pauline; McEleney, Kevin; Bujnicki, Janusz M.; McKenna, Sean A.

2017-01-01

Highly structured RNA derived from viral genomes is a key cellular indicator of viral infection. In response, cells produce the interferon inducible RNA-dependent protein kinase (PKR) that, when bound to viral dsRNA, phosphorylates eukaryotic initiation factor 2α and attenuates viral protein translation. Adenovirus can evade this line of defence through transcription of a non-coding RNA, VAI, an inhibitor of PKR. VAI consists of three base-paired regions that meet at a three-way junction; an apical stem responsible for the interaction with PKR, a central stem required for inhibition, and a terminal stem. Recent studies have highlighted the potential importance of the tertiary structure of the three-way junction to PKR inhibition by enabling interaction between regions of the central and terminal stems. To further investigate the role of the three-way junction, we characterized the binding affinity and inhibitory potential of central stem mutants designed to introduce subtle alterations. These results were then correlated with small-angle X-ray scattering solution studies and computational tertiary structural models. Our results demonstrate that while mutations to the central stem have no observable effect on binding affinity to PKR, mutations that appear to disrupt the structure of the three-way junction prevent inhibition of PKR. Therefore, we propose that instead of simply sequestering PKR, a specific structural conformation of the PKR-VAI complex may be required for inhibition. PMID:29053745

Rapid synthesis of acetylcholine receptors at neuromuscular junctions.

PubMed

Ramsay, D A; Drachman, D B; Pestronk, A

1988-10-11

The rate of acetylcholine receptor (AChR) degradation in mature, innervated mammalian neuromuscular junctions has recently been shown to be biphasic; up to 20% are rapidly turned over (RTOs; half life less than 1 day) whereas the remainder are lost more slowly ('stable' AChRs; half life 10-12 days). In order to maintain normal junctional receptor density, synthesis and insertion of AChRs should presumably be sufficiently rapid to replace both the RTOs and the stable receptors. We have tested this prediction by blocking pre-existing AChRs in the mouse sternomastoid muscle with alpha-bungarotoxin (alpha-BuTx), and monitoring the subsequent appearance of 'new' junctional AChRs at intervals of 3 h to 20 days by labeling them with 125I-alpha-BuTx. The results show that new receptors were initially inserted rapidly (16% at 24 h and 28% at 48 h). The rate of increase of 'new' 125I-alpha-BuTx binding sites gradually slowed down during the remainder of the time period studied. Control observations excluded possible artifacts of the experimental procedure including incomplete blockade of AChRs, dissociation of toxin-receptor complexes, or experimentally induced alteration of receptor synthesis. The present demonstration of rapid synthesis and incorporation of AChRs at innervated neuromuscular junctions provides support for the concept of a subpopulation of rapidly turned over AChRs. The RTOs may serve as precursors for the larger population of stable receptors and have an important role in the metabolism of the neuromuscular synapse.

Surface obstacles in pulsatile flow

NASA Astrophysics Data System (ADS)

Carr, Ian A.; Plesniak, Michael W.

2017-11-01

Flows past obstacles mounted on flat surfaces have been widely studied due to their ubiquity in nature and engineering. For nearly all of these studies, the freestream flow over the obstacle was steady, i.e., constant velocity, unidirectional flow. Unsteady, pulsatile flows occur frequently in biology, geophysics, biomedical engineering, etc. Our study is aimed at extending the comprehensive knowledge base that exists for steady flows to considerably more complex pulsatile flows. Characterizing the vortex and wake dynamics of flows around surface obstacles embedded in pulsatile flows can provide insights into the underlying physics in all wake and junction flows. In this study, we experimentally investigate the wake of two canonical obstacles: a cube and a circular cylinder with an aspect ratio of unity. Our previous studies of a surface-mounted hemisphere in pulsatile flow are used as a baseline for these two new, more complex geometries. Phase-averaged PIV and hot-wire anemometry are used to characterize the dynamics of coherent structures in the wake and at the windward junction of the obstacles. Complex physics occur during the deceleration phase of the pulsatile inflow. We propose a framework for understanding these physics based on self-induced vortex propagation, similar to the phenomena exhibited by vortex rings.

Cadherin complexes recruit mRNAs and RISC to regulate epithelial cell signaling

PubMed Central

Lin, Wan-Hsin; Lu, Ruifeng; Feathers, Ryan W.; Asmann, Yan W.; Thompson, E. Aubrey

2017-01-01

Cumulative evidence demonstrates that most RNAs exhibit specific subcellular distribution. However, the mechanisms regulating this phenomenon and its functional consequences are still under investigation. Here, we reveal that cadherin complexes at the apical zonula adherens (ZA) of epithelial adherens junctions recruit the core components of the RNA-induced silencing complex (RISC) Ago2, GW182, and PABPC1, as well as a set of 522 messenger RNAs (mRNAs) and 28 mature microRNAs (miRNAs or miRs), via PLEKHA7. Top canonical pathways represented by these mRNAs include Wnt/β-catenin, TGF-β, and stem cell signaling. We specifically demonstrate the presence and silencing of MYC, JUN, and SOX2 mRNAs by miR-24 and miR-200c at the ZA. PLEKHA7 knockdown dissociates RISC from the ZA, decreases loading of the ZA-associated mRNAs and miRNAs to Ago2, and results in a corresponding increase of MYC, JUN, and SOX2 protein expression. The present work reveals a mechanism that directly links junction integrity to the silencing of a set of mRNAs that critically affect epithelial homeostasis. PMID:28877994

Cadherin complexes recruit mRNAs and RISC to regulate epithelial cell signaling.

PubMed

Kourtidis, Antonis; Necela, Brian; Lin, Wan-Hsin; Lu, Ruifeng; Feathers, Ryan W; Asmann, Yan W; Thompson, E Aubrey; Anastasiadis, Panos Z

2017-10-02

Cumulative evidence demonstrates that most RNAs exhibit specific subcellular distribution. However, the mechanisms regulating this phenomenon and its functional consequences are still under investigation. Here, we reveal that cadherin complexes at the apical zonula adherens (ZA) of epithelial adherens junctions recruit the core components of the RNA-induced silencing complex (RISC) Ago2, GW182, and PABPC1, as well as a set of 522 messenger RNAs (mRNAs) and 28 mature microRNAs (miRNAs or miRs), via PLEKHA7. Top canonical pathways represented by these mRNAs include Wnt/β-catenin, TGF-β, and stem cell signaling. We specifically demonstrate the presence and silencing of MYC, JUN, and SOX2 mRNAs by miR-24 and miR-200c at the ZA. PLEKHA7 knockdown dissociates RISC from the ZA, decreases loading of the ZA-associated mRNAs and miRNAs to Ago2, and results in a corresponding increase of MYC, JUN, and SOX2 protein expression. The present work reveals a mechanism that directly links junction integrity to the silencing of a set of mRNAs that critically affect epithelial homeostasis. © 2017 Kourtidis et al.

Crystal structure of the Mus81-Eme1 complex.

PubMed

Chang, Jeong Ho; Kim, Jeong Joo; Choi, Jung Min; Lee, Jung Hoon; Cho, Yunje

2008-04-15

The Mus81-Eme1 complex is a structure-specific endonuclease that plays an important role in rescuing stalled replication forks and resolving the meiotic recombination intermediates in eukaryotes. We have determined the crystal structure of the Mus81-Eme1 complex. Both Mus81 and Eme1 consist of a central nuclease domain, two repeats of the helix-hairpin-helix (HhH) motif at their C-terminal region, and a linker helix. While each domain structure resembles archaeal XPF homologs, the overall structure is significantly different from those due to the structure of a linker helix. We show that a flexible intradomain linker that formed with 36 residues in the nuclease domain of Eme1 is essential for the recognition of DNA. We identified several basic residues lining the outer surface of the active site cleft of Mus81 that are involved in the interaction with a flexible arm of a nicked Holliday junction (HJ). These interactions might contribute to the optimal positioning of the opposite junction across the nick into the catalytic site, which provided the basis for the "nick and counternick" mechanism of Mus81-Eme1 and for the nicked HJ to be the favored in vitro substrate of this enzyme.

Tunneling magnetoresistance and electroresistance in Fe/PbTiO{sub 3}/Fe multiferroic tunnel junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Jian-Qing, E-mail: djqkust@sina.com

We perform first-principles electronic structure and spin-dependent transport calculations for a Fe/PbTiO{sub 3}/Fe multiferroic tunnel junction with asymmetric TiO{sub 2}- and PbO-terminated interfaces. We demonstrate that the interfacial electronic reconstruction driven by the in situ screening of ferroelectric polarization, in conjunction with the intricate complex band structure of barrier, play a decisive role in controlling the spin-dependent tunneling. Reversal of ferroelectric polarization results in a transition from insulating to half-metal-like conducting state for the interfacial Pb 6p{sub z} orbitals, which acts as an atomic-scale spin-valve by releasing the tunneling current in antiparallel magnetization configuration as the ferroelectric polarization pointing tomore » the PbO-terminated interface. This effect produces large change in tunneling conductance. Our results open an attractive avenue in designing multiferroic tunnel junctions with excellent performance by exploiting the interfacial electronic reconstruction originated from the in situ screening of ferroelectric polarization.« less

Identification of vibrational signatures from short chains of interlinked molecule-nanoparticle junctions obtained by inelastic electron tunnelling spectroscopy.

PubMed

Jafri, S H M; Löfås, H; Fransson, J; Blom, T; Grigoriev, A; Wallner, A; Ahuja, R; Ottosson, H; Leifer, K

2013-06-07

Short chains containing a series of metal-molecule-nanoparticle nanojunctions are a nano-material system with the potential to give electrical signatures close to those from single molecule experiments while enabling us to build portable devices on a chip. Inelastic electron tunnelling spectroscopy (IETS) measurements provide one of the most characteristic electrical signals of single and few molecules. In interlinked molecule-nanoparticle (NP) chains containing typically 5-7 molecules in a chain, the spectrum is expected to be a superposition of the vibrational signatures of individual molecules. We have established a stable and reproducible molecule-AuNP multi-junction by placing a few 1,8-octanedithiol (ODT) molecules onto a versatile and portable nanoparticle-nanoelectrode platform and measured for the first time vibrational molecular signatures at complex and coupled few-molecule-NP junctions. From quantum transport calculations, we model the IETS spectra and identify vibrational modes as well as the number of molecules contributing to the electron transport in the measured spectra.

The Voronoi Implicit Interface Method for computing multiphase physics

PubMed Central

Saye, Robert I.; Sethian, James A.

2011-01-01

We introduce a numerical framework, the Voronoi Implicit Interface Method for tracking multiple interacting and evolving regions (phases) whose motion is determined by complex physics (fluids, mechanics, elasticity, etc.), intricate jump conditions, internal constraints, and boundary conditions. The method works in two and three dimensions, handles tens of thousands of interfaces and separate phases, and easily and automatically handles multiple junctions, triple points, and quadruple points in two dimensions, as well as triple lines, etc., in higher dimensions. Topological changes occur naturally, with no surgery required. The method is first-order accurate at junction points/lines, and of arbitrarily high-order accuracy away from such degeneracies. The method uses a single function to describe all phases simultaneously, represented on a fixed Eulerian mesh. We test the method’s accuracy through convergence tests, and demonstrate its applications to geometric flows, accurate prediction of von Neumann’s law for multiphase curvature flow, and robustness under complex fluid flow with surface tension and large shearing forces. PMID:22106269

Mitochondrial cardiolipin/phospholipid trafficking: the role of membrane contact site complexes and lipid transfer proteins.

PubMed

Schlattner, Uwe; Tokarska-Schlattner, Malgorzata; Rousseau, Denis; Boissan, Mathieu; Mannella, Carmen; Epand, Richard; Lacombe, Marie-Lise

2014-04-01

Historically, cellular trafficking of lipids has received much less attention than protein trafficking, mostly because its biological importance was underestimated, involved sorting and translocation mechanisms were not known, and analytical tools were limiting. This has changed during the last decade, and we discuss here some progress made in respect to mitochondria and the trafficking of phospholipids, in particular cardiolipin. Different membrane contact site or junction complexes and putative lipid transfer proteins for intra- and intermembrane lipid translocation have been described, involving mitochondrial inner and outer membrane, and the adjacent membranes of the endoplasmic reticulum. An image emerges how cardiolipin precursors, remodeling intermediates, mature cardiolipin and its oxidation products could migrate between membranes, and how this trafficking is involved in cardiolipin biosynthesis and cell signaling events. Particular emphasis in this review is given to mitochondrial nucleoside diphosphate kinase D and mitochondrial creatine kinases, which emerge to have roles in both, membrane junction formation and lipid transfer. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

The Voronoi Implicit Interface Method for computing multiphase physics.

PubMed

Saye, Robert I; Sethian, James A

2011-12-06

We introduce a numerical framework, the Voronoi Implicit Interface Method for tracking multiple interacting and evolving regions (phases) whose motion is determined by complex physics (fluids, mechanics, elasticity, etc.), intricate jump conditions, internal constraints, and boundary conditions. The method works in two and three dimensions, handles tens of thousands of interfaces and separate phases, and easily and automatically handles multiple junctions, triple points, and quadruple points in two dimensions, as well as triple lines, etc., in higher dimensions. Topological changes occur naturally, with no surgery required. The method is first-order accurate at junction points/lines, and of arbitrarily high-order accuracy away from such degeneracies. The method uses a single function to describe all phases simultaneously, represented on a fixed Eulerian mesh. We test the method's accuracy through convergence tests, and demonstrate its applications to geometric flows, accurate prediction of von Neumann's law for multiphase curvature flow, and robustness under complex fluid flow with surface tension and large shearing forces.

[Dermoepidermic junction: a selective, complex and vital barrier].

PubMed

Frede, Silvia C; Dionisio de Cabalier, María E; Zaya, Alejandro; Hliba, Ernesto

2004-01-01

Dermoepidermic junction (DEJ) is a highly complex region, containing a great variety of cellular elements, which despite of having different embriogenesis, interact with each other, generating different substances that keep the function and homeostasis of the greatest organ of the human body. DEJ is regarded as a highly specialized basal lamina, which acts as a highly selective pathway for the migration of cells and macromolecules, inducing cellular differentiation and micro enviromental metabolism modifications. DEJ may be divided into three zones regarding the basal lamina 1--the nearest to epidermic zone, having tonofilaments and hemidesmosomes, which keep anchored basal cells. This region is limited by the lamina densa 2--the intermediate zone, represented exclusively by lamina densa and finally the lamina 3,--the third region--extends from lamina densa to the upper dermis and extracelullar matrix. Despite there is much to learn about DEJ, the knowledge about each molecule and function of every compartment will enable us to know more about the pathogenesis of several dermatologic diseases, with a great prevalence in the clinical practice.

The Voronoi Implicit Interface Method for computing multiphase physics

DOE PAGES

Saye, Robert I.; Sethian, James A.

2011-11-21

In this paper, we introduce a numerical framework, the Voronoi Implicit Interface Method for tracking multiple interacting and evolving regions (phases) whose motion is determined by complex physics (fluids, mechanics, elasticity, etc.), intricate jump conditions, internal constraints, and boundary conditions. The method works in two and three dimensions, handles tens of thousands of interfaces and separate phases, and easily and automatically handles multiple junctions, triple points, and quadruple points in two dimensions, as well as triple lines, etc., in higher dimensions. Topological changes occur naturally, with no surgery required. The method is first-order accurate at junction points/lines, and of arbitrarilymore » high-order accuracy away from such degeneracies. The method uses a single function to describe all phases simultaneously, represented on a fixed Eulerian mesh. Finally, we test the method’s accuracy through convergence tests, and demonstrate its applications to geometric flows, accurate prediction of von Neumann’s law for multiphase curvature flow, and robustness under complex fluid flow with surface tension and large shearing forces.« less

Modulation of the Pyrococcus abyssi NucS Endonuclease Activity by Replication Clamp at Functional and Structural Levels*

PubMed Central

Creze, Christophe; Ligabue, Alessio; Laurent, Sébastien; Lestini, Roxane; Laptenok, Sergey P.; Khun, Joelle; Vos, Marten H.; Czjzek, Mirjam; Myllykallio, Hannu; Flament, Didier

2012-01-01

Pyrococcus abyssi NucS is the founding member of a new family of structure-specific DNA endonucleases that interact with the replication clamp proliferating cell nuclear antigen (PCNA). Using a combination of small angle x-ray scattering and surface plasmon resonance analyses, we demonstrate the formation of a stable complex in solution, in which one molecule of the PabNucS homodimer binds to the outside surface of the PabPCNA homotrimer. Using fluorescent labels, PCNA is shown to increase the binding affinity of NucS toward single-strand/double-strand junctions on 5′ and 3′ flaps, as well as to modulate the cleavage specificity on the branched DNA structures. Our results indicate that the presence of a single major contact between the PabNucS and PabPCNA proteins, together with the complex-induced DNA bending, facilitate conformational flexibility required for specific cleavage at the single-strand/double-strand DNA junction. PMID:22431731

Modulation of the Pyrococcus abyssi NucS endonuclease activity by replication clamp at functional and structural levels.

PubMed

Creze, Christophe; Ligabue, Alessio; Laurent, Sébastien; Lestini, Roxane; Laptenok, Sergey P; Khun, Joelle; Vos, Marten H; Czjzek, Mirjam; Myllykallio, Hannu; Flament, Didier

2012-05-04

Pyrococcus abyssi NucS is the founding member of a new family of structure-specific DNA endonucleases that interact with the replication clamp proliferating cell nuclear antigen (PCNA). Using a combination of small angle x-ray scattering and surface plasmon resonance analyses, we demonstrate the formation of a stable complex in solution, in which one molecule of the PabNucS homodimer binds to the outside surface of the PabPCNA homotrimer. Using fluorescent labels, PCNA is shown to increase the binding affinity of NucS toward single-strand/double-strand junctions on 5' and 3' flaps, as well as to modulate the cleavage specificity on the branched DNA structures. Our results indicate that the presence of a single major contact between the PabNucS and PabPCNA proteins, together with the complex-induced DNA bending, facilitate conformational flexibility required for specific cleavage at the single-strand/double-strand DNA junction.

Conjugated ionomers for photovoltaic applications: electric field driven charge separation in organic photovoltaics. Final Technical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lonergan, Mark

Final technical report for Conjugated ionomers for photovoltaic applications, electric field driven charge separation in organic photovoltaics. The central goal of the work we completed was been to understand the photochemical and photovoltaic properties of ionically functionalized conjugated polymers (conjugated ionomers or polyelectrolytes) and energy conversion systems based on them. We primarily studied two classes of conjugated polymer interfaces that we developed based either upon undoped conjugated polymers with an asymmetry in ionic composition (the ionic junction) or doped conjugated polymers with an asymmetry in doping type (the p-n junction). The materials used for these studies have primarily been themore » polyacetylene ionomers. We completed a detailed study of p-n junctions with systematically varying dopant density, photochemical creation of doped junctions, and experimental and theoretical work on charge transport and injection in polyacetylene ionomers. We have also completed related work on the use of conjugated ionomers as interlayers that improve the efficiency or organic photovoltaic systems and studied several important aspects of the chemistry of ionically functionalized semiconductors, including mechanisms of so-called "anion-doping", the formation of charge transfer complexes with oxygen, and the synthesis of new polyfluorene polyelectrolytes. We also worked worked with the Haley group at the University of Oregon on new indenofluorene-based organic acceptors.« less

Gap-junction-mediated communication in human periodontal ligament cells.

PubMed

Kato, R; Ishihara, Y; Kawanabe, N; Sumiyoshi, K; Yoshikawa, Y; Nakamura, M; Imai, Y; Yanagita, T; Fukushima, H; Kamioka, H; Takano-Yamamoto, T; Yamashiro, T

2013-07-01

Periodontal tissue homeostasis depends on a complex cellular network that conveys cell-cell communication. Gap junctions (GJs), one of the intercellular communication systems, are found between adjacent human periodontal ligament (hPDL) cells; however, the functional GJ coupling between hPDL cells has not yet been elucidated. In this study, we investigated functional gap-junction-mediated intercellular communication in isolated primary hPDL cells. SEM images indicated that the cells were in contact with each other via dendritic processes, and also showed high anti-connexin43 (Cx43) immunoreactivity on these processes. Gap-junctional intercellular communication (GJIC) among hPDL cells was assessed by fluorescence recovery after a photobleaching (FRAP) analysis, which exhibited dye coupling between hPDL cells, and was remarkably down-regulated when the cells were treated with a GJ blocker. Additionally, we examined GJs under hypoxic stress. The fluorescence recovery and expression levels of Cx43 decreased time-dependently under the hypoxic condition. Exposure to GJ inhibitor or hypoxia increased RANKL expression, and decreased OPG expression. This study shows that GJIC is responsible for hPDL cells and that its activity is reduced under hypoxia. This is consistent with the possible role of hPDL cells in regulating the biochemical reactions in response to changes in the hypoxic environment.

Agonist-activated Ca2+ influx occurs at stable plasma membrane and endoplasmic reticulum junctions

PubMed Central

Treves, Susan; Vukcevic, Mirko; Griesser, Johanna; Armstrong, Clara-Franzini; Zhu, Michael X.; Zorzato, Fancesco

2010-01-01

Junctate is a 33 kDa integral protein of sarco(endo)plasmic reticulum membranes that forms a macromolecular complex with inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] receptors and TRPC3 channels. TIRF microscopy shows that junctate enhances the number of fluorescent puncta on the plasma membrane. The size and distribution of these puncta are not affected by the addition of agonists that mobilize Ca2+ from Ins(1,4,5)P3-sensitive stores. Puncta are associated with a significantly larger number of peripheral junctions between endoplasmic reticulum and plasma membrane, which are further enhanced upon stable co-expression of junctate and TRPC3. The gap between the membranes of peripheral junctions is bridged by regularly spaced electron-dense structures of 10 nm. Ins(1,4,5)P3 inhibits the interaction of the cytoplasmic N-terminus of junctate with the ligand-binding domain of the Ins(1,4,5)P3 receptor. Furthermore, Ca2+ influx evoked by activation of Ins(1,4,5)P3 receptors is increased where puncta are located. We conclude that stable peripheral junctions between the plasma membrane and endoplasmic reticulum are the anatomical sites of agonist-activated Ca2+ entry. PMID:21062895

Homophilic and heterophilic polycystin 1 interactions regulate E-cadherin recruitment and junction assembly in MDCK cells

PubMed Central

Streets, Andrew J.; Wagner, Bart E.; Harris, Peter C.; Ward, Christopher J.; Ong, Albert C. M.

2009-01-01

Summary Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited human renal disease and is caused by mutations in two genes, PKD1 (85%) and PKD2 (15%). Cyst epithelial cells are characterised by a complex cellular phenotype including changes in proliferation, apoptosis, basement membrane composition and apicobasal polarity. Since polycystin 1 (PC1), the PKD1 protein, has been located in the basolateral membrane of kidney epithelial cells, we hypothesised that it might have a key role in mediating or stabilising cell-cell interactions. In non-ciliated L929 cells, stable or transient surface expression of the PC1 extracellular domain was sufficient to confer an adhesive phenotype and stimulate junction formation. In MDCK cells, we found that PC1 was recruited to the lateral membranes coincident with E-cadherin within 30 minutes after a `calcium switch'. Recruitment of both proteins was significantly delayed when cells were treated with a PC1 blocking antibody raised to the PKD domains. Finally, PC1 and E-cadherin could be coimmunoprecipitated together from MDCK cells. We conclude that PC1 has a key role in initiating junction formation via initial homophilic interactions and facilitates junction assembly and the establishment of apicobasal polarity by E-cadherin recruitment. PMID:19351715

The ultrastructure of cerebral blood capillaries in the ratfish, Chimaera monstrosa.

PubMed

Bundgaard, M

1982-01-01

Sharks and skates (Chondrichthyes: Elasmobranchii) have a glial blood-brain barrier, while all other vertebrates examined so far have an endothelial barrier. For comparative reasons it is desirable to examine the blood-brain barrier in species from the other subclass of cartilaginous fish, the holocephalans. The ultrastructure of cerebral capillaries in the chimaera (Chondrichthyes: Holocephali) is described in the present study. The endothelial cells are remarkably thick. Fenestrae and transendothelial channels were not observed. The endothelial cells are joined by elaborate tight junctions. The perivascular glial processes are separated by wide spaces (15-60 nm) without obliterating junctional complexes. These findings indicate that the chimaera has an endothelial blood-brain barrier.

Detection of in situ protein-protein complexes at the Drosophila larval neuromuscular junction using proximity ligation assay.

PubMed

Wang, Simon; Yoo, SooHyun; Kim, Hae-Yoon; Wang, Mannan; Zheng, Clare; Parkhouse, Wade; Krieger, Charles; Harden, Nicholas

2015-01-20

Discs large (Dlg) is a conserved member of the membrane-associated guanylate kinase family, and serves as a major scaffolding protein at the larval neuromuscular junction (NMJ) in Drosophila. Previous studies have shown that the postsynaptic distribution of Dlg at the larval NMJ overlaps with that of Hu-li tai shao (Hts), a homologue to the mammalian adducins. In addition, Dlg and Hts are observed to form a complex with each other based on co-immunoprecipitation experiments involving whole adult fly lysates. Due to the nature of these experiments, however, it was unknown whether this complex exists specifically at the NMJ during larval development. Proximity Ligation Assay (PLA) is a recently developed technique used mostly in cell and tissue culture that can detect protein-protein interactions in situ. In this assay, samples are incubated with primary antibodies against the two proteins of interest using standard immunohistochemical procedures. The primary antibodies are then detected with a specially designed pair of oligonucleotide-conjugated secondary antibodies, termed PLA probes, which can be used to generate a signal only when the two probes have bound in close proximity to each other. Thus, proteins that are in a complex can be visualized. Here, it is demonstrated how PLA can be used to detect in situ protein-protein interactions at the Drosophila larval NMJ. The technique is performed on larval body wall muscle preparations to show that a complex between Dlg and Hts does indeed exist at the postsynaptic region of NMJs.

Cell type-specific recruitment of Drosophila Lin-7 to distinct MAGUK-based protein complexes defines novel roles for Sdt and Dlg-S97.

PubMed

Bachmann, André; Timmer, Marco; Sierralta, Jimena; Pietrini, Grazia; Gundelfinger, Eckart D; Knust, Elisabeth; Thomas, Ulrich

2004-04-15

Stardust (Sdt) and Discs-Large (Dlg) are membrane-associated guanylate kinases (MAGUKs) involved in the organization of supramolecular protein complexes at distinct epithelial membrane compartments in Drosophila. Loss of either Sdt or Dlg affects epithelial development with severe effects on apico-basal polarity. Moreover, Dlg is required for the structural and functional integrity of synaptic junctions. Recent biochemical and cell culture studies have revealed that various mammalian MAGUKs can interact with mLin-7/Veli/MALS, a small PDZ-domain protein. To substantiate these findings for their in vivo significance with regard to Sdt- and Dlg-based protein complexes, we analyzed the subcellular distribution of Drosophila Lin-7 (DLin-7) and performed genetic and biochemical assays to characterize its interaction with either of the two MAGUKs. In epithelia, Sdt mediates the recruitment of DLin-7 to the subapical region, while at larval neuromuscular junctions, a particular isoform of Dlg, Dlg-S97, is required for postsynaptic localization of DLin-7. Ectopic expression of Dlg-S97 in epithelia, however, was not sufficient to induce a redistribution of DLin-7. These results imply that the recruitment of DLin-7 to MAGUK-based protein complexes is defined by cell-type specific mechanisms and that DLin-7 acts downstream of Sdt in epithelia and downstream of Dlg at synapses.

Mechanism of T7 RNAP pausing and termination at the T7 concatemer junction: a local change in transcription bubble structure drives a large change in transcription complex architecture.

PubMed

Nayak, Dhananjaya; Siller, Sylvester; Guo, Qing; Sousa, Rui

2008-02-15

The T7RNA polymerase (RNAP) elongation complex (EC) pauses and is destabilized at a unique 8 nucleotide (nt) sequence found at the junction of the head-to-tail concatemers of T7 genomic DNA generated during T7 DNA replication. The paused EC may recruit the T7 DNA processing machinery, which cleaves the concatemerized DNA within this 8 nt concatemer junction (CJ). Pausing of the EC at the CJ involves structural changes in both the RNAP and transcription bubble. However, these structural changes have not been fully defined, nor is it understood how the CJ sequence itself causes the EC to change its structure, to pause, and to become less stable. Here we use solution and RNAP-tethered chemical nucleases to probe the CJ transcript and changes in the EC structure as the polymerase pauses and terminates at the CJ. Together with extensive mutational scanning of regions of the polymerase that are likely to be involved in recognition of the CJ, we are able to develop a description of the events that occur as the EC transcribes through the CJ and subsequently pauses. In this process, a local change in the structure of the transcription bubble drives a large change in the architecture of the EC. This altered EC structure may then serve as the signal that recruits the processing machinery to the CJ.

Interleukin 2 Activates Brain Microvascular Endothelial Cells Resulting in Destabilization of Adherens Junctions.

PubMed

Wylezinski, Lukasz S; Hawiger, Jacek

2016-10-28

The pleiotropic cytokine interleukin 2 (IL2) disrupts the blood-brain barrier and alters brain microcirculation, underlying vascular leak syndrome that complicates cancer immunotherapy with IL2. The microvascular effects of IL2 also play a role in the development of multiple sclerosis and other chronic neurological disorders. The mechanism of IL2-induced disruption of brain microcirculation has not been determined previously. We found that both human and murine brain microvascular endothelial cells express constituents of the IL2 receptor complex. Then we established that signaling through this receptor complex leads to activation of the transcription factor, nuclear factor κB, resulting in expression of proinflammatory interleukin 6 and monocyte chemoattractant protein 1. We also discovered that IL2 induces disruption of adherens junctions, concomitant with cytoskeletal reorganization, ultimately leading to increased endothelial cell permeability. IL2-induced phosphorylation of vascular endothelial cadherin (VE-cadherin), a constituent of adherens junctions, leads to dissociation of its stabilizing adaptor partners, p120-catenin and β-catenin. Increased phosphorylation of VE-cadherin was also accompanied by a reduction of Src homology 2 domain-containing protein-tyrosine phosphatase 2, known to maintain vascular barrier function. These results unravel the mechanism of deleterious effects induced by IL2 on brain microvascular endothelial cells and may inform the development of new measures to improve IL2 cancer immunotherapy, as well as treatments for autoimmune diseases affecting the central nervous system. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Vocal Fold Epithelial Barrier in Health and Injury: A Research Review

ERIC Educational Resources Information Center

Levendoski, Elizabeth Erickson; Leydon, Ciara; Thibeault, Susan L.

2014-01-01

Purpose: Vocal fold epithelium is composed of layers of individual epithelial cells joined by junctional complexes constituting a unique interface with the external environment. This barrier provides structural stability to the vocal folds and protects underlying connective tissue from injury while being nearly continuously exposed to potentially…

Junction restructuring and spermatogenesis: the biology, regulation, and implication in male contraceptive development.

PubMed

Yan, Helen H N; Mruk, Dolores D; Cheng, C Yan

2008-01-01

Spermatogenesis that occurs in the seminiferous epithelium of adult mammalian testes is associated with extensive junction restructuring at the Sertoli-Sertoli cell, Sertoli-germ cell, and Sertoli-basement membrane interface. While this morphological phenomenon is known and has been described in great details for decades, the biochemical and molecular changes as well as the mechanisms/signaling pathways that define changes at the cell-cell and cell-matrix interface remain largely unknown until recently. In this chapter, we summarize and discuss findings in the field regarding the coordinated efforts of the anchoring [e.g., adherens junction (AJ), such as basal ectoplasmic specialization (basal ES)] and tight junctions (TJs) that are present in the same microenvironment, such as at the blood-testis barrier (BTB), or at distinctly opposite ends of the Sertoli cell epithelium, such as between apical ectoplasmic specialization (apical ES) in the apical compartment, and the BTB adjacent to the basal compartment of the epithelium. These efforts, in turn, regulate and coordinate different cellular events that occur during the seminiferous epithelial cycle. For instance, the events of spermiation and of preleptotene spermatocyte migration across the BTB both take place concurrently at stage VIII of the epithelial cycle of spermatogenesis. Recent findings suggest that these events are coordinated by protein complexes found at the apical and basal ES and TJ, which are located at different ends of the Sertoli cell epithelium. Besides, we highlight important areas of research that can now be undertaken, and functional studies that can be designed to tackle different issues pertinent to junction restructuring during spermatogenesis.

Sparse short-distance connections enhance calcium wave propagation in a 3D model of astrocyte networks

PubMed Central

Lallouette, Jules; De Pittà, Maurizio; Ben-Jacob, Eshel; Berry, Hugues

2014-01-01

Traditionally, astrocytes have been considered to couple via gap-junctions into a syncytium with only rudimentary spatial organization. However, this view is challenged by growing experimental evidence that astrocytes organize as a proper gap-junction mediated network with more complex region-dependent properties. On the other hand, the propagation range of intercellular calcium waves (ICW) within astrocyte populations is as well highly variable, depending on the brain region considered. This suggests that the variability of the topology of gap-junction couplings could play a role in the variability of the ICW propagation range. Since this hypothesis is very difficult to investigate with current experimental approaches, we explore it here using a biophysically realistic model of three-dimensional astrocyte networks in which we varied the topology of the astrocyte network, while keeping intracellular properties and spatial cell distribution and density constant. Computer simulations of the model suggest that changing the topology of the network is indeed sufficient to reproduce the distinct ranges of ICW propagation reported experimentally. Unexpectedly, our simulations also predict that sparse connectivity and restriction of gap-junction couplings to short distances should favor propagation while long–distance or dense connectivity should impair it. Altogether, our results provide support to recent experimental findings that point toward a significant functional role of the organization of gap-junction couplings into proper astroglial networks. Dynamic control of this topology by neurons and signaling molecules could thus constitute a new type of regulation of neuron-glia and glia-glia interactions. PMID:24795613

Measurement and control of detailed electronic properties in a single molecule break junction.

PubMed

Wang, Kun; Hamill, Joseph; Zhou, Jianfeng; Guo, Cunlan; Xu, Bingqian

2014-01-01

The lack of detailed experimental controls has been one of the major obstacles hindering progress in molecular electronics. While large fluctuations have been occurring in the experimental data, specific details, related mechanisms, and data analysis techniques are in high demand to promote our physical understanding at the single-molecule level. A series of modulations we recently developed, based on traditional scanning probe microscopy break junctions (SPMBJs), have helped to discover significant properties in detail which are hidden in the contact interfaces of a single-molecule break junction (SMBJ). For example, in the past we have shown that the correlated force and conductance changes under the saw tooth modulation and stretch-hold mode of PZT movement revealed inherent differences in the contact geometries of a molecular junction. In this paper, using a bias-modulated SPMBJ and utilizing emerging data analysis techniques, we report on the measurement of the altered alignment of the HOMO of benzene molecules with changing the anchoring group which coupled the molecule to metal electrodes. Further calculations based on Landauer fitting and transition voltage spectroscopy (TVS) demonstrated the effects of modulated bias on the location of the frontier molecular orbitals. Understanding the alignment of the molecular orbitals with the Fermi level of the electrodes is essential for understanding the behaviour of SMBJs and for the future design of more complex devices. With these modulations and analysis techniques, fruitful information has been found about the nature of the metal-molecule junction, providing us insightful clues towards the next step for in-depth study.

High-LET Radiation Induced Chromosome Aberrations in Normal and Ataxia Telangiectasia Fibroblast Cells

NASA Astrophysics Data System (ADS)

Kawata, Tetsuya; George, Ms Kerry; Cucinotta, Francis A.; Shigematsu, Naoyuki; Ito, Hisao; Furusawa, Yoshiya; Uno, Takashi

We investigated the effects of heavy ions beams on chromosomal aberrations in normal and AT cells. Normal and AT fibroblast cells arrested at G0/G1 phase were irradiated with 2 Gy of X-rays, 490 MeV/u Silicon (LET 55 keV/micron), 500 MeV/u Iron (LET 185 keV/micron) and 200 MeV/u Iron (LET 440 keV/micron) particles, and then cells were allowed to repair for 24 hours at 37 degrees before subculture. Calyculin-A induced PCC method was employed to collect G2/M chromosomes and whole DNA probes 1 and 3 were used to analyze chromosomal aberrations such as color-junctions, deletions, simple exchanges (incomplete and reciprocal exchanges) and complex-type exchanges. The percentages of aberrant cells were higher when normal and AT cells were exposed to heavy ions compared to X-rays, and had a tendency to increase with increasing LET up to 185 keV/micron and then decreased at 440 keV/micron. When the frequency of color-junctions per cell was compared after X-ray exposure, AT cells had around three times higher frequency of color-junctions (mis-rejoining) than normal cells. However, at 185 keV/micron there was no difference in the frequency of color-junctions between two cell lines. It was also found that the frequency of simple exchanges per cell was almost constant in AT cells regardless LET levels, but it was LET dependent for normal cells. Interestingly, the frequency of simple exchanges was higher for normal fibroblast cells when it was compared at 185 keV/micron, but AT cells had more complex-type exchanges at the same LET levels. Heavy ions are more efficient in inducing chromosome aberrations in normal and AT cells compared to X-rays, and the aberration types between normal and AT fibroblast appeared different probably due to difference in the ATM gene function.

Comparative 1D and 3D numerical investigation of open-channel junction flows and energy losses

NASA Astrophysics Data System (ADS)

Luo, Hao; Fytanidis, Dimitrios K.; Schmidt, Arthur R.; García, Marcelo H.

2018-07-01

The complexity of open channel confluences stems from flow mixing, secondary circulation, post-confluence flow separation, contraction and backwater effects. These effects in turn result in a large number of parameters required to adequately quantify the junction induced hydraulic resistance and describe mean flow pattern and turbulent flow structures due to flow merging. The recent development in computing power advances the application of 3D Computational Fluid Dynamics (CFD) codes to visualize and understand the Confluence Hydrodynamic Zone (CHZ). Nevertheless, 1D approaches remain the mainstay in large drainage network or waterway system modeling considering computational efficiency and data availability. This paper presents (i) a modified 1D nonlinear dynamic model; (ii) a fully 3D non-hydrostatic, Reynolds-averaged Navier-Stokes Equations (RANS)-based, Computational Fluid Dynamics (CFD) model; (iii) an analysis of changing confluence hydrodynamics and 3D turbulent flow structure under various controls; (iv) a comparison of flow features (i.e. upstream water depths, energy losses and post-confluence contraction) predicted by 1D and 3D models; and (v) parameterization of 3D flow characteristics in 1D modeling through the computation of correction coefficients associated with contraction, energy and momentum. The present comprehensive 3D numerical investigation highlights the driving mechanisms for junction induced energy losses. Moreover, the comparative 1D and 3D study quantifies the deviation of 1D approximations and associated underlying assumptions from the 'true' resultant flow field. The study may also shed light on improving the accuracy of the 1D large network modeling through the parameterization of the complex 3D feature of the flow field and correction of interior boundary conditions at junctions of larger angles and/or with substantial lateral inflows. Moreover, the enclosed numerical investigations may enhance the understanding of the primary mechanisms contributing to hydraulic structure induced turbulent flow behavior and increased hydraulic resistance.

Morphologically mixed chemical-electrical synapses formed by primary afferents in rodent vestibular nuclei as revealed by immunofluorescence detection of connexin36 and vesicular glutamate transporter-1

PubMed Central

Nagy, James I.; Bautista, Wendy; Blakley, Brian; Rash, John E.

2013-01-01

Axon terminals forming mixed chemical/electrical synapses in the lateral vestibular nucleus of rat were described over forty years ago. Because gap junctions formed by connexins are the morphological correlate of electrical synapses, and with demonstrations of widespread expression of the gap junction protein connexin36 (Cx36) in neurons, we investigated the distribution and cellular localization of electrical synapses in the adult and developing rodent vestibular nuclear complex, using immunofluorescence detection of Cx36 as a marker for these synapses. In addition, we examined Cx36 localization in relation to that of the nerve terminal marker vesicular glutamate transporter-1 (vglut-1). An abundance of immunolabelling for Cx36 in the form of Cx36-puncta was found in each of the four major vestibular nuclei of adult rat and mouse. Immunolabelling was associated with somata and initial dendrites of medium and large neurons, and was absent in vestibular nuclei of Cx36 knockout mice. Cx36-puncta were seen either dispersed or aggregated into clusters on the surface of neurons, and were never found to occur intracellularly. Nearly all Cx36-puncta were localized to large nerve terminals immunolabelled for vglut-1. These terminals and their associated Cx36-puncta were substantially depleted after labyrinthectomy. Developmentally, labelling for Cx36 was already present in the vestibular nuclei at postnatal day 5, where it was only partially co-localized with vglut-1, and did not become fully associated with vglut-1-positive terminals until postnatal day 20 to 25. The results show that vglut-1-positive primary afferent nerve terminals form mixed synapses throughout the vestibular nuclear complex, that the gap junction component of these synapses contain Cx36, that multiple Cx36-containing gap junctions are associated with individual vglut-1 terminals and that the development of these mixed synapses is protracted over several postnatal weeks. PMID:23912039

Complex Critical Exponents for Percolation Transitions in Josephson-Junction Arrays, Antiferromagnets, and Interacting Bosons

NASA Astrophysics Data System (ADS)

Fernandes, Rafael M.; Schmalian, Jörg

2011-02-01

We show that the critical behavior of the XY quantum-rotor model undergoing a percolation transition is dramatically affected by its topological Berry phase 2πρ. In particular, for irrational ρ, its low-energy excitations emerge as spinless fermions with fractal spectrum. As a result, critical properties not captured by the usual Ginzburg-Landau-Wilson description of phase transitions arise, such as complex critical exponents, log-periodic oscillations and dynamically broken scale invariance.

Modeling and experimental characterization of electromigration in interconnect trees

NASA Astrophysics Data System (ADS)

Thompson, C. V.; Hau-Riege, S. P.; Andleigh, V. K.

1999-11-01

Most modeling and experimental characterization of interconnect reliability is focussed on simple straight lines terminating at pads or vias. However, laid-out integrated circuits often have interconnects with junctions and wide-to-narrow transitions. In carrying out circuit-level reliability assessments it is important to be able to assess the reliability of these more complex shapes, generally referred to as `trees.' An interconnect tree consists of continuously connected high-conductivity metal within one layer of metallization. Trees terminate at diffusion barriers at vias and contacts, and, in the general case, can have more than one terminating branch when they include junctions. We have extended the understanding of `immortality' demonstrated and analyzed for straight stud-to-stud lines, to trees of arbitrary complexity. This leads to a hierarchical approach for identifying immortal trees for specific circuit layouts and models for operation. To complete a circuit-level-reliability analysis, it is also necessary to estimate the lifetimes of the mortal trees. We have developed simulation tools that allow modeling of stress evolution and failure in arbitrarily complex trees. We are testing our models and simulations through comparisons with experiments on simple trees, such as lines broken into two segments with different currents in each segment. Models, simulations and early experimental results on the reliability of interconnect trees are shown to be consistent.

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

PubMed

Biswas, Sondip K; Lee, Jai Eun; Brako, Lawrence; Jiang, Jean X; Lo, Woo-Kuen

2010-11-09

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. 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. 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 cholesterol (i.e., cholesterol-rich versus cholesterol-free) as seen with the filipin-cholesterol-complexes (FCC) in different cortical regions during maturation. In contrast, the protrusions contained consistently high cholesterol amounts (i.e., 402 FCCs/μm2 membrane) which were approximately two times greater than that of the cholesterol-rich gap junctions (i.e., 188 FCCs/μm2 membrane) found in ball-and-sockets. Gap junctions are regularly associated with all ball-and-sockets examined in metabolically active young cortical fibers, but not with protrusions, in both chicken and monkey lenses. Since these unique gap junctions often protrude deeply into neighboring cells to increase membrane surface areas, they may significantly facilitate cell-to-cell communication between young cortical fiber cells. In particular, the large number of ball-and-socket gap junctions found near the equatorial region may effectively facilitate the flow of outward current toward the equatorial surface for internal circulation of ions in the lens. In contrast, a consistent distribution of high concentrations of cholesterol in protrusions would make the protrusion membrane less deformable and would be more suitable for maintaining fiber-to-fiber stability during visual accommodation. Thus, the ball-and-sockets and protrusions are two structurally and functionally distinct membrane domains in the lens.

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 cholesterol (i.e., cholesterol-rich versus cholesterol-free) as seen with the filipin-cholesterol-complexes (FCC) in different cortical regions during maturation. In contrast, the protrusions contained consistently high cholesterol amounts (i.e., 402 FCCs/μm2 membrane) which were approximately two times greater than that of the cholesterol-rich gap junctions (i.e., 188 FCCs/μm2 membrane) found in ball-and-sockets. Conclusions Gap junctions are regularly associated with all ball-and-sockets examined in metabolically active young cortical fibers, but not with protrusions, in both chicken and monkey lenses. Since these unique gap junctions often protrude deeply into neighboring cells to increase membrane surface areas, they may significantly facilitate cell-to-cell communication between young cortical fiber cells. In particular, the large number of ball-and-socket gap junctions found near the equatorial region may effectively facilitate the flow of outward current toward the equatorial surface for internal circulation of ions in the lens. In contrast, a consistent distribution of high concentrations of cholesterol in protrusions would make the protrusion membrane less deformable and would be more suitable for maintaining fiber-to-fiber stability during visual accommodation. Thus, the ball-and-sockets and protrusions are two structurally and functionally distinct membrane domains in the lens. PMID:21139982

The Drosophila blood-brain barrier: development and function of a glial endothelium.

PubMed

Limmer, Stefanie; Weiler, Astrid; Volkenhoff, Anne; Babatz, Felix; Klämbt, Christian

2014-01-01

The efficacy of neuronal function requires a well-balanced extracellular ion homeostasis and a steady supply with nutrients and metabolites. Therefore, all organisms equipped with a complex nervous system developed a so-called blood-brain barrier, protecting it from an uncontrolled entry of solutes, metabolites or pathogens. In higher vertebrates, this diffusion barrier is established by polarized endothelial cells that form extensive tight junctions, whereas in lower vertebrates and invertebrates the blood-brain barrier is exclusively formed by glial cells. Here, we review the development and function of the glial blood-brain barrier of Drosophila melanogaster. In the Drosophila nervous system, at least seven morphologically distinct glial cell classes can be distinguished. Two of these glial classes form the blood-brain barrier. Perineurial glial cells participate in nutrient uptake and establish a first diffusion barrier. The subperineurial glial (SPG) cells form septate junctions, which block paracellular diffusion and thus seal the nervous system from the hemolymph. We summarize the molecular basis of septate junction formation and address the different transport systems expressed by the blood-brain barrier forming glial cells.

Metal/Ion Interactions Induced p–i–n Junction in Methylammonium Lead Triiodide Perovskite Single Crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Ting; Mukherjee, Rupam; Ovchinnikova, Olga S.

Hybrid perovskites, as emerging multifunctional semiconductors, have demonstrated dual electronic/ionic conduction properties. Here, we report a metal/ion interaction induced p-i-n junction across slightly n-type doped MAPbI 3 single crystals with Au/MAPbI 3/Ag configuration based on interface dependent Seebeck effect, Hall effect and time-of-flight secondary ion mass spectrometry analysis. The organic cations (MA +) interact with Au atoms, forming positively charged coordination complexes at Au/MAPbI 3 interface, whereas iodine anions (I –) can react with Ag contacts, leading to interfacial ionic polarization. Such metal/ion interactions establish a p-doped region near the Au/MAPbI 3 interface due to the formation of MA +more » vacancies, and an n-doped region near the Ag/MAPbI 3 interface due to formation of I – vacancies, consequently forming a p-i-n junction across the crystal in Au/MAPbI 3/Ag configuration. Therefore, the metal/ion interaction plays a role in determining the surface electronic structure and semiconducting properties of hybrid perovskites.« less

Anisotropy induced Kondo splitting in a mechanically stretched molecular junction: A first-principles based study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xiaoli; Hou, Dong, E-mail: houdong@ustc.edu.cn; Zheng, Xiao, E-mail: xz58@ustc.edu.cn

2016-01-21

The magnetic anisotropy and Kondo phenomena in a mechanically stretched magnetic molecular junction are investigated by combining the density functional theory (DFT) and hierarchical equations of motion (HEOM) approach. The system is comprised of a magnetic complex Co(tpy–SH){sub 2} sandwiched between adjacent gold electrodes, which is mechanically stretched in experiments done by Parks et al. [Science 328, 1370 (2010)]. The electronic structure and mechanical property of the stretched system are investigated via the DFT calculations. The HEOM approach is then employed to characterize the Kondo resonance features, based on the Anderson impurity model parameterized from the DFT results. It ismore » confirmed that the ground state prefers the S = 1 local spin state. The structural properties, the magnetic anisotropy, and corresponding Kondo peak splitting in the axial stretching process are systematically evaluated. The results reveal that the strong electron correlations and the local magnetic properties of the molecule magnet are very sensitive to structural distortion. This work demonstrates that the combined DFT+HEOM approach could be useful in understanding and designing mechanically controlled molecular junctions.« less

Size-dependent protein segregation at membrane interfaces

PubMed Central

Schmid, Eva M; Bakalar, Matthew H; Choudhuri, Kaushik; Weichsel, Julian; Ann, HyoungSook; Geissler, Phillip L; Dustin, Michael L; Fletcher, Daniel A

2016-01-01

Membrane interfaces formed at cell-cell junctions are associated with characteristic patterns of membrane protein organization, such as E-cadherin enrichment in epithelial junctional complexes and CD45 exclusion from the signaling foci of immunological synapses. To isolate the role of protein size in these processes, we reconstituted membrane interfaces in vitro using giant unilamellar vesicles decorated with synthetic binding and non-binding proteins. We show that size differences between binding and non-binding proteins can dramatically alter their organization at membrane interfaces in the absence of active contributions from the cytoskeleton, with as little as a ~5 nm increase in non-binding protein size driving its exclusion from the interface. Combining in vitro measurements with Monte Carlo simulations, we find that non-binding protein exclusion is also influenced by lateral crowding, binding protein affinity, and thermally-driven membrane height fluctuations that transiently limit access to the interface. This simple, sensitive, and highly effective means of passively segregating proteins has implications for signaling at cell-cell junctions and protein sorting at intracellular contact points between membrane-bound organelles. PMID:27980602

Tunneling anisotropic magnetoresistance in complex oxide tunnel junctions

NASA Astrophysics Data System (ADS)

Martínez, Benjamín; López-Mir, Laura; Galceran, Regina; Balcells, Lluis; Pomar, Alberto; Konstantinovic, Zorica; Sandiumenge, Felip; Frontera, Carlos; Advanced Characterization of Nanostructured Materials Team

The magnetotransport properties of La2/3Sr1/3MnO3(LSMO)/LaAlO3(LAO)/ Pt tunneling junctions have been analyzed as a function of temperature and magnetic field. The junctions exhibit magnetoresistance (MR) values of about 37%, at H = 90 kOe at low temperature. However, the temperature dependence of MR indicates a clear distinct origin than that of conventional colossal MR. In addition, tunneling anisotropic MR (TAMR) values around 4% are found at low temperature and its angular dependence reflects the expected uniaxial anisotropy. The use of TAMR response could be an alternative of much easier technological implementation than conventional MTJs since only one magnetic electrode is required, thus opening the door to the implementation of more versatile devices. However, further studies are required in order to improve the strong temperature dependence at the present stage. Finantial support from Spanish Ministry of Economy and Competitiveness through the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0496), and projects MAT2012-33207 and MAT2015-71664-R is acknowledged.

Structural and mechanical heterogeneity of the erythrocyte membrane reveals hallmarks of membrane stability.

PubMed

Picas, Laura; Rico, Félix; Deforet, Maxime; Scheuring, Simon

2013-02-26

The erythrocyte membrane, a metabolically regulated active structure that comprises lipid molecules, junctional complexes, and the spectrin network, enables the cell to undergo large passive deformations when passing through the microvascular system. Here we use atomic force microscopy (AFM) imaging and quantitative mechanical mapping at nanometer resolution to correlate structure and mechanics of key components of the erythrocyte membrane, crucial for cell integrity and function. Our data reveal structural and mechanical heterogeneity modulated by the metabolic state at unprecedented nanometer resolution. ATP-depletion, reducing skeletal junction phosphorylation in RBC cells, leads to membrane stiffening. Analysis of ghosts and shear-force opened erythrocytes show that, in the absence of cytosolic kinases, spectrin phosphorylation results in membrane stiffening at the extracellular face and a reduced junction remodeling in response to loading forces. Topography and mechanical mapping of single components at the cytoplasmic face reveal that, surprisingly, spectrin phosphorylation by ATP softens individual filaments. Our findings suggest that, besides the mechanical signature of each component, the RBC membrane mechanics is regulated by the metabolic state and the assembly of its structural elements.

Remodeling the zonula adherens in response to tension and the role of afadin in this response

PubMed Central

Acharya, Bipul R.; Peyret, Grégoire; Fardin, Marc-Antoine; Mège, René-Marc; Ladoux, Benoit; Yap, Alpha S.; Fanning, Alan S.

2016-01-01

Morphogenesis requires dynamic coordination between cell–cell adhesion and the cytoskeleton to allow cells to change shape and move without losing tissue integrity. We used genetic tools and superresolution microscopy in a simple model epithelial cell line to define how the molecular architecture of cell–cell zonula adherens (ZA) is modified in response to elevated contractility, and how these cells maintain tissue integrity. We previously found that depleting zonula occludens 1 (ZO-1) family proteins in MDCK cells induces a highly organized contractile actomyosin array at the ZA. We find that ZO knockdown elevates contractility via a Shroom3/Rho-associated, coiled-coil containing protein kinase (ROCK) pathway. Our data suggest that each bicellular border is an independent contractile unit, with actin cables anchored end-on to cadherin complexes at tricellular junctions. Cells respond to elevated contractility by increasing junctional afadin. Although ZO/afadin knockdown did not prevent contractile array assembly, it dramatically altered cell shape and barrier function in response to elevated contractility. We propose that afadin acts as a robust protein scaffold that maintains ZA architecture at tricellular junctions. PMID:27114502

Acetylcholine receptor distribution and synapse elimination at the developing neuromuscular junction of mdx mice.

PubMed

Minatel, Elaine; Neto, Humberto Santo; Marques, Maria Julia

2003-11-01

The pattern of innervation of the vertebrate neuromuscular junction is established during early development, when junctions go from multiple to single innervation in the phenomenon of synapse elimination, suggesting that changes at the molecular level in the postsynaptic cell lead to the removal of nerve terminals. The mdx mouse is deficient in dystrophin and associated proteins that are part of the postsynaptic cytoskeleton. We used rhodamine-alpha-bungarotoxin and anti-neurofilament IgG-FITC to stain acetylcholine receptors and nerve terminals of the sternomastoid muscle during postnatal development in mdx and control C57BL/10 mice. Using fluorescence confocal microscopy, we observed that, 7 days after birth, 86.7% of the endplates of mdx mice were monoinnervated (n = 200) compared with 41.4% in control mice (n = 200). By the end of the second postnatal week, all endplates were innervated singly (100% mdx and 94.7% controls, n = 200 per group). These results show that dystrophic fibers achieve single innervation earlier, perhaps because dystrophin or a normal cytoskeletal complex is implicated in this phenomenon.

Metal/Ion Interactions Induced p–i–n Junction in Methylammonium Lead Triiodide Perovskite Single Crystals

DOE PAGES

Wu, Ting; Mukherjee, Rupam; Ovchinnikova, Olga S.; ...

2017-11-17

Hybrid perovskites, as emerging multifunctional semiconductors, have demonstrated dual electronic/ionic conduction properties. Here, we report a metal/ion interaction induced p-i-n junction across slightly n-type doped MAPbI 3 single crystals with Au/MAPbI 3/Ag configuration based on interface dependent Seebeck effect, Hall effect and time-of-flight secondary ion mass spectrometry analysis. The organic cations (MA +) interact with Au atoms, forming positively charged coordination complexes at Au/MAPbI 3 interface, whereas iodine anions (I –) can react with Ag contacts, leading to interfacial ionic polarization. Such metal/ion interactions establish a p-doped region near the Au/MAPbI 3 interface due to the formation of MA +more » vacancies, and an n-doped region near the Ag/MAPbI 3 interface due to formation of I – vacancies, consequently forming a p-i-n junction across the crystal in Au/MAPbI 3/Ag configuration. Therefore, the metal/ion interaction plays a role in determining the surface electronic structure and semiconducting properties of hybrid perovskites.« less

Top 50 most-cited articles on craniovertebral junction surgery.

PubMed

Alan, Nima; Cohen, Jonathan Andrew; Zhou, James; Pease, Matthew; Kanter, Adam S; Okonkwo, David O; Hamilton, David Kojo

2017-01-01

Craniovertebral junction is a complex anatomical location posing unique challenges to the surgical management of its pathologies. We aimed to identify the fifty most-cited articles that are dedicated to this field. A keyword search using the Thomson Reuters Web of Knowledge was conducted to identify articles relevant to the field of craniovertebral junction surgery. The articles were reviewed based on title, abstract, and methods, if necessary, and then ranked based on the total number of citations to identify the fifty most-cited articles. Characteristics of the articles were determined and analyzed. The earliest top-cited article was published in 1948. When stratified by decade, 1990s was the most productive with 16 articles. The most-cited article was by Anderson and Dalonzo on a classification of odontoid fractures. By citation rate, the most-cited article was by Herms and Melcher who described Goel's technique of atlantoaxial fixation using C1 lateral mass screws and C2 pedicle screws with rod fixation. Atlantoaxial fixation was the most common topic. The United States, Barrow Neurological Institute, and VH Sonntag were the most represented country, institute, and author, respectively. The significant majority of articles were designed as case series providing level IV evidence. Using citation analysis, we have provided a list of the most-cited articles representing important contributions of various authors from many institutions across the world to the field of craniovertebral junction surgery.

House dust mite allergen Der p 1 effects on sinonasal epithelial tight junctions.

PubMed

Henriquez, Oswaldo A; Den Beste, Kyle; Hoddeson, Elizabeth K; Parkos, Charles A; Nusrat, Asma; Wise, Sarah K

2013-08-01

Epithelial permeability is highly dependent upon the integrity of tight junctions, which are cell-cell adhesion complexes located at the apical aspect of the lateral membrane of polarized epithelial cells. We hypothesize that sinonasal epithelial exposure to Der p 1 house dust mite antigen decreases expression of tight junction proteins (TJPs), representing a potential mechanism for increased permeability and presentation of antigens across the sinonasal epithelial layer. Confluent cultured primary human sinonasal epithelial cells were exposed to recombinant Der p 1 antigen vs control, and transepithelial resistance measurements were performed over 24 hours. Antibody staining for a panel of TJPs was examined with immunofluorescence/confocal microscopy and Western blotting. Tissue for these experiments was obtained from 4 patients total. Der p 1 exposed sinonasal cells showed a marked decrease in transepithelial resistance when compared to control cells. In addition, results of Western immunoblot and immunofluorescent labeling demonstrated decreased expression of TJPs claudin-1 and junction adhesion molecule-A (JAM-A) in Der p 1-exposed cultured sinonasal cells vs controls. Der p 1 antigen exposure decreases sinonasal epithelium TJP expression, most notably seen in JAM-A and claudin-1 in these preliminary experiments. This decreased TJP expression likely contributes to increased epithelial permeability and represents a potential mechanism for transepithelial antigen exposure in allergic rhinitis. © 2013 ARS-AAOA, LLC.

Geology of the southernmost Piedmont from Columbus to Junction City, GA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanley, T.B.

1993-03-01

Mapping in the Piedmont from the Chattahoochee River to Junction City, GA, is critical to understanding contacts with Southern Appalachian outboard terranes, relationships to the Piedmont allochthon, strike slip displacements along major faults and late Paleozoic and post Paleozoic tectonic activity. Three major map units defining a large synform are recognized in western Muscogee County: the North Columbus Migmatite Complex, the Moffitts Mill Schist (MMS), and the Phenix City gneiss. The distinctive but poorly exposed fine grained feldspar augen MMS, which extends at least as far east as Geneva, contains small enclaves of amphibolite and calcsilicate and large enclaves ofmore » lineated granitoid gneiss. Protomylonites and mylonitic gneiss with a N-S to N45E strike are exposed from Geneva to Junction City. Three brecciated quartz dikes transect the area in eastern Muscogee Co. and Talbot Co., converging on Talbotton from the southwest. The northern dike strikes ENE and is associated with an augen schist; the middle dike strikes NE and projects to the southwest deep into Muscogee County as a silicified fracture zone with minor associated granite. The southern dike has a NNE strike and is parallel to and locally silicifies the mylonitic foliation that dominates gneisses to the east. Deflections of the magnetic anomaly patterns to the northeast in the Geneva - Junction City area are parallel to quartz dikes and mylonitic foliations.« less

Elucidating cytochrome C release from mitochondria: insights from an in silico three-dimensional model.

PubMed

Tam, Zhi Yang; Cai, Yi Hui; Gunawan, Rudiyanto

2010-11-17

Mitochondrial regulation of apoptosis depends on the programmed release of proapoptotic proteins such as cytochrome c (Cyt c) through the outer mitochondrial membrane (OMM). Although a few key processes involved in this release have been identified, including the liberation of inner membrane-bound Cyt c and formation of diffusible pores on the OMM, other details like the transport of Cyt c within complex mitochondrial compartments, e.g., the cristae and crista junctions, are not yet fully understood (to our knowledge). In particular, a remodeling of the inner mitochondrial membrane accompanying apoptosis seen in a few studies, in which crista junctions widen, has been hypothesized to be a necessary step in the Cyt c release. Using a three-dimensional spatial modeling of mitochondrial crista and the crista junction, model simulations and analysis illustrated how the interplay among solubilization of Cyt c, fast diffusion of Cyt c, and OMM permeabilization gives rise to the observed experimental release profile. Importantly, the widening of the crista junction was found to have a negligible effect on the transport of free Cyt c from cristae. Finally, model simulations showed that increasing the fraction of free/loosely-bound Cyt c can sensitize the cell to apoptotic stimuli in a threshold manner, which may explain increased sensitivity to cell death associated with aging. Copyright © 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Myosin VI facilitates connexin 43 gap junction accretion.

PubMed

Waxse, Bennett J; Sengupta, Prabuddha; Hesketh, Geoffrey G; Lippincott-Schwartz, Jennifer; Buss, Folma

2017-03-01

In this study, we demonstrate myosin VI enrichment at Cx43 (also known as GJA1)-containing gap junctions (GJs) in heart tissue, primary cardiomyocytes and cell culture models. In primary cardiac tissue and in fibroblasts from the myosin VI-null mouse as well as in tissue culture cells transfected with siRNA against myosin VI, we observe reduced GJ plaque size with a concomitant reduction in intercellular communication, as shown by fluorescence recovery after photobleaching (FRAP) and a new method of selective calcein administration. Analysis of the molecular role of myosin VI in Cx43 trafficking indicates that myosin VI is dispensable for the delivery of Cx43 to the cell surface and connexon movement in the plasma membrane. Furthermore, we cannot corroborate clathrin or Dab2 localization at gap junctions and we do not observe a function for the myosin-VI-Dab2 complex in clathrin-dependent endocytosis of annular gap junctions. Instead, we found that myosin VI was localized at the edge of Cx43 plaques by using total internal reflection fluorescence (TIRF) microscopy and use FRAP to identify a plaque accretion defect as the primary manifestation of myosin VI loss in Cx43 homeostasis. A fuller understanding of this derangement may explain the cardiomyopathy or gliosis associated with the loss of myosin VI. © 2017. Published by The Company of Biologists Ltd.

Abnormal Moral Reasoning in Complete and Partial Callosotomy Patients

ERIC Educational Resources Information Center

Miller, Michael B.; Sinnott-Armstrong, Walter; Young, Liane; King, Danielle; Paggi, Aldo; Fabri, Mara; Polonara, Gabriele; Gazzaniga, Michael S.

2010-01-01

Recent neuroimaging studies suggest lateralized cerebral mechanisms in the right temporal parietal junction are involved in complex social and moral reasoning, such as ascribing beliefs to others. Based on this evidence, we tested 3 anterior-resected and 3 complete callosotomy patients along with 22 normal subjects on a reasoning task that…

Animation Based Learning of Electronic Devices

ERIC Educational Resources Information Center

Gero, Aharon; Zoabi, Wishah; Sabag, Nissim

2014-01-01

Two-year college teachers face great difficulty when they teach the principle of operation of the bipolar junction transistor--a subject which forms the basis for electronics studies. The difficulty arises from both the complexity of the device and by the lack of adequate scientific background among the students. We, therefore, developed a unique…

Strong coupling in F-theory and geometrically non-Higgsable seven-branes

NASA Astrophysics Data System (ADS)

Halverson, James

2017-06-01

Geometrically non-Higgsable seven-branes carry gauge sectors that cannot be broken by complex structure deformation, and there is growing evidence that such configurations are typical in F-theory. We study strongly coupled physics associated with these branes. Axiodilaton profiles are computed using Ramanujan's theories of elliptic functions to alternative bases, showing explicitly that the string coupling is O (1) in the vicinity of the brane; that it sources nilpotent SL (2 , Z) monodromy and therefore the associated brane charges are modular; and that essentially all F-theory compactifications have regions with order one string coupling. It is shown that non-perturbative SU (3) and SU (2) seven-branes are related to weakly coupled counterparts with D7-branes via deformation-induced Hanany-Witten moves on (p , q) string junctions that turn them into fundamental open strings; only the former may exist for generic complex structure. D3-brane near these and the Kodaira type II seven-branes probe Argyres-Douglas theories. The BPS states of slightly deformed theories are shown to be dyonic string junctions.

A dual switch controls bacterial enhancer-dependent transcription

PubMed Central

Wiesler, Simone C.; Burrows, Patricia C.; Buck, Martin

2012-01-01

Bacterial RNA polymerases (RNAPs) are targets for antibiotics. Myxopyronin binds to the RNAP switch regions to block structural rearrangements needed for formation of open promoter complexes. Bacterial RNAPs containing the major variant σ54 factor are activated by enhancer-binding proteins (bEBPs) and transcribe genes whose products are needed in pathogenicity and stress responses. We show that (i) enhancer-dependent RNAPs help Escherichia coli to survive in the presence of myxopyronin, (ii) enhancer-dependent RNAPs partially resist inhibition by myxopyronin and (iii) ATP hydrolysis catalysed by bEBPs is obligatory for functional interaction of the RNAP switch regions with the transcription start site. We demonstrate that enhancer-dependent promoters contain two barriers to full DNA opening, allowing tight regulation of transcription initiation. bEBPs engage in a dual switch to (i) allow propagation of nucleated DNA melting from an upstream DNA fork junction and (ii) complete the formation of the transcription bubble and downstream DNA fork junction at the RNA synthesis start site, resulting in switch region-dependent RNAP clamp closure and open promoter complex formation. PMID:22965125

Gap junctions are essential for murine primordial follicle assembly immediately before birth.

PubMed

Teng, Zhen; Wang, Chao; Wang, Yijing; Huang, Kun; Xiang, Xi; Niu, Wanbao; Feng, Lizhao; Zhao, Lihua; Yan, Hao; Zhang, Hua

2016-02-01

The reserve of primordial follicles determines the reproductive ability of the female mammal over its reproductive life. The primordial follicle is composed of two types of cells: oocytes and surrounding pre-granulosa cells. However, the underlying mechanism regulating primordial follicle assembly is largely undefined. In this study, we found that gap junction communication (GJC) established between the ovarian cells in the perinatal mouse ovary may be involved in the process. First, gap junction structures between the oocyte and surrounding pre-granulosa cells appear at about 19.0 dpc (days post coitum). As many as 12 gap junction-related genes are upregulated at birth, implying that a complex communication may exist between ovarian cells, because specifically silencing the genes of individual gap junction proteins, such as Gja1, Gja4 or both, has no influence on primordial follicle assembly. On the other hand, non-specific blockers of GJC, such as carbenoxolone (CBX) and 18α-glycyrrhetinic acid (AGA), significantly inhibit mouse primordial follicle assembly. We proved that the temporal window for establishment of GJC in the fetal ovary is from 19.5 dpc to 1 dpp (days postpartum). In addition, the expression of ovarian somatic cell (OSC)-specific genes, such as Notch2, Foxl2 and Irx3, was negatively affected by GJC blockers, whereas oocyte-related genes, such as Ybx2, Nobox and Sohlh1, were hardly affected, implying that the establishment of GJC during this period may be more important to OSCs than to oocytes. In summary, our results indicated that GJC involves in the mouse primordial follicle assembly process at a specific temporal window that needs Notch signaling cross-talking. © 2016 Society for Reproduction and Fertility.

Synergistic effects of arsenic trioxide combined with ascorbic acid in human osteosarcoma MG-63 cells: a systems biology analysis.

PubMed

Huang, X C; Maimaiti, X Y M; Huang, C W; Zhang, L; Li, Z B; Chen, Z G; Gao, X; Chen, T Y

2014-01-01

To further understand the synergistic mechanism of As2O3 and asscorbic acid (AA) in human osteosarcoma MG-63 cells by systems biology analysis. Human osteosarcoma MG-63 cells were treated by As2O3 (1 µmol/L), AA (62.5 µmol/L) and combined drugs (1 µmol/L As2O3 plus 62.5 µmol/L AA). Dynamic morphological characteristics were recorded by Cell-IQ system, and growth rate was calculated. Illumina beadchip assay was used to analyze the differential expression genes in different groups. Synergic effects on differential expression genes (DEGs) were analyzed by mixture linear model and singular value decomposition model. KEGG pathway annotations and GO enrichment analysis were performed to figure out the pathways involved in the synergic effects. We captured 1987 differential expression genes in combined therapy MG-63 cells. FAT1 gene was significantly upregulated in all three groups, which is a promising drug target as an important tumor suppressor analogue; meanwhile, HIST1H2BD gene was markedly downregulated in the As2O3 monotherapy group and the combined therapy group, which was found to be upregulated in prostatic cancer. These two genes might play critical roles in synergetic effects of AA and As2O3, although the exact mechanism needs further investigation. KEGG pathway analysis showed many DEGs were related with tight junction, and GO analysis also indicated that DEGs in the combined therapy cells gathered in occluding junction, apical junction complex, cell junction, and tight junction. AA potentiates the efficacy of As2O3 in MG-63 cells. Systems biology analysis showed the synergic effect on the DEGs.

Diagnostic glenohumeral arthroscopy fails to fully evaluate the biceps-labral complex.

PubMed

Taylor, Samuel A; Khair, M Michael; Gulotta, Lawrence V; Pearle, Andrew D; Baret, Nikolas J; Newman, Ashley M; Dy, Christopher J; O'Brien, Stephen J

2015-02-01

The purpose of this study was to define the limits of diagnostic glenohumeral arthroscopy and determine the prevalence and frequency of hidden extra-articular "bicipital tunnel" lesions among chronically symptomatic patients. Eight fresh-frozen cadaveric specimens underwent diagnostic glenohumeral arthroscopy with percutaneous tagging of the long head of the biceps tendon (LHBT) during maximal tendon excursion. The percentage of visualized LHBT was calculated relative to the distal margin of subscapularis tendon and the proximal margin of the pectoralis major tendon. Then, a retrospective review of 277 patients who underwent subdeltoid transfer of the LHBT to the conjoint tendon were retrospectively analyzed for lesions of the biceps-labral complex. Lesions were categorized by anatomic location (inside, junctional, or bicipital tunnel). Inside lesions were labral tears. Junctional lesions were LHBT tears visualized during glenohumeral arthroscopy. Bicipital tunnel lesions were extra-articular lesions hidden from view during standard glenohumeral arthroscopy. Seventy-eight percent of LHBT were visualized relative to the distal margin of the subscapularis tendon and only 55% relative to the proximal margin of the pectoralis major tendon. No portion of the LHBT inferior to the subscapularis tendon was visualized. Forty-seven percent of patients had hidden bicipital tunnel lesions. Scarring was most common and accounted for 48% of all such lesions. Thirty-seven percent of patients had multiple lesion locations. Forty-five percent of patients with junctional lesions also had hidden bicipital tunnel lesions. The only offending lesion was in the bicipital tunnel for 18% of patients. Diagnostic glenohumeral arthroscopy fails to fully evaluate the biceps-labral complex because it visualizes only 55% of the LHBT relative to the proximal margin of the pectoralis major tendon and did not identify extra-articular bicipital tunnel lesions present in 47% of chronically symptomatic patients. Level IV, therapeutic case series and cadaveric study. Copyright © 2015 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Multiplexed multi-scale imaging: novel roles for the scaffold protein IQGAP1 in epithelial cell development (Conference Presentation)

NASA Astrophysics Data System (ADS)

Schweikhard, Volker

2016-02-01

The precise sub-cellular spatial localization of multi-protein complexes is increasingly recognized as a key mechanism governing the organization of mammalian cells. Consequently, there is a need for novel microscopy techniques capable of investigating such sub-cellular architectures in comprehensive detail. Here, we applied a novel multiplexed STORM super-resolution microscopy technique, in combination with high-throughput immunofluorescence microscopy and live-cell imaging, to investigate the roles of the scaffold protein IQGAP1 in epithelial cells. IQGAP1 is known to orchestrate a wide range of biological processes, including intracellular signaling, cytoskeletal regulation, cell-cell adhesion, and protein trafficking, by forming distinct complexes with a number of known interaction partners, and recruiting these complexes to specific subcellular locations. Our results demonstrate that, in addition to supporting epithelial adherens junctions by associating with specialized cortical actin structures, IQGAP1 plays a second role in which it controls the confinement of a unique, previously undocumented class of membranous compartments to the basal actin cortex. These largely immotile yet highly dynamic structures appear transiently as cells merge into clusters and establish of apical-basolateral (epithelial) polarity, and are identified as an intermediate compartment in the endocytic recycling pathways for cell junction complexes and cell surface receptors. Although these two functions of IQGAP1 occur in parallel and largely independently of each other, they both support the maturation and maintenance of polarized epithelial cell architectures.

Tumoral micro-blood vessels and vascular microenvironment in human astrocytic tumors. A transmission electron microscopy study.

PubMed

Arismendi-Morillo, Gabriel; Castellano, Alan

2005-07-01

The development of peritumoral edema is thought to be due to extravasation of plasma water and macromolecules through a defective blood-brain barrier (BBB), but the exact mechanism by which occurs is poorly understood. The aim of this study was analyze at submicroscopic level the morphological changes in both micro-blood vessels and vascular microenvironment of astrocytic tumors in an attempt of understanding the pathological aspects that may help in the future researches for the design of future therapeutic strategies. Biopsies of 25 patients with pathological diagnosis of astrocytic tumors were examined with the transmission electron microscope. Both open and close tight junctions were observed in the micro-blood vessels, inclusive in a same tumor. Cytoskeletal disorganization associated with disintegrated perijunctional actin filaments were seen. The paracellular space showed enlargement and commonly occupied by fluid proteinaceous, endothelial cells display oncotic and ischemic changes, basal lamina reveals enlargement, edema, vacuolization and collagen fibers disposed in irregular array. Pericytes exhibited edema and phagocytoced material, astrocytic perivascular-feet showed signs of oncosis and necrosis, co-option vessels totally surrounding by neoplastic cells also were seen. The ultrastructural abnormalities observed in both junctional complexes and vascular microenvironment suggest a multi-factorial pathobiology process, probably hypoxia intratumoral, calcium overload in endothelial cells, and degradative effects of metalloproteinases over the basal membrane appear as determinant factors that leading to structural modifications of junctional complexes, therefore, treatment with both HIF-1alpha and metalloproteinases inhibitors possibly can contribute with the pharmacological handling of the peritumoral edema associated with astrocytic tumors.

Mammalian target of rapamycin complex (mTOR) pathway modulates blood-testis barrier (BTB) function through F-actin organization and gap junction

PubMed Central

Li, Nan; Cheng, C. Yan

2016-01-01

mTOR (mammalian target of rapamycin) is one of the most important signaling molecules in mammalian cells which regulates an array of cellular events, ranging from cell metabolism to cell proliferation. Based on the association of mTOR with the core component proteins, such as Raptor or Rictor, mTOR can become the mTORC1 (mammalian target of rapamycin complex 1) or mTORC2, respectively. Studies have shown that during the epithelial cycle of spermatogenesis, mTORC1 promotes remodeling and restructuring of the blood-testis barrier (BTB) in vitro and in vivo, making the Sertoli cell tight junction (TJ)-permeability barrier “leaky”; whereas mTORC2 promotes BTB integrity, making the Sertoli cell TJ-barrier “tighter”. These contrasting effects, coupled with the spatiotemporal expression of the core signaling proteins at the BTB that confer the respective functions of mTORC1 vs. mTORC2 thus provide a unique mechanism to modulate BTB dynamics, allowing or disallowing the transport of biomolecules and also preleptotene spermatocytes across the immunological barrier. More importantly, studies have shown that these changes to BTB dynamics conferred by mTORC1 and mTORC2 are mediated by changes in the organization of the actin microfilament networks at the BTB, and involve gap junction (GJ) intercellular communication. Since GJ has recently been shown to be crucial to reboot spermatogenesis and meiosis following toxicant-induced aspermatogenesis, these findings thus provide new insightful information regarding the integration of mTOR and GJ to regulate spermatogenesis. PMID:26957088

Modeling of charge transport in ion bipolar junction transistors.

PubMed

Volkov, Anton V; Tybrandt, Klas; Berggren, Magnus; Zozoulenko, Igor V

2014-06-17

Spatiotemporal control of the complex chemical microenvironment is of great importance to many fields within life science. One way to facilitate such control is to construct delivery circuits, comprising arrays of dispensing outlets, for ions and charged biomolecules based on ionic transistors. This allows for addressability of ionic signals, which opens up for spatiotemporally controlled delivery in a highly complex manner. One class of ionic transistors, the ion bipolar junction transistors (IBJTs), is especially attractive for these applications because these transistors are functional at physiological conditions and have been employed to modulate the delivery of neurotransmitters to regulate signaling in neuronal cells. Further, the first integrated complementary ionic circuits were recently developed on the basis of these ionic transistors. However, a detailed understanding of the device physics of these transistors is still lacking and hampers further development of components and circuits. Here, we report on the modeling of IBJTs using Poisson's and Nernst-Planck equations and the finite element method. A two-dimensional model of the device is employed that successfully reproduces the main characteristics of the measurement data. On the basis of the detailed concentration and potential profiles provided by the model, the different modes of operation of the transistor are analyzed as well as the transitions between the different modes. The model correctly predicts the measured threshold voltage, which is explained in terms of membrane potentials. All in all, the results provide the basis for a detailed understanding of IBJT operation. This new knowledge is employed to discuss potential improvements of ion bipolar junction transistors in terms of miniaturization and device parameters.

Mammary collective cell migration involves transient loss of epithelial features and individual cell migration within the epithelium

PubMed Central

Ewald, Andrew J.; Huebner, Robert J.; Palsdottir, Hildur; Lee, Jessie K.; Perez, Melissa J.; Jorgens, Danielle M.; Tauscher, Andrew N.; Cheung, Kevin J.; Werb, Zena; Auer, Manfred

2012-01-01

Normal mammary morphogenesis involves transitions between simple and multilayered epithelial organizations. We used electron microscopy and molecular markers to determine whether intercellular junctions and apico-basal polarity were maintained in the multilayered epithelium. We found that multilayered elongating ducts had polarized apical and basal tissue surfaces both in three-dimensional culture and in vivo. However, individual cells were only polarized on surfaces in contact with the lumen or extracellular matrix. The basolateral marker scribble and the apical marker atypical protein kinase C zeta localized to all interior cell membranes, whereas PAR3 displayed a cytoplasmic localization, suggesting that the apico-basal polarity was incomplete. Despite membrane localization of E-cadherin and β-catenin, we did not observe a defined zonula adherens connecting interior cells. Instead, interior cells were connected through desmosomes and exhibited complex interdigitating membrane protrusions. Single-cell labeling revealed that individual cells were both protrusive and migratory within the epithelial multilayer. Inhibition of Rho kinase (ROCK) further reduced intercellular adhesion on apical and lateral surfaces but did not disrupt basal tissue organization. Following morphogenesis, segregated membrane domains were re-established and junctional complexes re-formed. We observed similar epithelial organization during mammary morphogenesis in organotypic culture and in vivo. We conclude that mammary epithelial morphogenesis involves a reversible, spatially limited, reduction in polarity and intercellular junctions and active individualistic cell migration. Our data suggest that reductions in polarity and adhesion during breast cancer progression might reflect partial recapitulation of a normal developmental program. PMID:22344263

Blasting preparation for selective mining of complex structured ore deposition

NASA Astrophysics Data System (ADS)

Marinin, M. A.; Dolzhikov, V. V.

2017-10-01

Technological features of ore mining in the open pit development for processing of complex structured ore deposit of steeply falling occurrence have been considered. The technological schemes of ore bodies mining under different conditions of occurrence, consistency and capacity have been considered and offered in the paper. These technologies permit to reduce losses and dilution, but to increase the completeness and quality of mined ore. A method of subsequent selective excavation of ore bodies has been proposed. The method is based on the complex use of buffer-blasting technology for the muck mass and the principle of trim blasting at ore-rock junctions.

Faster Mass Spectrometry-based Protein Inference: Junction Trees are More Efficient than Sampling and Marginalization by Enumeration

PubMed Central

Serang, Oliver; Noble, William Stafford

2012-01-01

The problem of identifying the proteins in a complex mixture using tandem mass spectrometry can be framed as an inference problem on a graph that connects peptides to proteins. Several existing protein identification methods make use of statistical inference methods for graphical models, including expectation maximization, Markov chain Monte Carlo, and full marginalization coupled with approximation heuristics. We show that, for this problem, the majority of the cost of inference usually comes from a few highly connected subgraphs. Furthermore, we evaluate three different statistical inference methods using a common graphical model, and we demonstrate that junction tree inference substantially improves rates of convergence compared to existing methods. The python code used for this paper is available at http://noble.gs.washington.edu/proj/fido. PMID:22331862

Enhanced ferromagnetic resonance linewidth of the free layer in perpendicular magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Gopman, D. B.; Dennis, C. L.; McMichael, R. D.; Hao, X.; Wang, Z.; Wang, X.; Gan, H.; Zhou, Y.; Zhang, J.; Huai, Y.

2017-05-01

We report the frequency dependence of the ferromagnetic resonance linewidth of the free layer in magnetic tunnel junctions with all perpendicular-to-the-plane magnetized layers. While the magnetic-field-swept linewidth nominally shows a linear growth with frequency in agreement with Gilbert damping, an additional frequency-dependent linewidth broadening occurs that shows a strong asymmetry between the absorption spectra for increasing and decreasing external magnetic field. Inhomogeneous magnetic fields produced during reversal of the reference and pinned layer complex is demonstrated to be at the origin of the symmetry breaking and the linewidth enhancement. Consequentially, this linewidth enhancement provides indirect information on the magnetic coercivity of the reference and pinned layers. These results have important implications for the characterization of perpendicular magnetized magnetic random access memory bit cells.

Self-Assembly of Hierarchical DNA Nanotube Architectures with Well-Defined Geometries.

PubMed

Jorgenson, Tyler D; Mohammed, Abdul M; Agrawal, Deepak K; Schulman, Rebecca

2017-02-28

An essential motif for the assembly of biological materials such as actin at the scale of hundreds of nanometers and beyond is a network of one-dimensional fibers with well-defined geometry. Here, we demonstrate the programmed organization of DNA filaments into micron-scale architectures where component filaments are oriented at preprogrammed angles. We assemble L-, T-, and Y-shaped DNA origami junctions that nucleate two or three micron length DNA nanotubes at high yields. The angles between the nanotubes mirror the angles between the templates on the junctions, demonstrating that nanoscale structures can control precisely how micron-scale architectures form. The ability to precisely program filament orientation could allow the assembly of complex filament architectures in two and three dimensions, including circuit structures, bundles, and extended materials.

Terahertz Mixing Characteristics of NbN Superconducting Tunnel Junctions and Related Astronomical Observations

NASA Astrophysics Data System (ADS)

Li, J.

2010-01-01

High-sensitivity superconducting SIS (superconductor-insulator-superconductor) mixers are playing an increasingly important role in the terahertz (THz) astronomical observation, which is an emerging research frontier in modern astrophysics. Superconducting SIS mixers with niobium (Nb) tunnel junctions have reached a sensitivity close to the quantum limit, but have a frequency limit about 0.7 THz (i.e., gap frequency of Nb tunnel junctions). Beyond this frequency Nb superconducting films will absorb energetic photons (i.e., energy loss) to break Cooper pairs, thereby resulting in significant degradation of the mixer performance. Therefore, it is of particular interest to develop THz superconducting SIS mixers incorporating tunnel junctions with a larger energy gap. Niobium-nitride (NbN) superconducting tunnel junctions have been long known for their large energy gap, almost double that of Nb ones. With the introduction of epitaxially grown NbN films, the fabrication technology of NbN superconducting tunnel junctions has been considerably improved in the recent years. Nevertheless, their performances are still not as good as Nb ones, and furthermore they are not yet demonstrated in real astronomical applications. Given the facts mentioned above, in this paper we systematically study the quantum mixing behaviors of NbN superconducting tunnel junctions in the THz regime and demonstrate an astronomical testing observation with a 0.5 THz superconducting SIS mixer developed with NbN tunnel junctions. The main results of this study include: (1) successful design and fabrication of a 0.4˜0.6 THz waveguide mixing circuit with the high-dielectric-constant MgO substrate; (2) successful fabrication of NbN superconducting tunnel junctions with the gap voltage reaching 5.6 mV and the quality factor as high as 15; (3) demonstration of a 0.5 THz waveguide NbN superconducting SIS mixer with a measured receiver noise temperature (no correction) as low as five times the quantum limit (5hω/kB), which is the best among NbN superconducting SIS mixers developed in this frequency band; (4) demonstration of high sensitivity for NbN superconducting SIS mixers operated at temperatures as high as 10 K, and demonstration of much less interference resulting from the Josephson effect; (5) demonstration of the first astronomical observation ever done with an NbN superconducting SIS mixer. This study has provided further understanding of the quantum mixing behaviors of NbN superconducting SIS mixers. It has been demonstrated that NbN superconducting SIS mixers can reach nearly quantum-limited sensitivity and have good stability. Furthermore, NbN superconducting SIS mixers have less stringent requirement for cooling and magnetic field compared with Nb ones. Hence they can be used in astronomical applications, especially for space-borne projects and complex systems such as multi-beam receivers.

To What Extent is Primate Second Molar Enamel Occlusal Morphology Shaped by the Enamel-Dentine Junction?

PubMed Central

Gilissen, Emmanuel; Thiery, Ghislain

2015-01-01

The form of two hard tissues of the mammalian tooth, dentine and enamel, is the result of a combination of the phylogenetic inheritance of dental traits and the adaptive selection of these traits during evolution. Recent decades have been significant in unveiling developmental processes controlling tooth morphogenesis, dental variation and the origination of dental novelties. The enamel-dentine junction constitutes a precursor for the morphology of the outer enamel surface through growth of the enamel cap which may go along with the addition of original features. The relative contribution of these two tooth components to morphological variation and their respective response to natural selection is a major issue in paleoanthropology. This study will determine how much enamel morphology relies on the form of the enamel-dentine junction. The outer occlusal enamel surface and the enamel-dentine junction surface of 76 primate second upper molars are represented by polygonal meshes and investigated using tridimensional topometrical analysis. Quantitative criteria (elevation, inclination, orientation, curvature and occlusal patch count) are introduced to show that the enamel-dentine junction significantly constrains the topographical properties of the outer enamel surface. Our results show a significant correlation for elevation, orientation, inclination, curvature and occlusal complexity between the outer enamel surface and the enamel dentine junction for all studied primate taxa with the exception of four modern humans for curvature (p<0.05). Moreover, we show that, for all selected topometrical parameters apart from occlusal patch count, the recorded correlations significantly decrease along with enamel thickening in our sample. While preserving tooth integrity by providing resistance to wear and fractures, the variation of enamel thickness may modify the curvature present at the occlusal enamel surface in relation to enamel-dentine junction, potentially modifying dental functionalities such as blunt versus sharp dental tools. In terms of natural selection, there is a balance between increasing tooth resistance and maintaining efficient dental tools. In this sense the enamel cap acts as a functional buffer for the molar occlusal pattern. In primates, results suggest a primary emergence of dental novelties on the enamel-dentine junction and a secondary transposition of these novelties with no or minor modifications of dental functionalities by the enamel cap. Whereas enamel crenations have been reported by previous studies, our analysis do not support the presence of enamel tubercles without dentine relief nuclei. As is, the enamel cap is, at most, a secondary source of morphological novelty. PMID:26406597

Single-molecule conductance studies of photo-active and photochromic molecules

NASA Astrophysics Data System (ADS)

Tam, E. S.; Parks, J. J.; Santiago-Berrios, M. B.; Zhong, Y.-W.; Abruna, H. D.; Ralph, D. C.

2010-03-01

We perform statistical measurements of single molecule conductance in repeatedly-formed metal-molecule-metal junctions at room temperature. Our results on diaminoalkanes are consistent with those reported by the Venkataraman group. We focus on photo-active and photochromic molecules, including a series of transition-metal complexes with different metal centers and endgroups. We compare the trend in conductance across the family of complexes with that expected from electrochemical measurements. We will also report initial results on the voltage dependence of single-molecule conductances and the effects of optical excitations.

Spacer type mediated tunable spin crossover (SCO) characteristics of pyrene decorated 2,6-bis(pyrazol-1-yl)pyridine (bpp) based Fe(ii) molecular spintronic modules.

PubMed

Kumar, Kuppusamy Senthil; Šalitroš, Ivan; Moreno-Pineda, Eufemio; Ruben, Mario

2017-08-14

A simple "isomer-like" variation of the spacer group in a set of Fe(ii) spin crossover (SCO) complexes designed to probe spin state dependence of electrical conductivity in graphene-based molecular spintronic junctions led to the observation of remarkable variations in the thermal- and light-induced magnetic characteristics, paving a simple route for the design of functional SCO complexes with different temperature switching regimes based on a 2,6-bis(pyrazol-1-yl)pyridine ligand skeleton.

Glycogen Synthase Kinase 3 (GSK-3) influences epithelial barrier function by regulating Occludin, Claudin-1 and E-cadherin expression

DOE Office of Scientific and Technical Information (OSTI.GOV)

Severson, Eric A.; Kwon, Mike; Hilgarth, Roland S.

2010-07-02

The Apical Junctional Complex (AJC) encompassing the tight junction (TJ) and adherens junction (AJ) plays a pivotal role in regulating epithelial barrier function and epithelial cell proliferative processes through signaling events that remain poorly characterized. A potential regulator of AJC protein expression is Glycogen Synthase Kinase-3 (GSK-3). GSK-3 is a constitutively active kinase that is repressed during epithelial-mesenchymal transition (EMT). In the present study, we report that GSK-3 activity regulates the structure and function of the AJC in polarized model intestinal (SK-CO15) and kidney (Madin-Darby Canine Kidney (MDCK)) epithelial cells. Reduction of GSK-3 activity, either by small molecule inhibitors ormore » siRNA targeting GSK-3 alpha and beta mRNA, resulted in increased permeability to both ions and bulk solutes. Immunofluorescence labeling and immunoblot analyses revealed that the barrier defects correlated with decreased protein expression of AJC transmembrane proteins Occludin, Claudin-1 and E-cadherin without influencing other TJ proteins, Zonula Occludens-1 (ZO-1) and Junctional Adhesion Molecule A (JAM-A). The decrease in Occludin and E-cadherin protein expression correlated with downregulation of the corresponding mRNA levels for these respective proteins following GSK-3 inhibition. These observations implicate an important role of GSK-3 in the regulation of the structure and function of the AJC that is mediated by differential modulation of mRNA transcription of key AJC proteins, Occludin, Claudin-1 and E-cadherin.« less

Glucocorticoids induce transactivation of tight junction genes occludin and claudin-5 in retinal endothelial cells via a novel cis-element.

PubMed

Felinski, Edward A; Cox, Amy E; Phillips, Brett E; Antonetti, David A

2008-06-01

Tight junctions between vascular endothelial cells help to create the blood-brain and blood-retinal barriers. Breakdown of the retinal tight junction complex is problematic in several disease states including diabetic retinopathy. Glucocorticoids can restore and/or preserve the endothelial barrier to paracellular permeability, although the mechanism remains unclear. We show that glucocorticoid treatment of primary retinal endothelial cells increases content of the tight junction proteins occludin and claudin-5, co-incident with an increase in barrier properties of endothelial monolayers. The glucocorticoid receptor antagonist RU486 reverses both the glucocorticoid-stimulated increase in occludin content and the increase in barrier properties. Transcriptional activity from the human occludin and claudin-5 promoters increases in retinal endothelial cells upon glucocorticoid treatment, and is dependent on the glucocorticoid receptor (GR) as demonstrated by siRNA. Deletion analysis of the occludin promoter reveals a 205bp sequence responsible for the glucocorticoid response. However, this region does not possess a canonical glucocorticoid response element and does not bind to the GR in a chromatin immunoprecipitation (ChIP) assay. Mutational analysis of this region revealed a novel 40bp occludin enhancer element (OEE), containing two highly conserved regions of 10 and 13 base pairs, that is both necessary and sufficient for glucocorticoid-induced gene expression in retinal endothelial cells. These data suggest a novel mechanism for glucocorticoid induction of vascular endothelial barrier properties through increased occludin and claudin-5 gene expression.

GLUCOCORTICOIDS INDUCE TRANSACTIVATION OF TIGHT JUNCTION GENES OCCLUDIN AND CLAUDIN-5 IN RETINAL ENDOTHELIAL CELLS VIA A NOVEL CIS-ELEMENT

PubMed Central

Felinski, Edward A.; Cox, Amy E.; Phillips, Brett E.; Antonetti, David A.

2008-01-01

Tight junctions between vascular endothelial cells help to create the blood-brain and blood-retinal barriers. Breakdown of the retinal tight junction complex is problematic in several disease states including diabetic retinopathy. Glucocorticoids can restore and/or preserve the endothelial barrier to paracellular permeability, although the mechanism remains unclear. We show that glucocorticoid treatment of primary retinal endothelial cells increases content of the tight junction proteins occludin and claudin-5, co-incident with an increase in barrier properties of endothelial monolayers. The glucocorticoid receptor antagonist RU486 reverses both the glucocorticoid-stimulated increase in occludin content and the increase in barrier properties. Transcriptional activity from the human occludin and claudin-5 promoters increases in retinal endothelial cells upon glucocorticoid treatment, and is dependent on the glucocorticoid receptor (GR) as demonstrated by siRNA. Deletion analysis of the occludin promoter reveals a 205 bp sequence responsible for the glucocorticoid response. However, this region does not posses a canonical glucocorticoid response element and does not bind to the GR in a chromatin immunoprecipitation (ChIP) assay. Mutational analysis of this region revealed a novel 40 bp occludin enhancer element (OEE), containing two highly-conserved regions of 10 and 13 base pairs, that is both necessary and sufficient for glucocorticoid-induced gene expression in retinal endothelial cells. These data suggest a novel mechanism for glucocorticoid induction of vascular endothelial barrier properties through increased occludin and claudin-5 gene expression. PMID:18501346

Disequilibrium dihedral angles in dolerite sills

USGS Publications Warehouse

Holness, Marian B.; Richardson, Chris; Helz, Rosalind T.

2012-01-01

The geometry of clinopyroxene-plagioclase-plagioclase junctions in mafic rocks, measured by the median dihedral angle Θcpp, is created during solidification. In the solidifying Kilauea Iki (Hawaii) lava lake, the wider junctions between plagioclase grains are the first to be filled by pyroxene, followed by the narrower junctions. The final Θcpp, attained when all clinopyroxene-plagioclase-plagioclase junctions are formed, is 78° in the upper crust of the lake, and 85° in the lower solidification front. Θcpp in the 3.5-m-thick Traigh Bhàn na Sgùrra sill (Inner Hebrides) is everywhere 78°. In the Whin Sill (northern England, 38 m thick) and the Portal Peak sill (Antarctica, 129 m thick), Θcpp varies symmetrically, with the lowest values at the margins. The 266-m-thick Basement Sill (Antarctica) has asymmetric variation of Θcpp, attributed to a complex filling history. The chilled margins of the Basement Sill are partially texturally equilibrated, with high Θcpp. The plagioclase grain size in the two widest sills varies asymmetrically, with the coarsest rocks found in the upper third. Both Θcpp and average grain size are functions of model crystallization times. Θcpp increases from 78° to a maximum of ∼100° as the crystallization time increases from 1 to 500 yr. Because the use of grain size as a measure of crystallization time is dependent on an estimate of crystal growth rates, dihedral angles provide a more direct proxy for cooling rates in dolerites.

HIV-1 gp120 Glycoprotein Interacting with Dendritic Cell-specific Intercellular Adhesion Molecule 3-grabbing Non-integrin (DC-SIGN) Down-Regulates Tight Junction Proteins to Disrupt the Blood Retinal Barrier and Increase Its Permeability.

PubMed

Qian, Yi-Wen; Li, Chuan; Jiang, Ai-Ping; Ge, Shengfang; Gu, Ping; Fan, Xianqun; Li, Tai-Sheng; Jin, Xia; Wang, Jian-Hua; Wang, Zhi-Liang

2016-10-28

Approximately 70% of HIV-1 infected patients acquire ocular opportunistic infections and manifest eye disorders during the course of their illness. The mechanisms by which pathogens invade the ocular site, however, are unclear. Under normal circumstances, vascular endothelium and retinal pigment epithelium (RPE), which possess a well developed tight junction complex, form the blood-retinal barrier (BRB) to prevent pathogen invasion. We hypothesize that disruption of the BRB allows pathogen entry into ocular sites. The hypothesis was tested using in vitro models. We discovered that human RPE cells could bind to either HIV-1 gp120 glycoproteins or HIV-1 viral particles. Furthermore, the binding was mediated by dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) expressed on RPE cells. Upon gp120 binding to DC-SIGN, cellular NF-κB signaling was triggered, leading to the induction of matrix metalloproteinases, which subsequently degraded tight junction proteins and disrupted the BRB integrity. DC-SIGN knockdown or prior blocking with a specific antibody abolished gp120-induced matrix metalloproteinase expression and reduced the degradation of tight junction proteins. This study elucidates a novel mechanism by which HIV, type 1 invades ocular tissues and provides additional insights into the translocation or invasion process of ocular complication-associated pathogens. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Quantitative cell polarity imaging defines leader-to-follower transitions during collective migration and the key role of microtubule-dependent adherens junction formation.

PubMed

Revenu, Céline; Streichan, Sebastian; Donà, Erika; Lecaudey, Virginie; Hufnagel, Lars; Gilmour, Darren

2014-03-01

The directed migration of cell collectives drives the formation of complex organ systems. A characteristic feature of many migrating collectives is a 'tissue-scale' polarity, whereby 'leader' cells at the edge of the tissue guide trailing 'followers' that become assembled into polarised epithelial tissues en route. Here, we combine quantitative imaging and perturbation approaches to investigate epithelial cell state transitions during collective migration and organogenesis, using the zebrafish lateral line primordium as an in vivo model. A readout of three-dimensional cell polarity, based on centrosomal-nucleus axes, allows the transition from migrating leaders to assembled followers to be quantitatively resolved for the first time in vivo. Using live reporters and a novel fluorescent protein timer approach, we investigate changes in cell-cell adhesion underlying this transition by monitoring cadherin receptor localisation and stability. This reveals that while cadherin 2 is expressed across the entire tissue, functional apical junctions are first assembled in the transition zone and become progressively more stable across the leader-follower axis of the tissue. Perturbation experiments demonstrate that the formation of these apical adherens junctions requires dynamic microtubules. However, once stabilised, adherens junction maintenance is microtubule independent. Combined, these data identify a mechanism for regulating leader-to-follower transitions within migrating collectives, based on the relocation and stabilisation of cadherins, and reveal a key role for dynamic microtubules in this process.

Ultrastructure of identified fast excitatory, slow excitatory and inhibitory neuromuscular junctions in the locust.

PubMed

Titmus, M J

1981-06-01

The specialized jumping muscle of the locust, the metathoracic extensor tibiae (ETi), is innervated by four physiologically different motoneurons, including FETi, a phasic excitor, SETi, a tonic excitor, and CI, a tonic common inhibitor. FETi neuromuscular junctions were examined in three phasic ETi bundles innervated by FETi. FETi terminals were characterized by patchy contacts on to granular sarcoplasm. The ETi accessory extensor, innervated by both SETi and CI, contains two morphologically different types of axon ending. When this muscle was soaked in horseradish peroxidase, stimulation of SETi led to selective uptake in vesicles in terminals similar to those of FETi axons but containing smaller vesicles, while stimulation by CI caused increased uptake into terminals with more extensive contact directly on to fibrillar sarcoplasm. As has been observed in excitatory and inhibitory synapses in some crustacean and vertebrate nervous systems, the synaptic vesicles in the locust excitatory endings are round and electron-lucent while those in the inhibitory endings are more irregular in shape. The tonic neuromuscular junctions, SETi and CI, are more densely packed with vesicles, larger in cross-sectional area and appear to be of more complex shape than the smaller, vesicle-sparse, phasic FETi terminals. Following long duration stimulation at 10 Hz, the tonic neuromuscular junctions showed little morphological change. FETi endings, which fatigue within minutes at the same stimulation frequency, showed a 20% decrease in synaptic vesicle density and an increase in irregularly shaped membrane inclusions.

σ2-Adaptin Facilitates Basal Synaptic Transmission and Is Required for Regenerating Endo-Exo Cycling Pool Under High-Frequency Nerve Stimulation in Drosophila.

PubMed

Choudhury, Saumitra Dey; Mushtaq, Zeeshan; Reddy-Alla, Suneel; Balakrishnan, Sruthi S; Thakur, Rajan S; Krishnan, Kozhalmannom S; Raghu, Padinjat; Ramaswami, Mani; Kumar, Vimlesh

2016-05-01

The functional requirement of adapter protein 2 (AP2) complex in synaptic membrane retrieval by clathrin-mediated endocytosis is not fully understood. Here we isolated and functionally characterized a mutation that dramatically altered synaptic development. Based on the aberrant neuromuscular junction (NMJ) synapse, we named this mutation angur (a Hindi word meaning "grapes"). Loss-of-function alleles of angur show more than twofold overgrowth in bouton numbers and a dramatic decrease in bouton size. We mapped the angur mutation to σ2-adaptin, the smallest subunit of the AP2 complex. Reducing the neuronal level of any of the subunits of the AP2 complex or disrupting AP2 complex assembly in neurons phenocopied the σ2-adaptin mutation. Genetic perturbation of σ2-adaptin in neurons leads to a reversible temperature-sensitive paralysis at 38°. Electrophysiological analysis of the mutants revealed reduced evoked junction potentials and quantal content. Interestingly, high-frequency nerve stimulation caused prolonged synaptic fatigue at the NMJs. The synaptic levels of subunits of the AP2 complex and clathrin, but not other endocytic proteins, were reduced in the mutants. Moreover, bone morphogenetic protein (BMP)/transforming growth factor β (TGFβ) signaling was altered in these mutants and was restored by normalizing σ2-adaptin in neurons. Thus, our data suggest that (1) while σ2-adaptin facilitates synaptic vesicle (SV) recycling for basal synaptic transmission, its activity is also required for regenerating SVs during high-frequency nerve stimulation, and (2) σ2-adaptin regulates NMJ morphology by attenuating TGFβ signaling. Copyright © 2016 by the Genetics Society of America.

CUB domain-containing protein 1 and the epidermal growth factor receptor cooperate to induce cell detachment.

PubMed

Law, Mary E; Ferreira, Renan B; Davis, Bradley J; Higgins, Paul J; Kim, Jae-Sung; Castellano, Ronald K; Chen, Sixue; Luesch, Hendrik; Law, Brian K

2016-08-05

While localized malignancies often respond to available therapies, most disseminated cancers are refractory. Novel approaches, therefore, are needed for the treatment of metastatic disease. CUB domain-containing protein1 (CDCP1) plays an important role in metastasis and drug resistance; the mechanism however, is poorly understood. Breast cancer cell lines were engineered to stably express EGFR, CDCP1 or phosphorylation site mutants of CDCP1. These cell lines were used for immunoblot analysis or affinity purification followed by immunoblot analysis to assess protein phosphorylation and/or protein complex formation with CDCP1. Kinase activity was evaluated using phosphorylation site-specific antibodies and immunoblot analysis in in vitro kinase assays. Protein band excision and mass spectrometry was utilized to further identify proteins complexed with CDCP1 or ΔCDCP1, which is a mimetic of the cleaved form of CDCP1. Cell detachment was assessed using cell counting. This paper reports that CDCP1 forms ternary protein complexes with Src and EGFR, facilitating Src activation and Src-dependent EGFR transactivation. Importantly, we have discovered that a class of compounds termed Disulfide bond Disrupting Agents (DDAs) blocks CDCP1/EGFR/Src ternary complex formation and downstream signaling. CDCP1 and EGFR cooperate to induce detachment of breast cancer cells from the substratum and to disrupt adherens junctions. Analysis of CDCP1-containing complexes using proteomics techniques reveals that CDCP1 associates with several proteins involved in cell adhesion, including adherens junction and desmosomal cadherins, and cytoskeletal elements. Together, these results suggest that CDCP1 may facilitate loss of adhesion by promoting activation of EGFR and Src at sites of cell-cell and cell-substratum contact.

Individualized treatment of craniovertebral junction malformation guided by intraoperative computed tomography.

PubMed

Li, Lianfeng; Wang, Peng; Chen, LiFeng; Ma, Xiaodong; Bu, Bo; Yu, Xinguang

2012-04-01

This study was designed to report our preliminary experience of intraoperative computed tomography (iCT) using a mobile scanner with integrated neuronavigation system (NNS). The objective of this study was to assess the feasibility and potential utility of iCT with integrated NNS in individualized treatment of craniovertebral junction malformation (CVJM). The surgical management of congenital craniovertebral anomalies is complex due to the relative difficulty in accessing the region, critical relationships of neurovascular structures, and the intricate biomechanical issues involved. We reported our first 19 complex CVJM cases including 11 male and 8 female patients from January, 2009 to June, 2009 (mean age, 33.9 y; age range, 13 to 58 y). A sliding gantry 40-slice CT scanner was installed in a preexisting operating room. Image data was transferred directly from the scanner into the NNS using an automated registration system. We applied this technology to transoral odontoidectomy in 17 patients. Moreover, with the extra help of iCT integrated with NNS, odontoidectomy through posterior midline approach, and transoral atlantal lateral mass resection were, for the first time, performed for treatment of complex CVJM. NNS was found to correlate well with the intraoperative findings, and the recalibration was uneven in all cases with an accuracy of 1.6 mm (1.6: 1.2 to 2.0). All patients were clinically evaluated by Nurick grade criteria, and neurological deficits were monitored after 3 months of surgery. Fifteen patients (79%) were improved by at least 1 Nurick grade, whereas the grade did not change in 4 patients (21%). iCT scanning with integrated NNS was both feasible and beneficial for the surgical management of complex CVJM. In this unusual patient population, the technique seemed to be valuable in negotiating complex anatomy and achieving a safe and predictable decompression.

Structural and functional changes associated with normal and abnormal fundus autofluorescence in patients with retinitis pigmentosa.

PubMed

Greenstein, Vivienne C; Duncker, Tobias; Holopigian, Karen; Carr, Ronald E; Greenberg, Jonathan P; Tsang, Stephen H; Hood, Donald C

2012-02-01

To analyze the structure and visual function of regions bordering the hyperautofluorescent ring/arcs in retinitis pigmentosa. Twenty-one retinitis pigmentosa patients (21 eyes) with rings/arcs and 21 normal individuals (21 eyes) were studied. Visual sensitivity in the central 10° was measured with microperimetry. Retinal structure was evaluated with spectral-domain optical coherence tomography. The distance from the fovea to disruption/loss of the inner outer segment (IS/OS) junction and thicknesses of the total receptor plus retinal pigment epithelial complex and outer segment plus retinal pigment epithelial complex layers were measured. Results were compared with measurements of the distance from the fovea to the inner and outer borders of the ring/arc seen on fundus autofluorescence. Disruption/loss of the inner outer segment junction occurred closer to the inner border of the ring/arc and it was closer to the fovea in eight eyes. For 19 eyes, outer segment plus and receptor plus RPE complex thicknesses were significantly decreased at locations closer to the fovea than the appearance of the inner border of hyperautofluorescence. Mean visual sensitivity was decreased inside, across, and outside the ring/arc by 3.5 ± 3.8, 8.9 ± 4.8, and 17.0 ± 2.4 dB, respectively. Structural and functional changes can occur inside the hyperfluorescent ring/arc in retinitis pigmentosa.

Drosophila Kette coordinates myoblast junction dissolution and the ratio of Scar-to-WASp during myoblast fusion

PubMed Central

Hamp, Julia; Löwer, Andreas; Dottermusch-Heidel, Christine; Beck, Lothar; Moussian, Bernard; Flötenmeyer, Matthias

2016-01-01

ABSTRACT The fusion of founder cells and fusion-competent myoblasts (FCMs) is crucial for muscle formation in Drosophila. Characteristic events of myoblast fusion include the recognition and adhesion of myoblasts, and the formation of branched F-actin by the Arp2/3 complex at the site of cell–cell contact. At the ultrastructural level, these events are reflected by the appearance of finger-like protrusions and electron-dense plaques that appear prior to fusion. Severe defects in myoblast fusion are caused by the loss of Kette (a homolog of Nap1 and Hem-2, also known as NCKAP1 and NCKAP1L, respectively), a member of the regulatory complex formed by Scar or WAVE proteins (represented by the single protein, Scar, in flies). kette mutants form finger-like protrusions, but the electron-dense plaques are extended. Here, we show that the electron-dense plaques in wild-type and kette mutant myoblasts resemble other electron-dense structures that are known to function as cellular junctions. Furthermore, analysis of double mutants and attempts to rescue the kette mutant phenotype with N-cadherin, wasp and genes of members of the regulatory Scar complex revealed that Kette has two functions during myoblast fusion. First, Kette controls the dissolution of electron-dense plaques. Second, Kette controls the ratio of the Arp2/3 activators Scar and WASp in FCMs. PMID:27521427

Distinct regions of triadin are required for targeting and retention at the junctional domain of the sarcoplasmic reticulum.

PubMed

Rossi, Daniela; Bencini, Cristina; Maritati, Marina; Benini, Francesca; Lorenzini, Stefania; Pierantozzi, Enrico; Scarcella, Angela Maria; Paolini, Cecilia; Protasi, Feliciano; Sorrentino, Vincenzo

2014-03-01

Ca2+ release, which is necessary for muscle contraction, occurs at the j-SR (junctional domain of the sarcoplasmic reticulum). It requires the assembly of a large multiprotein complex containing the RyR (ryanodine receptor) and additional proteins, including triadin and calsequestrin. The signals which drive these proteins to the j-SR and how they assemble to form this multiprotein complex are poorly understood. To address aspects of these questions we studied the localization, dynamic properties and molecular interactions of triadin. We identified three regions, named TR1 (targeting region 1), TR2 and TR3, that contribute to the localization of triadin at the j-SR. FRAP experiments showed that triadin is stably associated with the j-SR and that this association is mediated by TR3. Protein pull-down experiments indicated that TR3 contains binding sites for calsequestrin-1 and that triadin clustering can be enhanced by binding to calsequestrin-1. These findings were confirmed by FRET experiments. Interestingly, the stable association of triadin to the j-SR was significantly decreased in myotubes from calsequestrin-1 knockout mice. Taken together, these results identify three regions in triadin that mediate targeting to the j-SR and reveal a role for calsequestrin-1 in promoting the stable association of triadin to the multiprotein complex associated with RyR.

Tunneling current in HfO2 and Hf0.5Zr0.5O2-based ferroelectric tunnel junction

NASA Astrophysics Data System (ADS)

Dong, Zhipeng; Cao, Xi; Wu, Tong; Guo, Jing

2018-03-01

Ferroelectric tunnel junctions (FTJs) have been intensively explored for future low power data storage and information processing applications. Among various ferroelectric (FE) materials studied, HfO2 and H0.5Zr0.5O2 (HZO) have the advantage of CMOS process compatibility. The validity of the simple effective mass approximation, for describing the tunneling process in these materials, is examined by computing the complex band structure from ab initio simulations. The results show that the simple effective mass approximation is insufficient to describe the tunneling current in HfO2 and HZO materials, and quantitative accurate descriptions of the complex band structures are indispensable for calculation of the tunneling current. A compact k . p Hamiltonian is parameterized to and validated by ab initio complex band structures, which provides a method for efficiently and accurately computing the tunneling current in HfO2 and HZO. The device characteristics of a metal/FE/metal structure and a metal/FE/semiconductor (M-F-S) structure are investigated by using the non-equilibrium Green's function formalism with the parameterized effective Hamiltonian. The result shows that the M-F-S structure offers a larger resistance window due to an extra barrier in the semiconductor region at off-state. A FTJ utilizing M-F-S structure is beneficial for memory design.

STED super-resolution microscopy reveals an array of MINOS clusters along human mitochondria

PubMed Central

Jans, Daniel C.; Wurm, Christian A.; Riedel, Dietmar; Wenzel, Dirk; Stagge, Franziska; Deckers, Markus; Rehling, Peter; Jakobs, Stefan

2013-01-01

The mitochondrial inner membrane organizing system (MINOS) is a conserved large hetero-oligomeric protein complex in the mitochondrial inner membrane, crucial for the maintenance of cristae morphology. MINOS has been suggested to represent the core of an extended protein network that controls mitochondrial function and structure, and has been linked to several human diseases. The spatial arrangement of MINOS within mitochondria is ill-defined, however. Using super-resolution stimulated emission depletion (STED) microscopy and immunogold electron microscopy, we determined the distribution of three known human MINOS subunits (mitofilin, MINOS1, and CHCHD3) in mammalian cells. Super-resolution microscopy revealed that all three subunits form similar clusters within mitochondria, and that MINOS is more abundant in mitochondria around the nucleus than in peripheral mitochondria. At the submitochondrial level, mitofilin, a core MINOS subunit, is preferentially localized at cristae junctions. In primary human fibroblasts, mitofilin labeling uncovered a regularly spaced pattern of clusters arranged in parallel to the cell growth surfaces. We suggest that this array of MINOS complexes might explain the observed phenomenon of largely horizontally arranged cristae junctions that connect the inner boundary membrane to lamellar cristae. The super-resolution images demonstrate an unexpectedly high level of regularity in the nanoscale distribution of the MINOS complex in human mitochondria, supporting an integrating role of MINOS in the structural organization of the organelle. PMID:23676277

[Histomorphological analyse of accelerating the fibrocartilage layer repair of patella-patellar tendon junction in rabbits by low intensity pulsed ultrasound stimulation].

PubMed

Zhang, Baoliang; Lü, Hongbin; Hu, Jianzhong; Xu, Daqi; Zhou, Jingyong; Wang, Ye

2013-08-01

To analyse the effect of low intensity pulsed ultrasound stimulation (LIPUS) on accelerating the fibrocartilage layer repair of patella-patellar tendon junction. A total of 60 mature female New Zealand white rabbits undergoing standard partial patellectomy were divided into 2 groups randomly. The control group was given comfort treatment and the treatment group was given LIPUS treatment starting from day 3 to the end of week 6 postoperatively. The scheduled time points of animal euthanization would be at week 6, week 12 and week 18 postoperatively. The patella-patellar tendon (PPT) complex would be harvested and cut into sections after decalcification for H&E staining, Safranine o/fast green staining. The thickness and gray value of fibrocartilage layer were analyzed by SANO Microscope Partner image analyzer. At week 6, week 12 and week 18 postoperatively, the fibrocartilage layer in the treatment group was significantly thicker than that in the control group (P<0.01), and the gray value of fibrocartilage layer was significantly smaller than that in the control group (P<0.01). LIPUS helps to accelerate the fibrocartilage layer repair of patella-patellar tendon junction in rabbit models.

Fine structure of the ependyma and intercellular junctions in the area postrema of the rat.

PubMed

Gotow, T; Hashimoto, P H

1979-09-03

Ependymal cells and their junctional complexes in the area postrema of the rat were studied in detail by tracer experiments using horseradish peroxidase (HRP) and colloidal lanthanum and by freeze-etch techniques, in addition to routine electron microscopy. The ependyma of the area postrema is characterized as flattened cells possessing very few cilia, a moderate amount of microvilli, a well-developed Golgi apparatus and rough endoplasmic reticulum. Numerous vesicles or tubular formations with internal dense content were found to accumulate in the basal processes of ependymal cells; the basal process makes contact with the perivascular basal lamina. It is suggested that the dense material in the tubulovesicular formations is synthesized within the ependymal cell and discharged into the perivascular space. The apical junctions between adjacent ependymal cells display very close apposition, with a gap of 2--3 nm, but no fusion of adjacent plasma membranes; they thus represent a transitional form between the zonulae adhaerentes present in the ordinary mural ependyma and the zonulae occludentes in the choroidal epithelium. A direct intercommunication between the ventricular cerebrospinal fluid (CSF) and the blood vascular system indicates that a region exists lacking a blood-ventricular CSF barrier.

Peripheral nerve hyperexcitability with preterminal nerve and neuromuscular junction remodeling is a hallmark of Schwartz-Jampel syndrome.

PubMed

Bauché, Stéphanie; Boerio, Delphine; Davoine, Claire-Sophie; Bernard, Véronique; Stum, Morgane; Bureau, Cécile; Fardeau, Michel; Romero, Norma Beatriz; Fontaine, Bertrand; Koenig, Jeanine; Hantaï, Daniel; Gueguen, Antoine; Fournier, Emmanuel; Eymard, Bruno; Nicole, Sophie

2013-12-01

Schwartz-Jampel syndrome (SJS) is a recessive disorder with muscle hyperactivity that results from hypomorphic mutations in the perlecan gene, a basement membrane proteoglycan. Analyses done on a mouse model have suggested that SJS is a congenital form of distal peripheral nerve hyperexcitability resulting from synaptic acetylcholinesterase deficiency, nerve terminal instability with preterminal amyelination, and subtle peripheral nerve changes. We investigated one adult patient with SJS to study this statement in humans. Perlecan deficiency due to hypomorphic mutations was observed in the patient biological samples. Electroneuromyography showed normal nerve conduction, neuromuscular transmission, and compound nerve action potentials while multiple measures of peripheral nerve excitability along the nerve trunk did not detect changes. Needle electromyography detected complex repetitive discharges without any evidence for neuromuscular transmission failure. The study of muscle biopsies containing neuromuscular junctions showed well-formed post-synaptic element, synaptic acetylcholinesterase deficiency, denervation of synaptic gutters with reinnervation by terminal sprouting, and long nonmyelinated preterminal nerve segments. These data support the notion of peripheral nerve hyperexcitability in SJS, which would originate distally from synergistic actions of peripheral nerve and neuromuscular junction changes as a result of perlecan deficiency. Copyright © 2013 Elsevier B.V. All rights reserved.

Direct numerical simulation of transitional hydrodynamics of the cerebrospinal fluid in Chiari I malformation: The role of cranio-vertebral junction.

PubMed

Jain, Kartik; Ringstad, Geir; Eide, Per-Kristian; Mardal, Kent-André

2017-09-01

Obstruction to the cerebrospinal fluid (CSF) outflow caused by the herniation of cerebellar tonsils as a result of Chiari malformation type I leads to altered CSF hydrodynamics. This contribution explores the minutest characteristics of the CSF hydrodynamics in cervical subarachnoid space (SAS) of a healthy subject and 2 Chiari patients by performing highly resolved direct numerical simulation. The lattice Boltzmann method is used for the simulations because of its scalability on modern supercomputers that allow us to simulate up to approximately 10 9 cells while resolving the Kolmogorov microscales. The results depict that whereas the complex CSF flow remains largely laminar in the SAS of a healthy subject, constriction of the cranio-vertebral junction in Chiari I patients causes manifold fluctuations in the hydrodynamics of the CSF. These fluctuations resemble a flow that is in a transitional regime rather than laminar or fully developed turbulence. The fluctuations confine near the cranio-vertebral junction and are triggered due to the tonsillar herniation, which perturbs the flow as a result of altered anatomy of the SAS. Copyright © 2016 John Wiley & Sons, Ltd.

Propofol inhibits gap junctions by attenuating sevoflurane-induced cytotoxicity against rat liver cells in vitro.

PubMed

Huang, Fei; Li, Shangrong; Gan, Xiaoliang; Wang, Ren; Chen, Zhonggang

2014-04-01

Liver abnormalities are seen in a small proportion of patients following anaesthesia with sevoflurane. To investigate whether the cytotoxicity of sevoflurane against rat liver cells was mediated by gap junction intercellular communications, and the effect of propofol on sevoflurane-induced cytotoxicity. Experimental study. The study was carried out in the central laboratory of The Third Affiliated Hospital, Sun Yat-sen University. BRL-3A rat liver cells. Immortal rat liver cells BRL-3A were grown at low and high density. Colony-forming assays were performed to determine clonogenic growth of these cells. To investigate the effect of oleamide and propofol on gap junction function, we measured fluorescence transmission between cells using parachute dye-coupling assays. Immunoblotting assays were performed to determine connexin32 and connexin43 expression. Our colony formation assays revealed that, in low-density culture, sevoflurane caused no apparent inhibition of clonogenic growth of BRL-3A cells. In high-density culture, 2.2 to 4.4% sevoflurane markedly inhibited clonogenic growth of BRL-3A cells with 67.6 (0.34)% and 61.2 (0.17)% of the cells being viable, respectively (P = 0.003 vs. low-density culture), suggesting cell density dependency of sevoflurane-induced cytotoxicity. Our colony formation assays revealed that propofol markedly attenuated the suppression by sevoflurane of the clonogenic growth of BRL-3A cells (viability: propofol and sevoflurane, 91.5 (0.014)% vs. sevoflurane, 56.6 (0.019)%; P <0.01). Blocking gap junctions with 10 μmol l oleamide significantly attenuated 4.4% sevoflurane-induced suppression with a viability of 83.6 ± 0.138% (oleamide and sevoflurane vs. sevoflurane, P < 0.01). Immunoblotting assays further showed that propofol (3.2 μg ml) markedly reduced CX32 levels and significantly inhibited gap junctional intercellular communications as revealed by parachute dye-coupling assays. Values are mean (SD). This study provides the first direct evidence that sevoflurane-induced cytotoxicity, which is mediated through gap junctions, is attenuated by propofol, possibly by its action on Cx32 homomeric or heteromeric complexes.

Progressive Hearing Loss in Mice Carrying a Mutation in Usp53

PubMed Central

Kazmierczak, Marcin; Harris, Suzan L.; Kazmierczak, Piotr; Shah, Prahar; Starovoytov, Valentin; Ohlemiller, Kevin K.

2015-01-01

Disordered protein ubiquitination has been linked to neurodegenerative disease, yet its role in inner ear homeostasis and hearing loss is essentially unknown. Here we show that progressive hearing loss in the ethylnitrosourea-generated mambo mouse line is caused by a mutation in Usp53, a member of the deubiquitinating enzyme family. USP53 contains a catalytically inactive ubiquitin-specific protease domain and is expressed in cochlear hair cells and a subset of supporting cells. Although hair cell differentiation is unaffected in mambo mice, outer hair cells degenerate rapidly after the first postnatal week. USP53 colocalizes and interacts with the tight junction scaffolding proteins TJP1 and TJP2 in polarized epithelial cells, suggesting that USP53 is part of the tight junction complex. The barrier properties of tight junctions of the stria vascularis appeared intact in a biotin tracer assay, but the endocochlear potential is reduced in adult mambo mice. Hair cell degeneration in mambo mice precedes endocochlear potential decline and is rescued in cochlear organotypic cultures in low potassium milieu, indicating that hair cell loss is triggered by extracellular factors. Remarkably, heterozygous mambo mice show increased susceptibility to noise injury at high frequencies. We conclude that USP53 is a novel tight junction-associated protein that is essential for the survival of auditory hair cells and normal hearing in mice, possibly by modulating the barrier properties and mechanical stability of tight junctions. SIGNIFICANCE STATEMENT Hereditary hearing loss is extremely prevalent in the human population, but many genes linked to hearing loss remain to be discovered. Forward genetics screens in mice have facilitated the identification of genes involved in sensory perception and provided valuable animal models for hearing loss in humans. This involves introducing random mutations in mice, screening the mice for hearing defects, and mapping the causative mutation. Here, we have identified a mutation in the Usp53 gene that causes progressive hearing loss in the mambo mouse line. We demonstrate that USP53 is a catalytically inactive deubiquitinating enzyme and a novel component of tight junctions that is necessary for sensory hair cell survival and inner ear homeostasis. PMID:26609154

Intraepithelial gammadelta+ lymphocytes maintain the integrity of intestinal epithelial tight junctions in response to infection.

PubMed

Dalton, Jane E; Cruickshank, Sheena M; Egan, Charlotte E; Mears, Rainy; Newton, Darren J; Andrew, Elizabeth M; Lawrence, Beth; Howell, Gareth; Else, Kathryn J; Gubbels, Marc-Jan; Striepen, Boris; Smith, Judith E; White, Stanley J; Carding, Simon R

2006-09-01

Intestinal epithelial integrity and permeability is dependent on intercellular tight junction (TJ) complexes. How TJ integrity is regulated remains unclear, although phosphorylation and dephosphorylation of the integral membrane protein occludin is an important determinant of TJ formation and epithelial permeability. We have investigated the role intestinal intraepithelial lymphocytes (iIELs) play in regulating epithelial permeability in response to infection. Recombinant strains of Toxoplasma gondii were used to assess intestinal epithelial barrier function and TJ integrity in mice with intact or depleted populations of iIELs. Alterations in epithelial permeability were correlated with TJ structure and the state of phosphorylation of occludin. iIEL in vivo reconstitution experiments were used to identify the iIELs required to maintain epithelial permeability and TJ integrity. In the absence of gammadelta+ iIELs, intestinal epithelial barrier function and the ability to restrict epithelial transmigration of Toxoplasma and the unrelated intracellular bacterial pathogen Salmonella typhimurium was severely compromised. Leaky epithelium in gammadelta+ iIEL-deficient mice was associated with the absence of phosphorylation of serine residues of occludin and lack of claudin 3 and zona occludens-1 proteins in TJ complexes. These deficiencies were attributable to the absence of a single subset of gammadelta T-cell receptor (TCR-Vgamma7+) iIELs that, after reconstituting gammadelta iIEL-deficient mice, restored epithelial barrier function and TJ complexes, resulting in increased resistance to infection. These findings identify a novel role for gammadelta+ iIELs in maintaining TJ integrity and epithelial barrier function that have implications for understanding the pathogenesis of intestinal inflammatory diseases associated with disruption of TJ complexes.

WAVE2 regulates epithelial morphology and cadherin isoform switching through regulation of Twist and Abl.

PubMed

Bryce, Nicole S; Reynolds, Albert B; Koleske, Anthony J; Weaver, Alissa M

2013-01-01

Epithelial morphogenesis is a dynamic process that involves coordination of signaling and actin cytoskeletal rearrangements. We analyzed the contribution of the branched actin regulator WAVE2 in the development of 3-dimensional (3D) epithelial structures. WAVE2-knockdown (WAVE2-KD) cells formed large multi-lobular acini that continued to proliferate at an abnormally late stage compared to control acini. Immunostaining of the cell-cell junctions of WAVE2-KD acini revealed weak and heterogeneous E-cadherin staining despite little change in actin filament localization to the same junctions. Analysis of cadherin expression demonstrated a decrease in E-cadherin and an increase in N-cadherin protein and mRNA abundance in total cell lysates. In addition, WAVE2-KD cells exhibited an increase in the mRNA levels of the epithelial-mesenchymal transition (EMT)-associated transcription factor Twist1. KD of Twist1 expression in WAVE2-KD cells reversed the cadherin switching and completely rescued the aberrant 3D morphological phenotype. Activity of the WAVE2 complex binding partner Abl kinase was also increased in WAVE2-KD cells, as assessed by tyrosine phosphorylation of the Abl substrate CrkL. Inhibition of Abl with STI571 rescued the multi-lobular WAVE2-KD 3D phenotype whereas overexpression of Abl kinase phenocopied the WAVE2-KD phenotype. The WAVE2 complex regulates breast epithelial morphology by a complex mechanism involving repression of Twist1 expression and Abl kinase activity. These data reveal a critical role for WAVE2 complex in regulation of cellular signaling and epithelial morphogenesis.

Phosphothreonine 218 is required for the function of SR45.1 in regulating flower petal development in Arabidopsis

USDA-ARS?s Scientific Manuscript database

RNA splicing is crucial to the production of mature messenger RNAs (mRNA). The protein Arginine/Serine-rich 45 (SR45) acts as an RNA splicing activator and initiates the spliceosome assembly. It is also a peripheral component of the exon-exon junction complex, which assures the quality and availabil...

Complexity of gap junctions between horizontal cells of the carp retina.

PubMed

Greb, H; Hermann, S; Dirks, P; Ommen, G; Kretschmer, V; Schultz, K; Zoidl, G; Weiler, R; Janssen-Bienhold, U

2017-01-06

In the vertebrate retina, horizontal cells (HCs) reveal homologous coupling by gap junctions (gj), which are thought to consist of different connexins (Cx). However, recent studies in mouse, rabbit and zebrafish retina indicate that individual HCs express more than one connexin. To provide further insights into the composition of gj connecting HCs and to determine whether HCs express multiple connexins, we examined the molecular identity and distribution of gj between HCs of the carp retina. We have cloned four carp connexins designated Cx49.5, Cx55.5, Cx52.6 and Cx53.8 with a close relationship to connexins previously reported in HCs of mouse, rabbit and zebrafish, respectively. Using in situ hybridization, Cx49.5 expression was detected in different subpopulations of retinal neurons including HCs, whereas the Cx52.6 transcript was localized exclusively in HCs. Using specific antibodies, Cx55.5 and Cx53.8 were detected on dendrites of all four HC subtypes and axon terminals. Immunoelectron microscopy confirmed the presence of Cx55.5 and Cx53.8 in gap junctions between these processes and Cx55.5 was additionally observed in HC dendrites invaginating cone pedicles, suggesting its participation in the modulation of photoreceptor output in the carp retina. Furthermore, using single-cell RT-PCR, all four connexins were detected in different subtypes of HCs, suggesting overlapping expression patterns. Thus, the composition of gj mediating homologous coupling between subtypes of carp HCs appears to be more complex than expected. Moreover, BLAST searches of the preliminary carp genome, using novel sequences as query, suggest that most of the analyzed connexin genes are duplicated in carp. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Epidermal growth factor receptor and integrins control force-dependent vinculin recruitment to E-cadherin junctions.

PubMed

Sehgal, Poonam; Kong, Xinyu; Wu, Jun; Sunyer, Raimon; Trepat, Xavier; Leckband, Deborah

2018-03-20

This study reports novel findings that link E-cadherin (also known as CDH1)-mediated force-transduction signaling to vinculin targeting to intercellular junctions via epidermal growth factor receptor (EGFR) and integrins. These results build on previous findings that demonstrated that mechanically perturbed E-cadherin receptors activate phosphoinositide 3-kinase and downstream integrins in an EGFR-dependent manner. Results of this study show that this EGFR-mediated kinase cascade controls the force-dependent recruitment of vinculin to stressed E-cadherin complexes - a key early signature of cadherin-based mechanotransduction. Vinculin targeting requires its phosphorylation at tyrosine 822 by Abl family kinases (hereafter Abl), but the origin of force-dependent Abl activation had not been identified. We now present evidence that integrin activation, which is downstream of EGFR signaling, controls Abl activation, thus linking E-cadherin to Abl through a mechanosensitive signaling network. These findings place EGFR and integrins at the center of a positive-feedback loop, through which force-activated E-cadherin signals regulate vinculin recruitment to cadherin complexes in response to increased intercellular tension.This article has an associated First Person interview with the first author of the paper. © 2018. Published by The Company of Biologists Ltd.

The metastasis-associated gene MTA3, a component of the Mi-2/NuRD transcriptional repression complex, predicts prognosis of gastroesophageal junction adenocarcinoma.

PubMed

Dong, Hongmei; Guo, Hong; Xie, Liangxi; Wang, Geng; Zhong, Xueyun; Khoury, Thaer; Tan, Dongfeng; Zhang, Hao

2013-01-01

Gastroesophageal junction (GEJ) adenocarcinoma carries a poor prognosis that is largely attributable to early and frequent metastasis. The acquisition of metastatic potential in cancer involves epithelial-to-mesenchymal transition (EMT). The metastasis-associated gene MTA3, a novel component of the Mi-2/NuRD transcriptional repression complex, was identified as master regulator of EMT through inhibition of Snail to increase E-cadherin expression in breast cancer. Here, we evaluated the expression pattern of the components of MTA3 pathway and the corresponding prognostic significance in GEJ adenocarcinoma. MTA3 expression was decreased at both protein and mRNA levels in tumor tissues compared to the non-tumorous and lowed MTA3 levels were noted in tumor cell lines with stronger metastatic potential. Immunohistochemical analysis of a cohort of 128 cases exhibited that patients with lower expression of MTA3 had poorer outcomes. Combined misexpression of MTA3, Snail and E-cadherin had stronger correlation with malignant properties. Collectively, results suggest that the MTA3-regulated EMT pathway is altered to favor EMT and, therefore, disease progression and that MTA3 expression was an independent prognostic factor in patients with GEJ adenocarcinoma.

Adducin forms a bridge between the erythrocyte membrane and its cytoskeleton and regulates membrane cohesion

PubMed Central

Anong, William A.; Franco, Taina; Chu, Haiyan; Weis, Tahlia L.; Devlin, Emily E.; Bodine, David M.; An, Xiuli; Mohandas, Narla

2009-01-01

The erythrocyte membrane skeleton is the best understood cytoskeleton. Because its protein components have homologs in virtually all other cells, the membrane serves as a fundamental model of biologic membranes. Modern textbooks portray the membrane as a 2-dimensional spectrin-based membrane skeleton attached to a lipid bilayer through 2 linkages: band 3–ankyrin–β-spectrin and glycophorin C–protein 4.1–β-spectrin.1–7 Although evidence supports an essential role for the first bridge in regulating membrane cohesion, rupture of the glycophorin C–protein 4.1 interaction has little effect on membrane stability.8 We demonstrate the existence of a novel band 3–adducin–spectrin bridge that connects the spectrin/actin/protein 4.1 junctional complex to the bilayer. As rupture of this bridge leads to spontaneous membrane fragmentation, we conclude that the band 3–adducin–spectrin bridge is important to membrane stability. The required relocation of part of the band 3 population to the spectrin/actin junctional complex and its formation of a new bridge with adducin necessitates a significant revision of accepted models of the erythrocyte membrane. PMID:19567882

The Hippo-YAP signaling pathway and contact inhibition of growth

PubMed Central

Gumbiner, Barry M.; Kim, Nam-Gyun

2014-01-01

ABSTRACT The Hippo-YAP pathway mediates the control of cell proliferation by contact inhibition as well as other attributes of the physical state of cells in tissues. Several mechanisms sense the spatial and physical organization of cells, and function through distinct upstream modules to stimulate Hippo-YAP signaling: adherens junction or cadherin–catenin complexes, epithelial polarity and tight junction complexes, the FAT-Dachsous morphogen pathway, as well as cell shape, actomyosin or mechanotransduction. Soluble extracellular factors also regulate Hippo pathway signaling, often inhibiting its activity. Indeed, the Hippo pathway mediates a reciprocal relationship between contact inhibition and mitogenic signaling. As a result, cells at the edges of a colony, a wound in a tissue or a tumor are more sensitive to ambient levels of growth factors and more likely to proliferate, migrate or differentiate through a YAP and/or TAZ-dependent process. Thus, the Hippo-YAP pathway senses and responds to the physical organization of cells in tissues and coordinates these physical cues with classic growth-factor-mediated signaling pathways. This Commentary is focused on the biological significance of Hippo-YAP signaling and how upstream regulatory modules of the pathway interact to produce biological outcomes. PMID:24532814

Single molecule junction conductance and binding geometry

NASA Astrophysics Data System (ADS)

Kamenetska, Maria

This Thesis addresses the fundamental problem of controlling transport through a metal-organic interface by studying electronic and mechanical properties of single organic molecule-metal junctions. Using a Scanning Tunneling Microscope (STM) we image, probe energy-level alignment and perform STM-based break junction (BJ) measurements on molecules bound to a gold surface. Using Scanning Tunneling Microscope-based break-junction (STM-BJ) techniques, we explore the effect of binding geometry on single-molecule conductance by varying the structure of the molecules, metal-molecule binding chemistry and by applying sub-nanometer manipulation control to the junction. These experiments are performed both in ambient conditions and in ultra high vacuum (UHV) at cryogenic temperatures. First, using STM imaging and scanning tunneling spectroscopy (STS) measurements we explore binding configurations and electronic properties of an amine-terminated benzene derivative on gold. We find that details of metal-molecule binding affect energy-level alignment at the interface. Next, using the STM-BJ technique, we form and rupture metal-molecule-metal junctions ˜104 times to obtain conductance-vs-extension curves and extract most likely conductance values for each molecule. With these measurements, we demonstrated that the control of junction conductance is possible through a choice of metal-molecule binding chemistry and sub-nanometer positioning. First, we show that molecules terminated with amines, sulfides and phosphines bind selectively on gold and therefore demonstrate constant conductance levels even as the junction is elongated and the metal-molecule attachment point is modified. Such well-defined conductance is also obtained with paracyclophane molecules which bind to gold directly through the pi system. Next, we are able to create metal-molecule-metal junctions with more than one reproducible conductance signatures that can be accessed by changing junction geometry. In the case of pyridine-linked molecules, conductance can be reliably switched between two distinct conductance states using sub-nanometer mechanical manipulation. Using a methyl sulfide linker attached to an oligoene backbone, we are able to create a 3-nm-long molecular potentiometer, whose resistance can be tuned exponentially with Angstom-scale modulations in metal-molecule configuration. These experiments points to a new paradigm for attaining reproducible electrical characteristics of metal-organic devices which involves controlling linker-metal chemistry rather than fabricating identically structured metal-molecule interfaces. By choosing a linker group which is either insensitive to or responds reproducibly to changes in metal-molecule configuration, one can design single molecule devices with functionality more complex than a simple resistor. These ambient temperature experiments were combined with UHV conductance measurements performed in a commercial STM on amine-terminated benzene derivatives which conduct through a non-resonant tunneling mechanism, at temperatures varying from 5 to 300 Kelvin. Our results indicate that while amine-gold binding remains selective irrespective of environment, conductance is not temperature independent, in contrast to what is expected for a tunneling mechanism. Furthermore, using temperature-dependent measurements in ambient conditions we find that HOMO-conducting amines and LUMO-conducting pyridines show opposite dependence of conductance on temperature. These results indicate that energy-level alignment between the molecule and the electrodes changes as a result of varying electrode structure at different temperatures. We find that temperature can serve as a knob with which to tune transport properties of single molecule-metal junctions.

Control and manipulation of antiferromagnetic skyrmions in racetrack

NASA Astrophysics Data System (ADS)

Xia, Haiyan; Jin, Chendong; Song, Chengkun; Wang, Jinshuai; Wang, Jianbo; Liu, Qingfang

2017-12-01

Controllable manipulations of magnetic skyrmions are essential for next-generation spintronic devices. Here, the duplication and merging of skyrmions, as well as logical AND and OR functions, are designed in antiferromagnetic (AFM) materials with a cusp or smooth Y-junction structures. The operational time are in the dozens of picoseconds, enabling ultrafast information processing. A key factor for the successful operation is the relatively complex Y-junction structures, where domain walls propagate through in a controlled manner, without significant risks of pinning, vanishing or unwanted depinning of existing domain walls, as well as the nucleation of new domain walls. The motions of a multi-bit, namely the motion of an AFM skyrmion-chain in racetrack, are also investigated. Those micromagnetic simulations may contribute to future AFM skyrmion-based spintronic devices, such as nanotrack memory, logic gates and other information processes.

Targeting blood–brain barrier changes during inflammatory pain: an opportunity for optimizing CNS drug delivery

PubMed Central

Ronaldson, Patrick T; Davis, Thomas P

2012-01-01

The blood–brain barrier (BBB) is the most significant obstacle to effective CNS drug delivery. It possesses structural and biochemical features (i.e., tight-junction protein complexes and, influx and efflux transporters) that restrict xenobiotic permeation. Pathophysiological stressors (i.e., peripheral inflammatory pain) can alter BBB tight junctions and transporters, which leads to drug-permeation changes. This is especially critical for opioids, which require precise CNS concentrations to be safe and effective analgesics. Recent studies have identified molecular targets (i.e., endogenous transporters and intracellular signaling systems) that can be exploited for optimization of CNS drug delivery. This article summarizes current knowledge in this area and emphasizes those targets that present the greatest opportunity for controlling drug permeation and/or drug transport across the BBB in an effort to achieve optimal CNS opioid delivery. PMID:22468221

Thermobarometric and fluid expulsion history of subduction zones

NASA Astrophysics Data System (ADS)

Ernst, W. G.

1990-06-01

Phanerozoic, unmetamorphosed, weathered, and altered lithotectonic complexes subjected to subduction exhibit the prograde metamorphic facies sequence: zeolite → prehnite-pumpellyite → glaucophane schist → eclogite. Parageneses reflect relatively high-P trajectories, accompanied by semicontinuous devolatilization. The thermal evolution of convergent plate junctions results in early production of high-rank blueschists, high-P amphibolites, and eclogues at depth within narrow subduction zones while the hanging wall lithosphere is still hot. Protracted underflow drains heat from the nonsubducted plate and, even at profound depths, generates very low-T/high-P parageneses. Inclusion studies suggest that two-phase immiscible volatiles (liquid H2O, and gaseous high-hydrocarbons, CH4 and CO2) are evolved in turn during progressive metamorphism of the subducted sections. Expulsion of pore fluids and transitions from weathered and altered supracrustal rocks to zeolite facies assemblages release far more fluid than the better understood higher-grade transformations. Many blueschist parageneses, such as those of the internal Western Alps, have been partially overprinted by later greenschist and/or epidote-amphibolite facies assemblages. Alpine-type postblueschist metamorphic paths involved fairly rapid, nearly adiabatic decompression; some terranes even underwent modest continued heating and fluid evolution during early stages of ascent. Uplift probably occurred as a consequence of the underthrusting of low-density island arc or microcontinental crust along the convergent plate junction, resulting in marked deceleration or cessation of lithospheric underflow, decoupling, and nearly isothermal rise of the recrystallized subduction complex. Other, less common blueschist terranes, such as the eastern Franciscan belt of western California, preserve metamorphic aragonite and other high-P minerals, and lack a low-pressure overprint; physical conditions during retrogression approximately retraced the prograde path or, for early formed high-grade blocks, reflect somewhat higher pressures and lower temperatures. Subducted sections constituting portions of the Franciscan-type of metamorphic belt evidently moved slowly back up the inclined lithospheric plate junction during continued convergence and sustained refrigeration. Upward motion due to isostatic forces was produced by tectonic imbrication of fault suces, laminar return flow in melange zones, and lateral extension of the underplated accretionary prism. The ease with which volatiles are expelled from a subduction complex and migrate upward along the plate junction zone is roughly proportional to the sandstone/shale ratio: low-permeability mudstones tend to maintain fluid values approaching lithostatic, lose strength, and deform chaotically (forming melange belts), whereas permeable sandstone-rich sections retain structural/stratigraphic coherence and fail brittlely (forming coherent terranes). Because of substantial updip expulsion of volatiles during prograde recrystallization, only small amounts of H2O and CO2 are available to support hydration and carbonation of the accretionary complex during its return toward the surface; thus limited back reaction takes place and occurs at low Pfluid/Plithostatic ratios, unless an abundance of volatiles is introduced during uplift.

Models for the Binary Complex of Bacteriophage T4 Gp59 Helicase Loading Protein. GP32 Single-Stranded DNA-Binding Protein and Ternary Complex with Pseudo-Y Junction DNA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hinerman, Jennifer M.; Dignam, J. David; Mueser, Timothy C.

2012-04-05

The bacteriophage T4 gp59 helicase assembly protein (gp59) is required for loading of gp41 replicative helicase onto DNA protected by gp32 single-stranded DNA-binding protein. The gp59 protein recognizes branched DNA structures found at replication and recombination sites. Binding of gp32 protein (full-length and deletion constructs) to gp59 protein measured by isothermal titration calorimetry demonstrates that the gp32 protein C-terminal A-domain is essential for protein-protein interaction in the absence of DNA. Sedimentation velocity experiments with gp59 protein and gp32ΔB protein (an N-terminal B-domain deletion) show that these proteins are monomers but form a 1:1 complex with a dissociation constant comparable withmore » that determined by isothermal titration calorimetry. Small angle x-ray scattering (SAXS) studies indicate that the gp59 protein is a prolate monomer, consistent with the crystal structure and hydrodynamic properties determined from sedimentation velocity experiments. SAXS experiments also demonstrate that gp32ΔB protein is a prolate monomer with an elongated A-domain protruding from the core. Moreover, fitting structures of gp59 protein and the gp32 core into the SAXS-derived molecular envelope supports a model for the gp59 protein-gp32ΔB protein complex. Our earlier work demonstrated that gp59 protein attracts full-length gp32 protein to pseudo-Y junctions. A model of the gp59 protein-DNA complex, modified to accommodate new SAXS data for the binary complex together with mutational analysis of gp59 protein, is presented in the accompanying article (Dolezal, D., Jones, C. E., Lai, X., Brister, J. R., Mueser, T. C., Nossal, N. G., and Hinton, D. M. (2012) J. Biol. Chem. 287, 18596–18607).« less

Three-junction solar cell

DOEpatents

Ludowise, Michael J.

1986-01-01

A photovoltaic solar cell is formed in a monolithic semiconductor. The cell contains three junctions. In sequence from the light-entering face, the junctions have a high, a medium, and a low energy gap. The lower junctions are connected in series by one or more metallic members connecting the top of the lower junction through apertures to the bottom of the middle junction. The upper junction is connected in voltage opposition to the lower and middle junctions by second metallic electrodes deposited in holes 60 through the upper junction. The second electrodes are connected to an external terminal.

Environmental toxicants and male reproductive function

PubMed Central

Wong, Elissa W.P; Lie, Pearl P.Y; Li, Michelle W.M; Su, Linlin; Siu, Erica R; Yan, Helen H.N; Mannu, Jayakanthan; Mathur, Premendu P; Bonanomi, Michele; Silvestrini, Bruno; Mruk, Dolores D

2011-01-01

Environmental toxicants, such as cadmium and bisphenol A (BPA) are endocrine disruptors. In utero, perinatal or neonatal exposure of BPA to rats affect the male reproductive function, such as the blood-testis barrier (BTB) integrity. This effect of BPA on BTB integrity in immature rats is likely mediated via a loss of gap junction function at the BTB, failing to coordinate tight junction and anchoring junction function at the site to maintain the immunological barrier integrity. This in turn activates the extracellular signal-regulated kinases 1/2 (Erk1/2) downstream and an increase in protein endocytosis, destabilizing the BTB. The cadmium-induced disruption of testicular dysfunction is mediated initially via its effects on the occludin/ZO-1/focal adhesion kinase (FAK) complex at the BTB, causing redistribution of proteins at the Sertoli-Sertoli cell interface, leading to the BTB disruption. The damaging effects of these toxicants to testicular function are mediated by mitogen-activated protein kinases (MAPK) downstream, which in turn perturbs the actin bundling and accelerates the actin-branching activity, causing disruption of the Sertoli cell tight junction (TJ)-barrier function at the BTB and perturbing spermatid adhesion at the apical ectoplasmic specialization (apical ES, a testis-specific anchoring junction type) that leads to premature release of germ cells from the testis. However, the use of specific inhibitors against MAPK was shown to block or delay the cadmium-induced testicular injury, such as BTB disruption and germ cell loss. These findings suggest that there may be a common downstream p38 and/or Erk1/2 MAPK-based signaling pathway involving polarity proteins and actin regulators that is shared between different toxicants that induce male reproductive dysfunction. As such, the use of inhibitors and/or antagonists against specific MAPKs can possibly be used to “manage” the illnesses caused by these toxicants and/or “protect” industrial workers being exposed to high levels of these toxicants in their work environment. PMID:21866273

3D Architecture of the Trypanosoma brucei Flagella Connector, a Mobile Transmembrane Junction.

PubMed

Höög, Johanna L; Lacomble, Sylvain; Bouchet-Marquis, Cedric; Briggs, Laura; Park, Kristin; Hoenger, Andreas; Gull, Keith

2016-01-01

Cellular junctions are crucial for the formation of multicellular organisms, where they anchor cells to each other and/or supportive tissue and enable cell-to-cell communication. Some unicellular organisms, such as the parasitic protist Trypanosoma brucei, also have complex cellular junctions. The flagella connector (FC) is a three-layered transmembrane junction that moves with the growing tip of a new flagellum and attaches it to the side of the old flagellum. The FC moves via an unknown molecular mechanism, independent of new flagellum growth. Here we describe the detailed 3D architecture of the FC suggesting explanations for how it functions and its mechanism of motility. We have used a combination of electron tomography and cryo-electron tomography to reveal the 3D architecture of the FC. Cryo-electron tomography revealed layers of repetitive filamentous electron densities between the two flagella in the interstitial zone. Though the FC does not change in length and width during the growth of the new flagellum, the interstitial zone thickness decreases as the FC matures. This investigation also shows interactions between the FC layers and the axonemes of the new and old flagellum, sufficiently strong to displace the axoneme in the old flagellum. We describe a novel filament, the flagella connector fibre, found between the FC and the axoneme in the old flagellum. The FC is similar to other cellular junctions in that filamentous proteins bridge the extracellular space and are anchored to underlying cytoskeletal structures; however, it is built between different portions of the same cell and is unique because of its intrinsic motility. The detailed description of its structure will be an important tool to use in attributing structure / function relationships as its molecular components are discovered in the future. The FC is involved in the inheritance of cell shape, which is important for the life cycle of this human parasite.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 5: intercellular junctions and contacts between germs cells and Sertoli cells and their regulatory interactions, testicular cholesterol, and genes/proteins associated with more than one germ cell generation.

PubMed

Hermo, Louis; Pelletier, R-Marc; Cyr, Daniel G; Smith, Charles E

2010-04-01

In the testis, cell adhesion and junctional molecules permit specific interactions and intracellular communication between germ and Sertoli cells and apposed Sertoli cells. Among the many adhesion family of proteins, NCAM, nectin and nectin-like, catenins, and cadherens will be discussed, along with gap junctions between germ and Sertoli cells and the many members of the connexin family. The blood-testis barrier separates the haploid spermatids from blood borne elements. In the barrier, the intercellular junctions consist of many proteins such as occludin, tricellulin, and claudins. Changes in the expression of cell adhesion molecules are also an essential part of the mechanism that allows germ cells to move from the basal compartment of the seminiferous tubule to the adluminal compartment thus crossing the blood-testis barrier and well-defined proteins have been shown to assist in this process. Several structural components show interactions between germ cells to Sertoli cells such as the ectoplasmic specialization which are more closely related to Sertoli cells and tubulobulbar complexes that are processes of elongating spermatids embedded into Sertoli cells. Germ cells also modify several Sertoli functions and this also appears to be the case for residual bodies. Cholesterol plays a significant role during spermatogenesis and is essential for germ cell development. Lastly, we list genes/proteins that are expressed not only in any one specific generation of germ cells but across more than one generation. Copyright 2009 Wiley-Liss, Inc.

Intercellular Diffusion of a Fluorescent Sucrose Analog via the Septal Junctions in a Filamentous Cyanobacterium

PubMed Central

Nürnberg, Dennis J.; Mariscal, Vicente; Bornikoel, Jan; Nieves-Morión, Mercedes; Krauß, Norbert; Herrero, Antonia

2015-01-01

ABSTRACT Many filamentous cyanobacteria produce specialized nitrogen-fixing cells called heterocysts, which are located at semiregular intervals along the filament with about 10 to 20 photosynthetic vegetative cells in between. Nitrogen fixation in these complex multicellular bacteria depends on metabolite exchange between the two cell types, with the heterocysts supplying combined-nitrogen compounds but dependent on the vegetative cells for photosynthetically produced carbon compounds. Here, we used a fluorescent tracer to probe intercellular metabolite exchange in the filamentous heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. We show that esculin, a fluorescent sucrose analog, is incorporated by a sucrose import system into the cytoplasm of Anabaena cells. The cytoplasmic esculin is rapidly and reversibly exchanged across vegetative-vegetative and vegetative-heterocyst cell junctions. Our measurements reveal the kinetics of esculin exchange and also show that intercellular metabolic communication is lost in a significant fraction of older heterocysts. SepJ, FraC, and FraD are proteins located at the intercellular septa and are suggested to form structures analogous to gap junctions. We show that a ΔsepJ ΔfraC ΔfraD triple mutant shows an altered septum structure with thinner septa but a denser peptidoglycan layer. Intercellular diffusion of esculin and fluorescein derivatives is impaired in this mutant, which also shows a greatly reduced frequency of nanopores in the intercellular septal cross walls. These findings suggest that FraC, FraD, and SepJ are important for the formation of junctional structures that constitute the major pathway for feeding heterocysts with sucrose. PMID:25784700

Accurate chromatic control and color rendering optimization in LED lighting systems using junction temperature feedback

NASA Astrophysics Data System (ADS)

Sisto, Marco Michele; Gauvin, Jonny

2014-09-01

Accurate color control of LED lighting systems is a challenging task: noticeable chromaticity shifts are commonly observed in mixed-color and phosphor converted LEDs due to intensity dimming. Furthermore, the emitted color varies with the LED temperature. We present a novel color control method for tri-chromatic and tetra-chromatic LEDs, which enable to set and maintain the LED emission at a target color, or combination of correlated color temperature (CCT) and intensity. The LED color point is maintained over variations in the LED junctions' temperatures and intensity dimming levels. The method does not require color feedback sensors, so to minimize system complexity and cost, but relies on estimation of the LED junctions' temperatures from the junction voltages. If operated with tetra-chromatic LEDs, the method allows meeting an additional optimization criterion: for example, the maximization of a color rendering metric like the Color Rendering Index (CRI) or the Color Quality Scale (CQS), thus providing a high quality and clarity of colors on the surface illuminated by the LED. We demonstrate the control of a RGBW LED at target D65 white point with CIELAB color difference metric triangle;a,bE < 1 for simultaneous variations of flux from approximately 30 lm to 100 lm and LED heat sink temperature from 25°C to 58°C. In the same conditions, we demonstrate a CCT error <1%. Furthermore, the method allows varying the LED CCT from 5500K to 8000K while maintaining luminance within 1% of target. Further work is ongoing to evaluate the stability of the method over LED aging.

Design of RNA splicing analysis null models for post hoc filtering of Drosophila head RNA-Seq data with the splicing analysis kit (Spanki)

PubMed Central

2013-01-01

Background The production of multiple transcript isoforms from one gene is a major source of transcriptome complexity. RNA-Seq experiments, in which transcripts are converted to cDNA and sequenced, allow the resolution and quantification of alternative transcript isoforms. However, methods to analyze splicing are underdeveloped and errors resulting in incorrect splicing calls occur in every experiment. Results We used RNA-Seq data to develop sequencing and aligner error models. By applying these error models to known input from simulations, we found that errors result from false alignment to minor splice motifs and antisense stands, shifted junction positions, paralog joining, and repeat induced gaps. By using a series of quantitative and qualitative filters, we eliminated diagnosed errors in the simulation, and applied this to RNA-Seq data from Drosophila melanogaster heads. We used high-confidence junction detections to specifically interrogate local splicing differences between transcripts. This method out-performed commonly used RNA-seq methods to identify known alternative splicing events in the Drosophila sex determination pathway. We describe a flexible software package to perform these tasks called Splicing Analysis Kit (Spanki), available at http://www.cbcb.umd.edu/software/spanki. Conclusions Splice-junction centric analysis of RNA-Seq data provides advantages in specificity for detection of alternative splicing. Our software provides tools to better understand error profiles in RNA-Seq data and improve inference from this new technology. The splice-junction centric approach that this software enables will provide more accurate estimates of differentially regulated splicing than current tools. PMID:24209455

Delocalized Claudin-1 promotes metastasis of human osteosarcoma cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jian, Yuekui; Chen, Changqiong; Li, Bo

2015-10-23

Tight junction proteins (TJPs) including Claudins, Occludin and tight junction associated protein Zonula occludens-1 (ZO-1), are the most apical component of junctional complex that mediates cell–cell adhesion in epithelial and endothelial cells. In human malignancies, TJPs are often deregulated and affect cellular behaviors of tumor cells. In this study, we investigated alternations of TJPs and related biological characteristics in human osteosarcoma (OS). Claudin1 was increased in the metastatic OS cells (KRIB and KHOS) compared with the normal osteoblast cells (hFOB1.19) or primary tumor cells (HOS and U2OS), whereas no significant difference was found in Occludin and ZO-1. Immunohistochemistry, immunofluorescence andmore » Western blotting revealed that Claudin1 was initially localized at cell junctions of normal osteoblasts, but substantially delocalized to the nucleus of metastatic OS cells. Phenotypically, inhibition of the nucleus Claudin1 expression compromised the metastatic potential of KRIB and KHOS cells. Moreover, we found that protein kinase C (PKC) but not PKA phosphorylation influenced Claudin1 expression and cellular functions, as PKC inhibitor (Go 6983 and Staurosporine) or genetic silencing of PKC reduced Claudin1 expression and decreased the motility of KRIB and KHOS cells. Taken together, our study implied that delocalization of claudin-1 induced by PKC phosphorylation contributes to metastatic capacity of OS cells. - Highlights: • Claudin1 is increased during the malignant transformation of human OS. • Delocalization of Claudin1 in metastatic OS cells. • Silencing nuclear Claudin1 expression inhibits cell invasion of OS. • Deregulated Claudin1 is regulated by PKC.« less

Design of RNA splicing analysis null models for post hoc filtering of Drosophila head RNA-Seq data with the splicing analysis kit (Spanki).

PubMed

Sturgill, David; Malone, John H; Sun, Xia; Smith, Harold E; Rabinow, Leonard; Samson, Marie-Laure; Oliver, Brian

2013-11-09

The production of multiple transcript isoforms from one gene is a major source of transcriptome complexity. RNA-Seq experiments, in which transcripts are converted to cDNA and sequenced, allow the resolution and quantification of alternative transcript isoforms. However, methods to analyze splicing are underdeveloped and errors resulting in incorrect splicing calls occur in every experiment. We used RNA-Seq data to develop sequencing and aligner error models. By applying these error models to known input from simulations, we found that errors result from false alignment to minor splice motifs and antisense stands, shifted junction positions, paralog joining, and repeat induced gaps. By using a series of quantitative and qualitative filters, we eliminated diagnosed errors in the simulation, and applied this to RNA-Seq data from Drosophila melanogaster heads. We used high-confidence junction detections to specifically interrogate local splicing differences between transcripts. This method out-performed commonly used RNA-seq methods to identify known alternative splicing events in the Drosophila sex determination pathway. We describe a flexible software package to perform these tasks called Splicing Analysis Kit (Spanki), available at http://www.cbcb.umd.edu/software/spanki. Splice-junction centric analysis of RNA-Seq data provides advantages in specificity for detection of alternative splicing. Our software provides tools to better understand error profiles in RNA-Seq data and improve inference from this new technology. The splice-junction centric approach that this software enables will provide more accurate estimates of differentially regulated splicing than current tools.

Label-free viscosity measurement of complex fluids using reversal flow switching manipulation in a microfluidic channel

PubMed Central

Jun Kang, Yang; Ryu, Jeongeun; Lee, Sang-Joon

2013-01-01

The accurate viscosity measurement of complex fluids is essential for characterizing fluidic behaviors in blood vessels and in microfluidic channels of lab-on-a-chip devices. A microfluidic platform that accurately identifies biophysical properties of blood can be used as a promising tool for the early detections of cardiovascular and microcirculation diseases. In this study, a flow-switching phenomenon depending on hydrodynamic balancing in a microfluidic channel was adopted to conduct viscosity measurement of complex fluids with label-free operation. A microfluidic device for demonstrating this proposed method was designed to have two inlets for supplying the test and reference fluids, two side channels in parallel, and a junction channel connected to the midpoint of the two side channels. According to this proposed method, viscosities of various fluids with different phases (aqueous, oil, and blood) in relation to that of reference fluid were accurately determined by measuring the switching flow-rate ratio between the test and reference fluids, when a reverse flow of the test or reference fluid occurs in the junction channel. An analytical viscosity formula was derived to measure the viscosity of a test fluid in relation to that of the corresponding reference fluid using a discrete circuit model for the microfluidic device. The experimental analysis for evaluating the effects of various parameters on the performance of the proposed method revealed that the fluidic resistance ratio (RJL/RL, fluidic resistance in the junction channel (RJL) to fluidic resistance in the side channel (RL)) strongly affects the measurement accuracy. The microfluidic device with smaller RJL/RL values is helpful to measure accurately the viscosity of the test fluid. The proposed method accurately measured the viscosities of various fluids, including single-phase (Glycerin and plasma) and oil-water phase (oil vs. deionized water) fluids, compared with conventional methods. The proposed method was also successfully applied to measure viscosities of blood with varying hematocrits, chemically fixed RBCS, and channel sizes. Based on these experimental results, the proposed method can be effectively used to measure the viscosities of various fluids easily, without any fluorescent labeling and tedious calibration procedures. PMID:24404040

CarD uses a minor groove wedge mechanism to stabilize the RNA polymerase open promoter complex.

PubMed

Bae, Brian; Chen, James; Davis, Elizabeth; Leon, Katherine; Darst, Seth A; Campbell, Elizabeth A

2015-09-08

A key point to regulate gene expression is at transcription initiation, and activators play a major role. CarD, an essential activator in Mycobacterium tuberculosis, is found in many bacteria, including Thermus species, but absent in Escherichia coli. To delineate the molecular mechanism of CarD, we determined crystal structures of Thermus transcription initiation complexes containing CarD. The structures show CarD interacts with the unique DNA topology presented by the upstream double-stranded/single-stranded DNA junction of the transcription bubble. We confirm that our structures correspond to functional activation complexes, and extend our understanding of the role of a conserved CarD Trp residue that serves as a minor groove wedge, preventing collapse of the transcription bubble to stabilize the transcription initiation complex. Unlike E. coli RNAP, many bacterial RNAPs form unstable promoter complexes, explaining the need for CarD.

Complex Dynamics of Droplet Traffic in a Bifurcating Microfluidic Channel: Periodicity, Multistability, and Selection Rules

NASA Astrophysics Data System (ADS)

Sessoms, D. A.; Amon, A.; Courbin, L.; Panizza, P.

2010-10-01

The binary path selection of droplets reaching a T junction is regulated by time-delayed feedback and nonlinear couplings. Such mechanisms result in complex dynamics of droplet partitioning: numerous discrete bifurcations between periodic regimes are observed. We introduce a model based on an approximation that makes this problem tractable. This allows us to derive analytical formulae that predict the occurrence of the bifurcations between consecutive regimes, establish selection rules for the period of a regime, and describe the evolutions of the period and complexity of droplet pattern in a cycle with the key parameters of the system. We discuss the validity and limitations of our model which describes semiquantitatively both numerical simulations and microfluidic experiments.

Supramolecular Systems and Chemical Reactions in Single-Molecule Break Junctions.

PubMed

Li, Xiaohui; Hu, Duan; Tan, Zhibing; Bai, Jie; Xiao, Zongyuan; Yang, Yang; Shi, Jia; Hong, Wenjing

2017-04-01

The major challenges of molecular electronics are the understanding and manipulation of the electron transport through the single-molecule junction. With the single-molecule break junction techniques, including scanning tunneling microscope break junction technique and mechanically controllable break junction technique, the charge transport through various single-molecule and supramolecular junctions has been studied during the dynamic fabrication and continuous characterization of molecular junctions. This review starts from the charge transport characterization of supramolecular junctions through a variety of noncovalent interactions, such as hydrogen bond, π-π interaction, and electrostatic force. We further review the recent progress in constructing highly conductive molecular junctions via chemical reactions, the response of molecular junctions to external stimuli, as well as the application of break junction techniques in controlling and monitoring chemical reactions in situ. We suggest that beyond the measurement of single molecular conductance, the single-molecule break junction techniques provide a promising access to study molecular assembly and chemical reactions at the single-molecule scale.

At the Atrioventricular Crossroads: Dual Pathway Electrophysiology in the Atrioventricular Node and its Underlying Heterogeneities

PubMed Central

George, Sharon A; Faye, N Rokhaya; Murillo-Berlioz, Alejandro; Lee, K Benjamin; Trachiotis, Gregory D; Efimov, Igor R

2017-01-01

The atrioventricular node (AVN) is a complex structure that performs a variety of functions in the heart. The AVN is primarily an electrical gatekeeper between the atria and ventricles and introduces a delay between atrial and ventricular excitation, allowing for efficient ventricular filling. The AVN is composed of several compartments that safely transmit electrical excitation from the atria to the ventricles via the fast or slow pathways. There are many electrophysiological differences between these pathways, including conduction time and electrical refractoriness, that increase the predisposition of the atrioventricular junction to arrhythmias such as atrioventricular nodal re-entrant tachycardia. These varied electrophysiological characteristics of the fast and slow pathways stem from their unique structural and molecular composition (tissue and cellular geometry, ion channels and gap junctions). This review summarises the structural and molecular heterogeneities of the human AVN and how they result in electrophysiological variations and arrhythmias. PMID:29326832

Electronic Transport Properties of Carbon-Nanotube Networks: The Effect of Nitrate Doping on Intratube and Intertube Conductances

NASA Astrophysics Data System (ADS)

Ketolainen, T.; Havu, V.; Jónsson, E. Ö.; Puska, M. J.

2018-03-01

The conductivity of carbon-nanotube (CNT) networks can be improved markedly by doping with nitric acid. In the present work, CNTs and junctions of CNTs functionalized with NO3 molecules are investigated to understand the microscopic mechanism of nitric acid doping. According to our density-functional-theory band-structure calculations, there is charge transfer from the CNT to adsorbed molecules indicating p -type doping. The average doping efficiency of the NO3 molecules is higher if the NO3 molecules form complexes with water molecules. In addition to electron transport along individual CNTs, we also study electron transport between different types (metallic, semiconducting) of CNTs. Reflecting the differences in the electronic structures of semiconducting and metallic CNTs, we find that in addition to turning semiconducting CNTs metallic, doping further increases electron transport most efficiently along semiconducting CNTs as well as through the junctions between them.

A feedback mechanism converts individual cell features into a supracellular ECM structure in Drosophila trachea

PubMed Central

Öztürk-Çolak, Arzu; Moussian, Bernard; Araújo, Sofia J; Casanova, Jordi

2016-01-01

The extracellular matrix (ECM), a structure contributed to and commonly shared by many cells in an organism, plays an active role during morphogenesis. Here, we used the Drosophila tracheal system to study the complex relationship between the ECM and epithelial cells during development. We show that there is an active feedback mechanism between the apical ECM (aECM) and the apical F-actin in tracheal cells. Furthermore, we reveal that cell-cell junctions are key players in this aECM patterning and organisation and that individual cells contribute autonomously to their aECM. Strikingly, changes in the aECM influence the levels of phosphorylated Src42A (pSrc) at cell junctions. Therefore, we propose that Src42A phosphorylation levels provide a link for the ECM environment to ensure proper cytoskeletal organisation. DOI: http://dx.doi.org/10.7554/eLife.09373.001 PMID:26836303

Novel Handheld Magnetometer Probe Based on Magnetic Tunnelling Junction Sensors for Intraoperative Sentinel Lymph Node Identification

PubMed Central

Cousins, A.; Balalis, G. L.; Thompson, S. K.; Forero Morales, D.; Mohtar, A.; Wedding, A. B.; Thierry, B.

2015-01-01

Using magnetic tunnelling junction sensors, a novel magnetometer probe for the identification of the sentinel lymph node using magnetic tracers was developed. Probe performance was characterised in vitro and validated in a preclinical swine model. Compared to conventional gamma probes, the magnetometer probe showed excellent spatial resolution of 4.0 mm, and the potential to detect as few as 5 μg of magnetic tracer. Due to the high sensitivity of the magnetometer, all first-tier nodes were identified in the preclinical experiments, and there were no instances of false positive or false negative detection. Furthermore, these preliminary data encourage the application of the magnetometer probe for use in more complex lymphatic environments, such as in gastrointestinal cancers, where the sentinel node is often in close proximity to other non-sentinel nodes, and high spatial resolution detection is required. PMID:26038833

Hemichannels in neurodegenerative diseases: is there a link to pathology?

PubMed Central

Bosch, Megan; Kielian, Tammy

2014-01-01

Although originally considered a structural component of gap junctions, connexin hemichannels (HCs) are now recognized as functional entities capable of influencing metabolic gradients within the CNS, allowing direct communication between the intra- and extracellular milieus. Besides connexins, HCs can also be formed by pannexins, which are not capable of gap junction assembly. Both positive and negative effects have been attributed to HC activity in the context of neurodegenerative diseases. For example, HCs can exert neuroprotective effects by promoting the uptake of neurotoxic molecules, whereas chronic HC opening can disrupt molecular gradients leading to cellular dysfunction and death. The latter scenario has been suggested for multiple neurodegenerative disorders, including Alzheimer’s disease (AD) and more recently, lysosomal storage disorders, which are the focus of this perspective. Currently available evidence suggests a complex role for HCs in neurodegenerative disorders, which sets the stage for future studies to determine whether targeting HC action may improve disease outcomes. PMID:25191227

Hemichannel composition and electrical synaptic transmission: molecular diversity and its implications for electrical rectification

PubMed Central

Palacios-Prado, Nicolás; Huetteroth, Wolf; Pereda, Alberto E.

2014-01-01

Unapposed hemichannels (HCs) formed by hexamers of gap junction proteins are now known to be involved in various cellular processes under both physiological and pathological conditions. On the other hand, less is known regarding how differences in the molecular composition of HCs impact electrical synaptic transmission between neurons when they form intercellular heterotypic gap junctions (GJs). Here we review data indicating that molecular differences between apposed HCs at electrical synapses are generally associated with rectification of electrical transmission. Furthermore, this association has been observed at both innexin and connexin (Cx) based electrical synapses. We discuss the possible molecular mechanisms underlying electrical rectification, as well as the potential contribution of intracellular soluble factors to this phenomenon. We conclude that asymmetries in molecular composition and sensitivity to cellular factors of each contributing hemichannel can profoundly influence the transmission of electrical signals, endowing electrical synapses with more complex functional properties. PMID:25360082

Negative differential resistance observation in complex convoluted fullerene junctions

NASA Astrophysics Data System (ADS)

Kaur, Milanpreet; Sawhney, Ravinder Singh; Engles, Derick

2018-04-01

In this work, we simulated the smallest fullerene molecule, C20 in a two-probe device model with gold electrodes. The gold electrodes comprised of (011) miller planes were carved to construct the novel geometry based four unique shapes, which were strung to fullerene molecules through mechanically controlled break junction techniques. The organized devices were later scrutinized using non-equilibrium Green's function based on the density functional theory to calculate their molecular orbitals, energy levels, charge transfers, and electrical parameters. After intense scrutiny, we concluded that five-edged and six-edged devices have the lowest and highest current-conductance values, which result from their electrode-dominating and electrode-subsidiary effects, respectively. However, an interesting observation was that the three-edged and four-edged electrodes functioned as semi-metallic in nature, allowing the C20 molecule to demonstrate its performance with the complementary effect of these electrodes in the electron conduction process of a two-probe device.

The need for control of magnetic parameters for energy efficient performance of magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Farhat, I. A. H.; Gale, E.; Alpha, C.; Isakovic, A. F.

2017-07-01

Optimizing energy performance of Magnetic Tunnel Junctions (MTJs) is the key for embedding Spin Transfer Torque-Random Access Memory (STT-RAM) in low power circuits. Due to the complex interdependencies of the parameters and variables of the device operating energy, it is important to analyse parameters with most effective control of MTJ power. The impact of threshold current density, Jco , on the energy and the impact of HK on Jco are studied analytically, following the expressions that stem from Landau-Lifshitz-Gilbert-Slonczewski (LLGS-STT) model. In addition, the impact of other magnetic material parameters, such as Ms , and geometric parameters such as tfree and λ is discussed. Device modelling study was conducted to analyse the impact at the circuit level. Nano-magnetism simulation based on NMAGTM package was conducted to analyse the impact of controlling HK on the switching dynamics of the film.

Steady-state currents in p-n junction filaments or grains in case of large surface recombination velocities at lateral surfaces

NASA Technical Reports Server (NTRS)

Von Roos, O.; Lindholm, F. A.

1985-01-01

Recently it has been pointed out that the saturation current of a semiconductor filament which constitutes part of a p-n junction diverges when the surface recombination velocity at the faces become infinitely large. Here it is pointed out that this is to be expected on physical grounds since, whenever the carrier concentration is kept off equilibrium by an outside agent, and at the same time recombination lifetimes in the bulk or in surface layers tend to zero, concentration gradients tend to infinity. As also previously noted, the situation can be remedied by using realistic (finite) surface recombination velocities in model calculations. However, this procedure leads to mathematical complexities which have been circumvented recently by the introduction of a heuristic approach. It is the aim of this paper to assess the validity of the heuristic approach by means of detailed and exact calculations.

Managing the complexity of communication: regulation of gap junctions by post-translational modification

PubMed Central

Axelsen, Lene N.; Calloe, Kirstine; Holstein-Rathlou, Niels-Henrik; Nielsen, Morten S.

2013-01-01

Gap junctions are comprised of connexins that form cell-to-cell channels which couple neighboring cells to accommodate the exchange of information. The need for communication does, however, change over time and therefore must be tightly controlled. Although the regulation of connexin protein expression by transcription and translation is of great importance, the trafficking, channel activity and degradation are also under tight control. The function of connexins can be regulated by several post translational modifications, which affect numerous parameters; including number of channels, open probability, single channel conductance or selectivity. The most extensively investigated post translational modifications are phosphorylations, which have been documented in all mammalian connexins. Besides phosphorylations, some connexins are known to be ubiquitinated, SUMOylated, nitrosylated, hydroxylated, acetylated, methylated, and γ-carboxyglutamated. The aim of the present review is to summarize our current knowledge of post translational regulation of the connexin family of proteins. PMID:24155720

Optic Atrophy 1 Is Epistatic to the Core MICOS Component MIC60 in Mitochondrial Cristae Shape Control.

PubMed

Glytsou, Christina; Calvo, Enrique; Cogliati, Sara; Mehrotra, Arpit; Anastasia, Irene; Rigoni, Giovanni; Raimondi, Andrea; Shintani, Norihito; Loureiro, Marta; Vazquez, Jesùs; Pellegrini, Luca; Enriquez, Jose Antonio; Scorrano, Luca; Soriano, Maria Eugenia

2016-12-13

The mitochondrial contact site and cristae organizing system (MICOS) and Optic atrophy 1 (OPA1) control cristae shape, thus affecting mitochondrial function and apoptosis. Whether and how they physically and functionally interact is unclear. Here, we provide evidence that OPA1 is epistatic to MICOS in the regulation of cristae shape. Proteomic analysis identifies multiple MICOS components in native OPA1-containing high molecular weight complexes disrupted during cristae remodeling. MIC60, a core MICOS protein, physically interacts with OPA1, and together, they control cristae junction number and stability, OPA1 being epistatic to MIC60. OPA1 defines cristae width and junction diameter independently of MIC60. Our combination of proteomics, biochemistry, genetics, and electron tomography provides a unifying model for mammalian cristae biogenesis by OPA1 and MICOS. Copyright © 2016 The Author(s). Published by Elsevier Inc. All rights reserved.

Negative differential resistance and switch behavior of T-BxNy (x, y = 5, 6, 11) molecular junctions

NASA Astrophysics Data System (ADS)

Wang, Shi-Liang; Yang, Chuan-Lu; Wang, Mei-Shan; Ma, Xiao-Guang; Xin, Jian-Guo

2017-05-01

The electronic transport properties of T-BxNy (x, y = 5, 6, 11) molecular junction are investigated based on first-principle density functional theory and non-equilibrium Green's function method. Strong negative differential resistance (NDR) behavior is observed for T-B5N6 molecule under negative and positive bias voltages, with an obvious switch effect for T-B6N5. However, only small NDR is shown for the complex of the two molecules. The projected device density of states, the spatial distribution of molecular orbitals, and the effect of transmission spectra under various bias voltages on the electronic transport properties are analyzed. The obvious effect of bias voltage on the changes in the electronic distribution of frontier molecular orbitals is responsible for the NDR or switch behavior. Therefore, different functional molecular devices can be obtained with different structures of T-BxNy.

Features specific to retinal pigment epithelium cells derived from three-dimensional human embryonic stem cell cultures - a new donor for cell therapy.

PubMed

Wu, Wei; Zeng, Yuxiao; Li, Zhengya; Li, Qiyou; Xu, Haiwei; Yin, Zheng Qin

2016-04-19

Retinal pigment epithelium (RPE) transplantation is a particularly promising treatment of retinal degenerative diseases affecting RPE-photoreceptor complex. Embryonic stem cells (ESCs) provide an abundant donor source for RPE transplantation. Herein, we studied the time-course characteristics of RPE cells derived from three-dimensional human ESCs cultures (3D-RPE). We showed that 3D-RPE cells possessed morphology, ultrastructure, gene expression profile, and functions of authentic RPE. As differentiation proceeded, 3D-RPE cells could mature gradually with decreasing proliferation but increasing functions. Besides, 3D-RPE cells could form polarized monolayer with functional tight junction and gap junction. When grafted into the subretinal space of Royal College of Surgeons rats, 3D-RPE cells were safe and efficient to rescue retinal degeneration. This study showed that 3D-RPE cells were a new donor for cell therapy of retinal degenerative diseases.

Gap-junctional channel and hemichannel activity of two recently identified connexin 26 mutants associated with deafness.

PubMed

Dalamon, Viviana; Fiori, Mariana C; Figueroa, Vania A; Oliva, Carolina A; Del Rio, Rodrigo; Gonzalez, Wendy; Canan, Jonathan; Elgoyhen, Ana B; Altenberg, Guillermo A; Retamal, Mauricio A

2016-05-01

Gap-junction channels (GJCs) are formed by head-to-head association of two hemichannels (HCs, connexin hexamers). HCs and GJCs are permeable to ions and hydrophilic molecules of up to Mr ~1 kDa. Hearing impairment of genetic origin is common, and mutations of connexin 26 (Cx26) are its major cause. We recently identified two novel Cx26 mutations in hearing-impaired subjects, L10P and G109V. L10P forms functional GJCs with slightly altered voltage dependence and HCs with decrease ATP/cationic dye selectivity. G109V does not form functional GJCs, but forms functional HCs with enhanced extracellular Ca(2+) sensitivity and subtle alterations in voltage dependence and ATP/cationic dye selectivity. Deafness associated with G109V could result from decreased GJCs activity, whereas deafness associated to L10P may have a more complex mechanism that involves changes in HC permeability.

Monolithic multi-color light emission/detection device

DOEpatents

Wanlass, Mark W.

1995-01-01

A single-crystal, monolithic, tandem, multi-color optical transceiver device is described, including (a) an InP substrate having upper and lower surfaces, (b) a first junction on the upper surface of the InP substrate, (c) a second junction on the first junction. The first junction is preferably GaInAsP of defined composition, and the second junction is preferably InP. The two junctions are lattice matched. The second junction has a larger energy band gap than the first junction. Additional junctions having successively larger energy band gaps may be included. The device is capable of simultaneous and distinct multi-color emission and detection over a single optical fiber.

Electronic thermometry in tunable tunnel junction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maksymovych, Petro

A tunable tunnel junction thermometry circuit includes a variable width tunnel junction between a test object and a probe. The junction width is varied and a change in thermovoltage across the junction with respect to the change in distance across the junction is determined. Also, a change in biased current with respect to a change in distance across the junction is determined. A temperature gradient across the junction is determined based on a mathematical relationship between the temperature gradient, the change in thermovoltage with respect to distance and the change in biased current with respect to distance. Thermovoltage may bemore » measured by nullifying a thermoelectric tunneling current with an applied voltage supply level. A piezoelectric actuator may modulate the probe, and thus the junction width, to vary thermovoltage and biased current across the junction. Lock-in amplifiers measure the derivatives of the thermovoltage and biased current modulated by varying junction width.« less

Simultaneous antegrade/retrograde upper urinary tract access: Bart's modified lateral position for complex upper tract endourologic pathologic features.

PubMed

Moraitis, Konstantinos; Philippou, Prodromos; El-Husseiny, Tamer; Wazait, Hassan; Masood, Junaid; Buchholz, Noor

2012-02-01

To determine whether the Bart's modified lateral position is safe and effective for achieving simultaneous anterograde and retrograde access in complex upper urinary tract pathologic features. From November 2006 to September 2010, 45 procedures were performed, with the patients in the modified lateral position. The indication for these procedures was the presence of complex unilateral upper urinary tract pathologic features. The patients with muscular and/or skeletal abnormalities were excluded. All procedures were performed using simultaneous anterograde and retrograde access with the patient under general anesthesia. The preoperative investigation protocol included assessment of the stone burden and location using enhanced abdominal computed tomography. The patients were routinely examined 6 weeks after the procedure with a combination of plain abdominal radiography and renal ultrasonography. For patients treated for conditions causing upper urinary tract obstruction (pelviureteral junction obstruction and/or ureteral strictures), a mercaptoacetyltriglycine renography was performed at 4, 12, and 24 months postoperatively. The mean patient age was 51.2 years (range 17-79). Stone clearance was achieved by a single combined procedure in 36 patients (80%). Successful recanalization was achieved in all patients with pelviureteral junction obstruction and ureteral strictures. In 4 patients (8.8%), persistent hematuria was noted, and 2 patients (4.4%) developed postoperative urinary sepsis and were treated conservatively. Modification to the lateral position compares equally with contemporary percutaneous nephrolithotomy series. It provides wide exposure of the flank, allowing the choice of multiple access sites, enhanced control, and a wide angle for handling of the antegrade instruments. Two surgeons can work simultaneously, addressing complex endourologic pathologic features in high-risk patients. Copyright © 2012. Published by Elsevier Inc.

The EhCPADH112 Complex of Entamoeba histolytica Interacts with Tight Junction Proteins Occludin and Claudin-1 to Produce Epithelial Damage

PubMed Central

Betanzos, Abigail; Javier-Reyna, Rosario; García-Rivera, Guillermina; Bañuelos, Cecilia; González-Mariscal, Lorenza; Schnoor, Michael; Orozco, Esther

2013-01-01

Entamoeba histolytica, the protozoan responsible for human amoebiasis, causes between 30,000 and 100,000 deaths per year worldwide. Amoebiasis is characterized by intestinal epithelial damage provoking severe diarrhea. However, the molecular mechanisms by which this protozoan causes epithelial damage are poorly understood. Here, we studied the initial molecular interactions between the E. histolytica EhCPADH112 virulence complex and epithelial MDCK and Caco-2 cells. By confocal microscopy, we discovered that after contact with trophozoites or trophozoite extracts (TE), EhCPADH112 and proteins forming this complex (EhCP112 and EhADH112) co-localize with occludin and claudin-1 at tight junctions (TJ). Immunoprecipitation assays revealed interaction between EhCPADH112 and occludin, claudin-1, ZO-1 and ZO-2. Overlay assays confirmed an interaction of EhCP112 and EhADH112 with occludin and claudin-1, whereas only EhADH112 interacted also with ZO-2. We observed degradation of all mentioned TJ proteins after incubation with TE. Importantly, inhibiting proteolytic activity or blocking the complex with a specific antibody not only prevented TJ protein degradation but also epithelial barrier disruption. Furthermore, we discovered that TE treatment induces autophagy and apoptosis in MDCK cells that could contribute to the observed barrier disruption. Our results suggest a model in which epithelial damage caused by E. histolytica is initiated by the interaction of EhCP112 and EhADH112 with TJ proteins followed by their degradation. Disruption of TJs then induces increased paracellular permeability, thus facilitating the entry of more proteases and other parasite molecules leading eventually to tissue destruction. PMID:23762290

Magnesium Lowers the Incidence of Postoperative Junctional Ectopic Tachycardia in Congenital Heart Surgical Patients: Is There a Relationship to Surgical Procedure Complexity?

PubMed Central

He, Dingchao; Sznycer-Taub, Nathaniel; Cheng, Yao; McCarter, Robert; Jonas, Richard A.; Hanumanthaiah, Sridhar; Moak, Jeffrey P.

2015-01-01

Magnesium sulfate was given to pediatric cardiac surgical patients during cardiopulmonary bypass period in an attempt to reduce the occurrence of postoperative junctional ectopic tachycardia (PO JET). We reviewed our data to evaluate the effect of magnesium on the occurrence of JET and assess a possible relationship between PO JET and procedure complexity. A total of 1088 congenital heart surgeries (CHS), performed from 2005 to 2010, were reviewed. A total of 750 cases did not receive magnesium, and 338 cases received magnesium (25 mg/kg). All procedures were classified according to Aristotle score from 1 to 4. Overall, there was a statistically significant decrease in PO JET occurrence between the two groups regardless of the Aristotle score, 15.3 % (115/750) in non-magnesium group versus 7.1 % (24/338) in magnesium group, P < 0.001. In the absence of magnesium, the risk of JET increased with increasing Aristotle score, P = 0.01. Following magnesium administration and controlling for body weight, surgical and aortic cross-clamp times in the analyses, reduction in adjusted risk of JET was significantly greater with increasing Aristotle level of complexity (JET in non-magnesium vs. magnesium group, Aristotle level 1: 9.8 vs. 14.3 %, level 4: 11.5 vs. 3.2 %; odds ratio 0.54, 95 % CI 0.31–0.94, P = 0.028). Our data confirmed that intra-operative usage of magnesium reduced the occurrence of PO JET in a larger number and more diverse group of CHS patients than has previously been reported. Further, our data suggest that magnesium’s effect on PO JET occurrence seemed more effective in CHS with higher levels of Aristotle complexity. PMID:25762470

Export of a Toxoplasma gondii Rhoptry Neck Protein Complex at the Host Cell Membrane to Form the Moving Junction during Invasion

PubMed Central

Poncet, Joël; Dubremetz, Jean-François; Lebrun, Maryse

2009-01-01

One of the most conserved features of the invasion process in Apicomplexa parasites is the formation of a moving junction (MJ) between the apex of the parasite and the host cell membrane that moves along the parasite and serves as support to propel it inside the host cell. The MJ was, up to a recent period, completely unknown at the molecular level. Recently, proteins originated from two distinct post-Golgi specialised secretory organelles, the micronemes (for AMA1) and the neck of the rhoptries (for RON2/RON4/RON5 proteins), have been shown to form a complex. AMA1 and RON4 in particular, have been localised to the MJ during invasion. Using biochemical approaches, we have identified RON8 as an additional member of the complex. We also demonstrated that all RON proteins are present at the MJ during invasion. Using metabolic labelling and immunoprecipitation, we showed that RON2 and AMA1 were able to interact in the absence of the other members. We also discovered that all MJ proteins are subjected to proteolytic maturation during trafficking to their respective organelles and that they could associate as non-mature forms in vitro. Finally, whereas AMA1 has previously been shown to be inserted into the parasite membrane upon secretion, we demonstrated, using differential permeabilization and loading of RON-specific antibodies into the host cell, that the RON complex is targeted to the host cell membrane, where RON4/5/8 remain associated with the cytoplasmic face. Globally, these results point toward a model of MJ organization where the parasite would be secreting and inserting interacting components on either side of the MJ, both at the host and at its own plasma membranes. PMID:19247437

WAVE2 Regulates Epithelial Morphology and Cadherin Isoform Switching through Regulation of Twist and Abl

PubMed Central

Bryce, Nicole S.; Reynolds, Albert B.; Koleske, Anthony J.; Weaver, Alissa M.

2013-01-01

Background Epithelial morphogenesis is a dynamic process that involves coordination of signaling and actin cytoskeletal rearrangements. Principal Findings We analyzed the contribution of the branched actin regulator WAVE2 in the development of 3-dimensional (3D) epithelial structures. WAVE2-knockdown (WAVE2-KD) cells formed large multi-lobular acini that continued to proliferate at an abnormally late stage compared to control acini. Immunostaining of the cell-cell junctions of WAVE2-KD acini revealed weak and heterogeneous E-cadherin staining despite little change in actin filament localization to the same junctions. Analysis of cadherin expression demonstrated a decrease in E-cadherin and an increase in N-cadherin protein and mRNA abundance in total cell lysates. In addition, WAVE2-KD cells exhibited an increase in the mRNA levels of the epithelial-mesenchymal transition (EMT)-associated transcription factor Twist1. KD of Twist1 expression in WAVE2-KD cells reversed the cadherin switching and completely rescued the aberrant 3D morphological phenotype. Activity of the WAVE2 complex binding partner Abl kinase was also increased in WAVE2-KD cells, as assessed by tyrosine phosphorylation of the Abl substrate CrkL. Inhibition of Abl with STI571 rescued the multi-lobular WAVE2-KD 3D phenotype whereas overexpression of Abl kinase phenocopied the WAVE2-KD phenotype. Conclusions The WAVE2 complex regulates breast epithelial morphology by a complex mechanism involving repression of Twist1 expression and Abl kinase activity. These data reveal a critical role for WAVE2 complex in regulation of cellular signaling and epithelial morphogenesis. PMID:23691243

The armadillo repeat region targets ARVCF to cadherin-based cellular junctions.

PubMed

Kaufmann, U; Zuppinger, C; Waibler, Z; Rudiger, M; Urbich, C; Martin, B; Jockusch, B M; Eppenberger, H; Starzinski-Powitz, A

2000-11-01

The cytoplasmic domain of the transmembrane protein M-cadherin is involved in anchoring cytoskeletal elements to the plasma membrane at cell-cell contact sites. Several members of the armadillo repeat protein family mediate this linkage. We show here that ARVCF, a member of the p120 (ctn) subfamily, is a ligand for the cytoplasmic domain of M-cadherin, and characterize the regions involved in this interaction in detail. Complex formation in an in vivo environment was demonstrated in (1) yeast two-hybrid screens, using a cDNA library from differentiating skeletal muscle and part of the cytoplasmic M-cadherin tail as a bait, and (2) mammalian cells, using a novel experimental system, the MOM recruitment assay. Immunoprecipitation and in vitro binding assays confirmed this interaction. Ectopically expressed EGFP-ARVCF-C11, an N-terminal truncated fragment, targets to junctional structures in epithelial MCF7 cells and cardiomyocytes, where it colocalizes with the respective cadherins, beta-catenin and p120 (ctn). Hence, the N terminus of ARVCF is not required for junctional localization. In contrast, deletion of the four N-terminal armadillo repeats abolishes this ability in cardiomyocytes. Detailed mutational analysis revealed the armadillo repeat region of ARVCF as sufficient and necessary for interaction with the 55 membrane-proximal amino acids of the M-cadherin tail.

Molecular mechanisms of cell-cell spread of intracellular bacterial pathogens.

PubMed

Ireton, Keith

2013-07-17

Several bacterial pathogens, including Listeria monocytogenes, Shigella flexneri and Rickettsia spp., have evolved mechanisms to actively spread within human tissues. Spreading is initiated by the pathogen-induced recruitment of host filamentous (F)-actin. F-actin forms a tail behind the microbe, propelling it through the cytoplasm. The motile pathogen then encounters the host plasma membrane, forming a bacterium-containing protrusion that is engulfed by an adjacent cell. Over the past two decades, much progress has been made in elucidating mechanisms of F-actin tail formation. Listeria and Shigella produce tails of branched actin filaments by subverting the host Arp2/3 complex. By contrast, Rickettsia forms tails with linear actin filaments through a bacterial mimic of eukaryotic formins. Compared with F-actin tail formation, mechanisms controlling bacterial protrusions are less well understood. However, recent findings have highlighted the importance of pathogen manipulation of host cell-cell junctions in spread. Listeria produces a soluble protein that enhances bacterial protrusions by perturbing tight junctions. Shigella protrusions are engulfed through a clathrin-mediated pathway at 'tricellular junctions'--specialized membrane regions at the intersection of three epithelial cells. This review summarizes key past findings in pathogen spread, and focuses on recent developments in actin-based motility and the formation and internalization of bacterial protrusions.

Neuroglian, Gliotactin, and the Na+/K+ ATPase are essential for septate junction function in Drosophila

PubMed Central

Genova, Jennifer L.; Fehon, Richard G.

2003-01-01

One essential function of epithelia is to form a barrier between the apical and basolateral surfaces of the epithelium. In vertebrate epithelia, the tight junction is the primary barrier to paracellular flow across epithelia, whereas in invertebrate epithelia, the septate junction (SJ) provides this function. In this study, we identify new proteins that are required for a functional paracellular barrier in Drosophila. In addition to the previously known components Coracle (COR) and Neurexin (NRX), we show that four other proteins, Gliotactin, Neuroglian (NRG), and both the α and β subunits of the Na+/K+ ATPase, are required for formation of the paracellular barrier. In contrast to previous reports, we demonstrate that the Na pump is not localized basolaterally in epithelial cells, but instead is concentrated at the SJ. Data from immunoprecipitation and somatic mosaic studies suggest that COR, NRX, NRG, and the Na+/K+ ATPase form an interdependent complex. Furthermore, the observation that NRG, a Drosophila homologue of vertebrate neurofascin, is an SJ component is consistent with the notion that the invertebrate SJ is homologous to the vertebrate paranodal SJ. These findings have implications not only for invertebrate epithelia and barrier functions, but also for understanding of neuron–glial interactions in the mammalian nervous system. PMID:12782686

Neuroglian, Gliotactin, and the Na+/K+ ATPase are essential for septate junction function in Drosophila.

PubMed

Genova, Jennifer L; Fehon, Richard G

2003-06-09

One essential function of epithelia is to form a barrier between the apical and basolateral surfaces of the epithelium. In vertebrate epithelia, the tight junction is the primary barrier to paracellular flow across epithelia, whereas in invertebrate epithelia, the septate junction (SJ) provides this function. In this study, we identify new proteins that are required for a functional paracellular barrier in Drosophila. In addition to the previously known components Coracle (COR) and Neurexin (NRX), we show that four other proteins, Gliotactin, Neuroglian (NRG), and both the alpha and beta subunits of the Na+/K+ ATPase, are required for formation of the paracellular barrier. In contrast to previous reports, we demonstrate that the Na pump is not localized basolaterally in epithelial cells, but instead is concentrated at the SJ. Data from immunoprecipitation and somatic mosaic studies suggest that COR, NRX, NRG, and the Na+/K+ ATPase form an interdependent complex. Furthermore, the observation that NRG, a Drosophila homologue of vertebrate neurofascin, is an SJ component is consistent with the notion that the invertebrate SJ is homologous to the vertebrate paranodal SJ. These findings have implications not only for invertebrate epithelia and barrier functions, but also for understanding of neuron-glial interactions in the mammalian nervous system.

Actomyosin tension is required for correct recruitment of adherens junction components and zonula occludens formation.

PubMed

Miyake, Yuka; Inoue, Naoko; Nishimura, Koji; Kinoshita, Nagatoki; Hosoya, Hiroshi; Yonemura, Shigenobu

2006-05-15

The adherens junction (AJ) densely associated with actin filaments is a major cell-cell adhesion structure. To understand the importance of actin filament association in AJ formation, we first analyzed punctate AJs in NRK fibroblasts where one actin cable binds to one AJ structure unit. The accumulation of AJ components such as the cadherin/catenin complex and vinculin, as well as the formation of AJ-associated actin cables depended on Rho activity. Inhibitors for the Rho target, ROCK, which regulates myosin II activity, and for myosin II ATPase prevented the accumulation of AJ components, indicating that myosin II activity is more directly involved than Rho activity. Depletion of myosin II by RNAi showed similar results. The inhibition of myosin II activity in polarized epithelial MTD-1A cells affected the accumulation of vinculin to circumferential AJ (zonula adherens). Furthermore, correct zonula occludens (tight junction) formation along the apicobasal axis that requires cadherin activity was also impaired. Although MDCK cells which are often used as typical epithelial cells do not have a typical zonula adherens, punctate AJs formed dependently on myosin II activity by inducing wound closure in a MDCK cell sheet. These findings suggest that tension generated by actomyosin is essential for correct AJ assembly.

Crumbs3 Is Essential for Proper Epithelial Development and Viability

PubMed Central

Whiteman, Eileen L.; Fan, Shuling; Harder, Jennifer L.; Walton, Katherine D.; Liu, Chia-Jen; Soofi, Abdul; Fogg, Vanessa C.; Hershenson, Marc B.; Dressler, Gregory R.; Deutsch, Gail H.; Gumucio, Deborah L.

2014-01-01

First identified in Drosophila, the Crumbs (Crb) proteins are important in epithelial polarity, apical membrane formation, and tight junction (TJ) assembly. The conserved Crb intracellular region includes a FERM (band 4.1/ezrin/radixin/moesin) binding domain (FBD) whose mammalian binding partners are not well understood and a PDZ binding motif that interacts with mammalian Pals1 (protein associated with lin seven) (also known as MPP5). Pals1 binds Patj (Pals1-associated tight-junction protein), a multi-PDZ-domain protein that associates with many tight junction proteins. The Crb complex also binds the conserved Par3/Par6/atypical protein kinase C (aPKC) polarity cassette that restricts migration of basolateral proteins through phosphorylation. Here, we describe a Crb3 knockout mouse that demonstrates extensive defects in epithelial morphogenesis. The mice die shortly after birth, with cystic kidneys and proteinaceous debris throughout the lungs. The intestines display villus fusion, apical membrane blebs, and disrupted microvilli. These intestinal defects phenocopy those of Ezrin knockout mice, and we demonstrate an interaction between Crumbs3 and ezrin. Taken together, our data indicate that Crumbs3 is crucial for epithelial morphogenesis and plays a role in linking the apical membrane to the underlying ezrin-containing cytoskeleton. PMID:24164893

Endocochlear potential generation is associated with intercellular communication in the stria vascularis: structural analysis in the viable dominant spotting mouse mutant.

PubMed

Carlisle, L; Steel, K; Forge, A

1990-11-01

Deafness in the viable dominant spotting mouse mutant is due to a primary defect of the stria vascularis which results in absence of the positive endocochlear potential in scala media. Endocochlear potentials were measured and the structure of stria vascularis of mutants with potentials close to zero was compared with that in normal littermate controls by use of morphometric methods. The stria vascularis was significantly thinner in mutants. Marginal cells were not significantly different from controls in terms of volume density or intramembrane particle density but the network density of tight junctions was significantly reduced in the mutants. A virtual absence of gap junctions between basal cells and marginal or intermediate cells was observed, but intramembrane particle density and junctional complexes between adjacent basal cells were not different from controls. The volume density of basal cells was significantly greater in mutants. Intermediate cells accounted for a significantly smaller volume density of the stria vascularis in mutants and had a lower density of intramembrane particles than controls. Melanocytes were not identified in the stria vascularis of mutants. These results suggest that communication between marginal, intermediate and basal cells might be important to the normal function of the stria vascularis.

Ultralow power artificial synapses using nanotextured magnetic Josephson junctions.

PubMed

Schneider, Michael L; Donnelly, Christine A; Russek, Stephen E; Baek, Burm; Pufall, Matthew R; Hopkins, Peter F; Dresselhaus, Paul D; Benz, Samuel P; Rippard, William H

2018-01-01

Neuromorphic computing promises to markedly improve the efficiency of certain computational tasks, such as perception and decision-making. Although software and specialized hardware implementations of neural networks have made tremendous accomplishments, both implementations are still many orders of magnitude less energy efficient than the human brain. We demonstrate a new form of artificial synapse based on dynamically reconfigurable superconducting Josephson junctions with magnetic nanoclusters in the barrier. The spiking energy per pulse varies with the magnetic configuration, but in our demonstration devices, the spiking energy is always less than 1 aJ. This compares very favorably with the roughly 10 fJ per synaptic event in the human brain. Each artificial synapse is composed of a Si barrier containing Mn nanoclusters with superconducting Nb electrodes. The critical current of each synapse junction, which is analogous to the synaptic weight, can be tuned using input voltage spikes that change the spin alignment of Mn nanoclusters. We demonstrate synaptic weight training with electrical pulses as small as 3 aJ. Further, the Josephson plasma frequencies of the devices, which determine the dynamical time scales, all exceed 100 GHz. These new artificial synapses provide a significant step toward a neuromorphic platform that is faster, more energy-efficient, and thus can attain far greater complexity than has been demonstrated with other technologies.

Inhibition of β-Glucocerebrosidase Activity Preserves Motor Unit Integrity in a Mouse Model of Amyotrophic Lateral Sclerosis.

PubMed

Henriques, Alexandre; Huebecker, Mylene; Blasco, Hélène; Keime, Céline; Andres, Christian R; Corcia, Philippe; Priestman, David A; Platt, Frances M; Spedding, Michael; Loeffler, Jean-Philippe

2017-07-12

Recent metabolomic reports connect dysregulation of glycosphingolipids, particularly ceramide and glucosylceramide, to neurodegeneration and to motor unit dismantling in amyotrophic lateral sclerosis at late disease stage. We report here altered levels of gangliosides in the cerebrospinal fluid of amyotrophic lateral sclerosis patients in early disease stage. Conduritol B epoxide is an inhibitor of acid beta-glucosidase, and lowers glucosylceramide degradation. Glucosylceramide is the precursor for all of the more complex glycosphingolipids. In SOD1 G86R mice, an animal model of amyotrophic lateral sclerosis, conduritol B epoxide preserved ganglioside distribution at the neuromuscular junction, delayed disease onset, improved motor function and preserved motor neurons as well as neuromuscular junctions from degeneration. Conduritol B epoxide mitigated gene dysregulation in the spinal cord and restored the expression of genes involved in signal transduction and axonal elongation. Inhibition of acid beta-glucosidase promoted faster axonal elongation in an in vitro model of neuromuscular junctions and hastened recovery after peripheral nerve injury in wild type mice. Here, we provide evidence that glycosphingolipids play an important role in muscle innervation, which degenerates in amyotrophic lateral sclerosis from the early disease stage. This is a first proof of concept study showing that modulating the catabolism of glucosylceramide may be a therapeutic target for this devastating disease.

An unusual colon atresia in a calf: at the junction of the distal loop and transverse colon. A brief overview

PubMed Central

Lombardero, Matilde; Yllera, María del Mar

2014-01-01

Congenital defects are those abnormalities present at birth. During embryogenesis, many anomalies can occur. The primitive gut tube lengthens quickly and rotates, allowing the gastrointestinal tract acquire its final position and orientation. Because the colon of large animals is complex, most changes occur in this segment. Thus, in ruminants, colon atresia is the most frequent malformation, affecting mainly ascending colon, at the level of the spiral loop. There are no previous references about a very atypical colon atresia at the junction of distal loop and transverse colon, such we have described in a 5-day-old calf, after a history of abdominal distention and absence of feces at birth, even with a patent anal opening. Atresia coli was detected at distal position of the typical colon atresia, at the junction of distal loop and transverse colon. In addition, the distal blind end was bent into a U-shape supported by the mesocolon. Besides the anatomical findings of this worthwhile atresia coli we discuss its possible etiology, in which local factors, such as a compromised blood supply during embryogenesis, are more consistent than genetic factors. Finding out the causes of atresia coli would help to reduce its incidence, lessen animal suffering and economic loss. PMID:25495264

Ultralow power artificial synapses using nanotextured magnetic Josephson junctions

PubMed Central

Schneider, Michael L.; Donnelly, Christine A.; Russek, Stephen E.; Baek, Burm; Pufall, Matthew R.; Hopkins, Peter F.; Dresselhaus, Paul D.; Benz, Samuel P.; Rippard, William H.

2018-01-01

Neuromorphic computing promises to markedly improve the efficiency of certain computational tasks, such as perception and decision-making. Although software and specialized hardware implementations of neural networks have made tremendous accomplishments, both implementations are still many orders of magnitude less energy efficient than the human brain. We demonstrate a new form of artificial synapse based on dynamically reconfigurable superconducting Josephson junctions with magnetic nanoclusters in the barrier. The spiking energy per pulse varies with the magnetic configuration, but in our demonstration devices, the spiking energy is always less than 1 aJ. This compares very favorably with the roughly 10 fJ per synaptic event in the human brain. Each artificial synapse is composed of a Si barrier containing Mn nanoclusters with superconducting Nb electrodes. The critical current of each synapse junction, which is analogous to the synaptic weight, can be tuned using input voltage spikes that change the spin alignment of Mn nanoclusters. We demonstrate synaptic weight training with electrical pulses as small as 3 aJ. Further, the Josephson plasma frequencies of the devices, which determine the dynamical time scales, all exceed 100 GHz. These new artificial synapses provide a significant step toward a neuromorphic platform that is faster, more energy-efficient, and thus can attain far greater complexity than has been demonstrated with other technologies. PMID:29387787

Monolithic multi-color light emission/detection device

DOEpatents

Wanlass, M.W.

1995-02-21

A single-crystal, monolithic, tandem, multi-color optical transceiver device is described, including (a) an InP substrate having upper and lower surfaces, (b) a first junction on the upper surface of the InP substrate, (c) a second junction on the first junction. The first junction is preferably GaInAsP of defined composition, and the second junction is preferably InP. The two junctions are lattice matched. The second junction has a larger energy band gap than the first junction. Additional junctions having successively larger energy band gaps may be included. The device is capable of simultaneous and distinct multi-color emission and detection over a single optical fiber. 5 figs.

Surface obstacles in pulsatile flow

NASA Astrophysics Data System (ADS)

Carr, Ian A.; Plesniak, Michael W.

2016-11-01

Flows past obstacles mounted on flat surfaces have been widely studied due to their ubiquity in nature and engineering. For nearly all of these studies, the freestream flow over the obstacle was steady, i.e. constant velocity unidirectional flow. Unsteady, pulsatile flows occur frequently in biology, geophysics, biomedical engineering, etc. Our study is aimed at extending the comprehensive knowledge base that exists for steady flows to considerably more complex pulsatile flows. Beyond the important practical applications, characterizing the vortex and wake dynamics of flows around surface obstacles embedded in pulsatile flows can provide insights into the underlying physics in all wake and junction flows. In this study, we experimentally investigated the wake of four canonical surface obstacles: hemisphere, cube, and circular cylinders with aspect ratio of 1:1 and 2:1. Phase-averaged PIV and hot-wire anemometry are used to characterize the dynamics of coherent structures in the wake and at the windward junction of the obstacles. Complex physics occur during the deceleration phase of the pulsatile inflow. We propose a framework for understanding these physics based on self-induced vortex propagation, similar to the phenomena exhibited by vortex rings. This material is based in part upon work supported by the National Science Foundation under Grant Number CBET-1236351, and GW Centeor Biomimetics and Bioinspired Engineering (COBRE).

A Point Mutation in the Exon Junction Complex Factor Y14 Disrupts Its Function in mRNA Cap Binding and Translation Enhancement*

PubMed Central

Chuang, Tzu-Wei; Lee, Kuo-Ming; Lou, Yuan-Chao; Lu, Chia-Chen; Tarn, Woan-Yuh

2016-01-01

Eukaryotic mRNA biogenesis involves a series of interconnected steps mediated by RNA-binding proteins. The exon junction complex core protein Y14 is required for nonsense-mediated mRNA decay (NMD) and promotes translation. Moreover, Y14 binds the cap structure of mRNAs and inhibits the activity of the decapping enzyme Dcp2. In this report, we show that an evolutionarily conserved tryptophan residue (Trp-73) of Y14 is critical for its binding to the mRNA cap structure. A Trp-73 mutant (W73V) bound weakly to mRNAs and failed to protect them from degradation. However, this mutant could still interact with the NMD and mRNA degradation factors and retained partial NMD activity. In addition, we found that the W73V mutant could not interact with translation initiation factors. Overexpression of W73V suppressed reporter mRNA translation in vitro and in vivo and reduced the level of a set of nascent proteins. These results reveal a residue of Y14 that confers cap-binding activity and is essential for Y14-mediated enhancement of translation. Finally, we demonstrated that Y14 may selectively and differentially modulate protein biosynthesis. PMID:26887951

Purification of complex samples: Implementation of a modular and reconfigurable droplet-based microfluidic platform with cascaded deterministic lateral displacement separation modules

PubMed Central

Pudda, Catherine; Boizot, François; Verplanck, Nicolas; Revol-Cavalier, Frédéric; Berthier, Jean; Thuaire, Aurélie

2018-01-01

Particle separation in microfluidic devices is a common problematic for sample preparation in biology. Deterministic lateral displacement (DLD) is efficiently implemented as a size-based fractionation technique to separate two populations of particles around a specific size. However, real biological samples contain components of many different sizes and a single DLD separation step is not sufficient to purify these complex samples. When connecting several DLD modules in series, pressure balancing at the DLD outlets of each step becomes critical to ensure an optimal separation efficiency. A generic microfluidic platform is presented in this paper to optimize pressure balancing, when DLD separation is connected either to another DLD module or to a different microfluidic function. This is made possible by generating droplets at T-junctions connected to the DLD outlets. Droplets act as pressure controllers, which perform at the same time the encapsulation of DLD sorted particles and the balance of output pressures. The optimized pressures to apply on DLD modules and on T-junctions are determined by a general model that ensures the equilibrium of the entire platform. The proposed separation platform is completely modular and reconfigurable since the same predictive model applies to any cascaded DLD modules of the droplet-based cartridge. PMID:29768490

Understanding spatial and temporal patterning of astrocyte calcium transients via interactions between network transport and extracellular diffusion

NASA Astrophysics Data System (ADS)

Shtrahman, E.; Maruyama, D.; Olariu, E.; Fink, C. G.; Zochowski, M.

2017-02-01

Astrocytes form interconnected networks in the brain and communicate via calcium signaling. We investigate how modes of coupling between astrocytes influence the spatio-temporal patterns of calcium signaling within astrocyte networks and specifically how these network interactions promote coordination within this group of cells. To investigate these complex phenomena, we study reduced cultured networks of astrocytes and neurons. We image the spatial temporal patterns of astrocyte calcium activity and quantify how perturbing the coupling between astrocytes influences astrocyte activity patterns. To gain insight into the pattern formation observed in these cultured networks, we compare the experimentally observed calcium activity patterns to the patterns produced by a reduced computational model, where we represent astrocytes as simple units that integrate input through two mechanisms: gap junction coupling (network transport) and chemical release (extracellular diffusion). We examine the activity patterns in the simulated astrocyte network and their dependence upon these two coupling mechanisms. We find that gap junctions and extracellular chemical release interact in astrocyte networks to modulate the spatiotemporal patterns of their calcium dynamics. We show agreement between the computational and experimental findings, which suggests that the complex global patterns can be understood as a result of simple local coupling mechanisms.

Effects of Radiographic Contrast Media on the Micromorphology of the Junctional Complex of Erythrocytes Visualized by Immunocytology

PubMed Central

Franke, Ralf-Peter; Krüger, Anne; Scharnweber, Tim; Wenzel, Folker; Jung, Friedrich

2014-01-01

Effects of radiographic contrast media (RCM) application were demonstrated in vitro and in vivo where the injection of RCM into the A. axillaris of patients with coronary artery disease was followed by a significant and RCM-dependent decrease of erythrocyte velocity in downstream skin capillaries. Another study in pigs revealed that the deceleration of erythrocytes coincided with a significant reduction of the oxygen partial pressure in the myocardium—supplied by the left coronary artery—after the administration of RCM into this artery. Further reports showed RCM dependent alterations of erythrocytes like echinocyte formation and exocytosis, sequestration of actin or band 3 and the buckling of endothelial cells coinciding with a formation of interendothelial fenestrations leading to areas devoid of endothelial cells. Key to morphological alterations of erythrocytes is the membrane cytoskeleton, which is linked to the band 3 in the erythrocyte membrane via the junctional complex. Fundamental observations regarding the cell biological and biochemical aspects of the structure and function of the cell membrane and the membrane cytoskeleton of erythrocytes have been reported. This review focuses on recent results gained, e.g., by advanced confocal laser scanning microscopy of different double-stained structural elements of the erythrocyte membrane cytoskeleton. PMID:25222553

The Bcr Kinase Downregulates Ras Signaling by Phosphorylating AF-6 and Binding to Its PDZ Domain

PubMed Central

Radziwill, G.; Erdmann, R. A.; Margelisch, U.; Moelling, K.

2003-01-01

The protein kinase Bcr is a negative regulator of cell proliferation and oncogenic transformation. We identified Bcr as a ligand for the PDZ domain of the cell junction and Ras-interacting protein AF-6. The Bcr kinase phosphorylates AF-6, which subsequently allows efficient binding of Bcr to AF-6, showing that the Bcr kinase is a regulator of the PDZ domain-ligand interaction. Bcr and AF-6 colocalize in epithelial cells at the plasma membrane. In addition, Bcr, AF-6, and Ras form a trimeric complex. Bcr increases the affinity of AF-6 to Ras, and a mutant of AF-6 that lacks a specific phosphorylation site for Bcr shows a reduced binding to Ras. Wild-type Bcr, but not Bcr mutants defective in binding to AF-6, interferes with the Ras-dependent stimulation of the Raf/MEK/ERK pathway. Since AF-6 binds to Bcr via its PDZ domain and to Ras via its Ras-binding domain, we propose that AF-6 functions as a scaffold-like protein that links Bcr and Ras to cellular junctions. We suggest that this trimeric complex is involved in downregulation of Ras-mediated signaling at sites of cell-cell contact to maintain cells in a nonproliferating state. PMID:12808105

Manipulating Hydrophobic Interactions in Associative Polymer Solutions via Surfactant-Cyclodextrin Complexation

NASA Astrophysics Data System (ADS)

Talwar, Sachin; Harding, Jonathon; Khan, Saad A.

2008-07-01

Associative polymers in combination with cyclodextrin (CD) provide a potent tool to manipulate the solution rheology of aqueous solutions. In this study, we discuss the viability and scope of employing surfactants in such systems to facilitate a more versatile and effective tailoring of rheological properties. A model hydrophobically modified alkali-soluble emulsion (HASE) polymer is used which forms a transient physical network of intra- and inter-molecular hydrophobic junctions in solution arising from the interactions between hydrophobic groups grafted on the polymer backbone. The presence of these hydrophobic junctions significantly enhances the solution rheological properties with both the steady state viscosity and dynamic moduli exhibiting an increase by several orders of magnitude. The ability of nonionic surfactants to modulate and recover the hydrophobic interactions in these polymer solutions in the presence of cyclodextrin is examined. The presence of either a- or β-CD results in a dramatic decrease in viscosity and viscoelastic properties of the HASE polymer solution resulting from the encapsulation of polymer hydrophobes by CDs. Addition of nonionic surfactants to such systems promotes a competition between CDs and surfactant molecules to complex with polymer hydrophobes thereby altering the hydrophobic interactions. In this regard, nonylphenol ethoxylates (NPe) with different ethylene oxide (EO) chain lengths, which determine the surfactant hydrophilic-lipophilic balance (HLB), are used.

Effects of dietary supplementation of arginine-silicate-inositol complex on absorption and metabolism of calcium of laying hens

PubMed Central

Orhan, Cemal; Tuzcu, Mehmet; Hayirli, Armagan; Komorowski, James R.; Sahin, Nurhan

2018-01-01

The effects of supplementation of arginine-silicate-inositol complex (ASI; 49.5–8.2–25 g/kg, respectively) to laying hens were investigated with respect to eggshell quality, calcium (Ca) balance, and expression of duodenal proteins related to Ca metabolism (calbindin and tight junction proteins). A total of 360 laying hens, 25 weeks old, were divided into 3 groups consisting of 6 replicate of cages, 20 birds per cage. The groups were fed a basal diet and the basal diet supplemented with 500 or 1000 mg ASI complex per kilogram for 90 days. Data were analyzed by ANCOVA using data during the first week of the adaptation period as covariates. As the ASI complex supplementation level increased, there were increases in feed intake (P < 0.0001), egg production (P < 0.001), egg weight (P < 0.0001) and eggshell weight (P < 0.001) weight, and shell thickness (P < 0.001) and decreases in feed conversion ratio and cracked egg percentage (P < 0.0001 for both). Concentrations of serum osteocalcin (P < 0.0001), vitamin D (P < 0.0001), calcium (P < 0.001), phosphorus (P < 0.001), and alkaline phosphatase (P < 0.008) as well as amounts of calcium retention (P < 0.0001) and eggshell calcium deposition (P < 0.001), and Ca balance (P < 0.0001) increased, whereas amount of calcium excretion (P < 0.001) decreased linearly in a dose-dependent manner. The ASI complex supplementation increased expressions of calcium transporters (calbindin-D28k, N sodium-calcium exchanger, plasma membrane calcium ATPase, and vitamin D receptor) and tight junction proteins (zonula occludens-1 and occludin) in the duodenum in a linear fashion (P < 0.0001 for all). In conclusion, provision of dietary ASI complex to laying hens during the peak laying period improved eggshell quality through improving calcium utilization as reflected by upregulation of genes related to the calcium metabolism. Further studies are needed to elucidate the contribution of each of the ASI complex ingredients. PMID:29360830

Chromosome Aberrations in Normal and Ataxia-Telangiectasia Cells Exposed to Heavy Ions

NASA Technical Reports Server (NTRS)

Kawata, T.; Ito, H.; Liu, C.; Shigematsu, N.; George, K.; Cucinotta, F. A.

2007-01-01

Although cells derived from Ataxia Telangiectasia (AT) patients are known to exhibit abnormal responses to ionizing radiations, its underlying mechanism still remains unclear. Previously, the authors reported that at the same gamma-irradiation dose AT cells show higher frequencies of misrepair and deletions compared to normal human fibroblast cells. In this study, we investigated the effects of heavy ions beams on chromosomal aberrations in normal and AT cells. Normal and AT fibroblast cells arrested at G0/G1 phase were irradiated with 2 Gy of X-rays, 490 MeV/u Silicon (LET 55 keV/m), 500 MeV/u Iron (LET 185 keV/m) and 200 MeV/u Iron (LET 440 keV/m) particles, and then cells were allowed to repair for 24 hours at 37 degrees before subculture. Calyculin-A induced PCC method was employed to collect G2/M chromosomes and whole DNA probes 1 and 3 were used to analyze chromosomal aberrations such as color-junctions, deletions, simple exchanges (incomplete and reciprocal exanges) and complex-type exchanges. The percentages of aberrant cells were higher when normal and AT cells were exposed to heavy ions compared to X-rays, and had a tendency to increase with increasing LET up to 185 keV/m and then decreased at 440 keV/m. When the frequency of color-junctions per cell was compared after X-ray exposure, AT cells had around three times higher frequency of color-junctions (mis-rejoining) than normal cells. However, at 185 keV/m there was no difference in the frequency of color-junctions between two cell lines. It was also found that the frequency of simple exchanges per cell was almost constant in AT cells regardless LET levels, but it was LET dependent for normal cells. Interestingly, the frequency of simple exchanges was higher for AT cells when it was compared at 185 keV/m but AT cells had more complex-type exchanges at the same LET levels. Heavy ions are more efficient in inducing chromosome aberrations in normal and AT cells compared to X-rays, and the aberration types between normal and AT fibroblast appeared different probably due to difference in the ATM gene function.

InP tunnel junction for InGaAs/InP tandem solar cells

NASA Technical Reports Server (NTRS)

Vilela, M. F.; Freundlich, A.; Bensaoula, A.; Medelci, N.; Renaud, P.

1995-01-01

Chemical beam epitaxy (CBE) has been shown to allow the growth of high quality materials with reproducible complex compositional and doping profiles. The main advantage of CBE compared to metalorganic chemical vapor deposition (MOCVD), the most popular technique for InP-based photovoltaic device fabrication, is the ability to grow high purity epilayers at much lower temperatures (450-530 C). We have previously shown that CBE is perfectly suited toward the fabrication of complex photovoltaic devices such as InP/InGaAs monolithically integrated tandem solar cells, because its low process temperature preserves the electrical characteristics of the InGaAs tunnel junction commonly used as an ohmic interconnect. In this work using CBE for the fabrication of optically transparent (with respect to the bottom cell) InP tunnel diodes is demonstrated. Epitaxial growth were performed in a Riber CBE 32 system using PH3 and TMIn as III and V precursors. Solid Be (p-type) and Si (n-type) have been used as doping sources, allowing doping levels up to 2 x 10(exp -19)/cu cm and 1 x 10(exp -19)/cu cm for n and p type respectively. The InP tunnel junction characteristics and the influence of the growth's conditions (temperature, growth rate) over its performance have been carefully investigated. InP p(++)/n(++) tunnel junction with peak current densities up to 1600 A/sq cm and maximum specific resistivities (V(sub p)/I(sub p) - peak voltage to peak current ratio) in the range of 10(exp -4) Omega-sq cm were obtained. The obtained peak current densities exceed the highest results previously reported for their lattice matched counterparts, In(0.53)Ga( 0.47)As and should allow the realization of improved minimal absorption losses in the interconnect InP/InGaAs tandem devices for Space applications. Owing to the low process temperature required for the top cell, these devices exhibit almost no degradation of its characteristics after the growth of subsequent thick InP layer suggesting minimal doping cross diffusion in the narrow space-charge region (approximately 1-5 nm) of the device. The fabrication of tandem devices using InP tunnel diodes as interconnect is in progress and will be reported at the conference.

Structural and functional analysis of the human POT1-TPP1 telomeric complex

DOE PAGES

Rice, Cory; Shastrula, Prashanth Krishna; Kossenkov, Andrew V.; ...

2017-04-10

POT1 and TPP1 are part of the shelterin complex and are essential for telomere length regulation and maintenance. Naturally occurring mutations of the telomeric POT1–TPP1 complex are implicated in familial glioma, melanoma and chronic lymphocytic leukaemia. Here we report the atomic structure of the interacting portion of the human telomeric POT1–TPP1 complex and suggest how several of these mutations contribute to malignant cancer. The POT1 C-terminus (POT1C) forms a bilobal structure consisting of an OB-fold and a holiday junction resolvase domain. TPP1 consists of several loops and helices involved in extensive interactions with POT1C. Biochemical data shows that several ofmore » the cancer-associated mutations, partially disrupt the POT1–TPP1 complex, which affects its ability to bind telomeric DNA efficiently. A defective POT1–TPP1 complex leads to longer and fragile telomeres, which in turn promotes genomic instability and cancer.« less

Structural and functional analysis of the human POT1-TPP1 telomeric complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rice, Cory; Shastrula, Prashanth Krishna; Kossenkov, Andrew V.

POT1 and TPP1 are part of the shelterin complex and are essential for telomere length regulation and maintenance. Naturally occurring mutations of the telomeric POT1–TPP1 complex are implicated in familial glioma, melanoma and chronic lymphocytic leukaemia. Here we report the atomic structure of the interacting portion of the human telomeric POT1–TPP1 complex and suggest how several of these mutations contribute to malignant cancer. The POT1 C-terminus (POT1C) forms a bilobal structure consisting of an OB-fold and a holiday junction resolvase domain. TPP1 consists of several loops and helices involved in extensive interactions with POT1C. Biochemical data shows that several ofmore » the cancer-associated mutations, partially disrupt the POT1–TPP1 complex, which affects its ability to bind telomeric DNA efficiently. A defective POT1–TPP1 complex leads to longer and fragile telomeres, which in turn promotes genomic instability and cancer.« less

Gap/silicon Tandem Solar Cell with Extended Temperature Range

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A. (Inventor)

2006-01-01

A two-junction solar cell has a bottom solar cell junction of crystalline silicon, and a top solar cell junction of gallium phosphide. A three (or more) junction solar cell has bottom solar cell junctions of silicon, and a top solar cell junction of gallium phosphide. The resulting solar cells exhibit improved extended temperature operation.

Uterine inactivation of muscle segment homeobox (Msx) genes alters epithelial cell junction proteins during embryo implantation.

PubMed

Sun, Xiaofei; Park, Craig B; Deng, Wenbo; Potter, S Steven; Dey, Sudhansu K

2016-04-01

Embryo implantation requires that the uterus differentiate into the receptive state. Failure to attain uterine receptivity will impede blastocyst attachment and result in a compromised pregnancy. The molecular mechanism by which the uterus transitions from the prereceptive to the receptive stage is complex, involving an intricate interplay of various molecules. We recently found that mice with uterine deletion ofMsxgenes (Msx1(d/d)/Msx2(d/d)) are infertile because of implantation failure associated with heightened apicobasal polarity of luminal epithelial cells during the receptive period. However, information on Msx's roles in regulating epithelial polarity remains limited. To gain further insight, we analyzed cell-type-specific gene expression by RNA sequencing of separated luminal epithelial and stromal cells by laser capture microdissection fromMsx1(d/d)/Msx2(d/d)and floxed mouse uteri on d 4 of pseudopregnancy. We found that claudin-1, a tight junction protein, and small proline-rich (Sprr2) protein, a major component of cornified envelopes in keratinized epidermis, were substantially up-regulated inMsx1(d/d)/Msx2(d/d)uterine epithelia. These factors also exhibited unique epithelial expression patterns at the implantation chamber (crypt) inMsx1(f/f)/Msx2(f/f)females; the patterns were lost inMsx1(d/d)/Msx2(d/d)epithelia on d 5, suggesting important roles during implantation. The results suggest thatMsxgenes play important roles during uterine receptivity including modulation of epithelial junctional activity.-Sun, X., Park, C. B., Deng, W., Potter, S. S., Dey, S. K. Uterine inactivation of muscle segment homeobox (Msx) genes alters epithelial cell junction proteins during embryo implantation. © FASEB.

[Effect of self-microemulsifying system on cell tight junctions].

PubMed

Sha, Xian-Yi; Fang, Xiao-Ling

2006-01-01

To study the effect of negatively charged and positively charged self-microemulsifying systems (SMES) on the cellular tight junction complex was to be investigated at molecular cell level. Human intestinal epithelial Caco-2 cell model was established. Effect of formulations on the transepithelial electrical resistance (TEER) and permeability of the paracellular transport marker mannitol were measured to evaluate the cell integrity. Changes in subcellular localization of the tight junction protein zona occludens 1 (ZO-1) and cytoskeleton protein actin by immunofluorescence were also assessed after treatment of two SMESs in different dilutions. The TEER of cell monolayers was not markedly affected by negatively charged SMES in different dilutions. The positively charged SMES could significantly decrease the TEER (P < 0.05) in three dilutions. The full recovery of TEER was found after the treatment of lower dilution for 2 h, then cultured for 48 h, while the recovery of TEER was 81.3% of control in 1 : 50 dilution. Two SMESs could enhance the apparent permeability coefficient of mannitol (2.9 - 64.6 folds), which depended on the dilution times. The immunofluorescent results indicated that the distribution of ZO-1 and actin were discrete in cell membrane after the treatment of formulation. Since the positively charged microemulsion could bind to the epithelial cell membrane by electrostatic interaction, the actin of the cells undergone some kind of stress stimulated by the higher concentration of microemulsion was more markedly affected than the negatively charged SMES. Effect of formulations on ZO-1 and actin relied on the dilution. SMES is able to enhance the paracellular transport marker mannitol. The mechanism of opening of tight junctions by SMES might be the change of distribution of ZO-1 and actin.

BK Channels Localize to the Paranodal Junction and Regulate Action Potentials in Myelinated Axons of Cerebellar Purkinje Cells.

PubMed

Hirono, Moritoshi; Ogawa, Yasuhiro; Misono, Kaori; Zollinger, Daniel R; Trimmer, James S; Rasband, Matthew N; Misonou, Hiroaki

2015-05-06

In myelinated axons, K(+) channels are clustered in distinct membrane domains to regulate action potentials (APs). At nodes of Ranvier, Kv7 channels are expressed with Na(+) channels, whereas Kv1 channels flank nodes at juxtaparanodes. Regulation of axonal APs by K(+) channels would be particularly important in fast-spiking projection neurons such as cerebellar Purkinje cells. Here, we show that BK/Slo1 channels are clustered at the paranodal junctions of myelinated Purkinje cell axons of rat and mouse. The paranodal junction is formed by a set of cell-adhesion molecules, including Caspr, between the node and juxtaparanodes in which it separates nodal from internodal membrane domains. Remarkably, only Purkinje cell axons have detectable paranodal BK channels, whose clustering requires the formation of the paranodal junction via Caspr. Thus, BK channels occupy this unique domain in Purkinje cell axons along with the other K(+) channel complexes at nodes and juxtaparanodes. To investigate the physiological role of novel paranodal BK channels, we examined the effect of BK channel blockers on antidromic AP conduction. We found that local application of blockers to the axon resulted in a significant increase in antidromic AP failure at frequencies above 100 Hz. We also found that Ni(2+) elicited a similar effect on APs, indicating the involvement of Ni(2+)-sensitive Ca(2+) channels. Furthermore, axonal application of BK channel blockers decreased the inhibitory synaptic response in the deep cerebellar nuclei. Thus, paranodal BK channels uniquely support high-fidelity firing of APs in myelinated Purkinje cell axons, thereby underpinning the output of the cerebellar cortex. Copyright © 2015 the authors 0270-6474/15/357082-13$15.00/0.

Tectonic fabric of northern North Fiji and Lau basins from GLORIA sidescan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tiffin, D.L.; Clarke, J.E.H.; Johnson, D.

1990-06-01

GLORIA mosaics, Seabeam, and seismic data over parts of the backarc New Hebrides arc, northwest and central North Fiji basin, Fiji Fracture Zone north of Fiji, Peggy Ridge, northeast Lau basin, northern Tonga arc, northwestern Tonga Trench, and Western Samoa reveal a complex tectonic framework for the region. Two triple junctions and several rifts are clearly delineated by outcrops and ridges of neovolcanic rocks. Backarc troughs in the New Hebrides Arc are commonly floored by volcanic rocks with little sediment cover. The locus of major faults are well defined in places by volcanic ridges and scarps. On the Fiji Fracturemore » Zone north of Fiji, scarps indicate the trace, but west of Fiji it disappears for about 100 km, becoming well pronounced again near the central North Fiji basin triple junction. At Peggy Ridge a very extensive area of sheet-like volcanics indicates activity extends northeast from Peggy Ridge toward the western extension of the Tonga Trench passing west of Niuafo'ou Island, possibly marking a fault-to-trench transition. East of Niuafo'ou Island, backarc spreading close to the Tofua Arc is seen at a nascent triple junction, its northern arm approaching close to the western Tonga Trench. Long linear fault scarps in the trench result from bending of the crust. Only a few areas, including the seafloor north of Samoa, are mainly sediment covered. Two known hydrothermal deposits near the two triple junctions have been imaged, but other mapped areas of extensive neo-volcanics in the vicinity of propagators and pull-apart basins suggest sites for further investigation. The prevalence of ridge propagators and extensional basins suggests their significant role in the development of the region.« less

Performance, defect behavior and carrier enhancement in low energy, proton irradiated p+nn+ InP solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Rybicki, G. C.; Vargas-Aburto, C.; Jain, R. K.; Scheiman, D.

1994-01-01

The highest AMO efficiency (19.1 percent) InP solar cell consisted of an n+pp+ structure epitaxially grown on a p+ InP substrate. However, the high cost and relative fragility of InP served as motivation for research efforts directed at heteroepitaxial growth of InP on more viable substrates. The highest AMO efficiency (13.7 percent) for this type of cell was achieved using a GaAs substrate. Considering only cost and fracture toughness, Si would be the preferred substrate. The fact that Si is a donor in InP introduces complexities which are necessary in order to avoid the formation of an efficiency limiting counterdiode. One method used to overcome this problem lies in employing an n+p+ tunnel junction in contact with the cell's p region. A simpler method consists of using an n+ substrate and processing the cell in the p+ nn+ configuration. This eliminates the need for a tunnel junction. Unfortunately, the p/n configuration has received relatively little attention the best cell with this geometry having achieved an efficiency of 17 percent. Irradiation of these homoepitaxial cells, with 1 Mev electrons, showed that they were slightly more radiation resistant than diffused junction n/p cells. Additional p/n InP cells have been processed by some activity aimed at diffusion. Currently, there has been some activity aimed at producing heteroepitaxial p+nn+ InP cells using n+ Ge substrates. Since, like Si, Ge is an n-dopant in InP, use of this configuration obviates the need for a tunnel junction. Obviously, before attempting to process heteroepitaxial cells, one must produce a reasonably good homoepitaxial cell. In the present case we focus our attention on homoepitaxially on an n+ Ge substrate.

Establishment and characterization of novel epithelial-like cell lines derived from human periodontal ligament tissue in vitro.

PubMed

Tansriratanawong, Kallapat; Ishikawa, Hiroshi; Toyomura, Junko; Sato, Soh

2017-10-01

In this study, novel human-derived epithelial-like cells (hEPLCs) lines were established from periodontal ligament (PDL) tissues, which were composed of a variety of cell types and exhibited complex cellular activities. To elucidate the putative features distinguishing these from epithelial rest of Malassez (ERM), we characterized hEPLCs based on cell lineage markers and tight junction protein expression. The aim of this study was, therefore, to establish and characterize hEPLCs lines from PDL tissues. The hEPLCs were isolated from PDL of third molar teeth. Cellular morphology and cell organelles were observed thoroughly. The characteristics of epithelial-endothelial-mesenchymal-like cells were compared in several markers by gene expression and immunofluorescence, to ERM and human umbilical-vein endothelial cells (HUVECs). The resistance between cellular junctions was assessed by transepithelial electron resistance, and inflammatory cytokines were detected by ELISA after infecting hEPLCs with periodontopathic bacteria. The hEPLCs developed into small epithelial-like cells in pavement appearance similar to ERM. However, gene expression patterns and immunofluorescence results were different from ERM and HUVECs, especially in tight junction markers (Claudin, ZO-1, and Occludins), and endothelial markers (vWF, CD34). The transepithelial electron resistance indicated higher resistance in hEPLCs, as compared to ERM. Periodontopathic bacteria were phagocytosed with upregulation of inflammatory cytokine secretion within 24 h. In conclusion, hEPLCs that were derived using the single cell isolation method formed tight multilayers colonies, as well as strongly expressed tight junction markers in gene expression and immunofluorescence. Novel hEPLCs lines exhibited differently from ERM, which might provide some specific functions such as metabolic exchange and defense mechanism against bacterial invasion in periodontal tissue.

Beta-catenin interacts with low-molecular-weight protein tyrosine phosphatase leading to cadherin-mediated cell-cell adhesion increase.

PubMed

Taddei, Maria Letizia; Chiarugi, Paola; Cirri, Paolo; Buricchi, Francesca; Fiaschi, Tania; Giannoni, Elisa; Talini, Doriana; Cozzi, Giacomo; Formigli, Lucia; Raugei, Giovanni; Ramponi, Giampietro

2002-11-15

Beta-catenin plays a dual role as a major constituent of cadherin-based adherens junctions and also as a transcriptional coactivator. In normal ephitelial cells, at adherens junction level, beta-catenin links cadherins to the actin cytoskeleton. The structure of adherens junctions is dynamically regulated by tyrosine phosphorylation. In particular, cell-cell adhesion can be negatively regulated through the tyrosine phosphorylation of beta-catenin. Furthermore, the loss of beta-catenin-cadherin association has been correlated with the transition from a benign tumor to an invasive, metastatic cancer. Low-molecular-weight protein tyrosine phosphatase (LMW-PTP) is a ubiquitous PTP implicated in the regulation of mitosis and cytoskeleton rearrangement. Here we demonstrate that the amount of free cytoplasmic beta-catenin is decreased in NIH3T3, which overexpresses active LMW-PTP, and this results in a stronger association between cadherin complexes and the actin-based cytoskeleton with respect to control cells. Confocal microscopy analysis shows that beta-catenin colocalizes with LMW-PTP at the plasma membrane. Furthermore, we provide evidence that beta-catenin is able to associate with LMW-PTP both in vitro and in vivo. Moreover, overexpression of active LMW-PTP strongly potentiates cadherin-mediated cell-cell adhesion, whereas a dominant-negative form of LMW-PTP induces the opposite phenotype, both in NIH3T3 and in MCF-7 carcinoma cells. On the basis of these results, we propose that the stability of cell-cell contacts at the adherens junction level is positively influenced by LMW-PTP expression, mainly because of the beta-catenin and LMW-PTP interaction at the plasma membrane level with consequent dephosphorylation.

Exploring Instructive Physiological Signaling with the Bioelectric Tissue Simulation Engine

PubMed Central

Pietak, Alexis; Levin, Michael

2016-01-01

Bioelectric cell properties have been revealed as powerful targets for modulating stem cell function, regenerative response, developmental patterning, and tumor reprograming. Spatio-temporal distributions of endogenous resting potential, ion flows, and electric fields are influenced not only by the genome and external signals but also by their own intrinsic dynamics. Ion channels and electrical synapses (gap junctions) both determine, and are themselves gated by, cellular resting potential. Thus, the origin and progression of bioelectric patterns in multicellular tissues is complex, which hampers the rational control of voltage distributions for biomedical interventions. To improve understanding of these dynamics and facilitate the development of bioelectric pattern control strategies, we developed the BioElectric Tissue Simulation Engine (BETSE), a finite volume method multiphysics simulator, which predicts bioelectric patterns and their spatio-temporal dynamics by modeling ion channel and gap junction activity and tracking changes to the fundamental property of ion concentration. We validate performance of the simulator by matching experimentally obtained data on membrane permeability, ion concentration and resting potential to simulated values, and by demonstrating the expected outcomes for a range of well-known cases, such as predicting the correct transmembrane voltage changes for perturbation of single cell membrane states and environmental ion concentrations, in addition to the development of realistic transepithelial potentials and bioelectric wounding signals. In silico experiments reveal factors influencing transmembrane potential are significantly different in gap junction-networked cell clusters with tight junctions, and identify non-linear feedback mechanisms capable of generating strong, emergent, cluster-wide resting potential gradients. The BETSE platform will enable a deep understanding of local and long-range bioelectrical dynamics in tissues, and assist the development of specific interventions to achieve greater control of pattern during morphogenesis and remodeling. PMID:27458581

Uterine inactivation of muscle segment homeobox (Msx) genes alters epithelial cell junction proteins during embryo implantation

PubMed Central

Sun, Xiaofei; Park, Craig B.; Deng, Wenbo; Potter, S. Steven; Dey, Sudhansu K.

2016-01-01

Embryo implantation requires that the uterus differentiate into the receptive state. Failure to attain uterine receptivity will impede blastocyst attachment and result in a compromised pregnancy. The molecular mechanism by which the uterus transitions from the prereceptive to the receptive stage is complex, involving an intricate interplay of various molecules. We recently found that mice with uterine deletion of Msx genes (Msx1d/d/Msx2d/d) are infertile because of implantation failure associated with heightened apicobasal polarity of luminal epithelial cells during the receptive period. However, information on Msx’s roles in regulating epithelial polarity remains limited. To gain further insight, we analyzed cell-type–specific gene expression by RNA sequencing of separated luminal epithelial and stromal cells by laser capture microdissection from Msx1d/d/Msx2d/d and floxed mouse uteri on d 4 of pseudopregnancy. We found that claudin-1, a tight junction protein, and small proline-rich (Sprr2) protein, a major component of cornified envelopes in keratinized epidermis, were substantially up-regulated in Msx1d/d/Msx2d/d uterine epithelia. These factors also exhibited unique epithelial expression patterns at the implantation chamber (crypt) in Msx1f/f/Msx2f/f females; the patterns were lost in Msx1d/d/Msx2d/d epithelia on d 5, suggesting important roles during implantation. The results suggest that Msx genes play important roles during uterine receptivity including modulation of epithelial junctional activity.—Sun, X., Park, C. B., Deng, W., Potter, S. S., Dey, S. K. Uterine inactivation of muscle segment homeobox (Msx) genes alters epithelial cell junction proteins during embryo implantation. PMID:26667042

A refined model of claudin-15 tight junction paracellular architecture by molecular dynamics simulations

PubMed Central

Alberini, Giulio; Benfenati, Fabio

2017-01-01

Tight-junctions between epithelial cells of biological barriers are specialized molecular structures that regulate the flux of solutes across the barrier, parallel to cell walls. The tight-junction backbone is made of strands of transmembrane proteins from the claudin family, but the molecular mechanism of its function is still not completely understood. Recently, the crystal structure of a mammalian claudin-15 was reported, displaying for the first time the detailed features of transmembrane and extracellular domains. Successively, a structural model of claudin-15-based paracellular channels has been proposed, suggesting a putative assembly that illustrates how claudins associate in the same cell (via cis interactions) and across adjacent cells (via trans interactions). Although very promising, the model offers only a static conformation, with residues missing in the most important extracellular regions and potential steric clashes. Here we present detailed atomic models of paracellular single and double pore architectures, obtained from the putative assembly and refined via structural modeling and all-atom molecular dynamics simulations in double membrane bilayer and water environment. Our results show an overall stable configuration of the complex with a fluctuating pore size. Extracellular residue loops in trans interaction are able to form stable contacts and regulate the size of the pore, which displays a stationary radius of 2.5–3.0 Å at the narrowest region. The side-by-side interactions of the cis configuration are preserved via stable hydrogen bonds, already predicted by cysteine crosslinking experiments. Overall, this work introduces an improved version of the claudin-15-based paracellular channel model that strengthens its validity and that can be used in further computational studies to understand the structural features of tight-junctions regulation. PMID:28863193

Gap and tight junctions in the formation of feather branches: A descriptive ultrastructural study.

PubMed

Alibardi, Lorenzo

2010-08-20

The present study has focused on the distribution and ultrastructure of gap and tight junctions responsible for the formation of the barb/barbule branching in developing feathers using immunocytochemical detection. Apart from desmosomes, both tight and gap junctions are present between differentiating barb/barbule cells and during keratinization. While gap junctions are rare along the perimeter of these cells, tight junctions tend to remain localized in nodes joining barbule cells and between barb cells of the ramus. Occludin and connexin-26 but not connexin-43 have been detected between barb medullary, barb cortical and barbule cells during formation of barbs. Gap junctions are present in supportive cells located in the vicinity of barbule cells and destined to degenerate, but no close junctions are present between supportive and barb/barbule cells. Close junctions mature into penta-laminar junctions that are present between mature barb/barbule cells. Immunolabeling for occludin and Cx26 is rare along these cornified junctions. The junctions allow barb/barbule cells to remain connected until feather-keratin form the mature corneous syncytium that constitutes the barbs. A discussion of the role of gap and tight junctions during feather morphogenesis is presented. 2010 Elsevier GmbH. All rights reserved.

Abundance and ultrastructural diversity of neuronal gap junctions in the OFF and ON sublaminae of the inner plexiform layer of rat and mouse retina.

PubMed

Kamasawa, N; Furman, C S; Davidson, K G V; Sampson, J A; Magnie, A R; Gebhardt, B R; Kamasawa, M; Yasumura, T; Zumbrunnen, J R; Pickard, G E; Nagy, J I; Rash, J E

2006-11-03

Neuronal gap junctions are abundant in both outer and inner plexiform layers of the mammalian retina. In the inner plexiform layer (IPL), ultrastructurally-identified gap junctions were reported primarily in the functionally-defined and anatomically-distinct ON sublamina, with few reported in the OFF sublamina. We used freeze-fracture replica immunogold labeling and confocal microscopy to quantitatively analyze the morphologies and distributions of neuronal gap junctions in the IPL of adult rat and mouse retina. Under "baseline" conditions (photopic illumination/general anesthesia), 649 neuronal gap junctions immunogold-labeled for connexin36 were identified in rat IPL, of which 375 were photomapped to OFF vs. ON sublaminae. In contrast to previous reports, the volume-density of gap junctions was equally abundant in both sublaminae. Five distinctive morphologies of gap junctions were identified: conventional crystalline and non-crystalline "plaques" (71% and 3%), plus unusual "string" (14%), "ribbon" (7%) and "reticular" (2%) forms. Plaque and reticular gap junctions were distributed throughout the IPL. However, string and ribbon gap junctions were restricted to the OFF sublamina, where they represented 48% of gap junctions in that layer. In string and ribbon junctions, curvilinear strands of connexons were dispersed over 5 to 20 times the area of conventional plaques having equal numbers of connexons. To define morphologies of gap junctions under different light-adaptation conditions, we examined an additional 1150 gap junctions from rats and mice prepared after 30 min of photopic, mesopic and scotopic illumination, with and without general anesthesia. Under these conditions, string and ribbon gap junctions remained abundant in the OFF sublamina and absent in the ON sublamina. Abundant gap junctions in the OFF sublamina of these two rodents with rod-dominant retinas revealed previously-undescribed but extensive pathways for inter-neuronal communication; and the wide dispersion of connexons in string and ribbon gap junctions suggests unique structural features of gap junctional coupling in the OFF vs. ON sublamina.

1.00 MeV proton radiation resistance studies of single-junction and single gap dual-junction amorphous-silicon alloy solar cells

NASA Technical Reports Server (NTRS)

Abdulaziz, Salman; Payson, J. S.; Li, Yang; Woodyard, James R.

1990-01-01

A comparative study of the radiation resistance of a-Si:H and a-SiGe:H single-junction and a-Si:H dual-junction solar cells was conducted. The cells were irradiated with 1.00-MeV protons with fluences of 1.0 x 10 to the 14th, 5.0 x 10 to the 14th and 1.0 x 10 to the 15th/sq cm and characterized using I-V and quantum efficiency measurements. The radiation resistance of single-junction cells cannot be used to explain the behavior of dual-junction cells at a fluence of 1.0 x 10 to the 15th/sq cm. The a-Si H single-junction cells degraded the least of the three cells; a-SiGe:H single-junction cells showed the largest reduction in short-circuit current, while a-Si:H dual-junction cells exhibited the largest degradation in the open-circuit voltage. The quantum efficiency of the cells degraded more in the red part of the spectrum; the bottom junction degrades first in dual-junction cells.

p21-Activated kinase (Pak) regulates airway smooth muscle contraction by regulating paxillin complexes that mediate actin polymerization.

PubMed

Zhang, Wenwu; Huang, Youliang; Gunst, Susan J

2016-09-01

In airway smooth muscle, tension development caused by a contractile stimulus requires phosphorylation of the 20 kDa myosin light chain (MLC), which activates crossbridge cycling and the polymerization of a pool of submembraneous actin. The p21-activated kinases (Paks) can regulate the contractility of smooth muscle and non-muscle cells, and there is evidence that this occurs through the regulation of MLC phosphorylation. We show that Pak has no effect on MLC phosphorylation during the contraction of airway smooth muscle, and that it regulates contraction by mediating actin polymerization. We find that Pak phosphorylates the adhesion junction protein, paxillin, on Ser273, which promotes the formation of a signalling complex that activates the small GTPase, cdc42, and the actin polymerization catalyst, neuronal Wiskott-Aldrich syndrome protein (N-WASP). These studies demonstrate a novel role for Pak in regulating the contractility of smooth muscle by regulating actin polymerization. The p21-activated kinases (Pak) can regulate contractility in smooth muscle and other cell and tissue types, but the mechanisms by which Paks regulate cell contractility are unclear. In airway smooth muscle, stimulus-induced contraction requires phosphorylation of the 20 kDa light chain of myosin, which activates crossbridge cycling, as well as the polymerization of a small pool of actin. The role of Pak in airway smooth muscle contraction was evaluated by inhibiting acetylcholine (ACh)-induced Pak activation through the expression of a kinase inactive mutant, Pak1 K299R, or by treating tissues with the Pak inhibitor, IPA3. Pak inhibition suppressed actin polymerization and contraction in response to ACh, but it did not affect myosin light chain phosphorylation. Pak activation induced paxillin phosphorylation on Ser273; the paxillin mutant, paxillin S273A, inhibited paxillin Ser273 phosphorylation and inhibited actin polymerization and contraction. Immunoprecipitation analysis of tissue extracts and proximity ligation assays in dissociated cells showed that Pak activation and paxillin Ser273 phosphorylation triggered the formation of an adhesion junction signalling complex with paxillin that included G-protein-coupled receptor kinase-interacting protein (GIT1) and the cdc42 guanine exchange factor, βPIX (Pak interactive exchange factor). Assembly of the Pak-GIT1-βPIX-paxillin complex was necessary for cdc42 and neuronal Wiskott-Aldrich syndrome protein (N-WASP) activation, actin polymerization and contraction in response to ACh. RhoA activation was also required for the recruitment of Pak to adhesion junctions, Pak activation, paxillin Ser273 phosphorylation and paxillin complex assembly. These studies demonstrate a novel role for Pak in the regulation of N-WASP activation, actin dynamics and cell contractility. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.

p21‐Activated kinase (Pak) regulates airway smooth muscle contraction by regulating paxillin complexes that mediate actin polymerization

PubMed Central

Zhang, Wenwu; Huang, Youliang

2016-01-01

Key points In airway smooth muscle, tension development caused by a contractile stimulus requires phosphorylation of the 20 kDa myosin light chain (MLC), which activates crossbridge cycling and the polymerization of a pool of submembraneous actin.The p21‐activated kinases (Paks) can regulate the contractility of smooth muscle and non‐muscle cells, and there is evidence that this occurs through the regulation of MLC phosphorylation.We show that Pak has no effect on MLC phosphorylation during the contraction of airway smooth muscle, and that it regulates contraction by mediating actin polymerization.We find that Pak phosphorylates the adhesion junction protein, paxillin, on Ser273, which promotes the formation of a signalling complex that activates the small GTPase, cdc42, and the actin polymerization catalyst, neuronal Wiskott–Aldrich syndrome protein (N‐WASP).These studies demonstrate a novel role for Pak in regulating the contractility of smooth muscle by regulating actin polymerization. Abstract The p21‐activated kinases (Pak) can regulate contractility in smooth muscle and other cell and tissue types, but the mechanisms by which Paks regulate cell contractility are unclear. In airway smooth muscle, stimulus‐induced contraction requires phosphorylation of the 20 kDa light chain of myosin, which activates crossbridge cycling, as well as the polymerization of a small pool of actin. The role of Pak in airway smooth muscle contraction was evaluated by inhibiting acetylcholine (ACh)‐induced Pak activation through the expression of a kinase inactive mutant, Pak1 K299R, or by treating tissues with the Pak inhibitor, IPA3. Pak inhibition suppressed actin polymerization and contraction in response to ACh, but it did not affect myosin light chain phosphorylation. Pak activation induced paxillin phosphorylation on Ser273; the paxillin mutant, paxillin S273A, inhibited paxillin Ser273 phosphorylation and inhibited actin polymerization and contraction. Immunoprecipitation analysis of tissue extracts and proximity ligation assays in dissociated cells showed that Pak activation and paxillin Ser273 phosphorylation triggered the formation of an adhesion junction signalling complex with paxillin that included G‐protein‐coupled receptor kinase‐interacting protein (GIT1) and the cdc42 guanine exchange factor, βPIX (Pak interactive exchange factor). Assembly of the Pak–GIT1–βPIX–paxillin complex was necessary for cdc42 and neuronal Wiskott–Aldrich syndrome protein (N‐WASP) activation, actin polymerization and contraction in response to ACh. RhoA activation was also required for the recruitment of Pak to adhesion junctions, Pak activation, paxillin Ser273 phosphorylation and paxillin complex assembly. These studies demonstrate a novel role for Pak in the regulation of N‐WASP activation, actin dynamics and cell contractility. PMID:27038336

Fabrication of magnetic tunnel junctions with epitaxial and textured ferromagnetic layers

DOEpatents

Chang, Y. Austin; Yang, Jianhua Joshua

2008-11-11

This invention relates to magnetic tunnel junctions and methods for making the magnetic tunnel junctions. The magnetic tunnel junctions include a tunnel barrier oxide layer sandwiched between two ferromagnetic layers both of which are epitaxial or textured with respect to the underlying substrate upon which the magnetic tunnel junctions are grown. The magnetic tunnel junctions provide improved magnetic properties, sharper interfaces and few defects.

Possible involvement of gap junctions in the barrier function of tight junctions of brain and lung endothelial cells.

PubMed

Nagasawa, Kunihiko; Chiba, Hideki; Fujita, Hiroki; Kojima, Takashi; Saito, Tsuyoshi; Endo, Toshiaki; Sawada, Norimasa

2006-07-01

Gap-junction plaques are often observed with tight-junction strands of vascular endothelial cells but the molecular interaction and functional relationships between these two junctions remain obscure. We herein show that gap-junction proteins connexin40 (Cx40) and Cx43 are colocalized and coprecipitated with tight-junction molecules occludin, claudin-5, and ZO-1 in porcine blood-brain barrier (BBB) endothelial cells. Gap junction blockers 18beta-glycyrrhetinic acid (18beta-GA) and oleamide (OA) did not influence expression of Cx40, Cx43, occludin, claudin-5, junctional adhesion molecule (JAM)-A, JAM-B, JAM-C, or ZO-1, or their subcellular localization in the porcine BBB endothelial cells. In contrast, these gap-junction blocking agents inhibited the barrier function of tight junctions in cells, determined by measurement of transendothelial electrical resistance and paracellular flux of mannitol and inulin. 18beta-GA also significantly reduced the barrier property in rat lung endothelial (RLE) cells expressing doxycycline-induced claudin-1, but did not change the interaction between Cx43 and either claudin-1 or ZO-1, nor their expression levels or subcellular distribution. These findings suggest that Cx40- and/or Cx43-based gap junctions might be required to maintain the endothelial barrier function without altering the expression and localization of the tight-junction components analyzed. Copyright 2006 Wiley-Liss, Inc.

Research and develop locking design for NJDOT junction boxes : final report, April 2009.

DOT National Transportation Integrated Search

2009-04-01

The report outlines the guidelines for securing electrical junction box covers to the junction box to prevent vandalism. The report provides details drawings that show various methods for securing the junction box cover to the junction box.

Four-junction superconducting circuit

PubMed Central

Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

2016-01-01

We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

Intercellular junctions between palisade nerve endings and outer root sheath cells of rat vellus hairs.

PubMed

Kaidoh, T; Inoué, T

2000-05-15

Hair follicles have a longitudinal set of sensory nerve endings called palisade nerve endings (PN). We examined the junctional structures between the PN and outer root sheath (ORS) cells of hair follicles in the rat external ear. Transmission electron microscopy of serial thin sections showed that the processes of the ORS cells penetrated the basal lamina of the hair follicle, forming intercellular junctions with the PN (PN-ORS junctions). Two types of junctions were found: junctions between nerve endings and ORS cells (N-ORS junctions) and those between Schwann cell processes and ORS cells (S-ORS junctions). The N-ORS junctions had two subtypes: 1) a short process or small eminence of the ORS cell was attached to the nerve ending (type I); or 2) a process of the ORS cell was invaginated into the nerve ending (type II). The S-ORS junctions also had two subtypes: 1) a short process or small eminence of the ORS cell was abutted on the Schwann cell process (type I); or 2) a process of the ORS cell was invaginated into the Schwann cell process (type II). Vesicles, coated pits, coated vesicles, and endosomes were sometimes seen in nerve endings, Schwann cells, and ORS cells near the junctions. Computer-aided reconstruction of the serial thin sections displayed the three-dimensional structure of these junctions. These results suggested that the PN-ORS junctions provided direct relationships between the PN and ORS in at least four different patterns. The discovery of these junctions shows the PN-ORS relationship to be closer than previously realized. We speculate that these junctions may have roles in attachment of the PN to the ORS, contributing to increases in the sensitivity of the PN, and in chemical signaling between the PN and ORS.

Superstrate sub-cell voltage-matched multijunction solar cells

DOEpatents

Mascarenhas, Angelo; Alberi, Kirstin

2016-03-15

Voltage-matched thin film multijunction solar cell and methods of producing cells having upper CdTe pn junction layers formed on a transparent substrate which in the completed device is operatively positioned in a superstate configuration. The solar cell also includes a lower pn junction formed independently of the CdTe pn junction and an insulating layer between CdTe and lower pn junctions. The voltage-matched thin film multijunction solar cells further include a parallel connection between the CdTe pn junction and lower pn junctions to form a two-terminal photonic device. Methods of fabricating devices from independently produced upper CdTe junction layers and lower junction layers are also disclosed.

Effect of solar-cell junction geometry on open-circuit voltage

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Godlewski, M. P.

1985-01-01

Simple analytical models have been found that adequately describe the voltage behavior of both the stripe junction and dot junction grating cells as a function of junction area. While the voltage in the former case is found to be insensitive to junction area reduction, significant voltage increases are shown to be possible for the dot junction cell. With regard to cells in which the junction area has been increased in a quest for better performance, it was found that (1) texturation does not affect the average saturation current density J0, indicating that the texturation process is equivalent to a simple extension of junction area by a factor of square root of 3 and (2) the vertical junction cell geometry produces a sizable decrease in J0 that, unfortunately, is more than offset by the effects of attendant areal increases.

Anisotropic-Scale Junction Detection and Matching for Indoor Images.

PubMed

Xue, Nan; Xia, Gui-Song; Bai, Xiang; Zhang, Liangpei; Shen, Weiming

Junctions play an important role in characterizing local geometrical structures of images, and the detection of which is a longstanding but challenging task. Existing junction detectors usually focus on identifying the location and orientations of junction branches while ignoring their scales, which, however, contain rich geometries of images. This paper presents a novel approach for junction detection and characterization, which especially exploits the locally anisotropic geometries of a junction and estimates its scales by relying on an a-contrario model. The output junctions are with anisotropic scales, saying that a scale parameter is associated with each branch of a junction and are thus named as anisotropic-scale junctions (ASJs). We then apply the new detected ASJs for matching indoor images, where there are dramatic changes of viewpoints and the detected local visual features, e.g., key-points, are usually insufficient and lack distinctive ability. We propose to use the anisotropic geometries of our junctions to improve the matching precision of indoor images. The matching results on sets of indoor images demonstrate that our approach achieves the state-of-the-art performance on indoor image matching.Junctions play an important role in characterizing local geometrical structures of images, and the detection of which is a longstanding but challenging task. Existing junction detectors usually focus on identifying the location and orientations of junction branches while ignoring their scales, which, however, contain rich geometries of images. This paper presents a novel approach for junction detection and characterization, which especially exploits the locally anisotropic geometries of a junction and estimates its scales by relying on an a-contrario model. The output junctions are with anisotropic scales, saying that a scale parameter is associated with each branch of a junction and are thus named as anisotropic-scale junctions (ASJs). We then apply the new detected ASJs for matching indoor images, where there are dramatic changes of viewpoints and the detected local visual features, e.g., key-points, are usually insufficient and lack distinctive ability. We propose to use the anisotropic geometries of our junctions to improve the matching precision of indoor images. The matching results on sets of indoor images demonstrate that our approach achieves the state-of-the-art performance on indoor image matching.

High-efficiency solar cell and method for fabrication

DOEpatents

Hou, Hong Q.; Reinhardt, Kitt C.

1999-01-01

A high-efficiency 3- or 4-junction solar cell is disclosed with a theoretical AM0 energy conversion efficiency of about 40%. The solar cell includes p-n junctions formed from indium gallium arsenide nitride (InGaAsN), gallium arsenide (GaAs) and indium gallium aluminum phosphide (InGaAlP) separated by n-p tunnel junctions. An optional germanium (Ge) p-n junction can be formed in the substrate upon which the other p-n junctions are grown. The bandgap energies for each p-n junction are tailored to provide substantially equal short-circuit currents for each p-n junction, thereby eliminating current bottlenecks and improving the overall energy conversion efficiency of the solar cell. Additionally, the use of an InGaAsN p-n junction overcomes super-bandgap energy losses that are present in conventional multi-junction solar cells. A method is also disclosed for fabricating the high-efficiency 3- or 4-junction solar cell by metal-organic chemical vapor deposition (MOCVD).

High-efficiency solar cell and method for fabrication

DOEpatents

Hou, H.Q.; Reinhardt, K.C.

1999-08-31

A high-efficiency 3- or 4-junction solar cell is disclosed with a theoretical AM0 energy conversion efficiency of about 40%. The solar cell includes p-n junctions formed from indium gallium arsenide nitride (InGaAsN), gallium arsenide (GaAs) and indium gallium aluminum phosphide (InGaAlP) separated by n-p tunnel junctions. An optional germanium (Ge) p-n junction can be formed in the substrate upon which the other p-n junctions are grown. The bandgap energies for each p-n junction are tailored to provide substantially equal short-circuit currents for each p-n junction, thereby eliminating current bottlenecks and improving the overall energy conversion efficiency of the solar cell. Additionally, the use of an InGaAsN p-n junction overcomes super-bandgap energy losses that are present in conventional multi-junction solar cells. A method is also disclosed for fabricating the high-efficiency 3- or 4-junction solar cell by metal-organic chemical vapor deposition (MOCVD). 4 figs.

[Influence of Cx26/Cx32 gap junction channel on antineoplastic effect of etoposide in Hela cells].

PubMed

Tong, Xu-Hui; Dong, Shu-Ying; Jiang, Guo-Jun; Fan, Gao-Fu

2012-03-01

To observe the influence of Cx26/Cx32 gap junction channel on the antineoplastic effect of etoposide in Hela cervical cancer cells. Fluorescence trace was used to assay the gap junction intercellular communication mediated by Cx26/Cx32 in Hela cells and its functional modulation by the pharmacological agents (oleamide, retinoid acid). A standard colony-forming assay was applied to determine the cell growth-inhibiting effect of etoposide in Hela cells with functional modulation of the gap junction. Hoechst 33258 staining was used to assess the changes in etoposide-induced apoptosis of Hela cells with altered gap junction functions. Oleamide markedly decreased while retinoid acid obviously increased the gap junction function in Hela cells. Standard colony-forming assay showed that etoposide produced a lowered antiproliferative effect in Hela cells with reduced gap junction and an increased antiproliferative effect in cells with enhanced gap junction function. In cells with a reduced gap junction function, etoposide induced a lowered apoptosis rate, which increased obviously in cells with an enhanced gap junction function. The antineoplastic effect of etoposide is reduced in Hela cells with a decreased gap junction intercellular communication mediated by Cx26/Cx32 and is enhanced in cells with an increased gap junction intercellular communication.

Gap junctions modulate glioma invasion by direct transfer of microRNA.

PubMed

Hong, Xiaoting; Sin, Wun Chey; Harris, Andrew L; Naus, Christian C

2015-06-20

The invasiveness of high-grade glioma is the primary reason for poor survival following treatment. Interaction between glioma cells and surrounding astrocytes are crucial to invasion. We investigated the role of gap junction mediated miRNA transfer in this context. By manipulating gap junctions with a gap junction inhibitor, siRNAs, and a dominant negative connexin mutant, we showed that functional glioma-glioma gap junctions suppress glioma invasion while glioma-astrocyte and astrocyte-astrocyte gap junctions promote it in an in vitro transwell invasion assay. After demonstrating that glioma-astrocyte gap junctions are permeable to microRNA, we compared the microRNA profiles of astrocytes before and after co-culture with glioma cells, identifying specific microRNAs as candidates for transfer through gap junctions from glioma cells to astrocytes. Further analysis showed that transfer of miR-5096 from glioma cells to astrocytes is through gap junctions; this transfer is responsible, in part, for the pro-invasive effect. Our results establish a role for glioma-astrocyte gap junction mediated microRNA signaling in modulation of glioma invasive behavior, and that gap junction coupling among astrocytes magnifies the pro-invasive signaling. Our findings reveal the potential for therapeutic interventions based on abolishing alteration of stromal cells by tumor cells via manipulation of microRNA and gap junction channel activity.

Gap junctions modulate glioma invasion by direct transfer of microRNA

PubMed Central

Hong, Xiaoting; Sin, Wun Chey; Harris, Andrew L.; Naus, Christian C.

2015-01-01

The invasiveness of high-grade glioma is the primary reason for poor survival following treatment. Interaction between glioma cells and surrounding astrocytes are crucial to invasion. We investigated the role of gap junction mediated miRNA transfer in this context. By manipulating gap junctions with a gap junction inhibitor, siRNAs, and a dominant negative connexin mutant, we showed that functional glioma-glioma gap junctions suppress glioma invasion while glioma-astrocyte and astrocyte-astrocyte gap junctions promote it in an in vitro transwell invasion assay. After demonstrating that glioma-astrocyte gap junctions are permeable to microRNA, we compared the microRNA profiles of astrocytes before and after co-culture with glioma cells, identifying specific microRNAs as candidates for transfer through gap junctions from glioma cells to astrocytes. Further analysis showed that transfer of miR-5096 from glioma cells to astrocytes is through gap junctions; this transfer is responsible, in part, for the pro-invasive effect. Our results establish a role for glioma-astrocyte gap junction mediated microRNA signaling in modulation of glioma invasive behavior, and that gap junction coupling among astrocytes magnifies the pro-invasive signaling. Our findings reveal the potential for therapeutic interventions based on abolishing alteration of stromal cells by tumor cells via manipulation of microRNA and gap junction channel activity. PMID:25978028

CSReport: A New Computational Tool Designed for Automatic Analysis of Class Switch Recombination Junctions Sequenced by High-Throughput Sequencing.

PubMed

Boyer, François; Boutouil, Hend; Dalloul, Iman; Dalloul, Zeinab; Cook-Moreau, Jeanne; Aldigier, Jean-Claude; Carrion, Claire; Herve, Bastien; Scaon, Erwan; Cogné, Michel; Péron, Sophie

2017-05-15

B cells ensure humoral immune responses due to the production of Ag-specific memory B cells and Ab-secreting plasma cells. In secondary lymphoid organs, Ag-driven B cell activation induces terminal maturation and Ig isotype class switch (class switch recombination [CSR]). CSR creates a virtually unique IgH locus in every B cell clone by intrachromosomal recombination between two switch (S) regions upstream of each C region gene. Amount and structural features of CSR junctions reveal valuable information about the CSR mechanism, and analysis of CSR junctions is useful in basic and clinical research studies of B cell functions. To provide an automated tool able to analyze large data sets of CSR junction sequences produced by high-throughput sequencing (HTS), we designed CSReport, a software program dedicated to support analysis of CSR recombination junctions sequenced with a HTS-based protocol (Ion Torrent technology). CSReport was assessed using simulated data sets of CSR junctions and then used for analysis of Sμ-Sα and Sμ-Sγ1 junctions from CH12F3 cells and primary murine B cells, respectively. CSReport identifies junction segment breakpoints on reference sequences and junction structure (blunt-ended junctions or junctions with insertions or microhomology). Besides the ability to analyze unprecedentedly large libraries of junction sequences, CSReport will provide a unified framework for CSR junction studies. Our results show that CSReport is an accurate tool for analysis of sequences from our HTS-based protocol for CSR junctions, thereby facilitating and accelerating their study. Copyright © 2017 by The American Association of Immunologists, Inc.

Regulation of gap junctional charge selectivity in cells coexpressing connexin 40 and connexin 43.

PubMed

Heyman, Nathanael S; Kurjiaka, David T; Ek Vitorin, Jose F; Burt, Janis M

2009-07-01

Expression of connexin 40 (Cx40) and Cx43 in cardiovascular tissues varies as a function of age, injury, and development with unknown consequences on the selectivity of junctional communication and its acute regulation. We investigated the PKC-dependent regulation of charge selectivity in junctions composed of Cx43, Cx40, or both by simultaneous assessment of junctional permeance rate constants (B(dye)) for dyes of similar size but opposite charge, N,N,N-trimethyl-2-[methyl-(7-nitro-2,1,3-benzoxadiol-4-yl)amino]ethanaminium (NBD-M-TMA; +1) and Alexa 350 (-1). The ratio of dye rate constants (B(NBD-M-TMA)/B(Alexa 350)) indicated that Cx40 junctions are cation selective (10.7 +/- 0.5), whereas Cx43 junction are nonselective (1.22 +/- 0.14). In coexpressing cells, a broad range of junctional selectivities was observed with mean cation selectivity increasing as the Cx40 to Cx43 expression ratio increased. PKC activation reduced or eliminated dye permeability of Cx43 junctions without altering their charge selectivity, had no effect on either permeability or charge selectivity of Cx40 junctions, and significantly increased the cation selectivity of junctions formed by coexpressing cells (approaching charge selectivity of Cx40 junctions). Junctions composed of Cx43 truncated at residue 257 (Cx43tr) were also not charge selective, but when Cx43tr was coexpressed with Cx40, a broad range of junctional selectivities that was unaffected by PKC activation was observed. Thus, whereas the charge selectivities of homomeric/homotypic Cx43 and Cx40 junctions appear invariant, the selectivities of junctions formed by cells coexpressing Cx40 and Cx43 vary considerably, reflecting both their relative expression levels and phosphorylation-dependent regulation. Such regulation could represent a mechanism by which coexpressing cells such as vascular endothelium and atrial cells regulate acutely the selective intercellular communication mediated by their gap junctions.

Continuous throughput and long-term observation of single-molecule FRET without immobilization.

PubMed

Tyagi, Swati; VanDelinder, Virginia; Banterle, Niccolò; Fuertes, Gustavo; Milles, Sigrid; Agez, Morgane; Lemke, Edward A

2014-03-01

We present an automated microfluidic platform that performs multisecond observation of single molecules with millisecond time resolution while bypassing the need for immobilization procedures. With this system, we confine biomolecules to a thin excitation field by reversibly collapsing microchannels to nanochannels. We demonstrate the power of our method by studying a variety of complex nucleic acid and protein systems, including DNA Holliday junctions, nucleosomes and human transglutaminase 2.

A Review of Accident Modelling Approaches for Complex Critical Sociotechnical Systems

DTIC Science & Technology

2008-01-01

several Signals Passed at Danger ( SPADs ) but a signal sighting committee was not convened 4. An inspection of the signalling system at Watford...Junction was never carried out 5. The driver did not know of the reduced overlap between signals 6. The driver had committed SPADs recently and...cause. One philosophical approach to causation views counterfactual dependence as the key to the explanation of causal facts: for example, events c (the

Block copolymer libraries: modular versatility of the macromolecular Lego system.

PubMed

Lohmeijer, Bas G G; Wouters, Daan; Yin, Zhihui; Schubert, Ulrich S

2004-12-21

The synthesis and characterization of a new 4 x 4 library of block copolymers based on polystyrene and poly(ethylene oxide) connected by an asymmetrical octahedral bis(terpyridine) ruthenium complex at the block junction are described, while initial studies on the thin film morphology of the components of the library are presented by the use of Atomic Force Microscopy, demonstrating the impact of a library approach to derive structure-property relationships.

'Special K' and a Loss of Cell-To-Cell Adhesion in Proximal Tubule-Derived Epithelial Cells: Modulation of the Adherens Junction Complex by Ketamine

PubMed Central

Hills, Claire E.; Jin, Tianrong; Siamantouras, Eleftherios; Liu, Issac K-K; Jefferson, Kieran P.; Squires, Paul E.

2013-01-01

Ketamine, a mild hallucinogenic class C drug, is the fastest growing ‘party drug’ used by 16–24 year olds in the UK. As the recreational use of Ketamine increases we are beginning to see the signs of major renal and bladder complications. To date however, we know nothing of a role for Ketamine in modulating both structure and function of the human renal proximal tubule. In the current study we have used an established model cell line for human epithelial cells of the proximal tubule (HK2) to demonstrate that Ketamine evokes early changes in expression of proteins central to the adherens junction complex. Furthermore we use AFM single-cell force spectroscopy to assess if these changes functionally uncouple cells of the proximal tubule ahead of any overt loss in epithelial cell function. Our data suggests that Ketamine (24–48 hrs) produces gross changes in cell morphology and cytoskeletal architecture towards a fibrotic phenotype. These physical changes matched the concentration-dependent (0.1–1 mg/mL) cytotoxic effect of Ketamine and reflect a loss in expression of the key adherens junction proteins epithelial (E)- and neural (N)-cadherin and β-catenin. Down-regulation of protein expression does not involve the pro-fibrotic cytokine TGFβ, nor is it regulated by the usual increase in expression of Slug or Snail, the transcriptional regulators for E-cadherin. However, the loss in E-cadherin can be partially rescued pharmacologically by blocking p38 MAPK using SB203580. These data provide compelling evidence that Ketamine alters epithelial cell-to-cell adhesion and cell-coupling in the proximal kidney via a non-classical pro-fibrotic mechanism and the data provides the first indication that this illicit substance can have major implications on renal function. Understanding Ketamine-induced renal pathology may identify targets for future therapeutic intervention. PMID:24009666

Methyl-beta-cyclodextrin increases permeability of Caco-2 cell monolayers by displacing specific claudins from cholesterol rich domains associated with tight junctions.

PubMed

Lambert, Daniel; O'Neill, Catherine A; Padfield, Philip J

2007-01-01

In a previous study we demonstrated that depletion of Caco-2 cell cholesterol results in the loss of tight junction (TJ) integrity through the movement of claudins 3 and 4 and occludin, but not claudin 1, out of the TJs [1]. The aims of this study were to determine whether the major tight junction (TJ) proteins in Caco-2 cells are associated with cholesterol rich, membrane raft-like domains and if the loss of TJ integrity produced by the extraction of cholesterol reflects the dissolution of these domains resulting in the loss of TJ organisation. We have demonstrated that in Caco-2 cells claudins 1, 3, 4 and 7, JAM-A and occludin, are associated with cholesterol rich membrane domains that are insoluble in Lubrol WX. Co-immunoprecipitation studies demonstrated that there is no apparent restriction on the combination of claudins present in the rafts and that interaction between the proteins is dependent on cholesterol. JAM-A was not co-immunoprecipitated with the other TJ proteins indicating that it is resident within in a distinct population of rafts and therefore is likely not directly associated with the claudins/occludin present in the TJ complexes. Depletion of Caco-2 cell cholesterol with methyl-beta-cyclodextrin resulted in the displacement of claudins 3, 4 and 7, JAM-A and occludin, but not claudin 1, out of the cholesterol rich domains. Our data indicate that depletion of cholesterol does not result in the loss of the TJ-associated membrane rafts. However, the sterol is required to maintain the association of key proteins with the TJ associated membrane rafts and therefore the TJs. Furthermore, the data suggest that cholesterol may actually directly stabilise the multi-protein complexes that form the TJ strands. Copyright (c) 2007 S. Karger AG, Basel.

Connexin Channel Permeability to Cytoplasmic Molecules

PubMed Central

Harris, Andrew L.

2007-01-01

Connexin channels are known to be permeable to a variety of cytoplasmic molecules. The first observation of second messenger junctional permeability, made ∼30 years ago, sparked broad interest in gap junction channels as mediators of intercellular molecular signaling. Since then, much has been learned about the diversity of connexin channels with regard to isoform diversity, tissue and developmental distribution, modes of channel regulation, assembly and expression, biochemical modification and permeability, all of which appear to be dynamically regulated. This information has expanded the potential roles of connexin channels in development, physiology and disease, and made their elucidation much more complex - 30 years ago such an orchestra of junctional dynamics was unanticipated. Only recently, however, have investigators been able to directly address, in this more complex framework, the key issue: What specific biological molecules, second messengers and others, are able to permeate the various types of connexin channels, and how well? An important related issue, given the ever-growing list of connexin-related pathologies, is how these permeabilities are altered by disease-causing connexin mutations. Together, many studies show that a variety of cytoplasmic molecules can permeate the different types of connexin channels. A few studies reveal differences in permeation by different molecules through a particular type of connexin channel, and differences in permeation by a particular molecule through different types of connexin channels. This article describes and evaluates the various methods used to obtain these data, presents an annotated compilation of the results, and discusses the findings in the context of what can be inferred about mechanism of selectivity and potential relevance to signaling. The data strongly suggest that highly specific interactions take place between connexin pores and specific biological molecular permeants, and that those interactions determine which cytoplasmic molecules can permeate and how well. At this time, the nature of those interactions is unclear. One hopes that with more detailed permeability and structural information, the specific molecular mechanisms of the selectivity can be elucidated. PMID:17470375

Method of making high breakdown voltage semiconductor device

DOEpatents

Arthur, Stephen D.; Temple, Victor A. K.

1990-01-01

A semiconductor device having at least one P-N junction and a multiple-zone junction termination extension (JTE) region which uniformly merges with the reverse blocking junction is disclosed. The blocking junction is graded into multiple zones of lower concentration dopant adjacent termination to facilitate merging of the JTE to the blocking junction and placing of the JTE at or near the high field point of the blocking junction. Preferably, the JTE region substantially overlaps the graded blocking junction region. A novel device fabrication method is also provided which eliminates the prior art step of separately diffusing the JTE region.

Methods for the fabrication of thermally stable magnetic tunnel junctions

DOEpatents

Chang, Y Austin [Middleton, WI; Yang, Jianhua J [Madison, WI; Ladwig, Peter F [Hutchinson, MN

2009-08-25

Magnetic tunnel junctions and method for making the magnetic tunnel junctions are provided. The magnetic tunnel junctions are characterized by a tunnel barrier oxide layer sandwiched between two ferromagnetic layers. The methods used to fabricate the magnetic tunnel junctions are capable of completely and selectively oxidizing a tunnel junction precursor material using an oxidizing gas containing a mixture of gases to provide a tunnel junction oxide without oxidizing the adjacent ferromagnetic materials. In some embodiments the gas mixture is a mixture of CO and CO.sub.2 or a mixture of H.sub.2 and H.sub.2O.

Possible Involvement of Tight Junctions, Extracellular Matrix and Nuclear Receptors in Epithelial Differentiation

PubMed Central

Ichikawa-Tomikawa, Naoki; Sugimoto, Kotaro; Satohisa, Seiro; Nishiura, Keisuke; Chiba, Hideki

2011-01-01

Tight junctions are intercellular junctions localized at the most apical end of the lateral plasma membrane. They consist of four kinds of transmembrane proteins (occludin, claudins, junctional adhesion molecules, and tricellulin) and huge numbers of scaffolding proteins and contribute to the paracellular barrier and fence function. The mutation and deletion of these proteins impair the functions of tight junctions and cause various human diseases. In this paper, we provide an overview of recent studies on transmembrane proteins of tight junctions and highlight the functional significance of tight junctions, extracellular matrix, and nuclear receptors in epithelial differentiation. PMID:22162632

Gap junction- and hemichannel-independent actions of connexins.

PubMed

Jiang, Jean X; Gu, Sumin

2005-06-10

Connexins have been known to be the protein building blocks of gap junctions and mediate cell-cell communication. In contrast to the conventional dogma, recent evidence suggests that in addition to forming gap junction channels, connexins possess gap junction-independent functions. One important gap junction-independent function for connexins is to serve as the major functional component for hemichannels, the un-apposed halves of gap junctions. Hemichannels, as independent functional units, play roles that are different from that of gap junctions in the cell. The other functions of connexins appear to be gap junction- and hemichannel-independent. Published studies implicate the latter functions of connexins in cell growth, differentiation, tumorigenicity, injury, and apoptosis, although the mechanistic aspects of these actions remain largely unknown. In this review, gap junction- and hemichannel-independent functions of connexins are summarized, and the molecular mechanisms underlying these connexin functions are speculated and discussed.

Atomic-scaled characterization of graphene PN junctions

NASA Astrophysics Data System (ADS)

Zhou, Xiaodong; Wang, Dennis; Dadgar, Ali; Agnihotri, Pratik; Lee, Ji Ung; Reuter, Mark C.; Ross, Frances M.; Pasupathy, Abhay N.

Graphene p-n junctions are essential devices for studying relativistic Klein tunneling and the Veselago lensing effect in graphene. We have successfully fabricated graphene p-n junctions using both lithographically pre-patterned substrates and the stacking of vertical heterostructures. We then use our 4-probe STM system to characterize the junctions. The ability to carry out scanning electron microscopy (SEM) in our STM instrument is essential for us to locate and measure the junction interface. We obtain both the topography and dI/dV spectra at the junction area, from which we track the shift of the graphene chemical potential with position across the junction interface. This allows us to directly measure the spatial width and roughness of the junction and its potential barrier height. We will compare the junction properties of devices fabricated by the aforementioned two methods and discuss their effects on the performance as a Veselago lens.

Molecular mechanisms regulating formation, trafficking and processing of annular gap junctions.

PubMed

Falk, Matthias M; Bell, Cheryl L; Kells Andrews, Rachael M; Murray, Sandra A

2016-05-24

Internalization of gap junction plaques results in the formation of annular gap junction vesicles. The factors that regulate the coordinated internalization of the gap junction plaques to form annular gap junction vesicles, and the subsequent events involved in annular gap junction processing have only relatively recently been investigated in detail. However it is becoming clear that while annular gap junction vesicles have been demonstrated to be degraded by autophagosomal and endo-lysosomal pathways, they undergo a number of additional processing events. Here, we characterize the morphology of the annular gap junction vesicle and review the current knowledge of the processes involved in their formation, fission, fusion, and degradation. In addition, we address the possibility for connexin protein recycling back to the plasma membrane to contribute to gap junction formation and intercellular communication. Information on gap junction plaque removal from the plasma membrane and the subsequent processing of annular gap junction vesicles is critical to our understanding of cell-cell communication as it relates to events regulating development, cell homeostasis, unstable proliferation of cancer cells, wound healing, changes in the ischemic heart, and many other physiological and pathological cellular phenomena.

ABUNDANCE AND ULTRASTRUCTURAL DIVERSITY OF NEURONAL GAP JUNCTIONS IN THE OFF AND ON SUBLAMINAE OF THE INNER PLEXIFORM LAYER OF RAT AND MOUSE RETINA

PubMed Central

KAMASAWA, N.; FURMAN, C. S.; DAVIDSON, K. G. V.; SAMPSON, J. A.; MAGNIE, A. R.; GEBHARDT, B. R.; KAMASAWA, M.; YASUMURA, T.; ZUMBRUNNEN, J. R.; PICKARD, G. E.; NAGY, J. I.; RASH, J. E.

2007-01-01

Neuronal gap junctions are abundant in both outer and inner plexiform layers of the mammalian retina. In the inner plexiform layer (IPL), ultrastructurally-identified gap junctions were reported primarily in the functionally-defined and anatomically-distinct ON sublamina, with few reported in the OFF sublamina. We used freeze-fracture replica immunogold labeling and confocal microscopy to quantitatively analyze the morphologies and distributions of neuronal gap junctions in the IPL of adult rat and mouse retina. Under “baseline” conditions (photopic illumination/general anesthesia), 649 neuronal gap junctions immunogold-labeled for connexin36 were identified in rat IPL, of which 375 were photomapped to OFF vs. ON sublaminae. In contrast to previous reports, the volume-density of gap junctions was equally abundant in both sublaminae. Five distinctive morphologies of gap junctions were identified: conventional crystalline and non-crystalline “plaques” (71% and 3%), plus unusual “string” (14%), “ribbon” (7%) and “reticular” (2%) forms. Plaque and reticular gap junctions were distributed throughout the IPL. However, string and ribbon gap junctions were restricted to the OFF sublamina, where they represented 48% of gap junctions in that layer. In string and ribbon junctions, curvilinear strands of connexons were dispersed over 5 to 20 times the area of conventional plaques having equal numbers of connexons. To define morphologies of gap junctions under different light-adaptation conditions, we examined an additional 1150 gap junctions from rats and mice prepared after 30 min of photopic, mesopic and scotopic illumination, with and without general anesthesia. Under these conditions, string and ribbon gap junctions remained abundant in the OFF sublamina and absent in the ON sublamina. Abundant gap junctions in the OFF sublamina of these two rodents with rod-dominant retinas revealed previously-undescribed but extensive pathways for inter-neuronal communication; and the wide dispersion of connexons in string and ribbon gap junctions suggests unique structural features of gap junctional coupling in the OFF vs. ON sublamina. PMID:17010526

Bottom-up and top-down fabrication of nanowire-based electronic devices: In situ doping of vapor liquid solid grown silicon nanowires and etch-dependent leakage current in InGaAs tunnel junctions

NASA Astrophysics Data System (ADS)

Kuo, Meng-Wei

Semiconductor nanowires are important components in future nanoelectronic and optoelectronic device applications. These nanowires can be fabricated using either bottom-up or top-down methods. While bottom-up techniques can achieve higher aspect ratio at reduced dimension without having surface and sub-surface damage, uniform doping distributions with abrupt junction profiles are less challenging for top-down methods. In this dissertation, nanowires fabricated by both methods were systematically investigated to understand: (1) the in situ incorporation of boron (B) dopants in Si nanowires grown by the bottom-up vapor-liquid-solid (VLS) technique, and (2) the impact of plasma-induced etch damage on InGaAs p +-i-n+ nanowire junctions for tunnel field-effect transistors (TFETs) applications. In Chapter 2 and 3, the in situ incorporation of B in Si nanowires grown using silane (SiH4) or silicon tetrachloride (SiCl4) as the Si precursor and trimethylboron (TMB) as the p-type dopant source is investigated by I-V measurements of individual nanowires. The results from measurements using a global-back-gated test structure reveal nonuniform B doping profiles on nanowires grown from SiH4, which is due to simultaneous incorporation of B from nanowire surface and the catalyst during VLS growth. In contrast, a uniform B doping profile in both the axial and radial directions is achieved for TMBdoped Si nanowires grown using SiCl4 at high substrate temperatures. In Chapter 4, the I-V characteristics of wet- and dry-etched InGaAs p+-i-n+ junctions with different mesa geometries, orientations, and perimeter-to-area ratios are compared to evaluate the impact of the dry etch process on the junction leakage current properties. Different post-dry etch treatments, including wet etching and thermal annealing, are performed and the effectiveness of each is assessed by temperaturedependent I-V measurements. As compared to wet-etched control devices, dry-etched junctions have a significantly higher leakage current and a current kink in the reverse bias regime, which is likely due to additional trap states created by plasma-induced damage during the Cl2/Ar/H2 mesa isolation step. These states extend more than 60 nm from the mesa surface and can only be partially passivated after a thermal anneal at 350°C for 20 minutes. The evolution of the electrical properties with post-dry etch treatments indicates that the shallow and deep-level trap states resulting from ion-induced point defects, arsenic vacancies and hydrogen-dopant complexes are the primary cause of degradation in the electrical properties of the dry-etched junctions.

Scribble is required for normal epithelial cell–cell contacts and lumen morphogenesis in the mammalian lung

PubMed Central

Yates, Laura L.; Schnatwinkel, Carsten; Hazelwood, Lee; Chessum, Lauren; Paudyal, Anju; Hilton, Helen; Romero, M. Rosario; Wilde, Jonathan; Bogani, Debora; Sanderson, Jeremy; Formstone, Caroline; Murdoch, Jennifer N.; Niswander, Lee A.; Greenfield, Andy; Dean, Charlotte H.

2013-01-01

During lung development, proper epithelial cell arrangements are critical for the formation of an arborized network of tubes. Each tube requires a lumen, the diameter of which must be tightly regulated to enable optimal lung function. Lung branching and lumen morphogenesis require close epithelial cell–cell contacts that are maintained as a result of adherens junctions, tight junctions and by intact apical–basal (A/B) polarity. However, the molecular mechanisms that maintain epithelial cohesion and lumen diameter in the mammalian lung are unknown. Here we show that Scribble, a protein implicated in planar cell polarity (PCP) signalling, is necessary for normal lung morphogenesis. Lungs of the Scrib mouse mutant Circletail (Crc) are abnormally shaped with fewer airways, and these airways often lack a visible, ‘open’ lumen. Mechanistically we show that Scrib genetically interacts with the core PCP gene Vangl2 in the developing lung and that the distribution of PCP pathway proteins and Rho mediated cytoskeletal modification is perturbed in ScribCrc/Crc lungs. However A/B polarity, which is disrupted in Drosophila Scrib mutants, is largely unaffected. Notably, we find that Scrib mediates functions not attributed to other PCP proteins in the lung. Specifically, Scrib localises to both adherens and tight junctions of lung epithelia and knockdown of Scrib in lung explants and organotypic cultures leads to reduced cohesion of lung epithelial cells. Live imaging of Scrib knockdown lungs shows that Scrib does not affect bud bifurcation, as previously shown for the PCP protein Celsr1, but is required to maintain epithelial cohesion. To understand the mechanism leading to reduced cell–cell association, we show that Scrib associates with β-catenin in embryonic lung and the sub-cellular distribution of adherens and tight junction proteins is perturbed in mutant lung epithelia. Our data reveal that Scrib is required for normal lung epithelial organisation and lumen morphogenesis by maintaining cell–cell contacts. Thus we reveal novel and important roles for Scrib in lung development operating via the PCP pathway, and in regulating junctional complexes and cell cohesion. PMID:23195221

Neutrophil proteinase 3 (PR3) acts on protease-activated receptor-2 (PAR-2) to enhance vascular endothelial cell barrier function

PubMed Central

Kuckleburg, Christopher J.; Newman, Peter J.

2013-01-01

The principle role of the vascular endothelium is to present a semi-impermeable barrier to soluble factors and circulating cells, while still permitting the passage of leukocytes from the bloodstream into the tissue. The process of diapedesis involves the selective disruption of endothelial cell junctions, an event that could in theory compromise vascular integrity. It is therefore somewhat surprising that neutrophil transmigration does not significantly impair endothelial barrier function. We examined whether neutrophils might secrete factors that promote vascular integrity during the latter stages of neutrophil transmigration, and found that neutrophil proteinase 3 (PR3) – a serine protease harbored in azurophilic granules – markedly enhanced barrier function in endothelial cells. PR3 functioned in this capacity both in its soluble form and in a complex with cell-surface NB1. PR3-mediated enhancement of endothelial cell junctional integrity required its proteolytic activity, as well as endothelial cell expression of the protease-activated receptor, PAR-2. Importantly, PR3 suppressed the vascular permeability changes and disruption of junctional proteins induced by the action of PAR-1 agonists. These findings establish the potential for neutrophil-derived PR3 to play a role in reestablishing vascular integrity following leukocyte transmigration, and in protecting endothelial cells from PAR-1-induced permeability changes that occur during thrombotic and inflammatory events. PMID:23202369

Bioelectrical coupling in multicellular domains regulated by gap junctions: A conceptual approach.

PubMed

Cervera, Javier; Pietak, Alexis; Levin, Michael; Mafe, Salvador

2018-04-21

We review the basic concepts involved in bioelectrically-coupled multicellular domains, focusing on the role of membrane potentials (V mem ). In the first model, single-cell V mem is modulated by two generic polarizing and depolarizing ion channels, while intercellular coupling is implemented via voltage-gated gap junctions. Biochemical and bioelectrical signals are integrated via a feedback loop between V mem and the transcription and translation of a protein forming an ion channel. The effective rate constants depend on the single-cell V mem because these potentials modulate the local concentrations of signaling molecules and ions. This electrochemically-based idealization of the complex biophysical problem suggests that the spatio-temporal map of single-cell potentials can influence downstream patterning processes by means of the voltage-gated gap junction interconnectivity, much as in the case of electronic devices where the control of electric potentials and currents allows the local modulation of the circuitry to achieve full functionality. An alternative theoretical approach, the BioElectrical Tissue Simulation Engine (BETSE), is also presented. The BETSE modeling environment utilizes finite volume techniques to simulate bioelectric states from the perspective of ion concentrations and fluxes. This model has been successfully applied to make predictions and explain experimental observations in a variety of embryonic, regenerative, and oncogenic contexts. Copyright © 2018 Elsevier B.V. All rights reserved.

Exploring Hot Gas at Junctions of Galaxy Filaments

NASA Astrophysics Data System (ADS)

Mitsuishi, Ikuyuki; Yamasaki, Noriko; Kawahara, Hajime; Sekiya, Norio; Sasaki, Shin; Sousbie, Thierry

Because galaxies are forced to follow the strong gravitational potential created by the underlying cosmic web of the dark matter, their distribution reflects its filamentary structures. By identifying the filamentary structures, one can therefore recover a map of the network that drives structure formation. Filamentary junctions are regions of particular interest as they identify places where mergers and other interesting astrophysical phenomena have high chances to occur. We identified the galaxy filaments by our original method (Sousbie (2011) & Sousbie et al. (2011)) and X-ray pointing observations were conducted for the six fields locating in the junctions of the galaxy filaments where no specific diffuse X-ray emissions had previously been detected so far. We discovered significant X-ray signals in their images and spectra of the all regions. Spectral analysis demonstrated that six sources originate from diffuse emissions associated with optically bright galaxies, group-scale, or cluster-scale X-ray halos with kT˜1-4 keV, while the others are compact object origin. Interestingly, all of the newly discovered three intracluster media show peculiar features such as complex or elongated morphologies in X-ray and/or optical and hot spot involved in ongoing merger events (Kawahara et al. (2011) & Mitsuishi et al. (2014)). In this conference, results of follow-up radio observations for the merging groups as well as the details of the X-ray observations will be reported.

Fast, clash-free RNA conformational morphing using molecular junctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heliou, Amelie; Budday, Dominik; Fonseca, Rasmus

Non-coding ribonucleic acids (ncRNA) are functional RNA molecules that are not translated into protein. They are extremely dynamic, adopting diverse conformational substates, which enables them to modulate their interaction with a large number of other molecules. The flexibility of ncRNA provides a challenge for probing their complex 3D conformational landscape, both experimentally and computationally. As a result, despite their conformational diversity, ncRNAs mostly preserve their secondary structure throughout the dynamic ensemble. Here we present a kinematics-based procedure to morph an RNA molecule between conformational substates, while avoiding inter-atomic clashes. We represent an RNA as a kinematic linkage, with fixed groupsmore » of atoms as rigid bodies and rotatable bonds as degrees of freedom. Our procedure maintains RNA secondary structure by treating hydrogen bonds between base pairs as constraints. The constraints define a lower-dimensional, secondary-structure constraint manifold in conformation space, where motions are largely governed by molecular junctions of unpaired nucleotides. On a large benchmark set, we show that our morphing procedure compares favorably to peer algorithms, and can approach goal conformations to within a low all-atom RMSD by directing fewer than 1% of its atoms. Furthermore, our results suggest that molecular junctions can modulate 3D structural rearrangements, while secondary structure elements guide large parts of the molecule along the transition to the correct final conformation.« less

Regulation of intestinal permeability: The role of proteases

PubMed Central

Van Spaendonk, Hanne; Ceuleers, Hannah; Witters, Leonie; Patteet, Eveline; Joossens, Jurgen; Augustyns, Koen; Lambeir, Anne-Marie; De Meester, Ingrid; De Man, Joris G; De Winter, Benedicte Y

2017-01-01

The gastrointestinal barrier is - with approximately 400 m2 - the human body’s largest surface separating the external environment from the internal milieu. This barrier serves a dual function: permitting the absorption of nutrients, water and electrolytes on the one hand, while limiting host contact with noxious luminal antigens on the other hand. To maintain this selective barrier, junction protein complexes seal the intercellular space between adjacent epithelial cells and regulate the paracellular transport. Increased intestinal permeability is associated with and suggested as a player in the pathophysiology of various gastrointestinal and extra-intestinal diseases such as inflammatory bowel disease, celiac disease and type 1 diabetes. The gastrointestinal tract is exposed to high levels of endogenous and exogenous proteases, both in the lumen and in the mucosa. There is increasing evidence to suggest that a dysregulation of the protease/antiprotease balance in the gut contributes to epithelial damage and increased permeability. Excessive proteolysis leads to direct cleavage of intercellular junction proteins, or to opening of the junction proteins via activation of protease activated receptors. In addition, proteases regulate the activity and availability of cytokines and growth factors, which are also known modulators of intestinal permeability. This review aims at outlining the mechanisms by which proteases alter the intestinal permeability. More knowledge on the role of proteases in mucosal homeostasis and gastrointestinal barrier function will definitely contribute to the identification of new therapeutic targets for permeability-related diseases. PMID:28405139

Strain-balanced type-II superlattices for efficient multi-junction solar cells.

PubMed

Gonzalo, A; Utrilla, A D; Reyes, D F; Braza, V; Llorens, J M; Fuertes Marrón, D; Alén, B; Ben, T; González, D; Guzman, A; Hierro, A; Ulloa, J M

2017-06-21

Multi-junction solar cells made by assembling semiconductor materials with different bandgap energies have hold the record conversion efficiencies for many years and are currently approaching 50%. Theoretical efficiency limits make use of optimum designs with the right lattice constant-bandgap energy combination, which requires a 1.0-1.15 eV material lattice-matched to GaAs/Ge. Nevertheless, the lack of suitable semiconductor materials is hindering the achievement of the predicted efficiencies, since the only candidates were up to now complex quaternary and quinary alloys with inherent epitaxial growth problems that degrade carrier dynamics. Here we show how the use of strain-balanced GaAsSb/GaAsN superlattices might solve this problem. We demonstrate that the spatial separation of Sb and N atoms avoids the ubiquitous growth problems and improves crystal quality. Moreover, these new structures allow for additional control of the effective bandgap through the period thickness and provide a type-II band alignment with long carrier lifetimes. All this leads to a strong enhancement of the external quantum efficiency under photovoltaic conditions with respect to bulk layers of equivalent thickness. Our results show that GaAsSb/GaAsN superlattices with short periods are the ideal (pseudo)material to be integrated in new GaAs/Ge-based multi-junction solar cells that could approach the theoretical efficiency limit.

Fast, clash-free RNA conformational morphing using molecular junctions

DOE PAGES

Heliou, Amelie; Budday, Dominik; Fonseca, Rasmus; ...

2017-03-13

Non-coding ribonucleic acids (ncRNA) are functional RNA molecules that are not translated into protein. They are extremely dynamic, adopting diverse conformational substates, which enables them to modulate their interaction with a large number of other molecules. The flexibility of ncRNA provides a challenge for probing their complex 3D conformational landscape, both experimentally and computationally. As a result, despite their conformational diversity, ncRNAs mostly preserve their secondary structure throughout the dynamic ensemble. Here we present a kinematics-based procedure to morph an RNA molecule between conformational substates, while avoiding inter-atomic clashes. We represent an RNA as a kinematic linkage, with fixed groupsmore » of atoms as rigid bodies and rotatable bonds as degrees of freedom. Our procedure maintains RNA secondary structure by treating hydrogen bonds between base pairs as constraints. The constraints define a lower-dimensional, secondary-structure constraint manifold in conformation space, where motions are largely governed by molecular junctions of unpaired nucleotides. On a large benchmark set, we show that our morphing procedure compares favorably to peer algorithms, and can approach goal conformations to within a low all-atom RMSD by directing fewer than 1% of its atoms. Furthermore, our results suggest that molecular junctions can modulate 3D structural rearrangements, while secondary structure elements guide large parts of the molecule along the transition to the correct final conformation.« less

Visualizing the effect of dynamin inhibition on annular gap vesicle formation and fission

PubMed Central

Nickel, Beth; Boller, Marie; Schneider, Kimberly; Shakespeare, Teresa; Gay, Vernon; Murray, Sandra A.

2013-01-01

Summary Although gap junction plaque assembly has been extensively studied, mechanisms involved in plaque disassembly are not well understood. Disassembly involves an internalization process in which annular gap junction vesicles are formed. These vesicles undergo fission, but the molecular machinery needed for these fissions has not been described. The mechanoenzyme dynamin has been previously demonstrated to play a role in gap junction plaque internalization. To investigate the role of dynamin in annular gap junction vesicle fission, immunocytochemical, time-lapse and transmission electron microscopy were used to analyze SW-13 adrenocortical cells in culture. Dynamin was demonstrated to colocalize with gap junction plaques and vesicles. Dynamin inhibition, by siRNA knockdown or treatment with the dynamin GTPase inhibitor dynasore, increased the number and size of gap junction ‘buds’ suspended from the gap junction plaques. Buds, in control populations, were frequently released to form annular gap junction vesicles. In dynamin-inhibited populations, the buds were larger and infrequently released and thus fewer annular gap junction vesicles were formed. In addition, the number of annular gap junction vesicle fissions per hour was reduced in the dynamin-inhibited populations. We believe this to be the first report addressing the details of annular gap junction vesicle fissions and demonstrating a role of dynamin in this process. This information is crucial for elucidating the relationship between gap junctions, membrane regulation and cell behavior. PMID:23591819

Role of heteromeric gap junctions in the cytotoxicity of cisplatin.

PubMed

Tong, Xuhui; Dong, Shuying; Yu, Meiling; Wang, Qin; Tao, Liang

2013-08-09

In several systems, the presence of gap junctions made of a single connexin has been shown to enhance the cytotoxicity of cisplatin. However, most gap junction channels in vivo appear to be heteromeric (composed of more than one connexin isoform). Here we explore in HeLa cells the cytotoxicity to cisplatin that is enhanced by heteromeric gap junctions composed of Cx26 and Cx32, which have been shown to be more selective among biological permeants than the corresponding homomeric channels. We found that survival and subsequent proliferation of cells exposed to cisplatin were substantially reduced when gap junctions were present than when there were no gap junctions. Functional inhibition of gap junctions by oleamide enhanced survival/proliferation, and enhancement of gap junctions by retinoic acid decreased survival/proliferation. These effects occurred only in high density cultures, and the treatments were without effect when there was no opportunity for gap junction formation. The presence of functional gap junctions enhanced apoptosis as reflected in markers of both early-stage and late-stage apoptosis. Furthermore, analysis of caspases 3, 8 and 9 showed that functional gap junctions specifically induced apoptosis by the mitochondrial pathway. These results demonstrate that heteromeric Cx26/Cx32 gap junctions increase the cytotoxicity of cisplatin by induction of apoptosis via the mitochondrial pathway. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Visualizing the effect of dynamin inhibition on annular gap vesicle formation and fission.

PubMed

Nickel, Beth; Boller, Marie; Schneider, Kimberly; Shakespeare, Teresa; Gay, Vernon; Murray, Sandra A

2013-06-15

Although gap junction plaque assembly has been extensively studied, mechanisms involved in plaque disassembly are not well understood. Disassembly involves an internalization process in which annular gap junction vesicles are formed. These vesicles undergo fission, but the molecular machinery needed for these fissions has not been described. The mechanoenzyme dynamin has been previously demonstrated to play a role in gap junction plaque internalization. To investigate the role of dynamin in annular gap junction vesicle fission, immunocytochemical, time-lapse and transmission electron microscopy were used to analyze SW-13 adrenocortical cells in culture. Dynamin was demonstrated to colocalize with gap junction plaques and vesicles. Dynamin inhibition, by siRNA knockdown or treatment with the dynamin GTPase inhibitor dynasore, increased the number and size of gap junction 'buds' suspended from the gap junction plaques. Buds, in control populations, were frequently released to form annular gap junction vesicles. In dynamin-inhibited populations, the buds were larger and infrequently released and thus fewer annular gap junction vesicles were formed. In addition, the number of annular gap junction vesicle fissions per hour was reduced in the dynamin-inhibited populations. We believe this to be the first report addressing the details of annular gap junction vesicle fissions and demonstrating a role of dynamin in this process. This information is crucial for elucidating the relationship between gap junctions, membrane regulation and cell behavior.

A WAVE2–Arp2/3 actin nucleator apparatus supports junctional tension at the epithelial zonula adherens

PubMed Central

Verma, Suzie; Han, Siew Ping; Michael, Magdalene; Gomez, Guillermo A.; Yang, Zhe; Teasdale, Rohan D.; Ratheesh, Aparna; Kovacs, Eva M.; Ali, Radiya G.; Yap, Alpha S.

2012-01-01

The epithelial zonula adherens (ZA) is a specialized adhesive junction where actin dynamics and myosin-driven contractility coincide. The junctional cytoskeleton is enriched in myosin II, which generates contractile force to support junctional tension. It is also enriched in dynamic actin filaments, which are replenished by ongoing actin assembly. In this study we sought to pursue the relationship between actin assembly and junctional contractility. We demonstrate that WAVE2–Arp2/3 is a major nucleator of actin assembly at the ZA and likely acts in response to junctional Rac signaling. Furthermore, WAVE2–Arp2/3 is necessary for junctional integrity and contractile tension at the ZA. Maneuvers that disrupt the function of either WAVE2 or Arp2/3 reduced junctional tension and compromised the ability of cells to buffer side-to-side forces acting on the ZA. WAVE2–Arp2/3 disruption depleted junctions of both myosin IIA and IIB, suggesting that dynamic actin assembly may support junctional tension by facilitating the local recruitment of myosin. PMID:23051739

A WAVE2-Arp2/3 actin nucleator apparatus supports junctional tension at the epithelial zonula adherens.

PubMed

Verma, Suzie; Han, Siew Ping; Michael, Magdalene; Gomez, Guillermo A; Yang, Zhe; Teasdale, Rohan D; Ratheesh, Aparna; Kovacs, Eva M; Ali, Radiya G; Yap, Alpha S

2012-12-01

The epithelial zonula adherens (ZA) is a specialized adhesive junction where actin dynamics and myosin-driven contractility coincide. The junctional cytoskeleton is enriched in myosin II, which generates contractile force to support junctional tension. It is also enriched in dynamic actin filaments, which are replenished by ongoing actin assembly. In this study we sought to pursue the relationship between actin assembly and junctional contractility. We demonstrate that WAVE2-Arp2/3 is a major nucleator of actin assembly at the ZA and likely acts in response to junctional Rac signaling. Furthermore, WAVE2-Arp2/3 is necessary for junctional integrity and contractile tension at the ZA. Maneuvers that disrupt the function of either WAVE2 or Arp2/3 reduced junctional tension and compromised the ability of cells to buffer side-to-side forces acting on the ZA. WAVE2-Arp2/3 disruption depleted junctions of both myosin IIA and IIB, suggesting that dynamic actin assembly may support junctional tension by facilitating the local recruitment of myosin.

Disruption of gap junctions attenuates aminoglycoside-elicited renal tubular cell injury.

PubMed

Yao, Jian; Huang, Tao; Fang, Xin; Chi, Yuan; Zhu, Ying; Wan, Yigang; Matsue, Hiroyuki; Kitamura, Masanori

2010-08-01

Gap junctions play important roles in the regulation of cell phenotype and in determining cell survival after various insults. Here, we investigated the role of gap junctions in aminoglycoside-induced injury to renal tubular cells. Two tubular epithelial cell lines NRK-E52 and LLC-PK1 were compared for gap junction protein expression and function by immunofluorescent staining, Western blot and dye transfer assay. Cell viability after exposure to aminoglycosides was evaluated by WST assay. Gap junctions were modulated by transfection of the gap junction protein, connexin 43 (Cx43), use of Cx43 siRNA and gap junction inhibitors. NRK-E52 cells expressed abundant Cx43 and were functionally coupled by gap junctional intercellular communication (GJIC). Exposure of NRK-E52 cells to aminoglycosides, G418 and hygromycin, increased Cx43 phosphorylation and GJIC. The aminoglycosides also decreased cell viability that was prevented by gap junction inhibitors and Cx43 siRNA. LLC-PK1 cells were gap junction-deficient and resistant to aminoglycoside-induced cytotoxicity. Over-expression of a wild-type Cx43 converted LLC-PK1 cells to a drug-sensitive phenotype. The gap junction inhibitor alpha-glycyrrhetinic acid (alpha-GA) activated Akt in NRK-E52 cells. Inhibition of the Akt pathway enhanced cell toxicity to G418 and abolished the protective effects of alpha-GA. In addition, gentamycin-elicited cytotoxicity in NRK-E52 cells was also significantly attenuated by alpha-GA. Gap junctions contributed to the cytotoxic effects of aminoglycosides. Modulation of gap junctions could be a promising approach for prevention and treatment of aminoglycoside-induced renal tubular cell injury.

Coincidence of features of emitted THz electromagnetic wave power form a single Josephson junction and different current components

NASA Astrophysics Data System (ADS)

Hamdipour, Mohammad

2017-12-01

By applying a voltage to a Josephson junction, the charge in superconducting layers (S-layers) will oscillate. Wavelength of the charge oscillations in S-layers is related to external current in junction, by increasing the external current, the wavelength will decrease which cause in some currents the wavelength be incommensurate with width of junction, so the CVC shows Fiske like steps. External current throwing along junction has some components, resistive, capacitive and superconducting current, beside these currents there is a current in lateral direction of junction, (x direction). On the other hand, the emitted electromagnetic wave power in THz region is related to AC component of electric field in junction, which itself is related to charge density in S-layers, which is related to currents in the system. So we expect that features of variation of current components reflect the features of emitted THz power form junction. Here we study in detail the superconductive current in a long Josephson junction (JJ), the current voltage characteristics (CVC) of junction and emitted THz power from the system. Then we compare the results. Comparing the results we see that there is a good qualitative coincidence in features of emitted THz power and supercurrent in junction.

Tunnel junction multiple wavelength light-emitting diodes

DOEpatents

Olson, Jerry M.; Kurtz, Sarah R.

1992-01-01

A multiple wavelength LED having a monolithic cascade cell structure comprising at least two p-n junctions, wherein each of said at least two p-n junctions have substantially different band gaps, and electrical connector means by which said at least two p-n junctions may be collectively energized; and wherein said diode comprises a tunnel junction or interconnect.

Specific Cx43 phosphorylation events regulate gap junction turnover in vivo

PubMed Central

Solan, Joell L.; Lampe, Paul D.

2014-01-01

Gap junctions, composed of proteins from the connexin gene family, are highly dynamic structures that are regulated by kinase-mediated signaling pathways and interactions with other proteins. Phosphorylation of Connexin43 (Cx43) at different sites controls gap junction assembly, gap junction size and gap junction turnover. Here we present a model describing how Akt, mitogen activated protein kinase (MAPK) and src kinase coordinate to regulate rapid turnover of gap junctions. Specifically, Akt phosphorylates Cx43 at S373 eliminating interaction with zona occludens-1 (ZO-1) allowing gap junctions to enlarge. Then MAPK and src phosphorylate Cx43 to initiate turnover. We integrate published data with new data to test and refine this model. Finally, we propose that differential coordination of kinase activation and Cx43 phosphorylation controls the specific routes of disassembly, e.g., annular junction formation or gap junctions can potentially “unzip” and be internalized/endocytosed into the cell that produced each connexin. PMID:24508467

Pulpal and periradicular response to caries: current management and regenerative options.

PubMed

Chogle, Sami M A; Goodis, Harold E; Kinaia, Bassam Michael

2012-07-01

The pulp-dentin complex is a strategic and dynamic barrier to various insults that plague the dentition. Researchers have yet to understand the complete potential of this shifting junction and its components. The most common cause of injury to the pulp-dentin complex is carious breakdown of enamel and dentin. In recent years, there has been a change in restorative management of caries. The emphasis is on strategies to preserve dentin and protect the pulp. This article provides a brief review of the effect of caries on the pulp, of subsequent events on the periradicular tissues, and of current understanding of treatment modalities. Copyright © 2012 Elsevier Inc. All rights reserved.

Nanotube junctions

DOEpatents

Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon; Zettl, Alexander Karlwalte

2004-12-28

The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

Nanotube junctions

DOEpatents

Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon Sheng; Zettl, Alexander Karlwalter

2003-01-01

The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

Short Ballistic Josephson Coupling in Planar Graphene Junctions with Inhomogeneous Carrier Doping

NASA Astrophysics Data System (ADS)

Park, Jinho; Lee, Jae Hyeong; Lee, Gil-Ho; Takane, Yositake; Imura, Ken-Ichiro; Taniguchi, Takashi; Watanabe, Kenji; Lee, Hu-Jong

2018-02-01

We report on short ballistic (SB) Josephson coupling in junctions embedded in a planar heterostructure of graphene. Ballistic Josephson coupling is confirmed by the Fabry-Perot-type interference of the junction critical current Ic . The product of Ic and the normal-state junction resistance RN , normalized by the zero-temperature gap energy Δ0 of the superconducting electrodes, turns out to be exceptionally large close to 2, an indication of strong Josephson coupling in the SB junction limit. However, Ic shows a temperature dependence that is inconsistent with the conventional short-junction-like behavior based on the standard Kulik-Omel'yanchuk prediction. We argue that this feature stems from the effects of inhomogeneous carrier doping in graphene near the superconducting contacts, although the junction is in fact in the short-junction limit.

Correlation between the graft-host junction of penetrating keratoplasty by anterior segment-optical coherence tomography and the magnitude of postoperative astigmatism.

PubMed

Nassar, Ghada Azab; Arfeen, Shaimaa Abd El Salam

2017-07-01

This study aimed to evaluate the alignment pattern of the graft-host junction after penetrating keratoplasty (PK) by anterior segment-optical coherence tomography (AS-OCT) and to correlate this pattern with the magnitude of postoperative astigmatism. This retrospective observational study was carried out on forty patients who underwent PK from February 2013 to August 2014. AS-OCT was performed, and the graft-host junctions were classified into well-apposed junction, malapposed junction, and equally apposed junction. Mal-apposition is subdivided into gap and protrusion. The correlations between clinical characteristics, wound profiles from the AS-OCT, and the magnitude of postoperative astigmatism by Sirius camera (Costruzione Strumenti Oftalmici [CSO], Florence, Italy (CSO, Sirius), were analyzed. Graft-host junctions from forty patients were analyzed; 18 eyes had well-apposed junctions, ten eyes had malapposed junctions, and 12 had equally apposed junctions. The mean cylinder was -9.44 ± -4.00D in well-apposed group, -13.40 ± -5.01D in malapposed group, and -4.67 ± -0.94D in equally apposed group. Alignment pattern of the graft-host junction correlated significantly with the magnitude of astigmatism (P = 0.034). Preoperative corneal diseases did not have an effect on the magnitude of astigmatism (P = 0.123). The alignment pattern of the graft-host junction by AS-OCT can explain the postoperative astigmatism after PK where it correlates significantly with the magnitude of astigmatism.

Membrane junctions in Xenopus eggs: their distribution suggests a role in calcium regulation.

PubMed

Gardiner, D M; Grey, R D

1983-04-01

We have observed the presence of membrane junctions formed between the plasma membrane and cortical endoplasmic reticulum of mature, unactivated eggs of xenopus laevis. The parallel, paired membranes of the junction are separated by a 10-mn gap within which electron-dense material is present. This material occurs in patches with an average center-to-center distance of approximately 30 nm. These junctions are rare in immature (but fully grown) oocytes (approximately 2 percent of the plasma membrane is associated with junctions) and increase dramatically during progesterone-induced maturation. Junctions in the mature, unactivated egg are two to three times more abundant in the animal hemisphere (25-30 percent of the plasma membrane associated with junction) as compared with the vegetal hemisphere (10-15 percent). Junction density decreases rapidly to values characteristic of immature oocytes in response to egg activation. The plasma membrane-ER junctions of xenopus eggs are strikingly similar in structure to membrane junctions in muscle cells thought to be essential in the triggering of intracellular calcium release from the sarcoplasmic reticulum. In addition, the junctions' distinctive, animal-vegetal polarity of distribution, their dramatic appearance during maturation, and their disapperance during activation are correlated with previously documented patterns of calcium-mediated events in anuran eggs. We discuss several lines of evidence supporting the hypothesis that these junctions in xenopus eggs are sites that transduce extracellular events into intracellular calcium release during fertilization and activation of development.

SRY, like HMG1, recognizes sharp angles in DNA.

PubMed Central

Ferrari, S; Harley, V R; Pontiggia, A; Goodfellow, P N; Lovell-Badge, R; Bianchi, M E

1992-01-01

HMG boxes are DNA binding domains present in chromatin proteins, general transcription factors for nucleolar and mitochondrial RNA polymerases, and gene- and tissue-specific transcriptional regulators. The HMG boxes of HMG1, an abundant component of chromatin, interact specifically with four-way junctions, DNA structures that are cross-shaped and contain angles of approximately 60 and 120 degrees between their arms. We show here also that the HMG box of SRY, the protein that determines the expression of male-specific genes in humans, recognizes four-way junction DNAs irrespective of their sequence. In addition, when SRY binds to linear duplex DNA containing its specific target AACAAAG, it produces a sharp bend. Therefore, the interaction between HMG boxes and DNA appears to be predominantly structure-specific. The production of the recognition of a kink in DNA can serve several distinct functions, such as the repair of DNA lesions, the folding of DNA segments with bound transcriptional factors into productive complexes or the wrapping of DNA in chromatin. Images PMID:1425584

Epithelial-stromal interface in normal and neoplastic human bladder epithelium.

PubMed

Alroy, J; Gould, V E

1980-01-01

The ultrastructure of the epithelial-stromal interface of the human urinary bladder was studied in biopsy specimens that included 7 normal controls, 1 inverted papilloma, 18 noninvasive papillary carcinomas, and 19 invasive transitional cell carcinomas. In the invasive foci of the transitional cell carcinomas, the underlying basal lamina was attenuated or absent and the number of hemidesmosomes was decreased. These neoplastic cells displayed notably increased numbers of lysosomes, some of which appeared to be in the process of exocytosis. Increased numbers of cytoplasmic filaments adjacent to the plasma membranes at the invading pole of these cells were also observed. Tight junctions and junctional complexes were noticed adjacent to the tumor-stromal interface. None of the aforementioned features was observed in normal transitional epithelium, in inverted papilloma, in noninvasive papillary carcinomas, or in the noninvasive portions of invasive transitional cell carcinomas. Alterations of the epithelial-stromal interface deserve additional studies for they may constitute important parameters in the evaluation of actual or potential invasiveness in the various types of carcinoma of the bladder.

Multi-junction Thin-film Solar Cells on Flexible Substrates for Space Power

NASA Technical Reports Server (NTRS)

Hepp, Aloysius F.; Smith, Mark; Scofield, John H.; Dickman, John E.; Lush, Gregory B.; Morel, Donald L.; Ferekides, Christos; Dhere, Neelkanth G.

2002-01-01

The ultimate objective of the thin-film program at NASA GRC is development of a 20 percent AM0 thin-film device technology with high power/weight ratio. Several approaches are outlined to improve overall device efficiency and power/weight ratio. One approach involves the use of very lightweight flexible substrates such as polyimides (i.e., Kapton(Trademark)) or metal foil. Also, a compound semiconductor tandem device structure that can meet this objective is proposed and simulated using Analysis of Microelectronic and Photonic Structures (AMPS). AMPS modeling of current devices in tandem format indicate that AM0 efficiencies near 20 percent can be achieved. And with improvements in materials, efficiencies approaching 25 percent are achievable. Several important technical issues need to be resolved to realize these complex devices: development of a wide bandgap material with good electronic properties, development of transparent contacts, and targeting a 2-terminal device structure (with more complicated processing and tunnel junction) or 4-terminal device. Recent progress in the NASA GRC program is outlined.

Ring modulators with enhanced efficiency based on standing-wave operation on a field-matched, interdigitated p-n junction.

PubMed

Pavanello, Fabio; Zeng, Xiaoge; Wade, Mark T; Popović, Miloš A

2016-11-28

We propose ring modulators based on interdigitated p-n junctions that exploit standing rather than traveling-wave resonant modes to improve modulation efficiency, insertion loss and speed. Matching the longitudinal nodes and antinodes of a standing-wave mode with high (contacts) and low (depletion regions) carrier density regions, respectively, simultaneously lowers loss and increases sensitivity significantly. This approach permits further to relax optical constraints on contacts placement and can lead to lower device capacitance. Such structures are well-matched to fabrication in advanced microelectronics CMOS processes. Device architectures that exploit this concept are presented along with their benefits and drawbacks. A temporal coupled mode theory model is used to investigate the static and dynamic response. We show that modulation efficiencies or loss Q factors up to 2 times higher than in previous traveling-wave geometries can be achieved leading to much larger extinction ratios. Finally, we discuss more complex doping geometries that can improve carrier dynamics for higher modulation speeds in this context.

Claudins and the Kidney Volume 75: Annual Review of Physiology

PubMed Central

Hou, Jianghui; Rajagopal, Madhumitha; Yu, Alan S. L.

2013-01-01

Claudins are tight junction membrane proteins that regulate paracellular permeability of renal epithelia to small ions, solutes and water. Claudins interact within the cell membrane and between neighboring cells to form tight junction strands and constitute both the paracellular barrier and pore. The first extracellular domain of claudins is thought to be the pore-lining domain and contains the determinants of charge selectivity. Multiple claudins are expressed in different nephron segments and this likely determines the permeability properties of each segment. Recent evidence has identified claudin-2 as constituting the cation-reabsorptive pathway in the proximal tubule, claudin-14, -16 and -19 as forming a complex that regulates calcium transport in the thick ascending limb of the loop of Henle, and claudin-4, -7 and -8 as determinants of collecting duct choride permeability. Mutations in claudin-16 and -19 cause familial hypercalciuric hypomagnesemia. The roles of other claudins in kidney diseases remain to be fully elucidated. PMID:23140368

An Organismal CNV Mutator Phenotype Restricted to Early Human Development.

PubMed

Liu, Pengfei; Yuan, Bo; Carvalho, Claudia M B; Wuster, Arthur; Walter, Klaudia; Zhang, Ling; Gambin, Tomasz; Chong, Zechen; Campbell, Ian M; Coban Akdemir, Zeynep; Gelowani, Violet; Writzl, Karin; Bacino, Carlos A; Lindsay, Sarah J; Withers, Marjorie; Gonzaga-Jauregui, Claudia; Wiszniewska, Joanna; Scull, Jennifer; Stankiewicz, Paweł; Jhangiani, Shalini N; Muzny, Donna M; Zhang, Feng; Chen, Ken; Gibbs, Richard A; Rautenstrauss, Bernd; Cheung, Sau Wai; Smith, Janice; Breman, Amy; Shaw, Chad A; Patel, Ankita; Hurles, Matthew E; Lupski, James R

2017-02-23

De novo copy number variants (dnCNVs) arising at multiple loci in a personal genome have usually been considered to reflect cancer somatic genomic instabilities. We describe a multiple dnCNV (MdnCNV) phenomenon in which individuals with genomic disorders carry five to ten constitutional dnCNVs. These CNVs originate from independent formation incidences, are predominantly tandem duplications or complex gains, exhibit breakpoint junction features reminiscent of replicative repair, and show increased de novo point mutations flanking the rearrangement junctions. The active CNV mutation shower appears to be restricted to a transient perizygotic period. We propose that a defect in the CNV formation process is responsible for the "CNV-mutator state," and this state is dampened after early embryogenesis. The constitutional MdnCNV phenomenon resembles chromosomal instability in various cancers. Investigations of this phenomenon may provide unique access to understanding genomic disorders, structural variant mutagenesis, human evolution, and cancer biology. Copyright © 2017 Elsevier Inc. All rights reserved.

A malaria parasite formin regulates actin polymerization and localizes to the parasite-erythrocyte moving junction during invasion.

PubMed

Baum, Jake; Tonkin, Christopher J; Paul, Aditya S; Rug, Melanie; Smith, Brian J; Gould, Sven B; Richard, Dave; Pollard, Thomas D; Cowman, Alan F

2008-03-13

Malaria parasites invade host cells using actin-based motility, a process requiring parasite actin filament nucleation and polymerization. Malaria and other apicomplexan parasites lack Arp2/3 complex, an actin nucleator widely conserved across eukaryotes, but do express formins, another type of actin nucleator. Here, we demonstrate that one of two malaria parasite formins, Plasmodium falciparum formin 1 (PfFormin 1), and its ortholog in the related parasite Toxoplasma gondii, follows the moving tight junction between the invading parasite and the host cell, which is the predicted site of the actomyosin motor that powers motility. Furthermore, in vitro, the PfFormin1 actin-binding formin homology 2 domain is a potent nucleator, stimulating actin polymerization and, like other formins, localizing to the barbed end during filament elongation. These findings support a conserved molecular mechanism underlying apicomplexan parasite motility and, given the essential role that actin plays in cell invasion, highlight formins as important determinants of malaria parasite pathogenicity.

Polarization curling and flux closures in multiferroic tunnel junctions

NASA Astrophysics Data System (ADS)

Peters, Jonathan J. P.; Apachitei, Geanina; Beanland, Richard; Alexe, Marin; Sanchez, Ana M.

2016-11-01

Formation of domain walls in ferroelectrics is not energetically favourable in low-dimensional systems. Instead, vortex-type structures are formed that are driven by depolarization fields occurring in such systems. Consequently, polarization vortices have only been experimentally found in systems in which these fields are deliberately maximized, that is, in films between insulating layers. As such configurations are devoid of screening charges provided by metal electrodes, commonly used in electronic devices, it is wise to investigate if curling polarization structures are innate to ferroelectricity or induced by the absence of electrodes. Here we show that in unpoled Co/PbTiO3/(La,Sr)MnO3 ferroelectric tunnel junctions, the polarization in active PbTiO3 layers 9 unit cells thick forms Kittel-like domains, while at 6 unit cells there is a complex flux-closure curling behaviour resembling an incommensurate phase. Reducing the thickness to 3 unit cells, there is an almost complete loss of switchable polarization associated with an internal gradient.

Centralspindlin and α-catenin regulate Rho signalling at the epithelial zonula adherens

PubMed Central

Priya, Rashmi; Verma, Suzie; Kovacs, Eva M.; Jiang, Kai; Brown, Nicholas H.; Akhmanova, Anna; Stehbens, Samantha J.; Yap, Alpha S.

2014-01-01

Summary The biological impact of Rho depends critically on the precise subcellular localization of its active, GTP-loaded form. The spatio-temporal balance between molecules that promote nucleotide exchange or GTP hydrolysis can potentially determine the sites of Rho signalling. But how these activities may be coordinated is poorly understood. We now report a molecular pathway that achieves exactly this coordination at the epithelial zonula adherens. We identify an extramitotic activity of the centralspindlin complex, better understood as a cytokinetic regulator, which localises to the zonula adherens during interphase by interacting with the cadherin-associated protein, α-catenin. Centralspindlin recruits the Rho GEF, Ect2, to the zonula adherens to activate Rho and support junctional integrity through myosin IIA. Centralspindlin also inhibits the junctional localisation of p190RhoGAP B, which can inactivate Rho. Thus, a conserved molecular ensemble that governs Rho activation during cytokinesis is utilized in interphase cells to control the Rho GTPase cycle at the zonula adherens. PMID:22750944

In-Operando Spatial Imaging of Edge Termination Electric Fields in GaN Vertical p-n Junction Diodes

DOE PAGES

Leonard, Francois; Dickerson, J. R.; King, M. P.; ...

2016-05-03

Control of electric fields with edge terminations is critical to maximize the performance of high-power electronic devices. We proposed a variety of edge termination designs which makes the optimization of such designs challenging due to many parameters that impact their effectiveness. And while modeling has recently allowed new insight into the detailed workings of edge terminations, the experimental verification of the design effectiveness is usually done through indirect means, such as the impact on breakdown voltages. In this letter, we use scanning photocurrent microscopy to spatially map the electric fields in vertical GaN p-n junction diodes in operando. We alsomore » reveal the complex behavior of seemingly simple edge termination designs, and show how the device breakdown voltage correlates with the electric field behavior. Modeling suggests that an incomplete compensation of the p-type layer in the edge termination creates a bilayer structure that leads to these effects, with variations that significantly impact the breakdown voltage.« less

Deconstructing the brain’s moral network: dissociable functionality between the temporoparietal junction and ventro-medial prefrontal cortex

PubMed Central

Mobbs, Dean; Dalgleish, Tim

2014-01-01

Research has illustrated that the brain regions implicated in moral cognition comprise a robust and broadly distributed network. However, understanding how these brain regions interact and give rise to the complex interplay of cognitive processes underpinning human moral cognition is still in its infancy. We used functional magnetic resonance imaging to examine patterns of activation for ‘difficult’ and ‘easy’ moral decisions relative to matched non-moral comparators. This revealed an activation pattern consistent with a relative functional double dissociation between the temporoparietal junction (TPJ) and ventro-medial prefrontal cortex (vmPFC). Difficult moral decisions activated bilateral TPJ and deactivated the vmPFC and OFC. In contrast, easy moral decisions revealed patterns of activation in the vmPFC and deactivation in bilateral TPJ and dorsolateral PFC. Together these results suggest that moral cognition is a dynamic process implemented by a distributed network that involves interacting, yet functionally dissociable networks. PMID:23322890

The regulation of vascular endothelial growth factor-induced microvascular permeability requires Rac and reactive oxygen species.

PubMed

Monaghan-Benson, Elizabeth; Burridge, Keith

2009-09-18

Vascular permeability is a complex process involving the coordinated regulation of multiple signaling pathways in the endothelial cell. It has long been documented that vascular endothelial growth factor (VEGF) greatly enhances microvascular permeability; however, the molecular mechanisms controlling VEGF-induced permeability remain unknown. Treatment of microvascular endothelial cells with VEGF led to an increase in reactive oxygen species (ROS) production. ROS are required for VEGF-induced permeability as treatment with the free radical scavenger, N-acetylcysteine, inhibited this effect. Additionally, treatment with VEGF caused ROS-dependent tyrosine phosphorylation of both vascular-endothelial (VE)-cadherin and beta-catenin. Rac1 was required for the VEGF-induced increase in permeability and adherens junction protein phosphorylation. Knockdown of Rac1 inhibited VEGF-induced ROS production consistent with Rac lying upstream of ROS in this pathway. Collectively, these data suggest that VEGF leads to a Rac-mediated generation of ROS, which, in turn, elevates the tyrosine phosphorylation of VE-cadherin and beta-catenin, ultimately regulating adherens junction integrity.

Polarization curling and flux closures in multiferroic tunnel junctions

PubMed Central

Peters, Jonathan J. P.; Apachitei, Geanina; Beanland, Richard; Alexe, Marin; Sanchez, Ana M.

2016-01-01

Formation of domain walls in ferroelectrics is not energetically favourable in low-dimensional systems. Instead, vortex-type structures are formed that are driven by depolarization fields occurring in such systems. Consequently, polarization vortices have only been experimentally found in systems in which these fields are deliberately maximized, that is, in films between insulating layers. As such configurations are devoid of screening charges provided by metal electrodes, commonly used in electronic devices, it is wise to investigate if curling polarization structures are innate to ferroelectricity or induced by the absence of electrodes. Here we show that in unpoled Co/PbTiO3/(La,Sr)MnO3 ferroelectric tunnel junctions, the polarization in active PbTiO3 layers 9 unit cells thick forms Kittel-like domains, while at 6 unit cells there is a complex flux-closure curling behaviour resembling an incommensurate phase. Reducing the thickness to 3 unit cells, there is an almost complete loss of switchable polarization associated with an internal gradient. PMID:27848970

Insight into spin transport in oxide heterostructures from interface-resolved magnetic mapping

DOE PAGES

Bruno, F. Y.; Grisolia, M. N.; Visani, C.; ...

2015-02-17

At interfaces between complex oxides, electronic, orbital and magnetic reconstructions may produce states of matter absent from the materials involved, offering novel possibilities for electronic and spintronic devices. Here we show that magnetic reconstruction has a strong influence on the interfacial spin selectivity, a key parameter controlling spin transport in magnetic tunnel junctions. In epitaxial heterostructures combining layers of antiferromagnetic LaFeO 3 (LFO) and ferromagnetic La 0.7Sr 0.3MnO 3 (LSMO), we find that a net magnetic moment is induced in the first few unit planes of LFO near the interface with LSMO. Using X-ray photoemission electron microscopy, we show thatmore » the ferromagnetic domain structure of the manganite electrodes is imprinted into the antiferromagnetic tunnel barrier, endowing it with spin selectivity. Finally, we find that the spin arrangement resulting from coexisting ferromagnetic and antiferromagnetic interactions strongly influences the tunnel magnetoresistance of LSMO/LFO/LSMO junctions through competing spin-polarization and spin-filtering effects.« less

HolT Hunter: Software for Identifying and Characterizing Low-Strain DNA Holliday Triangles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sherman W. B.

2012-06-05

Synthetic DNA nanostructures are most commonly held together via Holliday junctions. These junctions allow for a wide variety of different angles between the double helices they connect. Nevertheless, only constructs with a very limited selection of angles have been built, to date, because of the computational complexity of identifying structures that fit together with low strain at odd angles. I have developed an algorithm that finds over 95% of the possible solutions by breaking the problem down into two portions. First, there is a problem of how smooth rods can form triangles by lying across one another. This problem ismore » easily handled by numerical computation. Second, there is the question of how distorted DNA double helices would need to be to fit onto the rod structure. This strain is calculated directly. The algorithm has been implemented in a Mathematica 8 notebook called Holliday Triangle Hunter. A large database of solutions has been identified. Additional interface software is available to facilitate drawing and viewing models.« less

Vertebrobasilar junction giant aneurysm: Lessons learned from a neurosurgical audit and anatomical investigation.

PubMed

Graziano, Francesca; Ganau, Mario; Russo, Vittorio Maria; Iacopino, Domenico G; Ulm, Arthur John

2015-01-01

The treatment of vascular lesions of the vertebrobasilar junction (VBJ) remains a challenging task in the neurosurgical practice and the gold standard therapy is still under debate. In this article, the authors report a detailed postmortem study of a VBJ giant aneurysm (GA) previously endovascularly treated. Although the decision-making process for the vast majority of neurosurgical treatment can nowadays be accurately carried out during the preoperative planning (i.e., with the aid of neuroimaging fusion protocols, neuronavigation platforms, etc.) meant to maximize the anatomical understanding of the lesions and minimize possible intraprocedural challenges, this postmortem study represents the ultimate essence of neurosurgical audit as the laboratory investigations allowed to reevaluate the clinical history of VBJ GA, and reassess the multiple strategies available for its treatment with a straightforward anatomical perspective. Specifically, the lessons learned through this clinical and laboratory work uphold a great educational value regarding the complex management of those lesions, including the possible role of combined skull base surgical approaches.

13th Annual Conference on the Foundations of Nanoscience (FNANO 2016) Held in Snowbird Cliff Lodge, Snowbird, Utah, April 11-14, 2016

DTIC Science & Technology

2017-01-30

Friedrich C . Simmel Salt and Temperature Dependence of Shape and Interhelical Spacing of DNA Origami Nanostructures Studied by Small Angle X-Ray Scattering...Nuclear Pore Complex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Patrick D. Ellis, Qi Shen, Thomas J . Melia, C . Patrick...and C . Mao, “Tensegrity: Construction of rigid DNA triangles with flexible four-arm junctions,” J . Am. Chem. Soc., 126, 2324 (2004). [3] J . Zheng et

Network complexity and synchronous behavior--an experimental approach.

PubMed

Neefs, P J; Steur, E; Nijmeijer, H

2010-06-01

We discuss synchronization in networks of Hindmarsh-Rose neurons that are interconnected via gap junctions, also known as electrical synapses. We present theoretical results for interactions without time-delay. These results are supported by experiments with a setup consisting of sixteen electronic equivalents of the Hindmarsh-Rose neuron. We show experimental results of networks where time-delay on the interaction is taken into account. We discuss in particular the influence of the network topology on the synchronization.

Ballistic Graphene Josephson Junctions from the Short to the Long Junction Regimes.

PubMed

Borzenets, I V; Amet, F; Ke, C T; Draelos, A W; Wei, M T; Seredinski, A; Watanabe, K; Taniguchi, T; Bomze, Y; Yamamoto, M; Tarucha, S; Finkelstein, G

2016-12-02

We investigate the critical current I_{C} of ballistic Josephson junctions made of encapsulated graphene-boron-nitride heterostructures. We observe a crossover from the short to the long junction regimes as the length of the device increases. In long ballistic junctions, I_{C} is found to scale as ∝exp(-k_{B}T/δE). The extracted energies δE are independent of the carrier density and proportional to the level spacing of the ballistic cavity. As T→0 the critical current of a long (or short) junction saturates at a level determined by the product of δE (or Δ) and the number of the junction's transversal modes.

Single P-N junction tandem photovoltaic device

DOEpatents

Walukiewicz, Wladyslaw [Kensington, CA; Ager, III, Joel W.; Yu, Kin Man [Lafayette, CA

2012-03-06

A single P-N junction solar cell is provided having two depletion regions for charge separation while allowing the electrons and holes to recombine such that the voltages associated with both depletion regions of the solar cell will add together. The single p-n junction solar cell includes an alloy of either InGaN or InAlN formed on one side of the P-N junction with Si formed on the other side in order to produce characteristics of a two junction (2J) tandem solar cell through only a single P-N junction. A single P-N junction solar cell having tandem solar cell characteristics will achieve power conversion efficiencies exceeding 30%.