JOURNAL OF PHYCOLOGY, Issue 6 2003
Michael J. Higgins
We investigated the adhesive mucilage and mechanism of cell-substratum adhesion of two benthic raphid diatoms, the marine species Craspedostauros australis E. J. Cox and the freshwater species Pinnularia viridis (Nitzsch) Ehrenberg. SEM images of P. viridis and C. australis cells revealed the presence of multistranded tethers that appear to arise along the raphe openings and extend for a considerable distance from the cell before forming a "holdfast-like" attachment with the substratum. We propose that the tethers result from the elongation/stretching of composite adhesive mucilage strands secreted from raphes during the onset of cell adhesion and reorientation. Atomic force microscopy (AFM) force measurements reveal that the adhesive strands originating from the nondriving raphe of live C. australis and P. viridis are highly extensible and accumulate to form tethers. During force measurements tethers can be chemically stained and are seen to extend between the cantilever tip and a cell during elongation and relaxation. In most cases, AFM force measurements recorded an interaction with a number of adhesive strands that are secreted from the raphe. The force curves of C. australis and P. viridis revealed a sawtooth pattern, suggesting the successive unbinding of modular domains when the adhesive strands were placed under stress. In addition, we applied the "fly-fishing" technique that allowed the cantilever, suspended a distance above the cell, to interact with single adhesive strands protruding from the raphe. These force curves revealed sawtooth patterns, although the binding forces recorded were in the range for single molecule interactions. [source]

Cell Motility and the Cytoskeleton in transition

CYTOSKELETON, Issue 8 2009
B.R. Brinkley Editor-in-Chief
No abstract is available for this article. [source]

Microtubule-dependent motility and orientation of the cortical endoplasmic reticulum in elongating characean internodal cells

CYTOSKELETON, Issue 3 2009
Ilse Foissner
Abstract Motility of the endoplasmic reticulum (ER) is predominantly microtubule- dependent in animal cells but thought to be entirely actomyosin-dependent in plant cells. Using live cell imaging and transmission electron microscopy to examine ER motility and structural organization in giant internodal cells of characean algae, we discovered that at the onset of cell elongation, the cortical ER situated near the plasma membrane formed a tight meshwork of predominantly transverse ER tubules that frequently coaligned with microtubules. Microtubule depolymerization increased mesh size and decreased the dynamics of the cortical ER. In contrast, perturbing the cortical actin array with cytochalasins did not affect the transverse orientation but decreased mesh size and increased ER dynamics. Our data suggest that myosin-dependent ER motility is confined to the ER strands in the streaming endoplasm, while the more sedate cortical ER uses microtubule-based mechanisms for organization and motility during early stages of cell elongation. We show further that the ER has an inherent, NEM-sensitive dynamics which can be altered via interaction with the cytoskeleton and that tubule formation and fusion events are cytoskeleton-independent. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source]

Evidence for a sliding-resistance at the tip of the trypanosome flagellum

CYTOSKELETON, Issue 12 2006
David Woolley
Abstract Motility in trypanosomes is achieved through the undulating behaviour of a single "9 + 2" flagellum; normally the flagellar waves begin at the flagellar tip and propagate towards the base. For flagella in general, however, propagation is from base-to-tip and it is believed that bend formation, and sustained regular oscillation, depend upon a localised resistance to inter-doublet sliding - which is normally conferred by structures at the flagellar base, typically the basal body. We therefore predicted that in trypanosomes there must be a resistive structure at the flagellar tip. Electron micrographs of Crithidia deanei, Herpetomonas megaseliae, Trypanosoma brucei and Leishmania major have confirmed that such attachments are present. Thus, it can be assumed that in trypanosomes microtubule sliding at the flagellar tip is resisted sufficiently to permit bend formation. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source]

Measurement of barbed ends, actin polymerization, and motility in live carcinoma cells after growth factor stimulation,

CYTOSKELETON, Issue 4 2004
Mike Lorenz
Abstract Motility is associated with the ability to extend F-actin-rich protrusions and depends on free barbed ends as new actin polymerization sites. To understand the function and regulation of different proteins involved in the process of generating barbed ends, e.g., cofilin and Arp2/3, fixed cell approaches have been used to determine the relative barbed end concentration in cells. The major disadvantages of these approaches are permeabilization and fixation of cells. In this work, we describe a new live-cell time-lapse microscopy assay to determine the increase of barbed ends after cell stimulation that does not use permeabilization and provides a better time resolution. We established a metastatic carcinoma cell line (MTLn3) stably expressing GFP-,-actin at physiological levels. Stimulation of MTLn3 cells with epidermal growth factor (EGF) causes rapid and transient lamellipod protrusion along with an increase in actin polymerization at the leading edge, which can be followed in live cell experiments. By measuring the increase of F-actin at the leading edge vs. time, we were able to determine the relative increase of barbed ends after stimulation with a high temporal resolution. The F-actin as well as the barbed end concentration agrees well with published data for this cell line. Using this newly developed assay, a decrease in lamellipod extension and a large reduction of barbed ends was documented after microinjecting an anti-cofilin function blocking antibody. This assay has a high potential for applications where rapid changes in the dynamic filament population are to be measured. Cell Motil. Cytoskeleton 57:207,217, 2004. © 2004 Wiley-Liss, Inc. [source]

Recovery of flagellar dynein function in a Chlamydomonas actin/dynein-deficient mutant upon introduction of muscle actin by electroporation

CYTOSKELETON, Issue 3 2001
Masahito Hayashi
Abstract Flagellar and ciliary inner-arm dyneins contain actin as a subunit; however, the function of this actin subunit remains unknown. As a first step toward experimental manipulation of actin in dynein, we developed a method for introducing exogenous actin into Chlamydomonas cells by electroporation. A non-motile mutant, ida5oda1, lacking inner-arm dyneins due to the absence of conventional actin, was electroporated in the presence of rabbit skeletal muscle actin. About 20% of the electroporated cells recovered motility under optimal conditions. In addition, by taking advantage of their phototactic behavior, the rescued cells could be concentrated. Motility was also recovered with fluorescently labeled actin; in this case, axonemes became fluorescent after electroporation, suggesting that actin was in fact incorporated as a dynein subunit. The feasibility of incorporating a substantial amount of macromolecules by electroporation will be useful not only for studying actin function, but also for a variety of studies using Chlamydomonas in which no efficient methods have been developed for expressing or introducing foreign proteins and other macromolecules. Cell Motil. Cytoskeleton 49:146,153, 2001. © 2001 Wiley-Liss, Inc. [source]

Temperature and pyoverdine-mediated iron acquisition control surface motility of Pseudomonas putida

ENVIRONMENTAL MICROBIOLOGY, Issue 7 2007
Miguel A. Matilla
Summary Pseudomonas putida KT2440 is unable to swarm at its common temperature of growth in the laboratory (30°C) but exhibits surface motility similar to swarming patterns in other Pseudomonas between 18°C and 28°C. These motile cells show differentiation, consisting on elongation and the presence of surface appendages. Analysis of a collection of mutants to define the molecular determinants of this type of surface movement in KT2440 shows that while type IV pili and lipopolysaccharide O-antigen are requisites flagella are not. Although surface motility of flagellar mutants was macroscopically undistinguishable from that of the wild type, microscopy analysis revealed that these mutants move using a distinct mechanism to that of the wild-type strain. Mutants either in the siderophore pyoverdine (ppsD) or in the FpvA siderophore receptor were also unable to spread on surfaces. Motility in the ppsD strain was totally restored with pyoverdine and partially with the wild-type ppsD allele. Phenotype of the fpvA strain was not complemented by this siderophore. We discuss that iron influences surface motility and that it can be an environmental cue for swarming-like movement in P. putida. This study constitutes the first report assigning an important role to pyoverdine iron acquisition in en masse bacterial surface movement. [source]

Bacterial motility: links to the environment and a driving force for microbial physics

FEMS MICROBIOLOGY ECOLOGY, Issue 1 2006
James G. Mitchell
Abstract Bacterial motility was recognized 300 years ago. Throughout this history, research into motility has led to advances in microbiology and physics. Thirty years ago, this union helped to make run and tumble chemotaxis the paradigm for bacterial movement. This review highlights how this paradigm has expanded and changed, and emphasizes the following points. The absolute magnitude of swimming speed is ecologically important because it helps determine vulnerability to Brownian motion, sensitivity to gradients, the type of receptors used and the cost of moving, with some bacteria moving at 1 mm s,1. High costs for high speeds are offset by the benefit of resource translocation across submillimetre redox and other environmental gradients. Much of environmental chemotaxis appears adapted to respond to gradients of micrometres, rather than migrations of centimetres. In such gradients, control of ion pumps is particularly important. Motility, at least in the ocean, is highly intermittent and the speed is variable within a run. Subtleties in flagellar physics provide a variety of reorientation mechanisms. Finally, while careful physical analysis has contributed to our current understanding of bacterial movement, tactic bacteria are increasingly widely used as experimental and theoretical model systems in physics. [source]

Mechanical Gradient Cues for Guided Cell Motility and Control of Cell Behavior on Uniform Substrates

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2009
Barbara Cortese
Abstract A novel method for the fabrication and the use of simple uniform poly(dimethylsiloxane) PDMS substrates for controlling cell motility by a mechanical gradient is reported. The substrate is fabricated in PDMS using soft lithography and consists of a soft membrane suspended on top of a patterned PDMS substrate. The difference in the gradient stiffness is related to the underlying pattern. It is shown experimentally that these uniform substrates can modulate the response of cell motility, thus enabling patterning on the surfaces with precise cell motility. Because of the uniformity of the substrate, cells can spread equally and a directional movement to stiffer regions is clearly observed. Varying the geometry underlying the membrane, cell patterning and movement can be quantitatively characterized. This procedure is capable of controlling cell motility with high fidelity over large substrate areas. The most significant advance embodied in this method is that it offers the use of mechanical features to control cell adhesion and not topographical or chemical variations, which has not been reported so far. This modulation of the response of cell motility will be useful for the design and fabrication of advanced planar and 3D biological assemblies suitable for applications in the field of biotechnology and for tissue-engineering purposes. [source]

From Molecular Machines to Microscale Motility of Objects: Application as "Smart Materials", Sensors, and Nanodevices

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2007
I. Willner
Abstract Machinelike operations are common functions in biological systems, and substantial recent research efforts are directed to mimic such processes at the molecular or nanoscale dimensions. The present Feature Article presents three complementary approaches to design machinelike operations: by the signal-triggered mechanical shuttling of molecular components; by the signal-triggering of chemical processes on surfaces, resulting in mechanical motion of micro/nanoscale objects; and by the fuel-triggered motility of biomolecule,metal nanowire hybrid systems. The shuttling of molecular components on molecular wires assembled on surfaces in semirotaxane configurations using electrical or optical triggering signals is described. The control of the hydrophilic/hydrophobic surface properties through molecular shuttling or by molecular bending/stretching processes is presented. Stress generated on microelements, such as cantilevers, results in the mechanical deflection of the cantilever. The deposition of a redox-active polyaniline film on a cantilever allows the reversible electrochemically induced deflection and retraction of the cantilever by the electrochemical oxidation or reduction of the polymer film, respectively. A micro-robot consisting of the polypyrrole (PPy) polymer deposited on a multi-addressable configuration of electrodes is described. Au magnetic core/shell nanoparticles are incorporated into a polyaniline film, and the conductivity of the composite polymer is controlled by an external magnet. Finally, the synthesis of a hybrid nanostructure consisting of two actin filaments tethered to the two ends of a Au nanowire is described. The adenosine triphosphate (ATP)-fueled motility of the hybrid nanostructure on a myosin monolayer associated with a solid support is demonstrated. [source]

Helicobacter pylori HP1034 (ylxH) is required for motility

HELICOBACTER, Issue 5 2004
Karin Van Amsterdam
ABSTRACT Background.,Helicobacter pylori motility is essential for the colonization and persistence in the human gastric mucosa. So far, more than 50 genes have been described to play a role in flagellar biosynthesis. H. pylori YlxH (HP1034) is annotated as an ATP-binding protein. However, H. pylori YlxH shows similarity to proteins involved in the flagellar biosynthesis of other bacterial species. Moreover, H. pylori ylxH is found adjacent to genes involved in flagellar biosynthesis in the sequenced genomes of H. pylori 26695 and J99. We therefore aimed to determine the role of YlxH in H. pylori motility. Materials and methods., Motility, flagellar biosynthesis and transcriptional regulation of genes encoding flagellar proteins was compared between H. pylori 11A and a knockout of ylxH in H. pylori 11A. Results., The ylxH knockout in H. pylori 11A was nonmotile on soft agar plates, whereas H. pylori 11A was motile. Furthermore, the H. pylori 11A ylxH knockout lacked flagella, while H. pylori 11A possessed two to three flagella. Transcription of H. pylori flaG (HP0751), fliM (HP1031) and fliA (HP1032) was reduced in the H. pylori 11A ylxH¯ knockout, whereas transcription of flaA (HP0601) was not altered. However, Western blot analysis showed substantially reduced amounts of the major flagellin subunit FlaA in the H. pylori 11A ylxH knockout compared to H. pylori 11A. Conclusions.,H. pylori YlxH is essential for the assembly of flagella and hence for the motility of H. pylori. [source]

Motility: mobility as capital

INTERNATIONAL JOURNAL OF URBAN AND REGIONAL RESEARCH, Issue 4 2004
Vincent Kaufmann
Social and territorial structures form intricate relations that transcend a social stratification or spatial focus. Territorial features and geographic displacements are structuring principles for society, as societal features and social change effect the structure and use of territory. Based on our examination of the conceptual and theoretical links between spatial and social mobility, we propose a concept that represents a new form of inequality. Termed ,motility', this construct describes the potential and actual capacity of goods, information or people to be mobile both geographically and socially. Three major features of motility , access, competence and appropriation , are introduced. In this article, we focus on conceptual and theoretical contributions of motility. In addition, we suggest a number of possible empirical investigations. Motility presents us with an innovative perspective on societal changes without prematurely committing researchers to work within structuralist or postmodern perspectives. More generally, we propose to revisit the fluidification debate in the social sciences with a battery of questions that do not begin and end with whether or not society is in flux. Instead, we introduce a field of research that takes advantage of the insights from competing paradigms in order to reveal the social dynamics and consequences of displacements in geographic and social space. Les structures sociales et territoriales forment des relations complexes qui dépassent toute stratification sociale ou convergence spatiale. Les caractéristiques territoriales et déplacements géographiques sont, pour la société, des principes structurants, tout comme les caractéristiques sociétales et le changement social font naître la structure et l'usage d'un territoire. A partir d'un examen des liens conceptuels et théoriques entre les mobilités spatiale et sociale, cet article propose un concept traduisant une nouvelle forme d'inégalité: appelé,motilité', il décrit le potentiel et l'aptitude réelle des marchandises, informations ou individus àêtre mobiles sur un plan tant géographique que social. Trois traits essentiels de la motilité, accès, compétence et appropriation , sont présentés. Si l'article s'attache aux contributions conceptuelles et théoriques de la motilité, il suggère aussi plusieurs axes possibles d'études empiriques. La motilité offre une perspective novatrice sur les changements sociétaux, sans engager prématurément les travaux de recherches sur des rails structuralistes ou post-modernes. Plus généralement, il s'agit de revisiter le débat sur la fluidification en sciences sociales à l'aide d'une batterie de questions qui, ni au début ni à la fin, ne demande si la société est fluctuante ou non. En revanche, l'article propose un domaine de recherches qui exploite les réflexions tirées de paradigmes concurrents afin de révéler la dynamique sociale et les conséquences des déplacements dans l'espace géographique et social. [source]

Protein profile study in European eel (Anguilla anguilla) seminal plasma and its correlation with sperm quality

JOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2010
D. S. Peñaranda
Summary Along with sperm quality parameters, the protein profile of European eel seminal plasma was analyzed during induced spermiation (n = 56 samples). Motility, Percentage of live cells, spermatozoa head morphometry and concentration showed low values during the initial weeks of spermiation and maintained high levels throughout the rest of the experiment. The protein profile gradient by SDS-PAGE (4,15%) registered four important electrophoretic bands around 80, 40, 26 and 12 KDa. Three of them showed significant differences in concentration during treatment (80, 40 and 12 KDa), and all of them showed the highest value on the 8th week. Both 80 and 12 KDa bands increased until the 8th week, followed by a progressive decline. One possible explanation for these profiles is that, in the first weeks of treatment, proteins originated from blood plasma are accumulated in the seminal plasma, and from the 8th week some of these proteins are incorporated into the spermatic membranes. The 40 KDa protein band also increased during the first 8 weeks, but maintained high concentrations in the seminal plasma for the rest of the experiment. One result confirms the theory that the presence of proteins in the seminal plasma having a molecular weight lower than 50 KDa increased spermatozoa motility, since the 40 KDa band displayed significantly higher values coinciding with the high percentages of spermatozoa motility. Seminal plasma proteins seem to have an important role in spermatogenesis and spermatozoa movement, but further studies are necessary to discover the identity of these proteins and their precise functions. [source]

Relationship between sperm density, spermatocrit, sperm motility and spawning date in wild and cultured haddock

JOURNAL OF FISH BIOLOGY, Issue 2 2004
R. M. Rideout
Semen was collected repeatedly from captive haddock Melanogrammus aeglefinus and the effect of seasonality on various sperm parameters was investigated. No differences in sperm traits were observed for wild and cultured haddock. A highly significant positive relationship existed between spermatocrit and spermatozoa density. A significant increase in mean spermatocrit occurred throughout the spawning season but the amount of variability explained by collection date was low (35·1%) due to variability between males. Each of 10 males sampled repeatedly throughout the spawning season demonstrated an increase in spermatocrit. No relationship existed between spermatocrit and proportion of motile spermatozoa when spermatocrit was ,70%. Motility was reduced in semen samples with spermatocrits >70%. The proportion of spermatozoa that were motile decreased with time since activation. Some motility was still observed after 60 min in sea water (0·1,15·2%) for sperm collected at all times within the spawning season. Of those spermatozoa that were motile, the proportion that exhibited forward swimming motion decreased and the proportion that had only vibratory movement increased with time post-activation. The speed of forward swimming spermatozoa showed no significant relationship with spermatocrit at any time between 0 and 60 min after activation. Swimming speed was negatively related to time since activation, decreasing from 174,240 ,m s,1 at 0 min to 80,128 ,m s,1 at 60 min after activation. [source]

Alcohol Stimulates Ciliary Motility of Isolated Airway Axonemes Through a Nitric Oxide, Cyclase, and Cyclic Nucleotide-Dependent Kinase Mechanism

ALCOHOLISM, Issue 4 2009
Joseph H. Sisson
Background:, Lung mucociliary clearance provides the first line of defense from lung infections and is impaired in individuals who consume heavy amounts of alcohol. Previous studies have demonstrated that this alcohol-induced ciliary dysfunction occurs through impairment of nitric oxide (NO) and cyclic nucleotide-dependent kinase-signaling pathways in lung airway ciliated epithelial cells. Recent studies have established that all key elements of this alcohol-driven signaling pathway co-localize to the apical surface of the ciliated cells with the basal bodies. These findings led us to hypothesize that alcohol activates the cilia stimulation pathway at the organelle level. To test this hypothesis we performed experiments exposing isolated demembranated cilia (isolated axonemes) to alcohol and studied the effect of alcohol-stimulated ciliary motility on the pathways involved with isolated axoneme activation. Methods:, Isolated demembranated cilia were prepared from bovine trachea and activated with adenosine triphosphate. Ciliary beat frequency, NO production, adenylyl and guanylyl cyclase activities, cAMP- and cGMP-dependent kinase activities were measured following exposure to biologically relevant concentrations of alcohol. Results:, Alcohol rapidly stimulated axoneme beating 40% above baseline at very low concentrations of alcohol (1 to 10 mM). This activation was specific to ethanol, required the synthesis of NO, the activation of soluble adenylyl cyclase (sAC), and the activation of both cAMP- and cGMP-dependent kinases (PKA and PKG), all of which were present in the isolated organelle preparation. Conclusions:, Alcohol rapidly and sequentially activates the eNOS,NO,GC,cGMP,PKG and sAC,cAMP, PKA dual signaling pathways in isolated airway axonemes. These findings indicate a direct effect of alcohol on airway cilia organelle function and fully recapitulate the alcohol-driven activation of cilia known to exist in vivo and in intact lung ciliated cells in vitro following brief moderate alcohol exposure. Furthermore, these findings indicate that airway cilia are exquisitely sensitive to the effects of alcohol and substantiate a key role for alcohol in the alterations of mucociliary clearance associated with even low levels of alcohol intake. We speculate that this same axoneme-based alcohol activation pathway is down regulated following long-term high alcohol exposure and that the isolated axoneme preparation provides an excellent model for studying the mechanism of alcohol-mediated cilia dysfunction. [source]

Cryopreservation of YamúBrycon siebenthalae Milt

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 4 2004
Pablo E. Cruz-Casallas
The yamúBrycon siebenthalae is an endemic fish of the Orinoco river basin, but wild stocks are decreasing because of the disruption of their habitat. We evaluated a protocol for the cryopreservation of yamú sperm to contribute to the preservation of this endangered genetic resource. Milt was mixed with a cryoprotectant medium (5.5% glucose, 12% egg yolk, and 5%, 10%, or 15% dimethyl sulfoxide - DMSO) in a ratio 1:4 (milt:medium), stored in 0.5-mL French straws, frozen in nitrogen liquid vapor (-76 C), then immersed and stored in liquid nitrogen for 10 d or 12 mo. Motility of thawed spermatozoa was higher (P < 0.001) in 10% DMSO medium than 5% DMSO or 15% DMSO mediums; but lower than the control (P < 0.001). With sperm cryopreserved, the highest level of fertilization was achieved with 10% DMSO (P < 0.001) after 10 d or 12 mo of cryopreservation. Fertilization of eggs inseminated with 6.4 × 109 spermatozoa per g of eggs was higher (P <0.05) than with 1.6 × 109 spermatozoa per g of eggs. There was no difference (P > 0.05) in fertilization between insemination doses of 3.2 × 109 and 6.4 × 109 spermatozoa per g of eggs. Cryopreservation of yamu milt can be performed successfully with a simple medium combined with 10% of DMSO as cryoprotectant. The highest level of fertility was achieved using between 3 × 109 and 6 × 109 spermatozoa per g of fresh eggs. [source]

The Effects of Osmolality, Cryoprotectant and Equilibration Time on Striped Bass Morone saxatilis Sperm Motility

JOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 3 2003
Shuyang He
Four experiments were designed to evaluate the effects of osmolality, cryoprotectant, and equilibration time on striped bass sperm motility. In the first experiment, solutions of NaCI or KCI with osmolalities ranging from 0 to 700 mmol/kg were tested on sperm activation. Over 60% of the sperm were activated by isotonic NaCI and KCI solutions with a treatment osmolality of 350 mmol/kg. Sperm remained motile until osmolality increased to 600 mmol/ kg. In the second and third experiments, Extenders 1, 2 and 3 with osmolalities of 350, 500, and 600 mmol/kg, respectively, were tested. Sperm samples stored in Extender 2 showed significantly higher (P 0.01) sperm motility after 10 min of exposure as well as greater (P < 0.01) post-thaw motility when compared to samples stored in Extenders 1 and 3. In the fourth experiment, two trials were carried out to evaluate the effects of cryoprotectant and equilibration time. In the first trial, methanol with a concentration of 5% and 10% yielded the highest (P < 0.05) sperm motility prior to freezing at all equilibration times examined. However, 5% DMSO yielded the highest (P < 0.01) post-thaw motility (38 ± 3.6%). DMSO with concentrations of 10% and 15% resulted in 17 ± 2.3% and 6 ± 1.0% post-thaw motility, respectively. Both methanol and DMA, at all concentrations tested, resulted in less than 10% post-thaw motility. In the second trial, four DMSO concentrations with three different equilibration times were examined. We observed a significant (P < 0.001) interaction effect between DMSO concentration and equilibration time. Post-thaw motility was significantly greater (P < 0.01) with a concentration of 5% DMSO at all equilibration times examined, compared to 1.25, 2.5, and 10% DMSO. An average post-thaw motility of 40 ± 2.9% was achieved after 10 min equilibration using 5% DMSO. [source]

Three independent signalling pathways repress motility in Pseudomonas fluorescens F113

MICROBIAL BIOTECHNOLOGY, Issue 4 2009
Ana Navazo
Summary Motility is one of the most important traits for rhizosphere colonization by pseudomonads. Despite this importance, motility is severely repressed in the rhizosphere-colonizing strain Pseudomonas fluorescens F113. This bacterium is unable to swarm under laboratory conditions and produce relatively small swimming haloes. However, phenotypic variants with the ability to swarm and producing swimming haloes up to 300% larger than the wild-type strain, arise during rhizosphere colonization. These variants harbour mutations in the genes encoding the GacA/GacS two-component system and in other genes. In order to identify genes and pathways implicated in motility repression, we have used generalized mutagenesis with transposons. Analysis of the mutants has shown that besides the Gac system, the Wsp system and the sadB gene, which have been previously implicated in cyclic di-GMP turnover, are implicated in motility repression: mutants in the gacS, sadB or wspR genes can swarm and produce swimming haloes larger than the wild-type strain. Epistasis analysis has shown that the pathways defined by each of these genes are independent, because double and triple mutants show an additive phenotype. Furthermore, GacS, SadB and WspR act at different levels. Expression of the fleQ gene, encoding the master regulator of flagella synthesis is higher in the gacS - and sadB - backgrounds than in the wild-type strain and this differential expression is reflected by a higher secretion of the flagellin protein FliC. Conversely, no differences in fleQ expression or FliC secretion were observed between the wild-type strain and the wspR - mutant. [source]

Neural control of the gastrointestinal tract: Implications for Parkinson disease

MOVEMENT DISORDERS, Issue 8 2008
Maria G. Cersosimo MD
Abstract Disorders of swallowing and gastrointestinal motility are prominent nonmotor manifestations of Parkinson disease (PD). Motility of the gut is controlled both by extrinsic inputs from the dorsal motor nucleus of the vagus (DMV) and paravertebral sympathetic ganglia and by local reflexes mediated by intrinsic neurons of the enteric nervous system (ENS). Both the ENS and the DMV are affected by Lewy body pathology at early stages of PD. This early involvement provides insights into the pathophysiology of gastrointestinal dysmotility in this disorder and may constitute an important step in the etiopathogenesis of Lewy body disease. © 2008 Movement Disorder Society. [source]

Missing link identified: GpBAR1 is a neuronal bile acid receptor

NEUROGASTROENTEROLOGY & MOTILITY, Issue 7 2010
S. J. Keely
Abstract,In addition to their classical functions in aiding the digestion and absorption of lipids, bile acids are increasingly gaining appreciation for their roles in regulating intestinal physiology. Bile acids are now widely considered as hormones that exert a wide range of physiological and pathophysiological effects both within and outside the gastrointestinal (GI) tract. The discovery of the bile acid receptor, GpBAR1, represented a major step forward in our understanding of how cells can sense and respond to bile acids. GpBAR1 is a cell surface G protein-coupled receptor expressed on adipose tissue and skeletal muscle where it has been found to be an important regulator of cellular metabolism. In a paper published in the current issue of Neurogastroenterology and Motility, Poole et al. investigated the expression and function of GpBAR1 in mouse intestine. They found the receptor to be expressed throughout the GI tract but predominantly on nerves within the myenteric and submucosal plexuses. Employing in vitro and in vivo techniques they demonstrated that activation of GpBAR1 by bile acids inhibits small and large intestinal motor function and delays intestinal transit. The effects of GpBAR1 activation are mediated through activation of cholinergic and nitrergic interneurons. The data reported by Poole et al. provides novel and exciting insights into how bile acids exert their actions in the intestine. This Editorial Viewpoint aims to further consider the potential physiological and pathophysiological implications of their findings. [source]

Protease-activated receptors: novel central role in modulation of gastric functions

NEUROGASTROENTEROLOGY & MOTILITY, Issue 4 2010
K. N. Browning
Abstract, Protease-activated receptors (PARs) are members of a subfamily of G-protein-coupled receptors that regulate diverse cell functions in response to proteolytic cleavage of an anchored peptide domain that acts as a ,tethered' receptor-activating ligand. PAR-1 and PAR-2 in particular are present throughout the gastrointestinal (GI) tract and play prominent roles in the regulation of GI epithelial function, motility, inflammation and nociception. In a recent article in Neurogastroenterology and Motility, Wang et al. demonstrate, for the first time, that PAR-1 and PAR-2 are present on preganglionic parasympathetic neurons within the rat brainstem. As in other cellular systems, proteases such as thrombin and trypsin activate PAR-1 and PAR-2 on neurons of the dorsal motor nucleus of the vagus (DMV), leading to an increase in intracellular calcium levels via signal transduction mechanisms involving activation of phospholipase C and inositol triphosphate (IP3). The authors also report that the level of PAR-1 and PAR-2 transcripts in DMV tissue is increased following experimental colitis, suggesting that inflammatory conditions may modulate neuronal behavior or induce plasticity within central vagal neurocircuits. It seems reasonable to hypothesize, therefore, that the activity and behavior of vagal efferent motoneurons may be modulated directly by local and/or systemic proteases released during inflammation. This, in turn, may contribute to the increased incidence of functional GI disorders, including gastric dysmotility, delayed emptying and gastritis observed in patients with inflammatory bowel diseases. [source]

PAR4: A new role in the modulation of visceral nociception

NEUROGASTROENTEROLOGY & MOTILITY, Issue 11 2009
S. Bradesi
Abstract,Protease-activated receptors (PARs) are a family of G-protein-coupled receptors with a widespread distribution that are involved in various physiological functions including inflammation and nociception. In a recent study in Neurogastroenterology and Motility, Augé et al. describe for the first time the presence of PAR4 on visceral primary afferent neurons and its role in modulating colonic nociceptive responses, colonic hypersensitivity and primary afferent responses to PAR2 and Transient Receptor Potential Vanilloid-4 (TRPV4). Using the model of visceromotor response (VMR) to colorectal distension (CRD), they show that a PAR4 agonist delivered into the colon lumen decreases basal visceral response to CRD and reduces the exacerbated VMR to CRD induced by treatment with PAR2 or TRPV4 agonists. In isolated sensory neurons, they show that a PAR4 agonist inhibits calcium mobilization induced by PAR2 or TRPV4 agonists. Finally, they describe increased pain behaviour evoked by luminal application of mustard oil in PAR4 deficient mice compared to wild type controls. The newly discovered role of PAR4 in modulating visceral pain adds to our growing understanding of the contribution of colonic proteases and PARs to the mechanisms involved in colonic hypersensitivity and their potential role as therapeutic targets for irritable bowel syndrome. [source]

Cannabinoid signalling in the enteric nervous system

NEUROGASTROENTEROLOGY & MOTILITY, Issue 9 2009
J. J. Galligan
Abstract, Cannabinoid signalling is an important mechanism of synaptic modulation in the nervous system. Endogenous cannabinoids (anandamide and 2-arachidonyl-glycerol) are synthesized and released via calcium-activated biosynthetic pathways. Exogenous cannabinoids and endocannabinoids act on CB1 and CB2 receptors. CB1 receptors are neuronal receptors which couple via G-proteins to inhibition of adenylate cyclase or to activation or inhibition of ion channels. CB2 receptors are expressed by immune cells and cannabinoids can suppress immune function. In the central nervous system, the endocannabinoids may function as retrograde signals released by the postsynaptic neuron to inhibit neurotransmitter release from presynaptic nerve terminals. Enteric neurons also express CB receptors. Exogenously applied CB receptor agonists inhibit enteric neuronal activity but it is not clear if endocannabinoids released by enteric neurons can produce similar responses in the enteric nervous system (ENS). In this issue of Neurogastroenterology and Motility, Boesmans et al. show that CB1 receptor activation on myenteric neurons maintained in primary culture can suppress neuronal activity, inhibit synaptic transmission and mitochondrial transport along axons. They also provide initial evidence that myenteric neurons (or other cell types present in the cultures) release endocannabinoids and which activate CB1 receptors constitutively. These data provide new information about targets for cannabinoid signalling in the ENS and highlight the potential importance of CB receptors as drug targets. It is necessary that future work extends these interesting findings to intact tissues and ideally to the in vivo setting. [source]

Proximal oesophagus: the added value in understanding GORD symptoms

NEUROGASTROENTEROLOGY & MOTILITY, Issue 8 2009
M. Cicala
Abstract, Over the past decade, the approach to the understanding of the mechanisms involved in the aetiology of gastro-oesophageal reflux disease (GORD) symptoms has changed, and growing evidence now supports the concept that visceral hyper-sensitivity to intra-oesophageal stimuli plays a major role. Among the recent advances, one of the more consistent findings is that the contact of the refluxate, either acidic or weakly acidic, with the proximal oesophageal mucosa, is a main determinant of GORD symptoms, particularly in the large majority of patients affected by non-erosive reflux disease. The data reported in the current issue of Neurogastroenterology and Motility by Bredenoord et al., showing only a small proportion of proximal reflux in patients with Barrett's oesophagus, who are less sensitive to gastro-oesophageal reflux, further support the consistency of this finding in the pathogenesis of symptoms. In the light of these results, we shall look forward, in the management of patients, to approaches aimed at restoring the antireflux barrier, hopefully decreasing the amount of reflux and, in turn, its proximal extent. [source]

Death comes early: apoptosis observed in ENS precursors

NEUROGASTROENTEROLOGY & MOTILITY, Issue 7 2009
H. Enomoto
Abstract, Cell death is a physiological and fundamental process in normal organogenesis. During the development of the nervous system, cell death or apoptosis occurs in early and late developmental time periods, affecting neural precursors and neurons respectively. In the development of the enteric nervous system (ENS), however, apoptosis of neurons has not been detected, a feature unique to enteric neurons. In this issue of Neurogastroenterology and Motility, Wallace et al. focused on an early phase of ENS development and identified apoptotic cell death in vagal neural crest cells, the primary cellular source for the ENS. Introduction of an antiapoptotic molecule in the vagal neural crest and its derivatives resulted in the overproduction of neurons in the foregut. Thus, unlike the neurons themselves, ENS precursors do undergo apoptosis, which may, by regulating the size of the ENS precursor pool, be a crucial factor in determining the final cell number in the ENS. [source]

Probiotics effects on gastrointestinal function: beyond the gut?

NEUROGASTROENTEROLOGY & MOTILITY, Issue 5 2009
E. F. Verdu
Abstract, The digestive tract works through a complex network of integrative functions. At the level of the gut, this integration occurs between the immune, neuromotor and enteroendocrine systems, coordinating the physical and chemical elements of the intestinal barrier in order to facilitate digestion whilst protecting the gut from unwanted components of the luminal contents. Gastrointestinal function is controlled and coordinated by the central nervous system to ensure effective motility, secretion, absorption and mucosal immunity. It follows that perturbations in this complex network could lead to gut dysfunction and symptom generation. Recently, attention has been focused on the emerging hypothesis that gut luminal content contributes to determine normal GI function and on the therapeutic possibilities arising from modulating its impact on gut physiology and immunity using probiotic bacteria. In this issue of Neurogastroenterology and Motility, two papers explore the effect of specific probiotic bacteria on spinal neuronal activation and in vitro muscle contractility. These papers support the notion that the composition of the intestinal microbiota can influence gut neuro-motor function and enhance our understanding on the mechanisms of action underlying the effects of specific probiotics on gut functional disorders. [source]

A new high-content model system for studies of gastrointestinal transit: the zebrafish

NEUROGASTROENTEROLOGY & MOTILITY, Issue 3 2009
A. Rich
Abstract, The zebrafish gastrointestinal (GI) tract displays an anatomy and cellular architecture that is similar to the human GI tract, with concentric layers of inner epithelia, connective tissue, circular muscle and outer longitudinal muscle layers. Propulsion of luminal content results from the integrated activity of smooth muscle cells, enteric neurons and the interstitial cells of Cajal (ICC). Zebrafish larvae are transparent and propagating contractions in the entire GI tract are easily visualized. A new moderate-throughput zebrafish-based GI transit assay is described in this issue of Neurogastroenterology and Motility. This assay utilizes intact zebrafish larvae which contain essential regulatory elements (ICC and enteric neurons). Forward genetic analysis, which identifies genes underlying specific phenotypes, is possible using the zebrafish system. The zebrafish model system compliments existing models for studies of GI motility and will contribute to the understanding of the regulation of GI motility, and to identification of novel drug targets. [source]

Electrochemical detection of neurotransmitters in the gut wall

NEUROGASTROENTEROLOGY & MOTILITY, Issue 11 2008
P. Vanden Berghe
Abstract, Cells interact with each other by releasing signalling molecules, which can activate or inactivate target cells. In order to understand how coordination results from this communication, accurate measurements of these signalling molecules are prerequisite. Several different techniques exist to monitor and quantify these compounds, including enzymatic and histochemical assays, electrophysiological and optical recordings. However, there has been little use of electrochemical recordings in gastroenterological research, although these are very fast and sensitive. Electrochemical techniques rely on the simple fact that electroactive molecules can be oxidized at a given potential. The currents, elicited by the oxidation, are directly proportional to the concentration of the compound. In the current issue of Neurogastroenterology and Motility, electrochemical detection was successfully applied to measure nitric oxide (NO) from intestinal preparations. Although there are some important specificity, timing and spatial aspects to consider, this direct NO-probing technique is definitely a great asset to the field of gastrointestinal research and advances our understanding of NO signalling in the intestinal wall. [source]

Smooth muscle phenotypic plasticity in mechanical obstruction of the small intestine

NEUROGASTROENTEROLOGY & MOTILITY, Issue 7 2008
J. A. Macdonald
Abstract, Chronic, partial obstruction of the small intestine can dramatically alter peristaltic contractile properties. Morphological studies have revealed hypertrophy of the circular smooth muscle cells in the constricted part of the intestine. In this issue of Neurogastroenterology and Motility, Chen et al. show that hyperplasia and hypertrophy of intestinal smooth muscle cells occur at distinct times in response to partial obstruction of the ileum. Furthermore, the first evidence is provided to link intestinal smooth muscle remodelling during mechanical obstruction with changes in serum response factor and two of its co-regulating factors, myocardin and Elk-1. [source]

Observations on a vestigial organ: a potential surrogate for enteric neuromesenchymal disease

NEUROGASTROENTEROLOGY & MOTILITY, Issue 4 2008
C. H. Knowles
Abstract, Abnormalities of enteric nerves, interstitial cells of Cajal (ICC) and smooth muscle are often associated with severe gastrointestinal motility disorders. In this context, full-thickness biopsy of the gut may provide important diagnostic and prognostic clues as well as some possible therapeutic implications. Nonetheless, the unavoidable risk to further worsen prognosis evoked by laparotomy, and the unclear yield of histopathological analysis has hampered full-thickness gut sampling in patients with severe dysmotility. However, recent advances in minimally invasive surgery have refuelled enthusiasm in gastrointestinal neuromuscular pathology. In this issue of Neurogastroenterology and Motility, Miller et al. provide novel and exciting evidence that the appendix might be used as a surrogate tissue to analyse changes to enteric nerves, ICC and smooth muscle cells in patients with diabetic gastroenteropathy. The objective of this short review was to place this very important work in the context of current understanding of enteric neuromuscular dysfunction. [source]