Sample records for chemotaxis leukocyte

  1. Metallothionein mediates leukocyte chemotaxis

    Directory of Open Access Journals (Sweden)

    Lynes Michael A


    Full Text Available Abstract Background Metallothionein (MT is a cysteine-rich, metal-binding protein that can be induced by a variety of agents. Modulation of MT levels has also been shown to alter specific immune functions. We have noticed that the MT genes map close to the chemokines Ccl17 and Cx3cl1. Cysteine motifs that characterize these chemokines are also found in the MT sequence suggesting that MT might also act as a chemotactic factor. Results In the experiments reported here, we show that immune cells migrate chemotactically in the presence of a gradient of MT. This response can be specifically blocked by two different monoclonal anti-MT antibodies. Exposure of cells to MT also leads to a rapid increase in F-actin content. Incubation of Jurkat T cells with cholera toxin or pertussis toxin completely abrogates the chemotactic response to MT. Thus MT may act via G-protein coupled receptors and through the cyclic AMP signaling pathway to initiate chemotaxis. Conclusion These results suggest that, under inflammatory conditions, metallothionein in the extracellular environment may support the beneficial movement of leukocytes to the site of inflammation. MT may therefore represent a "danger signal"; modifying the character of the immune response when cells sense cellular stress. Elevated metallothionein produced in the context of exposure to environmental toxicants, or as a result of chronic inflammatory disease, may alter the normal chemotactic responses that regulate leukocyte trafficking. Thus, MT synthesis may represent an important factor in immunomodulation that is associated with autoimmune disease and toxicant exposure.

  2. Chemokines in the corpus luteum: Implications of leukocyte chemotaxis

    Directory of Open Access Journals (Sweden)

    Liptak Amy R


    Full Text Available Abstract Chemokines are small molecular weight peptides responsible for adhesion, activation, and recruitment of leukocytes into tissues. Leukocytes are thought to influence follicular atresia, ovulation, and luteal function. Many studies in recent years have focused attention on the characterization of leukocyte populations within the ovary, the importance of leukocyte-ovarian cell interactions, and more recently, the mechanisms of ovarian leukocyte recruitment. Information about the role of chemokines and leukocyte trafficking (chemotaxis during ovarian function is important to understanding paracrine-autocrine relationships shared between reproductive and immune systems. Recent advances regarding chemokine expression and leukocyte accumulation within the ovulatory follicle and the corpus luteum are the subject of this mini-review.

  3. Effect of p-cymene on chemotaxis, phagocytosis and leukocyte behaviors

    Directory of Open Access Journals (Sweden)

    Raquel Kummer


    Full Text Available Summary. In this study, we investigated the effects of p-cymene (CYM in vitro and in vivo on leukocyte activity. In the cell viability assay, CYM (3, 10, 30, 90 g/mL had low cytotoxicity. In vitro chemotaxis revealed that CYM (3, 10, 30, 60 g/mL promoted a significant reduction of neutrophil migration toward fMLP, but not toward LTB4 stimulation. In carrageenan-induced peritonitis, CYM (100, 200, 400 mg/kg decreased the infiltration of peritoneal exudate leukocytes and of polymorphonuclear leukocytes. CYM pretreatment resulted in a significant decrease in the number of rolling (100, 200 mg/kg and in the number of adherent leukocytes (100, 200, 400 mg/kg to the perivascular tissue. The macrophage phagocytic index was increased significantly in concentrations of CYM (3, 10, 30 µg/ml. Treatment with CYM (10, 90 µg/ml also reduced TNF- levels but did not alter IL-10 levels in fMLP-stimulated neutrophils. In conclusion, CYM may be considered as a potential agent for treatment inflammatory injury, however, further studies are necessary to elucidate the anti-inflammatory mechanism.Industrial relevance. The CYM is a secondary metabolite, belongs to the class of monoterpene and is found in essential oils from plants, food and in several spices. It is an important intermediate used in pharmaceutical, flavor and aroma industries and for the production of fungicides. The investigation of the anti-inflammatory activity of this compound may be useful to development of new drug anti-inflammatory, on a commercial scale.Keywords. p-cymene; chemotaxis; in vivo microcirculation; phagocytosis; anti-inflammatory.

  4. Chemotaxis of human and rat leukocytes by the delta-selective non-peptidic opioid SNC 80. (United States)

    Ordaz-Sánchez, Iván; Weber, Richard J; Rice, Kenner C; Zhang, Xiaoyan; Rodríguez-Padilla, C; Tamez-Guerra, R; Méndez-Vázquez, José L; Gómez-Flores, R


    Opioids like morphine, represent a major source of relief for most chronic moderate to severe nonmalignant pain. However, opioid abuse may lead to infections such as hepatitis and AIDS because opioids have been associated with suppressing various parameters of immune function including antimicrobial resistance, antibody production, monocyte-mediated phagocytosis, and both neutrophil and monocyte chemotaxis. We have previously reported immunopotentiating properties of non-peptidic opioid receptor selective agonists and antagonists. In this study, we evaluated the effects of the nonpeptidic delta-opioid receptor agonist (+)-4-((alpha R)-alpha-((2S, 5R)-4-allyl-2, 5-dimethyl-1-piperazinyl)-3-methoxybenzyl)-N, N-diethyl-benzamide (SNC 80) on chemotaxis of rat thymic and human peripheral blood mononuclear cells by using a modified Wilkinson chamber. Cell recruitment is an essential process in acute and chronic inflammatory responses. We observed that SNC 80 at concentrations of 10(-10), 10(-9), 10(-8), 10(-7), and 10(-6) M, significantly (p SNC 80 on chemotaxis of rat and human leukocytes were antagonized by naloxone, indicating that the modulation of chemotaxis by SNC 80 is via a classic opioid receptor. The development and use of non-peptidic opioids like SNC 80 could have an immediate impact not only as potent analgesics, but in immunoregulation.

  5. Pretreatment with Fish Oil-Based Lipid Emulsion Modulates Muscle Leukocyte Chemotaxis in Murine Model of Sublethal Lower Limb Ischemia (United States)

    Shih, Yao-Ming; Shih, Juey-Ming; Yeh, Chiu-Li; Li, Cheng-Che


    This study investigated the effects of a fish oil- (FO-) based lipid emulsion on muscle leukocyte chemotaxis and inflammatory responses in a murine model of limb ischemia-reperfusion (IR) injury. Mice were assigned randomly to 1 sham (sham) group, 2 ischemic groups, and 2 IR groups. The sham group did not undergo the ischemic procedure. The mice assigned to the ischemic or IR groups were pretreated intraperitoneally with either saline or FO-based lipid emulsion for 3 consecutive days. The IR procedure was induced by applying a 4.5 oz orthodontic rubber band to the left thigh above the greater trochanter for 120 min and then cutting the band to allow reperfusion. The ischemic groups were sacrificed immediately while the IR groups were sacrificed 24 h after reperfusion. Blood, IR-injured gastrocnemius, and lung tissues were collected for analysis. The results showed that FO pretreatment suppressed the local and systemic expression of several IR-induced proinflammatory mediators. Also, the FO-pretreated group had lower blood Ly6ChiCCR2hi monocyte percentage and muscle M1/M2 ratio than the saline group at 24 h after reperfusion. These findings suggest that FO pretreatment may have a protective role in limb IR injury by modulating the expression of proinflammatory mediators and regulating the polarization of macrophage. PMID:28182087

  6. "In vivo" leukocyte chemotaxis in experimental mice Schistosoma mansoni infection Quimiotaxia de leucócitos "in vivo" na infecção experimental por Schistosoma mansoni

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    Kirte Maria Teixeira


    Full Text Available The "in vivo" chemotaxis was studied in C57B1/10 mice 10, 30, 50 and 60 days after a Schistosoma mansoni infection in comparison to a control group (uninfected mice. Staphylococcal protein A was injected into a connective tissue air pouch of control and experimental mice and the leukocyte chemotaxis was counted. A decrease in polymorphonuclear (PMN leukocyte response was found in infected mice in comparison to the control group (pA quimiotaxia de leucócitos "in vivo" foi avaliada em camundongos da linhagem C57B1/10 e estudada 10, 30, 50 e 60 dias após a infecção por Schistosoma mansoni. A proteína A foi utilizada como quimiotático e injetada no tecido conjuntivo no dorso dos camundongos dos grupos experimentais e controle. Nos grupos experimentais foi observado uma diminuição na resposta dos leucócitos polimorfonucleares (PMN em comparação com o grupo controle (p<0.05. Os camundongos estudados 10 dias após a infecção, mostraram uma diminuição na resposta quimiotática de leucócitos PMN, comparando com o grupo controle (p<0.05 e este dado tornou-se mais evidente nos grupos experimentais estudados 30 e 50 dias após a infecção. Apesar da resposta quimiotática dos leucócitos PMN nos camundongos estudados 60 dias após a infecção aumentarem em comparação aos animais analisados 50 dias após a infecção, este aumento foi bem menor em relação ao grupo controle. A resposta quimiotática dos mononucleares não apresentou diferença significativa entre camundongos experimentais e controles

  7. Signaling mechanisms for regulation of chemotaxis

    Institute of Scientific and Technical Information of China (English)

    Dianqing WU


    Chemotaxis is a fascinating biological process, through which a cell migrates along a shallow chemoattractant gradient that is less than 5% difference between the anterior and posterior of the cell. Chemotaxis is composed of two independent,but interrelated processes-motility and directionality, both of which are regulated by extracellular stimuli, chemoattractants.In this mini-review, recent progresses in the understanding of the regulation of leukocyte chemotaxis by chemoattractant signaling are reviewed.

  8. Effects of Pneumolysin on Human Polymorphonuclear Leukocytes and Platelets


    Johnson, M K; Boese-Marrazzo, D; Pierce, W. A.


    Pneumolysin was bound by human polymorphonuclear leukocytes in a reaction which occurred very rapidly at 0 degrees C. Low concentrations of pneumolysin were found to stimulate leukocyte migration and lysosomal enzyme secretion. At increasing lysin levels, inhibition of spontaneous migration and chemotaxis, cell death, and lysis were observed. Pneumolysin was also found to lyse platelets and to activate serum to become chemotactic.

  9. Influência de extratos hidroetanólicos de plantas medicinais sobre a quimiotaxia de leucócitos humanos Influence of some medicinal plant hydroethanolic extracts on human leukocyte chemotaxis

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    M. M. Presibella


    leukocytes migration induced by casein, using the Boyden chamber method. Dexamethasone has been used as a positive control for leukocyte inhibition in the same experimental approach. The data herein presented showed a significant inhibition of the casein-induced polymorphonuclear leukocytes migration for all plants studied. However, the intensity of such activity was variable according to the dose and plant tested. For pau-pra-tudo, canela-de-veado, and cipó-suma extracts the average number of migrated polymorphonuclear leukocytes was 81.6±3.9%, 85.4±2.4% and 91.7±2.2% of the input for the doses of 1000, 10, and 1mg/ml, respectively, while for dexamethasone, the value found was 70.3±5.9%. Although further studies are needed, the results presented in this study may be useful to clarify the anti-inflammatory properties of these herbal medicines, supporting their ethnobothanical use for the treatment of inflammatory diseases.

  10. Fractional Chemotaxis Diffusion Equations

    CERN Document Server

    Langlands, T A M


    We introduce mesoscopic and macroscopic model equations of chemotaxis with anomalous subdiffusion for modelling chemically directed transport of biological organisms in changing chemical environments with diffusion hindered by traps or macro-molecular crowding. The mesoscopic models are formulated using Continuous Time Random Walk master equations and the macroscopic models are formulated with fractional order differential equations. Different models are proposed depending on the timing of the chemotactic forcing. Generalizations of the models to include linear reaction dynamics are also derived. Finally a Monte Carlo method for simulating anomalous subdiffusion with chemotaxis is introduced and simulation results are compared with numerical solutions of the model equations. The model equations developed here could be used to replace Keller-Segel type equations in biological systems with transport hindered by traps, macro-molecular crowding or other obstacles.

  11. Modeling leukocyte-leukocyte non-contact interactions in a lymph node.

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    Nicola Gritti

    Full Text Available The interaction among leukocytes is at the basis of the innate and adaptive immune-response and it is largely ascribed to direct cell-cell contacts. However, the exchange of a number of chemical stimuli (chemokines allows also non-contact interaction during the immunological response. We want here to evaluate the extent of the effect of the non-contact interactions on the observed leukocyte-leukocyte kinematics and their interaction duration. To this aim we adopt a simplified mean field description inspired by the Keller-Segel chemotaxis model, of which we report an analytical solution suited for slowly varying sources of chemokines. Since our focus is on the non-contact interactions, leukocyte-leukocyte contact interactions are simulated only by means of a space dependent friction coefficient of the cells. The analytical solution of the Keller-Segel model is then taken as the basis of numerical simulations of interactions between leukocytes and their duration. The mean field interaction force that we derive has a time-space separable form and depends on the chemotaxis sensitivity parameter as well as on the chemokines diffusion coefficient and their degradation rate. All these parameters affect the distribution of the interaction durations. We draw a successful qualitative comparison between simulated data and sets of experimental data for DC-NK cells interaction duration and other kinematic parameters. Remarkably, the predicted percentage of the leukocyte-leukocyte interactions falls in the experimental range and depends (~25% increase upon the chemotactic parameter indicating a non-negligible direct effect of the non-contact interaction on the leukocyte interactions.

  12. Tracking neutrophil intraluminal crawling, transendothelial migration and chemotaxis in tissue by intravital video microscopy. (United States)

    Xu, Najia; Lei, Xi; Liu, Lixin


    The recruitment of circulating leukocytes from blood stream to the inflamed tissue is a crucial and complex process of inflammation(1,2). In the postcapillary venules of inflamed tissue, leukocytes initially tether and roll on the luminal surface of venular wall. Rolling leukocytes arrest on endothelium and undergo firm adhesion in response to chemokine or other chemoattractants on the venular surface. Many adherent leukocytes relocate from the initial site of adhesion to the junctional extravasation site in endothelium, a process termed intraluminal crawling(3). Following crawling, leukocytes move across endothelium (transmigration) and migrate in extravascular tissue toward the source of chemoattractant (chemotaxis)(4). Intravital microscopy is a powerful tool for visualizing leukocyte-endothelial cell interactions in vivo and revealing cellular and molecular mechanisms of leukocyte recruitment(2,5). In this report, we provide a comprehensive description of using brightfield intravital microscopy to visualize and determine the detailed processes of neutrophil recruitment in mouse cremaster muscle in response to the gradient of a neutrophil chemoattractant. To induce neutrophil recruitment, a small piece of agarose gel (~1-mm(3) size) containing neutrophil chemoattractant MIP-2 (CXCL2, a CXC chemokine) or WKYMVm (Trp-Lys-Tyr-Val-D-Met, a synthetic analog of bacterial peptide) is placed on the muscle tissue adjacent to the observed postcapillary venule. With time-lapsed video photography and computer software ImageJ, neutrophil intraluminal crawling on endothelium, neutrophil transendothelial migration and the migration and chemotaxis in tissue are visualized and tracked. This protocol allows reliable and quantitative analysis of many neutrophil recruitment parameters such as intraluminal crawling velocity, transmigration time, detachment time, migration velocity, chemotaxis velocity and chemotaxis index in tissue. We demonstrate that using this protocol, these


    KAUST Repository



    We consider a model system for the collective behavior of oxygen-driven swimming bacteria in an aquatic fluid. In certain parameter regimes, such suspensions of bacteria feature large-scale convection patterns as a result of the hydrodynamic interaction between bacteria. The presented model consist of a parabolicparabolic chemotaxis system for the oxygen concentration and the bacteria density coupled to an incompressible Stokes equation for the fluid driven by a gravitational force of the heavier bacteria. We show local existence of weak solutions in a bounded domain in d, d = 2, 3 with no-flux boundary condition and in 2 in the case of inhomogeneous Dirichlet conditions for the oxygen. © 2010 World Scientific Publishing Company.

  14. Dictyostelium Chemotaxis studied with fluorescence fluctuation spectroscopy

    NARCIS (Netherlands)

    Ruchira, A.


    The movement of cells in the direction of a chemical gradient, also known as chemotaxis, is a vital biological process. During chemotaxis, minute extracellular signals are translated into complex cellular responses such as change in morphology and motility. To understand the chemotaxis mechanism at

  15. Engineering Hybrid Chemotaxis Receptors in Bacteria. (United States)

    Bi, Shuangyu; Pollard, Abiola M; Yang, Yiling; Jin, Fan; Sourjik, Victor


    Most bacteria use transmembrane sensors to detect a wide range of environmental stimuli. A large class of such sensors are the chemotaxis receptors used by motile bacteria to follow environmental chemical gradients. In Escherichia coli, chemotaxis receptors are known to mediate highly sensitive responses to ligands, making them potentially useful for biosensory applications. However, with only four ligand-binding chemotaxis receptors, the natural ligand spectrum of E. coli is limited. The design of novel chemoreceptors to extend the sensing capabilities of E. coli is therefore a critical aspect of chemotaxis-based biosensor development. One path for novel sensor design is to harvest the large natural diversity of chemosensory functions found in bacteria by creating hybrids that have the signaling domain from E. coli chemotaxis receptors and sensory domains from other species. In this work, we demonstrate that the E. coli receptor Tar can be successfully combined with most typical sensory domains found in chemotaxis receptors and in evolutionary-related two-component histidine kinases. We show that such functional hybrids can be generated using several different fusion points. Our work further illustrates how hybrid receptors could be used to quantitatively characterize ligand specificity of chemotaxis receptors and histidine kinases using standardized assays in E. coli.

  16. Strenuous physical exercise adversely affects monocyte chemotaxis

    DEFF Research Database (Denmark)

    Czepluch, Frauke S; Barres, Romain; Caidahl, Kenneth


    Physical exercise is important for proper cardiovascular function and disease prevention, but it may influence the immune system. We evaluated the effect of strenuous exercise on monocyte chemotaxis. Monocytes were isolated from blood of 13 young, healthy, sedentary individuals participating...... in a three-week training program which consisted of repeated exercise bouts. Monocyte chemotaxis and serological biomarkers were investigated at baseline, after three weeks training and after four weeks recovery. Chemotaxis towards vascular endothelial growth factor-A (VEGF-A) and transforming growth factor...

  17. Slit2 regulates attractive eosinophil and repulsive neutrophil chemotaxis through differential srGAP1 expression during lung inflammation. (United States)

    Ye, Bu-Qing; Geng, Zhen H; Ma, Li; Geng, Jian-Guo


    Directional migration of leukocytes is an essential step in leukocyte trafficking during inflammatory responses. However, the molecular mechanisms governing directional chemotaxis of leukocytes remain poorly understood. The Slit family of guidance cues has been implicated for inhibition of leuocyte migration. We report that Clara cells in the bronchial epithelium secreted Slit2, whereas eosinophils and neutrophils expressed its cell-surface receptor, Robo1. Compared to neutrophils, eosinophils exhibited a significantly lower level of Slit-Robo GTPase-activating protein 1 (srGAP1), leading to activation of Cdc42, recruitment of PI3K to Robo1, enhancment of eotaxin-induced eosinophil chemotaxis, and exaggeration of allergic airway inflammation. Notably, OVA sensitization elicited a Slit2 gradient at so-called bronchus-alveoli axis, with a higher level of Slit2 in the bronchial epithelium and a lower level in the alveolar tissue. Aerosol administration of rSlit2 accelerated eosinophil infiltration, whereas i.v. administered Slit2 reduced eosinophil deposition. In contrast, Slit2 inactivated Cdc42 and suppressed stromal cell-derived factor-1α-induced chemotaxis of neutrophils for inhibiting endotoxin-induced lung inflammation, which were reversed by blockade of srGAP1 binding to Robo1. These results indicate that the newly identified Slit2 gradient at the bronchus-alveoli axis induces attractive PI3K signaling in eosinophils and repulsive srGAP1 signaling in neutrophils through differential srGAP1 expression during lung inflammation.

  18. Leukocyte Activation and Circulating Leukocyte-Derived Microparticles in Preeclampsia

    NARCIS (Netherlands)

    Lok, Christianne A. R.; Jebbink, Jiska; Nieuwland, Rienk; Faas, Marijke M.; Boer, Kees; Sturk, Augueste; Van Der Post, Joris A. M.


    Preeclampsia shows characteristics of an inflammatory disease including leukocyte activation. Analyses of leukocyte-derived microparticles (MP) and mRNA expression of inflammation-related genes in leukocytes may establish which subgroups of leukocytes contribute to the development of preeclampsia. B

  19. Strain-specific chemotaxis of Azospirillum spp.


    Reinhold, B; Hurek, T; Fendrik, I


    Chemotactic responses of three Azospirillum strains originating from different host plants were compared to examine the possible role of chemotaxis in the adaptation of these bacteria to their respective hosts. The chemotaxis to several sugars, amino acids, and organic acids was determined qualitatively by an agar plate assay and quantitatively by a channeled-chamber technique. High chemotactic ratios, up to 40, were obtained with the latter technique. The chemotactic response did not rely up...

  20. Leukocytes in capillary flow. (United States)

    Schmid-Schönbein, G W; Lee, J


    During disease, the flow of blood cells through the capillary network is one of the most perilous events in the microcirculation. Capillary distensibility, cytoplasmic activity of endothelial cells, red cells and leukocytes play an important role in capillary perfusion. Occlusion of capillaries is one of the early signs of vascular failure and is encountered in many different conditions and organs. Adhesion of leukocytes to the endothelium via expression of membrane adhesion molecules leads to microvascular entrapment with capillary occlusion.

  1. Chemotaxis when bacteria remember: drift versus diffusion.

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    Sakuntala Chatterjee


    Full Text Available Escherichia coli (E. coli bacteria govern their trajectories by switching between running and tumbling modes as a function of the nutrient concentration they experienced in the past. At short time one observes a drift of the bacterial population, while at long time one observes accumulation in high-nutrient regions. Recent work has viewed chemotaxis as a compromise between drift toward favorable regions and accumulation in favorable regions. A number of earlier studies assume that a bacterium resets its memory at tumbles - a fact not borne out by experiment - and make use of approximate coarse-grained descriptions. Here, we revisit the problem of chemotaxis without resorting to any memory resets. We find that when bacteria respond to the environment in a non-adaptive manner, chemotaxis is generally dominated by diffusion, whereas when bacteria respond in an adaptive manner, chemotaxis is dominated by a bias in the motion. In the adaptive case, favorable drift occurs together with favorable accumulation. We derive our results from detailed simulations and a variety of analytical arguments. In particular, we introduce a new coarse-grained description of chemotaxis as biased diffusion, and we discuss the way it departs from older coarse-grained descriptions.

  2. Slit-2/Robo-1 modulates the CXCL12/CXCR4-induced chemotaxis of T cells. (United States)

    Prasad, Anil; Qamri, Zahida; Wu, Jane; Ganju, Ramesh K


    Slit, which mediates its function by binding to the Roundabout (Robo) receptor, has been shown to regulate neuronal, dendritic, and leukocyte migration. However, the molecular mechanism by which the Slit/Robo complex inhibits the migration of cells is not well defined. Here, we showed that Slit-2 can inhibit the CXCL12-induced chemotaxis and transendothelial migration of T cells and monocytes. We observed that CXCR4 associates with Robo-1 and that Slit-2 treatment enhances this association with the Robo-1 receptor. Robo-1 is a single-pass transmembrane receptor whose intracellular region contains four conserved motifs designated as CC0, CC1, CC2, and CC3. Structural and functional analyses of Robo receptors revealed that interaction of the CC3 motif with the CXCR4 receptor may regulate the CXCL12-induced chemotaxis of T cells. We further characterized Slit-2-mediated inhibition of the CXCL12/CXCR4 chemotactic pathway and found that Slit-2 can block the CXCL12-induced activation of the Src and Lck kinases but not Lyn kinase. Although Slit-2 did not inhibit the CXCL12-induced activation of MAPKs, it did inhibit the Akt phosphorylation and Rac activation induced by this chemokine. Altogether, our studies indicate a novel mechanism by which the Slit/Robo complex may inhibit the CXCR4/CXCL12-mediated chemotaxis of T cells.

  3. Fundamental constraints on the abundances of chemotaxis proteins

    CERN Document Server

    Bitbol, Anne-Florence


    Flagellated bacteria, such as Escherichia coli, perform directed motion in gradients of concentration of attractants and repellents in a process called chemotaxis. The E. coli chemotaxis signaling pathway is a model for signal transduction, but it has unique features. We demonstrate that the need for fast signaling necessitates high abundances of the proteins involved in this pathway. We show that further constraints on the abundances of chemotaxis proteins arise from the requirements of self-assembly, both of flagellar motors and of chemoreceptor arrays. All these constraints are specific to chemotaxis, and published data confirm that chemotaxis proteins tend to be more highly expressed than their homologs in other pathways. Employing a chemotaxis pathway model, we show that the gain of the pathway at the level of the response regulator CheY increases with overall chemotaxis protein abundances. This may explain why, at least in one E. coli strain, the abundance of all chemotaxis proteins is higher in media w...

  4. Independent control of locomotion and orientation during Dictyostelium discoideum chemotaxis

    NARCIS (Netherlands)

    Duijn, Bert van; Haastert, Peter J.M. van


    Chemotaxis is cell movement in the direction of a chemical and is composed of two components: movement and directionality. The directionality of eukaryotic chemotaxis is probably derived from orientation: the detection of the spacial gradient of chemoattractant over the cell length. Chemotaxis was i

  5. Travelling Waves in Hybrid Chemotaxis Models

    KAUST Repository

    Franz, Benjamin


    Hybrid models of chemotaxis combine agent-based models of cells with partial differential equation models of extracellular chemical signals. In this paper, travelling wave properties of hybrid models of bacterial chemotaxis are investigated. Bacteria are modelled using an agent-based (individual-based) approach with internal dynamics describing signal transduction. In addition to the chemotactic behaviour of the bacteria, the individual-based model also includes cell proliferation and death. Cells consume the extracellular nutrient field (chemoattractant), which is modelled using a partial differential equation. Mesoscopic and macroscopic equations representing the behaviour of the hybrid model are derived and the existence of travelling wave solutions for these models is established. It is shown that cell proliferation is necessary for the existence of non-transient (stationary) travelling waves in hybrid models. Additionally, a numerical comparison between the wave speeds of the continuum models and the hybrid models shows good agreement in the case of weak chemotaxis and qualitative agreement for the strong chemotaxis case. In the case of slow cell adaptation, we detect oscillating behaviour of the wave, which cannot be explained by mean-field approximations. © 2013 Society for Mathematical Biology.

  6. Biomixing by chemotaxis and enhancement of biological reactions

    CERN Document Server

    Kiselev, Alexander


    Many processes in biology involve both reactions and chemotaxis. However, to the best of our knowledge, the question of interaction between chemotaxis and reactions has not yet been addressed either analytically or numerically. We consider a model with a single density function involving diffusion, advection, chemotaxis, and absorbing reaction. The model is motivated, in particular, by studies of coral broadcast spawning, where experimental observations of the efficiency of fertilization rates significantly exceed the data obtained from numerical models that do not take chemotaxis (attraction of sperm gametes by a chemical secreted by egg gametes) into account. We prove that in the framework of our model, chemotaxis plays a crucial role. There is a rigid limit to how much the fertilization efficiency can be enhanced if there is no chemotaxis but only advection and diffusion. On the other hand, when chemotaxis is present, the fertilization rate can be arbitrarily close to being complete provided that the chemo...

  7. Chemotaxis: new role for Ras revealed

    Institute of Scientific and Technical Information of China (English)

    Jianshe Yan; Dale Hereld; Tian Jin


    @@ A recent study of chemotaxis revealed a new role for the proto-oncogene Ras in the social ameba Dictyostelium discoideum.Chemotaxis,the directional movement of cells toward chemokines and other chemoattractants,plays critical roles in diverse physiological processes,such as mobilization of immune cells to fight invading microorganisms,targeting of metastatic cancer cells to specific tissues,and guidance of sperm cells to ova during fertilization.This work,published in the July 26 issue of The Journal of Cell Biology,was conducted in Dr.Devreotes' lab at John Hopkins University and Dr.Parent's lab at National Cancer Institute.This research team demonstrated that RasC functions as an upstream regulator of TORC2 and thereby governs the effects of TORC2-PKB signaling on the cytoskeleton and cell migration.

  8. Travelling waves in hybrid chemotaxis models

    CERN Document Server

    Franz, Benjamin; Painter, Kevin J; Erban, Radek


    Hybrid models of chemotaxis combine agent-based models of cells with partial differential equation models of extracellular chemical signals. In this paper, travelling wave properties of hybrid models of bacterial chemotaxis are investigated. Bacteria are modelled using an agent-based (individual-based) approach with internal dynamics describing signal transduction. In addition to the chemotactic behaviour of the bacteria, the individual-based model also includes cell proliferation and death. Cells consume the extracellular nutrient field (chemoattractant) which is modelled using a partial differential equation. Mesoscopic and macroscopic equations representing the behaviour of the hybrid model are derived and the existence of travelling wave solutions for these models is established. It is shown that cell proliferation is necessary for the existence of non-transient (stationary) travelling waves in hybrid models. Additionally, a numerical comparison between the wave speeds of the continuum models and the hybr...

  9. Chemotaxis of crawling and swimming Caenorhabditis Elegans (United States)

    Patel, Amar; Bilbao, Alejandro; Padmanabhan, Venkat; Khan, Zeina; Armstrong, Andrew; Rumbaugh, Kendra; Vanapalli, Siva; Blawzdziewicz, Jerzy


    A soil-dwelling nematode Caenorhabditis Elegans efficiently navigates through complex environments, responding to chemical signals to find food or avoid danger. According to previous studies, the nematode uses both gradual-turn and run-and-tumble strategies to move in the direction of the increasing concentration of chemical attractants. We show that both these chemotaxis strategies can be described using our kinematic model [PLoS ONE, 7: e40121 (2012)] in which harmonic-curvature modes represent elementary nematode movements. In our chemotaxis model, the statistics of mode changes is governed by the time history of the chemoattractant concentration at the position of the nematode head. We present results for both nematodes crawling without transverse slip and for swimming nematodes. This work was supported by NSF grant No. CBET 1059745.

  10. μ-Slide Chemotaxis: A new chamber for long-term chemotaxis studies

    Directory of Open Access Journals (Sweden)

    Zantl Roman


    Full Text Available Abstract Background Effective tools for measurement of chemotaxis are desirable since cell migration towards given stimuli plays a crucial role in tumour metastasis, angiogenesis, inflammation, and wound healing. As for now, the Boyden chamber assay is the longstanding "gold-standard" for in vitro chemotaxis measurements. However, support for live cell microscopy is weak, concentration gradients are rather steep and poorly defined, and chemotaxis cannot be distinguished from migration in a single experiment. Results Here, we describe a novel all-in-one chamber system for long-term analysis of chemotaxis in vitro that improves upon many of the shortcomings of the Boyden chamber assay. This chemotaxis chamber was developed to provide high quality microscopy, linear concentration gradients, support for long-term assays, and observation of slowly migrating cells via video microscopy. AlexaFluor 488 dye was used to demonstrate the establishment, shape and time development of linear chemical gradients. Human fibrosarcoma cell line HT1080 and freshly isolated human umbilical vein endothelial cells (HUVEC were used to assess chemotaxis towards 10% fetal calf serum (FCS and FaDu cells' supernatant. Time-lapse video microscopy was conducted for 48 hours, and cell tracking and analysis was performed using ImageJ plugins. The results disclosed a linear steady-state gradient that was reached after approximately 8 hours and remained stable for at least 48 hours. Both cell types were chemotactically active and cell movement as well as cell-to-cell interaction was assessable. Conclusions Compared to the Boyden chamber assay, this innovative system allows for the generation of a stable gradient for a much longer time period as well as for the tracking of cell locomotion along this gradient and over long distances. Finally, random migration can be distinguished from primed and directed migration along chemotactic gradients in the same experiment, a feature, which

  11. Highlighting the role of Ras and Rap during Dictyostelium chemotaxis

    NARCIS (Netherlands)

    Kortholt, Arjan; van Haastert, Peter J. M.


    Chemotaxis, the directional movement towards a chemical compound, is an essential property of many cells and has been linked to the development and progression of many diseases. Eukaryotic chemotaxis is a complex process involving gradient sensing, cell polarity, remodelling of the cytoskeleton and

  12. Chemotaxis signaling systems in model beneficial plant-bacteria associations. (United States)

    Scharf, Birgit E; Hynes, Michael F; Alexandre, Gladys M


    Beneficial plant-microbe associations play critical roles in plant health. Bacterial chemotaxis provides a competitive advantage to motile flagellated bacteria in colonization of plant root surfaces, which is a prerequisite for the establishment of beneficial associations. Chemotaxis signaling enables motile soil bacteria to sense and respond to gradients of chemical compounds released by plant roots. This process allows bacteria to actively swim towards plant roots and is thus critical for competitive root surface colonization. The complete genome sequences of several plant-associated bacterial species indicate the presence of multiple chemotaxis systems and a large number of chemoreceptors. Further, most soil bacteria are motile and capable of chemotaxis, and chemotaxis-encoding genes are enriched in the bacteria found in the rhizosphere compared to the bulk soil. This review compares the architecture and diversity of chemotaxis signaling systems in model beneficial plant-associated bacteria and discusses their relevance to the rhizosphere lifestyle. While it is unclear how controlling chemotaxis via multiple parallel chemotaxis systems provides a competitive advantage to certain bacterial species, the presence of a larger number of chemoreceptors is likely to contribute to the ability of motile bacteria to survive in the soil and to compete for root surface colonization.

  13. Recent developments in microfluidics-based chemotaxis studies. (United States)

    Wu, Jiandong; Wu, Xun; Lin, Francis


    Microfluidic devices can better control cellular microenvironments compared to conventional cell migration assays. Over the past few years, microfluidics-based chemotaxis studies showed a rapid growth. New strategies were developed to explore cell migration in manipulated chemical gradients. In addition to expanding the use of microfluidic devices for a broader range of cell types, microfluidic devices were used to study cell migration and chemotaxis in complex environments. Furthermore, high-throughput microfluidic chemotaxis devices and integrated microfluidic chemotaxis systems were developed for medical and commercial applications. In this article, we review recent developments in microfluidics-based chemotaxis studies and discuss the new trends in this field observed over the past few years.

  14. Glucocorticoids Suppress CCR9-Mediated Chemotaxis, Calcium Flux, and Adhesion to MAdCAM-1 in Human T Cells. (United States)

    Wendt, Emily; White, Gemma E; Ferry, Helen; Huhn, Michael; Greaves, David R; Keshav, Satish


    CCR9 expressed on T lymphocytes mediates migration to the small intestine in response to a gradient of CCL25. CCL25-stimulated activation of α4β7 integrin promotes cell adherence to mucosal addressin cell adhesion molecule-1 (MAdCAM-1) expressed by vascular endothelial cells of the intestine, further mediating gut-specific homing. Inflammatory bowel disease is a chronic inflammatory condition that primarily affects the gastrointestinal tract and is characterized by leukocyte infiltration. Glucocorticoids (GCs) are widely used to treat inflammatory bowel disease but their effect on intestinal leukocyte homing is not well understood. We investigated the effect of GCs on the gut-specific chemokine receptor pair, CCR9 and CCL25. Using human peripheral blood-derived T lymphocytes enriched for CCR9 by cell sorting or culturing with all-trans retinoic acid, we measured chemotaxis, intracellular calcium flux, and α4β7-mediated cell adhesion to plate-bound MAdCAM-1. Dexamethasone (DEX), a specific GC receptor agonist, significantly reduced CCR9-mediated chemotaxis and adhesion to MAdCAM-1 without affecting CCR9 surface expression. In contrast, in the same cells, DEX increased CXCR4 surface expression and CXCL12-mediated signaling and downstream functions. The effects of DEX on human primary T cells were reversed by the GC receptor antagonist mifepristone. These results demonstrate that GCs suppress CCR9-mediated chemotaxis, intracellular calcium flux, and α4β7-mediated cell adhesion in vitro, and these effects could contribute to the efficacy of GCs in treating intestinal inflammation in vivo.

  15. A stochastic description of Dictyostelium chemotaxis.

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    Gabriel Amselem

    Full Text Available Chemotaxis, the directed motion of a cell toward a chemical source, plays a key role in many essential biological processes. Here, we derive a statistical model that quantitatively describes the chemotactic motion of eukaryotic cells in a chemical gradient. Our model is based on observations of the chemotactic motion of the social ameba Dictyostelium discoideum, a model organism for eukaryotic chemotaxis. A large number of cell trajectories in stationary, linear chemoattractant gradients is measured, using microfluidic tools in combination with automated cell tracking. We describe the directional motion as the interplay between deterministic and stochastic contributions based on a Langevin equation. The functional form of this equation is directly extracted from experimental data by angle-resolved conditional averages. It contains quadratic deterministic damping and multiplicative noise. In the presence of an external gradient, the deterministic part shows a clear angular dependence that takes the form of a force pointing in gradient direction. With increasing gradient steepness, this force passes through a maximum that coincides with maxima in both speed and directionality of the cells. The stochastic part, on the other hand, does not depend on the orientation of the directional cue and remains independent of the gradient magnitude. Numerical simulations of our probabilistic model yield quantitative agreement with the experimental distribution functions. Thus our model captures well the dynamics of chemotactic cells and can serve to quantify differences and similarities of different chemotactic eukaryotes. Finally, on the basis of our model, we can characterize the heterogeneity within a population of chemotactic cells.

  16. A Model of Drosophila Larva Chemotaxis. (United States)

    Davies, Alex; Louis, Matthieu; Webb, Barbara


    Detailed observations of larval Drosophila chemotaxis have characterised the relationship between the odour gradient and the runs, head casts and turns made by the animal. We use a computational model to test whether hypothesised sensorimotor control mechanisms are sufficient to account for larval behaviour. The model combines three mechanisms based on simple transformations of the recent history of odour intensity at the head location. The first is an increased probability of terminating runs in response to gradually decreasing concentration, the second an increased probability of terminating head casts in response to rapidly increasing concentration, and the third a biasing of run directions up concentration gradients through modulation of small head casts. We show that this model can be tuned to produce behavioural statistics comparable to those reported for the larva, and that this tuning results in similar chemotaxis performance to the larva. We demonstrate that each mechanism can enable odour approach but the combination of mechanisms is most effective, and investigate how these low-level control mechanisms relate to behavioural measures such as the preference indices used to investigate larval learning behaviour in group assays.

  17. Modeling Transverse Chemotaxis in Porous Media (United States)

    Porter, M. L.; Valdés-Parada, F. J.; Wood, B. D.


    The movement of microorganisms toward a chemical attractant (chemotaxis) has been shown to aid in subsurface contaminant degradation and enhanced oil recovery. However, chemotaxis is inherently a pore scale process that must be upscaled to arrive at continuum scale models for field applications. In this work, the method of volume averaging is used to upscale the microscale chemotactic microbial transport equations in order to obtain the corresponding macroscale models for the mass balance of bacteria and the chemical attractant to which they respond. As a first approach, cellular growth/death and consumption of the attractant by chemical reaction are assumed to be negligible with respect to convective and diffusive transport mechanisms. Two effective medium coefficients are introduced in the model, namely a total motility tensor and a total velocity vector. Under certain conditions, it is shown that the coefficients can differ considerably from the values corresponding to non-chemotactic transport. The model is validated by comparing the predicted transverse motility coefficients and concentration profiles to those measured within an engineered porous medium. For the concentration profiles, we introduced a lag that accounts for the difference between the arrival time of the microorganisms and the their chemotactic response to the attractant.

  18. A Model of Drosophila Larva Chemotaxis.

    Directory of Open Access Journals (Sweden)

    Alex Davies


    Full Text Available Detailed observations of larval Drosophila chemotaxis have characterised the relationship between the odour gradient and the runs, head casts and turns made by the animal. We use a computational model to test whether hypothesised sensorimotor control mechanisms are sufficient to account for larval behaviour. The model combines three mechanisms based on simple transformations of the recent history of odour intensity at the head location. The first is an increased probability of terminating runs in response to gradually decreasing concentration, the second an increased probability of terminating head casts in response to rapidly increasing concentration, and the third a biasing of run directions up concentration gradients through modulation of small head casts. We show that this model can be tuned to produce behavioural statistics comparable to those reported for the larva, and that this tuning results in similar chemotaxis performance to the larva. We demonstrate that each mechanism can enable odour approach but the combination of mechanisms is most effective, and investigate how these low-level control mechanisms relate to behavioural measures such as the preference indices used to investigate larval learning behaviour in group assays.

  19. Pharmacological inhibition of p38 mitogen-activated protein kinases affects KC/CXCL1-induced intraluminal crawling, transendothelial migration, and chemotaxis of neutrophils in vivo. (United States)

    Xu, Najia; Hossain, Mokarram; Liu, Lixin


    p38 mitogen-activated protein kinase (MAPK) signalling is critical in the pathophysiology of a variety of inflammatory processes. Leukocyte recruitment to the site of inflammation is a multistep process governed by specific signalling cascades. After adhesion in the lumen, many leukocytes crawl to optimal sites at endothelial junctions and transmigrate to extravascular tissue in a Mac-1-dependent manner. The signalling mechanisms that regulate postadhesion steps of intraluminal crawling, transmigration, and chemotaxis in tissue remain incompletely understood. The present study explored the effect of p38 MAPK inhibitor SB203580 on various parameters of neutrophil recruitment triggered by chemokine KC (CXCL1) gradient. Neutrophil-endothelial interactions in microvasculature of murine cremaster muscle were determined using intravital microscopy and time-lapsed video analysis. SB203580 (100 nM) did not change leukocyte rolling but significantly attenuated neutrophil adhesion, emigration, and transmigration and impaired the initiation of neutrophil crawling and transmigration. In response to KC chemotactic gradient, SB203580 significantly reduced the velocity of migration and chemotaxis index of neutrophils in tissue. The upregulation of Mac-1 expression in neutrophils stimulated by KC was significantly blunted by SB203580 in vitro. Collectively, our findings demonstrate that pharmacological suppression of p38 MAPK significantly impairs multiple steps of neutrophil recruitment in vivo.

  20. A coupled chemotaxis-fluid model: Global existence

    KAUST Repository

    Liu, Jian-Guo


    We consider a model arising from biology, consisting of chemotaxis equations coupled to viscous incompressible fluid equations through transport and external forcing. Global existence of solutions to the Cauchy problem is investigated under certain conditions. Precisely, for the chemotaxis-Navier- Stokes system in two space dimensions, we obtain global existence for large data. In three space dimensions, we prove global existence of weak solutions for the chemotaxis-Stokes system with nonlinear diffusion for the cell density.© 2011 Elsevier Masson SAS. All rights reserved.

  1. A Sensitive Chemotaxis Assay Using a Novel Microfluidic Device

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    Chen Zhang


    Full Text Available Existing chemotaxis assays do not generate stable chemotactic gradients and thus—over time—functionally measure only nonspecific random motion (chemokinesis. In comparison, microfluidic technology has the capacity to generate a tightly controlled microenvironment that can be stably maintained for extended periods of time and is, therefore, amenable to adaptation for assaying chemotaxis. We describe here a novel microfluidic device for sensitive assay of cellular migration and show its application for evaluating the chemotaxis of smooth muscle cells in a chemokine gradient.

  2. Chemotaxis to Excitable Waves in Dictyostelium Discoideum (United States)

    Bhowmik, Arpan; Rappel, Wouter-Jan; Levine, Herbert

    In recent years, there have been significant advances in our understanding of the mechanisms underlying chemically directed motility by eukaryotic cells such as Dictyostelium. In particular, the LEGI model has proven capable of providing a framework for quantitatively explaining many experiments that present Dictyostelium cells with tailored chemical stimuli and monitor their subsequent polarization. Here, we couple the LEGI approach to an excitable medium model of the cAMP wave-field that is self-generated by the cells and investigate the extent to which this class of models enables accurate chemotaxis to the cAMP waveforms expected in vivo. Our results indicate that the ultra-sensitive version of the model does an excellent job in providing natural wave rectification, thereby providing a compelling solution to the ``back-of-the-wave paradox'' during cellular aggregation. This work was supported by National Institutes of Health Grant P01 GM078586.

  3. Three-dimensional chemotaxis model for a crawling neutrophil. (United States)

    Song, Jihwan; Kim, Dongchoul


    Chemotactic cell migration is a fundamental phenomenon in complex biological processes. A rigorous understanding of the chemotactic mechanism of crawling cells has important implications for various medical and biological applications. In this paper, we propose a three-dimensional model of a single crawling cell to study its chemotaxis. A single-cell study of chemotaxis has an advantage over studies of a population of cells in that it provides a clearer observation of cell migration, which leads to more accurate assessments of chemotaxis. The model incorporates the surface energy of the cell and the interfacial interaction between the cell and substrate. The semi-implicit Fourier spectral method is applied to achieve high efficiency and numerical stability. The simulation results provide the kinetic and morphological traits of a crawling cell during chemotaxis.

  4. Dispatch. Dictyostelium chemotaxis: fascism through the back door? (United States)

    Insall, Robert


    Aggregating Dictyostelium cells secrete cyclic AMP to attract their neighbours by chemotaxis. It has now been shown that adenylyl cyclase is enriched in the rear of cells, and this localisation is required for normal aggregation.


    Institute of Scientific and Technical Information of China (English)

    Chen Hua; Wu Shaohua


    We prove the local existence and uniqueness of week solution of the hyperbolic-parabolic Chemotaxis system with some nonlinear product terms. For one dimensional case, we prove also the global existence and uniqueness of the solution for the problem.

  6. Different Modulating Effects of Adenosine on Neonatal and Adult Polymorphonuclear Leukocytes

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    Pei-Chen Hou


    Full Text Available Polymorphonuclear leukocytes (PMNs are the major leukocytes in the circulation and play an important role in host defense. Intact PMN functions include adhesion, migration, phagocytosis, and reactive oxygen species (ROS release. It has been known for a long time that adenosine can function as a modulator of adult PMN functions. Neonatal plasma has a higher adenosine level than that of adults; however, little is known about the modulating effects of adenosine on neonatal PMNs. The aim of this study was to investigate the effects of adenosine on neonatal PMN functions. We found that neonatal PMNs had impaired adhesion, chemotaxis, and ROS production abilities, but not phagocytosis compared to adult PMNs. As with adult PMNs, adenosine could suppress the CD11b expressions of neonatal PMNs, but had no significant suppressive effect on phagocytosis. In contrast to adult PMNs, adenosine did not significantly suppress chemotaxis and ROS production of neonatal PMNs. This may be due to impaired phagocyte reactions and a poor neonatal PMN response to adenosine. Adenosine may not be a good strategy for the treatment of neonatal sepsis because of impaired phagocyte reactions and poor response.

  7. Integrin Regulation during Leukocyte Recruitment. (United States)

    Herter, Jan; Zarbock, Alexander


    Integrins are recognized as vital players in leukocyte recruitment. Integrin malfunction causes severe disease patterns characterized by the inability to fight pathogens. Although inflammatory reactions are beneficial and necessary for host defense, these reactions have to be controlled to prevent tissue destruction and harmful sequelae. In this review, we discuss the different signaling pathways leading to the change of integrin adhesiveness in neutrophils, monocytes, and lymphocytes. We thereby focus on the importance of integrin activation for the different steps of the leukocyte recruitment cascade, including rolling, adhesion, postadhesion strengthening, intravascular crawling, and transmigration, as each step necessitates the proper functioning of a distinct set of integrin molecules that has to be activated specifically. Additionally, we discuss endogenous mechanisms that balance and counteract integrin activation and limit leukocyte recruitment at the site of inflammation. Further insight into these complex mechanisms may provide new approaches for developing new anti-inflammatory therapies.

  8. LPS responsiveness and neutrophil chemotaxis in vivo require PMN MMP-8 activity.

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    Angus M Tester

    Full Text Available We identify matrix metalloproteinase (MMP-8, the polymorphonuclear (PMN leukocyte collagenase, as a critical mediator initiating lipopolysaccharide (LPS-responsiveness in vivo. PMN infiltration towards LPS is abrogated in Mmp8-null mice. MMP-8 cleaves LPS-induced CXC chemokine (LIX at Ser(4-Val(5 and Lys(79-Arg(80. LIX bioactivity is increased upon N-terminal cleavage, enhancing intracellular calcium mobilization and chemotaxis upon binding its cognate receptor, CXCR2. As there is no difference in PMN chemotaxis in Mmp8-null mice compared with wild-type mice towards synthetic analogues of MMP-8-cleaved LIX, MMP-8 is not essential for extravasation or cell migration in collagenous matrices in vivo. However, with biochemical redundancy between MMPs 1, 2, 9, and 13, which also cleave LIX at position 4 approximately 5, it was surprising to observe such a markedly reduced PMN infiltration towards LPS and LIX in Mmp8-/- mice. This lack of physiological redundancy in vivo identifies MMP-8 as a key mediator in the regulation of innate immunity. Comparable results were found with CXCL8/IL-8 and CXCL5/ENA-78, the human orthologues of LIX. MMP-8 cleaves CXCL8 at Arg(5-Ser(6 and at Val(7-Leu(8 in CXCL5 to activate respective chemokines. Hence, rather than collagen, these PMN chemoattractants are important MMP-8 substrates in vivo; PMN-derived MMP-8 cleaves and activates LIX to execute an in cis PMN-controlled feed-forward mechanism to orchestrate the initial inflammatory response and promote LPS responsiveness in tissue.

  9. Radioassay of granulocyte chemotaxis. Studies of human granulocytes and chemotactic factors. [/sup 51/Cr tracer technique

    Energy Technology Data Exchange (ETDEWEB)

    Gallin, J.I.


    The above studies demonstrate that the /sup 51/Cr radiolabel chemotactic assay is a relatively simple and objective means for studying leukocyte chemotaxis in both normal and pathological conditions. Application of this method to studies of normal human chemotaxis revealed a relatively narrow range of normal and little day-to-day variability. Analysis of this variability revealed that there is more variability among the response of different granulocytes to a constant chemotactic stimulus than among the chemotactic activity of different sera to a single cell source. Utilizing the /sup 51/Cr radioassay, the abnormal granulocyte chemotactic behavior reported in Chediak-Higashi syndrome and a patient with recurrent pyogenic infections and mucocutaneous candidiasis has been confirmed. The /sup 51/Cr chemotactic assay has also been used to assess the generation of chemotactic activity from human serum and plasma. The in vitro generation of two distinct chemotactic factors were examined; the complement product (C5a) and kallikrein, an enzyme of the kinin-generating pathway. Kinetic analysis of complement-related chemotactic factor formation, utilizing immune complexes or endotoxin to activate normal sera in the presence or absence of EGTA as well as kinetic analysis of activation of C2-deficient human serum, provided an easy means of distinguishing the classical (antibody-mediated) complement pathway from the alternate pathway. Such kinetic analysis is necessary to detect clinically important abnormalities since, after 60 min of generation time, normal chemotactic activity may be present despite complete absence or inhibition of one complement pathway. The chemotactic factor generated by either pathway of complement activation appears to be predominately attributable to C5a.

  10. Protein Connectivity in Chemotaxis Receptor Complexes.

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    Stephan Eismann


    Full Text Available The chemotaxis sensory system allows bacteria such as Escherichia coli to swim towards nutrients and away from repellents. The underlying pathway is remarkably sensitive in detecting chemical gradients over a wide range of ambient concentrations. Interactions among receptors, which are predominantly clustered at the cell poles, are crucial to this sensitivity. Although it has been suggested that the kinase CheA and the adapter protein CheW are integral for receptor connectivity, the exact coupling mechanism remains unclear. Here, we present a statistical-mechanics approach to model the receptor linkage mechanism itself, building on nanodisc and electron cryotomography experiments. Specifically, we investigate how the sensing behavior of mixed receptor clusters is affected by variations in the expression levels of CheA and CheW at a constant receptor density in the membrane. Our model compares favorably with dose-response curves from in vivo Förster resonance energy transfer (FRET measurements, demonstrating that the receptor-methylation level has only minor effects on receptor cooperativity. Importantly, our model provides an explanation for the non-intuitive conclusion that the receptor cooperativity decreases with increasing levels of CheA, a core signaling protein associated with the receptors, whereas the receptor cooperativity increases with increasing levels of CheW, a key adapter protein. Finally, we propose an evolutionary advantage as explanation for the recently suggested CheW-only linker structures.

  11. Fluidic control over cell proliferation and chemotaxis (United States)

    Groisman, Alex


    Microscopic flows are almost always stable and laminar that allows precise control of chemical environment in micro-channels. We describe design and operation of several microfluidic devices, in which various types of environments are created for different experimental assays with live cells. In a microfluidic chemostat, colonies of non-adherent bacterial and yeast cells are trapped in micro-chambers with walls permeable for chemicals. Fast chemical exchange between the chambers and nearby flow-through channels creates essentially chemostatic medium conditions in the chambers and leads to exponential growth of the colonies up to very high cell densities. Another microfluidic device allows creation of linear concentration profiles of a pheromone (α-factor) across channels with non-adherent yeast cells, without exposure of the cells to flow or other mechanical perturbation. The concentration profile remains stable for hours enabling studies of chemotropic response of the cells to the pheromone gradient. A third type of the microfluidic devices is used to study chemotaxis of human neutrophils exposed to gradients of a chemoattractant (fMLP). The devices generate concentration profiles of various shapes, with adjustable steepness and mean concentration. The ``gradient'' of the chemoattractant can be imposed and reversed within less than a second, allowing repeated quantitative experiments.

  12. Sphingosylphosphorylcholine stimulates human monocyte-derived dendritic cell chemotaxis

    Institute of Scientific and Technical Information of China (English)

    Ha-young LEE; Eun-ha SHIN; Yoe-sik BAE


    Aim: To investigate the effects of Sphingosylphosphorylcholine (SPC) on human monocyte-derived dendritic cell (DC) chemotaxis. Methods: Human DC were generated from peripheral blood monocytes by culturing them with granulocyte macrophage-colony stimulating factor and interleukin-4. The effect of SPC on the DC chemotactic migration was measured by chemotaxis assay. Intracellular signaling event involved in the SPC-induced DC chemotaxis was investigated with several inhibitors for specific kinase. The expression of the SPC receptors was examined by reverse transcription polymerase chain reaction. Results: We found that SPC induced chemotactic migration in immature DC (iDC) and mature DC (mDC). In terms of SPC-induced signaling events, mitogen activated protein kinase activation and Akt activation in iDC and mDC were stimulated. SPC-induced chemotaxis was mediated by extracellular signal-regulated protein kinase and phosphoino-sitide-3-kinase, but not by calcium in both iDC and mDC. Although mDC express ovarian cancer G protein-coupled receptor 1, but not G protein-coupled receptor 4, iDC do not express any of these receptors. To examine the involvement of sphin-gosine-1-phosphate (SIP) receptors, we checked the effect of an SIP receptor antagonist (VPC23019) on SPC-induced DC chemotaxis. VPC23019 did not affect SPC-induced DC chemotaxis. Conclusion: The results suggest that SPC may play a role in regulating DC trafficking during phagocytosis and the T cell-stimulating phase, and the unique SPC receptor, which is different from SIP receptors, is involved in SPC-induced chemotaxis.

  13. Gαi2 and Gαi3 Differentially Regulate Arrest from Flow and Chemotaxis in Mouse Neutrophils. (United States)

    Kuwano, Yoshihiro; Adler, Micha; Zhang, Hong; Groisman, Alex; Ley, Klaus


    Leukocyte recruitment to inflammation sites progresses in a multistep cascade. Chemokines regulate multiple steps of the cascade, including arrest, transmigration, and chemotaxis. The most important chemokine receptor in mouse neutrophils is CXCR2, which couples through Gαi2- and Gαi3-containing heterotrimeric G proteins. Neutrophils arrest in response to CXCR2 stimulation. This is defective in Gαi2-deficient neutrophils. In this study, we show that Gαi3-deficient neutrophils showed reduced transmigration but normal arrest in mice. We also tested Gαi2- or Gαi3-deficient neutrophils in a CXCL1 gradient generated by a microfluidic device. Gαi3-, but not Gαi2-, deficient neutrophils showed significantly reduced migration and directionality. This was confirmed in a model of sterile inflammation in vivo. Gαi2-, but not Gαi3-, deficient neutrophils showed decreased Ca(2+) flux in response to CXCR2 stimulation. Conversely, Gαi3-, but not Gαi2-, deficient neutrophils exhibited reduced AKT phosphorylation upon CXCR2 stimulation. We conclude that Gαi2 controls arrest and Gαi3 controls transmigration and chemotaxis in response to chemokine stimulation of neutrophils.

  14. Leukocyte adhesion - a fundamental process in leukocyte physiology

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    Gahmberg C.G.


    Full Text Available Leukocyte adhesion is of pivotal functional importance. The adhesion involves several different adhesion molecules, the most important of which are the leukocyte ß2-integrins (CD11/CD18, the intercellular adhesion molecules, and the selectins. We and others have extensively studied the specificity and binding sites in the integrins and the intercellular adhesion molecules for their receptors and ligands. The integrins have to become activated to exert their functions but the possible mechanisms of activation remain poorly understood. Importantly, a few novel intercellular adhesion molecules have been recently described, which seem to function only in specific tissues. Furthermore, it is becoming increasingly apparent that changes in integrins and intercellular adhesion molecules are associated with a number of acute and chronic diseases.

  15. The sensory transduction pathways in bacterial chemotaxis (United States)

    Taylor, Barry L.


    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.

  16. A portable chemotaxis platform for short and long term analysis.

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    Chenjie Xu

    Full Text Available Flow-based microfluidic systems have been widely utilized for cell migration studies given their ability to generate versatile and precisely defined chemical gradients and to permit direct visualization of migrating cells. Nonetheless, the general need for bulky peripherals such as mechanical pumps and tubing and the complicated setup procedures significantly limit the widespread use of these microfluidic systems for cell migration studies. Here we present a simple method to power microfluidic devices for chemotaxis assays using the commercially available ALZET® osmotic pumps. Specifically, we developed a standalone chemotaxis platform that has the same footprint as a multiwell plate and can generate well-defined, stable chemical gradients continuously for up to 7 days. Using this platform, we validated the short-term (24 hours and long-term (72 hours concentration dependent PDGF-BB chemotaxis response of human bone marrow derived mesenchymal stem cells.

  17. EDU pretreatment decreases polymorphonuclear leukocyte migration into rat lung airways. (United States)

    Bassett, D J; Elbon, C L; Ishii, Y; Yang, H; Otterbein, L; Boswell, G A; Kerr, J S


    Pretreatment with the heterocyclic compound EDU (N-[2-(2-oxo-1-imidazolindinyl)ethyl]-N'-phenylurea) has previously been shown to reduce polymorphonuclear leukocyte (PMN) infiltration into the airways of ozone-exposed rats. The present study further examined the effects of 1 and 2 days EDU pretreatment on rat lung inflammatory responses by determining PMN infiltration in response to intratracheal instillation with the chemoattractant formyl-norleucine-leucine-phenylalanine (fNLP). Maximal recovery of PMNs by bronchoalveolar lavage was observed 4 hr after fNLP instillation with no alteration in the numbers of recoverable macrophages and lymphocytes. Although 1-day pretreatment with EDU did not affect PMN recovery from fNLP-instilled rat lungs, 2 days of EDU pretreatment prevented PMN infiltration as indicated by PMN recoveries that were similar to those obtained from saline-instilled lungs. Measurements of lung-marginated and interstitial pools of inflammatory cells using collagenase tissue digestion demonstrated no effect of 2 days EDU pretreatment. Although 2 days EDU pretreatment alone did not alter blood PMN content, lung permeability, and the lavage recoveries of inflammatory cells, blood PMN responses to chemotactic stimuli in vitro were impaired. In addition, EDU was shown to directly inhibit PMN chemotaxis and superoxide anion generation in vitro. These data demonstrated that EDU acts by interfering with PMN activation and migration rather than by decreasing PMN availability. EDU, by modulating the inflammatory response, represents a useful compound for preventing PMN-associated amplification of acute lung injuries.

  18. Activation of AMPK enhances neutrophil chemotaxis and bacterial killing. (United States)

    Park, Dae Won; Jiang, Shaoning; Tadie, Jean-Marc; Stigler, William S; Gao, Yong; Deshane, Jessy; Abraham, Edward; Zmijewski, Jaroslaw W


    An inability of neutrophils to eliminate invading microorganisms is frequently associated with severe infection and may contribute to the high mortality rates associated with sepsis. In the present studies, we examined whether metformin and other 5' adenosine monophosphate-activated protein kinase (AMPK) activators affect neutrophil motility, phagocytosis and bacterial killing. We found that activation of AMPK enhanced neutrophil chemotaxis in vitro and in vivo, and also counteracted the inhibition of chemotaxis induced by exposure of neutrophils to lipopolysaccharide (LPS). In contrast, small interfering RNA (siRNA)-mediated knockdown of AMPKα1 or blockade of AMPK activation through treatment of neutrophils with the AMPK inhibitor compound C diminished neutrophil chemotaxis. In addition to their effects on chemotaxis, treatment of neutrophils with metformin or aminoimidazole carboxamide ribonucleotide (AICAR) improved phagocytosis and bacterial killing, including more efficient eradication of bacteria in a mouse model of peritonitis-induced sepsis. Immunocytochemistry showed that, in contrast to LPS, metformin or AICAR induced robust actin polymerization and distinct formation of neutrophil leading edges. Although LPS diminished AMPK phosphorylation, metformin or AICAR was able to partially decrease the effects of LPS/toll-like receptor 4 (TLR4) engagement on downstream signaling events, particularly LPS-induced IκBα degradation. The IκB kinase (IKK) inhibitor PS-1145 diminished IκBα degradation and also prevented LPS-induced inhibition of chemotaxis. These results suggest that AMPK activation with clinically approved agents, such as metformin, may facilitate bacterial eradication in sepsis and other inflammatory conditions associated with inhibition of neutrophil activation and chemotaxis.

  19. Piracy on the molecular level: human herpesviruses manipulate cellular chemotaxis. (United States)

    Cornaby, Caleb; Tanner, Anne; Stutz, Eric W; Poole, Brian D; Berges, Bradford K


    Cellular chemotaxis is important to tissue homeostasis and proper development. Human herpesvirus species influence cellular chemotaxis by regulating cellular chemokines and chemokine receptors. Herpesviruses also express various viral chemokines and chemokine receptors during infection. These changes to chemokine concentrations and receptor availability assist in the pathogenesis of herpesviruses and contribute to a variety of diseases and malignancies. By interfering with the positioning of host cells during herpesvirus infection, viral spread is assisted, latency can be established and the immune system is prevented from eradicating viral infection.

  20. The level of CD147 expression correlates with cyclophilin-induced signalling and chemotaxis

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    Constant Stephanie


    Full Text Available Abstract Background Previous studies identified CD147 as the chemotactic receptor on inflammatory leukocytes for extracellular cyclophilins (eCyp. However, CD147 is not known to associate with signal transducing molecules, so other transmembrane proteins, such as proteoglycans, integrins, and CD98, were suggested as receptor or co-receptor for eCyp. CD147 is ubiquitously expressed on many cell types, but relationship between the level of CD147 expression and cellular responses to eCyp has never been analyzed. Given the role of eCyp in pathogenesis of many diseases, it is important to know whether cellular responses to eCyp are regulated at the level of CD147 expression. Results Here, we manipulated CD147 expression levels on HeLa cells using RNAi and investigated the signalling and chemotactic responses to eCypA. Both Erk activation and chemotaxis correlated with the level of CD147 expression, with cells exhibiting low level expression being practically unresponsive to eCypA. Conclusions Our results provide the first demonstration of a chemotactic response of HeLa cells to eCypA, establish a correlation between the level of CD147 expression and the magnitude of cellular responses to eCypA, and indicate that CD147 may be a limiting factor in the receptor complex determining cyclophilin-induced Erk activation and cell migration.

  1. Chemotaxis : signalling modules join hands at front and tail

    NARCIS (Netherlands)

    Haastert, Peter J.M. van; Devreotes, Peter N.


    Chemotaxis is the result of a refined interplay among various intracellular molecules that process spatial and temporal information. Here we present a modular scheme of the complex interactions between the front and the back of cells that allows them to navigate. First, at the front of the cell, act

  2. Comparative genomics of Geobacter chemotaxis genes reveals diverse signaling function

    Directory of Open Access Journals (Sweden)

    Antommattei Frances M


    Full Text Available Abstract Background Geobacter species are δ-Proteobacteria and are often the predominant species in a variety of sedimentary environments where Fe(III reduction is important. Their ability to remediate contaminated environments and produce electricity makes them attractive for further study. Cell motility, biofilm formation, and type IV pili all appear important for the growth of Geobacter in changing environments and for electricity production. Recent studies in other bacteria have demonstrated that signaling pathways homologous to the paradigm established for Escherichia coli chemotaxis can regulate type IV pili-dependent motility, the synthesis of flagella and type IV pili, the production of extracellular matrix material, and biofilm formation. The classification of these pathways by comparative genomics improves the ability to understand how Geobacter thrives in natural environments and better their use in microbial fuel cells. Results The genomes of G. sulfurreducens, G. metallireducens, and G. uraniireducens contain multiple (~70 homologs of chemotaxis genes arranged in several major clusters (six, seven, and seven, respectively. Unlike the single gene cluster of E. coli, the Geobacter clusters are not all located near the flagellar genes. The probable functions of some Geobacter clusters are assignable by homology to known pathways; others appear to be unique to the Geobacter sp. and contain genes of unknown function. We identified large numbers of methyl-accepting chemotaxis protein (MCP homologs that have diverse sensing domain architectures and generate a potential for sensing a great variety of environmental signals. We discuss mechanisms for class-specific segregation of the MCPs in the cell membrane, which serve to maintain pathway specificity and diminish crosstalk. Finally, the regulation of gene expression in Geobacter differs from E. coli. The sequences of predicted promoter elements suggest that the alternative sigma factors

  3. Leukocyte telomere dynamics in the elderly

    DEFF Research Database (Denmark)

    Steenstrup, Troels; Hjelmborg, Jacob V B; Mortensen, Laust H;


    Limited data suggest that leukocytes of the elderly display ultra-short telomeres. It was reported that in some elderly persons leukocyte telomere length (LTL) shows age-dependent elongation. Using cross-sectional and longitudinal models, we characterized LTL dynamics in participants...

  4. Bacillus subtilis Hfq: A role in chemotaxis and motility

    Indian Academy of Sciences (India)



    Hfq is a global post-transcriptional regulator that modulates the translation and stability of target mRNAs and therebyregulates pleiotropic functions, such as growth, stress, virulence and motility, in many Gram-negative bacteria.However, comparatively little is known about the regulation and function(s) of Hfq in Gram-positive bacteria.Recently, in Bacillus subtilis, a role for Hfq in stationary phase survival has been suggested, although the possibilityof Hfq having an additional role(s) cannot be ruled out. In this study we show that an ortholog of Hfq in B. subtilis isregulated by the stress sigma factor, σB, in addition to the stationary phase sigma factor, σH. We further demonstratethat Hfq positively regulates the expression of flagellum and chemotaxis genes (fla/che) that control chemotaxis andmotility, thus assigning a new function for Hfq in B. subtilis.

  5. Global Solutions to the Coupled Chemotaxis-Fluid Equations

    KAUST Repository

    Duan, Renjun


    In this paper, we are concerned with a model arising from biology, which is a coupled system of the chemotaxis equations and the viscous incompressible fluid equations through transport and external forcing. The global existence of solutions to the Cauchy problem is investigated under certain conditions. Precisely, for the Chemotaxis-Navier-Stokes system over three space dimensions, we obtain global existence and rates of convergence on classical solutions near constant states. When the fluid motion is described by the simpler Stokes equations, we prove global existence of weak solutions in two space dimensions for cell density with finite mass, first-order spatial moment and entropy provided that the external forcing is weak or the substrate concentration is small. © Taylor & Francis Group, LLC.

  6. Emergent collective chemotaxis without single-cell gradient sensing

    CERN Document Server

    Camley, Brian A; Levine, Herbert; Rappel, Wouter-Jan


    Many eukaryotic cells chemotax, sensing and following chemical gradients. However, even if single cells do not chemotax significantly, small clusters may still follow a gradient; this behavior is observed in neural crest cells and during border cell migration in Drosophila, but its origin remains puzzling. Here, we study this "collective guidance" analytically and computationally. We show collective chemotaxis can exist without single-cell chemotaxis if contact inhibition of locomotion (CIL), where cells polarize away from cell-cell contact, is regulated by the chemoattractant. We present explicit formulas for how cluster velocity and chemotactic index depend on the number and organization of cells in the cluster. Pairs of cells will have velocities that are strongly dependent on the cell pair's orientation: this provides a simple test for the presence of collective guidance in neural crest cells and other systems. We also study cluster-level adaptation, amplification, and cohesion via co-attraction.

  7. A Multiobjective Optimization Algorithm Based on Discrete Bacterial Colony Chemotaxis

    Directory of Open Access Journals (Sweden)

    Zhigang Lu


    Full Text Available Bacterial colony chemotaxis algorithm was originally developed for optimal problem with continuous space. In this paper the discrete bacterial colony chemotaxis (DBCC algorithm is developed to solve multiobjective optimization problems. The basic DBCC algorithm has the disadvantage of being trapped into the local minimum. Therefore, some improvements are adopted in the new algorithm, such as adding chaos transfer mechanism when the bacterium choose their next locations and the crowding distance operation to maintain the population diversity in the Pareto Front. The definition of chaos transfer mechanism is used to retain the elite solution produced during the operation, and the definition of crowding distance is used to guide the bacteria for determinate variation, thus enabling the algorithm obtain well-distributed solution in the Pareto optimal set. The convergence properties of the DBCC strategy are tested on some test functions. At last, some numerical results are given to demonstrate the effectiveness of the results obtained by the new algorithm.

  8. Feeding ducks, bacterial chemotaxis, and the Gini index

    CERN Document Server

    Peaudecerf, Francois J


    Classic experiments on the distribution of ducks around separated food sources found consistency with the `ideal free' distribution in which the local population is proportional to the local supply rate. Motivated by this experiment and others, we examine the analogous problem in the microbial world: the distribution of chemotactic bacteria around multiple nearby food sources. In contrast to the optimization of uptake rate that may hold at the level of a single cell in a spatially varying nutrient field, nutrient consumption by a population of chemotactic cells will modify the nutrient field, and the uptake rate will generally vary throughout the population. Through a simple model we study the distribution of resource uptake in the presence of chemotaxis, consumption, and diffusion of both bacteria and nutrients. Borrowing from the field of theoretical economics, we explore how the Gini index can be used as a means to quantify the inequalities of uptake. The redistributive effect of chemotaxis can lead to a p...

  9. Oscillatory traveling wave solutions to an attractive chemotaxis system (United States)

    Li, Tong; Liu, Hailiang; Wang, Lihe


    This paper investigates oscillatory traveling wave solutions to an attractive chemotaxis system. The convective part of this system changes its type when crossing a parabola in the phase space. The oscillatory nature of the traveling wave comes from the fact that one far-field state is in the elliptic region and another in the hyperbolic region. Such traveling wave solutions are shown to be linearly unstable. Detailed construction of some traveling wave solutions is presented.

  10. Quantitative analysis of experiments on bacterial chemotaxis to naphthalene. (United States)

    Pedit, Joseph A; Marx, Randall B; Miller, Cass T; Aitken, Michael D


    A mathematical model was developed to quantify chemotaxis to naphthalene by Pseudomonas putida G7 (PpG7) and its influence on naphthalene degradation. The model was first used to estimate the three transport parameters (coefficients for naphthalene diffusion, random motility, and chemotactic sensitivity) by fitting it to experimental data on naphthalene removal from a discrete source in an aqueous system. The best-fit value of naphthalene diffusivity was close to the value estimated from molecular properties with the Wilke-Chang equation. Simulations applied to a non-chemotactic mutant strain only fit the experimental data well if random motility was negligible, suggesting that motility may be lost rapidly in the absence of substrate or that gravity may influence net random motion in a vertically oriented experimental system. For the chemotactic wild-type strain, random motility and gravity were predicted to have a negligible impact on naphthalene removal relative to the impact of chemotaxis. Based on simulations using the best-fit value of the chemotactic sensitivity coefficient, initial cell concentrations for a non-chemotactic strain would have to be several orders of magnitude higher than for a chemotactic strain to achieve similar rates of naphthalene removal under the experimental conditions we evaluated. The model was also applied to an experimental system representing an adaptation of the conventional capillary assay to evaluate chemotaxis in porous media. Our analysis suggests that it may be possible to quantify chemotaxis in porous media systems by simply adjusting the model's transport parameters to account for tortuosity, as has been suggested by others.

  11. A model of excitation and adaptation in bacterial chemotaxis



    Bacterial chemotaxis is widely studied because of its accessibility and because it incorporates processes that are important in a number of sensory systems: signal transduction, excitation, adaptation, and a change in behavior, all in response to stimuli. Quantitative data on the change in behavior are available for this system, and the major biochemical steps in the signal transduction/processing pathway have been identified. We have incorporated recent biochemica...

  12. Localization of chemical sources using e. coli chemotaxis (United States)

    Davison, Timothy; Nguyen, Hoa; Nickels, Kevin; Frasch, Duncan; Basagaoglu, Hakan


    This paper furthers the application of chemotaxis to small-scale robots by simulating a system that localizes a chemical source in a dynamic fluid environment. This type of system responds to a chemical stimulus by mimicking, for example, the way that E. Coli bacteria move toward attractants (nutrients) and away from repellents. E. Coli use the intracellular signaling pathway to process the temporal change in the chemical concentration to determine if the cells should run or tumble. Previous work has shown that this process can be simulated with robots and used to localize chemical sources based upon a fixed nutrient gradient. Our work furthers this study by simulating the injection of an effluent of chemical at a specified location in an environment and uses computational fluid dynamics to model the interactions of the robot with the fluid while performing chemotaxis. The interactions between the chemical and fluid are also modelled with the advection diffusion equation to determine the concentration gradient. This method allows us to compute, over a lattice, the chemical concentration at all points and feed these results into an existing E. Coli controller for the robot, which results in the robot executing a tumble or a run according to a probabilistic formula. By simulating the robot in this complex environment, our work facilitates refinement of the chemotaxis controller while proving the ability of chemotactic robots to localize specific chemicals in environments that more closely resemble those encountered in the wide-ranging types of locations in which this robotic system might be deployed.

  13. Chemotaxis of bio-hybrid multiple bacteria-driven microswimmers (United States)

    Zhuang, Jiang; Sitti, Metin


    In this study, in a bio-hybrid microswimmer system driven by multiple Serratia marcescens bacteria, we quantify the chemotactic drift of a large number of microswimmers towards L-serine and elucidate the associated collective chemotaxis behavior by statistical analysis of over a thousand swimming trajectories of the microswimmers. The results show that the microswimmers have a strong heading preference for moving up the L-serine gradient, while their speed does not change considerably when moving up and down the gradient; therefore, the heading bias constitutes the major factor that produces the chemotactic drift. The heading direction of a microswimmer is found to be significantly more persistent when it moves up the L-serine gradient than when it travels down the gradient; this effect causes the apparent heading preference of the microswimmers and is the crucial reason that enables the seemingly cooperative chemotaxis of multiple bacteria on a microswimmer. In addition, we find that their chemotactic drift velocity increases superquadratically with their mean swimming speed, suggesting that chemotaxis of bio-hybrid microsystems can be enhanced by designing and building faster microswimmers. Such bio-hybrid microswimmers with chemotactic steering capability may find future applications in targeted drug delivery, bioengineering, and lab-on-a-chip devices.

  14. Chemotaxis of bio-hybrid multiple bacteria-driven microswimmers (United States)

    Zhuang, Jiang; Sitti, Metin


    In this study, in a bio-hybrid microswimmer system driven by multiple Serratia marcescens bacteria, we quantify the chemotactic drift of a large number of microswimmers towards L-serine and elucidate the associated collective chemotaxis behavior by statistical analysis of over a thousand swimming trajectories of the microswimmers. The results show that the microswimmers have a strong heading preference for moving up the L-serine gradient, while their speed does not change considerably when moving up and down the gradient; therefore, the heading bias constitutes the major factor that produces the chemotactic drift. The heading direction of a microswimmer is found to be significantly more persistent when it moves up the L-serine gradient than when it travels down the gradient; this effect causes the apparent heading preference of the microswimmers and is the crucial reason that enables the seemingly cooperative chemotaxis of multiple bacteria on a microswimmer. In addition, we find that their chemotactic drift velocity increases superquadratically with their mean swimming speed, suggesting that chemotaxis of bio-hybrid microsystems can be enhanced by designing and building faster microswimmers. Such bio-hybrid microswimmers with chemotactic steering capability may find future applications in targeted drug delivery, bioengineering, and lab-on-a-chip devices. PMID:27555465

  15. Computational model of mesenchymal migration in 3D under chemotaxis. (United States)

    Ribeiro, F O; Gómez-Benito, M J; Folgado, J; Fernandes, P R; García-Aznar, J M


    Cell chemotaxis is an important characteristic of cellular migration, which takes part in crucial aspects of life and development. In this work, we propose a novel in silico model of mesenchymal 3D migration with competing protrusions under a chemotactic gradient. Based on recent experimental observations, we identify three main stages that can regulate mesenchymal chemotaxis: chemosensing, dendritic protrusion dynamics and cell-matrix interactions. Therefore, each of these features is considered as a different module of the main regulatory computational algorithm. The numerical model was particularized for the case of fibroblast chemotaxis under a PDGF-bb gradient. Fibroblasts migration was simulated embedded in two different 3D matrices - collagen and fibrin - and under several PDGF-bb concentrations. Validation of the model results was provided through qualitative and quantitative comparison with in vitro studies. Our numerical predictions of cell trajectories and speeds were within the measured in vitro ranges in both collagen and fibrin matrices. Although in fibrin, the migration speed of fibroblasts is very low, because fibrin is a stiffer and more entangling matrix. Testing PDGF-bb concentrations, we noticed that an increment of this factor produces a speed increment. At 1 ng mL(-1) a speed peak is reached after which the migration speed diminishes again. Moreover, we observed that fibrin exerts a dampening behavior on migration, significantly affecting the migration efficiency.

  16. Interactions Between Stably Rolling Leukocytes In Vivo

    CERN Document Server

    King, M R; Kim, M B; Sarelius, I H; King, Michael R.; Ruscio, Aimee D.; Kim, Michael B.; Sarelius, Ingrid H.


    We have characterized the two-dimensional spatial dependence of the hydrodynamic interactions between two adhesively rolling leukocytes in a live venule in the mouse cremaster muscle. Two rolling leukocytes were observed to slow each other down when rolling together in close proximity, due to mutual sheltering from the external blood flow in the vessel lumen. These results are in agreement with a previous study of leukocyte rolling interactions using carbohydrate-coated beads in a parallel-plate flow chamber and a detailed computer model of adhesion in a multicellular environment.

  17. Interaction between serum amyloid A and leukocytes - a possible role in the progression of vascular complications in diabetes. (United States)

    Hatanaka, Elaine; Monteagudo, Patrícia Teófilo; Marrocos, Mauro Sérgio Martins; Campa, Ana


    Diabetes mellitus is associated with an increased incidence of cardiovascular events and microvascular complications. Serum amyloid A (SAA), a HDL apolipoprotein is a risk marker for cardiovascular disease. A permanent increase in SAA plasma levels is observed in diabetics. Because SAA acts on leukocytes, we evaluated whether the synthesis of proinflammatory cytokines and migration of neutrophils and monocytes induced by SAA is affected in diabetics. Cells, isolated from human blood, were cultured in the presence of SAA. TNF-alpha, IL-1beta, IL-8 and IL-1ra levels were measured by ELISA in the culture supernatants and in serum of subjects. Neutrophils and monocytes migration were followed in a chemotaxis chamber. We make the novel observation that neutrophils and monocytes of diabetics are more responsive to SAA for the induction of the proinflammatory cytokine IL-1beta and the proangiogenic and chemotactic protein IL-8. Incremental TNF-alpha production was also found to occur when monocytes were stimulated with SAA. Cell migration was also increased. The increased production of cytokines and increased migration of leukocytes from diabetics in response to SAA may contribute to a sustained accumulation and activation of inflammatory cells in the disease. Accordingly, the hyper-responsiveness of leukocytes to SAA may be relevant to the proinflammatory conditions associated to vascular complications in diabetic patients.

  18. Effects of ochratoxin a on broiler leukocytes

    Directory of Open Access Journals (Sweden)

    MA Moura


    Full Text Available This study evaluated alterations in the qualitative cellular profile of leukocytes caused by the administration of low doses of ochratoxin-A (OTA in poultry. Sixty chicks were separated in three experimental groups: control, PBS-treated and OTA-treated. Blood smears from all birds were analyzed three and six hours post-treatment. Differential leukocyte counting demonstrated that OTA reduced the percentage of lymphocytes and eosinophils and significantly increased the number of heterophils and monocytes.

  19. Biomixing by chemotaxis and efficiency of biological reactions: The critical reaction case (United States)

    Kiselev, Alexander; Ryzhik, Lenya


    Many phenomena in biology involve both reactions and chemotaxis. These processes can clearly influence each other, and chemotaxis can play an important role in sustaining and speeding up the reaction. In continuation of our work [A. Kiselev and L. Ryzhik, "Biomixing by chemotaxis and enhancement of biological reactions," Comm. Partial Differential Equations 37, 298-318 (2012)], 10.1080/03605302.2011.589879, we consider a model with a single density function involving diffusion, advection, chemotaxis, and absorbing reaction. The model is motivated, in particular, by the studies of coral broadcast spawning, where experimental observations of the efficiency of fertilization rates significantly exceed the data obtained from numerical models that do not take chemotaxis (attraction of sperm gametes by a chemical secreted by egg gametes) into account. We consider the case of the weakly coupled quadratic reaction term, which is the most natural from the biological point of view and was left open in Kiselev and Ryzhik ["Biomixing by chemotaxis and enhancement of biological reactions," Comm. Partial Differential Equations 37, 298-318 (2012)], 10.1080/03605302.2011.589879. The result is that similarly to Kiselev and Ryzhik ["Biomixing by chemotaxis and enhancement of biological reactions," Comm. Partial Differential Equations 37, 298-318 (2012)], 10.1080/03605302.2011.589879, the chemotaxis plays a crucial role in ensuring efficiency of reaction. However, mathematically, the picture is quite different in the quadratic reaction case and is more subtle. The reaction is now complete even in the absence of chemotaxis, but the timescales are very different. Without chemotaxis, the reaction is very slow, especially for the weak reaction coupling. With chemotaxis, the timescale and efficiency of reaction are independent of the coupling parameter.

  20. Dependence of bacterial chemotaxis on gradient shape and adaptation rate.

    Directory of Open Access Journals (Sweden)

    Nikita Vladimirov


    Full Text Available Simulation of cellular behavior on multiple scales requires models that are sufficiently detailed to capture central intracellular processes but at the same time enable the simulation of entire cell populations in a computationally cheap way. In this paper we present RapidCell, a hybrid model of chemotactic Escherichia coli that combines the Monod-Wyman-Changeux signal processing by mixed chemoreceptor clusters, the adaptation dynamics described by ordinary differential equations, and a detailed model of cell tumbling. Our model dramatically reduces computational costs and allows the highly efficient simulation of E. coli chemotaxis. We use the model to investigate chemotaxis in different gradients, and suggest a new, constant-activity type of gradient to systematically study chemotactic behavior of virtual bacteria. Using the unique properties of this gradient, we show that optimal chemotaxis is observed in a narrow range of CheA kinase activity, where concentration of the response regulator CheY-P falls into the operating range of flagellar motors. Our simulations also confirm that the CheB phosphorylation feedback improves chemotactic efficiency by shifting the average CheY-P concentration to fit the motor operating range. Our results suggest that in liquid media the variability in adaptation times among cells may be evolutionary favorable to ensure coexistence of subpopulations that will be optimally tactic in different gradients. However, in a porous medium (agar such variability appears to be less important, because agar structure poses mainly negative selection against subpopulations with low levels of adaptation enzymes. RapidCell is available from the authors upon request.

  1. Role of extracellular cations in cell motility, polarity, and chemotaxis

    Directory of Open Access Journals (Sweden)

    Soll D


    Full Text Available David R Soll1, Deborah Wessels1, Daniel F Lusche1, Spencer Kuhl1, Amanda Scherer1, Shawna Grimm1,21Monoclonal Antibody Research Institute, Developmental Studies, Hybridoma Bank, Department of Biology, University of Iowa, Iowa City; 2Mercy Medical Center, Surgical Residency Program, Des Moines, Iowa, USAAbstract: The concentration of cations in the aqueous environment of free living organisms and cells within the human body influence motility, shape, and chemotaxis. The role of extracellular cations is usually perceived to be the source for intracellular cations in the process of homeostasis. The role of surface molecules that interact with extracellular cations is believed to be that of channels, transporters, and exchangers. However, the role of Ca2+ as a signal and chemoattractant and the discovery of the Ca2+ receptor have demonstrated that extracellular cations can function as signals at the cell surface, and the plasma membrane molecules they interact with can function as bona fide receptors that activate coupled signal transduction pathways, associated molecules in the plasma membrane, or the cytoskeleton. With this perspective in mind, we have reviewed the cationic composition of aqueous environments of free living cells and cells that move in multicellular organisms, most notably humans, the range of molecules interacting with cations at the cell surface, the concept of a cell surface cation receptor, and the roles extracellular cations and plasma membrane proteins that interact with them play in the regulation of motility, shape, and chemotaxis. Hopefully, the perspective of this review will increase awareness of the roles extracellular cations play and the possibility that many of the plasma membrane proteins that interact with them could also play roles as receptors.Keywords: extracellular cations, chemotaxis, transporters, calcium, receptors

  2. Exact solutions of certain nonlinear chemotaxis diffusion reaction equations

    Indian Academy of Sciences (India)



    Using the auxiliary equation method, we obtain exact solutions of certain nonlinear chemotaxis diffusion reaction equations in the presence of a stimulant. In particular, we account for the nonlinearities arising not only from the density-dependent source terms contributed by the particles and the stimulant but also from the coupling term of the stimulant. In addition to this, the diffusion of the stimulant and the effect of long-range interactions are also accounted for in theconstructed coupled differential equations. The results obtained here could be useful in the studies of several biological systems and processes, e.g., in bacterial infection, chemotherapy, etc.

  3. Confinement dependent chemotaxis in two-photon polymerized linear migration constructs with highly definable concentration gradients

    DEFF Research Database (Denmark)

    Hjortø, Gertrud Malene; Olsen, Mark Holm; Svane, Inge Marie


    Dendritic cell chemotaxis is known to follow chemoattractant concentration gradients through tissue of heterogeneous pore sizes, but the dependence of migration velocity on pore size and gradient steepness is not fully understood. We enabled chemotaxis studies for at least 42 hours at confinement...

  4. Leukocyte margination in a model microvessel (United States)

    Freund, Jonathan B.


    The physiological inflammation response depends upon the multibody interactions of blood cells in the microcirculation that bring leukocytes (white blood cells) to the vessel walls. We investigate the fluid mechanics of this using numerical simulations of 29 red blood cells and one leukocyte flowing in a two-dimensional microvessel, with the cells modeled as linearly elastic shell membranes. Despite its obvious simplifications, this model successfully reproduces the increasingly blunted velocity profiles and increased leukocyte margination observed at lower shear rates in actual microvessels. Red cell aggregation is shown to be unnecessary for margination. The relative stiffness of the red cells in our simulations is varied by over a factor of 10, but the margination is found to be much less correlated with this than it is to changes associated with the blunting of the mean velocity profile at lower shear rates. While velocity around the leukocyte when it is near the wall depends upon the red cell properties, it changes little for strongly versus weakly marginating cases. In the more strongly marginating cases, however, a red cell is frequently observed to be leaning on the upstream side of the leukocyte and appears to stabilize it, preventing other red cells from coming between it and the wall. A well-known feature of the microcirculation is a near-wall cell-free layer. In our simulations, it is observed that the leukocyte's most probable position is at the edge of this layer. This wall stand-off distance increases with velocity following a scaling that would be expected for a lubrication mechanism, assuming that there were a nearly constant force pushing the cells toward the wall. The leukocyte's near-wall position is observed to be less stable with increasing mean stand-off distance, but this distance would have potentially greater effect on adhesion since the range of the molecular binding is so short.

  5. Biomixing by chemotaxis and efficiency of biological reactions: the critical reaction case

    CERN Document Server

    Kiselev, Alexander


    Many phenomena in biology involve both reactions and chemotaxis. These processes can clearly influence each other, and chemotaxis can play an important role in sustaining and speeding up the reaction. In continuation of our earlier work, we consider a model with a single density function involving diffusion, advection, chemotaxis, and absorbing reaction. The model is motivated, in particular, by the studies of coral broadcast spawning, where experimental observations of the efficiency of fertilization rates significantly exceed the data obtained from numerical models that do not take chemotaxis (attraction of sperm gametes by a chemical secreted by egg gametes) into account. We consider the case of the weakly coupled quadratic reaction term, which is the most natural from the biological point of view and was left open. The result is that similarly to higher power coupling, the chemotaxis plays a crucial role in ensuring efficiency of reaction. However, mathematically, the picture is quite different in the qua...

  6. Bovine CCL28 Mediates Chemotaxis via CCR10 and Demonstrates Direct Antimicrobial Activity against Mastitis Causing Bacteria.

    Directory of Open Access Journals (Sweden)

    Kyler B Pallister

    Full Text Available In addition to the well characterized function of chemokines in mediating the homing and accumulation of leukocytes to tissues, some chemokines also exhibit potent antimicrobial activity. Little is known of the potential role of chemokines in bovine mammary gland health and disease. The chemokine CCL28 has previously been shown to play a key role in the homing and accumulation of IgA antibody secreting cells to the lactating murine mammary gland. CCL28 has also been shown to act as an antimicrobial peptide with activity demonstrated against a wide range of pathogens including bacteria, fungi and protozoans. Here we describe the cloning and function of bovine CCL28 and document the concentration of this chemokine in bovine milk. Bovine CCL28 was shown to mediate cellular chemotaxis via the CCR10 chemokine receptor and exhibited antimicrobial activity against a variety of bovine mastitis causing organisms. The concentration of bovine CCL28 in milk was found to be highly correlated with the lactation cycle. Highest concentrations of CCL28 were observed soon after parturition, with levels decreasing over time. These results suggest a potential role for CCL28 in the prevention/resolution of bovine mastitis.

  7. Chemotaxis of Dictyostelium discoideum: collective oscillation of cellular contacts.

    Directory of Open Access Journals (Sweden)

    Edith Schäfer

    Full Text Available Chemotactic responses of Dictyostelium discoideum cells to periodic self-generated signals of extracellular cAMP comprise a large number of intricate morphological changes on different length scales. Here, we scrutinized chemotaxis of single Dictyostelium discoideum cells under conditions of starvation using a variety of optical, electrical and acoustic methods. Amebas were seeded on gold electrodes displaying impedance oscillations that were simultaneously analyzed by optical video microscopy to relate synchronous changes in cell density, morphology, and distance from the surface to the transient impedance signal. We found that starved amebas periodically reduce their overall distance from the surface producing a larger impedance and higher total fluorescence intensity in total internal reflection fluorescence microscopy. Therefore, we propose that the dominant sources of the observed impedance oscillations observed on electric cell-substrate impedance sensing electrodes are periodic changes of the overall cell-substrate distance of a cell. These synchronous changes of the cell-electrode distance were also observed in the oscillating signal of acoustic resonators covered with amebas. We also found that periodic cell-cell aggregation into transient clusters correlates with changes in the cell-substrate distance and might also contribute to the impedance signal. It turned out that cell-cell contacts as well as cell-substrate contacts form synchronously during chemotaxis of Dictyostelium discoideum cells.

  8. Chemotaxis toward phytoplankton drives organic matter partitioning among marine bacteria. (United States)

    Smriga, Steven; Fernandez, Vicente I; Mitchell, James G; Stocker, Roman


    The microenvironment surrounding individual phytoplankton cells is often rich in dissolved organic matter (DOM), which can attract bacteria by chemotaxis. These "phycospheres" may be prominent sources of resource heterogeneity in the ocean, affecting the growth of bacterial populations and the fate of DOM. However, these effects remain poorly quantified due to a lack of quantitative ecological frameworks. Here, we used video microscopy to dissect with unprecedented resolution the chemotactic accumulation of marine bacteria around individual Chaetoceros affinis diatoms undergoing lysis. The observed spatiotemporal distribution of bacteria was used in a resource utilization model to map the conditions under which competition between different bacterial groups favors chemotaxis. The model predicts that chemotactic, copiotrophic populations outcompete nonmotile, oligotrophic populations during diatom blooms and bloom collapse conditions, resulting in an increase in the ratio of motile to nonmotile cells and in the succession of populations. Partitioning of DOM between the two populations is strongly dependent on the overall concentration of bacteria and the diffusivity of different DOM substances, and within each population, the growth benefit from phycospheres is experienced by only a small fraction of cells. By informing a DOM utilization model with highly resolved behavioral data, the hybrid approach used here represents a new path toward the elusive goal of predicting the consequences of microscale interactions in the ocean.

  9. Nematode Chemotaxis: Gradual Turns, Sharp Turns, and Modulated Turn Angles (United States)

    Patel, Amar; Padmanabhan, Venkat; Rumbaugh, Kendra; Vanapalli, Siva; Blawzdziewicz, Jerzy


    We examine strategies used by the soil-dwelling nematode Caenorhabditis Elegans for chemotaxis in complex environments. The proposed description is based on our recently developed piecewise-harmonic-curvature model of nematode locomotion [PLoS ONE, 7(7) e40121 (2012)], where random harmonic-curvature modes represent elementary locomotory movements. We show that the previously described gradual-turn and sharp-turn chemotaxis strategies can be unified in our model. The gradual-turn mechanism relies on crawling amplitude changes commensurate with the undulation frequency. The sharp-turn mechanism consists in modulation of the frequency of jumps to large-amplitude modes. We hypothesize that there exists a third strategy, where the nematode adjusts the variance of the amplitude distribution. Such adjustments result in a modulation of the magnitude of random turns, with smaller turns performed when the nematode moves toward the increasing chemoatractant concentration. Experiments are proposed to determine if the third strategy is present in the nematode behavior. This work was supported by NSF grant No. CBET 1059745.

  10. Halloysite Nanotube Coatings Suppress Leukocyte Spreading. (United States)

    Hughes, Andrew D; Marsh, Graham; Waugh, Richard E; Foster, David G; King, Michael R


    The nanoscale topography of adhesive surfaces is known to be an important factor governing cellular behavior. Previous work has shown that surface coatings composed of halloysite nanotubes enhance the adhesion, and therefore capture of, rare target cells such as circulating tumor cells. Here we demonstrate a unique feature of these coatings in their ability to reduce the adhesion of leukocytes and prevent leukocyte spreading. Surfaces were prepared with coatings of halloysite nanotubes and functionalized for leukocyte adhesion with E-selectin, and the dilution of nanotube concentration revealed a threshold concentration below which cell spreading became comparable to smooth surfaces. Evaluation of surface roughness characteristics determined that the average distance between discrete surface features correlated with adhesion metrics, with a separation distance of ∼2 μm identified as the critical threshold. Computational modeling of the interaction of leukocytes with halloysite nanotube-coated surfaces of varying concentrations demonstrates that the geometry of the cell surface and adhesive counter-surface produces a significantly diminished effective contact area compared to a leukocyte interacting with a smooth surface.

  11. Cigarette smoking and leukocyte subpopulations in men. (United States)

    Freedman, D S; Flanders, W D; Barboriak, J J; Malarcher, A M; Gates, L


    Because of previously reported associations among the total leukocyte count, cigarette smoking, and risk of cardiovascular disease, we examined the relation of cigarette smoking to various leukocyte subpopulations among 3467 men aged 31 to 45 years. The median total leukocyte count was 36% higher (7840 vs. 5760 cells/mL) among current cigarette smokers than among men who had never smoked, and both stratification and regression analyses were used to examine independent associations with leukocyte subpopulations. At equivalent counts of other subpopulations, CD4+ lymphocytes and neutrophils were the cell types most strongly associated with cigarette smoking; each standard deviation change in counts of these subpopulations increased the odds of current (vs. never) smoking by approximately threefold. Furthermore, whereas 15% of the 238 men with relatively low (men with relatively high counts of both subpopulations were current smokers. Counts of T lymphocytes also tended to be higher among the 32 men with self-reported ischemic heart disease than among other men. These results, along with previous reports of immunologically active T lymphocytes in atherosclerotic plaques, suggest that this subpopulation may be of particular interest in studies examining the relation of leukocytes to cardiovascular disease.

  12. Computational Chemotaxis in Ants and Bacteria over Dynamic Environments

    CERN Document Server

    Ramos, Vitorino; Rosa, A C; Abraham, A


    Chemotaxis can be defined as an innate behavioural response by an organism to a directional stimulus, in which bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food (e.g., glucose) by swimming towards the highest concentration of food molecules, or to flee from poisons. Based on self-organized computational approaches and similar stigmergic concepts we derive a novel swarm intelligent algorithm. What strikes from these observations is that both eusocial insects as ant colonies and bacteria have similar natural mechanisms based on stigmergy in order to emerge coherent and sophisticated patterns of global collective behaviour. Keeping in mind the above characteristics we will present a simple model to tackle the collective adaptation of a social swarm based on real ant colony behaviors (SSA algorithm) for tracking extrema in dynamic environments and highly multimodal complex functions des...

  13. A model of excitation and adaptation in bacterial chemotaxis. (United States)

    Spiro, P A; Parkinson, J S; Othmer, H G


    Bacterial chemotaxis is widely studied because of its accessibility and because it incorporates processes that are important in a number of sensory systems: signal transduction, excitation, adaptation, and a change in behavior, all in response to stimuli. Quantitative data on the change in behavior are available for this system, and the major biochemical steps in the signal transduction/processing pathway have been identified. We have incorporated recent biochemical data into a mathematical model that can reproduce many of the major features of the intracellular response, including the change in the level of chemotactic proteins to step and ramp stimuli such as those used in experimental protocols. The interaction of the chemotactic proteins with the motor is not modeled, but we can estimate the degree of cooperativity needed to produce the observed gain under the assumption that the chemotactic proteins interact directly with the motor proteins.

  14. Epac inhibits apoptosis of human leukocytes

    NARCIS (Netherlands)

    Grandoch, M.; Bujok, V.; Fleckenstein, D.; Schmidt, M.; Fischer, J. W.; Weber, A. -A.


    cAMP is known to participate in the regulation of apoptosis in leukocytes. Depending on the cell type, pro- and antiapoptotic effects of cAMP have been described. Thus far, most of the cAMP-dependent effects have been attributed to the activation of PKA. However, Epac proteins (direct cAMP targets a

  15. Qualitative analysis of stationary Keller-Segel chemotaxis models with logistic growth (United States)

    Wang, Qi; Yan, Jingda; Gai, Chunyi


    We study the stationary Keller-Segel chemotaxis models with logistic cellular growth over a one-dimensional region subject to the Neumann boundary condition. We show that nonconstant solutions emerge in the sense of Turing's instability as the chemotaxis rate {χ} surpasses a threshold number. By taking the chemotaxis rate as the bifurcation parameter, we carry out bifurcation analysis on the system to obtain the explicit formulas of bifurcation values and small amplitude nonconstant positive solutions. Moreover, we show that solutions stay strictly positive in the continuum of each branch. The stabilities of these steady-state solutions are well studied when the creation and degradation rate of the chemical is assumed to be a linear function. Finally, we investigate the asymptotic behaviors of the monotone steady states. We construct solutions with interesting patterns such as a boundary spike when the chemotaxis rate is large enough and/or the cell motility is small.

  16. An optimal adaptive time-stepping scheme for solving reaction-diffusion-chemotaxis systems. (United States)

    Chiu, Chichia; Yu, Jui-Ling


    Reaction-diffusion-chemotaxis systems have proven to be fairly accurate mathematical models for many pattern formation problems in chemistry and biology. These systems are important for computer simulations of patterns, parameter estimations as well as analysis of the biological systems. To solve reaction-diffusion-chemotaxis systems, efficient and reliable numerical algorithms are essential for pattern generations. In this paper, a general reaction-diffusion-chemotaxis system is considered for specific numerical issues of pattern simulations. We propose a fully explicit discretization combined with a variable optimal time step strategy for solving the reaction-diffusion-chemotaxis system. Theorems about stability and convergence of the algorithm are given to show that the algorithm is highly stable and efficient. Numerical experiment results on a model problem are given for comparison with other numerical methods. Simulations on two real biological experiments will also be shown.

  17. Numerical study of plume patterns in the chemotaxis-diffusion-convection coupling system

    CERN Document Server

    Deleuze, Yannick; Thiriet, Marc; Sheu, Tony W H


    A chemotaxis-diffusion-convection coupling system for describing a form of buoyant convection in which the fluid develops convection cells and plume patterns will be investigated numerically in this study. Based on the two-dimensional convective chemotaxis-fluid model proposed in the literature, we developed an upwind finite element method to investigate the pattern formation and the hydrodynamical stability of the system. The numerical simulations illustrate different predicted physical regimes in the system. In the convective regime, the predicted plumes resemble B\\'enard instabilities. Our numerical results show how structured layers of bacteria are formed before bacterium rich plumes fall in the fluid. The plumes have a well defined spectrum of wavelengths and have an exponential growth rate, yet their position can only be predicted in very simple examples. In the chemotactic and diffusive regimes, the effects of chemotaxis are investigated. Our results indicate that the chemotaxis can stabilize the overa...

  18. Neutrophil chemotaxis and arachidonic acid metabolism are not linked: evidence from metal ion probe studies

    Energy Technology Data Exchange (ETDEWEB)

    Turner, S.R.; Turner, R.A.; Smith, D.M.; Johnson, J.A.


    Heavy metal ions can inhibit arachidonic acid (AA) metabolism protect against ionophore cytotoxicity (ibid) and inhibit neutrophil chemotaxis. In this study they used Au/sup 3 +/, Zn/sup 2 +/, Cr/sup 3 +/, Mn/sup 2 +/ and Cu/sup 2 +/ as probes of the interrelationships among AA metabolism, ionophore-mediated cytotoxicity, and chemotaxis. Phospholipid deacylation was measured in ionophore-treated cells prelabeled with /sup 3/H-AA. Eicosanoid release from ionophore-treated cells was monitored by radioimmunoassay. Cytoprotection was quantitated as ability to exclude trypan blue. Chemotaxis toward f-met-leu-phe was measured by leading front analysis. The results imply that metal ions attenuate ionophore cytotoxicity by blocking phospholipid deacylation and eicosanoid release. In contrast to previous reports, no correlation between AA metabolism and chemotaxis was demonstrated, suggesting that these 2 processes are not linked.

  19. L-fucose influences chemotaxis and biofilm formation in Campylobacter jejuni. (United States)

    Dwivedi, Ritika; Nothaft, Harald; Garber, Jolene; Xin Kin, Lin; Stahl, Martin; Flint, Annika; van Vliet, Arnoud H M; Stintzi, Alain; Szymanski, Christine M


    Campylobacter jejuni and Campylobacter coli are zoonotic pathogens once considered asaccharolytic, but are now known to encode pathways for glucose and fucose uptake/metabolism. For C. jejuni, strains with the fuc locus possess a competitive advantage in animal colonization models. We demonstrate that this locus is present in > 50% of genome-sequenced strains and is prevalent in livestock-associated isolates of both species. To better understand how these campylobacters sense nutrient availability, we examined biofilm formation and chemotaxis to fucose. C. jejuni NCTC11168 forms less biofilms in the presence of fucose, although its fucose permease mutant (fucP) shows no change. In a newly developed chemotaxis assay, both wild-type and the fucP mutant are chemotactic towards fucose. C. jejuni 81-176 naturally lacks the fuc locus and is unable to swim towards fucose. Transfer of the NCTC11168 locus into 81-176 activated fucose uptake and chemotaxis. Fucose chemotaxis also correlated with possession of the pathway for C. jejuni RM1221 (fuc+) and 81116 (fuc-). Systematic mutation of the NCTC11168 locus revealed that Cj0485 is necessary for fucose metabolism and chemotaxis. This study suggests that components for fucose chemotaxis are encoded within the fuc locus, but downstream signals only in fuc + strains, are involved in coordinating fucose availability with biofilm development.

  20. Quantification of chemotaxis-related alkane accumulation in Acinetobacter baylyi using Raman microspectroscopy. (United States)

    Li, Hanbing; L Martin, Francis Luke; Zhang, Dayi


    Alkanes are one of the most widespread contaminants in the natural environment, primarily as a consequence of biological synthesis and oil spills. Many indigenous microbes metabolize alkanes, and the chemotaxis and accumulation in some strains has been identified. For the first time, we apply Raman microspectroscopy to identify such chemotaxis-related affinity, and quantify the alkane concentrations via spectral alterations. Raman spectral alterations were only found for the alkane chemo-attractant bacteria Acinetobacter baylyi ADP1, not for Pseudomonas fluorescence, which exhibits limited chemotaxis towards alkane. The significant alterations were attributed to the strong chemotactic ability of A. baylyi enhancing the affinity and accumulation of alkane molecules on cell membranes or cellular internalization. Spectral fingerprints of A. baylyi significantly altered after 1-h exposure to pure alkanes (dodecane or tetradecane) and alkane mixtures (mineral oil or crude oil), but not monocyclic aromatic hydrocarbons (MAHs) or polycyclic aromatic hydrocarbons (PAHs). A semi-log linear regression relationship between Raman spectral alterations and alkane concentrations showed its feasibility in quantifying alkane concentration in environmental samples. Pure alkanes or alkane mixtures exhibited different limits of detection and regression slopes, indicating that the chemotaxis-related alkane accumulation in A. baylyi is dependent on the carbon chain length. This work provides a novel biospectroscopy approach to characterize the chemotaxis-related alkane bioaccumulation, and has immense potential for fast and high-throughput screening bacterial chemotaxis.

  1. Effects of flow and diffusion on chemotaxis studies in a microfabricated gradient generator. (United States)

    Walker, Glenn M; Sai, Jiqing; Richmond, Ann; Stremler, Mark; Chung, Chang Y; Wikswo, John P


    An understanding of chemotaxis at the level of cell-molecule interactions is important because of its relevance in cancer, immunology, and microbiology, just to name a few. This study quantifies the effects of flow on cell migration during chemotaxis in a microfluidic device. The chemotaxis gradient within the device was modeled and compared to experimental results. Chemotaxis experiments were performed using the chemokine CXCL8 under different flow rates with human HL60 promyelocytic leukemia cells expressing a transfected CXCR2 chemokine receptor. Cell trajectories were separated into x and y axis components. When the microchannel flow rates were increased, cell trajectories along the x axis were found to be significantly affected (p < 0.05). Total migration distances were not affected. These results should be considered when using similar microfluidic devices for chemotaxis studies so that flow bias can be minimized. It may be possible to use this effect to estimate the total tractile force exerted by a cell during chemotaxis, which would be particularly valuable for cells whose tractile forces are below the level of detection with standard techniques of traction-force microscopy.

  2. Different migration patterns of sea urchin and mouse sperm revealed by a microfluidic chemotaxis device.

    Directory of Open Access Journals (Sweden)

    Haixin Chang

    Full Text Available Chemotaxis refers to a process whereby cells move up or down a chemical gradient. Sperm chemotaxis is known to be a strategy exploited by marine invertebrates such as sea urchins to reach eggs efficiently in moving water. Less is understood about how or whether chemotaxis is used by mammalian sperm to reach eggs, where fertilization takes place within the confinement of a reproductive tract. In this report, we quantitatively assessed sea urchin and mouse sperm chemotaxis using a recently developed microfluidic model and high-speed imaging. Results demonstrated that sea urchin Arbacia punctulata sperm were chemotactic toward the peptide resact with high chemotactic sensitivity, with an average velocity Vx up the chemical gradient as high as 20% of its average speed (238 μm/s, while mouse sperm displayed no statistically significant chemotactic behavior in progesterone gradients, which had been proposed to guide mammalian sperm toward eggs. This work demonstrates the validity of a microfluidic model for quantitative sperm chemotaxis studies, and reveals a biological insight that chemotaxis up a progesterone gradient may not be a universal strategy for mammalian sperm to reach eggs.

  3. Automated leukocyte recognition using fuzzy divergence. (United States)

    Ghosh, Madhumala; Das, Devkumar; Chakraborty, Chandan; Ray, Ajoy K


    This paper aims at introducing an automated approach to leukocyte recognition using fuzzy divergence and modified thresholding techniques. The recognition is done through the segmentation of nuclei where Gamma, Gaussian and Cauchy type of fuzzy membership functions are studied for the image pixels. It is in fact found that Cauchy leads better segmentation as compared to others. In addition, image thresholding is modified for better recognition. Results are studied and discussed.

  4. Bovine leukocyte adhesion deficiency (BLAD): a review. (United States)

    Nagahata, Hajime


    Bovine leukocyte adhesion deficiency (BLAD) in Holstein cattle is an autosomal recessive congenital disease characterized by recurrent bacterial infections, delayed wound healing and stunted growth, and is also associated with persistent marked neutrophilia. The molecular basis of BLAD is a single point mutation (adenine to guanine) at position 383 of the CD18 gene, which caused an aspartic acid to glycine substitution at amino acid 128 (D128G) in the adhesion molecule CD18. Neutrophils from BLAD cattle have impaired expression of the beta2 integrin (CD11a,b,c/CD18) of the leukocyte adhesion molecule. Abnormalities in a wide spectrum of adherence dependent functions of leukocytes have been fully characterized. Cattle affected with BLAD have severe ulcers on oral mucous membranes, severe periodontitis, loss of teeth, chronic pneumonia and recurrent or chronic diarrhea. Affected cattle die at an early age due to the infectious complications. Holstein bulls, including carrier sires that had a mutant BLAD gene in heterozygote were controlled from dairy cattle for a decade. The control of BLAD in Holstein cattle by publishing the genotypes and avoiding the mating between BLAD carriers was found to be successful. This paper provides an overview of the genetic disease BLAD with reference to the disease in Holstein cattle.

  5. Microfluidic chip containing porous gradient for chemotaxis study (United States)

    Al-Abboodi, Aswan; Tjeung, Ricky; Doran, Pauline; Yeo, Leslie; Friend, James; Chan, Peggy


    We have developed a new porous gradient microfluidic device based on in situ Gtn-HPA/CMC-Tyr hydrogel that comprises gelatin hydroxyphenylpropionic acid (Gtn-HPA) conjugate and carboxymethyl cellulose tyramine (CMC-Tyr) conjugate. The device is fabricated using a soft lithographic technique, in which microstructures were patterned on a thin layer of polydimethylsiloxane (PDMS) using a polymeric mold. Human fibrosarcoma cells (HT1080) were employed as invasive cancer cell model. Porosity gradients were generated by flowing pore etching fluid in the gradient generator network. Results suggested that spatial control of the porosity can be obtained, which mimics the 3-dimensional microenvironment in vivo for cell-based screening applications including real time chemotaxis, cytotoxicity, and continuous drug-response monitoring. A chemoattractant gradient is then generated and cell migration is monitored in real time using fluorescence microscopy. The viability of cells was evaluated using calcien AM stain. Herein, we successfully monitored the chemotactic responses of cancer cells, confirmed the validity of using in situ porous hydrogels as a construction material for a microchemotaxis device, and demonstrated the potential of the hydrogel with tunable porosity based microfluidic device in biological experiments. This device will also be practical in controlling the chemical and mechanical properties of the surroundings during the formation of tissue engineered constructs.

  6. Spatiotemporal evolution in a (2+1)-dimensional chemotaxis model (United States)

    Banerjee, Santo; Misra, Amar P.; Rondoni, L.


    Simulations are performed to investigate the nonlinear dynamics of a (2+1)-dimensional chemotaxis model of Keller-Segel (KS) type, with a logistic growth term. Because of its ability to display auto-aggregation, the KS model has been widely used to simulate self-organization in many biological systems. We show that the corresponding dynamics may lead to steady-states, to divergencies in a finite time as well as to the formation of spatiotemporal irregular patterns. The latter, in particular, appears to be chaotic in part of the range of bounded solutions, as demonstrated by the analysis of wavelet power spectra. Steady-states are achieved with sufficiently large values of the chemotactic coefficient (χ) and/or with growth rates r below a critical value rc. For r>rc, the solutions of the differential equations of the model diverge in a finite time. We also report on the pattern formation regime, for different values of χ, r and of the diffusion coefficient D.

  7. Spatiotemporal evolution in a (2+1)-dimensional chemotaxis model

    CERN Document Server

    Banerjee, S; Rondoni, L


    Simulations are performed to investigate the nonlinear dynamics of a (2+1)-dimensional chemotaxis model of Keller-Segel (KS) type with a logistic growth term. Because of its ability to display auto-aggregation, the KS model has been widely used to simulate self-organization in many biological systems. We show that the corresponding dynamics may lead to a steady-state, divergence in a finite time as well as the formation of spatiotemporal irregular patterns. The latter, in particular, appear to be chaotic in part of the range of bounded solutions, as demonstrated by the analysis of wavelet power spectra. Steady states are achieved with sufficiently large values of the chemotactic coefficient $(\\chi)$ and/or with growth rates $r$ below a critical value $r_c$. For $r > r_c$, the solutions of the differential equations of the model diverge in a finite time. We also report on the pattern formation regime for different values of $\\chi$, $r$ and the diffusion coefficient $D$.

  8. Specific epidermal growth factor receptor autophosphorylation sites promote mouse colon epithelial cell chemotaxis and restitution. (United States)

    Yamaoka, Toshimitsu; Frey, Mark R; Dise, Rebecca S; Bernard, Jessica K; Polk, D Brent


    Upon ligand binding, epidermal growth factor (EGF) receptor (R) autophosphorylates on COOH-terminal tyrosines, generating docking sites for signaling partners that stimulate proliferation, restitution, and chemotaxis. Specificity for individual EGFR tyrosines in cellular responses has been hypothesized but not well documented. Here we tested the requirement for particular tyrosines, and associated downstream pathways, in mouse colon epithelial cell chemotactic migration. We compared these requirements to those for the phenotypically distinct restitution (wound healing) migration. Wild-type, Y992/1173F, Y1045F, Y1068F, and Y1086F EGFR constructs were expressed in EGFR(-/-) cells; EGF-induced chemotaxis or restitution were determined by Boyden chamber or modified scratch wound assay, respectively. Pharmacological inhibitors of p38, phospholipase C (PLC), Src, MEK, JNK/SAPK, phosphatidylinositol 3-kinase (PI 3-kinase), and protein kinase C (PKC) were used to block EGF-stimulated signaling. Pathway activation was determined by immunoblot analysis. Unlike wild-type EGFR, Y992/1173F and Y1086F EGFR did not stimulate colon epithelial cell chemotaxis toward EGF; Y1045F and Y1068F EGFR partially stimulated chemotaxis. Only wild-type EGFR promoted colonocyte restitution. Inhibition of p38, PLC, and Src, or Grb2 knockdown, blocked chemotaxis; JNK, PI 3-kinase, and PKC inhibitors or c-Cbl knockdown blocked restitution but not chemotaxis. All four EGFR mutants stimulated downstream signaling in response to EGF, but Y992/1173F EGFR was partially defective in PLCγ activation whereas both Y1068F and Y1086F EGFR failed to activate Src. We conclude that specific EGFR tyrosines play key roles in determining cellular responses to ligand. Chemotaxis and restitution, which have different migration phenotypes and physiological consequences, have overlapping but not identical EGFR signaling requirements.

  9. An alternative smooth particle hydrodynamics formulation to simulate chemotaxis in porous media. (United States)

    Avesani, Diego; Dumbser, Michael; Chiogna, Gabriele; Bellin, Alberto


    Chemotaxis, the microorganisms autonomous motility along or against the concentration gradients of a chemical species, is an important, yet often neglected factor controlling the transport of bacteria through saturated porous media. For example, chemotactic bacteria could enhance bioremediation by directing their own motion to residual contaminants trapped in low hydraulic conductive zones of contaminated aquifers. The aim of the present work is to develop an accurate numerical scheme to model chemotaxis in saturated porous media and other advective dominating flow systems. We propose to model chemotaxis by using a new class of meshless Lagrangian particle methods we recently developed for applications in fluid mechanics. The method is based on the Smooth Particle Hydrodynamics (SPH) formulation of (Ben Moussa et al., Int Ser Numer Math, 13(1):29-62, 2006), combined with a new Weighted Essentially Non-Oscillatory (WENO) reconstruction technique on moving point clouds in multiple space dimensions. The purpose of this new numerical scheme is to fully exploit the advantages of SPH among traditional mesh-based and mesh-free schemes and to overcome drawbacks related to the use of standard SPH for modeling chemotaxis in porous media. First, we test the new scheme against analytical reference solutions. Then, under the assumption of complete mixing at the Darcy scale, we perform two-dimensional conservative solute transport simulations under steady-state flow conditions, to show the capability of the proposed new scheme to model chemotaxis.

  10. Classification of human leukocyte antigen (HLA) supertypes

    DEFF Research Database (Denmark)

    Wang, Mingjun; Claesson, Mogens H


    Identification of new antigenic peptides, derived from infectious agents or cancer cells, which bind to human leukocyte antigen (HLA) class I and II molecules, is of importance for the development of new effective vaccines capable of activating the cellular arm of the immune response. However...... this complexity is to group thousands of different HLA molecules into several so-called HLA supertypes: a classification that refers to a group of HLA alleles with largely overlapping peptide binding specificities. In this chapter, we focus on the state-of-the-art classification of HLA supertypes including HLA...

  11. Analysis of leukocyte rolling in vivo and in vitro. (United States)

    Sperandio, Markus; Pickard, John; Unnikrishnan, Sunil; Acton, Scott T; Ley, Klaus


    Leukocyte rolling is an important step for the successful recruitment of leukocytes from blood to tissues mediated by a specialized group of glycoproteins termed selectins. Because of the dynamic process of leukocyte rolling, binding of selectins to their respective counter-receptors (selectin ligands) needs to fulfill three major requirements: (1) rapid bond formation, (2) high tensile strength, and (3) fast dissociation rates. These criteria are perfectly met by selectins, which interact with specific carbohydrate determinants on selectin ligands. This chapter describes the theoretical background, technical requirements, and analytical tools needed to quantitatively assess leukocyte rolling in vivo and in vitro. For the in vivo setting, intravital microscopy allows the observation and recording of leukocyte rolling under different physiological and pathological conditions in almost every organ. Real-time and off-line analysis tools help to assess geometric, hemodynamic, and rolling parameters. Under in vitro conditions, flow chamber assays such as parallel plate flow chamber systems have been the mainstay to study interactions between leukocytes and adhesion molecules under flow. In this setting, adhesion molecules are immobilized on plastic, in a lipid monolayer, or presented on cultured endothelial cells on the chamber surface. Microflow chambers are available for studying leukocyte adhesion in the context of whole blood and without blood cell isolation. The microscopic observation of leukocyte rolling in different in vivo and in vitro settings has significantly contributed to our understanding of the molecular mechanisms responsible for the stepwise extravasation of leukocytes into inflamed tissues.

  12. Intravital leukocyte detection using the gradient inverse coefficient of variation. (United States)

    Dong, Gang; Ray, Nilanjan; Acton, Scott T


    The problem of identifying and counting rolling leukocytes within intravital microscopy is of both theoretical and practical interest. Currently, methods exist for tracking rolling leukocytes in vivo, but these methods rely on manual detection of the cells. In this paper we propose a technique for accurately detecting rolling leukocytes based on Bayesian classification. The classification depends on a feature score, the gradient inverse coefficient of variation (GICOV), which serves to discriminate rolling leukocytes from a cluttered environment. The leukocyte detection process consists of three sequential steps: the first step utilizes an ellipse matching algorithm to coarsely identify the leukocytes by finding the ellipses with a locally maximal GICOV. In the second step, starting from each of the ellipses found in the first step, a B-spline snake is evolved to refine the leukocytes boundaries by maximizing the associated GICOV score. The third and final step retains only the extracted contours that have a GICOV score above the analytically determined threshold. Experimental results using 327 rolling leukocytes were compared to those of human experts and currently used methods. The proposed GICOV method achieves 78.6% leukocyte detection accuracy with 13.1% false alarm rate.

  13. Modulating chemotaxis of lung cancer cells by using electric fields in a microfluidic device. (United States)

    Kao, Yu-Chiu; Hsieh, Meng-Hua; Liu, Chung-Chun; Pan, Huei-Jyuan; Liao, Wei-Yu; Cheng, Ji-Yen; Kuo, Po-Ling; Lee, Chau-Hwang


    We employed direct-current electric fields (dcEFs) to modulate the chemotaxis of lung cancer cells in a microfluidic cell culture device that incorporates both stable concentration gradients and dcEFs. We found that the chemotaxis induced by a 0.5 μM/mm concentration gradient of epidermal growth factor can be nearly compensated by a 360 mV/mm dcEF. When the effect of chemical stimulation was balanced by the electrical drive, the cells migrated randomly, and the path lengths were largely reduced. We also demonstrated electrically modulated chemotaxis of two types of lung cancer cells with opposite directions of electrotaxis in this device.

  14. Symmetry breaking in navigating cells : The role of heterotrimeric and monomeric G-proteins in Dictyostelium chemotaxis

    NARCIS (Netherlands)

    Kataria, Rama


    Chemotaxis is the property of cells to migrate towards gradients of chemicals. It is a highly dynamic process that involves directional sensing, cellular polarity and cell motility. Chemotaxis is important for all organisms for many processes including, immune reponse, embryo organization and it’s a

  15. Effect of fatty acids on leukocyte function

    Directory of Open Access Journals (Sweden)

    Pompéia C.


    Full Text Available Fatty acids have various effects on immune and inflammatory responses, acting as intracellular and intercellular mediators. Polyunsaturated fatty acids (PUFAs of the omega-3 family have overall suppressive effects, inhibiting lymphocyte proliferation, antibody and cytokine production, adhesion molecule expression, natural killer cell activity and triggering cell death. The omega-6 PUFAs have both inhibitory and stimulatory effects. The most studied of these is arachidonic acid that can be oxidized to eicosanoids, such as prostaglandins, leukotrienes and thromboxanes, all of which are potent mediators of inflammation. Nevertheless, it has been found that many of the effects of PUFA on immune and inflammatory responses are not dependent on eicosanoid generation. Fatty acids have also been found to modulate phagocytosis, reactive oxygen species production, cytokine production and leukocyte migration, also interfering with antigen presentation by macrophages. The importance of fatty acids in immune function has been corroborated by many clinical trials in which patients show improvement when submitted to fatty acid supplementation. Several mechanisms have been proposed to explain fatty acid modulation of immune response, such as changes in membrane fluidity and signal transduction pathways, regulation of gene transcription, protein acylation, and calcium release. In this review, evidence is presented to support the proposition that changes in cell metabolism also play an important role in the effect of fatty acids on leukocyte functioning, as fatty acids regulate glucose and glutamine metabolism and mitochondrial depolarization.

  16. Inhibition of neutrophil and eosinophil induced chemotaxis by nedocromil sodium and sodium cromoglycate. (United States)

    Bruijnzeel, P. L.; Warringa, R. A.; Kok, P. T.; Kreukniet, J.


    1. Neutrophils and eosinophils infiltrate the airways in association with the allergen-induced late phase asthmatic reaction. Mobilization of these cells takes place via lipid-like and protein-like chemotactic factors. In this study platelet-activating factor (PAF), leukotriene B4 (LTB4), zymosan-activated serum (ZAS) and N-formyl-methionyl-leucyl-phenylalanine (FMLP) were used as illustrative examples of both groups. Chemotaxis was studied in human neutrophils and eosinophils. The inhibitory effects of nedocromil sodium and sodium cromoglycate were evaluated. 2. All chemotactic factors tested attracted neutrophils with the following rank order of activity: ZAS greater than PAF identical to FMLP identical to LTB4. Eosinophils were only mobilized by PAF, LTB4 and ZAS with the following rank order of activity: ZAS greater than PAF greater than LTB4. 3. Nedocromil sodium and sodium cromoglycate were equally active as the PAF antagonist BN 52021 in inhibiting the PAF-induced chemotaxis of neutrophils (IC50 approximately 10(-8) M). Both drugs were also equally active in inhibiting the chemotaxis of neutrophils induced by ZAS (IC50 approximately 10(-7)-10(-6) M), FMLP (IC50 approximately 10(-7) M) and LTB4 (IC50 approximately 10(-6) M). 4. Nedocromil sodium significantly inhibited the chemotaxis of eosinophils induced by PAF (IC50 approximately 10(-6) M) and LTB4 (IC50 approximately 10(-7) M). The inhibitory potency of BN 52021 was similar to that of nedocromil sodium on the PAF-induced chemotaxis of eosinophils. Sodium cromoglycate was incapable of eliciting significant inhibition of these chemotactic responses. However, sodium cromoglycate significantly inhibited the chemotaxis of eosinophils induced by ZAS (IC50 approximately 10(-7) M), whereas nedocromil sodium was ineffective. PMID:2163279

  17. Generalized Keller-Segel models of chemotaxis. Analogy with nonlinear mean field Fokker-Planck equations

    CERN Document Server

    Chavanis, Pierre-Henri


    We consider a generalized class of Keller-Segel models describing the chemotaxis of biological populations (bacteria, amoebae, endothelial cells, social insects,...). We show the analogy with nonlinear mean field Fokker-Planck equations and generalized thermodynamics. As an illustration, we introduce a new model of chemotaxis incorporating both effects of anomalous diffusion and exclusion principle (volume filling). We also discuss the analogy between biological populations described by the Keller-Segel model and self-gravitating Brownian particles described by the Smoluchowski-Poisson system.

  18. Endomorphins 1 and 2 modulate chemotaxis, phagocytosis and superoxide anion production by microglia. (United States)

    Azuma, Y; Ohura, K; Wang, P L; Shinohara, M


    We evaluate the role of endomorphins 1 and 2 on microglial functions. Endomorphins 1 and 2 blocked phagocytosis of Escherichia coli. In addition, both markedly inhibited chemotaxis toward zymosan-activated serum. In contrast, when microglia was preincubated with these endomorphins, followed by incubation with LPS before stimulation with phorbol 12-myristate 13-acetate (PMA) at 200 nM, they potentiated superoxide anion production. Furthermore, when microglia was preincubated with these endomorphins together with PMA at 20 nM, followed by stimulation with PMA at 200 nM, superoxide anion production was potentiated. These results suggest that endomorphins 1 and 2 modulate phagocytosis, chemotaxis and superoxide anion production by microglia.

  19. Asymmetric membrane filters for the removal of leukocytes from blood

    NARCIS (Netherlands)

    Bruil, A.; Aken, van W.G.; Beugeling, T.; Feijen, J.; Steneker, I.; Huisman, J.G.; Prins, H.K.


    As part of a study on the mechanisms of leukocyte filtration, the influence of pore size distribution on filter efficiency was investigated. Conventional leukocyte filters are not suitable for model studies, as these filters are composed of tightly packed synthetic fibers, with a poorly defined poro

  20. 21 CFR 864.7675 - Leukocyte peroxidase test. (United States)


    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Leukocyte peroxidase test. 864.7675 Section 864... peroxidase test. (a) Identification. A leukocyte peroxidase test is a device used to distinguish certain... peroxidase activity as evidenced by staining. The results of this test are used in the differential...

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  19. Leukocytic oxygen activation and microbicidal oxidative toxins. (United States)

    Hurst, J K; Barrette, W C


    Following a brief introduction of cellular response to stimulation comprising leukocyte activation, three major areas are discussed: (1) the neutrophil oxidase; (2) myeloperoxidase (MPO)-dependent oxidative microbicidal reactions; and (3) MPO-independent oxidative reactions. Topics included in section (A) are current views on the activation mechanism, redox composition, structural and topographic organization of the oxidase, and its respiratory products. In section (B), emphasis is placed on recent research on cidal mechanisms of HOCl, including the oxidative biochemistry of active chlorine compounds, identification of sites of lesions in bacteria, and attendant metabolic consequences. In section (C), we review the (bio)chemistry of H2O2 and .OH microbicidal reactions, with particular attention being given to addressing the controversial issue of probe methods to identify .OH radical and critical assessment of the recent proposal that MPO-independent killing arises from site-specific metal-catalyzed Fenton-type chemistry.

  20. The Pseudomonas aeruginosa chemotaxis methyltransferase CheR1 impacts on bacterial surface sampling.

    Directory of Open Access Journals (Sweden)

    Juliane Schmidt

    Full Text Available The characterization of factors contributing to the formation and development of surface-associated bacterial communities known as biofilms has become an area of intense interest since biofilms have a major impact on human health, the environment and industry. Various studies have demonstrated that motility, including swimming, swarming and twitching, seems to play an important role in the surface colonization and establishment of structured biofilms. Thereby, the impact of chemotaxis on biofilm formation has been less intensively studied. Pseudomonas aeruginosa has a very complex chemosensory system with two Che systems implicated in flagella-mediated motility. In this study, we demonstrate that the chemotaxis protein CheR1 is a methyltransferase that binds S-adenosylmethionine and transfers a methyl group from this methyl donor to the chemoreceptor PctA, an activity which can be stimulated by the attractant serine but not by glutamine. We furthermore demonstrate that CheR1 does not only play a role in flagella-mediated chemotaxis but that its activity is essential for the formation and maintenance of bacterial biofilm structures. We propose a model in which motility and chemotaxis impact on initial attachment processes, dispersion and reattachment and increase the efficiency and frequency of surface sampling in P. aeruginosa.

  1. Transient dynamic phenotypes as criteria for model discrimination: fold-change detection in Rhodobacter sphaeroides chemotaxis. (United States)

    Hamadeh, Abdullah; Ingalls, Brian; Sontag, Eduardo


    The chemotaxis pathway of the bacterium Rhodobacter sphaeroides shares many similarities with that of Escherichia coli. It exhibits robust adaptation and has several homologues of the latter's chemotaxis proteins. Recent theoretical results have correctly predicted that the E. coli output behaviour is unchanged under scaling of its ligand input signal; this property is known as fold-change detection (FCD). In the light of recent experimental results suggesting that R. sphaeroides may also show FCD, we present theoretical assumptions on the R. sphaeroides chemosensory dynamics that can be shown to yield FCD behaviour. Furthermore, it is shown that these assumptions make FCD a property of this system that is robust to structural and parametric variations in the chemotaxis pathway, in agreement with experimental results. We construct and examine models of the full chemotaxis pathway that satisfy these assumptions and reproduce experimental time-series data from earlier studies. We then propose experiments in which models satisfying our theoretical assumptions predict robust FCD behaviour where earlier models do not. In this way, we illustrate how transient dynamic phenotypes such as FCD can be used for the purposes of discriminating between models that reproduce the same experimental time-series data.

  2. Prostaglandin E₂ inhibits human lung fibroblast chemotaxis through disparate actions on different E-prostanoid receptors. (United States)

    Li, Ying-Ji; Wang, Xing-Qi; Sato, Tadashi; Kanaji, Nobuhiro; Nakanishi, Masanori; Kim, Miok; Michalski, Joel; Nelson, Amy J; Sun, Jian-Hong; Farid, Maha; Basma, Hesham; Patil, Amol; Toews, Myron L; Liu, Xiangde; Rennard, Stephen I


    The migration of fibroblasts is believed to play a key role in both normal wound repair and abnormal tissue remodeling. Prostaglandin E (PGE)(2), a mediator that can inhibit many fibroblast functions including chemotaxis, was reported to be mediated by the E-prostanoid (EP) receptor EP2. PGE(2), however, can act on four receptors. This study was designed to determine if EP receptors, in addition to EP2, can modulate fibroblast chemotaxis. Using human fetal lung fibroblasts, the expression of all four EP receptors was demonstrated by Western blotting. EP2-selective and EP4-selective agonists inhibited both chemotaxis toward fibronectin in the blindwell assay and migration in a wound-closure assay. In contrast, EP1-selective and EP3-selective agonists stimulated cell migration in both assay systems. These results were confirmed using EP-selective antagonists. The role of both EP2 and EP4 receptors in mediating the PGE(2) inhibition of chemotaxis was also confirmed by small interfering RNA suppression. Furthermore, the role of EP receptors was confirmed by blocking the expected signaling pathways. Taken together, these results demonstrate that PGE(2) can act on multiple EP receptors in human lung fibroblasts, to exert disparate effects. Alterations in EP receptor expression may have the potential to alter PGE(2) action. Targeting specific EP receptors may offer therapeutic opportunities in conditions characterized by abnormal tissue repair and remodeling.

  3. Primary Macrophage Chemotaxis Induced by Cannabinoid Receptor 2 Agonists Occurs Independently of the CB2 Receptor. (United States)

    Taylor, Lewis; Christou, Ivy; Kapellos, Theodore S; Buchan, Alice; Brodermann, Maximillian H; Gianella-Borradori, Matteo; Russell, Angela; Iqbal, Asif J; Greaves, David R


    Activation of CB2 has been demonstrated to induce directed immune cell migration. However, the ability of CB2 to act as a chemoattractant receptor in macrophages remains largely unexplored. Using a real-time chemotaxis assay and a panel of chemically diverse and widely used CB2 agonists, we set out to examine whether CB2 modulates primary murine macrophage chemotaxis. We report that of 12 agonists tested, only JWH133, HU308, L-759,656 and L-759,633 acted as macrophage chemoattractants. Surprisingly, neither pharmacological inhibition nor genetic ablation of CB2 had any effect on CB2 agonist-induced macrophage chemotaxis. As chemotaxis was pertussis toxin sensitive in both WT and CB2(-/-) macrophages, we concluded that a non-CB1/CB2, Gi/o-coupled GPCR must be responsible for CB2 agonist-induced macrophage migration. The obvious candidate receptors GPR18 and GPR55 could not mediate JWH133 or HU308-induced cytoskeletal rearrangement or JWH133-induced β-arrestin recruitment in cells transfected with either receptor, demonstrating that neither are the unidentified GPCR. Taken together our results conclusively demonstrate that CB2 is not a chemoattractant receptor for murine macrophages. Furthermore we show for the first time that JWH133, HU308, L-759,656 and L-759,633 have off-target effects of functional consequence in primary cells and we believe that our findings have wide ranging implications for the entire cannabinoid field.

  4. Chemotaxis to cyclic AMP and folic acid is mediated by different G proteins in Dictyostelium discoideum

    NARCIS (Netherlands)

    Kesbeke, Fanja; Haastert, Peter J.M. van; Wit, René J.W. de; Snaar-Jagalska, B. Ewa


    Mutant Frigid A (fgdA) of Dictyostelium discoideum is defective in a functional Gα2 subunit of a G protein and is characterized by a complete blockade of the cyclic AMP-mediated sensory transduction steps, including cyclic AMP relay, chemotaxis and the cyclic GMP response. Folic acid-mediated transm

  5. α-1 Antitrypsin regulates human neutrophil chemotaxis induced by soluble immune complexes and IL-8.

    LENUS (Irish Health Repository)

    Bergin, David A


    Hereditary deficiency of the protein α-1 antitrypsin (AAT) causes a chronic lung disease in humans that is characterized by excessive mobilization of neutrophils into the lung. However, the reason for the increased neutrophil burden has not been fully elucidated. In this study we have demonstrated using human neutrophils that serum AAT coordinates both CXCR1- and soluble immune complex (sIC) receptor-mediated chemotaxis by divergent pathways. We demonstrated that glycosylated AAT can bind to IL-8 (a ligand for CXCR1) and that AAT-IL-8 complex formation prevented IL-8 interaction with CXCR1. Second, AAT modulated neutrophil chemotaxis in response to sIC by controlling membrane expression of the glycosylphosphatidylinositol-anchored (GPI-anchored) Fc receptor FcγRIIIb. This process was mediated through inhibition of ADAM-17 enzymatic activity. Neutrophils isolated from clinically stable AAT-deficient patients were characterized by low membrane expression of FcγRIIIb and increased chemotaxis in response to IL-8 and sIC. Treatment of AAT-deficient individuals with AAT augmentation therapy resulted in increased AAT binding to IL-8, increased AAT binding to the neutrophil membrane, decreased FcγRIIIb release from the neutrophil membrane, and normalization of chemotaxis. These results provide new insight into the mechanism underlying the effect of AAT augmentation therapy in the pulmonary disease associated with AAT deficiency.

  6. Effect of heavy metal ions on neutrophil arachidonic acid metabolism and chemotaxis

    Energy Technology Data Exchange (ETDEWEB)

    Smith, D.M.; Turner, S.R.; Johnson, J.A.; Turner, R.A.


    Heavy metal ions can inhibit arachidonic acid (AA) metabolism, protect against ionophore cytotoxicity (ibid) and inhibit neutrophil chemotaxis. In this study they used Au/sup +3/, Zn/sup +2/, Cr/sup +3/, Mn/sup +2/, and Cu/sup +2/ as probes of the interrelationships among AA metabolism, ionophore-mediated cytotoxicity, and chemotaxis. Phospholipid deacylation was measured in ionophore-treated cells prelabeled with /sup 3/H-AA. Eicosanoid release from ionophore-treated cells was monitored both qualitatively by thin-layer chromatography of /sup 3/H-AA metabolities and quantitatively by radioimmunoassay. Cytoprotection was quantitated as ability to exclude trypan blue. Chemotaxis toward f-Met-Leu-Phe was measured by leading front analysis. The results imply that metal ions attenuate ionophore cytotoxicity by blocking phospholipid deacylation and eicosanoid production. In contrast to previous reports, the data obtained using Au/sup +3/ and Cu/sup +2/ demonstrates no correlation between AA metabolism and chemotaxis, suggesting that these 2 processes are not linked.

  7. Gas/liquid sensing via chemotaxis of Euglena cells confined in an isolated micro-aquarium. (United States)

    Ozasa, Kazunari; Lee, Jeesoo; Song, Simon; Hara, Masahiko; Maeda, Mizuo


    We demonstrate on-chip gas/liquid sensing by using the chemotaxis of live bacteria (Euglena gracilis) confined in an isolated micro-aquarium, and gas/liquid permeation through porous polydimethylsiloxane (PDMS). The sensing chip consisted of one closed micro-aquarium and two separated bypass microchannels along the perimeter of the micro-aquarium. Test gas/liquid and reference samples were introduced into the two individual microchannels separately, and the gas/liquid permeated through the PDMS walls and dissolved in the micro-aquarium water, resulting in a chemical concentration gradient in the micro-aquarium. By employing the closed micro-aquarium isolated from sample flows, we succeeded in measuring the chemotaxis of Euglena for a gas substance quantitatively, which cannot be achieved with the conventional flow-type or hydro-gel-type microfluidic devices. We found positive (negative) chemotaxis for CO2 concentrations below (above) 15%, with 64 ppm as the minimum concentration affecting the cells. We also observed chemotaxis for ethanol and H2O2. By supplying culture medium via the microchannels, the Euglena culture remained alive for more than 2 months. The sensing chip is thus useful for culturing cells and using them for environmental toxicity/nutrition studies by monitoring their motion.

  8. A study of blow-ups in the Keller-Segel model of chemotaxis

    CERN Document Server

    Fatkullin, Ibrahim


    We study the Keller-Segel model of chemotaxis and develop a composite particle-grid numerical method with adaptive time stepping which allows us to accurately resolve singular solutions. The numerical findings (in two dimensions) are then compared with analytical predictions regarding formation and interaction of singularities obtained via analysis of the stochastic differential equations associated with the Keller-Segel model.

  9. NemaCount: quantification of nematode chemotaxis behavior in a browser. (United States)

    O'Halloran, Damien M


    Nematodes such as Caenorhabditis elegans offer a very effective and tractable system to probe the underlying mechanisms of diverse sensory behaviors. Numerous platforms exist for quantifying nematode behavior and often require separate dependencies or software. Here I describe a novel and simple tool called NemaCount that provides a versatile solution for the quantification of nematode chemotaxis behavior. The ease of installation and user-friendly interface makes NemaCount a practical tool for measuring diverse behaviors and image features of nematodes such as C. elegans. The main advantage of NemaCount is that it operates from within a modern browser such as Google Chrome or Apple Safari. Any features that change in total number, size, shape, or angular distance between control and experimental preparations are suited to NemaCount for image analysis, while commonly used chemotaxis assays can be quantified, and statistically analyzed using a suite of functions from within NemaCount. NemaCount also offers image filtering options that allow the user to improve object detection and measurements. NemaCount was validated by examining nematode chemotaxis behavior; angular distances of locomotory tracks in C. elegans; and body lengths of Heterorhabditis bacteriophora nematodes. Apart from a modern browser, no additional software is required to operate NemaCount, making NemaCount a cheap, simple option for the analysis of nematode images and chemotaxis behavior.

  10. Identification of a Chemoreceptor in Pseudomonas aeruginosa That Specifically Mediates Chemotaxis Toward α-Ketoglutarate (United States)

    Martín-Mora, David; Ortega, Alvaro; Reyes-Darias, José A.; García, Vanina; López-Farfán, Diana; Matilla, Miguel A.; Krell, Tino


    Pseudomonas aeruginosa is an ubiquitous pathogen able to infect humans, animals, and plants. Chemotaxis was found to be associated with the virulence of this and other pathogens. Although established as a model for chemotaxis research, the majority of the 26 P. aeruginosa chemoreceptors remain functionally un-annotated. We report here the identification of PA5072 (named McpK) as chemoreceptor for α-ketoglutarate (αKG). High-throughput thermal shift assays and isothermal titration calorimetry studies (ITC) of the recombinant McpK ligand binding domain (LBD) showed that it recognizes exclusively α-ketoglutarate. The ITC analysis indicated that the ligand bound with positive cooperativity (Kd1 = 301 μM, Kd2 = 81 μM). McpK is predicted to possess a helical bimodular (HBM) type of LBD and this and other studies suggest that this domain type may be associated with the recognition of organic acids. Analytical ultracentrifugation (AUC) studies revealed that McpK-LBD is present in monomer-dimer equilibrium. Alpha-KG binding stabilized the dimer and dimer self-dissociation constants of 55 μM and 5.9 μM were derived for ligand-free and αKG-bound forms of McpK-LBD, respectively. Ligand-induced LBD dimer stabilization has been observed for other HBM domain containing receptors and may correspond to a general mechanism of this protein family. Quantitative capillary chemotaxis assays demonstrated that P. aeruginosa showed chemotaxis to a broad range of αKG concentrations with maximal responses at 500 μM. Deletion of the mcpK gene reduced chemotaxis over the entire concentration range to close to background levels and wild type like chemotaxis was recovered following complementation. Real-time PCR studies indicated that the presence of αKG does not modulate mcpK expression. Since αKG is present in plant root exudates it was investigated whether the deletion of mcpK altered maize root colonization. However, no significant changes with respect to the wild type strain

  11. Identification of a Chemoreceptor in Pseudomonas aeruginosa that specifically mediates Chemotaxis towards alpha-Ketoglutarate

    Directory of Open Access Journals (Sweden)

    David Martin-Mora


    Full Text Available Pseudomonas aeruginosa is an ubiquitous pathogen able to infect humans, animals and plants. Chemotaxis was found to be associated with the virulence of this and other pathogens. Although established as a model for chemotaxis research, the majority of the 26 P. aeruginosa chemoreceptors remain functionally un-annotated. We report here the identification of PA5072 (named McpK as chemoreceptor for -ketoglutarate (KG. High-throughput thermal shift assays and isothermal titration calorimetry studies (ITC of the recombinant McpK ligand binding domain (LBD show that it recognizes exclusively -ketoglutarate. The ITC analysis indicated that the ligand bound with positive cooperativity (Kd1=301 µM, Kd2=81 µM. McpK is predicted to possess a helical bimodular (HBM type of LBD and this and other studies suggest that this domain type may be associated with the recognition of organic acids. Analytical ultracentrifugation (AUC studies revealed that McpK-LBD is present in a monomer-dimer equilibrium. Alpha-KG binding stabilized the dimer and dimer self-dissociation constants of 55 µM and 5.9 µM were derived for ligand-free and KG-bound forms of McpK-LBD, respectively. Ligand-induced LBD dimer stabilization has been observed for other HBM domain containing receptors and may correspond to a general mechanism of this protein family. Quantitative capillary chemotaxis assays demonstrated that P. aeruginosa showed chemotaxis to a broad range of KG concentrations with maximal responses at 500 µM. Deletion of the mcpK gene reduced chemotaxis over the entire concentration range to close to background levels and wild type like chemotaxis was recovered following complementation. Real-time PCR studies indicated that the presence of KG does not modulate mcpK expression. Since KG is present in plant root exudates it was investigated whether the deletion of mcpK altered maize root colonization. However, no significant changes with respect to the wild

  12. Niflumic acid disrupts marine spermatozoan chemotaxis without impairing the spatiotemporal detection of chemoattractant gradients. (United States)

    Guerrero, Adán; Espinal, Jesús; Wood, Christopher D; Rendón, Juan M; Carneiro, Jorge; Martínez-Mekler, Gustavo; Darszon, Alberto


    In many broadcast-spawning marine organisms, oocytes release chemicals that guide conspecific spermatozoa towards them through chemotaxis. In the sea urchin Lytechinus pictus, the chemoattractant peptide speract triggers a train of fluctuations of intracellular Ca(2+) concentration in the sperm flagella. Each transient Ca(2+) elevation leads to a momentary increase in flagellar bending asymmetry, known as a chemotactic turn. Furthermore, chemotaxis requires a precise spatiotemporal coordination between the Ca(2+)-dependent turns and the form of chemoattractant gradient. Spermatozoa that perform Ca(2+)-dependent turns while swimming down the chemoattractant gradient, and conversely suppress turning events while swimming up the gradient, successfully approach the center of the gradient. Previous experiments in Strongylocentrotus purpuratus sea urchin spermatozoa showed that niflumic acid (NFA), an inhibitor of several ion channels, drastically altered the speract-induced Ca(2+) fluctuations and swimming patterns. In this study, mathematical modeling of the speract-dependent Ca(2+) signaling pathway suggests that NFA, by potentially affecting hyperpolarization-activated and cyclic nucleotide-gated channels, Ca(2+)-regulated Cl(-) channels and/or Ca(2+)-regulated K(+) channels, may alter the temporal organization of Ca(2+) fluctuations, and therefore disrupt chemotaxis. We used a novel automated method for analyzing sperm behavior and we identified that NFA does indeed disrupt chemotactic responses of L. pictus spermatozoa, although the temporal coordination between the Ca(2+)-dependent turns and the form of chemoattractant gradient is unaltered. Instead, NFA disrupts sperm chemotaxis by altering the arc length traveled during each chemotactic turning event. This alteration in the chemotactic turn trajectory disorientates spermatozoa at the termination of the turning event. We conclude that NFA disrupts chemotaxis without affecting how the spermatozoa decode

  13. Sinorhizobium meliloti chemoreceptor McpU mediates chemotaxis toward host plant exudates through direct proline sensing. (United States)

    Webb, Benjamin A; Hildreth, Sherry; Helm, Richard F; Scharf, Birgit E


    Bacterial chemotaxis is an important attribute that aids in establishing symbiosis between rhizobia and their legume hosts. Plant roots and seeds exude a spectrum of molecules into the soil to attract their bacterial symbionts. The alfalfa symbiont Sinorhizobium meliloti possesses eight chemoreceptors to sense its environment and mediate chemotaxis toward its host. The methyl accepting chemotaxis protein McpU is one of the more abundant S. meliloti chemoreceptors and an important sensor for the potent attractant proline. We established a dominant role of McpU in sensing molecules exuded by alfalfa seeds. Mass spectrometry analysis determined that a single germinating seed exudes 3.72 nmol of proline, producing a millimolar concentration near the seed surface which can be detected by the chemosensory system of S. meliloti. Complementation analysis of the mcpU deletion strain verified McpU as the key proline sensor. A structure-based homology search identified tandem Cache (calcium channels and chemotaxis receptors) domains in the periplasmic region of McpU. Conserved residues Asp-155 and Asp-182 of the N-terminal Cache domain were determined to be important for proline sensing by evaluating mutant strains in capillary and swim plate assays. Differential scanning fluorimetry revealed interaction of the isolated periplasmic region of McpU (McpU40-284) with proline and the importance of Asp-182 in this interaction. Using isothermal titration calorimetry, we determined that proline binds with a Kd (dissociation constant) of 104 μM to McpU40-284, while binding was abolished when Asp-182 was substituted by Glu. Our results show that McpU is mediating chemotaxis toward host plants by direct proline sensing.

  14. Direct sensing and signal transduction during bacterial chemotaxis toward aromatic compounds in Comamonas testosteroni. (United States)

    Huang, Zhou; Ni, Bin; Jiang, Cheng-Ying; Wu, Yu-Fan; He, Yun-Zhe; Parales, Rebecca E; Liu, Shuang-Jiang


    Micro-organisms sense and chemotactically respond to aromatic compounds. Although the existence of chemoreceptors that bind to aromatic attractants and subsequently trigger chemotaxis have long been speculated, such a chemoreceptor has not been demonstrated. In this report, we demonstrated that the chemoreceptor MCP2901 from Comamonas testosteroni CNB-1 binds to aromatic compounds and initiates downstream chemotactic signaling in addition to its ability to trigger chemotaxis via citrate binding. The function of gene MCP2901 was investigated by genetic deletion from CNB-1 and genetic complementation of the methyl-accepting chemotaxis protein (MCP)-null mutant CNB-1Δ20. Results showed that the expression of MCP2901 in the MCP-null mutant restored chemotaxis toward nine tested aromatic compounds and nine carboxylic acids. Isothermal titration calorimetry (ITC) analyses demonstrated that the ligand-binding domain of MCP2901 (MCP2901LBD) bound to citrate, and weakly to gentisate and 4-hydroxybenzoate. Additionally, ITC assays indicated that MCP2901LBD bound strongly to 2,6-dihydroxybenzoate and 2-hydroxybenzoate, which are isomers of gentisate and 4-hydroxybenzoate respectively that are not metabolized by CNB-1. Agarose-in-plug and capillary assays showed that these two molecules serve as chemoattractants for CNB-1. Through constructing membrane-like MCP2901-inserted Nanodiscs and phosphorelay activity assays, we demonstrated that 2,6-dihydroxybenzoate and 2-hydroxybenzoate altered kinase activity of CheA. This is the first evidence of an MCP binding to an aromatic molecule and triggering signal transduction for bacterial chemotaxis.

  15. Chemotaxis toward carbohydrates and peptides by mixed ruminal protozoa when fed, fasted, or incubated with polyunsaturated fatty acids. (United States)

    Diaz, H L; Karnati, S K R; Lyons, M A; Dehority, B A; Firkins, J L


    In contrast to the well-characterized chemotaxis and migratory behavior between the dorsal and ventral locations of the rumen by isotrichids, we hypothesized that chemotaxis toward soluble nutrients maintains entodiniomorphid protozoa in the particulate fraction. The objectives of these experiments were to compare the dose-responsive chemotaxis (1) toward different glucose concentrations when ruminal samples were harvested from fed versus fasted cows; (2) toward increasing concentrations of glucose compared with xylose when protozoa were harvested from a fed cow; (3) toward peptides of bacterial, protozoal, and soy origin; and (4) toward glucose when mixed ruminal protozoa were previously incubated for 0, 3, or 6h in the presence of emulsified polyunsaturated fatty acids (PUFA; Liposyn II, Hospira, Lake Forest, IL). In experiment 1, isotrichid protozoa decreased chemotaxis toward increasing glucose concentration when cows were fasted. Entodiniomorphids exhibited chemotaxis to similar concentrations of glucose as did isotrichids, but to a lesser magnitude of response. In experiment 2, xylose was chemotactic to both groups. Xylose might draw fibrolytic entodiniomorphid protozoa toward newly ingested feed. In contrast, even though isotrichids should not use xylose as an energy source, they were highly chemoattracted to xylose. In experiment 3, entodiniomorphids were not selectively chemoattracted toward bacterial or protozoal peptides compared with soy peptides. In experiment 4, despite isotrichid populations decreasing in abundance with increasing time of incubation in PUFA, chemotaxis to glucose remained unchanged. In contrast, entodiniomorphids recovered chemotaxis to glucose with increased time of PUFA incubation. Current results support isotrichid chemotaxis to sugars but also our hypothesis that a more moderate chemotaxis toward glucose and peptides explains how they swim in the fluid but pass from the rumen with the potentially digestible fraction of

  16. Harvesting the noncirculating pool of polymorphonuclear leukocytes in rats by hetastarch exchange transfusion (HET): yield and functional assessment

    Energy Technology Data Exchange (ETDEWEB)

    Williams, J.H. Jr.; Moser, K.M.; Ulich, T.; Cairo, M.S.


    Isolation of polymorphonuclear leukocytes (PMN) provides an opportunity to study PMN activity in vitro and to label PMN for study of in vivo kinetics. However, simple phlebotomy (SP) of a small animal frequently yields too few PMN for in vitro handling, while PMN harvested from an induced-peritonitis may not accurately reflect PMN in a less stimulated state. We report a novel method of harvesting PMN from the circulation of rats, using hetastarch exchange transfusion (HET), which is both time and animal sparing. HET harvested 8-fold more PMN than SP. In vitro cell function was examined with assays of adherence, chemotaxis, bacterial killing, and superoxide generation. No significant (p less than 0.05) difference was found between PMN obtained by HET and pooled-PMN obtained by SP. In vivo function was examined following labeling with indium 111-oxine. The kinetics pattern described suggested normal migratory activity when compared to previous reports. The data demonstrate that rats possess a relatively large, noncirculating pool of PMN which is readily accessible by HET.

  17. Influence of Magnetite Nanoparticles on Human Leukocyte Activity (United States)

    Džarová, Anežka; Dubničková, Martina; Závišová, Vlasta; Koneracká, Martina; Kopčanský, Peter; Gojzewski, Hubert; Timko, Milan


    Chemically synthesized magnetite particles coated by sodium oleate and PEG (MNP), and magnetosomes (MS) influence the process of phagocytosis and the metabolic activity (lysozyme and peroxidase activity) in leukocytes. Lysozyme activity is oxygen-independent liquidation mechanisms of engulfed microorganism, peroxidase activity is an oxygen-dependent mechanism. Both tested types of nanoparticles lysed leukocyte cells during incubation. MNP at concentrations of 10 and 20 μg/mL lysed almost all leukocytes and their cell viability was in the 14±0.05% range. On the other hand MS begin to influence leukocytes activity at the concentration of 1 μg/ml and this influence grows with increasing concentration up to 20 μg/ml. MS are more suitable for biological applications than MNP which are more aggressive material than MS. MS should not be used above 10 μg/mL.

  18. PI3K accelerates, but is not required for, neutrophil chemotaxis to fMLP. (United States)

    Heit, Bryan; Liu, Lixin; Colarusso, Pina; Puri, Kamal D; Kubes, Paul


    PI3K activity, resulting in the accumulation of PIP(3) along the leading edge of a chemotaxing cell, has been proposed to be an indispensable signaling event that is required for cells to undergo chemotaxis to endogenous and exogenous chemoattractants. Some studies have suggested that this might be the case for chemoattractants such as IL8, whereas chemotaxis to other stimuli, such as the bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP), might occur normally in the absence of PI3K activity. Herein, we systematically analyze the role of PI3K in mediating chemotaxis to fMLP, both in vitro and in vivo. Using short- and long-term in vitro assays, as well as an in vivo chemotaxis assay, we investigated the importance of PI3K in response to the prototypic chemoattractant fMLP. Exposure of neutrophils to fMLP induced an immediate polarization, which resulted in directional migration towards fMLP within 2-3 minutes. PI3K-inhibited cells also polarized and migrated in a directional fashion towards fMLP; however, this process was delayed by approximately 15 minutes, demonstrating that PI3K accelerates the initial response to fMLP, but an alternative pathway replaces PI3K over time. By contrast, p38-MAPK-inhibited cells, or cells lacking MK2, were unable to polarize in response to fMLP. Long-term chemotaxis assays using a pan-PI3K inhibitor, a PI3Kdelta-specific inhibitor or PI3Kgamma-knockout neutrophils, demonstrated no role for PI3K in mediating chemotaxis to fMLP, regardless of the steepness of the fMLP gradient. Similar results were observed in vivo, with PI3Kgamma(-/-) cells displaying a delayed, but otherwise normal, chemotactic response to gradients of fMLP. Together, these data demonstrate that, although PI3K can enhance early responses to the bacterial chemoattractant fMLP, it is not required for migration towards this chemoattractant.

  19. Synthesis and evaluation of chalcone derivatives as inhibitors of neutrophils' chemotaxis, phagocytosis and production of reactive oxygen species. (United States)

    Bukhari, Syed N A; Tajuddin, Yasmin; Benedict, Vannessa J; Lam, Kok W; Jantan, Ibrahim; Jalil, Juriyati; Jasamai, Malina


    Inhibitory effects on neutrophils' chemotaxis, phagocytosis and production of reactive oxygen species (ROS) are among the important targets in developing anti-inflammatory agents and immunosuppressants. Eight series of chalcone derivatives including five newly synthesized series were assessed for their inhibitory effects on chemotaxis, phagocytosis and ROS production in human polymorphonuclear neutrophils (PMNs). Inhibition of PMNs' chemotaxis and phagocytosis abilities were investigated using the Boyden chamber technique and the Phagotest kit, respectively, while ROS production was evaluated using luminol- and lucigenin-based chemiluminescence assay. The new derivatives (4d and 8d), which contain 4-methylaminoethanol functional group were active in all the assays performed. It was also observed that some of the compounds were active in inhibiting chemotaxis while others suppressed phagocytosis and ROS production. The information obtained gave new insight into chalcone derivatives with the potential to be developed as immunomodulators.

  20. Hesperidin displays relevant role in the nutrigenomic effect of orange juice on blood leukocytes in human volunteers: a randomized controlled cross-over study.

    Directory of Open Access Journals (Sweden)

    Dragan Milenkovic

    Full Text Available BACKGROUND: We previously showed, in healthy, middle-aged, moderately overweight men, that orange juice decreases diastolic blood pressure and significantly improves postprandial microvascular endothelial reactivity and that hesperidin could be causally linked to the observed beneficial effect of orange juice. The objective was to determine the effect of chronic consumption of orange juice on the gene expression profile of leukocytes in healthy volunteers and to assess to what extent hesperidin is involved in the effect of orange juice. METHODOLOGY/PRINCIPAL FINDINGS: Volunteers were included in a randomized, controlled, crossover study. Throughout three 4-week periods, volunteers consumed daily: 500 ml orange juice, 500 ml control drink plus hesperidin or 500 ml control drink and placebo. Blood samplings were performed on 10 overnight-fasted subjects after the 4-week treatment period. Global gene expression profiles were determined using human whole genome cDNA microarrays. Both orange juice and hesperidin consumption significantly affected leukocyte gene expression. Orange juice consumption induced changes in expression of, 3,422 genes, while hesperidin intake modulated the expression of 1,819 genes. Between the orange juice and hesperidin consumption groups, 1,582 regulated genes were in common. Many of these genes are implicated in chemotaxis, adhesion, infiltration and lipid transport, which is suggestive of lower recruitment and infiltration of circulating cells to vascular wall and lower lipid accumulation. CONCLUSIONS: This study shows that regular consumption of orange juice for 4 weeks alters leukocyte gene expression to an anti-inflammatory and anti-atherogenic profile, and hesperidin displays a relevant role in the genomic effect of this beverage. TRIAL REGISTRATION: NCT 00983086.

  1. Ammonia differentially suppresses the cAMP chemotaxis of anterior-like cells and prestalk cells in Dictyostelium discoideum

    Indian Academy of Sciences (India)

    Ira N Feit; Erika J Medynski; Michael J Rothrock


    A drop assay for chemotaxis to cAMP confirms that both anterior-like cells (ALC) and prestalk cells (pst cells) respond to cAMP gradients. We present evidence that the chemotactic response of both ALC and pst cells is suppressed by ammonia, but a higher concentration of ammonia is required to suppress the response in pst cells. ALC show a chemotactic response to cAMP when moving on a substratum of prespore cells in isolated slug posteriors incubated under oxygen. ALC chemotaxis on a prespore cell substratum is suppressed by the same concentration of ammonia that suppresses ALC chemotaxis on the agar substratum in drop assays. Chemotaxis suppression is mediated by the unprotonated (NH3) species of ammonia. The observed suppression, by ammonia, of ALC chemotaxis to cAMP supports our earlier hypothesis that ammonia is the tip-produced suppressor of such chemotaxis. We discuss implications of ammonia sensitivity of pst cells and ALC with regard to the movement and localization of ALC and pst cells in the slug and to the roles played by ALC in fruiting body formation. In addition, we suggest that a progressive decrease in sensitivity to ammonia is an important part of the maturation of ALC into pst cells.

  2. C-type natriuretic peptide inhibits leukocyte recruitment and platelet-leukocyte interactions via suppression of P-selectin expression (United States)

    Scotland, Ramona S.; Cohen, Marc; Foster, Paul; Lovell, Matthew; Mathur, Anthony; Ahluwalia, Amrita; Hobbs, Adrian J.


    The multifaceted process of immune cell recruitment to sites of tissue injury is key to the development of an inflammatory response and involved in the pathogenesis of numerous cardiovascular disorders. We recently identified C-type natriuretic peptide (CNP) as an important endothelium-derived mediator that regulates vascular tone and protects against myocardial ischemia/reperfusion injury. Herein, we investigated whether CNP inhibits leukocyte recruitment and platelet aggregation and thereby exerts a potential antiinflammatory influence on the blood vessel wall. We assessed the effects of CNP on leukocyte-endothelial cell interactions in mouse mesenteric postcapillary venules in vivo in animals with high basal leukocyte activation (endothelial nitric oxide synthase knockout mice, eNOS-/-) or under acute inflammatory conditions (induced by interleukin-1 or histamine). CNP suppressed basal leukocyte rolling in eNOS-/- mice in a rapid, reversible, and concentration-dependent manner. These effects of CNP were mimicked by the selective natriuretic peptide receptor-C agonist cANF4-23. CNP also suppressed leukocyte rolling induced by IL-1 or histamine, inhibited platelet-leukocyte interactions, and prevented thrombin-induced platelet aggregation of human blood. Furthermore, analysis of human umbilical vein endothelial cells, leukocytes, and platelets revealed that CNP selectively attenuates expression of P-selectin. Thus, CNP is a modulator of acute inflammation in the blood vessel wall characterized by leukocyte and platelet activation. These antiinflammatory effects appear to be mediated, at least in part, via suppression of P-selectin expression. These observations suggest that endothelial CNP might maintain an anti-atherogenic influence on the blood vessel wall and represent a target for therapeutic intervention in inflammatory cardiovascular disorders. endothelium | natriuretic peptide receptor type C | atherosclerosis | thrombosis

  3. The Vi capsular polysaccharide enables Salmonella enterica serovar typhi to evade microbe-guided neutrophil chemotaxis.

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    Tamding Wangdi


    Full Text Available Salmonella enterica serovar Typhi (S. Typhi causes typhoid fever, a disseminated infection, while the closely related pathogen S. enterica serovar Typhimurium (S. Typhimurium is associated with a localized gastroenteritis in humans. Here we investigated whether both pathogens differ in the chemotactic response they induce in neutrophils using a single-cell experimental approach. Surprisingly, neutrophils extended chemotactic pseudopodia toward Escherichia coli and S. Typhimurium, but not toward S. Typhi. Bacterial-guided chemotaxis was dependent on the presence of complement component 5a (C5a and C5a receptor (C5aR. Deletion of S. Typhi capsule biosynthesis genes markedly enhanced the chemotactic response of neutrophils in vitro. Furthermore, deletion of capsule biosynthesis genes heightened the association of S. Typhi with neutrophils in vivo through a C5aR-dependent mechanism. Collectively, these data suggest that expression of the virulence-associated (Vi capsular polysaccharide of S. Typhi obstructs bacterial-guided neutrophil chemotaxis.

  4. The Vi capsular polysaccharide enables Salmonella enterica serovar typhi to evade microbe-guided neutrophil chemotaxis. (United States)

    Wangdi, Tamding; Lee, Cheng-Yuk; Spees, Alanna M; Yu, Chenzhou; Kingsbury, Dawn D; Winter, Sebastian E; Hastey, Christine J; Wilson, R Paul; Heinrich, Volkmar; Bäumler, Andreas J


    Salmonella enterica serovar Typhi (S. Typhi) causes typhoid fever, a disseminated infection, while the closely related pathogen S. enterica serovar Typhimurium (S. Typhimurium) is associated with a localized gastroenteritis in humans. Here we investigated whether both pathogens differ in the chemotactic response they induce in neutrophils using a single-cell experimental approach. Surprisingly, neutrophils extended chemotactic pseudopodia toward Escherichia coli and S. Typhimurium, but not toward S. Typhi. Bacterial-guided chemotaxis was dependent on the presence of complement component 5a (C5a) and C5a receptor (C5aR). Deletion of S. Typhi capsule biosynthesis genes markedly enhanced the chemotactic response of neutrophils in vitro. Furthermore, deletion of capsule biosynthesis genes heightened the association of S. Typhi with neutrophils in vivo through a C5aR-dependent mechanism. Collectively, these data suggest that expression of the virulence-associated (Vi) capsular polysaccharide of S. Typhi obstructs bacterial-guided neutrophil chemotaxis.

  5. Metabolism-independent chemotaxis of Pseudomonas sp.strain WBC-3 toward aromatic compounds

    Institute of Scientific and Technical Information of China (English)

    ZHANG Junjie; XIN Yufeng; LIU Hong; WANG Shujun; ZHOU Ningyi


    Pseudomonas sp. Strain WBC-3 utilized methyl parathion or para-nitrophenol (PNP) as the sole source of carbon, nitrogen, andenergy, and methyl parathion hydrolase had been previously characterized. Its chemotactic behaviors to aromatics were investigated.The results indicated that strain WBC-3 was attracted to multiple aromatic compounds, including metabolizable or transformablesubstrates PNP, 4-nitrocatehol, and hydroquinone. Disruption of PNP catabolic genes had no effect on its chemotactic behaviors with the same substrates, indicating that the chemotactic response in this swain was metabolism-independent. Furthermore, it was shownthat strain WBC-3 had a constitutive β-ketoadipate chemotaxis system that responded to a broad range of aromatic compounds, whichwas different from the inducible β-ketoadipate chemotaxis described in other Pseudomonas signs.

  6. Genomic signatures characterize leukocyte infiltration in myositis muscles

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    Zhu Wei


    Full Text Available Abstract Background Leukocyte infiltration plays an important role in the pathogenesis and progression of myositis, and is highly associated with disease severity. Currently, there is a lack of: efficacious therapies for myositis; understanding of the molecular features important for disease pathogenesis; and potential molecular biomarkers for characterizing inflammatory myopathies to aid in clinical development. Methods In this study, we developed a simple model and predicted that 1 leukocyte-specific transcripts (including both protein-coding transcripts and microRNAs should be coherently overexpressed in myositis muscle and 2 the level of over-expression of these transcripts should be correlated with leukocyte infiltration. We applied this model to assess immune cell infiltration in myositis by examining mRNA and microRNA (miRNA expression profiles in muscle biopsies from 31 myositis patients and 5 normal controls. Results Several gene signatures, including a leukocyte index, type 1 interferon (IFN, MHC class I, and immunoglobulin signature, were developed to characterize myositis patients at the molecular level. The leukocyte index, consisting of genes predominantly associated with immune function, displayed strong concordance with pathological assessment of immune cell infiltration. This leukocyte index was subsequently utilized to differentiate transcriptional changes due to leukocyte infiltration from other alterations in myositis muscle. Results from this differentiation revealed biologically relevant differences in the relationship between the type 1 IFN pathway, miR-146a, and leukocyte infiltration within various myositis subtypes. Conclusions Results indicate that a likely interaction between miR-146a expression and the type 1 IFN pathway is confounded by the level of leukocyte infiltration into muscle tissue. Although the role of miR-146a in myositis remains uncertain, our results highlight the potential benefit of deconvoluting the

  7. Role of chemotaxis in the transport of bacteria through saturated porous media (United States)

    Ford, R.M.; Harvey, R.W.


    Populations of chemotactic bacteria are able to sense and respond to chemical gradients in their surroundings and direct their migration toward increasing concentrations of chemicals that they perceive to be beneficial to their survival. It has been suggested that this phenomenon may facilitate bioremediation processes by bringing bacteria into closer proximity to the chemical contaminants that they degrade. To determine the significance of chemotaxis in these processes it is necessary to quantify the magnitude of the response and compare it to other groundwater processes that affect the fate and transport of bacteria. We present a systematic approach toward quantifying the chemotactic response of bacteria in laboratory scale experiments by starting with simple, well-defined systems and gradually increasing their complexity. Swimming properties of individual cells were assessed from trajectories recorded by a tracking microscope. These properties were used to calculate motility and chemotaxis coefficients of bacterial populations in bulk aqueous media which were compared to experimental results of diffusion studies. Then effective values of motility and chemotaxis coefficients in single pores, pore networks and packed columns were analyzed. These were used to estimate the magnitude of the chemotactic response in porous media and to compare with dispersion coefficients reported in the field. This represents a compilation of many studies over a number of years. While there are certainly limitations with this approach for ultimately quantifying motility and chemotaxis in granular aquifer media, it does provide insight into what order of magnitude responses are possible and which characteristics of the bacteria and media are expected to be important. ?? 2006 Elsevier Ltd. All rights reserved.

  8. On blowup dynamics in the Keller-Segel model of chemotaxis

    CERN Document Server

    Dejak, S I; Lushnikov, P M; Sigal, I M


    We investigate the (reduced) Keller-Segel equations modeling chemotaxis of bio-organisms. We present a formal derivation and partial rigorous results of the blowup dynamics of solution of these equations describing the chemotactic aggregation of the organisms. Our results are confirmed by numerical simulations and the formula we derive coincides with the formula of Herrero and Vel\\'{a}zquez for specially constructed solutions.

  9. Chemotaxis of Spirochaeta aurantia: involvement of membrane potential in chemosensory signal transduction.


    Goulbourne, E A; Greenberg, E P


    The effects of valinomycin and nigericin on sugar chemotaxis in Spirochaeta aurantia were investigated by using a quantitative capillary assay, and the fluorescent cation, 3,3'-dipropyl-2,2'-thiodicarbocyanine iodide was used as a probe to study effects of chemoattractants on membrane potential. Addition of a chemoattractant, D-xylose, to cells in either potassium or sodium phosphate buffer resulted in a transient membrane depolarization. In the presence of valinomycin, the membrane potential...

  10. Modeling ant foraging: A chemotaxis approach with pheromones and trail formation. (United States)

    Amorim, Paulo


    We consider a continuous mathematical description of a population of ants and simulate numerically their foraging behavior using a system of partial differential equations of chemotaxis type. We show that this system accurately reproduces observed foraging behavior, especially spontaneous trail formation and efficient removal of food sources. We show through numerical experiments that trail formation is correlated with efficient food removal. Our results illustrate the emergence of trail formation from simple modeling principles.

  11. Transport genes and chemotaxis in Laribacter hongkongensis: a genome-wide analysis

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    Lau Susanna KP


    Full Text Available Abstract Background Laribacter hongkongensis is a Gram-negative, sea gull-shaped rod associated with community-acquired gastroenteritis. The bacterium has been found in diverse freshwater environments including fish, frogs and drinking water reservoirs. Using the complete genome sequence data of L. hongkongensis, we performed a comprehensive analysis of putative transport-related genes and genes related to chemotaxis, motility and quorum sensing, which may help the bacterium adapt to the changing environments and combat harmful substances. Results A genome-wide analysis using Transport Classification Database TCDB, similarity and keyword searches revealed the presence of a large diversity of transporters (n = 457 and genes related to chemotaxis (n = 52 and flagellar biosynthesis (n = 40 in the L. hongkongensis genome. The transporters included those from all seven major transporter categories, which may allow the uptake of essential nutrients or ions, and extrusion of metabolic end products and hazardous substances. L. hongkongensis is unique among closely related members of Neisseriaceae family in possessing higher number of proteins related to transport of ammonium, urea and dicarboxylate, which may reflect the importance of nitrogen and dicarboxylate metabolism in this assacharolytic bacterium. Structural modeling of two C4-dicarboxylate transporters showed that they possessed similar structures to the determined structures of other DctP-TRAP transporters, with one having an unusual disulfide bond. Diverse mechanisms for iron transport, including hemin transporters for iron acquisition from host proteins, were also identified. In addition to the chemotaxis and flagella-related genes, the L. hongkongensis genome also contained two copies of qseB/qseC homologues of the AI-3 quorum sensing system. Conclusions The large number of diverse transporters and genes involved in chemotaxis, motility and quorum sensing suggested that the bacterium may

  12. The Singular Limit of a Chemotaxis-Growth System with General Initial Data

    CERN Document Server

    Alfaro, Matthieu


    We study the singular limit of a system of partial differential equations which is a model for an aggregation of amoebae subjected to three effects: diffusion, growth and chemotaxis. The limit problem involves motion by mean curvature together with a nonlocal drift term. We consider rather general initial data. We prove a generation of interface property and study the motion of interfaces. We also obtain an optimal estimate of the thickness and the location of the transition layer that develops.

  13. A population-level model from the microscopic dynamics in Escherichia coli chemotaxis via Langevin approximation

    Institute of Scientific and Technical Information of China (English)

    He Zhuo-Ran; Wu Tai-Lin; Ouyang Qi; Tu Yu-Hai


    Recent extensive studies of Escherichia coli (E.coli) chemotaxis have achieved a deep understanding of its microscopic control dynamics.As a result,various quantitatively predictive models have been developed to describe the chemotactic behavior of E.coli motion.However,a population-level partial differential equation (PDE) that rationally incorporates such microscopic dynamics is still insufficient.Apart from the traditional Keller-Segel (K-S) equation,many existing population-level models developed from the microscopic dynamics are integro-PDEs.The difficulty comes mainly from cell tumbles which yield a velocity jumping process.Here,we propose a Langevin approximation method that avoids such a difficulty without appreciable loss of precision.The resulting model not only quantitatively reproduces the results of pathway-based single-cell simulators,but also provides new inside information on the mechanism of E.coli chemotaxis.Our study demonstrates a possible alternative in establishing a simple population-level model that allows for the complex microscopic mechanisms in bacterial chemotaxis.

  14. Design and diversity in bacterial chemotaxis: a comparative study in Escherichia coli and Bacillus subtilis.

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    Christopher V Rao


    Full Text Available Comparable processes in different species often involve homologous genes. One question is whether the network structure, in particular the feedback control structure, is also conserved. The bacterial chemotaxis pathways in E. coli and B. subtilis both regulate the same task, namely, excitation and adaptation to environmental signals. Both pathways employ many orthologous genes. Yet how these orthologs contribute to network function in each organism is different. To investigate this problem, we propose what is to our knowledge the first computational model for B. subtilis chemotaxis and compare it to previously published models for chemotaxis in E. coli. The models reveal that the core control strategy for signal processing is the same in both organisms, though in B. subtilis there are two additional feedback loops that provide an additional layer of regulation and robustness. Furthermore, the network structures are different despite the similarity of the proteins in each organism. These results demonstrate the limitations of pathway inferences based solely on homology and suggest that the control strategy is an evolutionarily conserved property.

  15. Chemotaxis study using optical tweezers to observe the strength and directionality of forces of Leishmania amazonensis (United States)

    Pozzo, Liliana d. Y.; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz C.; Ayres, Diana C.; Giorgio, Selma; Cesar, Carlos L.


    The displacements of a dielectric microspheres trapped by an optical tweezers (OT) can be used as a force transducer for mechanical measurements in life sciences. This system can measure forces on the 50 femto Newtons to 200 pico Newtons range, of the same order of magnitude of a typical forces induced by flagellar motion. The process in which living microorganisms search for food and run away from poison chemicals is known is chemotaxy. Optical tweezers can be used to obtain a better understanding of chemotaxy by observing the force response of the microorganism when placed in a gradient of attractors and or repelling chemicals. This report shows such observations for the protozoa Leishmania amazomenzis, responsible for the leishmaniasis, a serious tropical disease. We used a quadrant detector to monitor the movement of the protozoa for different chemicals gradient. This way we have been able to observe both the force strength and its directionality. The characterization of the chemotaxis of these parasites can help to understand the infection mechanics and improve the diagnosis and the treatments employed for this disease.

  16. Observing Chemotaxis in Vibrio fischeri Using Soft Agar Assays in an Undergraduate Microbiology Laboratory

    Directory of Open Access Journals (Sweden)

    Cindy R. DeLoney-Marino


    Full Text Available Chemotaxis, the directed movement of cells towards or away from a chemical, is both an exciting and complicated behavior observed in many bacterial species. Attempting to adequately visualize or demonstrate the chemotaxic response of bacteria in the classroom is difficult at best, with good models to illustrate the concept lacking. The BSL-1 marine bacterium Vibrio fischeri (a.k.a. Aliivibrio fischeri is easy to culture, making it an ideal candidate for experiments in an undergraduate microbiology course. A number of chemoattractants for V. fischeri have been identified, including a variety of sugars, nucleosides, and amino acids (1, 2. Below presents how the soft agar-based chemotaxis assay can be implemented in the undergraduate laboratory. As bacterial cells migrate towards one or more attractants in soft agar, students can directly observe the chemotaxic behavior of V. fischeri without the need to learn complicated techniques or use specialized equipment. Once the bands of bacterial cells are observed, the migration can then be disrupted by the addition of excess attractant to the soft agar, thereby visualizing what happens once cells are no longer in a gradient of attractant. In addition, soft agar plates lacking attractants can be used to visualize the random movements of bacterial cells that are non-chemotaxing. These exercises can be used in the microbiology laboratory to help students understand the complex behavior of bacterial chemotaxis.

  17. Self-organization of the Escherichia coli chemotaxis network imaged with super-resolution light microscopy.

    Directory of Open Access Journals (Sweden)

    Derek Greenfield


    Full Text Available The Escherichia coli chemotaxis network is a model system for biological signal processing. In E. coli, transmembrane receptors responsible for signal transduction assemble into large clusters containing several thousand proteins. These sensory clusters have been observed at cell poles and future division sites. Despite extensive study, it remains unclear how chemotaxis clusters form, what controls cluster size and density, and how the cellular location of clusters is robustly maintained in growing and dividing cells. Here, we use photoactivated localization microscopy (PALM to map the cellular locations of three proteins central to bacterial chemotaxis (the Tar receptor, CheY, and CheW with a precision of 15 nm. We find that cluster sizes are approximately exponentially distributed, with no characteristic cluster size. One-third of Tar receptors are part of smaller lateral clusters and not of the large polar clusters. Analysis of the relative cellular locations of 1.1 million individual proteins (from 326 cells suggests that clusters form via stochastic self-assembly. The super-resolution PALM maps of E. coli receptors support the notion that stochastic self-assembly can create and maintain approximately periodic structures in biological membranes, without direct cytoskeletal involvement or active transport.

  18. A diffusive virus infection dynamic model with nonlinear functional response, absorption effect and chemotaxis (United States)

    Wang, Wei; Ma, Wanbiao; Lai, Xiulan


    From a biological perspective, a diffusive virus infection dynamic model with nonlinear functional response, absorption effect and chemotaxis is proposed. In the model, the diffusion of virus consists of two parts, the random diffusion and the chemotactic movement. The chemotaxis flux of virus depends not only on their own density, but also on the density of infected cells, and the density gradient of infected cells. The well posedness of the proposed model is deeply investigated. For the proposed model, the linear stabilities of the infection-free steady state E0 and the infection steady state E* are extensively performed. We show that the threshold dynamics can be expressed by the basic reproduction number R0 of the model without chemotaxis. That is, the infection-free steady state E0 is globally asymptotically stable if R0 virus is uniformly persistent if R0 > 1. In addition, we use the cross iteration method and the Schauder's fixed point theorem to prove the existence of travelling wave solutions connecting the infection-free steady state E0 and the infection steady state E* by constructing a pair of upper-lower solutions. At last, numerical simulations are presented to confirm theoretical findings.

  19. Cloning, expression, cellular distribution, and role in chemotaxis of a C5a receptor in rainbow trout: the first identification of a C5a receptor in a nonmammalian species (United States)

    Boshra, Hani; Li, Jun; Peters, Rodney; Hansen, John; Matlapudi, Anjan; Sunyer, J. Oriol


    C3a, C4a, and C5a anaphylatoxins generated during complement activation play a key role in inflammation. C5a is the most potent of the three anaphylatoxins in eliciting biological responses. The effects of C5a are mediated by its binding to C5a receptor (C5aR, CD88). To date, C5aR has only been identified and cloned in mammalian species, and its evolutionary history remains ill-defined. To gain insights into the evolution, conserved structural domains, and functions of C5aR, we have cloned and characterized a C5aR in rainbow trout, a teleost fish. The isolated cDNA encoded a 350-aa protein that showed the highest sequence similarity to C5aR from other species. Genomic analysis revealed the presence of one continuous exon encoding the entire open reading frame. Northern blot analysis showed significant expression of the trout C5a receptor (TC5aR) message in PBLs and kidney. Flow cytometric analysis showed that two Abs generated against two different areas of the extracellular N-terminal region of TC5aR positively stained the same leukocyte populations from PBLs. B lymphocytes and granulocytes comprised the majority of cells recognized by the anti-TC5aR. More importantly, these Abs inhibited chemotaxis of PBLs toward a chemoattractant fraction purified from complement-activated trout serum. Our data suggest that the split between C5aR and C3aR from a common ancestral molecule occurred before the emergence of teleost fish. Moreover, we demonstrate that the overall structure of C5aR as well as its role in chemotaxis have remained conserved for >300 million years.

  20. Expression of β2-integrin on leukocytes in liver cirrhosis

    Institute of Scientific and Technical Information of China (English)

    Anatol Panasiuk; Janusz Zak; Elzbieta Maciorkowska; Bozena Panasiuk; Danuta Prokopowicz


    AIM: To analyze β2-integrin expression on blood leukocytes in liver cirrhosis.METHODS: In 40 patients with liver cirrhosis and 20healthy individuals, the evaluation of expression of CD11a (LFA-1α), CD11b (Mac-1α), CD11c (αX) and CD49d (VLA-4α) on peripheral blood leukocytes was performed using flow cytometry. The analysis was carried out in groups of patients divided into B and C according to Child-Pugh's classification.RESULTS: An increased CD11a, CD11b, CD11c and CD49d integrin expression was observed on peripheral blood leukocytes in liver cirrhosis. The integrin levels were elevated as the advancement of liver failure progressed. The highest expression of integrins occurred predominantly on monocytes. A slight expression of VLA-4 was found on lymphocytes and granulocytes and it increased together with liver failure. A positive correlation was noted between median intensity of fluorescence (MIF) expression on polymorphonuclear cells of CD11a and CD11c and CD49d (r = 0.42, P < 0.01; r = 053, P < 0.01, respectively) in liver cirrhosis stage C. However,no correlation was observed between integrin expression on leukocytes. The concentrations of sICAM-1, sVCAM-1,and TNFα, were significantly elevated in liver cirrhosis.CONCLUSION: β2-integrin expression on leukocytes increases in liver cirrhosis decompensated as the stage of liver failure increases, which is a result of permanent activation of leukocytes circulating through the inflamed liver environment. β2-integrin expression on circulating leukocytes can intensify liver cirrhosis.

  1. Identification of Archaea-specific chemotaxis proteins which interact with the flagellar apparatus

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    Müller Judith


    Full Text Available Abstract Background Archaea share with bacteria the ability to bias their movement towards more favorable locations, a process known as taxis. Two molecular systems drive this process: the motility apparatus and the chemotaxis signal transduction system. The first consists of the flagellum, the flagellar motor, and its switch, which allows cells to reverse the rotation of flagella. The second targets the flagellar motor switch in order to modulate the switching frequency in response to external stimuli. While the signal transduction system is conserved throughout archaea and bacteria, the archaeal flagellar apparatus is different from the bacterial one. The proteins constituting the flagellar motor and its switch in archaea have not yet been identified, and the connection between the bacterial-like chemotaxis signal transduction system and the archaeal motility apparatus is unknown. Results Using protein-protein interaction analysis, we have identified three proteins in Halobacterium salinarum that interact with the chemotaxis (Che proteins CheY, CheD, and CheC2, as well as the flagella accessory (Fla proteins FlaCE and FlaD. Two of the proteins belong to the protein family DUF439, the third is a HEAT_PBS family protein. In-frame deletion strains for all three proteins were generated and analyzed as follows: a photophobic responses were measured by a computer-based cell tracking system b flagellar rotational bias was determined by dark-field microscopy, and c chemotactic behavior was analyzed by a swarm plate assay. Strains deleted for the HEAT_PBS protein or one of the DUF439 proteins proved unable to switch the direction of flagellar rotation. In these mutants, flagella rotate only clockwise, resulting in exclusively forward swimming cells that are unable to respond to tactic signals. Deletion of the second DUF439 protein had only minimal effects. HEAT_PBS proteins could be identified in the chemotaxis gene regions of all motile haloarchaea

  2. Attempted Depletion of Passenger Leukocytes by Irradiation in Pigs

    Directory of Open Access Journals (Sweden)

    Hao-Chih Tai


    Full Text Available Allograft/xenograft rejection is associated with “passenger leukocyte” migration from the organ into recipient lymph nodes. In Study 1, we attempted to deplete leukocytes from potential kidney “donor” pigs, using two regimens of total body irradiation. A dose of 700 cGy was administered, followed by either 800 cGy (“low-dose” or 1,300 cGy (“high dose” with the kidneys shielded. Neither regimen was entirely successful in depleting all leukocytes, although remaining T and 8 cell numbers were negligible. Study 2 was aimed at providing an indication of whether near-complete depletion of leukocytes had any major impact on kidney allograft survival. In non-immunosuppressed recipient pigs, survival of a kidney from a donor that received high-dose irradiation was compared with that of a kidney taken from a non-irradiated donor. Kidney graft survival was 9 and 7 days, respectively, suggesting that depletion had little impact on graft survival. The lack of effect may have been related to (i inadequate depletion of passenger leukocytes, thus not preventing a direct T cell response, (ii the presence of dead or dying leukocytes (antigens, thus not preventing an indirect T cell response, or (iii constitutive expression of MHC class II and B7 molecules on the porcine vascular endothelium, activating recipient T cells.

  3. Crossing the Vascular Wall: Common and Unique Mechanisms Exploited by Different Leukocyte Subsets during Extravasation

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    Michael Schnoor


    Full Text Available Leukocyte extravasation is one of the essential and first steps during the initiation of inflammation. Therefore, a better understanding of the key molecules that regulate this process may help to develop novel therapeutics for treatment of inflammation-based diseases such as atherosclerosis or rheumatoid arthritis. The endothelial adhesion molecules ICAM-1 and VCAM-1 are known as the central mediators of leukocyte adhesion to and transmigration across the endothelium. Engagement of these molecules by their leukocyte integrin receptors initiates the activation of several signaling pathways within both leukocytes and endothelium. Several of such events have been described to occur during transendothelial migration of all leukocyte subsets, whereas other mechanisms are known only for a single leukocyte subset. Here, we summarize current knowledge on regulatory mechanisms of leukocyte extravasation from a leukocyte and endothelial point of view, respectively. Specifically, we will focus on highlighting common and unique mechanisms that specific leukocyte subsets exploit to succeed in crossing endothelial monolayers.

  4. Role of VASP phosphorylation for the regulation of microglia chemotaxis via the regulation of focal adhesion formation/maturation. (United States)

    Lee, S; Chung, C Y


    Microglia activation and migration are known to play crucial roles for the response to brain injuries. Extracellular ADP was reported to induce microglia chemotaxis and membrane ruffles through P2Y12 receptor. In this study, we examined the role of VASP phosphorylation in ADP-induced microglia chemotaxis and membrane ruffle formation. ADP stimulation transiently increased intracellular cAMP level, VASP phosphorylation at Ser153, membrane ruffle formation, and chemotaxis. PKA inhibitor effectively inhibited VASP phosphorylation and chemotaxis, indicating that P2Y12-mediated activation of PKA and subsequent VASP phosphorylation are involved in the regulation of microglia chemotaxis. Forskolin and okadaic acid induced sustained VASP phosphorylation at a high level, causing a significant reduction of the retraction of membrane ruffles and chemotaxis. In forskolin- or okadaic acid-treated cells, phosphorylated VASP remained at the membrane cortex, and size and number of mature focal adhesions were not increased, indicating that prolonged phosphorylation of VASP could inhibit transformation of focal complexes into focal adhesions. VASP knockdown cells showed markedly reduced frequency and distance of membrane ruffling upon ADP stimulation, reinforcing the idea that VASP is required for the ruffle formation. Cells expressing GFP-VASP(S153A) also showed a significant reduction of protrusion distance during ruffle formation, but the frequency and the distance of retraction were not affected by FSK at all. This result suggests that dephosphorylation of VASP might be required for the growth of adhesion strength during membrane retraction. Our results suggest that VASP phosphorylation by PKA plays an important role in membrane ruffle formation and chemotaxis via the regulation of focal adhesion formation/maturation.

  5. Improving diagnosis of appendicitis. Early autologous leukocyte scanning. (United States)

    DeLaney, A R; Raviola, C A; Weber, P N; McDonald, P T; Navarro, D A; Jasko, I


    A prospective nonrandomized study investigating the accuracy and utility of autologous leukocyte scanning in the diagnosis of apendicitis was performed. One hundred patients in whom the clinical diagnosis of appendicitis was uncertain underwent indium 111 oxyquinoline labelling of autologous leukocytes and underwent scanning 2 hours following reinjection. Of 32 patients with proved appendicitis, three scans revealed normal results (false-negative rate, 0.09). Of 68 patients without appendicitis, three scans had positive results (false-positive rate, 0.03; sensitivity, 0.91; specificity, 0.97; predictive value of positive scan, 0.94; predictive value of negative scan, 0.96; and overall accuracy, 0.95). Scan results altered clinical decisions in 19 patients. In 13 cases, the scan produced images consistent with diagnoses other than appendicitis, expediting appropriate management. Early-imaging111 In oxyquinoline autologous leukocyte scanning is a practical and highly accurate adjunct for diagnosing appendicitis.

  6. Leukocyte depletion during CPB: effects on inflammation and lung function. (United States)

    de Amorim, Célio Gomes; Malbouisson, Luiz Marcelo Sá; da Silva, Francisco Costa; Fiorelli, Alfredo Inácio; Murakami, Caroline Kameio Fernandes; Carmona, Maria José Carvalho


    Cardiopulmonary bypass (CPB) is related to inflammatory response and pulmonary dysfunction. The aim of this study was to evaluate the effects of CPB leukocyte filtration on inflammation and lung function after coronary artery bypass grafting (CABG). A prospective randomized study was performed to compare CABG patients undergoing CPB leukocyte filtration (n = 9) or standard CPB (n = 11). Computed tomography, oxygenation, leukocyte count, hemodynamic data, PaO2/FiO2, shunt fraction, interleukins, elastase, and myeloperoxidase were evaluated. Data were analyzed using two-factor ANOVA for repeated measurements. The filtered group showed lower neutrophil counts up to 50 min of CPB, lower shunt fraction up to 6 h after surgery, and lower levels of IL-10 at the end of surgery (p CPB results in neutrophil sequestration by a short time, decreased IL-10 serum levels, and lower worsening of lung function only temporarily.

  7. 精子趋化运动的研究近况%Current Advances in Sperm Chemotaxis Research

    Institute of Scientific and Technical Information of China (English)



    精子趋化作用具有重要的生理功能,体现在这种趋化过程促使大量的精子到达受精部位,从而实现精子与卵子的相遇、顶体反应的发生及精卵融合.近年,人们研究发现精子在趋化运动存在一种新的运动模式 (turn-and-straight 模式).同时,在信号转导方面认为 CatSper 就是孕酮在精子膜上的受体,并参与信号的跨膜转导.%Sperm chemotaxis plays an important physiological role and guides a large number of spermatozoa in their journey towards the egg , further achieving sperm-egg meet, acrosome reaction and sperm-egg fusion. Recently, scientists have found a new movement pattern , turn-and-straight model, guiding the sperm chemotaxis. Meanwhile, it has been believed that CatSper is the membrane receptor for progesterone on the sperm. This review introduces the recent studies on sperm chemotaxis, including the discovery of sperm chemotaxis , and the chemoattractants, movement patterns and molecular mechanisms that are relevant to sperm chemotaxis .

  8. Impact of fluorochrome stains used to study bacterial transport in shallow aquifers on motility and chemotaxis of Pseudomonas species. (United States)

    Toepfer, J Amanda; Ford, Roseanne M; Metge, David; Harvey, Ronald W


    One of the most common methods of tracking movement of bacteria in groundwater environments involves a priori fluorescent staining. A major concern in using these stains to label bacteria in subsurface injection-and-recovery studies is the effect they may have on the bacterium's transport properties. Previous studies investigated the impact of fluorophores on bacterial surface properties (e.g. zeta potential). However, no previous study has looked at the impact of fluorescent staining on swimming speed and chemotaxis. It was found that DAPI lowered the mean population swimming speed of Pseudomonas putida F1 by 46% and Pseudomonas stutzeri by 55%. DAPI also inhibited the chemotaxis in both strains. The swimming speeds of P. putida F1 and P. stutzeri were diminished slightly by CFDA/SE, but not to a statistically significant extent. CFDA/SE had no effect on chemotaxis of either strain to acetate. SYBR(®) Gold had no effect on swimming speed or the chemotactic response to acetate for either strain. This research indicates that although DAPI may not affect sorption to grain surfaces, it adversely affects other potentially important transport properties such as swimming and chemotaxis. Consequently, bacterial transport studies conducted using DAPI are biased to nonchemotactic conditions and do not appear to be suitable for monitoring the effect of chemotaxis on bacterial transport in shallow aquifers.

  9. The Effect of Hemiscorpius lepturus (Scorpionida: Hemiscorpiidae Venom on Leukocytes and the Leukocyte Subgroups in Peripheral Blood of Rat

    Directory of Open Access Journals (Sweden)

    Mehri Ghafourian


    Full Text Available Background: The aim of this study was to investigate the effect of Hemiscorpius lepturus venom on leukocytes and the leukocyte subgroups in peripheral blood of rat.Methods: In this experimental study, sixty N-Mari rats were divided into three groups of 20 rats. Then the rats in each group were divided into four subgroups based on the blood sampling time that was 2, 6, 24 and 48 hours after the venom injection, respectively. The control group did not receive anything, however, the first and the second ex­perimental groups received 0.1 and 0.01mg/kg of venom, subcutaneously. In accordance with a designated four sam­pling times, the blood sampling was carried out in three groups. After RBC lysis, the leukocytes and leukocyte sub­populations were determined and counted using appropriate hematological standard methods.Results: The leukocyte and the neutrophil count at two (P<0.05, six (P<0.01 and 24 (P<0.05 hours after the venom injection showed a significant decline compared with the control group, this decrease was significant at the dose of 0.1 mg/kg until 48 hours after the venom injection (P<0.05. The lymphocyte count showed a significant decline throughout the all hours of the experiment, compared with the control group (P<0.05.Conclusion: Leukocytes are probably affected by the cytotoxicity effect of the H. lepturus venom in a dose-dependent manner. This could be a wakeup call for the medical staff to perform quick and accurate treatment in the least time possible.

  10. Contact-inhibited chemotaxis in de novo and sprouting blood-vessel growth.

    Directory of Open Access Journals (Sweden)

    Roeland M H Merks

    Full Text Available Blood vessels form either when dispersed endothelial cells (the cells lining the inner walls of fully formed blood vessels organize into a vessel network (vasculogenesis, or by sprouting or splitting of existing blood vessels (angiogenesis. Although they are closely related biologically, no current model explains both phenomena with a single biophysical mechanism. Most computational models describe sprouting at the level of the blood vessel, ignoring how cell behavior drives branch splitting during sprouting. We present a cell-based, Glazier-Graner-Hogeweg model (also called Cellular Potts Model simulation of the initial patterning before the vascular cords form lumens, based on plausible behaviors of endothelial cells. The endothelial cells secrete a chemoattractant, which attracts other endothelial cells. As in the classic Keller-Segel model, chemotaxis by itself causes cells to aggregate into isolated clusters. However, including experimentally observed VE-cadherin-mediated contact inhibition of chemotaxis in the simulation causes randomly distributed cells to organize into networks and cell aggregates to sprout, reproducing aspects of both de novo and sprouting blood-vessel growth. We discuss two branching instabilities responsible for our results. Cells at the surfaces of cell clusters attempting to migrate to the centers of the clusters produce a buckling instability. In a model variant that eliminates the surface-normal force, a dissipative mechanism drives sprouting, with the secreted chemical acting both as a chemoattractant and as an inhibitor of pseudopod extension. Both mechanisms would also apply if force transmission through the extracellular matrix rather than chemical signaling mediated cell-cell interactions. The branching instabilities responsible for our results, which result from contact inhibition of chemotaxis, are both generic developmental mechanisms and interesting examples of unusual patterning instabilities.

  11. ErbB2-dependent chemotaxis requires microtubule capture and stabilization coordinated by distinct signaling pathways.

    Directory of Open Access Journals (Sweden)

    Khedidja Benseddik

    Full Text Available Activation of the ErbB2 receptor tyrosine kinase stimulates breast cancer cell migration. Cell migration is a complex process that requires the synchronized reorganization of numerous subcellular structures including cell-to-matrix adhesions, the actin cytoskeleton and microtubules. How the multiple signaling pathways triggered by ErbB2 coordinate, in time and space, the various processes involved in cell motility, is poorly defined. We investigated the mechanism whereby ErbB2 controls microtubules and chemotaxis. We report that activation of ErbB2 increased both cell velocity and directed migration. Impairment of the Cdc42 and RhoA GTPases, but not of Rac1, prevented the chemotactic response. RhoA is a key component of the Memo/ACF7 pathway whereby ErbB2 controls microtubule capture at the leading edge. Upon Memo or ACF7 depletion, microtubules failed to reach the leading edge and cells lost their ability to follow the chemotactic gradient. Constitutive ACF7 targeting to the membrane in Memo-depleted cells reestablished directed migration. ErbB2-mediated activation of phospholipase C gamma (PLCγ also contributed to cell guidance. We further showed that PLCγ signaling, via classical protein kinases C, and Memo signaling converged towards a single pathway controlling the microtubule capture complex. Finally, inhibiting the PI3K/Akt pathway did not affect microtubule capture, but disturbed microtubule stability, which also resulted in defective chemotaxis. PI3K/Akt-dependent stabilization of microtubules involved repression of GSK3 activity on the one hand and inhibition of the microtubule destabilizing protein, Stathmin, on the other hand. Thus, ErbB2 triggers distinct and complementary pathways that tightly coordinate microtubule capture and microtubule stability to control chemotaxis.

  12. A Discrete Velocity Kinetic Model with Food Metric: Chemotaxis Traveling Waves. (United States)

    Choi, Sun-Ho; Kim, Yong-Jung


    We introduce a mesoscopic scale chemotaxis model for traveling wave phenomena which is induced by food metric. The organisms of this simplified kinetic model have two discrete velocity modes, [Formula: see text] and a constant tumbling rate. The main feature of the model is that the speed of organisms is constant [Formula: see text] with respect to the food metric, not the Euclidean metric. The uniqueness and the existence of the traveling wave solution of the model are obtained. Unlike the classical logarithmic model case there exist traveling waves under super-linear consumption rates and infinite population pulse-type traveling waves are obtained. Numerical simulations are also provided.

  13. The chemical-in-plug bacterial chemotaxis assay is prone to false positive responses

    Directory of Open Access Journals (Sweden)

    Ward Mandy J


    Full Text Available Abstract Background Chemical-in-plug assays are commonly used to study bacterial chemotaxis, sometimes in the absence of stringent controls. Results We report that non-chemotactic and non-motile mutants in two distinct bacterial species (Shewanella oneidensis and Helicobacter pylori show apparent zones of accumulation or clearing around test plugs containing potential attractants or repellents, respectively. Conclusions Our results suggest that the chemical-in-plug assay should be used with caution, that non-motile or non-chemotactic mutants should be employed as controls, and that results should be confirmed with other types of assays.

  14. Pioglitazone Suppresses CXCR7 Expression To Inhibit Human Macrophage Chemotaxis through Peroxisome Proliferator-Activated Receptor γ. (United States)

    Zhao, Duo; Zhu, Zhicheng; Li, Dan; Xu, Rihao; Wang, Tiance; Liu, Kexiang


    Cardiovascular disease is the leading cause of morbidity and mortality in patients with type 2 diabetes mellitus (T2DM). Pioglitazone, the widely used thiazolidinedione, is shown to be efficient in the prevention of cardiovascular complications of T2DM. In this study, we report that pioglitazone inhibits CXCR7 expression and thus blocks chemotaxis in differentiated macrophage without perturbing cell viability or macrophage differentiation. In addition, pioglitazone-mediated CXCR7 suppression and chemotaxis inhibition occur via activating peroxisome proliferator-activated receptor γ (PPARγ) but not PPARα in differentiated macrophage. More importantly, pioglitazone therapy-induced PPARγ activation suppresses CXCR7 expression in human carotid atherosclerotic lesions. Collectively, our data demonstrate that pioglitazone suppresses CXCR7 expression to inhibit human macrophage chemotaxis through PPARγ.

  15. Production and characterization of monoclonal antibodies against mink leukocytes

    DEFF Research Database (Denmark)

    Chen, W.S.; Pedersen, Mikael; Gram-Nielsen, S.;


    Three monoclonal antibodies (mAbs) were generated against mink leukocytes. One antibody reacted with all T lymphocytes, one with all monocytes and one had platelet reactivity. Under reducing conditions, the T lymphocyte reactive antibody immunoprecipitated 18 kDa, 23 kDa, 25 kDa and 32-40 kDa pol...

  16. Human leukocyte antigen (HLA)-G during pregnancy part II

    DEFF Research Database (Denmark)

    Dahl, Mette; Klitkou, Louise; Christiansen, Ole B;


    Human leukocyte antigen (HLA)-G is a class Ib molecule with restricted tissue distribution expressed on the extra-villous trophoblast and seems to have immunomodulatory functions during pregnancy. Studies have linked HLA-G polymorphisms to pregnancy complications such as preeclampsia and recurren...

  17. Differential MSC activation leads to distinct mononuclear leukocyte binding mechanisms (United States)

    Kota, Daniel J.; Dicarlo, Bryan; Hetz, Robert A.; Smith, Philippa; Cox, Charles S.; Olson, Scott D.


    Advances in the field of Multipotent Mesenchymal Stromal cell (MSC) biology have demonstrated that MSCs can improve disease outcome when `activated' to exert immunomodulatory effects. However, the precise mechanisms modulating MSC-immune cells interactions remain largely elusive. In here, we activated MSC based on a recent polarization paradigm, in which MSCs can be polarized towards a pro- or anti-inflammatory phenotype depending on the Toll-like receptor stimulated, to dissect the mechanisms through which MSCs physically interact with and modulate leukocytes in this context. Our data show that MSCs activated through the Toll-like receptor (TLR) 4 pathway increased VCAM-1 and ICAM-1 dependent binding of leukocytes. On the other hand, TLR3 stimulation strongly increases leukocytes affinity to MSC comparatively, through the formation of cable-like hyaluronic acid structures. In addition, TLR4 activation elicited secretion of pro-inflammatory mediators by MSCs, whereas TLR3-activated MSCs displayed a milder pro-inflammatory phenotype, similar to inactivated MSCs. However, the differently activated MSCs maintained their ability to suppress leukocyte activation at similar levels in our in vitro model, and this immunomodulatory property was shown here to be partially mediated by prostaglandin. These results reinforce the concept that alternate activation profiles control MSC responses and may impact the therapeutic use of MSCs.

  18. Radiolabelled leukocytes for imaging inflammation: how radiochemistry affects clinical use. (United States)

    Ballinger, J R; Gnanasegaran, G


    Indium-111((111)In)-labelled leukocytes were introduced for imaging inflammation about 25 years ago. A few years later methods to label leukocytes with Technetium-99m ((99m)Tc) were developed, but the two radiolabels cannot be used interchangeably. The amount of radioactivity which can be administered with (111)In is low, because of its 67-h half-life and associated radiation dose. This results in low count density in images. However, (111)In labelling is very stable, with binding to intracellular macromolecules and particulates, and there is minimal urinary or faecal excretion. In contrast, (99m)Tc has a half-life of 6 h and can be administered in higher doses, resulting in improved image quality. However, (99m)Tc labelling is less stable because the trapped form is soluble and there is excretion of (99m)Tc through both the kidneys and intestine, which limits imaging of disease in the abdomen except at early times. There is interest in extending inflammation imaging to PET. Although leukocytes can be labelled with (18)F-FDG, its half-life and stability are not optimal and radiometals such as Copper-64 are being evaluated. Despite the laborious nature of leukocyte labelling, it has yet to be replaced by direct injection agents.

  19. Leukocyte telomere length dynamics in women and men

    DEFF Research Database (Denmark)

    Dalgård, Christine; Benetos, Athanase; Verhulst, Simon;


    BACKGROUND: A longer leukocyte telomere length (LTL) in women than men has been attributed to a slow rate of LTL attrition in women, perhaps due to high estrogen exposure during the premenopausal period. METHODS: To test this premise we performed a longitudinal study (an average follow-up of 12...

  20. Longitudinal Changes in Leukocyte Telomere Length and Mortality in Humans

    DEFF Research Database (Denmark)

    Bendix, Laila; Thinggaard, Mikael; Fenger, Mogens;


    Leukocyte telomere length (LTL) ostensibly shortens with age and has been moderately associated with mortality. In humans, these findings have come almost solely from cross-sectional studies. Only recently has LTL shortening within individuals been analyzed in longitudinal studies. Such studies...... are relevant to establish LTL dynamics as biomarkers of mortality as well as to disentangle the causality of telomeres on aging....

  1. Expression of the gltP gene of Escherichia coli in a glutamate transport-deficient mutant of Rhodobacter sphaeroides restores chemotaxis to glutamate

    NARCIS (Netherlands)

    Jacobs, M.H J; van der Heide, T.; Tolner, B; Driessen, A.J.M.; Konings, W.N


    Rhodobacter sphaeroides is chemotactic to glutamate and most other amino acids. In Escherichia coli, chemotaxis involves a membrane-bound sensor that either binds the amino acid directly or interacts with the binding protein loaded with the amino acid. In R. sphaeroides, chemotaxis is thought to req

  2. Transducer like proteins of Campylobacter jejuni 81-176: role in chemotaxis and colonization of the chicken gastrointestinal tract. (United States)

    Chandrashekhar, Kshipra; Gangaiah, Dharanesh; Pina-Mimbela, Ruby; Kassem, Issmat I; Jeon, Byeong H; Rajashekara, Gireesh


    Transducer Like Proteins (Tlps), also known as methyl accepting chemotaxis proteins (MCP), enable enteric pathogens to respond to changing nutrient levels in the environment by mediating taxis toward or away from specific chemoeffector molecules. Despite recent advances in the characterization of chemotaxis responses in Campylobacter jejuni, the impact of Tlps on the adaptation of this pathogen to disparate niches and hosts is not fully characterized. The latter is particularly evident in the case of C. jejuni 81-176, a strain that is known to be highly invasive. Furthermore, the cytoplasmic group C Tlps (Tlp5, 6, and 8) were not extensively evaluated. Here, we investigated the role of C. jejuni 81-176 Tlps in chemotaxis toward various substrates, biofilm formation, in vitro interaction with human intestinal cells, and chicken colonization. We found that the Δtlp6 and Δtlp10 mutants exhibited decreased chemotaxis toward aspartate, whereas the Δtlp6 mutant displayed a decreased chemotaxis toward Tri-Carboxylic Acid (TCA) cycle intermediates such as pyruvate, isocitrate, and succinate. Our findings also corroborated that more than one Tlp is involved in mediating chemotaxis toward the same nutrient. The deletion of tlps affected important phenotypes such as motility, biofilm formation, and invasion of human intestinal epithelial cells (INT-407). The Δtlp8 mutant displayed increased motility in soft agar and showed decreased biofilm formation. The Δtlp8 and Δtlp9 mutants were significantly defective in invasion in INT-407 cells. The Δtlp10 mutant was defective in colonization of the chicken proximal and distal gastrointestinal tract, while the Δtlp6 and Δtlp8 mutants showed reduced colonization of the duodenum and jejunum. Our results highlight the importance of Tlps in C. jejuni's adaptation and pathobiology.

  3. Transducer Like Proteins of Campylobacter jejuni 81-176: Role in chemotaxis and colonization of the chicken gastrointestinal tract

    Directory of Open Access Journals (Sweden)

    Gireesh eRajashekara


    Full Text Available Transducer Like Proteins (Tlps, also known as Methyl accepting chemotaxis proteins (MCP, enable enteric pathogens to respond to changing nutrient levels in the environment by mediating taxis towards or away from specific chemoeffector molecules such as nutrients. Despite recent advances in the characterization of chemotaxis responses in Campylobacter jejuni, the impact of Tlps on the adaptation of this pathogen to disparate niches and hosts is not fully characterized. The latter is particularly evident in the case of C. jejuni 81-176, a strain that is known to be highly invasive. Furthermore, the cytoplasmic group C Tlps (Tlp5, 6, and 8 was not extensively evaluated. Here, we investigated the role of C. jejuni 81-176 Tlps in chemotaxis towards various substrates, biofilm formation, in vitro interaction with human intestinal cells, and chicken colonization. We found that the ∆tlp6 and ∆tlp10 mutants exhibited decreased chemotaxis towards aspartate whereas the ∆tlp6 mutant displayed a decreased chemotaxis towards Tri-Carboxylic Acid (TCA cycle intermediates such as pyruvate, isocitrate, and succinate. Our findings also corroborated that more than one Tlp is involved in mediating chemotaxis towards the same nutrient. The deletion of tlps affected important phenotypes such as motility, biofilm formation, and invasion of human intestinal epithelial cells (INT-407. The ∆tlp8 mutant displayed increased motility in soft agar and showed decreased biofilm formation. The ∆tlp8 and ∆tlp9 mutants were significantly defective in invasion in INT-407 cells. The ∆tlp10 mutant was defective in colonization of the chicken proximal and distal gastrointestinal tract, while the ∆tlp6 and ∆tlp8 mutants showed reduced colonization of the duodenum and jejunum. Our results highlight the importance of Tlps in C. jejuni’s adaptation and pathobiology.

  4. Computational modeling reveals that a combination of chemotaxis and differential adhesion leads to robust cell sorting during tissue patterning.

    Directory of Open Access Journals (Sweden)

    Rui Zhen Tan

    Full Text Available Robust tissue patterning is crucial to many processes during development. The "French Flag" model of patterning, whereby naïve cells in a gradient of diffusible morphogen signal adopt different fates due to exposure to different amounts of morphogen concentration, has been the most widely proposed model for tissue patterning. However, recently, using time-lapse experiments, cell sorting has been found to be an alternative model for tissue patterning in the zebrafish neural tube. But it remains unclear what the sorting mechanism is. In this article, we used computational modeling to show that two mechanisms, chemotaxis and differential adhesion, are needed for robust cell sorting. We assessed the performance of each of the two mechanisms by quantifying the fraction of correct sorting, the fraction of stable clusters formed after correct sorting, the time needed to achieve correct sorting, and the size variations of the cells having different fates. We found that chemotaxis and differential adhesion confer different advantages to the sorting process. Chemotaxis leads to high fraction of correct sorting as individual cells will either migrate towards or away from the source depending on its cell type. However after the cells have sorted correctly, there is no interaction among cells of the same type to stabilize the sorted boundaries, leading to cell clusters that are unstable. On the other hand, differential adhesion results in low fraction of correct clusters that are more stable. In the absence of morphogen gradient noise, a combination of both chemotaxis and differential adhesion yields cell sorting that is both accurate and robust. However, in the presence of gradient noise, the simple combination of chemotaxis and differential adhesion is insufficient for cell sorting; instead, chemotaxis coupled with delayed differential adhesion is required to yield optimal sorting.


    Directory of Open Access Journals (Sweden)



    Full Text Available INTRODUCTION Hypertension, a globally prevailing non communicable disease has been linked to various pathophysiological mechanisms. The new spotlight is on the inflammatory mechanism, which has been embarked on this study by utilising the White blood cell counts as the predominant marker. The pathogenesis behind this concept is the endothelial alteration which occurs in hypertension, causing increased oxidative stress and release of inflammatory mediators and further causing damage to the vascular walls and may result in sustained hypertension. OBJECTIVE To substantiate the difference in leukocyte count among the hypertensives and normotensives, to assess the variation in the leukocyte count among varied grades of hypertension. METHODS 80 subjects and 40 controls of both sex and age between 20-60 years were taken. Subjects with other chronic medical disorders, pregnancy, menstruation phase, history of infections in past 3 months, obesity, smokers and regular alcoholics were excluded. Three recordings of blood pressure were measured with a standard mercury sphygmomanometer. The differential leukocyte count was estimated with an automated counter. RESULTS Statistical analysis was done using independent sample t-test and one-way ANOVA. Total Leukocyte count (Mean = 8397.50 ± 1666.57 was raised significantly among the hypertensives, with P value <0.001. Comparison was done on the total count with the varied hypertensive years, which was suggestive of increase in total count among the pre hypertensives (systolic pressure and there was linear increase in total count with diastolic pressure though not statistically significant. CONCLUSION The elevation of white blood cell count is suggestive of underlying inflammatory mechanism among the hypertensives. The onset of inflammation could be at the onset of hypertension, as there is rise in total leukocyte count among the pre hypertensives which could also lead to sustained hypertension.

  6. Efficiency and safety of leukocyte filtration during cardiopulmonary bypass for cardiac surgery

    NARCIS (Netherlands)

    Smit, JJJ; de Vries, AJ; Gu, YJ; van Oeveren, W


    Background. Leukocyte filtration of systemic blood during cardiopulmonary bypass surgery to reduce post-operative morbidity has not yet been established because of the enormous leukocyte release from the third space. This study was designed to examine the efficiency and safety of leukocyte filtratio

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  19. NahY, a Catabolic Plasmid-Encoded Receptor Required for Chemotaxis of Pseudomonas putida to the Aromatic Hydrocarbon Naphthalene



    Pseudomonas putida G7 exhibits chemotaxis to naphthalene, but the molecular basis for this was not known. A new gene, nahY, was found to be cotranscribed with meta cleavage pathway genes on the NAH7 catabolic plasmid for naphthalene degradation. The nahY gene encodes a 538-amino-acid protein with a membrane topology and a C-terminal region that resemble those of chemotaxis transducer proteins. A P. putida G7 nahY mutant grew on naphthalene but was not chemotactic to this aromatic hydrocarbon....

  20. Monocyte function in intravenous drug abusers with lymphadenopathy syndrome and in patients with acquired immunodeficiency syndrome: selective impairment of chemotaxis. (United States)

    Poli, G; Bottazzi, B; Acero, R; Bersani, L; Rossi, V; Introna, M; Lazzarin, A; Galli, M; Mantovani, A


    We have investigated monocyte function in 17 intravenous drug abusers with the clinical and laboratory features of lymphadenopathy syndrome (LAS). LAS patients had normal numbers of circulating monocytes. Monocytes from LAS patients were comparable to cells from normal donors in terms of phagocytosis of latex beads, interleukin-1 secretion, O2- release and killing of antibody-sensitized lymphoma cells or actinomycin D pretreated WEHI 164 cells. In contrast 13 out of 17 LAS subjects tested in this respect as well as six out of nine AIDS patients showed a marked defect of monocyte chemotaxis. Thus monocytes from patients with LAS or AIDS have a selective defect of monocyte chemotaxis. PMID:2998656

  1. Histamine H3 receptor in primary mouse microglia inhibits chemotaxis, phagocytosis, and cytokine secretion. (United States)

    Iida, Tomomitsu; Yoshikawa, Takeo; Matsuzawa, Takuro; Naganuma, Fumito; Nakamura, Tadaho; Miura, Yamato; Mohsen, Attayeb S; Harada, Ryuichi; Iwata, Ren; Yanai, Kazuhiko


    Histamine is a physiological amine which initiates a multitude of physiological responses by binding to four known G-protein coupled histamine receptor subtypes as follows: histamine H1 receptor (H1 R), H2 R, H3 R, and H4 R. Brain histamine elicits neuronal excitation and regulates a variety of physiological processes such as learning and memory, sleep-awake cycle and appetite regulation. Microglia, the resident macrophages in the brain, express histamine receptors; however, the effects of histamine on critical microglial functions such as chemotaxis, phagocytosis, and cytokine secretion have not been examined in primary cells. We demonstrated that mouse primary microglia express H2 R, H3 R, histidine decarboxylase, a histamine synthase, and histamine N-methyltransferase, a histamine metabolizing enzyme. Both forskolin-induced cAMP accumulation and ATP-induced intracellular Ca(2+) transients were reduced by the H3 R agonist imetit but not the H2 R agonist amthamine. H3 R activation on two ubiquitous second messenger signalling pathways suggests that H3 R can regulate various microglial functions. In fact, histamine and imetit dose-dependently inhibited microglial chemotaxis, phagocytosis, and lipopolysaccharide (LPS)-induced cytokine production. Furthermore, we confirmed that microglia produced histamine in the presence of LPS, suggesting that H3 R activation regulate microglial function by autocrine and/or paracrine signalling. In conclusion, we demonstrate the involvement of histamine in primary microglial functions, providing the novel insight into physiological roles of brain histamine.

  2. Sinorhizobium meliloti chemotaxis to quaternary ammonium compounds is mediated by the chemoreceptor McpX. (United States)

    Webb, Benjamin A; Karl Compton, K; Castañeda Saldaña, Rafael; Arapov, Timofey D; Keith Ray, W; Helm, Richard F; Scharf, Birgit E


    The bacterium Sinorhizobium meliloti is attracted to seed exudates of its host plant alfalfa (Medicago sativa). Since quaternary ammonium compounds (QACs) are exuded by germinating seeds, we assayed chemotaxis of S. meliloti towards betonicine, choline, glycine betaine, stachydrine and trigonelline. The wild type displayed a positive response to all QACs. Using LC-MS, we determined that each germinating alfalfa seed exuded QACs in the nanogram range. Compared to the closely related nonhost species, spotted medic (Medicago arabica), unique profiles were released. Further assessments of single chemoreceptor deletion strains revealed that an mcpX deletion strain displayed little to no response to these compounds. Differential scanning fluorimetry showed interaction of the isolated periplasmic region of McpX (McpX(PR) and McpX34-306 ) with QACs. Isothermal titration calorimetry experiments revealed tight binding to McpX(PR) with dissociation constants (Kd ) in the nanomolar range for choline and glycine betaine, micromolar Kd for stachydrine and trigonelline and a Kd in the millimolar range for betonicine. Our discovery of S. meliloti chemotaxis to plant-derived QACs adds another role to this group of compounds, which are known to serve as nutrient sources, osmoprotectants and cell-to-cell signalling molecules. This is the first report of a chemoreceptor that mediates QACs taxis through direct binding.

  3. PP2A/B56 and GSK3/Ras suppress PKB activity during Dictyostelium chemotaxis. (United States)

    Rodriguez Pino, Marbelys; Castillo, Boris; Kim, Bohye; Kim, Lou W


    We have previously shown that the Dictyostelium protein phosphatase 2A regulatory subunit B56, encoded by psrA, modulates Dictyostelium cell differentiation through negatively affecting glycogen synthase kinase 3 (GSK3) function. Our follow-up research uncovered that B56 preferentially associated with GDP forms of RasC and RasD, but not with RasG in vitro, and psrA(-) cells displayed inefficient activation of multiple Ras species, decreased random motility, and inefficient chemotaxis toward cAMP and folic acid gradient. Surprisingly, psrA(-) cells displayed aberrantly high basal and poststimulus phosphorylation of Dictyostelium protein kinase B (PKB) kinase family member PKBR1 and PKB substrates. Expression of constitutively active Ras mutants or inhibition of GSK3 in psrA(-) cells increased activities of both PKBR1 and PKBA, but only the PKBR1 activity was increased in wild-type cells under the equivalent conditions, indicating that either B56- or GSK3-mediated suppressive mechanism is sufficient to maintain low PKBA activity, but both mechanisms are necessary for suppressing PKBR1. Finally, cells lacking RasD or RasC displayed normal PKBR1 regulation under GSK3-inhibiting conditions, indicating that RasC or RasD proteins are essential for GSK3-mediated PKBR1 inhibition. In summary, B56 constitutes inhibitory circuits for PKBA and PKBR1 and thus heavily affects Dictyostelium chemotaxis.

  4. Laminar flow assisted anisotropic bacteria absorption for chemotaxis delivery of bacteria-attached microparticle (United States)

    Huh, Keon; Oh, Darong; Son, Seok Young; Yoo, Hyung Jung; Song, Byeonghwa; Cho, Dong-il Dan; Seo, Jong-Mo; Kim, Sung Jae


    The concepts of microrobots has been drawn significant attentions recently since its unprecedented applicability in nanotechnology and biomedical field. Bacteria attached microparticles presented in this work are one of pioneering microrobot technology for self-propulsion or producing kinetic energy from ambient for their motions. Microfluidic device, especially utilizing laminar flow characteristics, were employed for anisotropic attachment of Salmonella typhimurium flagellated chemotactic bacteria to 30 um × 30 um and 50 um × 50 um microparticles that made of biodegradable polymer. Any toxic chemicals or harmful treatments were excluded during the attachment process and it finished within 100 s for the anisotropic attachment. The attachments were directly confirmed by fluorescent intensity changes and SEM visualization. Chemotaxis motions were tracked using aspartate and the maximum velocity of the bacteria-attached microrobot was measured to be 5 um/s which is comparable to prior state of art technologies. This reusable and scalable method could play a key role in chemotaxis delivery of functional microparticles such as drug delivery system.

  5. A hybrid two-component system protein from Azospirillum brasilense Sp7 was involved in chemotaxis. (United States)

    Cui, Yanhua; Tu, Ran; Wu, Lixian; Hong, Yuanyuan; Chen, Sanfeng


    We here report the sequence and functional analysis of org35 of Azospirillum brasilense Sp7, which was originally identified to be able to interact with NifA in yeast-two-hybrid system. The org35 encodes a hybrid two-component system protein, including N-terminal PAS domains, a histidine kinase (HPK) domain and a response regulator (RR) domain in C-terminal. To determine the function of the Org35, a deletion-insertion mutant in PAS domain [named Sp7353] and a complemental strain Sp7353C were constructed. The mutant had reduced chemotaxis ability compared to that of wild-type, and the complemental strain was similar to the wild-type strain. These data suggested that the A. brasilense org35 played a key role in chemotaxis. Variants containing different domains of the org35 were expressed, and the functions of these domains were studied in vitro. Phosphorylation assays in vitro demonstrated that the HPK domain of Org35 possessed the autokinase activity and that the phosphorylated HPK was able to transfer phosphate groups to the RR domain. The result indicated Org35 was a phosphorylation-communicating protein.

  6. Exponential signaling gain at the receptor level enhances signal-to-noise ratio in bacterial chemotaxis.

    Directory of Open Access Journals (Sweden)

    Silke Neumann

    Full Text Available Cellular signaling systems show astonishing precision in their response to external stimuli despite strong fluctuations in the molecular components that determine pathway activity. To control the effects of noise on signaling most efficiently, living cells employ compensatory mechanisms that reach from simple negative feedback loops to robustly designed signaling architectures. Here, we report on a novel control mechanism that allows living cells to keep precision in their signaling characteristics - stationary pathway output, response amplitude, and relaxation time - in the presence of strong intracellular perturbations. The concept relies on the surprising fact that for systems showing perfect adaptation an exponential signal amplification at the receptor level suffices to eliminate slowly varying multiplicative noise. To show this mechanism at work in living systems, we quantified the response dynamics of the E. coli chemotaxis network after genetically perturbing the information flux between upstream and downstream signaling components. We give strong evidence that this signaling system results in dynamic invariance of the activated response regulator against multiplicative intracellular noise. We further demonstrate that for environmental conditions, for which precision in chemosensing is crucial, the invariant response behavior results in highest chemotactic efficiency. Our results resolve several puzzling features of the chemotaxis pathway that are widely conserved across prokaryotes but so far could not be attributed any functional role.

  7. Subtle CXCR3-Dependent Chemotaxis of CTLs within Infected Tissue Allows Efficient Target Localization. (United States)

    Ariotti, Silvia; Beltman, Joost B; Borsje, Rianne; Hoekstra, Mirjam E; Halford, William P; Haanen, John B A G; de Boer, Rob J; Schumacher, Ton N M


    It is well established how effector T cells exit the vasculature to enter the peripheral tissues in which an infection is ongoing. However, less is known regarding how CTLs migrate toward infected cells after entry into peripheral organs. Recently, it was shown that the chemokine receptor CXCR3 on T cells has an important role in their ability to localize infected cells and to control vaccinia virus infection. However, the search strategy of T cells for virus-infected targets has not been investigated in detail and could involve chemotaxis toward infected cells, chemokinesis (i.e., increased motility) combined with CTL arrest when targets are detected, or both. In this study, we describe and analyze the migration of CTLs within HSV-1-infected epidermis in vivo. We demonstrate that activated T cells display a subtle distance-dependent chemotaxis toward clusters of infected cells and confirm that this is mediated by CXCR3 and its ligands. Although the chemotactic migration is weak, computer simulations based on short-term experimental data, combined with subsequent long-term imaging indicate that this behavior is crucial for efficient target localization and T cell accumulation at effector sites. Thus, chemotactic migration of effector T cells within peripheral tissue forms an important factor in the speed with which T cells are able to arrive at sites of infection.

  8. An orphan chemotaxis sensor regulates virulence and antibiotic tolerance in the human pathogen Pseudomonas aeruginosa.

    Directory of Open Access Journals (Sweden)

    Heather Pearl McLaughlin

    Full Text Available The synthesis of virulence factors by pathogenic bacteria is highly regulated and occurs in response to diverse environmental cues. An array of two component systems (TCSs serves to link perception of different cues to specific changes in gene expression and/or bacterial behaviour. Those TCSs that regulate functions associated with virulence represent attractive targets for interference in anti-infective strategies for disease control. We have previously identified PA2572 as a putative response regulator required for full virulence of Pseudomonas aeruginosa, the opportunistic human pathogen, to Galleria mellonella (Wax moth larvae. Here we have investigated the involvement of candidate sensors for signal transduction involving PA2572. Mutation of PA2573, encoding a probable methyl-accepting chemotaxis protein, gave rise to alterations in motility, virulence, and antibiotic resistance, functions which are also controlled by PA2572. Comparative transcriptome profiling of mutants revealed that PA2572 and PA2573 regulate expression of a common set of 49 genes that are involved in a range of biological functions including virulence and antibiotic resistance. Bacterial two-hybrid analysis indicated a REC-dependent interaction between PA2572 and PA2573 proteins. Finally expression of PA2572 in the PA2573 mutant background restored virulence to G. mellonella towards wild-type levels. The findings indicate a role for the orphan chemotaxis sensor PA2573 in the regulation of virulence and antibiotic tolerance in P. aeruginosa and indicate that these effects are exerted in part through signal transduction involving PA2572.

  9. ProBDNF inhibits collective migration and chemotaxis of rat Schwann cells. (United States)

    Ding, You-Quan; Li, Xuan-Yang; Xia, Guan-Nan; Ren, Hong-Yi; Zhou, Xin-Fu; Su, Bing-Yin; Qi, Jian-Guo


    Schwann cell migration, including collective migration and chemotaxis, is essential for the formation of coordinate interactions between Schwann cells and axons during peripheral nerve development and regeneration. Moreover, limited migration of Schwann cells imposed a serious obstacle on Schwann cell-astrocytes intermingling and spinal cord repair after Schwann cell transplantation into injured spinal cords. Recent studies have shown that mature brain-derived neurotrophic factor, a member of the neurotrophin family, inhibits Schwann cell migration. The precursor form of brain-derived neurotrophic factor, proBDNF, was expressed in the developing or degenerating peripheral nerves and the injured spinal cords. Since "the yin and yang of neurotrophin action" has been established as a common sense, proBDNF would be expected to promote Schwann cell migration. However, we found, in the present study, that exogenous proBDNF also inhibited in vitro collective migration and chemotaxis of RSC 96 cells, a spontaneously immortalized rat Schwann cell line. Moreover, proBDNF suppressed adhesion and spreading of those cells. At molecular level, proBDNF inhibits F-actin polymerization and focal adhesion dynamics in cultured RSC 96 cells. Therefore, our results suggested a special case against the classical opinion of "the yin and yang of neurotrophin action" and implied that proBDNF might modulate peripheral nerve development or regeneration and spinal cord repair through perturbing native or transplanted Schwann cell migration.

  10. CYP4F18-Deficient Neutrophils Exhibit Increased Chemotaxis to Complement Component C5a

    Directory of Open Access Journals (Sweden)

    Rachel Vaivoda


    Full Text Available CYP4Fs were first identified as enzymes that catalyze hydroxylation of leukotriene B4 (LTB4. CYP4F18 has an unusual expression in neutrophils and was predicted to play a role in regulating LTB4-dependent inflammation. We compared chemotaxis of wild-type and Cyp4f18 knockout neutrophils using an in vitro assay. There was no significant difference in the chemotactic response to LTB4, but the response to complement component C5a increased 1.9–2.25-fold in knockout cells compared to wild-type (P < 0.01. This increase was still observed when neutrophils were treated with inhibitors of eicosanoid synthesis. There were no changes in expression of other CYP4 enzymes in knockout neutrophils that might compensate for loss of CYP4F18 or lead to differences in activity. A mouse model of dextran sodium sulfate colitis was used to investigate the consequences of increased C5a-dependent chemotaxis in vivo, but there was no significant difference in weight loss, disease activity, or colonic tissue myeloperoxidase between wild-type and Cyp4f18 knockout mice. This study demonstrates the limitations of inferring CYP4F function based on an ability to use LTB4 as a substrate, points to expanding roles for CYP4F enzymes in immune regulation, and underscores the in vivo challenges of CYP knockout studies.

  11. Directed transport of bacteria-based drug delivery vehicles: bacterial chemotaxis dominates particle shape. (United States)

    Sahari, Ali; Traore, Mahama A; Scharf, Birgit E; Behkam, Bahareh


    Several attenuated and non-pathogenic bacterial species have been demonstrated to actively target diseased sites and successfully deliver plasmid DNA, proteins and other therapeutic agents into mammalian cells. These disease-targeting bacteria can be employed for targeted delivery of therapeutic and imaging cargos in the form of a bio-hybrid system. The bio-hybrid drug delivery system constructed here is comprised of motile Escherichia coli MG1655 bacteria and elliptical disk-shaped polymeric microparticles. The transport direction for these vehicles can be controlled through biased random walk of the attached bacteria in presence of chemoattractant gradients in a process known as chemotaxis. In this work, we utilize a diffusion-based microfluidic platform to establish steady linear concentration gradients of a chemoattractant and investigate the roles of chemotaxis and geometry in transport of bio-hybrid drug delivery vehicles. Our experimental results demonstrate for the first time that bacterial chemotactic response dominates the effect of body shape in extravascular transport; thus, the non-spherical system could be more favorable for drug delivery applications owing to the known benefits of using non-spherical particles for vascular transport (e.g. relatively long circulation time).

  12. Preparation of /sup 111/In leukocytes after hemolytic removal of erythrocytes

    Energy Technology Data Exchange (ETDEWEB)

    Karesh, S.M.; Henkin, R.E.


    An optimized procedure is described for isolation and high-efficiency radiolabeling of leukocytes using /sup 111/In-oxine. The chief advantages over conventional methods include virtually no loss of leukocytes during washing and separation steps; a significant reduction in the time required to prepare leukocytes for radiolabeling compared to non-hemolytic preparations; a 28% increase in the average labeling efficiency obtained using /sup 111/In-oxine; > 95% cell viability as measured by the trypan blue exclusion test; elimination of contaminating red blood cells from the leukocyte pellet prior to labeling; and 80% survivability at 15 min post injection (measured as per cent of blood activity on leukocyte fraction).

  13. Combined bone scintigraphy and indium-111 leukocyte scans in neuropathic foot disease

    Energy Technology Data Exchange (ETDEWEB)

    Schauwecker, D.S.; Park, H.M.; Burt, R.W.; Mock, B.H.; Wellman, H.N.


    It is difficult to diagnose osteomyelitis in the presence of neurotrophic osteoarthropathy. We performed combined (99mTc)MDP bone scans and indium-111 (111In) leukocyte studies on 35 patients who had radiographic evidence of neuropathic foot disease and clinically suspected osteomyelitis. The (111In)leukocyte study determined if there was an infection and the bone scan provided the anatomic landmarks so that the infection could be localized to the bone or the adjacent soft tissue. Seventeen patients had osteomyelitis and all showed increased (111In)leukocyte activity localized to the bone, giving a sensitivity of 100%. Among the 18 patients without osteomyelitis, eight had no accumulation of (111In)leukocytes, seven had the (111In)leukocyte activity correctly localized to the soft tissue, two had (111In)leukocyte activity mistakenly attributed to the bone, and one had (111In)leukocyte accumulation in a proven neuroma which was mistakenly attributed to bone. These three false-positive results for osteomyelitis reduced the specificity to 83%. Considering only the 27 patients with a positive (111In)leukocyte study, the combined bone scan and (111In)leukocyte study correctly localized the infection to the soft tissues or bone in 89%. Uninfected neurotrophic osteoarthropathy does not accumulate (111In)leukocytes. We found the combined bone scan and (111In) leukocyte study useful for the detection and localization of infection to soft tissue or bone in patients with neuropathic foot disease.

  14. On the existence of local strong solutions to chemotaxis-shallow water system with large data and vacuum (United States)

    Che, Jiahang; Chen, Li; Duan, Ben; Luo, Zhen


    In this paper, motivated by the chemotaxis-Navier-Stokes system arising from mathematical biology [43], a modified shallow water type chemotactic model is derived. For large initial data allowing vacuum, the local existence of strong solutions together with the blow-up criterion is established.

  15. Induction of chemotaxis to sodium chloride and diacetyl and thermotaxis defects by microcystin-LR exposure in nematode Caenorhabditis elegans

    Institute of Scientific and Technical Information of China (English)

    LI Yunhui; YE Huayue; DU Min; ZHANG Yanfen; YE Boping; PU Yuepu; WANG Dayong


    Apart from the liver disruption, embryotoxicity and genotoxicity, microcystin (MC)-LR also could cause neurotoxicity. Nematode Caenorhabditis elegans was explored as a model to study the neurotoxicity. In the present study, we provided evidence to indicate the neurotoxicity on chemotaxis to NaCl and diacetyl, and thermotaxis from MC-LR exposure to C. elegans. As a result, higher concentrations of MC-LR caused significantly severe defects of chemotaxis to NaC1 and diacetyl, and thermotaxis. The neurotoxicity on chemotaxis to NaCl and diacetyl, and thennotaxis from MC-LR exposure might be largely mediated by the damage on the corresponding sensory neurons (ASE, AWA, and AFD) and interneuron AIY. The expression levels of che-1 and odr-7 were significantly decreased (P<0.01) in animals exposed to MC-LR at concentrations lower than 10 μg/L, whereas the expression levels of ttx-1 and ttx-3 could be significantly (P<0.01) lowered in animals even exposed to 1 μg/L of MC-LR. Moreover, both the chemotaxis to NaCl and diacetyl and the thermotaxis were more significantly reduced m MC-LR exposed mutants of che-1(p674), odr-7(ky4), ttx-1(p767), and ttx-3(ks5) than those in exposed wild-type N2 animals at the same concentrations.

  16. Chemotaxis of Caenorhabditis elegans in complex media: crawling, burrowing, 2D and 3D swimming, and controlled fluctuations hypothesis (United States)

    Patel, Amar; Bilbao, Alejandro; Rahman, Mizanur; Vanapalli, Siva; Blawzdziewicz, Jerzy

    Caenorhabditis elegans is a powerful genetic model, essential for studies in diverse areas ranging from behavior to neuroscience to aging, and locomotion and chemotaxis are the two key observables used. We combine our recently developed theory of nematode locomotion and turning maneuvers [Phys. Fluids 25, 081902 (2013)] with simple models of chemosensation to analyze nematode chemotaxis strategies in 2D and 3D environments. We show that the sharp-turn (pirouette) chemotaxis mechanism is efficient in diverse media; in particular, the nematode does not need to adjust the sensing or motion-control parameters to efficiently chemotax in 2D crawling, 3D burrowing, and 2D or 3D swimming. In contrast, the graduate-turn mechanism becomes inefficient in swimming, unless a phase-shift is introduced between the sensing signal and modulation of body wave to generate the gradual turn. We hypothesize that there exists a new ``controlled fluctuations'' chemotaxis mechanism, in which the nematode changes the intensity of undulation fluctuations to adjust the persistence length of the trajectory in response to a variation in chemoattractant concentration. Supported by NSF Grant No. CBET 1059745.

  17. The chemotaxis regulator pilG of Xylella fastidiosa is required for virulence in Vitis vinifera grapevines (United States)

    Xylella fastidiosa is a Gram-negative, xylem-limited pathogenic bacterium that causes Pierce’s disease of grapevines. Type IV pili of X. fastidiosa are regulated by pilG, a chemotaxis regulator in Pil-Chp operon involving signal transduction pathways. To elucidate the role of pilG in twitching motil...

  18. Effect of radiographic contrast agents on leukocyte metabolic response

    Energy Technology Data Exchange (ETDEWEB)

    Hernanz-Schulman, M. [Dept. of Pediatric Radiology, Vanderbilt Children' s Hospital, Nashville, TN (United States); Vanholder, R.; Waterloos, M.A. [Dept. of Internal Medicine, Nephrology Section, University Hospital, Gent (Belgium); Hakim, R.; Schulman, G. [Department of Nephrology, Vanderbilt University Medical Center, Nashville, TN (United States)


    Barium, at clinical dilutions, causes a significant increase of baseline ''resting state'' phagocytic activity, which in turn leads to significant blunting of subsequent response to phagocytic challenge and adversely affects the response to all bacteria tested. There is no baseline activation of leukocytes by the water-soluble media, although there was some inhibition (rather than activation) of leukocyte metabolic activity. The effect of the water-soluble media in bacteria was more complex (although inhibition is minor compared to barium). Our data demonstrate that barium is a significat activator of phagocytic cells, which results in deactivation of phagocytic response when challenged; these dsata serve to explain the enhanced adverse effect of barium in cased of fecal peritonitis. (orig.)

  19. Imaging Cytometry of Human Leukocytes with Third Harmonic Generation Microscopy (United States)

    Wu, Cheng-Ham; Wang, Tzung-Dau; Hsieh, Chia-Hung; Huang, Shih-Hung; Lin, Jong-Wei; Hsu, Szu-Chun; Wu, Hau-Tieng; Wu, Yao-Ming; Liu, Tzu-Ming


    Based on third-harmonic-generation (THG) microscopy and a k-means clustering algorithm, we developed a label-free imaging cytometry method to differentiate and determine the types of human leukocytes. According to the size and average intensity of cells in THG images, in a two-dimensional scatter plot, the neutrophils, monocytes, and lymphocytes in peripheral blood samples from healthy volunteers were clustered into three differentiable groups. Using these features in THG images, we could count the number of each of the three leukocyte types both in vitro and in vivo. The THG imaging-based counting results agreed well with conventional blood count results. In the future, we believe that the combination of this THG microscopy-based imaging cytometry approach with advanced texture analysis of sub-cellular features can differentiate and count more types of blood cells with smaller quantities of blood.

  20. Segmentation of leukocytes and erythrocytes in blood smear images. (United States)

    Bergen, Tobias; Steckhan, Dirk; Wittenberg, Thomas; Zerfass, Thorsten


    Differential blood count is a standard method in hematological laboratory diagnosis. In the course of developing a computer-assisted microscopy system for the generation of differential blood counts, the detection and segmentation of white and red blood cells forms an essential step and its exactness is a fundamental prerequisite for the effectiveness of the subsequent classification step. We propose a method for the exact segmentation of leukocytes and erythrocytes in a simultaneous and cooperative way. We combine pixel-wise classification with template matching to locate erythrocytes and use a level-set approach in order to get the exact cell contours of leukocyte nucleus and plasma regions as well as erythrocyte regions. An evaluation comparing the performance of the algorithm to the manual segmentation performed by several persons yielded good results.

  1. Influence of light sources on the migration of polymorphonuclear leukocytes (United States)

    DellaVecchia, Michael A.; Beard, Richard B.; Dai, Xiaoyan


    In the process of inflammation, leukocytes must travel from the intraluminal space of the capillary to the interstitial space in order to reach the site of the inflammation. The two major populations of mature human leukocytes based on the morphology are the polymorphonuclear leukocytes (PMN), and mononuclear leukocytes (MNL). Previous research on PMNs and MNLs at the Biomedical Engineering and Science Institute of Drexel University have shown that their migration can be markedly enhanced by excitation with electric and magnetic fields. This presentation demonstrates that the migration of PMNs under excitation of photons is enhanced in the red light region of (lambda) equals 660 nm and inhibited in the green light region of (lambda) equals 565 nm. There is an intensity threshold at which red light enhances migration and an intensity threshold at which green light inhibits migration. In these experiments the Boyden technique was used with the distance of the cell migration through a cellulose filter measured in terms of the leading edge. The comparison of the relative value of the distance to cell migration under a light to cell migration without a light stimulus was recorded as a cytokinetic index, K.I.. K.I. is a measure of the cytokinesis which is the progress of the cell movement in which the migration is enhanced by substances in the cell environment irrespective of a concentration gradient. The cytotactic index is a measure of cytotaxis which is the directional movement along a chemical gradient formed by a chemotactic factor. A Russian pulsed commercial laser biostimulator in the near infrared wavelength above an intensity threshold enhances PMN migration. Intermittent green and red stimulators below the intensity threshold markedly influence the cytokinetic index of PMNs while above the intensity threshold, this influence is deminished.

  2. Myxoma and vaccinia viruses bind differentially to human leukocytes. (United States)

    Chan, Winnie M; Bartee, Eric C; Moreb, Jan S; Dower, Ken; Connor, John H; McFadden, Grant


    Myxoma virus (MYXV) and vaccinia virus (VACV), two distinct members of the family Poxviridae, are both currently being developed as oncolytic virotherapeutic agents. Recent studies have demonstrated that ex vivo treatment with MYXV can selectively recognize and kill contaminating cancerous cells from autologous bone marrow transplants without perturbing the engraftment of normal CD34(+) hematopoietic stem and progenitor cells. However, the mechanism(s) by which MYXV specifically recognizes and eliminates the cancer cells in the autografts is not understood. While little is known about the cellular attachment factor(s) exploited by MYXV for entry into any target cells, VACV has been shown to utilize cell surface glycosaminoglycans such as heparan sulfate (HS), the extracellular matrix protein laminin, and/or integrin β1. We have constructed MYXV and VACV virions tagged with the Venus fluorescent protein and compared their characteristics of binding to various human cancer cell lines as well as to primary human leukocytes. We report that the binding of MYXV or VACV to some adherent cell lines could be partially inhibited by heparin, but laminin blocked only VACV binding. In contrast to cultured fibroblasts, the binding of MYXV and VACV to a wide spectrum of primary human leukocytes could not be competed by either HS or laminin. Additionally, MYXV and VACV exhibited very different binding characteristics against certain select human leukocytes, suggesting that the two poxviruses utilize different cell surface determinants for the attachment to these cells. These results indicate that VACV and MYXV can exhibit very different oncolytic tropisms against some cancerous human leukocytes.

  3. Dimensions of religious involvement and leukocyte telomere length. (United States)

    Hill, Terrence D; Ellison, Christopher G; Burdette, Amy M; Taylor, John; Friedman, Katherine L


    Although numerous studies suggest that religious involvement is associated with a wide range of favorable health outcomes, it is unclear whether this general pattern extends to cellular aging. In this paper, we tested whether leukocyte telomere length varies according to several dimensions of religious involvement. We used cross-sectional data from the Nashville Stress and Health Study (2011-2014), a large probability sample of 1252 black and white adults aged 22 to 69 living in Davidson County, TN, USA. Leukocyte telomere length was measured using the monochrome multiplex quantitative polymerase chain reaction method with albumin as the single-copy reference sequence. Dimensions of religious involvement included religiosity, religious support, and religious coping. Our multivariate analyses showed that religiosity (an index of religious attendance, prayer frequency, and religious identity) was positively associated with leukocyte telomere length, even with adjustments for religious support, religious coping, age, gender, race, education, employment status, income, financial strain, stressful life events, marital status, family support, friend support, depressive symptoms, smoking, heavy drinking, and allostatic load. Unlike religiosity, religious support and religious coping were unrelated to leukocyte telomere length across models. Depressive symptoms, smoking, heavy drinking, and allostatic load failed to explain any of the association between religiosity and telomere length. To our knowledge, this is the first population-based study to link religious involvement and cellular aging. Although our data suggest that adults who frequently attend religious services, pray with regularity, and consider themselves to be religious tend to exhibit longer telomeres than those who attend and pray less frequently and do not consider themselves to be religious, additional research is needed to establish the mechanisms underlying this association.

  4. Leukocyte Trafficking to the Small Intestine and Colon. (United States)

    Habtezion, Aida; Nguyen, Linh P; Hadeiba, Husein; Butcher, Eugene C


    Leukocyte trafficking to the small and large intestines is tightly controlled to maintain intestinal immune homeostasis, mediate immune responses, and regulate inflammation. A wide array of chemoattractants, chemoattractant receptors, and adhesion molecules expressed by leukocytes, mucosal endothelium, epithelium, and stromal cells controls leukocyte recruitment and microenvironmental localization in intestine and in the gut-associated lymphoid tissues (GALTs). Naive lymphocytes traffic to the gut-draining mesenteric lymph nodes where they undergo antigen-induced activation and priming; these processes determine their memory/effector phenotypes and imprint them with the capacity to migrate via the lymph and blood to the intestines. Mechanisms of T-cell recruitment to GALT and of T cells and plasmablasts to the small intestine are well described. Recent advances include the discovery of an unexpected role for lectin CD22 as a B-cell homing receptor GALT, and identification of the orphan G-protein-coupled receptor 15 (GPR15) as a T-cell chemoattractant/trafficking receptor for the colon. GPR15 decorates distinct subsets of T cells in mice and humans, a difference in species that could affect translation of the results of mouse colitis models to humans. Clinical studies with antibodies to integrin α4β7 and its vascular ligand mucosal vascular addressin cell adhesion molecule 1 are proving the value of lymphocyte trafficking mechanisms as therapeutic targets for inflammatory bowel diseases. In contrast to lymphocytes, cells of the innate immune system express adhesion and chemoattractant receptors that allow them to migrate directly to effector tissue sites during inflammation. We review the mechanisms for innate and adaptive leukocyte localization to the intestinal tract and GALT, and discuss their relevance to human intestinal homeostasis and inflammation.

  5. Indium-111 leukocyte localization in infected prosthetic graft

    Energy Technology Data Exchange (ETDEWEB)

    Purnell, G.L.; Walker, C.W.; Allison, J.W.; Dalrymple, G.V. (Univ. of Arkansas for Medical Sciences, Little Rock (USA))


    Infective endocarditis can be difficult to prove, even in the face of strong clinical suspicion. A case in which standard methods of diagnosis failed to demonstrate endocarditis in a patient with recurrent Staphylococcus aureus bacteremia and porcine aortic valve is reported. An In-111 labelled leukocyte SPECT study demonstrated uptake in the aortic root and leaflets, and autopsy demonstrated vegetations on the leaflets. In-111 may prove useful in demonstrating endocarditis in patients with prosthetic valve infection.

  6. Comparison of photonic and electromagnetic effects on the human leukocyte (United States)

    DellaVecchia, Michael A.; Beard, Richard B.; Feng, D.; Dai, Xiaoyan; Pourrezaei, Kambiz; Priezzhev, Alexander V.


    The dielectric and magnetic influence on human cells have been widely studied previously by the authors. Recently, the effects of energy in the visible electromagnetic spectrum have been investigated. In this subsequent study, the photonic effects on the in vitro migration of the polymorphonuclear and mononuclear leukocytes are compared with the corresponding electromagnetic field effects. Dielectric spectra of the polymorph in the 300 KHz to 400 KHz and 700 KHz to 800 KHz range have been measured. At frequencies of 350 KHz and 720 KHz an increase in the migration of the polymorphonuclear leukocyte have been observed. This stimulation was attributed to the charges on the nuclear surface. Recent preliminary data have shown a similar increased migration in the 20 MHz range. Photonic studies have indicated an enhanced migration for the polymorphonuclear leukocytes at a wavelength of 660 nm (red) and an inhibited migration at 565 nm (green). The photonic effects were postulated to be the results of a biochemical interaction rather than a membranous surface charge displacement secondary to an electric field. The migration of the white blood cells were measurement via the Boyden chamber technique and expressed in terms of a cytokinetic index which expresses the cellular movement independent of its environmental concentration gradient.

  7. Increased oxidative DNA damage in mononuclear leukocytes in vitiligo

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    Giovannelli, Lisa [Department of Preclinical and Clinical Pharmacology, University of Florence, Viale Pieraccini 6, 50139 Florence (Italy)]. E-mail:; Bellandi, Serena [Department of Dermatological Sciences, University of Florence, Viale Pieraccini 6, 50139 Florence (Italy); Pitozzi, Vanessa [Department of Preclinical and Clinical Pharmacology, University of Florence, Viale Pieraccini 6, 50139 Florence (Italy); Fabbri, Paolo [Department of Dermatological Sciences, University of Florence, Viale Pieraccini 6, 50139 Florence (Italy); Dolara, Piero [Department of Preclinical and Clinical Pharmacology, University of Florence, Viale Pieraccini 6, 50139 Florence (Italy); Moretti, Silvia [Department of Dermatological Sciences, University of Florence, Viale Pieraccini 6, 50139 Florence (Italy)


    Vitiligo is an acquired pigmentary disorder of the skin of unknown aetiology. The autocytotoxic hypothesis suggests that melanocyte impairment could be related to increased oxidative stress. Evidences have been reported that in vitiligo oxidative stress might also be present systemically. We used the comet assay (single cell alkaline gel electrophoresis) to evaluate DNA strand breaks and DNA base oxidation, measured as formamidopyrimidine DNA glycosylase (FPG)-sensitive sites, in peripheral blood cells from patients with active vitiligo and healthy controls. The basal level of oxidative DNA damage in mononuclear leukocytes was increased in vitiligo compared to normal subjects, whereas DNA strand breaks (SBs) were not changed. This alteration was not accompanied by a different capability to respond to in vitro oxidative challenge. No differences in the basal levels of DNA damage in polymorphonuclear leukocytes were found between patients and healthy subjects. Thus, this study supports the hypothesis that in vitiligo a systemic oxidative stress exists, and demonstrates for the first time the presence of oxidative alterations at the nuclear level. The increase in oxidative DNA damage shown in the mononuclear component of peripheral blood leukocytes from vitiligo patients was not particularly severe. However, these findings support an adjuvant role of antioxidant treatment in vitiligo.

  8. Common leukocyte antigen staining of a primitive sarcoma. (United States)

    McDonnell, J M; Beschorner, W E; Kuhajda, F P; deMent, S H


    A 4-year-old boy presented with symptoms of tracheal obstruction and was found to have a polypoid tracheal mass, which was studied by biopsy. Light microscopy showed a tumor composed of small cells with round to oval dark nuclei, clumped chromatin, one to two nucleoli, and small, variable amounts of indistinct pink cytoplasm. In other areas the tumor had a loose, spindle appearance, with some cells showing more elongated nuclei, and fibrillar pink cytoplasm consistent with strap cells. Cross striations were not found. Electron microscopy showed desmosomes and 7 to 10 nm cytoplasmic filaments forming dense bodies. The findings are most consistent with a primitive sarcoma, probably rhabdomyosarcoma. Immunoperoxidase with three monoclonal antibodies for common leukocyte antigen showed diffuse membraneous staining with fresh-frozen tissue. All other lymphocyte and monocyte marker studies were negative. We believe that this case of anticommon leukocyte antigen staining, a rhabdomyosarcoma, represents the first report of a false positive reaction with monoclonal antibody to common leukocyte antigen.

  9. Macrophage recognition of ICAM-3 on apoptotic leukocytes. (United States)

    Moffatt, O D; Devitt, A; Bell, E D; Simmons, D L; Gregory, C D


    Cells undergoing apoptosis are cleared rapidly by phagocytes, thus preventing tissue damage caused by loss of plasma membrane integrity. In this study, we show that the surface of leukocytes is altered during apoptosis such that the first Ig-like domain of ICAM-3 (CD50) can participate in the recognition and phagocytosis of the apoptotic cells by macrophages. Macrophage recognition of apoptotic cell-associated ICAM-3 was demonstrated both on leukocytes and, following transfection of exogenous ICAM-3, on nonleukocytes. The change in ICAM-3 was a consistent consequence of apoptosis triggered by various stimuli, suggesting that it occurs as part of a final common pathway of apoptosis. Alteration of ICAM-3 on apoptotic cells permitting recognition by macrophages resulted in a switch in ICAM-3-binding preference from the prototypic ICAM-3 counterreceptor, LFA-1, to an alternative macrophage receptor. Using mAbs to block macrophage/apoptotic cell interactions, we were unable to obtain evidence that either the alternative ICAM-3 counterreceptor alpha d beta 2 or the apoptotic cell receptor alpha v beta 3 was involved in the recognition of ICAM-3. By contrast, mAb blockade of macrophage CD14 inhibited ICAM-3-dependent recognition of apoptotic cells. These results show that ICAM-3 can function as a phagocytic marker of apoptotic leukocytes on which it acquires altered macrophage receptor-binding activity.

  10. Tracking flow of leukocytes in blood for drug analysis (United States)

    Basharat, Arslan; Turner, Wesley; Stephens, Gillian; Badillo, Benjamin; Lumpkin, Rick; Andre, Patrick; Perera, Amitha


    Modern microscopy techniques allow imaging of circulating blood components under vascular flow conditions. The resulting video sequences provide unique insights into the behavior of blood cells within the vasculature and can be used as a method to monitor and quantitate the recruitment of inflammatory cells at sites of vascular injury/ inflammation and potentially serve as a pharmacodynamic biomarker, helping screen new therapies and individualize dose and combinations of drugs. However, manual analysis of these video sequences is intractable, requiring hours per 400 second video clip. In this paper, we present an automated technique to analyze the behavior and recruitment of human leukocytes in whole blood under physiological conditions of shear through a simple multi-channel fluorescence microscope in real-time. This technique detects and tracks the recruitment of leukocytes to a bioactive surface coated on a flow chamber. Rolling cells (cells which partially bind to the bioactive matrix) are detected counted, and have their velocity measured and graphed. The challenges here include: high cell density, appearance similarity, and low (1Hz) frame rate. Our approach performs frame differencing based motion segmentation, track initialization and online tracking of individual leukocytes.

  11. Motility and chemotaxis mediate the preferential colonization of gastric injury sites by Helicobacter pylori.

    Directory of Open Access Journals (Sweden)

    Eitaro Aihara


    Full Text Available Helicobacter pylori (H. pylori is a pathogen contributing to peptic inflammation, ulceration, and cancer. A crucial step in the pathogenic sequence is when the bacterium first interacts with gastric tissue, an event that is poorly understood in vivo. We have shown that the luminal space adjacent to gastric epithelial damage is a microenvironment, and we hypothesized that this microenvironment might enhance H. pylori colonization. Inoculation with 106 H. pylori (wild-type Sydney Strain 1, SS1 significantly delayed healing of acetic-acid induced ulcers at Day 1, 7 and 30 post-inoculation, and wild-type SS1 preferentially colonized the ulcerated area compared to uninjured gastric tissue in the same animal at all time points. Gastric resident Lactobacillus spp. did not preferentially colonize ulcerated tissue. To determine whether bacterial motility and chemotaxis are important to ulcer healing and colonization, we analyzed isogenic H. pylori mutants defective in motility (ΔmotB or chemotaxis (ΔcheY. ΔmotB (10(6 failed to colonize ulcerated or healthy stomach tissue. ΔcheY (10(6 colonized both tissues, but without preferential colonization of ulcerated tissue. However, ΔcheY did modestly delay ulcer healing, suggesting that chemotaxis is not required for this process. We used two-photon microscopy to induce microscopic epithelial lesions in vivo, and evaluated accumulation of fluorescently labeled H. pylori at gastric damage sites in the time frame of minutes instead of days. By 5 min after inducing damage, H. pylori SS1 preferentially accumulated at the site of damage and inhibited gastric epithelial restitution. H. pylori ΔcheY modestly accumulated at the gastric surface and inhibited restitution, but did not preferentially accumulate at the injury site. H. pylori ΔmotB neither accumulated at the surface nor inhibited restitution. We conclude that bacterial chemosensing and motility rapidly promote H. pylori colonization of injury sites

  12. A diffusion based long-range and steady chemical gradient generator on a microfluidic device for studying bacterial chemotaxis (United States)

    Murugesan, Nithya; Singha, Siddhartha; Panda, Tapobrata; Das, Sarit K.


    Studies on chemotaxis in microfluidics device have become a major area of research to generate physiologically similar environment in vitro. In this work, a novel micro-fluidic device has been developed to study chemo-taxis of cells in near physiological condition which can create controllable, steady and long-range chemical gradients using various chemo-effectors in a micro-channel. Hydrogels like agarose, collagen, etc, can be used in the device to maintain exclusive diffusive flux of various chemical species into the micro-channel under study. Variations of concentrations and flow rates of Texas Red dextran in the device revealed that an increase in the concentration of the dye in the feed from 6 to 18 μg ml-1, causes a steeper chemical gradient in the device, whereas the flow rate of the dye has practically no effect on the chemical gradient in the device. This observation confirms that a diffusion controlled chemical gradient is generated in the micro-channel. Chemo-taxis of E. coli cells were studied under the steady gradient of a chemo-attractant and a chemo-repellent separately in the same chemical gradient generator. For sorbitol and NiSO4·6H2O, the bacterial cells exhibit a steady distribution in the micro channel after 1 h and 30 min, respectively. From the distribution of bacterial population chemo-tactic strength of the chemo-effectors was estimated for E. coli. In a long microfluidic channel, migration behavior of bacterial cells under diffusion controlled chemical gradient showed chemotaxis, random movement, aggregation, and concentration dependent reverse chemotaxis.

  13. Plasmodium vivax: paroxysm-associated lipids mediate leukocyte aggregation

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    Mendis Kamini


    Full Text Available Abstract Background Paroxysms are recurrent febrile episodes, characteristic of Plasmodium vivax infections, which coincide with the rupture of schizont-infected erythrocytes in the patients' circulation. The present study describes the formation of prominent aggregates of leukocytes in vitro in the presence of parasite and host factors released during paroxysms. Methods Whole blood cells from uninfected malaria-naïve donors were incubated with plasma taken during a paroxysm or normal human plasma as a control and cell smears were observed under the microscope for the presence of leukocyte aggregates. Plasma factors involved in mediating the leukocyte aggregation were identified using immune depletion and reconstitution experiments. Furthermore, biochemical characterization was carried out to determine the chemical nature of the active moieties in plasma present during paroxysms. Results Leukocyte aggregates were seen exclusively when cells were incubated in plasma collected during a paroxysm. Immune depletion and reconstitution experiments revealed that the host cytokines TNF-alpha, GM-CSF, IL-6 and IL-10 and two lipid fractions of paroxysm plasma comprise the necessary and sufficient mediators of this phenomenon. The two lipid components of the paroxysm plasmas speculated to be of putative parasite origin, were a phospholipid-containing fraction and another containing cholesterol and triglycerides. The phospholipid fraction was dependent upon the presence of cytokines for its activity unlike the cholesterol/triglyceride-containing fraction which in the absence of added cytokines was much more active than the phospholipids fraction. The biological activity of the paroxysm plasmas from non-immune patients who presented with acute P. vivax infections was neutralized by immune sera raised against schizont extracts of either P. vivax or Plasmodium falciparum. However, immune sera against P. vivax were more effective than that against P. falciparum

  14. Intra-amoeba multiplication induces chemotaxis and biofilm colonization and formation for Legionella.

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    Renaud Bigot

    Full Text Available Legionella pneumophila, a facultative intracellular bacterium, is the causative agent of legionellosis. In the environment this pathogenic bacterium colonizes the biofilms as well as amoebae, which provide a rich environment for the replication of Legionella. When seeded on pre-formed biofilms, L. pneumophila was able to establish and survive and was only found at the surface of the biofilms. Different phenotypes were observed when the L. pneumophila, used to implement pre-formed biofilms or to form mono-species biofilms, were cultivated in a laboratory culture broth or had grown intracellulary within the amoeba. Indeed, the bacteria, which developed within the amoeba, formed clusters when deposited on a solid surface. Moreover, our results demonstrate that multiplication inside the amoeba increased the capacity of L. pneumophila to produce polysaccharides and therefore enhanced its capacity to establish biofilms. Finally, it was shown that the clusters formed by L. pneumophila were probably related to the secretion of a chemotaxis molecular agent.

  15. Lotka-Volterra equations with chemotaxis: walls, barriers and travelling waves. (United States)

    Pettet, G J; McElwain, D L; Norbury, J


    In this paper we consider a simple two species model for the growth of new blood vessels. The model is based upon the Lotka-Volterra system of predator and prey interaction, where we identify newly developed capillary tips as the predator species and a chemoattractant which directs their motion as the prey. We extend the Lotka-Volterra system to include a one-dimensional spatial dependence, by allowing the predators to migrate in a manner modelled on the phenomenon of chemotaxis. A feature of this model is its potential to support travelling wave solutions. We emphasize that in order to determine the existence of such travelling waves it is essential that the global relationships of a number of phase plane features other than the equilibria be investigated.

  16. Intra-amoeba multiplication induces chemotaxis and biofilm colonization and formation for Legionella. (United States)

    Bigot, Renaud; Bertaux, Joanne; Frere, Jacques; Berjeaud, Jean-Marc


    Legionella pneumophila, a facultative intracellular bacterium, is the causative agent of legionellosis. In the environment this pathogenic bacterium colonizes the biofilms as well as amoebae, which provide a rich environment for the replication of Legionella. When seeded on pre-formed biofilms, L. pneumophila was able to establish and survive and was only found at the surface of the biofilms. Different phenotypes were observed when the L. pneumophila, used to implement pre-formed biofilms or to form mono-species biofilms, were cultivated in a laboratory culture broth or had grown intracellulary within the amoeba. Indeed, the bacteria, which developed within the amoeba, formed clusters when deposited on a solid surface. Moreover, our results demonstrate that multiplication inside the amoeba increased the capacity of L. pneumophila to produce polysaccharides and therefore enhanced its capacity to establish biofilms. Finally, it was shown that the clusters formed by L. pneumophila were probably related to the secretion of a chemotaxis molecular agent.

  17. Mixture Theory Study of Role of Growth Factor Gradients on Breast Cancer Chemotaxis (United States)

    Chakraborty, Sreyashi; Schuff, Mary; Voigt, Elizabeth; Nauman, Eric; Rylander, Marissa; Vlachos, Pavlos


    The transport of chemotactic agents is strongly influenced by variation in interstitial flows in different types of tissue. The mixture theory model of the fluid and solute transport in the microvasculature of tissues accounts for transport in the vessel lumen, vessel wall and the interstitial space separately. In the present study we use this model to develop a three dimensional geometry of the tumor microenvironment platform incorporating a physiological concentration of growth factor protein through blood flow in an extracellular collagen matrix. We quantify chemotaxis in response to solute gradients of varying magnitude formed by diffusion of proteins into the surrounding collagen. The numerical analysis delineates the dependence of hydraulic permeability coefficient on solute concentration. The preliminary results show the existence of a linear concentration gradient in the central plane between the micro-channels and a strong nonlinear gradient at the remaining parts of the system.

  18. Using structural information to change the phosphotransfer specificity of a two-component chemotaxis signalling complex.

    Directory of Open Access Journals (Sweden)

    Christian H Bell


    Full Text Available Two-component signal transduction pathways comprising histidine protein kinases (HPKs and their response regulators (RRs are widely used to control bacterial responses to environmental challenges. Some bacteria have over 150 different two-component pathways, and the specificity of the phosphotransfer reactions within these systems is tightly controlled to prevent unwanted crosstalk. One of the best understood two-component signalling pathways is the chemotaxis pathway. Here, we present the 1.40 A crystal structure of the histidine-containing phosphotransfer domain of the chemotaxis HPK, CheA(3, in complex with its cognate RR, CheY(6. A methionine finger on CheY(6 that nestles in a hydrophobic pocket in CheA(3 was shown to be important for the interaction and was found to only occur in the cognate RRs of CheA(3, CheY(6, and CheB(2. Site-directed mutagenesis of this methionine in combination with two adjacent residues abolished binding, as shown by surface plasmon resonance studies, and phosphotransfer from CheA(3-P to CheY(6. Introduction of this methionine and an adjacent alanine residue into a range of noncognate CheYs, dramatically changed their specificity, allowing protein interaction and rapid phosphotransfer from CheA(3-P. The structure presented here has allowed us to identify specificity determinants for the CheA-CheY interaction and subsequently to successfully reengineer phosphotransfer signalling. In summary, our results provide valuable insight into how cells mediate specificity in one of the most abundant signalling pathways in biology, two-component signal transduction.

  19. Inhibitory effects of cryptoporus polysaccharide on airway constriction, eosinophil release, and chemotaxis in guinea pigs

    Institute of Scientific and Technical Information of China (English)

    Xiao-yan ZHAO; Qiang-min XIE; Ji-qiang CHEN; Chuan-kui KE


    AIM: To study effects of cryptoporus polysaccharide (CP) on antigen-induced bronchoconstriction, eosinophil peroxidase (EPO) release in vivo, and on platelet activating factor (PAF)-induced eosinophil chemotaxis in vitro in guinea pig. METHODS: The asthma model of guinea pig was formed with ovalbumin (OVA). The changes of lung resistance (RL) and dynamic lung compliance (Cdyn), EPO level in bronchoalveolar lavage fluids (BALF) and eosinophil migration were determined. RESULTS: Pretreatment of CP at doses of 3, 9, and 27 mg/kg by intragastric gavage (ig), qd for 10 d, inhibited early asthma response in a dose-dependent manner. Inhibitory rates of mean increase value from 1 to 30 min of RL were 34.8 %, 74.4 % (P<0.05), and 79.6 % (P<0.05), respectively. Inhibitory rate of mean reduction value of Cdyn were 22.9 %, 40.5 % (P<0.01), and 66.5 % (P<0.01), respectively.Pretreatment of CP at doses of 3, 9, and 27 mg/kg also inhibited late asthma response, and the reduction of EPO level in BALF were 3.1%, 16.9 % (P<0.01), and 20.1% (P<0.01), respectively. The inhibitory rates of CP at concentrations of 0.13, 1.3, 13, 130 nmol/L to eosinophil migration induced by PAF were 6.8 %, 17.2 % (P<0.05),29.6 % (P<0.01), and 35.9 % (P<0.01). CONCLUSION: CP protects lung against increase of RL and reduction of Cdyn, decreases EPO level in the asthma model, and inhibits eosinophil chemotaxis induced by PAF. The results suggest that CP may be a novel antiinflammatory agent for the treatment of asthma and allergic diseases.

  20. Hem-1 complexes are essential for Rac activation, actin polymerization, and myosin regulation during neutrophil chemotaxis.

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    Orion D Weiner


    Full Text Available Migrating cells need to make different actin assemblies at the cell's leading and trailing edges and to maintain physical separation of signals for these assemblies. This asymmetric control of activities represents one important form of cell polarity. There are significant gaps in our understanding of the components involved in generating and maintaining polarity during chemotaxis. Here we characterize a family of complexes (which we term leading edge complexes, scaffolded by hematopoietic protein 1 (Hem-1, that organize the neutrophil's leading edge. The Wiskott-Aldrich syndrome protein family Verprolin-homologous protein (WAVE2 complex, which mediates activation of actin polymerization by Rac, is only one member of this family. A subset of these leading edge complexes are biochemically separable from the WAVE2 complex and contain a diverse set of potential polarity-regulating proteins. RNA interference-mediated knockdown of Hem-1-containing complexes in neutrophil-like cells: (a dramatically impairs attractant-induced actin polymerization, polarity, and chemotaxis; (b substantially weakens Rac activation and phosphatidylinositol-(3,4,5-tris-phosphate production, disrupting the (phosphatidylinositol-(3,4,5-tris-phosphate/Rac/F-actin-mediated feedback circuit that organizes the leading edge; and (c prevents exclusion of activated myosin from the leading edge, perhaps by misregulating leading edge complexes that contain inhibitors of the Rho-actomyosin pathway. Taken together, these observations show that versatile Hem-1-containing complexes coordinate diverse regulatory signals at the leading edge of polarized neutrophils, including but not confined to those involving WAVE2-dependent actin polymerization.

  1. Importance of Primary Capture and L-Selectin–Dependent Secondary Capture in Leukocyte Accumulation in Inflammation and Atherosclerosis in Vivo



    In the multistep process of leukocyte extravasation, the mechanisms by which leukocytes establish the initial contact with the endothelium are unclear. In parallel, there is a controversy regarding the role for L-selectin in leukocyte recruitment. Here, using intravital microscopy in the mouse, we investigated leukocyte capture from the free flow directly to the endothelium (primary capture), and capture mediated through interactions with rolling leukocytes (secondary capture) in venules, in ...

  2. Biomimetic Leukocyte Adhesion: A Review of Microfluidic and Computational Approaches and Applications

    Institute of Scientific and Technical Information of China (English)

    J.Hanzlik; E.Cretekos; K.A.Lamkin-Kennard


    Leukocyte rolling and adhesion are complex physiological processes that have received a great deal of attention over the past decade. Significant increases in the knowledge base related to how leukocytes adhere in shear flows have occurred as a result of the development of novel experimental and computational techniques. Micro- and nano-fabrication techniques have enabled the development of novel flow devices for studying leukocyte adhesion in simple and complex geometries. Improve-ments in computer technology have enabled simulations of complex flow processes to be developed. As a result of these ad-vances in knowledge related to leukocyte adhesion, numerous novel devices have been developed that mimic the leukocyte rolling and adhesion process. Examples of these devices include cell separation and enrichment devices and targeted ultrasound contrast agents. Future advances related to leukocyte rolling and adhesion processes hold great promise for advancing our knowledge of disease processes as well as development of novel therapeutic devices.

  3. Transepithelial activation of human leukocytes by probiotics and commensal bacteria: Role of Enterobacteriaceae-type endotoxin

    DEFF Research Database (Denmark)

    Baeuerlein, Annette; Ackermann, Stefanie; Parlesak, Alexandr


    strains, and some of their pathogen-associated molecular patterns, were incubated apically on a confluent layer of intestinal epithelial cells (Caco-2), which were basolaterally co-cultured with human mononuclear leukocytes. Only Gram-negative bacteria having Enterobacteriaceae-type endotoxin (commensal...... fermenters (Lactobacillus spp.) did not stimulate leukocytes transepithelially. Endotoxin from E. coli and Salmonella enterica Typhimurium induced comparable transepithelial stimulation of leukocytes, but not endotoxin from B. vulgatus or lipoteichoic acid from E. faecalis. Endotoxin-binding agents...... (polymyxin, colistin) completely abrogated transepithelial activation of leukocytes. Enterobacteriaceae-type endotoxin is a crucial factor in transepithelial stimulation of leukocytes, regardless of whether it is produced by probiotics or other bacteria. Hence, transepithelial stimulation of leukocytes...

  4. Chemotaxis cluster 1 proteins form cytoplasmic arrays in Vibrio cholerae and are stabilized by a double signaling domain receptor DosM

    DEFF Research Database (Denmark)

    Briegel, Ariane; Ortega, Davi R; Mann, Petra


    motile bacteria contain one or more additional, sometimes purely cytoplasmic, chemoreceptor systems. Vibrio cholerae contains three chemotaxis clusters (I, II, and III). Here, using electron cryotomography, we explore V. cholerae's cytoplasmic chemoreceptor array and establish that it is formed...

  5. Cell-fluid Interaction: Coupling Between the Deformation of an Adherent Leukocyte and the Shear Flow

    Institute of Scientific and Technical Information of China (English)


    1 IntroductionLeukocyte adhesion is a natural physiopathological phenomenon and the balance between the hemodynamic forces and adhesion forces (molecular bonds) plays a key role. According to hemodynamic theories, blood flow induces the change of the shape and the spatial arrangement of leukocytes. These changes may in turn induce the redistribution of blood flow around the cell. Therefore there exist interaction of the adherent leukocyte with blood flow, which is called as the coupling between the hemodyna...

  6. Cystine accumulation and clearance by normal and cystinotic leukocytes exposed to cystine dimethyl ester.


    Steinherz, R; Tietze, F.; Gahl, W A; Triche, T J; Chiang, H.; Modesti, A.; Schulman, J D


    Upon exposure to 0.25 mM cystine dimethyl ester, normal and cystinotic leukocytes accumulate substantially more intracellular cystine than is present endogenously in cystinotic cells. Leukocytes loaded by exposure to cystine dimethyl ester may have abnormally lucent and distended lysosomes, and the cystine is compartmentalized within the granular fraction of the cells. After the cells are exposed to cystine dimethyl ester, cystine clearance from normal leukocytes is much faster than from cyst...

  7. Imaging of leukocyte trafficking in Alzheimer’s disease

    Directory of Open Access Journals (Sweden)

    Gabriela eConstantin


    Full Text Available Alzheimer’s disease (AD is the most common neurodegenerative disorder and is characterized by a progressive decline of cognitive functions. The neuropathological features of AD include amyloid beta (Aβ deposition, intracellular neurofibrillary tangles derived from the cytoskeletal hyperphosphorylated tau protein, amyloid angiopathy, the loss of synapses, and neuronal degeneration. In the last decade, inflammation has emerged as a key feature of AD, but most studies have focused on the role of microglia-driven neuroinflammation mechanisms. A dysfunctional blood–brain barrier (BBB has also been implicated in the pathogenesis of AD, and several studies have demonstrated that the vascular deposition of Aβ induces the expression of adhesion molecules and alters the expression of tight junction proteins, potentially facilitating the transmigration of circulating leukocytes. Two-photon laser scanning microscopy (TPLSM has become an indispensable tool to dissect the molecular mechanisms controlling leukocyte trafficking in the central nervous system (CNS. Recent TPLSM studies have shown that vascular deposition of Aβ in the CNS promotes intraluminal neutrophil adhesion and crawling on the brain endothelium, and also that neutrophils extravasate in the parenchyma preferentially in areas with Aβ deposits. These studies have also highlighted a role for LFA-1 integrin in neutrophil accumulation in the CNS of AD-like disease models, revealing that LFA-1 inhibition reduces the corresponding cognitive deficit and AD neuropathology. In this article, we consider how current imaging techniques can help to unravel new inflammation mechanisms in the pathogenesis of AD and identify novel therapeutic strategies to treat the disease by interfering with leukocyte trafficking mechanisms.

  8. Role of Gallium and labeled leukocyte scintigraphy in AIDS patient

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    Palestro, C.J. [Division of nuclear medicine, Long Island Jewish Medical Center, New Hyde Park, New York (United States); Goldsmith, S.J. [Division of nuclear medicine, New York Hospital, Cornell Medical Center, New York (United States)


    Because AIDS patients frequently present with minimal symptomatology, radionuclide imaging with its ability to survey the entire body, is especially valuable. Gallium-67 citrate, the most commonly performed radionuclide study for localizing infection in these patients, is most useful for detecting opportunistic infections, especially in the thorax. A negative gallium scan, particularly when the chest X-ray is unremarkable, rules strongly against pulmonary disease. A negative gallium scan in a patient with an abnormal chest X-ray and Kaposi`s sarcoma, suggests that the patient`s respiratory distress is related to the neoplasm. Diffuse pulmonary parenchymal uptake of gallium in the HIV (+) patient is most often associated with PCP. While there are other causes of diffuse pulmonary uptake, the more intense or heterogeneous the uptake, the more likely the patient is to have PCP. Focal pulmonary uptake is usually associated with bacterial pneumonia although PCP may occasionally present in this fashion. Lymph node uptake of gallium is usually associated with Mycob acterium avium complex, tuberculosis, or Iymphoma. When corresponding abnormalities are present on thallium scintigraphy lymphoma is likely. Gallium positive, thallium negative, studies suggest mycobacterial disease. Labeled leukocyte imaging is not useful for detecting opportunistic infections probably because of the inflammatory response incited by these organisms. Leukocyte imaging is, however, more sensitive for detecting bacterial pneumonia. In the abdomen, gallium imaging is most useful for identifying lymphadenopathy, while labeled leukocyte imaging is superior for detecting AlDS-associated colitides. In summary, radionuclide studies are valuable diagnostic modalities in AIDS. Their success can be maximized by tailoring the study to the individual`s needs.

  9. Longitudinal evaluation of leukocyte transcripts in killer whales (Orcinus Orca) (United States)

    Sitt, Tatjana; Bowen, Lizabeth; Lee, Chia-Shan; Blanchard, Myra; McBain, James; Dold, Christopher; Stott, Jeffrey L.


    Early identification of illness and/or presence of environmental and/or social stressors in free-ranging and domestic cetaceans is a priority for marine mammal health care professionals. Incorporation of leukocyte gene transcript analysis into the diagnostic tool kit has the potential to augment classical diagnostics based upon ease of sample storage and shipment, inducible nature and well-defined roles of transcription and associated downstream actions. Development of biomarkers that could serve to identify “insults” and potentially differentiate disease etiology would be of great diagnostic value. To this end, a modest number of peripheral blood leukocyte gene transcripts were selected for application to a domestic killer whale population with a focus on broad representation of inducible immunologically relevant genes. Normalized leukocyte transcript values, longitudinally acquired from 232 blood samples derived from 26 clinically healthy whales, were not visibly influenced temporally nor by sex or the specific Park in which they resided. Stability in leukocyte transcript number during periods of health enhances their potential use in diagnostics through identification of outliers. Transcript levels of two cytokine genes, IL-4 and IL-17, were highly variable within the group as compared to the other transcripts. IL-4 transcripts were typically absent. Analysis of transcript levels on the other genes of interest, on an individual animal basis, identified more outliers than were visible when analyzed in the context of the entire population. The majority of outliers (9 samples) were low, though elevated transcripts were identified for IL-17 from 2 animals and one each for Cox-2 and IL-10. The low number of outliers was not unexpected as sample selection was intentionally directed towards animals that were clinically healthy at the time of collection. Outliers may reflect animals experiencing subclinical disease that is transient and self-limiting. The

  10. Longitudinal evaluation of leukocyte transcripts in killer whales (Orcinus Orca). (United States)

    Sitt, Tatjana; Bowen, Lizabeth; Lee, Chia-Shan; Blanchard, Myra T; McBain, James; Dold, Christopher; Stott, Jeffrey L


    Early identification of illness and/or presence of environmental and/or social stressors in free-ranging and domestic cetaceans is a priority for marine mammal health care professionals. Incorporation of leukocyte gene transcript analysis into the diagnostic tool kit has the potential to augment classical diagnostics based upon ease of sample storage and shipment, inducible nature and well-defined roles of transcription and associated downstream actions. Development of biomarkers that could serve to identify "insults" and potentially differentiate disease etiology would be of great diagnostic value. To this end, a modest number of peripheral blood leukocyte gene transcripts were selected for application to a domestic killer whale population with a focus on broad representation of inducible immunologically relevant genes. Normalized leukocyte transcript values, longitudinally acquired from 232 blood samples derived from 26 clinically healthy whales, were not visibly influenced temporally nor by sex or the specific Park in which they resided. Stability in leukocyte transcript number during periods of health enhances their potential use in diagnostics through identification of outliers. Transcript levels of two cytokine genes, IL-4 and IL-17, were highly variable within the group as compared to the other transcripts. IL-4 transcripts were typically absent. Analysis of transcript levels on the other genes of interest, on an individual animal basis, identified more outliers than were visible when analyzed in the context of the entire population. The majority of outliers (9 samples) were low, though elevated transcripts were identified for IL-17 from 2 animals and one each for Cox-2 and IL-10. The low number of outliers was not unexpected as sample selection was intentionally directed towards animals that were clinically healthy at the time of collection. Outliers may reflect animals experiencing subclinical disease that is transient and self-limiting. The immunologic

  11. Theileria-transformed bovine leukocytes have cancer hallmarks. (United States)

    Tretina, Kyle; Gotia, Hanzel T; Mann, David J; Silva, Joana C


    The genus Theileria includes tick-transmitted apicomplexan parasites of ruminants with substantial economic impact in endemic countries. Some species, including Theileria parva and Theileria annulata, infect leukocytes where they induce phenotypes that are shared with some cancers, most notably immortalization, hyperproliferation, and dissemination. Despite considerable research into the affected host signaling pathways, the parasite proteins directly responsible for these host phenotypes remain unknown. In this review we outline current knowledge on the manipulation of host cells by transformation-inducing Theileria, and we propose that comparisons between cancer biology and host-Theileria interactions can reveal chemotherapeutic targets against Theileria-induced pathogenesis based on cancer treatment approaches.

  12. The Many Faces of Human Leukocyte Antigen-G

    DEFF Research Database (Denmark)

    Dahl, Mette; Djurisic, Snezana; Hviid, Thomas Vauvert F


    is the human leukocyte antigen (HLA)-G, a nonclassical HLA protein displaying limited polymorphism, restricted tissue distribution, and a unique alternative splice pattern. HLA-G is primarily expressed in placenta and plays multifaceted roles during pregnancy, both as a soluble and a membrane-bound molecule...... pregnancy and pregnancy complications, such as preeclampsia, recurrent spontaneous abortions, and subfertility or infertility. This review aims to clarify the multifunctional role of HLA-G in pregnancy-related disorders by focusing on genetic variation, differences in mRNA stability between HLA-G alleles...

  13. Osteomyelitis in leukocyte adhesion deficiency type 1 syndrome

    DEFF Research Database (Denmark)

    Jabbari Azad, Farahzad; Ardalan, Maryam; H.Rafati, Ali;


    Leukocyte adhesion deficiency type 1 (LAD-1) is a rare, inherited immunodeficiency that affects one per million people yearly and usually presents with recurrent, indolent bacterial infections of the skin, mouth, and respiratory tract and impaired pus formation and wound healing. A 13-year-old gi......(10.60%). A plain radiography of the left leg revealed osteomyelitis. It is highly suggested that patients diagnosed mild to moderate LAD-1 with recurrent skin infection and simultaneous weak response to conventional therapy undergo (BMT) marrow transplant to prohibit subsequent life...

  14. Kinetics of reversible-sequestration of leukocytes by the isolated perfused rat lung

    Energy Technology Data Exchange (ETDEWEB)

    Goliaei, B.


    The kinetics and morphology of sequestration and margination of rat leukocytes were studied using an isolated perfused and ventilated rat lung preparation. Whole rat blood, bone marrow suspension, or leukocyte suspensions, were used to perfuse the isolated rat lung. The lung was also perfused with latex particle suspensions and the passage of particles through the lung capillaries was studied. When a leukocyte suspension was perfused through the lung in the single-pass mode, the rate of sequestration decreased as more cells were perfused. In contrast, latex particles of a size comparable to that of leukocytes were totally stopped by the lung. When the leukocyte suspension was recirculated through the lung, cells were rapidly removed from circulation until a steady state was reached, after which no net removal of cells by the lung occurred. These results indicate that leukocytes are reversibly sequestered from circulation. The sequestered cells marginated and attached to the luminal surface of the endothelium of post-capillary venules and veins. A mathematical model was developed based on the assumption that the attachment and detachment of leukocytes to blood vessel walls follows first-order kinetics. The model correctly predicts the following characteristics of the system: (a) the kinetics of the sequestration of leukocytes by the lung; (b) the existence of a steady state when a suspension of leukocytes is recirculated through the lung; and (c) the independence of the fraction of cells remaining in circulation from the starting concentration for all values of starting concentration. (ERB)

  15. Leukocytes Breach Endothelial Barriers by Insertion of Nuclear Lobes and Disassembly of Endothelial Actin Filaments

    Directory of Open Access Journals (Sweden)

    Sagi Barzilai


    Full Text Available The endothelial cytoskeleton is a barrier for leukocyte transendothelial migration (TEM. Mononuclear and polymorphonuclear leukocytes generate gaps of similar micron-scale size when squeezing through inflamed endothelial barriers in vitro and in vivo. To elucidate how leukocytes squeeze through these barriers, we co-tracked the endothelial actin filaments and leukocyte nuclei in real time. Nuclear squeezing involved either preexistent or de novo-generated lobes inserted into the leukocyte lamellipodia. Leukocyte nuclei reversibly bent the endothelial actin stress fibers. Surprisingly, formation of both paracellular gaps and transcellular pores by squeezing leukocytes did not require Rho kinase or myosin II-mediated endothelial contractility. Electron-microscopic analysis suggested that nuclear squeezing displaced without condensing the endothelial actin filaments. Blocking endothelial actin turnover abolished leukocyte nuclear squeezing, whereas increasing actin filament density did not. We propose that leukocyte nuclei must disassemble the thin endothelial actin filaments interlaced between endothelial stress fibers in order to complete TEM.

  16. The Prognostic Values of Leukocyte Rho Kinase Activity in Acute Ischemic Stroke

    Directory of Open Access Journals (Sweden)

    Cheng-I. Cheng


    Full Text Available Objective. It has been reported that leukocyte ROCK activity is elevated in patients after ischemic stroke, but it is unclear whether leukocyte ROCK activity is associated with clinical outcomes following acute stroke events. The objective of this study is to investigate if leukocyte ROCK activity can predict the outcomes in patients with acute ischemic stroke. Materials and Methods. We enrolled 110 patients of acute ischemic stroke and measured the leukocyte ROCK activity and plasma level of inflammatory cytokines to correlate the clinical outcomes of these patients. Results. The leukocyte ROCK activity at 48 hours after admission in acute ischemic stroke patients was higher as compared to a risk-matched population. The leukocyte ROCK activity significantly correlated with National Institute of Health Stroke Scale (NIHSS difference between admission and 90 days after stroke event. Kaplan-Meier survival estimates showed lower stroke-free survival during follow-up period in patients with high leukocyte ROCK activity or plasma hsCRP level. Leukocyte ROCK activity independently predicted the recurrent stroke in patients with atherosclerotic stroke. Conclusions. This study shows elevated leukocyte ROCK activity in patients with ischemic stroke as compared to risk-matched subjects and is an independent predictor for recurrent stroke.

  17. Local histamine release increases leukocyte rolling in the cerebral microcirculation of the mouse. (United States)

    Yong, T; Zheng, M Q; Linthicum, D S


    Histamine-mediated induction of leukocyte rolling and adhesion in the cerebral microcirculation was examined in two inbred strains of mice (SJL/J and BALB/c). A cranial window was surgically prepared for the visualization of the cerebral microcirculation using intra-vital microscopy. Leukocyte rolling and adhesion to pial venular walls were assessed during off-line video playback analyses. The surgical preparation of the cranial windows was found to trigger 'spontaneous' leukocyte rolling, and this was attributed to disruption of dural mast cells and localized release of vasoactive histamine. This spontaneous leukocyte rolling was observed only in the SJL/J strain of mice, and could be prevented by presurgical treatment with the mast cell stabilizer sodium cromoglycate. BALB/c mice did not show 'spontaneous' leukocyte rolling or adhesion; this strain is known to have low numbers of CNS-associated mast cells. Exogenous histamine, applied topically to the cerebral microcirculation via the cranial window in mice pretreated with sodium cromoglycate, produced significant dose-dependent increases in leukocyte rolling and adhesion to pial venules in SJL/J mice, but not in BALB/c mice. Diphenhydramine (H1 receptor antagonist), but not cimetidine (H2 receptor antagonist), abolished both 'spontaneous' and histamine-induced leukocyte rolling. Anti-P-selectin antibody was found efficiently to block both spontaneous and histamine-induced increases in leukocyte rolling, but not leukocyte adhesion.

  18. Development of bactericidal capacity and phagocytosis-associated metabolism of fetal pig leukocytes. (United States)

    Holmes, B; Day, N; Haseman, J; Good, R A


    Evidence that the bactericidal ability and the stimulated oxidative metabolism of leukocytes appear in parallel during fetal development of the Minnesota Miniature pig has been obtained by application of the techniques applied to studies of human cells. It was demonstrated that leukocytes from 87- to 90-day fetuses were fully capable of ingesting Staphylococcus aureus but greatly diminished in bactericidal capacity as compared to leukocytes of older fetuses and adults. Although resting levels of oxygen consumption and hexose monophosphate pathway activity of leukocytes from the younger fetuses compared well with those of leukocytes from older animals, the phagocytosis-stimulated increments of metabolism were much less at 87 to 90 days of gestation than at later developmental stages. Both bactericidal capacity and increased metabolism of leukocytes reach adult levels by 100 days of gestation (normal gestation period of 115 to 120 days). Acrylamide gels stained for reduced nicotinamide adenine dinucleotide (NADH) and NADH phosphate (NADPH) diaphorase activity after disc electrophoresis of leukocyte extracts revealed normal mobility and intensity of NADH diaphorase bands. Three NADPH diaphorase bands were present in adult leukocyte extracts. Only the fast-migrating NADPH diaphorase band of 87- to 90-day cells stained with decreased intensity. This "deficiency" was no longer present at the later fetal period. The fast-migrating NADPH diaphorase band may represent an electron transfer protein which functions in cyanide-insensitive respiration of the leukocytes of the pig.

  19. Sinking, merging and stationary plumes in a coupled chemotaxis-fluid model: a high-resolution numerical approach

    KAUST Repository

    Chertock, A.


    Aquatic bacteria like Bacillus subtilis are heavier than water yet they are able to swim up an oxygen gradient and concentrate in a layer below the water surface, which will undergo Rayleigh-Taylor-type instabilities for sufficiently high concentrations. In the literature, a simplified chemotaxis-fluid system has been proposed as a model for bio-convection in modestly diluted cell suspensions. It couples a convective chemotaxis system for the oxygen-consuming and oxytactic bacteria with the incompressible Navier-Stokes equations subject to a gravitational force proportional to the relative surplus of the cell density compared to the water density. In this paper, we derive a high-resolution vorticity-based hybrid finite-volume finite-difference scheme, which allows us to investigate the nonlinear dynamics of a two-dimensional chemotaxis-fluid system with boundary conditions matching an experiment of Hillesdon et al. (Bull. Math. Biol., vol. 57, 1995, pp. 299-344). We present selected numerical examples, which illustrate (i) the formation of sinking plumes, (ii) the possible merging of neighbouring plumes and (iii) the convergence towards numerically stable stationary plumes. The examples with stable stationary plumes show how the surface-directed oxytaxis continuously feeds cells into a high-concentration layer near the surface, from where the fluid flow (recurring upwards in the space between the plumes) transports the cells into the plumes, where then gravity makes the cells sink and constitutes the driving force in maintaining the fluid convection and, thus, in shaping the plumes into (numerically) stable stationary states. Our numerical method is fully capable of solving the coupled chemotaxis-fluid system and enabling a full exploration of its dynamics, which cannot be done in a linearised framework. © 2012 Cambridge University Press.

  20. Comparative genomics of Pseudomonas syringae pathovar tomato reveals novel chemotaxis pathways associated with motility and plant pathogenicity

    Directory of Open Access Journals (Sweden)

    Christopher R. Clarke


    Full Text Available The majority of bacterial foliar plant pathogens must invade the apoplast of host plants through points of ingress, such as stomata or wounds, to replicate to high population density and cause disease. How pathogens navigate plant surfaces to locate invasion sites remains poorly understood. Many bacteria use chemical-directed regulation of flagellar rotation, a process known as chemotaxis, to move towards favorable environmental conditions. Chemotactic sensing of the plant surface is a potential mechanism through which foliar plant pathogens home in on wounds or stomata, but chemotactic systems in foliar plant pathogens are not well characterized. Comparative genomics of the plant pathogen Pseudomonas syringae pathovar tomato (Pto implicated annotated chemotaxis genes in the recent adaptations of one Pto lineage. We therefore characterized the chemosensory system of Pto. The Pto genome contains two primary chemotaxis gene clusters, che1 and che2. The che2 cluster is flanked by flagellar biosynthesis genes and similar to the canonical chemotaxis gene clusters of other bacteria based on sequence and synteny. Disruption of the primary phosphorelay kinase gene of the che2 cluster, cheA2, eliminated all swimming and surface motility at 21 °C but not 28 °C for Pto. The che1 cluster is located next to Type IV pili biosynthesis genes but disruption of cheA1 has no observable effect on twitching motility for Pto. Disruption of cheA2 also alters in planta fitness of the pathogen with strains lacking functional cheA2 being less fit in host plants but more fit in a non-host interaction.

  1. The Azospirillum brasilense Che1 chemotaxis pathway controls swimming velocity, which affects transient cell-to-cell clumping. (United States)

    Bible, Amber; Russell, Matthew H; Alexandre, Gladys


    The Che1 chemotaxis-like pathway of Azospirillum brasilense contributes to chemotaxis and aerotaxis, and it has also been found to contribute to regulating changes in cell surface adhesive properties that affect the propensity of cells to clump and to flocculate. The exact contribution of Che1 to the control of chemotaxis and flocculation in A. brasilense remains poorly understood. Here, we show that Che1 affects reversible cell-to-cell clumping, a cellular behavior in which motile cells transiently interact by adhering to one another at their nonflagellated poles before swimming apart. Clumping precedes and is required for flocculation, and both processes appear to be independently regulated. The phenotypes of a ΔaerC receptor mutant and of mutant strains lacking cheA1, cheY1, cheB1, or cheR1 (alone or in combination) or with che1 deleted show that Che1 directly mediates changes in the flagellar swimming velocity and that this behavior directly modulates the transient nature of clumping. Our results also suggest that an additional receptor(s) and signaling pathway(s) are implicated in mediating other Che1-independent changes in clumping identified in the present study. Transient clumping precedes the transition to stable clump formation, which involves the production of specific extracellular polysaccharides (EPS); however, production of these clumping-specific EPS is not directly controlled by Che1 activity. Che1-dependent clumping may antagonize motility and prevent chemotaxis, thereby maintaining cells in a metabolically favorable niche.

  2. The 1D parabolic-parabolic Patlak-Keller-Segel model of chemotaxis: The particular integrable case and soliton solution (United States)

    Shubina, Maria


    In this paper, we investigate the one-dimensional parabolic-parabolic Patlak-Keller-Segel model of chemotaxis. For the case when the diffusion coefficient of chemical substance is equal to two, in terms of travelling wave variables the reduced system appears integrable and allows the analytical solution. We obtain the exact soliton solutions, one of which is exactly the one-soliton solution of the Korteweg-de Vries equation.

  3. Leukocyte subsets and neutrophil function after short-term spaceflight (United States)

    Stowe, R. P.; Sams, C. F.; Mehta, S. K.; Kaur, I.; Jones, M. L.; Feeback, D. L.; Pierson, D. L.


    Changes in leukocyte subpopulations and function after spaceflight have been observed but the mechanisms underlying these changes are not well defined. This study investigated the effects of short-term spaceflight (8-15 days) on circulating leukocyte subsets, stress hormones, immunoglobulin levels, and neutrophil function. At landing, a 1.5-fold increase in neutrophils was observed compared with preflight values; lymphocytes were slightly decreased, whereas the results were variable for monocytes. No significant changes were observed in plasma levels of immunoglobulins, cortisol, or adrenocorticotropic hormone. In contrast, urinary epinephrine, norepinephrine, and cortisol were significantly elevated at landing. Band neutrophils were observed in 9 of 16 astronauts. Neutrophil chemotactic assays showed a 10-fold decrease in the optimal dose response after landing. Neutrophil adhesion to endothelial cells was increased both before and after spaceflight. At landing, the expression of MAC-1 was significantly decreased while L-selectin was significantly increased. These functional alterations may be of clinical significance on long-duration space missions.

  4. Peripheral blood and milk leukocytes subsets of lactating Sarda ewes

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    Piero Bonelli


    Full Text Available Leukocytes subpopulations in blood and milk of lactating Sarda ewes were investigated. Animals characterized by a SSC level <500×103cells/mL and a negative bacteriological examination were sampled in early, mid and late lactation. Milk differential cell count evidenced that macrophage represented the main population (42.8%±3.5 followed by lymphocytes (40.2%±3.4 and neutrophils (8,6%±2.1. Flow cytometry analysis showed that lymphocytes subsets in milk were quite different from blood. High CD8+ and low CD4+ lymphocytes percentages determined a CD4/CD8 ratio inversion in milk compared to blood (0.3%±0.03 vs 1.8%±0.08. CD8+ decreased while, conversely, CD4+ increased in late lactation. γδ T cells were more represented in milk (12.6%±1.3 than in blood (6.8%±0.3 and their proportions appeared similar throughout lactation in both compartments. IL-2 receptor was mainly expressed in milk on T cytotoxic lymphocytes. Data obtained in uninfected mammary glands could allow an early discrimination between physiological and pathological changes occurring in ewe milk. Further phenotypical and functional studies on milk leukocytes subsets might help to understand defense mechanisms of the ovine mammary gland against IMI.

  5. Stable and unstable angina: Identifying novel markers on circulating leukocytes. (United States)

    Brown, Angus; Lattimore, Jo-Dee; McGrady, Michele; Sullivan, David; Dyer, Wayne; Braet, Filip; Dos Remedios, Cristobal


    There is currently no blood-based test that can rapidly and objectively distinguish between chest pain which is initiated by increased myocardial oxygen demand (stable angina pectoris (SAP)) and chest pain initiated due to decreased coronary blood flow (unstable angina pectoris (UAP)). Since leukocytes play an active role in the progression of coronary artery disease (CAD), we hypothesize these can provide novel markers of SAP and UAP. Here we use a microarray of 82 cluster of differentiation (CD) antibodies (plus controls) to selectively immobilize peripheral blood mononuclear cells. We find that the pattern of leukocyte immobilization from patients with CAD significantly differs from healthy donors. Within the CAD group, 15 SAP patients exhibited significant (p<0.05) changes in 8 of 82 CD antibody spots compared to 19 age-matched healthy blood donors. An additional ten CD antigens differed between healthy donors and patients with UAP (p<0.05). Furthermore, seven CD antibody spots are significantly different between SAP and UAP patients. These preliminary data suggest it is now appropriate to undertake a larger clinical trial to test the hypothesis that these antibody microarrays can monitor the progression from SAP to UAP.

  6. Fcγ Receptor Heterogeneity in Leukocyte Functional Responses (United States)

    Rosales, Carlos


    Antibodies participate in defense of the organism from all types of pathogens, including viruses, bacteria, fungi, and protozoa. IgG antibodies recognize their associated antigen via their two Fab portions and are in turn recognized though their Fc portion by specific Fcγ receptors (FcγRs) on the membrane of immune cells. Multiple types and polymorphic variants of FcγR exist. These receptors are expressed in many cells types and are also redundant in inducing cell responses. Crosslinking of FcγR on the surface of leukocytes activates several effector functions aimed toward the destruction of pathogens and the induction of an inflammatory response. In the past few years, new evidence on how the particular IgG subclass and the glycosylation pattern of the antibody modulate the IgG–FcγR interaction has been presented. Despite these advances, our knowledge of what particular effector function is activated in a certain cell and in response to a specific type of FcγR remains very limited today. On one hand, each immune cell could be programmed to perform a particular cell function after FcγR crosslinking. On the other, each FcγR could activate a particular signaling pathway leading to a unique cell response. In this review, I describe the main types of FcγRs and our current view of how particular FcγRs activate various signaling pathways to promote unique leukocyte functions. PMID:28373871

  7. Leukocyte responses to immobilized patterns of CXCL8. (United States)

    Girrbach, Maria; Rink, Ina; Ladnorg, Tatjana; Azucena, Carlos; Heißler, Stefan; Haraszti, Tamás; Schepers, Ute; Schmitz, Katja


    The attachment of neutrophils to the endothelial surface and their migration towards the site of inflammation following chemokine gradients play an essential role in the innate immune response. Chemokines adhere to glycosaminoglycans on the endothelial surface to be detected by leukocytes and trigger their movement along surface- bound gradients in a process called haptotaxis. In assays to systematically study the response of leukocytes to surface-bound compounds both the spatial arrangement of the compound as well as the mode of immobilization need to be controlled. In this study microcontact printing was employed to create patterns of hydrophobic or functionalized thiols on gold-coated glass slides and CXCL8 was immobilized on the thiol coated areas using three different strategies. Human neutrophils adhered to the CXCL8-coated lines but not to the PEG-coated background. We could show that more cells adhered to CXCL8 adsorbed to hydrophobic octadecanethiol than on CXCL8 covalently bound to amino undecanethiol or CXCL8 specifically bound to immobilized heparin on aminothiol. Likewise general cell activity such as lamellipodia formation and random migration were most pronounced for CXCL8 adsorbed on a hydrophobic surface which may be attributed to the larger amounts of protein immobilized on this type of surface.

  8. Contribution of Individual Chemoreceptors to Sinorhizobium meliloti Chemotaxis Towards Amino Acids of Host and Nonhost Seed Exudates. (United States)

    Webb, Benjamin A; Helm, Richard F; Scharf, Birgit E


    Plant seeds and roots exude a spectrum of molecules into the soil that attract bacteria to the spermosphere and rhizosphere, respectively. The alfalfa symbiont Sinorhizobium meliloti utilizes eight chemoreceptors (McpT to McpZ and IcpA) to mediate chemotaxis. Using a modified hydrogel capillary chemotaxis assay that allows data quantification and larger throughput screening, we defined the role of S. meliloti chemoreceptors in sensing its host, Medicago sativa, and a closely related nonhost, Medicago arabica. S. meliloti wild type and most single-deletion strains displayed comparable chemotaxis responses to host or nonhost seed exudate. However, while the mcpZ mutant responded like wild type to M. sativa exudate, its reaction to M. arabica exudate was reduced by 80%. Even though the amino acid (AA) amounts released by both plant species were similar, synthetic AA mixtures that matched exudate profiles contributed differentially to the S. meliloti wild-type response to M. sativa (23%) and M. arabica (37%) exudates, with McpU identified as the most important chemoreceptor for AA. Our results show that S. meliloti is equally attracted to host and nonhost legumes; however, AA play a greater role in attraction to M. arabica than to M. sativa, with McpZ being specifically important in sensing M. arabica.

  9. BAFF enhances chemotaxis of primary human B cells: a particular synergy between BAFF and CXCL13 on memory B cells. (United States)

    Badr, Gamal; Borhis, Gwenoline; Lefevre, Eric A; Chaoul, Nada; Deshayes, Frederique; Dessirier, Valérie; Lapree, Genevieve; Tsapis, Andreas; Richard, Yolande


    B-cell-activating factor of the TNF family, (BAFF), and a proliferation-inducing ligand (APRIL) regulate B-lymphocyte survival and activation. We report that BAFF, but not APRIL, increased the chemotactic response of primary human B cells to CCL21, CXCL12, and CXCL13. The BAFF-induced increase in B-cell chemotaxis was totally abolished by blockade of BAFF-R and was strongly dependent on the activation of PI3K/AKT, NF-kappaB, and p38MAPK pathways. BAFF had similar effects on the chemotaxis of naive and memory B cells in response to CCL21 but increased more strongly that of memory B cells to CXCL13 than that of naive B cells. Our findings indicate a previously unreported role for the BAFF/BAFF-R pair in mature B-cell chemotaxis. The synergy between CXCL13 and BAFF produced by stromal cells and follicular dendritic cells may have important implications for B-cell homeostasis, the development of normal B-cell areas, and for the formation of germinal center-like follicles that may be observed in various autoimmune diseases.

  10. Synergy between IL-8 and GM-CSF in reproductive tract epithelial cell secretions promotes enhanced neutrophil chemotaxis. (United States)

    Shen, Li; Fahey, John V; Hussey, Stephen B; Asin, Susana N; Wira, Charles R; Fanger, Michael W


    Neutrophils occur in tissues of the female reproductive tract (FRT) under non-infected conditions. These cells generally enter tissues under the influence of chemoattractants called chemokines. Primary epithelial cells (EC) from FRT were a potent source of chemokines, IL-8 being the chief neutrophil chemoattractant secreted. Blocking with neutralizing anti-IL-8 showed that IL-8 did not account for all of the chemoattraction observed. A mixture of 25 ng/mL rIL-8 and 1 ng/mL rGM-CSF mediated 2.7-fold more chemotaxis than that expected if the two agents were additive. We then found that GM-CSF was produced by EC in amounts that synergised strongly with IL-8 to enhance chemotaxis. Treatment of uterine EC conditioned medium with saturating doses of anti-IL-8 plus anti-GM-CSF antibodies produced an 84% inhibition of chemotaxis. These findings demonstrate that the majority of neutrophil chemoattractant activity produced by FRT EC results from the synergistic effects of IL-8 and GM-CSF.

  11. Thymoquinone inhibits the CXCL12-induced chemotaxis of multiple myeloma cells and increases their susceptibility to Fas-mediated apoptosis.

    Directory of Open Access Journals (Sweden)

    Gamal Badr

    Full Text Available In multiple myeloma (MM, malignant plasma cells reside in the bone marrow, where they accumulate in close contact with stromal cells. The mechanisms responsible for the chemotaxis of malignant plasma cells are still poorly understood. Thus, we investigated the mechanisms involved in the chemotaxis of MDN and XG2 MM cell lines. Both cell lines strongly expressed CCR9, CXCR3 and CXCR4 chemokine receptors but only migrated toward CXCL12. Activation of CXCR4 by CXCL12 resulted in the association of CXCR4 with CD45 and activation of PLCβ3, AKT, RhoA, IκBα and ERK1/2. Using siRNA-silencing techniques, we showed CD45/CXCR4 association is essential for CXCL12-induced migration of MM cells. Thymoquinone (TQ, the major active component of the medicinal herb Nigella sativa Linn, has been described as a chemopreventive and chemotherapeutic compound. TQ treatment strongly inhibited CXCL12-mediated chemotaxis in MM cell lines as well as primary cells isolated from MM patients, but not normal PBMCs. Moreover, TQ significantly down-regulated CXCR4 expression and CXCL12-mediated CXCR4/CD45 association in MM cells. Finally, TQ also induced the relocalization of cytoplasmic Fas/CD95 to the membrane of MM cells and increased CD95-mediated apoptosis by 80%. In conclusion, we demonstrate the potent anti-myeloma activity of TQ, providing a rationale for further clinical evaluation.

  12. Chemotaxis and Binding of Pseudomonas aeruginosa to Scratch-Wounded Human Cystic Fibrosis Airway Epithelial Cells.

    Directory of Open Access Journals (Sweden)

    Christian Schwarzer

    Full Text Available Confocal imaging was used to characterize interactions of Pseudomonas aeruginosa (PA, expressing GFP or labeled with Syto 11 with CF airway epithelial cells (CFBE41o-, grown as confluent monolayers with unknown polarity on coverglasses in control conditions and following scratch wounding. Epithelia and PAO1-GFP or PAK-GFP (2 MOI were incubated with Ringer containing typical extracellular salts, pH and glucose and propidium iodide (PI, to identify dead cells. PAO1 and PAK swam randomly over and did not bind to nonwounded CFBE41o- cells. PA migrated rapidly (began within 20 sec, maximum by 5 mins and massively (10-80 fold increase, termed "swarming", but transiently (random swimming after 15 mins, to wounds, particularly near cells that took up PI. Some PA remained immobilized on cells near the wound. PA swam randomly over intact CFBE41o- monolayers and wounded monolayers that had been incubated with medium for 1 hr. Expression of CFTR and altered pH of the media did not affect PA interactions with CFBE41o- wounds. In contrast, PAO1 swarming and immobilization along wounds was abolished in PAO1 (PAO1ΔcheYZABW, no expression of chemotaxis regulatory components cheY, cheZ, cheA, cheB and cheW and greatly reduced in PAO1 that did not express amino acid receptors pctA, B and C (PAO1ΔpctABC and in PAO1 incubated in Ringer containing a high concentration of mixed amino acids. Non-piliated PAKΔpilA swarmed normally towards wounded areas but bound infrequently to CFBE41o- cells. In contrast, both swarming and binding of PA to CFBE41o- cells near wounds were prevented in non-flagellated PAKΔfliC. Data are consistent with the idea that (i PA use amino acid sensor-driven chemotaxis and flagella-driven swimming to swarm to CF airway epithelial cells near wounds and (ii PA use pili to bind to epithelial cells near wounds.

  13. Production of fibrogenic cytokines by interleukin-2-treated peripheral blood leukocytes

    DEFF Research Database (Denmark)

    Kovacs, E J; Brock, B; Silber, I E;


    was tested for induction of fibroblast proliferation, collagen synthesis, and expression of cytokine genes. RESULTS: Supernatants from IL-2-treated peripheral blood leukocytes induced six times more fibroblast proliferation than medium from leukocytes cultured without IL-2. The expression of type I...

  14. Blockade of leukocyte haptokinesis and haptotaxis by ketoprofen, diclofenac and SC-560

    Directory of Open Access Journals (Sweden)

    Paskauskas Saulius


    Full Text Available Abstract Background Nonsteroidal anti-inflammatory drugs (NSAID represent a one of the most widely used anti-inflammatory substances. Their anti-inflammatory effects are mainly based on inhibition of cyclooxygenase. The potential direct effect of NSAID on leukocyte migration was poorly investigated. Using time-lapse microscopy and 96-well fluorescence-based assay, we studied the effect of three different NSAID, ketoprofen, diclofenac and SC-560, on leukocyte haptokinesis and haptotaxis in vivo and in vitro. Results NSAID induced an immediate inhibiting effect on leukocyte migration both in vitro and in vivo. This effect was dose-dependent and was not restricted to a specific type of leukocytes. The inhibition of leukocyte migration by NSAID was partially re-stored after removal of inhibiting agent. Only complete blockade of leukocyte migration was accompanied by a strong reduction of [Ca2+]i. Conclusions NSAID strongly supress leukocyte migration. The results of the present study may have important clinical implications since blockade of leukocyte migration can be achieved after topical application of NSAID.

  15. Broadly altered gene expression in blood leukocytes in essential hypertension is absent during treatment

    NARCIS (Netherlands)

    Chon, H; Gaillard, CAJM; van der Meijden, BB; Dijstelbloem, HM; Kraaijenhagen, RJ; van Leenen, D; Holstege, FCP; Joles, JA; Bluyssen, HAR; Koomans, HA; Braam, B


    We assessed whether large-scale expression profiling of leukocytes of patients with essential hypertension reflects characteristics of systemic disease and whether such changes are responsive to antihypertensive therapy. Total RNA from leukocytes were obtained from untreated (n=6) and treated (n=6)

  16. Sex difference in leukocyte telomere length is ablated in opposite-sex co-twins

    NARCIS (Netherlands)

    Benetos, Athanase; Dalgard, Christine; Labat, Carlos; Kark, Jeremy D.; Verhulst, Simon; Christensen, Kaare; Kimura, Masayuki; Horvath, Kent; Kyvik, Kirsten Ohm; Aviv, Abraham


    Background: In eutherian mammals and in humans, the female fetus may be masculinized while sharing the intra-uterine environment with a male fetus. Telomere length (TL), as expressed in leukocytes, is heritable and is longer in women than in men. The main determinant of leukocyte TL (LTL) is LTL at

  17. Leukocyte accumulation promoting fibrin deposition is mediated in vivo by P-selectin on adherent platelets (United States)

    Palabrica, Theresa; Lobb, Roy; Furie, Barbara C.; Aronovitz, Mark; Benjamin, Christopher; Hsu, Yen-Ming; Sajer, Susan A.; Furie, Bruce


    THE glycoprotein P-selectin is a cell adhesion molecule of stimulated platelets and endothelial cells, which mediates the interaction of these cells with neutrophils and monocytes1,2. It is a membrane component of cell storage granules3-6, and is a member of the selectin family which includes E-selectin and L-selectin7,8. P-selectin recognizes both lineage-specific carbohydrate ligands on monocytes and neutrophils, including the Lewis x antigen, sialic acid, and a protein component9-12. In inflammation and thrombosis, P-selectin may mediate the interaction of leukocytes with platelets bound in the region of tissue injury and with stimulated endothelium1,2. To evaluate the role of P-selectin in platelet-leukocyte adhesion in vivo, the accumulation of leukocytes within an experimental thrombus was explored in an arteriovenous shunt model in baboons13. A Dacron graft implanted within an arteriovenous shunt is thrombogenic, accumulating platelets and fibrin within its lumen. These bound platelets express P-selectin14. Here we show that antibody inhibition of leukocyte binding to P-selectin expressed on platelets immobilized on the graft blocks leukocyte accumulation and inhibits the deposition of fibrin within the thrombus. These results indicate that P-selectin is an important adhesion molecule on platelets, mediating platelet-leukocyte binding in vivo, that the presence of leukocytes in thrombi is mediated by P-selectin, and that these leukocytes promote fibrin deposition.

  18. Tc-99m HM-PAO labelling of leukocytes for detection of inflammatory bowel disease

    Energy Technology Data Exchange (ETDEWEB)

    Schuemichen, C.; Schoelmerich, J.


    Labelling of purified leukocytes with the brain imaging agent Tc-99m HM-PAO proved to be a reliable method, yielding a 45% labelling efficiency in phosphate buffer and leaving more than 85% of the leukocytes viable. In fifteen patients with M. Crohn, a positive finding was shown in all cases on the six hour image.

  19. Sex difference in leukocyte telomere length is ablated in opposite-sex co-twins

    DEFF Research Database (Denmark)

    Benetos, Athanase; Dalgård, Christine; Labat, Carlos;


    BACKGROUND: In eutherian mammals and in humans, the female fetus may be masculinized while sharing the intra-uterine environment with a male fetus. Telomere length (TL), as expressed in leukocytes, is heritable and is longer in women than in men. The main determinant of leukocyte TL (LTL) is LTL...

  20. JAM-A promotes neutrophil chemotaxis by controlling integrin internalization and recycling. (United States)

    Cera, Maria Rosaria; Fabbri, Monica; Molendini, Cinzia; Corada, Monica; Orsenigo, Fabrizio; Rehberg, Markus; Reichel, Christoph A; Krombach, Fritz; Pardi, Ruggero; Dejana, Elisabetta


    The membrane-associated adhesion molecule JAM-A is required for neutrophil infiltration in inflammatory or ischemic tissues. JAM-A expressed in both endothelial cells and neutrophils has such a role, but the mechanism of action remains elusive. Here we show that JAM-A has a cell-autonomous role in neutrophil chemotaxis both in vivo and in vitro, which is independent of the interaction of neutrophils with endothelial cells. On activated neutrophils, JAM-A concentrates in a polarized fashion at the leading edge and uropod. Surprisingly, a significant amount of this protein is internalized in intracellular endosomal-like vesicles where it codistributes with integrin beta1. Clustering of beta1 integrin leads to JAM-A co-clustering, whereas clustering of JAM-A does not induce integrin association. Neutrophils derived from JAM-A-null mice are unable to correctly internalize beta1 integrins upon chemotactic stimuli and this causes impaired uropod retraction and cell motility. Consistently, inhibition of integrin internalization upon treatment with BAPTA-AM induces a comparable phenotype. These data indicate that JAM-A is required for the correct internalization and recycling of integrins during cell migration and might explain why, in its absence, the directional migration of neutrophils towards an inflammatory stimulus is markedly impaired.

  1. Monte Carlo simulation for kinetic chemotaxis model: An application to the traveling population wave (United States)

    Yasuda, Shugo


    A Monte Carlo simulation of chemotactic bacteria is developed on the basis of the kinetic model and is applied to a one-dimensional traveling population wave in a microchannel. In this simulation, the Monte Carlo method, which calculates the run-and-tumble motions of bacteria, is coupled with a finite volume method to calculate the macroscopic transport of the chemical cues in the environment. The simulation method can successfully reproduce the traveling population wave of bacteria that was observed experimentally and reveal the microscopic dynamics of bacterium coupled with the macroscopic transports of the chemical cues and bacteria population density. The results obtained by the Monte Carlo method are also compared with the asymptotic solution derived from the kinetic chemotaxis equation in the continuum limit, where the Knudsen number, which is defined by the ratio of the mean free path of bacterium to the characteristic length of the system, vanishes. The validity of the Monte Carlo method in the asymptotic behaviors for small Knudsen numbers is numerically verified.

  2. Heterotrimeric G-protein shuttling via Gip1 extends the dynamic range of eukaryotic chemotaxis. (United States)

    Kamimura, Yoichiro; Miyanaga, Yukihiro; Ueda, Masahiro


    Chemotactic eukaryote cells can sense chemical gradients over a wide range of concentrations via heterotrimeric G-protein signaling; however, the underlying wide-range sensing mechanisms are only partially understood. Here we report that a novel regulator of G proteins, G protein-interacting protein 1 (Gip1), is essential for extending the chemotactic range ofDictyosteliumcells. Genetic disruption of Gip1 caused severe defects in gradient sensing and directed cell migration at high but not low concentrations of chemoattractant. Also, Gip1 was found to bind and sequester G proteins in cytosolic pools. Receptor activation induced G-protein translocation to the plasma membrane from the cytosol in a Gip1-dependent manner, causing a biased redistribution of G protein on the membrane along a chemoattractant gradient. These findings suggest that Gip1 regulates G-protein shuttling between the cytosol and the membrane to ensure the availability and biased redistribution of G protein on the membrane for receptor-mediated chemotactic signaling. This mechanism offers an explanation for the wide-range sensing seen in eukaryotic chemotaxis.

  3. Reversible receptor methylation is essential for normal chemotaxis of Escherichia coli in gradients of aspartic acid. (United States)

    Weis, R M; Koshland, D E


    The chemotaxis of wild-type cells of Escherichia coli and double mutants lacking the methyltransferase and the methylesterase activities of the receptor modification system has been compared in spatial gradients of aspartic acid. Previous studies showing that a chemotactic response can be observed for the mutant raised questions about the role of methylation in the bacterial memory. To clarify the role of methylation, the redistribution of bacteria in stabilized defined gradients of aspartic acid was monitored by light scattering. There was no redistribution of the mutant cells in nonsaturating gradients of aspartic acid, but over the same range these mutant bacteria were observed to respond and to adapt during tethering experiments. In large saturating gradients of aspartate, slight movement of the mutant up the gradient was observed. These results show that dynamic receptor methylation is required for the chemotactic response to gentle gradients of aspartic acid and that methylation resets to zero and is part of the normal wild-type memory. There are certain gradients, however, in which the methylation-deficient mutants show chemotactic ability, thus explaining the apparent anomaly. Images PMID:2829179

  4. Chemotaxis can provide biological organisms with good solutions to the travelling salesman problem (United States)

    Reynolds, A. M.


    The ability to find good solutions to the traveling salesman problem can benefit some biological organisms. Bacterial infection would, for instance, be eradicated most promptly if cells of the immune system minimized the total distance they traveled when moving between bacteria. Similarly, foragers would maximize their net energy gain if the distance that they traveled between multiple dispersed prey items was minimized. The traveling salesman problem is one of the most intensively studied problems in combinatorial optimization. There are no efficient algorithms for even solving the problem approximately (within a guaranteed constant factor from the optimum) because the problem is nondeterministic polynomial time complete. The best approximate algorithms can typically find solutions within 1%-2% of the optimal, but these are computationally intensive and can not be implemented by biological organisms. Biological organisms could, in principle, implement the less efficient greedy nearest-neighbor algorithm, i.e., always move to the nearest surviving target. Implementation of this strategy does, however, require quite sophisticated cognitive abilities and prior knowledge of the target locations. Here, with the aid of numerical simulations, it is shown that biological organisms can simply use chemotaxis to solve, or at worst provide good solutions (comparable to those found by the greedy algorithm) to, the traveling salesman problem when the targets are sources of a chemoattractant and are modest in number (n < 10). This applies to neutrophils and macrophages in microbial defense and to some predators.

  5. Biomimetic control based on a model of chemotaxis in Escherichia coli. (United States)

    Tsuji, Toshio; Suzuki, Michiyo; Takiguchi, Noboru; Ohtake, Hisao


    In the field of molecular biology, extending now to the more comprehensive area of systems biology, the development of computer models for synthetic cell simulation has accelerated extensively and has begun to be used for various purposes, such as biochemical analysis. These models, describing the highly efficient environmental searching mechanisms and adaptability of living organisms, can be used as machine-control algorithms in the field of systems engineering. To realize this biomimetic intelligent control, we require a stripped-down model that expresses a series of information-processing tasks from stimulation input to movement. Here we selected the bacterium Escherichia coli as a target organism because it has a relatively simple molecular and organizational structure, which can be characterized using biochemical and genetic analyses. We particularly focused on a motility response known as chemotaxis and developed a computer model that includes not only intracellular information processing but also motor control. After confirming the effectiveness and validity of the proposed model by a series of computer simulations, we applied it to a mobile robot control problem. This is probably the first study showing that a bacterial model can be used as an autonomous control algorithm. Our results suggest that many excellent models proposed thus far for biochemical purposes can be applied to problems in other fields.

  6. Acute exposure to apolipoprotein A1 inhibits macrophage chemotaxis in vitro and monocyte recruitment in vivo (United States)

    Iqbal, Asif J; Barrett, Tessa J; Taylor, Lewis; McNeill, Eileen; Manmadhan, Arun; Recio, Carlota; Carmineri, Alfredo; Brodermann, Maximillian H; White, Gemma E; Cooper, Dianne; DiDonato, Joseph A; Zamanian-Daryoush, Maryam; Hazen, Stanley L; Channon, Keith M


    Apolipoprotein A1 (apoA1) is the major protein component of high-density lipoprotein (HDL) and has well documented anti-inflammatory properties. To better understand the cellular and molecular basis of the anti-inflammatory actions of apoA1, we explored the effect of acute human apoA1 exposure on the migratory capacity of monocyte-derived cells in vitro and in vivo. Acute (20–60 min) apoA1 treatment induced a substantial (50–90%) reduction in macrophage chemotaxis to a range of chemoattractants. This acute treatment was anti-inflammatory in vivo as shown by pre-treatment of monocytes prior to adoptive transfer into an on-going murine peritonitis model. We find that apoA1 rapidly disrupts membrane lipid rafts, and as a consequence, dampens the PI3K/Akt signalling pathway that coordinates reorganization of the actin cytoskeleton and cell migration. Our data strengthen the evidence base for therapeutic apoA1 infusions in situations where reduced monocyte recruitment to sites of inflammation could have beneficial outcomes. DOI: PMID:27572261

  7. Fractional Adams-Bashforth/Moulton methods: An application to the fractional Keller-Segel chemotaxis system (United States)

    Zayernouri, Mohsen; Matzavinos, Anastasios


    We first formulate a fractional class of explicit Adams-Bashforth (A-B) and implicit Adams-Moulton (A-M) methods of first- and second-order accuracy for the time-integration of 0 CD t τ u (x , t) = g (t ; u), τ ∈ (0 , 1 ], where 0 CD t τ denotes the fractional derivative in the Caputo sense. In this fractional setting and in contrast to the standard Adams methods, an extra history load term emerges and the associated weight coefficients are τ-dependent. However when τ = 1, the developed schemes reduce to the well-known A-B and A-M methods with standard coefficients. Hence, in terms of scientific computing, our approach constitutes a minimal modification of the existing Adams libraries. Next, we develop an implicit-explicit (IMEX) splitting scheme for linear and nonlinear fractional PDEs of a general advection-reaction-diffusion type, and we apply our scheme to the time-space fractional Keller-Segel chemotaxis system. In this context, we evaluate the nonlinear advection term explicitly, employing the fractional A-B method in the prediction step, and we treat the corresponding diffusion term implicitly in the correction step using the fractional A-M scheme. Moreover, we perform the corresponding spatial discretization by employing an efficient and spectrally-accurate fractional spectral collocation method. Our numerical experiments exhibit the efficiency of the proposed IMEX scheme in solving nonlinear fractional PDEs.

  8. Maneuverability and chemotaxis of Caenorhabditis elegans in three-dimensional environments (United States)

    Blawzdziewicz, Jerzy; Bilbao, Alejandro; Patel, Amar; Vanapalli, Siva


    Locomotion of the nematode C. elegans in water and complex fluids has recently been investigated to gain insight into neuromuscular control of locomotion and to shed light on nematode evolutionary adaptation to environments with varying mechanical properties. Previous studies focused mainly on locomotion efficiency and on adaptation of the nematode gait to the surrounding medium. Much less attention has been devoted to nematode maneuverability, in spite of its crucial role in the survival of the animal. Recently we have provided a quantitative analysis of turning maneuvers of crawling and swimming nematodes on flat surfaces and in 2D fluid layers. Based on this work, we follow with the first full 3D description of how C. elegans moves in complex 3D environments. We show that by superposing body twist and 2D undulations, a burrowing or swimming nematode can rotate the undulation plane and change the direction of motion within that plane by varying undulation-wave parameters. A combination of these corkscrew maneuvers and 2D turns allows the nematode to explore 3D space. We conclude by analyzing 3D chemotaxis of nematodes burrowing in gel and swimming in water, which demonstrates an important application of our maneuverability model. This work was supported by NSF grant CBET-1059745.

  9. The green tea catechin epigallocatechin gallate (EGCG blocks cell motility, chemotaxis and development in Dictyostelium discoideum.

    Directory of Open Access Journals (Sweden)

    Kyle J McQuade

    Full Text Available Catechins, flavanols found at high levels in green tea, have received significant attention due to their potential health benefits related to cancer, autoimmunity and metabolic disease, but little is known about the mechanisms by which these compounds affect cellular behavior. Here, we assess whether the model organism Dictyostelium discoideum is a useful tool with which to characterize the effects of catechins. Epigallocatechin gallate (EGCG, the most abundant and potent catechin in green tea, has significant effects on the Dictyostelium life cycle. In the presence of EGCG aggregation is delayed, cells do not stream and development is typically stalled at the loose aggregate stage. The developmental effects very likely result from defects in motility, as EGCG reduces both random movement and chemotaxis of Dictyostelium amoebae. These results suggest that catechins and their derivatives may be useful tools with which to better understand cell motility and development in Dictyostelium and that this organism is a useful model to further characterize the activities of catechins.

  10. The rate of change in Ca(2+) concentration controls sperm chemotaxis. (United States)

    Alvarez, Luis; Dai, Luru; Friedrich, Benjamin M; Kashikar, Nachiket D; Gregor, Ingo; Pascal, René; Kaupp, U Benjamin


    During chemotaxis and phototaxis, sperm, algae, marine zooplankton, and other microswimmers move on helical paths or drifting circles by rhythmically bending cell protrusions called motile cilia or flagella. Sperm of marine invertebrates navigate in a chemoattractant gradient by adjusting the flagellar waveform and, thereby, the swimming path. The waveform is periodically modulated by Ca(2+) oscillations. How Ca(2+) signals elicit steering responses and shape the path is unknown. We unveil the signal transfer between the changes in intracellular Ca(2+) concentration ([Ca(2+)](i)) and path curvature (κ). We show that κ is modulated by the time derivative d[Ca(2+)](i)/dt rather than the absolute [Ca(2+)](i). Furthermore, simulation of swimming paths using various Ca(2+) waveforms reproduces the wealth of swimming paths observed for sperm of marine invertebrates. We propose a cellular mechanism for a chemical differentiator that computes a time derivative. The cytoskeleton of cilia, the axoneme, is highly conserved. Thus, motile ciliated cells in general might use a similar cellular computation to translate changes of [Ca(2+)](i) into motion.

  11. In-111-labeled leukocyte brain SPECT imaging. Clinical significance in evaluating acute ischemic stroke

    Energy Technology Data Exchange (ETDEWEB)

    Fujinuma, Kunihiko [Kitasato Univ., Sagamihara, Kanagawa (Japan). School of Medicine


    Many experimental studies have demonstrated that leukocyte infiltration plays an important role in the progression of ischemic cellular damage or post perfusion brain injury. However, only a few clinical studies have been reported. The purpose of this study is to evaluate the clinical significance of leukocyte accumulation in the ischemic brain tissue. Seventy six patients (49 men, 27 women; mean age: 65.5{+-}13.9 years) with acute ischemic stroke were studied by leukocyte brain SPECT imaging. A diagnosis included cardioembolism (n=46), atherothrombotic infarction (n=24), TIA (n=3) and lacuna (n=3). Immediately after the CBF study using Tc-99m-ECD (600 MBq), indium-111-labeled autologous leukocytes were injected. A brain scan for leukocytes was performed 48 hours later. The leukocyte-SPECT study was made 11.1{+-}7.7 days after the onset of stroke. Regional accumulation of leukocytes in the ischemic tissue was evaluated both by visual assessment and by measuring the hemispheric asymmetry index for leukocyte (AI-leuko), and was evaluated by comparison with variable factors including age, gender, infarction size, hemorrhagic transformation, timing of study after the onset, type of stroke and functional outcome. Of the 61 patients with acute ischemic stroke within 2 weeks of onset, 28 patients showed the accumulation of leukocytes in the central zone of ischemia. Six of 7 patients with repeated studies showed a reduction in leukocyte accumulation with time after the onset. Factors significantly associated with the higher accumulation of leukocyte included cardioembolic stroke, larger size of infarct, presence of hemorrhagic transformation and significant reduction in flow. In the 61 patients within 2 weeks of onset, the functional outcome was significantly correlated with the accumulation of leukocyte (p<0.001). The accumulation of leukocytes was seen more in patients with embolic stroke, larger infarction, and hemorrhagic transformation. The higher accumulation

  12. Preclinical studies for the gene therapy of leukocyte adhesion deficiency type I

    Energy Technology Data Exchange (ETDEWEB)

    Leon Rico, D.


    Leukocyte Adhesion Deficiency Type I (LAD-I) is a primary immunodeficiency caused by mutations in ITGB2 gene, encoding for CD18 protein (also known as 2 subunit). This protein binds to different CD11 subunits to form 2 integrins, which are expressed in the leukocyte membrane and allow leukocytes to firmly adhere to the endothelium as a previous step to the extravasation. In LAD-I patients, ITGB2 mutations lead to absent, low or aberrant CD18 expression, which results in absent or low 2 integrin expression on the leukocyte membrane. CD18 deficient leukocytes, especially neutrophils, fail to extravasate from the bloodstream to infected tissues. LAD-I patients suffer from recurrent and severe infections leading normally to death. (Author)

  13. Filtration of activated granulocytes during cardiopulmonary bypass surgery : A morphologic and immunologic study to characterize the trapped leukocytes

    NARCIS (Netherlands)

    Smit, JJJ; de Vries, AJ; Gu, YJ; van Oeveren, W


    Cardiopulmonary bypass surgery induces an inflammatory reaction among others by activation of granulocytes. Leukocyte filtration has been shown to reduce the postoperative morbidity mediated by activated granulocytes. However, little is known about the mechanism of filter-leukocyte interaction, This

  14. Influence of antioxidant complex on the adhesion of leukocytes in chronic venous insufficiency of lower limbs in rats

    Directory of Open Access Journals (Sweden)

    Mark Plotnikov


    Conclusions: Model of CVI of lower limb is accompanied by increased venous pressure and raised adhesion activity of leukocytes. Administration of AOC for 14 days reduces the adhesive activity of leukocytes.

  15. Human Leukocyte Antigen Diversity: A Southern African Perspective

    Directory of Open Access Journals (Sweden)

    Mqondisi Tshabalala


    Full Text Available Despite the increasingly well-documented evidence of high genetic, ethnic, and linguistic diversity amongst African populations, there is limited data on human leukocyte antigen (HLA diversity in these populations. HLA is part of the host defense mechanism mediated through antigen presentation to effector cells of the immune system. With the high disease burden in southern Africa, HLA diversity data is increasingly important in the design of population-specific vaccines and the improvement of transplantation therapeutic interventions. This review highlights the paucity of HLA diversity data amongst southern African populations and defines a need for information of this kind. This information will support disease association studies, provide guidance in vaccine design, and improve transplantation outcomes.

  16. In vitro effect of benzodiazepines on polymorphonuclear leukocyte oxidative activity. (United States)

    Goldfarb, G; Belghiti, J; Gautero, H; Boivin, P


    The effect of three benzodiazepine compounds, diazepam, flunitrazepam, and clorazepate, on oxidative activity of human polymorphonuclear leukocyte (PMN) was investigated. The oxidative activity of zymosan-stimulated PMN in the presence of three concentrations (10, 20, and 40 micrograms/ml) of these compounds was measured polarographically. In addition, zymosan-stimulated nitroblue tetrazolium (NBT) reduction was measured in the presence of various concentrations of flunitrazepam. All three compounds inhibited oxygen consumption of the PMN. The extent of inhibition was linear with respect to log-concentrations; oxygen consumption was reduced 50% for concentrations of diazepam, flunitrazepam, and clorazepate of 13 micrograms/ml, 56 micrograms/ml, and 285 micrograms/ml, respectively. In addition 30% and 100% inhibition of NBT reduction by flunitrazepam were observed at respective concentrations of 10 micrograms/ml and 60 micrograms/ml. The clinical relevance of these findings remains to be determined.

  17. Diterpenoids from Tetraclinis articulata that inhibit various human leukocyte functions. (United States)

    Barrero, Alejandro F; Quílez del Moral, José F; Lucas, Rut; Payá, Miguel; Akssira, Mohamed; Akaad, Said; Mellouki, Fouad


    Ten new compounds, eight of them pimarane derivatives (1-8), together with a menthane dimer (9) and a totarane diterpenoid (10), were isolated from the leaves and wood of Tetraclinis articulata. The structures of 1-10 were established by using spectroscopic techniques, including 2D NMR spectra. Pimaranes 1-5 were found to possess an unusual cis interannular union of the B and C rings, which, from a biogenetic perspective, could be derived from the hydration of a carbocation at C-8. Compounds 4-6 and a mixture of 7 and 11 modulated different human leukocyte functions at a concentration of 10 microM, mainly the degranulation process measured as myeloperoxidase release and, to a lesser extent, the superoxide production measured by chemiluminescence.

  18. Leukocyte apheresis in the management of ulcerative colitis

    Directory of Open Access Journals (Sweden)

    Helmy Ahmed


    Full Text Available Ulcerative colitis is a chronic inflammatory disease that affects the colon and rectum. Its pathogenesis is probably multifactorial including the influx of certain cytokines into the colonic mucosa, causing disease activity and relapse. The hypothesis of removing such cytokines from the circulation by leukocytapheresis was implemented to reduce disease activity, maintain remission, and prevent relapse. Many recent reports not only in Japan, but also in the West, have highlighted its beneficial effects in both adult and pediatric patients. Large placebo-controlled studies are needed to confirm the available data in this regard. In this article, we shed some light on the use of leukocyte apheresis in the management of autoimmune diseases, especially ulcerative colitis.

  19. Characterization of Leukocyte-platelet Rich Fibrin, A Novel Biomaterial. (United States)

    Madurantakam, Parthasarathy; Yoganarasimha, Suyog; Hasan, Fadi K


    Autologous platelet concentrates represent promising innovative tools in the field of regenerative medicine and have been extensively used in oral surgery. Unlike platelet rich plasma (PRP) that is a gel or a suspension, Leukocyte-Platelet Rich Fibrin (L-PRF) is a solid 3D fibrin membrane generated chair-side from whole blood containing no anti-coagulant. The membrane has a dense three dimensional fibrin matrix with enriched platelets and abundant growth factors. L-PRF is a popular adjunct in surgeries because of its superior handling characteristics as well as its suturability to the wound bed. The goal of the study is to demonstrate generation as well as provide detailed characterization of relevant properties of L-PRF that underlie its clinical success.

  20. Correlation between Leukocyte Numbers and Body Size of Rainbow Trout

    DEFF Research Database (Denmark)

    Mohammad, Rezkar Jaafar; Otani, Maki; Kania, Per Walter;


    towards an antigen to be initiated even in fry. The number of leukocytes in individual fish at different developmental stages is likely to influence the capacity of the fish to respond simultaneously to several antigens (pathogens and vaccine components). This parameter may therefore be crucial for both...... - 780 g (group IV) were investigated. The number of lymphocytes was generally higher in head kidney compared to blood and spleen but they dominated in all samples (blood, head kidney and spleen) and their numbers increased exponentially with fish size. Percentages of lymphocytes in relation...... to neutrophils and macrophages were higher in spleen (98% - 99%) compared to blood and head kidney in all groups. Fish fry is therefore equipped to respond specifically against one or a few vaccine antigens, but the capacity to raise protective responses against a repertoire of pathogens may be limited until...

  1. Susceptibility of different leukocyte cell types to Vaccinia virus infection

    Directory of Open Access Journals (Sweden)

    Sánchez-Puig Juana M


    Full Text Available Abstract Background Vaccinia virus, the prototype member of the family Poxviridae, was used extensively in the past as the Smallpox vaccine, and is currently considered as a candidate vector for new recombinant vaccines. Vaccinia virus has a wide host range, and is known to infect cultures of a variety of cell lines of mammalian origin. However, little is known about the virus tropism in human leukocyte populations. We report here that various cell types within leukocyte populations have widely different susceptibility to infection with vaccinia virus. Results We have investigated the ability of vaccinia virus to infect human PBLs by using virus recombinants expressing green fluorescent protein (GFP, and monoclonal antibodies specific for PBL subpopulations. Flow cytometry allowed the identification of infected cells within the PBL mixture 1–5 hours after infection. Antibody labeling revealed that different cell populations had very different infection rates. Monocytes showed the highest percentage of infected cells, followed by B lymphocytes and NK cells. In contrast to those cell types, the rate of infection of T lymphocytes was low. Comparison of vaccinia virus strains WR and MVA showed that both strains infected efficiently the monocyte population, although producing different expression levels. Our results suggest that MVA was less efficient than WR in infecting NK cells and B lymphocytes. Overall, both WR and MVA consistently showed a strong preference for the infection of non-T cells. Conclusions When infecting fresh human PBL preparations, vaccinia virus showed a strong bias towards the infection of monocytes, followed by B lymphocytes and NK cells. In contrast, very poor infection of T lymphocytes was detected. These finding may have important implications both in our understanding of poxvirus pathogenesis and in the development of improved smallpox vaccines.

  2. Detection of CFTR protein in human leukocytes by flow cytometry. (United States)

    Johansson, Jan; Vezzalini, Marzia; Verzè, Genny; Caldrer, Sara; Bolognin, Silvia; Buffelli, Mario; Bellisola, Giuseppe; Tridello, Gloria; Assael, Baroukh Maurice; Melotti, Paola; Sorio, Claudio


    Leukocytes have previously been shown to express detectable levels of the protein cystic fibrosis transmembrane conductance regulator (CFTR). This study aims to evaluate the application of flow cytometric (FC) analysis to detect CFTR expression, and changes thereof, in these cells. Aliquots (200 μL) of peripheral whole blood from 12 healthy control volunteers (CTRLs), 12 carriers of a CFTR mutation (CFC), and 40 patients with cystic fibrosis (CF) carrying various combinations of CFTR mutations were incubated with specific fluorescent probes recognizing CFTR protein expressed on the plasma membrane of leukocytes. FC was applied to analyze CFTR expression in monocytes, lymphocytes, and polymorphonuclear (PMN) cells. CFTR protein was detected in monocytes and lymphocytes, whereas inconclusive results were obtained from the analysis of PMN cells. Mean fluorescence intensity (MFI) ratio value and %CFTR-positive cells above a selected threshold were the two parameters selected to quantify CFTR expression in cells. Lowest variability and the highest reproducibility were obtained when analyzing monocytes. ANOVA results indicated that both parameters were able to discriminate monocytes of healthy controls and CF individuals according to CFTR mutation classes with high accuracy. Significantly increased MFI ratio values were recorded in CFTR-defective cells that were also able to improve CFTR function after ex vivo treatment with PTC124 (Ataluren), an investigative drug designed to permit the ribosome to read through nonsense CFTR mutations. The method described is minimally invasive and may be used in the monitoring of responses to drugs whose efficacy can depend on increased CFTR protein expression levels. © 2014 International Society for Advancement of Cytometry.

  3. Relationship between leukocyte count and angiographical characteristics of coronary atherosclerosis

    Institute of Scientific and Technical Information of China (English)

    En-zhi JIA; Zhi-jian YANG; Biao YUAN; Xiao-ling ZANG; Rong-hu WANG; Tie-bing ZHU; Lian-sheng WANG; Bo CHEN; Wen-zhu MA


    Aim: To explore the relationship between differential leucocyte count and coronary atherosclerosis. Methods: The study population consisted of 507 consecutive patients (376 male and 131 female) who underwent coronary angiography for suspected or known coronary atherosclerosis. The patients' smoking and drinking habits were investigated, and anthropometric measurements, serum measurements, and hematological measurements were conducted for every patient.The severity of coronary atherosclerosis was defined by using Gensini' s score system. One-way ANOVA, Spearman's correlation analysis, and multivariate stepwise linear regression analysis were employed to explore the relationship between differential leucocyte count and coronary atherosclerosis. Results: Oneway ANOVA indicated that the diastolic blood pressure, glucose, urea, creatinine,leukocyte count, neutrophil count, monocyte count, hemoglobin, and platelet count differed among the groups according to Gensini's score, the tertile values of which were used as cutoff points. Spearman's correlation analysis suggested that Gensini's score was significantly correlated with age, diastolic blood pressure,glucose, urea, creatinine, leukocyte count, neutrophil count, monocyte count,hemoglobin, and erythrocyte count, respectively. Multivariate stepwise linear regression analysis show that neutrophil count (β=0.247, P=0.000), age (β=0.141,P=0.001), glucose (β=0.173, P=0.000), creatinine (β=0.088, P=0.063), hemoglobin (β=-0.168, P=0.013) and sex (men were coded as 1 and women were coded as 2;β=-0.121, P=0.012) were significantly independently associated with the Gensini's score. Conclusion: The independent association of neutrophil count with the angiographical characteristics of coronary atherosclerosis, as estimated by Gensini's score, strongly suggests that granulocytosis may play a role in the development of coronary atherosclerosis.

  4. Serum stimulation of CCR7 chemotaxis due to coagulation factor XIIa-dependent production of high-molecular-weight kininogen domain 5. (United States)

    Ponda, Manish P; Breslow, Jan L


    Chemokines and their receptors play a critical role in immune function by directing cell-specific movement. C-C chemokine receptor 7 (CCR7) facilitates entry of T cells into lymph nodes. CCR7-dependent chemotaxis requires either of the cognate ligands C-C chemokine ligand 19 (CCL19) or CCL21. Although CCR7-dependent chemotaxis can be augmented through receptor up-regulation or by increased chemokine concentrations, we found that chemotaxis is also markedly enhanced by serum in vitro. Upon purification, the serum cofactor activity was ascribed to domain 5 of high-molecular-weight kininogen. This peptide was necessary and sufficient for accelerated chemotaxis. The cofactor activity in serum was dependent on coagulation factor XIIa, a serine protease known to induce cleavage of high-molecular-weight kininogen (HK) at sites of inflammation. Within domain 5, we synthesized a 24-amino acid peptide that could recapitulate the activity of intact serum through a mechanism distinct from up-regulating CCR7 expression or promoting chemokine binding to CCR7. This peptide interacts with the extracellular matrix protein thrombospondin 4 (TSP4), and antibodies to TSP4 neutralize its activity. In vivo, an HK domain 5 peptide stimulated homing of both T and B cells to lymph nodes. A circulating cofactor that is activated at inflammatory foci to enhance lymphocyte chemotaxis represents a powerful mechanism coupling inflammation to adaptive immunity.

  5. Lysophosphatidic acid induces chemotaxis in MC3T3-E1 osteoblastic cells

    Energy Technology Data Exchange (ETDEWEB)

    Masiello, Lisa M.; Fotos, Joseph S.; Galileo, Deni S.; Karin, Norm J.


    Lysophosphatidic acid (LPA) is a bioactive lipid that has pleiotropic effects on a variety of cell types and enhances the migration of endothelial and cancer cells, but it is not known if this lipid can alter osteoblast motility. We performed transwell migration assays using MC3T3-E1 osteoblastic cells and found LPA to be a potent chemotactic agent. Quantitative time-lapse video analysis of osteoblast migration after wounds were introduced into cell monolayers indicated that LPA stimulated both migration velocity and the average migration distance per cell. LPA also elicited substantial changes in cell shape and actin cytoskeletal structure; lipid-treated cells contained fewer stress fibers and displayed long membrane processes that were enriched in F-actin. Quantitative RT-PCR analysis showed that MC3T3-E1 cells express all four known LPA-specific G protein-coupled receptors (LPA1-LPA4) with a relative mRNA abundance of LPA1 > LPA4 > LPA2 >> LPA3. LPA-induced changes in osteoblast motility and morphology were antagonized by both pertussis toxin and Ki16425, a subtype-specific blocker of LPA1 and LPA3 receptor function. Cell migration in many cell types is linked to changes in intracellular Ca2+. Ki16425 also inhibited LPA-induced Ca2+ signaling in a dose-dependent manner, suggesting a link between LPA-induced Ca2+ transients and osteoblast chemotaxis. Our data show that LPA stimulates MC3T3-E1 osteoblast motility via a mechanism that is linked primarily to the G protein-coupled receptor LPA1.

  6. Impaired NK Cell Activation and Chemotaxis toward Dendritic Cells Exposed to Complement-Opsonized HIV-1 (United States)

    Ellegård, Rada; Crisci, Elisa; Andersson, Jonas; Shankar, Esaki M.; Nyström, Sofia; Hinkula, Jorma


    Mucosa resident dendritic cells (DCs) may represent one of the first immune cells that HIV-1 encounters during sexual transmission. The virions in body fluids can be opsonized with complement factors because of HIV-mediated triggering of the complement cascade, and this appears to influence numerous aspects of the immune defense targeting the virus. One key attribute of host defense is the ability to attract immune cells to the site of infection. In this study, we investigated whether the opsonization of HIV with complement (C-HIV) or a mixture of complement and Abs (CI-HIV) affected the cytokine and chemokine responses generated by DCs, as well as their ability to attract other immune cells. We found that the expression levels of CXCL8, CXCL10, CCL3, and CCL17 were lowered after exposure to either C-HIV or CI-HIV relative to free HIV (F-HIV). DCs exposed to F-HIV induced higher cell migration, consisting mainly of NK cells, compared with opsonized virus, and the chemotaxis of NK cells was dependent on CCL3 and CXCL10. NK cell exposure to supernatants derived from HIV-exposed DCs showed that F-HIV induced phenotypic activation (e.g., increased levels of TIM3, CD69, and CD25) and effector function (e.g., production of IFNγ and killing of target cells) in NK cells, whereas C-HIV and CI-HIV did not. The impairment of NK cell recruitment by DCs exposed to complement-opsonized HIV and the lack of NK activation may contribute to the failure of innate immune responses to control HIV at the site of initial mucosa infection. PMID:26157174

  7. Analogs of cyclic AMP as chemoattractants and inhibitors of Dictyostelium chemotaxis. (United States)

    Van Haastert, P J; Jastorff, B; Pinas, J E; Konijn, T M


    Aggregative amoebae of Dictyostelium discoideum, D. mucoroides, D. purpureum, and D. rosarium react chemotactically to cyclic AMP (cAMP). We measured the chemotactic activity of 14 cAMP analogs and found that these four species have a similar sensitivity to chemical modifications of cAMP; this suggests that the cAMP receptor is identical in all of these species. Besides the induction of a chemotactic response, cAMP analogs also may delay or prevent cell aggregation. cAMP analogs like N1-O-cAMP, 2'-H-cAMP, and 5'NH-cAMP are chemotactically nearly as active as cAMP and induced no, or only a short, delay of cell aggregation. Other cAMP derivatives, such as 6-Cl-cPMP and 8-Br-cAMP, are chemotactically active only at high concentrations and delayed cell aggregation for several hours. Still other cAMP analogs, which do not induce a chemotactic reaction in D. mucoroides, D. purpureum, and D. rosarium, either prevented cell aggregation [cAMPS(S), cAMPS(R), and 3'-NH-cAMP[ or had no effect on cell aggregation [cAMPN(CH3)2(S) and cAMPN(CH3)2(R)]. cAMP analog 3'-NH-cAMP prevented cell aggregation by the inhibition of chemotaxis, whereas cell locomotion was not affected. Although we cannot provide a satisfactory explantation for these observations, our data suggest that occupation and activation of the cAMP receptors do not always induced a chemotactic response.

  8. A high-throughput microfluidic approach for 1000-fold leukocyte reduction of platelet-rich plasma (United States)

    Xia, Hui; Strachan, Briony C.; Gifford, Sean C.; Shevkoplyas, Sergey S.


    Leukocyte reduction of donated blood products substantially reduces the risk of a number of transfusion-related complications. Current ‘leukoreduction’ filters operate by trapping leukocytes within specialized filtration material, while allowing desired blood components to pass through. However, the continuous release of inflammatory cytokines from the retained leukocytes, as well as the potential for platelet activation and clogging, are significant drawbacks of conventional ‘dead end’ filtration. To address these limitations, here we demonstrate our newly-developed ‘controlled incremental filtration’ (CIF) approach to perform high-throughput microfluidic removal of leukocytes from platelet-rich plasma (PRP) in a continuous flow regime. Leukocytes are separated from platelets within the PRP by progressively syphoning clarified PRP away from the concentrated leukocyte flowstream. Filtrate PRP collected from an optimally-designed CIF device typically showed a ~1000-fold (i.e. 99.9%) reduction in leukocyte concentration, while recovering >80% of the original platelets, at volumetric throughputs of ~1 mL/min. These results suggest that the CIF approach will enable users in many fields to now apply the advantages of microfluidic devices to particle separation, even for applications requiring macroscale flowrates.

  9. A multiscale SPH particle model of the near-wall dynamics of leukocytes in flow. (United States)

    Gholami, Babak; Comerford, Andrew; Ellero, Marco


    A novel multiscale Lagrangian particle solver based on SPH is developed with the intended application of leukocyte transport in large arteries. In such arteries, the transport of leukocytes and red blood cells can be divided into two distinct regions: the bulk flow and the near-wall region. In the bulk flow, the transport can be modeled on a continuum basis as the transport of passive scalar concentrations. Whereas in the near-wall region, specific particle tracking of the leukocytes is required and lubrication forces need to be separately taken into account. Because of large separation of spatio-temporal scales involved in the problem, simulations of red blood cells and leukocytes are handled separately. In order to take the exchange of leukocytes between the bulk fluid and the near-wall region into account, solutions are communicated through coupling of conserved quantities at the interface between these regions. Because the particle tracking is limited to those leukocytes lying in the near-wall region only, our approach brings considerable speedup to the simulation of leukocyte circulation in a test geometry of a backward-facing step, which encompasses many flow features observed in vivo.

  10. Effect of leukocyte filtration on the P-selectin expression of apheresis platelets. (United States)

    Xie, Z T; Chen, C; Zhang, S H; Yang, H M; Tao, Z H


    The aim of this study was to investigate the effect of leukocyte filtration on the P-selectin (CD62P) surface expression of apheresis platelets during the retention period. Ten bags of apheresis platelets stored for 1 day (0-24 h) and 10 bags of apheresis platelets stored for 2 days (24-48 h) were used for leukocyte filtration (experimental group). Ten bags of apheresis platelets with the corresponding retention periods but without filtration were used as a negative control (control group). Thereafter, 100 μL of platelet suspensions from apheresis platelets with or without leukocyte filtration were sampled before and after leukocyte filtration for the detection of CD62P surface expression by flow cytometry. No statistical difference in the CD62P surface expression of apheresis platelets was observed before and after leukocyte filtration (P > 0.05), neither did the CD62P surface expression exhibit any change among the different retention periods. Leukocyte filtration does not affect the CD62P surface expression of apheresis platelets stored for up to 2 days, which indicates that leukocyte filtration does not damage the activation of apheresis platelets within the retention period.

  11. Single Cell Analysis of Leukocyte Protease Activity Using Integrated Continuous-Flow Microfluidics. (United States)

    Jing, Tengyang; Lai, Zhangxing; Wu, Lidan; Han, Jongyoon; Lim, Chwee Teck; Chen, Chia-Hung


    Leukocytes are the essential cells of the immune system that protect the human body against bacteria, viruses, and other foreign invaders. Secretory products of individual leukocytes, such as matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase (ADAMs), are critical for regulating the inflammatory response and mediating host defense. Conventional single cell analytical methods, such as flow cytometry for cellular surface biomarker studies, are insufficient for performing functional assays of the protease activity of individual leukocytes. Here, an integrated continuous-flow microfluidic assay is developed to effectively detect secretory protease activity of individual viable leukocytes. Leukocytes in blood are first washed on-chip with defined buffer to remove background activity, followed by encapsulating individual leukocytes with protease sensors in water-in-oil droplets and incubating for 1 h to measure protease secretion. With this design, single leukocyte protease profiles under naive and phorbol 12-myristate 13-acetate (PMA)-stimulated conditions are reliably measured. It is found that PMA treatment not only elevates the average protease activity level but also reduces the cellular heterogeneity in protease secretion, which is important in understanding immune capability and the disease condition of individual patients.

  12. A high-throughput microfluidic approach for 1000-fold leukocyte reduction of platelet-rich plasma. (United States)

    Xia, Hui; Strachan, Briony C; Gifford, Sean C; Shevkoplyas, Sergey S


    Leukocyte reduction of donated blood products substantially reduces the risk of a number of transfusion-related complications. Current 'leukoreduction' filters operate by trapping leukocytes within specialized filtration material, while allowing desired blood components to pass through. However, the continuous release of inflammatory cytokines from the retained leukocytes, as well as the potential for platelet activation and clogging, are significant drawbacks of conventional 'dead end' filtration. To address these limitations, here we demonstrate our newly-developed 'controlled incremental filtration' (CIF) approach to perform high-throughput microfluidic removal of leukocytes from platelet-rich plasma (PRP) in a continuous flow regime. Leukocytes are separated from platelets within the PRP by progressively syphoning clarified PRP away from the concentrated leukocyte flowstream. Filtrate PRP collected from an optimally-designed CIF device typically showed a ~1000-fold (i.e. 99.9%) reduction in leukocyte concentration, while recovering >80% of the original platelets, at volumetric throughputs of ~1 mL/min. These results suggest that the CIF approach will enable users in many fields to now apply the advantages of microfluidic devices to particle separation, even for applications requiring macroscale flowrates.

  13. Deformation mechanism of leukocyte adhering to vascular surface under steady shear flow

    Institute of Scientific and Technical Information of China (English)

    LIU; Xiaoheng; WANG; Xiong; YIN; Hongmei; CHEN; Huaiqing


    The adhesion of leukocytes to vascular surface is an important biomedical problem and has drawn extensive attention. In this study, we propose a compound drop model to simulate a leukocyte with a nucleus adhering to the surface of blood vessel under steady shear flow. A two-dimensional computational fluid dynamics (CFD) is conducted to determine the local distribution of pressure on the surface of the adherent model cell. By introducing the parameter of deformation index (DI), we investigate the deformation of the leukocyte and its nucleus under controlled conditions. Our numerical results show that: (i) the leukocyte is capable of deformation under external exposed flow field. The deformation index increases with initial contact angle and Reynolds number of external exposed flow. (ii) The nucleus deforms with the cell, and the deformation index of the leukocyte is greater than that of the nucleus. The leukocyte is more deformable while the nucleus is more capable of resisting external shear flow. (iii) The leukocyte and the nucleus are not able to deform infinitely with the increase of Reynolds number because the deformation index reaches a maximum. (iv) Pressure distribution confirms that there exists a region downstream of the cell, which produces high pressure to retard continuous deformation and provide a positive lift force on the cell. Meanwhile, we have measured the deformation of human leukocytes exposed to shear flow by using a flow chamber system. We found that the numerical results are well consistent with those of experiment. We conclude that the nucleus with high viscosity plays a particular role in leukocyte deformation.

  14. Is Chronic Asthma Associated with Shorter Leukocyte Telomere Length at Midlife? (United States)

    Shalev, Idan; Sears, Malcolm R.; Hancox, Robert J.; Lee Harrington, Hona; Houts, Renate; Moffitt, Terrie E.; Sugden, Karen; Williams, Benjamin; Poulton, Richie; Caspi, Avshalom


    Rationale: Asthma is prospectively associated with age-related chronic diseases and mortality, suggesting the hypothesis that asthma may relate to a general, multisystem phenotype of accelerated aging. Objectives: To test whether chronic asthma is associated with a proposed biomarker of accelerated aging, leukocyte telomere length. Methods: Asthma was ascertained prospectively in the Dunedin Multidisciplinary Health and Development Study cohort (n = 1,037) at nine in-person assessments spanning ages 9–38 years. Leukocyte telomere length was measured at ages 26 and 38 years. Asthma was classified as life-course-persistent, childhood-onset not meeting criteria for persistence, and adolescent/adult-onset. We tested associations between asthma and leukocyte telomere length using regression models. We tested for confounding of asthma-leukocyte telomere length associations using covariate adjustment. We tested serum C-reactive protein and white blood cell counts as potential mediators of asthma-leukocyte telomere length associations. Measurements and Main Results: Study members with life-course-persistent asthma had shorter leukocyte telomere length as compared with sex- and age-matched peers with no reported asthma. In contrast, leukocyte telomere length in study members with childhood-onset and adolescent/adult-onset asthma was not different from leukocyte telomere length in peers with no reported asthma. Adjustment for life histories of obesity and smoking did not change results. Study members with life-course-persistent asthma had elevated blood eosinophil counts. Blood eosinophil count mediated 29% of the life-course-persistent asthma-leukocyte telomere length association. Conclusions: Life-course-persistent asthma is related to a proposed biomarker of accelerated aging, possibly via systemic eosinophilic inflammation. Life histories of asthma can inform studies of aging. PMID:24956257

  15. Human Neutrophil’S Chemotaxis and Intracellular Killing in Response to Type 1 Piliated Uropathogenic Escherichia Coli

    Directory of Open Access Journals (Sweden)

    N Nooritalab


    Full Text Available Introduction: Uropathogenic Escherichia coli (UPEC, the commonest cause of urinary tract infections, bind to target cells and phagocytes via several distinct pairs of adhesins and receptors. In some cases bacterial binding to phagocytes ends to bacterial elimination. The survival and spread of bacteria in infected tissues are determined by the resistance of bacteria to elimination by phagocytic cells like neutrophils. The aim of this study was to determine the role of type 1 pili in interaction of UPEC with human neutrophils and its effect on bacterial killing. Methods: We used 3 clinical and 1 standard strains of type 1 piliated and 1 unpiliated standard strain of UPEC. Type 1 piliated and unpiliated strains (obtained by growth at a pilus-restrictive temperature of UPEC were used for determining the effect of this pili on migration of neutrophils towards bacteria in Boyden chamber. Also intracellular killing of bacteria by human neutrophils was estimated by counting of the number of viable bacteria in 45 minutes after incubation of piliated and unpiliated strains with purified neutrophils.The results were analyzed with t-test. Results: In chemotaxis assay, PMN migration towards piliated strains was 46-73% of that observed with FMLP, but it was 34-41% in unpiliated strains.The results obtained showed that type 1 piliated UPEC stimulated significantly greater chemotaxis than did unpiliated ones(P<0.05.In phagocytic killing assay, 40-70% of piliated strains were killed in 30 min after incubation with PMN, but the number of viable unpiliated strains was increased in this period of time .There was a significant difference between the intracellular killing of piliated and unpiliated strains with neutrophils (P<0.05. Discusion: Human granulocytes recognize type 1 piliated UPEC via α-mannose-containing structures. So the existence of this adhesin on UPEC strains can leads to increase of neutrophil chemotaxis towards bacteria, phagocytosis and

  16. Leukocytes respiratory burst activity as indicator of innate immunity of pacu Piaractus mesopotamicus

    Directory of Open Access Journals (Sweden)

    JD Biller-Takahashi

    Full Text Available The present study evaluated the assay to quantify the respiratory burst activity of blood leukocytes of pacu as an indicator of the innate immune system, using the reduction of nitroblue tetrazolium (NBT to formazan as a measure of the production of reactive oxygen species (ROS. In order to assess the accuracy of the assay, fish were challenged by Aeromonas hydrophila and sampled one week after challenge. The A. hydrophila infection increased the leukocyte respiratory burst activity. The protocol showed a reliable and easy assay, appropriate to determine the respiratory burst activity of blood leukocytes of pacu, a neotropical fish, in the present experimental conditions.

  17. Longer leukocyte telomere length in Costa Rica's Nicoya Peninsula: a population-based study. (United States)

    Rehkopf, David H; Dow, William H; Rosero-Bixby, Luis; Lin, Jue; Epel, Elissa S; Blackburn, Elizabeth H


    Studies in humans suggest that leukocyte telomere length may act as a marker of biological aging. We investigated whether individuals in the Nicoya region of Costa Rica, known for exceptional longevity, had longer telomere length than those in other parts of the country. After controlling for age, age squared, rurality, rainy season and gender, the mean leukocyte telomere length in Nicoya was substantially longer (81 base pairs, ptelomere length that characterizes this unique region does not appear to be explainable by traditional behavioral and biological risk factors. More detailed examination of mean leukocyte telomere length by age shows that the regional telomere length difference declines at older ages.

  18. Increased thymidylate synthase mRNA concentration in blood leukocytes following an experimental stressor

    DEFF Research Database (Denmark)

    Ehrnrooth, Eva; Zacharia, Robert; Svendsen, Gunner


    to a computerized mental stressor; (2) relaxation, and (3) control. Measurements included TS mRNA levels, total leukocyte number, leukocyte subtypes, and serum cortisol before (baseline), immediately after, and 1 h after each experimental condition. RESULTS: While no significant differences were found between...... in percentage of neutrophil cells after stress. CONCLUSION: The results suggest that TS mRNA levels in peripheral leukocytes may be sensitive to mental stress and confirm previous findings indicating that subjects scoring high on the personality trait of absorption exhibit greater physiological stress...

  19. Study of terahertz-radiation-induced DNA damage in human blood leukocytes

    Energy Technology Data Exchange (ETDEWEB)

    Angeluts, A A; Esaulkov, M N; Kosareva, O G; Solyankin, P M; Shkurinov, A P [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation); Gapeyev, A B; Pashovkin, T N [Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region (Russian Federation); Matyunin, S N [Section of Applied Problems at the Presidium of the Russian Academy of Sciences, Moscow (Russian Federation); Nazarov, M M [Institute on Laser and Information Technologies, Russian Academy of Sciences, Shatura, Moscow Region (Russian Federation); Cherkasova, O P [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)


    We have carried out the studies aimed at assessing the effect of terahertz radiation on DNA molecules in human blood leukocytes. Genotoxic testing of terahertz radiation was performed in three different oscillation regimes, the blood leukocytes from healthy donors being irradiated for 20 minutes with the mean intensity of 8 – 200 μW cm{sup -2} within the frequency range of 0.1 – 6.5 THz. Using the comet assay it is shown that in the selected regimes such radiation does not induce a direct DNA damage in viable human blood leukocytes. (biophotonics)

  20. Efficiency of application original preservatives for conservation leukocytes at -40 °C

    Directory of Open Access Journals (Sweden)

    Utemov S.V.


    Full Text Available When frozen leukocytes exposed to harmful factors of the complex, due to their complex cellular structure and high metabolism. Cryopreservatives allow to avoid damages, but most of which are toxic. The aim of the present was to compare the efficacy of application of two non-toxic solutions for conservation of leukocytes at -40°С for 1 day. It was show that solution containing cryoprotector mixed action (a derivative of urea and antihypoxant (sodium fumarate is most effective in preserving the functional activity of leukocytes.

  1. Draft genome sequence of Sinorhizobium meliloti RU11/001, a model organism for flagellum structure, motility and chemotaxis. (United States)

    Wibberg, Daniel; Blom, Jochen; Rückert, Christian; Winkler, Anika; Albersmeier, Andreas; Pühler, Alfred; Schlüter, Andreas; Scharf, Birgit E


    Sinorhizobium meliloti of the order Rhizobiales is a symbiotic nitrogen-fixing bacterium nodulating plants of the genera Medicago, Trigonella and Melilotus and hence is of great agricultural importance. In its free-living state it is motile and capable of modulating its movement patterns in response to chemical attractants. Here, the draft genome consisting of a circular chromosome, the megaplasmids pSymA and pSymB and three accessory plasmids of Sinorhizobium meliloti RU11/001, a model organism for flagellum structure, motility and chemotaxis, is reported.

  2. Integrin activation by P-Rex1 is required for selectin-mediated slow leukocyte rolling and intravascular crawling. (United States)

    Herter, Jan M; Rossaint, Jan; Block, Helena; Welch, Heidi; Zarbock, Alexander


    Integrin activation is essential for the function of leukocytes. Impaired integrin activation on leukocytes is the hallmark of the leukocyte adhesion deficiency syndrome in humans, characterized by impaired leukocyte recruitment and recurrent infections. In inflammation, leukocytes collect different signals during the contact with the microvasculature, which activate signaling pathways leading to integrin activation and leukocyte recruitment. We report the role of P-Rex1, a Rac-specific guanine nucleotide exchanging factor, in integrin activation and leukocyte recruitment. We find that P-Rex1 is required for inducing selectin-mediated lymphocyte function-associated antigen-1 (LFA-1) extension that corresponds to intermediate affinity and induces slow leukocyte rolling, whereas P-Rex1 is not involved in the induction of the high-affinity conformation of LFA-1 obligatory for leukocyte arrest. Furthermore, we demonstrate that P-Rex1 is involved in Mac-1-dependent intravascular crawling. In vivo, both LFA-1-dependent slow rolling and Mac-1-dependent crawling are defective in P-Rex1(-/-) leukocytes, whereas chemokine-induced arrest and postadhesion strengthening remain intact in P-Rex1-deficient leukocytes. Rac1 is involved in E-selectin-mediated slow rolling and crawling. In vivo, in an ischemia-reperfusion-induced model of acute kidney injury, abolished selectin-mediated integrin activation contributed to decreased neutrophil recruitment and reduced kidney damage in P-Rex1-deficient mice. We conclude that P-Rex1 serves distinct functions in LFA-1 and Mac-1 activation.

  3. Differential regulation of neutrophil chemotaxis to IL-8 and fMLP by GM-CSF: lack of direct effect of oestradiol. (United States)

    Shen, Li; Smith, Jennifer M; Shen, Zheng; Hussey, Stephen B; Wira, Charles R; Fanger, Michael W


    Neutrophils are a normal constituent of the female reproductive tract and their numbers increase in the late secretory phase of the menstrual cycle prior to menses. Several cytokines are produced in female reproductive tract tissue. In particular granulocyte-macrophage colony-stimulating factor (GM-CSF), a potent activator of neutrophils, is secreted in high concentrations by female reproductive tract epithelia. We previously observed that GM-CSF synergizes strongly with interleukin-8 (IL-8) in enhancing chemotaxis of neutrophils. Thus we investigated whether pretreatment of neutrophils with GM-CSF would prime subsequent chemotaxis to IL-8 in the absence of GM-CSF. Surprisingly, a 3-hr pulse of GM-CSF severely diminished chemotaxis to IL-8, whereas N-formyl-methyl-leucyl-phenylalanine (fMLP)-mediated chemotaxis was retained. Conversely, when cells were incubated without GM-CSF they retained IL-8-mediated migration but lost fMLP chemotaxis. These changes in chemotaxis did not correlate with expression of CXCR1, CXCR2 or formyl peptide receptor. However, IL-8-mediated phosphorylation of p44/42 mitogen-activated protein kinase was greatly reduced in neutrophils that no longer migrated to IL-8, and was diminished in cells that no longer migrated to fMLP. Oestradiol, which is reported by some to exert an anti-inflammatory effect on neutrophils, did not change the effects of GM-CSF. These data suggest that neutrophil function may be altered by cytokines such as GM-CSF through modulation of signalling and independently of surface receptor expression.

  4. Intestinal invasion of Salmonella enterica serovar Typhimurium in the avian host is dose dependent and does not depend on motility and chemotaxis

    DEFF Research Database (Denmark)

    Olsen, John Elmerdahl; Hoegh-Andersen, Kirsten Hobolt; Rosenkrantz, Jesper Tjørnholt;


    Salmonella enterica serotype Typhimurium (S. Typhimurium) can invade in the intestine of the avian host, and knowledge on the mechanisms that govern this is potentially important for prevention of disease. This study investigated the invasion of S. Typhimurium in the avian host and to which extent...... functional flagella or chemotaxis genes. In support of the results from intestinal loop experiments, flagella and chemotaxis genes were not significantly important to the outcome of an oral infection. The results showed that S. Typhimurium invasion in the avian host was dose dependent and was not affected...

  5. Automatic leukocyte nucleus segmentation by intuitionistic fuzzy divergence based thresholding. (United States)

    Jati, Arindam; Singh, Garima; Mukherjee, Rashmi; Ghosh, Madhumala; Konar, Amit; Chakraborty, Chandan; Nagar, Atulya K


    The paper proposes a robust approach to automatic segmentation of leukocyte's nucleus from microscopic blood smear images under normal as well as noisy environment by employing a new exponential intuitionistic fuzzy divergence based thresholding technique. The algorithm minimizes the divergence between the actual image and the ideally thresholded image to search for the final threshold. A new divergence formula based on exponential intuitionistic fuzzy entropy has been proposed. Further, to increase its noise handling capacity, a neighborhood-based membership function for the image pixels has been designed. The proposed scheme has been applied on 110 normal and 54 leukemia (chronic myelogenous leukemia) affected blood samples. The nucleus segmentation results have been validated by three expert hematologists. The algorithm achieves an average segmentation accuracy of 98.52% in noise-free environment. It beats the competitor algorithms in terms of several other metrics. The proposed scheme with neighborhood based membership function outperforms the competitor algorithms in terms of segmentation accuracy under noisy environment. It achieves 93.90% and 94.93% accuracies for Speckle and Gaussian noises, respectively. The average area under the ROC curves comes out to be 0.9514 in noisy conditions, which proves the robustness of the proposed algorithm.

  6. Role of salivary leukocyte protease inhibitor in periodontal disease progression

    Directory of Open Access Journals (Sweden)

    Pateel Deepak


    Full Text Available Context: Proteases play a major role in the tissue destruction involved in periodontal disease. It is known that the balance between proteases and their inhibitors is a major determinant in maintaining tissue integrity. The association between the proteases and periodontitis is well established, but not many studies have been carried out to know the role played by a protease inhibitor like salivary leukocyte protease inhibitor (SLPI in periodontitis. Aim: The aim of the present study was to correlate SLPI with periodontitis. Settings and Design: Case-control study. Materials and Methods: Seventy-five clinically confirmed cases of periodontitis and 20 controls were included in the study. A detailed case history and periodontal index (PI were recorded. Two milliliters of unstimulated saliva samples was obtained and subjected to quantification of SLPI leaves using SLPI in enzyme-linked immunosorbent assay (ELISA kit. Based on the periodontal index score of the individuals, the cases and controls were divided into groups A, B and C, and the obtained SLPI levels were compared among the groups. Statistical Analysis: Mann-Whitney U test and correlation coefficient test. Results: The results showed that in the initial stages of periodontitis there is a tendency of SLPI levels to be raised. The SLPI levels were found to be reduced in the terminal stages of periodontitis. Conclusion: It appears that SLPI accumulates in the local environment, at least in the initial stages of the periodontal disease, probably to inhibit the action of increased elastic activity.

  7. Identifying coevolutionary patterns in human leukocyte antigen (HLA) molecules. (United States)

    Jiang, Xiaowei; Fares, Mario A


    The antigenic peptide, major histocompatibility complex molecule (MHC; also called human leukocyte antigen, HLA), coreceptor CD8, or CD4 and T-cell receptor (TCR) function as a complex to initiate effectors' mechanisms of the immune system. The tight functional and physical interaction among these molecules may have involved strong coevolution links among domains within and between proteins. Despite the importance of unraveling such dependencies to understand the arms race of host-pathogen interaction, no previous studies have aimed at achieving such an objective. Here, we perform an exhaustive coevolution analysis and show that indeed such dependencies are strongly shaping the evolution and probably the function of these molecules. We identify intramolecular coevolution in HLA class I and II at domains important for their immune activity. Most of the amino acid sites identified to be coevolving in HLAI have been also detected to undergo positive Darwinian selection highlighting therefore their adaptive value. We also identify coevolution among antigen-binding pockets (P1-P9) and among these and TCR-binding sites. Conversely to HLAI, coevolution is weaker in HLAII. Our results support that such coevolutionary patterns are due to selective pressures of host-pathogen coevolution and cooperative binding of TCRs, antigenic peptides, and CD8/CD4 to HLAI and HLAII.

  8. Swine leukocyte antigen (SLA) diversity in Sinclair and Hanford swine. (United States)

    Ho, Chak-Sum; Martens, Gregory W; Amoss, Max S; Gomez-Raya, Luis; Beattie, Craig W; Smith, Douglas M


    The swine leukocyte antigen (SLA) haplotype B is associated with increased penetrance of the tumor traits in Sinclair swine cutaneous melanoma (SSCM). We established a series of SinclairxHanford swine crosses to facilitate genetic mapping of the tumor-associated loci. In this study, the SLA diversity in the founding animals was characterized for effective selection of maximum tumor penetrance in the pedigrees. Using the sequence-based typing (SBT) method we identified a total of 29 alleles at five polymorphic SLA loci (SLA-1, SLA-3, SLA-2, DRB1 and DQB1) representing six class I and five class II haplotypes. We subsequently developed a rapid PCR-based typing assay using sequence-specific primers (PCR-SSP) to efficiently follow the SLA types of the crossbred progeny. In a total of 469 animals we identified three crossovers within the class I region and three between the class I and class II regions, which corresponded to recombination frequencies of 0.39% and 0.56%, respectively. We also confirmed the presence of two expressed SLA-1 loci in three of the class I haplotypes and were able to determine the relative chromosomal arrangement of the duplicated loci in two haplotypes. This study furthers our understanding of the allelic architecture and polymorphism of the SLA system and will facilitate the mapping of loci associated with the expression of SSCM.

  9. HLA-Modeler: Automated Homology Modeling of Human Leukocyte Antigens

    Directory of Open Access Journals (Sweden)

    Shinji Amari


    Full Text Available The three-dimensional (3D structures of human leukocyte antigen (HLA molecules are indispensable for the studies on the functions at molecular level. We have developed a homology modeling system named HLA-modeler specialized in the HLA molecules. Segment matching algorithm is employed for modeling and the optimization of the model is carried out by use of the PFROSST force field considering the implicit solvent model. In order to efficiently construct the homology models, HLA-modeler uses a local database of the 3D structures of HLA molecules. The structure of the antigenic peptide-binding site is important for the function and the 3D structure is highly conserved between various alleles. HLA-modeler optimizes the use of this structural motif. The leave-one-out cross-validation using the crystal structures of class I and class II HLA molecules has demonstrated that the rmsds of nonhydrogen atoms of the sites between homology models and crystal structures are less than 1.0 Å in most cases. The results have indicated that the 3D structures of the antigenic peptide-binding sites can be reproduced by HLA-modeler at the level almost corresponding to the crystal structures.

  10. HLA-Modeler: Automated Homology Modeling of Human Leukocyte Antigens. (United States)

    Amari, Shinji; Kataoka, Ryoichi; Ikegami, Takashi; Hirayama, Noriaki


    The three-dimensional (3D) structures of human leukocyte antigen (HLA) molecules are indispensable for the studies on the functions at molecular level. We have developed a homology modeling system named HLA-modeler specialized in the HLA molecules. Segment matching algorithm is employed for modeling and the optimization of the model is carried out by use of the PFROSST force field considering the implicit solvent model. In order to efficiently construct the homology models, HLA-modeler uses a local database of the 3D structures of HLA molecules. The structure of the antigenic peptide-binding site is important for the function and the 3D structure is highly conserved between various alleles. HLA-modeler optimizes the use of this structural motif. The leave-one-out cross-validation using the crystal structures of class I and class II HLA molecules has demonstrated that the rmsds of nonhydrogen atoms of the sites between homology models and crystal structures are less than 1.0 Å in most cases. The results have indicated that the 3D structures of the antigenic peptide-binding sites can be reproduced by HLA-modeler at the level almost corresponding to the crystal structures.

  11. Current opinion on human leukocyte antigen-G in China

    Institute of Scientific and Technical Information of China (English)

    YAN Wei-hua; LIN Ai-fen


    @@ Since discovery and cloning of the non-classical human leukocyte antigen (HLA) class Ⅰ antigen HLA-G by Geraghty et al1 in 1987, a large number of studies have been carried out. HLA-G has a low polymorphism, limited distribution to normal tissues and seven isoforms resulting from its primary mRNA alternative splicing.2 HLA-G expression was first found on the extravillous cytotrophoblasts, at the fetal-maternal interface during normal pregnancy, which lacks the expression of HLA-A, -B and HLA Ⅱ antigens. Initial studies on HLA-G mainly addressed its function in fetal-maternal immunotolerance.3 Two decades later,HLA-G is now considered to be a very important immune molecule which plays a vital immune inhibitory role in the context of reproduction, oncology, transplantation,infection and also in autoimmune disease.4 A number of Chinese research teams are interested in, and have contributed to, the publication of more than 80 peer-reviewed articles and reviews on HLA-G over the past ten years. We summarize the key points in this field that were presented and discussed by them.

  12. Acoustic and photoacoustic microscopy imaging of single leukocytes (United States)

    Strohm, Eric M.; Moore, Michael J.; Kolios, Michael C.


    An acoustic/photoacoustic microscope was used to create micrometer resolution images of stained cells from a blood smear. Pulse echo ultrasound images were made using a 1000 MHz transducer with 1 μm resolution. Photoacoustic images were made using a fiber coupled 532 nm laser, where energy losses through stimulated Raman scattering enabled output wavelengths from 532 nm to 620 nm. The laser was focused onto the sample using a 20x objective, and the laser spot co-aligned with the 1000 MHz transducer opposite the laser. The blood smear was stained with Wright-Giemsa, a common metachromatic dye that differentially stains the cellular components for visual identification. A neutrophil, lymphocyte and a monocyte were imaged using acoustic and photoacoustic microscopy at two different wavelengths, 532 nm and 600 nm. Unique features in each imaging modality enabled identification of the different cell types. This imaging method provides a new way of imaging stained leukocytes, with applications towards identifying and differentiating cell types, and detecting disease at the single cell level.

  13. Leukocyte deformability: finite element modeling of large viscoelastic deformation. (United States)

    Dong, C; Skalak, R


    An axisymmetric deformation of a viscoelastic sphere bounded by a prestressed elastic thin shell in response to external pressure is studied by a finite element method. The research is motivated by the need for understanding the passive behavior of human leukocytes (white blood cells) and interpreting extensive experimental data in terms of the mechanical properties. The cell at rest is modeled as a sphere consisting of a cortical prestressed shell with incompressible Maxwell fluid interior. A large-strain deformation theory is developed based on the proposed model. General non-linear, large strain constitutive relations for the cortical shell are derived by neglecting the bending stiffness. A representation of the constitutive equations in the form of an integral of strain history for the incompressible Maxwell interior is used in the formulation of numerical scheme. A finite element program is developed, in which a sliding boundary condition is imposed on all contact surfaces. The mathematical model developed is applied to evaluate experimental data of pipette tests and observations of blood flow.

  14. Impact of Dehydroepiandrosterone Sulfate on Newborn Leukocyte Telomere Length (United States)

    Liu, Han; Zhou, Guangdi; Chen, Qian; Ouyang, Fengxiu; Little, Julian; Zhang, Jun; Chen, Dan


    The newborn setting of leukocyte telomere length (LTL) likely has important implications for telomere dynamics over the lifespan. However, its determinants are poorly understood. Hormones play an important role during pregnancy and delivery. We hypothesized that exposure to hormones may impact the fetal telomere biology system. To test this hypothesis, cortisol, estradiol, dehydroepiandrosterone sulfate (DHEAS) and reactive oxygen species (ROS) were measured in cord blood of 821 newborns from a prospective study. After accounting for the effects of potential determinants of newborn LTL, a 10-fold increase in DHEAS concentration was associated with a 0.021 increase in T/S ratio of newborn LTL (95% confidence interval: 0.009–0.034, P = 0.0008). For newborns who fell in the lowest quartile of DHEAS level, the mean newborn LTL was estimated to be approximately 2.0% shorter than the newborns in the highest DHEAS concentration quartile (P = 0.0014). However, no association was found between newborn LTL and cortisol or estradiol. As expected, newborns with higher ROS level (ROS > 260 mol/L) had lower LTL compared to that with lower ROS level (ROS ≤ 260 mol/L) (P = 0.007). There was also an inverse relationship between DHEAS and ROS (P programming” effect on the newborn telomere biology system. PMID:28186106

  15. Plasminogen activator inhibitor-2 (PAI-2) in eosinophilic leukocytes. (United States)

    Swartz, Jonathan M; Byström, Jonas; Dyer, Kimberly D; Nitto, Takeaki; Wynn, Thomas A; Rosenberg, Helene F


    Plasminogen activator inhibitor-2 (PAI-2) as a potential eosinophil protein was inferred from our gene microarray study of mouse eosinophilopoiesis. Here, we detect 47 kDa intracellular and approximately 60 kDa secretory forms of PAI-2 in purified human eosinophil extracts. PAI-2 is present at variable concentrations in eosinophil lysates, ranging from 30 to 444 ng/10(6) cells, with a mean of 182 ng/10(6) cells from 10 normal donors, which is the highest per-cell concentration among all leukocyte subtypes evaluated. Enzymatic assay confirmed that eosinophil-derived PAI-2 is biologically active and inhibits activation of its preferred substrate, urokinase. Immunohistochemical and immunogold staining demonstrated PAI-2 localization in eosinophil-specific granules. Immunoreactive PAI-2 was detected in extracellular deposits in and around the eosinophil-enriched granuloma tissue encapsulating the parasitic egg in livers of wild-type mice infected with the helminthic parasite Schistosoma mansoni. Among the possibilities, we consider a role for eosinophil-derived PAI-2 in inflammation and remodeling associated with parasitic infection as well as allergic airways disease, respiratory virus infection, and host responses to tumors and metastasis in vivo.

  16. Leukocyte and leukocyte function

    Institute of Scientific and Technical Information of China (English)


    2010367 The clinical characteristics of newly diagnosed acute myeloid leukemia patients with NPM1 mutation. ZHU Honghu(主鸿鹄),et al.Instit Hematol,People’ s Hosp,Peking Univ,Beijing 100044.Chin J Hematol 2010;31(5):315-318. Objective To investigate the clinical characteristics of newly diagnosed acute myeloid leukemia (AML) with NPM1 mutation.Methods

  17. Leukocyte and leukocyte function

    Institute of Scientific and Technical Information of China (English)


    2009228 A new prognostic stratification for patients with acute myeloid leukemia.JIANG Bo(姜波),et al.Instit Hematol & Blood Dis Hosp,CAMS & PUMC,Tianjin 300020.Chin J Intern Med,2009;48(4):316-320.

  18. Leukocyte and leukocyte function

    Institute of Scientific and Technical Information of China (English)


    930574 Phase II clinical trial of domestic ant-saerine in patients with acute leukemias.Cooper-ative Group headed by Blood dis Hosp,InstitHematol,CAMS,Tianjin,300020.Chin J In-tern Med 1993;32(2):80—83.One hundred and eighteen patients with acuteleukemias,including initial,relapsed and refrac-tory cases,were treated with domestic Am-sacrine(m—AMSA),single or in combinationwith other drugs.The total CR rate was 39.5%in ALL and 38.8% in ANLL and the responserate was 47.5% for both types of acuteleukemias.The CR rates of relapsed and refrac-

  19. Leukocyte and leukocyte function

    Institute of Scientific and Technical Information of China (English)


    2008333 The clinical and laboratory features of acute promyelocytic leukemia: an analysis of 513 cases. LIANG Jianying(梁建英), et al. Dept Hematol, 1st Affili Hosp, Soochow Univ, Suzhou 215006. Chin J Interm Med 2008;47(5):389-392.Objective To investigate the clinical and laboratory features of acute promyelocytic leukemia(APL).Methods 513 APL patients in the last two decades were retrospectively analyzed in this research.We investigated the clinical features including age,sex,abnormality of

  20. Leukocyte and leukocyte function

    Institute of Scientific and Technical Information of China (English)


    950368 A study on the relationship hetween morphol-ogy and gene hepterogeneity in acute promyelocyticleukemia.XIONG Shumin(熊树民),et al.shanghaiHematol Instit & Ruijin Hosp,Shanghai,200025.ChinJ Intern Med 1995;34(3):165-168.Aucte promyelocytic leukemia (APL) can be treatedby all-trans retinoic acid (ATRA) with high completeremission rate.50 cases of APL diagnosed morphologi-cally were studied on their cytogenetics,molecular bi-ology and response to treatment with ATRA.Fortyfive cases showed chromosomal translocation t(5;17)and PML/RAR α fusion gene (PML+RARα+APL)

  1. Appearance of acute gouty arthritis on indium-111-labeled leukocyte scintigraphy

    Energy Technology Data Exchange (ETDEWEB)

    Palestro, C.J.; Vega, A.; Kim, C.K.; Swyer, A.J.; Goldsmith, S.J. (Mt. Sinai Medical Center, New York, NY (USA))


    Indium-111-labeled leukocyte scintigraphy was performed on a 66-yr-old male with polyarticular acute gouty arthritis. Images revealed intense labeled leukocyte accumulation in a pattern indistinguishable from septic arthritis, in both knees and ankles, and the metatarsophalangeal joint of both great toes, all of which were involved in the acute gouty attack. Joint aspirate as well as blood cultures were reported as no growth; the patient was treated with intravenous colchicine and ACTH for 10 days with dramatic improvement noted. Labeled leukocyte imaging, repeated 12 days after the initial study, revealed near total resolution of joint abnormalities, concordant with the patient's clinical improvement. This case demonstrates that while acute gouty arthritis is a potential pitfall in labeled leukocyte imaging, in the presence of known gout, it may provide a simple, objective, noninvasive method of evaluating patient response to therapy.

  2. Microfluidic isolation of leukocytes from whole blood for phenotype and gene expression analysis. (United States)

    Sethu, Palaniappan; Moldawer, Lyle L; Mindrinos, Michael N; Scumpia, Philip O; Tannahill, Cynthia L; Wilhelmy, Julie; Efron, Philip A; Brownstein, Bernard H; Tompkins, Ronald G; Toner, Mehmet


    Technologies that enable the isolation of cell subtypes from small samples of complex populations will greatly facilitate the implementation of proteomics and genomics to human diseases. Transcriptome analysis of blood requires the depletion of contaminating erythrocytes. We report an automated microfluidic device to rapidly deplete erythrocytes from whole blood via deionized water lysis and to collect enriched leukocytes for phenotype and genomic analyses. Starting with blood from healthy subjects, we demonstrate the utility of this microfluidic cassette and lysis protocol to prepare unstimulated leukocytes, and leukocytes stimulated ex vivo with Staphylococcal enterotoxin B, which mimics some of the cellular effects seen in patients with severe bacterial infections. Microarrays are used to assess the global gene expression response to enterotoxin B. The results demonstrate that this system can isolate unactivated leukocytes from small blood samples without any significant loss, which permits more information to be obtained from subsequent analysis, and will be readily applicable to clinical settings.

  3. The role of human leukocyte antigen in susceptibility and clinical manifestations of sarcoidosis.

    Institute of Scientific and Technical Information of China (English)


    To investigate the association of human leukocyte antigen (HLA) with susceptibility and clinical manifestations of sarcoidosis, fifty-five patients with sarcoidosis were studied by using allele group specific polymerase chain reaction technique (PCR). Our data

  4. Inflammation after Ischemic Stroke: The Role of Leukocytes and Glial Cells (United States)

    Kim, Jong Youl; Park, Joohyun; Chang, Ji Young; Kim, Sa-Hyun


    The immune response after stroke is known to play a major role in ischemic brain pathobiology. The inflammatory signals released by immune mediators activated by brain injury sets off a complex series of biochemical and molecular events which have been increasingly recognized as a key contributor to neuronal cell death. The primary immune mediators involved are glial cells and infiltrating leukocytes, including neutrophils, monocytes and lymphocyte. After ischemic stroke, activation of glial cells and subsequent release of pro- and anti-inflammatory signals are important for modulating both neuronal cell damage and wound healing. Infiltrated leukocytes release inflammatory mediators into the site of the lesion, thereby exacerbating brain injury. This review describes how the roles of glial cells and circulating leukocytes are a double-edged sword for neuroinflammation by focusing on their detrimental and protective effects in ischemic stroke. Here, we will focus on underlying characterize of glial cells and leukocytes under inflammation after ischemic stroke.

  5. Syntenin-1 and ezrin proteins link activated leukocyte cell adhesion molecule to the actin cytoskeleton

    NARCIS (Netherlands)

    Tudor, C.; Riet, J. te; Eich, C.; Harkes, R.; Smisdom, N.; Bouhuijzen-Wenger, J.; Ameloot, M.; Holt, M.; Kanger, J.S.; Figdor, C.G.; Cambi, A.; Subramaniam, V.


    Activated leukocyte cell adhesion molecule (ALCAM) is a type I transmembrane protein member of the immunoglobulin superfamily of cell adhesion molecules. Involved in important pathophysiological processes such as the immune response, cancer metastasis, and neuronal development, ALCAM undergoes both

  6. Activated leukocyte cell adhesion molecule and prognosis in acute ischemic stroke

    DEFF Research Database (Denmark)

    Smedbakken, Linda; Jensen, Jesper K; Hallén, Jonas


    Biomarkers predicting mortality and functional outcome in stroke may be clinically helpful in identification of patients likely to benefit from intervention. Activated leukocyte cell adhesion molecule (ALCAM) is upregulated during neuroinflammation; we investigated whether ALCAM concentrations...

  7. In vitro phagocytosis of several Candida berkhout species by murine leukocytes. (United States)

    Fontenla de Petrino, S E; Bibas Bonet de Jorrat, M E; Sirena, A


    In vitro phagocytosis of thirteen Candida berkhout species by rat leukocytes was studied to assess a possible correlation between pathogenicity and phagocytosis Yeast-leukocyte suspensions were mixed up for 3 h and phagocytic index, germ-tube formation and leukocyte candidacidal activity were evaluated. Highest values for phagocytosis were reached in all cases at the end of the first hour. Leukocyte candidacidal activity was absent. Only C. albicans produced germ-tubes. The various phagocytosis indices were determined depending on the Candida species assayed. Under these conditions, the more pathogenic species presented the lower indices of phagocytosis. It is determined that the in vitro phagocytic index may bear a close relationship with the pathogenicity of the Candida berkhout.

  8. Evaluation of leukocyte esterase and nitrite strip tests to detect spontaneous bacterial peritonitis in cirrhotic patients

    Institute of Scientific and Technical Information of China (English)


    AIM: To investigate the diagnostic efficacy of leukocyte esterase and nitrite reagent strips for bedside diagnosis of spontaneous bacterial peritonitis (SBP).METHODS: A total of 63 consecutive patients with cirrhotic ascites (38 male, 25 female) tested between April 2005 and July 2006 were included in the study. Bedside reagent strip testing was performed on ascitic fluid and the results compared to manual cell counting and ascitic fluid culture. SBP was defined as having a olymorphonuclear ascites count of ≥ 250/mm3.RESULTS: Fifteen samples showed SBP. The sensitivity,specificity, positive and negative predictive values of the leukocyte esterase reagent strips were; 93%, 100%, 100%, and 98%, respectively. The sensitivity,specificity, positive and negative predictive value of the nitrite reagent strips were 13%, 93%, 40%, and 77%, respectively. The combination of leukocyte esterase and nitrite reagents strips did not yield statistically significant effects on diagnostic accuracy. CONCLUSION: Leukocyte esterase reagent strips may provide a rapid, bedside diagnostic test for SBP.

  9. Leukocyte scintigraphy compared to intraoperative small bowel enteroscopy and laparotomy findings in Crohn's disease

    DEFF Research Database (Denmark)

    Almen, Sven; Granerus, Göran; Ström, Magnus


    Background: Leukocyte scintigraphy is a noninvasive investigation to assess inflammation. We evaluated the utility of labeled leukocytes to detect small bowel inflammation and disease complications in Crohn's disease and compared it to whole small bowel enteroscopy and laparotomy findings. Methods......: Scintigraphy with technetium-99m exametazime-labeled leukocytes was prospectively performed in 48 patients with Crohn's disease a few days before laparotomy; 41 also had an intraoperative small bowel enteroscopy. The same procedures were performed in 8 control patients. Independent grading of scans...... was compared with the results of enteroscopy and with surgical, histopathologic, and clinical data. Results: In the 8 control patients leukocyte scan, endoscopy, and histopathology were all negative for the small bowel. In patients with Crohn's disease and small bowel inflammation seen at enteroscopy and...

  10. Cognitive Change during the Life Course and Leukocyte Telomere Length in Late Middle-Aged Men

    DEFF Research Database (Denmark)

    Rask, Lene; Bendix, Laila; Harbo, Maria;


    Importance: Cognitive skills are known to decline through the lifespan with large individual differences. The molecular mechanisms for this decline are incompletely understood. Although leukocyte telomere length provides an index of cellular age that predicts the incidence of age-related diseases......, it is unclear whether there is an association between cognitive decline and leukocyte telomere length. Objective: To examine the association between changes in cognitive function during adult life and leukocyte telomere length after adjusting for confounding factors such as education, mental health and life...... style. Design, Setting, and Participants: Two groups of men with negative (n = 97) and positive (n = 93) change in cognitive performance were selected from a birth cohort of 1985 Danish men born in 1953. Cognitive performance of each individual was assessed at age ~20 and 56 years. Leukocyte telomere...

  11. Therapeutic relevance of penicillin-induced hypersensitivity of Staphylococcus aureus to killing by polymorphonuclear leukocytes.


    Lam, C; Georgopoulos, A.; Laber, G.; Schütze, E


    There is an overwhelming body of evidence that certain Staphylococcus aureus strains become more sensitive to killing by polymorphonuclear leukocytes after their growth in media containing subinhibitory concentrations of penicillin. However, it is not clear to what extent this phenomenon contributes to the curative effect of penicillin in vivo. To explore its therapeutic relevance, we evaluated the interaction of staphylococci pretreated with penicillin in vitro with leukocytes in cell-proof ...

  12. In-111 labeled leukocyte scintigraphy in a case of multifocal candidiasis

    Energy Technology Data Exchange (ETDEWEB)

    Palestro, C.J.; Vega, A.; Kim, C.K.; Goldsmith, S.J. (Mount Sinai School of Medicine, New York, NY (USA))


    The value of indium-111 labeled leukocyte scintigraphy for the diagnosis of infection in the general population is well documented; there is less information available on its role in the evaluation of the immunocompromised patient. In this study, leukocyte scintigraphy was performed on a 31-year-old immunocompromised woman who had a possible intra-abdominal abscess. No abscess was detected, but intense oral, esophageal, gastric, and vaginal uptake was observed. Candida infection was histologically confirmed at all four sites.

  13. Identifying the rules of engagement enabling leukocyte rolling, activation, and adhesion. (United States)

    Tang, Jonathan; Hunt, C Anthony


    The LFA-1 integrin plays a pivotal role in sustained leukocyte adhesion to the endothelial surface, which is a precondition for leukocyte recruitment into inflammation sites. Strong correlative evidence implicates LFA-1 clustering as being essential for sustained adhesion, and it may also facilitate rebinding events with its ligand ICAM-1. We cannot challenge those hypotheses directly because it is infeasible to measure either process during leukocyte adhesion following rolling. The alternative approach undertaken was to challenge the hypothesized mechanisms by experimenting on validated, working counterparts: simulations in which diffusible, LFA1 objects on the surfaces of quasi-autonomous leukocytes interact with simulated, diffusible, ICAM1 objects on endothelial surfaces during simulated adhesion following rolling. We used object-oriented, agent-based methods to build and execute multi-level, multi-attribute analogues of leukocytes and endothelial surfaces. Validation was achieved across different experimental conditions, in vitro, ex vivo, and in vivo, at both the individual cell and population levels. Because those mechanisms exhibit all of the characteristics of biological mechanisms, they can stand as a concrete, working theory about detailed events occurring at the leukocyte-surface interface during leukocyte rolling and adhesion experiments. We challenged mechanistic hypotheses by conducting experiments in which the consequences of multiple mechanistic events were tracked. We quantified rebinding events between individual components under different conditions, and the role of LFA1 clustering in sustaining leukocyte-surface adhesion and in improving adhesion efficiency. Early during simulations ICAM1 rebinding (to LFA1) but not LFA1 rebinding (to ICAM1) was enhanced by clustering. Later, clustering caused both types of rebinding events to increase. We discovered that clustering was not necessary to achieve adhesion as long as LFA1 and ICAM1 object

  14. Leukocyte extravasation as a target for anti-inflammatory therapy - Which molecule to choose?

    DEFF Research Database (Denmark)

    Boehncke, W-H; Schön, M P; Girolomoni, G


    of these agents and despite their crippling price tag, the recent incorporation of biologicals that target defined molecular controls of leukocyte extravasation into dermatological and rheumatological practise, consequently, has greatly enriched our therapeutic options for battling major, chronic, inflammatory...... dermatoses such as psoriasis. However, the - as yet unresolved and still rather controversially discussed - critical question is: Which of the multiple steps that control leukocyte extravasation in the human system really offer the most promising, most pragmatic, and safest molecular targets for therapeutic...

  15. Herpes Murine Model as a Biological Assay to Test Dialyzable Leukocyte Extracts Activity


    Nohemí Salinas-Jazmín; Sergio Estrada-Parra; Miguel Angel Becerril-García; Alberto Yairh Limón-Flores; Said Vázquez-Leyva; Emilio Medina-Rivero; Lenin Pavón; Marco Antonio Velasco-Velázquez; Sonia Mayra Pérez-Tapia


    Human dialyzable leukocyte extracts (DLEs) are heterogeneous mixtures of low-molecular-weight peptides that are released on disruption of peripheral blood leukocytes from healthy donors. DLEs improve clinical responses in infections, allergies, cancer, and immunodeficiencies. Transferon is a human DLE that has been registered as a hemoderivate by Mexican health authorities and commercialized nationally. To develop an animal model that could be used routinely as a quality control assay for Tra...

  16. The antioxidant effect of free bilirubin on cumene-hydroperoxide treated human leukocytes. (United States)

    Yesilkaya, A; Altinayak, R; Korgun, D K


    To examine the antioxidant effect of bilirubin (BR) on leukocyte, we treated leukocytes obtained from healthy subjects with an oxidant and various concentrations of BR. High concentrations of BR decreased thiobarbituric acid reactive substances (TBARS) and catalase activities, increased superoxide dismutase (SOD) activity, but had no effect on glutathione (GSH) concentration. Our results showed that under physiological conditions, BR has an antioxidant effect only in high concentrations.

  17. Adjusting MtDNA Quantification in Whole Blood for Peripheral Blood Platelet and Leukocyte Counts (United States)

    Gonzalez-Lazaro, Monica; Moreno-Loshuertos, Raquel; Fernandez-Silva, Patricio; Enriquez, Jose Antonio; Laclaustra, Martin


    Alterations of mitochondrial DNA copy number (mtDNAcn) in the blood (mitochondrial to nuclear DNA ratio) appear associated with several systemic diseases, including primary mitochondrial disorders, carcinogenesis, and hematologic diseases. Measuring mtDNAcn in DNA extracted from whole blood (WB) instead of from peripheral blood mononuclear cells or buffy coat may yield different results due to mitochondrial DNA present in platelets. The aim of this work is to quantify the contribution of platelets to mtDNAcn in whole blood [mtDNAcn(WB)] and to propose a correction formula to estimate leukocytes' mtDNAcn [mtDNAcn(L)] from mtDNAcn(WB). Blood samples from 10 healthy adults were combined with platelet-enriched plasma and saline solution to produce artificial blood preparations. Aliquots of each sample were combined with five different platelet concentrations. In 46 of these blood preparations, mtDNAcn was measured by qPCR. MtDNAcn(WB) increased 1.07 (95%CI 0.86, 1.29; p<0.001) per 1000 platelets present in the preparation. We proved that leukocyte count should also be taken into account as mtDNAcn(WB) was inversely associated with leukocyte count; it increased 1.10 (95%CI 0.95, 1.25, p<0.001) per unit increase of the ratio between platelet and leukocyte counts. If hematological measurements are available, subtracting 1.10 the platelets/leukocyte ratio from mtDNAcn(WB) may serve as an estimation for mtDNAcn(L). Both platelet and leukocyte counts in the sample are important sources of variation if comparing mtDNAcn among groups of patients when mtDNAcn is measured in DNA extracted from whole blood. Not taking the platelet/leukocyte ratio into account in whole blood measurements, may lead to overestimation and misclassification if interpreted as leukocytes' mtDNAcn. PMID:27736919

  18. Identifying the rules of engagement enabling leukocyte rolling, activation, and adhesion.

    Directory of Open Access Journals (Sweden)

    Jonathan Tang


    Full Text Available The LFA-1 integrin plays a pivotal role in sustained leukocyte adhesion to the endothelial surface, which is a precondition for leukocyte recruitment into inflammation sites. Strong correlative evidence implicates LFA-1 clustering as being essential for sustained adhesion, and it may also facilitate rebinding events with its ligand ICAM-1. We cannot challenge those hypotheses directly because it is infeasible to measure either process during leukocyte adhesion following rolling. The alternative approach undertaken was to challenge the hypothesized mechanisms by experimenting on validated, working counterparts: simulations in which diffusible, LFA1 objects on the surfaces of quasi-autonomous leukocytes interact with simulated, diffusible, ICAM1 objects on endothelial surfaces during simulated adhesion following rolling. We used object-oriented, agent-based methods to build and execute multi-level, multi-attribute analogues of leukocytes and endothelial surfaces. Validation was achieved across different experimental conditions, in vitro, ex vivo, and in vivo, at both the individual cell and population levels. Because those mechanisms exhibit all of the characteristics of biological mechanisms, they can stand as a concrete, working theory about detailed events occurring at the leukocyte-surface interface during leukocyte rolling and adhesion experiments. We challenged mechanistic hypotheses by conducting experiments in which the consequences of multiple mechanistic events were tracked. We quantified rebinding events between individual components under different conditions, and the role of LFA1 clustering in sustaining leukocyte-surface adhesion and in improving adhesion efficiency. Early during simulations ICAM1 rebinding (to LFA1 but not LFA1 rebinding (to ICAM1 was enhanced by clustering. Later, clustering caused both types of rebinding events to increase. We discovered that clustering was not necessary to achieve adhesion as long as LFA1 and

  19. Clinical Associations of Leukocyte Telomere Length in a Cohort of Repatriated Prisoners of War (United States)


    1 RPW TELOMERE LENGTH 1. Title Page Clinical Associations of Leukocyte Telomere Length in a Cohort of Repatriated Prisoners of War Authors...Reprints will not be available from the authors Short Title: RPW Telomere Length Manuscript metrics: Word count for abstract - 200 Word count 01-07-2014 4. TITLE AND SUBTITLE Clinical Associations of Leukocyte Telomere Length in a Cohort of Repatriated Prisoners of War 5a. CONTRACT

  20. Protein folding modulates the swapped dimerization mechanism of methyl-accepting chemotaxis heme sensors.

    Directory of Open Access Journals (Sweden)

    Marta A Silva

    Full Text Available The periplasmic sensor domains GSU0582 and GSU0935 are part of methyl accepting chemotaxis proteins in the bacterium Geobacter sulfurreducens. Both contain one c-type heme group and their crystal structures revealed that these domains form swapped dimers with a PAS fold formed from the two protein chains. The swapped dimerization of these sensors is related to the mechanism of signal transduction and the formation of the swapped dimer involves significant folding changes and conformational rearrangements within each monomeric component. However, the structural changes occurring during this process are poorly understood and lack a mechanistic framework. To address this issue, we have studied the folding and stability properties of two distinct heme-sensor PAS domains, using biophysical spectroscopies. We observed substantial differences in the thermodynamic stability (ΔG = 14.6 kJ.mol(-1 for GSU0935 and ΔG = 26.3 kJ.mol(-1 for GSU0582, and demonstrated that the heme moiety undergoes conformational changes that match those occurring at the global protein structure. This indicates that sensing by the heme cofactor induces conformational changes that rapidly propagate to the protein structure, an effect which is directly linked to the signal transduction mechanism. Interestingly, the two analyzed proteins have distinct levels of intrinsic disorder (25% for GSU0935 and 13% for GSU0582, which correlate with conformational stability differences. This provides evidence that the sensing threshold and intensity of the propagated allosteric effect is linked to the stability of the PAS-fold, as this property modulates domain swapping and dimerization. Analysis of the PAS-domain shows that disorder segments are found either at the hinge region that controls helix motions or in connecting segments of the β-sheet interface. The latter is known to be widely involved in both intra- and intermolecular interactions, supporting the view that it's folding

  1. Discrete kinetic and lattice Boltzmann formulations for reaction cross-diffusion systems and their hyperbolic extensions in chemotaxis (United States)

    Dellar, Paul


    We present discrete kinetic and lattice Boltzmann formulations for reaction cross-diffusion systems, as commonly used to model microbiological chemotaxis and macroscopic predator-prey interactions, and their hyperbolic extensions with fluid-like persistence terms. For example, the canonical Patlak-Keller-Segal model for chemotaxis involves a flux of cells up the gradient of a chemical secreted by the cells, in addition to the usual down-gradient diffusive fluxes. Existing lattice Boltzmann approaches for such systems use finite difference approximations to compute the flux of cells due to the chemical gradient. The resulting coupling between, and necessary synchronisation of the evolution of, adjacent grid points greatly complicates boundary conditions, and efficient implementation on graphical processing units (GPUs). We present a kinetic formulation using cross-collisions between bases of moments for the two sets of distribution functions to couple the fluxes of the two species, from which we construct lattice Boltzmann algorithms using second-order Strang splitting. We demonstrate an efficient GPU implementation, and verify second-order spatial convergence towards spectral solutions for benchmark problems such as the finite-time blow-up in the Patlak-Keller-Segal model.

  2. Collective Signal Processing in Cluster Chemotaxis: Roles of Adaptation, Amplification, and Co-attraction in Collective Guidance. (United States)

    Camley, Brian A; Zimmermann, Juliane; Levine, Herbert; Rappel, Wouter-Jan


    Single eukaryotic cells commonly sense and follow chemical gradients, performing chemotaxis. Recent experiments and theories, however, show that even when single cells do not chemotax, clusters of cells may, if their interactions are regulated by the chemoattractant. We study this general mechanism of "collective guidance" computationally with models that integrate stochastic dynamics for individual cells with biochemical reactions within the cells, and diffusion of chemical signals between the cells. We show that if clusters of cells use the well-known local excitation, global inhibition (LEGI) mechanism to sense chemoattractant gradients, the speed of the cell cluster becomes non-monotonic in the cluster's size-clusters either larger or smaller than an optimal size will have lower speed. We argue that the cell cluster speed is a crucial readout of how the cluster processes chemotactic signals; both amplification and adaptation will alter the behavior of cluster speed as a function of size. We also show that, contrary to the assumptions of earlier theories, collective guidance does not require persistent cell-cell contacts and strong short range adhesion. If cell-cell adhesion is absent, and the cluster cohesion is instead provided by a co-attraction mechanism, e.g. chemotaxis toward a secreted molecule, collective guidance may still function. However, new behaviors, such as cluster rotation, may also appear in this case. Co-attraction and adaptation allow for collective guidance that is robust to varying chemoattractant concentrations while not requiring strong cell-cell adhesion.

  3. In Entamoeba histolytica, a BspA family protein is required for chemotaxis toward tumour necrosis factor

    Directory of Open Access Journals (Sweden)

    Anne Silvestre


    Full Text Available Background: Entamoeba histolytica cell migration is essential for the development of human amoebiasis (an infectious disease characterized by tissue invasion and destruction. The tissue inflammation associated with tumour necrosis factor (TNF secretion by host cells is a well-documented feature of amoebiasis. Tumour necrosis factor is a chemoattractant for E. histolytica, and the parasite may have a TNF receptor at its cell surface. Methods: confocal microscopy, RNA Sequencing, bioinformatics, RNA antisense techniques and histological analysis of human colon explants were used to characterize the interplay between TNF and E. histolytica. Results: an antibody against human TNF receptor 1 (TNFR1 stained the E. histolytica trophozoite surface and (on immunoblots binds to a 150-kDa protein. Proteome screening with the TNFR1 sequence revealed a BspA family protein in E. histolytica that carries a TNFR signature domain and six leucine-rich repeats (named here as "cell surface protein", CSP, in view of its cellular location. Cell surface protein shares structural homologies with Toll-Like receptors, colocalizes with TNF and is internalized in TNF-containing vesicles. Reduction of cellular CSP levels abolished chemotaxis toward TNF and blocked parasite invasion of human colon. Conclusions: there is a clear link between TNF chemotaxis, CSP and pathogenesis.

  4. Regulation of sperm flagellar motility activation and chemotaxis caused by egg-derived substance(s) in sea cucumber. (United States)

    Morita, Masaya; Kitamura, Makoto; Nakajima, Ayako; Sri Susilo, Endang; Takemura, Akihiro; Okuno, Makoto


    The sea cucumber Holothuria atra is a broadcast spawner. Among broadcast spawners, fertilization occurs by means of an egg-derived substance(s) that induces sperm flagellar motility activation and chemotaxis. Holothuria atra sperm were quiescent in seawater, but exhibited flagellar motility activation near eggs with chorion (intact eggs). In addition, they moved in a helical motion toward intact eggs as well as a capillary filled with the water layer of the egg extracts, suggesting that an egg-derived compound(s) causes motility activation and chemotaxis. Furthermore, demembranated sperm flagella were reactivated in high pH (> 7.8) solution without cAMP, and a phosphorylation assay using (gamma-32P)ATP showed that axonemal protein phosphorylation and dephosphorylation also occurred in a pH-dependent manner. These results suggest that the activation of sperm motility in holothurians is controlled by pH-sensitive changes in axonemal protein phosphorylation. Ca2+ concentration affected the swimming trajectory of demembranated sperm, indicating that Ca2+-binding proteins present at the flagella may be associated with regulation of flagellar waveform. Moreover, the phosphorylation states of several axonemal proteins were Ca2+-sensitive, indicating that Ca2+ impacts both kinase and phosphatase activities. In addition, in vivo sperm protein phosphorylation occurred after treatment with a water-soluble egg extract. Our results suggest that one or more egg-derived compounds activate motility and subsequent chemotactic behavior via Ca2+-sensitive flagellar protein phosphorylation.

  5. The chemotaxis-like Che1 pathway has an indirect role in adhesive cell properties of Azospirillum brasilense. (United States)

    Siuti, Piro; Green, Calvin; Edwards, Amanda Nicole; Doktycz, Mitchel J; Alexandre, Gladys


    The Azospirillum brasilense chemotaxis-like Che1 signal transduction pathway was recently shown to modulate changes in adhesive cell surface properties that, in turn, affect cell-to-cell aggregation and flocculation behaviors rather than flagellar-mediated chemotaxis. Attachment to surfaces and root colonization may be functions related to flocculation. Here, the conditions under which A. brasilense wild-type Sp7 and che1 mutant strains attach to abiotic and biotic surfaces were examined using in vitro attachment and biofilm assays combined with atomic force microscopy and confocal microscopy. The nitrogen source available for growth is found to be a major modulator of surface attachment by A. brasilense and could be promoted in vitro by lectins, suggesting that it depends on interaction with surface-exposed residues within the extracellular matrix of cells. However, Che1-dependent signaling is shown to contribute indirectly to surface attachment, indicating that distinct mechanisms are likely underlying flocculation and attachment to surfaces in A. brasilense.

  6. Dark chocolate consumption improves leukocyte adhesion factors and vascular function in overweight men. (United States)

    Esser, Diederik; Mars, Monica; Oosterink, Els; Stalmach, Angelique; Müller, Michael; Afman, Lydia A


    Flavanol-enriched chocolate consumption increases endothelium-dependent vasodilation. Most research so far has focused on flow-mediated dilation (FMD) only; the effects on other factors relevant to endothelial health, such as inflammation and leukocyte adhesion, have hardly been addressed. We investigated whether consumption of regular dark chocolate also affects other markers of endothelial health, and whether chocolate enrichment with flavanols has additional benefits. In a randomized double-blind crossover study, the effects of acute and of 4 wk daily consumption of high flavanol chocolate (HFC) and normal flavanol chocolate (NFC) on FMD, augmentation index (AIX), leukocyte count, plasma cytokines, and leukocyte cell surface molecules in overweight men (age 45-70 yr) were investigated. Sensory profiles and motivation scores to eat chocolate were also collected. Findings showed that a 4 wk chocolate intake increased FMD by 1%, which was paralleled by a decreased AIX of 1%, decreased leukocyte cell count, decreased plasma sICAM1 and sICAM3, and decreased leukocyte adhesion marker expression (Pchocolate. This study provides new insights on how chocolate affects endothelial health by demonstrating that chocolate consumption, besides improving vascular function, also lowers the adherence capacity of leukocytes in the circulation.

  7. Stress-induced enhancement of leukocyte trafficking into sites of surgery or immune activation (United States)

    Viswanathan, Kavitha; Dhabhar, Firdaus S.


    Effective immunoprotection requires rapid recruitment of leukocytes into sites of surgery, wounding, infection, or vaccination. In contrast to immunosuppressive chronic stressors, short-term acute stressors have immunoenhancing effects. Here, we quantify leukocyte infiltration within a surgical sponge to elucidate the kinetics, magnitude, subpopulation, and chemoattractant specificity of an acute stress-induced increase in leukocyte trafficking to a site of immune activation. Mice acutely stressed before sponge implantation showed 200-300% higher neutrophil, macrophage, natural killer cell, and T cell infiltration than did nonstressed animals. We also quantified the effects of acute stress on lymphotactin- (LTN; a predominantly lymphocyte-specific chemokine), and TNF-- (a proinflammatory cytokine) stimulated leukocyte infiltration. An additional stress-induced increase in infiltration was observed for neutrophils, in response to TNF-, macrophages, in response to TNF- and LTN, and natural killer cells and T cells in response to LTN. These results show that acute stress initially increases trafficking of all major leukocyte subpopulations to a site of immune activation. Tissue damage-, antigen-, or pathogen-driven chemoattractants subsequently determine which subpopulations are recruited more vigorously. Such stress-induced increases in leukocyte trafficking may enhance immunoprotection during surgery, vaccination, or infection, but may also exacerbate immunopathology during inflammatory (cardiovascular disease or gingivitis) or autoimmune (psoriasis, arthritis, or multiple sclerosis) diseases. chemokine | psychophysiological stress | surgical sponge | wound healing | lymphotactin

  8. Thrombopoietin induces p-selectin expression on platelets and subsequent platelet/leukocyte interactions. (United States)

    Tibbles, Heather E; Navara, Christopher S; Hupke, Michael A; Vassilev, Alexei O; Uckun, Fatih M


    Ligation of thrombopoietin (TPO) to the platelet c-Mpl receptor induces numerous biochemical pathways in the absence of aggregation. Two forms of recombinant TPO are currently in clinical trials for the treatment of thrombocytopenia. This study focuses on the effects of the full-length recombinant human TPO (rhTPO) on platelets in a whole blood system. Platelet-leukocyte associations (PLAs) were visualized following rhTPO stimulation as CD42b/CD 45 double positive clusters by FACS analysis. Treatment of washed platelets with rhTPO induced granule release and expression of the leukocyte adhesion receptor P-selectin (CD 62P) in the absence of aggregation and calcium mobilization. RhTPO also induced platelet-leukocyte interactions in whole blood. Following stimulation, leukocytes were recruited by platelets through P-selectin in a calcium-dependent manner. rhTPO stimulates platelet-leukocyte associations in whole blood through expression of platelet P-selectin. To our knowledge, this is the first report that identifies TPO as a promoter of platelet-leukocyte interactions.

  9. Highly specific blockade of CCR5 inhibits leukocyte trafficking and reduces mucosal inflammation in murine colitis. (United States)

    Mencarelli, Andrea; Cipriani, Sabrina; Francisci, Daniela; Santucci, Luca; Baldelli, Franco; Distrutti, Eleonora; Fiorucci, Stefano


    Targeted disruption of leukocyte trafficking to the gut represents a promising approach for the treatment of inflammatory bowel diseases (IBDs). CCR5, the shared receptor for MIP1α and β and RANTES, is expressed by multiple leukocytes. Here, we aimed to determine the role of CCR5 in mediating leukocyte trafficking in models of colitis, and evaluate the therapeutic potential of maraviroc, an orally active CCR5 antagonist used in the treatment of CCR5-tropic HIV. Acute and chronic colitis were induced by administration of DSS or TNBS to wild-type and CCR5(-/-) mice or adoptive transfer of splenic naïve CD4(+) T-cells from wild type or CCR5(-/-) mice into RAG-1(-/-). CCR5 gene ablation reduced the mucosal recruitment and activation of CCR5-bearing CD4(+) and CD11b(+) leukocytes, resulting in profound attenuation of signs and symptoms of inflammation in the TNBS and transfer models of colitis. In the DSS/TNBS colitis and in the transfer model, maraviroc attenuated development of intestinal inflammation by selectively reducing the recruitment of CCR5 bearing leukocytes. In summary, CCR5 regulates recruitment of blood leukocytes into the colon indicating that targeting CCR5 may offer therapeutic options in IBDs.

  10. Reduced Arylsulfatase B Activity in Leukocytes from Cystic Fibrosis Patients (United States)

    Sharma, Girish; Burke, Jenifer; Bhattacharyya, Sumit; Sharma, Neha; Katyal, Shivani; Park, R. Lucy; Tobacman, Joanne


    Summary The enzyme Arylsulfatase B (ARSB; N-acetylgalactosamine-4-sulfatase) removes 4-sulfate groups from chondroitin-4-sulfate and dermatan sulfate and is required for the degradation of these sulfated glycosaminoglycans (GAGs). Since these GAGs accumulate in patients with Cystic Fibrosis (CF), we investigated the activity of ARSB in leukocytes of patients with CF, to consider if reduced activity of ARSB might contribute to the pathophysiology of CF. Previous cell-based experiments had demonstrated that when the deficiency of the cystic fibrosis transmembrane regulator (CFTR) was corrected in bronchial epithelial cells, the ARSB activity increased significantly. De-identified, citrated blood samples were collected from 16 children with cystic fibrosis and 31 control subjects, seen in the Pediatric Clinic at Rush University Medical Center. Polymorphonuclear (PMN) and mononuclear cell (MC) populations were separated by density gradient, and blinded determinations of ARSB activity were performed using the exogenous substrate 4-methylumbilliferyl sulfate. Interleukin-6 was measured in the plasma samples by ELISA. ARSB activity was significantly less in the PMN and MC from the CF patients than controls (p<0.0001, unpaired t-test, two-tailed). Interleukin-6 levels in plasma were significantly greater in the CF population (p<0.001). Mean age, age range, and male:female ratio of CF patients and controls were similar, and no association of ARSB activity with age, gender, or CFTR genotype was evident. Since recombinant human ARSB is used successfully for replacement therapy in Mucopolysaccharidosis VI, it may be useful to restore ARSB activity to normal levels and increase degradation of sulfated GAGs in CF patients. PMID:22550062

  11. Altered DNA methylation in leukocytes with trisomy 21.

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    Kristi Kerkel


    Full Text Available The primary abnormality in Down syndrome (DS, trisomy 21, is well known; but how this chromosomal gain produces the complex DS phenotype, including immune system defects, is not well understood. We profiled DNA methylation in total peripheral blood leukocytes (PBL and T-lymphocytes from adults with DS and normal controls and found gene-specific abnormalities of CpG methylation in DS, with many of the differentially methylated genes having known or predicted roles in lymphocyte development and function. Validation of the microarray data by bisulfite sequencing and methylation-sensitive Pyrosequencing (MS-Pyroseq confirmed strong differences in methylation (p<0.0001 for each of 8 genes tested: TMEM131, TCF7, CD3Z/CD247, SH3BP2, EIF4E, PLD6, SUMO3, and CPT1B, in DS versus control PBL. In addition, we validated differential methylation of NOD2/CARD15 by bisulfite sequencing in DS versus control T-cells. The differentially methylated genes were found on various autosomes, with no enrichment on chromosome 21. Differences in methylation were generally stable in a given individual, remained significant after adjusting for age, and were not due to altered cell counts. Some but not all of the differentially methylated genes showed different mean mRNA expression in DS versus control PBL; and the altered expression of 5 of these genes, TMEM131, TCF7, CD3Z, NOD2, and NPDC1, was recapitulated by exposing normal lymphocytes to the demethylating drug 5-aza-2'deoxycytidine (5aza-dC plus mitogens. We conclude that altered gene-specific DNA methylation is a recurrent and functionally relevant downstream response to trisomy 21 in human cells.

  12. Imputing amino acid polymorphisms in human leukocyte antigens.

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    Xiaoming Jia

    Full Text Available DNA sequence variation within human leukocyte antigen (HLA genes mediate susceptibility to a wide range of human diseases. The complex genetic structure of the major histocompatibility complex (MHC makes it difficult, however, to collect genotyping data in large cohorts. Long-range linkage disequilibrium between HLA loci and SNP markers across the major histocompatibility complex (MHC region offers an alternative approach through imputation to interrogate HLA variation in existing GWAS data sets. Here we describe a computational strategy, SNP2HLA, to impute classical alleles and amino acid polymorphisms at class I (HLA-A, -B, -C and class II (-DPA1, -DPB1, -DQA1, -DQB1, and -DRB1 loci. To characterize performance of SNP2HLA, we constructed two European ancestry reference panels, one based on data collected in HapMap-CEPH pedigrees (90 individuals and another based on data collected by the Type 1 Diabetes Genetics Consortium (T1DGC, 5,225 individuals. We imputed HLA alleles in an independent data set from the British 1958 Birth Cohort (N = 918 with gold standard four-digit HLA types and SNPs genotyped using the Affymetrix GeneChip 500 K and Illumina Immunochip microarrays. We demonstrate that the sample size of the reference panel, rather than SNP density of the genotyping platform, is critical to achieve high imputation accuracy. Using the larger T1DGC reference panel, the average accuracy at four-digit resolution is 94.7% using the low-density Affymetrix GeneChip 500 K, and 96.7% using the high-density Illumina Immunochip. For amino acid polymorphisms within HLA genes, we achieve 98.6% and 99.3% accuracy using the Affymetrix GeneChip 500 K and Illumina Immunochip, respectively. Finally, we demonstrate how imputation and association testing at amino acid resolution can facilitate fine-mapping of primary MHC association signals, giving a specific example from type 1 diabetes.

  13. Toxaphene, but not beryllium, induces human neutrophil chemotaxis and apoptosis via reactive oxygen species (ROS): involvement of caspases and ROS in the degradation of cytoskeletal proteins. (United States)

    Lavastre, Valérie; Roberge, Charles J; Pelletier, Martin; Gauthier, Marc; Girard, Denis


    Chemicals of environmental concern are known to alter the immune system. Recent data indicate that some contaminants possess proinflammatory properties by activating neutrophils, an area of research that is still poorly investigated. We have previously documented that toxaphene activates human neutrophils to produce reactive oxygen species (ROS) and accelerates apoptosis by a yet unknown mechanism. In this study, we found that toxaphene induces another neutrophil function, chemotaxis. Furthermore, we found that toxaphene induces both chemotaxis and apoptosis via a ROS-dependent mechanism, since these responses were blocked by the addition of catalase to the culture. In addition, toxaphene was found to induce the degradation of the cytoskeletal proteins gelsolin, paxillin, and vimentin during apoptosis, and this was reversed by the addition of z-VAD-FMK (caspase inhibitor) or catalase, demonstrating the importance of caspases and ROS in this process. In contrast to toxaphene, we found that beryllium does not induce superoxide production, and, this correlates with its inability to induce chemotaxis and apoptosis. We conclude that toxaphene induces chemotaxis and apoptosis via ROS and that caspases and ROS are involved in the degradation of cytoskeletal proteins.

  14. The mDial formin is required for neutrophil polarization, migration, and activation of the LARG/RhoA/ROCK signaling axis during chemotaxis. (United States)

    Shi, Yongquan; Zhang, Jinyi; Mullin, Michael; Dong, Baoxia; Alberts, Arthur S; Siminovitch, Katherine A


    Neutrophil chemotaxis depends on actin dynamics, but the roles for specific cytoskeleton regulators in this response remain unclear. By analysis of mammalian diaphanous-related formin 1 (mDia1)-deficient mice, we have identified an essential role for this actin nucleator in neutrophil chemotaxis. Lack of mDia1 was associated with defects in chemoattractant-induced neutrophil actin polymerization, polarization, and directional migration, and also with impaired activation of RhoA, its downstream target p160-Rho-associated coil-containing protein kinase (ROCK), and the leukemia-associated RhoA guanine nucleotide exchange factor (LARG). Our data also revealed mDia1 to be associated with another cytoskeletal regulator, Wiskott-Aldrich syndrome protein (WASp), at the leading edge of chemotaxing neutrophils and revealed polarized morphology and chemotaxis to be more mildly impaired in WAS(-/-) than in mDia1(-/-) neutrophils, but essentially abrogated by combined mDia1/WASp deficiency. Thus, mDia1 roles in neutrophil chemotaxis appear to be subserved in concert with WASp and are realized at least in part by activation of the LARG/RhoA/ROCK signaling pathway.

  15. Nanowire array chips for molecular typing of rare trafficking leukocytes with application to neurodegenerative pathology (United States)

    Kwak, Minsuk; Kim, Dong-Joo; Lee, Mi-Ri; Wu, Yu; Han, Lin; Lee, Sang-Kwon; Fan, Rong


    Despite the presence of the blood-brain barrier (BBB) that restricts the entry of immune cells and mediators into the central nervous system (CNS), a small number of peripheral leukocytes can traverse the BBB and infiltrate into the CNS. The cerebrospinal fluid (CSF) is one of the major routes through which trafficking leukocytes migrate into the CNS. Therefore, the number of leukocytes and their phenotypic compositions in the CSF may represent important sources to investigate immune-to-brain interactions or diagnose and monitor neurodegenerative diseases. Due to the paucity of trafficking leucocytes in the CSF, a technology capable of efficient isolation, enumeration, and molecular typing of these cells in the clinical settings has not been achieved. In this study, we report on a biofunctionalized silicon nanowire array chip for highly efficient capture and multiplexed phenotyping of rare trafficking leukocytes in small quantities (50 microliters) of clinical CSF specimens collected from neurodegenerative disease patients. The antibody coated 3D nanostructured materials exhibited vastly improved rare cell capture efficiency due to high-affinity binding and enhanced cell-substrate interactions. Moreover, our platform creates multiple cell capture interfaces, each of which can selectively isolate specific leukocyte phenotypes. A comparison with the traditional immunophenotyping using flow cytometry demonstrated that our novel silicon nanowire-based rare cell analysis platform can perform rapid detection and simultaneous molecular characterization of heterogeneous immune cells. Multiplexed molecular typing of rare leukocytes in CSF samples collected from Alzheimer's disease patients revealed the elevation of white blood cell counts and significant alterations in the distribution of major leukocyte phenotypes. Our technology represents a practical tool for potentially diagnosing and monitoring the pathogenesis of neurodegenerative diseases by allowing an effective

  16. Chemokine Ligand 20: A Signal for Leukocyte Recruitment During Human Ovulation? (United States)

    Al-Alem, Linah; Puttabyatappa, Muraly; Rosewell, Kathy; Brännström, Mats; Akin, James; Boldt, Jeffrey; Muse, Ken; Curry, Thomas E


    Ovulation is one of the cornerstones of female fertility. Disruption of the ovulatory process results in infertility, which affects approximately 10% of couples. Using a unique model in which the dominant follicle is collected across the periovulatory period in women, we have identified a leukocyte chemoattractant, chemokine ligand 20 (CCL20), in the human ovary. CCL20 mRNA is massively induced after an in vivo human chorionic gonadotropin (hCG) stimulus in granulosa (>10 000-fold) and theca (>4000-fold) cells collected during the early ovulatory (12-18 h) and late ovulatory (18-34 h) periods after hCG administration. Because the LH surge sets in motion an inflammatory reaction characterized by an influx of leukocytes and CCL20 is known to recruit leukocytes in other systems, the composition of ovarian leukocytes (CD45+) containing the CCL20 receptor CCR6 was determined immediately prior to ovulation. CD45+/CCR6+ cells were primarily natural killer cells (41%) along with B cells (12%), T cells (11%), neutrophils (10%), and monocytes (9%). Importantly, exogenous CCL20 stimulated ovarian leukocyte migration 59% within 90 minutes. Due to the difficulties in obtaining human follicles, an in vitro model was developed using granulosa-lutein cells to explore CCL20 regulation. CCL20 expression increased 40-fold within 6 hours after hCG, was regulated partially by the epithelial growth factor pathway, and was positively correlated with progesterone production. These results demonstrate that hCG dramatically increases CCL20 expression in the human ovary, that ovarian leukocytes contain the CCL20 receptor, and that CCL20 stimulates leukocyte migration. Our findings raise the prospect that CCL20 may aid in the final ovulatory events and contribute to fertility in women.

  17. Altered expression of adhesion molecules on peripheral blood leukocytes in feline infectious peritonitis. (United States)

    Olyslaegers, Dominique A J; Dedeurwaerder, Annelike; Desmarets, Lowiese M B; Vermeulen, Ben L; Dewerchin, Hannah L; Nauwynck, Hans J


    Feline infectious peritonitis (FIP) is a fatal, coronavirus-induced systemic disease in domestic and wild felids. The pathology associated with FIP (multifocal granulomatous vasculitis) is considered to be elicited by exaggerated activation and subsequent extravasation of leukocytes. As changes in the expression of adhesion molecules on circulating leukocytes precede their margination and emigration, we reasoned that the expression of leukocyte adhesion molecules may be altered in FIP. In present study, the expression of principal adhesion molecules involved in leukocyte transmigration (CD15s, CD11a, CD11b, CD18, CD49d, and CD54) on peripheral blood leukocytes from cats with naturally occurring FIP (n=15) and controls (n=12) was quantified by flow cytometry using a formaldehyde-based rapid leukocyte preparation technique. T- and B-lymphocytes from FIP patients exhibit higher expression of both subunits (CD11a and CD18) composing the β2 integrin lymphocyte function-associated antigen (LFA)-1. In addition, the expression of the α4 subunit (CD49d) of the β1 integrin very late antigen (VLA)-4 was elevated on B-lymphocytes from FIP patients. The expression of CD11b and CD18, that combine to form the β2 integrin macrophage-1 antigen (Mac-1), was elevated on monocytes, whereas the density of CD49d was reduced on this population in FIP. Granulocytes of FIP cats displayed an increased expression of the α chain of Mac-1 (CD11b). These observations suggest that leukocytes from FIP patients show signs of systemic activation causing them to extravasate into surrounding tissues and ultimately contribute to pyogranuloma formation seen in FIP.

  18. Identification of an anchor residue for CheA-CheY interactions in the chemotaxis system of Escherichia coli. (United States)

    Thakor, Hemang; Nicholas, Sarah; Porter, Ian M; Hand, Nicole; Stewart, Richard C


    Transfer of a phosphoryl group from autophosphorylated CheA (P-CheA) to CheY is an important step in the bacterial chemotaxis signal transduction pathway. This reaction involves CheY (i) binding to the P2 domain of P-CheA and then (ii) acquiring the phosphoryl group from the P1 domain. Crystal structures indicated numerous side chain interactions at the CheY-P2 binding interface. To investigate the individual contributions of the P2 side chains involved in these contacts, we analyzed the effects of eight alanine substitution mutations on CheA-CheY binding interactions. An F214A substitution in P2 caused ∼1,000-fold reduction in CheA-CheY binding affinity, while Ala substitutions at other P2 positions had small effects (E171A, E178A, and I216A) or no detectable effects (H181A, D202A, D207A, and C213A) on binding affinity. These results are discussed in relation to previous in silico predictions of hot-spot and anchor positions at the CheA-CheY interface. We also investigated the consequences of these mutations for chemotaxis signal transduction in living cells. CheA(F214A) was defective in mediating localization of CheY-YFP to the large clusters of signaling proteins that form at the poles of Escherichia coli cells, while the other CheA variants did not differ from wild-type (wt) CheA (CheA(wt)) in this regard. In our set of mutants, only CheA(F214A) exhibited a markedly diminished ability to support chemotaxis in motility agar assays. Surprisingly, however, in FRET assays that monitored receptor-regulated production of phospho-CheY, CheA(F214A) (and each of the other Ala substitution mutants) performed just as well as CheA(wt). Overall, our findings indicate that F214 serves as an anchor residue at the CheA-CheY interface and makes an important contribution to the binding energy in vitro and in vivo; however, loss of this contribution does not have a large negative effect on the overall ability of the signaling pathway to modulate P-CheY levels in response to

  19. Cells on the run: shear-regulated integrin activation in leukocyte rolling and arrest on endothelial cells. (United States)

    Alon, Ronen; Ley, Klaus


    The arrest of rolling leukocytes on various target vascular beds is mediated by specialized leukocyte integrins and their endothelial immunoglobulin superfamily (IgSF) ligands. These integrins are kept in largely inactive states and undergo in situ activation upon leukocyte-endothelial contact by both biochemical and mechanical signals from flow-derived shear forces. In vivo and in vitro studies suggest that leukocyte integrin activation involves conformational alterations through inside-out signaling followed by ligand-induced rearrangements accelerated by external forces. This activation process takes place within fractions of seconds by in situ signals transduced to the rolling leukocyte as it encounters specialized endothelial-displayed chemoattractants, collectively termed arrest chemokines. In neutrophils, selectin rolling engagements trigger intermediate affinity integrins to support reversible adhesions before chemokine-triggered arrest. Different leukocyte subsets appear to use different modalities of integrin activation during rolling and arrest at distinct endothelial sites.

  20. Microscopic observation of leukocyte kinesis in the vascular bed during hemodialysis using the rabbit ear chamber technique. (United States)

    Teraoka, S; Sugawara, M; Kitano, Y; Hoshino, T; Takahashi, M; Minagawa, Y; Naganuma, S; Sanaka, T; Mineshima, M; Era, K


    Leukocyte kinesis in the capillary vascular bed during hemodialysis (HD) was investigated to elucidate the mechanism of transient leukopenia. Leukocyte movement was observed microscopically during HD using the rabbit ear chamber (REC) technique, which permits visualization of the movement of blood corpuscles in capillaries. Blood was drawn from the femoral artery and returned into the auricular and/or carotid artery so that the blood passing through the hollow fiber artificial kidney (HFAK) flowed into capillaries in the REC. Leukocyte counts of blood samples taken from the afferent and efferent limbs of the HD circuit, the right jugular vein and the right atrium were determined consecutively during HD. The difference in the leukocyte count was observed between the afferent and efferent limbs for the first 15 minutes and thereafter between the efferent limb and the jugular vein. The "transpulmonary" difference in the leukocyte count was not noticed throughout HD. Between 15 and 90 minutes after the start of HD, scarcely any circulating leukocytes were found in capillaries in the REC and some leukocytes were attached to the endothelial surface. Thereafter circulating leukocytes were seen again and detachment of leukocytes from the endothelial surface was observed. No leukocyte aggregation or embolization of aggregating leukocytes was noticed. This evidence suggests that leukopenia may be attributed to the transient shift of leukocytes to the marginal pool of the vessel lumen and this process may not be specific for the pulmonary vasculature, but may occur in the first capillary bed into which the blood passing through the HFAK flows.(ABSTRACT TRUNCATED AT 250 WORDS)

  1. Human Leukocyte Antigen Alleles and Cytomegalovirus Infection After Renal Transplantation

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    Full Text Available Background Several studies have been conducted on the relationship between a number of human leukocyte antigen (HLA alleles and cytomegalovirus infection (CMV, in kidney transplant recipients, after transplantation. However, only a limited number of HLAs have been investigated, so far, and the results have been contradictory. Objectives This study aimed to investigate the relationship between 59 HLA alleles and the CMV infection, in transplant recipients, after kidney transplantation. Patients and Methods This retrospective cohort study was conducted on 200 patients, receiving a kidney transplant, in Baqiyatallah Hospital, in Tehran, during 2013. Throughout a one-year follow-up of kidney transplant recipients, in case of detecting the CMV antigen in patients’ blood, at any time, they were placed in the group of patients with CMV infection, whereas, if no CMV-specific antigen was developed, over a year, patients were placed in the group of patients without CMV infection, after transplantation. This study investigated the relationship between CMV infection in kidney transplant recipients and 59 HLA alleles, including 14 HLA-A, 28 HLA-B, and 17 HLA-DRB1 cases. Results Of all participants, 104 patients (52% were diagnosed with CMV infection. There was no significant difference between the two groups, with and without CMV infection, in terms of patient’s characteristics. The CMV infection, in patients receiving a transplanted organ from deceased donor, was significantly more prevalent than in those receiving kidney transplant from living donor (63% vs. 39%, respectively, P = 0.001. Recipients with HLA-B44 were more infected with CMV compared with patients without this allele (80% vs. 50%, respectively, P = 0.024; on the contrary, kidney recipients with HLA-DRB1-1 were less infected with CMV than patients without this allele (31% vs. 55%, respectively, P = 0.020. There was no significant relationship between CMV infection and other HLA alleles

  2. Channel catfish (Ictalurus punctatus) leukocytes express estrogen receptor isoforms ERα and ERβ2 and are functionally modulated by estrogens (United States)

    Iwanowicz, Luke R.; Stafford, James L.; Patiño, Reynaldo; Bengten, Eva; Miller, Norman W.; Blazer, Vicki


    Estrogens are recognized as modulators of immune responses in mammals and teleosts. While it is known that the effects of estrogens are mediated via leukocyte-specific estrogen receptors (ERs) in humans and mice, leucocyte-specific estrogen receptor expression and the effects of estrogens on this cell population is less explored and poorly understood in teleosts. Here in, we verify that channel catfish (Ictalurus punctaus) leukocytes express ERα and ERβ2. Transcripts of these isoforms were detected in tissue-associated leukocyte populations by PCR, but ERβ2 was rarely detected in PBLs. Expression of these receptors was temporally regulated in PBLs following polyclonal activation by concanavalin A, lipopolysaccharide or alloantigen based on evaluation by quantitative and end-point PCR. Examination of long-term leukocyte cell lines demonstrated that these receptors are differentially expressed depending on leukocyte lineage and phenotype. Expression of ERs was also temporally dynamic in some leukocyte lineages and may reflect stage of cell maturity. Estrogens affect the responsiveness of channel catfish peripheral blood leukocytes (PBLs) to mitogens in vitro. Similarly, bactericidal activity and phorbol 12-myristate 13-acetate induced respiratory burst was modulated by 17β-estradiol. These actions were blocked by the pure ER antagonist ICI 182780 indicating that response is, in part, mediated via ERα. In summary, estrogen receptors are expressed in channel catfish leukocytes and participate in the regulation of the immune response. This is the first time leukocyte lineage expression has been reported in teleost cell lines.

  3. Effect of Leukocytes Transfer on the Induction of Liver Damage after Renal Ischemia- Reperfusion in Inbred Mice

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    Hossein Khastar


    Full Text Available Introduction: Renal ischemia-reperfusion (IR induces organ damage in remote organs such as liver, brain and lung. The aim of this study was to assess the role of leukocytes in the induction of liver damage after renal IR injury.Methods: Inbred mice were subjected to either sham operation or bilateral renal IR injury (60 min ischemia followed by 3h reperfusion. Mice were then anesthetized for collection of leukocytes by heart puncture. Isolated leukocytes were transferred to two other groups: intact recipient mice that received leukocytes from IR mice and intact recipient mice that received leukocytes from sham-operated control mice. After 24h, recipient mice were anesthetized and blood and hepatic samples were collected.Results: Alanine aminotransferase (ALT, aspartate aminotransferase (AST and hepatic malondialdehyde (MDA increased significantly in intact recipient mice that received leukocytes from IR mice in comparison to intact recipient mice receiving leukocytes from sham-operated control mice. In addition, loss of normal liver architecture, cytoplasmic vacuolization and focal infiltration of leukocytes were observed.Conclusion: These results suggest that leukocytes are one of the possible factors that contribute to liver damage after renal IR injury and this damage is partly due to the induction of oxidative stress.

  4. Search for CEA-like molecules in polymorphonuclear leukocytes of non-human primates using monoclonal antibodies. (United States)

    Jantscheff, P; Indzhiia, L V; Micheel, B


    The monoclonal anti-CEA antibody ZIK-A42-A/C1 which reacts with NCA of human polymorphonuclear leukocytes was found to bind also to polymorphonuclear blood leukocytes of the following non-human primates tested: hamadryas baboon (Papio hamadryas), stump-tailed monkey (Macaca arctoides), pig-tailed monkey (Macaca nemestrina), and rhesus monkey (Macaca mulata). No binding was observed to mononuclear blood leukocytes. It was concluded that non-human primates contain CEA-like substances in their polymorphonuclear leukocytes as humans do and that these substances carry some identical epitopes.

  5. Directional migration of leukocytes: their pathological roles in inflammation and strategies for development of anti-inflammatory therapies

    Institute of Scientific and Technical Information of China (English)


    Directional migration of leukocytes is indispensable to innate immunity for host defense.However,recruitment of leukocytes to a site of tissue injury also constitutes a leading cause for inflammatory responses.Mechanistically,it involves a cascade of cellular events precisely regulated by temporal and spatial presentation of a repertoire of molecules in the migrating leukocytes and their surroundings(microenvironments).Here I will summarize the emerging evidence that has shed lights on the underlying molecular mechanism for directional migration of leukocytes,which has guided the therapeutical development for innovative anti-inflammatory medicines.

  6. Relationship between chemical composition and biological function of Pseudomonas aeruginosa lipopolysaccharide: effect on human neutrophil chemotaxis and oxidative burst

    DEFF Research Database (Denmark)

    Kharazmi, A; Fomsgaard, A; Conrad, R S;


    There are conflicting data on the effect of bacterial lipopolysaccharides (LPS) on the function of human neutrophils. The present study was designed to examine the relationship between chemical composition and the modulatory effect of LPS on human neutrophil function. LPS was extracted from five ...... composition of the LPS molecule may play an important role in biological activity of LPS.......There are conflicting data on the effect of bacterial lipopolysaccharides (LPS) on the function of human neutrophils. The present study was designed to examine the relationship between chemical composition and the modulatory effect of LPS on human neutrophil function. LPS was extracted from five...... no effect on neutrophil chemotaxis and a slight effect on chemiluminescence. The major differences in chemical composition of the LPS from these two strains are in the rhamnose and heptose content of the O side chain and in the alanine content of the core region. These data indicate that chemical...

  7. Global existence and boundedness of radial solutions to a two dimensional fully parabolic chemotaxis system with general sensitivity (United States)

    Fujie, Kentarou; Senba, Takasi


    This paper deals with positive radially symmetric solutions of the Neumann boundary value problem for the fully parabolic chemotaxis system, {ut=Δu-∇ṡ(u∇χ(v))in Ω×(0,∞),τvt=Δv-v+uin Ω×(0,∞), in a ball Ω \\subset {{{R}}2} with general sensitivity function χ (v) satisfying {χ\\prime}>0 and decaying property {χ\\prime}(s)\\to 0 (s\\to ∞ ), parameter τ \\in ≤ft(0,1\\right] and nonnegative radially symmetric initial data. It is shown that if τ \\in ≤ft(0,1\\right] is sufficiently small, then the problem has a unique classical radially symmetric solution, which exists globally and remains uniformly bounded in time. Especially, this result establishes global existence of solutions in the case χ (v)={χ0}log v for all {χ0}>0 , which has been left as an open problem.

  8. Cellular softening mediates leukocyte demargination and trafficking, thereby increasing clinical blood counts. (United States)

    Fay, Meredith E; Myers, David R; Kumar, Amit; Turbyfield, Cory T; Byler, Rebecca; Crawford, Kaci; Mannino, Robert G; Laohapant, Alvin; Tyburski, Erika A; Sakurai, Yumiko; Rosenbluth, Michael J; Switz, Neil A; Sulchek, Todd A; Graham, Michael D; Lam, Wilbur A


    Leukocytes normally marginate toward the vascular wall in large vessels and within the microvasculature. Reversal of this process, leukocyte demargination, leads to substantial increases in the clinical white blood cell and granulocyte count and is a well-documented effect of glucocorticoid and catecholamine hormones, although the underlying mechanisms remain unclear. Here we show that alterations in granulocyte mechanical properties are the driving force behind glucocorticoid- and catecholamine-induced demargination. First, we found that the proportions of granulocytes from healthy human subjects that traversed and demarginated from microfluidic models of capillary beds and veins, respectively, increased after the subjects ingested glucocorticoids. Also, we show that glucocorticoid and catecholamine exposure reorganizes cellular cortical actin, significantly reducing granulocyte stiffness, as measured with atomic force microscopy. Furthermore, using simple kinetic theory computational modeling, we found that this reduction in stiffness alone is sufficient to cause granulocyte demargination. Taken together, our findings reveal a biomechanical answer to an old hematologic question regarding how glucocorticoids and catecholamines cause leukocyte demargination. In addition, in a broader sense, we have discovered a temporally and energetically efficient mechanism in which the innate immune system can simply alter leukocyte stiffness to fine tune margination/demargination and therefore leukocyte trafficking in general. These observations have broad clinically relevant implications for the inflammatory process overall as well as hematopoietic stem cell mobilization and homing.

  9. KCNE gene expression is dependent on the proliferation and mode of activation of leukocytes. (United States)

    Solé, Laura; Vallejo-Gracia, Albert; Roig, Sara R; Serrano-Albarrás, Antonio; Marruecos, Laura; Manils, Joan; Gómez, Diana; Soler, Concepció; Felipe, Antonio


    Voltage-dependent K (+) (Kv) channels are tightly regulated during the immune system response. Leukocytes have a limited repertoire of Kv channels, whose physiological role is under intense investigation. A functional Kv channel is an oligomeric complex composed of pore-forming and ancillary subunits. The KCNE gene family is a novel group of modulatory Kv channel elements in leukocytes. Here, we characterized the gene expression of KCNEs (1-5) in leukocytes and investigated their regulation during leukocyte proliferation and mode of activation. Murine bone-marrow-derived macrophages, human Jurkat T-lymphocytes and human Raji B-cells were analyzed. KCNEs (1-5) are expressed in all leukocytes lineages. Most KCNE mRNAs show cell cycle-dependent regulation and are differentially regulated under specific insults. Our results further suggest a new and yet undefined physiological role for KCNE subunits in the immune system. Putative associations of these ancillary proteins with Kv channels would yield a wide variety of biophysically and pharmacologically distinct channels that fine-tune the immunological response.

  10. Leukocyte telomere length and hippocampus volume: a meta-analysis [version 1; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Gustav Nilsonne


    Full Text Available Leukocyte telomere length has been shown to correlate to hippocampus volume, but effect estimates differ in magnitude and are not uniformly positive. This study aimed primarily to investigate the relationship between leukocyte telomere length and hippocampus gray matter volume by meta-analysis and secondarily to investigate possible effect moderators. Five studies were included with a total of 2107 participants, of which 1960 were contributed by one single influential study. A random-effects meta-analysis estimated the effect to r = 0.12 [95% CI -0.13, 0.37] in the presence of heterogeneity and a subjectively estimated moderate to high risk of bias. There was no evidence that apolipoprotein E (APOE genotype was an effect moderator, nor that the ratio of leukocyte telomerase activity to telomere length was a better predictor than leukocyte telomere length for hippocampus volume. This meta-analysis, while not proving a positive relationship, also is not able to disprove the earlier finding of a positive correlation in the one large study included in analyses. We propose that a relationship between leukocyte telomere length and hippocamus volume may be mediated by transmigrating monocytes which differentiate into microglia in the brain parenchyma.

  11. Exposure to sodium fluoride produces signs of apoptosis in rat leukocytes. (United States)

    Gutiérrez-Salinas, José; Morales-González, José A; Madrigal-Santillán, Eduardo; Esquivel-Soto, Jaime; Esquivel-Chirino, César; González-Rubio, Manuel García-Luna Y; Suástegui-Domínguez, Sigrit; Valadez-Vega, Carmen


    Fluoride is naturally present in the earth's crust and can be found in rocks, coal, and clay; thus, it can be found in small quantities in water, air, plants, and animals. Therefore, humans are exposed to fluoride through food, drinking water, and in the air they breathe. Flouride is essential to maintain bone strength and to protect against dental decay, but if it is absorbed too frequently, it can cause tooth decay, osteoporosis, and damage to kidneys, bones, nerves, and muscles. Therefore, the present work was aimed at determining the effect of intake of sodium fluoride (NaF) as an apoptosis inducer in leukocytes of rats treated for eight weeks with 1 or 50 parts per million (ppm) NaF. Expression of p53, bcl-2, and caspade-3 were used as apoptotic and general metabolism indicators of leukocyte-like indicators of the (INT) oxidation system. Male rats were exposed to NaF (1 and 500 ppm) for eight weeks, and then sacrificed weekly to obtain blood samples. Expression of p53, bcl-2, and caspase-3 were determined in leukocytes by Western blot, and general metabolism of leukocytes was analyzed with a commercial kit. We found changes in the expression of the proteins described, especially when the animals received 50 ppm of NaF. These results indicate that NaF intoxication can be an apoptosis inducer in rat leukocytes treated with the compound for eight weeks.

  12. Microfluidic chambers for monitoring leukocyte trafficking and humanized nano-proresolving medicines interactions. (United States)

    Jones, Caroline N; Dalli, Jesmond; Dimisko, Laurie; Wong, Elisabeth; Serhan, Charles N; Irimia, Daniel


    Leukocyte trafficking plays a critical role in determining the progress and resolution of inflammation. Although significant progress has been made in understanding the role of leukocyte activation in inflammation, dissecting the interactions between different leukocyte subpopulations during trafficking is hampered by the complexity of in vivo conditions and the lack of detail of current in vitro assays. To measure the effects of the interactions between neutrophils and monocytes migrating in response to various chemoattractants, at single-cell resolution, we developed a microfluidic platform that replicates critical features of focal inflammation sites. We integrated an elastase assay into the focal chemotactic chambers (FCCs) of our device that enabled us to distinguish between phlogistic and nonphlogistic cell recruitment. We found that lipoxin A(4) and resolvin D1, in solution or incorporated into nano-proresolving medicines, reduced neutrophil and monocyte trafficking toward leukotriene B(4). Lipoxin A(4) also reduced the elastase release from homogenous and heterogenous mixtures of neutrophils and monocytes. Surprisingly, the effect of resolvin D1 on heterogenous mixtures was antisynergistic, resulting in a transient spike in elastase activity, which was quickly terminated, and the degraded elastin removed by the leukocytes inside the FCCs. Therefore, the microfluidic assay provides a robust platform for measuring the effect of leukocyte interactions during trafficking and for characterizing the effects of inflammation mediators.

  13. Reduced platelet-mediated and enhanced leukocyte-mediated fibrinolysis in experimentally induced diabetes in rats

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    Winocour, P.D.; Colwell, J.A.


    Studies of fibrinolytic activity in diabetes mellitus have produced conflicting results. This may be a result of methodologic insensitivity or of variable contributions of the different blood components to whole blood fibrinolysis. To explore these two possibilities, the authors used a sensitive solid-phase radiometric assay to examine the fibrinolytic activity of whole blood, platelet-rich plasma, leukocytes, and platelet- and leukocyte-poor plasma prepared from control rats and rats with streptozocin-induced diabetes at various times after induction of diabetes. Fibrinolytic activity of whole blood from diabetic rats after 7 days was significantly reduced, and remained reduced after longer durations of diabetes up to 28 days. Platelet-rich plasma from diabetic rats had decreased fibrinolytic activity, which followed the same time course of changes as in whole blood. The platelet contribution to whole blood fibrinolysis was further reduced in vivo after 14 days of diabetes by a reduced whole blood platelet count. In contrast, fibrinolytic activity of leukocytes from diabetic rats became enhanced after 7 days of diabetes. After 49 days of diabetes, the whole blood leukocyte count was reduced, and in vivo would offset the enhanced activity. Plasma fibrinolytic activity was small compared with that of whole blood and was unaltered in diabetic rats. The authors conclude that altered platelet function contributes to decreased fibrinolytic activity of whole blood in diabetic rats, and that this may be partially offset by enhanced leukocyte-mediated fibrinolysis.


    Directory of Open Access Journals (Sweden)

    Chiara Cerletti


    Full Text Available The aim of this review is to summarize the contribution of platelets and leukocytes and their interactions in inflammation and blood coagulation and its possible relevance in the pathogenesis of  thrombosis. There is some evidence of an association between infection/inflammation and thrombosis. This is likely a bidirectional relationship. The presence of a thrombus may serve as a nidus of infection. Vascular injury indeed promotes platelet and leukocyte activation and thrombus formation and the thrombus and its components facilitate adherence of bacteria to the vessel wall. Alternatively, an infection and the associated inflammation can trigger platelet and leukocyte activation and thrombus formation. In either case platelets and leukocytes co-localize and interact in the area of vascular injury, at sites of inflammation and/or at sites of thrombosis. Following vascular injury, the subendothelial tissue, a thrombogenic surface, becomes available for interaction with these blood cells. Tissue factor, found not only in media and adventitia of the vascular wall, but also on activated platelets and leukocytes, triggers blood coagulation. Vascular-blood cell interactions, mediated by the release of preformed components of the endothelium, is modulated by both cell adhesion and production of soluble stimulatory or inhibitory molecules that alter cell function: adhesion molecules regulate cell-cell contact and facilitate the modulation of biochemical pathways relevant to inflammatory and/or thrombotic processes.

  15. Clinical evaluation of {sup 99m}Tc-HMPAO labeled leukocyte imaging in ulcerative colitis

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    Saitoh, Yasuhiro; Aburano, Tamio; Takashio, Tetsuya; Shuke, Noriyuki; Ayabe, Tokiyoshi; Nomura, Masashi; Kohgo, Yutaka; Ishikawa, Yukio; Satoh, Junichi [Asahikawa Medical Coll., Hokkaido (Japan)


    Inflammatory imaging using {sup 99m}Tc-HMPAO-labeled mixed leukocytes was assessed for use in treating 11 cases diagnosed as ulcerative colitis: 10 cases with total colitis and 1 with left-sided colitis. They consisted of 8 patients with relapse-remitting type and 3 with chronic continuous type. Radionuclide abdominal images were obtained at 1 hr, 4 hr and 24 hr after intravenous injection of 200 MBq prepared {sup 99m}Tc leukocytes. Obvious colonic activity noted at 4 hr served as the basis for positive comparative criterion in the present study. The diagnostic efficacy of radionuclide imaging was compared with endoscopic findings (based on Matts` classification) and the clinical manifestations as reference. The sensitivity and specificity of this imaging were 83.3% and 85.7%, respectively, these values being consistent with endoscopic findings and clinical manifestations at sites of disease activity. All of positive images changed to negative after treatment by leukocyte apheresis or glucocorticoid. Based on these results, {sup 99m}Tc leukocyte imaging can be used to accurately evaluate severity and treatment response in ulcerative colitis. Leukocytes may be closely related to the pathogenesis of ulcerative colitis. (author)

  16. Exposure to Sodium Fluoride Produces Signs of Apoptosis in Rat Leukocytes

    Directory of Open Access Journals (Sweden)

    Sigrit Suástegui-Domínguez


    Full Text Available Fluoride is naturally present in the earth's crust and can be found in rocks, coal, and clay; thus, it can be found in small quantities in water, air, plants, and animals. Therefore, humans are exposed to fluoride through food, drinking water, and in the air they breathe. Flouride is essential to maintain bone strength and to protect against dental decay, but if it is absorbed too frequently, it can cause tooth decay, osteoporosis, and damage to kidneys, bones, nerves, and muscles. Therefore, the present work was aimed at determining the effect of intake of sodium fluoride (NaF as an apoptosis inducer in leukocytes of rats treated for eight weeks with 1 or 50 parts per million (ppm NaF. Expression of p53, bcl-2, and caspade-3 were used as apoptotic and general metabolism indicators of leukocyte-like indicators of the (INT oxidation system. Male rats were exposed to NaF (1 and 500 ppm for eight weeks, and then sacrificed weekly to obtain blood samples. Expression of p53, bcl-2, and caspase-3 were determined in leukocytes by Western blot, and general metabolism of leukocytes was analyzed with a commercial kit. We found changes in the expression of the proteins described, especially when the animals received 50 ppm of NaF. These results indicate that NaF intoxication can be an apoptosis inducer in rat leukocytes treated with the compound for eight weeks.

  17. Induction of macrophage chemotaxis by aortic extracts from patients with Marfan syndrome is related to elastin binding protein.

    Directory of Open Access Journals (Sweden)

    Gao Guo

    Full Text Available Marfan syndrome is an autosomal dominantly inherited disorder of connective tissue with prominent skeletal, ocular, and cardiovascular manifestations. Aortic aneurysm and dissection are the major determinants of premature death in untreated patients. In previous work, we showed that extracts of aortic tissues from the mgR mouse model of Marfan syndrome showed increased chemotactic stimulatory activity related to the elastin-binding protein. Aortic samples were collected from 6 patients with Marfan syndrome and 8 with isolated aneurysms of the ascending aorta. Control samples were obtained from 11 organ donors without known vascular or connective tissue diseases. Soluble proteins extracted from the aortic samples of the two patient groups were compared against buffer controls and against the aortic samples from controls with respect to the ability to induce macrophage chemotaxis as measured using a modified Boyden chamber, as well as the reactivity to a monoclonal antibody BA4 against bioactive elastin peptides using ELISA. Samples from Marfan patients displayed a statistically significant increase in chemotactic inductive activity compared to control samples. Additionally, reactivity to BA4 was significantly increased. Similar statistically significant increases were identified for the samples from patients with idiopathic thoracic aortic aneurysm. There was a significant correlation between the chemotactic index and BA4 reactivity, and the increases in chemotactic activity of extracts from Marfan patients could be inhibited by pretreatment with lactose, VGVAPG peptides, or BA4, which indicates the involvement of EBP in mediating the effects. Our results demonstrate that aortic extracts of patients with Marfan syndrome can elicit macrophage chemotaxis, similar to our previous study on aortic extracts of the mgR mouse model of Marfan syndrome (Guo et al., Circulation 2006; 114:1855-62.

  18. Protein kinase A regulates 3-phosphatidylinositide dynamics during platelet-derived growth factor-induced membrane ruffling and chemotaxis. (United States)

    Deming, Paula B; Campbell, Shirley L; Baldor, Linda C; Howe, Alan K


    Spatial regulation of the cAMP-dependent protein kinase (PKA) is required for chemotaxis in fibroblasts; however, the mechanism(s) by which PKA regulates the cell migration machinery remain largely unknown. Here we report that one function of PKA during platelet-derived growth factor (PDGF)-induced chemotaxis was to promote membrane ruffling by regulating phosphatidylinositol 3,4,5-trisphosphate (PIP(3)) dynamics. Inhibition of PKA activity dramatically altered membrane dynamics and attenuated formation of peripheral membrane ruffles in response to PDGF. PKA inhibition also significantly decreased the number and size of PIP(3)-rich membrane ruffles in response to uniform stimulation and to gradients of PDGF. This ruffling defect was quantified using a newly developed method, based on computer vision edge-detection algorithms. PKA inhibition caused a marked attenuation in the bulk accumulation of PIP(3) following PDGF stimulation, without effects on PI3-kinase (PI3K) activity. The deficits in PIP(3) dynamics correlated with a significant inhibition of growth factor-induced membrane recruitment of endogenous Akt and Rac activation in PKA-inhibited cells. Simultaneous inhibition of PKA and Rac had an additive inhibitory effect on growth factor-induced ruffling dynamics. Conversely, the expression of a constitutively active Rac allele was able to rescue the defect in membrane ruffling and restore the localization of a fluorescent PIP(3) marker to membrane ruffles in PKA-inhibited cells, even in the absence of PI3K activity. These data demonstrate that, like Rac, PKA contributes to PIP(3) and membrane dynamics independently of direct regulation of PI3K activity and suggest that modulation of PIP(3)/3-phosphatidylinositol (3-PI) lipids represents a major target for PKA in the regulation of PDGF-induced chemotactic events.

  19. CSF Biomarkers of Monocyte Activation and Chemotaxis correlate with Magnetic Resonance Spectroscopy Metabolites during Chronic HIV Disease (United States)

    Anderson, Albert M.; Fennema-Notestine, Christine; Umlauf, Anya; Taylor, Michael J.; Clifford, David B.; Marra, Christina M.; Collier, Ann C.; Gelman, Benjamin B.; McArthur, Justin C.; McCutchan, J. Allen; Simpson, David M.; Morgello, Susan; Grant, Igor; Letendre, Scott L.


    Background HIV-associated neurocognitive disorders (HAND) persist despite combination antiretroviral therapy (cART), supporting the need to better understand HIV neuropathogenesis. Magnetic resonance spectroscopy (MRS) of the brain has demonstrated abnormalities in HIV-infected individuals despite cART. We examined the associations between MRS metabolites and selected cerebrospinal fluid (CSF) biomarkers reflecting monocyte/macrophage activation and chemotaxis. Methods A multicenter cross-sectional study involving five sites in the United States was conducted. The following CSF biomarkers were measured: soluble CD14 (sCD14), monocyte chemotactic protein 1 (MCP-1), interferon inducible protein 10 (IP-10), and stromal cell derived growth factor 1 alpha (SDF-1α). The following MRS metabolites were measured from basal ganglia (BG), frontal white matter (FWM) and frontal gray matter (FGM): N-acetyl-aspartate (NAA), Myo-inositol (MI), Choline (Cho), and Creatine (Cr). CSF biomarkers were compared to absolute MRS metabolites as well as metabolite/Cr ratios using linear regression. Results 83 HIV-infected individuals were included, 78% on cART and 37% with HAND. The most robust positive correlations were between MCP-1 and Cho in BG (R2 0.179, p<0.001) as well as MCP-1 and MI in FWM (R2 0.137, p=0.002). Higher Cr levels in FWM were associated with MCP-1 (R2 0. 075, p=0.01) and IP-10 (R2 0.106, p=0.003). Comparing biomarkers to MRS metabolite/Cr ratios impacted some relationships, e.g., higher sCD14 levels were associated with lower Cho/Cr ratios in FGM (R2 0.224, p<0.001), although higher MCP-1 levels remained associated with Cho/Cr in BG. Conclusion These findings provide evidence that monocyte activation and chemotaxis continue to contribute to HIV-associated brain abnormalities in cART-treated individuals. PMID:26069183

  20. Leukocyte Beta-Catenin Expression Is Disturbed in Systemic Lupus Erythematosus. (United States)

    Orme, Jacob J; Du, Yong; Vanarsa, Kamala; Wu, Tianfu; Satterthwaite, Anne B; Mohan, Chandra


    Wnt/β-catenin signaling is relatively understudied in immunity and autoimmunity. β-catenin blocks inflammatory mediators and favors tolerogenic dendritic cell (DC) phenotypes. We show here that leukocytes from lupus-prone mice and SLE patients express diminished β-catenin transcriptional activity, particularly in myeloid cells, although other leukocytes revealed similar trends. Serum levels of DKK-1, an inhibitor under transcriptional control of Wnt/β-catenin, were also decreased in lupus-prone mice. Surprisingly, however, preemptive deletion of β-catenin from macrophages appears to have no effect on lupus development, even in mice with varying genetic loads for lupus. Although myeloid-specific loss of β-catenin does not seem to be important for lupus development, the potential role of this transcription factor in other leukocytes and renal cells remain to be elucidated.

  1. Peripheral Leukocyte Apoptosis in Patients with Parkinsonism: Correlation with Clinical Characteristics and Neuroimaging Findings

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    Wei-Che Lin


    Full Text Available Apoptosis of both brain neurons and peripheral blood leukocyte is believed to be an important biomarker for evaluating the functional status of Parkinson’s disease (PD. However, their correlation remains unknown. A better understanding of the pathophysiology of neurodegeneration is essential for the treatment and prevention of PD. The present study demonstrated that leukocyte apoptosis is significantly higher in PD patients and is associated with central dopamine neuron loss by using Tc99m-TRODAT-1 SPECT. The leukocyte apoptosis and striatal dopamine transporter uptake ratios were further associated with increased severity and longer duration of disease. The interaction between brain and systemic inflammation may be responsible for the neurodegenerative disease progression.

  2. Human leukocyte mobilization and morphology in nickel contact allergy using a skin chamber technique

    DEFF Research Database (Denmark)

    Lerche, A; Bisgaard, H; Christensen, J D


    An improved skin chamber technique has been devised and used for quantitative evaluation of the leukocyte mobilization rate (LMR). The method was applied in 10 nickel-hypersensitive patients exposed to nickel sulphate. Each patient served as his own control and for additional control purpose, 5...... healthy individuals without nickel hypersensitivity were studied. The kinetics of the mobilized leukocytes were followed over a 48-hour period. After an initial lag phase of 2-4 hours, maximum migration was observed from the 24th to the 48th hour, with a wide interindividual variability in the number...... is a valuable means for quantitative evaluation of leukocyte mobilization and morphology in skin exudates during exposure to an allergen in delayed hypersensitivity reactions....

  3. Jon Van Rood: pioneer at the crossroad of human leukocyte antigens and transplantation. (United States)

    Jansen, Jan


    Jon Van Rood (born in 1926) has made major contributions to the fields of transfusion medicine as well as organ and stem cell transplantation. His group was the first to start unraveling the complexity of the human leukocyte antigen (HLA) system through collaborative studies that used panels of sera and leukocyte samples. Furthermore, using HLA typing, he introduced the first HLA-matched platelet transfusions and developed routine leukocyte depletion as a means to prevent HLA alloimmunization. Van Rood has also been active in the fields of kidney transplantation (Eurotransplant) and stem cell transplantation (Europdonor). He combined scientific laboratory research with application to clinical medicine. He retired from his university position in 1991 but remains active in the field.

  4. Leukocyte Subset Changes in Response to a 164-km Road Cycle Ride in a Hot Environment (United States)



    The purpose of this observational study was to determine the circulating leukocyte subset response to completing the 2013 Hotter’N Hell Hundred recreational 164-km road cycle event in a hot and humid environmental condition. Twenty-eight men and four women were included in this study. Whole blood samples were obtained 1–2 hours before (PRE) and immediately after (POST) the event. Electronic sizing/sorting and cytometry were used to determine complete blood counts (CBC) including neutrophil, monocyte, and lymphocyte subsets. The concentration of circulating total leukocytes (103·μL−1) increased 134% from PRE to POST with the greatest increase in neutrophils (319%, pexercise in stressful environmental conditions affects the complement of circulating immune cells, although activational state and characterization of specific leukocyte subsets remains unclear. The observed increase in circulating cell sub-populations suggests that the circulating immune surveillance system may be acutely affected by exercise in hot and humid conditions. PMID:27293505

  5. Limitations of indium-111 leukocyte scanning in febrile renal transplant patients

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    Sebrechts, C.; Biberstein, M.; Klein, J.L.; Witztum, K.F.


    Indium-111-labeled leukocyte scanning was evaluated as a technique for investigating possible abscess as the cause of fever in 10 renal allograft recipients under therapy for rejection, acute tubular necrosis, or urinary infection. The usefulness of the method in this setting was found to be limited by marked nonspecificity of renal, pulmonary, and other focal leukocyte accumulation. Although wound infections were correctly identified, false-positive scans resulted in multiple nonproductive consultations and radiologic procedures (some invasive) and contributed to the decision to perform one negative exploratory laparotomy. Such generalized nonspecificity in this patient population is in distinct contrast to the experience with this diagnostic test in nontransplant patients, and has not previously been reported. Possible explanations and implications of these findings are discussed. Consequently, great caution is recommended in the use of indium-111 leukocyte scans to diagnose infection in febrile renal transplant patients who present in a similar clinical setting.

  6. Importance of Primary Capture and L-Selectin–Dependent Secondary Capture in Leukocyte Accumulation in Inflammation and Atherosclerosis in Vivo (United States)

    Eriksson, Einar E.; Xie, Xun; Werr, Joachim; Thoren, Peter; Lindbom, Lennart


    In the multistep process of leukocyte extravasation, the mechanisms by which leukocytes establish the initial contact with the endothelium are unclear. In parallel, there is a controversy regarding the role for L-selectin in leukocyte recruitment. Here, using intravital microscopy in the mouse, we investigated leukocyte capture from the free flow directly to the endothelium (primary capture), and capture mediated through interactions with rolling leukocytes (secondary capture) in venules, in cytokine-stimulated arterial vessels, and on atherosclerotic lesions in the aorta. Capture was more prominent in arterial vessels compared with venules. In venules, the incidence of capture increased with increasing vessel diameter and wall shear rate. Secondary capture required a minimum rolling leukocyte flux and contributed by ∼20–50% of total capture in all studied vessel types. In arteries, secondary capture induced formation of clusters and strings of rolling leukocytes. Function inhibition of L-selectin blocked secondary capture and thereby decreased the flux of rolling leukocytes in arterial vessels and in large (>45 μm in diameter), but not small (<45 μm), venules. These findings demonstrate the importance of leukocyte capture from the free flow in vivo. The different impact of blockage of secondary capture in venules of distinct diameter range, rolling flux, and wall shear rate provides explanations for the controversy regarding the role of L-selectin in various situations of leukocyte recruitment. What is more, secondary capture occurs on atherosclerotic lesions, a fact that provides the first evidence for roles of L-selectin in leukocyte accumulation in atherogenesis. PMID:11457895

  7. Initial afferent lymphatic vessels controlling outbound leukocyte traffic from skin to lymph nodes.

    Directory of Open Access Journals (Sweden)

    Ignacio eMelero


    Full Text Available Tissue drains fluid and macromolecules through lymphatic vessels, which are lined by a specialized endothelium that expresses peculiar differentiation proteins, not found in blood vessels (i.e: LYVE-1, Podoplanin, PROX-1 and VEGFR-3. Lymphatic capillaries are characteristically devoid of a continuous basal membrane and are anchored to the ECM by elastic fibers that act as pulling ropes which open the vessel to avoid oedema if tissue volume increases, as it occurs upon inflammation. Lymphatic vessels are also crucial for the transit of T lymphocytes and antigen presenting cells from tissue to draining lymph nodes. Importantly, cell traffic control across lymphatic endothelium is differently regulated under resting and inflammatory conditions. Under steady-state non-inflammatory conditions, leukocytes enter into the lymphatic capillaries through basal membrane gaps (portals. This entrance is integrin-independent and seems to be mainly guided by CCL21 chemokine gradients acting on leukocytes expressing CCR7. In contrast, inflammatory processes in lymphatic capillaries involve a plethora of cytokines, chemokines, leukocyte integrins and other adhesion molecules. Importantly, under inflammation a role for integrins and their ligands becomes apparent and, as a consequence, the number of leukocytes entering the lymphatic capillaries multiplies several-fold. Enhancing transmigration of dendritic cells en route to lymph nodes is conceivably useful for vaccination and cancer immunotherapy, whereas interference with such key mechanisms may ameliorate autoimmunity or excessive inflammation. Recent findings illustrate how, transient cell-to-cell interactions between lymphatic endothelial cells and leukocytes contribute to shape the subsequent behaviour of leukocytes and condition the lymphatic vessel for subsequent trans-migratory events.

  8. Enhancement of leukocyte adhesion after percutaneous irradiation in rats with hepatocellular carcinoma

    Institute of Scientific and Technical Information of China (English)

    Sasa-Marcel Maksan; Eduard Schmidt; Eduard Ryschich; Wolfgang Harms; Jan Schmidt


    AIM: To evaluate the effects of percutaneous radiation on leukocyte-endothelium interaction (LEI) in experimental hepatocellular carcinoma (HCC).METHODS: Twelve ACI rats underwent HCC-inoculation,six of which on day 12 received low-dose external radiation and six did not. After 12 h intravital microscopy was performed.RESULTS: LEI was significantly reduced in tumor tissue.However, irradiation of liver sinusoids and tumor tissue with 6 Gy led to a significant activation of leukocyte adhesion in the tumor with a marked increase of the proinfiammatory cytokine TNF-α.CONCLUSION: The findings indicate that the immunological tumor-endothelial barrier can be overcome by external irradiation.

  9. Radioresponse of peripheral blood and its modification by MPG (2-mercaptopropionylglycine) in mice leukocytes

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    Kumar, S.; Devi, P.U. (Rajasthan Univ., Jaipur (India). Radiation Biology Lab.)


    The protective effect of MPG on the peripheral blood leukocytes of Swiss albino mice was studied after a single whole-body exposure to 10 Gy of /sup 60/Co radiation with or without prior injection of MPG. The results indicated that the drug was not effective in modifying the radiation-induced changes in the total leukocyte, lymphocyte and neutrophil counts, whereas a significant drop in the number of degenerating cells was observed at the early postirradiation intervals in the drug-treated animals, indicating a protection against the direct cell killing effect of radiation.

  10. Effect of Vitamin C Administration on Leukocyte Vitamin C Level and Severity of Bronchial Asthma

    Directory of Open Access Journals (Sweden)

    Seyed Hamid Hashemi


    Full Text Available Oxidative stress mediated by reactive oxygen species is known to contribute to the inflammatory process of bronchial asthma. Reactive oxygen species are released into the bronchial tree by activated inflammatory cells. In this study, we aimed to determine the effect of vitamin C administration on leukocyte vitamin C level as well as severity of asthma. In this double blind clinical trial study we evaluated 60 patients with chronic stable asthma. The patients were divided into two groups (A and B including 30 patients in each group. Patients in these groups were matched according to their age, weight, height, gender, BMI and drug consumption. In addition to standard asthma treatment (according to stepwise therapy in 4th step of bronchial asthma in which the patients were controlled appropriately, group A received 1000 mg vitamin C daily and group B received placebo. At the baseline and after one month treatment, non-fasting blood samples were drawn for laboratory evaluations. Asthmatic patient's clinical condition was evaluated through standard pulmonary function test (PFT. The mean (±SD leukocyte vitamin C level in group A at the baseline and after one month treatment with 1000 mg/day vitamin C, were 0.0903 (±0.0787 µg/108 leukocytes and 0.1400 (±0.0953 µg/108 leukocytes respectively (P<0.05. The mean (±SD leukocyte vitamin C level in group B at the baseline and after one month administration of placebo, were 0.0867 (±0.0629 µg/108 leukocytes and 0.0805(±0.0736 µg/108 leukocytes respectively. The leukocyte vitamin C level in group A was higher than those of group B after one month treatment with vitamin C and placebo and the difference was statistically significant (P<0.05. Comparing PFT (FEV1, FVC and FEV1/FVC in group B during the study period showed a significant increase in FEV1 (P<0.05, while the other two parameters remained unchanged. In group A, who received 1000 mg/day vitamin C, none of the spirometry parameters changed after

  11. Association of the leukocyte immunoglobulin G (Fcgamma) receptor IIIa-158V/F polymorphism with inflammatory myopathies in Dutch patients

    NARCIS (Netherlands)

    Bronner, I.M.; Hoogendijk, J.E.; de Visser, M.; van de Vlekkert, J.; Badrising, U.A.; Wintzen, A.R.; Uitdehaag, B.M.; Blokland-Fromme, M.; Leusen, J.H.W.; van der Pol, W.L.


    Leukocytes are involved in the pathogenesis of idiopathic inflammatory myopathies (IIMs). Immunoglobulin G (IgG) receptors (FcgammaR) link the specificity of IgG to the effector functions of leukocytes. Several FcgammaR subclasses display functional polymorphisms that determine in part the vigour of

  12. Circulating Leukocyte and Carotid Atherosclerotic Plaque Telomere Length Interrelation, Association With Plaque Characteristics, and Restenosis After Endarterectomy

    NARCIS (Netherlands)

    Huzen, Jardi; Peeters, Wouter; de Boer, Rudolf A.; Moll, Frans L.; Wong, Liza S. M.; Codd, Veryan; de Kleijn, Dominique P. V.; de Smet, Bart J. G. L.; van Veldhuisen, Dirk J.; Samani, Nilesh J.; van Gilst, Wiek H.; Pasterkamp, Gerard; van der Harst, Pim


    Objective-Shorter leukocyte telomeres are associated with atherosclerosis and predict future heart disease. The goal of the present study was to determine whether leukocyte telomere length is related to atherosclerotic plaque telomere length and whether it is associated with plaque characteristics o

  13. Morphogen and proinflammatory cytokine release kinetics from PRGF-Endoret fibrin scaffolds: evaluation of the effect of leukocyte inclusion. (United States)

    Anitua, E; Zalduendo, M M; Prado, R; Alkhraisat, M H; Orive, G


    The potential influence of leukocyte incorporation in the kinetic release of growth factors from platelet-rich plasma (PRP) may explain the conflicting efficiency of leukocyte platelet-rich plasma (L-PRP) scaffolds in tissue regeneration. To assess this hypothesis, leukocyte-free (PRGF-Endoret) and L-PRP fibrin scaffolds were prepared, and both morphogen and proinflammatory cytokine release kinetics were analyzed. Clots were incubated with culture medium to monitor protein release over 8 days. Furthermore, the different fibrin scaffolds were morphologically characterized. Results show that leukocyte-free fibrin matrices were homogenous while leukocyte-containing ones were heterogeneous, loose and cellular. Leukocyte incorporation produced a significant increase in the contents of proinflammatory cytokines interleukin (IL)-1β and IL-16 but not in the platelet-derived growth factors release (<1.5-fold). Surprisingly, the availability of vascular endothelial growth factor suffered an important decrease after 3 days of incubation in the case of L-PRP matrices. While the release of proinflammatory cytokines was almost absent or very low from PRGF-Endoret, the inclusion of leukocytes induced a major increase in these cytokines, which was characterized by the presence of a latent period. The PRGF-Endoret matrices were stable during the 8 days of incubation. The inclusion of leukocytes alters the growth factors release profile and also increased the dose of proinflammatory cytokines.

  14. A CheR/CheB fusion protein is involved in cyst cell development and chemotaxis in Azospirillum brasilense Sp7. (United States)

    Wu, Lixian; Cui, Yanhua; Hong, Yuanyuan; Chen, Sanfeng


    We here report the sequence and functional analysis of cstB of Azospirillum brasilense Sp7. The predicted cstB contains C-terminal two PAS domains and N-terminal part which has similarity with CheB-CheR fusion protein. cstB mutants had reduced swarming ability compared to that of A. brasilense wild-type strain, implying that cstB was involved in chemotaxis in A. brasilense. A microscopic analysis revealed that cstB mutants developed mature cyst cells more quickly than wild type, indicating that cstB is involved in cyst formation. cstB mutants were affected in colony morphology and the production of exopolysaccharides (EPS) which are essential for A. brasilense cells to differentiate into cyst-like forms. These observations suggested that cstB was a multi-effector involved in cyst development and chemotaxis in A. brasilense.

  15. The effect of n-3 polyunsaturated fatty acids on lipids, platelet function, coagulation, fibrinolysis and monocyte chemotaxis in patients with hypertension. (United States)

    Schmidt, E B; Nielsen, L K; Pedersen, J O; Kornerup, H J; Dyerberg, J


    We have studied the effect of dietary supplementation with 4 g of n-3 polyunsaturated fatty acids (n-3 PUFA) daily for 6 wk on plasma lipids, haemostasis and monocyte chemotaxis in 10 patients with untreated hypertension. Total cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides did not change, but the ratio of total to HDL-cholesterol was significantly reduced after the fish oil supplement. Platelet function was unaltered by intake of n-3. Plasma fibrinogen and fibronectin decreased after supplementation with n-3 PUFA, while the effects on fibrinolysis were equivocal. Monocyte chemotaxis was reduced by the supplement. These data lend support to a role for an increased intake of n-3 PUFA in the management of patients with hypertension.

  16. Cardiopulmonary bypass during cardiac surgery modulates systemic inflammation by affecting different steps of the leukocyte recruitment cascade.

    Directory of Open Access Journals (Sweden)

    Jan Rossaint

    Full Text Available BACKGROUND: It is known that the use of a cardiopulmonary bypass (CPB during cardiac surgery leads to leukocyte activation and may, among other causes, induce organ dysfunction due to increased leukocyte recruitment into different organs. Leukocyte extravasation occurs in a cascade-like fashion, including capturing, rolling, adhesion, and transmigration. However, the molecular mechanisms of increased leukocyte recruitment caused by CPB are not known. This clinical study was undertaken in order to investigate which steps of the leukocyte recruitment cascade are affected by the systemic inflammation during CPB. METHODS: We investigated the effects of CPB on the different steps of the leukocyte recruitment cascade in whole blood from healthy volunteers (n = 9 and patients undergoing cardiac surgery with the use of cardiopulmonary bypass (n = 7 or in off-pump coronary artery bypass-technique (OPCAB, n = 9 by using flow chamber experiments, transmigration assays, and biochemical analysis. RESULTS: CPB abrogated selectin-induced slow leukocyte rolling on E-selectin/ICAM-1 and P-selectin/ICAM-1. In contrast, chemokine-induced arrest and transmigration was significantly increased by CPB. Mechanistically, the abolishment of slow leukocyte rolling was due to disturbances in intracellular signaling with reduced phosphorylation of phospholipase C (PLC γ2, Akt, and p38 MAP kinase. Furthermore, CPB induced an elevated transmigration which was caused by upregulation of Mac-1 on neutrophils. CONCLUSION: These data suggest that CPB abrogates selectin-mediated slow leukocyte rolling by disturbing intracellular signaling, but that the clinically observed increased leukocyte recruitment caused by CPB is due to increased chemokine-induced arrest and transmigration. A better understanding of the underlying molecular mechanisms causing systemic inflammation after CPB may aid in the development of new therapeutic approaches.

  17. ETS-1-mediated transcriptional up-regulation of CD44 is required for sphingosine-1-phosphate receptor subtype 3-stimulated chemotaxis. (United States)

    Zhang, Wenliang; Zhao, Jiawei; Lee, Jen-Fu; Gartung, Allison; Jawadi, Hiba; Lambiv, Wanyu Louis; Honn, Kenneth V; Lee, Menq-Jer


    Sphingosine-1-phosphate (S1P)-regulated chemotaxis plays critical roles in various physiological and pathophysiological conditions. S1P-regulated chemotaxis is mediated by the S1P family of G-protein-coupled receptors. However, molecular details of the S1P-regulated chemotaxis are incompletely understood. Cultured human lung adenocarcinoma cell lines abundantly express S1P receptor subtype 3 (S1P3), thus providing a tractable in vitro system to characterize molecular mechanism(s) underlying the S1P3 receptor-regulated chemotactic response. S1P treatment enhances CD44 expression and induces membrane localization of CD44 polypeptides via the S1P3/Rho kinase (ROCK) signaling pathway. Knockdown of CD44 completely diminishes the S1P-stimulated chemotaxis. Promoter analysis suggests that the CD44 promoter contains binding sites of the ETS-1 (v-ets erythroblastosis virus E26 oncogene homolog 1) transcriptional factor. ChIP assay confirms that S1P treatment stimulates the binding of ETS-1 to the CD44 promoter region. Moreover, S1P induces the expression and nuclear translocation of ETS-1. Knockdown of S1P3 or inhibition of ROCK abrogates the S1P-induced ETS-1 expression. Furthermore, knockdown of ETS-1 inhibits the S1P-induced CD44 expression and cell migration. In addition, we showed that S1P3/ROCK signaling up-regulates ETS-1 via the activity of JNK. Collectively, we characterized a novel signaling axis, i.e., ROCK-JNK-ETS-1-CD44 pathway, which plays an essential role in the S1P3-regulated chemotactic response.

  18. In vitro leukocyte adhesion to modified polyurethane surfaces. II. Effect of wettability

    NARCIS (Netherlands)

    Bruil, Anton; Brenneisen, Laura M.; Terlingen, Johannes G.A.; Beugeling, Tom; Aken, van Willem G.; Feijen, J.


    The influence of substrate wettability on leukocyte adhesion was studied using a series of polyurethane films with different surface wettabilities, prepared by a two step gas plasma modification procedure. In the first step the films were made hydrophobic by exposure to a tetrafluoromethane plasma.

  19. Usefulness of Leukocyte Esterase Test Versus Rapid Strep Test for Diagnosis of Acute Strep Pharyngitis

    Directory of Open Access Journals (Sweden)

    Kumara V. Nibhanipudi MD


    Full Text Available Objective: A study to compare the usage of throat swab testing for leukocyte esterase on a test strip(urine dip stick-multi stick to rapid strep test for rapid diagnosis of Group A Beta hemolytic streptococci in cases of acute pharyngitis in children. Hypothesis: The testing of throat swab for leukocyte esterase on test strip currently used for urine testing may be used to detect throat infection and might be as useful as rapid strep. Methods: All patients who come with a complaint of sore throat and fever were examined clinically for erythema of pharynx, tonsils and also for any exudates. Informed consent was obtained from the parents and assent from the subjects. 3 swabs were taken from pharyngo-tonsillar region, testing for culture, rapid strep & Leukocyte Esterase. Results: Total number is 100. Cultures 9(+; for rapid strep== 84(- and16 (+; For LE== 80(- and 20(+ Statistics: From data configuration Rapid Strep versus LE test don’t seem to be a random (independent assignment but extremely aligned. The Statistical results show rapid and LE show very agreeable results. Calculated Value of Chi Squared Exceeds Tabulated under 1 Degree Of Freedom (P<.0.0001 reject Null Hypothesis and Conclude Alternative Conclusions: Leukocyte esterase on throat swab is as useful as rapid strep test for rapid diagnosis of strep pharyngitis on test strip currently used for urine dip stick causing acute pharyngitis in children.

  20. Serial Serum Leukocyte Apoptosis Levels as Predictors of Outcome in Acute Traumatic Brain Injury

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    Hung-Chen Wang


    Full Text Available Background. Apoptosis associates with secondary brain injury after traumatic brain injury (TBI. This study posits that serum leukocyte apoptosis levels in acute TBI are predictive of outcome. Methods. Two hundred and twenty-nine blood samples from 88 patients after acute TBI were obtained on admission and on Days 4 and 7. Serial apoptosis levels of different leukocyte subsets were examined in 88 TBI patients and 27 control subjects. Results. The leukocyte apoptosis was significantly higher in TBI patients than in controls. Brief unconsciousness (P=0.009, motor deficits (P≤0.001, GCS (P≤0.001, ISS (P=0.001, WBC count (P=0.015, late apoptosis in lymphocytes and monocytes on Day 1 (P=0.004 and P=0.022, resp., subdural hemorrhage on initial brain CT (P=0.002, neurosurgical intervention (P≤0.001, and acute posttraumatic seizure (P=0.046 were significant risk factors of outcome. Only motor deficits (P=0.033 and late apoptosis in monocytes on Day 1 (P=0.037 were independently associated with outcome. A cutoff value of 5.72% of late apoptosis in monocytes was associated with poor outcome in acute TBI patients. Conclusion. There are varying degrees of apoptosis in patients following TBI and in healthy individuals. Such differential expression suggests that apoptosis in different leukocyte subsets plays an important role in outcome following injury.

  1. Phylogenetic analysis of the swine leukocyte antigen - 2 gene for Korean native pigs (United States)

    The objective of this study was to investigate genetic distances of the SLA-2 gene, to characterize SLA-2 alleles, and to provide basic genetic information of Korean pigs. The swine leukocyte antigen - 2 (SLA-2) gene in the MHC classical region was cloned with spleen tissues from Korean native pigs ...

  2. Poly(ethyleneimine) modified filters for the removal of leukocytes from blood

    NARCIS (Netherlands)

    Bruil, Anton; Oosterom, Hieke A.; Steneker, Ingeborg


    Polyurethane membrane filters and filters coated with poly(ethyleneimine) were used to investigate the influence of leukocyte adhesion during filtration. Treatment of the filters with an aqueous solution of 1% (w/v) poly(ethyleneimine) (PEI) led to the introduction of amine groups at the filter surf

  3. Rapid, high-efficiency labeling of leukocytes with In-111 after hemolytic removal of erythrocytes

    Energy Technology Data Exchange (ETDEWEB)

    Karesh, S.M.; Henkin, R.E.


    During the labeling of leukocytes with Indium-111, conventional methodology involves separation and washing to remove red cells. This technique results in the loss of a significant number of leukocytes. Citrated whole blood of ten normal volunteers was studied for an alternate labeling method following sedimentation for 30 to 45 minutes and low speed centrifugation of the leukocyte-rich plasma. The average labeling for these ten volunteers by Indium-111 was 90% versus 60% by the older technique. Viability as measured by the trypan blue exclusion test was greater than 95%, WBC losses were essentially zero, and no WBC clumping was observed. Eighteen patients referred for leukocyte imaging were studied by this method. In this patient population, there was 91% labeling with viability greater than 95% and no evidence of clumping. Less than 5% RBC's were noted in any lot. Indium-111 WBC activity 20 minutes post injection averaged 79% of whole blood activity. This modification results in decreased losses of white cells, reduces preparation time to less than 2 hours, and significantly improves the labeling efficiency of the final product. Liver/spleen ratios and image quality were unchanged from the original method.

  4. Mechanisms involved in apoptosis of carp leukocytes upon in vitro and in vivo immunostimulation

    NARCIS (Netherlands)

    Kepka, M.; Verburg-van Kemenade, B.M.L.; Homa, J.; Chadzinska, M.K.


    During inflammation leukocyte activity must be carefully regulated, as high concentrations and/or prolonged action of pro-inflammatory mediators e.g. reactive oxygen species (ROS) can be detrimental not only for pathogens but also for host tissues. Programmed cell death – apoptosis is a most effecti

  5. Rac-null leukocytes are associated with increased inflammation-mediated alveolar bone loss. (United States)

    Sima, Corneliu; Gastfreund, Shoshi; Sun, Chunxiang; Glogauer, Michael


    Periodontitis is characterized by altered host-biofilm interactions that result in irreversible inflammation-mediated alveolar bone loss. Genetic and epigenetic factors that predispose to ineffective control of biofilm composition and maintenance of tissue homeostasis are not fully understood. We elucidated how leukocytes affect the course of periodontitis in Rac-null mice. Mouse models of acute gingivitis and periodontitis were used to assess the early inflammatory response and patterns of chronicity leading to loss of alveolar bone due to inflammation in Rac-null mice. Leukocyte margination was differentially impaired in these mice during attachment in conditional Rac1-null (granulocyte/monocyte lineage) mice and during rolling and attachment in Rac2-null (all blood cells) mice. Inflammatory responses to subgingival ligatures, assessed by changes in peripheral blood differential leukocyte numbers, were altered in Rac-null compared with wild-type mice. In response to persistent subgingival ligature-mediated challenge, Rac-null mice had increased loss of alveolar bone with patterns of resorption characteristic of aggressive forms of periodontitis. These findings were partially explained by higher osteoclastic coverage of the bone-periodontal ligament interface in Rac-null compared with wild-type mice. In conclusion, this study demonstrates that leukocyte defects, such as decreased endothelial margination and tissue recruitment, are rate-limiting steps in the periodontal inflammatory process that lead to more aggressive forms of periodontitis.

  6. Potential Predictors of Poor Visual Outcome in Human Leukocyte Antigen-B27-Associated Uveitis

    NARCIS (Netherlands)

    Verhagen, Fleurieke H; Brouwer, Anna H; Kuiper, Jonas J W; Ossewaarde-van Norel, Jeannette; ten Dam-van Loon, Ninette H; de Boer, Joke H


    PURPOSE: To identify potential predictors of permanent vision loss in patients with human leukocyte antigen (HLA)-B27-associated uveitis in a tertiary referral center. DESIGN: Retrospective case-control study. METHODS: The charts of 212 patients (338 eyes) with HLA-B27-associated uveitis that visite

  7. Recent advances in microscopic techniques for visualizing leukocytes in vivo [version 1; referees: 3 approved

    Directory of Open Access Journals (Sweden)

    Rohit Jain


    Full Text Available Leukocytes are inherently motile and interactive cells. Recent advances in intravital microscopy approaches have enabled a new vista of their behavior within intact tissues in real time. This brief review summarizes the developments enabling the tracking of immune responses in vivo.

  8. Familial occurrence of subacute thyroiditis associated with human leukocyte antigen-B35

    NARCIS (Netherlands)

    Kramer, AB; Roozendaal, C; Dullaart, RPF


    Subacute thyroiditis (SAT) is a spontaneously remitting inflammatory disorder of the thyroid, associated with human leukocyte antigen (HLA)-B35, and may be virally induced in genetically predisposed individuals. A 57-year-old Caucasian man presented with symptoms of hyperthyroidism as well as enlarg

  9. Isolation of RNA and DNA from leukocytes and cDNA synthesis.

    NARCIS (Netherlands)

    Jansen, J.H.; Reijden, B.A. van der


    In this chapter, methods to isolate RNA and DNA from human leukocytes for the subsequent use in molecular diagnostic tests are described. In addition, protocols for cDNA synthesis are given, both for the use in conventional reverse transcription (RT)-polymerase chain reaction (PCR), and for the use

  10. Human neutrophil defensins and secretory leukocyte proteinase inhibitor in squamous metaplastic epithelium of bronchial airways.

    NARCIS (Netherlands)

    Aarbiou, J.; Schadewijk, A. van; Stolk, J.; Sont, J.K.; Boer, W.I.; Rabe, K.F.; Krieken, J.H.J.M. van; Mauad, T.; Hiemstra, P.S.


    OBJECTIVE: The aim of this study was to analyze a possible contribution of human neutrophil defensins and secretory leukocyte proteinase inhibitor (SLPI) to the induction of airway epithelial changes such as squamous cell metaplasia. MATERIALS AND METHODS: The presence of these molecules and the num

  11. Secretory leukocyte proteinase inhibitor-competent DNA deposits are potent stimulators of plasmacytoid dendritic cells

    DEFF Research Database (Denmark)

    Skrzeczynska-Moncznik, Joanna; Wlodarczyk, Agnieszka; Zabieglo, Katarzyna;


    Secretory leukocyte proteinase inhibitor (SLPI) is a well-established inhibitor of serine proteases such as human neutrophil elastase (HNE) and a NF-κB regulatory agent in immune cells. In this paper, we report that SLPI plays a previously uncharacterized role in regulating activation...

  12. Dark chocolate consumption improves leukocyte adhesion factors and vascular function in overweight men

    NARCIS (Netherlands)

    Esser, D.; Mars, M.; Oosterink, E.; Stalmach, A.; Müller, M.R.; Afman, L.A.


    Flavanol-enriched chocolate consumption increases endothelium-dependent vasodilation. Most research so far has focused on flow-mediated dilation (FMD) only; the effects on other factors relevant to endothelial health, such as inflammation and leukocyte adhesion, have hardly been addressed. We invest

  13. Transfusion of Leukocyte-Depleted RBCs Is Independently Associated With Increased Morbidity After Pediatric Cardiac Surgery

    NARCIS (Netherlands)

    Kneyber, Martin C. J.; Grotenhuis, Femke; Berger, Rolf F. M.; Ebels, Tjark W.; Burgerhof, Johannes G. M.; Albers, Marcel J. I. J.


    Objective: To test the hypothesis that transfusion of leukocyte-depleted RBC preparations within the first 48 hours of PICU stay was independently associated with prolonged duration of mechanical ventilation, irrespective of surgery type and disease severity. Design: Retrospective, observational stu

  14. Reduction in mitochondrial DNA copy number in peripheral leukocytes after onset of Huntington's disease

    DEFF Research Database (Denmark)

    Petersen, Maria Hvidberg; Budtz-Jørgensen, Esben; Sørensen, Sven Asger;


    to the investigation of the mitochondrial DNA (mtDNA) copy number relative to nuclear DNA (nDNA) in leukocytes from carriers of the HD mutation compared to healthy individuals. We found significantly reduced mtDNA/nDNA in HD mutation carriers compared to controls. A longitudinal study of archive DNA sample pairs from...

  15. Effect of cardiopulmonary bypass on leukocyte activation : changes in membrane-bound elastase on neutrophils

    NARCIS (Netherlands)

    Tang, M; Gu, YJ; Wang, WJ; Xu, YP; Chen, CZ


    Background: Neutrophil elastase is known to be released from the activated leukocytes as a result of cardiopulmonary bypass (CPB). However, its biological effect on organ injury is questionable because it is quickly bound by natural proteinase inhibitors (PIs). Recently, membrane-bound elastase ( MB

  16. Sphingosine-1-phosphate receptor 3 promotes leukocyte rolling by mobilizing endothelial P-selectin. (United States)

    Nussbaum, Claudia; Bannenberg, Sarah; Keul, Petra; Gräler, Markus H; Gonçalves-de-Albuquerque, Cassiano F; Korhonen, Hanna; von Wnuck Lipinski, Karin; Heusch, Gerd; de Castro Faria Neto, Hugo C; Rohwedder, Ina; Göthert, Joachim R; Prasad, Vysakh Pushpa; Haufe, Günter; Lange-Sperandio, Baerbel; Offermanns, Stefan; Sperandio, Markus; Levkau, Bodo


    Sphingosine-1-phosphate (S1P) participates in inflammation; however, its role in leukocyte rolling is still unclear. Here we use intravital microscopy in inflamed mouse cremaster muscle venules and human endothelial cells to show that S1P contributes to P-selectin-dependent leukocyte rolling through endothelial S1P receptor 3 (S1P3) and Gαq, PLCβ and Ca(2+). Intra-arterial S1P administration increases leukocyte rolling, while S1P3 deficiency or inhibition dramatically reduces it. Mast cells involved in triggering rolling also release S1P that mobilizes P-selectin through S1P3. Histamine and epinephrine require S1P3 for full-scale effect accomplishing it by stimulating sphingosine kinase 1 (Sphk1). In a counter-regulatory manner, S1P1 inhibits cAMP-stimulated Sphk1 and blocks rolling as observed in endothelial-specific S1P1(-/-) mice. In agreement with a dominant pro-rolling effect of S1P3, FTY720 inhibits rolling in control and S1P1(-/-) but not in S1P3(-/-) mice. Our findings identify S1P as a direct and indirect contributor to leukocyte rolling and characterize the receptors mediating its action.

  17. Localization and activity of inflammatory bowel disease using /sup 111/In leukocyte imaging

    Energy Technology Data Exchange (ETDEWEB)

    Hotze, A.; Biersack, H.J.; Biele, B.; Wolf, F.; Knapp, F.F.


    A prospective study was initiated to compare the clinically proven results concerning localization/extent and activity of inflammatory bowel diseases with those of /sup 111/In-oxine leukocyte imaging. All patients studied were completely examined with barium enema x-ray, clinical and laboratory investigations, and endoscopy with histopathology. A total of 31 leukocyte scans were performed in 15 patients (12 with Crohn's desease, 3 with ulcerative colitis). The scans were graded by comparing the cell uptake of a lesion (when present) and a bone marrow area providing a count ratio (CR). The inflammatory lesions were correctly localized on 26 leukocyte scans, and in 21 scans the scintigraphically estimated extent of disease was identical to endoscopy. In 5 cases the disease extent was underestimated, 4 scans in patients with relapse of Crohn's disease were falsely negative, and in one patient with remission truly negative. The scintigraphically assessed disease activity was also in a good agreement with clinical disease activity based on histopathology in all cases. We conclude that leukocyte imaging provides valuable information about localization and activity of inflammatory bowel disease.

  18. Vero cytotoxin binding to polymorphonuclear leukocytes among households with children with hemolytic uremic syndrome.

    NARCIS (Netherlands)

    Loo, D.M.W.M. te; Heuvelink, A.E.; Boer, E. de; Nauta, J.; Walle, J. van der; Schröder, C.H.; Hinsbergh, V.W.H. van; Chart, H.; Kar, N.C.A.J. van de; Heuvel, L.P.W.J. van den


    Hemolytic uremic syndrome (HUS), the leading cause of acute renal failure in childhood, can be caused by different serotypes of vero cytotoxin (VT; i.e., Shiga toxin)-producing Escherichia coli (VTEC). Recently, VT was shown to bind to polymorphonuclear leukocytes (PMNL) in the systemic circulation

  19. No Evidence of Human Leukocyte Antigen Gene Association With Rheumatic Fever Among Children in Samoa. (United States)

    Erdem, Guliz; Seifried, Steven E


    Human leukocyte antigens (HLAs) have been implicated in rheumatic fever pathogenesis. This pilot whole genome association study compares genotypes of Samoan children with rheumatic fever to unaffected siblings and unrelated healthy controls. No risk-related genotypes were associated with HLA genes. Thirteen Regions of Interest were identified as candidates for further study.

  20. A simple skin blister technique for the study of in vivo transmigration of human leukocytes. (United States)

    Davidsson, Lisa; Björkman, Lena; Christenson, Karin; Alsterholm, Mikael; Movitz, Charlotta; Thorén, Fredrik B; Karlsson, Anna; Welin, Amanda; Bylund, Johan


    The study of human leukocytes is almost exclusively conducted using cells isolated from peripheral blood. This is especially true for neutrophils, despite the fact that these cells are of main (pathological) importance in extravascular tissues upon e.g., infection and/or tissue damage. The journey from circulation to tissue is typically associated with a number of cellular changes, making the cells primed, or hyper-responsive, and in many aspects distinct from the cells present in circulation. Models to obtain in vivo transmigrated leukocytes from human tissue are available, but not widely used. We describe here an easy-to-use model for the study of local inflammation, stemming from limited tissue damage, which can be used to isolate viable and functional leukocytes. The model is based on the generation of aseptic skin blisters, formed by the application of negative pressure, and allows for investigations of the cellular infiltrate as well as of soluble mediators present in the exudate. We believe that this method, combined with modern analysis equipment suitable for small volumes and cell numbers, could be of great use for increasing our understanding of the nature and function of leukocytes that have left circulation and transmigrated to inflamed tissues.

  1. Use of {sup 99m}Tc-Mononuclear Leukocyte Scintigraphy in Nosocomial Fever

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    Gutfilen, B.; Lopes de Souza, S.A.; Martins, F.P.P.; Cardoso, L.R.; Pinheiro Pessoa, M.C.; Fonseca, L.M.B. [Univ. Federal do Rio de Janeiro (Brazil). Dept. de Radiologia


    Purpose: To determine the overall diagnostic accuracy of mononuclear leukocyte-{sup 99m}Tc scintigraphy in the routine detection of infectious lesions and fever of unknown origin (FUO) in inpatients. Material and Methods: The use of mononuclear leukocyte {sup 99m}Tc scintigraphy is presented in 87 patients who fulfilled the Durack and Street diagnostic criteria of nosocomial FUO; 66 patients were suspected of having infectious lesions (myocarditis, endocarditis, infected catheters, diabetic foot, and osteomyelitis) and 21 patients presented with unknown causes of FUO. Scans were carried out 1, 3, and 24 h after injection of labeled leukocytes. Results: In three cases (3/27) where scintigraphs were negative, biopsies were positive. There were two (2/87) false-positive scintigrams. We found a 95.8% sensitivity and 92.3% specificity. PPV was 93.8%, PPN 94.7%, and accuracy 94.2%. Conclusion: Mononuclear leukocyte {sup 99m}Tc scintigraphy showed high sensitivity, specificity, positive and negative predictive values in patients with nosocomial FUO. These results suggest an important role for nuclear medicine in the management of patients with infection/inflammation.

  2. Effects of indomethacin on ovarian leukocytes during the periovulatory period in the rat

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    Tarradas Esteban


    Full Text Available Abstract We have investigated the effects of indomethacin (IM, a non-steroidal anti-inflammatory drug, and the role of prostaglandins on the accumulation of leukocytes in the rat ovary during the periovulatory period. Adult cycling rats were injected sc with 1 mg of IM in olive oil or vehicle on the morning of proestrus. Some animals were killed at 16:00 h in proestrus. On the evening (19:00 h of proestrus, IM-treated rats were injected with 500 micrograms of prostaglandin E1 in saline or vehicle. Animals were killed at 01:30 and 09:00 h in estrus. There was an influx of macrophages, neutrophils, and eosinophils into the theca layers of preovulatory follicles, and of neutrophils and eosinophils into the ovarian medulla from 16:00 h in proestrus to 01:30 h in estrus. All these changes, except the accumulation of neutrophils in the theca layers of preovulatory follicles, were blocked by IM treatment. At 09:00 h in estrus, large clusters of neutrophils were observed in IM-treated rats, around abnormally ruptured follicles. The accumulation of leukocytes was not restored by prostaglandin supplementation, despite the inhibition of abnormal follicle rupture and restoration of ovulation in these animals. These results suggest that different mechanisms are involved in leukocyte accumulation in the ovary during the periovulatory period, and that the inhibitory effects of IM on the influx of leukocytes are not dependent on prostaglandin synthesis inhibition.

  3. Enzyme analysis for Pompe disease in leukocytes; superior results with natural substrate compared with artificial substrates. (United States)

    van Diggelen, O P; Oemardien, L F; van der Beek, N A M E; Kroos, M A; Wind, H K; Voznyi, Y V; Burke, D; Jackson, M; Winchester, B G; Reuser, A J J


    Enzyme analysis for Pompe disease in leukocytes has been greatly improved by the introduction of acarbose, a powerful inhibitor of interfering alpha-glucosidases, which are present in granulocytes but not in lymphocytes. Here we show that the application of acarbose in the enzymatic assay employing the artificial substrate 4-methylumbelliferyl-alpha-D: -glucoside (MU-alphaGlc) is insufficient to clearly distinguish patients from healthy individuals in all cases. Also, the ratios of the activities without/with acarbose only marginally discriminated Pompe patients and healthy individuals. By contrast, when the natural substrate glycogen is used, the activity in leukocytes from patients (n = 82) with Pompe disease is at most 17% of the lowest control value. The use of artificial substrate in an assay with isolated lymphocytes instead of total leukocytes is a poor alternative as blood samples older than one day invariably yield lymphocyte preparations that are contaminated with granulocytes. To diagnose Pompe disease in leukocytes we recommend the use of glycogen as substrate in the presence of acarbose. This assay unequivocally excludes Pompe disease. To also exclude pseudo-deficiency of acid alpha-glucosidase caused by the sequence change c.271G>A (p.D91N or GAA2; homozygosity in approximately 1:1000 caucasians), a second assay employing MU-alphaGlc substrate plus acarbose or DNA analysis is required.

  4. Cell-stiffness-induced mechanosignaling - a key driver of leukocyte transendothelial migration

    NARCIS (Netherlands)

    A. Schaefer; P.L. Hordijk


    The breaching of cellular and structural barriers by migrating cells is a driving factor in development, inflammation and tumor cell metastasis. One of the most extensively studied examples is the extravasation of activated leukocytes across the vascular endothelium, the inner lining of blood vessel

  5. Long telomeres in blood leukocytes are associated with a high risk of ascending aortic aneurysm.

    Directory of Open Access Journals (Sweden)

    Tuija J Huusko

    Full Text Available Ascending aortic aneurysm is a connective tissue disorder. Even though multiple novel gene mutations have been identified, risk profiling and diagnosis before rupture still represent a challenge. There are studies demonstrating shorter telomere lengths in the blood leukocytes of abdominal aortic aneurysm patients. The aim of this study was to measure whether relative telomere lengths are changed in the blood leukocytes of ascending aortic aneurysm patients. We also studied the expression of telomerase in aortic tissue samples of ascending aortic aneurysms. Relative lengths of leukocyte telomeres were determined from blood samples of patients with ascending aortic aneurysms and compared with healthy controls. Telomerase expression, both at the level of mRNA and protein, was quantified from the aortic tissue samples. Mean relative telomere length was significantly longer in ascending aortic aneurysm blood samples compared with controls (T/S ratio 0.87 vs. 0.61, p<0.001. Expressions of telomerase mRNA and protein were elevated in the aortic aneurysm samples (p<0.05 and p<0.01. Our study reveals a significant difference in the mean length of blood leukocyte telomeres in ascending aortic aneurysm and controls. Furthermore, expression of telomerase, the main compensating factor for telomere loss, is elevated at both the mRNA and protein level in the samples of aneurysmal aorta. Further studies will be needed to confirm if this change in telomere length can serve as a tool for assessing the risk of ascending aortic aneurysm.

  6. Leukocyte-stimulating effect and phytochemical screening of Trichilia hirta extracts. (United States)

    Sosa, Edgar Hernandez; Castejón, Yulianis Martín; Duharte, Alexander Batista; Portuondo, Deivys; Tamayo, Vivian; Quevedo, Humberto J Morris; Manrique, Clara Esther Martínez


    Trichilia hirta (Family Meliaceae) is a tree traditionally used in the folk medicine of Cuba to treat asthma, cancer, and ulcers. The objective of this study was to determine the phytochemical composition of ethanol extracts obtained from leaves, roots, and stem bark and to evaluate the leukocyte-stimulating effect of T. hirta root extracts on BALB/c mice. The chemical composition of the extracts was determined by phytochemical screening. Saponins, tannins, flavonoids, and coumarins were detected in extracts of T. hirta. The leukocyte-stimulating effect was evaluated by oral application of ethanol extracts (81.8 and 976 mg/kg) in BALB/c mice for 7 days. The application of 976 mg of extract/kg increased the total leukocyte count up to 15-33%; this effect was significant for neutrophil counts compared with control animals (Pphytochemicals reported as immunostimulants. The administration of these extracts to BALB/c mice indicated that ethanol extract could exhibit leukocyte-stimulating properties and makes it a promising alternative for the development of an immunoprotective agent.

  7. Tracking and fixed ranking of leukocyte telomere length across the adult life course

    DEFF Research Database (Denmark)

    Benetos, Athanase; Kark, Jeremy D; Susser, Ezra;


    Short leukocyte telomere length (LTL) is associated with atherosclerosis in adults and diminished survival in the elderly. LTL dynamics are defined by LTL at birth, which is highly variable, and its age-dependent attrition thereafter, which is rapid during the first 20 years of life. We examined...

  8. Leukocyte telomere length is inversely correlated with plasma Von Willebrand factor

    DEFF Research Database (Denmark)

    Hjelmborg, Jacob V B; Nzietchueng, Rosine; Kimura, Masayuki;


    INTRODUCTION: Leukocyte telomere length (LTL) is short, while the plasma level of Von Willebrand (VWF) is high in persons with atherosclerosis. Moreover, both short LTLs and high VWF levels are observed in individuals who display risks for atherosclerosis, including hypertension, obesity, insulin...

  9. Higher circulating levels of IGF-1 are associated with longer leukocyte telomere length in healthy subjects

    DEFF Research Database (Denmark)

    Barbieri, Michelangela; Paolisso, Giuseppe; Kimura, Masayuki;


    Mutations that inhibit the insulin-like growth factor-1 (IGF-1) extend the lifespan of worms, flies and mice. However, it appears that relatively low circulating levels of IGF-1 in humans are associated with aging-related diseases and diminished longevity. As leukocyte telomere length (LTL...

  10. Association of leukocyte telomere length with fatigue in nondisabled older adults

    DEFF Research Database (Denmark)

    Bendix, Laila; Thinggaard, Mikael; Kimura, Masayuki;


    Introduction: Fatigue is often present in older adults with no identified underlying cause. The accruing burden of oxidative stress and inflammation might be underlying factors of fatigue. We therefore hypothesized that leukocyte telomere length (LTL) is relatively short in older adults who...

  11. Leukocyte telomere length and physical ability among Danish twins age 70+

    DEFF Research Database (Denmark)

    Bendix, Laila; Gade, Maria Monrad; Staun, Pia Wirenfeldt;


    Leukocyte telomere length (LTL) shortens with age and is potentially a biomarker of human aging. We examined the relation of LTL with physical ability and cognitive function in 548 same-sex twins from the Longitudinal Study of Aging Danish Twins. LTL was measured by Southern blots of the terminal...

  12. Chemotaxis in densely populated tissue determines germinal center anatomy and cell motility: a new paradigm for the development of complex tissues.

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    Jared B Hawkins

    Full Text Available Germinal centers (GCs are complex dynamic structures that form within lymph nodes as an essential process in the humoral immune response. They represent a paradigm for studying the regulation of cell movement in the development of complex anatomical structures. We have developed a simulation of a modified cyclic re-entry model of GC dynamics which successfully employs chemotaxis to recapitulate the anatomy of the primary follicle and the development of a mature GC, including correctly structured mantle, dark and light zones. We then show that correct single cell movement dynamics (including persistent random walk and inter-zonal crossing arise from this simulation as purely emergent properties. The major insight of our study is that chemotaxis can only achieve this when constrained by the known biological properties that cells are incompressible, exist in a densely packed environment, and must therefore compete for space. It is this interplay of chemotaxis and competition for limited space that generates all the complex and biologically accurate behaviors described here. Thus, from a single simple mechanism that is well documented in the biological literature, we can explain both higher level structure and single cell movement behaviors. To our knowledge this is the first GC model that is able to recapitulate both correctly detailed anatomy and single cell movement. This mechanism may have wide application for modeling other biological systems where cells undergo complex patterns of movement to produce defined anatomical structures with sharp tissue boundaries.

  13. RpoS and quorum sensing control expression and polar localization of Vibrio cholerae chemotaxis cluster III proteins in vitro and in vivo. (United States)

    Ringgaard, Simon; Hubbard, Troy; Mandlik, Anjali; Davis, Brigid M; Waldor, Matthew K


    The diarrheal pathogen Vibrio cholerae contains three gene clusters that encode chemotaxis-related proteins, but only cluster II appears to be required for chemotaxis. Here, we present the first characterization of V. cholerae's 'cluster III' chemotaxis system. We found that cluster III proteins assemble into foci at bacterial poles, like those formed by cluster II proteins, but the two systems assemble independently and do not colocalize. Cluster III proteins are expressed in vitro during stationary phase and in conjunction with growth arrest linked to carbon starvation. This expression, as well as expression in vivo in suckling rabbits, is dependent upon RpoS. V. cholerae's CAI-1 quorum sensing (QS) system is also required for cluster III expression in stationary phase and modulates its expression in vivo, but is not required for cluster III expression in response to carbon starvation. Surprisingly, even though the CAI-1 and AI-2 QS systems are thought to feed into the same signaling pathway, the AI-2 system inhibited cluster III gene expression, revealing that the outputs of the two QS systems are not always the same. The distinctions between genetic determinants of cluster III expression in vitro and in vivo highlight the distinctive nature of the in vivo environment.

  14. The importance of the interaction of CheD with CheC and the chemoreceptors compared to its enzymatic activity during chemotaxis in Bacillus subtilis.

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    Wei Yuan

    Full Text Available Bacillus subtilis use three systems for adaptation during chemotaxis. One of these systems involves two interacting proteins, CheC and CheD. CheD binds to the receptors and increases their ability to activate the CheA kinase. CheD also binds CheC, and the strength of this interaction is increased by phosphorylated CheY. CheC is believed to control the binding of CheD to the receptors in response to the levels of phosphorylated CheY. In addition to their role in adaptation, CheC and CheD also have separate enzymatic functions. CheC is a CheY phosphatase and CheD is a receptor deamidase. Previously, we demonstrated that CheC's phosphatase activity plays a minor role in chemotaxis whereas its ability to bind CheD plays a major one. In the present study, we demonstrate that CheD's deamidase activity also plays a minor role in chemotaxis whereas its ability to bind CheC plays a major one. In addition, we quantified the interaction between CheC and CheD using surface plasmon resonance. These results suggest that the most important features of CheC and CheD are not their enzymatic activities but rather their roles in adaptation.

  15. A multiple-relaxation-time lattice-boltzmann model for bacterial chemotaxis: effects of initial concentration, diffusion, and hydrodynamic dispersion on traveling bacterial bands. (United States)

    Yan, Zhifeng; Hilpert, Markus


    Bacterial chemotaxis can enhance the bioremediation of contaminants in aqueous and subsurface environments if the contaminant is a chemoattractant that the bacteria degrade. The process can be promoted by traveling bands of chemotactic bacteria that form due to metabolism-generated gradients in chemoattractant concentration. We developed a multiple-relaxation-time (MRT) lattice-Boltzmann method (LBM) to model chemotaxis, because LBMs are well suited to model reactive transport in the complex geometries that are typical for subsurface porous media. This MRT-LBM can attain a better numerical stability than its corresponding single-relaxation-time LBM. We performed simulations to investigate the effects of substrate diffusion, initial bacterial concentration, and hydrodynamic dispersion on the formation, shape, and propagation of bacterial bands. Band formation requires a sufficiently high initial number of bacteria and a small substrate diffusion coefficient. Uniform flow does not affect the bands while shear flow does. Bacterial bands can move both upstream and downstream when the flow velocity is small. However, the bands disappear once the velocity becomes too large due to hydrodynamic dispersion. Generally bands can only be observed if the dimensionless ratio between the chemotactic sensitivity coefficient and the effective diffusion coefficient of the bacteria exceeds a critical value, that is, when the biased movement due to chemotaxis overcomes the diffusion-like movement due to the random motility and hydrodynamic dispersion.

  16. DNA Microarray and Gene Ontology Enrichment Analysis Reveals That a Mutation in opsX Affects Virulence and Chemotaxis in Xanthomonas oryzae pv. oryzae

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    Hong-Il Kim


    Full Text Available Xanthomonas oryzae pv. oryzae (Xoo causes bacterial leaf blight (BLB in rice (Oryza sativa L.. In this study, we investigated the effect of a mutation in opsX (XOO1056, which encodes a saccharide biosynthesis regulatory protein, on the virulence and bacterial chemotaxis of Xoo. We performed DNA microarray analysis, which showed that 63 of 2,678 genes, including genes related to bacterial motility (flagellar and chemotaxis proteins were significantly downregulated (<−2 log₂ fold changes by the mutation in opsX. Indeed, motility assays showed that the mutant strain was nonmotile on semisolid agar swarm plates. In addition, a mutant strain (opsX::Tn5 showed decreased virulence against the susceptible rice cultivar, IR24. Quantitative real-time RT-PCR reaction was performed to confirm the expression levels of these genes, including those related to flagella and chemotaxis, in the opsX mutant. Our findings revealed that mutation of opsX affects both virulence and bacterial motility. These results will help to improve our understanding of Xoo and provide insight into Xoo-rice interactions.

  17. PsHint1, associated with the G-protein α subunit PsGPA1, is required for the chemotaxis and pathogenicity of Phytophthora sojae. (United States)

    Zhang, Xin; Zhai, Chunhua; Hua, Chenlei; Qiu, Min; Hao, Yujuan; Nie, Pingping; Ye, Wenwu; Wang, Yuanchao


    Zoospore chemotaxis to soybean isoflavones is essential in the early stages of infection by the oomycete pathogen Phytophthora sojae. Previously, we have identified a G-protein α subunit encoded by PsGPA1 which regulates the chemotaxis and pathogenicity of P. sojae. In the present study, we used affinity purification to identify PsGPA1-interacting proteins, including PsHint1, a histidine triad (HIT) domain-containing protein orthologous to human HIT nucleotide-binding protein 1 (HINT1). PsHint1 interacted with both the guanosine triphosphate (GTP)- and guanosine diphosphate (GDP)-bound forms of PsGPA1. An analysis of the gene-silenced transformants revealed that PsHint1 was involved in the chemotropic response of zoospores to the isoflavone daidzein. During interaction with a susceptible soybean cultivar, PsHint1-silenced transformants displayed significantly reduced infectious hyphal extension and caused a strong cell death in plants. In addition, the transformants displayed defective cyst germination, forming abnormal germ tubes that were highly branched and exhibited apical swelling. These results suggest that PsHint1 not only regulates chemotaxis by interacting with PsGPA1, but also participates in a Gα-independent pathway involved in the pathogenicity of P. sojae.

  18. Inhibition of platelet-activating factor- and zymosan-activated serum-induced chemotaxis of human neutrophils by nedocromil sodium, BN 52021 and sodium cromoglycate. (United States)

    Bruijnzeel, P. L.; Warringa, R. A.; Kok, P. T.


    1. Inflammatory cells such as eosinophils and neutrophils are thought to contribute actively to the pathogenesis of asthma since they infiltrate into the lung tissue. These cells are mobilized by lipid-like and protein-like chemotactic factors. As illustrative examples of both groups, platelet-activating-factor (Paf) and zymosan-activated-serum (ZAS) were used in this study. The inhibitory effects of nedocromil sodium, the Paf antagonist BN 52021 and sodium cromoglycate on Paf- and ZAS-induced neutrophil chemotaxis were evaluated. 2. All tested drugs inhibited Paf-induced neutrophil chemotaxis with approximately the same potency (IC50 approximately 1 nM). 3. Nedocromil sodium and sodium cromoglycate were equally potent in inhibiting ZAS-induced neutrophil chemotaxis (IC50 = 0.1-1 microM), whereas BN 52021 was considerably less potent (IC30 = 10 microM). 4. To find out whether the drugs tested could inhibit early events in cell activation, their capacity to inhibit Paf- and ZAS-induced cytosolic free Ca2+-mobilization was investigated. BN 52021, at a concentration of 100 microM, completely inhibited Paf-induced Ca2+-mobilization and inhibited ZAS-induced Ca2+-mobilization by about 50%. Nedocromil sodium and sodium cromoglycate were ineffective. PMID:2551444

  19. A predictive computational model of the kinetic mechanism of stimulus-induced transducer methylation and feedback regulation through CheY in archaeal phototaxis and chemotaxis

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    Oesterhelt Dieter


    Full Text Available Abstract Background Photo- and chemotaxis of the archaeon Halobacterium salinarum is based on the control of flagellar motor switching through stimulus-specific methyl-accepting transducer proteins that relay the sensory input signal to a two-component system. Certain members of the transducer family function as receptor proteins by directly sensing specific chemical or physical stimuli. Others interact with specific receptor proteins like the phototaxis photoreceptors sensory rhodopsin I and II, or require specific binding proteins as for example some chemotaxis transducers. Receptor activation by light or a change in receptor occupancy by chemical stimuli results in reversible methylation of glutamate residues of the transducer proteins. Both, methylation and demethylation reactions are involved in sensory adaptation and are modulated by the response regulator CheY. Results By mathematical modeling we infer the kinetic mechanisms of stimulus-induced transducer methylation and adaptation. The model (deterministic and in the form of ordinary differential equations correctly predicts experimentally observed transducer demethylation (as detected by released methanol in response to attractant and repellent stimuli of wildtype cells, a cheY deletion mutant, and a mutant in which the stimulated transducer species is methylation-deficient. Conclusions We provide a kinetic model for signal processing in photo- and chemotaxis in the archaeon H. salinarum suggesting an essential role of receptor cooperativity, antagonistic reversible methylation, and a CheY-dependent feedback on transducer demethylation.

  20. Interleukin-17 (IL-17 Expression Is Reduced during Acute Myocardial Infarction: Role on Chemokine Receptor Expression in Monocytes and Their in Vitro Chemotaxis towards Chemokines

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    Guro Valen


    Full Text Available The roles of immune cells and their soluble products during myocardial infarction (MI are not completely understood. Here, we observed that the percentages of IL-17, but not IL-22, producing cells are reduced in mice splenocytes after developing MI. To correlate this finding with the functional activity of IL-17, we sought to determine its effect on monocytes. In particular, we presumed that this cytokine might affect the chemotaxis of monocytes important for cardiac inflammation and remodeling. We observed that IL-17 tends to reduce the expression of two major chemokine receptors involved in monocyte chemotaxis, namely CCR2 and CXCR4. Further analysis showed that monocytes pretreated with IL-17 have reduced in vitro chemotaxis towards the ligand for CCR2, i.e., MCP-1/CCL2, and the ligand for CXCR4, i.e., SDF-1α/CXCL12. Our results support the possibility that IL-17 may be beneficial in MI, and this could be due to its ability to inhibit the migration of monocytes.

  1. Comparison of the effect of timegadine, levamisole, and D-penicillamine on human neutrophil metabolism of endogenous arachidonic acid and chemotaxis

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, O.H.; Ahnfelt-Roenne, I. Department of Pharmacology, Leo Pharmaceutical Products, Ballerup; Elmgreen, J.


    The effect of timegadine, a novel experimental antirheumatic drug, on human neutrophil (PMN) 5-lipoxygenase activity and leukotriene B/sub 4/ (LTB/sub 4/) chemotaxis was compared with that of two second-line antiinflammatory drugs, D-penicillamine and levamisole. 1-/sup 14/C-Arachidonic acid (AA) was incorporated into the purified cells until steady state conditions were obtained. After preincubation with serial dilutions of the three drugs, AA release and metabolism was stimulated with calcium ionophore A23187. The radioactive eicosanoids released were extracted and separated by thinlayer chromatography, followed by autoradiography and quantitative laser densitometry. Chemotaxi of PMNs towards LTB/sub 4/ was measured in a modified Boyden chamber. Timegardine showed dose-dependent inhibition of both the 5-lipoxygenase pathway (IC50 3.4 x 10/sup -5/ M), and of chemotaxis (IC50 3 x 10/sup -4/ M). Inhibition of the release of AA from phospholipids, however, occurred only at therapeutically irrelevant doses (millimolar concentrations). Levamisole and D-penicillamine did not inhibit any of the cell functions investigated. Inhibition of both neutrophil motility and cellular synthesis of pro-inflammatory eicosanoids, may thus contribute to the clinical effects of timegadine in rheumatoid arthritis.

  2. Influence of Motility and Chemotaxis on Transport Properties for Swimming Bacteria in Porous Media under Static and Flow Conditions (United States)

    Liu, J.; Long, T.; Ford, R. M.


    In-situ bioremediation is an effective method to reduce groundwater contamination. Understanding bacterial swimming behaviors in the subsurface can facilitate its application and improve the remediation efficiency. Many motile bacteria that are able to degrade chemical contaminants in groundwater are also able to sense increasing concentrations of these chemicals and swim preferentially towards sources of the contamination, a phenomenon known as chemotaxis. According to several published studies, a single bacterium appears to idle near the granular surface for an extended period of time exhibiting no translational motion until it reorients in a direction that allows itself to swim away from the surface. In this study, the bacterial breakthrough curves (BTCs) measured from a packed column with 1 m/day averaged linear velocity revealed that the motile smooth-swimming mutants E. coli HCB437 displayed BTCs with greater retardation than the motile wild-type bacterial strains E. coli HCB1, which were more retarded than those of the non-motile control E. coli HCB137, as these three bacterial strains exhibit a decreasing degree of surface association with the solid particles. To investigate bacterial chemotaxis within porous media without flow, a modified capillary assay was conducted to observe the migration behaviors of wild-type bacterial strain E. coli HCB1 at the interface between an aqueous solution and a Gelrite particulate suspension, the model porous medium, which contained 0.1 mM α-methylaspartate as the chemoattractant. The experimental results indicated that chemotactic bacteria not only had a larger accumulation at the porous media interface but also exhibited a more significant degree of penetration into the porous media region than in the experiments performed without chemoattractants. In addition, computer simulations using a Monte Carlo algorithm further revealed that chemotactic bacteria were inclined to be less associated with the solid surface in the

  3. Bacterial Chemotaxis Toward A NAPL Source Within A Pore-Scale Model Subject to A Range of Groundwater Flow Velocities (United States)

    Wang, X.; Ford, R. M.


    Organic solvents such as toluene are the most widely distributed pollutants in groundwater. Biodegradation of these industrial pollutants requires that microorganisms in the aqueous phase are brought in contact with sources of contamination, which may be dispersed as pore-size organic-phase droplets within the saturated soil matrix. Chemotaxis toward chemical pollutants provides a mechanism for bacteria to migrate to locations of high contamination, which may not normally be accessible to bacteria carried along by groundwater flow, and thus it may improve the efficiency of bioremediation. A microfluidic device was designed to mimic the dissolution of an organic-phase contaminant from a single pore into a larger macropore representing a preferred pathway for microorganisms that are carried along by groundwater flow. The glass windows of the µ-chip allowed image analysis of bacterial distributions within the vicinity of the organic contaminant. Concentrations of chemotactic bacteria P. putida F1 near the organic/aqueous interface were 25% greater than those of a nonchemotactic mutant in the vicinity of toluene for a fluid velocity of 0.5 m/d. For E. coli responding to phenol, the bacterial concentrations were 60% greater than the controls, also at a velocity of 0.5 m/d. Velocities in the macropore were varied over a range that is typical of groundwater velocities from 0.5 to 10 m/d. The accumulation of chemotactic bacteria near the NAPL (nonaqueous phase liquid) chemoattractant source decreased as the fluid velocity increased. At the higher velocities, accumulation of chemotactic bacteria was comparable to the non-chemotactic control experiments. Computer-based simulation using finite element analysis software (COMSOL) was also performed to understand the effects of various model parameters on bacterial chemotaxis to NAPL. There was good agreement between the simulations (generated using reasonable values of the model parameters) and the experimental data for P

  4. Identification of the mcpA and mcpM Genes, Encoding Methyl-Accepting Proteins Involved in Amino Acid and l-Malate Chemotaxis, and Involvement of McpM-Mediated Chemotaxis in Plant Infection by Ralstonia pseudosolanacearum (Formerly Ralstonia solanacearum Phylotypes I and III) (United States)

    Hida, Akiko; Oku, Shota; Kawasaki, Takeru; Tajima, Takahisa


    Sequence analysis has revealed the presence of 22 putative methyl-accepting chemotaxis protein (mcp) genes in the Ralstonia pseudosolanacearum GMI1000 genome. PCR analysis and DNA sequencing showed that the highly motile R. pseudosolanacearum strain Ps29 possesses homologs of all 22 R. pseudosolanacearum GMI1000 mcp genes. We constructed a complete collection of single mcp gene deletion mutants of R. pseudosolanacearum Ps29 by unmarked gene deletion. Screening of the mutant collection revealed that R. pseudosolanacearum Ps29 mutants of RSp0507 and RSc0606 homologs were defective in chemotaxis to l-malate and amino acids, respectively. RSp0507 and RSc0606 homologs were designated mcpM and mcpA. While wild-type R. pseudosolanacearum strain Ps29 displayed attraction to 16 amino acids, the mcpA mutant showed no response to 12 of these amino acids and decreased responses to 4 amino acids. We constructed mcpA and mcpM deletion mutants of highly virulent R. pseudosolanacearum strain MAFF106611 to investigate the contribution of chemotaxis to l-malate and amino acids to tomato plant infection. Neither single mutant exhibited altered virulence for tomato plants when tested by root dip inoculation assays. In contrast, the mcpM mutant (but not the mcpA mutant) was significantly less infectious than the wild type when tested by a sand soak inoculation assay, which requires bacteria to locate and invade host roots from sand. Thus, McpM-mediated chemotaxis, possibly reflecting chemotaxis to l-malate, facilitates R. pseudosolanacearum motility to tomato roots in sand. PMID:26276117

  5. Flow and deformation of the capillary glycocalyx in the wake of a leukocyte (United States)

    Damiano, Edward R.; Stace, Thomas M.


    An analysis is presented of the axisymmetric axial and radial flow and deformation fields throughout the endothelial-cell glycocalyx surface layer in the wake region behind a leukocyte moving steadily through a capillary. The glycocalyx, modeled as a thin poroelastic surface layer lining the capillary wall, is assumed to consist of a binary mixture of a linearly viscous fluid constituent and an isotropic, highly compressible, linearly elastic solid constituent having a vanishingly small solid-volume fraction. Invoking the asymptotic approximations of lubrication theory in a frame of reference translating with the leukocyte, closed-form solutions are obtained to the leading-order boundary-value problems governing the axial and radial flow and deformation fields throughout the glycocalyx as well as the axial and radial flow fields throughout the free capillary lumen within the wake. A simple asymptotic expression is obtained for the length lchar of the wake region in terms of the translational speed U0 of the leukocyte, and the equilibrium thickness h0, permeability k0, and aggregate elastic modulus HA of the glycocalyx. The predicted wake length, as seen from an observer moving in a reference frame attached to the leukocyte, is consistent with the recovery time predicted from a one-dimensional analysis of glycocalyx deformation through a quiescent inviscid fluid. The two-dimensional fluid dynamical analysis presented here thus provides the appropriate relationships for extracting estimates of the mechanoelectrochemical properties of the glycocalyx from physiologically realistic constitutive models developed under simplified one-dimensional flow regimes. The directly measurable quantities lchar,U0, and h0, which are obtainable from in vivo observations of the wake region behind a leukocyte moving steadily through a capillary, can therefore be connected, through the results of this analysis, to estimates of the mechanoelectrochemical properties of the glycocalyx on

  6. Goat uterine DBA+ leukocytes differentiation and cytokines expression respond differently to cloned versus fertilized embryos.

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    Lijuan Qin

    Full Text Available High rate of fetal mortality in ruminant somatic cell nuclear transfer (SCNT pregnancies is due, at least in part, to immune-mediated abortion of fetuses. In the present study, goat uterine leukocytes were isolated by Dolichos biflorus agglutinin (DBA coated magnetic beads, and with majority being were CD56+CD16- in phenotype with low levels of perforin and Granzyme B expression. The responses of the isolated cells to SCNT and in vitro fertilization (IVF embryos conditioned mediums containing hormone steroids were compared by measuring their phenotype and cytokines expression. The results showed there was a 2-fold increase in the numbers of isolated uterine leukocytes after incubation with different conditioned mediums for 120 h. However, significantly lower percentage and absolute numbers of uterine CD56+CD16- leukocytes incubated with SCNT conditioned mediums were detected as compared with those incubated with IVF conditioned mediums (P < 0.05. The group treated with progesterone (P4 or the combination of P4 and 17β-estradiol (E2 were associated with significantly higher percentage and absolute numbers of CD56+CD16- cells as compared with those treated with E2 alone (P < 0.05. Furthermore, in the presence of steroids, the isolated leukocytes incubated with SCNT conditioned mediums associated with greater levels of IFN-γ secretion and expression, as well as lesser levels of VEGF, as compared with those treated with IVF conditioned mediums (P < 0.05. In conclusion, this study demonstrates that SCNT embryos have a profound effect on the phenotype expression of goat uterine DBA+ leukocytes, as well as the secretion and expression of IFN-γ and VEGF by these cells in vitro.

  7. Association of postmenopausal endogenous sex hormones with global methylation level of leukocyte DNA among Japanese women

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    Iwasaki Motoki


    Full Text Available Abstract Background Although global hypomethylation of leukocyte DNA has been associated with an increased risk of several sites of cancer, including breast cancer, determinants of global methylation level among healthy individuals remain largely unexplored. Here, we examined whether postmenopausal endogenous sex hormones were associated with the global methylation level of leukocyte DNA. Methods A cross-sectional study was conducted using the control group of a breast cancer case–control study in Nagano, Japan. Subjects were postmenopausal women aged 55 years or over who provided blood samples. We measured global methylation level of peripheral blood leukocyte DNA by luminometric methylation assay; estradiol, estrone, androstenedione, dehydroepiandrosterone sulfate, testosterone and free testosterone by radioimmunoassay; bioavailable estradiol by the ammonium sulfate precipitation method; and sex-hormone binding globulin by immunoradiometric assay. A linear trend of association between methylation and hormone levels was evaluated by regression coefficients in a multivariable liner regression model. A total of 185 women were included in the analyses. Results Mean global methylation level (standard deviation was 70.3% (3.1 and range was from 60.3% to 79.2%. Global methylation level decreased 0.27% per quartile category for estradiol and 0.39% per quartile category for estrone while it increased 0.41% per quartile category for bioavailable estradiol. However, we found no statistically significant association of any sex hormone level measured in the present study with global methylation level of leukocyte DNA. Conclusions Our findings suggest that endogenous sex hormones are not major determinants of the global methylation level of leukocyte DNA.

  8. Induction of autoantibody-producing cells after the coculture of haptenated and normal human mononuclear leukocytes. (United States)

    Pisko, E J; Foster, S L; Turner, R A


    The coculture of normal human peripheral blood mononuclear leukocytes (PBL) and autologous mononuclear leukocytes coupled to the trinitrophenyl (TNP) hapten (TNP-PBL) was found to induce a polyclonal activation of antibody-producing cells. The polyclonal activation of antibody-producing cells was demonstrated by detecting the induction of cells producing antibody to sheep red blood cells using a complement-dependent, direct, hemolytic plaque-forming cell (PFC) assay. A ratio of four normal to one haptenated mononuclear leukocyte was found to be optimal for inducing the polyclonal activation of antibody-producing cell in these cultures. The plaque-forming cells assay in these experiments utilized monolayers of indicator red cells. Further evidence for the polyclonal induction of antibody-producing cells by TNP-PBL was provided by demonstrating PFC on monolayers of not only sheep red blood cells, but also autologous human red cells, bromelain-treated autologous red cells, TNP-coupled human and sheep red cells, and human autologous red cells coupled to human heat-aggregated IgG with chromic chloride. Thus cells secreting antibody to TNP, human red cells, and human IgG were induced. Anti-IgG and anti-human red cell-producing cells were first detected on Day 2 of culture and were still present on Day 9. Mononuclear leukocytes altered by chemical haptenation polyclonally stimulate normal mononuclear leukocytes to become antibody-producing cells. This polyclonal stimulation of antibody-producing cells includes cells producing antibodies to human IgG and human autologous red blood cells suggesting that autoantibody-producing cells are induced.

  9. Determination of an unrelated donor pool size for human leukocyte antigen-matched platelets in Brazil

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    Carolina Bonet Bub


    Full Text Available ABSTRACT Background: Successful transfusion of platelet refractory patients is a challenge. Many potential donors are needed to sustain human leukocyte antigen matched-platelet transfusion programs because of the different types of antigens and the constant needs of these patients. For a highly mixed population such as the Brazilian population, the pool size required to provide adequate platelet support is unknown. Methods: A mathematical model was created to estimate the appropriate size of an unrelated donor pool to provide human leukocyte antigen-compatible platelet support for a Brazilian population. A group of 154 hematologic human leukocyte antigen-typed patients was used as the potential patient population and a database of 65,500 human leukocyte antigen-typed bone marrow registered donors was used as the donor population. Platelet compatibility was based on the grading system of Duquesnoy. Results: Using the mathematical model, a pool containing 31,940, 1710 and 321 donors would be necessary to match more than 80% of the patients with at least five completely compatible (no cross-reactive group, partial compatible (one cross-reactive group or less compatible (two cross-reactive group donors, respectively. Conclusion: The phenotypic diversity of the Brazilian population has probably made it more difficulty to find completely compatible donors. However, this heterogeneity seems to have facilitated finding donors when cross-reactive groups are accepted as proposed by the grading system of Duquesnoy. The results of this study may help to establish unrelated human leukocyte antigen-compatible platelet transfusions, a procedure not routinely performed in most Brazilian transfusion services.

  10. Altered mitochondrial function and oxidative stress in leukocytes of anorexia nervosa patients.

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    Victor M Victor

    Full Text Available CONTEXT: Anorexia nervosa is a common illness among adolescents and is characterised by oxidative stress. OBJECTIVE: The effects of anorexia on mitochondrial function and redox state in leukocytes from anorexic subjects were evaluated. DESIGN AND SETTING: A multi-centre, cross-sectional case-control study was performed. PATIENTS: Our study population consisted of 20 anorexic patients and 20 age-matched controls, all of which were Caucasian women. MAIN OUTCOME MEASURES: Anthropometric and metabolic parameters were evaluated in the study population. To assess whether anorexia nervosa affects mitochondrial function and redox state in leukocytes of anorexic patients, we measured mitochondrial oxygen consumption, membrane potential, reactive oxygen species production, glutathione levels, mitochondrial mass, and complex I and III activity in polymorphonuclear cells. RESULTS: Mitochondrial function was impaired in the leukocytes of the anorexic patients. This was evident in a decrease in mitochondrial O2 consumption (P<0.05, mitochondrial membrane potential (P<0.01 and GSH levels (P<0.05, and an increase in ROS production (P<0.05 with respect to control subjects. Furthermore, a reduction of mitochondrial mass was detected in leukocytes of the anorexic patients (P<0.05, while the activity of mitochondrial complex I (P<0.001, but not that of complex III, was found to be inhibited in the same population. CONCLUSIONS: Oxidative stress is produced in the leukocytes of anorexic patients and is closely related to mitochondrial dysfunction. Our results lead us to propose that the oxidative stress that occurs in anorexia takes place at mitochondrial complex I. Future research concerning mitochondrial dysfunction and oxidative stress should aim to determine the physiological mechanism involved in this effect and the physiological impact of anorexia.

  11. [Dynamic studies of the leukocyte phagocytic activity after exposure of rats to asbestos and basalt fibers]. (United States)

    Hurbánková, M


    The paper presents the results of the dynamic one-year follow-up of the phagocytic activity of Wistar-rats peripheral blood leukocytes following intraperitoneal administration of asbestos and basalt fibres (Man-Made Mineral Fibres--MMMF). We investigated the phagocytic activity of leukocytes in peripheral blood following intraperitoneal administration of asbestos and basalt fibres to rats 2, 24, 48 h as well as 1, 2, 4, 8 weeks and 6 and 12 months after dosing. We investigated the time dependent of the changes of relative granulocytes count, percentage of phagocytizing cells from leukocytes, percentage of phagocytizing granulocytes and percentage of phagocytizing monocytes. The results of our experiment showed that asbestos and basalt fibres differed in their effects on the parameters studied. Granulocyte count as well as the phagocytic activity of leukocytes during the one-year dynamic follow-up in both dust--exposed groups of animals were found to change in two phases, characterised by the initial stimulation of the acute phase (I), followed by the suppression of the parameters in the chronic phase (II). Exposure to asbestos and basalt fibres led, in phase II, to impairment of the phagocytic activity of granulocytes. Asbestos fibres at the same time significantly decreased also the phagocytic activity of monocytes. Exposure to basalt fibres did not affect the phagocytic activity of monocytes in phase II. It follows from the results of the experiment, that the monocytic component of leukocytes probably plays an important role in the development of diseases caused by exposure to fibrous dusts and basalt fibres have smaller biological effects compared with asbestos fibres.

  12. Functional role of gap junctions in cytokine-induced leukocyte adhesion to endothelium in vivo (United States)

    Véliz, Loreto P.; González, Francisco G.; Duling, Brian R.; Sáez, Juan C.; Boric, Mauricio P.


    To assess the hypothesis that gap junctions (GJs) participate on leukocyte-endothelium interactions in the inflammatory response, we compared leukocyte adhesion and transmigration elicited by cytokine stimulation in the presence or absence of GJ blockers in the hamster cheek pouch and also in the cremaster muscle of wild-type (WT) and endothelium-specific connexin 43 (Cx43) null mice (Cx43e−/−). In the cheek pouch, topical tumor necrosis factor-α (TNF-α; 150 ng/ml, 15 min) caused a sustained increment in the number of leukocytes adhered to venular endothelium (LAV) and located at perivenular regions (LPV). Superfusion with the GJ blockers 18-α-glycyrrhetinic acid (AGA; 75 μM) or 18-β-glycyrrhetinic acid (50 μM) abolished the TNF-α-induced increase in LAV and LPV; carbenoxolone (75 μM) or oleamide (100 μM) reduced LAV by 50 and 75%, respectively, and LPV to a lesser extent. None of these GJ blockers modified venular diameter, blood flow, or leukocyte rolling. In contrast, glycyrrhizin (75 μM), a non-GJ blocker analog of AGA, was devoid of effect. Interestingly, when AGA was removed 90 min after TNF-α stimulation, LAV started to rise at a similar rate as in control. Conversely, application of AGA 90 min after TNF-α reduced the number of previously adhered cells. In WT mice, intrascrotal injection of TNF-α (0.5 μg/0.3 ml) increased LAV (fourfold) and LPV (threefold) compared with saline-injected controls. In contrast to the observations in WT animals, TNF-α stimulation did not increase LAV or LPV in Cx43e−/− mice. These results demonstrate an important role for GJ communication in leukocyte adhesion and transmigration during acute inflammation in vivo and further suggest that endothelial Cx43 is key in these processes. PMID:18599597

  13. Increased expression of telomere-regulating genes in endurance athletes with long leukocyte telomeres. (United States)

    Denham, Joshua; O'Brien, Brendan J; Prestes, Priscilla R; Brown, Nicholas J; Charchar, Fadi J


    Leukocyte telomeres shorten with age, and excessive shortening is associated with age-related cardiometabolic diseases. Exercise training may prevent disease through telomere length maintenance although the optimal amount of exercise that attenuates telomere attrition is unknown. Furthermore, the underlying molecular mechanisms responsible for the enhanced telomere maintenance observed in endurance athletes is poorly understood. We quantified the leukocyte telomere length and analyzed the expression of telomere-regulating genes in endurance athletes and healthy controls (both n = 61), using quantitative PCR. We found endurance athletes have significantly longer (7.1%, 208-416 nt) leukocyte telomeres and upregulated TERT (2.0-fold) and TPP1 (1.3-fold) mRNA expression compared with controls in age-adjusted analysis. The telomere length and telomere-regulating gene expression differences were no longer statistically significant after adjustment for resting heart rate and relative V̇O(2 max) (all P > 0.05). Resting heart rate emerged as an independent predictor of leukocyte telomere length and TERT and TPP1 mRNA expression in stepwise regression models. To gauge whether volume of exercise was associated with leukocyte telomere length, we divided subjects into running and cycling tertiles (distance covered per week) and found individuals in the middle and highest tertiles had longer telomeres than individuals in the lowest tertile. These data emphasize the importance of cardiorespiratory fitness and exercise training in the prevention of biological aging. They also support the concept that moderate amounts of exercise training protects against biological aging, while higher amounts may not elicit additional benefits.

  14. Leukocyte telomere length in major depression: correlations with chronicity, inflammation and oxidative stress--preliminary findings.

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    Owen M Wolkowitz

    Full Text Available BACKGROUND: Depression is associated with an unusually high rate of aging-related illnesses and early mortality. One aspect of "accelerated aging" in depression may be shortened leukocyte telomeres. When telomeres critically shorten, as often occurs with repeated mitoses or in response to oxidation and inflammation, cells may die. Indeed, leukocyte telomere shortening predicts early mortality and medical illnesses in non-depressed populations. We sought to determine if leukocyte telomeres are shortened in Major Depressive Disorder (MDD, whether this is a function of lifetime depression exposure and whether this is related to putative mediators, oxidation and inflammation. METHODOLOGY: Leukocyte telomere length was compared between 18 unmedicated MDD subjects and 17 controls and was correlated with lifetime depression chronicity and peripheral markers of oxidation (F2-isoprostane/Vitamin C ratio and inflammation (IL-6. Analyses were controlled for age and sex. PRINCIPAL FINDINGS: The depressed group, as a whole, did not differ from the controls in telomere length. However, telomere length was significantly inversely correlated with lifetime depression exposure, even after controlling for age (p<0.05. Average telomere length in the depressed subjects who were above the median of lifetime depression exposure (≥9.2 years' cumulative duration was 281 base pairs shorter than that in controls (p<0.05, corresponding to approximately seven years of "accelerated cell aging." Telomere length was inversely correlated with oxidative stress in the depressed subjects (p<0.01 and in the controls (p<0.05 and with inflammation in the depressed subjects (p<0.05. CONCLUSIONS: These preliminary data indicate that accelerated aging at the level of leukocyte telomeres is proportional to lifetime exposure to MDD. This might be related to cumulative exposure to oxidative stress and inflammation in MDD. This suggest that telomere shortening does not antedate depression

  15. Healthy lifestyle and leukocyte telomere length in U.S. women.

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    Qi Sun

    Full Text Available CONTEXT: Whether a healthy lifestyle may be associated with longer telomere length is largely unknown. OBJECTIVES: To examine healthy lifestyle practices, which are primary prevention measures against major age-related chronic diseases, in relation to leukocyte telomere length. DESIGN AND SETTING: Cross-sectional analysis in the Nurses' Health Study (NHS. PARTICIPANTS: The population consisted of 5,862 women who participated in multiple prospective case-control studies within the NHS cohort. Z scores of leukocyte telomere length were derived within each case-control study. Based on prior work, we defined low-risk or healthy categories for five major modifiable factors assessed in 1988 or 1990: non-current smoking, maintaining a healthy body weight (body mass index in 18.5-24.9 kg/m(2, engaging in regular moderate or vigorous physical activities (≥150 minutes/week, drinking alcohol in moderation (1 drink/week to <2 drinks/day, and eating a healthy diet (Alternate Healthy Eating Index score in top 50%. We calculated difference (% of the z scores contrasting low-risk groups with reference groups to evaluate the association of interest. RESULTS: Although none of the individual low-risk factors was significantly associated with larger leukocyte telomere length z scores, we observed a significant, positive relationship between the number of low-risk factors and the z scores. In comparison with women who had zero low-risk factors (1.9% of the total population and were, therefore, considered the least healthy group, the leukocyte telomere length z scores were 16.4%, 22.1%, 28.7%, 22.6%, and 31.2% (P for trend = 0.015 higher for women who had 1 to 5 low-risk factors, respectively. CONCLUSIONS: Adherence to a healthy lifestyle, defined by major modifiable risk factors, was associated with longer telomere length in leukocytes.

  16. SRC protein tyrosine kinase, c-Jun N-terminal kinase (JNK), and NF-kappaBp65 signaling in commercial and wild-type turkey leukocytes (United States)

    Studies comparing signaling in wild-type turkey (WT) leukocytes and commercial turkey (CT) leukocytes found that the activity of protein tyrosine kinases (PTK) and MAP kinases, ERK 1/2 and p38, were significantly higher in WT leukocytes compared to CT lines upon exposure to both SE and OPSE on days...

  17. Involvement of leukotriene B4 receptor 1 signaling in platelet-activating factor-mediated neutrophil degranulation and chemotaxis. (United States)

    Gaudreault, Eric; Stankova, Jana; Rola-Pleszczynski, Marek


    Platelet-activating factor (PAF) is a potent lipid mediator of inflammation that can act on human neutrophils. When neutrophils are stimulated with PAF at concentrations greater than 10 nM, a double peak of intracellular calcium mobilization is observed. The second calcium peak observed in PAF-treated neutrophils has already been suggested to come from the production of endogenous leukotriene B4 (LTB4). Here we demonstrate the involvement of endogenous LTB4 production and subsequent activation of the high affinity LTB4 receptor (BLT1) in this second calcium mobilization peak observed after stimulation with PAF. We also show that the second, but not the first peak, could be desensitized by prior exposure to LTB4. Moreover, when neutrophils were pre-treated with pharmacological inhibitors of LTB4 production or with the specific BLT1 antagonist, U75302, PAF-mediated neutrophil degranulation was inhibited by more than 50%. On the other hand, pre-treating neutrophils with the PAF receptor specific antagonist (WEB2086) did not prevent any LTB4-induced degranulation. Also, when human neutrophils were pre-treated with U75302, PAF-mediated chemotaxis was reduced by more than 60%. These data indicate the involvement of BLT1 signaling in PAF-mediated neutrophil activities.

  18. Associative learning for danger avoidance nullifies innate positive chemotaxis to host olfactory stimuli in a parasitic wasp (United States)

    Benelli, Giovanni; Stefanini, Cesare; Giunti, Giulia; Geri, Serena; Messing, Russell H.; Canale, Angelo


    Animals rely on associative learning for a wide range of purposes, including danger avoidance. This has been demonstrated for several insects, including cockroaches, mosquitoes, drosophilid flies, paper wasps, stingless bees, bumblebees and honeybees, but less is known for parasitic wasps. We tested the ability of Psyttalia concolor (Hymenoptera: Braconidae) females to associate different dosages of two innately attractive host-induced plant volatiles (HIPVs), ethyl octanoate and decanal, with danger (electric shocks). We conducted an associative treatment involving odours and shocks and two non-associative controls involving shocks but not odours and odours but not shocks. In shock-only and odour-only trained wasps, females preferred on HIPV-treated than on blank discs. In associative-trained wasps, however, P. concolor's innate positive chemotaxis for HIPVs was nullified (lowest HIPV dosage tested) or reversed (highest HIPV dosage tested). This is the first report of associative learning of olfactory cues for danger avoidance in parasitic wasps, showing that the effects of learning can override innate positive chemotaxes.

  19. Dual chemotaxis signalling regulates Dictyostelium development: intercellular cyclic AMP pulses and intracellular F-actin disassembly waves induce each other. (United States)

    Vicker, Michael G; Grutsch, James F


    Aggregating Dictyostelium discoideum amoebae periodically emit and relay cAMP, which regulates their chemotaxis and morphogenesis into a multicellular, differentiated organism. Cyclic AMP also stimulates F-actin assembly and chemotactic pseudopodium extension. We used actin-GFP expression to visualise for the first time intracellular F-actin assembly as a spatio-temporal indicator of cell reactions to cAMP, and thus the kinematics of cell communication, in aggregating streams. Every natural cAMP signal pulse induces an autowave of F-actin disassembly, which propagates from each cell's leading end to its trailing end at a linear rate, much slower than the calculated and measured velocities of cAMP diffusion in aggregating Dictyostelium. A sequence of transient reactions follows behind the wave, including anterior F-actin assembly, chemotactic pseudopodium extension and cell advance at the cell front and, at the back, F-actin assembly, extension of a small retrograde pseudopodium (forcing a brief cell retreat) and chemotactic stimulation of the following cell, yielding a 20s cAMP relay delay. These dynamics indicate that stream cell behaviour is mediated by a dual signalling system: a short-range cAMP pulse directed from one cell tail to an immediately following cell front and a slower, long-range wave of intracellular F-actin disassembly, each inducing the other.

  20. Antigen-engaged B cells undergo chemotaxis toward the T zone and form motile conjugates with helper T cells.

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    Takaharu Okada


    Full Text Available Interactions between B and T cells are essential for most antibody responses, but the dynamics of these interactions are poorly understood. By two-photon microscopy of intact lymph nodes, we show that upon exposure to antigen, B cells migrate with directional preference toward the B-zone-T-zone boundary in a CCR7-dependent manner, through a region that exhibits a CCR7-ligand gradient. Initially the B cells show reduced motility, but after 1 d, motility is increased to approximately 9 microm/min. Antigen-engaged B cells pair with antigen-specific helper T cells for 10 to more than 60 min, whereas non-antigen-specific interactions last less than 10 min. B cell-T cell conjugates are highly dynamic and migrate extensively, being led by B cells. B cells occasionally contact more than one T cell, whereas T cells are strictly monogamous in their interactions. These findings provide evidence of lymphocyte chemotaxis in vivo, and they begin to define the spatiotemporal cellular dynamics associated with T cell-dependent antibody responses.