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Sample records for comparative transduction mechanisms

  1. Comparative transduction mechanisms of hair cells in the bullfrog utriculus. 1: Responses to intracellular current

    NASA Technical Reports Server (NTRS)

    Baird, Richard A.

    1994-01-01

    Hair cells in the bullfrog sacculus are specifically adapted to sense small-amplitude, high-frequency linear accelerations. These hair cells display many properties that are undesirable or inappropriate for hair cells that must provide static gravity sensitivity. This study resulted in part due to an interest in seeing how the transduction mechanisms of hair cells in a gravity-sensing otolith endorgan would differ from those in the bullfrog sacculus. The bullfrog utriculus is an appropriate model for these studies, because its structure is representative of higher vertebrates in general and its function as a sensor of static gravity and dynamic linear acceleration is well known. Hair cells in the bullfrog utriculus, classifiable as Type 2 by cell body and synapse morphology, differ markedly in hair bundle morphology from those in the bullfrog sacculus. Moreover, the hair bundle morphologies of utricular hair cells, unlike those in the sacculus, differ in different membrane regions.

  2. Comparative mechanisms of protein transduction mediated by cell-penetrating peptides in prokaryotes.

    PubMed

    Liu, Betty Revon; Huang, Yue-Wern; Aronstam, Robert S; Lee, Han-Jung

    2015-04-01

    Bacterial and archaeal cell envelopes are complex multilayered barriers that serve to protect these microorganisms from their extremely harsh and often hostile environments. Import of exogenous proteins and nanoparticles into cells is important for biotechnological applications in prokaryotes. In this report, we demonstrate that cell-penetrating peptides (CPPs), both bacteria-expressed nona-arginine peptide (R9) and synthetic R9 (SR9), are able to deliver noncovalently associated proteins or quantum dots into four representative species of prokaryotes: cyanobacteria (Synechocystis sp. PCC 6803), bacteria (Escherichia coli DH5α and Arthrobacter ilicis D-50), and archaea (Thermus aquaticus). Although energy-dependent endocytosis is generally accepted as a hallmark that distinguishes eukaryotes from prokaryotes, cellular uptake of uncomplexed green fluorescent protein (GFP) by cyanobacteria was mediated by classical endocytosis. Mechanistic studies revealed that macropinocytosis plays a critical and major role in CPP-mediated protein transduction in all four prokaryotes. Membrane damage was not observed when cyanobacterial cells were treated with R9/GFP complexes, nor was cytotoxicity detected when bacteria or archaea were treated with SR9/QD complexes in the presence of macropinocytic inhibitors. These results indicate that the uptake of protein is not due to a compromise of membrane integrity in cyanobacteria, and that CPP can be an effective and safe carrier for membrane trafficking in prokaryotic cells. Our investigation provides important new insights into the transport of exogenous proteins and nanoparticles across the complex membrane systems of prokaryotes.

  3. Comparative transduction mechanisms of hair cells in the bullfrog uticulus. 2: Sensitivity and response dynamics to hair bundle displacement

    NASA Technical Reports Server (NTRS)

    Baird, Richard A.

    1994-01-01

    The present study was motivated by an interest in seeing whether hair cell types in the bullfrog utriculus might differ in their voltage responses to hair bundle displacement. Particular interest was in assessing the contributions of two factors to the responses of utricular hair cells. First, interest in examining the effect of hair bundle morphology on the sensitivity of hair cells to natural stimulation was motivated by the observation that vestibular hair cells, unlike many auditory hair cells, are not free-standing but rather linked to an accessory cupular or otolithic membrane via the tip of their kinocilium. Interest also laid in examining the contribution, if any, of adaptation to the response properties of utricular hair cells. Hair cells in auditory and vibratory inner ear endorgans adapt to maintained displacements of their hair bundles, sharply limiting their low frequency sensitivity. This adaptation is mediated by a shift in the displacement-response curve (DRC) of the hair cell along the displacement axis. Observations suggest that the adaptation process occurs within the hair bundle and precedes mechanoelectric transduction. Recent observations of time-dependent changes in hair bundle stiffness are consistent with this conclusion. Adaptation would be expected to be most useful in inner ear endorgans in which hair cells are subject to large static displacements that could potentially saturate their instantaneous response and compromise their sensitivity to high frequency stimulation. The adaptation process also permits hair cells to maintain their sensory hair bundle in the most sensitive portion of their DRC. In vestibular otolith organs in which static sensitivity is desirable, any adaptation process in the hair cells may be undesirable. The rate and extent of the decline of the voltage responses was measured of utricular hair cells to step and sinusoidal hair bundle displacements. Then for similar resting potentials and response amplitudes, the

  4. Comparative transduction mechanisms of hair cells in the bullfrog utriculus. II. Sensitivity and response dynamics to hair bundle displacement

    NASA Technical Reports Server (NTRS)

    Baird, R. A.

    1994-01-01

    lever arm between kinociliary and stereociliary displacement; 2) tip link extension/linear displacement, largely a function of stereociliary height and separation; and 3) stereociliary number, an estimate of the number of transduction channels, were considered in this analysis. The first of these factors was quantitatively more important than the latter two factors and their total contribution was largest in Type B and Type C cells. Theoretical models were also used to calculate the relation between rotary and linear displacement.(ABSTRACT TRUNCATED AT 400 WORDS).

  5. Transduction of mechanical strain in bone

    NASA Technical Reports Server (NTRS)

    Duncan, R. L.

    1995-01-01

    One physiologic consequence of extended periods of weightlessness is the rapid loss of bone mass associated with skeletal unloading. Conversely, mechanical loading has been shown to increase bone formation and stimulate osteoblastic function. The mechanisms underlying mechanotransduction, or how the osteoblast senses and converts biophysical stimuli into cellular responses has yet to be determined. For non-innervated mechanosensitive cells like the osteoblast, mechanotransduction can be divided into four distinct phases: 1) mechanocoupling, or the characteristics of the mechanical force applied to the osteoblast, 2) biochemical coupling, or the mechanism through which mechanical strain is transduced into a cellular biochemical signal, 3) transmission of signal from sensor to effector cell and 4) the effector cell response. This review examines the characteristics of the mechanical strain encountered by osteoblasts, possible biochemical coupling mechanisms, and how the osteoblast responds to mechanical strain. Differences in osteoblastic responses to mechanical strain are discussed in relation to the types of strain encountered and the possible transduction pathways involved.

  6. Signal transduction mechanisms in plants: an overview

    NASA Technical Reports Server (NTRS)

    Clark, G. B.; Thompson, G. Jr; Roux, S. J.

    2001-01-01

    This article provides an overview on recent advances in some of the basic signalling mechanisms that participate in a wide variety of stimulus-response pathways. The mechanisms include calcium-based signalling, G-protein-mediated-signalling and signalling involving inositol phospholipids, with discussion on the role of protein kinases and phosphatases interspersed. As a further defining feature, the article highlights recent exciting findings on three extracellular components that have not been given coverage in previous reviews of signal transduction in plants, extracellular calmodulin, extracellular ATP, and integrin-like receptors, all of which affect plant growth and development.

  7. Cell-penetrating peptides: Possible transduction mechanisms and therapeutic applications

    PubMed Central

    GUO, ZHENGRONG; PENG, HUANYAN; KANG, JIWEN; SUN, DIANXING

    2016-01-01

    Cell-penetrating peptides (CPPs), also known as protein transduction domains, are a class of diverse peptides with 5–30 amino acids. CPPs are divided into cationic, amphipathic and hydrophobic CPPs. They are able to carry small molecules, plasmid DNA, small interfering RNA, proteins, viruses, imaging agents and other various nanoparticles across the cellular membrane, resulting in internalization of the intact cargos. However, the mechanisms of CPP internalization remain to be elucidated. Recently, CPPs have received considerable attention due to their high transduction efficiency and low cytotoxicity. These peptides have a significant potential for diagnostic and therapeutic applications, such as delivery of fluorescent or radioactive compounds for imaging, delivery of peptides and proteins for therapeutic application, and delivery of molecules into induced pluripotent stem cells for directing differentiation. The present study reviews the classifications and transduction mechanisms of CPPs, as well as their potential applications. PMID:27123243

  8. Mechanism and evolution of cytosolic Hedgehog signal transduction

    PubMed Central

    Wilson, Christopher W.; Chuang, Pao-Tien

    2010-01-01

    Hedgehog (Hh) signaling is required for embryonic patterning and postnatal physiology in invertebrates and vertebrates. With the revelation that the primary cilium is crucial for mammalian Hh signaling, the prevailing view that Hh signal transduction mechanisms are conserved across species has been challenged. However, more recent progress on elucidating the function of core Hh pathway cytosolic regulators in Drosophila, zebrafish and mice has confirmed that the essential logic of Hh transduction is similar between species. Here, we review Hh signaling events at the membrane and in the cytosol, and focus on parallel and divergent functions of cytosolic Hh regulators in Drosophila and mammals. PMID:20530542

  9. Mechanical signal transduction in skeletal muscle growth and adaptation.

    PubMed

    Tidball, James G

    2005-05-01

    The adaptability of skeletal muscle to changes in the mechanical environment has been well characterized at the tissue and system levels, but the mechanisms through which mechanical signals are transduced to chemical signals that influence muscle growth and metabolism remain largely unidentified. However, several findings have suggested that mechanical signal transduction in muscle may occur through signaling pathways that are shared with insulin-like growth factor (IGF)-I. The involvement of IGF-I-mediated signaling for mechanical signal transduction in muscle was originally suggested by the observations that muscle releases IGF-I on mechanical stimulation, that IGF-I is a potent agent for promoting muscle growth and affecting phenotype, and that IGF-I can function as an autocrine hormone in muscle. Accumulating evidence shows that at least two signaling pathways downstream of IGF-I binding can influence muscle growth and adaptation. Signaling via the calcineurin/nuclear factor of activated T-cell pathway has been shown to have a powerful influence on promoting the slow/type I phenotype in muscle but can also increase muscle mass. Neural stimulation of muscle can activate this pathway, although whether neural activation of the pathway can occur independent of mechanical activation or independent of IGF-I-mediated signaling remains to be explored. Signaling via the Akt/mammalian target of rapamycin pathway can also increase muscle growth, and recent findings show that activation of this pathway can occur as a response to mechanical stimulation applied directly to muscle cells, independent of signals derived from other cells. In addition, mechanical activation of mammalian target of rapamycin, Akt, and other downstream signals is apparently independent of autocrine factors, which suggests that activation of the mechanical pathway occurs independent of muscle-mediated IGF-I release.

  10. Molecular Mechanisms of Two-Component Signal Transduction.

    PubMed

    Zschiedrich, Christopher P; Keidel, Victoria; Szurmant, Hendrik

    2016-09-25

    Two-component systems (TCS) comprising sensor histidine kinases and response regulator proteins are among the most important players in bacterial and archaeal signal transduction and also occur in reduced numbers in some eukaryotic organisms. Given their importance to cellular survival, virulence, and cellular development, these systems are among the most scrutinized bacterial proteins. In the recent years, a flurry of bioinformatics, genetic, biochemical, and structural studies have provided detailed insights into many molecular mechanisms that underlie the detection of signals and the generation of the appropriate response by TCS. Importantly, it has become clear that there is significant diversity in the mechanisms employed by individual systems. This review discusses the current knowledge on common themes and divergences from the paradigm of TCS signaling. An emphasis is on the information gained by a flurry of recent structural and bioinformatics studies.

  11. The mechanism of signal transduction by two-component systems.

    PubMed

    Casino, Patricia; Rubio, Vicente; Marina, Alberto

    2010-12-01

    Two-component systems, composed of a homodimeric histidine kinase (HK) and a response regulator (RR), are major signal transduction devices in bacteria. Typically the signal triggers HK autophosphorylation at one His residue, followed by phosphoryl transfer from the phospho-His to an Asp residue in the RR. Signal extinction frequently involves phospho-RR dephosphorylation by a phosphatase activity of the HK. Our understanding of these reactions and of the determinants of partner specificity among HK-RR couples has been greatly increased by recent crystal structures and biochemical experiments on HK-RR complexes. Cis-autophosphorylation (one subunit phosphorylates itself) occurs in some HKs while trans-autophosphorylation takes place in others. We review and integrate this new information, discuss the mechanism of the three reactions and propose a model for transmembrane signaling by these systems.

  12. Exploring transduction mechanisms of protein transduction domains (PTDs) in living cells utilizing single-quantum dot tracking (SQT) technology.

    PubMed

    Suzuki, Yasuhiro

    2012-01-01

    Specific protein domains known as protein transduction domains (PTDs) can permeate cell membranes and deliver proteins or bioactive materials into living cells. Various approaches have been applied for improving their transduction efficacy. It is, therefore, crucial to clarify the entry mechanisms and to identify the rate-limiting steps. Because of technical limitations for imaging PTD behavior on cells with conventional fluorescent-dyes, how PTDs enter the cells has been a topic of much debate. Utilizing quantum dots (QDs), we recently tracked the behavior of PTD that was derived from HIV-1 Tat (TatP) in living cells at the single-molecule level with 7-nm special precision. In this review article, we initially summarize the controversy on TatP entry mechanisms; thereafter, we will focus on our recent findings on single-TatP-QD tracking (SQT), to identify the major sequential steps of intracellular delivery in living cells and to discuss how SQT can easily provide direct information on TatP entry mechanisms. As a primer for SQT study, we also discuss the latest findings on single particle tracking of various molecules on the plasma membrane. Finally, we discuss the problems of QDs and the challenges for the future in utilizing currently available QD probes for SQT. In conclusion, direct identification of the rate-limiting steps of PTD entry with SQT should dramatically improve the methods for enhancing transduction efficiency. PMID:22368485

  13. Nonreciprocal Radio Frequency Transduction in a Parametric Mechanical Artificial Lattice

    NASA Astrophysics Data System (ADS)

    Huang, Pu; Zhang, Liang; Zhou, Jingwei; Tian, Tian; Yin, Peiran; Duan, Changkui; Du, Jiangfeng

    2016-07-01

    Generating nonreciprocal radio frequency transduction plays important roles in a wide range of research and applications, and an aspiration is to integrate this functionality into microcircuits without introducing a magnetic field, which, however, remains challenging. By designing a 1D artificial lattice structure with a neighbor interaction engineered parametrically, we predicted a nonreciprocity transduction with a large unidirectionality. We then experimentally demonstrated the phenomenon on a nanoelectromechanical chip fabricated by conventional complementary metal-silicon processing. A unidirectionality with isolation as high as 24 dB is achieved, and several different transduction schemes are realized by programing the control voltage topology. Apart from being used as a radio frequency isolator, the system provides a way to build a practical on-chip programmable device for broad research and applications in the radio frequency domain.

  14. Nonreciprocal Radio Frequency Transduction in a Parametric Mechanical Artificial Lattice.

    PubMed

    Huang, Pu; Zhang, Liang; Zhou, Jingwei; Tian, Tian; Yin, Peiran; Duan, Changkui; Du, Jiangfeng

    2016-07-01

    Generating nonreciprocal radio frequency transduction plays important roles in a wide range of research and applications, and an aspiration is to integrate this functionality into microcircuits without introducing a magnetic field, which, however, remains challenging. By designing a 1D artificial lattice structure with a neighbor interaction engineered parametrically, we predicted a nonreciprocity transduction with a large unidirectionality. We then experimentally demonstrated the phenomenon on a nanoelectromechanical chip fabricated by conventional complementary metal-silicon processing. A unidirectionality with isolation as high as 24 dB is achieved, and several different transduction schemes are realized by programing the control voltage topology. Apart from being used as a radio frequency isolator, the system provides a way to build a practical on-chip programmable device for broad research and applications in the radio frequency domain. PMID:27419591

  15. MOLECULAR MECHANISMS OF RECEPTOR KINASE ACTION IN BRASSINOSTEROID SIGNAL TRANSDUCTION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Brassinosteroids (BRs) regulate multiple aspects of plant growth and development and require an active BRASSINOSTEROID INSENSITIVE 1 (BRI1) and BRI1-ASSOCIATED RECEPTOR KINASE 1 (BAK1) for hormone perception and signal transduction. To examine early events in BR signaling, we used co-immunoprecipita...

  16. Nanosecond pulsed electric fields modulate cell function through intracellular signal transduction mechanisms.

    PubMed

    Beebe, Stephen J; Blackmore, Peter F; White, Jody; Joshi, Ravindra P; Schoenbach, Karl H

    2004-08-01

    These studies describe the effects of nanosecond (10-300 ns) pulsed electric fields (nsPEF) on mammalian cell structure and function. As the pulse durations decrease, effects on the plasma membrane (PM) decrease and effects on intracellular signal transduction mechanisms increase. When nsPEF-induced PM electroporation effects occur, they are distinct from classical PM electroporation effects, suggesting unique, nsPEF-induced PM modulations. In HL-60 cells, nsPEF that are well below the threshold for PM electroporation and apoptosis induction induce effects that are similar to purinergic agonistmediated calcium release from intracellular stores, which secondarily initiate capacitive calcium influx through store-operated calcium channels in the PM. NsPEF with durations and electric field intensities that do or do not cause PM electroporation, induce apoptosis in mammalian cells with a well-characterized phenotype typified by externalization of phosphatidylserine on the outer PM and activation of caspase proteases. Treatment of mouse fibrosarcoma tumors with nsPEF also results in apoptosis induction. When Jurkat cells were transfected by electroporation and then treated with nsPEF, green fluorescent protein expression was enhanced compared to electroporation alone. The results indicate that nsPEF activate intracellular mechanisms that can determine cell function and fate, providing an important new tool for probing signal transduction mechanisms that modulate cell structure and function and for potential therapeutic applications for cancer and gene therapy.

  17. Phage Transduction.

    PubMed

    Goh, Shan

    2016-01-01

    Bacteriophages mediate horizontal gene transfer through a mechanism known as transduction. Phage transduction carried out in the laboratory involves a bacterial donor and a recipient, both of which are susceptible to infection by the phage of interest. Phage is propagated in the donor, concentrated, and exposed transiently to recipient at different multiplicity of infection ratios. Transductants are selected for the desired phenotype by culture on selective medium. Here we describe transduction of ermB conferring resistance to erythromycin by the C. difficile phage ϕC2. PMID:27507341

  18. Mechanical regulation of a molecular clutch defines force transmission and transduction in response to matrix rigidity.

    PubMed

    Elosegui-Artola, Alberto; Oria, Roger; Chen, Yunfeng; Kosmalska, Anita; Pérez-González, Carlos; Castro, Natalia; Zhu, Cheng; Trepat, Xavier; Roca-Cusachs, Pere

    2016-05-01

    Cell function depends on tissue rigidity, which cells probe by applying and transmitting forces to their extracellular matrix, and then transducing them into biochemical signals. Here we show that in response to matrix rigidity and density, force transmission and transduction are explained by the mechanical properties of the actin-talin-integrin-fibronectin clutch. We demonstrate that force transmission is regulated by a dynamic clutch mechanism, which unveils its fundamental biphasic force/rigidity relationship on talin depletion. Force transduction is triggered by talin unfolding above a stiffness threshold. Below this threshold, integrins unbind and release force before talin can unfold. Above the threshold, talin unfolds and binds to vinculin, leading to adhesion growth and YAP nuclear translocation. Matrix density, myosin contractility, integrin ligation and talin mechanical stability differently and nonlinearly regulate both force transmission and the transduction threshold. In all cases, coupling of talin unfolding dynamics to a theoretical clutch model quantitatively predicts cell response. PMID:27065098

  19. Mechanical code comparator

    DOEpatents

    Peter, Frank J.; Dalton, Larry J.; Plummer, David W.

    2002-01-01

    A new class of mechanical code comparators is described which have broad potential for application in safety, surety, and security applications. These devices can be implemented as micro-scale electromechanical systems that isolate a secure or otherwise controlled device until an access code is entered. This access code is converted into a series of mechanical inputs to the mechanical code comparator, which compares the access code to a pre-input combination, entered previously into the mechanical code comparator by an operator at the system security control point. These devices provide extremely high levels of robust security. Being totally mechanical in operation, an access control system properly based on such devices cannot be circumvented by software attack alone.

  20. In search of the cochlear amplifier: New mechanical and molecular tools to probe transduction channel function

    NASA Astrophysics Data System (ADS)

    Karavitaki, K. Domenica; Indzhykulian, Artur A.; Zhang, Duan-Sun; Corey, David P.

    2015-12-01

    The study of mechanotransduction in cochlear hair cells requires stimulus methods that mimic the in-vivo stimulation. We have developed a new mechanical probe to better mimic the physiological stimulus delivered to cochlear hair cells through the overlying tectorial membrane. We combine these new probes with electroporation to study the contribution of different components of the transduction apparatus.

  1. Molecular mechanisms of gravity perception and signal transduction in plants.

    PubMed

    Kolesnikov, Yaroslav S; Kretynin, Serhiy V; Volotovsky, Igor D; Kordyum, Elizabeth L; Ruelland, Eric; Kravets, Volodymyr S

    2016-07-01

    Gravity is one of the environmental cues that direct plant growth and development. Recent investigations of different gravity signalling pathways have added complexity to how we think gravity is perceived. Particular cells within specific organs or tissues perceive gravity stimulus. Many downstream signalling events transmit the perceived information into subcellular, biochemical, and genomic responses. They are rapid, non-genomic, regulatory, and cell-specific. The chain of events may pass by signalling lipids, the cytoskeleton, intracellular calcium levels, protein phosphorylation-dependent pathways, proteome changes, membrane transport, vacuolar biogenesis mechanisms, or nuclear events. These events culminate in changes in gene expression and auxin lateral redistribution in gravity response sites. The possible integration of these signalling events with amyloplast movements or with other perception mechanisms is discussed. Further investigation is needed to understand how plants coordinate mechanisms and signals to sense this important physical factor.

  2. Structural mechanism for signal transduction in RXR nuclear receptor heterodimers

    PubMed Central

    Kojetin, Douglas J.; Matta-Camacho, Edna; Hughes, Travis S.; Srinivasan, Sathish; Nwachukwu, Jerome C.; Cavett, Valerie; Nowak, Jason; Chalmers, Michael J.; Marciano, David P.; Kamenecka, Theodore M.; Shulman, Andrew I.; Rance, Mark; Griffin, Patrick R.; Bruning, John B.; Nettles, Kendall W.

    2015-01-01

    A subset of nuclear receptors (NRs) function as obligate heterodimers with retinoid X receptor (RXR), allowing integration of ligand-dependent signals across the dimer interface via an unknown structural mechanism. Using nuclear magnetic resonance (NMR) spectroscopy, x-ray crystallography and hydrogen/deuterium exchange (HDX) mass spectrometry, here we show an allosteric mechanism through which RXR co-operates with a permissive dimer partner, peroxisome proliferator-activated receptor (PPAR)-γ, while rendered generally unresponsive by a non-permissive dimer partner, thyroid hormone (TR) receptor. Amino acid residues that mediate this allosteric mechanism comprise an evolutionarily conserved network discovered by statistical coupling analysis (SCA). This SCA network acts as a signalling rheostat to integrate signals between dimer partners, ligands and coregulator-binding sites, thereby affecting signal transmission in RXR heterodimers. These findings define rules guiding how NRs integrate two ligand-dependent signalling pathways into RXR heterodimer-specific responses. PMID:26289479

  3. Molecular mechanisms of gravity perception and signal transduction in plants.

    PubMed

    Kolesnikov, Yaroslav S; Kretynin, Serhiy V; Volotovsky, Igor D; Kordyum, Elizabeth L; Ruelland, Eric; Kravets, Volodymyr S

    2016-07-01

    Gravity is one of the environmental cues that direct plant growth and development. Recent investigations of different gravity signalling pathways have added complexity to how we think gravity is perceived. Particular cells within specific organs or tissues perceive gravity stimulus. Many downstream signalling events transmit the perceived information into subcellular, biochemical, and genomic responses. They are rapid, non-genomic, regulatory, and cell-specific. The chain of events may pass by signalling lipids, the cytoskeleton, intracellular calcium levels, protein phosphorylation-dependent pathways, proteome changes, membrane transport, vacuolar biogenesis mechanisms, or nuclear events. These events culminate in changes in gene expression and auxin lateral redistribution in gravity response sites. The possible integration of these signalling events with amyloplast movements or with other perception mechanisms is discussed. Further investigation is needed to understand how plants coordinate mechanisms and signals to sense this important physical factor. PMID:26215561

  4. Cerebral Artery Signal Transduction Mechanisms: Developmental Changes in Dynamics and Ca2+ Sensitivity

    PubMed Central

    Longo, Lawrence D.; Goyal, Ravi

    2012-01-01

    As compared to the adult, the developing fetus and newborn infant are at much greater risk for dysregulation of cerebral blood flow (CBF), with complications such as intraventricular and germinal matrix hemorrhage with resultant neurologic sequelae. To minimize this dysregulation and its consequences presents a major challenge. Although in many respects the fundamental signal transduction mechanisms that regulate relaxation and contraction pathways, and thus cerebrovascular tone and CBF in the immature organism are similar to those of the adult, the individual elements, pathways, and roles differ greatly. Here, we review aspects of these maturational changes of relaxation/contraction mechanisms in terms of both electro-mechanical and pharmaco-mechanical coupling, their biochemical pathways and signaling networks. In contrast to the adult cerebrovasculature, in addition to attenuated structure with differences in multiple cytoskeletal elements, developing cerebrovasculature of fetus and newborn differs in many respects, such as a strikingly increased sensitivity to [Ca2+]i and requirement for extracellular Ca2+ for contraction. In essence, the immature cerebrovasculature demonstrates both “hyper-relaxation” and “hypo-contraction”. A challenge is to unravel the manner in which these mechanisms are integrated, particularly in terms of both Ca2+-dependent and Ca2+-independent pathways to increase Ca2+ sensitivity. Gaining an appreciation of these significant age-related differences in signal mechanisms also will be critical to understanding more completely the vulnerability of the developing cerebral vasculature to hypoxia and other stresses. Of vital importance, a more complete understanding of these mechanisms promises hope for improved strategies for therapeutic intervention and clinical management of intensive care of the premature newborn. PMID:24063382

  5. Plasma membrane poration by opioid neuropeptides: a possible mechanism of pathological signal transduction.

    PubMed

    Maximyuk, O; Khmyz, V; Lindskog, C-J; Vukojević, V; Ivanova, T; Bazov, I; Hauser, K F; Bakalkin, G; Krishtal, O

    2015-01-01

    Neuropeptides induce signal transduction across the plasma membrane by acting through cell-surface receptors. The dynorphins, endogenous ligands for opioid receptors, are an exception; they also produce non-receptor-mediated effects causing pain and neurodegeneration. To understand non-receptor mechanism(s), we examined interactions of dynorphins with plasma membrane. Using fluorescence correlation spectroscopy and patch-clamp electrophysiology, we demonstrate that dynorphins accumulate in the membrane and induce a continuum of transient increases in ionic conductance. This phenomenon is consistent with stochastic formation of giant (~2.7 nm estimated diameter) unstructured non-ion-selective membrane pores. The potency of dynorphins to porate the plasma membrane correlates with their pathogenic effects in cellular and animal models. Membrane poration by dynorphins may represent a mechanism of pathological signal transduction. Persistent neuronal excitation by this mechanism may lead to profound neuropathological alterations, including neurodegeneration and cell death. PMID:25766322

  6. Comparative Transduction Mechanisms of Vestibular Otolith Hair Cells

    NASA Technical Reports Server (NTRS)

    Baird, Richard A.

    1994-01-01

    Hair cells in the bullfrog vestibular otolith organs regenerate following aminoglycoside ototoxicity. Hair cells in these organs are differentially sensitive to gentamicin, with saccular hair cells and hair cells in the utricular striola being damaged at lower gentamicin concentrations than hair cells in the utricular extrastriola. Regenerating hair cells in these organs have short hair bundles and can be classified into a number of phenotypes using the same morphological criteria used to identify their mature counterparts. Our studies suggest that some supporting cells can convert, or transdifferentiate,into hair cells without an intervening cell division. By stimulating these processes in humans, clinicians may be able to alleviate human deafness and peripheral vestibular disorders by regenerating and replacing lost hair cells. In vivo and in vitro studies were done on cell proliferation and hair cell regeneration.

  7. Do certain signal transduction mechanisms explain the comorbidity of epilepsy and mood disorders?

    PubMed

    Rocha, Luisa; Alonso-Vanegas, Mario; Orozco-Suárez, Sandra; Alcántara-González, David; Cruzblanca, Humberto; Castro, Elena

    2014-09-01

    It is well known that mood disorders are highly prevalent in patients with epilepsy. Although several studies have aimed to characterize alterations in different types of receptors associated with both disturbances, there is a lack of studies focused on identifying the causes of this comorbidity. Here, we described some changes at the biochemical level involving serotonin, dopamine, and γ-aminobutyric acid (GABA) receptors as well as signal transduction mechanisms that may explain the coexistence of both epilepsy and mood disorders. Finally, the identification of common pathophysiological mechanisms associated with receptor-receptor interaction (heterodimers) could allow designing new strategies for treatment of patients with epilepsy and comorbid mood disorders.

  8. Transduction mechanism(s) of Na-saccharin in the blowfly Protophormia terraenovae: evidence for potassium and calcium conductance involvement.

    PubMed

    Masala, Carla; Solari, Paolo; Sollai, Giorgia; Crnjar, Roberto; Liscia, Anna

    2009-12-01

    The study on transduction mechanisms underlying bitter stimuli is a particularly intriguing challenge for taste researchers. The present study investigates, in the labellar chemosensilla of the blowfly Protophormia terraenovae, the transduction mechanism by which saccharin evokes the response of the "deterrent" cell, with particular attention to the contribution of K(+) and Ca(2+) current and the role of cyclic nucleotides, since second messengers modulate Ca(2+), Cl(-) and K(+) currents to different extents. As assessed by extracellular single-sensillum recordings, our results show that the addition of a Ca(2+) chelator such as EGTA or the Ca(2+) current blockers SK&F-96365, Mibefradil, Nifedipine and W-7 decrease the response of the "deterrent" cell to saccharin. A similar decreasing effect was also obtained following the addition of 4-aminopyridine, a K(+) current blocker. On the contrary, the membrane-permeable cyclic nucleotide 8-bromoguanosine 3',5'-cyclic monophosphate (8Br-cGMP) activates this cell and shows an additive effect when presented mixed with saccharin. Our results are consistent with the hypothesis that in the labellar chemosensilla of the blowfly both Ca(2+) and K(+) ions are involved in the transduction mechanism of the "deterrent" cell in response to saccharin. Our results also suggest a possible pathway common to saccharin and 8Br-cGMP.

  9. External Mechanical Work and Pendular Energy Transduction of Overground and Treadmill Walking in Adolescents with Unilateral Cerebral Palsy

    PubMed Central

    Zollinger, Marie; Degache, Francis; Currat, Gabriel; Pochon, Ludmila; Peyrot, Nicolas; Newman, Christopher J.; Malatesta, Davide

    2016-01-01

    Purpose: Motor impairments affect functional abilities and gait in children and adolescents with cerebral palsy (CP). Improving their walking is an essential objective of treatment, and the use of a treadmill for gait analysis and training could offer several advantages in adolescents with CP. However, there is a controversy regarding the similarity between treadmill and overground walking both for gait analysis and training in children and adolescents. The aim of this study was to compare the external mechanical work and pendular energy transduction of these two types of gait modalities at standard and preferred walking speeds in adolescents with unilateral cerebral palsy (UCP) and typically developing (TD) adolescents matched on age, height and body mass. Methods: Spatiotemporal parameters, external mechanical work and pendular energy transduction of walking were computed using two inertial sensors equipped with a triaxial accelerometer and gyroscope and compared in 10 UCP (14.2 ± 1.7 year) and 10 TD (14.1 ± 1.9 year) adolescents during treadmill and overground walking at standard and preferred speeds. Results: The treadmill induced almost identical mechanical changes to overground walking in TD adolescents and those with UCP, with the exception of potential and kinetic vertical and lateral mechanical works, which are both significantly increased in the overground-treadmill transition only in UCP (P < 0.05). Conclusions: Adolescents with UCP have a reduced adaptive capacity in absorbing and decelerating the speed created by a treadmill (i.e., dynamic stability) compared to TD adolescents. This may have an important implication in rehabilitation programs that assess and train gait by using a treadmill in adolescents with UCP. PMID:27148062

  10. Novel optical methodologies in studying mechanical signal transduction in mammalian cells

    NASA Technical Reports Server (NTRS)

    Stamatas, G. N.; McIntire, L. V.

    1999-01-01

    For the last 3 decades evidence has been accumulating that some types of mammalian cells respond to their mechanically active environment by altering their morphology, growth rate, and metabolism. The study of such responses is very important in understanding, physiological and pathological conditions ranging from bone formation to atherosclerosis. Obtaining this knowledge has been the goal for an active research area in bioengineering termed cell mechanotransduction. The advancement of optical methodologies used in cell biology research has given the tools to elucidate cellular mechanisms that would otherwise be impossible to visualize. Combined with molecular biology techniques, they give engineers invaluable tools in understanding the chemical pathways involved in mechanotransduction. Herein we briefly review the current knowledge on mechanical signal transduction in mammalian cells, focusing on the application of novel optical techniques in the ongoing research.

  11. Lessons in Fundamental Mechanisms and Diverse Adaptations from the 2015 Bacterial Locomotion and Signal Transduction Meeting

    PubMed Central

    Prüβ, Birgit M.; Liu, Jun; Higgs, Penelope I.

    2015-01-01

    In response to rapid changes in their environment, bacteria control a number of processes, including motility, cell division, biofilm formation, and virulence. Research presented in January 2015 at the biennial Bacterial Locomotion and Signal Transduction (BLAST) meeting in Tucson, AZ, illustrates the elegant complexity of the nanoarrays, nanomachines, and networks of interacting proteins that mediate such processes. Studies employing an array of biophysical, genetic, cell biology, and mathematical methods are providing an increasingly detailed understanding of the mechanisms of these systems within well-studied bacteria. Furthermore, comparisons of these processes in diverse bacterial species are providing insight into novel regulatory and functional mechanisms. This review summarizes research presented at the BLAST meeting on these fundamental mechanisms and diverse adaptations, including findings of importance for applications involving bacteria of medical or agricultural relevance. PMID:26195592

  12. Sentra : a database of signal transduction proteins for comparative genome analysis.

    SciTech Connect

    D'Souza, M.; Glass, E. M.; Syed, M. H.; Zhang, Y.; Rodriguez, A.; Maltsev, N.; Galerpin, M. Y.; Mathematics and Computer Science; Univ. of Chicago; NIH

    2007-01-01

    Sentra (http://compbio.mcs.anl.gov/sentra), a database of signal transduction proteins encoded in completely sequenced prokaryotic genomes, has been updated to reflect recent advances in understanding signal transduction events on a whole-genome scale. Sentra consists of two principal components, a manually curated list of signal transduction proteins in 202 completely sequenced prokaryotic genomes and an automatically generated listing of predicted signaling proteins in 235 sequenced genomes that are awaiting manual curation. In addition to two-component histidine kinases and response regulators, the database now lists manually curated Ser/Thr/Tyr protein kinases and protein phosphatases, as well as adenylate and diguanylate cyclases and c-di-GMP phosphodiesterases, as defined in several recent reviews. All entries in Sentra are extensively annotated with relevant information from public databases (e.g. UniProt, KEGG, PDB and NCBI). Sentra's infrastructure was redesigned to support interactive cross-genome comparisons of signal transduction capabilities of prokaryotic organisms from a taxonomic and phenotypic perspective and in the framework of signal transduction pathways from KEGG. Sentra leverages the PUMA2 system to support interactive analysis and annotation of signal transduction proteins by the users.

  13. The Clickable Guard Cell, Version II: Interactive Model of Guard Cell Signal Transduction Mechanisms and Pathways.

    PubMed

    Kwak, June M; Mäser, Pascal; Schroeder, Julian I

    2008-01-01

    Guard cells are located in the leaf epidermis and pairs of guard cells surround and form stomatal pores, which regulate CO(2) influx from the atmosphere into leaves for photosynthetic carbon fixation. Stomatal guard cells also regulate water loss of plants via transpiration to the atmosphere. Signal transduction mechanisms in guard cells integrate a multitude of different stimuli to modulate stomatal apertures. Stomata open in response to light. Stomata close in response to drought stress, elevated CO(2), ozone and low humidity. In response to drought, plants synthesize the hormone abscisic acid (ABA) that triggers closing of stomatal pores. Guard cells have become a highly developed model system for dissecting signal transduction mechanisms in plants and for elucidating how individual signaling mechanisms can interact within a network in a single cell. Many new findings have been made in the last few years. This chapter is an update of an electronic interactive chapter in the previous edition of The Arabidopsis Book (Mäser et al. 2003). Here we focus on mechanisms for which genes and mutations have been characterized, including signaling components for which there is substantial signaling, biochemical and genetic evidence. Ion channels have been shown to represent targets of early signal transduction mechanisms and provide functional signaling and quantitative analysis points to determine where and how mutations affect branches within the guard cell signaling network. Although a substantial number of genes and proteins that function in guard cell signaling have been identified in recent years, there are many more left to be identified and the protein-protein interactions within this network will be an important subject of future research. A fully interactive clickable electronic version of this publication can be accessed at the following web site: http://www-biology.ucsd.edu/labs/schroeder/clickablegc2/. The interactive clickable version includes the following

  14. Architecture and signal transduction mechanism of the bacterial chemosensory array: progress, controversies, and challenges.

    PubMed

    Falke, Joseph J; Piasta, Kene N

    2014-12-01

    Recent research has deepened our understanding of the ancient, conserved chemosensory array that detects small molecule attractants and repellents, and directs the chemotaxis of bacterial and archaeal cells towards an optimal chemical environment. Here we review advances towards a molecular description of the ultrastable lattice architecture and ultrasensitive signal transduction mechanism of the chemosensory array, as well as controversies and challenges requiring further research. Ultimately, a full molecular understanding of array structure and on-off switching will foster (i) the design of novel therapies that block pathogenic wound seeking and infection, (ii) the development of highly specific, sensitive, stable biosensors, and (iii) the elucidation of general functional principles shared by receptor patches in all branches of life.

  15. TRPA1 contributes to cold, mechanical, and chemical nociception but is not essential for hair-cell transduction.

    PubMed

    Kwan, Kelvin Y; Allchorne, Andrew J; Vollrath, Melissa A; Christensen, Adam P; Zhang, Duan-Sun; Woolf, Clifford J; Corey, David P

    2006-04-20

    TRPA1, a member of the transient receptor potential (TRP) family of ion channels, is expressed by dorsal root ganglion neurons and by cells of the inner ear, where it has proposed roles in sensing sound, painful cold, and irritating chemicals. To test the in vivo roles of TRPA1, we generated a mouse in which the essential exons required for proper function of the Trpa1 gene were deleted. Knockout mice display behavioral deficits in response to mustard oil, to cold ( approximately 0 degrees C), and to punctate mechanical stimuli. These mice have a normal startle reflex to loud noise, a normal sense of balance, a normal auditory brainstem response, and normal transduction currents in vestibular hair cells. TRPA1 is apparently not essential for hair-cell transduction but contributes to the transduction of mechanical, cold, and chemical stimuli in nociceptor sensory neurons. PMID:16630838

  16. Early abscisic acid signal transduction mechanisms: newly discovered components and newly emerging questions

    PubMed Central

    Hubbard, Katharine E.; Nishimura, Noriyuki; Hitomi, Kenichi; Getzoff, Elizabeth D.; Schroeder, Julian I.

    2010-01-01

    The plant hormone abscisic acid (ABA) regulates many key processes in plants, including seed germination and development and abiotic stress tolerance, particularly drought resistance. Understanding early events in ABA signal transduction has been a major goal of plant research. The recent identification of the PYRABACTIN (4-bromo-N-[pyridin-2-yl methyl]naphthalene-1-sulfonamide) RESISTANCE (PYR)/REGULATORY COMPONENT OF ABA RECEPTOR (RCAR) family of ABA receptors and their biochemical mode of action represents a major breakthrough in the field. The solving of PYR/RCAR structures provides a context for resolving mechanisms mediating ABA control of protein–protein interactions for downstream signaling. Recent studies show that a pathway based on PYR/RCAR ABA receptors, PROTEIN PHOSPHATASE 2Cs (PP2Cs), and SNF1-RELATED PROTEIN KINASE 2s (SnRK2s) forms the primary basis of an early ABA signaling module. This pathway interfaces with ion channels, transcription factors, and other targets, thus providing a mechanistic connection between the phytohormone and ABA-induced responses. This emerging PYR/RCAR–PP2C–SnRK2 model of ABA signal transduction is reviewed here, and provides an opportunity for testing novel hypotheses concerning ABA signaling. We address newly emerging questions, including the potential roles of different PYR/RCAR isoforms, and the significance of ABA-induced versus constitutive PYR/RCAR–PP2C interactions. We also consider how the PYR/RCAR–PP2C–SnRK2 pathway interfaces with ABA-dependent gene expression, ion channel regulation, and control of small molecule signaling. These exciting developments provide researchers with a framework through which early ABA signaling can be understood, and allow novel questions about the hormone response pathway and possible applications in stress resistance engineering of plants to be addressed. PMID:20713515

  17. Calcium specificity signaling mechanisms in abscisic acid signal transduction in Arabidopsis guard cells

    PubMed Central

    Brandt, Benjamin; Munemasa, Shintaro; Wang, Cun; Nguyen, Desiree; Yong, Taiming; Yang, Paul G; Poretsky, Elly; Belknap, Thomas F; Waadt, Rainer; Alemán, Fernando; Schroeder, Julian I

    2015-01-01

    A central question is how specificity in cellular responses to the eukaryotic second messenger Ca2+ is achieved. Plant guard cells, that form stomatal pores for gas exchange, provide a powerful system for in depth investigation of Ca2+-signaling specificity in plants. In intact guard cells, abscisic acid (ABA) enhances (primes) the Ca2+-sensitivity of downstream signaling events that result in activation of S-type anion channels during stomatal closure, providing a specificity mechanism in Ca2+-signaling. However, the underlying genetic and biochemical mechanisms remain unknown. Here we show impairment of ABA signal transduction in stomata of calcium-dependent protein kinase quadruple mutant plants. Interestingly, protein phosphatase 2Cs prevent non-specific Ca2+-signaling. Moreover, we demonstrate an unexpected interdependence of the Ca2+-dependent and Ca2+-independent ABA-signaling branches and the in planta requirement of simultaneous phosphorylation at two key phosphorylation sites in SLAC1. We identify novel mechanisms ensuring specificity and robustness within stomatal Ca2+-signaling on a cellular, genetic, and biochemical level. DOI: http://dx.doi.org/10.7554/eLife.03599.001 PMID:26192964

  18. Calcium specificity signaling mechanisms in abscisic acid signal transduction in Arabidopsis guard cells.

    PubMed

    Brandt, Benjamin; Munemasa, Shintaro; Wang, Cun; Nguyen, Desiree; Yong, Taiming; Yang, Paul G; Poretsky, Elly; Belknap, Thomas F; Waadt, Rainer; Alemán, Fernando; Schroeder, Julian I

    2015-07-20

    A central question is how specificity in cellular responses to the eukaryotic second messenger Ca(2+) is achieved. Plant guard cells, that form stomatal pores for gas exchange, provide a powerful system for in depth investigation of Ca(2+)-signaling specificity in plants. In intact guard cells, abscisic acid (ABA) enhances (primes) the Ca(2+)-sensitivity of downstream signaling events that result in activation of S-type anion channels during stomatal closure, providing a specificity mechanism in Ca(2+)-signaling. However, the underlying genetic and biochemical mechanisms remain unknown. Here we show impairment of ABA signal transduction in stomata of calcium-dependent protein kinase quadruple mutant plants. Interestingly, protein phosphatase 2Cs prevent non-specific Ca(2+)-signaling. Moreover, we demonstrate an unexpected interdependence of the Ca(2+)-dependent and Ca(2+)-independent ABA-signaling branches and the in planta requirement of simultaneous phosphorylation at two key phosphorylation sites in SLAC1. We identify novel mechanisms ensuring specificity and robustness within stomatal Ca(2+)-signaling on a cellular, genetic, and biochemical level.

  19. Mechanical basis of osmosensory transduction in magnocellular neurosecretory neurones of the rat supraoptic nucleus.

    PubMed

    Prager-Khoutorsky, M; Bourque, C W

    2015-06-01

    Rat magnocellular neurosecretory cells (MNCs) release vasopressin and oxytocin to promote antidiuresis and natriuresis at the kidney. The osmotic control of oxytocin and vasopressin release at the neurohypophysis is required for osmoregulation in these animals, and this release is mediated by a modulation of the action potential firing rate by the MNCs. Under basal (isotonic) conditions, MNCs fire action potentials at a slow rate, and this activity is inhibited by hypo-osmotic conditions and enhanced by hypertonicity. The effects of changes in osmolality on MNCs are mediated by a number of different factors, including the involvement of synaptic inputs, the release of taurine by local glial cells and regulation of ion channels expressed within the neurosecretory neurones themselves. We review recent findings that have clarified our understanding of how osmotic stimuli modulate the activity of nonselective cation channels in MNCs. Previous studies have shown that osmotically-evoked changes in membrane potential and action potential firing rate in acutely isolated MNCs are provoked mainly by a modulation of nonselective cation channels. Notably, the excitation of isolated MNCs during hypertonicity is mediated by the activation of a capsaicin-insensitive cation channel that MNCs express as an N-terminal variant of the transient receptor potential vanilloid 1 (Trpv1) channel. The activation of this channel during hypertonicity is a mechanical process associated with cell shrinking. The effectiveness of this mechanical process depends on the presence of a thin layer of actin filaments (F-actin) beneath the plasma membrane, as well as a densely interweaved network of microtubules (MTs) occupying the bulk of the cytoplasm of MNCs. Although the mechanism by which F-actin contributes to Trpv1 activation remains unknown, recent data have shown that MTs interact with Trpv1 channels via binding sites on the C-terminus, and that the force mediated through this complex is

  20. Cell cycle requirements for transduction by foamy virus vectors compared to those of oncovirus and lentivirus vectors.

    PubMed

    Trobridge, Grant; Russell, David W

    2004-03-01

    Retroviral vectors based on foamy viruses (FV) are efficient gene delivery vehicles for therapeutic and research applications. While previous studies have shown that FV vectors transduce quiescent cell cultures more efficiently than oncoviral vectors, their specific cell cycle requirements have not been determined. Here we compare the transduction frequencies of FV vectors with those of onco- and lentiviral vectors in nondividing and dividing normal human fibroblasts by several methods. FV vectors transduced serum-deprived fibroblast cultures more efficiently than oncoretroviral vectors and at rates comparable to those of lentiviral vectors. However, in these cultures FV vectors only transduced a subpopulation of proliferating cells, as determined by bromodeoxyuridine staining for DNA synthesis. In contrast to lentiviral vectors, FV vectors were unable to transduce human fibroblasts arrested by aphidicolin (G(1)/S phase) or gamma-irradiation (G(2) phase), and a partial cell cycle that included mitosis but not DNA synthesis was required. We could not determine if mitosis facilitated nuclear entry of FV vectors, since cell-free vector preparations contained long terminal repeat circles, precluding their use as nuclear markers. In contrast to oncoviral vectors, both FV and lentiviral vectors efficiently transduced G(0) fibroblasts that were later stimulated to divide. In the case of FV vectors, this was due to the persistence of a stable transduction intermediate in quiescent cells. Our findings support the use of FV vectors as a safe and effective alternative to lentiviral vectors for ex vivo transduction of stem cells that are quiescent during culture but divide following transplantation.

  1. The condensed chromatin fiber: an allosteric chemo-mechanical machine for signal transduction and genome processing

    NASA Astrophysics Data System (ADS)

    Lesne, Annick; Bécavin, Christophe; Victor, Jean–Marc

    2012-02-01

    Allostery is a key concept of molecular biology which refers to the control of an enzyme activity by an effector molecule binding the enzyme at another site rather than the active site (allos = other in Greek). We revisit here allostery in the context of chromatin and argue that allosteric principles underlie and explain the functional architecture required for spacetime coordination of gene expression at all scales from DNA to the whole chromosome. We further suggest that this functional architecture is provided by the chromatin fiber itself. The structural, mechanical and topological features of the chromatin fiber endow chromosomes with a tunable signal transduction from specific (or nonspecific) effectors to specific (or nonspecific) active sites. Mechanical constraints can travel along the fiber all the better since the fiber is more compact and regular, which speaks in favor of the actual existence of the (so-called 30 nm) chromatin fiber. Chromatin fiber allostery reconciles both the physical and biochemical approaches of chromatin. We illustrate this view with two supporting specific examples. Moreover, from a methodological point of view, we suggest that the notion of chromatin fiber allostery is particularly relevant for systemic approaches. Finally we discuss the evolutionary power of allostery in the context of chromatin and its relation to modularity.

  2. Generalized transduction.

    PubMed

    Thierauf, Anne; Perez, Gerardo; Maloy, And Stanley

    2009-01-01

    Transduction is the process in which bacterial DNA is transferred from one bacterial cell to another by means of a phage particle. There are two types of transduction, generalized transduction and specialized transduction. In this chapter two of the best-studied systems - Escherichia coli-phage P1, and Salmonella enterica-phage P22 - are discussed from theoretical and practical perspectives.

  3. Development of a CMOS MEMS pressure sensor with a mechanical force-displacement transduction structure

    NASA Astrophysics Data System (ADS)

    Cheng, Chao-Lin; Chang, Heng-Chung; Chang, Chun-I.; Fang, Weileun

    2015-12-01

    This study presents a capacitive pressure sensor with a mechanical force-displacement transduction structure based on the commercially available standard CMOS process (the TSMC 0.18 μm 1P6M CMOS process). The pressure sensor has a deformable diaphragm to support a movable plate with an embedded sensing electrode. As the diaphragm is deformed by the ambient pressure, the movable plate and its embedded sensing electrode are displaced. Thus, the pressure is detected from the capacitance change between the movable and fixed electrodes. The undeformed movable electrode will increase the effective sensing area between the sensing electrodes, thereby improving the sensitivity. Experimental results show that the proposed pressure sensor with a force-displacement transducer will increase the sensitivity by 126% within the 20 kPa-300 kPa absolute pressure range. Moreover, this study extends the design to add pillars inside the pressure sensor to further increase its sensing area as well as sensitivity. A sensitivity improvement of 117% is also demonstrated for a pressure sensor with an enlarged sensing electrode (the overlap area is increased two fold).

  4. Chemical to electrical transduction mechanisms from single metal oxide nanowire measurements: response time constant analysis

    NASA Astrophysics Data System (ADS)

    Morante, J. R.

    2013-11-01

    Insight into chemical to electrical transduction mechanisms taking place at the surface of a single metal oxide nanowire is reported due to its outstanding importance for determining the characteristics of resistive solid state gas sensors. The surface chemical reaction kinetics is discussed considering competitiveness phenomena among different active sites and gas species on the nanowire taken as a metal oxide monocrystal at the nanoscale level. Experimental results for different representative gas molecules are shown to determine and understand sensor selectivity. The reported gas species are carbon monoxide and water vapour as general reference molecules, and ethanol and ammonia species as special references for gas-solid interactions, respectively, on acid and basic sites. Kinetic properties are proposed as particular signatures for each of the possible surface chemical reactions, allowing their identification and distinction. Likewise, features such as thermal inertia limitation and effects of the molecular and monoatomic absorbed oxygen are also estimated considering operation working modes based on nanowire self-heating. Furthermore, the applicability of a surface electrical field on a one-dimensional metal oxide nanostructure to enhance the surface ionization of the absorbed molecules is also reviewed as a new type of metal oxide based nanosensor for achieving improved selectivity.

  5. Endothelin receptors and their cellular signal transduction mechanism in human cultured prostatic smooth muscle cells.

    PubMed

    Saita, Y; Koizumi, T; Yazawa, H; Morita, T; Takenaka, T; Honda, K

    1997-06-01

    1. Endothelin (ET) receptors, and their cellular signal transduction mechanism, were characterized in a primary culture of human prostatic smooth muscle cells (HP cell). 2. [125I]-ET-1 and [125I]-ET-3 binding studies revealed that both ETA and ETB receptors were present in the HP cells, and the ratio of ETA to ETB receptors was 1.4:1. 3. Analysis of ET receptor mRNA by reverse transcription-polymerase chain reaction also demonstrated that HP cells express both ETA and ETB receptors. 4. ET-1 and ET-3 increased intracellular free Ca2+ concentration ([Ca2+]i) in the HP cells in a concentration-dependent manner. Use of subtype selective antagonists BQ-123 and BQ-788, indicated that both ETA and ETB receptors were coupled to an increase in [Ca2+]i. 5. Pretreatment of the cells with pertussis toxin resulted in a significant but partial attenuation of the [Ca2+]i increase mediated through the ETA and ETB receptors. However, sensitivity to pertussis toxin (PTX) was significantly different between them. 6. In conclusion, HP cells possess ETA and ETB receptors. Further, these two endothelin receptor subtypes evoke an increase in [Ca2+]i possibly via the action of different GTP-binding proteins. PMID:9208135

  6. Virus-based assay for antigen detection using infective growth as signal transduction mechanism.

    PubMed

    Cheok, Hui Shan; Jaworski, Justyn

    2016-03-15

    Viruses have the ability to infect and thereby confer new phenotypes on host cells. E. coli, for example, if infected by viruses containing antibiotic resistance genes, can benefit by surviving in the presence of the corresponding antibiotics to grow into colonies observable by the naked eye. Using this concept as a signal transduction mechanism for our immunoassay, we have engineered ampicillin resistant virions to display a dimer of the z domain from Protein A. This zz-domain selectively binds to the conserved heavy domain of IgG across various species. As commercially available antibodies are in no short supply, this engineered virion can be used modularly with existing antibodies for converting the presence of target antigen into a visually detectable colony forming unit. Here we demonstrate that this scheme for zz-phage transfection and selective growth of infected E. coli can facilitate sub-nanomolar detection limits for target antigen. Moreover, this phage infectivity assay works over a range of concentrations competitive with existing ELISA techniques. Because this system is derived from self-regenerating components (i.e., virus and bacteria) and furthermore obviates the need for chromogenic substrates or spectroscopic equipment, we find it particularly suitable for use in regions where cost effective detection is a necessity.

  7. Endothelin receptors and their cellular signal transduction mechanism in human cultured prostatic smooth muscle cells

    PubMed Central

    Saita, Yuji; Koizumi, Tomonobu; Yazawa, Hidenori; Morita, Takashi; Takenaka, Toichi; Honda, Kazuo

    1997-01-01

    Endothelin (ET) receptors, and their cellular signal transduction mechanism, were characterized in a primary culture of human prostatic smooth muscle cells (HP cell). [125I]-ET-1 and [125I]-ET-3 binding studies revealed that both ETA and ETB receptors were present in the HP cells, and the ratio of ETA to ETB receptors was 1.4:1. Analysis of ET receptor mRNA by reverse transcription-polymerase chain reaction also demonstrated that HP cells express both ETA and ETB receptors. ET-1 and ET-3 increased intracellular free Ca2+ concentration ([Ca2+]i) in the HP cells in a concentration-dependent manner. Use of subtype selective antagonists BQ-123 and BQ-788, indicated that both ETA and ETB receptors were coupled to an increase in [Ca2+]i. Pretreatment of the cells with pertussis toxin resulted in a significant but partial attenuation of the [Ca2+]i increase mediated through the ETA and ETB receptors. However, sensitivity to pertussis toxin (PTX) was significantly different between them. In conclusion, HP cells possess ETA and ETB receptors. Further, these two endothelin receptor subtypes evoke an increase in [Ca2+]i possibly via the action of different GTP-binding proteins. PMID:9208135

  8. Transduction mechanism of acoustic-wave based chemical and biochemical sensors

    NASA Astrophysics Data System (ADS)

    Lucklum, Ralf; Hauptmann, Peter

    2003-11-01

    Acoustic-wave-based sensors are commonly known as mass-sensitive devices. However, acoustic chemical and biochemical sensors also face so-called non-gravimetric effects, especially if they work in a liquid environment. The one-dimensional transmission-line model (TLM) is a powerful tool, which considers the influence of geometric and material properties on the sensor transduction mechanism, most importantly the influence of viscoelastic phenomena. This paper demonstrates the concept of modelling acoustic microsensors on quartz crystal resonators. Particular attention is paid to special cases which allow for simplifications or specific solutions of the TLM, like the acoustic load concept (ALC), the BVD model or the Sauerbrey equation. Deviations from the one-dimensional assumption of the TLM are suspected to significantly contribute to the acoustic sensor response in biosystems. We therefore introduce a generalization of the ALC to get access to two- or three-dimensional effects, which are up to now not considered in the TLM. As examples, signatures of interfacial phenomena or non-uniform films are discussed.

  9. Mechanisms of Regulation of Olfactory Transduction and Adaptation in the Olfactory Cilium

    PubMed Central

    Antunes, Gabriela; Sebastião, Ana Maria; Simoes de Souza, Fabio Marques

    2014-01-01

    Olfactory adaptation is a fundamental process for the functioning of the olfactory system, but the underlying mechanisms regulating its occurrence in intact olfactory sensory neurons (OSNs) are not fully understood. In this work, we have combined stochastic computational modeling and a systematic pharmacological study of different signaling pathways to investigate their impact during short-term adaptation (STA). We used odorant stimulation and electroolfactogram (EOG) recordings of the olfactory epithelium treated with pharmacological blockers to study the molecular mechanisms regulating the occurrence of adaptation in OSNs. EOG responses to paired-pulses of odorants showed that inhibition of phosphodiesterases (PDEs) and phosphatases enhanced the levels of STA in the olfactory epithelium, and this effect was mimicked by blocking vesicle exocytosis and reduced by blocking cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) and vesicle endocytosis. These results suggest that G-coupled receptors (GPCRs) cycling is involved with the occurrence of STA. To gain insights on the dynamical aspects of this process, we developed a stochastic computational model. The model consists of the olfactory transduction currents mediated by the cyclic nucleotide gated (CNG) channels and calcium ion (Ca2+)-activated chloride (CAC) channels, and the dynamics of their respective ligands, cAMP and Ca2+, and it simulates the EOG results obtained under different experimental conditions through changes in the amplitude and duration of cAMP and Ca2+ response, two second messengers implicated with STA occurrence. The model reproduced the experimental data for each pharmacological treatment and provided a mechanistic explanation for the action of GPCR cycling in the levels of second messengers modulating the levels of STA. All together, these experimental and theoretical results indicate the existence of a mechanism of regulation of STA by signaling pathways that control GPCR

  10. Mechanism of Poly(A) Signal Transduction to RNA Polymerase II In Vitro

    PubMed Central

    Tran, Dong P.; Kim, Steven J.; Park, Noh Jin; Jew, Tiffany M.; Martinson, Harold G.

    2001-01-01

    Termination of transcription by RNA polymerase II usually requires the presence of a functional poly(A) site. How the poly(A) site signals its presence to the polymerase is unknown. All models assume that the signal is generated after the poly(A) site has been extruded from the polymerase, but this has never been tested experimentally. It is also widely accepted that a “pause” element in the DNA stops the polymerase and that cleavage at the poly(A) site then signals termination. These ideas also have never been tested. The lack of any direct tests of the poly(A) signaling mechanism reflects a lack of success in reproducing the poly(A) signaling phenomenon in vitro. Here we describe a cell-free transcription elongation assay that faithfully recapitulates poly(A) signaling in a crude nuclear extract. The assay requires the use of citrate, an inhibitor of RNA polymerase II carboxyl-terminal domain phosphorylation. Using this assay we show the following. (i) Wild-type but not mutant poly(A) signals instruct the polymerase to stop transcription on downstream DNA in a manner that parallels true transcription termination in vivo. (ii) Transcription stops without the need of downstream elements in the DNA. (iii) cis-antisense inhibition blocks signal transduction, indicating that the signal to stop transcription is generated following extrusion of the poly(A) site from the polymerase. (iv) Signaling can be uncoupled from processing, demonstrating that signaling does not require cleavage at the poly(A) site. PMID:11585929

  11. Real-time PCR monitoring of signal transduction related genes involved in water stress tolerance mechanism of sunflower.

    PubMed

    Roche, Jane; Hewezi, Tarek; Bouniols, Andrée; Gentzbittel, Laurent

    2009-02-01

    The study deals with the quantitative expression pattern of genes involved in signaling transduction pathways in response to water stress in leaves and embryos of a water stress tolerant genotype compared to a non-tolerant genotype using real-time quantitative PCR. The experiment was conducted in the field. The results showed a high quantitative up-regulation of genes belonging to protein kinase, phosphatase and transcription factor pathways (from two to 70 fold) only in leaves of the tolerant genotype compared to the non-tolerant genotype. Moreover, genes related to the protein kinase pathway were down-regulated in leaves of the non-tolerant genotype. On the contrary, in seeds, our study showed that the positive regulation of genes related to the signal transduction pathway observed in leaves of the tolerant genotype is turned off, suggesting different transcriptional control of signaling water stress in reproductive organs compared to vegetative organs. PMID:19054682

  12. An investigation into membrane bound redox carriers involved in energy transduction mechanism in Brevibacterium linens DSM 20158 with unsequenced genome.

    PubMed

    Shabbiri, Khadija; Botting, Catherine H; Adnan, Ahmad; Fuszard, Matthew; Naseem, Shahid; Ahmed, Safeer; Shujaat, Shahida; Syed, Quratulain; Ahmad, Waqar

    2014-04-01

    Brevibacterium linens (B. linens) DSM 20158 with an unsequenced genome can be used as a non-pathogenic model to study features it has in common with other unsequenced pathogens of the same genus on the basis of comparative proteome analysis. The most efficient way to kill a pathogen is to target its energy transduction mechanism. In the present study, we have identified the redox protein complexes involved in the electron transport chain of B. linens DSM 20158 from their clear homology with the shot-gun genome sequenced strain BL2 of B. linens by using the SDS-Polyacrylamide gel electrophoresis coupled with nano LC-MS/MS mass spectrometry. B. linens is found to have a branched electron transport chain (Respiratory chain), in which electrons can enter the respiratory chain either at NADH (Complex I) or at Complex II level or at the cytochrome level. Moreover, we are able to isolate, purify, and characterize the membrane bound Complex II (succinate dehydrogenase), Complex III (menaquinone cytochrome c reductase cytochrome c subunit, Complex IV (cytochrome c oxidase), and Complex V (ATP synthase) of B. linens strain DSM 20158. PMID:24573306

  13. Mechanisms of signal transduction by ethylene: overlapping and non-overlapping signalling roles in a receptor family

    PubMed Central

    Shakeel, Samina N.; Wang, Xiaomin; Binder, Brad M.; Schaller, G. Eric

    2013-01-01

    The plant hormone ethylene regulates growth and development as well as responses to biotic and abiotic stresses. Over the last few decades, key elements involved in ethylene signal transduction have been identified through genetic approaches, these elements defining a pathway that extends from initial ethylene perception at the endoplasmic reticulum to changes in transcriptional regulation within the nucleus. Here, we present our current understanding of ethylene signal transduction, focusing on recent developments that support a model with overlapping and non-overlapping roles for members of the ethylene receptor family. We consider the evidence supporting this model for sub-functionalization within the receptor family, and then discuss mechanisms by which such a sub-functionalization may occur. To this end, we consider the importance of receptor interactions in modulating their signal output and how such interactions vary in the receptor family. In addition, we consider evidence indicating that ethylene signal output by the receptors involves both phosphorylation-dependent and phosphorylation-independent mechanisms. We conclude with a current model for signalling by the ethylene receptors placed within the overall context of ethylene signal transduction. PMID:23543258

  14. Alteration of membrane transductive mechanisms induced by ethanol in human lymphocyte cultures.

    PubMed

    Fanò, G; Belia, S; Mariggiò, M A; Antonica, A; Agea, E; Spinozzi, F

    1993-03-01

    Ethanol, in millimolar concentrations, significantly modifies different transductive systems in human lymphocyte cultures. In particular, the presence of alcohol in the medium more than doubles the [Ca2+]i (from 70-90 to 200-250 nM), increasing Ca2+ fluxes from outside, and inhibits the active transport carried out by the calcium pump. The Ca2+ release from intracellular stores is not involved because 10 mM EGTA in the medium completely abolished the rise of [Ca2+]i. Since IP3 levels and cAMP concentrations are also involved in ethanol events (although with opposite effects), it seems that the alcohol may have a specific target on cell membranes (G-proteins) which influence many transductive pathways. PMID:8388700

  15. TRPV Ion Channels and Sensory Transduction of Osmotic and Mechanical Stimuli in Mammals

    NASA Astrophysics Data System (ADS)

    Liedtke, Wolfgang

    In signal transduction in metazoan cells, ion channels of the transient receptor potential (TRP) family have been identified as responding to diverse external and internal stimuli, amongst them osmotic stimuli. This chapter will highlight findings on the TRP vanilloid (TRPV) subfamily - both vertebrate and invertebrate members. Of the six mammalian TRPV channels, TRPV1, 2 and 4 have been demonstrated to function in transduction of osmotic stimuli. TRPV channels have been found to function in cellular as well as systemic osmotic homeostasis in vertebrates. Invertebrate TRPV channels - five in Caenorhabditis elegans and two in Drosophila - have been shown to play a role in mechanosensation such as hearing and proprioception in Drosophila and nose touch in C. elegans, and in the response to osmotic stimuli in C. elegans. In a striking example of evolutionary conservation of function, mammalian TRPV4 has been found to rescue osmo- and mechano-sensory deficits of the TRPV mutant strain osm-9 in C. elegans, despite the fact that the respective proteins share not more than 26% orthology.

  16. New mechanisms of signal transduction inhibitor action: receptor tyrosine kinase down-regulation and blockade of signal transactivation.

    PubMed

    Lee, Adrian V; Schiff, Rachel; Cui, Xiaojiang; Sachdev, Deepali; Yee, Douglas; Gilmore, Andrew P; Streuli, Charles H; Oesterreich, Steffi; Hadsell, Darryl L

    2003-01-01

    The explosion of signal transduction research over the last 10 years has provided a unique insight into the complexity of these intricate pathways. Whereas intermediates of multiple signaling pathways have been identified, understanding their function and, in particular, the interactions between them has become a daunting task. The increasing evidence that many of these pathways can cross-talk with each other via signal transactivation inevitably raises the question of how cells determine specificity in signaling. Despite the mind-numbing complexity of these pathways, progress has been made in developing highly specific and potent signal transduction inhibitors (STIs). STIs show promise in the treatment of cancer in preclinical studies and are currently in a number of clinical trials. Whereas many of these agents were "rationally designed," we barely understand their mechanisms of action. This review will highlight how recent studies using these STIs have elucidated novel mechanisms of STI action that may be used in the development of new therapeutic strategies for the treatment of cancer.

  17. Signal transduction in the activation of spermatozoa compared to other signalling pathways: a biological networks study.

    PubMed

    Bernabò, Nicola; Mattioli, Mauro; Barboni, Barbara

    2015-01-01

    In this paper we represented Spermatozoa Activation (SA) the process that leads male gametes to reach their fertilising ability of sea urchin, Caenorhabditis elegans and human as biological networks, i.e. as networks of nodes (molecules) linked by edges (their interactions). Then, we compared them with networks representing ten pathways of relevant physio-pathological importance and with a computer-generated network. We have found that the number of nodes and edges composing each network is not related with the amount of published papers on each specific topic and that all the topological parameters examined are similar in all the networks, thus conferring them a scale free topology and small world behaviour. In conclusion, SA topology, independently from the reproductive biology of considered organism, as others signalling networks is characterised by robustness against random failure, controllability and efficiency in signal transmission. PMID:26489142

  18. Comparative genomics of protists: new insights into the evolution of eukaryotic signal transduction and gene regulation.

    PubMed

    Anantharaman, Vivek; Iyer, Lakshminarayan M; Aravind, L

    2007-01-01

    Data from protist genomes suggest that eukaryotes show enormous variability in their gene complements, especially of genes coding regulatory proteins. Overall counts of eukaryotic signaling proteins show weak nonlinear scaling with proteome size, but individual superfamilies of signaling domains might show vast expansions in certain protists. Alteration of domain architectural complexity of signaling proteins and repeated lineage-specific reshaping of architectures might have played a major role in the emergence of new signaling interactions in different eukaryotes. Lateral transfer of various signaling domains from bacteria or from hosts, in parasites such as apicomplexans, appears to also have played a major role in the origin of new functional networks. Lineage-specific expansion of regulatory proteins, particularly of transcription factors, has played a critical role in the adaptive radiation of different protist lineages. Comparative genomics allows objective reconstruction of the ancestral conditions and subsequent diversification of several regulatory systems involved in phosphorylation, cyclic nucleotide signaling, Ubiquitin conjugation, chromatin remodeling, and posttranscriptional gene silencing.

  19. Comparative RNA-sequencing analysis of mthl1 functions and signal transductions in Tribolium castaneum.

    PubMed

    Li, Chengjun; Wu, Wei; Sang, Ming; Liu, Xing; Hu, Xingxing; Yun, Xiaopei; Li, Bin

    2014-09-01

    Methuselah-like 1 of Tribolium castaneum (TcMthl1) has been reported to play crucial roles in development, lifespan, stress resistance and reproduction. However, the signaling system of TcMthl1 is unknown. Thus, we compare the transcriptome profile of RNAi treated larvae (ds-Tcmthl1) and control larvae of T. castaneum by RNA-sequencing, and obtained 14,613,514 sequence reads aligned with 13,533 genes; 812 differentially expressed genes (DEGs) were identified. These DEGs were classified into 47 GO functional groups, including such functions as the immune system process, the response to stimulus, the developmental process and reproduction. Interestingly, knock-down of Tcmthl1 suppressed both of Toll and IMD immunity pathways which most likely modulated the effects of Tcmthl1 on lifespan and stress resistance. Additionally, the DEGs encoding Blimp-1, Ftz-F1, E74 and Timeless may participate in the development and reproduction of ds-Tcmthl1 insects. The findings of these DEGs and pathways will provide valuable insight into TcMthl1 signaling and regulation system.

  20. Comparative genomics of the vertebrate insulin/TOR signal transduction pathway: a network-level analysis of selective pressures.

    PubMed

    Alvarez-Ponce, David; Aguadé, Montserrat; Rozas, Julio

    2011-01-01

    Complexity of biological function relies on large networks of interacting molecules. However, the evolutionary properties of these networks are not fully understood. It has been shown that selective pressures depend on the position of genes in the network. We have previously shown that in the Drosophila insulin/target of rapamycin (TOR) signal transduction pathway there is a correlation between the pathway position and the strength of purifying selection, with the downstream genes being most constrained. In this study, we investigated the evolutionary dynamics of this well-characterized pathway in vertebrates. More specifically, we determined the impact of natural selection on the evolution of 72 genes of this pathway. We found that in vertebrates there is a similar gradient of selective constraint in the insulin/TOR pathway to that found in Drosophila. This feature is neither the result of a polarity in the impact of positive selection nor of a series of factors affecting selective constraint levels (gene expression level and breadth, codon bias, protein length, and connectivity). We also found that pathway genes encoding physically interacting proteins tend to evolve under similar selective constraints. The results indicate that the architecture of the vertebrate insulin/TOR pathway constrains the molecular evolution of its components. Therefore, the polarity detected in Drosophila is neither specific nor incidental of this genus. Hence, although the underlying biological mechanisms remain unclear, these may be similar in both vertebrates and Drosophila.

  1. Structure and mechanism of the essential two-component signal-transduction system WalKR in Staphylococcus aureus

    DOE PAGESBeta

    Ji, Quanjiang; Chen, Peter J.; Qin, Guangrong; Deng, Xin; Hao, Ziyang; Wawrzak, Zdzislaw; Yeo, Won -Sik; Quang, Jenny Winjing; Cho, Hoonsik; Luo, Guan -Zheng; et al

    2016-03-18

    Most low GC Gram-positive bacteria possess an essential walKR two-component system (TCS) for signal transduction involved in regulating cell wall homoeostasis. Despite the well-established intracellular regulatory mechanism, the role of this TCS in extracellular signal recognition and factors that modulate the activity of this TCS remain largely unknown. Here we identify the extracellular receptor of the kinase ‘WalK’ (erWalK) as a key hub for bridging extracellular signal input and intracellular kinase activity modulation in Staphylococcus aureus. Characterization of the crystal structure of erWalK revealed a canonical Per-Arnt-Sim (PAS) domain for signal sensing. Single amino-acid mutation of potential signal-transduction residues resultedmore » in severely impaired function of WalKR. A small molecule derived from structure-based virtual screening against erWalK is capable of selectively activating the walKR TCS. Lastly, the molecular level characterization of erWalK will not only facilitate exploration of natural signal(s) but also provide a template for rational design of erWalK inhibitors.« less

  2. Structure and mechanism of the essential two-component signal-transduction system WalKR in Staphylococcus aureus

    PubMed Central

    Ji, Quanjiang; Chen, Peter J.; Qin, Guangrong; Deng, Xin; Hao, Ziyang; Wawrzak, Zdzislaw; Yeo, Won-Sik; Quang, Jenny Winjing; Cho, Hoonsik; Luo, Guan-Zheng; Weng, Xiaocheng; You, Qiancheng; Luan, Chi-Hao; Yang, Xiaojing; Bae, Taeok; Yu, Kunqian; Jiang, Hualiang; He, Chuan

    2016-01-01

    Most low GC Gram-positive bacteria possess an essential walKR two-component system (TCS) for signal transduction involved in regulating cell wall homoeostasis. Despite the well-established intracellular regulatory mechanism, the role of this TCS in extracellular signal recognition and factors that modulate the activity of this TCS remain largely unknown. Here we identify the extracellular receptor of the kinase ‘WalK' (erWalK) as a key hub for bridging extracellular signal input and intracellular kinase activity modulation in Staphylococcus aureus. Characterization of the crystal structure of erWalK revealed a canonical Per-Arnt-Sim (PAS) domain for signal sensing. Single amino-acid mutation of potential signal-transduction residues resulted in severely impaired function of WalKR. A small molecule derived from structure-based virtual screening against erWalK is capable of selectively activating the walKR TCS. The molecular level characterization of erWalK will not only facilitate exploration of natural signal(s) but also provide a template for rational design of erWalK inhibitors. PMID:26987594

  3. Covariation in individuals' sensitivities to bitter compounds: evidence supporting multiple receptor/transduction mechanisms.

    PubMed

    Delwiche, J F; Buletic, Z; Breslin, P A

    2001-07-01

    People vary widely in their sensitivities to bitter compounds, but the intercorrelation of these sensitivities is unknown. Our goal was to investigate correlations as a function of individual sensitivities to several bitter compounds representative of different chemical classes and, from these correlations, infer the number and variety of potential bitterness transduction systems for these compounds. Twenty-six subjects rated and ranked quinine HCl, caffeine, (-)-epicatechin, tetralone, L-phenylalanine, L-tryptophan, magnesium sulfate, urea, sucrose octaacetate (SOA), denatonium benzoate, and n-propylthiouracil (PROP) for bitterness. By examining individual differences, ratings and rankings could be grouped into two general clusters--urea/phenylalanine/tryptophan/epicatechin, and quinine/caffeine/SOA/denatonium benzoate/tetralone/magnesium sulfate-none of which contained PROP. When subjects were grouped into the extremes of sensitivity to PROP, a significant difference was found in the bitterness ratings, but not in the rankings. Therefore, there are also subjects who possess diminished absolute sensitivity to bitter stimuli but do not differ from other subjects in their relative sensitivities to these compounds. PMID:11521845

  4. Potential insight for drug discovery from high fidelity receptor-mediated transduction mechanisms in insects

    PubMed Central

    Raffa, Robert B.; Raffa, Kenneth F.

    2011-01-01

    Introduction There is a pervasive and growing concern about the small number of new pharmaceutical agents. There are many proposed explanations for this trend that do not involve the drug-discovery process per se, but the discovery process itself has also come under scrutiny. If the current paradigms are indeed not working, where are novel ideas to come from? Perhaps it is time to look to novel sources. Areas covered The receptor-signaling and 2nd-messenger transduction processes present in insects are quite similar to those in mammals (involving G proteins, ion channels, etc.). However, a review of these systems reveals an unprecedented degree of high potency and receptor selectivity to an extent greater than that modeled in most current drug-discovery approaches. Expert opinion A better understanding of insect receptor pharmacology could stimulate novel theoretical and practical ideas in mammalian pharmacology (drug discovery) and, conversely, the application of pharmacology and medicinal chemistry principles could stimulate novel advances in entomology (safer and more targeted control of pest species). PMID:21984882

  5. Toward Quantifying the Electrostatic Transduction Mechanism in Carbon Nanotube Biomolecular Sensors

    NASA Astrophysics Data System (ADS)

    Lerner, Mitchell; Kybert, Nicholas; Mendoza, Ryan; Dailey, Jennifer; Johnson, A. T. Charlie

    2013-03-01

    Despite the great promise of carbon nanotube field-effect transistors (CNT FETs) for applications in chemical and biochemical detection, a quantitative understanding of sensor responses is lacking. To explore the role of electrostatics in sensor transduction, experiments were conducted with a set of similar compounds designed to adsorb onto the CNT FET via a pyrene linker group and take on a set of known charge states under ambient conditions. Acidic and basic species were observed to induce threshold voltage shifts of opposite sign, consistent with gating of the CNT FET by local charges due to protonation or deprotonation of the pyrene compounds by interfacial water. The magnitude of the gate voltage shift was controlled by the distance between the charged group and the CNT. Additionally, functionalization with an uncharged pyrene compound showed a threshold shift ascribed to its molecular dipole moment. This work illustrates a method for producing CNT FETs with controlled values of the turnoff gate voltage, and more generally, these results will inform the development of quantitative models for the response of CNT FET chemical and biochemical sensors. As an example, the results of an experiment detecting biomarkers of Lyme disease will be discussed in the context of this model.

  6. Interaction of the protein transduction domain of HIV-1 TAT with heparan sulfate: binding mechanism and thermodynamic parameters.

    PubMed

    Ziegler, André; Seelig, Joachim

    2004-01-01

    The positively charged protein transduction domain of the HIV-1 TAT protein (TAT-PTD; residues 47-57 of TAT) rapidly translocates across the plasma membrane of living cells. This property is exploited for the delivery of proteins, drugs, and genes into cells. The mechanism of this translocation is, however, not yet understood. Recent theories for translocation suggest binding of the protein transduction domain (PTD) to extracellular glycosaminoglycans as a possible mechanism. We have studied the binding equilibrium between TAT-PTD and three different glycosaminoglycans with high sensitivity isothermal titration calorimetry and provide the first quantitative thermodynamic description. The polysulfonated macromolecules were found to exhibit multiple identical binding sites for TAT-PTD with only small differences between the three species as far as the thermodynamic parameters are concerned. Heparan sulfate (HS, molecular weight, 14.2 +/- 2 kDa) has 6.3 +/- 1.0 independent binding sites for TAT-PTD which are characterized by a binding constant K0 = (6.0 +/- 0.6) x 10(5) M(-1) and a reaction enthalpy deltaHpep0 = -4.6 +/- 1.0 kcal/mol at 28 degrees C. The binding affinity, deltaGpep0, is determined to equal extent by enthalpic and entropic contributions. The HS-TAT-PTD complex formation entails a positive heat capacity change of deltaCp0 = +135 cal/mol peptide, which is characteristic of a charge neutralization reaction. This is in contrast to hydrophobic binding reactions which display a large negative heat capacity change. The stoichiometry of 6-7 TAT-PTD molecules per HS corresponds to an electric charge neutralization. Light scattering data demonstrate a maximum scattering intensity at this stoichiometric ratio, the intensity of which depends on the order of mixing of the two components. The data suggest cross-linking and/or aggregation of HS-TAT-PTD complexes. Two other glycosaminoglycans, namely heparin and chondroitin sulfate B, were also studied with isothermal

  7. Radiative ion-ion neutralization: a new gas-phase atmospheric pressure ion transduction mechanism.

    PubMed

    Davis, Eric J; Siems, William F; Hill, Herbert H

    2012-06-01

    All atmospheric pressure ion detectors, including photo ionization detectors, flame ionization detectors, electron capture detectors, and ion mobility spectrometers, utilize Faraday plate designs in which ionic charge is collected and amplified. The sensitivity of these Faraday plate ion detectors are limited by thermal (Johnson) noise in the associated electronics. Thus approximately 10(6) ions per second are required for a minimal detection. This is not the case for ion detection under vacuum conditions where secondary electron multipliers (SEMs) can be used. SEMs produce a cascade of approximately 10(6) electrons per ion impinging on the conversion dynode. Similarly, photomultiplier tubes (PMTs) can generate approximately 10(6) electrons per photon. Unlike SEMs, however, PMTs are evacuated and sealed so that they are commonly used under atmospheric pressure conditions. This paper describes an atmospheric pressure ion detector based on coupling a PMT with light emitted from ion-ion neutralization reactions. The normal Faraday plate collector electrode was replaced with an electrode "needle" used to concentrate the anions as they were drawn to the tip of the needle by a strong focusing electric field. Light was emitted near the surface of the electrode when analyte ions were neutralized with cations produced from the anode. Although radiative-ion-ion recombination has been previously reported, this is the first time ions from separate ionization sources have been combined to produce light. The light from this radiative-ion-ion-neutralization (RIIN) was detected using a photon multiplier such that an ion mobility spectrum was obtained by monitoring the light emitted from mobility separated ions. An IMS spectrum of nitroglycerin (NG) was obtained utilizing RIIN for tranducing the mobility separated ions into an analytical signal. The implications of this novel ion transduction method are the potential for counting ions at atmospheric pressure and for obtaining ion

  8. Mechanosensing and mechanochemical transduction: how is mechanical energy sensed and converted into chemical energy in an extracellular matrix?

    PubMed

    Silver, Frederick H; Siperko, Lorraine M

    2003-01-01

    Gravity plays a central role in vertebrate development and evolution. Gravitational forces acting on mammalian tissues cause the net muscle forces required for locomotion to be higher on earth than on a body subjected to a microgravitational field. As body mass increases during development, the musculoskeleton must be able to adapt by increasing the size of its functional units. Thus mechanical forces required to do the work (mechanical energy) of locomotion must be sensed by cells and converted into chemical energy (synthesis of new tissue). Extracellular matrices (ECMs) are multicomponent tissues that transduce internal and external mechanical signals into changes in tissue structure and function through a process termed mechanochemical transduction. Under the influence of an external gravitational field, both mineralized and unmineralized vertebrate tissues exhibit internal tensile forces that serve to preserve a synthetic phenotype in the resident cell population. Application of additional external forces alters the balance between the external gravitational force and internal forces acting on resident cells leading to changes in the expression of genes and production of protein that ultimately may alter the exact structure and function of the extracellular matrix. Changes in the equilibrium between internal and external forces acting on ECMs and changes in mechanochemical transduction processes at the cellular level appear to be important mechanisms by which mammals adjust their needs to store, transmit, and dissipate energy that is required during development and for bodily movements. Mechanosensing is postulated to involve many different cellular and extracellular components. Mechanical forces cause direct stretching of protein-cell surface integrin binding sites that occur on all eukaryotic cells. Stress-induced conformational changes in the extracellular matrix may alter integrin structure and lead to activation of several secondary messenger pathways

  9. Comparative advantages of mechanical biosensors

    PubMed Central

    Arlett, J.L.; Myers, E.B.; Roukes, M.L.

    2013-01-01

    Mechanical interactions are fundamental to biology. Mechanical forces of chemical origin determine motility and adhesion on the cellular scale, and govern transport and affinity on the molecular scale. Biological sensing in the mechanical domain provides unique opportunities to measure forces, displacements and mass changes from cellular and subcellular processes. Nanomechanical systems are particularly well matched in size with molecular interactions, and provide a basis for biological probes with single-molecule sensitivity. Here we review micro- and nanoscale biosensors, with a particular focus on fast mechanical biosensing in fluid by mass- and force-based methods, and the challenges presented by non-specific interactions. We explain the general issues that will be critical to the success of any type of next-generation mechanical biosensor, such as the need to improve intrinsic device performance, fabrication reproducibility and system integration. We also discuss the need for a greater understanding of analyte–sensor interactions on the nanoscale and of stochastic processes in the sensing environment. PMID:21441911

  10. Novel effects of Helicobacter pylori CagA on key genes of gastric cancer signal transduction: a comparative transfection study.

    PubMed

    Vaziri, Farzam; Peerayeh, Shahin N; Alebouyeh, Masoud; Maghsoudi, Nader; Azimzadeh, Pedram; Siadat, Seyed D; Zali, Mohammad R

    2015-04-01

    Helicobacter pylori (H. pylori) infection is now recognized as a worldwide problem. Helicobacter pylori CagA is the first bacterial oncoprotein to be identified in relation to human cancer. Helicobacter pylori CagA is noted for structural diversity in its C-terminal region (contains EPIYA motifs), with which CagA interacts with numerous host cell proteins. Deregulation of host signaling by translocated bacterial proteins provides a new aspect of microbial-host cell interaction. The aim of this study is to compare the cellular effects of two different CagA EPIYA motifs on identified signaling pathways involve in gastric carcinogenesis. To investigate the effects of CagA protein carboxyl region variations on the transcription of genes involved in gastric epithelial carcinogenesis pathways, the eukaryotic vector carrying the cagA gene (ABC and ABCCC types) was transfected into gastric cancer cell line. The 42 identified key genes of signal transduction involved in gastric cancer were analyzed at the transcription level by real-time PCR. The results of real-time PCR provide us important clue that the ABCCC oncoprotein variant can change the fate of the cell completely different from ABC type. In fact, these result proposed that the ABCCC type can induce the intestinal metaplasia, IL-8, perturbation of Crk adaptor proteins, anti-apoptotic effect and carcinogenic effect more significantly than ABC type. These data support our hypothesis of a complex interaction of host cell and these two different H. pylori effector variants that determines host cellular fate.

  11. A local difference in Hedgehog signal transduction increases mechanical cell bond tension and biases cell intercalations along the Drosophila anteroposterior compartment boundary.

    PubMed

    Rudolf, Katrin; Umetsu, Daiki; Aliee, Maryam; Sui, Liyuan; Jülicher, Frank; Dahmann, Christian

    2015-11-15

    Tissue organization requires the interplay between biochemical signaling and cellular force generation. The formation of straight boundaries separating cells with different fates into compartments is important for growth and patterning during tissue development. In the developing Drosophila wing disc, maintenance of the straight anteroposterior (AP) compartment boundary involves a local increase in mechanical tension at cell bonds along the boundary. The biochemical signals that regulate mechanical tension along the AP boundary, however, remain unknown. Here, we show that a local difference in Hedgehog signal transduction activity between anterior and posterior cells is necessary and sufficient to increase mechanical tension along the AP boundary. This difference in Hedgehog signal transduction is also required to bias cell rearrangements during cell intercalations to keep the characteristic straight shape of the AP boundary. Moreover, severing cell bonds along the AP boundary does not reduce tension at neighboring bonds, implying that active mechanical tension is upregulated, cell bond by cell bond. Finally, differences in the expression of the homeodomain-containing protein Engrailed also contribute to the straight shape of the AP boundary, independently of Hedgehog signal transduction and without modulating cell bond tension. Our data reveal a novel link between local differences in Hedgehog signal transduction and a local increase in active mechanical tension of cell bonds that biases junctional rearrangements. The large-scale shape of the AP boundary thus emerges from biochemical signals inducing patterns of active tension on cell bonds.

  12. Amiloride-Insensitive Salt Taste Is Mediated by Two Populations of Type III Taste Cells with Distinct Transduction Mechanisms

    PubMed Central

    Sukumaran, Sunil K.; Margolskee, Robert F.; Bachmanov, Alexander A.

    2016-01-01

    Responses in the amiloride-insensitive (AI) pathway, one of the two pathways mediating salty taste in mammals, are modulated by the size of the anion of a salt. This “anion effect” has been hypothesized to result from inhibitory transepithelial potentials (TPs) generated across the lingual epithelium as cations permeate through tight junctions and leave their larger and less permeable anions behind (Ye et al., 1991). We tested directly the necessity of TPs for the anion effect by measuring responses to NaCl and Na-gluconate (small and large anion sodium salts, respectively) in isolated taste cells from mouse circumvallate papillae. Using calcium imaging, we identified AI salt-responsive type III taste cells and demonstrated that they compose a subpopulation of acid-responsive taste cells. Even in the absence of TPs, many (66%) AI salt-responsive type III taste cells still exhibited the anion effect, demonstrating that some component of the transduction machinery for salty taste in type III cells is sensitive to anion size. We hypothesized that osmotic responses could explain why a minority of type III cells (34%) had AI salt responses but lacked anion sensitivity. All AI type III cells had osmotic responses to cellobiose, which were significantly modulated by extracellular sodium concentration, suggesting the presence of a sodium-conducting osmotically sensitive ion channel. However, these responses were significantly larger in AI type III cells that did not exhibit the anion effect. These findings indicate that multiple mechanisms could underlie AI salt responses in type III taste cells, one of which may contribute to the anion effect. SIGNIFICANCE STATEMENT Understanding the mechanisms underlying salty taste will help inform strategies to combat the health problems associated with NaCl overconsumption by humans. Of the two pathways underlying salty taste in mammals, the amiloride-insensitive (AI) pathway is the least understood. Using calcium imaging of

  13. In situ tip-recordings found no evidence for an Orco-based ionotropic mechanism of pheromone-transduction in Manduca sexta.

    PubMed

    Nolte, Andreas; Funk, Nico W; Mukunda, Latha; Gawalek, Petra; Werckenthin, Achim; Hansson, Bill S; Wicher, Dieter; Stengl, Monika

    2013-01-01

    The mechanisms of insect odor transduction are still controversial. Insect odorant receptors (ORs) are 7TM receptors with inverted membrane topology. They colocalize with a conserved coreceptor (Orco) with chaperone and ion channel function. Some studies suggest that insects employ exclusively ionotropic odor transduction via OR-Orco heteromers. Other studies provide evidence for different metabotropic odor transduction cascades, which employ second messenger-gated ion channel families for odor transduction. The hawkmoth Manduca sexta is an established model organism for studies of insect olfaction, also due to the availability of the hawkmoth-specific pheromone blend with its main component bombykal. Previous patch-clamp studies on primary cell cultures of M. sexta olfactory receptor neurons provided evidence for a pheromone-dependent activation of a phospholipase Cβ. Pheromone application elicited a sequence of one rapid, apparently IP3-dependent, transient and two slower Ca(2+)-dependent inward currents. It remains unknown whether additionally an ionotropic pheromone-transduction mechanism is employed. If indeed an OR-Orco ion channel complex underlies an ionotropic mechanism, then Orco agonist-dependent opening of the OR-Orco channel pore should add up to pheromone-dependent opening of the pore. Here, in tip-recordings from intact pheromone-sensitive sensilla, perfusion with the Orco agonist VUAA1 did not increase pheromone-responses within the first 1000 ms. However, VUAA1 increased spontaneous activity of olfactory receptor neurons Zeitgebertime- and dose-dependently. We conclude that we find no evidence for an Orco-dependent ionotropic pheromone transduction cascade in M. sexta. Instead, in M. sexta Orco appears to be a slower, second messenger-dependent pacemaker channel which affects kinetics and threshold of pheromone-detection via changes of intracellular Ca(2+) baseline concentrations. PMID:23671617

  14. Yifuning postpones ovarian aging through antioxidant mechanisms and suppression of the Rb/p53 signal transduction pathway.

    PubMed

    Liang, Lei; Zhang, Xu-Hui; Ji, Bo; Yao, Hui; Ling, Xiao-Mei; Guo, Zhi-Jian; Deng, Hong-Zhu; Wu, Xin-Rong

    2016-07-01

    Yifuning is a traditional Chinese medicine recipe that has been used for many years in China for its effects on treating climacteric syndrome in women. The present study aimed to demonstrate the effects and underlying molecular mechanism of Yifuning on the ovaries of aging rats. Selected aging rats were administered different doses of Yifuning (1.0 or 2.0 g/kg by lavage), and after 6 weeks the rats were sacrificed. The activit of indicators of oxidative stress in the serum were measured. The expression levels of 8-oxo-2'-deoxyguanosine (8-OHDG) and p53 in the ovaries were examined using immunohistochemistry. The expression levels of the corresponding genes and proteins were detected by reverse transcription‑quantitative polymerase chain reaction and western blotting analyses, respectively. The results indicated that Yifuning significantly prevented ovarian failure, as indicated by improvements in estrous cycling, reproductive organ weights and sex hormone serum levels. Yifuning significantly increased the levels of superoxide dismutase, glutathione peroxidase, catalase and reduced malondialdehyde and hydrogen peroxide levels. Yifuning reduced DNA damage in the ovaries by reducing the expression of 8‑OHDG and p53. Treatment with Yifuning significantly reduced the age‑induced p19, p53, p21 and Rb activity in the ovaries. The present study demonstrates that Yifuning prevents ovarian failure and the mechanism involved is partly associated with antioxidants and suppression of the Rb/p53 signal transduction pathway. PMID:27222316

  15. Yifuning postpones ovarian aging through antioxidant mechanisms and suppression of the Rb/p53 signal transduction pathway.

    PubMed

    Liang, Lei; Zhang, Xu-Hui; Ji, Bo; Yao, Hui; Ling, Xiao-Mei; Guo, Zhi-Jian; Deng, Hong-Zhu; Wu, Xin-Rong

    2016-07-01

    Yifuning is a traditional Chinese medicine recipe that has been used for many years in China for its effects on treating climacteric syndrome in women. The present study aimed to demonstrate the effects and underlying molecular mechanism of Yifuning on the ovaries of aging rats. Selected aging rats were administered different doses of Yifuning (1.0 or 2.0 g/kg by lavage), and after 6 weeks the rats were sacrificed. The activit of indicators of oxidative stress in the serum were measured. The expression levels of 8-oxo-2'-deoxyguanosine (8-OHDG) and p53 in the ovaries were examined using immunohistochemistry. The expression levels of the corresponding genes and proteins were detected by reverse transcription‑quantitative polymerase chain reaction and western blotting analyses, respectively. The results indicated that Yifuning significantly prevented ovarian failure, as indicated by improvements in estrous cycling, reproductive organ weights and sex hormone serum levels. Yifuning significantly increased the levels of superoxide dismutase, glutathione peroxidase, catalase and reduced malondialdehyde and hydrogen peroxide levels. Yifuning reduced DNA damage in the ovaries by reducing the expression of 8‑OHDG and p53. Treatment with Yifuning significantly reduced the age‑induced p19, p53, p21 and Rb activity in the ovaries. The present study demonstrates that Yifuning prevents ovarian failure and the mechanism involved is partly associated with antioxidants and suppression of the Rb/p53 signal transduction pathway.

  16. Nano-mechanical transduction of polymer micro-cantilevers to detect bio-molecular interactions.

    PubMed

    Urwyler, Prabitha; Köser, Joachim; Schift, Helmut; Gobrecht, Jens; Müller, Bert

    2012-12-01

    Using variothermal polymer micro-injection molding, disposable arrays of eight polymer micro-cantilevers each 500 μm long, 100 μm wide and 25 μm thick were fabricated. The present study took advantage of an easy flow grade polypropylene. After gold coating for optical read-out and asymmetrical sensitization, the arrays were introduced into the Cantisens(®) Research system to perform mechanical and functional testing. We demonstrate that polypropylene cantilevers can be used as biosensors for medical purposes in the same manner as the established silicon ones to detect single-stranded DNA sequences and metal ions in real-time. A differential signal of 7 nm was detected for the hybridization of 1 μM complementary DNA sequences. For 100 nM copper ions the differential signal was found to be (36 ± 5) nm. Nano-mechanical sensing of medically relevant, nanometer-size species is essential for fast and efficient diagnosis.

  17. Therapeutic effects of tyroservatide on metastasis of lung cancer and its mechanism affecting integrin–focal adhesion kinase signal transduction

    PubMed Central

    Huang, Yu-ting; Zhao, Lan; Fu, Zheng; Zhao, Meng; Song, Xiao-meng; Jia, Jing; Wang, Song; Li, Jin-ping; Zhu, Zhi-feng; Lin, Gang; Lu, Rong; Yao, Zhi

    2016-01-01

    Tyroservatide (YSV) can inhibit the growth and metastasis of mouse lung cancer significantly. This study investigated the therapeutic effects of tripeptide YSV on metastasis of human lung cancer cells and explored its possible mechanism that affects integrin–focal adhesion kinase (FAK) signal transduction in tumor cells. YSV significantly inhibited the adhesion and the invasion of highly metastatic human lung cancer cell lines 95D, A549, and NCI-H1299. In addition, YSV significantly inhibited phosphorylation of FAK Tyr397 and FAK Tyr576/577 in the 95D, A549, and NCI-H1299 human lung cancer cells in vitro. And the mRNA level and protein expression of FAK in these human lung cancer cells decreased at the same time. YSV also significantly inhibited mRNA and protein levels of integrin β1 and integrin β3 in the 95D, A549, and NCI-H1299 human lung cancer cells. Our research showed that YSV inhibited adhesion and invasion of human lung cancer cells and exhibited therapeutic effects on metastasis of lung cancer. PMID:27041993

  18. Therapeutic effects of tyroservatide on metastasis of lung cancer and its mechanism affecting integrin-focal adhesion kinase signal transduction.

    PubMed

    Huang, Yu-ting; Zhao, Lan; Fu, Zheng; Zhao, Meng; Song, Xiao-meng; Jia, Jing; Wang, Song; Li, Jin-ping; Zhu, Zhi-feng; Lin, Gang; Lu, Rong; Yao, Zhi

    2016-01-01

    Tyroservatide (YSV) can inhibit the growth and metastasis of mouse lung cancer significantly. This study investigated the therapeutic effects of tripeptide YSV on metastasis of human lung cancer cells and explored its possible mechanism that affects integrin-focal adhesion kinase (FAK) signal transduction in tumor cells. YSV significantly inhibited the adhesion and the invasion of highly metastatic human lung cancer cell lines 95D, A549, and NCI-H1299. In addition, YSV significantly inhibited phosphorylation of FAK Tyr397 and FAK Tyr576/577 in the 95D, A549, and NCI-H1299 human lung cancer cells in vitro. And the mRNA level and protein expression of FAK in these human lung cancer cells decreased at the same time. YSV also significantly inhibited mRNA and protein levels of integrin β1 and integrin β3 in the 95D, A549, and NCI-H1299 human lung cancer cells. Our research showed that YSV inhibited adhesion and invasion of human lung cancer cells and exhibited therapeutic effects on metastasis of lung cancer.

  19. An HLA-DRB1-coded signal transduction ligand facilitates inflammatory arthritis: a new mechanism of autoimmunity.

    PubMed

    Holoshitz, Joseph; Liu, Ying; Fu, Jiaqi; Joseph, Jeena; Ling, Song; Colletta, Alessandro; Sharma, Prannda; Begun, Dana; Goldstein, Steven; Taichman, Russell

    2013-01-01

    Particular alleles of HLA contribute to disease susceptibility and severity in many autoimmune conditions, but the mechanisms underlying these associations are often unknown. In this study, we demonstrate that the shared epitope (SE), an HLA-DRB1-coded sequence motif that is the single most significant genetic risk factor for erosive rheumatoid arthritis, acts as a signal transduction ligand that potently activates osteoclastogenesis, both in vitro and in vivo. The SE enhanced the production of several pro-osteoclastogenic factors and facilitated osteoclast (OC) differentiation in mouse and human cells in vitro. Transgenic mice expressing a human HLA-DRB1 allele that code the SE motif demonstrated markedly higher propensity for osteoclastogenesis and enhanced bone degradation capacity ex vivo. In addition, the SE enhanced the differentiation of Th17 cells expressing the receptor activator for NF-κB ligand. When the two agents were combined, IL-17 and the SE enhanced OC differentiation synergistically. When administered in vivo to mice with collagen-induced arthritis, the SE ligand significantly increased arthritis severity, synovial tissue OC abundance, and bone erosion. Thus, the SE contributes to arthritis severity by activating an OC-mediated bone-destructive pathway. These findings suggest that besides determining the target specificity of autoimmune responses, HLA molecules may influence disease outcomes by shaping the pathogenic consequences of such responses.

  20. Experimental and theoretical investigation of the precise transduction mechanism in giant magnetoresistive biosensors.

    PubMed

    Lee, Jung-Rok; Sato, Noriyuki; Bechstein, Daniel J B; Osterfeld, Sebastian J; Wang, Junyi; Gani, Adi Wijaya; Hall, Drew A; Wang, Shan X

    2016-01-05

    Giant magnetoresistive (GMR) biosensors consisting of many rectangular stripes are being developed for high sensitivity medical diagnostics of diseases at early stages, but many aspects of the sensing mechanism remain to be clarified. Using e-beam patterned masks on the sensors, we showed that the magnetic nanoparticles with a diameter of 50 nm located between the stripes predominantly determine the sensor signals over those located on the sensor stripes. Based on computational analysis, it was confirmed that the particles in the trench, particularly those near the edges of the stripes, mainly affect the sensor signals due to additional field from the stripe under an applied field. We also demonstrated that the direction of the average magnetic field from the particles that contributes to the signal is indeed the same as that of the applied field, indicating that the particles in the trench are pivotal to produce sensor signal. Importantly, the same detection principle was validated with a duplex protein assay. Also, 8 different types of sensor stripes were fabricated and design parameters were explored. According to the detection principle uncovered, GMR biosensors can be further optimized to improve their sensitivity, which is highly desirable for early diagnosis of diseases.

  1. Experimental and theoretical investigation of the precise transduction mechanism in giant magnetoresistive biosensors

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Rok; Sato, Noriyuki; Bechstein, Daniel J. B.; Osterfeld, Sebastian J.; Wang, Junyi; Gani, Adi Wijaya; Hall, Drew A.; Wang, Shan X.

    2016-01-01

    Giant magnetoresistive (GMR) biosensors consisting of many rectangular stripes are being developed for high sensitivity medical diagnostics of diseases at early stages, but many aspects of the sensing mechanism remain to be clarified. Using e-beam patterned masks on the sensors, we showed that the magnetic nanoparticles with a diameter of 50 nm located between the stripes predominantly determine the sensor signals over those located on the sensor stripes. Based on computational analysis, it was confirmed that the particles in the trench, particularly those near the edges of the stripes, mainly affect the sensor signals due to additional field from the stripe under an applied field. We also demonstrated that the direction of the average magnetic field from the particles that contributes to the signal is indeed the same as that of the applied field, indicating that the particles in the trench are pivotal to produce sensor signal. Importantly, the same detection principle was validated with a duplex protein assay. Also, 8 different types of sensor stripes were fabricated and design parameters were explored. According to the detection principle uncovered, GMR biosensors can be further optimized to improve their sensitivity, which is highly desirable for early diagnosis of diseases.

  2. Control of CREB expression in tumors: from molecular mechanisms and signal transduction pathways to therapeutic target

    PubMed Central

    Steven, André; Seliger, Barbara

    2016-01-01

    The cyclic AMP response element binding (CREB) protein has pleiotropic activities in physiologic processes. Due to its central position downstream of many growth signaling pathways CREB has the ability to influence cell survival, growth and differentiation of normal, but also of tumor cells suggesting an oncogenic potential of CREB. Indeed, increased CREB expression and activation is associated with tumor progression, chemotherapy resistance and reduced patients' survival. We summarize here the different cellular functions of CREB in tumors of distinct histology as well as its use as potential prognostic marker. In addition, the underlying molecular mechanisms to achieve constitutive activation of CREB including structural alterations, such as gene amplification and chromosomal translocation, and deregulation, which could occur at the transcriptional, post-transcriptional and post-translational level, will be described. Since downregulation of CREB by different strategies resulted in inhibition of cell proliferation, invasion and induction of apoptosis, the role of CREB as a promising target for cancer therapy will be also discussed. PMID:26934558

  3. Experimental and theoretical investigation of the precise transduction mechanism in giant magnetoresistive biosensors

    PubMed Central

    Lee, Jung-Rok; Sato, Noriyuki; Bechstein, Daniel J. B.; Osterfeld, Sebastian J.; Wang, Junyi; Gani, Adi Wijaya; Hall, Drew A.; Wang, Shan X.

    2016-01-01

    Giant magnetoresistive (GMR) biosensors consisting of many rectangular stripes are being developed for high sensitivity medical diagnostics of diseases at early stages, but many aspects of the sensing mechanism remain to be clarified. Using e-beam patterned masks on the sensors, we showed that the magnetic nanoparticles with a diameter of 50 nm located between the stripes predominantly determine the sensor signals over those located on the sensor stripes. Based on computational analysis, it was confirmed that the particles in the trench, particularly those near the edges of the stripes, mainly affect the sensor signals due to additional field from the stripe under an applied field. We also demonstrated that the direction of the average magnetic field from the particles that contributes to the signal is indeed the same as that of the applied field, indicating that the particles in the trench are pivotal to produce sensor signal. Importantly, the same detection principle was validated with a duplex protein assay. Also, 8 different types of sensor stripes were fabricated and design parameters were explored. According to the detection principle uncovered, GMR biosensors can be further optimized to improve their sensitivity, which is highly desirable for early diagnosis of diseases. PMID:26728870

  4. Embedded damage sensor using triboluminescence as a transduction mechanism for detecting failure of a material under load

    NASA Astrophysics Data System (ADS)

    Lesho, Jeffery Carl

    Damage sensors are devices that monitor the state of health of structures or materials and that provide a signal indication when external forces or other conditions have caused the structure to fail. Continuous monitoring of structures is vital for safety reasons as well as for reduction of maintenance costs. The present study investigated the use of triboluminescent materials as a transduction mechanism for the detection of failure, combined with development of an electronic system to telemeter the optical pulses to a remote receiver for analysis and classification. The goal of the latter work was to create a low cost system that was small enough to be implanted into a smart material with a useful life of one year. The investigation had four main parts. First a search for an intense triboluminescent radiative material was undertaken. When an appropriate material was identified, a new improved method was developed that yielded a more efficient approach to processing. Research into the mechanism for the chosen material was conducted to determine if a new material could be engineered to yield larger signals. Second, a very low power opto-electronics system was developed that included an electronic circuit designed to monitor the sensor, and when a triboluminescent optical pulse is detected, it activates a transmitter that telemeters the optical decay signal to an external receiver. The receiver captures the optical decay as sampled digital data and correlates the signal with the known optical decay of the triboluminescent radiation. Third, a 'smart material' was fabricated with the triboluminescent sensor embedded in a block of epoxy. This material was tested to failure and the failure event was captured and the data was classified. Lastly, a correlation procedure for classifying the optical decays was written to actively look for failure events and filter out noise. Positive correlation results indicate that fracture has actually occurred.

  5. Identification of Proteins Likely To Be Involved in Morphogenesis, Cell Division, and Signal Transduction in Planctomycetes by Comparative Genomics

    PubMed Central

    Waldmann, Jost; Huang, Xiaoluo; Jogler, Mareike; Glöckner, Frank Oliver; Mascher, Thorsten; Kolter, Roberto

    2012-01-01

    Members of the Planctomycetes clade share many unusual features for bacteria. Their cytoplasm contains membrane-bound compartments, they lack peptidoglycan and FtsZ, they divide by polar budding, and they are capable of endocytosis. Planctomycete genomes have remained enigmatic, generally being quite large (up to 9 Mb), and on average, 55% of their predicted proteins are of unknown function. Importantly, proteins related to the unusual traits of Planctomycetes remain largely unknown. Thus, we embarked on bioinformatic analyses of these genomes in an effort to predict proteins that are likely to be involved in compartmentalization, cell division, and signal transduction. We used three complementary strategies. First, we defined the Planctomycetes core genome and subtracted genes of well-studied model organisms. Second, we analyzed the gene content and synteny of morphogenesis and cell division genes and combined both methods using a “guilt-by-association” approach. Third, we identified signal transduction systems as well as sigma factors. These analyses provide a manageable list of candidate genes for future genetic studies and provide evidence for complex signaling in the Planctomycetes akin to that observed for bacteria with complex life-styles, such as Myxococcus xanthus. PMID:23002222

  6. Two-component signal transduction in Agaricus bisporus: a comparative genomic analysis with other basidiomycetes through the web-based tool BASID2CS.

    PubMed

    Lavín, José L; García-Yoldi, Alberto; Ramírez, Lucía; Pisabarro, Antonio G; Oguiza, José A

    2013-06-01

    Two-component systems (TCSs) are signal transduction mechanisms present in many eukaryotes, including fungi that play essential roles in the regulation of several cellular functions and responses. In this study, we carry out a genomic analysis of the TCS proteins in two varieties of the white button mushroom Agaricus bisporus. The genomes of both A. bisporus varieties contain eight genes coding for TCS proteins, which include four hybrid Histidine Kinases (HKs), a single histidine-containing phosphotransfer (HPt) protein and three Response Regulators (RRs). Comparison of the TCS proteins among A. bisporus and the sequenced basidiomycetes showed a conserved core complement of five TCS proteins including the Tco1/Nik1 hybrid HK, HPt protein and Ssk1, Skn7 and Rim15-like RRs. In addition, Dual-HKs, unusual hybrid HKs with 2 HK and 2 RR domains, are absent in A. bisporus and are limited to various species of basidiomycetes. Differential expression analysis showed no significant up- or down-regulation of the Agaricus TCS genes in the conditions/tissue analyzed with the exception of the Skn7-like RR gene (Agabi_varbisH97_2|198669) that is significantly up-regulated on compost compared to cultured mycelia. Furthermore, the pipeline web server BASID2CS (http://bioinformatics.unavarra.es:1000/B2CS/BASID2CS.htm) has been specifically designed for the identification, classification and functional annotation of putative TCS proteins from any predicted proteome of basidiomycetes using a combination of several bioinformatic approaches.

  7. Comparative analyses of downstream signal transduction targets modulated after activation of the AT1 receptor by two β-arrestin-biased agonists.

    PubMed

    Santos, Geisa A; Duarte, Diego A; Parreiras-E-Silva, Lucas T; Teixeira, Felipe R; Silva-Rocha, Rafael; Oliveira, Eduardo B; Bouvier, Michel; Costa-Neto, Claudio M

    2015-01-01

    G protein-coupled receptors (GPCRs) are involved in essentially all physiological processes in mammals. The classical GPCR signal transduction mechanism occurs by coupling to G protein, but it has recently been demonstrated that interaction with β-arrestins leads to activation of pathways that are independent of the G protein pathway. Also, it has been reported that some ligands can preferentially activate one of these signaling pathways; being therefore called biased agonists for G protein or β-arrestin pathways. The angiotensin II (AngII) AT1 receptor is a prototype GPCR in the study of biased agonism due to the existence of well-known β-arrestin-biased agonists, such as [Sar(1), Ile(4), Ile(8)]-AngII (SII), and [Sar(1), D-Ala(8)]-AngII (TRV027). The aim of this study was to comparatively analyze the two above mentioned β-arrestin-biased agonists on downstream phosphorylation events and gene expression profiles. Our data reveal that activation of AT1 receptor by each ligand led to a diversity of activation profiles that is far broader than that expected from a simple dichotomy between "G protein-dependent" and "β-arrestin-dependent" signaling. We observed clusters of activation profiles common to AngII, SII, and TRV027, as well as downstream effector activation that are unique to AngII, SII, or TRV027. Analyses of β-arrestin conformational changes after AT1 receptor stimulation with SII or TRV027 suggests that the observed differences could account, at least partially, for the diversity of modulated targets observed. Our data reveal that, although the categorization "G protein-dependent" vs. "β-arrestin-dependent" signaling can be of pharmacological relevance, broader analyses of signaling pathways and downstream targets are necessary to generate an accurate activation profile for a given ligand. This may bring relevant information for drug development, as it may allow more refined comparison of drugs with similar mechanism of action and effects, but with

  8. Gαi2-protein-mediated signal transduction: central nervous system molecular mechanism countering the development of sodium-dependent hypertension.

    PubMed

    Wainford, Richard D; Carmichael, Casey Y; Pascale, Crissey L; Kuwabara, Jill T

    2015-01-01

    Excess dietary salt intake is an established cause of hypertension. At present, our understanding of the neuropathophysiology of salt-sensitive hypertension is limited by a lack of identification of the central nervous system mechanisms that modulate sympathetic outflow and blood pressure in response to dietary salt intake. We hypothesized that impairment of brain Gαi2-protein-gated signal transduction pathways would result in increased sympathetically mediated renal sodium retention, thus promoting the development of salt-sensitive hypertension. To test this hypothesis, naive or renal denervated Dahl salt-resistant and Dahl salt-sensitive (DSS) rats were assigned to receive a continuous intracerebroventricular control scrambled or a targeted Gαi2-oligodeoxynucleotide infusion, and naive Brown Norway and 8-congenic DSS rats were fed a 21-day normal or high-salt diet. High salt intake did not alter blood pressure, suppressed plasma norepinephrine, and evoked a site-specific increase in hypothalamic paraventricular nucleus Gαi2-protein levels in naive Brown Norway, Dahl salt-resistant, and scrambled oligodeoxynucleotide-infused Dahl salt-resistant but not DSS rats. In Dahl salt-resistant rats, Gαi2 downregulation evoked rapid renal nerve-dependent hypertension, sodium retention, and sympathoexcitation. In DSS rats, Gαi2 downregulation exacerbated salt-sensitive hypertension via a renal nerve-dependent mechanism. Congenic-8 DSS rats exhibited sodium-evoked paraventricular nucleus-specific Gαi2-protein upregulation and attenuated hypertension, sodium retention, and global sympathoexcitation compared with DSS rats. These data demonstrate that paraventricular nucleus Gαi2-protein-gated pathways represent a conserved central molecular pathway mediating sympathoinhibitory renal nerve-dependent responses evoked to maintain sodium homeostasis and a salt-resistant phenotype. Impairment of this mechanism contributes to the development of salt-sensitive hypertension.

  9. Comparative spring mechanics in mantis shrimp.

    PubMed

    Patek, S N; Rosario, M V; Taylor, J R A

    2013-04-01

    Elastic mechanisms are fundamental to fast and efficient movements. Mantis shrimp power their fast raptorial appendages using a conserved network of exoskeletal springs, linkages and latches. Their appendages are fantastically diverse, ranging from spears to hammers. We measured the spring mechanics of 12 mantis shrimp species from five different families exhibiting hammer-shaped, spear-shaped and undifferentiated appendages. Across species, spring force and work increase with size of the appendage and spring constant is not correlated with size. Species that hammer their prey exhibit significantly greater spring resilience compared with species that impale evasive prey ('spearers'); mixed statistical results show that species that hammer prey also produce greater work relative to size during spring loading compared with spearers. Disabling part of the spring mechanism, the 'saddle', significantly decreases spring force and work in three smasher species; cross-species analyses show a greater effect of cutting the saddle on the spring force and spring constant in species without hammers compared with species with hammers. Overall, the study shows a more potent spring mechanism in the faster and more powerful hammering species compared with spearing species while also highlighting the challenges of reconciling within-species and cross-species mechanical analyses when different processes may be acting at these two different levels of analysis. The observed mechanical variation in spring mechanics provides insights into the evolutionary history, morphological components and mechanical behavior, which were not discernible in prior single-species studies. The results also suggest that, even with a conserved spring mechanism, spring behavior, potency and component structures can be varied within a clade with implications for the behavioral functions of power-amplified devices. PMID:23239886

  10. Comparative spring mechanics in mantis shrimp.

    PubMed

    Patek, S N; Rosario, M V; Taylor, J R A

    2013-04-01

    Elastic mechanisms are fundamental to fast and efficient movements. Mantis shrimp power their fast raptorial appendages using a conserved network of exoskeletal springs, linkages and latches. Their appendages are fantastically diverse, ranging from spears to hammers. We measured the spring mechanics of 12 mantis shrimp species from five different families exhibiting hammer-shaped, spear-shaped and undifferentiated appendages. Across species, spring force and work increase with size of the appendage and spring constant is not correlated with size. Species that hammer their prey exhibit significantly greater spring resilience compared with species that impale evasive prey ('spearers'); mixed statistical results show that species that hammer prey also produce greater work relative to size during spring loading compared with spearers. Disabling part of the spring mechanism, the 'saddle', significantly decreases spring force and work in three smasher species; cross-species analyses show a greater effect of cutting the saddle on the spring force and spring constant in species without hammers compared with species with hammers. Overall, the study shows a more potent spring mechanism in the faster and more powerful hammering species compared with spearing species while also highlighting the challenges of reconciling within-species and cross-species mechanical analyses when different processes may be acting at these two different levels of analysis. The observed mechanical variation in spring mechanics provides insights into the evolutionary history, morphological components and mechanical behavior, which were not discernible in prior single-species studies. The results also suggest that, even with a conserved spring mechanism, spring behavior, potency and component structures can be varied within a clade with implications for the behavioral functions of power-amplified devices.

  11. Sensory Transduction in Caenorhabditis elegans

    NASA Astrophysics Data System (ADS)

    Brown, Austin L.; Ramot, Daniel; Goodman, Miriam B.

    The roundworm Caenorhabditis elegans has a well-defined and comparatively simple repertoire of sensory-guided behaviors, all of which rely on its ability to detect chemical, mechanical or thermal stimuli. In this chapter, we review what is known about the ion channels that mediate sensation in this remarkable model organism. Genetic screens for mutants defective in sensory-guided behaviors have identified genes encoding channel proteins, which are likely transducers of chemical, thermal, and mechanical stimuli. Such classical genetic approaches are now being coupled with molecular genetics and in vivo cellular physiology to elucidate how these channels are activated in specific sensory neurons. The ion channel superfamilies implicated in sensory transduction in C. elegans - CNG, TRP, and DEG/ENaC - are conserved across phyla and also appear to contribute to sensory transduction in other organisms, including vertebrates. What we learn about the role of these ion channels in C. elegans sensation is likely to illuminate analogous processes in other animals, including humans.

  12. Comparative analysis reveals the underlying mechanism of vertebrate seasonal reproduction.

    PubMed

    Ikegami, Keisuke; Yoshimura, Takashi

    2016-02-01

    Animals utilize photoperiodic changes as a calendar to regulate seasonal reproduction. Birds have highly sophisticated photoperiodic mechanisms and functional genomics analysis in quail uncovered the signal transduction pathway regulating avian seasonal reproduction. Birds detect light with deep brain photoreceptors. Long day (LD) stimulus induces secretion of thyroid-stimulating hormone (TSH) from the pars tuberalis (PT) of the pituitary gland. PT-derived TSH locally activates thyroid hormone (TH) in the hypothalamus, which induces gonadotropin-releasing hormone (GnRH) and hence gonadotropin secretion. However, during winter, low temperatures increase serum TH for adaptive thermogenesis, which accelerates germ cell apoptosis by activating the genes involved in metamorphosis. Therefore, TH has a dual role in the regulation of seasonal reproduction. Studies using TSH receptor knockout mice confirmed the involvement of PT-derived TSH in mammalian seasonal reproduction. In addition, studies in mice revealed that the tissue-specific glycosylation of TSH diversifies its function in the circulation to avoid crosstalk. In contrast to birds and mammals, one of the molecular machineries necessary for the seasonal reproduction of fish are localized in the saccus vasculosus from the photoreceptor to the neuroendocrine output. Thus, comparative analysis is a powerful tool to uncover the universality and diversity of fundamental properties in various organisms.

  13. Molecular basis of mechanosensory transduction

    NASA Astrophysics Data System (ADS)

    Gillespie, Peter G.; Walker, Richard G.

    2001-09-01

    Mechanotransduction - a cell's conversion of a mechanical stimulus into an electrical signal - reveals vital features of an organism's environment. From hair cells and skin mechanoreceptors in vertebrates, to bristle receptors in flies and touch receptors in worms, mechanically sensitive cells are essential in the life of an organism. The scarcity of these cells and the uniqueness of their transduction mechanisms have conspired to slow molecular characterization of the ensembles that carry out mechanotransduction. But recent progress in both invertebrates and vertebrates is beginning to reveal the identities of proteins essential for transduction.

  14. Investigation of nasal CO₂ receptor transduction mechanisms in wild-type and GC-D knockout mice.

    PubMed

    Kenemuth, Jessica K; Hennessy, Shane P; Hanson, Ryan J; Hensler, Allison J; Coates, E Lee

    2013-11-01

    The main olfactory system of mice contains a small subset of olfactory sensory neurons (OSNs) that are stimulated by CO₂. The objective of this study was to record olfactory receptor responses to a range of CO₂ concentrations to further elucidate steps in the proposed CO₂ transduction pathway in mice. Electro-olfactograms (EOGs) were recorded before and after inhibiting specific steps in the CO₂ transduction pathway with topically applied inhibitors. Inhibition of extracellular carbonic anhydrase (CA) did not significantly affect EOG responses to CO₂ but did decrease EOG responses to several control odorants. Inhibition of intracellular CA or cyclic nucleotide-gated channels attenuated EOG responses to CO₂, confirming the role of these components in CO₂ sensing in mice. We also show that, like canonical OSNs, CO₂-sensitive OSNs depend on Ca²⁺-activated Cl⁻ channels for depolarization of receptor neurons. Lastly, we found that guanylyl cyclase-D knockout mice were still able to respond to CO₂, indicating that other pathways may exist for the detection of low concentrations of nasal CO₂. We discuss these findings as they relate to previous studies on CO₂-sensitive OSNs in mice and other animals.

  15. Alternative mechanism of cholera toxin acquisition by Vibrio cholerae: generalized transduction of CTXPhi by bacteriophage CP-T1.

    PubMed

    Boyd, E F; Waldor, M K

    1999-11-01

    Horizontal transfer of genes encoding virulence factors has played a central role in the evolution of many pathogenic bacteria. The unexpected discovery that the genes encoding cholera toxin (ctxAB), the main cause of the profuse secretory diarrhea characteristic of cholera, are encoded on a novel filamentous phage named CTXPhi, has resulted in a renewed interest in the potential mechanisms of transfer of virulence genes among Vibrio cholerae. We describe here an alternative mechanism of cholera toxin gene transfer into nontoxigenic V. cholerae isolates, including strains that lack both the CTXPhi receptor, the toxin coregulated pilus (TCP), and attRS, the chromosomal attachment site for CTXPhi integration. A temperature-sensitive mutant of the V. cholerae generalized transducing bacteriophage CP-T1 (CP-T1ts) was used to transfer a genetically marked derivative of the CTX prophage into four nontoxigenic V. cholerae strains, including two V. cholerae vaccine strains. We demonstrate that CTXPhi transduced by CP-T1ts can replicate and integrate into these nontoxigenic V. cholerae strains with high efficiency. In fact, CP-T1ts transduces the CTX prophage preferentially when compared with other chromosomal markers. These results reveal a potential mechanism by which CTXPhi(+) V. cholerae strains that lack the TCP receptor may have arisen. Finally, these findings indicate an additional pathway for reversion of live-attenuated V. cholerae vaccine strains.

  16. Comment on 'Comparative analysis of the isovolume calibration method for non-invasive respiratory monitoring techniques based on area transduction versus circumference transduction using the connected cylinders model' (2011 Physiol. Meas. 32 1265-74).

    PubMed

    Augousti, A T; Radosz, A

    2015-05-01

    An analysis introduced by the authors in 2011 examining the robustness of the isovolume method for the calibration of the respiratory inductive plethysmograph based on the connected cylinders particular model of Konno and Mead's generalized two-compartment model of respiration is extended. It is demonstrated that extending this to a more physically realistic geometrical model, termed the connected prismatic elliptical segments model, does not enhance the earlier analysis, and that the analysis can easily be proven to cover all area-based transduction sensors, irrespective of the actual geometry of the compartments.

  17. Chloroplast His-to-Asp signal transduction: a potential mechanism for plastid gene regulation in Heterosigma akashiwo (Raphidophyceae)

    PubMed Central

    Duplessis, Melinda R; Karol, Kenneth G; Adman, Elinor T; Choi, Lauren YS; Jacobs, Michael A; Cattolico, Rose Ann

    2007-01-01

    Background Maintenance of homeostasis requires that an organism perceive selected physical and chemical signals within an informationally dense environment. Functionally, an organism uses a variety of signal transduction arrays to amplify and convert these perceived signals into appropriate gene transcriptional responses. These changes in gene expression serve to modify selective metabolic processes and thus optimize reproductive success. Here we analyze a chloroplast-encoded His-to-Asp signal transduction circuit in the stramenopile Heterosigma akashiwo (Hada) Hada ex Y. Hara et Chihara [syn. H. carterae (Hulburt) F.J.R. Taylor]. The presence, structure and putative function of this protein pair are discussed in the context of their evolutionary homologues. Results Bioinformatic analysis of the Heterosigma akashiwo chloroplast genome sequence revealed the presence of a single two-component His-to-Asp (designated Tsg1/Trg1) pair in this stramenopile (golden-brown alga). These data represent the first documentation of a His-to-Asp array in stramenopiles and counter previous reports suggesting that such regulatory proteins are lacking in this taxonomic cluster. Comparison of the 43 kDa H. akashiwo Tsg1 with bacterial sensor kinases showed that the algal protein exhibits a moderately maintained PAS motif in the sensor kinase domain as well as highly conserved H, N, G1 and F motifs within the histidine kinase ATP binding site. Molecular modelling of the 27 kDa H. akashiwo Trg1 regulator protein was consistent with a winged helix-turn-helix identity – a class of proteins that is known to impact gene expression at the level of transcription. The occurrence of Trg1 protein in actively growing H. akashiwo cells was verified by Western analysis. The presence of a PhoB-like RNA polymerase loop in Trg1 and its homologues in the red-algal lineage support the hypothesis that Trg1 and its homologues interact with a sigma 70 (σ70) subunit (encoded by rpoD) of a eubacterial

  18. Quantitative phosphoproteomics of murine Fmr1-KO cell lines provides new insights into FMRP-dependent signal transduction mechanisms.

    PubMed

    Matic, Katarina; Eninger, Timo; Bardoni, Barbara; Davidovic, Laetitia; Macek, Boris

    2014-10-01

    Fragile X mental retardation protein (FMRP) is an RNA-binding protein that has a major effect on neuronal protein synthesis. Transcriptional silencing of the FMR1 gene leads to loss of FMRP and development of Fragile X syndrome (FXS), the most common known hereditary cause of intellectual impairment and autism. Here we utilize SILAC-based quantitative phosphoproteomics to analyze murine FMR1(-) and FMR1(+) fibroblastic cell lines derived from FMR1-KO embryos to identify proteins and phosphorylation sites dysregulated as a consequence of FMRP loss. We quantify FMRP-related changes in the levels of 5,023 proteins and 6,133 phosphorylation events and map them onto major signal transduction pathways. Our study confirms global downregulation of the MAPK/ERK pathway and decrease in phosphorylation level of ERK1/2 in the absence of FMRP, which is connected to attenuation of long-term potentiation. We detect differential expression of several key proteins from the p53 pathway, pointing to the involvement of p53 signaling in dysregulated cell cycle control in FXS. Finally, we detect differential expression and phosphorylation of proteins involved in pre-mRNA processing and nuclear transport, as well as Wnt and calcium signaling, such as PLC, PKC, NFAT, and cPLA2. We postulate that calcium homeostasis is likely affected in molecular pathogenesis of FXS. PMID:25168779

  19. Quantitative phosphoproteomics of murine Fmr1-KO cell lines provides new insights into FMRP-dependent signal transduction mechanisms.

    PubMed

    Matic, Katarina; Eninger, Timo; Bardoni, Barbara; Davidovic, Laetitia; Macek, Boris

    2014-10-01

    Fragile X mental retardation protein (FMRP) is an RNA-binding protein that has a major effect on neuronal protein synthesis. Transcriptional silencing of the FMR1 gene leads to loss of FMRP and development of Fragile X syndrome (FXS), the most common known hereditary cause of intellectual impairment and autism. Here we utilize SILAC-based quantitative phosphoproteomics to analyze murine FMR1(-) and FMR1(+) fibroblastic cell lines derived from FMR1-KO embryos to identify proteins and phosphorylation sites dysregulated as a consequence of FMRP loss. We quantify FMRP-related changes in the levels of 5,023 proteins and 6,133 phosphorylation events and map them onto major signal transduction pathways. Our study confirms global downregulation of the MAPK/ERK pathway and decrease in phosphorylation level of ERK1/2 in the absence of FMRP, which is connected to attenuation of long-term potentiation. We detect differential expression of several key proteins from the p53 pathway, pointing to the involvement of p53 signaling in dysregulated cell cycle control in FXS. Finally, we detect differential expression and phosphorylation of proteins involved in pre-mRNA processing and nuclear transport, as well as Wnt and calcium signaling, such as PLC, PKC, NFAT, and cPLA2. We postulate that calcium homeostasis is likely affected in molecular pathogenesis of FXS.

  20. Comparing fluid mechanics models with experimental data.

    PubMed Central

    Spedding, G R

    2003-01-01

    The art of modelling the physical world lies in the appropriate simplification and abstraction of the complete problem. In fluid mechanics, the Navier-Stokes equations provide a model that is valid under most circumstances germane to animal locomotion, but the complexity of solutions provides strong incentive for the development of further, more simplified practical models. When the flow organizes itself so that all shearing motions are collected into localized patches, then various mathematical vortex models have been very successful in predicting and furthering the physical understanding of many flows, particularly in aerodynamics. Experimental models have the significant added convenience that the fluid mechanics can be generated by a real fluid, not a model, provided the appropriate dimensionless groups have similar values. Then, analogous problems can be encountered in making intelligible but independent descriptions of the experimental results. Finally, model predictions and experimental results may be compared if, and only if, numerical estimates of the likely variations in the tested quantities are provided. Examples from recent experimental measurements of wakes behind a fixed wing and behind a bird in free flight are used to illustrate these principles. PMID:14561348

  1. Beyond the chemiosmotic theory: analysis of key fundamental aspects of energy coupling in oxidative phosphorylation in the light of a torsional mechanism of energy transduction and ATP synthesis--invited review part 1.

    PubMed

    Nath, Sunil

    2010-08-01

    In Part 1 of this invited article, we consider the fundamental aspects of energy coupling in oxidative phosphorylation. The central concepts of the chemiosmotic theory are re-examined and the major problems with its experimental verification are analyzed and reassessed from first principles. Several of its assumptions and interpretations (with regard, for instance, to consideration of the membrane as an inert barrier, the occurrence of energy transduction at thermodynamic equilibrium, the completely delocalized nature of the protonmotive force, and the notion of indirect coupling) are shown to be questionable. Important biological implications of this analysis for molecular mechanisms of biological energy transduction are enumerated. A fresh molecular mechanism of the uncoupling of oxidative phosphorylation by classical weak acid anion uncouplers and an adequate explanation for the existence of uncoupler-resistant mutants (which until now has remained a mystery) has been proposed based on novel insights arising from a new torsional mechanism of energy transduction and ATP synthesis.

  2. Regulation of epidermal-growth-factor-receptor signal transduction by cis-unsaturated fatty acids. Evidence for a protein kinase C-independent mechanism.

    PubMed Central

    Casabiell, X; Pandiella, A; Casanueva, F F

    1991-01-01

    The effect of acute treatment with non-esterified fatty acids (NEFA) on transmembrane signalling has been investigated in three different cell lines. In EGFR T17 cells, pretreatment with cis-unsaturated (oleic and palmitoleic acids) NEFA, but not with saturated or trans-unsaturated NEFA, inhibited the epidermal-growth-factor (EGF)-induced increases in cytosolic [Ca2+], membrane potential and Ins(1,4,5)P3 generation. The blocking effect was found to be time- and dose-dependent and rapidly reversible after washout. However, oleic acid treatment did not block either binding of 125I-EGF to its receptor or EGF-induced autophosphorylation of the EGF receptor. The mechanism of action of NEFA could not be attributed to protein kinase C activation, since (i) down-regulation of the enzyme by long-term treatment with phorbol esters did not prevent blockade by oleic acid, and (ii) the effects of acutely administered phorbol ester and oleic acid were additive. In this cell line, signalling at bradykinin and bombesin receptors was also impaired by oleic acid. In A431 cells, oleic acid also blocked signal transduction at the EGF and B2 bradykinin receptors. Finally, in PC12 cells, oleic acid blocked the Ca2+ influx mediated by the activation of B2 bradykinin receptors. In conclusion: (1) NEFA block signal transduction by interfering with receptor-phospholipase C or phospholipase C-substrate interaction without preventing ligand binding; (2) NEFA do not act by a protein kinase C-mediated mechanism; (3) the effect of NEFA is dependent on their configuration rather than hydrophobicity or chain length; (4) this effect is evident in several different cell lines and receptor systems. Images Fig. 4. PMID:1898356

  3. 17 beta-estradiol-BSA conjugates and 17 beta-estradiol regulate growth plate chondrocytes by common membrane associated mechanisms involving PKC dependent and independent signal transduction.

    PubMed

    Sylvia, V L; Walton, J; Lopez, D; Dean, D D; Boyan, B D; Schwartz, Z

    2001-01-01

    Nuclear receptors for 17 beta-estradiol (E(2)) are present in growth plate chondrocytes from both male and female rats and regulation of chondrocytes through these receptors has been studied for many years; however, recent studies indicate that an alternative pathway involving a membrane receptor may also be involved in the cell response. E(2) was found to directly affect the fluidity of chondrocyte membranes derived from female, but not male, rats. In addition, E(2) activates protein kinase C (PKC) in a nongenomic manner in female cells, and chelerythrine, a specific inhibitor of PKC, inhibits E(2)-dependent alkaline phosphatase activity and proteoglycan sulfation in these cells, indicating PKC is involved in the signal transduction mechanism. The aims of the present study were: (1) to examine the effect of a cell membrane-impermeable 17 beta-estradiol-bovine serum albumin conjugate (E(2)-BSA) on chondrocyte proliferation, differentiation, and matrix synthesis; (2) to determine the pathway that mediates the membrane effect of E(2)-BSA on PKC; and (3) to compare the action of E(2)-BSA to that of E(2). Confluent, fourth passage resting zone (RC) and growth zone (GC) chondrocytes from female rat costochondral cartilage were treated with 10(-9) to 10(-7) M E(2) or E(2)-BSA and changes in alkaline phosphatase specific activity, proteoglycan sulfation, and [(3)H]-thymidine incorporation measured. To examine the pathway of PKC activation, chondrocyte cultures were treated with E(2)-BSA in the presence or absence of GDP beta S (inhibitor of G-proteins), GTP gamma S (activator of G-proteins), U73122 or D609 (inhibitors of phospholipase C [PLC]), wortmannin (inhibitor of phospholipase D [PLD]) or LY294002 (inhibitor of phosphatidylinositol 3-kinase). E(2)-BSA mimicked the effects of E(2) on alkaline phosphatase specific activity and proteoglycan sulfation, causing dose-dependent increases in both RC and GC cell cultures. Both forms of estradiol inhibited [(3)H

  4. Generalized transduction in Rhizobium meliloti.

    PubMed

    Sik, T; Horváth, J; Chatterjee, S

    1980-01-01

    The phage 11 of R. meliloti performs generalized transduction. This was confirmed by the variety of single markers transferred and by separating transducing particles containing BUdR-labelled bacterial DNA. The transduction frequencies depended on the marker. Linked alleles were mapped by cotransduction on fragments of bacterial DNA equal in size to the phage DNA. With crosses between antibiotic resistancy and auxotrophic markers a partial map was constructed with str, cml, pur-19, and leu-44 sites. With a few multi-auxotrophic mutants linkage data of conjugation were compared with the linkage by cotransduction.

  5. Melatonin receptor activation regulates GnRH gene expression and secretion in GT1-7 GnRH neurons. Signal transduction mechanisms.

    PubMed

    Roy, Deboleena; Belsham, Denise D

    2002-01-01

    Melatonin plays a significant role in the control of the hypothalamic-pituitary-gonadal axis. Using the GT1-7 cell line, an in vitro model of GnRH-secreting neurons of the hypothalamus, we examined the potential signal transduction pathways activated by melatonin directly at the level of the GT1-7 neuron. We found that melatonin inhibits forskolin-stimulated adenosine 3'-, 5'-cyclic monophosphate accumulation in GT1-7 cells through an inhibitory G protein. Melatonin induced protein kinase C activity by 1.65-fold over basal levels, increased the phosphorylation of extracellular signal-regulated kinase 1 and 2 proteins, and activated c-fos and junB mRNA expression in GT1-7 cells. Using the protein kinase A inhibitor H-89, the protein kinase C inhibitor bisindolylmaleimide, and the mitogen-activated protein kinase kinase inhibitor PD98059, we found that the melatonin-mediated cyclical regulation of GnRH mRNA expression may involve the protein kinase C and the extracellular signal-regulated kinase 1 and 2 pathways, but not the protein kinase A pathway. We found that melatonin suppresses GnRH secretion by approximately 45% in the GT1-7 neurons. However, in the presence of the inhibitors H-89, bisindolylmaleimide, and PD98059 melatonin was unable to suppress GnRH secretion. These results provide insights into the potential signal transduction mechanisms involved in the control of GnRH gene expression and secretion by melatonin.

  6. SENTRA, a database of signal transduction proteins.

    SciTech Connect

    D'Souza, M.; Romine, M. F.; Maltsev, N.; Mathematics and Computer Science; PNNL

    2000-01-01

    SENTRA, available via URL http://wit.mcs.anl.gov/WIT2/Sentra/, is a database of proteins associated with microbial signal transduction. The database currently includes the classical two-component signal transduction pathway proteins and methyl-accepting chemotaxis proteins, but will be expanded to also include other classes of signal transduction systems that are modulated by phosphorylation or methylation reactions. Although the majority of database entries are from prokaryotic systems, eukaroytic proteins with bacterial-like signal transduction domains are also included. Currently SENTRA contains signal transduction proteins in 34 complete and almost completely sequenced prokaryotic genomes, as well as sequences from 243 organisms available in public databases (SWISS-PROT and EMBL). The analysis was carried out within the framework of the WIT2 system, which is designed and implemented to support genetic sequence analysis and comparative analysis of sequenced genomes.

  7. Tetrodotoxin as a Tool to Elucidate Sensory Transduction Mechanisms: The Case for the Arterial Chemoreceptors of the Carotid Body

    PubMed Central

    Rocher, Asuncion; Caceres, Ana Isabel; Obeso, Ana; Gonzalez, Constancio

    2011-01-01

    Carotid bodies (CBs) are secondary sensory receptors in which the sensing elements, chemoreceptor cells, are activated by decreases in arterial PO2 (hypoxic hypoxia). Upon activation, chemoreceptor cells (also known as Type I and glomus cells) increase their rate of release of neurotransmitters that drive the sensory activity in the carotid sinus nerve (CSN) which ends in the brain stem where reflex responses are coordinated. When challenged with hypoxic hypoxia, the physiopathologically most relevant stimulus to the CBs, they are activated and initiate ventilatory and cardiocirculatory reflexes. Reflex increase in minute volume ventilation promotes CO2 removal from alveoli and a decrease in alveolar PCO2 ensues. Reduced alveolar PCO2 makes possible alveolar and arterial PO2 to increase minimizing the intensity of hypoxia. The ventilatory effect, in conjunction the cardiocirculatory components of the CB chemoreflex, tend to maintain an adequate supply of oxygen to the tissues. The CB has been the focus of attention since the discovery of its nature as a sensory organ by de Castro (1928) and the discovery of its function as the origin of ventilatory reflexes by Heymans group (1930). A great deal of effort has been focused on the study of the mechanisms involved in O2 detection. This review is devoted to this topic, mechanisms of oxygen sensing. Starting from a summary of the main theories evolving through the years, we will emphasize the nature and significance of the findings obtained with veratridine and tetrodotoxin (TTX) in the genesis of current models of O2-sensing. PMID:22363245

  8. How Does Protein Architecture Facilitate the Transduction of ATP Chemical-Bond Energy into Mechanical Work? The Cases of Nitrogenase and ATP Binding-Cassette Proteins

    PubMed Central

    Liao, Jie-Lou; Beratan, David N.

    2004-01-01

    Transduction of adenosine triphosphate (ATP) chemical-bond energy into work to drive large-scale conformational changes is common in proteins. Two specific examples of ATP-utilizing proteins are the nitrogenase iron protein and the ATP binding-cassette transporter protein, BtuCD. Nitrogenase catalyzes biological nitrogen fixation whereas BtuCD transports vitamin B12 across membranes. Both proteins drive their reactions with ATP. To interpret how the mechanical force generated by ATP binding and hydrolysis is propagated in these proteins, a coarse-grained elastic network model is employed. The analysis shows that subunits of the proteins move against each other in a concerted manner. The lowest-frequency modes of the nitrogenase iron protein and of the ATP binding-cassette transporter BtuCD protein are found to link the functionally critical domains, and these modes are suggested to be responsible for (at least the initial stages) large-scale ATP-coupled conformational changes. PMID:15298939

  9. Mechanical diode: Comparing numerical and experimental characterizations

    SciTech Connect

    Sagartz, M.J.; Segalman, D.; Simmermacher, T.

    1998-02-01

    In this introductory work, joint compliance is studied in both a numerical and experimental setting. A simple bolted interface is used as the test article and compliance is measured for the joint in both compression and in tension. This simple interface is shown to exhibit a strong non-linearity near the transition from compression to tension (or vice-versa). Modeling issues pertaining to numerically solving for the compliance are addressed. It is shown that the model predictions, in spite of convergence being very sensitive to numerical artifacts of the interface model, are in good agreement with experimentally measured strains and joint compliances. The joint behavior is a mechanical analogy to a diode, i.e., in compression, the joint is very stiff, acting almost as a rigid link, while in tension the joint is relatively soft, acting as a spring.

  10. Signal Transduction Mechanism for Serotonin 5-HT2B Receptor-Mediated DNA Synthesis and Proliferation in Primary Cultures of Adult Rat Hepatocytes.

    PubMed

    Naito, Kota; Tanaka, Chizuru; Mitsuhashi, Manami; Moteki, Hajime; Kimura, Mitsutoshi; Natsume, Hideshi; Ogihara, Masahiko

    2016-01-01

    The involvement of serotonin (5-hydroxytryptamine; 5-HT) and the 5-HT2 receptor subtypes in the induction of DNA synthesis and proliferation was investigated in primary cultures of adult rat hepatocytes to elucidate the intracellular signal transduction mechanisms. Hepatocyte parenchymal cells maintained in a serum-free, defined medium, synthesized DNA and proliferated in the presence of 5-HT or a selective 5-HT2B receptor agonist, BW723C86, but not in the presence of 5-HT2A, or 5-HT2C receptor agonists (TCB-2 and CP809101, respectively), in a time- and dose-dependent manner. A selective 5-HT2B receptor antagonist, LY272015 (10(-7) M), and a specific phospholipase C (PLC) inhibitor, U-73122 (10(-6) M), as well as specific inhibitors of growth-related signal transducers-including AG1478, LY294002, PD98059, and rapamycin-completely inhibited 5-HT (10(-6) M)- or BW723C86 (10(-6) M)-induced hepatocyte DNA synthesis and proliferation. Both 5-HT and BW723C86 were shown to significantly stimulate the phosphorylation of epidermal growth factor (EGF)/transforming growth factor (TGF)-α receptor tyrosine kinase (p175 kDa) and extracellular signal-regulated kinase (ERK) 2 on Western blot analysis. These results suggest that the proliferative mechanism of activating 5-HT is mediated mainly through 5-HT2B receptor-stimulated Gq/PLC and EGF/TGF-α-receptor/phosphatidylinositol 3-kinase (PI3K)/ERK2/mammalian target of rapamycin (mTOR) signaling pathways in primary cultured hepatocytes.

  11. Transduction of chemical into electrical energy.

    PubMed Central

    Nachmansohn, D

    1976-01-01

    The paper recalls some fundamental notions, developed by Otto Meyerhof, which were used in the analysis of the transduction of chemical into mechanical energy during muscular contraction. These notions formed the basis of the approach to the analysis of the transduction of chemical into electrical energy, i.e., the very principle underlying nerve and muscle excitability and bioelectricity. Instrumental for this purpose was the use, since 1937, of electric organs of fish, a tissue highly specialized for bioelectrogenesis. Images PMID:1061129

  12. Transduction of chemical into electrical energy.

    PubMed

    Nachmansohn, D

    1976-01-01

    The paper recalls some fundamental notions, developed by Otto Meyerhof, which were used in the analysis of the transduction of chemical into mechanical energy during muscular contraction. These notions formed the basis of the approach to the analysis of the transduction of chemical into electrical energy, i.e., the very principle underlying nerve and muscle excitability and bioelectricity. Instrumental for this purpose was the use, since 1937, of electric organs of fish, a tissue highly specialized for bioelectrogenesis.

  13. ROS-dependent signal transduction

    PubMed Central

    Reczek, Colleen R; Chandel, Navdeep S

    2014-01-01

    Reactive oxygen species (ROS) are no longer viewed as just a toxic by-product of mitochondrial respiration, but are now appreciated for their role in regulating a myriad of cellular signaling pathways. H2O2, a type of ROS, is a signaling molecule that confers target specificity through thiol oxidation. Although redox-dependent signaling has been implicated in numerous cellular processes, the mechanism by which the ROS signal is transmitted to its target protein in the face of highly reactive and abundant antioxidants is not fully understood. In this review of redox-signaling biology, we discuss the possible mechanisms for H2O2-dependent signal transduction. PMID:25305438

  14. Transduction in Bacillus subtilis.

    PubMed

    THORNE, C B

    1962-01-01

    Thorne, Curtis B. (Fort Detrick, Frederick, Md.). Transduction in Bacillus subtilis. J. Bacteriol. 83:106-111. 1962.-A bacteriophage, SP-10, isolated from soil carries out general transduction in Bacillus subtilis. Phage propagated on a streptomycin-resistant mutant of the wild-type strain W-23 was capable of transducing to prototrophy strain 168 (indole(-)), as well as all of the auxotrophic mutants of W-23-S(r) tested, which included mutants requiring arginine, histidine, adenine, guanine, thiamine, leucine, or methionine. Although strain 168 was transduced by phage SP-10, lytic activity on this strain could not be detected and attempts to propagate the phage on it failed. Transductions occurred at frequencies in the range of 10(-6) to 10(-5) per plaque-forming unit. Homologous phage was ineffective, deoxyribonuclease had no effect on the frequency of transduction, and transduction was prevented by the addition of phage antiserum. Phage SP-10 was capable of lysogenizing strain W-23-S(r), and this condition was maintained through repeated growth and sporulation cycles in potato-extract medium. Although heating at 65 C for 60 min inactivated free phage particles, spores retained their lysogenic condition after such heat treatment. When heat-treated spores of the lysogenic cultures were used as inocula for growth in a nutrient broth-yeast extract-glucose medium, filtrates contained 10(9), or more, phage particles per ml.

  15. Laminin-6 assembles into multimolecular fibrillar complexes with perlecan and participates in mechanical-signal transduction via a dystroglycan-dependent, integrin-independent mechanism

    PubMed Central

    Jones, Jonathan C. R.; Lane, Kimberly; Hopkinson, Susan B.; Lecuona, Emilia; Geiger, Robert C.; Dean, David A.; Correa-Meyer, Eduardo; Gonzales, Meredith; Campbell, Kevin; Sznajder, Jacob I.; Budinger, Scott

    2010-01-01

    Summary Mechanical ventilation is a valuable treatment regimen for respiratory failure. However, mechanical ventilation (especially with high tidal volumes) is implicated in the initiation and/or exacerbation of lung injury. Hence, it is important to understand how the cells that line the inner surface of the lung [alveolar epithelial cells (AECs)] sense cyclic stretching. Here, we tested the hypothesis that matrix molecules, via their interaction with surface receptors, transduce mechanical signals in AECs. We first determined that rat AECs secrete an extracellular matrix (ECM) rich in anastamosing fibers composed of the α3 laminin subunit, complexed with β1 and γ1 laminin subunits (i.e. laminin-6), and perlecan by a combination of immunofluorescence microscopy and immunoblotting analyses. The fibrous network exhibits isotropic expansion when exposed to cyclic stretching (30 cycles per minute, 10% strain). Moreover, this same stretching regimen activates mitogen-activated-protein kinase (MAPK) in AECs. Stretch-induced MAPK activation is not inhibited in AECs treated with antagonists to α3 or β1 integrin. However, MAPK activation is significantly reduced in cells treated with function-inhibiting antibodies against the α3 laminin subunit and dystroglycan, and when dystroglycan is knocked down in AECs using short hairpin RNA. In summary, our results support a novel mechanism by which laminin-6, via interaction with dystroglycan, transduces a mechanical signal initiated by stretching that subsequently activates the MAPK pathway in rat AECs. These results are the first to indicate a function for laminin-6. They also provide novel insight into the role of the pericellular environment in dictating the response of epithelial cells to mechanical stimulation and have broad implications for the pathophysiology of lung injury. PMID:15928048

  16. Unstable generalized transduction in Achromobacter.

    PubMed

    Woods, D R; Thomson, J A

    1975-05-01

    Six auxotrophic markers of a halotolerant collagenolytic strain of Achromobacter were transduced by four alpha hages. Abortive transduction was also demonstrated. The generalized transduction system is unusual as the transductants were unstable, characteristic of transduction by lysogeny. The Achromobacter strain is a cryptic lysogen for alpha and purified transductants were either sensitive or resistant to alpha. Purified clones from four resistant transductants and one sensitive transductant liberated phage spontaneously. The host ranges of these spontaneous phage differed from that of the alpha phage used for the transduction experiment. Some initially resistant transductants became simi-sensitive to alpha (efficiency to plating) e.o.p. (10minus-1 to 10minus-2) after repeated cloning.

  17. CSF-1 signal transduction.

    PubMed

    Hamilton, J A

    1997-08-01

    Colony-stimulating factor-1 (CSF-1) or macrophage-CSF (M-CSF) is a growth factor involved in the proliferation, differentiation, and activation of cells of the monocyte/macrophage lineage. Its receptor is the homodimeric, tyrosine kinase product of the c-fms proto-oncogene, which contains a so-called kinase insert domain. This review focuses mainly on recent studies of signal transduction events that are initiated on interaction of CSF-1 and its receptor. A summary is given of the tyrosine autophosphorylation sites on c-Fms identified to date, including their interaction with various substrates and their possible significance for signal transduction and cellular function. In addition, the signal transduction pathways that have been identified to lie downstream of activated c-Fms are reviewed. Although it is apparent that there have been many recent significant developments in our understanding of CSF-1 signaling, a number of examples are mentioned of significant discrepancies in the literature, some possible reasons for which can sometimes be offered. It is also apparent that any particular biochemical response or signal transduction pathway, even though widespread in other ligand receptor/cellular systems, including those with similar receptor structures to c-Fms, may not be relevant to CSF-1 signaling. The relevance of any potentially important molecular signaling pathway activated by CSF-1 in cells in vitro will ultimately have to be related to the functions of monocytes/macrophages in vivo.

  18. Oxysterols and calcium signal transduction.

    PubMed

    Mackrill, John J

    2011-09-01

    Ionised calcium (Ca(2+)) is a key second messenger, regulating almost every cellular process from cell death to muscle contraction. Cytosolic levels of this ion can be increased via gating of channel proteins located in the plasma membrane, endoplasmic reticulum and other membrane-delimited organelles. Ca(2+) can be removed from cells by extrusion across the plasma membrane, uptake into organelles and buffering by anionic components. Ca(2+) channels and extrusion mechanisms work in concert to generate diverse spatiotemporal patterns of this second messenger, the distinct profiles of which determine different cellular outcomes. Increases in cytoplasmic Ca(2+) concentration are one of the most rapid cellular responses upon exposure to certain oxysterol congeners or to oxidised low-density lipoprotein, occurring within seconds of addition and preceding increases in levels of reactive oxygen species, or changes in gene expression. Furthermore, exposure of cells to oxysterols for periods of hours to days modulates Ca(2+) signal transduction, with these longer-term alterations in cellular Ca(2+) homeostasis potentially underlying pathological events within atherosclerotic lesions, such as hyporeactivity to vasoconstrictors observed in vascular smooth muscle, or ER stress-induced cell death in macrophages. Despite their candidate roles in physiology and disease, little is known about the molecular mechanisms that couple changes in oxysterol concentrations to alterations in Ca(2+) signalling. This review examines the ways in which oxysterols could influence Ca(2+) signal transduction and the potential roles of this in health and disease. PMID:21513705

  19. Oxidants as stimulators of signal transduction.

    PubMed

    Suzuki, Y J; Forman, H J; Sevanian, A

    1997-01-01

    Redox (oxidation-reduction) reactions regulate signal transduction. Oxidants such as superoxide, hydrogen peroxide, hydroxyl radicals, and lipid hydroperoxides (i.e., reactive oxygen species) are now realized as signaling molecules under subtoxic conditions. Nitric oxide is also an example of a redox mediator. Reactive oxygen species induce various biological processes such as gene expression by stimulating signal transduction components such as Ca(2+)-signaling and protein phosphorylation. Various oxidants increase cytosolic Ca2+; however, the exact origin of Ca2+ is controversial. Ca2+ may be released from the endoplasmic reticulum, extracellular space, or mitochondria in response to oxidant-influence on Ca2+ pumps, channels, and transporters. Alternatively, oxidants may release Ca2+ from Ca2+ binding proteins. Various oxidants stimulate tyrosine as well as serine/threonine phosphorylation, and direct stimulation of protein kinases and inhibition of protein phosphatases by oxidants have been proposed as mechanisms. The oxidant-stimulation of the effector molecules such as phospholipase A2 as well as the activation of oxidative stress-responsive transcription factors may also depend on the oxidant-mediated activation of Ca(2+)-signaling and/or protein phosphorylation. In addition to the stimulation of signal transduction by oxidants, the observations that ligand-receptor interactions produce reactive oxygen species and that antioxidants block receptor-mediated signal transduction led to a proposal that reactive oxygen species may be second messengers for transcription factor activation, apoptosis, bone resorption, cell growth, and chemotaxis. Physiological significance of the role of biological oxidants in the regulation of signal transduction as well as the mechanisms of the oxidant-stimulation of signal transduction are discussed.

  20. Pathway to the piezoelectronic transduction logic device.

    PubMed

    Solomon, P M; Bryce, B A; Kuroda, M A; Keech, R; Shetty, S; Shaw, T M; Copel, M; Hung, L-W; Schrott, A G; Armstrong, C; Gordon, M S; Reuter, K B; Theis, T N; Haensch, W; Rossnagel, S M; Miyazoe, H; Elmegreen, B G; Liu, X-H; Trolier-McKinstry, S; Martyna, G J; Newns, D M

    2015-04-01

    The piezoelectronic transistor (PET) has been proposed as a transduction device not subject to the voltage limits of field-effect transistors. The PET transduces voltage to stress, activating a facile insulator-metal transition, thereby achieving multigigahertz switching speeds, as predicted by modeling, at lower power than the comparable generation field effect transistor (FET). Here, the fabrication and measurement of the first physical PET devices are reported, showing both on/off switching and cycling. The results demonstrate the realization of a stress-based transduction principle, representing the early steps on a developmental pathway to PET technology with potential to contribute to the IT industry.

  1. Beyond the chemiosmotic theory: analysis of key fundamental aspects of energy coupling in oxidative phosphorylation in the light of a torsional mechanism of energy transduction and ATP synthesis--invited review part 2.

    PubMed

    Nath, Sunil

    2010-08-01

    The core of this second article shows how logical errors and inconsistencies in previous theories of energy coupling in oxidative phosphorylation are overcome by use of a torsional mechanism and the unified theory of ATP synthesis/hydrolysis. The torsional mechanism is shown to satisfy the pioneering and verified features of previous mechanisms. A considerable amount of data is identified that is incompatible with older theories but is now explained in a logically consistent and unified way. Key deficiencies in older theories are pinpointed and their resolution elucidated. Finally, major differences between old and new approaches are tabulated. The new theory now provides the elusive details of energy coupling and transduction, and allows several novel and experimentally verifiable predictions to be made and a considerable number of applications in nanotechnology, energy conversion, systems biology, and in health and disease are foreseen.

  2. Mechanical Properties Comparing Composite Fiber Length to Amalgam

    PubMed Central

    Petersen, Richard C.; Liu, Perng-Ru

    2016-01-01

    Photocure fiber-reinforced composites (FRCs) with varying chopped quartz-fiber lengths were incorporated into a dental photocure zirconia-silicate particulate-filled composite (PFC) for mechanical test comparisons with a popular commercial spherical-particle amalgam. FRC lengths included 0.5-mm, 1.0 mm, 2.0 mm, and 3.0 mm all at a constant 28.2 volume percent. Four-point fully articulated fixtures were used according to American Standards Test Methods with sample dimensions of 2×2×50 mm3 across a 40 mm span to provide sufficient Euler flexural bending and prevent top-load compressive shear error. Mechanical properties for flexural strength, modulus, yield strength, resilience, work of fracture, critical strain energy release, critical stress intensity factor, and strain were obtained for comparison. Fiber length subsequently correlated with increasing all mechanical properties, p < 1.1×10−5. Although the modulus was significantly statistically higher for amalgam than all composites, all FRCs and even the PFC had higher values than amalgam for all other mechanical properties. Because amalgams provide increased longevity during clinical use compared to the standard PFCs, modulus would appear to be a mechanical property that might sufficiently reduce margin interlaminar shear stress and strain-related microcracking that could reduce failure rates. Also, since FRCs were tested with all mechanical properties that statistically significantly increased over the PFC, new avenues for future development could be provided toward surpassing amalgam in clinical longevity. PMID:27642629

  3. Mechanical Properties Comparing Composite Fiber Length to Amalgam

    PubMed Central

    Petersen, Richard C.; Liu, Perng-Ru

    2016-01-01

    Photocure fiber-reinforced composites (FRCs) with varying chopped quartz-fiber lengths were incorporated into a dental photocure zirconia-silicate particulate-filled composite (PFC) for mechanical test comparisons with a popular commercial spherical-particle amalgam. FRC lengths included 0.5-mm, 1.0 mm, 2.0 mm, and 3.0 mm all at a constant 28.2 volume percent. Four-point fully articulated fixtures were used according to American Standards Test Methods with sample dimensions of 2×2×50 mm3 across a 40 mm span to provide sufficient Euler flexural bending and prevent top-load compressive shear error. Mechanical properties for flexural strength, modulus, yield strength, resilience, work of fracture, critical strain energy release, critical stress intensity factor, and strain were obtained for comparison. Fiber length subsequently correlated with increasing all mechanical properties, p < 1.1×10−5. Although the modulus was significantly statistically higher for amalgam than all composites, all FRCs and even the PFC had higher values than amalgam for all other mechanical properties. Because amalgams provide increased longevity during clinical use compared to the standard PFCs, modulus would appear to be a mechanical property that might sufficiently reduce margin interlaminar shear stress and strain-related microcracking that could reduce failure rates. Also, since FRCs were tested with all mechanical properties that statistically significantly increased over the PFC, new avenues for future development could be provided toward surpassing amalgam in clinical longevity.

  4. Separate TRP channels mediate amplification and transduction in drosophila

    NASA Astrophysics Data System (ADS)

    Lehnert, Brendan P.; Baker, Allison E.; Wilson, Rachel I.

    2015-12-01

    Auditory receptor cells rely on mechanically-gated channels to transform sound stimuli into neural activity. Several TRP channels have been implicated in Drosophila auditory transduction, but mechanistic studies have been hampered by the inability to record subthreshold signals from receptor neurons. We developed a non-invasive method for measuring these signals by recording from a central neuron that is electrically coupled to a genetically-defined population of auditory receptors. We find that the TRPN family member NompC, which is necessary for the active amplification of motion by the auditory organ, is not required for transduction. Instead, NompC sensitizes the transduction complex to movement and precisely regulates the static forces on the complex. In contrast, the TRPV channels Nanchung and Inactive are required for responses to sound, suggesting they are components of the transduction complex. Thus, transduction and active amplification are genetically separable processes in Drosophila hearing.

  5. Nuclear Technology. Course 27: Metrology. Module 27-3, Gage Blocks, Mechanical Comparators and Electronic Comparators.

    ERIC Educational Resources Information Center

    Selleck, Ben; Espy, John

    This third in a series of eight modules for a course titled Metrology describes gage blocks and mechanical and electronic comparators. The module follows a typical format that includes the following sections: (1) introduction, (2) module prerequisites, (3) objectives, (4) notes to instructor/student, (5) subject matter, (6) materials needed, (7)…

  6. Advances in Targeting Signal Transduction Pathways

    PubMed Central

    McCubrey, James A.; Steelman, Linda S.; Chappell, William H.; Sun, Lin; Davis, Nicole M.; Abrams, Stephen L.; Franklin, Richard A.; Cocco, Lucio; Evangelisti, Camilla; Chiarini, Francesca; Martelli, Alberto M.; Libra, Massimo; Candido, Saverio; Ligresti, Giovanni; Malaponte, Grazia; Mazzarino, Maria C.; Fagone, Paolo; Donia, Marco; Nicoletti, Ferdinando; Polesel, Jerry; Talamini, Renato; Bäsecke, Jörg; Mijatovic, Sanja; Maksimovic-Ivanic, Danijela; Milella, Michele; Tafuri, Agostino; Dulińska-Litewka, Joanna; Laidler, Piotr; D'Assoro, Antonio B.; Drobot, Lyudmyla; Umezawa, Kazuo; Montalto, Giuseppe; Cervello, Melchiorre; Demidenko, Zoya N.

    2012-01-01

    Over the past few years, significant advances have occurred in both our understanding of the complexity of signal transduction pathways as well as the isolation of specific inhibitors which target key components in those pathways. Furthermore critical information is being accrued regarding how genetic mutations can affect the sensitivity of various types of patients to targeted therapy. Finally, genetic mechanisms responsible for the development of resistance after targeted therapy are being discovered which may allow the creation of alternative therapies to overcome resistance. This review will discuss some of the highlights over the past few years on the roles of key signaling pathways in various diseases, the targeting of signal transduction pathways and the genetic mechanisms governing sensitivity and resistance to targeted therapies. PMID:23455493

  7. Comparing Ultrasound and Mechanical Steering in a Biodiesel Production Process

    NASA Astrophysics Data System (ADS)

    Costa-Felix, Rodrigo P. B.; Ferreira, Jerusa R. L.

    The analysis of the kinetics of the transesterification reaction is crucial to compare different routes or routes with different catalysts or reaction accelerators. The use of ultrasound is considereda method for accelerating the biodiesel production. However, little effort has been done and is reported in the literature about how and under what conditions the use of ultrasound really speeds up the process, or the conditions under which its use is unnecessary or even harmful, burdening the process. Two dissimilar energy injections into a typical route were tested: ultrasound (@ 1 MHz and no heating) and mechanical steering (with heating), both applied in an 8:1 ratio of soybean oil and methanol, adding 1% of KOH as catalyzer. As results, during the first 10 minutes of reaction ultrasound showed unbearable effect on the transesterification, whilst mechanical steering and heating achieved almost 70% of conversion ratio. However, during the following 10 minutes, the mechanical steering and heating got nothing more than 80% of conversion, a considerable less efficient process than ultrasound assisted one, which achieved more than 90%. The straightforward explanation is that ultrasound continually inserts energy in a slower rate, what can result in a more stable conversion scenario. On the other hand, mechanical steering and heating provides more energy at a glance, but cannot push the final conversion rate beyond a limit, as the transesterification is a double-way chemical process. The instability mechanical steering and heating settles in the reaction medium pulls the components back to their original states more than pushes than to the converted equilibrium state of the matter.

  8. The Molecular Basis of Mechanosensory Transduction

    PubMed Central

    Marshall, Kara L.; Lumpkin, Ellen A.

    2014-01-01

    Multiple senses including hearing, touch, and osmotic regulation, require the ability to convert force into an electrical signal: a process called mechanotransduction. Mechanotransduction occurs through specialized proteins that open an ion channel pore in response to a mechanical stimulus. Many of these proteins remain unidentified in vertebrates, but known mechanotransduction channels in lower organisms provide clues into their identity and mechanism. Bacteria, fruit flies, and nematodes have all been used to elucidate the molecules necessary for force transduction. This chapter discusses many different mechanical senses and takes an evolutionary approach to review the proteins responsible for mechanotransduction in various biological kingdoms. PMID:22399400

  9. Generalized Transduction in CAULOBACTER CRESCENTUS.

    PubMed

    Ely, B; Johnson, R C

    1977-11-01

    Two closely related bacteriophage, varphiCr30 and varphiCr35, are the first bacteriophage shown to mediate generalized transduction in Caulobacter crescentus. Unlike most other transducing phage, they are virulent and do not form any sort of lysogenic relationship with their host. However, they are rather inefficient at adsorption, so that transductants have a good chance of survival. The phage particles have a head 80 nm in diameter and a contractile tail 140 nm in length. Procedures for growth and transduction with varphiCr30 are relatively simple; thus, it will be of great value for the genetic analysis of C. crescentus.

  10. Generalized transduction by lytic bacteriophages.

    PubMed

    Waddell, Thomas E; Franklin, Kristyn; Mazzocco, Amanda; Kropinski, Andrew M; Johnson, Roger P

    2009-01-01

    As interest in lytic phages as antimicrobial therapies or as treatments to reduce environmental contamination with pathogenic bacteria has increased, so has the need to determine if the use of lytic phages may lead to dissemination of virulence factors through generalized transduction, as occurs with temperate phages. Here we describe simple methods we have developed to determine if a lytic phage, rV5, can mediate generalized transduction in Escherichia coli O157:H7. These sensitive methods can be easily adapted to study generalized transduction between virulent and avirulent strains of bacteria.

  11. Aging of signal transduction pathways, and pathology

    PubMed Central

    Carlson, Morgan E.; Silva, Haroldo S.; Conboy, Irina M.

    2008-01-01

    The major cell signaling pathways, and their specific mechanisms of transduction, have been a subject of investigation for many years. As our understanding of these pathways advances, we find that they are evolutionarily well-conserved not only individually, but also at the level of their crosstalk and signal integration. Productive interactions within the key signal transduction networks determine success in embryonic organogenesis, and postnatal tissue repair throughout adulthood. However, aside from clues revealed through examining age-related degenerative diseases, much remains uncertain about imbalances within these pathways during normal aging. Further, little is known about the molecular mechanisms by which alterations in the major cell signal transduction networks cause age-related pathologies. The aim of this review is to describe the complex interplay between the Notch, TGFβ, WNT, RTK-Ras and Hh signaling pathways, with a specific focus on the changes introduced within these networks by the aging process, and those typical of age-associated human pathologies. PMID:18474281

  12. On the nanotoxicity of PAMAM dendrimers: Superfect® stimulates the EGFR-ERK1/2 signal transduction pathway via an oxidative stress-dependent mechanism in HEK 293 cells.

    PubMed

    Akhtar, Saghir; Chandrasekhar, Bindu; Attur, Sreeja; Yousif, Mariam H M; Benter, Ibrahim F

    2013-05-01

    Polyamidoamine (PAMAM) dendrimers are cationic branch-like macromolecules that may serve as drug delivery systems for gene-based therapies such as RNA interference. For their safe use in the clinic, they should ideally only enhance drug delivery to target tissues and exhibit no adverse effects. However, little is known about their toxicological profiles in terms of their interactions with cellular signal transduction pathways such as the epidermal growth factor receptor (EGFR). The EGFR is an important signaling cascade that regulates cell growth, differentiation, migration, survival and apoptosis. Here, we investigated the impact of naked, unmodified Superfect (SF), a commercially available generation 6 PAMAM dendrimer, on the epidermal growth factor receptor (EGFR) tyrosine kinase-extracellular-regulated kinase 1/2 (ERK1/2) signaling pathway in human embryonic kidney (HEK 293) cells. At concentrations routinely used for transfection, SF exhibited time and dose-dependent stimulation of EGFR and ERK1/2 phosphorylation whereas AG1478, a selective EGFR tyrosine kinase antagonist, inhibited EGFR-ERK1/2 signaling. SF-induced phosphorylation of EGFR for 1h was partly reversible upon removal of the dendrimer and examination of cells 24 later. Co-treatment of SF with epidermal growth factor (EGF) ligand resulted in greater EGFR stimulation than either agent alone implying that the stimulatory effects of SF and the ligand are synergistic. Dendrimer-induced stimulation of EGFR-ERK1/2 signaling could be attenuated by the antioxidants apocynin, catalase and tempol implying that an oxidative stress dependent mechanism was involved. These results show for the first time that PAMAM dendrimers, aside from their ability to improve drug delivery, can modulate the important EGFR-ERK1/2 cellular signal transduction pathway - a novel finding that may have a bearing on their safe application as drug delivery systems.

  13. Confocal Scanner for Highly Sensitive Photonic Transduction of Nanomechanical Resonators

    NASA Astrophysics Data System (ADS)

    Diao, Zhu; Losby, Joseph E.; Sauer, Vincent T. K.; Westwood, Jocelyn N.; Freeman, Mark R.; Hiebert, Wayne K.

    2013-06-01

    We show that a simple confocal laser scanning system can be used to couple light through grating couplers into nanophotonic circuits. The coupling efficiency is better than 15% per coupler. Our technique avoids using multi-axis fibre stages and is especially advantageous when the nanophotonic circuit is kept in vacuum, e.g., for nanomechanical resonator displacement transduction. This was demonstrated by recording the resonant response of a nanomechanical doubly clamped beam embedded in a race-track optical cavity. The nanophotonic transduction offers an increase of two orders of magnitude in transduction responsivity compared with conventional free-space optical interferometry.

  14. Gravitational Effects on Signal Transduction

    NASA Technical Reports Server (NTRS)

    Sytkowski, Arthur J.

    1999-01-01

    An understanding of the mechanisms by which individual cells perceive gravity and how these cells transduce and respond to gravitational stimuli is critical for the development of long-term manned space flight experiments. We now propose to use a well-characterized model erythroid cell system and to investigate gravitational perturbations of its erythropoietin (Epo) signaling pathway and gene regulation. Cells will be grown at 1-G and in simulated microgravity in the NASA Rotating Wall Vessel bioreactor (RWV). Cell growth and differentiation, the Epo-receptor, the protein kinase C pathway to the c-myc gene, and the protein phosphatase pathway to the c-myb gene will be studied and evaluated as reporters of gravitational stimuli. The results of these experiments will have impact on the problems of 1) gravitational sensing by individual cells, and 2) the anemia of space flight. This ground-based study also will serve as a Space Station Development Study in gravitational effects on intracellular signal transduction.

  15. Graviperception in ciliates: steps in the transduction chain

    NASA Astrophysics Data System (ADS)

    Hemmersbach, R.; Krause, M.; Bräucker, R.; Ivanova, K.

    Due to their clear gravity-induced behavioural responses (gravitaxis and gravikinesis) ciliates represent suitable model systems to study the mechanisms of gravity perception and signal transduction. While the development of distinct gravisensory organelles is the exception in ciliates (e.g. mueller organelles in Loxodes), a common strategy seems to be that the whole cytoplasm acts as statolith stimulating mechanosensitive ion channels in the cell membrane. In order to test this hypothesis, electrophysiological studies were performed, revealing the proposed changes (de- or hyperpolarizations) depending on the cell's (Stylonychia mytilus) spatial orientation. In order to test the involvement of second messengers in the gravity-signal transduction-chain, cAMP levels of Paramecium were measured under altered gravitational stimulation (TEXUS 37; centrifuge). We found a decrease in cAMP in microgravity and an increase in hypergravity (5 x g) compared to the 1 x g controls. Furthermore, the behaviour of Paramecium and Stylonychia was analyzed during the variable acceleration conditions of parabolic flights (5th German Parabolic Flight Campaign) and compared to data already known from TEXUS, MAXUS, and drop facilities (ZARM, JAMIC). The feasibility of parabolic flights with respect to threshold determination will be discussed.

  16. Electromechanical Energy Transduction for Hybrid Vehicles

    NASA Astrophysics Data System (ADS)

    Reddy Vanja, Sridhar; Kelly, Michael W.; Caruso, A. N.

    2010-03-01

    Hybrid vehicle technology seeks to reduce the total energy consumption used for vehicle locomotion by recovering and reutilizing kinetic energy that is otherwise unrecovered or dissipated in conventional vehicle deceleration. The goal of the work is to determine the transduction mechanisms that work towards a Carnot efficiency without considering constraints or limitations placed by cost or materials. Specifically, this talk will present ideal thermodynamic models of energy exchange between mechanical, electrostatic, electromechanical and electrochemical devices with a goal of projecting an ideal hybrid vehicle.

  17. mTOR Signal Transduction Pathways Contribute to TN-C FNIII A1 Overexpression by Mechanical Stress in Osteosarcoma Cells

    PubMed Central

    Zheng, Lianhe; Zhang, Dianzhong; Zhang, Yunfei; Wen, Yanhua; Wang, Yucai

    2014-01-01

    Osteosarcoma is the most common primary malignant bone tumor with a very poor prognosis. Treating osteosarcoma remains a challenge due to its high transitivity. Tenascin-C, with large molecular weight variants including different combinations of its alternative spliced FNIII repeats, is specifically over expressed in tumor tissues. This study examined the expression of Tenascin-C FNIIIA1 in osteosarcoma tissues, and estimated the effect of mechanical stimulation on A1 expression in MG-63 cells. Through immunohistochemical analysis, we found that the A1 protein was expressed at a higher level in osteosarcoma tissues than in adjacent normal tissues. By cell migration assay, we observed that there was a significant correlation between A1 expression and MG-63 cell migra-tion. The relation is that Tenascin-C FNIIIA1 can promote MG-63 cell migration. According to our further study into the effect of mechanical stimulation on A1 expression in MG-63 cells, the mRNA and protein levels of A1 were significantly up-regulated under mechanical stress with the mTOR molecule proving indispensable. Meanwhile, 4E-BP1 and S6K1 (downstream molecule of mTOR) are necessary for A1 normal expression in MG-63 cells whether or not mechanical stress has been encountered. We found that Tenascin-C FNIIIA1 is over-expressed in osteosar-coma tissues and can promote MG-63 cell migration. Furthermore, mechanical stress can facilitate MG-63 cell migration though facilitating A1 overexpression with the necessary molecules (mTOR, 4E-BP1 and S6K1). In con-clusion, high expression of A1 may promote the meta-stasis of osteosarcoma by facilitating MG-63 cell migration. Tenascin-C FNIIIA1 could be used as an indicator in metastatic osteosarcoma patients. PMID:24598996

  18. Neuroendocrine aging in birds: comparing lifespan differences and conserved mechanisms.

    PubMed

    Ottinger, Mary Ann

    2007-05-01

    As more comparative data become available, it is clear that the process of aging has fundamental similarities across classes of vertebrates. Birds provide a fascinating collection of species because of the considerable range in reproductive lifespan and variation in reproductive strategies that often relate to lifespan. One fascinating aspect of the comparative biology of aging in different avian species is the conserved mechanisms that appear very similar to those observed in mammals. Despite marked differences in sexual differentiation and reproductive function, including a single functional ovary and the internal testes, there appears to be remarkable similarity in elements of neuroendocrine aging and their end results. Furthermore, although beyond the scope of this review, the intense endocrine and energetic demands on many species of temperate zone birds for long migration and the accompanying seasonal alterations in endocrine responses add an additional layer of complexity in understanding aging. It is the purpose of this review to focus on neuroendocrine changes that accompany aging in a short-lived bird, with mention of some of the available data in field birds and long-lived species. Unfortunately, few neuroendocrine data are available for these long-lived avian species. It would be very interesting to determine if these long-lived birds somehow manage to delay the cascade of changes that contribute to the demise of metabolic and reproductive endocrine function. This review will also attempt to integrate the time-related events that occur in the responses of the hypothalamus and the gonads, especially relative to the neuroregulatory systems that have been implicated in the age-related decline in reproductive function. Finally, emerging areas of interest will be considered in the context of future research areas. PMID:17452025

  19. Mechano-chemical energy transduction in biological systems. The effect of mechanical stimulation on the polymerization of actin: a kinetic study.

    PubMed Central

    Ferri, A; Grazi, E

    1982-01-01

    Mechanical stimulation (forced circulation in narrow tubing) accelerates as much as 10-fold the rate of polymerization of actin. The increase in the rate is proportional to the intensity of the stimulation for flow rates between 0 and 3 cm/s. This supports the hypothesis that a statistical factor (the orientation of the flowing particles) is influenced by the flow. Comparison of the kinetics of the polymerization of resting and of mechanically stimulated actin solutions shows that both the nucleation and the elongation steps are accelerated. It is thus concluded that flow orients not only the oligomeric structures but also the actin monomers. The elongation reaction, also in the flow-stimulated samples, occurs always by the addition of ATP--G-actin (or ATP-containing oligomers) and not by the fusion of ADP-containing oligomeric structures. PMID:7138502

  20. Signal transduction pathways involved in mechanotransduction in bone cells

    SciTech Connect

    Liedert, Astrid . E-mail: astrid.liedert@uni-ulm.de; Kaspar, Daniela; Blakytny, Robert; Claes, Lutz; Ignatius, Anita

    2006-10-13

    Several in vivo and in vitro studies with different loading regimens showed that mechanical stimuli have an influence on proliferation and differentiation of bone cells. Prerequisite for this influence is the transduction of mechanical signals into the cell, a phenomenon that is termed mechanotransduction, which is essential for the maintenance of skeletal homeostasis in adults. Mechanoreceptors, such as the integrins, cadherins, and stretch-activated Ca{sup 2+} channels, together with various signal transduction pathways, are involved in the mechanotransduction process that ultimately regulates gene expression in the nucleus. Mechanotransduction itself is considered to be regulated by hormones, the extracellular matrix of the osteoblastic cells and the mode of the mechanical stimulus.

  1. Cavity optoelectromechanical system combining strong electrical actuation with ultrasensitive transduction

    SciTech Connect

    McRae, Terry G.; Lee, Kwan H.; Harris, Glen I.; Knittel, Joachim; Bowen, Warwick P.

    2010-08-15

    A cavity optoelectromechanical system is reported which combines the ultrasensitive transduction of cavity optomechanical systems with the electrical actuation of nanoelectromechanical systems. Ultrasensitive mechanical transduction is achieved via optomechanical coupling. Electrical gradient forces as large as 0.40 {mu}N are realized, facilitating strong actuation with ultralow dissipation. A scanning probe microscope is implemented, capable of characterizing the mechanical modes. The integration of electrical actuation into optomechanical devices is an enabling step toward the regime of quantum nonlinear dynamics and provides capabilities for quantum control of mechanical motion.

  2. Virtual screening of LPXTG competitive SrtA inhibitors targeting signal transduction mechanism in Bacillus anthracis: a combined experimental and theoretical study.

    PubMed

    Selvaraj, Chandrabose; Sivakamavalli, Jeyachandran; Baskaralingam, Vaseeharan; Singh, Sanjeev Kumar

    2014-06-01

    Members of the sortase enzyme super family decorate the surfaces of Bacillus anthracis cell wall with proteins that play key roles in microbial pathogenesis and its biofilm formation. Bacillus anthracis Sortase-A (Ba-SrtA) is a potential target for new therapeutics as it is required for B. anthracis survival and replication within macrophages. An understanding of the binding site pocket and substrate recognition mechanism by SrtA enzymes may serve to be beneficial in the rational development of sortase inhibitors. Here, the LPXTG signal peptide-based competitive inhibitors are screened against the Ba-SrtA and compounds with reasonable inhibition, specificity, and mechanisms of inactivation of SrtA have been covered. The screened compounds are experimentally validated against the phylogenetically similar Gram-positive pathogen B. cereus. In situ microscopic visualizations suggest that these screened compounds showed the microbial and biofilm inhibitory activity against B. cereus. It facilitates the further development of these molecules into useful anti-infective agents to treat infections caused by B. anthracis and other Gram-positive pathogens. These results provide insight into basic design principles for generating new clinically relevant lead molecules. It also provides an alternative strategy where a screened ligand molecule can be used in combination to battle increasingly against the Gram-positive pathogens.

  3. Modeling Signal Transduction and Lipid Rafts in Immune Cells

    NASA Astrophysics Data System (ADS)

    Prasad, Ashok

    2011-03-01

    Experimental evidence increasingly suggests that lipid rafts are nanometer sized cholesterol dependent dynamic assemblies enriched in sphingolipids and associated proteins. Lipid rafts are dynamic structures that break-up and reform on a relatively short time-scale, and are believed to facilitate the interactions of raft-associated proteins. The role of these rafts in signaling has been controversial, partly due to controversies regarding the existence and nature of the rafts themselves. Experimental evidence has indicated that in several cell types, especially T cells, rafts do influence signal transduction and T cell activation. Given the emerging consensus on the biophysical character of lipid rafts, the question can be asked as to what roles they possibly play in signal transduction. Here we carry out simulations of minimal models of the signal transduction network that regulates Src-family kinase dynamics in T cells and other cell types. By separately treating raft-based biochemical interactions, we find that rafts can indeed putatively play an important role in signal transduction, and in particular may affect the sensitivity of signal transduction. This illuminates possible functional consequences of membrane heterogeneities on signal transduction and points towards mechanisms for spatial control of signaling by cells.

  4. Gravitational sensory transduction chain in flagellates

    NASA Astrophysics Data System (ADS)

    Häder, D.-P.; Richter, P.; Ntefidou, M.; Lebert, M.

    Earlier hypotheses have assumed that gravitactic orientation in flagellates, such as the photosynthetic unicell Euglena gracilis, is brought about by passive alignment of the cells in the water column by being tail heavy. A recent experiment on a sounding rocket (TEXUS 40) comparing immobilized cells with mobile cells demonstrated that the passive buoy effect can account for approximately 20% of the orientation of the cells in a gravity field. The cells show either positive or negative gravitaxis depending on other external or internal factors. Shortly after inoculation, the tendency of young cells to swim downward in the water column can be readily reverted by adding micromolar concentrations of some heavy metal ions including copper, cadmium or lead. The negative gravitaxis of older cells is converted into a positive one by stress factors such as increasing salinity or exposure to excessive visible or UV radiation. The mechanism for this switch seems to involve reactive oxygen species since the gravitactic sign change was suppressed when oxygen was removed by flushing the cell suspension with nitrogen. Also, the addition of radical scavengers (Trolox, ascorbic acid or potassium cyanide) abolished or reduced the gravitactic sign change. Addition of hydrogen peroxide induced a gravitactic sign change in the absence of external stress factors. The primary reception for the gravity vector seems to involve mechanosensitive ion channels which specifically gate calcium ions inward. We have identified several gene sequences for putative mechanosensory channels in Euglena and have applied RNAi to identify which of these channels are involved in graviperception. The influx of Ca 2+ activates calmodulin (CaM) which has been shown to be involved in the sensory transduction chain of graviorientation. It is known that an adenylyl cyclase is bound to the flagellar membrane in Euglena which is activated by CaM. This enzyme produces cAMP which has also been shown to be the key

  5. The sensory transduction pathways in bacterial chemotaxis

    NASA Technical Reports Server (NTRS)

    Taylor, Barry L.

    1989-01-01

    Bacterial chemotaxis is a useful model for investigating in molecular detail the behavioral response of cells to changes in their environment. Peritrichously flagellated bacteria such as coli and typhimurium swim by rotating helical flagella in a counterclockwise direction. If flagellar rotation is briefly reversed, the bacteria tumble and change the direction of swimming. The bacteria continuously sample the environment and use a temporal sensing mechanism to compare the present and immediate past environments. Bacteria respond to a broad range of stimuli including changes in temperature, oxygen concentration, pH and osmotic strength. Bacteria are attracted to potential sources of nutrition such as sugars and amino acids and are repelled by other chemicals. In the methylation-dependent pathways for sensory transduction and adaptation in E. coli and S. typhimurium, chemoeffectors bind to transducing proteins that span the plasma membrane. The transducing proteins are postulated to control the rate of autophosphorylation of the CheA protein, which in turn phosphorylates the CheY protein. The phospho-CheY protein binds to the switch on the flagellar motor and is the signal for clockwise rotation of the motor. Adaptation to an attractant is achieved by increasing methylation of the transducing protein until the attractant stimulus is cancelled. Responses to oxygen and certain sugars involve methylation-independent pathways in which adaption occurs without methylation of a transducing protein. Taxis toward oxygen is mediated by the electron transport system and changes in the proton motive force. Recent studies have shown that the methylation-independent pathway converges with the methylation-dependent pathway at or before the CheA protein.

  6. Mechano-Transduction: From Molecules to Tissues

    PubMed Central

    Pruitt, Beth L.; Dunn, Alexander R.; Weis, William I.; Nelson, W. James

    2014-01-01

    External forces play complex roles in cell organization, fate, and homeostasis. Changes in these forces, or how cells respond to them, can result in abnormal embryonic development and diseases in adults. How cells sense and respond to these mechanical stimuli requires an understanding of the biophysical principles that underlie changes in protein conformation and result in alterations in the organization and function of cells and tissues. Here, we discuss mechano-transduction as it applies to protein conformation, cellular organization, and multi-cell (tissue) function. PMID:25405923

  7. A comparative review of four formulations of noncommutative quantum mechanics

    NASA Astrophysics Data System (ADS)

    Gouba, Laure

    2016-07-01

    Four formulations of quantum mechanics on noncommutative Moyal phase spaces are reviewed. These are the canonical, path-integral, Weyl-Wigner and systematic formulations. Although all these formulations represent quantum mechanics on a phase space with the same deformed Heisenberg algebra, there are mathematical and conceptual differences which we discuss.

  8. Monocyte Signal Transduction Receptors in Active and Latent Tuberculosis

    PubMed Central

    Druszczynska, Magdalena; Wlodarczyk, Marcin; Janiszewska-Drobinska, Beata; Kielnierowski, Grzegorz; Zawadzka, Joanna; Kowalewicz-Kulbat, Magdalena; Fol, Marek; Szpakowski, Piotr; Rudnicka, Karolina; Chmiela, Magdalena; Rudnicka, Wieslawa

    2013-01-01

    The mechanisms that promote either resistance or susceptibility to TB disease remain insufficiently understood. Our aim was to compare the expression of cell signaling transduction receptors, CD14, TLR2, CD206, and β2 integrin LFA-1 on monocytes from patients with active TB or nonmycobacterial lung disease and healthy individuals with M.tb latency and uninfected controls to explain the background of the differences between clinical and subclinical forms of M.tb infection. A simultaneous increase in the expression of the membrane bound mCD14 receptor and LFA-1 integrin in patients with active TB may be considered a prodrome of breaking immune control by M.tb bacilli in subjects with the latent TB and absence of clinical symptoms. PMID:23401703

  9. Girdin/GIV is upregulated by cyclic tension, propagates mechanical signal transduction, and is required for the cellular proliferation and migration of MG-63 cells

    SciTech Connect

    Hu, Jiang-Tian; Li, Yan; Yu, Bing; Gao, Guo-Jie; Zhou, Ting; Li, Song

    2015-08-21

    To explore how Girdin/GIV is regulated by cyclic tension and propagates downstream signals to affect cell proliferation and migration. Human osteoblast-like MG-63 cells were exposed to cyclic tension force at 4000 μstrain and 0.5 Hz for 6 h, produced by a four-point bending system. Cyclic tension force upregulated Girdin and Akt expression and phosphorylation in cultured MG-63 cells. Girdin and Akt each promoted the phosphorylation of the other under stimulated tension. In vitro MTT and transwell assays showed that Girdin and Akt are required for cell proliferation and migration during cellular quiescence. Moreover, STAT3 was determined to be essential for Girdin expression under stimulated tension force in the physiological condition, as well as for osteoblast proliferation and migration during quiescence. These findings suggest that the STAT3/Girdin/Akt pathway activates in osteoblasts in response to mechanical stimulation and may play a significant role in triggering osteoblast proliferation and migration during orthodontic treatment. - Highlights: • Tension force upregulates Girdin and Akt expression and phosphorylation. • Girdin and Akt promotes the phosphorylation of each other under tension stimulation. • Girdin and Akt are required for MG-63 cell proliferation and migration. • STAT3 is essential for Girdin expression after application of the tension forces.

  10. Morphogengineering roots: comparing mechanisms of morphogen gradient formation

    PubMed Central

    2012-01-01

    Background In developmental biology, there has been a recent focus on the robustness of morphogen gradients as possible providers of positional information. It was shown that functional morphogen gradients present strong biophysical constraints and lack of robustness to noise. Here we explore how the details of the mechanism which underlies the generation of a morphogen gradient can influence those properties. Results We contrast three gradient-generating mechanisms, (i) a source-decay mechanism; and (ii) a unidirectional transport mechanism; and (iii) a so-called reflux-loop mechanism. Focusing on the dynamics of the phytohormone auxin in the root, we show that only the reflux-loop mechanism can generate a gradient that would be adequate to supply functional positional information for the Arabidopsis root, for biophysically reasonable kinetic parameters. Conclusions We argue that traits that differ in spatial and temporal time-scales can impose complex selective pressures on the mechanism of morphogen gradient formation used for the development of the particular organism. PMID:22583698

  11. Meeting Report: Teaching Signal Transduction

    ERIC Educational Resources Information Center

    Kramer, IJsbrand; Thomas, Geraint

    2006-01-01

    In July, 2005, the European Institute of Chemistry and Biology at the campus of the University of Bordeaux, France, hosted a focused week of seminars, workshops, and discussions around the theme of "teaching signal transduction." The purpose of the summer school was to offer both junior and senior university instructors a chance to reflect on the…

  12. SPP1-mediated plasmid transduction.

    PubMed Central

    Canosi, U; Lüder, G; Trautner, T A

    1982-01-01

    The virulent Bacillus subtilis phage SPP1 transduces plasmid DNA. Plasmid-transducing phages contain only plasmid DNA. Such DNA represents a concatemer of monomeric plasmid molecules with the molecular weight of mature SPP1 DNA. Biological parameters of plasmid transduction are described. Images PMID:6292508

  13. Generalized transduction in Streptomyces coelicolor.

    PubMed

    Burke, J; Schneider, D; Westpheling, J

    2001-05-22

    We report the isolation of generalized transducing phages for Streptomyces species able to transduce chromosomal markers or plasmids between derivatives of Streptomyces coelicolor, the principal genetic model system for this important bacterial genus. We describe four apparently distinct phages (DAH2, DAH4, DAH5, and DAH6) that are capable of transducing multiple chromosomal markers at frequencies ranging from 10(-5) to 10(-9) per plaque-forming unit. The phages contain DNA ranging in size from 93 to 121 kb and mediate linked transfer of genetic loci at neighboring chromosomal sites sufficiently close to be packaged within the same phage particle. The key to our ability to demonstrate transduction by these phages was the establishment of conditions expected to severely reduce superinfection killing during the selection of transductants. The host range of these phages, as measured by the ability to form plaques, extends to species as distantly related as Streptomyces avermitilis and Streptomyces verticillus, which are among the most commercially important species of this genus. Transduction of plasmid DNA between S. coelicolor and S. verticillus was observed at frequencies of approximately 10(-4) transductants per colony-forming unit.

  14. Taste transduction mechanism: similar effects of various modifications of gustatory receptors on neural responses to chemical and electrical stimulation in the frog

    SciTech Connect

    Kashiwayanagi, M.; Yoshii, K.; Kobatake, Y.; Kurihara, K.

    1981-09-01

    Responses in the frog glossopharyngeal nerve induced by electrical stimulation of the tongue were compared with those induced by chemical stimuli under various conditions. (a) Anodal stimulation induced much larger responses than cathodal stimulation, and anodal stimulation of the tongue adapted to 5 mM MgCl2 produced much larger responses than stimulation with the tongue adapted to 10 mM NaCl at equal current intensities, as chemical stimulation with MgCl2 produced much larger responses than stimulation with NaCl at equal concentration. (b) The enhansive and suppressive effects of 8-anilino-1-naphthalenesulfonate, NiCl2, and uranyl acetate on the responses to anodal current were similar to those on the responses to chemical stimulation. (c) Anodal stimulation of the tongue adapted to 50 mM CaCl2 resulted in a large response, whereas application of 1 M CaCl2 to the tongue adapted to 50 mM CaCl2 produced only a small response. This, together with theoretical considerations, suggested that the accumulation of salts on the tongue surface is not the cause of the generation of the response to anodal current. (d) Cathodal current suppressed the responses induced by 1 mM CaCl2, 0.3 M ethanol, and distilled water. (e) The addition of EGTA or Ca-channel blockers (CdCl2 and verapamil) to the perfusing solution of the lingual artery reversibly suppressed both the responses to chemical stimulus (NaCl) and to anodal current with 10 mM NaCl. (f) We assume from the results obtained that electrical current from the microvillus membrane of a taste cell to the synaptic area supplied by anodal stimulation or induced by chemical stimulation activates the voltage-dependent Ca channel at the synaptic area.

  15. Epigenetic mechanisms and memory strength: a comparative study.

    PubMed

    Federman, Noel; Zalcman, Gisela; de la Fuente, Verónica; Fustiñana, Maria Sol; Romano, Arturo

    2014-01-01

    Memory consolidation requires de novo mRNA and protein synthesis. Transcriptional activation is controlled by transcription factors, their cofactors and repressors. Cofactors and repressors regulate gene expression by interacting with basal transcription machinery, remodeling chromatin structure and/or chemically modifying histones. Acetylation is the most studied epigenetic mechanism of histones modifications related to gene expression. This process is regulated by histone acetylases (HATs) and histone deacetylases (HDACs). More than 5 years ago, we began a line of research about the role of histone acetylation during memory consolidation. Here we review our work, presenting evidence about the critical role of this epigenetic mechanism during consolidation of context-signal memory in the crab Neohelice granulata, as well as during consolidation of novel object recognition memory in the mouse Mus musculus. Our evidence demonstrates that histone acetylation is a key mechanism in memory consolidation, functioning as a distinctive molecular feature of strong memories. Furthermore, we found that the strength of a memory can be characterized by its persistence or its resistance to extinction. Besides, we found that the role of this epigenetic mechanism regulating gene expression only in the formation of strongest memories is evolutionarily conserved.

  16. Reliable Signal Transduction

    NASA Astrophysics Data System (ADS)

    Wollman, Roy

    Stochasticity inherent to biochemical reactions (intrinsic noise) and variability in cellular states (extrinsic noise) degrade information transmitted through signaling networks. We analyzed the ability of temporal signal modulation - that is dynamics - to reduce noise-induced information loss. In the extracellular signal-regulated kinase (ERK), calcium (Ca(2 +)) , and nuclear factor kappa-B (NF- κB) pathways, response dynamics resulted in significantly greater information transmission capacities compared to nondynamic responses. Theoretical analysis demonstrated that signaling dynamics has a key role in overcoming extrinsic noise. Experimental measurements of information transmission in the ERK network under varying signal-to-noise levels confirmed our predictions and showed that signaling dynamics mitigate, and can potentially eliminate, extrinsic noise-induced information loss. By curbing the information-degrading effects of cell-to-cell variability, dynamic responses substantially increase the accuracy of biochemical signaling networks.

  17. Comparative transcriptome and metabolome provides new insights into the regulatory mechanisms of accelerated senescence in litchi fruit after cold storage

    PubMed Central

    Yun, Ze; Qu, Hongxia; Wang, Hui; Zhu, Feng; Zhang, Zhengke; Duan, Xuewu; Yang, Bao; Cheng, Yunjiang; Jiang, Yueming

    2016-01-01

    Litchi is a non-climacteric subtropical fruit of high commercial value. The shelf life of litchi fruit under ambient conditions (AC) is approximately 4–6 days. Post-harvest cold storage prolongs the life of litchi fruit for up to 30 days with few changes in pericarp browning and total soluble solids. However, the shelf life of litchi fruits at ambient temperatures after pre-cold storage (PCS) is only 1–2 days. To better understand the mechanisms involved in the rapid fruit senescence induced by pre-cold storage, a transcriptome of litchi pericarp was constructed to assemble the reference genes, followed by comparative transcriptomic and metabolomic analyses. Results suggested that the senescence of harvested litchi fruit was likely to be an oxidative process initiated by ABA, including oxidation of lipids, polyphenols and anthocyanins. After cold storage, PCS fruit exhibited energy deficiency, and respiratory burst was elicited through aerobic and anaerobic respiration, which was regulated specifically by an up-regulated calcium signal, G-protein-coupled receptor signalling pathway and small GTPase-mediated signal transduction. The respiratory burst was largely associated with increased production of reactive oxygen species, up-regulated peroxidase activity and initiation of the lipoxygenase pathway, which were closely related to the accelerated senescence of PCS fruit. PMID:26763309

  18. Comparative transcriptome and metabolome provides new insights into the regulatory mechanisms of accelerated senescence in litchi fruit after cold storage.

    PubMed

    Yun, Ze; Qu, Hongxia; Wang, Hui; Zhu, Feng; Zhang, Zhengke; Duan, Xuewu; Yang, Bao; Cheng, Yunjiang; Jiang, Yueming

    2016-01-01

    Litchi is a non-climacteric subtropical fruit of high commercial value. The shelf life of litchi fruit under ambient conditions (AC) is approximately 4-6 days. Post-harvest cold storage prolongs the life of litchi fruit for up to 30 days with few changes in pericarp browning and total soluble solids. However, the shelf life of litchi fruits at ambient temperatures after pre-cold storage (PCS) is only 1-2 days. To better understand the mechanisms involved in the rapid fruit senescence induced by pre-cold storage, a transcriptome of litchi pericarp was constructed to assemble the reference genes, followed by comparative transcriptomic and metabolomic analyses. Results suggested that the senescence of harvested litchi fruit was likely to be an oxidative process initiated by ABA, including oxidation of lipids, polyphenols and anthocyanins. After cold storage, PCS fruit exhibited energy deficiency, and respiratory burst was elicited through aerobic and anaerobic respiration, which was regulated specifically by an up-regulated calcium signal, G-protein-coupled receptor signalling pathway and small GTPase-mediated signal transduction. The respiratory burst was largely associated with increased production of reactive oxygen species, up-regulated peroxidase activity and initiation of the lipoxygenase pathway, which were closely related to the accelerated senescence of PCS fruit. PMID:26763309

  19. Striatal signal transduction and drug addiction.

    PubMed

    Philibin, Scott D; Hernandez, Adan; Self, David W; Bibb, James A

    2011-01-01

    Drug addiction is a severe neuropsychiatric disorder characterized by loss of control over motivated behavior. The need for effective treatments mandates a greater understanding of the causes and identification of new therapeutic targets for drug development. Drugs of abuse subjugate normal reward-related behavior to uncontrollable drug-seeking and -taking. Contributions of brain reward circuitry are being mapped with increasing precision. The role of synaptic plasticity in addiction and underlying molecular mechanisms contributing to the formation of the addicted state are being delineated. Thus we may now consider the role of striatal signal transduction in addiction from a more integrative neurobiological perspective. Drugs of abuse alter dopaminergic and glutamatergic neurotransmission in medium spiny neurons of the striatum. Dopamine receptors important for reward serve as principle targets of drugs abuse, which interact with glutamate receptor signaling critical for reward learning. Complex networks of intracellular signal transduction mechanisms underlying these receptors are strongly stimulated by addictive drugs. Through these mechanisms, repeated drug exposure alters functional and structural neuroplasticity, resulting in transition to the addicted biological state and behavioral outcomes that typify addiction. Ca(2+) and cAMP represent key second messengers that initiate signaling cascades, which regulate synaptic strength and neuronal excitability. Protein phosphorylation and dephosphorylation are fundamental mechanisms underlying synaptic plasticity that are dysregulated by drugs of abuse. Increased understanding of the regulatory mechanisms by which protein kinases and phosphatases exert their effects during normal reward learning and the addiction process may lead to novel targets and pharmacotherapeutics with increased efficacy in promoting abstinence and decreased side effects, such as interference with natural reward, for drug addiction.

  20. A mechanical diode: Comparing numerical and experimental characterizations

    SciTech Connect

    Simmermacher, T.; Segalman, D.; Sagartz, M.

    1997-12-01

    The predictive modeling of vibration of many structural systems is crippled by an inability to predictively model the mechanics of joints. The lack of understanding of joint dynamics is evidenced by the substantial uncertainty of joint compliances in the numerical models and by the complete inability to predict joint damping. The lore is that at low amplitudes, joint mechanics are associated with Coulomb friction and stick-slip phenomena and that at high amplitudes, impact processes result in dissipation as well as shift of energy to other frequencies. Inadequate understanding of the physics precludes reliable predictions. In this introductory work, joint compliance is studied in both a numerical and experimental setting. A simple bolted interface is used as the test article and compliance is measured for the joint in both compression and in tension. This simple interface is shown to exhibit a strong non-linearity near the transition from compression to tension (or vice-versa). Modeling issues pertaining to numerically solving for the compliance are addressed. It is shown that the model predicts the experimental strains and compliance fairly well. It will be seen that the joint behavior is a mechanical analogy to a diode. In compression, the joint is very stiff, acting almost as a rigid link, while in tension the joint is soft, acting as a soft spring. Although there have been many other studies performed on bolted joints, the variety of joint geometries has demonstrated large variations in behavior. This study is an attempt to quantify the behavior of typical joints found in today`s weapon systems.

  1. Carbon acquisition by Cyanobacteria: Mechanisms, Comparative Genomics and Evolution

    SciTech Connect

    Kaplan, Aaron; Hagemann, Martin; Bauwe, Hermann; Kahlon, Shira; Ogawa, Teruo

    2008-01-01

    In this chapter we mainly focus on the mechanisms of inorganic carbon uptake, photorespiration, and the regulation between the metabolic fluxes involved in photoautotrophic, photomixotrophic and heterotrophic growth. We identify the genes involved, their regulation and phylogeny. Living in an environment where the CO₂ concentration is considerably lower than required to saturate their carboxylating enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), cyanobacteria acquired the CO₂ concentrating mechanism (CCM) that enables them to accumulate CO₂ at the carboxylation site. All the cyanobacteria examined to date are able to fix CO₂ into carbohydrates. However, in addition to variance in the range of physical growth conditions, cyanobacteria also vary substantially in their ability to consume organic carbon from their surroundings. Many strains are obligate photoautotrophs where the sole carbon source is CO₂, while others are able to perform photomixotrophic or even heterotrophic growth using a wide variety of organic substances (c.f. Rippka et al., 1979; Stal and Moezelaar, 1997b). Cyanobacteria constitute a unique case where the anabolic and catabolic carbohydrate metabolisms function in the same cellular compartment. In addition, the photosynthetic and respiratory electron transport pathways share components in the thylakoid membranes. Despite its importance to our understanding of cyanobacterial metabolism, little is known about the mechanisms involved in the shifts between photoautotrophic, heterotrophic and photomixotrophic modes of growth, and their regulation; between the different pathways of carbohydrate breakdown- glycolysis, fermentation, the oxidative pentose phosphate, the Krebs cycle and the photorespiratory pathways. In this chapter we shall briefly focus on recent advances in our understanding of the CCM and carbon metabolism in cyanobacteria.

  2. Carbon Acquisition by Cyanobacteria: Mechanisms, Comparative Genomics, and Evolution

    SciTech Connect

    Kaplan, Aaron; Hagemann, Martin; Bauwe, Hermann; Kahlon, Shira; Ogawa, Teruo

    2008-01-01

    In this chapter we mainly focus on the mechanisms of inorganic carbon uptake, photorespiration, and the regulation between the metabolic fluxes involved in photoautotrophic, photomixotrophic and heterotrophic growth. We identify the genes involved, their regulation and phylogeny. Living in an environment where the CO₂ concentration is considerably lower than required to saturate their carboxylating enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), cyanobacteria acquired the CO₂ concentrating mechanism (CCM) that enables them to accumulate CO₂ at the carboxylation site. All the cyanobacteria examined to date are able to fix CO₂ into carbohydrates. However, in addition to variance in the range of physical growth conditions, cyanobacteria also vary substantially in their ability to consume organic carbon from their surroundings. Many strains are obligate photoautotrophs where the sole carbon source is CO₂, while others are able to perform photomixotrophic or even heterotrophic growth using a wide variety of organic substances (c.f. Rippka et al., 1979; Stal and Moezelaar, 1997b). Cyanobacteria constitute a unique case where the anabolic and catabolic carbohydrate metabolisms function in the same cellular compartment. In addition, the photosynthetic and respiratory electron transport pathways share components in the thylakoid membranes. Despite its importance to our understanding of cyanobacterial metabolism, little is known about the mechanisms involved in the shifts between photoautotrophic, heterotrophic and photomixotrophic modes of growth, and their regulation; between the different pathways of carbohydrate breakdown- glycolysis, fermentation, the oxidative pentose phosphate, the Krebs cycle and the photorespiratory pathways. In this chapter we shall briefly focus on recent advances in our understanding of the CCM and carbon metabolism in cyanobacteria.

  3. Vocal mechanisms in birds and bats: a comparative view.

    PubMed

    Suthers, Roderick A

    2004-06-01

    Vocal signals play a very important role in the life of both birds and echolocating bats, but these two unrelated groups of flying vertebrates have very different vocal systems. They nevertheless must solve many of the same problems in producing sound. This brief review examines avian and microchiropteran motor mechanisms for: 1) coordinating the timing of phonation with the vocal motor pattern that controls its acoustic properties, and 2) achieving respiratory strategies that provide adequate ventilation for pulmonary gas exchange, while also facilitating longer duration songs or trains of sonar pulses. PMID:15258634

  4. Vocal mechanisms in birds and bats: a comparative view.

    PubMed

    Suthers, Roderick A

    2004-06-01

    Vocal signals play a very important role in the life of both birds and echolocating bats, but these two unrelated groups of flying vertebrates have very different vocal systems. They nevertheless must solve many of the same problems in producing sound. This brief review examines avian and microchiropteran motor mechanisms for: 1) coordinating the timing of phonation with the vocal motor pattern that controls its acoustic properties, and 2) achieving respiratory strategies that provide adequate ventilation for pulmonary gas exchange, while also facilitating longer duration songs or trains of sonar pulses.

  5. Bacteriophage Transduction in Staphylococcus epidermidis

    PubMed Central

    Olson, Michael E.; Horswill, Alexander R.

    2016-01-01

    The genetic manipulation of Staphylococcus epidermidis for molecular experimentation has long been an area of difficulty. Many of the traditional laboratory techniques for strain construction are laborious and hampered by poor efficiency. The ability to move chromosomal genetic markers and plasmids using bacteriophage transduction has greatly increased the speed and ease of S. epidermidis studies. These molecular genetic advances have advanced the S. epidermidis research field beyond a select few genetically tractable strains and facilitated investigations of clinically relevant isolates. PMID:24222465

  6. Bacteriophage Transduction in Staphylococcus aureus.

    PubMed

    Olson, Michael E

    2016-01-01

    The genetic manipulation of Staphylococcus aureus for molecular experimentation is a valuable tool for assessing gene function and virulence. Genetic variability between strains coupled with difficult laboratory techniques for strain construction is a frequent roadblock in S. aureus research. Bacteriophage transduction greatly increases the speed and ease of S. aureus studies by allowing movement of chromosomal markers and plasmids between strains. This technique enables the S. aureus research community to focus investigations on clinically relevant isolates.

  7. Generalized transduction in Rhizobium meliloti.

    PubMed

    Martin, M O; Long, S R

    1984-07-01

    Generalized transduction of Rhizobium meliloti 1021 was carried out by bacteriophage N3. Genetic markers on the chromosome and the pSym megaplasmid were transduced, along with markers on several IncP plasmids. Cotransduction between transposon Tn5 insertions and integrated recombinant plasmid markers permitted correlation of cotransductional frequencies and known physical distances. Bacteriophage N3 was capable of infecting several commonly used strains of R. meliloti.

  8. A comparative evaluation of mechanical properties of nanofibrous materials

    NASA Astrophysics Data System (ADS)

    Lyubun, German P.; Bessudnova, Nadezda O.

    2014-01-01

    Restoration or replacement of lost or damaged hard tooth tissues remain a reconstructive clinical dentistry challenge. One of the most promising solutions to this problem is the development of novel concepts and methodologies of tissue engineering for the synthesis of three-dimensional graft constructs that are equivalent to original organs and tissues. This structural and functional compatibility can be reached by producing ultra-thin polymer filament scaffolds. This research aims through a series of studies to examine different methods of polymer filament material special preparation and test mechanical properties of the produced materials subjected to a tensile strain. Nanofibrous material preparation using chemically pure acetone and mixtures of ethanol/water has shown no significant changes in sample surface morphology. The high temperature impact on material morphology has resulted in the modification of fiber structure. In the course of mechanical tests it has been revealed the dependence of the material strength on the spinning solution compositions. The results achieved point to the possibility to develop nanofibrous materials with required parameters changing the methodology of spinning solution production.

  9. Comparing potential copper chelation mechanisms in Parkinson's disease protein

    NASA Astrophysics Data System (ADS)

    Rose, Frisco; Hodak, Miroslav; Bernholc, Jerry

    2011-03-01

    We have implemented the nudged elastic band (NEB) as a guided dynamics framework for our real-space multigrid method of DFT-based quantum simulations. This highly parallel approach resolves a minimum energy pathway (MEP) on the energy hypersurface by relaxing intermediates in a chain-of-states. As an initial application we present an investigation of chelating agents acting on copper ion bound to α -synuclein, whose misfolding is implicated in Parkinson's disease (PD). Copper ions are known to act as highly effective misfolding agents in a-synuclein and are thus an important target in understanding PD. Furthermore, chelation therapy has shown promise in the treatment of Alzheimer's and other neuro-degenerative diseases with similar metal-correlated pathologies. At present, our candidate chelating agents include nicotine, curcumin and clioquinol. We examine their MEP activation barriers in the context of a PD onset mechanism to assess the viability of various chelators for PD remediation.

  10. Studying Chemoattractant Signal Transduction Dynamics in Dictyostelium by BRET.

    PubMed

    Islam, A F M Tariqul; Stepanski, Branden M; Charest, Pascale G

    2016-01-01

    Understanding the dynamics of chemoattractant signaling is key to our understanding of the mechanisms underlying the directed migration of cells, including that of neutrophils to sites of infections and of cancer cells during metastasis. A model frequently used for deciphering chemoattractant signal transduction is the social amoeba Dictyostelium discoideum. However, the methods available to quantitatively measure chemotactic signaling are limited. Here, we describe a protocol to quantitatively study chemoattractant signal transduction in Dictyostelium by monitoring protein-protein interactions and conformational changes using Bioluminescence Resonance Energy Transfer (BRET). PMID:27271894

  11. Signal transduction by the growth hormone receptor

    SciTech Connect

    Waters, M.J.; Rowlinson, S.W.; Clarkson, R.W.

    1994-12-31

    It has been proposed that dimerization of identical receptor subunits by growth hormone (GH) is the mechanism of signal transduction across the cell membrane. We present here data with analogs of porcine GH (pGH), with GH receptors (GHR) mutated in the dimerization domain and with monoclonal antibodies to the GHR which indicate that dimerization is necessary but not sufficient for transduction. We also report nuclear uptake of GH both in vivo and in vitro, along with nuclear localization of the receptor and GH-binding protein (GHBP). This suggests that GH acts directly at the nucleus, and one possible target for this action is a rapid increase in transcription of C/EBP delta seen in 3T3-F442A cells in response to GH. This tyrosine kinase-dependent event may be an archetype for induction of other immediate early gene transcription factors which then interact to determine the programming of the subsequent transcriptional response to GH. 29 refs., 1 fig., 1 tab.

  12. Signal Transduction in Histidine Kinases: Insights from New Structures

    PubMed Central

    Bhate, Manasi P.; Molnar, Kathleen S.; Goulian, Mark; DeGrado, William F.

    2015-01-01

    Histidine kinases (HKs) are major players in bacterial signaling. There has been an explosion of new HK crystal structures in the last five years. We globally analyze the structures of HKs to yield insights into the mechanisms by which signals are transmitted to and across protein structures in this family. We interpret known enzymological data in the context of new structural data to show how asymmetry across the dimer interface is a key feature of signal transduction in HKs, and discuss how different HK domains undergo asymmetric-to-symmetric transitions during signal transduction and catalysis. A thermodynamic framework for signaling that encompasses these various properties is presented and the consequences of weak thermodynamic coupling are discussed. The synthesis of observations from enzymology, structural biology, protein engineering and thermodynamics paves the way for a deeper molecular understanding of histidine kinase signal transduction. PMID:25982528

  13. Comparing mechanisms of host manipulation across host and parasite taxa.

    PubMed

    Lafferty, Kevin D; Shaw, Jenny C

    2013-01-01

    Parasites affect host behavior in several ways. They can alter activity, microhabitats or both. For trophically transmitted parasites (the focus of our study), decreased activity might impair the ability of hosts to respond to final-host predators, and increased activity and altered microhabitat choice might increase contact rates between hosts and final-host predators. In an analysis of trophically transmitted parasites, more parasite groups altered activity than altered microhabitat choice. Parasites that infected vertebrates were more likely to impair the host's reaction to predators, whereas parasites that infected invertebrates were more likely to increase the host's contact with predators. The site of infection might affect how parasites manipulate their hosts. For instance, parasites in the central nervous system seem particularly suited to manipulating host behavior. Manipulative parasites commonly occupy the body cavity, muscles and central nervous systems of their hosts. Acanthocephalans in the data set differed from other taxa in that they occurred exclusively in the body cavity of invertebrates. In addition, they were more likely to alter microhabitat choice than activity. Parasites in the body cavity (across parasite types) were more likely to be associated with increased host contact with predators. Parasites can manipulate the host through energetic drain, but most parasites use more sophisticated means. For instance, parasites target four physiological systems that shape behavior in both invertebrates and vertebrates: neural, endocrine, neuromodulatory and immunomodulatory. The interconnections between these systems make it difficult to isolate specific mechanisms of host behavioral manipulation.

  14. Comparing mechanisms of host manipulation across host and parasite taxa

    USGS Publications Warehouse

    Lafferty, Kevin D.; Shaw, Jenny C.

    2013-01-01

    Parasites affect host behavior in several ways. They can alter activity, microhabitats or both. For trophically transmitted parasites (the focus of our study), decreased activity might impair the ability of hosts to respond to final-host predators, and increased activity and altered microhabitat choice might increase contact rates between hosts and final-host predators. In an analysis of trophically transmitted parasites, more parasite groups altered activity than altered microhabitat choice. Parasites that infected vertebrates were more likely to impair the host’s reaction to predators, whereas parasites that infected invertebrates were more likely to increase the host’s contact with predators. The site of infection might affect how parasites manipulate their hosts. For instance, parasites in the central nervous system seem particularly suited to manipulating host behavior. Manipulative parasites commonly occupy the body cavity, muscles and central nervous systems of their hosts. Acanthocephalans in the data set differed from other taxa in that they occurred exclusively in the body cavity of invertebrates. In addition, they were more likely to alter microhabitat choice than activity. Parasites in the body cavity (across parasite types) were more likely to be associated with increased host contact with predators. Parasites can manipulate the host through energetic drain, but most parasites use more sophisticated means. For instance, parasites target four physiological systems that shape behavior in both invertebrates and vertebrates: neural, endocrine, neuromodulatory and immunomodulatory. The interconnections between these systems make it difficult to isolate specific mechanisms of host behavioral manipulation.

  15. Comparing Flow Mechanism Hypothesis with Mobility Data of Natural Tracers

    NASA Astrophysics Data System (ADS)

    Sanda, M.; Chárová, Z.; Zumr, D.; Císlerová, M.

    2009-04-01

    of the either isotope in the whole balanced mass on the input (precipitation) and the output (streamflow). There is a strong mixing of water already in the root zone, where transpiration takes place. Preferential flow in the soil profile proved to be a major transporting mechanism for water in the form of quick subsurface runoff. The hypothesis that the hillslope soil layers controls the distribution of the flow into the groundwater recharge and/or the shallow subsurface flow during the rainfall-runoff episode, was confirmed. Porous structures of the catchment play dominant role in initial mixing of the water. We want to acknowledge projects GACR 205/09/0831 and 205/08/1174 of the Grant Agency of the Czech Republic for support of this contribution.

  16. Theory and modeling of cylindrical thermo-acoustic transduction

    NASA Astrophysics Data System (ADS)

    Tong, Lihong; Lim, C. W.; Zhao, Xiushao; Geng, Daxing

    2016-06-01

    Models both for solid and thinfilm-solid cylindrical thermo-acoustic transductions are proposed and the corresponding acoustic pressure solutions are obtained. The acoustic pressure for an individual carbon nanotube (CNT) as a function of input power is investigated analytically and it is verified by comparing with the published experimental data. Further numerical analysis on the acoustic pressure response and characteristics for varying input frequency and distance are also examined both for solid and thinfilm-solid cylindrical thermo-acoustic transductions. Through detailed theoretical and numerical studies on the acoustic pressure solution for thinfilm-solid cylindrical transduction, it is concluded that a solid with smaller thermal conductivity favors to improve the acoustic performance. In general, the proposed models are applicable to a variety of cylindrical thermo-acoustic devices performing in different gaseous media.

  17. Meeting report: teaching signal transduction.

    PubMed

    Kramer, Ijsbrand; Thomas, Geraint

    2006-01-01

    In July, 2005, the European Institute of Chemistry and Biology at the campus of the University of Bordeaux, France, hosted a focused week of seminars, workshops, and discussions around the theme of "teaching signal transduction." The purpose of the summer school was to offer both junior and senior university instructors a chance to reflect on the development and delivery of their teaching activities in this area. This was achieved by combining open seminars with restricted access workshops and discussion events. The results suggest ways in which systems biology, information and communication technology, Web-based investigations, and high standard illustrations might be more effectively and efficiently incorporated into modern cell biology courses.

  18. High-sensitivity linear piezoresistive transduction for nanomechanical beam resonators.

    PubMed

    Sansa, Marc; Fernández-Regúlez, Marta; Llobet, Jordi; San Paulo, Álvaro; Pérez-Murano, Francesc

    2014-01-01

    Highly sensitive conversion of motion into readable electrical signals is a crucial and challenging issue for nanomechanical resonators. Efficient transduction is particularly difficult to realize in devices of low dimensionality, such as beam resonators based on carbon nanotubes or silicon nanowires, where mechanical vibrations combine very high frequencies with miniscule amplitudes. Here we describe an enhanced piezoresistive transduction mechanism based on the asymmetry of the beam shape at rest. We show that this mechanism enables highly sensitive linear detection of the vibration of low-resistivity silicon beams without the need of exceptionally large piezoresistive coefficients. The general application of this effect is demonstrated by detecting multiple-order modes of silicon nanowire resonators made by either top-down or bottom-up fabrication methods. These results reveal a promising approach for practical applications of the simplest mechanical resonators, facilitating its manufacturability by very large-scale integration technologies. PMID:25000256

  19. High-sensitivity linear piezoresistive transduction for nanomechanical beam resonators.

    PubMed

    Sansa, Marc; Fernández-Regúlez, Marta; Llobet, Jordi; San Paulo, Álvaro; Pérez-Murano, Francesc

    2014-01-01

    Highly sensitive conversion of motion into readable electrical signals is a crucial and challenging issue for nanomechanical resonators. Efficient transduction is particularly difficult to realize in devices of low dimensionality, such as beam resonators based on carbon nanotubes or silicon nanowires, where mechanical vibrations combine very high frequencies with miniscule amplitudes. Here we describe an enhanced piezoresistive transduction mechanism based on the asymmetry of the beam shape at rest. We show that this mechanism enables highly sensitive linear detection of the vibration of low-resistivity silicon beams without the need of exceptionally large piezoresistive coefficients. The general application of this effect is demonstrated by detecting multiple-order modes of silicon nanowire resonators made by either top-down or bottom-up fabrication methods. These results reveal a promising approach for practical applications of the simplest mechanical resonators, facilitating its manufacturability by very large-scale integration technologies.

  20. Nonequilibrium phase transitions in biomolecular signal transduction

    NASA Astrophysics Data System (ADS)

    Smith, Eric; Krishnamurthy, Supriya; Fontana, Walter; Krakauer, David

    2011-11-01

    We study a mechanism for reliable switching in biomolecular signal-transduction cascades. Steady bistable states are created by system-size cooperative effects in populations of proteins, in spite of the fact that the phosphorylation-state transitions of any molecule, by means of which the switch is implemented, are highly stochastic. The emergence of switching is a nonequilibrium phase transition in an energetically driven, dissipative system described by a master equation. We use operator and functional integral methods from reaction-diffusion theory to solve for the phase structure, noise spectrum, and escape trajectories and first-passage times of a class of minimal models of switches, showing how all critical properties for switch behavior can be computed within a unified framework.

  1. Calcium and signal transduction in plants

    NASA Technical Reports Server (NTRS)

    Poovaiah, B. W.; Reddy, A. S.

    1993-01-01

    Environmental and hormonal signals control diverse physiological processes in plants. The mechanisms by which plant cells perceive and transduce these signals are poorly understood. Understanding biochemical and molecular events involved in signal transduction pathways has become one of the most active areas of plant research. Research during the last 15 years has established that Ca2+ acts as a messenger in transducing external signals. The evidence in support of Ca2+ as a messenger is unequivocal and fulfills all the requirements of a messenger. The role of Ca2+ becomes even more important because it is the only messenger known so far in plants. Since our last review on the Ca2+ messenger system in 1987, there has been tremendous progress in elucidating various aspects of Ca(2+) -signaling pathways in plants. These include demonstration of signal-induced changes in cytosolic Ca2+, calmodulin and calmodulin-like proteins, identification of different Ca2+ channels, characterization of Ca(2+) -dependent protein kinases (CDPKs) both at the biochemical and molecular levels, evidence for the presence of calmodulin-dependent protein kinases, and increased evidence in support of the role of inositol phospholipids in the Ca(2+) -signaling system. Despite the progress in Ca2+ research in plants, it is still in its infancy and much more needs to be done to understand the precise mechanisms by which Ca2+ regulates a wide variety of physiological processes. The purpose of this review is to summarize some of these recent developments in Ca2+ research as it relates to signal transduction in plants.

  2. Generalized Transduction in the Phytopathogen Pseudomonas syringae.

    PubMed

    Nordeen, R O; Currier, T C

    1983-06-01

    Bacteriophages isolated from culture supernatants of Pseudomonas syringae pv. syringae and from sewage transferred various chromosomal genes to P. syringae PS224. Linkage between arginine and tryptophan loci was demonstrated. The number of transductants recovered per milliliter was not altered appreciably by UV irradiation of selected phage isolates. In addition, the presence of the IncP2 plasmid R38 in a P. syringae PS224 arginine auxotroph did not increase the transduction frequency as it does in Pseudomonas aeruginosa. Increasing the multiplicity of infection of transducing phage Pssy15 from 1 to 10 resulted in up to a 10-fold increase in the number of transductants recovered, although the actual transductional frequency remained about the same. Treatment of transduction mixtures with DNase did not affect transductional frequency.

  3. Hypergravity signal transduction and gene expression in cultured mammalian cells

    NASA Technical Reports Server (NTRS)

    Kumei, Y.; Whitson, P. A.

    1994-01-01

    A number of studies have been conducted during space flight and with clinostats and centrifuges, suggesting that gravity effects the proliferation and differentiation of mammalian cells in vitro. However, little is known about the mechanisms by which mammalian cells respond to changes in gravitational stress. This paper summarizes studies designed to clarify the effects of hypergravity on the cultured human HeLa cells and to investigate the mechanism of hypergravity signal transduction in these cells.

  4. Phototaxis and sensory transduction in Euglena.

    PubMed

    Diehn, B

    1973-09-14

    The accumulation of Euglena gracilis in an illuminated region is brought about by two main mechanisms: orientation and subsequent directed movement (positive phototaxis) toward light scattered from particles in the illuminated zone; and by the trapping of cells in this region because of shock reactions experienced upon the cells encountering a sudden decrease of light intensity at the light-dark boundary (inverse photophobic responses). Phototactic orientation is mediated by inverse photophobic reactions which occur when the shadow of the stigma periodically falls upon the photoreceptor proper. Euglena also exhibits shock reactions when an already high light intensity is increased further (direct photophobic responses). The expression of both types of phobic responses depends upon stimulus intensity and adaptation of the sensory system in a seemingly complex way. A definition of the minimum components of the stimulus transduction system and a systems analytical approach to the study of input-output relationships enables one to construct an electronic analog of the cell's signal processing system that converts the photoreceptor input to commands which activate or inhibit flagellar reorientation. Computer simulation studies show that this model has considerable predictive value. It is hoped that with the approach presented in this article, a generalized model has become available for dealing with the questions of sensory transduction in aneural systems. Certainly, at this point more questions have been raised than have been answered. Where is the processing device located? Are its kinetic properties determined by electrical processes or by the rates of chemical reactions? Is the processor, and thereby the behavior of the orgamism, modulated by natural environmental parameters, and can it be modified permanently through more drastic chemical treatment of the cell? Is the system capable of permanent or transitory modification through repeated response, that is, does it

  5. Studying Cellular Signal Transduction with OMIC Technologies

    PubMed Central

    Landry, Benjamin D.; Clarke, David C.; Lee, Michael J.

    2016-01-01

    In the gulf between genotype and phenotype exists proteins and, in particular, protein signal transduction systems. These systems use a relatively limited parts list to respond to a much longer list of extracellular, environmental, and/or mechanical cues with rapidity and specificity. Most signaling networks function in a highly nonlinear and often contextual manner. Furthermore, these processes occur dynamically across space and time. Because of these complexities, systems and “OMIC” approaches are essential for the study of signal transduction. One challenge in using OMIC-scale approaches to study signaling is that the “signal” can take different forms in different situations. Signals are encoded in diverse ways such as protein-protein interactions, enzyme activities, localizations, or post-translational modifications to proteins. Furthermore, in some cases signals may be encoded only in the dynamics, duration, or rates of change of these features. Accordingly, systems-level analyses of signaling may need to integrate multiple experimental and/or computational approaches. As the field has progressed, the non-triviality of integrating experimental and computational analyses has become apparent. Successful use of OMIC methods to study signaling will require the “right” experiments and the “right” modeling approaches, and it is critical to consider both in the design phase of the project. In this review, we discuss common OMIC and modeling approaches for studying signaling, emphasizing the philosophical and practical considerations for effectively merging these two types of approaches to maximize the probability of obtaining reliable and novel insights into signaling biology. PMID:26244521

  6. Meeting Report: Teaching Signal Transduction

    PubMed Central

    Kramer, IJsbrand; Thomas, Geraint

    2006-01-01

    In July, 2005, the European Institute of Chemistry and Biology at the campus of the University of Bordeaux, France, hosted a focused week of seminars, workshops, and discussions around the theme of “teaching signal transduction.” The purpose of the summer school was to offer both junior and senior university instructors a chance to reflect on the development and delivery of their teaching activities in this area. This was achieved by combining open seminars with restricted access workshops and discussion events. The results suggest ways in which systems biology, information and communication technology, Web-based investigations, and high standard illustrations might be more effectively and efficiently incorporated into modern cell biology courses. PMID:17012185

  7. Comparative Auditory Mechanics: From Species to Species and From Base to Apex—A Moderated Discussion

    NASA Astrophysics Data System (ADS)

    Cooper, Nigel P.; Manley, Geoffrey A.

    2011-11-01

    A discussion moderated by the authors on the topics "Comparative Auditory Mechanics" and "Mechanics in the Apex of the Cochlea" was held on 20 July 2011 at the 11th International Mechanics of Hearing Workshop in Williamstown, Massachusetts. The paper provides an edited transcript of the session.

  8. Protein phosphorylation and its role in archaeal signal transduction.

    PubMed

    Esser, Dominik; Hoffmann, Lena; Pham, Trong Khoa; Bräsen, Christopher; Qiu, Wen; Wright, Phillip C; Albers, Sonja-Verena; Siebers, Bettina

    2016-09-01

    Reversible protein phosphorylation is the main mechanism of signal transduction that enables cells to rapidly respond to environmental changes by controlling the functional properties of proteins in response to external stimuli. However, whereas signal transduction is well studied in Eukaryotes and Bacteria, the knowledge in Archaea is still rather scarce. Archaea are special with regard to protein phosphorylation, due to the fact that the two best studied phyla, the Euryarchaeota and Crenarchaeaota, seem to exhibit fundamental differences in regulatory systems. Euryarchaeota (e.g. halophiles, methanogens, thermophiles), like Bacteria and Eukaryotes, rely on bacterial-type two-component signal transduction systems (phosphorylation on His and Asp), as well as on the protein phosphorylation on Ser, Thr and Tyr by Hanks-type protein kinases. Instead, Crenarchaeota (e.g. acidophiles and (hyper)thermophiles) only depend on Hanks-type protein phosphorylation. In this review, the current knowledge of reversible protein phosphorylation in Archaea is presented. It combines results from identified phosphoproteins, biochemical characterization of protein kinases and protein phosphatases as well as target enzymes and first insights into archaeal signal transduction by biochemical, genetic and polyomic studies.

  9. Protein phosphorylation and its role in archaeal signal transduction.

    PubMed

    Esser, Dominik; Hoffmann, Lena; Pham, Trong Khoa; Bräsen, Christopher; Qiu, Wen; Wright, Phillip C; Albers, Sonja-Verena; Siebers, Bettina

    2016-09-01

    Reversible protein phosphorylation is the main mechanism of signal transduction that enables cells to rapidly respond to environmental changes by controlling the functional properties of proteins in response to external stimuli. However, whereas signal transduction is well studied in Eukaryotes and Bacteria, the knowledge in Archaea is still rather scarce. Archaea are special with regard to protein phosphorylation, due to the fact that the two best studied phyla, the Euryarchaeota and Crenarchaeaota, seem to exhibit fundamental differences in regulatory systems. Euryarchaeota (e.g. halophiles, methanogens, thermophiles), like Bacteria and Eukaryotes, rely on bacterial-type two-component signal transduction systems (phosphorylation on His and Asp), as well as on the protein phosphorylation on Ser, Thr and Tyr by Hanks-type protein kinases. Instead, Crenarchaeota (e.g. acidophiles and (hyper)thermophiles) only depend on Hanks-type protein phosphorylation. In this review, the current knowledge of reversible protein phosphorylation in Archaea is presented. It combines results from identified phosphoproteins, biochemical characterization of protein kinases and protein phosphatases as well as target enzymes and first insights into archaeal signal transduction by biochemical, genetic and polyomic studies. PMID:27476079

  10. Protein phosphorylation and its role in archaeal signal transduction

    PubMed Central

    Esser, Dominik; Hoffmann, Lena; Pham, Trong Khoa; Bräsen, Christopher; Qiu, Wen; Wright, Phillip C.; Albers, Sonja-Verena; Siebers, Bettina

    2016-01-01

    Reversible protein phosphorylation is the main mechanism of signal transduction that enables cells to rapidly respond to environmental changes by controlling the functional properties of proteins in response to external stimuli. However, whereas signal transduction is well studied in Eukaryotes and Bacteria, the knowledge in Archaea is still rather scarce. Archaea are special with regard to protein phosphorylation, due to the fact that the two best studied phyla, the Euryarchaeota and Crenarchaeaota, seem to exhibit fundamental differences in regulatory systems. Euryarchaeota (e.g. halophiles, methanogens, thermophiles), like Bacteria and Eukaryotes, rely on bacterial-type two-component signal transduction systems (phosphorylation on His and Asp), as well as on the protein phosphorylation on Ser, Thr and Tyr by Hanks-type protein kinases. Instead, Crenarchaeota (e.g. acidophiles and (hyper)thermophiles) only depend on Hanks-type protein phosphorylation. In this review, the current knowledge of reversible protein phosphorylation in Archaea is presented. It combines results from identified phosphoproteins, biochemical characterization of protein kinases and protein phosphatases as well as target enzymes and first insights into archaeal signal transduction by biochemical, genetic and polyomic studies. PMID:27476079

  11. Signal transduction activated by cannabinoid receptors.

    PubMed

    Díaz-Laviada, Inés; Ruiz-Llorente, Lidia

    2005-07-01

    Since the discovery that cannabinoids exert biological actions through binding to specific receptors, signal mechanisms triggered by these receptors have been focus of extensive study. This review summarizes the current knowledge of the signalling events produced by cannabinoids from membrane receptors to downstream regulators. Two types of cannabinoid receptors have been identified to date: CB(1) and CB(2) both belonging to the heptahelichoidal receptor family but with different tissue distribution and signalling mechanisms. Coupling to inhibitory guanine nucleotide-binding protein and thus inhibition of adenylyl cyclase has been observed in both receptors but other signal transduction pathways that are regulated or not by these G proteins are differently activated upon ligand-receptor binding including ion channels, sphingomyelin hydrolysis, ceramide generation, phospholipases activation and downstream targets as MAP kinase cascade, PI3K, FAK or NOS regulation. Cannabinoids may also act independently of CB(1)or CB(2) receptors. The existence of new unidentified putative cannabinoid receptors has been claimed by many investigators. Endocannabinoids activate vanilloid TRPV1 receptors that may mediate some of the cannabinoid effects. Other actions of cannabinoids can occur through non-receptor-mediated mechanisms.

  12. Gamma Interferon Augments Macrophage Activation by Lipopolysaccharide by Two Distinct Mechanisms, at the Signal Transduction Level and via an Autocrine Mechanism Involving Tumor Necrosis Factor Alpha and Interleukin-1

    PubMed Central

    Held, Thomas K.; Weihua, Xiao; Yuan, Liang; Kalvakolanu, Dhananjaya V.; Cross, Alan S.

    1999-01-01

    When given in the presence of gamma interferon (IFN-γ), otherwise nontoxic doses of lipopolysaccharide (LPS or endotoxin) become highly lethal for mice. The mechanisms of this synergistic toxicity are not known. We considered the possibility that an interaction between the LPS-induced NF-κB and IFN-γ-induced JAK-STAT pathways at the pretranscriptional level may enhance the LPS-induced signals. To test this hypothesis, we incubated murine macrophage RAW 264.7 cells with IFN-γ for 2 h before addition of different doses of LPS. Consistent with the synergistic induction of inducible nitric oxide synthase mRNA and nitric oxide production by a combination of LPS and IFN-γ, IFN-γ strongly augmented LPS-induced NF-κB activation and accelerated the binding of NF-κB to DNA to as early as 5 min. In agreement with this, IFN-γ pretreatment promoted rapid degradation of IκB-α but not that of IκB-β. Inhibition of protein synthesis during IFN-γ treatment suppressed LPS-initiated NF-κB binding. A rapidly induced protein appeared to be involved in IFN-γ priming. Preincubation of cells with antibodies to tumor necrosis factor alpha or the interleukin-1 receptor partially reduced the priming effect of IFN-γ. In a complementary manner, LPS enhanced the activation of signal-transducing activator of transcription 1 by IFN-γ. These data suggest novel mechanisms for the synergy between IFN-γ and LPS by which they cross-regulate the signal-transducing molecules. Through this mechanism, IFN-γ may transform a given dose of LPS into a lethal stimulus capable of causing sepsis. It may also serve a beneficial purpose by enabling the host to respond quickly to relatively low doses of LPS and thereby activating antibacterial defenses. PMID:9864217

  13. Sentra, a database of signal transduction proteins.

    SciTech Connect

    Maltsev, N.; Marland, E.; Yu, G. X.; Bhatnagar, S.; Lusk, R.; Mathematics and Computer Science

    2002-01-01

    Sentra (http://www-wit.mcs.anl.gov/sentra) is a database of signal transduction proteins with the emphasis on microbial signal transduction. The database was updated to include classes of signal transduction systems modulated by either phosphorylation or methylation reactions such as PAS proteins and serine/threonine kinases, as well as the classical two-component histidine kinases and methyl-accepting chemotaxis proteins. Currently, Sentra contains signal transduction proteins from 43 completely sequenced prokaryotic genomes as well as sequences from SWISS-PROT and TrEMBL. Signal transduction proteins are annotated with information describing conserved domains, paralogous and orthologous sequences, and conserved chromosomal gene clusters. The newly developed user interface supports flexible search capabilities and extensive visualization of the data.

  14. Genetic Analysis of Gravity Signal Transduction in Arabidopsis thaliana Seedlings

    NASA Astrophysics Data System (ADS)

    Boonsirichai, K.; Harrison, B.; Stanga, J.; Young, L.-S.; Neal, C.; Sabat, G.; Murthy, N.; Harms, A.; Sedbrook, J.; Masson, P.

    The primary roots of Arabidopsis thaliana seedlings respond to gravity stimulation by developing a tip curvature that results from differential cellular elongation on opposite flanks of the elongation zone. This curvature appears modulated by a lateral gradient of auxin that originates in the gravity-perceiving cells (statocytes) of the root cap through an apparent lateral repositioning of a component the auxin efflux carrier complex within these cells (Friml et al, 2002, Nature 415: 806-809). Unfortunately, little is known about the molecular mechanisms that govern early phases of gravity perception and signal transduction within the root-cap statocytes. We have used a molecular genetic approach to uncover some of these mechanisms. Mutations in the Arabidopsis ARG1 and ARL2 genes, which encode J-domain proteins, resulted in specific alterations in root and hypocotyl gravitropism, without pleiotropic phenotypes. Interestingly, ARG1 and ARL2 appear to function in the same genetic pathway. A combination of molecular genetic, biochemical and cell-biological approaches were used to demonstrate that ARG1 functions in early phases of gravity signal transduction within the root and hypocotyl statocytes, and is needed for efficient lateral auxin transport within the cap. The ARG1 protein is associated with components of the secretory and/or endosomal pathways, suggesting its role in the recycling of components of the auxin efflux carrier complex between plasma membrane and endosome (Boonsirichai et al, 2003, Plant Cell 15:2612-2625). Genetic modifiers of arg1-2 were isolated and shown to enhance the gravitropic defect of arg1-2, while resulting in little or no gravitropic defects in a wild type ARG1 background. A slight tendency for arg1-2;mar1-1 and arg1-2;mar2-1 double-mutant organs to display an opposite gravitropic response compared to wild type suggests that all three genes contribute to the interpretation of the gravity-vector information by seedling organs. The

  15. Tuning piezoresistive transduction in nanomechanical resonators by geometrical asymmetries

    SciTech Connect

    Llobet, J.; Sansa, M.; Lorenzoni, M.; Pérez-Murano, F.; Borrisé, X.; San Paulo, A.

    2015-08-17

    The effect of geometrical asymmetries on the piezoresistive transduction in suspended double clamped beam nanomechanical resonators is investigated. Tapered silicon nano-beams, fabricated using a fast and flexible prototyping method, are employed to determine how the asymmetry affects the transduced piezoresistive signal for different mechanical resonant modes. This effect is attributed to the modulation of the strain in pre-strained double clamped beams, and it is confirmed by means of finite element simulations.

  16. Comparative Proteomic Analysis of Cultured Suspension Cells of the Halophyte Halogeton glomeratus by iTRAQ Provides Insights into Response Mechanisms to Salt Stress

    PubMed Central

    Wang, Juncheng; Yao, Lirong; Li, Baochun; Meng, Yaxiong; Ma, Xiaole; Lai, Yong; Si, Erjing; Ren, Panrong; Yang, Ke; Shang, Xunwu; Wang, Huajun

    2016-01-01

    Soil salinity severely threatens land use capability and crop yields worldwide. An analysis of the molecular mechanisms of salt tolerance in halophytes will contribute to the development of salt-tolerant crops. In this study, a combination of physiological characteristics and iTRAQ-based proteomic approaches was conducted to investigate the molecular mechanisms underlying the salt response of suspension cell cultures of halophytic Halogeton glomeratus. These cells showed halophytic growth responses comparable to those of the whole plant. In total, 97 up-regulated proteins and 192 down-regulated proteins were identified as common to both 200 and 400 mM NaCl concentration treatments. Such salinity responsive proteins were mainly involved in energy, carbohydrate metabolism, stress defense, protein metabolism, signal transduction, cell growth, and cytoskeleton metabolism. Effective regulatory protein expression related to energy, stress defense, and carbohydrate metabolism play important roles in the salt-tolerance of H. glomeratus suspension cell cultures. However, known proteins regulating Na+ efflux from the cytoplasm and its compartmentalization into the vacuole did not change significantly under salinity stress suggesting our existing knowledge concerning Na+ extrusion and compartmentalization in halophytes needs to be evaluated further. Such data are discussed in the context of our current understandings of the mechanisms involved in the salinity response of the halophyte, H. glomeratus. PMID:26904073

  17. Generalized transduction: new aspects of the events in the water column

    NASA Astrophysics Data System (ADS)

    Velimirov, B.; Chiura, H. X.; Kogure, K.

    2003-04-01

    Virus mediated transfer of genetic elements among bacteria in nature has become a major research topic in the last decade. Along with conjugation and transformation, transduction is a well-known mechanism resulting in horizontal gene transfer in procaryotic organisms. In the case of generalized transduction, all regions of the procaryotic chromosome or other genetic elements in the donor cell are transferred with nearly the same frequency to the recipient. The injection of this DNA induces the generation of stable transductants. Both virulent and temperate phages have the capability to induce general transduction.Within the frame of a study on intergeneric phage-mediated gene transfer between marine bacteria and enteric bacteria, namely an auxotrophic mutant of Escherichia coli (AB1157) we used virus like particles (VLPs) from an oligotrophic marine environment (Mediterranean Sea, West coast of Corsica) and obtained gene transfer frequencies ranging between 10-2 to 10-6 per viral particle. Consequently we had to assume that an important fraction of the VLPs obtained via ultrafiltration (Minitan Ultrafiltration System, Millipore, USA. 30 kDA cut-off filter) from surface seawater have the capability to induce general transduction. In the process of this investigation we made a number of new observations which were not compatible with the concept of general transduction. The obtained transductants were able to produce new VLPs, which had again the capability to induce transduction. In an attempt to characterize these particles we show that their appearance in the experiment was neither related to plaque formation nor to cell lysis and we discuss the concept of transduction in the light of new experimental evidence concerning transducing particles. Furthermore, a preliminary numerical model allowing an estimation of the transduction events, taking place in the water column within a year is presented.

  18. Effect of propranolol on platelet signal transduction.

    PubMed Central

    Dash, D; Rao, K

    1995-01-01

    Propranolol inhibits platelet secondary aggregation and secretion by mechanisms unrelated to its beta-adrenergic-blocking activity. We previously reported that a major effect of the drug is perturbation of the physical microenvironment of the human platelet membrane. To explore further the molecular mechanisms underlying propranolol-mediated platelet inhibition, we studied protein kinase C activity, estimated from the phosphorylation of the substrate protein pleckstrin, in propranolol-treated human platelets. The drug inhibited activation of the enzyme in thrombin-stimulated platelets but not in platelets stimulated with phorbol esters, indicating that its site of action might be upstream of protein kinase C. It also inhibited the activity of phospholipase C, determined from the extent of generation of inositol phosphates and phosphatidic acid, in platelets stimulated with thrombin as well as the non-hydrolysable GTP analogue guanosine 5'-[beta, gamma-imido]triphosphate in a dose-dependent manner. These data suggest that propranolol inhibits signal transduction in thrombin-stimulated platelets by interacting at the level of phospholipase C and exclude interaction of the drug with the downstream effector enzyme protein kinase C. Images Figure 1 Figure 2 Figure 3 PMID:7619088

  19. Hair-bundle friction from transduction channels' gating forces

    NASA Astrophysics Data System (ADS)

    Bormuth, Volker; Barral, Jérémie; Joanny, Jean-François; Jülicher, Frank; Martin, Pascal

    2015-12-01

    Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. We have shown recently that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle and thus provide a major source of damping [2]. We develop here a physical theory of passive hair-bundle mechanics that explains the origin of channel friction. We show that channel friction can be understood quantitatively by coupling the dynamics of the conformational change associated with channel gating to tip-link tension. As a result, varying channel properties affects friction, with faster channels producing smaller friction. The analysis emphasizes the dual role of transduction channels' gating forces, which affect both hair-bundle stiffness and drag. Friction originating from gating of ion channels is a general concept that is relevant to all mechanosensitive channels.

  20. Generalized transduction of small Yersinia enterocolitica plasmids.

    PubMed

    Hertwig, S; Popp, A; Freytag, B; Lurz, R; Appel, B

    1999-09-01

    To study phage-mediated gene transfer in Yersinia, the ability of Yersinia phages to transduce naturally occurring plasmids was investigated. The transduction experiments were performed with a temperate phage isolated from a pathogenic Yersinia enterocolitica strain and phage mixtures isolated from sewage. Small plasmids (4.3 and 5.8 kb) were transduced at a frequency of 10(-5) to 10(-7)/PFU. However, we could not detect the transduction of any indigenous virulence plasmid (ca. 72 kb) in pathogenic Yersinia strains. Transductants obtained by infection with the temperate phage were lysogenic and harbored the phage genome in their chromosomes.

  1. Recipient gene duplication during generalized transduction.

    PubMed

    Stodolsky, M

    1974-11-01

    An Hfr13 Delta(proA-lac) deletion recipient, -Delta(proA-lac)-F-purE(+)-, has been utilized in a study of the origins of duplications formed during chromosome fragment integration. Among the Pro(-)Lac(+) transductants, some have duplications spanning the F locus. These transductants are, or segregate, strains with F' episomes carrying genes of the duplication. Some of the duplications include purE(+), a gene which is not coinherited with lac(+) during bacteriophage P1-mediated transduction. Thus recipient genes have been duplicated during recombinant formation. Crossing-over models including replication steps provide a basis for explaining the duplication process.

  2. Signal transduction and information processing in mammalian taste buds

    PubMed Central

    2013-01-01

    The molecular machinery for chemosensory transduction in taste buds has received considerable attention within the last decade. Consequently, we now know a great deal about sweet, bitter, and umami taste mechanisms and are gaining ground rapidly on salty and sour transduction. Sweet, bitter, and umami tastes are transduced by G-protein-coupled receptors. Salty taste may be transduced by epithelial Na channels similar to those found in renal tissues. Sour transduction appears to be initiated by intracellular acidification acting on acid-sensitive membrane proteins. Once a taste signal is generated in a taste cell, the subsequent steps involve secretion of neurotransmitters, including ATP and serotonin. It is now recognized that the cells responding to sweet, bitter, and umami taste stimuli do not possess synapses and instead secrete the neurotransmitter ATP via a novel mechanism not involving conventional vesicular exocytosis. ATP is believed to excite primary sensory afferent fibers that convey gustatory signals to the brain. In contrast, taste cells that do have synapses release serotonin in response to gustatory stimulation. The postsynaptic targets of serotonin have not yet been identified. Finally, ATP secreted from receptor cells also acts on neighboring taste cells to stimulate their release of serotonin. This suggests that there is important information processing and signal coding taking place in the mammalian taste bud after gustatory stimulation. PMID:17468883

  3. Polyethyleneimine-coating enhances adenoviral transduction of mesenchymal stem cells.

    PubMed

    Yao, Xinglei; Zhou, Na; Wan, Li; Su, Xiaodong; Sun, Zhao; Mizuguchi, Hiroyuki; Yoshioka, Yasuo; Nakagawa, Shinsaku; Zhao, Robert Chunhua; Gao, Jian-Qing

    2014-05-01

    Mesenchymal stem cells (MSCs) are non-hematopoietic cells with multi-lineage potential, which makes them attractive targets for regenerative medicine applications. Efficient gene transfer into MSCs is essential for basic research in developmental biology and for therapeutic applications involving gene-modification in regenerative medicine. Adenovirus vectors (Advs) can efficiently and transiently introduce an exogenous gene into many cell types via their primary receptors, the coxsackievirus and adenovirus receptors (CARs), but not into MSCs, which lack CAR expression. To overcome this problem, an Adv coated with cationic polymer polyethyleneimine (PEI) was developed. In this study, we demonstrated that PEI coating with an optimal ratio can enhance adenoviral transduction of MSCs without cytotoxicity. We also investigated the physicochemical properties and internalization mechanisms of the PEI-coated Adv. These results could help to evaluate the potentiality of the PEI-coated Adv as a prototype vector for efficient and safe transduction into MSCs. PMID:24727452

  4. Modeling Signal Transduction Networks: A comparison of two Stochastic Kinetic Simulation Algorithms

    SciTech Connect

    Pettigrew, Michel F.; Resat, Haluk

    2005-09-15

    Simulations of a scalable four compartment reaction model based on the well known epidermal growth factor receptor (EGFR) signal transduction system are used to compare two stochastic algorithms ? StochSim and the Gibson-Gillespie. It is concluded that the Gibson-Gillespie is the algorithm of choice for most realistic cases with the possible exception of signal transduction networks characterized by a moderate number (< 100) of complex types, each with a very small population, but with a high degree of connectivity amongst the complex types. Keywords: Signal transduction networks, Stochastic simulation, StochSim, Gillespie

  5. Gravitational Effects on Signal Transduction

    NASA Technical Reports Server (NTRS)

    Sytkowski, Arthur J.

    1999-01-01

    The purpose of this study was to investigate in ground-based experiments, the effect of microgravity on in vitro erythroid differentiation triggered by the hematopoietic growth factor erythropoietin (Epo) and to begin to determine whether this is associated with the anemia of space flight. We chose to use a model cell culture system with which we have had a long and successful experience. These cells, designated Rauscher murine erythroleukemia, grow independently in suspension culture. We first compared the growth rate of Rauscher cells under conditions of simulated microgravity with that of cells grown at 1XG in standard tissue culture flasks. Therefore, since there were fewer cells in the RWV at each specified time, glucose consumption per cell was increased in simulated microgravity. We next began to study the effect of simulated microgravity on erythropoietin induced differentiation of these cells. In another experiment, we allow the cells to grown in flasks or in the RWV for 24 hours prior to the addition of Epo. We initiated studies of c-myb, a proto-oncogene the down-regulation of which is necessary for erythroid differentiation. These preliminary results suggest that simulated microgravity interferes with the signal to c-myb. This may be part of the mechanism that blocks differentiation. A flight experiment is planned within the next 18- 24 months.

  6. EDITORIAL: Special section on signal transduction Special section on signal transduction

    NASA Astrophysics Data System (ADS)

    Shvartsman, Stanislav

    2012-08-01

    This special section of Physical Biology focuses on multiple aspects of signal transduction, broadly defined as the study of the mechanisms by which cells communicate with their environment. Mechanisms of cell communication involve detection of incoming signals, which can be chemical, mechanical or electromagnetic, relaying these signals to intracellular processes, such as cytoskeletal networks or gene expression systems, and, ultimately, converting these signals to responses such as cell differentiation or death. Given the multiscale nature of signal transduction systems, they must be studied at multiple levels, from the identities and structures of molecules comprising signal detection and interpretation networks, to the systems-level properties of these networks. The 11 papers in this special section illustrate some of the most exciting aspects of signal transduction research. The first two papers, by Marie-Anne Félix [1] and by Efrat Oron and Natalia Ivanova [2], focus on cell-cell interactions in developing tissues, using vulval patterning in worm and cell fate specification in mammalian embryos as prime examples of emergent cell behaviors. Next come two papers from the groups of Julio Saez-Rodriguez [3] and Kevin Janes [4]. These papers discuss how the causal relationships between multiple components of signaling systems can be inferred using multivariable statistical analysis of empirical data. An authoritative review by Zarnitsyna and Zhu [5] presents a detailed discussion of the sequence of signaling events involved in T-cell triggering. Once the structure and components of the signaling systems are determined, they can be modeled using approaches that have been successful in other physical sciences. As two examples of such approaches, reviews by Rubinstein [6] and Kholodenko [7], present reaction-diffusion models of cell polarization and thermodynamics-based models of gene regulation. An important class of models takes the form of enzymatic networks

  7. Ion channels and the transduction of light signals

    NASA Technical Reports Server (NTRS)

    Spalding, E. P.; Evans, M. L. (Principal Investigator)

    2000-01-01

    Studies of biological light-sensing mechanisms are revealing important roles for ion channels. Photosensory transduction in plants is no exception. In this article, the evidence that ion channels perform such signal-transducing functions in the complex array of mechanisms that bring about plant photomorphogenesis will be reviewed and discussed. The examples selected for discussion range from light-gradient detection in unicellular algae to the photocontrol of stem growth in Arabidopsis. Also included is some discussion of the technical aspects of studies that combine electrophysiology and photobiology.

  8. Prenatal Exposure to Arsenic and Cadmium Impacts Infectious Disease-Related Genes within the Glucocorticoid Receptor Signal Transduction Pathway

    PubMed Central

    Rager, Julia E.; Yosim, Andrew; Fry, Rebecca C.

    2014-01-01

    There is increasing evidence that environmental agents mediate susceptibility to infectious disease. Studies support the impact of prenatal/early life exposure to the environmental metals inorganic arsenic (iAs) and cadmium (Cd) on increased risk for susceptibility to infection. The specific biological mechanisms that underlie such exposure-mediated effects remain understudied. This research aimed to identify key genes/signal transduction pathways that associate prenatal exposure to these toxic metals with changes in infectious disease susceptibility using a Comparative Genomic Enrichment Method (CGEM). Using CGEM an infectious disease gene (IDG) database was developed comprising 1085 genes with known roles in viral, bacterial, and parasitic disease pathways. Subsequently, datasets collected from human pregnancy cohorts exposed to iAs or Cd were examined in relationship to the IDGs, specifically focusing on data representing epigenetic modifications (5-methyl cytosine), genomic perturbations (mRNA expression), and proteomic shifts (protein expression). A set of 82 infection and exposure-related genes was identified and found to be enriched for their role in the glucocorticoid receptor signal transduction pathway. Given their common identification across numerous human cohorts and their known toxicological role in disease, the identified genes within the glucocorticoid signal transduction pathway may underlie altered infectious disease susceptibility associated with prenatal exposures to the toxic metals iAs and Cd in humans. PMID:25479081

  9. An Electrokinetic Model of Transduction in the Semicircular Canal

    PubMed Central

    O'Leary, Dennis P.

    1970-01-01

    Transduction in the semicircular canal was studied by focusing an infrared beam on either side of exposed ampullae from the posterior canals of Rana pipiens. The direction of fluid movement resulting from a stimulus was inferred by observing the polarity of the change in afferent impulse mean rate relative to the spontaneous value. On the basis of the accepted functional polarization of this receptor, the results indicate that fluid moved toward the warmer side of the ampulla. Convection and thermal reception were shown to be unlikely explanations for these results. Morover, cupular displacements toward the warmer side would not be expected. Because thermo-osmosis can cause fluid to move toward the warmer side in a gelatin membrane, the results can be interpreted as evidence that thermo-osmosis occurred in the gelatinous cupula and influenced the transduction mechanism. Thermo-osmosis of liquids appears to be due to an electric field that is set up in a charged membrane; hence, the hair cells might have detected an electric field that occurred in the cupula during thermo-osmosis. Electroreception might be an important link in the transduction of physiological stimuli also. Rotational stimuli could result in weak electric fields in the cupula by the mechanoelectric effect. Cupular displacements could be important for large stimuli, but extrapolations to threshold stimuli suggest displacements of angstrom amplitudes. Therefore, electroreception by the hair cells could be an explanation of the great sensitivity that has been observed in the semicircular canal and other labyrinthine receptors. PMID:5496906

  10. Soliton growth-signal transduction in topologically quantized T cells

    NASA Astrophysics Data System (ADS)

    Matsson, Leif

    1993-09-01

    A model for growth-signal transduction of the T cell and its growth factor, interleukin-2, is presented. It is obtained as a generalization of the usual rate equation and is founded on the observation that a definite number of receptor occupations must take place in order to promote transition to the S phase and subsequent DNA replication. The generalized rate equation is identified as the equation of motion of a Lagrangian field theory of Ginzburg-Landau (Goldstone) type. However it is not an ad hoc model but is a microscopic theory of the interaction of interleukin-2 and its receptor. The topological quantum number of the model is related to the observed definite number of receptor occupations required to elicit growth-signal transduction. Individual receptor quanta, up to this limit, are subjected to a type of Bose condensation. This collective excitation constitutes the growth signal in the form of a topological kink soliton which is then launched by the next potential receptor occupation that makes the interaction repulsive. The model provides a possible long-absent explanation of the triggering mechanism for growth-signal transduction by means of the ambivalent interaction, which switches sign after a definite number of receptor occupations. Moreover, it offers an explanation of how Nature screens out fractional signals in the growth-signal-transduction process of T cells. Although the model is derived for assumed point-like cells and certain other restrictions, the obtained dose-response curves are in striking agreement with proliferation data from studies of both the leukemic T cell line MLA-144 from gibbon ape and normal human T cells in, and without, the presence of monoclonal anti-Tac antibodies.

  11. Signal transduction disturbance related to hepatocarcinogenesis in mouse by prolonged exposure to Nanjing drinking water.

    PubMed

    Zhang, Rui; Sun, Jie; Zhang, Yan; Cheng, Shupei; Zhang, Xiaowei

    2013-09-01

    Toxicogenomic approaches were used to investigate the potential hepatocarcinogenic effects on mice by oral exposure to Nanjing drinking water (NJDW). Changes in the hepatic transcriptome of 3 weeks male mice (Mus musculus) were monitored and dissected after oral exposure to NJDW for 90 days. No preneoplastic and neoplastic lesions were observed in the hepatic tissue by the end of NJDW exposure. However, total of 746 genes were changed transcriptionally. Thirty-one percent of differentially expressed genes (DEGs) were associated with the functional categories of cell cycle regulation, adhesion, growth, apoptosis, and signal transduction, which are closely implicated in tumorigenesis and progression. Interrogation of Kyoto Encyclopedia of Genes and Genomes revealed that 43 DEGs were mapped to several crucial signaling pathways implicated in the pathogenesis of hepatocellular carcinoma (HCC). In signal transduction network constructed via Genes2Networks software, Egfr, Akt1, Atf2, Ctnnb1, Hras, Mapk1, Smad2, and Ccnd1 were hubs. Direct gene-disease relationships obtained from Comparative Toxicogenomics Database and scientific literatures revealed that the hubs have direct mechanism or biomarker relationships with hepatocellular preneoplastic lesions or hepatocarcinogenesis. Therefore, prolonged intake of NJDW without employing any indoor water treatment strategy might predispose mouse to HCC. Furthermore, Egfr, Akt1, Ctnnb1, Hras, Mapk1, Smad2, and Ccnd1 were identified as promising biomarkers of the potential combined hepatocarcinogenicity.

  12. Meeting report: Signal transduction meets systems biology

    PubMed Central

    2012-01-01

    In the 21st century, systems-wide analyses of biological processes are getting more and more realistic. Especially for the in depth analysis of signal transduction pathways and networks, various approaches of systems biology are now successfully used. The EU FP7 large integrated project SYBILLA (Systems Biology of T-cell Activation in Health and Disease) coordinates such an endeavor. By using a combination of experimental data sets and computational modelling, the consortium strives for gaining a detailed and mechanistic understanding of signal transduction processes that govern T-cell activation. In order to foster the interaction between systems biologists and experimentally working groups, SYBILLA co-organized the 15th meeting “Signal Transduction: Receptors, Mediators and Genes” together with the Signal Transduction Society (STS). Thus, the annual STS conference, held from November 7 to 9, 2011 in Weimar, Germany, provided an interdisciplinary forum for research on signal transduction with a major focus on systems biology addressing signalling events in T-cells. Here we report on a selection of ongoing projects of SYBILLA and how they were discussed at this interdisciplinary conference. PMID:22546078

  13. A comparative study of mineralized biocomposites: Hierarchical structure, quasi-static and dynamic mechanical behavior, and toughening mechanisms

    NASA Astrophysics Data System (ADS)

    Chen, Po-Yu

    Antlers have a primary function in combat and are designed for sustaining high impact loading and bending moment without fracture. Learning from antler may shed a new light on traumatic bone fracture prevention and development of novel fracture-resistant, impact-absorbent materials. Antlers have a similar microstructure as bones, composed mainly of type-I collagen fibrils and carbonated apatite crystals, arranged in osteons in the compact bone and trabeculae in the cancellous bone. However, antlers have lower mineral content and consist mainly of primary osteons. The structure of antler at various hierarchical levels was thoroughly characterized and examined using various techniques and compared with bovine femur. Quasi-static mechanical tests (three-point bending, compression, and nanoindentation) were conducted on elk antlers and the results were compared to reported data. The flexural strength and elastic modulus are similar to other antlers but lower than bovine femur. However, the antler has much higher work of fracture and fracture toughness compared with bone. Dynamic behavior of antler was investigated using a split-Hopkinson pressure bar system. Results showed that antler can sustain large amount of deformation without catastrophic fracture. In situ mechanical testing under ESEM was performed to examine crack propagation in the longitudinal and transverse orientations in compact antler. Nonlinear-elastic fracture mechanics were applied to determine R-curves. The fracture toughness in the transverse orientation is much higher than that in the longitudinal orientation due to crack deflections/twists at the hypermineralized interface and the rising R-curve behavior was observed. Synchrotron X-ray computed tomography and SEM images showed toughening mechanisms, including crack deflections/twists, uncracked ligament and collagen fiber bridging. The structure and compressive mechanical properties of the mineral and protein constituents in cancellous antler and

  14. Piezotransistive transduction of femtoscale displacement for photoacoustic spectroscopy.

    PubMed

    Talukdar, Abdul; Faheem Khan, M; Lee, Dongkyu; Kim, Seonghwan; Thundat, Thomas; Koley, Goutam

    2015-01-01

    Measurement of femtoscale displacements in the ultrasonic frequency range is attractive for advanced material characterization and sensing, yet major challenges remain in their reliable transduction using non-optical modalities, which can dramatically reduce the size and complexity of the transducer assembly. Here we demonstrate femtoscale displacement transduction using an AlGaN/GaN heterojunction field effect transistor-integrated GaN microcantilever that utilizes piezoelectric polarization-induced changes in two-dimensional electron gas to transduce displacement with very high sensitivity. The piezotransistor demonstrated an ultra-high gauge factor of 8,700 while consuming an extremely low power of 1.36 nW, and transduced external excitation with a superior noise-limited resolution of 12.43 fm Hz(-1/2) and an outstanding responsivity of 170 nV fm(-1), which is comparable to the optical transduction limits. These extraordinary characteristics, which enabled unique detection of nanogram quantity of analytes using photoacoustic spectroscopy, can be readily exploited in realizing a multitude of novel sensing paradigms. PMID:26258983

  15. Piezotransistive transduction of femtoscale displacement for photoacoustic spectroscopy.

    PubMed

    Talukdar, Abdul; Faheem Khan, M; Lee, Dongkyu; Kim, Seonghwan; Thundat, Thomas; Koley, Goutam

    2015-08-10

    Measurement of femtoscale displacements in the ultrasonic frequency range is attractive for advanced material characterization and sensing, yet major challenges remain in their reliable transduction using non-optical modalities, which can dramatically reduce the size and complexity of the transducer assembly. Here we demonstrate femtoscale displacement transduction using an AlGaN/GaN heterojunction field effect transistor-integrated GaN microcantilever that utilizes piezoelectric polarization-induced changes in two-dimensional electron gas to transduce displacement with very high sensitivity. The piezotransistor demonstrated an ultra-high gauge factor of 8,700 while consuming an extremely low power of 1.36 nW, and transduced external excitation with a superior noise-limited resolution of 12.43 fm Hz(-1/2) and an outstanding responsivity of 170 nV fm(-1), which is comparable to the optical transduction limits. These extraordinary characteristics, which enabled unique detection of nanogram quantity of analytes using photoacoustic spectroscopy, can be readily exploited in realizing a multitude of novel sensing paradigms.

  16. Piezotransistive transduction of femtoscale displacement for photoacoustic spectroscopy

    PubMed Central

    Talukdar, Abdul; Faheem Khan, M.; Lee, Dongkyu; Kim, Seonghwan; Thundat, Thomas; Koley, Goutam

    2015-01-01

    Measurement of femtoscale displacements in the ultrasonic frequency range is attractive for advanced material characterization and sensing, yet major challenges remain in their reliable transduction using non-optical modalities, which can dramatically reduce the size and complexity of the transducer assembly. Here we demonstrate femtoscale displacement transduction using an AlGaN/GaN heterojunction field effect transistor-integrated GaN microcantilever that utilizes piezoelectric polarization-induced changes in two-dimensional electron gas to transduce displacement with very high sensitivity. The piezotransistor demonstrated an ultra-high gauge factor of 8,700 while consuming an extremely low power of 1.36 nW, and transduced external excitation with a superior noise-limited resolution of 12.43 fm Hz−1/2 and an outstanding responsivity of 170 nV fm−1, which is comparable to the optical transduction limits. These extraordinary characteristics, which enabled unique detection of nanogram quantity of analytes using photoacoustic spectroscopy, can be readily exploited in realizing a multitude of novel sensing paradigms. PMID:26258983

  17. Sympathetic vascular transduction is augmented in young normotensive blacks

    NASA Technical Reports Server (NTRS)

    Ray, Chester A.; Monahan, Kevin D.

    2002-01-01

    The purpose of the present study was to determine sympathetic vascular transduction in young normotensive black and white adults. We hypothesized that blacks would demonstrate augmented transduction of muscle sympathetic nerve activity (MSNA) into vascular resistance. To test this hypothesis, MSNA, forearm blood flow, heart rate, and arterial blood pressure were measured during lower body negative pressure (LBNP). At rest, no differences existed in arterial blood pressure, heart rate, forearm blood flow, and forearm vascular resistance (FVR). Likewise, LBNP elicited comparable responses of these variables for blacks and whites. Baseline MSNA did not differ between blacks and whites, but whites demonstrated greater increases during LBNP (28 +/- 7 vs. 55 +/- 18%, 81 +/- 21 vs. 137 +/- 42%, 174 +/- 81 vs. 556 +/- 98% for -5, -15, and -40 mmHg LBNP, respectively; P < 0.001). Consistent with smaller increases in MSNA but similar FVR responses during LBNP, blacks demonstrated greater sympathetic vascular transduction (%FVR/%MSNA) than whites (0.95 +/- 0.07 vs. 0.82 +/- 0.07 U; 0.82 +/- 0.11 vs. 0.64 +/- 0.09 U; 0.95 +/- 0.37 vs. 0.35 +/- 0.09 U; P < 0.01). In summary, young whites demonstrate greater increases in MSNA during baroreceptor unloading than age-matched normotensive blacks. However, more importantly, for a given increase in MSNA, blacks demonstrate greater forearm vasoconstriction than whites. This finding may contribute to augmented blood pressure reactivity in blacks.

  18. The transduction properties of intercostal muscle mechanoreceptors

    PubMed Central

    Holt, Gregory A; Johnson, Richard D; Davenport, Paul W

    2002-01-01

    Background Intercostal muscles are richly innervated by mechanoreceptors. In vivo studies of cat intercostal muscle have shown that there are 3 populations of intercostal muscle mechanoreceptors: primary muscle spindles (1°), secondary muscle spindles (2°) and Golgi tendon organs (GTO). The purpose of this study was to determine the mechanical transduction properties of intercostal muscle mechanoreceptors in response to controlled length and velocity displacements of the intercostal space. Mechanoreceptors, recorded from dorsal root fibers, were localized within an isolated intercostal muscle space (ICS). Changes in ICS displacement and the velocity of ICS displacement were independently controlled with an electromagnetic motor. ICS velocity (0.5 – 100 μm/msec to a displacement of 2,000 μm) and displacement (50–2,000 μm at a constant velocity of 10 μm/msec) parameters encompassed the full range of rib motion. Results Both 1° and 2° muscle spindles were found evenly distributed within the ICS. GTOs were localized along the rib borders. The 1° spindles had the greatest discharge frequency in response to displacement amplitude followed by the 2° afferents and GTOs. The 1° muscle spindles also possessed the greatest discharge frequency in response to graded velocity changes, 3.0 spikes·sec-1/μm·msec-1. GTOs had a velocity response of 2.4 spikes·sec-1/μm·msec-1 followed by 2° muscle spindles at 0.6 spikes·sec-1/μm·msec-1. Conclusion The results of this study provide a systematic description of the mechanosenitivity of the 3 types of intercostal muscle mechanoreceptors. These mechanoreceptors have discharge properties that transduce the magnitude and velocity of intercostal muscle length. PMID:12392601

  19. Mechanical characteristics of optical coatings prepared by various techniques: a comparative study.

    PubMed

    Klemberg-Sapieha, Jolanta E; Oberste-Berghaus, Jörg; Martinu, Ludvik; Blacker, Richard; Stevenson, Ian; Sadkhin, George; Morton, Dale; McEldowney, Scott; Klinger, Robert; Martin, Phil J; Court, Nadia; Dligatch, Svetlana; Gross, Mark; Netterfield, Roger P

    2004-05-01

    Good performance of optical coatings depends on the appropriate combination of optical and mechanical properties. Therefore, successful applications require good understanding of the relationship between optical microstructural and mechanical characteristics and film stability. In addition, there is a lack of standard mechanical tests that allow one to compare film properties measured in different laboratories. We give an overview of the methodology of mechanical measurements suitable for optical coatings; this includes depth-sensing indentation, scratch resistance, friction, abrasion and wear testing, and stress and adhesion evaluation. We used the techniques mentioned above in the same laboratory to systematically compare the mechanical behavior of frequently used high- and low-index materials, namely, TiO2, Ta2O5, and SiO2, prepared by different complementary techniques. They include ion-beam-assisted deposition by electron-beam evaporation, magnetron sputtering, dual-ion-beam sputtering, plasma-enhanced chemical-vapor deposition, and filtered cathodic arc deposition. The mechanical properties are correlated with the film microstructure that is inherently related to energetic conditions during film growth.

  20. Feeding Behavior of Aplysia: A Model System for Comparing Cellular Mechanisms of Classical and Operant Conditioning

    ERIC Educational Resources Information Center

    Baxter, Douglas A.; Byrne, John H.

    2006-01-01

    Feeding behavior of Aplysia provides an excellent model system for analyzing and comparing mechanisms underlying appetitive classical conditioning and reward operant conditioning. Behavioral protocols have been developed for both forms of associative learning, both of which increase the occurrence of biting following training. Because the neural…

  1. Comparing Spelling Mechanisms of Beginning and Pre-Intermediate EFL Students.

    ERIC Educational Resources Information Center

    Badr, Mostafa M. A.

    This paper describes studies conducted in Saudi Arabia that: (1) investigated the effect of the number of orthographic alternatives of English consonant sounds on the spelling responses of 48 first-year secondary students studying English as a foreign language (EFL); and (2) compared the use of two spelling mechanisms of these first-year secondary…

  2. Probing visual transduction in a plant cell

    PubMed Central

    Uhl, Rainer; Hegemann, Peter

    1990-01-01

    Light scattering studies of vertebrate rod cells have greatly aided our understanding of the visual transduction process. This technique has now been successfully applied to study visual transduction in a unicellular alga. Flash-induced light scattering changes have been recorded which are repeatable, graded with photon exposure, and adaptive. They appear on a timescale of 15-1,000 ms and correlate kinetically with flash-induced movement responses. The responsible photoreceptor is a rhodopsin. Evidence is provided for the ability of the organism to count single photons. PMID:19431775

  3. A comparative mechanical analysis of plant and animal cells reveals convergence across kingdoms.

    PubMed

    Durand-Smet, Pauline; Chastrette, Nicolas; Guiroy, Axel; Richert, Alain; Berne-Dedieu, Annick; Szecsi, Judit; Boudaoud, Arezki; Frachisse, Jean-Marie; Bendahmane, Mohammed; Bendhamane, Mohammed; Hamant, Oliver; Asnacios, Atef

    2014-11-18

    Plant and animals have evolved different strategies for their development. Whether this is linked to major differences in their cell mechanics remains unclear, mainly because measurements on plant and animal cells relied on independent experiments and setups, thus hindering any direct comparison. In this study we used the same micro-rheometer to compare animal and plant single cell rheology. We found that wall-less plant cells exhibit the same weak power law rheology as animal cells, with comparable values of elastic and loss moduli. Remarkably, microtubules primarily contributed to the rheological behavior of wall-less plant cells whereas rheology of animal cells was mainly dependent on the actin network. Thus, plant and animal cells evolved different molecular strategies to reach a comparable cytoplasmic mechanical core, suggesting that evolutionary convergence could include the internal biophysical properties of cells.

  4. Changes in gene expression and signal transduction in microgravity

    NASA Technical Reports Server (NTRS)

    Hughes-Fulford, M.

    2001-01-01

    Studies from space flights over the past three decades have demonstrated that basic physiological changes occur in humans during space flight. These changes include cephalic fluid shifts, loss of fluid and electrolytes, loss of muscle mass, space motion sickness, anemia, reduced immune response, and loss of calcium and mineralized bone. The cause of most of these manifestations is not known and until recently, the general approach was to investigate general systemic changes, not basic cellular responses to microgravity. This laboratory has recently studied gene growth and activation of normal osteoblasts (MC3T3-El) during spaceflight. Osteoblast cells were grown on glass coverslips and loaded in the Biorack plunger boxes. The osteoblasts were launched in a serum deprived state, activated in microgravity and collected in microgravity. The osteoblasts were examined for changes in gene expression and signal transduction. Approximately one day after growth activation significant changes were observed in gene expression in 0-G flight samples. Immediate early growth genes/growth factors cox-2, c-myc, bcl2, TGF beta1, bFGF and PCNA showed a significant diminished mRNA induction in microgravity FCS activated cells when compared to ground and 1-G flight controls. Cox-1 was not detected in any of the samples. There were no significant differences in the expression of reference gene mRNA between the ground, 0-G and 1-G samples. The data suggest that quiescent osteoblasts are slower to enter the cell cycle in microgravity and that the lack of gravity itself may be a significant factor in bone loss in spaceflight. Preliminary data from our STS 76 flight experiment support our hypothesis that a basic biological response occurs at the tissue, cellular, and molecular level in 0-G. Here we examine ground-based and space flown data to help us understand the mechanism of bone loss in microgravity.

  5. Inositol trisphosphate, a novel second messenger in cellular signal transduction

    NASA Astrophysics Data System (ADS)

    Berridge, Michael J.; Irvine, Robin F.

    1984-11-01

    There has recently been rapid progress in understanding receptors that generate intracellular signals from inositol lipids. One of these lipids, phosphatidylinositol 4,5-bisphosphate, is hydrolysed to diacylglycerol and inositol trisphosphate as part of a signal transduction mechanism for controlling a variety of cellular processes including secretion, metabolism, phototransduction and cell proliferation. Diacylglycerol operates within the plane of the membrane to activate protein kinase C, whereas inositol trisphosphate is released into the cytoplasm to function as a second messenger for mobilizing intracellular calcium.

  6. Electrochemical transduction of DNA hybridization at modified electrodes by using an electroactive pyridoacridone intercalator.

    PubMed

    Bouffier, Laurent; Wang, Bingquan Stuart; Roget, André; Livache, Thierry; Demeunynck, Martine; Mailley, Pascal

    2014-02-01

    A synthetic redox probe structurally related to natural pyridoacridones was designed and electrochemically characterised. These heterocycles behave as DNA intercalators due to their extended planar structure that promotes stacking in between nucleic acid base pairs. Electrochemical characterization by cyclic voltammetry revealed a quasi-reversible electrochemical behaviour occurring at a mild negative potential in aqueous solution. The study of the mechanism showed that the iminoquinone redox moiety acts similarly to quinone involving a two-electron reduction coupled with proton transfer. The easily accessible potential region with respect to aqueous electro-inactive window makes the pyridoacridone ring suitable for the indirect electrochemical detection of chemically unlabelled DNA. Its usefulness as electrochemical hybridization indicator was assessed on immobilised DNA and compared to doxorubicin. The voltamperometric response of the intercalator acts as an indicator of the presence of double-stranded DNA at the electrode surface and allows the selective transduction of immobilised oligonucleotide hybridization at both macro- and microscale electrodes.

  7. A comparative study between axial and radial fluxfocusing magnetic gear topologies and mechanical gearboxes

    NASA Astrophysics Data System (ADS)

    Calvin, Matthew

    A variety of magnetic gear topologies have been investigated in recent years as alternatives to traditional mechanical gearboxes. In general these magnetic gears offer advantages in the non-contact transmission of torque including inherent overload protection, reduced acoustic emissions, and a reduction in the number of contacting components subject to wear. The earliest magnetic gear designs however suffered from low volumetric torque densities, which limited their utility for industrial applications. Research into flux focusing magnetic gearbox topologies has resulted in increased volumetric torque densities by actively engaging all of the magnets in the transmission of torque throughout the process. This research compared the volumetric torque density of axial and radial flux focusing magnetic gearbox designs and prototypes to planetary, cycloidal, and harmonic mechanical gearboxes. The rare earth scaled up radial and axial flux focusing topologies were found to have consistently higher volumetric torque densities than planetary gearboxes of comparable diameter. The cycloidal and harmonic gearboxes had comparable volumetric torque densities, with greater volumetric torque densities for some models and lesser volumetric torque densities for others. The expectation is that further improvements in volumetric torque density are possible for flux focusing magnetic gears with additional refinement and optimization of the designs. The current study does show that flux focusing magnetic gear topologies are a plausible future alternative to mechanical gearboxes in applications where their unique torque transmission mechanism would be advantageous.

  8. Insect mandibles--comparative mechanical properties and links with metal incorporation.

    PubMed

    Cribb, Bronwen W; Stewart, Aaron; Huang, Han; Truss, Rowan; Noller, Barry; Rasch, Ronald; Zalucki, Myron P

    2008-01-01

    A number of arthropod taxa contain metals in their mandibles (jaws), such as zinc, manganese, iron, and calcium. The occurrence of zinc and its co-located halogen chlorine have been studied in relation to the mechanical properties and shown to be linked in a direct fashion with increasing concentration. Hardness along with elastic modulus (stiffness) has also been linked to zinc and halogen concentration in some marine polychaete worms. The metal appears to be incorporated within the biological matrix, possibly bonding with proteins. However, the comparative advantage of metal inclusion has not been tested. It is possible that without metals, alternative mechanisms are used to achieve hardness of equal value in similar 'tools' such as mandibles. This question has direct bearing on the significance of metal hardening. In the present article, we compare across mandibles from six termite species, including samples with major zinc concentration, minor manganese, and no metals. Nanoindentation, electron microscopy, and electron microanalysis are used to assess metal concentration, form, and mechanical properties. The data demonstrate that termite mandibles lacking metals when fully developed have lower values for hardness and elastic modulus. Zinc is linked to a relative 20% increase in hardness when compared with mandibles devoid of metals. The similar transition metal, manganese, found in minor concentrations, is not linked to any significant increase in these mechanical properties. This raises the question of the function of manganese, which is as commonly found in insect mandibles as zinc and often located in the same mandibles.

  9. Insect mandibles--comparative mechanical properties and links with metal incorporation.

    PubMed

    Cribb, Bronwen W; Stewart, Aaron; Huang, Han; Truss, Rowan; Noller, Barry; Rasch, Ronald; Zalucki, Myron P

    2008-01-01

    A number of arthropod taxa contain metals in their mandibles (jaws), such as zinc, manganese, iron, and calcium. The occurrence of zinc and its co-located halogen chlorine have been studied in relation to the mechanical properties and shown to be linked in a direct fashion with increasing concentration. Hardness along with elastic modulus (stiffness) has also been linked to zinc and halogen concentration in some marine polychaete worms. The metal appears to be incorporated within the biological matrix, possibly bonding with proteins. However, the comparative advantage of metal inclusion has not been tested. It is possible that without metals, alternative mechanisms are used to achieve hardness of equal value in similar 'tools' such as mandibles. This question has direct bearing on the significance of metal hardening. In the present article, we compare across mandibles from six termite species, including samples with major zinc concentration, minor manganese, and no metals. Nanoindentation, electron microscopy, and electron microanalysis are used to assess metal concentration, form, and mechanical properties. The data demonstrate that termite mandibles lacking metals when fully developed have lower values for hardness and elastic modulus. Zinc is linked to a relative 20% increase in hardness when compared with mandibles devoid of metals. The similar transition metal, manganese, found in minor concentrations, is not linked to any significant increase in these mechanical properties. This raises the question of the function of manganese, which is as commonly found in insect mandibles as zinc and often located in the same mandibles. PMID:17646951

  10. Abscisic acid perception and signaling transduction in strawberry

    PubMed Central

    Li, Chunli; Jia, Haifeng; Chai, Yemao; Shen, Yuanyue

    2011-01-01

    On basis of fruit differential respiration and ethylene effects, climacteric and non-climacteric fruits have been classically defined. Over the past decades, the molecular mechanisms of climacteric fruit ripening were abundantly described and found to focus on ethylene perception and signaling transduction. In contrast, until our most recent breakthroughs, much progress has been made toward understanding the signaling perception and transduction mechanisms for abscisic acid (ABA) in strawberry, a model for non-climacteric fruit ripening. Our reports not only have provided several lines of strong evidences for ABA-regulated ripening of strawberry fruit, but also have demonstrated that homology proteins of Arabidopsis ABA receptors, including PYR/PYL/RCAR and ABAR/CHLH, act as positive regulators of ripening in response to ABA. These receptors also trigger a set of ABA downstream signaling components, and determine significant changes in the expression levels of both sugar and pigment metabolism-related genes that are closely associated with ripening. Soluble sugars, especially sucrose, may act as a signal molecular to trigger ABA accumulation through an enzymatic action of 9-cis-epoxycarotenoid dioxygenase 1 (FaNCED1). This mini-review offers an overview of these processes and also outlines the possible, molecular mechanisms for ABA in the regulation of strawberry fruit ripening through the ABA receptors. PMID:22095148

  11. Transcriptome Analysis Reveals Common and Distinct Mechanisms for Sheepgrass (Leymus chinensis) Responses to Defoliation Compared to Mechanical Wounding

    PubMed Central

    Chen, Shuangyan; Cai, Yueyue; Zhang, Lexin; Yan, Xueqing; Cheng, Liqin; Qi, Dongmei; Zhou, Qingyuan; Li, Xiaoxia; Liu, Gongshe

    2014-01-01

    Background Herbivore grazing is a multiple-component process that includes wounding, defoliation, and saliva deposition. Despite the extensive published research on mechanical wounding and defoliation, no analysis to identify the genes that specify defoliation and mechanical wounding has been performed. Moreover, the influence of the expression of these genes on plant regrowth after defoliation remains poorly understood. Results Seven cDNA libraries for RNA samples collected from stubble tissues that had been mechanically wounded or defoliated at 2, 6 and 24 h along with the control were sequenced using the Illumina/Solexa platform. A comparative transcriptomic analysis of the sequencing data was conducted. In total, 1,836 and 3,238 genes were detected with significant differential expression levels after wounding and defoliation, respectively, during one day. GO, KOG and pathway-based enrichment analyses were performed to determine and further understand the biological functions of those differentially expressed genes (DEGs). The results demonstrated that both wounding and defoliation activated the systemic synthesis of jasmonate (JA). However, defoliation specifically reduced the expression levels of ribosomal protein genes, cell division or cell expansion-related genes, and lignin biosynthesis genes and may have negatively affected plant growth. Further analysis revealed that the regrowth of elongating leaves was significantly retarded after defoliation at 6 h through the following 7 days of measurement, suggesting that the gene expression pattern and phenotype are consistent. Fifteen genes were selected, and their expression levels were confirmed by quantitative RT-PCR (qRT-PCR). Thirteen of them exhibited expression patterns consistent with the digital gene expression (DGE) data. Conclusions These sequencing datasets allowed us to elucidate the common and distinct mechanisms of plant responses to defoliation and wounding. Additionally, the distinct DEGs

  12. Evidence that membrane transduction of oligoarginine does not require vesicle formation

    SciTech Connect

    Zaro, Jennica L.; Shen Weichiang . E-mail: weishen@usc.edu

    2005-07-01

    The involvement of vesicular formation processes in the membrane transduction and nuclear transport of oligoarginine is currently a subject of controversy. In this report, a novel quantitative method which allows for the selective measurement of membrane transduction excluding concurrent endocytosis was used to determine the effects of temperature, endosomal acidification, endosomolysis, and several known inhibitors of endocytic pathways on the internalization of oligoarginine. The results show that, unlike endocytosis, transduction of oligoarginine was not affected by incubation at 16 deg. C as compared to the 37 deg. C control, and was only partially inhibited at 4 deg. C incubation. Additionally, membrane transduction was not inhibited to the same extent as endocytosis following treatment with ammonium chloride, hypertonic medium, amiloride, or filipin. The endosomolytic activity of oligoarginine was investigated by examining the leakage of FITC-dextran into the cytosolic compartment, which was not higher in the presence of oligoarginine. Furthermore, ammonium chloride showed no effect on the nuclear transport of oligoarginine. The data presented in this report indicate that membrane transduction is likely to occur at the plasma membrane without the formation of membrane vesicles, and the nuclear localization involves membrane transduction, rather than endocytosis of oligoarginine.

  13. Polyploidization without mitosis improves in vivo liver transduction with lentiviral vectors.

    PubMed

    Pichard, Virginie; Couton, Dominique; Desdouets, Chantal; Ferry, Nicolas

    2013-02-01

    Lentiviral vectors are efficient gene delivery vehicles for therapeutic and research applications. In contrast to oncoretroviral vectors, they are able to infect most nonproliferating cells. In the liver, induction of cell proliferation dramatically improved hepatocyte transduction using all types of retroviral vectors. However, the precise relationship between hepatocyte division and transduction efficiency has not been determined yet. Here we compared gene transfer efficiency in the liver after in vivo injection of recombinant lentiviral or Moloney murine leukemia viral (MoMuLV) vectors in hepatectomized rats treated or not with retrorsine, an alkaloid that blocks hepatocyte division and induces megalocytosis. Partial hepatectomy alone resulted in a similar increase in hepatocyte transduction using either vector. In retrorsine-treated and partially hepatectomized rats, transduction with MoMuLV vectors dropped dramatically. In contrast, we observed that retrorsine treatment combined with partial hepatectomy increased lentiviral transduction to higher levels than hepatectomy alone. Analysis of nuclear ploidy in single cells showed that a high level of transduction was associated with polyploidization. In conclusion, endoreplication could be exploited to improve the efficiency of liver-directed lentiviral gene therapy.

  14. The Hedgehog Signal Transduction Network

    PubMed Central

    Robbins, David J.; Fei, Dennis Liang; Riobo, Natalia A.

    2013-01-01

    Hedgehog (Hh) proteins regulate the development of a wide range of metazoan embryonic and adult structures, and disruption of Hh signaling pathways results in various human diseases. Here, we provide a comprehensive review of the signaling pathways regulated by Hh, consolidating data from a diverse array of organisms in a variety of scientific disciplines. Similar to the elucidation of many other signaling pathways, our knowledge of Hh signaling developed in a sequential manner centered on its earliest discoveries. Thus, our knowledge of Hh signaling has for the most part focused on elucidating the mechanism by which Hh regulates the Gli family of transcription factors, the so-called “canonical” Hh signaling pathway. However, in the past few years, numerous studies have shown that Hh proteins can also signal through Gli-independent mechanisms collectively referred to as “noncanonical” signaling pathways. Noncanonical Hh signaling is itself subdivided into two distinct signaling modules: (i) those not requiring Smoothened (Smo) and (ii) those downstream of Smo that do not require Gli transcription factors. Thus, Hh signaling is now proposed to occur through a variety of distinct context-dependent signaling modules that have the ability to crosstalk with one another to form an interacting, dynamic Hh signaling network. PMID:23074268

  15. Invaded grassland communities have altered stability-maintenance mechanisms but equal stability compared to native communities.

    PubMed

    Wilsey, Brian J; Daneshgar, Pedram P; Hofmockel, Kirsten; Polley, H Wayne

    2014-01-01

    Theory predicts that stability should increase with diversity via several mechanisms. We tested predictions in a 5-year experiment that compared low-diversity exotic to high-diversity native plant mixtures under two irrigation treatments. The study included both wet and dry years. Variation in biomass across years (CV) was 50% lower in mixtures than monocultures of both native and exotic species. Growth among species was more asynchronous and overyielding values were greater during and after a drought in native than exotic mixtures. Mean-variance slopes indicated strong portfolio effects in both community types, but the intercept was higher for exotics than for natives, suggesting that exotics were inherently more variable than native species. However, this failed to result in higher CV's in exotic communities because species that heavily dominated plots tended to have lower than expected variance. Results indicate that diversity-stability mechanisms are altered in invaded systems compared to native ones they replaced. PMID:24325664

  16. Invaded grassland communities have altered stability-maintenance mechanisms but equal stability compared to native communities.

    PubMed

    Wilsey, Brian J; Daneshgar, Pedram P; Hofmockel, Kirsten; Polley, H Wayne

    2014-01-01

    Theory predicts that stability should increase with diversity via several mechanisms. We tested predictions in a 5-year experiment that compared low-diversity exotic to high-diversity native plant mixtures under two irrigation treatments. The study included both wet and dry years. Variation in biomass across years (CV) was 50% lower in mixtures than monocultures of both native and exotic species. Growth among species was more asynchronous and overyielding values were greater during and after a drought in native than exotic mixtures. Mean-variance slopes indicated strong portfolio effects in both community types, but the intercept was higher for exotics than for natives, suggesting that exotics were inherently more variable than native species. However, this failed to result in higher CV's in exotic communities because species that heavily dominated plots tended to have lower than expected variance. Results indicate that diversity-stability mechanisms are altered in invaded systems compared to native ones they replaced.

  17. Comparative study of key exchange and authentication methods in application, transport and network level security mechanisms

    NASA Astrophysics Data System (ADS)

    Fathirad, Iraj; Devlin, John; Jiang, Frank

    2012-09-01

    The key-exchange and authentication are two crucial elements of any network security mechanism. IPsec, SSL/TLS, PGP and S/MIME are well-known security approaches in providing security service to network, transport and application layers; these protocols use different methods (based on their requirements) to establish keying materials and authenticates key-negotiation and participated parties. This paper studies and compares the authenticated key negotiation methods in mentioned protocols.

  18. Signal perception, transduction, and response in gravity resistance. Another graviresponse in plants

    NASA Astrophysics Data System (ADS)

    Hoson, T.; Saito, Y.; Soga, K.; Wakabayashi, K.

    Resistance to the gravitational force is a serious problem that plants have had to solve to survive on land. Mechanical resistance to the pull of gravity is thus a principal graviresponse in plants, comparable to gravitropism. Nevertheless, only limited information has been obtained for this gravity response. We have examined the mechanism of gravity-induced mechanical resistance using hypergravity conditions produced by centrifugation. As a result, we have clarified the outline of the sequence of events leading to the development of mechanical resistance. The gravity signal may be perceived by mechanoreceptors (mechanosensitive ion channels) on the plasma membrane and it appears that amyloplast sedimentation in statocytes is not involved. Transformation and transduction of the perceived signal may be mediated by the structural or physiological continuum of microtubule-cell membrane-cell wall. As the final step in the development of mechanical resistance, plants construct a tough body by increasing cell wall rigidity. The increase in cell wall rigidity is brought about by modification of the metabolism of certain wall constituents and modification of the cell wall environment, especially pH. We need to clarify the details of each step by future space and ground-based experiments.

  19. The Physiology of Mechanoelectrical Transduction Channels in Hearing

    PubMed Central

    Fettiplace, Robert; Kim, Kyunghee X.

    2014-01-01

    Much is known about the mechanotransducer (MT) channels mediating transduction in hair cells of the vertrbrate inner ear. With the use of isolated preparations, it is experimentally feasible to deliver precise mechanical stimuli to individual cells and record the ensuing transducer currents. This approach has shown that small (1–100 nm) deflections of the hair-cell stereociliary bundle are transmitted via interciliary tip links to open MT channels at the tops of the stereocilia. These channels are cation-permeable with a high selectivity for Ca2+; two channels are thought to be localized at the lower end of the tip link, each with a large single-channel conductance that increases from the low- to high-frequency end of the cochlea. Ca2+ influx through open channels regulates their resting open probability, which may contribute to setting the hair cell resting potential in vivo. Ca2+ also controls transducer fast adaptation and force generation by the hair bundle, the two coupled processes increasing in speed from cochlear apex to base. The molecular intricacy of the stereocilary bundle and the transduction apparatus is reflected by the large number of single-gene mutations that are linked to sensorineural deafness, especially those in Usher syndrome. Studies of such mutants have led to the discovery of many of the molecules of the transduction complex, including the tip link and its attachments to the stereociliary core. However, the MT channel protein is still not firmly identified, nor is it known whether the channel is activated by force delivered through accessory proteins or by deformation of the lipid bilayer. PMID:24987009

  20. Signal transduction by M3 muscarinic acetylcholine receptor in prostate cancer

    PubMed Central

    GUO, LIQIANG; LIU, YUQIANG; DING, ZHIBO; SUN, WENDONG; YUAN, MINGZHEN

    2016-01-01

    The present study aimed to investigate the potential mechanisms used during signal transduction by M3 muscarinic acetylcholine receptor (CHRM3) in prostate cancer. The microarray datasets of GSE3325, including 5 clinically localized primary prostate cancers and 4 benign prostate tissues, were downloaded from the Gene Expression Omnibus database. The differentially-expressed genes (DEGs) in primary prostate cancer tissues compared with benign controls were screened using the Limma package. Gene Ontology and pathway enrichment analyses were performed using the Database for Annotation Visualization and Integrated Discovery. Next, a protein-protein interaction (PPI) network was constructed. Additionally, microRNAs (miRNAs) associated with DEGs were predicted and miRNA-target DEG analysis was performed using a Web-based Gene Set Analysis Toolkit. Finally, the PPI network and the miRNA-target DEG network were integrated using Cytoscape. In total, 224 DEGs were screened in the prostate cancer tissues, including 113 upregulated and 111 downregulated genes. CHRM3 and epidermal growth factor (EGF) were enriched in the regulation of the actin cytoskeleton. EGF and v-myc avian myelocytomatosis viral oncogene homolog (Myc) were enriched in the mitogen-activated protein kinase (MAPK) signaling pathway. EGF with the highest degree of connectivity was the hub node in the PPI network, and miR-34b could interact with Myc directly in the miRNA-target DEG network. EGF and Myc may exhibit significant roles in the progression of prostate cancer via regulation of the actin cytoskeleton and the MAPK signaling pathway. CHRM3 may activate these two pathways in prostate cancer progression. Thus, these two key factors and pathways may be crucial mechanisms during signal transduction by CHRM3 in prostate cancer. PMID:26870222

  1. Holdfast heroics: comparing the molecular and mechanical properties of Mytilus californianus byssal threads.

    PubMed

    Harrington, Matthew J; Waite, J Herbert

    2007-12-01

    The marine mussel Mytilus californianus Conrad inhabits the most wave-exposed regions of the rocky intertidal by dint of its extraordinary tenacity. Tenacity is mediated in large part by the byssus, a fibrous holdfast structure. M. californianus byssal threads, which are mechanically superior to the byssal threads of other mytilids, are composed almost entirely of a consortium of three modular proteins known as the preCols. In this study, the complete primary sequence of preCols from M. californianus was deduced and compared to that of two related species with mechanically inferior byssal threads, M. edulis Linnaeus and M. galloprovincialis Lamarck in order to explore structure-function relationships. The preCols from M. californianus are more divergent from the other two species than they are from one another. However, the degree of divergence is not uniform among the various domains of the preCols, allowing us to speculate on their mechanical role. For instance, the extra spider silk-like runs of alanine-rich sequence in the flanking domains of M. californianus may increase crystalline order, enhancing strength and stiffness. Histidine-rich domains at the termini, in contrast, are highly conserved between species, suggesting a mechanical role common to all three. Mechanical testing of pH-treated and chemically derivatized distal threads strongly suggests that histidine side chains are ligands in reversible, metal-mediated cross-links in situ. By combining the mechanical and sequence data, yield and self-healing in the distal region of threads have been modeled to emphasize the intricate interplay of enthalpic and entropic effects during tensile load and recovery.

  2. Feeding behavior of Aplysia: a model system for comparing cellular mechanisms of classical and operant conditioning.

    PubMed

    Baxter, Douglas A; Byrne, John H

    2006-01-01

    Feeding behavior of Aplysia provides an excellent model system for analyzing and comparing mechanisms underlying appetitive classical conditioning and reward operant conditioning. Behavioral protocols have been developed for both forms of associative learning, both of which increase the occurrence of biting following training. Because the neural circuitry that mediates the behavior is well characterized and amenable to detailed cellular analyses, substantial progress has been made toward a comparative analysis of the cellular mechanisms underlying these two forms of associative learning. Both forms of associative learning use the same reinforcement pathway (the esophageal nerve, En) and the same reinforcement transmitter (dopamine, DA). In addition, at least one cellular locus of plasticity (cell B51) is modified by both forms of associative learning. However, the two forms of associative learning have opposite effects on B51. Classical conditioning decreases the excitability of B51, whereas operant conditioning increases the excitability of B51. Thus, the approach of using two forms of associative learning to modify a single behavior, which is mediated by an analytically tractable neural circuit, is revealing similarities and differences in the mechanisms that underlie classical and operant conditioning.

  3. A Comparative Data-Based Modeling Study on Respiratory CO2 Gas Exchange during Mechanical Ventilation

    PubMed Central

    Kim, Chang-Sei; Ansermino, J. Mark; Hahn, Jin-Oh

    2016-01-01

    The goal of this study is to derive a minimally complex but credible model of respiratory CO2 gas exchange that may be used in systematic design and pilot testing of closed-loop end-tidal CO2 controllers in mechanical ventilation. We first derived a candidate model that captures the essential mechanisms involved in the respiratory CO2 gas exchange process. Then, we simplified the candidate model to derive two lower-order candidate models. We compared these candidate models for predictive capability and reliability using experimental data collected from 25 pediatric subjects undergoing dynamically varying mechanical ventilation during surgical procedures. A two-compartment model equipped with transport delay to account for CO2 delivery between the lungs and the tissues showed modest but statistically significant improvement in predictive capability over the same model without transport delay. Aggregating the lungs and the tissues into a single compartment further degraded the predictive fidelity of the model. In addition, the model equipped with transport delay demonstrated superior reliability to the one without transport delay. Further, the respiratory parameters derived from the model equipped with transport delay, but not the one without transport delay, were physiologically plausible. The results suggest that gas transport between the lungs and the tissues must be taken into account to accurately reproduce the respiratory CO2 gas exchange process under conditions of wide-ranging and dynamically varying mechanical ventilation conditions. PMID:26870728

  4. The ethylene signal transduction pathway in Arabidopsis

    NASA Technical Reports Server (NTRS)

    Kieber, J. J.; Evans, M. L. (Principal Investigator)

    1997-01-01

    The gaseous hormone ethylene is an important regulator of plant growth and development. Using a simple response of etiolated seedlings to ethylene as a genetic screen, genes involved in ethylene signal transduction have been identified in Arabidopsis. Analysis of two of these genes that have been cloned reveals that ethylene signalling involves a combination of a protein (ETR1) with similarity to bacterial histidine kinases and a protein (CTR1) with similarity to Raf-1, a protein kinase involved in multiple signalling cascades in eukaryotic cells. Several lines of investigation provide compelling evidence that ETR1 encodes an ethylene receptor. For the first time there is a glimpse of the molecular circuitry underlying the signal transduction pathway for a plant hormone.

  5. Signal transduction in T lymphocytes in microgravity

    NASA Technical Reports Server (NTRS)

    Cogoli, A.

    1997-01-01

    More than 120 experiments conducted in space in the last 15 years have shown that dramatic changes are occurring in several types of single cells during their exposure to microgravity. One focus of today's research on cells in space is on signal transduction, especially those steps involving the cytoskeleton and cell-cell interactions. Signal transduction is often altered in microgravity as well as in hypergravity. This leads to changes in cell proliferation, genetic expression and differentiation. Interesting examples are leukocytes, HeLa cells, epidermoid cells and osteoblastic cells. Signalling pathways were studied in T lymphocytes in microgravity by several investigators after the discovery that mitogenic activation in vitro is virtually nil at 0g. T cells are a good model to study signal transduction because three extracellular signals (mitogen, IL-1 and IL-2) are required for full activation, and two classical pathways (via proteins G and PKC) are activated within the cell. In addition, low molecular weight GTP-binding proteins (Ras and Rap) are interacting with the cytoskeleton. The data at 0g support the notion that the expression of IL-2 receptor is inhibited at 0g, while mitogen binding and the transmission of IL-1 by accessory cells occur normally. In addition, alterations of the cytoskeleton suggest that the interaction with Rap proteins is disturbed. Data obtained with phorbol esters indicate that the function of PKC is changed in microgravity. Similar conclusions are drawn from the results with epidermoid cells A431.

  6. Differentially piezoresistive transduction of high-Q encapsulated SOI-MEMS resonators with sub-100 nm gaps.

    PubMed

    Li, Cheng-Syun; Li, Ming-Huang; Li, Sheng-Shian

    2015-01-01

    A differentially piezoresistive (piezo-R) readout proposed for single-crystal-silicon (SCS) microelectromechanical systems (MEMS) resonators is implemented in a foundrybased resonator platform, demonstrating effective feedthrough cancellation using just simple piezoresistors from the resonator supports while maximizing their capacitively transduced driving areas. The SCS resonators are fabricated by a CMOS foundry using an SOI-MEMS technology together with a polysilicon refill process. A high electromechanical coupling coefficient is attained by the use of 50-nm transducer gap spacing. Moreover, a vacuum package of the fabricated resonators is carried out through wafer-level bonding process. In this work, the corner supporting beams of the resonator serve not only mechanical supports but also piezoresistors for detecting the motional signal, hence substantially simplifying the overall resonator design to realize the piezo-R sensing. In addition, the fabricated resonators are capable of either capacitive sensing or piezo-R detection under the same capacitive drive. To mitigate feedthrough signals from parasitics, a differential measurement configuration of the piezo-R transduction is implemented in this work, featuring more than 30-dB improvement on the feedthrough level as compared with the single-ended piezo-R counterpart and purely capacitive sensing readout. Furthermore, the high-Q design of the mechanical supports is also investigated, offering Q more than 10 000 with efficient piezo-R transduction for MEMS resonators.

  7. Differentially piezoresistive transduction of high-Q encapsulated SOI-MEMS resonators with sub-100 nm gaps.

    PubMed

    Li, Cheng-Syun; Li, Ming-Huang; Li, Sheng-Shian

    2015-01-01

    A differentially piezoresistive (piezo-R) readout proposed for single-crystal-silicon (SCS) microelectromechanical systems (MEMS) resonators is implemented in a foundrybased resonator platform, demonstrating effective feedthrough cancellation using just simple piezoresistors from the resonator supports while maximizing their capacitively transduced driving areas. The SCS resonators are fabricated by a CMOS foundry using an SOI-MEMS technology together with a polysilicon refill process. A high electromechanical coupling coefficient is attained by the use of 50-nm transducer gap spacing. Moreover, a vacuum package of the fabricated resonators is carried out through wafer-level bonding process. In this work, the corner supporting beams of the resonator serve not only mechanical supports but also piezoresistors for detecting the motional signal, hence substantially simplifying the overall resonator design to realize the piezo-R sensing. In addition, the fabricated resonators are capable of either capacitive sensing or piezo-R detection under the same capacitive drive. To mitigate feedthrough signals from parasitics, a differential measurement configuration of the piezo-R transduction is implemented in this work, featuring more than 30-dB improvement on the feedthrough level as compared with the single-ended piezo-R counterpart and purely capacitive sensing readout. Furthermore, the high-Q design of the mechanical supports is also investigated, offering Q more than 10 000 with efficient piezo-R transduction for MEMS resonators. PMID:25585404

  8. Generalized transduction Of shigella flexneri by converting phage PE5.

    PubMed

    Financsek, I; Kétyi, I

    1976-01-01

    Phage PE5, responsible for the conversion of type V antigen in Shigella flexneri, has the ability to produce generalized transduction. The correlation between phage multiplicity and the number of transductants, the specific inhibitory activity of anti-PE5 serum, and the lack of transduction in PE5 resistant recipients, indicate the role of phage PE5 in generalized transduction. Transduction of the R100-1 factor resulted in a non-transmissible tetracycline resistance segragation. The characteristics of the tetracycline resistance determinant suggest the possibility of integration.

  9. Reduced modeling of signal transduction – a modular approach

    PubMed Central

    Koschorreck, Markus; Conzelmann, Holger; Ebert, Sybille; Ederer, Michael; Gilles, Ernst Dieter

    2007-01-01

    Background Combinatorial complexity is a challenging problem in detailed and mechanistic mathematical modeling of signal transduction. This subject has been discussed intensively and a lot of progress has been made within the last few years. A software tool (BioNetGen) was developed which allows an automatic rule-based set-up of mechanistic model equations. In many cases these models can be reduced by an exact domain-oriented lumping technique. However, the resulting models can still consist of a very large number of differential equations. Results We introduce a new reduction technique, which allows building modularized and highly reduced models. Compared to existing approaches further reduction of signal transduction networks is possible. The method also provides a new modularization criterion, which allows to dissect the model into smaller modules that are called layers and can be modeled independently. Hallmarks of the approach are conservation relations within each layer and connection of layers by signal flows instead of mass flows. The reduced model can be formulated directly without previous generation of detailed model equations. It can be understood and interpreted intuitively, as model variables are macroscopic quantities that are converted by rates following simple kinetics. The proposed technique is applicable without using complex mathematical tools and even without detailed knowledge of the mathematical background. However, we provide a detailed mathematical analysis to show performance and limitations of the method. For physiologically relevant parameter domains the transient as well as the stationary errors caused by the reduction are negligible. Conclusion The new layer based reduced modeling method allows building modularized and strongly reduced models of signal transduction networks. Reduced model equations can be directly formulated and are intuitively interpretable. Additionally, the method provides very good approximations especially for

  10. Lentiviral vector-mediated transduction of goat undifferentiated spermatogonia.

    PubMed

    Abbasi, Hassan; Hosseini, Sayyed Morteza; Hajian, Mahdi; Nasiri, Zahra; Bahadorani, Mehrnoosh; Tahmoorespur, Mojtaba; Nasiri, Mohammad Reza; Nasr-Esfahani, Mohammad Hossein

    2015-12-01

    Recent studies show that spermatogonial stem cells (SSCs) are able to colonize and form mature spermatozoa following transplantation into germ cell depleted testes of recipient males. Therefore, efficient ways for enrichment and gene transfer into SSCs provides a powerful tool for production of transgenic animals. In order to adapt the technique to goats, three issues were addressed: (i) enrichment of the undifferentiated spermatogonia including SSCs using magnetic activated cell sorting (MACS), (ii) lentiviral vector-mediated transduction of an enhanced green fluorescent protein (EGFP) transgene into enriched cells, and (iii) transplantation of transduced undifferentiated spermatogonia into the germ cell depleted testes of immune-suppressed mice to assess for migration and colony formation ability. Enriched cells were transduced by lentiviral vectors and subsequently analyzed for expression of THY1, PLZF, VASA, UCHL1 and BCL6B genes. Cells were also analyzed for GFP and PLZF by flow cytometry. Enriched transduced cells were transplanted into germ cell depleted mice testis. Quantitative analysis of transcripts revealed that MACS-enrichment significantly increased the expression of SSC-characteristic genes THY1, PLZF, VASA, UCHL1 and BCL6B compared to non-enriched population (P≤0.05). EGFP transduction did not affect the expression levels of SSC-characteristic genes. Flow cytometry revealed that 72% of transduced-enriched cells were positive for EGFP. Finally, transduced-enriched goat SSCs could colonize within the cells into the seminiferous tubules of germ cell depleted recipient mice at higher frequency than non-enriched cells. The results indicated that enrichment of goat undifferentiated spermatogonia by magnetic-activated cell sorting for THY1 antibody combined with lentiviral vector-mediated transduction has the potential to be used for production of transgenic goats.

  11. Mechanistic Insights in Ethylene Perception and Signal Transduction1

    PubMed Central

    Ju, Chuanli; Chang, Caren

    2015-01-01

    The gaseous hormone ethylene profoundly affects plant growth, development, and stress responses. Ethylene perception occurs at the endoplasmic reticulum membrane, and signal transduction leads to a transcriptional cascade that initiates diverse responses, often in conjunction with other signals. Recent findings provide a more complete picture of the components and mechanisms in ethylene signaling, now rendering a more dynamic view of this conserved pathway. This includes newly identified protein-protein interactions at the endoplasmic reticulum membrane, as well as the major discoveries that the central regulator ETHYLENE INSENSITIVE2 (EIN2) is the long-sought phosphorylation substrate for the CONSTITUTIVE RESPONSE1 protein kinase, and that cleavage of EIN2 transmits the signal to the nucleus. In the nucleus, hundreds of potential gene targets of the EIN3 master transcription factor have been identified and found to be induced in transcriptional waves, and transcriptional coregulation has been shown to be a mechanism of ethylene cross talk. PMID:26246449

  12. Perspective: Adhesion Mediated Signal Transduction in Bacterial Pathogens.

    PubMed

    Moorthy, Sudha; Keklak, Julia; Klein, Eric A

    2016-01-01

    During the infection process, pathogenic bacteria undergo large-scale transcriptional changes to promote virulence and increase intrahost survival. While much of this reprogramming occurs in response to changes in chemical environment, such as nutrient availability and pH, there is increasing evidence that adhesion to host-tissue can also trigger signal transduction pathways resulting in differential gene expression. Determining the molecular mechanisms of adhesion-mediated signaling requires disentangling the contributions of chemical and mechanical stimuli. Here we highlight recent work demonstrating that surface attachment drives a transcriptional response in bacterial pathogens, including uropathogenic Escherichia coli (E. coli), and discuss the complexity of experimental design when dissecting the specific role of adhesion-mediated signaling during infection.

  13. Transduction of the gravity stimulus in the root statocyte.

    PubMed

    Perbal, G; Driss-Ecole, D

    1994-01-01

    The amyloplasts of root statocytes are considered to be the perceptors of gravity. However, their displacement and the starch they contain are not required for gravisensing. The mechanism of the transduction of gravistimulus remains therefore controversial. It is well known that the amplitude of the stimulus is dependent upon the intensity of the acceleration and the inclination of the root with respect to gravity. This strongly supports the hypothesis that the stimulus results in a mechanical effect (pressure or tension) on a cellular structure. Three cellular components are proposed as possible candidates for the role of transducer: the actin filaments, the endoplasmic reticulum and the plasma membrane with its ion channels. Recent results obtained in the frame of the IML 1 Mission of Spacelab show that the endoplasmic reticulum should rather be responsible for the termination of the stimulus. The contacts of amyloplasts with the distal ER could therefore be involved in the regulation of root growth. PMID:11537906

  14. Perspective: Adhesion Mediated Signal Transduction in Bacterial Pathogens

    PubMed Central

    Moorthy, Sudha; Keklak, Julia; Klein, Eric A.

    2016-01-01

    During the infection process, pathogenic bacteria undergo large-scale transcriptional changes to promote virulence and increase intrahost survival. While much of this reprogramming occurs in response to changes in chemical environment, such as nutrient availability and pH, there is increasing evidence that adhesion to host-tissue can also trigger signal transduction pathways resulting in differential gene expression. Determining the molecular mechanisms of adhesion-mediated signaling requires disentangling the contributions of chemical and mechanical stimuli. Here we highlight recent work demonstrating that surface attachment drives a transcriptional response in bacterial pathogens, including uropathogenic Escherichia coli (E. coli), and discuss the complexity of experimental design when dissecting the specific role of adhesion-mediated signaling during infection. PMID:26901228

  15. Mechanistic Insights in Ethylene Perception and Signal Transduction.

    PubMed

    Ju, Chuanli; Chang, Caren

    2015-09-01

    The gaseous hormone ethylene profoundly affects plant growth, development, and stress responses. Ethylene perception occurs at the endoplasmic reticulum membrane, and signal transduction leads to a transcriptional cascade that initiates diverse responses, often in conjunction with other signals. Recent findings provide a more complete picture of the components and mechanisms in ethylene signaling, now rendering a more dynamic view of this conserved pathway. This includes newly identified protein-protein interactions at the endoplasmic reticulum membrane, as well as the major discoveries that the central regulator ETHYLENE INSENSITIVE2 (EIN2) is the long-sought phosphorylation substrate for the CONSTITUTIVE RESPONSE1 protein kinase, and that cleavage of EIN2 transmits the signal to the nucleus. In the nucleus, hundreds of potential gene targets of the EIN3 master transcription factor have been identified and found to be induced in transcriptional waves, and transcriptional coregulation has been shown to be a mechanism of ethylene cross talk.

  16. A transductive neuro-fuzzy controller: application to a drilling process.

    PubMed

    Gajate, Agustín; Haber, Rodolfo E; Vega, Pastora I; Alique, José R

    2010-07-01

    Recently, new neuro-fuzzy inference algorithms have been developed to deal with the time-varying behavior and uncertainty of many complex systems. This paper presents the design and application of a novel transductive neuro-fuzzy inference method to control force in a high-performance drilling process. The main goal is to study, analyze, and verify the behavior of a transductive neuro-fuzzy inference system for controlling this complex process, specifically addressing the dynamic modeling, computational efficiency, and viability of the real-time application of this algorithm as well as assessing the topology of the neuro-fuzzy system (e.g., number of clusters, number of rules). A transductive reasoning method is used to create local neuro-fuzzy models for each input/output data set in a case study. The direct and inverse dynamics of a complex process are modeled using this strategy. The synergies among fuzzy, neural, and transductive strategies are then exploited to deal with process complexity and uncertainty through the application of the neuro-fuzzy models within an internal model control (IMC) scheme. A comparative study is made of the adaptive neuro-fuzzy inference system (ANFIS) and the suggested method inspired in a transductive neuro-fuzzy inference strategy. The two neuro-fuzzy strategies are evaluated in a real drilling force control problem. The experimental results demonstrated that the transductive neuro-fuzzy control system provides a good transient response (without overshoot) and better error-based performance indices than the ANFIS-based control system. In particular, the IMC system based on a transductive neuro-fuzzy inference approach reduces the influence of the increase in cutting force that occurs as the drill depth increases, reducing the risk of rapid tool wear and catastrophic tool breakage.

  17. A transductive neuro-fuzzy controller: application to a drilling process.

    PubMed

    Gajate, Agustín; Haber, Rodolfo E; Vega, Pastora I; Alique, José R

    2010-07-01

    Recently, new neuro-fuzzy inference algorithms have been developed to deal with the time-varying behavior and uncertainty of many complex systems. This paper presents the design and application of a novel transductive neuro-fuzzy inference method to control force in a high-performance drilling process. The main goal is to study, analyze, and verify the behavior of a transductive neuro-fuzzy inference system for controlling this complex process, specifically addressing the dynamic modeling, computational efficiency, and viability of the real-time application of this algorithm as well as assessing the topology of the neuro-fuzzy system (e.g., number of clusters, number of rules). A transductive reasoning method is used to create local neuro-fuzzy models for each input/output data set in a case study. The direct and inverse dynamics of a complex process are modeled using this strategy. The synergies among fuzzy, neural, and transductive strategies are then exploited to deal with process complexity and uncertainty through the application of the neuro-fuzzy models within an internal model control (IMC) scheme. A comparative study is made of the adaptive neuro-fuzzy inference system (ANFIS) and the suggested method inspired in a transductive neuro-fuzzy inference strategy. The two neuro-fuzzy strategies are evaluated in a real drilling force control problem. The experimental results demonstrated that the transductive neuro-fuzzy control system provides a good transient response (without overshoot) and better error-based performance indices than the ANFIS-based control system. In particular, the IMC system based on a transductive neuro-fuzzy inference approach reduces the influence of the increase in cutting force that occurs as the drill depth increases, reducing the risk of rapid tool wear and catastrophic tool breakage. PMID:20659865

  18. Plasmid Transduction Using Bacteriophage Φadh for Expression of CC Chemokines by Lactobacillus gasseri ADH▿

    PubMed Central

    Damelin, Leonard H.; Mavri-Damelin, Demetra; Klaenhammer, Todd R.; Tiemessen, Caroline T.

    2010-01-01

    Vaginal mucosal microfloras are typically dominated by Gram-positive Lactobacillus species, and colonization of vaginal mucosa by exogenous microbicide-secreting Lactobacillus strains has been proposed as a means of enhancing this natural mucosal barrier against human immunodeficiency virus (HIV) infection. We asked whether an alternative strategy could be utilized whereby anti-HIV molecules are expressed within the cervicovaginal milieu by endogenous vaginal Lactobacillus populations which have been engineered in situ via transduction. In this study, we therefore investigated the feasibility of utilizing transduction for the expression of two HIV coreceptor antagonists, the CC chemokines CCL5 and CCL3, in a predominant vaginal Lactobacillus species, Lactobacillus gasseri. Modifying a previously established transduction model, which utilizes L. gasseri ADH and its prophage Φadh, we show that mitomycin C induction of L. gasseri ADH transformants containing pGK12-based plasmids with CCL5 and CCL3 expression and secretion cassettes (under the control of promoters P6 and P59, respectively) and a 232-bp Φadh cos site fragment results in the production of transducing particles which contain 8 to 9 copies of concatemeric plasmid DNA. High-frequency transduction for these particles (almost 6 orders of magnitude greater than that for pGK12 alone) was observed, and transductants were found to contain recircularized expression plasmids upon subsequent culture. Importantly, transductants produced CC chemokines at levels comparable to those produced by electroporation-derived transformants. Our findings therefore lend support to the potential use of transduction in vaginal Lactobacillus species as a novel strategy for the prevention of HIV infection across mucosal membranes. PMID:20418431

  19. Plasmid transduction using bacteriophage Phi(adh) for expression of CC chemokines by Lactobacillus gasseri ADH.

    PubMed

    Damelin, Leonard H; Mavri-Damelin, Demetra; Klaenhammer, Todd R; Tiemessen, Caroline T

    2010-06-01

    Vaginal mucosal microfloras are typically dominated by Gram-positive Lactobacillus species, and colonization of vaginal mucosa by exogenous microbicide-secreting Lactobacillus strains has been proposed as a means of enhancing this natural mucosal barrier against human immunodeficiency virus (HIV) infection. We asked whether an alternative strategy could be utilized whereby anti-HIV molecules are expressed within the cervicovaginal milieu by endogenous vaginal Lactobacillus populations which have been engineered in situ via transduction. In this study, we therefore investigated the feasibility of utilizing transduction for the expression of two HIV coreceptor antagonists, the CC chemokines CCL5 and CCL3, in a predominant vaginal Lactobacillus species, Lactobacillus gasseri. Modifying a previously established transduction model, which utilizes L. gasseri ADH and its prophage Phiadh, we show that mitomycin C induction of L. gasseri ADH transformants containing pGK12-based plasmids with CCL5 and CCL3 expression and secretion cassettes (under the control of promoters P6 and P59, respectively) and a 232-bp Phiadh cos site fragment results in the production of transducing particles which contain 8 to 9 copies of concatemeric plasmid DNA. High-frequency transduction for these particles (almost 6 orders of magnitude greater than that for pGK12 alone) was observed, and transductants were found to contain recircularized expression plasmids upon subsequent culture. Importantly, transductants produced CC chemokines at levels comparable to those produced by electroporation-derived transformants. Our findings therefore lend support to the potential use of transduction in vaginal Lactobacillus species as a novel strategy for the prevention of HIV infection across mucosal membranes.

  20. A comparative analysis of three self-balancing wheelchair balancing mechanisms.

    PubMed

    Olson, Zachery L; Van Moorhem, William K; Roemer, Robert B

    2006-12-01

    In the last 20 years, three different basic, dynamic balancing designs have been proposed for a self-balancing wheelchair (SBW) that allows the wheelchair user to transition from driving on all four wheels to driving while balanced on the two large rear wheels. The dynamic performance of these three SBW designs, the hanging pendulum counterweight (HPC), the single inverted pendulum (SIP), and the double inverted pendulum (DIP), are compared when controlled by a common state space controller. The four dynamic performance considerations of stability, driver dynamic stress, maneuverability and technical requirements were used to compare these designs while performing the following five tests: 1) transition from four-wheel to two-wheel, balancing mode; 2) stationary, self-balancing stability when subjected to an impact disturbance; 3) movement initiation, and stopping while balancing; 4) response to impact disturbances while moving; and 5) stability on low traction surfaces. In addition, the movement initiation and stopping test was repeated with increased chair mass and inertia to investigate the sensitivity of model performance to changes in model parameters. After comparing the three models it was determined that the HPC mechanism is the best choice for further development based on the criteria of stability, driver dynamic stress, maneuverability, and technical requirements. The HPC ranked equal or better compared to the SIP and DIP on 15 of 29 stability and performance factors. It was also the only design that was stable for all normally expected driving conditions.

  1. A comparative analysis of three self-balancing wheelchair balancing mechanisms.

    PubMed

    Olson, Zachery L; Van Moorhem, William K; Roemer, Robert B

    2006-12-01

    In the last 20 years, three different basic, dynamic balancing designs have been proposed for a self-balancing wheelchair (SBW) that allows the wheelchair user to transition from driving on all four wheels to driving while balanced on the two large rear wheels. The dynamic performance of these three SBW designs, the hanging pendulum counterweight (HPC), the single inverted pendulum (SIP), and the double inverted pendulum (DIP), are compared when controlled by a common state space controller. The four dynamic performance considerations of stability, driver dynamic stress, maneuverability and technical requirements were used to compare these designs while performing the following five tests: 1) transition from four-wheel to two-wheel, balancing mode; 2) stationary, self-balancing stability when subjected to an impact disturbance; 3) movement initiation, and stopping while balancing; 4) response to impact disturbances while moving; and 5) stability on low traction surfaces. In addition, the movement initiation and stopping test was repeated with increased chair mass and inertia to investigate the sensitivity of model performance to changes in model parameters. After comparing the three models it was determined that the HPC mechanism is the best choice for further development based on the criteria of stability, driver dynamic stress, maneuverability, and technical requirements. The HPC ranked equal or better compared to the SIP and DIP on 15 of 29 stability and performance factors. It was also the only design that was stable for all normally expected driving conditions. PMID:17190039

  2. Phosphoglycerolipids are master players in plant hormone signal transduction.

    PubMed

    Janda, Martin; Planchais, Severine; Djafi, Nabila; Martinec, Jan; Burketova, Lenka; Valentova, Olga; Zachowski, Alain; Ruelland, Eric

    2013-06-01

    Phosphoglycerolipids are essential structural constituents of membranes and some also have important cell signalling roles. In this review, we focus on phosphoglycerolipids that are mediators in hormone signal transduction in plants. We first describe the structures of the main signalling phosphoglycerolipids and the metabolic pathways that generate them, namely the phospholipase and lipid kinase pathways. In silico analysis of Arabidopsis transcriptome data provides evidence that the genes encoding the enzymes of these pathways are transcriptionally regulated in responses to hormones, suggesting some link with hormone signal transduction. The involvement of phosphoglycerolipid signalling in the early responses to abscisic acid, salicylic acid and auxins is then detailed. One of the most important signalling lipids in plants is phosphatidic acid. It can activate or inactivate protein kinases and/or protein phosphatases involved in hormone signalling. It can also activate NADPH oxidase leading to the production of reactive oxygen species. We will interrogate the mechanisms that allow the activation/deactivation of the lipid pathways, in particular the roles of G proteins and calcium. Mediating lipids thus appear as master players of cell signalling, modulating, if not controlling, major transducing steps of hormone signals.

  3. Gravity perception and signal transduction in single cells

    NASA Astrophysics Data System (ADS)

    Block, I.; Wolke, A.; Briegleb, W.; Ivanova, K.

    Cellular signal processing in multi-, as well as in unicellular organisms, has to rely on fundamentally similar mechanisms. Free-living single cells often use the gravity vector for their spatial orientation (gravitaxis) and show distinct gravisensitivities. In this investigation the gravisensitive giant ameboid cell Physarum polycephalum (Myxomycetes, acellular slime molds) is used. Its gravitaxis and the modulation of its intrinsic rhythmic contraction activity by gravity was demonstrated in 180 °turn experiments and in simulated, as well as in actual, near-weightlessness studies (fast-rotating clinostat; Spacelab D1, IML-1). The stimulus perception was addressed in an IML-2 experiment, which provided information on the gravireceptor itself by the determination of the cell's acceleration-sensitivity threshold. Ground-based experiments designed to elucidate the subsequent steps in signal transduction leading to a motor response, suggest that an acceleration stimulus induces changes in the level of second messenger, adenosine 3',5'-cyclic monophosphate (cAMP), indicating also that the acceleration-stimulus signal transduction chain of Physarum uses an ubiquitous second messenger pathway.

  4. The control of specificity in guard cell signal transduction

    PubMed Central

    Hetherington, A. M.

    1998-01-01

    Stomatal guard cells have proven to be an attractive system for dissecting the mechanisms of stimulus-response coupling in plants. In this review we focus on the intracellular signal transduction pathways by which extracellular signals bring about closure and opening of the stomatal pore. It is proposed that guard cell signal transduction pathways may be organized into functional arrays or signalling cassettes that contain elements common to a number of converging signalling pathways. The purpose of these signalling cassettes may be to funnel extracellular signals down onto the ion transporters that control the fluxes of ions that underlie stomatal movements. Evidence is emerging that specificity in guard cell signalling may be, in part, encoded in complex spatio-temporal patterns of increases in the concentration of cytosolic-free calcium ([Ca2+]cyt). It is suggested that oscillations in [Ca2+]cyt may generate calcium signatures that encode information concerning the stimulus type and strength. New evidence is presented that suggests that these calcium signatures may integrate information when many stimuli are present.

  5. Comparing large lecture mechanics curricula using the Force Concept Inventory: A five thousand student study

    NASA Astrophysics Data System (ADS)

    Caballero, Marcos D.; Greco, Edwin F.; Murray, Eric R.; Bujak, Keith R.; Jackson Marr, M.; Catrambone, Richard; Kohlmyer, Matthew A.; Schatz, Michael F.

    2012-07-01

    The performance of over 5000 students in introductory calculus-based mechanics courses at the Georgia Institute of Technology was assessed using the Force Concept Inventory (FCI). Results from two different curricula were compared: a traditional mechanics curriculum and the Matter & Interactions (M&I) curriculum. Both were taught with similar interactive pedagogy. Post-instruction FCI averages were significantly higher for the traditional curriculum than for the M&I curriculum; the differences between curricula persist after accounting for factors such as pre-instruction FCI scores, grade point averages, and SAT scores. FCI performance on categories of items organized by concepts was also compared; traditional averages were significantly higher in each concept. We examined differences in student preparation between the curricula and found that the relative fraction of homework and lecture topics devoted to FCI force and motion concepts correlated with the observed performance differences. Concept inventories, as instruments for evaluating curricular reforms, are generally limited to the particular choice of content and goals of the instrument. Moreover, concept inventories fail to measure what are perhaps the most interesting aspects of reform: the non-overlapping content and goals that are not present in courses without reform.

  6. The mechanical properties of various chemical vapor deposition diamond structures compared to the ideal single crystal

    NASA Astrophysics Data System (ADS)

    Hess, Peter

    2012-03-01

    The structural and electronic properties of the diamond lattice, leading to its outstanding mechanical properties, are discussed. These include the highest elastic moduli and fracture strength of any known material. Its extreme hardness is strongly connected with the extreme shear modulus, which even exceeds the large bulk modulus, revealing that diamond is more resistant to shear deformation than to volume changes. These unique features protect the ideal diamond lattice also against mechanical failure and fracture. Besides fast heat conduction, the fast vibrational movement of carbon atoms results in an extreme speed of sound and propagation of crack tips with comparable velocity. The ideal mechanical properties are compared with those of real diamond films, plates, and crystals, such as ultrananocrystalline (UNC), nanocrystalline, microcrystalline, and homo- and heteroepitaxial single-crystal chemical vapor deposition (CVD) diamond, produced by metastable synthesis using CVD. Ultrasonic methods have played and continue to play a dominant role in the determination of the linear elastic properties, such as elastic moduli of crystals or the Young's modulus of thin films with substantially varying impurity levels and morphologies. A surprising result of these extensive measurements is that even UNC diamond may approach the extreme Young's modulus of single-crystal diamond under optimized deposition conditions. The physical reasons for why the stiffness often deviates by no more than a factor of two from the ideal value are discussed, keeping in mind the large variety of diamond materials grown by various deposition conditions. Diamond is also known for its extreme hardness and fracture strength, despite its brittle nature. However, even for the best natural and synthetic diamond crystals, the measured critical fracture stress is one to two orders of magnitude smaller than the ideal value obtained by ab initio calculations for the ideal cubic lattice. Currently

  7. How realistic are flat-ramp-flat fault kinematic models? Comparing mechanical and kinematic models

    NASA Astrophysics Data System (ADS)

    Cruz, L.; Nevitt, J. M.; Hilley, G. E.; Seixas, G.

    2015-12-01

    Rock within the upper crust appears to deform according to elasto-plastic constitutive rules, but structural geologists often employ kinematic descriptions that prescribe particle motions irrespective of these physical properties. In this contribution, we examine the range of constitutive properties that are approximately implied by kinematic models by comparing predicted deformations between mechanical and kinematic models for identical fault geometric configurations. Specifically, we use the ABAQUS finite-element package to model a fault-bend-fold geometry using an elasto-plastic constitutive rule (the elastic component is linear and the plastic failure occurs according to a Mohr-Coulomb failure criterion). We varied physical properties in the mechanical model (i.e., Young's modulus, Poisson ratio, cohesion yield strength, internal friction angle, sliding friction angle) to determine the impact of each on the observed deformations, which were then compared to predictions of kinematic models parameterized with identical geometries. We found that a limited sub-set of physical properties were required to produce deformations that were similar to those predicted by the kinematic models. Specifically, mechanical models with low cohesion are required to allow the kink at the bottom of the flat-ramp geometry to remain stationary over time. Additionally, deformations produced by steep ramp geometries (30 degrees) are difficult to reconcile between the two types of models, while lower slope gradients better conform to the geometric assumptions. These physical properties may fall within the range of those observed in laboratory experiments, suggesting that particle motions predicted by kinematic models may provide an approximate representation of those produced by a physically consistent model under some circumstances.

  8. Comparative role of potential structure in classical, semiclassical, and quantum mechanics

    SciTech Connect

    Judson, R.S.; Shi, S.; Rabitz, H.

    1989-02-15

    The corresponding effects of features in the potential on classical, semiclassical, and quantum mechanics are probed using the technique of functional sensitivity analysis. It is shown that the classical and quantum functional sensitivities are equivalent in the classical (small (h/2..pi..)) and harmonic limits. Classical and quantum mechanics are known to react in qualitatively similar ways provided that features on the potential are smooth on the length scale of oscillations in the quantum wave function. By using functional sensitivity analysis, we are able to show in detail how the classical and quantum dynamics differ in the way that they sense the potential. Two examples are given, the first of which is the harmonic oscillator. This problem is well understood by other means but is useful to examine because it illustrates the detailed information about the interaction of the potential and the dynamics which can be provided by functional sensitivity analysis, simplifying the analysis of more complex systems. The second example is the collinear H+H/sub 2/ reaction. In that case there are a number of detailed and striking differences between the ways that classical and quantum mechanics react to features on the potential. For features which are broad compared to oscillations in the wave function, the two react in qualitatively the same way. The sensitivities are oscillatory, however, and there are phasing differences between the classical and quantum sensitivity functions. This means that using classical mechanics plus experimental data in an inversion scheme intended to find the ''true'' potential will necessarily introduce sizeable errors.

  9. Comparing the mechanical properties of the porcine knee meniscus when hydrated in saline versus synovial fluid.

    PubMed

    Lakes, Emily H; Kline, Courtney L; McFetridge, Peter S; Allen, Kyle D

    2015-12-16

    As research progresses to find a suitable knee meniscus replacement, accurate in vitro testing becomes critical for feasibility and comparison studies of mechanical integrity. Within the knee, the meniscus is bathed in synovial fluid, yet the most common hydration fluid in laboratory testing is phosphate buffered saline (PBS). PBS is a relatively simple salt solution, while synovial fluid is a complex non-Newtonian fluid with multiple lubricating factors. As such, PBS may interact with meniscal tissue differently than synovial fluid, and thus, the hydration fluid may be an important factor in obtaining accurate results during in vitro testing. To evaluate these effects, medial porcine menisci were used to evaluate tissue mechanics in tension (n=11) and compression (n=15). In all tests, two samples from the same meniscus were taken, where one sample was hydrated in PBS and the other was hydrated in synovial fluid. Statistical analysis revealed no significant differences between the mean mechanical properties of samples tested in PBS compared to synovial fluid; however, compressive testing revealed the variability between samples was significantly reduced if samples were tested in synovial fluid. For example, the compressive Young׳s Modulus was 12.69±7.49MPa in PBS versus 12.34±4.27MPa in synovial fluid. These results indicate testing meniscal tissue in PBS will largely not affect the mean value of the mechanical properties, but performing compression testing in synovial fluid may provide more consistent results between samples and assist in reducing sample numbers in some experiments.

  10. Comparing the mechanical properties of the porcine knee meniscus when hydrated in saline versus synovial fluid.

    PubMed

    Lakes, Emily H; Kline, Courtney L; McFetridge, Peter S; Allen, Kyle D

    2015-12-16

    As research progresses to find a suitable knee meniscus replacement, accurate in vitro testing becomes critical for feasibility and comparison studies of mechanical integrity. Within the knee, the meniscus is bathed in synovial fluid, yet the most common hydration fluid in laboratory testing is phosphate buffered saline (PBS). PBS is a relatively simple salt solution, while synovial fluid is a complex non-Newtonian fluid with multiple lubricating factors. As such, PBS may interact with meniscal tissue differently than synovial fluid, and thus, the hydration fluid may be an important factor in obtaining accurate results during in vitro testing. To evaluate these effects, medial porcine menisci were used to evaluate tissue mechanics in tension (n=11) and compression (n=15). In all tests, two samples from the same meniscus were taken, where one sample was hydrated in PBS and the other was hydrated in synovial fluid. Statistical analysis revealed no significant differences between the mean mechanical properties of samples tested in PBS compared to synovial fluid; however, compressive testing revealed the variability between samples was significantly reduced if samples were tested in synovial fluid. For example, the compressive Young׳s Modulus was 12.69±7.49MPa in PBS versus 12.34±4.27MPa in synovial fluid. These results indicate testing meniscal tissue in PBS will largely not affect the mean value of the mechanical properties, but performing compression testing in synovial fluid may provide more consistent results between samples and assist in reducing sample numbers in some experiments. PMID:26592438

  11. The SUMOylation Pathway Restricts Gene Transduction by Adeno-Associated Viruses.

    PubMed

    Hölscher, Christina; Sonntag, Florian; Henrich, Katharina; Chen, Qingxin; Beneke, Jürgen; Matula, Petr; Rohr, Karl; Kaderali, Lars; Beil, Nina; Erfle, Holger; Kleinschmidt, Jürgen A; Müller, Martin

    2015-12-01

    Adeno-associated viruses are members of the genus dependoviruses of the parvoviridae family. AAV vectors are considered promising vectors for gene therapy and genetic vaccination as they can be easily produced, are highly stable and non-pathogenic. Nevertheless, transduction of cells in vitro and in vivo by AAV in the absence of a helper virus is comparatively inefficient requiring high multiplicity of infection. Several bottlenecks for AAV transduction have previously been described, including release from endosomes, nuclear transport and conversion of the single stranded DNA into a double stranded molecule. We hypothesized that the bottlenecks in AAV transduction are, in part, due to the presence of host cell restriction factors acting directly or indirectly on the AAV-mediated gene transduction. In order to identify such factors we performed a whole genome siRNA screen which identified a number of putative genes interfering with AAV gene transduction. A number of factors, yielding the highest scores, were identified as members of the SUMOylation pathway. We identified Ubc9, the E2 conjugating enzyme as well as Sae1 and Sae2, enzymes responsible for activating E1, as factors involved in restricting AAV. The restriction effect, mediated by these factors, was validated and reproduced independently. Our data indicate that SUMOylation targets entry of AAV capsids and not downstream processes of uncoating, including DNA single strand conversion or DNA damage signaling. We suggest that transiently targeting SUMOylation will enhance application of AAV in vitro and in vivo.

  12. Full Piezoelectric Multilayer-Stacked Hybrid Actuation/Transduction Systems

    NASA Technical Reports Server (NTRS)

    Su, Ji; Jiang, Xiaoning; Zu, Tian-Bing

    2011-01-01

    The Stacked HYBATS (Hybrid Actuation/Transduction system) demonstrates significantly enhanced electromechanical performance by using the cooperative contributions of the electromechanical responses of multilayer, stacked negative strain components and positive strain components. Both experimental and theoretical studies indicate that, for Stacked HYBATS, the displacement is over three times that of a same-sized conventional flextensional actuator/transducer. The coupled resonance mode between positive strain and negative strain components of Stacked HYBATS is much stronger than the resonance of a single element actuation only when the effective lengths of the two kinds of elements match each other. Compared with the previously invented hybrid actuation system (HYBAS), the multilayer Stacked HYBATS can be designed to provide high mechanical load capability, low voltage driving, and a highly effective piezoelectric constant. The negative strain component will contract, and the positive strain component will expand in the length directions when an electric field is applied on the device. The interaction between the two elements makes an enhanced motion along the Z direction for Stacked-HYBATS. In order to dominate the dynamic length of Stacked-HYBATS by the negative strain component, the area of the cross-section for the negative strain component will be much larger than the total cross-section areas of the two positive strain components. The transverse strain is negative and longitudinal strain positive in inorganic materials, such as ceramics/single crystals. Different piezoelectric multilayer stack configurations can make a piezoelectric ceramic/single-crystal multilayer stack exhibit negative strain or positive strain at a certain direction without increasing the applied voltage. The difference of this innovation from the HYBAS is that all the elements can be made from one-of-a-kind materials. Stacked HYBATS can provide an extremely effective piezoelectric

  13. In Vitro Comparative Assessment of Mechanical Blood Damage Induced by Different Hemodialysis Treatments.

    PubMed

    Sakota, Ranko; Lodi, Carlo Alberto; Sconziano, Sara Antonia; Beck, Werner; Bosch, Juan P

    2015-12-01

    Gradual deterioration of red blood cells (RBCs) due to mechanical stress (chronic hemolysis) is unavoidable during treatments that involve extracorporeal blood circulation, such as hemodialysis (HD). This effect is generally undetectable and does not generate any acute symptoms, but it leads to an increase in plasma free hemoglobin (fHb). There are no absolute safety levels for fHb increase, indicating the need for an empirical evaluation using comparative testing. The increase in fHb levels was investigated in vitro by applying double-needle double-pump HD (HD-DNDP), a new modality in which arterial and venous pumps both run continuously. fHb was measured during typical and worst-case simulated dialysis treatments (double-needle single-pump HD [HD-DNSP], hemodiafiltration [HDF-DN], single-needle double-pump HD [HD-SNDP], and HD-DNDP) performed in vitro using bovine blood for 4 h. Hemolysis-related indices (fHb%; index of hemolysis, IH; and normalized IH) were calculated and used for comparison. The increase in fHb during either HDF-DN or HD-SNDP with Artis and AK200 dialysis machines was similar, while the fHb at the maximum real blood flow rate (Qbreal ) at the completion of the HD-DNDP treatment on Artis was higher than that for HD-DNSP using a Phoenix dialysis machine (fHb% = 1.24 ± 0.13 and 0.92 ± 0.12 for the Artis machine with HD-DNDP at Qbreal  = 450 mL/min and Phoenix with HD-DNSP at Qbreal  = 500 mL/min, respectively). However, the fHb levels increased linearly, and no steep changes were observed. The increases observed during HD-DNDP were the same order of magnitude as those for widely used bloodlines and treatment modes for delivering dialysis treatments. The observed results matched literature findings, and thus the measured fHb trends are not predicted to have clinical side effects. HD-DNDP treatment with Artis does not merit any additional concern regarding mechanical stress to RBCs compared with that observed for

  14. In Vitro Comparative Assessment of Mechanical Blood Damage Induced by Different Hemodialysis Treatments

    PubMed Central

    Lodi, Carlo Alberto; Sconziano, Sara Antonia; Beck, Werner; Bosch, Juan P.

    2015-01-01

    Abstract Gradual deterioration of red blood cells (RBCs) due to mechanical stress (chronic hemolysis) is unavoidable during treatments that involve extracorporeal blood circulation, such as hemodialysis (HD). This effect is generally undetectable and does not generate any acute symptoms, but it leads to an increase in plasma free hemoglobin (fHb). There are no absolute safety levels for fHb increase, indicating the need for an empirical evaluation using comparative testing. The increase in fHb levels was investigated in vitro by applying double‐needle double‐pump HD (HD‐DNDP), a new modality in which arterial and venous pumps both run continuously. fHb was measured during typical and worst‐case simulated dialysis treatments (double‐needle single‐pump HD [HD‐DNSP], hemodiafiltration [HDF‐DN], single‐needle double‐pump HD [HD‐SNDP], and HD‐DNDP) performed in vitro using bovine blood for 4 h. Hemolysis‐related indices (fHb%; index of hemolysis, IH; and normalized IH) were calculated and used for comparison. The increase in fHb during either HDF‐DN or HD‐SNDP with Artis and AK200 dialysis machines was similar, while the fHb at the maximum real blood flow rate (Qbreal) at the completion of the HD‐DNDP treatment on Artis was higher than that for HD‐DNSP using a Phoenix dialysis machine (fHb % = 1.24 ± 0.13 and 0.92 ± 0.12 for the Artis machine with HD‐DNDP at Qbreal = 450 mL/min and Phoenix with HD‐DNSP at Qbreal = 500 mL/min, respectively). However, the fHb levels increased linearly, and no steep changes were observed. The increases observed during HD‐DNDP were the same order of magnitude as those for widely used bloodlines and treatment modes for delivering dialysis treatments. The observed results matched literature findings, and thus the measured fHb trends are not predicted to have clinical side effects. HD‐DNDP treatment with Artis does not merit any additional concern regarding mechanical stress

  15. Potential Mechanisms for Cancer Resistance in Elephants and Comparative Cellular Response to DNA Damage in Humans

    PubMed Central

    Abegglen, Lisa M.; Caulin, Aleah F.; Chan, Ashley; Lee, Kristy; Robinson, Rosann; Campbell, Michael S.; Kiso, Wendy K.; Schmitt, Dennis L.; Waddell, Peter J; Bhaskara, Srividya; Jensen, Shane T.; Maley, Carlo C.; Schiffman, Joshua D.

    2016-01-01

    IMPORTANCE Evolutionary medicine may provide insights into human physiology and pathophysiology, including tumor biology. OBJECTIVE To identify mechanisms for cancer resistance in elephants and compare cellular response to DNA damage among elephants, healthy human controls, and cancer-prone patients with Li-Fraumeni syndrome (LFS). DESIGN, SETTING, AND PARTICIPANTS A comprehensive survey of necropsy data was performed across 36 mammalian species to validate cancer resistance in large and long-lived organisms, including elephants (n = 644). The African and Asian elephant genomes were analyzed for potential mechanisms of cancer resistance. Peripheral blood lymphocytes from elephants, healthy human controls, and patients with LFS were tested in vitro in the laboratory for DNA damage response. The study included African and Asian elephants (n = 8), patients with LFS (n = 10), and age-matched human controls (n = 11). Human samples were collected at the University of Utah between June 2014 and July 2015. EXPOSURES Ionizing radiation and doxorubicin. MAIN OUTCOMES AND MEASURES Cancer mortality across species was calculated and compared by body size and life span. The elephant genome was investigated for alterations in cancer-related genes. DNA repair and apoptosis were compared in elephant vs human peripheral blood lymphocytes. RESULTS Across mammals, cancer mortality did not increase with body size and/or maximum life span (eg, for rock hyrax, 1% [95%CI, 0%–5%]; African wild dog, 8%[95%CI, 0%–16%]; lion, 2%[95%CI, 0% –7%]). Despite their large body size and long life span, elephants remain cancer resistant, with an estimated cancer mortality of 4.81% (95%CI, 3.14%–6.49%), compared with humans, who have 11% to 25%cancer mortality. While humans have 1 copy (2 alleles) of TP53, African elephants have at least 20 copies (40 alleles), including 19 retrogenes (38 alleles) with evidence of transcriptional activity measured by reverse transcription polymerase chain

  16. Comparing Student Learning in Mechanics Using Simulations and Hands-on Activities

    NASA Astrophysics Data System (ADS)

    Carmichael, Adrian; Chini, Jacquelyn J.; Rebello, N. Sanjay; Puntambekar, Sadhana

    2010-10-01

    Often computer simulation environments present students with an idealized version of the real world which can affect students' conceptual understanding. In this study we investigate the effects of completing an experiment in mechanics using this ideal world as compared to an identical experiment in the real world. Students in three of five conceptual physics laboratory sections completed the physical experiment while the other two sections performed the virtual experiment. The experiments were part of a unit on simple machines from the CoMPASS curriculum [1] which integrates hypertext-based concept maps in a design-based context. There was no statistically significant difference between the pre and post data of the students in the two groups. Students who performed the virtual experiment were able to answer questions dealing with work and potential energy more correctly, though neither group was able to offer sound reasoning to support their answers.

  17. A comparative study on industrial waste fillers affecting mechanical properties of polymer-matrix composites

    NASA Astrophysics Data System (ADS)

    Erkliğ, Ahmet; Alsaadi, Mohamad; Bulut, Mehmet

    2016-10-01

    This paper investigates the mechanical properties of the various inorganic filler-filled polymer composites. Sewage sludge ash (SSA), fly ash (FA) and silicon carbide (SiC) micro-particles were used as filler in the polyester resin. Composite samples were prepared with various filler content of 5, 10, 15 and 20 wt%. The results indicated that the tensile and flexural strength increased at the particle content of 5 wt% and then followed a decreasing trend with further particle inclusion. The tensile and flexural modulus values of the particulate polyester composites were significantly enhanced compared with the unfilled polyester composite. SEM micrograph results showed good indication for dispersion of FA, SSA and SiC particles within the polymer matrix.

  18. Locomotor loading mechanics in the hindlimbs of tegu lizards (Tupinambis merianae): comparative and evolutionary implications.

    PubMed

    Sheffield, K Megan; Butcher, Michael T; Shugart, S Katherine; Gander, Jennifer C; Blob, Richard W

    2011-08-01

    Skeletal elements are usually able to withstand several times their usual load before they yield, and this ratio is known as the bone's safety factor. Limited studies on amphibians and non-avian reptiles have shown that they have much higher limb bone safety factors than birds and mammals. It has been hypothesized that this difference is related to the difference in posture between upright birds and mammals and sprawling ectotherms; however, limb bone loading data from a wider range of sprawling species are needed in order to determine whether the higher safety factors seen in amphibians and non-avian reptiles are ancestral or derived conditions. Tegus (family Teiidae) are an ideal lineage with which to expand sampling of limb bone loading mechanics for sprawling taxa, particularly for lizards, because they are from a different clade than previously sampled iguanas and exhibit different foraging and locomotor habits (actively foraging carnivore versus burst-activity herbivore). We evaluated the mechanics of locomotor loading for the femur of the Argentine black and white tegu (Tupinambus merianae) using three-dimensional measurements of the ground reaction force and hindlimb kinematics, in vivo bone strains and femoral mechanical properties. Peak bending stresses experienced by the femur were low (tensile: 10.4 ± 1.1 MPa; compressive: -17.4 ± 0.9 MPa) and comparable to those in other reptiles, with moderate shear stresses and strains also present. Analyses of peak femoral stresses and strains led to estimated safety factor ranges of 8.8-18.6 in bending and 7.8-17.5 in torsion, both substantially higher than typical for birds and mammals but similar to other sprawling tetrapods. These results broaden the range of reptilian and amphibian taxa in which high femoral safety factors have been evaluated and further indicate a trend for the independent evolution of lower limb bone safety factors in endothermic taxa.

  19. Comparative Study of Transcriptome Profiles of Mechanical- and Skin-Transformed Schistosoma mansoni Schistosomula

    PubMed Central

    Protasio, Anna V.; Dunne, David W.; Berriman, Matthew

    2013-01-01

    Schistosome infection begins with the penetration of cercariae through healthy unbroken host skin. This process leads to the transformation of the free-living larvae into obligate parasites called schistosomula. This irreversible transformation, which occurs in as little as two hours, involves casting the cercaria tail and complete remodelling of the surface membrane. At this stage, parasites are vulnerable to host immune attack and oxidative stress. Consequently, the mechanisms by which the parasite recognises and swiftly adapts to the human host are still the subject of many studies, especially in the context of development of intervention strategies against schistosomiasis infection. Because obtaining enough material from in vivo infections is not always feasible for such studies, the transformation process is often mimicked in the laboratory by application of shear pressure to a cercarial sample resulting in mechanically transformed (MT) schistosomula. These parasites share remarkable morphological and biochemical similarity to the naturally transformed counterparts and have been considered a good proxy for parasites undergoing natural infection. Relying on this equivalency, MT schistosomula have been used almost exclusively in high-throughput studies of gene expression, identification of drug targets and identification of effective drugs against schistosomes. However, the transcriptional equivalency between skin-transformed (ST) and MT schistosomula has never been proven. In our approach to compare these two types of schistosomula preparations and to explore differences in gene expression triggered by the presence of a skin barrier, we performed RNA-seq transcriptome profiling of ST and MT schistosomula at 24 hours post transformation. We report that these two very distinct schistosomula preparations differ only in the expression of 38 genes (out of ∼11,000), providing convincing evidence to resolve the skin vs. mechanical long-lasting controversy. PMID

  20. Intraoral laser welding: ultrastructural and mechanical analysis to compare laboratory laser and dental laser.

    PubMed

    Fornaini, Carlo; Passaretti, Francesca; Villa, Elena; Rocca, Jean-Paul; Merigo, Elisabetta; Vescovi, Paolo; Meleti, Marco; Manfredi, Maddalena; Nammour, Samir

    2011-07-01

    The Nd:YAG laser has been used since 1970 in dental laboratories to weld metals on dental prostheses. Recently in several clinical cases, we have suggested that the Nd:YAG laser device commonly utilized in the dental office could be used to repair broken fixed, removable and orthodontic prostheses and to weld metals directly in the mouth. The aim of this work was to evaluate, using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and dynamic mechanical analysis (DMA), the quality of the weld and its mechanical strength, comparing a device normally used in dental laboratory and a device normally used in the dental office for oral surgery, the same as that described for intraoral welding. Metal plates of a Co-Cr-Mo dental alloy and steel orthodontic wires were subjected to four welding procedures: welding without filler metal using the laboratory laser, welding with filler metal using the laboratory laser, welding without filler metal using the office laser, and welding with filler metal using the office laser. The welded materials were then analysed by SEM, EDS and DMA. SEM analysis did not show significant differences between the samples although the plates welded using the office laser without filler metal showed a greater number of fissures than the other samples. EDS microanalysis of the welding zone showed a homogeneous composition of the metals. Mechanical tests showed similar elastic behaviours of the samples, with minimal differences between the samples welded with the two devices. No wire broke even under the maximum force applied by the analyser. This study seems to demonstrate that the welds produced using the office Nd:YAG laser device and the laboratory Nd:YAG laser device, as analysed by SEM, EDS and DMA, showed minimal and nonsignificant differences, although these findings need to be confirmed using a greater number of samples.

  1. Comparative study of mechanical properties of direct core build-up materials

    PubMed Central

    Kumar, Girish; Shivrayan, Amit

    2015-01-01

    Background and Objectives: The strength greatly influences the selection of core material because core must withstand forces due to mastication and para-function for many years. This study was conducted to evaluate certain mechanical properties of commonly used materials for direct core build-up, including visible light cured composite, polyacid modified composite, resin modified glass ionomer, high copper amalgam, and silver cermet cement. Materials and Methods: All the materials were manipulated according to the manufacturer's recommendations and standard test specimens were prepared. A universal testing machine at different cross-head speed was used to determine all the four mechanical properties. Mean compressive strength, diametral tensile strength, flexural strength, and elastic modulus with standard deviations were calculated. Multiple comparisons of the materials were also done. Results: Considerable differences in compressive strength, diametral tensile strength, and flexural strength were observed. Visible light cured composite showed relatively high compressive strength, diametral tensile strength, and flexural strength compared with the other tested materials. Amalgam showed the highest value for elastic modulus. Silver cermet showed less value for all the properties except for elastic modulus. Conclusions: Strength is one of the most important criteria for selection of a core material. Stronger materials better resist deformation and fracture provide more equitable stress distribution, greater stability, and greater probability of clinical success. PMID:25684905

  2. Comparative anatomy of gall development on Gypsophila paniculata induced by bacteria with different mechanisms of pathogenicity.

    PubMed

    Chalupowicz, L; Barash, I; Schwartz, M; Aloni, R; Manulis, S

    2006-07-01

    Galls induced on Gypsophila paniculata by Pantoea agglomerans pv. gypsophilae (Pag) and Agrobacterium tumefaciens (At), bacteria with different mechanisms of pathogenicity, were compared morphologically and anatomically. The pathogenicity of Pag is dependent on the presence of an indigenous plasmid that harbors hrp gene cluster, genes encoding Hop virulence proteins and biosynthetic genes for auxin (IAA) and cytokinins (CKs), whereas that of At involves host transformation. The Pag-induced gall was rough, brittle and exhibited limited growth, in contrast to the smooth, firm appearance and continuous growth of the At-induced gall. Anatomical analysis revealed the presence of cells with enlarged nuclei and multiple nucleoli, giant cells and suberin deposition in Pag that were absent from At-induced galls. Although circular vessels were observed in both gall types, they were more numerous and the vascular system was more organized in At. An aerenchymal tissue was observed in the upper part of the galls. Ethylene emission from Pag galls, recorded 6 days after inoculation, was eight times as great as that from non-infected controls. In contrast, a significant decrease in ethylene production was observed in Gypsophila cuttings infected with Pag mutants deficient in IAA and CK production. The results presented are best accounted for by the two pathogens having distinct pathogenicity mechanisms that lead to their differential recognition by the host as non-self (Pag) and self (At).

  3. Expression of the synaptic exocytosis-regulating molecule complexin 2 in taste buds and its participation in peripheral taste transduction.

    PubMed

    Kurokawa, Azusa; Narukawa, Masataka; Ohmoto, Makoto; Yoshimoto, Joto; Abe, Keiko; Misaka, Takumi

    2015-06-01

    Taste information from type III taste cells to gustatory neurons is thought to be transmitted via synapses. However, the molecular mechanisms underlying taste transduction through this pathway have not been fully elucidated. In this study, to identify molecules that participate in synaptic taste transduction, we investigated whether complexins (Cplxs), which play roles in regulating membrane fusion in synaptic vesicle exocytosis, were expressed in taste bud cells. Among four Cplx isoforms, strong expression of Cplx2 mRNA was detected in type III taste cells. To investigate the function of CPLX2 in taste transduction, we observed taste responses in CPLX2-knockout mice. When assessed with electrophysiological and behavioral assays, taste responses to some sour stimuli in CPLX2-knockout mice were significantly lower than those in wild-type mice. These results suggested that CPLX2 participated in synaptic taste transduction from type III taste cells to gustatory neurons. A part of taste information is thought to be transmitted via synapses. However, the molecular mechanisms have not been fully elucidated. To identify molecules that participate in synaptic taste transduction, we investigated complexins (Cplxs) expression in taste bud cells. Strong expression of Cplx2 mRNA was detected in taste bud cells. Furthermore, taste responses to some sour stimuli in CPLX2- knockout mice were significantly lower than those in wild-type mice. These suggested that CPLX2 participated in synaptic taste transduction.

  4. Effects of electromagnetic field stimulation on cellular signal transduction mechanisms: Analyses of the effects of low frequency electromagnetic fields on calcium spiking in ROS 17/2.8 cells. Final report

    SciTech Connect

    Sisken, B.F.; Sisken, J.E.

    1997-12-01

    The general goals of this work were to determine whether resting levels of cellular second messengers, especially calcium, are affected by low-level electromagnetic fields and the mechanisms that could lead to such changes. The work performed was directed at (1) verifying the report of McLeod et al (1990) that low frequency sinusoidal EMF can alter basal calcium fluctuations in cultured ROS 17/2.8 osteoblast-like cells and (2) reproducing the findings of Luben et al (1982) that pulsed electromagnetic fields can affect PTH-stimulated adenylate cyclase activity in osteoblasts. Initially a system was constructed so that cells could be exposed to sinusoidal electric fields using platinum electrodes. In this system, the electrodes were separated from the cells and culture medium by agar barriers. A series of experiments indicated that this system was subject to a significant, though little-known artifact in which a not well understood interaction between the electrodes and sodium ions in the medium or in plain salt solutions led to frequency and amplitude dependent emission of photons that are recorded by the detection system. They therefore designed and constructed an air gap reactor system that utilizes a ferromagnetic core to direct the magnetic flux generated by a sinusoidal coil. Studies on the effects of a 15 Hz pulsed electromagnetic field (PEMF) on cyclic AMP metabolism were performed on ROS 17/2.8 and MC3T3 cells.

  5. Structural insight into partner specificity and phosphoryl transfer in two-component signal transduction.

    PubMed

    Casino, Patricia; Rubio, Vicente; Marina, Alberto

    2009-10-16

    The chief mechanism used by bacteria for sensing their environment is based on two conserved proteins: a sensor histidine kinase (HK) and an effector response regulator (RR). The signal transduction process involves highly conserved domains of both proteins that mediate autokinase, phosphotransfer, and phosphatase activities whose output is a finely tuned RR phosphorylation level. Here, we report the structure of the complex between the entire cytoplasmic portion of Thermotoga maritima class I HK853 and its cognate, RR468, as well as the structure of the isolated RR468, both free and BeF(3)(-) bound. Our results provide insight into partner specificity in two-component systems, recognition of the phosphorylation state of each partner, and the catalytic mechanism of the phosphatase reaction. Biochemical analysis shows that the HK853-catalyzed autokinase reaction proceeds by a cis autophosphorylation mechanism within the HK subunit. The results suggest a model for the signal transduction mechanism in two-component systems.

  6. Reactive oxygen species mediate insulin signal transduction in mouse hypothalamus.

    PubMed

    Onoue, Takeshi; Goto, Motomitsu; Tominaga, Takashi; Sugiyama, Mariko; Tsunekawa, Taku; Hagiwara, Daisuke; Banno, Ryoichi; Suga, Hidetaka; Sugimura, Yoshihisa; Arima, Hiroshi

    2016-04-21

    In the hypothalamus, several reports have implied that ROS mediate physiological effects of insulin. In this study, we investigated the mechanisms of insulin-induced ROS production and the effect of ROS on insulin signal transduction in mouse hypothalamic organotypic cultures. Insulin increased intracellular ROS, which were suppressed by NADPH oxidase inhibitor. H2O2 increased phospho-insulin receptor β (p-IRβ) and phospho-Akt (p-Akt) levels. Insulin-induced increases in p-IRβ and p-Akt levels were attenuated by ROS scavenger or NADPH oxidase inhibitor. Our data suggest that insulin-induced phosphorylation of IRβ and Akt is mediated via ROS which are predominantly produced by NADPH oxidase in mouse hypothalamus.

  7. Signal Transduction Model of Magnetic Sensing in Cryptochrome Mediated Photoreception

    NASA Astrophysics Data System (ADS)

    Todd, Phillise Tiffeny

    While migratory birds have long been known to use the Earth's magnetic field for navigation, the precise biophysical mechanism behind this magnetic sense remains unconfirmed. A leading theory of magnetoreception suggests a chemical compass model with a yet undetermined molecular reaction site and unknown magnetically sensitive reactants. The cryptochrome photoreceptor has emerged as a promising candidate site. This investigation numerically models the first order kinetics of cryptochrome mediated photoreception, in order to evaluate its ability to function as a magnetic sensor and transduce orientation information along a neural pathway. A signal-to-noise ratio is defined to quantify the threshold for the functioning of a cryptochrome-based chemical compass. The model suggests that a flavin-superoxide radical pair in cryptochrome functions as the chemical reactants for magnetoreception. Such a cryptochrome-based signal transduction model reasonably predicts the general light intensity and wavelength effects that have been experimentally observed in migratory birds.

  8. Graviperception in ciliates: steps in the transduction chain.

    PubMed

    Hemmersbach, R; Krause, M; Bräucker, R; Ivanova, K

    2005-01-01

    Ciliates represent suitable model systems to study the mechanisms of graviperception and signal transduction as they show clear gravity-induced behavioural responses (gravitaxis and gravikinesis). The cytoplasm seems to act as a "statolith" stimulating mechanosensitive ion channels in the cell membrane. In order to test this hypothesis, electrophysiological studies with Stylonychia mytilus were performed, revealing the proposed changes (de- or hyperpolarization) depending on the cell's spatial orientation. The behaviour of Paramecium and Stylonychia was also analyzed during variable acceleration conditions of parabolic flights (5th German Parabolic Flight Campaign, 2003). The corresponding data confirm the relaxation of the graviresponses in microgravity as well as the existence of thresholds of graviresponses, which are found to be in the range of 0.4xg (gravikinesis) and 0.6xg (gravitaxis).

  9. Graviperception in ciliates: Steps in the transduction chain

    NASA Astrophysics Data System (ADS)

    Hemmersbach, R.; Krause, M.; Bräucker, R.; Ivanova, K.

    Ciliates represent suitable model systems to study the mechanisms of graviperception and signal transduction as they show clear gravity-induced behavioural responses (gravitaxis and gravikinesis). The cytoplasm seems to act as a "statolith" stimulating mechanosensitive ion channels in the cell membrane. In order to test this hypothesis, electrophysiological studies with Stylonychia mytilus were performed, revealing the proposed changes (de- or hyperpolarization) depending on the cell's spatial orientation. The behaviour of Paramecium and Stylonychia was also analyzed during variable acceleration conditions of parabolic flights (5th German Parabolic Flight Campaign, 2003). The corresponding data confirm the relaxation of the graviresponses in microgravity as well as the existence of thresholds of graviresponses, which are found to be in the range of 0.4× g (gravikinesis) and 0.6× g (gravitaxis).

  10. Molecular biology of thermosensory transduction in C. elegans.

    PubMed

    Aoki, Ichiro; Mori, Ikue

    2015-10-01

    As the environmental temperature prominently influences diverse biological aspects of the animals, thermosensation and the subsequent information processing in the nervous system has attracted much attention in biology. Thermotaxis in the nematode Caenorhabditis elegans is an ideal behavioral paradigm by which to address the molecular mechanism underlying thermosensory transduction. Molecular genetic analysis in combination with other physiological and behavioral studies revealed that sensation of ambient temperature is mediated mainly by cyclic guanosine monophosphate (cGMP) signaling in thermosensory neurons. The information of the previously perceived temperature is also stored within the thermosensory neurons, and the consequence of the comparison between the past and the present temperature is conveyed to the downstream interneurons to further regulate the motor-circuits that encode the locomotion.

  11. Potential mechanism of apoptosis induced by ultrasound in human hepatocarcinoma cells via comparative proteomic analysis.

    PubMed

    Feng, Yi; Wan, Mingxi

    2015-01-01

    To analyze the potential molecular mechanism of ultrasound induced apoptosis in cancer cells, comparative proteomic methods were introduced in the study. After ultrasound exposure at the intensity of 1.2 W/cm2, the human SMMC-7721 hepatocarcinoma cells were stained by trypan blue to detect the morphologic changes, and then the flow cytometry was used to examine the percentage of early apoptosis via double staining of FITC-labelled Annexin V and Propidium iodide. The proteins were separated by two-dimensional (2D) SDS polyacrylamide gel electrophoresis (PAGE). Among them, the differently expressed proteins were identified by MALDI-TOF mass spectrometry to reveal the key proteins response to ultrasound exposure. It's proved early apoptosis of cells were induced by focused ultrasound. After ultrasound exposure, the expressing characteristics of several proteins changed, in which some proteins in HSP family are associated with apoptosis initiation. It is suggested that the focused ultrasound could be applied in the assistant cancer therapy. Moreover, it is proved the comparative proteomic methods could supply information about the protein expression to analyze the metabolic processes related to bio-effects of biomedical ultrasound.

  12. Galectin-3-induced cell spreading and motility relies on distinct signaling mechanisms compared to fibronectin.

    PubMed

    More, Shyam K; Chiplunkar, Shubhada V; Kalraiya, Rajiv D

    2016-05-01

    Secreted galectin-3 often gets incorporated into extracellular matrix and is utilized by cancer cells for spreading, movement, and metastatic dissemination. Here we investigate molecular mechanisms by which galectin-3 brings about these effects and compare it with fibronectin. Imaging of cells spread on fibronectin showed stress fibers throughout cell body, however, galectin-3-induced formation of parallel actin bundles in the lamellipodial region resulting in unique morphological features. FRAP analysis showed that the actin turnover in the lamellipodial region was much higher in cells spread on galectin-3 as compared to that on fibronectin. Rac1 activation is correlated with lamellipodial organization on both the substrates. Activation of Akt and Rac1, the regulators of actin dynamics, show inverse correlation with each other on both galectin-3 and fibronectin. Activation of Erk however, remained similar. Further, inhibition of activation of Akt and Erk inhibited spreading and motility of cells on galectin-3 but not on fibronectin. The results very comprehensively demonstrate distinct signaling pathways that regulate microfilament organization, lamellipodial structures, spreading, and movement of cells plated on galectin-3 as opposed to fibronectin.

  13. Genetic Analysis of Gravity Signal Transduction in Arabidopsis Roots

    NASA Astrophysics Data System (ADS)

    Masson, Patrick; Strohm, Allison; Barker, Richard; Su, Shih-Heng

    Like most other plant organs, roots use gravity as a directional guide for growth. Specialized cells within the columella region of the root cap (the statocytes) sense the direction of gravity through the sedimentation of starch-filled plastids (amyloplasts). Amyloplast movement and/or pressure on sensitive membranes triggers a gravity signal transduction pathway within these cells, which leads to a fast transcytotic relocalization of plasma-membrane associated auxin-efflux carrier proteins of the PIN family (PIN3 and PIN7) toward the bottom membrane. This leads to a polar transport of auxin toward the bottom flank of the cap. The resulting lateral auxin gradient is then transmitted toward the elongation zones where it triggers a curvature that ultimately leads to a restoration of vertical downward growth. Our laboratory is using strategies derived from genetics and systems biology to elucidate the molecular mechanisms that modulate gravity sensing and signal transduction in the columella cells of the root cap. Our previous research uncovered two J-domain-containing proteins, ARG1 and ARL2, as contributing to this process. Mutations in the corresponding paralogous genes led to alterations of root and hypocotyl gravitropism accompanied by an inability for the statocytes to develop a cytoplasmic alkalinization, relocalize PIN3, and transport auxin laterally, in response to gravistimulation. Both proteins are associated peripherally to membranes belonging to various compartments of the vesicular trafficking pathway, potentially modulating the trafficking of defined proteins between plasma membrane and endosomes. MAR1 and MAR2, on the other end, are distinct proteins of the plastidic outer envelope protein import TOC complex (the transmembrane channel TOC75 and the receptor TOC132, respectively). Mutations in the corresponding genes enhance the gravitropic defects of arg1. Using transformation-rescue experiments with truncated versions of TOC132 (MAR2), we have shown

  14. In search of cellular control: signal transduction in context

    NASA Technical Reports Server (NTRS)

    Ingber, D.

    1998-01-01

    The field of molecular cell biology has experienced enormous advances over the last century by reducing the complexity of living cells into simpler molecular components and binding interactions that are amenable to rigorous biochemical analysis. However, as our tools become more powerful, there is a tendency to define mechanisms by what we can measure. The field is currently dominated by efforts to identify the key molecules and sequences that mediate the function of critical receptors, signal transducers, and molecular switches. Unfortunately, these conventional experimental approaches ignore the importance of supramolecular control mechanisms that play a critical role in cellular regulation. Thus, the significance of individual molecular constituents cannot be fully understood when studied in isolation because their function may vary depending on their context within the structural complexity of the living cell. These higher-order regulatory mechanisms are based on the cell's use of a form of solid-state biochemistry in which molecular components that mediate biochemical processing and signal transduction are immobilized on insoluble cytoskeletal scaffolds in the cytoplasm and nucleus. Key to the understanding of this form of cellular regulation is the realization that chemistry is structure and hence, recognition of the the importance of architecture and mechanics for signal integration and biochemical control. Recent work that has unified chemical and mechanical signaling pathways provides a glimpse of how this form of higher-order cellular control may function and where paths may lie in the future.

  15. Structural insights of homotypic interaction domains in the ligand-receptor signal transduction of tumor necrosis factor (TNF)

    PubMed Central

    Park, Young-Hoon; Jeong, Mi Suk; Jang, Se Bok

    2016-01-01

    Several members of tumor necrosis factor receptor (TNFR) superfamily that these members activate caspase-8 from death-inducing signaling complex (DISC) in TNF ligand-receptor signal transduction have been identified. In the extrinsic pathway, apoptotic signal transduction is induced in death domain (DD) superfamily; it consists of a hexahelical bundle that contains 80 amino acids. The DD superfamily includes about 100 members that belong to four subfamilies: death domain (DD), caspase recruitment domain (CARD), pyrin domain (PYD), and death effector domain (DED). This superfamily contains key building blocks: with these blocks, multimeric complexes are formed through homotypic interactions. Furthermore, each DD-binding event occurs exclusively. The DD superfamily regulates the balance between death and survival of cells. In this study, the structures, functions, and unique features of DD superfamily members are compared with their complexes. By elucidating structural insights of DD superfamily members, we investigate the interaction mechanisms of DD domains; these domains are involved in TNF ligand-receptor signaling. These DD superfamily members play a pivotal role in the development of more specific treatments of cancer. [BMB Reports 2016; 49(3): 159-166] PMID:26615973

  16. Activity Dependent Signal Transduction in Skeletal Muscle

    NASA Technical Reports Server (NTRS)

    Hamilton, Susan L.

    1999-01-01

    The overall goals of this project are: 1) to define the initial signal transduction events whereby the removal of gravitational load from antigravity muscles, such as the soleus, triggers muscle atrophy, and 2) to develop countermeasures to prevent this from happening. Our rationale for this approach is that, if countermeasures can be developed to regulate these early events, we could avoid having to deal with the multiple cascades of events that occur downstream from the initial event. One of our major findings is that hind limb suspension causes an early and sustained increase in intracellular Ca(2+) concentration ([Ca (2+)](sub i)). In most cells the consequences of changes in ([Ca (2+)](sub i))depend on the amplitude, frequency and duration of the Ca(2+) signal and on other factors in the intracellular environment. We propose that muscle remodeling in microgravity represents a change in the balance among several CA(2+) regulated signal transduction pathways, in particular those involving the transcription factors NFAT and NFkB and the pro-apoptotic protein BAD. Other Ca(2+) sensitive pathways involving PKC, ras, rac, and CaM kinase II may also contribute to muscle remodeling.

  17. Simulated evolution of signal transduction networks.

    PubMed

    Mobashir, Mohammad; Schraven, Burkhart; Beyer, Tilo

    2012-01-01

    Signal transduction is the process of routing information inside cells when receiving stimuli from their environment that modulate the behavior and function. In such biological processes, the receptors, after receiving the corresponding signals, activate a number of biomolecules which eventually transduce the signal to the nucleus. The main objective of our work is to develop a theoretical approach which will help to better understand the behavior of signal transduction networks due to changes in kinetic parameters and network topology. By using an evolutionary algorithm, we designed a mathematical model which performs basic signaling tasks similar to the signaling process of living cells. We use a simple dynamical model of signaling networks of interacting proteins and their complexes. We study the evolution of signaling networks described by mass-action kinetics. The fitness of the networks is determined by the number of signals detected out of a series of signals with varying strength. The mutations include changes in the reaction rate and network topology. We found that stronger interactions and addition of new nodes lead to improved evolved responses. The strength of the signal does not play any role in determining the response type. This model will help to understand the dynamic behavior of the proteins involved in signaling pathways. It will also help to understand the robustness of the kinetics of the output response upon changes in the rate of reactions and the topology of the network.

  18. Driving DNA transposition by lentiviral protein transduction

    PubMed Central

    Cai, Yujia; Mikkelsen, Jacob Giehm

    2014-01-01

    Gene vectors derived from DNA transposable elements have become powerful molecular tools in biomedical research and are slowly moving into the clinic as carriers of therapeutic genes. Conventional uses of DNA transposon-based gene vehicles rely on the intracellular production of the transposase protein from transfected nucleic acids. The transposase mediates mobilization of the DNA transposon, which is typically provided in the context of plasmid DNA. In recent work, we established lentiviral protein transduction from Gag precursors as a new strategy for direct delivery of the transposase protein. Inspired by the natural properties of infecting viruses to carry their own enzymes, we loaded lentivirus-derived particles not only with vector genomes carrying the DNA transposon vector but also with hundreds of transposase subunits. Such particles were found to drive efficient transposition of the piggyBac transposable element in a range of different cell types, including primary cells, and offer a new transposase delivery approach that guarantees short-term activity and limits potential cytotoxicity. DNA transposon vectors, originally developed and launched as a non-viral alternative to viral integrating vectors, have truly become viral. Here, we briefly review our findings and speculate on the perspectives and potential advantages of transposase delivery by lentiviral protein transduction. PMID:25057443

  19. Gene Expressions for Signal Transduction under Acidic Conditions

    PubMed Central

    Fukamachi, Toshihiko; Ikeda, Syunsuke; Wang, Xin; Saito, Hiromi; Tagawa, Masatoshi; Kobayashi, Hiroshi

    2013-01-01

    Although it is now well known that some diseased areas, such as cancer nests, inflammation loci, and infarction areas, are acidified, little is known about cellular signal transduction, gene expression, and cellular functions under acidic conditions. Our group showed that different signal proteins were activated under acidic conditions compared with those observed in a typical medium of around pH 7.4 that has been used until now. Investigations of gene expression under acidic conditions may be crucial to our understanding of signal transduction in acidic diseased areas. In this study, we investigated gene expression in mesothelioma cells cultured at an acidic pH using a DNA microarray technique. After 24 h culture at pH 6.7, expressions of 379 genes were increased more than twofold compared with those in cells cultured at pH 7.5. Genes encoding receptors, signal proteins including transcription factors, and cytokines including growth factors numbered 35, 32, and 17 among the 379 genes, respectively. Since the functions of 78 genes are unknown, it can be argued that cells may have other genes for signaling under acidic conditions. The expressions of 37 of the 379 genes were observed to increase after as little as 2 h. After 24 h culture at pH 6.7, expressions of 412 genes were repressed more than twofold compared with those in cells cultured at pH 7.5, and the 412 genes contained 35, 76, and 7 genes encoding receptors, signal proteins including transcription factors, and cytokines including growth factors, respectively. These results suggest that the signal pathways in acidic diseased areas are different, at least in part, from those examined with cells cultured at a pH of around 7.4. PMID:24705103

  20. The application of multiple biophysical cues to engineer functional neocartilage for treatment of osteoarthritis. Part II: signal transduction.

    PubMed

    Brady, Mariea A; Waldman, Stephen D; Ethier, C Ross

    2015-02-01

    The unique mechanoelectrochemical environment of cartilage has motivated researchers to investigate the effect of multiple biophysical cues, including mechanical, magnetic, and electrical stimulation, on chondrocyte biology. It is well established that biophysical stimuli promote chondrocyte proliferation, differentiation, and maturation within "biological windows" of defined dose parameters, including mode, frequency, magnitude, and duration of stimuli (see companion review Part I: Cellular Response). However, the underlying molecular mechanisms and signal transduction pathways activated in response to multiple biophysical stimuli remain to be elucidated. Understanding the mechanisms of biophysical signal transduction will deepen knowledge of tissue organogenesis, remodeling, and regeneration and aiding in the treatment of pathologies such as osteoarthritis. Further, this knowledge will provide the tissue engineer with a potent toolset to manipulate and control cell fate and subsequently develop functional replacement cartilage. The aim of this article is to review chondrocyte signal transduction pathways in response to mechanical, magnetic, and electrical cues. Signal transduction does not occur along a single pathway; rather a number of parallel pathways appear to be activated, with calcium signaling apparently common to all three types of stimuli, though there are different modes of activation. Current tissue engineering strategies, such as the development of "smart" functionalized biomaterials that enable the delivery of growth factors or integration of conjugated nanoparticles, may further benefit from targeting known signal transduction pathways in combination with external biophysical cues. PMID:25065615

  1. AAV-mediated photoreceptor transduction of the pig cone-enriched retina

    PubMed Central

    Mussolino, C; della Corte, M; Rossi, S; Viola, F; Di Vicino, U; Marrocco, E; Neglia, S; Doria, M; Testa, F; Giovannoni, R; Crasta, M; Giunti, M; Villani, E; Lavitrano, M; Bacci, M L; Ratiglia, R; Simonelli, F; Auricchio, A; Surace, E M

    2011-01-01

    Recent success in clinical trials supports the use of adeno-associated viral (AAV) vectors for gene therapy of retinal diseases caused by defects in the retinal pigment epithelium (RPE). In contrast, evidence of the efficacy of AAV-mediated gene transfer to retinal photoreceptors, the major site of inherited retinal diseases, is less robust. In addition, although AAV-mediated RPE transduction appears efficient, independently of the serotype used and species treated, AAV-mediated photoreceptor gene transfer has not been systematically investigated thus so far in large animal models, which also may allow identifying relevant species-specific differences in AAV-mediated retinal transduction. In the present study, we used the porcine retina, which has a high cone/rod ratio. This feature allows to properly evaluate both cone and rod photoreceptors transduction and compare the transduction characteristics of AAV2/5 and 2/8, the two most efficient AAV vector serotypes for photoreceptor targeting. Here we show that AAV2/5 and 2/8 transduces both RPE and photoreceptors. AAV2/8 infects and transduces photoreceptor more efficiently than AAV2/5, similarly to what we have observed in the murine retina. The use of the photoreceptor-specific rhodopsin promoter restricts transgene expression to porcine rods and cones, and results in photoreceptor transduction levels similar to those obtained with the ubiquitous promoters tested. Finally, immunological, toxicological and biodistribution studies support the safety of AAV subretinal administration to the large porcine retina. The data presented here on AAV-mediated transduction of the cone-enriched porcine retina may affect the development of gene-based therapies for rare and common severe photoreceptor diseases. PMID:21412286

  2. Reading Abilities of College Senior Industrial Arts Majors with Emphasis in Power Mechanics Compared with Readability of Power Mechanics Textbooks.

    ERIC Educational Resources Information Center

    Rose, Phillip Allen

    The purpose of this study was to determine the compatibility of the reading level of students with the required power-mechanics textbooks used by senior industrial arts majors in the California State University and Colleges System. The data for this study were obtained from responses to the Schrammel-Gray High School and College Reading Test…

  3. Sensory Transduction of the CO2 Response of Guard Cells

    SciTech Connect

    Dr. Eduardo Zeiger

    2003-06-30

    Stomata have a key role in the regulation of gas exchange and intercellular CO2 concentrations of leaves. Guard cells sense internal and external signals in the leaf environment and transduce these signals into osmoregulatory processes that control stomatal apertures. This research proposal addresses the characterization of the sensory transduction of the CO2 signal in guard cells. Recent studies have shown that in Vicia leaves kept at constant light and temperature in a growth chamber, changes in ambient CO2 concentrations cause large changes in guard cell zeaxanthin that are linear with CO2-dependent changes in stomatal apertures. Research proposed here will test the hypothesis that zeaxanthin function as a transducer of CO2 signals in guard cells. Three central aspects of this hypothesis will be investigated: CO2 sensing by the carboxylation reaction of Rubisco in the guard cell chloroplast, which would modulate zeaxanthin concentrations via changes in lumen pH; transduction of the CO2 signal by zeaxanthin via a transducing cascade that controls guard cell osmoregulation; and blue light dependence of the CO2 signal transduction by zeaxanthin, required for the formation of an isomeric form of zeaxanthin that is physiologically active as a transducer. The role of Rubisco in CO2 sensing will be investigated in experiments characterizing the stomatal response to CO2 in the Arabidopsis mutants R100 and rca-, which have reduced rates of Rubisco-dependent carboxylation. The role of zeaxanthin as a CO2 transducer will be studied in npq1, a zeaxanthin-less mutant. The blue light-dependence of CO2 sensing will be studied in experiments characterizing the stomatal response to CO2 under red light. Arabidopsis mutants will also be used in further studies of an acclimation of the stomatal response to CO2, and a possible role of the xanthophyll cycle of the guard cell chloroplast in acclimations of the stomatal response to CO2. Studies on the osmoregulatory role of sucrose in

  4. Comparing the mechanical influence of vinculin, focal adhesion kinase and p53 in mouse embryonic fibroblasts

    SciTech Connect

    Klemm, Anna H.; Diez, Gerold; Alonso, Jose-Luis

    2009-02-13

    Cytoskeletal reorganization is an ongoing process when cells adhere, move or invade extracellular substrates. The cellular force generation and transmission are determined by the intactness of the actomyosin-(focal adhesion complex)-integrin connection. We investigated the intracellular course of action in mouse embryonic fibroblasts deficient in the focal adhesion proteins vinculin and focal adhesion kinase (FAK) and the nuclear matrix protein p53 using magnetic tweezer and nanoparticle tracking techniques. Results show that the lack of these proteins decrease cellular stiffness and affect cell rheological behavior. The decrease in cellular binding strength was higher in FAK- to vinculin-deficient cells, whilst p53-deficient cells showed no effect compared to wildtype cells. The intracellular cytoskeletal activity was lowest in wildtype cells, but increased in the following order when cells lacked FAK+p53 > p53 > vinculin. In summary, cell mechanical processes are differently affected by the focal adhesion proteins vinculin and FAK than by the nuclear matrix protein, p53.

  5. Comparative study of the mechanical properties of nanostructured thin films on stretchable substrates

    SciTech Connect

    Djaziri, S.; Renault, P.-O.; Le Bourhis, E.; Goudeau, Ph.; Faurie, D.; Geandier, G.; Mocuta, C.; Thiaudière, D.

    2014-09-07

    Comparative studies of the mechanical behavior between copper, tungsten, and W/Cu nanocomposite based on copper dispersoïd thin films were performed under in-situ controlled tensile equi-biaxial loadings using both synchrotron X-ray diffraction and digital image correlation techniques. The films first deform elastically with the lattice strain equal to the true strain given by digital image correlation measurements. The Cu single thin film intrinsic elastic limit of 0.27% is determined below the apparent elastic limit of W and W/Cu nanocomposite thin films, 0.30% and 0.49%, respectively. This difference is found to be driven by the existence of as-deposited residual stresses. Above the elastic limit on the lattice strain-true strain curves, we discriminate two different behaviors presumably footprints of plasticity and fracture. The Cu thin film shows a large transition domain (0.60% true strain range) to a plateau with a smooth evolution of the curve which is associated to peak broadening. In contrast, W and W/Cu nanocomposite thin films show a less smooth and reduced transition domain (0.30% true strain range) to a plateau with no peak broadening. These observations indicate that copper thin film shows some ductility while tungsten/copper nanocomposites thin films are brittle. Fracture resistance of W/Cu nanocomposite thin film is improved thanks to the high compressive residual stress and the elimination of the metastable β-W phase.

  6. Knowledge representation model for systems-level analysis of signal transduction networks.

    PubMed

    Lee, Dong-Yup; Zimmer, Ralf; Lee, Sang-Yup; Hanisch, Daniel; Park, Sunwon

    2004-01-01

    A Petri-net based model for knowledge representation has been developed to describe as explicitly and formally as possible the molecular mechanisms of cell signaling and their pathological implications. A conceptual framework has been established for reconstructing and analyzing signal transduction networks on the basis of the formal representation. Such a conceptual framework renders it possible to qualitatively understand the cell signaling behavior at systems-level. The mechanisms of the complex signaling network are explored by applying the established framework to the signal transduction induced by potent proinflammatory cytokines, IL-1beta and TNF-alpha The corresponding expert-knowledge network is constructed to evaluate its mechanisms in detail. This strategy should be useful in drug target discovery and its validation.

  7. Energy implications of mechanical and mechanical–biological treatment compared to direct waste-to-energy

    SciTech Connect

    Cimpan, Ciprian Wenzel, Henrik

    2013-07-15

    Highlights: • Compared systems achieve primary energy savings between 34 and 140 MJ{sub primary}/100 MJ{sub input} {sub waste.} • Savings magnitude is foremost determined by chosen primary energy and materials production. • Energy consumption and process losses can be upset by increased technology efficiency. • Material recovery accounts for significant shares of primary energy savings. • Direct waste-to-energy is highly efficient if cogeneration (CHP) is possible. - Abstract: Primary energy savings potential is used to compare five residual municipal solid waste treatment systems, including configurations with mechanical (MT) and mechanical–biological (MBT) pre-treatment, which produce waste-derived fuels (RDF and SRF), biogas and/or recover additional materials for recycling, alongside a system based on conventional mass burn waste-to-energy and ash treatment. To examine the magnitude of potential savings we consider two energy efficiency levels (state-of-the-art and best available technology), the inclusion/exclusion of heat recovery (CHP vs. PP) and three different background end-use energy production systems (coal condensing electricity and natural gas heat, Nordic electricity mix and natural gas heat, and coal CHP energy quality allocation). The systems achieved net primary energy savings in a range between 34 and 140 MJ{sub primary}/100 MJ{sub input} {sub waste}, in the different scenario settings. The energy footprint of transportation needs, pre-treatment and reprocessing of recyclable materials was 3–9.5%, 1–18% and 1–8% respectively, relative to total energy savings. Mass combustion WtE achieved the highest savings in scenarios with CHP production, nonetheless, MBT-based systems had similarly high performance if SRF streams were co-combusted with coal. When RDF and SRF was only used in dedicated WtE plants, MBT-based systems totalled lower savings due to inherent system losses and additional energy costs. In scenarios without heat

  8. Influence of Unweighting on Insulin Signal Transduction in Muscle

    NASA Technical Reports Server (NTRS)

    Tischler, Marc E.

    2002-01-01

    Unweighting of the juvenile soleus muscle is characterized by an increased binding capacity for insulin relative to muscle mass due to sparing of the receptors during atrophy. Although carbohydrate metabolism and protein degradation in the unweighted muscle develop increased sensitivity to insulin in vivo, protein synthesis in vivo and system A amino acid transport in vitro do not appear to develop such an enhanced response. The long-term goal is to identify the precise nature of this apparent resistance in the insulin signal transduction pathway and to consider how reduced weight-bearing may elicit this effect, by evaluating specific components of the insulin signalling pathway. Because the insulin-signalling pathway has components in common with the signal transduction pathway for insulin-like growth factor (IGF-1) and potentially other growth factors, the study could have important implications in the role of weight-bearing function on muscle growth and development. Since the insulin signalling pathway diverges following activation of insulin receptor tyrosine kinase, the immediate specific aims will be to study the receptor tyrosine kinase (IRTK) and those branches, which lead to phosphorylation of insulin receptor substrate-1 (IRS-1) and of Shc protein. To achieve these broader objectives, we will test in situ, by intramuscular injection, the responses of glucose transport, system A amino acid transport and protein synthesis to insulin analogues for which the receptor has either a weaker or much stronger binding affinity compared to insulin. Studies will include: (1) estimation of the ED(sub 50) for each analogue for these three processes; (2) the effect of duration (one to four days) of unweighting on the response of each process to all analogues tested; (3) the effect of unweighting and the analogues on IRTK activity; and (4) the comparative effects of unweighting and analogue binding on the tyrosine phosphorylation of IRTK, IRS-1, and Shc protein.

  9. Modeling the infection dynamics of bacteriophages in enteric Escherichia coli: estimating the contribution of transduction to antimicrobial gene spread.

    PubMed

    Volkova, Victoriya V; Lu, Zhao; Besser, Thomas; Gröhn, Yrjö T

    2014-07-01

    Animal-associated bacterial communities are infected by bacteriophages, although the dynamics of these infections are poorly understood. Transduction by bacteriophages may contribute to transfer of antimicrobial resistance genes, but the relative importance of transduction among other gene transfer mechanisms is unknown. We therefore developed a candidate deterministic mathematical model of the infection dynamics of enteric coliphages in commensal Escherichia coli in the large intestine of cattle. We assumed the phages were associated with the intestine and were predominantly temperate. Model simulations demonstrated how, given the bacterial ecology and infection dynamics, most (>90%) commensal enteric E. coli bacteria may become lysogens of enteric coliphages during intestinal transit. Using the model and the most liberal assumptions about transduction efficiency and resistance gene frequency, we approximated the upper numerical limits ("worst-case scenario") of gene transfer through specialized and generalized transduction in E. coli by enteric coliphages when the transduced genetic segment is picked at random. The estimates were consistent with a relatively small contribution of transduction to lateral gene spread; for example, generalized transduction delivered the chromosomal resistance gene to up to 8 E. coli bacteria/hour within the population of 1.47 × 10(8) E. coli bacteria/liter luminal contents. In comparison, the plasmidic blaCMY-2 gene carried by ~2% of enteric E. coli was transferred by conjugation at a rate at least 1.4 × 10(3) times greater than our generalized transduction estimate. The estimated numbers of transductants varied nonlinearly depending on the ecology of bacteria available for phages to infect, that is, on the assumed rates of turnover and replication of enteric E. coli.

  10. Comparative study of mechanical properties of dental restorative materials and dental hard tissues in compressive loads

    PubMed Central

    Lee, Jong Yeop

    2014-01-01

    There are two objectives. One is to show the differences in the mechanical properties of various dental restorative materials compared to those of enamel and dentin. The other is to ascertain which dental restorative materials are more suitable for clinical treatments. Amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy were processed as dental restorative material specimens. The specimens (width, height, and length of 1.2, 1.2, and 3.0 mm, respectively) were compressed at a constant loading speed of 0.1 mm/min. The maximum stress (115.0 ± 40.6, 55.0 ± 24.8, 291.2 ± 45.3, 274.6 ± 52.2, 2206.0 ± 522.9, and 953.4 ± 132.1 MPa), maximum strain (7.8% ± 0.5%, 4.0% ± 0.1%, 12.7% ± 0.8%, 32.8% ± 0.5%, 63.5% ± 14.0%, and 45.3% ± 7.4%), and elastic modulus (1437.5 ± 507.2, 1548.4 ± 583.5, 2323.4 ± 322.4, 833.1 ± 92.4, 3895.2 ± 202.9, and 2222.7 ± 277.6 MPa) were evident for amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy, respectively. The reference hardness value of amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy was 90, 420, 130–135, 86.6–124.2, 1250, and 349, respectively. Since enamel grinds food, its abrasion resistance is important. Therefore, hardness value should be prioritized for enamel. Since dentin absorbs bite forces, mechanical properties should be prioritized for dentin. The results suggest that gold alloy simultaneously has a hardness value lower than enamel (74.8 ± 18.1), which is important in the wear of the opposing natural teeth, and higher maximum stress, maximum strain, and elastic modulus than dentin (193.7 ± 30.6 MPa, 11.9% ± 0.1%, 1653.7 ± 277.9 MPa, respectively), which are important considering the rigidity to absorb bite forces. PMID:25352921

  11. Decitabine suspends human CD34+ cell differentiation and proliferation during lentiviral transduction.

    PubMed

    Uchida, Naoya; Hsieh, Matthew M; Platner, Charlotte; Saunthararajah, Yogen; Tisdale, John F

    2014-01-01

    Efficient ex vivo transduction of hematopoietic stem cells (HSCs) is encumbered by differentiation which reduces engraftment. We hypothesized that inhibiting DNA methyltransferase with decitabine would block differentiation of transduced CD34+ cells under cytokine stimulation and thus improve transduction efficiency for engrafting HSCs. Human CD34+ cells in cytokine-containing media were treated with or without decitabine for 24 or 48 hours, and then these cells were transduced with a GFP-expressing lentiviral vector. Utilizing decitabine pre-treatment for 48 hours, we observed an equivalent percentage of successfully transduced cells (GFP-positivity) and a higher percentage of cells that retained CD34 positivity, compared to no decitabine exposure. Cell proliferation was inhibited after decitabine exposure. Similar results were observed among CD34+ cells from six different donors. Repopulating activity was evaluated by transplantation into NOD/SCID/IL2Rγnull mice and demonstrated an equivalent percentage of GFP-positivity in human cells from decitabine-treated samples and a trend for higher human cell engraftment (measured 20-24 weeks after transplantation), compared to no decitabine exposure. In conclusion, ex vivo decitabine exposure inhibits both differentiation and proliferation in transduced human CD34+ cells and modestly increases the engraftment ability in xenograft mice, while the transduction efficiency is equivalent in decitabine exposure, suggesting improvement of lentiviral transduction for HSCs.

  12. Hedgehog Secretion and Signal Transduction in Vertebrates

    PubMed Central

    Ryan, Kaitlyn E.; Chiang, Chin

    2012-01-01

    Signaling by the Hedgehog (Hh) family of secreted proteins is essential for proper embryonic patterning and development. Dysregulation of Hh signaling is associated with a variety of human diseases ranging from developmental disorders such as holoprosencephaly to certain forms of cancer, including medulloblastoma and basal cell carcinoma. Genetic studies in flies and mice have shaped our understanding of Hh signaling and revealed that nearly all core components of the pathway are highly conserved. Although many aspects of the Drosophila Hh pathway are conserved in vertebrates, mechanistic differences between the two species have begun to emerge. Perhaps the most striking divergence in vertebrate Hh signaling is its dependence on the primary cilium, a vestigial organelle that is largely absent in flies. This minireview will provide an overview of Hh signaling and present recent insights into vertebrate Hh secretion, receptor binding, and signal transduction. PMID:22474285

  13. Green Light to Illuminate Signal Transduction Events

    PubMed Central

    Balla, Tamas

    2009-01-01

    When cells are exposed to hormones that act on cell surface receptors, information is processed through the plasma membrane into the cell interior via second messengers generated in the inner leaflet of the plasma membrane. Individual biochemical steps along this cascade, starting with ligand binding to receptors to activation of guanine nucleotide binding proteins and their downstream effectors such as adenylate cyclase or phospholipase C, have been biochemically characterized. However, the complexity of temporal and spatial integration of these molecular events requires that they be studied in intact cells. The great expansion of fluorescent techniques and improved imaging technologies such as confocal- and TIRF microscopy combined with genetically engineered protein modules has provided a completely new approach to signal transduction research. Spatial definition of biochemical events followed with real-time temporal resolution has become a standard goal and we are breaking the resolution barrier of light microscopes with several new techniques. PMID:19818623

  14. Mechanical Signal Transduction in Countermeasures to Muscle Atrophy

    NASA Technical Reports Server (NTRS)

    Tidball, James G.; Chu, Amy (Technical Monitor)

    2002-01-01

    We have shown that modifications in muscle use result in changes in the expression and activity of calpains and nitric oxide synthase (NOS). Although muscle unloading for 10 days produced no change in the concentrations of calpain 1 or 2 and no change in calpain activation, muscle reloading produced a 90% increase in calpain 2 concentration. We developed an in vitro model to test our hypothesis that nitric oxide can inhibit cytoskeletal breakdown in skeletal muscle cells by inhibiting calpain cleavage of talin. Talin was selected because it is a well-characterized calpain substrate and it is codistributed with calpain in muscle cells. We found that intermittant loading during hindlimb suspension that is sufficient to prevent muscle mass loss that occurs during muscle unloading is also sufficient to prevent the decrease in NOS expression that normally occurs during hindlimb unloading. These findings indicate that therapeutics directed toward regulating the calpain/calpastatin system may be beneficial in preventing muscle mass loss in muscle injury, unloading and disease.

  15. Enrichment of human hematopoietic stem/progenitor cells facilitates transduction for stem cell gene therapy.

    PubMed

    Baldwin, Kismet; Urbinati, Fabrizia; Romero, Zulema; Campo-Fernandez, Beatriz; Kaufman, Michael L; Cooper, Aaron R; Masiuk, Katelyn; Hollis, Roger P; Kohn, Donald B

    2015-05-01

    Autologous hematopoietic stem cell (HSC) gene therapy for sickle cell disease has the potential to treat this illness without the major immunological complications associated with allogeneic transplantation. However, transduction efficiency by β-globin lentiviral vectors using CD34-enriched cell populations is suboptimal and large vector production batches may be needed for clinical trials. Transducing a cell population more enriched for HSC could greatly reduce vector needs and, potentially, increase transduction efficiency. CD34(+) /CD38(-) cells, comprising ∼1%-3% of all CD34(+) cells, were isolated from healthy cord blood CD34(+) cells by fluorescence-activated cell sorting and transduced with a lentiviral vector expressing an antisickling form of beta-globin (CCL-β(AS3) -FB). Isolated CD34(+) /CD38(-) cells were able to generate progeny over an extended period of long-term culture (LTC) compared to the CD34(+) cells and required up to 40-fold less vector for transduction compared to bulk CD34(+) preparations containing an equivalent number of CD34(+) /CD38(-) cells. Transduction of isolated CD34(+) /CD38(-) cells was comparable to CD34(+) cells measured by quantitative PCR at day 14 with reduced vector needs, and average vector copy/cell remained higher over time for LTC initiated from CD34(+) /38(-) cells. Following in vitro erythroid differentiation, HBBAS3 mRNA expression was similar in cultures derived from CD34(+) /CD38(-) cells or unfractionated CD34(+) cells. In vivo studies showed equivalent engraftment of transduced CD34(+) /CD38(-) cells when transplanted in competition with 100-fold more CD34(+) /CD38(+) cells. This work provides initial evidence for the beneficial effects from isolating human CD34(+) /CD38(-) cells to use significantly less vector and potentially improve transduction for HSC gene therapy.

  16. Bacterial stimulus perception and signal transduction: response to osmotic stress.

    PubMed

    Krämer, Reinhard

    2010-08-01

    When exposed to osmotic stress from the environment, bacteria act to maintain cell turgor and hydration by responding both on the level of gene transcription and protein activity. Upon a sudden decrease in external osmolality, internal solutes are released by the action of membrane embedded mechanosensitive channels. In response to an osmotic upshift, the concentration of osmolytes in the cytoplasm is increased both by de novo synthesis and by active uptake. In order to coordinate these processes of osmoregulation, cells are equipped with systems and mechanisms of sensing physical stimuli correlated to changes in the external osmolality (osmosensing), with pathways to transduce these stimuli into useful signals which can be processed in the cell (signal transduction), and mechanisms of regulating proper responses in the cell to recover from the environmental stress and to maintain all necessary physiological functions (osmoregulation). These processes will be described by a number of representative examples, mainly of osmoreactive transport systems with a focus on available data of their molecular mechanism.

  17. High frequency generalized transduction by miniMu plasmid phage.

    PubMed

    Wang, B M; Liu, L; Groisman, E A; Casadaban, M J; Berg, C M

    1987-06-01

    Deletion derivatives of phage Mu which replicate as multicopy plasmids, and also transpose and package like Mu, have been developed for the in vivo cloning of bacterial genes. We show here that these miniMu plasmid phage are also efficient at generalized transduction and that both in vivo cloning and generalized transduction of a given gene can be accomplished in a single experiment.

  18. Role of functionality in two-component signal transduction: A stochastic study

    NASA Astrophysics Data System (ADS)

    Maity, Alok Kumar; Bandyopadhyay, Arnab; Chaudhury, Pinaki; Banik, Suman K.

    2014-03-01

    We present a stochastic formalism for signal transduction processes in a bacterial two-component system. Using elementary mass action kinetics, the proposed model takes care of signal transduction in terms of a phosphotransfer mechanism between the cognate partners of a two-component system, viz., the sensor kinase and the response regulator. Based on the difference in functionality of the sensor kinase, the noisy phosphotransfer mechanism has been studied for monofunctional and bifunctional two-component systems using the formalism of the linear noise approximation. Steady-state analysis of both models quantifies different physically realizable quantities, e.g., the variance, the Fano factor (variance/mean), and mutual information. The resultant data reveal that both systems reliably transfer information of extracellular environment under low external stimulus and in a high-kinase-and-phosphatase regime. We extend our analysis further by studying the role of the two-component system in downstream gene regulation.

  19. The Membrane and Lipids as Integral Participants in Signal Transduction: Lipid Signal Transduction for the Non-Lipid Biochemist

    ERIC Educational Resources Information Center

    Eyster, Kathleen M.

    2007-01-01

    Reviews of signal transduction have often focused on the cascades of protein kinases and protein phosphatases and their cytoplasmic substrates that become activated in response to extracellular signals. Lipids, lipid kinases, and lipid phosphatases have not received the same amount of attention as proteins in studies of signal transduction.…

  20. The MiST2 database: a comprehensive genomics resource on microbial signal transduction

    PubMed Central

    Ulrich, Luke E.; Zhulin, Igor B.

    2010-01-01

    The MiST2 database (http://mistdb.com) identifies and catalogs the repertoire of signal transduction proteins in microbial genomes. Signal transduction systems regulate the majority of cellular activities including the metabolism, development, host-recognition, biofilm production, virulence, and antibiotic resistance of human pathogens. Thus, knowledge of the proteins and interactions that comprise these communication networks is an essential component to furthering biomedical discovery. These are identified by searching protein sequences for specific domain profiles that implicate a protein in signal transduction. Compared to the previous version of the database, MiST2 contains a host of new features and improvements including the following: draft genomes; extracytoplasmic function (ECF) sigma factor protein identification; enhanced classification of signaling proteins; novel, high-quality domain models for identifying histidine kinases and response regulators; neighboring two-component genes; gene cart; better search capabilities; enhanced taxonomy browser; advanced genome browser; and a modern, biologist-friendly web interface. MiST2 currently contains 966 complete and 157 draft bacterial and archaeal genomes, which collectively contain more than 245 000 signal transduction proteins. The majority (66%) of these are one-component systems, followed by two-component proteins (26%), chemotaxis (6%), and finally ECF factors (2%). PMID:19900966

  1. Mechanical properties of adsorption layers in solutions of human blood serum proteins: A comparative assessment

    NASA Astrophysics Data System (ADS)

    Yakhno, T. A.; Kazakov, V. V.; Sanin, A. G.; Shaposhnikova, O. B.; Chernov, A. S.

    2007-04-01

    The mechanical properties of adsorption layers in small volumes (0.1 ml) of protein solutions in a saline are studied using small-diameter indenters. In an albumin solution, the partial substitution of the protein by an equivalent (by weight) amount of immunoglobulins G or M reduces the surface energy, whereas the addition of fibronectin improves the mechanical strength of the layer. The data obtained may provide a deeper insight into the mechanisms of specific dynamic processes responsible for the structuring of biological fluids in drying drops. In particular, such information is of value for medical diagnosis.

  2. [Polyurethane denture base material "Pentalur" and modified polyurethane compositions: comparative study of mechanical properties].

    PubMed

    Al'ter, Iu M; Tkachuk, A-M P; Poiurovskaia, I Ia; Sutugina, T F; Ogorodnikov, M Iu

    2013-01-01

    Results of laboratory tests of polyurethane based material "Pentalur" conducted to determine its mechanical properties proved the material to meet basic requirements for removable dentures materials. The introduction of simple poluethers with certain molecular weight as well as 1,4-butanediol allows varying polyurethane properties in a fairly wide range. This range of polyurethane mechanical properties along with good biocompatibility opens new possibilities in creation of removable dentures with improved functional properties as well as maxillofacial prosthesis.

  3. Glycosphingolipid–Protein Interaction in Signal Transduction

    PubMed Central

    Russo, Domenico; Parashuraman, Seetharaman; D’Angelo, Giovanni

    2016-01-01

    Glycosphingolipids (GSLs) are a class of ceramide-based glycolipids essential for embryo development in mammals. The synthesis of specific GSLs depends on the expression of distinctive sets of GSL synthesizing enzymes that is tightly regulated during development. Several reports have described how cell surface receptors can be kept in a resting state or activate alternative signalling events as a consequence of their interaction with GSLs. Specific GSLs, indeed, interface with specific protein domains that are found in signalling molecules and which act as GSL sensors to modify signalling responses. The regulation exerted by GSLs on signal transduction is orthogonal to the ligand–receptor axis, as it usually does not directly interfere with the ligand binding to receptors. Due to their properties of adjustable production and orthogonal action on receptors, GSLs add a new dimension to the control of the signalling in development. GSLs can, indeed, dynamically influence progenitor cell response to morphogenetic stimuli, resulting in alternative differentiation fates. Here, we review the available literature on GSL–protein interactions and their effects on cell signalling and development. PMID:27754465

  4. Pinniped diving response mechanism and evolution: a window on the paradigm of comparative biochemistry and physiology.

    PubMed

    Hochachka, P W

    2000-08-01

    Starting even before the end of World War II, the discipline of comparative physiology and biochemistry experienced a period of unprecedented growth and development that pioneers in this field thought would never end. However, by the mid-1970s many of the major mechanistic problems in the field were pretty well understood in principle, and by the mid-1980s workers in the field widely recognized that the discipline was at the point of diminishing returns. One response to this was disillusionment, which turned out to be premature because the field was already absorbing molecular biology tools which has now caused a kind of renaissance in mechanistic physiology studies. The second major response to the sense of disillusionment led to a search for new approaches, and out of this endeavor the newly rejuvenated field of evolutionary physiology arose, and this research area too is now in a growth phase. These general patterns of growth and development in our discipline as a whole are particularly clearly evident in the field of aquatic mammals and birds. Between the 1930s and the 1970s, studies of diving physiology and biochemistry made great progress in mechanistically explaining the basic diving response of aquatic mammals and birds. Key components of the diving response (apnea, bradycardia, peripheral vasoconstriction, redistribution of cardiac output) were found in essentially all species analyzed and were generally taken to be biological adaptations. By the mid-1970s, this approach to unraveling the diving response had run 'out of steam' and was in conceptual stasis. The breakthrough which gave renewal to the field at this time was the development of microprocessor based monitoring of diving animals in their natural environments, which led to a flurry of studies mostly confirming the essential outlines of the diving response based upon laboratory studies and firmly placing it into a proper biological context, underlining its plasticity and species specificities. Now

  5. Cytoplasmic transduction peptide (CTP): New approach for the delivery of biomolecules into cytoplasm in vitro and in vivo

    SciTech Connect

    Kim, Daeyou; Jeon, Choonju; Kim, Jeong-Hwan; Kim, Mi-Seon; Yoon, Cheol-Hee; Choi, In-Soo; Kim, Sung-Hoon; Bae, Yong-Soo . E-mail: ysbae04@skku.edu

    2006-05-01

    The protein transduction domain (PTD) of HIV-1 TAT has been extensively documented with regard to its membrane transduction potential, as well as its efficient delivery of biomolecules in vivo. However, the majority of PTD and PTD-conjugated molecules translocate to the nucleus rather than to the cytoplasm after transduction, due to the functional nuclear localization sequence (NLS). Here, we report a cytoplasmic transduction peptide (CTP), which was deliberately designed to ensure the efficient cytoplasmic delivery of the CTP-fused biomolecules. In comparison with PTD, CTP and its fusion partners exhibited a clear preference for cytoplasmic localization, and also markedly enhanced membrane transduction potential. Unlike the mechanism underlying PTD-mediated transduction, CTP-mediated transduction occurs independently of the lipid raft-dependent macropinocytosis pathway. The CTP-conjugated Smac/DIABLO peptide (Smac-CTP) was also shown to be much more efficient than Smac-PTD in the blockage of the antiapoptotic properties of XIAP, suggesting that cytoplasmic functional molecules can be more efficiently targeted by CTP-mediated delivery. In in vivo trafficking studies, CTP-fused {beta}-gal exhibited unique organ tropisms to the liver and lymph nodes when systemically injected into mice, whereas PTD-{beta}-gal exhibited no such tropisms. Taken together, our findings implicate CTP as a novel delivery peptide appropriate for (i) molecular targeting to cytoplasmic compartments in vitro, (ii) the development of class I-associated CTL vaccines, and (iii) special drug delivery in vivo, without causing any untoward effects on nuclear genetic material.

  6. Ultrasonic Transduction of DNA into Central Nervous System Cells

    NASA Astrophysics Data System (ADS)

    Manome, Yoshinobu; Nakayama, Naoto; Furuhata, Hiroshi

    2005-03-01

    Many diseases involving the central nervous system are intractable to conventional therapies, thereby requiring an alternative treatment such as gene therapy. Therapy requires safety since the central nervous system is a critical organ. The choice of non-viral vectors, such as naked plasmid DNA, may have merit. However, transduction efficiencies of these vectors are low. We have investigated the use of ultrasound and found that insonation effectively enhanced transduction of naked plasmid DNA into cultured slices of mouse brain. Since ultrasound successfully facilitated the transduction of naked plasmid DNA into the neural tissue, this approach may have a role in gene therapy for the central nervous system.

  7. A comparative study of commercial lithium ion battery cycle life in electrical vehicle: Aging mechanism identification

    NASA Astrophysics Data System (ADS)

    Han, Xuebing; Ouyang, Minggao; Lu, Languang; Li, Jianqiu; Zheng, Yuejiu; Li, Zhe

    2014-04-01

    When lithium-ion batteries age with cycling, the battery capacity decreases and the resistance increases. The aging mechanism of different types of lithium-ion batteries differs. The loss of lithium inventory, loss of active material, and the increase in resistance may result in battery aging. Generally, analysis of the battery aging mechanism requires dismantling of batteries and using methods such as X-ray diffraction and scanning electron microscopy. These methods may permanently damage the battery. Therefore, the methods are inappropriate for the battery management system (BMS) in an electric vehicle. The constant current charging curves while charging the battery could be used to get the incremental capacity and differential voltage curves for identifying the aging mechanism; the battery state-of-health can then be estimated. This method can be potentially used in the BMS for online diagnostic and prognostic services. The genetic algorithm could be used to quantitatively analyze the battery aging offline. And the membership function could be used for onboard aging mechanism identification.

  8. MiR-10a improves hepatic fibrosis by regulating the TGFβl/Smads signal transduction pathway

    PubMed Central

    Zhou, Guangyao; Lin, Wei; Fang, Peipei; Lin, Xiuzhen; Zhuge, Lu; Hu, Zhiqiu; Jin, Lingxiang

    2016-01-01

    The aim of the present study was to examine the expression variation of the mouse hepatic fibrosis tissue transforming growth factor (TGF)-βl/Smads signal transduction pathway and its correlation with progression of hepatic fibrosis. The promotion effect of microRNA (miR)-10a on hepatic fibrosis and its possible mechanism was also assessed. Forty healthy female 8-week-old C57BL6/J mice were randomly divided into the control group (intraperitoneal injection of 5 µl/g normal saline, twice per week for 8 weeks) and the hepatic fibrosis group (intraperitoneal injection of 5 µl/g 10% CCI4 olive oil, twice per week for 8 weeks), with 20 mice per group. RT-PCR was used to test miR-10a expression in cells in the control and hepatic fibrosis groups. Cell culture and transfection of miR-10a mimics were conducted in the two groups and a Cell Counting Kit-8 was used to test the expression of TGF-β1 and Smad7 in hepatic fibroblasts. It was found that in comparison with the control group, miR-10a expression was significantly increased in the hepatic fibrosis group compared with the control group (P<0.05). The expression quantity of miR-10a was significantly increased in the transfection group compared with the control group (P<0.05). A high expression of miR-10a significantly improved TGF-β1 expression and reduced Smad7 expression in the hepatic fibrosis group (P<0.05). In conclusion, miR-10a expression was high in mouse hepatic tissues, transfection of miR-10a mimics significantly promoted the cell proliferation of hepatic fibrosis, and miR-10a improved hepatic fibrosis by regulating the TGF-βl/Smads signal transduction pathway. PMID:27602086

  9. MiR-10a improves hepatic fibrosis by regulating the TGFβl/Smads signal transduction pathway

    PubMed Central

    Zhou, Guangyao; Lin, Wei; Fang, Peipei; Lin, Xiuzhen; Zhuge, Lu; Hu, Zhiqiu; Jin, Lingxiang

    2016-01-01

    The aim of the present study was to examine the expression variation of the mouse hepatic fibrosis tissue transforming growth factor (TGF)-βl/Smads signal transduction pathway and its correlation with progression of hepatic fibrosis. The promotion effect of microRNA (miR)-10a on hepatic fibrosis and its possible mechanism was also assessed. Forty healthy female 8-week-old C57BL6/J mice were randomly divided into the control group (intraperitoneal injection of 5 µl/g normal saline, twice per week for 8 weeks) and the hepatic fibrosis group (intraperitoneal injection of 5 µl/g 10% CCI4 olive oil, twice per week for 8 weeks), with 20 mice per group. RT-PCR was used to test miR-10a expression in cells in the control and hepatic fibrosis groups. Cell culture and transfection of miR-10a mimics were conducted in the two groups and a Cell Counting Kit-8 was used to test the expression of TGF-β1 and Smad7 in hepatic fibroblasts. It was found that in comparison with the control group, miR-10a expression was significantly increased in the hepatic fibrosis group compared with the control group (P<0.05). The expression quantity of miR-10a was significantly increased in the transfection group compared with the control group (P<0.05). A high expression of miR-10a significantly improved TGF-β1 expression and reduced Smad7 expression in the hepatic fibrosis group (P<0.05). In conclusion, miR-10a expression was high in mouse hepatic tissues, transfection of miR-10a mimics significantly promoted the cell proliferation of hepatic fibrosis, and miR-10a improved hepatic fibrosis by regulating the TGF-βl/Smads signal transduction pathway.

  10. A scalable, high resolution strain sensing matrix suitable for tactile transduction.

    PubMed

    Scibelli, Anthony E; Krans, Jacob L

    2016-02-01

    The integration of tactile information, such as contact area, displacement magnitude, velocity, and acceleration, is paramount to the optimization of robotics in human-centric environments. Cost effective embeddable sensors with scalable receptive field size and strain sensitivity are not readily commercially available and would benefit investigations of in situ tissue mechanics. We describe the design and performance of a scalable sensor matrix that transduces fine parameters of strain and is made of combinable "modules". The sensors transduce static and dynamic strains of both uniaxial and multi-dimensional nature. Modules consist of three silicon wafers placed on top of and three on the bottom of a hexagonal collar, wafers are thus positioned 120° to one another to facilitate force vector extrapolation. Analog signals from each sensor can be easily compared to neighboring sensor output to determine mechanical phenomena such as slip or shear. The smallest of our prototype multiunit matrices consisted of seven hexes in a honeycomb orientation of 4.1mm diameter (containing 42 silicon gauges). Unamplified, unshielded output from this embodiment (3 Vexc button cell) yielded 1 mV from 5 μm displacement. Transduction linearity was high (R>0.99 nearest displacement) and exhibited nominal hysteresis. Modules may be placed upon or embedded into a multitude of materials and the size of individual hexagons may be scaled for favorable stiffness to strain ratio and to scale receptive field. Given the scalability of matrix size and resolution, we believe the sensor matrices could benefit the fields of prosthetics, robotics, and physiologic investigation of tissue mechanics. PMID:26710986

  11. Ethics Oversight Mechanisms for Surgical Innovation: A Systematic and Comparative Review of Arguments.

    PubMed

    Karpowicz, Lila; Bell, Emily; Racine, Eric

    2016-04-01

    Surgical innovation typically falls under the purview of neither conventional clinical ethics nor research ethics. Due to a lack of oversight for surgical innovation-combined with a potential for significant risk-a wide range of arguments has been advanced in the literature to support or undermine various oversight mechanisms. To scrutinize the argumentation surrounding oversight options, we conducted a systematic review of published arguments. We found that the arguments are typically grounded in common sense and speculation instead of evidence. Presently, the justification or superiority for any single oversight mechanism for surgical innovation cannot be established convincingly. We suggest ways to improve the argument-based literature and discuss the value of systematic reviews of arguments and reasons.

  12. Cellular Mechanisms and Behavioral Outcomes in Blast-Induced Neurotrauma: Comparing Experimental Setups.

    PubMed

    Bailey, Zachary S; Hubbard, W Brad; VandeVord, Pamela J

    2016-01-01

    Blast-induced neurotrauma (BINT) has increased in incidence over the past decades and can result in cognitive issues that have debilitating consequences. The exact primary and secondary mechanisms of injury have not been elucidated and appearance of cellular injury can vary based on many factors, such as blast overpressure magnitude and duration. Many methodologies to study blast neurotrauma have been employed, ranging from open-field explosives to experimental shock tubes for producing free-field blast waves. While there are benefits to the various methods, certain specifications need to be accounted for in order to properly examine BINT. Primary cell injury mechanisms, occurring as a direct result of the blast wave, have been identified in several studies and include cerebral vascular damage, blood-brain barrier disruption, axonal injury, and cytoskeletal damage. Secondary cell injury mechanisms, triggered subsequent to the initial insult, result in the activation of several molecular cascades and can include, but are not limited to, neuroinflammation and oxidative stress. The collective result of these secondary injuries can lead to functional deficits. Behavioral measures examining motor function, anxiety traits, and cognition/memory problems have been utilized to determine the level of injury severity. While cellular injury mechanisms have been identified following blast exposure, the various experimental models present both concurrent and conflicting results. Furthermore, the temporal response and progression of pathology after blast exposure have yet to be detailed and remain unclear due to limited resemblance of methodologies. This chapter summarizes the current state of blast neuropathology and emphasizes the need for a standardized preclinical model of blast neurotrauma.

  13. Cellular Mechanisms and Behavioral Outcomes in Blast-Induced Neurotrauma: Comparing Experimental Setups.

    PubMed

    Bailey, Zachary S; Hubbard, W Brad; VandeVord, Pamela J

    2016-01-01

    Blast-induced neurotrauma (BINT) has increased in incidence over the past decades and can result in cognitive issues that have debilitating consequences. The exact primary and secondary mechanisms of injury have not been elucidated and appearance of cellular injury can vary based on many factors, such as blast overpressure magnitude and duration. Many methodologies to study blast neurotrauma have been employed, ranging from open-field explosives to experimental shock tubes for producing free-field blast waves. While there are benefits to the various methods, certain specifications need to be accounted for in order to properly examine BINT. Primary cell injury mechanisms, occurring as a direct result of the blast wave, have been identified in several studies and include cerebral vascular damage, blood-brain barrier disruption, axonal injury, and cytoskeletal damage. Secondary cell injury mechanisms, triggered subsequent to the initial insult, result in the activation of several molecular cascades and can include, but are not limited to, neuroinflammation and oxidative stress. The collective result of these secondary injuries can lead to functional deficits. Behavioral measures examining motor function, anxiety traits, and cognition/memory problems have been utilized to determine the level of injury severity. While cellular injury mechanisms have been identified following blast exposure, the various experimental models present both concurrent and conflicting results. Furthermore, the temporal response and progression of pathology after blast exposure have yet to be detailed and remain unclear due to limited resemblance of methodologies. This chapter summarizes the current state of blast neuropathology and emphasizes the need for a standardized preclinical model of blast neurotrauma. PMID:27604716

  14. Signal transduction across cellular membranes can be mediated by coupling of the clustering of anchored proteins in both leaflets

    NASA Astrophysics Data System (ADS)

    Yue, Tongtao; Zhang, Xianren

    2012-01-01

    One key question in signal transduction is how the signal is relayed from the outer leaflet of a cellular membrane to the inner leaflet. Using a simulation model, a mechanism for the mediation of signal transduction is proposed here in which the coupling between membrane proteins in different leaflets can be achieved by the clustering of anchored proteins, without recruiting transmembrane proteins. Depending on the hydrophobic length of the anchored proteins, three coupling patterns, including face-to-face clustering, interdigitated clustering, and weak-coupled clustering, are observed in this work. This observation provides a possible explanation of how a particular downstream signaling pathway is selected.

  15. Transductional instability of Tn5-induced mutations: generalized and specialized transduction of Tn5 by bacteriophage P1.

    PubMed

    Berg, C M; Grullón, C A; Wang, A; Whalen, W A; Berg, D E

    1983-10-01

    Generalized transduction is commonly used to move transposon-induced mutations among bacterial strains by selecting for inheritance of a transposon-encoded resistance determinant. Although complete cotransduction of the resistance determinant and the chromosomal mutation might be expected, it is often found that when Tn5(Kan) insertion mutations are transduced by bacteriophage P1 most of the nonmutant kanamycin-resistant transductants area due to specialized transduction of Tn5. Such P1::Tn5 specialized transducing phage are not found when a mutant Tn5 element lacking a functional transposase is employed.

  16. Effects of arsenite in astrocytes on neuronal signaling transduction.

    PubMed

    Wang, Yan; Zhao, Fenghong; Liao, Yingjun; Jin, Yaping; Sun, Guifan

    2013-01-01

    The main purpose of this study was to test the hypothesis that arsenite induces neurotoxicity via effects on astrocytes. Astrocytes were exposed to 0, 5 or 10 μM arsenite in medium for 24 h, and then astrocyte-conditioned medium (ACM) was collected after incubation with fresh medium for 6 h. Primary neuron cultures were divided into four groups due to ACM, which were neurons without ACM exposure (group I) and neurons exposed to ACM from 0, 5 or 10 μM arsenite treated astrocytes (group II-IV). Protein expression of N-methyl-d-aspartate receptors (NR1, NR2A, NR2B), calmodulin-dependent protein kinase II (CaMKII) and adenylate cyclase (AC) in neurons were measured after incubation with ACM for 4, 8 or 12 h. Morphological changes and synaptic formation were observed after a 72 h-incubation with ACM. Compared to group II, synaptic formation and protein expression of NR2A, NR2B, CaMKII and AC in group III and IV were significantly suppressed. Moreover, synaptic formation and protein expression of CaMKII and AC in group II were significantly enhanced when compared with group I. Taken together, findings from this study suggested that arsenic in astrocytes might impair synaptic formation through disturbing astrocytic effects on neuronal signal transduction.

  17. Inquiry into Chemotherapy-Induced P53 Activation in Cancer Cells as a Model for Teaching Signal Transduction

    ERIC Educational Resources Information Center

    Srougi, Melissa C.; Carson, Susan

    2013-01-01

    Intracellular and extracellular communication is conducted through an intricate and interwoven network of signal transduction pathways. The mechanisms for how cells speak with one another are of significant biological importance to both basic and industrial scientists from a number of different disciplines. We have therefore developed and…

  18. Influence of arsenate and arsenite on signal transduction pathways: an update.

    PubMed

    Druwe, Ingrid L; Vaillancourt, Richard R

    2010-08-01

    Arsenic has been a recognized contaminant and toxicant, as well as a medicinal compound throughout human history. Populations throughout the world are exposed to arsenic and these exposures have been associated with a number of human cancers. Not much is known about the role of arsenic as a human carcinogen and more recently its role in non-cancerous diseases, such as cardiovascular disease, hypertension and diabetes mellitus have been uncovered. The health effects associated with arsenic are numerous and the association between arsenic exposure and human disease has intensified the search for molecular mechanisms that describe the biological activity of arsenic in humans and leads to the aforementioned disease states. Arsenic poses a human health risk due in part to the regulation of cellular signal transduction pathways and over the last few decades, some cellular mechanisms that account for arsenic toxicity, as well as, signal transduction pathways have been discovered. However, given the ubiquitous nature of arsenic in the environment, making sense of all the data remains a challenge. This review will focus on our knowledge of signal transduction pathways that are regulated by arsenic.

  19. Influence of arsenate and arsenite on signal transduction pathways: an update

    PubMed Central

    Druwe, Ingrid L.

    2010-01-01

    Arsenic has been a recognized contaminant and toxicant, as well as a medicinal compound throughout human history. Populations throughout the world are exposed to arsenic and these exposures have been associated with a number of human cancers. Not much is known about the role of arsenic as a human carcinogen and more recently its role in non-cancerous diseases, such as cardiovascular disease, hypertension and diabetes mellitus have been uncovered. The health effects associated with arsenic are numerous and the association between arsenic exposure and human disease has intensified the search for molecular mechanisms that describe the biological activity of arsenic in humans and leads to the aforementioned disease states. Arsenic poses a human health risk due in part to the regulation of cellular signal transduction pathways and over the last few decades, some cellular mechanisms that account for arsenic toxicity, as well as, signal transduction pathways have been discovered. However, given the ubiquitous nature of arsenic in the environment, making sense of all the data remains a challenge. This review will focus on our knowledge of signal transduction pathways that are regulated by arsenic. PMID:20502880

  20. Signal transduction across alamethicin ion channels in the presence of noise.

    PubMed Central

    Bezrukov, S M; Vodyanoy, I

    1997-01-01

    We have studied voltage-dependent ion channels of alamethicin reconstituted into an artificial planar lipid bilayer membrane from the point of view of electric signal transduction. Signal transduction properties of these channels are highly sensitive to the external electric noise. Specifically, addition of bandwidth-restricted "white" noise of 10-20 mV (r.m.s.) to a small sine wave input signal increases the output signal by approximately 20-40 dB conserving, and even slightly increasing, the signal-to-noise ratio at the system output. We have developed a small-signal adiabatic theory of stochastic resonance for a threshold-free system of voltage-dependent ion channels. This theory describes our main experimental findings giving good qualitative understanding of the underlying mechanism. It predicts the right value of the output signal-to-noise ratio and provides a reliable estimate for the noise intensity corresponding to its maximum. Our results suggest that the alamethicin channel in a lipid bilayer is a good model system for studies of mechanisms of primary electrical signal processing in biology showing an important feature of signal transduction improvement by a fluctuating environment. Images FIGURE 1 PMID:9370439

  1. Transduction channels' gating can control friction on vibrating hair-cell bundles in the ear.

    PubMed

    Bormuth, Volker; Barral, Jérémie; Joanny, Jean-François; Jülicher, Frank; Martin, Pascal

    2014-05-20

    Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. Friction is generally thought to result mainly from viscous drag by the surrounding fluid. We demonstrate here that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle. We characterized friction by analyzing hysteresis in the force-displacement relation of single hair-cell bundles in response to periodic triangular stimuli. For bundle velocities high enough to outrun adaptation, we found that frictional forces were maximal within the narrow region of deflections that elicited significant channel gating, plummeted upon application of a channel blocker, and displayed a sublinear growth for increasing bundle velocity. At low velocity, the slope of the relation between the frictional force and velocity was nearly fivefold larger than the hydrodynamic friction coefficient that was measured when the transduction machinery was decoupled from bundle motion by severing tip links. A theoretical analysis reveals that channel friction arises from coupling the dynamics of the conformational change associated with channel gating to tip-link tension. Varying channel properties affects friction, with faster channels producing smaller friction. We propose that this intrinsic source of friction may contribute to the process that sets the hair cell's characteristic frequency of responsiveness.

  2. Transduction channels’ gating can control friction on vibrating hair-cell bundles in the ear

    PubMed Central

    Bormuth, Volker; Barral, Jérémie; Joanny, Jean-François; Jülicher, Frank; Martin, Pascal

    2014-01-01

    Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. Friction is generally thought to result mainly from viscous drag by the surrounding fluid. We demonstrate here that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle. We characterized friction by analyzing hysteresis in the force–displacement relation of single hair-cell bundles in response to periodic triangular stimuli. For bundle velocities high enough to outrun adaptation, we found that frictional forces were maximal within the narrow region of deflections that elicited significant channel gating, plummeted upon application of a channel blocker, and displayed a sublinear growth for increasing bundle velocity. At low velocity, the slope of the relation between the frictional force and velocity was nearly fivefold larger than the hydrodynamic friction coefficient that was measured when the transduction machinery was decoupled from bundle motion by severing tip links. A theoretical analysis reveals that channel friction arises from coupling the dynamics of the conformational change associated with channel gating to tip-link tension. Varying channel properties affects friction, with faster channels producing smaller friction. We propose that this intrinsic source of friction may contribute to the process that sets the hair cell’s characteristic frequency of responsiveness. PMID:24799674

  3. Role of the mammalian target of rapamycin pathway and rapamycin in lentiviral vector gene transduction of hematopoietic stem cells

    PubMed Central

    Wang, Cathy X.; Torbett, Bruce E.

    2015-01-01

    Purpose of review A major goal in repopulating hematopoietic stem cell (HSC) gene therapies is achieving high-efficacy gene transfer, while maintaining robust HSC engraftment and differentiation in vivo. Recent studies have documented that rapamycin treatment of HSC during lentiviral vector transduction enhances gene transfer to human and mouse HSCs and maintains engraftment capacity. In this review, we place into context the role of mammalian target of rapamycin (mTOR) pathways in HSC quiescence and function, endocytic regulation, and lentiviral gene delivery. Recent findings Lentiviral vector transduction of human and mouse HSCs is considerably enhanced by rapamycin treatment. Furthermore, rapamycin preserves long-term engraftment of human and mouse HSCs. Investigations of cellular mechanisms that contribute to increased transduction in HSCs uncovered a role for mTOR inhibition-dependent activation of endocytosis. Summary Rapamycin enhances lentiviral vector transduction of HSCs through regulation of endocytic activity via mTOR inhibition. An important attribute of rapamycin treatment during transduction is the preservation of HSC function, allowing reconstitution of long-term hematopoiesis in vivo in murine models. PMID:26049750

  4. Chemical potential of bound ligand, an important parameter for free energy transduction

    PubMed Central

    Tanford, Charles

    1981-01-01

    The chemical potential (μL,b) of a ligand L bound to a protein or enzyme can be rigorously defined, and this paper describes some of its properties in relation to other thermodynamic parameters, with emphasis on thermodynamic parameters that may be used in the elucidation of the mechanism of biological free energy transduction. Free energy transduction involves the transfer of free energy from one molecule to another, and the actual transfer may often occur while both molecules are bound to the transducer enzyme, which means that μL,b for one bound ligand increases at the expense of μL,b for the other. The free energy change for the overall reaction may be very small, and it is not possible to express the phenomenon of transfer, in thermodynamic terms, without the explicit use of μL,b as a parameter. PMID:16592948

  5. GAP-43 augments G protein-coupled receptor transduction in Xenopus laevis oocytes.

    PubMed Central

    Strittmatter, S M; Cannon, S C; Ross, E M; Higashijima, T; Fishman, M C

    1993-01-01

    The neuronal protein GAP-43 is thought to play a role in determining growth-cone motility, perhaps as an intracellular regulator of signal transduction, but its molecular mechanism of action has remained unclear. We find that GAP-43, when microinjected into Xenopus laevis oocytes, increases the oocyte response to G protein-coupled receptor agonists by 10- to 100-fold. Higher levels of GAP-43 cause a transient current flow, even without receptor stimulation. The GAP-43-induced current, like receptor-stimulated currents, is mediated by a calcium-activated chloride channel and can be desensitized by injection of inositol 1,4,5-trisphosphate. This suggests that neuronal GAP-43 may serve as an intracellular signal to greatly enhance the sensitivity of G protein-coupled receptor transduction. Images Fig. 1 Fig. 2 PMID:7685122

  6. Osmotin, a plant antifungal protein, subverts signal transduction to enhance fungal cell susceptibility.

    PubMed

    Yun, D J; Ibeas, J I; Lee, H; Coca, M A; Narasimhan, M L; Uesono, Y; Hasegawa, P M; Pardo, J M; Bressan, R A

    1998-05-01

    The plant pathogenesis-related protein osmotin is an antifungal cytotoxic agent that causes rapid cell death in the yeast S. cerevisiae. We show here that osmotin uses a signal transduction pathway to weaken defensive cell wall barriers and increase its cytotoxic efficacy. The pathway activated by osmotin includes the regulatory elements of the mating pheromone response STE4, STE18, STE20, STE5, STE11, STE7, FUS3, KSS1, and STE12. Neither the pheromone receptor nor its associated G protein alpha subunit GPA1 are required for osmotin action. However, mutation of SST2, a negative regulator of G alpha proteins, resulted in supersensitivity to osmotin. Phosphorylation of STE7 was rapidly stimulated by osmotin preceding any changes in cell vitality or morphology. These results demonstrate that osmotin subverts target cell signal transduction as part of its mechanism of action. PMID:9660964

  7. Systematic Prediction of Scaffold Proteins Reveals New Design Principles in Scaffold-Mediated Signal Transduction

    PubMed Central

    Hu, Jianfei; Neiswinger, Johnathan; Zhang, Jin; Zhu, Heng; Qian, Jiang

    2015-01-01

    Scaffold proteins play a crucial role in facilitating signal transduction in eukaryotes by bringing together multiple signaling components. In this study, we performed a systematic analysis of scaffold proteins in signal transduction by integrating protein-protein interaction and kinase-substrate relationship networks. We predicted 212 scaffold proteins that are involved in 605 distinct signaling pathways. The computational prediction was validated using a protein microarray-based approach. The predicted scaffold proteins showed several interesting characteristics, as we expected from the functionality of scaffold proteins. We found that the scaffold proteins are likely to interact with each other, which is consistent with previous finding that scaffold proteins tend to form homodimers and heterodimers. Interestingly, a single scaffold protein can be involved in multiple signaling pathways by interacting with other scaffold protein partners. Furthermore, we propose two possible regulatory mechanisms by which the activity of scaffold proteins is coordinated with their associated pathways through phosphorylation process. PMID:26393507

  8. Subthreshold Dynamics and Its Effect on Signal Transduction in a Neural System

    NASA Astrophysics Data System (ADS)

    Wang, Yuqing; Wang, Z.; Wang, Wei

    1998-10-01

    Subthreshold dynamics and its effect on signal transduction in a neural system are studied by using the Hindmarsh-Rose neuron model. Under a periodic stimulation, as the constant bias of the stimulus increases, the neuron exhibits subthreshold periodic and subthreshold chaotic responses, suprathreshold chaotic firing of spikes, and mode-locked firing. The phase diagram of the system is obtained. The dynamic behavior obtained is in agreement with experiments on the squid giant axon. In particular, the subthreshold periodic oscillatory state is related to a number of experimental results, such as those found in the neurons of the inferior olivary nucleus. More importantly, we also find that subthreshold chaotic responses play a role analogous to the internal deterministic noise, and can enhance weak signal transduction via a mechanism similar to stochastic resonance.

  9. Biofilm as an environment for dissemination of stx genes by transduction.

    PubMed

    Solheim, H T; Sekse, C; Urdahl, A M; Wasteson, Y; Nesse, L L

    2013-02-01

    Dissemination of Shiga toxin (Stx)-encoding bacteriophages is the most likely mechanism for the spread of Stx-encoding genes and the emergence of new Stx-producing Escherichia coli (STEC). Biofilm has been reported to be a place where horizontal gene transfer by plasmid conjugation and DNA transformation may occur, and in this study, horizontal gene transfer by transduction has been demonstrated. Transfer of Stx-encoding bacteriophages to potentially pathogenic E. coli in biofilm was observed at both 20°C and 37°C. The infection rates were higher at 37°C than at 20°C. To our knowledge, this study is the first to show lateral gene transfer in biofilm mediated by a temperate bacteriophage. The study shows that the biofilm environment can be suitable for transduction events and can thereby be an environment for the emergence of new pathogenic E. coli.

  10. Systematic Prediction of Scaffold Proteins Reveals New Design Principles in Scaffold-Mediated Signal Transduction.

    PubMed

    Hu, Jianfei; Neiswinger, Johnathan; Zhang, Jin; Zhu, Heng; Qian, Jiang

    2015-01-01

    Scaffold proteins play a crucial role in facilitating signal transduction in eukaryotes by bringing together multiple signaling components. In this study, we performed a systematic analysis of scaffold proteins in signal transduction by integrating protein-protein interaction and kinase-substrate relationship networks. We predicted 212 scaffold proteins that are involved in 605 distinct signaling pathways. The computational prediction was validated using a protein microarray-based approach. The predicted scaffold proteins showed several interesting characteristics, as we expected from the functionality of scaffold proteins. We found that the scaffold proteins are likely to interact with each other, which is consistent with previous finding that scaffold proteins tend to form homodimers and heterodimers. Interestingly, a single scaffold protein can be involved in multiple signaling pathways by interacting with other scaffold protein partners. Furthermore, we propose two possible regulatory mechanisms by which the activity of scaffold proteins is coordinated with their associated pathways through phosphorylation process.

  11. Genome, integration, and transduction of a novel temperate phage of Helicobacter pylori.

    PubMed

    Luo, Cheng-Hung; Chiou, Pei-Yu; Yang, Chiou-Ying; Lin, Nien-Tsung

    2012-08-01

    Helicobacter pylori is a common human pathogen that has been identified to be carcinogenic. This study isolated the temperate bacteriophage 1961P from the lysate of a clinical strain of H. pylori isolated in Taiwan. The bacteriophage has an icosahedral head and a short tail, typical of the Podoviridae family. Its double-stranded DNA genome is 26,836 bp long and has 33 open reading frames. Only 9 of the predicted proteins have homologs of known functions, while the remaining 24 are only similar to unknown proteins encoded by Helicobacter prophages and remnants. Analysis of sequences proximal to the phage-host junctions suggests that 1961P may integrate into the host chromosome via a mechanism similar to that of bacteriophage lambda. In addition, 1961P is capable of generalized transduction. To the best of our knowledge, this is the first report of the isolation, characterization, genome analysis, integration, and transduction of a Helicobacter pylori phage.

  12. Genome, Integration, and Transduction of a Novel Temperate Phage of Helicobacter pylori

    PubMed Central

    Luo, Cheng-Hung; Chiou, Pei-Yu; Yang, Chiou-Ying

    2012-01-01

    Helicobacter pylori is a common human pathogen that has been identified to be carcinogenic. This study isolated the temperate bacteriophage 1961P from the lysate of a clinical strain of H. pylori isolated in Taiwan. The bacteriophage has an icosahedral head and a short tail, typical of the Podoviridae family. Its double-stranded DNA genome is 26,836 bp long and has 33 open reading frames. Only 9 of the predicted proteins have homologs of known functions, while the remaining 24 are only similar to unknown proteins encoded by Helicobacter prophages and remnants. Analysis of sequences proximal to the phage-host junctions suggests that 1961P may integrate into the host chromosome via a mechanism similar to that of bacteriophage lambda. In addition, 1961P is capable of generalized transduction. To the best of our knowledge, this is the first report of the isolation, characterization, genome analysis, integration, and transduction of a Helicobacter pylori phage. PMID:22696647

  13. Microstructure and compressive mechanical properties of cortical bone in children with osteogenesis imperfecta treated with bisphosphonates compared with healthy children.

    PubMed

    Imbert, Laurianne; Aurégan, Jean-Charles; Pernelle, Kélig; Hoc, Thierry

    2015-06-01

    Osteogenesis imperfecta (OI) is a genetic disorder characterized by a change in bone tissue quality, but little data are available to describe the factors involved at the macroscopic scale. To better understand the effect of microstructure alterations on the mechanical properties at the sample scale, we studied the structural and mechanical properties of six cortical bone samples from children with OI treated with bisphosphonates and compared them to the properties of three controls. Scanning electron microscopy, high resolution computed tomography and compression testing were used to assess these properties. More resorption cavities and a higher osteocyte lacunar density were observed in OI bone compared with controls. Moreover, a higher porosity was measured for OI bones along with lower macroscopic Young's modulus, yield stress and ultimate stress. The microstructure was impaired in OI bones; the higher porosity and osteocyte lacunar density negatively impacted the mechanical properties and made the bone more prone to fracture.

  14. Signal transduction in the footsteps of goethe and schiller.

    PubMed

    Friedrich, Karlheinz; Lindquist, Jonathan A; Entschladen, Frank; Serfling, Edgar; Thiel, Gerald; Kieser, Arnd; Giehl, Klaudia; Ehrhardt, Christina; Feller, Stephan M; Ullrich, Oliver; Schaper, Fred; Janssen, Ottmar; Hass, Ralf

    2009-02-04

    The historical town of Weimar in Thuringia, the "green heart of Germany" was the sphere of Goethe and Schiller, the two most famous representatives of German literature's classic era. Not yet entirely as influential as those two cultural icons, the Signal Transduction Society (STS) has nevertheless in the last decade established within the walls of Weimar an annual interdisciplinary Meeting on "Signal Transduction - Receptors, Mediators and Genes", which is well recognized as a most attractive opportunity to exchange results and ideas in the field.The 12th STS Meeting was held from October 28 to 31 and provided a state-of-the-art overview of various areas of signal transduction research in which progress is fast and discussion lively. This report is intended to share with the readers of CCS some highlights of the Meeting Workshops devoted to specific aspects of signal transduction.

  15. Analysis of intercellular signal transduction in the tumor microenvironment

    PubMed Central

    2013-01-01

    Background Recent cancer studies revealed, the interaction between pancreatic cancer cells and pancreatic stellate cells is of importance in the cancer progression. The activation of stellate cells is mediated by some growth factors and cytokines secreted by the cancer cells. In turn, the activated stellate cells will synthesize and secrete multiple growth factors to continuously stimulate the growth of surrounding cancer cells through paracrine pathways. The mechanism behind the evolution of stellate cells from quiescent state to a cancer-associated phenotype is still not well understood. Results To systematically investigate the interaction between cancer cells and stellate cells, we constructed a multicellular discrete value model, which is composed of several intracellular and intercellular signaling pathways that are frequently mutated in the pancreatic cancer, to study the cell cycle progression and angiogenesis. We, then, introduced and applied a formal verification technique, Symbolic Model Checking, to automatically analyze the cells' proliferation, angiogenesis and apoptosis in the proposed signal transduction model of tumor microenvironment. Conclusions Our studies predicted some important temporal logic properties and dynamic behaviors in the pancreatic cancer cells and stellate cells. The verification technique identified several signaling components, including the RAS, RAGE, AKT, IKK, DVL, RB and PTEN, whose mutation or loss of function can promote cell growth and inhibit apoptosis, some of which have been confirmed by existing experiments. Our formal studies demonstrated that, the bidirectional interaction between cancer cells and stellate cells could significantly increase cell proliferation, inhibit apoptosis, induce tumor angiogenesis, and promote cancer metastasis. PMID:24555417

  16. Signal transduction in cells of the immune system in microgravity

    PubMed Central

    Ullrich, Oliver; Huber, Kathrin; Lang, Kerstin

    2008-01-01

    Life on Earth developed in the presence and under the constant influence of gravity. Gravity has been present during the entire evolution, from the first organic molecule to mammals and humans. Modern research revealed clearly that gravity is important, probably indispensable for the function of living systems, from unicellular organisms to men. Thus, gravity research is no more or less a fundamental question about the conditions of life on Earth. Since the first space missions and supported thereafter by a multitude of space and ground-based experiments, it is well known that immune cell function is severely suppressed in microgravity, which renders the cells of the immune system an ideal model organism to investigate the influence of gravity on the cellular and molecular level. Here we review the current knowledge about the question, if and how cellular signal transduction depends on the existence of gravity, with special focus on cells of the immune system. Since immune cell function is fundamental to keep the organism under imnological surveillance during the defence against pathogens, to investigate the effects and possible molecular mechanisms of altered gravity is indispensable for long-term space flights to Earth Moon or Mars. Thus, understanding the impact of gravity on cellular functions on Earth will provide not only important informations about the development of life on Earth, but also for therapeutic and preventive strategies to cope successfully with medical problems during space exploration. PMID:18957108

  17. The interleukin-4 receptor: signal transduction by a hematopoietin receptor.

    PubMed

    Keegan, A D; Pierce, J H

    1994-02-01

    Over the last several years, the receptors for numerous cytokines have been molecularly characterized. Analysis of their amino acid sequences shows that some of these receptors bear certain motifs in their extracellular domains that define a family of receptors called the Hematopoietin receptor superfamily. Significant advances in characterizing the structure, function, and mechanisms of signal transduction have been made for several members of this family. The purpose of this review is to discuss the recent advances made for one of the family members, the interleukin (IL) 4 receptor. Other receptor systems have recently been reviewed elsewhere. The IL-4 receptor consists of, at the minimum, the cloned 140 kDa IL-4-binding chain with the potential for associating with other chains. The IL-4 receptor transduces its signal by activating a tyrosine kinase that phosphorylates cellular substrates, including the receptor itself, and the 170 kDa substrate called 4PS. Phosphorylated 4PS interacts with the SH2 domain of the enzyme PI-3'-kinase and increases its enzymatic activity. These early events in the IL-4 receptor initiated signaling pathway may trigger a series of signals that will ultimately lead to an IL-4 specific biologic outcome.

  18. Bacteriophage Transduction in Staphylococcus aureus: Broth-Based Method.

    PubMed

    Krausz, Kelsey L; Bose, Jeffrey L

    2016-01-01

    The ability to move DNA between Staphylococcus strains is essential for the genetic manipulation of this bacterium. Often in the Staphylococci, this is accomplished through transduction using generalized transducing phage and can be performed in different ways and therefore the presence of two transduction procedures in this book. The following protocol is a relatively easy-to-perform, broth-based procedure that we have used extensively to move both plasmids and chromosomal fragments between strains of Staphylococcus aureus.

  19. Expansion of Signal Transduction Pathways in Fungi by Extensive Genome Duplication.

    PubMed

    Corrochano, Luis M; Kuo, Alan; Marcet-Houben, Marina; Polaino, Silvia; Salamov, Asaf; Villalobos-Escobedo, José M; Grimwood, Jane; Álvarez, M Isabel; Avalos, Javier; Bauer, Diane; Benito, Ernesto P; Benoit, Isabelle; Burger, Gertraud; Camino, Lola P; Cánovas, David; Cerdá-Olmedo, Enrique; Cheng, Jan-Fang; Domínguez, Angel; Eliáš, Marek; Eslava, Arturo P; Glaser, Fabian; Gutiérrez, Gabriel; Heitman, Joseph; Henrissat, Bernard; Iturriaga, Enrique A; Lang, B Franz; Lavín, José L; Lee, Soo Chan; Li, Wenjun; Lindquist, Erika; López-García, Sergio; Luque, Eva M; Marcos, Ana T; Martin, Joel; McCluskey, Kevin; Medina, Humberto R; Miralles-Durán, Alejandro; Miyazaki, Atsushi; Muñoz-Torres, Elisa; Oguiza, José A; Ohm, Robin A; Olmedo, María; Orejas, Margarita; Ortiz-Castellanos, Lucila; Pisabarro, Antonio G; Rodríguez-Romero, Julio; Ruiz-Herrera, José; Ruiz-Vázquez, Rosa; Sanz, Catalina; Schackwitz, Wendy; Shahriari, Mahdi; Shelest, Ekaterina; Silva-Franco, Fátima; Soanes, Darren; Syed, Khajamohiddin; Tagua, Víctor G; Talbot, Nicholas J; Thon, Michael R; Tice, Hope; de Vries, Ronald P; Wiebenga, Ad; Yadav, Jagjit S; Braun, Edward L; Baker, Scott E; Garre, Victoriano; Schmutz, Jeremy; Horwitz, Benjamin A; Torres-Martínez, Santiago; Idnurm, Alexander; Herrera-Estrella, Alfredo; Gabaldón, Toni; Grigoriev, Igor V

    2016-06-20

    Plants and fungi use light and other signals to regulate development, growth, and metabolism. The fruiting bodies of the fungus Phycomyces blakesleeanus are single cells that react to environmental cues, including light, but the mechanisms are largely unknown [1]. The related fungus Mucor circinelloides is an opportunistic human pathogen that changes its mode of growth upon receipt of signals from the environment to facilitate pathogenesis [2]. Understanding how these organisms respond to environmental cues should provide insights into the mechanisms of sensory perception and signal transduction by a single eukaryotic cell, and their role in pathogenesis. We sequenced the genomes of P. blakesleeanus and M. circinelloides and show that they have been shaped by an extensive genome duplication or, most likely, a whole-genome duplication (WGD), which is rarely observed in fungi [3-6]. We show that the genome duplication has expanded gene families, including those involved in signal transduction, and that duplicated genes have specialized, as evidenced by differences in their regulation by light. The transcriptional response to light varies with the developmental stage and is still observed in a photoreceptor mutant of P. blakesleeanus. A phototropic mutant of P. blakesleeanus with a heterozygous mutation in the photoreceptor gene madA demonstrates that photosensor dosage is important for the magnitude of signal transduction. We conclude that the genome duplication provided the means to improve signal transduction for enhanced perception of environmental signals. Our results will help to understand the role of genome dynamics in the evolution of sensory perception in eukaryotes. PMID:27238284

  20. Expansion of Signal Transduction Pathways in Fungi by Extensive Genome Duplication.

    PubMed

    Corrochano, Luis M; Kuo, Alan; Marcet-Houben, Marina; Polaino, Silvia; Salamov, Asaf; Villalobos-Escobedo, José M; Grimwood, Jane; Álvarez, M Isabel; Avalos, Javier; Bauer, Diane; Benito, Ernesto P; Benoit, Isabelle; Burger, Gertraud; Camino, Lola P; Cánovas, David; Cerdá-Olmedo, Enrique; Cheng, Jan-Fang; Domínguez, Angel; Eliáš, Marek; Eslava, Arturo P; Glaser, Fabian; Gutiérrez, Gabriel; Heitman, Joseph; Henrissat, Bernard; Iturriaga, Enrique A; Lang, B Franz; Lavín, José L; Lee, Soo Chan; Li, Wenjun; Lindquist, Erika; López-García, Sergio; Luque, Eva M; Marcos, Ana T; Martin, Joel; McCluskey, Kevin; Medina, Humberto R; Miralles-Durán, Alejandro; Miyazaki, Atsushi; Muñoz-Torres, Elisa; Oguiza, José A; Ohm, Robin A; Olmedo, María; Orejas, Margarita; Ortiz-Castellanos, Lucila; Pisabarro, Antonio G; Rodríguez-Romero, Julio; Ruiz-Herrera, José; Ruiz-Vázquez, Rosa; Sanz, Catalina; Schackwitz, Wendy; Shahriari, Mahdi; Shelest, Ekaterina; Silva-Franco, Fátima; Soanes, Darren; Syed, Khajamohiddin; Tagua, Víctor G; Talbot, Nicholas J; Thon, Michael R; Tice, Hope; de Vries, Ronald P; Wiebenga, Ad; Yadav, Jagjit S; Braun, Edward L; Baker, Scott E; Garre, Victoriano; Schmutz, Jeremy; Horwitz, Benjamin A; Torres-Martínez, Santiago; Idnurm, Alexander; Herrera-Estrella, Alfredo; Gabaldón, Toni; Grigoriev, Igor V

    2016-06-20

    Plants and fungi use light and other signals to regulate development, growth, and metabolism. The fruiting bodies of the fungus Phycomyces blakesleeanus are single cells that react to environmental cues, including light, but the mechanisms are largely unknown [1]. The related fungus Mucor circinelloides is an opportunistic human pathogen that changes its mode of growth upon receipt of signals from the environment to facilitate pathogenesis [2]. Understanding how these organisms respond to environmental cues should provide insights into the mechanisms of sensory perception and signal transduction by a single eukaryotic cell, and their role in pathogenesis. We sequenced the genomes of P. blakesleeanus and M. circinelloides and show that they have been shaped by an extensive genome duplication or, most likely, a whole-genome duplication (WGD), which is rarely observed in fungi [3-6]. We show that the genome duplication has expanded gene families, including those involved in signal transduction, and that duplicated genes have specialized, as evidenced by differences in their regulation by light. The transcriptional response to light varies with the developmental stage and is still observed in a photoreceptor mutant of P. blakesleeanus. A phototropic mutant of P. blakesleeanus with a heterozygous mutation in the photoreceptor gene madA demonstrates that photosensor dosage is important for the magnitude of signal transduction. We conclude that the genome duplication provided the means to improve signal transduction for enhanced perception of environmental signals. Our results will help to understand the role of genome dynamics in the evolution of sensory perception in eukaryotes.

  1. Gravitactic signal transduction elements in Astasia longa investigated during parabolic flights.

    PubMed

    Richter, Peter R; Schuster, Martin; Lebert, Michael; Hader, Donat-P

    2003-01-01

    Euglena gracilis and its close relative Astasia longa show a pronounced negative gravitactic behavior. Many experiments revealed that gravitaxis is most likely mediated by an active physiological mechanism. The goal of the present study was to examine elements in the sensory transduction by means of inhibitors of gravitaxis and the intracellular calcium concentration during short microgravity periods. During the course of six parabolic flights (ESA 31th parabolic flight campaign and DLR 6th parabolic flight campaign) the effects of trifluoperazine (calmodulin inhibitor), caffeine (phosphodiesterase inhibitor) and gadolinium (blocks mechano-sensitive ion channels) was investigated. Due to the extreme parabolic flight maneuvers of the aircraft alternating phases of 1.8 x g(n) (about 20 s) and microgravity (about 22 s) were achieved (g(n): acceleration of Earth's gravity field). The duration of the microgravity periods was sufficient to detect a loss of cell orientation in the samples. In the presence of gadolinium impaired gravitaxis was found during acceleration, while caffeine-treated cells showed, compared to the controls, a very precise gravitaxis and faster reorientation in the 1.8 x g(n) period following microgravity. A transient increase of the intracellular calcium upon increased acceleration was detected also in inhibitor-treated samples. Additionally, it was found that the cells showed a higher calcium signal when they deviated from the vertical swimming direction. In the presence of trifluoperazine a slightly higher general calcium signal was detected compared to untreated controls, while gadolinium was found to decrease the intracellular calcium concentration. In the presence of caffeine no clear changes of intracellular calcium were detected compared to the control.

  2. Engineering key components in a synthetic eukaryotic signal transduction pathway

    PubMed Central

    Antunes, Mauricio S; Morey, Kevin J; Tewari-Singh, Neera; Bowen, Tessa A; Smith, J Jeff; Webb, Colleen T; Hellinga, Homme W; Medford, June I

    2009-01-01

    Signal transduction underlies how living organisms detect and respond to stimuli. A goal of synthetic biology is to rewire natural signal transduction systems. Bacteria, yeast, and plants sense environmental aspects through conserved histidine kinase (HK) signal transduction systems. HK protein components are typically comprised of multiple, relatively modular, and conserved domains. Phosphate transfer between these components may exhibit considerable cross talk between the otherwise apparently linear pathways, thereby establishing networks that integrate multiple signals. We show that sequence conservation and cross talk can extend across kingdoms and can be exploited to produce a synthetic plant signal transduction system. In response to HK cross talk, heterologously expressed bacterial response regulators, PhoB and OmpR, translocate to the nucleus on HK activation. Using this discovery, combined with modification of PhoB (PhoB-VP64), we produced a key component of a eukaryotic synthetic signal transduction pathway. In response to exogenous cytokinin, PhoB-VP64 translocates to the nucleus, binds a synthetic PlantPho promoter, and activates gene expression. These results show that conserved-signaling components can be used across kingdoms and adapted to produce synthetic eukaryotic signal transduction pathways. PMID:19455134

  3. Introducing mechanical biological waste treatment in South Africa: a comparative study.

    PubMed

    Trois, C; Griffith, M; Brummack, J; Mollekopf, N

    2007-01-01

    This paper presents the results of the first pilot project on mechanical biological waste treatment (MBWT) in South Africa. The study has shown that biological waste treatment in windrows using a passive aeration system that utilises thermal convection to drive the aeration process within a windrow of waste is appropriate for South Africa, in relation to low capital costs, low energy inputs, limited plant requirements and potential for labour-intensive operations. The influence of climate, waste composition and operational facilities was evaluated to optimise the treatment technique to local conditions. The maximum temperatures reached during the intensive thermophilic stage were effectively equivalent to the German experience. The lower CO2 production experienced in the South African trials was attributed to a different waste stream (high presence of plastics) due to the absence of a proper source separated waste collection system. An accurate adjustment of the input material (structural matter in particular) to the specific ambient conditions and irrigation during composting should result in higher organic carbon degradation efficiency in equivalent timeframes. This preliminary experience suggests that the applicability of MBWT in emerging countries, such as South Africa, is directly dependant on the mechanical treatment steps, available operational facilities and nature of the input material.

  4. Genome-wide Comparative Analysis of Atopic Dermatitis and Psoriasis Gives Insight into Opposing Genetic Mechanisms

    PubMed Central

    Baurecht, Hansjörg; Hotze, Melanie; Brand, Stephan; Büning, Carsten; Cormican, Paul; Corvin, Aiden; Ellinghaus, David; Ellinghaus, Eva; Esparza-Gordillo, Jorge; Fölster-Holst, Regina; Franke, Andre; Gieger, Christian; Hubner, Norbert; Illig, Thomas; Irvine, Alan D.; Kabesch, Michael; Lee, Young A.E.; Lieb, Wolfgang; Marenholz, Ingo; McLean, W.H. Irwin; Morris, Derek W.; Mrowietz, Ulrich; Nair, Rajan; Nöthen, Markus M.; Novak, Natalija; O’Regan, Grainne M.; Schreiber, Stefan; Smith, Catherine; Strauch, Konstantin; Stuart, Philip E.; Trembath, Richard; Tsoi, Lam C.; Weichenthal, Michael; Barker, Jonathan; Elder, James T.; Weidinger, Stephan; Cordell, Heather J.; Brown, Sara J.

    2015-01-01

    Atopic dermatitis and psoriasis are the two most common immune-mediated inflammatory disorders affecting the skin. Genome-wide studies demonstrate a high degree of genetic overlap, but these diseases have mutually exclusive clinical phenotypes and opposing immune mechanisms. Despite their prevalence, atopic dermatitis and psoriasis very rarely co-occur within one individual. By utilizing genome-wide association study and ImmunoChip data from >19,000 individuals and methodologies developed from meta-analysis, we have identified opposing risk alleles at shared loci as well as independent disease-specific loci within the epidermal differentiation complex (chromosome 1q21.3), the Th2 locus control region (chromosome 5q31.1), and the major histocompatibility complex (chromosome 6p21–22). We further identified previously unreported pleiotropic alleles with opposing effects on atopic dermatitis and psoriasis risk in PRKRA and ANXA6/TNIP1. In contrast, there was no evidence for shared loci with effects operating in the same direction on both diseases. Our results show that atopic dermatitis and psoriasis have distinct genetic mechanisms with opposing effects in shared pathways influencing epidermal differentiation and immune response. The statistical analysis methods developed in the conduct of this study have produced additional insight from previously published data sets. The approach is likely to be applicable to the investigation of the genetic basis of other complex traits with overlapping and distinct clinical features. PMID:25574825

  5. Comparative analysis of disease pathogenesis and molecular mechanisms of New World and Old World arenavirus infections

    PubMed Central

    McLay, Lisa; Liang, Yuying

    2014-01-01

    Arenaviruses can cause fatal human haemorrhagic fever (HF) diseases for which vaccines and therapies are extremely limited. Both the New World (NW) and Old World (OW) groups of arenaviruses contain HF-causing pathogens. Although these two groups share many similarities, important differences with regard to pathogenicity and molecular mechanisms of virus infection exist. These closely related pathogens share many characteristics, including genome structure, viral assembly, natural host selection and the ability to interfere with innate immune signalling. However, members of the NW and OW viruses appear to use different receptors for cellular entry, as well as different mechanisms of virus internalization. General differences in disease signs and symptoms and pathological lesions in patients infected with either NW or OW arenaviruses are also noted and discussed herein. Whilst both the OW Lassa virus (LASV) and the NW Junin virus (JUNV) can cause disruption of the vascular endothelium, which is an important pathological feature of HF, the immune responses to these related pathogens seem to be quite distinct. Whereas LASV infection results in an overall generalized immune suppression, patients infected with JUNV seem to develop a cytokine storm. Additionally, the type of immune response required for recovery and clearance of the virus is different between NW and OW infections. These differences may be important to allow the viruses to evade host immune detection. Understanding these differences will aid the development of new vaccines and treatment strategies against deadly HF viral infections. PMID:24068704

  6. Microbial iron management mechanisms in extremely acidic environments: comparative genomics evidence for diversity and versatility

    PubMed Central

    Osorio, Héctor; Martínez, Verónica; Nieto, Pamela A; Holmes, David S; Quatrini, Raquel

    2008-01-01

    Background Iron is an essential nutrient but can be toxic at high intracellular concentrations and organisms have evolved tightly regulated mechanisms for iron uptake and homeostasis. Information on iron management mechanisms is available for organisms living at circumneutral pH. However, very little is known about how acidophilic bacteria, especially those used for industrial copper bioleaching, cope with environmental iron loads that can be 1018 times the concentration found in pH neutral environments. This study was motivated by the need to fill this lacuna in knowledge. An understanding of how microorganisms thrive in acidic ecosystems with high iron loads requires a comprehensive investigation of the strategies to acquire iron and to coordinate this acquisition with utilization, storage and oxidation of iron through metal responsive regulation. In silico prediction of iron management genes and Fur regulation was carried out for three Acidithiobacilli: Acidithiobacillus ferrooxidans (iron and sulfur oxidizer) A. thiooxidans and A. caldus (sulfur oxidizers) that can live between pH 1 and pH 5 and for three strict iron oxidizers of the Leptospirillum genus that live at pH 1 or below. Results Acidithiobacilli have predicted FeoB-like Fe(II) and Nramp-like Fe(II)-Mn(II) transporters. They also have 14 different TonB dependent ferri-siderophore transporters of diverse siderophore affinity, although they do not produce classical siderophores. Instead they have predicted novel mechanisms for dicitrate synthesis and possibly also for phosphate-chelation mediated iron uptake. It is hypothesized that the unexpectedly large number and diversity of Fe(III)-uptake systems confers versatility to this group of acidophiles, especially in higher pH environments (pH 4–5) where soluble iron may not be abundant. In contrast, Leptospirilla have only a FtrI-Fet3P-like permease and three TonB dependent ferri-dicitrate siderophore systems. This paucity of iron uptake systems could

  7. Elucidation of Cross-Talk and Specificity of Early Response Mechanisms to Salt and PEG-Simulated Drought Stresses in Brassica napus Using Comparative Proteomic Analysis.

    PubMed

    Luo, Junling; Tang, Shaohua; Peng, Xiaojue; Yan, Xiaohong; Zeng, Xinhua; Li, Jun; Li, Xiaofei; Wu, Gang

    2015-01-01

    To understand the cross-talk and specificity of the early responses of plants to salt and drought, we performed physiological and proteome analyses of Brassica napus seedlings pretreated with 245 mM NaCl or 25% polyethylene glycol (PEG) 6000 under identical osmotic pressure (-1.0 MPa). Significant decreases in water content and photosynthetic rate and excessive accumulation of compatible osmolytes and oxidative damage were observed in response to both stresses. Unexpectedly, the drought response was more severe than the salt response. We further identified 45 common differentially expressed proteins (DEPs), 143 salt-specific DEPs and 160 drought-specific DEPs by isobaric tags for relative and absolute quantitation (iTRAQ) analysis. The proteome quantitative data were then confirmed by multiple reaction monitoring (MRM). The differences in the proteomic profiles between drought-treated and salt-treated seedlings exceeded the similarities in the early stress responses. Signal perception and transduction, transport and membrane trafficking, and photosynthesis-related proteins were enriched as part of the molecular cross-talk and specificity mechanism in the early responses to the two abiotic stresses. The Ca2+ signaling, G protein-related signaling, 14-3-3 signaling pathway and phosphorylation cascades were the common signal transduction pathways shared by both salt and drought stress responses; however, the proteins with executive functions varied. These results indicate functional specialization of family proteins in response to different stresses, i.e., CDPK21, TPR, and CTR1 specific to phosphorylation cascades under early salt stress, whereas STN7 and BSL were specific to phosphorylation cascades under early drought stress. Only the calcium-binding EF-hand family protein and ZKT were clearly identified as signaling proteins that acted as cross-talk nodes for salt and drought signaling pathways. Our study provides new clues and insights for developing strategies to

  8. Elucidation of Cross-Talk and Specificity of Early Response Mechanisms to Salt and PEG-Simulated Drought Stresses in Brassica napus Using Comparative Proteomic Analysis

    PubMed Central

    Luo, Junling; Tang, Shaohua; Peng, Xiaojue; Yan, Xiaohong; Zeng, Xinhua; Li, Jun; Li, Xiaofei; Wu, Gang

    2015-01-01

    To understand the cross-talk and specificity of the early responses of plants to salt and drought, we performed physiological and proteome analyses of Brassica napus seedlings pretreated with 245 mM NaCl or 25% polyethylene glycol (PEG) 6000 under identical osmotic pressure (-1.0 MPa). Significant decreases in water content and photosynthetic rate and excessive accumulation of compatible osmolytes and oxidative damage were observed in response to both stresses. Unexpectedly, the drought response was more severe than the salt response. We further identified 45 common differentially expressed proteins (DEPs), 143 salt-specific DEPs and 160 drought-specific DEPs by isobaric tags for relative and absolute quantitation (iTRAQ) analysis. The proteome quantitative data were then confirmed by multiple reaction monitoring (MRM). The differences in the proteomic profiles between drought-treated and salt-treated seedlings exceeded the similarities in the early stress responses. Signal perception and transduction, transport and membrane trafficking, and photosynthesis-related proteins were enriched as part of the molecular cross-talk and specificity mechanism in the early responses to the two abiotic stresses. The Ca2+ signaling, G protein-related signaling, 14-3-3 signaling pathway and phosphorylation cascades were the common signal transduction pathways shared by both salt and drought stress responses; however, the proteins with executive functions varied. These results indicate functional specialization of family proteins in response to different stresses, i.e., CDPK21, TPR, and CTR1 specific to phosphorylation cascades under early salt stress, whereas STN7 and BSL were specific to phosphorylation cascades under early drought stress. Only the calcium-binding EF-hand family protein and ZKT were clearly identified as signaling proteins that acted as cross-talk nodes for salt and drought signaling pathways. Our study provides new clues and insights for developing strategies to

  9. Elucidation of Cross-Talk and Specificity of Early Response Mechanisms to Salt and PEG-Simulated Drought Stresses in Brassica napus Using Comparative Proteomic Analysis.

    PubMed

    Luo, Junling; Tang, Shaohua; Peng, Xiaojue; Yan, Xiaohong; Zeng, Xinhua; Li, Jun; Li, Xiaofei; Wu, Gang

    2015-01-01

    To understand the cross-talk and specificity of the early responses of plants to salt and drought, we performed physiological and proteome analyses of Brassica napus seedlings pretreated with 245 mM NaCl or 25% polyethylene glycol (PEG) 6000 under identical osmotic pressure (-1.0 MPa). Significant decreases in water content and photosynthetic rate and excessive accumulation of compatible osmolytes and oxidative damage were observed in response to both stresses. Unexpectedly, the drought response was more severe than the salt response. We further identified 45 common differentially expressed proteins (DEPs), 143 salt-specific DEPs and 160 drought-specific DEPs by isobaric tags for relative and absolute quantitation (iTRAQ) analysis. The proteome quantitative data were then confirmed by multiple reaction monitoring (MRM). The differences in the proteomic profiles between drought-treated and salt-treated seedlings exceeded the similarities in the early stress responses. Signal perception and transduction, transport and membrane trafficking, and photosynthesis-related proteins were enriched as part of the molecular cross-talk and specificity mechanism in the early responses to the two abiotic stresses. The Ca2+ signaling, G protein-related signaling, 14-3-3 signaling pathway and phosphorylation cascades were the common signal transduction pathways shared by both salt and drought stress responses; however, the proteins with executive functions varied. These results indicate functional specialization of family proteins in response to different stresses, i.e., CDPK21, TPR, and CTR1 specific to phosphorylation cascades under early salt stress, whereas STN7 and BSL were specific to phosphorylation cascades under early drought stress. Only the calcium-binding EF-hand family protein and ZKT were clearly identified as signaling proteins that acted as cross-talk nodes for salt and drought signaling pathways. Our study provides new clues and insights for developing strategies to

  10. Mechanism of amorphous silica particles precipitation: simulation approach compared to experimental results

    NASA Astrophysics Data System (ADS)

    Noguera, Claudine; Fritz, Bertrand; Clement, Alain

    2015-04-01

    Despite its importance in numerous industrial and natural processes, many unsolved questions remain regarding the mechanism of silica precipitation in aqueous solutions: order of the reaction, role of silica oligomers, existence of an induction time and characteristics of the particle population. Beyond empirical approaches used in the past, we demonstrate that the classical nucleation theory associated to a size dependent growth law, as embedded in the NANOKIN code (1-3), allows a quantitative description of precipitation occurring under largely different experimental conditions : preexisting initial supersaturation in a large domain of temperature (5-150°C) and chemical composition (4), supersaturation reached by neutralization of a high pH silica solution (5) or by fast cooling (6). In that way, the mechanism of silica precipitation can be unraveled. We are able to discard the hypothesis of an induction time as an explanation for the plateaus observed in the saturation curves in these experiments. We challenge the role of oligomer incorporation at the growth stage to account for the observed rate laws and we stress the difference between the order of the growth law and the order of the total reaction rate. We also demonstrate that the characteristics of the particle population are strongly dependent on the way supersaturation is reached (7). Such a microscopic approach thus proves to be well suited to elucidate the mechanism of nanoparticle formation in natural and industrial contexts, involving silica, but also other mineral phases produced as nanoparticles (8). (1) Noguera C., Fritz B., Clément A. and Barronet A., J. Cryst. Growth, 2006, 297, 180. (2) Noguera C., Fritz B., Clément A. and Barronet A., J. Cryst. Growth, 2006, 297, 187. (3) Fritz B., Clément A., Amal Y. and Noguera C., Geochim. Cosmochim. Acta, 2009, 73, 1340. (4) Rothbaum, H.P. and Rohde A.G., J. Colloid Interf. Sci., 1979,71, 533. (5) Tobler D.J., Shaw S. and Benning L.G., Geochim

  11. Comparing dynamic connective tissue in echinoderms and sponges: morphological and mechanical aspects and environmental sensitivity.

    PubMed

    Sugni, Michela; Fassini, Dario; Barbaglio, Alice; Biressi, Anna; Di Benedetto, Cristiano; Tricarico, Serena; Bonasoro, Francesco; Wilkie, Iain C; Candia Carnevali, Maria Daniela

    2014-02-01

    Echinoderms and sponges share a unique feature that helps them face predators and other environmental pressures. They both possess collagenous tissues with adaptable viscoelastic properties. In terms of morphology these structures are typical connective tissues containing collagen fibrils, fibroblast- and fibroclast-like cells, as well as unusual components such as, in echinoderms, neurosecretory-like cells that receive motor innervation. The mechanisms underpinning the adaptability of these tissues are not completely understood. Biomechanical changes can lead to an abrupt increase in stiffness (increasing protection against predation) or to the detachment of body parts (in response to a predator or to adverse environmental conditions) that are regenerated. Apart from these advantages, the responsiveness of echinoderm and sponge collagenous tissues to ionic composition and temperature makes them potentially vulnerable to global environmental changes.

  12. The emerging role of phosphoinositide clustering in intracellular trafficking and signal transduction

    PubMed Central

    Picas, Laura; Gaits-Iacovoni, Frederique; Goud, Bruno

    2016-01-01

    Phosphoinositides are master regulators of multiple cellular processes: from vesicular trafficking to signaling, cytoskeleton dynamics, and cell growth. They are synthesized by the spatiotemporal regulated activity of phosphoinositide-metabolizing enzymes. The recent observation that some protein modules are able to cluster phosphoinositides suggests that alternative or complementary mechanisms might operate to stabilize the different phosphoinositide pools within cellular compartments. Herein, we discuss the different known and potential molecular players that are prone to engage phosphoinositide clustering and elaborate on how such a mechanism might take part in the regulation of intracellular trafficking and signal transduction. PMID:27092250

  13. Comparative Transcriptome Analyses Reveal a Special Glucosinolate Metabolism Mechanism in Brassica alboglabra Sprouts

    PubMed Central

    Guo, Rongfang; Huang, Zhongkai; Deng, Yanping; Chen, Xiaodong; XuHan, Xu; Lai, Zhongxiong

    2016-01-01

    Brassica sprouts contain abundant phytochemicals, especially glucosinolates (GSs). Various methods have been used to enhance GS content in sprouts. However, the molecular basis of GS metabolism in sprouts remains an open question. Here we employed RNA-seq analysis to compare the transcriptomes of high-GS (JL-08) and low-GS (JL-09) Brassica alboglabra sprouts. Paired-end Illumina RNA-seq reads were generated and mapped to the Brassica oleracea reference genome. The differentially expressed genes were analyzed between JL-08 and JL-09. Among these, 1477 genes were up-regulated and 1239 down-regulated in JL-09 compared with JL-08. Enrichment analysis of these differentially expressed genes showed that the GS biosynthesis had the smallest enrichment factor and the highest Q-value of all metabolic pathways in Kyoto Encyclopedia of Genes and Genomes database, indicating the main metabolic difference between JL-08 and JL-09 is the GS biosynthetic pathway. Thirty-seven genes of the sequenced data were annotated as putatively involved in GS biosynthesis, degradation, and regulation, of which 11 were differentially expressed in JL-08 and JL-09. The expression level of GS degradation enzyme myrosinase in high-GS JL-08 was lower compared with low-GS JL-09. Surprisingly, in high-GS JL-08, the expression levels of GS biosynthesis genes were also lower than those in low-GS JL-09. As the GS contents in sprouts are determined by dynamic equilibrium of seed stored GS mobilization, de novo synthesis, degradation, and extra transport, the result of this study leads us to suggest that efforts to increase GS content should focus on either raising GS content in seeds or decreasing myrosinase activity, rather than improving the expression level of GS biosynthesis genes in sprouts. PMID:27757119

  14. Postsynaptic Signal Transduction Models for Long-Term Potentiation and Depression

    PubMed Central

    Manninen, Tiina; Hituri, Katri; Kotaleski, Jeanette Hellgren; Blackwell, Kim T.; Linne, Marja-Leena

    2010-01-01

    More than a hundred biochemical species, activated by neurotransmitters binding to transmembrane receptors, are important in long-term potentiation (LTP) and long-term depression (LTD). To investigate which species and interactions are critical for synaptic plasticity, many computational postsynaptic signal transduction models have been developed. The models range from simple models with a single reversible reaction to detailed models with several hundred kinetic reactions. In this study, more than a hundred models are reviewed, and their features are compared and contrasted so that similarities and differences are more readily apparent. The models are classified according to the type of synaptic plasticity that is modeled (LTP or LTD) and whether they include diffusion or electrophysiological phenomena. Other characteristics that discriminate the models include the phase of synaptic plasticity modeled (induction, expression, or maintenance) and the simulation method used (deterministic or stochastic). We find that models are becoming increasingly sophisticated, by including stochastic properties, integrating with electrophysiological properties of entire neurons, or incorporating diffusion of signaling molecules. Simpler models continue to be developed because they are computationally efficient and allow theoretical analysis. The more complex models permit investigation of mechanisms underlying specific properties and experimental verification of model predictions. Nonetheless, it is difficult to fully comprehend the evolution of these models because (1) several models are not described in detail in the publications, (2) only a few models are provided in existing model databases, and (3) comparison to previous models is lacking. We conclude that the value of these models for understanding molecular mechanisms of synaptic plasticity is increasing and will be enhanced further with more complete descriptions and sharing of the published models. PMID:21188161

  15. Microgravity-induced alterations in signal transduction in cells of the immune system

    NASA Astrophysics Data System (ADS)

    Paulsen, Katrin; Thiel, Cora; Timm, Johanna; Schmidt, Peter M.; Huber, Kathrin; Tauber, Svantje; Hemmersbach, Ruth; Seibt, Dieter; Kroll, Hartmut; Grote, Karl-Heinrich; Zipp, Frauke; Schneider-Stock, Regine; Cogoli, Augusto; Hilliger, Andre; Engelmann, Frank; Ullrich, Oliver

    2010-11-01

    Since decades it is known that the activity of cells of the immune system is severely dysregulated in microgravity, however, the underlying molecular aspects have not been elucidated yet. The identification of gravity-sensitive molecular mechanisms in cells of the immune system is an important and indispensable prerequisite for the development of counteractive measures to prevent or treat disturbed immune cell function of astronauts during long-term space missions. Moreover, their sensitivity to altered gravity renders immune cells an ideal model system to understand if and how gravity on Earth is required for normal mammalian cell function and signal transduction. We investigated the effect of simulated weightlessness (2D clinostat) and of real microgravity (parabolic flights) on key signal pathways in a human monocytic and a T lymphocyte cell line. We found that cellular responses to microgravity strongly depend on the cell-type and the conditions in which the cells are subjected to microgravity. In Jurkat T cells, enhanced phosphorylation of the MAP kinases ERK-1/2, MEK and p38 and inhibition of nuclear translocation of NF-kB were the predominant responses to simulated weightlessness, in either stimulated or non-stimulated cells. In contrast, non-stimulated monocytic U937 cells responded to simulated weightlessness with enhanced overall tyrosine-phosphorylation and activation of c-jun, whereas PMA-stimulated U937 cells responded the opposite way with reduced tyrosine-phosphorylation and reduced activation of c-jun, compared with PMA-stimulated 1 g controls. P53 protein was phosphorylated rapidly in microgravity. The identification of gravi-sensitive mechanisms in cells of the immune system will not only enable us to understand and prevent the negative effects of long time exposure to microgravity on Astronauts, but could also lead to novel therapeutic targets in general.

  16. Molecular Mechanisms of Reception and Perireception in Crustacean Chemoreception: A Comparative Review.

    PubMed

    Derby, Charles D; Kozma, Mihika T; Senatore, Adriano; Schmidt, Manfred

    2016-06-01

    This review summarizes our present knowledge of chemoreceptor proteins in crustaceans, using a comparative perspective to review these molecules in crustaceans relative to other metazoan models of chemoreception including mammals, insects, nematodes, and molluscs. Evolution has resulted in unique expansions of specific gene families and repurposing of them for chemosensation in various clades, including crustaceans. A major class of chemoreceptor proteins across crustaceans is the Ionotropic Receptors, which diversified from ionotropic glutamate receptors in ancient protostomes but which are not present in deuterostomes. Representatives of another major class of chemoreceptor proteins-the Grl/GR/OR family of ionotropic 7-transmembrane receptors-are diversified in insects but to date have been reported in only one crustacean species, Daphnia pulex So far, canonic 7-transmembrane G-protein coupled receptors, the principal chemoreceptors in vertebrates and reported in a few protostome clades, have not been identified in crustaceans. More types of chemoreceptors are known throughout the metazoans and might well be expected to be discovered in crustaceans. Our review also provides a comparative coverage of perireceptor events in crustacean chemoreception, including molecules involved in stimulus acquisition, stimulus delivery, and stimulus removal, though much less is known about these events in crustaceans, particularly at the molecular level.

  17. Molecular Mechanisms of Reception and Perireception in Crustacean Chemoreception: A Comparative Review.

    PubMed

    Derby, Charles D; Kozma, Mihika T; Senatore, Adriano; Schmidt, Manfred

    2016-06-01

    This review summarizes our present knowledge of chemoreceptor proteins in crustaceans, using a comparative perspective to review these molecules in crustaceans relative to other metazoan models of chemoreception including mammals, insects, nematodes, and molluscs. Evolution has resulted in unique expansions of specific gene families and repurposing of them for chemosensation in various clades, including crustaceans. A major class of chemoreceptor proteins across crustaceans is the Ionotropic Receptors, which diversified from ionotropic glutamate receptors in ancient protostomes but which are not present in deuterostomes. Representatives of another major class of chemoreceptor proteins-the Grl/GR/OR family of ionotropic 7-transmembrane receptors-are diversified in insects but to date have been reported in only one crustacean species, Daphnia pulex So far, canonic 7-transmembrane G-protein coupled receptors, the principal chemoreceptors in vertebrates and reported in a few protostome clades, have not been identified in crustaceans. More types of chemoreceptors are known throughout the metazoans and might well be expected to be discovered in crustaceans. Our review also provides a comparative coverage of perireceptor events in crustacean chemoreception, including molecules involved in stimulus acquisition, stimulus delivery, and stimulus removal, though much less is known about these events in crustaceans, particularly at the molecular level. PMID:27107425

  18. Comparing Residue Clusters from Thermophilic and Mesophilic Enzymes Reveals Adaptive Mechanisms

    PubMed Central

    Sammond, Deanne W.; Kastelowitz, Noah; Himmel, Michael E.; Yin, Hang; Crowley, Michael F.; Bomble, Yannick J.

    2016-01-01

    Understanding how proteins adapt to function at high temperatures is important for deciphering the energetics that dictate protein stability and folding. While multiple principles important for thermostability have been identified, we lack a unified understanding of how internal protein structural and chemical environment determine qualitative or quantitative impact of evolutionary mutations. In this work we compare equivalent clusters of spatially neighboring residues between paired thermophilic and mesophilic homologues to evaluate adaptations under the selective pressure of high temperature. We find the residue clusters in thermophilic enzymes generally display improved atomic packing compared to mesophilic enzymes, in agreement with previous research. Unlike residue clusters from mesophilic enzymes, however, thermophilic residue clusters do not have significant cavities. In addition, anchor residues found in many clusters are highly conserved with respect to atomic packing between both thermophilic and mesophilic enzymes. Thus the improvements in atomic packing observed in thermophilic homologues are not derived from these anchor residues but from neighboring positions, which may serve to expand optimized protein core regions. PMID:26741367

  19. Comparing residue clusters from thermophilic and mesophilic enzymes reveals adaptive mechanisms

    DOE PAGESBeta

    Sammond, Deanne W.; Kastelowitz, Noah; Himmel, Michael E.; Yin, Hang; Crowley, Michael F.; Bomble, Yannick J.

    2016-01-07

    Understanding how proteins adapt to function at high temperatures is important for deciphering the energetics that dictate protein stability and folding. While multiple principles important for thermostability have been identified, we lack a unified understanding of how internal protein structural and chemical environment determine qualitative or quantitative impact of evolutionary mutations. In this work we compare equivalent clusters of spatially neighboring residues between paired thermophilic and mesophilic homologues to evaluate adaptations under the selective pressure of high temperature. We find the residue clusters in thermophilic enzymes generally display improved atomic packing compared to mesophilic enzymes, in agreement with previous research.more » Unlike residue clusters from mesophilic enzymes, however, thermophilic residue clusters do not have significant cavities. In addition, anchor residues found in many clusters are highly conserved with respect to atomic packing between both thermophilic and mesophilic enzymes. As a result, the improvements in atomic packing observed in thermophilic homologues are not derived from these anchor residues but from neighboring positions, which may serve to expand optimized protein core regions.« less

  20. Phosphoproteomic analysis of induced resistance reveals activation of signal transduction processes by beneficial and pathogenic interaction in grapevine.

    PubMed

    Perazzolli, Michele; Palmieri, Maria Cristina; Matafora, Vittoria; Bachi, Angela; Pertot, Ilaria

    2016-05-20

    Protein phosphorylation regulates several key processes of the plant immune system. Protein kinases and phosphatases are pivotal regulators of defense mechanisms elicited by resistance inducers. However, the phosphorylation cascades that trigger the induced resistance mechanisms in plants have not yet been deeply investigated. The beneficial fungus Trichoderma harzianum T39 (T39) induces resistance against grapevine downy mildew (Plasmopara viticola), but its efficacy could be further improved by a better understanding of the cellular regulations involved. We investigated quantitative changes in the grapevine phosphoproteome during T39-induced resistance to get an overview of regulatory mechanisms of downy mildew resistance. Immunodetection experiments revealed activation of the 45 and 49kDa kinases by T39 treatment both before and after pathogen inoculation, and the phosphoproteomic analysis identified 103 phosphopeptides that were significantly affected by the phosphorylation cascades during T39-induced resistance. Peptides affected by T39 treatment showed comparable phosphorylation levels after P. viticola inoculation, indicating activation of the microbial recognition machinery before pathogen infection. Phosphorylation profiles of proteins related to photosynthetic processes and protein ubiquitination indicated a partial overlap of cellular responses in T39-treated and control plants. However, phosphorylation changes of proteins involved in response to stimuli, signal transduction, hormone signaling, gene expression regulation, and RNA metabolism were exclusively elicited by P. viticola inoculation in T39-treated plants. These results highlighted the relevance of phosphorylation changes during T39-induced resistance and identified key regulator candidates of the grapevine defense against downy mildew. PMID:27010348

  1. Cultural capital or relative risk aversion? Two mechanisms for educational inequality compared.

    PubMed

    van de Werfhorst, Herman G; Hofstede, Saskia

    2007-09-01

    In this paper we empirically examined two explanatory mechanisms for educational inequality: cultural reproduction and relative risk aversion, using survey data taken from secondary school pupils in Amsterdam. Cultural reproduction theory seeks to explain class variations in schooling by cultural differences between social classes. Relative risk aversion theory argues that educational inequalities can be understood by between-class variation in the necessity of pursuing education at branching points in order to avoid downward mobility. We showed that class variations in early demonstrated ability are for a substantial part cultural: cultural capital - measured by parental involvement in highbrow culture - affected school performance at the primary and secondary level. However, relative risk aversion - operationalized by being concerned with downward mobility - strongly affects schooling ambitions, whereas cultural capital had no effect. Thus, we conclude that 'primary effects' of social origin on schooling outcomes are manifested through cultural capital and not through relative risk aversion (in addition to other potential sources of class variations such as genetics). Relative risk aversion, and not cultural capital, affects schooling ambitions, which is relevant for our understanding of secondary effects.

  2. Comparative population genetics of two invading ticks: evidence of the ecological mechanisms underlying tick range expansions

    PubMed Central

    Nadolny, Robyn; Gaff, Holly; Carlsson, Jens; Gauthier, David

    2015-01-01

    Two species of ixodid tick, Ixodes affinis Neumann and Amblyomma maculatum Koch, are simultaneously expanding their ranges throughout the mid-Atlantic region of the US. Although we have some understanding of the ecology and life history of these species, the ecological mechanisms governing where and how new populations establish and persist are unclear. To assess population connectivity and ancestry, we sequenced a fragment of the 16S mitochondrial rRNA gene from a representative sample of individuals of both species from populations throughout the eastern US. We found that despite overlapping host preferences throughout ontogeny, each species exhibited very different genetic and geographic patterns of population establishment and connectivity. Ixodes affinis was of two distinct mitochondrial clades, with a clear geographic break separating northern and southern populations. Both I. affinis populations showed evidence of recent expansion, although the southern population was more genetically diverse, indicating a longer history of establishment. Amblyomma maculatum exhibited diverse haplotypes that showed no significant relationship with geographic patterns and little apparent connectivity between sites. Heteroplasmy was also observed in the 16S mitochondrial rRNA gene in 3.5% of A. maculatum individuals. Genetic evidence suggests that these species rely on different key life stages to successfully disperse into novel environments, and that host vagility, habitat stability and habitat connectivity all play critical roles in the establishment of new tick populations. PMID:26254575

  3. Comparative Analysis of the Tour Jete and Aerial with Detailed Analysis of Aerial Takeoff Mechanics

    NASA Astrophysics Data System (ADS)

    Pierson, Mimi; Coplin, Kim

    2006-10-01

    Whether internally as muscle tension or from external sources, forces are necessary for all motion. This research focused on athletic rotations where conditions of flight are established during takeoff. By studying reaction forces that produce torques, moments of inertia, and linear and angular differences between distinct rotations around different principle axes of the body (tour jete in ballet - longitudinal axis; aerial in gymnastics - anteroposterior axis), and by looking at the values of angular momentum in the specific mechanics of aerial takeoff, we can gain insight into possible causes of injury, flaws in technique and limitations of athletes. Results showed significant differences in the horizontal and vertical components of takeoff between the tour jete and the aerial, and a realization that torque was produced in different biomechanical planes. Both rotations showed braking forces before takeoff to counteract forward momentum and increase vertical lift, but the angle of applied force varied, and the horizontal components of velocity and force and vertical velocity as well as moment of inertia throughout flight were consistently greater for the aerial. Breakdown of aerial takeoff highlighted the relative importance of the takeoff phases, showing that completion depends fundamentally upon the rotation of the rear foot and torso twisting during takeoff rather than the last foot in contact with the ground.

  4. Comparative Transcriptional Profiling and Preliminary Study on Heterosis Mechanism of Super-Hybrid Rice

    PubMed Central

    Song, Gui-Sheng; Zhai, Hong-Li; Peng, Yong-Gang; Zhang, Lei; Wei, Gang; Chen, Xiao-Ying; Xiao, Yu-Guo; Wang, Lili; Wu, Bin; Zhang, Yu; Feng, Xiu-Jing; Gong, Wan-Kui; Liu, Yao; Yin, Zhi-Jie; Wang, Feng; Liu, Guo-Zhen; Xu, Hong-Lin; Wei, Xiao-Li; Zhao, Xiao-Ling; Ouwerkerk, Pieter B.F.; Hankemeier, Thomas; Reijmers, Theo; van der Heijden, Rob; Wang, Mei; van der Greef, Jan; Zhu, Zhen

    2010-01-01

    Heterosis is a biological phenomenon whereby the offspring from two parents show improved and superior performance than either inbred parental lines. Hybrid rice is one of the most successful apotheoses in crops utilizing heterosis. Transcriptional profiling of F1 super-hybrid rice Liangyou-2186 and its parents by serial analysis of gene expression (SAGE) revealed 1183 differentially expressed genes (DGs), among which DGs were found significantly enriched in pathways such as photosynthesis and carbon-fixation, and most of the key genes involved in the carbon-fixation pathway exhibited up-regulated expression in F1 hybrid rice. Moreover, increased catabolic activity of corresponding enzymes and photosynthetic efficiency were also detected, which combined to indicate that carbon fixation is enhanced in F1 hybrid, and might probably be associated with the yield vigor and heterosis in super-hybrid rice. By correlating DGs with yield-related quantitative trait loci (QTL), a potential relationship between differential gene expression and phenotypic changes was also found. In addition, a regulatory network involving circadian-rhythms and light signaling pathways was also found, as previously reported in Arabidopsis, which suggest that such a network might also be related with heterosis in hybrid rice. Altogether, the present study provides another view for understanding the molecular mechanism underlying heterosis in rice. PMID:20729474

  5. The octopus: a model for a comparative analysis of the evolution of learning and memory mechanisms.

    PubMed

    Hochner, Binyamin; Shomrat, Tal; Fiorito, Graziano

    2006-06-01

    Comparative analysis of brain function in invertebrates with sophisticated behaviors, such as the octopus, may advance our understanding of the evolution of the neural processes that mediate complex behaviors. Until the last few years, this approach was infeasible due to the lack of neurophysiological tools for testing the neural circuits mediating learning and memory in the brains of octopus and other cephalopods. Now, for the first time, the adaptation of modern neurophysiological methods to the study of the central nervous system of the octopus allows this avenue of research. The emerging results suggest that a convergent evolutionary process has led to the selection of vertebrate-like neural organization and activity-dependent long-term synaptic plasticity. As octopuses and vertebrates are very remote phylogenetically, this convergence suggests the importance of the shared properties for the mediation of learning and memory.

  6. Coupled hydro-mechanical processes in crytalline rock and ininduratedand plastic clays: A comparative discussion

    SciTech Connect

    Tsang, Chin-Fu; Blumling, Peter; Bernier, Frederic

    2006-02-15

    This paper provides a comparative discussion of coupledhydromechanical processes in three different geological formations:crystalline rock, plastic clay, and indurated clay. First, the importantprocesses and associated property characteristics in the three rock typesare discussed. Then, one particular hydromechanical coupling is broughtup for detailed consideration, that of pore pressure changes in nearbyrock during tunnel excavation. Three field experiments in the three rocktypes are presented and their results are discussed. It is shown that themain physical processes are common to all three rock types, but with verydifferent time constants. The different issues raised by these cases arepointed out, and the transferable lessons learned are identified. Suchcross fertilization and simultaneous understanding of coupled processesin three very different rock types help to greatly enhance confidence inthe state of science in this field.

  7. Comparative study on the mechanisms of rotavirus inactivation by sodium dodecyl sulfate and ethylenediaminetetraacetate

    SciTech Connect

    Ward, R.L.; Ashley, C.S.

    1980-06-01

    This report describes a comparative study on the effects of the anionic detergent sodium dodecyl sulfate and the chelating agent ethylenediaminetetraacetate on purified rotavirus SA-11 particles. Both chemicals readily inactivated rotavirus at quite low concentrations and under very mild conditions. In addition, both agents modified the viral capsid and prevented the adsorption of inactivated virions to cells. Capsid damage by ethylenediaminetetraacetate caused a shift in the densities of rotavirions from about l.35 to about 1.37 g/ml and a reduction in their sedimentation coefficients. Sodium dodcyl sulfate, on the other hand, did not detectably alter either of these physical properties of rotavirions. Both agents caused some alteration of the isoelectric points of the virions. Finally, analysis of rotavirus proteins showed that ethylenediaminetetraacetate caused the loss of two protein peaks from the electrophoretic pattern of virions but sodium dodecyl sulfate caused the loss of only one of these same protein peaks.

  8. Comparative study of mechanical, hydrothermal, chemical and enzymatic treatments of digested biofibers to improve biogas production.

    PubMed

    Bruni, Emiliano; Jensen, Anders Peter; Angelidaki, Irini

    2010-11-01

    Organic waste such as manure is an important resource for biogas production. The biodegradability of manures is however limited because of the recalcitrant nature of the biofibers it contains. To increase the biogas potential of the biofibers in digested manure, we investigated physical treatment (milling), chemical treatment (CaO), biological treatment (enzymatic and partial aerobic microbial conversion), steam treatment with catalyst (H(3)PO(4) or NaOH) and combination of biological and steam treatments (biofibers steam-treated with catalyst were treated with laccase enzyme). We obtained the highest methane yield increase through the chemical treatment that resulted in 66% higher methane production compared to untreated biofibers. The combination of steam treatment with NaOH and subsequent enzymatic treatment increased the methane yield by 34%. To choose the optimal treatment, the energy requirements relative to the energy gain as extra biogas production have to be taken into account, as well as the costs of chemicals or enzymes.

  9. A Comparative Study of the Physical and Mechanical Properties of Hydrogen Using Data Mining Research Techniques

    NASA Astrophysics Data System (ADS)

    Settouti, Nadera; Aourag, Hafid

    2015-09-01

    Hydrogen was the first element to exist in the universe. It is the lightest and simplest element, but chemists do not agree about its placement in the periodic table; its position has given rise to much confusion. Metallization of hydrogen under high pressure influences its properties and its placement in the periodic table. The properties of groups I, IV, and VII are investigated, and are then compared to those of hydrogen. In this study, we present a data mining approach to determine models and discover the similarities included in the datasets. Principal component analysis and partial least squares regression were applied as data analysis techniques in order to explore multivariate data. Our results indicate that hydrogen shares some properties with certain elements and groups in the periodic table, such as carbon group elements, but not entirely, because hydrogen is still considered as an element that is special and apart.

  10. Mechanics of the implant-abutment connection: an 8-degree taper compared to a butt joint connection.

    PubMed

    Merz, B R; Hunenbart, S; Belser, U C

    2000-01-01

    This paper presents aa comparison between the 8-degree Morse Taper and the butt joint aa connections between an implant and an abutment. Three-dimensional, non-linear finite element models were created to compare the 2 connection principles under equal conditions. The loading configuration was thereby modeled according to a test setup actually used for the dynamic long-term testing of dental implants as required for regulatory purposes. The results give insight into the mechanics involved in each type of connection and are compared to actual findings with the testing machine. The comparison indicates the superior mechanics of conical abutment connections and helps to explain their significantly better long-term stability in the clinical application.

  11. Ionic mechanisms limiting cardiac repolarization reserve in humans compared to dogs.

    PubMed

    Jost, Norbert; Virág, László; Comtois, Philippe; Ordög, Balázs; Szuts, Viktória; Seprényi, György; Bitay, Miklós; Kohajda, Zsófia; Koncz, István; Nagy, Norbert; Szél, Tamás; Magyar, János; Kovács, Mária; Puskás, László G; Lengyel, Csaba; Wettwer, Erich; Ravens, Ursula; Nánási, Péter P; Papp, Julius Gy; Varró, András; Nattel, Stanley

    2013-09-01

    The species-specific determinants of repolarization are poorly understood. This study compared the contribution of various currents to cardiac repolarization in canine and human ventricle. Conventional microelectrode, whole-cell patch-clamp, molecular biological and mathematical modelling techniques were used. Selective IKr block (50-100 nmol l(-1) dofetilide) lengthened AP duration at 90% of repolarization (APD90) >3-fold more in human than dog, suggesting smaller repolarization reserve in humans. Selective IK1 block (10 μmol l(-1) BaCl2) and IKs block (1 μmol l(-1) HMR-1556) increased APD90 more in canine than human right ventricular papillary muscle. Ion current measurements in isolated cardiomyocytes showed that IK1 and IKs densities were 3- and 4.5-fold larger in dogs than humans, respectively. IKr density and kinetics were similar in human versus dog. ICa and Ito were respectively ~30% larger and ~29% smaller in human, and Na(+)-Ca(2+) exchange current was comparable. Cardiac mRNA levels for the main IK1 ion channel subunit Kir2.1 and the IKs accessory subunit minK were significantly lower, but mRNA expression of ERG and KvLQT1 (IKr and IKs α-subunits) were not significantly different, in human versus dog. Immunostaining suggested lower Kir2.1 and minK, and higher KvLQT1 protein expression in human versus canine cardiomyocytes. IK1 and IKs inhibition increased the APD-prolonging effect of IKr block more in dog (by 56% and 49%, respectively) than human (34 and 16%), indicating that both currents contribute to increased repolarization reserve in the dog. A mathematical model incorporating observed human-canine ion current differences confirmed the role of IK1 and IKs in repolarization reserve differences. Thus, humans show greater repolarization-delaying effects of IKr block than dogs, because of lower repolarization reserve contributions from IK1 and IKs, emphasizing species-specific determinants of repolarization and the limitations of animal models for

  12. Mitochondria-derived hydrogen peroxide selectively enhances T cell receptor-initiated signal transduction.

    PubMed

    Gill, Tejpal; Levine, Alan D

    2013-09-01

    T cell receptor (TCR)-initiated signal transduction is reported to increase production of intracellular reactive oxygen species, such as superoxide (O2˙(-)) and hydrogen peroxide (H2O2), as second messengers. Although H2O2 can modulate signal transduction by inactivating protein phosphatases, the mechanism and the subcellular localization of intracellular H2O2 as a second messenger of the TCR are not known. The antioxidant enzyme superoxide dismutase (SOD) catalyzes the dismutation of highly reactive O2˙(-) into H2O2 and thus acts as an intracellular generator of H2O2. As charged O2˙(-) is unable to diffuse through intracellular membranes, cells express distinct SOD isoforms in the cytosol (Cu,Zn-SOD) and mitochondria (Mn-SOD), where they locally scavenge O2˙(-) leading to production of H2O2. A 2-fold organelle-specific overexpression of either SOD in Jurkat T cell lines increases intracellular production of H2O2 but does not alter the levels of intracellular H2O2 scavenging enzymes such as catalase, membrane-bound peroxiredoxin1 (Prx1), and cytosolic Prx2. We report that overexpression of Mn-SOD enhances tyrosine phosphorylation of TCR-associated membrane proximal signal transduction molecules Lck, LAT, ZAP70, PLCγ1, and SLP76 within 1 min of TCR cross-linking. This increase in mitochondrial H2O2 specifically modulates MAPK signaling through the JNK/cJun pathway, whereas overexpressing Cu,Zn-SOD had no effect on any of these TCR-mediated signaling molecules. As mitochondria translocate to the immunological synapse during TCR activation, we hypothesize this translocation provides the effective concentration of H2O2 required to selectively modulate downstream signal transduction pathways.

  13. Comparative Metagenomic Analysis Reveals Mechanisms for Stress Response in Hypoliths from Extreme Hyperarid Deserts.

    PubMed

    Le, Phuong Thi; Makhalanyane, Thulani P; Guerrero, Leandro D; Vikram, Surendra; Van de Peer, Yves; Cowan, Don A

    2016-01-01

    Understanding microbial adaptation to environmental stressors is crucial for interpreting broader ecological patterns. In the most extreme hot and cold deserts, cryptic niche communities are thought to play key roles in ecosystem processes and represent excellent model systems for investigating microbial responses to environmental stressors. However, relatively little is known about the genetic diversity underlying such functional processes in climatically extreme desert systems. This study presents the first comparative metagenome analysis of cyanobacteria-dominated hypolithic communities in hot (Namib Desert, Namibia) and cold (Miers Valley, Antarctica) hyperarid deserts. The most abundant phyla in both hypolith metagenomes were Actinobacteria, Proteobacteria, Cyanobacteria and Bacteroidetes with Cyanobacteria dominating in Antarctic hypoliths. However, no significant differences between the two metagenomes were identified. The Antarctic hypolithic metagenome displayed a high number of sequences assigned to sigma factors, replication, recombination and repair, translation, ribosomal structure, and biogenesis. In contrast, the Namib Desert metagenome showed a high abundance of sequences assigned to carbohydrate transport and metabolism. Metagenome data analysis also revealed significant divergence in the genetic determinants of amino acid and nucleotide metabolism between these two metagenomes and those of soil from other polar deserts, hot deserts, and non-desert soils. Our results suggest extensive niche differentiation in hypolithic microbial communities from these two extreme environments and a high genetic capacity for survival under environmental extremes. PMID:27503299

  14. Understanding the mechanism of non-polar Diels-Alder reactions. A comparative ELF analysis of concerted and stepwise diradical mechanisms.

    PubMed

    Domingo, Luis R; Chamorro, Eduardo; Pérez, Patricia

    2010-12-21

    The electron-reorganization along the concerted and stepwise pathways associated with the non-polar Diels-Alder reaction between cyclopentadiene (Cp, 1) and ethylene (2) has been studied using the topological analysis of the electron localization function (ELF) at the B3LYP/6-31G(d) level of theory. ELF results for the concerted mechanism stresses that the electron-reorganization demanded on the diene and ethylene reagents to reach two pseudo-diradical structures is responsible for the high activation energy. A comparative ELF analysis of some relevant points of the non-polar Diels-Alder reaction between Cp and styrene (10) suggests that these concerted mechanisms do not have a pericyclic electron-reorganization.

  15. Comparing the similarity of responses received from studies in Amazon's Mechanical Turk to studies conducted online and with direct recruitment.

    PubMed

    Bartneck, Christoph; Duenser, Andreas; Moltchanova, Elena; Zawieska, Karolina

    2015-01-01

    Computer and internet based questionnaires have become a standard tool in Human-Computer Interaction research and other related fields, such as psychology and sociology. Amazon's Mechanical Turk (AMT) service is a new method of recruiting participants and conducting certain types of experiments. This study compares whether participants recruited through AMT give different responses than participants recruited through an online forum or recruited directly on a university campus. Moreover, we compare whether a study conducted within AMT results in different responses compared to a study for which participants are recruited through AMT but which is conducted using an external online questionnaire service. The results of this study show that there is a statistical difference between results obtained from participants recruited through AMT compared to the results from the participant recruited on campus or through online forums. We do, however, argue that this difference is so small that it has no practical consequence. There was no significant difference between running the study within AMT compared to running it with an online questionnaire service. There was no significant difference between results obtained directly from within AMT compared to results obtained in the campus and online forum condition. This may suggest that AMT is a viable and economical option for recruiting participants and for conducting studies as setting up and running a study with AMT generally requires less effort and time compared to other frequently used methods. We discuss our findings as well as limitations of using AMT for empirical studies.

  16. Gene amplification in thyroid cancer: A new mechanism defined by comparative genomic hybridization

    SciTech Connect

    Chen, X.N.; Lai, E.; Fagin, J.A.

    1994-09-01

    More than 12,000 new cases of thyroid cancer develop each year in the USA for which scant information is available on cytogenetic abnormalities. Comparative genomic hybridization (CGH) now permits the detection and mapping of amplified regions in DNAs without the need for metaphase tumor preparations. Using CGH, we have analyzed the DNA copy number changes in 10 human thyroid tumors. Further, the procedure of CGH was modified by using a chromomycin and sitamycin reverse-banding technique to provide a high resolution assignment of amplified regions. The results revealed a series of copy number changes including amplifications of chromosome bands 1p36, 1q42, 2p13, 2p21, 19q13.1 and losses of chromosome bands 16q12-13 and 16q22-23. The most striking regions of amplifications, band 2p21 and 2p13 were further analyzed by constructing a 90-member chromosome 2 BAC map and using 9 members of this to analyze WRO, a thyroid follicular carcinoma cell line containing double minutes (dm). Eight BACs revealed three copies of chromosome 2; one BAC mapping at the 2p21-22 border revealed significant and variable amplification in all of the metaphase dm`s suggesting a local amplification. Interphase analyses revealed about 40-70 signals per nucleus. The variable signals seen in the WRO cell population suggest the existence of a minor population with higher copy number and smaller amplicon size. In summary, high resolution CGH has been combined with BAC contig construction for the analysis of thyroid tumor to reveal a very specific region amplification on chromosome 2p21 likely to contain a new gene involved in thyroid cancer tumorigenesis.

  17. Reciprocity and gyrotropism in magnetic resonance transduction

    SciTech Connect

    Tropp, James

    2006-12-15

    We give formulas for transduction in magnetic resonance - i.e., the appearance of an emf due to Larmor precession of spins - based upon the modified Lorentz reciprocity principle for gyrotropic (also called 'nonreciprocal') media, i.e., in which a susceptibility tensor is carried to its transpose by reversal of an external static field [cf., R. F. Harrington and A. T. Villeneuve IRE Trans. Microwave Theory and Technique MTT6, 308 (1958)]. Prior applications of reciprocity to magnetic resonance, despite much success, have ignored the gyrotropism which necessarily arises due to nuclear and/or unpaired electronic spins. For detection with linearly polarized fields, oscillating at the Larmor frequency, the emf is written in terms of a volume integral containing a product of two factors which we define as the antenna patterns, i.e. (H{sub 1x}{+-}iH{sub 1y}), where, e.g., for a single transceive antenna, the H's are just the spatially dependent oscillatory magnetic field strengths, per the application of some reference current at the antenna terminals, with the negative sign obtaining for transmission, and the positive for reception. Similar expressions hold for separate transmit and receive antennas; expressions are also given for circular polarization of the fields. We then exhibit a receive-only array antenna of two elements for magnetic resonance imaging of protons, which, due an intensity artifact arising from stray reactive coupling of the elements, produces, despite its own bilateral symmetry, asymmetric proton NMR images of a symmetric cylindrical phantom containing aqueous saline solution [J. Tropp and T. Schirmer, J. Magn. Reson. 151, 146 (2001)]. Modification of this two-port antenna, to function in transmit-receive mode, allows us to demonstrate highly nonreciprocal behavior: that is, to record images (of cylindrical test phantoms containing aqueous saline solution) whose appearance dramatically changes, when the roles of transmission and reception are

  18. Antitumor Activity of Tenacissoside H on Esophageal Cancer through Arresting Cell Cycle and Regulating PI3K/Akt-NF-κB Transduction Cascade

    PubMed Central

    Jia, Yong-sen; Hu, Xue-qin; Gabriella, Hegyi; Qin, Li-juan; Meggyeshazi, Nora

    2015-01-01

    Objective. The purpose of the study was to elucidate the molecular mechanism of tenacissoside H (TDH) inhibiting esophageal carcinoma infiltration and proliferation. Methods. In vitro, EC9706 cells were treated with TDH. Cells proliferation and cell cycle were assayed. PI3K and NF-κB mRNAs expression were determined by real time PCR. In vivo, model of nude mice with tumor was established. Mice were treated with TDH. Inhibition ratio of tumor volume was calculated. PCNA expression was examined. Protein expression in PI3K/Akt-NF-κB signaling pathway was determined. Results. In vitro, TDH significantly inhibited cells proliferation in a time-and-dose-dependent manner. TDH arrested the cell cycle in S phase and significantly inhibited PI3K and NF-κB mRNA expression, compared with blank controlled group (P < 0.05). In vivo, TDH strongly inhibits tumor growth and volume. PCNA expression was significantly decreased after treatment of TDH. TDH downregulated proteins expression in PI3K/Akt-NF-κB transduction cascade (P < 0.05). Conclusion. TDH inhibited esophageal carcinoma infiltration and proliferation both in vitro and in vivo. The anticancer activity has relation to arresting the cell cycle at the S phase, inhibited the PCNA expression of transplanted tumors in nude mice, and regulated the protein expression in the PI3K/Akt-NF-κB transduction cascade. PMID:26495015

  19. The mechanism of action of endothelin-1 as compared with other agonists in vascular smooth muscle

    SciTech Connect

    Wallnoefer, A.W.; Weir, S.; Rueegg, U.C.; Cauvin, C. )

    1989-01-01

    The effects of endothelin-1 (ET-1) on tension and membrane potential in rat isolated mesenteric resistance vessels (MRVs) and on 45Ca influx, 45Ca efflux, inositol-1,4,5-triphosphate (IP3) production, and cytoplasmic Ca2+ concentration ((Ca2+)1) in cultured aortic smooth muscle cells were compared with those of other agonists. ET-1 induced contractions of the MRVs, which were slow in onset, but reached a similar maximum amplitude (at 10 nM ET-1) as that seen with norepinephrine (NE, 10 microM) or (arg8)vasopressin (AVP, 0.1 microM). The EC50 for ET-1 was 1.3 +/- 0.1 nM. Removal of extracellular Ca2+ reduced ET-1-induced contractions to 11 +/- 3% of those in Ca2+-containing medium. With NE, the same procedure reduced contractions to 47 +/- 7% of those in Ca2+-containing medium, while with AVP, the reduction was similar in magnitude to that induced by ET-1 (11 +/- 5% of those in Ca2+-containing medium). Relaxation of ET-1-induced and NE-induced contractions by diltiazem was not complete (maximal at 58 +/- 6% with 10 microM diltiazem after 6 nM ET-1, and at 70 +/- 3% after 0.1 microM NE), in contrast to that of 80 mM K+-induced contractions, which were potently (IC50 = 0.2 microM) and completely reversed (100% relaxation at 10 microM diltiazem). ET-1 (6 nM) caused a small but significant depolarization of the MRVs (approximately 7 mV), the magnitude of which was only about one-third of that induced by equieffective contractile concentrations of NE and AVP. The voltage-sensitive Ca2+ channel agonist Bay K 8644 (1 microM), in contrast to ET-1, NE, and AVP, produced a small contraction (30 +/- 2% of the maximum response to NE), but no further depolarization when added in the presence of 15 mM K+ (which elicited approximately 12 mV depolarization but no contraction).

  20. Receptor clustering affects signal transduction at the membrane level in the reaction-limited regime

    NASA Astrophysics Data System (ADS)

    Caré, Bertrand R.; Soula, Hédi A.

    2013-01-01

    Many types of membrane receptors are found to be organized as clusters on the cell surface. We investigate the potential effect of such receptor clustering on the intracellular signal transduction stage. We consider a canonical pathway with a membrane receptor (R) activating a membrane-bound intracellular relay protein (G). We use Monte Carlo simulations to recreate biochemical reactions using different receptor spatial distributions and explore the dynamics of the signal transduction. Results show that activation of G by R is severely impaired by R clustering, leading to an apparent blunted biological effect compared to control. Paradoxically, this clustering decreases the half maximal effective dose (ED50) of the transduction stage, increasing the apparent affinity. We study an example of inter-receptor interaction in order to account for possible compensatory effects of clustering and observe the parameter range in which such interactions slightly counterbalance the loss of activation of G. The membrane receptors’ spatial distribution affects the internal stages of signal amplification, suggesting a functional role for membrane domains and receptor clustering independently of proximity-induced receptor-receptor interactions.

  1. Ex Vivo and In Vivo Lentivirus-Mediated Transduction of Airway Epithelial Progenitor Cells.

    PubMed

    Leoni, Giulia; Wasowicz, Marguerite Y; Chan, Mario; Meng, Cuixiang; Farley, Raymond; Brody, Steven L; Inoue, Makoto; Hasegawa, Mamoru; Alton, Eric W F W; Griesenbach, Uta

    2015-01-01

    A key challenge in pulmonary gene therapy for cystic fibrosis is to provide long-term correction of the genetic defect. This may be achievable by targeting airway epithelial stem/progenitor cells with an integrating vector. Here, we evaluated the ability of a lentiviral vector, derived from the simian immunodeficiency virus and pseudotyped with F and HN envelope proteins from Sendai virus, to transduce progenitor basal cells of the mouse nasal airways. We first transduced basal cell-enriched cultures ex vivo and confirmed efficient transduction of cytokeratin-5 positive cells. We next asked whether progenitor cells could be transduced in vivo. We evaluated the transduction efficiency in mice pretreated by intranasal administration of polidocanol to expose the progenitor cell layer. Compared to control mice, polidocanol treated mice demonstrated a significant increase in the number of transduced basal cells at 3 and 14 days post vector administration. At 14 days, the epithelium of treated mice contained clusters (4 to 8 adjacent cells) of well differentiated ciliated, as well as basal cells suggesting a clonal expansion. These results indicate that our lentiviral vector can transduce progenitor basal cells in vivo, although transduction required denudation of the surface epithelium prior to vector administration. PMID:26471068

  2. Priming of hepatocytes enhances in vivo liver transduction with lentiviral vectors in adult mice.

    PubMed

    Pichard, Virginie; Boni, Sébastien; Baron, William; Nguyen, Tuan Huy; Ferry, Nicolas

    2012-02-01

    Lentiviral vectors are promising tools for liver disease gene therapy, because they can achieve protracted expression of transgenes in hepatocytes. However, the question as to whether cell division is required for optimal hepatocyte transduction has still not been completely answered. Liver gene-transfer efficiency after in vivo administration of recombinant lentiviral vectors carrying a green fluorescent protein reporter gene under the control of a liver-specific promoter in mice that were either hepatectomized or treated with cholic acid or phenobarbital was compared. Phenobarbital is known as a weak inducer of hepatocyte proliferation, whereas cholic acid has no direct effect on the cell cycle. This study shows that cholic acid is able to prime hepatocytes without mitosis induction. Both phenobarbital and cholic acid significantly increased hepatocyte transduction six- to ninefold, although cholic acid did not modify the mitotic index or cell-cycle entry. However, the effect of either compound was weaker than that observed after partial hepatectomy. In no cases was there a correlation between the expression of cell-cycle marker and transduction efficiency. We conclude that priming of hepatocytes should be considered a clinically applicable strategy to enhance in vivo liver gene therapy with lentiviral vectors.

  3. Efficient biotechnological approach for lentiviral transduction of induced pluripotent stem cells.

    PubMed

    Zare, Mehrak; Soleimani, Masoud; Mohammadian, Mozhdeh; Akbarzadeh, Abolfazl; Havasi, Parvaneh; Zarghami, Nosratollah

    2016-01-01

    Induced pluripotent stem (iPS) cells are generated from differentiated adult somatic cells by reprogramming them. Unlimited self-renewal, and the potential to differentiate into any cell type, make iPS cells very promising candidates for basic and clinical research. Furthermore, iPS cells can be genetically manipulated for use as therapeutic tools. DNA can be introduced into iPS cells, using lentiviral vectors, which represent a helpful choice for efficient transduction and stable integration of transgenes. In this study, we compare two methods of lentiviral transduction of iPS cells, namely, the suspension method and the hanging drop method. In contrast to the conventional suspension method, in the hanging drop method, embryoid body (EB) formation and transduction occur concurrently. The iPS cells were cultured to form EBs, and then transduced with lentiviruses, using the conventional suspension method and the hanging drop method, to express miR-128 and green fluorescent protein (GFP). The number of transduced cells were assessed by fluorescent microscopy and flow cytometry. MTT assay and real-time PCR were performed to determine the cell viability and transgene expression, respectively. Morphologically, GFP+ cells were more detectable in the hanging drop method, and this finding was quantified by flow cytometric analysis. According to the results of the MTT assay, cell viability was considerably higher in the hanging drop method, and real-time PCR represented a higher relative expression of miR-128 in the iPS cells introduced with lentiviruses in drops. Altogether, it seems that lentiviral transduction of challenging iPS cells using the hanging drop method offers a suitable and sufficient strategy in their gene transfer, with less toxicity than the conventional suspension method.

  4. Physiological performance of warm-adapted marine ectotherms: Thermal limits of mitochondrial energy transduction efficiency.

    PubMed

    Martinez, Eloy; Hendricks, Eric; Menze, Michael A; Torres, Joseph J

    2016-01-01

    Thermal regimes in aquatic systems have profound implications for the physiology of ectotherms. In particular, the effect of elevated temperatures on mitochondrial energy transduction in tropical and subtropical teleosts may have profound consequences on organismal performance and population viability. Upper and lower whole-organism critical temperatures for teleosts suggest that subtropical and tropical species are not susceptible to the warming trends associated with climate change, but sub-lethal effects on energy transduction efficiency and population dynamics remain unclear. The goal of the present study was to compare the thermal sensitivity of processes associated with mitochondrial energy transduction in liver mitochondria from the striped mojarra (Eugerres plumieri), the whitemouth croaker (Micropogonias furnieri) and the palometa (Trachinotus goodei), to those of the subtropical pinfish (Lagodon rhomboides) and the blue runner (Caranx crysos). Mitochondrial function was assayed at temperatures ranging from 10 to 40°C and results obtained for both tropical and subtropical species showed a reduction in the energy transduction efficiency of the oxidative phosphorylation (OXPHOS) system in most species studied at temperatures below whole-organism critical temperature thresholds. Our results show a loss of coupling between O2 consumption and ATP production before the onset of the critical thermal maxima, indicating that elevated temperature may severely impact the yield of ATP production per carbon unit oxidized. As warming trends are projected for tropical regions, increasing water temperatures in tropical estuaries and coral reefs could impact long-term growth and reproductive performance in tropical organisms, which are already close to their upper thermal limit.

  5. Serotype-dependent transduction efficiencies of recombinant adeno-associated viral vectors in monkey neocortex

    PubMed Central

    Gerits, Annelies; Vancraeyenest, Pascaline; Vreysen, Samme; Laramée, Marie-Eve; Michiels, Annelies; Gijsbers, Rik; Van den Haute, Chris; Moons, Lieve; Debyser, Zeger; Baekelandt, Veerle; Arckens, Lutgarde; Vanduffel, Wim

    2015-01-01

    Abstract. Viral vector-mediated expression of genes (e.g., coding for opsins and designer receptors) has grown increasingly popular. Cell-type specific expression is achieved by altering viral vector tropism through crosspackaging or by cell-specific promoters driving gene expression. Detailed information about transduction properties of most recombinant adeno-associated viral vector (rAAV) serotypes in macaque cortex is gradually becoming available. Here, we compare transduction efficiencies and expression patterns of reporter genes in two macaque neocortical areas employing different rAAV serotypes and promoters. A short version of the calmodulin-kinase-II (CaMKIIα0.4) promoter resulted in reporter gene expression in cortical neurons for all tested rAAVs, albeit with different efficiencies for spread: rAAV2/5>>rAAV2/7>rAAV2/8>rAAV2/9>>rAAV2/1 and proportion of transduced cells: rAAV2/1>rAAV2/5>rAAV2/7=rAAV2/9>rAAV2/8. In contrast to rodent studies, the cytomegalovirus (CMV) promoter appeared least efficient in macaque cortex. The human synapsin-1 promoter preceded by the CMV enhancer (enhSyn1) produced homogeneous reporter gene expression across all layers, while two variants of the CaMKIIα promoter resulted in different laminar transduction patterns and cell specificities. Finally, differences in expression patterns were observed when the same viral vector was injected in two neocortical areas. Our results corroborate previous findings that reporter-gene expression patterns and efficiency of rAAV transduction depend on serotype, promoter, cortical layer, and area. PMID:26839901

  6. Physiological performance of warm-adapted marine ectotherms: Thermal limits of mitochondrial energy transduction efficiency.

    PubMed

    Martinez, Eloy; Hendricks, Eric; Menze, Michael A; Torres, Joseph J

    2016-01-01

    Thermal regimes in aquatic systems have profound implications for the physiology of ectotherms. In particular, the effect of elevated temperatures on mitochondrial energy transduction in tropical and subtropical teleosts may have profound consequences on organismal performance and population viability. Upper and lower whole-organism critical temperatures for teleosts suggest that subtropical and tropical species are not susceptible to the warming trends associated with climate change, but sub-lethal effects on energy transduction efficiency and population dynamics remain unclear. The goal of the present study was to compare the thermal sensitivity of processes associated with mitochondrial energy transduction in liver mitochondria from the striped mojarra (Eugerres plumieri), the whitemouth croaker (Micropogonias furnieri) and the palometa (Trachinotus goodei), to those of the subtropical pinfish (Lagodon rhomboides) and the blue runner (Caranx crysos). Mitochondrial function was assayed at temperatures ranging from 10 to 40°C and results obtained for both tropical and subtropical species showed a reduction in the energy transduction efficiency of the oxidative phosphorylation (OXPHOS) system in most species studied at temperatures below whole-organism critical temperature thresholds. Our results show a loss of coupling between O2 consumption and ATP production before the onset of the critical thermal maxima, indicating that elevated temperature may severely impact the yield of ATP production per carbon unit oxidized. As warming trends are projected for tropical regions, increasing water temperatures in tropical estuaries and coral reefs could impact long-term growth and reproductive performance in tropical organisms, which are already close to their upper thermal limit. PMID:26297983

  7. Cell death-resistance of differentiated myotubes is associated with enhanced anti-apoptotic mechanisms compared to myoblasts

    PubMed Central

    Xiao, Rijin; Ferry, Amy L.

    2011-01-01

    Skeletal muscle atrophy is associated with elevated apoptosis while muscle differentiation results in apoptosis resistance, indicating that the role of apoptosis in skeletal muscle is multifaceted. The objective of this study was to investigate mechanisms underlying apoptosis susceptibility in proliferating myoblasts compared to differentiated myotubes and we hypothesized that cell death-resistance in differentiated myotubes is mediated by enhanced anti-apoptotic pathways. C2C12 myoblasts and myotubes were treated with H2O2 or staurosporine (Stsp) to induce cell death. H2O2 and Stsp induced DNA fragmentation in more than 50% of myoblasts, but in myotubes less than 10% of nuclei showed apoptotic changes. Mitochondrial membrane potential dissipation was detected with H2O2 and Stsp in myoblasts, while this response was greatly diminished in myotubes. Caspase-3 activity was 10-fold higher in myotubes compared to myoblasts, and Stsp caused a significant caspase-3 induction in both. However, exposure to H2O2 did not lead to caspase-3 activation in myoblasts, and only to a modest induction in myotubes. A similar response was observed for caspase-2, -8 and -9. Abundance of caspase-inhibitors (apoptosis repressor with caspase recruitment domain (ARC), and heat shock protein (HSP) 70 and -25 was significantly higher in myotubes compared to myoblasts, and in addition ARC was suppressed in response to Stsp in myotubes. Moreover, increased expression of HSPs in myoblasts attenuated cell death in response to H2O2 and Stsp. Protein abundance of the pro-apoptotic protein endonuclease G (EndoG) and apoptosis-inducing factor (AIF) was higher in myotubes compared to myoblasts. These results show that resistance to apoptosis in myotubes is increased despite high levels of pro-apoptotic signaling mechanisms, and we suggest that this protective effect is mediated by enhanced anti-caspase mechanisms. PMID:21161388

  8. Biomechanical Origins of Muscle Stem Cell Signal Transduction.

    PubMed

    Morrissey, James B; Cheng, Richard Y; Davoudi, Sadegh; Gilbert, Penney M

    2016-04-10

    Skeletal muscle, the most abundant and widespread tissue in the human body, contracts upon receiving electrochemical signals from the nervous system to support essential functions such as thermoregulation, limb movement, blinking, swallowing and breathing. Reconstruction of adult muscle tissue relies on a pool of mononucleate, resident muscle stem cells, known as "satellite cells", expressing the paired-box transcription factor Pax7 necessary for their specification during embryonic development and long-term maintenance during adult life. Satellite cells are located around the myofibres in a niche at the interface of the basal lamina and the host fibre plasma membrane (i.e., sarcolemma), at a very low frequency. Upon damage to the myofibres, quiescent satellite cells are activated and give rise to a population of transient amplifying myogenic progenitor cells, which eventually exit the cell cycle permanently and fuse to form new myofibres and regenerate the tissue. A subpopulation of satellite cells self-renew and repopulate the niche, poised to respond to future demands. Harnessing the potential of satellite cells relies on a complete understanding of the molecular mechanisms guiding their regulation in vivo. Over the past several decades, studies revealed many signal transduction pathways responsible for satellite cell fate decisions, but the niche cues driving the activation and silencing of these pathways are less clear. Here we explore the scintillating possibility that considering the dynamic changes in the biophysical properties of the skeletal muscle, namely stiffness, and the stretch and shear forces to which a myofibre can be subjected to may provide missing information necessary to gain a full understanding of satellite cell niche regulation. PMID:26004541

  9. Second-Chance Signal Transduction Explains Cooperative Flagellar Switching

    PubMed Central

    Zot, Henry G.; Hasbun, Javier E.; Van Minh, Nguyen

    2012-01-01

    The reversal of flagellar motion (switching) results from the interaction between a switch complex of the flagellar rotor and a torque-generating stationary unit, or stator (motor unit). To explain the steeply cooperative ligand-induced switching, present models propose allosteric interactions between subunits of the rotor, but do not address the possibility of a reaction that stimulates a bidirectional motor unit to reverse direction of torque. During flagellar motion, the binding of a ligand-bound switch complex at the dwell site could excite a motor unit. The probability that another switch complex of the rotor, moving according to steady-state rotation, will reach the same dwell site before that motor unit returns to ground state will be determined by the independent decay rate of the excited-state motor unit. Here, we derive an analytical expression for the energy coupling between a switch complex and a motor unit of the stator complex of a flagellum, and demonstrate that this model accounts for the cooperative switching response without the need for allosteric interactions. The analytical result can be reproduced by simulation when (1) the motion of the rotor delivers a subsequent ligand-bound switch to the excited motor unit, thereby providing the excited motor unit with a second chance to remain excited, and (2) the outputs from multiple independent motor units are constrained to a single all-or-none event. In this proposed model, a motor unit and switch complex represent the components of a mathematically defined signal transduction mechanism in which energy coupling is driven by steady-state and is regulated by stochastic ligand binding. Mathematical derivation of the model shows the analytical function to be a general form of the Hill equation (Hill AV (1910) The possible effects of the aggregation of the molecules of haemoglobin on its dissociation curves. J Physiol 40: iv–vii). PMID:22844429

  10. Signal Transduction by BvgS Sensor Kinase

    PubMed Central

    Dupré, Elian; Lesne, Elodie; Guérin, Jérémy; Lensink, Marc F.; Verger, Alexis; de Ruyck, Jérôme; Brysbaert, Guillaume; Vezin, Hervé; Locht, Camille; Antoine, Rudy; Jacob-Dubuisson, Françoise

    2015-01-01

    The two-component sensory transduction system BvgAS controls the virulence regulon of the whooping-cough agent Bordetella pertussis. The periplasmic moiety of the homodimeric sensor kinase BvgS is composed of four bilobed Venus flytrap (VFT) perception domains followed by α helices that extend into the cytoplasmic membrane. In the virulent phase, the default state of B. pertussis, the cytoplasmic enzymatic moiety of BvgS acts as kinase by autophosphorylating and transferring the phosphoryl group to the response regulator BvgA. Under laboratory conditions, BvgS shifts to phosphatase activity in response to modulators, notably nicotinate ions. Here we characterized the effects of nicotinate and related modulators on the BvgS periplasmic moiety by using site-directed mutagenesis and in silico and biophysical approaches. Modulators bind with low affinity to BvgS in the VFT2 cavity. Electron paramagnetic resonance shows that their binding globally affects the conformation and dynamics of the periplasmic moiety. Specific amino acid substitutions designed to slacken interactions within and between the VFT lobes prevent BvgS from responding to nicotinate, showing that BvgS shifts from kinase to phosphatase activity in response to this modulator via a tense transition state that involves a large periplasmic structural block. We propose that this transition enables the transmembrane helices to adopt a distinct conformation that sets the cytoplasmic enzymatic moiety in the phosphatase mode. The bona fide, in vivo VFT ligands that remain to be identified are likely to trigger similar effects on the transmembrane and cytoplasmic moieties. This mechanism may be relevant to the other VFT-containing sensor kinases homologous to BvgS. PMID:26203186

  11. New insights into transduction pathways that regulate boar sperm function.

    PubMed

    Hurtado de Llera, A; Martin-Hidalgo, D; Gil, M C; Garcia-Marin, L J; Bragado, M J

    2016-01-01

    Detailed molecular mechanisms mediating signal transduction cascades that regulate boar sperm function involving Ser/Thr and tyrosine phosphorylation of proteins have been reviewed previously. Therefore, this review will focus in those kinase pathways identified recently (<10 years) in boar spermatozoa that regulate different functional spermatozoa processes. AMP-activated protein kinase (AMPK) is a cell energy sensor kinase that was first identified in mammalian spermatozoa in 2012, and since then it has emerged as an essential regulator of boar sperm function. Signaling pathways leading to AMPK activation in boar sperm are highlighted in this review (PKA, CaMKKα/β, and PKC as well as Ca(2+) and cAMP messengers as upstream regulators). Interestingly, stimuli considered as cell stress (hyperosmotic stress, inhibition of mitochondrial activity, absence of intracellular Ca(2+)) markedly activate AMPK in boar spermatozoa. Moreover, AMPK plays a remarkable and necessary regulatory role in mammalian sperm function, controlling essential boar sperm functional processes such as motility, viability, mitochondrial membrane potential, organization and fluidity of plasma membrane, and outer acrosome membrane integrity. These mentioned processes are all required under fluctuating environment of spermatozoa when transiting through the female reproductive tract to achieve fertilization. An applied role of AMPK in artificial insemination techniques is also suggested as during boar seminal doses preservation at 17 °C, physiological levels of AMPK activity markedly increase (maximum on Day 7) and result essential to maintain the aforementioned fundamental sperm processes. Moreover, regulation of sperm function exerted by the glycogen synthase kinase 3 and Src family kinase pathways is summarized.

  12. Physical and genetical analysis of bacteriophage T4 generalized transduction.

    PubMed

    Young, K K; Edlin, G

    1983-01-01

    This report describes a comparison of the efficiency of transduction of genes in E. coli by the generalized transducing bacteriophages T4GT7 and P1CM. Both phages are capable of transducing many genetic markers in E. coli although the frequency of transduction for particular genes varies over a wide range. The frequency of transduction for most genes depends on which transducing phage is used as well as on the donor and recipient bacterial strains. Analysis of T4GT7 phage lysates by cesium chloride density gradient centrifugation shows that transducing phage particles contain primarily bacterial DNA and carry little, if any, phage DNA. In this regard transducing phages P1CM and T4GT7 are similar; both phages package either bacterial or phage DNA but not both DNAs into the same particle.

  13. A comparative study on the mechanical properties of the healthy and varicose human saphenous vein under uniaxial loading.

    PubMed

    Karimi, Alireza; Navidbakhsh, Mahdi; Kudo, Susumu

    2015-01-01

    Saphenous Vein (SV) due to fatness, age, inactiveness, etc. can be afflicted with varicose. The main reason of the varicose vein is believed to be related to the leg muscle pump which is unable to return the blood to the heart in contradiction of the effect of gravity. As a result of the varicose vein, both the structure and mechanical properties of the vein wall would alter. However, so far there is a lack of knowledge on the mechanical properties of the varicose vein. In this study, a comparative study was carried out to measure the elastic and hyperelastic mechanical properties of the healthy and varicose SVs. Healthy and varicose SVs were removed at autopsy and surgery from seven individuals and then axial tensile load was applied to them up to the failure point. In order to investigate the mechanical behaviour of the vein, this study was benefitted from three different stress definitions, such as 2nd Piola-Kichhoff, engineering and true stresses and four different strain definitions, i.e. Almansi-Hamel, Green-St. Venant, engineering and true strains, to determine the linear mechanical properties of the SVs. A Digital Image Correlation (DIC) technique was used to measure the true strain of the vein walls during load bearing. The non-linear mechanical behaviour of the SVs was also computationally evaluated via the Mooney-Rivlin material model. The true/Cauchy stress-strain diagram exhibited the elastic modulus of the varicose SVs as 45.11% lower than that of the healthy ones. Furthermore, by variation of the stress a significant alteration on the maximum stress of the healthy SVs was observed, but then not for the varicose veins. Additionally, the highest stresses of 4.99 and 0.65 MPa were observed for the healthy and varicose SVs, respectively. These results indicate a weakness in the mechanical strength of the SV when it becomes varicose, owing to the degradation of the elastin and collagen content of the SV. The Mooney-Rivlin hyperelastic and the Finite

  14. Efficient transduction of vascular endothelial cells with recombinant adeno-associated virus serotype 1 and 5 vectors.

    PubMed

    Chen, Sifeng; Kapturczak, Matthias; Loiler, Scott A; Zolotukhin, Sergei; Glushakova, Olena Y; Madsen, Kirsten M; Samulski, Richard J; Hauswirth, William W; Campbell-Thompson, Martha; Berns, Kenneth I; Flotte, Terence R; Atkinson, Mark A; Tisher, C Craig; Agarwal, Anupam

    2005-02-01

    Recombinant adeno-associated virus (rAAV) has become an attractive tool for gene therapy because of its ability to transduce both dividing and nondividing cells, elicit a limited immune response, and the capacity for imparting long-term transgene expression. Previous studies have utilized rAAV serotype 2 predominantly and found that transduction of vascular cells is relatively inefficient. The purpose of the present study was to evaluate the transduction efficiency of rAAV serotypes 1 through 5 in human and rat aortic endothelial cells (HAEC and RAEC). rAAV vectors with AAV2 inverted terminal repeats containing the human alpha1-antitrypsin (hAAT) gene were transcapsidated using helper plasmids to provide viral capsids for the AAV1 through 5 serotypes. True type rAAV2 and 5 vectors encoding beta-galactosidase or green fluorescence protein were also studied. Infection with rAAV1 resulted in the most efficient transduction in both HAEC and RAEC compared to other serotypes (p < 0.001) at 7 days posttransduction. Interestingly, expression was increased in cells transduced with rAAV5 to levels surpassing rAAV1 by day 14 and 21. Transduction with rAAV1 was completely inhibited by removal of sialic acid with sialidase, while heparin had no effect. These studies are the first demonstration that sialic acid residues are required for rAAV1 transduction in endothelial cells. Transduction of rat aortic segments ex vivo and in vivo demonstrated significant transgene expression in endothelial and smooth muscle cells with rAAV1 and 5 serotype vectors, in comparison to rAAV2. These results suggest the unique potential of rAAV1 and rAAV5-based vectors for vascular-targeted gene-based therapeutic strategies.

  15. Mechanosensing and signal transduction in tendrils.

    PubMed

    Engelberth, Jürgen

    2003-01-01

    The perception of thigmic stimuli is a widespread phenomenon among plants with decisive meaning for the ability to survive. Beside a general sensitivity for mechanical stimuli many plants have evolved specialized organs with highly developed mechanisms to perceive and transduce the applied forces. Tendrils of Bryonia dioica and Pisum sativum have been chosen to study the effects of mechanical stimulation on plant physiology. Both types of tendrils, although exhibiting different morphology, respond to such a stimulus with a rapid coiling response to the dorsal side of the organ within minutes. The actual perception of the stimulus is most likely coupled to the cytoskeleton serving as the mediator between the physical stimulus and the biochemical response. Drugs affecting the status of the cytoskeleton were used to get more insights into this specific process. The results indicate that microtubuli (MT) play the most important role in the perception of thigmic stimuli in tendrils. Colchicine-mediated disruption of MT lead to total inhibition of the response to the thigmic stimulus in tendrils of Pisum and to a reduced response in Bryonia. Alamethicin, an ionophore that can mimic action potentials in membranes, was able to bypass this inhibition suggesting a direct involvement of MT in depolarization of the membranes. Auxin, however, which is also supposed to be involved in the regulation of the coiling response, failed to bypass colchicine-dependent inhibition. Vinblastine, another microtubule depolimerizing agent, did induce tendril coiling in Pisum without further stimulation. Application of taxol and other MT-stabilizing drugs as well as disruption of the actin network did not affect the coiling response of tendrils. In Pisum indole-3-acetic acid (IAA) is induced after mechanical stimulation during the coiling response, but not jasmonic acid. A further consequence of mechanical stimulation is the induction of an oxidative burst and an increase in soluble sugar. A

  16. A comparative study of the effects of vein-joints on the mechanical behaviour of insect wings: I. Single joints.

    PubMed

    Rajabi, H; Ghoroubi, N; Darvizeh, A; Dirks, J-H; Appel, E; Gorb, S N

    2015-08-20

    The flight performance of insects is strongly affected by the deformation of the wing during a stroke cycle. Many insects therefore use both active and passive mechanisms to control the deformation of their wings in flight. Several studies have focused on the wing kinematics, and plenty is known about the mechanism of their passive deformability. However, given the small size of the vein-joints, accurate direct mechanical experiments are almost impossible to perform. We therefore developed numerical models to perform a comparative and comprehensive investigation of the mechanical behaviour of the vein-joints under external loading conditions. The results illustrate the effect of the geometry and the presence of the rubberlike protein resilin on the flexibility of the joints. Our simulations further show the contribution of the spikes to the anisotropic flexural stiffness in the dorsal and ventral directions. In addition, our results show that the cross veins, only in one joint type, help to transfer the stress to the thicker longitudinal veins. The deformation pattern and the stress distribution in each vein-joint are discussed in detail. This study provides a strong background for further realistic modelling of the dragonfly wing deformation.

  17. Comparative acoustic performance and mechanical properties of silk membranes for the repair of chronic tympanic membrane perforations.

    PubMed

    Allardyce, Benjamin J; Rajkhowa, Rangam; Dilley, Rodney J; Xie, Zhigang; Campbell, Luke; Keating, Adrian; Atlas, Marcus D; von Unge, Magnus; Wang, Xungai

    2016-12-01

    The acoustic and mechanical properties of silk membranes of different thicknesses were tested to determine their suitability as a repair material for tympanic membrane perforations. Membranes of different thickness (10-100μm) were tested to determine their frequency response and their resistance to pressure loads in a simulated ear canal model. Their mechanical rigidity to pressure loads was confirmed by tensile testing. These membranes were tested alongside animal cartilage, currently the strongest available myringoplasty graft as well as paper, which is commonly used for simpler procedures. Silk membranes showed resonant frequencies within the human hearing range and a higher vibrational amplitude than cartilage, suggesting that silk may offer good acoustic energy transfer characteristics. Silk membranes were also highly resistant to simulated pressure changes in the middle ear, suggesting they can resist retraction, a common cause of graft failure resulting from chronic negative pressures in the middle ear. Part of this strength can be explained by the substantially higher modulus of silk films compared with cartilage. This allows for the production of films that are much thinner than cartilage, with superior acoustic properties, but that still provide the same level of mechanical support as thicker cartilage. Together, these in vitro results suggest that silk membranes may provide good hearing outcomes while offering similar levels of mechanical support to the reconstructed middle ear. PMID:27479895

  18. A Comparative Numerical Study on the Performances and Vortical Patterns of Two Bioinspired Oscillatory Mechanisms: Undulating and Pure Heaving.

    PubMed

    Ebrahimi, Mohsen; Abbaspour, Madjid

    2015-01-01

    The hydrodynamics and energetics of bioinspired oscillating mechanisms have received significant attentions by engineers and biologists to develop the underwater and air vehicles. Undulating and pure heaving (or plunging) motions are two significant mechanisms which are utilized in nature to provide propulsive, maneuvering, and stabilization forces. This study aims to elucidate and compare the propulsive vortical signature and performance of these two important natural mechanisms through a systematic numerical study. Navier-Stokes equations are solved, by a pressure-based finite volume method solver, in an arbitrary Lagrangian-Eulerian (ALE) framework domain containing a 2D NACA0012 foil moving with prescribed kinematics. Some of the important findings are (1) the thrust production of the heaving foil begins at lower St and has a greater growing slope with respect to the St; (2) the undulating mechanism has some limitations to produce high thrust forces; (3) the undulating foil shows a lower power consumption and higher efficiency; (4) changing the Reynolds number (Re) in a constant St affects the performance of the oscillations; and (5) there is a distinguishable appearance of leading edge vortices in the wake of the heaving foil without observable ones in the wake of the undulating foil, especially at higher St.

  19. A Comparative Numerical Study on the Performances and Vortical Patterns of Two Bioinspired Oscillatory Mechanisms: Undulating and Pure Heaving

    PubMed Central

    Ebrahimi, Mohsen; Abbaspour, Madjid

    2015-01-01

    The hydrodynamics and energetics of bioinspired oscillating mechanisms have received significant attentions by engineers and biologists to develop the underwater and air vehicles. Undulating and pure heaving (or plunging) motions are two significant mechanisms which are utilized in nature to provide propulsive, maneuvering, and stabilization forces. This study aims to elucidate and compare the propulsive vortical signature and performance of these two important natural mechanisms through a systematic numerical study. Navier-Stokes equations are solved, by a pressure-based finite volume method solver, in an arbitrary Lagrangian-Eulerian (ALE) framework domain containing a 2D NACA0012 foil moving with prescribed kinematics. Some of the important findings are (1) the thrust production of the heaving foil begins at lower St and has a greater growing slope with respect to the St; (2) the undulating mechanism has some limitations to produce high thrust forces; (3) the undulating foil shows a lower power consumption and higher efficiency; (4) changing the Reynolds number (Re) in a constant St affects the performance of the oscillations; and (5) there is a distinguishable appearance of leading edge vortices in the wake of the heaving foil without observable ones in the wake of the undulating foil, especially at higher St. PMID:27057133

  20. Quantitative structure-activity relationships of insecticides and plant growth regulators: comparative studies toward understanding the molecular mechanism of action.

    PubMed Central

    Iwamura, H; Nishimura, K; Fujita, T

    1985-01-01

    Emphasis was put on the comparative quantitative structure-activity approaches to the exploration of action mechanisms of structurally different classes of compounds showing the same type of activity as well as those of the same type of compounds having different actions. Examples were selected from studies performed on insecticides and plant growth regulators, i.e., neurotoxic carbamates, phosphates, pyrethroids and DDT analogs, insect juvenile hormone mimics, and cytokinin agonistic and antagonistic compounds. Similarities and dissimilarities in structures required to elicit activity between compounds classes were revealed in terms of physicochemical parameters, provoking further exploration and evoking insights into the molecular mechanisms of action which may lead to the development of new structures having better qualities. PMID:3905379

  1. Modelling protein functional domains in signal transduction using Maude

    NASA Technical Reports Server (NTRS)

    Sriram, M. G.

    2003-01-01

    Modelling of protein-protein interactions in signal transduction is receiving increased attention in computational biology. This paper describes recent research in the application of Maude, a symbolic language founded on rewriting logic, to the modelling of functional domains within signalling proteins. Protein functional domains (PFDs) are a critical focus of modern signal transduction research. In general, Maude models can simulate biological signalling networks and produce specific testable hypotheses at various levels of abstraction. Developing symbolic models of signalling proteins containing functional domains is important because of the potential to generate analyses of complex signalling networks based on structure-function relationships.

  2. Intracellular transduction using cell-penetrating peptides.

    PubMed

    Sawant, Rupa; Torchilin, Vladimir

    2010-04-01

    Cell penetrating peptides (CPPs), TATp, in particular, has been used widely for intracellular delivery of various agents ranging from small molecules to proteins, peptides, range of pharmaceutical nanocarriers and imaging agents. This review highlights the mechanisms of CPP-mediated delivery and summarizes numerous examples illustrating the potential of CPPs in the fields of biology and medicine. PMID:20237640

  3. Regulation of Early Steps of GPVI Signal Transduction by Phosphatases: A Systems Biology Approach

    PubMed Central

    Dunster, Joanne L.; Mazet, Francoise; Fry, Michael J.; Gibbins, Jonathan M.; Tindall, Marcus J.

    2015-01-01

    We present a data-driven mathematical model of a key initiating step in platelet activation, a central process in the prevention of bleeding following Injury. In vascular disease, this process is activated inappropriately and causes thrombosis, heart attacks and stroke. The collagen receptor GPVI is the primary trigger for platelet activation at sites of injury. Understanding the complex molecular mechanisms initiated by this receptor is important for development of more effective antithrombotic medicines. In this work we developed a series of nonlinear ordinary differential equation models that are direct representations of biological hypotheses surrounding the initial steps in GPVI-stimulated signal transduction. At each stage model simulations were compared to our own quantitative, high-temporal experimental data that guides further experimental design, data collection and model refinement. Much is known about the linear forward reactions within platelet signalling pathways but knowledge of the roles of putative reverse reactions are poorly understood. An initial model, that includes a simple constitutively active phosphatase, was unable to explain experimental data. Model revisions, incorporating a complex pathway of interactions (and specifically the phosphatase TULA-2), provided a good description of the experimental data both based on observations of phosphorylation in samples from one donor and in those of a wider population. Our model was used to investigate the levels of proteins involved in regulating the pathway and the effect of low GPVI levels that have been associated with disease. Results indicate a clear separation in healthy and GPVI deficient states in respect of the signalling cascade dynamics associated with Syk tyrosine phosphorylation and activation. Our approach reveals the central importance of this negative feedback pathway that results in the temporal regulation of a specific class of protein tyrosine phosphatases in controlling the rate

  4. Fluoride blocks an inactivation step of transduction in a locust photoreceptor

    PubMed Central

    Payne, Richard

    1982-01-01

    1. Photoreceptors in a superfused retina of a locust compound eye are treated with saline containing 10 mM-NaF, while their intracellular resting potential and responses are recorded using glass micropipettes. 2. Treatment for two minutes with 10 mM-NaF, followed by a series of brief, bright flashes of light, results in an irreversible, noisy depolarization of approximately 10 mV. The final, stable level of depolarization is reached through the summed effect of each of the noisy, depolarizing afterpotentials that follow every response of the cell to a light flash. If kept in darkness after treatment with NaF, the noisy depolarization still develops, but more gradually, over a period of 5 min. 3. The voltage noise induced by NaF mimics light-induced voltage noise when the two are compared at mean depolarizations of more than 15 mV. At very small depolarizations, however, fluoride-induced noise cannot be resolved into the large discrete events (bumps) that are typical of the response of a dark-adapted photoreceptor to a single photon. 4. The complete replacement of the superfusate sodium by choline reversibly reduces the fluoride-induced noise and depolarization to the same extent as it does the light-induced noise and depolarization of an illuminated cell. 5. Increasing the superfusate calcium concentration from 0·5 to 10 mM also reversibly reduces fluoride-induced noise and depolarization to the same extent as it does light-induced noise and depolarization. This action of calcium is accompanied by an increase in a cell's input resistance which opposes the reduction caused by light or fluoride treatment. 6. The results confirm the proposal (Payne, 1981) that anionic metabolic inhibitors cause spontaneous activity in sodium channels that are normally opened by light. A model is proposed in which fluoride acts by blocking the inactivation of a late stage in the transduction mechanism. PMID:6286940

  5. Prolonged hyperinsulinemia affects metabolic signal transduction markers in a tissue specific manner.

    PubMed

    Campolo, A; de Laat, M A; Keith, L; Gruntmeir, K J; Lacombe, V A

    2016-04-01

    Insulin dysregulation is common in horses although the mechanisms of metabolic dysfunction are poorly understood. We hypothesized that insulin signaling in striated (cardiac and skeletal) muscle and lamellae may be mediated through different receptors as a result of receptor content, and that transcriptional regulation of downstream signal transduction and glucose transport may also differ between tissues sites during hyperinsulinemia. Archived samples from horses treated with a prolonged insulin infusion or a balanced electrolyte solution were used. All treated horses developed marked hyperinsulinemia and clinical laminitis. Protein expression was compared across tissues for the insulin receptor and insulin-like growth factor 1 receptor (IGF-1R) by immunoblotting. Gene expression of metabolic insulin-signaling markers (insulin receptor substrate 1, Akt2, and glycogen synthase kinase 3 beta [GSK-3β]) and glucose transport (basal glucose transporter 1 and insulin-sensitive glucose transporter 4) was evaluated using real-time reverse transcription polymerase chain reaction. Lamellar tissue contained significantly more IGF-1R protein than skeletal muscle, indicating the potential significance of IGF-1R signaling for this tissue. Gene expression of the selected markers of insulin signaling and glucose transport in skeletal muscle and lamellar tissues was unaffected by prolonged hyperinsulinemia. In contrast, the significant upregulation of Akt2, GSK-3β, GLUT1, and GLUT4 gene expression in cardiac tissue suggested that the prolonged hyperinsulinemia induced an increase in insulin sensitivity and a transcriptional activation of glucose transport. Responses to insulin are tissue-specific, and extrapolation of data across tissue sites is inappropriate. PMID:26773366

  6. Regulation of Early Steps of GPVI Signal Transduction by Phosphatases: A Systems Biology Approach.

    PubMed

    Dunster, Joanne L; Mazet, Francoise; Fry, Michael J; Gibbins, Jonathan M; Tindall, Marcus J

    2015-11-01

    We present a data-driven mathematical model of a key initiating step in platelet activation, a central process in the prevention of bleeding following Injury. In vascular disease, this process is activated inappropriately and causes thrombosis, heart attacks and stroke. The collagen receptor GPVI is the primary trigger for platelet activation at sites of injury. Understanding the complex molecular mechanisms initiated by this receptor is important for development of more effective antithrombotic medicines. In this work we developed a series of nonlinear ordinary differential equation models that are direct representations of biological hypotheses surrounding the initial steps in GPVI-stimulated signal transduction. At each stage model simulations were compared to our own quantitative, high-temporal experimental data that guides further experimental design, data collection and model refinement. Much is known about the linear forward reactions within platelet signalling pathways but knowledge of the roles of putative reverse reactions are poorly understood. An initial model, that includes a simple constitutively active phosphatase, was unable to explain experimental data. Model revisions, incorporating a complex pathway of interactions (and specifically the phosphatase TULA-2), provided a good description of the experimental data both based on observations of phosphorylation in samples from one donor and in those of a wider population. Our model was used to investigate the levels of proteins involved in regulating the pathway and the effect of low GPVI levels that have been associated with disease. Results indicate a clear separation in healthy and GPVI deficient states in respect of the signalling cascade dynamics associated with Syk tyrosine phosphorylation and activation. Our approach reveals the central importance of this negative feedback pathway that results in the temporal regulation of a specific class of protein tyrosine phosphatases in controlling the rate

  7. Structure-function relationships in the IL-17 receptor: Implications for signal transduction and therapy

    PubMed Central

    Shen, Fang; Gaffen, Sarah L.

    2008-01-01

    IL-17 is the defining cytokine of a newly-described “Th17” population that plays critical roles in mediating inflammation and autoimmunity. The IL-17/IL-17 receptor superfamily is the most recent class of cytokines and receptors to be described, and until recently very little was known about its function or molecular biology. However, in the last year important new insights into the composition and dynamics of the receptor complex and mechanisms of downstream signal transduction have been made, which will be reviewed here. PMID:18178098

  8. The role of protein kinase C in cell surface signal transduction and tumour promotion

    NASA Astrophysics Data System (ADS)

    Nishizuka, Yasutomi

    1984-04-01

    Protein kinase C has a crucial role in signal transduction for a variety of biologically active substances which activate cellular functions and proliferation. When cells are stimulated, protein kinase C is transiently activated by diacylglycerol which is produced in the membrane during the signal-induced turnover of inositol phospholipids. Tumour-promoting phorbol esters, when intercalated into the cell membrane, may substitute for diacylglycerol and permanently activate protein kinase C. The enzyme probably serves as a receptor for the tumour promoters. Further exploration of the roles of this enzyme may provide clues for understanding the mechanism of cell growth and differentiation.

  9. Mechanical properties and structure of Haliotis discus hannai Ino and Hemifusus tuba conch shells: a comparative study

    NASA Astrophysics Data System (ADS)

    Zhao, Jie; Chen, Chen; Liang, Yan; Wang, Jian

    2010-03-01

    Haliotis discus hannai Ino (abalone shell) and Hemifusus tuba conch shell have been studied for the purpose to comparatively investigate the mechanisms by which nature designs composites. It is shown that both shells are composed of aragonite and a small amount of proteins while the conch shell shows finer microstructure but lower strength than abalone shell. It is also shown that the fresh shells exhibits better property than those after heat-treatments. It is therefore supposed that the size of inorganic substance is not a dominant factor to improve strength, while both proteins in shells and the microstructure of inorganic matter also play important roles.

  10. [Comparative study of tensile strength of enamel/resin/metal interface. Effect of bonding resins, retention mechanisms and metal alloys].

    PubMed

    Camparis Bussadori, C M; de Angelis Porto, C L

    1990-01-01

    The purpose of this study was to compare the enamel/resin/metal bond tensile strength by using human canines, in which castings were bonded. These castings were obtained by Co-Cr or Ni-Cr alloys and showed four types of mechanisms of retention: 50 micrograms aluminum oxide abrasive, electrochemical etch, acrylic beads metal mesh. The castings were bonded utilizing Comspan Opaque and Panavia Ex. The specimens were subjected to tensile forces after 24 hours in an Instron machine. The castings subjected to 50 micrograms aluminum oxide abrasive and bonded utilizing Panavia EX showed the biggest bond tensile strength. PMID:2099553

  11. Matricellular signal transduction involving calmodulin in the social amoebozoan dictyostelium.

    PubMed

    O'Day, Danton H; Huber, Robert J

    2013-01-01

    The social amoebozoan Dictyostelium discoideum undergoes a developmental sequence wherein an extracellular matrix (ECM) sheath surrounds a group of differentiating cells. This sheath is comprised of proteins and carbohydrates, like the ECM of mammalian tissues. One of the characterized ECM proteins is the cysteine-rich, EGF-like (EGFL) repeat-containing, calmodulin (CaM)-binding protein (CaMBP) CyrA. The first EGFL repeat of CyrA increases the rate of random cell motility and cyclic AMP-mediated chemotaxis. Processing of full-length CyrA (~63 kDa) releases two major EGFL repeat-containing fragments (~45 kDa and ~40 kDa) in an event that is developmentally regulated. Evidence for an EGFL repeat receptor also exists and downstream intracellular signaling pathways involving CaM, Ras, protein kinase A and vinculin B phosphorylation have been characterized. In total, these results identify CyrA as a true matricellular protein comparable in function to tenascin C and other matricellular proteins from mammalian cells. Insight into the regulation and processing of CyrA has also been revealed. CyrA is the first identified extracellular CaMBP in this eukaryotic microbe. In keeping with this, extracellular CaM (extCaM) has been shown to be present in the ECM sheath where it binds to CyrA and inhibits its cleavage to release the 45 kDa and 40 kDa EGFL repeat-containing fragments. The presence of extCaM and its role in regulating a matricellular protein during morphogenesis extends our understanding of CaM-mediated signal transduction in eukaryotes. PMID:24705101

  12. Matricellular signal transduction involving calmodulin in the social amoebozoan dictyostelium.

    PubMed

    O'Day, Danton H; Huber, Robert J

    2013-02-15

    The social amoebozoan Dictyostelium discoideum undergoes a developmental sequence wherein an extracellular matrix (ECM) sheath surrounds a group of differentiating cells. This sheath is comprised of proteins and carbohydrates, like the ECM of mammalian tissues. One of the characterized ECM proteins is the cysteine-rich, EGF-like (EGFL) repeat-containing, calmodulin (CaM)-binding protein (CaMBP) CyrA. The first EGFL repeat of CyrA increases the rate of random cell motility and cyclic AMP-mediated chemotaxis. Processing of full-length CyrA (~63 kDa) releases two major EGFL repeat-containing fragments (~45 kDa and ~40 kDa) in an event that is developmentally regulated. Evidence for an EGFL repeat receptor also exists and downstream intracellular signaling pathways involving CaM, Ras, protein kinase A and vinculin B phosphorylation have been characterized. In total, these results identify CyrA as a true matricellular protein comparable in function to tenascin C and other matricellular proteins from mammalian cells. Insight into the regulation and processing of CyrA has also been revealed. CyrA is the first identified extracellular CaMBP in this eukaryotic microbe. In keeping with this, extracellular CaM (extCaM) has been shown to be present in the ECM sheath where it binds to CyrA and inhibits its cleavage to release the 45 kDa and 40 kDa EGFL repeat-containing fragments. The presence of extCaM and its role in regulating a matricellular protein during morphogenesis extends our understanding of CaM-mediated signal transduction in eukaryotes.

  13. Phosphodiesterase 4D acts downstream of Neuropilin to control Hedgehog signal transduction and the growth of medulloblastoma.

    PubMed

    Ge, Xuecai; Milenkovic, Ljiljana; Suyama, Kaye; Hartl, Tom; Purzner, Teresa; Winans, Amy; Meyer, Tobias; Scott, Matthew P

    2015-01-01

    Alterations in Hedgehog (Hh) signaling lead to birth defects and cancers including medulloblastoma, the most common pediatric brain tumor. Although inhibitors targeting the membrane protein Smoothened suppress Hh signaling, acquired drug resistance and tumor relapse call for additional therapeutic targets. Here we show that phosphodiesterase 4D (PDE4D) acts downstream of Neuropilins to control Hh transduction and medulloblastoma growth. PDE4D interacts directly with Neuropilins, positive regulators of Hh pathway. The Neuropilin ligand Semaphorin3 enhances this interaction, promoting PDE4D translocation to the plasma membrane and cAMP degradation. The consequent inhibition of protein kinase A (PKA) enhances Hh transduction. In the developing cerebellum, genetic removal of Neuropilins reduces Hh signaling activity and suppresses proliferation of granule neuron precursors. In mouse medulloblastoma allografts, PDE4D inhibitors suppress Hh transduction and inhibit tumor growth. Our findings reveal a new regulatory mechanism of Hh transduction, and highlight PDE4D as a promising target to treat Hh-related tumors. PMID:26371509

  14. Phosphodiesterase 4D acts downstream of Neuropilin to control Hedgehog signal transduction and the growth of medulloblastoma

    PubMed Central

    Ge, Xuecai; Milenkovic, Ljiljana; Suyama, Kaye; Hartl, Tom; Purzner, Teresa; Winans, Amy; Meyer, Tobias; Scott, Matthew P

    2015-01-01

    Alterations in Hedgehog (Hh) signaling lead to birth defects and cancers including medulloblastoma, the most common pediatric brain tumor. Although inhibitors targeting the membrane protein Smoothened suppress Hh signaling, acquired drug resistance and tumor relapse call for additional therapeutic targets. Here we show that phosphodiesterase 4D (PDE4D) acts downstream of Neuropilins to control Hh transduction and medulloblastoma growth. PDE4D interacts directly with Neuropilins, positive regulators of Hh pathway. The Neuropilin ligand Semaphorin3 enhances this interaction, promoting PDE4D translocation to the plasma membrane and cAMP degradation. The consequent inhibition of protein kinase A (PKA) enhances Hh transduction. In the developing cerebellum, genetic removal of Neuropilins reduces Hh signaling activity and suppresses proliferation of granule neuron precursors. In mouse medulloblastoma allografts, PDE4D inhibitors suppress Hh transduction and inhibit tumor growth. Our findings reveal a new regulatory mechanism of Hh transduction, and highlight PDE4D as a promising target to treat Hh-related tumors. DOI: http://dx.doi.org/10.7554/eLife.07068.001 PMID:26371509

  15. Transmembrane signal transduction by peptide hormones via family B G protein-coupled receptors

    PubMed Central

    Culhane, Kelly J.; Liu, Yuting; Cai, Yingying; Yan, Elsa C. Y.

    2015-01-01

    Although family B G protein-coupled receptors (GPCRs) contain only 15 members, they play key roles in transmembrane signal transduction of hormones. Family B GPCRs are drug targets for developing therapeutics for diseases ranging from metabolic to neurological disorders. Despite their importance, the molecular mechanism of activation of family B GPCRs remains largely unexplored due to the challenges in expression and purification of functional receptors to the quantity for biophysical characterization. Currently, there is no crystal structure available of a full-length family B GPCR. However, structures of key domains, including the extracellular ligand binding regions and seven-helical transmembrane regions, have been solved by X-ray crystallography and NMR, providing insights into the mechanisms of ligand recognition and selectivity, and helical arrangements within the cell membrane. Moreover, biophysical and biochemical methods have been used to explore functions, key residues for signaling, and the kinetics and dynamics of signaling processes. This review summarizes the current knowledge of the signal transduction mechanism of family B GPCRs at the molecular level and comments on the challenges and outlook for mechanistic studies of family B GPCRs. PMID:26594176

  16. Alpha-1, alpha-2, and beta adrenergic signal transduction in cultured uterine myocytes.

    PubMed

    Phillippe, M; Saunders, T; Bangalore, S

    1990-04-01

    The following studies were undertaken to develop a cultured uterine myocyte model which would allow further clarification of the adrenergic signal transduction mechanisms utilized by these myocytes. After mechanical removal of the endometrium, rabbit uterine myocytes were isolated by an overnight enzymatic disaggregation using collagenase and DNase I. The isolated myocytes were maintained in culture in 75-cm2 flasks containing Waymouth's MB 751/1 medium-10% fetal bovine serum along with 10(-8) M estradiol, penicillin, streptomycin, and Fungizone. The phase contrast and electron micrographic appearance of these cells was consistent with that previously reported for smooth muscle myocytes in culture. Immunocytochemical studies utilizing monoclonal anti-alpha-smooth muscle actin antibodies confirmed the presence of smooth muscle actin in these cultured myocytes. Western blot studies similarly confirmed the presence of alpha-smooth muscle actin in rabbit myometrial tissue and the cultured myocytes, both the primary and F1 generation. After prelabeling the myocytes with [3H]inositol, adrenergic stimulation experiments demonstrated alpha-1 receptor mediated stimulation of inositol phosphates. Beta receptor stimulation experiments confirmed cAMP production in these cultured myocytes, and the ability of clonidine, an alpha-2 agonist, to inhibit forskolin stimulated cAMP production confirmed the presence of functional alpha-2 adrenergic receptors in these myocytes. In conclusion, these cultured rabbit uterine myocytes have provided an in vitro model which can be utilized to further clarify the adrenergic receptor signal transduction mechanisms in genital tract smooth muscle.

  17. Global insights into acetic acid resistance mechanisms and genetic stability of Acetobacter pasteurianus strains by comparative genomics

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Shao, Yanchun; Chen, Tao; Chen, Wanping; Chen, Fusheng

    2015-12-01

    Acetobacter pasteurianus (Ap) CICC 20001 and CGMCC 1.41 are two acetic acid bacteria strains that, because of their strong abilities to produce and tolerate high concentrations of acetic acid, have been widely used to brew vinegar in China. To globally understand the fermentation characteristics, acid-tolerant mechanisms and genetic stabilities, their genomes were sequenced. Genomic comparisons with 9 other sequenced Ap strains revealed that their chromosomes were evolutionarily conserved, whereas the plasmids were unique compared with other Ap strains. Analysis of the acid-tolerant metabolic pathway at the genomic level indicated that the metabolism of some amino acids and the known mechanisms of acetic acid tolerance, might collaboratively contribute to acetic acid resistance in Ap strains. The balance of instability factors and stability factors in the genomes of Ap CICC 20001 and CGMCC 1.41 strains might be the basis for their genetic stability, consistent with their stable industrial performances. These observations provide important insights into the acid resistance mechanism and the genetic stability of Ap strains and lay a foundation for future genetic manipulation and engineering of these two strains.

  18. Global insights into acetic acid resistance mechanisms and genetic stability of Acetobacter pasteurianus strains by comparative genomics

    PubMed Central

    Wang, Bin; Shao, Yanchun; Chen, Tao; Chen, Wanping; Chen, Fusheng

    2015-01-01

    Acetobacter pasteurianus (Ap) CICC 20001 and CGMCC 1.41 are two acetic acid bacteria strains that, because of their strong abilities to produce and tolerate high concentrations of acetic acid, have been widely used to brew vinegar in China. To globally understand the fermentation characteristics, acid-tolerant mechanisms and genetic stabilities, their genomes were sequenced. Genomic comparisons with 9 other sequenced Ap strains revealed that their chromosomes were evolutionarily conserved, whereas the plasmids were unique compared with other Ap strains. Analysis of the acid-tolerant metabolic pathway at the genomic level indicated that the metabolism of some amino acids and the known mechanisms of acetic acid tolerance, might collaboratively contribute to acetic acid resistance in Ap strains. The balance of instability factors and stability factors in the genomes of Ap CICC 20001 and CGMCC 1.41 strains might be the basis for their genetic stability, consistent with their stable industrial performances. These observations provide important insights into the acid resistance mechanism and the genetic stability of Ap strains and lay a foundation for future genetic manipulation and engineering of these two strains. PMID:26691589

  19. Global insights into acetic acid resistance mechanisms and genetic stability of Acetobacter pasteurianus strains by comparative genomics.

    PubMed

    Wang, Bin; Shao, Yanchun; Chen, Tao; Chen, Wanping; Chen, Fusheng

    2015-12-22

    Acetobacter pasteurianus (Ap) CICC 20001 and CGMCC 1.41 are two acetic acid bacteria strains that, because of their strong abilities to produce and tolerate high concentrations of acetic acid, have been widely used to brew vinegar in China. To globally understand the fermentation characteristics, acid-tolerant mechanisms and genetic stabilities, their genomes were sequenced. Genomic comparisons with 9 other sequenced Ap strains revealed that their chromosomes were evolutionarily conserved, whereas the plasmids were unique compared with other Ap strains. Analysis of the acid-tolerant metabolic pathway at the genomic level indicated that the metabolism of some amino acids and the known mechanisms of acetic acid tolerance, might collaboratively contribute to acetic acid resistance in Ap strains. The balance of instability factors and stability factors in the genomes of Ap CICC 20001 and CGMCC 1.41 strains might be the basis for their genetic stability, consistent with their stable industrial performances. These observations provide important insights into the acid resistance mechanism and the genetic stability of Ap strains and lay a foundation for future genetic manipulation and engineering of these two strains.

  20. Comparative Analysis of Mechanical Properties of PWV, NO and Ascending Aorta between WHY Rats and SHR Rats

    PubMed Central

    Yu, Bo; Xu, De-Jun; Sun, Huan; Yang, Kun; Luo, Min

    2015-01-01

    Background The aim of this study was to compare and analyze the tensile mechanical properties of the ascending aorta (AA) in Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs), for the purpose of providing a biomechanical basis for hypertension prevention. Methods Pulse wave velocities (PWV) and serum nitric oxide (NO) concentrations were determined in 6-month-old WKY rats and SHRs (n = 21, n = 21, respectively). Then, 20 AAs from each group were obtained for longitudinal tensile testing. Results The maximum stress, maximum strain, and strain at a tensile stress of 16 Kpa were greater in WKY rats than in SHRs (p < 0.05). The aortic elastic modulus and PWV value were greater in SHRs than in WKY rats (p < 0.05 for both), while NO concentrations were lower in the SHR group than in the WKY group (p < 0.05). Conclusions The AA tensile mechanical properties differed between the WKY rats and SHRs, and the tensile mechanical properties of the SHR model had changed. PMID:27122902

  1. Comparative genomics analysis of the companion mechanisms of Bacillus thuringiensis Bc601 and Bacillus endophyticus Hbe603 in bacterial consortium.

    PubMed

    Jia, Nan; Ding, Ming-Zhu; Gao, Feng; Yuan, Ying-Jin

    2016-01-01

    Bacillus thuringiensis and Bacillus endophyticus both act as the companion bacteria, which cooperate with Ketogulonigenium vulgare in vitamin C two-step fermentation. Two Bacillus species have different morphologies, swarming motility and 2-keto-L-gulonic acid productivities when they co-culture with K. vulgare. Here, we report the complete genome sequencing of B. thuringiensis Bc601 and eight plasmids of B. endophyticus Hbe603, and carry out the comparative genomics analysis. Consequently, B. thuringiensis Bc601, with greater ability of response to the external environment, has been found more two-component system, sporulation coat and peptidoglycan biosynthesis related proteins than B. endophyticus Hbe603, and B. endophyticus Hbe603, with greater ability of nutrients biosynthesis, has been found more alpha-galactosidase, propanoate, glutathione and inositol phosphate metabolism, and amino acid degradation related proteins than B. thuringiensis Bc601. Different ability of swarming motility, response to the external environment and nutrients biosynthesis may reflect different companion mechanisms of two Bacillus species. Comparative genomic analysis of B. endophyticus and B. thuringiensis enables us to further understand the cooperative mechanism with K. vulgare, and facilitate the optimization of bacterial consortium. PMID:27353048

  2. Comparative genomics analysis of the companion mechanisms of Bacillus thuringiensis Bc601 and Bacillus endophyticus Hbe603 in bacterial consortium

    PubMed Central

    Jia, Nan; Ding, Ming-Zhu; Gao, Feng; Yuan, Ying-Jin

    2016-01-01

    Bacillus thuringiensis and Bacillus endophyticus both act as the companion bacteria, which cooperate with Ketogulonigenium vulgare in vitamin C two-step fermentation. Two Bacillus species have different morphologies, swarming motility and 2-keto-L-gulonic acid productivities when they co-culture with K. vulgare. Here, we report the complete genome sequencing of B. thuringiensis Bc601 and eight plasmids of B. endophyticus Hbe603, and carry out the comparative genomics analysis. Consequently, B. thuringiensis Bc601, with greater ability of response to the external environment, has been found more two-component system, sporulation coat and peptidoglycan biosynthesis related proteins than B. endophyticus Hbe603, and B. endophyticus Hbe603, with greater ability of nutrients biosynthesis, has been found more alpha-galactosidase, propanoate, glutathione and inositol phosphate metabolism, and amino acid degradation related proteins than B. thuringiensis Bc601. Different ability of swarming motility, response to the external environment and nutrients biosynthesis may reflect different companion mechanisms of two Bacillus species. Comparative genomic analysis of B. endophyticus and B. thuringiensis enables us to further understand the cooperative mechanism with K. vulgare, and facilitate the optimization of bacterial consortium. PMID:27353048

  3. A comparative study on the mechanical, thermal and morphological characterization of poly(lactic acid)/epoxidized Palm Oil blend.

    PubMed

    Giita Silverajah, V S; Ibrahim, Nor Azowa; Yunus, Wan Md Zin Wan; Hassan, Hazimah Abu; Woei, Chieng Buong

    2012-01-01

    In this work, poly(lactic acid) (PLA) a fully biodegradable thermoplastic polymer matrix was melt blended with three different epoxidized palm oil (EPO). The aim of this research was to enhance the flexibility, mechanical and thermal properties of PLA. The blends were prepared at various EPO contents of 1, 2, 3, 4 and 5 wt% and characterized. The SEM analysis evidenced successful modification on the neat PLA brittle morphology. Tensile tests indicate that the addition of 1 wt% EPO is sufficient to improve the strength and flexibility compared to neat PLA. Additionally, the flexural and impact properties were also enhanced. Further, DSC analysis showed that the addition of EPO results in a decrease in T(g), which implies an increase in the PLA chain mobility. In the presence of 1 wt% EPO, TGA results revealed significant increase in the thermal stability by 27%. Among the three EPOs used, EPO(3) showed the best mechanical and thermal properties compared to the other EPO's, with an optimum loading of 1 wt%. Conclusively, EPO showed a promising outcome to overcome the brittleness and improve the overall properties of neat PLA, thus can be considered as a potential plasticizer. PMID:22754338

  4. A Comparative Study on the Mechanical, Thermal and Morphological Characterization of Poly(lactic acid)/Epoxidized Palm Oil Blend

    PubMed Central

    Giita Silverajah, V. S.; Ibrahim, Nor Azowa; Yunus, Wan Md Zin Wan; Hassan, Hazimah Abu; Woei, Chieng Buong

    2012-01-01

    In this work, poly(lactic acid) (PLA) a fully biodegradable thermoplastic polymer matrix was melt blended with three different epoxidized palm oil (EPO). The aim of this research was to enhance the flexibility, mechanical and thermal properties of PLA. The blends were prepared at various EPO contents of 1, 2, 3, 4 and 5 wt% and characterized. The SEM analysis evidenced successful modification on the neat PLA brittle morphology. Tensile tests indicate that the addition of 1 wt% EPO is sufficient to improve the strength and flexibility compared to neat PLA. Additionally, the flexural and impact properties were also enhanced. Further, DSC analysis showed that the addition of EPO results in a decrease in Tg, which implies an increase in the PLA chain mobility. In the presence of 1 wt% EPO, TGA results revealed significant increase in the thermal stability by 27%. Among the three EPOs used, EPO(3) showed the best mechanical and thermal properties compared to the other EPO’s, with an optimum loading of 1 wt%. Conclusively, EPO showed a promising outcome to overcome the brittleness and improve the overall properties of neat PLA, thus can be considered as a potential plasticizer. PMID:22754338

  5. Syngeneic AAV pseudo-vectors potentiates full vector transduction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An excessive amount of empty capsids are generated during regular AAV vector production process. These pseudo-vectors often remain in final vectors used for animal studies or clinical trials. The potential effects of these pseudo-vectors on AAV transduction have been a major concern. In the current ...

  6. Mitogen-activated protein kinase and abscisic acid signal transduction.

    PubMed

    Heimovaara-Dijkstra, S; Testerink, C; Wang, M

    2000-01-01

    The phytohormone abscisic acid (ABA) is a classical plant hormone, responsible for regulation of abscission, diverse aspects of plant and seed development, stress responses and germination. It was found that ABA signal transduction in plants can involve the activity of type 2C-phosphatases (PP2C), calcium, potassium, pH and a transient activation of MAP kinase. The ABA signal transduction cascades have been shown to be tissue-specific, the transient activation of MAP kinase has until now only been found in barley aleurone cells. However, type 2C phosphatases are involved in the induction of most ABA responses, as shown by the PP2C-deficient abi-mutants. These phosphatases show high homology with phosphatases that regulate MAP kinase activity in yeast. In addition, the role of farnesyl transferase as a negative regulator of ABA responses also indicates towards involvement of MAP kinase in ABA signal transduction. Farnesyl transferase is known to regulate Ras proteins, Ras proteins in turn are known to regulate MAP kinase activation. Interestingly, Ras-like proteins were detected in barley aleurone cells. Further establishment of the involvement of MAP kinase in ABA signal transduction and its role therein, still awaits more study.

  7. Rapid methods for generalized transduction of Salmonella typhimurium mutants.

    PubMed

    Rosenfeld, S A; Brenchley, J

    1979-04-01

    A procedure has been developed that allows the propagation of generalized transducing phage directly on cells growing on solid media. After the donor cells are killed with chloroform, the phage can be transferred directly to recipient cells and transductants can be selected.

  8. The discovery of signal transduction by G proteins. A personal account and an overview of the initial findings and contributions that led to our present understanding

    PubMed Central

    Birnbaumer, Lutz

    2007-01-01

    The realization that there existed a G-protein coupled signal transduction mechanism developed gradually and was initially the result of an ill fated quest for uncovering the mechanism of action of insulin, followed by a refocused research in many laboratories, including mine, on how GTP acted to increase hormonal stimulation of adenylyl cyclase. Independent research into how light-activated rhodopsin triggers a response in photoreceptor cells of the retina and the attendant biochemical studies joined midway and, without the left hand knowing well what the right hand was doing, preceded classical G protein research in identifying the molecular players responsible for signal transduction by G proteins. PMID:17141178

  9. Toxicity of ozone and nitrogen dioxide to alveolar macrophages: comparative study revealing differences in their mechanism of toxic action

    SciTech Connect

    Rietjens, I.M.; Poelen, M.C.; Hempenius, R.A.; Gijbels, M.J.; Alink, G.M.

    1986-01-01

    In this study the toxic mechanisms of action of ozone and nitrogen dioxide were compared using an intact cell model. Rat alveolar macrophages were exposed by means of gas diffusion through a Teflon film. In this in vitro system, ozone appeared to be 10 times more toxic than nitrogen dioxide. alpha-Tocopherol protected equally well against ozone and nitrogen dioxide. It was demonstrated that alpha-tocopherol provided its protection by its action as a radical scavenger and not by its stabilizing structural membrane effect, as (1) concentrations of alpha-tocopherol that already provided optimal protection against ozone and nitrogen dioxide did not influence the membrane fluidity of alveolar macrophages and (2) neither one of the structural alpha-tocopherol analogs tested (phytol and the methyl ether of alpha-tocopherol) could provide a protection against ozone or nitrogen dioxide comparable to the one provided by alpha-tocopherol. It was concluded that reactive intermediates scavenged by alpha-tocopherol are important in the toxic mechanism of both ozone and nitrogen dioxide induced cell damage. However, further results presented strongly confirmed that the kind of radicals and/or reactive intermediates, and thus the toxic reaction mechanism involved, must be different in ozone- and nitrogen dioxide-induced cell damage. This was concluded from the observations that showed that (1) vitamin C provided significantly better protection against nitrogen dioxide than against an equally toxic dose of ozone, (2) glutathione depletion affected the cellular sensitivity toward ozone to a significantly greater extent than the sensitivity towards nitrogen dioxide, and (3) the scavenging action of alpha-tocopherol was accompanied by a significantly greater reduction in its cellular level during nitrogen dioxide exposure than during exposure to ozone.

  10. Comparative Transcriptome Analysis of Latex Reveals Molecular Mechanisms Underlying Increased Rubber Yield in Hevea brasiliensis Self-Rooting Juvenile Clones

    PubMed Central

    Li, Hui-Liang; Guo, Dong; Zhu, Jia-Hong; Wang, Ying; Chen, Xiong-Ting; Peng, Shi-Qing

    2016-01-01

    Rubber tree (Hevea brasiliensis) self-rooting juvenile clones (JCs) are promising planting materials for rubber production. In a comparative trial between self-rooting JCs and donor clones (DCs), self-rooting JCs exhibited better performance in rubber yield. To study the molecular mechanism associated with higher rubber yield in self-rooting JCs, we sequenced and comparatively analyzed the latex of rubber tree self-rooting JCs and DCs at the transcriptome level. Total raw reads of 34,632,012 and 35,913,020 bp were obtained from the library of self-rooting JCs and DCs, respectively, by using Illumina HiSeq 2000 sequencing technology. De novo assemblies yielded 54689 unigenes from the library of self-rooting JCs and DCs. Among 54689 genes, 1716 genes were identified as differentially expressed between self-rooting JCs and DCs via comparative transcript profiling. Functional analysis showed that the genes related to the mass of categories were differentially enriched between the two clones. Several genes involved in carbohydrate metabolism, hormone metabolism and reactive oxygen species scavenging were up-regulated in self-rooting JCs, suggesting that the self-rooting JCs provide sufficient molecular basis for the increased rubber yielding, especially in the aspects of improved latex metabolisms and latex flow. Some genes encoding epigenetic modification enzymes were also differentially expressed between self-rooting JCs and DCs. Epigenetic modifications may lead to gene differential expression between self-rooting JCs and DCs. These data will provide new cues to understand the molecular mechanism underlying the improved rubber yield of H. brasiliensis self-rooting clones. PMID:27555864

  11. Comparative Transcriptome Analysis of Latex Reveals Molecular Mechanisms Underlying Increased Rubber Yield in Hevea brasiliensis Self-Rooting Juvenile Clones.

    PubMed

    Li, Hui-Liang; Guo, Dong; Zhu, Jia-Hong; Wang, Ying; Chen, Xiong-Ting; Peng, Shi-Qing

    2016-01-01

    Rubber tree (Hevea brasiliensis) self-rooting juvenile clones (JCs) are promising planting materials for rubber production. In a comparative trial between self-rooting JCs and donor clones (DCs), self-rooting JCs exhibited better performance in rubber yield. To study the molecular mechanism associated with higher rubber yield in self-rooting JCs, we sequenced and comparatively analyzed the latex of rubber tree self-rooting JCs and DCs at the transcriptome level. Total raw reads of 34,632,012 and 35,913,020 bp were obtained from the library of self-rooting JCs and DCs, respectively, by using Illumina HiSeq 2000 sequencing technology. De novo assemblies yielded 54689 unigenes from the library of self-rooting JCs and DCs. Among 54689 genes, 1716 genes were identified as differentially expressed between self-rooting JCs and DCs via comparative transcript profiling. Functional analysis showed that the genes related to the mass of categories were differentially enriched between the two clones. Several genes involved in carbohydrate metabolism, hormone metabolism and reactive oxygen species scavenging were up-regulated in self-rooting JCs, suggesting that the self-rooting JCs provide sufficient molecular basis for the increased rubber yielding, especially in the aspects of improved latex metabolisms and latex flow. Some genes encoding epigenetic modification enzymes were also differentially expressed between self-rooting JCs and DCs. Epigenetic modifications may lead to gene differential expression between self-rooting JCs and DCs. These data will provide new cues to understand the molecular mechanism underlying the improved rubber yield of H. brasiliensis self-rooting clones. PMID:27555864

  12. Comparative Transcriptome Analysis of Latex Reveals Molecular Mechanisms Underlying Increased Rubber Yield in Hevea brasiliensis Self-Rooting Juvenile Clones.

    PubMed

    Li, Hui-Liang; Guo, Dong; Zhu, Jia-Hong; Wang, Ying; Chen, Xiong-Ting; Peng, Shi-Qing

    2016-01-01

    Rubber tree (Hevea brasiliensis) self-rooting juvenile clones (JCs) are promising planting materials for rubber production. In a comparative trial between self-rooting JCs and donor clones (DCs), self-rooting JCs exhibited better performance in rubber yield. To study the molecular mechanism associated with higher rubber yield in self-rooting JCs, we sequenced and comparatively analyzed the latex of rubber tree self-rooting JCs and DCs at the transcriptome level. Total raw reads of 34,632,012 and 35,913,020 bp were obtained from the library of self-rooting JCs and DCs, respectively, by using Illumina HiSeq 2000 sequencing technology. De novo assemblies yielded 54689 unigenes from the library of self-rooting JCs and DCs. Among 54689 genes, 1716 genes were identified as differentially expressed between self-rooting JCs and DCs via comparative transcript profiling. Functional analysis showed that the genes related to the mass of categories were differentially enriched between the two clones. Several genes involved in carbohydrate metabolism, hormone metabolism and reactive oxygen species scavenging were up-regulated in self-rooting JCs, suggesting that the self-rooting JCs provide sufficient molecular basis for the increased rubber yielding, especially in the aspects of improved latex metabolisms and latex flow. Some genes encoding epigenetic modification enzymes were also differentially expressed between self-rooting JCs and DCs. Epigenetic modifications may lead to gene differential expression between self-rooting JCs and DCs. These data will provide new cues to understand the molecular mechanism underlying the improved rubber yield of H. brasiliensis self-rooting clones.

  13. Novel protective mechanisms of antidepressants against 3-nitropropionic acid induced Huntington's-like symptoms: a comparative study.

    PubMed

    Kumar, Puneet; Kalonia, Harikesh; Kumar, Anil

    2011-10-01

    Huntington's disease (HD) is characterized by progressive degeneration of neurons in the striatum, cortex and other parts of the brain, causing motor and cognitive dysfunction. 3-Nitropropionic acid (3-NP) is a well-known mycotoxin that significantly induces motor dysfunction in animals. Studies suggested the involvement of oxidative stress and nitric oxide mechanisms in HD pathogenesis. Clinical reports have also indicated the neuroprotective potential of antidepressants. Therefore, the present study has been designed to elucidate and compare the mechanistic role of different antidepressants (sertraline, venlafaxine, imipramine and trazodone) and their interaction with nitric oxide modulators if any, against 3-NP-induced neurotoxicity. Systemic 3-NP (10 mg/kg) administration for 14 days significantly reduced locomotor activity, body weight, motor coordination, oxidative defense and impaired mitochondrial complex enzyme activities in the striatum. Sertraline, venlafaxine, imipramine and trazodone treatments significantly improved behavioral, oxidative defense and mitochondrial complex enzyme activities as compared with the 3-NP-treated group. Systemic L-arginine (50 mg/kg) pretreatment with sub-effective dose of sertraline (10 mg/kg), venlafaxine (10 mg/kg), imipramine (10 mg/kg) and trazodone (10 mg/kg) for 14 days significantly attenuated their protective effect. Similarly, L-nitro-arginine methyl ester (L-NAME) (10 mg/kg) pretreatment with sub-effective dose of sertraline (10 mg/kg), venlafaxine (10 mg/kg), imipramine (10 mg/kg) and trazodone (10 mg/kg) for 14 days significantly potentiated their protective effects which were significant as compared with their effect alone, respectively. The results of the present study suggest that a nitric oxide mechanism might be involved in their protective effect against 3-NP-induced neurotoxicity. PMID:20305041

  14. Alterations in Energy Metabolism, Neuroprotection and Visual Signal Transduction in the Retina of Parkinsonian, MPTP-Treated Monkeys

    PubMed Central

    Bru-Martínez, Roque; Herrero, María Trinidad; Fernández-Villalba, Emiliano; Cuenca, Nicolás; Martín-Nieto, José

    2013-01-01

    Parkinson disease is mainly characterized by the degeneration of dopaminergic neurons in the central nervous system, including the retina. Different interrelated molecular mechanisms underlying Parkinson disease-associated neuronal death have been put forward in the brain, including oxidative stress and mitochondrial dysfunction. Systemic injection of the proneurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to monkeys elicits the appearance of a parkinsonian syndrome, including morphological and functional impairments in the retina. However, the intracellular events leading to derangement of dopaminergic and other retinal neurons in MPTP-treated animal models have not been so far investigated. Here we have used a comparative proteomics approach to identify proteins differentially expressed in the retina of MPTP-treated monkeys. Proteins were solubilized from the neural retinas of control and MPTP-treated animals, labelled separately with two different cyanine fluorophores and run pairwise on 2D DIGE gels. Out of >700 protein spots resolved and quantified, 36 were found to exhibit statistically significant differences in their expression levels, of at least ±1.4-fold, in the parkinsonian monkey retina compared with controls. Most of these spots were excised from preparative 2D gels, trypsinized and subjected to MALDI-TOF MS and LC-MS/MS analyses. Data obtained were used for protein sequence database interrogation, and 15 different proteins were successfully identified, of which 13 were underexpressed and 2 overexpressed. These proteins were involved in key cellular functional pathways such as glycolysis and mitochondrial electron transport, neuronal protection against stress and survival, and phototransduction processes. These functional categories underscore that alterations in energy metabolism, neuroprotective mechanisms and signal transduction are involved in MPTP-induced neuronal degeneration in the retina, in similarity to mechanisms thought to

  15. Two-Component Signal Transduction Systems of Desulfovibrio Vulgaris: Structural and Phylogenetic Analysis and Deduction of Putative Cognate Pairs

    SciTech Connect

    Zhang, Weiwen; Culley, David E.; Wu, Gang; Brockman, Fred J.

    2006-01-20

    ABSTRACT-Two-component signal transduction systems (TCSTS) composed of sensory histidine kinases (HK) and response regulators (RR), constitute a key element of the mechanism by which bacteria sense and respond to changes in environments. A large number of TCSTSs including 59 putative HKs and 55 RRs were identified from the Desulfovibrio vulgaris genome, indicating their important roles in regulation of cellular metabolism. In this study, the structural and phylogenetic analysis of all putative TCSTSs in D. vulgaris was performed. The results showed D. vulgaris contained an unexpectedly large number of hybrid-type HKs, implying that multiple-step phosphorelay may be a common signal transduction mechanism in D. vulgaris. Most TCSTS components of D. vulgaris were found clustered into several subfamilies previously recognized in other bacteria and extensive co-evolution between D. vulgaris HKs and RRs was observed, suggesting that the concordance of HKs and RRs in cognate phylogenetic groups could be indicative of cognate TCSTSs...

  16. A comparative microbiological study to assess caries excavation by conventional rotary method and a chemo-mechanical method

    PubMed Central

    Anegundi, Rajesh T.; Patil, Shruthi B.; Tegginmani, Viresh; Shetty, Sheetal D.

    2012-01-01

    Aims: This study was aimed to determine the effectiveness of Papacárie® for caries removal as compared to the conventional method with respect to microbial flora, time, the amount of tissue removal, child's behavior, pain perception, and preference of treatment. Materials and Methods: Sixty primary molars of 30 children of age 4-9 years were selected randomly and divided into two groups of 30 teeth each: Group A treated by conventional method and group B with Papacárie® method. Results: Comparatively, no statistical difference was seen in microbial growth, total bacterial count, and lactobacilli count in both the groups (P = 0.36). The mean cavity entrance size with group A was 0.98133 mm and group B was 0.26083 mm (P < 0.001). The mean preparation time for group A was 4.7 Mins (minutes) and group B was 17.96 min s (P < 0.001). Majority of kids of both group A and B scored 3 (Frankl Behavior Rating Scale) before and after the treatment showing no statistical difference in their behavioral score (P = 1). In group A 50% of children experienced no pain as compared to 86.7% in group B (P = 0.01). There was no statistical difference in the preference of treatment (P = 0.12). Conclusion: Thus, the Chemo mechanical caries removal method can be considered as an effective method to control pain and preserve sound tooth structure during caries excavation. PMID:23633794

  17. Studying Signal Transduction in Single Dendritic Spines

    PubMed Central

    Yasuda, Ryohei

    2012-01-01

    Many forms of synaptic plasticity are triggered by biochemical signaling that occurs in small postsynaptic compartments called dendritic spines, each of which typically houses the postsynaptic terminal associated with a single glutamatergic synapse. Recent advances in optical techniques allow investigators to monitor biochemical signaling in single dendritic spines and thus reveal the signaling mechanisms that link synaptic activity and the induction of synaptic plasticity. This is mostly in the study of Ca2+-dependent forms of synaptic plasticity for which many of the steps between Ca2+ influx and changes to the synapse are now known. This article introduces the new techniques used to investigate signaling in single dendritic spines and the neurobiological insights that they have produced. PMID:22843821

  18. Smartphone Operated Signal Transduction by Ion Nanogating (STING) Amplifier for Nanopore Sensors: Design and Analytical Application

    PubMed Central

    Özel, Rıfat Emrah; Kahnemouyi, Sina; Fan, Hsinwen; Mak, Wai Han; Lohith, Akshar; Seger, Adam; Teodorescu, Mircea; Pourmand, Nader

    2016-01-01

    In this report, we demonstrated a handheld wireless voltage-clamp amplifier for current measurement of nanopore sensors. This amplifier interfaces a sensing probe and connects wirelessly with a computer or smartphone for the required stimulus input, data processing and storage. To test the proposed Signal Transduction by Ion Nanogating (STING) wireless amplifier, in the current study the system was tested with a nano-pH sensor to measure pH of standard buffer solutions and the performance was compared against the commercial voltage-clamp amplifier. To our best knowledge, STING amplifier is the first miniaturized wireless voltage-clamp platform operated with a customized smart-phone application (app).

  19. Characterization and Expression of Genes Involved in the Ethylene Biosynthesis and Signal Transduction during Ripening of Mulberry Fruit

    PubMed Central

    Liu, Changying; Zhao, Aichun; Zhu, Panpan; Li, Jun; Han, Leng; Wang, Xiling; Fan, Wei; Lü, Ruihua; Wang, Chuanhong; Li, Zhengang; Lu, Cheng; Yu, Maode

    2015-01-01

    Although ethylene is well known as an essential regulator of fruit development, little work has examined the role ethylene plays in the development and maturation of mulberry (Morus L.) fruit. To study the mechanism of ethylene action during fruit development in this species, we measured the ethylene production, fruit firmness, and soluble solids content (SSC) during fruit development and harvest. By comparing the results with those from other climacteric fruit, we concluded that Morus fruit are probably climacteric. Genes associated with the ethylene signal transduction pathway of Morus were characterized from M. notabilis Genome Database, including four ethylene receptor genes, a EIN2-like gene, a CTR1-like gene, four EIN3-like genes, and a RTE1-like gene. The expression patterns of these genes were analyzed in the fruit of M. atropurpurea cv. Jialing No.40. During fruit development, transcript levels of MaETR2, MaERS, MaEIN4, MaRTE, and MaCTR1 were lower at the early stages and higher after 26 days after full bloom (DAF), while MaETR1, MaEIL1, MaEIL2, and MaEIL3 remained constant. In ripening fruit, the transcripts of MaACO1 and MaACS3 increased, while MaACS1 and MaACO2 decreased after harvest. The transcripts of MaACO1, MaACO2, and MaACS3 were inhibited by ethylene, and 1-MCP (1–methylcyclopropene) upregulated MaACS3. The transcripts of the MaETR-like genes, MaRTE, and MaCTR1 were inhibited by ethylene and 1-MCP, suggesting that ethylene may accelerate the decline of MaETRs transcripts. No significant changes in the expression of MaEIN2, MaEIL1, and MaEIL3 were observed during ripening or in response to ethylene, while the expressions of MaEIL2 and MaEIL4 increased rapidly after 24 h after harvest (HAH) and were upregulated by ethylene. The present study provides insights into ethylene biosynthesis and signal transduction in Morus plants and lays a foundation for the further understanding of the mechanisms underlying Morus fruit development and ripening. PMID

  20. Characterization and expression of genes involved in the ethylene biosynthesis and signal transduction during ripening of mulberry fruit.

    PubMed

    Liu, Changying; Zhao, Aichun; Zhu, Panpan; Li, Jun; Han, Leng; Wang, Xiling; Fan, Wei; Lü, Ruihua; Wang, Chuanhong; Li, Zhengang; Lu, Cheng; Yu, Maode

    2015-01-01

    Although ethylene is well known as an essential regulator of fruit development, little work has examined the role ethylene plays in the development and maturation of mulberry (Morus L.) fruit. To study the mechanism of ethylene action during fruit development in this species, we measured the ethylene production, fruit firmness, and soluble solids content (SSC) during fruit development and harvest. By comparing the results with those from other climacteric fruit, we concluded that Morus fruit are probably climacteric. Genes associated with the ethylene signal transduction pathway of Morus were characterized from M. notabilis Genome Database, including four ethylene receptor genes, a EIN2-like gene, a CTR1-like gene, four EIN3-like genes, and a RTE1-like gene. The expression patterns of these genes were analyzed in the fruit of M. atropurpurea cv. Jialing No.40. During fruit development, transcript levels of MaETR2, MaERS, MaEIN4, MaRTE, and MaCTR1 were lower at the early stages and higher after 26 days after full bloom (DAF), while MaETR1, MaEIL1, MaEIL2, and MaEIL3 remained constant. In ripening fruit, the transcripts of MaACO1 and MaACS3 increased, while MaACS1 and MaACO2 decreased after harvest. The transcripts of MaACO1, MaACO2, and MaACS3 were inhibited by ethylene, and 1-MCP (1-methylcyclopropene) upregulated MaACS3. The transcripts of the MaETR-like genes, MaRTE, and MaCTR1 were inhibited by ethylene and 1-MCP, suggesting that ethylene may accelerate the decline of MaETRs transcripts. No significant changes in the expression of MaEIN2, MaEIL1, and MaEIL3 were observed during ripening or in response to ethylene, while the expressions of MaEIL2 and MaEIL4 increased rapidly after 24 h after harvest (HAH) and were upregulated by ethylene. The present study provides insights into ethylene biosynthesis and signal transduction in Morus plants and lays a foundation for the further understanding of the mechanisms underlying Morus fruit development and ripening. PMID

  1. Characterization and expression of genes involved in the ethylene biosynthesis and signal transduction during ripening of mulberry fruit.

    PubMed

    Liu, Changying; Zhao, Aichun; Zhu, Panpan; Li, Jun; Han, Leng; Wang, Xiling; Fan, Wei; Lü, Ruihua; Wang, Chuanhong; Li, Zhengang; Lu, Cheng; Yu, Maode

    2015-01-01

    Although ethylene is well known as an essential regulator of fruit development, little work has examined the role ethylene plays in the development and maturation of mulberry (Morus L.) fruit. To study the mechanism of ethylene action during fruit development in this species, we measured the ethylene production, fruit firmness, and soluble solids content (SSC) during fruit development and harvest. By comparing the results with those from other climacteric fruit, we concluded that Morus fruit are probably climacteric. Genes associated with the ethylene signal transduction pathway of Morus were characterized from M. notabilis Genome Database, including four ethylene receptor genes, a EIN2-like gene, a CTR1-like gene, four EIN3-like genes, and a RTE1-like gene. The expression patterns of these genes were analyzed in the fruit of M. atropurpurea cv. Jialing No.40. During fruit development, transcript levels of MaETR2, MaERS, MaEIN4, MaRTE, and MaCTR1 were lower at the early stages and higher after 26 days after full bloom (DAF), while MaETR1, MaEIL1, MaEIL2, and MaEIL3 remained constant. In ripening fruit, the transcripts of MaACO1 and MaACS3 increased, while MaACS1 and MaACO2 decreased after harvest. The transcripts of MaACO1, MaACO2, and MaACS3 were inhibited by ethylene, and 1-MCP (1-methylcyclopropene) upregulated MaACS3. The transcripts of the MaETR-like genes, MaRTE, and MaCTR1 were inhibited by ethylene and 1-MCP, suggesting that ethylene may accelerate the decline of MaETRs transcripts. No significant changes in the expression of MaEIN2, MaEIL1, and MaEIL3 were observed during ripening or in response to ethylene, while the expressions of MaEIL2 and MaEIL4 increased rapidly after 24 h after harvest (HAH) and were upregulated by ethylene. The present study provides insights into ethylene biosynthesis and signal transduction in Morus plants and lays a foundation for the further understanding of the mechanisms underlying Morus fruit development and ripening.

  2. In situ patch-clamp recordings from Merkel cells in rat whisker hair follicles, an experimental protocol for studying tactile transduction in tactile-end organs.

    PubMed

    Ikeda, Ryo; Ling, Jennifer; Cha, Myeounghoon; Gu, Jianguo G

    2015-01-01

    Mammals use tactile end-organs to perform sensory tasks such as environmental exploration, social interaction, and tactile discrimination. However, cellular and molecular mechanisms underlying tactile transduction in tactile end-organs remain poorly understood. The patch-clamp recording technique may be the most valuable approach for detecting and studying tactile transduction in tactile end-organs, but it is technically challenging because tactile transduction elements in an end-organ are normally inaccessible by patch-clamp recording electrodes. Here we describe an in situ patch-clamp recording protocol for the study of tactile transduction in Merkel cells of rat whisker hair follicles, one of the most sensitive tactile end-organs in mammals. This technique offers an opportunity to explore the identities and properties of ion channels that are involved in tactile transduction in whisker hair follicles, and it may also lend a useful tool for researchers to study other tactile end-organs. The experimental protocol describes procedures for 1) tissue dissection and whisker hair follicle preparation, 2) device setup and steps for performing patch-clamp recordings from Merkel cells in a whisker hair follicle, 3) methods of delivering mechanical stimuli, and 4) intra-follicle microinjection for receptor knockdown in whisker hair follicles. The main procedures in this protocol, from tissue preparation to whole-cell patch-clamp recordings, can be completed in a few hours. PMID:25907165

  3. Signal transduction meets vesicle traffic: the software and hardware of GLUT4 translocation.

    PubMed

    Klip, Amira; Sun, Yi; Chiu, Tim Ting; Foley, Kevin P

    2014-05-15

    Skeletal muscle is the major tissue disposing of dietary glucose, a function regulated by insulin-elicited signals that impart mobilization of GLUT4 glucose transporters to the plasma membrane. This phenomenon, also central to adipocyte biology, has been the subject of intense and productive research for decades. We focus on muscle cell studies scrutinizing insulin signals and vesicle traffic in a spatiotemporal manner. Using the analogy of an integrated circuit to approach the intersection between signal transduction and vesicle mobilization, we identify signaling relays ("software") that engage structural/mechanical elements ("hardware") to enact the rapid mobilization and incorporation of GLUT4 into the cell surface. We emphasize how insulin signal transduction switches from tyrosine through lipid and serine phosphorylation down to activation of small G proteins of the Rab and Rho families, describe key negative regulation step of Rab GTPases through the GTPase-activating protein activity of the Akt substrate of 160 kDa (AS160), and focus on the mechanical effectors engaged by Rabs 8A and 10 (the molecular motor myosin Va), and the Rho GTPase Rac1 (actin filament branching and severing through Arp2/3 and cofilin). Finally, we illustrate how actin filaments interact with myosin 1c and α-Actinin4 to promote vesicle tethering as preamble to fusion with the membrane.

  4. Coupling of signal transduction to alternative pre-mRNA splicing by a composite splice regulator.

    PubMed Central

    König, H; Ponta, H; Herrlich, P

    1998-01-01

    Alternative splicing of pre-mRNA is a fundamental mechanism of differential gene expression in that it can give rise to functionally distinct proteins from a single gene, according to the developmental or physiological state of cells in multicellular organisms. In the pre-mRNA of the cell surface molecule CD44, the inclusion of up to 10 variant exons (v1-v10) is regulated during development, upon activation of lymphocytes and dendritic cells, and during tumour progression. Using minigene constructs containing CD44 exon v5, we have discovered exonic RNA elements that couple signal transduction to alternative splicing. They form a composite splice regulator encompassing an exon recognition element and splice silencer elements. Both type of elements are necessary to govern cell type-specific inclusion of the exon as well as inducible inclusion in T cells after stimulation by concanavalin A, by Ras signalling or after activation of protein kinase C by phorbol ester. Inducible splicing does not depend on de novo protein synthesis. The coupling of signal transduction to alternative splicing by such elements probably represents the mechanism whereby splice patterns of genes are established during development and can be changed under physiological and pathological conditions. PMID:9582284

  5. Ca2+ Changes the Force Sensitivity of the Hair-Cell Transduction Channel

    PubMed Central

    Cheung, Eunice L. M.; Corey, David P.

    2006-01-01

    The mechanically gated transduction channels of vertebrate hair cells tend to close in ∼1 ms after their activation by hair bundle deflection. This fast adaptation is correlated with a quick negative movement of the bundle (a “twitch”), which can exert force and may mediate an active mechanical amplification of sound stimuli in hearing organs. We used an optical trap to deflect bullfrog hair bundles and to measure bundle movement while controlling Ca2+ entry with a voltage clamp. The twitch elicited by repolarization of the cell varied with force applied to the bundle, going to zero where channels were all open or closed. The force dependence is quantitatively consistent with a model in which a Ca2+-bound channel requires ∼3 pN more force to open, and rules out other models for the site of Ca2+ action. In addition, we characterized a faster, voltage-dependent “flick”, which requires intact tip links but not current through transduction channels. PMID:16214875

  6. [Comparative analysis of mechanisms of the modification of microorganism viability under the effect of UHF heating and hyperthermia].

    PubMed

    Kuchma, T N; Alipov, E D; Samoĭlenko, I I; Lystsov, V N

    1992-01-01

    In experiments with models of isogenic Escherichia coli strains, a comparative study was made of the effect of SHF of electromagnetic field and hyperthermia. The survival rate of bacteria was determined and, simultaneously, injuries to genetic supramolecular structures were registered through measuring the anomalous time dependence of cell lysate viscosity. The combined effects of the mixture of these factors with H2O2 microconcentrations were studied. The differences observed in their realization were attributed to the different mechanisms of action of these factors on the repair enzyme systems of the studied cells. It has been found that the effect of microwaves on microorganisms causes much severer damages to DNA that hyperthermia does. PMID:1494658

  7. Comparative Study by MS and XRD of Fe50Al50 Alloys Produced by Mechanical Alloying, Using Different Ball Mills

    NASA Astrophysics Data System (ADS)

    Rojas Martínez, Y.; Pérez Alcázar, G. A.; Bustos Rodríguez, H.; Oyola Lozano, D.

    2005-02-01

    In this work we report a comparative study of the magnetic and structural properties of Fe50Al50 alloys produced by mechanical alloying using two different planetary ball mills with the same ball mass to powder mass relation. The Fe50Al50 sample milled during 48 h using the Fritsch planetary ball mill pulverisette 5 and balls of 20 mm, presents only a bcc alloy phase with a majority of paramagnetic sites, whereas that sample milled during the same time using the Fritsch planetary ball mill pulverisette 7 with balls of 15 mm, presents a bcc alloy phase with paramagnetic site (doublet) and a majority of ferromagnetic sites which include pure Fe. However for 72 h of milling this sample presents a bcc paramagnetic phase, very similar to that prepared with the first system during 48 h. These results show that the conditions used in the first ball mill equipment make more efficient the milling process.

  8. Signal transduction of stress via ceramide.

    PubMed Central

    Mathias, S; Peña, L A; Kolesnick, R N

    1998-01-01

    The sphingomyelin (SM) pathway is a ubiquitous, evolutionarily conserved signalling system analogous to conventional systems such as the cAMP and phosphoinositide pathways. Ceramide, which serves as second messenger in this pathway, is generated from SM by the action of a neutral or acidic SMase, or by de novo synthesis co-ordinated through the enzyme ceramide synthase. A number of direct targets for ceramide action have now been identified, including ceramide-activated protein kinase, ceramide-activated protein phosphatase and protein kinase Czeta, which couple the SM pathway to well defined intracellular signalling cascades. The SM pathway induces differentiation, proliferation or growth arrest, depending on the cell type. Very often, however, the outcome of signalling through this pathway is apoptosis. Mammalian systems respond to diverse stresses with ceramide generation, and recent studies show that yeast manifest a form of this response. Thus ceramide signalling is an older stress response system than the caspase/apoptotic death pathway, and hence these two pathways must have become linked later in evolution. Signalling of the stress response through ceramide appears to play a role in the development of human diseases, including ischaemia/reperfusion injury, insulin resistance and diabetes, atherogenesis, septic shock and ovarian failure. Further, ceramide signalling mediates the therapeutic effects of chemotherapy and radiation in some cells. An understanding of the mechanisms by which ceramide regulates physiological and pathological events in specific cells may provide new targets for pharmacological intervention. PMID:9794783

  9. Detection and transduction of daylength in birds.

    PubMed

    Saldanha, C J; Leak, R K; Silver, R

    1994-01-01

    Daylength is an important environmental cue used by temperate zone avian species to time the onset of seasonal reproductive activity. Photic cues are detected by extra-retinal, extra-pineal central nervous system elements, and are rapidly transduced to an efferent signal. In this paper, we describe the brain locus of putative encephalic photoreceptors in birds, and explore the pathway of information transfer from photic input to the reproductive axis. To this end, we examine how photoreceptors might communicate with the hypothalamic-pituitary axis, and how brain peptides vary seasonally. Recent studies indicate that brain photoreceptors lie in the lateral septum and in the tuberal hypothalamus, and co-express proteins characteristic of retinal photoreceptors, as well as vasoactive-intestinal polypeptide (VIP). At the light microscopic level, photoreceptor cells appear to communicate with gonadotropin-releasing hormone (GnRH) neurons, and vice versa. Expression of VIP-like immunoreactivity is highest in photorefractory animals while GnRH-like immunoreactivity is highest in photosensitive birds. Expression of these CNS peptides is correlated with changes in plasma prolactin and luteinizing hormone (LH), suggesting a mechanism mediating seasonal cyclicity.

  10. Comparative analysis of the mechanisms of sulfur anion oxidation and reduction by dsr operon to maintain environmental sulfur balance.

    PubMed

    Ghosh, Semanti; Bagchi, Angshuman

    2015-12-01

    Sulfur metabolism is one of the oldest known redox geochemical cycles in our atmosphere. These redox processes utilize different sulfur anions and the reactions are performed by the gene products of dsr operon from phylogenetically diverse sets of microorganisms. The operon is involved in the maintenance of environmental sulfur balance. Interestingly, the dsr operon is found to be present in both sulfur anion oxidizing and reducing microorganisms and in both types of organisms DsrAB protein complex plays a vital role. Though there are various reports regarding the genetics of dsr operon there are practically no reports dealing with the structural aspects of sulfur metabolism by dsr operon. In our present study, we tried to compare the mechanisms of sulfur anion oxidation and reduction by Allochromatium vinosum and Desulfovibrio vulgaris respectively through DsrAB protein complex. We analyzed the modes of bindings of sulfur anions to the DsrAB protein complex and observed that for sulfur anion oxidizers, sulfide and thiosulfate are the best substrates whereas for reducers sulfate and sulfite have the best binding abilities. We analyzed the binding interaction pattern of the DsrA and DsrB proteins while forming the DsrAB protein complexes in Desulfovibrio vulgaris and Allochromatium vinosum. To our knowledge this is the first report that analyzes the differences in binding patterns of sulfur substrates with DsrAB protein from these two microorganisms. This study would therefore be essential to predict the biochemical mechanism of sulfur anion oxidation and reduction by these two microorganisms i.e., Desulfovibrio vulgaris (sulfur anion reducer) and Allochromatium vinosum (sulfur anion oxidizer). Our observations also highlight the mechanism of sulfur geochemical cycle which has important implications in future study of sulfur metabolism as it has a huge application in waste remediation and production of industrial bio-products viz. vitamins, bio-polyesters and bio

  11. Comparative analysis of the mechanisms of sulfur anion oxidation and reduction by dsr operon to maintain environmental sulfur balance.

    PubMed

    Ghosh, Semanti; Bagchi, Angshuman

    2015-12-01

    Sulfur metabolism is one of the oldest known redox geochemical cycles in our atmosphere. These redox processes utilize different sulfur anions and the reactions are performed by the gene products of dsr operon from phylogenetically diverse sets of microorganisms. The operon is involved in the maintenance of environmental sulfur balance. Interestingly, the dsr operon is found to be present in both sulfur anion oxidizing and reducing microorganisms and in both types of organisms DsrAB protein complex plays a vital role. Though there are various reports regarding the genetics of dsr operon there are practically no reports dealing with the structural aspects of sulfur metabolism by dsr operon. In our present study, we tried to compare the mechanisms of sulfur anion oxidation and reduction by Allochromatium vinosum and Desulfovibrio vulgaris respectively through DsrAB protein complex. We analyzed the modes of bindings of sulfur anions to the DsrAB protein complex and observed that for sulfur anion oxidizers, sulfide and thiosulfate are the best substrates whereas for reducers sulfate and sulfite have the best binding abilities. We analyzed the binding interaction pattern of the DsrA and DsrB proteins while forming the DsrAB protein complexes in Desulfovibrio vulgaris and Allochromatium vinosum. To our knowledge this is the first report that analyzes the differences in binding patterns of sulfur substrates with DsrAB protein from these two microorganisms. This study would therefore be essential to predict the biochemical mechanism of sulfur anion oxidation and reduction by these two microorganisms i.e., Desulfovibrio vulgaris (sulfur anion reducer) and Allochromatium vinosum (sulfur anion oxidizer). Our observations also highlight the mechanism of sulfur geochemical cycle which has important implications in future study of sulfur metabolism as it has a huge application in waste remediation and production of industrial bio-products viz. vitamins, bio-polyesters and bio-hydrogen.

  12. Understanding abiotic stress tolerance mechanisms in soybean: a comparative evaluation of soybean response to drought and flooding stress.

    PubMed

    Mutava, Raymond N; Prince, Silvas Jebakumar K; Syed, Naeem Hasan; Song, Li; Valliyodan, Babu; Chen, Wei; Nguyen, Henry T

    2015-01-01

    Many sources of drought and flooding tolerance have been identified in soybean, however underlying molecular and physiological mechanisms are poorly understood. Therefore, it is important to illuminate different plant responses to these abiotic stresses and understand the mechanisms that confer tolerance. Towards this goal we used four contrasting soybean (Glycine max) genotypes (PI 567690--drought tolerant, Pana--drought susceptible, PI 408105A--flooding tolerant, S99-2281--flooding susceptible) grown under greenhouse conditions and compared genotypic responses to drought and flooding at the physiological, biochemical, and cellular level. We also quantified these variations and tried to infer their role in drought and flooding tolerance in soybean. Our results revealed that different mechanisms contribute to reduction in net photosynthesis under drought and flooding stress. Under drought stress, ABA and stomatal conductance are responsible for reduced photosynthetic rate; while under flooding stress, accumulation of starch granules played a major role. Drought tolerant genotypes PI 567690 and PI 408105A had higher plastoglobule numbers than the susceptible Pana and S99-2281. Drought stress increased the number and size of plastoglobules in most of the genotypes pointing to a possible role in stress tolerance. Interestingly, there were seven fibrillin proteins localized within the plastoglobules that were up-regulated in the drought and flooding tolerant genotypes PI 567690 and PI 408105A, respectively, but down-regulated in the drought susceptible genotype Pana. These results suggest a potential role of Fibrillin proteins, FBN1a, 1b and 7a in soybean response to drought and flooding stress.

  13. Comparing apples and oranges-the influence of food mechanical properties on ingestive bite sizes in lemurs.

    PubMed

    Hartstone-Rose, Adam; Parkinson, Jennifer A; Criste, Taylor; Perry, Jonathan M G

    2015-07-01

    Previously we found that Maximum Ingested Bite Size (Vb )-the largest piece of food that an animal will ingest whole without biting first-scales isometrically with body size in 17 species of strepsirrhines at the Duke Lemur Center (DLC). However, because this earlier study focused on only three food types (two with similar mechanical properties), it did not yield results that were easily applied to describing the broad diets of these taxa. Expressing Vb in terms of food mechanical properties allows us to compare data across food types, including foods of wild lemurs, to better understand dietary adaptations in lemurs. To this end, we quantified Vb in five species of lemurs at the DLC representing large and small frugivores and folivores using ten types of food that vary widely in stiffness and toughness to determine how these properties relate to bite sizes. We found that although most species take smaller bites of stiffer foods, this negative relationship was not statistically significant across the whole sample. However, there is a significant relationship between bite size and toughness. All three of the more frugivorous taxa in our sample take significantly smaller bites of tougher foods. However, the two more folivorous lemurs do not. They take small bites for all foods. This suggests that the species most adapted to the consumption of tough foods do not modulate their ingestive sizes to accommodate larger pieces of weak foods.

  14. Comparative behavior of membrane protein-antibody complexes on motile fibroblasts: implications for a mechanism of capping

    PubMed Central

    1990-01-01

    A characteristic feature of fibroblast locomotory activity is the rearward transport across the leading lamella of various materials used to mark the cell surface. The two processes most frequently invoked as explanations for this transport phenomenon, called capping, are (a) retrograde membrane flow arising from directed membrane insertion and (b) rearward cortical cytoskeletal flow arising from cytoskeletal assembly and contraction. The retrograde lipid flow hypothesis, the most current form of the membrane flow scheme, makes explicit predictions about the movement of membrane proteins subjected to the postulated rearward lipid flow. Several of these predictions were tested by comparing the behavior of four membrane proteins, Pgp-1, Thy- 1, H-2, and influenza HA0, identified by fluorescent antibodies. With the exception of Pgp-1, these proteins were uniformly distributed under nonaggregated conditions but were capped when aggregated into patches. In contrast, Pgp-1 was capped in similar time frames in both nonaggregated and aggregated states where the lateral diffusion coefficients were very different. Furthermore, the capping behavior of two tagged membrane proteins was markedly different yet both had similar diffusion coefficients. The results from these tests disprove the bulk membrane flow hypothesis and are at odds with explicit predictions of the retrograde lipid flow hypothesis for the mechanism of capping. This work, therefore, supports the alternative cytoskeletal- based mechanism for driving capping. Requirements for coupling cytoskeletal movement to membrane components are discussed. PMID:2277071

  15. Bioinformatics investigation of therapeutic mechanisms of Xuesaitong capsule treating ischemic cerebrovascular rat model with comparative transcriptome analysis

    PubMed Central

    Liao, Jiangquan; Wei, Benjun; Chen, Hengwen; Liu, Yongmei; Wang, Jie

    2016-01-01

    Background: Xuesaitong soft capsule (XST) which consists of panax notoginseng saponin (PNS) has been used to treat ischemic cerebrovascular diseases in China. The therapeutic mechanism of XST has not been elucidated yet from prospective of genomics and bioinformatics. Methods: A transcriptome analysis was performed to review series concerning middle cerebral artery occlusion (MCAO) rat model and XST intervention after MCAO from Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) were compared between blank group and model group, model group and XST group. Functional enrichment and pathway analysis were performed. Protein-Protein interaction network was constructed. The overlapping genes from two DEGs sets were screened out and profound analysis was performed. Results: Two series including 22 samples were obtained. 870 DEGs were identified between blank group and model group, and 1189 DEGs were identified between model group and XST group. GO terms and KEGG pathways of MCAO and XST intervention were significantly enriched. PPI networks were constructed to demonstrate the gene-gene interactions. The overlapping genes from two DEGs sets were highlighted. ANTXR2, FHL3, PRCP, TYROBP, TAF9B, FGFR2, BCL11B, RB1CC1 and MBNL2 were the pivotal genes and possible action sites of XST therapeutic mechanisms. Conclusion: MCAO is a pathological process with multiple. PMID:27347353

  16. A comparative fluid flow characterisation in a low frequency/high power sonoreactor and mechanical stirred vessel.

    PubMed

    Sajjadi, Baharak; Raman, Abdul Aziz Abdul; Ibrahim, Shaliza

    2015-11-01

    This study aims at analysing the jet-like acoustic streaming generated under low-frequency and high-power ultrasound irradiation and comparing it with fluid streaming generated by traditional mechanical mixing. The main characteristics of fluid flow, which include radial, axial and tangential terms of velocity and their effects on fluid flow pattern, pressure distribution, axial mixing time and turbulence intensity were considered at different power inputs. Both 3D CFD simulation and Particle Image Velocimetry (PIV) were used in this study. The CFD results indicated that the jet-like acoustic streaming reached the velocity magnitude of 145 cm/s at 400 W, which reduced the mixing time to 1.38 s. However, the minimum mixing time of 3.18 s corresponding to the impeller rotational speed of 800 RPM was observed for mechanical stirring. A uniform axial flow pattern was generated under ultrasound irradiation whereas the tangential flow pattern was more prominent in the stirred vessel. Besides, the highest turbulence was observed in the vicinity of the ultrasound transducer and impeller with the values of 138% and 82% for the ultrasonicator and stirred vessel, respectively. The predicted fluid flow pattern under ultrasound irradiation was in a reasonable agreement with that obtained from PIV, with a reasonable accuracy.

  17. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Comparative Study of Activity of Different Agings of Aluminum Nanopowders

    NASA Astrophysics Data System (ADS)

    Yan, Zheng-Xin; Deng, Jun; Wanf, Ya-Min; Liu, Wei

    2009-08-01

    The structure and activity of aluminum nanopowders with a 3 nm oxide layer on their surface (3-nm-OLA) and 30 nm oxide layers on their surface (30-nm-OLA) are investigated comparably under the same normal incident shock wave intensity. Their corresponding reaction products are characterized by x-ray diffraction, high-resolution transmission electron microscopy and x-ray photoelectron spectroscopy. The spectrum of x-ray diffraction shows that there are different phases of alumina in their products, which evidences directly the different reacting temperature in the shock tube. The x-ray photoelectron spectroscopy reveals that the oxide layer thickness is 30 nm on the product surface of 30-nm-OLA, while it is only 3 nm on 3-nm-OLA. Images of transmission electron microscopy present additional evidence that the agglomeration mechanism is over sintering one in the containing-30-nm-OLA system, the reversed mechanism is observed in the containing-3-nm-OLA reaction system.

  18. Two Component Signal Transduction in Desulfovibrio Species

    SciTech Connect

    Luning, Eric; Rajeev, Lara; Ray, Jayashree; Mukhopadhyay, Aindrila

    2010-05-17

    The environmentally relevant Desulfovibrio species are sulfate-reducing bacteria that are of interest in the bioremediation of heavy metal contaminated water. Among these, the genome of D. vulgaris Hildenborough encodes a large number of two component systems consisting of 72 putative response regulators (RR) and 64 putative histidinekinases (HK), the majority of which are uncharacterized. We classified the D. vulgaris Hildenborough RRs based on their output domains and compared the distribution of RRs in other sequenced Desulfovibrio species. We have successfully purified most RRs and several HKs as His-tagged proteins. We performed phospho-transfer experiments to verify relationships between cognate pairs of HK and RR, and we have also mapped a few non-cognate HK-RR pairs. Presented here are our discoveries from the Desulfovibrio RR categorization and results from the in vitro studies using purified His tagged D. vulgaris HKs and RRs.

  19. Self-Complementary Adeno-Associated Virus Vectors Improve Transduction Efficiency of Corneal Endothelial Cells

    PubMed Central

    Gruenert, Anja K.; Czugala, Marta; Mueller, Chris; Schmeer, Marco; Schleef, Martin; Kruse, Friedrich E.; Fuchsluger, Thomas A.

    2016-01-01

    Transplantation of a donor cornea to restore vision is the most frequently performed transplantation in the world. Corneal endothelial cells (CEC) are crucial for the outcome of a graft as they maintain corneal transparency and avoid graft failure due to corneal opaqueness. Given the characteristic of being a monolayer and in direct contact with culture medium during cultivation in eye banks, CEC are specifically suitable for gene therapeutic approaches prior to transplantation. Recombinant adeno-associated virus 2 (rAAV2) vectors represent a promising tool for gene therapy of CEC. However, high vector titers are needed to achieve sufficient gene expression. One of the rate-limiting steps for transgene expression is the conversion of single-stranded (ss-) DNA vector genome into double-stranded (ds-) DNA. This step can be bypassed by using self-complementary (sc-) AAV2 vectors. Aim of this study was to compare for the first time transduction efficiencies of ss- and scAAV2 vectors in CEC. For this purpose AAV2 vectors containing enhanced green fluorescent protein (GFP) as transgene were used. Both in CEC and in donor corneas, transduction with scAAV2 resulted in significantly higher transgene expression compared to ssAAV2. The difference in transduction efficiency decreased with increasing vector titer. In most cases, only half the vector titer of scAAV2 was required for equal or higher gene expression rates than those of ssAAV2. In human donor corneas, GFP expression was 64.7±11.3% (scAAV) and 38.0±8.6% (ssAAV) (p<0.001), respectively. Furthermore, transduced cells maintained their viability and showed regular morphology. Working together with regulatory authorities, a translation of AAV2 vector-mediated gene therapy to achieve a temporary protection of corneal allografts during cultivation and transplantation could therefore become more realistic. PMID:27023329

  20. Signal transduction in mammalian oocytes during fertilization.

    PubMed

    Machaty, Zoltan

    2016-01-01

    Mammalian embryo development begins when the fertilizing sperm triggers a series of elevations in the oocyte's intracellular free Ca(2+) concentration. The elevations are the result of repeated release and re-uptake of Ca(2+) stored in the smooth endoplasmic reticulum. Ca(2+) release is primarily mediated by the phosphoinositide signaling system of the oocyte. The system is stimulated when the sperm causes the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG); IP3 then binds its receptor on the surface of the endoplasmic reticulum that induces Ca(2+) release. The manner in which the sperm generates IP3, the Ca(2+) mobilizing second messenger, has been the subject of extensive research for a long time. The sperm factor hypothesis has eventually gained general acceptance, according to which it is a molecule from the sperm that diffuses into the ooplasm and stimulates the phosphoinositide cascade. Much evidence now indicates that the sperm-derived factor is phospholipase C-zeta (PLCζ) that cleaves PIP2 and generates IP3, eventually leading to oocyte activation. A recent addition to the candidate sperm factor list is the post-acrosomal sheath WW domain-binding protein (PAWP), whose role at fertilization is currently under debate. Ca(2+) influx across the plasma membrane is also important as, in the absence of extracellular Ca(2+), the oscillations run down prematurely. In pig oocytes, the influx that sustains the oscillations seems to be regulated by the filling status of the stores, whereas in the mouse other mechanisms might be involved. This work summarizes the current understanding of Ca(2+) signaling in mammalian oocytes.

  1. Developing a synthetic signal transduction system in plants.

    PubMed

    Morey, Kevin J; Antunes, Mauricio S; Albrecht, Kirk D; Bowen, Tessa A; Troupe, Jared F; Havens, Keira L; Medford, June I

    2011-01-01

    One area of focus in the emerging field of plant synthetic biology is the manipulation of systems involved in sensing and response to environmental signals. Sensing and responding to signals, including ligands, typically involves biological signal transduction. Plants use a wide variety of signaling systems to sense and respond to their environment. One of these systems, a histidine kinase (HK) based signaling system, lends itself to manipulation using the tools of synthetic biology. Both plants and bacteria use HKs to relay signals, which in bacteria can involve as few as two proteins (two-component systems or TCS). HK proteins are evolutionarily conserved between plants and bacteria and plant HK components have been shown to be functional in bacteria. We found that this conservation also applies to bacterial HK components which can function in plants. This conservation of function led us to hypothesize that synthetic HK signaling components can be designed and rapidly tested in bacteria. These novel HK signaling components form the foundation for a synthetic signaling system in plants, but typically require modifications such as codon optimization and proper targeting to allow optimal function. We describe the process and methodology of producing a synthetic signal transduction system in plants. We discovered that the bacterial response regulator (RR) PhoB shows HK-dependent nuclear translocation in planta. Using this discovery, we engineered a partial synthetic pathway in which a synthetic promoter (PlantPho) is activated using a plant-adapted PhoB (PhoB-VP64) and the endogenous HK-based cytokinin signaling pathway. Building on this work, we adapted an input or sensing system based on bacterial chemotactic binding proteins and HKs, resulting in a complete eukaryotic signal transduction system. Input to our eukaryotic signal transduction system is provided by a periplasmic binding protein (PBP), ribose-binding protein (RBP). RBP interacts with the membrane

  2. Prostaglandin E2 regulates renal cell carcinoma invasion through the EP4 receptor-Rap GTPase signal transduction pathway.

    PubMed

    Wu, Juanjuan; Zhang, Yushan; Frilot, Nicole; Kim, Jae I; Kim, Wan-Ju; Daaka, Yehia

    2011-09-30

    Prognosis for patients with early stage kidney cancer has improved, but the treatment options for patients with locally advanced disease and metastasis remain few. Understanding the molecular mechanisms that regulate invasion and metastasis is critical for developing successful therapies to treat these patients. Proinflammatory prostaglandin E(2) plays an important role in cancer initiation and progression via activation of cognate EP receptors that belong to the superfamily of G protein-coupled receptors. Here we report that prostaglandin E(2) promotes renal cancer cell invasion through a signal transduction pathway that encompasses EP4 and small GTPase Rap. Inactivation of Rap signaling with Rap1GAP, like inhibition of EP4 signaling with ligand antagonist or knockdown with shRNA, reduces the kidney cancer cell invasion. Human kidney cells evidence increased EP4 and decreased Rap1GAP expression levels in the malignant compared with benign samples. These results support the idea that targeted inhibition of EP4 signaling and restoration of Rap1GAP expression constitute a new strategy to control kidney cancer progression.

  3. The two-component signal transduction system YvcPQ regulates the bacterial resistance to bacitracin in Bacillus thuringiensis.

    PubMed

    Zhang, Shumeng; Li, Xinfeng; Wang, Xun; Li, Zhou; He, Jin

    2016-10-01

    YvcPQ is one of the two-component signal transduction systems that respond to specific stimuli and enable cells to adjust multiple cellular functions. It consists of a histidine kinase YvcQ and a response regulator YvcP. In this study, through searching the consensus sequence recognized by YvcP, we found four YvcP-binding motifs in the promoter regions of genes yvcR (BMB171_C4100), BMB171_C4385, kapD (BMB171_C4525) and BMB171_C4835 in Bacillus thuringiensis BMB171 which is a representative of Bacillus cereus group, and confirmed that these genes are regulated by YvcP. We compared the sequence of yvcPQ and its downstream genes in genus Bacillus, and found two different kinds of yvc locus, one was the yvcPQ-RS in B. subtilis species and the other was the yvcPQ-R-S1S2 in B. cereus group. Furthermore, we found that YvcP activates the transcription of yvcS1S2 (downstream of yvcR) to promote bacterial resistance to bacitracin and deletion of either yvcPQ operon or yvcS1S2 operon renders the bacterial cells more sensitive to bacitracin. This study enriched our understanding of both the YvcPQ's function and the mechanism of bacterial resistance to bacitracin.

  4. Comparative transcriptional analysis of asexual and sexual morphs reveals possible mechanisms in reproductive polyphenism of the cotton aphid.

    PubMed

    Liu, Li-Jun; Zheng, Hong-Yuan; Jiang, Feng; Guo, Wei; Zhou, Shu-Tang

    2014-01-01

    Aphids, the destructive insect pests in the agriculture, horticulture and forestry, are capable of reproducing asexually and sexually upon environmental change. However, the molecular basis of aphid reproductive mode switch remains an enigma. Here we report a comparative analysis of differential gene expression profiling among parthenogenetic females, gynoparae and sexual females of the cotton aphid Aphis gossypii, using the RNA-seq approach with next-generation sequencing platforms, followed by RT-qPCR. At the cutoff criteria of fold change ≥2 and P<0.01, we identified 741 up- and 879 down-regulated genes in gynoparae versus parthenogenetic females, 2,101 up- and 2,210 down-regulated genes in sexual females compared to gynoparae, and 1,614 up- and 2,238 down-regulated genes in sexual females relative to parthenogenetic females. Gene ontology category and KEGG pathway analysis suggest the involvement of differentially expressed genes in multiple cellular signaling pathways into the reproductive mode transition, including phototransduction, cuticle composition, progesterone-mediated oocyte maturation and endocrine regulation. This study forms a basis for deciphering the molecular mechanisms underlying the shift from asexual to sexual reproduction in the cotton aphid. It also provides valuable resources for future studies on this host-alternating aphid species, and the insight into the understanding of reproductive mode plasticity in different aphid species.

  5. Comparative assessment of time-related bioactive glass and calcium hydroxide effects on mechanical properties of human root dentin.

    PubMed

    Marending, Monika; Stark, Wendelin J; Brunner, Tobias J; Fischer, Jens; Zehnder, Matthias

    2009-02-01

    Suspensions of micro- or nanoparticulate SiO(2)-Na(2)O-CaO-P(2)O(5) bioactive glasses could potentially be used as dressings in traumatized front teeth with open apices as an alternative to Ca(OH)(2). These materials have a disinfecting capacity similar to Ca(OH)(2), but bear the advantage of bioactivity. However, because bioactive glasses initially act as alkaline biocides just as Ca(OH)(2) does, they may also negatively affect mechanical dentin properties over time. This was assessed in the current study using standardized human root dentin bars. Specimens were immersed in 1:20 (wt vol(-1)) suspensions of nanometric bioactive glass 45S5 or calcium hydroxide for 1, 10, or 30 days. Control specimens were immersed in pure saline for 30 days (n = 20 per group). Subsequently, modulus of elasticity (E) and flexural strength (FS) of the specimens were determined. Results were compared between groups using one-way anova and Scheffé's post-hoc test. Ca(OH)(2) caused a significant (P < 0.001) 35% drop in mean flexural strength values compared to the control treatment after 10 days. No further change was observed between 10 days and 30 days. Bioactive glass caused a 20% drop in mean flexural strength as compared to the control after 10 days. However, this difference did not reach statistical significance (P > 0.05). No effects of either material on dentin modulus of elasticity values were observed. It was concluded that the calcium hydroxide suspension affected the dentin more than the bioactive glass counterpart; however, the effect was self-limiting and probably restricted to superficial dentin layers, as suggested by the mere decrease in flexural strength but not in modulus of elasticity values.

  6. Maxwell's demon in biochemical signal transduction with feedback loop

    NASA Astrophysics Data System (ADS)

    Ito, Sosuke; Sagawa, Takahiro

    2015-06-01

    Signal transduction in living cells is vital to maintain life itself, where information transfer in noisy environment plays a significant role. In a rather different context, the recent intensive research on `Maxwell's demon'--a feedback controller that utilizes information of individual molecules--have led to a unified theory of information and thermodynamics. Here we combine these two streams of research, and show that the second law of thermodynamics with information reveals the fundamental limit of the robustness of signal transduction against environmental fluctuations. Especially, we find that the degree of robustness is quantitatively characterized by an informational quantity called transfer entropy. Our information-thermodynamic approach is applicable to biological communication inside cells, in which there is no explicit channel coding in contrast to artificial communication. Our result could open up a novel biophysical approach to understand information processing in living systems on the basis of the fundamental information-thermodynamics link.

  7. Study of spatial signal transduction in bistable switches

    NASA Astrophysics Data System (ADS)

    Zhao, Qi; Yao, Cheng-Gui; Tang, Jun; Liu, Li-Wei

    2016-10-01

    Bistable switch modules are among the most important fundamental motifs in signal-transduction pathways. To better understand their spatial signal transduction, we model the diffusion process in the one-dimensional (1-D) domain. We find that when none of the elements diffuse, the response of the system exhibits a spatial switch-like property. However, when one of the elements is highly diffusible, the response of the system does not show any spatial switching behavior. Furthermore, we observe that the spatial responses of the system are more sensitive to the time constant of the switch when none of the elements are diffusible. Further, a slow loop keeps the system in the high steady state more positions than that in the fast loop. Finally, we consolidate our numerical results analytically by performing a mathematical method.

  8. Dynamic disorder and the energetic costs of information transduction

    SciTech Connect

    Thill, Peter

    2014-07-07

    We study a model of dynamic disorder relevant for signal transduction pathways in which enzymatic reaction rates fluctuate over several orders of magnitude. For the simple networks we consider, dynamic disorder drives the system far from equilibrium and imposes an energetic burden for high fidelity signaling capability. We study how the dynamics of the underlying stochastic behavior in the reaction rate process is related to the energetic cost of transmitting information through the network.

  9. Mucopolysaccharidosis IIIB confers enhanced neonatal intracranial transduction by AAV8 but not by 5, 9 or rh10

    PubMed Central

    Gilkes, J A; Bloom, M D; Heldermon, C D

    2016-01-01

    Sanfilippo syndrome type B (mucopolysaccharidosis IIIB, MPS IIIB) is a lysosomal storage disease resulting from deficiency of N-acetyl-glucosaminidase (NAGLU) activity. To determine the possible therapeutic utility of recombinant adeno-associated virus (rAAV) in early gene therapy-based interventions, we performed a comprehensive assessment of transduction and biodistribution profiles of four central nervous system (CNS) administered rAAV serotypes, -5, -8, -9 and -rh10. To simulate optimal earliest treatment of the disease, each rAAV serotype was injected into the CNS of neonatal MPS IIIB and control animals. We observed marked differences in biodistribution and transduction profiles between the serotypes and this differed in MPS IIIB compared with healthy control mice. Overall, in control mice, all serotypes performed comparably, although some differences were observed in certain focal areas. In MPS IIIB mice, AAV8 was more efficient than AAV5, -9 and -rh10 for gene delivery to most structures analyzed, including the cerebral cortex, hippocampus and thalamus. Noteworthy, the pattern of biodistribution within the CNS varied by serotype and genotype. In